Biology (School of)https://hdl.handle.net/10023/172024-03-29T08:30:26Z2024-03-29T08:30:26ZComparative analysis of ISGylation during the antiviral response against Paramyxovirus infectionSeaton, Andrew Vasilihttps://hdl.handle.net/10023/294902024-03-15T03:02:30Z2024-06-12T00:00:00ZViral infection induces a significant antiviral response through the interferon response. This response leads to the production of hundreds of interferon stimulated genes (ISGs) including ISG15; a Ubl protein with multiple roles in the antiviral response. Within the antiviral response ISG15 plays a role as a negative regulator of the IFN response with loss of ISG15 generating an overactive response, plays a role in extracellular signalling and is capable of post-translationally modifying host and viral proteins through a process known as ISGylation. ISGylation is known to alter functions of proteins through aiding host defence and playing an antiviral role when modifying viral proteins. We have identified a novel modification of parainfluenza virus type-5 (PIV5) phosphoprotein (P protein) and through use of CRISPR/Cas9 and immunoblot analysis have confirmed that this modification is ISG15. Further to this we have shown that this appears to be the only modified protein of PIV5. As the P protein plays a critical role in viral replication we took a comparative approach through analysis of effects of ISGylation PIV5, PIV2 and PIV3. In order to comparatively analyse effects of ISGylation on plaque size we used a computationally-aided plaque assay approach to determine effects of ISGylation. Our initial dataset suggested that ISGylation had little to no effect on replication of these paramyxoviruses. However further investigation using IFIT1.ko cell lines yielded data suggesting that loss of ISGylation lead to an increase in plaque size in PIV2 and PIV5 suggesting ISGylation was antiviral to these viruses but noted no effect on PIV3. Importantly we noted that loss of ISG15 lead to a decrease in plaque size which is attributed to the role of ISG15 as a negative regulator of the antiviral response. These findings suggested that ISGylation plays a minor antiviral role with respect to PIV2 and PIV5 and potentially may impact other members of the Paramyxoviridae family, however this requires further investigation. As noted, we observed small plaque sizes present within ISG15.ko IFIT1.ko cells, particularly those infected with PIV3. We further investigated these plaques and observed a strange phenotype wherein immunostaining of viral plaques yielded only tiny viral plaques while counter staining for cell viability revealed large areas of cell death surrounding these small areas of viral activity. Further investigation into this suggested an IFN-alpha signalling dependent pathway causing cell death highlighting differences between the IFN-alpha and beta responses. Overall our data has shown that ISGylation is a minor antiviral factor for the Paramyxoviridae family, especially in comparison to the major antiviral role ISG15 plays within its negative regulation of the IFN response. This major role of ISG15 as a negative regulator is detracted from as cells lacking ISG15 undergo high levels of cell death in response to signalling from infected cells. Further investigations would be needed to identify the antiviral mechanism of ISGylation as well as whether other Paramyxoviridae are affected by this modification as well as the exact pathway that triggers cell death within ISG15.ko cells.
2024-06-12T00:00:00ZSeaton, Andrew VasiliViral infection induces a significant antiviral response through the interferon response. This response leads to the production of hundreds of interferon stimulated genes (ISGs) including ISG15; a Ubl protein with multiple roles in the antiviral response. Within the antiviral response ISG15 plays a role as a negative regulator of the IFN response with loss of ISG15 generating an overactive response, plays a role in extracellular signalling and is capable of post-translationally modifying host and viral proteins through a process known as ISGylation. ISGylation is known to alter functions of proteins through aiding host defence and playing an antiviral role when modifying viral proteins. We have identified a novel modification of parainfluenza virus type-5 (PIV5) phosphoprotein (P protein) and through use of CRISPR/Cas9 and immunoblot analysis have confirmed that this modification is ISG15. Further to this we have shown that this appears to be the only modified protein of PIV5. As the P protein plays a critical role in viral replication we took a comparative approach through analysis of effects of ISGylation PIV5, PIV2 and PIV3. In order to comparatively analyse effects of ISGylation on plaque size we used a computationally-aided plaque assay approach to determine effects of ISGylation. Our initial dataset suggested that ISGylation had little to no effect on replication of these paramyxoviruses. However further investigation using IFIT1.ko cell lines yielded data suggesting that loss of ISGylation lead to an increase in plaque size in PIV2 and PIV5 suggesting ISGylation was antiviral to these viruses but noted no effect on PIV3. Importantly we noted that loss of ISG15 lead to a decrease in plaque size which is attributed to the role of ISG15 as a negative regulator of the antiviral response. These findings suggested that ISGylation plays a minor antiviral role with respect to PIV2 and PIV5 and potentially may impact other members of the Paramyxoviridae family, however this requires further investigation. As noted, we observed small plaque sizes present within ISG15.ko IFIT1.ko cells, particularly those infected with PIV3. We further investigated these plaques and observed a strange phenotype wherein immunostaining of viral plaques yielded only tiny viral plaques while counter staining for cell viability revealed large areas of cell death surrounding these small areas of viral activity. Further investigation into this suggested an IFN-alpha signalling dependent pathway causing cell death highlighting differences between the IFN-alpha and beta responses. Overall our data has shown that ISGylation is a minor antiviral factor for the Paramyxoviridae family, especially in comparison to the major antiviral role ISG15 plays within its negative regulation of the IFN response. This major role of ISG15 as a negative regulator is detracted from as cells lacking ISG15 undergo high levels of cell death in response to signalling from infected cells. Further investigations would be needed to identify the antiviral mechanism of ISGylation as well as whether other Paramyxoviridae are affected by this modification as well as the exact pathway that triggers cell death within ISG15.ko cells.An investigation of the social behaviour of archerfish Toxotes spp.Der Weduwen, Dagmar Jacquelinehttps://hdl.handle.net/10023/294372024-03-07T03:02:40Z2024-06-12T00:00:00ZSociality has evolved multiple times in animals. Social living is a balance between the advantages and disadvantages of the increased presence of conspecifics. These costs and benefits are especially prevalent when foraging, as both the chance to discover resources and the rate at which they are depleted increase with group size. This holds true for archerfish Toxotes spp., a genus known for shooting down terrestrial prey using concentrated jets of water. This hunting method leaves the shooters open to theft, but whether and how their foraging behaviour and decision-making are affected by this threat is unclear. I investigated how group size affected aiming duration and shooting success, performed a pilot investigation into the use of video demonstrators for standardising social stimuli in such experiments, and tested whether archerfish socially learn target preferences when foraging in a group. I found evidence that archerfish decrease their aiming duration in the presence of more conspecifics. My results contradict previous research on kleptoparasitism in archerfish, mainly that the rate of kleptoparasitism is dependent on the behaviour of the shooter’s neighbours rather than group size. I also showed that archerfish avoid videos of conspecifics, although the explanation for this remains elusive. I attempted to find out whether archerfish can learn socially but instead found no evidence of learning. As scientists, we must study the natural world and share our findings with the public who fund our work. Accordingly, I created a tabletop role-playing style game based on archerfish ecology to test whether it could educate the public about my research and found that most participants improved their knowledge of archerfish. This thesis not only helps to further elucidate the social behaviour of archerfish but also illustrates how an animal’s ecology must be taken into consideration when conducting research and conveying the results to the public.
2024-06-12T00:00:00ZDer Weduwen, Dagmar JacquelineSociality has evolved multiple times in animals. Social living is a balance between the advantages and disadvantages of the increased presence of conspecifics. These costs and benefits are especially prevalent when foraging, as both the chance to discover resources and the rate at which they are depleted increase with group size. This holds true for archerfish Toxotes spp., a genus known for shooting down terrestrial prey using concentrated jets of water. This hunting method leaves the shooters open to theft, but whether and how their foraging behaviour and decision-making are affected by this threat is unclear. I investigated how group size affected aiming duration and shooting success, performed a pilot investigation into the use of video demonstrators for standardising social stimuli in such experiments, and tested whether archerfish socially learn target preferences when foraging in a group. I found evidence that archerfish decrease their aiming duration in the presence of more conspecifics. My results contradict previous research on kleptoparasitism in archerfish, mainly that the rate of kleptoparasitism is dependent on the behaviour of the shooter’s neighbours rather than group size. I also showed that archerfish avoid videos of conspecifics, although the explanation for this remains elusive. I attempted to find out whether archerfish can learn socially but instead found no evidence of learning. As scientists, we must study the natural world and share our findings with the public who fund our work. Accordingly, I created a tabletop role-playing style game based on archerfish ecology to test whether it could educate the public about my research and found that most participants improved their knowledge of archerfish. This thesis not only helps to further elucidate the social behaviour of archerfish but also illustrates how an animal’s ecology must be taken into consideration when conducting research and conveying the results to the public.Killing the messenger : discovery of enzymes degrading cyclic oligoadenylate defence activators synthesised by type III CRISPR immune systemsAthukoralage, Januka Sahanhttps://hdl.handle.net/10023/294282024-03-08T16:56:18Z2021-06-30T00:00:00ZCRISPR-Cas systems provide prokaryotes with adaptative immunity from invading Mobile Genetic Elements (MGEs). Type III CRISPR-Cas systems consist of a multiprotein effector complex and CRISPR ancillary proteins; both essential for MGE elimination. In 2017, two groups independently identified that type III CRISPR-Cas complexes synthesised cyclic oligoadenylate (cOA) second messengers in response to detection of foreign RNA. cOA was made using ATP (adenosine triphosphate) and consisted of 3-6, 3’-5’ linked AMP subunits (cAn, n=3-6). cOA was found to activate CRISPR ancillary nucleases, which eliminated MGEs by cleaving nucleic acids non- specifically. CRISPR ancillary proteins are diverse, consisting of a cOA sensor domain fused to a toxin effector domain. This led to speculation that, if not controlled, collateral damage from the immune response could lead to cell dormancy or death, an unfavourable outcome for unicellular organisms.
The work described herein details the identification of a new class of enzyme, termed “ring nuclease”, which degrades cyclic tetra-adenylate (cA4) second messengers and regulates the type III CRISPR immune response. The publications presented characterise five distinct ring nuclease families. These include the CRISPR ring nuclease 1 (Crn1) limited to the archaea, cOA activated self-inactivating CRISPR ancillary ribonucleases and the highly unusual Csx3/Crn3 family, which collectively extend ring nuclease distribution. Also presented are the anti-CRISPR DUF1874 family variant ring nucleases, which viruses employ to subvert type III CRISPR immunity, and the homologous Crn2 family found in association with type III CRISPR-Cas systems in prokaryotic genomes. Biochemical and biophysical characterisation of these proteins reveal diverse mechanisms underlying regulation of type III CRISPR defence, and kinetic modelling demonstrate the key roles of ring nucleases in governing the outcome of infections.
These works provide fundamental insights into the regulation of a sophisticated, widespread and potent prokaryotic immune system, and select ring nucleases hold great promise for increasing the efficacy of bacteriophage therapies targeting pathogenic bacteria.
2021-06-30T00:00:00ZAthukoralage, Januka SahanCRISPR-Cas systems provide prokaryotes with adaptative immunity from invading Mobile Genetic Elements (MGEs). Type III CRISPR-Cas systems consist of a multiprotein effector complex and CRISPR ancillary proteins; both essential for MGE elimination. In 2017, two groups independently identified that type III CRISPR-Cas complexes synthesised cyclic oligoadenylate (cOA) second messengers in response to detection of foreign RNA. cOA was made using ATP (adenosine triphosphate) and consisted of 3-6, 3’-5’ linked AMP subunits (cAn, n=3-6). cOA was found to activate CRISPR ancillary nucleases, which eliminated MGEs by cleaving nucleic acids non- specifically. CRISPR ancillary proteins are diverse, consisting of a cOA sensor domain fused to a toxin effector domain. This led to speculation that, if not controlled, collateral damage from the immune response could lead to cell dormancy or death, an unfavourable outcome for unicellular organisms.
The work described herein details the identification of a new class of enzyme, termed “ring nuclease”, which degrades cyclic tetra-adenylate (cA4) second messengers and regulates the type III CRISPR immune response. The publications presented characterise five distinct ring nuclease families. These include the CRISPR ring nuclease 1 (Crn1) limited to the archaea, cOA activated self-inactivating CRISPR ancillary ribonucleases and the highly unusual Csx3/Crn3 family, which collectively extend ring nuclease distribution. Also presented are the anti-CRISPR DUF1874 family variant ring nucleases, which viruses employ to subvert type III CRISPR immunity, and the homologous Crn2 family found in association with type III CRISPR-Cas systems in prokaryotic genomes. Biochemical and biophysical characterisation of these proteins reveal diverse mechanisms underlying regulation of type III CRISPR defence, and kinetic modelling demonstrate the key roles of ring nucleases in governing the outcome of infections.
These works provide fundamental insights into the regulation of a sophisticated, widespread and potent prokaryotic immune system, and select ring nucleases hold great promise for increasing the efficacy of bacteriophage therapies targeting pathogenic bacteria.Investigating the gating mechanism of the large conductance mechanosensitive channel by SDSL and EPR spectroscopyKapsalis, Charalamposhttps://hdl.handle.net/10023/294232024-03-06T03:01:13Z2020-12-01T00:00:00ZMechanosensation is the ability of cells to sense and respond to mechanical stimuli deriving from their environment. Despite being a fundamental cellular response though, the molecular basis of mechanotransduction is still largely unknown. The mechanosensitive (MS) channel of large conductance, MscL, is expressed by all prokaryotes, it is the MS channel with the highest pressure activation threshold and acts as a last resort safety valve. It responds to the lateral tension of the membrane and, by opening its pore of ≈35Å, it rapidly allows solutes to exit the cell in order to rescue it from lysis during severe hypoosmotic shock. Despite its importance and abundance, the gating and activation mechanism of MscL has not been elucidated. Thus, in the main project presented, MscL’s gating mechanism is investigated as a means to gain insight on the mode of mechanosensation itself. Activation of the channel through site-directed spin labelling (SDSL) reveals that the nano-pockets, transmembrane hydrophobic crevices of the protein, are crucial for the activation of MscL. SDSL at the nano-pockets’ entrance hinders lipid acyl chains from penetrating them and this causes the channel to adopt a more expanded state, as demonstrated by EPR spectroscopy, which is more prone to opening, as revealed by single-molecule electrophysiology. Since MscL is only found in prokaryotes, manipulation of its gating mechanism could lead to the channel being used as a novel form of antibiotic target. Moreover, due to its large pore, it could also be utilized in nanotechnological applications for targeted drug delivery.
2020-12-01T00:00:00ZKapsalis, CharalamposMechanosensation is the ability of cells to sense and respond to mechanical stimuli deriving from their environment. Despite being a fundamental cellular response though, the molecular basis of mechanotransduction is still largely unknown. The mechanosensitive (MS) channel of large conductance, MscL, is expressed by all prokaryotes, it is the MS channel with the highest pressure activation threshold and acts as a last resort safety valve. It responds to the lateral tension of the membrane and, by opening its pore of ≈35Å, it rapidly allows solutes to exit the cell in order to rescue it from lysis during severe hypoosmotic shock. Despite its importance and abundance, the gating and activation mechanism of MscL has not been elucidated. Thus, in the main project presented, MscL’s gating mechanism is investigated as a means to gain insight on the mode of mechanosensation itself. Activation of the channel through site-directed spin labelling (SDSL) reveals that the nano-pockets, transmembrane hydrophobic crevices of the protein, are crucial for the activation of MscL. SDSL at the nano-pockets’ entrance hinders lipid acyl chains from penetrating them and this causes the channel to adopt a more expanded state, as demonstrated by EPR spectroscopy, which is more prone to opening, as revealed by single-molecule electrophysiology. Since MscL is only found in prokaryotes, manipulation of its gating mechanism could lead to the channel being used as a novel form of antibiotic target. Moreover, due to its large pore, it could also be utilized in nanotechnological applications for targeted drug delivery.Novel signalling pathways in type III CRISPR defence systemsChi, Haotianhttps://hdl.handle.net/10023/294052024-03-06T03:01:19Z2024-06-13T00:00:00ZCRISPR-Cas systems offer prokaryotes an adaptive defence mechanism, allowing them to respond to the invading nucleic acids. Type III CRISPR systems feature the capacity of synthesising cyclic oligoadenylate (cOA) species, which serve as second messengers to activate ancillary effectors, enhancing immune response. A diverse array of ancillary proteins is predicted to participate in cOA-mediated signalling for immunity enhancement. Nevertheless, the specific functions of many of these ancillary effectors have remained elusive. Here we have unravelled the workings of two novel type III-B CRISPR systems. The first
system, from the human gut bacteria Bacteroides fragilis (BfrCmr), associates with an uncharacterised CorA family membrane protein and a NrN family phosphodiesterase. BfrCmr provides defence against mobile genetic elements when expressed in the heterologous host E. coli. A remarkable discovery was the identification of a novel signal molecule, S-adenosyl methionine (SAM)-AMP by conjugating ATP to SAM through a phosphodiester bond, when the BfrCmr system was activated. SAM-AMP in turn binds to the membrane protein CorA, presumably leading to membrane disruption and ultimately cell death. The cognate phosphodiesterase NrN or SAM lyase from Clostridium botulinum degrades SAM-AMP, offering two different means of regulating the signalling pathway.
The second type III CRISPR system investigated is associated with three ancillary proteins, including a Lon protease CalpL, extracytoplasmic function sigma factor CalpS and a toxin MazF homologue CalpT. CalpL consist of a SAVED sensor domain fused with a Lon protease effector domain. CalpL forms a tripartite complex with CalpS and CalpT. When SAVED domain bound to activator cA4, CalpL oligomerises and specifically cleaves CalpT, resulting in the release of the sigma factor CalpS from the complex. This identification of a SAVED domain-containing protease that responses to cOA and triggers the transcriptional regulation provides insights into the sophisticated multi-layered defence mechanisms characterised in type III CRISPR signal-mediated immunity.
2024-06-13T00:00:00ZChi, HaotianCRISPR-Cas systems offer prokaryotes an adaptive defence mechanism, allowing them to respond to the invading nucleic acids. Type III CRISPR systems feature the capacity of synthesising cyclic oligoadenylate (cOA) species, which serve as second messengers to activate ancillary effectors, enhancing immune response. A diverse array of ancillary proteins is predicted to participate in cOA-mediated signalling for immunity enhancement. Nevertheless, the specific functions of many of these ancillary effectors have remained elusive. Here we have unravelled the workings of two novel type III-B CRISPR systems. The first
system, from the human gut bacteria Bacteroides fragilis (BfrCmr), associates with an uncharacterised CorA family membrane protein and a NrN family phosphodiesterase. BfrCmr provides defence against mobile genetic elements when expressed in the heterologous host E. coli. A remarkable discovery was the identification of a novel signal molecule, S-adenosyl methionine (SAM)-AMP by conjugating ATP to SAM through a phosphodiester bond, when the BfrCmr system was activated. SAM-AMP in turn binds to the membrane protein CorA, presumably leading to membrane disruption and ultimately cell death. The cognate phosphodiesterase NrN or SAM lyase from Clostridium botulinum degrades SAM-AMP, offering two different means of regulating the signalling pathway.
The second type III CRISPR system investigated is associated with three ancillary proteins, including a Lon protease CalpL, extracytoplasmic function sigma factor CalpS and a toxin MazF homologue CalpT. CalpL consist of a SAVED sensor domain fused with a Lon protease effector domain. CalpL forms a tripartite complex with CalpS and CalpT. When SAVED domain bound to activator cA4, CalpL oligomerises and specifically cleaves CalpT, resulting in the release of the sigma factor CalpS from the complex. This identification of a SAVED domain-containing protease that responses to cOA and triggers the transcriptional regulation provides insights into the sophisticated multi-layered defence mechanisms characterised in type III CRISPR signal-mediated immunity.The role of ecology in sexual selection in the HeteropteraGourevitch, Eleanorhttps://hdl.handle.net/10023/292382024-02-27T03:08:14Z2024-06-12T00:00:00ZIn this thesis I explore our current view of sexual selection, with a focus on the insect sub-order Heteroptera and the role of ecology. I first review sexual selection in the Heteroptera across two chapters, presenting the diverse range of sexually selected
phenotypes found in these bugs. In doing so, I highlight the limitations of a "model systems" approach to sexual selection. Next, I explore male mate choice in the seed bug Lygaeus simulans, a species with high rates of mating failure, suggestive of cryptic mate choice. It is unclear why males do not exhibit pre-copulatory choice and to investigate this I manipulated morphological cues of female fecundity (body width and genitalia extension). Mate choice trials revealed that these cues do not influence female mating success. I next assess the impact of environmental change on L. simulans life history, fecundity, and fertility in a multi-factorial experiment that manipulated temperature, the opportunity for sexual selection and reproductive interference. The results highlight transgenerational fitness effects plus interactions amongst environmental stressors, reinforcing the importance of ecological complexity. I then present a meta-analyses investigating the occurrence of endurance rivalry, an underdiscussed mechanism of sexual selection. I explore how this mechanism adds to the discussion surrounding the alignment of natural and sexual selection. My penultimate chapter explores the traditional assignment of sexually selected phenotypes to male and female sex-roles, the history of this categorisation, and the positives and negatives of this approach. Throughout my thesis, I find a tension between the general and specific approaches to sexual selection, and evolutionary biology more generally. This is the theme of my General Discussion in which I consider the incorporation of evolution into conservation biology and our progression towards a predictive evolutionary theory. Ecology is presented as a potential solution a way to embrace explanations of diversity.
2024-06-12T00:00:00ZGourevitch, EleanorIn this thesis I explore our current view of sexual selection, with a focus on the insect sub-order Heteroptera and the role of ecology. I first review sexual selection in the Heteroptera across two chapters, presenting the diverse range of sexually selected
phenotypes found in these bugs. In doing so, I highlight the limitations of a "model systems" approach to sexual selection. Next, I explore male mate choice in the seed bug Lygaeus simulans, a species with high rates of mating failure, suggestive of cryptic mate choice. It is unclear why males do not exhibit pre-copulatory choice and to investigate this I manipulated morphological cues of female fecundity (body width and genitalia extension). Mate choice trials revealed that these cues do not influence female mating success. I next assess the impact of environmental change on L. simulans life history, fecundity, and fertility in a multi-factorial experiment that manipulated temperature, the opportunity for sexual selection and reproductive interference. The results highlight transgenerational fitness effects plus interactions amongst environmental stressors, reinforcing the importance of ecological complexity. I then present a meta-analyses investigating the occurrence of endurance rivalry, an underdiscussed mechanism of sexual selection. I explore how this mechanism adds to the discussion surrounding the alignment of natural and sexual selection. My penultimate chapter explores the traditional assignment of sexually selected phenotypes to male and female sex-roles, the history of this categorisation, and the positives and negatives of this approach. Throughout my thesis, I find a tension between the general and specific approaches to sexual selection, and evolutionary biology more generally. This is the theme of my General Discussion in which I consider the incorporation of evolution into conservation biology and our progression towards a predictive evolutionary theory. Ecology is presented as a potential solution a way to embrace explanations of diversity.Phenotypic screening and functional characterisation of anti-protozoan unnatural productsMosedale, William Robert Toddunhttps://hdl.handle.net/10023/292162024-03-19T12:35:29Z2024-06-12T00:00:00ZTrypanosoma brucei is a vector borne protozoan parasite of the class kinetoplastida and is the causative agent of human African trypanosomiasis (HAT), a neglected tropical disease of sub-Saharan Africa that is fatal if untreated, and is also a causative agent of Nagana, a disease of animals and livestock with great economic importance. Having been at forefront of drug discovery during the pioneering days of modern medicine, the development of new therapeutics has since slowed, and the disease had seen little innovation in treatment since the mid-1900s until the recent introduction of eflornithine and most recently Fexinidazole in 2018. While
Fexinidazole has been demonstrated to be effective at treating most cases, the rarer but more aggressive form of the disease caused by T. brucei rhodesiense still requires treatment with the dangerous and dated drug, melarsoprol. This project aims to utilise the tried and tested method of phenotypic screening, in combination with activity directed synthesis to identify novel anti-
trypanosomal unnatural products of high therapeutic potential based upon selectivity and potency. This will be in addition to an exploration of a sulfonyl-fluoride based covalent warhead aryl compound library as both a potential therapeutic and a proof of concept for chemical proteomics as a tool for anti-parasitic drug discovery. Selected compounds were characterised using well
established techniques such as microscopy, live / dead assays, and growth curves, in addition to more in-depth analysis of the strongest candidate using quantitative proteomics of a compound resistant cell line. A variety of cellular assays were used to validate the finding of the proteomics and help elucidate the mode of action. Three highly active and selective sulfonyl-fluoride warheads are identified in which preliminary evidence suggests a mode of action associated with the dysregulation of the stable acetylated microtubule cytoskeleton for which the parasites rely on for morphology and replication, as well as an iridium based cationic compound, which disrupts the mitochondria and multiple other essential processes within the parasite including glycolysis and nucleotide metabolism.
2024-06-12T00:00:00ZMosedale, William Robert ToddunTrypanosoma brucei is a vector borne protozoan parasite of the class kinetoplastida and is the causative agent of human African trypanosomiasis (HAT), a neglected tropical disease of sub-Saharan Africa that is fatal if untreated, and is also a causative agent of Nagana, a disease of animals and livestock with great economic importance. Having been at forefront of drug discovery during the pioneering days of modern medicine, the development of new therapeutics has since slowed, and the disease had seen little innovation in treatment since the mid-1900s until the recent introduction of eflornithine and most recently Fexinidazole in 2018. While
Fexinidazole has been demonstrated to be effective at treating most cases, the rarer but more aggressive form of the disease caused by T. brucei rhodesiense still requires treatment with the dangerous and dated drug, melarsoprol. This project aims to utilise the tried and tested method of phenotypic screening, in combination with activity directed synthesis to identify novel anti-
trypanosomal unnatural products of high therapeutic potential based upon selectivity and potency. This will be in addition to an exploration of a sulfonyl-fluoride based covalent warhead aryl compound library as both a potential therapeutic and a proof of concept for chemical proteomics as a tool for anti-parasitic drug discovery. Selected compounds were characterised using well
established techniques such as microscopy, live / dead assays, and growth curves, in addition to more in-depth analysis of the strongest candidate using quantitative proteomics of a compound resistant cell line. A variety of cellular assays were used to validate the finding of the proteomics and help elucidate the mode of action. Three highly active and selective sulfonyl-fluoride warheads are identified in which preliminary evidence suggests a mode of action associated with the dysregulation of the stable acetylated microtubule cytoskeleton for which the parasites rely on for morphology and replication, as well as an iridium based cationic compound, which disrupts the mitochondria and multiple other essential processes within the parasite including glycolysis and nucleotide metabolism.Quantifying costs and rewards in optimal foraging models of the marine environment. Using bulk feeding mysticete whales as an exampleSwift, René Jameshttps://hdl.handle.net/10023/291972024-02-09T11:30:19Z2021-06-30T00:00:00ZAnimals feed to maintain body condition and maximise fitness. Feeding is a multi-stage behaviour that encapsulates aspects of an animals' sensory and foraging ecology, and that can be divided into the following broad functional categories; prey detection, capture, and handling (assimilation of acquired energy stores). The evolutionary consequences of foraging have the potential to shape predator-prey dynamics, influence community and ecosystem structure; and to drive the evolution of physiological and morphological adaptations that minimise energetic costs and maximise energy uptake. Excess energy can be converted to fat (lipids) and stored to enhance reproductive potential or to protect against temporary (voluntary) starvation associated often with long distance migration or changes in prey distribution. Understanding how an animal balances these conflicting forces, and makes key foraging decisions is an important aspect to understanding their ecology. Simple questions such as how, when, where, why and what an animal chooses to feed on are difficult to answer without the development and application of new technologies. The development of new tools and analytical approaches is particularly important in the marine environment where these key life history decisions occur offshore and or at depth. Bulk feeding rorqual whales are amongst the largest species to have lived on Earth, and are major consumers of schooling krill and forage fish. Because of their size and ability to consume significant quantities of fish and krill they have an important role in structuring ecological communities. Lunge feeding is an energetically costly bulk feeding behaviour that is practised by all members of this super-family. To understand how energy fluxes pass through the consumer to be expressed as body condition it is first necessary to have reliable proxies of the energetic costs and gains associated with feeding. In this thesis methods for estimating these energy fluxes were explored using data from summer feeding (Balaenoptera physalus) and humpback whales (Megaptera novaeangliae) in Canada, and winter feeding humpback whales in northern Norway. Calibrated speed measurements were used as a proxy for the energetic costs associated with bulk feeding (lunge) and transport in baleen whales (chapter 2). Speed measurements were used to develop a lunge detector (chapter 3). Lunge speed and other kinematic variables associated with bulk feeding were used to identify species-specific signatures in feeding behaviour as a potential method for identifying prey type, and thus their caloric value as a proxy for energy uptake (chapter 4)). The feasibility of using new sensors, (i) sonar to measure prey density and dynamics from the perspective of the feeding whale (chapter 5), and (ii) an ultrasound to measure blubber depth in wild marine mammals as a proxy of body condition (chapter 6) were tested.
2021-06-30T00:00:00ZSwift, René JamesAnimals feed to maintain body condition and maximise fitness. Feeding is a multi-stage behaviour that encapsulates aspects of an animals' sensory and foraging ecology, and that can be divided into the following broad functional categories; prey detection, capture, and handling (assimilation of acquired energy stores). The evolutionary consequences of foraging have the potential to shape predator-prey dynamics, influence community and ecosystem structure; and to drive the evolution of physiological and morphological adaptations that minimise energetic costs and maximise energy uptake. Excess energy can be converted to fat (lipids) and stored to enhance reproductive potential or to protect against temporary (voluntary) starvation associated often with long distance migration or changes in prey distribution. Understanding how an animal balances these conflicting forces, and makes key foraging decisions is an important aspect to understanding their ecology. Simple questions such as how, when, where, why and what an animal chooses to feed on are difficult to answer without the development and application of new technologies. The development of new tools and analytical approaches is particularly important in the marine environment where these key life history decisions occur offshore and or at depth. Bulk feeding rorqual whales are amongst the largest species to have lived on Earth, and are major consumers of schooling krill and forage fish. Because of their size and ability to consume significant quantities of fish and krill they have an important role in structuring ecological communities. Lunge feeding is an energetically costly bulk feeding behaviour that is practised by all members of this super-family. To understand how energy fluxes pass through the consumer to be expressed as body condition it is first necessary to have reliable proxies of the energetic costs and gains associated with feeding. In this thesis methods for estimating these energy fluxes were explored using data from summer feeding (Balaenoptera physalus) and humpback whales (Megaptera novaeangliae) in Canada, and winter feeding humpback whales in northern Norway. Calibrated speed measurements were used as a proxy for the energetic costs associated with bulk feeding (lunge) and transport in baleen whales (chapter 2). Speed measurements were used to develop a lunge detector (chapter 3). Lunge speed and other kinematic variables associated with bulk feeding were used to identify species-specific signatures in feeding behaviour as a potential method for identifying prey type, and thus their caloric value as a proxy for energy uptake (chapter 4)). The feasibility of using new sensors, (i) sonar to measure prey density and dynamics from the perspective of the feeding whale (chapter 5), and (ii) an ultrasound to measure blubber depth in wild marine mammals as a proxy of body condition (chapter 6) were tested.The social evolution of religion : modelling genetic and cultural evolutionStucky, Kerstin Ingehttps://hdl.handle.net/10023/291882024-02-08T03:05:15Z2024-06-12T00:00:00ZAbstract redacted
2024-06-12T00:00:00ZStucky, Kerstin IngeAbstract redactedInvestigating the role of the chromatin remodeller XNP-1 in C. elegansOlver, Janiehttps://hdl.handle.net/10023/290712024-01-26T03:02:44Z2024-06-12T00:00:00ZATRX is a member of the SWI/SNF family of chromatin remodellers. ATRX loss causes pleiotropic phenotypes, including the neurodevelopmental disorder ATR-X syndrome, de-repression of the alternative lengthening of telomere pathway, increased LTR retrotransposon expression and sensitivity to replication stress. How ATRX activity suppresses these phenotypes within a developmental context is unclear.
Here, we use the model organism Caenorhabditis elegans to investigate the role of XNP-1, the ATRX homologue in worms. Unlike in other organisms, previous studies have shown that XNP-1 is not embryonic lethal, and only has slightly reduced fertility compared to a wildtype strain at 20°C. Only when grown at 25°C does XNP-1 loss cause sterility. We used this fact to explore the role of XNP-1/ATRX and how it suppressed such diverse phenotypes within a developmental context, which would not have been possible in other experimental systems.
We found that XNP-1 represses LTR retrotransposon expression during germline development, in a mechanism independent of SET-25, a H3K9 trimethylase, but dependent on the replication-independent histone variant HIS-72. However, we discovered that LTR retrotransposon misexpression is unlikely to cause the developmental defects observed in xnp-1 mutants. We then took a more unbiased transcriptomic approach to investigate gene expression changes upon XNP-1 loss in embryos and the first larval stage. We found that XNP-1 represses the ectopic expression of germline genes, probably in a parallel pathway to the SynMuvB family of transcriptional regulators. Finally, we identified the causative mutation in a suppressor line previously isolated in a forward genetic screen. This enabled us to theorise on possible molecular roles XNP-1 may play at higher temperatures.
Overall, we propose a model where germline misexpression is sufficient to cause the reduced brood size observed upon XNP-1 loss at 20°C, and where this misexpression contributes to the sterility phenotype observed upon XNP-1 loss at 25°C.
2024-06-12T00:00:00ZOlver, JanieATRX is a member of the SWI/SNF family of chromatin remodellers. ATRX loss causes pleiotropic phenotypes, including the neurodevelopmental disorder ATR-X syndrome, de-repression of the alternative lengthening of telomere pathway, increased LTR retrotransposon expression and sensitivity to replication stress. How ATRX activity suppresses these phenotypes within a developmental context is unclear.
Here, we use the model organism Caenorhabditis elegans to investigate the role of XNP-1, the ATRX homologue in worms. Unlike in other organisms, previous studies have shown that XNP-1 is not embryonic lethal, and only has slightly reduced fertility compared to a wildtype strain at 20°C. Only when grown at 25°C does XNP-1 loss cause sterility. We used this fact to explore the role of XNP-1/ATRX and how it suppressed such diverse phenotypes within a developmental context, which would not have been possible in other experimental systems.
We found that XNP-1 represses LTR retrotransposon expression during germline development, in a mechanism independent of SET-25, a H3K9 trimethylase, but dependent on the replication-independent histone variant HIS-72. However, we discovered that LTR retrotransposon misexpression is unlikely to cause the developmental defects observed in xnp-1 mutants. We then took a more unbiased transcriptomic approach to investigate gene expression changes upon XNP-1 loss in embryos and the first larval stage. We found that XNP-1 represses the ectopic expression of germline genes, probably in a parallel pathway to the SynMuvB family of transcriptional regulators. Finally, we identified the causative mutation in a suppressor line previously isolated in a forward genetic screen. This enabled us to theorise on possible molecular roles XNP-1 may play at higher temperatures.
Overall, we propose a model where germline misexpression is sufficient to cause the reduced brood size observed upon XNP-1 loss at 20°C, and where this misexpression contributes to the sterility phenotype observed upon XNP-1 loss at 25°C.Unravelling the complex reproductive tactics of male humpback whales : an integrative analysis of paternity, age, testosterone, and genetic diversityEichenberger, Francahttps://hdl.handle.net/10023/290702024-02-15T03:07:58Z2024-06-12T00:00:00ZHow the underlying forces of sexual selection impact reproductive tactics including elaborate acoustic displays in cetaceans remains poorly understood. Here, I combined 26 years (1995-2020) of photo-identification, behavioural, (epi)genetic, and endocrine data from an endangered population of humpback whales (New Caledonia), to explore male reproductive success, age, physiology, and population dynamics over almost a third of the lifespan of a humpback whale. First, I conducted a paternity analysis on 177 known mother-offspring pairs and confirmed previous findings of low variation in reproductive success in male humpback whales. Second, epigenetic age estimates of 485 males revealed a left-skewed population age structure in the first half of the study period that became more balanced in the second half. Further, older males (> 23 years) more often engaged in certain reproductive tactics (singing and escorting) and were more successful in siring offspring once the population age structure stabilised, suggesting reproductive tactics and reproductive success in male humpback whales may be age-dependent. Third, using enzyme immunoassays on 457 blubber samples, I observed a seasonal decline in male testosterone in the population over the breeding season. Testosterone levels appeared highest during puberty, then decreased and levelled off at the onset of maturity, yet were highly variable at any point during the breeding season and across males of all ages. Lastly, I investigated the influence of genetic diversity at the major histocompatibility complex (MHC) class I and class IIa (DQB and DRB-a) on patterns of male reproductive success in humpback whales. Mating pairs shared fewer alleles than expected under random mating at MHC class I and IIa, thus, providing evidence of an MHC-mediated female mate choice in humpback whales. This thesis provides novel, critical insights into the evolutionary consequences of commercial whaling on the demography, patterns of reproduction and sexual selection of exploited populations of baleen whales.
2024-06-12T00:00:00ZEichenberger, FrancaHow the underlying forces of sexual selection impact reproductive tactics including elaborate acoustic displays in cetaceans remains poorly understood. Here, I combined 26 years (1995-2020) of photo-identification, behavioural, (epi)genetic, and endocrine data from an endangered population of humpback whales (New Caledonia), to explore male reproductive success, age, physiology, and population dynamics over almost a third of the lifespan of a humpback whale. First, I conducted a paternity analysis on 177 known mother-offspring pairs and confirmed previous findings of low variation in reproductive success in male humpback whales. Second, epigenetic age estimates of 485 males revealed a left-skewed population age structure in the first half of the study period that became more balanced in the second half. Further, older males (> 23 years) more often engaged in certain reproductive tactics (singing and escorting) and were more successful in siring offspring once the population age structure stabilised, suggesting reproductive tactics and reproductive success in male humpback whales may be age-dependent. Third, using enzyme immunoassays on 457 blubber samples, I observed a seasonal decline in male testosterone in the population over the breeding season. Testosterone levels appeared highest during puberty, then decreased and levelled off at the onset of maturity, yet were highly variable at any point during the breeding season and across males of all ages. Lastly, I investigated the influence of genetic diversity at the major histocompatibility complex (MHC) class I and class IIa (DQB and DRB-a) on patterns of male reproductive success in humpback whales. Mating pairs shared fewer alleles than expected under random mating at MHC class I and IIa, thus, providing evidence of an MHC-mediated female mate choice in humpback whales. This thesis provides novel, critical insights into the evolutionary consequences of commercial whaling on the demography, patterns of reproduction and sexual selection of exploited populations of baleen whales.The cultural evolution of humpback whale song in the North Atlantic and South Pacific Oceans : a study of cumulative culture, fine-scale evolution, and public engagementSinclair, Natalie Catherinehttps://hdl.handle.net/10023/290042024-02-03T03:07:26Z2024-06-12T00:00:00ZThis PhD thesis explores humpback whale song research, cumulative cultural evolution (CCE), aesthetics, and public engagement. It comprises five chapters, each offering a comprehensive analysis of these topics. Chapter 1 outlines humpback whale song research and its relevance to CCE and vocal learning debates. It emphasises the effective use of whale song in public engagement for science and conservation. Chapter 2 presents a conceptual analysis of the compatibility between CCE and aesthetics. Interdisciplinary discussions explore challenges in reconciling aesthetic culture with prevailing philosophical views. The chapter also highlights tensions between cultural evolution in aesthetic and technological domains, contributing to debates on reconstructive and preservative theories. Chapter 3 tracks the evolution of a specific humpback whale song unit type across different themes within a song type over a breeding season. Methodological efficiencies enable a larger dataset analysis, providing insights into vocal production learning hypotheses. Chapter 4 expands on Chapter 3 by examining the evolution of a song unit type over two seasons and in a different ocean basin. Matching song types across locations reveals the extraordinary scale of humpback song cultural evolution. Evidence supports the vocal production learning hypothesis and challenges the notion of an innate template. Chapter 5 diverges thematically and methodologically, focusing on two case studies in public engagement. An interactive science exhibition and a community science event demonstrate successful engagement and impact on low science capital public groups. This thesis contributes to understanding humpback whale song research, CCE, aesthetics, and public engagement. It offers interdisciplinary perspectives, empirical investigations, and valuable insights into cultural evolution complexities. The thesis emphasises the importance of engaging the public in science while showcasing the impact on both the public and the researcher.
2024-06-12T00:00:00ZSinclair, Natalie CatherineThis PhD thesis explores humpback whale song research, cumulative cultural evolution (CCE), aesthetics, and public engagement. It comprises five chapters, each offering a comprehensive analysis of these topics. Chapter 1 outlines humpback whale song research and its relevance to CCE and vocal learning debates. It emphasises the effective use of whale song in public engagement for science and conservation. Chapter 2 presents a conceptual analysis of the compatibility between CCE and aesthetics. Interdisciplinary discussions explore challenges in reconciling aesthetic culture with prevailing philosophical views. The chapter also highlights tensions between cultural evolution in aesthetic and technological domains, contributing to debates on reconstructive and preservative theories. Chapter 3 tracks the evolution of a specific humpback whale song unit type across different themes within a song type over a breeding season. Methodological efficiencies enable a larger dataset analysis, providing insights into vocal production learning hypotheses. Chapter 4 expands on Chapter 3 by examining the evolution of a song unit type over two seasons and in a different ocean basin. Matching song types across locations reveals the extraordinary scale of humpback song cultural evolution. Evidence supports the vocal production learning hypothesis and challenges the notion of an innate template. Chapter 5 diverges thematically and methodologically, focusing on two case studies in public engagement. An interactive science exhibition and a community science event demonstrate successful engagement and impact on low science capital public groups. This thesis contributes to understanding humpback whale song research, CCE, aesthetics, and public engagement. It offers interdisciplinary perspectives, empirical investigations, and valuable insights into cultural evolution complexities. The thesis emphasises the importance of engaging the public in science while showcasing the impact on both the public and the researcher.Refining acoustic estimation of fish biomass in the ocean and a lake using broadband sampling and target strength modellingYang, Yanghttps://hdl.handle.net/10023/290012024-01-17T10:29:10Z2024-06-12T00:00:00ZAcoustic technology has been widely accepted as one of the most efficient methods for underwater biological investigation. The paucity of information on the target strength of fish can curb the understanding of their species composition, biomass and distribution, during acoustic studies. In addition, the limitations, regarding the resolution, of traditional continuous wave (CW) echosounders also restricted the acoustic species classification. In this thesis, the more recent broadband (or frequency modulated, FM) echosounders, which offer better range resolution and signal-to-noise ratio (SNR) than traditional echosounders, were used in research in Lake Victoria, East Africa, and the ocean's mesopelagic zone (200-1000 m depth) in order to tackle several key challenges in these fields.
This PhD project uses a combination of broadband echosounding, theoretical modelling, and horizontal acoustic beaming techniques to address the key challenges surrounding fish biomass estimation in different environments. The main themes of the thesis are: 1) developing a Kirchhoff-ray mode (KRM) TS model for dagaa (Rastrineobola argentea), a key species in Lake Victoria, East Africa, to improve its lake-wide biomass estimates, 2) using a horizontal beaming method to investigate the fish distribution and biomass in shallow water (<10 m depth) of Lake Victoria, to aid the lake-wide fisheries management in Lake Victoria, and 3) improving knowledge of the biomass, species composition, and distribution pattern of fish in mesopelagic layers, and aiding in the development of a lowered echosounder suitable for investigating mesopelagic layers.
Key findings from the TS modelling (Chapter 2) indicate that the swimbladder (which comprises 2.6 to 8.2% of body volume) of dagaa accounts for 65% to 90% of the total backscattering intensity at 120 kHz. The KRM model-informed relationship will lead to a substantial reduction (by ca. 30%) in lake-wide estimated biomass. Shallow water (<10 m depth) surveys in Lake Victoria in the Tanzanian (Chapter 3 and Chapter 4) sector suggest that from 2019 to 2023 fish biomass in these shallow margins ranged from 0.15 to 0.36 million tonnes (MT), which equates to between 9.1% and 22.6% of the fish biomass in the Tanzanian open lake (based on the 2020 lake-wide acoustic survey, that observed fish biomass of 1.6 MT). Avoidance behaviour of fish was observed and can result in a 41.5% reduction in the fish density estimation. GAMM (generalized additive mixed effect model) showed the highest fish densities in the major rainy season (February to April). During the dry season (June to August), shallow-water fish density was lower and more variable between regions. Chapter 5 revealed that mesopelagic populations in Mediterranean waters were predominantly comprised of numerous small fish with low individual biomasses. This differs from the situation in Atlantic waters, which exhibit higher biomass but lower biodiversity. Further, estimated fish abundance from trawl nets, ship-borne echosounders, and DSV (Deep-water Sonar and Visual sampler) indicated that DSV reported higher fish density compared to ship-borne echosounders and trawl nets, by factors of up to 3.04 and 20.85, respectively. This suggests that DSV may be less prone to avoidance and sampling biases than ship-borne echosounders and trawl nets, thereby advocating for the use of DSV in surveying the mesopelagic zone.
The TS modelling and broadband acoustic sampling strategies derived in this PhD serve to advance the field of active acoustic observation and enhance our understanding of underwater biological resources. The consequent results will aid both fisheries and conservation management, which now requires more holistic investigation methods for monitoring and assessing the ecosystem.
2024-06-12T00:00:00ZYang, YangAcoustic technology has been widely accepted as one of the most efficient methods for underwater biological investigation. The paucity of information on the target strength of fish can curb the understanding of their species composition, biomass and distribution, during acoustic studies. In addition, the limitations, regarding the resolution, of traditional continuous wave (CW) echosounders also restricted the acoustic species classification. In this thesis, the more recent broadband (or frequency modulated, FM) echosounders, which offer better range resolution and signal-to-noise ratio (SNR) than traditional echosounders, were used in research in Lake Victoria, East Africa, and the ocean's mesopelagic zone (200-1000 m depth) in order to tackle several key challenges in these fields.
This PhD project uses a combination of broadband echosounding, theoretical modelling, and horizontal acoustic beaming techniques to address the key challenges surrounding fish biomass estimation in different environments. The main themes of the thesis are: 1) developing a Kirchhoff-ray mode (KRM) TS model for dagaa (Rastrineobola argentea), a key species in Lake Victoria, East Africa, to improve its lake-wide biomass estimates, 2) using a horizontal beaming method to investigate the fish distribution and biomass in shallow water (<10 m depth) of Lake Victoria, to aid the lake-wide fisheries management in Lake Victoria, and 3) improving knowledge of the biomass, species composition, and distribution pattern of fish in mesopelagic layers, and aiding in the development of a lowered echosounder suitable for investigating mesopelagic layers.
Key findings from the TS modelling (Chapter 2) indicate that the swimbladder (which comprises 2.6 to 8.2% of body volume) of dagaa accounts for 65% to 90% of the total backscattering intensity at 120 kHz. The KRM model-informed relationship will lead to a substantial reduction (by ca. 30%) in lake-wide estimated biomass. Shallow water (<10 m depth) surveys in Lake Victoria in the Tanzanian (Chapter 3 and Chapter 4) sector suggest that from 2019 to 2023 fish biomass in these shallow margins ranged from 0.15 to 0.36 million tonnes (MT), which equates to between 9.1% and 22.6% of the fish biomass in the Tanzanian open lake (based on the 2020 lake-wide acoustic survey, that observed fish biomass of 1.6 MT). Avoidance behaviour of fish was observed and can result in a 41.5% reduction in the fish density estimation. GAMM (generalized additive mixed effect model) showed the highest fish densities in the major rainy season (February to April). During the dry season (June to August), shallow-water fish density was lower and more variable between regions. Chapter 5 revealed that mesopelagic populations in Mediterranean waters were predominantly comprised of numerous small fish with low individual biomasses. This differs from the situation in Atlantic waters, which exhibit higher biomass but lower biodiversity. Further, estimated fish abundance from trawl nets, ship-borne echosounders, and DSV (Deep-water Sonar and Visual sampler) indicated that DSV reported higher fish density compared to ship-borne echosounders and trawl nets, by factors of up to 3.04 and 20.85, respectively. This suggests that DSV may be less prone to avoidance and sampling biases than ship-borne echosounders and trawl nets, thereby advocating for the use of DSV in surveying the mesopelagic zone.
The TS modelling and broadband acoustic sampling strategies derived in this PhD serve to advance the field of active acoustic observation and enhance our understanding of underwater biological resources. The consequent results will aid both fisheries and conservation management, which now requires more holistic investigation methods for monitoring and assessing the ecosystem.Mitochondrial function and dysfunction in astrocytes : the role of 17βHSD10 in Alzheimer's diseaseMetodieva, Vanya Vladimirovahttps://hdl.handle.net/10023/288522024-01-15T09:40:32Z2021-06-30T00:00:00ZIn an effort to find novel therapeutic targets and biomarkers for Alzheimer’s disease (AD), recent research discovered that astrocytic metabolism is disrupted very early on in the disease and may contribute to disease-specific regional vulnerability to neurodegeneration.
The current work provides evidence that in vitro mouse astrocytes isolated from the cortex, the hippocampus (both affected early in AD progression) and the cerebellum (affected in late stages) are characterised by distinct morphological and metabolic phenotypes. While cortical astrocytes exhibited overall higher metabolic activity, the hippocampal population had the highest glycolytic capacity of all three groups. These disparities were suggested to stem from different capacity for substrate import, utilisation, and metabolic reserve, which in turn determine astrocytic metabolic flexibility. These differences were associated with distinct capability for adaptation to metabolic stress with cerebellar astrocytes being more vulnerable to such conditions. Furthermore, ketone body supplementation was found to have more potent protective effects during nutrient deprivation in cerebellar as compared to other astrocytes. Interestingly, oxidative stress was more detrimental to cortical and hippocampal cells and this is associated with severe alterations in their mitochondrial number and morphology, suggesting that mitochondria may be more involved in astrocytic stress adaptation than previously reported.
The role of the mitochondrial 17β-hydroxysteroid dehydrogenase type 10 (17βHSD10) in astrocytic metabolism is the other main focus of this work. This mitochondrial enzyme is a hypothesised metabolic switch, which directly binds Aβ, exacerbating mitochondrial dysfunction in AD-affected cortical and hippocampal areas. The current work presents the first characterisation of 17βHSD10 function in astrocytes, showing that the protein is an important regulator of mitochondrial respiration and adaptation to metabolic and amyloidogenic stress. Importantly, stress-induced regulation of 17βHSD10 activity and expression showed a region-dependent phenotype, implying that the enzyme may be an important regulator in the reported metabolic heterogeneity of astrocytes. Finally, the impact of the protein on astrocytic function was largely determined by metabolic demand and substrate availability.
In summary, in vitro astrocytes isolated from different brain regions differ in their morphology, metabolic function, and resilience to AD-related stress conditions. 17βHSD10 was identified as an important regulator of their mitochondrial metabolism and regiondependent response to amyloid-induced and metabolic stress. These findings suggest that astrocytic 17βHSD10 could be a central component in the transition between early (amyloiddriven) and late (hypometabolism-driven) neurodegeneration in AD.
2021-06-30T00:00:00ZMetodieva, Vanya VladimirovaIn an effort to find novel therapeutic targets and biomarkers for Alzheimer’s disease (AD), recent research discovered that astrocytic metabolism is disrupted very early on in the disease and may contribute to disease-specific regional vulnerability to neurodegeneration.
The current work provides evidence that in vitro mouse astrocytes isolated from the cortex, the hippocampus (both affected early in AD progression) and the cerebellum (affected in late stages) are characterised by distinct morphological and metabolic phenotypes. While cortical astrocytes exhibited overall higher metabolic activity, the hippocampal population had the highest glycolytic capacity of all three groups. These disparities were suggested to stem from different capacity for substrate import, utilisation, and metabolic reserve, which in turn determine astrocytic metabolic flexibility. These differences were associated with distinct capability for adaptation to metabolic stress with cerebellar astrocytes being more vulnerable to such conditions. Furthermore, ketone body supplementation was found to have more potent protective effects during nutrient deprivation in cerebellar as compared to other astrocytes. Interestingly, oxidative stress was more detrimental to cortical and hippocampal cells and this is associated with severe alterations in their mitochondrial number and morphology, suggesting that mitochondria may be more involved in astrocytic stress adaptation than previously reported.
The role of the mitochondrial 17β-hydroxysteroid dehydrogenase type 10 (17βHSD10) in astrocytic metabolism is the other main focus of this work. This mitochondrial enzyme is a hypothesised metabolic switch, which directly binds Aβ, exacerbating mitochondrial dysfunction in AD-affected cortical and hippocampal areas. The current work presents the first characterisation of 17βHSD10 function in astrocytes, showing that the protein is an important regulator of mitochondrial respiration and adaptation to metabolic and amyloidogenic stress. Importantly, stress-induced regulation of 17βHSD10 activity and expression showed a region-dependent phenotype, implying that the enzyme may be an important regulator in the reported metabolic heterogeneity of astrocytes. Finally, the impact of the protein on astrocytic function was largely determined by metabolic demand and substrate availability.
In summary, in vitro astrocytes isolated from different brain regions differ in their morphology, metabolic function, and resilience to AD-related stress conditions. 17βHSD10 was identified as an important regulator of their mitochondrial metabolism and regiondependent response to amyloid-induced and metabolic stress. These findings suggest that astrocytic 17βHSD10 could be a central component in the transition between early (amyloiddriven) and late (hypometabolism-driven) neurodegeneration in AD.From the field to the laboratory, investigating the effects of Deformed wing virus on honey bee healthWoodford, Lukehttps://hdl.handle.net/10023/288082024-01-30T03:08:12Z2022-06-15T00:00:00ZVarroa destructor is an ectoparasitic mite associated with significant losses of honey bee colonies globally. The mite vectors a range of pathogenic viruses, most notably Deformed wing virus (DWV). DWV is transmitted orally between generations of bees and by this route rarely causes symptomatic infection, but the introduction of Varroa alters the transmission route of the virus and leads to highly elevated virus titres. Annual overwintering colony losses of ~25% are associated with high levels of Varroa-DWV infestation. Effective miticide treatments are available to control Varroa. However, the absence of coordinated treatment means environmental transmission of mites continues unchecked. One of the aims of this study was to determine whether rational, coordinated treatment is beneficial to colony health. Over a period of three years, all colonies managed on the island of Arran were treated in unison. Changes in the mite levels and DWV levels and diversity were measured as indicators of changing colony health. Across the three years of analysis, total mite numbers decreased by 58% and the number of managed colonies increased by 50%. In parallel to the Arran study, a colony management technique – a shook swarm – combined with appropriate miticide treatments was shown to be highly effective in reducing mite infestations and DWV titres. The impact of no mite management was investigated by placing healthy colonies in a high-mite apiary and measuring their rates of mite uptake. This study indicated that mites rapidly enter the colonies, altering the DWV dynamic and typically resulting in colony death. A mite-virus-bee in-silico model, simulating the dynamic changes in the virus population across multiple generations of pupae was designed and recombination between two DWV variants was investigated to examine recombination junctions. These studies shed light on how Varroa-control and colony management techniques impact DWV levels and diversity and honey bee colony health.
2022-06-15T00:00:00ZWoodford, LukeVarroa destructor is an ectoparasitic mite associated with significant losses of honey bee colonies globally. The mite vectors a range of pathogenic viruses, most notably Deformed wing virus (DWV). DWV is transmitted orally between generations of bees and by this route rarely causes symptomatic infection, but the introduction of Varroa alters the transmission route of the virus and leads to highly elevated virus titres. Annual overwintering colony losses of ~25% are associated with high levels of Varroa-DWV infestation. Effective miticide treatments are available to control Varroa. However, the absence of coordinated treatment means environmental transmission of mites continues unchecked. One of the aims of this study was to determine whether rational, coordinated treatment is beneficial to colony health. Over a period of three years, all colonies managed on the island of Arran were treated in unison. Changes in the mite levels and DWV levels and diversity were measured as indicators of changing colony health. Across the three years of analysis, total mite numbers decreased by 58% and the number of managed colonies increased by 50%. In parallel to the Arran study, a colony management technique – a shook swarm – combined with appropriate miticide treatments was shown to be highly effective in reducing mite infestations and DWV titres. The impact of no mite management was investigated by placing healthy colonies in a high-mite apiary and measuring their rates of mite uptake. This study indicated that mites rapidly enter the colonies, altering the DWV dynamic and typically resulting in colony death. A mite-virus-bee in-silico model, simulating the dynamic changes in the virus population across multiple generations of pupae was designed and recombination between two DWV variants was investigated to examine recombination junctions. These studies shed light on how Varroa-control and colony management techniques impact DWV levels and diversity and honey bee colony health.Social adaptation across the genome : trade-offs and conflicts in relation to sexHitchcock, Thomashttps://hdl.handle.net/10023/287442024-01-15T11:57:31Z2022-06-15T00:00:00ZNatural selection explains both how and why biological organisms appear well adapted to their environments. Some of the most successful tests of our understanding of adaptation have focused on two phenomena: trade-offs, when organisms have to simultaneously optimise multiple conflicting objectives; and conflicts, when organisms – or their constituent genes – have different inclusive fitness agendas. In this thesis, I explore both of these phenomena, with a particular focus on problems relating to sex. Part I focuses on trade-offs between female and male fitness. I consider how different genetical systems, sexual ecologies, and life-history details modulate the relative weights placed on female and male fitness, and thus generate biases concerning the fates of such sexually antagonistic alleles. Part II focuses on conflicts within the genome which may emerge when genes differ in how they flow between males and females. Combined with sex-specific aspects of demography and ecology, this may result in genes placing different values upon the fitness of their carrier and social partners. I explore a series of such models, considering how intragenomic conflicts may emerge over various intersexual and intrasexual social behaviours.
2022-06-15T00:00:00ZHitchcock, ThomasNatural selection explains both how and why biological organisms appear well adapted to their environments. Some of the most successful tests of our understanding of adaptation have focused on two phenomena: trade-offs, when organisms have to simultaneously optimise multiple conflicting objectives; and conflicts, when organisms – or their constituent genes – have different inclusive fitness agendas. In this thesis, I explore both of these phenomena, with a particular focus on problems relating to sex. Part I focuses on trade-offs between female and male fitness. I consider how different genetical systems, sexual ecologies, and life-history details modulate the relative weights placed on female and male fitness, and thus generate biases concerning the fates of such sexually antagonistic alleles. Part II focuses on conflicts within the genome which may emerge when genes differ in how they flow between males and females. Combined with sex-specific aspects of demography and ecology, this may result in genes placing different values upon the fitness of their carrier and social partners. I explore a series of such models, considering how intragenomic conflicts may emerge over various intersexual and intrasexual social behaviours.Neuronal functions of Willin/FRMD6 relevant to Alzheimer's diseaseChen, Dorishttps://hdl.handle.net/10023/286332023-11-07T03:07:32Z2023-11-28T00:00:00ZAbstract redacted
2023-11-28T00:00:00ZChen, DorisAbstract redactedA genome wide screening approach for investigating the interplay between host defence and parainfluenza virusesJones, Chloehttps://hdl.handle.net/10023/286302023-11-06T22:34:52Z2023-11-28T00:00:00ZViruses are obligate intracellular pathogens, so virus-host interactions are crucial to their infectivity. A successful infection is a trade-off between the virus’s utilisation of host dependency factors that permit virus replication, and its ability to overcome the host innate immune response. Broadening our understanding of what permits or restricts replication may provide us with novel targets for antiviral therapies.
Human parainfluenza virus type 3 (hPIV3) is a leading cause of pneumonia and hospitalisation of children under 5 years worldwide. Using a genome wide CRISPR knockout screen, targeting approximately 18,000 individual genes, we identified host factors that facilitate hPIV3 replication, including solute carrier family 35 member A1 (SLC35A1), a sialic acid transporter, alongside antiviral factors. Infection of independent gene knockout cell lines validated a role of three genes important for the antiviral response: Merlin (NF2), Hydroxysteroid 17-Beta Dehydrogenase 12 (HSD1712), and Zinc Finger CCCH-Type Containing, Antiviral 1 (also known as zinc finger antiviral protein, ZAP). Using flow cytometry and RT-qPCR, we showed that IFN-treated knockout cells were permissive to hPIV3 infection when compared to control cells. We also showed, by RT-qPCR, that all three hits regulated IFN induction. Importantly, NF2 also regulated IFN signalling; a novel phenotype not previously described. Using plaque assays, we demonstrated that all three hits restricted the replication of other paramyxo- and pneumoviruses, revealing their broad antiviral activity.
However, the IFN response is a vast response with significant redundancy and where several interferon stimulated genes (ISGs), that individually have low activity, culminate to restrict infection. Current screening methods rely on strong phenotypes, leading to low power in elucidating antiviral restriction factors. To overcome this, we carried out proof-of-principle studies, using an established ISG15-deficient cell line and model Paramyxovirus, PIV5, to enhance signal-to-noise and expand the quantitative working window required for the discovery of low acting ISGs. Building on this, future work will provide a broad overview of the host antiviral response that could inform the development of new therapeutics.
2023-11-28T00:00:00ZJones, ChloeViruses are obligate intracellular pathogens, so virus-host interactions are crucial to their infectivity. A successful infection is a trade-off between the virus’s utilisation of host dependency factors that permit virus replication, and its ability to overcome the host innate immune response. Broadening our understanding of what permits or restricts replication may provide us with novel targets for antiviral therapies.
Human parainfluenza virus type 3 (hPIV3) is a leading cause of pneumonia and hospitalisation of children under 5 years worldwide. Using a genome wide CRISPR knockout screen, targeting approximately 18,000 individual genes, we identified host factors that facilitate hPIV3 replication, including solute carrier family 35 member A1 (SLC35A1), a sialic acid transporter, alongside antiviral factors. Infection of independent gene knockout cell lines validated a role of three genes important for the antiviral response: Merlin (NF2), Hydroxysteroid 17-Beta Dehydrogenase 12 (HSD1712), and Zinc Finger CCCH-Type Containing, Antiviral 1 (also known as zinc finger antiviral protein, ZAP). Using flow cytometry and RT-qPCR, we showed that IFN-treated knockout cells were permissive to hPIV3 infection when compared to control cells. We also showed, by RT-qPCR, that all three hits regulated IFN induction. Importantly, NF2 also regulated IFN signalling; a novel phenotype not previously described. Using plaque assays, we demonstrated that all three hits restricted the replication of other paramyxo- and pneumoviruses, revealing their broad antiviral activity.
However, the IFN response is a vast response with significant redundancy and where several interferon stimulated genes (ISGs), that individually have low activity, culminate to restrict infection. Current screening methods rely on strong phenotypes, leading to low power in elucidating antiviral restriction factors. To overcome this, we carried out proof-of-principle studies, using an established ISG15-deficient cell line and model Paramyxovirus, PIV5, to enhance signal-to-noise and expand the quantitative working window required for the discovery of low acting ISGs. Building on this, future work will provide a broad overview of the host antiviral response that could inform the development of new therapeutics.The type I-G CRISPR system : mechanism, structure and applicationShangguan, Qilinhttps://hdl.handle.net/10023/286102023-11-04T03:03:01Z2023-11-28T00:00:00ZCRISPR is originally discovered as an adaptive immune system in prokaryotes. It has been widely repurposed for application in different microbiological fields attributed to its ability to target DNA or RNA in a sequence-specific manner. But there is always an uncharted area of CRISPR systems in nature, awaiting exploration.
The type I-G CRISPR system is one of the subtypes of type I CRISPR systems with a multi-subunit effector complex compared to type II CRISPR-Cas9, a single subunit effector. Characterised by the enigmatic cas proteins Csb2 and Cas8g, type I-G system is the least understood type I system and possesses a unique mechanism in CRISPR recognition and interference.
In this thesis, we expressed and reconstructed a type I-G system from Thioalkalivibrio sulfidiphilus. We present key insights into the biochemistry and mechanism of the system, and a first view of the structure of the effector complex of type I-G is provided. Heterologous expression of type I-G in Escherichia coli provides immunity against mobile genetic elements. Repurposing type I-G for genome editing in E. coli with atypical Cas3 generates desirable editing. These observations provide an overview of the type I-G system, potentiating fundamental studies and further applications.
2023-11-28T00:00:00ZShangguan, QilinCRISPR is originally discovered as an adaptive immune system in prokaryotes. It has been widely repurposed for application in different microbiological fields attributed to its ability to target DNA or RNA in a sequence-specific manner. But there is always an uncharted area of CRISPR systems in nature, awaiting exploration.
The type I-G CRISPR system is one of the subtypes of type I CRISPR systems with a multi-subunit effector complex compared to type II CRISPR-Cas9, a single subunit effector. Characterised by the enigmatic cas proteins Csb2 and Cas8g, type I-G system is the least understood type I system and possesses a unique mechanism in CRISPR recognition and interference.
In this thesis, we expressed and reconstructed a type I-G system from Thioalkalivibrio sulfidiphilus. We present key insights into the biochemistry and mechanism of the system, and a first view of the structure of the effector complex of type I-G is provided. Heterologous expression of type I-G in Escherichia coli provides immunity against mobile genetic elements. Repurposing type I-G for genome editing in E. coli with atypical Cas3 generates desirable editing. These observations provide an overview of the type I-G system, potentiating fundamental studies and further applications.Assessing the response of microphytobenthic biofilms to multiple stressorsRimmer, Jameshttps://hdl.handle.net/10023/285582023-10-28T02:03:36Z2023-11-28T00:00:00ZEcological systems are exposed to a range of drivers, often referred to as stressors if detrimental or resulting from anthropogenic activities, which affect their functioning. To understand how these systems respond to stressors requires testing their effects on scaled ecosystems or biological components therein, or making predictions based on a mechanistic understanding of their modes of action. However, few stressors occur in isolation, and many – perhaps most – ecological responses are affected by non-additive interactions; net effects which are greater, or less than, the sum of the individual effects of multiple stressors.
Cumulative stressor effects on estuarine, intertidal microphytobenthic (MPB) biofilms were examined, as knowledge concerning responses to such effects in soft-sediment habitats is presently limited. The MPB perform key roles in estuaries, such as primary production and biogenic sediment stabilisation. Unexpected, combined stressor effects may propagate to higher trophic levels, and inhibit ecosystem functions provided by the MPB. Mesocosm experiments examined the effects of the herbicide glyphosate and nanoparticles of titanium dioxide, revealing variable stressor responses which appeared to be affected by contextual influences, such as abiotic environmental factors and biofilm condition. A meta-analysis of the experimental data suggested that the nanoparticles mitigated some of the detrimental effects of the herbicide on the biofilms.
Experimental findings, with MPB-driver relationship data, were used to predict the probability of detecting stressor effects in natural systems, as well as to estimate statistical power and inform experimental design. Field experiments demonstrated that whilst exposure to glyphosate was likely to detrimentally affect MPB assemblages in accordance with findings from mesocosm experiments, there was little evidence to suggest that antagonistic interactions occurred in a natural system. The ramifications of these results for ecosystem management are considered, and gaps in our understanding of cumulative stressor effects in estuarine systems and more broadly are discussed.
2023-11-28T00:00:00ZRimmer, JamesEcological systems are exposed to a range of drivers, often referred to as stressors if detrimental or resulting from anthropogenic activities, which affect their functioning. To understand how these systems respond to stressors requires testing their effects on scaled ecosystems or biological components therein, or making predictions based on a mechanistic understanding of their modes of action. However, few stressors occur in isolation, and many – perhaps most – ecological responses are affected by non-additive interactions; net effects which are greater, or less than, the sum of the individual effects of multiple stressors.
Cumulative stressor effects on estuarine, intertidal microphytobenthic (MPB) biofilms were examined, as knowledge concerning responses to such effects in soft-sediment habitats is presently limited. The MPB perform key roles in estuaries, such as primary production and biogenic sediment stabilisation. Unexpected, combined stressor effects may propagate to higher trophic levels, and inhibit ecosystem functions provided by the MPB. Mesocosm experiments examined the effects of the herbicide glyphosate and nanoparticles of titanium dioxide, revealing variable stressor responses which appeared to be affected by contextual influences, such as abiotic environmental factors and biofilm condition. A meta-analysis of the experimental data suggested that the nanoparticles mitigated some of the detrimental effects of the herbicide on the biofilms.
Experimental findings, with MPB-driver relationship data, were used to predict the probability of detecting stressor effects in natural systems, as well as to estimate statistical power and inform experimental design. Field experiments demonstrated that whilst exposure to glyphosate was likely to detrimentally affect MPB assemblages in accordance with findings from mesocosm experiments, there was little evidence to suggest that antagonistic interactions occurred in a natural system. The ramifications of these results for ecosystem management are considered, and gaps in our understanding of cumulative stressor effects in estuarine systems and more broadly are discussed.Sounds beneath the surface : a multiple-approach study of bottlenose dolphin acoustic communicationCasoli, Marcohttps://hdl.handle.net/10023/284292023-09-21T10:43:26Z2023-11-28T00:00:00ZBottlenose dolphins (Tursiops truncatus) live in complex individualized societies that combine stable social units with fluid groups, and they largely rely on sound to interact with one another. This thesis applies a suite of approaches to study their acoustic communication. I studied the wild population of Sarasota, which offers long-term behavioural data and opportunities to deploy sound-and-movement recording tags. Bottlenose dolphins display a wide call repertoire, including graded sounds challenging to classify. I use dolphin social interactions to present a novel tag-based approach for studying communicative roles of call parameters changes. Applying continuously-sampled parameters, this approach examines how individuals change movements as a function of signal features. I focus then on signature whistles, sounds encoding identity information that in Sarasota are documented for most individuals. Signature whistles function as individually-distinctive contact calls, for instance between closely-bonded animals during separation, but their function between groups is poorly documented. Analysing Dtag data from instances of group encounters, I show that dolphins did not regularly produce signature whistles upon detecting another group, nor systematically before joining; instead, signatures appeared to be used strategically depending on the encountered individuals. Dolphins sometimes imitate the signature whistle of others, which is thought to function for addressing known individuals. Performing first-ever playbacks of natural signature whistle copies, I show that free-ranging subjects turned more frequently towards the playback upon hearing copies of their signature vs signature whistles of others, supporting the addressing function of copies. Signature whistle copies are often produced right after the subject’s signature, in so-called vocal matching interactions. Using playbacks with temporarily-captured subjects, I test whether signature whistle matching, or vocal matching per se, has an addressing signalling role. Subjects turned more times and produced their signature more frequently in response to signature whistle matching vs matching of other calls, supporting the former hypothesis.
2023-11-28T00:00:00ZCasoli, MarcoBottlenose dolphins (Tursiops truncatus) live in complex individualized societies that combine stable social units with fluid groups, and they largely rely on sound to interact with one another. This thesis applies a suite of approaches to study their acoustic communication. I studied the wild population of Sarasota, which offers long-term behavioural data and opportunities to deploy sound-and-movement recording tags. Bottlenose dolphins display a wide call repertoire, including graded sounds challenging to classify. I use dolphin social interactions to present a novel tag-based approach for studying communicative roles of call parameters changes. Applying continuously-sampled parameters, this approach examines how individuals change movements as a function of signal features. I focus then on signature whistles, sounds encoding identity information that in Sarasota are documented for most individuals. Signature whistles function as individually-distinctive contact calls, for instance between closely-bonded animals during separation, but their function between groups is poorly documented. Analysing Dtag data from instances of group encounters, I show that dolphins did not regularly produce signature whistles upon detecting another group, nor systematically before joining; instead, signatures appeared to be used strategically depending on the encountered individuals. Dolphins sometimes imitate the signature whistle of others, which is thought to function for addressing known individuals. Performing first-ever playbacks of natural signature whistle copies, I show that free-ranging subjects turned more frequently towards the playback upon hearing copies of their signature vs signature whistles of others, supporting the addressing function of copies. Signature whistle copies are often produced right after the subject’s signature, in so-called vocal matching interactions. Using playbacks with temporarily-captured subjects, I test whether signature whistle matching, or vocal matching per se, has an addressing signalling role. Subjects turned more times and produced their signature more frequently in response to signature whistle matching vs matching of other calls, supporting the former hypothesis.A half century of change in global marine fish biodiversityTrindade Santos, Isaachttps://hdl.handle.net/10023/283332024-03-03T17:08:58Z2022-06-15T00:00:00ZThe aim of this PhD thesis is to understand how marine fish biodiversity is changing in space and time, and how, over the last half century, global fisheries are exploiting species that play diverse roles in ecosystem functioning. The biological diversity, including its spatial and temporal biogeography, has been reshaped by human activities. New methodological advances, and large databases, have allowed the development of approaches that can provide novel insights into these challenges, but some knowledge shortfalls remain. The classical facet of biodiversity, known as taxonomic diversity, draws on information about species richness and abundance. However, the ecological roles played by all species within ecological communities can now also be quantified using data on functional traits; this is known as functional diversity. This thesis uncovered new insights into the biogeography of functional traits by showing that 11,961 bony fishes and 866 cartilaginous fishes have general trends across latitudinal gradients. It also documented greater concentrations of species, rare in multiple facets of biodiversity, towards higher latitudes and in coastal systems, and showed that those concentrations are higher than expected by chance. A further key finding in the thesis was that the species contributing most to biodiversity change have clear differences in functional trait characteristics compared with the remaining species within assemblages. As these results make clear, the species that contribute the most to biodiversity change are also targeted by marine
fisheries exploitation. Moreover, the functional diversity of exploited bony and cartilaginous species is changing in magnitude and direction. Taken together my work highlights the importance of considering multiple facets of biodiversity when examining biodiversity in exploited marine systems.
2022-06-15T00:00:00ZTrindade Santos, IsaacThe aim of this PhD thesis is to understand how marine fish biodiversity is changing in space and time, and how, over the last half century, global fisheries are exploiting species that play diverse roles in ecosystem functioning. The biological diversity, including its spatial and temporal biogeography, has been reshaped by human activities. New methodological advances, and large databases, have allowed the development of approaches that can provide novel insights into these challenges, but some knowledge shortfalls remain. The classical facet of biodiversity, known as taxonomic diversity, draws on information about species richness and abundance. However, the ecological roles played by all species within ecological communities can now also be quantified using data on functional traits; this is known as functional diversity. This thesis uncovered new insights into the biogeography of functional traits by showing that 11,961 bony fishes and 866 cartilaginous fishes have general trends across latitudinal gradients. It also documented greater concentrations of species, rare in multiple facets of biodiversity, towards higher latitudes and in coastal systems, and showed that those concentrations are higher than expected by chance. A further key finding in the thesis was that the species contributing most to biodiversity change have clear differences in functional trait characteristics compared with the remaining species within assemblages. As these results make clear, the species that contribute the most to biodiversity change are also targeted by marine
fisheries exploitation. Moreover, the functional diversity of exploited bony and cartilaginous species is changing in magnitude and direction. Taken together my work highlights the importance of considering multiple facets of biodiversity when examining biodiversity in exploited marine systems.Investigating the Kennedy pathway : phosphatidylcholine and phosphatidylethanolamine biosynthesis in Trypanosoma cruziBooth, Leigh-Annhttps://hdl.handle.net/10023/281622023-08-15T02:05:34Z2022-11-29T00:00:00ZThe Kennedy pathway is a ubiquitous pathway in eukaryotes that synthesises two major phospholipids, phosphatidylcholine (PC) and phosphatidylethanolamine (PE). Numerous studies have found that the enzymes of the Kennedy pathway are essential for the survival of many organisms, including important human parasites. In this study, we wanted to understand the importance of the Kennedy pathway in the protozoan parasite Trypanosoma crusi, which causes Chagas disease, a neglected tropical disease in humans. Understanding the biology of Trypanosoma cruzi will help to develop novel,tolerable drugs.
This study focused on the characterisation of three enzymes in the Kennedy pathway: choline kinase (CK), ethanolamine kinase (EK) and the ethanolamine phosphate-cytidyltransferase (ECT). Kinetic parameters and substrate range and preferences were determined through activity assays. To understand the enzyme in vivo, knockout and overexpression cell lines were generated. These cell lines were biochemically phenotyped by various means, including quantitative and qualitative lipidomics. Stable isotope labeling experiments were performed to elucidate effects on phospholipid biosynthesis.
This work has shown that the putative CK and EK in Trypanosoma cruzi are bifunctional and produce both choline phosphate and ethanolamine phosphate; these enzymes are now denoted as C/Ek and E/CK, respectively. Furthermore, C/EK and E/CK are promiscuous and can accept various "non-natural" substrate analogues. A double knockout of E/CK was not possible without an ectopic copy of E/CK, suggesting that it is essential. Biochemical phenotyping indicate that removal of one E/CK allele does not grossly affect PC or PE biosynthesis, suggesting the remaining allele and C/EK homologue might compensate. Radiolabelling experiments revealed a link between the Kennedy pathway and phosphatidylserine and ceramide biosynthesis, where reduced biosynthesis was observed in E/CK single knockout cells. Other work in this thesis revealed that ECT can accept both ethanolamine phosphate and 2-aminoethylphosphonate, suggesting that ECT may play important roles in both phosphonolipid and glycosylphosphatidylinositol biosynthesis in T. cruzi.
2022-11-29T00:00:00ZBooth, Leigh-AnnThe Kennedy pathway is a ubiquitous pathway in eukaryotes that synthesises two major phospholipids, phosphatidylcholine (PC) and phosphatidylethanolamine (PE). Numerous studies have found that the enzymes of the Kennedy pathway are essential for the survival of many organisms, including important human parasites. In this study, we wanted to understand the importance of the Kennedy pathway in the protozoan parasite Trypanosoma crusi, which causes Chagas disease, a neglected tropical disease in humans. Understanding the biology of Trypanosoma cruzi will help to develop novel,tolerable drugs.
This study focused on the characterisation of three enzymes in the Kennedy pathway: choline kinase (CK), ethanolamine kinase (EK) and the ethanolamine phosphate-cytidyltransferase (ECT). Kinetic parameters and substrate range and preferences were determined through activity assays. To understand the enzyme in vivo, knockout and overexpression cell lines were generated. These cell lines were biochemically phenotyped by various means, including quantitative and qualitative lipidomics. Stable isotope labeling experiments were performed to elucidate effects on phospholipid biosynthesis.
This work has shown that the putative CK and EK in Trypanosoma cruzi are bifunctional and produce both choline phosphate and ethanolamine phosphate; these enzymes are now denoted as C/Ek and E/CK, respectively. Furthermore, C/EK and E/CK are promiscuous and can accept various "non-natural" substrate analogues. A double knockout of E/CK was not possible without an ectopic copy of E/CK, suggesting that it is essential. Biochemical phenotyping indicate that removal of one E/CK allele does not grossly affect PC or PE biosynthesis, suggesting the remaining allele and C/EK homologue might compensate. Radiolabelling experiments revealed a link between the Kennedy pathway and phosphatidylserine and ceramide biosynthesis, where reduced biosynthesis was observed in E/CK single knockout cells. Other work in this thesis revealed that ECT can accept both ethanolamine phosphate and 2-aminoethylphosphonate, suggesting that ECT may play important roles in both phosphonolipid and glycosylphosphatidylinositol biosynthesis in T. cruzi.Factors affecting the distribution of cetaceans in European Atlantic watersLacey, Clairehttps://hdl.handle.net/10023/278452023-07-07T14:07:39Z2023-11-28T00:00:00ZThe waters of the European North Atlantic are subject to an increasing amount of anthropogenic pressure. Much of the environmental legislation designed to protect cetaceans requires detailed knowledge of the abundance and distribution of cetaceans within these waters. This data often comes from large-scale surveys. Data from two such series of surveys, spanning two time periods: the SCANS-II and CODA surveys in 2005/07 and the SCANS-III and ObSERVE surveys in 2016 were analysed using Generalised Additive Models to describe relationships between cetacean density and static and remotely accessed dynamic environmental features.
Predictive models using spatial covariates as well as environmental predictors were created for the entire survey area using the most recently available data. This was done to conduct a “baseline” snapshot, representing the best possible picture of cetacean distribution for the summer of 2016. Subsequent chapters focus on specific ecoregions. These regions of relatively homogeneous habitat were selected with the aim of finding the best environmental predictors of genuine ecological relationships.
In the North Sea ecoregion, models for harbour porpoise, minke whale, and white-beaked dolphin were also constructed using additional prey data available only for this region. This was found to be no better than modelling only environmental covariates. Depth was one of the most commonly retained covariates for all three species in this ecoregion.
White-sided, bottlenose, common and striped dolphins and fin whale were investigated in the Celtic Seas, and Bay of Biscay and Iberian Peninsula ecoregions. Despite these two ecoregions being quite different, in most cases, model fits did not improve by including ecoregion as a factor covariate, suggesting that relationships between species and their environment were similar across both regions.
2023-11-28T00:00:00ZLacey, ClaireThe waters of the European North Atlantic are subject to an increasing amount of anthropogenic pressure. Much of the environmental legislation designed to protect cetaceans requires detailed knowledge of the abundance and distribution of cetaceans within these waters. This data often comes from large-scale surveys. Data from two such series of surveys, spanning two time periods: the SCANS-II and CODA surveys in 2005/07 and the SCANS-III and ObSERVE surveys in 2016 were analysed using Generalised Additive Models to describe relationships between cetacean density and static and remotely accessed dynamic environmental features.
Predictive models using spatial covariates as well as environmental predictors were created for the entire survey area using the most recently available data. This was done to conduct a “baseline” snapshot, representing the best possible picture of cetacean distribution for the summer of 2016. Subsequent chapters focus on specific ecoregions. These regions of relatively homogeneous habitat were selected with the aim of finding the best environmental predictors of genuine ecological relationships.
In the North Sea ecoregion, models for harbour porpoise, minke whale, and white-beaked dolphin were also constructed using additional prey data available only for this region. This was found to be no better than modelling only environmental covariates. Depth was one of the most commonly retained covariates for all three species in this ecoregion.
White-sided, bottlenose, common and striped dolphins and fin whale were investigated in the Celtic Seas, and Bay of Biscay and Iberian Peninsula ecoregions. Despite these two ecoregions being quite different, in most cases, model fits did not improve by including ecoregion as a factor covariate, suggesting that relationships between species and their environment were similar across both regions.Modelling and inferring neutral and non-neutral forces shaping genomic site frequenciesMikula, Lynette Caitlinhttps://hdl.handle.net/10023/278412023-06-30T02:06:06Z2023-11-28T00:00:00ZSingle nucleotide polymorphisms in samples of DNA sequences from one or multiple populations can be summarised as site frequency spectra. Since polymorphic sites are known to be predominantly biallelic, models for the evolution of allele frequencies that assume low scaled mutation rates are justified. The biallelic boundary-mutation Moran model with reversible mutations (BMM) arises as an approximation to the classic Moran model under this consideration, and it underpins this PhD thesis.
In the introduction, the BMM is presented as a mathematically tractable model that is e cient in its use of site frequency data for inferring mutation and selection parameters.
Chapter 2 of this thesis extends the BMM to include balancing selection, in addition to biased mutations and a directional component (e.g., directional selection or biased gene conversion).
In Chapter 3, discrete and stochastic demographic changes are incorporated into the spectral representation of the neutral BMM. A Hidden Markov Model inspired approach is used to simulate sample spectra under di↵erent scenarios, and propose a new inference method.
A novel class of Hidden Markov Models with ordered hidden states and emission densities (oHMMed) is introduced in Chapter 4 alongside the source code of a corresponding R-package.
In Chapter 5, oHMMed is used to annotate the genome of orangutans according to average levels of GC content and recombination rates. Site frequency spectra of similar regions are subjected to Markov Chain Monte Carlo analyses based on the BMM, and to demographic inference per Chapter 3. They are further characterised by structural genomic features. Overall, this provides a quantification of how biased gene conversion and recombination shape the background variation in hominid site frequency data.
Utilised conjointly, the methods developed in this thesis could help inform an extended null model of evolution, and improve genome scans.
2023-11-28T00:00:00ZMikula, Lynette CaitlinSingle nucleotide polymorphisms in samples of DNA sequences from one or multiple populations can be summarised as site frequency spectra. Since polymorphic sites are known to be predominantly biallelic, models for the evolution of allele frequencies that assume low scaled mutation rates are justified. The biallelic boundary-mutation Moran model with reversible mutations (BMM) arises as an approximation to the classic Moran model under this consideration, and it underpins this PhD thesis.
In the introduction, the BMM is presented as a mathematically tractable model that is e cient in its use of site frequency data for inferring mutation and selection parameters.
Chapter 2 of this thesis extends the BMM to include balancing selection, in addition to biased mutations and a directional component (e.g., directional selection or biased gene conversion).
In Chapter 3, discrete and stochastic demographic changes are incorporated into the spectral representation of the neutral BMM. A Hidden Markov Model inspired approach is used to simulate sample spectra under di↵erent scenarios, and propose a new inference method.
A novel class of Hidden Markov Models with ordered hidden states and emission densities (oHMMed) is introduced in Chapter 4 alongside the source code of a corresponding R-package.
In Chapter 5, oHMMed is used to annotate the genome of orangutans according to average levels of GC content and recombination rates. Site frequency spectra of similar regions are subjected to Markov Chain Monte Carlo analyses based on the BMM, and to demographic inference per Chapter 3. They are further characterised by structural genomic features. Overall, this provides a quantification of how biased gene conversion and recombination shape the background variation in hominid site frequency data.
Utilised conjointly, the methods developed in this thesis could help inform an extended null model of evolution, and improve genome scans.Investigating the causes of mating failure in Lygaeus simulans seed bugsBalfour, Vickihttps://hdl.handle.net/10023/277552023-06-20T13:00:34Z2023-11-28T00:00:00ZWe should expect mating systems to evolve to maximise the relative fitness of individuals, i.e. through sexual selection acting on individuals to maximise the number of offspring they produce. However, some mating systems can appear to ‘go wrong’. This is when apparently non-adaptive behavioural phenotypes, which cause fitness losses during reproduction, arise, such as same-sex sexual behaviours, reproductive interference, and mating failure. In this thesis I focus on the phenomenon of mating failure – when copulations fail to result in the production of offspring. Recorded levels of mating failure across taxa are non-trivial, and I here investigate the causes of mating failure in Lygaeus simulans seed bugs, a species known to suffer from high levels of failure (40-60%). I first investigated the genetics behind a pale mutant colour morph, which was inherited in a Mendelian fashion, providing a visible genetic marker for the investigation of post-copulatory selection processes. I found that mating failure caused extreme bimodality in second-male paternity, which could lead to misinterpretations of sperm competition mechanisms. I also found a strong link between copulation duration and mating failure, with longer copulations less likely to fail. Additionally, mating failure decreased when pairs were allowed to copulate for longer, or multiple times, indicating it is not primarily due to infertility or mechanical failures. Instead, evidence points towards mating failure being caused by cryptic male choice (CMC). In terms of post-copulatory outcomes, larger females were consistently more likely to lay eggs, have offspring (and hence not experience mating failure) and have more offspring. Males preferred to copulate, and copulate for longer, with larger females, suggesting CMC. Unfortunately, I was unsuccessful at teasing apart male and female effects to definitively demonstrate that mating failure is caused by CMC, but I believe the methods used could be useful in investigating CMC in the future.
2023-11-28T00:00:00ZBalfour, VickiWe should expect mating systems to evolve to maximise the relative fitness of individuals, i.e. through sexual selection acting on individuals to maximise the number of offspring they produce. However, some mating systems can appear to ‘go wrong’. This is when apparently non-adaptive behavioural phenotypes, which cause fitness losses during reproduction, arise, such as same-sex sexual behaviours, reproductive interference, and mating failure. In this thesis I focus on the phenomenon of mating failure – when copulations fail to result in the production of offspring. Recorded levels of mating failure across taxa are non-trivial, and I here investigate the causes of mating failure in Lygaeus simulans seed bugs, a species known to suffer from high levels of failure (40-60%). I first investigated the genetics behind a pale mutant colour morph, which was inherited in a Mendelian fashion, providing a visible genetic marker for the investigation of post-copulatory selection processes. I found that mating failure caused extreme bimodality in second-male paternity, which could lead to misinterpretations of sperm competition mechanisms. I also found a strong link between copulation duration and mating failure, with longer copulations less likely to fail. Additionally, mating failure decreased when pairs were allowed to copulate for longer, or multiple times, indicating it is not primarily due to infertility or mechanical failures. Instead, evidence points towards mating failure being caused by cryptic male choice (CMC). In terms of post-copulatory outcomes, larger females were consistently more likely to lay eggs, have offspring (and hence not experience mating failure) and have more offspring. Males preferred to copulate, and copulate for longer, with larger females, suggesting CMC. Unfortunately, I was unsuccessful at teasing apart male and female effects to definitively demonstrate that mating failure is caused by CMC, but I believe the methods used could be useful in investigating CMC in the future.DNA in the deep : comparative molecular ecology for the conservation of beaked whalesOnoufriou, Aubrie Boothhttps://hdl.handle.net/10023/277212023-06-06T15:59:17Z2023-06-14T00:00:00ZBeaked whales (Ziphiidae) are an incredibly diverse and elusive family, and behavioural responses linked to certain anthropogenic sounds have resulted in mass stranding events. The substantial knowledge gaps regarding abundance and population structure for most ziphiids highlight that more information is required for their effective management and conservation. To this end, next-generation DNA sequencing was used to investigate beaked whale ecology and evolution, showcasing the utility of reduced representation sequencing in non-model organisms. Single nucleotide polymorphisms (SNPs) were derived using double-digest restriction site associated DNA sequencing (ddRAD) from a newly established international beaked whale tissue and DNA archive.
Globally, hierarchical genetic structure and diversity of cosmopolitan Cuvier’s and Blainville’s beaked whales (Ziphius cavirostris and Mesoplodon densirostris, “Cuvier’s” and “Blainville’s”) were investigated. Biogeographic barriers and differing life and evolutionary histories have contributed to the observed patterns, and the findings are evaluated in the context of management units for conservation. Regionally, population structure and demographic history were characterised for four North Atlantic beaked whales: Cuvier’s, Blainville’s, Sowerby’s beaked whales (M. bidens) and northern bottlenose whales (Hyperoodon ampullatus). Fluctuations in effective population size (Ne) were likely responses to climatic change. With these findings, potential responses of beaked whale populations to future climate change are discussed. Locally, genetic Essential Biodiversity Variables (EBVs) were calculated for paired ‘disturbed’ and ‘semi-pristine’ populations of Cuvier’s and Blainville’s in three well studied populations: the Bahamas, Canary Islands and Mediterranean Sea (Cuvier’s only). At least one ‘disturbed’ site was found in each region with reduced genetic variation and at risk of genetic erosion.
In summary, genetic population structure has been identified in many ziphiids. These populations have different levels of genetic diversity, different demographic responses to historic climatic change and it is likely that they have different abilities to adapt to future anthropogenic and climate impacts and should be managed on a population level.
2023-06-14T00:00:00ZOnoufriou, Aubrie BoothBeaked whales (Ziphiidae) are an incredibly diverse and elusive family, and behavioural responses linked to certain anthropogenic sounds have resulted in mass stranding events. The substantial knowledge gaps regarding abundance and population structure for most ziphiids highlight that more information is required for their effective management and conservation. To this end, next-generation DNA sequencing was used to investigate beaked whale ecology and evolution, showcasing the utility of reduced representation sequencing in non-model organisms. Single nucleotide polymorphisms (SNPs) were derived using double-digest restriction site associated DNA sequencing (ddRAD) from a newly established international beaked whale tissue and DNA archive.
Globally, hierarchical genetic structure and diversity of cosmopolitan Cuvier’s and Blainville’s beaked whales (Ziphius cavirostris and Mesoplodon densirostris, “Cuvier’s” and “Blainville’s”) were investigated. Biogeographic barriers and differing life and evolutionary histories have contributed to the observed patterns, and the findings are evaluated in the context of management units for conservation. Regionally, population structure and demographic history were characterised for four North Atlantic beaked whales: Cuvier’s, Blainville’s, Sowerby’s beaked whales (M. bidens) and northern bottlenose whales (Hyperoodon ampullatus). Fluctuations in effective population size (Ne) were likely responses to climatic change. With these findings, potential responses of beaked whale populations to future climate change are discussed. Locally, genetic Essential Biodiversity Variables (EBVs) were calculated for paired ‘disturbed’ and ‘semi-pristine’ populations of Cuvier’s and Blainville’s in three well studied populations: the Bahamas, Canary Islands and Mediterranean Sea (Cuvier’s only). At least one ‘disturbed’ site was found in each region with reduced genetic variation and at risk of genetic erosion.
In summary, genetic population structure has been identified in many ziphiids. These populations have different levels of genetic diversity, different demographic responses to historic climatic change and it is likely that they have different abilities to adapt to future anthropogenic and climate impacts and should be managed on a population level.Zika virus recombination - from cultured cells to whole mosquitoesDermendjieva, Michaelahttps://hdl.handle.net/10023/276002023-07-06T14:46:27Z2023-06-14T00:00:00ZAbstract redacted
2023-06-14T00:00:00ZDermendjieva, MichaelaAbstract redactedRole of human cytomegalovirus immediate-early 1 protein and STAT binding in myeloid cellsMcNeil, Markhttps://hdl.handle.net/10023/275922023-07-06T15:26:22Z2023-06-14T00:00:00ZAbstract redacted
2023-06-14T00:00:00ZMcNeil, MarkAbstract redactedExploring biosynthetic routes to novel histidine containing cyclodipeptidesSutherland, Emmajayhttps://hdl.handle.net/10023/275772023-05-12T02:02:07Z2023-06-14T00:00:00ZAbstract redacted
2023-06-14T00:00:00ZSutherland, EmmajayAbstract redactedBiodiversity change in Scottish marine fish assemblagesMoyes, Faye Helenhttps://hdl.handle.net/10023/275712023-05-12T02:08:24Z2023-06-14T00:00:00ZMarine fish are an irreplaceable natural resource but are currently under threat due to anthropogenic pressures. To date, most of the emphasis has been on single stocks or populations of economic importance. However, commercially valuable marine fish are embedded in assemblages of many species and there is only limited understanding of the extent to which the structure of whole communities has altered in recent years. Research suggests that recent years have seen rapid compositional and reorganisation of marine assemblages but how these taxonomic changes are related to functional diversity is less evident. Biodiversity is multifaceted but fisheries science has historically focused mainly on taxonomic diversity, for example, by taking species abundance combined with mortality rates to produce an estimate of stock size. This thesis fills a gap in marine fisheries research by using a range of different metrics to help understand diversity change in the whole assemblage from both a taxonomic and a functional perspective, and by identifying influential species in compositional change.
This thesis aims to quantify how two geographically close, but distinct ecosystems from around the Scottish coast (part of the Celtic-Biscay shelf region on the west and the North Sea region on the east), have changed over a thirty-year time frame by utilising two facets of biodiversity and analysing at a whole assemblage level. The consistent nature of the scientific trawl surveys that form the basis for this work give an ideal study system for the analysis undertaken. Moreover, the statistical bounding areas provided by the ICES rectangles allow sample-based rarefaction and enable fair comparisons between systems and latitudes. My main hypothesis is that despite the distinctions between coastal systems, their geographic proximity and similarity of species will lead to no clear difference in diversity change. This thesis will examine this biodiversity change in four main ways: spatio-temporal change in taxonomic diversity; spatio-temporal change in functional diversity; spatio-temporal change in rarity; and identification of influential species within the systems.
My results clearly indicate that it is possible to reject the null hypothesis of no difference between systems. I find contrasting patterns between the coastal systems when examining trends in both taxonomic and functional diversity, in addition to key differences between those species most influential in contributing to compositional change and the types of contributions they make. I also examine trends in rarity to ask how the different dimensions covary over time and find that the direction of temporal shifts in taxonomic rarity is consistent with a null model of change in assemblage size. However, the observed data depart from the null expectation of a decrease in functional rarity suggesting that the functional integrity of the systems is maintained, even when assemblage size increases. Gaining an understanding of the reorganisation of assemblages based on the shared dynamics of the species within them can aid with the monitoring and restoring of biodiversity.
These results underline the importance of measuring both taxonomic and functional dimensions of diversity when assessing and interpreting biodiversity change. A multidimensional, integrated approach to biodiversity assessments, as undertaken here, has an important role to play in the ecosystem-based management of fisheries. This thesis fills a gap in the current knowledge regarding biodiversity monitoring of fisheries data and as such is of potential importance to policy makers and managers.
2023-06-14T00:00:00ZMoyes, Faye HelenMarine fish are an irreplaceable natural resource but are currently under threat due to anthropogenic pressures. To date, most of the emphasis has been on single stocks or populations of economic importance. However, commercially valuable marine fish are embedded in assemblages of many species and there is only limited understanding of the extent to which the structure of whole communities has altered in recent years. Research suggests that recent years have seen rapid compositional and reorganisation of marine assemblages but how these taxonomic changes are related to functional diversity is less evident. Biodiversity is multifaceted but fisheries science has historically focused mainly on taxonomic diversity, for example, by taking species abundance combined with mortality rates to produce an estimate of stock size. This thesis fills a gap in marine fisheries research by using a range of different metrics to help understand diversity change in the whole assemblage from both a taxonomic and a functional perspective, and by identifying influential species in compositional change.
This thesis aims to quantify how two geographically close, but distinct ecosystems from around the Scottish coast (part of the Celtic-Biscay shelf region on the west and the North Sea region on the east), have changed over a thirty-year time frame by utilising two facets of biodiversity and analysing at a whole assemblage level. The consistent nature of the scientific trawl surveys that form the basis for this work give an ideal study system for the analysis undertaken. Moreover, the statistical bounding areas provided by the ICES rectangles allow sample-based rarefaction and enable fair comparisons between systems and latitudes. My main hypothesis is that despite the distinctions between coastal systems, their geographic proximity and similarity of species will lead to no clear difference in diversity change. This thesis will examine this biodiversity change in four main ways: spatio-temporal change in taxonomic diversity; spatio-temporal change in functional diversity; spatio-temporal change in rarity; and identification of influential species within the systems.
My results clearly indicate that it is possible to reject the null hypothesis of no difference between systems. I find contrasting patterns between the coastal systems when examining trends in both taxonomic and functional diversity, in addition to key differences between those species most influential in contributing to compositional change and the types of contributions they make. I also examine trends in rarity to ask how the different dimensions covary over time and find that the direction of temporal shifts in taxonomic rarity is consistent with a null model of change in assemblage size. However, the observed data depart from the null expectation of a decrease in functional rarity suggesting that the functional integrity of the systems is maintained, even when assemblage size increases. Gaining an understanding of the reorganisation of assemblages based on the shared dynamics of the species within them can aid with the monitoring and restoring of biodiversity.
These results underline the importance of measuring both taxonomic and functional dimensions of diversity when assessing and interpreting biodiversity change. A multidimensional, integrated approach to biodiversity assessments, as undertaken here, has an important role to play in the ecosystem-based management of fisheries. This thesis fills a gap in the current knowledge regarding biodiversity monitoring of fisheries data and as such is of potential importance to policy makers and managers.Shedding light on DNA-protein interactions involved in the nucleotide excision repair pathwayFritzen, Remihttps://hdl.handle.net/10023/274152023-11-18T03:10:36Z2021-11-30T00:00:00ZDNA, or deoxyribonucleic acid, contains the molecular blueprint of organisms. Although, very stable, DNA can be damaged by genotoxic agents such as UV-light, reactive oxygen species or chemotherapeutic drugs, amongs others. Organisms have evolved several biological pathways to repair different types of damage and nucleotide excision repair (NER) is one of them. NER repairs mainly lesions inducing structural distortion of the double helix. Briefly, the lesion is detected, unwinding takes place to create a 30 nucleotides long bubble, the damage-containing single strand is then excised; using the opposite strand as a template, the DNA is resynthesized and ligated. Nucleotide Excision Repair is a non-mutagenic repair system. Single-strand DNA binding proteins (SSB) are involved in NER and many other pathways. Their role is to coat and protect the ssDNA from degradation and re-hybridisation. Here, we studied SSBs from Saccharolobus solfataricus and Sulfolobus acidocaldarius as well as a chimeric protein containing DNA binding domains from both organisms. We showed that the chimeric protein had better resistance to extreme conditions of temperature, ionic strength or acidic pH. We also proved that our chimeric SSB can be used as a tool to image single strand DNA or RNA using super resolution microscopy. The first step of NER is damage recognition by XPC. We studied XPC binding to a DNA substrate and showed the possibility of two XPC binding to a damage whilst demonstrating that the presence of a nick on the DNA backbone does not constitute a substrate for XPC. Furthermore, we used single molecule FRET technique to show that XPC could bind a three nucleotides bubble in two different modes, showing a strong preference for one of these binding modes. The second step is the unwinding by the XPD helicase, we studied the impact of the purine/pyrimidine composition on the unwinding activity and investigated a possible damage sensor role of XPD, using Archaean models. To complete our work, we demonstrated a cooperative effect on the distortion of the repair bubble of XPA and RPA.
2021-11-30T00:00:00ZFritzen, RemiDNA, or deoxyribonucleic acid, contains the molecular blueprint of organisms. Although, very stable, DNA can be damaged by genotoxic agents such as UV-light, reactive oxygen species or chemotherapeutic drugs, amongs others. Organisms have evolved several biological pathways to repair different types of damage and nucleotide excision repair (NER) is one of them. NER repairs mainly lesions inducing structural distortion of the double helix. Briefly, the lesion is detected, unwinding takes place to create a 30 nucleotides long bubble, the damage-containing single strand is then excised; using the opposite strand as a template, the DNA is resynthesized and ligated. Nucleotide Excision Repair is a non-mutagenic repair system. Single-strand DNA binding proteins (SSB) are involved in NER and many other pathways. Their role is to coat and protect the ssDNA from degradation and re-hybridisation. Here, we studied SSBs from Saccharolobus solfataricus and Sulfolobus acidocaldarius as well as a chimeric protein containing DNA binding domains from both organisms. We showed that the chimeric protein had better resistance to extreme conditions of temperature, ionic strength or acidic pH. We also proved that our chimeric SSB can be used as a tool to image single strand DNA or RNA using super resolution microscopy. The first step of NER is damage recognition by XPC. We studied XPC binding to a DNA substrate and showed the possibility of two XPC binding to a damage whilst demonstrating that the presence of a nick on the DNA backbone does not constitute a substrate for XPC. Furthermore, we used single molecule FRET technique to show that XPC could bind a three nucleotides bubble in two different modes, showing a strong preference for one of these binding modes. The second step is the unwinding by the XPD helicase, we studied the impact of the purine/pyrimidine composition on the unwinding activity and investigated a possible damage sensor role of XPD, using Archaean models. To complete our work, we demonstrated a cooperative effect on the distortion of the repair bubble of XPA and RPA.The non-breeding ecology of Common Whitethroats Curruca communis in central NigeriaTapia Harris, Claudiahttps://hdl.handle.net/10023/274002023-11-03T03:03:18Z2022-06-15T00:00:00ZIdentifying what drives or prevents long-distance migrants from responding to environmental changes requires a complete understanding of the ecology and behaviour of individuals throughout their annual cycle. The non-breeding period represents a significant part of an Afro-Palearctic migratory bird’s life; what occurs during this period influences an individual’s survival and future reproductive success. I studied factors that influence the population dynamics of Common Whitethroats Curruca communis during three non-breeding periods in Nigeria (2017–2020). First, I collected and analysed data from six geolocators deployed in 2019 to understand how non-breeding and breeding sites are connected. Second, I used data collected from >300 colour-ringed individuals and daily resightings to understand site persistence, within- and between-years site fidelity, fine-scale spatial movements, and habitat preference and availability. Lastly, I used daily resighting and long-term ringing data to calculate annual and overwinter survival rates. Results indicate that Whitethroats bred across eastern Europe, suggesting a somewhat high migratory spread defined by a north-eastern flight pattern, and a predominantly intermittent migratory strategy. All birds undertook a loop migration and stopped at a first non-breeding site in the Sahel. At core wintering grounds Whitethroats showed a great degree of individual variation regarding temporal and spatial behaviour: individuals exhibited different residency periods (from 1–165 days), a high degree of within- and between-years site fidelity, and many individuals established small home ranges with little significant variation through time, age, sex, and residency, despite habitat changing through the winter. Shrubs were identified as the preferred main vegetation type. High overwinter survival rates and a potential generalist strategy during the wintering period all strongly indicate that this period is likely a low-mortality period for Whitethroats. This study highlights the importance of conserving suitable habitats for Whitethroats over a very large area in both the breeding and non-breeding grounds, particularly the Sahel region, an important refuelling and stationary site.
2022-06-15T00:00:00ZTapia Harris, ClaudiaIdentifying what drives or prevents long-distance migrants from responding to environmental changes requires a complete understanding of the ecology and behaviour of individuals throughout their annual cycle. The non-breeding period represents a significant part of an Afro-Palearctic migratory bird’s life; what occurs during this period influences an individual’s survival and future reproductive success. I studied factors that influence the population dynamics of Common Whitethroats Curruca communis during three non-breeding periods in Nigeria (2017–2020). First, I collected and analysed data from six geolocators deployed in 2019 to understand how non-breeding and breeding sites are connected. Second, I used data collected from >300 colour-ringed individuals and daily resightings to understand site persistence, within- and between-years site fidelity, fine-scale spatial movements, and habitat preference and availability. Lastly, I used daily resighting and long-term ringing data to calculate annual and overwinter survival rates. Results indicate that Whitethroats bred across eastern Europe, suggesting a somewhat high migratory spread defined by a north-eastern flight pattern, and a predominantly intermittent migratory strategy. All birds undertook a loop migration and stopped at a first non-breeding site in the Sahel. At core wintering grounds Whitethroats showed a great degree of individual variation regarding temporal and spatial behaviour: individuals exhibited different residency periods (from 1–165 days), a high degree of within- and between-years site fidelity, and many individuals established small home ranges with little significant variation through time, age, sex, and residency, despite habitat changing through the winter. Shrubs were identified as the preferred main vegetation type. High overwinter survival rates and a potential generalist strategy during the wintering period all strongly indicate that this period is likely a low-mortality period for Whitethroats. This study highlights the importance of conserving suitable habitats for Whitethroats over a very large area in both the breeding and non-breeding grounds, particularly the Sahel region, an important refuelling and stationary site.Short-term adaptation in the lab : an analysis of evolutionary trajectories using time-series dataBarata, Carolina de Castro Barbosa Rodrigueshttps://hdl.handle.net/10023/273612024-01-16T03:03:22Z2022-06-15T00:00:00ZExperimental evolution has led to remarkable discoveries on the evolution of adaptive phenotypes. However, an understanding of the genetic basis of adaptation is only just starting to emerge, especially in eukaryotes. My thesis aims to take full advantage of genomic time-series data by examining Evolve & Resequence (E&R) experiments. This approach typically monitors the genomes of lab populations over the course of several generations. Firstly, I introduce Bait-ER: a fully Bayesian approach to investigate allele frequency trajectories while testing for selection. It implements a Moran model to estimate selection paramaters at each biallelic site. Bait-ER models varying coverage explicitly to account for sampling error. My method is robust even when studying small populations, and it proved accurate in both real and simulated genomic datasets. Secondly, I investigate the response to sexual selection in lab populations of Drosophila pseudoobscura using an E&R approach. These flies were subject to an altered mating regime where the intensity of sexual selection was either relaxed in monogamous populations - M - or intensified in polyandrous populations - E. I resequenced the genomes of each population at five separate time points. I estimated diversity and the effective population size (Nₑ) across the genome, and found that overall estimates of Nₑ match neutral expectations. However, Nₑ was lower at the start of the experiment, especially on the X chromosome in E populations. This indicates that sexual selection is strongest at the start in E lines, and that the X is responsible for early adaptation. Lastly, I performed a genome scan using Bait-ER to detect any potential targets of selection on the full genomic time-series. E lines show a stronger signal of selection where the X dominates, but the third chromosome also seems to be a hotspot. In summary, I found clear signals of adaptation in the genome of lab populations at several levels. This is in spite of strong genetic drift acting to slow down the adaptive process.
2022-06-15T00:00:00ZBarata, Carolina de Castro Barbosa RodriguesExperimental evolution has led to remarkable discoveries on the evolution of adaptive phenotypes. However, an understanding of the genetic basis of adaptation is only just starting to emerge, especially in eukaryotes. My thesis aims to take full advantage of genomic time-series data by examining Evolve & Resequence (E&R) experiments. This approach typically monitors the genomes of lab populations over the course of several generations. Firstly, I introduce Bait-ER: a fully Bayesian approach to investigate allele frequency trajectories while testing for selection. It implements a Moran model to estimate selection paramaters at each biallelic site. Bait-ER models varying coverage explicitly to account for sampling error. My method is robust even when studying small populations, and it proved accurate in both real and simulated genomic datasets. Secondly, I investigate the response to sexual selection in lab populations of Drosophila pseudoobscura using an E&R approach. These flies were subject to an altered mating regime where the intensity of sexual selection was either relaxed in monogamous populations - M - or intensified in polyandrous populations - E. I resequenced the genomes of each population at five separate time points. I estimated diversity and the effective population size (Nₑ) across the genome, and found that overall estimates of Nₑ match neutral expectations. However, Nₑ was lower at the start of the experiment, especially on the X chromosome in E populations. This indicates that sexual selection is strongest at the start in E lines, and that the X is responsible for early adaptation. Lastly, I performed a genome scan using Bait-ER to detect any potential targets of selection on the full genomic time-series. E lines show a stronger signal of selection where the X dominates, but the third chromosome also seems to be a hotspot. In summary, I found clear signals of adaptation in the genome of lab populations at several levels. This is in spite of strong genetic drift acting to slow down the adaptive process.Exploring patterns of coral ecological niche construction in coral reef ecosystemsBrambilla, Vivianahttps://hdl.handle.net/10023/273552024-03-12T11:22:05Z2021-11-30T00:00:00ZEcological niche construction is the process through which (i) organisms modify
environmental states and (ii) their modifications favour the organisms’ fitness in return.
Ecosystem engineers are an obvious class of putative niche constructors since they produce
environmental change modulating resource flow within their ecosystems. Corals, a well-established
group
of
autogenic
ecosystem
engineers,
are
a
prime
example
of
this
class
since
through
their
own
skeletal
structures,
they
create
the
reef
habitats
they
inhabit.
This
thesis
aims
at
investigating
coral
ecological
niche
construction
patterns
in
coral
reef
ecosystems.
To understand how corals modify the reef environment (i), I show that reef quantitative
surface descriptors that measure coral reef engineering affect patterns of light availability
among reef habitats (chapter 2). Furthermore, I performed a coral reciprocal transplant
experiment to assess to what extent coral could provide diverse habitats through plasticity. I
detected that high plasticity in niche-constructing traits results in a higher ability to provide
diverse habitats, under different environmental conditions (chapter 3).
To understand if coral engineering activity was favourable to their own fitness (ii), I
have studied patterns of coral recruitment across differently engineered habitats. I showed
an increase in settler presence on artificial tiles deployed in the field along a gradient of coralbuilt
structural complexity, measured as surface rugosity (chapter 4). I also showed an
increase of juvenile abundance across reefs characterized by small-scale high fractal
dimension and large-scale high surface rugosity, both being measures of coral engineering
activity (chapter 5).
With this thesis I aimed at clarifying the role of corals as ecological niche constructors,
enabling a future description of coral niche construction as evolutionary agent.
2021-11-30T00:00:00ZBrambilla, VivianaEcological niche construction is the process through which (i) organisms modify
environmental states and (ii) their modifications favour the organisms’ fitness in return.
Ecosystem engineers are an obvious class of putative niche constructors since they produce
environmental change modulating resource flow within their ecosystems. Corals, a well-established
group
of
autogenic
ecosystem
engineers,
are
a
prime
example
of
this
class
since
through
their
own
skeletal
structures,
they
create
the
reef
habitats
they
inhabit.
This
thesis
aims
at
investigating
coral
ecological
niche
construction
patterns
in
coral
reef
ecosystems.
To understand how corals modify the reef environment (i), I show that reef quantitative
surface descriptors that measure coral reef engineering affect patterns of light availability
among reef habitats (chapter 2). Furthermore, I performed a coral reciprocal transplant
experiment to assess to what extent coral could provide diverse habitats through plasticity. I
detected that high plasticity in niche-constructing traits results in a higher ability to provide
diverse habitats, under different environmental conditions (chapter 3).
To understand if coral engineering activity was favourable to their own fitness (ii), I
have studied patterns of coral recruitment across differently engineered habitats. I showed
an increase in settler presence on artificial tiles deployed in the field along a gradient of coralbuilt
structural complexity, measured as surface rugosity (chapter 4). I also showed an
increase of juvenile abundance across reefs characterized by small-scale high fractal
dimension and large-scale high surface rugosity, both being measures of coral engineering
activity (chapter 5).
With this thesis I aimed at clarifying the role of corals as ecological niche constructors,
enabling a future description of coral niche construction as evolutionary agent.Population ecology, behaviour and conservation status of common bottlenose dolphins (Tursiops truncatus) in the Gulf of Trieste and adjacent waters of the northern Adriatic SeaGenov, Tilenhttps://hdl.handle.net/10023/273092023-04-01T02:02:22Z2022-11-29T00:00:00ZThis thesis aims to explore a combination of distinct but interconnected aspects of dolphin population ecology, behaviour and interactions with human activities in the Gulf of Trieste and adjacent waters of the northern Adriatic Sea. Boat surveys, photo-identification techniques and biopsy sampling between 2003 and 2018 were used to investigate social structure, interactions with local fisheries, isotopic niche variation and levels of organochlorine contaminants, and estimate dolphin abundance. The population was found to be structured into distinct social clusters, two of which displayed marked differences in fisheries-related behaviour and temporal partitioning previously unknown for this species or marine mammals generally. Stable isotope analysis showed isotopic niche differences among social groups. Levels of polychlorinated biphenyls (PCBs) were high, with evidence of maternal offloading of these pollutants to offspring, but no differences among social groups. Abundance estimates suggest that the total abundance of bottlenose dolphins in the study area during 2013–2018 ranged between 161 (95% CI = 153–170) and 245 (95% CI = 219–273). Finally, a novel method for individually identifying dolphins by facial features is described, which can complement existing photo-identification techniques. Together, these results provide a reasonably holistic picture of the dolphin population inhabiting the Gulf of Trieste and provide insights into social, ecological and anthropogenic drivers of its population dynamics. This study extends the available knowledge on Adriatic dolphins and provides a baseline for further studies.
2022-11-29T00:00:00ZGenov, TilenThis thesis aims to explore a combination of distinct but interconnected aspects of dolphin population ecology, behaviour and interactions with human activities in the Gulf of Trieste and adjacent waters of the northern Adriatic Sea. Boat surveys, photo-identification techniques and biopsy sampling between 2003 and 2018 were used to investigate social structure, interactions with local fisheries, isotopic niche variation and levels of organochlorine contaminants, and estimate dolphin abundance. The population was found to be structured into distinct social clusters, two of which displayed marked differences in fisheries-related behaviour and temporal partitioning previously unknown for this species or marine mammals generally. Stable isotope analysis showed isotopic niche differences among social groups. Levels of polychlorinated biphenyls (PCBs) were high, with evidence of maternal offloading of these pollutants to offspring, but no differences among social groups. Abundance estimates suggest that the total abundance of bottlenose dolphins in the study area during 2013–2018 ranged between 161 (95% CI = 153–170) and 245 (95% CI = 219–273). Finally, a novel method for individually identifying dolphins by facial features is described, which can complement existing photo-identification techniques. Together, these results provide a reasonably holistic picture of the dolphin population inhabiting the Gulf of Trieste and provide insights into social, ecological and anthropogenic drivers of its population dynamics. This study extends the available knowledge on Adriatic dolphins and provides a baseline for further studies.Building models : developing the behavioural model of Temnothorax collective wall building to study the evolutionary robustness of self-organised algorithmsInvernizzi, Edithhttps://hdl.handle.net/10023/272782024-01-11T16:44:17Z2022-11-29T00:00:00ZThis thesis focuses on wall building behaviour in Temnothorax ants as a case study of self-organised collective behaviour. It contains a progressing series of research packages, building towards one evolutionary question: how eusocial insect nest building algorithms successfully make the transition between two rule variants. I start by revising the existent behavioural model of Temnothorax wall building. By replicating the original agent-based model, I identify two issues: 1. the behavioural model performs poorly in conditions of low building material availability; and 2. the behavioural model lacks behavioural termination. I then introduce a revised version of the behavioural model (the gradual model) in which high stone density at building sites triggers a decrease in building activity, eventually leading to behavioural termination. I then compare the fit of both models to empirical data using laboratory observations of T. rugatulus wall building, applying a hidden Markov model framework to interpret the data. The gradual model provides the best match to the observed data. Finally, I use the revised model to test, in an agent-based model setting, how wall quality responds to different types of inter-worker variation in the building rule used: the presence of a mutant variant spreading within the colony; the co-existence of multiple variants; and widespread epigenetic individual variation. I find wall quality to be very robust to nearly any degree and frequency of variants. With additional simulations, I identify the two key elements of the building algorithm that provide robustness: the positive feedback effect, co-localising worker effort despite starting individual variation; and the existence of an area of overlap where activity occurs with high frequency under all variants (a buffer zone). I predict that these two components have been under selection for evolvability in wall building Temnothorax ants.
2022-11-29T00:00:00ZInvernizzi, EdithThis thesis focuses on wall building behaviour in Temnothorax ants as a case study of self-organised collective behaviour. It contains a progressing series of research packages, building towards one evolutionary question: how eusocial insect nest building algorithms successfully make the transition between two rule variants. I start by revising the existent behavioural model of Temnothorax wall building. By replicating the original agent-based model, I identify two issues: 1. the behavioural model performs poorly in conditions of low building material availability; and 2. the behavioural model lacks behavioural termination. I then introduce a revised version of the behavioural model (the gradual model) in which high stone density at building sites triggers a decrease in building activity, eventually leading to behavioural termination. I then compare the fit of both models to empirical data using laboratory observations of T. rugatulus wall building, applying a hidden Markov model framework to interpret the data. The gradual model provides the best match to the observed data. Finally, I use the revised model to test, in an agent-based model setting, how wall quality responds to different types of inter-worker variation in the building rule used: the presence of a mutant variant spreading within the colony; the co-existence of multiple variants; and widespread epigenetic individual variation. I find wall quality to be very robust to nearly any degree and frequency of variants. With additional simulations, I identify the two key elements of the building algorithm that provide robustness: the positive feedback effect, co-localising worker effort despite starting individual variation; and the existence of an area of overlap where activity occurs with high frequency under all variants (a buffer zone). I predict that these two components have been under selection for evolvability in wall building Temnothorax ants.Trends in taxonomic and functional diversity over succession in tropical secondary forestsArnold, Haleyhttps://hdl.handle.net/10023/272452024-03-22T03:02:47Z2023-06-14T00:00:00ZBiodiverse tropical forests are declining rapidly, due in part to the appropriation of natural land for human use. There is an urgent need to better understand how biodiversity changes in response to this landscape transformation, and to find conservation solutions that support both people and nature. Cacao farming, a valuable source of agricultural revenue in many tropical countries, can lead to a mosaic of both active and abandoned agroforests. These abandoned agroforests undergo secondary succession and have the potential to be important reservoirs of biodiversity. To evaluate this potential, I assessed the biodiversity of active cacao agroforests, abandoned agroforests, and primary forest on the tropical island of Trinidad. I surveyed tree, ground vegetation, epiphyte, and bird assemblages, and computed taxonomic and functional diversity. I further asked whether there are generalisable patterns of biodiversity change over succession across taxa, and how my results fit within the wider narrative of ecological succession theory and research. I found that taxonomic and functional alpha-diversity in all assemblages were mostly either maintained throughout succession, or recovered quickly across taxa. There were, however, substantial changes in taxonomic and functional composition (beta- diversity) over succession, with patterns of biodiversity change largely uncorrelated across taxa. Overall, there was little congruence between expectations based on theory and existing empirical research, and the results of my study. This outcome emphasises the need to deepen our understanding of successional processes across biomes, starting points of succession, and taxa. My research also highlights that, while primary forests contain more specialist species, actively cultivated cacao agroforests and young secondary forests in Trinidad are remarkably biodiverse and jointly contribute to supporting regional gamma diversity. These results place cacao agroforests within a people and nature framework, and demonstrate that human-altered habitats can be important reservoirs of tropical biodiversity.
2023-06-14T00:00:00ZArnold, HaleyBiodiverse tropical forests are declining rapidly, due in part to the appropriation of natural land for human use. There is an urgent need to better understand how biodiversity changes in response to this landscape transformation, and to find conservation solutions that support both people and nature. Cacao farming, a valuable source of agricultural revenue in many tropical countries, can lead to a mosaic of both active and abandoned agroforests. These abandoned agroforests undergo secondary succession and have the potential to be important reservoirs of biodiversity. To evaluate this potential, I assessed the biodiversity of active cacao agroforests, abandoned agroforests, and primary forest on the tropical island of Trinidad. I surveyed tree, ground vegetation, epiphyte, and bird assemblages, and computed taxonomic and functional diversity. I further asked whether there are generalisable patterns of biodiversity change over succession across taxa, and how my results fit within the wider narrative of ecological succession theory and research. I found that taxonomic and functional alpha-diversity in all assemblages were mostly either maintained throughout succession, or recovered quickly across taxa. There were, however, substantial changes in taxonomic and functional composition (beta- diversity) over succession, with patterns of biodiversity change largely uncorrelated across taxa. Overall, there was little congruence between expectations based on theory and existing empirical research, and the results of my study. This outcome emphasises the need to deepen our understanding of successional processes across biomes, starting points of succession, and taxa. My research also highlights that, while primary forests contain more specialist species, actively cultivated cacao agroforests and young secondary forests in Trinidad are remarkably biodiverse and jointly contribute to supporting regional gamma diversity. These results place cacao agroforests within a people and nature framework, and demonstrate that human-altered habitats can be important reservoirs of tropical biodiversity.Biophysical characterization of nanodiscs and nanodisc-reconstituted mechanosensitive ion channelsLi, Tiangehttps://hdl.handle.net/10023/272232024-01-06T03:07:02Z2023-06-14T00:00:00ZLipid-protein interactions are crucial for life. Research into this area is continuously growing, not only in the context of basic science, but also from a technological perspective aiming to facilitate their handling and stability for further studies. The development of nanodisc (ND) technology, with apolipoprotein-A1 derived membrane scaffold protein (MSP), has become key to the study of lipid-protein complexes, including mechanosensitive (MS) proteins. Although it is a widely used artificial lipid environment for membrane proteins in vitro, how ND structures assembly together remains poorly understood. In this thesis, I apply ensemble and single-molecule Förster Resonance Energy Transfer (FRET) assays to investigate the dynamics of ND structures and ND-reconstituted MS channels. First, I describe a FRET-based characterization of NDs. My studies reveal the stepwise mechanism of ND assembly and disassembly, the timescales of these processes and the stability of ND under detergents with or without the membrane protein. Next, I use this MSP-ND technology to investigate the structure of the pentameric MS channel of large conductance (MscL), which has attracted considerable attention over the past years. MS channels allow cells to sense and response to external mechanical stimuli. However, most studies have used ensemble measurements providing only average-conformation values. Here, I present a library of FRET-labelled MscL proteins to characterize the conformation of MscL channels at single-molecule level. Lastly, completely understanding mechanosensation requires to manipulate membrane tension and simultaneously image their response one by one. In the last part of this thesis, I demonstrate the feasibility of incorporating magnetic beads inside Giant Unilamellar Vesicles (GUVs) as a step towards the future development of a combined FRET-magnetic tweezers to explore mechanosensation under varying tension. Overall, this project expands our knowledge of NDs and explores potential methods to study single MS channels by fluorescence-force hybrid microscopy.
2023-06-14T00:00:00ZLi, TiangeLipid-protein interactions are crucial for life. Research into this area is continuously growing, not only in the context of basic science, but also from a technological perspective aiming to facilitate their handling and stability for further studies. The development of nanodisc (ND) technology, with apolipoprotein-A1 derived membrane scaffold protein (MSP), has become key to the study of lipid-protein complexes, including mechanosensitive (MS) proteins. Although it is a widely used artificial lipid environment for membrane proteins in vitro, how ND structures assembly together remains poorly understood. In this thesis, I apply ensemble and single-molecule Förster Resonance Energy Transfer (FRET) assays to investigate the dynamics of ND structures and ND-reconstituted MS channels. First, I describe a FRET-based characterization of NDs. My studies reveal the stepwise mechanism of ND assembly and disassembly, the timescales of these processes and the stability of ND under detergents with or without the membrane protein. Next, I use this MSP-ND technology to investigate the structure of the pentameric MS channel of large conductance (MscL), which has attracted considerable attention over the past years. MS channels allow cells to sense and response to external mechanical stimuli. However, most studies have used ensemble measurements providing only average-conformation values. Here, I present a library of FRET-labelled MscL proteins to characterize the conformation of MscL channels at single-molecule level. Lastly, completely understanding mechanosensation requires to manipulate membrane tension and simultaneously image their response one by one. In the last part of this thesis, I demonstrate the feasibility of incorporating magnetic beads inside Giant Unilamellar Vesicles (GUVs) as a step towards the future development of a combined FRET-magnetic tweezers to explore mechanosensation under varying tension. Overall, this project expands our knowledge of NDs and explores potential methods to study single MS channels by fluorescence-force hybrid microscopy.Genomic patterns of divergence and gene flow in Drosophila and GoodeidaeYusuf, Leebanhttps://hdl.handle.net/10023/272132023-04-25T10:18:03Z2023-06-14T00:00:00ZUnderstanding the impact of the presence or absence of geographic barriers on speciation has been a source of enduring interest in evolutionary biology. The degree of geographical isolation and the prevalence of gene flow during divergence may often determine the rate of reproductive isolation and the relative importance of other evolutionary forces. In this thesis, I use comparative genomic approaches to ask how frequent gene flow is, understand the contributions of ancient and recent gene flow to divergence, and finally, examine how patterns of genetic divergence between closely-related species are affected by geography and gene flow in two different systems: Drosophila and Splitfins (Goodeidae). I investigate the evolutionary history of divergence in the virilis group of Drosophila using de novo whole-genome sequences. I show that ancient and recent gene flow is common complicating phylogenetic inference and confounding levels of genetic divergence on the X chromosome across species pairs in the group. Next, I test whether gene flow is common across 96 species pairs in Drosophila. Using model-based inference from whole-genome data, I demonstrate that both allopatric and sympatric species pairs in Drosophila show similar support for models of speciation-with-gene-flow. Additionally, using inferred migration and divergence time estimates for species pairs across Drosophila, I show that evidence for reinforcement is mixed. In the final two chapters, I examined patterns of divergence and gene flow in Goodeidae. Using whole-genome sequences and de novo assemblies, I show that divergence of Goodeidae occurred rapidly, alongside consistent fluctuations in population size and limited ancient gene flow. Finally, I employ a broad comparative genomic approach using 21 genomes across Cyprinodontiformes to identify signatures of molecular convergence and positive selection linked to the evolution of viviparity in Goodeidae and Poecilidae. Altogether, this thesis demonstrates that complex speciation histories with gene flow are the rule rather than the exception.
2023-06-14T00:00:00ZYusuf, LeebanUnderstanding the impact of the presence or absence of geographic barriers on speciation has been a source of enduring interest in evolutionary biology. The degree of geographical isolation and the prevalence of gene flow during divergence may often determine the rate of reproductive isolation and the relative importance of other evolutionary forces. In this thesis, I use comparative genomic approaches to ask how frequent gene flow is, understand the contributions of ancient and recent gene flow to divergence, and finally, examine how patterns of genetic divergence between closely-related species are affected by geography and gene flow in two different systems: Drosophila and Splitfins (Goodeidae). I investigate the evolutionary history of divergence in the virilis group of Drosophila using de novo whole-genome sequences. I show that ancient and recent gene flow is common complicating phylogenetic inference and confounding levels of genetic divergence on the X chromosome across species pairs in the group. Next, I test whether gene flow is common across 96 species pairs in Drosophila. Using model-based inference from whole-genome data, I demonstrate that both allopatric and sympatric species pairs in Drosophila show similar support for models of speciation-with-gene-flow. Additionally, using inferred migration and divergence time estimates for species pairs across Drosophila, I show that evidence for reinforcement is mixed. In the final two chapters, I examined patterns of divergence and gene flow in Goodeidae. Using whole-genome sequences and de novo assemblies, I show that divergence of Goodeidae occurred rapidly, alongside consistent fluctuations in population size and limited ancient gene flow. Finally, I employ a broad comparative genomic approach using 21 genomes across Cyprinodontiformes to identify signatures of molecular convergence and positive selection linked to the evolution of viviparity in Goodeidae and Poecilidae. Altogether, this thesis demonstrates that complex speciation histories with gene flow are the rule rather than the exception. Towards a structural understanding of DNA polymerase δ using the thermophilic fungus Chaetomium thermophilum as a modelYang, Dongxiaohttps://hdl.handle.net/10023/271992023-03-17T03:07:54Z2022-06-15T00:00:00ZEukaryotic DNA polymerase δ plays a critical role in DNA replication and repair. At the replication fork, Pol δ carries out the bulk of lagging strand DNA synthesis and plays transient but crucial roles in leading strand DNA replication as well. Human Pol δ consists of a catalytic subunit (PolD1) and three accessory subunits (PolD2, PolD3 and PolD4). The regulated degradation of PolD4 in response to DNA damage reflects the important role of this protein, however, its precise function remains to be fully understood. Structural studies have located the PolD4 protein between PolD1 and PolD2, leading to the suggestion that PolD4 degradation is likely to bring about a subtle change in the three-dimensional architecture of Pol δ to modulate the enzyme’s activity.
This work used PolD4 proteins from fission yeast Schizosaccharomyces pombe and thermophilic fungus Chaetomium thermophilum (Ct) as models to explore the function and structure of PolD4. Overexpression of S. pombe PolD4 could supress mutations in genes encoding PolD1, PolD2 and PolD3. We investigated how the conserved residues at the C-terminal domain of PolD4 contribute to this function. We identified a PCNA interacting protein (PIP) motif in the N-terminal region of CtPolD4 and solved the crystal structure of CtPolD4 PIP peptide bound to CtPCNA. This structure reveals a non-canonical mode of binding that contrasts with the recently characterised human PolD4 (p12) PIP-PCNA interaction.
As part of a wider study dissecting the structure and function of Pol δ, we developed protocols for expression and purification of CtPol δ and obtained its cryo-EM structure to near 4 Å. Our studies may provide insights on the role of PolD4 in contribution to Pol δ function, regulation of DNA replication and maintenance of genome stability.
2022-06-15T00:00:00ZYang, DongxiaoEukaryotic DNA polymerase δ plays a critical role in DNA replication and repair. At the replication fork, Pol δ carries out the bulk of lagging strand DNA synthesis and plays transient but crucial roles in leading strand DNA replication as well. Human Pol δ consists of a catalytic subunit (PolD1) and three accessory subunits (PolD2, PolD3 and PolD4). The regulated degradation of PolD4 in response to DNA damage reflects the important role of this protein, however, its precise function remains to be fully understood. Structural studies have located the PolD4 protein between PolD1 and PolD2, leading to the suggestion that PolD4 degradation is likely to bring about a subtle change in the three-dimensional architecture of Pol δ to modulate the enzyme’s activity.
This work used PolD4 proteins from fission yeast Schizosaccharomyces pombe and thermophilic fungus Chaetomium thermophilum (Ct) as models to explore the function and structure of PolD4. Overexpression of S. pombe PolD4 could supress mutations in genes encoding PolD1, PolD2 and PolD3. We investigated how the conserved residues at the C-terminal domain of PolD4 contribute to this function. We identified a PCNA interacting protein (PIP) motif in the N-terminal region of CtPolD4 and solved the crystal structure of CtPolD4 PIP peptide bound to CtPCNA. This structure reveals a non-canonical mode of binding that contrasts with the recently characterised human PolD4 (p12) PIP-PCNA interaction.
As part of a wider study dissecting the structure and function of Pol δ, we developed protocols for expression and purification of CtPol δ and obtained its cryo-EM structure to near 4 Å. Our studies may provide insights on the role of PolD4 in contribution to Pol δ function, regulation of DNA replication and maintenance of genome stability.Predator-prey behavioural interactions on plants, with special emphasis on aphid dropping defence and ladybird search strategiesHumphreys, Rosalind Kayhttps://hdl.handle.net/10023/271922023-04-04T13:51:28Z2022-06-15T00:00:00ZPredator-prey interactions have significant short- and long-term implications for the individuals involved, their populations’ dynamics, and the broader ecological community. Predation is a strong selective force that has led to prey evolving a great diversity of defensive adaptations, while predators undergo strong selection to successfully locate and capture prey. For both ‘sides’ of these interactions, behavioural adaptations offer flexibility in deployment, and so are expected to be context-sensitive. In this thesis, I use the ladybird-aphid predator-prey system to examine both prey defence behaviours and predator search strategies. Considering the prey, dropping – a widespread but understudied antipredator behaviour – is my focus. My findings suggest that, although dropping seems superficially simple, the selective pressures on it are complex. Dropping is affected by internal factors, such as genotype and the presence of endosymbionts. The nature and proximity of the predatory threat also affect dropping. Further, the consequences of dropping depend on many factors, including where on a plant predator-prey encounters occur; this in turn will be influenced by predator search strategies. Considering predator search, my focus is ladybird movements when searching branched environments, particularly potential turning biases and turn alternation. My work suggests that predators do not follow simple rules when searching a plant for prey, but they may exhibit some innate turning tendencies under particular conditions. Predator search strategies will be highly influential in affecting the context (e.g. location on plant) in which predator-prey interactions take place. Future work should investigate predator search further in order to provide a deeper understanding of the selective pressures on dropping in prey. For both prey dropping and predator search strategies, researchers must also appreciate the context-sensitivity of the different behaviours, and work to understand influencing cues, triggers, and outcomes specific to the species and circumstances involved.
2022-06-15T00:00:00ZHumphreys, Rosalind KayPredator-prey interactions have significant short- and long-term implications for the individuals involved, their populations’ dynamics, and the broader ecological community. Predation is a strong selective force that has led to prey evolving a great diversity of defensive adaptations, while predators undergo strong selection to successfully locate and capture prey. For both ‘sides’ of these interactions, behavioural adaptations offer flexibility in deployment, and so are expected to be context-sensitive. In this thesis, I use the ladybird-aphid predator-prey system to examine both prey defence behaviours and predator search strategies. Considering the prey, dropping – a widespread but understudied antipredator behaviour – is my focus. My findings suggest that, although dropping seems superficially simple, the selective pressures on it are complex. Dropping is affected by internal factors, such as genotype and the presence of endosymbionts. The nature and proximity of the predatory threat also affect dropping. Further, the consequences of dropping depend on many factors, including where on a plant predator-prey encounters occur; this in turn will be influenced by predator search strategies. Considering predator search, my focus is ladybird movements when searching branched environments, particularly potential turning biases and turn alternation. My work suggests that predators do not follow simple rules when searching a plant for prey, but they may exhibit some innate turning tendencies under particular conditions. Predator search strategies will be highly influential in affecting the context (e.g. location on plant) in which predator-prey interactions take place. Future work should investigate predator search further in order to provide a deeper understanding of the selective pressures on dropping in prey. For both prey dropping and predator search strategies, researchers must also appreciate the context-sensitivity of the different behaviours, and work to understand influencing cues, triggers, and outcomes specific to the species and circumstances involved.Marine mammal predator-prey interactions in the North SeaRansijn, Jannekehttps://hdl.handle.net/10023/271822023-03-16T15:33:03Z2023-06-14T00:00:00ZTrophic levels within an ecosystem are linked by the functional response which describes how the consumption rate of a predator varies in relation to prey density. Knowledge of functional responses is key to understanding predator-prey interactions, population dynamics, predation pressure, prey preference, and the ecosystem. This thesis explores multi-species functional responses (MSFR) of key marine mammal predators in the North Sea, and the prey energy available to them. Spatiotemporal variation in prey energy available to harbour porpoises (Phocoena phocoena) was modelled, using species distribution models, and showed that large amounts of energy were available both within and outside the Southern North Sea (SAC). Sandeels are energy-rich, their patchy restricted distribution drove the observed patterns of the spatiotemporal distribution of all porpoise prey energy. The MSFR of three predator species (harbour porpoise, grey (Halichoerus grypus) and harbour seal (Phoca vitulina)) were modelled using Bayesian methodology. Fitted responses indicated that all predators exhibit a type III functional response, and that sandeels are important and more strongly preferred by grey seals and harbour porpoise compared to harbour seals. They may be preferred as they are probably easy to catch due to their immobility and predictable occurrence, as inferred from their restricted modelled distribution. Harbour seals have more diverse diets than grey seals and seem to show a more sigmoidal response which may indicate a greater tendency to switch between prey types. Of the predators, harbour porpoise had the highest consumption estimates, mainly due to the larger number of animals in the area. Generally, marine mammal consumption was low compared to fisheries landings (≤ 20%). Overall, this thesis shows the benefit of MSFR modelling to improve ecological understanding of important marine predators and the results allow future integration of the MSFRs into ecosystem models to explore the consequences of predation on various fish stocks.
2023-06-14T00:00:00ZRansijn, JannekeTrophic levels within an ecosystem are linked by the functional response which describes how the consumption rate of a predator varies in relation to prey density. Knowledge of functional responses is key to understanding predator-prey interactions, population dynamics, predation pressure, prey preference, and the ecosystem. This thesis explores multi-species functional responses (MSFR) of key marine mammal predators in the North Sea, and the prey energy available to them. Spatiotemporal variation in prey energy available to harbour porpoises (Phocoena phocoena) was modelled, using species distribution models, and showed that large amounts of energy were available both within and outside the Southern North Sea (SAC). Sandeels are energy-rich, their patchy restricted distribution drove the observed patterns of the spatiotemporal distribution of all porpoise prey energy. The MSFR of three predator species (harbour porpoise, grey (Halichoerus grypus) and harbour seal (Phoca vitulina)) were modelled using Bayesian methodology. Fitted responses indicated that all predators exhibit a type III functional response, and that sandeels are important and more strongly preferred by grey seals and harbour porpoise compared to harbour seals. They may be preferred as they are probably easy to catch due to their immobility and predictable occurrence, as inferred from their restricted modelled distribution. Harbour seals have more diverse diets than grey seals and seem to show a more sigmoidal response which may indicate a greater tendency to switch between prey types. Of the predators, harbour porpoise had the highest consumption estimates, mainly due to the larger number of animals in the area. Generally, marine mammal consumption was low compared to fisheries landings (≤ 20%). Overall, this thesis shows the benefit of MSFR modelling to improve ecological understanding of important marine predators and the results allow future integration of the MSFRs into ecosystem models to explore the consequences of predation on various fish stocks.Gene and genome duplication in animal evolutionAase-Remedios, Madeleine Emmahttps://hdl.handle.net/10023/271522023-08-24T02:02:17Z2023-06-14T00:00:00ZGene and genome duplications have an important role in evolution as a mechanism that creates novel genetic material. Paralogues created by duplication can diversify in function and contribute to the complexity of genetic networks, especially in the context of the gene regulation and signalling pathways that control animal development. Clusters of related genes that have arisen by tandem duplication illustrate the role of regulatory elements in preserving synteny by constraining gene neighbourhoods. Whole genome duplications have occurred on the stems of lineages characterised by the evolution of novel structures, adaptations to different environments, and species diversity. Here, I aim to understand how gene and genome duplications have impacted specific developmental gene families and processes throughout animal evolution with a comparative genomics approach. I make use of genomic resources from phylogenetically informative lineages, including new genomes of early-branching chordates, spiralians, and ecdysozoans. I have examined the impact of the vertebrate two rounds of whole genome duplication on chordate muscle development including the highly conserved family of myogenic regulatory factors and muscle gene expression. I have also investigated the evolution of homeobox gene families, with a focus on clusters of genes found across bilaterians, and specifically focus on the Hox cluster. With phylogenetic and synteny analyses, I found that a tandem duplication underpins the origin of two vertebrate muscle gene types. I examined the impact of whole genome duplication on a diversity of genes encoding proteins in a highly conserved signalling pathway in muscle, and I surveyed and revised the hypotheses for the evolution of homeobox genes across the bilaterians. In doing so, I have also generated a large resource of genomic annotations and protein sequences to facilitate functional studies in the future. These findings not only have identified certain duplications that have underpinned certain known instances of subfunctionalisation among paralogues, but also indicate gene families to target for future study.
2023-06-14T00:00:00ZAase-Remedios, Madeleine EmmaGene and genome duplications have an important role in evolution as a mechanism that creates novel genetic material. Paralogues created by duplication can diversify in function and contribute to the complexity of genetic networks, especially in the context of the gene regulation and signalling pathways that control animal development. Clusters of related genes that have arisen by tandem duplication illustrate the role of regulatory elements in preserving synteny by constraining gene neighbourhoods. Whole genome duplications have occurred on the stems of lineages characterised by the evolution of novel structures, adaptations to different environments, and species diversity. Here, I aim to understand how gene and genome duplications have impacted specific developmental gene families and processes throughout animal evolution with a comparative genomics approach. I make use of genomic resources from phylogenetically informative lineages, including new genomes of early-branching chordates, spiralians, and ecdysozoans. I have examined the impact of the vertebrate two rounds of whole genome duplication on chordate muscle development including the highly conserved family of myogenic regulatory factors and muscle gene expression. I have also investigated the evolution of homeobox gene families, with a focus on clusters of genes found across bilaterians, and specifically focus on the Hox cluster. With phylogenetic and synteny analyses, I found that a tandem duplication underpins the origin of two vertebrate muscle gene types. I examined the impact of whole genome duplication on a diversity of genes encoding proteins in a highly conserved signalling pathway in muscle, and I surveyed and revised the hypotheses for the evolution of homeobox genes across the bilaterians. In doing so, I have also generated a large resource of genomic annotations and protein sequences to facilitate functional studies in the future. These findings not only have identified certain duplications that have underpinned certain known instances of subfunctionalisation among paralogues, but also indicate gene families to target for future study.Studying cell sorting during Drosophila abdominal morphogenesis. How is positional information encoded?Chatzimatthaiou, Sotiroulahttps://hdl.handle.net/10023/271292023-10-19T02:03:39Z2023-06-14T00:00:00ZAbstract redacted
2023-06-14T00:00:00ZChatzimatthaiou, SotiroulaAbstract redactedExploring and exploiting the resistance to Globodera pallida in potatoGartner, Ulrikehttps://hdl.handle.net/10023/270942023-04-26T21:52:40Z2023-06-14T00:00:00ZThe potato cyst nematodes (PCN) Globodera pallida and G. rostochiensis are economically important potato pests in almost all regions where potato is grown. Studying the composition, distribution and virulence of PCN populations in fields, and finding new sources of naturally occurring resistance in wild potato species is important for the management of these pests.
In Scotland, up to three different introductions of G. pallida, determined by mitotyping, were found to be present in fields. To investigate whether cysts in a population show a correlation between mitotype and different virulence levels, “single cyst” lines were generated, mitotyped, and their virulence to different potato cultivars was determined. One mitotype was shown to correlate with G. pallida pathotype Pa3, but overall, the mitotypes are not usable as reliable virulence markers. A phylogenetic analysis was performed to determine the relationships between British G. pallida populations. In addition, single nucleotide polymorphisms (SNPs) in genomic DNA were identified that represent candidate virulence markers.
A screen of wild potato germplasm was undertaken to identify new resistance against G. pallida. The diploid species Solanum spegazzinii Bitter accession 7195 shows resistance to G. pallida pathotypes Pa1 and Pa2/3. A cross and first backcross of S. spegazzinii with S. tuberosum group Phureja cultivar Mayan Gold was performed, and the level of resistance to G. pallida Pa2/3 was determined in progeny. Bulked-segregant analysis sing generic mapping enrichment sequencing and genotyping-by-sequencing was performed to identify SNPs that are genetically linked to the resistance, using S. tuberosum group Phureja clone DM1-3 516 R44 as a reference genome. These SNPs were converted into allele specific PCR assays, and the resistance was mapped using graphical genotyping. The resistance was successfully introgressed into a tetraploid potato cultivar by a tetraploid-diploid interploidy cross.
2023-06-14T00:00:00ZGartner, UlrikeThe potato cyst nematodes (PCN) Globodera pallida and G. rostochiensis are economically important potato pests in almost all regions where potato is grown. Studying the composition, distribution and virulence of PCN populations in fields, and finding new sources of naturally occurring resistance in wild potato species is important for the management of these pests.
In Scotland, up to three different introductions of G. pallida, determined by mitotyping, were found to be present in fields. To investigate whether cysts in a population show a correlation between mitotype and different virulence levels, “single cyst” lines were generated, mitotyped, and their virulence to different potato cultivars was determined. One mitotype was shown to correlate with G. pallida pathotype Pa3, but overall, the mitotypes are not usable as reliable virulence markers. A phylogenetic analysis was performed to determine the relationships between British G. pallida populations. In addition, single nucleotide polymorphisms (SNPs) in genomic DNA were identified that represent candidate virulence markers.
A screen of wild potato germplasm was undertaken to identify new resistance against G. pallida. The diploid species Solanum spegazzinii Bitter accession 7195 shows resistance to G. pallida pathotypes Pa1 and Pa2/3. A cross and first backcross of S. spegazzinii with S. tuberosum group Phureja cultivar Mayan Gold was performed, and the level of resistance to G. pallida Pa2/3 was determined in progeny. Bulked-segregant analysis sing generic mapping enrichment sequencing and genotyping-by-sequencing was performed to identify SNPs that are genetically linked to the resistance, using S. tuberosum group Phureja clone DM1-3 516 R44 as a reference genome. These SNPs were converted into allele specific PCR assays, and the resistance was mapped using graphical genotyping. The resistance was successfully introgressed into a tetraploid potato cultivar by a tetraploid-diploid interploidy cross.Title redactedFoltanyi, Florahttps://hdl.handle.net/10023/269312023-06-28T22:25:14Z2023-06-14T00:00:00ZAbstract redacted
2023-06-14T00:00:00ZFoltanyi, FloraAbstract redactedThe evolution of parental care and associated life-history traits in teleost fishes and passerine birds : comparative and experimental approachesVanadzina, Karinahttps://hdl.handle.net/10023/269142023-04-06T11:03:16Z2022-11-29T00:00:00ZParental care is any form of provisioning that improves offspring survival and can range from brief guarding of young to advanced adaptations such as viviparity. Despite the wide taxonomic spread of care, the evolution of such diversity and its impact on other aspects of species’ life history are not well understood and quantified. Using phylogenetic comparative methods and experimental approaches, I explore how variation in care provision, together with environmental context, affect a range of life-history traits in teleost fishes and passerines. In contrast to birds where advanced and prolonged care dominates, parental care in fishes encompasses a broad spectrum of strategies with varying levels of investment. Chapter 1 provides an overview of research into the evolution of parental care. In Chapter 2, I assess the relative effect of environment and care strategies on variation in offspring size across 1,639 species of marine teleosts. While investment in eggs is driven primarily by temperature, I find that species with parental care exhibit larger sizes at hatching compared to species with no care. I also show that large hatchlings promote the evolution of advanced forms of care but there is no evidence that post-spawning care in general, including simpler forms of care provided predominantly by males, co-evolves with offspring size. In Chapter 3, I use an experimental approach to investigate the potential trade-off between the provision of a safe environment for offspring development and attracting a mate in three-spined stickleback (Gasterosteus aculeatus) males that construct nests. I find that stickleback males build more conspicuous nests on backgrounds that are perceived as safer, but that their investment in nests is balanced against other courtship activities. In Chapter 4, I identify global correlates of variation in nest size using measurements from 1,117 species of cup-nesting passerines. I observe that the pattern of building larger nests in colder environments or habitats with reduced predation threat – first detected at population-level studies – does scale up globally and across a multitude of species. Finally, in Chapter 5, I evaluate the importance of predation and competition in shaping the evolution of nest type and associated life-history traits in passerines. Using data from 4,105 species, I determine that enclosed nests are associated with larger clutch sizes and longer periods of care irrespective of the level of competition in the breeding environment.
2022-11-29T00:00:00ZVanadzina, KarinaParental care is any form of provisioning that improves offspring survival and can range from brief guarding of young to advanced adaptations such as viviparity. Despite the wide taxonomic spread of care, the evolution of such diversity and its impact on other aspects of species’ life history are not well understood and quantified. Using phylogenetic comparative methods and experimental approaches, I explore how variation in care provision, together with environmental context, affect a range of life-history traits in teleost fishes and passerines. In contrast to birds where advanced and prolonged care dominates, parental care in fishes encompasses a broad spectrum of strategies with varying levels of investment. Chapter 1 provides an overview of research into the evolution of parental care. In Chapter 2, I assess the relative effect of environment and care strategies on variation in offspring size across 1,639 species of marine teleosts. While investment in eggs is driven primarily by temperature, I find that species with parental care exhibit larger sizes at hatching compared to species with no care. I also show that large hatchlings promote the evolution of advanced forms of care but there is no evidence that post-spawning care in general, including simpler forms of care provided predominantly by males, co-evolves with offspring size. In Chapter 3, I use an experimental approach to investigate the potential trade-off between the provision of a safe environment for offspring development and attracting a mate in three-spined stickleback (Gasterosteus aculeatus) males that construct nests. I find that stickleback males build more conspicuous nests on backgrounds that are perceived as safer, but that their investment in nests is balanced against other courtship activities. In Chapter 4, I identify global correlates of variation in nest size using measurements from 1,117 species of cup-nesting passerines. I observe that the pattern of building larger nests in colder environments or habitats with reduced predation threat – first detected at population-level studies – does scale up globally and across a multitude of species. Finally, in Chapter 5, I evaluate the importance of predation and competition in shaping the evolution of nest type and associated life-history traits in passerines. Using data from 4,105 species, I determine that enclosed nests are associated with larger clutch sizes and longer periods of care irrespective of the level of competition in the breeding environment.Core effectors of plant-parasitic nematodes and their host targetsLeslie, Kerryhttps://hdl.handle.net/10023/265242023-03-09T14:54:10Z2022-06-15T00:00:00ZPlant parasitic nematodes infect many major food crops worldwide, causing damage valued at approximately 80 billion U.S. dollars per year (Nicol et al. 2011). As part of the parasitic process, some nematodes form a feeding site called a syncytium in the roots of their host. Specialised pathogen proteins known as effectors are thought to play critical roles in these processes.
This thesis identifies and characterises a subset of core effectors conserved in the syncytia forming nematode species Globodera rostochiensis, Globodera pallida, Rotylenchulus reniformis, and Nacobbus aberrans, but that are absent from other nematodes. Three of the candidates (GROS_g02394, GROS_g02469, and GROS_g05682) have been validated as effectors using in situ hybridisation to confirm expression in the oesophageal gland cells. Further functional characterisation using in planta localisation, yeast two-hybrid (Y2H) analysis, and co immunoprecipitation for host target identification were undertaken. Using Y2H it was possible to identify an arginine N-methyltransferase (stPRMT1.1) from Solanum tuberosum as an interacting host protein for GROS_g02394.
In addition, a set of novel GH53 endo-β-1, 4-galactanase effectors has been identified which may assist in invasion of the host and migration through root tissue. These genes have likely been acquired through a horizontal gene transfer event. This has given a greater insight into the invasion process and the co evolution between the nematode and its host plant. A conserved family of Cathepsin L-like peptidases has also been identified. Analysis using in situ hybridisation showed these to be intestinal proteins. Expression analysis suggests conserved functions for different family members across a range of species.
2022-06-15T00:00:00ZLeslie, KerryPlant parasitic nematodes infect many major food crops worldwide, causing damage valued at approximately 80 billion U.S. dollars per year (Nicol et al. 2011). As part of the parasitic process, some nematodes form a feeding site called a syncytium in the roots of their host. Specialised pathogen proteins known as effectors are thought to play critical roles in these processes.
This thesis identifies and characterises a subset of core effectors conserved in the syncytia forming nematode species Globodera rostochiensis, Globodera pallida, Rotylenchulus reniformis, and Nacobbus aberrans, but that are absent from other nematodes. Three of the candidates (GROS_g02394, GROS_g02469, and GROS_g05682) have been validated as effectors using in situ hybridisation to confirm expression in the oesophageal gland cells. Further functional characterisation using in planta localisation, yeast two-hybrid (Y2H) analysis, and co immunoprecipitation for host target identification were undertaken. Using Y2H it was possible to identify an arginine N-methyltransferase (stPRMT1.1) from Solanum tuberosum as an interacting host protein for GROS_g02394.
In addition, a set of novel GH53 endo-β-1, 4-galactanase effectors has been identified which may assist in invasion of the host and migration through root tissue. These genes have likely been acquired through a horizontal gene transfer event. This has given a greater insight into the invasion process and the co evolution between the nematode and its host plant. A conserved family of Cathepsin L-like peptidases has also been identified. Analysis using in situ hybridisation showed these to be intestinal proteins. Expression analysis suggests conserved functions for different family members across a range of species.Degrading heparan sulfate : structural and functional analysis of sulfatases for drug discovery applicationsBogucka, Agnieszkahttps://hdl.handle.net/10023/264742022-11-25T09:45:22Z2022-11-29T00:00:00ZHeparan sulfate proteoglycans (HSPGs) are a fundamental and evolving part of the cell surface and within the extracellular matrix (ECM). Turnover of HSPGs is aided by sulfatases, a family of enzymes which catalyzes cleavage of sulfate esters and plays an important role in step-wise degradation and lysosomal turnover of HSPGs. Deficiency of glycosaminoglycan (GAG) degradation due to autosomal recessive gene mutations causes a subclass of lysosomal storage disorders called mucopolysaccharidoses (MPSs), where there is accumulation of incomplete degradation products in the lysosome. Many of MPS type disorders are paired with severe neurocognitive deficiencies, hence, the difficulty in treatment. Out of eight human heparan sulfate degrading lysosomal sulfatases, three are described here: N-acetylglucosamine-6-sulfatase (GNS), arylsulfatase K and arylsulfatase G. Overall, this work explores various approaches to drug discovery through small fragment screening and computational-based protein engineering. The resulting fragment based screening performed on GNS identified an allosteric binding site, which can be used for the rational design of molecular chaperones that function to stabilise misfolded GNS in MPS IIID patients. The approach to engineer the pH optimum of GNS activity could serve as a way to treat an ultra-low molecular weight heparin (ULMWH) overdose.
2022-11-29T00:00:00ZBogucka, AgnieszkaHeparan sulfate proteoglycans (HSPGs) are a fundamental and evolving part of the cell surface and within the extracellular matrix (ECM). Turnover of HSPGs is aided by sulfatases, a family of enzymes which catalyzes cleavage of sulfate esters and plays an important role in step-wise degradation and lysosomal turnover of HSPGs. Deficiency of glycosaminoglycan (GAG) degradation due to autosomal recessive gene mutations causes a subclass of lysosomal storage disorders called mucopolysaccharidoses (MPSs), where there is accumulation of incomplete degradation products in the lysosome. Many of MPS type disorders are paired with severe neurocognitive deficiencies, hence, the difficulty in treatment. Out of eight human heparan sulfate degrading lysosomal sulfatases, three are described here: N-acetylglucosamine-6-sulfatase (GNS), arylsulfatase K and arylsulfatase G. Overall, this work explores various approaches to drug discovery through small fragment screening and computational-based protein engineering. The resulting fragment based screening performed on GNS identified an allosteric binding site, which can be used for the rational design of molecular chaperones that function to stabilise misfolded GNS in MPS IIID patients. The approach to engineer the pH optimum of GNS activity could serve as a way to treat an ultra-low molecular weight heparin (ULMWH) overdose.Behavioural responses by seals to offshore energy activitiesWhyte, Katherine Faehttps://hdl.handle.net/10023/263972022-11-16T03:03:58Z2022-06-15T00:00:00ZTo effectively manage interactions between industrial activities and wildlife populations in increasingly urbanised environments, it is essential to understand how animals may be affected by different anthropogenic activities. In this thesis, I used biologging devices to investigate the potential effects of sound disturbance on seals. By simulation study, I evaluated the use of statistical tools (Mahalanobis distance) to detect unusual instances of movement and dive behaviour in seal biologging data. The results of these simulations were used to produce recommendations for future studies aiming to detect behavioural changes in animal movement data. Building on the findings of this work, I examined the movement and dive behaviour of 24 harbour seals (Phoca vitulina) during pile driving construction at an offshore wind farm in the UK. Using GPS location data collected on animal-borne tags, I identified statistically unusual horizontal movement events during pile driving, typically consisting of increases in speed, the cessation of horizontal movement, or the sudden initiation of travel. Using dive data from animal-borne tags, I identified statistically unusual groups of dives, and also characterised the effect of pile driving activity on behaviour-switching between different dive types (by hidden Markov models). Seals were found to switch dive behaviours more often during pile driving (compared to baseline periods), and the identified unusual dives were typically shorter and shallower, with longer post-dive surface intervals. For both horizontal and diving responses, dose-response curves were produced to estimate the relationship between the received sound level of pile driving and the probability of a behavioural change. By examining behaviour at the individual-level, improved insights of at-sea seal behaviour during disturbance events were gained. The results of this thesis also inform future offshore activities, enabling the renewable energy industry to develop in a timely and environmentally-responsible manner.
2022-06-15T00:00:00ZWhyte, Katherine FaeTo effectively manage interactions between industrial activities and wildlife populations in increasingly urbanised environments, it is essential to understand how animals may be affected by different anthropogenic activities. In this thesis, I used biologging devices to investigate the potential effects of sound disturbance on seals. By simulation study, I evaluated the use of statistical tools (Mahalanobis distance) to detect unusual instances of movement and dive behaviour in seal biologging data. The results of these simulations were used to produce recommendations for future studies aiming to detect behavioural changes in animal movement data. Building on the findings of this work, I examined the movement and dive behaviour of 24 harbour seals (Phoca vitulina) during pile driving construction at an offshore wind farm in the UK. Using GPS location data collected on animal-borne tags, I identified statistically unusual horizontal movement events during pile driving, typically consisting of increases in speed, the cessation of horizontal movement, or the sudden initiation of travel. Using dive data from animal-borne tags, I identified statistically unusual groups of dives, and also characterised the effect of pile driving activity on behaviour-switching between different dive types (by hidden Markov models). Seals were found to switch dive behaviours more often during pile driving (compared to baseline periods), and the identified unusual dives were typically shorter and shallower, with longer post-dive surface intervals. For both horizontal and diving responses, dose-response curves were produced to estimate the relationship between the received sound level of pile driving and the probability of a behavioural change. By examining behaviour at the individual-level, improved insights of at-sea seal behaviour during disturbance events were gained. The results of this thesis also inform future offshore activities, enabling the renewable energy industry to develop in a timely and environmentally-responsible manner.Mechanistic enzymology of short-form ATP phosphoribosyltransferase and bifunctional phosphoribosyl-ATP pyrophosphohydrolase/phosphoribosyl-AMP cyclohydrolaseFisher, Gemmahttps://hdl.handle.net/10023/261482022-10-07T09:50:23Z2022-11-29T00:00:00ZAbstract redacted
2022-11-29T00:00:00ZFisher, GemmaAbstract redactedModelling the movements of flapper skate (Dipturus intermedius) in relation to a Scottish Marine Protected AreaLavender, Edwardhttps://hdl.handle.net/10023/260562023-11-30T03:01:17Z2022-11-29T00:00:00Z1. Movement shapes the lives of animals and their interactions with human activities. In recent decades, the emergence of movement ecology as a discipline and developments in electronic tagging and tracking have led to substantial improvements in our understanding of animal movement and its implications for species conservation. Yet while research has burgeoned for many taxa, including sharks, other groups in aquatic ecosystems, such as skate (Rajidae), remain comparatively understudied.
2. The flapper skate (Dipturus intermedius) is a large, Critically Endangered elasmobranch. The species has been extirpated from much of its former range, but individuals are still found off west Scotland where the Loch Sunart to the Sound of Jura Marine Protected Area (MPA) has been designated for flapper skate conservation. However, skate movements within and around the MPA remain poorly understood.
3. This thesis investigates the movements of flapper skate in relation to the MPA using electronic tagging and tracking data from passive acoustic telemetry, archival (depth and temperature) tags and mark-recapture angling. Objectives include the examination of site affinity, vertical movements and responses to disturbance. Research in these areas motivates the development of a flexible, mechanistic modelling framework for passive acoustic telemetry systems.
4. For flapper skate, the key finding is the prevalence of site affinity to the MPA. Vertical movements are shaped by depth-specific periodic behaviours and individual variation. These movements can be perturbed by angling, but on the whole skate appear to be behaviourally resilient to this practice.
5. Beyond flapper skate, this thesis highlights multifarious uses of electronic tagging and tracking data, brings underutilised analytical methods to the attention of the movement ecology community and establishes a holistic framework for movement modelling in passive acoustic telemetry systems. This work demonstrates the wide-ranging contributions of species-specific studies in the fields of movement ecology and conservation.
2022-11-29T00:00:00ZLavender, Edward1. Movement shapes the lives of animals and their interactions with human activities. In recent decades, the emergence of movement ecology as a discipline and developments in electronic tagging and tracking have led to substantial improvements in our understanding of animal movement and its implications for species conservation. Yet while research has burgeoned for many taxa, including sharks, other groups in aquatic ecosystems, such as skate (Rajidae), remain comparatively understudied.
2. The flapper skate (Dipturus intermedius) is a large, Critically Endangered elasmobranch. The species has been extirpated from much of its former range, but individuals are still found off west Scotland where the Loch Sunart to the Sound of Jura Marine Protected Area (MPA) has been designated for flapper skate conservation. However, skate movements within and around the MPA remain poorly understood.
3. This thesis investigates the movements of flapper skate in relation to the MPA using electronic tagging and tracking data from passive acoustic telemetry, archival (depth and temperature) tags and mark-recapture angling. Objectives include the examination of site affinity, vertical movements and responses to disturbance. Research in these areas motivates the development of a flexible, mechanistic modelling framework for passive acoustic telemetry systems.
4. For flapper skate, the key finding is the prevalence of site affinity to the MPA. Vertical movements are shaped by depth-specific periodic behaviours and individual variation. These movements can be perturbed by angling, but on the whole skate appear to be behaviourally resilient to this practice.
5. Beyond flapper skate, this thesis highlights multifarious uses of electronic tagging and tracking data, brings underutilised analytical methods to the attention of the movement ecology community and establishes a holistic framework for movement modelling in passive acoustic telemetry systems. This work demonstrates the wide-ranging contributions of species-specific studies in the fields of movement ecology and conservation.Social plasticity within and across generations : testing the role of plasticity in rapid evolution in field cricket Teleogryllus oceanicusSturiale, Samantha Leighhttps://hdl.handle.net/10023/254012022-05-19T02:03:38Z2021-06-30T00:00:00ZThe field of evolutionary biology lacks a full understanding of how phenotypic plasticity influences
adaptive evolution, despite over a century of research effort. One under-studied question within this topic
is whether plastic responses occurring within the lifetime of an individual (within-generational plasticity or
WGP) versus across generations (transgenerational plasticity or TGP) produce different evolutionary
outcomes. To understand how these two forms of plasticity interact, I investigated to what extent an
individual’s phenotype is shaped by its own social environment and the social environment experienced by
its mother using a field cricket model, Teleogryllus oceanicus. Crickets in the Hawaiian Islands are targeted
by acoustically orienting parasitoid flies, and a mutant form of silent male (‘flatwing’) recently invaded and
rapidly spread under this pressure. Some populations have undergone a full shift from all normal, singing
males to all flatwing, silent males, dramatically changing the social environment, and providing the
opportunity to explore the hypothesis that both WGP and TGP play a role in adaptive evolution following
abrupt environmental change. First, I explored what variation exists in the juvenile morphology and
behavior of individuals carrying normal-wing vs. flatwing genotypes, prior to maternal social manipulation.
At multiple juvenile stages, flatwing-carrying individuals exhibit greater locomotive activity than normalwing individuals, suggesting a co-evolved genetic response or the prior genetic coupling of locomotor
activity with flatwing variants. Second, I tested consequences of social plasticity for the fitness traits of
reproductive investment and mating behavior in adult females carrying the flatwing genotype, which might
permit them to adjust to the absence of song in their environment. This demonstrated that females
homozygous for flatwing raised in silence exhibit reduced body condition and reproductive investment
compared to those raised in song, as predicted. Mating behavior, in contrast, was not sensitive to social
environment in these females. Third, I tested whether maternal acoustic environment affects juvenile
offspring behavior and morphology, whether effects of maternal acoustic environment persist through
offspring development into adulthood, and how the adult social environment of offspring interacts with
transgenerational plasticity induced by their mothers’ social environment. Unexpectedly, adult, but not
juvenile, offspring of mothers raised in different social environments exhibit differences in several
ecologically relevant characteristics such as pronotum length, somatic condition, and reproductive
investment. Taken together, these results illustrate that genetic and plastic responses may jointly influence
the dynamics of rapid adaptive evolution. Further, when exploring the effects of plasticity in adaptive
evolution, it is important to consider how WGP and TGP may act simultaneously, and in a non-additive
nature, to influence an individual’s phenotype.
2021-06-30T00:00:00ZSturiale, Samantha LeighThe field of evolutionary biology lacks a full understanding of how phenotypic plasticity influences
adaptive evolution, despite over a century of research effort. One under-studied question within this topic
is whether plastic responses occurring within the lifetime of an individual (within-generational plasticity or
WGP) versus across generations (transgenerational plasticity or TGP) produce different evolutionary
outcomes. To understand how these two forms of plasticity interact, I investigated to what extent an
individual’s phenotype is shaped by its own social environment and the social environment experienced by
its mother using a field cricket model, Teleogryllus oceanicus. Crickets in the Hawaiian Islands are targeted
by acoustically orienting parasitoid flies, and a mutant form of silent male (‘flatwing’) recently invaded and
rapidly spread under this pressure. Some populations have undergone a full shift from all normal, singing
males to all flatwing, silent males, dramatically changing the social environment, and providing the
opportunity to explore the hypothesis that both WGP and TGP play a role in adaptive evolution following
abrupt environmental change. First, I explored what variation exists in the juvenile morphology and
behavior of individuals carrying normal-wing vs. flatwing genotypes, prior to maternal social manipulation.
At multiple juvenile stages, flatwing-carrying individuals exhibit greater locomotive activity than normalwing individuals, suggesting a co-evolved genetic response or the prior genetic coupling of locomotor
activity with flatwing variants. Second, I tested consequences of social plasticity for the fitness traits of
reproductive investment and mating behavior in adult females carrying the flatwing genotype, which might
permit them to adjust to the absence of song in their environment. This demonstrated that females
homozygous for flatwing raised in silence exhibit reduced body condition and reproductive investment
compared to those raised in song, as predicted. Mating behavior, in contrast, was not sensitive to social
environment in these females. Third, I tested whether maternal acoustic environment affects juvenile
offspring behavior and morphology, whether effects of maternal acoustic environment persist through
offspring development into adulthood, and how the adult social environment of offspring interacts with
transgenerational plasticity induced by their mothers’ social environment. Unexpectedly, adult, but not
juvenile, offspring of mothers raised in different social environments exhibit differences in several
ecologically relevant characteristics such as pronotum length, somatic condition, and reproductive
investment. Taken together, these results illustrate that genetic and plastic responses may jointly influence
the dynamics of rapid adaptive evolution. Further, when exploring the effects of plasticity in adaptive
evolution, it is important to consider how WGP and TGP may act simultaneously, and in a non-additive
nature, to influence an individual’s phenotype.Molecular mechanisms and functional consequences of chromatin binding by the human cytomegalovirus proteins IE1 and pUL83Deb, Anasuahttps://hdl.handle.net/10023/253992023-06-22T16:25:51Z2022-06-15T00:00:00ZInterferons (IFN) are an essential component of the vertebrate innate immune system against
viruses and other pathogens. Human Cytomegalovirus (HCMV), like other viruses, has
developed strategies to evade the host IFN response, enabling lifelong viral persistence in the
infected host. In this work, we explore how two HCMV proteins, immediate-early protein 1
(IE1), the first viral protein produced in infected cells, and pUL83, the most abundant protein
in the virus particle, counteract the host IFN response in the initial stages of infection by
interacting with chromatin.
First, we identified the molecular mechanism by which pUL83 interacts with host chromatin
using various techniques including fluorescence microscopy and in-vitro histone binding
studies. The Linker domain of pUL83 (amino acids 388-479) binds with the core histones for
this interaction. The Linker targets the nucleosome acidic patch formed by histones H2A-H2B
via residues R₄₅₃ and R₄₅₅. It also has distinct charged residue clusters that mediate binding to
all four core histones.
Nucleosome targeting by IE1 and pUL83 inhibits host IFN-β and IFN-λ production, enabling
HCMV to efficiently spread from the initial infected cell to its neighbouring cells, resulting in
the formation of larger and more foci of infection. Our results suggest that inhibition of IFN
induction by IE1-nucleosome interaction is unlikely due to changes in nucleosome occupancy,
but it may rather be attributable to inhibition of NFkB binding to the IFNB1 promoter.
Furthermore, we demonstrate that nucleosome binding by IE1 prevents DNA double strand
break repair by non-homologous end joining. Finally, we noticed that IE1-nucleosome
interaction limits HCMV reactivation in monocytic cells, allowing the virus to persist in a latent
state.
Overall, we propose that pUL83 and IE1 promote efficient viral spread by inhibiting IFN gene
induction via a novel chromatin-based molecular mechanism involving core histones.
2022-06-15T00:00:00ZDeb, AnasuaInterferons (IFN) are an essential component of the vertebrate innate immune system against
viruses and other pathogens. Human Cytomegalovirus (HCMV), like other viruses, has
developed strategies to evade the host IFN response, enabling lifelong viral persistence in the
infected host. In this work, we explore how two HCMV proteins, immediate-early protein 1
(IE1), the first viral protein produced in infected cells, and pUL83, the most abundant protein
in the virus particle, counteract the host IFN response in the initial stages of infection by
interacting with chromatin.
First, we identified the molecular mechanism by which pUL83 interacts with host chromatin
using various techniques including fluorescence microscopy and in-vitro histone binding
studies. The Linker domain of pUL83 (amino acids 388-479) binds with the core histones for
this interaction. The Linker targets the nucleosome acidic patch formed by histones H2A-H2B
via residues R₄₅₃ and R₄₅₅. It also has distinct charged residue clusters that mediate binding to
all four core histones.
Nucleosome targeting by IE1 and pUL83 inhibits host IFN-β and IFN-λ production, enabling
HCMV to efficiently spread from the initial infected cell to its neighbouring cells, resulting in
the formation of larger and more foci of infection. Our results suggest that inhibition of IFN
induction by IE1-nucleosome interaction is unlikely due to changes in nucleosome occupancy,
but it may rather be attributable to inhibition of NFkB binding to the IFNB1 promoter.
Furthermore, we demonstrate that nucleosome binding by IE1 prevents DNA double strand
break repair by non-homologous end joining. Finally, we noticed that IE1-nucleosome
interaction limits HCMV reactivation in monocytic cells, allowing the virus to persist in a latent
state.
Overall, we propose that pUL83 and IE1 promote efficient viral spread by inhibiting IFN gene
induction via a novel chromatin-based molecular mechanism involving core histones.An experimental investigation of the evolutionary dynamics of phenotypic plasticity under relaxed selection in threespine sticklebacks (Gasterosteus aculeatus)Spence-Jones, Helen Clarehttps://hdl.handle.net/10023/253812024-03-04T11:34:10Z2022-06-27T00:00:00ZHere I provide an overview of the ways in which phenotypic plasticity is suggested to be relevant to evolutionary dynamics, and examine the various predicted dynamics of plastic traits in novel environments. Following on from this, I use adaptive radiation of threespine stickleback (Gasterosteus aculeatus) into freshwater environments as a model system to examine the dynamics of multiple plastic traits under relaxed selection. I find that - as expected - overall survival plasticity appears to initially increase upon exposure to a novel environment before generally (but not always) decreasing under relaxed selection over time. My results suggest that morphological variation increases in the environments no longer experienced by daughter populations, implying that plasticity declines chiefly through accumulation of drifted cryptic genetic variation. From this I conclude that the plasticity of a trait may be relevant to its evolutionary dynamics (and those of the lineage) in novel environments - and that environment-dependent expression of alleles in rare environmental conditions may represent a limiting factor of adaptive phenotypic plasticity.
2022-06-27T00:00:00ZSpence-Jones, Helen ClareHere I provide an overview of the ways in which phenotypic plasticity is suggested to be relevant to evolutionary dynamics, and examine the various predicted dynamics of plastic traits in novel environments. Following on from this, I use adaptive radiation of threespine stickleback (Gasterosteus aculeatus) into freshwater environments as a model system to examine the dynamics of multiple plastic traits under relaxed selection. I find that - as expected - overall survival plasticity appears to initially increase upon exposure to a novel environment before generally (but not always) decreasing under relaxed selection over time. My results suggest that morphological variation increases in the environments no longer experienced by daughter populations, implying that plasticity declines chiefly through accumulation of drifted cryptic genetic variation. From this I conclude that the plasticity of a trait may be relevant to its evolutionary dynamics (and those of the lineage) in novel environments - and that environment-dependent expression of alleles in rare environmental conditions may represent a limiting factor of adaptive phenotypic plasticity.Structure and mechanism of two type III CRISPR defence nucleases activated by cyclic oligoadenylateZhu, Wenlonghttps://hdl.handle.net/10023/253492023-06-22T11:47:56Z2022-06-15T00:00:00ZProkaryotes have a wide range of antiviral strategies to defend against invading mobile genetic elements (MGEs). Type III CRISPR-Cas systems typically synthesise cyclic oligoadenylate (cOA) second messengers upon binding to cognate foreign RNA. These second messengers allosterically activate type III CRISPR ancillary proteins, potentiating a powerful immune response. Following the discovery of cOA signalling pathway, several ancillary proteins from Csx1/Csm6 family had been described. They sense cOA molecules with their CARF (CRISPR associated Rossman fold) domains and non-specifically cleave RNA with their effector domains. Here, we describe the structure and mechanism of two novel ancillary proteins Can1 and Can2. Can1 has a unique monomeric architecture that contains two CARF domains, a PD-(D/E)XK nuclease domain and a nuclease-like domain. It favours nicking scDNA in the presence of cyclic tetra-adenylate (cA₄) and metal ions. Can2 forms a canonical homodimer and each monomer contains a CARF domain and a PD-(D/E)XK nuclease domain. It exhibits both DNase and RNase activity in the presence of cA₄ and metal ions. It also provides effective immunity against plasmid and bacteriophage infection in a recombinant type III CRISPR-Cas system.
2022-06-15T00:00:00ZZhu, WenlongProkaryotes have a wide range of antiviral strategies to defend against invading mobile genetic elements (MGEs). Type III CRISPR-Cas systems typically synthesise cyclic oligoadenylate (cOA) second messengers upon binding to cognate foreign RNA. These second messengers allosterically activate type III CRISPR ancillary proteins, potentiating a powerful immune response. Following the discovery of cOA signalling pathway, several ancillary proteins from Csx1/Csm6 family had been described. They sense cOA molecules with their CARF (CRISPR associated Rossman fold) domains and non-specifically cleave RNA with their effector domains. Here, we describe the structure and mechanism of two novel ancillary proteins Can1 and Can2. Can1 has a unique monomeric architecture that contains two CARF domains, a PD-(D/E)XK nuclease domain and a nuclease-like domain. It favours nicking scDNA in the presence of cyclic tetra-adenylate (cA₄) and metal ions. Can2 forms a canonical homodimer and each monomer contains a CARF domain and a PD-(D/E)XK nuclease domain. It exhibits both DNase and RNase activity in the presence of cA₄ and metal ions. It also provides effective immunity against plasmid and bacteriophage infection in a recombinant type III CRISPR-Cas system.Exploring mixed-species grouping effects through antipredator mechanismsGu, Haohttps://hdl.handle.net/10023/252112023-06-22T08:52:34Z2022-06-15T00:00:00ZPredation is an important selective force for prey organisms, which have also developed different antipredator adaptions. Individuals of many animal species live in the group, which is generally believed to offer prey benefits from reduced predation risk and/or increased foraging efficiency. Different antipredator mechanisms of grouping prey have been well-developed theoretically and studied extensively for single species groups as compared to mixed-species groups. Yet, there has been a lack of understanding of how some antipredator mechanisms would be affected when applied to a mixed-species group due to additional effect of the within-group heterogeneity of prey.
This thesis explored the consequence of mixed-species grouping on the risk related to predation, with the intention to expand current understanding of the antipredator mechanisms for heterogeneous prey groups of multi-species or more broadly multi-phenotypes. Using artificial prey to simulate prey groups, the first several studies empirically examined how the prey group as a whole—varied in prey composition, group size, within-group position and compactness—would affect the ease of detection by free-living animals and/or ‘human predators’. The last study investigated grouping effects, especially the effect of the nearest associated species on individual’s vigilance and foraging in the aggregation of avian species feeding on a feeder.
Significant effects of group patterns on the detection risk of artificial prey groups were mostly found in experiments with ‘human predators’ rather than animal predators. Despite some contradictory findings between different predator-prey systems, these studies generally lent support to the idea consistent with the ‘giveaway cue’ hypothesis, where polymorphic population with prey of conspicuous morph may attract predations’ attention; and showed that the inclusion of conspicuous prey in mixed-species group would increase the detection risk of prey compared to some single species groups. Together, all the studies demonstrated the influence of mixed-species association on prey detection and/or predation risk.
2022-06-15T00:00:00ZGu, HaoPredation is an important selective force for prey organisms, which have also developed different antipredator adaptions. Individuals of many animal species live in the group, which is generally believed to offer prey benefits from reduced predation risk and/or increased foraging efficiency. Different antipredator mechanisms of grouping prey have been well-developed theoretically and studied extensively for single species groups as compared to mixed-species groups. Yet, there has been a lack of understanding of how some antipredator mechanisms would be affected when applied to a mixed-species group due to additional effect of the within-group heterogeneity of prey.
This thesis explored the consequence of mixed-species grouping on the risk related to predation, with the intention to expand current understanding of the antipredator mechanisms for heterogeneous prey groups of multi-species or more broadly multi-phenotypes. Using artificial prey to simulate prey groups, the first several studies empirically examined how the prey group as a whole—varied in prey composition, group size, within-group position and compactness—would affect the ease of detection by free-living animals and/or ‘human predators’. The last study investigated grouping effects, especially the effect of the nearest associated species on individual’s vigilance and foraging in the aggregation of avian species feeding on a feeder.
Significant effects of group patterns on the detection risk of artificial prey groups were mostly found in experiments with ‘human predators’ rather than animal predators. Despite some contradictory findings between different predator-prey systems, these studies generally lent support to the idea consistent with the ‘giveaway cue’ hypothesis, where polymorphic population with prey of conspicuous morph may attract predations’ attention; and showed that the inclusion of conspicuous prey in mixed-species group would increase the detection risk of prey compared to some single species groups. Together, all the studies demonstrated the influence of mixed-species association on prey detection and/or predation risk.Rhythmically repeated patterns of pulsed vocalizations in wild narwhals (Monodon monoceros)Walmsley, Samhttps://hdl.handle.net/10023/250912022-03-25T03:02:05Z2018-12-06T00:00:00ZSequences of vocalizations are indicative of communicative complexity. However, relative to
birds and terrestrial mammals, the extent to which marine mammals use vocal sequences is not
well understood. I provide the first investigation into vocal sequences in narwhals (Monodon
monoceros), a gregarious Arctic cetacean.
Eight female narwhals were fitted with animal-borne recording devices, resulting in one
of the largest datasets of narwhal acoustic behaviour to date. I used a combination of visual and
quantitative classification procedures to rigorously demonstrate stereotyped organizational
properties of subjectively defined sequence types. Next, acoustic characteristics were used to
generate coarse inferences regarding patterns of sequence use across individuals. Finally, I used
generalized linear models (GLMs) to assess the behavioural and acoustic contexts under which
sequences were produced.
I identified two types of sequences: “paired” patterns, consisting of combinations of two
stereotyped click-based calls, the pair of which were often repeated in rapid succession. While
these calls were rare, I found multiple subtypes that were predominantly associated with
recordings from specific tags. I secondly identified “burst pulse series”, temporally stereotyped
sets of short burst-pulses which themselves were combined into repetitive vocalization events. I
found few links between sequence use and behaviour, though burst-pulse series were more likely
to be produced in periods when other vocalizations were heard, suggesting possible use in social
contexts.
These findings extend the set of odontocetes which are known to use sequences of
vocalizations. Both sequence types show rhythmic repetition of lower-level patterns, suggestive
of hierarchical organizational principles. Furthermore, paired patterns constitute the first evidence
of multi-unit sequences in the family Monodontidae. I propose that further inquiry into vocal
sequences in narwhals and other understudied marine mammals is warranted.
2018-12-06T00:00:00ZWalmsley, SamSequences of vocalizations are indicative of communicative complexity. However, relative to
birds and terrestrial mammals, the extent to which marine mammals use vocal sequences is not
well understood. I provide the first investigation into vocal sequences in narwhals (Monodon
monoceros), a gregarious Arctic cetacean.
Eight female narwhals were fitted with animal-borne recording devices, resulting in one
of the largest datasets of narwhal acoustic behaviour to date. I used a combination of visual and
quantitative classification procedures to rigorously demonstrate stereotyped organizational
properties of subjectively defined sequence types. Next, acoustic characteristics were used to
generate coarse inferences regarding patterns of sequence use across individuals. Finally, I used
generalized linear models (GLMs) to assess the behavioural and acoustic contexts under which
sequences were produced.
I identified two types of sequences: “paired” patterns, consisting of combinations of two
stereotyped click-based calls, the pair of which were often repeated in rapid succession. While
these calls were rare, I found multiple subtypes that were predominantly associated with
recordings from specific tags. I secondly identified “burst pulse series”, temporally stereotyped
sets of short burst-pulses which themselves were combined into repetitive vocalization events. I
found few links between sequence use and behaviour, though burst-pulse series were more likely
to be produced in periods when other vocalizations were heard, suggesting possible use in social
contexts.
These findings extend the set of odontocetes which are known to use sequences of
vocalizations. Both sequence types show rhythmic repetition of lower-level patterns, suggestive
of hierarchical organizational principles. Furthermore, paired patterns constitute the first evidence
of multi-unit sequences in the family Monodontidae. I propose that further inquiry into vocal
sequences in narwhals and other understudied marine mammals is warranted.Social behaviour and learning in archerfishJones, Nicholas Andrew Roderickhttps://hdl.handle.net/10023/241132022-05-16T13:34:41Z2021-06-30T00:00:00ZLearning is crucial to making behavioural adjustments and fish are adept at using the behaviour of others to more easily find and discriminate between different sources of food, recognise novel predators and other challenges for life in a dynamic environment. This social learning is a powerful process known to impact the success and survival of all animals, humans and non-human animals alike. Yet we understand little about the processes that underpin social learning, and the taxonomic breadth of various mechanisms through which animals can learn from others. Archerfish represent an interesting species to test social learning as there is some evidence to suggest they may be capable of social learning through imitation, currently considered taxonomically restricted and not shown for fish. They are also, unlike most species used in studies of social learning, not highly social: if proven capable of social learning they would afford opportunities to compare social learning species with different levels of sociality. In this thesis I present the first studies exploring archerfish as candidate species for social learning and explore some of the factors that may affect learning performance in experimental conditions. I found that archerfish are sensitive to the presence of conspecifics: increasing their latency to shoot and frequency of orientation prior to shooting. I also found that archerfish display consistent inter-individual differences in latency to shoot and these differences relate to differences in learning speed and discrimination success. Fish with low latencies to shoot learn to shoot novel rewards faster, but fish with higher latencies to shoot achieve greater discrimination success. Despite this sensitivity to others, there was no obvious effect of social presence on learning rates. Finally, I present the results of an initial study of their social foraging dynamics – groups of fish show consistent foraging orders where specific individuals within the group where individuals could be ranked from most to least likely to perform a foraging behaviour when first presented with a prey. Individuals show consistent differences in proportion of foraging activity across successive foraging opportunities - a form of temporal resource partitioning. These results increase our understanding of the behaviour and, by highlighting factors that can may impact their learning, will hopefully be useful in designing further studies of social learning in this unique fish species.
2021-06-30T00:00:00ZJones, Nicholas Andrew RoderickLearning is crucial to making behavioural adjustments and fish are adept at using the behaviour of others to more easily find and discriminate between different sources of food, recognise novel predators and other challenges for life in a dynamic environment. This social learning is a powerful process known to impact the success and survival of all animals, humans and non-human animals alike. Yet we understand little about the processes that underpin social learning, and the taxonomic breadth of various mechanisms through which animals can learn from others. Archerfish represent an interesting species to test social learning as there is some evidence to suggest they may be capable of social learning through imitation, currently considered taxonomically restricted and not shown for fish. They are also, unlike most species used in studies of social learning, not highly social: if proven capable of social learning they would afford opportunities to compare social learning species with different levels of sociality. In this thesis I present the first studies exploring archerfish as candidate species for social learning and explore some of the factors that may affect learning performance in experimental conditions. I found that archerfish are sensitive to the presence of conspecifics: increasing their latency to shoot and frequency of orientation prior to shooting. I also found that archerfish display consistent inter-individual differences in latency to shoot and these differences relate to differences in learning speed and discrimination success. Fish with low latencies to shoot learn to shoot novel rewards faster, but fish with higher latencies to shoot achieve greater discrimination success. Despite this sensitivity to others, there was no obvious effect of social presence on learning rates. Finally, I present the results of an initial study of their social foraging dynamics – groups of fish show consistent foraging orders where specific individuals within the group where individuals could be ranked from most to least likely to perform a foraging behaviour when first presented with a prey. Individuals show consistent differences in proportion of foraging activity across successive foraging opportunities - a form of temporal resource partitioning. These results increase our understanding of the behaviour and, by highlighting factors that can may impact their learning, will hopefully be useful in designing further studies of social learning in this unique fish species.The genomic signature of extremely rapid adaptive evolution in Hawaiian cricketsZhang, Xiaohttps://hdl.handle.net/10023/238962021-09-03T13:28:19Z2021-12-01T00:00:00Z2021-12-01T00:00:00ZZhang, XiaoFantastic feasts and where to find them : using biologging to investigate foraging behaviour of marine megafauna across a range of spatiotemporal scalesVance, Heather Margarethttps://hdl.handle.net/10023/238352021-08-25T11:30:31Z2021-12-01T00:00:00ZUnderstanding the strategies animals use to locate, select, and capture prey can guide more robust conservation efforts. In marine megafauna, foraging is often inferred from infrequent surface positions using biotelemetry tags. In this thesis I argue that finer-scale measurements of predator movements, prey availability and behaviour are critical to understanding foraging decisions. To explore this I used multi-sensor, high-resolution biologging tags on three megafauna species and compared optimal foraging predictions to actual behaviour over a hierarchy of spatiotemporal scales. At the landscape scale, I studied a central-place forager, the harbour seal, which accesses distant and nearshore prey although the relative importance of these resources is poorly understood. I found that prey encounter rates were similar for the two resources but while prey were distributed extensively offshore, inshore foraging was concentrated in just a few discrete patches. I suggest that the trade-off between accessibility and conspecific competition may influence site selection. At the patch scale, I studied a bulk-filter feeder, whale sharks, which are presumed to be highly-selective to offset the energetic cost of this strategy. Using novel sonar tags to record fine-scale behaviour and prey densities, I found that sharks did not selectively harvest rare dense patches. Instead, a less-selective strategy with continual-patch assessment may be advantageous when prey density is highly heterogenous. At the scale of prey captures, I studied the sensory and locomotor responses of an echolocating predator to evasive prey. Results revealed rapid responses to prey movements which scale with the acceleration of prey, enabling this energetically constrained mammal to reliably capture high-energy prey. Within each study, detailed biologging measurements were critical to understanding factors influencing foraging choices and capabilities. Such data help define the plasticity with which predators can respond to changing prey distribution, density, and performance, and provide critical insights to focus effective conservation actions.
2021-12-01T00:00:00ZVance, Heather MargaretUnderstanding the strategies animals use to locate, select, and capture prey can guide more robust conservation efforts. In marine megafauna, foraging is often inferred from infrequent surface positions using biotelemetry tags. In this thesis I argue that finer-scale measurements of predator movements, prey availability and behaviour are critical to understanding foraging decisions. To explore this I used multi-sensor, high-resolution biologging tags on three megafauna species and compared optimal foraging predictions to actual behaviour over a hierarchy of spatiotemporal scales. At the landscape scale, I studied a central-place forager, the harbour seal, which accesses distant and nearshore prey although the relative importance of these resources is poorly understood. I found that prey encounter rates were similar for the two resources but while prey were distributed extensively offshore, inshore foraging was concentrated in just a few discrete patches. I suggest that the trade-off between accessibility and conspecific competition may influence site selection. At the patch scale, I studied a bulk-filter feeder, whale sharks, which are presumed to be highly-selective to offset the energetic cost of this strategy. Using novel sonar tags to record fine-scale behaviour and prey densities, I found that sharks did not selectively harvest rare dense patches. Instead, a less-selective strategy with continual-patch assessment may be advantageous when prey density is highly heterogenous. At the scale of prey captures, I studied the sensory and locomotor responses of an echolocating predator to evasive prey. Results revealed rapid responses to prey movements which scale with the acceleration of prey, enabling this energetically constrained mammal to reliably capture high-energy prey. Within each study, detailed biologging measurements were critical to understanding factors influencing foraging choices and capabilities. Such data help define the plasticity with which predators can respond to changing prey distribution, density, and performance, and provide critical insights to focus effective conservation actions.Statistics, machine learning and deep learning for population genetic inferenceQin, Xinghuhttps://hdl.handle.net/10023/236652021-08-09T12:05:52Z2021-06-30T00:00:00ZDeciphering the evolutionary changes from raw DNA data effectively without the loss of intrinsic information has been the fundamental and core work in population genetics. However, some statistical challenges still restrict the inferential performance in population genetics, for example, the undue emphasis on rare or common alleles measured by different statistics, the ubiquitous multimodal genetic structure within populations, and complex genotype-by-environment associations. In this thesis, I propose to integrate the information-based statistics with machine learning approaches to address these problems and challenges for population genetic inference. First, I evaluated the performance of the information-based summary statistics for spatial demography inference. I showed that the summary statistics based on Shannon differentiation and the transformed diversity of order q=1 had higher power to discriminate spatially-structured scenarios than the traditional allelic richness and heterozygosity-based summary statistics. This provides guidelines for using summary statistics to make inference of spatial demography and for developing new statistical methods to detect signatures of evolutionary changes. Second, I proposed to use Kernel Local Fisher Discriminant Analysis of Principal Components (KLFDAPC) for population genetic structure inference considering the nonlinear and multimodal genetic information between individuals. KLFDAPC outperformed both PCA and DAPC in discriminatory power and in predicting individual geographic origin. KLFDAPC is useful for geographic ancestry inference and correction of population stratification in GWAS. Finally, I proposed a deep learning-based approach (DeepGenomeScan) to detect signals of selection. DeepGenomeScan had higher power than the commonly used machine learning approaches such as pcadapt and RDA in identifying signatures of selection. Furthermore, DeepGenomeScan can be extended to implement various genome-wide association studies (GWAS, TWAS, PWAS, and MWAS) by performing a systematic scanning on genome-wide variants to detect the genetic variations responsible for complex traits or involved in adaptation. In summary, this dissertation addresses several foundational questions in statistics-based and machine learning-based inference, contributing several the-state-of-the-art statistical tools for population genetic inference.
2021-06-30T00:00:00ZQin, XinghuDeciphering the evolutionary changes from raw DNA data effectively without the loss of intrinsic information has been the fundamental and core work in population genetics. However, some statistical challenges still restrict the inferential performance in population genetics, for example, the undue emphasis on rare or common alleles measured by different statistics, the ubiquitous multimodal genetic structure within populations, and complex genotype-by-environment associations. In this thesis, I propose to integrate the information-based statistics with machine learning approaches to address these problems and challenges for population genetic inference. First, I evaluated the performance of the information-based summary statistics for spatial demography inference. I showed that the summary statistics based on Shannon differentiation and the transformed diversity of order q=1 had higher power to discriminate spatially-structured scenarios than the traditional allelic richness and heterozygosity-based summary statistics. This provides guidelines for using summary statistics to make inference of spatial demography and for developing new statistical methods to detect signatures of evolutionary changes. Second, I proposed to use Kernel Local Fisher Discriminant Analysis of Principal Components (KLFDAPC) for population genetic structure inference considering the nonlinear and multimodal genetic information between individuals. KLFDAPC outperformed both PCA and DAPC in discriminatory power and in predicting individual geographic origin. KLFDAPC is useful for geographic ancestry inference and correction of population stratification in GWAS. Finally, I proposed a deep learning-based approach (DeepGenomeScan) to detect signals of selection. DeepGenomeScan had higher power than the commonly used machine learning approaches such as pcadapt and RDA in identifying signatures of selection. Furthermore, DeepGenomeScan can be extended to implement various genome-wide association studies (GWAS, TWAS, PWAS, and MWAS) by performing a systematic scanning on genome-wide variants to detect the genetic variations responsible for complex traits or involved in adaptation. In summary, this dissertation addresses several foundational questions in statistics-based and machine learning-based inference, contributing several the-state-of-the-art statistical tools for population genetic inference.The investigation into protein Willin/FRMD6 in neuronal polarization and associated molecular mechanismsYu, Wanjiahttps://hdl.handle.net/10023/235302021-07-21T14:54:26Z2021-06-30T00:00:00ZNeuronal polarization is defined as the biological process where neurons obtain their molecular, morphological, and functional asymmetries between dendritic and axonal compartments. Establishing neuronal polarity, especially the growth of the axon, is of fundamental importance. By utilising a range of optical imaging methods, this thesis investigates how Willin, a cell architecture regulatory Hippo signalling component, might affect the polarization process of neuronal cells.
By creating different levels of Willin expression in neuronal cells using molecular gene-editing, specifically in the HT-22 cell line, it was observed that the modification of Willin expression levels changed the number and length of axons as observed under conventional fluorescent microscopes. As the cell cytoskeleton dynamics greatly shape how neuronal cells adapt to a new morphology, the organization of the F-actin filaments was examined at the sub-diffraction level (<200 nm) by applying a super-resolution 3D-Structured Illumination Microscope. Additionally, modifications of Willin expression led to the cytoskeleton becoming more mobile, a loss of the actin cortex, and the formation of irregular actin protrusions at the cell membrane of HT-22 cells, as well as changes in cell proliferation, migration, and adhesion of SHSY-5Y cells. Lastly, by applying an all-optical calcium imaging technique, OptoCaMP imaging, it was shown that changing Willin expression levels can affect the activity of rat cortical neurons. Surprisingly, the reduction of Willin expression in mouse cortical neurons caused axon disintegration and impaired neuronal health, supporting the notion that Willin might regulate the growth and integrity of the axonal compartment. What is more, the biochemical analysis suggested that the above changes might be independent of the PI3K/aPKC signalling pathway but relies on the Hippo signalling pathway; however, in a cell type specific manner.
Collectively, the evidence presented in this thesis supports the involvement of Willin in various neuronal behaviours, specifically in neuronal polarization, and therefore opens a new and promising area for future studies involved in understanding the roles of Willin in the central nervous system.
2021-06-30T00:00:00ZYu, WanjiaNeuronal polarization is defined as the biological process where neurons obtain their molecular, morphological, and functional asymmetries between dendritic and axonal compartments. Establishing neuronal polarity, especially the growth of the axon, is of fundamental importance. By utilising a range of optical imaging methods, this thesis investigates how Willin, a cell architecture regulatory Hippo signalling component, might affect the polarization process of neuronal cells.
By creating different levels of Willin expression in neuronal cells using molecular gene-editing, specifically in the HT-22 cell line, it was observed that the modification of Willin expression levels changed the number and length of axons as observed under conventional fluorescent microscopes. As the cell cytoskeleton dynamics greatly shape how neuronal cells adapt to a new morphology, the organization of the F-actin filaments was examined at the sub-diffraction level (<200 nm) by applying a super-resolution 3D-Structured Illumination Microscope. Additionally, modifications of Willin expression led to the cytoskeleton becoming more mobile, a loss of the actin cortex, and the formation of irregular actin protrusions at the cell membrane of HT-22 cells, as well as changes in cell proliferation, migration, and adhesion of SHSY-5Y cells. Lastly, by applying an all-optical calcium imaging technique, OptoCaMP imaging, it was shown that changing Willin expression levels can affect the activity of rat cortical neurons. Surprisingly, the reduction of Willin expression in mouse cortical neurons caused axon disintegration and impaired neuronal health, supporting the notion that Willin might regulate the growth and integrity of the axonal compartment. What is more, the biochemical analysis suggested that the above changes might be independent of the PI3K/aPKC signalling pathway but relies on the Hippo signalling pathway; however, in a cell type specific manner.
Collectively, the evidence presented in this thesis supports the involvement of Willin in various neuronal behaviours, specifically in neuronal polarization, and therefore opens a new and promising area for future studies involved in understanding the roles of Willin in the central nervous system.Harbour seals (Phoca vitulina) in a tidal stream environment : movement ecology and the effects of a renewable energy installationOnoufriou, Josephhttps://hdl.handle.net/10023/234472022-09-22T13:49:22Z2020-07-29T00:00:00ZDespite ever increasing information on the importance of oceanographic processes for marine predators, movement ecology of higher trophic level species in tidal stream environments remains relatively under-studied. This represents a significant knowledge gap for certain species which spend large portions of their lives in these energetic habitats. In this thesis I show that a top predator, the harbour seal (Phoca vitulina), inhabiting one of the most tidally energetic regions in Europe, the Pentland Firth, shows a complex range of behaviours as a consequence of the strong current flows they are subjected to. Both horizontal movement and diving behaviour elucidate a degree of foraging plasticity, hitherto undocumented in a single population of harbour seals. I also demonstrate that, by using multiple perspectives of movement, researchers can better tease apart ecologically important areas for animals inhabiting these habitats. Given the importance of tidally energetic systems for harbour seals, I then go on to study the impact of tidal energy installations on their movements and physical fitness. Using telemetry data, I determine an overt avoidance response of the local population to an operational turbine array and demonstrate the effect this can have on our understanding of collision risk. To further augment our predictions of the population level effect of these devices, I then go on to demonstrate that not all collisions between seals and tidal turbine blades are likely to result in fatality. In combination, these results suggest that currently held views on the lethal effects of tidal turbines are overly-conservative, and the likely behavioural and physical responses to these devices may result in a more ecologically favourable outcome than previously assumed.
2020-07-29T00:00:00ZOnoufriou, JosephDespite ever increasing information on the importance of oceanographic processes for marine predators, movement ecology of higher trophic level species in tidal stream environments remains relatively under-studied. This represents a significant knowledge gap for certain species which spend large portions of their lives in these energetic habitats. In this thesis I show that a top predator, the harbour seal (Phoca vitulina), inhabiting one of the most tidally energetic regions in Europe, the Pentland Firth, shows a complex range of behaviours as a consequence of the strong current flows they are subjected to. Both horizontal movement and diving behaviour elucidate a degree of foraging plasticity, hitherto undocumented in a single population of harbour seals. I also demonstrate that, by using multiple perspectives of movement, researchers can better tease apart ecologically important areas for animals inhabiting these habitats. Given the importance of tidally energetic systems for harbour seals, I then go on to study the impact of tidal energy installations on their movements and physical fitness. Using telemetry data, I determine an overt avoidance response of the local population to an operational turbine array and demonstrate the effect this can have on our understanding of collision risk. To further augment our predictions of the population level effect of these devices, I then go on to demonstrate that not all collisions between seals and tidal turbine blades are likely to result in fatality. In combination, these results suggest that currently held views on the lethal effects of tidal turbines are overly-conservative, and the likely behavioural and physical responses to these devices may result in a more ecologically favourable outcome than previously assumed.The foraging behaviour and body condition of northern bottlenose whales (Hyperoodon ampullatus)Siegal, Eilidhhttps://hdl.handle.net/10023/230232023-06-12T14:34:50Z2020-12-01T00:00:00ZDespite foraging being critical for survival, characterising foraging behaviour in marine animals is inherently challenging. Found in deep offshore habitats, beaked whales are the least known cetacean family, whose foraging behaviour (besides echolocation) remains poorly understood. This thesis provides insights into the foraging behaviour of northern bottlenose whales, a data-deficient species of beaked whale with an uncertain conservation status. Fine-scale sound- and movement-recording tags were deployed on the little-known north-eastern Atlantic population. Using echolocation buzzes as a proxy for prey-capture attempts, Chapter Two characterises prey-capture kinematics. Buzz-associated movements consisted of dynamic translational and rotational motions, and complex rolling manoeuvres. Building on this knowledge, Chapter Three develops a method of detecting prey-capture attempts using accelerometer data. Concordance with rolling behaviour demonstrated that rapid changes in acceleration (jerk) successfully predicted foraging buzzes, paving the way for detecting foraging behaviour over longer time-scales. The starvation-predation trade-off and condition-dependent risk-taking concepts are cornerstones of foraging theory, but little explored in marine top predators. Chapter Four shows that the whales exchanged foraging effort for predator-avoidance behaviour; however, contrary to theoretical predictions, individuals in poorer body condition foraged less and had higher levels of predator-avoidance behaviour, which suggests that body condition was a consequence rather than driver of behaviour for the animals sampled in this study. Chapter Five reveals that northern bottlenose whales at two sites (the Gully and Jan Mayen in the western and eastern North Atlantic respectively) varied substantially in foraging depths and time budgets, possibly reflecting differences in prey availability and interspecific competition. Although this thesis provides an understanding of the foraging behaviour and ecology of a little-known whale species, the methods developed (e.g. for determining prey-capture kinematics) and the knowledge revealed (e.g. how body condition relates to behavioural trade-offs) are applicable and relevant to both marine and terrestrial animals.
2020-12-01T00:00:00ZSiegal, EilidhDespite foraging being critical for survival, characterising foraging behaviour in marine animals is inherently challenging. Found in deep offshore habitats, beaked whales are the least known cetacean family, whose foraging behaviour (besides echolocation) remains poorly understood. This thesis provides insights into the foraging behaviour of northern bottlenose whales, a data-deficient species of beaked whale with an uncertain conservation status. Fine-scale sound- and movement-recording tags were deployed on the little-known north-eastern Atlantic population. Using echolocation buzzes as a proxy for prey-capture attempts, Chapter Two characterises prey-capture kinematics. Buzz-associated movements consisted of dynamic translational and rotational motions, and complex rolling manoeuvres. Building on this knowledge, Chapter Three develops a method of detecting prey-capture attempts using accelerometer data. Concordance with rolling behaviour demonstrated that rapid changes in acceleration (jerk) successfully predicted foraging buzzes, paving the way for detecting foraging behaviour over longer time-scales. The starvation-predation trade-off and condition-dependent risk-taking concepts are cornerstones of foraging theory, but little explored in marine top predators. Chapter Four shows that the whales exchanged foraging effort for predator-avoidance behaviour; however, contrary to theoretical predictions, individuals in poorer body condition foraged less and had higher levels of predator-avoidance behaviour, which suggests that body condition was a consequence rather than driver of behaviour for the animals sampled in this study. Chapter Five reveals that northern bottlenose whales at two sites (the Gully and Jan Mayen in the western and eastern North Atlantic respectively) varied substantially in foraging depths and time budgets, possibly reflecting differences in prey availability and interspecific competition. Although this thesis provides an understanding of the foraging behaviour and ecology of a little-known whale species, the methods developed (e.g. for determining prey-capture kinematics) and the knowledge revealed (e.g. how body condition relates to behavioural trade-offs) are applicable and relevant to both marine and terrestrial animals.Nuclear phenomena in the life-history of Sphacelaria britannica sauv.Jackson, David Charleshttps://hdl.handle.net/10023/220412022-04-28T08:55:27Z1967-01-01T00:00:00Z1967-01-01T00:00:00ZJackson, David CharlesRole of hnRNP A1 in NF-κB transcriptional activationHay, David Colinhttps://hdl.handle.net/10023/220382022-04-21T08:27:43Z2000-01-01T00:00:00ZThe correct temporal and spatial expression of genetic material governs the phenotypic differences that characterise the multitude of cells observed in higher eukaryotic organisms. Gene expression is controlled at many levels. For most genes the primary control point is the regulation of transcriptional initiation.
NF-κB is a ubiquitously expressed transcription factor that is retained cytoplasmically in an inactive form by the inhibitor protein IκBα. Following cell stimulation, by a variety of different inducers including UV irradiation, cytokines and bacterial or viral products, IκBα is degraded. Active NF-κB then translocates to the nucleus where it activates transcription in a protein synthesis independent manner. To identify proteins involved in the activity of the transcription factor NF-κB, proteins bound to the IκBα inhibitor were isolated by immuno affinity chromatography. The data clearly demonstrated the association of IκBα with both forms of hnRNP A1 in vivo. In vitro experiments with bacterially produced recombinant proteins indicated that the interaction between hnRNPAl and IκBα was direct and was not mediated by a bridging protein present in the human cell extracts. Gel electrophoresis DNA binding experiments indicated that the ability of IkBcc to inhibit the DNA binding activity of NF-κB p65 was not influenced by hnRNP Al. Sites of interaction between hnRNP Al and IκBα were determined by deletion analysis and revealed that the acidic carboxy terminus of IkBcx (residues 265-303) was the minimal region required for binding to hnRNP Al. A single RNA binding domain linked to part of the RGG box (residues 95-207) was the minimal region of hnRNP Al required for interaction with IκBα. Immunofluoresence experiments demonstrated that hnRNPAl, in response to actinomycin D treatment, partially delocalises from the nucleus to the cytoplasm. Under these conditions IκBα wt also delocalised from the nucleus to the cytoplasm although the carboxy terminally truncated form of IκBα was not delocalised in response to actinomycin D treatment . Functional consequences of the interaction between IκBα and hnRNPAl were investigated in vivo using a mouse erythroleukaemia cell line (CB3) which lacks endogenous hnRNPAl (Ben-David et al., 1992). Cells lacking hnRNP A1 are defective in NF-κB dependent transcriptional activation but the defect in these cells is restored by ectopic expression of hnRNP Al. Thus in addition to regulating mRNA processing and transport, hnRNP Al may also contribute to the control of NF-κB dependent transcription.
2000-01-01T00:00:00ZHay, David ColinThe correct temporal and spatial expression of genetic material governs the phenotypic differences that characterise the multitude of cells observed in higher eukaryotic organisms. Gene expression is controlled at many levels. For most genes the primary control point is the regulation of transcriptional initiation.
NF-κB is a ubiquitously expressed transcription factor that is retained cytoplasmically in an inactive form by the inhibitor protein IκBα. Following cell stimulation, by a variety of different inducers including UV irradiation, cytokines and bacterial or viral products, IκBα is degraded. Active NF-κB then translocates to the nucleus where it activates transcription in a protein synthesis independent manner. To identify proteins involved in the activity of the transcription factor NF-κB, proteins bound to the IκBα inhibitor were isolated by immuno affinity chromatography. The data clearly demonstrated the association of IκBα with both forms of hnRNP A1 in vivo. In vitro experiments with bacterially produced recombinant proteins indicated that the interaction between hnRNPAl and IκBα was direct and was not mediated by a bridging protein present in the human cell extracts. Gel electrophoresis DNA binding experiments indicated that the ability of IkBcc to inhibit the DNA binding activity of NF-κB p65 was not influenced by hnRNP Al. Sites of interaction between hnRNP Al and IκBα were determined by deletion analysis and revealed that the acidic carboxy terminus of IkBcx (residues 265-303) was the minimal region required for binding to hnRNP Al. A single RNA binding domain linked to part of the RGG box (residues 95-207) was the minimal region of hnRNP Al required for interaction with IκBα. Immunofluoresence experiments demonstrated that hnRNPAl, in response to actinomycin D treatment, partially delocalises from the nucleus to the cytoplasm. Under these conditions IκBα wt also delocalised from the nucleus to the cytoplasm although the carboxy terminally truncated form of IκBα was not delocalised in response to actinomycin D treatment . Functional consequences of the interaction between IκBα and hnRNPAl were investigated in vivo using a mouse erythroleukaemia cell line (CB3) which lacks endogenous hnRNPAl (Ben-David et al., 1992). Cells lacking hnRNP A1 are defective in NF-κB dependent transcriptional activation but the defect in these cells is restored by ectopic expression of hnRNP Al. Thus in addition to regulating mRNA processing and transport, hnRNP Al may also contribute to the control of NF-κB dependent transcription.Computer graphic manipulations in the study of face perceptionsBurt, David Michaelhttps://hdl.handle.net/10023/220332022-04-15T09:41:22Z2002-01-01T00:00:00ZThe face is of unparalleled importance in communication, containing cues used not only in identity recognition but, also for the assessment of character, mood, health and attractiveness. Computer graphic image (CGI) manipulation has enabled the effects of facial cues on perception to be studied from cognitive neuroscience and evolutionary psychology perspectives. A set of studies employing novel computer graphic methods to investigate facial expression, symmetry and dynamic cues related to taste is presented in six experimental chapters (2-7). In Chapter 2 novel photo-realistic stimuli are employed to study the perceptual lateralization of facial cues for perceptions of age, gender, attractiveness, expression and lip-reading. Results suggest a right hemisphere lateralization for all perceptions except lip-reading, which appears left lateralized. Previous studies with photographic and CGI manipulations have implied that humans unlike other animals prefer asymmetry in attractiveness judgements. In Chapter 3, new, more appropriate, CGI techniques were applied to investigate facial symmetry preference. In a series of experiments humans were found to judge more symmetrical faces as more attractive and possible individuals differences in symmetry preference strength were investigated. CGI techniques have enabled consistent qualities related to attractiveness and age to be captured from groups of face images and subsequently manipulated. In Chapter 4, these techniques are applied to capture and manipulate qualities associated with perceived skin health. Chapter 5 represents a foray into dynamic cues related to food consumption using video. Possible facial cues to the strength, taste and the hedonic value of flavours that an observed individual was consuming were investigated. Chapter 6 presents a novel test investigating individual differences in the percept of neutral expression. To illustrate the test: when asked to make faces expressively neutral, depressed individuals chose higher levels anger and disgust compared to controls. The test used novel 'anti-face' expression stimuli. These were later used in Chapter 7 to investigate a recent finding that adaptation to the anti-faces of individuals (faces with the opposite characteristics to a particular individual), facilitated recognition of subsequently presented corresponding individuals. The presence of analogous effects for emotional expressions was found. This effect appears to be robust to changes in individual identity, pattern masking and delays of up to a second between the adaptation and test stimuli. Overall the thesis demonstrates the use of CGI manipulation in testing hypotheses from a variety of areas within face perception and presents a number of novel techniques that may be useful in future face perception research.
2002-01-01T00:00:00ZBurt, David MichaelThe face is of unparalleled importance in communication, containing cues used not only in identity recognition but, also for the assessment of character, mood, health and attractiveness. Computer graphic image (CGI) manipulation has enabled the effects of facial cues on perception to be studied from cognitive neuroscience and evolutionary psychology perspectives. A set of studies employing novel computer graphic methods to investigate facial expression, symmetry and dynamic cues related to taste is presented in six experimental chapters (2-7). In Chapter 2 novel photo-realistic stimuli are employed to study the perceptual lateralization of facial cues for perceptions of age, gender, attractiveness, expression and lip-reading. Results suggest a right hemisphere lateralization for all perceptions except lip-reading, which appears left lateralized. Previous studies with photographic and CGI manipulations have implied that humans unlike other animals prefer asymmetry in attractiveness judgements. In Chapter 3, new, more appropriate, CGI techniques were applied to investigate facial symmetry preference. In a series of experiments humans were found to judge more symmetrical faces as more attractive and possible individuals differences in symmetry preference strength were investigated. CGI techniques have enabled consistent qualities related to attractiveness and age to be captured from groups of face images and subsequently manipulated. In Chapter 4, these techniques are applied to capture and manipulate qualities associated with perceived skin health. Chapter 5 represents a foray into dynamic cues related to food consumption using video. Possible facial cues to the strength, taste and the hedonic value of flavours that an observed individual was consuming were investigated. Chapter 6 presents a novel test investigating individual differences in the percept of neutral expression. To illustrate the test: when asked to make faces expressively neutral, depressed individuals chose higher levels anger and disgust compared to controls. The test used novel 'anti-face' expression stimuli. These were later used in Chapter 7 to investigate a recent finding that adaptation to the anti-faces of individuals (faces with the opposite characteristics to a particular individual), facilitated recognition of subsequently presented corresponding individuals. The presence of analogous effects for emotional expressions was found. This effect appears to be robust to changes in individual identity, pattern masking and delays of up to a second between the adaptation and test stimuli. Overall the thesis demonstrates the use of CGI manipulation in testing hypotheses from a variety of areas within face perception and presents a number of novel techniques that may be useful in future face perception research.Studies on the antigenic determinants of paramyxovirusesYoung, Danhttps://hdl.handle.net/10023/220252022-04-13T14:35:52Z1991-01-01T00:00:00ZMonoclonal antibodies (MAbs) were produced to study the antigenic relationships between SV5, PIV-2 and other paramyxoviruses, these MAbs had specificities for the HN, F, M, NP and P-proteins of SV5 and for the HN, NP and P-proteins of PIV-2. A minority of these MAbs reacted with Western blotted virus polypeptides. All anti-HN and anti-F MAbs neutralized virus infectivity. At least 4 and 3 antigenic sites were demonstrated on the HN-proteins of SV5 and PIV-2 respectively. Immunofluorescence revealed different patterns and distributions of virus proteins between SV5 and PIV-2. The majority (55 out of 60) of MAbs were specific for the virus against which they were raised, the minority that did cross-react between SV5 and PIV-2 had specificities for the M, NP and P-proteins and one of these MAbs, with specificity for the P-protein, also showed cross reaction with mumps virus. In contrast only minor differences were detected between canine, human and simian isolates of SV5. None of the MAbs showed cross-reactivity between the HN-proteins of SV5 and PIV-2 but, polyclonal sera raised against purified preparations of these proteins did show limited cross-reactivity. Anti-SV5 and anti-PIV-2 antibodies, in the same human sera, were shown to be a mixture of specific and cross-reacting species of antibody.
1991-01-01T00:00:00ZYoung, DanMonoclonal antibodies (MAbs) were produced to study the antigenic relationships between SV5, PIV-2 and other paramyxoviruses, these MAbs had specificities for the HN, F, M, NP and P-proteins of SV5 and for the HN, NP and P-proteins of PIV-2. A minority of these MAbs reacted with Western blotted virus polypeptides. All anti-HN and anti-F MAbs neutralized virus infectivity. At least 4 and 3 antigenic sites were demonstrated on the HN-proteins of SV5 and PIV-2 respectively. Immunofluorescence revealed different patterns and distributions of virus proteins between SV5 and PIV-2. The majority (55 out of 60) of MAbs were specific for the virus against which they were raised, the minority that did cross-react between SV5 and PIV-2 had specificities for the M, NP and P-proteins and one of these MAbs, with specificity for the P-protein, also showed cross reaction with mumps virus. In contrast only minor differences were detected between canine, human and simian isolates of SV5. None of the MAbs showed cross-reactivity between the HN-proteins of SV5 and PIV-2 but, polyclonal sera raised against purified preparations of these proteins did show limited cross-reactivity. Anti-SV5 and anti-PIV-2 antibodies, in the same human sera, were shown to be a mixture of specific and cross-reacting species of antibody.Water quality functioning of an upland reservoir and its catchment area : with particular emphasis on iron and manganeseAbesser, Corinnahttps://hdl.handle.net/10023/220132022-04-04T08:45:47Z2003-01-01T00:00:00ZWater quality problems associated with high iron and manganese concentrations in the water column are a common feature in many upland water supplies and have been experienced at the Megget Reservoir during a period of major draw down in 1997/98. The peaty soils covering such upland catchments favour metal mobilisation processes resulting in high iron and manganese loading in the streams draining into lakes and reservoirs. When removed from the water column by sedimentation, the metals accumulate in the bottom sediments from where they can be remobilised when conditions in the water body change.
In this thesis, extensive investigations at the reservoir body and its surrounding catchment area have been carried out to study the hydrological processes in the catchment, the reservoir and processes operating at the sediment-water interface in the reservoir. The temporal and spatial variability in iron and manganese concentrations in the water column of the reservoir and in the feeder streams is a particular focus of the study. A combination of analytical techniques and process-based laboratory experiments has been employed to investigate the relative importance of physical and chemical processes in determining iron and manganese mobilisation within, and release from, the bottom sediments of the Megget Reservoir.
Evaluation of the catchment data reveals that stream chemistry is influenced by flow pathways through the catchments and by catchment characteristics, in particular soil type distribution, which control the iron and manganese fluxes into the reservoir, especially during high rainfall episodes. Evidence is presented that sediment release and re-suspension processes can introduce large amounts of iron and manganese into the reservoir water column and appear to have contributed significantly to the experienced water quality problems. The results of this study have significant implications for the management of the water supply itself and also highlight the importance of catchment-based management strategies for water supplies in other upland regions.
2003-01-01T00:00:00ZAbesser, CorinnaWater quality problems associated with high iron and manganese concentrations in the water column are a common feature in many upland water supplies and have been experienced at the Megget Reservoir during a period of major draw down in 1997/98. The peaty soils covering such upland catchments favour metal mobilisation processes resulting in high iron and manganese loading in the streams draining into lakes and reservoirs. When removed from the water column by sedimentation, the metals accumulate in the bottom sediments from where they can be remobilised when conditions in the water body change.
In this thesis, extensive investigations at the reservoir body and its surrounding catchment area have been carried out to study the hydrological processes in the catchment, the reservoir and processes operating at the sediment-water interface in the reservoir. The temporal and spatial variability in iron and manganese concentrations in the water column of the reservoir and in the feeder streams is a particular focus of the study. A combination of analytical techniques and process-based laboratory experiments has been employed to investigate the relative importance of physical and chemical processes in determining iron and manganese mobilisation within, and release from, the bottom sediments of the Megget Reservoir.
Evaluation of the catchment data reveals that stream chemistry is influenced by flow pathways through the catchments and by catchment characteristics, in particular soil type distribution, which control the iron and manganese fluxes into the reservoir, especially during high rainfall episodes. Evidence is presented that sediment release and re-suspension processes can introduce large amounts of iron and manganese into the reservoir water column and appear to have contributed significantly to the experienced water quality problems. The results of this study have significant implications for the management of the water supply itself and also highlight the importance of catchment-based management strategies for water supplies in other upland regions.Mechanistic studies on enzymes of secondary metabolism : 5'-fluoro-5'-deoxyadenosine synthase and 1-deoxy-D-xylulose-5-phosphate reductoisomeraseCadicamo, Cosimo Damianohttps://hdl.handle.net/10023/220142022-04-05T08:14:08Z2006-01-01T00:00:00ZA fluorination enzyme (fluorinase) has recently been isolated in St. Andrews from the bacterium Streptomyces cattleya. This enzyme mediates a reaction between fluoride ion and Sadenosyl-L-methionine (SAM) to generate 5'-fluoro-5'-deoxy-adenosine (5'-FDA).
In this thesis the stereochemical course of biological fluorination has been evaluated. This involved the preparation of a stereospecifically labelled sample of ATP {(5'R)-[²H₁]-ATP}.
This substrate generated a stereospecifically labelled sample of 5'-FDA after a coupled enzyme reaction involving the SAM synthase and then the fluorinase.
Evaluation of the absolute configuration of the chiral fluoromethyl group at the 5'-carbon of 5'-FDA (HDFC-) by ²H-NMR analysis in a chiral liquid-crystalline medium, and by comparison with a stereospecifically labelled sample of (5'S)-[²H₁]-FDA, established that the fluorinase catalyses fluorination with an inversion of configuration, consistent with an Sₙ2 reaction mechanism. This is discussed in detail in chapter 4.
An investigation into halide binding prior to nucleophilic substitution of SAM was also addressed. This involved the preparation of a sample of 9-(β-D-erytho-furanosyl)adenosine a compound which was co-crystallised with the fluorinase. An enzyme crystal structure with 9-(β-D-eythro-furanosyl)adenosine was obtained, although the chloride ion was not evident. This is discussed in chapter 3.
The DXR is an enzyme on the non-mevalonate pathway to isopentenyl diphosphate and dimethylallyl diphosphate that catalyses the conversion of 1-deoxy-D-xylulose 5-phosphate (DXP) to 2-C-methyl-D-erythritol 4-phosphate (MEP). A candidate inhibitor was designed and prepared to explore the mechanism of this enzyme. This is discussed in detail in chapter 6.
2006-01-01T00:00:00ZCadicamo, Cosimo DamianoA fluorination enzyme (fluorinase) has recently been isolated in St. Andrews from the bacterium Streptomyces cattleya. This enzyme mediates a reaction between fluoride ion and Sadenosyl-L-methionine (SAM) to generate 5'-fluoro-5'-deoxy-adenosine (5'-FDA).
In this thesis the stereochemical course of biological fluorination has been evaluated. This involved the preparation of a stereospecifically labelled sample of ATP {(5'R)-[²H₁]-ATP}.
This substrate generated a stereospecifically labelled sample of 5'-FDA after a coupled enzyme reaction involving the SAM synthase and then the fluorinase.
Evaluation of the absolute configuration of the chiral fluoromethyl group at the 5'-carbon of 5'-FDA (HDFC-) by ²H-NMR analysis in a chiral liquid-crystalline medium, and by comparison with a stereospecifically labelled sample of (5'S)-[²H₁]-FDA, established that the fluorinase catalyses fluorination with an inversion of configuration, consistent with an Sₙ2 reaction mechanism. This is discussed in detail in chapter 4.
An investigation into halide binding prior to nucleophilic substitution of SAM was also addressed. This involved the preparation of a sample of 9-(β-D-erytho-furanosyl)adenosine a compound which was co-crystallised with the fluorinase. An enzyme crystal structure with 9-(β-D-eythro-furanosyl)adenosine was obtained, although the chloride ion was not evident. This is discussed in chapter 3.
The DXR is an enzyme on the non-mevalonate pathway to isopentenyl diphosphate and dimethylallyl diphosphate that catalyses the conversion of 1-deoxy-D-xylulose 5-phosphate (DXP) to 2-C-methyl-D-erythritol 4-phosphate (MEP). A candidate inhibitor was designed and prepared to explore the mechanism of this enzyme. This is discussed in detail in chapter 6.Studies of excitotoxicity in cerebellar granule neuronsSinclair, Colin Jameshttps://hdl.handle.net/10023/220072022-03-23T03:06:23Z2004-01-01T00:00:00ZExcitotoxicity is defined as neuronal cell death caused by hyperactivation of ionotropic glutamate receptors (namely NMDA-, AMPA- and KA-receptors). The excitotoxic potential of a novel AMPA receptor subtype-selective agonist, (S)-CPW 399 was investigated, using 7 div cultured cerebellar granule neurons as an in vitro model system of glutamatergic neurons. The results demonstrate that (S)-CPW 399 induces excitotoxicity by stimulating Ca²⁺ influx through Ca²⁺-permeable AMPA receptors, with no other coincident mechanism of Ca²⁺ infux being involved. Uniquely among AMPA receptor-selective agonists, (S)-CPW 399 appeared to have the ability to induce AMPA receptor-mediated functional responses without the need for blockade of AMPA receptor desensitisation. These results suggest that (S)-CPW 399 may be used as a pharmacological tool to aid in the investigation of the role of AMPA receptors in excitotoxicity and their molecular mechanisms of desensitisation.
In a supporting study, it was shown that classic desensitising AMPA receptorselective agonists produced similar results to that seen for (S)-CPW 399 under an identical experimental paradigm only when AMPA receptor desensitisation was inhibited by cyclothiazide.
Previously published data suggest that the normal physiological temporal profile of c-fos mRNA expression following stimulation of cells is altered following excitotoxic insult. More precisely, the transient expression observed under non-excitotoxic conditions is replaced by delayed, elevated and sustained expression under excitotoxic conditions. As a result, it has been postulated that ratiometric analysis of c-fos mRNA expression at selected timepoints following stimulation could provide a mechanistically relevant in vitro predictive test for excitotoxicity. This was assessed in an industrial context using real time RT-PCR for mRNA quantitation following exposure of granule cells to high and low concentrations of excitotoxic and non.- excitotoxic compounds. The results suggest that the proposed test requires further modification and validation to achieve a robust, reliable large-scale screening test for excitotoxic potential of compounds.
2004-01-01T00:00:00ZSinclair, Colin JamesExcitotoxicity is defined as neuronal cell death caused by hyperactivation of ionotropic glutamate receptors (namely NMDA-, AMPA- and KA-receptors). The excitotoxic potential of a novel AMPA receptor subtype-selective agonist, (S)-CPW 399 was investigated, using 7 div cultured cerebellar granule neurons as an in vitro model system of glutamatergic neurons. The results demonstrate that (S)-CPW 399 induces excitotoxicity by stimulating Ca²⁺ influx through Ca²⁺-permeable AMPA receptors, with no other coincident mechanism of Ca²⁺ infux being involved. Uniquely among AMPA receptor-selective agonists, (S)-CPW 399 appeared to have the ability to induce AMPA receptor-mediated functional responses without the need for blockade of AMPA receptor desensitisation. These results suggest that (S)-CPW 399 may be used as a pharmacological tool to aid in the investigation of the role of AMPA receptors in excitotoxicity and their molecular mechanisms of desensitisation.
In a supporting study, it was shown that classic desensitising AMPA receptorselective agonists produced similar results to that seen for (S)-CPW 399 under an identical experimental paradigm only when AMPA receptor desensitisation was inhibited by cyclothiazide.
Previously published data suggest that the normal physiological temporal profile of c-fos mRNA expression following stimulation of cells is altered following excitotoxic insult. More precisely, the transient expression observed under non-excitotoxic conditions is replaced by delayed, elevated and sustained expression under excitotoxic conditions. As a result, it has been postulated that ratiometric analysis of c-fos mRNA expression at selected timepoints following stimulation could provide a mechanistically relevant in vitro predictive test for excitotoxicity. This was assessed in an industrial context using real time RT-PCR for mRNA quantitation following exposure of granule cells to high and low concentrations of excitotoxic and non.- excitotoxic compounds. The results suggest that the proposed test requires further modification and validation to achieve a robust, reliable large-scale screening test for excitotoxic potential of compounds.Mechanisms of G2 chromosomal radiosensitivity of murine SCID cellsFinnegan, Clodagh E.https://hdl.handle.net/10023/220032022-03-22T11:16:52Z2001-01-01T00:00:00ZThe non-homologous end-joining (NHEJ) pathway of DNA repair has become a recent focus of attention and one of the central players of this pathway is DNA-PKCs which is mutated in murine Severe Combined Immunodeficiency (SCID).
The underlying mechanisms of the variable G2 chromosomal radiosensitivity in different individuals or cell lines has been the subject of much discussion, and the use of mutant radiosensitive rodent cell lines has provided a way to begin to understand the genetics and mechanisms of chromosomal radiosensitivity. As an example of this approach SCID cells have shown an elevated G2 chromosomal response to ionising radiation (IR). This response is generally thought to be caused by the underlying double-strand break (dsb) rejoining deficiency. However, recently Bryant (1998) proposed the signal model suggesting that G2 radiosensitivity is not directly related to dsb rejoining, but is due to an enhanced conversion of dsb to chromatid breaks via a recombinational mechanism. Therefore, the aim of the work presented in this thesis was to increase our understanding of the relationship between dsb and chromatid breaks in the G2 phase of the cell cycle. The cell lines used in this research were murine fibroblastic SCID, normal CB17, 100E+ (hybrid SCID cells complemented for DNA-PKcs) and 50D⁻ (hybrid non-complemented SCID) cells.
The kinetics of the disappearance of chromatid breaks with time in G2 SCID and CB17 (normal wildtype) cells after gamma-irradiation showed a similar rate in the two cell lines. However, there was a 1.3-1.7 fold elevated frequency of chromatid breaks in SCID relative to CB17 cells. Analysis of dsb induction in SCID and CB17 cells showed similar initial frequencies of dsb. Analysis of dsb rejoining showed a higher residual frequency of dsb in SCID compared with CB17 cells from 10 min up to 3h, which appeared to be correlated with the observed elevated frequencies of chromatid breaks.
However, further experiments involving treatment of irradiated G2 cells with the DNA synthesis inhibitor 9- β-D arabinofuranosyladenine (araA) enhanced the frequency of chromatid breaks without showing a significant effect on dsb rejoining as measured by constant field gel electrophoresis. Thus, while acknowledging the conflicting nature of these results, the araA experiments throw serious doubt upon the direct relationship between the two end-points. The reasons for these results are not at present clear and further investigation is obviously required. However, a mechanism such as that recently proposed under the signal model, where dsb are not directly involved in chromatid break formation might offer a possible explanation, namely that araA acts on the semi-final stage in the recombinational rearrangement leading to chromatid breaks.
Another factor influencing the induction of chromatid breaks was the end-structure of dsb, and this was more pronounced in SCID than normal cells, as shown by an elevated frequency of chromatid breaks in response to restriction endonucleases (RE) inducing blunt- and 3' cohesive-ends compared to those inducing 5' cohesive ends. These results suggest the molecular configuration of the dsb influences the mechanism by which dsb are converted to chromatid breaks.
Furthermore, the chromatin structure of SCID and CB17 cells was studied by flow cytometry of nucleoids under various conditions and the results revealed differences between the two lines. In addition, SCID nucleoids were in general more compact, an effect possibly correlated with an observed reduction in overall chromosome length.
2001-01-01T00:00:00ZFinnegan, Clodagh E.The non-homologous end-joining (NHEJ) pathway of DNA repair has become a recent focus of attention and one of the central players of this pathway is DNA-PKCs which is mutated in murine Severe Combined Immunodeficiency (SCID).
The underlying mechanisms of the variable G2 chromosomal radiosensitivity in different individuals or cell lines has been the subject of much discussion, and the use of mutant radiosensitive rodent cell lines has provided a way to begin to understand the genetics and mechanisms of chromosomal radiosensitivity. As an example of this approach SCID cells have shown an elevated G2 chromosomal response to ionising radiation (IR). This response is generally thought to be caused by the underlying double-strand break (dsb) rejoining deficiency. However, recently Bryant (1998) proposed the signal model suggesting that G2 radiosensitivity is not directly related to dsb rejoining, but is due to an enhanced conversion of dsb to chromatid breaks via a recombinational mechanism. Therefore, the aim of the work presented in this thesis was to increase our understanding of the relationship between dsb and chromatid breaks in the G2 phase of the cell cycle. The cell lines used in this research were murine fibroblastic SCID, normal CB17, 100E+ (hybrid SCID cells complemented for DNA-PKcs) and 50D⁻ (hybrid non-complemented SCID) cells.
The kinetics of the disappearance of chromatid breaks with time in G2 SCID and CB17 (normal wildtype) cells after gamma-irradiation showed a similar rate in the two cell lines. However, there was a 1.3-1.7 fold elevated frequency of chromatid breaks in SCID relative to CB17 cells. Analysis of dsb induction in SCID and CB17 cells showed similar initial frequencies of dsb. Analysis of dsb rejoining showed a higher residual frequency of dsb in SCID compared with CB17 cells from 10 min up to 3h, which appeared to be correlated with the observed elevated frequencies of chromatid breaks.
However, further experiments involving treatment of irradiated G2 cells with the DNA synthesis inhibitor 9- β-D arabinofuranosyladenine (araA) enhanced the frequency of chromatid breaks without showing a significant effect on dsb rejoining as measured by constant field gel electrophoresis. Thus, while acknowledging the conflicting nature of these results, the araA experiments throw serious doubt upon the direct relationship between the two end-points. The reasons for these results are not at present clear and further investigation is obviously required. However, a mechanism such as that recently proposed under the signal model, where dsb are not directly involved in chromatid break formation might offer a possible explanation, namely that araA acts on the semi-final stage in the recombinational rearrangement leading to chromatid breaks.
Another factor influencing the induction of chromatid breaks was the end-structure of dsb, and this was more pronounced in SCID than normal cells, as shown by an elevated frequency of chromatid breaks in response to restriction endonucleases (RE) inducing blunt- and 3' cohesive-ends compared to those inducing 5' cohesive ends. These results suggest the molecular configuration of the dsb influences the mechanism by which dsb are converted to chromatid breaks.
Furthermore, the chromatin structure of SCID and CB17 cells was studied by flow cytometry of nucleoids under various conditions and the results revealed differences between the two lines. In addition, SCID nucleoids were in general more compact, an effect possibly correlated with an observed reduction in overall chromosome length.The effects of insect visitation on floral colour changeNuttman, Clivehttps://hdl.handle.net/10023/220012022-03-21T12:24:57Z2003-01-01T00:00:00ZThis study investigated the effects of flower visitation on floral colour change and the subsequent influence of such change on insect foraging behaviour. Colour change was examined in six plant species; Myosotis sylvatica, Echium vulgare and Lonicera periclymenum were studied locally to St. Andrews, Fife, Scotland and Echium judaeum, Lupirtus pilosus and Alkanna orientalis were studied in various locations in the eastern Mediterranean region. Patterns of colour change were recorded both with natural insect visitation allowed and excluded, to establish whether the rate of colour change could be altered through visitation per se or rate of visitation. Detailed observation of the flower handling characteristics of all visiting insects allowed artificial floral manipulations to be devised that simulated the different aspects of visitor behaviour. This enabled the effects of simple mechanical handling on colour change to be separated from those of pollen deposition and post pollination events. Floral reward was measured in relation to flower colour phases to assess whether the change in colour was acting as a functional signal to flower visitors; insect choice of flower colour was noted, to determine whether reward status affected foraging behaviour. One or more factors significantly altered the characteristics of colour change in all species except Lonicera periclymenum. The triggering factor could be the exclusion of visitors, rate of natural visitation, floral manipulation, or aspects of the pollination process. In Lupinus pilosus pollen deposition and/or pollen tube growth was the trigger for colour change. Pollen deposition was also the most likely trigger in both Alkanna orientalis and Myosotis sylvatica, although the varied patterns of colour change in these species could be related to wound responses and/or senescence. Pollination processes were not involved in colour change in either species of Echium. The first recorded example of a 'reverse' colour change is reported fox Echiumjudaeum. Floral reward varied between colour phases in all plants except Echium vulgare, and visiting insects did not show any bias towards particular flower colour phases in this plant. In all other species a variety of flies and bees visited the most rewarding colour phase preferentially. A model is presented that incorporates all influences on floral colour change in a single framework, potentially unifying the concepts of age-related' and 'inducible' change which have previously been thought to be distinct.
2003-01-01T00:00:00ZNuttman, CliveThis study investigated the effects of flower visitation on floral colour change and the subsequent influence of such change on insect foraging behaviour. Colour change was examined in six plant species; Myosotis sylvatica, Echium vulgare and Lonicera periclymenum were studied locally to St. Andrews, Fife, Scotland and Echium judaeum, Lupirtus pilosus and Alkanna orientalis were studied in various locations in the eastern Mediterranean region. Patterns of colour change were recorded both with natural insect visitation allowed and excluded, to establish whether the rate of colour change could be altered through visitation per se or rate of visitation. Detailed observation of the flower handling characteristics of all visiting insects allowed artificial floral manipulations to be devised that simulated the different aspects of visitor behaviour. This enabled the effects of simple mechanical handling on colour change to be separated from those of pollen deposition and post pollination events. Floral reward was measured in relation to flower colour phases to assess whether the change in colour was acting as a functional signal to flower visitors; insect choice of flower colour was noted, to determine whether reward status affected foraging behaviour. One or more factors significantly altered the characteristics of colour change in all species except Lonicera periclymenum. The triggering factor could be the exclusion of visitors, rate of natural visitation, floral manipulation, or aspects of the pollination process. In Lupinus pilosus pollen deposition and/or pollen tube growth was the trigger for colour change. Pollen deposition was also the most likely trigger in both Alkanna orientalis and Myosotis sylvatica, although the varied patterns of colour change in these species could be related to wound responses and/or senescence. Pollination processes were not involved in colour change in either species of Echium. The first recorded example of a 'reverse' colour change is reported fox Echiumjudaeum. Floral reward varied between colour phases in all plants except Echium vulgare, and visiting insects did not show any bias towards particular flower colour phases in this plant. In all other species a variety of flies and bees visited the most rewarding colour phase preferentially. A model is presented that incorporates all influences on floral colour change in a single framework, potentially unifying the concepts of age-related' and 'inducible' change which have previously been thought to be distinct.Development of foraging in wild chimpanzeesAssersohn, Cleahttps://hdl.handle.net/10023/219992022-03-21T10:33:30Z2000-01-01T00:00:00ZRecent work on social learning in primates has primarily been approached from a perspective that focuses on demonstrating human-like learning abilities rather than the efficacy of social learning within natural and ecologically relevant conditions. This thesis takes a functional approach and investigates the development of foraging behaviour in wild chimpanzees. Data were collected over 12 months on mother, infant and juvenile chimpanzees in Budongo Forest, Uganda. Feeding behaviour was studied comparatively, relating infants' foraging with the more competent patters of juveniles and mothers. Infants started to feed independently in the second half of their first year but only on soft-shelled, easily processed foods. The infant's diet was similar to the mother's by the end of the fourth year in terms of the breadth of food items consumed but at this age infants were still less proficient at processing foods. Infants had particular difficulty processing some embedded foods and these were the final items to be incorporated into the diet. Young infants under the age of 2.5 years selectively spent time near their mother when she was feeding, visually attended at higher levels to their mother's feeding behaviour, and synchronised playful manipulations of food items and later their own independent feeding attempts when their mother was feeding. However, none of these effects were more evident when their mothers were feeding on difficult food items. The sharing of food between mother and infant emerged as a more important opportunity for social learning. Infants initiated these interactions by soliciting food from their mothers. Difficult foods were shared at higher rates than easy foods and most frequently in the infant's first and second year. The higher sharing rate of difficult foods was due to infants focusing their solicitations on these items that they found difficult to procure or process. These results suggest that infants are refined not only in their attempts to acquire food from their mothers but perhaps also information about feeding habits.
2000-01-01T00:00:00ZAssersohn, CleaRecent work on social learning in primates has primarily been approached from a perspective that focuses on demonstrating human-like learning abilities rather than the efficacy of social learning within natural and ecologically relevant conditions. This thesis takes a functional approach and investigates the development of foraging behaviour in wild chimpanzees. Data were collected over 12 months on mother, infant and juvenile chimpanzees in Budongo Forest, Uganda. Feeding behaviour was studied comparatively, relating infants' foraging with the more competent patters of juveniles and mothers. Infants started to feed independently in the second half of their first year but only on soft-shelled, easily processed foods. The infant's diet was similar to the mother's by the end of the fourth year in terms of the breadth of food items consumed but at this age infants were still less proficient at processing foods. Infants had particular difficulty processing some embedded foods and these were the final items to be incorporated into the diet. Young infants under the age of 2.5 years selectively spent time near their mother when she was feeding, visually attended at higher levels to their mother's feeding behaviour, and synchronised playful manipulations of food items and later their own independent feeding attempts when their mother was feeding. However, none of these effects were more evident when their mothers were feeding on difficult food items. The sharing of food between mother and infant emerged as a more important opportunity for social learning. Infants initiated these interactions by soliciting food from their mothers. Difficult foods were shared at higher rates than easy foods and most frequently in the infant's first and second year. The higher sharing rate of difficult foods was due to infants focusing their solicitations on these items that they found difficult to procure or process. These results suggest that infants are refined not only in their attempts to acquire food from their mothers but perhaps also information about feeding habits.The role of the intestine in the osmoregulation of the European eelPhillips, Clairehttps://hdl.handle.net/10023/219962022-03-21T10:40:11Z2006-01-01T00:00:00ZEuropean silver eels 378g ± 11 (SEM) were transferred freshwater - freshwater and freshwater - seawater, their blood sampled and plasma ions, osmolality and circulating concentrations of Cortisol and ANG-II measured to determine the effects of freshwater - seawater transfer.
• Sodium and water uptake occurs via transporters and channels present at different ratios in different intestinal regions and showing regional inhibition to specific drugs. Na+,K+-ATPase and NKCC-2 are present in all sections of the intestine, but have greater activity in the mid and posterior intestinal regions. NKCC-2 (inhibited by bumetanide) has greatest activity in the mid intestinal section. CCC-3 (inhibited by thiazide) is functionally present in the mid intestinal region alone.
• HgCl₂sensitive aquaporins are present in the mid and posterior regions of the eel intestine and significantly increased in yellow eels on seawater transfer. Inhibition of aquaporins did not alter sodium uptake.
• Freshwater silver eel intestines showed greater inhibition of Na+ and H2O uptake with ouabain, bumetanide and HgCl₂ compared with freshwater yellow eels, potentially indicating pre-acclimation for seawater migration.
• Infusion of single osmoregulatory hormones (Cortisol, ANG-II and AVT) via intra¬ peritoneal implantation in freshwater yellow and silver eels were used to determine hormonal effects on sodium and water uptake inhibited by ouabain, bumetanide and HgCl₂
• Cortisol infusion reduced basal sodium and water transport across the intestine, in both yellow and silver eels. ANG-II infusion reduces sodium and water transport in yellow but not the silver eel. Cortisol and ANG-II infusion increased HgCl₂ inhibition of AQP water channels confirming their presence and also their importance in water transport.
• AVT infusion increases basal sodium and water transport, and HgCl₂ sensitive water transport was dramatically increased, indicating AQPs in the intestine under hormonal regulation and identifying the eel as a potential tool for medical research.
2006-01-01T00:00:00ZPhillips, ClaireEuropean silver eels 378g ± 11 (SEM) were transferred freshwater - freshwater and freshwater - seawater, their blood sampled and plasma ions, osmolality and circulating concentrations of Cortisol and ANG-II measured to determine the effects of freshwater - seawater transfer.
• Sodium and water uptake occurs via transporters and channels present at different ratios in different intestinal regions and showing regional inhibition to specific drugs. Na+,K+-ATPase and NKCC-2 are present in all sections of the intestine, but have greater activity in the mid and posterior intestinal regions. NKCC-2 (inhibited by bumetanide) has greatest activity in the mid intestinal section. CCC-3 (inhibited by thiazide) is functionally present in the mid intestinal region alone.
• HgCl₂sensitive aquaporins are present in the mid and posterior regions of the eel intestine and significantly increased in yellow eels on seawater transfer. Inhibition of aquaporins did not alter sodium uptake.
• Freshwater silver eel intestines showed greater inhibition of Na+ and H2O uptake with ouabain, bumetanide and HgCl₂ compared with freshwater yellow eels, potentially indicating pre-acclimation for seawater migration.
• Infusion of single osmoregulatory hormones (Cortisol, ANG-II and AVT) via intra¬ peritoneal implantation in freshwater yellow and silver eels were used to determine hormonal effects on sodium and water uptake inhibited by ouabain, bumetanide and HgCl₂
• Cortisol infusion reduced basal sodium and water transport across the intestine, in both yellow and silver eels. ANG-II infusion reduces sodium and water transport in yellow but not the silver eel. Cortisol and ANG-II infusion increased HgCl₂ inhibition of AQP water channels confirming their presence and also their importance in water transport.
• AVT infusion increases basal sodium and water transport, and HgCl₂ sensitive water transport was dramatically increased, indicating AQPs in the intestine under hormonal regulation and identifying the eel as a potential tool for medical research.Appetitive associative conditioning in the basolateral amygdalaBirch, Claire Stirlinghttps://hdl.handle.net/10023/219932022-03-10T15:52:45Z2005-01-01T00:00:00ZThis thesis is concerned with the neural basis of appetitive associative conditioning or 'reward learning' in rats. Research has implicated several brain structures within what is known as the cortico-striato-pallido-thalamic or 'limbic' loop in reward learning, including the nucleus accumbens and the amygdala. Wolfram Schultz and colleagues recently proposed that dopamine neurons, which project from the midbrain ventral tegmental area (VTA) to the ventral striatum (including the nucleus accumbens), signal expectancy of reward. They have shown that, not only do dopamine neurons markedly increase their activity at the presentation of unexpected rewards, but that with training this response transfers to stimuli predictive of those rewards. Moreover, once this transfer has occurred, if an expected reward does not in fact occur, there is a brief reduction in dopaminergic activity at the time that it should have occurred. The experimental work undertaken for the first part of this thesis describes the behavioural testing of an appetitive 'blocking' paradigm which was intended to explore and substantiate Schultz et al's proposal that dopamine signals a reward prediction error by assessing whether the transfer in dopaminergic activity is indeed due to contingency or merely to temporal contiguity. The results of the blocking paradigm were inconclusive. The amygdala, closely associated with the limbic loop, has long been associated with 'emotional' behaviour with damage leading to hypoemotionality in animals and to deficits in the perception of emotions in facial expression and impaired learning of and memory for emotional events in humans. It is becoming increasingly clear that the amygdala is also important for appetitive associative learning. The experimental work undertaken for the second part of this thesis investigates the relative contributions of the basolateral nucleus of the amygdala (BLA) and the central nucleus of the amygdala (CeN) to reward learning by assessing the performance of BLA- and CeN-lesioned rats on the Schedule Fraction Cue (SFC) task. In this task rats must make three, two, or one correct responses in order to receive reward, and are able to use information provided by cue lights to notify them as to their progress. Since previous research has suggested that the BLA is critical for the acquisition of positive incentive value by formerly neutral stimuli, and since it has also been suggested that Pavlovian conditioned stimuli can exert a motivational influence on instrumental behaviour (Pavlovian-to-instrumental transfer), it was initially predicted that BLA-lesioned rats would be impaired in their performance of this task. The results of Experiment A suggested that this was not the case. More recent research has suggested that CeN lesions abolish Pavlovian-to-instrumental transfer, and so the experiment was repeated, using both BLA- and CeN-lesioned rats. The results of Experiment B showed very little impairment in performance in the BLA- or CeN lesioned rats. It is concluded that any impairments present in BLA- or CeN-lesioned rats are very subtle and will require further investigation.
2005-01-01T00:00:00ZBirch, Claire StirlingThis thesis is concerned with the neural basis of appetitive associative conditioning or 'reward learning' in rats. Research has implicated several brain structures within what is known as the cortico-striato-pallido-thalamic or 'limbic' loop in reward learning, including the nucleus accumbens and the amygdala. Wolfram Schultz and colleagues recently proposed that dopamine neurons, which project from the midbrain ventral tegmental area (VTA) to the ventral striatum (including the nucleus accumbens), signal expectancy of reward. They have shown that, not only do dopamine neurons markedly increase their activity at the presentation of unexpected rewards, but that with training this response transfers to stimuli predictive of those rewards. Moreover, once this transfer has occurred, if an expected reward does not in fact occur, there is a brief reduction in dopaminergic activity at the time that it should have occurred. The experimental work undertaken for the first part of this thesis describes the behavioural testing of an appetitive 'blocking' paradigm which was intended to explore and substantiate Schultz et al's proposal that dopamine signals a reward prediction error by assessing whether the transfer in dopaminergic activity is indeed due to contingency or merely to temporal contiguity. The results of the blocking paradigm were inconclusive. The amygdala, closely associated with the limbic loop, has long been associated with 'emotional' behaviour with damage leading to hypoemotionality in animals and to deficits in the perception of emotions in facial expression and impaired learning of and memory for emotional events in humans. It is becoming increasingly clear that the amygdala is also important for appetitive associative learning. The experimental work undertaken for the second part of this thesis investigates the relative contributions of the basolateral nucleus of the amygdala (BLA) and the central nucleus of the amygdala (CeN) to reward learning by assessing the performance of BLA- and CeN-lesioned rats on the Schedule Fraction Cue (SFC) task. In this task rats must make three, two, or one correct responses in order to receive reward, and are able to use information provided by cue lights to notify them as to their progress. Since previous research has suggested that the BLA is critical for the acquisition of positive incentive value by formerly neutral stimuli, and since it has also been suggested that Pavlovian conditioned stimuli can exert a motivational influence on instrumental behaviour (Pavlovian-to-instrumental transfer), it was initially predicted that BLA-lesioned rats would be impaired in their performance of this task. The results of Experiment A suggested that this was not the case. More recent research has suggested that CeN lesions abolish Pavlovian-to-instrumental transfer, and so the experiment was repeated, using both BLA- and CeN-lesioned rats. The results of Experiment B showed very little impairment in performance in the BLA- or CeN lesioned rats. It is concluded that any impairments present in BLA- or CeN-lesioned rats are very subtle and will require further investigation.In situ' analysis of the biomass and distribution of microphytobenthosHoneywill, Clairehttps://hdl.handle.net/10023/219942022-03-10T16:30:25Z2001-01-01T00:00:00ZThis thesis investigates the use of fluorescence techniques for the remote sensing of microphytobenthic biomass and distribution. Firstly, hardware was developed to facilitate the use of fluorometry for measuring microphytobenthos in situ. Comparisons between minimum fluorescence (Fo¹⁵) and chlorophyll a, as proxies for microalgal biomass, were made over varied seasonal and spatial scales. The relationship between Fo¹⁵ and Chl a was strongest for diatom dominated samples where micro-sections (0.2 mm) of sediment were sampled. No spatial patterns were found in diatom patch size or dispersion. The coefficient of variation between patches (using the proxy Fo¹⁵) made at scales from 2.5 - 500 cm, ranged from 5 to 150 %. The first non-destructive quantitative temporal study of microphytobenthos at the sediment surface (Fo¹⁵) was conducted. A proportion of the microphytobenthic community was found at the surface of the sediment during daylight tidal ebb and cells did not migrate from the surface at the end of tidal exposure. This has implications for re-suspension of cells during daylight immersion. Algal stress measurements (Fv/Fm) were unreliable at low biomass. The calculation of photosynthetic parameters from relative electron transport rate on undisturbed cores was found to be unrepresentative of those made in situ. The use of different units of expression for Chl a (both content and concentration) were investigated over temporal and vertical scales. Chl a content (μg Chl a g⁻¹ dry sediment) decreased over an emersion period. In contrast Chi a concentration (mg Chl a m⁻²) increased over this period. In this situation, contrasting Chi a determination could be wholly explained by the decrease in sediment water content over the period. These findings have implications for the estimation of biomass specific primary productivity.
2001-01-01T00:00:00ZHoneywill, ClaireThis thesis investigates the use of fluorescence techniques for the remote sensing of microphytobenthic biomass and distribution. Firstly, hardware was developed to facilitate the use of fluorometry for measuring microphytobenthos in situ. Comparisons between minimum fluorescence (Fo¹⁵) and chlorophyll a, as proxies for microalgal biomass, were made over varied seasonal and spatial scales. The relationship between Fo¹⁵ and Chl a was strongest for diatom dominated samples where micro-sections (0.2 mm) of sediment were sampled. No spatial patterns were found in diatom patch size or dispersion. The coefficient of variation between patches (using the proxy Fo¹⁵) made at scales from 2.5 - 500 cm, ranged from 5 to 150 %. The first non-destructive quantitative temporal study of microphytobenthos at the sediment surface (Fo¹⁵) was conducted. A proportion of the microphytobenthic community was found at the surface of the sediment during daylight tidal ebb and cells did not migrate from the surface at the end of tidal exposure. This has implications for re-suspension of cells during daylight immersion. Algal stress measurements (Fv/Fm) were unreliable at low biomass. The calculation of photosynthetic parameters from relative electron transport rate on undisturbed cores was found to be unrepresentative of those made in situ. The use of different units of expression for Chl a (both content and concentration) were investigated over temporal and vertical scales. Chl a content (μg Chl a g⁻¹ dry sediment) decreased over an emersion period. In contrast Chi a concentration (mg Chl a m⁻²) increased over this period. In this situation, contrasting Chi a determination could be wholly explained by the decrease in sediment water content over the period. These findings have implications for the estimation of biomass specific primary productivity.Aspects of the distribution of Na⁺,K⁺ ATPase in cultured cells with particular reference to the effects of fluid shear stressLazarus, Cindyhttps://hdl.handle.net/10023/219922022-03-10T15:41:40Z2001-01-01T00:00:00ZA two-part study was conducted into aspects of the distribution of Na⁺,K⁺ATPase α1 and β-1subunits in HeLa and bovine aortic endothelial cells (BAECs). The primary experimental emphasis was to examine Na⁺,K⁺ATPase distribution in relation to cell type, cell morphology and age using immunocytochemical, Western blot analysis, 3H ouabain assays and various cell permeabilisation techniques. This forms Part I of the study. Part II of the study focussed on the potential up/down regulation in addition to changes in Na⁺,K⁺ATPase distribution throughout the cytoskeleton under the influence of laminar fluid shear stress.
Initially aspects of HeLa cell morphology were examined using anthroylouabain, a fluorescence derivative of the cardiac glycoside ouabain. It was discovered that affinity for ouabain in HeLa cells decreases for cells that are actively dividing whereas confluent cells exhibit a 3-fold increase in sensitivity to ouabain. Initial findings by Lamb (1996) showed that the dissociation constant Kd for ouabain binding to the sodium pump of HeLa cells is dependent on cell morphology. Results of this study show that rounder cells take up more anthroylouabain compared to flatter cells. Laser scanning confocal microscopy reveals this was not an artefact of differing depth of cells, but a real difference of ca. 5-fold. Further studies examined BAECs in addition to HeLa cells in order to compare the quantity of ouabain binding between young and old cells. The results demonstrate that both HeLa cells and BAECs used for experimentation at Day 4 after plating have similar levels of ouabain binding, whereas BAECs harvested at Day 14 show less ouabain binding in comparison to younger cells (one-way ANOVA F₂.₅₆=8.60, p<0.001). Different pretreatments were used before BAEC cells were stained for the α -1 subunit of the Na pump and actin. These were permeabilising with SDS (sodium dodecylsulphate) and hypotonically rupturing the cell membrane. The aim was to expose antigenic sites in intra-cellular compartments leading to the augmentation of α -1 subunit staining. Results of this experiment showed α -1 subunits a similar distribution pattern to actin. However it is difficult to state with certainty that there is an actual co-localisation.
BAECs were subjected to steady laminar shear stresses using specialised parallel plate chambers of 15 and 50 dyn cm⁻². Immunocytochemical techniques were used to reveal any physical differences in pump distribution after exposure to flow stresses. In addition Western blot analysis was used to explore possible up or down regulation of the α -1 subunit. Results indicate that under a flow stress of 50 dyn cm⁻² for 4 hours there is a marked change in sodium pump distribution from the cell periphery to the cytoplasm. In addition, there are concurrent and specific morphological changes in BAECs i.e. reorganisation and alignment of actin stress fibres with the direction of flow. Protein estimations derived from gel densitometry analysis of ECLs for cells sheared at 15 and 50 cm⁻²over a time course experiment showed no significant difference with either time or flow stress (two-way ANOVA without replication: df=l, F=32.85 p=0.001). Additional experiments were designed to expose cells to the same shear magnitude but then incubate them for 8 hours at 37°C to look for down or up-regulation of sodium pump protein over time. Shearing under a flow stress of 50 cm⁻²produced a characteristic bell-shaped distribution over time. Statistical analysis showed a significant difference with time and flow stress (two-way ANOVA with replication df=7, F=4.47, p=0.033) indicating possible up-regulation of pump protein after incubation.
2001-01-01T00:00:00ZLazarus, CindyA two-part study was conducted into aspects of the distribution of Na⁺,K⁺ATPase α1 and β-1subunits in HeLa and bovine aortic endothelial cells (BAECs). The primary experimental emphasis was to examine Na⁺,K⁺ATPase distribution in relation to cell type, cell morphology and age using immunocytochemical, Western blot analysis, 3H ouabain assays and various cell permeabilisation techniques. This forms Part I of the study. Part II of the study focussed on the potential up/down regulation in addition to changes in Na⁺,K⁺ATPase distribution throughout the cytoskeleton under the influence of laminar fluid shear stress.
Initially aspects of HeLa cell morphology were examined using anthroylouabain, a fluorescence derivative of the cardiac glycoside ouabain. It was discovered that affinity for ouabain in HeLa cells decreases for cells that are actively dividing whereas confluent cells exhibit a 3-fold increase in sensitivity to ouabain. Initial findings by Lamb (1996) showed that the dissociation constant Kd for ouabain binding to the sodium pump of HeLa cells is dependent on cell morphology. Results of this study show that rounder cells take up more anthroylouabain compared to flatter cells. Laser scanning confocal microscopy reveals this was not an artefact of differing depth of cells, but a real difference of ca. 5-fold. Further studies examined BAECs in addition to HeLa cells in order to compare the quantity of ouabain binding between young and old cells. The results demonstrate that both HeLa cells and BAECs used for experimentation at Day 4 after plating have similar levels of ouabain binding, whereas BAECs harvested at Day 14 show less ouabain binding in comparison to younger cells (one-way ANOVA F₂.₅₆=8.60, p<0.001). Different pretreatments were used before BAEC cells were stained for the α -1 subunit of the Na pump and actin. These were permeabilising with SDS (sodium dodecylsulphate) and hypotonically rupturing the cell membrane. The aim was to expose antigenic sites in intra-cellular compartments leading to the augmentation of α -1 subunit staining. Results of this experiment showed α -1 subunits a similar distribution pattern to actin. However it is difficult to state with certainty that there is an actual co-localisation.
BAECs were subjected to steady laminar shear stresses using specialised parallel plate chambers of 15 and 50 dyn cm⁻². Immunocytochemical techniques were used to reveal any physical differences in pump distribution after exposure to flow stresses. In addition Western blot analysis was used to explore possible up or down regulation of the α -1 subunit. Results indicate that under a flow stress of 50 dyn cm⁻² for 4 hours there is a marked change in sodium pump distribution from the cell periphery to the cytoplasm. In addition, there are concurrent and specific morphological changes in BAECs i.e. reorganisation and alignment of actin stress fibres with the direction of flow. Protein estimations derived from gel densitometry analysis of ECLs for cells sheared at 15 and 50 cm⁻²over a time course experiment showed no significant difference with either time or flow stress (two-way ANOVA without replication: df=l, F=32.85 p=0.001). Additional experiments were designed to expose cells to the same shear magnitude but then incubate them for 8 hours at 37°C to look for down or up-regulation of sodium pump protein over time. Shearing under a flow stress of 50 cm⁻²produced a characteristic bell-shaped distribution over time. Statistical analysis showed a significant difference with time and flow stress (two-way ANOVA with replication df=7, F=4.47, p=0.033) indicating possible up-regulation of pump protein after incubation.The effect of exercise on muscle growth and muscle-specific gene expression in the common carp (Cyprinus carpio L.) and rainbow trout (Oncorhynchus mykiss Walbaum)Martin, Christopher Ianhttps://hdl.handle.net/10023/219872022-03-09T11:57:17Z2003-01-01T00:00:00ZForced exercise training has long been known to be a powerful stimulus for muscle growth in several families of teleosts. The effect of exercise on muscle growth in the common carp (Cyprinus carpio L.) was studied in five experiments, at a range of swimming velocities between 1.7 and 3.0 body lengths per second (bls⁻¹)
Muscle fibre cross-sectional area was measured in fast, slow and where identified, intermediate muscle fibres. Exercise was shown to affect the fast and slow musculature differently in a manner analogous to the teleost starvation response. In response to moderate endurance exercise training fast muscle fibres were recruited to the myotome, but this process was balanced by atrophy of larger existing fast fibres. In contrast, slow to moderate exercise training induced slow muscle fibre hypertrophy. In response to a hyperplastic stimulus, the number of myonuclei per myofibre increased, implying a single population of myogenic progenitor cells provides the cells for post-embryonic muscle growth. A comparative study was conducted on rainbow trout (Oncorhynchus mykiss Walbaum), a species associated with a high inherent swimming capacity. Exercise training at 0.8 and 1.6 bls⁻¹ induced a 24 - 30% increase in mean fast muscle cross-sectional area through hypertrophy. To identify putative molecular signaling pathways underlying teleost muscle growth, the nuclear localisation and/or overall expression of myogenic regulatory factors (MRFs), calcineurin and associated substrate transcription factors and myostatin was compared between exercised and tank rested controls. The overall expression of MRFs was invariant in all experimental treatments. In common carp, increased nuclear localisation of the primary MRFs, especially MyoD, was positively correlated with larger mean fibre cross-sectional area. Increased nuclear localisation of the calcineurin protein was associated with hypertrophic growth of fast and slow muscle fibres in the common carp. Exercise-induced fast fibre hypertrophy was strongly correlated with increased calcineurin nuclear localisation in rainbow trout. However, a second experiment on common carp revealed no association between extensive fibre hypertrophy and nuclear localisation of the calcineurin protein. Furthermore, NFAT2 nuclear localisation did not follow a pattern that suggested NFAT2-mediated transcriptional activity was concurrent with muscle growth in the common carp or rainbow trout. In rainbow trout, myostatin active peptide was downregulated slightly (6 - 7%) in groups exhibiting exercise-induced hypertrophy of fast muscle fibres, consistent with its proposed role as a negative regulator of muscle growth. It was concluded that the molecular pathways examined might contribute to the regulation of muscle growth in teleosts but only as part of a more complex regulatory network.
2003-01-01T00:00:00ZMartin, Christopher IanForced exercise training has long been known to be a powerful stimulus for muscle growth in several families of teleosts. The effect of exercise on muscle growth in the common carp (Cyprinus carpio L.) was studied in five experiments, at a range of swimming velocities between 1.7 and 3.0 body lengths per second (bls⁻¹)
Muscle fibre cross-sectional area was measured in fast, slow and where identified, intermediate muscle fibres. Exercise was shown to affect the fast and slow musculature differently in a manner analogous to the teleost starvation response. In response to moderate endurance exercise training fast muscle fibres were recruited to the myotome, but this process was balanced by atrophy of larger existing fast fibres. In contrast, slow to moderate exercise training induced slow muscle fibre hypertrophy. In response to a hyperplastic stimulus, the number of myonuclei per myofibre increased, implying a single population of myogenic progenitor cells provides the cells for post-embryonic muscle growth. A comparative study was conducted on rainbow trout (Oncorhynchus mykiss Walbaum), a species associated with a high inherent swimming capacity. Exercise training at 0.8 and 1.6 bls⁻¹ induced a 24 - 30% increase in mean fast muscle cross-sectional area through hypertrophy. To identify putative molecular signaling pathways underlying teleost muscle growth, the nuclear localisation and/or overall expression of myogenic regulatory factors (MRFs), calcineurin and associated substrate transcription factors and myostatin was compared between exercised and tank rested controls. The overall expression of MRFs was invariant in all experimental treatments. In common carp, increased nuclear localisation of the primary MRFs, especially MyoD, was positively correlated with larger mean fibre cross-sectional area. Increased nuclear localisation of the calcineurin protein was associated with hypertrophic growth of fast and slow muscle fibres in the common carp. Exercise-induced fast fibre hypertrophy was strongly correlated with increased calcineurin nuclear localisation in rainbow trout. However, a second experiment on common carp revealed no association between extensive fibre hypertrophy and nuclear localisation of the calcineurin protein. Furthermore, NFAT2 nuclear localisation did not follow a pattern that suggested NFAT2-mediated transcriptional activity was concurrent with muscle growth in the common carp or rainbow trout. In rainbow trout, myostatin active peptide was downregulated slightly (6 - 7%) in groups exhibiting exercise-induced hypertrophy of fast muscle fibres, consistent with its proposed role as a negative regulator of muscle growth. It was concluded that the molecular pathways examined might contribute to the regulation of muscle growth in teleosts but only as part of a more complex regulatory network.Biochemical and genetic analysis of the nitrate assimilatory yeast Hansenula wingeiJones, Christopher Peterhttps://hdl.handle.net/10023/219832022-03-08T16:11:06Z1987-01-01T00:00:00ZThe heterothallic, haploid, nitrate assimilatory yeast Hansenula Wingei was investigated with respect to three aspects of nitrate assimilation.
1) One natural isolate, ATCC 28162 was chosen -for investigation. An efficient extraction procedure was developed. Attempts to assay xanthine dehydrogenase were unsuccessful. Nitrate reductase was not inhibited in vitro by either 1mM or 100mM ammonium, glutamate, or glutamine. However nitrite reductase was inhibited in vitro by 100mM glutamate or 100mM glutamine. A low constitutive level of nitrate and nitrite reductase activity was detectable in repressed cultures. Only nitrate alone was able to induce the enzymes. In derepressed cultures nitrate and nitrite reductase activity diminished if ammonium, glutamate, or glutamine was added, even in the presence of nitrate. Cycloheximide prevented diminution of activity.
2) 300mM chlorate plus glutamate was used to select spontaneous mutants. The mutation frequency for chlorate resistance was estimated as 20%. The following classes were found: Class 1: nitrate non-utilising, nitrite utilising; Class 2: nitrate and nitrite non-utilising; Class 3: nitrate utilising, nitrite non-utilising; Class 4: nitrate and nitrite utilising. All mutants utilised hypoxanthine and other nitrogen sources. In Class 1 (nnu) a complicated pattern of 15 complementation groups was found. In Class 2 (nan) 3 inter—allelic complementation groups were found. Nitrate reductase was absent in all nnu mutants. nan mutants lacked virtually all activities. Class 1 mutants complemented Class 2. A model involving autogenous regulation was discussed to explain the complicated enzyme activities of nnu mutants. The possibility was discussed of nan mutants representing a positive regulatory locus concerned with the induction of nitrate reductase, nitrate reductase, and molybdenum cofactor biosynthesis. Attempts at performing tetrad analysis were unsuccessful.
3) A transformation protocol was optimised for H. Wingei. Attempts were made to transform leucine auxotrophs to prorotrophy, and wild type strains to hygromycin B resistance. No replicating plasmid was detected. It was assumed that transformation had resulted in the integration of the plasmid. Auxtotrophic mutants were found to be generally epistatic to nitrate assimilation mutants.
1987-01-01T00:00:00ZJones, Christopher PeterThe heterothallic, haploid, nitrate assimilatory yeast Hansenula Wingei was investigated with respect to three aspects of nitrate assimilation.
1) One natural isolate, ATCC 28162 was chosen -for investigation. An efficient extraction procedure was developed. Attempts to assay xanthine dehydrogenase were unsuccessful. Nitrate reductase was not inhibited in vitro by either 1mM or 100mM ammonium, glutamate, or glutamine. However nitrite reductase was inhibited in vitro by 100mM glutamate or 100mM glutamine. A low constitutive level of nitrate and nitrite reductase activity was detectable in repressed cultures. Only nitrate alone was able to induce the enzymes. In derepressed cultures nitrate and nitrite reductase activity diminished if ammonium, glutamate, or glutamine was added, even in the presence of nitrate. Cycloheximide prevented diminution of activity.
2) 300mM chlorate plus glutamate was used to select spontaneous mutants. The mutation frequency for chlorate resistance was estimated as 20%. The following classes were found: Class 1: nitrate non-utilising, nitrite utilising; Class 2: nitrate and nitrite non-utilising; Class 3: nitrate utilising, nitrite non-utilising; Class 4: nitrate and nitrite utilising. All mutants utilised hypoxanthine and other nitrogen sources. In Class 1 (nnu) a complicated pattern of 15 complementation groups was found. In Class 2 (nan) 3 inter—allelic complementation groups were found. Nitrate reductase was absent in all nnu mutants. nan mutants lacked virtually all activities. Class 1 mutants complemented Class 2. A model involving autogenous regulation was discussed to explain the complicated enzyme activities of nnu mutants. The possibility was discussed of nan mutants representing a positive regulatory locus concerned with the induction of nitrate reductase, nitrate reductase, and molybdenum cofactor biosynthesis. Attempts at performing tetrad analysis were unsuccessful.
3) A transformation protocol was optimised for H. Wingei. Attempts were made to transform leucine auxotrophs to prorotrophy, and wild type strains to hygromycin B resistance. No replicating plasmid was detected. It was assumed that transformation had resulted in the integration of the plasmid. Auxtotrophic mutants were found to be generally epistatic to nitrate assimilation mutants.A neuropsychological investigation into nasotemporal overlap in the human retina.Lines, Christopher Rowanhttps://hdl.handle.net/10023/219852022-03-08T16:44:08Z1984-01-01T00:00:00ZWhen light flashes are presented laterally simple vocal and manual responses are faster to stimuli in the visual half-field having direct access to the responding hemisphere (an 'uncrossed' reaction) than stimuli which go initially to the non-responding hemisphere (a 'crossed' reaction) . In the latter case an interheraispheric crossing is presumably necessary and so the crossed-minus-uncrossed difference (CUD) can be tentatively identified with interhemispheric transmission time. This paradigm was used to investigate the problem of whether or not there is an overlap of ipsi- and contralaterally projecting ganglion cells at the border between nasal and temporal areas of the human retina, resulting in dual representation of the midline in the brain. If such an overlap does exist then presenting stimuli on this region ought to result in an abolition of the CUD since information would be equally available to both hemispheres and there would be no need for any interhemispheric crossing. Four experiments failed to confirm this prediction in that a CUD was found to be present with stimuli presented down to an eccentricity of 1/2 deg in conditions of: vocal (Experiment 1) and manual (Experiment 2) responding in partially dark adapted subjects; manual finger release and thumb press responding in light adapted subjects (Experiment 3); manual responding in an acallosal subject (Experiment A). The results are interpreted as arguing against the existence of overlap in man though some possible reasons why this conclusion may be premature are discussed.
1984-01-01T00:00:00ZLines, Christopher RowanWhen light flashes are presented laterally simple vocal and manual responses are faster to stimuli in the visual half-field having direct access to the responding hemisphere (an 'uncrossed' reaction) than stimuli which go initially to the non-responding hemisphere (a 'crossed' reaction) . In the latter case an interheraispheric crossing is presumably necessary and so the crossed-minus-uncrossed difference (CUD) can be tentatively identified with interhemispheric transmission time. This paradigm was used to investigate the problem of whether or not there is an overlap of ipsi- and contralaterally projecting ganglion cells at the border between nasal and temporal areas of the human retina, resulting in dual representation of the midline in the brain. If such an overlap does exist then presenting stimuli on this region ought to result in an abolition of the CUD since information would be equally available to both hemispheres and there would be no need for any interhemispheric crossing. Four experiments failed to confirm this prediction in that a CUD was found to be present with stimuli presented down to an eccentricity of 1/2 deg in conditions of: vocal (Experiment 1) and manual (Experiment 2) responding in partially dark adapted subjects; manual finger release and thumb press responding in light adapted subjects (Experiment 3); manual responding in an acallosal subject (Experiment A). The results are interpreted as arguing against the existence of overlap in man though some possible reasons why this conclusion may be premature are discussed.Environmental influences on muscle growth and flesh quality in farmed Atlantic salmon (Salmo salar L.)Beattie, Christopherhttps://hdl.handle.net/10023/219812022-03-08T15:12:15Z2000-01-01T00:00:00ZChapter 1 - General Introduction : The general introduction sets out the rationale for the study and it's applicability to aquaculture. A description of the life history of the Atlantic salmon {Salmo salar L.) is given, together with a description of the origin and current status of fish farming. The structure and function of fish muscle is explained in addition to its growth, development and inherent plasticity. Finally, the environmental influences on muscle growth in fish are discussed and this is followed by the aims of the thesis.
Chapter 2 - Egg incubation temperature influences muscle fibre recruitment during seawater stages of Atlantic salmon (Salmo salar L.) : Eggs of Atlantic salmon {Salmo salar L.) were incubated in either heated or ambient water temperatures. The comparative whole animal and muscle growth performance of the two groups was monitored for 26 months. The number of white muscle fibres per myotome was significantly higher at hatch in the ambient group, resulting in a greater muscle cross sectional area. However, muscle fibre number was almost four-fold higher in the heated group at the SI parr stage relative to the ambient group. Six months following seawater transfer the number of fast white muscle fibres was not significantly different between groups. The 5th and 10th percentile fibre diameters decreased significantly in both groups during winter and spring, indicating a relative increase in the contribution of new fibre recruitment which was correlated with seasonal lows in water temperature and day-length. The results indicate that egg incubation temperature has persistent effects on muscle cellularity throughout the freshwater and early seawater stages of Atlantic salmon.
Chapter 3 - Advanced photoperiod treatment affects smoltification and muscle growth in Atlantic salmon (Salmo salar L.) : Juvenile Atlantic salmon {Salmo salar L.) were reared under three different photoperiod regimes: constant light (CL), simulated short winter (SW) and simulated long winter (LW) from July to December 1997. Muscle fibre frequency analysis suggested increased contribution of muscle hypertrophy towards somatic growth in all groups during summer and autumn while increased fibre recruitment was found in the CL and SW groups during winter. The number of white muscle fibres per myotome was linearly related to total white muscle cross-sectional area with no significant differences between groups. This indicates that the SW treatment increased muscle growth but that the relative contribution of hypertrophy to fibre recruitment was not affected by photoperiod treatment at this stage in the life cycle.
Chapter 4 - Cage systems and light manipulation influence muscle fibre cellularity and harvest quality of underyearling (0+) Atlantic salmon in seawater : Underyearling (0+) Atlantic salmon {Salmo salar L.) were reared in conventional sea cages and closed pens systems under natural light and additional continuous light for 14 months up to harvest. The comparative muscle cellularity of all groups was assessed in November 1995, together with harvest quality parameters including texture (hardness), percentage lipid and fillet colour. Muscle fibre frequency analysis revealed increased variation in fibre frequency in fish reared under constant light regimes. Two-way analysis of variance showed no significant differences in the 5th, 10th or 50th percentiles between treatment, however a significant effect of light treatment was found on the 95th percentile diameter value. Muscle fibre density (fibres/mm2) was not significantly different between treatments although a within-fish comparison of the steak-section revealed significantly higher fibre densities in the dorsal compared to the lateral epaxial area. Lipid was positively correlated to body mass and regression analysis revealed no significant relationship between muscle fibre density and fillet hardness as measured by texture profile analysis or fillet colour measured by Roche colour card.
Chapter 5 - Instrumental measurements of texture and it's relation to muscle fibre density in Atlantic salmon (Salmo salar L.) : Atlantic salmon {Salmo salar L.), l-5kg (pre-gutted body mass) were subjected to a series of standard flesh quality tests along the length of the fillet and the results related to muscle fibre density. The NQC cut had a firmer texture than the Mowi. The NQC cut was also found to be significantly leaner with a lower % lipid than the Mowi region. Significant differences in Hunterlab® colour score were also found with the NQC region having significantly higher readings than those in the Mowi region. Muscle fibre density (MFD) (no. muscle fibres/mm2 muscle cross-sectional area) was found to be significantly higher in the NQC region than the MOWI region. A weak correlation was found between body mass and MFD in the Mowi but not in the NQC region. Muscle fibre density did however, show a positive correlation with maximum shear force. The results indicate that muscle fibre density influences texture in Atlantic salmon. The potential for the manipulation of muscle cellularity and hence flesh quality are briefly discussed.
Chapter 6 - General Discussion : The major findings of the thesis are discussed in relation to previous work in addition to possible implications for salmon aquaculture and the scope for future study is evaluated.
2000-01-01T00:00:00ZBeattie, ChristopherChapter 1 - General Introduction : The general introduction sets out the rationale for the study and it's applicability to aquaculture. A description of the life history of the Atlantic salmon {Salmo salar L.) is given, together with a description of the origin and current status of fish farming. The structure and function of fish muscle is explained in addition to its growth, development and inherent plasticity. Finally, the environmental influences on muscle growth in fish are discussed and this is followed by the aims of the thesis.
Chapter 2 - Egg incubation temperature influences muscle fibre recruitment during seawater stages of Atlantic salmon (Salmo salar L.) : Eggs of Atlantic salmon {Salmo salar L.) were incubated in either heated or ambient water temperatures. The comparative whole animal and muscle growth performance of the two groups was monitored for 26 months. The number of white muscle fibres per myotome was significantly higher at hatch in the ambient group, resulting in a greater muscle cross sectional area. However, muscle fibre number was almost four-fold higher in the heated group at the SI parr stage relative to the ambient group. Six months following seawater transfer the number of fast white muscle fibres was not significantly different between groups. The 5th and 10th percentile fibre diameters decreased significantly in both groups during winter and spring, indicating a relative increase in the contribution of new fibre recruitment which was correlated with seasonal lows in water temperature and day-length. The results indicate that egg incubation temperature has persistent effects on muscle cellularity throughout the freshwater and early seawater stages of Atlantic salmon.
Chapter 3 - Advanced photoperiod treatment affects smoltification and muscle growth in Atlantic salmon (Salmo salar L.) : Juvenile Atlantic salmon {Salmo salar L.) were reared under three different photoperiod regimes: constant light (CL), simulated short winter (SW) and simulated long winter (LW) from July to December 1997. Muscle fibre frequency analysis suggested increased contribution of muscle hypertrophy towards somatic growth in all groups during summer and autumn while increased fibre recruitment was found in the CL and SW groups during winter. The number of white muscle fibres per myotome was linearly related to total white muscle cross-sectional area with no significant differences between groups. This indicates that the SW treatment increased muscle growth but that the relative contribution of hypertrophy to fibre recruitment was not affected by photoperiod treatment at this stage in the life cycle.
Chapter 4 - Cage systems and light manipulation influence muscle fibre cellularity and harvest quality of underyearling (0+) Atlantic salmon in seawater : Underyearling (0+) Atlantic salmon {Salmo salar L.) were reared in conventional sea cages and closed pens systems under natural light and additional continuous light for 14 months up to harvest. The comparative muscle cellularity of all groups was assessed in November 1995, together with harvest quality parameters including texture (hardness), percentage lipid and fillet colour. Muscle fibre frequency analysis revealed increased variation in fibre frequency in fish reared under constant light regimes. Two-way analysis of variance showed no significant differences in the 5th, 10th or 50th percentiles between treatment, however a significant effect of light treatment was found on the 95th percentile diameter value. Muscle fibre density (fibres/mm2) was not significantly different between treatments although a within-fish comparison of the steak-section revealed significantly higher fibre densities in the dorsal compared to the lateral epaxial area. Lipid was positively correlated to body mass and regression analysis revealed no significant relationship between muscle fibre density and fillet hardness as measured by texture profile analysis or fillet colour measured by Roche colour card.
Chapter 5 - Instrumental measurements of texture and it's relation to muscle fibre density in Atlantic salmon (Salmo salar L.) : Atlantic salmon {Salmo salar L.), l-5kg (pre-gutted body mass) were subjected to a series of standard flesh quality tests along the length of the fillet and the results related to muscle fibre density. The NQC cut had a firmer texture than the Mowi. The NQC cut was also found to be significantly leaner with a lower % lipid than the Mowi region. Significant differences in Hunterlab® colour score were also found with the NQC region having significantly higher readings than those in the Mowi region. Muscle fibre density (MFD) (no. muscle fibres/mm2 muscle cross-sectional area) was found to be significantly higher in the NQC region than the MOWI region. A weak correlation was found between body mass and MFD in the Mowi but not in the NQC region. Muscle fibre density did however, show a positive correlation with maximum shear force. The results indicate that muscle fibre density influences texture in Atlantic salmon. The potential for the manipulation of muscle cellularity and hence flesh quality are briefly discussed.
Chapter 6 - General Discussion : The major findings of the thesis are discussed in relation to previous work in addition to possible implications for salmon aquaculture and the scope for future study is evaluated.Social learning and the influence of social context : studies with common marmosets and olive baboonsCaldwell, Christine Annahttps://hdl.handle.net/10023/219792022-03-08T14:47:56Z2003-01-01T00:00:00ZThe traditional layman's view of "monkey see, monkey do" contrasts strikingly with the general opinion of the scientific community, which has all but written off the imitative abilities of monkeys. This thesis presents an argument that proposes various ways in which the existing experimental literature may have led to an underestimation of the social learning abilities of monkeys. Firstly, a literature review of comparative approaches to the study of imitation reveals that species have rarely been tested in truly comparative ways, i.e. by comparing performance on analogous task designs. Furthermore, even when analogous tasks are used, confounds (many of them peculiar to social learning research) may be rife. The first experimental chapter examines the performance of common marmoset subjects on a task designed to be similar to one used to test for imitation in several other primate species. Using this paradigm, clear effects of observation of a skilled demonstrator are found. Moving on to the issue of potential confounds in social learning research, the next three experimental chapters address the issue of the effect of social context on social learning. The first of these studies demonstrates that marmosets' skill learning can be strongly facilitated by close social interaction with a trained demonstrator, a result which contrasts quite strongly with many similar studies involving species with less tolerant social structures. The final four studies therefore involve comparisons between common marmosets (which are very tolerant within their family group) and olive baboons (which have a steeply hierarchical social organisation). It is shown that in the baboons, but not the marmosets, a skilled individual's demonstration quality is impaired by the presence of a dominant observer. Furthermore, the baboons, again in contrast with the marmosets, are inhibited from approaching and jointly interacting with a dominant demonstrator, reducing opportunities for skill transmission.
2003-01-01T00:00:00ZCaldwell, Christine AnnaThe traditional layman's view of "monkey see, monkey do" contrasts strikingly with the general opinion of the scientific community, which has all but written off the imitative abilities of monkeys. This thesis presents an argument that proposes various ways in which the existing experimental literature may have led to an underestimation of the social learning abilities of monkeys. Firstly, a literature review of comparative approaches to the study of imitation reveals that species have rarely been tested in truly comparative ways, i.e. by comparing performance on analogous task designs. Furthermore, even when analogous tasks are used, confounds (many of them peculiar to social learning research) may be rife. The first experimental chapter examines the performance of common marmoset subjects on a task designed to be similar to one used to test for imitation in several other primate species. Using this paradigm, clear effects of observation of a skilled demonstrator are found. Moving on to the issue of potential confounds in social learning research, the next three experimental chapters address the issue of the effect of social context on social learning. The first of these studies demonstrates that marmosets' skill learning can be strongly facilitated by close social interaction with a trained demonstrator, a result which contrasts quite strongly with many similar studies involving species with less tolerant social structures. The final four studies therefore involve comparisons between common marmosets (which are very tolerant within their family group) and olive baboons (which have a steeply hierarchical social organisation). It is shown that in the baboons, but not the marmosets, a skilled individual's demonstration quality is impaired by the presence of a dominant observer. Furthermore, the baboons, again in contrast with the marmosets, are inhibited from approaching and jointly interacting with a dominant demonstrator, reducing opportunities for skill transmission.The speed of sight : neural correlates of perceptual reports in RSVPKeysers, Christianhttps://hdl.handle.net/10023/219782022-03-08T14:43:23Z2000-01-01T00:00:00ZMacaque monkeys were presented with continuous rapid serial visual presentation (RSVP) sequences of unrelated naturalistic images at rates of 14ms/image to 222ms/image, while neurones that responded selectively to complex patterns (e.g. faces) were recorded in the anterior superior temporal sulcus (STSa). Stimulus selectivity was preserved for 65% of these neurones even at surprisingly fast presentation rates (14ms/image=72images/s). Such rapid processing constrains theories of visual processing. Five human subjects were asked to detect or remember specific images in the RSVP sequences under equivalent conditions. Their performance in both tasks was above chance at all rates (14-11lms/image). The neurometric performance of single neurones was quantitatively comparable to the psychophysical performance of human observers and responded in a similar way to changes in presentation rate.
Large sections (51 or 93ms) of the stimulus presentation duration in the RSVP sequences were then replaced with gaps of blank screen. This manipulation affected neither the neurometric performance of single neurones nor the recognition performance of human observers. This indicates that in STSa neural persistence after a stimulus has been turned off is quantitatively identical to the response that occurs if the stimulus stays on for up to 93ms longer: a neural correlate of human visual persistence. This maintained performance in judging the identity of a stimulus is surprising considering how different sequences with and without gaps appeared to the observers: introducing gaps as short as 23ms consistently created a perception of flicker.
Together these findings indicate that the perception of stimulus identity is dissociated from other aspects of perception such as flicker, and that the responses of STSa cells are a neural correlate of visual identity perception but not of other aspects of visual perception such as flicker.
2000-01-01T00:00:00ZKeysers, ChristianMacaque monkeys were presented with continuous rapid serial visual presentation (RSVP) sequences of unrelated naturalistic images at rates of 14ms/image to 222ms/image, while neurones that responded selectively to complex patterns (e.g. faces) were recorded in the anterior superior temporal sulcus (STSa). Stimulus selectivity was preserved for 65% of these neurones even at surprisingly fast presentation rates (14ms/image=72images/s). Such rapid processing constrains theories of visual processing. Five human subjects were asked to detect or remember specific images in the RSVP sequences under equivalent conditions. Their performance in both tasks was above chance at all rates (14-11lms/image). The neurometric performance of single neurones was quantitatively comparable to the psychophysical performance of human observers and responded in a similar way to changes in presentation rate.
Large sections (51 or 93ms) of the stimulus presentation duration in the RSVP sequences were then replaced with gaps of blank screen. This manipulation affected neither the neurometric performance of single neurones nor the recognition performance of human observers. This indicates that in STSa neural persistence after a stimulus has been turned off is quantitatively identical to the response that occurs if the stimulus stays on for up to 93ms longer: a neural correlate of human visual persistence. This maintained performance in judging the identity of a stimulus is surprising considering how different sequences with and without gaps appeared to the observers: introducing gaps as short as 23ms consistently created a perception of flicker.
Together these findings indicate that the perception of stimulus identity is dissociated from other aspects of perception such as flicker, and that the responses of STSa cells are a neural correlate of visual identity perception but not of other aspects of visual perception such as flicker.Negative strand RNA viruses : a structural studyRyan, Charlottehttps://hdl.handle.net/10023/219722022-03-08T11:50:55Z2005-01-01T00:00:00ZThis thesis details the study of proteins derived from four negative strand RNA viruses: Simian Virus 5 (SV5), Bunyamwera virus (BUN), Rabies virus and Newcastle Disease virus (NDV). Each virus is an important human and/or animal pathogen with the capacity to cause outbreaks of epidemic proportions. Biochemical and biological characterisation of viral proteins has been fundamental in determining the pathogenic potential of their associated viruses. Elucidation of a polypeptide's tertiary structure can be pivotal in the full interpretation of this data by defining structure-function relationships intrinsic to protein activity. However, to date the number of solved virus protein structures remains relatively small.
The predominant focus of this work was interpretation of biophysical evidence gathered during attempts to elucidate the tertiary structures of the phosphoprotein (SV5 P), nucleoprotein (BUN N) and rabies glycoprotein (CVS G).
Following successful expression and purification of SV5 P, attempts to crystallise the protein failed. Further characterisation revealed the N-terminal domain to be predominantly disordered. Several strategies were developed to induce globularity by co-expression with an in vivo binding partner, but concluded without success. Finally, truncated regions of SV5 P were expressed, purified and placed into crystallisation screens.
BUN N crystals were successfully obtained following optimisation of an established purification procedure. Pursuit of better quality crystals was hindered by precipitation of BUN N at low concentrations. The aggregation of the protein precluded all attempts to increase soluble protein yield.
To produce glycosylated CVS G, recombinant P. pastoris clones were constructed and tested for expression. Initial success in small-scale expression trials was not repeatable in volumes suitable for producing significant protein yields. Finally, this thesis furthers previous studies on the catalytic domain of the hemagglutinin-neuraminidase protein (HN) from NDV. The structures of two HN-inhibitor complexes were solved to 2.5 and 2.8 Å respectively. The inhibitory actions of the substrate analogues are discussed in terms of inhibitor HN interactions.
2005-01-01T00:00:00ZRyan, CharlotteThis thesis details the study of proteins derived from four negative strand RNA viruses: Simian Virus 5 (SV5), Bunyamwera virus (BUN), Rabies virus and Newcastle Disease virus (NDV). Each virus is an important human and/or animal pathogen with the capacity to cause outbreaks of epidemic proportions. Biochemical and biological characterisation of viral proteins has been fundamental in determining the pathogenic potential of their associated viruses. Elucidation of a polypeptide's tertiary structure can be pivotal in the full interpretation of this data by defining structure-function relationships intrinsic to protein activity. However, to date the number of solved virus protein structures remains relatively small.
The predominant focus of this work was interpretation of biophysical evidence gathered during attempts to elucidate the tertiary structures of the phosphoprotein (SV5 P), nucleoprotein (BUN N) and rabies glycoprotein (CVS G).
Following successful expression and purification of SV5 P, attempts to crystallise the protein failed. Further characterisation revealed the N-terminal domain to be predominantly disordered. Several strategies were developed to induce globularity by co-expression with an in vivo binding partner, but concluded without success. Finally, truncated regions of SV5 P were expressed, purified and placed into crystallisation screens.
BUN N crystals were successfully obtained following optimisation of an established purification procedure. Pursuit of better quality crystals was hindered by precipitation of BUN N at low concentrations. The aggregation of the protein precluded all attempts to increase soluble protein yield.
To produce glycosylated CVS G, recombinant P. pastoris clones were constructed and tested for expression. Initial success in small-scale expression trials was not repeatable in volumes suitable for producing significant protein yields. Finally, this thesis furthers previous studies on the catalytic domain of the hemagglutinin-neuraminidase protein (HN) from NDV. The structures of two HN-inhibitor complexes were solved to 2.5 and 2.8 Å respectively. The inhibitory actions of the substrate analogues are discussed in terms of inhibitor HN interactions.The recovery of tryptophan from hydrolysis of proteins with trifluoroacetic acid and hydrochloric acidAkiode, Cherub Adeoluhttps://hdl.handle.net/10023/219732022-03-08T12:09:35Z1980-01-01T00:00:00ZA method has been developed for the determination of tryptophan in proteins. This technique modified the use of strong acid such as 6M HC1 containing mercapto-acetic acid (thioglycollic acid). Tri-fluoro acetic acid has been used to dilute concentrated HC1 and mercapto acetic acid was added to prevent the destruction of labile tryptophan during acid hydrolysis of lyophilized proteins in an evacuated sealed tube. Trifluoro acetic acid and hydrochloric acid (1:1) mixture serves several advanges: (1) The two reagents are miscible, (2) Trifluoro acetic acid is a good solvent for peptides and in strong acid, amino groups are protonated and hence not acetylated, (3) Trifluoro acetate can be easily removed and the point of attack is probably trifluro acetyl as well as carbonyl carbon. The activation of the β-carboxyl group of some amino acids could result in the formation of cyclic imide by displacement of tri-fluoro acetic acid. But this is doubtful, because if it occurs, there will be incomplete hydrolysis.
The sample proteins were lyophilized and suspended in freshly prepared Hydrochloric acid diluted to 6M with trifluoro-acetic acid containing mercapto acetic acid. The tube was then placed in solid-carbon dioxide and ethanol. When frozen, the tube was evacuated to 0.1mm Hg and sealed under vacuum. Hydrolysis was conducted at a controlled temperature of 110° + 1°C for 24, 36 and 43 hours in a DRI-BLOCK heater. The excess solvent was removed on a rotatory vacuum evaporator connected to Paxman Cooling System, water bath at 37°C and oil pump pressure within 20 minutes. The residue was quantitively estimated using norleucine which is used as internal standard for J63LJLC-5AH Amino Acid Analyzer. The values of tryptophan and other amino acids obtained were close to the expected integral values and recoveries of all other amino acids were comparable to those observed after hydrolysis with 6M HC1 or 6M HC1 containing 4% mercapto acetic acid or p-toluene sulphonic acid. The method can also be used for protein containing about 5% (w/w) carbohydrate.
The hydrolysate can also w be used in Miller's colorimetric method for the determination of tryptophan in purified proteins. The procedure, however, is not yet tested with feedingstuffs. Hence, a new method for the microanalysis of tryptophan by acid hydrolysis is proposed.
1980-01-01T00:00:00ZAkiode, Cherub AdeoluA method has been developed for the determination of tryptophan in proteins. This technique modified the use of strong acid such as 6M HC1 containing mercapto-acetic acid (thioglycollic acid). Tri-fluoro acetic acid has been used to dilute concentrated HC1 and mercapto acetic acid was added to prevent the destruction of labile tryptophan during acid hydrolysis of lyophilized proteins in an evacuated sealed tube. Trifluoro acetic acid and hydrochloric acid (1:1) mixture serves several advanges: (1) The two reagents are miscible, (2) Trifluoro acetic acid is a good solvent for peptides and in strong acid, amino groups are protonated and hence not acetylated, (3) Trifluoro acetate can be easily removed and the point of attack is probably trifluro acetyl as well as carbonyl carbon. The activation of the β-carboxyl group of some amino acids could result in the formation of cyclic imide by displacement of tri-fluoro acetic acid. But this is doubtful, because if it occurs, there will be incomplete hydrolysis.
The sample proteins were lyophilized and suspended in freshly prepared Hydrochloric acid diluted to 6M with trifluoro-acetic acid containing mercapto acetic acid. The tube was then placed in solid-carbon dioxide and ethanol. When frozen, the tube was evacuated to 0.1mm Hg and sealed under vacuum. Hydrolysis was conducted at a controlled temperature of 110° + 1°C for 24, 36 and 43 hours in a DRI-BLOCK heater. The excess solvent was removed on a rotatory vacuum evaporator connected to Paxman Cooling System, water bath at 37°C and oil pump pressure within 20 minutes. The residue was quantitively estimated using norleucine which is used as internal standard for J63LJLC-5AH Amino Acid Analyzer. The values of tryptophan and other amino acids obtained were close to the expected integral values and recoveries of all other amino acids were comparable to those observed after hydrolysis with 6M HC1 or 6M HC1 containing 4% mercapto acetic acid or p-toluene sulphonic acid. The method can also be used for protein containing about 5% (w/w) carbohydrate.
The hydrolysate can also w be used in Miller's colorimetric method for the determination of tryptophan in purified proteins. The procedure, however, is not yet tested with feedingstuffs. Hence, a new method for the microanalysis of tryptophan by acid hydrolysis is proposed.Counterimmunoelectrophoresis in the detection of surface antigens of Neisseria gonorrhoeaeFox, Charles Christopherhttps://hdl.handle.net/10023/219672022-03-01T12:44:14Z1983-01-01T00:00:00ZThe study was initiated to investigate the possibility of developing a new serological method for the diagnosis of infection caused "by Neisseria gonorrhoeae. A full description of the organism is given, with regard to its "biochemical and serological characteristics, and its pathogenicity and disease pathology. A resume of the methods used for isolation and identification of the organism is presented together with an ' evaluation of the reliability of each method. The rationale of the method under investigation, using a counterimmunoelectrophoresis system to detect capsulate Neisseria gonorrhoeae in infectious exudates, is discussed.
A full investigation of capsule-staining methods was undertaken in order to identify reliably capsulate organisms in vivo and in vitro; the most reliable method being found to be the India ink stain.
A number of capsule-promoting media were developed and examined to ascertain their capacity to sustain rapid, luxuriant growth of capsulate N. gonorrhoeae for use in raising antibodies, in rabbits, to the N. gonorrhoeae capsule, using both capsulate whole cells and purified capsular material.
A description of the use of the counterimrronoelecirophoresis system in assessing the reactivity of the antisera raised in rabbits towards capsulate N. gonorrhoeae strains and strains of other bacterial species is given, together with possible reasons for the cross-reactivity of both sera toward the other bacterial species.
A discussion is presented of the possible use of the N. gonorrhoeae capsule in vaccine development and suggested lines of further research into the biochemical and serological make-up of the capsule.
1983-01-01T00:00:00ZFox, Charles ChristopherThe study was initiated to investigate the possibility of developing a new serological method for the diagnosis of infection caused "by Neisseria gonorrhoeae. A full description of the organism is given, with regard to its "biochemical and serological characteristics, and its pathogenicity and disease pathology. A resume of the methods used for isolation and identification of the organism is presented together with an ' evaluation of the reliability of each method. The rationale of the method under investigation, using a counterimmunoelectrophoresis system to detect capsulate Neisseria gonorrhoeae in infectious exudates, is discussed.
A full investigation of capsule-staining methods was undertaken in order to identify reliably capsulate organisms in vivo and in vitro; the most reliable method being found to be the India ink stain.
A number of capsule-promoting media were developed and examined to ascertain their capacity to sustain rapid, luxuriant growth of capsulate N. gonorrhoeae for use in raising antibodies, in rabbits, to the N. gonorrhoeae capsule, using both capsulate whole cells and purified capsular material.
A description of the use of the counterimrronoelecirophoresis system in assessing the reactivity of the antisera raised in rabbits towards capsulate N. gonorrhoeae strains and strains of other bacterial species is given, together with possible reasons for the cross-reactivity of both sera toward the other bacterial species.
A discussion is presented of the possible use of the N. gonorrhoeae capsule in vaccine development and suggested lines of further research into the biochemical and serological make-up of the capsule.A molecular analysis of the ostrich 'Struthio camelus massaicus' communal nesting systemKimwele, Charles Ngulihttps://hdl.handle.net/10023/219682022-03-02T09:43:18Z2000-01-01T00:00:00ZSeven hypervariable molecular microsatellite markers were isolated and characterised to investigate the colonial nesting of the East African ostrich subspecies Struthio camelus massaicus. The study was based at Nairobi National Park, a 117 km2 park just 7 km south of the city centre. The ostrich breeding system is complex: I estimated that the territorial male defends a territory of 1.15 ± 0.27 (SD) km2 when nesting. Females have larger breeding home ranges that overlap several male territories. From parentage analysis, I estimated that 3-7 females mate with a territorial male and lay up to 66 eggs in a communal nest within the male's territory. One female, the first (major female) to initiate egg laying in a nest, pairs with the territorial male and provides parental care in the form of egg guarding, incubation and escort of the chicks. What makes the communal nesting system of the ostrich unique is that the major female gives free access to other (minor) females to lay in her nest. The major female, who lays a mean of 9.15 ± 2.47 (SD) eggs partitions the clutch into a central clutch comprising an average of 22.9 ± 3.7 (SD) eggs for incubation and peripheral clutch consisting of excess eggs that are not incubated. This study found that the major female may be able to select her eggs for retention in the central clutch. I investigated the possibility that the other central clutch eggs retained were laid by her close relatives. This was not the case. Both the territorial males and the major female had incubated extra pair fertilised eggs. This study found that 71.2% of the incubated eggs were not parented by either the territorial male or the major female. All the major females were found to lay in other nests as minor females, probably before becoming a major female. The conflict arising from communal nesting and biparental care results in the territorial male copulating with his major female and other females venturing into his territory; the female also seeks extra pair matings and selectively favours her eggs for placement into the central clutch where they are incubated by herself and the territorial male. The major female and the territorial male both seek to maximise their individual reproductive success.
2000-01-01T00:00:00ZKimwele, Charles NguliSeven hypervariable molecular microsatellite markers were isolated and characterised to investigate the colonial nesting of the East African ostrich subspecies Struthio camelus massaicus. The study was based at Nairobi National Park, a 117 km2 park just 7 km south of the city centre. The ostrich breeding system is complex: I estimated that the territorial male defends a territory of 1.15 ± 0.27 (SD) km2 when nesting. Females have larger breeding home ranges that overlap several male territories. From parentage analysis, I estimated that 3-7 females mate with a territorial male and lay up to 66 eggs in a communal nest within the male's territory. One female, the first (major female) to initiate egg laying in a nest, pairs with the territorial male and provides parental care in the form of egg guarding, incubation and escort of the chicks. What makes the communal nesting system of the ostrich unique is that the major female gives free access to other (minor) females to lay in her nest. The major female, who lays a mean of 9.15 ± 2.47 (SD) eggs partitions the clutch into a central clutch comprising an average of 22.9 ± 3.7 (SD) eggs for incubation and peripheral clutch consisting of excess eggs that are not incubated. This study found that the major female may be able to select her eggs for retention in the central clutch. I investigated the possibility that the other central clutch eggs retained were laid by her close relatives. This was not the case. Both the territorial males and the major female had incubated extra pair fertilised eggs. This study found that 71.2% of the incubated eggs were not parented by either the territorial male or the major female. All the major females were found to lay in other nests as minor females, probably before becoming a major female. The conflict arising from communal nesting and biparental care results in the territorial male copulating with his major female and other females venturing into his territory; the female also seeks extra pair matings and selectively favours her eggs for placement into the central clutch where they are incubated by herself and the territorial male. The major female and the territorial male both seek to maximise their individual reproductive success.Height selection and frequency measurements of signals originating from biological preparationsRoemmélé, Charles J.https://hdl.handle.net/10023/219692022-03-02T09:53:35Z1970-01-01T00:00:00Z1970-01-01T00:00:00ZRoemmélé, Charles J.Structure of the major capsid protein (hexon) of adenovirus types 40 and 41 and the use of hexon-derived oligonucleotide probes for diagnosisToogood, Celiahttps://hdl.handle.net/10023/219622022-03-01T11:38:05Z1991-01-01T00:00:00ZThe genes encoding the major capsid proteins (hexons) of human adenovirus types 40 and 41 were isolated and sequenced. Comparison of the predicted amino acid sequences with the hexons of adenovirus types 2 and 5 revealed regions of high homology, interspersed with regions of extreme variability across the four serotypes. Fitting of the Ad40 and 41 hexons to the known three-dimensional structure of the Ad2 protein, reveal that the majority of changes are confined to the loop domains which form the surface of the virion, while the P1 and P2 β-barrels which comprise the base are well conserved. A major exception to this is the absence in both Ad 40 and 41 of 32 consecutive amino acids present in adenovirus type 2. In Ad2 this sequencee extends from the top of the l1 loop down into the D-strand of the P1 domain, and includes a highly acidic domain which may be responsible for pH-induced conformation changes at the surface of the virion. Molecular-modelling suggests that, despite the absence of these amino acids, residues in both the Ad40 and 41 hexons can be accommodated into the P1 domain to form an alternative D-strand, hence maintaining the integrity of the base. However, it is predicted that the Ad 40 and 41 D-strands would be shorter than their type 2 counterpart. Thus it is likely that the hexons of the enteric adenoviruses closely resemble the Ad2 protein in the basal domains, but differ significantly in the architecture of their surface towers. Unique sequences identified in the Ad40 and 41 hexon genes were used to design type-specific radioactive oligonucleotide probes which were tested for their usefulness as tools for the diagnosis of enteric adenovirus infection. These oligonucleotides were successful in demonstrating the presence of enteric adenovirus DNA in faecal and infected cell extracts using a dot-blot hybridisation assay.
1991-01-01T00:00:00ZToogood, CeliaThe genes encoding the major capsid proteins (hexons) of human adenovirus types 40 and 41 were isolated and sequenced. Comparison of the predicted amino acid sequences with the hexons of adenovirus types 2 and 5 revealed regions of high homology, interspersed with regions of extreme variability across the four serotypes. Fitting of the Ad40 and 41 hexons to the known three-dimensional structure of the Ad2 protein, reveal that the majority of changes are confined to the loop domains which form the surface of the virion, while the P1 and P2 β-barrels which comprise the base are well conserved. A major exception to this is the absence in both Ad 40 and 41 of 32 consecutive amino acids present in adenovirus type 2. In Ad2 this sequencee extends from the top of the l1 loop down into the D-strand of the P1 domain, and includes a highly acidic domain which may be responsible for pH-induced conformation changes at the surface of the virion. Molecular-modelling suggests that, despite the absence of these amino acids, residues in both the Ad40 and 41 hexons can be accommodated into the P1 domain to form an alternative D-strand, hence maintaining the integrity of the base. However, it is predicted that the Ad 40 and 41 D-strands would be shorter than their type 2 counterpart. Thus it is likely that the hexons of the enteric adenoviruses closely resemble the Ad2 protein in the basal domains, but differ significantly in the architecture of their surface towers. Unique sequences identified in the Ad40 and 41 hexon genes were used to design type-specific radioactive oligonucleotide probes which were tested for their usefulness as tools for the diagnosis of enteric adenovirus infection. These oligonucleotides were successful in demonstrating the presence of enteric adenovirus DNA in faecal and infected cell extracts using a dot-blot hybridisation assay.Factors affecting the distribution and abundance of grey seals, (Halichoerus grypus) around the U.K.Stephenson, Catriona M.https://hdl.handle.net/10023/219582022-03-01T10:34:46Z2003-01-01T00:00:00ZThe UK grey seal (Halichoerus grypus) population has been increasing steadily for at least 30 years. During this period, the number of pups born at all major colonies has been monitored annually by the Natural Environment Research Council (NERC) Sea Mammal Research Unit (SMRU) using aerial photography. Some colonies have remained constant for decades, many have increased exponentially, and a few have decreased or even become extinct. The aim of this study was to identify the environmental factors that determine where a female grey seal chooses to give birth, in order to develop predictive models of colony spread.
A technique for extracting fine resolution data on topography and seal distribution from aerial survey photographs was developed and applied to a number of colonies in Orkney, Scotland, in different years. There was a consistent relationship between pup location and distance to water and slope at these colonies, but a varying relationship between pup location and distance to access to the sea.
The occurrence of aggression between female seals at the Isle of May in the 2000 breeding season could be predicted using models fitted to observations of variables that are measurable in aerial photographs. The locations of new-born pups could be modelled by a combination of topography, and variation in the presence of conspecifics and aggressive behaviour over time. These models were used to simulate variations in levels of aggression and hence pup distributions in space and time on two colonies in Orkney. The general applicability of the Isle of May models was limited, probably due to a number of specific characteristics of the original study site. However, the model did identify areas of preferred habitat towards the middle and end of the breeding season when the numbers of pups on an island is greatest.
2003-01-01T00:00:00ZStephenson, Catriona M.The UK grey seal (Halichoerus grypus) population has been increasing steadily for at least 30 years. During this period, the number of pups born at all major colonies has been monitored annually by the Natural Environment Research Council (NERC) Sea Mammal Research Unit (SMRU) using aerial photography. Some colonies have remained constant for decades, many have increased exponentially, and a few have decreased or even become extinct. The aim of this study was to identify the environmental factors that determine where a female grey seal chooses to give birth, in order to develop predictive models of colony spread.
A technique for extracting fine resolution data on topography and seal distribution from aerial survey photographs was developed and applied to a number of colonies in Orkney, Scotland, in different years. There was a consistent relationship between pup location and distance to water and slope at these colonies, but a varying relationship between pup location and distance to access to the sea.
The occurrence of aggression between female seals at the Isle of May in the 2000 breeding season could be predicted using models fitted to observations of variables that are measurable in aerial photographs. The locations of new-born pups could be modelled by a combination of topography, and variation in the presence of conspecifics and aggressive behaviour over time. These models were used to simulate variations in levels of aggression and hence pup distributions in space and time on two colonies in Orkney. The general applicability of the Isle of May models was limited, probably due to a number of specific characteristics of the original study site. However, the model did identify areas of preferred habitat towards the middle and end of the breeding season when the numbers of pups on an island is greatest.Flow-dependent restructuring of the intermediate filament cytoskeleton and activation of NF-κB in cultured endothelial cellsBeers, Catherinehttps://hdl.handle.net/10023/219542022-03-01T09:45:15Z2002-01-01T00:00:00ZEndothelial cells are profoundly influenced by shear stresses associated with blood flow. A parallel plate chamber was used to study the effects of flow on (i) the morphology of the intermediate filament cytoskeleton; and (ii) the activation of an inducible nuclear transcription factor, NF-KB/Rel, in cultured human and bovine endothelial cells.
The experiments described in Part One show that the distribution of intermediate filaments in static cultures is dramatically altered when cells become confluent. Immunostaining with antibody to vimentin showed that the diffuse meshwork of fine intermediate filaments characteristic of sub-confluent cells is reconfigured, forming a network dominated by a prominent 'ring' of intermediate filaments that surrounds the nucleus. The transition between the two states is triggered by the formation of cell-cell contacts. Immunoblots of whole cell lysates showed a time-dependent increase in vimentin expression and a simultaneous down-regulation of both actin and tubulin. The effect of exposing confluent and sub-confluent cultures to flow was therefore quite different. However, in both circumstances, some cells were seen to respond more rapidly than others and were affected to a much greater extent. This heterogeneity is attributed to spatial gradients of shear stress caused by irregularities in cell surface topography.
The distribution of the intermediate filament-associated protein (IFAP) plectin was also investigated. Immunostaining using a monoclonal antibody (417D) to plectin showed that the protein is associated with the intermediate filament network. However, the staining was not uniform and the intensity was greatest on the basal cell surface, in the form of discrete 'streaks', a pattern very similar to that seen using antibodies to focal adhesion proteins. Studies have since shown that the tips of actin stress fibres and vimentin co-localise with plectin 'streaks', and with staining for the αᵥβ₃ integrin and the α4 sub unit of laminin. These so-called vimentin-associated matrix adhesions (VMA) serve to anchor both actin stress fibres and vimentin to the extracellular matrix, with plectin possibly acting as a cytoskeletal 'linker' protein.
Part Two describes the results of experiments on the activation of NF-kB by flow. Cells were grown on cover slips or on glass microscope slides and then subjected to steady laminar flow. Indirect immunofluoresence was used to monitor nuclear translocation of the p65 sub-unit in endothelial cells over-expressing either wild type or catalytically inactive mutant forms of putative 'upstream' kinases (including IKK1, IKK2 and NIK).
Endogenous IKK1 and DCK2 activities were determined by measuring ³²P incorporation into a GST-IKBα fusion protein substrate.
Transcriptional activity of NF-kB was quantified by means of a Con A Luciferase reporter gene, driven by a 3kB enhancer element. A 19-fold increase in reporter activity confirmed that NF-kB induced by flow is transcriptionally active. Immunoblots of whole cell extracts were used to investigate the time course of the degradation of NF-kB inhibitor proteins (IkBα, IkBβ₁ and p105). The results show that flow rapidly activates IKK1 and IKK2 and transiently degrades IkBα and IkBβ₁, but not p105. Nuclear translocation of p65 is induced by flow in wild type cells, and also in cells over-expressing wild type IKK1, IKK2 and NIK but it is prevented in cells transfected with kinase-inactive mutants. These results show that IKK1, IKK2 and NIK are essential components of the signalling pathway activated by flow.
2002-01-01T00:00:00ZBeers, CatherineEndothelial cells are profoundly influenced by shear stresses associated with blood flow. A parallel plate chamber was used to study the effects of flow on (i) the morphology of the intermediate filament cytoskeleton; and (ii) the activation of an inducible nuclear transcription factor, NF-KB/Rel, in cultured human and bovine endothelial cells.
The experiments described in Part One show that the distribution of intermediate filaments in static cultures is dramatically altered when cells become confluent. Immunostaining with antibody to vimentin showed that the diffuse meshwork of fine intermediate filaments characteristic of sub-confluent cells is reconfigured, forming a network dominated by a prominent 'ring' of intermediate filaments that surrounds the nucleus. The transition between the two states is triggered by the formation of cell-cell contacts. Immunoblots of whole cell lysates showed a time-dependent increase in vimentin expression and a simultaneous down-regulation of both actin and tubulin. The effect of exposing confluent and sub-confluent cultures to flow was therefore quite different. However, in both circumstances, some cells were seen to respond more rapidly than others and were affected to a much greater extent. This heterogeneity is attributed to spatial gradients of shear stress caused by irregularities in cell surface topography.
The distribution of the intermediate filament-associated protein (IFAP) plectin was also investigated. Immunostaining using a monoclonal antibody (417D) to plectin showed that the protein is associated with the intermediate filament network. However, the staining was not uniform and the intensity was greatest on the basal cell surface, in the form of discrete 'streaks', a pattern very similar to that seen using antibodies to focal adhesion proteins. Studies have since shown that the tips of actin stress fibres and vimentin co-localise with plectin 'streaks', and with staining for the αᵥβ₃ integrin and the α4 sub unit of laminin. These so-called vimentin-associated matrix adhesions (VMA) serve to anchor both actin stress fibres and vimentin to the extracellular matrix, with plectin possibly acting as a cytoskeletal 'linker' protein.
Part Two describes the results of experiments on the activation of NF-kB by flow. Cells were grown on cover slips or on glass microscope slides and then subjected to steady laminar flow. Indirect immunofluoresence was used to monitor nuclear translocation of the p65 sub-unit in endothelial cells over-expressing either wild type or catalytically inactive mutant forms of putative 'upstream' kinases (including IKK1, IKK2 and NIK).
Endogenous IKK1 and DCK2 activities were determined by measuring ³²P incorporation into a GST-IKBα fusion protein substrate.
Transcriptional activity of NF-kB was quantified by means of a Con A Luciferase reporter gene, driven by a 3kB enhancer element. A 19-fold increase in reporter activity confirmed that NF-kB induced by flow is transcriptionally active. Immunoblots of whole cell extracts were used to investigate the time course of the degradation of NF-kB inhibitor proteins (IkBα, IkBβ₁ and p105). The results show that flow rapidly activates IKK1 and IKK2 and transiently degrades IkBα and IkBβ₁, but not p105. Nuclear translocation of p65 is induced by flow in wild type cells, and also in cells over-expressing wild type IKK1, IKK2 and NIK but it is prevented in cells transfected with kinase-inactive mutants. These results show that IKK1, IKK2 and NIK are essential components of the signalling pathway activated by flow.Marine benthic system function and biodiversityBiles, Catherine Lucyhttps://hdl.handle.net/10023/219552022-03-01T09:59:03Z2003-01-01T00:00:00ZUnderstanding the influence of biodiversity on the functioning of ecosystems is vital given current rates of species loss. The relationship between biodiversity and ecosystem functioning was explored in marine sediment systems, where few studies have investigated biodiversity-ecosystem functioning relationships. In addition, the influence of flow on these processes was examined, as this is an important abiotic factor in marine benthic systems.
Ecosystem functioning was measured by nutrient concentration in the water column above the sediment, particle redistribution, particle resuspension, sediment shear strength and microbial community composition and activity. Benthic chambers with flow facility were designed and the flow rate calibrated. The chambers were used in both laboratory and in situ experiments to assess the effect of macrofauna in single species and multispecies treatments on these aspects of the functioning of the system. Species richness, species evenness and functional trait richness were varied in order to assess the effects of different measures of diversity on the functioning of the system.
Single species treatments had highly variable effects on ecosystem functioning, probably resulting from differences in species behavioural traits. Species diversity was found to have significant effects on ecosystem functioning, with functional richness accounting for most variation. Functional richness was the only measure of diversity to consider the influence of species behaviour on the ecosystem and therefore best explained the changes in ecosystem functioning.
Flow was found to have a significant effect on nutrient concentration in the presence of macrofauna. Microbial activity was also affected by flow, though species treatment alone had no discernible affect. Flow may therefore be acting to alter macrofaunal behaviour, which changes microbial activity, affecting nutrient cycling processes.
This work showed the importance of biodiversity-functioning relationships in a marine sediment system, with results providing most support for the idiosyncratic model describing ecosystem response to biodiversity.
2003-01-01T00:00:00ZBiles, Catherine LucyUnderstanding the influence of biodiversity on the functioning of ecosystems is vital given current rates of species loss. The relationship between biodiversity and ecosystem functioning was explored in marine sediment systems, where few studies have investigated biodiversity-ecosystem functioning relationships. In addition, the influence of flow on these processes was examined, as this is an important abiotic factor in marine benthic systems.
Ecosystem functioning was measured by nutrient concentration in the water column above the sediment, particle redistribution, particle resuspension, sediment shear strength and microbial community composition and activity. Benthic chambers with flow facility were designed and the flow rate calibrated. The chambers were used in both laboratory and in situ experiments to assess the effect of macrofauna in single species and multispecies treatments on these aspects of the functioning of the system. Species richness, species evenness and functional trait richness were varied in order to assess the effects of different measures of diversity on the functioning of the system.
Single species treatments had highly variable effects on ecosystem functioning, probably resulting from differences in species behavioural traits. Species diversity was found to have significant effects on ecosystem functioning, with functional richness accounting for most variation. Functional richness was the only measure of diversity to consider the influence of species behaviour on the ecosystem and therefore best explained the changes in ecosystem functioning.
Flow was found to have a significant effect on nutrient concentration in the presence of macrofauna. Microbial activity was also affected by flow, though species treatment alone had no discernible affect. Flow may therefore be acting to alter macrofaunal behaviour, which changes microbial activity, affecting nutrient cycling processes.
This work showed the importance of biodiversity-functioning relationships in a marine sediment system, with results providing most support for the idiosyncratic model describing ecosystem response to biodiversity.GABAergic modulation of locomotor rhythmicity during post-embryonic development in 'Xenopus laevis'Reith, Carolyn A.https://hdl.handle.net/10023/219512022-02-24T15:36:15Z1996-01-01T00:00:00Z1. The role of the inhibitory amino acid, GABA acting at GABAa receptors during embryonic and larval Active swimming in Xenopus laevis has been investigated.
2. Intracellular recordings, under tetrodotoxin, reveal two types of spontaneous inhibitory postsynaptic potential: short duration glycinergic ipsps and longer duration GABAergic ipsps.
3. The neurosteroid, 5β-pregnan-3α-ol-20-one (5β3α), enhances the presynaptic release of GABA and the postsynaptic effects of GABAa receptor activation, without affecting glycinergic ipsps.
4. At embryonic stage 37/8, GABAa receptor activation has an overall inhibitory action on the swimming pattern. 5β3α causes a decrease in the frequency and duration of Active swim episodes.
5. By larval stage 42, GABAa receptor activation influences various parameters of fictive swimming (burst duration, cycle period and rostrocaudal delay) and thus finely tunes the motor output. Bicucullineblockade of GABAa receptors causes swimming frequency and burst durations to increase and rostro-caudal delays to decrease.
6. GABA release from the descending projections of midhindbrain reticulospinal neurons also appears to play a role in the intrinsic termination of larval swimming, as opposed to their previous involvement in a reflex stopping response in the embryo.
7. By stage 42, the dimming response, which elicits swimming following a sudden dimming of the illumination, is declining. GABAergic neurotransmission plays a role in down regulating this sensory reflex.
8. As opposed to embryonic swimming, sustained larval swimming requires a certain level of inhibition since it is abolished when both glycine and GABAa receptors are blocked.
9. When GABAa and glycine receptors are blocked dining NMDA-induced swimming activity, a slow network oscillation is revealed. This appears to result from the enhancement of a pre-existing low amplitude oscillation already present during NMDA-induced rhythmic activity.
10. Pharmacological evidence suggests that the slow network modulation of NMDA-induced swimming results from the expression of intrinsic 5HT-dependent membrane potential oscillations, since both are abolished by a specific 5HTla antagonist, pindobind-5HTla.
1996-01-01T00:00:00ZReith, Carolyn A.1. The role of the inhibitory amino acid, GABA acting at GABAa receptors during embryonic and larval Active swimming in Xenopus laevis has been investigated.
2. Intracellular recordings, under tetrodotoxin, reveal two types of spontaneous inhibitory postsynaptic potential: short duration glycinergic ipsps and longer duration GABAergic ipsps.
3. The neurosteroid, 5β-pregnan-3α-ol-20-one (5β3α), enhances the presynaptic release of GABA and the postsynaptic effects of GABAa receptor activation, without affecting glycinergic ipsps.
4. At embryonic stage 37/8, GABAa receptor activation has an overall inhibitory action on the swimming pattern. 5β3α causes a decrease in the frequency and duration of Active swim episodes.
5. By larval stage 42, GABAa receptor activation influences various parameters of fictive swimming (burst duration, cycle period and rostrocaudal delay) and thus finely tunes the motor output. Bicucullineblockade of GABAa receptors causes swimming frequency and burst durations to increase and rostro-caudal delays to decrease.
6. GABA release from the descending projections of midhindbrain reticulospinal neurons also appears to play a role in the intrinsic termination of larval swimming, as opposed to their previous involvement in a reflex stopping response in the embryo.
7. By stage 42, the dimming response, which elicits swimming following a sudden dimming of the illumination, is declining. GABAergic neurotransmission plays a role in down regulating this sensory reflex.
8. As opposed to embryonic swimming, sustained larval swimming requires a certain level of inhibition since it is abolished when both glycine and GABAa receptors are blocked.
9. When GABAa and glycine receptors are blocked dining NMDA-induced swimming activity, a slow network oscillation is revealed. This appears to result from the enhancement of a pre-existing low amplitude oscillation already present during NMDA-induced rhythmic activity.
10. Pharmacological evidence suggests that the slow network modulation of NMDA-induced swimming results from the expression of intrinsic 5HT-dependent membrane potential oscillations, since both are abolished by a specific 5HTla antagonist, pindobind-5HTla.The quantitative genetics of pheromone blend in 'Drosophila'Adamson, Carriehttps://hdl.handle.net/10023/219522022-02-24T16:03:47Z2001-01-01T00:00:00ZDrosophila simulans and D. sechellia are sibling species of the melanogaster group and are so closely related that crosses between them produce fertile female offspring. Recognition of a potential mate in Drosophila depends on many cues including olfactory and auditory stimulation by female pheromones and male courtship song respectively. Once recognition of a potential mate has occurred then behavioural signals indicate acceptance or rejection. Female pheromones play an important role in conspecific mating and interspecific differences appear to be due to a few loci, mainly on the third chromosome. These were identified using only morphological marker loci in the past. This study investigates the location of loci contributing to differences in pheromone blend using QTL analysis of flies produced by backcrossing hybrid females to D. simulans males. The more modern method of using molecular markers will be used for this analysis. The scored markers are analysed using the QTL cartographer program to determine the level of association of the regions between pairs of markers to the trait.
2001-01-01T00:00:00ZAdamson, CarrieDrosophila simulans and D. sechellia are sibling species of the melanogaster group and are so closely related that crosses between them produce fertile female offspring. Recognition of a potential mate in Drosophila depends on many cues including olfactory and auditory stimulation by female pheromones and male courtship song respectively. Once recognition of a potential mate has occurred then behavioural signals indicate acceptance or rejection. Female pheromones play an important role in conspecific mating and interspecific differences appear to be due to a few loci, mainly on the third chromosome. These were identified using only morphological marker loci in the past. This study investigates the location of loci contributing to differences in pheromone blend using QTL analysis of flies produced by backcrossing hybrid females to D. simulans males. The more modern method of using molecular markers will be used for this analysis. The scored markers are analysed using the QTL cartographer program to determine the level of association of the regions between pairs of markers to the trait.The role of acid labile surfactant-I in protein extraction from sodium dodecyl sulfate polyacrylamide gelsBuckner, Carolyn Ricehttps://hdl.handle.net/10023/219492022-02-24T14:34:31Z2005-01-01T00:00:00ZThe surfactant known as acid labile surfactant I (ALS-I) (RapiGest) was investigated to probe its effectiveness in enhancing protein digestion and subsequent protein identification and to determine its suitability for use in whole protein extraction methods. Tryptic solution and in-gel digests of several standard proteins showed a distinct increase in the number of peptides matched in ALS-I aided digests versus digests performed without ALS-I. Several experiments gave no identification unless ALS-I was present.
The ability to analyse whole protein samples with detergent or extracted from gels has eluded scientists and slowed certain areas of research such as the investigation and analysis of membrane proteins. ALS-I was ascertained to be compatible with and enhance whole protein extractions from sodium dodecyl sulfate-polyacrylamide gels (SDS-PA). Extraction was optimized by testing a series of extraction solutions containing ALS-I, DTT and tris/glycine. Extraction efficiency was shown to vary with incubation time and larger proteins proved harder to extract from a gel than smaller proteins. Subsequent analysis of protein extracts was performed by matrix-assisted laser desorption/ionisation mass spectrometry and liquid chromatography-electrospray ionisation mass spectrometry.
In order to analyse ALS-I extracted protein by MALDI-TOF MS it was necessary to develop a novel slow crystallisation using neutral matrix systems and sample preparation techniques. The neutral matrices 2-amino-4-methyl-5-nitropyridine, 4- nitroaniline and 6-aza-2-thiothymine gave good whole protein signals at M+H and M+2H.
Whole protein extracts from SDS-polyacrylamide gels were also analysed by LC-ESI MS, giving good spectra for a range of proteins from superoxide dismutase (SOD) to bovine serum albumin (BSA). Despite small mass inaccuracies, the novel possibility of analysing whole protein extracts from SDS-polyacrylamide gels containing detergent and sufficient protein to give clear protein spectra by LC-ESI MS is very promising, and progress in this technique may prove invaluable to further research into the proteome.
2005-01-01T00:00:00ZBuckner, Carolyn RiceThe surfactant known as acid labile surfactant I (ALS-I) (RapiGest) was investigated to probe its effectiveness in enhancing protein digestion and subsequent protein identification and to determine its suitability for use in whole protein extraction methods. Tryptic solution and in-gel digests of several standard proteins showed a distinct increase in the number of peptides matched in ALS-I aided digests versus digests performed without ALS-I. Several experiments gave no identification unless ALS-I was present.
The ability to analyse whole protein samples with detergent or extracted from gels has eluded scientists and slowed certain areas of research such as the investigation and analysis of membrane proteins. ALS-I was ascertained to be compatible with and enhance whole protein extractions from sodium dodecyl sulfate-polyacrylamide gels (SDS-PA). Extraction was optimized by testing a series of extraction solutions containing ALS-I, DTT and tris/glycine. Extraction efficiency was shown to vary with incubation time and larger proteins proved harder to extract from a gel than smaller proteins. Subsequent analysis of protein extracts was performed by matrix-assisted laser desorption/ionisation mass spectrometry and liquid chromatography-electrospray ionisation mass spectrometry.
In order to analyse ALS-I extracted protein by MALDI-TOF MS it was necessary to develop a novel slow crystallisation using neutral matrix systems and sample preparation techniques. The neutral matrices 2-amino-4-methyl-5-nitropyridine, 4- nitroaniline and 6-aza-2-thiothymine gave good whole protein signals at M+H and M+2H.
Whole protein extracts from SDS-polyacrylamide gels were also analysed by LC-ESI MS, giving good spectra for a range of proteins from superoxide dismutase (SOD) to bovine serum albumin (BSA). Despite small mass inaccuracies, the novel possibility of analysing whole protein extracts from SDS-polyacrylamide gels containing detergent and sufficient protein to give clear protein spectra by LC-ESI MS is very promising, and progress in this technique may prove invaluable to further research into the proteome.Infection by Ophiobolus graminis of some perennial weed grassesWhiteman, Caroline Maryhttps://hdl.handle.net/10023/219482022-02-24T12:56:12Z1967-01-01T00:00:00ZThe appearance of serious outbreaks of take-all in wheat and barley crops can often be correlated with the presence of infected perennial grasses, such as Agropyron repens, Agrostis spp., and Holcus lanatus, growing amongst the crop. Holcus mollis is a weed prevalent amongst cereals growing on light, acid soils. Although this grass has been mentioned in the literature as a possible carrier of the disease, little experimental work appears to have been done to determine the susceptibility of the grass to the take-all fungus, Ophiobolus graminis Sacc.. An investigation was undertaken in this connection. Vegetative segments of H. mollis were found to be only slightly less susceptible than vegetative segments of Agropyron repens, which are heavily attacked by the fungus, but more susceptible than vegetative segments of Agrostis stolonifera.
A number of methods were used for estimating the amount of disease on these grasses. The symptoms of the disease, a blackening of the stele of the roots and ectotrophic runner hyphae, are less easy to discriminate on grass than on wheat roots, so an attempt was made to find a method particularly suitable for use with grasses. A method used extensively throughout this work was one of direct observation. Grass plants, seedlings or vegetative fragments, were viewed under water against a white background to determine the presence of stelar lesions. This was the most suitable method for differentiating between a discoloured, diseased root and. one discoloured by some other cause. The presence of runner hyphae, on what appeared to be healthy roots, could be seen when the roots were viewed under a binocular dissecting microscope under the same conditions as for stelar lesions. The percentage infection was calculated from the total number of roots and the total number infected with one or more stelar lesions. The runner hyphae were not used in this calculation but their number was noted. When present on Holcus spp. and A stolonifera seedlings but without any stelar infection they were found to cause stelar lesions on subsequent wheat seedlings. These hyphae must, therefore, be considered a potential hazard, to cereal crops.
There were seldom any above ground signs of attack by the fungus on the grasses; no withering of the leaves nor plate mycelium, which are generally associated with severe attacks of the fungus on wheat seedlings. However, A. repens did show some browning and withering of the leaves when the roots were heavily invaded.
Mature vegetative fragments of A. repens and A. stolonifera were found to be more susceptible to the disease than those nearer the terminal growing point of a rhizome or stolon. Seedlings of A. repens and Holcus spp. were found to vary in their susceptibility to the fungus, and this did not appear to be affected by the age of the seedlings, over the duration of time of the experiments.
Six mycelial isolates of Ophiobolus graminis were obtained from different parts of the country. Five of the isolates were found to be highly pathogenic on wheat, but the sixth was only moderately so. This sixth isolate (3s) survived as chaffed inoculum in unsterile soil in a heated greenhouse for only four months, whereas the other five were still present, although at a low level, after eight months in the same soil under identical conditions. This isolate, was found on two occasions to cause more severe damage to A. repens vegetative segments than to wheat seedlings, a result which was contrary to those obtained with the other isolates.
Throughout this work an effort was made to use grass material from the same source in order to avoid variation wher^-ever possible. Hblcus mollis exists as a number of different cytotypes, tetraploid (4n = 28), pentaploid (5n = 35), hexaploid (6n = 42) and heptaploid (7n = 49). Triploid (3n = 21) and aneuploid plants are also frequently found. Rhizome material was collected from different habitats and localities throughout the British Isles. In order to determine the cytotype, chromosome counts of the rhizome material had to be made. Suitable lengths of rhizome were placed in shallow dishes of water, and when adventitious roots, which grew out from the nodes, were of sufficient length, the root tips were stained with aceto-orcein, squashed and the number of chromosomes counted. Seven clones of vegetative H. mollis were grown, three tetraploid, three pentaploid and. one aneuploid clone. A comparison made of the vegetative characters of these clones shaved that they varied considerably. These differences could not have been entirely due to the different environmental conditions of the habitats from which they were collected, as they did not alter after a year in identical conditions in a heated greenhouse.
The clones were found to vary in their susceptibility to the six isolates of O, graminis. Vegetative fragments of the clones, all as similar as possible, were inoculated with each of the isolates. The results of the experiment were interesting in several respects. Three of the clones were found statistically to be significantly less susceptible to the isolates than the other three. (The aneuploid material was not included in the statistical analysis of the results owing to the limited, amount available for inoculation). This is interesting in view of the fact that no one variety of wheat has been found to be more resistant to take-all than any other. The more resistant clones were not all of one cytotype, but two were pentaploid and one tetraploid. It appeared that the aneuploid was highly susceptible to the fungus, but few definite conclusions can be drawn from the results because of the small amount of material.
There was considerable variation of the results of some experiments, which could have been caused by differences in the O. graminis isolates as well as in the grass material. These isolates were mycelial and therefore not as pure as single ascospore isolates, the mycelium having possibly grown from a number of ascospores. This may have accounted for some of the variation in the cultural characteristics of the isolates,, and their varying pathogenicity in different experiments, as it has been found that mycelia grown from different ascospores from the same ascus, vary in their pathogenicity on wheat seedlings.
1967-01-01T00:00:00ZWhiteman, Caroline MaryThe appearance of serious outbreaks of take-all in wheat and barley crops can often be correlated with the presence of infected perennial grasses, such as Agropyron repens, Agrostis spp., and Holcus lanatus, growing amongst the crop. Holcus mollis is a weed prevalent amongst cereals growing on light, acid soils. Although this grass has been mentioned in the literature as a possible carrier of the disease, little experimental work appears to have been done to determine the susceptibility of the grass to the take-all fungus, Ophiobolus graminis Sacc.. An investigation was undertaken in this connection. Vegetative segments of H. mollis were found to be only slightly less susceptible than vegetative segments of Agropyron repens, which are heavily attacked by the fungus, but more susceptible than vegetative segments of Agrostis stolonifera.
A number of methods were used for estimating the amount of disease on these grasses. The symptoms of the disease, a blackening of the stele of the roots and ectotrophic runner hyphae, are less easy to discriminate on grass than on wheat roots, so an attempt was made to find a method particularly suitable for use with grasses. A method used extensively throughout this work was one of direct observation. Grass plants, seedlings or vegetative fragments, were viewed under water against a white background to determine the presence of stelar lesions. This was the most suitable method for differentiating between a discoloured, diseased root and. one discoloured by some other cause. The presence of runner hyphae, on what appeared to be healthy roots, could be seen when the roots were viewed under a binocular dissecting microscope under the same conditions as for stelar lesions. The percentage infection was calculated from the total number of roots and the total number infected with one or more stelar lesions. The runner hyphae were not used in this calculation but their number was noted. When present on Holcus spp. and A stolonifera seedlings but without any stelar infection they were found to cause stelar lesions on subsequent wheat seedlings. These hyphae must, therefore, be considered a potential hazard, to cereal crops.
There were seldom any above ground signs of attack by the fungus on the grasses; no withering of the leaves nor plate mycelium, which are generally associated with severe attacks of the fungus on wheat seedlings. However, A. repens did show some browning and withering of the leaves when the roots were heavily invaded.
Mature vegetative fragments of A. repens and A. stolonifera were found to be more susceptible to the disease than those nearer the terminal growing point of a rhizome or stolon. Seedlings of A. repens and Holcus spp. were found to vary in their susceptibility to the fungus, and this did not appear to be affected by the age of the seedlings, over the duration of time of the experiments.
Six mycelial isolates of Ophiobolus graminis were obtained from different parts of the country. Five of the isolates were found to be highly pathogenic on wheat, but the sixth was only moderately so. This sixth isolate (3s) survived as chaffed inoculum in unsterile soil in a heated greenhouse for only four months, whereas the other five were still present, although at a low level, after eight months in the same soil under identical conditions. This isolate, was found on two occasions to cause more severe damage to A. repens vegetative segments than to wheat seedlings, a result which was contrary to those obtained with the other isolates.
Throughout this work an effort was made to use grass material from the same source in order to avoid variation wher^-ever possible. Hblcus mollis exists as a number of different cytotypes, tetraploid (4n = 28), pentaploid (5n = 35), hexaploid (6n = 42) and heptaploid (7n = 49). Triploid (3n = 21) and aneuploid plants are also frequently found. Rhizome material was collected from different habitats and localities throughout the British Isles. In order to determine the cytotype, chromosome counts of the rhizome material had to be made. Suitable lengths of rhizome were placed in shallow dishes of water, and when adventitious roots, which grew out from the nodes, were of sufficient length, the root tips were stained with aceto-orcein, squashed and the number of chromosomes counted. Seven clones of vegetative H. mollis were grown, three tetraploid, three pentaploid and. one aneuploid clone. A comparison made of the vegetative characters of these clones shaved that they varied considerably. These differences could not have been entirely due to the different environmental conditions of the habitats from which they were collected, as they did not alter after a year in identical conditions in a heated greenhouse.
The clones were found to vary in their susceptibility to the six isolates of O, graminis. Vegetative fragments of the clones, all as similar as possible, were inoculated with each of the isolates. The results of the experiment were interesting in several respects. Three of the clones were found statistically to be significantly less susceptible to the isolates than the other three. (The aneuploid material was not included in the statistical analysis of the results owing to the limited, amount available for inoculation). This is interesting in view of the fact that no one variety of wheat has been found to be more resistant to take-all than any other. The more resistant clones were not all of one cytotype, but two were pentaploid and one tetraploid. It appeared that the aneuploid was highly susceptible to the fungus, but few definite conclusions can be drawn from the results because of the small amount of material.
There was considerable variation of the results of some experiments, which could have been caused by differences in the O. graminis isolates as well as in the grass material. These isolates were mycelial and therefore not as pure as single ascospore isolates, the mycelium having possibly grown from a number of ascospores. This may have accounted for some of the variation in the cultural characteristics of the isolates,, and their varying pathogenicity in different experiments, as it has been found that mycelia grown from different ascospores from the same ascus, vary in their pathogenicity on wheat seedlings.The identification and characterisation of excreted proteins during early chick developmentConnolly, Carolinehttps://hdl.handle.net/10023/219462022-02-24T12:15:16Z1993-01-01T00:00:00ZProteins are transferred to medium conditioned by chick embryonic tissue. These secreted proteins are a diverse group of molecules including growth factors, proteases and glycoproteins. The majority of the secreted proteins present in conditioned medium are less than 70 kDa in molecular weight. Stage 17 to 22 embryos were used.
TGF—β is present in this medium as a 25 kDa active protein and is formed from the breakdown of an inactive molecular weight form. To obtain an adequate quantity of conditioned medium to carry out protein assays a proportion of 1 head : 6 wing buds : 6 leg buds : 3 tail buds were used. A spatial distribution of this growth factor was thought to exist in the conditioned medium of head, wing buds, leg buds and tail buds and was present at a ratio of 5 : 1.4 : 1.6 :1, respectively.
This suggested that TGF- β is present in regions of increased developmental activity. When the amount of secreted protein was compared to the amount of total protein in secreting tissue the ratio of TGF- β in the head, wing, leg and tail buds was 1 : 1.3 : 1.9 : 1.8, respectively. This suggested that no significant distribution of the growth factor existed in these regions and that head conditioned medium contained more TGF- β because there was more tissue present in the head than the limbs and tail.
During the investigation, loss of activity was observed for many of the proteins of conditioned medium. This led to the discovery of a single proteolytic activity in conditioned medium. From 2 to 8 days of development this activity was present in the head, wing buds, leg buds and tail of the embryo, at a constant level. Other stages were not tested. It is active at physiological temperature and a pH of 7.5. It does not fit into any of the four known classes of proteases and is not one of the known proteases associated with development. It is therefore suggested that it is of a novel class. Since the protease is present in the media conditioned by chick tissue at a constant level from days 2 to 8 of development and TGF- β is also present but in increasing amounts, a role the protease may have on TGF- β processing was investigated. The protease does not activate latent TGF- β or inactivate active TGF- β. During an investigation into the effect TGF- β had on the proteolytic activity of the protease, to determine if TGF— β affected the proteolytic activity of the protease, it was discovered that TGF- β displayed proteolytic activity. The proteolytic properties of other growth factors were investigated to determine if proteolytic activity is a general property of growth factors.
An effect was observed when the growth factors EGF or FGF and the protease were incubated together but since the growth factors also displayed proteolytic activity, it was impossible to say which protein affected which.
Finally conditioned medium evokes a primary anchorage independent growth response in the presence of NRK 49F cells. This activity has been demonstrated to be due to a low molecular weight (less than 30 kDa), charged glycoprotein. Purification of a single molecule which produced this activity proved not to be possible and it is suggested that this activity requires the action of more than one glycoprotein. The glycoprotein mixture which displayed this primary response also possessed proteolytic activity. It is suggested that many of the proteins of conditioned medium possess more than one type of activity as a means of increasing efficiency.
1993-01-01T00:00:00ZConnolly, CarolineProteins are transferred to medium conditioned by chick embryonic tissue. These secreted proteins are a diverse group of molecules including growth factors, proteases and glycoproteins. The majority of the secreted proteins present in conditioned medium are less than 70 kDa in molecular weight. Stage 17 to 22 embryos were used.
TGF—β is present in this medium as a 25 kDa active protein and is formed from the breakdown of an inactive molecular weight form. To obtain an adequate quantity of conditioned medium to carry out protein assays a proportion of 1 head : 6 wing buds : 6 leg buds : 3 tail buds were used. A spatial distribution of this growth factor was thought to exist in the conditioned medium of head, wing buds, leg buds and tail buds and was present at a ratio of 5 : 1.4 : 1.6 :1, respectively.
This suggested that TGF- β is present in regions of increased developmental activity. When the amount of secreted protein was compared to the amount of total protein in secreting tissue the ratio of TGF- β in the head, wing, leg and tail buds was 1 : 1.3 : 1.9 : 1.8, respectively. This suggested that no significant distribution of the growth factor existed in these regions and that head conditioned medium contained more TGF- β because there was more tissue present in the head than the limbs and tail.
During the investigation, loss of activity was observed for many of the proteins of conditioned medium. This led to the discovery of a single proteolytic activity in conditioned medium. From 2 to 8 days of development this activity was present in the head, wing buds, leg buds and tail of the embryo, at a constant level. Other stages were not tested. It is active at physiological temperature and a pH of 7.5. It does not fit into any of the four known classes of proteases and is not one of the known proteases associated with development. It is therefore suggested that it is of a novel class. Since the protease is present in the media conditioned by chick tissue at a constant level from days 2 to 8 of development and TGF- β is also present but in increasing amounts, a role the protease may have on TGF- β processing was investigated. The protease does not activate latent TGF- β or inactivate active TGF- β. During an investigation into the effect TGF- β had on the proteolytic activity of the protease, to determine if TGF— β affected the proteolytic activity of the protease, it was discovered that TGF- β displayed proteolytic activity. The proteolytic properties of other growth factors were investigated to determine if proteolytic activity is a general property of growth factors.
An effect was observed when the growth factors EGF or FGF and the protease were incubated together but since the growth factors also displayed proteolytic activity, it was impossible to say which protein affected which.
Finally conditioned medium evokes a primary anchorage independent growth response in the presence of NRK 49F cells. This activity has been demonstrated to be due to a low molecular weight (less than 30 kDa), charged glycoprotein. Purification of a single molecule which produced this activity proved not to be possible and it is suggested that this activity requires the action of more than one glycoprotein. The glycoprotein mixture which displayed this primary response also possessed proteolytic activity. It is suggested that many of the proteins of conditioned medium possess more than one type of activity as a means of increasing efficiency.Morphological patterns of perturbation and recovery in populations of blood cells and their precursors : an annotated selection of publicationsVilliers-Briscoe, Cäcilia A.https://hdl.handle.net/10023/219392022-02-23T16:45:33Z1992-01-01T00:00:00ZThe development of microscopy, coinciding with the synthesis of appropriate dyes, allowed blood cells to be differentiated one from another. The accessibility of blood cells and their extravascular precursors allowed full advantage to be taken of these techniques. As a result, information about the patterns of production and accumulation of blood cells was readily exploited in the diagnosis, management and analysis of haematological disorders. An attempt is made to elucidate the behaviour of haematopoietic cell populations, which are normally in a state of dynamic equilibrium. To obtain an insight into this equilibrium, the system was exposed to measured perturbations by endotoxin, cytotoxic drugs and X-irradiation. The analysis is based mainly on microscopical observations of cell morphology, but also includes observations on the behaviour of transplanted haematopoietic cells and the results of assays conducted to monitor changes in the stem cell compartment. In vivo and in vitro observations on radiationinduced murine myeloid leukaemias reveal similarities with the human form of the disease. Fifteen leukaemias were studied in detail with particular reference to their cellular morphology and the proliferative status of cells derived from different haematopoietic tissues. The present classified selection of publications illustrates the use and continuing importance of morphological techniques in investigations designed to provide information about the perturbation of haematopoiesis, the properties of the earliest precursors of the blood cells and the manifestations of abnormal production or accumulation in the leukaemias.
1992-01-01T00:00:00ZVilliers-Briscoe, Cäcilia A.The development of microscopy, coinciding with the synthesis of appropriate dyes, allowed blood cells to be differentiated one from another. The accessibility of blood cells and their extravascular precursors allowed full advantage to be taken of these techniques. As a result, information about the patterns of production and accumulation of blood cells was readily exploited in the diagnosis, management and analysis of haematological disorders. An attempt is made to elucidate the behaviour of haematopoietic cell populations, which are normally in a state of dynamic equilibrium. To obtain an insight into this equilibrium, the system was exposed to measured perturbations by endotoxin, cytotoxic drugs and X-irradiation. The analysis is based mainly on microscopical observations of cell morphology, but also includes observations on the behaviour of transplanted haematopoietic cells and the results of assays conducted to monitor changes in the stem cell compartment. In vivo and in vitro observations on radiationinduced murine myeloid leukaemias reveal similarities with the human form of the disease. Fifteen leukaemias were studied in detail with particular reference to their cellular morphology and the proliferative status of cells derived from different haematopoietic tissues. The present classified selection of publications illustrates the use and continuing importance of morphological techniques in investigations designed to provide information about the perturbation of haematopoiesis, the properties of the earliest precursors of the blood cells and the manifestations of abnormal production or accumulation in the leukaemias.Microtubule assembly in the cochlea of the mousePaton, Calum C.https://hdl.handle.net/10023/219412022-02-24T09:34:37Z1991-01-01T00:00:00ZPillar cells of the organ of Corti of the mouse were examined after fixation and embedding for transmission electron microscopy. These specialised epithelial cells have transcellular microtubule arrays which are parallel to the longitudinal axes of the cells.
Array microtubules have diameters of about 28 nm and are probably composed of 15 protofilaments. These microtubules have, in Inner pillar cells, nucleating sites which are associated with the lateral plasmalemma. Microtubules of the inner pillar cell array start to elongate during the second day post-partum. Assembly of microtubules of outer pillar cells Is temporally distinct. This assembly does not appear to start until about the third day post-partum.
Array assembly in inner pillar cells occurs at the same stages in vitro as in vivo but with a reduction in the overall number of microtubules present. These have the same diameter as those which elongate in vivo and also exhibit similar end-on anchorage to the lateral plasmalemma.
After culturing the organ of Corti in vitro, the microtubule array is similar in structure to that which assembles in situ, the arrays have a tubular configuration. This is produced by the annular configuration of lateral plasmalemma-associated microtubule nucleating sites. This contrasts with the array configuration in outer pillar cells. Nucleatlon sites in these cells are situated in a small apical turret-like process which produces the rod-like configuration of the microtubule array.
In both inner and outer pillar cells, microtubules which have small diameters of about 21 nm, are associated with the centrosome. These microtubules are randomly oriented at the apical region of each cell.
1991-01-01T00:00:00ZPaton, Calum C.Pillar cells of the organ of Corti of the mouse were examined after fixation and embedding for transmission electron microscopy. These specialised epithelial cells have transcellular microtubule arrays which are parallel to the longitudinal axes of the cells.
Array microtubules have diameters of about 28 nm and are probably composed of 15 protofilaments. These microtubules have, in Inner pillar cells, nucleating sites which are associated with the lateral plasmalemma. Microtubules of the inner pillar cell array start to elongate during the second day post-partum. Assembly of microtubules of outer pillar cells Is temporally distinct. This assembly does not appear to start until about the third day post-partum.
Array assembly in inner pillar cells occurs at the same stages in vitro as in vivo but with a reduction in the overall number of microtubules present. These have the same diameter as those which elongate in vivo and also exhibit similar end-on anchorage to the lateral plasmalemma.
After culturing the organ of Corti in vitro, the microtubule array is similar in structure to that which assembles in situ, the arrays have a tubular configuration. This is produced by the annular configuration of lateral plasmalemma-associated microtubule nucleating sites. This contrasts with the array configuration in outer pillar cells. Nucleatlon sites in these cells are situated in a small apical turret-like process which produces the rod-like configuration of the microtubule array.
In both inner and outer pillar cells, microtubules which have small diameters of about 21 nm, are associated with the centrosome. These microtubules are randomly oriented at the apical region of each cell.Isolation and maintenance in culture of identified neurones from 'Helix aspersa'Powell, Brianhttps://hdl.handle.net/10023/219352022-02-23T15:33:59Z1991-01-01T00:00:00Z1991-01-01T00:00:00ZPowell, BrianA study of the effects of physical education lessons on the cardiorespiratory endurance of secondary schoolboysGreen, Brian Neilhttps://hdl.handle.net/10023/219312022-02-01T12:29:39Z1990-01-01T00:00:00ZThe research investigated the effects of a school PE programme on a representative group of 9 boys, aged 12 years, 6 months, from a first year class in a Glasgow secondary school. Cardiorespiratory endurance was assessed using the PWC 170 test [EUROFIT (1988)] on 7 occasions during a 12 month period, before and after blocks of teaching in Rugby, HRPF, Basketball, Volleyball and Athletics. Physical activity levels during lessons were assessed by heart rate monitoring using the Sports Tester PE3000 telemetry system. Evaluation of the conditioning effects was carried out in relation to standard guidelines for cardiorespiratory fitness improvement. There was no significant change in PWC 170 during the 12 month period. However there were instances in all five teaching activities where activity levels were of sufficient intensity to increase cardiorespiratory endurance. Subjects were sub-divided into three groups of similar fitness (high, middle and low) and lesson activity levels were further examined in relation to each of these sub-groups. Results showed considerable variation in subjects response to lessons but established no relationship between fitness sub-group and lessons' conditioning effect. Results indicated that the PE programme in general made no improvement in cardiorespiratory fitness and confirmed the individualised nature of heart rate response to PE lessons, highlighting the importance of teaching content and methodology if improved cardiorespiratory endurance is to be an objective for PE in schools.
1990-01-01T00:00:00ZGreen, Brian NeilThe research investigated the effects of a school PE programme on a representative group of 9 boys, aged 12 years, 6 months, from a first year class in a Glasgow secondary school. Cardiorespiratory endurance was assessed using the PWC 170 test [EUROFIT (1988)] on 7 occasions during a 12 month period, before and after blocks of teaching in Rugby, HRPF, Basketball, Volleyball and Athletics. Physical activity levels during lessons were assessed by heart rate monitoring using the Sports Tester PE3000 telemetry system. Evaluation of the conditioning effects was carried out in relation to standard guidelines for cardiorespiratory fitness improvement. There was no significant change in PWC 170 during the 12 month period. However there were instances in all five teaching activities where activity levels were of sufficient intensity to increase cardiorespiratory endurance. Subjects were sub-divided into three groups of similar fitness (high, middle and low) and lesson activity levels were further examined in relation to each of these sub-groups. Results showed considerable variation in subjects response to lessons but established no relationship between fitness sub-group and lessons' conditioning effect. Results indicated that the PE programme in general made no improvement in cardiorespiratory fitness and confirmed the individualised nature of heart rate response to PE lessons, highlighting the importance of teaching content and methodology if improved cardiorespiratory endurance is to be an objective for PE in schools.The activation of adenovirus type 2 protease and the function of the activating peptidePollard, Brett Davidhttps://hdl.handle.net/10023/219282022-02-01T11:45:34Z2001-01-01T00:00:00ZSome 42 serotypes of Adenovirus are infectious to Humans. To be able to prevent infection using vaccination would be difficult to say the least, since one might have to administer as many as 42 vaccines, one for each serotype. However, if one could produce an antiviral agent specific to an event within the virus's life cycle to prevent the infectiousness one agent could potentially be effective to all serotypes. One such target is the 23 kD protease enzyme responsible primarily for maturation cleavages of structural proteins comprising the viral capsid and the cytoskeletal proteins to escape the cell. The work described here is aimed at understanding more about the role of the peptide responsible for the activation of the protease and determining whether the unusual activation mechanism of this protease is a suitable target for the therapeutic inhibition. Another aim of the study was to attempt to develop an in vivo protease inhibitor assay to complement in vitro activation studies which required the development of a single step purification protocol for the protease. However, attempts to stably integrate the protease and pVI in HeLa and 293 cell lines were not successful due to the toxicity of the basal level of expression and the cocktail of antibiotics required for the selection for integration. Use of transient transfections illustrated that the protease could cleave cytokeratin in vivo in the absence of activating peptide, and suggested that the protease was still toxic to the cells. Studies revealed that the protease from the human serotype 2 could be activated by the peptide from the avian Adenovirus responsible for Egg Drop Syndrome (EDS virus). Since the sequence of the EDS peptide and protease are the most distinct in evolutionary terms from the human type 2, such a cross-activation suggests that any interference with the activation system could be effective across the serotype range. Results obtained here show that the length of the peptide is critical, and contrary to previous reports no evidence was obtained to support the suggestion that the peptide VEGGS is capable of activating the protease. Mutation studies on the contiguous stretch of 4 basic residues within the activating peptide sequence suggested that this does not have a critical role in activation. However, parallel studies showed that this motif could act as a nuclear localisation signal as it is capable of targeting a chimeric protein to the nucleus in a model system. Finally a rapid assay was developed for assessing the binding affinity of peptides to the protease, and results obtained with this suggested variants which are worthy of further study in the search for a possible inhibitor.
2001-01-01T00:00:00ZPollard, Brett DavidSome 42 serotypes of Adenovirus are infectious to Humans. To be able to prevent infection using vaccination would be difficult to say the least, since one might have to administer as many as 42 vaccines, one for each serotype. However, if one could produce an antiviral agent specific to an event within the virus's life cycle to prevent the infectiousness one agent could potentially be effective to all serotypes. One such target is the 23 kD protease enzyme responsible primarily for maturation cleavages of structural proteins comprising the viral capsid and the cytoskeletal proteins to escape the cell. The work described here is aimed at understanding more about the role of the peptide responsible for the activation of the protease and determining whether the unusual activation mechanism of this protease is a suitable target for the therapeutic inhibition. Another aim of the study was to attempt to develop an in vivo protease inhibitor assay to complement in vitro activation studies which required the development of a single step purification protocol for the protease. However, attempts to stably integrate the protease and pVI in HeLa and 293 cell lines were not successful due to the toxicity of the basal level of expression and the cocktail of antibiotics required for the selection for integration. Use of transient transfections illustrated that the protease could cleave cytokeratin in vivo in the absence of activating peptide, and suggested that the protease was still toxic to the cells. Studies revealed that the protease from the human serotype 2 could be activated by the peptide from the avian Adenovirus responsible for Egg Drop Syndrome (EDS virus). Since the sequence of the EDS peptide and protease are the most distinct in evolutionary terms from the human type 2, such a cross-activation suggests that any interference with the activation system could be effective across the serotype range. Results obtained here show that the length of the peptide is critical, and contrary to previous reports no evidence was obtained to support the suggestion that the peptide VEGGS is capable of activating the protease. Mutation studies on the contiguous stretch of 4 basic residues within the activating peptide sequence suggested that this does not have a critical role in activation. However, parallel studies showed that this motif could act as a nuclear localisation signal as it is capable of targeting a chimeric protein to the nucleus in a model system. Finally a rapid assay was developed for assessing the binding affinity of peptides to the protease, and results obtained with this suggested variants which are worthy of further study in the search for a possible inhibitor.Factors influencing the foraging and roosting behaviour of wintering black-tailed godwits (Limosa limosa)Combes, Brian A.https://hdl.handle.net/10023/219302022-02-01T12:14:33Z1989-01-01T00:00:00ZThis thesis examined the behaviour and ecology of a small population of black-tailed godwits wintering on the Eden Estuary, Scotland. The godwits exhibited the typical behaviour of waders using an inter-tidal habitat during the non-breeding season. However, the godwits spent a surprisingly low proportion of the day feeding and formed a low-water roost. Energy intake during the day was not enough for overall requirements and much feeding must have been occurring at night. The frequency of the two foraging methods of the species was dependent on their relative energy intake rate. Kleptoparasitism occurred between godwits. Although this behaviour was rare, the specialisation of the attacking bird was marked. A food-stealing attempt was targeted in such a way that the probability of a high energy item being taken was great. The godwits were gregarious. Assessing the costs, of interference, and advantages, mainly to do with predators, to an individual of flocking, helped to explain the relative spacing behaviour of birds using the two feeding methods. Godwit3 feeding in their preferred area were adversely influenced by the presence of roosting gulls and plovers. When these heterospecifics were present fewer godwits fed there and those that did foraged in deeper, less profitable, water. In the presence of the roosting flock, the godwits reduced their vigilance rate.-. However, for most individuals this advantage was not great enough to allow them to maintain their feeding performance. Juvenile godwits nave much lower foraging rates than adults. An analysis of the components of foraging investigated the causes of the difference. A detailed study of the low-water roost was made. Although there were microclimate and foraging benefits of being in the roost the overriding advantages were concerned with vigilance and predators.
1989-01-01T00:00:00ZCombes, Brian A.This thesis examined the behaviour and ecology of a small population of black-tailed godwits wintering on the Eden Estuary, Scotland. The godwits exhibited the typical behaviour of waders using an inter-tidal habitat during the non-breeding season. However, the godwits spent a surprisingly low proportion of the day feeding and formed a low-water roost. Energy intake during the day was not enough for overall requirements and much feeding must have been occurring at night. The frequency of the two foraging methods of the species was dependent on their relative energy intake rate. Kleptoparasitism occurred between godwits. Although this behaviour was rare, the specialisation of the attacking bird was marked. A food-stealing attempt was targeted in such a way that the probability of a high energy item being taken was great. The godwits were gregarious. Assessing the costs, of interference, and advantages, mainly to do with predators, to an individual of flocking, helped to explain the relative spacing behaviour of birds using the two feeding methods. Godwit3 feeding in their preferred area were adversely influenced by the presence of roosting gulls and plovers. When these heterospecifics were present fewer godwits fed there and those that did foraged in deeper, less profitable, water. In the presence of the roosting flock, the godwits reduced their vigilance rate.-. However, for most individuals this advantage was not great enough to allow them to maintain their feeding performance. Juvenile godwits nave much lower foraging rates than adults. An analysis of the components of foraging investigated the causes of the difference. A detailed study of the low-water roost was made. Although there were microclimate and foraging benefits of being in the roost the overriding advantages were concerned with vigilance and predators.Development and application of telemetry techniques to investigate seal behaviour and survivalMcConnell, Berniehttps://hdl.handle.net/10023/219222022-01-31T16:06:02Z2004-01-01T00:00:00ZThe work described in this thesis covers the development and application of telemetry techniques to investigate seal behaviour and survival. The accuracy of animal location fixes derived from the Argos satellite system was determined, and filtering methods were constructed which removed the more erroneous locations fixes. We developed Argos Satellite Relay Data Loggers (SRDLs) which collect and relay dive and behavioural information from marine mammals via the Argos satellite system. SRDLs were used to describe the foraging and dive behaviour of adult South Georgia southern elephant seals (Miroimga leonina) in relation to bathymetric and oceanographic features. SRDLs were also deployed on naive southern elephant seal pups at Macquarie Island to determine the patterns of dispersal and to relate these patterns to oceanographic variability. Body condition measures and energy expenditure estimates suggested that the smaller weaned pups were almost at the stage of starvation before they encountered foraging areas. UK Grey seal (Halichoerus grypus) foraging was also studied using SRDLs. Most patterns of movement were within 40 km of haulout sites and foraging was inferred to take place in localised areas that were often the preferred habitat of sandeels (.Ammodytes spp). Grey seals could also move many hundreds of kilometres from one region to another. Factors that influence the first year survivouship of grey seal pups were studied in a markrecapture experiment at the Isle of May (UK). Survivourship was greater for females and for those weaned pups with a greater weaned body mass. Also higher postweaning circulating levels of immunoglobulin decreased the probability of survival. A novel telemetry mark-recapture technique based on mobile phone technology was developed to collect 'resighting' data more efficiently and from which survivorship could be modelled with fewer assumptions.
2004-01-01T00:00:00ZMcConnell, BernieThe work described in this thesis covers the development and application of telemetry techniques to investigate seal behaviour and survival. The accuracy of animal location fixes derived from the Argos satellite system was determined, and filtering methods were constructed which removed the more erroneous locations fixes. We developed Argos Satellite Relay Data Loggers (SRDLs) which collect and relay dive and behavioural information from marine mammals via the Argos satellite system. SRDLs were used to describe the foraging and dive behaviour of adult South Georgia southern elephant seals (Miroimga leonina) in relation to bathymetric and oceanographic features. SRDLs were also deployed on naive southern elephant seal pups at Macquarie Island to determine the patterns of dispersal and to relate these patterns to oceanographic variability. Body condition measures and energy expenditure estimates suggested that the smaller weaned pups were almost at the stage of starvation before they encountered foraging areas. UK Grey seal (Halichoerus grypus) foraging was also studied using SRDLs. Most patterns of movement were within 40 km of haulout sites and foraging was inferred to take place in localised areas that were often the preferred habitat of sandeels (.Ammodytes spp). Grey seals could also move many hundreds of kilometres from one region to another. Factors that influence the first year survivouship of grey seal pups were studied in a markrecapture experiment at the Isle of May (UK). Survivourship was greater for females and for those weaned pups with a greater weaned body mass. Also higher postweaning circulating levels of immunoglobulin decreased the probability of survival. A novel telemetry mark-recapture technique based on mobile phone technology was developed to collect 'resighting' data more efficiently and from which survivorship could be modelled with fewer assumptions.The effects of grazing on the recovery of plant-pollinator systems following fire in the MediterraneanVulliamy, Betsyhttps://hdl.handle.net/10023/219242022-02-01T09:40:10Z2003-01-01T00:00:00ZThis study was carried out in phrygana and maquis habitats of the Eastern Mediterranean (hot-spots for bee diversity), to assess grazing impacts on bee communities in habitats also experiencing frequent wildfires, and to explain the mechanisms of such effects. On Mount Carmel, Israel, in 1999 and 2000, habitats with varying intensities of cattle grazing and post-burn age were surveyed. Bee diversity and abundance were measured, together with grazing levels, floral diversity and abundance, nectar and pollen rewards and vegetation structure. On the Island of Lesvos, in 2001, the effects of grazing on vegetation structure and reward production of two shrub species were investigated. Exclosures were used in both sites to show the immediate effects on flowers of removing livestock form formerly grazed areas. Close relationships were found between bee diversity and abundance and flower diversity and abundance, bee abundance being better explained by the previous year's flower abundance. Bee abundance also increased with pollen abundance, but not with nectar availability. Bee and flower species richness were highest at moderate grazing intensities, but abundance, increased even at the highest intensities. Path-analysis showed that the effects of both grazing and fire on bee diversity occurred mainly via changes in herb flower diversity. Conversely, bee abundance was affected mainly by changes in halictid bees, which became more numerous in grazed sites, where ground was compacted and composites were abundant. Grazing also created a mosaic of tall scrub and open patches of herbs. This "patchiness" helped maintain a diverse herb flora. Studies of Cistus creticus and Lavandula stoechas in Lesvos showed that shrub species also produced more flowers, and higher rewards, at patch edges. Overall, bee communities benefit from a relatively high level of grazing in phrygana, and may be further increased if grazing pressure is relaxed during the peak flowering season.
2003-01-01T00:00:00ZVulliamy, BetsyThis study was carried out in phrygana and maquis habitats of the Eastern Mediterranean (hot-spots for bee diversity), to assess grazing impacts on bee communities in habitats also experiencing frequent wildfires, and to explain the mechanisms of such effects. On Mount Carmel, Israel, in 1999 and 2000, habitats with varying intensities of cattle grazing and post-burn age were surveyed. Bee diversity and abundance were measured, together with grazing levels, floral diversity and abundance, nectar and pollen rewards and vegetation structure. On the Island of Lesvos, in 2001, the effects of grazing on vegetation structure and reward production of two shrub species were investigated. Exclosures were used in both sites to show the immediate effects on flowers of removing livestock form formerly grazed areas. Close relationships were found between bee diversity and abundance and flower diversity and abundance, bee abundance being better explained by the previous year's flower abundance. Bee abundance also increased with pollen abundance, but not with nectar availability. Bee and flower species richness were highest at moderate grazing intensities, but abundance, increased even at the highest intensities. Path-analysis showed that the effects of both grazing and fire on bee diversity occurred mainly via changes in herb flower diversity. Conversely, bee abundance was affected mainly by changes in halictid bees, which became more numerous in grazed sites, where ground was compacted and composites were abundant. Grazing also created a mosaic of tall scrub and open patches of herbs. This "patchiness" helped maintain a diverse herb flora. Studies of Cistus creticus and Lavandula stoechas in Lesvos showed that shrub species also produced more flowers, and higher rewards, at patch edges. Overall, bee communities benefit from a relatively high level of grazing in phrygana, and may be further increased if grazing pressure is relaxed during the peak flowering season.Quantification and valuation of the effects of traffic-induced air pollution on mortality : an analysis of fourteen British citiesWalter, Bernhard F.https://hdl.handle.net/10023/219212022-01-31T15:44:34Z2000-01-01T00:00:00ZAn effective transport system is vital for economic well-being and the quality of life. Yet negative external effects of road traffic play a growing role in the environmental political discussion. The majority of these effects produce so-called external costs as they are not paid by generators but are inflicted on society as a whole. In particular, emissions form motor vehicles are of serious concern as they are widely recognised in causing damage to human health, ranging from breathing discomfort to cardio-respiratory diseases resulting in premature death. The latter are the focus of this study, where the ultimate objective is the valuation of the effects of traffic-generated air pollution on mortality. The valuation procedure is undertaken in a stepwise manner. First, the short-term association between daily mortality and ambient air pollution in 14 major British cities between 1992 and 1997 is assessed, using time-series analysis. Second, based on the estimated exposure-response functions the total numbers of premature deaths attributable to air pollution in general, and to road traffic in particular is quantified. Finally, by applying willingness to pay estimates for the value of a statistical life (employing air pollution related adjustments) the total external costs attributable to air pollution are calculated. These figures are an important element for transport policy decision-making, particular on a decentralised local authority level.
2000-01-01T00:00:00ZWalter, Bernhard F.An effective transport system is vital for economic well-being and the quality of life. Yet negative external effects of road traffic play a growing role in the environmental political discussion. The majority of these effects produce so-called external costs as they are not paid by generators but are inflicted on society as a whole. In particular, emissions form motor vehicles are of serious concern as they are widely recognised in causing damage to human health, ranging from breathing discomfort to cardio-respiratory diseases resulting in premature death. The latter are the focus of this study, where the ultimate objective is the valuation of the effects of traffic-generated air pollution on mortality. The valuation procedure is undertaken in a stepwise manner. First, the short-term association between daily mortality and ambient air pollution in 14 major British cities between 1992 and 1997 is assessed, using time-series analysis. Second, based on the estimated exposure-response functions the total numbers of premature deaths attributable to air pollution in general, and to road traffic in particular is quantified. Finally, by applying willingness to pay estimates for the value of a statistical life (employing air pollution related adjustments) the total external costs attributable to air pollution are calculated. These figures are an important element for transport policy decision-making, particular on a decentralised local authority level.A comparative study on the incidence of Barr Bodies in mammalian blood and some factors influencing itAkpogomeh, Benjamin Agbayemiehttps://hdl.handle.net/10023/219172022-01-31T11:52:15Z1982-01-01T00:00:00ZEarly beliefs that Barr Bodies (sex chromatin; drumsticks) were due merely to the XX Chromosomes in the female mere challenged as far back as 1956. That they only appear in a percentage of neutrophils, polymorphs and other somatic cells mas a starting point and that they are more frequent when nuclear segmentation is increased either by ageing or folate deficiency suggested that the explanation originally held required closer investigation. A great deal of research has been undertaken to establish the factors involved. Some account of these are listed and recorded in this thesis. The comparative incidence of Barr Bodies in mammalian blood appears to have little coverage and go round an aspect worthy of investigation. Apart from humans the range of available mammals was limited largely to domestic animals; although an attempt was made (with small success) to obtain material from more exotic mammals. The range of the different groups (13 in all) is set out in the tables which includes mainly normal mammals with a small section on the megaloblastic anaemias as a readily available source of hypersegmentation associated with folate deficiency. The main difficulties encountered mere the limited time available; the difficulty in obtaining material in sufficient quantity to have numerical significance; the nature of this work which is very labour intensive in that it cannot successfully be automated in any of the aspects. Within the frame work of this thesis, there is scope for a very great deal of development which the writer intends to undertake on his required return home.
1982-01-01T00:00:00ZAkpogomeh, Benjamin AgbayemieEarly beliefs that Barr Bodies (sex chromatin; drumsticks) were due merely to the XX Chromosomes in the female mere challenged as far back as 1956. That they only appear in a percentage of neutrophils, polymorphs and other somatic cells mas a starting point and that they are more frequent when nuclear segmentation is increased either by ageing or folate deficiency suggested that the explanation originally held required closer investigation. A great deal of research has been undertaken to establish the factors involved. Some account of these are listed and recorded in this thesis. The comparative incidence of Barr Bodies in mammalian blood appears to have little coverage and go round an aspect worthy of investigation. Apart from humans the range of available mammals was limited largely to domestic animals; although an attempt was made (with small success) to obtain material from more exotic mammals. The range of the different groups (13 in all) is set out in the tables which includes mainly normal mammals with a small section on the megaloblastic anaemias as a readily available source of hypersegmentation associated with folate deficiency. The main difficulties encountered mere the limited time available; the difficulty in obtaining material in sufficient quantity to have numerical significance; the nature of this work which is very labour intensive in that it cannot successfully be automated in any of the aspects. Within the frame work of this thesis, there is scope for a very great deal of development which the writer intends to undertake on his required return home.Human emotional memory : physiological, pharmacological and neuropsychological investigationsPapps, Benjamin Philiphttps://hdl.handle.net/10023/219192022-01-31T12:59:08Z2001-01-01T00:00:00ZThis thesis addressed the nature of arousal and its impact on human memory by assessing the degree to which response characteristics, stimulus characteristics, pharmacological and neurological characteristics affect memory for emotional material. Understanding the mechanisms by which emotions affect memory may contribute to attempts to ameliorate clinical disorders, which are characterized by intrusive traumatic memories.
In experimental Chapter 2, frequency-matched words rated as highly arousing were remembered consistently better than low arousal rated words with a normal pattern of decay over a series of 4 recall intervals occurring over one week in a within-subject design. Galvanic skin responses to the same words that were high or low at the time of stimulus presentation did not predict memory at these intervals. Chapter 3 assessed the role of the central noradrenergic (NA) system in memory for emotional material. Pharmacological processes believed to occur at the time of arousal and which are believed to be involved in the encoding of specifically emotional memories were manipulated. It was predicted that NA re-uptake inhibition would result in an increase in memory for the emotional compared to neutral material. The study demonstrated a dose-dependent effect opposite to the predicted direction. The fourth experimental chapter studied the effects of physiological response characteristics alone on memory. Memory was assessed in subjects who demonstrated low physiological reactivity to images (high 'alexithymics') compared to controls (low 'alexithymics') but who did not demonstrate differences in subjective emotional responses. While differences in physiological reactivity existed between high and low alexithymics, no differences in memory were observed. In Chapter 5, free-recall memory for images combined with incongruent sounds was better than free-recall memory for images that were combined with congruent sounds. Presentations that were rated as unpleasant (low valence) and highly arousing were remembered better than other categories regardless of stimulus incongruity. Chapter 6 investigated hemispheric differences in emotional memory functioning in man. A patient with right amygdala damage showed evidence of an emotional but not neutral memory impairment over four tasks compared to age and education matched healthy controls. By contrast, another patient with damage to the left amygdala performed similarly to the controls on the same tasks. These findings, taken together indicate a) subjective rather than physiological responses to stimuli predict memory performance in healthy adults, b) the interaction of low valence (pleasantness) ratings and high arousal ratings is associated with superior recall in healthy adults, c) the effects of emotion on memory are not due to other stimulus characteristics such as distinctiveness d) that increasing the level of the neurotransmitter noradrenaline (modulated by emotional arousal) does not improve emotional memory and e) the right amygdala in humans may be more critical for emotional memory functioning than the left amygdala in humans.
2001-01-01T00:00:00ZPapps, Benjamin PhilipThis thesis addressed the nature of arousal and its impact on human memory by assessing the degree to which response characteristics, stimulus characteristics, pharmacological and neurological characteristics affect memory for emotional material. Understanding the mechanisms by which emotions affect memory may contribute to attempts to ameliorate clinical disorders, which are characterized by intrusive traumatic memories.
In experimental Chapter 2, frequency-matched words rated as highly arousing were remembered consistently better than low arousal rated words with a normal pattern of decay over a series of 4 recall intervals occurring over one week in a within-subject design. Galvanic skin responses to the same words that were high or low at the time of stimulus presentation did not predict memory at these intervals. Chapter 3 assessed the role of the central noradrenergic (NA) system in memory for emotional material. Pharmacological processes believed to occur at the time of arousal and which are believed to be involved in the encoding of specifically emotional memories were manipulated. It was predicted that NA re-uptake inhibition would result in an increase in memory for the emotional compared to neutral material. The study demonstrated a dose-dependent effect opposite to the predicted direction. The fourth experimental chapter studied the effects of physiological response characteristics alone on memory. Memory was assessed in subjects who demonstrated low physiological reactivity to images (high 'alexithymics') compared to controls (low 'alexithymics') but who did not demonstrate differences in subjective emotional responses. While differences in physiological reactivity existed between high and low alexithymics, no differences in memory were observed. In Chapter 5, free-recall memory for images combined with incongruent sounds was better than free-recall memory for images that were combined with congruent sounds. Presentations that were rated as unpleasant (low valence) and highly arousing were remembered better than other categories regardless of stimulus incongruity. Chapter 6 investigated hemispheric differences in emotional memory functioning in man. A patient with right amygdala damage showed evidence of an emotional but not neutral memory impairment over four tasks compared to age and education matched healthy controls. By contrast, another patient with damage to the left amygdala performed similarly to the controls on the same tasks. These findings, taken together indicate a) subjective rather than physiological responses to stimuli predict memory performance in healthy adults, b) the interaction of low valence (pleasantness) ratings and high arousal ratings is associated with superior recall in healthy adults, c) the effects of emotion on memory are not due to other stimulus characteristics such as distinctiveness d) that increasing the level of the neurotransmitter noradrenaline (modulated by emotional arousal) does not improve emotional memory and e) the right amygdala in humans may be more critical for emotional memory functioning than the left amygdala in humans.Synthesis of labelled desulfoglucosinolates and novel glucosinolate analoguesRobertson, Avril A. B.https://hdl.handle.net/10023/219092022-01-13T09:34:09Z2000-01-01T00:00:00ZA number of novel deuterated desulfoglucosinolates have been prepared. These have been shown to be suitable internal standards for the quantitative LC-MS analysis of glucosinolates. Use of the deuterated desulfoglucosinolates results in a 100-fold improvement in the sensitivity over existing methods. This should allow improved analysis of leaf surface glucosinolales, including determination of the amount present on a single leaf.
Desulfo-[²H₅]gluconasturtiin was the first compound prepared to establish the methodology. Then two indolyl desulfoglucosinolates were prepared, desulfo-4- [²H₃]methoxyglucobrassicin and desulfo-l-[²H₃]methoxyglucobrassicin, as the corresponding glucosinolates of these derivatives are more potent as oviposition cues when present on the leaf surface. These structures contained deuterium in the aglycone. Finally, β-D-[1-²H₁, 6-²H₂]glucopyranosyl phenethyl thiohydroximate was synthesised where the deuterium was incorporated into the glucose fragment. This synthetic methodology should thus be applicable to any glucosinolate of analytical interest.
Some novel glucosinolates and glucosinolate analogues have been prepared in order to probe the chemical mechanism of glucosinolate cleavage by myrosinase. This reaction gives (3-D-glucose and an aglycone which undergoes Lossen rearrangement to give sulfate and an isothiocyanate. Three novel substituted phenyl glucosinolates were prepared to probe the involvement of the rearrangement in the overall rate of reaction. Changes in the electronic nature of the side chain were expected to alter the rate of rearrangement (p-MeO > H > P-NO₂). However the opposite trend was observed, implying that changes in the pKa of the leaving group were more important. An analogue designed to mimic glucosinolate binding to myrosinase but unable to rearrange was designed and synthesised. Surprisingly this was neither a substrate nor an inhibitor for myrosinase.
2000-01-01T00:00:00ZRobertson, Avril A. B.A number of novel deuterated desulfoglucosinolates have been prepared. These have been shown to be suitable internal standards for the quantitative LC-MS analysis of glucosinolates. Use of the deuterated desulfoglucosinolates results in a 100-fold improvement in the sensitivity over existing methods. This should allow improved analysis of leaf surface glucosinolales, including determination of the amount present on a single leaf.
Desulfo-[²H₅]gluconasturtiin was the first compound prepared to establish the methodology. Then two indolyl desulfoglucosinolates were prepared, desulfo-4- [²H₃]methoxyglucobrassicin and desulfo-l-[²H₃]methoxyglucobrassicin, as the corresponding glucosinolates of these derivatives are more potent as oviposition cues when present on the leaf surface. These structures contained deuterium in the aglycone. Finally, β-D-[1-²H₁, 6-²H₂]glucopyranosyl phenethyl thiohydroximate was synthesised where the deuterium was incorporated into the glucose fragment. This synthetic methodology should thus be applicable to any glucosinolate of analytical interest.
Some novel glucosinolates and glucosinolate analogues have been prepared in order to probe the chemical mechanism of glucosinolate cleavage by myrosinase. This reaction gives (3-D-glucose and an aglycone which undergoes Lossen rearrangement to give sulfate and an isothiocyanate. Three novel substituted phenyl glucosinolates were prepared to probe the involvement of the rearrangement in the overall rate of reaction. Changes in the electronic nature of the side chain were expected to alter the rate of rearrangement (p-MeO > H > P-NO₂). However the opposite trend was observed, implying that changes in the pKa of the leaving group were more important. An analogue designed to mimic glucosinolate binding to myrosinase but unable to rearrange was designed and synthesised. Surprisingly this was neither a substrate nor an inhibitor for myrosinase.Molluscan populations of the Eden Estuary, Fife, and the use of numerical taxonomy methods to determine their distribution patternsZenetos, Argyrohttps://hdl.handle.net/10023/219052022-01-07T11:15:48Z1980-01-01T00:00:00ZThe aim of this study is twofold, firstly to recognize life and death assemblages among subfossils by using standard criteria and secondly to test the applicability of Numerical Taxonomy methods in defining biotopes and biofacies in Palaeoecclogy. Among the criteria applied in distinguishing life and death assemblages, the following: dispersion of subfossils, faunal composition and diversity, population density, surface condition of shells and ratio of opposite valves, indicate that little postmortem transportation has taken place and that the subfossil assemblages represent accurately the life assemblages from which they were derived. Other criteria were either not applicable or when applied proved unreliable. In examining biotopes and biofacies, several sets of data are combined in alternative techniques. For biofacies the most ecologically meaningful results are obtained by the correlation coefficient with numerical data or by the Matching coefficient with binary data. Most cluster methods produce similar results with the above coefficients. For biotopes analysis, both similarity coefficient and cluster method are critical to the resultant classification.
The most successful distribution patterns are derived by use of the Matching coefficient and W.P.G.A. with binary data or Squared Euclidean Distance and Ward's method with standardized-by-species numerical data. It is suggested that the grain size of the substrate is the main factor determining the distribution of Mollusca in the Eden estuary, since the "textural facies" defined by Eastwood (1977) on the basis of the grain-size distribution in the Eden, are consistent with the biotopes delineated in this study.
1980-01-01T00:00:00ZZenetos, ArgyroThe aim of this study is twofold, firstly to recognize life and death assemblages among subfossils by using standard criteria and secondly to test the applicability of Numerical Taxonomy methods in defining biotopes and biofacies in Palaeoecclogy. Among the criteria applied in distinguishing life and death assemblages, the following: dispersion of subfossils, faunal composition and diversity, population density, surface condition of shells and ratio of opposite valves, indicate that little postmortem transportation has taken place and that the subfossil assemblages represent accurately the life assemblages from which they were derived. Other criteria were either not applicable or when applied proved unreliable. In examining biotopes and biofacies, several sets of data are combined in alternative techniques. For biofacies the most ecologically meaningful results are obtained by the correlation coefficient with numerical data or by the Matching coefficient with binary data. Most cluster methods produce similar results with the above coefficients. For biotopes analysis, both similarity coefficient and cluster method are critical to the resultant classification.
The most successful distribution patterns are derived by use of the Matching coefficient and W.P.G.A. with binary data or Squared Euclidean Distance and Ward's method with standardized-by-species numerical data. It is suggested that the grain size of the substrate is the main factor determining the distribution of Mollusca in the Eden estuary, since the "textural facies" defined by Eastwood (1977) on the basis of the grain-size distribution in the Eden, are consistent with the biotopes delineated in this study.Vocal learning in the grey seal, (Halichoerus grypus) : an experimental approachShapiro, Arihttps://hdl.handle.net/10023/219062022-01-07T11:27:21Z2003-01-01T00:00:00ZThis thesis presents a series of training experiments on three captive grey seal (Halichoerus grypus) pups in an effort to demonstrate vocal learning, the modifying of vocalisations in form due to experiences with those of other individuals. One pup was non-vocal but participated in four experiments in which her responses to centre and off-centre pointing gestures and directional cues to laterally and centrally-placed objects were investigated. She oriented successfully only towards laterally-positioned objects indicated by centre and off centre pointing, pointing and head turning, and upper body turning. These results and her failure to follow pointing gestures towards an object located centrally behind her suggested she simply advanced in the direction of movement of the experimenter, stopping once she located an object. The other two pups were trained to vocalise when presented with a light and to remain silent otherwise and subsequently to match a total of nine moan and growl playbacks with vocalisations of the same type. Twelve novel moan and growl playback stimuli were then used, but these primarily elicited growls as responses. The animals failed to generalise the matching of vocal category, revealing they had been trained only to respond correctly and specifically to the nine original playbacks. These results demonstrated a capacity for contextual learning in which experience with the training procedure caused the pups to pair their production of particular vocalisations with new contexts (i.e. a light and specific playback stimuli). Lastly, one of these pups was trained to produce moans that had fundamental frequencies below 250 Hz. A comparison before and after the training protocol demonstrated that his responses had become both significantly lower and longer. Maturation was not responsible for this result since this pup continued to produce higher-pitched moans in non-experimental contexts. His control over the vocal apparatus to make these frequency and temporal adjustments represents an initial step in establishing whether grey seals are capable of vocal learning. Further studies are required to determine whether additional control over vocal production is possible in this and other pinniped species.
2003-01-01T00:00:00ZShapiro, AriThis thesis presents a series of training experiments on three captive grey seal (Halichoerus grypus) pups in an effort to demonstrate vocal learning, the modifying of vocalisations in form due to experiences with those of other individuals. One pup was non-vocal but participated in four experiments in which her responses to centre and off-centre pointing gestures and directional cues to laterally and centrally-placed objects were investigated. She oriented successfully only towards laterally-positioned objects indicated by centre and off centre pointing, pointing and head turning, and upper body turning. These results and her failure to follow pointing gestures towards an object located centrally behind her suggested she simply advanced in the direction of movement of the experimenter, stopping once she located an object. The other two pups were trained to vocalise when presented with a light and to remain silent otherwise and subsequently to match a total of nine moan and growl playbacks with vocalisations of the same type. Twelve novel moan and growl playback stimuli were then used, but these primarily elicited growls as responses. The animals failed to generalise the matching of vocal category, revealing they had been trained only to respond correctly and specifically to the nine original playbacks. These results demonstrated a capacity for contextual learning in which experience with the training procedure caused the pups to pair their production of particular vocalisations with new contexts (i.e. a light and specific playback stimuli). Lastly, one of these pups was trained to produce moans that had fundamental frequencies below 250 Hz. A comparison before and after the training protocol demonstrated that his responses had become both significantly lower and longer. Maturation was not responsible for this result since this pup continued to produce higher-pitched moans in non-experimental contexts. His control over the vocal apparatus to make these frequency and temporal adjustments represents an initial step in establishing whether grey seals are capable of vocal learning. Further studies are required to determine whether additional control over vocal production is possible in this and other pinniped species.Solution of the crystal structure of human milk xanthine oxidoreductasePearson, Arwenhttps://hdl.handle.net/10023/219082022-01-10T16:52:48Z2002-01-01T00:00:00ZThis thesis reports the crystallization, structure solution and preliminary refinement of the demolybdo form of human milk XOR to a resolution of 3.5 A. Although the bovine milk XOR structure was also recently determined, this is the first demolybdo XOR structure to be determined and also the first structure of a human XOR. Also reported is the determination of the cDNA sequence of human mammary gland XDH. Xanthine oxidoreductase is a complex molybdenum and iron-sulphur containing flavoprotein. Due to its abundance, the enzyme from bovine milk has been extensively studied over the last 100 years. More recently the human milk enzyme has been investigated and has been shown to have surprising properties, in particular a very low specific activity. Traditionally associated with the last stages of purine catabolism, XOR has recently been shown to produce reactive oxygen species through reduction of oxygen and also to be capable of reducing nitrates and nitrites to NO. These findings implicate XOR in a variety of disease states, in particular ischaemia reperfusion injury. The low specific activity of human milk XOR is due to a low content of molybdenum (~ 5 %). Higher molybdenum content and specific activity has been reported for certain other human tissues, notably liver and small intestine. This work aimed to investigate possible reasons for the low level of incorporation of molybdenum and its associated molybdopterin cofactor into the human milk enzyme.
2002-01-01T00:00:00ZPearson, ArwenThis thesis reports the crystallization, structure solution and preliminary refinement of the demolybdo form of human milk XOR to a resolution of 3.5 A. Although the bovine milk XOR structure was also recently determined, this is the first demolybdo XOR structure to be determined and also the first structure of a human XOR. Also reported is the determination of the cDNA sequence of human mammary gland XDH. Xanthine oxidoreductase is a complex molybdenum and iron-sulphur containing flavoprotein. Due to its abundance, the enzyme from bovine milk has been extensively studied over the last 100 years. More recently the human milk enzyme has been investigated and has been shown to have surprising properties, in particular a very low specific activity. Traditionally associated with the last stages of purine catabolism, XOR has recently been shown to produce reactive oxygen species through reduction of oxygen and also to be capable of reducing nitrates and nitrites to NO. These findings implicate XOR in a variety of disease states, in particular ischaemia reperfusion injury. The low specific activity of human milk XOR is due to a low content of molybdenum (~ 5 %). Higher molybdenum content and specific activity has been reported for certain other human tissues, notably liver and small intestine. This work aimed to investigate possible reasons for the low level of incorporation of molybdenum and its associated molybdopterin cofactor into the human milk enzyme.Aggressive behaviour in tiger barbs (Barbus tetrazona)Gallagher, Anne E. C.https://hdl.handle.net/10023/218932022-01-05T14:39:04Z1990-01-01T00:00:00ZThe aim of this project was to study aggressive behaviour in tiger barbs, Barbus tetrazona, and their hierarchy systems and to determine some of the factors which influence them. The linearity of hierarchies was investigated and it was found that tiger barbs do not form stable linear hierarchies. Nor did the relative weights of fish influence their dominance/subordination relationships. The effect of the amount of cover on the outcomes of agonistic interactions was examined. A greater amount of cover resulted in earlier terminations of fights due to the loser being more able to hide from its assailant. The subordinate fish were found to play as important a role in agonistic encounters as the dominant fish. The effects of group-living on subsequent agonistic interactions was investigated to determine whether prior experience of fish from the same group had any effect on subsequent encounters. This was found not to be the case. The possibility of individual recognition taking place was also examined but was found not to be involved in the outcomes of agonistic encounters. The possibility that each fish had its own individual level of aggression was investigated. This did not appear to be the case, but rather, each individual's level of aggression was affected by the relative fighting abilities of other individuals present. However, the most subordinate fish in a group may have been adopting a different strategy, deterring them from engaging in conflicts. This strategy was possibly maintained by the presence of more dominant fish. The results obtained lead to the suggestion that the fighting ability of tiger barbs may develop through experience of fighting and differ in rate of development between individual fish.
1990-01-01T00:00:00ZGallagher, Anne E. C.The aim of this project was to study aggressive behaviour in tiger barbs, Barbus tetrazona, and their hierarchy systems and to determine some of the factors which influence them. The linearity of hierarchies was investigated and it was found that tiger barbs do not form stable linear hierarchies. Nor did the relative weights of fish influence their dominance/subordination relationships. The effect of the amount of cover on the outcomes of agonistic interactions was examined. A greater amount of cover resulted in earlier terminations of fights due to the loser being more able to hide from its assailant. The subordinate fish were found to play as important a role in agonistic encounters as the dominant fish. The effects of group-living on subsequent agonistic interactions was investigated to determine whether prior experience of fish from the same group had any effect on subsequent encounters. This was found not to be the case. The possibility of individual recognition taking place was also examined but was found not to be involved in the outcomes of agonistic encounters. The possibility that each fish had its own individual level of aggression was investigated. This did not appear to be the case, but rather, each individual's level of aggression was affected by the relative fighting abilities of other individuals present. However, the most subordinate fish in a group may have been adopting a different strategy, deterring them from engaging in conflicts. This strategy was possibly maintained by the presence of more dominant fish. The results obtained lead to the suggestion that the fighting ability of tiger barbs may develop through experience of fighting and differ in rate of development between individual fish.The early development of serotonergic raphe-spinal interneurons in two related amphibians : 'Xenopus laevis' and 'Rana temporaria'Woolston, Anne-Mariehttps://hdl.handle.net/10023/218942022-01-05T15:16:26Z1992-01-01T00:00:00Z1) A method has been devised to enable visualisation of 5HT immunoreactive neurons in the CNS of embryonic amphibians in wholemount. The technique relies upon a rather long incubation in primary antiserum to allow thorough access of antibodies to central neurons. 2) Using this technique, the results of van Mier et al (1986), using serially sectioned material, have largely been substantiated. 5HTi neurons in Xenopus embryos (developmental stage 37/38) comprise a cluster of some 60 cell bodies in the raphe region of the rostral, ventral hindbrain. A second, smaller cluster, noted by van Mier, in the caudal midbrain could not be detected in the present study until developmental stage 42. The descending axonal projections of raphe interneurons are located exclusively in the dorsolateral margins of the spinal cord of Xenopus embryos. At stage 42 about 70 somata are now present in the brainstem and their descending processes now also extend into the ventromedial regions of the cord. 3) Serotonergic neurons in Xenopus were succesfully ablated during embryogenesis, following exposure to the specific 5HT neurotoxin, 5,7 DHT, at ImM. This procedure enabled a preliminary physiological investigation of the effects of serotonergic input to the spinal cord on the development of spinal cord function. The absence of raphe interneurons appears to retard the normal development of neuronal circuitry underlying swimming movements. 4) A comparative study of serotonergic raphe-spinal interneurones in a related amphibian embryo, Rana temporaria was undertaken. In contrast to Xenopus embryos, the descending projections of serotonergic raphe neurons in Rana embryos at the time of hatching (stage 20; Gosner, 1960), are exclusively located in the ventral aspect of the spinal cord. 5) The results of raphe ablation studies in Xenopus larvae suggest that a causal link may exist between raphe projections and the developmental modulation of locomotor output in postembryonic larvae. The interspecific differences observed in the development of 5HTi projections in Rana, coupled with existing knowledge of the physiology of swimming in Rana compared with Xenopus, lend further support to this notion. The hypothesis is now amenable to rigorous experimental testing, using the techniques devised and presented in this thesis.
1992-01-01T00:00:00ZWoolston, Anne-Marie1) A method has been devised to enable visualisation of 5HT immunoreactive neurons in the CNS of embryonic amphibians in wholemount. The technique relies upon a rather long incubation in primary antiserum to allow thorough access of antibodies to central neurons. 2) Using this technique, the results of van Mier et al (1986), using serially sectioned material, have largely been substantiated. 5HTi neurons in Xenopus embryos (developmental stage 37/38) comprise a cluster of some 60 cell bodies in the raphe region of the rostral, ventral hindbrain. A second, smaller cluster, noted by van Mier, in the caudal midbrain could not be detected in the present study until developmental stage 42. The descending axonal projections of raphe interneurons are located exclusively in the dorsolateral margins of the spinal cord of Xenopus embryos. At stage 42 about 70 somata are now present in the brainstem and their descending processes now also extend into the ventromedial regions of the cord. 3) Serotonergic neurons in Xenopus were succesfully ablated during embryogenesis, following exposure to the specific 5HT neurotoxin, 5,7 DHT, at ImM. This procedure enabled a preliminary physiological investigation of the effects of serotonergic input to the spinal cord on the development of spinal cord function. The absence of raphe interneurons appears to retard the normal development of neuronal circuitry underlying swimming movements. 4) A comparative study of serotonergic raphe-spinal interneurones in a related amphibian embryo, Rana temporaria was undertaken. In contrast to Xenopus embryos, the descending projections of serotonergic raphe neurons in Rana embryos at the time of hatching (stage 20; Gosner, 1960), are exclusively located in the ventral aspect of the spinal cord. 5) The results of raphe ablation studies in Xenopus larvae suggest that a causal link may exist between raphe projections and the developmental modulation of locomotor output in postembryonic larvae. The interspecific differences observed in the development of 5HTi projections in Rana, coupled with existing knowledge of the physiology of swimming in Rana compared with Xenopus, lend further support to this notion. The hypothesis is now amenable to rigorous experimental testing, using the techniques devised and presented in this thesis.Automated identification and network analyses in 'Acacia' pollination ecologyWatson, Anna T. (Anna Tamsin)https://hdl.handle.net/10023/218902021-11-26T15:32:23Z2006-01-01T00:00:00ZAcacia trees are an important source of pollen and nectar to a wide range of savannah insects. Identifying Acacia-visiting insects and the herb pollens they also carry is essential for pollination studies but problematic as expert entomologists and palynologists are overworked. Automated identification offers a solution to this problem. The DAISY automated identification system can identify insects accurately but the pattern selection methodology has been time consuming and impractical for large applications. Two new methodological approaches are investigated that allow quicker processing or avoid wing removal. They showed great promise, identifying species with more than 90% accuracy. Pollens provide very different challenges to computer vision, they are three dimensional, often vary substantially within a single species and have complex shapes. In the initial DAISY identification of pollens accuracy was low (34% at best) so several methodological means to improve accuracy were investigated. The processing regime recommended for greatest accuracy is clean pollens, imaged with dark field microscopy and which had their relative sizes maintained. Cleaned and sized pollens were identified with 100% accuracy when only 5 pollens were considered but this fell to around 50% accuracy when 50+ pollens were considered. As most applications will require many pollens to be considered at once this is not yet a useful system for pollens. Network analysis is a recent technique in pollination ecology, well suited to pollen load analysis. The most important insects to the pollination network were all bees: Apis mellifera, Megachile and the small halictids Lipotriches and Patellapis. The damage from removing a single insect genus was generally below 5% and never more than 10% of network integrity. Removal of combinations of insects showed great tolerance to extinction, this is likely to be due to functional redundancy and nestedness of the network, with specialists visiting plants that are also visited by generalists.
2006-01-01T00:00:00ZWatson, Anna T. (Anna Tamsin)Acacia trees are an important source of pollen and nectar to a wide range of savannah insects. Identifying Acacia-visiting insects and the herb pollens they also carry is essential for pollination studies but problematic as expert entomologists and palynologists are overworked. Automated identification offers a solution to this problem. The DAISY automated identification system can identify insects accurately but the pattern selection methodology has been time consuming and impractical for large applications. Two new methodological approaches are investigated that allow quicker processing or avoid wing removal. They showed great promise, identifying species with more than 90% accuracy. Pollens provide very different challenges to computer vision, they are three dimensional, often vary substantially within a single species and have complex shapes. In the initial DAISY identification of pollens accuracy was low (34% at best) so several methodological means to improve accuracy were investigated. The processing regime recommended for greatest accuracy is clean pollens, imaged with dark field microscopy and which had their relative sizes maintained. Cleaned and sized pollens were identified with 100% accuracy when only 5 pollens were considered but this fell to around 50% accuracy when 50+ pollens were considered. As most applications will require many pollens to be considered at once this is not yet a useful system for pollens. Network analysis is a recent technique in pollination ecology, well suited to pollen load analysis. The most important insects to the pollination network were all bees: Apis mellifera, Megachile and the small halictids Lipotriches and Patellapis. The damage from removing a single insect genus was generally below 5% and never more than 10% of network integrity. Removal of combinations of insects showed great tolerance to extinction, this is likely to be due to functional redundancy and nestedness of the network, with specialists visiting plants that are also visited by generalists.The influence of social structure on vocal signatures in group-living resident killer whales (Orcinus orca)Nousek, Anna E.https://hdl.handle.net/10023/218872021-11-24T11:20:25Z2005-01-01T00:00:00ZConstant association with a specific set of individuals appears to be advantageous for some species. This lifestyle then generates many modifications on individual behavior, especially to coordinate relationships between individuals within the group, and vocal signals are likely to be shaped by social interactions as they may play a role in mediating social roles. Northern resident killer whales (orcinus orca) use group-specific signatures within their stable social system but to date no study has thoroughly examined calling behavior amongst individuals within different family groups. Thus, the potential for individual-specific signatures has not been identified. This study aimed to describe the effects of their rigid social structure on the vocal behavior of individuals through comparing the intra-individual call similarity with their inter-individual similarity. A towed beamforming array of hydrophones allowed calls to be ascribed to specific individuals. This study quantified call similarity through the ability of a pattern recognition neural network to discriminate between frequency contours of individuals within the same matrilineal group, in different matrilineal groups but the same vocal clan and across different clans. Calls were found to contain features distinct to an individual, but these features are less prominent than group-specific features. Similarity of both the high and low frequency contours was strongly affected by the social relationship of pairs of whales, with the network having the highest error rate for same whale comparisons, a lower error rate for comparisons within a matrilineal group, and the lowest error rate for comparisons between individuals in different matrilineal groups. The correlation between social relationship and acoustic similarity suggests social learning as the mechanism for transmission and that group identity has a stronger influence on the time-frequency structure of stereotyped killer whale calls than individual identity. The social bonds between groups of individuals appear to take precedence over individual relationships within this population.
2005-01-01T00:00:00ZNousek, Anna E.Constant association with a specific set of individuals appears to be advantageous for some species. This lifestyle then generates many modifications on individual behavior, especially to coordinate relationships between individuals within the group, and vocal signals are likely to be shaped by social interactions as they may play a role in mediating social roles. Northern resident killer whales (orcinus orca) use group-specific signatures within their stable social system but to date no study has thoroughly examined calling behavior amongst individuals within different family groups. Thus, the potential for individual-specific signatures has not been identified. This study aimed to describe the effects of their rigid social structure on the vocal behavior of individuals through comparing the intra-individual call similarity with their inter-individual similarity. A towed beamforming array of hydrophones allowed calls to be ascribed to specific individuals. This study quantified call similarity through the ability of a pattern recognition neural network to discriminate between frequency contours of individuals within the same matrilineal group, in different matrilineal groups but the same vocal clan and across different clans. Calls were found to contain features distinct to an individual, but these features are less prominent than group-specific features. Similarity of both the high and low frequency contours was strongly affected by the social relationship of pairs of whales, with the network having the highest error rate for same whale comparisons, a lower error rate for comparisons within a matrilineal group, and the lowest error rate for comparisons between individuals in different matrilineal groups. The correlation between social relationship and acoustic similarity suggests social learning as the mechanism for transmission and that group identity has a stronger influence on the time-frequency structure of stereotyped killer whale calls than individual identity. The social bonds between groups of individuals appear to take precedence over individual relationships within this population.Attention & response control : a neural and behavioural enquiryFarovik, Anjahttps://hdl.handle.net/10023/218852021-11-24T09:45:49Z2007-01-01T00:00:00ZGoal directed responding is the behavioural expression of the myriad of cognitive processes which are involved in the translation of motivation to a motor program. These processes include learning, memory, expectation, anticipation, working memory and attention. The purpose of this thesis is to explore how and when attention exerts influence over responding and the neural basis of this. The introduction reviews the experimental literature on working memory and attention, noting that most work on attention stands quite separately from studies of working memory, although the contents of working memory may be regarded in some sense as the product of attentional selection. Chapter III describes work developing a new task of working memory. However, rats failed to learn the discrimination and so this line of investigation was not pursued further. In Chapter IV, a different approach was taken. The subthalamic nucleus (STN) is a key structure in the motor output pathways of the basal ganglia. However, a role for the STN in attentional selection, movement and switching has recently been raised. This chapter used a task of divided attention to examine the ability of rats with lesions of the STN to switch attention between modalities. However, an increased attentional load was not associated with an increase in the magnitude of lesion-induced performance deficits, suggesting that this nucleus is more likely involved in motor rather than attentional aspects of behaviour. Previous findings also suggest that an intact STN is important for response preparation in a task used to assess endogenous covert orienting of attention, while the attentional aspect of the task remained intact. Noradrenaline has been implicated in selective attention and in particular to play a role when stimuli are not fully predictable. Chapter V reports a study to investigate the role of noradrenaline in a test of covert spatial attentional orienting to endogenous cues. Depletions of the ascending noradrenergic system (DNAB) result in impairments supporting a role for this system in selective attention, however, there were no impairments in covert spatial attentional orienting. Previous work has suggested that the basal forebrain cholinergic system is important in covert orienting when the cues are exogenous. Therefore, Chapter VI examined the role of the basal forebrain cholinergic system in the test of covert orienting used in Chapter V, employing endogenous cues. Basal forebrain lesions impaired endogenous covert attentional orienting by abolishing the cost/benefit of the cue on reaction time to the visual target. Systemic injection of nicotine (a cholinergic agonist) did not re-establish directed attention in lesioned animals. This finding is the first to show the neural basis of endogenous covert orienting of attention, and suggest a common neural substrate for both exogenous and endogenous covert attention. Chapter VII considers the work of the thesis as a whole in the context of previous work and suggests directions for further research of this topic.
2007-01-01T00:00:00ZFarovik, AnjaGoal directed responding is the behavioural expression of the myriad of cognitive processes which are involved in the translation of motivation to a motor program. These processes include learning, memory, expectation, anticipation, working memory and attention. The purpose of this thesis is to explore how and when attention exerts influence over responding and the neural basis of this. The introduction reviews the experimental literature on working memory and attention, noting that most work on attention stands quite separately from studies of working memory, although the contents of working memory may be regarded in some sense as the product of attentional selection. Chapter III describes work developing a new task of working memory. However, rats failed to learn the discrimination and so this line of investigation was not pursued further. In Chapter IV, a different approach was taken. The subthalamic nucleus (STN) is a key structure in the motor output pathways of the basal ganglia. However, a role for the STN in attentional selection, movement and switching has recently been raised. This chapter used a task of divided attention to examine the ability of rats with lesions of the STN to switch attention between modalities. However, an increased attentional load was not associated with an increase in the magnitude of lesion-induced performance deficits, suggesting that this nucleus is more likely involved in motor rather than attentional aspects of behaviour. Previous findings also suggest that an intact STN is important for response preparation in a task used to assess endogenous covert orienting of attention, while the attentional aspect of the task remained intact. Noradrenaline has been implicated in selective attention and in particular to play a role when stimuli are not fully predictable. Chapter V reports a study to investigate the role of noradrenaline in a test of covert spatial attentional orienting to endogenous cues. Depletions of the ascending noradrenergic system (DNAB) result in impairments supporting a role for this system in selective attention, however, there were no impairments in covert spatial attentional orienting. Previous work has suggested that the basal forebrain cholinergic system is important in covert orienting when the cues are exogenous. Therefore, Chapter VI examined the role of the basal forebrain cholinergic system in the test of covert orienting used in Chapter V, employing endogenous cues. Basal forebrain lesions impaired endogenous covert attentional orienting by abolishing the cost/benefit of the cue on reaction time to the visual target. Systemic injection of nicotine (a cholinergic agonist) did not re-establish directed attention in lesioned animals. This finding is the first to show the neural basis of endogenous covert orienting of attention, and suggest a common neural substrate for both exogenous and endogenous covert attention. Chapter VII considers the work of the thesis as a whole in the context of previous work and suggests directions for further research of this topic.Kinetic characterisation of the plasma membrane transport of excitatory sulphur-containing amino acids in cultured brain cells and isolated nerve endingsGrieve, Angushttps://hdl.handle.net/10023/218812021-11-17T10:31:19Z1993-01-01T00:00:00ZThe endogenous neuroexcitatory sulphur-containing amino acids (SAAs) are generally regarded as putative transmitter substances. Of many criteria that need to be satisfied before acceptance as a transmitter, one is that a mechanism exists for termination of post-synaptic receptor activation. For amino acids such inactivation normally requires participation of a plasma membrane transport system for rapid and efficient removal of transmitter from the extracellular environment. This thesis reports on the kinetic characterisation of the plasma membrane transport of the SAAs, namely L-cysteine sulphinate (CSA), L-cysteate (CA), L-homocysteine sulphinate (HCSA) and L-homocysteate (HCA) in (i) synaptosome fractions from rat cerebral cortex and (ii) primary cultures of neurons from distinct brain regions and astrocytes from prefrontal cortex.
It was shown that each SAA acted as a substrate for the plasma membrane transporter in the different brain preparations studied with CSA and CA exhibiting a high-affinity for uptake (Kₘ200< 100μM) HCSA and HCA exhibiting a low-affinity for uptake (Kₘ200 > 100μM). The plasma membrane carrier specificity of the SAAs which was studied using cerebrocortical synaptosome fractions was established following comparison with other high-affinity neurotransmitter systems. The results obtained strongly suggest that the SAAs share a common synaptosomal transport system with L-glutamate and L- and D-aspartate.
A detailed kinetic analysis of the inhibition by the proposed selective inhibitor of HCA uptake, β-p-chlorophenylglutamate (chlorpheg), on HCA and D-aspartate uptake using (i) cerebrocortical synaptosomes and (ii) primary cultures of cerebellar granule cells and cortical astrocytes has been undertaken. The results from this kinetic inhibition study show clearly a non-selective competitive inhibition of D-aspartate and L-HCA uptake by chlorpheg in all the brain preparations studied. In a tangential HPLC study, the cellular localisation of HCA and HCSA was investigated using ethanolic amino acid extracts prepared from primary cultures of cerebellar neurons and astrocytes. The results suggest a predominant astrocytic, rather than neuronal, localisation of HCA and HCSA.
1993-01-01T00:00:00ZGrieve, AngusThe endogenous neuroexcitatory sulphur-containing amino acids (SAAs) are generally regarded as putative transmitter substances. Of many criteria that need to be satisfied before acceptance as a transmitter, one is that a mechanism exists for termination of post-synaptic receptor activation. For amino acids such inactivation normally requires participation of a plasma membrane transport system for rapid and efficient removal of transmitter from the extracellular environment. This thesis reports on the kinetic characterisation of the plasma membrane transport of the SAAs, namely L-cysteine sulphinate (CSA), L-cysteate (CA), L-homocysteine sulphinate (HCSA) and L-homocysteate (HCA) in (i) synaptosome fractions from rat cerebral cortex and (ii) primary cultures of neurons from distinct brain regions and astrocytes from prefrontal cortex.
It was shown that each SAA acted as a substrate for the plasma membrane transporter in the different brain preparations studied with CSA and CA exhibiting a high-affinity for uptake (Kₘ200< 100μM) HCSA and HCA exhibiting a low-affinity for uptake (Kₘ200 > 100μM). The plasma membrane carrier specificity of the SAAs which was studied using cerebrocortical synaptosome fractions was established following comparison with other high-affinity neurotransmitter systems. The results obtained strongly suggest that the SAAs share a common synaptosomal transport system with L-glutamate and L- and D-aspartate.
A detailed kinetic analysis of the inhibition by the proposed selective inhibitor of HCA uptake, β-p-chlorophenylglutamate (chlorpheg), on HCA and D-aspartate uptake using (i) cerebrocortical synaptosomes and (ii) primary cultures of cerebellar granule cells and cortical astrocytes has been undertaken. The results from this kinetic inhibition study show clearly a non-selective competitive inhibition of D-aspartate and L-HCA uptake by chlorpheg in all the brain preparations studied. In a tangential HPLC study, the cellular localisation of HCA and HCSA was investigated using ethanolic amino acid extracts prepared from primary cultures of cerebellar neurons and astrocytes. The results suggest a predominant astrocytic, rather than neuronal, localisation of HCA and HCSA.Activities of RNA helicase Xp54 in translational control during Xenopus oogenesisWeston, Andrew Johnhttps://hdl.handle.net/10023/218772021-11-17T09:20:31Z2005-01-01T00:00:00Z2005-01-01T00:00:00ZWeston, Andrew JohnThe oxygen uptake and energy charge under hypoxia and anoxia of excised plant roots from flood-tolerant and flood-sensitive speciesMcCreath, Andrew J.https://hdl.handle.net/10023/218692021-11-16T10:35:51Z1980-01-01T00:00:00ZA study is presented of two aspects of plant adaptation to soil waterlogging. The first part of this study is an investigation into the relation between the uptake of oxygen by plant root tips and the external concentration of oxygen. A range of plant species was collected and grown in the glasshouse in both flooded and unflooded sand cultures. Experiments were carried out on these plants after at least one month's growth in the glasshouse, and also on plants collected from the wild without any pre-treatment in the glasshouse. Oxygen uptake measurements were carried out using excised root apices in a Rank Memebrane Oxygen Electrode assembly. It was found in nearly all experiments that the rate of oxygen uptake was highly dependent on the external oxygen concentration in both flood-tolerant and flood-sensitive species. Samples which had been grown in a flooded sand culture, however, were less dependent on the supply of external oxygen than those which had been grown in an unflooded sand culture These results were interpreted with the aid of a simple mathematical model of oxygen uptake in a plant root apex. The model was designed to predict the relation between oxygen uptake rate and the external concentration of oxygen for roots with different porosities, different rates of uptake and possessing respiratory systems with different affinities for oxygen. Using this model, it was found that a normal plant root apex, in which the respiratory systems have a high affinity for oxygen and in which the presence of intercellular air spaces allows a rapid radial movement of oxygen, should exhibit a rate of oxygen uptake which is largely independent of the external concentration of oxygen. Prom this prediction and from theoretical calculations on the movement of oxygen within individual root cells, it was concluded that the high dependence of oxygen uptake on external oxygen concentration which was found in the experiments was largely an artefact resulting from flooding of the intercellular air spaces under the in vitro conditions of the experiments. Affinity for oxygen and the ability to maintain high rates of oxygen uptake under conditions of low oxygen availability are not therefore considered to be criteria by which flood-tolerant and flood-intolerant species can be distinguished. The second part of this study was an investigation into the energy relations of excised plant root systems, by the measurement of ATP/ADP ratios under anoxia. Root systems were harvested from plants which had previously been grown under a flooded or an unflooded sand culture regime in the glasshouse, and were incubated under nitrogen gas in deoxygenated phosphate buffer for up' to 4 hours. Control samples were incubated in air-saturated buffer under an atmosphere of air. It was found that ATP/ADP ratios were lower when the excised root systems were incubated under nitrogen than when they were incubated in an aerobic environment. However, the values obtained suggest a higher energy charge in the root tissues under anoxia than has generally been reported by other workers. No difference was found between flood-tolerant and flood-sensitive species, but it is pointed out that since the experiments did not measure the total size of the adenylate pool, such differences may have been overlooked. It is suggested that energy charge measurements may be more useful as a general indication of the metabolic activity within the root tissue rather than as a criterion for distinguishing flood tolerant and flood intolerant plant species.
1980-01-01T00:00:00ZMcCreath, Andrew J.A study is presented of two aspects of plant adaptation to soil waterlogging. The first part of this study is an investigation into the relation between the uptake of oxygen by plant root tips and the external concentration of oxygen. A range of plant species was collected and grown in the glasshouse in both flooded and unflooded sand cultures. Experiments were carried out on these plants after at least one month's growth in the glasshouse, and also on plants collected from the wild without any pre-treatment in the glasshouse. Oxygen uptake measurements were carried out using excised root apices in a Rank Memebrane Oxygen Electrode assembly. It was found in nearly all experiments that the rate of oxygen uptake was highly dependent on the external oxygen concentration in both flood-tolerant and flood-sensitive species. Samples which had been grown in a flooded sand culture, however, were less dependent on the supply of external oxygen than those which had been grown in an unflooded sand culture These results were interpreted with the aid of a simple mathematical model of oxygen uptake in a plant root apex. The model was designed to predict the relation between oxygen uptake rate and the external concentration of oxygen for roots with different porosities, different rates of uptake and possessing respiratory systems with different affinities for oxygen. Using this model, it was found that a normal plant root apex, in which the respiratory systems have a high affinity for oxygen and in which the presence of intercellular air spaces allows a rapid radial movement of oxygen, should exhibit a rate of oxygen uptake which is largely independent of the external concentration of oxygen. Prom this prediction and from theoretical calculations on the movement of oxygen within individual root cells, it was concluded that the high dependence of oxygen uptake on external oxygen concentration which was found in the experiments was largely an artefact resulting from flooding of the intercellular air spaces under the in vitro conditions of the experiments. Affinity for oxygen and the ability to maintain high rates of oxygen uptake under conditions of low oxygen availability are not therefore considered to be criteria by which flood-tolerant and flood-intolerant species can be distinguished. The second part of this study was an investigation into the energy relations of excised plant root systems, by the measurement of ATP/ADP ratios under anoxia. Root systems were harvested from plants which had previously been grown under a flooded or an unflooded sand culture regime in the glasshouse, and were incubated under nitrogen gas in deoxygenated phosphate buffer for up' to 4 hours. Control samples were incubated in air-saturated buffer under an atmosphere of air. It was found that ATP/ADP ratios were lower when the excised root systems were incubated under nitrogen than when they were incubated in an aerobic environment. However, the values obtained suggest a higher energy charge in the root tissues under anoxia than has generally been reported by other workers. No difference was found between flood-tolerant and flood-sensitive species, but it is pointed out that since the experiments did not measure the total size of the adenylate pool, such differences may have been overlooked. It is suggested that energy charge measurements may be more useful as a general indication of the metabolic activity within the root tissue rather than as a criterion for distinguishing flood tolerant and flood intolerant plant species.Structures and function of 5'-fluorodeoxyadenosine synthaseMcEwan, Andrew Roberthttps://hdl.handle.net/10023/218702021-11-16T10:43:59Z2006-01-01T00:00:00ZHalogenation in nature is becoming better understood and in recent studies (Harper etal., 2003; Murphy, 2003) there appears to be several mechanisms available to nature for halogenation. 5'-Fluorodeoxyadenosine synthase (FDAS) is the only enzyme identified in nature that is capable of formation of a C-F bond. FDAS does this by catalysing the transformation of S-adenosyl-L-methionine (SAM) and inorganic fluoride to 5'-fluoro-5'-deoxyadenosine (FDA). It is the essential enzyme in the fluorinase pathway in Streptomyces cattleya which results in the production of 4-fluorothreonine and fluoroacetate. This thesis describes a structural investigation into FDAS. Adenosine was identified as a contaminant and removed, permitting the X-ray crystal structures of FDAS in apo-form and in complex with several important substrates and substrate analogues. FDAS was identified to catalyse incorporation of chlorine by a nucleophilic mechanism. FDAS is also capable of utilising 2'-deoxy substrate analogues but not 3'- deoxy ones. The structural data allow both substrate specificity and chlorine incorporation to be rationalised. Thermodynamic studies were carried out on FDAS using isothermal calorimetry and contribute to improving our understanding of the enzyme. Sso6206 is a small acidic protein with unknown function from Sulfolobus solfataricus (Sso). The protein was overexpressed, purified and crystallized in native and selenomethionine derivative forms. Data were measured to 2.4 A indicating that the asymmetric unit contains between 15 and 30 monomers. This could be a result of a large protomer complex formation, suggesting an unusual function. Attempts to obtain phases using several methods are described. 2-Keto-3-deoxy-6-phosphogalactonate (KDPGal) aldolase was identified in E. coli as responsible for the reversible conversion of KDPGal to glyceraldehyde-3- phosphate (G3P) and pyruvate. The protein is homologous to the 2-keto-3-deoxy-6- phosphogluconte (KDPG) aldolase which performs a similar reaction with KDPG. These protein are important biosynthetic tools. The apo-stmcture was solved in a previous study, however the reasons for the observed stereo-specificity were not clear. This thesis reports several complex structures and permits a rationalisation of the different stereochemistry between the enzymes.
2006-01-01T00:00:00ZMcEwan, Andrew RobertHalogenation in nature is becoming better understood and in recent studies (Harper etal., 2003; Murphy, 2003) there appears to be several mechanisms available to nature for halogenation. 5'-Fluorodeoxyadenosine synthase (FDAS) is the only enzyme identified in nature that is capable of formation of a C-F bond. FDAS does this by catalysing the transformation of S-adenosyl-L-methionine (SAM) and inorganic fluoride to 5'-fluoro-5'-deoxyadenosine (FDA). It is the essential enzyme in the fluorinase pathway in Streptomyces cattleya which results in the production of 4-fluorothreonine and fluoroacetate. This thesis describes a structural investigation into FDAS. Adenosine was identified as a contaminant and removed, permitting the X-ray crystal structures of FDAS in apo-form and in complex with several important substrates and substrate analogues. FDAS was identified to catalyse incorporation of chlorine by a nucleophilic mechanism. FDAS is also capable of utilising 2'-deoxy substrate analogues but not 3'- deoxy ones. The structural data allow both substrate specificity and chlorine incorporation to be rationalised. Thermodynamic studies were carried out on FDAS using isothermal calorimetry and contribute to improving our understanding of the enzyme. Sso6206 is a small acidic protein with unknown function from Sulfolobus solfataricus (Sso). The protein was overexpressed, purified and crystallized in native and selenomethionine derivative forms. Data were measured to 2.4 A indicating that the asymmetric unit contains between 15 and 30 monomers. This could be a result of a large protomer complex formation, suggesting an unusual function. Attempts to obtain phases using several methods are described. 2-Keto-3-deoxy-6-phosphogalactonate (KDPGal) aldolase was identified in E. coli as responsible for the reversible conversion of KDPGal to glyceraldehyde-3- phosphate (G3P) and pyruvate. The protein is homologous to the 2-keto-3-deoxy-6- phosphogluconte (KDPG) aldolase which performs a similar reaction with KDPG. These protein are important biosynthetic tools. The apo-stmcture was solved in a previous study, however the reasons for the observed stereo-specificity were not clear. This thesis reports several complex structures and permits a rationalisation of the different stereochemistry between the enzymes.Cloning, expression and functional analysis of picornavirus protein 2CKinver, Andreahttps://hdl.handle.net/10023/218612021-10-28T11:25:55Z2003-01-01T00:00:00ZPicornavirus-infected cells are characterised by the appearance of smooth vesicles and the disappearance of the Golgi apparatus. Replication of the viral RNA takes place on these virus-induced vesicles. Expression of the viral protein 2BC, and to some extent 2C, has similar effects on cells. Protein 2C has been proposed to hold these replication complexes together and is known to bind to the membranes, however the mechanism of this binding is unknown. Previous work by Knox et al showed an interaction between FMDV protein 2C and the protein kinase A anchoring protein 10 (AKAP 10). The 2C gene from the CA9, ECHO 22, FMDV, HAV HM175, HAV wt1, HeCV, HRV 85 and TME picornaviruses were cloned into both translation and expression vectors (the FMDV and HRV 85 were donated by C. Knox and N. Moir respectively). Translation products were then used in a binding assay and interaction with AKAP 10 was shown for ECHO 22, FMDV, HAV wt1, HeCV, HRV 85 and TME. These results indicate AKAP 10 binding as a general function of 2C in all picornaviruses. An expression system was optimised for HRV 85 2ABC, 2BC and 2C proteins, and was shown to produce the other picornavirus 2C proteins at similar levels. Cellular expression of protein 2BC is known to bring about membrane rearrangements and the binding of 2C to AKAP 10 may help explain this aspect of the cytopathic effect and the targeting of virus replication to membranes.
2003-01-01T00:00:00ZKinver, AndreaPicornavirus-infected cells are characterised by the appearance of smooth vesicles and the disappearance of the Golgi apparatus. Replication of the viral RNA takes place on these virus-induced vesicles. Expression of the viral protein 2BC, and to some extent 2C, has similar effects on cells. Protein 2C has been proposed to hold these replication complexes together and is known to bind to the membranes, however the mechanism of this binding is unknown. Previous work by Knox et al showed an interaction between FMDV protein 2C and the protein kinase A anchoring protein 10 (AKAP 10). The 2C gene from the CA9, ECHO 22, FMDV, HAV HM175, HAV wt1, HeCV, HRV 85 and TME picornaviruses were cloned into both translation and expression vectors (the FMDV and HRV 85 were donated by C. Knox and N. Moir respectively). Translation products were then used in a binding assay and interaction with AKAP 10 was shown for ECHO 22, FMDV, HAV wt1, HeCV, HRV 85 and TME. These results indicate AKAP 10 binding as a general function of 2C in all picornaviruses. An expression system was optimised for HRV 85 2ABC, 2BC and 2C proteins, and was shown to produce the other picornavirus 2C proteins at similar levels. Cellular expression of protein 2BC is known to bring about membrane rearrangements and the binding of 2C to AKAP 10 may help explain this aspect of the cytopathic effect and the targeting of virus replication to membranes.The autecology of Elachista fucicola (Vell.) Aresch. and Elachista scutulata (Sm.) Duby.Katpitia, Amy Dhunjishawhttps://hdl.handle.net/10023/218592021-10-28T10:52:27Z1962-01-01T00:00:00ZThe genus Elachista was founded by Duby in 1830, and he placed Conferva scutulata Sm. in it. This is the type specimen of the genus and is figured in English Botany by Sowerby. The illustration is dated August 1st, 1811. Elachista scutulata (Sm.) Duby was first found by Mr. Borer at Brighton growing on Himanthalia elongata. The genus in Britain contains two other species, Elachista fucicola (Vell.) Aresch. and Elachista flaccida, Elachista fucicola (Vell.) Aresch. is the oldest known and the commonest species of the genus Elachista in Britain. Colonel Velley first discovered this brown alga and he gave a correct representation and description of it growing on Fuous serratus as Conferva fucicola in the year 1795, in his book, Coloured Figures of Marine Plants Found on the Southern Coast of England. Velley found this plant growing in great abundance, particularly in the spring under an elevated cliff near Weymouth called "The Look Out". The plant Velley described and figured is in his herbarium in Liverpool Museum and this is the type specimen of Elachista fuclcola. Areschoug in 1842 placed Velley's Conferva fucicola in the genus Elachista.
Elachista flaccida (Dillw.) Aresch. In 1843 Areschoug placed this in the genus Elachista Harvey. Formerly there was a fourth species Elachista grevillei now reduced to a form of Elachista fucicola. E. grevillei was found by Dr. Greville in July 1852 growing on Cladophora rupestris at Largs. In the same year, but in the month of August, it was found by Professor Walker Arnott at Corrighills, Arran. The plant consists of a basal disc, from which assimilatory filaments and paraphyses arise.
1962-01-01T00:00:00ZKatpitia, Amy DhunjishawThe genus Elachista was founded by Duby in 1830, and he placed Conferva scutulata Sm. in it. This is the type specimen of the genus and is figured in English Botany by Sowerby. The illustration is dated August 1st, 1811. Elachista scutulata (Sm.) Duby was first found by Mr. Borer at Brighton growing on Himanthalia elongata. The genus in Britain contains two other species, Elachista fucicola (Vell.) Aresch. and Elachista flaccida, Elachista fucicola (Vell.) Aresch. is the oldest known and the commonest species of the genus Elachista in Britain. Colonel Velley first discovered this brown alga and he gave a correct representation and description of it growing on Fuous serratus as Conferva fucicola in the year 1795, in his book, Coloured Figures of Marine Plants Found on the Southern Coast of England. Velley found this plant growing in great abundance, particularly in the spring under an elevated cliff near Weymouth called "The Look Out". The plant Velley described and figured is in his herbarium in Liverpool Museum and this is the type specimen of Elachista fuclcola. Areschoug in 1842 placed Velley's Conferva fucicola in the genus Elachista.
Elachista flaccida (Dillw.) Aresch. In 1843 Areschoug placed this in the genus Elachista Harvey. Formerly there was a fourth species Elachista grevillei now reduced to a form of Elachista fucicola. E. grevillei was found by Dr. Greville in July 1852 growing on Cladophora rupestris at Largs. In the same year, but in the month of August, it was found by Professor Walker Arnott at Corrighills, Arran. The plant consists of a basal disc, from which assimilatory filaments and paraphyses arise.Influence of cysteine residues on monoamine oxidases catalysisVintém, Ana Paula Barradashttps://hdl.handle.net/10023/218602021-10-28T11:13:35Z2003-01-01T00:00:00ZMonoamine oxidases (MAO), types A and B, are flavin-containing enzymes important in the regulation of biogenic amines, including the neurotransmitters, serotonin and dopamine. Cysteine modification inactivates MAO and alters the flavin redox properties, yet the crystal structure has shown that there are no conserved cysteines in the active site of MAO B and that the cysteine 365, modified after inactivation by a cyclopropylamine, was on the surface. The aim of this project was to find how the cysteine residues influence MAO catalysis. MAO A and B cysteine mutants to alanine were constructed and expressed in P. pastoris. MAO A C374A was purified and characterised kinetically. The mutant was active but had decreased Kcₐₜ/kₘ values with a series of substrates compared to the native enzyme. The Kᵢ values for inhibitors were not changed. Mechanism-based inactivators, cyclopropylamines, showed the same pattern as the substrates. Spectra studies and free thiol counts established that 1-phenylcyclopropylamine (1-PCPA) forms a flavin adduct whereas 2-phenylcyclopropylamine (2-PCPA) and A-cyclo- α-methylbenzylamine (N-CαMBA) form adducts with a cysteine in both native and mutant MAO A. Thus, the cysteine modified by N-CαMBA in MAO A is not the 374, as it would be expected by correspondence to the MAO B cysteine 365. For the 1-PCPA and N-CαMBA, the partition ratio was decreased by more than 50%. The data suggest the mutation of cysteine 374 decreases the efficiency of MAO A catalytic process without affecting the ligand binding. A revised mechanism for inactivation of MAO by cyclopropylamines is proposed.
2003-01-01T00:00:00ZVintém, Ana Paula BarradasMonoamine oxidases (MAO), types A and B, are flavin-containing enzymes important in the regulation of biogenic amines, including the neurotransmitters, serotonin and dopamine. Cysteine modification inactivates MAO and alters the flavin redox properties, yet the crystal structure has shown that there are no conserved cysteines in the active site of MAO B and that the cysteine 365, modified after inactivation by a cyclopropylamine, was on the surface. The aim of this project was to find how the cysteine residues influence MAO catalysis. MAO A and B cysteine mutants to alanine were constructed and expressed in P. pastoris. MAO A C374A was purified and characterised kinetically. The mutant was active but had decreased Kcₐₜ/kₘ values with a series of substrates compared to the native enzyme. The Kᵢ values for inhibitors were not changed. Mechanism-based inactivators, cyclopropylamines, showed the same pattern as the substrates. Spectra studies and free thiol counts established that 1-phenylcyclopropylamine (1-PCPA) forms a flavin adduct whereas 2-phenylcyclopropylamine (2-PCPA) and A-cyclo- α-methylbenzylamine (N-CαMBA) form adducts with a cysteine in both native and mutant MAO A. Thus, the cysteine modified by N-CαMBA in MAO A is not the 374, as it would be expected by correspondence to the MAO B cysteine 365. For the 1-PCPA and N-CαMBA, the partition ratio was decreased by more than 50%. The data suggest the mutation of cysteine 374 decreases the efficiency of MAO A catalytic process without affecting the ligand binding. A revised mechanism for inactivation of MAO by cyclopropylamines is proposed.The biochemical genetics of sulphate assimilation in barley (Hordeum vulgare)Gilkes, Amanda Franceshttps://hdl.handle.net/10023/218542021-10-28T08:37:26Z1995-01-01T00:00:00ZThe sulphate assimilation pathway was investigated in barley (Hordeum vulgare). The enzymes ATP sulphurylase, thiosulphate reductase, sulphite reductase, serine acetyltransferase and cysteine synthase proposed as steps in the pathway of higher plants, have been detected in barley seedling leaves. Cysteine synthase was purified ca 400 fold from extract of 7 day old barley seedling leaves to give an activity of 52 μmols cysteine produced/min/mg protein. Differential centrifugation of mechanically ruptured protoplasts showed cysteine synthase was likely to be predominantly or exclusively located within the chloroplast. Specific staining for cysteine synthase activity of non-denaturing polyacrylamide gels suggest the presence of a single form of the enzyme in barley. Development of cysteine synthase activity in barley seedlings was shown not to be dependent on light but was influenced by nutritional status. Selenate, which was shown to be toxic to barley seedlings, was used as the positive selection agent in a screen designed to isolate whole plant mutants defective in sulphate assimilation. Over 70,000 M₂ seedlings (mutagenised in the Mi with 2mM sodium azide) were screened for resistance to selenate. Nine M₂ seedlings were selected as most likely to be defective in sulphate assimilation. M₃ progeny were obtained from four of the M₂ selections. The M₃ progeny showed no resistance to selenate and specific activity staining of non-denaturing polyacrylamide gels showed the presence of functional ATP sulphurylase, thiosulphate reductase, sulphite reductase and cysteine synthase. These results suggest it is unlikely that these M₂ selections carry a heritable mutation in sulphate assimilation.
1995-01-01T00:00:00ZGilkes, Amanda FrancesThe sulphate assimilation pathway was investigated in barley (Hordeum vulgare). The enzymes ATP sulphurylase, thiosulphate reductase, sulphite reductase, serine acetyltransferase and cysteine synthase proposed as steps in the pathway of higher plants, have been detected in barley seedling leaves. Cysteine synthase was purified ca 400 fold from extract of 7 day old barley seedling leaves to give an activity of 52 μmols cysteine produced/min/mg protein. Differential centrifugation of mechanically ruptured protoplasts showed cysteine synthase was likely to be predominantly or exclusively located within the chloroplast. Specific staining for cysteine synthase activity of non-denaturing polyacrylamide gels suggest the presence of a single form of the enzyme in barley. Development of cysteine synthase activity in barley seedlings was shown not to be dependent on light but was influenced by nutritional status. Selenate, which was shown to be toxic to barley seedlings, was used as the positive selection agent in a screen designed to isolate whole plant mutants defective in sulphate assimilation. Over 70,000 M₂ seedlings (mutagenised in the Mi with 2mM sodium azide) were screened for resistance to selenate. Nine M₂ seedlings were selected as most likely to be defective in sulphate assimilation. M₃ progeny were obtained from four of the M₂ selections. The M₃ progeny showed no resistance to selenate and specific activity staining of non-denaturing polyacrylamide gels showed the presence of functional ATP sulphurylase, thiosulphate reductase, sulphite reductase and cysteine synthase. These results suggest it is unlikely that these M₂ selections carry a heritable mutation in sulphate assimilation.The effects of foliar damage on flower characteristics and pollinator visits in Vicia fabaOrozumbekov, Almazbek Anarbekovichhttps://hdl.handle.net/10023/218512021-10-27T11:48:29Z2002-01-01T00:00:00ZThis thesis addresses aspects of the interaction of plant herbivory and plant pollination. The experiments examine the effects of leaf damage on the flower characteristics of broad beans (Vicia faba) and resultant changes in the visiting behaviour of bees. Early experiments suffered from some experimental inconsistency, and only the later experiments gave results regarded as reliable. Here I found that in broad bean plants, grown under greenhouse conditions, damage to leaves (simulating herbivory) does affect some floral characters. Most importantly, damage (usually at the level of 50% leaf area removal) had the effects of a reduction in the overall number of flowers, decreased flower width, decreased floral nectar concentration (which would lead to lower sugar reward per flower) and at least in some cases a reduction in number of pollen grains per flower. Bumblebees were the most important visitors to field bean flowers, especially Bombus pascuorum and to a lesser extent B. hortorum. Flower visits by bees were more frequent in the afternoon, but trip durations were longer in the morning when nectar rewards were lower. Control (undamaged) plants received more visits overall than either of the two (33% and 50%) damaged groups, and times spent per flower were also usually higher on the control plants compared to damaged plants. For the commonest visitor B pascuorum overall trip lengths were also reduced with 33% and 50% damage, suggesting an ability in this species to detect the effects of damage, either on flower size or on nectar concentration, or on both. Thus, the smaller flowers on damaged plants got fewer and shorter visits overall, and their potential for effective entomophilous pollination may have been reduced. Thus a potential interaction of herbivory levels (as simulated damage) and overall pollination effectiveness is suggested for this species.
2002-01-01T00:00:00ZOrozumbekov, Almazbek AnarbekovichThis thesis addresses aspects of the interaction of plant herbivory and plant pollination. The experiments examine the effects of leaf damage on the flower characteristics of broad beans (Vicia faba) and resultant changes in the visiting behaviour of bees. Early experiments suffered from some experimental inconsistency, and only the later experiments gave results regarded as reliable. Here I found that in broad bean plants, grown under greenhouse conditions, damage to leaves (simulating herbivory) does affect some floral characters. Most importantly, damage (usually at the level of 50% leaf area removal) had the effects of a reduction in the overall number of flowers, decreased flower width, decreased floral nectar concentration (which would lead to lower sugar reward per flower) and at least in some cases a reduction in number of pollen grains per flower. Bumblebees were the most important visitors to field bean flowers, especially Bombus pascuorum and to a lesser extent B. hortorum. Flower visits by bees were more frequent in the afternoon, but trip durations were longer in the morning when nectar rewards were lower. Control (undamaged) plants received more visits overall than either of the two (33% and 50%) damaged groups, and times spent per flower were also usually higher on the control plants compared to damaged plants. For the commonest visitor B pascuorum overall trip lengths were also reduced with 33% and 50% damage, suggesting an ability in this species to detect the effects of damage, either on flower size or on nectar concentration, or on both. Thus, the smaller flowers on damaged plants got fewer and shorter visits overall, and their potential for effective entomophilous pollination may have been reduced. Thus a potential interaction of herbivory levels (as simulated damage) and overall pollination effectiveness is suggested for this species.Reproductive investment in the zebra finch, Taeniopygia guttataRutstein, Alison N.https://hdl.handle.net/10023/218462021-10-27T10:12:41Z2003-01-01T00:00:00ZReproduction is costly; therefore females are predicted to allocate resources depending upon the perceived costs and benefits of a particular breeding attempt. Within a clutch, females are also predicted to invest in offspring according to their perceived fitness returns, which may depend upon their sex and position in the hatching sequence. This thesis examines female resource allocation in zebra finches, Taeniopygia guttata, in relation to changes in mate attractiveness and diet quality, with an emphasis on primary investment and differential sex allocation. Females that were given an attractive male as their first mate were found to lay heavier eggs than females that were given an unattractive male as their first mate, but there was no difference in offspring quality between treatments at any stage of development. There was also no evidence of differential sex allocation in either treatment. Diet quality had a stronger effect on resource allocation and reproductive success. Females on a high quality (HQ) diet laid heavier clutches and reared more and higher quality young than on a low quality (LQ) diet. This could have partly resulted from differences in egg size and quality. Eggs laid on the HQ diet were better provisioned with yolk and albumen and had higher concentrations of yolk androgens. In line with sex allocation theory, female-biased broods were produced on the HQ diet and male-biased broods on the LQ diet. There were also sex differences in androgen deposition between the diets, with greater concentrations of yolk androgens in male eggs on the LQ diet and female eggs on the HQ diet. Egg mass increased with position in the laying sequence on the HQ diet but not on the LQ diet, which affected within-brood patterns of post-hatching mortality. Yolk androgen and carotenoid concentrations, however, decreased with laying sequence on both diets.
2003-01-01T00:00:00ZRutstein, Alison N.Reproduction is costly; therefore females are predicted to allocate resources depending upon the perceived costs and benefits of a particular breeding attempt. Within a clutch, females are also predicted to invest in offspring according to their perceived fitness returns, which may depend upon their sex and position in the hatching sequence. This thesis examines female resource allocation in zebra finches, Taeniopygia guttata, in relation to changes in mate attractiveness and diet quality, with an emphasis on primary investment and differential sex allocation. Females that were given an attractive male as their first mate were found to lay heavier eggs than females that were given an unattractive male as their first mate, but there was no difference in offspring quality between treatments at any stage of development. There was also no evidence of differential sex allocation in either treatment. Diet quality had a stronger effect on resource allocation and reproductive success. Females on a high quality (HQ) diet laid heavier clutches and reared more and higher quality young than on a low quality (LQ) diet. This could have partly resulted from differences in egg size and quality. Eggs laid on the HQ diet were better provisioned with yolk and albumen and had higher concentrations of yolk androgens. In line with sex allocation theory, female-biased broods were produced on the HQ diet and male-biased broods on the LQ diet. There were also sex differences in androgen deposition between the diets, with greater concentrations of yolk androgens in male eggs on the LQ diet and female eggs on the HQ diet. Egg mass increased with position in the laying sequence on the HQ diet but not on the LQ diet, which affected within-brood patterns of post-hatching mortality. Yolk androgen and carotenoid concentrations, however, decreased with laying sequence on both diets.Functions of different neurotrophic factors in regulating neuronal survival in the developing peripheral nervous systemForgie, Alison Janehttps://hdl.handle.net/10023/218432021-10-26T14:56:21Z2000-01-01T00:00:00ZThe main aim of this thesis was to clarify the significance of the GDNF family of neurotrophic factors in neural development. The ability of GDNF, neurturin, persephin and artemin to promote the survival of embryonic chicken parasympathetic, sympathetic and sensory neurons was studied in vitro. All of these neurons responded to GDNF and neurturin, but failed to respond to artemin and persephin. The sensitivity to GDNF and neurturin differed for each type of neuron and varied with age. Competitive RT-PCR revealed correlations between sensitivity to GDNF and neurturin and the level of mRNAs encoding the GPI-linked receptor components for these factors. An attempt was made to generate antibodies against these receptor components so that the relationship between receptor expression and responsiveness could be examined. Although antibodies were successfully generated, they were of limited use due to a lack of specificity. To clarify the ligand specificity of the GPI-linked receptors for members of the GDNF family, the response of neurons from wild-type and GFRal-/- embryos was studied in vitro. Whereas GFRal-deficient nodose neurons failed to respond to GDNF and neurturin, GFRal-deficient submandibular neurons retained normal responsiveness. These results suggest that GFRal mediates GDNF and neurturin signalling in nodose sensory neurons, whereas an alternative receptor mediates the response of submandibular parasympathetic neurons to these factors. Finally, in the course of studying the survival responses of PNS neurons to the GDNF family, compelling evidence for the existence of an NGF-dependent subpopulation of nodose neurons was obtained. In addition to in vitro survival data, RT-PCR demonstrated that TrkA mRNA is expressed at relatively high levels in the developing nodose ganglion and histological analysis of nodose ganglia in NGF-/- mice revealed a significant loss of neurons in the absence of NGF.
2000-01-01T00:00:00ZForgie, Alison JaneThe main aim of this thesis was to clarify the significance of the GDNF family of neurotrophic factors in neural development. The ability of GDNF, neurturin, persephin and artemin to promote the survival of embryonic chicken parasympathetic, sympathetic and sensory neurons was studied in vitro. All of these neurons responded to GDNF and neurturin, but failed to respond to artemin and persephin. The sensitivity to GDNF and neurturin differed for each type of neuron and varied with age. Competitive RT-PCR revealed correlations between sensitivity to GDNF and neurturin and the level of mRNAs encoding the GPI-linked receptor components for these factors. An attempt was made to generate antibodies against these receptor components so that the relationship between receptor expression and responsiveness could be examined. Although antibodies were successfully generated, they were of limited use due to a lack of specificity. To clarify the ligand specificity of the GPI-linked receptors for members of the GDNF family, the response of neurons from wild-type and GFRal-/- embryos was studied in vitro. Whereas GFRal-deficient nodose neurons failed to respond to GDNF and neurturin, GFRal-deficient submandibular neurons retained normal responsiveness. These results suggest that GFRal mediates GDNF and neurturin signalling in nodose sensory neurons, whereas an alternative receptor mediates the response of submandibular parasympathetic neurons to these factors. Finally, in the course of studying the survival responses of PNS neurons to the GDNF family, compelling evidence for the existence of an NGF-dependent subpopulation of nodose neurons was obtained. In addition to in vitro survival data, RT-PCR demonstrated that TrkA mRNA is expressed at relatively high levels in the developing nodose ganglion and histological analysis of nodose ganglia in NGF-/- mice revealed a significant loss of neurons in the absence of NGF.Structural studies into the mechanism of substrate binding and catalysis in a promiscuous hyperthermophilic aldolaseTheodossis, Alexanderhttps://hdl.handle.net/10023/218352021-10-25T13:34:52Z2006-01-01T00:00:00ZSulfolobus solfataricus is a hyperthermophilic archaeon that grows optimally between 80 and 85°C. It metabolises glucose and galactose by a promiscuous variant of the Entner-Doudoroff pathway, in which both a non-phosphorylative and a part phosphorylative branch have been proposed to operate in parallel. A single, broad specificity aldolase (SsKDGA) has been shown to catalyse the C-C bond cleavage of intermediates arising from both sugars, in either of the branches. The structure of this enzyme has previously been solved by MAD-phasing of a SeMet derivative, confirming that it belongs to the N-acetylneuraminate lyase (NAL) subfamily of type I aldolases. The current study has focused on the investigation of SsKDGA's mechanisms of substrate binding and catalysis. The resolution of the apoenzyme model has been extended from 2.5 to 1.7 A, using native crystals grown at physiological pH, and a detailed characterisation of the active site region has been carried out. Also, high resolution complexes have been obtained of the aldolase with its natural substrates as Schiff base intermediates. These structures have afforded a better understanding of SsKDGA's promiscuous activity and permitted mechanistic comparisons to be made with other type I aldolases. The insights gained are providing the means by which a rational design approach can be used to tailor the enzyme's selectivity. So far, work has focused on dissecting SsKDGA's catalytic mechanism and inducing stereocontrol in the condensation reaction. However, the potential for generating novel aldol products has also being examined.
2006-01-01T00:00:00ZTheodossis, AlexanderSulfolobus solfataricus is a hyperthermophilic archaeon that grows optimally between 80 and 85°C. It metabolises glucose and galactose by a promiscuous variant of the Entner-Doudoroff pathway, in which both a non-phosphorylative and a part phosphorylative branch have been proposed to operate in parallel. A single, broad specificity aldolase (SsKDGA) has been shown to catalyse the C-C bond cleavage of intermediates arising from both sugars, in either of the branches. The structure of this enzyme has previously been solved by MAD-phasing of a SeMet derivative, confirming that it belongs to the N-acetylneuraminate lyase (NAL) subfamily of type I aldolases. The current study has focused on the investigation of SsKDGA's mechanisms of substrate binding and catalysis. The resolution of the apoenzyme model has been extended from 2.5 to 1.7 A, using native crystals grown at physiological pH, and a detailed characterisation of the active site region has been carried out. Also, high resolution complexes have been obtained of the aldolase with its natural substrates as Schiff base intermediates. These structures have afforded a better understanding of SsKDGA's promiscuous activity and permitted mechanistic comparisons to be made with other type I aldolases. The insights gained are providing the means by which a rational design approach can be used to tailor the enzyme's selectivity. So far, work has focused on dissecting SsKDGA's catalytic mechanism and inducing stereocontrol in the condensation reaction. However, the potential for generating novel aldol products has also being examined.Role of ubiquitin-like modification during adenovirus infectionErrico, Alessiahttps://hdl.handle.net/10023/218292021-10-25T10:29:33Z2001-01-01T00:00:00ZSUMO-1 is a small ubiquitin like protein that can be covalently linked to lysine residues in target substrates with a range of biological consequences. Following viral infection, various cellular mechanisms are subverted. In particular, it has been demonstrated that in adenovirus infected cells SUMO-1 conjugated proteins accumulate. This is exemplified by the cellular substrate RanGAP where an increase in the SUMO-1 conjugated form of the protein is detected. In addition it has been shown that two adenovirus gene products, E1B-55kDa and protein V, undergo SUMO-1 conjugation. Indeed, from in vivo and in vitro experiments, it appears that ElB-55kDa is mono-SUMO-1 modified, while protein V seems to be a substrate for multiple SUMO-1 conjugation. Immunofluorescence studies have indicated that there are sites in the nucleus where ElB-55kDa and SUMO-1, and protein V and SUMO-1, colocalise. To establish the basis for the observed changes in SUMO-1 modification the metabolism and cellular localisation of the enzymes involved in SUMO-1 conjugation were examined. While the total amount of SUMO-1 activating enzyme was not altered by adenovirus infection it was noted that a number of higher molecular weight species of the protein were induced by the virus. However the cellular localisation of the protein was not altered by adenovirus infection. Western blotting indicated that Ubch9 was not modified, but after infection the cellular localisation of the protein was altered from diffuse nuclear to a highly punctuate distribution. These changes suggest that adenovirus infection alters the activity and/or cellular localisation of the enzymes involved in SUMO-1 conjugation. It was also noted that adenovirus infection induced activation of the transcription factor NF-kB. This appeared to result from a dramatic increase in the ubiquitination and turnover of the IkBα inhibitor protein. After adenovirus induced nuclear translocation, NF-kB was sequestered into discrete subnuclear sites, which may alter the activity of the protein. Together these data indicate that ubiquitin-like protein modifications are important cellular functions that are targeted by viral activities after infection.
2001-01-01T00:00:00ZErrico, AlessiaSUMO-1 is a small ubiquitin like protein that can be covalently linked to lysine residues in target substrates with a range of biological consequences. Following viral infection, various cellular mechanisms are subverted. In particular, it has been demonstrated that in adenovirus infected cells SUMO-1 conjugated proteins accumulate. This is exemplified by the cellular substrate RanGAP where an increase in the SUMO-1 conjugated form of the protein is detected. In addition it has been shown that two adenovirus gene products, E1B-55kDa and protein V, undergo SUMO-1 conjugation. Indeed, from in vivo and in vitro experiments, it appears that ElB-55kDa is mono-SUMO-1 modified, while protein V seems to be a substrate for multiple SUMO-1 conjugation. Immunofluorescence studies have indicated that there are sites in the nucleus where ElB-55kDa and SUMO-1, and protein V and SUMO-1, colocalise. To establish the basis for the observed changes in SUMO-1 modification the metabolism and cellular localisation of the enzymes involved in SUMO-1 conjugation were examined. While the total amount of SUMO-1 activating enzyme was not altered by adenovirus infection it was noted that a number of higher molecular weight species of the protein were induced by the virus. However the cellular localisation of the protein was not altered by adenovirus infection. Western blotting indicated that Ubch9 was not modified, but after infection the cellular localisation of the protein was altered from diffuse nuclear to a highly punctuate distribution. These changes suggest that adenovirus infection alters the activity and/or cellular localisation of the enzymes involved in SUMO-1 conjugation. It was also noted that adenovirus infection induced activation of the transcription factor NF-kB. This appeared to result from a dramatic increase in the ubiquitination and turnover of the IkBα inhibitor protein. After adenovirus induced nuclear translocation, NF-kB was sequestered into discrete subnuclear sites, which may alter the activity of the protein. Together these data indicate that ubiquitin-like protein modifications are important cellular functions that are targeted by viral activities after infection.The endocrine control of renal function in elasmobranch fishWells, Alanhttps://hdl.handle.net/10023/218192021-10-22T11:37:04Z2003-01-01T00:00:00Z1. Urine flow rate was measured in vivo, as fish were acclimated to reduced salinity (70% SW). Urine flow increased in a step-wise manner, whilst plasma osmolality, urea, chloride and sodium concentrations were all significantly reduced. Associated with this reduction in plasma osmolality was a significant increase in the renal clearance of ions.
2. An in situ perfused renal preparation has been developed and established as a viable tool for the investigation of renal function in the dogfish in fish acclimated to both SW and 85% SW. The preparation recovered from a high dose of arginine vasotocin and remained viable for a sufficient period of time to investigate the renal effects of osmoregulatory peptides.
3. On perfusion through the renal trunk preparation, arginine vasotocin and angiotensin II caused a significant glomerular antidiuresis and decreases in the tubular transport maxima for glucose and perfusate flow in trunks from both SW and 85% SW acclimated fish. However, C-type natriuretic peptide, had the opposite effect, causing a glomerular diuresis and an increase in the tubular transport maxima for glucose trunk preparations from fish acclimated to both salinities. Tubular parameters remained unchanged by all three hormones under test.
4. Preliminary evidence for the existence of an intra-renal renin-angiotensin system has been presented. The angiotensin converting enzyme inhibitor captopril caused a significant glomerular diuresis and an increase in transport maxima for glucose in SW-acclimated preparations.
5. The filtering population of glomeruli was examined directly using the ferrocyanide technique. Perfusion of arginine vasotocin or angiotensin II caused a significant reduction in the proportion of filtering glomeruli. This reduction was greater than that previously predicted by the measurement of transport maxima for glucose. Large discrepancies between TmG and direct measurements of the filtering population of glomeruli have cast further doubt on the effectiveness of TmG as a measure of the functional tubular mass. These results have serious implications for the use of TmG as a measure of functional tubular mass in elasmobranch fish. Perfusion of C-type natriuretic peptide had no significant effect on the proportion of filtering glomeruli in SW-acclimated preparations and only a slight increase in preparations acclimated to 85% SW. These results strongly suggest alterations in single-nephron glomerular filtration rate.
2003-01-01T00:00:00ZWells, Alan1. Urine flow rate was measured in vivo, as fish were acclimated to reduced salinity (70% SW). Urine flow increased in a step-wise manner, whilst plasma osmolality, urea, chloride and sodium concentrations were all significantly reduced. Associated with this reduction in plasma osmolality was a significant increase in the renal clearance of ions.
2. An in situ perfused renal preparation has been developed and established as a viable tool for the investigation of renal function in the dogfish in fish acclimated to both SW and 85% SW. The preparation recovered from a high dose of arginine vasotocin and remained viable for a sufficient period of time to investigate the renal effects of osmoregulatory peptides.
3. On perfusion through the renal trunk preparation, arginine vasotocin and angiotensin II caused a significant glomerular antidiuresis and decreases in the tubular transport maxima for glucose and perfusate flow in trunks from both SW and 85% SW acclimated fish. However, C-type natriuretic peptide, had the opposite effect, causing a glomerular diuresis and an increase in the tubular transport maxima for glucose trunk preparations from fish acclimated to both salinities. Tubular parameters remained unchanged by all three hormones under test.
4. Preliminary evidence for the existence of an intra-renal renin-angiotensin system has been presented. The angiotensin converting enzyme inhibitor captopril caused a significant glomerular diuresis and an increase in transport maxima for glucose in SW-acclimated preparations.
5. The filtering population of glomeruli was examined directly using the ferrocyanide technique. Perfusion of arginine vasotocin or angiotensin II caused a significant reduction in the proportion of filtering glomeruli. This reduction was greater than that previously predicted by the measurement of transport maxima for glucose. Large discrepancies between TmG and direct measurements of the filtering population of glomeruli have cast further doubt on the effectiveness of TmG as a measure of the functional tubular mass. These results have serious implications for the use of TmG as a measure of functional tubular mass in elasmobranch fish. Perfusion of C-type natriuretic peptide had no significant effect on the proportion of filtering glomeruli in SW-acclimated preparations and only a slight increase in preparations acclimated to 85% SW. These results strongly suggest alterations in single-nephron glomerular filtration rate.Experiments on the effects of cultural conditions, increasing age on respiratory rates, weight and resistance to metabolic inhibitors on drosophila melanogaster males of the mutant, vestigial ebonyPhillips, Alan .E.H.https://hdl.handle.net/10023/218152021-10-22T09:43:09Z1970-01-01T00:00:00Z1970-01-01T00:00:00ZPhillips, Alan .E.H.Studies on the effects of variable terbutryne concentrations and temperatures on some physiological responses of 'Elodea Canadensis Michx.'Matin, Abdulhttps://hdl.handle.net/10023/217962021-09-27T15:28:18Z1980-01-01T00:00:00ZEffects of different concentrations of terbutryne on photosynthesis, respiration, chlorophyll concentration and dry matter accumulation of Blodea canadensis Michx. over a wide range of temperature, under natural and artificial light climates have been described in this thesis. At a given temperature, effects of terbutryne increased with increased concentration, and at a given concentration phototoxicity increased with rising temperature. There was a highly significant concentration x temperature interaction of terbutryne activity. The difference in the metabolic and physiological responses of B. canadensis to terbutryne treatment under the two light climates were not wide. At all concentrations and temperatures the maximum inhibitory effects on net photosynthesis were expressed by the second day and on dark respiration by the third day of treatment. Fifty percent inhibition (I₅₀) in net photosynthesis occurred at the lowest concentration of 0.0125 mgL⁻¹ and temperature 10°C and dark respiration at a concentration of 0.025 mgL⁻¹ and temperature 20 C. Complete suppression of net photosynthesis (100% inhibition) occurred at the highest concentration of 0.05 mgL⁻¹ at temperatures 20° and 25°C, under natural light conditions, while it did not occur under artificial light conditions at the same concentration and temperature. Complete suppression of dark respiration never occurred at any concentration and temperature. Recovery from photosynthetic inhibition of terbutryne started from third day of treatment in all concentrations at most of the temperatures. Recovery was higher at lower concentrations and temperatures. Recovery from respiratory inhibition never occurred.at any concentration and temperature. Dry weight of the treated plants decreased at all concentrations and temperatures. The general trend was for the dry weight to decrease most with increasing concentration of terbutryne. Despite some variation, the chlorophyll (a+b) concentration in the tissues of the treated plants remained more or less unaffected and the plants suffered no visible physical damage due to terbutryne treatment over the experimental period. The relevance of these findings to aquatic weed control in tropical conditions of Bangladesh (i.e. at the equivalent high ambient temperatures) is discussed.
1980-01-01T00:00:00ZMatin, AbdulEffects of different concentrations of terbutryne on photosynthesis, respiration, chlorophyll concentration and dry matter accumulation of Blodea canadensis Michx. over a wide range of temperature, under natural and artificial light climates have been described in this thesis. At a given temperature, effects of terbutryne increased with increased concentration, and at a given concentration phototoxicity increased with rising temperature. There was a highly significant concentration x temperature interaction of terbutryne activity. The difference in the metabolic and physiological responses of B. canadensis to terbutryne treatment under the two light climates were not wide. At all concentrations and temperatures the maximum inhibitory effects on net photosynthesis were expressed by the second day and on dark respiration by the third day of treatment. Fifty percent inhibition (I₅₀) in net photosynthesis occurred at the lowest concentration of 0.0125 mgL⁻¹ and temperature 10°C and dark respiration at a concentration of 0.025 mgL⁻¹ and temperature 20 C. Complete suppression of net photosynthesis (100% inhibition) occurred at the highest concentration of 0.05 mgL⁻¹ at temperatures 20° and 25°C, under natural light conditions, while it did not occur under artificial light conditions at the same concentration and temperature. Complete suppression of dark respiration never occurred at any concentration and temperature. Recovery from photosynthetic inhibition of terbutryne started from third day of treatment in all concentrations at most of the temperatures. Recovery was higher at lower concentrations and temperatures. Recovery from respiratory inhibition never occurred.at any concentration and temperature. Dry weight of the treated plants decreased at all concentrations and temperatures. The general trend was for the dry weight to decrease most with increasing concentration of terbutryne. Despite some variation, the chlorophyll (a+b) concentration in the tissues of the treated plants remained more or less unaffected and the plants suffered no visible physical damage due to terbutryne treatment over the experimental period. The relevance of these findings to aquatic weed control in tropical conditions of Bangladesh (i.e. at the equivalent high ambient temperatures) is discussed.Acoustic deep scattering layers as dynamic prey landscapes for air-breathing deep-diving Antarctic predatorsLe Guen, Camille Melanie Marie-Annehttps://hdl.handle.net/10023/216042021-08-14T10:12:22Z2020-12-01T00:00:00ZThis PhD addresses the central hypothesis that acoustic Deep Scattering Layers (DSLs) are a prey landscape for deep-diving air-breathing Southern Ocean predators. In the open ocean, mesopelagic fish (including myctophids), zooplankton and other animals migrate down from the surface at dawn to the mesopelagic zone (200-1000 m) to avoid visual predators during daylight. There, they form layer-like aggregations known as Deep Scattering Layers that can be detected using echosounders. A large component of DSL biomass is comprised of myctophids, which are both a potential resource for fisheries and important in the diets of several iconic Antarctic predators such as King Penguins (Aptenodytes patagonicus) and Southern Elephant Seals (Mirounga leonina). Although these two predator species are amenable to bio-logging, there are very few simultaneous observations of DSLs and their foraging behaviour. Therefore, the importance of DSLs to Antarctic air-breathing diving predators is unknown. This is problematic given the predicted changes in DSLs in response to climate change and to the increasing interest shown in DSL harvest by commercial fishers. The 2017 Antarctic Circumnavigation Expedition (ACE), which is the first scientific expedition around the Antarctic continent stopping at most subantarctic islands to investigate a range of aspects of the Southern Ocean, provided a unique opportunity to simultaneously observe DSL characteristics acoustically from the ACE ship (at 12.5 kHz) and the foraging behaviour of predators using bio-logging. King Penguins and female Southern Elephant Seals appeared as good candidates to study the link with DSLs as they both mainly feed on myctophids, are both deep-diving predators potentially capable of reaching the depth of DSLs and are both known to dive deeper during the day compared to night time (like the Diel Vertical Migration (DVM) pattern of the components of DSLs), several clues that initially suggest that DSLs could be a prey landscape for them. I compiled a dataset of DSL depth and echo-intensity (proxy for biomass) along the circum-continental cruise track (~ 90,000 km, across 6 different frontal zones) and obtained dive data from 18 adult King Penguins breeding at South Georgia and from 8 adult female Southern Elephant Seals breeding at Kerguelen. This study aims to describe the distribution of DSLs in the Southern Ocean in order to build a DSL biogeography for this region and to investigate whether these Antarctic deep-diving predators rely on DSLs for food. In Chapter 2, it was found that DSL echo-intensity (proxy for biomass) was a function of Sea Surface Temperature (SST), and that DSL depth was significantly related to sub-surface temperature and salinity or surface density. These relationships were used to infer DSL properties throughout the Southern Ocean, and especially at predator dive locations. In addition, rather than being ubiquitous, the data from the present study suggest that DSLs disappear in places where SST values become lower than -0.4°C. Results from Chapter 3 showed that Southern Elephant Seals seemed to reach the bottom of the principal DSL (i.e. strongest DSL) or the top of the deepest DSL (i.e. most predictable DSL). In contrast, results from chapter 4 revealed that King Penguins preferentially selected habitats with dense and shallow DSLs, where the availability of DSL components was supposedly high. However, the dive depths of penguins were generally shallower than the DSL, suggesting that they did not feed on the layers themselves, but on prey patches that were observed acoustically above them. These patches may be associated with the layers. DSLs, as a prey landscape for these two species, also play an important role in the biological pump of the ocean (acting on climate regulation by sequestering carbon at depth) due to their DVMs. It is likely that DVMs have other implications, such as vertical mixing of nutrients or transport of contaminants through the water column. In this regard, it was found that King Penguin faeces contain relatively high concentrations of microfibers, which were likely indirectly ingested (i.e. from migrating prey consumed at depth) and might potentially be deleterious for them (Chapter 5). Chick-rearing penguins had lower levels of contamination compared to incubating birds, which are known to perform longer foraging trips and to reach lower latitudes, and are potentially more exposed to microfibre contamination. In that way, results suggest that microfibres provide a potential signature of foraging in King Penguins. The importance of DSLs for contamination should be further investigated (including the impact of DVMs and the quantities of microplastics that are brought on land). These findings resulting from a multidisciplinary approach using in-situ and remote sensing environmental data, acoustic surveys and bio-logging improve our understanding of predator-prey interactions in the Southern Ocean. Although Antarctic focused, the present study is relevant more broadly because several seal and whale species also feed on DSL components. Because the Southern Ocean is undergoing various threats such as climate change, overfishing and marine pollution, our findings regarding the biophysical relationships with DSLs and the link between DSLs and Antarctic predators serve to improve our understanding of mesopelagic dynamics. This study informs ecosystem-based management and conservation, which now adopt more holistic approaches when monitoring and assessing ecosystem health status, before any large-scale fishery exploitation of mesopelagic fish begins.
2020-12-01T00:00:00ZLe Guen, Camille Melanie Marie-AnneThis PhD addresses the central hypothesis that acoustic Deep Scattering Layers (DSLs) are a prey landscape for deep-diving air-breathing Southern Ocean predators. In the open ocean, mesopelagic fish (including myctophids), zooplankton and other animals migrate down from the surface at dawn to the mesopelagic zone (200-1000 m) to avoid visual predators during daylight. There, they form layer-like aggregations known as Deep Scattering Layers that can be detected using echosounders. A large component of DSL biomass is comprised of myctophids, which are both a potential resource for fisheries and important in the diets of several iconic Antarctic predators such as King Penguins (Aptenodytes patagonicus) and Southern Elephant Seals (Mirounga leonina). Although these two predator species are amenable to bio-logging, there are very few simultaneous observations of DSLs and their foraging behaviour. Therefore, the importance of DSLs to Antarctic air-breathing diving predators is unknown. This is problematic given the predicted changes in DSLs in response to climate change and to the increasing interest shown in DSL harvest by commercial fishers. The 2017 Antarctic Circumnavigation Expedition (ACE), which is the first scientific expedition around the Antarctic continent stopping at most subantarctic islands to investigate a range of aspects of the Southern Ocean, provided a unique opportunity to simultaneously observe DSL characteristics acoustically from the ACE ship (at 12.5 kHz) and the foraging behaviour of predators using bio-logging. King Penguins and female Southern Elephant Seals appeared as good candidates to study the link with DSLs as they both mainly feed on myctophids, are both deep-diving predators potentially capable of reaching the depth of DSLs and are both known to dive deeper during the day compared to night time (like the Diel Vertical Migration (DVM) pattern of the components of DSLs), several clues that initially suggest that DSLs could be a prey landscape for them. I compiled a dataset of DSL depth and echo-intensity (proxy for biomass) along the circum-continental cruise track (~ 90,000 km, across 6 different frontal zones) and obtained dive data from 18 adult King Penguins breeding at South Georgia and from 8 adult female Southern Elephant Seals breeding at Kerguelen. This study aims to describe the distribution of DSLs in the Southern Ocean in order to build a DSL biogeography for this region and to investigate whether these Antarctic deep-diving predators rely on DSLs for food. In Chapter 2, it was found that DSL echo-intensity (proxy for biomass) was a function of Sea Surface Temperature (SST), and that DSL depth was significantly related to sub-surface temperature and salinity or surface density. These relationships were used to infer DSL properties throughout the Southern Ocean, and especially at predator dive locations. In addition, rather than being ubiquitous, the data from the present study suggest that DSLs disappear in places where SST values become lower than -0.4°C. Results from Chapter 3 showed that Southern Elephant Seals seemed to reach the bottom of the principal DSL (i.e. strongest DSL) or the top of the deepest DSL (i.e. most predictable DSL). In contrast, results from chapter 4 revealed that King Penguins preferentially selected habitats with dense and shallow DSLs, where the availability of DSL components was supposedly high. However, the dive depths of penguins were generally shallower than the DSL, suggesting that they did not feed on the layers themselves, but on prey patches that were observed acoustically above them. These patches may be associated with the layers. DSLs, as a prey landscape for these two species, also play an important role in the biological pump of the ocean (acting on climate regulation by sequestering carbon at depth) due to their DVMs. It is likely that DVMs have other implications, such as vertical mixing of nutrients or transport of contaminants through the water column. In this regard, it was found that King Penguin faeces contain relatively high concentrations of microfibers, which were likely indirectly ingested (i.e. from migrating prey consumed at depth) and might potentially be deleterious for them (Chapter 5). Chick-rearing penguins had lower levels of contamination compared to incubating birds, which are known to perform longer foraging trips and to reach lower latitudes, and are potentially more exposed to microfibre contamination. In that way, results suggest that microfibres provide a potential signature of foraging in King Penguins. The importance of DSLs for contamination should be further investigated (including the impact of DVMs and the quantities of microplastics that are brought on land). These findings resulting from a multidisciplinary approach using in-situ and remote sensing environmental data, acoustic surveys and bio-logging improve our understanding of predator-prey interactions in the Southern Ocean. Although Antarctic focused, the present study is relevant more broadly because several seal and whale species also feed on DSL components. Because the Southern Ocean is undergoing various threats such as climate change, overfishing and marine pollution, our findings regarding the biophysical relationships with DSLs and the link between DSLs and Antarctic predators serve to improve our understanding of mesopelagic dynamics. This study informs ecosystem-based management and conservation, which now adopt more holistic approaches when monitoring and assessing ecosystem health status, before any large-scale fishery exploitation of mesopelagic fish begins.Passive acoustic monitoring of harbour porpoise behaviour, distribution and density in tidal rapid habitatsMacaulay, Jamie Donald Johnhttps://hdl.handle.net/10023/214992021-08-06T14:06:03Z2020-12-01T00:00:00ZToothed whales produce regular echolocation clicks to sense their surroundings and hunt. These clicks can be detected on hydrophones allowing researchers to study and monitor animals, a methodology known as passive acoustic monitoring (PAM). PAM methods can be used to detect behaviours such as foraging, calculate the absolute abundance and determine the 3D positions of soniferous animals. However, this requires robust detection, species classification and localisation algorithms alongside a statistical framework to estimate animal density. Detection, classification and localisation methods were developed to obtain fine scale behavioural information of toothed whales which was then integrated with a distance sampling-based framework to estimate density. These methods were applied to calculate the behaviour, 3D distribution and density of harbour porpoises in a tidal stream habitat.
Toothed whales produce clicks in sequences (clicks trains) which can provide information on behavioural state and aid in species identification. A click train detection algorithm was developed to extract these sequences and performance then tested on PAM data from sperm whales, delphinids and harbour porpoise datasets.
Localisation in tidal rapids is difficult due to fast moving currents and high densities of toothed whales producing a complex soundscape. A drifting free-hanging vertical hydrophone array with movement sensors, click aliasing and track association algorithms was developed to collect geo-referenced 3D tracks of toothed whales in tidal streams.
The full 4π beam profile of a free-swimming captive harbour porpoise was measured. This showed that harbour porpoises have significant acoustic energy at extreme off-axis angles (>30°) which has implications for detectability on PAM devices.
Drifting sound recorders and vertical hydrophones arrays were used to survey a tidal rapid site. Detected click trains, dive data and the measured beam profile were used to inform simulations of detection probability of harbour porpoise clicks and calculate animal density and foraging rates.
2020-12-01T00:00:00ZMacaulay, Jamie Donald JohnToothed whales produce regular echolocation clicks to sense their surroundings and hunt. These clicks can be detected on hydrophones allowing researchers to study and monitor animals, a methodology known as passive acoustic monitoring (PAM). PAM methods can be used to detect behaviours such as foraging, calculate the absolute abundance and determine the 3D positions of soniferous animals. However, this requires robust detection, species classification and localisation algorithms alongside a statistical framework to estimate animal density. Detection, classification and localisation methods were developed to obtain fine scale behavioural information of toothed whales which was then integrated with a distance sampling-based framework to estimate density. These methods were applied to calculate the behaviour, 3D distribution and density of harbour porpoises in a tidal stream habitat.
Toothed whales produce clicks in sequences (clicks trains) which can provide information on behavioural state and aid in species identification. A click train detection algorithm was developed to extract these sequences and performance then tested on PAM data from sperm whales, delphinids and harbour porpoise datasets.
Localisation in tidal rapids is difficult due to fast moving currents and high densities of toothed whales producing a complex soundscape. A drifting free-hanging vertical hydrophone array with movement sensors, click aliasing and track association algorithms was developed to collect geo-referenced 3D tracks of toothed whales in tidal streams.
The full 4π beam profile of a free-swimming captive harbour porpoise was measured. This showed that harbour porpoises have significant acoustic energy at extreme off-axis angles (>30°) which has implications for detectability on PAM devices.
Drifting sound recorders and vertical hydrophones arrays were used to survey a tidal rapid site. Detected click trains, dive data and the measured beam profile were used to inform simulations of detection probability of harbour porpoise clicks and calculate animal density and foraging rates.Characterisation of organic osmolytes and biomarkers of smoltification in the Atlantic salmon (Salmo salar)Dagen, Claire Alexandrahttps://hdl.handle.net/10023/214912021-07-22T14:07:09Z2020-12-01T00:00:00ZAtlantic salmon are an economically important species, particularly in Scotland. The aquaculture of this species is complicated by its anadromous life cycle, requiring transfer to seawater. Smoltification is a complex process whereby fish prepare for entry to seawater, the “smolt window” is the time at which fish are best adapted for the transition to seawater. In the aquaculture setting fish are unable to self-select and may be transferred to the marine environment outwith their optimal smolt window, it is thus important that the mechanisms involved in seawater adaptation are well understood. The accumulation of organic osmolytes forms an important part of the adaptation to seawater, allowing fish to maintain osmotic and ionic balance within their tissues. A novel osmolyte identified in a pilot study was characterised and the metabolism of this compound investigated. The novel compound was identified as hypoxanthine, a purine involved in the nucleotide salvage pathway. This osmolyte and taurine were found be accumulated in the skin of Atlantic salmon in the days and weeks following seawater transfer. A number of potential biomarkers of smoltification were also investigated with an aim to develop a more robust set of markers of the hypo-osmoregulatory ability of fish. Genes involved in the transport of ions were found to be the most reliable indicators of smoltification.
2020-12-01T00:00:00ZDagen, Claire AlexandraAtlantic salmon are an economically important species, particularly in Scotland. The aquaculture of this species is complicated by its anadromous life cycle, requiring transfer to seawater. Smoltification is a complex process whereby fish prepare for entry to seawater, the “smolt window” is the time at which fish are best adapted for the transition to seawater. In the aquaculture setting fish are unable to self-select and may be transferred to the marine environment outwith their optimal smolt window, it is thus important that the mechanisms involved in seawater adaptation are well understood. The accumulation of organic osmolytes forms an important part of the adaptation to seawater, allowing fish to maintain osmotic and ionic balance within their tissues. A novel osmolyte identified in a pilot study was characterised and the metabolism of this compound investigated. The novel compound was identified as hypoxanthine, a purine involved in the nucleotide salvage pathway. This osmolyte and taurine were found be accumulated in the skin of Atlantic salmon in the days and weeks following seawater transfer. A number of potential biomarkers of smoltification were also investigated with an aim to develop a more robust set of markers of the hypo-osmoregulatory ability of fish. Genes involved in the transport of ions were found to be the most reliable indicators of smoltification.Informing the conservation and restoration of a keystone species : the larval behaviour of the European oyster Ostrea edulisRodriguez Perez, Anahttps://hdl.handle.net/10023/210212021-08-14T11:01:19Z2020-06-23T00:00:00ZThe European oyster Ostrea edulis is a keystone species that is internationally recognised as ‘threatened and declining’ in the North-East Atlantic and several nations have adopted strategies for its conservation and restoration. The overall goal of the present work was to inform conservation and restoration efforts. The purpose of this thesis, therefore, was to study the larval behaviour and ecology of O. edulis in as much as is relevant to the dispersal of this species. Specifically, the larvae’s vertical distribution, swimming speeds, settlement preferences and pelagic duration were studied in laboratory experiments. Most larvae concentrated at the bottom of the aquarium, independently of the developmental stage, light, food or temperature. In addition, larvae behaved actively in ~50% of all bottom observations, indicating a behavioural function other than resting. Advection close to the seabed is known to be slower than in any other part of the water column. The observed demersal behaviour would therefore most likely reduce dispersal from natal populations and enhance self-recruitment. At the surface, larvae frequently formed aggregations. In the water column, larvae swam with high vertical directionality and their distribution was homogenous. Swimming speeds ranged from 0.001 mm/s to 9.07 mm/s. O. edulis larvae settled preferentially among conspecifics (100% in < 24h), and if conspecifics were absent, larvae also settled in response to habitat-associated biofilms (81% of settlement after a 45h delay). Sterile shells and terrestrial stones did not induce more settlement than control treatments (0-14% settlement). Pelagic duration was strongly dependent on temperature, food and a suitable settlement cue. In the absence of an appropriate settlement cue, 80% of larvae delayed metamorphosis for up to 14 days, when the experiment was terminated. In contrast, 95-100% of larvae delaying their metamorphosis settled when presented with a conspecific. Such a delay in metamorphosis enhances the risk of predation and, ultimately, of losing most larvae to mortality if target habitats are absent. The results of this thesis provide strong evidence that O. edulis larvae are targeting their own beds, and that the behaviour of larvae plays a crucial role in their dispersal and successful recruitment. Restoring European oyster beds at a scale that is large and dense enough to promote the retention of larvae may be crucial to the success of restoration efforts.
2020-06-23T00:00:00ZRodriguez Perez, AnaThe European oyster Ostrea edulis is a keystone species that is internationally recognised as ‘threatened and declining’ in the North-East Atlantic and several nations have adopted strategies for its conservation and restoration. The overall goal of the present work was to inform conservation and restoration efforts. The purpose of this thesis, therefore, was to study the larval behaviour and ecology of O. edulis in as much as is relevant to the dispersal of this species. Specifically, the larvae’s vertical distribution, swimming speeds, settlement preferences and pelagic duration were studied in laboratory experiments. Most larvae concentrated at the bottom of the aquarium, independently of the developmental stage, light, food or temperature. In addition, larvae behaved actively in ~50% of all bottom observations, indicating a behavioural function other than resting. Advection close to the seabed is known to be slower than in any other part of the water column. The observed demersal behaviour would therefore most likely reduce dispersal from natal populations and enhance self-recruitment. At the surface, larvae frequently formed aggregations. In the water column, larvae swam with high vertical directionality and their distribution was homogenous. Swimming speeds ranged from 0.001 mm/s to 9.07 mm/s. O. edulis larvae settled preferentially among conspecifics (100% in < 24h), and if conspecifics were absent, larvae also settled in response to habitat-associated biofilms (81% of settlement after a 45h delay). Sterile shells and terrestrial stones did not induce more settlement than control treatments (0-14% settlement). Pelagic duration was strongly dependent on temperature, food and a suitable settlement cue. In the absence of an appropriate settlement cue, 80% of larvae delayed metamorphosis for up to 14 days, when the experiment was terminated. In contrast, 95-100% of larvae delaying their metamorphosis settled when presented with a conspecific. Such a delay in metamorphosis enhances the risk of predation and, ultimately, of losing most larvae to mortality if target habitats are absent. The results of this thesis provide strong evidence that O. edulis larvae are targeting their own beds, and that the behaviour of larvae plays a crucial role in their dispersal and successful recruitment. Restoring European oyster beds at a scale that is large and dense enough to promote the retention of larvae may be crucial to the success of restoration efforts.Saltmarsh restoration and blue carbon dynamics in a Scottish estuaryTaylor, Benjaminhttps://hdl.handle.net/10023/208912023-11-24T03:07:07Z2019-12-03T00:00:00ZSaltmarshes are biogeomorphic intertidal systems of halophytic plant communities,
typically found on low-energy temperate coasts. These provide valuable ecosystem
services, such as biodiversity provision, coastal protection and climate change mitigation.
They are sites of extensive carbon sequestration and storage, termed Blue Carbon, largely
attributed to their deep organic rich sediments which continue to build with marsh
development. Saltmarshes are amongst the most threatened ecosystems globally, estimated
to have lost over 25 % since 1800s. Their past and future losses require action to be taken to
conserve and restore this valuable ecosystem.
Restoration can be achieved through direct-transplantation of existing vegetation onto
potential saltmarsh habitat within an estuary. This approach has been carried out on the
Eden Estuary, Scotland since the start of the millennium. Restoration aimed to enhance the
degraded saltmarsh of the estuary. These areas are likely to increase carbon sequestration
and storage capacity of the ecosystem; this capacity was investigated during this study.
The Blue carbon benefit afforded by restored saltmarsh areas was compared to the ‘business
as usual’ mudflat and the possible end point state of a ‘natural’ saltmarsh extent. The study
assessed the influence of vegetation structure, sediment dynamics and buried sediments on
the area’s carbon sink.
Restoration activities have increased the current total amount of carbon stored in sediment
and vegetation by over 0.5 t, and furthermore, contain the largest sedimentary carbon store
per unit area, of 23.48 kgC m². Areas of restoration exhibited, on average, higher rates of
carbon burial than found on mudflats, being 14 gC m² yr⁻¹. At present their relatively small
extent limits their added value to both store significant quantities of carbon and provide a
monetary self-subsidisation. In the future it is likely their value will increase as a function
of their increased spatial extent and temporal development.
2019-12-03T00:00:00ZTaylor, BenjaminSaltmarshes are biogeomorphic intertidal systems of halophytic plant communities,
typically found on low-energy temperate coasts. These provide valuable ecosystem
services, such as biodiversity provision, coastal protection and climate change mitigation.
They are sites of extensive carbon sequestration and storage, termed Blue Carbon, largely
attributed to their deep organic rich sediments which continue to build with marsh
development. Saltmarshes are amongst the most threatened ecosystems globally, estimated
to have lost over 25 % since 1800s. Their past and future losses require action to be taken to
conserve and restore this valuable ecosystem.
Restoration can be achieved through direct-transplantation of existing vegetation onto
potential saltmarsh habitat within an estuary. This approach has been carried out on the
Eden Estuary, Scotland since the start of the millennium. Restoration aimed to enhance the
degraded saltmarsh of the estuary. These areas are likely to increase carbon sequestration
and storage capacity of the ecosystem; this capacity was investigated during this study.
The Blue carbon benefit afforded by restored saltmarsh areas was compared to the ‘business
as usual’ mudflat and the possible end point state of a ‘natural’ saltmarsh extent. The study
assessed the influence of vegetation structure, sediment dynamics and buried sediments on
the area’s carbon sink.
Restoration activities have increased the current total amount of carbon stored in sediment
and vegetation by over 0.5 t, and furthermore, contain the largest sedimentary carbon store
per unit area, of 23.48 kgC m². Areas of restoration exhibited, on average, higher rates of
carbon burial than found on mudflats, being 14 gC m² yr⁻¹. At present their relatively small
extent limits their added value to both store significant quantities of carbon and provide a
monetary self-subsidisation. In the future it is likely their value will increase as a function
of their increased spatial extent and temporal development.Evolutionary dynamics promoting and accompanying rapid adaptive trait lossRayner, Jack Gregoryhttps://hdl.handle.net/10023/207772021-07-26T17:38:43Z2020-07-29T00:00:00ZUnderstanding the conditions which promote adaptation is a key goal of evolutionary biology, and a pressing issue across fields of biology. Addressing this involves investigating not just the genetic and developmental mechanisms through which adaptive phenotypes arise, but also the environmental and ecological conditions which promote their spread. A major challenge in addressing these aims is that contemporary examples of rapid adaptive evolution are difficult to study, owing to the difficulty of identifying traits under selection during the early stages of adaptation. In this thesis, I use a Hawaiian field cricket system which provides a useful exception; males of the species Teleogryllus oceanicus ordinarily sing to attract females, however adaptive male-silencing (‘flatwing’) phenotypes have recently emerged and spread on at least three islands, under selection against male song exerted by a parasitoid fly, Ormia ochracea, which is attracted to singing males. Prior work indicates at least two of these flatwing phenotypes, from islands of Kauai and Oahu, have evolved independently under this shared selection pressure. This example of rapid, convergent evolution provides an opportunity to identify conditions which have promoted and resulted from rapid adaptation in wild populations evolving under extreme selection pressure. I investigate features which have contributed to the ability of these populations to rapidly, and repeatedly, adapt under strong selection against male song. The results indicate convergent sexual trait loss has been promoted by sex-biased development pathways maintained by sexually antagonistic selection; that pleiotropic, or associated, effects of adaptive mutation(s) in both sexes have played an important role in their spread; that adaptive male song-loss phenotypes have evolved repeatedly, above and beyond flatwing morphology; and that silent males nevertheless invest as much energy in practicing wing movement patterns associated with song and, despite reduced sexual dimorphism, are just as likely to be involved in aggressive intrasexual contests.
2020-07-29T00:00:00ZRayner, Jack GregoryUnderstanding the conditions which promote adaptation is a key goal of evolutionary biology, and a pressing issue across fields of biology. Addressing this involves investigating not just the genetic and developmental mechanisms through which adaptive phenotypes arise, but also the environmental and ecological conditions which promote their spread. A major challenge in addressing these aims is that contemporary examples of rapid adaptive evolution are difficult to study, owing to the difficulty of identifying traits under selection during the early stages of adaptation. In this thesis, I use a Hawaiian field cricket system which provides a useful exception; males of the species Teleogryllus oceanicus ordinarily sing to attract females, however adaptive male-silencing (‘flatwing’) phenotypes have recently emerged and spread on at least three islands, under selection against male song exerted by a parasitoid fly, Ormia ochracea, which is attracted to singing males. Prior work indicates at least two of these flatwing phenotypes, from islands of Kauai and Oahu, have evolved independently under this shared selection pressure. This example of rapid, convergent evolution provides an opportunity to identify conditions which have promoted and resulted from rapid adaptation in wild populations evolving under extreme selection pressure. I investigate features which have contributed to the ability of these populations to rapidly, and repeatedly, adapt under strong selection against male song. The results indicate convergent sexual trait loss has been promoted by sex-biased development pathways maintained by sexually antagonistic selection; that pleiotropic, or associated, effects of adaptive mutation(s) in both sexes have played an important role in their spread; that adaptive male song-loss phenotypes have evolved repeatedly, above and beyond flatwing morphology; and that silent males nevertheless invest as much energy in practicing wing movement patterns associated with song and, despite reduced sexual dimorphism, are just as likely to be involved in aggressive intrasexual contests.Title redactedAllen, Zoe Eleanorhttps://hdl.handle.net/10023/205432021-06-10T14:29:10Z2017-06-21T00:00:00Z2017-06-21T00:00:00ZAllen, Zoe EleanorInvestigating the role of XNP-1/ATRX in telomere maintenance in the model nematode Caenorhabditis elegansHussain, Karimhttps://hdl.handle.net/10023/202572021-02-04T09:58:07Z2020-07-29T00:00:00Z2020-07-29T00:00:00ZHussain, KarimEstablishing Galleria mellonella, the larvae of the greater wax moth, as a model for mycobacterial infections to assess existing and novel treatmentder Weduwen, Franceshttps://hdl.handle.net/10023/198142023-04-04T02:05:13Z2020-12-01T00:00:00ZGalleria mellonella, the larvae of the greater wax moth, are cheap, practical and readily-available organisms which can be utilised for a comprehensive range of experimental protocols. They are valuable in vivo intermediaries between in vitro studies and models which require greater investments of time, equipment, and ethical approval. Larvae exhibit cellular and humoral immune responses with structural and functional similarities to mammals. They are ideal for high-throughput screens of pathogens, antimicrobials, toxicity tests, and novel treatments.
In this thesis, G. mellonella was used with a range of Mycobacterium species and strains. Mycobacteria represent a unique challenge as they are intrinsically resistant to antibiotics, “hide” from immune responses, and interact directly with immune cells. Mycobacterium tuberculosis, the causative agent in tuberculosis, has infected billions of humans and is notoriously difficult to study due to its slow generation time and ability to infect immunocompetent humans. Hence, using related Mycobacterial species allows assessment of this genus with minimal risk and inconvenience. Using these bacteria in tandem with a simple, easily used in vivo model allows for a greater range of experiments in a standard laboratory.
When this thesis commenced, Mycobacteria had not been used with a Galleria model in the modern era, Therefore, M. fortuitum, M. marinum and M. aurum were assessed with G. mellonella and confirmed to cause larval death. Various anti-Mycobacterials were assessed, alongside uncommon treatment combinations such as β lactams and efflux pump inhibitors. The immune response to infection and treatment was evaluated – the number of immune cells, their ability to phagocytose Mycobacteria, and the formation of melanised nodules were all affected by infection and the antibiotics used to treat them.
This work demonstrates the suitability of G. mellonella as a model for Mycobacterial infections and indicates how they may be used in further research efforts.
2020-12-01T00:00:00Zder Weduwen, FrancesGalleria mellonella, the larvae of the greater wax moth, are cheap, practical and readily-available organisms which can be utilised for a comprehensive range of experimental protocols. They are valuable in vivo intermediaries between in vitro studies and models which require greater investments of time, equipment, and ethical approval. Larvae exhibit cellular and humoral immune responses with structural and functional similarities to mammals. They are ideal for high-throughput screens of pathogens, antimicrobials, toxicity tests, and novel treatments.
In this thesis, G. mellonella was used with a range of Mycobacterium species and strains. Mycobacteria represent a unique challenge as they are intrinsically resistant to antibiotics, “hide” from immune responses, and interact directly with immune cells. Mycobacterium tuberculosis, the causative agent in tuberculosis, has infected billions of humans and is notoriously difficult to study due to its slow generation time and ability to infect immunocompetent humans. Hence, using related Mycobacterial species allows assessment of this genus with minimal risk and inconvenience. Using these bacteria in tandem with a simple, easily used in vivo model allows for a greater range of experiments in a standard laboratory.
When this thesis commenced, Mycobacteria had not been used with a Galleria model in the modern era, Therefore, M. fortuitum, M. marinum and M. aurum were assessed with G. mellonella and confirmed to cause larval death. Various anti-Mycobacterials were assessed, alongside uncommon treatment combinations such as β lactams and efflux pump inhibitors. The immune response to infection and treatment was evaluated – the number of immune cells, their ability to phagocytose Mycobacteria, and the formation of melanised nodules were all affected by infection and the antibiotics used to treat them.
This work demonstrates the suitability of G. mellonella as a model for Mycobacterial infections and indicates how they may be used in further research efforts.Allostery and inhibition of Psychrobacter arcticus adenosine 5'-triphosphate phosphoribosyltransferaseThomson, Catherine M.https://hdl.handle.net/10023/194302021-02-16T12:09:48Z2020-06-24T00:00:00ZAllostery is the regulation of a protein by binding in an area distinct from the enzyme
active site, but despite having clear applications in biotechnology and in drug discovery, elucidation of its complexities is still ongoing. Allostery can be either activating or inhibiting and the allosteric site is often distant to the one affected. The enzyme Psychrobacter arcticus ATP phosphoribosyl transferase (ATPPRT) is both allosterically activated and inhibited and is therefore useful as a model organism for understanding allostery. P. arcticus, ATPPRT is a Type IV ATPPRT, catalyzes the first step in histidine biosynthesis, and is comprised of two subunits: a short form HisG[sub]S and HisZ. HisG[sub]S is the catalytic domain and is allosterically activated by HisZ. HisZ also contains an allosteric binding site for inhibition by histidine. Short form HisG[sub]S alone is catalytically active but insensitive to histidine. This work establishes the kinetic mechanism of histidine inhibition in PaATPPRT, with histidine binding non-competitively with respect to both substrates (ATP and PRPP). AMP was confirmed as a competitive inhibitor with respect to both substrates for both PaATPPRT and PaHisGS and ADP was determined to be an alternative substrate. This work demonstrates the first example of histidine binding in a site analogous to that of HisRS in a short-form ATPPRT. It also highlights an interaction between two loops in PaHisZ, mediated by a hydrogen bond between Tyr263 and His104, that is likely to greatly reduce the probability of the complex sampling the activated conformation necessary for successful reaction. Additionally, a clear distinction between the activated form of PaATPPRT with ATP bound compared to all other structures is observed. Overall, this work demonstrates a clear reliance on key structural changes for the allosteric regulation of PaATPPRT.
Attempts to purify Staphylococcus aureus ATPPRT were unsuccessful.
2020-06-24T00:00:00ZThomson, Catherine M.Allostery is the regulation of a protein by binding in an area distinct from the enzyme
active site, but despite having clear applications in biotechnology and in drug discovery, elucidation of its complexities is still ongoing. Allostery can be either activating or inhibiting and the allosteric site is often distant to the one affected. The enzyme Psychrobacter arcticus ATP phosphoribosyl transferase (ATPPRT) is both allosterically activated and inhibited and is therefore useful as a model organism for understanding allostery. P. arcticus, ATPPRT is a Type IV ATPPRT, catalyzes the first step in histidine biosynthesis, and is comprised of two subunits: a short form HisG[sub]S and HisZ. HisG[sub]S is the catalytic domain and is allosterically activated by HisZ. HisZ also contains an allosteric binding site for inhibition by histidine. Short form HisG[sub]S alone is catalytically active but insensitive to histidine. This work establishes the kinetic mechanism of histidine inhibition in PaATPPRT, with histidine binding non-competitively with respect to both substrates (ATP and PRPP). AMP was confirmed as a competitive inhibitor with respect to both substrates for both PaATPPRT and PaHisGS and ADP was determined to be an alternative substrate. This work demonstrates the first example of histidine binding in a site analogous to that of HisRS in a short-form ATPPRT. It also highlights an interaction between two loops in PaHisZ, mediated by a hydrogen bond between Tyr263 and His104, that is likely to greatly reduce the probability of the complex sampling the activated conformation necessary for successful reaction. Additionally, a clear distinction between the activated form of PaATPPRT with ATP bound compared to all other structures is observed. Overall, this work demonstrates a clear reliance on key structural changes for the allosteric regulation of PaATPPRT.
Attempts to purify Staphylococcus aureus ATPPRT were unsuccessful.Estimating the effect of mid-frequency active sonar on the population health of Blainville's beaked whales (Mesoplodon densirostris) in the Tongue of the OceanMoretti, Davidhttps://hdl.handle.net/10023/192502021-04-16T09:45:42Z2019-12-03T00:00:00ZPassive acoustic methods were used to study the effect of mid-frequency active sonar (MFAS)
on a population of Blainville’s beaked whales (Mesoplodon densirostris, Md) at the U.S. Navy
Atlantic Undersea Test and Evaluation Centre (AUTEC), Bahamas. AUTEC contains an array
of bottom-mounted hydrophones that can detect Md echolocation clicks. Methods to estimate
abundance, the risk of behavioural disruption, and the population level effect of repeated MFAS
exposure are presented. A passive acoustic abundance estimation method, a parametric equation
that predicts the probability of foraging dive disruption as a function of MFAS received level and
an Md bioenergetics model were developed. The effect of changes in energy flow on the
demographic characteristics of an Md population were explored. Passive acoustic data from
AUTEC were used to estimate the behavioural disturbance resulting from sonar operations;
combined with the bioenergetic model, this suggested that the effect of sonar operations could
cause an increase in a female’s age at maturity, a longer inter-calf-interval, calf survival rate and
probability of giving birth that could in turn result in a declining population. Model results were
also compared to those from an expert elicitation study. A power analysis for predicting
abundance via passive acoustic and visual monitoring were used to inform recommendations for
a long-term monitoring plan that includes passive acoustic monitoring of Md abundance
combined with a photo-identification study at both AUTEC and a reference site (Abaco) to
improve demographic rate estimates.
2019-12-03T00:00:00ZMoretti, DavidPassive acoustic methods were used to study the effect of mid-frequency active sonar (MFAS)
on a population of Blainville’s beaked whales (Mesoplodon densirostris, Md) at the U.S. Navy
Atlantic Undersea Test and Evaluation Centre (AUTEC), Bahamas. AUTEC contains an array
of bottom-mounted hydrophones that can detect Md echolocation clicks. Methods to estimate
abundance, the risk of behavioural disruption, and the population level effect of repeated MFAS
exposure are presented. A passive acoustic abundance estimation method, a parametric equation
that predicts the probability of foraging dive disruption as a function of MFAS received level and
an Md bioenergetics model were developed. The effect of changes in energy flow on the
demographic characteristics of an Md population were explored. Passive acoustic data from
AUTEC were used to estimate the behavioural disturbance resulting from sonar operations;
combined with the bioenergetic model, this suggested that the effect of sonar operations could
cause an increase in a female’s age at maturity, a longer inter-calf-interval, calf survival rate and
probability of giving birth that could in turn result in a declining population. Model results were
also compared to those from an expert elicitation study. A power analysis for predicting
abundance via passive acoustic and visual monitoring were used to inform recommendations for
a long-term monitoring plan that includes passive acoustic monitoring of Md abundance
combined with a photo-identification study at both AUTEC and a reference site (Abaco) to
improve demographic rate estimates.Biodiversity in the Anthropocene : quantifying assemblage level changeJones, Faith Annhttps://hdl.handle.net/10023/192412021-04-12T09:38:51Z2019-12-03T00:00:00ZHumans are altering ecosystems at alarming rates, but we do not fully know how
anthropogenic pressures are affecting local biodiversity. This knowledge gap poses problems
for understanding ecological systems and for undertaking effective conservation initiatives.
The aim of this thesis was to increase our understanding of local scale biodiversity change by
focusing on assemblages, which are groups of species from the same taxonomic group that
live in the same place. I focused on assemblage size, structure and species composition, with
the end-goal of making informed suggestions on how to monitor change effectively. First, I
asked whether sampling approach was highly influential when estimating species richness
and composition of Trinidadian freshwater fish assemblages. I compared assemblage
composition of two very different data collections: a systematic survey endeavour and the
historical museum records of The University of West Indies. Both datasets provided
comparable estimates of species richness, and they both contained mostly the same species.
Where they did differ in species lists, they did so among the locally uncommon or specialist
species. Next, I asked how closely changes in assemblage size measured in the currencies of
numerical abundance and biomass relate. My analysis showed that neither assemblage size
quantified in terms of numerical abundance, nor in terms of biomass, is systematically
changing across systems, but that change in one currency usually predicted change in the
other currency. Thirdly, I asked whether there is evidence for other directional changes
across assemblages. There was no evidence of changes in the dominance structure or
dominant species body size. There was, however, evidence from increasing numbers of rare
species entering assemblages and driving up local species richness, as well as a suggestion of
increased turnover among dominant species. Local assemblages therefore are displaying
measurable change, but not all metrics capture these changes.
2019-12-03T00:00:00ZJones, Faith AnnHumans are altering ecosystems at alarming rates, but we do not fully know how
anthropogenic pressures are affecting local biodiversity. This knowledge gap poses problems
for understanding ecological systems and for undertaking effective conservation initiatives.
The aim of this thesis was to increase our understanding of local scale biodiversity change by
focusing on assemblages, which are groups of species from the same taxonomic group that
live in the same place. I focused on assemblage size, structure and species composition, with
the end-goal of making informed suggestions on how to monitor change effectively. First, I
asked whether sampling approach was highly influential when estimating species richness
and composition of Trinidadian freshwater fish assemblages. I compared assemblage
composition of two very different data collections: a systematic survey endeavour and the
historical museum records of The University of West Indies. Both datasets provided
comparable estimates of species richness, and they both contained mostly the same species.
Where they did differ in species lists, they did so among the locally uncommon or specialist
species. Next, I asked how closely changes in assemblage size measured in the currencies of
numerical abundance and biomass relate. My analysis showed that neither assemblage size
quantified in terms of numerical abundance, nor in terms of biomass, is systematically
changing across systems, but that change in one currency usually predicted change in the
other currency. Thirdly, I asked whether there is evidence for other directional changes
across assemblages. There was no evidence of changes in the dominance structure or
dominant species body size. There was, however, evidence from increasing numbers of rare
species entering assemblages and driving up local species richness, as well as a suggestion of
increased turnover among dominant species. Local assemblages therefore are displaying
measurable change, but not all metrics capture these changes.Selection, genetics and evolution of growth and sizeJaneiro Silva, Maria Joãohttps://hdl.handle.net/10023/190562021-03-16T10:44:24Z2019-06-26T00:00:00ZA considerable body of work in recent decades in the field of evolutionary quantitative genetics has
been motivated by the paradox of stasis. Mismatches between observed dynamics of size in wild
populations and evolutionary predictions must arise from deficient understanding of the theoretical
grounds underlying the evolution in a particular system, and/or the adoption of methodological tools making assumptions that are unrealistic. Although different in their nature, these classes of explanation are difficult to tear apart, as very often quantitative genetics (statistical) tools make either implicit
or explicit assumptions about biology and ecology. In this thesis, I investigate inheritance and/or
selection mechanisms when conventional applications of theory are expected to lead to biased or
erroneous predictions of evolutionary change in size. Specifically, I adopt a methodology to handle
genetic constraints in a fairly phenotypic perspective, which facilitates quantification of bias that
would exist if such constraint was not accounted for (Chapter 3). I use this methodology to tear apart
the selection in Soay sheep body mass that occurs directly through its effect on fitness and indirectly
through its effect on pregnancy during the first year of life. Next, I provide analytical proofs of several
issues with applications of integral projection models (IPMs) that incorporate inheritance and development,
concluding that these will predict no evolutionary change regardless of whether it should,
will, or has occurred (Chapter 4). Another main topic of this thesis is the development of a two-sex
individual-based model (IBM) of horn length (Chapter 6), equivalent to an IPM, that uses quantitative
genetics theory to model trait transmission (with development functions estimated in Chapter 5).
This IBM, parameterised using data from the bighorn sheep (Ovis canadensis) of Ram Mountain, is
used to quantify the evolutionary response to trophy hunting, while accounting for a large number of
ecological complexities.
2019-06-26T00:00:00ZJaneiro Silva, Maria JoãoA considerable body of work in recent decades in the field of evolutionary quantitative genetics has
been motivated by the paradox of stasis. Mismatches between observed dynamics of size in wild
populations and evolutionary predictions must arise from deficient understanding of the theoretical
grounds underlying the evolution in a particular system, and/or the adoption of methodological tools making assumptions that are unrealistic. Although different in their nature, these classes of explanation are difficult to tear apart, as very often quantitative genetics (statistical) tools make either implicit
or explicit assumptions about biology and ecology. In this thesis, I investigate inheritance and/or
selection mechanisms when conventional applications of theory are expected to lead to biased or
erroneous predictions of evolutionary change in size. Specifically, I adopt a methodology to handle
genetic constraints in a fairly phenotypic perspective, which facilitates quantification of bias that
would exist if such constraint was not accounted for (Chapter 3). I use this methodology to tear apart
the selection in Soay sheep body mass that occurs directly through its effect on fitness and indirectly
through its effect on pregnancy during the first year of life. Next, I provide analytical proofs of several
issues with applications of integral projection models (IPMs) that incorporate inheritance and development,
concluding that these will predict no evolutionary change regardless of whether it should,
will, or has occurred (Chapter 4). Another main topic of this thesis is the development of a two-sex
individual-based model (IBM) of horn length (Chapter 6), equivalent to an IPM, that uses quantitative
genetics theory to model trait transmission (with development functions estimated in Chapter 5).
This IBM, parameterised using data from the bighorn sheep (Ovis canadensis) of Ram Mountain, is
used to quantify the evolutionary response to trophy hunting, while accounting for a large number of
ecological complexities.Variation in selection and its evolutionary consequencesHunter, Darren Clarkehttps://hdl.handle.net/10023/189702021-03-04T15:08:11Z2019-06-26T00:00:00ZIt is widely appreciated that many aspects of selection change temporally when populations
experience stochastic environments. However, the long term consequences for
adaptive evolution has received less consideration. The availability of long term data,
including phenotypic and life history information, along with high quality pedigrees,
allows old approaches and theoretical ideas to be re-considered, and applied, empirically.
To investigate viability selection in a wild population of Soay sheep (Ovis aries) I
estimated the sensitivity of selection to changes in population size. Using environmentally
structured fitness functions I investigated pathways through which changes in
population size drive changes in selection estimates. Much of the observed variation in
selection was driven by changes in mean fitness. If generally true in other populations
this may have important consequences regarding the occurrence of fluctuating selection.
I then developed a method to estimate both individual, and cohort, success using
theory based around Fisher’s reproductive value. This approach overcomes some complications
associated with overlapping generations and age structure common in natural
populations. Using pedigree information I tracked relative contributions to the future
population through time and additionally used alternative theory from demographic
literature to calculate stochastic total cohort reproductive values. The different estimates
corresponded closely. Finally, I weighted selection differentials by measures of cohort
reproductive success. When generations overlap, correctly considering the contribution
a cohort makes to the future population can greatly reduce the expected response, as
cohorts that experience stronger selection typically contribute less. This might provide
one explanation for the paradox of stasis.
By linking approaches from multiple different fields with high quality, long term,
data, I demonstrate that ecological pathways that influence selection can be identified,
providing greater understanding of longer term evolutionary dynamics. Further applications
of the methods developed could generate opportunities to investigate generalities
in temporal evolutionary patterns not previously considered.
2019-06-26T00:00:00ZHunter, Darren ClarkeIt is widely appreciated that many aspects of selection change temporally when populations
experience stochastic environments. However, the long term consequences for
adaptive evolution has received less consideration. The availability of long term data,
including phenotypic and life history information, along with high quality pedigrees,
allows old approaches and theoretical ideas to be re-considered, and applied, empirically.
To investigate viability selection in a wild population of Soay sheep (Ovis aries) I
estimated the sensitivity of selection to changes in population size. Using environmentally
structured fitness functions I investigated pathways through which changes in
population size drive changes in selection estimates. Much of the observed variation in
selection was driven by changes in mean fitness. If generally true in other populations
this may have important consequences regarding the occurrence of fluctuating selection.
I then developed a method to estimate both individual, and cohort, success using
theory based around Fisher’s reproductive value. This approach overcomes some complications
associated with overlapping generations and age structure common in natural
populations. Using pedigree information I tracked relative contributions to the future
population through time and additionally used alternative theory from demographic
literature to calculate stochastic total cohort reproductive values. The different estimates
corresponded closely. Finally, I weighted selection differentials by measures of cohort
reproductive success. When generations overlap, correctly considering the contribution
a cohort makes to the future population can greatly reduce the expected response, as
cohorts that experience stronger selection typically contribute less. This might provide
one explanation for the paradox of stasis.
By linking approaches from multiple different fields with high quality, long term,
data, I demonstrate that ecological pathways that influence selection can be identified,
providing greater understanding of longer term evolutionary dynamics. Further applications
of the methods developed could generate opportunities to investigate generalities
in temporal evolutionary patterns not previously considered.The ontogeny and function of duet codes in territory dynamics of the riverside wrenQuiros Guerrero, Esmeraldahttps://hdl.handle.net/10023/189672021-03-15T14:26:47Z2019-06-26T00:00:00ZIn some species of songbirds, both females and males sing and coordinate their
vocalizations to create highly complex joint performances known as duets. Additionally, in
some of these species, pair mates combine their individual vocalizations following consistent
pair-specific associations, known as duet codes. Investigating how birds create their
individual and pair repertoires and how duet codes are used in within- and between-pair
interactions is essential for understanding how each sex benefits from learning this complex
behaviour and to characterize the nature of the selective mechanisms that promoted the
evolution of this joint signaling system. This thesis focuses on a population of riverside
wrens, Cantorchilus semibadius, as a means to investigate the song learning strategies of
each sex, to elucidate the functions of duet codes in intra- and inter-sexual interactions, and
to measure the cooperative nature of the defence strategy of both sexes. To achieve these
goals I conducted a long-term study and a series of playback experiments. I found an
unusually high turnover rate compared to other duetting species. I also found that individual
and pair repertoires are considerably stable over time and are highly shared across the
population, which suggests that individuals create their repertoires as juveniles and settle
nearby their tutors, as vacancies arise frequently. During territory defence, partners
maintained a close distance with each other, both sexes approached closely to both
simulated intruders, and both sexes matched the songs of same-sex rivals at similar rates
but mostly sung in coordination with their partner. This indicates females and males benefit
from displaying a strong partnership and perform a joint defence against rivals. My thesis
suggests duetting is a cooperative behaviour and the function of duet codes might be mostly
related to within-pair interactions in the riverside wrens.
2019-06-26T00:00:00ZQuiros Guerrero, EsmeraldaIn some species of songbirds, both females and males sing and coordinate their
vocalizations to create highly complex joint performances known as duets. Additionally, in
some of these species, pair mates combine their individual vocalizations following consistent
pair-specific associations, known as duet codes. Investigating how birds create their
individual and pair repertoires and how duet codes are used in within- and between-pair
interactions is essential for understanding how each sex benefits from learning this complex
behaviour and to characterize the nature of the selective mechanisms that promoted the
evolution of this joint signaling system. This thesis focuses on a population of riverside
wrens, Cantorchilus semibadius, as a means to investigate the song learning strategies of
each sex, to elucidate the functions of duet codes in intra- and inter-sexual interactions, and
to measure the cooperative nature of the defence strategy of both sexes. To achieve these
goals I conducted a long-term study and a series of playback experiments. I found an
unusually high turnover rate compared to other duetting species. I also found that individual
and pair repertoires are considerably stable over time and are highly shared across the
population, which suggests that individuals create their repertoires as juveniles and settle
nearby their tutors, as vacancies arise frequently. During territory defence, partners
maintained a close distance with each other, both sexes approached closely to both
simulated intruders, and both sexes matched the songs of same-sex rivals at similar rates
but mostly sung in coordination with their partner. This indicates females and males benefit
from displaying a strong partnership and perform a joint defence against rivals. My thesis
suggests duetting is a cooperative behaviour and the function of duet codes might be mostly
related to within-pair interactions in the riverside wrens.Investigating mitochondrial dysfunction and lipid abnormalities in Alzheimer's diseaseDey, Madhurimahttps://hdl.handle.net/10023/189342021-04-13T15:45:00Z2019-12-03T00:00:00ZAlzheimer’s disease (AD) is the most prevalent form of neurodegenerative dementia, estimated to affect 50 million people worldwide. Despite extensive research into AD, current therapeutic options provide only symptomatic relief, with no disease-modifying treatments presently available, which highlights the need to understand the aetiology of AD. Increasing evidence implicates mitochondrial dysfunction and metabolic deficits in the early stages of AD pathogenesis. In AD, the accumulation of oligomeric amyloid-β (Aβ) within the mitochondria allows it to interact with key mitochondrial proteins, such as 17β-hydroxysteroid dehydrogenase type 10 (17β-HSD10) – a multifunctional protein which can modulate the cellular response to metabolic stress. Levels of 17β-HSD10 are upregulated within several disease-relevant regions of the human brain in AD, and the high affinity interaction between 17β-HSD10 and Aβ has been linked to cellular toxicity. Previous research shows that the catalytic function of 17β-HSD10 is essential to propagate the Aβ-induced toxicity, hence indicating that either inhibiting the enzyme or preventing the interaction between 17β-HSD10 and Aβ may hold potential as a point of therapeutic intervention. Therefore, the primary aim of the research presented within this project was to develop cellular models to advance screening of small molecule inhibitors of 17β-HSD10 developed by the group. HEK293 and differentiated SH-SY5Y cellular models overexpressing 17β-HSD10 showed that the toxicity arising from the protein’s interaction with Aβ may selectively impact vulnerable cells with a high metabolic demand. To explore the disease-relevant implications of metabolic deficits within the brain, lipidomics analysis was performed using a murine model of AD and human post mortem AD brain tissue, which revealed an increased susceptibility of the hippocampus to lipid dysregulation, and a potential role for lipid abnormalities in the white matter degeneration observed within the human brain in AD.
2019-12-03T00:00:00ZDey, MadhurimaAlzheimer’s disease (AD) is the most prevalent form of neurodegenerative dementia, estimated to affect 50 million people worldwide. Despite extensive research into AD, current therapeutic options provide only symptomatic relief, with no disease-modifying treatments presently available, which highlights the need to understand the aetiology of AD. Increasing evidence implicates mitochondrial dysfunction and metabolic deficits in the early stages of AD pathogenesis. In AD, the accumulation of oligomeric amyloid-β (Aβ) within the mitochondria allows it to interact with key mitochondrial proteins, such as 17β-hydroxysteroid dehydrogenase type 10 (17β-HSD10) – a multifunctional protein which can modulate the cellular response to metabolic stress. Levels of 17β-HSD10 are upregulated within several disease-relevant regions of the human brain in AD, and the high affinity interaction between 17β-HSD10 and Aβ has been linked to cellular toxicity. Previous research shows that the catalytic function of 17β-HSD10 is essential to propagate the Aβ-induced toxicity, hence indicating that either inhibiting the enzyme or preventing the interaction between 17β-HSD10 and Aβ may hold potential as a point of therapeutic intervention. Therefore, the primary aim of the research presented within this project was to develop cellular models to advance screening of small molecule inhibitors of 17β-HSD10 developed by the group. HEK293 and differentiated SH-SY5Y cellular models overexpressing 17β-HSD10 showed that the toxicity arising from the protein’s interaction with Aβ may selectively impact vulnerable cells with a high metabolic demand. To explore the disease-relevant implications of metabolic deficits within the brain, lipidomics analysis was performed using a murine model of AD and human post mortem AD brain tissue, which revealed an increased susceptibility of the hippocampus to lipid dysregulation, and a potential role for lipid abnormalities in the white matter degeneration observed within the human brain in AD.Humpback whales in Brazil : distribution, abundance and human impactsBortolotto, Guilherme Augustohttps://hdl.handle.net/10023/189322021-04-12T15:55:01Z2019-12-03T00:00:00ZThe humpback whale population breeding in Brazilian waters has greatly increased, after near extinction due to whaling in the twentieth century. Today, these animals are under pressure from human activities in the area. In this thesis, habitat use, distribution, abundance, population status and potential threat from oil spills were investigated to improve knowledge of the population’s ecology and provide useful information for conservation and management. Distribution and habitat use were investigated through spatial models applied to line transect data and to tracking data. Line transect data were also used to estimate abundance. Distribution maps from both data types were used with a simulation of oil dispersion to evaluate risk of impact from oil spills. The new abundance estimates, together with information on population increase from another study, were used to update a Bayesian population dynamics model to re-assess population status. Modelling of line transect data indicated whale density to be higher in slower currents, at shorter distances to both the coastline and shelf edge, and at sea surface temperatures between 24 and 25°C, and to be related to shelter. A higher concentration of animals was predicted in the southern portion of Abrolhos bank, an enlargement of the continental shelf. Modelling of tracking data agreed with those findings, despite differences in the nature of the data and analytical methods. Risk maps of oil spill impact indicated that areas in the south of the breeding range present highest risks to the animals. Abundance estimates (14,264, CV = 0.084, in 2008; 20,389, CV = 0.071, in 2012) provide further evidence that the population is increasing, and contributed to improved precision in the population status assessment. New information provided here will inform conservation of the humpback whale population breeding in Brazilian waters and the need for, and implementation of, any necessary management action.
2019-12-03T00:00:00ZBortolotto, Guilherme AugustoThe humpback whale population breeding in Brazilian waters has greatly increased, after near extinction due to whaling in the twentieth century. Today, these animals are under pressure from human activities in the area. In this thesis, habitat use, distribution, abundance, population status and potential threat from oil spills were investigated to improve knowledge of the population’s ecology and provide useful information for conservation and management. Distribution and habitat use were investigated through spatial models applied to line transect data and to tracking data. Line transect data were also used to estimate abundance. Distribution maps from both data types were used with a simulation of oil dispersion to evaluate risk of impact from oil spills. The new abundance estimates, together with information on population increase from another study, were used to update a Bayesian population dynamics model to re-assess population status. Modelling of line transect data indicated whale density to be higher in slower currents, at shorter distances to both the coastline and shelf edge, and at sea surface temperatures between 24 and 25°C, and to be related to shelter. A higher concentration of animals was predicted in the southern portion of Abrolhos bank, an enlargement of the continental shelf. Modelling of tracking data agreed with those findings, despite differences in the nature of the data and analytical methods. Risk maps of oil spill impact indicated that areas in the south of the breeding range present highest risks to the animals. Abundance estimates (14,264, CV = 0.084, in 2008; 20,389, CV = 0.071, in 2012) provide further evidence that the population is increasing, and contributed to improved precision in the population status assessment. New information provided here will inform conservation of the humpback whale population breeding in Brazilian waters and the need for, and implementation of, any necessary management action.As the crow, flies : identifying genomic loci contributing to adaptation in Drosophila and the corvid radiationWiberg, R. Axel W.https://hdl.handle.net/10023/188682023-03-31T02:05:30Z2019-06-27T00:00:00ZIdentifying loci that contribute to adaptive traits is an important goal of
evolutionary biology. I take a comparative genomic approach to identify loci that have
responded to divergent selection. First I consider the challenges of identifying consistent
genomic responses to selection during experimental evolution. I use population genetic
simulations to show that commonly applied statistical tests perform poorly and identify
superior methods. These will also be useful in comparing allele frequencies in other
contexts. Next I analyse whole genome data from an experimental evolution study of
Drosophila pseudoobscura evolving under altered mating systems. I find that around
300 SNPs show consistent allele frequency differences between experimental
treatments. These are clustered in genomic regions which also show signatures of
selective sweeps or background selection. These regions contain genes with mutant
phenotypes related to changes already documented in this system. In another chapter I
use a novel approach to identify markers potentially influencing female re-mating rate
among lines of D. pseudoobscura. I use simulations to show that there are more fixed
differences between extreme pairs of isofemale lines from different populations than
expected by chance. Many of the genes are implicated in female mating behaviour in
other studies. I then focus on local adaptation in wild Drosophila montana populations.
I use Bayesian methods to relate genetic and environmental differentiation among
populations. Finally, I take a broader comparative approach using multiple genomes
from 14 species of crow to identify potential signatures of selection in the New
Caledonian (NC) (Corvus moneduloides) and Hawai’ian crow (Corvus hawaiiensis)
lineages. The NC and, more recently, Hawai’ian crows are of great interest for their
unusual tool-using foraging behaviour. I find only modest evidence for greater rates of
molecular evolution at coding regions within these lineages. This thesis applies novel
techniques to genomic data to identify candidate loci for evolutionary divergence in
these different systems and highlight analytical methods that will be generally useful in
other systems.
2019-06-27T00:00:00ZWiberg, R. Axel W.Identifying loci that contribute to adaptive traits is an important goal of
evolutionary biology. I take a comparative genomic approach to identify loci that have
responded to divergent selection. First I consider the challenges of identifying consistent
genomic responses to selection during experimental evolution. I use population genetic
simulations to show that commonly applied statistical tests perform poorly and identify
superior methods. These will also be useful in comparing allele frequencies in other
contexts. Next I analyse whole genome data from an experimental evolution study of
Drosophila pseudoobscura evolving under altered mating systems. I find that around
300 SNPs show consistent allele frequency differences between experimental
treatments. These are clustered in genomic regions which also show signatures of
selective sweeps or background selection. These regions contain genes with mutant
phenotypes related to changes already documented in this system. In another chapter I
use a novel approach to identify markers potentially influencing female re-mating rate
among lines of D. pseudoobscura. I use simulations to show that there are more fixed
differences between extreme pairs of isofemale lines from different populations than
expected by chance. Many of the genes are implicated in female mating behaviour in
other studies. I then focus on local adaptation in wild Drosophila montana populations.
I use Bayesian methods to relate genetic and environmental differentiation among
populations. Finally, I take a broader comparative approach using multiple genomes
from 14 species of crow to identify potential signatures of selection in the New
Caledonian (NC) (Corvus moneduloides) and Hawai’ian crow (Corvus hawaiiensis)
lineages. The NC and, more recently, Hawai’ian crows are of great interest for their
unusual tool-using foraging behaviour. I find only modest evidence for greater rates of
molecular evolution at coding regions within these lineages. This thesis applies novel
techniques to genomic data to identify candidate loci for evolutionary divergence in
these different systems and highlight analytical methods that will be generally useful in
other systems.Acoustic signals as indicators of animal behavior, presence and location in delphinidsRoberts, Bethanyhttps://hdl.handle.net/10023/187182021-09-11T09:57:45Z2019-12-03T00:00:00ZAnimal acoustic behavior systems are complex and the lifestyle of marine mammals makes understanding these systems difficult as they spend much time submerged underwater and are often difficult to observe visually. Using passive acoustic monitoring to record and interpret cetacean vocalizations provides insights into how these animals use different vocalizations in various contexts. This thesis investigates the use of acoustic signals in foraging and communication in two wild delphinid species, the short-finned pilot whale and the bottlenose dolphin using animal attached digital recording devices (DTAG). In chapter 2, bottlenose dolphin clicks were recorded in Sarasota Bay, Florida to document click production rates among three behavioral contexts for application in density estimations. In chapter 3, bottlenose dolphin signature whistles were identified using the SIGID method to document temporal variations in signature whistle production. Combined application of passive acoustic monitoring with mark-recapture methods proved feasible with information on temporal variations in signature whistle production. In chapter 4, short-finned pilot whale buzzes were defined based on a maximum inter-click interval. Furthermore, the relationship of pilot whale buzzes and whistles with depth was investigated. A buzz duration, number of buzz clicks, whistle output, duration and energy flux density significantly decreased with increasing dive depths. In chapter 5, three buzz types produced by pilot whales were categorized. Analysis of the acoustic events occurring after each buzz showed that different buzz types are used for different biosonar tactics in foraging or communication. Gulps were investigated to identify potential cues for foraging success. The acoustic repertoire of delphinids is highly complex and the research in this thesis documents the variability in whistle and click production in bottlenose dolphins and pilot whales, which is fundamental to understand how passive acoustic monitoring can be used for interpreting delphinid behavior and documenting presence and location of animals.
2019-12-03T00:00:00ZRoberts, BethanyAnimal acoustic behavior systems are complex and the lifestyle of marine mammals makes understanding these systems difficult as they spend much time submerged underwater and are often difficult to observe visually. Using passive acoustic monitoring to record and interpret cetacean vocalizations provides insights into how these animals use different vocalizations in various contexts. This thesis investigates the use of acoustic signals in foraging and communication in two wild delphinid species, the short-finned pilot whale and the bottlenose dolphin using animal attached digital recording devices (DTAG). In chapter 2, bottlenose dolphin clicks were recorded in Sarasota Bay, Florida to document click production rates among three behavioral contexts for application in density estimations. In chapter 3, bottlenose dolphin signature whistles were identified using the SIGID method to document temporal variations in signature whistle production. Combined application of passive acoustic monitoring with mark-recapture methods proved feasible with information on temporal variations in signature whistle production. In chapter 4, short-finned pilot whale buzzes were defined based on a maximum inter-click interval. Furthermore, the relationship of pilot whale buzzes and whistles with depth was investigated. A buzz duration, number of buzz clicks, whistle output, duration and energy flux density significantly decreased with increasing dive depths. In chapter 5, three buzz types produced by pilot whales were categorized. Analysis of the acoustic events occurring after each buzz showed that different buzz types are used for different biosonar tactics in foraging or communication. Gulps were investigated to identify potential cues for foraging success. The acoustic repertoire of delphinids is highly complex and the research in this thesis documents the variability in whistle and click production in bottlenose dolphins and pilot whales, which is fundamental to understand how passive acoustic monitoring can be used for interpreting delphinid behavior and documenting presence and location of animals.Integrating the theories of kin selection and sexual selectionFaria, G. S.https://hdl.handle.net/10023/186742021-04-09T15:26:46Z2019-12-03T00:00:00Z2019-12-03T00:00:00ZFaria, G. S.The role of individual behaviour in the collective cultural evolution of humpback whale songsLamoni, Luca Ubaldohttps://hdl.handle.net/10023/186212019-10-08T02:06:03Z2018-12-06T00:00:00ZFor more than forty years, the complex songs emitted by humpback whales have
fascinated the scientific community as well as the general public. These songs are
produced by males during the breeding season, and are hierarchically structured and
population specific. Within a population, males tend to conform to the same song type,
but songs undergo gradual unidirectional change. Instances of more rapid song changes
have also been recorded, where the song sung by a population has been replaced by the
song of an adjacent population. The learning mechanisms that concurrently drive song
conformity, and simultaneously allow gradual (evolution) and rapid (revolution) song
change are not currently understood. This thesis aims to address this gap by using
innovative theoretical models as well as more established empirical methods.
Chapter 1 provides a general introduction to the thesis topics. In chapter 2 I
introduce a spatially explicit agent-based modelling approach to investigate humpback
whale song evolution and transmission. I found that shared feeding grounds promote
inter-population song transmission, song conformity emerges as a function of breeding
ground geographical segregation, and production errors facilitate gradual evolution of
songs. In chapter 3, the same modelling approach is extended to simulate song
revolutions using a new learning bias in combination with different movement
scenarios. I found that the consistent emergence of song revolutions is dependent on
cognitive (song memory), behavioural (singing probability) and spatial (agent density)
factors. Finally, in chapter 4, I analyse intra- and inter- individual song variability at
different hierarchical levels of organisation in songs recorded off eastern Australia. I
found that variability is not homogeneously distributed across the different song levels.
Furthermore, I identified consistent and distinctive individual patterns of song
production consistent with the theory that songs could represent mate quality
advertisements for females.
2018-12-06T00:00:00ZLamoni, Luca UbaldoFor more than forty years, the complex songs emitted by humpback whales have
fascinated the scientific community as well as the general public. These songs are
produced by males during the breeding season, and are hierarchically structured and
population specific. Within a population, males tend to conform to the same song type,
but songs undergo gradual unidirectional change. Instances of more rapid song changes
have also been recorded, where the song sung by a population has been replaced by the
song of an adjacent population. The learning mechanisms that concurrently drive song
conformity, and simultaneously allow gradual (evolution) and rapid (revolution) song
change are not currently understood. This thesis aims to address this gap by using
innovative theoretical models as well as more established empirical methods.
Chapter 1 provides a general introduction to the thesis topics. In chapter 2 I
introduce a spatially explicit agent-based modelling approach to investigate humpback
whale song evolution and transmission. I found that shared feeding grounds promote
inter-population song transmission, song conformity emerges as a function of breeding
ground geographical segregation, and production errors facilitate gradual evolution of
songs. In chapter 3, the same modelling approach is extended to simulate song
revolutions using a new learning bias in combination with different movement
scenarios. I found that the consistent emergence of song revolutions is dependent on
cognitive (song memory), behavioural (singing probability) and spatial (agent density)
factors. Finally, in chapter 4, I analyse intra- and inter- individual song variability at
different hierarchical levels of organisation in songs recorded off eastern Australia. I
found that variability is not homogeneously distributed across the different song levels.
Furthermore, I identified consistent and distinctive individual patterns of song
production consistent with the theory that songs could represent mate quality
advertisements for females.Avian life in a seasonally arid tropical environment : adaptations and mechanisms in breeding, molt and immune functionNwaogu, Chima Josiahhttps://hdl.handle.net/10023/185982021-03-23T15:37:04Z2019-06-14T00:00:00ZThere is a growing appreciation of the diversity and uniqueness of tropical organisms, but evidence about the selection pressures that shape this diversity remains sketchy. In this thesis, I investigated how variation in life history traits arises from tropical environmental seasonality, starting with the exploration of the annual cycle of the Common Bulbul Pycnonotus barbatus in Nigeria. This revealed that breeding was not seasonal, but moult was timed almost entirely to the wet season with only few individuals extending moult into the dry season This confirmed that breeding and to a lesser extent moult, are decoupled from season, thus, allowing me to test how breeding and moult affect immune function independent of seasonal environmental conditions. On testing this, I found that season explained variation in immune function better than breeding or moult, but unexpectedly, immune indices were higher in the dry season and during breeding, contrary to what I would expect if infection risk is higher in the wet season, and if breeding constrains resources for immune function. Furthermore, I compared immune indices along the cool-wet to hot-dry environmental gradient in Nigeria and found that immune indices were rather similar. I then tested the effect of diet alteration on immune function, body mass and moult of Common Bulbuls in captivity and found that bulbuls fed on fruits had a more immune function, body mass and onset of moult than those fed on invertebrates. These findings together suggest that environmental conditions affect immune function more directly than via resource allocation trade-offs, but that variation in immune function does not follow simple environmental productivity pattern as previously expected. **********
Samenvatting:
Het doorgronden van de evolutie van de levensloop d.w.z. hoe organismen hun beschikbare
energie en nutriënten verdelen tussen overleven en reproduceren, is een fundamenteel
probleem. Het merendeel van onze kennis hierover komt voort uit onderzoek in gematigde
klimaten, terwijl het leven echter in de tropen is geëvolueerd. Hoewel er groeiende aandacht is
voor de biologische diversiteit en het unieke karakter van levensvormen in tropische systemen,
is er nog weinig bekend over de verschillende selectiedrukken en evolutionaire aanpassingen
waardoor diverse levensloopstrategieën zich hebben ontwikkeld. Dit proefschrift is bedoelt om
bij te dragen aan het herstellen van deze scheve balans en is daarom gericht op het beter
begrijpen van hoe seizoensgebonden omgevingsfactoren en dieetvariatie in de tropen leidt tot
variatie in kenmerken van de levensloop.
Voor sommige tropische vogels is het broeden, op populatieniveau, niet sterk
seizoensgebonden, ondanks dat er voorspelbare seizoensoptima voor omgevingsomstandigheden bestaan. Het blijft daarom onduidelijk of individuen zijn aangepast om te
broeden op specifieke tijden durende een jaar, of juist flexibel zijn als gevolg van variabele
omgevingsomstandigheden. In het tweede hoofdstuk (eerste data-hoofdstuk) van dit
proefschrift testte ik of de broedactiviteit van de door het hele jaar broedende grauwe buulbuul
Pycnonotus barbatus, is ontstaan als gevolg van individuele variabiliteit in broedperiode. Ik
analyseerde de broedactiviteit en ruikenmerken van vogels gevangen gedurende een periode
van twee jaar, en vond dat de broedgegevens van individuen net zo variabel kunnen zijn als in
de populatie. Het voorkomen van broeden kon niet worden verklaard aan de hand van de
hoeveelheid neerslag of temperatuur, hoewel vogels tijdens de rui zelden broedden. In
tegenstelling tot broeden was de rui wel sterk seizoensgebonden maar was niet gecorreleerd
aan neerslag of temperatuur. Ik stel daarom voor dat, gezien omgevingsomstandigheden het
hele jaar door broeden in deze soort mogelijk maken en omdat voortplantingssucces
onderhevig is aan een hoog predatierisico, er waarschijnlijk een zwakke selectie is voor
individuen om het broeden samen te laten vallen met pieken in variabele omgevingsomstandigheden.
In tegenstelling daarvan is het waarschijnlijk dat rui, een jaarlijks
voorkomend fenomeen, onder sterke selectie staat om gelijktijdig plaats te vinden met de
pieken in variabele omgevingsomstandigheden, waarbij een verhoogde overlevingskans het
voortplantingssucces bevordert.
Het hele jaar door broeden kan het voortplantingssucces bevorderen, maar het individu
moet in staat zijn zich aan te passen aan een variërende mate van voedselbeschikbaarheid
tussen de seizoenen. Aannemelijk is dat vogels mogelijk lichaamsreserves opslaan als er een
verhonger risico ontstaat vanwege beperkte beschikbare foerageertijd. Als het foerageren
echter onbeperkt is, zou het lichaamsgewicht laag moeten blijven om het predatierisico te
beperken dat het verkrijgen en meedragen van lichaamsreserves met zich meebrengt. In mijn
tweede data-hoofdstuk testte ik aan de hand van 15 jaar aan gegevens over lichaamsmassa's
van grauwe buulbuul vrouwtjes of lichaamsgewichtsvariatie kan worden verklaard door
beperkte foerageertijd tijdens het broeden,. Ik vond dat de broedfase het lichaamsgewicht van
vrouwtjes voorspelde: het lichaamsgewicht piekte abrupt tijdens de incubatietijd en daalde tijdens de broedzorg. Broedende vrouwtjes waren zwaarder in het droge seizoen dan in het
natte seizoen. In het droge seizoen was het waarschijnlijker dat zwaardere vogels aan het
broeden of incuberen waren, wat suggereert dat verhoogde lichaamsreserves nodig kunnen
zijn als buffer voor de beperkte foerageertijd of verarmde foerageeromstandigheden, die het
meest uitgesproken kunnen zijn tijdens respectievelijk de incubatie en in het droge seizoen.
Naast het vinden van voedsel moeten dieren zichzelf beschermen tegen infecties die per
seizoen kunnen verschillen. De hoeveelheid beschikbare middelen voor verdediging kan echter
afhankelijk zijn van hoeveel al is verbruikt in andere processen. Seizoensvariatie in immuniteit
kan dus ofwel worden toegeschreven aan veranderingen in omgevingsomstandigheden als aan
compromissen die optreden wanneer middelen worden toegewezen aan andere processen. Het
loskoppelen van deze factoren is lastig in het wild. In mijn derde data-hoofdstuk heb ik, door
gebruik te maken van niet-seizoensgebonden broeden en ruien in de grauwe buulbuul, het
effect van seizoensgebonden omgevingscondities effectief losgekoppeld van dat van het
jaarlijkse cyclusstadium, en getest hoe beide factoren de immuunfunctie beïnvloeden. Ik
voorspelde dat indien de kans op infecties toeneemt met regenval het immuunsysteem sterker
zou zijn in het natte seizoen, maar indien broeden of rui beperkingen oplegt aan vogels, dat dan
de immuun parameters lager zijn tijdens het broeden of ruien. Door het kwantificeren van vijf
aangeboren immuun parameters gedurende twee jaar vond ik dat seizoen en niet stadia van de
jaarcyclus de variatie in alle immuun parameters verklaarde, behalve één: NOx, waarvan de
concentratie verschilde tussen de jaarlijkse cyclusstadia maar niet tussen seizoenen. Tegen mijn
verwachting in waren de meeste immuun parameters hoger in het droge seizoen en tijdens het
broeden, terwijl ik verwacht dat regen de infectiekans verhoogde en het broeden
immuunfunctie verminderde. Ondanks dat, kon ik concluderen dat omgevingsfactoren de
aangeboren immuniteit rechtstreeks beïnvloeden in plaats van via compromissen in het
toewijzen van middelen tussen verschillende levensloopprocessen.
Zoals voorspeld door de regel van Bergmann kan lichaamsgrootte variëren als reactie
op omgevingsomstandigheden. Deze regel is een biofysische generalisatie dat endotherme
dieren de neiging hebben groter te zijn in koudere klimaten. In mijn vierde data-hoofdstuk
testte ik of de lichaamsgrootte van grauwe buulbuul varieert in overeenstemming met de regel
van Bergmann. Ik mat vogels op 22 locaties tussen 6 en 13°N en schatte vervolgens de
gemiddelde verhouding tussen lichaamsoppervlak en -gewicht per locatie. In
overeenstemming met de regel van Bergmann ontdekte ik dat vogels een grotere verhouding
tussen lichaamsoppervlak en -gewicht hadden in warmere omgevingen, onafhankelijk van de
breedtegraad en hoogte (ten opzichte van zeeniveau).
Neerslag is een belangrijke bepalende factor voor de omgevingstoestand in de tropen,
maar omdat regenval vaak seizoensgebonden is, is het moeilijk om het effect ervan te
onderscheiden van dat van andere seizoensgebonden factoren en co-variërende
levensloopkenmerken. Bijvoorbeeld, grauwe buulbuuls ruien in het natte seizoen in centraal
Nigeria, maar het is niet bekend of de rui op hetzelfde tijdstip op alle locaties plaatsvindt of op
een tijdstip dat samenvalt met de lokale regenval. In het vijfde data-hoofdstuk van dit
proefschrift modelleerde ik de mate van rui als een functie van de timing van neerslag op 15
locaties tussen 6° N en 13° N. Ik vond dat vogels eerder ruiden op plekken waar het natte seizoen eerder begon, wat suggereert dat de rui in grauwe buulbuuls is gekoppeld aan timing
van de regenval.
Variatie in regenval en temperatuur zou ook het infectierisico kunnen bepalen langs een
gradiënt van omgevingscondities. Zo voorspelde ik dat als het infectierisico afneemt met
toenemende droogte, maar gepaard gaat met immuun functie, de aangeboren immuunfunctie
zou moeten afnemen met toenemende droogte van het koud-natte bos tot de hete-droge Sahelzone in Nigeria. Ik testte deze voorspelling in het zesde data-hoofdstuk van dit proefschrift door het meten van aangeboren immuun parameters in grauwe buulbuuls op 15 locaties tussen
6° N en 13° N. Tegen mijn verwachting in daalden de immuun parameters niet met toenemende
droogte, maar in plaats daarvan waren ze op verschillende locaties vergelijkbaar, wat
suggereert dat in dit systeem de aangeboren immuunfunctie niet varieert met verschillende
mate van droogte. Dit resultaat onderstreept de behoefte aan voorzichtigheid bij het voorspellen
van de effecten van klimaatvariabiliteit op ziekterisico.
Dieet is een cruciaal onderdeel van de omgeving en wordt sterk beïnvloed door
omgevingsveranderingen, met soms grote gevolgen. In mijn laatste data-hoofdstuk, testte ik
hoe de samenstelling van het dieet van invloed is op de aangeboren immuunfunctie,
lichaamsgewicht en rui. Gedurende 24 weken voedde ik 40 in het wild gevangen grauwe
buulbuuls ad libitum vruchten of ongewervelde dieren in buitenvolières in Nigeria. Ik
beoordeelde aangeboren immuunindexen, lichaamsgewicht en primaire rui tweewekelijks en
vond dat fruit-gevoede buulbuuls een robuustere aangeboren immuunfunctie, hoger
lichaamsgewicht en eerdere handpenrui hadden in vergelijking met vogels gevoed met
ongewervelde dieren. Deze resultaten zijn uniek omdat ze een effect aantonen van een
dieetaanpassing bij wilde vogels - wat korte termijn gevolgen van omgevingsverandering
aantoont.
Door klassieke natuurstudie en fysiologie te integreren in de context van de directe
omgeving waarin een soort leeft, biedt dit proefschrift nieuw inzicht in hoe variatie in broed-
en ruipatronen en immuunfunctie verschillende aspecten van de levensloop van een tropische
vogel met elkaar verbindt. Mijn bevindingen in dit proefschrift suggereren met name dat het al
lang bestaande paradigma dat de kostbare aard van immuunfunctie benadrukt, het belang van
het overlevingsvoordeel ondermijnt en grotendeels voorbijgaat aan de uiteindelijke rol van het
immuunsysteem, overleving. De voor- en nadelen van de immuunfunctie kunnen alleen worden
bepaald als rekening wordt gehouden met de omgevingsomstandigheden én levensloop
waaronder variaties optreden.
2019-06-14T00:00:00ZNwaogu, Chima JosiahThere is a growing appreciation of the diversity and uniqueness of tropical organisms, but evidence about the selection pressures that shape this diversity remains sketchy. In this thesis, I investigated how variation in life history traits arises from tropical environmental seasonality, starting with the exploration of the annual cycle of the Common Bulbul Pycnonotus barbatus in Nigeria. This revealed that breeding was not seasonal, but moult was timed almost entirely to the wet season with only few individuals extending moult into the dry season This confirmed that breeding and to a lesser extent moult, are decoupled from season, thus, allowing me to test how breeding and moult affect immune function independent of seasonal environmental conditions. On testing this, I found that season explained variation in immune function better than breeding or moult, but unexpectedly, immune indices were higher in the dry season and during breeding, contrary to what I would expect if infection risk is higher in the wet season, and if breeding constrains resources for immune function. Furthermore, I compared immune indices along the cool-wet to hot-dry environmental gradient in Nigeria and found that immune indices were rather similar. I then tested the effect of diet alteration on immune function, body mass and moult of Common Bulbuls in captivity and found that bulbuls fed on fruits had a more immune function, body mass and onset of moult than those fed on invertebrates. These findings together suggest that environmental conditions affect immune function more directly than via resource allocation trade-offs, but that variation in immune function does not follow simple environmental productivity pattern as previously expected. **********
Samenvatting:
Het doorgronden van de evolutie van de levensloop d.w.z. hoe organismen hun beschikbare
energie en nutriënten verdelen tussen overleven en reproduceren, is een fundamenteel
probleem. Het merendeel van onze kennis hierover komt voort uit onderzoek in gematigde
klimaten, terwijl het leven echter in de tropen is geëvolueerd. Hoewel er groeiende aandacht is
voor de biologische diversiteit en het unieke karakter van levensvormen in tropische systemen,
is er nog weinig bekend over de verschillende selectiedrukken en evolutionaire aanpassingen
waardoor diverse levensloopstrategieën zich hebben ontwikkeld. Dit proefschrift is bedoelt om
bij te dragen aan het herstellen van deze scheve balans en is daarom gericht op het beter
begrijpen van hoe seizoensgebonden omgevingsfactoren en dieetvariatie in de tropen leidt tot
variatie in kenmerken van de levensloop.
Voor sommige tropische vogels is het broeden, op populatieniveau, niet sterk
seizoensgebonden, ondanks dat er voorspelbare seizoensoptima voor omgevingsomstandigheden bestaan. Het blijft daarom onduidelijk of individuen zijn aangepast om te
broeden op specifieke tijden durende een jaar, of juist flexibel zijn als gevolg van variabele
omgevingsomstandigheden. In het tweede hoofdstuk (eerste data-hoofdstuk) van dit
proefschrift testte ik of de broedactiviteit van de door het hele jaar broedende grauwe buulbuul
Pycnonotus barbatus, is ontstaan als gevolg van individuele variabiliteit in broedperiode. Ik
analyseerde de broedactiviteit en ruikenmerken van vogels gevangen gedurende een periode
van twee jaar, en vond dat de broedgegevens van individuen net zo variabel kunnen zijn als in
de populatie. Het voorkomen van broeden kon niet worden verklaard aan de hand van de
hoeveelheid neerslag of temperatuur, hoewel vogels tijdens de rui zelden broedden. In
tegenstelling tot broeden was de rui wel sterk seizoensgebonden maar was niet gecorreleerd
aan neerslag of temperatuur. Ik stel daarom voor dat, gezien omgevingsomstandigheden het
hele jaar door broeden in deze soort mogelijk maken en omdat voortplantingssucces
onderhevig is aan een hoog predatierisico, er waarschijnlijk een zwakke selectie is voor
individuen om het broeden samen te laten vallen met pieken in variabele omgevingsomstandigheden.
In tegenstelling daarvan is het waarschijnlijk dat rui, een jaarlijks
voorkomend fenomeen, onder sterke selectie staat om gelijktijdig plaats te vinden met de
pieken in variabele omgevingsomstandigheden, waarbij een verhoogde overlevingskans het
voortplantingssucces bevordert.
Het hele jaar door broeden kan het voortplantingssucces bevorderen, maar het individu
moet in staat zijn zich aan te passen aan een variërende mate van voedselbeschikbaarheid
tussen de seizoenen. Aannemelijk is dat vogels mogelijk lichaamsreserves opslaan als er een
verhonger risico ontstaat vanwege beperkte beschikbare foerageertijd. Als het foerageren
echter onbeperkt is, zou het lichaamsgewicht laag moeten blijven om het predatierisico te
beperken dat het verkrijgen en meedragen van lichaamsreserves met zich meebrengt. In mijn
tweede data-hoofdstuk testte ik aan de hand van 15 jaar aan gegevens over lichaamsmassa's
van grauwe buulbuul vrouwtjes of lichaamsgewichtsvariatie kan worden verklaard door
beperkte foerageertijd tijdens het broeden,. Ik vond dat de broedfase het lichaamsgewicht van
vrouwtjes voorspelde: het lichaamsgewicht piekte abrupt tijdens de incubatietijd en daalde tijdens de broedzorg. Broedende vrouwtjes waren zwaarder in het droge seizoen dan in het
natte seizoen. In het droge seizoen was het waarschijnlijker dat zwaardere vogels aan het
broeden of incuberen waren, wat suggereert dat verhoogde lichaamsreserves nodig kunnen
zijn als buffer voor de beperkte foerageertijd of verarmde foerageeromstandigheden, die het
meest uitgesproken kunnen zijn tijdens respectievelijk de incubatie en in het droge seizoen.
Naast het vinden van voedsel moeten dieren zichzelf beschermen tegen infecties die per
seizoen kunnen verschillen. De hoeveelheid beschikbare middelen voor verdediging kan echter
afhankelijk zijn van hoeveel al is verbruikt in andere processen. Seizoensvariatie in immuniteit
kan dus ofwel worden toegeschreven aan veranderingen in omgevingsomstandigheden als aan
compromissen die optreden wanneer middelen worden toegewezen aan andere processen. Het
loskoppelen van deze factoren is lastig in het wild. In mijn derde data-hoofdstuk heb ik, door
gebruik te maken van niet-seizoensgebonden broeden en ruien in de grauwe buulbuul, het
effect van seizoensgebonden omgevingscondities effectief losgekoppeld van dat van het
jaarlijkse cyclusstadium, en getest hoe beide factoren de immuunfunctie beïnvloeden. Ik
voorspelde dat indien de kans op infecties toeneemt met regenval het immuunsysteem sterker
zou zijn in het natte seizoen, maar indien broeden of rui beperkingen oplegt aan vogels, dat dan
de immuun parameters lager zijn tijdens het broeden of ruien. Door het kwantificeren van vijf
aangeboren immuun parameters gedurende twee jaar vond ik dat seizoen en niet stadia van de
jaarcyclus de variatie in alle immuun parameters verklaarde, behalve één: NOx, waarvan de
concentratie verschilde tussen de jaarlijkse cyclusstadia maar niet tussen seizoenen. Tegen mijn
verwachting in waren de meeste immuun parameters hoger in het droge seizoen en tijdens het
broeden, terwijl ik verwacht dat regen de infectiekans verhoogde en het broeden
immuunfunctie verminderde. Ondanks dat, kon ik concluderen dat omgevingsfactoren de
aangeboren immuniteit rechtstreeks beïnvloeden in plaats van via compromissen in het
toewijzen van middelen tussen verschillende levensloopprocessen.
Zoals voorspeld door de regel van Bergmann kan lichaamsgrootte variëren als reactie
op omgevingsomstandigheden. Deze regel is een biofysische generalisatie dat endotherme
dieren de neiging hebben groter te zijn in koudere klimaten. In mijn vierde data-hoofdstuk
testte ik of de lichaamsgrootte van grauwe buulbuul varieert in overeenstemming met de regel
van Bergmann. Ik mat vogels op 22 locaties tussen 6 en 13°N en schatte vervolgens de
gemiddelde verhouding tussen lichaamsoppervlak en -gewicht per locatie. In
overeenstemming met de regel van Bergmann ontdekte ik dat vogels een grotere verhouding
tussen lichaamsoppervlak en -gewicht hadden in warmere omgevingen, onafhankelijk van de
breedtegraad en hoogte (ten opzichte van zeeniveau).
Neerslag is een belangrijke bepalende factor voor de omgevingstoestand in de tropen,
maar omdat regenval vaak seizoensgebonden is, is het moeilijk om het effect ervan te
onderscheiden van dat van andere seizoensgebonden factoren en co-variërende
levensloopkenmerken. Bijvoorbeeld, grauwe buulbuuls ruien in het natte seizoen in centraal
Nigeria, maar het is niet bekend of de rui op hetzelfde tijdstip op alle locaties plaatsvindt of op
een tijdstip dat samenvalt met de lokale regenval. In het vijfde data-hoofdstuk van dit
proefschrift modelleerde ik de mate van rui als een functie van de timing van neerslag op 15
locaties tussen 6° N en 13° N. Ik vond dat vogels eerder ruiden op plekken waar het natte seizoen eerder begon, wat suggereert dat de rui in grauwe buulbuuls is gekoppeld aan timing
van de regenval.
Variatie in regenval en temperatuur zou ook het infectierisico kunnen bepalen langs een
gradiënt van omgevingscondities. Zo voorspelde ik dat als het infectierisico afneemt met
toenemende droogte, maar gepaard gaat met immuun functie, de aangeboren immuunfunctie
zou moeten afnemen met toenemende droogte van het koud-natte bos tot de hete-droge Sahelzone in Nigeria. Ik testte deze voorspelling in het zesde data-hoofdstuk van dit proefschrift door het meten van aangeboren immuun parameters in grauwe buulbuuls op 15 locaties tussen
6° N en 13° N. Tegen mijn verwachting in daalden de immuun parameters niet met toenemende
droogte, maar in plaats daarvan waren ze op verschillende locaties vergelijkbaar, wat
suggereert dat in dit systeem de aangeboren immuunfunctie niet varieert met verschillende
mate van droogte. Dit resultaat onderstreept de behoefte aan voorzichtigheid bij het voorspellen
van de effecten van klimaatvariabiliteit op ziekterisico.
Dieet is een cruciaal onderdeel van de omgeving en wordt sterk beïnvloed door
omgevingsveranderingen, met soms grote gevolgen. In mijn laatste data-hoofdstuk, testte ik
hoe de samenstelling van het dieet van invloed is op de aangeboren immuunfunctie,
lichaamsgewicht en rui. Gedurende 24 weken voedde ik 40 in het wild gevangen grauwe
buulbuuls ad libitum vruchten of ongewervelde dieren in buitenvolières in Nigeria. Ik
beoordeelde aangeboren immuunindexen, lichaamsgewicht en primaire rui tweewekelijks en
vond dat fruit-gevoede buulbuuls een robuustere aangeboren immuunfunctie, hoger
lichaamsgewicht en eerdere handpenrui hadden in vergelijking met vogels gevoed met
ongewervelde dieren. Deze resultaten zijn uniek omdat ze een effect aantonen van een
dieetaanpassing bij wilde vogels - wat korte termijn gevolgen van omgevingsverandering
aantoont.
Door klassieke natuurstudie en fysiologie te integreren in de context van de directe
omgeving waarin een soort leeft, biedt dit proefschrift nieuw inzicht in hoe variatie in broed-
en ruipatronen en immuunfunctie verschillende aspecten van de levensloop van een tropische
vogel met elkaar verbindt. Mijn bevindingen in dit proefschrift suggereren met name dat het al
lang bestaande paradigma dat de kostbare aard van immuunfunctie benadrukt, het belang van
het overlevingsvoordeel ondermijnt en grotendeels voorbijgaat aan de uiteindelijke rol van het
immuunsysteem, overleving. De voor- en nadelen van de immuunfunctie kunnen alleen worden
bepaald als rekening wordt gehouden met de omgevingsomstandigheden én levensloop
waaronder variaties optreden.Genome-based approaches for identification of avirulence genes in potato cyst nematodesVarypatakis, Kyriakoshttps://hdl.handle.net/10023/183422021-03-30T14:54:15Z2019-12-03T00:00:00ZThe use of natural resistance is the most effective way to control the potato cyst nematodes Globodera pallida and G. rostochiensis. Although pathotypes of the latter species can now be fully controlled, control of G. pallida is a real challenge because of the existence of multiple pathotypes with different virulence behaviour. Although the available resistance sources confer partial resistance only, such as that from Solanum vernei (Gpa5) and S. tuberosum ssp. andigena CPC2802 (H3), their use may drive strong selection towards virulence. Resistance operates through the detection of nematode-derived effectors by plant resistance (R) proteins. Upon recognition, immune responses are activated in plants and the recognised effectors are then characterised as avirulence (avr) proteins.
The study of the effectors and avr genes can provide important information on the mechanisms underlying selection. Fortunately, the development of novel sequencing technologies and genomic tools have enabled us to gain better insight towards complex genomes, such as that of potato cyst nematodes. Here, long-read sequencing was used for the generation of a new, more complete G. pallida genome. Based on this, analysis of captured, targeted effector-encoding genomic regions from virulent populations selected on the above resistance sources showed the presence of up to 54 candidate effectors that may determine virulence on these resistance sources. By cross-referencing those with the candidates identified from the re-sequencing of the same populations, 3 high-confidence candidate avr genes were listed. In parallel, the analysis of their allele frequencies and SNP distribution revealed that many potential effector genes are located within genomic “islands”, which are all selected on a specific resistance. This organisation is believed to facilitate selection evolution and host adaptation.
Lastly, the G. rostochiensis candidate effector g13394 was cloned from an avirulent and virulent to H1 population, and subsequently was functionally validated through Agrobacterium-mediated transient expression using two different methods.
2019-12-03T00:00:00ZVarypatakis, KyriakosThe use of natural resistance is the most effective way to control the potato cyst nematodes Globodera pallida and G. rostochiensis. Although pathotypes of the latter species can now be fully controlled, control of G. pallida is a real challenge because of the existence of multiple pathotypes with different virulence behaviour. Although the available resistance sources confer partial resistance only, such as that from Solanum vernei (Gpa5) and S. tuberosum ssp. andigena CPC2802 (H3), their use may drive strong selection towards virulence. Resistance operates through the detection of nematode-derived effectors by plant resistance (R) proteins. Upon recognition, immune responses are activated in plants and the recognised effectors are then characterised as avirulence (avr) proteins.
The study of the effectors and avr genes can provide important information on the mechanisms underlying selection. Fortunately, the development of novel sequencing technologies and genomic tools have enabled us to gain better insight towards complex genomes, such as that of potato cyst nematodes. Here, long-read sequencing was used for the generation of a new, more complete G. pallida genome. Based on this, analysis of captured, targeted effector-encoding genomic regions from virulent populations selected on the above resistance sources showed the presence of up to 54 candidate effectors that may determine virulence on these resistance sources. By cross-referencing those with the candidates identified from the re-sequencing of the same populations, 3 high-confidence candidate avr genes were listed. In parallel, the analysis of their allele frequencies and SNP distribution revealed that many potential effector genes are located within genomic “islands”, which are all selected on a specific resistance. This organisation is believed to facilitate selection evolution and host adaptation.
Lastly, the G. rostochiensis candidate effector g13394 was cloned from an avirulent and virulent to H1 population, and subsequently was functionally validated through Agrobacterium-mediated transient expression using two different methods.Molecular analysis of the eggshell and cuticle surface of the potato cyst nematode, Globodera rostochiensisPrice, James A.https://hdl.handle.net/10023/182482021-03-29T11:24:53Z2019-12-03T00:00:00ZPlant-parasitic nematodes regulate their interactions with the external environment and their host. The surface of the nematodes, whether the cuticle or the eggshell, plays a key role in this process. Work undertaken in this project aimed to exploit new genome resources for potato cyst nematodes (PCN) to allow characterisation of these structures.
The eggshell is a key survival structure for PCN. Hatching of juvenile potato cyst nematodes occurs in response to host derived hatching factors. Little is known about the molecular mechanisms that underpin hatching in response to these host diffusates and nothing is known about the molecular composition of the PCN eggshell. Methods that allow extraction of proteins and lipids from large numbers of isolated PCN eggshells were developed. These extraction techniques permitted identification of a range of proteins present in the eggshell, including chondroitin proteoglycans and a calcium dependent phospholipid-binding annexin. The annexin was focused on due to the apparent major role of calcium in PCN hatching. This annexin was localised to the eggshells of Globodera rostochiensis by immunofluorescence. To our knowledge, this makes the annexin the first eggshell protein to be identified and localised in any plant-parasitic nematode. The annexin was shown to bind to phospholipids and RNAi of the annexin showed that reducing expression of the eggshell annexin alters nematode hatching patterns in response to host hatching factors.
The eggshell permeability barrier is essential for the development of a juvenile within the embryo. Eggshell lipid analysis has given insight into components of the permeability barrier. Identified lipid species highlight potential function within the nematode hatching cascade through calcium interaction or down stream signalling. Attempts to identify the presence of nematode specific glycolipids, ascarosides, within the PCN eggshell showed that ascarosides or ascarylose were not detectable within PCN eggs, cysts or juveniles.
It has previously been shown that the infective juveniles are able to alter their surface composition to avoid damage from host defence mechanisms. Here, methods that allow labelling of proteins present on the cuticle surface of PCN were developed. Three proteins; Galectin-5, Cri-2 and a nematode specific hypothetical protein that are present on the surface of PCN second stage juveniles were further investigated. These proteins were tested for their potential to suppress host defences through a variety of protein-small molecule interactions. This analysis showed that surface coat associated galectins could offer protection to an invasive juvenile through sequestering cell wall breakdown products, silencing detection of the pathogen.
2019-12-03T00:00:00ZPrice, James A.Plant-parasitic nematodes regulate their interactions with the external environment and their host. The surface of the nematodes, whether the cuticle or the eggshell, plays a key role in this process. Work undertaken in this project aimed to exploit new genome resources for potato cyst nematodes (PCN) to allow characterisation of these structures.
The eggshell is a key survival structure for PCN. Hatching of juvenile potato cyst nematodes occurs in response to host derived hatching factors. Little is known about the molecular mechanisms that underpin hatching in response to these host diffusates and nothing is known about the molecular composition of the PCN eggshell. Methods that allow extraction of proteins and lipids from large numbers of isolated PCN eggshells were developed. These extraction techniques permitted identification of a range of proteins present in the eggshell, including chondroitin proteoglycans and a calcium dependent phospholipid-binding annexin. The annexin was focused on due to the apparent major role of calcium in PCN hatching. This annexin was localised to the eggshells of Globodera rostochiensis by immunofluorescence. To our knowledge, this makes the annexin the first eggshell protein to be identified and localised in any plant-parasitic nematode. The annexin was shown to bind to phospholipids and RNAi of the annexin showed that reducing expression of the eggshell annexin alters nematode hatching patterns in response to host hatching factors.
The eggshell permeability barrier is essential for the development of a juvenile within the embryo. Eggshell lipid analysis has given insight into components of the permeability barrier. Identified lipid species highlight potential function within the nematode hatching cascade through calcium interaction or down stream signalling. Attempts to identify the presence of nematode specific glycolipids, ascarosides, within the PCN eggshell showed that ascarosides or ascarylose were not detectable within PCN eggs, cysts or juveniles.
It has previously been shown that the infective juveniles are able to alter their surface composition to avoid damage from host defence mechanisms. Here, methods that allow labelling of proteins present on the cuticle surface of PCN were developed. Three proteins; Galectin-5, Cri-2 and a nematode specific hypothetical protein that are present on the surface of PCN second stage juveniles were further investigated. These proteins were tested for their potential to suppress host defences through a variety of protein-small molecule interactions. This analysis showed that surface coat associated galectins could offer protection to an invasive juvenile through sequestering cell wall breakdown products, silencing detection of the pathogen.Not just fat : investigating novel physiological state biomarkers in cetacean blubberKershaw, Joannahttps://hdl.handle.net/10023/179772021-03-19T12:05:21Z2019-06-26T00:00:00ZDespite its importance as a predictor of fitness, no consensus has been reached about how to
assess the nutritive body condition of free-ranging cetaceans. Standard indices of condition
used in terrestrial ecology were assessed in cetaceans using data and samples from stranded
animals. The most appropriate morphometric indices were identified as mass/length2 and
girth/length (where mass data were unavailable). Blubber thickness, and blubber lipid content
were poor indicators of condition. Variation in lipid content suggested that there may be tradeoffs
occurring between different blubber functions involved in energy storage, controlling
buoyancy, and preserving thermoregulatory properties in species with different life-history
strategies.
Novel blubber biomarkers of physiological state were investigated as objective and widely
applicable tools for estimating body condition. Blubber cortisol concentrations were negatively
correlated with morphometric indices of condition in stranded animals from two cetacean
families. Blubber cortisol concentrations were thus identified as a candidate biomarker. When
applied to a 13-year dataset of biopsy samples from female humpback whales (Megaptera
novaeangliae), cortisol concentrations showed significant inter-annual variation.
Concentrations were weakly correlated with annual pregnancy rates. High individual
variability in blubber cortisol concentrations was likely a result of the multi-functional nature
of cortisol. Cortisol concentrations thus probably provide a ‘snap shot’ of the metabolic state
of the tissue when sampled.
A proteomic approach was developed to extract and identify proteins in blubber. A range of
proteins involved in numerous metabolic processes and pathways were identified. These
proteins likely capture the range of physiological processes experienced by individuals at the
time of sampling. This new proteomic approach will help to assign novel functions to marine
mammal blubber in keeping with current understanding of the multi-functional role of adipose
tissue as an endocrine organ in mammals. It will also allow the future development of protein
biomarkers of health and physiological state.
2019-06-26T00:00:00ZKershaw, JoannaDespite its importance as a predictor of fitness, no consensus has been reached about how to
assess the nutritive body condition of free-ranging cetaceans. Standard indices of condition
used in terrestrial ecology were assessed in cetaceans using data and samples from stranded
animals. The most appropriate morphometric indices were identified as mass/length2 and
girth/length (where mass data were unavailable). Blubber thickness, and blubber lipid content
were poor indicators of condition. Variation in lipid content suggested that there may be tradeoffs
occurring between different blubber functions involved in energy storage, controlling
buoyancy, and preserving thermoregulatory properties in species with different life-history
strategies.
Novel blubber biomarkers of physiological state were investigated as objective and widely
applicable tools for estimating body condition. Blubber cortisol concentrations were negatively
correlated with morphometric indices of condition in stranded animals from two cetacean
families. Blubber cortisol concentrations were thus identified as a candidate biomarker. When
applied to a 13-year dataset of biopsy samples from female humpback whales (Megaptera
novaeangliae), cortisol concentrations showed significant inter-annual variation.
Concentrations were weakly correlated with annual pregnancy rates. High individual
variability in blubber cortisol concentrations was likely a result of the multi-functional nature
of cortisol. Cortisol concentrations thus probably provide a ‘snap shot’ of the metabolic state
of the tissue when sampled.
A proteomic approach was developed to extract and identify proteins in blubber. A range of
proteins involved in numerous metabolic processes and pathways were identified. These
proteins likely capture the range of physiological processes experienced by individuals at the
time of sampling. This new proteomic approach will help to assign novel functions to marine
mammal blubber in keeping with current understanding of the multi-functional role of adipose
tissue as an endocrine organ in mammals. It will also allow the future development of protein
biomarkers of health and physiological state.Homeobox genes in the development and regeneration of the cephalochordate Branchiostoma lanceolatum and the polychaete annelid Spirobranchus lamarckiBarton-Owen, Tomhttps://hdl.handle.net/10023/179732021-03-16T09:40:22Z2019-01-01T00:00:00ZThe development of complex animal morphology requires the extremely sophisticated spatiotemporal coordination of cell behaviour and communication. Homeobox genes
encode transcription factors that are deployed in developmental processes to control the
expression of other genes in particular locations and contexts. Many homeobox genes are
highly conserved and act in similar roles between distantly-related animals that derive
from the roles of their ancestral orthologues. The way that these genes have differentially
evolved between taxa, and the effect that these changes have on the development and
morphology of animals, is critical to our understanding of metazoan evolution. One particular developmental context, the regeneration of missing tissue, offers a unique perspective on evolutionary developmental biology because of its relationship to ontogenic development and its surprising diversity of retention and process between animal taxa.
I examined the homeobox gene content of transcriptomes taken from the mature
and regenerating tissue of the post-anal tail of Branchiostoma lanceolatum, a well-studied
cephalochordate with a highly conserved genome, and the evolutionarily novel operculum
of Spirobranchus lamarcki, a sedentarian annelid. In S. lamarcki regeneration, a diverse
variety of homeobox genes is expressed, and the regenerative expression response is substantial. The discovery of several difficult-to-classify homeobox genes lead to the substantial expansion and improvement of the classification of a variety of homeobox genes undergoing unusual rapid and expansive evolution in the Spiralia, including dozens of TALE
and PRD class genes, a new orthology group, and a strange S. lamarcki Hox gene.
In B. lanceolatum, a similar diversity of expressed genes is observed but a milder
regenerative response. One transcriptomic sequence in particular, identified as Pax3/7, led
to the discovery that this well-studied gene has a previously unnoticed duplication in
cephalochordates. This discovery has implications for ongoing study of vertebrate and
cephalochordate neural plate border evolution.
2019-01-01T00:00:00ZBarton-Owen, TomThe development of complex animal morphology requires the extremely sophisticated spatiotemporal coordination of cell behaviour and communication. Homeobox genes
encode transcription factors that are deployed in developmental processes to control the
expression of other genes in particular locations and contexts. Many homeobox genes are
highly conserved and act in similar roles between distantly-related animals that derive
from the roles of their ancestral orthologues. The way that these genes have differentially
evolved between taxa, and the effect that these changes have on the development and
morphology of animals, is critical to our understanding of metazoan evolution. One particular developmental context, the regeneration of missing tissue, offers a unique perspective on evolutionary developmental biology because of its relationship to ontogenic development and its surprising diversity of retention and process between animal taxa.
I examined the homeobox gene content of transcriptomes taken from the mature
and regenerating tissue of the post-anal tail of Branchiostoma lanceolatum, a well-studied
cephalochordate with a highly conserved genome, and the evolutionarily novel operculum
of Spirobranchus lamarcki, a sedentarian annelid. In S. lamarcki regeneration, a diverse
variety of homeobox genes is expressed, and the regenerative expression response is substantial. The discovery of several difficult-to-classify homeobox genes lead to the substantial expansion and improvement of the classification of a variety of homeobox genes undergoing unusual rapid and expansive evolution in the Spiralia, including dozens of TALE
and PRD class genes, a new orthology group, and a strange S. lamarcki Hox gene.
In B. lanceolatum, a similar diversity of expressed genes is observed but a milder
regenerative response. One transcriptomic sequence in particular, identified as Pax3/7, led
to the discovery that this well-studied gene has a previously unnoticed duplication in
cephalochordates. This discovery has implications for ongoing study of vertebrate and
cephalochordate neural plate border evolution.Building a molecular machine : heterologous expression and biochemical characterisation of transcription factor IIHSanles-Falagan, Reyeshttps://hdl.handle.net/10023/176292021-07-27T02:03:27Z2019-06-26T00:00:00ZOrganisms across Archaea, Bacteria and Eukarya possess a series of mechanisms to protect the integrity of the deoxyribonucleic acid (DNA) from the constant attack of internal and external factors that modify the structure of the double helix, potentially causing an increase in mutagenesis. The Nucleotide Excision Repair (NER) pathway removes bulky lesions in the DNA caused by ultraviolet (UV) radiation and other sources that can introduce a strong distortion in the double helix. A key element in this repair mechanism is the transcription factor IIH (TFIIH), a ten-subunit complex which opens and extends the DNA bubble originated at the damaged site to allow the subsequent repair factors access to the lesion, so the insult can be removed. Mutations in TFIIH subunits xeroderma pigmentosum group B (XPB), xeroderma pigmentosum group D (XPD) or p8 can cause a series of autosomal recessive disorders with symptoms that include mild-to-extreme photosensitivity, progeria, physical and neurological abnormalities, and in some cases an increased susceptibility to cancer.
This thesis describes the processes of cloning, expression and purification followed to obtain damage-detector heterodimer XPC-HR23B, the 7-subunit TFIIH Core sub-complex and the 10-subunit TFIIH complex by means of a powerful baculoviral expression vector (BEV) called MultiBacTM, a tool specifically conceived for the obtaining of multi-subunit eukaryotic complexes. The biochemical characterization of TFIIH Core showed that the sub-complex can bind a series of double-stranded DNA (dsDNA) substrates with an affinity in the nM range, and the presence of a bubble or damage at the duplex does not change TFIIH Core’s binding affinity significantly. The study of TFIIH Core’s unwinding ability confirmed that the sub-complex can open a series of dsDNA substrates only when a 5’ overhang end is available, and this activity can be stalled by a lesion located in both the translocating and non-translocating strands.
2019-06-26T00:00:00ZSanles-Falagan, ReyesOrganisms across Archaea, Bacteria and Eukarya possess a series of mechanisms to protect the integrity of the deoxyribonucleic acid (DNA) from the constant attack of internal and external factors that modify the structure of the double helix, potentially causing an increase in mutagenesis. The Nucleotide Excision Repair (NER) pathway removes bulky lesions in the DNA caused by ultraviolet (UV) radiation and other sources that can introduce a strong distortion in the double helix. A key element in this repair mechanism is the transcription factor IIH (TFIIH), a ten-subunit complex which opens and extends the DNA bubble originated at the damaged site to allow the subsequent repair factors access to the lesion, so the insult can be removed. Mutations in TFIIH subunits xeroderma pigmentosum group B (XPB), xeroderma pigmentosum group D (XPD) or p8 can cause a series of autosomal recessive disorders with symptoms that include mild-to-extreme photosensitivity, progeria, physical and neurological abnormalities, and in some cases an increased susceptibility to cancer.
This thesis describes the processes of cloning, expression and purification followed to obtain damage-detector heterodimer XPC-HR23B, the 7-subunit TFIIH Core sub-complex and the 10-subunit TFIIH complex by means of a powerful baculoviral expression vector (BEV) called MultiBacTM, a tool specifically conceived for the obtaining of multi-subunit eukaryotic complexes. The biochemical characterization of TFIIH Core showed that the sub-complex can bind a series of double-stranded DNA (dsDNA) substrates with an affinity in the nM range, and the presence of a bubble or damage at the duplex does not change TFIIH Core’s binding affinity significantly. The study of TFIIH Core’s unwinding ability confirmed that the sub-complex can open a series of dsDNA substrates only when a 5’ overhang end is available, and this activity can be stalled by a lesion located in both the translocating and non-translocating strands.The biodiversity, ecosystem functioning and value of restored salt marshes in the Eden Estuary, ScotlandWade, Katherine Scarletthttps://hdl.handle.net/10023/175412020-11-03T10:31:11Z2018-01-01T00:00:00ZThe ecosystem service (ES) framework is increasingly being incorporated into management decisions, providing a basis by which ES can be quantified to understand the impact of decisions to society and the environment. Our ability to effectively implement this framework is dependent on our knowledge of the links between natural capital, ecosystem functions and ES. A need to ensure that the theoretical model is grounded in scientific evidence exists. This thesis employed ecological and economic methods to apply the ES framework in assessing the ability of restored salt marsh to provide coastal defences, and the perceived value of this by the public.
Using sites planted as part of ongoing restoration in the Eden Estuary, Scotland, ecosystem functions important to the provision of coastal flood defence were assessed for equivalence to natural salt marsh sites. Plant structure was found to develop along a trajectory expected to attain comparable ecosystem function to a natural marsh. Comparable plant height was attained 10 years after planting, however marginal significant differences were still present in plant density. Due to high spatial and temporal variation no trajectory for sediment stability could be inferred. Overall, this work suggests that equivalent coastal defence provision is highly likely to be attained within the planted sites. Comparable benthic macrofaunal species richness and abundance were observed 2-3 and 4–9 years after planting, respectively; community assemblage continued to differ after 11 years. A choice experiment indicated a clear dislike for the use of engineered walls and a preference for nature-based defences within the Eden Estuary. A combination of a low wall and fronting salt marsh was preferred with the highest willingness to pay.
Combining the findings from ecological and economic research enables insights that can assist in the planning of coastal flood defence providing valuable information to managers and policy makers.
2018-01-01T00:00:00ZWade, Katherine ScarlettThe ecosystem service (ES) framework is increasingly being incorporated into management decisions, providing a basis by which ES can be quantified to understand the impact of decisions to society and the environment. Our ability to effectively implement this framework is dependent on our knowledge of the links between natural capital, ecosystem functions and ES. A need to ensure that the theoretical model is grounded in scientific evidence exists. This thesis employed ecological and economic methods to apply the ES framework in assessing the ability of restored salt marsh to provide coastal defences, and the perceived value of this by the public.
Using sites planted as part of ongoing restoration in the Eden Estuary, Scotland, ecosystem functions important to the provision of coastal flood defence were assessed for equivalence to natural salt marsh sites. Plant structure was found to develop along a trajectory expected to attain comparable ecosystem function to a natural marsh. Comparable plant height was attained 10 years after planting, however marginal significant differences were still present in plant density. Due to high spatial and temporal variation no trajectory for sediment stability could be inferred. Overall, this work suggests that equivalent coastal defence provision is highly likely to be attained within the planted sites. Comparable benthic macrofaunal species richness and abundance were observed 2-3 and 4–9 years after planting, respectively; community assemblage continued to differ after 11 years. A choice experiment indicated a clear dislike for the use of engineered walls and a preference for nature-based defences within the Eden Estuary. A combination of a low wall and fronting salt marsh was preferred with the highest willingness to pay.
Combining the findings from ecological and economic research enables insights that can assist in the planning of coastal flood defence providing valuable information to managers and policy makers.Evolutionary theory of human warfare : genes, individuals, groupsMicheletti, Alberto Jacopo Cesarehttps://hdl.handle.net/10023/174942021-03-02T12:34:11Z2019-06-26T00:00:00Z2019-06-26T00:00:00ZMicheletti, Alberto Jacopo CesareInvestigation of the chromatin remodelling enzyme Uls1 and its interactions with Topoisomerase 2 in S. cerevisiaeSwanston, Amyhttps://hdl.handle.net/10023/174922021-03-02T11:10:52Z2019-06-26T00:00:00ZAcriflavine (ACF) is a Topoisomerase 2 (Top2) poison, a class of drugs which stall Top2 during its reaction cycle causing the formation of persistent DNA breaks to which Top2 remains covalently bound. Deletion of ULS1 causes sensitivity to ACF, with cells showing activation of the Rad53 DNA damage checkpoint. Uls1 is a chromatin remodelling enzyme also implicated in the regulation of levels of SUMO conjugated proteins. We show that Uls1 has both a genetic and physical interaction with Top2, with uls1Δ sensitivity to ACF being linked to Top2 activity. Analysis of Uls1 and Top2 localisation genome wide via ChIP-seq reveals areas where the two proteins co-localise, with Top2 enrichment on chromatin being altered upon deletion of ULS1. At these areas, the presence of Uls1 prevents accumulation of Top2 upon addition of ACF. Our data suggests that Uls1 is required for regulation of stalled Top2.
Top2 poisons are used therapeutically as anti-cancer drugs, however these drugs have been implicated in the formation of secondary cancers due to chromosomal translocations arising during the repair of Top2 generated double strand breaks (DSB). The use of dual targeted therapies where a Top2 poison is paired with an inhibitor of another pathway that increases sensitivity to the Top2 poison allows a lower dose to be used, therefore reducing harmful side effects. Our work looked to identify Top2 poison sensitive pathways in S. cerevisiae, where non-essential and essential gene mutants were assayed for sensitivity to ACF. This allowed a comprehensive analysis of 83% of the genes in S. cerevisiae, identifying novel genes within the areas of DNA repair, DNA replication, transcription, chromatin structure, protein modification/degradation, cell division/cell cycle and cellular organisation/cytoskeleton as being important in the response to this bulky adduct.
2019-06-26T00:00:00ZSwanston, AmyAcriflavine (ACF) is a Topoisomerase 2 (Top2) poison, a class of drugs which stall Top2 during its reaction cycle causing the formation of persistent DNA breaks to which Top2 remains covalently bound. Deletion of ULS1 causes sensitivity to ACF, with cells showing activation of the Rad53 DNA damage checkpoint. Uls1 is a chromatin remodelling enzyme also implicated in the regulation of levels of SUMO conjugated proteins. We show that Uls1 has both a genetic and physical interaction with Top2, with uls1Δ sensitivity to ACF being linked to Top2 activity. Analysis of Uls1 and Top2 localisation genome wide via ChIP-seq reveals areas where the two proteins co-localise, with Top2 enrichment on chromatin being altered upon deletion of ULS1. At these areas, the presence of Uls1 prevents accumulation of Top2 upon addition of ACF. Our data suggests that Uls1 is required for regulation of stalled Top2.
Top2 poisons are used therapeutically as anti-cancer drugs, however these drugs have been implicated in the formation of secondary cancers due to chromosomal translocations arising during the repair of Top2 generated double strand breaks (DSB). The use of dual targeted therapies where a Top2 poison is paired with an inhibitor of another pathway that increases sensitivity to the Top2 poison allows a lower dose to be used, therefore reducing harmful side effects. Our work looked to identify Top2 poison sensitive pathways in S. cerevisiae, where non-essential and essential gene mutants were assayed for sensitivity to ACF. This allowed a comprehensive analysis of 83% of the genes in S. cerevisiae, identifying novel genes within the areas of DNA repair, DNA replication, transcription, chromatin structure, protein modification/degradation, cell division/cell cycle and cellular organisation/cytoskeleton as being important in the response to this bulky adduct.Sources of variation in the tool-use behaviour of two tropical island corvidsKlump, Barbara Christinahttps://hdl.handle.net/10023/173952019-06-28T10:52:08Z2017-06-21T00:00:00Z2017-06-21T00:00:00ZKlump, Barbara ChristinaInvestigating the behavioural consequences of evolutionary signal loss in the context of a naturalistic environmentSchneider, Willhttps://hdl.handle.net/10023/173372021-03-01T14:50:22Z2019-06-26T00:00:00ZThe evolutionary loss of sexual traits is thought to be common, but empirical examples of it
occurring are rare. In this thesis, I investigate social and other behavioural factors that might
facilitate signal loss. Specifically, I took an empirical approach to evaluate the ways in which
the loss of a long-range acoustic signal, song, alters the mating dynamics and social behaviours
of individuals in affected populations. This confronts a methodological challenge in behavioural
research – the difficulty of observing and measuring behaviours from within a natural context - a context that includes the physical and social environmental conditions in which they evolved.
To overcome this challenge and to study the consequences of sexual signal loss, I developed a
novel tracking system to monitor, in a laboratory setting that mimicked field-like conditions,
the behaviour of a cricket species in which some males have lost the ability to sing. In
populations of the Hawaiian field cricket, Teleogryllus oceanicus, silent ‘flatwing’ males carry
mutations that remove key wing structures, eliminating acoustic signalling and affording
protection against an acoustically-orientating parasitoid fly (Ormia ochracea). This also
removes their ability to attract females via song. Despite this, largely silent populations persist
in the wild. Using the developed tracking system to monitor groups of individually-tagged
crickets, I show how behavioural plasticity of both males and females might accommodate the
disappearance of song and mitigate negative effects on reproductive fitness. This appears to
be achieved by increased movement activity and changes to key social interaction dynamics.
My results highlight the flexible and potentially compensatory nature of animal behaviour in
facilitating rapid evolutionary change.
2019-06-26T00:00:00ZSchneider, WillThe evolutionary loss of sexual traits is thought to be common, but empirical examples of it
occurring are rare. In this thesis, I investigate social and other behavioural factors that might
facilitate signal loss. Specifically, I took an empirical approach to evaluate the ways in which
the loss of a long-range acoustic signal, song, alters the mating dynamics and social behaviours
of individuals in affected populations. This confronts a methodological challenge in behavioural
research – the difficulty of observing and measuring behaviours from within a natural context - a context that includes the physical and social environmental conditions in which they evolved.
To overcome this challenge and to study the consequences of sexual signal loss, I developed a
novel tracking system to monitor, in a laboratory setting that mimicked field-like conditions,
the behaviour of a cricket species in which some males have lost the ability to sing. In
populations of the Hawaiian field cricket, Teleogryllus oceanicus, silent ‘flatwing’ males carry
mutations that remove key wing structures, eliminating acoustic signalling and affording
protection against an acoustically-orientating parasitoid fly (Ormia ochracea). This also
removes their ability to attract females via song. Despite this, largely silent populations persist
in the wild. Using the developed tracking system to monitor groups of individually-tagged
crickets, I show how behavioural plasticity of both males and females might accommodate the
disappearance of song and mitigate negative effects on reproductive fitness. This appears to
be achieved by increased movement activity and changes to key social interaction dynamics.
My results highlight the flexible and potentially compensatory nature of animal behaviour in
facilitating rapid evolutionary change.Characterisation of the potato H2 resistance gene against Globodera pallidaStrachan, Shonahttps://hdl.handle.net/10023/172282021-02-19T11:39:34Z2018-12-13T00:00:00ZMultiple pathotypes of the potato cyst nematode Globodera pallida are present in British potato fields; however, no single resistance gene has been identified which confers resistance to all three pathotypes which are present in British fields (Pa1, Pa2/3). Fortunately, the H2 resistance gene has been identified from the wild potato diploid S. multidissectum which confers a high level of resistance to Pa1, and a lower level of resistance to Pa2/3.
A segregating F1 population was generated using susceptible cultivar Picasso and resistant breeding line P55/7 and using an initial population of 154 progeny clones the H2 gene was verified to be a simplex dominant resistance gene. Bulked segregant analysis was undertaken with GenSeq and RenSeq enrichment to identify informative SNPs. Allele specific markers based on these informative SNPs were used to map the H2 gene to a 4.7Mb region of potato chromosome 5, using the dihaploid DM genome as a reference. Using an expanded F1 population of 656 clones in combination with designed markers allowed the region of interest to be narrowed to 0.8Mb at the distal end of chromosome 5. Analysis of this region identified two NB-LRR structure resistance genes which became putative candidates of the H2 gene.
Gene enrichment was also undertaken in pathotype Pa1 of G. pallida in order to identify putative candidate effectors which initiate resistance gene mediated cell death. A comparative analysis between virulent Pa2/3 and avirulent Pa1 revealed 19,873 allelic differences, which were stringently filtered to 23 variants in 10 candidate genes. One candidate gene was cloned and functionally tested via vacuum infiltration in resistant P55/7 potato leaves to observe a potential hypersensitive response. The data from the presented work will aid future research into cloning the functional H2 gene.
2018-12-13T00:00:00ZStrachan, ShonaMultiple pathotypes of the potato cyst nematode Globodera pallida are present in British potato fields; however, no single resistance gene has been identified which confers resistance to all three pathotypes which are present in British fields (Pa1, Pa2/3). Fortunately, the H2 resistance gene has been identified from the wild potato diploid S. multidissectum which confers a high level of resistance to Pa1, and a lower level of resistance to Pa2/3.
A segregating F1 population was generated using susceptible cultivar Picasso and resistant breeding line P55/7 and using an initial population of 154 progeny clones the H2 gene was verified to be a simplex dominant resistance gene. Bulked segregant analysis was undertaken with GenSeq and RenSeq enrichment to identify informative SNPs. Allele specific markers based on these informative SNPs were used to map the H2 gene to a 4.7Mb region of potato chromosome 5, using the dihaploid DM genome as a reference. Using an expanded F1 population of 656 clones in combination with designed markers allowed the region of interest to be narrowed to 0.8Mb at the distal end of chromosome 5. Analysis of this region identified two NB-LRR structure resistance genes which became putative candidates of the H2 gene.
Gene enrichment was also undertaken in pathotype Pa1 of G. pallida in order to identify putative candidate effectors which initiate resistance gene mediated cell death. A comparative analysis between virulent Pa2/3 and avirulent Pa1 revealed 19,873 allelic differences, which were stringently filtered to 23 variants in 10 candidate genes. One candidate gene was cloned and functionally tested via vacuum infiltration in resistant P55/7 potato leaves to observe a potential hypersensitive response. The data from the presented work will aid future research into cloning the functional H2 gene.Climate change effects on dimethylated sulphur dynamics in tropical coral reef systemsGreen, Tamara Kirstyhttps://hdl.handle.net/10023/171352021-02-18T12:41:23Z2019-06-26T00:00:00ZDimethylsulphoniopropionate (DMSP) and dimethylsulphoxide (DMSO) (collectively DMSP/O) are produced by marine algae, including symbiotic algae within corals. These sulphur compounds are important not only in sulphur cycle dynamics but also in potentially mediating atmospheric conditions, alleviating the effects of climate change and contributing to reef health.
Most research has focused on the production of DMSP and its major degradation product, the climatically active gas, dimethylsulphide (DMS) by Acropora corals in the Great Barrier Reef. However, mechanisms for the production and release of DMSP/O by different reef taxa is poorly understood. Recently the importance of mesophotic reefs as refugia for shallow water corals has been postulated, however their role in the marine sulphur cycle is unknown. This research aimed to improve our understanding of the contemporary and climate change induced seawater and tissue production of DMSP/O in a range of reef environments and taxa. This was achieved through a combination of laboratory and field - based studies, using modern and established techniques.
An effect of both elevated temperature and OA on increased tissue and seawater concentrations of DMSP/O production is reported in field and laboratory studies. Contrasting effects of benthic cover on tissue DMSP/O distributions and seawater DMSP are also noted. The importance of the physical and hydrodynamic environment on biogeochemical connectivity both within a reef and between neighbouring reefs is also focussed on. Crucially, however, the novel tissue and seawater data from mesophotic sites suggests that deeper reefs could affect the biogeochemistry of their shallow water counterparts. The key finding from this work is that climate change will result in increased seawater DMSP concentrations via two mechanisms; through the increase of cellular production of DMSP/O in all reef taxa, and by increasing the biomass of prolific DMSP producers as reefs transition to a fleshy/macroalgal assemblage. Whilst this could potentially mediate the effects of climate change, it will probably also worsen overall reef health, lead to a restructuring of reef communities from the microbial level upwards and will have possibly permanent and deleterious effects on overall ecosystem function.
2019-06-26T00:00:00ZGreen, Tamara KirstyDimethylsulphoniopropionate (DMSP) and dimethylsulphoxide (DMSO) (collectively DMSP/O) are produced by marine algae, including symbiotic algae within corals. These sulphur compounds are important not only in sulphur cycle dynamics but also in potentially mediating atmospheric conditions, alleviating the effects of climate change and contributing to reef health.
Most research has focused on the production of DMSP and its major degradation product, the climatically active gas, dimethylsulphide (DMS) by Acropora corals in the Great Barrier Reef. However, mechanisms for the production and release of DMSP/O by different reef taxa is poorly understood. Recently the importance of mesophotic reefs as refugia for shallow water corals has been postulated, however their role in the marine sulphur cycle is unknown. This research aimed to improve our understanding of the contemporary and climate change induced seawater and tissue production of DMSP/O in a range of reef environments and taxa. This was achieved through a combination of laboratory and field - based studies, using modern and established techniques.
An effect of both elevated temperature and OA on increased tissue and seawater concentrations of DMSP/O production is reported in field and laboratory studies. Contrasting effects of benthic cover on tissue DMSP/O distributions and seawater DMSP are also noted. The importance of the physical and hydrodynamic environment on biogeochemical connectivity both within a reef and between neighbouring reefs is also focussed on. Crucially, however, the novel tissue and seawater data from mesophotic sites suggests that deeper reefs could affect the biogeochemistry of their shallow water counterparts. The key finding from this work is that climate change will result in increased seawater DMSP concentrations via two mechanisms; through the increase of cellular production of DMSP/O in all reef taxa, and by increasing the biomass of prolific DMSP producers as reefs transition to a fleshy/macroalgal assemblage. Whilst this could potentially mediate the effects of climate change, it will probably also worsen overall reef health, lead to a restructuring of reef communities from the microbial level upwards and will have possibly permanent and deleterious effects on overall ecosystem function.Effects of the social and physical environment on avian nest constructionBreen, Alexis Juliehttps://hdl.handle.net/10023/171022021-02-17T17:06:44Z2019-06-24T00:00:00Z2019-06-24T00:00:00ZBreen, Alexis JulieTitle redactedDickie, Emily Ahttps://hdl.handle.net/10023/170092019-08-05T11:16:25Z2018-02-23T00:00:00Z2018-02-23T00:00:00ZDickie, Emily ATitle redactedSugasawa, Shokohttps://hdl.handle.net/10023/169582019-01-30T09:31:31Z2016-06-01T00:00:00Z2016-06-01T00:00:00ZSugasawa, ShokoHydrozoan jellyfish and their interactions with Scottish salmon aquacultureKintner, Anna Helenhttps://hdl.handle.net/10023/169392019-03-29T10:36:12Z2016-11-30T00:00:00ZMedusozoan jellyfish (Classes Scyphozoa and Hydrozoa) have gained a degree of worldwide
notoriety in the last fifteen years, particularly as anthropogenic influences such as climate
change and overfishing push some ecosystems toward their advantage (Lynam et al. 2005,
Purcell and Arai 2001, Purcell et al. 2007, Purcell 2012, Flynn et al. 2012, Dawson et al. 2014).
Accordingly, both the lay and scientific media have paid a good deal of attention to jellyfish
bloom phenomena and their impacts on human activities, but the bulk of this attention has
been devoted to larger, visually obvious species of Class Scyphozoa. Only recently have their
smaller cousins, the hydrozoans, come to be recognized as potentially problematic. This
thesis examines population ecology of hydrozoan medusae (hydromedusae) and their
implications for salmon aquaculture in Scotland.
My review of available literature has found hydrozoans to be a recognized – though under-
studied – problem for Scottish salmon (Chapter 1, Prospective monitoring of hydromedusa
populations at salmon aquaculture facilities). Typically, hydrozoan populations at salmon
farms have been discussed in the scientific literature only in the context of extremely dense
visible blooms or in the wake of major mortality incidents. This retrospective, rather than
prospective, approach has left a dearth of knowledge pertaining to hydromedusan
interactions with farmed fish, with both fish welfare and industry economics vulnerable to
future blooms.
This thesis sought to build a basis for the goals of prediction, avoidance, and mitigation of
harmful hydrozoan jellyfish blooms. First and foremost, this required the development of a
prospective time-series dataset of hydromedusan occurrences at salmon farms (Chapter 2,
Bacterial genera biodiversity in three medusozoan species in Shetland). To this end, four
farms were recruited as participants across a three-year survey. Weekly plankton tow-based
sampling at these sites identified which hydrozoan species could be expected to produce
blooms, the seasonality of such blooms, and the pathological sequelae that could be
expected in salmon after exposure to such blooms. Following one particularly dramatic
bloom, a spike in gill pathologies in salmon was observed, followed by a spike in overall
mortality and the eventual loss of up to £2.5 million value as the fish were humanely culled.
This survey also demonstrated that hydromedusan blooms are usually spatially and
temporally patchy, limiting the opportunities for geographically-encompassing predictive
power. Instead, individual aquaculture facilities may require site-specific risk assessment
and planning frameworks to monitor and cope with blooms. Potential methods for
continued basic monitoring and a mitigation strategy based on minimizing contact between
fish and high-density blooms are suggested.
A second mitigation goal examined the theory that medusae may act as vectors for microbial
pathogens, particularly Tenacibaculum maritimum (Ferguson et al. 2010, Delannoy et al.
2011; Chapter 3). Sampling methods designed to target T. maritimum were employed with
the aim of determining its distribution and role as a symbiont in various life stages of
medusozoan species. While T. maritimum itself was not observed, a number of other fish
pathogens were found in close association with several species. This included Aeromonas
salmonicida, known to cause furunculosis in aquaculture of both salmon and trout (Nomura
et al. 1992). Further work is required to piece together the nature of these associations.
Finally, Chapter 2 identified a particular hydrozoan genus, Obelia, as a likely significant
contributor to blooms at salmon aquaculture sites. One of its species, O. geniculata, has a
widely distributed and well-recognized benthic colonial life stage (called the hydroid stage)
in Scottish nearshore sublittoral environments. In attempting to sample these hydroids from
previously well-colonized sites in Shetland in late 2012, it became apparent that a severe
local reduction in the benthic population was taking place. This allowed for the opportunity
to study phylogeographic population structure – i.e. the boundaries of its gene pool(s) in
Scottish waters and its potential for dispersal during one seasonal reproductive period –
using a molecular study of the mitochondrial cytochrome oxidase subunit I (mtCOI) gene
(Chapter 4, Phylogeographic analysis of Obelia geniculata populations in the north of
Scotland). In sampling immediately after the observed dieback, O. geniculata was found to
follow a south-to-north pattern of genetic grouping, as well as a confirmed dieback.
However, this pattern disappeared in samples collected after the population had recovered,
probably due to the immigration of genetically novel individuals. This finding, in conjunction
with the spatial-temporal patchiness found in the medusa bloom stage, suggests the
importance of the larval stage as the primary stage for dispersal in the plankton. This study
was also able to compare present population genetic data with a set of O. geniculata mtCOI data collected between 1998 and 2002. The combined data potentially show a high degree
of mixing across a number of North Atlantic regions, including Icelandic and North American
sites. Further investigation will be required to discern whether this pattern is temporally
based (i.e. artefact of 15 years’ elapsed time in opportunities for population mixing), or
whether ecological, anthropogenic, or combined mechanisms are facilitating rapid transport
of propagules to yield a well-mixed population.
Further work in refining prediction and mitigation is still needed, as are effective veterinary
interventions in the event of blooms. Continued study into the ecological patterns of
colonization and dispersal may help to minimize exposure to blooms, by helping to assess
site-based risks. This research forms the basis for such studies into hydrozoan interactions
with salmon farms in Scotland, and how the industry might seek to minimize their impacts.
2016-11-30T00:00:00ZKintner, Anna HelenMedusozoan jellyfish (Classes Scyphozoa and Hydrozoa) have gained a degree of worldwide
notoriety in the last fifteen years, particularly as anthropogenic influences such as climate
change and overfishing push some ecosystems toward their advantage (Lynam et al. 2005,
Purcell and Arai 2001, Purcell et al. 2007, Purcell 2012, Flynn et al. 2012, Dawson et al. 2014).
Accordingly, both the lay and scientific media have paid a good deal of attention to jellyfish
bloom phenomena and their impacts on human activities, but the bulk of this attention has
been devoted to larger, visually obvious species of Class Scyphozoa. Only recently have their
smaller cousins, the hydrozoans, come to be recognized as potentially problematic. This
thesis examines population ecology of hydrozoan medusae (hydromedusae) and their
implications for salmon aquaculture in Scotland.
My review of available literature has found hydrozoans to be a recognized – though under-
studied – problem for Scottish salmon (Chapter 1, Prospective monitoring of hydromedusa
populations at salmon aquaculture facilities). Typically, hydrozoan populations at salmon
farms have been discussed in the scientific literature only in the context of extremely dense
visible blooms or in the wake of major mortality incidents. This retrospective, rather than
prospective, approach has left a dearth of knowledge pertaining to hydromedusan
interactions with farmed fish, with both fish welfare and industry economics vulnerable to
future blooms.
This thesis sought to build a basis for the goals of prediction, avoidance, and mitigation of
harmful hydrozoan jellyfish blooms. First and foremost, this required the development of a
prospective time-series dataset of hydromedusan occurrences at salmon farms (Chapter 2,
Bacterial genera biodiversity in three medusozoan species in Shetland). To this end, four
farms were recruited as participants across a three-year survey. Weekly plankton tow-based
sampling at these sites identified which hydrozoan species could be expected to produce
blooms, the seasonality of such blooms, and the pathological sequelae that could be
expected in salmon after exposure to such blooms. Following one particularly dramatic
bloom, a spike in gill pathologies in salmon was observed, followed by a spike in overall
mortality and the eventual loss of up to £2.5 million value as the fish were humanely culled.
This survey also demonstrated that hydromedusan blooms are usually spatially and
temporally patchy, limiting the opportunities for geographically-encompassing predictive
power. Instead, individual aquaculture facilities may require site-specific risk assessment
and planning frameworks to monitor and cope with blooms. Potential methods for
continued basic monitoring and a mitigation strategy based on minimizing contact between
fish and high-density blooms are suggested.
A second mitigation goal examined the theory that medusae may act as vectors for microbial
pathogens, particularly Tenacibaculum maritimum (Ferguson et al. 2010, Delannoy et al.
2011; Chapter 3). Sampling methods designed to target T. maritimum were employed with
the aim of determining its distribution and role as a symbiont in various life stages of
medusozoan species. While T. maritimum itself was not observed, a number of other fish
pathogens were found in close association with several species. This included Aeromonas
salmonicida, known to cause furunculosis in aquaculture of both salmon and trout (Nomura
et al. 1992). Further work is required to piece together the nature of these associations.
Finally, Chapter 2 identified a particular hydrozoan genus, Obelia, as a likely significant
contributor to blooms at salmon aquaculture sites. One of its species, O. geniculata, has a
widely distributed and well-recognized benthic colonial life stage (called the hydroid stage)
in Scottish nearshore sublittoral environments. In attempting to sample these hydroids from
previously well-colonized sites in Shetland in late 2012, it became apparent that a severe
local reduction in the benthic population was taking place. This allowed for the opportunity
to study phylogeographic population structure – i.e. the boundaries of its gene pool(s) in
Scottish waters and its potential for dispersal during one seasonal reproductive period –
using a molecular study of the mitochondrial cytochrome oxidase subunit I (mtCOI) gene
(Chapter 4, Phylogeographic analysis of Obelia geniculata populations in the north of
Scotland). In sampling immediately after the observed dieback, O. geniculata was found to
follow a south-to-north pattern of genetic grouping, as well as a confirmed dieback.
However, this pattern disappeared in samples collected after the population had recovered,
probably due to the immigration of genetically novel individuals. This finding, in conjunction
with the spatial-temporal patchiness found in the medusa bloom stage, suggests the
importance of the larval stage as the primary stage for dispersal in the plankton. This study
was also able to compare present population genetic data with a set of O. geniculata mtCOI data collected between 1998 and 2002. The combined data potentially show a high degree
of mixing across a number of North Atlantic regions, including Icelandic and North American
sites. Further investigation will be required to discern whether this pattern is temporally
based (i.e. artefact of 15 years’ elapsed time in opportunities for population mixing), or
whether ecological, anthropogenic, or combined mechanisms are facilitating rapid transport
of propagules to yield a well-mixed population.
Further work in refining prediction and mitigation is still needed, as are effective veterinary
interventions in the event of blooms. Continued study into the ecological patterns of
colonization and dispersal may help to minimize exposure to blooms, by helping to assess
site-based risks. This research forms the basis for such studies into hydrozoan interactions
with salmon farms in Scotland, and how the industry might seek to minimize their impacts.The impact of multiple stressors on coastal biodiversity and associated ecosystem servicesWatson, Stephen C. L.https://hdl.handle.net/10023/168172019-03-29T10:39:56Z2017-06-21T00:00:00ZMarine and coastal ecosystems are subject to diverse and increasingly intensive anthropogenic
activities, making understanding cumulative effects critically important. However, accurately
accounting for the cumulative effects of human impacts can be difficult, with the possibility of multiple
stressors interacting and having greater impacts than expected, compounding direct and indirect
effects on individuals, populations, communities and ecosystems. Assessment of multiple stressors
therefore requires extensive scientific research that directly tests how single or multiple ecological
components are affected by stressors, both singly and when combined, and as a consequence,
cumulative effects assessments are now increasingly included in environmental assessments.
Currently, there is a need to assess these at larger spatial scales, with additional research also urgently
needed on the responses of ecological components, processes and functions to single and cumulative
stressors. As cumulative environmental impacts could be better addressed by regional stressor effects
assessments that combine methods for predicting multiple pressures on ecosystem recovery
alongside degradation, this study used several separate approaches that can be used in parallel to give
support for local management measures. I tested four completely different methods – a range of
multi-metric indices, a food web model (Ecopath), a predictive model (Ecosim) and a Bayesian Belief
Network model. Each approach was tested and compared in two shallow water estuarine systems, in
Scotland and England, initially concerning the impact of nutrient enrichment and subsequent recovery
and was followed by an investigation of how the addition of multiple stressors (nutrient levels,
temperature and river-flow rates) would impact the future state of each system. The response to
stressors was highly context dependent, varying between and within geographic locations. Overall,
each of the four different approaches complemented each other and gave strong support for the need
to make big reductions in the pressures and to consider trade-offs between impacting pressures. The
models and tools also indicate that in order to reach an improved overall environmental state of each
ecosystem, a focus on nutrient reductions are likely to be the most effective of the controls on
stressors explored and that cumulative effects of the management of nutrient inputs and increased
water temperatures and river-flow are likely to exist.
2017-06-21T00:00:00ZWatson, Stephen C. L.Marine and coastal ecosystems are subject to diverse and increasingly intensive anthropogenic
activities, making understanding cumulative effects critically important. However, accurately
accounting for the cumulative effects of human impacts can be difficult, with the possibility of multiple
stressors interacting and having greater impacts than expected, compounding direct and indirect
effects on individuals, populations, communities and ecosystems. Assessment of multiple stressors
therefore requires extensive scientific research that directly tests how single or multiple ecological
components are affected by stressors, both singly and when combined, and as a consequence,
cumulative effects assessments are now increasingly included in environmental assessments.
Currently, there is a need to assess these at larger spatial scales, with additional research also urgently
needed on the responses of ecological components, processes and functions to single and cumulative
stressors. As cumulative environmental impacts could be better addressed by regional stressor effects
assessments that combine methods for predicting multiple pressures on ecosystem recovery
alongside degradation, this study used several separate approaches that can be used in parallel to give
support for local management measures. I tested four completely different methods – a range of
multi-metric indices, a food web model (Ecopath), a predictive model (Ecosim) and a Bayesian Belief
Network model. Each approach was tested and compared in two shallow water estuarine systems, in
Scotland and England, initially concerning the impact of nutrient enrichment and subsequent recovery
and was followed by an investigation of how the addition of multiple stressors (nutrient levels,
temperature and river-flow rates) would impact the future state of each system. The response to
stressors was highly context dependent, varying between and within geographic locations. Overall,
each of the four different approaches complemented each other and gave strong support for the need
to make big reductions in the pressures and to consider trade-offs between impacting pressures. The
models and tools also indicate that in order to reach an improved overall environmental state of each
ecosystem, a focus on nutrient reductions are likely to be the most effective of the controls on
stressors explored and that cumulative effects of the management of nutrient inputs and increased
water temperatures and river-flow are likely to exist.BayesPiles : visualisation support for Bayesian network structure learningVogogias, AthanasiosKennedy, JessieArchambault, DanielBach, BenjaminSmith, V AnneCurrant, Hannahhttps://hdl.handle.net/10023/166362023-04-18T23:47:32Z2018-11-01T00:00:00ZWe address the problem of exploring, combining, and comparing large collections of scored, directed networks for understanding inferred Bayesian networks used in biology. In this field, heuristic algorithms explore the space of possible network solutions, sampling this space based on algorithm parameters and a network score that encodes the statistical fit to the data. The goal of the analyst is to guide the heuristic search and decide how to determine a final consensus network structure, usually by selecting the top-scoring network or constructing the consensus network from a collection of high-scoring networks. BayesPiles, our visualisation tool, helps with understanding the structure of the solution space and supporting the construction of a final consensus network that is representative of the underlying dataset. BayesPiles builds upon and extends MultiPiles to meet our domain requirements. We developed BayesPiles in conjunction with computational biologists who have used this tool on datasets used in their research. The biologists found our solution provides them with new insights and helps them achieve results that are representative of the underlying data.
2018-11-01T00:00:00ZVogogias, AthanasiosKennedy, JessieArchambault, DanielBach, BenjaminSmith, V AnneCurrant, HannahWe address the problem of exploring, combining, and comparing large collections of scored, directed networks for understanding inferred Bayesian networks used in biology. In this field, heuristic algorithms explore the space of possible network solutions, sampling this space based on algorithm parameters and a network score that encodes the statistical fit to the data. The goal of the analyst is to guide the heuristic search and decide how to determine a final consensus network structure, usually by selecting the top-scoring network or constructing the consensus network from a collection of high-scoring networks. BayesPiles, our visualisation tool, helps with understanding the structure of the solution space and supporting the construction of a final consensus network that is representative of the underlying dataset. BayesPiles builds upon and extends MultiPiles to meet our domain requirements. We developed BayesPiles in conjunction with computational biologists who have used this tool on datasets used in their research. The biologists found our solution provides them with new insights and helps them achieve results that are representative of the underlying data.Differential responses to gosling distress calls in parental and non-parental Greylag GeeseLoth, AlinaFrigerio, DidoneKotrschal, KurtSzipl, Georginehttps://hdl.handle.net/10023/165322022-04-14T20:35:55Z2018-04-01T00:00:00ZThe pre-fledging survival of Greylag goslings (Anser anser) is known to be influenced by parenting style and particularly parental vigilance. Visual and acoustic cues may be important in parental vigilance: if vision is blocked, for example in a highly structured habitat, acoustic recognition of the goslings by their parents would be beneficial. We confronted parental and non-parental Greylag Geese with playbacks of gosling distress calls and analyzed their behavioral responses. Parental geese showed a significant increase in their vigilance behavior during and after playbacks while geese without offspring showed increased comfort behavior. In a permutated discriminant function analysis, we found no family-specific vocal cues in gosling calls, and potential call familiarity did not have any effect on parental behavioral responses. Vigilance in families was further influenced by the number of goslings and gosling age, with increased vigilance when the number of goslings was high, and when goslings were younger. Parental females were more vigilant than parental males, suggesting differences in parental investment between males and females. We conclude that visual cues may be more important in offspring-related vigilance than calls, which elicited different behavioral responses depending on the social class of the geese.
GS received funding by the Austrian Science Fund (FWF) projects Y-366-B17 and W-1234-G17. AL was funded by the Austrian Federal Ministry of Science, Research and Economy (BMWFW, former BMWF) project SPA/03-005/Graugänse and DF by the Austrian Science Fund (FWF) project P-21489-B17.
2018-04-01T00:00:00ZLoth, AlinaFrigerio, DidoneKotrschal, KurtSzipl, GeorgineThe pre-fledging survival of Greylag goslings (Anser anser) is known to be influenced by parenting style and particularly parental vigilance. Visual and acoustic cues may be important in parental vigilance: if vision is blocked, for example in a highly structured habitat, acoustic recognition of the goslings by their parents would be beneficial. We confronted parental and non-parental Greylag Geese with playbacks of gosling distress calls and analyzed their behavioral responses. Parental geese showed a significant increase in their vigilance behavior during and after playbacks while geese without offspring showed increased comfort behavior. In a permutated discriminant function analysis, we found no family-specific vocal cues in gosling calls, and potential call familiarity did not have any effect on parental behavioral responses. Vigilance in families was further influenced by the number of goslings and gosling age, with increased vigilance when the number of goslings was high, and when goslings were younger. Parental females were more vigilant than parental males, suggesting differences in parental investment between males and females. We conclude that visual cues may be more important in offspring-related vigilance than calls, which elicited different behavioral responses depending on the social class of the geese.Living and learning together : integrating developmental systems theory, radical embodied cognitive science, and relational thinking in the study of social learningPagnotta, Murillohttps://hdl.handle.net/10023/163862019-03-29T10:41:29Z2018-12-06T00:00:00ZBehavioural scientists argue that ‘social learning’ provides the link between biological phenomena and cultural phenomena because of its role in the ‘cultural transmission’ of knowledge among individuals within and across generations. However, leading authors within the social sciences have proposed alternative ways of thinking about social life not founded on the Modern oppositions including nature-culture, biology-culture, body-mind, and individual-society. Similarly, the distinction between a domain of nature and a domain of nurture has also been extensively criticized within biology. Finally, advocates of ‘radical embodied cognitive science’ offer an alternative to the representational-computational view of the mind which supports the conventional notion of culture and cultural information. This thesis attempts to integrate developmental systems theory, radical embodied cognitive science, and relational thinking, with the goal to bring the field of social learning closer to these critical theoretical developments. In Chapter 2, I find no justification for the claim that the genome carries information in the sense of specification of biological form. Chapter 3 presents a view of ontogeny as a historical, relational, constructive and contingent process. Chapter 4 uses the notions of environmental information, abilities, affordances, and intentions to make sense of behaviour and learning. In Chapter 5, I argue that the notion of social learning can be understood in terms of relational histories of development rather than in terms of transmission of information. I then report empirical studies investigating behavioural coordination and social learning consistent with this theoretical framework. Chapter 6 presents evidence that dyads in a joint making activity synchronize their attention constrained by their changing situation and that coordination of attention is predictive of implicit and explicit learning. Chapter 7 presents evidence that joint attention does not require gaze following and that attentional coordination is predictive of learning a manual task. Together, these theoretical and empirical studies suggest a new way of thinking about how humans and other animals live and learn socially, one that is consistent with critical theoretical and philosophical developments that are currently neglected in the literature on social learning.
2018-12-06T00:00:00ZPagnotta, MurilloBehavioural scientists argue that ‘social learning’ provides the link between biological phenomena and cultural phenomena because of its role in the ‘cultural transmission’ of knowledge among individuals within and across generations. However, leading authors within the social sciences have proposed alternative ways of thinking about social life not founded on the Modern oppositions including nature-culture, biology-culture, body-mind, and individual-society. Similarly, the distinction between a domain of nature and a domain of nurture has also been extensively criticized within biology. Finally, advocates of ‘radical embodied cognitive science’ offer an alternative to the representational-computational view of the mind which supports the conventional notion of culture and cultural information. This thesis attempts to integrate developmental systems theory, radical embodied cognitive science, and relational thinking, with the goal to bring the field of social learning closer to these critical theoretical developments. In Chapter 2, I find no justification for the claim that the genome carries information in the sense of specification of biological form. Chapter 3 presents a view of ontogeny as a historical, relational, constructive and contingent process. Chapter 4 uses the notions of environmental information, abilities, affordances, and intentions to make sense of behaviour and learning. In Chapter 5, I argue that the notion of social learning can be understood in terms of relational histories of development rather than in terms of transmission of information. I then report empirical studies investigating behavioural coordination and social learning consistent with this theoretical framework. Chapter 6 presents evidence that dyads in a joint making activity synchronize their attention constrained by their changing situation and that coordination of attention is predictive of implicit and explicit learning. Chapter 7 presents evidence that joint attention does not require gaze following and that attentional coordination is predictive of learning a manual task. Together, these theoretical and empirical studies suggest a new way of thinking about how humans and other animals live and learn socially, one that is consistent with critical theoretical and philosophical developments that are currently neglected in the literature on social learning.Investigation of thioester, isopeptide, and ester domain proteins from Gram-positive pathogensMiller, Ona Kealohahttps://hdl.handle.net/10023/163832021-09-23T07:55:49Z2018-04-17T00:00:00Z2018-04-17T00:00:00ZMiller, Ona KealohaTitle redactedWeckener, Miriamhttps://hdl.handle.net/10023/163412018-10-26T11:43:05Z2018-03-16T00:00:00Z2018-03-16T00:00:00ZWeckener, MiriamAssessing the utility and limitations of accelerometers and machine learning approaches in classifying behaviour during lactation in a phocid sealSchuert, CourtneyPomeroy, PatrickTwiss, Seanhttps://hdl.handle.net/10023/162532024-03-09T00:43:37Z2018-10-16T00:00:00ZBackground: Classifying behaviour with animal-borne accelerometers is quickly becoming a popular tool for remotely observing behavioural states in a variety of species. Most accelerometry work in pinnipeds has focused on classifying behaviour at sea often quantifying behavioural trade-offs associated with foraging and diving in income breeders. Very little work to date has been done to resolve behaviour during the critical period of lactation in a capital breeder. Capital breeding phocids possess finite reserves that they must allocate appropriately to maintain themselves and their new offspring during their brief nursing period. Within this short time, fine-scale behavioural trade-offs can have significant fitness consequences for mother and offspring and must be carefully managed. Here, we present a case study in extracting and classifying lactation behaviours in a wild, breeding pinniped, the grey seal (Halichoerus grypus). Results: Using random forest models, we were able to resolve 4 behavioural states that constitute the majority of a female grey seals’ activity budget during lactation. Resting, alert, nursing, and a form of pup interaction were extracted and classified reliably. For the first time, we quantified the potential confounding variance associated with individual differences in a wild context as well as differences due to sampling location in a largely inactive model species. Conclusions: At this stage, the majority of a female grey seal’s activity budget was classified well using accelerometers, but some rare and context-dependent behaviours were not well captured. While we did find significant variation between individuals in behavioural mechanics, individuals did not differ significantly within themselves; inter-individual variability should be an important consideration in future efforts. These methods can be extended to other efforts to study grey seals and other pinnipeds who exhibit a capital breeding system. Using accelerometers to classify behaviour during lactation allows for fine-scale assessments of time and energy trade-offs for species with fixed stores.
Funding for this work was provided by the Durham Doctoral Studentship scheme at Durham University and supported by Natural Environment Research Council’s core funding to the Sea Mammal Research Unit at the University of St. Andrews.
2018-10-16T00:00:00ZSchuert, CourtneyPomeroy, PatrickTwiss, SeanBackground: Classifying behaviour with animal-borne accelerometers is quickly becoming a popular tool for remotely observing behavioural states in a variety of species. Most accelerometry work in pinnipeds has focused on classifying behaviour at sea often quantifying behavioural trade-offs associated with foraging and diving in income breeders. Very little work to date has been done to resolve behaviour during the critical period of lactation in a capital breeder. Capital breeding phocids possess finite reserves that they must allocate appropriately to maintain themselves and their new offspring during their brief nursing period. Within this short time, fine-scale behavioural trade-offs can have significant fitness consequences for mother and offspring and must be carefully managed. Here, we present a case study in extracting and classifying lactation behaviours in a wild, breeding pinniped, the grey seal (Halichoerus grypus). Results: Using random forest models, we were able to resolve 4 behavioural states that constitute the majority of a female grey seals’ activity budget during lactation. Resting, alert, nursing, and a form of pup interaction were extracted and classified reliably. For the first time, we quantified the potential confounding variance associated with individual differences in a wild context as well as differences due to sampling location in a largely inactive model species. Conclusions: At this stage, the majority of a female grey seal’s activity budget was classified well using accelerometers, but some rare and context-dependent behaviours were not well captured. While we did find significant variation between individuals in behavioural mechanics, individuals did not differ significantly within themselves; inter-individual variability should be an important consideration in future efforts. These methods can be extended to other efforts to study grey seals and other pinnipeds who exhibit a capital breeding system. Using accelerometers to classify behaviour during lactation allows for fine-scale assessments of time and energy trade-offs for species with fixed stores.The identification and investigation of neurochondrin as a novel interactor of the survival of motor neuron protein, through analysis of the interactomes of Sm family proteins and cell fractionationThompson, Lukehttps://hdl.handle.net/10023/161542019-01-08T10:52:35Z2018-06-27T00:00:00ZSpinal Muscular Atrophy (SMA) is a neurodegenerative, inherited disease caused by an insufficient amount of functional Survival of Motor Neurone protein (SMN), though the exact mechanism underlying this is not fully understood. The primary function of SMN is assembling a ring of Sm proteins around small nuclear RNA (snRNA) in an early, cytoplasmic stage of small nuclear ribonucleoprotein (snRNP) biogenesis, a process essential in eukaryotes. SMN, together with several mRNA binding proteins, has been linked to neural transport of mRNA towards areas of growth in Motor neurons for local translation of transcripts. Previous research in our group has found that this may involve Coatomer protein-containing vesicles transported by Dynein and requiring the Sm family protein, SmB, for maintenance. Little is known, however, about what other proteins are also present and required for correct transport and localisation of these vesicles.
To further investigate this, we have produced plasmids expressing each Sm protein tagged to fluorescent proteins to help track their behaviour, in some cases for the first time, and developed a detergent-free fractionation protocol to enrich for SMN containing vesicles, providing tools that can be used to further probe behaviour and interactions in the future. Using these approaches, SmN, a neural specific Sm protein, was identified to also be present in SMN-containing vesicles similarly to SmB. Analysis of the interactomes of different Sm proteins identified a novel interactor of SMN, Neurochondrin (NCDN), that appears to be required for the correct localisation of SMN in neural cells. NCDN was found to not associate with snRNPs, indicating an snRNP-independent interaction with SMN. NCDN and SMN both independently associated and co-enriched with Rab5, indicating a potential endocytic and cell polarity role for the interaction. This interaction has the potential to be key in SMA pathology and may have therapeutic potential.
2018-06-27T00:00:00ZThompson, LukeSpinal Muscular Atrophy (SMA) is a neurodegenerative, inherited disease caused by an insufficient amount of functional Survival of Motor Neurone protein (SMN), though the exact mechanism underlying this is not fully understood. The primary function of SMN is assembling a ring of Sm proteins around small nuclear RNA (snRNA) in an early, cytoplasmic stage of small nuclear ribonucleoprotein (snRNP) biogenesis, a process essential in eukaryotes. SMN, together with several mRNA binding proteins, has been linked to neural transport of mRNA towards areas of growth in Motor neurons for local translation of transcripts. Previous research in our group has found that this may involve Coatomer protein-containing vesicles transported by Dynein and requiring the Sm family protein, SmB, for maintenance. Little is known, however, about what other proteins are also present and required for correct transport and localisation of these vesicles.
To further investigate this, we have produced plasmids expressing each Sm protein tagged to fluorescent proteins to help track their behaviour, in some cases for the first time, and developed a detergent-free fractionation protocol to enrich for SMN containing vesicles, providing tools that can be used to further probe behaviour and interactions in the future. Using these approaches, SmN, a neural specific Sm protein, was identified to also be present in SMN-containing vesicles similarly to SmB. Analysis of the interactomes of different Sm proteins identified a novel interactor of SMN, Neurochondrin (NCDN), that appears to be required for the correct localisation of SMN in neural cells. NCDN was found to not associate with snRNPs, indicating an snRNP-independent interaction with SMN. NCDN and SMN both independently associated and co-enriched with Rab5, indicating a potential endocytic and cell polarity role for the interaction. This interaction has the potential to be key in SMA pathology and may have therapeutic potential.Evolution of muscle regulatory genes in chordatesColl-Lladó, Clarahttps://hdl.handle.net/10023/161362018-12-12T11:18:27Z2016-11-30T00:00:00Z2016-11-30T00:00:00ZColl-Lladó, ClaraDistinguishing pollination from visitation : the value of a pollinator effectiveness and pollinator importance networkCunnold, Helen Elizabethhttps://hdl.handle.net/10023/161212020-02-29T03:03:12Z2018-06-27T00:00:00ZFor over twenty years, flower-visitation networks have been used to assess the effects of
pollinator decline, linked to habitat loss, climate change and invasive species, on entire
communities. However, most rely on flower visit frequency as a proxy for pollination; very
few sample pollen from flower visitor’s bodies or from stigmas and so do not include a
quantitative measure of pollination success. Here, I add pollinator effectiveness (as single visit
pollen deposition) into a traditional flower visitation network, creating a pollinator importance
network that better evaluates the flower visitor community from the plant’s perspective. Given
recent interest in pollination in urban areas, I use an urban garden habitat, and compare
visitation, pollen transport and pollinator importance networks, giving several novel
conclusions.
Firstly, although there are similarities in the structure of my networks, interactions were
most specialised in the pollinator importance network, with pollen transport proving to be a
better proxy for pollinator importance than visitation alone. Secondly, the specialisation of
individual plants and the role of individual flower visitors varied between the networks,
suggesting that community-level patterns in simple visitation networks can mask important
individual differences. Thirdly, the correlation between flower visit frequency and pollinator
importance largely depends on bees, and may not hold in plant-pollinator communities that are
not bee-dominated. Fourthly, heterospecific pollen deposition was relatively low, despite the
unusually diverse plant community of a garden. Finally, bees (particularly Bombus and non-eusocial halictids) carried the largest pollen loads and were the most effective at depositing
pollen on to the stigma during a single visit in this garden habitat.
The implications of this thesis highlight the strengths and limitations of each network for
future studies, and raise important questions for the future of urban pollination studies.
2018-06-27T00:00:00ZCunnold, Helen ElizabethFor over twenty years, flower-visitation networks have been used to assess the effects of
pollinator decline, linked to habitat loss, climate change and invasive species, on entire
communities. However, most rely on flower visit frequency as a proxy for pollination; very
few sample pollen from flower visitor’s bodies or from stigmas and so do not include a
quantitative measure of pollination success. Here, I add pollinator effectiveness (as single visit
pollen deposition) into a traditional flower visitation network, creating a pollinator importance
network that better evaluates the flower visitor community from the plant’s perspective. Given
recent interest in pollination in urban areas, I use an urban garden habitat, and compare
visitation, pollen transport and pollinator importance networks, giving several novel
conclusions.
Firstly, although there are similarities in the structure of my networks, interactions were
most specialised in the pollinator importance network, with pollen transport proving to be a
better proxy for pollinator importance than visitation alone. Secondly, the specialisation of
individual plants and the role of individual flower visitors varied between the networks,
suggesting that community-level patterns in simple visitation networks can mask important
individual differences. Thirdly, the correlation between flower visit frequency and pollinator
importance largely depends on bees, and may not hold in plant-pollinator communities that are
not bee-dominated. Fourthly, heterospecific pollen deposition was relatively low, despite the
unusually diverse plant community of a garden. Finally, bees (particularly Bombus and non-eusocial halictids) carried the largest pollen loads and were the most effective at depositing
pollen on to the stigma during a single visit in this garden habitat.
The implications of this thesis highlight the strengths and limitations of each network for
future studies, and raise important questions for the future of urban pollination studies.Decision-making across species, contexts, and behaviourGlaser, Georgina Louisehttps://hdl.handle.net/10023/160242023-06-26T12:46:40Z2018-06-27T00:00:00Z2018-06-27T00:00:00ZGlaser, Georgina LouiseThe evolutionary causes and consequences of polyandry in Nasonia vitripennisBoulton, Rebecca A.https://hdl.handle.net/10023/156962023-03-14T12:50:33Z2016-01-01T00:00:00ZExplaining the ubiquity of and variation in female multiple mating remains a key problem in evolutionary ecology. Much of the empirical work regarding the costs and benefits of mating has for obvious reasons relied on species that are already polyandrous. In this thesis I investigate the costs and benefits of polyandry in the parasitoid wasp Nasonia vitripennis, which is mostly monandrous in the wild, but that evolves polyandry under laboratory culture conditions. This has given me the rare opportunity to explore what initiated the evolution of polyandry, rather than what maintains it. In N. vitripennis polyandrous females gain a fecundity benefit when mating with virgin males. However mating also results in a sex allocation cost. Females produce more male biased sex ratios immediately after mating resulting in reduced fitness. I found no evidence that this sex allocation cost occurred because males block, displace or incapacitate the sperm of their rivals, instead it appears that this cost represents a female physiological constraint. Additionally, N. vitripennis females are more likely to re-mate when hosts are available and male density is high. However, mating under these conditions does not mitigate the costs of harassment, arguing against convenience polyandry. My results demonstrate that changing the local mating structure alters the economics of mating. In the wild females oviposit alone and maximise their fitness by laying mostly daughters. In laboratory culture many females oviposit together which reduces selection on adaptive sex allocation so the ‘sex allocation cost’ of polyandry is lifted. Furthermore, less female-biased sex ratios in the laboratory increase the opportunity for polyandrous females to benefit from re-mating with virgin males. My work highlights how studying monandrous species could be key to understanding why polyandry is so ubiquitous in nature, studying the exceptions may in this case help us to understand the rule.
2016-01-01T00:00:00ZBoulton, Rebecca A.Explaining the ubiquity of and variation in female multiple mating remains a key problem in evolutionary ecology. Much of the empirical work regarding the costs and benefits of mating has for obvious reasons relied on species that are already polyandrous. In this thesis I investigate the costs and benefits of polyandry in the parasitoid wasp Nasonia vitripennis, which is mostly monandrous in the wild, but that evolves polyandry under laboratory culture conditions. This has given me the rare opportunity to explore what initiated the evolution of polyandry, rather than what maintains it. In N. vitripennis polyandrous females gain a fecundity benefit when mating with virgin males. However mating also results in a sex allocation cost. Females produce more male biased sex ratios immediately after mating resulting in reduced fitness. I found no evidence that this sex allocation cost occurred because males block, displace or incapacitate the sperm of their rivals, instead it appears that this cost represents a female physiological constraint. Additionally, N. vitripennis females are more likely to re-mate when hosts are available and male density is high. However, mating under these conditions does not mitigate the costs of harassment, arguing against convenience polyandry. My results demonstrate that changing the local mating structure alters the economics of mating. In the wild females oviposit alone and maximise their fitness by laying mostly daughters. In laboratory culture many females oviposit together which reduces selection on adaptive sex allocation so the ‘sex allocation cost’ of polyandry is lifted. Furthermore, less female-biased sex ratios in the laboratory increase the opportunity for polyandrous females to benefit from re-mating with virgin males. My work highlights how studying monandrous species could be key to understanding why polyandry is so ubiquitous in nature, studying the exceptions may in this case help us to understand the rule.Title redactedWebster, Clare Noellehttps://hdl.handle.net/10023/156952019-07-25T11:52:55Z2016-01-01T00:00:00Z2016-01-01T00:00:00ZWebster, Clare NoelleAn investigation into the (2-aminoethyl)phosphonate pathway in Trypanosoma cruzi - etiological agent of Chagas' diseaseCoron, Ross P.https://hdl.handle.net/10023/156892023-12-07T16:57:41Z2016-01-01T00:00:00ZThe neglected tropical disease, American Trypanosomiasis (also known as Chagas’
disease) is the most important parasitic infection in Latin America, and the most lethal
endemic infectious disease in the Western Hemisphere. 8‐9 million individuals are
currently infected with the disease, and a further 25 million are at risk. Currently
available chemotherapies approved for the treatment of Chagas’ disease are ageing,
ineffective, and exhibit severe side effects ‐ new treatments are urgently required.
One possible drug target against Trypanosoma cruzi ‐ the protozoan etiological agent
of Chagas’ disease ‐ is the biosynthesis of the parasitic glycosylphosphatidylinositol
(GPI) anchor and GPI‐related molecules such as glycosylinositolphospholipids (GIPLs),
which dominate the organism’s cell surface. Despite structural variations, these
complex structures are ubiquitously decorated with an unusual (2‐aminoethyl)
phosphonate (AEP) moiety on the O‐6 of glucosamine in the GPI core motif, and is
hypothesized to play a role in both host‐infection and parasitic persistence. Entirely
absent in higher eukaryotes ‐ including humans ‐ a greater understanding of the
Trypanosoma cruzi AEP biosynthetic / biodegradative pathway may allow for the
development of novel, parasite‐specific chemotherapeutics.
This study determined the essentiality of the T. cruzi AEP biosynthetic / biodegradative
pathway through both chemical and genetic methodologies, including a classical two‐
step gene replacement and ectopic reintroduction strategy. Validation was provided
through both qRT‐PCR and Southern blot analysis. The resulting genetically modified cell‐line phenotypes were extensively described through a number of techniques
including: cell growth studies, radiolabelling experiments, gas chromatography mass‐spectrometry (GC‐MS), multiple reaction monitoring mass‐spectrometry (MRM), and
lipidomic analysis.
Furthermore, the three enzymes of the poorly characterised T. cruzi AEP biosynthetic
pathway (i.e. phosphoenolpyruvate mutase, phosphonopyruvate decarboxylase, and
(2‐aminoethyl)phosphonate transaminase) were recombinantly expressed and purified
for characterization through a series of biochemical assays. Immunofluorescence
microscopy studies additionally were performed to determine the subcellular
localization of these enzymes. Significant progress was also made in generating a
crystal structure of the T. cruzi PEP mutase enzyme, whilst in silico modeling efforts
provided catalytic insights into the TcAEP pathway enzymes in the interim. An
interrogation of the T. cruzi genome provided evidence that the parasite does not
encode for phosphonoacetaldehyde hydrolase (phosphonatase) ‐ an enzyme present
in a number of other organisms capable of AEP biosynthesis. High throughput
screening of compounds by differential scanning fluorimetry (DSF) was additionally
performed against the T. cruzi AEP transaminase. Putative hits were further screened
against T. cruzi epimastigotes in vivo. These efforts identified a number of fragments
with EC₅₀ values in‐line with the current frontline treatment against Chagas’ disease.
Finally, this body of work also reported the putative identification of a novel, high‐energy donor of AEP, and other AEP‐containing metabolites through both lipidomic
and mass‐spectrometric techniques.
2016-01-01T00:00:00ZCoron, Ross P.The neglected tropical disease, American Trypanosomiasis (also known as Chagas’
disease) is the most important parasitic infection in Latin America, and the most lethal
endemic infectious disease in the Western Hemisphere. 8‐9 million individuals are
currently infected with the disease, and a further 25 million are at risk. Currently
available chemotherapies approved for the treatment of Chagas’ disease are ageing,
ineffective, and exhibit severe side effects ‐ new treatments are urgently required.
One possible drug target against Trypanosoma cruzi ‐ the protozoan etiological agent
of Chagas’ disease ‐ is the biosynthesis of the parasitic glycosylphosphatidylinositol
(GPI) anchor and GPI‐related molecules such as glycosylinositolphospholipids (GIPLs),
which dominate the organism’s cell surface. Despite structural variations, these
complex structures are ubiquitously decorated with an unusual (2‐aminoethyl)
phosphonate (AEP) moiety on the O‐6 of glucosamine in the GPI core motif, and is
hypothesized to play a role in both host‐infection and parasitic persistence. Entirely
absent in higher eukaryotes ‐ including humans ‐ a greater understanding of the
Trypanosoma cruzi AEP biosynthetic / biodegradative pathway may allow for the
development of novel, parasite‐specific chemotherapeutics.
This study determined the essentiality of the T. cruzi AEP biosynthetic / biodegradative
pathway through both chemical and genetic methodologies, including a classical two‐
step gene replacement and ectopic reintroduction strategy. Validation was provided
through both qRT‐PCR and Southern blot analysis. The resulting genetically modified cell‐line phenotypes were extensively described through a number of techniques
including: cell growth studies, radiolabelling experiments, gas chromatography mass‐spectrometry (GC‐MS), multiple reaction monitoring mass‐spectrometry (MRM), and
lipidomic analysis.
Furthermore, the three enzymes of the poorly characterised T. cruzi AEP biosynthetic
pathway (i.e. phosphoenolpyruvate mutase, phosphonopyruvate decarboxylase, and
(2‐aminoethyl)phosphonate transaminase) were recombinantly expressed and purified
for characterization through a series of biochemical assays. Immunofluorescence
microscopy studies additionally were performed to determine the subcellular
localization of these enzymes. Significant progress was also made in generating a
crystal structure of the T. cruzi PEP mutase enzyme, whilst in silico modeling efforts
provided catalytic insights into the TcAEP pathway enzymes in the interim. An
interrogation of the T. cruzi genome provided evidence that the parasite does not
encode for phosphonoacetaldehyde hydrolase (phosphonatase) ‐ an enzyme present
in a number of other organisms capable of AEP biosynthesis. High throughput
screening of compounds by differential scanning fluorimetry (DSF) was additionally
performed against the T. cruzi AEP transaminase. Putative hits were further screened
against T. cruzi epimastigotes in vivo. These efforts identified a number of fragments
with EC₅₀ values in‐line with the current frontline treatment against Chagas’ disease.
Finally, this body of work also reported the putative identification of a novel, high‐energy donor of AEP, and other AEP‐containing metabolites through both lipidomic
and mass‐spectrometric techniques.Title redactedPritchard, David Jameshttps://hdl.handle.net/10023/156822018-11-20T10:33:13Z2016-01-01T00:00:00Z2016-01-01T00:00:00ZPritchard, David JamesTitle redactedMartín López, Lucía Martinahttps://hdl.handle.net/10023/156762019-11-21T09:41:54Z2016-01-01T00:00:00Z2016-01-01T00:00:00ZMartín López, Lucía MartinaGetting below the surface : density estimation methods for deep diving animals using slow autonomous underwater vehiclesGkikopoulou, Kalliopi Charitomenihttps://hdl.handle.net/10023/156452023-03-20T13:35:47Z2018-01-01T00:00:00ZUnderwater gliders can provide an alternative cost-effective platform for passive acoustic monitoring surveys, compared to boat surveys, for abundance estimation and to collect high resolution environmental data for habitat studies. Gliders are usually equipped with one acoustic sensor, which limits the methods available for abundance estimation from acoustic data. Estimation of parameters used in distance sampling methodology, such as the detection function and cue rates, must be estimated separately from the glider deployment. A methodology for deriving the acoustic detection function of vocal animals is demonstrated in chapter 2 with a combined biologging and passive acoustic experiment. The methodology consists of distance estimation of the clicks produced by the tagged animal and detected at acoustic receivers placed at different depths, using surface bounce detections to estimate range. In addition, different detection algorithms were tested for the detectability of Blainville’s beaked whales. Detectability was found to vary with depth for Blainville’s beaked whales in the area of El Hierro (Canary Islands). The depth dependent detectability for this species was tested further in chapter 3 with a wider dataset from two different geographic populations of Blainville’s beaked whales, those of El Hierro and the Bahamas. Differences in detectability were found using depth and animal movement data as recorded on the DTAG in a simulated network of receivers placed at different depths. In addition, sequences of clicks, called click scans, were tested as an additional “cue” for cue counting methodology. The high directionality of beaked whale regular clicks leads to reduced detection ranges for receivers close to the surface or for receivers placed much deeper than the foraging depths of the wales and this reduction translates into varying lengths and numbers of detected click clusters as a function of distance and receiver depth. Chapter 4 presents a method for estimating density of animals from underwater gliders and tests the method in a simulated glider survey using different distribution and density scenarios using clicks and click scans as cue for density estimation.
2018-01-01T00:00:00ZGkikopoulou, Kalliopi CharitomeniUnderwater gliders can provide an alternative cost-effective platform for passive acoustic monitoring surveys, compared to boat surveys, for abundance estimation and to collect high resolution environmental data for habitat studies. Gliders are usually equipped with one acoustic sensor, which limits the methods available for abundance estimation from acoustic data. Estimation of parameters used in distance sampling methodology, such as the detection function and cue rates, must be estimated separately from the glider deployment. A methodology for deriving the acoustic detection function of vocal animals is demonstrated in chapter 2 with a combined biologging and passive acoustic experiment. The methodology consists of distance estimation of the clicks produced by the tagged animal and detected at acoustic receivers placed at different depths, using surface bounce detections to estimate range. In addition, different detection algorithms were tested for the detectability of Blainville’s beaked whales. Detectability was found to vary with depth for Blainville’s beaked whales in the area of El Hierro (Canary Islands). The depth dependent detectability for this species was tested further in chapter 3 with a wider dataset from two different geographic populations of Blainville’s beaked whales, those of El Hierro and the Bahamas. Differences in detectability were found using depth and animal movement data as recorded on the DTAG in a simulated network of receivers placed at different depths. In addition, sequences of clicks, called click scans, were tested as an additional “cue” for cue counting methodology. The high directionality of beaked whale regular clicks leads to reduced detection ranges for receivers close to the surface or for receivers placed much deeper than the foraging depths of the wales and this reduction translates into varying lengths and numbers of detected click clusters as a function of distance and receiver depth. Chapter 4 presents a method for estimating density of animals from underwater gliders and tests the method in a simulated glider survey using different distribution and density scenarios using clicks and click scans as cue for density estimation.Membrane interactions of plant virus movement proteinsAitken, Angus Iainhttps://hdl.handle.net/10023/156172019-10-15T10:10:46Z2018-01-01T00:00:00ZPlant viruses post a significant risk to both global food security, and industrial agriculture, however very little is known regarding their molecular mechanisms. Despite intensive study since the discovery of a multitude of plant virtual movement proteins, it remains unknown how they transverse the plasmodesmata, and thus move between cells. The CMV virus is widespread, infecting over a thousand plant species, and yet the means by which the movement protein CMV 3a associates to cellular membranes, targets itself and viral genomes to plasmodesmata have not been described. This study initially attempted to purify the CMV 3a protein from bacterial expression for structural and biophysical studies to examine viral protein and host membrane interactions. The study also began mapping the CMV 3a protein surface to investigate protein localisation and membrane attachment in planta, identifying structural features, including two potentially amphipathic helices which bear further investigation for potential roles in membrane association. Finally, this thesis examined the potential for the lipid modification S-acylation (Palmitoylation) as a membrane anchor, across a range of viral movement proteins. Describing this modification of viral movement proteins for the first time, S-acylation was demonstrated to not only be widespread, but potentially play different roles across a range of plant virus movement systems. This information is vital for the advancement of the field’s understanding of the cell to cell movement of plant viruses, and the potential development of control strategies; and hence the safeguarding of global food security.
2018-01-01T00:00:00ZAitken, Angus IainPlant viruses post a significant risk to both global food security, and industrial agriculture, however very little is known regarding their molecular mechanisms. Despite intensive study since the discovery of a multitude of plant virtual movement proteins, it remains unknown how they transverse the plasmodesmata, and thus move between cells. The CMV virus is widespread, infecting over a thousand plant species, and yet the means by which the movement protein CMV 3a associates to cellular membranes, targets itself and viral genomes to plasmodesmata have not been described. This study initially attempted to purify the CMV 3a protein from bacterial expression for structural and biophysical studies to examine viral protein and host membrane interactions. The study also began mapping the CMV 3a protein surface to investigate protein localisation and membrane attachment in planta, identifying structural features, including two potentially amphipathic helices which bear further investigation for potential roles in membrane association. Finally, this thesis examined the potential for the lipid modification S-acylation (Palmitoylation) as a membrane anchor, across a range of viral movement proteins. Describing this modification of viral movement proteins for the first time, S-acylation was demonstrated to not only be widespread, but potentially play different roles across a range of plant virus movement systems. This information is vital for the advancement of the field’s understanding of the cell to cell movement of plant viruses, and the potential development of control strategies; and hence the safeguarding of global food security.Causes and consequences of mating failure in the LygaeidaeGreenway, Elisabeth Virginiahttps://hdl.handle.net/10023/156152020-09-04T06:40:18Z2018-01-01T00:00:00ZNatural selection should favour fertile individuals who are able to successfully copulate and pass or receive sperm. However a non-trivial number of copulations fail to result in offspring production across a wide range of taxa, despite investment in securing access to mates and their gametes. Over the course of this thesis, I investigate both the causes and consequences of this phenomenon in the seed bug species Lygaeus simulans, in which mating failure rates of up to 60% have been documented. Lygaeids are highly polyandrous and engage in prolonged matings and males possess elongate genitalia which display high levels of inter-specific morphological diversity. Despite this variation, after performing comparative behavioural trials across five related lygaeid species, I found mating failure rates were ubiquitously high. Upon dissection, mating failure was shown to be predominantly caused by sperm transfer failure. Rather than occurring randomly, these mating failures were significantly repeatable within individual males, constituting a male-associated phenotype. Subsequent quantitative genetic analysis revealed genetic variation underlying failure and associated behavioural traits, but no heritability, implying high levels of environmental variation determine this phenotype. Despite the non-random occurrence of mating failure, ‘L. simulans’ females were found to show no pre-copulatory discrimination between previously successful and previously unsuccessful mates. In an effort to establish if cryptic female choice is partially responsible for the rates of mating failure observed I then experimentally manipulated female muscular control during mating using anaesthesia. Female anaesthesia greatly shortened mating duration, but I found little conclusive evidence that females either actively prevent or enable successful male intromission. Uncovering and characterising the presence of such counter-intuitively high and potentially adaptive levels of mating failure challenges out understanding of how natural and sexual selection shape primary sexual function and fertility, and highlights the importance of post-copulatory interactions in successful reproduction.
2018-01-01T00:00:00ZGreenway, Elisabeth VirginiaNatural selection should favour fertile individuals who are able to successfully copulate and pass or receive sperm. However a non-trivial number of copulations fail to result in offspring production across a wide range of taxa, despite investment in securing access to mates and their gametes. Over the course of this thesis, I investigate both the causes and consequences of this phenomenon in the seed bug species Lygaeus simulans, in which mating failure rates of up to 60% have been documented. Lygaeids are highly polyandrous and engage in prolonged matings and males possess elongate genitalia which display high levels of inter-specific morphological diversity. Despite this variation, after performing comparative behavioural trials across five related lygaeid species, I found mating failure rates were ubiquitously high. Upon dissection, mating failure was shown to be predominantly caused by sperm transfer failure. Rather than occurring randomly, these mating failures were significantly repeatable within individual males, constituting a male-associated phenotype. Subsequent quantitative genetic analysis revealed genetic variation underlying failure and associated behavioural traits, but no heritability, implying high levels of environmental variation determine this phenotype. Despite the non-random occurrence of mating failure, ‘L. simulans’ females were found to show no pre-copulatory discrimination between previously successful and previously unsuccessful mates. In an effort to establish if cryptic female choice is partially responsible for the rates of mating failure observed I then experimentally manipulated female muscular control during mating using anaesthesia. Female anaesthesia greatly shortened mating duration, but I found little conclusive evidence that females either actively prevent or enable successful male intromission. Uncovering and characterising the presence of such counter-intuitively high and potentially adaptive levels of mating failure challenges out understanding of how natural and sexual selection shape primary sexual function and fertility, and highlights the importance of post-copulatory interactions in successful reproduction.An assessment of MODIS products in the Southern Ocean using tagged southern elephant seals, in the context of an increasingly positive Southern Annular ModeBiermann, Laurenhttps://hdl.handle.net/10023/156132019-10-18T02:00:51Z2018-01-01T00:00:00ZThe Southern Ocean maintains a complex, dynamic marine food web based on its
stock of photosynthesising phytoplankton. For the same reason, it is our most significant sink of carbon, vital to functioning of global atmospheric systems. However,
this key polar ocean is also responsive to atmospheric variability dominated by the
Southern Annular Mode (SAM), with unknown implications for phytoplankton patterns in space and over time.
MODIS surface chlorophyll-a concentration ([Chl-a]) and the depth of the 1% light
level (Z[sub]eu) were evaluated against in situ fluorescence and light data collected by
tagged southern elephant seals. Light data were processed to minimize self-shading
and environmental sources of variability, and Lee Z[sub]eu outperformed Morel Z[sub]eu when
examined relative to the resultant in situ measures of the 1% light level. Based on these
results, fluorescence data were corrected for quenching at the surface using Lee Z[sub]eu
as a reference depth; conserving deep chlorophyll maxima within hydrographically
defined mixed layers. [Chl-a] was evaluated against quenching-corrected fluorescence
and satellite products mirrored in situ trends over time.
The MODIS timeseries was interrogated for spatio-temporal shifts to phytoplankton abundance in surface waters. Trends over 13 years of austral summers point to
overall declines and perturbations to the timing of the bloom, with changes that were
significantly related to the SAM presenting as regional rather than annular. In this
context, to assess if perturbations may impact top predators, the at-sea behaviour of
tagged seals were examined relative to the fluorescence and light data they collected.
Using a cumulative sums analysis of speed, foraging phases were distinguishable
from ’outbound’ and ’homebound’ travel. When all phases were examined relative to
fluorescence and the 1% light level, foraging appeared to be associated with increased
phytoplankton abundance. This suggests that the future of these marine predators
may be linked to shifting phytoplankton patterns.
2018-01-01T00:00:00ZBiermann, LaurenThe Southern Ocean maintains a complex, dynamic marine food web based on its
stock of photosynthesising phytoplankton. For the same reason, it is our most significant sink of carbon, vital to functioning of global atmospheric systems. However,
this key polar ocean is also responsive to atmospheric variability dominated by the
Southern Annular Mode (SAM), with unknown implications for phytoplankton patterns in space and over time.
MODIS surface chlorophyll-a concentration ([Chl-a]) and the depth of the 1% light
level (Z[sub]eu) were evaluated against in situ fluorescence and light data collected by
tagged southern elephant seals. Light data were processed to minimize self-shading
and environmental sources of variability, and Lee Z[sub]eu outperformed Morel Z[sub]eu when
examined relative to the resultant in situ measures of the 1% light level. Based on these
results, fluorescence data were corrected for quenching at the surface using Lee Z[sub]eu
as a reference depth; conserving deep chlorophyll maxima within hydrographically
defined mixed layers. [Chl-a] was evaluated against quenching-corrected fluorescence
and satellite products mirrored in situ trends over time.
The MODIS timeseries was interrogated for spatio-temporal shifts to phytoplankton abundance in surface waters. Trends over 13 years of austral summers point to
overall declines and perturbations to the timing of the bloom, with changes that were
significantly related to the SAM presenting as regional rather than annular. In this
context, to assess if perturbations may impact top predators, the at-sea behaviour of
tagged seals were examined relative to the fluorescence and light data they collected.
Using a cumulative sums analysis of speed, foraging phases were distinguishable
from ’outbound’ and ’homebound’ travel. When all phases were examined relative to
fluorescence and the 1% light level, foraging appeared to be associated with increased
phytoplankton abundance. This suggests that the future of these marine predators
may be linked to shifting phytoplankton patterns.Modal arguments, possible evidence and contingent metaphysicsTraynor, Michael Thomashttps://hdl.handle.net/10023/155952019-03-29T10:34:36Z2017-01-01T00:00:00ZThe present work explores various ways in which contingent evidence can impact
metaphysics, while advocating that, just as a scientific realist allows for ampliative inferences to the unobservable, ampliative inferences from possible evidence can warrant possibility claims that lie beyond the reach of sensorial imagination. In slogan form: possible evidence is a guide to possibility. Drawing on Shoemaker’s (1969) argument for the possibility of time without change, I advocate the following principle: If there is a possible world at which the observable facts make it objectively reasonable to conclude that p, then we should conclude that p is possibly true. This provides a route to contingentism in metaphysics, for, if one considers that there are worlds in which the observable facts make it objectively reasonable to conclude that p, and worlds in which the observable facts make it objectively reasonable to conclude that not-p, then my principle tells us that we should conclude that possibly-p and possibly not-p, i.e. that p is contingent. This contingency in what is reasonable to conclude, I suggest, occurs most saliently in debates where evidence of phenomenal experience and empirical science are marshalled to support one theory over another. I also explore some consequences of taking possible evidence to be a guide to possibility in this way, among them being an interesting modal analogue of the lottery paradox.
2017-01-01T00:00:00ZTraynor, Michael ThomasThe present work explores various ways in which contingent evidence can impact
metaphysics, while advocating that, just as a scientific realist allows for ampliative inferences to the unobservable, ampliative inferences from possible evidence can warrant possibility claims that lie beyond the reach of sensorial imagination. In slogan form: possible evidence is a guide to possibility. Drawing on Shoemaker’s (1969) argument for the possibility of time without change, I advocate the following principle: If there is a possible world at which the observable facts make it objectively reasonable to conclude that p, then we should conclude that p is possibly true. This provides a route to contingentism in metaphysics, for, if one considers that there are worlds in which the observable facts make it objectively reasonable to conclude that p, and worlds in which the observable facts make it objectively reasonable to conclude that not-p, then my principle tells us that we should conclude that possibly-p and possibly not-p, i.e. that p is contingent. This contingency in what is reasonable to conclude, I suggest, occurs most saliently in debates where evidence of phenomenal experience and empirical science are marshalled to support one theory over another. I also explore some consequences of taking possible evidence to be a guide to possibility in this way, among them being an interesting modal analogue of the lottery paradox.The diffusion of culture: computational and statistical models of social learning and cultural transmissionOunsley, James P.https://hdl.handle.net/10023/155272019-01-14T09:41:00Z2017-01-01T00:00:00ZCulture is a hugely important process in the evolution of humans and many non-human animals. Through the formation of long lasting traditions, culture provides an extragenetic inheritance mechanism that can facilitate rapid behavioural adaptation to novel environments. This can ultimately alter the selection pressures acting on different phenotypes including those that underlie cultural transmission itself, i.e. the mechanisms of social learning.
Understanding culture poses many challenges for researchers due to the complex nature of interacting biological processes at multiple organisational and temporal scales. In this thesis I investigate some of these complexities through the integration of different theoretical and statistical modelling approaches, and argue that rich models are particularly important for the study of culture.
In chapters 3 & 4 I use an evolutionary agent-based model to study the functional value and cultural significance of strategically copying from other individuals based on particular cues, such as age or payoff. I find that a bias to copy the successful can provide substantial adaptive advantages, potentially outweighing other strategic considerations such as when to engage in social learning. I also demonstrate that the strength of selection on social learning strategies is closely linked to the cultural diversity within a population.
In chapters 5 & 6 I study the mechanisms of learning and how social influences can impact decision making. In chapter 5 I model the behaviour of nursery children and chimpanzee groups when solving a complex task and identify clear species differences in the importance of different forms of learning on decision making. Finally, in chapter 6 I use an agent-based model to examine the influence of population structure on the spread of novel behaviour. I demonstrate that, contrary to infectious disease type models, when learning occurs through operant conditioning, highly clustered network structures promote cultural transmission rather than hinder it.
2017-01-01T00:00:00ZOunsley, James P.Culture is a hugely important process in the evolution of humans and many non-human animals. Through the formation of long lasting traditions, culture provides an extragenetic inheritance mechanism that can facilitate rapid behavioural adaptation to novel environments. This can ultimately alter the selection pressures acting on different phenotypes including those that underlie cultural transmission itself, i.e. the mechanisms of social learning.
Understanding culture poses many challenges for researchers due to the complex nature of interacting biological processes at multiple organisational and temporal scales. In this thesis I investigate some of these complexities through the integration of different theoretical and statistical modelling approaches, and argue that rich models are particularly important for the study of culture.
In chapters 3 & 4 I use an evolutionary agent-based model to study the functional value and cultural significance of strategically copying from other individuals based on particular cues, such as age or payoff. I find that a bias to copy the successful can provide substantial adaptive advantages, potentially outweighing other strategic considerations such as when to engage in social learning. I also demonstrate that the strength of selection on social learning strategies is closely linked to the cultural diversity within a population.
In chapters 5 & 6 I study the mechanisms of learning and how social influences can impact decision making. In chapter 5 I model the behaviour of nursery children and chimpanzee groups when solving a complex task and identify clear species differences in the importance of different forms of learning on decision making. Finally, in chapter 6 I use an agent-based model to examine the influence of population structure on the spread of novel behaviour. I demonstrate that, contrary to infectious disease type models, when learning occurs through operant conditioning, highly clustered network structures promote cultural transmission rather than hinder it.The mechanisms and consequences of oviposition decisions in the European bitterlingPhillips, Andréhttps://hdl.handle.net/10023/155242019-12-05T03:05:02Z2018-01-01T00:00:00ZOviposition-site decisions can have disproportionate effects on offspring survival and success, and while the effects of these decisions are frequently investigated, the processes underpinning these decisions and the cues used are often less well understood. The aim of this thesis was to understand the mechanisms associated with making oviposition decisions, and their consequences, using the European bitterling (Rhodeus amarus), a small freshwater fish that lays its eggs in the gills of freshwater mussels. Using an artificial mussel, females were shown to respond to dissolved oxygen, relating to offspring survival, while males attend to water flow velocity, with implications for sperm competition. Oviposition decisions by either sex were unaffected by olfactory cues associated with sperm release, though males and females were responsive to visual cues associated with ejaculation. An analysis of the placement of eggs within the mussel gills by females failed to show evidence of “handedness”, though there was a tendency to place eggs in a mussel’s inner gills, which may be adaptive in avoiding competition with the mussel’s embryos. Male response to oviposition sites showed inter-population variation, with males from a population with high levels of mean crowding showing an elevated frequency of mussel inspection and probability of ejaculation. Males also increased the frequency of mussel inspection in response to the presence of a gravid female, suggesting a role for sperm competition and fertility assurance. Social network analysis was used to investigate how male interactions affect oviposition decisions. This approach showed that male mating tactics could be understood by quantifying how males distributed their sperm among oviposition sites. Findings are discussed in the context of our understanding of the bitterling mating system and research on oviposition-site decisions.
2018-01-01T00:00:00ZPhillips, AndréOviposition-site decisions can have disproportionate effects on offspring survival and success, and while the effects of these decisions are frequently investigated, the processes underpinning these decisions and the cues used are often less well understood. The aim of this thesis was to understand the mechanisms associated with making oviposition decisions, and their consequences, using the European bitterling (Rhodeus amarus), a small freshwater fish that lays its eggs in the gills of freshwater mussels. Using an artificial mussel, females were shown to respond to dissolved oxygen, relating to offspring survival, while males attend to water flow velocity, with implications for sperm competition. Oviposition decisions by either sex were unaffected by olfactory cues associated with sperm release, though males and females were responsive to visual cues associated with ejaculation. An analysis of the placement of eggs within the mussel gills by females failed to show evidence of “handedness”, though there was a tendency to place eggs in a mussel’s inner gills, which may be adaptive in avoiding competition with the mussel’s embryos. Male response to oviposition sites showed inter-population variation, with males from a population with high levels of mean crowding showing an elevated frequency of mussel inspection and probability of ejaculation. Males also increased the frequency of mussel inspection in response to the presence of a gravid female, suggesting a role for sperm competition and fertility assurance. Social network analysis was used to investigate how male interactions affect oviposition decisions. This approach showed that male mating tactics could be understood by quantifying how males distributed their sperm among oviposition sites. Findings are discussed in the context of our understanding of the bitterling mating system and research on oviposition-site decisions.Investigating the foot-and-mouth disease virus 3A proteinHowes, Emma Louisehttps://hdl.handle.net/10023/155212019-03-29T10:31:45Z2018-01-01T00:00:00ZFoot-and-Mouth Disease Virus (FMDV) is a globally important pathogen responsible for causing Foot-and-Mouth Disease (FMD) in wildlife and domestic livestock species and has significant economic impacts. FMD is difficult to control due to its highly infectious nature, wide diversity of host species and the existence of multiple serotypes; therefore, understanding the processes of FMDV infection and viral RNA replication are key to the development of improved diagnostics and vaccines. This thesis investigates the potential roles of the FMDV 3A non-structural protein using a combination of sub-genomic replicons, recombinant viruses and proteomics techniques. The picornavirus 3A protein has previously been linked with roles in replication complex formation, virulence and determining viral host range.
This thesis presents findings showing that a naturally occurring deletion in 3A had differing effects on replication in cells lines derived from different natural hosts thereby supporting the conclusion that 3A has an important role in viral host range.
Proteomic (immunoprecipitation and mass spectroscopy) investigations were carried out to identify potential cellular interaction partners of FMDV 3A, and the impact on infection and replication of reducing expression of two selected cellular proteins Rab7L1 and TBC1D20 was investigated. The 3A protein of FMDV was shown to include a conserved FFAT motif (which bind the ER resident protein VAP) in its N terminal domain. A role for this motif was also investigated with the results suggesting that the 3A FFAT motif is important for efficient viral replication.
Finally, the potential role of 3A to act as the donor of 3B during replication was investigated. Key findings from experiments using FMDV replicons and recombinant viruses showed that full-length P3 and the processing intermediate 3ABBB are not required for viral RNA replication suggesting that the preferred donor of 3B for uridylation is likely a 3BC containing precursor protein.
2018-01-01T00:00:00ZHowes, Emma LouiseFoot-and-Mouth Disease Virus (FMDV) is a globally important pathogen responsible for causing Foot-and-Mouth Disease (FMD) in wildlife and domestic livestock species and has significant economic impacts. FMD is difficult to control due to its highly infectious nature, wide diversity of host species and the existence of multiple serotypes; therefore, understanding the processes of FMDV infection and viral RNA replication are key to the development of improved diagnostics and vaccines. This thesis investigates the potential roles of the FMDV 3A non-structural protein using a combination of sub-genomic replicons, recombinant viruses and proteomics techniques. The picornavirus 3A protein has previously been linked with roles in replication complex formation, virulence and determining viral host range.
This thesis presents findings showing that a naturally occurring deletion in 3A had differing effects on replication in cells lines derived from different natural hosts thereby supporting the conclusion that 3A has an important role in viral host range.
Proteomic (immunoprecipitation and mass spectroscopy) investigations were carried out to identify potential cellular interaction partners of FMDV 3A, and the impact on infection and replication of reducing expression of two selected cellular proteins Rab7L1 and TBC1D20 was investigated. The 3A protein of FMDV was shown to include a conserved FFAT motif (which bind the ER resident protein VAP) in its N terminal domain. A role for this motif was also investigated with the results suggesting that the 3A FFAT motif is important for efficient viral replication.
Finally, the potential role of 3A to act as the donor of 3B during replication was investigated. Key findings from experiments using FMDV replicons and recombinant viruses showed that full-length P3 and the processing intermediate 3ABBB are not required for viral RNA replication suggesting that the preferred donor of 3B for uridylation is likely a 3BC containing precursor protein.The development of sialidase inhibitors using structure-based drug designRogers, Graeme W.https://hdl.handle.net/10023/155162019-03-29T10:41:07Z2017-01-01T00:00:00ZThe sialidases/neuraminidases represent a family of enzymes whose function is important in the
pathogenicity of bacteria and the virulence of influenza. Relenza and Tamiflu represent two drugs
that were developed using structure-based drug design (SBDD) and computational-assisted drug
design (CADD). These drugs target the active site of the influenza neuraminidase A and B (GH-34
family). Sialidases in the GH-33 family could represent novel drug targets for the treatment of
bacterial or parasitic infection. SBDD was employed to develop chemical tools of two GH-33
sialidases, NanB and TcTS.
NanB is a potential drug target for S. pneumoniae. The chemical tool developed for NanB follows
on from work within the Taylor and Westwood research groups, in which a molecule of CHES and a
glycerol were found serendipitously bound within a water channel at an allosteric site. Using this
information as a basis for SBDD an allosteric inhibitor of NanB, Optactin was developed. Within this
work, synthesis of this inhibitor was achieved and optimised. Optactin was then modified to improve
potency. This proceeded through an amide analogue and addition of an arene resulting in a mid-
micromolar inhibitor (IC₅₀: 55.4±2.5 µM). Addition of polar substituents improved potency further
resulting in a low micromolar inhibitor of NanB, Optactamide (IC₅₀: 3.0±1.7 µM). Application of this
tool in vitro demonstrated that NanB and NanA have a role in invasion of S. pneumoniae into lung
epithelial cells.
TcTS is a potential drug target for the treatment of Chagas disease. A CADD approach using a
fragment library was unsuccessful at identifying an allosteric inhibitor of TcTS despite structural
similarity with NanB. A re-task of the CADD approach towards the active site was successful in
identifying an inhibitor of TcTS and a fragment useful for further development. This work sets the
groundwork for the development of a chemical tool targeting TcTS.
2017-01-01T00:00:00ZRogers, Graeme W.The sialidases/neuraminidases represent a family of enzymes whose function is important in the
pathogenicity of bacteria and the virulence of influenza. Relenza and Tamiflu represent two drugs
that were developed using structure-based drug design (SBDD) and computational-assisted drug
design (CADD). These drugs target the active site of the influenza neuraminidase A and B (GH-34
family). Sialidases in the GH-33 family could represent novel drug targets for the treatment of
bacterial or parasitic infection. SBDD was employed to develop chemical tools of two GH-33
sialidases, NanB and TcTS.
NanB is a potential drug target for S. pneumoniae. The chemical tool developed for NanB follows
on from work within the Taylor and Westwood research groups, in which a molecule of CHES and a
glycerol were found serendipitously bound within a water channel at an allosteric site. Using this
information as a basis for SBDD an allosteric inhibitor of NanB, Optactin was developed. Within this
work, synthesis of this inhibitor was achieved and optimised. Optactin was then modified to improve
potency. This proceeded through an amide analogue and addition of an arene resulting in a mid-
micromolar inhibitor (IC₅₀: 55.4±2.5 µM). Addition of polar substituents improved potency further
resulting in a low micromolar inhibitor of NanB, Optactamide (IC₅₀: 3.0±1.7 µM). Application of this
tool in vitro demonstrated that NanB and NanA have a role in invasion of S. pneumoniae into lung
epithelial cells.
TcTS is a potential drug target for the treatment of Chagas disease. A CADD approach using a
fragment library was unsuccessful at identifying an allosteric inhibitor of TcTS despite structural
similarity with NanB. A re-task of the CADD approach towards the active site was successful in
identifying an inhibitor of TcTS and a fragment useful for further development. This work sets the
groundwork for the development of a chemical tool targeting TcTS.A conceptual methodology for studying the geoarchaeology of fluvial systems : with case studies from the Oklawaha River (Florida) and the River Earn (Scotland)Denson, Robyn L.https://hdl.handle.net/10023/151482019-03-29T10:42:06Z1995-01-01T00:00:00ZThis thesis explores a conceptual methodology for studying archaeological sites in fluvial settings. The methodology stems from geoarchaeology, an approach to the past that focuses upon the geomorphic context of artifacts or the application of geological principles and techniques to the solution of archaeological problems. The paper will examine its application to fluvial systems in two different geomorphic environments, the Oklawaha River in Florida and the Earn River Valley in Scotland. In these different environmental settings, the geoarchaeological approach makes use of different kinds of evidence available to it. Survey in submerged and eroding river margins offers additional information on site distribution and density within the landscape that can go unnoticed by traditional terrestrial surveys. Through conceptualization and application of the methodology that has developed from these studies, the arbitrary land/water interface can effectively be erased from research areas and rivers can begin to be viewed not as permanent and non-moving barriers, but as significant and dynamic components of the archaeological landscape.
1995-01-01T00:00:00ZDenson, Robyn L.This thesis explores a conceptual methodology for studying archaeological sites in fluvial settings. The methodology stems from geoarchaeology, an approach to the past that focuses upon the geomorphic context of artifacts or the application of geological principles and techniques to the solution of archaeological problems. The paper will examine its application to fluvial systems in two different geomorphic environments, the Oklawaha River in Florida and the Earn River Valley in Scotland. In these different environmental settings, the geoarchaeological approach makes use of different kinds of evidence available to it. Survey in submerged and eroding river margins offers additional information on site distribution and density within the landscape that can go unnoticed by traditional terrestrial surveys. Through conceptualization and application of the methodology that has developed from these studies, the arbitrary land/water interface can effectively be erased from research areas and rivers can begin to be viewed not as permanent and non-moving barriers, but as significant and dynamic components of the archaeological landscape.Cholecystokinin: measurement, biological action and clinical significanceMarshall, Christopher Edwinhttps://hdl.handle.net/10023/151022019-03-29T10:30:07Z1979-01-01T00:00:00ZThis thesis describes in full the development of a biological method of estimating cholecystokinin (CCK) in human serum by superfusion of rabbit gall-bladder strips, from the early stages of the manual technique, which would estimate approximately twelve samples per day, to the more sophisticated and clinically useful automated technique of today which can estimate up to forty eight sample solutions in duplicate each day. In developing this bioassay for CCK it was necessary to determine whether the gall-bladder preparation was stable for the duration of the experiment, and also whether or not there were other factors influencing the response of the gallbladder strips to a given stimulus. It was also necessary to determine whether the assay was entirely specific for CCK in human serum and to counteract any possible degradation of CCK during processing and storage of serum. In the light of the findings during the above experiments the technique was modified to eliminate errors that would otherwise be made in estimating the CCK content of a serum sample. Since our attempts to set up a radioimmunoassay were unsuccessful a comparison of this bioassay was made with another groups' radioimmunoassay. Although no direct comparison could be made as the two assays measure CCK in totally different units, nevertheless a straight line relationship between the two very different methods was found, and this experiment led directly to the discovery by bioassay of CCK mimicking substances in serum. The action of trypsin on CCK has been clearly demonstrated and its ability to release the C-terminal octa and more probably the dodeca peptide, both of which are considerably more active than the full molecule, is beyond question. It is therefore important that an enzyme inhibitor is added to blood samples to prevent this spontaneous breakdown of more active fragments and prevent false readings of serum cholecystokinin activity. During chromatographic investigations a new molecule in human serum which possessed cholecystokinetic activity but had a molecular weight in excess of 30,000 (c/f 3,900 for normal CCK) was discovered. This molecule appeared to predominate in the fasting state but to decrease in concentration during the response to a meal. The practical use of measuring serum CCK is demonstrated in some clinical trials in which CCK's target organs are removed or the stimulation for its release is modified by various surgical procedures. Some interesting changes are noted.
1979-01-01T00:00:00ZMarshall, Christopher EdwinThis thesis describes in full the development of a biological method of estimating cholecystokinin (CCK) in human serum by superfusion of rabbit gall-bladder strips, from the early stages of the manual technique, which would estimate approximately twelve samples per day, to the more sophisticated and clinically useful automated technique of today which can estimate up to forty eight sample solutions in duplicate each day. In developing this bioassay for CCK it was necessary to determine whether the gall-bladder preparation was stable for the duration of the experiment, and also whether or not there were other factors influencing the response of the gallbladder strips to a given stimulus. It was also necessary to determine whether the assay was entirely specific for CCK in human serum and to counteract any possible degradation of CCK during processing and storage of serum. In the light of the findings during the above experiments the technique was modified to eliminate errors that would otherwise be made in estimating the CCK content of a serum sample. Since our attempts to set up a radioimmunoassay were unsuccessful a comparison of this bioassay was made with another groups' radioimmunoassay. Although no direct comparison could be made as the two assays measure CCK in totally different units, nevertheless a straight line relationship between the two very different methods was found, and this experiment led directly to the discovery by bioassay of CCK mimicking substances in serum. The action of trypsin on CCK has been clearly demonstrated and its ability to release the C-terminal octa and more probably the dodeca peptide, both of which are considerably more active than the full molecule, is beyond question. It is therefore important that an enzyme inhibitor is added to blood samples to prevent this spontaneous breakdown of more active fragments and prevent false readings of serum cholecystokinin activity. During chromatographic investigations a new molecule in human serum which possessed cholecystokinetic activity but had a molecular weight in excess of 30,000 (c/f 3,900 for normal CCK) was discovered. This molecule appeared to predominate in the fasting state but to decrease in concentration during the response to a meal. The practical use of measuring serum CCK is demonstrated in some clinical trials in which CCK's target organs are removed or the stimulation for its release is modified by various surgical procedures. Some interesting changes are noted.The effects of experience on tool use by Capuchin monkeysBabitz, Mindy Annhttps://hdl.handle.net/10023/151012019-07-15T10:12:37Z1999-01-01T00:00:00ZThis thesis investigated effects of manipulative experience on tool-using ability of tufted capuchins. Two groups of capuchins were tested on variations of a tool-using task, involving use of an object as a tool to dislodge a reward from a tube. The tasks were modelled after those developed by Visalberghi and Limongelli (1994) and Visalberghi and Trinca (1989). One group of monkeys was provided the opportunity to manipulate task materials without reward; the other group was not. Experiment 1 required subjects to push a rod through the tube. Experience with task materials improved capuchins' efficiency, evidenced by faster completion of trials. In Experiment 2, short pipes could be combined to create a tool of sufficient length. Due to procedural problems, results were inconclusive. Experiment 3 required subjects to manufacture the appropriate tool. Experience with task materials improved capuchins' performance, evidenced by faster completion of trials, less frequent performance of inefficient behaviours, and decrease in errors across trials. When capuchins' performance was compared with enculturated chimpanzees tested previously on the task (Visalberghi, Fragaszy, and Savage-Rumbaugh, 1995), experienced capuchins performed as efficiently after 15 trials as had chimpanzees originally. In Experiment 4, subjects had to dislodge the reward from a tube containing a trap. Because successful levels of performance were not reached, results were inconclusive. In Experiments 5 and 6, appreciation of object affordances was examined. The capuchins demonstrated an ability to distinguish between functional characteristics of objects. These results suggest previous claims regarding limitations of capuchin tool-use may have underestimated their abilities. Further, because object experience enhances tool-using ability, previous comparisons of capuchins with enculturated chimpanzees seem to have misrepresented the magnitude of difference in their abilities. However, future research comparing species with the same experiential backgrounds is necessary to elaborate on differences in cognitive processes underlying capuchin and chimpanzee tool-using behaviour.
1999-01-01T00:00:00ZBabitz, Mindy AnnThis thesis investigated effects of manipulative experience on tool-using ability of tufted capuchins. Two groups of capuchins were tested on variations of a tool-using task, involving use of an object as a tool to dislodge a reward from a tube. The tasks were modelled after those developed by Visalberghi and Limongelli (1994) and Visalberghi and Trinca (1989). One group of monkeys was provided the opportunity to manipulate task materials without reward; the other group was not. Experiment 1 required subjects to push a rod through the tube. Experience with task materials improved capuchins' efficiency, evidenced by faster completion of trials. In Experiment 2, short pipes could be combined to create a tool of sufficient length. Due to procedural problems, results were inconclusive. Experiment 3 required subjects to manufacture the appropriate tool. Experience with task materials improved capuchins' performance, evidenced by faster completion of trials, less frequent performance of inefficient behaviours, and decrease in errors across trials. When capuchins' performance was compared with enculturated chimpanzees tested previously on the task (Visalberghi, Fragaszy, and Savage-Rumbaugh, 1995), experienced capuchins performed as efficiently after 15 trials as had chimpanzees originally. In Experiment 4, subjects had to dislodge the reward from a tube containing a trap. Because successful levels of performance were not reached, results were inconclusive. In Experiments 5 and 6, appreciation of object affordances was examined. The capuchins demonstrated an ability to distinguish between functional characteristics of objects. These results suggest previous claims regarding limitations of capuchin tool-use may have underestimated their abilities. Further, because object experience enhances tool-using ability, previous comparisons of capuchins with enculturated chimpanzees seem to have misrepresented the magnitude of difference in their abilities. However, future research comparing species with the same experiential backgrounds is necessary to elaborate on differences in cognitive processes underlying capuchin and chimpanzee tool-using behaviour.Post-conflict behaviour and relationship quality of cercopithecine primatesCastles, Duncan Lorimerhttps://hdl.handle.net/10023/150992019-03-29T10:35:42Z1997-01-01T00:00:00ZThis thesis investigates the nature of post-conflict behaviour and relationships among individuals in two captive groups of pigtail macaques, Macaca nemestrina, and one wild troop of olive baboons, Papio anubis. Data were collected during periods of seven and twelve months respectively. In both pigtail groups, conflicts were more frequently reconciled between opponents with strong affiliative ties. However, reconciliation was twice as common in the well-established group where individuals' social networks were more compact. It is argued that the more intense ties produced by restricted networks increased the likelihood of reconciliation. Reconciliation was demonstrated among wild olive baboons, occurring at a rate consistent with a relatively intolerant dominance style. Opponents who were close kin or of similar rank reconciled relatively frequently, but reconciliation rarely followed conflicts associated with food. Olive baboons did not 'console' each other, consistent with the hypothesis that consolation requires an ability to empathise with victim distress. Initiation of post-conflict attacks on third parties was not elevated in victims of aggression. Among the baboons, both victims and initiators of aggression exhibited elevated rates of post-conflict self-directed behaviour (a combined measure of scratching, autogrooming, body-shaking and yawning). Reconciliation reduced both SDB and the incidence of further aggression. However, reconciliation only reduced SDB among individuals involved in conflicts in which they had both received and delivered aggression. Female baboons showed significantly higher rates of SDB when their nearest neighbour (within 5 m) was a dominant conspecific than when he or she was a subordinate individual, supporting the hypothesis that SDB indexes stress in primates. This result suggests that SDB can be used to index relationship security in primates.
1997-01-01T00:00:00ZCastles, Duncan LorimerThis thesis investigates the nature of post-conflict behaviour and relationships among individuals in two captive groups of pigtail macaques, Macaca nemestrina, and one wild troop of olive baboons, Papio anubis. Data were collected during periods of seven and twelve months respectively. In both pigtail groups, conflicts were more frequently reconciled between opponents with strong affiliative ties. However, reconciliation was twice as common in the well-established group where individuals' social networks were more compact. It is argued that the more intense ties produced by restricted networks increased the likelihood of reconciliation. Reconciliation was demonstrated among wild olive baboons, occurring at a rate consistent with a relatively intolerant dominance style. Opponents who were close kin or of similar rank reconciled relatively frequently, but reconciliation rarely followed conflicts associated with food. Olive baboons did not 'console' each other, consistent with the hypothesis that consolation requires an ability to empathise with victim distress. Initiation of post-conflict attacks on third parties was not elevated in victims of aggression. Among the baboons, both victims and initiators of aggression exhibited elevated rates of post-conflict self-directed behaviour (a combined measure of scratching, autogrooming, body-shaking and yawning). Reconciliation reduced both SDB and the incidence of further aggression. However, reconciliation only reduced SDB among individuals involved in conflicts in which they had both received and delivered aggression. Female baboons showed significantly higher rates of SDB when their nearest neighbour (within 5 m) was a dominant conspecific than when he or she was a subordinate individual, supporting the hypothesis that SDB indexes stress in primates. This result suggests that SDB can be used to index relationship security in primates.The behavioural ecology of young baboonsMarsh, Frances J.https://hdl.handle.net/10023/150972019-03-29T10:29:38Z1993-01-01T00:00:00ZIt is hypothesised that young baboons are potentially vulnerable to the effects of seasonal stress. Data were collected on the behaviour of this age group during a 12 month field study of a troop of olive baboons (Papio anubis) on the Laikipia plateau, Kenya, using a hand-held computer and a new program written by the author. Long-term environmental records for this site were continued. At this site there is a seasonal pattern of rainfall with inter-annual variation. Measures of biomass indicate that there are seasonal fluctuations in baboon food availability. Patterns in the occurrence of one component of the baboon's diet, Acacia species, are presented. The varying behaviour of the troop as a whole is related to food availability. Differential use of the home range and observed sub-trooping behaviour are interpreted as adaptive strategies for living in a seasonal environment. Developmental change in the behaviour associated with the mother-offspring relationship is described. Patterns in the time spent in contact with and close proximity to the mother from this site are compared with those from other sites, and striking similarities are found. Many of the behavioural activities of infants and young juveniles, i.e. feeding, moving, types of exploring, visually attending, grooming, and receiving affiliative approaches, exhibit patterns of developmental change. Interactions between activities are examined in the context of the complete activity budget. The effect of seasonal stress on young baboons is examined by using a technique of curve fitting. Data are compared between periods of higher and lower food availability. Significantly more time is spent feeding and less time spent in social and attending activities in the 'worst' than the 'best' months. Young baboons vary their diets seasonally. There is evidence that older infants (weanlings) are more vulnerable to the impact of seasonal stress than either young infants or young juveniles.
1993-01-01T00:00:00ZMarsh, Frances J.It is hypothesised that young baboons are potentially vulnerable to the effects of seasonal stress. Data were collected on the behaviour of this age group during a 12 month field study of a troop of olive baboons (Papio anubis) on the Laikipia plateau, Kenya, using a hand-held computer and a new program written by the author. Long-term environmental records for this site were continued. At this site there is a seasonal pattern of rainfall with inter-annual variation. Measures of biomass indicate that there are seasonal fluctuations in baboon food availability. Patterns in the occurrence of one component of the baboon's diet, Acacia species, are presented. The varying behaviour of the troop as a whole is related to food availability. Differential use of the home range and observed sub-trooping behaviour are interpreted as adaptive strategies for living in a seasonal environment. Developmental change in the behaviour associated with the mother-offspring relationship is described. Patterns in the time spent in contact with and close proximity to the mother from this site are compared with those from other sites, and striking similarities are found. Many of the behavioural activities of infants and young juveniles, i.e. feeding, moving, types of exploring, visually attending, grooming, and receiving affiliative approaches, exhibit patterns of developmental change. Interactions between activities are examined in the context of the complete activity budget. The effect of seasonal stress on young baboons is examined by using a technique of curve fitting. Data are compared between periods of higher and lower food availability. Significantly more time is spent feeding and less time spent in social and attending activities in the 'worst' than the 'best' months. Young baboons vary their diets seasonally. There is evidence that older infants (weanlings) are more vulnerable to the impact of seasonal stress than either young infants or young juveniles.The function of 'referential' calls in two fission-fusion species: spider monkeys (Ateles geoffroyi) and chimpanzees (Pan troglodytes)Teixidor, Patriciahttps://hdl.handle.net/10023/150952019-03-29T10:28:46Z1997-01-01T00:00:00ZThe problems of what primates communicate with their vocalizations and to what extent they refer to events in the external environment are raised in numerous studies of primate vocal communication. To investigate these issues, I concentrate on the calls of two primate species with a similar fission-fusion social organization. I report here the results of a one year field study on the Central American spider monkey (Ateles geoffroyi frontatus) and of a captive study on the chimpanzee (Pan troglodytes). I collected observational data and conducted playback experiments on two types of calls of the spider monkey, whinnies and alarm barks. Spider monkeys use two functionally distinct whinnies, a feeding whinny and a locational whinny. Detailed acoustic analyses of whinnies given in different contexts showed that in three females an acoustic feature-number of arches in the fundamental frequency of the call- could be used to differentiate between them. Although the whinnies of different monkeys within the same community exhibit enough acoustical differences for individual vocal recognition to take place, spider monkeys did not discriminate familiar individuals' whinnies from those of strangers from another community. In predator contexts spider monkeys use barks to attract other conspecifics to a site. However, my data do not support the existence of two types of alarm barks for aerial versus terrestrial predators. I conducted two different types of experiments on the calling behaviour of captive chimpanzees in response to food-finding. I examined whether the quantity and divisibility of food, or the presence of an audience, influence calling behaviour. Chimpanzees' food- associated calls, i.e. rough grunts, functioned to indicate food availability, and they were produced or suppressed depending on how shareable the food was and whether or not other individuals were nearly. Several spider monkeys' and chimpanzees' calls have the ability to function referentially, but cannot be considered devoid of a motivational content.
1997-01-01T00:00:00ZTeixidor, PatriciaThe problems of what primates communicate with their vocalizations and to what extent they refer to events in the external environment are raised in numerous studies of primate vocal communication. To investigate these issues, I concentrate on the calls of two primate species with a similar fission-fusion social organization. I report here the results of a one year field study on the Central American spider monkey (Ateles geoffroyi frontatus) and of a captive study on the chimpanzee (Pan troglodytes). I collected observational data and conducted playback experiments on two types of calls of the spider monkey, whinnies and alarm barks. Spider monkeys use two functionally distinct whinnies, a feeding whinny and a locational whinny. Detailed acoustic analyses of whinnies given in different contexts showed that in three females an acoustic feature-number of arches in the fundamental frequency of the call- could be used to differentiate between them. Although the whinnies of different monkeys within the same community exhibit enough acoustical differences for individual vocal recognition to take place, spider monkeys did not discriminate familiar individuals' whinnies from those of strangers from another community. In predator contexts spider monkeys use barks to attract other conspecifics to a site. However, my data do not support the existence of two types of alarm barks for aerial versus terrestrial predators. I conducted two different types of experiments on the calling behaviour of captive chimpanzees in response to food-finding. I examined whether the quantity and divisibility of food, or the presence of an audience, influence calling behaviour. Chimpanzees' food- associated calls, i.e. rough grunts, functioned to indicate food availability, and they were produced or suppressed depending on how shareable the food was and whether or not other individuals were nearly. Several spider monkeys' and chimpanzees' calls have the ability to function referentially, but cannot be considered devoid of a motivational content.Feeding skills and the effect of injury on wild chimpanzeesStokes, Emma Janehttps://hdl.handle.net/10023/150932019-03-29T10:40:08Z1999-01-01T00:00:00ZWhile gorillas and orangutans have been shown to display considerable manual skill in obtaining certain plant foods, complex feeding skills in chimpanzees have only been described in the restricted context of tool use. This thesis provides the first study of plant-processing skills in a non-tool using community of chimpanzees in Budongo Forest, Uganda. Furthermore, this community contains over 20% of individuals with upper or lower limb injuries. The strategies used by injured individuals in compensating for injury were investigated through a comparison of feeding skill between the able-bodied and injured population. A cognitive approach to feeding behaviour in chimpanzees was adopted, with respect to the implications this may have for overcoming the effects of injury. Chimpanzees were found to employ a broad range of skills in feeding, reflecting variation in their environment and in their diet. Three food types were examined, each illustrating a particular aspect of feeding skill. In processing leaves of Broussonettia papyrifera, chimpanzees use complex multi-stage feeding techniques, employ bimanual co-ordination at several stages and elicit behaviour that is hierarchical in overall organisation. Able-bodied individuals show considerable standardisation in their feeding with a preference for two techniques. In contrast, when feeding on figs, chimpanzees rely upon simple processing techniques but at the same time employ strategies that serve to minimize the effects of feeding competition. In the case of Ficus mucuso chimpanzees co-ordinate several handfuls of food simultaneously between limbs, and with Ficus sur, chimpanzees display a range of dynamic feeding postures and positions in order to access food patches and increase relative food availability. No significant hand preferences were found in any of the three feeding tasks. Even the most severe of injuries does not result in a decline in feeding efficiency, and the possible mechanisms contributing to this were addressed. Injured individuals were found not to invent novel solutions to familiar tasks, but instead to modify their existing repertoire in order to work around their injuries, thus sharing the program-level organisation observed in able-bodied individuals and compensating at the level of individual actions. However, the physical limitations imposed by the injured limb considerably reduce bimanual coordination and manoeuvrability in the tree, which may have long-term negative implications.
1999-01-01T00:00:00ZStokes, Emma JaneWhile gorillas and orangutans have been shown to display considerable manual skill in obtaining certain plant foods, complex feeding skills in chimpanzees have only been described in the restricted context of tool use. This thesis provides the first study of plant-processing skills in a non-tool using community of chimpanzees in Budongo Forest, Uganda. Furthermore, this community contains over 20% of individuals with upper or lower limb injuries. The strategies used by injured individuals in compensating for injury were investigated through a comparison of feeding skill between the able-bodied and injured population. A cognitive approach to feeding behaviour in chimpanzees was adopted, with respect to the implications this may have for overcoming the effects of injury. Chimpanzees were found to employ a broad range of skills in feeding, reflecting variation in their environment and in their diet. Three food types were examined, each illustrating a particular aspect of feeding skill. In processing leaves of Broussonettia papyrifera, chimpanzees use complex multi-stage feeding techniques, employ bimanual co-ordination at several stages and elicit behaviour that is hierarchical in overall organisation. Able-bodied individuals show considerable standardisation in their feeding with a preference for two techniques. In contrast, when feeding on figs, chimpanzees rely upon simple processing techniques but at the same time employ strategies that serve to minimize the effects of feeding competition. In the case of Ficus mucuso chimpanzees co-ordinate several handfuls of food simultaneously between limbs, and with Ficus sur, chimpanzees display a range of dynamic feeding postures and positions in order to access food patches and increase relative food availability. No significant hand preferences were found in any of the three feeding tasks. Even the most severe of injuries does not result in a decline in feeding efficiency, and the possible mechanisms contributing to this were addressed. Injured individuals were found not to invent novel solutions to familiar tasks, but instead to modify their existing repertoire in order to work around their injuries, thus sharing the program-level organisation observed in able-bodied individuals and compensating at the level of individual actions. However, the physical limitations imposed by the injured limb considerably reduce bimanual coordination and manoeuvrability in the tree, which may have long-term negative implications.Gestural communication in a group of zoo-living lowland gorillasTanner, Joanne E.https://hdl.handle.net/10023/150882019-03-29T10:37:13Z1998-01-01T00:00:00ZGestural communication in a group of zoo-living lowland gorillas Videotaped observations of a group of zoo-living lowland gorillas collected over a seven- year period were used to study aspects of non-vocal communication. I discerned three classes of gesture: 1) tactile gestures, that depict motion paths iconically; 2) non-tactile silent gestures, some of which appear to be iconic and others deictic; and 3) audible gestures, that, unlike the other two classes, are species-typical gorilla behaviour. The iconic gestures appear to represent activities desired of another gorilla. In addition, one gorilla developed a gesture that was regularly used to suppress the playface, a facial expression that was presumably involuntary. Certain social and environmental conditions, such as the presence of competing males and a physical environment that permits female choice as to proximity with males, may promote the development of such forms of visual communication. I trace the development of gestures throughout the gorilla lifetime, and approach the acquisition of gestures from several viewpoints. "Ontogenic ritualization" and imitation are both found to have a limited explanatory value. One gorilla imitated human gestures, but there was no concrete evidence that these gorillas imitated each other. Repeated strings of gestures or other actions showed, however, that memory capacity exists in gorillas for reproducing complex sequences. Finally, I compare the gestural inventions of my zoo subjects with those of a gorilla taught American Sign Language, finding continuity in styles of depiction from portrayal of pure action to description of stationary objects. Gesture, in portraying action as well as in its ability to depict object shapes, can be seen as a necessary foundation for die eventual development of language in die hominid line.
1998-01-01T00:00:00ZTanner, Joanne E.Gestural communication in a group of zoo-living lowland gorillas Videotaped observations of a group of zoo-living lowland gorillas collected over a seven- year period were used to study aspects of non-vocal communication. I discerned three classes of gesture: 1) tactile gestures, that depict motion paths iconically; 2) non-tactile silent gestures, some of which appear to be iconic and others deictic; and 3) audible gestures, that, unlike the other two classes, are species-typical gorilla behaviour. The iconic gestures appear to represent activities desired of another gorilla. In addition, one gorilla developed a gesture that was regularly used to suppress the playface, a facial expression that was presumably involuntary. Certain social and environmental conditions, such as the presence of competing males and a physical environment that permits female choice as to proximity with males, may promote the development of such forms of visual communication. I trace the development of gestures throughout the gorilla lifetime, and approach the acquisition of gestures from several viewpoints. "Ontogenic ritualization" and imitation are both found to have a limited explanatory value. One gorilla imitated human gestures, but there was no concrete evidence that these gorillas imitated each other. Repeated strings of gestures or other actions showed, however, that memory capacity exists in gorillas for reproducing complex sequences. Finally, I compare the gestural inventions of my zoo subjects with those of a gorilla taught American Sign Language, finding continuity in styles of depiction from portrayal of pure action to description of stationary objects. Gesture, in portraying action as well as in its ability to depict object shapes, can be seen as a necessary foundation for die eventual development of language in die hominid line.Parasitological studiesBurt, Michael David Brunskillhttps://hdl.handle.net/10023/150872019-03-29T10:40:01Z1967-01-01T00:00:00Z1967-01-01T00:00:00ZBurt, Michael David BrunskillThe development of predation in catsCaro, T. M.https://hdl.handle.net/10023/150842019-03-29T10:33:35Z1979-01-01T00:00:00ZThis study is concerned with some of the processes that occur during the development of behaviour, and these are examined in the context how predatory behaviour develops in domestic cats, initially some of the problems that have beleaguered the study of behavioural development are examined and current issues in this field ae outlined. The experimental design of the study, the definitions of recorded behaviour and the methods of data analysis are then discussed. The study then focusses on the multiple effects that experiences in development can have on adult behaviour. It shows that cats were better able to catch prey as adults if they had had experiences of it as kittens, that cats specialized on the type of prey with which they had had prior experiences, and that little generalization to other prey types occurred in cats with experience of one prey type. Several other factors likely to affect adult predatory behaviour were than examined. Both the presence of the mother during kittens' exposure to prey, and experience of prey as adults were found to improve adult predatory competence. Object play had no effect on predatory behaviour. The study went on to relate the development of social play in kittens to the development of predatory behaviour. Some aspects of play became more associated with predatory behaviour aspects grew older, others less so. Different patterns of play appeared to increasingly come under separate types of control as kittens developed. One of the factors affecting the development of predatory behaviour, the effect of the mother, was then examined in detail. Some of the ways in which mothers encouraged their offspring to interact with prey were outlined together with the ways that offspring responded to the mother's predatory behaviour. Finally, the relationship between predatory behaviour in kittens and their subsequent predatory behaviour as adults was investigated. Many aspects of kitten predation were found to correlate with adult predatory activity. Some individuals that were poor predators as kittens showed competent predatory behaviour as adults. The implications of those findings were discussed in relation to the development of predatory behaviour, the development of play and the timing of events in kitten ontogeny.
1979-01-01T00:00:00ZCaro, T. M.This study is concerned with some of the processes that occur during the development of behaviour, and these are examined in the context how predatory behaviour develops in domestic cats, initially some of the problems that have beleaguered the study of behavioural development are examined and current issues in this field ae outlined. The experimental design of the study, the definitions of recorded behaviour and the methods of data analysis are then discussed. The study then focusses on the multiple effects that experiences in development can have on adult behaviour. It shows that cats were better able to catch prey as adults if they had had experiences of it as kittens, that cats specialized on the type of prey with which they had had prior experiences, and that little generalization to other prey types occurred in cats with experience of one prey type. Several other factors likely to affect adult predatory behaviour were than examined. Both the presence of the mother during kittens' exposure to prey, and experience of prey as adults were found to improve adult predatory competence. Object play had no effect on predatory behaviour. The study went on to relate the development of social play in kittens to the development of predatory behaviour. Some aspects of play became more associated with predatory behaviour aspects grew older, others less so. Different patterns of play appeared to increasingly come under separate types of control as kittens developed. One of the factors affecting the development of predatory behaviour, the effect of the mother, was then examined in detail. Some of the ways in which mothers encouraged their offspring to interact with prey were outlined together with the ways that offspring responded to the mother's predatory behaviour. Finally, the relationship between predatory behaviour in kittens and their subsequent predatory behaviour as adults was investigated. Many aspects of kitten predation were found to correlate with adult predatory activity. Some individuals that were poor predators as kittens showed competent predatory behaviour as adults. The implications of those findings were discussed in relation to the development of predatory behaviour, the development of play and the timing of events in kitten ontogeny.The effects of temporal relationships on the associability of both conditioned and unconditioned stimuliDavison, Ianhttps://hdl.handle.net/10023/150832019-03-29T10:39:35Z1988-01-01T00:00:00ZSeveral models of animal associative learning are described. The evidence for the concept of associability is reviewed. The review contains a detailed account of blocking, including the Mackintosh, Bygrave and Picton (1977) experiment. It is shown that the two major associability models need to be modified, mathematically, to simulate the results of this experiment. A general, simple framework for investigating putative associability changes is suggested. A review of stimulus pre-exposure effects is put into this framework, and indicates a suitable direction for research. The experiments looked for associability changes of both conditioned and unconditioned stimuli. Sometimes the stimulus was a predictor of subsequent events; if not, it was predicted by another stimulus. A variety of procedures was employed. Experiments 1, 2, and 3 tried to replicate and extend previous work with a conditioned stimulus predicting subsequent events, but they were unsuccessful. Experiments 4, 5, 6, 7, and 8 investigated whether conditioned and unconditioned stimuli would change in associability when they were well predicted. Unfortunately, the data were difficult to interpret. An appetitive-aversive transfer paradigm was used in Experiments 9, 10, and 11; there was some evidence that a tone could change in associability, both when it was acting as a predictor, and when it was being predicted. Alternative Interpretations were also discussed. In Experiments 12 and 13, a shock was used to predict the occurrence of food; and there was no evidence that the associability of the shock could be increased in this way.
1988-01-01T00:00:00ZDavison, IanSeveral models of animal associative learning are described. The evidence for the concept of associability is reviewed. The review contains a detailed account of blocking, including the Mackintosh, Bygrave and Picton (1977) experiment. It is shown that the two major associability models need to be modified, mathematically, to simulate the results of this experiment. A general, simple framework for investigating putative associability changes is suggested. A review of stimulus pre-exposure effects is put into this framework, and indicates a suitable direction for research. The experiments looked for associability changes of both conditioned and unconditioned stimuli. Sometimes the stimulus was a predictor of subsequent events; if not, it was predicted by another stimulus. A variety of procedures was employed. Experiments 1, 2, and 3 tried to replicate and extend previous work with a conditioned stimulus predicting subsequent events, but they were unsuccessful. Experiments 4, 5, 6, 7, and 8 investigated whether conditioned and unconditioned stimuli would change in associability when they were well predicted. Unfortunately, the data were difficult to interpret. An appetitive-aversive transfer paradigm was used in Experiments 9, 10, and 11; there was some evidence that a tone could change in associability, both when it was acting as a predictor, and when it was being predicted. Alternative Interpretations were also discussed. In Experiments 12 and 13, a shock was used to predict the occurrence of food; and there was no evidence that the associability of the shock could be increased in this way.Neuroethological studies of primate social perceptionEmery, Nathan J.https://hdl.handle.net/10023/150782019-03-29T10:36:09Z1997-01-01T00:00:00ZThe neuroethological basis of social signals was investigated using a multidisciplinary approach, involving connectional and comparative analysis of anatomical data, single cell recording and behavioural techniques. Previous literature implicates the amygdala, anterior temporal and prefrontal cortex in primate social functions. Non-metric multidimensional scaling (NMDS) and cluster analysis were used to analyse the connectional relatedness of macaque cortico-cortical and amygdalo-cortical connections. This objective analysis separated the amygdala nuclei into two groups, the basolateral (BL) and centromedial (CM) complexes. A comparative analysis was made of the possible functions of the amygdala nuclei by correlating amygdala nuclear volume with 5 socio-ecological indices, across 44 primate species. The lateral basal (LB) nucleus and BL size was found to correlate positively with social complexity. CM size correlated negatively. The LB nucleus receives information from the STS, which contains visual neurons responsive to eyes, heads and bodies. These cells were assessed for coding of socially relevant information. Single cell recording localised within the macaque superior temporal sulcus (STS) revealed neurons responsive to specific views, elevations and orientations of the head, eye position, and specific views of bodies walking in specific directions and reaching to objects. The tuning of these neurons could therefore support the function of recognition of another's purposive behaviour (e.g. direction of attention or intention). Visually responsive neurons in the STS also differentiated faces of different species (i.e. monkeys, humans and other animals). Behavioural studies suggest that monkeys do not follow the direction of attention of humans, yet monkeys appear to have the neural capacity. A behavioural study using video stimuli, revealed that monkeys spontaneously follow other monkeys' gaze onto an object or point in space. It is concluded that the amygdala and STS are part of a neural system which enable monkeys to interpret another's gaze and actions within a purposive behavioural framework.
1997-01-01T00:00:00ZEmery, Nathan J.The neuroethological basis of social signals was investigated using a multidisciplinary approach, involving connectional and comparative analysis of anatomical data, single cell recording and behavioural techniques. Previous literature implicates the amygdala, anterior temporal and prefrontal cortex in primate social functions. Non-metric multidimensional scaling (NMDS) and cluster analysis were used to analyse the connectional relatedness of macaque cortico-cortical and amygdalo-cortical connections. This objective analysis separated the amygdala nuclei into two groups, the basolateral (BL) and centromedial (CM) complexes. A comparative analysis was made of the possible functions of the amygdala nuclei by correlating amygdala nuclear volume with 5 socio-ecological indices, across 44 primate species. The lateral basal (LB) nucleus and BL size was found to correlate positively with social complexity. CM size correlated negatively. The LB nucleus receives information from the STS, which contains visual neurons responsive to eyes, heads and bodies. These cells were assessed for coding of socially relevant information. Single cell recording localised within the macaque superior temporal sulcus (STS) revealed neurons responsive to specific views, elevations and orientations of the head, eye position, and specific views of bodies walking in specific directions and reaching to objects. The tuning of these neurons could therefore support the function of recognition of another's purposive behaviour (e.g. direction of attention or intention). Visually responsive neurons in the STS also differentiated faces of different species (i.e. monkeys, humans and other animals). Behavioural studies suggest that monkeys do not follow the direction of attention of humans, yet monkeys appear to have the neural capacity. A behavioural study using video stimuli, revealed that monkeys spontaneously follow other monkeys' gaze onto an object or point in space. It is concluded that the amygdala and STS are part of a neural system which enable monkeys to interpret another's gaze and actions within a purposive behavioural framework.Social learning and imitation in human and nonhuman primatesCustance, Deborah M.https://hdl.handle.net/10023/150762019-03-29T10:34:02Z1995-01-01T00:00:00ZMost people assume that monkeys and apes can imitate, but recently, several researchers have suggested there is little convincing evidence of imitation in any nonhuman species. The purpose of the present thesis is to compare the imitative abilities of human and non-human primates. Some of the most convincing evidence for imitation comes from anecdotal reports of imitative behaviour in great apes. A survey of the literature was performed and a database of imitative episodes in chimpanzees, gorillas and orangutans was compiled (using a similar approach to Whiten & Byrne's 1988a tactical deception database). Each report was subjected to a strict evaluation, and it was deemed that 23 reports from chimpanzees, 3 from gorillas and 4 from orangutans provided relatively convincing evidence of imitation. An experiment was conducted to test if chimpanzees can imitate as the anecdotal data suggests. Two chimpanzees were taught to reproduce 15 arbitrary gestures on the command "Do this". Next they were presented with 48 novel items. They imitated 13 and 20 novel gestures respectively. Using a rigorous coding system, two independent observers correctly identified a significant number of the chimpanzees' imitations (P< 0.0001). These results show that chimpanzees are capable of the complex intermodal visual-motor co-ordination and control necessary for imitation. The second experimental chapter explores whether monkeys, apes, and/or humans imitate in the context of a functional task. Six capuchin monkeys (Cebus apella), eight chimpanzees (Pan troglodytes) and 24 children were presented with an analogue of a natural food processing task. The subjects were divided into two groups and each saw a different method for opening an artificial fruit. The children showed quite extensive imitation; the capuchin monkeys showed little to none; while the chimpanzees showed marginal imitative abilities. This constitutes the first experimental evidence of functional object imitation in a nonhuman specie.
1995-01-01T00:00:00ZCustance, Deborah M.Most people assume that monkeys and apes can imitate, but recently, several researchers have suggested there is little convincing evidence of imitation in any nonhuman species. The purpose of the present thesis is to compare the imitative abilities of human and non-human primates. Some of the most convincing evidence for imitation comes from anecdotal reports of imitative behaviour in great apes. A survey of the literature was performed and a database of imitative episodes in chimpanzees, gorillas and orangutans was compiled (using a similar approach to Whiten & Byrne's 1988a tactical deception database). Each report was subjected to a strict evaluation, and it was deemed that 23 reports from chimpanzees, 3 from gorillas and 4 from orangutans provided relatively convincing evidence of imitation. An experiment was conducted to test if chimpanzees can imitate as the anecdotal data suggests. Two chimpanzees were taught to reproduce 15 arbitrary gestures on the command "Do this". Next they were presented with 48 novel items. They imitated 13 and 20 novel gestures respectively. Using a rigorous coding system, two independent observers correctly identified a significant number of the chimpanzees' imitations (P< 0.0001). These results show that chimpanzees are capable of the complex intermodal visual-motor co-ordination and control necessary for imitation. The second experimental chapter explores whether monkeys, apes, and/or humans imitate in the context of a functional task. Six capuchin monkeys (Cebus apella), eight chimpanzees (Pan troglodytes) and 24 children were presented with an analogue of a natural food processing task. The subjects were divided into two groups and each saw a different method for opening an artificial fruit. The children showed quite extensive imitation; the capuchin monkeys showed little to none; while the chimpanzees showed marginal imitative abilities. This constitutes the first experimental evidence of functional object imitation in a nonhuman specie.Functional and organizational aspects of vocal repertoires in bottlenose dolphins "Tursiops truncatus"Janik, Vincenthttps://hdl.handle.net/10023/150752019-06-10T14:58:36Z1983-01-01T00:00:00ZBottlenose dolphins (Tursiops truncatus) produce a wide variety of sounds but little is known about the function and organization of their vocal repertoires. This thesis investigates several aspects of call usage and compares the biological validity of classification methods for dolphin whistles. Passive acoustic localisation methods were used to identify which animal produced a sound. Observations of captive dolphins in the Zoo Duisburg, Germany, showed that signature whistles are almost only used when the group was split up, but not if all animals swam in together in the same pool. This finding supported the hypothesis that signature whistles are cohesion calls. Whistles from these observations were used to compare whistle classification conducted by eye with three computer methods using different similarity measures. Only the human observer classification was able to recognize whistle types that were used in a context- specific way by the animals confirming the power of this common classification method. Copying of signature whistles and whistle matching between animals was rare in captivity. However, observations of whistle interactions in the Moray Firth, Scotland, showed that wild dolphins do not tend to interact vocally in general, but that whistle matching was more frequent than expected by chance. Whistle matching in captivity was rare. Sound pressure measurements of dolphin whistles in the wild showed that source levels can reach up to 169 dB re 1 μPa and that the active space of a dolphin whistle can range up to 38 km. Finally, observations of foraging in wild dolphins revealed that they produce low frequency braying sounds in this context. Other dolphins would rapidly approach the caller in response to a bray. However, it is not clear whether brays function to attract conspecifics or manipulate prey behaviour.
1983-01-01T00:00:00ZJanik, VincentBottlenose dolphins (Tursiops truncatus) produce a wide variety of sounds but little is known about the function and organization of their vocal repertoires. This thesis investigates several aspects of call usage and compares the biological validity of classification methods for dolphin whistles. Passive acoustic localisation methods were used to identify which animal produced a sound. Observations of captive dolphins in the Zoo Duisburg, Germany, showed that signature whistles are almost only used when the group was split up, but not if all animals swam in together in the same pool. This finding supported the hypothesis that signature whistles are cohesion calls. Whistles from these observations were used to compare whistle classification conducted by eye with three computer methods using different similarity measures. Only the human observer classification was able to recognize whistle types that were used in a context- specific way by the animals confirming the power of this common classification method. Copying of signature whistles and whistle matching between animals was rare in captivity. However, observations of whistle interactions in the Moray Firth, Scotland, showed that wild dolphins do not tend to interact vocally in general, but that whistle matching was more frequent than expected by chance. Whistle matching in captivity was rare. Sound pressure measurements of dolphin whistles in the wild showed that source levels can reach up to 169 dB re 1 μPa and that the active space of a dolphin whistle can range up to 38 km. Finally, observations of foraging in wild dolphins revealed that they produce low frequency braying sounds in this context. Other dolphins would rapidly approach the caller in response to a bray. However, it is not clear whether brays function to attract conspecifics or manipulate prey behaviour.Predator-prey interactions between great black-backed gulls (Larus marinus) and puffins (Fratercula arctica L.), and the evolutionary significance of puffin grouping behaviourTaylor, G. Kennethhttps://hdl.handle.net/10023/150742019-03-29T10:36:40Z1983-01-01T00:00:00ZThe alms of this study were to quantify various aspects of predator-prey interactions between Great Black Backed Gulls (Larus marinus) and Common Puffins (Frateroula arotica Le) in order to assess the possible long term effects of predation by gulls on a single Puffin colony and to examine the possible influence of avian predators on Puffin social behaviour. Kiore has been little quantification of the extent of Great Black-Backed Gull predation of Puffins throughout the gull breeding season. Chapter One extends data already published on gull predation of Puffins on the island of Dun, St Kilda, by showing what proportion of gall diet comprised Puffins and by indicating the importance of Puffin prey to gull breading success. Chapter Two describes the ranging behaviour and hunting success of gulls on Dun. Gulls only hunted flying Puffins and concentrated their hunting efforts in areas near, but not directly over, their own nests. Any one pair of gulls shared on average about one third of its hunting range with two or three other pairs of Gulls attempted to catch Puffins most often in areas where Puffins, flying in polarised flocks termed 'wheels', habitually turned in to fly over land or out to fly over the sea. With increasing numbers of Puffins in a wheel, gulls made fewer attempts to catch Puffins and took longer to make a successful kill. The grouping behaviour of Puffins is one of the most striking features of the species' social life at the breeding colony. Chapter Three describes and quantifies temporal and spatial aspects of Puffin grouping behaviour at a. variety of colonies. Differences in the diurnal phasing of the formation of different types of Puffin groups and Abstract (cont.) regularities in the spatial distribution of groups in the sea and in the air indicate that individual Puffins regularly synchronised some of their movements in and around the breeding colony with numbers of other Puffins breeding in or using the same part of the colony. The flight behaviour of an individual Puffin in a wheel flock above a sub-colony was influenced by the number of other Puffins in the wheel, b-wind speed and direction, and by the presence of a hunting gull in the vicinity of the wheel. To conclude, the implications of the present study for the management, monitoring and future study of Great Black-Backed Gulls and Puffins are outlined.
1983-01-01T00:00:00ZTaylor, G. KennethThe alms of this study were to quantify various aspects of predator-prey interactions between Great Black Backed Gulls (Larus marinus) and Common Puffins (Frateroula arotica Le) in order to assess the possible long term effects of predation by gulls on a single Puffin colony and to examine the possible influence of avian predators on Puffin social behaviour. Kiore has been little quantification of the extent of Great Black-Backed Gull predation of Puffins throughout the gull breeding season. Chapter One extends data already published on gull predation of Puffins on the island of Dun, St Kilda, by showing what proportion of gall diet comprised Puffins and by indicating the importance of Puffin prey to gull breading success. Chapter Two describes the ranging behaviour and hunting success of gulls on Dun. Gulls only hunted flying Puffins and concentrated their hunting efforts in areas near, but not directly over, their own nests. Any one pair of gulls shared on average about one third of its hunting range with two or three other pairs of Gulls attempted to catch Puffins most often in areas where Puffins, flying in polarised flocks termed 'wheels', habitually turned in to fly over land or out to fly over the sea. With increasing numbers of Puffins in a wheel, gulls made fewer attempts to catch Puffins and took longer to make a successful kill. The grouping behaviour of Puffins is one of the most striking features of the species' social life at the breeding colony. Chapter Three describes and quantifies temporal and spatial aspects of Puffin grouping behaviour at a. variety of colonies. Differences in the diurnal phasing of the formation of different types of Puffin groups and Abstract (cont.) regularities in the spatial distribution of groups in the sea and in the air indicate that individual Puffins regularly synchronised some of their movements in and around the breeding colony with numbers of other Puffins breeding in or using the same part of the colony. The flight behaviour of an individual Puffin in a wheel flock above a sub-colony was influenced by the number of other Puffins in the wheel, b-wind speed and direction, and by the presence of a hunting gull in the vicinity of the wheel. To conclude, the implications of the present study for the management, monitoring and future study of Great Black-Backed Gulls and Puffins are outlined.The singing behaviour of coal tits (Parus ater)Adhikerana, Asep Sunjayahttps://hdl.handle.net/10023/150732019-03-29T10:42:58Z1992-01-01T00:00:00ZThis thesis investigates the singing behaviour of coal tits (Parus ater) from two different study sites. A background to the functional significance of songs in a broad context is given in Chapter 1. This chapter also briefly introduces the biology of coal tits. Chapter 2 describes more general aspects of coal tit songs, and evaluates and compares the variability in song structure of two coal tit populations. The study has looked at the distribution of songs within populations, and at the effect of distance between individuals on the composition of their repertoires. The results are presented in Chapter 3. A new hypothesis has been proposed to explain the significance of song repertoires, namely the anti-exhaustion hypothesis. The hypothesis was tested on coal tits, and the results are presented in Chapter 4. Using playback experiments the singing interaction in coal tits was investigated. Two experiments were carried out in order to test the predictions that a bout of song could give information about individual's fitness, and that song length might indicate individual 'strength'. The results are presented in Chapter 5.
1992-01-01T00:00:00ZAdhikerana, Asep SunjayaThis thesis investigates the singing behaviour of coal tits (Parus ater) from two different study sites. A background to the functional significance of songs in a broad context is given in Chapter 1. This chapter also briefly introduces the biology of coal tits. Chapter 2 describes more general aspects of coal tit songs, and evaluates and compares the variability in song structure of two coal tit populations. The study has looked at the distribution of songs within populations, and at the effect of distance between individuals on the composition of their repertoires. The results are presented in Chapter 3. A new hypothesis has been proposed to explain the significance of song repertoires, namely the anti-exhaustion hypothesis. The hypothesis was tested on coal tits, and the results are presented in Chapter 4. Using playback experiments the singing interaction in coal tits was investigated. Two experiments were carried out in order to test the predictions that a bout of song could give information about individual's fitness, and that song length might indicate individual 'strength'. The results are presented in Chapter 5.Song characteristics and sexual selection in the willow warbler ('Phylloscopus trochilus')Gil, Diegohttps://hdl.handle.net/10023/150722019-03-29T10:32:04Z1998-01-01T00:00:00ZIn many species of birds, males have complex song repertoires, which are used in the context of breeding. The succinct rationale of the research done in this thesis is the following paradox; assuming that song repertoires are costly to produce and store, why do males have repertoires of songs rather than a single song? A possible reason is that, if only males of good quality or in good condition are able to produce these repertoires, good quality males would outweigh the costs of the repertoire by increased benefits in mating success. I studied this issue in a population of willow warblers (Pbylloscopus trocbilus). I found some evidence that repertoire size was correlated with male quality. Male age was found to correlate with repertoire size, and there was a positive correlation between repertoire size and survival. The probability of a male having an offspring recruiting into the population was also correlated with repertoire size. Number of fledglings was positively correlated with repertoire size, even when the effect of arrival date was taken into account. However, female choice bore no relation to repertoire size. Females patted first with early arriving males. Females did not use repertoire size either when choosing extra-pair partners. Another characteristic, song length, seemed to be behind this choice, and males with short songs were more likely to be cuckolded. The effects of song repertoires in male-male competition were examined by means of a playback experiment. The results did not provide conclusive evidence of an effect of repertoire in male-male competition. Taken together, the evidence gathered in this thesis suggests that, although repertoire size correlates with several measures of male quality in this species, the maintenance of this trait does not seem to be based on a disproportionally higher mating benefit.
1998-01-01T00:00:00ZGil, DiegoIn many species of birds, males have complex song repertoires, which are used in the context of breeding. The succinct rationale of the research done in this thesis is the following paradox; assuming that song repertoires are costly to produce and store, why do males have repertoires of songs rather than a single song? A possible reason is that, if only males of good quality or in good condition are able to produce these repertoires, good quality males would outweigh the costs of the repertoire by increased benefits in mating success. I studied this issue in a population of willow warblers (Pbylloscopus trocbilus). I found some evidence that repertoire size was correlated with male quality. Male age was found to correlate with repertoire size, and there was a positive correlation between repertoire size and survival. The probability of a male having an offspring recruiting into the population was also correlated with repertoire size. Number of fledglings was positively correlated with repertoire size, even when the effect of arrival date was taken into account. However, female choice bore no relation to repertoire size. Females patted first with early arriving males. Females did not use repertoire size either when choosing extra-pair partners. Another characteristic, song length, seemed to be behind this choice, and males with short songs were more likely to be cuckolded. The effects of song repertoires in male-male competition were examined by means of a playback experiment. The results did not provide conclusive evidence of an effect of repertoire in male-male competition. Taken together, the evidence gathered in this thesis suggests that, although repertoire size correlates with several measures of male quality in this species, the maintenance of this trait does not seem to be based on a disproportionally higher mating benefit.Habitat matching and cultural change in chaffinch songWilliams, James Michaelhttps://hdl.handle.net/10023/150702019-03-29T10:33:13Z1992-01-01T00:00:00ZThe acoustic adaptation hypothesis was reviewed. This predicts that the sounds used by birds singing in a dense habitat should be of lower frequency than those in a more open habitat, and that sounds should be spaced out more in time in denser habitats to avoid degradation by reverberations. These predictions were tested by recording chaffinch (Fringilla coelebs) songs in open scrub, coniferous plantations, and a natural Scots pine forest, but the results obtained gave little support to the predictions made. Transmission of white noise and the songs of blue (F. teydea) arid Canary Islands chaffinches (F. c. tintillon) through laurel and Canarian pine forests on Tenerife revealed a sound window of less excess attenuation than expected in both habitats at frequencies of 2-3kHz. The song of the blue chaffinch appears to be better adapted for transmission through both habitats. Computer simulations of the formation of dialects by random copying of the songs possessed by neighbours predicted a strong effect of both the number of neighbours available to learn from, and the repertoire size, upon the songs' longevity and the number of birds sharing a particular song type. If the song type which was commonest amongst those sung by neighbours was learnt, larger groups of birds were found to share song types. At low copying error rates these groups approached the size of those described for the white-crowned sparrow (Zonotrichia leucophrys). A computer program which uses the dynamic programming algorithm to compare objectively shapes digitised from sonagrams was developed and tested with syllables from chaffinch songs.
1992-01-01T00:00:00ZWilliams, James MichaelThe acoustic adaptation hypothesis was reviewed. This predicts that the sounds used by birds singing in a dense habitat should be of lower frequency than those in a more open habitat, and that sounds should be spaced out more in time in denser habitats to avoid degradation by reverberations. These predictions were tested by recording chaffinch (Fringilla coelebs) songs in open scrub, coniferous plantations, and a natural Scots pine forest, but the results obtained gave little support to the predictions made. Transmission of white noise and the songs of blue (F. teydea) arid Canary Islands chaffinches (F. c. tintillon) through laurel and Canarian pine forests on Tenerife revealed a sound window of less excess attenuation than expected in both habitats at frequencies of 2-3kHz. The song of the blue chaffinch appears to be better adapted for transmission through both habitats. Computer simulations of the formation of dialects by random copying of the songs possessed by neighbours predicted a strong effect of both the number of neighbours available to learn from, and the repertoire size, upon the songs' longevity and the number of birds sharing a particular song type. If the song type which was commonest amongst those sung by neighbours was learnt, larger groups of birds were found to share song types. At low copying error rates these groups approached the size of those described for the white-crowned sparrow (Zonotrichia leucophrys). A computer program which uses the dynamic programming algorithm to compare objectively shapes digitised from sonagrams was developed and tested with syllables from chaffinch songs.Song acquisition and control in the chaffinch 'Fringilla coelebs' : the organisation of a behavioural repertoireRiebel, Katharinahttps://hdl.handle.net/10023/150682019-03-29T10:38:02Z1998-01-01T00:00:00ZBird song provides us with one of the best models with which to investigate learning, communication and the organisation of behavioural repertoires. This study describes temporal organisation and song pattern choice in the chaffinch in order to develop hypotheses for possible song control mechanisms. Influences of the song learning process and motivation on performance are tested in experiments. The role of nature and nurture in shaping females' song preferences is investigated by using operant tasks. A first quantitative assessment of temporal organisation within songs is provided in Chapter 2. Chaffinches sing with eventual variety, each song type in a male's repertoire is repeated a few times before a switch to the next type occurs. Chapter 3 tests two hypotheses for mechanisms controlling song type switching: that a maximum number of repetitions or that a maximum duration (time window) sets the upper limit. Clear evidence for a time window as an upper constraint was found in wild birds as song type bouts with many repetitions were sung at fast rates only, whereas those with few repetitions could be sung at either fast or slow rates. However, the mean number of song type repetitions depended strongly both on the subject and the song type. No evidence could be found that number of repetitions per song type were influenced by the tutor's singing style in hand-reared chaffinches (Chapter 4). Playbacks of single songs to wild males revealed the motivation dependent flexibility of the system as the birds reacted with distinct increases in bout duration (Chapter 5) but showed a different response to playbacks of songs that were the same or different from that being performed by the subject. Song was used as a positive reinforcer in an operant conditioning task with female chaffinches (Chapter 6). The influence of early exposure to song on later preferences and the relative importance of the trill and flourish sections of the song were tested this way. Females showed no preference for familiar over unfamiliar songs, but preferred songs with flourishes over those without.
1998-01-01T00:00:00ZRiebel, KatharinaBird song provides us with one of the best models with which to investigate learning, communication and the organisation of behavioural repertoires. This study describes temporal organisation and song pattern choice in the chaffinch in order to develop hypotheses for possible song control mechanisms. Influences of the song learning process and motivation on performance are tested in experiments. The role of nature and nurture in shaping females' song preferences is investigated by using operant tasks. A first quantitative assessment of temporal organisation within songs is provided in Chapter 2. Chaffinches sing with eventual variety, each song type in a male's repertoire is repeated a few times before a switch to the next type occurs. Chapter 3 tests two hypotheses for mechanisms controlling song type switching: that a maximum number of repetitions or that a maximum duration (time window) sets the upper limit. Clear evidence for a time window as an upper constraint was found in wild birds as song type bouts with many repetitions were sung at fast rates only, whereas those with few repetitions could be sung at either fast or slow rates. However, the mean number of song type repetitions depended strongly both on the subject and the song type. No evidence could be found that number of repetitions per song type were influenced by the tutor's singing style in hand-reared chaffinches (Chapter 4). Playbacks of single songs to wild males revealed the motivation dependent flexibility of the system as the birds reacted with distinct increases in bout duration (Chapter 5) but showed a different response to playbacks of songs that were the same or different from that being performed by the subject. Song was used as a positive reinforcer in an operant conditioning task with female chaffinches (Chapter 6). The influence of early exposure to song on later preferences and the relative importance of the trill and flourish sections of the song were tested this way. Females showed no preference for familiar over unfamiliar songs, but preferred songs with flourishes over those without.Visual and behavioural influences on song tutor choice in Zebra finches (Taeniopygia guttata)Mann, Nigelhttps://hdl.handle.net/10023/150672019-03-29T10:37:15Z1992-01-01T00:00:00ZUsing a laboratory approach, this thesis further' investigates patterns of song learning in the zebra finch (Taeniopygia guttata). Chapter 1 provides a background to the form and function of song learning in a broad context, and introduces the zebra finch and the major role it has played in this field of research. In Chapters 2 and 3, a strong influence of early visual imprinting on song tutor choice is demonstrated. Tutors of the same colour morph as the parents were much preferred. Song heard before or after the sensitive phase was often produced, if no tutor of the parental morph was present during this period. There was no clear evidence for one parent having a greater influence in this respect than the other. Differences were found between the morph preference for mates and song tutors, and possible reasons for these are discussed. Chapter 4 revealed that the mother may influence tutor choice, probably by attentiveness to her by her offspring increasing their exposure to the song of an accompanying male. There was also a preference for a paired, rather than a single, male. In Chapter 5, song tutor choice was studied in aviaries and related to behaviour occurring in this more naturalistic environment. A preference for learning the father's song was found). Specific types of interaction did not link overall with song copying, but the amount of time that birds spent within close proximity did. General aspects of behaviour evident in the aviaries are discussed. The final chapter demonstrated that a short distance (38 cm) between tutor and tutee can be sufficient to inhibit song learning, probably because of the reduced scope for interaction.
1992-01-01T00:00:00ZMann, NigelUsing a laboratory approach, this thesis further' investigates patterns of song learning in the zebra finch (Taeniopygia guttata). Chapter 1 provides a background to the form and function of song learning in a broad context, and introduces the zebra finch and the major role it has played in this field of research. In Chapters 2 and 3, a strong influence of early visual imprinting on song tutor choice is demonstrated. Tutors of the same colour morph as the parents were much preferred. Song heard before or after the sensitive phase was often produced, if no tutor of the parental morph was present during this period. There was no clear evidence for one parent having a greater influence in this respect than the other. Differences were found between the morph preference for mates and song tutors, and possible reasons for these are discussed. Chapter 4 revealed that the mother may influence tutor choice, probably by attentiveness to her by her offspring increasing their exposure to the song of an accompanying male. There was also a preference for a paired, rather than a single, male. In Chapter 5, song tutor choice was studied in aviaries and related to behaviour occurring in this more naturalistic environment. A preference for learning the father's song was found). Specific types of interaction did not link overall with song copying, but the amount of time that birds spent within close proximity did. General aspects of behaviour evident in the aviaries are discussed. The final chapter demonstrated that a short distance (38 cm) between tutor and tutee can be sufficient to inhibit song learning, probably because of the reduced scope for interaction.The importance of visual, vocal and behavioural cues for song tutor choice in Zebra finchesClayton, Nicky S.https://hdl.handle.net/10023/150652019-03-29T10:42:50Z1988-01-01T00:00:00ZThis thesis examines the importance of visual, vocal and behavioural cues for song tutor choice in zebra finches, Taeniopygia guttata. Zebra finch males normally copy song at 35 to 65 days of age. In the wild the young become independent at about 35 days of age and form small flocks in the area of the colony where they will be exposed to a variety of song tutors. In Chapter 3 captive zebra finches are provided with the opportunity to learn from two conspecifics at 35 days of age. Female-raised males which are housed with two unrelated tutors prefer to learn from the one who is, most aggressive towards them. Normally-raised males which are housed with an unrelated tutor and one, whose song is similar to the father's tend to copy the tutor with the similar song: this relies on the young bird learning some characteristics of his father's song before independence. Chapter 4 shows that males and females can discriminate between their father's song and those of other males. Visual, vocal and behavioural cues are all important for species-specificity. Cross-fostering using Bengalese finches, Lonchura striata, as foster-parents is an important tool for studying this. Chapter 5 looks at Bengalese finch song development; Chapter 6 compares song development in cross-fostered zebra finches and Bengalese finches. Visual cues are important for tutor choice and young males of both species which are provided with a zebra finch singing Bengalese song and a Bengalese finch singing zebra finch song prefer the conspecific tutor (Chapter 7). Chapter 8 suggests that conspecific song elements are not important for zebra finches: there is no tendency to prefer a tutor with normal song over one singing Bengalese song. Cross-fostering can also, influence the timing of song learning. Males which are housed successively (Chapter 9) or simultaneously (Chapter 10) with both species tend to reproduce song which they heard before independence in addition to learning from the tutor which they heard after independence at 35 to 65 days of age: this indicates that the timing of the sensitive phase is flexible and mediated by both experience and age. There are a number of similarities between song learning and sexual imprinting which are discussed in Chapter 11. Crucial to these studies is a knowledge of the two species' behaviours. Chapter 12 compares, parental behaviour in captivity. Chapter 12 concludes with a plea for more research in the wild.
1988-01-01T00:00:00ZClayton, Nicky S.This thesis examines the importance of visual, vocal and behavioural cues for song tutor choice in zebra finches, Taeniopygia guttata. Zebra finch males normally copy song at 35 to 65 days of age. In the wild the young become independent at about 35 days of age and form small flocks in the area of the colony where they will be exposed to a variety of song tutors. In Chapter 3 captive zebra finches are provided with the opportunity to learn from two conspecifics at 35 days of age. Female-raised males which are housed with two unrelated tutors prefer to learn from the one who is, most aggressive towards them. Normally-raised males which are housed with an unrelated tutor and one, whose song is similar to the father's tend to copy the tutor with the similar song: this relies on the young bird learning some characteristics of his father's song before independence. Chapter 4 shows that males and females can discriminate between their father's song and those of other males. Visual, vocal and behavioural cues are all important for species-specificity. Cross-fostering using Bengalese finches, Lonchura striata, as foster-parents is an important tool for studying this. Chapter 5 looks at Bengalese finch song development; Chapter 6 compares song development in cross-fostered zebra finches and Bengalese finches. Visual cues are important for tutor choice and young males of both species which are provided with a zebra finch singing Bengalese song and a Bengalese finch singing zebra finch song prefer the conspecific tutor (Chapter 7). Chapter 8 suggests that conspecific song elements are not important for zebra finches: there is no tendency to prefer a tutor with normal song over one singing Bengalese song. Cross-fostering can also, influence the timing of song learning. Males which are housed successively (Chapter 9) or simultaneously (Chapter 10) with both species tend to reproduce song which they heard before independence in addition to learning from the tutor which they heard after independence at 35 to 65 days of age: this indicates that the timing of the sensitive phase is flexible and mediated by both experience and age. There are a number of similarities between song learning and sexual imprinting which are discussed in Chapter 11. Crucial to these studies is a knowledge of the two species' behaviours. Chapter 12 compares, parental behaviour in captivity. Chapter 12 concludes with a plea for more research in the wild.Social aspects of call learning in the zebra finch (Taeniopygia guttata) and the budgerigar (Melopsittacus undulatus)Bartlett, Paulhttps://hdl.handle.net/10023/150642019-03-29T10:31:21Z1999-01-01T00:00:00ZChapter 1 provides an introduction to the thesis by discussing the relevant literature on vocal learning in songbirds and parrots, with particular reference to calls, and setting out the aims of the following chapters. Chapter 2 concerned an investigation of the similarity in the distance calls within and between families of zebra finches, involving fostering young birds to non-related parents. Male offspring were most similar in their distance calls to their male siblings with which they were raised and the adult male which raised them, suggesting an environmental influence in the acquisition of the call. There was also an indication that the call may be, at least in part, inherited. Females were most similar to their mothers and female siblings, though not to the same extent as in males. Chapter 3 examined whether male zebra finches could exhibit vocal plasticity in adulthood, by learning new calls from other conspecifics, and whether social deprivation during a young bird's development would accentuate this tendency. Adult zebra finches could not learn new calls from other similarly raised cagemates, even if these birds were reared under conditions of extreme social deprivation and were presented with an appropriate normally-raised adult male tutor. Chapter 4 described a study which investigated whether adult male budgerigars housed in soundproof boxes, could learn new calls from a tape recording in the absence of any social stimuli. Learning from tapes was very limited with only one bird producing an accurate copy of the playback, emphasising the importance of an interactive social context in vocal learning. Chapter 5 attempted to determine exactly which social factors were most influential in determining the extent of call matching between adult male budgerigars. Certain individuals did match more closely in their contact calls; close proximity appeared to promote call convergence between cagemates. Chapter 6 examined the effect of adding an unfamiliar budgerigar to an established flock, on the group specific call. It was found that, contrary to expectation, mutual imitation by all flock mates did not occur as other studies have shown, and that 'new recruits' conformed to the shared group call. Chapter 7 concluded the findings of the five experimental chapters, and discussed their significance with reference to previous studies, including ideas for further investigation.
1999-01-01T00:00:00ZBartlett, PaulChapter 1 provides an introduction to the thesis by discussing the relevant literature on vocal learning in songbirds and parrots, with particular reference to calls, and setting out the aims of the following chapters. Chapter 2 concerned an investigation of the similarity in the distance calls within and between families of zebra finches, involving fostering young birds to non-related parents. Male offspring were most similar in their distance calls to their male siblings with which they were raised and the adult male which raised them, suggesting an environmental influence in the acquisition of the call. There was also an indication that the call may be, at least in part, inherited. Females were most similar to their mothers and female siblings, though not to the same extent as in males. Chapter 3 examined whether male zebra finches could exhibit vocal plasticity in adulthood, by learning new calls from other conspecifics, and whether social deprivation during a young bird's development would accentuate this tendency. Adult zebra finches could not learn new calls from other similarly raised cagemates, even if these birds were reared under conditions of extreme social deprivation and were presented with an appropriate normally-raised adult male tutor. Chapter 4 described a study which investigated whether adult male budgerigars housed in soundproof boxes, could learn new calls from a tape recording in the absence of any social stimuli. Learning from tapes was very limited with only one bird producing an accurate copy of the playback, emphasising the importance of an interactive social context in vocal learning. Chapter 5 attempted to determine exactly which social factors were most influential in determining the extent of call matching between adult male budgerigars. Certain individuals did match more closely in their contact calls; close proximity appeared to promote call convergence between cagemates. Chapter 6 examined the effect of adding an unfamiliar budgerigar to an established flock, on the group specific call. It was found that, contrary to expectation, mutual imitation by all flock mates did not occur as other studies have shown, and that 'new recruits' conformed to the shared group call. Chapter 7 concluded the findings of the five experimental chapters, and discussed their significance with reference to previous studies, including ideas for further investigation.The rook : aspects of its behaviour and ecologyReid, James Beatonhttps://hdl.handle.net/10023/150622019-03-29T10:31:00Z1985-01-01T00:00:00ZAspects of the ecology and behaviour of the rook Corvus frugilegus L. were studied. The decline of rook populations in Britain since the 1940's is documented and the extent and reasons for the decline in north east Fife examined in detail. The most likely causes of this were changes in agricultural practices, including the way the land is used and possibly the use of organo-chlorine insecticides. The ecological relationship between the rook and the carrion crow C. corone L. is explored in an investigation of their habitat use and associated niche metrics. Both species are heavily dependent on agricultural land, especially grassland, for foraging. The carrion crow narrows its niche breadth more than the rook does at times of possible food shortage. Observations on captive birds show rooks to be subordinate to carrion crows. Analysis of nestling rook gizzard contents revealed cereal to be an abundant food as well as invertebrates, particularly beetles and tipulids. A review of tool-use in birds is presented and the conditions under which tool-use is likely to arise are elucidated. The proximate causation of an example of this category of behaviour performed by at least one captive rook is reported. The rook is identified as an ecologically and behaviourally adaptable bird.
1985-01-01T00:00:00ZReid, James BeatonAspects of the ecology and behaviour of the rook Corvus frugilegus L. were studied. The decline of rook populations in Britain since the 1940's is documented and the extent and reasons for the decline in north east Fife examined in detail. The most likely causes of this were changes in agricultural practices, including the way the land is used and possibly the use of organo-chlorine insecticides. The ecological relationship between the rook and the carrion crow C. corone L. is explored in an investigation of their habitat use and associated niche metrics. Both species are heavily dependent on agricultural land, especially grassland, for foraging. The carrion crow narrows its niche breadth more than the rook does at times of possible food shortage. Observations on captive birds show rooks to be subordinate to carrion crows. Analysis of nestling rook gizzard contents revealed cereal to be an abundant food as well as invertebrates, particularly beetles and tipulids. A review of tool-use in birds is presented and the conditions under which tool-use is likely to arise are elucidated. The proximate causation of an example of this category of behaviour performed by at least one captive rook is reported. The rook is identified as an ecologically and behaviourally adaptable bird.Reproductive behaviour in a small inland colony of black-headed gulls (larus ridibundus)McCulloch, Fiona M.https://hdl.handle.net/10023/150612019-03-29T10:34:17Z1990-01-01T00:00:00ZThis study was carried out over three breeding seasons at a small marsh-nesting black-headed gull (Larus ridibundus) colony. Two of the years proved to be atypically hot and dry, resulting in the drying out of parts of the colony. This facilitated predation by foxes and resulted in almost complete breeding failure in these two years. Synchronisation of breeding was evident but the average clutch size was smaller than generally recorded for black-headed gulls. There was a tendency for third laid eggs and third hatched chicks to have the highest mortality rate, and third hatched chicks put on less weight during their first three days of life than all other chicks. Pairs of gulls that did not successfully retain their territories and lay eggs spent less time on the territory than those that were successful. The unsuccessful males were also more restless and more aggressive than successful males. In general, the gulls spent most time on the territory during the incubation stage, although partners spent the most time together on the territory during the pre-egg stage. The territory was never left unattended during the incubation stage, but it was occasionally deserted during the pre-egg stage, and increasingly deserted as the chick stage proceeded. In one year, but not another, males spent most time on the territory and incubating during the egg stage, while females spent most time on the territory and brooding during the chick stage. The gulls were most aggressive during the pre-egg stage and least aggressive during the incubation stage, and the males played the greater role in defence during the pre-egg and egg stages. The sexes shared equally the feeding of the chicks and became less eager to feed the chicks as they grew. The number of feeds given per hour per chick decreased with increasing brood size.
1990-01-01T00:00:00ZMcCulloch, Fiona M.This study was carried out over three breeding seasons at a small marsh-nesting black-headed gull (Larus ridibundus) colony. Two of the years proved to be atypically hot and dry, resulting in the drying out of parts of the colony. This facilitated predation by foxes and resulted in almost complete breeding failure in these two years. Synchronisation of breeding was evident but the average clutch size was smaller than generally recorded for black-headed gulls. There was a tendency for third laid eggs and third hatched chicks to have the highest mortality rate, and third hatched chicks put on less weight during their first three days of life than all other chicks. Pairs of gulls that did not successfully retain their territories and lay eggs spent less time on the territory than those that were successful. The unsuccessful males were also more restless and more aggressive than successful males. In general, the gulls spent most time on the territory during the incubation stage, although partners spent the most time together on the territory during the pre-egg stage. The territory was never left unattended during the incubation stage, but it was occasionally deserted during the pre-egg stage, and increasingly deserted as the chick stage proceeded. In one year, but not another, males spent most time on the territory and incubating during the egg stage, while females spent most time on the territory and brooding during the chick stage. The gulls were most aggressive during the pre-egg stage and least aggressive during the incubation stage, and the males played the greater role in defence during the pre-egg and egg stages. The sexes shared equally the feeding of the chicks and became less eager to feed the chicks as they grew. The number of feeds given per hour per chick decreased with increasing brood size.Behaviour, ecology and recruitment of immature guillemots 'Uria aalge'Halley, Duncanhttps://hdl.handle.net/10023/150602019-03-29T10:31:22Z1993-01-01T00:00:00ZGuillemots have been studied on the Isle of May since 1980. Between 184 and 581 individually identifiable birds were ringed as chicks each year since 1983. Cumulative known survival rates varied from 14-39% for cohorts at least 3 years of age. Survival rate was highly significantly negatively correlated with the number of hours of gale force winds in the three months after a cohort first goes to sea. Immatures did not return to the colony until at least 2 years of age. The proportion of a cohort attending the colony increased, cohorts arrived at the colony earlier in the season, and individuals were seen more often up to the age of 4-5. Experienced individuals arrived earlier, were seen more often, and were more likely to recruit than inexperienced birds of the same age. Two and 3 years olds but very few older birds visited sea rocks below the colony; all ages were seen on top ledges and on sites within the breeding colony. Immatures tended to visit the same subcolony repeatedly; older cohorts were more sedentary. Guillemots were highly philopatric to their natal subcolonies as prebreeders and recruits. Recruitment age varied from 3 years to 8+, median 6. Recruits fledged 0.26 chicks/pair compared to 0.79/pair in the breeding population as a whole. Recruits arrived earlier in the year of recruitment, and in the previous year, than same-aged birds which did not recruit. Substantial numbers of immatures from other colonies visited the Isle of May and Isle of May bred birds were observed elsewhere. Non-native immatures were seen fewer times than natives. Activity at the colony varied little between immature cohorts, but suggested increasing competitive ability with age. The results are discussed in relation to wider issues in seabird behaviour and ecology.
1993-01-01T00:00:00ZHalley, DuncanGuillemots have been studied on the Isle of May since 1980. Between 184 and 581 individually identifiable birds were ringed as chicks each year since 1983. Cumulative known survival rates varied from 14-39% for cohorts at least 3 years of age. Survival rate was highly significantly negatively correlated with the number of hours of gale force winds in the three months after a cohort first goes to sea. Immatures did not return to the colony until at least 2 years of age. The proportion of a cohort attending the colony increased, cohorts arrived at the colony earlier in the season, and individuals were seen more often up to the age of 4-5. Experienced individuals arrived earlier, were seen more often, and were more likely to recruit than inexperienced birds of the same age. Two and 3 years olds but very few older birds visited sea rocks below the colony; all ages were seen on top ledges and on sites within the breeding colony. Immatures tended to visit the same subcolony repeatedly; older cohorts were more sedentary. Guillemots were highly philopatric to their natal subcolonies as prebreeders and recruits. Recruitment age varied from 3 years to 8+, median 6. Recruits fledged 0.26 chicks/pair compared to 0.79/pair in the breeding population as a whole. Recruits arrived earlier in the year of recruitment, and in the previous year, than same-aged birds which did not recruit. Substantial numbers of immatures from other colonies visited the Isle of May and Isle of May bred birds were observed elsewhere. Non-native immatures were seen fewer times than natives. Activity at the colony varied little between immature cohorts, but suggested increasing competitive ability with age. The results are discussed in relation to wider issues in seabird behaviour and ecology.Noradrenergic control of spinal motor circuitry in two related amphibian species 'Xenopus laevis' and 'Rama temporaria'McDearmid, Jonathan R.https://hdl.handle.net/10023/150582019-03-29T10:34:45Z1998-01-01T00:00:00Z1. The role of the catecholamine noradrenaline (NA) was examined during fictive swimming in Xenopus laevis tadpoles. 2. The primary effects of the amine in both embryonic and larval Xenopus was to markedly decrease motor frequency whilst simultaneously reducing rostrocaudal delays during swimming. 3. The NA-mediated modulation of swimming activity in Xenopus larvae can be reversed with phentolamine, a non-selective an adrenergic receptor antagonist, suggesting that NA may be acting through either α₁ or α₂ receptors, or a combination of both. 4. Intracellular recordings made from embryo spinal motorneurones revealed that reciprocal inhibitory glycinergic potentials are enhanced by NA. This effect is most prominent in caudal regions of the spinal cord where inhibitory synaptic drive is generally weaker. 5. NA was also found to enhance glycinergic reciprocal inhibition during swimming in larval spinal cord motomeurones. 6. Intracellular recordings, under tetrodotoxin, reveal that NA enhances the occurrence of spontaneous glycinergic inhibitory post synaptic potentials arising from the terminals of inhibitory intemeurones, suggesting that the amine is acting presynaptically to enhance evoked release of glycine during swimming. 7. The effects of NA on swimming frequency and rostrocaudal delay appear to be largely mediated through an enhancement of glycinergic reciprocal inhibition as blockade of glycine receptors with strychnine weakens the ability of the amine affect these parameters of motor output. 8. The effects of NA on motor output were also examined in embryos of the amphibian Rana temporaria. Whilst NA did not obviously affect swimming activity, the amine induced a non-rhythmic pattern of motor activity. 9. The free radical gas, nitric oxide also induced a non-rhythmic pattern of motor discharge that was remarkably similar to that elicited by NA, indicating that this neural messenger may be important for motor control.
1998-01-01T00:00:00ZMcDearmid, Jonathan R.1. The role of the catecholamine noradrenaline (NA) was examined during fictive swimming in Xenopus laevis tadpoles. 2. The primary effects of the amine in both embryonic and larval Xenopus was to markedly decrease motor frequency whilst simultaneously reducing rostrocaudal delays during swimming. 3. The NA-mediated modulation of swimming activity in Xenopus larvae can be reversed with phentolamine, a non-selective an adrenergic receptor antagonist, suggesting that NA may be acting through either α₁ or α₂ receptors, or a combination of both. 4. Intracellular recordings made from embryo spinal motorneurones revealed that reciprocal inhibitory glycinergic potentials are enhanced by NA. This effect is most prominent in caudal regions of the spinal cord where inhibitory synaptic drive is generally weaker. 5. NA was also found to enhance glycinergic reciprocal inhibition during swimming in larval spinal cord motomeurones. 6. Intracellular recordings, under tetrodotoxin, reveal that NA enhances the occurrence of spontaneous glycinergic inhibitory post synaptic potentials arising from the terminals of inhibitory intemeurones, suggesting that the amine is acting presynaptically to enhance evoked release of glycine during swimming. 7. The effects of NA on swimming frequency and rostrocaudal delay appear to be largely mediated through an enhancement of glycinergic reciprocal inhibition as blockade of glycine receptors with strychnine weakens the ability of the amine affect these parameters of motor output. 8. The effects of NA on motor output were also examined in embryos of the amphibian Rana temporaria. Whilst NA did not obviously affect swimming activity, the amine induced a non-rhythmic pattern of motor activity. 9. The free radical gas, nitric oxide also induced a non-rhythmic pattern of motor discharge that was remarkably similar to that elicited by NA, indicating that this neural messenger may be important for motor control.The amphibian oocyte nucleusMacgregor, Herbert Cecilhttps://hdl.handle.net/10023/150562019-03-29T10:30:08Z1961-01-01T00:00:00Z1961-01-01T00:00:00ZMacgregor, Herbert CecilSchooling decisions and discriminatory abilities of fishGriffiths, Sian Wynhttps://hdl.handle.net/10023/150552019-03-29T10:42:19Z1997-01-01T00:00:00ZThe aim of this thesis has been to investigate the individual decision making abilities of schooling fish in order to understand the composition of fish schools. Do individuals choose particular school-mates, and if so, on what basis are these decisions made? The null hypothesis, that schools are composed of random assortments of individual fish, has been rejected. School membership and structure are profoundly affected by the cognitive abilities and partner choice decisions of fish. Field work carried out in Trinidad and Dorset, UK (on guppies, Poecilia reticulata, and European minnows, Phoxinus phoxinus, respectively) has demonstrated that familiarity does indeed influence choice of schooling partner. Individual guppies under laboratory conditions and in the wild recognise and prefer school-mates with whom they are familiar, and schools of minnows are composed of a significant proportion of individuals which are familiar to one another. Preference for familiar conspecifics develops gradually (over at least 12 days in the case of guppies) and observations of wild guppies shows that this schooling preference is mediated by group size. Tendency to school with familiar fish is strong when group size is small, but declines thereafter, no preference being made as group size increases beyond ~40 individual females. The effect of group size on these partner choice decisions suggests that individual recognition may be possible. Intriguingly, a gender difference in the partner choice decisions of guppy schools in the wild has also been identified. Females spend more time schooling with individuals from their natural schools than males. This has important evolutionary consequences in terms of population differentiation and speciation. It seems, therefore, that schools are by no means composed of a random assortment of individuals. Indeed school structure and membership are profoundly affected by the remarkable discriminatory abilities of individual fish.
1997-01-01T00:00:00ZGriffiths, Sian WynThe aim of this thesis has been to investigate the individual decision making abilities of schooling fish in order to understand the composition of fish schools. Do individuals choose particular school-mates, and if so, on what basis are these decisions made? The null hypothesis, that schools are composed of random assortments of individual fish, has been rejected. School membership and structure are profoundly affected by the cognitive abilities and partner choice decisions of fish. Field work carried out in Trinidad and Dorset, UK (on guppies, Poecilia reticulata, and European minnows, Phoxinus phoxinus, respectively) has demonstrated that familiarity does indeed influence choice of schooling partner. Individual guppies under laboratory conditions and in the wild recognise and prefer school-mates with whom they are familiar, and schools of minnows are composed of a significant proportion of individuals which are familiar to one another. Preference for familiar conspecifics develops gradually (over at least 12 days in the case of guppies) and observations of wild guppies shows that this schooling preference is mediated by group size. Tendency to school with familiar fish is strong when group size is small, but declines thereafter, no preference being made as group size increases beyond ~40 individual females. The effect of group size on these partner choice decisions suggests that individual recognition may be possible. Intriguingly, a gender difference in the partner choice decisions of guppy schools in the wild has also been identified. Females spend more time schooling with individuals from their natural schools than males. This has important evolutionary consequences in terms of population differentiation and speciation. It seems, therefore, that schools are by no means composed of a random assortment of individuals. Indeed school structure and membership are profoundly affected by the remarkable discriminatory abilities of individual fish.The role of angiotensin II in osmoregulation in teleost fishGrierson, Christal Elizabethhttps://hdl.handle.net/10023/150542021-02-23T15:29:17Z1991-01-01T00:00:00ZAn osmoregulatory role for angiotensin II was investigated in the euryhaline European eel Anguilla anguilla L., plaice (Pleuronectes platessa) and dab (Limanda limanda). 1. Ile5 - and val5 -AII increased blood pressure in all species. Ile5 -AII produced a greater effect than val5 - AII, at equal concentrations, in eels, however in plaice and dab, this trend was reversed. Papaverine reduced blood pressure, followed by recovery to control in all cases. 2. Both AII sequences increased drinking rates except ile5 -AII in dab. ile5 -AII again proved more potent than val5-AII in eels and val5 - was greater than ile5- AII in flatfish. Papaverine increased drinking in all species. Captopril had no effect on eel or dab drinking rates, but reduced those of plaice. 3. 1.0nM and 10.0nM AII increased ANP release from isolated eel myocytes, except from FW atria. At 1.0nM, ventricular release was greater than atrial, however at 10.0nM, AII ANP secretion was similar in both types of myocyte. In all cases ANP release was greater from SW than FW myocytes. 4. Tissue/plasma ratios revealed greatest binding in SW eel liver. Tissue receptor specific binding was also greatest in FW eel liver membranes, however in SW tissues gill was slightly greater than liver. A FW eel liver membrane radioreceptor assay was developed. Binding was optimal at 22°C, 25mM calcium, protein concentration of 700ug, 125I-AII concentration of 25pM and an incubation period of 60 minutes. 6. Initial FW eel liver binding studies indicated two receptor classes with Kd=1. 5x10-11M and 2.46x10-10. However subsequent studies reveal Kd =3.31x10-8M in FW liver and Kd=1.09x10-7M in SW liver preparations. 7. 125I-ile5 -AII produced greater binding than 125I-val5 -AII in eel liver preparations. 125I-val5 -AII produced greater binding in flatfish membranes. Investigations of 125I-ile5 -AII displacement from FW eel liver membranes revealed peptide potencies in the following order. sar-AII>ile5-AII>5-8AII>ile5-AI>val5-AI> ile4-AIII>val4-AIII>bradykinin>1-4AII
1991-01-01T00:00:00ZGrierson, Christal ElizabethAn osmoregulatory role for angiotensin II was investigated in the euryhaline European eel Anguilla anguilla L., plaice (Pleuronectes platessa) and dab (Limanda limanda). 1. Ile5 - and val5 -AII increased blood pressure in all species. Ile5 -AII produced a greater effect than val5 - AII, at equal concentrations, in eels, however in plaice and dab, this trend was reversed. Papaverine reduced blood pressure, followed by recovery to control in all cases. 2. Both AII sequences increased drinking rates except ile5 -AII in dab. ile5 -AII again proved more potent than val5-AII in eels and val5 - was greater than ile5- AII in flatfish. Papaverine increased drinking in all species. Captopril had no effect on eel or dab drinking rates, but reduced those of plaice. 3. 1.0nM and 10.0nM AII increased ANP release from isolated eel myocytes, except from FW atria. At 1.0nM, ventricular release was greater than atrial, however at 10.0nM, AII ANP secretion was similar in both types of myocyte. In all cases ANP release was greater from SW than FW myocytes. 4. Tissue/plasma ratios revealed greatest binding in SW eel liver. Tissue receptor specific binding was also greatest in FW eel liver membranes, however in SW tissues gill was slightly greater than liver. A FW eel liver membrane radioreceptor assay was developed. Binding was optimal at 22°C, 25mM calcium, protein concentration of 700ug, 125I-AII concentration of 25pM and an incubation period of 60 minutes. 6. Initial FW eel liver binding studies indicated two receptor classes with Kd=1. 5x10-11M and 2.46x10-10. However subsequent studies reveal Kd =3.31x10-8M in FW liver and Kd=1.09x10-7M in SW liver preparations. 7. 125I-ile5 -AII produced greater binding than 125I-val5 -AII in eel liver preparations. 125I-val5 -AII produced greater binding in flatfish membranes. Investigations of 125I-ile5 -AII displacement from FW eel liver membranes revealed peptide potencies in the following order. sar-AII>ile5-AII>5-8AII>ile5-AI>val5-AI> ile4-AIII>val4-AIII>bradykinin>1-4AIIThe mechanical properties of fish myotomal muscleAltringham, John Derekhttps://hdl.handle.net/10023/150532019-03-29T10:30:54Z1981-01-01T00:00:00ZCHAPTER 1 A brief introduction is given to the structure, biochemistry and electrophysiological and mechanical properties of fish muscle.
CHAPTER 2 1. The neuromuscular end plates and preterminal axons of cod, Gadus morhua, fast myotomal muscle were stained for cholinesterase activity. 2. The number of end plates per fibre on superficial fast fibres (17.88 ± 2.13, mean ± 1 S.D.) was significantly higher than that of deep fast fibres (14.79 ± 2.48, P<< 0.001). A small degree of multi-terminal innervation was noted. The end plates showed a great variety in structure and size. 3. Fast muscle contains fibres with a wide range of diameters (20-240 µm). However, no correlation was found between the number of end plates per fibre and fibre diameter.
CHAPTER 3 1. The force-velocity characteristics of threads of natural actomyosin, and purified component proteins, from dogfish fast and slow muscle, and rabbit fast skeletal and cardiac muscle have been investigated. 2. Maximum isometric tensions were around 30-70 g cm⁻². The time taken to reach full tension after activation with ATP was 2-8 min. 3. Force-velocity curves obtained could be fitted to a linear form of Hill's equation (1938). In common with intact and skinned fibre studies, points below 0.7 P₀ were found to lie on a straight line. 4. Maximum contraction velocities were around 10⁻² Ls⁻¹, 2-3 orders of magnitude lower than those of intact muscle fibres. 5. The relative velocities of the different thread types do not reflect those of the corresponding muscles, on the basis of measurements on intact fibres, and on measurements of actomyosin/myofibrillar ATPase activities. 6. It is concluded that filament formation, geometry and packing, and not differences in cross bridge cycling rates, largely determine the observed properties of actomyosin threads.
CHAPTER 4 A description of the apparatus used to study the isometric and isotonic properties of skinned fibres is given, together with the methods and protocol used in Chapters 5-7.
CHAPTER 5 1. The pCa-tension relationship of cod, Gadus morhua, and dogfish, Scyliorhinus canicula, fast and slow skinned fibres isolated from the myotomal muscles was investigated. 2. Maximum isometric tensions were 1.9 ± 0.12 (mean ± 1 S.E.) (fast) and 0.85 ± 0.10 (slow) for cod fibres, and 1.87 ± 0.09 (fast) and 0.84 ± 0.04 (slow) for dogfish (All values : kg cm⁻²). 3. Sigmoid pCa-tension curves were obtained for all fibre types. Values for the half maximally activating [Ca²⁺], and n, the minimum number of Ca²⁺ binding sites involved in activation, were calculated: Thus, the minimum number of Ca²⁺ binding sites in cod is two, in dogfish, four. In both fish, greater cooperativity is exhibited by the fast muscle.
CHAPTER 6 1. Force-velocity curves were derived from fast and slow skinned fibres isolated from cod and dogfish myotomal muscles. 2. The extrapolated V and the constants a and b were calculated max from a linear form of Hill's equation: 3. These results are discussed with reference to previous studies of the P-V relationship in amphibian and mammalian muscle. The relationship between a/P₀ and efficiency, and its bearing on the present results is discussed.4. Velocity transients showed a small departure from linearity in all experiments, with velocity decreasing continuously during release (usually < 25% over the first 250 ms after release). This is a feature common to many previous experiments on skinned and intact fibres. The decrease in velocity during release was particularly marked in cod slow fibres. Similar results have been reported in amphibian slow muscle.
CHAPTER 7 1. Contraction velocity at low loads was studied in dogfish fast fibres during maximal and submaximal activations. 2. The velocity of contraction during the second 50 ms interval after the onset of release was reduced significantly at low [Ca²⁺], The shape of the velocity transient was found to be dependent on [Ca²⁺]. The rate of decrease of velocity was greater in submaximal than in maximal activations. 3. A brief review of previous studies on the dependence of Vmax on max [Ca²⁺] is given. 4. The results are discussed in the light of recent evidence for length dependent changes in the contractile system. Possible mechanisms for a Ca²⁺ and length dependent inactivation process are considered.
CHAPTER 8 The major outstanding problems are stated, and suggestions are made for further work which may give a greater insight into the molecular events underlying contraction in fish muscle. (Abstract shortened)
1981-01-01T00:00:00ZAltringham, John DerekCHAPTER 1 A brief introduction is given to the structure, biochemistry and electrophysiological and mechanical properties of fish muscle.
CHAPTER 2 1. The neuromuscular end plates and preterminal axons of cod, Gadus morhua, fast myotomal muscle were stained for cholinesterase activity. 2. The number of end plates per fibre on superficial fast fibres (17.88 ± 2.13, mean ± 1 S.D.) was significantly higher than that of deep fast fibres (14.79 ± 2.48, P<< 0.001). A small degree of multi-terminal innervation was noted. The end plates showed a great variety in structure and size. 3. Fast muscle contains fibres with a wide range of diameters (20-240 µm). However, no correlation was found between the number of end plates per fibre and fibre diameter.
CHAPTER 3 1. The force-velocity characteristics of threads of natural actomyosin, and purified component proteins, from dogfish fast and slow muscle, and rabbit fast skeletal and cardiac muscle have been investigated. 2. Maximum isometric tensions were around 30-70 g cm⁻². The time taken to reach full tension after activation with ATP was 2-8 min. 3. Force-velocity curves obtained could be fitted to a linear form of Hill's equation (1938). In common with intact and skinned fibre studies, points below 0.7 P₀ were found to lie on a straight line. 4. Maximum contraction velocities were around 10⁻² Ls⁻¹, 2-3 orders of magnitude lower than those of intact muscle fibres. 5. The relative velocities of the different thread types do not reflect those of the corresponding muscles, on the basis of measurements on intact fibres, and on measurements of actomyosin/myofibrillar ATPase activities. 6. It is concluded that filament formation, geometry and packing, and not differences in cross bridge cycling rates, largely determine the observed properties of actomyosin threads.
CHAPTER 4 A description of the apparatus used to study the isometric and isotonic properties of skinned fibres is given, together with the methods and protocol used in Chapters 5-7.
CHAPTER 5 1. The pCa-tension relationship of cod, Gadus morhua, and dogfish, Scyliorhinus canicula, fast and slow skinned fibres isolated from the myotomal muscles was investigated. 2. Maximum isometric tensions were 1.9 ± 0.12 (mean ± 1 S.E.) (fast) and 0.85 ± 0.10 (slow) for cod fibres, and 1.87 ± 0.09 (fast) and 0.84 ± 0.04 (slow) for dogfish (All values : kg cm⁻²). 3. Sigmoid pCa-tension curves were obtained for all fibre types. Values for the half maximally activating [Ca²⁺], and n, the minimum number of Ca²⁺ binding sites involved in activation, were calculated: Thus, the minimum number of Ca²⁺ binding sites in cod is two, in dogfish, four. In both fish, greater cooperativity is exhibited by the fast muscle.
CHAPTER 6 1. Force-velocity curves were derived from fast and slow skinned fibres isolated from cod and dogfish myotomal muscles. 2. The extrapolated V and the constants a and b were calculated max from a linear form of Hill's equation: 3. These results are discussed with reference to previous studies of the P-V relationship in amphibian and mammalian muscle. The relationship between a/P₀ and efficiency, and its bearing on the present results is discussed.4. Velocity transients showed a small departure from linearity in all experiments, with velocity decreasing continuously during release (usually < 25% over the first 250 ms after release). This is a feature common to many previous experiments on skinned and intact fibres. The decrease in velocity during release was particularly marked in cod slow fibres. Similar results have been reported in amphibian slow muscle.
CHAPTER 7 1. Contraction velocity at low loads was studied in dogfish fast fibres during maximal and submaximal activations. 2. The velocity of contraction during the second 50 ms interval after the onset of release was reduced significantly at low [Ca²⁺], The shape of the velocity transient was found to be dependent on [Ca²⁺]. The rate of decrease of velocity was greater in submaximal than in maximal activations. 3. A brief review of previous studies on the dependence of Vmax on max [Ca²⁺] is given. 4. The results are discussed in the light of recent evidence for length dependent changes in the contractile system. Possible mechanisms for a Ca²⁺ and length dependent inactivation process are considered.
CHAPTER 8 The major outstanding problems are stated, and suggestions are made for further work which may give a greater insight into the molecular events underlying contraction in fish muscle. (Abstract shortened)The influence of temperature acclimation on isolated muscle properties and burst swimming performance of the sculpin (Myoxocephalus scorpius L.)Beddow, Toni Annhttps://hdl.handle.net/10023/150512019-03-29T10:30:15Z1994-01-01T00:00:00ZA brief history of fish biomechanical studies is given and a general introduction on the composition and functional properties of fish muscle, in relation to different swimming activities is presented. Thermal adaptations in teleost fish over both evolutionary and seasonal time scales are discussed at different levels of biological organisation.
Chapter 2 The isometric properties of live fast fibres, isolated from the abdominal myotomes of the short-horned sculpin (Myoxocephalus scorpius) were examined at temperatures of 5, 10 and 15°C. The properties of fibres isolated from laboratory-acclimated (5 and 15°C) and naturally-acclimatised, summer (July - September) and winter (January - March) fish were compared to assess the modulating effect of environmental factors other than temperature.
Chapter 3 Live fast fibre bundles were isolated from the abdominal myotomes of naturally acclimatised (summer and winter) and laboratory acclimated (5°C and 15°C) sculpin. Force-velocity (P-V) characteristics of the fibres were investigated using iso-velocity releases. The mechanisms behind the acclimatory increases in power output in summer and 15°C-acclimated fish, at 15°C are partly due to increases in the Vmax of the fibres. More importantly force generating capacity shows a major acclimatory adaptation which greatly enhances power output at warm temperatures.
Chapter 4 Short-horned sculpin were acclimated to either 5 or 15°C (12 h light: 12 h dark) for 6 - 8 weeks. Prey-capture of Crangon crangon was filmed at 200 frames s-1, using a high speed video. The fish employed the three classic kinematic stages as described by Weihs (1973) in a typical "S" shaped fast start. The kinematics of the fast start were unaffected by temperature or acclimation state. 5°C-acclimated sculpin were tested at 5, 10 and 15°C. Rates of acceleration doubled in the 5°C-acclimated fish between 5 and 15°C. Tail-beat frequency also increased significantly from 5.5 Hz at 5°C to 8 Hz at 15°C. However, mean and maximum velocity and tail-beat amplitude were relatively independent of test temperature.
Chapter 5 Fast muscle fibres were isolated from rostral and caudal myotomes of summer-caught, short-horned sculpin. Muscle strain patterns for three positions (0.31L, 0.52L, 0.77L) along the body were calculated from changes in body curvature, during fast-starts at 15°C. Isolated rostral and caudal muscle fibres were subjected to the in vivo strain fluctuations and stimulated with a similar duty cycle (25 - 32%) to that found in vivo. Work loops were generated by plotting force and length. The effect of varying muscle stimulation phase on power output and force generation was investigated. At the anterior position in the body the rostral fibres produced significantly greater force (41.9 kN m-2) compared to the caudal fibres (12.2 kN m-2). Similarly, power output at position 1 was also significantly greater in rostral fibres (28.0 W kg-1) compared to caudal fibres (3.7 W kg-1). No difference was found in the properties of the fibres at positions 2 and 3. This suggests that the rostral fibres have adapted to their local mechanical environment to increase force and power generation, although the mechanisms responsible are unknown.
Chapter 6 The major findings of this thesis are discussed relating different aspects of muscle performance to locomotory capabilities of sculpin. Thermal adaptations over the natural environmental temperature range encountered by sculpin are considered and the possible mechanisms involved are discussed. Finally, suggestions for elucidating the molecular mechanisms behind adaptations in the shortening speed and force generation are presented. (Abstract shortened by ProQuest.)
1994-01-01T00:00:00ZBeddow, Toni AnnA brief history of fish biomechanical studies is given and a general introduction on the composition and functional properties of fish muscle, in relation to different swimming activities is presented. Thermal adaptations in teleost fish over both evolutionary and seasonal time scales are discussed at different levels of biological organisation.
Chapter 2 The isometric properties of live fast fibres, isolated from the abdominal myotomes of the short-horned sculpin (Myoxocephalus scorpius) were examined at temperatures of 5, 10 and 15°C. The properties of fibres isolated from laboratory-acclimated (5 and 15°C) and naturally-acclimatised, summer (July - September) and winter (January - March) fish were compared to assess the modulating effect of environmental factors other than temperature.
Chapter 3 Live fast fibre bundles were isolated from the abdominal myotomes of naturally acclimatised (summer and winter) and laboratory acclimated (5°C and 15°C) sculpin. Force-velocity (P-V) characteristics of the fibres were investigated using iso-velocity releases. The mechanisms behind the acclimatory increases in power output in summer and 15°C-acclimated fish, at 15°C are partly due to increases in the Vmax of the fibres. More importantly force generating capacity shows a major acclimatory adaptation which greatly enhances power output at warm temperatures.
Chapter 4 Short-horned sculpin were acclimated to either 5 or 15°C (12 h light: 12 h dark) for 6 - 8 weeks. Prey-capture of Crangon crangon was filmed at 200 frames s-1, using a high speed video. The fish employed the three classic kinematic stages as described by Weihs (1973) in a typical "S" shaped fast start. The kinematics of the fast start were unaffected by temperature or acclimation state. 5°C-acclimated sculpin were tested at 5, 10 and 15°C. Rates of acceleration doubled in the 5°C-acclimated fish between 5 and 15°C. Tail-beat frequency also increased significantly from 5.5 Hz at 5°C to 8 Hz at 15°C. However, mean and maximum velocity and tail-beat amplitude were relatively independent of test temperature.
Chapter 5 Fast muscle fibres were isolated from rostral and caudal myotomes of summer-caught, short-horned sculpin. Muscle strain patterns for three positions (0.31L, 0.52L, 0.77L) along the body were calculated from changes in body curvature, during fast-starts at 15°C. Isolated rostral and caudal muscle fibres were subjected to the in vivo strain fluctuations and stimulated with a similar duty cycle (25 - 32%) to that found in vivo. Work loops were generated by plotting force and length. The effect of varying muscle stimulation phase on power output and force generation was investigated. At the anterior position in the body the rostral fibres produced significantly greater force (41.9 kN m-2) compared to the caudal fibres (12.2 kN m-2). Similarly, power output at position 1 was also significantly greater in rostral fibres (28.0 W kg-1) compared to caudal fibres (3.7 W kg-1). No difference was found in the properties of the fibres at positions 2 and 3. This suggests that the rostral fibres have adapted to their local mechanical environment to increase force and power generation, although the mechanisms responsible are unknown.
Chapter 6 The major findings of this thesis are discussed relating different aspects of muscle performance to locomotory capabilities of sculpin. Thermal adaptations over the natural environmental temperature range encountered by sculpin are considered and the possible mechanisms involved are discussed. Finally, suggestions for elucidating the molecular mechanisms behind adaptations in the shortening speed and force generation are presented. (Abstract shortened by ProQuest.)Phenotypic and evolutionary variation in fish myofibrillar proteinsCole, Nicholas Jameshttps://hdl.handle.net/10023/150502019-03-29T10:31:26Z1998-01-01T00:00:00ZChapter 1 General Introduction: The general introduction initially presents the major landmarks in muscle research of the last 3 millennia. The proteins of the contractile apparatus and their role in muscle contraction are described. There is then a description of how contractile proteins are known to alter through the expression of isoforms. Finally, a description of fish muscle and its fibre types is given, followed by the aims of the thesis.
Chapter 2 Materials and Methods: An account is given of the materials and methods used throughout this thesis. This includes myofibril preparation and electrophoretic techniques. The techniques described are one and two dimensional polyacrylamide gel electrophoresis (PAGE), iso-electric focusing (lEF), peptide mapping, and one and two dimensional alkali-urea PAGE. The methods used to fix, stain and store the gels are then given, followed by the protocol used for Western blotting. Finally, the analysis of proteins bands is described.
Chapter 3 Temperature and the plasticity of myofibrillar proteins during ontogeny in the Atlantic herring (Clupea harengus L.): Many aspects of development are influenced by temperature. The aim of this study was to investigate the effect of rearing temperature on the development and myofibrillar protein expression during ontogeny in the Atlantic herring (Clupea harengus L.).
Chapter 4 The effect of body size on the myofibrillar protein composition of fast muscle fibres in the short horn sculpin (Myoxocephalus scorpius L.): The contractile properties of muscle vary with body length in fish. The aim of this study was determine if the proteins altered with body size in the short-horn sculpin (Myoxocephalus scorpius L.). Furthermore, could changes in protein expression be related to differences in contractile properties.
Chapter 5 The myofibrillar proteins of Antarctic and sub-Antarctic fish: The myosins of Antarctic fish are specialised for function at low temperature. The aim of this study was to determine if the myofibrillar proteins present in Antarctic fish were highly conserved for function in this stable, low temperature environment. The variation in protein structure from myotomal fast muscles and the m. adductor profundis between five Antarctic fish species from two genera was compared with five sub-Antarctic species from four genera. The myofibrillar proteins of both the Antarctic and sub-Antarctic species showed a high degree of similarity between fish within the same genera. However, the isoforms present were considerably different between genera in both the Antarctic and sub-Antarctic species. Furthermore, the extent of the variation in protein isoforms between genera of the Antarctic fish was similar to that of the sub-Antarctic fish. This suggests that divergence in the tertiary structure of myosins from these species has occurred and that the Antarctic fish myofibrillar proteins are not highly conserved.
Chapter 6 General Discussion: The major findings of the thesis are discussed in relation to the expression of myofibrillar proteins, with reference to further studies. (Abstract shortened)
1998-01-01T00:00:00ZCole, Nicholas JamesChapter 1 General Introduction: The general introduction initially presents the major landmarks in muscle research of the last 3 millennia. The proteins of the contractile apparatus and their role in muscle contraction are described. There is then a description of how contractile proteins are known to alter through the expression of isoforms. Finally, a description of fish muscle and its fibre types is given, followed by the aims of the thesis.
Chapter 2 Materials and Methods: An account is given of the materials and methods used throughout this thesis. This includes myofibril preparation and electrophoretic techniques. The techniques described are one and two dimensional polyacrylamide gel electrophoresis (PAGE), iso-electric focusing (lEF), peptide mapping, and one and two dimensional alkali-urea PAGE. The methods used to fix, stain and store the gels are then given, followed by the protocol used for Western blotting. Finally, the analysis of proteins bands is described.
Chapter 3 Temperature and the plasticity of myofibrillar proteins during ontogeny in the Atlantic herring (Clupea harengus L.): Many aspects of development are influenced by temperature. The aim of this study was to investigate the effect of rearing temperature on the development and myofibrillar protein expression during ontogeny in the Atlantic herring (Clupea harengus L.).
Chapter 4 The effect of body size on the myofibrillar protein composition of fast muscle fibres in the short horn sculpin (Myoxocephalus scorpius L.): The contractile properties of muscle vary with body length in fish. The aim of this study was determine if the proteins altered with body size in the short-horn sculpin (Myoxocephalus scorpius L.). Furthermore, could changes in protein expression be related to differences in contractile properties.
Chapter 5 The myofibrillar proteins of Antarctic and sub-Antarctic fish: The myosins of Antarctic fish are specialised for function at low temperature. The aim of this study was to determine if the myofibrillar proteins present in Antarctic fish were highly conserved for function in this stable, low temperature environment. The variation in protein structure from myotomal fast muscles and the m. adductor profundis between five Antarctic fish species from two genera was compared with five sub-Antarctic species from four genera. The myofibrillar proteins of both the Antarctic and sub-Antarctic species showed a high degree of similarity between fish within the same genera. However, the isoforms present were considerably different between genera in both the Antarctic and sub-Antarctic species. Furthermore, the extent of the variation in protein isoforms between genera of the Antarctic fish was similar to that of the sub-Antarctic fish. This suggests that divergence in the tertiary structure of myosins from these species has occurred and that the Antarctic fish myofibrillar proteins are not highly conserved.
Chapter 6 General Discussion: The major findings of the thesis are discussed in relation to the expression of myofibrillar proteins, with reference to further studies. (Abstract shortened)The influence of temperature on the mechanics and energetics of contraction in fish muscleJohnson, Timothy Johnhttps://hdl.handle.net/10023/150492019-03-29T10:27:22Z1991-01-01T00:00:00ZChapter 1. A general introduction into the adaptation of teleost fish to changing thermal environments. The underlying mechanisms at all levels of organization are reviewed in relation to adaptive change over evolutionary and seasonal time-scales. Chapter 2. 1. The contractile properties of swimming muscles have been investigated in marine teleosts from Antarctic (Trematomus lepidorhinus, Pseudochaenichthys georgianus), temperate (Pollachius virens. Limanda limanda. Agonis cataphractus. Callionymus lyra) and tropical (Abudefduf abdominalis, Thalassoma duperrevi) latitudes. 2. Small bundles of fast twitch fibres were isolated from anterior myotomes and/or the pectoral fin adductor profundis muscle (m.add.p). Live fibre preparations were viable for several days at in vivo temperatures, but became progressively inexcitable at higher or lower temperatures. The stimulation frequency required to produce fused isometric tetani increased from 50Hz in Antarctic species at 0°C to around 400 Hz in tropical species at 25°C. Maximum isometric tension (P0) was produced at the normal body temperature (NBT) of each species (Antarctic, 0-2°C; North Sea and Atlantic, 8-10°C; Indo-West Pacific, 23-25°C). P0 values at physiological temperatures (200-300 kN m-2) were similar for Antarctic, temperate and tropical species. 3. A temperature induced "tension hysteresis" was observed in muscle fibres from the temperate and Antarctic species. Chapter 3. 1. Fast and slow muscle fibres were isolated from the myotomes of atlantic cod (Gadus morhua L.) and short-horned sculpin (Myoxocephalus scorpius L.). 2. Epinephrine was found to have no effect on twitch or sub-tetanic contractions in fast muscle fibres. 3. Isoprenaline (10-6M) had no effect on the contractility of slow muscle fibres. 4. In contrast, epinephrine elicited a dose-dependent decrease in the half-time for twitch relaxation (t1/2r), and in most cases a decrease in twitch amplitude. Chapter 4. 1. Fast muscle fibres were isolated from the abdominal myotomes of the short-horned sculpin, Myoxocephalus scorpius L. Sinusoidal length changes were imposed about resting muscle length and fibres stimulated at a selected phase during the strain cycle. The work output per cycle was calculated from the area of the resulting force- position loops. Chapter 5. 1. Bundles of 20-30 fast muscle fibres were isolated from the abdominal myotomes of the short-horned sculpin (Myoxocephalus scorpius L.). 2. The energy cost of contraction was measured during oscillatory work at 4°C and 15°C following treatment with iodoacetate and nitrogen gas to block glycolysis and aerobic metabolism. 3. Isolated fibres were subjected to sinusoidal length changes about in situ resting length and stimulated at a selected phase in the strain cycle. Preliminary experiments with untreated preparations established the strain amplitude and stimulation parameters required to maximize work output over a range of cycle frequencies at 4°C and 15°C. Chapter 6. The results of the thesis are discussed, particularly in relation to their evolutionary and locomotory significance. From the principles and ideas formulated, future lines of research are suggested. (Abstract shortened by ProQuest.)
1991-01-01T00:00:00ZJohnson, Timothy JohnChapter 1. A general introduction into the adaptation of teleost fish to changing thermal environments. The underlying mechanisms at all levels of organization are reviewed in relation to adaptive change over evolutionary and seasonal time-scales. Chapter 2. 1. The contractile properties of swimming muscles have been investigated in marine teleosts from Antarctic (Trematomus lepidorhinus, Pseudochaenichthys georgianus), temperate (Pollachius virens. Limanda limanda. Agonis cataphractus. Callionymus lyra) and tropical (Abudefduf abdominalis, Thalassoma duperrevi) latitudes. 2. Small bundles of fast twitch fibres were isolated from anterior myotomes and/or the pectoral fin adductor profundis muscle (m.add.p). Live fibre preparations were viable for several days at in vivo temperatures, but became progressively inexcitable at higher or lower temperatures. The stimulation frequency required to produce fused isometric tetani increased from 50Hz in Antarctic species at 0°C to around 400 Hz in tropical species at 25°C. Maximum isometric tension (P0) was produced at the normal body temperature (NBT) of each species (Antarctic, 0-2°C; North Sea and Atlantic, 8-10°C; Indo-West Pacific, 23-25°C). P0 values at physiological temperatures (200-300 kN m-2) were similar for Antarctic, temperate and tropical species. 3. A temperature induced "tension hysteresis" was observed in muscle fibres from the temperate and Antarctic species. Chapter 3. 1. Fast and slow muscle fibres were isolated from the myotomes of atlantic cod (Gadus morhua L.) and short-horned sculpin (Myoxocephalus scorpius L.). 2. Epinephrine was found to have no effect on twitch or sub-tetanic contractions in fast muscle fibres. 3. Isoprenaline (10-6M) had no effect on the contractility of slow muscle fibres. 4. In contrast, epinephrine elicited a dose-dependent decrease in the half-time for twitch relaxation (t1/2r), and in most cases a decrease in twitch amplitude. Chapter 4. 1. Fast muscle fibres were isolated from the abdominal myotomes of the short-horned sculpin, Myoxocephalus scorpius L. Sinusoidal length changes were imposed about resting muscle length and fibres stimulated at a selected phase during the strain cycle. The work output per cycle was calculated from the area of the resulting force- position loops. Chapter 5. 1. Bundles of 20-30 fast muscle fibres were isolated from the abdominal myotomes of the short-horned sculpin (Myoxocephalus scorpius L.). 2. The energy cost of contraction was measured during oscillatory work at 4°C and 15°C following treatment with iodoacetate and nitrogen gas to block glycolysis and aerobic metabolism. 3. Isolated fibres were subjected to sinusoidal length changes about in situ resting length and stimulated at a selected phase in the strain cycle. Preliminary experiments with untreated preparations established the strain amplitude and stimulation parameters required to maximize work output over a range of cycle frequencies at 4°C and 15°C. Chapter 6. The results of the thesis are discussed, particularly in relation to their evolutionary and locomotory significance. From the principles and ideas formulated, future lines of research are suggested. (Abstract shortened by ProQuest.)Comparative studies on the sarcoplasmic reticulum of fish muscleMcArdle, Harry J.https://hdl.handle.net/10023/150472019-03-29T10:41:11Z1980-01-01T00:00:00Z1. The sarcoplasmic reticulum from fish red and white muscle has been isolated and compared with that of mammalian sarcoplasmic reticulum (SR). The white muscle SR is shown to be similar to mammalian fast muscle with the majority of the protein being accounted for by a band with molecular weighty of approximately 100,000. This has been demonstrated in several species to correspond to the calcium pump protein. The red muscle SR pumps Ca2+ ions and hydrolyses ATP at approximately half the rate of the white SR. Gel electrophoresis of the SR vesicles shows that there is not sufficient 100,000 dalton protein in the red muscle SR to account for the relative rates of pumping. It is suggested that fish red muscle SR resembles mammalian slow fibres in that the pump protein's molecular weight is not the same as the white. Unlike mammalian SR, vesicles isolated from trout red muscle or not stimulated by commercially available cAMP dependent protein kinases. 2. The microsomal pellet of muscle is generally contaminated with mitochondrial fragments and sarcolemmal vesicles. Pure sarcoplasmic reticulum fractions have been obtained from plaice 2+ 2+ muscle and the characteristics of the Ca2+ ATPase and Ca2+ uptake studied. The protein composition of the vesicles, the dependence on Mg2+, Ca2+, K+ and ADP are demonstrated to be similar to that of rabbit muscle. A comparison of the levels of the phosphorylated enzyme intermediate with those obtained by other workers shows that the pump protein concentration is similar to rabbit fast skeletal muscle. 3. The effect of evolutionary temperature adaptation on the sarcoplasmic reticulum of different species of fish has been examined. The Ca2+ ATPase shows an inverse h correlation with the cell temperature of the species at O°C, and this difference is reflected in the relative rates of Ca2+ uptake. Activation enthalpy increases with increasing environmental temperature, while activation entropy goes from negative values in .the cold adapted to positive values in the hot adapted species. Unlike other enzyme systems, the activation energy shows no correlation with temperature. Acclimation to seasonal temperature changes has also been studied. Unlike adaptation on evolutionary time scales, acclimation does not affect the activation entropy of the ATPase, and there is no significant difference in the rates of ATP hydrolysis. It is concluded that the mechanisms of compensation are different in adaption to evolutionary and seasonal temperature changes. Evidence for acclimation to low temperatures involving an increase in the amount of sarcoplasmic reticulum is reviewed. 4. The enzyme-substrate affinity has been monitored by measuring the KCa of the Ca2+ ATPase at different temperatures for four different species of teleost. As with the Vmax estimations, compensatory changes are shown in the ATPase. KCa values, estimated at O°C are found to be inversely related Ca. to the animal's cell temperature. When estimated at that temperature, the values are similar. These results are discussed in relation to the observed prepondence of parvalbumins in fish muscle, and a possible role of the parvalbumins is considered. 5. In even the purest of SR preparations, i.e. those with no contaminating marker enzymes, a Ca2+ independent ATPase activity can be demonstrated. Unlike the Ca2+-ATPase the Ca2+ -independent ATPase activity is not related to habitat temperature, and the activation entropy is not proportional to cell temperature. As shown in the, rabbit, incubation of the SR in the presence of 0.1% Triton X-100 converts the basal ATPase activity in all except the lightest fractions to Ca2+ dependence. It is suggested that the Ca2+ independent ATPase represents a form of the pump protein uncoupled from Ca2+ transport, with the two forms of the ATPase in thermal equilibrium. Supportive evidence is provided for this theory. The ratio of Ca2+ dependent to total ATPase is temperature dependent, increasing to maximal value at and above the animal's cell temperature. For example, the ratio of approximately 0.25 at O°C in Tilapia mariae (a tropical species), increasing to 0.85 at 25°0. In contrast, the ratio for Myoxocephalus scorpius (North Sea) is only slightly affected by assay temperature and remains at about 0.95 throughout the range O - 33°C. The activation energy for the conversion has been estimated for two species and compared with that of rabbit. It is possible that the contribution of the activation energy for the conversion may account for the poor correlation of the DeltaG# of the Ca2+-dependent ATPase with environment temperature.
1980-01-01T00:00:00ZMcArdle, Harry J.1. The sarcoplasmic reticulum from fish red and white muscle has been isolated and compared with that of mammalian sarcoplasmic reticulum (SR). The white muscle SR is shown to be similar to mammalian fast muscle with the majority of the protein being accounted for by a band with molecular weighty of approximately 100,000. This has been demonstrated in several species to correspond to the calcium pump protein. The red muscle SR pumps Ca2+ ions and hydrolyses ATP at approximately half the rate of the white SR. Gel electrophoresis of the SR vesicles shows that there is not sufficient 100,000 dalton protein in the red muscle SR to account for the relative rates of pumping. It is suggested that fish red muscle SR resembles mammalian slow fibres in that the pump protein's molecular weight is not the same as the white. Unlike mammalian SR, vesicles isolated from trout red muscle or not stimulated by commercially available cAMP dependent protein kinases. 2. The microsomal pellet of muscle is generally contaminated with mitochondrial fragments and sarcolemmal vesicles. Pure sarcoplasmic reticulum fractions have been obtained from plaice 2+ 2+ muscle and the characteristics of the Ca2+ ATPase and Ca2+ uptake studied. The protein composition of the vesicles, the dependence on Mg2+, Ca2+, K+ and ADP are demonstrated to be similar to that of rabbit muscle. A comparison of the levels of the phosphorylated enzyme intermediate with those obtained by other workers shows that the pump protein concentration is similar to rabbit fast skeletal muscle. 3. The effect of evolutionary temperature adaptation on the sarcoplasmic reticulum of different species of fish has been examined. The Ca2+ ATPase shows an inverse h correlation with the cell temperature of the species at O°C, and this difference is reflected in the relative rates of Ca2+ uptake. Activation enthalpy increases with increasing environmental temperature, while activation entropy goes from negative values in .the cold adapted to positive values in the hot adapted species. Unlike other enzyme systems, the activation energy shows no correlation with temperature. Acclimation to seasonal temperature changes has also been studied. Unlike adaptation on evolutionary time scales, acclimation does not affect the activation entropy of the ATPase, and there is no significant difference in the rates of ATP hydrolysis. It is concluded that the mechanisms of compensation are different in adaption to evolutionary and seasonal temperature changes. Evidence for acclimation to low temperatures involving an increase in the amount of sarcoplasmic reticulum is reviewed. 4. The enzyme-substrate affinity has been monitored by measuring the KCa of the Ca2+ ATPase at different temperatures for four different species of teleost. As with the Vmax estimations, compensatory changes are shown in the ATPase. KCa values, estimated at O°C are found to be inversely related Ca. to the animal's cell temperature. When estimated at that temperature, the values are similar. These results are discussed in relation to the observed prepondence of parvalbumins in fish muscle, and a possible role of the parvalbumins is considered. 5. In even the purest of SR preparations, i.e. those with no contaminating marker enzymes, a Ca2+ independent ATPase activity can be demonstrated. Unlike the Ca2+-ATPase the Ca2+ -independent ATPase activity is not related to habitat temperature, and the activation entropy is not proportional to cell temperature. As shown in the, rabbit, incubation of the SR in the presence of 0.1% Triton X-100 converts the basal ATPase activity in all except the lightest fractions to Ca2+ dependence. It is suggested that the Ca2+ independent ATPase represents a form of the pump protein uncoupled from Ca2+ transport, with the two forms of the ATPase in thermal equilibrium. Supportive evidence is provided for this theory. The ratio of Ca2+ dependent to total ATPase is temperature dependent, increasing to maximal value at and above the animal's cell temperature. For example, the ratio of approximately 0.25 at O°C in Tilapia mariae (a tropical species), increasing to 0.85 at 25°0. In contrast, the ratio for Myoxocephalus scorpius (North Sea) is only slightly affected by assay temperature and remains at about 0.95 throughout the range O - 33°C. The activation energy for the conversion has been estimated for two species and compared with that of rabbit. It is possible that the contribution of the activation energy for the conversion may account for the poor correlation of the DeltaG# of the Ca2+-dependent ATPase with environment temperature.A comparitive study of the ventricles and the bulbus cordis of the vertebrate heartBiswas, Hrishikesh Dashttps://hdl.handle.net/10023/150442019-03-29T10:30:10Z1957-01-01T00:00:00Z1957-01-01T00:00:00ZBiswas, Hrishikesh DasPhysiology of the adrenocortical tissue in the whitefish, coregonus lavaretus, linnaeusFuller, Joan D.https://hdl.handle.net/10023/150432019-03-29T10:35:58Z1974-01-01T00:00:00Z1974-01-01T00:00:00ZFuller, Joan D.Catecholaminergic neurotransmission in the insect central nervous systemGifford, Andrew Nealhttps://hdl.handle.net/10023/150422018-07-06T09:54:41Z1989-01-01T00:00:00Z1989-01-01T00:00:00ZGifford, Andrew NealStudies on identifiable 5-hydroxytryptamine-containing neurones in the central nervous systems of some gastropod molluscsLogan, Stephen Douglashttps://hdl.handle.net/10023/150402019-03-29T10:39:22Z1979-01-01T00:00:00ZElectrophysiological and neurochemical studies have been made in identifiable neurones in the central nervous systems of the gastropod molluscs Helix pomatia, Helix aspersa and Planorbis corneus. Using a technique of intracellular injection of radioactively labelled precursors, the neurotransmitter synthesising capabilities of several neurones have been investigated. Methods have been developed to ensure that radioactive metabolites detected within the nervous system following intracellular injection are within, and confined to, the soma axons, dendrites and terminals of the injected neurones. The results demonstrate that, with one exception some identifiable neurones possess the ability to synthesise either 3H-5-hydroxytryptamine from 3H-tryptophan and 3H-5-hydroxytryptophan or 3H-acetylcholine from 3H-choline but not both transmitters from their precursors. The exception to this observation is the giant serotonin-containing neurones of Helix pomatia and Helix aspersa which can synthesise both 3H-5-hydroxytryptamine and 3H-acetylcholine from their precursors. Moreover this study has shown that both newly synthesised transmitters in the Helix serotonin-containing neurones are transported to the synaptic terminals of the neurone and are probably released there. Thus this neurone appears to be at variance with the concept that a neurone can utilise only one transmitter substance (Dale's Principle). The final part of the thesis is a study of an identifiable -5-hydroxytryptamine-containing neurone in the right pedal ganglion of Planorbis corneus. This neurone has been extensively characterised by neuroanatomical, pharmacological and electrophysiological methods with a view to determining whether it makes monosynaptic connections with other neurones in the central nervous system. Although no direct connections were observed the neurone did modulate spontaneous activity in other neurones. The role of 5-hydroxytryptamine as a neuromodulator is discussed.
1979-01-01T00:00:00ZLogan, Stephen DouglasElectrophysiological and neurochemical studies have been made in identifiable neurones in the central nervous systems of the gastropod molluscs Helix pomatia, Helix aspersa and Planorbis corneus. Using a technique of intracellular injection of radioactively labelled precursors, the neurotransmitter synthesising capabilities of several neurones have been investigated. Methods have been developed to ensure that radioactive metabolites detected within the nervous system following intracellular injection are within, and confined to, the soma axons, dendrites and terminals of the injected neurones. The results demonstrate that, with one exception some identifiable neurones possess the ability to synthesise either 3H-5-hydroxytryptamine from 3H-tryptophan and 3H-5-hydroxytryptophan or 3H-acetylcholine from 3H-choline but not both transmitters from their precursors. The exception to this observation is the giant serotonin-containing neurones of Helix pomatia and Helix aspersa which can synthesise both 3H-5-hydroxytryptamine and 3H-acetylcholine from their precursors. Moreover this study has shown that both newly synthesised transmitters in the Helix serotonin-containing neurones are transported to the synaptic terminals of the neurone and are probably released there. Thus this neurone appears to be at variance with the concept that a neurone can utilise only one transmitter substance (Dale's Principle). The final part of the thesis is a study of an identifiable -5-hydroxytryptamine-containing neurone in the right pedal ganglion of Planorbis corneus. This neurone has been extensively characterised by neuroanatomical, pharmacological and electrophysiological methods with a view to determining whether it makes monosynaptic connections with other neurones in the central nervous system. Although no direct connections were observed the neurone did modulate spontaneous activity in other neurones. The role of 5-hydroxytryptamine as a neuromodulator is discussed.Non-linear membrane properties of insect motorneuronesHancox, Julian C.https://hdl.handle.net/10023/150292019-03-29T10:31:16Z1991-01-01T00:00:00Z1. Electrical characteristics of the cell body of an identified motoneurone, the 'fast' coxal depressor motoneurone (Df), from the cockroach (Periplaneta americana) have been studied under current- and voltage-clamp. 2. In response to low magnitude, relatively long duration depolarising current pulses, Df could generate plateau potentials, regenerative events which often far outlived the duration of the applied depolarisation. 3. Plateau potentials constitute an inherent property of the neurone because they could be evoked in somata that had been surgically isolated from other parts of the neurone (the soma is devoid of synaptic contacts); these experiments also demonstrated that the soma of this neurone can participate in the generation of plateau potentials. 4. Plateau potentials were often surmounted by attenuated action potentials; these correlated 1:1 with axonal impulses recorded extracellularly from the axon of the neuron. 5. Plateau potentials were associated with an increase in membrane conductance. Under voltage- clamp, cells which exhibited plateau potentials possessed a region of negative slope resistance in their current-voltage relationship. 6. Plateau potentials in Df were observed to be calcium-dependent, A series of current- and voltage- damp experiments indicated that the calcium channels involved in plateau potential production differ from those which can mediate calcium-dependent action potentials following pharmacological treatment of this neurone. 7. Plateau potential production in Df was suppressed by the application of GABA (10-4M). Spontaneous plateau potentials could be recorded following application of picrotoxin (10-5M) or pentylenetetrazole (25mM). 8. Recordings taken from two other 'fast' motoneurones, cell 3 (from the cockroach) and FETi (from the locust, Schistocerca gregaria) indicated that the ability to generate plateau potentials may not be restricted to Df. 9. Although freshly dissected, recently impaled neurones responded to relatively brief depolarising current pulses with a series of graded, damped membrane oscillations, the excitability of many preparations increased with time from dissection: many cells became able to generate all-or-none action potentials in response to such pulses (these differed from the attenuated axonal spikes which often surmounted plateau potentials). The appearance of these events did not correlate with consistent changes to the resting potential or input resistance of neurones. 10. Time-dependent action potentials were calcium-dependent and could be recorded from 'intact' cells and isolated neurone somata. These action potentials could also co-exist with plateau potentials; such co-existence provides evidence for different classes of calcium channel in untreated insect neurones.
1991-01-01T00:00:00ZHancox, Julian C.1. Electrical characteristics of the cell body of an identified motoneurone, the 'fast' coxal depressor motoneurone (Df), from the cockroach (Periplaneta americana) have been studied under current- and voltage-clamp. 2. In response to low magnitude, relatively long duration depolarising current pulses, Df could generate plateau potentials, regenerative events which often far outlived the duration of the applied depolarisation. 3. Plateau potentials constitute an inherent property of the neurone because they could be evoked in somata that had been surgically isolated from other parts of the neurone (the soma is devoid of synaptic contacts); these experiments also demonstrated that the soma of this neurone can participate in the generation of plateau potentials. 4. Plateau potentials were often surmounted by attenuated action potentials; these correlated 1:1 with axonal impulses recorded extracellularly from the axon of the neuron. 5. Plateau potentials were associated with an increase in membrane conductance. Under voltage- clamp, cells which exhibited plateau potentials possessed a region of negative slope resistance in their current-voltage relationship. 6. Plateau potentials in Df were observed to be calcium-dependent, A series of current- and voltage- damp experiments indicated that the calcium channels involved in plateau potential production differ from those which can mediate calcium-dependent action potentials following pharmacological treatment of this neurone. 7. Plateau potential production in Df was suppressed by the application of GABA (10-4M). Spontaneous plateau potentials could be recorded following application of picrotoxin (10-5M) or pentylenetetrazole (25mM). 8. Recordings taken from two other 'fast' motoneurones, cell 3 (from the cockroach) and FETi (from the locust, Schistocerca gregaria) indicated that the ability to generate plateau potentials may not be restricted to Df. 9. Although freshly dissected, recently impaled neurones responded to relatively brief depolarising current pulses with a series of graded, damped membrane oscillations, the excitability of many preparations increased with time from dissection: many cells became able to generate all-or-none action potentials in response to such pulses (these differed from the attenuated axonal spikes which often surmounted plateau potentials). The appearance of these events did not correlate with consistent changes to the resting potential or input resistance of neurones. 10. Time-dependent action potentials were calcium-dependent and could be recorded from 'intact' cells and isolated neurone somata. These action potentials could also co-exist with plateau potentials; such co-existence provides evidence for different classes of calcium channel in untreated insect neurones.The comparitive anatomy of the tectum of the mid-brainRoy, Probodh Ranjanhttps://hdl.handle.net/10023/150262019-03-29T10:33:16Z1957-01-01T00:00:00Z1. The materials consisted of 20 Salmo salar (salmon parr), 12 Rana teroporaria (frog), 12 Lacerta viridis (Common green lizard), 45 Gallus domesticus (domestic fowl), and 20 Mus norvegious albinus (common white rat). 2. The brains, having been fixed by injection with 10% neutral formol-saline, were carefully dissected out. Some measurements and photographs were made, and the specimens were embedded in paraffin outing down the time of dehydration in the higher grades of alcohol to a minimum and avoiding cedar-wood oil as a clearing agent for reasons which have been given in the text. Three series of serial sections, out at 15?, were prepared from each brain embedded, and were respectively, (a) impregnated with silver by the Bodian Method, (b) stained with, carbol fuohsin and (c) stained with iron haematoxylin. One hundred and two such series were prepared. 3. The following conclusions were reached: (a) The size of the optic lobes, as observed from the surface and relative to the size of the cerebrum, was found to diminish as the vertebrate series of brains was ascended. Estimations of the volume of the optic lobes were, however, not made. (b) It was verified that the superior and the inferior colliculi of the mammals are homologous respectively with the optic tectum and the torus semi-circularis composing the sub mammalian optic lobe. Further, it was found that structurally the optic lobes (in: eluding the ventricles) of the pieces, amphibia and reptilia, and the tectum of the mammalia could be arranged in this order as a series. The optic lobes of the aves were, however, divergent, in that they could not be placed in the series as an intermediate stage between the reptilian and mammalian forms. (c) Throughout the vertebrate series the optic tectum including the superior colliculus of mammals presents a lamination of its constituent cells and fibres. The layers of the representative brains were numbered from without inwards and were compared and correlated with each other using Huber and Crosby's classification of the layers in the reptilian optic tectum as a standard. The lamination of the optic tectum at first increases as the vertebrate series is ascended; it reaches its peak development in the lizard and the bird, and undergoes a reduction again in the mammals. (d) Homologies in the structure of the torus semi-circular is of the lower vertebrates, the nucleus mesencephalicus lateralis pars dorsalis of the aves and the inferior colliculus of the Mammalia were noted. (e) The morphology of the torus longitudinalis, conspicuous in the teleostean fish, was examined. The torus is formed by the fusion in the median plane of two separate processes, from the dorso-medial part of the optic tectum all the layers of which take part in its formation.
1957-01-01T00:00:00ZRoy, Probodh Ranjan1. The materials consisted of 20 Salmo salar (salmon parr), 12 Rana teroporaria (frog), 12 Lacerta viridis (Common green lizard), 45 Gallus domesticus (domestic fowl), and 20 Mus norvegious albinus (common white rat). 2. The brains, having been fixed by injection with 10% neutral formol-saline, were carefully dissected out. Some measurements and photographs were made, and the specimens were embedded in paraffin outing down the time of dehydration in the higher grades of alcohol to a minimum and avoiding cedar-wood oil as a clearing agent for reasons which have been given in the text. Three series of serial sections, out at 15?, were prepared from each brain embedded, and were respectively, (a) impregnated with silver by the Bodian Method, (b) stained with, carbol fuohsin and (c) stained with iron haematoxylin. One hundred and two such series were prepared. 3. The following conclusions were reached: (a) The size of the optic lobes, as observed from the surface and relative to the size of the cerebrum, was found to diminish as the vertebrate series of brains was ascended. Estimations of the volume of the optic lobes were, however, not made. (b) It was verified that the superior and the inferior colliculi of the mammals are homologous respectively with the optic tectum and the torus semi-circularis composing the sub mammalian optic lobe. Further, it was found that structurally the optic lobes (in: eluding the ventricles) of the pieces, amphibia and reptilia, and the tectum of the mammalia could be arranged in this order as a series. The optic lobes of the aves were, however, divergent, in that they could not be placed in the series as an intermediate stage between the reptilian and mammalian forms. (c) Throughout the vertebrate series the optic tectum including the superior colliculus of mammals presents a lamination of its constituent cells and fibres. The layers of the representative brains were numbered from without inwards and were compared and correlated with each other using Huber and Crosby's classification of the layers in the reptilian optic tectum as a standard. The lamination of the optic tectum at first increases as the vertebrate series is ascended; it reaches its peak development in the lizard and the bird, and undergoes a reduction again in the mammals. (d) Homologies in the structure of the torus semi-circular is of the lower vertebrates, the nucleus mesencephalicus lateralis pars dorsalis of the aves and the inferior colliculus of the Mammalia were noted. (e) The morphology of the torus longitudinalis, conspicuous in the teleostean fish, was examined. The torus is formed by the fusion in the median plane of two separate processes, from the dorso-medial part of the optic tectum all the layers of which take part in its formation.Studies on neuronal 5-HT in a gastropod mollusc, helix pomatia (L.)Pentreath, V. W.https://hdl.handle.net/10023/150252019-03-29T10:34:25Z1973-01-01T00:00:00ZThis thesis describes information obtained on the structure of 5-HT-containing neurons, on the mechanisms of transport of 5-HT and its precursors into and within neurons, on the nature of the blood supply to the CNS, and on the function of 5-HT-containing neurons within the CNS of Hellix pomatia. In particular data is obtained for the giant serotonin-containing neuron (GSG) in each cerebral ganglion. Dense-cored vesicles of mean diameter 100 nm are present in the perikarya and axon branches of the GSCs. Vesicles of similar appearance are present in the presumed presynaptic endings of the GSCs. Evidence is presented which suggests that such vesicles sequester 5-HT, The fine structure of presumed presynaptic endings making synaptic connections with the GSCs is described. Following exposure to tritiated 5-HT, electron microscope autoradiography showed that silver grains, often in very high concentrations, were located over certain fine axon branches thought to be nerve endings. These processes contained small dense-cored vesicles, which were morpliologically similar to those thought to sequester 5-HT to the perikarya of the GSCs. It is suggested that re-uptake into nerve endings is a mechanism of inactivation of 5-HT in the Following exposure to tritiated 5-HTP, silver grains were observed over the perkarya of the GSCs and other known 5-HT-contalning neurons. There was no indication that 5-HTP was taken up by nerve endings or by non-nervous structures. The accumulation of tritiated tryptophan was less specific; all the neuron perikarya took up this substance. The CMS of H. pomatla is supplied by branches of the anterior aorta. Capillaries from these branches open into a, blood space which is adjacent to, and continuous over the surface of the nervous tissue. Blood passes from this space through the epineural sheath into the body cavity sinuses. Three tissue layers separate the blood spaces from the nervous tissue. These are (i) a luminal endothelium, (ii) a connective tissue layer, and (iii) glial cells. The luminal endothelium and connective tissue are freely permeable to uncharged particles of 10 nm or less. Eloctrophysiological analysis showed that each GSC sends axon branches to muscles in the lips of the animal. Selective stimulation of the GSCs resulted in an increase of electrical activity recorded from these muscles, but no change in their length. This effect was mimicked by 5-HT applied to the muscles. It is suggested that the GSC has a facilitatory effect on the lip muscle potentials.
1973-01-01T00:00:00ZPentreath, V. W.This thesis describes information obtained on the structure of 5-HT-containing neurons, on the mechanisms of transport of 5-HT and its precursors into and within neurons, on the nature of the blood supply to the CNS, and on the function of 5-HT-containing neurons within the CNS of Hellix pomatia. In particular data is obtained for the giant serotonin-containing neuron (GSG) in each cerebral ganglion. Dense-cored vesicles of mean diameter 100 nm are present in the perikarya and axon branches of the GSCs. Vesicles of similar appearance are present in the presumed presynaptic endings of the GSCs. Evidence is presented which suggests that such vesicles sequester 5-HT, The fine structure of presumed presynaptic endings making synaptic connections with the GSCs is described. Following exposure to tritiated 5-HT, electron microscope autoradiography showed that silver grains, often in very high concentrations, were located over certain fine axon branches thought to be nerve endings. These processes contained small dense-cored vesicles, which were morpliologically similar to those thought to sequester 5-HT to the perikarya of the GSCs. It is suggested that re-uptake into nerve endings is a mechanism of inactivation of 5-HT in the Following exposure to tritiated 5-HTP, silver grains were observed over the perkarya of the GSCs and other known 5-HT-contalning neurons. There was no indication that 5-HTP was taken up by nerve endings or by non-nervous structures. The accumulation of tritiated tryptophan was less specific; all the neuron perikarya took up this substance. The CMS of H. pomatla is supplied by branches of the anterior aorta. Capillaries from these branches open into a, blood space which is adjacent to, and continuous over the surface of the nervous tissue. Blood passes from this space through the epineural sheath into the body cavity sinuses. Three tissue layers separate the blood spaces from the nervous tissue. These are (i) a luminal endothelium, (ii) a connective tissue layer, and (iii) glial cells. The luminal endothelium and connective tissue are freely permeable to uncharged particles of 10 nm or less. Eloctrophysiological analysis showed that each GSC sends axon branches to muscles in the lips of the animal. Selective stimulation of the GSCs resulted in an increase of electrical activity recorded from these muscles, but no change in their length. This effect was mimicked by 5-HT applied to the muscles. It is suggested that the GSC has a facilitatory effect on the lip muscle potentials.Functional synaptic plasticity in the dentate gyrus of the rat hippocampusBaker, Mark Dickenshttps://hdl.handle.net/10023/150242019-03-29T10:34:37Z1986-01-01T00:00:00ZThe responses of hippocampal cell fields to stimulation of afferent pathways projecting from outside and within the hippocampus have been shown to exhibit a remarkable degree of plasticity. Subsequent to conditioning stimulation of either single shocks or trains of stimuli at high frequency, the relationship between afferent stimulus and postsynaptic response can be dramatically changed. The long-term potentiation (LTP) of responses generated by stimulus trains does not appear to involve whole-neurone excitability changes, but is the result of altered synaptic effectiveness and can be localized to the region of afferent fibre termination. In a series of acute experiments extracellular potentials generated by stimulation of the entorhinal projection to the dentate gyrus of the hippocampus in the rat, have been recorded in the dorsal hippocampus and quantified before and after conditioning stimulation. A simple computer model was developed to help explain the observed response plasticity. Synaptic field potential LTP after afferent tetanization was explained by increased synaptic current flow, and the altered spatial distribution of the potentials by suggesting that the electrotonic properties of the granule cell dendrites are changed by repeated synaptic activation: an increase in dendritic membrane resistance being a possible mechanism. Light-microscopic examination of the entorhinal fibres at the site of stimulation in the angular bundle after staining with solochrome cyanine, revealed heterogeneous myelination; the fibres lying dorsal and lateral to the subiculum being more heavily myelinated than those more ventro-medial. This histological inhomogeneity appeared to be confirmed by conduction velocity measurements, suggesting two functionally different groups of fibres. It has yet to be determined whether these two groups correspond to the lateral and medial perforant paths described by other workers.
1986-01-01T00:00:00ZBaker, Mark DickensThe responses of hippocampal cell fields to stimulation of afferent pathways projecting from outside and within the hippocampus have been shown to exhibit a remarkable degree of plasticity. Subsequent to conditioning stimulation of either single shocks or trains of stimuli at high frequency, the relationship between afferent stimulus and postsynaptic response can be dramatically changed. The long-term potentiation (LTP) of responses generated by stimulus trains does not appear to involve whole-neurone excitability changes, but is the result of altered synaptic effectiveness and can be localized to the region of afferent fibre termination. In a series of acute experiments extracellular potentials generated by stimulation of the entorhinal projection to the dentate gyrus of the hippocampus in the rat, have been recorded in the dorsal hippocampus and quantified before and after conditioning stimulation. A simple computer model was developed to help explain the observed response plasticity. Synaptic field potential LTP after afferent tetanization was explained by increased synaptic current flow, and the altered spatial distribution of the potentials by suggesting that the electrotonic properties of the granule cell dendrites are changed by repeated synaptic activation: an increase in dendritic membrane resistance being a possible mechanism. Light-microscopic examination of the entorhinal fibres at the site of stimulation in the angular bundle after staining with solochrome cyanine, revealed heterogeneous myelination; the fibres lying dorsal and lateral to the subiculum being more heavily myelinated than those more ventro-medial. This histological inhomogeneity appeared to be confirmed by conduction velocity measurements, suggesting two functionally different groups of fibres. It has yet to be determined whether these two groups correspond to the lateral and medial perforant paths described by other workers.Role of signalling molecules in the developing avian wingNikbakht, Nedahttps://hdl.handle.net/10023/150232019-03-29T10:41:53Z1999-01-01T00:00:00ZThe aim of this study was to investigate the role of signalling molecules during the development of the chick limb. First, it was demonstrated that a functional gradient of bioactive FGFs is present down the limb from distal to proximal. This functional FGF gradient decreased at stage 26, at the time of AER regression. Although morphogenetic gradients are of considerable theoretical importance in developmental biology, there are rather few practical demonstrations of their existence. The effects of prolonging the presence of active FGF on limb pattern formation were investigated. Application of ectopic FGF-4 to the distal tip of the limb at stage 26 had a number of effects on limb development. In particular, the cartilage structure conventionally labelled element "5" increased in size and in some instances acquired a digit-like morphology. The evolutionary considerations of this finding are briefly considered. Analysis, including 3D computer reconstruction, of the musculature and vasculature of limbs after FGF implants was carried out in the hope of establishing the identity of this digit like element. This proved not to be possible. However, both muscle mass and vascularisation had increased after the procedure. Known molecular pathways involving the proximo-distal patterning of the limb were then investigated. Whole mount in situ hybridisation studies were carried out with respect to FGF-4, sonic hedgehog, Hoxd-11 and FGF-8. These revealed that the shh/ FGF positive feedback loop was not involved in these changes. FGF-8 expression in late stage AERs was markedly increased. Hoxd-11 expression was not affected by ectopic FGF implants. Together, these findings suggest that the effect of FGF implants is mediated by a novel mechanism. The effect of FGF-4 implants on programmed cell death in the limb was examined. At stage 28 anterior necrotic zone was larger, and had shifted distally. However, the posterior necrotic zone was absent. The implications of these findings for limb development were discussed.
1999-01-01T00:00:00ZNikbakht, NedaThe aim of this study was to investigate the role of signalling molecules during the development of the chick limb. First, it was demonstrated that a functional gradient of bioactive FGFs is present down the limb from distal to proximal. This functional FGF gradient decreased at stage 26, at the time of AER regression. Although morphogenetic gradients are of considerable theoretical importance in developmental biology, there are rather few practical demonstrations of their existence. The effects of prolonging the presence of active FGF on limb pattern formation were investigated. Application of ectopic FGF-4 to the distal tip of the limb at stage 26 had a number of effects on limb development. In particular, the cartilage structure conventionally labelled element "5" increased in size and in some instances acquired a digit-like morphology. The evolutionary considerations of this finding are briefly considered. Analysis, including 3D computer reconstruction, of the musculature and vasculature of limbs after FGF implants was carried out in the hope of establishing the identity of this digit like element. This proved not to be possible. However, both muscle mass and vascularisation had increased after the procedure. Known molecular pathways involving the proximo-distal patterning of the limb were then investigated. Whole mount in situ hybridisation studies were carried out with respect to FGF-4, sonic hedgehog, Hoxd-11 and FGF-8. These revealed that the shh/ FGF positive feedback loop was not involved in these changes. FGF-8 expression in late stage AERs was markedly increased. Hoxd-11 expression was not affected by ectopic FGF implants. Together, these findings suggest that the effect of FGF implants is mediated by a novel mechanism. The effect of FGF-4 implants on programmed cell death in the limb was examined. At stage 28 anterior necrotic zone was larger, and had shifted distally. However, the posterior necrotic zone was absent. The implications of these findings for limb development were discussed.Electrophysiological observations on the teleost olfactory bulbMacLeod, Neil Kennethhttps://hdl.handle.net/10023/150212019-03-29T10:30:21Z1975-01-01T00:00:00ZPrevious electrophysiological research on the fish olfactory system is reviewed and the conclusion reached that present knowledge concerning, in particular, the fundamental physiology of neuronal connections within the olfactory bulb, was rudimentary and confused. Field potentials were evoked in the olfactory bulb of teleost fish by electrical stimulation of the olfactory tract and nerve. The potential wave recorded at the bulbar surface consists of four components, N1, N2, N3, AND P, all of which appear to be of post-synaptic origin when the nerve is stimulated, whence they are usually preceded by a triphasic potential thought to represent the compound action potential of olfactory nerve fibres. The N1 wave evoked by olfactory tract stimulated is not of synaptic origin. It probably represents the synchronous antidromic activation of secondary neurons. The waves analysed with respect to voltage and time related to the underlying histology. The results indicate that the extracellular current flow around bulbar neuronal elements is essentially similar to that already described for mammals and is probably generated by similar pathways. This is surprising in view of fundamental anatomical dissimilarities, particularly regarding the dendritic field of mitral cells. The field potentials proved to be useful in the identification of single units at the time of recording. The spontaneous and evoked activity of identified mitral and granule cells could often be inhibited by stimulation of either the nerve or tract. The evoked field potentials could usually be similarly inhibited. Evidence has been obtained that this inhibition is mediated GABA and that it may well take place via a recurrent pathway involving reciprocal dendrodendritic synapses as in the mammalian system. Evidence was also obtained that this inhibition may, in part, result from the activation of granule cells by andrenergic centrifugal fibres when the olfactory tract is stimulated. Natural chemical stimulation of the olfactory mucosa with amino acid solutions produced a complex pattern of responses. Each odorant normally produced a unique pattern of excitatory and inhibitory responses across all units. Chi-square values were calculated for stimulatory effectiveness between forty-five pairs of odours. L-serine and L-alanine consistently showed a high degree of similarity with several other odours. The converse was true for GABA and L-histidine, although this pair had a high chi-square value when mutually compared. Enantiomeric pairs of amino acids were often found to have opposite stimulatory effects on bulbar units. These results are discussed in relation to the possible properties and configurations of odorant receptor sites for amino acids in the fish olfactory mucosa.
1975-01-01T00:00:00ZMacLeod, Neil KennethPrevious electrophysiological research on the fish olfactory system is reviewed and the conclusion reached that present knowledge concerning, in particular, the fundamental physiology of neuronal connections within the olfactory bulb, was rudimentary and confused. Field potentials were evoked in the olfactory bulb of teleost fish by electrical stimulation of the olfactory tract and nerve. The potential wave recorded at the bulbar surface consists of four components, N1, N2, N3, AND P, all of which appear to be of post-synaptic origin when the nerve is stimulated, whence they are usually preceded by a triphasic potential thought to represent the compound action potential of olfactory nerve fibres. The N1 wave evoked by olfactory tract stimulated is not of synaptic origin. It probably represents the synchronous antidromic activation of secondary neurons. The waves analysed with respect to voltage and time related to the underlying histology. The results indicate that the extracellular current flow around bulbar neuronal elements is essentially similar to that already described for mammals and is probably generated by similar pathways. This is surprising in view of fundamental anatomical dissimilarities, particularly regarding the dendritic field of mitral cells. The field potentials proved to be useful in the identification of single units at the time of recording. The spontaneous and evoked activity of identified mitral and granule cells could often be inhibited by stimulation of either the nerve or tract. The evoked field potentials could usually be similarly inhibited. Evidence has been obtained that this inhibition is mediated GABA and that it may well take place via a recurrent pathway involving reciprocal dendrodendritic synapses as in the mammalian system. Evidence was also obtained that this inhibition may, in part, result from the activation of granule cells by andrenergic centrifugal fibres when the olfactory tract is stimulated. Natural chemical stimulation of the olfactory mucosa with amino acid solutions produced a complex pattern of responses. Each odorant normally produced a unique pattern of excitatory and inhibitory responses across all units. Chi-square values were calculated for stimulatory effectiveness between forty-five pairs of odours. L-serine and L-alanine consistently showed a high degree of similarity with several other odours. The converse was true for GABA and L-histidine, although this pair had a high chi-square value when mutually compared. Enantiomeric pairs of amino acids were often found to have opposite stimulatory effects on bulbar units. These results are discussed in relation to the possible properties and configurations of odorant receptor sites for amino acids in the fish olfactory mucosa.Endocrinology of the head-kidney tissues in teleost fishAl-Asgah, Nasser A.https://hdl.handle.net/10023/150202019-03-29T10:39:13Z1977-01-01T00:00:00ZThis is a study of the structure and functions of the endocrine tissues in the head-kidney of the teleost fish, the homologous tissues to the mammalian adrenal cortex (=adrenocortical tissue) and adrenal medulla (=chromaffin tissue). The study is divided into three main sections: 1.The first section comprises a study of the general morphology, at the anatomical and histological level, of the different types of head-kidney which occur in teleost fish. The range of types is illustrated by studies on twenty-four species, some of which have been previously investigated, and including in particular sixteen marine species from the Red Sea coast of Saudi Arabia collected by the author. 2. The second section of this thesis comprises a detailed study of the morphology of the head-kidney of one particular species, Phoxinus phoxinus (Linnaeus), and a two year study of seasonal variations in the activity of its adrenocortical and chromaffin tissue. Samples of fish were collected from a population in the Walton Reservoir, Scotland, at monthly intervals. The activity of the adrenocortical tissue was assessed by measuring nuclear diameter of the adrenocortical cells, a criterion already widely used for this purpose. The activity of the chromaffin cells was similarly assessed, though the methodology is less well established in this case. The effects were compared of electro-fishing followed by anaesthesis and immersion in Bouin's fixative while still under electronarcosis. Both proved to be relatively stress-free methods. 3. The third section of this thesis comprises a study of the fine structure of the endocrine tissues of the head-kidney of Phoxinus phoxinus and Salmo qairdnerii. Electron micrographs were prepared using fish caught under stress-free conditions in the Walton Reservoir, and from aquarium-maintained fish. The adrenocortical cells in both species are characterised by having a great many conspicuous mitochondria with tubule-vesicular internal structure. The nucleus is circular in section, and centrally situated in the cell. There is an extensive smooth endoplasmic reticulum and numerous ribosomes, Microvilli occur on cell surfaces in contact with veins. There is a wide range in the structure of the adrenocortical cells of individual fish; mitochondria range from small, elongated structure, with dark matrix to large, circular structures in which the internal structures eventually breaks down. The cytoplasm as a whole tends to be pale in cells with small dense mitochondria, and dense in cells with large, paler mitochondria. Pale highly vacuolated cytoplasm is associated with cells in which the mitochondria are breaking down; the vacuoles are probably associated with cells in which the mitochondria are breaking down; the vacuoles are probably associated with the degenerating mitochondria, In Phoxinus maintained in aquaria for twenty-four hours before killing, the proportion of adrenocortical cells with small mitochondria with dark matrices, -. as compared to fish caught by stress-free methods and fixed immediately. In Salmo which had been maintained in aquaria for longer periods, the proportion oft- cells showing mitochondrial degeneration and cytoplasmic vacuolation is higher. It is concluded that small, dark matrix mitochondria are typical of early stages of adrenal activity; dense cytoplasm and an increased number of large, circular mitochondria are typical of maximum activity; and mitochondrial degeneration and vacuolation of the cytoplasm is typical of exhaustion. Chromaffin cells, not hitherto described in teleost fish, are of the type found in other vertebrates, with many chromaffin vesicles containing varying amounts of granular inclusion. Synaptic contacts occur commonly, apparently all of cholinergic type. In Salmo the chromaffin and adrenocortical cells lie separately, but in Phoxinus the adrenocortical cells form a sheath round the posterior cardinal veins and their main tributaries, and the chromaffin cells lie beyond them, against the haemopoietic tissue. These chromaffin cells communicate with the vein by elongated projections running amongst the adrenocortical cells.
1977-01-01T00:00:00ZAl-Asgah, Nasser A.This is a study of the structure and functions of the endocrine tissues in the head-kidney of the teleost fish, the homologous tissues to the mammalian adrenal cortex (=adrenocortical tissue) and adrenal medulla (=chromaffin tissue). The study is divided into three main sections: 1.The first section comprises a study of the general morphology, at the anatomical and histological level, of the different types of head-kidney which occur in teleost fish. The range of types is illustrated by studies on twenty-four species, some of which have been previously investigated, and including in particular sixteen marine species from the Red Sea coast of Saudi Arabia collected by the author. 2. The second section of this thesis comprises a detailed study of the morphology of the head-kidney of one particular species, Phoxinus phoxinus (Linnaeus), and a two year study of seasonal variations in the activity of its adrenocortical and chromaffin tissue. Samples of fish were collected from a population in the Walton Reservoir, Scotland, at monthly intervals. The activity of the adrenocortical tissue was assessed by measuring nuclear diameter of the adrenocortical cells, a criterion already widely used for this purpose. The activity of the chromaffin cells was similarly assessed, though the methodology is less well established in this case. The effects were compared of electro-fishing followed by anaesthesis and immersion in Bouin's fixative while still under electronarcosis. Both proved to be relatively stress-free methods. 3. The third section of this thesis comprises a study of the fine structure of the endocrine tissues of the head-kidney of Phoxinus phoxinus and Salmo qairdnerii. Electron micrographs were prepared using fish caught under stress-free conditions in the Walton Reservoir, and from aquarium-maintained fish. The adrenocortical cells in both species are characterised by having a great many conspicuous mitochondria with tubule-vesicular internal structure. The nucleus is circular in section, and centrally situated in the cell. There is an extensive smooth endoplasmic reticulum and numerous ribosomes, Microvilli occur on cell surfaces in contact with veins. There is a wide range in the structure of the adrenocortical cells of individual fish; mitochondria range from small, elongated structure, with dark matrix to large, circular structures in which the internal structures eventually breaks down. The cytoplasm as a whole tends to be pale in cells with small dense mitochondria, and dense in cells with large, paler mitochondria. Pale highly vacuolated cytoplasm is associated with cells in which the mitochondria are breaking down; the vacuoles are probably associated with cells in which the mitochondria are breaking down; the vacuoles are probably associated with the degenerating mitochondria, In Phoxinus maintained in aquaria for twenty-four hours before killing, the proportion of adrenocortical cells with small mitochondria with dark matrices, -. as compared to fish caught by stress-free methods and fixed immediately. In Salmo which had been maintained in aquaria for longer periods, the proportion oft- cells showing mitochondrial degeneration and cytoplasmic vacuolation is higher. It is concluded that small, dark matrix mitochondria are typical of early stages of adrenal activity; dense cytoplasm and an increased number of large, circular mitochondria are typical of maximum activity; and mitochondrial degeneration and vacuolation of the cytoplasm is typical of exhaustion. Chromaffin cells, not hitherto described in teleost fish, are of the type found in other vertebrates, with many chromaffin vesicles containing varying amounts of granular inclusion. Synaptic contacts occur commonly, apparently all of cholinergic type. In Salmo the chromaffin and adrenocortical cells lie separately, but in Phoxinus the adrenocortical cells form a sheath round the posterior cardinal veins and their main tributaries, and the chromaffin cells lie beyond them, against the haemopoietic tissue. These chromaffin cells communicate with the vein by elongated projections running amongst the adrenocortical cells.A new method for culturing dogfish shark (Scyliorhinus canicula) rectal gland epithelial cellsNelson, David S.https://hdl.handle.net/10023/150192021-02-23T15:27:54Z1996-01-01T00:00:00Z1. Dogfish, Scyliorhinus canicula, rectal gland epithelial cells were successfully cultured using two different techniques: 1) a perfusion based technique and 2) a modified Valentich's technique (Valentich, 1991). 2. Growth stages of cultures were monitored, showing attachment of tubules at approximately two days with a complete monolayer formed between seven and ten days. Cultures were able to be maintained for up to twenty days. Photos were taken illustrating epithelial cell migration and cell viability. 3. Administration of Ca+2 and Mg+2 free Ringer + 2 mM ethylenediamine tetra-acetic acid (EDTA) + 1% trypsin successfully reduced cultures growing in 96-well plates to single cells after a time course of 20 min to allow for accurate cell counts of approximately 22,000 cells per well. 4. 10-6 M shark C-type natriuretic peptide (sCNP) induced stimulation of cGMP in cultured rectal gland epithelial cells over a time course of 240 sec with maximal stimulation occurring at 180 sec. Limited experiments with scyliorhinin II and rectin showed little effects in stimulating cGMP.
1996-01-01T00:00:00ZNelson, David S.1. Dogfish, Scyliorhinus canicula, rectal gland epithelial cells were successfully cultured using two different techniques: 1) a perfusion based technique and 2) a modified Valentich's technique (Valentich, 1991). 2. Growth stages of cultures were monitored, showing attachment of tubules at approximately two days with a complete monolayer formed between seven and ten days. Cultures were able to be maintained for up to twenty days. Photos were taken illustrating epithelial cell migration and cell viability. 3. Administration of Ca+2 and Mg+2 free Ringer + 2 mM ethylenediamine tetra-acetic acid (EDTA) + 1% trypsin successfully reduced cultures growing in 96-well plates to single cells after a time course of 20 min to allow for accurate cell counts of approximately 22,000 cells per well. 4. 10-6 M shark C-type natriuretic peptide (sCNP) induced stimulation of cGMP in cultured rectal gland epithelial cells over a time course of 240 sec with maximal stimulation occurring at 180 sec. Limited experiments with scyliorhinin II and rectin showed little effects in stimulating cGMP.The effect of feeding on ion transport in the rectal gland of the European dogfish (Scyliorhinus canicula)MacKenzie, Simonhttps://hdl.handle.net/10023/150182021-02-23T15:24:40Z1997-01-01T00:00:00ZPlasma sodium, chloride and urea concentrations and plasma osmolalities were determined after dogfish were dietary adapted to both acute and chronic feeding regimes. Following single feeding events (20g squid / kg body wt) plasma sodium and chloride concentrations dropped transiently by a maximum of 27% and 18% respectively, two days after feeding. There was however no significant change in the plasma urea concentration or plasma osmolality. Determination of blood vessel calibre by histological examination of rectal glands before, and 12 hours after, a single feeding event suggested an increase in the blood supply to the gland. Repeated feeding events (2.5g pellets / kg body wt) over a period of 1 month were conducted with pelleted diets containing either 1% or 6% w / w NaCl and blood samples were taken weekly for analysis. Plasma sodium concentrations were significantly reduced by approximately 10% after 1 and 3 weeks of feeding and plasma osmolalities fell again by approximately 10% at 1, 2 and 3 weeks when fish were fed on the 1% w / w NaCl pellet diet. However both parameters returned to normal values by the end of the study period. Likewise when fish were fed the high salt (6% w / w NaCl) pellet diet, plasma sodium concentrations and plasma osmolalities again fell by 10-15% after 1, 2 and 3 weeks of repeated feeding. Plasma sodium recovered to normal values within 28 days however the plasma osmolality remained significantly lower than controls. Total RNA was extracted from the rectal gland and homologous and heterologous cDNA probes for the alpha1, beta1 subunits of the Na, K-ATPase and the sCFTR and Na-K-Cl cotransporter were used in Northern and dot blot analyses to identify and quantify the levels of mRNA expression of these major ion transporter proteins during dietary adaptation. Maximal Na, K-ATPase activities in rectal gland homogenates increased transiently by over 40-fold, 9 hours after a single feeding episode (20g squid / kg body wt). There was no concomitant increase in either alpha1 or beta1 subunit of the Na, K-ATPase mRNAs over the same time period however the abundance of both al and (31 Na, K-ATPase subunit mRNAs slowly increased by 75% and 39% respectively two days after feeding and were maintained at that level for either 10 days or 5 days respectively. In chronic dietary adaptations to a squid diet, a 40% increase in beta1 Na, K-ATPase subunit mRNA was found after 4 weeks of repeated feeding however there was no significant increase in al subunit mRNA expression or Na, K-ATPase activity. In contrast chronic dietary adaptation to the 6% w / w NaCl pellet diet resulted in a 3-fold increase in Na, K-ATPase activity however there was no concomitant increase in either the alpha1 or beta1 subunit of the Na, K-ATPase mRNAs. After a single feeding event with the squid diet, mRNAs for both the sCFTR and Na-K-Cl cotransporter proteins were significantly increased, by 55% and 65% respectively, five days after the feeding episode compared to controls.
1997-01-01T00:00:00ZMacKenzie, SimonPlasma sodium, chloride and urea concentrations and plasma osmolalities were determined after dogfish were dietary adapted to both acute and chronic feeding regimes. Following single feeding events (20g squid / kg body wt) plasma sodium and chloride concentrations dropped transiently by a maximum of 27% and 18% respectively, two days after feeding. There was however no significant change in the plasma urea concentration or plasma osmolality. Determination of blood vessel calibre by histological examination of rectal glands before, and 12 hours after, a single feeding event suggested an increase in the blood supply to the gland. Repeated feeding events (2.5g pellets / kg body wt) over a period of 1 month were conducted with pelleted diets containing either 1% or 6% w / w NaCl and blood samples were taken weekly for analysis. Plasma sodium concentrations were significantly reduced by approximately 10% after 1 and 3 weeks of feeding and plasma osmolalities fell again by approximately 10% at 1, 2 and 3 weeks when fish were fed on the 1% w / w NaCl pellet diet. However both parameters returned to normal values by the end of the study period. Likewise when fish were fed the high salt (6% w / w NaCl) pellet diet, plasma sodium concentrations and plasma osmolalities again fell by 10-15% after 1, 2 and 3 weeks of repeated feeding. Plasma sodium recovered to normal values within 28 days however the plasma osmolality remained significantly lower than controls. Total RNA was extracted from the rectal gland and homologous and heterologous cDNA probes for the alpha1, beta1 subunits of the Na, K-ATPase and the sCFTR and Na-K-Cl cotransporter were used in Northern and dot blot analyses to identify and quantify the levels of mRNA expression of these major ion transporter proteins during dietary adaptation. Maximal Na, K-ATPase activities in rectal gland homogenates increased transiently by over 40-fold, 9 hours after a single feeding episode (20g squid / kg body wt). There was no concomitant increase in either alpha1 or beta1 subunit of the Na, K-ATPase mRNAs over the same time period however the abundance of both al and (31 Na, K-ATPase subunit mRNAs slowly increased by 75% and 39% respectively two days after feeding and were maintained at that level for either 10 days or 5 days respectively. In chronic dietary adaptations to a squid diet, a 40% increase in beta1 Na, K-ATPase subunit mRNA was found after 4 weeks of repeated feeding however there was no significant increase in al subunit mRNA expression or Na, K-ATPase activity. In contrast chronic dietary adaptation to the 6% w / w NaCl pellet diet resulted in a 3-fold increase in Na, K-ATPase activity however there was no concomitant increase in either the alpha1 or beta1 subunit of the Na, K-ATPase mRNAs. After a single feeding event with the squid diet, mRNAs for both the sCFTR and Na-K-Cl cotransporter proteins were significantly increased, by 55% and 65% respectively, five days after the feeding episode compared to controls.The effects of extracellular sodium chloride on the activity and expression of Na,K-ATPase in primary cultures of dogfish (Scyliorhinus canicula) rectal gland epithelial cellsEdwards, Joannehttps://hdl.handle.net/10023/150162019-03-29T10:32:51Z1998-01-01T00:00:00ZDogfish, Scyliorhinus canicula, rectal gland epithelial cells were successfully cultured using two different techniques: 1) a perfusion based technique and 2) a modified Valentich's technique. The morphology of the primary rectal gland epithelial cell cultures was investigated using light, fluorescence and electron microscopy. These studies demonstrated that the cell cultures express most of the structural features of native shark rectal gland cells, including numerous mitochondria, complex tight junctions and extensive membrane folding. The cultured cells using the perfusion technique adopted an extremely flattened morphology when grown on collagen. These cells whether grown in suspension or on collagen, displayed a striking level of vacuole formation, these vacuoles were not associated with transport epithelia. The rectal gland cell cultures were then used to investigate the effect increasing extracellular sodium chloride concentration has on rectal gland cells Na, K-ATPase activity. Increasing sodium chloride concentration in the growth medium by 50% (240 mM to 360 mM) resulted in a transient 3-4 fold increase in Na, K-ATPase activity in cell homogenates approximately 12 hours after the medium change. The response was dependent upon both sodium and chloride ions and was also inhibited by the loop diuretic bumetanide (0.1 mM within 30 minutes), indicating that entry of the ions into the cell is via the Na, K, C1 cotransporter. Incubation of cells in normal medium in the presence of the sodium ionophore monensin also resulted in a dose dependant sustained increase in Na, K-ATPase activity following a 12 hour incubation. The increase in Na, K-ATPase activity associated with increased extracellular sodium chloride concentration was only seen in cells grown on collagen and not in cells grown in suspension. Increases in activity are sensitive to the protein synthesis inhibitor cycloheximide (10 mug/ml), but not the transcriptional inhibitor actinomycin D suggesting that up-regulation of the Na, K-ATPase occurs at the level of translational regulation. Unfortunately this result could not be confirmed using Northern analysis due to unforeseen difficulties in extracting sufficient RNA from the cell cultures. Addition of bumetanide (0.1 mM) to cells grown in normal medium caused a rapid but reversible down-regulation (by 70%) of basal Na, K-ATPase activity within 30 minutes. The anti-microtubular agent colchicine (0.1 mug/ml) inhibited the bumetanide induced down-regulation of Na, K-ATPase and also the recovery of activity following bumetanide removal. The rectal gland cell cultures were used to investigate potential hormonal regulators of the shark rectal gland. The effect of the putative regulators of sodium chloride secretion scyliorhinin II and sCNP on intracellular concentrations of cAMP and cGMP was investigated. The cell cultures were shown be hormonally active as they responded with an increase in intracelllular cAMP concentration to forskolin, PGE1 and PGE2. When scyliorhinin II (10 muM) and IBMX (1 mM) was perfused through the isolated rectal gland a 2 fold increase in cAMP concentration was found in the perfusate after 8 minutes, however no increase was seen in cAMP levels when cell cultures were treated with scyliorhinin II. Shark CNP increased cGMP concentrations in the perfusates of the perfused rectal gland by up to four fold after seven minutes but there was no consistent effect on cGMP concentrations in the cultured cell monolayer. In conclusion it is believed that sCNP and scyliorhinin II mediate their actions on the regulation of sodium chloride secretion by the rectal gland at the vascular level, controlling the extent of perfusion of the gland. This study showed that high salt levels in the medium of shark rectal gland cell monolayers increased the measurable Na, K-ATPase activity and that this response was dependent on protein synthesis but not transcription. It also showed that the response is inhibited by the loop diuretic bumetanide, indicating that entry of the ions into the cell is via the Na, K, Cl cotransporter and that the increase in Na, K-ATPase activity is presumably due to an increase in intracellular sodium concentration. The hormones sCNP and scyliorhinin II appear to mediate their actions on the regulation of sodium chloride secretion by the rectal gland at the vascular level controlling the extent of perfusion of the gland. In conclusion although sodium chloride transport in the dogfish rectal gland requires much more investigation, this study has hopefully proved that dogfish epithelial cell cultures provide a good model for further investigations involving the regulation of activity and expression of the sodium pump.
1998-01-01T00:00:00ZEdwards, JoanneDogfish, Scyliorhinus canicula, rectal gland epithelial cells were successfully cultured using two different techniques: 1) a perfusion based technique and 2) a modified Valentich's technique. The morphology of the primary rectal gland epithelial cell cultures was investigated using light, fluorescence and electron microscopy. These studies demonstrated that the cell cultures express most of the structural features of native shark rectal gland cells, including numerous mitochondria, complex tight junctions and extensive membrane folding. The cultured cells using the perfusion technique adopted an extremely flattened morphology when grown on collagen. These cells whether grown in suspension or on collagen, displayed a striking level of vacuole formation, these vacuoles were not associated with transport epithelia. The rectal gland cell cultures were then used to investigate the effect increasing extracellular sodium chloride concentration has on rectal gland cells Na, K-ATPase activity. Increasing sodium chloride concentration in the growth medium by 50% (240 mM to 360 mM) resulted in a transient 3-4 fold increase in Na, K-ATPase activity in cell homogenates approximately 12 hours after the medium change. The response was dependent upon both sodium and chloride ions and was also inhibited by the loop diuretic bumetanide (0.1 mM within 30 minutes), indicating that entry of the ions into the cell is via the Na, K, C1 cotransporter. Incubation of cells in normal medium in the presence of the sodium ionophore monensin also resulted in a dose dependant sustained increase in Na, K-ATPase activity following a 12 hour incubation. The increase in Na, K-ATPase activity associated with increased extracellular sodium chloride concentration was only seen in cells grown on collagen and not in cells grown in suspension. Increases in activity are sensitive to the protein synthesis inhibitor cycloheximide (10 mug/ml), but not the transcriptional inhibitor actinomycin D suggesting that up-regulation of the Na, K-ATPase occurs at the level of translational regulation. Unfortunately this result could not be confirmed using Northern analysis due to unforeseen difficulties in extracting sufficient RNA from the cell cultures. Addition of bumetanide (0.1 mM) to cells grown in normal medium caused a rapid but reversible down-regulation (by 70%) of basal Na, K-ATPase activity within 30 minutes. The anti-microtubular agent colchicine (0.1 mug/ml) inhibited the bumetanide induced down-regulation of Na, K-ATPase and also the recovery of activity following bumetanide removal. The rectal gland cell cultures were used to investigate potential hormonal regulators of the shark rectal gland. The effect of the putative regulators of sodium chloride secretion scyliorhinin II and sCNP on intracellular concentrations of cAMP and cGMP was investigated. The cell cultures were shown be hormonally active as they responded with an increase in intracelllular cAMP concentration to forskolin, PGE1 and PGE2. When scyliorhinin II (10 muM) and IBMX (1 mM) was perfused through the isolated rectal gland a 2 fold increase in cAMP concentration was found in the perfusate after 8 minutes, however no increase was seen in cAMP levels when cell cultures were treated with scyliorhinin II. Shark CNP increased cGMP concentrations in the perfusates of the perfused rectal gland by up to four fold after seven minutes but there was no consistent effect on cGMP concentrations in the cultured cell monolayer. In conclusion it is believed that sCNP and scyliorhinin II mediate their actions on the regulation of sodium chloride secretion by the rectal gland at the vascular level, controlling the extent of perfusion of the gland. This study showed that high salt levels in the medium of shark rectal gland cell monolayers increased the measurable Na, K-ATPase activity and that this response was dependent on protein synthesis but not transcription. It also showed that the response is inhibited by the loop diuretic bumetanide, indicating that entry of the ions into the cell is via the Na, K, Cl cotransporter and that the increase in Na, K-ATPase activity is presumably due to an increase in intracellular sodium concentration. The hormones sCNP and scyliorhinin II appear to mediate their actions on the regulation of sodium chloride secretion by the rectal gland at the vascular level controlling the extent of perfusion of the gland. In conclusion although sodium chloride transport in the dogfish rectal gland requires much more investigation, this study has hopefully proved that dogfish epithelial cell cultures provide a good model for further investigations involving the regulation of activity and expression of the sodium pump.Osmoregulatory role and control of secretion of lα-hydroxycorticosterone in the lesser spotted dogfish 'Scyliorhinus canicula'Armour, Kennethhttps://hdl.handle.net/10023/150152021-02-23T15:23:43Z1991-01-01T00:00:00Z1. Groups of dogfish, Scyliorhinus canicula, were adapted to either a high or a low protein diet over a period of 30 days. The fish readily ate both diets and maintained body weights. 2. Dietary adapted fish were acclimated to 130%, 100% and 50% seawater and the metabolic clearance rates (MCR) and blood production rates (BPR) for urea and 1a-hydroxycorticosterone (1a-OH-B) determined. 3. In 100% seawater low protein diet (LPD) fish had significantly lower urea BPR and MCR than the high protein diet (HPD) fish. 4. In 50% seawater plasma osmolality, sodium, chloride and urea concentrations decreased in both dietary groups. Plasma 1a-OH-B concentration and BPR were significantly increased and in HPD fish this was accompanied by an increase in 1a-OH-B MCR. The increase in plasma 1a-OH-B concentration was significantly greater in the HPD fish than in the LPD fish. 5. In 130% seawater plasma osmolality was increased in both dietary groups. In HPD fish this was achieved by increasing plasma urea, sodium and chloride concentrations. In LPD fish this was achieved by significantly elevating plasma sodium concentration only. Plasma 1a-OH-B concentration and BPR were significantly increased and MCR significantly decreased in LPD fish, but remained unaltered in HPD fish. 6. An isolated perifused interrenal gland preparation was developed for Scyliorhinus canicula, which produced a constant 1a-OH-B basal secretion rate after two hours and remained viable for more than 22 hours. 7. ACTH, All, ANP, AVT, forskolin, dibutyryl cAMP and dibutyryl cGMP stimulated interrenal steroidogenesis. 8. ACTH-induced steroidogenesis was unaffected by the presence of dantrolene and verapamil but significantly increased in the presence of cholera toxin and significantly decreased in the absence of extracellular calcium. 9. Ile5-All-induced steroidogenesis was unaffected by the presence of verapamil but significantly decreased in the presence of dantrolene and in the absence of extracellular calcium. 10. Increases in potassium concentration were significantly steroidogenic only at 28mM and alterations in sodiimi concentration had no effect.
1991-01-01T00:00:00ZArmour, Kenneth1. Groups of dogfish, Scyliorhinus canicula, were adapted to either a high or a low protein diet over a period of 30 days. The fish readily ate both diets and maintained body weights. 2. Dietary adapted fish were acclimated to 130%, 100% and 50% seawater and the metabolic clearance rates (MCR) and blood production rates (BPR) for urea and 1a-hydroxycorticosterone (1a-OH-B) determined. 3. In 100% seawater low protein diet (LPD) fish had significantly lower urea BPR and MCR than the high protein diet (HPD) fish. 4. In 50% seawater plasma osmolality, sodium, chloride and urea concentrations decreased in both dietary groups. Plasma 1a-OH-B concentration and BPR were significantly increased and in HPD fish this was accompanied by an increase in 1a-OH-B MCR. The increase in plasma 1a-OH-B concentration was significantly greater in the HPD fish than in the LPD fish. 5. In 130% seawater plasma osmolality was increased in both dietary groups. In HPD fish this was achieved by increasing plasma urea, sodium and chloride concentrations. In LPD fish this was achieved by significantly elevating plasma sodium concentration only. Plasma 1a-OH-B concentration and BPR were significantly increased and MCR significantly decreased in LPD fish, but remained unaltered in HPD fish. 6. An isolated perifused interrenal gland preparation was developed for Scyliorhinus canicula, which produced a constant 1a-OH-B basal secretion rate after two hours and remained viable for more than 22 hours. 7. ACTH, All, ANP, AVT, forskolin, dibutyryl cAMP and dibutyryl cGMP stimulated interrenal steroidogenesis. 8. ACTH-induced steroidogenesis was unaffected by the presence of dantrolene and verapamil but significantly increased in the presence of cholera toxin and significantly decreased in the absence of extracellular calcium. 9. Ile5-All-induced steroidogenesis was unaffected by the presence of verapamil but significantly decreased in the presence of dantrolene and in the absence of extracellular calcium. 10. Increases in potassium concentration were significantly steroidogenic only at 28mM and alterations in sodiimi concentration had no effect.The thyrotrophic and gonadotrophic functions of the elasmobranch pituitaryGoddard, Charles Keithhttps://hdl.handle.net/10023/150122019-03-29T10:32:45Z1957-01-01T00:00:00Z1957-01-01T00:00:00ZGoddard, Charles KeithThe endocrine control of reproduction in the river lamprey Lampetra fluviatilis L.Evennett, Peter Johnhttps://hdl.handle.net/10023/150112019-03-29T10:39:24Z1963-01-01T00:00:00Z1963-01-01T00:00:00ZEvennett, Peter JohnThe influence of temperature on the development and swimming performance of flatfishGibson, Sandrahttps://hdl.handle.net/10023/150082019-03-29T10:33:15Z1995-01-01T00:00:00ZGrowth and development were studied in turbot {Scophthalmus maximus L.) reared at 12° and 16° until 26 days after hatching. Muscle growth occurred by fibre hypertrophy and hyperplasia and was faster at 16°. In larvae, the sequence of organogenesis was altered by temperature. The influence of temperature on the swimming performance of settled stages of turbot and plaice (Pleuronectes platessa) was studied. Maximum swimming speed (Umax), elicited following an escape response, scaled similarly between 13 and 23°, for turbot, and could be fitted by the model: A comparison of Umax between wild caught and laboratory reared turbot showed that Umax for farmed turbot was lower than for wild fish filmed within 2 weeks of capture. 3 months after capture the average differences in escape performance were no longer significant, suggesting they were due to an acclimation. Standardised Umax for eighteen wild juvenile turbot was determined at 18° and over a temperature change. Repeatability of ranking of the experimental Umax of individuals was maintained over a 6 week period, and through temperature change. For plaice Umax scaled in proportion to TL0.65 between 5° and 13°. Umax did not increase at temperatures above 9°. There was no difference in Umax or tail beat frequency (f) between laboratory reared and wild caught plaice. Umax and f decreased after an acute temperature reduction from 9° to 5° and showed no compensation for the reduction temperature after a 29 days acclimation period. Stride length (X) was independent of temperature. After the 29 day period at 5°, raising the temperature to 9° resulted in an increase in Umax without a corresponding increase in f, although tail beat amplitude (A) was higher. The effects of temperature change during early development on locomotory performance and phenotype are discussed.
1995-01-01T00:00:00ZGibson, SandraGrowth and development were studied in turbot {Scophthalmus maximus L.) reared at 12° and 16° until 26 days after hatching. Muscle growth occurred by fibre hypertrophy and hyperplasia and was faster at 16°. In larvae, the sequence of organogenesis was altered by temperature. The influence of temperature on the swimming performance of settled stages of turbot and plaice (Pleuronectes platessa) was studied. Maximum swimming speed (Umax), elicited following an escape response, scaled similarly between 13 and 23°, for turbot, and could be fitted by the model: A comparison of Umax between wild caught and laboratory reared turbot showed that Umax for farmed turbot was lower than for wild fish filmed within 2 weeks of capture. 3 months after capture the average differences in escape performance were no longer significant, suggesting they were due to an acclimation. Standardised Umax for eighteen wild juvenile turbot was determined at 18° and over a temperature change. Repeatability of ranking of the experimental Umax of individuals was maintained over a 6 week period, and through temperature change. For plaice Umax scaled in proportion to TL0.65 between 5° and 13°. Umax did not increase at temperatures above 9°. There was no difference in Umax or tail beat frequency (f) between laboratory reared and wild caught plaice. Umax and f decreased after an acute temperature reduction from 9° to 5° and showed no compensation for the reduction temperature after a 29 days acclimation period. Stride length (X) was independent of temperature. After the 29 day period at 5°, raising the temperature to 9° resulted in an increase in Umax without a corresponding increase in f, although tail beat amplitude (A) was higher. The effects of temperature change during early development on locomotory performance and phenotype are discussed.Hormonal control of rectal gland secretion in the European lesser spotted dogfish 'Scyliorhinus canicula'Anderson, W. Garyhttps://hdl.handle.net/10023/150072021-02-23T15:26:05Z1995-01-01T00:00:00Z1) Using the corrosion casting technique, which utilises a fast polymerising monomer resin, the vasculature of the rectal gland in Scyliorhinm canicula was studied using light and scanning electron microscopy. Possible control sites for altering blood flow through the rectal gland were identified. 2) A viable and reliable isolated perfused preparation of the rectal gland of S. canicula was developed by optimising flow rate, time of perfusion and viability of individual preparations. The combination of dibutryl cyclic adenosine monophosphate plus the potent phosphodiesterase inhibitor Isobutyl-methyl xanthine, was used as a test of viability for individual preparations. This combination potently stimulated chloride clearance rates from the isolated perfused rectal gland. 3) The isolated perfused preparation was then used to test a variety of hormones that could be involved in the control of rectal gland activity. The hormones, vasoactive intestinal peptide and urotensin II did not stimulate chloride clearance rates from the isolated perfused gland. However, the endogenous natriuretic peptide, C-type natriuretic peptide did stimulate chloride clearance rate from the perfused rectal gland in a dose dependant manner. Endogenous glucagon also stimulated chloride clearance rate. 4) Using cannulated fish, administration of angiotensin II and C-type natriuretic peptide in vivo, produced vasopressor and vasodepressor responses respectively and C-type natriuretic peptide inhibited the vasopressor action of angiotensin II when the two peptides were administered simultaneously. Administration of angiotensin II to the isolated perfused rectal gland produced a vasoconstrictor effect, increasing perfusion pressure. C-type natriuretic peptide did not produce any significant effect. A combination of the two peptides in vitro appeared to reduce the vasoconstrictor effect of angiotensin II. In addition this hormonal combination in vitro appeared to exert a synergistic effect increasing chloride clearance rates from the isolated perfused rectal gland. 5) The lack of a VIP stimulatory effect on the isolated perfused rectal gland in the present study is in agreement with previous reports. Using protein purification techniques including, gel-permeation, and reverse-phase high performance liquid chromatography an endogenous gut peptide was obtained that stimulated rectal gland activity in 5. canicula. This peptide was subsequently characterised as scyliorhinin II and it is proposed that the previously identified rectin and scyliorhinin II are the same peptide.
1995-01-01T00:00:00ZAnderson, W. Gary1) Using the corrosion casting technique, which utilises a fast polymerising monomer resin, the vasculature of the rectal gland in Scyliorhinm canicula was studied using light and scanning electron microscopy. Possible control sites for altering blood flow through the rectal gland were identified. 2) A viable and reliable isolated perfused preparation of the rectal gland of S. canicula was developed by optimising flow rate, time of perfusion and viability of individual preparations. The combination of dibutryl cyclic adenosine monophosphate plus the potent phosphodiesterase inhibitor Isobutyl-methyl xanthine, was used as a test of viability for individual preparations. This combination potently stimulated chloride clearance rates from the isolated perfused rectal gland. 3) The isolated perfused preparation was then used to test a variety of hormones that could be involved in the control of rectal gland activity. The hormones, vasoactive intestinal peptide and urotensin II did not stimulate chloride clearance rates from the isolated perfused gland. However, the endogenous natriuretic peptide, C-type natriuretic peptide did stimulate chloride clearance rate from the perfused rectal gland in a dose dependant manner. Endogenous glucagon also stimulated chloride clearance rate. 4) Using cannulated fish, administration of angiotensin II and C-type natriuretic peptide in vivo, produced vasopressor and vasodepressor responses respectively and C-type natriuretic peptide inhibited the vasopressor action of angiotensin II when the two peptides were administered simultaneously. Administration of angiotensin II to the isolated perfused rectal gland produced a vasoconstrictor effect, increasing perfusion pressure. C-type natriuretic peptide did not produce any significant effect. A combination of the two peptides in vitro appeared to reduce the vasoconstrictor effect of angiotensin II. In addition this hormonal combination in vitro appeared to exert a synergistic effect increasing chloride clearance rates from the isolated perfused rectal gland. 5) The lack of a VIP stimulatory effect on the isolated perfused rectal gland in the present study is in agreement with previous reports. Using protein purification techniques including, gel-permeation, and reverse-phase high performance liquid chromatography an endogenous gut peptide was obtained that stimulated rectal gland activity in 5. canicula. This peptide was subsequently characterised as scyliorhinin II and it is proposed that the previously identified rectin and scyliorhinin II are the same peptide.Aspects of the visceral autonomic and central aminergic nervous system of teleostsWatson, Alan H. D.https://hdl.handle.net/10023/150062019-03-29T10:36:31Z1979-01-01T00:00:00ZThe structure of the autonomic innervation of the gastro-intestinal tract and heart of a number of teleosts was examined using light and electron microscopy and fluorescence histochemistiy. In the scorpion fish, the structure of the coeliac ganglion and the distribution of aminergic neurones in the brain was also investigated. The distribution of monoamine-containing nerves in the gut of scorpion fish, plaice, herring and ice fish was described using fluorescence histochemistry. Castecholaminergic fibres are found in the myenteric plexus and in the submucosa where they frequently run with blood vessels. They also supply the longitudinal muscle of the rectum and are often prominent in the circular muscle of the pyloric and anal sphincters. Serotonergic nerves pass through the submucosa to the subepithelial plexus and 5HT can be isolated chromatographically from gut wall homogenates. Serotonergic enterochromaffin cells are present in the stomach and distal rectum and in the herring a catecholamine-containing form was observed in the pyloric stomach. Ultrastructurally two types of axonal profiles are seen in the gut. The first contains small agranular vesicles typical of cholinergic nerves and these synapse with the perikarya of myenteric neurones, while the second contains a mixture of large and small granular vesicles and though often found adjacent to ganglion and muscle cells is not involved in conventional synapses. Both types are present in the subepithelial plexus. Histochemical and drug depletion studies suggest that some of the granular vesicles contain biogenic amines. The hearts of plaice, dab and angler fish do not contain adrenergic nerves Taut these were found in all other species examined. In the lingcod, aminergic perikarya are also present in the cardiac ganglion. With the electron microscope, the densest innervation of cardiac muscle was found close to the cardiac ganglion but though fluorescent nerves are abundant, nerve profiles contain predominantly agranular vesicles. The coeliac ganglion of scorpion fish is similar in structure to sympathetic ganglia in other vertebrates. It contains two types of principal cell as well as a population of small intensely fluorescent (SIP) cells. The SIP cells appear to become more numerous in early summer when vesicles in the equivalent cells observed ultrastructurally develop electron dense granules. The catecholaminergic and serotonergic structures in the brain of scorpion fish were described and compared to those of other teleosts and higher vertebrates.
1979-01-01T00:00:00ZWatson, Alan H. D.The structure of the autonomic innervation of the gastro-intestinal tract and heart of a number of teleosts was examined using light and electron microscopy and fluorescence histochemistiy. In the scorpion fish, the structure of the coeliac ganglion and the distribution of aminergic neurones in the brain was also investigated. The distribution of monoamine-containing nerves in the gut of scorpion fish, plaice, herring and ice fish was described using fluorescence histochemistry. Castecholaminergic fibres are found in the myenteric plexus and in the submucosa where they frequently run with blood vessels. They also supply the longitudinal muscle of the rectum and are often prominent in the circular muscle of the pyloric and anal sphincters. Serotonergic nerves pass through the submucosa to the subepithelial plexus and 5HT can be isolated chromatographically from gut wall homogenates. Serotonergic enterochromaffin cells are present in the stomach and distal rectum and in the herring a catecholamine-containing form was observed in the pyloric stomach. Ultrastructurally two types of axonal profiles are seen in the gut. The first contains small agranular vesicles typical of cholinergic nerves and these synapse with the perikarya of myenteric neurones, while the second contains a mixture of large and small granular vesicles and though often found adjacent to ganglion and muscle cells is not involved in conventional synapses. Both types are present in the subepithelial plexus. Histochemical and drug depletion studies suggest that some of the granular vesicles contain biogenic amines. The hearts of plaice, dab and angler fish do not contain adrenergic nerves Taut these were found in all other species examined. In the lingcod, aminergic perikarya are also present in the cardiac ganglion. With the electron microscope, the densest innervation of cardiac muscle was found close to the cardiac ganglion but though fluorescent nerves are abundant, nerve profiles contain predominantly agranular vesicles. The coeliac ganglion of scorpion fish is similar in structure to sympathetic ganglia in other vertebrates. It contains two types of principal cell as well as a population of small intensely fluorescent (SIP) cells. The SIP cells appear to become more numerous in early summer when vesicles in the equivalent cells observed ultrastructurally develop electron dense granules. The catecholaminergic and serotonergic structures in the brain of scorpion fish were described and compared to those of other teleosts and higher vertebrates.Life history strategies in anadromous trout, 'Salmo trutta L.' : with special reference to osmoregulatory physiologyWalker, Alan Melvillehttps://hdl.handle.net/10023/150032021-02-23T15:26:43Z1998-01-01T00:00:00Z1. Juvenile trout, Salmo trutta L., from three parental groups - sympatric Sea trout and freshwater-Resident trout, and isolated trout from above a waterfall impassable by upstream migrating anadromous trout - were reared under three ration regimes to manipulate growth rates. The development of seawater tolerance was studied by measuring drinking rates after periodic salinity challenges during the first two years of juvenile growth. No trout were observed to undergo the parr-smolt transformation in any of the parental form/ration combinations after two years in freshwater. However, a considerable proportion did mature during this time period. The proportion of maturing trout was directly related to ration level but was also influenced by parental form, with isolated trout demonstrating a greater tendency to mature early. Seawater tolerance increased with age in all groups. However, mean drinking rates upon salinity challenge were generally lower, from Experiment 2 onwards, in Resident trout than in either of the other two groups. 2. Eight immature sea trout (finnock) were radiotracked in the River Eden, Fife, during September, October and November 1994. The individual finnock displayed considerable variation in patterns of movement; two remained in freshwater for at least 27 days whereas others moved downstream out of the river within days or even hours of release. In general, this highlighted the transient nature of the freshwater migrations of some finnock, indicating that they move in and out of rivers over brief periods of time and apparently do not necessarily remain in freshwater continuously throughout the winter. 3. The hypo-osmoregulatory ability of finnock during the winter was assessed in two experiments. The number of finnock was limited in Experiment 1. Therefore, this was designed as a preliminary assessment of the physiological response of finnock to acute freshwater-seawater transfer. Osmoregulatory abilities were assessed by measurement of drinking rates, plasma ion and plasma cortisol concentrations after acute freshwater-seawater challenge and compared with freshwater-adapted and seawater-adapted control groups. Finnock displayed physiological responses typical of euryhaline teleosts upon seawater challenge; a rapid increase in drinking rate, an increase in plasma ion concentrations (but only to levels similar to, or slightly greater than, those of seawater-adapted fish), and increased plasma cortisol concentrations. The second experiment, in which numbers of finnock were greater, made use of the same techniques to assess the longer term acclimation of finnock to both freshwater-seawater and seawater- vi freshwater challenge, to establish whether finnock might suffer from a more subtle reduction in seawater-tolerance which would not have been necessarily apparent in the acute challenge of Experiment 1. Finnock did not appear to be physiologically compromised by seawater challenge during the winter months, and therefore, a breakdown in hypo-osmoregulatory abilities alone cannot be considered a reason for finnock returning to estuaries and rivers during the winter. 4. The physiological effects of low to medium levels of infestation of the ectoparasitic copepod Lepeophtheirus salmonis (Kroyer) on wild sea trout post-smolts were assessed at intervals during the development of the parasite. A mean infestation level of 18 parasites caused significant disruption to the osmoregulatory ability of hosts, as demonstrated by significantly higher plasma osmolality and chloride ion concentrations when compared with naive post-smolts. In addition, since no skin lesions were apparent on the hosts, these physiological effects were considered to be the consequence of larval attachment to the gill filaments, thereby possibly puncturing the epithelia and also damaging vital branchial ion excretory cells. 5. The modern molecular genetic RAPD-PCR technique was used to screen DNA of Lepeophtheirus salmonis collected from wild and fanned salmonid hosts from around the Scottish coasts. This technique indicated markedly different patterns of genetic variation amongst L. salmonis of farmed and wild origin, and between different farms. A number of genetic markers were found to be exclusive to, or at considerably higher frequency amongst, sea lice collected from farmed salmonid hosts. This technique established the possibility of assigning provenance to L. salmonis collected from wild hosts.
1998-01-01T00:00:00ZWalker, Alan Melville1. Juvenile trout, Salmo trutta L., from three parental groups - sympatric Sea trout and freshwater-Resident trout, and isolated trout from above a waterfall impassable by upstream migrating anadromous trout - were reared under three ration regimes to manipulate growth rates. The development of seawater tolerance was studied by measuring drinking rates after periodic salinity challenges during the first two years of juvenile growth. No trout were observed to undergo the parr-smolt transformation in any of the parental form/ration combinations after two years in freshwater. However, a considerable proportion did mature during this time period. The proportion of maturing trout was directly related to ration level but was also influenced by parental form, with isolated trout demonstrating a greater tendency to mature early. Seawater tolerance increased with age in all groups. However, mean drinking rates upon salinity challenge were generally lower, from Experiment 2 onwards, in Resident trout than in either of the other two groups. 2. Eight immature sea trout (finnock) were radiotracked in the River Eden, Fife, during September, October and November 1994. The individual finnock displayed considerable variation in patterns of movement; two remained in freshwater for at least 27 days whereas others moved downstream out of the river within days or even hours of release. In general, this highlighted the transient nature of the freshwater migrations of some finnock, indicating that they move in and out of rivers over brief periods of time and apparently do not necessarily remain in freshwater continuously throughout the winter. 3. The hypo-osmoregulatory ability of finnock during the winter was assessed in two experiments. The number of finnock was limited in Experiment 1. Therefore, this was designed as a preliminary assessment of the physiological response of finnock to acute freshwater-seawater transfer. Osmoregulatory abilities were assessed by measurement of drinking rates, plasma ion and plasma cortisol concentrations after acute freshwater-seawater challenge and compared with freshwater-adapted and seawater-adapted control groups. Finnock displayed physiological responses typical of euryhaline teleosts upon seawater challenge; a rapid increase in drinking rate, an increase in plasma ion concentrations (but only to levels similar to, or slightly greater than, those of seawater-adapted fish), and increased plasma cortisol concentrations. The second experiment, in which numbers of finnock were greater, made use of the same techniques to assess the longer term acclimation of finnock to both freshwater-seawater and seawater- vi freshwater challenge, to establish whether finnock might suffer from a more subtle reduction in seawater-tolerance which would not have been necessarily apparent in the acute challenge of Experiment 1. Finnock did not appear to be physiologically compromised by seawater challenge during the winter months, and therefore, a breakdown in hypo-osmoregulatory abilities alone cannot be considered a reason for finnock returning to estuaries and rivers during the winter. 4. The physiological effects of low to medium levels of infestation of the ectoparasitic copepod Lepeophtheirus salmonis (Kroyer) on wild sea trout post-smolts were assessed at intervals during the development of the parasite. A mean infestation level of 18 parasites caused significant disruption to the osmoregulatory ability of hosts, as demonstrated by significantly higher plasma osmolality and chloride ion concentrations when compared with naive post-smolts. In addition, since no skin lesions were apparent on the hosts, these physiological effects were considered to be the consequence of larval attachment to the gill filaments, thereby possibly puncturing the epithelia and also damaging vital branchial ion excretory cells. 5. The modern molecular genetic RAPD-PCR technique was used to screen DNA of Lepeophtheirus salmonis collected from wild and fanned salmonid hosts from around the Scottish coasts. This technique indicated markedly different patterns of genetic variation amongst L. salmonis of farmed and wild origin, and between different farms. A number of genetic markers were found to be exclusive to, or at considerably higher frequency amongst, sea lice collected from farmed salmonid hosts. This technique established the possibility of assigning provenance to L. salmonis collected from wild hosts.A comparison of some aspects of the immune system in diploid and triploid Atlantic salmonLangston, Anne Louisehttps://hdl.handle.net/10023/150012019-03-29T10:36:46Z1999-01-01T00:00:00ZThis study investigated the differences imposed by the extra set of chromosomes on the immune system of a triploid animal. Various haematological and immunological parameters in diploid and triploid sibling Atlantic salmon (Salmo salar) were compared. Haematocrits were usually the same in diploid and triploid siblings. Erythrocytes and leucocytes were larger and fewer in number in triploid siblings. However, they were not larger or fewer in number by a factor of one third. The proportions of the different leucocyte populations did not differ between diploids and triploids. This was the case for 3 families of diploids and triploids. Non-specific, humoral factors were not consistently different between diploids and triploids. From an investigation of 3 families it was found that there may be family influences on how diploids and triploids compare. A study of the kinetics of responsiveness of non-specific, humoral factors showed that triploids did differ from diploids in the speed of the immune reaction or in the rate of recovery. However, the profile of the differences between diploids and triploids varied between parameters. The rate of increasing agglutinating titres in response to treatment with a commercial vaccine did not differ between diploids and triploids. However, triploids did have a higher average titre after 24 weeks in comparison to diploids. Non-specific, cellular parameters did differ between sibling diploids and triploids. Triploid kidney macrophages had an increased phagocytic capacity but the proportion of phagocytic cells did not differ. Intracellular respiratory burst activity was not different between diploid and triploid kidney macrophages. Diploids and triploids did not respond differently to predator stress and there was no difference in susceptibility to Aeromonas salmonicida ssp. salmonicida challenge. From this study there was no evidence of consistent differences in immmunocompetence or disease susceptibility of diploid or triploid Atlantic salmon.
1999-01-01T00:00:00ZLangston, Anne LouiseThis study investigated the differences imposed by the extra set of chromosomes on the immune system of a triploid animal. Various haematological and immunological parameters in diploid and triploid sibling Atlantic salmon (Salmo salar) were compared. Haematocrits were usually the same in diploid and triploid siblings. Erythrocytes and leucocytes were larger and fewer in number in triploid siblings. However, they were not larger or fewer in number by a factor of one third. The proportions of the different leucocyte populations did not differ between diploids and triploids. This was the case for 3 families of diploids and triploids. Non-specific, humoral factors were not consistently different between diploids and triploids. From an investigation of 3 families it was found that there may be family influences on how diploids and triploids compare. A study of the kinetics of responsiveness of non-specific, humoral factors showed that triploids did differ from diploids in the speed of the immune reaction or in the rate of recovery. However, the profile of the differences between diploids and triploids varied between parameters. The rate of increasing agglutinating titres in response to treatment with a commercial vaccine did not differ between diploids and triploids. However, triploids did have a higher average titre after 24 weeks in comparison to diploids. Non-specific, cellular parameters did differ between sibling diploids and triploids. Triploid kidney macrophages had an increased phagocytic capacity but the proportion of phagocytic cells did not differ. Intracellular respiratory burst activity was not different between diploid and triploid kidney macrophages. Diploids and triploids did not respond differently to predator stress and there was no difference in susceptibility to Aeromonas salmonicida ssp. salmonicida challenge. From this study there was no evidence of consistent differences in immmunocompetence or disease susceptibility of diploid or triploid Atlantic salmon.The effects of temperature on development and growth of muscle in the trout (Salmo trutta (L.))Killeen, James Richardhttps://hdl.handle.net/10023/150002019-03-29T10:28:49Z1999-01-01T00:00:00ZTrout (Salmo trutta L.) were reared in a hatchery environment under a variety of temperature regimes, and patterns of early development and growth were studied. The period from fertilisation to 'first feeding' (i.e. when the yolk supply was almost exhausted) was described as a series of forty successive developmental 'steps'. A quantitative scoring system, whereby individual embryos were assigned points ranging from 1 to 1000 on the basis of assessment of numerous developmental features, was also developed. Trout reared at 10° achieved greater values of developmental score and standard length, but lower values of body mass, from a given quantity of yolk compared to trout reared at 2°. Yolk was used less efficiently for differentiation but more efficiently for growth in larger eggs. Although certain events, such as hatching, occurred relatively earlier at higher temperatures, the relative timings of most individual developmental changes, including myotube and muscle fibre formation and many aspects of neural development, did not vary with temperature. Muscle growth, particularly recruitment of new muscle fibres, was lower relative to developmental score and to length at 10° than at 2°. However, trout at first feeding of comparable total muscle area had significantly greater numbers of post-embryonic fibres when reared at the higher temperature, indicating the onset of a compensatory 'catch-up' in fibre recruitment. The effects of the migratory type of the female parent on development and growth of embryos and alevins were also investigated, but were found to be minimal. During a study examining the effects of forced exercise on growth, juvenile trout reared at 10° as embryos exhibited a greater potential for somatic growth and recruitment of new muscle fibres than those reared at 2°. It is postulated that this difference in growth potential is related to the higher numbers of myonuclei present in the 10°-reared fish.
1999-01-01T00:00:00ZKilleen, James RichardTrout (Salmo trutta L.) were reared in a hatchery environment under a variety of temperature regimes, and patterns of early development and growth were studied. The period from fertilisation to 'first feeding' (i.e. when the yolk supply was almost exhausted) was described as a series of forty successive developmental 'steps'. A quantitative scoring system, whereby individual embryos were assigned points ranging from 1 to 1000 on the basis of assessment of numerous developmental features, was also developed. Trout reared at 10° achieved greater values of developmental score and standard length, but lower values of body mass, from a given quantity of yolk compared to trout reared at 2°. Yolk was used less efficiently for differentiation but more efficiently for growth in larger eggs. Although certain events, such as hatching, occurred relatively earlier at higher temperatures, the relative timings of most individual developmental changes, including myotube and muscle fibre formation and many aspects of neural development, did not vary with temperature. Muscle growth, particularly recruitment of new muscle fibres, was lower relative to developmental score and to length at 10° than at 2°. However, trout at first feeding of comparable total muscle area had significantly greater numbers of post-embryonic fibres when reared at the higher temperature, indicating the onset of a compensatory 'catch-up' in fibre recruitment. The effects of the migratory type of the female parent on development and growth of embryos and alevins were also investigated, but were found to be minimal. During a study examining the effects of forced exercise on growth, juvenile trout reared at 10° as embryos exhibited a greater potential for somatic growth and recruitment of new muscle fibres than those reared at 2°. It is postulated that this difference in growth potential is related to the higher numbers of myonuclei present in the 10°-reared fish.Ultrastructural, histochemical and physiological studies on cardiac structure and function in the teleost, Pleuronectes platessa L.Santer, Robert M.https://hdl.handle.net/10023/149982019-03-29T10:33:38Z1973-01-01T00:00:00ZA general study has been made on cardiac function in the plaice (Pleuronectes platessa) involving ultrastructural histochemical and physiological studies on the adult and developing fish. Myocardial cells have an average diameter of 3.2u. They lack a T-system and nexus contacts and have a very sparse sarcoplasmic reticulum. The sino-atrial region is heavily innervated but no pace maker cells have been identified. Cells resembling Purkinje cells of higher vertebrate myocardia are seen in the plaice myocardium but they do not run in tracts. There is no coronary blood supply which is a consequence of the absence of an outer cortical layer of myocardium. The development of the heart resembles that process as seen in the chick, but there are minor sequential differences. By Day 24 the "early larval" heart has formed which is a tri-laminar structure - a myocardial layer bounded externally by epicardium and internally by endocardium. This condition lasts until the 4a (Ryland) stage with the onset of endocardial invagination. This is the criterion distinguishing the "late larval" heart which persists until two months post-metamorphosis. Thus cardiogenesis is independent of hatching and metamorphosis. The heart is innervated only parasympathetically through the cardiac branch of the vagus. The cardiac ganglion situated at the sino-atrial region. The strium is sparsely innervated and the ventricle is aneural. The absence of a sympathetic innveration is concluded from the following a) No specific catecholamine fluorescence is seen with the Falck technique. b) 6-hydroxydopemine does not degenerate any axons. C) Intraaxonal granular vesicles are not depleted by reserpinc and AChE was localized around axons containing such vesicles. D) No adrenergic-type axons were seen by electron microscopy. Differential vagal stimulation of 3Hz and 7Hz causes excitation and inhibition respectively, both effects being blocked by 10-6 g/ml atropine and are thus cholinergically mediated. On cessation of prolonged inhibitory stimulation there is marked increase in heartrate, and in quiescent hearts one or two beats are initiated after stimulation. Vagal stimulation causes a hyperpolarization in atrial cells. It is proposed that all the excitatory effects of vagal stimulation are due to rebound excitation from an inhibitory hyperpolarization. At high frequencies the hyperpolarisations summate to give total inhibition. At lower frequencies of stimulation the heartbeat is increased to rates dependent upon the time course of the hyperpolarization and the refractory period of the heart. The rebound excitation persists in the presence of atropine and bretylium (both at 10-6 g/ml) and is therefore probably a response of the muscle cell membrane and is nerve-mediated.
1973-01-01T00:00:00ZSanter, Robert M.A general study has been made on cardiac function in the plaice (Pleuronectes platessa) involving ultrastructural histochemical and physiological studies on the adult and developing fish. Myocardial cells have an average diameter of 3.2u. They lack a T-system and nexus contacts and have a very sparse sarcoplasmic reticulum. The sino-atrial region is heavily innervated but no pace maker cells have been identified. Cells resembling Purkinje cells of higher vertebrate myocardia are seen in the plaice myocardium but they do not run in tracts. There is no coronary blood supply which is a consequence of the absence of an outer cortical layer of myocardium. The development of the heart resembles that process as seen in the chick, but there are minor sequential differences. By Day 24 the "early larval" heart has formed which is a tri-laminar structure - a myocardial layer bounded externally by epicardium and internally by endocardium. This condition lasts until the 4a (Ryland) stage with the onset of endocardial invagination. This is the criterion distinguishing the "late larval" heart which persists until two months post-metamorphosis. Thus cardiogenesis is independent of hatching and metamorphosis. The heart is innervated only parasympathetically through the cardiac branch of the vagus. The cardiac ganglion situated at the sino-atrial region. The strium is sparsely innervated and the ventricle is aneural. The absence of a sympathetic innveration is concluded from the following a) No specific catecholamine fluorescence is seen with the Falck technique. b) 6-hydroxydopemine does not degenerate any axons. C) Intraaxonal granular vesicles are not depleted by reserpinc and AChE was localized around axons containing such vesicles. D) No adrenergic-type axons were seen by electron microscopy. Differential vagal stimulation of 3Hz and 7Hz causes excitation and inhibition respectively, both effects being blocked by 10-6 g/ml atropine and are thus cholinergically mediated. On cessation of prolonged inhibitory stimulation there is marked increase in heartrate, and in quiescent hearts one or two beats are initiated after stimulation. Vagal stimulation causes a hyperpolarization in atrial cells. It is proposed that all the excitatory effects of vagal stimulation are due to rebound excitation from an inhibitory hyperpolarization. At high frequencies the hyperpolarisations summate to give total inhibition. At lower frequencies of stimulation the heartbeat is increased to rates dependent upon the time course of the hyperpolarization and the refractory period of the heart. The rebound excitation persists in the presence of atropine and bretylium (both at 10-6 g/ml) and is therefore probably a response of the muscle cell membrane and is nerve-mediated.Effects of acute temperature change and thermal acclimation on the contractile properties of teleost muscleLangfeld, Karen S.https://hdl.handle.net/10023/149942019-03-29T10:42:03Z1991-01-01T00:00:00ZChapter 1 - General Introduction. Part I reviews the structure and function of fish muscle, including fibre orientation, the properties of different muscle fibre types and the recruitment of muscle fibres during swimming. Part II concerns the effects of acute temperature changes on fish muscle and describes a variety of mechanisms underlying temperature adaptation, with particular emphasis on the mechanical performance of fish muscle. Chapter 2 - Temperature and the mechanical properties of live muscle fibres from the teleost Myoxocephalus scorpius. Small bundles of fast fibres were isolated from the myotomal muscle of the teleost Myoxocephalus scorpius. The temperature dependence of isometric contractile properties and the force-velocity (P-V) relation were studied. Fibres were found to deteriorate above 18°, and the force plateau during tetanic stimulation was not maintained above 15°. Twitch and tetanic tension (Po) showed optima at around 8°. Force-velocity curves were fitted using either Hill's hyperbolic equation or a hyperbolic-linear (hyp-lin) equation. The best fit to the data was provided by the hyp-1in equation, which gave consistently higher values for unloaded contraction velocity (Vmax): 4.3, 8.1 and 9.5 muscle lengths s-1 at °, 8°, and 12° respectively. Both isometric and isotonic data from live fibres was compared with skinned fibres and live fibres from other vertebrates. The P-V relation was found to become progressively more curved at higher temperatures. Muscle power output calculated from the hyp-lin equation was 124 Wkg-1 at ° and 256 Wkg-1 at 8°. Curves normalised for Po and Vmax at each temperature show that the change in curvature is sufficient to increase the relative power output of the muscle by around 15% on decreasing the temperature from 8° to °. Chapter 3 - The myology of the pectoral fin of the common carp Cyprinus carpio L. and variation in fibre composition with temperature acclimation. Common carp (Cyprinus carpio L.) were acclimated to either 8° or 20° for 8 weeks (12h light:12h dark). The myology and skeletal structure of the pectoral assemblage of the carp was studied. Cross-sections of the entire assemblage were taken for histochemistry in order to determine the distribution of fibre types within the musculature. Examination of the fibre diameter range data reveals a larger number of smaller slow fibres in the muscle of 8° C-acclimated fish, commensurate with a hypothesis that the slow fibre mass is proliferating during cold-acclimation by producing new slow fibres. Chapter 4 - Temperature acclimation in the common carp: force-velocity characteristics and myosin subunit composition of slow muscle fibres. Common carp were acclimated to either 8° or 20° for 6-12 weeks (12h light:12h dark). Bundles of 20-50 fibres were isolated from the superficial region of the pectoral fin abductor superficialis muscle. Histochemical studies showed preparations to contain 93-100% slow muscle fibres. The maximum tetanic tension (Po) produced by fibre bundles was similar when measured at the acclimation temperature of each group. Chapter 5 - General Discussion The results detailed in this thesis are discussed in relation to the effects of temperature on fish swimming. Recent developments in technique are described and some suggestions for further work using these techniques are outlined.
1991-01-01T00:00:00ZLangfeld, Karen S.Chapter 1 - General Introduction. Part I reviews the structure and function of fish muscle, including fibre orientation, the properties of different muscle fibre types and the recruitment of muscle fibres during swimming. Part II concerns the effects of acute temperature changes on fish muscle and describes a variety of mechanisms underlying temperature adaptation, with particular emphasis on the mechanical performance of fish muscle. Chapter 2 - Temperature and the mechanical properties of live muscle fibres from the teleost Myoxocephalus scorpius. Small bundles of fast fibres were isolated from the myotomal muscle of the teleost Myoxocephalus scorpius. The temperature dependence of isometric contractile properties and the force-velocity (P-V) relation were studied. Fibres were found to deteriorate above 18°, and the force plateau during tetanic stimulation was not maintained above 15°. Twitch and tetanic tension (Po) showed optima at around 8°. Force-velocity curves were fitted using either Hill's hyperbolic equation or a hyperbolic-linear (hyp-lin) equation. The best fit to the data was provided by the hyp-1in equation, which gave consistently higher values for unloaded contraction velocity (Vmax): 4.3, 8.1 and 9.5 muscle lengths s-1 at °, 8°, and 12° respectively. Both isometric and isotonic data from live fibres was compared with skinned fibres and live fibres from other vertebrates. The P-V relation was found to become progressively more curved at higher temperatures. Muscle power output calculated from the hyp-lin equation was 124 Wkg-1 at ° and 256 Wkg-1 at 8°. Curves normalised for Po and Vmax at each temperature show that the change in curvature is sufficient to increase the relative power output of the muscle by around 15% on decreasing the temperature from 8° to °. Chapter 3 - The myology of the pectoral fin of the common carp Cyprinus carpio L. and variation in fibre composition with temperature acclimation. Common carp (Cyprinus carpio L.) were acclimated to either 8° or 20° for 8 weeks (12h light:12h dark). The myology and skeletal structure of the pectoral assemblage of the carp was studied. Cross-sections of the entire assemblage were taken for histochemistry in order to determine the distribution of fibre types within the musculature. Examination of the fibre diameter range data reveals a larger number of smaller slow fibres in the muscle of 8° C-acclimated fish, commensurate with a hypothesis that the slow fibre mass is proliferating during cold-acclimation by producing new slow fibres. Chapter 4 - Temperature acclimation in the common carp: force-velocity characteristics and myosin subunit composition of slow muscle fibres. Common carp were acclimated to either 8° or 20° for 6-12 weeks (12h light:12h dark). Bundles of 20-50 fibres were isolated from the superficial region of the pectoral fin abductor superficialis muscle. Histochemical studies showed preparations to contain 93-100% slow muscle fibres. The maximum tetanic tension (Po) produced by fibre bundles was similar when measured at the acclimation temperature of each group. Chapter 5 - General Discussion The results detailed in this thesis are discussed in relation to the effects of temperature on fish swimming. Recent developments in technique are described and some suggestions for further work using these techniques are outlined.The influence of temperature on muscle development in the teleost 'Pleuronectes platessa L.'Brooks, Suzannehttps://hdl.handle.net/10023/149922019-03-29T10:27:31Z1994-01-01T00:00:00ZChapter 1. General Introduction The general Introduction begins with a brief description of the natural history of the plaice. This is followed by a review of the literature describing the development of teleost embryos and larvae. The pattern of innervation with development and the differentiation of muscle fibres are both discussed in detail, as are larval locomotion and patterns of swimming behaviour. The remainder of the general introduction concentrates upon the phenotypic plasticity of muscle and the mechanisms by which this may be achieved. Teleost muscle in particular has been found to show an extremely plastic response to changes in ambient temperature. The contractile protein composition, ultrastructure and contraction properties of fish muscle are all influenced by temperature. However most research has concentrated primarily upon adult teleosts and fewer studies have examined the effects of temperature on muscle in larval and juvenile fish. Experiments describing the effect of temperature upon muscle structure and contraction both in the larval and adult stages are discussed at the end of the Introduction. Chapter 3. The influence of temperature on somitogenesis and organogenesis in embryos of the plaice, Pleuronectes platessa L. The development of plaice embryos was examined at two temperatures, 8° and 12°. Temperature influenced the rate of embryonic development but did not affect the order of appearance of morphological characters. The rate of somitogenesis was observed in embryos reared at 5° and 12°. Chapter 4. Muscle development in plaice, Pleuronectes platessa L. The effects of temperature on muscle fibre ultrastructure were examined using larvae reared at 5, 8, 10, 12 and 15°. Two types of muscle fibre could be distinguished in the newly hatched larvae; beneath the skin was a single, superficial layer of smaller diameter muscle fibres, which completely surrounded the larger diameter inner muscle fibres. Larvae reared at 15° only survived for a few days and had significantly more myotomal muscle fibres of larger average cross-sectional area than those hatching at 5-10°. Chapter 5. Electrophoretic analysis of the myofibrillar components of red and white muscle fibres from adult plaice, Pleuronectes platessa L. The myofibrillar proteins of the two main fibre types were identified using various electrophoretic techniques, including SDS PAGE, IEF PAGE, NEPHGE PAGE and alkaii-urea gels. The myosin light chain composition of each of the four histochemically identified fibre types was determined. Chapter 6. Developmental transitions in myosin sub-unit composition from larval inner to adult fast muscle in plaice, Pleuronectes platessa L. The myosin sub-unit composition of plaice deep white muscle fibres was examined at different stages of development. The myosin heavy chain component of the inner muscle fibres was, however, found to be different in group 1 juveniles and adult deep white fibres. Chapter 7. General Discussion. The major findings of the study are discussed in relation to other experiments examining muscle development and differentiation in teleosts. The influence of temperature on the structure and development of plaice myotomal muscle is discussed, with particular reference to larval survival. Possible mechanisms by which muscle development in teleosts may be regulated are described together with suggestions for further work.
1994-01-01T00:00:00ZBrooks, SuzanneChapter 1. General Introduction The general Introduction begins with a brief description of the natural history of the plaice. This is followed by a review of the literature describing the development of teleost embryos and larvae. The pattern of innervation with development and the differentiation of muscle fibres are both discussed in detail, as are larval locomotion and patterns of swimming behaviour. The remainder of the general introduction concentrates upon the phenotypic plasticity of muscle and the mechanisms by which this may be achieved. Teleost muscle in particular has been found to show an extremely plastic response to changes in ambient temperature. The contractile protein composition, ultrastructure and contraction properties of fish muscle are all influenced by temperature. However most research has concentrated primarily upon adult teleosts and fewer studies have examined the effects of temperature on muscle in larval and juvenile fish. Experiments describing the effect of temperature upon muscle structure and contraction both in the larval and adult stages are discussed at the end of the Introduction. Chapter 3. The influence of temperature on somitogenesis and organogenesis in embryos of the plaice, Pleuronectes platessa L. The development of plaice embryos was examined at two temperatures, 8° and 12°. Temperature influenced the rate of embryonic development but did not affect the order of appearance of morphological characters. The rate of somitogenesis was observed in embryos reared at 5° and 12°. Chapter 4. Muscle development in plaice, Pleuronectes platessa L. The effects of temperature on muscle fibre ultrastructure were examined using larvae reared at 5, 8, 10, 12 and 15°. Two types of muscle fibre could be distinguished in the newly hatched larvae; beneath the skin was a single, superficial layer of smaller diameter muscle fibres, which completely surrounded the larger diameter inner muscle fibres. Larvae reared at 15° only survived for a few days and had significantly more myotomal muscle fibres of larger average cross-sectional area than those hatching at 5-10°. Chapter 5. Electrophoretic analysis of the myofibrillar components of red and white muscle fibres from adult plaice, Pleuronectes platessa L. The myofibrillar proteins of the two main fibre types were identified using various electrophoretic techniques, including SDS PAGE, IEF PAGE, NEPHGE PAGE and alkaii-urea gels. The myosin light chain composition of each of the four histochemically identified fibre types was determined. Chapter 6. Developmental transitions in myosin sub-unit composition from larval inner to adult fast muscle in plaice, Pleuronectes platessa L. The myosin sub-unit composition of plaice deep white muscle fibres was examined at different stages of development. The myosin heavy chain component of the inner muscle fibres was, however, found to be different in group 1 juveniles and adult deep white fibres. Chapter 7. General Discussion. The major findings of the study are discussed in relation to other experiments examining muscle development and differentiation in teleosts. The influence of temperature on the structure and development of plaice myotomal muscle is discussed, with particular reference to larval survival. Possible mechanisms by which muscle development in teleosts may be regulated are described together with suggestions for further work.The effects of starvation and refeeding on the musculature of the marine teleost Pollachius virens LBeardall, Charles Henryhttps://hdl.handle.net/10023/149902019-03-29T10:40:56Z1985-01-01T00:00:00ZChapter 1. A brief introduction is given reviewing the physiology and biochemistry of fish myotomal muscle. Aspects of protein turnover and metabolism in muscle are discussed and related with previous studies on starvation and refeeding in both mammals and fish. Chapter 2. The marine teleost Pollachius virens L. undergoes a natural starvation during the winter months, and provides a reversible, non-pathological model for studying muscle wasting. In this study fish were kept without food under laboratory conditions for up to 12 weeks. The effects of starvation on muscle fibre cross-sectional area, volume fractions of mitochondria and myofibrils, and capillary supply were determined. Mechanisms of myofibrillar degradation during muscle wasting are discussed. Chapter 3. Starvation in the winter months is followed by a period of refeeding in the late spring, and the musculature degraded during the winter is regenerated. In the present study muscle fine structure has been investigated for fish kept without food, under laboratory conditions, for 74 days, and following 10, 20, and 54 days' refeeding. Muscle fibre cross-sectional area, capillary supply, and volume fractions of myofibrils, nuclei and mitochondria were determined from electron micrographs, using digital planimetry and stereological techniques. In contrast to the starvation atrophy observed in chapter 2 the 74 day starvation reported in this chapter resulted in a decrease in the mean fibre cross-sectional area in both fast and slow muscle. Chapter 4. Experiments were performed using SDS/polyacrylamide gel electrophoresis, to consider the effects of starvation on the relative abundance of actin and myosin heavy chains. Both slow and fast muscle proteins were analysed from control and 66 day starved fish, using densitometric scans of comassie blue stained polyacrylamide gels. The results were expressed as the ratio of each protein relative to actin. Chapter 5. A wide range of biochemical parameters were determined to consider the metabolic effects of starvation and refeeding in saithe. Chapter 6. This chapter investigates the involvement of acid hydrolases and the lysosomal system in muscle atrophy and regeneration, during starvation and refeeding. The results suggest a role for lysosomal enzymes in the breakdown of myofibrillar proteins during starvation. Chapter 7. The results are discussed with reference to the overall strategy of fish to survive starvation immediately followed by a period of rapid muscle repair and growth, during refeeding. The mechanisms Involved in the disassembly and degradation of the myofibrillar proteins are discussed with specific reference to the involvment of the sarcoplasmic reticulum, t-tubules and proteinases. Suggestions are made for further work that may give an insight into some of the questions generated by this research.
1985-01-01T00:00:00ZBeardall, Charles HenryChapter 1. A brief introduction is given reviewing the physiology and biochemistry of fish myotomal muscle. Aspects of protein turnover and metabolism in muscle are discussed and related with previous studies on starvation and refeeding in both mammals and fish. Chapter 2. The marine teleost Pollachius virens L. undergoes a natural starvation during the winter months, and provides a reversible, non-pathological model for studying muscle wasting. In this study fish were kept without food under laboratory conditions for up to 12 weeks. The effects of starvation on muscle fibre cross-sectional area, volume fractions of mitochondria and myofibrils, and capillary supply were determined. Mechanisms of myofibrillar degradation during muscle wasting are discussed. Chapter 3. Starvation in the winter months is followed by a period of refeeding in the late spring, and the musculature degraded during the winter is regenerated. In the present study muscle fine structure has been investigated for fish kept without food, under laboratory conditions, for 74 days, and following 10, 20, and 54 days' refeeding. Muscle fibre cross-sectional area, capillary supply, and volume fractions of myofibrils, nuclei and mitochondria were determined from electron micrographs, using digital planimetry and stereological techniques. In contrast to the starvation atrophy observed in chapter 2 the 74 day starvation reported in this chapter resulted in a decrease in the mean fibre cross-sectional area in both fast and slow muscle. Chapter 4. Experiments were performed using SDS/polyacrylamide gel electrophoresis, to consider the effects of starvation on the relative abundance of actin and myosin heavy chains. Both slow and fast muscle proteins were analysed from control and 66 day starved fish, using densitometric scans of comassie blue stained polyacrylamide gels. The results were expressed as the ratio of each protein relative to actin. Chapter 5. A wide range of biochemical parameters were determined to consider the metabolic effects of starvation and refeeding in saithe. Chapter 6. This chapter investigates the involvement of acid hydrolases and the lysosomal system in muscle atrophy and regeneration, during starvation and refeeding. The results suggest a role for lysosomal enzymes in the breakdown of myofibrillar proteins during starvation. Chapter 7. The results are discussed with reference to the overall strategy of fish to survive starvation immediately followed by a period of rapid muscle repair and growth, during refeeding. The mechanisms Involved in the disassembly and degradation of the myofibrillar proteins are discussed with specific reference to the involvment of the sarcoplasmic reticulum, t-tubules and proteinases. Suggestions are made for further work that may give an insight into some of the questions generated by this research.Aspects of growth and metabolism in the musculature of Antarctic fishes : with particular reference to 'Notothenia neglecta' nybelinFitch, Neil Antonyhttps://hdl.handle.net/10023/149892019-03-29T10:33:59Z1986-01-01T00:00:00Z1. Aspects of the physiology and biochemistry of Antarctic fish muscle have been examined, principally for the nototheniid, Notothenia neglecta Nybelin. 2. Sampling was most successful during the late summer/autumn. The trammel net was the best method for catching fish above 200mm standard length. Smaller fish were best caught by SCUBA divers using hand-nets. 3. The condition factor for fish caught was highest during the summer (high food availability) and remained low during the winter months. Analysis of trunk muscle constituents (water, protein, lipid) indicated no evidence for marked depletion at any time of the year. Seasonal variation in relative gonad size and relative liver size were observed. 4. Metabolically the pectoral abductor muscle of N.neglecta had higher activities of anaerobic and aerobic enzymes than either the red or white trunk muscles. This is in line with the fact that this species normally swims using enlarged pectoral fins, while sprint swimming in short bursts is carried out by the white trunk muscle. 5. Differences in the metabolic profiles of the trunk muscles of 3 Antarctic species (N.neglecta, Notothenia gibberifrons and Trematomus newnesi) are related to their different lifestyles, particularily feeding behaviours. 6. Muscle growth in N.neglecta is probably both by hypertrophy, and recruitment of myosatellite cells. Both the fibres and capillaries in Antarctic species are much larger in cross-sectional area than for temperate species. 7. Lactate dehydrogenase isozymes in the trunk and cardiac muscles of N.neqlecta are electrophoretically and kinetically similar. This, along with its high activities of anaerobic enzymes indicates that the cardiac muscle is adapted to utilise fuels anaerobically if necessary. 8. The majority of physiological and cellular adaptations can be explained on the basis of physiological/ecological constraints rather than cold temperature per se.
1986-01-01T00:00:00ZFitch, Neil Antony1. Aspects of the physiology and biochemistry of Antarctic fish muscle have been examined, principally for the nototheniid, Notothenia neglecta Nybelin. 2. Sampling was most successful during the late summer/autumn. The trammel net was the best method for catching fish above 200mm standard length. Smaller fish were best caught by SCUBA divers using hand-nets. 3. The condition factor for fish caught was highest during the summer (high food availability) and remained low during the winter months. Analysis of trunk muscle constituents (water, protein, lipid) indicated no evidence for marked depletion at any time of the year. Seasonal variation in relative gonad size and relative liver size were observed. 4. Metabolically the pectoral abductor muscle of N.neglecta had higher activities of anaerobic and aerobic enzymes than either the red or white trunk muscles. This is in line with the fact that this species normally swims using enlarged pectoral fins, while sprint swimming in short bursts is carried out by the white trunk muscle. 5. Differences in the metabolic profiles of the trunk muscles of 3 Antarctic species (N.neglecta, Notothenia gibberifrons and Trematomus newnesi) are related to their different lifestyles, particularily feeding behaviours. 6. Muscle growth in N.neglecta is probably both by hypertrophy, and recruitment of myosatellite cells. Both the fibres and capillaries in Antarctic species are much larger in cross-sectional area than for temperate species. 7. Lactate dehydrogenase isozymes in the trunk and cardiac muscles of N.neqlecta are electrophoretically and kinetically similar. This, along with its high activities of anaerobic enzymes indicates that the cardiac muscle is adapted to utilise fuels anaerobically if necessary. 8. The majority of physiological and cellular adaptations can be explained on the basis of physiological/ecological constraints rather than cold temperature per se.Some aspects of early gametogenesis in amphibiaSnow, Michael Henry Lloydhttps://hdl.handle.net/10023/149822019-03-29T10:37:55Z1971-01-01T00:00:00Z1971-01-01T00:00:00ZSnow, Michael Henry LloydStudies on the proteins of the oocyte nucleus of the crested newt, triturus cristatus carnifexMaundrell, Kinsey Georgehttps://hdl.handle.net/10023/149792019-03-29T10:32:41Z1973-01-01T00:00:00Z1973-01-01T00:00:00ZMaundrell, Kinsey GeorgeStudies on spermiogenesis and the sperm of a prosobranch gastropod, nucella lapillus (l)Walker, Muriel Helenahttps://hdl.handle.net/10023/149772019-03-29T10:32:41Z1970-01-01T00:00:00Z1970-01-01T00:00:00ZWalker, Muriel HelenaThe comparitive anatomy of the intervertebral jointsBanerji, Kamal Kumarhttps://hdl.handle.net/10023/149752019-03-29T10:39:47Z1957-01-01T00:00:00Z1. A comparative study of the joints between the vertebral bodies in different vertebrate animals has been made. 2. The natures of the intervertebral joint in different -vertebrate groups is dependent on its inherent pattern of self-differentiation. 3. In Elasmobranchs the cartilaginous composition of the vertebrae contributes to the flexibility of the column, but the notochord remains as a well-defined structure throughout life, as it does also in the vertebral column of Teleostei. In Fish, special fibrous joints between the amphicoelous vertebrae allow an effective side to side movement, and the persisting notochord imparts an additional flexibility to the column. 4. Regional variation of the vertebral column is a characteristic feature of land animals; it is first encountered in Amphibia and is greatest in Mammals. In Anura, shortening of the vertebral column, associated/associated with absence of a tail, is a characteristic feature correlated with the jumping gait. In them, synovial ball and socket joint between the procoelous vertebrae are described, and an account is given of lateral intervertebral and central ligaments, to which there is no reference in the literature. The central ligament a degenerate oranio-caudally with advance in age, except whore functional, demand requires their persistence at the joints of the amphicoelous eighth vertebra of the frog. Degenerated vestiges of notochord are present within the vertebrae throughout life, and in the central ligaments as long as they persist. 6. Fibro-cartilagnious disks are a feature of many intervertebral joints of land animals and are first encountered between the procoelous vertebrae of Lizards. In them the solid fibrous, non-laminated nature of the disk is remarkably characteristics. The vestigeal remnant of notochord in the middle of the disk of Lacertilia is a noteworthy feature. The major part of the disk is considered homologous with the annulus fibrosus/fibrosus of the Mammalian disk. 7. In Birds, a description has been given of the synovial saddle joints between the free vertebrae of the cervical and thoracic regions. The articular cartilage, in fowls of over two years, is characterised by a heterogeneous matrix, fibrillation and a diminution in cellularity with occasional fissures and clefts. The central ligaments of the synovial joints degenerate and disappear within ten days of hatching. Secondary cartilaginous joints in the caudal region are described; in them the notochord degenerates and is replaced by an extension from the surrounding fibre-cartilage of the disk. The functional significance of alternating regions of free -and fused vertebrae has been discussed. The moniliform appearance and the curvatures of the notochord are peculiar to each animal species, at different periods of growth, and this has been discussed following observations on pre- and post- hatched chicks. The notochord possesses and inherent quality of local cell aggregation in the intervertebral/intervertebral regions resulting in segmental self-differentiation. 8. In Mammals, the annulus fibrosus and the nucleus pulposus of the intervertebral disk remain distinct for a short time after birth: later, the line of demarcation between them is lost. The fibre-architecture of the annulus fibrosus in the Rat shows a basic pattern, characterised by an intricate laminated fibre-system. Initially, the nucleus pulposus is formed by an intervertebral aggregation of notochordal cells, which later undergo gradual senescence: a progressive invasion of fibres occurs from the fibro-cartilaginous zone of the annulus into the peripheral part of the degenerating notochordal tissue.
1957-01-01T00:00:00ZBanerji, Kamal Kumar1. A comparative study of the joints between the vertebral bodies in different vertebrate animals has been made. 2. The natures of the intervertebral joint in different -vertebrate groups is dependent on its inherent pattern of self-differentiation. 3. In Elasmobranchs the cartilaginous composition of the vertebrae contributes to the flexibility of the column, but the notochord remains as a well-defined structure throughout life, as it does also in the vertebral column of Teleostei. In Fish, special fibrous joints between the amphicoelous vertebrae allow an effective side to side movement, and the persisting notochord imparts an additional flexibility to the column. 4. Regional variation of the vertebral column is a characteristic feature of land animals; it is first encountered in Amphibia and is greatest in Mammals. In Anura, shortening of the vertebral column, associated/associated with absence of a tail, is a characteristic feature correlated with the jumping gait. In them, synovial ball and socket joint between the procoelous vertebrae are described, and an account is given of lateral intervertebral and central ligaments, to which there is no reference in the literature. The central ligament a degenerate oranio-caudally with advance in age, except whore functional, demand requires their persistence at the joints of the amphicoelous eighth vertebra of the frog. Degenerated vestiges of notochord are present within the vertebrae throughout life, and in the central ligaments as long as they persist. 6. Fibro-cartilagnious disks are a feature of many intervertebral joints of land animals and are first encountered between the procoelous vertebrae of Lizards. In them the solid fibrous, non-laminated nature of the disk is remarkably characteristics. The vestigeal remnant of notochord in the middle of the disk of Lacertilia is a noteworthy feature. The major part of the disk is considered homologous with the annulus fibrosus/fibrosus of the Mammalian disk. 7. In Birds, a description has been given of the synovial saddle joints between the free vertebrae of the cervical and thoracic regions. The articular cartilage, in fowls of over two years, is characterised by a heterogeneous matrix, fibrillation and a diminution in cellularity with occasional fissures and clefts. The central ligaments of the synovial joints degenerate and disappear within ten days of hatching. Secondary cartilaginous joints in the caudal region are described; in them the notochord degenerates and is replaced by an extension from the surrounding fibre-cartilage of the disk. The functional significance of alternating regions of free -and fused vertebrae has been discussed. The moniliform appearance and the curvatures of the notochord are peculiar to each animal species, at different periods of growth, and this has been discussed following observations on pre- and post- hatched chicks. The notochord possesses and inherent quality of local cell aggregation in the intervertebral/intervertebral regions resulting in segmental self-differentiation. 8. In Mammals, the annulus fibrosus and the nucleus pulposus of the intervertebral disk remain distinct for a short time after birth: later, the line of demarcation between them is lost. The fibre-architecture of the annulus fibrosus in the Rat shows a basic pattern, characterised by an intricate laminated fibre-system. Initially, the nucleus pulposus is formed by an intervertebral aggregation of notochordal cells, which later undergo gradual senescence: a progressive invasion of fibres occurs from the fibro-cartilaginous zone of the annulus into the peripheral part of the degenerating notochordal tissue.A comparative study of the descent of the testisAaron, Harry Immanuelhttps://hdl.handle.net/10023/149742019-03-29T10:27:28Z1958-01-01T00:00:00Z1958-01-01T00:00:00ZAaron, Harry ImmanuelThe relation of cartilage canals to the process of ossificationMaung, Maung Tinhttps://hdl.handle.net/10023/149732019-03-29T10:27:34Z1956-01-01T00:00:00Z1. A review of the literature on cartilage canals is given. 2. The formation of cartilage canals commences when the cartilage mass exceeds the maximum thickness which can be nourished by diffusion of fluid from the surface. This maximum thickness or the critical size at which canalization would occur, has been worked out in the distal femoral epiphysis at various developmental stages. It varies with the age of the foetus 0.25 mm. at the fourth month and gradually increasing to about 0.6 mm. at full-term. 3. Because of the restricted area of origin of the cartilaginous epiphysis of long bones, the canals seldom found, to be arranged in a radial fashion to the whole epiphysis, but they arranged so as to distribute the blood evenly through the whole mass. 4. (i) The clear, well-formed communicating canals have been seen in the epiphysis of human long bone as early as the fourth month of foetal life. (ii) As development proceeds, some of the communicating canals appear to become obliterated in, the region of proliferating cartilage adjacent to the metaphysis: this obliteration of canals occurs more rapidly after the onset of epiphyseal ossification so that by the time ossification of the epiphysis is complete, no communications between the diaphysis and the epiphysis remain. (iii) It is suggested that probably the primary cause of the formation of the communicating canal is the chemio-taxio influence in the zone of actively growing cartilage in the region adjacent to metaphysis, which directs the ends of the canals arising from the perichondrium near the end of the shaft to bend towards the diaphyseal end. (iii) The probable function of the communicating canals is that they assist in the supply of nutrition to and in the removal of waste products from the cells in the active juxta-metaphyseal cartilage. The almost invariable absence of osteogenic elements in these canals given no support to the hypothesis that they take part in the formation of the centre of epiphyseal ossification. (v) The vascular connective tissue buds which are identical with the communicating canals in the epiphysis of long bone, have boon observed in the cartilaginous sternal end of the clavicle of a human foetus. 5. It is suggested that the cartilage canals grow by a combination of three methods that is by surface accretion, stretching due to interstitial growth and active invasion of the cartilage by the tip of the canal. 6. The cartilage canal connective tissue contents are of perichondrial origin, and are not formed by back differentiation of the cartilage to an embryonic type of connective tissue. 7. In the long bone of the human, the cartilage canals are probably responsible for the formation of the epiphyseal ossification centre.
1956-01-01T00:00:00ZMaung, Maung Tin1. A review of the literature on cartilage canals is given. 2. The formation of cartilage canals commences when the cartilage mass exceeds the maximum thickness which can be nourished by diffusion of fluid from the surface. This maximum thickness or the critical size at which canalization would occur, has been worked out in the distal femoral epiphysis at various developmental stages. It varies with the age of the foetus 0.25 mm. at the fourth month and gradually increasing to about 0.6 mm. at full-term. 3. Because of the restricted area of origin of the cartilaginous epiphysis of long bones, the canals seldom found, to be arranged in a radial fashion to the whole epiphysis, but they arranged so as to distribute the blood evenly through the whole mass. 4. (i) The clear, well-formed communicating canals have been seen in the epiphysis of human long bone as early as the fourth month of foetal life. (ii) As development proceeds, some of the communicating canals appear to become obliterated in, the region of proliferating cartilage adjacent to the metaphysis: this obliteration of canals occurs more rapidly after the onset of epiphyseal ossification so that by the time ossification of the epiphysis is complete, no communications between the diaphysis and the epiphysis remain. (iii) It is suggested that probably the primary cause of the formation of the communicating canal is the chemio-taxio influence in the zone of actively growing cartilage in the region adjacent to metaphysis, which directs the ends of the canals arising from the perichondrium near the end of the shaft to bend towards the diaphyseal end. (iii) The probable function of the communicating canals is that they assist in the supply of nutrition to and in the removal of waste products from the cells in the active juxta-metaphyseal cartilage. The almost invariable absence of osteogenic elements in these canals given no support to the hypothesis that they take part in the formation of the centre of epiphyseal ossification. (v) The vascular connective tissue buds which are identical with the communicating canals in the epiphysis of long bone, have boon observed in the cartilaginous sternal end of the clavicle of a human foetus. 5. It is suggested that the cartilage canals grow by a combination of three methods that is by surface accretion, stretching due to interstitial growth and active invasion of the cartilage by the tip of the canal. 6. The cartilage canal connective tissue contents are of perichondrial origin, and are not formed by back differentiation of the cartilage to an embryonic type of connective tissue. 7. In the long bone of the human, the cartilage canals are probably responsible for the formation of the epiphyseal ossification centre.The regulatory role of AcSDKP and angiotensin 1-converting enzyme (ACE) inhibitors on haematopoietic stem and progenitor cell proliferationChisi, John Eugeneshttps://hdl.handle.net/10023/149712019-03-29T10:32:14Z1999-01-01T00:00:00ZNegative regulatory factors inhibit the proliferation of haematopoietic stem cells thus protecting them from differentiation pressures. One of the negative regulators of stem cell proliferation is the tetrapeptide Acetyl-Seryl-Aspartyl-Lysyl-Proline (AcSDKP). This peptide is endogenously produced in vivo and long term bone marrow cultures and is degraded by angiotensin 1-converting enzyme (ACE) both in vivo and in vitro. The aim of these investigations was to study the role of ACE on haematopoietic stem and progenitor cell proliferation. Since the N-domain ACE active has been implicated in AcSDKP degradation, an analysis of two ACE inhibitors (captopril and lisinopril) shown to have differential effects on the N-domain ACE active site was conducted. Both captopril and lisinopril equally reduced ACE activity in plasma in vitro. However, captopril had a lesser effect on reducing serum ACE activity in vitro than lisinopril. Captopril and AcSDKP together reduced the proportion of GM-CFC in S-phase after 7 hours of in vitro incubation. In addition, ACE resistant AcSDKP analogue (AcSDPψKP) when incubated with bone marrow cells in the absence of captopril also reduced the proportion of GM-CFC in S-phase. This finding suggest that the effect of captopril and AcSDKP on GM-CFC proliferation was due to AcSDKP alone. Haematopoietic stem cells were induced into cell cycle by in vivo administration of either 2 Gy-γ-irradiation or the two cytotoxic drugs, cytosine arabinoside (Ara-C) (100 mg/kg i.p.) or 5 flourouracil (5 FU) (150 mg/kg i.v). Bone marrow cells were sampled and incubated in vitro for up to 24 hours. Captopril together with AcSDKP reduced the proportion of high proliferative colony forming cells-1 (HPP-CFC-1) in S-phase following 2 Gy-γ-irradiation. Lisinopril together with AcSDKP had no such effect. In addition, captopril alone in vitro reduced the proportion of HPP-CFC-1 in S-phase induced into cell cycle by cytotoxic drugs. Lisinopril had no such effect. Incubation alone reduced the proportion of HPP-CFC-1 in S-phase in cytotoxic drug treated bone marrow cells. When cultures, which were incubated with captopril, were assayed for AcSDKP levels, captopril induced an increase in AcSDKP levels in both control normal bone marrow cells and cells derived from Ara-C treated mice. However, it did not affect AcSDKP levels in cultures derived from 5 FU and 2 Gy treated mice, AcSDKP together with captopril were shown to inhibit S-phase cell entry of HPP-CFC-1 when they were incubated with bone marrow cells derived from mice treated with either 2 Gy-γ-irradiation or cytotoxic drug insults. Interestingly, captopril was unable to reduce the proportion of SA2 leukaemic cells in S-phase Captopril on its own at therapeutic doses reduced the proportion of HPP-CFC- 1 in S-phase in vivo regardless of the insult used to induce HPP-CFC-1 into cell cycle. Lisinopril slightly reduced the proportion of HPP-CFC-1 in S-phase following Ai-a-C treatment only. Captopril induced an in vivo increase in AcSDKP levels in all the models tested. Captopril also reduced the proportion of HPP-CFC-1 and GM-CFC in S-phase following fractionated doses of Ara-C. Captopril's inhibitory effect on GM- CFC proliferation following fractionated dose of Ara-C was diminished after 7 days while it was sustained with HPP-CFC-1. Long-term bone marrow cultures revealed that captopril and AcSDxj/KP had the same effect on cellularities of both layers and on the proliferation of HPP-CFC and GM-CFC in both layers. From the present investigations, it can be concluded that captopril is a potent inhibitor of HPP-CFC-1 proliferation. This effect may in part be mediated by AcSDKP mechanism.
1999-01-01T00:00:00ZChisi, John EugenesNegative regulatory factors inhibit the proliferation of haematopoietic stem cells thus protecting them from differentiation pressures. One of the negative regulators of stem cell proliferation is the tetrapeptide Acetyl-Seryl-Aspartyl-Lysyl-Proline (AcSDKP). This peptide is endogenously produced in vivo and long term bone marrow cultures and is degraded by angiotensin 1-converting enzyme (ACE) both in vivo and in vitro. The aim of these investigations was to study the role of ACE on haematopoietic stem and progenitor cell proliferation. Since the N-domain ACE active has been implicated in AcSDKP degradation, an analysis of two ACE inhibitors (captopril and lisinopril) shown to have differential effects on the N-domain ACE active site was conducted. Both captopril and lisinopril equally reduced ACE activity in plasma in vitro. However, captopril had a lesser effect on reducing serum ACE activity in vitro than lisinopril. Captopril and AcSDKP together reduced the proportion of GM-CFC in S-phase after 7 hours of in vitro incubation. In addition, ACE resistant AcSDKP analogue (AcSDPψKP) when incubated with bone marrow cells in the absence of captopril also reduced the proportion of GM-CFC in S-phase. This finding suggest that the effect of captopril and AcSDKP on GM-CFC proliferation was due to AcSDKP alone. Haematopoietic stem cells were induced into cell cycle by in vivo administration of either 2 Gy-γ-irradiation or the two cytotoxic drugs, cytosine arabinoside (Ara-C) (100 mg/kg i.p.) or 5 flourouracil (5 FU) (150 mg/kg i.v). Bone marrow cells were sampled and incubated in vitro for up to 24 hours. Captopril together with AcSDKP reduced the proportion of high proliferative colony forming cells-1 (HPP-CFC-1) in S-phase following 2 Gy-γ-irradiation. Lisinopril together with AcSDKP had no such effect. In addition, captopril alone in vitro reduced the proportion of HPP-CFC-1 in S-phase induced into cell cycle by cytotoxic drugs. Lisinopril had no such effect. Incubation alone reduced the proportion of HPP-CFC-1 in S-phase in cytotoxic drug treated bone marrow cells. When cultures, which were incubated with captopril, were assayed for AcSDKP levels, captopril induced an increase in AcSDKP levels in both control normal bone marrow cells and cells derived from Ara-C treated mice. However, it did not affect AcSDKP levels in cultures derived from 5 FU and 2 Gy treated mice, AcSDKP together with captopril were shown to inhibit S-phase cell entry of HPP-CFC-1 when they were incubated with bone marrow cells derived from mice treated with either 2 Gy-γ-irradiation or cytotoxic drug insults. Interestingly, captopril was unable to reduce the proportion of SA2 leukaemic cells in S-phase Captopril on its own at therapeutic doses reduced the proportion of HPP-CFC- 1 in S-phase in vivo regardless of the insult used to induce HPP-CFC-1 into cell cycle. Lisinopril slightly reduced the proportion of HPP-CFC-1 in S-phase following Ai-a-C treatment only. Captopril induced an in vivo increase in AcSDKP levels in all the models tested. Captopril also reduced the proportion of HPP-CFC-1 and GM-CFC in S-phase following fractionated doses of Ara-C. Captopril's inhibitory effect on GM- CFC proliferation following fractionated dose of Ara-C was diminished after 7 days while it was sustained with HPP-CFC-1. Long-term bone marrow cultures revealed that captopril and AcSDxj/KP had the same effect on cellularities of both layers and on the proliferation of HPP-CFC and GM-CFC in both layers. From the present investigations, it can be concluded that captopril is a potent inhibitor of HPP-CFC-1 proliferation. This effect may in part be mediated by AcSDKP mechanism.A study of molecules involved in the regulation of the growth of haematopoietic cells and heart muscle cells in cultureGilmore, William Samuelhttps://hdl.handle.net/10023/149702019-03-29T10:37:38Z1986-01-01T00:00:00ZThe description of the molecular events responsible for the control of cell division and differentiation is, currently, one of the major goals of molecular and cellular biologists. Cell and tissue culture techniques have proved to be promising laboratory tools for the study of the regulators of cellular growth and differentiation. Most cells in culture require specific polypeptide growth factors which are supplied by the addition of a complex biological fluid such as serum or, in some instances, by the cells themselves. These growth factors usually act on their target cell via a membrane receptor to which they bind. The events which occur after the growth factor binds to the membrane receptor have not been fully described, but the phosphorylation of tyrosine residues in certain proteins has been observed. A study was made of the polypeptide growth factors responsible for the growth and differentiation of haematopoietic cells in vitro. These growth factors, called colony - stimulating factors (C.S.F.'s) were prepared from human placental conditioned medium, giant cell tumour conditioned medium and pokeweed mitogen stimulated spleen conditioned medium. A C.S.F. from human placental conditioned medium was radioiodinated and the binding of the labelled growth factor to an anti-C.S.F. antiserum was studied. The binding studies indicated that a purer C.S.F. preparation and/or a more specific antiserum was necessary in order to establish a radioimmunoassay for C.S.F. The C.S.F.'s from giant cell tumour conditioned medium were purified by ultrafiltration, hydrophobic - interaction chromatography, gel filtration and thiolpropyl - sepharose 6B chromatography. Two peaks of biological activity were observed on gel filtration. One of these peaks gave an apparent MW of 63,000 and the other peak gave an apparent MW of 30,200. The C.S.F. from pokeweed mitogen stimulated spleen conditioned medium was labelled with peroxidase and the binding of the labelled-C.S.F. to bone marrow cell membranes studied. The labelled-C.S.F. bound to the membranes and the binding exhibited a linear relationship with membrane protein content. Also a defined growth medium for chick embryonic heart cells was developed. These cells were observed to differentiate from primitive foetal cells into mature "adult-type" cells. The cells grew as a monolayer, had spontaneous activity and were seen to beat.
1986-01-01T00:00:00ZGilmore, William SamuelThe description of the molecular events responsible for the control of cell division and differentiation is, currently, one of the major goals of molecular and cellular biologists. Cell and tissue culture techniques have proved to be promising laboratory tools for the study of the regulators of cellular growth and differentiation. Most cells in culture require specific polypeptide growth factors which are supplied by the addition of a complex biological fluid such as serum or, in some instances, by the cells themselves. These growth factors usually act on their target cell via a membrane receptor to which they bind. The events which occur after the growth factor binds to the membrane receptor have not been fully described, but the phosphorylation of tyrosine residues in certain proteins has been observed. A study was made of the polypeptide growth factors responsible for the growth and differentiation of haematopoietic cells in vitro. These growth factors, called colony - stimulating factors (C.S.F.'s) were prepared from human placental conditioned medium, giant cell tumour conditioned medium and pokeweed mitogen stimulated spleen conditioned medium. A C.S.F. from human placental conditioned medium was radioiodinated and the binding of the labelled growth factor to an anti-C.S.F. antiserum was studied. The binding studies indicated that a purer C.S.F. preparation and/or a more specific antiserum was necessary in order to establish a radioimmunoassay for C.S.F. The C.S.F.'s from giant cell tumour conditioned medium were purified by ultrafiltration, hydrophobic - interaction chromatography, gel filtration and thiolpropyl - sepharose 6B chromatography. Two peaks of biological activity were observed on gel filtration. One of these peaks gave an apparent MW of 63,000 and the other peak gave an apparent MW of 30,200. The C.S.F. from pokeweed mitogen stimulated spleen conditioned medium was labelled with peroxidase and the binding of the labelled-C.S.F. to bone marrow cell membranes studied. The labelled-C.S.F. bound to the membranes and the binding exhibited a linear relationship with membrane protein content. Also a defined growth medium for chick embryonic heart cells was developed. These cells were observed to differentiate from primitive foetal cells into mature "adult-type" cells. The cells grew as a monolayer, had spontaneous activity and were seen to beat.Cellular relationships in the developing murine liverBlair, Allisonhttps://hdl.handle.net/10023/149682019-03-29T10:35:01Z1994-01-01T00:00:00ZHaematopoietic activity in the murine fetal liver was observed to increase from the 12th day of gestation to reach a peak on the 15th day of gestation. Hepatic haematopoiesis is predominantly erythroid. As maturation proceeds the numbers of myelopoietic cells increase. Haematopoietic activity declines after the 15th day of gestation, though haematopoietic cells were still obvious in the liver of the 10 day neonate. Cellular interactions were studied in vivo with the electron microscope and in vitro using long term cultures. Haematopoietic cell clusters were abundant in fetal liver both in vivo and in vitro. Macrophages and hepatocytes act as the central supporting cells of these clusters. There was evidence of communication between the central supporting cells and the blood cells precursors, which may be essential for the maintenance of haematopoiesis both in vivo and in vitro. A high proportion of early HPP-CFC derived from fetal liver are synthesising DNA, while HPP-CFC derived from adult bone marrow are relatively quiescent. The kinetic properties of the HPP-CFC population are very similar to those of the CFU-S population both in fetal liver and in adult bone marrow. A high proportion of GM-CFC which are a more mature class of progenitor cells were cycling in both fetal liver and adult bone marrow. Fetal liver extract was shown to have an overall inhibitory effect on haematopoiesis in normal bone marrow and irradiated bone marrow and on colony formation by leukemic cells. Detrimental effects on normal bone marrow cells were observed only with high concentrations of fetal liver extract. Fetal liver blood cell precursors were found to adhere preferentially to bone marrow stromal layers, which could not be attributed to the kinetic properties of these cells. This preferential adhesion may promote the in vivo accumulation of haematopoietic stem cells derived from fetal liver in the medullary cavities.
1994-01-01T00:00:00ZBlair, AllisonHaematopoietic activity in the murine fetal liver was observed to increase from the 12th day of gestation to reach a peak on the 15th day of gestation. Hepatic haematopoiesis is predominantly erythroid. As maturation proceeds the numbers of myelopoietic cells increase. Haematopoietic activity declines after the 15th day of gestation, though haematopoietic cells were still obvious in the liver of the 10 day neonate. Cellular interactions were studied in vivo with the electron microscope and in vitro using long term cultures. Haematopoietic cell clusters were abundant in fetal liver both in vivo and in vitro. Macrophages and hepatocytes act as the central supporting cells of these clusters. There was evidence of communication between the central supporting cells and the blood cells precursors, which may be essential for the maintenance of haematopoiesis both in vivo and in vitro. A high proportion of early HPP-CFC derived from fetal liver are synthesising DNA, while HPP-CFC derived from adult bone marrow are relatively quiescent. The kinetic properties of the HPP-CFC population are very similar to those of the CFU-S population both in fetal liver and in adult bone marrow. A high proportion of GM-CFC which are a more mature class of progenitor cells were cycling in both fetal liver and adult bone marrow. Fetal liver extract was shown to have an overall inhibitory effect on haematopoiesis in normal bone marrow and irradiated bone marrow and on colony formation by leukemic cells. Detrimental effects on normal bone marrow cells were observed only with high concentrations of fetal liver extract. Fetal liver blood cell precursors were found to adhere preferentially to bone marrow stromal layers, which could not be attributed to the kinetic properties of these cells. This preferential adhesion may promote the in vivo accumulation of haematopoietic stem cells derived from fetal liver in the medullary cavities.Perturbation of cell renewal in the haemopoetic tissues of drug-treated and leukaemic miceMeldrum, Rosalind A.https://hdl.handle.net/10023/149662019-03-29T10:39:39Z1983-01-01T00:00:00ZThe murine lympho-myeloid complex is depleted by a large dose of nitrogen mustard and the pattern of recovery of the haemopoietic tissues and cells followed to establish the relationships ox the precursor and mature cells. Culture of bone marrow in agar and stathmokinetic techniques are used to examine the controlled proliferation for the granulocyte elements in the bone marrow recovering from nitrogen mustard and the influence of the spleen is also considered. The control of the proliferation of the granulocyte cells is lost in myeloid leukaemia. Stathmokinetic methods and spleen colon assays are used to asses cell proliferation in irradiation-induced myeloid leukaemias in mice and the relevance of these parameters so measured to those demonstrated by normal bone marrow is discussed.
1983-01-01T00:00:00ZMeldrum, Rosalind A.The murine lympho-myeloid complex is depleted by a large dose of nitrogen mustard and the pattern of recovery of the haemopoietic tissues and cells followed to establish the relationships ox the precursor and mature cells. Culture of bone marrow in agar and stathmokinetic techniques are used to examine the controlled proliferation for the granulocyte elements in the bone marrow recovering from nitrogen mustard and the influence of the spleen is also considered. The control of the proliferation of the granulocyte cells is lost in myeloid leukaemia. Stathmokinetic methods and spleen colon assays are used to asses cell proliferation in irradiation-induced myeloid leukaemias in mice and the relevance of these parameters so measured to those demonstrated by normal bone marrow is discussed.Proliferation regulation of haematopoietic stem cells in normal and leukaemic haematopoiesisRobinson, Simon N.https://hdl.handle.net/10023/149652019-03-29T10:28:56Z1992-01-01T00:00:00ZThe cellular integrity of the blood is maintained by the cellular output of the haematopoietic stem cell population which produces the specialized precursors and differentiated cells which constitute the blood. The investigation of haematopoietic stem cell behaviour and regulation has been hampered by both the difficulty in their identification and the development of relevant assay systems. The purpose of this investigation was to study the behaviour and regulation of the haematopoietic stem cell population in normal and leukaemic haematopoiesis using an in vitro assay of a primitive haematopoietic precursor. The use of a combination of haematopoietic colony-stimulating factors [interleukin 3 (IL3)/multi-CSF and macrophage colony-stimulating factor (M-CSF/CSF-1)] in semi-solid agar culture of murine haematopoietic tissue, stimulated the proliferation of a haematopoietic colony-forming cell, defined as the "HPP-CFCIL3+CSF-1" population, which was characterized by a high proliferative potential, a multipotency and behavioural and regulatory properties consistent with its being a primitive haematopoietic precursor and possibly a component of the haematopoietic stem cell population. The proportion of the in vitro HPP-CFCIL3+csf-1 population in S-phase in normal murine marrow, was determined to be relatively low at approximately 10%, increasing to approximately 40% in sublethally X-irradiated, regenerating murine marrow and the respective presence of the haematopoietic stem cell proliferation inhibitor and stimulator was demonstrable by the induction of appropriate kinetic changes in the in vitro HPP-CFCIL3+CSF-1 population. In leukaemic haematopoiesis, leukaemic proliferation often occurs at the expense of apparently suppressed normal haematopoiesis. In vitro HPP-CFCIL3+CSF-1 assay of the haematopoietic stem cell proliferation regulators in a number of murine, myeloid leukaemic cell lines, failed to demonstrate either increased levels of the haematopoietic stem cell proliferation inhibitor, or evidence of a direct-acting, leukaemia- associated proliferation inhibitor, however, evidence of a leukaemia- associated impairment of inhibitor and stimulator production was observed and this may be a possible mechanism by which the leukaemic population develops a proliferative advantage over normal haematopoietic tissue. The identification of a possible mechanism of leukaemic progression and suppression of normal haematopoiesis may subsequently allow the development of potentially more effective disease treatment and management regimes. The endogenous haemoregulatory tetrapeptide: Acetyl-N-Ser- Asp-Lys-Pro [AcSDKP, Mr=487 amu] is reported to prevent the G0-G1 transition of haematopoietic stem cells into S-phase. The mechanism of action of AcSDKP and a number of related peptides, was investigated in relation to the stem cell proliferation stimulator and inhibitor. AcSDKP demonstrated no direct haemoregulatory role against the in vitro HPP-CFCIL3+CSF-1 population, which is consistent with reports that AcSDKP is not active against cells already in late G1, or S-phase, rather it appeared to act indirectly by impairing the capacity of the haematopoietic stem cell proliferation stimulator to increase the proportion of the in vitro HPP-CFCIL3+CSF-1 population in S-phase. An apparent impairment of stimulator action may explain the reported AcSDKP-associated 'block' of haematopoietic stem cell recruitment. A putative endogenous AcSDKP precursor and synthetic and degradative enzyme systems have been reported and the possible physiopathological role of AcSDKP in a number of myeloproliferative disorders has been implicated. The potential application of AcSDKP as a 'haemoprotective' agent administered prior to the use of S-phase- specific chemotherapy may be of clinical significance. The in vitro HPP-CFCIL3+CSF-1 assay of a primitive haematopoietic precursor cell population, which may be a component of the haematopoietic stem cell population, should play a significant role in the investigation of haematopoietic stem cell behaviour and regulation in both normal and aberrant haematopoiesis. With the characterization of the mechanism(s) of action of the haematopoietic stem cell proliferation inhibitor and stimulator and the haemoregulatory tetrapeptide AcSDKP, the manipulation of the haematopoietic system to clinical advantage can be envisaged, while the identification of the aberrant regulatory mechanism(s) in haematopoietic dysfunction may allow, the development of more effective disease treatment and management regimes.
1992-01-01T00:00:00ZRobinson, Simon N.The cellular integrity of the blood is maintained by the cellular output of the haematopoietic stem cell population which produces the specialized precursors and differentiated cells which constitute the blood. The investigation of haematopoietic stem cell behaviour and regulation has been hampered by both the difficulty in their identification and the development of relevant assay systems. The purpose of this investigation was to study the behaviour and regulation of the haematopoietic stem cell population in normal and leukaemic haematopoiesis using an in vitro assay of a primitive haematopoietic precursor. The use of a combination of haematopoietic colony-stimulating factors [interleukin 3 (IL3)/multi-CSF and macrophage colony-stimulating factor (M-CSF/CSF-1)] in semi-solid agar culture of murine haematopoietic tissue, stimulated the proliferation of a haematopoietic colony-forming cell, defined as the "HPP-CFCIL3+CSF-1" population, which was characterized by a high proliferative potential, a multipotency and behavioural and regulatory properties consistent with its being a primitive haematopoietic precursor and possibly a component of the haematopoietic stem cell population. The proportion of the in vitro HPP-CFCIL3+csf-1 population in S-phase in normal murine marrow, was determined to be relatively low at approximately 10%, increasing to approximately 40% in sublethally X-irradiated, regenerating murine marrow and the respective presence of the haematopoietic stem cell proliferation inhibitor and stimulator was demonstrable by the induction of appropriate kinetic changes in the in vitro HPP-CFCIL3+CSF-1 population. In leukaemic haematopoiesis, leukaemic proliferation often occurs at the expense of apparently suppressed normal haematopoiesis. In vitro HPP-CFCIL3+CSF-1 assay of the haematopoietic stem cell proliferation regulators in a number of murine, myeloid leukaemic cell lines, failed to demonstrate either increased levels of the haematopoietic stem cell proliferation inhibitor, or evidence of a direct-acting, leukaemia- associated proliferation inhibitor, however, evidence of a leukaemia- associated impairment of inhibitor and stimulator production was observed and this may be a possible mechanism by which the leukaemic population develops a proliferative advantage over normal haematopoietic tissue. The identification of a possible mechanism of leukaemic progression and suppression of normal haematopoiesis may subsequently allow the development of potentially more effective disease treatment and management regimes. The endogenous haemoregulatory tetrapeptide: Acetyl-N-Ser- Asp-Lys-Pro [AcSDKP, Mr=487 amu] is reported to prevent the G0-G1 transition of haematopoietic stem cells into S-phase. The mechanism of action of AcSDKP and a number of related peptides, was investigated in relation to the stem cell proliferation stimulator and inhibitor. AcSDKP demonstrated no direct haemoregulatory role against the in vitro HPP-CFCIL3+CSF-1 population, which is consistent with reports that AcSDKP is not active against cells already in late G1, or S-phase, rather it appeared to act indirectly by impairing the capacity of the haematopoietic stem cell proliferation stimulator to increase the proportion of the in vitro HPP-CFCIL3+CSF-1 population in S-phase. An apparent impairment of stimulator action may explain the reported AcSDKP-associated 'block' of haematopoietic stem cell recruitment. A putative endogenous AcSDKP precursor and synthetic and degradative enzyme systems have been reported and the possible physiopathological role of AcSDKP in a number of myeloproliferative disorders has been implicated. The potential application of AcSDKP as a 'haemoprotective' agent administered prior to the use of S-phase- specific chemotherapy may be of clinical significance. The in vitro HPP-CFCIL3+CSF-1 assay of a primitive haematopoietic precursor cell population, which may be a component of the haematopoietic stem cell population, should play a significant role in the investigation of haematopoietic stem cell behaviour and regulation in both normal and aberrant haematopoiesis. With the characterization of the mechanism(s) of action of the haematopoietic stem cell proliferation inhibitor and stimulator and the haemoregulatory tetrapeptide AcSDKP, the manipulation of the haematopoietic system to clinical advantage can be envisaged, while the identification of the aberrant regulatory mechanism(s) in haematopoietic dysfunction may allow, the development of more effective disease treatment and management regimes.The role of leukaemia inhibitory factor and a leukaemic associated inhibitor in the control of the proliferation of haematopoietic stem cellsTaylor, Alanhttps://hdl.handle.net/10023/149622019-03-29T10:42:11Z1996-01-01T00:00:00ZActivities associated with, or interacting with, leukaemic cell populations were assayed for the ability to influence in vitro haematopoiesis. The first of these, the glycoprotein leukaemia inhibitory factor (LIF), has a role in aspects of murine, non human primate and human haematopoiesis. It is thought to be particularly important in the development of megakaryocytes and is also known to induce the terminal differentiation of certain leukaemic cell lines. LIF was assayed both for direct and indirect effects on the proliferation of haematopoietic precursor cell populations in vitro. As a direct acting agent in semi-solid agar culture of haematopoietic cell populations derived from normal bone marrow or 15 day foetal liver, LIF was unable to support colony formation. In cultures of cells derived from normal bone marrow stimulated with single, or combinations of, growth factors, the addition of LIF had no statistically significant effect on the level of colony formation. In cultures of cells derived from foetal liver, stimulated with particular growth factor combinations (medium conditioned by the Wehi3B leukaemic cell line + medium conditioned by the lung fibroblast cell line, L929); GM-CSF + M-CSF; IL-la + IL-3 + M-CSF), LIF, was shown to decrease the level of colony formation. LIF did not directly alter the proportion of the population in DNA synthesis in cell populations derived from normal femoral marrow, 15 day foetal liver or y- irradiated femoral marrow. As an indirect acting agent LIF failed to block the synthesis of a stem cell stimulator, or it's action, on a population of high proliferative potential colony forming cells derived from normal femoral marrow, cloned in the presence of Wehicm+L929cm. (HPP-CFC (Wehicm + L929cm)) LIF's actions on clones of a murine myeloid leukaemia (SA2JMB1) were also assessed. LIF had no statistically significant effect on colony formation or the level of DNA synthesis in populations of SA2JMB1 leukaemic cells. A second group of associated activities was produced by the X- irradiation induced murine myeloid leukaemia (SA2JMB1). Medium conditioned by the leukaemic cells was assayed in vitro both for direct and indirect effects on the proliferation of haematopoietic cells derived from femoral marrow. As a direct acting agent in 7 and 14-day semi-solid agar culture of femoral marrow, leukaemic conditioned medium alone stimulated limited colony formation. In 7 and 14 day cultures stimulated with single and combinations of specific colony stimulating factors: (rmGM-CSF, rhM-CSF, rhIL-1a) a significant increase in colony number was noted in all cases when cultures were supplemented with leukaemic conditioned medium. SA2JMBlcm was shown to support the proliferation of an IL-3 dependent cell line (FDCP-A4 cells). The colony enhancing ability of SA2JMBlcm was shown to be blocked by pretreatment with antibodies to IL-3. This suggested that SA2JMB1 conditioned medium contained IL-3 or an IL-3 like activity, as one of its components. The conditioned medium failed to directly alter the level of DNA synthesis in a population of HPP-CFC (Wehicm+L929cm) derived from normal bone marrow or y- irradiated bone marrow. As an indirect acting agent the conditioned medium did block the action of a stem cell proliferation stimulator on normal bone marrow derived HPP-CFC (Wehicm+L929cm). This leukaemia associated activity was shown to be larger than 50KD, sensitive to heat treatment and able to act in a different manner to the stem cell inhibitor MIP-1-a. Thus this novel activity may be important in blocking stimulator action in haematopoietic stem cells and thus contribute to the haematopoietic insufficiency seen in leukaemia.
1996-01-01T00:00:00ZTaylor, AlanActivities associated with, or interacting with, leukaemic cell populations were assayed for the ability to influence in vitro haematopoiesis. The first of these, the glycoprotein leukaemia inhibitory factor (LIF), has a role in aspects of murine, non human primate and human haematopoiesis. It is thought to be particularly important in the development of megakaryocytes and is also known to induce the terminal differentiation of certain leukaemic cell lines. LIF was assayed both for direct and indirect effects on the proliferation of haematopoietic precursor cell populations in vitro. As a direct acting agent in semi-solid agar culture of haematopoietic cell populations derived from normal bone marrow or 15 day foetal liver, LIF was unable to support colony formation. In cultures of cells derived from normal bone marrow stimulated with single, or combinations of, growth factors, the addition of LIF had no statistically significant effect on the level of colony formation. In cultures of cells derived from foetal liver, stimulated with particular growth factor combinations (medium conditioned by the Wehi3B leukaemic cell line + medium conditioned by the lung fibroblast cell line, L929); GM-CSF + M-CSF; IL-la + IL-3 + M-CSF), LIF, was shown to decrease the level of colony formation. LIF did not directly alter the proportion of the population in DNA synthesis in cell populations derived from normal femoral marrow, 15 day foetal liver or y- irradiated femoral marrow. As an indirect acting agent LIF failed to block the synthesis of a stem cell stimulator, or it's action, on a population of high proliferative potential colony forming cells derived from normal femoral marrow, cloned in the presence of Wehicm+L929cm. (HPP-CFC (Wehicm + L929cm)) LIF's actions on clones of a murine myeloid leukaemia (SA2JMB1) were also assessed. LIF had no statistically significant effect on colony formation or the level of DNA synthesis in populations of SA2JMB1 leukaemic cells. A second group of associated activities was produced by the X- irradiation induced murine myeloid leukaemia (SA2JMB1). Medium conditioned by the leukaemic cells was assayed in vitro both for direct and indirect effects on the proliferation of haematopoietic cells derived from femoral marrow. As a direct acting agent in 7 and 14-day semi-solid agar culture of femoral marrow, leukaemic conditioned medium alone stimulated limited colony formation. In 7 and 14 day cultures stimulated with single and combinations of specific colony stimulating factors: (rmGM-CSF, rhM-CSF, rhIL-1a) a significant increase in colony number was noted in all cases when cultures were supplemented with leukaemic conditioned medium. SA2JMBlcm was shown to support the proliferation of an IL-3 dependent cell line (FDCP-A4 cells). The colony enhancing ability of SA2JMBlcm was shown to be blocked by pretreatment with antibodies to IL-3. This suggested that SA2JMB1 conditioned medium contained IL-3 or an IL-3 like activity, as one of its components. The conditioned medium failed to directly alter the level of DNA synthesis in a population of HPP-CFC (Wehicm+L929cm) derived from normal bone marrow or y- irradiated bone marrow. As an indirect acting agent the conditioned medium did block the action of a stem cell proliferation stimulator on normal bone marrow derived HPP-CFC (Wehicm+L929cm). This leukaemia associated activity was shown to be larger than 50KD, sensitive to heat treatment and able to act in a different manner to the stem cell inhibitor MIP-1-a. Thus this novel activity may be important in blocking stimulator action in haematopoietic stem cells and thus contribute to the haematopoietic insufficiency seen in leukaemia.A fibrinolytic acid proteinase in human plasmaPejhan, Nooshabehhttps://hdl.handle.net/10023/149602019-03-29T10:37:08Z1984-01-01T00:00:00ZAn attempt has been made to purify an acid proteinase from human plasma, which is capable of dissolving fibrin clot in 1% (w/v) monochloroacetic acid. On SDS gel electrophoresis the enzyme isolated from plasma contains two protein bands with molecular weights of approximately 90,000 and 54,000. Different substrates were used to evaluate the proteolytic activity of the plasma enzyme, including fibrin clot, azo-casein, acid denatured haemoglobin (Hb), haemoglobin polyacrylamide gel (insoluble Hb), haemoglobin electrophoresis (soluble Hb) and the synthetic substrate N-acetyl-L-phenylalanyl-L-diiodotyrosine. The plasma enzyme seems to belong to the group of aspartyl proteinases as its activity against the above substrates was maximal at low pH, and was inhibited by pepstatin which is a powerful inhibitor of aspartyl proteinases.
1984-01-01T00:00:00ZPejhan, NooshabehAn attempt has been made to purify an acid proteinase from human plasma, which is capable of dissolving fibrin clot in 1% (w/v) monochloroacetic acid. On SDS gel electrophoresis the enzyme isolated from plasma contains two protein bands with molecular weights of approximately 90,000 and 54,000. Different substrates were used to evaluate the proteolytic activity of the plasma enzyme, including fibrin clot, azo-casein, acid denatured haemoglobin (Hb), haemoglobin polyacrylamide gel (insoluble Hb), haemoglobin electrophoresis (soluble Hb) and the synthetic substrate N-acetyl-L-phenylalanyl-L-diiodotyrosine. The plasma enzyme seems to belong to the group of aspartyl proteinases as its activity against the above substrates was maximal at low pH, and was inhibited by pepstatin which is a powerful inhibitor of aspartyl proteinases.Differentiation induction and growth factor responses of murine myeloid leukemiasKavnoudias, Helenhttps://hdl.handle.net/10023/149582019-03-29T10:37:42Z1993-01-01T00:00:00ZCurrent therapeutic regimes for the treatment of acute myeloid leukaemia employ aggressive cytotoxic strategies which have limited success and are not suitable for all patients. Manipulating myeloid leukaemic cells according to their responses to pharmacologically tolerable agents rather than employing aggressive non specific cell kill would be desirable. Differentiation induction of myeloid leukaemic cells as an alternative therapeutic regime was evaluated. To elucidate the growth and differentiation abnormalities of myeloid leukaemic cells the differentiation induction and growth factor responses of bone marrow from three myeloid leukaemic models (SA2, SA7, SA8) and a leukaemic cell line (SA2 CL) were investigated in microtitre suspension cultures and compared with normal. The regulators of normal haemopoiesis occupy a key position in attempts to understand the nature of the abnormal state existing in myeloid leukaemia and could potentially play an important role therapeutically by suppressing myeloid leukaemic populations. To evaluate differentiation induction as an alternative therapeutic regime for the treatment of myeloid leukaemia both the physiological regulators and the differentiation inducer β-all trans retinoic acid (βatRA) alone and in combination with ara-C were investigated. The effects of these agents directly on the leukaemic clonogenic cell populations in vitro were measured following in vivo transplantation. The proliferative effects of WEHI-3B CM, as a source of IL-3, L929 CM as a source of M-CSF, and recombinant murine GM-CSF alone and in combination were investigated. Bone marrow cells from the SA7 and SA8 transplanted leukaemias were growth factor dependent for proliferation in vitro. The SA2 transplanted leukaemia proliferated autonomously at low passage numbers, the dominant leukaemic clone changed characteristics with progressive transplantation and became growth factor dependent at high passage numbers. A cell line (SA2 CL) was derived from leukaemic bone marrow cells of a low passage number of the SA2 leukaemia and proliferated at a high rate autonomously with minimal spontaneous differentiation in culture. The growth factor dependent leukaemias were induced to proliferate with each of the growth factors. No differences were observed in the dose response relationships between normal and leukaemic cells. Differences were observed in the proliferative rates, the day to which exponential cell growth was sustained in culture and the growth factor which induced maximal proliferation. WEHI-3B CM induced the maximal proliferative response of normal bone marrow cells and two of the leukaemias whereas rGM-CSF induced a maximal response of the third leukaemia. Leukaemic cells proliferated at a higher rate than normal cells in the first two to three days in culture but were not sustained in culture for as long as normal bone marrow cells. It appeared therefore, that in the case of some leukaemias the haemopoietic growth factors were effective at inducing a high initial but short term proliferative response of leukaemic cells and were more effective in sustaining normal bone marrow cells in vitro. (Abstract shortened by ProQuest.)
1993-01-01T00:00:00ZKavnoudias, HelenCurrent therapeutic regimes for the treatment of acute myeloid leukaemia employ aggressive cytotoxic strategies which have limited success and are not suitable for all patients. Manipulating myeloid leukaemic cells according to their responses to pharmacologically tolerable agents rather than employing aggressive non specific cell kill would be desirable. Differentiation induction of myeloid leukaemic cells as an alternative therapeutic regime was evaluated. To elucidate the growth and differentiation abnormalities of myeloid leukaemic cells the differentiation induction and growth factor responses of bone marrow from three myeloid leukaemic models (SA2, SA7, SA8) and a leukaemic cell line (SA2 CL) were investigated in microtitre suspension cultures and compared with normal. The regulators of normal haemopoiesis occupy a key position in attempts to understand the nature of the abnormal state existing in myeloid leukaemia and could potentially play an important role therapeutically by suppressing myeloid leukaemic populations. To evaluate differentiation induction as an alternative therapeutic regime for the treatment of myeloid leukaemia both the physiological regulators and the differentiation inducer β-all trans retinoic acid (βatRA) alone and in combination with ara-C were investigated. The effects of these agents directly on the leukaemic clonogenic cell populations in vitro were measured following in vivo transplantation. The proliferative effects of WEHI-3B CM, as a source of IL-3, L929 CM as a source of M-CSF, and recombinant murine GM-CSF alone and in combination were investigated. Bone marrow cells from the SA7 and SA8 transplanted leukaemias were growth factor dependent for proliferation in vitro. The SA2 transplanted leukaemia proliferated autonomously at low passage numbers, the dominant leukaemic clone changed characteristics with progressive transplantation and became growth factor dependent at high passage numbers. A cell line (SA2 CL) was derived from leukaemic bone marrow cells of a low passage number of the SA2 leukaemia and proliferated at a high rate autonomously with minimal spontaneous differentiation in culture. The growth factor dependent leukaemias were induced to proliferate with each of the growth factors. No differences were observed in the dose response relationships between normal and leukaemic cells. Differences were observed in the proliferative rates, the day to which exponential cell growth was sustained in culture and the growth factor which induced maximal proliferation. WEHI-3B CM induced the maximal proliferative response of normal bone marrow cells and two of the leukaemias whereas rGM-CSF induced a maximal response of the third leukaemia. Leukaemic cells proliferated at a higher rate than normal cells in the first two to three days in culture but were not sustained in culture for as long as normal bone marrow cells. It appeared therefore, that in the case of some leukaemias the haemopoietic growth factors were effective at inducing a high initial but short term proliferative response of leukaemic cells and were more effective in sustaining normal bone marrow cells in vitro. (Abstract shortened by ProQuest.)Conformational studies of fibrinogen and its derivativesApap-Bologna, Angelahttps://hdl.handle.net/10023/149572019-07-15T10:11:26Z1988-01-01T00:00:00ZThere is much controversy regarding the conformation of fibrinogen. Several models have been proposed ranging from a trinodular arrangement to a globular conformation. It has also been suggested that fibrinogen has a flexible structure where the shape of the molecule is influenced by its environment, one major factor being calcium concentration, In addition, although the importance of tightly bound calcium ions (kd 1M) to the fibrinogen molecule is well established, the role of the larger number of low affinity sites (kd 1mM) is still a matter of some debate. In this study, the two techniques of photosensitized radioactive surface labelling and photosensitized cross-linking were selected for development and assessment. This was done with a view to examining the conformation of fibrinogen in its native state and under different solvent conditions, with particular reference to the influence of calcium. The two techniques have been shown to have definite applications in their use as probes into the conformation of fibrinogen. Results derived using these methods support the view put forward by various authors that fibrinogen is a dynamic molecule having a flexible conformation and that the conformation adopted is dependent on solvent composition. Calcium concentration in the millimolar range is particularly significant and consequently so is the saturation of the low affinity binding sites which may well have a regulatory function. Experimentally two extreme conformations have been demonstrated, - a closed, compact structure at low calcium concentrations compared to a more open one at higher calcium concentrations. More importantly, the techniques used also show the subtle changes which occur within the molecule as the calcium concentration is raised, changes which may be more significant physiologically. The most important of these are the effect of calcium on the C-terminal parts of the Aa-chains and the D domains of the molecule.
1988-01-01T00:00:00ZApap-Bologna, AngelaThere is much controversy regarding the conformation of fibrinogen. Several models have been proposed ranging from a trinodular arrangement to a globular conformation. It has also been suggested that fibrinogen has a flexible structure where the shape of the molecule is influenced by its environment, one major factor being calcium concentration, In addition, although the importance of tightly bound calcium ions (kd 1M) to the fibrinogen molecule is well established, the role of the larger number of low affinity sites (kd 1mM) is still a matter of some debate. In this study, the two techniques of photosensitized radioactive surface labelling and photosensitized cross-linking were selected for development and assessment. This was done with a view to examining the conformation of fibrinogen in its native state and under different solvent conditions, with particular reference to the influence of calcium. The two techniques have been shown to have definite applications in their use as probes into the conformation of fibrinogen. Results derived using these methods support the view put forward by various authors that fibrinogen is a dynamic molecule having a flexible conformation and that the conformation adopted is dependent on solvent composition. Calcium concentration in the millimolar range is particularly significant and consequently so is the saturation of the low affinity binding sites which may well have a regulatory function. Experimentally two extreme conformations have been demonstrated, - a closed, compact structure at low calcium concentrations compared to a more open one at higher calcium concentrations. More importantly, the techniques used also show the subtle changes which occur within the molecule as the calcium concentration is raised, changes which may be more significant physiologically. The most important of these are the effect of calcium on the C-terminal parts of the Aa-chains and the D domains of the molecule.Studies of the shape and calcium binding properties of fibrinogen and its degradation product fragment DBritton, David W.https://hdl.handle.net/10023/149562019-03-29T10:32:12Z1984-01-01T00:00:00ZThe main aims of this work were to develop and test methods for the analysis of the shape and calcium binding properties of fibrinogen and its degradation product fragment D. The techniques of photo-sensitized labelling and cross-linking were used to obtain information about the shape of these proteins and both revealed interesting information. Photosensitized labelling proved particularly useful and results obtained using this technique suggested that fragment D (Ca++) in solution and the fragment D domains of fibrinogen are conformationally very similar. These studies also suggested that the A chain of fibrinogen is highly exposed at the surface of the molecule and that it shields other portions, particularly the D-domains of the molecule. The use of chemical cross-linking reagents revealed a gross-conformational difference between fragment D (Ca++) and fragment D (EDTA) and it was further shown that this difference is a result of cleavage of the chain of fragment D (Ca++) rather than calcium removal. This suggests that the calcium ion bound by fragment D (Ca++) exercises a protective influence over a plasmin susceptible bond and that cleavage of this bond allows a gross conformational change. This is consistent with the results from photo-sensitized labelling which showed the C-terminal portion of the chain of fragment D to the surface exposed. It was also shown that the technique of photo-sensitized labelling could be modified to induce cross-linking yielding a plasmin digestable product. These studies confirmed results from labelling studies which suggested that the chain C-terminii protect the N-terminal portion of fibrinogen. Calcium binding studies revealed two classes of high affinity calcium binding site in fibrinogen. Two sites of high (Kd > 10-5m) were shown to exist in the D-domains of the molecule, a third site of even higher affinity (Kd > 10-7m) was also found although the position of this site was not identified. These results of the study may be used to reconcile some of the more extreme views of fibrinogen shape as they suggest that fibrinogen is a protected trinodular structure.
1984-01-01T00:00:00ZBritton, David W.The main aims of this work were to develop and test methods for the analysis of the shape and calcium binding properties of fibrinogen and its degradation product fragment D. The techniques of photo-sensitized labelling and cross-linking were used to obtain information about the shape of these proteins and both revealed interesting information. Photosensitized labelling proved particularly useful and results obtained using this technique suggested that fragment D (Ca++) in solution and the fragment D domains of fibrinogen are conformationally very similar. These studies also suggested that the A chain of fibrinogen is highly exposed at the surface of the molecule and that it shields other portions, particularly the D-domains of the molecule. The use of chemical cross-linking reagents revealed a gross-conformational difference between fragment D (Ca++) and fragment D (EDTA) and it was further shown that this difference is a result of cleavage of the chain of fragment D (Ca++) rather than calcium removal. This suggests that the calcium ion bound by fragment D (Ca++) exercises a protective influence over a plasmin susceptible bond and that cleavage of this bond allows a gross conformational change. This is consistent with the results from photo-sensitized labelling which showed the C-terminal portion of the chain of fragment D to the surface exposed. It was also shown that the technique of photo-sensitized labelling could be modified to induce cross-linking yielding a plasmin digestable product. These studies confirmed results from labelling studies which suggested that the chain C-terminii protect the N-terminal portion of fibrinogen. Calcium binding studies revealed two classes of high affinity calcium binding site in fibrinogen. Two sites of high (Kd > 10-5m) were shown to exist in the D-domains of the molecule, a third site of even higher affinity (Kd > 10-7m) was also found although the position of this site was not identified. These results of the study may be used to reconcile some of the more extreme views of fibrinogen shape as they suggest that fibrinogen is a protected trinodular structure.The structure and properties of human fibrinogen fragment DLawrie, Jan Sloanehttps://hdl.handle.net/10023/149532019-03-29T10:42:37Z1980-01-01T00:00:00Z(1) Three molecular weight forms of fragment D were isolated from a plasmic digest of human fibrinogen. Further heterogeneities within the preparation were revealed by NH2-terminal amino acid analysis and by digestion studies performed in the presence of 2 N-urea; the existence of conformationally different forms of the fragment D molecule is proposed. (2) Plasmic digestion of fibrinogen in the presence of 2 md-Ca2+ produced a homogeneous high molecular weight preparation of fragment D (designated DCa 2+) In the absence of Ca2+ or in the presence of EDTA, two lower molecular weight forms of fragment D, each containing a more degraded constituent γ chain, were identified. In the presence of 2 N-urea only slight plasmic degradation of fragment DCa2+ occurred. (3) Increased SDS-gel electrophoretic mobilities were demonstrated for the fragments D and Y prepared from fibrinogen in the presence of Ca2+. An anomalous electrophoretic mobility pattern was also described for the constituent γ chain of fragment DCa2+ and of fibrinogen exposed to Ca2+. It is suggested that Ca2+ bound to the constituent γ chain of fibrinogen and fragment D forms an intra chain Ca2+ -bridge towards the COOH-terminus thereby maintaining a 'hook-like' conformation. This form of fragment D, it is proposed, exhibits a decreased susceptibility to plasmic attack and an anomalously low electrophoretic mobility. (4) A method was developed employing ion-exchange chromatography and gel filtration for the preparation and isolation of fragment D both in the presence and absence of free Ca2+. (5) Studies employing purified samples of each type of fragment D confirmed that the two molecules differed in the extent of degradation of the constituent γ chain at the COOH-terminus. Furthermore an influence of Ca2+ on the charge heterogeneity of fragment D preparations was concluded from isoelectric focussing studies. (6) The proposal of a compact and thereby stable structure for the fragment DCa2+ molecule was strengthened by the results obtained from studies employing chemical crosslinking reagents and the technique of ultracentrifugation. (7) The possibility that serine, glycine and glutamate amino acid residues are located in the region of the γ chain associated with the binding of Ca2+ was suggested from amino acid analysis of fragment D.
1980-01-01T00:00:00ZLawrie, Jan Sloane(1) Three molecular weight forms of fragment D were isolated from a plasmic digest of human fibrinogen. Further heterogeneities within the preparation were revealed by NH2-terminal amino acid analysis and by digestion studies performed in the presence of 2 N-urea; the existence of conformationally different forms of the fragment D molecule is proposed. (2) Plasmic digestion of fibrinogen in the presence of 2 md-Ca2+ produced a homogeneous high molecular weight preparation of fragment D (designated DCa 2+) In the absence of Ca2+ or in the presence of EDTA, two lower molecular weight forms of fragment D, each containing a more degraded constituent γ chain, were identified. In the presence of 2 N-urea only slight plasmic degradation of fragment DCa2+ occurred. (3) Increased SDS-gel electrophoretic mobilities were demonstrated for the fragments D and Y prepared from fibrinogen in the presence of Ca2+. An anomalous electrophoretic mobility pattern was also described for the constituent γ chain of fragment DCa2+ and of fibrinogen exposed to Ca2+. It is suggested that Ca2+ bound to the constituent γ chain of fibrinogen and fragment D forms an intra chain Ca2+ -bridge towards the COOH-terminus thereby maintaining a 'hook-like' conformation. This form of fragment D, it is proposed, exhibits a decreased susceptibility to plasmic attack and an anomalously low electrophoretic mobility. (4) A method was developed employing ion-exchange chromatography and gel filtration for the preparation and isolation of fragment D both in the presence and absence of free Ca2+. (5) Studies employing purified samples of each type of fragment D confirmed that the two molecules differed in the extent of degradation of the constituent γ chain at the COOH-terminus. Furthermore an influence of Ca2+ on the charge heterogeneity of fragment D preparations was concluded from isoelectric focussing studies. (6) The proposal of a compact and thereby stable structure for the fragment DCa2+ molecule was strengthened by the results obtained from studies employing chemical crosslinking reagents and the technique of ultracentrifugation. (7) The possibility that serine, glycine and glutamate amino acid residues are located in the region of the γ chain associated with the binding of Ca2+ was suggested from amino acid analysis of fragment D.Seasonal variations in the biochemical composition and ultrastructure of liver and skeletal muscles in the dab 'Limanda limanda (L.)'Yu-shi, Zhanghttps://hdl.handle.net/10023/149422019-03-29T10:41:02Z1994-01-01T00:00:00ZChapter 1 General introduction Section 1 contains a brief review of the structure and function of different muscle fibre types in teleost fish. Section 2 concerns the structure and function of fish liver including the classification of different liver cell types, the ultrastructure of fish hepatocytes and liver metabolism Section 3 The concepts of evolutionary adaptation and physiological acclimation are explained and an outline is given of some of the underlying cellular and molecular mechanisms. Chapter 2 Seasonal influences on the biochemical composition of tissues in dab (Limanda limanda L.) Seasonal changes in the biochemical composition of liver and skeletal muscle have been investigated in juvenile dab (Limanda limanda L.) from the wild. Chapter 3 Seasonal influences on the ultrastructure of myotomal muscles of dab CLimanda limanda L.) Seasonal influences on the ultrastructure of myotomal muscles of the immature dab (Limanda limanda L.) have been studied. Fish specimens were taken from the same population of animals as in chapter 2. The fractional volume (%) of each fibre type occupied by mitochondria, myofibrils and lipid droplets was determined using a point counting morphormetric method. Chapter 4 Seasonal influenes on the ultrastructure of hepatocytes of dab (Limanda limanda L.) The dab (Limanda limanda L.) exhibited marked seasonal alterations in the ultrastructure of hepatocytes during the year. Endoplasmic reticulum (ER) was more dilated and Golgi complex were highly developed in the hepatocytes of winter- adapted dabs. Mitochondrial profiles were also found to be well organized in the hepatocytes of winter caught animals. The hepatocytes in the summer-adapted dabs were characterised by containing enormous lipid droplets whereas those in the autumn-adapted fish were featured by numerous lipopigment-like granules. Different forms of hepatic glycogen and triglyceride were observed in the hepatocytes of dab (Limanda limanda L.) throughout the year. In the autumn, the hepatic glycogen and triglyceride existed in a form of loosely packed homogeneous masses throughout the cytoplasm whereas a more densely packed form for both glycogen and triglyceride was observed during the winter. Chapter 5 General discussion The major findings in the present study are discussed in relation to seasonal influences on tissue composition and ultrastructure of myotomal muscle fibres and hepatocytes in the juvenile dab (Limanda limanda L.). Some suggestions for further works are given.
1994-01-01T00:00:00ZYu-shi, ZhangChapter 1 General introduction Section 1 contains a brief review of the structure and function of different muscle fibre types in teleost fish. Section 2 concerns the structure and function of fish liver including the classification of different liver cell types, the ultrastructure of fish hepatocytes and liver metabolism Section 3 The concepts of evolutionary adaptation and physiological acclimation are explained and an outline is given of some of the underlying cellular and molecular mechanisms. Chapter 2 Seasonal influences on the biochemical composition of tissues in dab (Limanda limanda L.) Seasonal changes in the biochemical composition of liver and skeletal muscle have been investigated in juvenile dab (Limanda limanda L.) from the wild. Chapter 3 Seasonal influences on the ultrastructure of myotomal muscles of dab CLimanda limanda L.) Seasonal influences on the ultrastructure of myotomal muscles of the immature dab (Limanda limanda L.) have been studied. Fish specimens were taken from the same population of animals as in chapter 2. The fractional volume (%) of each fibre type occupied by mitochondria, myofibrils and lipid droplets was determined using a point counting morphormetric method. Chapter 4 Seasonal influenes on the ultrastructure of hepatocytes of dab (Limanda limanda L.) The dab (Limanda limanda L.) exhibited marked seasonal alterations in the ultrastructure of hepatocytes during the year. Endoplasmic reticulum (ER) was more dilated and Golgi complex were highly developed in the hepatocytes of winter- adapted dabs. Mitochondrial profiles were also found to be well organized in the hepatocytes of winter caught animals. The hepatocytes in the summer-adapted dabs were characterised by containing enormous lipid droplets whereas those in the autumn-adapted fish were featured by numerous lipopigment-like granules. Different forms of hepatic glycogen and triglyceride were observed in the hepatocytes of dab (Limanda limanda L.) throughout the year. In the autumn, the hepatic glycogen and triglyceride existed in a form of loosely packed homogeneous masses throughout the cytoplasm whereas a more densely packed form for both glycogen and triglyceride was observed during the winter. Chapter 5 General discussion The major findings in the present study are discussed in relation to seasonal influences on tissue composition and ultrastructure of myotomal muscle fibres and hepatocytes in the juvenile dab (Limanda limanda L.). Some suggestions for further works are given.The effects of temperature acclimation on the structure and function of myotomal muscles from the carp (Cyprimus carpio, L.)Fleming, John Richardhttps://hdl.handle.net/10023/149412019-03-29T10:40:03Z1989-01-01T00:00:00ZChapter One Introduction Research in the structure, biochemistry, electrophysiology and mechanical properties of fish muscle is reviewed. A variety of mechanisms underlying temperature acclimation and adaptation is described. Chapter Two The effects of temperature acclimation on muscle relaxation in the carp (Cvprinus carpio L.1 1. Common carp were acclimated to either 7 or 21 ° for a minimum of one month, and the twitch contraction kinetics of a nerve-muscle preparation investigated. 2. A significant compensation for the acute effects of a temperature change was achieved in twitch kinetics by acclimation to 8 °. An acute drop in temperature from 20 to 8 ° in 20 °-acclimated preparations led to approximately 2 and 3 fold increases in the half times for activation and relaxation. Chapter Three The effects of temperature acclimation on the pCa-tension relationship of slow myotomal muscle fibres from the carp 1. Common carp Cvprinus carpio L.) were acclimated to either 7 ° or 2 3 ° for at least one month. 2. The pCa-tension relationship of skinned slow fibres isolated from the anterior myotomes was investigated at pH 7.0, 7.6 and at 0 ° and 15 °. 3. Sigmoid pCa-tension curves were obtained with 'n' (i.e. Hill coefficient) values between 2 and 3. 4. Temperature acclimation did not alter the sensitivity of the contractile apparatus to calcium under any of the conditions of pH or temperature investigated. Chapter Four The role of thyroid hormones in temperature acclimation 1. Common carp (Cyprinus carpio L.) were acclimated to either 8 ° or 22 ° for at least one month. 2. One group of cold-acclimated fish were made hypothyroid by treatment with methimazole (80mg/100ml 0.9% NaCl) 0.5?g/g body weight once every two days. 3. The level of T3 and T4 in the plasma of carp was determined using a radioimmunoassay technique. 4. Frozen sections of m. hyohyoideus muscles were cut and stained for the activity of succinic dehydrogenase and alkali-stable myosin ATPase to determine the percentage cross-sectional area of different fibre types. 5. m. hyohyoideus muscles from cold-acclimated fish had a higher proportion of slow oxidative fibres and fast oxidative glycolytic fibres than similar muscles from warm-acclimated carp. 6. The ultrastructure of slow myotomal muscle was investigated by electron microscopy. The volume fraction of mitochondria was higher in fibres from cold- than warm-acclimated fish (P<0.01). The volume fraction of myofibrils decreased in the series cold-acclimated > warm-acclimated > cold-acclimated, hypothyroid (P<0.01). The mean cross sectional area of individual myofibrils decreased in the series, warm-acclimated > cold-acclimated > cold-acclimated hypothyroid. 7. Hypothyroidism did not affect the total volume fraction of mitochondria in cold-acclimated fish. The volume fraction of mitochondria in the intermyofibrillar zone was higher in cold-acclimated euthyroid than hypothyroid fish (P<0.001). 8. Neither temperature acclimation nor hypothyroidism affected the volume or surface density of cristae within mitochondria. 9. The effects of temperature acclimation and hypothyroidism on the performance, composition and ultrastructure of muscle are compared and the involvement of thyroid hormones in temperature acclimation is discussed. Chapter Five General Discussion The results presented in this report are discussed in the context of providing mechanisms that may compensate for the effects of low temperature on the rate of diffusion of small molecules through the cytosol.
1989-01-01T00:00:00ZFleming, John RichardChapter One Introduction Research in the structure, biochemistry, electrophysiology and mechanical properties of fish muscle is reviewed. A variety of mechanisms underlying temperature acclimation and adaptation is described. Chapter Two The effects of temperature acclimation on muscle relaxation in the carp (Cvprinus carpio L.1 1. Common carp were acclimated to either 7 or 21 ° for a minimum of one month, and the twitch contraction kinetics of a nerve-muscle preparation investigated. 2. A significant compensation for the acute effects of a temperature change was achieved in twitch kinetics by acclimation to 8 °. An acute drop in temperature from 20 to 8 ° in 20 °-acclimated preparations led to approximately 2 and 3 fold increases in the half times for activation and relaxation. Chapter Three The effects of temperature acclimation on the pCa-tension relationship of slow myotomal muscle fibres from the carp 1. Common carp Cvprinus carpio L.) were acclimated to either 7 ° or 2 3 ° for at least one month. 2. The pCa-tension relationship of skinned slow fibres isolated from the anterior myotomes was investigated at pH 7.0, 7.6 and at 0 ° and 15 °. 3. Sigmoid pCa-tension curves were obtained with 'n' (i.e. Hill coefficient) values between 2 and 3. 4. Temperature acclimation did not alter the sensitivity of the contractile apparatus to calcium under any of the conditions of pH or temperature investigated. Chapter Four The role of thyroid hormones in temperature acclimation 1. Common carp (Cyprinus carpio L.) were acclimated to either 8 ° or 22 ° for at least one month. 2. One group of cold-acclimated fish were made hypothyroid by treatment with methimazole (80mg/100ml 0.9% NaCl) 0.5?g/g body weight once every two days. 3. The level of T3 and T4 in the plasma of carp was determined using a radioimmunoassay technique. 4. Frozen sections of m. hyohyoideus muscles were cut and stained for the activity of succinic dehydrogenase and alkali-stable myosin ATPase to determine the percentage cross-sectional area of different fibre types. 5. m. hyohyoideus muscles from cold-acclimated fish had a higher proportion of slow oxidative fibres and fast oxidative glycolytic fibres than similar muscles from warm-acclimated carp. 6. The ultrastructure of slow myotomal muscle was investigated by electron microscopy. The volume fraction of mitochondria was higher in fibres from cold- than warm-acclimated fish (P<0.01). The volume fraction of myofibrils decreased in the series cold-acclimated > warm-acclimated > cold-acclimated, hypothyroid (P<0.01). The mean cross sectional area of individual myofibrils decreased in the series, warm-acclimated > cold-acclimated > cold-acclimated hypothyroid. 7. Hypothyroidism did not affect the total volume fraction of mitochondria in cold-acclimated fish. The volume fraction of mitochondria in the intermyofibrillar zone was higher in cold-acclimated euthyroid than hypothyroid fish (P<0.001). 8. Neither temperature acclimation nor hypothyroidism affected the volume or surface density of cristae within mitochondria. 9. The effects of temperature acclimation and hypothyroidism on the performance, composition and ultrastructure of muscle are compared and the involvement of thyroid hormones in temperature acclimation is discussed. Chapter Five General Discussion The results presented in this report are discussed in the context of providing mechanisms that may compensate for the effects of low temperature on the rate of diffusion of small molecules through the cytosol.The effects of temperature acclimation on the expression of contractile protein isoforms in the skeletal muscle of the common carp (Cyprinus carpio)Crockford, Tonyhttps://hdl.handle.net/10023/149402019-03-29T10:42:49Z1989-01-01T00:00:00ZChapter 1. Part A reviews the current knowledge of temperature acclimation in teleost fish,with particular emphasis on skeletal muscle. There appear to be two types of response to low temperatures, dormancy or a homeostatic response. The homeostatic response serves to compensate for the reduced reaction rate usually seen at lower temperatures. In some species both responses occur depending on the water temperature. Part B reviews polymorphism in muscle proteins. All the myofibrillar proteins have been shown to exist as isoforms, which are differentially expressed in muscle types and with development. The isoforms expressed appear to be related to the contractile properties of the muscle. Chapter 2. The parvalbumin content, isoforms, and calcium binding characteristics were studied in the white muscle of 5° and 25° acclimated carp (Cyprinus carpio). The total parvalbumin concentration was 0.61-0.68mmols/kg wet weight. Two calcium binding sites per molecule and a dissociation constant of 2.1-2.4x10<super>-6</super> M were measured. No differences related to acclimation temperature were observed. Chapter 3. The myofibrillar ATPase from white muscle of 8° and 20°C acclimated carp (Cyprinus carpio) u/as shown to increase in cold-acclimated fish at both high and low assay temperatures. Electrophoretic analysis of the myofibrillar proteins showed a unique myosin light chain isoform to be present in cold-acclimated fish, and a unique troponin I isoform to be present in warm acclimated fish. The presence of tropomyosin and troponin T isoforms in carp white muscle was also noted. The (MLC3 + extra MLC):MLC1 ratio was found to be lower in cold- than in warm-acclimated fish Chapter 4. Myosin heavy chains and actin from the white muscle of carp (Cyprinus carpio) acclimated to 2°, 5°, 8°, 11°
C, 15°, and 23° were studied by peptide mapping. No differences were found between fish from any of the acclimation temperatures for either protein. Chapter 5. The major findings of the study are discussed, in relation to the mechanisms that produce protein isoforms, and with reference to further studies.
1989-01-01T00:00:00ZCrockford, TonyChapter 1. Part A reviews the current knowledge of temperature acclimation in teleost fish,with particular emphasis on skeletal muscle. There appear to be two types of response to low temperatures, dormancy or a homeostatic response. The homeostatic response serves to compensate for the reduced reaction rate usually seen at lower temperatures. In some species both responses occur depending on the water temperature. Part B reviews polymorphism in muscle proteins. All the myofibrillar proteins have been shown to exist as isoforms, which are differentially expressed in muscle types and with development. The isoforms expressed appear to be related to the contractile properties of the muscle. Chapter 2. The parvalbumin content, isoforms, and calcium binding characteristics were studied in the white muscle of 5° and 25° acclimated carp (Cyprinus carpio). The total parvalbumin concentration was 0.61-0.68mmols/kg wet weight. Two calcium binding sites per molecule and a dissociation constant of 2.1-2.4x10<super>-6</super> M were measured. No differences related to acclimation temperature were observed. Chapter 3. The myofibrillar ATPase from white muscle of 8° and 20°C acclimated carp (Cyprinus carpio) u/as shown to increase in cold-acclimated fish at both high and low assay temperatures. Electrophoretic analysis of the myofibrillar proteins showed a unique myosin light chain isoform to be present in cold-acclimated fish, and a unique troponin I isoform to be present in warm acclimated fish. The presence of tropomyosin and troponin T isoforms in carp white muscle was also noted. The (MLC3 + extra MLC):MLC1 ratio was found to be lower in cold- than in warm-acclimated fish Chapter 4. Myosin heavy chains and actin from the white muscle of carp (Cyprinus carpio) acclimated to 2°, 5°, 8°, 11°
C, 15°, and 23° were studied by peptide mapping. No differences were found between fish from any of the acclimation temperatures for either protein. Chapter 5. The major findings of the study are discussed, in relation to the mechanisms that produce protein isoforms, and with reference to further studies.Migration and habitat use of dace (Leuciscus leuciscus (L.)) in an English chalk streamClough, Stuarthttps://hdl.handle.net/10023/149392020-01-07T12:16:14Z1999-01-01T00:00:00ZThe dace (Leuciscus leuciscus (L.)) is a small, shoaling, rheophilic, lithophilic cyprinid fish, and is an important component of chalk stream ecosystems. Historical recaptures of marked dace in the River Frome suggested that some individuals were mobile, however it was unclear whether these movements occurred predictably in time or space. Migrations, defined as deliberate, temporally predictable translocations in space, allow individuals to exploit new resources, avoid predators and find a mate. However, energy is generally utilised during locomotion, and there are potential costs associated with moving to an unfamiliar environment, including reduced foraging opportunities, and increased predation risk. To be successful, individuals must find food, avoid predation and reproduce. If adult dace can solve these problems efficiently in one section of river, then considering the potential costs associated with migration, it would be most profitable for them to remain in this area. A range of techniques were used to study the migrations and habitat use of adult dace in the River Frome, covering both daily and seasonal cycles. The movements of 32 radio-tagged dace were tracked over a period covering over 16,000 hours. During this period 6864 radio locations were made, and radiotagged fish covered a combined minimum distance of over 109 km. A further 1724 dace were individually or batch marked, of which 128 were recaptured. In addition over 4000 dace were recorded on video as they passed through a fish counter. The daylight habitat use of 377 adult dace was visually observed from the bank, and habitat suitability indices created. The nocturnal habitat use of 11 adult dace was assessed using radio-active isotope tags, which were located on 247 occasions over a period covering 121 "fish nights". The adult dace observed in this study moved extensively, and their movements were both temporally and spatially predictable, and therefore constituted migrations. Of the 30 fish released at their capture sites, at least 19 moved more than 500m fi-om this site during the observation period. Spawning occurred in millstreams, and was preceded by an upstream migration. After spawning, slow flowing shaded sites out of the main river were selected by at least five out of six radio-tagged dace. A substantial upstream migration was observed in late spring, and diel migrations between separate distinct day and night habitats were observed during the summer. In autumn adult dace moved downstream and formed aggregations in the tidal reaches. Consequently, the hypothesis that dace occupy one section of the river throughout the year was rejected.
1999-01-01T00:00:00ZClough, StuartThe dace (Leuciscus leuciscus (L.)) is a small, shoaling, rheophilic, lithophilic cyprinid fish, and is an important component of chalk stream ecosystems. Historical recaptures of marked dace in the River Frome suggested that some individuals were mobile, however it was unclear whether these movements occurred predictably in time or space. Migrations, defined as deliberate, temporally predictable translocations in space, allow individuals to exploit new resources, avoid predators and find a mate. However, energy is generally utilised during locomotion, and there are potential costs associated with moving to an unfamiliar environment, including reduced foraging opportunities, and increased predation risk. To be successful, individuals must find food, avoid predation and reproduce. If adult dace can solve these problems efficiently in one section of river, then considering the potential costs associated with migration, it would be most profitable for them to remain in this area. A range of techniques were used to study the migrations and habitat use of adult dace in the River Frome, covering both daily and seasonal cycles. The movements of 32 radio-tagged dace were tracked over a period covering over 16,000 hours. During this period 6864 radio locations were made, and radiotagged fish covered a combined minimum distance of over 109 km. A further 1724 dace were individually or batch marked, of which 128 were recaptured. In addition over 4000 dace were recorded on video as they passed through a fish counter. The daylight habitat use of 377 adult dace was visually observed from the bank, and habitat suitability indices created. The nocturnal habitat use of 11 adult dace was assessed using radio-active isotope tags, which were located on 247 occasions over a period covering 121 "fish nights". The adult dace observed in this study moved extensively, and their movements were both temporally and spatially predictable, and therefore constituted migrations. Of the 30 fish released at their capture sites, at least 19 moved more than 500m fi-om this site during the observation period. Spawning occurred in millstreams, and was preceded by an upstream migration. After spawning, slow flowing shaded sites out of the main river were selected by at least five out of six radio-tagged dace. A substantial upstream migration was observed in late spring, and diel migrations between separate distinct day and night habitats were observed during the summer. In autumn adult dace moved downstream and formed aggregations in the tidal reaches. Consequently, the hypothesis that dace occupy one section of the river throughout the year was rejected.The phenotypic plasticity of whole animal and muscle performance during fast-starts in CottidaeTemple, Genevieve Katehttps://hdl.handle.net/10023/149382019-03-29T10:28:52Z1998-01-01T00:00:00ZChapter 1. Fast-starts are used by most fish species in order to capture prey and escape predators. An introduction to this mode of fish locomotion and the structure and function of the muscle powering swimming movements, is given. Temperature has the potential to alter fast-start behaviour at various levels of organisation ranging from the whole animal to the molecular and can act over time scales extending from the immediate to the evolutionary. The thermal dependence of fast-start performance is discussed. Chapter 2. The effects of acclimation and acute temperature on the kinematics of the escape response in two species of maidne Cottidae, the short-horn sculpin (Myoxocephalus scorpius L.) and the long-spined sea scorpion (Taurulus bubalis Euphr.) were examined. Hypotheses were formulated based on relevant studies and the natural history of the fish to test the idea that seasonal temperature acclimation conferred a fitness advantage and to examine whether acclimation responses were constant through development. Chapter 3. The effect of seasonal thermal acclimation on the in vivo strain and power output of the fast muscle fibres during escape responses in the short- horn sculpin was examined. Chapter 4. The kinematics, in vivo muscle action, power output and energetics of escape and prey capture responses in the short-horn sculpin are discussed. Fast-starts were filmed using high speed video synchronised with sonomicrometry and EMG. The in vivo muscle strain and activation recordings were abstracted for use in work loop experiments. Changes in the metabolic substrates following work loops from the two different types of fast-starts were analysed using high performance liquid chromatography (HPLC). Chapter 5 The velocity of the wave of curvature passing down the fish and the power requirements during fast-start escape responses were calculated non-invasively. This was carried out on both cottid species acclimated to 5 and 15 ° and filmed using high speed cinematography at 0.8, 5.0, 15.0 and 20.0 °. The power requirements for the contralateral contraction were 20 W. kg-1 muscle in 5 °-acclimated fish escaping at 5 ° and 58 W. kg-1 muscle in 15 °-acclimated fish swimming at 15 °. Comparative values of power output measured from work loop experiments in Chapter 3 were 33 and 66 W.kg-1 respectively.
1998-01-01T00:00:00ZTemple, Genevieve KateChapter 1. Fast-starts are used by most fish species in order to capture prey and escape predators. An introduction to this mode of fish locomotion and the structure and function of the muscle powering swimming movements, is given. Temperature has the potential to alter fast-start behaviour at various levels of organisation ranging from the whole animal to the molecular and can act over time scales extending from the immediate to the evolutionary. The thermal dependence of fast-start performance is discussed. Chapter 2. The effects of acclimation and acute temperature on the kinematics of the escape response in two species of maidne Cottidae, the short-horn sculpin (Myoxocephalus scorpius L.) and the long-spined sea scorpion (Taurulus bubalis Euphr.) were examined. Hypotheses were formulated based on relevant studies and the natural history of the fish to test the idea that seasonal temperature acclimation conferred a fitness advantage and to examine whether acclimation responses were constant through development. Chapter 3. The effect of seasonal thermal acclimation on the in vivo strain and power output of the fast muscle fibres during escape responses in the short- horn sculpin was examined. Chapter 4. The kinematics, in vivo muscle action, power output and energetics of escape and prey capture responses in the short-horn sculpin are discussed. Fast-starts were filmed using high speed video synchronised with sonomicrometry and EMG. The in vivo muscle strain and activation recordings were abstracted for use in work loop experiments. Changes in the metabolic substrates following work loops from the two different types of fast-starts were analysed using high performance liquid chromatography (HPLC). Chapter 5 The velocity of the wave of curvature passing down the fish and the power requirements during fast-start escape responses were calculated non-invasively. This was carried out on both cottid species acclimated to 5 and 15 ° and filmed using high speed cinematography at 0.8, 5.0, 15.0 and 20.0 °. The power requirements for the contralateral contraction were 20 W. kg-1 muscle in 5 °-acclimated fish escaping at 5 ° and 58 W. kg-1 muscle in 15 °-acclimated fish swimming at 15 °. Comparative values of power output measured from work loop experiments in Chapter 3 were 33 and 66 W.kg-1 respectively.Endocrine control of osmoregulation in the euryhaline eel, 'Anguilla anguilla'Tierney, Mary Louisehttps://hdl.handle.net/10023/149362021-02-23T15:25:22Z1993-01-01T00:00:00Z1. Groups of eels, Anguilla anguilla, were adapted from freshwater (FW) to seawater, (SW) for periods of 90 - 300 mins. maximum (acute transfer), 0 - 7 days (chronic transfer), or for more than 14 days (longterm seawater transfer). 2. Acute SW transfer led to a decline in blood pressure, an elevation in plasma osmolality and chloride concentration, an immediate "reflex" drinking response and a non-significant increase in plasma angiotensin II (AH) concentration. 3. Administration of papaverine to FW adapted eel caused hypotension, with subsequent recovery of blood pressure, elevation in the drinking rate and plasma All concentration, and a decline in plasma osmolality. Captopril alone had no effect on blood pressure, drinking rate, osmolality or All concentration, but was successful in partially blocking the papaverine-induced blood pressure recovery and increase in AH concentration, with complete inhibition of the drinking. 4. Administration of papaverine to SW adapted eel caused hypotension, with partial recovery of blood pressure, increased drinking rate, plasma All concentration and plasma osmolality. Captopril alone caused a sustained decrease in blood pressure, inhibition of basal SW drinking and a reduction in plasma All concentration, with change in plasma osmolality. Administration of captopril prior to papaverine was successful in partially blocking the papaverine-induced recovery in blood pressure, increase in drinking, plasma All concentration, and plasma osmolality. 5. Chronic SW transfer led to a general decline in blood pressure, increase in plasma electrolyte concentration, elevation in drinking rate after 4-5 days, an increase in plasma All concentration, and a rise in Na+-K+-ATPase, all leading to long term SW values. 6. Plasma arginine vasotocin concentrations were unchanged in long term-FW and SW adapted fish, with a small transitory rise after 4 days in SW. 7. Cortisol plasma concentrations were similar in both long term- FW and SW- adapted fish, with a rise observed 1 day after transfer to SW. 8. Metabolic clearance rates (MCR) and blood production rates (BPR) were significantly elevated in long term SW adapted fish and during chronic SW adaptation, compared to the FW levels. Binding of 125I-AII to gill (filaments and lamellae), brain (cerebellum and medulla oblongata), kidney (head and caudal), and liver was observed in long term FW and SW adapted fish and 6 day SW transfer animals, with significant increase observed in binding in the caudal kidney and cerebellum and medulla oblongata between the FW group and 6 day SW transfer group.
1993-01-01T00:00:00ZTierney, Mary Louise1. Groups of eels, Anguilla anguilla, were adapted from freshwater (FW) to seawater, (SW) for periods of 90 - 300 mins. maximum (acute transfer), 0 - 7 days (chronic transfer), or for more than 14 days (longterm seawater transfer). 2. Acute SW transfer led to a decline in blood pressure, an elevation in plasma osmolality and chloride concentration, an immediate "reflex" drinking response and a non-significant increase in plasma angiotensin II (AH) concentration. 3. Administration of papaverine to FW adapted eel caused hypotension, with subsequent recovery of blood pressure, elevation in the drinking rate and plasma All concentration, and a decline in plasma osmolality. Captopril alone had no effect on blood pressure, drinking rate, osmolality or All concentration, but was successful in partially blocking the papaverine-induced blood pressure recovery and increase in AH concentration, with complete inhibition of the drinking. 4. Administration of papaverine to SW adapted eel caused hypotension, with partial recovery of blood pressure, increased drinking rate, plasma All concentration and plasma osmolality. Captopril alone caused a sustained decrease in blood pressure, inhibition of basal SW drinking and a reduction in plasma All concentration, with change in plasma osmolality. Administration of captopril prior to papaverine was successful in partially blocking the papaverine-induced recovery in blood pressure, increase in drinking, plasma All concentration, and plasma osmolality. 5. Chronic SW transfer led to a general decline in blood pressure, increase in plasma electrolyte concentration, elevation in drinking rate after 4-5 days, an increase in plasma All concentration, and a rise in Na+-K+-ATPase, all leading to long term SW values. 6. Plasma arginine vasotocin concentrations were unchanged in long term-FW and SW adapted fish, with a small transitory rise after 4 days in SW. 7. Cortisol plasma concentrations were similar in both long term- FW and SW- adapted fish, with a rise observed 1 day after transfer to SW. 8. Metabolic clearance rates (MCR) and blood production rates (BPR) were significantly elevated in long term SW adapted fish and during chronic SW adaptation, compared to the FW levels. Binding of 125I-AII to gill (filaments and lamellae), brain (cerebellum and medulla oblongata), kidney (head and caudal), and liver was observed in long term FW and SW adapted fish and 6 day SW transfer animals, with significant increase observed in binding in the caudal kidney and cerebellum and medulla oblongata between the FW group and 6 day SW transfer group.Assessment of stress and growth of the eel "Anguilla anguilla" in a closed recirculating aquaculture systemDavid, Christopher Grahamhttps://hdl.handle.net/10023/149352021-02-23T15:24:12Z1997-01-01T00:00:00Z1) Closed recirculating intensive aquaculture potentially offers major advantages over existing technologies including reduction in normal production time, reduced water input and output and beneficial environmental effects. 2) The major aim of this study was to produce a basic scientific understanding of the factors that affect intensive recirculating culture of the European eel Anguilla anguilla in order to increase efficiency and economic viability of eel aquaculture in the E.U. 3) Unlike some intensively farmed fish such as salmonids little is known of the stress factors affecting optimal growth rates in intensive eel culture. The primary effects of stress are mediated by corticosteroids and catecholamines which may have profound effects on growth, appetite and ion and water balance. 4) Growth rates of the eel Anguilla anguilla were investigated in closed water recirculating systems utilising fresh water or saline water (12 ppt)at 23°C. Eels were initially graded into two similar populations consisting of three categories, small (12g), medium (24g) and large (48g) based on initial growth rates. 5) During a 300 day period the medium and large group's growth rates were significantly greater in 12 ppt saline water than in fresh water, although for the small fish group there was no such difference. Stocking densities were maintained at commercial levels of approximately 30-100 kg/m3. 6) Plasma cortisol concentrations increased throughout the growth period in both fresh and saline water, although there were no significant differences between the two groups during the experiment. Metabolic clearance rates of cortisol were however consistently higher in saline water fish. 7) Both groups showed an increase in plasma glucose concentration throughout the experiment. However there were no significant differences between fresh water and saline water fish for plasma concentrations of glucose, free fatty acids or lactate. 8) Eels held at stocking densities of 130 kg/m3 continued to grow in the saline water whereas the control fish in fresh water ceased growing. The results suggest that maintaining water salinity at 12 ppt in closed recirculating aquaculture systems produces increased growth rates and possibly increased efficiency of food conversion. 9) In response to acute grading stress, plasma osmolality and glucose concentrations were elevated in both fresh and salt water groups 20 minutes after grading but returned to pre-grading values within 90 minutes. Plasma cortisol concentrations were elevated after 20 and 40 minutes in saline water but returned to control values after 90 minutes. In fresh water fish, plasma cortisol concentrations were elevated after 20 minutes and remained elevated throughout the experiment. 10) Acute netting stress (tank transfer) resulted in a transient increase in plasma osmolality within 20 minutes after net transfer. Plasma cortisol concentrations were significantly elevated after 20 minutes in saline water but returned to control values after 60'minutes. In fresh water fish, plasma cortisol concentrations were elevated throughout the 90 minute period monitored after net transfer. 11) In both cases of acute stress (netting and grading), plasma catecholamines were elevated within a five minute period after the stressor was applied. This study has developed techniques to assess both long-term and short-term stress in eels and has optimised the environmental conditions leading to improved growth rates. Improvements in the performance of recirculating aquaculture for on-growing eels have been demonstrated and suggestions for future possible improvements as a way forward in commercial aquaculture have been suggested. These factors will, hopefully, lead to increased economic efficiency and increased profits in eel aquaculture within the E.U.
1997-01-01T00:00:00ZDavid, Christopher Graham1) Closed recirculating intensive aquaculture potentially offers major advantages over existing technologies including reduction in normal production time, reduced water input and output and beneficial environmental effects. 2) The major aim of this study was to produce a basic scientific understanding of the factors that affect intensive recirculating culture of the European eel Anguilla anguilla in order to increase efficiency and economic viability of eel aquaculture in the E.U. 3) Unlike some intensively farmed fish such as salmonids little is known of the stress factors affecting optimal growth rates in intensive eel culture. The primary effects of stress are mediated by corticosteroids and catecholamines which may have profound effects on growth, appetite and ion and water balance. 4) Growth rates of the eel Anguilla anguilla were investigated in closed water recirculating systems utilising fresh water or saline water (12 ppt)at 23°C. Eels were initially graded into two similar populations consisting of three categories, small (12g), medium (24g) and large (48g) based on initial growth rates. 5) During a 300 day period the medium and large group's growth rates were significantly greater in 12 ppt saline water than in fresh water, although for the small fish group there was no such difference. Stocking densities were maintained at commercial levels of approximately 30-100 kg/m3. 6) Plasma cortisol concentrations increased throughout the growth period in both fresh and saline water, although there were no significant differences between the two groups during the experiment. Metabolic clearance rates of cortisol were however consistently higher in saline water fish. 7) Both groups showed an increase in plasma glucose concentration throughout the experiment. However there were no significant differences between fresh water and saline water fish for plasma concentrations of glucose, free fatty acids or lactate. 8) Eels held at stocking densities of 130 kg/m3 continued to grow in the saline water whereas the control fish in fresh water ceased growing. The results suggest that maintaining water salinity at 12 ppt in closed recirculating aquaculture systems produces increased growth rates and possibly increased efficiency of food conversion. 9) In response to acute grading stress, plasma osmolality and glucose concentrations were elevated in both fresh and salt water groups 20 minutes after grading but returned to pre-grading values within 90 minutes. Plasma cortisol concentrations were elevated after 20 and 40 minutes in saline water but returned to control values after 90 minutes. In fresh water fish, plasma cortisol concentrations were elevated after 20 minutes and remained elevated throughout the experiment. 10) Acute netting stress (tank transfer) resulted in a transient increase in plasma osmolality within 20 minutes after net transfer. Plasma cortisol concentrations were significantly elevated after 20 minutes in saline water but returned to control values after 60'minutes. In fresh water fish, plasma cortisol concentrations were elevated throughout the 90 minute period monitored after net transfer. 11) In both cases of acute stress (netting and grading), plasma catecholamines were elevated within a five minute period after the stressor was applied. This study has developed techniques to assess both long-term and short-term stress in eels and has optimised the environmental conditions leading to improved growth rates. Improvements in the performance of recirculating aquaculture for on-growing eels have been demonstrated and suggestions for future possible improvements as a way forward in commercial aquaculture have been suggested. These factors will, hopefully, lead to increased economic efficiency and increased profits in eel aquaculture within the E.U.Osmoregulation in glass eels and elvers of the European eel, 'Anguilla anguilla'Birrell, Lynne M.https://hdl.handle.net/10023/149342021-02-23T15:28:43Z1999-01-01T00:00:00ZGlass eels of the European eel migrate from coastal waters inland to freshwater as part of the catadromous lifecycle. The osmotic challenge faced at this time is augmented by their large surface area to volume ratio, and by the fact that the migration may only be completed after several attempts, due to the effects of tide and river flow. Glass eels and elvers developed normally when maintained in waters of differing salinity over a six month period. Drinking rates increased with environmental acclimation salinity (from 0.072 +/- 0.023 mul/g/h to 0.698 +/- 0.099 mul/g/h in FW and SW respectively), and freshwater acclimated fish exhibited a rapid drinking response upon contact with seawater. These accounts of dipsogenic behaviour are similar to those previously reported for adult eels. Results obtained from determinations of branchial Na+K+ATPase activities were more equivocal. Only after nearly five months were activities higher in SW (508.52 +/- 99.76 nmoles/Spairs gills/h) as compared to FW fish (151.65 +/- 8.9 nmoles/5pairs gills/h). Following the transfer of FW acclimated fish to SW there was a trend towards increased Na+K+ATPase activity after seven days post-transfer, which reached a significant peak after two months post-transfer. A transient increase in whole body cortisol content was noted following the transfer of fish from freshwater (388.02 + 90.38 pg/g) to seawater (6268.44 +/- 773.14 pg/g). However, it was not possible to ascertain that this was due to a direct effect of environmental salinity change. There were no clear changes in interrenal cell morphology between salinity groups, although the cells did appear reduced in size with time, regardless of environmental salinity. Total body Na+ content increased with time, and was higher in SW (58.66 +/- 1.66 mumoles/g) as compared to FW reared fish (44.85 +/-1.01 mumoles/g).
1999-01-01T00:00:00ZBirrell, Lynne M.Glass eels of the European eel migrate from coastal waters inland to freshwater as part of the catadromous lifecycle. The osmotic challenge faced at this time is augmented by their large surface area to volume ratio, and by the fact that the migration may only be completed after several attempts, due to the effects of tide and river flow. Glass eels and elvers developed normally when maintained in waters of differing salinity over a six month period. Drinking rates increased with environmental acclimation salinity (from 0.072 +/- 0.023 mul/g/h to 0.698 +/- 0.099 mul/g/h in FW and SW respectively), and freshwater acclimated fish exhibited a rapid drinking response upon contact with seawater. These accounts of dipsogenic behaviour are similar to those previously reported for adult eels. Results obtained from determinations of branchial Na+K+ATPase activities were more equivocal. Only after nearly five months were activities higher in SW (508.52 +/- 99.76 nmoles/Spairs gills/h) as compared to FW fish (151.65 +/- 8.9 nmoles/5pairs gills/h). Following the transfer of FW acclimated fish to SW there was a trend towards increased Na+K+ATPase activity after seven days post-transfer, which reached a significant peak after two months post-transfer. A transient increase in whole body cortisol content was noted following the transfer of fish from freshwater (388.02 + 90.38 pg/g) to seawater (6268.44 +/- 773.14 pg/g). However, it was not possible to ascertain that this was due to a direct effect of environmental salinity change. There were no clear changes in interrenal cell morphology between salinity groups, although the cells did appear reduced in size with time, regardless of environmental salinity. Total body Na+ content increased with time, and was higher in SW (58.66 +/- 1.66 mumoles/g) as compared to FW reared fish (44.85 +/-1.01 mumoles/g).The effect of hypoxia acclimation on the skeletal muscle of three freshwater fishesBernard, Lynne Millshttps://hdl.handle.net/10023/149322019-03-29T10:41:19Z1985-01-01T00:00:00ZMany species of fish may be exposed to hypoxia in their natural habitats, either on a temporary or a more permanent basis. The survival of the animal may then be dependent on its ability to adapt to the conditions imposed upon it. There are several known ways in which a fish may adapt itself to coping with reduced oxygen levels such as by alterations in respiratory and ventilatory capacities and by changes in the oxygen carrying capacity of the blood. This study examines the effects of acclimation to hypoxia on the oxygen consumption, muscle ultrastructure and capillarisation of three species of freshwater fishes. The species studied could all expect to experience hypoxia in their natural environments. The tench, Tinea tinca, would very probably become hypoxic during its winter hibernation buried in the mud at the bottom of ponds and rivers. The Crucian carp, Carassius carassius, inhabits sluggish or still waters where rotting vegetation reduces oxygen levels and it often spends its winters under complete or near complete anoxia in ice-locked ponds. In terms of muscle ultrastructure and capillary supply, three very different responses to hypoxia acclimation have been found in the three species under study. Considering only the parameters studied the following hypothesis are proposed to explain the changes observed. Previous studies suggest that the increases in oxygen consumption observed after acclimation to hypoxia are due in part to increases in the oxygen affinity of the haemoglobin caused by decreases in the concentrations of the red cell nucleoside triphosphates. The decreases in mitochondrial volume density and capillary supply in tench muscle after acclimation to hypoxia could be due to a reduced level of spontaneous locomotory activity. Tench experience hypoxia mainly during their hibernation period where they remain totally quiescent. Energy requirement would be very low and metabolic rate would drop so some of the mitochondria and capillaries not required might be degraded. The Crucian carp show a marked increase in volume density of mitochondria, especially in the slow muscles, after acclimation to hypoxia however capillary supply is little affected. This may represent an adaptation to increase the utilisation of circulating oxygen stores. The increased mitochondrial volume density would increase the extraction of oxygen from the blood thus decreasing the PO2 of the venous blood which would facilitate an increase in the rate of oxygen transfer across the gills. The mitochondrial volume densities and muscle capillary supply were unchanged in the air breathing catfish after acclimation to hypoxia. In this species it is likely that the increased ventilation of the suprabranchial respiratory organs together with the increased oxygen extraction at the gills obviated the need for significant changes in these parameters. These studies have considered only a few of the possible adaptations which might occur in response to acclimation to hypoxia. There are many other factors such as the effects of the concentrations of the nucleoside triphosphates which would have to be studied before these hypotheses could be verified, thus there is much scope for further study on the subject of hypoxia acclimation in fish.
1985-01-01T00:00:00ZBernard, Lynne MillsMany species of fish may be exposed to hypoxia in their natural habitats, either on a temporary or a more permanent basis. The survival of the animal may then be dependent on its ability to adapt to the conditions imposed upon it. There are several known ways in which a fish may adapt itself to coping with reduced oxygen levels such as by alterations in respiratory and ventilatory capacities and by changes in the oxygen carrying capacity of the blood. This study examines the effects of acclimation to hypoxia on the oxygen consumption, muscle ultrastructure and capillarisation of three species of freshwater fishes. The species studied could all expect to experience hypoxia in their natural environments. The tench, Tinea tinca, would very probably become hypoxic during its winter hibernation buried in the mud at the bottom of ponds and rivers. The Crucian carp, Carassius carassius, inhabits sluggish or still waters where rotting vegetation reduces oxygen levels and it often spends its winters under complete or near complete anoxia in ice-locked ponds. In terms of muscle ultrastructure and capillary supply, three very different responses to hypoxia acclimation have been found in the three species under study. Considering only the parameters studied the following hypothesis are proposed to explain the changes observed. Previous studies suggest that the increases in oxygen consumption observed after acclimation to hypoxia are due in part to increases in the oxygen affinity of the haemoglobin caused by decreases in the concentrations of the red cell nucleoside triphosphates. The decreases in mitochondrial volume density and capillary supply in tench muscle after acclimation to hypoxia could be due to a reduced level of spontaneous locomotory activity. Tench experience hypoxia mainly during their hibernation period where they remain totally quiescent. Energy requirement would be very low and metabolic rate would drop so some of the mitochondria and capillaries not required might be degraded. The Crucian carp show a marked increase in volume density of mitochondria, especially in the slow muscles, after acclimation to hypoxia however capillary supply is little affected. This may represent an adaptation to increase the utilisation of circulating oxygen stores. The increased mitochondrial volume density would increase the extraction of oxygen from the blood thus decreasing the PO2 of the venous blood which would facilitate an increase in the rate of oxygen transfer across the gills. The mitochondrial volume densities and muscle capillary supply were unchanged in the air breathing catfish after acclimation to hypoxia. In this species it is likely that the increased ventilation of the suprabranchial respiratory organs together with the increased oxygen extraction at the gills obviated the need for significant changes in these parameters. These studies have considered only a few of the possible adaptations which might occur in response to acclimation to hypoxia. There are many other factors such as the effects of the concentrations of the nucleoside triphosphates which would have to be studied before these hypotheses could be verified, thus there is much scope for further study on the subject of hypoxia acclimation in fish.The effects of temperature and hypoxia acclimation on the metabolism of fishesAleleye-Wokoma, Irvine P.https://hdl.handle.net/10023/149312019-03-29T10:32:09Z1990-01-01T00:00:00ZCHAPTER 1. The organisation and anatomical design of fish myotomal muscles. The literature on the anatomy, physiology and biochemistry of fish muscle is reviewed. CHAPTER 2. The effect of thermal acclimation on the metabolism of the swimming musculature of flounder (Platichthys flesus L.) Chapter 3. The effect of epinephrine administration on phosphorylase activity of the slow and fast muscles of flounder (Platichthys flesus L.) The results suggest glycogenolysis in flounder due to increased formation of phosphorylase a resulting from epinephrine activation of membrane bound adenyl cyclase. Chapter 4. Effects of hypoxia acclimation on anaerobic metabolism in the plaice (Pleuronectes platessa L.) There were no detectable levels of alcohol dehydrogenase activities, matched by the absence of ethanol pathway utilization. This may contribute to the failure of plaice to survive anoxia exposure. Chapter 5. Effects of acclimation to periodic anoxia exposure on the utilization of the ethanol pathway in goldfish (Carassius auratus L.). Chapter 6. Effects of acclimation to periodic anoxia exposure on the ultrastructure of goldfish (Carassius auratus L.) . CHAPTER 7. General Discussion. This section contains a general discussion of the biochemical responses to thermal acclimation and hypoxia. These responses precede ultrastructural changes which are stimulated to partially offset the adverse effects to normal homoeostasis. It includes a critical survey of current techniques and suggestions for future research.
1990-01-01T00:00:00ZAleleye-Wokoma, Irvine P.CHAPTER 1. The organisation and anatomical design of fish myotomal muscles. The literature on the anatomy, physiology and biochemistry of fish muscle is reviewed. CHAPTER 2. The effect of thermal acclimation on the metabolism of the swimming musculature of flounder (Platichthys flesus L.) Chapter 3. The effect of epinephrine administration on phosphorylase activity of the slow and fast muscles of flounder (Platichthys flesus L.) The results suggest glycogenolysis in flounder due to increased formation of phosphorylase a resulting from epinephrine activation of membrane bound adenyl cyclase. Chapter 4. Effects of hypoxia acclimation on anaerobic metabolism in the plaice (Pleuronectes platessa L.) There were no detectable levels of alcohol dehydrogenase activities, matched by the absence of ethanol pathway utilization. This may contribute to the failure of plaice to survive anoxia exposure. Chapter 5. Effects of acclimation to periodic anoxia exposure on the utilization of the ethanol pathway in goldfish (Carassius auratus L.). Chapter 6. Effects of acclimation to periodic anoxia exposure on the ultrastructure of goldfish (Carassius auratus L.) . CHAPTER 7. General Discussion. This section contains a general discussion of the biochemical responses to thermal acclimation and hypoxia. These responses precede ultrastructural changes which are stimulated to partially offset the adverse effects to normal homoeostasis. It includes a critical survey of current techniques and suggestions for future research.Geographic variation in the morphology and behavioural ecology of a sphecid waspGhazoul, Jabouryhttps://hdl.handle.net/10023/149292019-03-29T10:37:40Z1993-01-01T00:00:00ZA comparative study between populations of Mellinus arvensis (Hymenoptera: Sphecidae) was carried out in Britain. Large variations in size were found between populations and these were correlated with environmental, thermal, and biological factors. A latitudinal dine accounted for some of the variation, with larger wasps found at southerly locations. This was partially explained by climatic patterns and wasp warm-up rates. A hypothesis involving the interaction of environmental, behavioural and morphological factors was suggested to account for the remaining unexplained size variation between populations. It was found that at sites where the ground is compact and difficult to dig through, nests are more valuable in terms of time required to dig them. A strategy of searching for rather than digging a nest becomes viable. Wasps do not seem to be able to distinguish between occupied and abandoned nests, and aggressive interactions at nests occur between wasps searching for a nest and the nest residents. Aggression is more frequent at sites where pressure from searchers is greatest, that is, at sites where nest construction is most difficult and costly. Consequently, large wasps, which have greater success in aggressive encounters, are selected for at these sites. At sites where the ground is loose and easy to dig through, a more successful reproductive tactic appears to be maximisation of offspring number, resulting in many, small offspring. Behavioural observations suggested that M. arvensis is capable of, at least, limited endothermy, although this could not be confirmed in laboratory experiments. Similar observations and results were obtained from several other sphecid species. However, endothermy was found in two sphecid species of the genus Bembix in Portugal, suggesting that endothermy may be more widespread than previously thought.
1993-01-01T00:00:00ZGhazoul, JabouryA comparative study between populations of Mellinus arvensis (Hymenoptera: Sphecidae) was carried out in Britain. Large variations in size were found between populations and these were correlated with environmental, thermal, and biological factors. A latitudinal dine accounted for some of the variation, with larger wasps found at southerly locations. This was partially explained by climatic patterns and wasp warm-up rates. A hypothesis involving the interaction of environmental, behavioural and morphological factors was suggested to account for the remaining unexplained size variation between populations. It was found that at sites where the ground is compact and difficult to dig through, nests are more valuable in terms of time required to dig them. A strategy of searching for rather than digging a nest becomes viable. Wasps do not seem to be able to distinguish between occupied and abandoned nests, and aggressive interactions at nests occur between wasps searching for a nest and the nest residents. Aggression is more frequent at sites where pressure from searchers is greatest, that is, at sites where nest construction is most difficult and costly. Consequently, large wasps, which have greater success in aggressive encounters, are selected for at these sites. At sites where the ground is loose and easy to dig through, a more successful reproductive tactic appears to be maximisation of offspring number, resulting in many, small offspring. Behavioural observations suggested that M. arvensis is capable of, at least, limited endothermy, although this could not be confirmed in laboratory experiments. Similar observations and results were obtained from several other sphecid species. However, endothermy was found in two sphecid species of the genus Bembix in Portugal, suggesting that endothermy may be more widespread than previously thought.Thermal biology and nest-site selection in the bee 'Halictus rubicundus' (Hymenoptera : Halictidae)Potts, Simon G.https://hdl.handle.net/10023/149282019-03-29T10:34:51Z1996-01-01T00:00:00ZAggregations of the ground-nesting bee Halictus rubicundus were found at several locations across the UK. The phenology, social organisation, nest architecture and foraging behaviour of this bee were described for the largest of these aggregations (Invergowrie, Scotland). This site was unusual in having an extremely high brood mortality due to the impact of an anthomyiid fly. Nest parasitism was found to be directly density-dependent and it lead to a marked decline in nest numbers over the period of this study, indicating the possible forthcoming extinction of the aggregation. The other sites contained smaller nesting aggregations and the level of parasitism was considerably less. There was a marked variation in size across UK populations and this was explained by a temperature rather than a latitudinal cline. There was no evidence from field or laboratory studies to suggest that this species is endothermic; H. rubicundus is purely a behavioural thermoregulator. The effect of size upon various rates of heat exchange were examined in the laboratory for both sexes, and related to behaviours observed at the nest-site. Thus the microclimatic windows for different activities were established. The abundance of flying individuals at the nest-site was highly predictable from ambient temperature and light intensity; with predictions during a single day being more accurate than those combining several days throughout the season. Furthermore the usefulness of standard operative temperatures in predicting flight activity was assessed. The thoracic temperature of both sexes depended on the prevailing ambient temperature and also on the size of the individual while either basking or flying. Body temperatures increased with both ambient temperature and head width. However when both these predictors were combined into a single model, then size was only a strong predictor at lower temperatures. These findings were used to explain many of the behavioural patterns observed at Invergowrie. The nest site selection behaviour of females was examined both within and across sites. H. rubicundus was able to utilise a range of edaphic and microclimatic conditions when choosing a site to excavate a nest. There were some factors with broad tolerances such as slope and hardness, and others with much narrower limits such as aspect, soil humidity and particle composition. The thermal advantages of having a warm nest meant that the most suitable areas were those with a southern aspect and a slope which maximised the absorption of solar radiation. Limited areas of substrate with the most desirable characteristics resulted in gregarious nesting ('limited substrate' hypothesis). There was a preference for softer soils that were easier to dig, within a site with a low overall density; but in much denser aggregations problems of maintaining the structural integrity of a nest lead to the favouring of harder soils. The tendency to nest in close proximity to the natal nest (philopatry) complemented the 'limited substrate' hypothesis in producing an aggregation of nests. The spatial distributions of nests within aggregations were examined using nearest neighbour distance analyses; at low densities, microscale variation in substrate quality produced clumped patterns, whereas at high densities the risk of adjacent nests collapsing into one another forced nest spacing to be more regular. Findings concerning temperature dependence of nesting and foraging activities, and broader environmental controls on nest-site selection, are considered in relation to key aspects of bee biology: the origins and function of social behaviours, the conservation of, or provision of, nest-sites, and the utility of solitary bees as crop pollinators.
1996-01-01T00:00:00ZPotts, Simon G.Aggregations of the ground-nesting bee Halictus rubicundus were found at several locations across the UK. The phenology, social organisation, nest architecture and foraging behaviour of this bee were described for the largest of these aggregations (Invergowrie, Scotland). This site was unusual in having an extremely high brood mortality due to the impact of an anthomyiid fly. Nest parasitism was found to be directly density-dependent and it lead to a marked decline in nest numbers over the period of this study, indicating the possible forthcoming extinction of the aggregation. The other sites contained smaller nesting aggregations and the level of parasitism was considerably less. There was a marked variation in size across UK populations and this was explained by a temperature rather than a latitudinal cline. There was no evidence from field or laboratory studies to suggest that this species is endothermic; H. rubicundus is purely a behavioural thermoregulator. The effect of size upon various rates of heat exchange were examined in the laboratory for both sexes, and related to behaviours observed at the nest-site. Thus the microclimatic windows for different activities were established. The abundance of flying individuals at the nest-site was highly predictable from ambient temperature and light intensity; with predictions during a single day being more accurate than those combining several days throughout the season. Furthermore the usefulness of standard operative temperatures in predicting flight activity was assessed. The thoracic temperature of both sexes depended on the prevailing ambient temperature and also on the size of the individual while either basking or flying. Body temperatures increased with both ambient temperature and head width. However when both these predictors were combined into a single model, then size was only a strong predictor at lower temperatures. These findings were used to explain many of the behavioural patterns observed at Invergowrie. The nest site selection behaviour of females was examined both within and across sites. H. rubicundus was able to utilise a range of edaphic and microclimatic conditions when choosing a site to excavate a nest. There were some factors with broad tolerances such as slope and hardness, and others with much narrower limits such as aspect, soil humidity and particle composition. The thermal advantages of having a warm nest meant that the most suitable areas were those with a southern aspect and a slope which maximised the absorption of solar radiation. Limited areas of substrate with the most desirable characteristics resulted in gregarious nesting ('limited substrate' hypothesis). There was a preference for softer soils that were easier to dig, within a site with a low overall density; but in much denser aggregations problems of maintaining the structural integrity of a nest lead to the favouring of harder soils. The tendency to nest in close proximity to the natal nest (philopatry) complemented the 'limited substrate' hypothesis in producing an aggregation of nests. The spatial distributions of nests within aggregations were examined using nearest neighbour distance analyses; at low densities, microscale variation in substrate quality produced clumped patterns, whereas at high densities the risk of adjacent nests collapsing into one another forced nest spacing to be more regular. Findings concerning temperature dependence of nesting and foraging activities, and broader environmental controls on nest-site selection, are considered in relation to key aspects of bee biology: the origins and function of social behaviours, the conservation of, or provision of, nest-sites, and the utility of solitary bees as crop pollinators.Studies of the foraging behaviour, activity patterns and community structure of bumblebees (Bombus spp.) pollinating field beans (Vicia faba) and phacelia (Phacelia tanacetifolia) in Eastern ScotlandGriffin, Harriet Emilyhttps://hdl.handle.net/10023/149262019-03-29T10:32:10Z1997-01-01T00:00:00ZThe nectar profiles of twelve cultivars of field bean (Vicia faha), and of Phacelia tanacetifolia in eastern Scotland were analysed in relation to climatic variables. Observations were made of the activity patterns of Apis mellifera and six species of bumblebees on the experimental cultivars of V. faba and on a large commercial crop of Phacelia. Foraging behaviour and flower visitation rates were analysed in relation to bee species, nectar rewards and to the architecture of the crop. The species composition of the bee communities on V. faba and Phacelia was recorded during timed walks and is discussed in relation to floral structure and to interspecific differences among bumblebees. Scientific literature relating to the pollination of field beans is reviewed in detail.
1997-01-01T00:00:00ZGriffin, Harriet EmilyThe nectar profiles of twelve cultivars of field bean (Vicia faha), and of Phacelia tanacetifolia in eastern Scotland were analysed in relation to climatic variables. Observations were made of the activity patterns of Apis mellifera and six species of bumblebees on the experimental cultivars of V. faba and on a large commercial crop of Phacelia. Foraging behaviour and flower visitation rates were analysed in relation to bee species, nectar rewards and to the architecture of the crop. The species composition of the bee communities on V. faba and Phacelia was recorded during timed walks and is discussed in relation to floral structure and to interspecific differences among bumblebees. Scientific literature relating to the pollination of field beans is reviewed in detail.Environmental physiology of two hoverflies, "Eristalis tenax" and "E. pertinax"Bressin, Sabinehttps://hdl.handle.net/10023/149242019-03-29T10:26:59Z1999-01-01T00:00:00ZEristalis tenax and E. pertinax are two closely related Scottish hoverflies that share various ecological features, such as feeding sources, but differ in others (e.g. only adult E. tenax overwinter). The physiological performances and behaviour of these flies were studied in relation to the hygrothermal constraints faced, as were the physiological adaptations in the two (summer and winter) generations of E. tenax. Their water loss rates are rather high, lying in the upper part of the range for mesic insects. Rates are higher in E. tenax than in E. pertinax, and higher in male than in female E. pertinax. Water loss rates can be modified, notably in overwintering, water stressed females. Because of the rather high levels of evaporative cooling, these flies equilibrate at a temperature lower than ambient temperature. This work supports Bakken's (1976) recommendation of using equilibrium temperature as the "external" temperature for the estimation of warming and cooling constants, and further analyses the effects of evaporative cooling on these constants. Both species have endothermic abilities. Only E. tenax thermoregulate to a moderate degree in forward flight, but hovering male E. pertinax are excellent thermoregulators. Haemolymph shunting appears to be in operation in E. tenax, but is unlikely to be a controlled process. Large flies exchange heat with the environment more slowly, have faster warm-up rates, and take off at (and fly with) higher thoracic temperatures than small ones. Both linear dimensions and mass have to be considered, as the various aspects of insects' biology are not affected by the same size factor and because only then can "real" sex differences be distinguished from ones resulting from a difference in shape in males and females. In Scotland, male E. pertinax hover whereas male E. tenax do not. Hovering duration is strongly influenced by temperature. The foraging activity of these flies appears to be controlled in part by a circadian rhythm with additional effects of temperature in male E. tenax, and of light in E. pertinax. Overwintering female E. tenax select crevices in caves and ruins that offer a relatively constant, warm and highly humid microclimate. The start and end of overwintering appear to be triggered by changes in ambient temperature. Further opportunities for comparative studies of eristalines across their broad geographical range and between summer and winter generations are considered.
1999-01-01T00:00:00ZBressin, SabineEristalis tenax and E. pertinax are two closely related Scottish hoverflies that share various ecological features, such as feeding sources, but differ in others (e.g. only adult E. tenax overwinter). The physiological performances and behaviour of these flies were studied in relation to the hygrothermal constraints faced, as were the physiological adaptations in the two (summer and winter) generations of E. tenax. Their water loss rates are rather high, lying in the upper part of the range for mesic insects. Rates are higher in E. tenax than in E. pertinax, and higher in male than in female E. pertinax. Water loss rates can be modified, notably in overwintering, water stressed females. Because of the rather high levels of evaporative cooling, these flies equilibrate at a temperature lower than ambient temperature. This work supports Bakken's (1976) recommendation of using equilibrium temperature as the "external" temperature for the estimation of warming and cooling constants, and further analyses the effects of evaporative cooling on these constants. Both species have endothermic abilities. Only E. tenax thermoregulate to a moderate degree in forward flight, but hovering male E. pertinax are excellent thermoregulators. Haemolymph shunting appears to be in operation in E. tenax, but is unlikely to be a controlled process. Large flies exchange heat with the environment more slowly, have faster warm-up rates, and take off at (and fly with) higher thoracic temperatures than small ones. Both linear dimensions and mass have to be considered, as the various aspects of insects' biology are not affected by the same size factor and because only then can "real" sex differences be distinguished from ones resulting from a difference in shape in males and females. In Scotland, male E. pertinax hover whereas male E. tenax do not. Hovering duration is strongly influenced by temperature. The foraging activity of these flies appears to be controlled in part by a circadian rhythm with additional effects of temperature in male E. tenax, and of light in E. pertinax. Overwintering female E. tenax select crevices in caves and ruins that offer a relatively constant, warm and highly humid microclimate. The start and end of overwintering appear to be triggered by changes in ambient temperature. Further opportunities for comparative studies of eristalines across their broad geographical range and between summer and winter generations are considered.A study of the courtship song parameter in the 'Drosophila melanogaster' species complexPugh, Adrian R. G.https://hdl.handle.net/10023/149222019-11-07T09:05:48Z1997-01-01T00:00:00ZSexual isolation between populations has long been thought to play a role in speciation and evolution. However, the genetic control of factors causing sexual isolation is still not clearly understood. The interpulse interval (IPI) of the pulse song of the Drosophila melanogaster complex is important in female preference and species recognition. This thesis examined the genetic control of IPI. IPI may be important in the sexual isolation of species within the D. melanogaster complex, notably the three species D. melanogaster, D. simulans, and D. mauritiana. The genetic control of differences in IPI between D. simulans and D. mauritiana was studied using backcrosses and marker loci. The results showed that the control of the difference in IPI between species was evenly spread across five equally sized regions of the genome. Bi-directional artificial selection for shorter and longer IPI was carried out using replicate lines to control for genetic drift. The difference between selection regimes achieved was over 4.5 msecs. The difference was fixed using chromosome balancers to prevent recombination. Mating speeds of females from the selection lines with males from the selected and unselected lines were not significantly different from the original unselected stock following selection. The mean IPI of an African strain of D. melanogaster that had previously been shown to demonstrate premating isolation from other strains of D. melanogaster was measured, and was found to be significantly shorter than the control strain. Female mating speed of the African strain with males of the same strain was significantly faster than mating speeds with males of two strains with differing distributions for IPI. Heritability and evolvability of two song traits including IPI, and four morphological traits were measured in two generations of a strain recently derived from a wild population. All values were low, and mostly non-significant. The values for IPI were compared to values obtained from laboratory stocks, and with the values obtained for morphological traits. This study has furthered the understanding of the genetic control of IPI, and female response to changes in IPI. The examination of differences in IPI between populations and species remains important in our understanding of traits affecting sexual selection and premating isolation.
1997-01-01T00:00:00ZPugh, Adrian R. G.Sexual isolation between populations has long been thought to play a role in speciation and evolution. However, the genetic control of factors causing sexual isolation is still not clearly understood. The interpulse interval (IPI) of the pulse song of the Drosophila melanogaster complex is important in female preference and species recognition. This thesis examined the genetic control of IPI. IPI may be important in the sexual isolation of species within the D. melanogaster complex, notably the three species D. melanogaster, D. simulans, and D. mauritiana. The genetic control of differences in IPI between D. simulans and D. mauritiana was studied using backcrosses and marker loci. The results showed that the control of the difference in IPI between species was evenly spread across five equally sized regions of the genome. Bi-directional artificial selection for shorter and longer IPI was carried out using replicate lines to control for genetic drift. The difference between selection regimes achieved was over 4.5 msecs. The difference was fixed using chromosome balancers to prevent recombination. Mating speeds of females from the selection lines with males from the selected and unselected lines were not significantly different from the original unselected stock following selection. The mean IPI of an African strain of D. melanogaster that had previously been shown to demonstrate premating isolation from other strains of D. melanogaster was measured, and was found to be significantly shorter than the control strain. Female mating speed of the African strain with males of the same strain was significantly faster than mating speeds with males of two strains with differing distributions for IPI. Heritability and evolvability of two song traits including IPI, and four morphological traits were measured in two generations of a strain recently derived from a wild population. All values were low, and mostly non-significant. The values for IPI were compared to values obtained from laboratory stocks, and with the values obtained for morphological traits. This study has furthered the understanding of the genetic control of IPI, and female response to changes in IPI. The examination of differences in IPI between populations and species remains important in our understanding of traits affecting sexual selection and premating isolation.Female preference for artificial courtship songs in 'Drosophila melanogaster' and 'D. simulans'Halsey, Elizabeth J.https://hdl.handle.net/10023/149212019-11-07T09:04:40Z1999-01-01T00:00:00ZFertilisation between species may be prevented by differences in their mating systems, if a mating signal of one species is not recognised as such by another species. Closely related species are often most differentiated in their mating systems. Speciation may come about as a consequence of divergence of mating signals and preferences of species. Reinforcement of differences in mating systems may be a consequence of sympatry of sibling species. Understanding mating systems, particularly in terms of how they contribute to reproductive isolation, is therefore central to the study of speciation and animal diversity. Visual, chemical and auditory stimuli are required for mate-recognition in the Drosophila melanogaster complex. Among these stimuli is a species-specific male auditory signal, pulse song. Female preference for conspecific mean interpulse-interval (IPX) and IPI rhythm may contribute towards reproductive isolation of species, and divergence in this aspect of the mating system may be an important cause or effect of speciation of fruit flies. The two chapters of this thesis examine different aspects of female preference for pulse song. The first chapter considers the contribution made by female preference for conspecific pulse song towards the sexual isolation of the sibling species Drosophila melanogaster and D. simulans. Synthetic pulse songs are shown to be most effective in stimulating females when they are of conspecific mean IPI and IPI cycle length. Preferences for conspecific signals are found to be broad. In the second chapter, it is asked which element of IPI periodicity accounts for its property as a sexual stimulant in D. melanogaster. The most likely explanation, increased variation in IPI, is eliminated: female receptivity is not increased by playback of a novel synthetic song which varies to the same degree as rhythmic song but does not oscillate. In an appendix, some differences between D. sechellia and D. simulans in microsatellite loci are reported.
1999-01-01T00:00:00ZHalsey, Elizabeth J.Fertilisation between species may be prevented by differences in their mating systems, if a mating signal of one species is not recognised as such by another species. Closely related species are often most differentiated in their mating systems. Speciation may come about as a consequence of divergence of mating signals and preferences of species. Reinforcement of differences in mating systems may be a consequence of sympatry of sibling species. Understanding mating systems, particularly in terms of how they contribute to reproductive isolation, is therefore central to the study of speciation and animal diversity. Visual, chemical and auditory stimuli are required for mate-recognition in the Drosophila melanogaster complex. Among these stimuli is a species-specific male auditory signal, pulse song. Female preference for conspecific mean interpulse-interval (IPX) and IPI rhythm may contribute towards reproductive isolation of species, and divergence in this aspect of the mating system may be an important cause or effect of speciation of fruit flies. The two chapters of this thesis examine different aspects of female preference for pulse song. The first chapter considers the contribution made by female preference for conspecific pulse song towards the sexual isolation of the sibling species Drosophila melanogaster and D. simulans. Synthetic pulse songs are shown to be most effective in stimulating females when they are of conspecific mean IPI and IPI cycle length. Preferences for conspecific signals are found to be broad. In the second chapter, it is asked which element of IPI periodicity accounts for its property as a sexual stimulant in D. melanogaster. The most likely explanation, increased variation in IPI, is eliminated: female receptivity is not increased by playback of a novel synthetic song which varies to the same degree as rhythmic song but does not oscillate. In an appendix, some differences between D. sechellia and D. simulans in microsatellite loci are reported.An exploration of the function of the lateral nerve and the femoral chordotonal organ in the African desert locust (Schistocerca gregaria)Tait, David Scotthttps://hdl.handle.net/10023/149192019-03-29T10:32:34Z1997-01-01T00:00:00ZAn investigation of proprioception in the African Desert Locust (Schistocerca gregaria) is the basis of the following work. Experiments were performed on the adults and 5th instars to investigate the relation between the size of the animal and their jumping and kicking ability. This lead to a study of the effects of proprioception, specifically proprioception of the lateral nerve and the chordotonal organ on the jump and kick of adults. In order to study these effects, the simplest method was used. The lateral nerves and chordotonal organs (of the metathoracic leg) were severed, both separately, and in combination. The consequences of this loss of information about the position of the tibia in relation to the femur resulting, was judged by the behavioural and electrophysiological effects on the jump and kick of the locust. Results indicate that the loss of the information supplied via the lateral nerve is not sufficient to significantly alter the jumping or kicking performance of the animal, and neither is that loss resulting from the severance of the chordotonal organ. Loss of information from both proprioceptors appeared to prohibit kicking in the locust, but it did not prevent the locust from jumping. This surprising finding was taken as meaning that when the locust jumps, it can get positional information from other sources, such as tibial-tarsal chordotonal organs, which are in contact with the ground prior to the jump, and that this information is sufficient to enable the expression of the motor programme. However, these additional sources of information are not available when the locust kicks, and thus the motor programme is not expressed.
1997-01-01T00:00:00ZTait, David ScottAn investigation of proprioception in the African Desert Locust (Schistocerca gregaria) is the basis of the following work. Experiments were performed on the adults and 5th instars to investigate the relation between the size of the animal and their jumping and kicking ability. This lead to a study of the effects of proprioception, specifically proprioception of the lateral nerve and the chordotonal organ on the jump and kick of adults. In order to study these effects, the simplest method was used. The lateral nerves and chordotonal organs (of the metathoracic leg) were severed, both separately, and in combination. The consequences of this loss of information about the position of the tibia in relation to the femur resulting, was judged by the behavioural and electrophysiological effects on the jump and kick of the locust. Results indicate that the loss of the information supplied via the lateral nerve is not sufficient to significantly alter the jumping or kicking performance of the animal, and neither is that loss resulting from the severance of the chordotonal organ. Loss of information from both proprioceptors appeared to prohibit kicking in the locust, but it did not prevent the locust from jumping. This surprising finding was taken as meaning that when the locust jumps, it can get positional information from other sources, such as tibial-tarsal chordotonal organs, which are in contact with the ground prior to the jump, and that this information is sufficient to enable the expression of the motor programme. However, these additional sources of information are not available when the locust kicks, and thus the motor programme is not expressed.Control of head movement in the locust schistocerca gregariaShepheard, Peterhttps://hdl.handle.net/10023/149172019-03-29T10:27:42Z1969-01-01T00:00:00Z1. Head movement in the locust Schistocerca gregaria is mediated by 14 pairs of muscles. The normal motor output to, and the innervation pattern and muscle fibre spectrum of many of these muscles have been examined by a variety of histological and experimental techniques. 2. The anatomy, histology and the fine structure of the neck muscalature and innervation have been examined by both light and electron microscopy. The axons to some muscles have been traced by serial sections from the ganglion of origin to the muscle concerned, and axon counts of each motor nerve have been made. 3. The inervation pattern of many muscles has been investigated by recording with two intracellular microelectrodes from different fibres of the same or different muscles during graded stimulation of the motor nerve or nerves. 4. Both the normal motor output to, and the innervation pattern and muscle fibre spectrum of, many muscles have been investigated in the intact insect by recording with two intracellular microelectrodes from different fibres of a muscle during optokinetic nystagmus elicited by rotation of a striped drum in the visual field. Each electrode is inserted through a small hole in the exoskeleton into a fibre of the muscle close to its fixed insertions on the prothorax. 5. The sensory innervation of the neck and prothoras has been examined, and some of the sense organs are described. A chordotonal organ is attached to each lateral longitudinal muscle of the neck, and the system is so arranged as to be ideally situated for monitoring lateral head movement. The sense organ is shown to serve such a proprioceptive function. Chordotonal organs attached to muscles have not been previously described in insects. 6. A number of structural differences are found between muscle fibres, and each muscle contains a variety of muscle fibre types classified on the basis of electrical responsiveness to innervation. In one muscle, a definite correlation is shown between the structural and physiological differences between different muscle fibres. In this muscle, the larger fibres are of phasic type and have shorter sarcomeres and smaller fibres are of tonic type and have longer sarcomeres. In general, however, the structural differences between fibres in different muscles are greater than the differences between fibres in the same muscle.
1969-01-01T00:00:00ZShepheard, Peter1. Head movement in the locust Schistocerca gregaria is mediated by 14 pairs of muscles. The normal motor output to, and the innervation pattern and muscle fibre spectrum of many of these muscles have been examined by a variety of histological and experimental techniques. 2. The anatomy, histology and the fine structure of the neck muscalature and innervation have been examined by both light and electron microscopy. The axons to some muscles have been traced by serial sections from the ganglion of origin to the muscle concerned, and axon counts of each motor nerve have been made. 3. The inervation pattern of many muscles has been investigated by recording with two intracellular microelectrodes from different fibres of the same or different muscles during graded stimulation of the motor nerve or nerves. 4. Both the normal motor output to, and the innervation pattern and muscle fibre spectrum of, many muscles have been investigated in the intact insect by recording with two intracellular microelectrodes from different fibres of a muscle during optokinetic nystagmus elicited by rotation of a striped drum in the visual field. Each electrode is inserted through a small hole in the exoskeleton into a fibre of the muscle close to its fixed insertions on the prothorax. 5. The sensory innervation of the neck and prothoras has been examined, and some of the sense organs are described. A chordotonal organ is attached to each lateral longitudinal muscle of the neck, and the system is so arranged as to be ideally situated for monitoring lateral head movement. The sense organ is shown to serve such a proprioceptive function. Chordotonal organs attached to muscles have not been previously described in insects. 6. A number of structural differences are found between muscle fibres, and each muscle contains a variety of muscle fibre types classified on the basis of electrical responsiveness to innervation. In one muscle, a definite correlation is shown between the structural and physiological differences between different muscle fibres. In this muscle, the larger fibres are of phasic type and have shorter sarcomeres and smaller fibres are of tonic type and have longer sarcomeres. In general, however, the structural differences between fibres in different muscles are greater than the differences between fibres in the same muscle.The high affinity calcium binding sites in fibrinogenRoss, Joanhttps://hdl.handle.net/10023/149132019-03-29T10:37:20Z1983-01-01T00:00:00ZA purification method to obtain a fibrinogen preparation with a high proportion of intact molecules and free from contaminating plasminogen and Factor XIII was developed. Such fibrinogen preparations were used in cross-linking and plasmin-digestion studies to investigate the possible involvement of the carboxyl terminal regions of the A-chain in a high affinity calcium-binding site. The results of these investigations gave no evidence to support such a role for the carboxyl terminals of the A-chains. Highly intact fibrinogen preparations were also used in experiments to re-assess the number of high affinity calcium-binding sites in the molecule. The technique of flow dialysis was employed. Results from these experiments were in agreement with previously published data that there are three high affinity calcium-binding sites in fibrinogen. Indirect evidence was obtained which suggests that the chelator EGTA binds to the fibrinogen molecule.
1983-01-01T00:00:00ZRoss, JoanA purification method to obtain a fibrinogen preparation with a high proportion of intact molecules and free from contaminating plasminogen and Factor XIII was developed. Such fibrinogen preparations were used in cross-linking and plasmin-digestion studies to investigate the possible involvement of the carboxyl terminal regions of the A-chain in a high affinity calcium-binding site. The results of these investigations gave no evidence to support such a role for the carboxyl terminals of the A-chains. Highly intact fibrinogen preparations were also used in experiments to re-assess the number of high affinity calcium-binding sites in the molecule. The technique of flow dialysis was employed. Results from these experiments were in agreement with previously published data that there are three high affinity calcium-binding sites in fibrinogen. Indirect evidence was obtained which suggests that the chelator EGTA binds to the fibrinogen molecule.The proteins of the human erythrocyte plasma membrane with respect to in vivo ageingKadlubowski, Michaelhttps://hdl.handle.net/10023/149112019-03-29T10:32:15Z1976-01-01T00:00:00ZFresh human red blood cells were fractionated according to their in vivo age by simple centrifugation in order that changes in the membrane proteins could be investigated. Accepted criteria were used to assess the fractionation obtained, A packed column of the youngest cells was found to contain much more extra-cellular space when compared to the oldest cells and the evidence pointed to this having arisen from a difference in surface charge repulsion rather than geometry, 25% of both the youngest and oldest cells appeared to be sphered. Analysis of the membrane proteins by SDS PAGE revealed an increase in proteins 2.5 and 4.1 and a decrease in protein 7 with age. A tentative classification of the proteins revealed by SDS PAGE was put forward based on their age-dependent behaviour and in situ loci, special attention being paid to membrane-cytoplasm interactions . In vitro ageing was found to produce quantitatively very different changes in the membrane proteins. The large increase in protein 4.l with age and the temperature dependence of its binding to the membrane made its isolation seem worthwhile. A protein which was almost certainly 4.1 was purified from the cytoplasm of outdated blood. A method was developed for the total solubilisation of the membrane proteins, permitting polyacrylamide gel electrophoresis whilst maintaining a very high degree of functional integrity. This was achieved using the four nonionic surfactants NP40, B35, T20 and T40. LDH, PNP, AChEase, NADH-MR and GAPD were visualised with this system and of these PNP, AChEase and NADH-MR exhibited an age-dependent decrease in band intensity. LDH was resolved into four discrete isozyme bands and PNP appeared to contain many unresolved bands. Nine membrane-associated enzymes were assayed by standard techniques. No change was found for Na, K-ATPase and GAPD but the specific activities of AChEase, PGK, PNP, AKase, Mg-ATPase, NADH-MR and alkaline phosphatase were all found to decrease with age by varying amounts. Reticulocyte contamination could only have accounted for the small AChEase decrease. Of the rest, all the decreases were considered to be genuinely age-dependent, although only the decreases in NADH-MR and alkaline phosphatase could unequivocally be said to have given a good indication of the in situ situation. The other decreases could easily have been caused by a decrease in membrane integrity with age leading to a greater' loss of enzyme protein from the older membranes during ghost preparation.
1976-01-01T00:00:00ZKadlubowski, MichaelFresh human red blood cells were fractionated according to their in vivo age by simple centrifugation in order that changes in the membrane proteins could be investigated. Accepted criteria were used to assess the fractionation obtained, A packed column of the youngest cells was found to contain much more extra-cellular space when compared to the oldest cells and the evidence pointed to this having arisen from a difference in surface charge repulsion rather than geometry, 25% of both the youngest and oldest cells appeared to be sphered. Analysis of the membrane proteins by SDS PAGE revealed an increase in proteins 2.5 and 4.1 and a decrease in protein 7 with age. A tentative classification of the proteins revealed by SDS PAGE was put forward based on their age-dependent behaviour and in situ loci, special attention being paid to membrane-cytoplasm interactions . In vitro ageing was found to produce quantitatively very different changes in the membrane proteins. The large increase in protein 4.l with age and the temperature dependence of its binding to the membrane made its isolation seem worthwhile. A protein which was almost certainly 4.1 was purified from the cytoplasm of outdated blood. A method was developed for the total solubilisation of the membrane proteins, permitting polyacrylamide gel electrophoresis whilst maintaining a very high degree of functional integrity. This was achieved using the four nonionic surfactants NP40, B35, T20 and T40. LDH, PNP, AChEase, NADH-MR and GAPD were visualised with this system and of these PNP, AChEase and NADH-MR exhibited an age-dependent decrease in band intensity. LDH was resolved into four discrete isozyme bands and PNP appeared to contain many unresolved bands. Nine membrane-associated enzymes were assayed by standard techniques. No change was found for Na, K-ATPase and GAPD but the specific activities of AChEase, PGK, PNP, AKase, Mg-ATPase, NADH-MR and alkaline phosphatase were all found to decrease with age by varying amounts. Reticulocyte contamination could only have accounted for the small AChEase decrease. Of the rest, all the decreases were considered to be genuinely age-dependent, although only the decreases in NADH-MR and alkaline phosphatase could unequivocally be said to have given a good indication of the in situ situation. The other decreases could easily have been caused by a decrease in membrane integrity with age leading to a greater' loss of enzyme protein from the older membranes during ghost preparation.An investigation into methods of assessing the interaction of platelets with immobilised collagenThomson, Shana W.https://hdl.handle.net/10023/149102019-03-29T10:38:54Z1984-01-01T00:00:00ZWhen platelets come into contact with collagen, they adhere to it then release the contents of their dense granules and granules and aggregate together. This interaction is dependent on the conformation and degree of multimerisation of the collagen as well as the experimental conditions. The fibrillar state of collagen varies with the pH and ionic strength of the solution so collagen was immobilised on to an insoluble support in order that its fibrillar state should remain unchanged during exposure to platelets and during modification. The first support used was polyamide sheet, but although the resulting collagen-strips induced measurable platelet adhesion and aggregation, there was insufficient collagen present to induce adequate aggregation or serotonin release to be of use in investigating these interactions. Sepharose 6B was then used as a support for collagen and this proved satisfactory, inducing approximately 20% serotonin release from platelets. The release reaction is nearer to the initial interaction between platelets and collagen than aggregation, which is the final step, and it therefore allows a better insight into the conditions necessary for the interaction to take place. The amino groups of collagen-Sepharose were modified in three ways, using succinic anhydride, trinitrobenzene sulphonic acid and dinitrofluorobenzene. Succinylation almost abolished serotonin release while di-and trinitrophenylation enhanced this reaction. amino groups of collagen are therefore not in themselves important in the recognition of collagen by platelets and the subsequent reactions, since they were blocked by the modifications. The suggestion is made that succinylation disrupted the fibrils because of the change in charge whereas di- and trinitrophenylation merely neutralised the charge and permitted realignment of any previously misaligned areas of the molecule. These results reinforce theories that the correct quaternary structure of collagen must be present in order that it will be recognised by platelets.
1984-01-01T00:00:00ZThomson, Shana W.When platelets come into contact with collagen, they adhere to it then release the contents of their dense granules and granules and aggregate together. This interaction is dependent on the conformation and degree of multimerisation of the collagen as well as the experimental conditions. The fibrillar state of collagen varies with the pH and ionic strength of the solution so collagen was immobilised on to an insoluble support in order that its fibrillar state should remain unchanged during exposure to platelets and during modification. The first support used was polyamide sheet, but although the resulting collagen-strips induced measurable platelet adhesion and aggregation, there was insufficient collagen present to induce adequate aggregation or serotonin release to be of use in investigating these interactions. Sepharose 6B was then used as a support for collagen and this proved satisfactory, inducing approximately 20% serotonin release from platelets. The release reaction is nearer to the initial interaction between platelets and collagen than aggregation, which is the final step, and it therefore allows a better insight into the conditions necessary for the interaction to take place. The amino groups of collagen-Sepharose were modified in three ways, using succinic anhydride, trinitrobenzene sulphonic acid and dinitrofluorobenzene. Succinylation almost abolished serotonin release while di-and trinitrophenylation enhanced this reaction. amino groups of collagen are therefore not in themselves important in the recognition of collagen by platelets and the subsequent reactions, since they were blocked by the modifications. The suggestion is made that succinylation disrupted the fibrils because of the change in charge whereas di- and trinitrophenylation merely neutralised the charge and permitted realignment of any previously misaligned areas of the molecule. These results reinforce theories that the correct quaternary structure of collagen must be present in order that it will be recognised by platelets.Investigation of the substrate specificity of recombinant Trypanosoma cruzi trans-sialidaseHarrison, Jennifer Amandahttps://hdl.handle.net/10023/149072019-03-29T10:34:01Z1999-01-01T00:00:00ZThe protozoan blood-borne parasite Trypanosoma cruzi is the causative agent of Chagas' disease, an enervating and often fatal illness prevalent in South and Central America for which there is no effective treatment. T. cruzi has a cell-surface trans- sialidase which transfers sialic acid from mammalian oligosaccharides to the parasite. This action allows adhesion to and invasion of mammalian cells, subsequently allowing parasitic replication. This protein therefore is exploitable and represents a potential target for the development of chemotherapeutic agents. This thesis describes the purification of recombinant trans-sialidase and the development of a rapid, reliable spectrophotometric coupled assay to measure trans-sialidase activity. It also details the use of three mutually exclusive synthetic oligosaccharide libraries to map substrate recognition for the enzyme. Synthetic fragments of the natural branched oligosaccharide substrates have also been sialylated on a preparative scale, demonstrating the use of trans-sialidase in synthetic oligosaccharide chemistry.
1999-01-01T00:00:00ZHarrison, Jennifer AmandaThe protozoan blood-borne parasite Trypanosoma cruzi is the causative agent of Chagas' disease, an enervating and often fatal illness prevalent in South and Central America for which there is no effective treatment. T. cruzi has a cell-surface trans- sialidase which transfers sialic acid from mammalian oligosaccharides to the parasite. This action allows adhesion to and invasion of mammalian cells, subsequently allowing parasitic replication. This protein therefore is exploitable and represents a potential target for the development of chemotherapeutic agents. This thesis describes the purification of recombinant trans-sialidase and the development of a rapid, reliable spectrophotometric coupled assay to measure trans-sialidase activity. It also details the use of three mutually exclusive synthetic oligosaccharide libraries to map substrate recognition for the enzyme. Synthetic fragments of the natural branched oligosaccharide substrates have also been sialylated on a preparative scale, demonstrating the use of trans-sialidase in synthetic oligosaccharide chemistry.Plasma protein changes in open cardiac surgeryLloyd, Allan Henryhttps://hdl.handle.net/10023/149062019-03-29T10:27:32Z1970-01-01T00:00:00ZThe literature on biochemical changes in open cardiac surgery with especial reference to plasma protein and amino acids has been reviewed. The changes that take place in plasma proteins during oxygenation of blood of open cardiac surgery have been investigated with emphasis on denaturation. This phenomena has been examined by the assay of blood and plasma sulfhydryl groups by different reagents and also viscosity and turbidity changes. The limitations of the two latter investigations has been discussed. Haemolytic changes in plasma have been examined and the related importance of sulfhydryl groups discussed. Plasma protein changes have been investigated by methods depending on net charge, shape, size, and molecular weight of individual molecules. Although adrenal cortical response to open cardiac surgery has been investigated it has been pertinent to reinvestigate adrenal cortical secretion pari passu with amino acid data from blood and urine samples of patients not only because of their metabolic associations, but also because of the opportunity of comparing surgical patients receiving supplementary haydrocortisone throughout open cardiac surgery with those not supplemented - the latter therefore depending on their own intrinsic secretion during surgical stress. A review of relevant literature has accordingly been presented with emphasis on the difficulties involved in ACTH assay of plasma from surgical patients, and the practical advantages of 17-hydroxycorticostereid assay in lieu of ACTH assays. The plasma and urinary amino acid increase have been examined together in detail comparing not only the increase in each amino acid at each operation but also comparing the increase of an amino acid in all the operations investigated thus obtaining mean values of each amino acid at regular intervals of time throughout each perfusion.
1970-01-01T00:00:00ZLloyd, Allan HenryThe literature on biochemical changes in open cardiac surgery with especial reference to plasma protein and amino acids has been reviewed. The changes that take place in plasma proteins during oxygenation of blood of open cardiac surgery have been investigated with emphasis on denaturation. This phenomena has been examined by the assay of blood and plasma sulfhydryl groups by different reagents and also viscosity and turbidity changes. The limitations of the two latter investigations has been discussed. Haemolytic changes in plasma have been examined and the related importance of sulfhydryl groups discussed. Plasma protein changes have been investigated by methods depending on net charge, shape, size, and molecular weight of individual molecules. Although adrenal cortical response to open cardiac surgery has been investigated it has been pertinent to reinvestigate adrenal cortical secretion pari passu with amino acid data from blood and urine samples of patients not only because of their metabolic associations, but also because of the opportunity of comparing surgical patients receiving supplementary haydrocortisone throughout open cardiac surgery with those not supplemented - the latter therefore depending on their own intrinsic secretion during surgical stress. A review of relevant literature has accordingly been presented with emphasis on the difficulties involved in ACTH assay of plasma from surgical patients, and the practical advantages of 17-hydroxycorticostereid assay in lieu of ACTH assays. The plasma and urinary amino acid increase have been examined together in detail comparing not only the increase in each amino acid at each operation but also comparing the increase of an amino acid in all the operations investigated thus obtaining mean values of each amino acid at regular intervals of time throughout each perfusion.Studies on the connective tissue matrix components of the arterial wall of humans and salmonids (salmo gairdneri and salmo salar): age-and species-related physical and chemical propertiesSpina, Michele Attiliohttps://hdl.handle.net/10023/149032019-03-29T10:42:25Z1982-01-01T00:00:00ZSection A of this thesis describes the non-degradative isolation procedure of elastin from the media of human thoracic aorta and the determination of its ponderal distribution as well as that of the other connective tissue matrix components in the aortic media of individuals of different ages. A cylindrical segment, free of complex atherosclerotic lesions, was resected at autopsy from each of fifty-nine descending human thoracic aortae by cutting just below the level of the first pair of intercostal arteries and 35 mm distal to this incision. In the isolated tunica media there was an age-related rise in the absolute concentration of the following components: (a) proteins and glycoproteins extractable in chaotropic agents, (b) collagen and (c) an insoluble polar protein(s) which was resistant to collagenase digestion but was solubilized by trypsin. In contrast, the absolute elastin concentration was constant at around 70 mg/cm in samples of all ages. Although after treatment with collagenase and trypsin, both the mechanical properties and amino acid composition of elastin did not vary with age, in samples tested prior to trypsin digestion the insoluble polar-protein contaminant affected the mechanical behaviour of the elastin network in a way akin to plasticisers in rubber. It is therefore suggested that the morphological changes .and stiffening observed in the ageing aortic wall are not due to degradation of its elastin network bu to variations in the supramolecular organisation of connective tissue components. Section B of this thesis describes the isolation of elastin and the determination of its distribution as well as that of collagen in the bulbus arteriosus and ventral aorta of trout (Salmo gairdneri) and salmon (Salmo salar). The isolation of elastin fibrils from these specimens did not require the use of proteolytic enzymzes as collagen and all the other components of the vessel wall were readily extracted in denaturing and reducing conditions. The arterial walls of trout and salmon are characterized by a high elastin content, with an elastin:collagen ratio exceeding 2.5:1. The elastin which display an amino acid composition highly at variance with that of the mammalian protein, is present as 250-A-diameter fibrils which have a strong affinity for electron-dense cations and which form in the intercellular matrix an isotropic reticulum. As in mammalian elastin, the fibrils can be resolved in negatively contrasted preparations into constituent primary filaments of about 25 A in diameter, aligned with an equatorial periodicity of about 55 A. The wide-angle X-ray diffraction pattern of the salmonid preparations showed broad reflections corresponding to spacings of 9.8, 4.5 and 2.2 A, similar to bovine elastin. The mechanical behaviour of the salmon preparation was characterized by a linear response to stress, with minimal hysteresis, a Young's modulus of 5.5 x 105 N m-2, and a breaking strain of 1.5.
1982-01-01T00:00:00ZSpina, Michele AttilioSection A of this thesis describes the non-degradative isolation procedure of elastin from the media of human thoracic aorta and the determination of its ponderal distribution as well as that of the other connective tissue matrix components in the aortic media of individuals of different ages. A cylindrical segment, free of complex atherosclerotic lesions, was resected at autopsy from each of fifty-nine descending human thoracic aortae by cutting just below the level of the first pair of intercostal arteries and 35 mm distal to this incision. In the isolated tunica media there was an age-related rise in the absolute concentration of the following components: (a) proteins and glycoproteins extractable in chaotropic agents, (b) collagen and (c) an insoluble polar protein(s) which was resistant to collagenase digestion but was solubilized by trypsin. In contrast, the absolute elastin concentration was constant at around 70 mg/cm in samples of all ages. Although after treatment with collagenase and trypsin, both the mechanical properties and amino acid composition of elastin did not vary with age, in samples tested prior to trypsin digestion the insoluble polar-protein contaminant affected the mechanical behaviour of the elastin network in a way akin to plasticisers in rubber. It is therefore suggested that the morphological changes .and stiffening observed in the ageing aortic wall are not due to degradation of its elastin network bu to variations in the supramolecular organisation of connective tissue components. Section B of this thesis describes the isolation of elastin and the determination of its distribution as well as that of collagen in the bulbus arteriosus and ventral aorta of trout (Salmo gairdneri) and salmon (Salmo salar). The isolation of elastin fibrils from these specimens did not require the use of proteolytic enzymzes as collagen and all the other components of the vessel wall were readily extracted in denaturing and reducing conditions. The arterial walls of trout and salmon are characterized by a high elastin content, with an elastin:collagen ratio exceeding 2.5:1. The elastin which display an amino acid composition highly at variance with that of the mammalian protein, is present as 250-A-diameter fibrils which have a strong affinity for electron-dense cations and which form in the intercellular matrix an isotropic reticulum. As in mammalian elastin, the fibrils can be resolved in negatively contrasted preparations into constituent primary filaments of about 25 A in diameter, aligned with an equatorial periodicity of about 55 A. The wide-angle X-ray diffraction pattern of the salmonid preparations showed broad reflections corresponding to spacings of 9.8, 4.5 and 2.2 A, similar to bovine elastin. The mechanical behaviour of the salmon preparation was characterized by a linear response to stress, with minimal hysteresis, a Young's modulus of 5.5 x 105 N m-2, and a breaking strain of 1.5.Evidence for the involvement of intracellular cyclic 3', 5' - nucleotides in regulating miocardial contractilitySingh, Jaipaulhttps://hdl.handle.net/10023/149022019-03-29T10:34:40Z1978-01-01T00:00:00ZAn investigation was made into one aspect of the molecular control of cardiac contractility, namely, the putative role of the two endogenous cyclic 3',5'-nucleotides, adenosine cyclic 3',5' monophosphate (cyclic AMP) and guanosine cyclic 3',5' monophosphate (cyclic GMP) in regulating the capacity of the heart to produce force. It began as a study of a poorly understood but well documented effect of exogenous adenosine 5'-triphosphate (ATP) on the electrical and mechanical properties of the isolated frog ventricle. In common with several related purine and pyrimidine nucleotides, treatment of the ventricle with ATP elicits a characteristic triphasic response which is not blocked by either atropine or propranolol. Preliminary experiments with ATP led to the hypothesis that it exerts a dual effect on the heart. The two effects were attributed tentatively to the induction of elevated levels of intracellular cyclic AMP and cyclic GMP respectively. Indirect evidence for the involvement of cyclic nucleotides in mediating the ATP-induced response comes from studies with agents which are known to influence cyclic 3',5'-nucleotide metabolism on the form of the ATP-induced response. Measurements of endogenous cyclic 3',5'-nucleotides during the development of the hypodynamic state is associated by a gradual decline in intracellular cyclic AMP and a progressive increase in cyclic GMP. This gradual loss in contractility is also accompanied by the release of prostaglandins E1 and E2 and one or more prostaglandin-related substances into the perfusate. Subsequent experiments with exogenous ATP elicits profound changes in cyclic 3',5'-nucleotides. Both cyclic AMP and cyclic GMP are affected as had been postulated. A third series of experiments with the -agonist isoprenaline (isoproterenol) was undertaken to investigate the generality of the relationship between intracellular cyclic nucleotide levels and contractility, and this produced similar results. The most significant feature to emerge from the results was the finding that in all three responses, which on the face of it appear to be physiologically distinct and quite unrelated, changes in the ratio of intracellular cyclic AMP / cyclic GMP almost exactly parallel the observed changes in contractile force. This observation has led to the formulation of a hypothesis which postulates that both endogenous cyclic 3',5'-nucleotides are integral components of an intracellular control mechanism which is responsible for regulating the contractility of the amphibian ventricle.
1978-01-01T00:00:00ZSingh, JaipaulAn investigation was made into one aspect of the molecular control of cardiac contractility, namely, the putative role of the two endogenous cyclic 3',5'-nucleotides, adenosine cyclic 3',5' monophosphate (cyclic AMP) and guanosine cyclic 3',5' monophosphate (cyclic GMP) in regulating the capacity of the heart to produce force. It began as a study of a poorly understood but well documented effect of exogenous adenosine 5'-triphosphate (ATP) on the electrical and mechanical properties of the isolated frog ventricle. In common with several related purine and pyrimidine nucleotides, treatment of the ventricle with ATP elicits a characteristic triphasic response which is not blocked by either atropine or propranolol. Preliminary experiments with ATP led to the hypothesis that it exerts a dual effect on the heart. The two effects were attributed tentatively to the induction of elevated levels of intracellular cyclic AMP and cyclic GMP respectively. Indirect evidence for the involvement of cyclic nucleotides in mediating the ATP-induced response comes from studies with agents which are known to influence cyclic 3',5'-nucleotide metabolism on the form of the ATP-induced response. Measurements of endogenous cyclic 3',5'-nucleotides during the development of the hypodynamic state is associated by a gradual decline in intracellular cyclic AMP and a progressive increase in cyclic GMP. This gradual loss in contractility is also accompanied by the release of prostaglandins E1 and E2 and one or more prostaglandin-related substances into the perfusate. Subsequent experiments with exogenous ATP elicits profound changes in cyclic 3',5'-nucleotides. Both cyclic AMP and cyclic GMP are affected as had been postulated. A third series of experiments with the -agonist isoprenaline (isoproterenol) was undertaken to investigate the generality of the relationship between intracellular cyclic nucleotide levels and contractility, and this produced similar results. The most significant feature to emerge from the results was the finding that in all three responses, which on the face of it appear to be physiologically distinct and quite unrelated, changes in the ratio of intracellular cyclic AMP / cyclic GMP almost exactly parallel the observed changes in contractile force. This observation has led to the formulation of a hypothesis which postulates that both endogenous cyclic 3',5'-nucleotides are integral components of an intracellular control mechanism which is responsible for regulating the contractility of the amphibian ventricle.An investigation into the mechanism of action of nitroprusside on isolated cardiovascular tissuesKennovin, Gordon D.https://hdl.handle.net/10023/149002019-03-29T10:30:02Z1989-01-01T00:00:00ZThe effect of photolysis of nitroprusside was investigated in both frog ventricular trabeculae and rabbit ear arterial strips. Unphotolysed nitroprusside failed to elicit any effect on frog ventricular twitch tension. However, upon photolysis it had a potent negative inotropic action. The extent of twitch depression was shown to depend on the degree of photolysis. It was postulated that these effects are due to a labile physiologically active photolytic product. This was positively identified as nitric oxide. Preliminary results of the negative inotropic action of thiols and synthesised nitrosothiols are also presented. In contrast to frog ventricle, intact nitroprusside does exert a relaxing effect on precontracted mammalian smooth muscle. This effect is markedly potentiated by photolysis. It is concluded that the mechanism of action of nitroprusside on both tissues involves the release of nitric oxide which is postulated to activate guanylate cyclase. This suggests that mammalian vascular smooth muscle has a mechanism for degrading nitroprusside which is absent in frog ventricle.
1989-01-01T00:00:00ZKennovin, Gordon D.The effect of photolysis of nitroprusside was investigated in both frog ventricular trabeculae and rabbit ear arterial strips. Unphotolysed nitroprusside failed to elicit any effect on frog ventricular twitch tension. However, upon photolysis it had a potent negative inotropic action. The extent of twitch depression was shown to depend on the degree of photolysis. It was postulated that these effects are due to a labile physiologically active photolytic product. This was positively identified as nitric oxide. Preliminary results of the negative inotropic action of thiols and synthesised nitrosothiols are also presented. In contrast to frog ventricle, intact nitroprusside does exert a relaxing effect on precontracted mammalian smooth muscle. This effect is markedly potentiated by photolysis. It is concluded that the mechanism of action of nitroprusside on both tissues involves the release of nitric oxide which is postulated to activate guanylate cyclase. This suggests that mammalian vascular smooth muscle has a mechanism for degrading nitroprusside which is absent in frog ventricle.A study of respiratory responses to various stimuliKosai, Abdul Wahab Datukhttps://hdl.handle.net/10023/148982019-03-29T10:30:06Z1977-01-01T00:00:00ZIn normal subjects, the ventilatory and mouth occlusion pressure (both total mouth occlusion at 0.1 sec. from beginning of inspiration (P0.1) and the maximum rate of change of mouth occlusion pressure, (dp/dt)max.,) responses to CO2 was studied. All three responses gave similar results. However, the P0.1 response has the dis-advantage that subjects anticipated and were conscious of the occlusion; thus it was not used further. In hypoxia tests too, (dp/dt)max. and ventilatory responses gave similar results. With added airways obstruction, the ventilatory response to CO2 was significantly reduced whereas the (dp/dt) max. response was unaffected, suggesting that (dp/dt) max. reflects the respiratory centre output. In patients with chronic airways obstruction, the normocapnic group showed a significantly lower ventilatory response to CO2 but the (dp/dt) max. response was in the range of the normal subjects in 87% of the patients. The hypercapnic patients showed significantly lower ventilatory and (dp/dt) max. responses to CO2 when compared to that of the normal subjects. The resting PaCO2 showed a better correlation with (dp/dt) max. response than with ventilatory response. The ventilatory response in the patients showed a significant correlation with the degree of airways obstruction whilst (dp/dt) max. response did not show any such relationship. This suggests that (dp/dt) max. may be a reliable index of respiratory centre output independent of airways obstruction. In anaesthetized rabbits, ventilation, (dp/dt) max. and the average rate and total diaphragmatic electrical activity (integrated EMG) in response to CO2 was compared. In unobstructed breathing, all four responses gave similar results. With added airways obstruction, the ventilatory response was significantly reduced whilst the other three responses were unaffected. Changes in (dp/dt) max. paralled changes in EMG activity with increases in PCO2. Thus it is shown again that (dp/dt) max. is independent of airways obstruction, and can be said to reflect the respiratory centre neural output. In 47 normal subjects, the ventilatory response to exercise (when exercise is expressed as CO2 produced and O2 uptake) was studied in trained and untrained subjects. The exercise ventilatory response was compared to the CO2 response as measured by ventilation and in some subjects by (dp/dt) max. response. It is found that trained subjects had a significantly lower CO2 response and a lower ventilatory response to exercise than the untrained. The ventilatory and (dp/dt) max. responses correlated significantly with exercise ventilatory response. A similar correlation was found between (dp/dt) max. and ventilatory response to hypoxia and exercise ventilatory response. The breathing pattern of man was also studied to find its relationship with the above findings.
1977-01-01T00:00:00ZKosai, Abdul Wahab DatukIn normal subjects, the ventilatory and mouth occlusion pressure (both total mouth occlusion at 0.1 sec. from beginning of inspiration (P0.1) and the maximum rate of change of mouth occlusion pressure, (dp/dt)max.,) responses to CO2 was studied. All three responses gave similar results. However, the P0.1 response has the dis-advantage that subjects anticipated and were conscious of the occlusion; thus it was not used further. In hypoxia tests too, (dp/dt)max. and ventilatory responses gave similar results. With added airways obstruction, the ventilatory response to CO2 was significantly reduced whereas the (dp/dt) max. response was unaffected, suggesting that (dp/dt) max. reflects the respiratory centre output. In patients with chronic airways obstruction, the normocapnic group showed a significantly lower ventilatory response to CO2 but the (dp/dt) max. response was in the range of the normal subjects in 87% of the patients. The hypercapnic patients showed significantly lower ventilatory and (dp/dt) max. responses to CO2 when compared to that of the normal subjects. The resting PaCO2 showed a better correlation with (dp/dt) max. response than with ventilatory response. The ventilatory response in the patients showed a significant correlation with the degree of airways obstruction whilst (dp/dt) max. response did not show any such relationship. This suggests that (dp/dt) max. may be a reliable index of respiratory centre output independent of airways obstruction. In anaesthetized rabbits, ventilation, (dp/dt) max. and the average rate and total diaphragmatic electrical activity (integrated EMG) in response to CO2 was compared. In unobstructed breathing, all four responses gave similar results. With added airways obstruction, the ventilatory response was significantly reduced whilst the other three responses were unaffected. Changes in (dp/dt) max. paralled changes in EMG activity with increases in PCO2. Thus it is shown again that (dp/dt) max. is independent of airways obstruction, and can be said to reflect the respiratory centre neural output. In 47 normal subjects, the ventilatory response to exercise (when exercise is expressed as CO2 produced and O2 uptake) was studied in trained and untrained subjects. The exercise ventilatory response was compared to the CO2 response as measured by ventilation and in some subjects by (dp/dt) max. response. It is found that trained subjects had a significantly lower CO2 response and a lower ventilatory response to exercise than the untrained. The ventilatory and (dp/dt) max. responses correlated significantly with exercise ventilatory response. A similar correlation was found between (dp/dt) max. and ventilatory response to hypoxia and exercise ventilatory response. The breathing pattern of man was also studied to find its relationship with the above findings.Studies on the structure and function of mechanoreceptors in the stomatogastric nervous system of some decapoda crustaceaDando, Malcolm Reginaldhttps://hdl.handle.net/10023/148962019-03-29T10:33:34Z1969-01-01T00:00:00Zi. The stomatogastric nervous system of some of the decapod crustacea contains several small isolated ganglia. At least one of these ganglia is useful for the detailed investigation of the generation of a patterned central output controlling movement. A review of previous work shows that little is known of the anatomy and physiology of the sense organs innervating the foregut. This knowledge would be valuable for understanding the control mechanisms governing the foregut function because reflex mechanisms are probable important in this situation. Therefore the aim of the thesis was to investigate the mechanoreceptors innervating the foregut. Work was concentrated on these sense organs because they are probably involved directly in the control of movement. ii. The large amount of previous work on this type of sense organ in the higher decapods is summarised in an appendix. An attempt is also revise to some of the terminology used in the study oi these receptors, and recent developments are reviewed in some detail. iii. Two new major receptor systems innervating the foregut are described. The posterior stomach (p.s.n.) contains a group of about 80 neurones which innervate the posterior of the gastric mill. These neurons respond to normal movements of the mill. Changes in the input from the receptors affect the output from the stomatogastric ganglion. The other system (MPRs) consists of three distinct organs totalling about 40 neurones which monitor normal movements of the structures around the mouth iv. Suggestions are made top further specific work on these two receptor systems. What is now known of the sensory innervation of the foregut is summarised and suggestions made for completing this knowledge. v. Further possible work on the ganglia and the role the associated mechanoreceptor organs is reviewed. Finally work on other problems related to the studies reported here is discussed.
1969-01-01T00:00:00ZDando, Malcolm Reginaldi. The stomatogastric nervous system of some of the decapod crustacea contains several small isolated ganglia. At least one of these ganglia is useful for the detailed investigation of the generation of a patterned central output controlling movement. A review of previous work shows that little is known of the anatomy and physiology of the sense organs innervating the foregut. This knowledge would be valuable for understanding the control mechanisms governing the foregut function because reflex mechanisms are probable important in this situation. Therefore the aim of the thesis was to investigate the mechanoreceptors innervating the foregut. Work was concentrated on these sense organs because they are probably involved directly in the control of movement. ii. The large amount of previous work on this type of sense organ in the higher decapods is summarised in an appendix. An attempt is also revise to some of the terminology used in the study oi these receptors, and recent developments are reviewed in some detail. iii. Two new major receptor systems innervating the foregut are described. The posterior stomach (p.s.n.) contains a group of about 80 neurones which innervate the posterior of the gastric mill. These neurons respond to normal movements of the mill. Changes in the input from the receptors affect the output from the stomatogastric ganglion. The other system (MPRs) consists of three distinct organs totalling about 40 neurones which monitor normal movements of the structures around the mouth iv. Suggestions are made top further specific work on these two receptor systems. What is now known of the sensory innervation of the foregut is summarised and suggestions made for completing this knowledge. v. Further possible work on the ganglia and the role the associated mechanoreceptor organs is reviewed. Finally work on other problems related to the studies reported here is discussed.The metabolism of methyl methanesulphonatePillinger, David J.https://hdl.handle.net/10023/148942019-03-29T10:42:20Z1964-01-01T00:00:00ZMethyl methanesulphenate has been prepared labelled with radioactive carbon and its metabolism studied in rat, mouse and rabbit. The distribution of the drug after injection has been determined in the rat. Quantitative studies in this species have shown that less than as % of the injected drug is excreted or exhaled in 24 hours. Assay of tissue levels of radioactivity after injection has confirmed that the majority of the drug remains bound within the animal body. In the rat, the principal metabolic reaction has been shown to take place in the liver with glutathione. The S-methylglutathione formed is excreted in bile and this intermediate was the source of the urinary metabolites. In the urine, conjugates of S-methylcyateine and S-methylthioglycollic acid, together with small quantities of radioactive urea, have been recognized. The main metabolite has not been identified but appears to be a substituted guanidine compound. The possible significance of these results of these results has been discussed in terms of sell biochemistry.
1964-01-01T00:00:00ZPillinger, David J.Methyl methanesulphenate has been prepared labelled with radioactive carbon and its metabolism studied in rat, mouse and rabbit. The distribution of the drug after injection has been determined in the rat. Quantitative studies in this species have shown that less than as % of the injected drug is excreted or exhaled in 24 hours. Assay of tissue levels of radioactivity after injection has confirmed that the majority of the drug remains bound within the animal body. In the rat, the principal metabolic reaction has been shown to take place in the liver with glutathione. The S-methylglutathione formed is excreted in bile and this intermediate was the source of the urinary metabolites. In the urine, conjugates of S-methylcyateine and S-methylthioglycollic acid, together with small quantities of radioactive urea, have been recognized. The main metabolite has not been identified but appears to be a substituted guanidine compound. The possible significance of these results of these results has been discussed in terms of sell biochemistry.The action of some enzymes on bovine collagenTyson, Ian Richardsonhttps://hdl.handle.net/10023/148922019-03-29T10:36:25Z1965-01-01T00:00:00ZThe literature on collagen has been reviewed, with especial emphasis on structural aspects of collagen and the collagenolytic effects of enzymes. The proteolytic enzyme of Streptotmyces griseus (Pronase) has been examined and shown to consist of four fractions, each having proteolytic activity. The collagenolytic effect of the above enzyme and its fractions, and to a lesser extent of other enzymes has been examined by a variety of methods, both physical and chemicals using both soluble and insoluble collagen as substrates. Pronase has been shown to have a collagenolytic effect on collagen in both the soluble and insoluble states, and the products of collagenolysis have been examined. The action of Pronase has been shown to result in peptide bond cleavage only in the terminal regions of the collagen molecule, resulting in the liberation of small peptides and free amino acids, while leaving the body of the molecule intact. Fractionation of Pronase-treated collagen after denaturation showed that the three constituent chains of the collagen molecule had been separated, indicating that the enzyme is also affecting lateral cross linkages. An extract of sisal has been shown to have a proteolytic effect using gelatine as substrate, but a very slight collagenolytic effect, which is limited to collagen in solution. Insoluble collagen has been shown to contain a small quantity of non-protein-nitrogen material which can be removed by physical methods, and which consists of free amino acids, small peptides and a carbohydrate component.
1965-01-01T00:00:00ZTyson, Ian RichardsonThe literature on collagen has been reviewed, with especial emphasis on structural aspects of collagen and the collagenolytic effects of enzymes. The proteolytic enzyme of Streptotmyces griseus (Pronase) has been examined and shown to consist of four fractions, each having proteolytic activity. The collagenolytic effect of the above enzyme and its fractions, and to a lesser extent of other enzymes has been examined by a variety of methods, both physical and chemicals using both soluble and insoluble collagen as substrates. Pronase has been shown to have a collagenolytic effect on collagen in both the soluble and insoluble states, and the products of collagenolysis have been examined. The action of Pronase has been shown to result in peptide bond cleavage only in the terminal regions of the collagen molecule, resulting in the liberation of small peptides and free amino acids, while leaving the body of the molecule intact. Fractionation of Pronase-treated collagen after denaturation showed that the three constituent chains of the collagen molecule had been separated, indicating that the enzyme is also affecting lateral cross linkages. An extract of sisal has been shown to have a proteolytic effect using gelatine as substrate, but a very slight collagenolytic effect, which is limited to collagen in solution. Insoluble collagen has been shown to contain a small quantity of non-protein-nitrogen material which can be removed by physical methods, and which consists of free amino acids, small peptides and a carbohydrate component.The measurement of thyroid stimulating hormone in body fluids. histometric and radiometric techniques using the xenopus larvaBrown, Judith Rosemaryhttps://hdl.handle.net/10023/148812019-03-29T10:33:26Z1959-01-01T00:00:00ZThe work described in the preceding chapters was undertaken to determine whether the tadpole of Xenopus laevis is a suitable test-animal for measuring TSH in biological fluids. It was intended that the assay should be applicable on a routine basis for use in investigation of thyroid disorders and the findings were assessed accordingly. Studies using a histometric technique demonstrated that this method reaches the required standards of sensitivity and reliability when large test-groups are employed; accordingly, it has been used to estimate the concentration of TSH in serum. The limiting factor, where clinical application of the method is concerned, was found to be the time and labour involved in completing the estimation. An attempt was made to overcome this difficulty by application of a projection technique whereby the time required to make cell-height measurements was reduced and the method made more objective. Although, from the point of view of technical simplicity, the histometric method does not complete with either of the radiometric techniques described, it has a lower limit of sensitivity of 0.1 imu/ml. of TSH and has yielded meaningful results in assays on serum. It may be concluded, therefore, that the histometric method can be employed in this type of work provided that the time required to complete an estimation is not of major importance. The factors influencing thyroidal iodine accumulation were investigated with the aim of developing an assay method based on estimation of -uptake by the glands. A considerable individual variability in iodine uptake was demonstrated in both Xenopus larvae, reared under artificial conditions, and in larvae of the common toad, collected from their natural surroundings. Although neither diet nor temperature was found to influence this variability greatly, pretreatment with a dilute solution of potassium iodide was found to be effective to a united extent. In animals pretreated with potassium iodide it was possible to demonstrate an increase in 131I-uptake in response to administration of TSH at a concentration of 10 imu/ml. Administration of TSH was also shown to have an effect on discharge of as demonstrated by increase in the radioactivity released into the water in which the animals are immersed. This method of measuring thyroid stimulation is indirect and probably less accurate than direct determination of the activity present in the glands. It is further complicated by the presence of comparatively large amounts of iodine retained in the extrathyroidal tissues. Improvement in the sensitivity of the radiometric techniques is entirely dependent on control of individual variability in iodine uptake. In their present form, however, both the 131I-uptake method and the 131I-discharge method are suitable for application where the concentration of is 10 imu/ml. or more, and where very little material is available. Such a situation arises in comparative work on vertebrate endocrinology where small quantities of pituitary material are available in which the expected concentration of TSH would be high as compared with that in serum samples. (Abstract shortened by ProQuest.)
1959-01-01T00:00:00ZBrown, Judith RosemaryThe work described in the preceding chapters was undertaken to determine whether the tadpole of Xenopus laevis is a suitable test-animal for measuring TSH in biological fluids. It was intended that the assay should be applicable on a routine basis for use in investigation of thyroid disorders and the findings were assessed accordingly. Studies using a histometric technique demonstrated that this method reaches the required standards of sensitivity and reliability when large test-groups are employed; accordingly, it has been used to estimate the concentration of TSH in serum. The limiting factor, where clinical application of the method is concerned, was found to be the time and labour involved in completing the estimation. An attempt was made to overcome this difficulty by application of a projection technique whereby the time required to make cell-height measurements was reduced and the method made more objective. Although, from the point of view of technical simplicity, the histometric method does not complete with either of the radiometric techniques described, it has a lower limit of sensitivity of 0.1 imu/ml. of TSH and has yielded meaningful results in assays on serum. It may be concluded, therefore, that the histometric method can be employed in this type of work provided that the time required to complete an estimation is not of major importance. The factors influencing thyroidal iodine accumulation were investigated with the aim of developing an assay method based on estimation of -uptake by the glands. A considerable individual variability in iodine uptake was demonstrated in both Xenopus larvae, reared under artificial conditions, and in larvae of the common toad, collected from their natural surroundings. Although neither diet nor temperature was found to influence this variability greatly, pretreatment with a dilute solution of potassium iodide was found to be effective to a united extent. In animals pretreated with potassium iodide it was possible to demonstrate an increase in 131I-uptake in response to administration of TSH at a concentration of 10 imu/ml. Administration of TSH was also shown to have an effect on discharge of as demonstrated by increase in the radioactivity released into the water in which the animals are immersed. This method of measuring thyroid stimulation is indirect and probably less accurate than direct determination of the activity present in the glands. It is further complicated by the presence of comparatively large amounts of iodine retained in the extrathyroidal tissues. Improvement in the sensitivity of the radiometric techniques is entirely dependent on control of individual variability in iodine uptake. In their present form, however, both the 131I-uptake method and the 131I-discharge method are suitable for application where the concentration of is 10 imu/ml. or more, and where very little material is available. Such a situation arises in comparative work on vertebrate endocrinology where small quantities of pituitary material are available in which the expected concentration of TSH would be high as compared with that in serum samples. (Abstract shortened by ProQuest.)An investigation into the mecanisms mediating calcium ion-stimulated ACTH secretion from AtT-20 anterior pituitary tumour cellsMcFerran, Brian Williamhttps://hdl.handle.net/10023/148802019-03-29T10:39:08Z1996-01-01T00:00:00ZThe mouse AtT-20/D16-16 anterior pituitary tumour cell line was employed as a model system for the study of the mechanisms mediating calcium ion-stimulated adrenocorticotropin (ACTH) secretion. The present study indicates that calcium ion-stimulated ACTH secretion from AtT-20 cells is mediated by a GTP-binding protein which is present in a variety of other cell types and has been dubbed Ge (for reviews see Gomperts, 1990; Lindau & Gomperts, 1991). In AtT-20 cells the nature of Ge remains elusive with the selective heterotrimeric GTP-binding protein activator AIF(3-5) proving not to be a useful pharmacological tool under the conditions employed in the present study. Ge present in this cell line does however display characteristics consistent with it being a heterotrimeric GTP-binding protein. The results of this study would also suggest that in AtT-20 cells Ge is insensitive to both pertussis toxin and cholera toxin. Both cyclic AMP-dependent protein kinase (PKA) (Guild, 1991) and protein kinase C (PKC) (Guild & Reisine, 1987; Reisine, 1989) have been implicated in the regulation of calcium ion-stimulated ACTH secretion from AtT-20 cells. Results from the present study suggest that calcium ion/Ge-stimulated ACTH secretion from AtT-20 cells is not mediated by PKA, PKC or any other kinase but is in fact mediated by a phosphatase. PKC appears to provide a direct stimulus to secretion, which is independent of calcium ion/Ge-stimulated secretion, in contrast to PKA which is unable to stimulate secretion by itself but seems to play a modulatory role with regard to both calcium ion/Ge- and PKC-stimulated secretion.
1996-01-01T00:00:00ZMcFerran, Brian WilliamThe mouse AtT-20/D16-16 anterior pituitary tumour cell line was employed as a model system for the study of the mechanisms mediating calcium ion-stimulated adrenocorticotropin (ACTH) secretion. The present study indicates that calcium ion-stimulated ACTH secretion from AtT-20 cells is mediated by a GTP-binding protein which is present in a variety of other cell types and has been dubbed Ge (for reviews see Gomperts, 1990; Lindau & Gomperts, 1991). In AtT-20 cells the nature of Ge remains elusive with the selective heterotrimeric GTP-binding protein activator AIF(3-5) proving not to be a useful pharmacological tool under the conditions employed in the present study. Ge present in this cell line does however display characteristics consistent with it being a heterotrimeric GTP-binding protein. The results of this study would also suggest that in AtT-20 cells Ge is insensitive to both pertussis toxin and cholera toxin. Both cyclic AMP-dependent protein kinase (PKA) (Guild, 1991) and protein kinase C (PKC) (Guild & Reisine, 1987; Reisine, 1989) have been implicated in the regulation of calcium ion-stimulated ACTH secretion from AtT-20 cells. Results from the present study suggest that calcium ion/Ge-stimulated ACTH secretion from AtT-20 cells is not mediated by PKA, PKC or any other kinase but is in fact mediated by a phosphatase. PKC appears to provide a direct stimulus to secretion, which is independent of calcium ion/Ge-stimulated secretion, in contrast to PKA which is unable to stimulate secretion by itself but seems to play a modulatory role with regard to both calcium ion/Ge- and PKC-stimulated secretion.A study of vertebrate corticotrophins and related peptidesScott, Alexander P.https://hdl.handle.net/10023/148782019-03-29T10:39:59Z1974-01-01T00:00:00ZLiterature concerning the structure and localisation of ACTH, MSI-1 and related peptides in mammalian pituitaries has been reviewed and the evidence for ACTH-like peptides in non-mammalian vertebrates summarised. The structure of ACTH in non-mammalian vertebrates was studied by bioassay and radioimmunoassay. Corticotrophin immunoreactivity in pituitary extracts from a variety of species was compared with that of natural human ACTH, using five antisera which cross-reacted with different parts of the ACTH molecule. The predominant binding sites of the antisera were determined by studies with synthetic ACTH fragments. Bioactivity and N-terminal immunoactivity were found in pituitary extracts of all species studies, Differences in reactivity with the C-terminally directed antisera indicated structural differences, between corticotrophins of the lower vertebrates, reptilian, avian and mammalian pituitary extracts cross-reacted with C-terminally directed, antisera. Whole reptile and mammal pituitaries were found to contain more C- than N-terminal activity. Determination of the relative concentrations of these activities in rat and guinea-pig pituitary lobes showed that the posterior lobes contained a large excess of C-terminal activity, which released into the media in organ culture. Fluorescent staining indicated that C-terminal activity was located in the pars intermedia. C-terminal immuno-active peptides were isolated from rat and pig pituitaries and a human tumour. On gel filtration they eluted between ACTH a-d a-MSH, and behaved as acidic peptides on ion-exchange chromatography. Amino acid and end group analysis showed that they closely resembled the alpha18-39 portion of ACTH. Consequently they have been termed 'Corticotrophin-like Intermediate lobe Peptide', (CLIP). The significance of the comparative studies with crude pituitary extracts of vertebrate origin and of the C-terminally immunoactive peptide isolated from rat, pig and human pituitaries has been discussed. The close resemblance of the latter to the C-terminal portion of ACTH, and of alpha-NSH to the N-terminal part of the ACTH molecule, suggest that alpha-NSH and the C-terminal peptide are the result of intracellular cleavage of ACTH. Implications of this mechanism have been considered.
1974-01-01T00:00:00ZScott, Alexander P.Literature concerning the structure and localisation of ACTH, MSI-1 and related peptides in mammalian pituitaries has been reviewed and the evidence for ACTH-like peptides in non-mammalian vertebrates summarised. The structure of ACTH in non-mammalian vertebrates was studied by bioassay and radioimmunoassay. Corticotrophin immunoreactivity in pituitary extracts from a variety of species was compared with that of natural human ACTH, using five antisera which cross-reacted with different parts of the ACTH molecule. The predominant binding sites of the antisera were determined by studies with synthetic ACTH fragments. Bioactivity and N-terminal immunoactivity were found in pituitary extracts of all species studies, Differences in reactivity with the C-terminally directed antisera indicated structural differences, between corticotrophins of the lower vertebrates, reptilian, avian and mammalian pituitary extracts cross-reacted with C-terminally directed, antisera. Whole reptile and mammal pituitaries were found to contain more C- than N-terminal activity. Determination of the relative concentrations of these activities in rat and guinea-pig pituitary lobes showed that the posterior lobes contained a large excess of C-terminal activity, which released into the media in organ culture. Fluorescent staining indicated that C-terminal activity was located in the pars intermedia. C-terminal immuno-active peptides were isolated from rat and pig pituitaries and a human tumour. On gel filtration they eluted between ACTH a-d a-MSH, and behaved as acidic peptides on ion-exchange chromatography. Amino acid and end group analysis showed that they closely resembled the alpha18-39 portion of ACTH. Consequently they have been termed 'Corticotrophin-like Intermediate lobe Peptide', (CLIP). The significance of the comparative studies with crude pituitary extracts of vertebrate origin and of the C-terminally immunoactive peptide isolated from rat, pig and human pituitaries has been discussed. The close resemblance of the latter to the C-terminal portion of ACTH, and of alpha-NSH to the N-terminal part of the ACTH molecule, suggest that alpha-NSH and the C-terminal peptide are the result of intracellular cleavage of ACTH. Implications of this mechanism have been considered.A study of neuromodulation using the isolated locust (Schistocerca gregaria) first basalar motoneurone as an 'in vitro' modelProthero, Larissa S.https://hdl.handle.net/10023/148752019-03-29T10:42:42Z1997-01-01T00:00:00Z1. A technique has been developed to isolate the first basalar (BA1) motoneurone of the locust (Schistocerca gregaria) from its ganglionic environment. The isolated neurone soma remained viable (often for up to 9hrs), enabling its electrophysiological and pharmacological properties to be investigated. The findings of these studies were comparable with those from the BA1 motoneurone in situ, and with other insect neurones whether studied in vitro or in situ. 2. The application of selected agonists to the isolated BA1 motoneurone soma demonstrated the presence of nicotinic and muscarinic acetylcholine receptors, GABA receptors and dopamine (DA) receptors. The membrane depolarization evoked by nicotine was blocked by BTX, while the GABA- induced membrane hyperpolarization response was sensitive to picrotoxin. Muscarinic receptor and DA receptor activation both induced membrane depolarization which was evoked without a detectable change in membrane conductance. The ionic dependency of these agonist-induced responses is discussed. 3. When applied between pressure applications of GABA, DA could induce either membrane depolarization or hyperpolarization, both of which were associated with an increase in membrane conductance. Furthermore, the amplitude and/or duration of the GABA response was potentiated by DA. Possible mechanisms underlying these observations are proposed. 4. Using the Ca2+-sensitive fluorescence probe, fluo-3, and confocal laser scarming microscopy, the effects of the muscarinic agonist, McN A-343, and DA on [Ca2+]i in the isolated BA1 motoneurone were examined. McN evoked an increase in [Ca2+]i, whilst DA evoked a decrease in [Ca2+]i. Similar observations were made from isolated cockroach fast coxal depressor (Df) motoneurones. The cellular events underlying these observations are discussed. 5. A technique was established to maintain dissociated unidentified adult locust neurones in culture for up to two weeks; a similar protocol was used to maintain isolated BA1 motoneurones in culture. Electrophysiological recording techniques demonstrated that the neurones remained viable in culture.
1997-01-01T00:00:00ZProthero, Larissa S.1. A technique has been developed to isolate the first basalar (BA1) motoneurone of the locust (Schistocerca gregaria) from its ganglionic environment. The isolated neurone soma remained viable (often for up to 9hrs), enabling its electrophysiological and pharmacological properties to be investigated. The findings of these studies were comparable with those from the BA1 motoneurone in situ, and with other insect neurones whether studied in vitro or in situ. 2. The application of selected agonists to the isolated BA1 motoneurone soma demonstrated the presence of nicotinic and muscarinic acetylcholine receptors, GABA receptors and dopamine (DA) receptors. The membrane depolarization evoked by nicotine was blocked by BTX, while the GABA- induced membrane hyperpolarization response was sensitive to picrotoxin. Muscarinic receptor and DA receptor activation both induced membrane depolarization which was evoked without a detectable change in membrane conductance. The ionic dependency of these agonist-induced responses is discussed. 3. When applied between pressure applications of GABA, DA could induce either membrane depolarization or hyperpolarization, both of which were associated with an increase in membrane conductance. Furthermore, the amplitude and/or duration of the GABA response was potentiated by DA. Possible mechanisms underlying these observations are proposed. 4. Using the Ca2+-sensitive fluorescence probe, fluo-3, and confocal laser scarming microscopy, the effects of the muscarinic agonist, McN A-343, and DA on [Ca2+]i in the isolated BA1 motoneurone were examined. McN evoked an increase in [Ca2+]i, whilst DA evoked a decrease in [Ca2+]i. Similar observations were made from isolated cockroach fast coxal depressor (Df) motoneurones. The cellular events underlying these observations are discussed. 5. A technique was established to maintain dissociated unidentified adult locust neurones in culture for up to two weeks; a similar protocol was used to maintain isolated BA1 motoneurones in culture. Electrophysiological recording techniques demonstrated that the neurones remained viable in culture.Alpha-bungarotoxin-resistant cholinergic receptors on an identified locust flight motoneuroneAnderson, Linda J.https://hdl.handle.net/10023/148742019-03-29T10:31:37Z1995-01-01T00:00:00Z1. There is a population of alpha-bungarotoxin-resistant cholinergic receptors on the soma of the first basalar motoneurone of the locust, Schistocerca gregaria. 2. The receptors have a broadly muscarinic pharmacology: the response to pressure-applied ACh can be reversibly reduced by the global muscarinic antagonists atropine and dexetimide, and the vertebrate muscarinic subtype-selective antagonists pirenzepine (M1 subtype-selective), 4-DAMP (M3), p-F-HHSiD (M3>M1>M2) and methoctramine (M2). 3. In the presence of alpha-bungarotoxin, however, nicotine evokes a current similar to those induced by the muscarinic agonists muscarine, McN-A-343 and carbachol under voltage clamp; the nicotine-induced current can be blocked by the muscarinic antagonist scopolamine, suggesting that these 'muscarinic' receptors have a 'mixed' cholinergic pharmacology. 4. Under voltage clamp, activation of the receptors by the muscarinic agonists muscarine and McN-A-343, and the cholinergic agonist carbachol (in the presence of alpha-bungarotoxin) evokes an inward current at command potentials between -100 and 0 mV. This current is time- and voltage-dependent: the current component evoked at potentials more negative than -40 mV is relatively small, and either increases continuously during 15 min exposure to agonist, or increases to a maximum after 5 or 10 min before decreasing. At potentials more positive than -40 mV, the current component is larger, and increases continuously in the presence of drug. In approximately 50% of neurones voltage clamped at a holding potential of -50 mV, the inward current is preceded by an initial outward current at potentials positive to -40 mV. After 1 min exposure to agonist, the outward current reverses and becomes inwardly-directed, increasing in amplitude in the presence of agonist. 5. The apparent inward current evoked by McN-A-343 at potentials positive to -40 mV is due to the inhibition of a voltage-dependent K+ current, and may involve the production of cAMP. Activation of the 'mixed' receptors also stimulates the release of Ca2+ from intracellular stores. 6. The input resistance of the neurone, measured under current clamp, is increased by McN-A-343 in some preparations and decreased in others. The agonist decreases the spike threshold of the neurone, and therefore the physiological role of these 'mixed' receptors may be to modulate the excitability of the neurone.
1995-01-01T00:00:00ZAnderson, Linda J.1. There is a population of alpha-bungarotoxin-resistant cholinergic receptors on the soma of the first basalar motoneurone of the locust, Schistocerca gregaria. 2. The receptors have a broadly muscarinic pharmacology: the response to pressure-applied ACh can be reversibly reduced by the global muscarinic antagonists atropine and dexetimide, and the vertebrate muscarinic subtype-selective antagonists pirenzepine (M1 subtype-selective), 4-DAMP (M3), p-F-HHSiD (M3>M1>M2) and methoctramine (M2). 3. In the presence of alpha-bungarotoxin, however, nicotine evokes a current similar to those induced by the muscarinic agonists muscarine, McN-A-343 and carbachol under voltage clamp; the nicotine-induced current can be blocked by the muscarinic antagonist scopolamine, suggesting that these 'muscarinic' receptors have a 'mixed' cholinergic pharmacology. 4. Under voltage clamp, activation of the receptors by the muscarinic agonists muscarine and McN-A-343, and the cholinergic agonist carbachol (in the presence of alpha-bungarotoxin) evokes an inward current at command potentials between -100 and 0 mV. This current is time- and voltage-dependent: the current component evoked at potentials more negative than -40 mV is relatively small, and either increases continuously during 15 min exposure to agonist, or increases to a maximum after 5 or 10 min before decreasing. At potentials more positive than -40 mV, the current component is larger, and increases continuously in the presence of drug. In approximately 50% of neurones voltage clamped at a holding potential of -50 mV, the inward current is preceded by an initial outward current at potentials positive to -40 mV. After 1 min exposure to agonist, the outward current reverses and becomes inwardly-directed, increasing in amplitude in the presence of agonist. 5. The apparent inward current evoked by McN-A-343 at potentials positive to -40 mV is due to the inhibition of a voltage-dependent K+ current, and may involve the production of cAMP. Activation of the 'mixed' receptors also stimulates the release of Ca2+ from intracellular stores. 6. The input resistance of the neurone, measured under current clamp, is increased by McN-A-343 in some preparations and decreased in others. The agonist decreases the spike threshold of the neurone, and therefore the physiological role of these 'mixed' receptors may be to modulate the excitability of the neurone.Some electrophysiological and biochemical effects of denervation on the central nervous system of the cockroach, Periplaneta Americana L.David, Jonathan Anthonyhttps://hdl.handle.net/10023/148732019-03-29T10:43:21Z1979-01-01T00:00:00ZThe effect of denervation on the excitability of cockroach central neurones has been investigated using both extracellular and Intracellular recording techniques. Stimulation of the anterior connectives produced a response in the flexor tibiae muscle 143b of the metathoracic segment. This muscle response could be correlated with action potentials in the anterior connective and fifth nerve trunk innervating the leg. The ganglionic delay for this pathway was 1,42 +/- 0.07 ms (n=6) suggesting the presence of a single synapse. This was reduced to 0.86 +/- 0.10 ms (n=10) 19-96 hours after cutting the contralateral fifth nerve trunk. It is suggested that this reduction in ganglionic delay could result from an increase in the excitability of the postsynatpic cell caused by differentiation. Intracellular recording were made from the cell body of the fast coxal depressor motoneurone (Df) in the me metathoracic ganglion. Acetylcholine (ACh) applied to the soma either topically or by iontophoresis caused dopolarisation of the cell membrane and if repeated in large doses resulted in rapid desensitisation and depression of the response. Some Df motoneurones were axotomised by cutting the ipsilateral fifth nerve trunk 4-118 days before the experiment. The sensitivity to ACh increased approximately three fold following axotomy. However there was no change in the mean resting potential, input resistance or membrane time constant. The change in sensitivity to ACh produced by axotomy was apparently not a result of a redistribution of cholinoceptors on the soma membrane since the rise Lime of the ACh responses were similar in control and axotomised preparations. Analysis also showed that there was no difference between control and axotomised cells in the number of ACh molecules needed to combine with individual cholinoceptors to produce a response. Similarly there was no significant difference in the mean values of the ACh reversal potential in control and axotomised neurones (as determined by extrapolation). It is suggested that the supersensitivity to ACh is due to a decreased inactivation of ACh by acetylcholinesterase since (i) the anticholinesterases physostigmine and neostigmine produced a greater potentiation of the ACh response in normal than in axotomised neurones and (ii) there was no significant difference in the sensitivity of control and axotomised cells to carbamylcholine. This suggestion is supported by the results obtained from a biochemical study in which the cholinesterase activity of normal and denervated metathoracic ganglia was determined. Denervation was produced by transection of both fifth nerve trunks 5-8 days before the assay. Denervated ganglia showed an approximately 33% reduction in their capacity to hydrolyse AThCh.
1979-01-01T00:00:00ZDavid, Jonathan AnthonyThe effect of denervation on the excitability of cockroach central neurones has been investigated using both extracellular and Intracellular recording techniques. Stimulation of the anterior connectives produced a response in the flexor tibiae muscle 143b of the metathoracic segment. This muscle response could be correlated with action potentials in the anterior connective and fifth nerve trunk innervating the leg. The ganglionic delay for this pathway was 1,42 +/- 0.07 ms (n=6) suggesting the presence of a single synapse. This was reduced to 0.86 +/- 0.10 ms (n=10) 19-96 hours after cutting the contralateral fifth nerve trunk. It is suggested that this reduction in ganglionic delay could result from an increase in the excitability of the postsynatpic cell caused by differentiation. Intracellular recording were made from the cell body of the fast coxal depressor motoneurone (Df) in the me metathoracic ganglion. Acetylcholine (ACh) applied to the soma either topically or by iontophoresis caused dopolarisation of the cell membrane and if repeated in large doses resulted in rapid desensitisation and depression of the response. Some Df motoneurones were axotomised by cutting the ipsilateral fifth nerve trunk 4-118 days before the experiment. The sensitivity to ACh increased approximately three fold following axotomy. However there was no change in the mean resting potential, input resistance or membrane time constant. The change in sensitivity to ACh produced by axotomy was apparently not a result of a redistribution of cholinoceptors on the soma membrane since the rise Lime of the ACh responses were similar in control and axotomised preparations. Analysis also showed that there was no difference between control and axotomised cells in the number of ACh molecules needed to combine with individual cholinoceptors to produce a response. Similarly there was no significant difference in the mean values of the ACh reversal potential in control and axotomised neurones (as determined by extrapolation). It is suggested that the supersensitivity to ACh is due to a decreased inactivation of ACh by acetylcholinesterase since (i) the anticholinesterases physostigmine and neostigmine produced a greater potentiation of the ACh response in normal than in axotomised neurones and (ii) there was no significant difference in the sensitivity of control and axotomised cells to carbamylcholine. This suggestion is supported by the results obtained from a biochemical study in which the cholinesterase activity of normal and denervated metathoracic ganglia was determined. Denervation was produced by transection of both fifth nerve trunks 5-8 days before the assay. Denervated ganglia showed an approximately 33% reduction in their capacity to hydrolyse AThCh.Human cytomegalovirus major immediate early 1 protein targets host chromosomes by docking to the acidic pocket on the nucleosome surfaceMücke, KatrinPaulus, ChristinaBernhardt, KatharinaGerrer, KatrinSchön, KathrinFink, AlinaSauer, Eva-MariaAsbach-Nitzsche, AlexandraHarwardt, ThomasKieninger, BärbelKremer, WernerKalbitzer, Hans RobertNevels, Michaelhttps://hdl.handle.net/10023/148712022-07-05T10:30:02Z2014-01-15T00:00:00ZThe 72-kDa immediate early 1 (IE1) protein encoded by human cytomegalovirus (hCMV) is a nuclearly localized promiscuous regulator of viral and cellular transcription. IE1 has long been known to associate with host mitotic chromatin, yet the mechanisms underlying this interaction have not been specified. In this study, we identify the cellular chromosome receptor for IE1. We demonstrate that the viral protein targets human nucleosomes by directly binding to core histones in a nucleic acid-independent manner. IE1 exhibits two separable histone-interacting regions with differential binding specificities for H2A-H2B and H3-H4. The H2A-H2B binding region was mapped to an evolutionarily conserved 10-amino-acid motif within the chromatin-tethering domain (CTD) of IE1. Results from experimental approaches combined with molecular modeling indicate that the IE1 CTD adopts a β-hairpin structure, docking with the acidic pocket formed by H2A-H2B on the nucleosome surface. IE1 binds to the acidic pocket in a way similar to that of the latency-associated nuclear antigen (LANA) of the Kaposi's sarcoma-associated herpesvirus. Consequently, the IE1 and LANA CTDs compete for binding to nucleosome cores and chromatin. Our work elucidates in detail how a key viral regulator is anchored to human chromosomes and identifies the nucleosomal acidic pocket as a joint target of proteins from distantly related viruses. Based on the striking similarities between the IE1 and LANA CTDs and the fact that nucleosome targeting by IE1 is dispensable for productive replication even in "clinical" strains of hCMV, we speculate that the two viral proteins may serve analogous functions during latency of their respective viruses.
2014-01-15T00:00:00ZMücke, KatrinPaulus, ChristinaBernhardt, KatharinaGerrer, KatrinSchön, KathrinFink, AlinaSauer, Eva-MariaAsbach-Nitzsche, AlexandraHarwardt, ThomasKieninger, BärbelKremer, WernerKalbitzer, Hans RobertNevels, MichaelThe 72-kDa immediate early 1 (IE1) protein encoded by human cytomegalovirus (hCMV) is a nuclearly localized promiscuous regulator of viral and cellular transcription. IE1 has long been known to associate with host mitotic chromatin, yet the mechanisms underlying this interaction have not been specified. In this study, we identify the cellular chromosome receptor for IE1. We demonstrate that the viral protein targets human nucleosomes by directly binding to core histones in a nucleic acid-independent manner. IE1 exhibits two separable histone-interacting regions with differential binding specificities for H2A-H2B and H3-H4. The H2A-H2B binding region was mapped to an evolutionarily conserved 10-amino-acid motif within the chromatin-tethering domain (CTD) of IE1. Results from experimental approaches combined with molecular modeling indicate that the IE1 CTD adopts a β-hairpin structure, docking with the acidic pocket formed by H2A-H2B on the nucleosome surface. IE1 binds to the acidic pocket in a way similar to that of the latency-associated nuclear antigen (LANA) of the Kaposi's sarcoma-associated herpesvirus. Consequently, the IE1 and LANA CTDs compete for binding to nucleosome cores and chromatin. Our work elucidates in detail how a key viral regulator is anchored to human chromosomes and identifies the nucleosomal acidic pocket as a joint target of proteins from distantly related viruses. Based on the striking similarities between the IE1 and LANA CTDs and the fact that nucleosome targeting by IE1 is dispensable for productive replication even in "clinical" strains of hCMV, we speculate that the two viral proteins may serve analogous functions during latency of their respective viruses.Visual responses in locustsWallace, George Kyddhttps://hdl.handle.net/10023/148702019-03-29T10:36:16Z1958-01-01T00:00:00ZThe investigation reported here is concerned with the study of certain visual responses in the Desert Locust Schistocerca gregaria. (Forsis). It is a behaviour study. The aim is to form some idea of the kind of information which the Insect is obtaining by means of compound eyes and the way in which this is manipulated. II Form perception. a. In spontaneous choice experiments it is shown that nymphs of the Desert Locust are attracted to black objects on a white background and to the contour lines of these objects. The degree of contrast between the object and the background is important. On a white background the darker the object the more attractive it is. III. Peering. a. It is shown that the swaying of the front part of the body and the head from side to side, called peering, is a visual response. An apparatus is described for measuring the angle through which the head moves laterally with respect to the original position of the longitudinal axis of the body. IV. Antenna waving. a. Two main types of antenna movement are distinguished - flicking and beating. The former is a movement of one antenna usually occurring as the insect passes an object. The latter is the alternate movement of both antennae as the insect is approaching head-on and close to an object. b. Flicking: The antenna to be flicked is the one on the same side as the object and the response occurs when the edge of the object is seen by the more lateral part of the eye. In conjunction with the flicking, the antenna in question is often pointed at the object edge. c. Beating: This takes place at a short distance from an object (less than one inch), the distance being independent of the angle sub-tended by the object. V. Responses to movement. a. Fright response to the movement of a large object across the visual field. The response varies in intensity. At low intensity the insect tenses; at higher intensity the insect jerks; at the highest intensity observed the insect moves (backs or moves sideways) away from the object. The response decreases with increased distance. b. Optomotor response; The insects show an optomotor response to moving stripes. They follow the movement of the stripes. The stimulus is effective even when it only occupies a small part of the visual field and the insects respond to stripes moving from front to rear of the eye and from rear to front. Moving stripes stimulating the anterior part of the eye appear to have less effect in releasing the optomotor response than when stimulating the lateral parts of the eye. The insects walk toward a steady movement of stripes in front of them. If the stripe movement is intermittent the insects show the fright response. VI. Discussion. The results of all the experiments are discussed and a system proposed whereby the insect responds to the stimulation of the visual receptors produced by the movement of the images of contours over the retina. The properties of the system are discussed well as the behaviour which would be expected as the results of these. A comparison is then made with the behaviour observed in the present investigation. One possible way in which such a system could be elaborated is briefly considered. VII. Conclusion. The conclusion is reached that, although the work has dealt with only few of the visual responses of these insects, sufficient information has been obtained to show that the insects possess a highly developed visual sense, that their compound eyes are quite efficient navigating instruments and that visual responses play a large part in the total behaviour repertoire, The analyses of the stimuli involved in each response studied gives some insight into the nature of this insect's visual environment.
1958-01-01T00:00:00ZWallace, George KyddThe investigation reported here is concerned with the study of certain visual responses in the Desert Locust Schistocerca gregaria. (Forsis). It is a behaviour study. The aim is to form some idea of the kind of information which the Insect is obtaining by means of compound eyes and the way in which this is manipulated. II Form perception. a. In spontaneous choice experiments it is shown that nymphs of the Desert Locust are attracted to black objects on a white background and to the contour lines of these objects. The degree of contrast between the object and the background is important. On a white background the darker the object the more attractive it is. III. Peering. a. It is shown that the swaying of the front part of the body and the head from side to side, called peering, is a visual response. An apparatus is described for measuring the angle through which the head moves laterally with respect to the original position of the longitudinal axis of the body. IV. Antenna waving. a. Two main types of antenna movement are distinguished - flicking and beating. The former is a movement of one antenna usually occurring as the insect passes an object. The latter is the alternate movement of both antennae as the insect is approaching head-on and close to an object. b. Flicking: The antenna to be flicked is the one on the same side as the object and the response occurs when the edge of the object is seen by the more lateral part of the eye. In conjunction with the flicking, the antenna in question is often pointed at the object edge. c. Beating: This takes place at a short distance from an object (less than one inch), the distance being independent of the angle sub-tended by the object. V. Responses to movement. a. Fright response to the movement of a large object across the visual field. The response varies in intensity. At low intensity the insect tenses; at higher intensity the insect jerks; at the highest intensity observed the insect moves (backs or moves sideways) away from the object. The response decreases with increased distance. b. Optomotor response; The insects show an optomotor response to moving stripes. They follow the movement of the stripes. The stimulus is effective even when it only occupies a small part of the visual field and the insects respond to stripes moving from front to rear of the eye and from rear to front. Moving stripes stimulating the anterior part of the eye appear to have less effect in releasing the optomotor response than when stimulating the lateral parts of the eye. The insects walk toward a steady movement of stripes in front of them. If the stripe movement is intermittent the insects show the fright response. VI. Discussion. The results of all the experiments are discussed and a system proposed whereby the insect responds to the stimulation of the visual receptors produced by the movement of the images of contours over the retina. The properties of the system are discussed well as the behaviour which would be expected as the results of these. A comparison is then made with the behaviour observed in the present investigation. One possible way in which such a system could be elaborated is briefly considered. VII. Conclusion. The conclusion is reached that, although the work has dealt with only few of the visual responses of these insects, sufficient information has been obtained to show that the insects possess a highly developed visual sense, that their compound eyes are quite efficient navigating instruments and that visual responses play a large part in the total behaviour repertoire, The analyses of the stimuli involved in each response studied gives some insight into the nature of this insect's visual environment.An electrophysiological study of putative neurotransmitters and histochemical localisation of biogenic amines in the central nervous system of the cockroach 'Periplanea Americana'Fleming, Jean Royhttps://hdl.handle.net/10023/148682019-03-29T10:37:45Z1987-01-01T00:00:00ZA modification of the fluorescent histochemical glyoxylic acid (GA) method was used for localization of biogenic amines in wholemount ventral nerve cord and suboesophageal ganglia of the cockroach, Periplaneta americana. The distributions of fluorescent neurone somata within each ganglion and of nerve processes within the ganglia, interganglionic connectives and peripheral nerves were determined. An assessment was made of the effects of colchicine, nialamide plus DOPA and reserpine on the specific tissue fluorescence. The available evidence suggests that most of the specific fluorescence is due to dopamine. Infusion of hexamminecobaltic chloride was used to identify which fluorescent neurone pairs in the prothoracic and suboesophageal ganglia projected into the interganglionic connnectives and peripheral nerves. In order to determine the detailed morphology of certain of the fluorescent neurones GA was combined with intracellular injection of either Lucifer Yellow, hexamminecobaltic chloride, or Horseradish peroxidase. Technical difficulties, however, were encountered with the identification and filling of the neurones. A prothoracic neurone was identified which depolarized in response to pressure ejected and bath applied dopamine and noradrenaline. Both phentolamine and propranolol reversibly inhibited the dopamine response, although these drugs were also effective at antagonizing the cell's response to acetylcholine. Bath application of the drugs forskolin, IBMX and dibutyryl cyclic AMP provided evidence that in this case dopamine does not act through the second messenger, cyclic AMP. Additional electrophysiological experiments determined the effect of pressure ejected application of glutamate and GABA upon the electrical response of an identified metathoracic motoneurone. Picrotoxin reversibly inhibited the amino acid responses. Long term application of both picrotoxin and 4-acetamido-4' -isothiocyanostilbene-2,2'-disulphonic acid (SITS) produced changes in the membrane properties of the neurone such that the neurone somata became able to actively support action potentials.
1987-01-01T00:00:00ZFleming, Jean RoyA modification of the fluorescent histochemical glyoxylic acid (GA) method was used for localization of biogenic amines in wholemount ventral nerve cord and suboesophageal ganglia of the cockroach, Periplaneta americana. The distributions of fluorescent neurone somata within each ganglion and of nerve processes within the ganglia, interganglionic connectives and peripheral nerves were determined. An assessment was made of the effects of colchicine, nialamide plus DOPA and reserpine on the specific tissue fluorescence. The available evidence suggests that most of the specific fluorescence is due to dopamine. Infusion of hexamminecobaltic chloride was used to identify which fluorescent neurone pairs in the prothoracic and suboesophageal ganglia projected into the interganglionic connnectives and peripheral nerves. In order to determine the detailed morphology of certain of the fluorescent neurones GA was combined with intracellular injection of either Lucifer Yellow, hexamminecobaltic chloride, or Horseradish peroxidase. Technical difficulties, however, were encountered with the identification and filling of the neurones. A prothoracic neurone was identified which depolarized in response to pressure ejected and bath applied dopamine and noradrenaline. Both phentolamine and propranolol reversibly inhibited the dopamine response, although these drugs were also effective at antagonizing the cell's response to acetylcholine. Bath application of the drugs forskolin, IBMX and dibutyryl cyclic AMP provided evidence that in this case dopamine does not act through the second messenger, cyclic AMP. Additional electrophysiological experiments determined the effect of pressure ejected application of glutamate and GABA upon the electrical response of an identified metathoracic motoneurone. Picrotoxin reversibly inhibited the amino acid responses. Long term application of both picrotoxin and 4-acetamido-4' -isothiocyanostilbene-2,2'-disulphonic acid (SITS) produced changes in the membrane properties of the neurone such that the neurone somata became able to actively support action potentials.The first and second neural projections of the insect eyeMeinertzhagen, Ian A.https://hdl.handle.net/10023/148652019-03-29T10:32:02Z1971-01-01T00:00:00Z1. The patterns of projection of some of the perpendicular neurones between the retina and medulla of the optic lobes of various insects have been studied. Axon paths have been studied from consecutive semi-thin plastic sections cut transversely and stained with toluidine blue. The termination positions and the paths of axons are both highly ordered and predictable. 2. In all insects with fused-rhabdomere eyes the axons of one ommatidium project to one cartridge of the lamina and the array of cartridges duplicates the array of ommatidia. In insects with open-rhabdomere eyes visual information is distributed amongst a number of lamina cartridges so that each cartridge receives information originating from one visual axis. 3. In both open- and fused-rhabdomere types the cartridge, array of the lamina is exactly duplicated in the medulla but by the intervention of the chiasma is reversed about a dorso-ventral plane. The axons of one lamina cartridge contribute to one medulla cartridge. Thus, in all insects studied, the visual field is projected exactly from retina to medulla. 4. Most of the retinula axons from one ommatidium terminate in the lamina but usually one pair passes directly to the medulla. These are from the central retinula cells (open-rhabdomere eyes) or from the small retinula cells (apposition type fused-rhabdomere eyes). Retinal responses are known mainly only for the short retinula axons so that visual information delivered to the medulla cartridge is still largely unresolved. 5. The lamina neuropile probably contains the elements responsible for the lateral correlation between parallel receptor inputs which is necessary for movement perception, but units with long lasting responses which could act as the delay circuit of movement perception are unknown. 6. The occurrence of errors in termination of the first projection of the optic lobe of the fly, which are reported for the first time in this work, provide no direct clues to the developmental processes by which such a morphologically complex system arises. Nevertheless errors may arise within a sequence of growth processes which are fundamentally quite simple and not obvious from knowledge of the generalized perfect pattern of connections.
1971-01-01T00:00:00ZMeinertzhagen, Ian A.1. The patterns of projection of some of the perpendicular neurones between the retina and medulla of the optic lobes of various insects have been studied. Axon paths have been studied from consecutive semi-thin plastic sections cut transversely and stained with toluidine blue. The termination positions and the paths of axons are both highly ordered and predictable. 2. In all insects with fused-rhabdomere eyes the axons of one ommatidium project to one cartridge of the lamina and the array of cartridges duplicates the array of ommatidia. In insects with open-rhabdomere eyes visual information is distributed amongst a number of lamina cartridges so that each cartridge receives information originating from one visual axis. 3. In both open- and fused-rhabdomere types the cartridge, array of the lamina is exactly duplicated in the medulla but by the intervention of the chiasma is reversed about a dorso-ventral plane. The axons of one lamina cartridge contribute to one medulla cartridge. Thus, in all insects studied, the visual field is projected exactly from retina to medulla. 4. Most of the retinula axons from one ommatidium terminate in the lamina but usually one pair passes directly to the medulla. These are from the central retinula cells (open-rhabdomere eyes) or from the small retinula cells (apposition type fused-rhabdomere eyes). Retinal responses are known mainly only for the short retinula axons so that visual information delivered to the medulla cartridge is still largely unresolved. 5. The lamina neuropile probably contains the elements responsible for the lateral correlation between parallel receptor inputs which is necessary for movement perception, but units with long lasting responses which could act as the delay circuit of movement perception are unknown. 6. The occurrence of errors in termination of the first projection of the optic lobe of the fly, which are reported for the first time in this work, provide no direct clues to the developmental processes by which such a morphologically complex system arises. Nevertheless errors may arise within a sequence of growth processes which are fundamentally quite simple and not obvious from knowledge of the generalized perfect pattern of connections.Cytotaxonomy of ticksKahn, Jacobhttps://hdl.handle.net/10023/148632019-03-29T10:29:22Z1961-01-01T00:00:00Z(1) This study of the nuclear cytology of ticks was undertaken in the hope that it might assist in problems of identification. Papers published hitherto on the nuclear cytology of ticks and mites are reviewed. (2) The material studied consists of laboratory bred specimens of ten species representing five Ixodid genera. The source and identifications as well as the rearing of Ixodid ticks are described in detail. (3) The preparation of organs and eggs, and the equipment used in this study are described. (4) An exhaustive account is given of (a) male and female mitosis of all ten species, (b) male meiosis of nine species and female meiosis of one species. (5) General aspects of the nuclear eytology of ticks, such as endomitosis, spermatogenesis and karyomerokinesis, are discussed in conjunction with the material described. (6) Incidental observations on the anatomy of Ixodes testes and their accessory glands are compared with Douglas' description of D. andersoni. (7) The discussion summarises the eytologioal observations and their bearing on taxonomy and phylogeny. It is suggested that Ixodes should be given the status of a family.
1961-01-01T00:00:00ZKahn, Jacob(1) This study of the nuclear cytology of ticks was undertaken in the hope that it might assist in problems of identification. Papers published hitherto on the nuclear cytology of ticks and mites are reviewed. (2) The material studied consists of laboratory bred specimens of ten species representing five Ixodid genera. The source and identifications as well as the rearing of Ixodid ticks are described in detail. (3) The preparation of organs and eggs, and the equipment used in this study are described. (4) An exhaustive account is given of (a) male and female mitosis of all ten species, (b) male meiosis of nine species and female meiosis of one species. (5) General aspects of the nuclear eytology of ticks, such as endomitosis, spermatogenesis and karyomerokinesis, are discussed in conjunction with the material described. (6) Incidental observations on the anatomy of Ixodes testes and their accessory glands are compared with Douglas' description of D. andersoni. (7) The discussion summarises the eytologioal observations and their bearing on taxonomy and phylogeny. It is suggested that Ixodes should be given the status of a family.Development of gene probes to P virus (Reoviridae) for disease diagnosis in crustaceansWalton, Alisonhttps://hdl.handle.net/10023/148612019-03-29T10:41:40Z1999-01-01T00:00:00ZThis study reports the development of two important techniques, gene probes and haemocyte cultures that have not been previously available to investigate viral diseases in temperate water marine decapods. These techniques were used to investigate numerous aspects of a reovirus infection of the swimming crab Liocarcinus depurator, P virus, both in vivo and in vitro. The construction and subsequent use of a gene probe has revealed that, not only can virus be experimentally transmitted to L. depurator by injection, but that it is present in natural populations of crabs from the North Sea. Seasonal variation in both incidence of P infection and in incubation time was observed. The incidence of infection increased with increasing temperature whereas incubation time decreased with increasing temperature. In vivo, P virus was found to cause marked haemocytopenia in infected L. depurator and a cytopathic effect, vacuolisation of haemocytes was observed. This effect was not observed in the haemocytes of the shore crab, Carcinus maenas, providing evidence that P virus does not infect this species. To address the lack of techniques for in vitro studies, a cell culture system for crustacean haemocytes was developed. Primary culture of two haemocyte types, hyaline and semi-granular haemocytes was established for haemocytes of both L. depurator and C. maenas. High haemocyte viability was obtained for at least two weeks and, cells retained their functional capabilities in vitro. Having successfully established a haemocyte culture system and the gene probe E2b, it was then possible to begin investigations on P virus infections in vitro. P virus produced a number of effects on haemocytes of L. depurator in vitro. Haemocyte number and haemocyte viability decreased after addition of P virus and a number of cytopathic effects were observed such as necrosis, pycnosis and vacuolisation.
1999-01-01T00:00:00ZWalton, AlisonThis study reports the development of two important techniques, gene probes and haemocyte cultures that have not been previously available to investigate viral diseases in temperate water marine decapods. These techniques were used to investigate numerous aspects of a reovirus infection of the swimming crab Liocarcinus depurator, P virus, both in vivo and in vitro. The construction and subsequent use of a gene probe has revealed that, not only can virus be experimentally transmitted to L. depurator by injection, but that it is present in natural populations of crabs from the North Sea. Seasonal variation in both incidence of P infection and in incubation time was observed. The incidence of infection increased with increasing temperature whereas incubation time decreased with increasing temperature. In vivo, P virus was found to cause marked haemocytopenia in infected L. depurator and a cytopathic effect, vacuolisation of haemocytes was observed. This effect was not observed in the haemocytes of the shore crab, Carcinus maenas, providing evidence that P virus does not infect this species. To address the lack of techniques for in vitro studies, a cell culture system for crustacean haemocytes was developed. Primary culture of two haemocyte types, hyaline and semi-granular haemocytes was established for haemocytes of both L. depurator and C. maenas. High haemocyte viability was obtained for at least two weeks and, cells retained their functional capabilities in vitro. Having successfully established a haemocyte culture system and the gene probe E2b, it was then possible to begin investigations on P virus infections in vitro. P virus produced a number of effects on haemocytes of L. depurator in vitro. Haemocyte number and haemocyte viability decreased after addition of P virus and a number of cytopathic effects were observed such as necrosis, pycnosis and vacuolisation.Antibacterial activity in the blood cells of 'Carcinas maenas' (L.) and other crustaceansChisholm, June R. S.https://hdl.handle.net/10023/148592019-03-29T10:33:41Z1993-01-01T00:00:00ZIn vitro antibacterial activity in the haemocytes of Carcinus maenas (L) was investigated. Haemocyte lysate supernatants (HLS) were assayed against twelve Gram-positive and Gram-negative marine bacteria, eight of which proved sensitive to the antibacterial factor or factors contained therein. Antibacterial activity was also found in HLS from four other marine crustaceans-Glyptonotus antarcticus, Galathea strigosa, Nephrops norvegicus and Crangon crangon. Activity in C. maenas HLS was independent of divalent cations, operated at high titre, was stable after treatment at 100 °C for 30 minutes and also after three months storage at -70 °C; it was present in the granular cells (which also contain the prophenoloxidase (proPO) activating system, a putative recognition mechanism in arthropods), but was absent from hyaline cells and plasma. In vitro studies were carried out to determine whether a relationship exists between the proPO system and the antibacterial activity in the haemocytes of C. maenas. It was shown that phenoloxidase and an activating serine protease were not responsible for the observed antimicrobial effects, although the possibility that activity resides with some other component of the proPO system has not been excluded. Seasonal variation in antibacterial activity, haemocyte counts and HLS protein concentrations was found, with conspicuous depression of antibacterial activity at two key points in the year. This occurred in conjunction with extremes of water temperature and it is proposed that the variation in antibacterial activity is due to underlying temperature effects on haemocyte counts and protein levels. Low levels of lytic activity against Micrococcus luteus cell walls and low levels of bacterial agglutination were recorded, but the powerful antibacterial activity in HLS could not be attributed to these alone. Gel filtration with Sephadex G-l00 revealed at least three antibacterial proteins of differing molecular size, with estimated MW of 72 kDa, 34 kDa and 4 kDa. The 72 kDa and 34 kDa proteins were bacteriostatic and the 4 kDa protein was bacteriolytic.
1993-01-01T00:00:00ZChisholm, June R. S.In vitro antibacterial activity in the haemocytes of Carcinus maenas (L) was investigated. Haemocyte lysate supernatants (HLS) were assayed against twelve Gram-positive and Gram-negative marine bacteria, eight of which proved sensitive to the antibacterial factor or factors contained therein. Antibacterial activity was also found in HLS from four other marine crustaceans-Glyptonotus antarcticus, Galathea strigosa, Nephrops norvegicus and Crangon crangon. Activity in C. maenas HLS was independent of divalent cations, operated at high titre, was stable after treatment at 100 °C for 30 minutes and also after three months storage at -70 °C; it was present in the granular cells (which also contain the prophenoloxidase (proPO) activating system, a putative recognition mechanism in arthropods), but was absent from hyaline cells and plasma. In vitro studies were carried out to determine whether a relationship exists between the proPO system and the antibacterial activity in the haemocytes of C. maenas. It was shown that phenoloxidase and an activating serine protease were not responsible for the observed antimicrobial effects, although the possibility that activity resides with some other component of the proPO system has not been excluded. Seasonal variation in antibacterial activity, haemocyte counts and HLS protein concentrations was found, with conspicuous depression of antibacterial activity at two key points in the year. This occurred in conjunction with extremes of water temperature and it is proposed that the variation in antibacterial activity is due to underlying temperature effects on haemocyte counts and protein levels. Low levels of lytic activity against Micrococcus luteus cell walls and low levels of bacterial agglutination were recorded, but the powerful antibacterial activity in HLS could not be attributed to these alone. Gel filtration with Sephadex G-l00 revealed at least three antibacterial proteins of differing molecular size, with estimated MW of 72 kDa, 34 kDa and 4 kDa. The 72 kDa and 34 kDa proteins were bacteriostatic and the 4 kDa protein was bacteriolytic.Two newly described sensory systems in decapod crustacea : 1. The campaniform organ system. 2. The chemoreceptor hair systemShelton, Richard Graham Johnhttps://hdl.handle.net/10023/148572019-03-29T10:31:38Z1968-01-01T00:00:00Z(1) Evidence is presented that the ''Funnel Canal Organs" described by Luther (1930) are not contact chemoreceptors. (2) Experiments are described which indicate that the Funnel Canal Organ is a mechanoreceptor which responds to strain applied to the cuticle. (3) Histological observations suggest that these sense organs are actually campaniform sensilla which occur both singly and in groups, to form compound sense organs. (4) The relationship between campaniform and chordotonal organs is discussed. (5) Further experiments show that a large variety of chemoreceptor hairs exits. Most are branched and there is a negative correlation between the surface area of the hair (degree of branching) and the amount of irrigation to which the hair is normally subject. (6) The view is expressed that the concert of contact chemoreception is of limited use when considering aquatic Crustacea. The Hair Plate Organs of the chelate pereiopods are suggested as the only chemoreceptor organs in aquatic Decapoda which fulfil a true contact role.
1968-01-01T00:00:00ZShelton, Richard Graham John(1) Evidence is presented that the ''Funnel Canal Organs" described by Luther (1930) are not contact chemoreceptors. (2) Experiments are described which indicate that the Funnel Canal Organ is a mechanoreceptor which responds to strain applied to the cuticle. (3) Histological observations suggest that these sense organs are actually campaniform sensilla which occur both singly and in groups, to form compound sense organs. (4) The relationship between campaniform and chordotonal organs is discussed. (5) Further experiments show that a large variety of chemoreceptor hairs exits. Most are branched and there is a negative correlation between the surface area of the hair (degree of branching) and the amount of irrigation to which the hair is normally subject. (6) The view is expressed that the concert of contact chemoreception is of limited use when considering aquatic Crustacea. The Hair Plate Organs of the chelate pereiopods are suggested as the only chemoreceptor organs in aquatic Decapoda which fulfil a true contact role.The optokinetic responses of the crab, Carcinus MaenasBarnes, William Jonathan Peterhttps://hdl.handle.net/10023/148552018-07-18T23:18:28Z1967-01-01T00:00:00ZThe movements of the eyecups of the common shore crab, Carcinus maenas L., that occur in response to a variety of different visual stimuli, have been studied with a view to analysing the mechanisms of eye movement control in the crustaces. In most experiments, a light flag was glued to one of the crab's eyecups. The flag was orientated so that is partially occluded a beam of light that was focused on a pair of photocells, mounted in opposition to one another. Flag movements thus caused changes in the amount of light reaching the photocells, whose outputs were amplified and displayed on a pen recorder. That small eyecup movements occur in the absence of moving stimuli has been confirmed. These movements have been classified into four categories; tremor - oscillations of peak to peak amplitude 0.01° - 0.2° and predominant frequency 1-3 o.p.s., which could be modified to a small extent by external stimuli; drift - slow wondering movements that mainly occurred when there were no contracts in the visual field; saccades - spontaneous jumps whose frequency and amplitude were extremely variable; and scanning movements of amplitude 0.1° -2.0° peak to peak, and frequency 2-3 o.p.s.; which were always associated with periods of leg waving. All other experiments were directly concerned with the optokinetic responses of Carcinus, which were usually elicited by rotating a black and white striped drum around the crab. Optokinetic nystagnus consists of two phases, a slow forward phase during which the eyes move in the direction of rotation of the stripes, and a fast return phase in which the eyes are flicked back in the opposite direction. Although the evidence is by no means conclusive, it appeared that carcinus has neither a proprioceptive nor a coulometer feedback loop in its eye movement control system. It may thus be unable to distinguish apparent motion, induced by its own eye movement, from world motion. Optokinetic responses also occurred to the movements of a pinlight in an otherwise dark visual field. When recorded in two dimensions on an X-Y plotter, the responses to the movement of a pinlight in a circle were seen to be approximate ellipses, though stepwise movements frequently occurred instead of diagonal movements. The possibility, suggested by this observation, that carcinus resolved diagonal movements into their horizontal and vertical components was confirmed by the finding that the angles of the responses to diagonal movements of the pinlight depended upon the ration of the gains (gain equals response divided by stimulus) to horizontal and vertical pinlight movements. The possibility that carcinus uses this ability to resolve the sun or moon's motion cannot be excluded. When one pinlight was switched off and a similar one was switched on nearby, the crab responded optokinetically, the amplitude of this response being proportional to the stimulus amplitude for apparent movements of up to 3° -4 °. This suggests that movement correlation takes place primarily between closely spaced ommatidia. The responses to the movement or apparent movement of two or more lights were proportional to the shift in the centre of light intensity, an indication that the spatial resolution of the eyes is poor. Optokinetic memory responses, which occur following shifts in the drum position that are not seen by the crab, were also studied. By varying the length of time that the crab viewed the stripes before they were moved, memory was shown to build-up approximately linearly, reaching a plateau representing a gain of between 6 and 30 after 40-100 seconds. The retention of memories allowed to build-up for different periods of time was also examined. There was no evidence for the existence of more than one memory store.
1967-01-01T00:00:00ZBarnes, William Jonathan PeterThe movements of the eyecups of the common shore crab, Carcinus maenas L., that occur in response to a variety of different visual stimuli, have been studied with a view to analysing the mechanisms of eye movement control in the crustaces. In most experiments, a light flag was glued to one of the crab's eyecups. The flag was orientated so that is partially occluded a beam of light that was focused on a pair of photocells, mounted in opposition to one another. Flag movements thus caused changes in the amount of light reaching the photocells, whose outputs were amplified and displayed on a pen recorder. That small eyecup movements occur in the absence of moving stimuli has been confirmed. These movements have been classified into four categories; tremor - oscillations of peak to peak amplitude 0.01° - 0.2° and predominant frequency 1-3 o.p.s., which could be modified to a small extent by external stimuli; drift - slow wondering movements that mainly occurred when there were no contracts in the visual field; saccades - spontaneous jumps whose frequency and amplitude were extremely variable; and scanning movements of amplitude 0.1° -2.0° peak to peak, and frequency 2-3 o.p.s.; which were always associated with periods of leg waving. All other experiments were directly concerned with the optokinetic responses of Carcinus, which were usually elicited by rotating a black and white striped drum around the crab. Optokinetic nystagnus consists of two phases, a slow forward phase during which the eyes move in the direction of rotation of the stripes, and a fast return phase in which the eyes are flicked back in the opposite direction. Although the evidence is by no means conclusive, it appeared that carcinus has neither a proprioceptive nor a coulometer feedback loop in its eye movement control system. It may thus be unable to distinguish apparent motion, induced by its own eye movement, from world motion. Optokinetic responses also occurred to the movements of a pinlight in an otherwise dark visual field. When recorded in two dimensions on an X-Y plotter, the responses to the movement of a pinlight in a circle were seen to be approximate ellipses, though stepwise movements frequently occurred instead of diagonal movements. The possibility, suggested by this observation, that carcinus resolved diagonal movements into their horizontal and vertical components was confirmed by the finding that the angles of the responses to diagonal movements of the pinlight depended upon the ration of the gains (gain equals response divided by stimulus) to horizontal and vertical pinlight movements. The possibility that carcinus uses this ability to resolve the sun or moon's motion cannot be excluded. When one pinlight was switched off and a similar one was switched on nearby, the crab responded optokinetically, the amplitude of this response being proportional to the stimulus amplitude for apparent movements of up to 3° -4 °. This suggests that movement correlation takes place primarily between closely spaced ommatidia. The responses to the movement or apparent movement of two or more lights were proportional to the shift in the centre of light intensity, an indication that the spatial resolution of the eyes is poor. Optokinetic memory responses, which occur following shifts in the drum position that are not seen by the crab, were also studied. By varying the length of time that the crab viewed the stripes before they were moved, memory was shown to build-up approximately linearly, reaching a plateau representing a gain of between 6 and 30 after 40-100 seconds. The retention of memories allowed to build-up for different periods of time was also examined. There was no evidence for the existence of more than one memory store.Antiviral defence and antibacterial proteins in the shore crab Carcinus maenasSchnapp, Dennihttps://hdl.handle.net/10023/148522019-03-29T10:33:31Z1997-01-01T00:00:00ZThe defence reactions of the shore crab, Carcinus maenas, to a range of viruses were investigated in vivo and in vitro. In vivo studies with injected bacteriophages showed that C. maenas is capable of discriminating between different bacteriophages and actively removes certain phages from the haemocoele. Rapid initial clearance of the coliphage T2 was followed by slower removal and the phage persisted in the circulation for at least two weeks. The phage was sequestered to the hepatopancreas where it persisted for at least 72 h. Haemocyte counts remained unchanged upon injection of T2. With respect to prophenoloxidase activation, of the viruses tested only the Chlorella phage PBCV-1 was found to activate haemolymph prophenoloxidase at concentrations above 107 particles ml-1This indicates that C. maenas may respond to high concentrations of viruses in vitro. However, neutralization assays failed to reveal inactivation of viruses in HLS, plasma, or extracts of the hepatopancreas, gut, gill or heart, although some activity against an insect baculovirus and parainfluenza vims was detected in digestive juice. At least four antibacterial proteins, of ca. 6.5 kDa, 11.6 kDa, 20 kDa or 25 kDa, are present in C. maenas haemocytes. One, a 6.5 kDa peptide with activity against Gram positive and Gram negative bacteria, was purified. The N-terminal 30 amino acids of this peptide share over 60% sequence identity with bovine Bac 7, a mammalian cathelicidin. This 6.5 kDa peptide in C. maenas is the first antimicrobial peptide described from the Crustacea. Because the sequence of the pre-propeptide is as yet unavailable, it is not known whether or not it can be included among the cathelicidins. It has not been established whether or not the C. maenas 6.5 kDa peptide has antiviral activity.
1997-01-01T00:00:00ZSchnapp, DenniThe defence reactions of the shore crab, Carcinus maenas, to a range of viruses were investigated in vivo and in vitro. In vivo studies with injected bacteriophages showed that C. maenas is capable of discriminating between different bacteriophages and actively removes certain phages from the haemocoele. Rapid initial clearance of the coliphage T2 was followed by slower removal and the phage persisted in the circulation for at least two weeks. The phage was sequestered to the hepatopancreas where it persisted for at least 72 h. Haemocyte counts remained unchanged upon injection of T2. With respect to prophenoloxidase activation, of the viruses tested only the Chlorella phage PBCV-1 was found to activate haemolymph prophenoloxidase at concentrations above 107 particles ml-1This indicates that C. maenas may respond to high concentrations of viruses in vitro. However, neutralization assays failed to reveal inactivation of viruses in HLS, plasma, or extracts of the hepatopancreas, gut, gill or heart, although some activity against an insect baculovirus and parainfluenza vims was detected in digestive juice. At least four antibacterial proteins, of ca. 6.5 kDa, 11.6 kDa, 20 kDa or 25 kDa, are present in C. maenas haemocytes. One, a 6.5 kDa peptide with activity against Gram positive and Gram negative bacteria, was purified. The N-terminal 30 amino acids of this peptide share over 60% sequence identity with bovine Bac 7, a mammalian cathelicidin. This 6.5 kDa peptide in C. maenas is the first antimicrobial peptide described from the Crustacea. Because the sequence of the pre-propeptide is as yet unavailable, it is not known whether or not it can be included among the cathelicidins. It has not been established whether or not the C. maenas 6.5 kDa peptide has antiviral activity.Studies of crustacean hyperglycaemic hormone in the Norway lobster 'Nephrops norvegicus' (Linnaeus, 1758)Smullen, Richard Paulhttps://hdl.handle.net/10023/148502019-03-29T10:36:28Z1993-01-01T00:00:00ZNephrops norvegicus is a deep water marine decapod crustacean which burrows in fine muddy substrata. It is a commercially important as a fisheries species, but knowledge of its biology, particularly concerning its endocrinology, is limited. This thesis describes the endocrinology of Nephrops norvegicus with particular reference to crustacean hyperglycaemic hormone. Histological investigations of the eyestalk of Nephrops norvegicus enabled the identification d" the X-organ sinus gland complex. The development of a microbioassay allowed the determination of increases of glycaemia following the injection of crude sinus gland extracts into a host animal. The optimal dose for induced haemolymph glycaemia was determined. HPLC separation was used to isolate and purify several neuropeptides from crude sinus gland extracts, which had varying degrees of hyperglycaemic activities. The use of ELISA (enzyme linked immunosorbent assay) showed that the peptides reacted with polyclonal rabbit antiserum raised against the CHH of the crayfish Orconectes limosus and with polyclonal guinea pig antiserum raised against the CHH of the lobster, Homarus americanus. SDS-PAGE of these peptides enabled an estimation of their molecular weights and the purity of one of the active peptides was determined using capillary electrophoresis. The effects of photoperiod and severe hypoxia on the CHH-induced hyperglycaemia of Nephrops norvegicus were also investigated. The responses of N. norvegicus appeared to differ in some respects from other decapods species. Pairs of oligonucleotide primers, based on the sequence of the lobster, Homarus americanus, complimentary to regions of the CHH sequence, were used in the polymerase chain reactions (PCR). Complimentary first strand DNA (cDNA) was synthesised from total Nephrops eyestalk RNA. 35 rounds and 40 rounds of PCR amplification produced a l00bp and 230bp double stranded DNA product respectively, which were resolved by electrophoresis on a tris-borate-EDTA gel. The product size was compared with known standards. Finally, the identification of CHH and GIH synthesis and storage in the eggs of Nephrops norvegicus at various stages of development was investigated. By the use of PCR, it was not possible to determine if synthesis of CHH was occurring in 50% developed eggs. The use of ELISA, however, demonstrated that in 90% developed eggs there was a significant increase of both CHH and GIH immunoactivity.
1993-01-01T00:00:00ZSmullen, Richard PaulNephrops norvegicus is a deep water marine decapod crustacean which burrows in fine muddy substrata. It is a commercially important as a fisheries species, but knowledge of its biology, particularly concerning its endocrinology, is limited. This thesis describes the endocrinology of Nephrops norvegicus with particular reference to crustacean hyperglycaemic hormone. Histological investigations of the eyestalk of Nephrops norvegicus enabled the identification d" the X-organ sinus gland complex. The development of a microbioassay allowed the determination of increases of glycaemia following the injection of crude sinus gland extracts into a host animal. The optimal dose for induced haemolymph glycaemia was determined. HPLC separation was used to isolate and purify several neuropeptides from crude sinus gland extracts, which had varying degrees of hyperglycaemic activities. The use of ELISA (enzyme linked immunosorbent assay) showed that the peptides reacted with polyclonal rabbit antiserum raised against the CHH of the crayfish Orconectes limosus and with polyclonal guinea pig antiserum raised against the CHH of the lobster, Homarus americanus. SDS-PAGE of these peptides enabled an estimation of their molecular weights and the purity of one of the active peptides was determined using capillary electrophoresis. The effects of photoperiod and severe hypoxia on the CHH-induced hyperglycaemia of Nephrops norvegicus were also investigated. The responses of N. norvegicus appeared to differ in some respects from other decapods species. Pairs of oligonucleotide primers, based on the sequence of the lobster, Homarus americanus, complimentary to regions of the CHH sequence, were used in the polymerase chain reactions (PCR). Complimentary first strand DNA (cDNA) was synthesised from total Nephrops eyestalk RNA. 35 rounds and 40 rounds of PCR amplification produced a l00bp and 230bp double stranded DNA product respectively, which were resolved by electrophoresis on a tris-borate-EDTA gel. The product size was compared with known standards. Finally, the identification of CHH and GIH synthesis and storage in the eggs of Nephrops norvegicus at various stages of development was investigated. By the use of PCR, it was not possible to determine if synthesis of CHH was occurring in 50% developed eggs. The use of ELISA, however, demonstrated that in 90% developed eggs there was a significant increase of both CHH and GIH immunoactivity.Anatomy and physiology of organs involved in food ingestion in the lobster, Homarus gammarus L.Robertson, R. Meldrumhttps://hdl.handle.net/10023/148492019-03-29T10:30:53Z1978-01-01T00:00:00ZThe dissertation describes the gross neuromuscular anatomy of the labrum (upper lip) and oesophagus of the lobster Homarus gammarue as a pre-requisite for studies on the mechanisms and control of food ingestion. Sense organs of the area are also described. Of particular interest are two paired sensors (the anterior and posterior oesophageal sensors) which are bilaterally situated at the oesophageal/cardiac sac valve. These are similar to contact chemoreceptors previously described in insects, and are classified as such on morphological grounds and with indirect electrophysiological evidence. The labrum undergoes rhythmical retraction/protraction movements during feeding and can be shown to participate in both the mandibular rhythm and oesophageal peristalsis. Its role in feeding is discussed. Subsequently, small labral protractions are used as an indication of the duration and frequency of oesophageal peristalsis. Oesophageal peristalsis is effected by the co-ordinated contraction of the oesophageal musculature. This is controlled by rhythmical bursting neuronal activity which can be recorded from the nerve trunks in the area, A characteristic burst recorded from the superior oesophageal nerve is used as an indication of oesophageal dilatation during peristalsis for studies on the feedback effects of the oesophageal sensors. Electrical and chemical stimulation of the posterior oesophageal sensors can initiate and increase the frequency of oesophageal peristalsis, while stimulation of the anterior oesophageal sensors can slow and terminate oesophageal peristalsis. The results are discussed and, in conclusion, a model of the role of the oesophageal sensors in feeding is presented.
1978-01-01T00:00:00ZRobertson, R. MeldrumThe dissertation describes the gross neuromuscular anatomy of the labrum (upper lip) and oesophagus of the lobster Homarus gammarue as a pre-requisite for studies on the mechanisms and control of food ingestion. Sense organs of the area are also described. Of particular interest are two paired sensors (the anterior and posterior oesophageal sensors) which are bilaterally situated at the oesophageal/cardiac sac valve. These are similar to contact chemoreceptors previously described in insects, and are classified as such on morphological grounds and with indirect electrophysiological evidence. The labrum undergoes rhythmical retraction/protraction movements during feeding and can be shown to participate in both the mandibular rhythm and oesophageal peristalsis. Its role in feeding is discussed. Subsequently, small labral protractions are used as an indication of the duration and frequency of oesophageal peristalsis. Oesophageal peristalsis is effected by the co-ordinated contraction of the oesophageal musculature. This is controlled by rhythmical bursting neuronal activity which can be recorded from the nerve trunks in the area, A characteristic burst recorded from the superior oesophageal nerve is used as an indication of oesophageal dilatation during peristalsis for studies on the feedback effects of the oesophageal sensors. Electrical and chemical stimulation of the posterior oesophageal sensors can initiate and increase the frequency of oesophageal peristalsis, while stimulation of the anterior oesophageal sensors can slow and terminate oesophageal peristalsis. The results are discussed and, in conclusion, a model of the role of the oesophageal sensors in feeding is presented.The commissural ganglia of the lobster, homarus gammarus, (L)Martin, S. M.https://hdl.handle.net/10023/148472019-03-29T10:29:58Z1981-01-01T00:00:00ZThe bilaterally paired commissural ganglia of the lobster, Homarus gammarus, form part of the stomatogastric nervous system. The functional organization of these ganglia has been investigated using a variety of anatomical and physiological techniques. There are no consistent differences between right and left commissural ganglia. Each contains the somata of several hundred interneurons and about sixty motorneurons which supply the labrum and oesophagus. There are many input and output pathways to and from the commissural ganglia, including a large number of sensory fibres. There appears to be much interaction between these ganglia and the central and stomatogastric nervous systems. A comparison of the vitro preparation and previous studies of the semi-intact animal have shown that the isolated commissural ganglion contains at least the minimal pattern generator for oesophageal peristalsis. The isolated ganglion can also produce other rhythms, including a putative labral rhythm. The small size of most commissural ganglion neurons precludes intracellular recording and dye injection. Most "recordable" somata are silent. The activity of several neurons, including labral motorneurons, is closely related to the oesophageal rhythm. At least one neuron exhibits rhythmic activity unrelated to the oesophageal cycle. Other neurons show a tonic firing pattern; their possible functions are discussed. A large dopamine-containing neuron sends a corollary discharge of foregut activity to at least the brain. The structure and function of this neuron is discussed in detail. This study suggests that the commissural ganglia have the integratory potential to act as coordination centres for the foregut. The findings are considered in the context of the operation of the stomatogastric nervous system and suggestions are made for further research.
1981-01-01T00:00:00ZMartin, S. M.The bilaterally paired commissural ganglia of the lobster, Homarus gammarus, form part of the stomatogastric nervous system. The functional organization of these ganglia has been investigated using a variety of anatomical and physiological techniques. There are no consistent differences between right and left commissural ganglia. Each contains the somata of several hundred interneurons and about sixty motorneurons which supply the labrum and oesophagus. There are many input and output pathways to and from the commissural ganglia, including a large number of sensory fibres. There appears to be much interaction between these ganglia and the central and stomatogastric nervous systems. A comparison of the vitro preparation and previous studies of the semi-intact animal have shown that the isolated commissural ganglion contains at least the minimal pattern generator for oesophageal peristalsis. The isolated ganglion can also produce other rhythms, including a putative labral rhythm. The small size of most commissural ganglion neurons precludes intracellular recording and dye injection. Most "recordable" somata are silent. The activity of several neurons, including labral motorneurons, is closely related to the oesophageal rhythm. At least one neuron exhibits rhythmic activity unrelated to the oesophageal cycle. Other neurons show a tonic firing pattern; their possible functions are discussed. A large dopamine-containing neuron sends a corollary discharge of foregut activity to at least the brain. The structure and function of this neuron is discussed in detail. This study suggests that the commissural ganglia have the integratory potential to act as coordination centres for the foregut. The findings are considered in the context of the operation of the stomatogastric nervous system and suggestions are made for further research.A study of the uptake and excretion of inorganic mercury, and the long term effects of exposure to low levels of the metal in the lobster, homarus gammarus (L) White 1874Brown, Janet H.https://hdl.handle.net/10023/148462019-03-29T10:34:03Z1976-01-01T00:00:00ZThe aim of this work has been to make an overall study of the uptake accumulation, and excretion of inorganic mercury, and the effects of long term exposure to the metal, in the lobster, Homarus gammarus, using relatively simple techniques considered appropriate to pollution studies. In this way it was hoped to gain an under- standing of the way in which the lobster deals with mercury and to be able to predict what organs were likely to be affected by low levels of mercury. The initial approach was to measure background levels in the different organs of the lobster, and also of lobsters exposed to 100ppb. and 10ppb. mercury for varying periods of time, using neutron activation analysis. These results were amplified by radioisotope tracer experiments so that besides the sites of principal accumulation being identified the route of uptake could be determined. By the same means, the ability of lobsters to excrete mercury was investigated. Long term studies of the effects of exposure to mercury on organs identified as being susceptible to damage because they were sites of uptake, major accumulation, or excretion were studied by histological techniques which were amplified in part by electron microscopical examination. Since it was likely that the lobster larvae might be weak links in the life history, measurements of mercury uptake by the larvae was attempted using X-ray microanalysis. This was unsuccessful, and studies of the effects of mercury on the survival of the lobster larvae were inconclusive. It was found by these varied approaches that uptake was mainly through the gills where highest levels of mercury accumulated, but it is probable that most of this mercury was bound to the cuticle or in the cells. A small proportion passes into the blood and is taken up and gradually excreted by the green glands, Long term damage is found in these organs but not in either the gills or the digestive gland. It is therefore suggested that damage due to mercury only occurs at sites of active control. The damage in the green glands due to exposure to levels even as low as 10ppb is likely to lead to death if exposure is prolonged, but a more important finding was evidence of greater susceptibility at different stages of the moult cycle. This is worthy of more detailed investigation.
1976-01-01T00:00:00ZBrown, Janet H.The aim of this work has been to make an overall study of the uptake accumulation, and excretion of inorganic mercury, and the effects of long term exposure to the metal, in the lobster, Homarus gammarus, using relatively simple techniques considered appropriate to pollution studies. In this way it was hoped to gain an under- standing of the way in which the lobster deals with mercury and to be able to predict what organs were likely to be affected by low levels of mercury. The initial approach was to measure background levels in the different organs of the lobster, and also of lobsters exposed to 100ppb. and 10ppb. mercury for varying periods of time, using neutron activation analysis. These results were amplified by radioisotope tracer experiments so that besides the sites of principal accumulation being identified the route of uptake could be determined. By the same means, the ability of lobsters to excrete mercury was investigated. Long term studies of the effects of exposure to mercury on organs identified as being susceptible to damage because they were sites of uptake, major accumulation, or excretion were studied by histological techniques which were amplified in part by electron microscopical examination. Since it was likely that the lobster larvae might be weak links in the life history, measurements of mercury uptake by the larvae was attempted using X-ray microanalysis. This was unsuccessful, and studies of the effects of mercury on the survival of the lobster larvae were inconclusive. It was found by these varied approaches that uptake was mainly through the gills where highest levels of mercury accumulated, but it is probable that most of this mercury was bound to the cuticle or in the cells. A small proportion passes into the blood and is taken up and gradually excreted by the green glands, Long term damage is found in these organs but not in either the gills or the digestive gland. It is therefore suggested that damage due to mercury only occurs at sites of active control. The damage in the green glands due to exposure to levels even as low as 10ppb is likely to lead to death if exposure is prolonged, but a more important finding was evidence of greater susceptibility at different stages of the moult cycle. This is worthy of more detailed investigation.Studies on phagocytosis in the shore crab 'Carcinus maenas' (Crustacea, Decapoda)Bell, Karen Lennoxhttps://hdl.handle.net/10023/148452019-03-29T10:42:07Z1994-01-01T00:00:00ZPhagocytosis by hyaline cells of the shore crab, Carcinus maenas, was investigated in vitro. In particular, the project examined the role of the prophenoloxidase activating system (proPO) in opsonisation, the metabolic requirements of the cells during phagocytosis and the extent of intracellular bacterial killing. Related work investigated the mechanism and regulation of bacterial killing. Uptake was assessed using monolayers of separated hyaline cells challenged with the bacterium, Psychrobacter iminobilis. The bacteria were pretreated with haemocyte lysate supernatant (HLS) to enhance uptake. The opsonic factor(s) were found to be freeze stable and to be generated during serine protease activation of the proPO system. Phagocytosis was also found to depend upon electron transfer and oxidative phosphorylation and to require an intact cytoskeleton for engulfment. Following ingestion, ca 84% of the bacteria were found to be killed within 3h. Experiments designed to investigate the mechanism of killing showed that treatment of the hyaline cells with phorbol 12-myristate 13-acetate, lipopolysaccharide, phytohaemagglutinin or concanavalin A, but not laminarin, sdmulates the production of superoxide ions (O2-). The semi-granular and granular cells did not produce O2- following stimulation. Incubation of the cells with superoxide dismutase (SOD) confirmed that O2- was produced. Parallel experiments were conducted on a range of marine invertebrates. In all cases O2- production was observed, showing that O2- production is a general phenomenon for invertebrate phagocytes. However, quantification of hydrogen peroxide (H2O2) production, using a H2O2 assay, showed that crab phagocytes produced more H2O2 than tunicate phagocytes indicating that the kinetics of the response varies between species. Using immunocytochemistry, the antioxidant enzymes, catalase, glutathione peroxidase and SOD were found to be located within the haemocytes and plasma of C. maenas. These enzymes may minimise the risk of damage to the host tissues by the O2- and H2O2 produced by the hyaline cells.
1994-01-01T00:00:00ZBell, Karen LennoxPhagocytosis by hyaline cells of the shore crab, Carcinus maenas, was investigated in vitro. In particular, the project examined the role of the prophenoloxidase activating system (proPO) in opsonisation, the metabolic requirements of the cells during phagocytosis and the extent of intracellular bacterial killing. Related work investigated the mechanism and regulation of bacterial killing. Uptake was assessed using monolayers of separated hyaline cells challenged with the bacterium, Psychrobacter iminobilis. The bacteria were pretreated with haemocyte lysate supernatant (HLS) to enhance uptake. The opsonic factor(s) were found to be freeze stable and to be generated during serine protease activation of the proPO system. Phagocytosis was also found to depend upon electron transfer and oxidative phosphorylation and to require an intact cytoskeleton for engulfment. Following ingestion, ca 84% of the bacteria were found to be killed within 3h. Experiments designed to investigate the mechanism of killing showed that treatment of the hyaline cells with phorbol 12-myristate 13-acetate, lipopolysaccharide, phytohaemagglutinin or concanavalin A, but not laminarin, sdmulates the production of superoxide ions (O2-). The semi-granular and granular cells did not produce O2- following stimulation. Incubation of the cells with superoxide dismutase (SOD) confirmed that O2- was produced. Parallel experiments were conducted on a range of marine invertebrates. In all cases O2- production was observed, showing that O2- production is a general phenomenon for invertebrate phagocytes. However, quantification of hydrogen peroxide (H2O2) production, using a H2O2 assay, showed that crab phagocytes produced more H2O2 than tunicate phagocytes indicating that the kinetics of the response varies between species. Using immunocytochemistry, the antioxidant enzymes, catalase, glutathione peroxidase and SOD were found to be located within the haemocytes and plasma of C. maenas. These enzymes may minimise the risk of damage to the host tissues by the O2- and H2O2 produced by the hyaline cells.Nervous control of ventilation in the shore crab carcinus maenasYoung, Ronald E.https://hdl.handle.net/10023/148442019-03-29T10:36:24Z1973-01-01T00:00:00Z1973-01-01T00:00:00ZYoung, Ronald E.Cellular interactions in the thymic microenvironmentJacob, Dinesh Andrewhttps://hdl.handle.net/10023/148332019-03-29T10:41:41Z1980-01-01T00:00:00ZThe haemopoietic multipotential stem cell differentiates in distinct maturational pathways to generate different populations of blood cells. Differentiation and proliferation within the thymus is a prerequisite of precursors committed to the T-lymphocyte lineage. These differentiative events involve an interaction with the non-lymphoid cells of the thymus. Monolayers derived from the non-lymphoid stromal elements of the murine thymus were established and maintained in vitro. The cells in culture were characterised on the basis of their morphological and functional features. They were found to be morphologically heterogenous at the light microscopical and ultrastructural level, and largely phagocytic. The possible maturation inducing properties of the cultured thymus cells were investigated. The PHA responsiveness of thymocytes, a feature of more mature lymphocytes was found to be marginally enhanced upon co-culture with these cells or after incubation in their conditioned medium. Similar effects were obtained with monolayers derived from peritoneal, exudate cells, but to a lesser extent. A method of depleting the endogenous lymphoid cells in explants of embryonic thymic tissue in culture was established, enabling the enrichment of the epithelial component. These epithelial thymuses were reconstituted with early undifferentiated haemopoietic cells and more mature lymphoid precursors in vitro. The latter were found to readily repopulate the explants, whereas the less differentiated cells did not. The lymphocytic cells of the bone marrow were isolated by differential centrifugation. The enriched cells were used as targets to investigate the possible differentiation inducing properties of the thymic monolayer cells, as well as their own capacity to repopulate the thymus in vitro. They were found to be refractory to any such maturational induction, and their thymus-seeding ability was not conclusively resolved. The significance of these findings are discussed with regard to the maturational potential of different haemopoietic cells in the lymphomyeloid tissues. The cell proliferation kinetics of the thymus during late gestation was investigated. The cell production rate was found to be greatly diminished in pregnancy, during which the spleen was found to sustain an increased extra-medullary erythropoietic activity. The responsiveness to PHA during pregnancy was investigated. The possible causes and consequences of haemopoietic imbalance are discussed, especially with regard to the possibly impaired immune competence of the pregnant animal.
1980-01-01T00:00:00ZJacob, Dinesh AndrewThe haemopoietic multipotential stem cell differentiates in distinct maturational pathways to generate different populations of blood cells. Differentiation and proliferation within the thymus is a prerequisite of precursors committed to the T-lymphocyte lineage. These differentiative events involve an interaction with the non-lymphoid cells of the thymus. Monolayers derived from the non-lymphoid stromal elements of the murine thymus were established and maintained in vitro. The cells in culture were characterised on the basis of their morphological and functional features. They were found to be morphologically heterogenous at the light microscopical and ultrastructural level, and largely phagocytic. The possible maturation inducing properties of the cultured thymus cells were investigated. The PHA responsiveness of thymocytes, a feature of more mature lymphocytes was found to be marginally enhanced upon co-culture with these cells or after incubation in their conditioned medium. Similar effects were obtained with monolayers derived from peritoneal, exudate cells, but to a lesser extent. A method of depleting the endogenous lymphoid cells in explants of embryonic thymic tissue in culture was established, enabling the enrichment of the epithelial component. These epithelial thymuses were reconstituted with early undifferentiated haemopoietic cells and more mature lymphoid precursors in vitro. The latter were found to readily repopulate the explants, whereas the less differentiated cells did not. The lymphocytic cells of the bone marrow were isolated by differential centrifugation. The enriched cells were used as targets to investigate the possible differentiation inducing properties of the thymic monolayer cells, as well as their own capacity to repopulate the thymus in vitro. They were found to be refractory to any such maturational induction, and their thymus-seeding ability was not conclusively resolved. The significance of these findings are discussed with regard to the maturational potential of different haemopoietic cells in the lymphomyeloid tissues. The cell proliferation kinetics of the thymus during late gestation was investigated. The cell production rate was found to be greatly diminished in pregnancy, during which the spleen was found to sustain an increased extra-medullary erythropoietic activity. The responsiveness to PHA during pregnancy was investigated. The possible causes and consequences of haemopoietic imbalance are discussed, especially with regard to the possibly impaired immune competence of the pregnant animal.Changes in the activity of some enzymes in the rat hemidiaphragm hypertrophying as a consequence of unilateral phrenicectomyTurner, Leslie Victorhttps://hdl.handle.net/10023/148312019-03-29T10:35:28Z1971-01-01T00:00:00ZThe post-denervation hypertrophy of the rat hemidiaphragm has been studied for up to 15 days after nerve section. The denervated tissue increases in wet weight to a maximum at 5 days of 40 % over its initial weight; by the 15th day the tissue has atrophied to below the control value. Measurements have been made throughout the hypertrophy period of the activities of some enzymes characteristic of particular aspects of muscle metabolism. In additions concentrations of glycogen from fed, and overnight fasted rats; of myoglobin; and of free amino acid concentrations in the denervated tissue have also been studied. Methods are described for the use in rats of the anaesthetic Halothane so as to preserve muscle glycogen concentrations and to prevent stress-mediated activation of phosphorylase a levels. Unilateral phrenicectomy causes a decrease in glycogen concentration and contents a decrease of total glycogen phosphorylase activity is also found, but total content of phosphoglucorautase increases slightly, Hexokinase and phosphorylase contents increase so that their concentrations are maintained. The validity of the hexokinase/ phosphorylase ratio as an indicator of fibre composition in pathological tissues is questioned. Phosphohexoisomerase activity remains constant for 1 week after denervation, then decreases, but glyceraldehyde phosphate dehydrogenase & lactate dehydrogenase demonstrate increased contents at 7 days before they decrease; the responses of the dehydrogenases may be related to the reported proliferation of the sarcoplasmic reticulum. No significant change is observed in the lactate dehydrogenase isoenzyme proportions until 7 days when a decrease of H-type subunits is indicated; 3 days later though control proportions are regained. Content of malate dehydrogenase, VAD-, & NADP-specific dehydro-genases demonstrate rapid decreases after nerve section to roughly half the initial levels at 3 days after nerve section. Glutamate dehydrogenase concentration also decreases in the early stages of the hypertrophy, but later increases when protein catabolism becomes a significant process. These decreases art in 'accord with the reported fragmentation of the mitochondria. Glucose G-phosphate dehydrogenase and 6-phosphogluconate dehydrogenase concentrations increase dramatically to a peak within the first few days after nerve section. The increased enzyme capacity could be responsible for provision of nentose phosphates for nucleotide and nucleic acid synthesis. Total creatine kinase activity remains constant for up to 5 days before a decline in observed; adenylate kinase & adenylate deaminase show increased contents. The responses are interpreted in terms of possible involvement in increased adenine nucleotide production. The validity of the adenylate kinase/creatine kinase activity- ratio for the identification of physiologically distinct muscles in questioned. Content of glutathione reductase shows two small peaks of increased activity at 3 and 10 days after denervation. Thus unlike other denervated or dystrophic muscles, the responses o NADP-linked dehydrogenoses are not similar. Myoglobin content increases slowly during the hypertrophy only reaching a peak of 20 % over control levels at 10 days. Concentration in the early stages is thus decreased but rises after 5 days. The response, as well as the changes in lactate dehydrogenase isoenzyme proportions, is interpreted in terms of an increased blood flow through the denervated tissue. Total free amino acid concentration in the denervated tissue is increased; responses of the individual species are interpreted in terms of possible modes of metabolism in the tissue. The responses in the denervated hemidiaphragm are interpreted in terms of a hypertrophy of the "red" &/or "intermediate" fibre types; suggestions are made as to possible causes for the responses.
1971-01-01T00:00:00ZTurner, Leslie VictorThe post-denervation hypertrophy of the rat hemidiaphragm has been studied for up to 15 days after nerve section. The denervated tissue increases in wet weight to a maximum at 5 days of 40 % over its initial weight; by the 15th day the tissue has atrophied to below the control value. Measurements have been made throughout the hypertrophy period of the activities of some enzymes characteristic of particular aspects of muscle metabolism. In additions concentrations of glycogen from fed, and overnight fasted rats; of myoglobin; and of free amino acid concentrations in the denervated tissue have also been studied. Methods are described for the use in rats of the anaesthetic Halothane so as to preserve muscle glycogen concentrations and to prevent stress-mediated activation of phosphorylase a levels. Unilateral phrenicectomy causes a decrease in glycogen concentration and contents a decrease of total glycogen phosphorylase activity is also found, but total content of phosphoglucorautase increases slightly, Hexokinase and phosphorylase contents increase so that their concentrations are maintained. The validity of the hexokinase/ phosphorylase ratio as an indicator of fibre composition in pathological tissues is questioned. Phosphohexoisomerase activity remains constant for 1 week after denervation, then decreases, but glyceraldehyde phosphate dehydrogenase & lactate dehydrogenase demonstrate increased contents at 7 days before they decrease; the responses of the dehydrogenases may be related to the reported proliferation of the sarcoplasmic reticulum. No significant change is observed in the lactate dehydrogenase isoenzyme proportions until 7 days when a decrease of H-type subunits is indicated; 3 days later though control proportions are regained. Content of malate dehydrogenase, VAD-, & NADP-specific dehydro-genases demonstrate rapid decreases after nerve section to roughly half the initial levels at 3 days after nerve section. Glutamate dehydrogenase concentration also decreases in the early stages of the hypertrophy, but later increases when protein catabolism becomes a significant process. These decreases art in 'accord with the reported fragmentation of the mitochondria. Glucose G-phosphate dehydrogenase and 6-phosphogluconate dehydrogenase concentrations increase dramatically to a peak within the first few days after nerve section. The increased enzyme capacity could be responsible for provision of nentose phosphates for nucleotide and nucleic acid synthesis. Total creatine kinase activity remains constant for up to 5 days before a decline in observed; adenylate kinase & adenylate deaminase show increased contents. The responses are interpreted in terms of possible involvement in increased adenine nucleotide production. The validity of the adenylate kinase/creatine kinase activity- ratio for the identification of physiologically distinct muscles in questioned. Content of glutathione reductase shows two small peaks of increased activity at 3 and 10 days after denervation. Thus unlike other denervated or dystrophic muscles, the responses o NADP-linked dehydrogenoses are not similar. Myoglobin content increases slowly during the hypertrophy only reaching a peak of 20 % over control levels at 10 days. Concentration in the early stages is thus decreased but rises after 5 days. The response, as well as the changes in lactate dehydrogenase isoenzyme proportions, is interpreted in terms of an increased blood flow through the denervated tissue. Total free amino acid concentration in the denervated tissue is increased; responses of the individual species are interpreted in terms of possible modes of metabolism in the tissue. The responses in the denervated hemidiaphragm are interpreted in terms of a hypertrophy of the "red" &/or "intermediate" fibre types; suggestions are made as to possible causes for the responses.The control of hindgut movements in the lobster, homarus gammarus (L)Winslow, Williamhttps://hdl.handle.net/10023/148302019-03-29T10:30:09Z1970-01-01T00:00:00Z1. The mechanisms underlying hindgut movements in the lobster, Homarus gammarus (Lo) have been studied. 2. The hindgut is innervated from the sixth abdominal ganglion (6A.G.) by the posterior intestinal nerves (P.I.N.'s). Stimulation of any of the connectives of the ventral nerve cord (V.N.C.) will elicit hindgut and anal movements. 3. The hindgut is divisible into anterior and posterior regions, whose basic co-ordination is undisturbed by sectioning the hindgut, so long as the nerves remain intact. 4. Numerous endogenous oscillators mediating spontaneous contractions are thought to lie within the muscles of the rectum. Oscillators within the radial muscles of the anus can be activated by nervous discharge. 5. Receptors responding to anal dilation and closure have been described both anatomically and physiologically. They lie in the anal nerves. No physiological evidence exists for the presence of receptors on the rectum. 6. Hindgut and anal movements may be initiated by either 'phasic' or 'tonic' motor neurones. Bursts of tonic discharge will cause powerful hindgut movements (the defaecatory response), whilst those elicited phasically are rather weaker. The form of the bursting discharge is, apparently, immutable and is unaffected by extirpation of all sensory input. 8. The structure of the 6A.G. has been determined. It is a highly complex ganglion and it is suggested that it was derived from three fused ganglia in the course of evolution. 9. The somata of neurones causing efferent discharge to the hindgut have been shown to lie in the anterior part of the posterior ventral cortical lobe of the 6A.G. 10. Some of these neurone somata have been penetrated using glass microelectrodes. Three categories of neurones, responsible for hindgut control at the level of tine 6A.G., are thought to exist phasic neurones, tonic neurones and driver neurons. 11. The neurones within the 6A.G. represent a final motor pathway to the hindgut. These neurones are thought to be under the ultimate control of a centre lying in the tritocerebral region of the brain. Several interneurones connect the two.
1970-01-01T00:00:00ZWinslow, William1. The mechanisms underlying hindgut movements in the lobster, Homarus gammarus (Lo) have been studied. 2. The hindgut is innervated from the sixth abdominal ganglion (6A.G.) by the posterior intestinal nerves (P.I.N.'s). Stimulation of any of the connectives of the ventral nerve cord (V.N.C.) will elicit hindgut and anal movements. 3. The hindgut is divisible into anterior and posterior regions, whose basic co-ordination is undisturbed by sectioning the hindgut, so long as the nerves remain intact. 4. Numerous endogenous oscillators mediating spontaneous contractions are thought to lie within the muscles of the rectum. Oscillators within the radial muscles of the anus can be activated by nervous discharge. 5. Receptors responding to anal dilation and closure have been described both anatomically and physiologically. They lie in the anal nerves. No physiological evidence exists for the presence of receptors on the rectum. 6. Hindgut and anal movements may be initiated by either 'phasic' or 'tonic' motor neurones. Bursts of tonic discharge will cause powerful hindgut movements (the defaecatory response), whilst those elicited phasically are rather weaker. The form of the bursting discharge is, apparently, immutable and is unaffected by extirpation of all sensory input. 8. The structure of the 6A.G. has been determined. It is a highly complex ganglion and it is suggested that it was derived from three fused ganglia in the course of evolution. 9. The somata of neurones causing efferent discharge to the hindgut have been shown to lie in the anterior part of the posterior ventral cortical lobe of the 6A.G. 10. Some of these neurone somata have been penetrated using glass microelectrodes. Three categories of neurones, responsible for hindgut control at the level of tine 6A.G., are thought to exist phasic neurones, tonic neurones and driver neurons. 11. The neurones within the 6A.G. represent a final motor pathway to the hindgut. These neurones are thought to be under the ultimate control of a centre lying in the tritocerebral region of the brain. Several interneurones connect the two.Eyecup muscle action of the crab Carcinus maenasBurrows, Malcolmhttps://hdl.handle.net/10023/148292019-03-29T10:36:45Z1967-01-01T00:00:00ZThe muscular control of eyecup movements in the crab Carcinus maenas has been studied by both extracellular and intracellular recording from the nine eyecup muscles. Each muscle involved in optokinetic movements is supplied by a fast and slow axon and each consists of a histologically mixed spectrum of fibres ranging from (Felderstruktur). Muscle 19a, which only participates in the withdrawal reflex consists of phasic fibres only. In general, a fast axon preferentially innervates the phasic fibres and a slow axon the tonic ones. During optokinetic movements the muscles are activated by a complex motor output programme, which is different, not merely the reverse for movements in opposite directions. Both tonic and phasic muscle fibres are active but the latter are only active at greater amplitudes of stimulus movement. Tonic activity is responsible from maintaining the eyecup position in space and for low velocity, small amplitude movements. Phasic activity is recruited during large amplitude movements and is also responsible for fast movement and eyecup tremor. The protective withdrawal reflex overrides any other eyecup movement and involves the firing of two axons in the optic tract, one supplying a group of two, the other a group of three muscles. One of the muscles involved in this eyecup withdrawal movement away from the mid-line is also active during horizontal optokinetic movements of the eyecup towards the mid-line. It is suggested that interpretation of eyecup muscle activity is more intelligible if the whole group of muscles, rather than the individual muscles themselves, is regarded as the functional unit.
1967-01-01T00:00:00ZBurrows, MalcolmThe muscular control of eyecup movements in the crab Carcinus maenas has been studied by both extracellular and intracellular recording from the nine eyecup muscles. Each muscle involved in optokinetic movements is supplied by a fast and slow axon and each consists of a histologically mixed spectrum of fibres ranging from (Felderstruktur). Muscle 19a, which only participates in the withdrawal reflex consists of phasic fibres only. In general, a fast axon preferentially innervates the phasic fibres and a slow axon the tonic ones. During optokinetic movements the muscles are activated by a complex motor output programme, which is different, not merely the reverse for movements in opposite directions. Both tonic and phasic muscle fibres are active but the latter are only active at greater amplitudes of stimulus movement. Tonic activity is responsible from maintaining the eyecup position in space and for low velocity, small amplitude movements. Phasic activity is recruited during large amplitude movements and is also responsible for fast movement and eyecup tremor. The protective withdrawal reflex overrides any other eyecup movement and involves the firing of two axons in the optic tract, one supplying a group of two, the other a group of three muscles. One of the muscles involved in this eyecup withdrawal movement away from the mid-line is also active during horizontal optokinetic movements of the eyecup towards the mid-line. It is suggested that interpretation of eyecup muscle activity is more intelligible if the whole group of muscles, rather than the individual muscles themselves, is regarded as the functional unit.The structure and function of certain neuromuscular systems in echinodermsCobb, James Leslie Stileshttps://hdl.handle.net/10023/148272019-03-29T10:34:35Z1967-01-01T00:00:00Z1. Physiological experiments were devised to study the electrical responses of ochinoderm muscle during contraction. The smooth muscle forming the lantern retractors of Eching conducts spike potentials at a speed off 4 cms. A sec. 2. Three muscle systems examined with the electron microscope reveal a layout that varies in complexity. The muscle cells give rise to processes that are synapsed upon by nerves. 3. The area containing the ribbon axons described by Smith (1950) was examined and the ribbon axons shown to be selectively stained muscle cells. 4. In the three muscle systems examined controlling ganglion was found to be associated sytams. 5. The ganglia contained large numbers of structures that are described as synapses. These synapses are of a simple type and do not possess the specialisations that are present in the synapses of some other invertebrate phyla. 6. The sensory cells of the epithalium are described and an examination has indicated that the cells of the general epithelial are all sensory and contribute axons to the nerve plexus. Some of these epithalial cells are modified into probable chemoreceptors, light receptors and are found in statocysts. 7. A hypothesis to account for the co-ordination of the behaviour of echinoderms in propounded.
1967-01-01T00:00:00ZCobb, James Leslie Stiles1. Physiological experiments were devised to study the electrical responses of ochinoderm muscle during contraction. The smooth muscle forming the lantern retractors of Eching conducts spike potentials at a speed off 4 cms. A sec. 2. Three muscle systems examined with the electron microscope reveal a layout that varies in complexity. The muscle cells give rise to processes that are synapsed upon by nerves. 3. The area containing the ribbon axons described by Smith (1950) was examined and the ribbon axons shown to be selectively stained muscle cells. 4. In the three muscle systems examined controlling ganglion was found to be associated sytams. 5. The ganglia contained large numbers of structures that are described as synapses. These synapses are of a simple type and do not possess the specialisations that are present in the synapses of some other invertebrate phyla. 6. The sensory cells of the epithalium are described and an examination has indicated that the cells of the general epithelial are all sensory and contribute axons to the nerve plexus. Some of these epithalial cells are modified into probable chemoreceptors, light receptors and are found in statocysts. 7. A hypothesis to account for the co-ordination of the behaviour of echinoderms in propounded.Structural and functional differentiation of teleost skeletal muscleEggington, Stuarthttps://hdl.handle.net/10023/148262019-03-29T10:43:12Z1983-01-01T00:00:00ZThe lateral musculature of elvers is differentiated into two fibre type on the basis of alkaline-labile (pH 10.2) myofibrillar ATPase activity. Slow muscle forms a relatively homogeneous fibre population, whereas fast muscle shows a heterogeneity with respect to both fibre size, and position in the myotome. The low aerobic capacity of slow fibres reflects the energetic requirement of anguilliform locomotion. A morphological continuum of myogenic cells occurs within mature; differentiated myotomal muscle similar to that described for embryonic myogenesis. No evidence could be found for regional growth nodes. Small fast fibres ( <100µm2) represent immature, but differentiated fibres undergoing hypertrophy. There is considerable variation in the capillary supply to both fast and slow muscle, and between homologous muscle off different species. Methods are described to determine the minimum sample size required for a stable, reproducible parameter estimate, and to assess the orientation of the capillary network. This is shown to be highly anisotropic. Capillary volume and surface densities are thought to be the most appropriated indices to use with fish muscle. The springs migration of elvers is shown to be a mixed population, of similar annual composition. The main migratory wave are true post-metamorphic, juvenile eels. There is a partial (Precht type 3) compensation in VO2 on acclimation to 10° and 29°C. The extent of the physiological acclimation reflects the environmental constraints of the migration. Differences in structure and complexity of multiple and focal innervation were investigated using fast muscle from representative teleosts. Endplate structure is similar in both types. Cod ventral spinal nerves have fewer motor, but more sensory axons than homologous nerves in eel. A novel way of visualizing the extent of inter- end intra segmental branching of nerves, intracellular marking of nerve routes with cobalt, reveals extensive branching in cod mytomes and cross-innervation between at least 3 segments. In cel, branching is restricted to a single mytome. These results reflect the mechanical and nervous control over the locomotory waveform.
1983-01-01T00:00:00ZEggington, StuartThe lateral musculature of elvers is differentiated into two fibre type on the basis of alkaline-labile (pH 10.2) myofibrillar ATPase activity. Slow muscle forms a relatively homogeneous fibre population, whereas fast muscle shows a heterogeneity with respect to both fibre size, and position in the myotome. The low aerobic capacity of slow fibres reflects the energetic requirement of anguilliform locomotion. A morphological continuum of myogenic cells occurs within mature; differentiated myotomal muscle similar to that described for embryonic myogenesis. No evidence could be found for regional growth nodes. Small fast fibres ( <100µm2) represent immature, but differentiated fibres undergoing hypertrophy. There is considerable variation in the capillary supply to both fast and slow muscle, and between homologous muscle off different species. Methods are described to determine the minimum sample size required for a stable, reproducible parameter estimate, and to assess the orientation of the capillary network. This is shown to be highly anisotropic. Capillary volume and surface densities are thought to be the most appropriated indices to use with fish muscle. The springs migration of elvers is shown to be a mixed population, of similar annual composition. The main migratory wave are true post-metamorphic, juvenile eels. There is a partial (Precht type 3) compensation in VO2 on acclimation to 10° and 29°C. The extent of the physiological acclimation reflects the environmental constraints of the migration. Differences in structure and complexity of multiple and focal innervation were investigated using fast muscle from representative teleosts. Endplate structure is similar in both types. Cod ventral spinal nerves have fewer motor, but more sensory axons than homologous nerves in eel. A novel way of visualizing the extent of inter- end intra segmental branching of nerves, intracellular marking of nerve routes with cobalt, reveals extensive branching in cod mytomes and cross-innervation between at least 3 segments. In cel, branching is restricted to a single mytome. These results reflect the mechanical and nervous control over the locomotory waveform.Mechanical properties of myosin cross-bridges in frog striated muscleHirst, David Grahamhttps://hdl.handle.net/10023/148252019-03-29T10:39:06Z1975-01-01T00:00:00ZA. A study has been made of the tension responses and relative sliding movements of the actin and myosin filaments which result when controlled length changes of variable amplitude and velocity are applied to contracting frog's muscle. B. The tension increment produced by a 'ramp and hold' stretch of approximately 1mm (about 4 % of muscle length) consists of three phases whose limits are defined by two points, designated S1 and S2, where the slope of the increase of tension changes abruptly. S1 and S2 correspond with muscle extensions of 40-45 mum and 325 - 375mum, respectively. C. Displacement of the actin and myosin filaments was recorded simultaneously by monitoring changes in the diffraction spectra produced by illuminating a small area of muscle with a laser. The spectra were projected onto a screen and photographed with a cine-camera. The spacing of the 1st order lines was measured and used to calculate sarcomere length. D. Cine photography of diffraction spectra showed that a variable, and sometimes large, proportion of the length change applied to the muscle is taken up by extension of elastic elements arranged in series with the sarcomeres. During the early part of the stretch, filament displacement is less than would be anticipated if all of the external length change was distributed uniformly amongst the sarcomeres. E. The way in which sarcomeres shorten during the onset and development of an isometric tetanus shows that the series elastic elements become progressively stiffer with increasing extension; at peak tetanic tension their compliance is found to be approximately 6.5 x 10-4m.N-1. F. When the actin and myosin filaments are forcibly displaced by about 11-12nm from their 'steady state' position at the peak of an isometric tetanus, the sarcomere length increases abruptly by some 20- 30nm, a phenomenon referred to as rapid 'give'. The 11-12nm displacement before rapid 'give' occurs, represents the range of movement of the filaments over which the myosin cross-bridges can be distorted yet remain attached to the actin active site. This range of movement is found to be independent of sarcomere length, and hence, of interfilamentary spacing. Crossbridges are bridges are forcibly broken when the filaments are made to move by more than 11-12nm. The sudden increase in compliance of the sarcomeres which results effects an abrupt shortening of the stretched elastic elements (elastic recoil) at the expense of the sarcomeres in series with them, producing rapid 'give'. G. The stiffness of the sarcomeres and the force they are able to bear immediately prior to rapid 'give' (the maximum 'holding' force, designated Ps2) both directly proportional to filament overlap. Hence, the stiffness of an individual cross-bridge and its affinity for the actin active region are quantities which must be independent of the surface-to-surface separation of the filaments. The minimum stiffness of a single cross-bridge is estimated to be around 2.7 x 10-4 N.m-1. H. Tension changes and sarcomere movements during single and double cycles of stretch and release were recorded. The events occurring during a second cycle stretch differ markedly from those during a first. Cross-bridges can accommodate a wider range of filament movement without detaching , 18 nm as compared with 12 nm, if the second stretch is applied without delay after the proceeding release. The stiffness of the sarcomeres is approximately the same for a second cycle stretch ( 5.3 x 1012N.m-2 per metre extension of each half sarcomere) as for a first (5.95 x 1012N. 9 m-2 per metre extension of each half sarcomere), indicating that the number of cross-bridges holding the filaments together is not altered appreciably. These results are compatible with Huxley & Simmons recent model. They suggest an actin active region of length 15 nm, made up of four regularly spaced (~5.0 nm separation) attachment sites, corresponding with individual actin monomers.
1975-01-01T00:00:00ZHirst, David GrahamA. A study has been made of the tension responses and relative sliding movements of the actin and myosin filaments which result when controlled length changes of variable amplitude and velocity are applied to contracting frog's muscle. B. The tension increment produced by a 'ramp and hold' stretch of approximately 1mm (about 4 % of muscle length) consists of three phases whose limits are defined by two points, designated S1 and S2, where the slope of the increase of tension changes abruptly. S1 and S2 correspond with muscle extensions of 40-45 mum and 325 - 375mum, respectively. C. Displacement of the actin and myosin filaments was recorded simultaneously by monitoring changes in the diffraction spectra produced by illuminating a small area of muscle with a laser. The spectra were projected onto a screen and photographed with a cine-camera. The spacing of the 1st order lines was measured and used to calculate sarcomere length. D. Cine photography of diffraction spectra showed that a variable, and sometimes large, proportion of the length change applied to the muscle is taken up by extension of elastic elements arranged in series with the sarcomeres. During the early part of the stretch, filament displacement is less than would be anticipated if all of the external length change was distributed uniformly amongst the sarcomeres. E. The way in which sarcomeres shorten during the onset and development of an isometric tetanus shows that the series elastic elements become progressively stiffer with increasing extension; at peak tetanic tension their compliance is found to be approximately 6.5 x 10-4m.N-1. F. When the actin and myosin filaments are forcibly displaced by about 11-12nm from their 'steady state' position at the peak of an isometric tetanus, the sarcomere length increases abruptly by some 20- 30nm, a phenomenon referred to as rapid 'give'. The 11-12nm displacement before rapid 'give' occurs, represents the range of movement of the filaments over which the myosin cross-bridges can be distorted yet remain attached to the actin active site. This range of movement is found to be independent of sarcomere length, and hence, of interfilamentary spacing. Crossbridges are bridges are forcibly broken when the filaments are made to move by more than 11-12nm. The sudden increase in compliance of the sarcomeres which results effects an abrupt shortening of the stretched elastic elements (elastic recoil) at the expense of the sarcomeres in series with them, producing rapid 'give'. G. The stiffness of the sarcomeres and the force they are able to bear immediately prior to rapid 'give' (the maximum 'holding' force, designated Ps2) both directly proportional to filament overlap. Hence, the stiffness of an individual cross-bridge and its affinity for the actin active region are quantities which must be independent of the surface-to-surface separation of the filaments. The minimum stiffness of a single cross-bridge is estimated to be around 2.7 x 10-4 N.m-1. H. Tension changes and sarcomere movements during single and double cycles of stretch and release were recorded. The events occurring during a second cycle stretch differ markedly from those during a first. Cross-bridges can accommodate a wider range of filament movement without detaching , 18 nm as compared with 12 nm, if the second stretch is applied without delay after the proceeding release. The stiffness of the sarcomeres is approximately the same for a second cycle stretch ( 5.3 x 1012N.m-2 per metre extension of each half sarcomere) as for a first (5.95 x 1012N. 9 m-2 per metre extension of each half sarcomere), indicating that the number of cross-bridges holding the filaments together is not altered appreciably. These results are compatible with Huxley & Simmons recent model. They suggest an actin active region of length 15 nm, made up of four regularly spaced (~5.0 nm separation) attachment sites, corresponding with individual actin monomers.A study of the effect of sudden cooling on tension development by the anterior byssus retractor muscle of mytilus edulisLinehan, Catherine Maryhttps://hdl.handle.net/10023/148242019-03-29T10:42:33Z1978-01-01T00:00:00ZThe effect of ambient temperature on the ACh-induced tension response of the ABRM of Mytilus edulis was examined. The latter was found to have many temperature dependent variables, these included the latent period, the rate of tension development, maximum tension and the relaxation rate. Pmax was found to show a negative temperature coefficent. K+ contractures also showed a negative temperature co-efficent, Pmax approximately doubling for a 20°C decrease in temperature. The application of a cold shock during an ACh-induced contraction-relaxation cycle resulted in a transient increase in tension, the CIC. The production of a CTC was found to be dependent on the immediate presence of a stimulant, the time of application of the cold shock after the addition of stimulant, muscle length and temperature difference. As the temperature difference (ΔT) between the initial and cold shock solutions increased so the size of the CIC increased. The production of a CIC was found not to be directly related to the ACh or to the active state level yet it did not appear to be a passive phenomenon. A CIC was not produced when cold shock was applied to a muscle at rest or during catchy however, when catch was abolished by the application of relaxant a CIC could once again be elicited. Kinetic analysis of the CIC showed that, however, complex the mechanism two steps appear to be rate limiting, and the increase in tension with increasing AT was probably due to an increase in the availability of activator responsible for its production, rather than a differential effect on one of the rate limiting steps. Although it is conceivable that cold shock may exert a direct effect on the contractile proteins, evidence from the literature, and the experiments reported here, suggest that it is more likely that the CTC results from a transient increase in the level of myoplasmic Ca+2 Pharmacological investigation did not disprove this hypothesis. Of the possible sources of Ca+2 responsible for the CIC membrane associated sites seemed the most likely since under conditions which deplete this site no CIC was observed. Also the involvement of cAMP in the production of the CIC was largely excluded.
1978-01-01T00:00:00ZLinehan, Catherine MaryThe effect of ambient temperature on the ACh-induced tension response of the ABRM of Mytilus edulis was examined. The latter was found to have many temperature dependent variables, these included the latent period, the rate of tension development, maximum tension and the relaxation rate. Pmax was found to show a negative temperature coefficent. K+ contractures also showed a negative temperature co-efficent, Pmax approximately doubling for a 20°C decrease in temperature. The application of a cold shock during an ACh-induced contraction-relaxation cycle resulted in a transient increase in tension, the CIC. The production of a CTC was found to be dependent on the immediate presence of a stimulant, the time of application of the cold shock after the addition of stimulant, muscle length and temperature difference. As the temperature difference (ΔT) between the initial and cold shock solutions increased so the size of the CIC increased. The production of a CIC was found not to be directly related to the ACh or to the active state level yet it did not appear to be a passive phenomenon. A CIC was not produced when cold shock was applied to a muscle at rest or during catchy however, when catch was abolished by the application of relaxant a CIC could once again be elicited. Kinetic analysis of the CIC showed that, however, complex the mechanism two steps appear to be rate limiting, and the increase in tension with increasing AT was probably due to an increase in the availability of activator responsible for its production, rather than a differential effect on one of the rate limiting steps. Although it is conceivable that cold shock may exert a direct effect on the contractile proteins, evidence from the literature, and the experiments reported here, suggest that it is more likely that the CTC results from a transient increase in the level of myoplasmic Ca+2 Pharmacological investigation did not disprove this hypothesis. Of the possible sources of Ca+2 responsible for the CIC membrane associated sites seemed the most likely since under conditions which deplete this site no CIC was observed. Also the involvement of cAMP in the production of the CIC was largely excluded.Effect of thyroid status on the contractile and biochemical properties of rat skeletal musclesMajid, Imtiazhttps://hdl.handle.net/10023/148222019-03-29T10:34:56Z1995-01-01T00:00:00ZChemically skinned single fibres from soleus (slow) and tensor fascia latae (fast) muscles of the euthyroid rat and guinea-pig generated maximal isometric tensions in a narrow range of 125 - 150 kN/m2 at a temperature of 25 °C and a sarcomere length of 2.75 µm. The maximum velocity of shortening (Vmax) of the tensor fascia latae (TFL) muscle fibres from the euthyroid rat (12.35 +/- 0.95 LoS-1 - Fibre lengths per second) and guinea-pig (9.93 + 1.14 LOS-1 ) were 2-3 fold higher (P < 0.05, unpaired t-test) as compared to the soleus muscle fibres of the euthyroid rat (5.61 +/- 0.54 LoS-1 ) and guinea-pig (3.92 + 0.35 LoS-1 ) respectively. This was consistent with previous (e.g. Reiser et al., 1985a, b) results on slow and fast muscle fibres. Storing bundles of soleus or TFL muscle fibres from euthyroid rats and guinea-pigs for short (weeks) or long term (months) resulted in significant (P < 0.05, unpaired t-test) reductions in both the maximum isometric tension (Po) and Vmax of stored single fibres in comparison to fresh single fibres. Therefore, all subsequent experiments were done using fresh single fibres. The maximum isometric tension of chemically skinned single fibres from the soleus of mildly hyperthyroid animals (rats), was lower than that generated by equivalent fibres from mildly hypothyroid animals (127.12 +/- 5.87 kN/m2vs. 169.02 +/- 6.62 kN/m2, P < 0.05, unpaired t-test). There was a corresponding reduction in tension production in TFL fibres comparing hyperthyroid with hypothyroid animals (121.30 +/- 6.80 kN/m2 vs. 142.73 +/- 6.38 kN/m2, P < 0.05). On the other hand, Vmax of single fibres from soleus muscles of hyperthyroid rats was higher than the hypothyroid counterparts (6.58 +/- V 0.32 LoS-1 vs. 5.52 +/- 0.27 LoS-1 , P < 0.05, unpaired t-test). Similarly, Vmax of hyperthyroid single TFL fibres was higher than the hypothyroid counterparts (13.81 +/- 0.50 LoS-1 vs. 11.18 +/- 0.65 LoS-1 , P < 0.05). These differences between the hyper- and hypothyroid results - within each muscle type - were observed in the same type of fibre as identified histochemically. These were the slow oxidative (SO) fibre type from the soleus and the fast glycolytic (FG) fibre type from the TFL muscles. It is postulated that the differences in PO and Vmax were due to alterations in the isoforms of the myosin molecule and more specifically to the myosin light chains. Mild dysthyreosis showed that single muscle fibres of the same histochemical type can generate heterogeneous tension/pCa (T/pCa) relationships. (Abstract shortened by ProQuest.)
1995-01-01T00:00:00ZMajid, ImtiazChemically skinned single fibres from soleus (slow) and tensor fascia latae (fast) muscles of the euthyroid rat and guinea-pig generated maximal isometric tensions in a narrow range of 125 - 150 kN/m2 at a temperature of 25 °C and a sarcomere length of 2.75 µm. The maximum velocity of shortening (Vmax) of the tensor fascia latae (TFL) muscle fibres from the euthyroid rat (12.35 +/- 0.95 LoS-1 - Fibre lengths per second) and guinea-pig (9.93 + 1.14 LOS-1 ) were 2-3 fold higher (P < 0.05, unpaired t-test) as compared to the soleus muscle fibres of the euthyroid rat (5.61 +/- 0.54 LoS-1 ) and guinea-pig (3.92 + 0.35 LoS-1 ) respectively. This was consistent with previous (e.g. Reiser et al., 1985a, b) results on slow and fast muscle fibres. Storing bundles of soleus or TFL muscle fibres from euthyroid rats and guinea-pigs for short (weeks) or long term (months) resulted in significant (P < 0.05, unpaired t-test) reductions in both the maximum isometric tension (Po) and Vmax of stored single fibres in comparison to fresh single fibres. Therefore, all subsequent experiments were done using fresh single fibres. The maximum isometric tension of chemically skinned single fibres from the soleus of mildly hyperthyroid animals (rats), was lower than that generated by equivalent fibres from mildly hypothyroid animals (127.12 +/- 5.87 kN/m2vs. 169.02 +/- 6.62 kN/m2, P < 0.05, unpaired t-test). There was a corresponding reduction in tension production in TFL fibres comparing hyperthyroid with hypothyroid animals (121.30 +/- 6.80 kN/m2 vs. 142.73 +/- 6.38 kN/m2, P < 0.05). On the other hand, Vmax of single fibres from soleus muscles of hyperthyroid rats was higher than the hypothyroid counterparts (6.58 +/- V 0.32 LoS-1 vs. 5.52 +/- 0.27 LoS-1 , P < 0.05, unpaired t-test). Similarly, Vmax of hyperthyroid single TFL fibres was higher than the hypothyroid counterparts (13.81 +/- 0.50 LoS-1 vs. 11.18 +/- 0.65 LoS-1 , P < 0.05). These differences between the hyper- and hypothyroid results - within each muscle type - were observed in the same type of fibre as identified histochemically. These were the slow oxidative (SO) fibre type from the soleus and the fast glycolytic (FG) fibre type from the TFL muscles. It is postulated that the differences in PO and Vmax were due to alterations in the isoforms of the myosin molecule and more specifically to the myosin light chains. Mild dysthyreosis showed that single muscle fibres of the same histochemical type can generate heterogeneous tension/pCa (T/pCa) relationships. (Abstract shortened by ProQuest.)Muscle stiffness and soreness following exerciseMcGlynn, Fraser Gillieshttps://hdl.handle.net/10023/148202019-03-29T10:32:16Z1997-01-01T00:00:00ZIt is in the best interests of sportsmen and sportswomen to try to avoid muscle stiffness and soreness. Apart from the discomfort experienced, muscle stiffness and soreness can cause unnecessary interruptions to training, may lead to injury and will reduce performance. Changes in muscle tone were quantified in terms of the Resonant Frequency (squared) (RF2) and the Amplitude of Movement (AM) in response to an applied torque. Muscle soreness was measured at twelve sites on the arm. Study One investigated the effects of a single bout of eccentric exercise on muscle stiffness and muscle soreness. RF2 increased and AM decreased following exercise and reached a maximum and minimum, respectively, 24-48 hours post exercise (p<0.01). Muscle soreness also reached a peak 24-48 hours post-exercise (p<0.01). Greatest soreness was in the biceps brachii and in the proximal ends of the brachioradialis and the flexor carpi radialis (p<0.01). Voluntary extension was more painful than voluntary flexion following eccentric exercise. Study Two investigated the effect of performing two subsequent exercise bouts (EX1 and EX2), each separated by six days and an adaptation was observed. Each of the variables measured (RF2, AM, Soreness, Creatine Kinase, Limb Girth) showed a reduced response following EX2 when compared to the results of EX1 (p<0.01). The resting angle of elbow flexion appeared to decrease following exercise. Study Three investigated the effect of muscle soreness on motor performance. The ability to perform a simple perception test was not affected while suffering from muscle soreness. The eccentric exercise is thought to cause damage to the connective tissue and muscle cell membrane leading to a build-up of fluid around the joint. This increased edema may explain the increase in muscle stiffness observed. Further research is required to determine whether changes in muscle tone are also observed following isometric and concentric exercise.
1997-01-01T00:00:00ZMcGlynn, Fraser GilliesIt is in the best interests of sportsmen and sportswomen to try to avoid muscle stiffness and soreness. Apart from the discomfort experienced, muscle stiffness and soreness can cause unnecessary interruptions to training, may lead to injury and will reduce performance. Changes in muscle tone were quantified in terms of the Resonant Frequency (squared) (RF2) and the Amplitude of Movement (AM) in response to an applied torque. Muscle soreness was measured at twelve sites on the arm. Study One investigated the effects of a single bout of eccentric exercise on muscle stiffness and muscle soreness. RF2 increased and AM decreased following exercise and reached a maximum and minimum, respectively, 24-48 hours post exercise (p<0.01). Muscle soreness also reached a peak 24-48 hours post-exercise (p<0.01). Greatest soreness was in the biceps brachii and in the proximal ends of the brachioradialis and the flexor carpi radialis (p<0.01). Voluntary extension was more painful than voluntary flexion following eccentric exercise. Study Two investigated the effect of performing two subsequent exercise bouts (EX1 and EX2), each separated by six days and an adaptation was observed. Each of the variables measured (RF2, AM, Soreness, Creatine Kinase, Limb Girth) showed a reduced response following EX2 when compared to the results of EX1 (p<0.01). The resting angle of elbow flexion appeared to decrease following exercise. Study Three investigated the effect of muscle soreness on motor performance. The ability to perform a simple perception test was not affected while suffering from muscle soreness. The eccentric exercise is thought to cause damage to the connective tissue and muscle cell membrane leading to a build-up of fluid around the joint. This increased edema may explain the increase in muscle stiffness observed. Further research is required to determine whether changes in muscle tone are also observed following isometric and concentric exercise.Biochemical basis of the muscular activity of erlangia cordifolia (S.Moore) - (Gathuna)Mugo, Njuguna Johnhttps://hdl.handle.net/10023/148012019-07-15T09:45:42Z1976-01-01T00:00:00ZWater extract of the leaves of Erlangla cordifolia (S. Moore) - compositae (commonly known in Gikuyuland as Gathuna) has been traditionally used by the Gikuyu people of Kenya for centuries for the purpose of stimulating myometrial contractions in the process of parturition. The use of this extract has been called for when the progress of the birth process has been judged to be unsatisfactorily slow. The introduction to this work (Chapter 1) therefore surveys this use of the plant material and proceeds on to show the validity of using Erlangia material for the study of the process of muscle contraction. The section also includes a short discussion on the validity of the use of what could be termed a pathological condition - that is, the obstetric 'lazy' uterus - for the purpose of studying a normal physiological process (muscle contraction) at the cellular and molecular levels. Chapter 2 explains the methods used to obtain the crude extract from Erlangia leaves andvalso a purified compound, cordifene, from the same source, that was found by the author of this work to have stimulatory activity on contracting muscle. The chapter also deals with the methods used to characterize cordifene chemically. Chapter 3 describes the physiological experiments carried out to confirm the stimulatory activity of Erlangia extract and also of cordifene on the smooth muscle of the myometrium and that of the intestinal wall, in addition to similar effects on skeletal muscle. These experiments therefore confirmed the fact that the activity of Erlangia material has a common biochemical basis for all types of muscle at the molecular level. Stimulation of muscle contraction can be brought about through biochemical effects on the nerve(s) supplying the muscle or through direct effects on biochemical mechanisms occurring within the muscle cell itself. Chapter 4 of this work is therefore concerned with an investigation into the possibility of a chemical compound or compounds from Erlangia leaves that may be capable of influencing biochemical processes within the peripheral autonomic nervous system, as this system is known to be intricately involved in muscle contraction. Acetylcholine metabolism is important not only for the autonomic nervous system's biochemical role in muscle contraction: it is also important for the biochemical processes that take place in nervous impulse transmissions in general - with all the consequences that this has on all muscles, both voluntary and involuntary. For this reason, a possible effect of Erlangia material on the cholinesterase enzymes has been searched for Chapter 5 is concerned with a series of investigations into the different biochemical processes that occur in the muscle cell during the contractile activity and the mode of action by which Erlangia material might be influencing such processes. Chapter 6 is a discussion based on the results of the investigations reported in the previous sections. Erlangia material was found to react with ADP forming a complex and, besides probably inducing increased myosin ATPase activity, it was also found to induce marked configurational changes within the actomyosin molecule. (Abstract shortened by ProQuest.)
1976-01-01T00:00:00ZMugo, Njuguna JohnWater extract of the leaves of Erlangla cordifolia (S. Moore) - compositae (commonly known in Gikuyuland as Gathuna) has been traditionally used by the Gikuyu people of Kenya for centuries for the purpose of stimulating myometrial contractions in the process of parturition. The use of this extract has been called for when the progress of the birth process has been judged to be unsatisfactorily slow. The introduction to this work (Chapter 1) therefore surveys this use of the plant material and proceeds on to show the validity of using Erlangia material for the study of the process of muscle contraction. The section also includes a short discussion on the validity of the use of what could be termed a pathological condition - that is, the obstetric 'lazy' uterus - for the purpose of studying a normal physiological process (muscle contraction) at the cellular and molecular levels. Chapter 2 explains the methods used to obtain the crude extract from Erlangia leaves andvalso a purified compound, cordifene, from the same source, that was found by the author of this work to have stimulatory activity on contracting muscle. The chapter also deals with the methods used to characterize cordifene chemically. Chapter 3 describes the physiological experiments carried out to confirm the stimulatory activity of Erlangia extract and also of cordifene on the smooth muscle of the myometrium and that of the intestinal wall, in addition to similar effects on skeletal muscle. These experiments therefore confirmed the fact that the activity of Erlangia material has a common biochemical basis for all types of muscle at the molecular level. Stimulation of muscle contraction can be brought about through biochemical effects on the nerve(s) supplying the muscle or through direct effects on biochemical mechanisms occurring within the muscle cell itself. Chapter 4 of this work is therefore concerned with an investigation into the possibility of a chemical compound or compounds from Erlangia leaves that may be capable of influencing biochemical processes within the peripheral autonomic nervous system, as this system is known to be intricately involved in muscle contraction. Acetylcholine metabolism is important not only for the autonomic nervous system's biochemical role in muscle contraction: it is also important for the biochemical processes that take place in nervous impulse transmissions in general - with all the consequences that this has on all muscles, both voluntary and involuntary. For this reason, a possible effect of Erlangia material on the cholinesterase enzymes has been searched for Chapter 5 is concerned with a series of investigations into the different biochemical processes that occur in the muscle cell during the contractile activity and the mode of action by which Erlangia material might be influencing such processes. Chapter 6 is a discussion based on the results of the investigations reported in the previous sections. Erlangia material was found to react with ADP forming a complex and, besides probably inducing increased myosin ATPase activity, it was also found to induce marked configurational changes within the actomyosin molecule. (Abstract shortened by ProQuest.)Excitation-contraction coupling in the rat anococcygeus muscleSaint, David Alberthttps://hdl.handle.net/10023/147992019-03-29T10:40:31Z1982-01-01T00:00:00ZSmooth muscles as a group exhibit great diversity of pharmacological and physiological properties. This makes it impossible to produce any but extremely generalised schemes for smooth muscle contractile mechanisms. However, knowledge of the detailed physiology and pharmacology of specific types of smooth muscle has been growing at an increasing rate, especially regarding vascular and visceral muscles. The rat anococcygeus muscle has, however, been investigated little. This work describes the excitation- contraction coupling mechanism in this preparation. The rat anococcygeus muscle was found to contract to all three of the agonists used (noradrenaline, acetylcholine and potassium chloride). In the first section of this work the properties of these contractions were investigated. It was found that the contractions induced by each agonist exhibited different pharmacological properties, (with regard to low calcium, sodium nitroprusside, verapamil, Stellazine and theophylline). This can be taken as an indication that the different agonists use different activation pathways. Electrophysiological studies showed that the membrane potential per se is not important in the regulation of contraction. (ie. the depolarisation produced by an agonist is not simply related to the tension produced ). KC1 produces the greatest change in membrane potential (from -55mV to -20mV for a maximal dose), but produces the least rise in tension of the three agonists. Evidence from other preparations and the results of the experiments with Stellazine suggest that the rise in tension produced by the agonists is not simply related to the rise in intracellular calcium concentration, but that some amplification of the response occurs. The way in which the agonists produce this amplification of the response is suggested as being related to changes in the levels of the cyclic nucleotides, cAMP and cGMP within the cells. It was found that the agonists did not substantially affect cAMP levels, but that all three reduced cGMP levels by varying amounts. The ratio of the levels of cAMP/cGMP produced by activation with each agonist correllates very well with the tension produced. This suggests that the ratio cAMP/cGMP is important in the regulation of contractility in this muscle. However, doubt is cast upon this theory by the results of experiments using sodium nitroprusside (NP). It was found that NP (2 X 10-7M) caused a pronounced change in the ratio cAMP/cGMP (by increasing cGMP levels ), but only a small change in tension (so that the tension in these experiments does not correllate well with the ratio cAMP/cGMP). In order to retain the hypothesis that cyclic nucleotides are important in the regulation of contractility in this preparation, it is proposed that some form of compartmentalisation of the cyclic nucleotide changes occurs within the cells.
1982-01-01T00:00:00ZSaint, David AlbertSmooth muscles as a group exhibit great diversity of pharmacological and physiological properties. This makes it impossible to produce any but extremely generalised schemes for smooth muscle contractile mechanisms. However, knowledge of the detailed physiology and pharmacology of specific types of smooth muscle has been growing at an increasing rate, especially regarding vascular and visceral muscles. The rat anococcygeus muscle has, however, been investigated little. This work describes the excitation- contraction coupling mechanism in this preparation. The rat anococcygeus muscle was found to contract to all three of the agonists used (noradrenaline, acetylcholine and potassium chloride). In the first section of this work the properties of these contractions were investigated. It was found that the contractions induced by each agonist exhibited different pharmacological properties, (with regard to low calcium, sodium nitroprusside, verapamil, Stellazine and theophylline). This can be taken as an indication that the different agonists use different activation pathways. Electrophysiological studies showed that the membrane potential per se is not important in the regulation of contraction. (ie. the depolarisation produced by an agonist is not simply related to the tension produced ). KC1 produces the greatest change in membrane potential (from -55mV to -20mV for a maximal dose), but produces the least rise in tension of the three agonists. Evidence from other preparations and the results of the experiments with Stellazine suggest that the rise in tension produced by the agonists is not simply related to the rise in intracellular calcium concentration, but that some amplification of the response occurs. The way in which the agonists produce this amplification of the response is suggested as being related to changes in the levels of the cyclic nucleotides, cAMP and cGMP within the cells. It was found that the agonists did not substantially affect cAMP levels, but that all three reduced cGMP levels by varying amounts. The ratio of the levels of cAMP/cGMP produced by activation with each agonist correllates very well with the tension produced. This suggests that the ratio cAMP/cGMP is important in the regulation of contractility in this muscle. However, doubt is cast upon this theory by the results of experiments using sodium nitroprusside (NP). It was found that NP (2 X 10-7M) caused a pronounced change in the ratio cAMP/cGMP (by increasing cGMP levels ), but only a small change in tension (so that the tension in these experiments does not correllate well with the ratio cAMP/cGMP). In order to retain the hypothesis that cyclic nucleotides are important in the regulation of contractility in this preparation, it is proposed that some form of compartmentalisation of the cyclic nucleotide changes occurs within the cells.The effects of rheumatoid arthritis and age on some properties of human tendon collagenWorsnip, David N.https://hdl.handle.net/10023/147972019-03-29T10:32:00Z1967-01-01T00:00:00Z1967-01-01T00:00:00ZWorsnip, David N.The permeability of the sheath and the selective uptake of nicotinic acid in crab axonsArmson, John Mosshttps://hdl.handle.net/10023/147872019-03-29T10:32:22Z1965-01-01T00:00:00Z1. Peripheral nerve from the crab walking leg was seen to take up nicotinic acid (NA) to an extent ten times greater than the surrounding tissues (p.37). 2. After a labelled dose of NA there was a gradient of radioactivity in the nerve trunk with the maximum peripherally (p.40). 3. Individual fibres from the trunk were seen to take the *NA up in equal amounts, irrespective of their function (p.47). 4. No such gradient was seen in a length of nerve immersed in a bath containing *NA (p.45). 5. A substance was extracted from the nerve after injection of the *NA which was radioactive (p.49), and which was seen to have reactions of a small peptide (p.57). 6. This substance was also seen to have an accelerating effect on the crab heart, but had no detected effect on the contractions of the closer muscle in the leg (p.68). 7. In the second part of the thesis, results show that there is no difference in the structure of the sheath around the different motor axons in the crab leg, as seen under the light microscope (p.108). 8. When the potassium concentration around an isolated axon was changed to three times its normal value, the resulting drop in the membrane potential and resistance was slower and smaller than for any other concentration tried (p.113). 9. The effect of applying to single fibres dinitrophenol and other compounds of pharmacological interest was studied; with the dinitrophenol the membrane resistance was seen to fall reversibly in the manner described for other preparations (p.120).
1965-01-01T00:00:00ZArmson, John Moss1. Peripheral nerve from the crab walking leg was seen to take up nicotinic acid (NA) to an extent ten times greater than the surrounding tissues (p.37). 2. After a labelled dose of NA there was a gradient of radioactivity in the nerve trunk with the maximum peripherally (p.40). 3. Individual fibres from the trunk were seen to take the *NA up in equal amounts, irrespective of their function (p.47). 4. No such gradient was seen in a length of nerve immersed in a bath containing *NA (p.45). 5. A substance was extracted from the nerve after injection of the *NA which was radioactive (p.49), and which was seen to have reactions of a small peptide (p.57). 6. This substance was also seen to have an accelerating effect on the crab heart, but had no detected effect on the contractions of the closer muscle in the leg (p.68). 7. In the second part of the thesis, results show that there is no difference in the structure of the sheath around the different motor axons in the crab leg, as seen under the light microscope (p.108). 8. When the potassium concentration around an isolated axon was changed to three times its normal value, the resulting drop in the membrane potential and resistance was slower and smaller than for any other concentration tried (p.113). 9. The effect of applying to single fibres dinitrophenol and other compounds of pharmacological interest was studied; with the dinitrophenol the membrane resistance was seen to fall reversibly in the manner described for other preparations (p.120).Repetition in isolated crab axonsChapman, R. A.https://hdl.handle.net/10023/147852019-03-29T10:38:09Z1963-01-01T00:00:00ZIsolated and identified crab axons have been used to study the forms of the repetitive responses to direct current. Using techniques which enable the responses of isolated axons to be studied at the site of imposed electrical currents, the responses can be classified into five major groups with two subdivisions:- Group 1. Axons showing no marked supernormality during the recovery cycle, that repeat over a wide range of frequencies when stimulated by direct current, with frequency increasing smoothly with the strength of applied current, Group ia. To direct current these axons yield a train of impulses, the intervals between which progressively lengthen. Group ib. To direct current these axons yield a train of impulses the Intervals between which, for some time at least, progressively shorten. Group ll. Axons showing a pronounced supemomality during the recovery cycle, that repeat over only a limited frequency range. Group lla. Axons capable of long latencies, with oscillatory subthreshold potentials before and after the repetitive response. Group llb. Axons showing only short latencies, and lacking subthreshold oscillations before the repetitive response, but nevertheless with oscillations following the response. Group lll. Axons with a prolonged long-lived supemormality during the recovery cycle, which can be correlated with a prolonged action potential. They can repeat over a wide range of frequencies stimulated by direct current, but lack true local potentials for all action potentials except the first. Group lV. Axons with a relatively prolonged subnormality during the recovery cycle. They show short trains of action potentials, the amplitude of which progressively decreases even to near threshold currents, and the interspike intervals show a smooth increase. Group V. Axons unable to repeat to direct current, having a low safety factor and high threshold. They are capable of only short latencies. The single action potential shows a considerable variation in amplitude. A wide varied of experiments have been carried out, which have shown that several factors influence the form of the repetitive response in crab axons, and that the inadequacy of previous theories stems from their oversimplification. The factors show to operate in determining the form of these responses are:- 1. Changes in the resistance of the axon membrane, so that a constant current pulse will not cause the sane potential displacement while it acts. These changes can occur as the result of ionic accumulation outside the axon, or from the active process of delayed rectification. 2. The duration and from of the recovery cycle limits the upper frequency of the repetitive response, as well as influencing it at other times. 3. Sustained depolarisation depresses excitability, by lengthening the repolarisation time of an action potential and the period of recovery following it, as can be seen when the threshold potential for the spike rises throughout a repetitive response. 4. Changes in the membrane potential that result from the accumulation of ions in the near vicinity of the axon membrane. These changes, although they show some interdependence, are often difficult to completely eliminate any particular one by experiment. Although these factors have not been measured quantitatively, on account of technical difficulties inherent in the use of crab axons, they are sufficient to provide a coherent interpretation of repetition.
1963-01-01T00:00:00ZChapman, R. A.Isolated and identified crab axons have been used to study the forms of the repetitive responses to direct current. Using techniques which enable the responses of isolated axons to be studied at the site of imposed electrical currents, the responses can be classified into five major groups with two subdivisions:- Group 1. Axons showing no marked supernormality during the recovery cycle, that repeat over a wide range of frequencies when stimulated by direct current, with frequency increasing smoothly with the strength of applied current, Group ia. To direct current these axons yield a train of impulses, the intervals between which progressively lengthen. Group ib. To direct current these axons yield a train of impulses the Intervals between which, for some time at least, progressively shorten. Group ll. Axons showing a pronounced supemomality during the recovery cycle, that repeat over only a limited frequency range. Group lla. Axons capable of long latencies, with oscillatory subthreshold potentials before and after the repetitive response. Group llb. Axons showing only short latencies, and lacking subthreshold oscillations before the repetitive response, but nevertheless with oscillations following the response. Group lll. Axons with a prolonged long-lived supemormality during the recovery cycle, which can be correlated with a prolonged action potential. They can repeat over a wide range of frequencies stimulated by direct current, but lack true local potentials for all action potentials except the first. Group lV. Axons with a relatively prolonged subnormality during the recovery cycle. They show short trains of action potentials, the amplitude of which progressively decreases even to near threshold currents, and the interspike intervals show a smooth increase. Group V. Axons unable to repeat to direct current, having a low safety factor and high threshold. They are capable of only short latencies. The single action potential shows a considerable variation in amplitude. A wide varied of experiments have been carried out, which have shown that several factors influence the form of the repetitive response in crab axons, and that the inadequacy of previous theories stems from their oversimplification. The factors show to operate in determining the form of these responses are:- 1. Changes in the resistance of the axon membrane, so that a constant current pulse will not cause the sane potential displacement while it acts. These changes can occur as the result of ionic accumulation outside the axon, or from the active process of delayed rectification. 2. The duration and from of the recovery cycle limits the upper frequency of the repetitive response, as well as influencing it at other times. 3. Sustained depolarisation depresses excitability, by lengthening the repolarisation time of an action potential and the period of recovery following it, as can be seen when the threshold potential for the spike rises throughout a repetitive response. 4. Changes in the membrane potential that result from the accumulation of ions in the near vicinity of the axon membrane. These changes, although they show some interdependence, are often difficult to completely eliminate any particular one by experiment. Although these factors have not been measured quantitatively, on account of technical difficulties inherent in the use of crab axons, they are sufficient to provide a coherent interpretation of repetition.Neural mechanisms underlying the perception of socially relevant stimuli in the macaque monkeyMistlin, Amanda J.https://hdl.handle.net/10023/147842019-03-29T10:41:15Z1988-01-01T00:00:00ZPresent knowledge indicates the importance of one region of monkey temporal association cortex, the superior temporal sulcus (STS), in predominantly high level analysis of 'biologically' important objects. To clarify and elaborate on the function of the monkey STS, the following questions are addressed: (1) what kind of tactile processing occurs in the polymodal STS and does it compare with the complex visual processing observed; (2) does behavioural sensitivity to face and body information parallel neural sensitivity (of STS cells) to the same stimulus dimensions; (3) does monkey STS ablation result in a behavioural indication of impairments in the perception of socially relevant stimuli; and (4) are visual cells in the STS sensitive to social communicational elements of facial or postural expression? Single-unit recording studies of the macaque STS (using standard techniques in awake, behaving animals) reveal a population of somatosensory neurones, with large receptive fields, sensitive only to unexpected (unpredictable) tactile stimulation. Complex tactual-visual interactions observed stress the importance of this dimension of processing. A separate population of visual cells exhibit sensitivity to compound facial expressions and head/body postures important in primate social communication. A behavioural study of monkeys' socio-emotional responses to configurational aspects of faces, the posture of the head and the interaction of form and motion, reveal their ability to discriminate salient cues in the context of social communication/interaction. It is tentatively shown that monkeys with the STS ablated are unable to make such discriminations, so reacting inappropriately to the stimuli (a symptom of Kluver-Bucy syndrome). The combined findings show that the STS performs a multimodal perceptual analysis of socially relevant stimuli, and suggest that the STS provides a sensory input to a limbic structure, such as the amygdala, through which it mediates appropriate emotional reactive behaviour.
1988-01-01T00:00:00ZMistlin, Amanda J.Present knowledge indicates the importance of one region of monkey temporal association cortex, the superior temporal sulcus (STS), in predominantly high level analysis of 'biologically' important objects. To clarify and elaborate on the function of the monkey STS, the following questions are addressed: (1) what kind of tactile processing occurs in the polymodal STS and does it compare with the complex visual processing observed; (2) does behavioural sensitivity to face and body information parallel neural sensitivity (of STS cells) to the same stimulus dimensions; (3) does monkey STS ablation result in a behavioural indication of impairments in the perception of socially relevant stimuli; and (4) are visual cells in the STS sensitive to social communicational elements of facial or postural expression? Single-unit recording studies of the macaque STS (using standard techniques in awake, behaving animals) reveal a population of somatosensory neurones, with large receptive fields, sensitive only to unexpected (unpredictable) tactile stimulation. Complex tactual-visual interactions observed stress the importance of this dimension of processing. A separate population of visual cells exhibit sensitivity to compound facial expressions and head/body postures important in primate social communication. A behavioural study of monkeys' socio-emotional responses to configurational aspects of faces, the posture of the head and the interaction of form and motion, reveal their ability to discriminate salient cues in the context of social communication/interaction. It is tentatively shown that monkeys with the STS ablated are unable to make such discriminations, so reacting inappropriately to the stimuli (a symptom of Kluver-Bucy syndrome). The combined findings show that the STS performs a multimodal perceptual analysis of socially relevant stimuli, and suggest that the STS provides a sensory input to a limbic structure, such as the amygdala, through which it mediates appropriate emotional reactive behaviour.Regeneration of the cockroach (periplaneta Americana) central nervous system in vitro and in vivoRand, Kathryn Annhttps://hdl.handle.net/10023/147822019-03-29T10:33:57Z1983-01-01T00:00:00ZThe central nervous system of the cockroach is able to recover following nerve lesions, by specific re-innervation of targets. Some aspects of such regeneration were studied in vitro and in vivo to discover how this is achieved. Neural explants from the cockroach central nervous system were maintained in culture for UP to six months. The effect of various parameters, such as temperature and growth medium composition upon the rate and extent of fibre outgrowth was studied. There was no apparent selectivity in the formation of connections between co-cultured neural or muscular explants, suggesting that the cues necessary for specific re-innervation in vivo may be absent in vitro. Under normal conditions, outgrowth usually began by about five days in culture. The delay before onset of fibre outgrowth, however, was reduced by prior section of nerves in situ two to three weeks before explantation of ganglia into culture. Outgrowth from these nerves which had received a 'conditioning lesion' was observed as soon as 12-24 hours after explantation into culture. Similarly, functional recovery occurred sooner in vivo after equivalent operations: normal function returned to animals more quickly after a second lesion to the same nerve, than after one lesion only. The morphology of an identifiesd motoneurone was studied by intracellular cobalt injection, to assess the effect of maintenance in culture, or of different nerve lesions performed in vivo. Nerve lesions caused changes in the branching pattern of this identified neurone. The extent of change appeared to be determined largely by the overall extent of damage to the nervous system. Direct damage to the cell was not a pre-requisite for changes to occur. In many cases, supernumerary branches entered territory which was normally foreign to the motoneurone. In some areas this growth appeared to be random, while in others sprouts gave the appearance of following paths of degenerating nerve fibres. It is concluded that at least some adult insect neurones are capable of extensive regenerative growth, and of undergoing a high degree of structural modification, both in vivo and in vitro, indicating that some plasticity is a feature of the adult insect nervous system.
1983-01-01T00:00:00ZRand, Kathryn AnnThe central nervous system of the cockroach is able to recover following nerve lesions, by specific re-innervation of targets. Some aspects of such regeneration were studied in vitro and in vivo to discover how this is achieved. Neural explants from the cockroach central nervous system were maintained in culture for UP to six months. The effect of various parameters, such as temperature and growth medium composition upon the rate and extent of fibre outgrowth was studied. There was no apparent selectivity in the formation of connections between co-cultured neural or muscular explants, suggesting that the cues necessary for specific re-innervation in vivo may be absent in vitro. Under normal conditions, outgrowth usually began by about five days in culture. The delay before onset of fibre outgrowth, however, was reduced by prior section of nerves in situ two to three weeks before explantation of ganglia into culture. Outgrowth from these nerves which had received a 'conditioning lesion' was observed as soon as 12-24 hours after explantation into culture. Similarly, functional recovery occurred sooner in vivo after equivalent operations: normal function returned to animals more quickly after a second lesion to the same nerve, than after one lesion only. The morphology of an identifiesd motoneurone was studied by intracellular cobalt injection, to assess the effect of maintenance in culture, or of different nerve lesions performed in vivo. Nerve lesions caused changes in the branching pattern of this identified neurone. The extent of change appeared to be determined largely by the overall extent of damage to the nervous system. Direct damage to the cell was not a pre-requisite for changes to occur. In many cases, supernumerary branches entered territory which was normally foreign to the motoneurone. In some areas this growth appeared to be random, while in others sprouts gave the appearance of following paths of degenerating nerve fibres. It is concluded that at least some adult insect neurones are capable of extensive regenerative growth, and of undergoing a high degree of structural modification, both in vivo and in vitro, indicating that some plasticity is a feature of the adult insect nervous system.Neurotrophic actions of GDNF and neurturin in the developing avian nervous system and cloning and expression of their receptorsBuj-Bello, Annahttps://hdl.handle.net/10023/147812019-03-29T10:27:16Z1997-01-01T00:00:00ZThe main aim of this project was to determine the neurotrophic actions of glial cell line-derived neurotrophic factor (GDNF) and neurturin, two novel members of the transforming growth factor-beta superfamily of proteins, on neurons from the peripheral nervous system and to identify their receptors. It is found that GDNF promotes the survival of multiple populations of chicken sensory and autonomic neurons in culture throughout development. Whereas sympathetic, parasympathetic and propioceptive neurons become less responsive to GDNF with age, enteroceptive and sensory cutaneous neurons become more responsive to GDNF. GDNF mRNA is expressed in the tissues innervated by these neurons, and developmental changes in its expression in several tissues mirror the changing responses of the innervating neurons to GDNF. These results have changed the previous notion that GDNF is a highly specific neurotrophic factor for motoneurons and dopaminergic neurons. It is shown that neurturin, which is structurally related to GDNF, also promotes the in vitro survival of embryonic chicken sensory and autonomic neurons. Thus, GDNF and neurturin compose a novel subfamily of homologous neurotrophic factors with a similar pattern of activity. The cloning of chicken GDNF receptor-α (GDNFR-α) and a novel receptor termed neurturin receptor-α (NTNR-α) is reported. GDNFR-α and NTNR-α are homologous receptors linked to the membrane via a glycosyl- phosphatidylinositol linkage. It is shown that ectopic co-expression in neurons of GDNFR-α with RET (rearranged during transfection), a transmembrane receptor tyrosine kinase, confers a survival response to GDNF, but not neurturin, and that co-expression of NTNR-α with RET confers a survival response to neurturin, but not GDNF. GDNFR-α and NTNR-α mRNAs are widely expressed in the nervous system, including GDNF and neurturin responsive neurons, and in non-neuronal tissues. These findings indicate that GDNF and neurturin promote neuronal survival by signalling via similar multicomponent receptors that consist of a common transducing receptor tyrosine kinase and a member of a newly emerging family of glycosyl-phosphatidylinositol-linked receptors that confer ligand- specificity.
1997-01-01T00:00:00ZBuj-Bello, AnnaThe main aim of this project was to determine the neurotrophic actions of glial cell line-derived neurotrophic factor (GDNF) and neurturin, two novel members of the transforming growth factor-beta superfamily of proteins, on neurons from the peripheral nervous system and to identify their receptors. It is found that GDNF promotes the survival of multiple populations of chicken sensory and autonomic neurons in culture throughout development. Whereas sympathetic, parasympathetic and propioceptive neurons become less responsive to GDNF with age, enteroceptive and sensory cutaneous neurons become more responsive to GDNF. GDNF mRNA is expressed in the tissues innervated by these neurons, and developmental changes in its expression in several tissues mirror the changing responses of the innervating neurons to GDNF. These results have changed the previous notion that GDNF is a highly specific neurotrophic factor for motoneurons and dopaminergic neurons. It is shown that neurturin, which is structurally related to GDNF, also promotes the in vitro survival of embryonic chicken sensory and autonomic neurons. Thus, GDNF and neurturin compose a novel subfamily of homologous neurotrophic factors with a similar pattern of activity. The cloning of chicken GDNF receptor-α (GDNFR-α) and a novel receptor termed neurturin receptor-α (NTNR-α) is reported. GDNFR-α and NTNR-α are homologous receptors linked to the membrane via a glycosyl- phosphatidylinositol linkage. It is shown that ectopic co-expression in neurons of GDNFR-α with RET (rearranged during transfection), a transmembrane receptor tyrosine kinase, confers a survival response to GDNF, but not neurturin, and that co-expression of NTNR-α with RET confers a survival response to neurturin, but not GDNF. GDNFR-α and NTNR-α mRNAs are widely expressed in the nervous system, including GDNF and neurturin responsive neurons, and in non-neuronal tissues. These findings indicate that GDNF and neurturin promote neuronal survival by signalling via similar multicomponent receptors that consist of a common transducing receptor tyrosine kinase and a member of a newly emerging family of glycosyl-phosphatidylinositol-linked receptors that confer ligand- specificity.Regulation of expression and role of the GDNF family receptors in neuronal developmentDoxakis, Epaminondashttps://hdl.handle.net/10023/147792019-03-29T10:41:34Z1999-01-01T00:00:00ZThe aim of this project was to determine the temporal and spatial pattern of expression of GDNF family receptors in the developing embryo, with particular emphasis on expression in the peripheral nervous system, and to investigate how expression of receptor mRNAs is regulated in developing neurons. It was hoped that the data obtained would prove useful in further characterizing the role that the GDNF family of neurotrophic factors play in embryonic development. Semi- quantitative PCR revealed that GFRα-1, GFRα-2, GFRα-4 and ret mRNAs are widely distributed with both complementary and overlapping, though distinct, patterns of expression in the chicken embryo during development. Different populations of PNS neurons display different levels of responsiveness to GDNF and NTN and their sensitivity to these factors change throughout development. Examination of receptor expression by quantitative RT-PCR revealed that neurons that are more sensitive to GDNF express higher levels of GFRα-1 mRNA than GFRα-2 mRNA, and neurons that are more sensitive to NTN express higher levels of GFRα-2 mRNA compared to GFRα-1 mRNA. However, developmental changes in responsiveness of a population of neurons to these factors are not consistently paralleled by changes in the relative levels of GFRα transcripts. Furthermore, all neuronal populations express relatively high levels of ret mRNA. These results indicate the responsiveness of PNS neurons to GDNF and NTN is in part governed by the relative levels of expression of their GPI-linked receptors. To determine how the expression of the GDNF family receptors is regulated, embryonic neurons were cultured under different experimental conditions. I found that GFRα-1, GFRα-2, GFRα-4 and ret mRNAs are not significantly regulated by GDNF and/or NTN. However, depolarizing levels of KC1 cause marked changes in the expression of GFRα mRNAs. The effects of KCl are inhibited by L-type Ca2+ channel antagonists, suggesting that they were mediated by elevation of intracellular free Ca2+. KCl treatment increases the response of neurons to GDNF and decreases their response to NTN. There is no marked effect of depolarization on ret mRNA expression.
1999-01-01T00:00:00ZDoxakis, EpaminondasThe aim of this project was to determine the temporal and spatial pattern of expression of GDNF family receptors in the developing embryo, with particular emphasis on expression in the peripheral nervous system, and to investigate how expression of receptor mRNAs is regulated in developing neurons. It was hoped that the data obtained would prove useful in further characterizing the role that the GDNF family of neurotrophic factors play in embryonic development. Semi- quantitative PCR revealed that GFRα-1, GFRα-2, GFRα-4 and ret mRNAs are widely distributed with both complementary and overlapping, though distinct, patterns of expression in the chicken embryo during development. Different populations of PNS neurons display different levels of responsiveness to GDNF and NTN and their sensitivity to these factors change throughout development. Examination of receptor expression by quantitative RT-PCR revealed that neurons that are more sensitive to GDNF express higher levels of GFRα-1 mRNA than GFRα-2 mRNA, and neurons that are more sensitive to NTN express higher levels of GFRα-2 mRNA compared to GFRα-1 mRNA. However, developmental changes in responsiveness of a population of neurons to these factors are not consistently paralleled by changes in the relative levels of GFRα transcripts. Furthermore, all neuronal populations express relatively high levels of ret mRNA. These results indicate the responsiveness of PNS neurons to GDNF and NTN is in part governed by the relative levels of expression of their GPI-linked receptors. To determine how the expression of the GDNF family receptors is regulated, embryonic neurons were cultured under different experimental conditions. I found that GFRα-1, GFRα-2, GFRα-4 and ret mRNAs are not significantly regulated by GDNF and/or NTN. However, depolarizing levels of KC1 cause marked changes in the expression of GFRα mRNAs. The effects of KCl are inhibited by L-type Ca2+ channel antagonists, suggesting that they were mediated by elevation of intracellular free Ca2+. KCl treatment increases the response of neurons to GDNF and decreases their response to NTN. There is no marked effect of depolarization on ret mRNA expression.Intrinsic and extrinsic factors involved in the axonal growth rate of embryonic neuronsHilton, Mark Christopherhttps://hdl.handle.net/10023/147762019-03-29T10:29:33Z1999-01-01T00:00:00ZThe main aim of this project has been to study the extrinsic and intrinsic factors involved in the axonal growth rate of sensory and sympathetic neurons during the early stages of their development. Using in vitro assays it was shown that Hepatocyte Growth Factor (HGF)/Met signalling significantly enhanced the survival and neurite length of early DRG neurons grown in the presence of NGF. This synergism was specific for NGF but not for the related neurotrophins BDNF or NT-3 (Maina et al., 1997). HGF/Met signalling was also shown to accelerate the differentiation of sympathetic neurons as well as promoting the survival of sympathetic neuroblasts but not postmitotic neurons. HGF was also shown to cooperate with NGF to enhance the axonal growth rate as well as increasing the amount of neurite branching of NGF- dependent sympathetic neurons throughout development (Maina et al., 1998). HGF was also shown to enhance the survival and growth of developing parasympathetic and proprioceptive neurons. The demonstration that HGF only enhanced the survival and growth of proprioceptive TMN neurons when grown in CNTF but not when grown in BDNF which promoted their survival as effectively as CNTF demonstrates that within the same neurons, the effects of HGF on survival and growth are selectively dependent on which other signalling pathways are concurrently activated. The anti-apoptotic protein Bcl-2 has been shown to play a key role in regulating cell survival in the nervous system. Cultured neurons expressing antisense Bcl-2 RNA have an attenuated survival response to neurotrophins, and neurons of postnatal Bcl-2 deficient mice die more rapidly following NGF deprivation in vitro and are present in reduced numbers in vivo. Here I show that Bcl-2 also plays a key role in regulating axonal outgrowth rates in embryonic neurons (Hilton et al., 1997). The effect of Bcl-2 on axonal growth rate was shown not to be a consequence of its well documented role in preventing apoptosis.
1999-01-01T00:00:00ZHilton, Mark ChristopherThe main aim of this project has been to study the extrinsic and intrinsic factors involved in the axonal growth rate of sensory and sympathetic neurons during the early stages of their development. Using in vitro assays it was shown that Hepatocyte Growth Factor (HGF)/Met signalling significantly enhanced the survival and neurite length of early DRG neurons grown in the presence of NGF. This synergism was specific for NGF but not for the related neurotrophins BDNF or NT-3 (Maina et al., 1997). HGF/Met signalling was also shown to accelerate the differentiation of sympathetic neurons as well as promoting the survival of sympathetic neuroblasts but not postmitotic neurons. HGF was also shown to cooperate with NGF to enhance the axonal growth rate as well as increasing the amount of neurite branching of NGF- dependent sympathetic neurons throughout development (Maina et al., 1998). HGF was also shown to enhance the survival and growth of developing parasympathetic and proprioceptive neurons. The demonstration that HGF only enhanced the survival and growth of proprioceptive TMN neurons when grown in CNTF but not when grown in BDNF which promoted their survival as effectively as CNTF demonstrates that within the same neurons, the effects of HGF on survival and growth are selectively dependent on which other signalling pathways are concurrently activated. The anti-apoptotic protein Bcl-2 has been shown to play a key role in regulating cell survival in the nervous system. Cultured neurons expressing antisense Bcl-2 RNA have an attenuated survival response to neurotrophins, and neurons of postnatal Bcl-2 deficient mice die more rapidly following NGF deprivation in vitro and are present in reduced numbers in vivo. Here I show that Bcl-2 also plays a key role in regulating axonal outgrowth rates in embryonic neurons (Hilton et al., 1997). The effect of Bcl-2 on axonal growth rate was shown not to be a consequence of its well documented role in preventing apoptosis.Neurotrophin switching in developing sensory neuronsPiñón, Luzia Giraldez Pereirahttps://hdl.handle.net/10023/147742019-03-29T10:29:35Z1997-01-01T00:00:00ZThe main aim of this project was to define the neurotrophin survival requirements of sensory neurons during the early stages of their development both in vivo and in vitro. The in vitro survival of neural crest-derived but not placode-derived cranial sensory neurons is promoted by several different neurotrophins early in their development. Neural crest-derived neurons subsequently lose responsiveness to all neurotrophins except NGF. Loss of responsiveness of neural crest-derived sensory neurons to BDNF and NT3 is associated with a marked shift in the dose responses of these neurons to higher neurotrophin concentrations. Analysis of the timing of cell death in the trigeminal ganglia of mouse embryos that are homozygous for null mutations in the TrkA, TrkB and TrkC genes which encode high affinity receptors for NGF, BDNF and NT3 respectively, show that there is an early peak of apoptosis in TrkB and TrkC knockouts which is consistent with the early survival response of trigeminal neurons to BDNF and NT3 in vitro. The elevated peak of apoptosis in TrkA knockouts occurs at the same development stages as in wild type embryos which is consistent with the later response of trigeminal neurons to NGF in vitro. Furthermore, there is a high level of expression of TrkC mRNA in early trigeminal neurons which accords with the early survival response of these neurons to NTS. It is also shown that subsets of trigeminal neurons discriminate between neurotrophins at very high concentrations during the period of cell death, indicating that neurotrophin responses can be far more highly specific than previously thought. Taken together, these results show that neurotrophin switching is a physiologically relevant phenomenon in certain populations of developing sensory neurons.
1997-01-01T00:00:00ZPiñón, Luzia Giraldez PereiraThe main aim of this project was to define the neurotrophin survival requirements of sensory neurons during the early stages of their development both in vivo and in vitro. The in vitro survival of neural crest-derived but not placode-derived cranial sensory neurons is promoted by several different neurotrophins early in their development. Neural crest-derived neurons subsequently lose responsiveness to all neurotrophins except NGF. Loss of responsiveness of neural crest-derived sensory neurons to BDNF and NT3 is associated with a marked shift in the dose responses of these neurons to higher neurotrophin concentrations. Analysis of the timing of cell death in the trigeminal ganglia of mouse embryos that are homozygous for null mutations in the TrkA, TrkB and TrkC genes which encode high affinity receptors for NGF, BDNF and NT3 respectively, show that there is an early peak of apoptosis in TrkB and TrkC knockouts which is consistent with the early survival response of trigeminal neurons to BDNF and NT3 in vitro. The elevated peak of apoptosis in TrkA knockouts occurs at the same development stages as in wild type embryos which is consistent with the later response of trigeminal neurons to NGF in vitro. Furthermore, there is a high level of expression of TrkC mRNA in early trigeminal neurons which accords with the early survival response of these neurons to NTS. It is also shown that subsets of trigeminal neurons discriminate between neurotrophins at very high concentrations during the period of cell death, indicating that neurotrophin responses can be far more highly specific than previously thought. Taken together, these results show that neurotrophin switching is a physiologically relevant phenomenon in certain populations of developing sensory neurons.Developmental changes in the trophic factor responses of peripheral nervous system neuronsHorton, Antony R.https://hdl.handle.net/10023/147732019-03-29T10:42:46Z1997-01-01T00:00:00ZThe aim of this project was to determine the neurotrophic factor survival requirements of PNS neurons during development and to clarify the role of certain receptors in mediating responsiveness. Members of the neurotrophin family of neurotrophic factors (NGF, BDNF, NT3 and NT4/5) and neurotrophic cytokines (CNTF, LIF, OSM, IL-6 and CT-1) were studied. The activity of a recently identified neurotrophin, NT4/5, was investigated in vitro. In cultures of mouse neurons, mammalian NT4/5 promoted the survival of the same kinds of neurons as BDNF and was as potent as BDNF, which is consistent with the action of both neurotrophins on the same receptor, TrkB. However, both mammalian NT-4/5 and the Xenopus homologue were less potent than mammalian BDNF on chicken embryo neurons, which is consistent with the lower evolutionary conservation of NT4/5. Interestingly, mammalian NT4/5 exhibited differences in potency on certain populations of chicken neurons that responded equally well to BDNF, and this may reflect differences in TrkB receptors in these different populations of neurons. To clarify the role of the common neurotrophin receptor in modulating the response of neurons to NGF, I then compared the actions of NGF with a mutated NGF protein that binds to TrkA, but does not bind to p75. At subsaturating concentrations, the NGF mutant was less effective than NGF in promoting the survival of embryonic sensory neurons and postnatal sympathetic neurons but was equally effective as NGF in promoting the survival of embryonic sympathetic neurons, indicating that binding of NGF to p75 enhances the sensitivity of NGF-dependent neurons to NGF at certain stages of development. To investigate if neurotrophic cytokines act on developing sensory neurons, I studied their effects in vitro. Whereas trigeminal neurons were responded to cytokines in the late fetal period, nodose neurons were supported by these factors throughout embryonic development. These findings indicate that different populations of PNS neurons display different patterns of responsiveness to neurotrophic cytokines during development.
1997-01-01T00:00:00ZHorton, Antony R.The aim of this project was to determine the neurotrophic factor survival requirements of PNS neurons during development and to clarify the role of certain receptors in mediating responsiveness. Members of the neurotrophin family of neurotrophic factors (NGF, BDNF, NT3 and NT4/5) and neurotrophic cytokines (CNTF, LIF, OSM, IL-6 and CT-1) were studied. The activity of a recently identified neurotrophin, NT4/5, was investigated in vitro. In cultures of mouse neurons, mammalian NT4/5 promoted the survival of the same kinds of neurons as BDNF and was as potent as BDNF, which is consistent with the action of both neurotrophins on the same receptor, TrkB. However, both mammalian NT-4/5 and the Xenopus homologue were less potent than mammalian BDNF on chicken embryo neurons, which is consistent with the lower evolutionary conservation of NT4/5. Interestingly, mammalian NT4/5 exhibited differences in potency on certain populations of chicken neurons that responded equally well to BDNF, and this may reflect differences in TrkB receptors in these different populations of neurons. To clarify the role of the common neurotrophin receptor in modulating the response of neurons to NGF, I then compared the actions of NGF with a mutated NGF protein that binds to TrkA, but does not bind to p75. At subsaturating concentrations, the NGF mutant was less effective than NGF in promoting the survival of embryonic sensory neurons and postnatal sympathetic neurons but was equally effective as NGF in promoting the survival of embryonic sympathetic neurons, indicating that binding of NGF to p75 enhances the sensitivity of NGF-dependent neurons to NGF at certain stages of development. To investigate if neurotrophic cytokines act on developing sensory neurons, I studied their effects in vitro. Whereas trigeminal neurons were responded to cytokines in the late fetal period, nodose neurons were supported by these factors throughout embryonic development. These findings indicate that different populations of PNS neurons display different patterns of responsiveness to neurotrophic cytokines during development.Regulation of the expression of BDNF and its receptors in the developing nervous systemRobinson, Michelle Yvonnehttps://hdl.handle.net/10023/147722019-03-29T10:28:55Z1996-01-01T00:00:00ZBDNF binds to two transmembrane receptors: trkB, which is a tyrosine kinase essential for signalling, and p75, which is a common neurotrophin receptor whose role is contoversial. To determine the relationship between BDNF synthesis, BDNF receptor expression, and neuronal responsiveness, the expression of BDNF, trkB, and p75 mRNAs were studied for different populations of sensory neurons whose axons reach their targets and become dependent on BDNF for survival at different times. BDNF mRNA was expressed in the peripheral and central targets of these neurons prior to the arrival of sensory axons. The onset of BDNF responsiveness was preceded by the expression of first p75 mRNA then trkB mRNA, and neurons that start responding to BDNF early were the first to express trkB mRNA. BDNF upregulated trkB mRNA expression just shortly before the onset of BDNF dependence. BDNF is expressed not only in sensory neuron targets but in some of these neurons themselves. To determine whether BDNF is synthesized in NGF-dependent or BDNF-dependent neurons, BDNF mRNA expression was studied in purified populations of cranial sensory neurons that depend on either NGF or BDNF for survival. During the period of neuronal death, BDNF mRNA expression was highest in NGF-dependent cutaneous sensory neurons, lower in BDNF-dependent cutaneous sensory neurons, and undetectable in BDNF-dependent proprioceptive neurons. In coculture, NGF-dependent neurons promoted the survival of BDNF-dependent neurons by the production and release of BDNF, implying a paracrine role for BDNF during the period of naturally occurring neuronal death. To determine if the level of p75 expression in sensory neurons is related to the particular neurotrophin they require for survival, p75 mRNA levels were measured in purified populations of cranial sensory neurons. No clear relationship between the level of p75 mRNA expression and neuron type was observed. Studies of the regulation of p75 mRNA expression in sympathetic neuroblasts revealed that retinoic acid increased and membrane depolarization using KCl decreased the levels of p75 mRNA.
1996-01-01T00:00:00ZRobinson, Michelle YvonneBDNF binds to two transmembrane receptors: trkB, which is a tyrosine kinase essential for signalling, and p75, which is a common neurotrophin receptor whose role is contoversial. To determine the relationship between BDNF synthesis, BDNF receptor expression, and neuronal responsiveness, the expression of BDNF, trkB, and p75 mRNAs were studied for different populations of sensory neurons whose axons reach their targets and become dependent on BDNF for survival at different times. BDNF mRNA was expressed in the peripheral and central targets of these neurons prior to the arrival of sensory axons. The onset of BDNF responsiveness was preceded by the expression of first p75 mRNA then trkB mRNA, and neurons that start responding to BDNF early were the first to express trkB mRNA. BDNF upregulated trkB mRNA expression just shortly before the onset of BDNF dependence. BDNF is expressed not only in sensory neuron targets but in some of these neurons themselves. To determine whether BDNF is synthesized in NGF-dependent or BDNF-dependent neurons, BDNF mRNA expression was studied in purified populations of cranial sensory neurons that depend on either NGF or BDNF for survival. During the period of neuronal death, BDNF mRNA expression was highest in NGF-dependent cutaneous sensory neurons, lower in BDNF-dependent cutaneous sensory neurons, and undetectable in BDNF-dependent proprioceptive neurons. In coculture, NGF-dependent neurons promoted the survival of BDNF-dependent neurons by the production and release of BDNF, implying a paracrine role for BDNF during the period of naturally occurring neuronal death. To determine if the level of p75 expression in sensory neurons is related to the particular neurotrophin they require for survival, p75 mRNA levels were measured in purified populations of cranial sensory neurons. No clear relationship between the level of p75 mRNA expression and neuron type was observed. Studies of the regulation of p75 mRNA expression in sympathetic neuroblasts revealed that retinoic acid increased and membrane depolarization using KCl decreased the levels of p75 mRNA.Laser spectroscopic studies of actin-myosin interaction in activated frog muscleEastwood, Julian Charleshttps://hdl.handle.net/10023/147692019-03-29T10:41:42Z1987-01-01T00:00:00ZFrog sartorius muscles were illuminated with laser light (λ = 457.9 - 632.8nm), stimulated electrically and stretched at the plateau of an isometric tetanus. An electro-optic system was used to rapidly (~7kHz) switch the electric vector of the incident beam through π/2 radians (between ϕ = 0° and 90°, relative to the muscle long axis) and 'simultaneous' recordings of transmitted light intensity (Ia) were made at orthogonal beam orientations during single contractions, using a sample-hold device. Stretch causes Ia to fall: this is represented either as a decrease of transparency or an increase of turbidity (τ). The amplitudes of the optical transients vary in direct proportion to the tension increment generated by stretch (which is related to the extent of actin-myosin filament overlap) and are highly anisotropic with respect to both λ and ϕ. At any given λ the amplitude for ϕ = 0° > ϕ - 90°. Both 0° and 90° signals vary inversely with λ: the wavelength exponent for the former is -2.39 and for the latter, -3.87. An attempt is made to analyse the changes in conservative dichroism (= Δτ0° - Δτ90°) using a model in which the scattering elements are forced to undergo a change of angular orientation (Δγ). The size of the scattering particles is estimated to be ~17nm (long axis) and to occupy ~0.038 of the fibre volume. It is postulated that the dichroic signal is due to a change in cross-bridge head (= S-1 HMM) orientation. The linear dimension of the actin-myosin interactive surface is estimated (from Δγ) to be >4.8nm. The results are interpreted in terms of a multi-step force generating cycle, based on the Huxley-Simmons model in which each head progresses through as many as 5 to 7 discrete positions during its working stroke, each separated from its neighbour by a potential difference energy of ~0.46x10-20J.
1987-01-01T00:00:00ZEastwood, Julian CharlesFrog sartorius muscles were illuminated with laser light (λ = 457.9 - 632.8nm), stimulated electrically and stretched at the plateau of an isometric tetanus. An electro-optic system was used to rapidly (~7kHz) switch the electric vector of the incident beam through π/2 radians (between ϕ = 0° and 90°, relative to the muscle long axis) and 'simultaneous' recordings of transmitted light intensity (Ia) were made at orthogonal beam orientations during single contractions, using a sample-hold device. Stretch causes Ia to fall: this is represented either as a decrease of transparency or an increase of turbidity (τ). The amplitudes of the optical transients vary in direct proportion to the tension increment generated by stretch (which is related to the extent of actin-myosin filament overlap) and are highly anisotropic with respect to both λ and ϕ. At any given λ the amplitude for ϕ = 0° > ϕ - 90°. Both 0° and 90° signals vary inversely with λ: the wavelength exponent for the former is -2.39 and for the latter, -3.87. An attempt is made to analyse the changes in conservative dichroism (= Δτ0° - Δτ90°) using a model in which the scattering elements are forced to undergo a change of angular orientation (Δγ). The size of the scattering particles is estimated to be ~17nm (long axis) and to occupy ~0.038 of the fibre volume. It is postulated that the dichroic signal is due to a change in cross-bridge head (= S-1 HMM) orientation. The linear dimension of the actin-myosin interactive surface is estimated (from Δγ) to be >4.8nm. The results are interpreted in terms of a multi-step force generating cycle, based on the Huxley-Simmons model in which each head progresses through as many as 5 to 7 discrete positions during its working stroke, each separated from its neighbour by a potential difference energy of ~0.46x10-20J.The effects of dopamine and dopaminergic agents on an identified cockroach motoneuroneDavis, Julian P. L.https://hdl.handle.net/10023/147672019-03-29T10:39:29Z1990-01-01T00:00:00ZDopamine is one of a number of neurotransmitter candidates found in the insect CNS, It has been localised in a number of neurones, and others have been shown to respond to the application of dopamine. This study investigates the response of the common inhibitory motoneurone D3 to dopamine, and its ionic basis. The response to dopamine is distinguished pharmacologically from responses to noradrenaline, octopamlne and acetylcholine, all neurotransmitter candidates within the insect CNS, and it is concluded that a receptor specific for dopamine is present on this cell. Finally, this putative dopamine receptor is characterised pharmacologically, and its position relative to the extant classification schemes for mammalian receptors, and its similarity or otherwise to other invertebrate dopamine receptors is discussed.
1990-01-01T00:00:00ZDavis, Julian P. L.Dopamine is one of a number of neurotransmitter candidates found in the insect CNS, It has been localised in a number of neurones, and others have been shown to respond to the application of dopamine. This study investigates the response of the common inhibitory motoneurone D3 to dopamine, and its ionic basis. The response to dopamine is distinguished pharmacologically from responses to noradrenaline, octopamlne and acetylcholine, all neurotransmitter candidates within the insect CNS, and it is concluded that a receptor specific for dopamine is present on this cell. Finally, this putative dopamine receptor is characterised pharmacologically, and its position relative to the extant classification schemes for mammalian receptors, and its similarity or otherwise to other invertebrate dopamine receptors is discussed.Properties of an identified dopamine containing neurone from the snail Helisoma trivolvisHarris, Stuart Julianhttps://hdl.handle.net/10023/147462019-03-29T10:39:45Z1996-01-01T00:00:00Z1. The giant neurone in the left pedal ganglion of Helisoma trivolvis is homologous with the giant dopamine containing neurone of Planorbis corneus. The neurones have a similar morphology, and both react with glyoxylic acid to produce fluorescence indicative of dopamine. The neurone is referred to as the giant dopaminergic neurone (GDN). 2. Conditions for the extension of neurites and the formation of chemical junctions in culture have been determined for the H. trivolvis GDN. 3. Some electrical properties of the GDN were altered when it was maintained in culture. The peak spike amplitude was increased, action potential half width was decreased and the firing pattern changed. 4. In culture, the GDN formed chemical connections only with neurones with which it was known to form chemical connections in-situ. The chemical connections were of the same sign as those observed in-situ. They formed rapidly within 18 hours, but were not stable and were lost within 48 hours to be replaced by electrical connections. 5. Chemical junctions formed in both directions between the GDN and the large serotonergic neurone (LSN). The direction in which junctions formed could be influenced by plating each neurone out at different times. 6. Local application of dopamine to the axon or axon hillock, but not the soma of the isolated GDN, evoked a fast strongly desensitising, depolarising response. 7. Intracellular perfusion of the GTP analogue GDP-?-S abolished the hyperpolarising effect of dopamine but left the fast depolarising effect intact. 8. Dopamine evoked small unitary outward currents, in outside-out patches prepared from the axon and axon hillock of the isolated GDN. 9. The results suggest that the fast depolarising response to dopamine of the GDN and its follower neurones is directly ligand gated. This is the first evidence of an ion channel that is directly gated by dopamine.
1996-01-01T00:00:00ZHarris, Stuart Julian1. The giant neurone in the left pedal ganglion of Helisoma trivolvis is homologous with the giant dopamine containing neurone of Planorbis corneus. The neurones have a similar morphology, and both react with glyoxylic acid to produce fluorescence indicative of dopamine. The neurone is referred to as the giant dopaminergic neurone (GDN). 2. Conditions for the extension of neurites and the formation of chemical junctions in culture have been determined for the H. trivolvis GDN. 3. Some electrical properties of the GDN were altered when it was maintained in culture. The peak spike amplitude was increased, action potential half width was decreased and the firing pattern changed. 4. In culture, the GDN formed chemical connections only with neurones with which it was known to form chemical connections in-situ. The chemical connections were of the same sign as those observed in-situ. They formed rapidly within 18 hours, but were not stable and were lost within 48 hours to be replaced by electrical connections. 5. Chemical junctions formed in both directions between the GDN and the large serotonergic neurone (LSN). The direction in which junctions formed could be influenced by plating each neurone out at different times. 6. Local application of dopamine to the axon or axon hillock, but not the soma of the isolated GDN, evoked a fast strongly desensitising, depolarising response. 7. Intracellular perfusion of the GTP analogue GDP-?-S abolished the hyperpolarising effect of dopamine but left the fast depolarising effect intact. 8. Dopamine evoked small unitary outward currents, in outside-out patches prepared from the axon and axon hillock of the isolated GDN. 9. The results suggest that the fast depolarising response to dopamine of the GDN and its follower neurones is directly ligand gated. This is the first evidence of an ion channel that is directly gated by dopamine.Mechanisms underlying two different FMRF amide induced ionic currents in identified neurones of 'Helix aspersa'Falconer, Stuart W. P.https://hdl.handle.net/10023/147452019-03-29T10:39:50Z1992-01-01T00:00:00ZApplication of the molluscan neuropeptide FMRFamide to two identified neurones in the cerebral ganglia of Helix aspersa induces quite different effects. In the Cl neurone, FMRFamide produces a slow hyperpolarizing current carried by K+ while with the C2 neurone it causes a fast depolarizing current carried by Na+. Possible mechanisms underlying the slow K+ response were examined and the fast response was characterized using voltage clamp techniques. Some patch clamp experiments were also used for the slow response. The slow response was shown to depend on a G protein, which was sensitive to inhibition by pertussis toxin, indicating that it was mediated by a Gi or Go protein. Second messengers such as cyclic AMP, cyclic GMP, IP3, arachidonic acid and Ca2+ along with the activation of protein kinase C were all found not to be directly involved in producing the FMRFamide response. These negative results with the second messengers gave rise to the view that the FMRFamide receptors and K+ ion channels may be linked directly through the activation of G proteins. 5-HT, probably acting through raised cyclic AMP levels, reduced the amplitude of the FMRFamide response which suggests that the channel opened by FMRFamide may be an "S" K+ type channel. Activation of protein kinase C by phorbol ester also reduced the FMRFamide response. A role for protein phosphorylation was indicated by the use of okadaic acid which inhibits protein phosphatases 1 and 2A. Its application reduced the amplitude of the FMRFamide response which suggested that increased protein phosphorylation levels lead to smaller responses. Thus, it seemed possible that protein phosphorylation levels controlled by cyclic AMP, protein kinase C activation and protein phosphatases 1 and 2A might modulate the activity of the receptor/ G protein/ ion channel complex. Alternatively, FMRFamide may operate through the activation of protein phosphatase(s) which reduce protein phosphorylation levels. Patch clamp studies in cell attached mode on the Cl neurone failed to reveal any channel openings induced by FMRFamide. This result also tends to rule out the direct involvement of a second messenger. The fast depolarizing FMRFamide response of the C2 neurone, which is due to the opening of a ligand gated channel, was found to be carried by Na+ and not Ca2+. Amiloride produced a reversible block of the current. Tetrodotoxin and lignocaine had no effect on the FMRFamide response while raised cyclic AMP levels potentiated the response. In the presence of okadaic acid and increased levels of cyclic AMP, the FMRFamide response is potentiated. This potentiation was not maintained in the presence of okadaic acid alone. The raised protein phosphorylation levels therefore did not cause potentiation, which suggested that cyclic AMP may have a direct effect on the receptor/channel complex.
1992-01-01T00:00:00ZFalconer, Stuart W. P.Application of the molluscan neuropeptide FMRFamide to two identified neurones in the cerebral ganglia of Helix aspersa induces quite different effects. In the Cl neurone, FMRFamide produces a slow hyperpolarizing current carried by K+ while with the C2 neurone it causes a fast depolarizing current carried by Na+. Possible mechanisms underlying the slow K+ response were examined and the fast response was characterized using voltage clamp techniques. Some patch clamp experiments were also used for the slow response. The slow response was shown to depend on a G protein, which was sensitive to inhibition by pertussis toxin, indicating that it was mediated by a Gi or Go protein. Second messengers such as cyclic AMP, cyclic GMP, IP3, arachidonic acid and Ca2+ along with the activation of protein kinase C were all found not to be directly involved in producing the FMRFamide response. These negative results with the second messengers gave rise to the view that the FMRFamide receptors and K+ ion channels may be linked directly through the activation of G proteins. 5-HT, probably acting through raised cyclic AMP levels, reduced the amplitude of the FMRFamide response which suggests that the channel opened by FMRFamide may be an "S" K+ type channel. Activation of protein kinase C by phorbol ester also reduced the FMRFamide response. A role for protein phosphorylation was indicated by the use of okadaic acid which inhibits protein phosphatases 1 and 2A. Its application reduced the amplitude of the FMRFamide response which suggested that increased protein phosphorylation levels lead to smaller responses. Thus, it seemed possible that protein phosphorylation levels controlled by cyclic AMP, protein kinase C activation and protein phosphatases 1 and 2A might modulate the activity of the receptor/ G protein/ ion channel complex. Alternatively, FMRFamide may operate through the activation of protein phosphatase(s) which reduce protein phosphorylation levels. Patch clamp studies in cell attached mode on the Cl neurone failed to reveal any channel openings induced by FMRFamide. This result also tends to rule out the direct involvement of a second messenger. The fast depolarizing FMRFamide response of the C2 neurone, which is due to the opening of a ligand gated channel, was found to be carried by Na+ and not Ca2+. Amiloride produced a reversible block of the current. Tetrodotoxin and lignocaine had no effect on the FMRFamide response while raised cyclic AMP levels potentiated the response. In the presence of okadaic acid and increased levels of cyclic AMP, the FMRFamide response is potentiated. This potentiation was not maintained in the presence of okadaic acid alone. The raised protein phosphorylation levels therefore did not cause potentiation, which suggested that cyclic AMP may have a direct effect on the receptor/channel complex.Actions of neuropeptides on mouse spinal neurones in cultureMcCarthy, Peter Williamhttps://hdl.handle.net/10023/147442020-11-24T11:27:59Z1985-01-01T00:00:00Z1] Spinal cords from mouse embryos were successfully prepared and maintained in primary dissociated cell culture, for periods in excess of 10 weeks. 2] Stable intracellular recordings were made from spinal neurones which had been sustained in these cultures. 3] Experiments were made on these spinal neurones using various amino acids and peptides. Solutions of these compounds were discretely applied by pressure ejection. 4] L-Glutamate, GABA and glycine evoked responses which appeared the same as those documented previously. 5] Ethylene-diamine did not evoke a response from the spinal neurones tested. 6] Only a small percentage of the spinal neurones responded to met5- and leu5 - enkephalin, FMRFamide, neurotensin and glycyl L-glutamine. Supplementing the cultures with tissue from other organs did not increase the percentage of spinal neurones which were capable of responding to peptide. 7] Met5 -enkephalin and leu5 -enkephalin each evoked responses from the spinal neurones. 8] The enkephalin-evoked depolarizations accompanied by an increased input resistance were apparently voltage dependent. These responses were abolished at potentials more negative than -90mV and did not invert under normal recording conditions. 9] The enkephalin-evoked depolarizations associated with a decreased input resistance had extrapolated inversion potentials of -20mV. No voltage dependence was seen. 10] Enkephalins also evoked responses which had an inversion potential close to the resting membrane potential. These were accompanied by a decreased input resistance and were not desensitized by prolonged application of peptide. 11] None of these responses showed obvious desensitization with prolonged application, however, they were all attenuated by naloxone. 12] Met5 -enkephalin was apparently more potent than leu5 -enkephalin on a small number of neurones. Furthermore, met5 -enkephalin application, during the weaker response from those neurones to leu5 -enkephalin, evoked a attenuated response. 13] FMRFamide evoked two responses from these spinal neurones. These responses were seen separately and mixed. In the latter case they were referred to as biphasic responses. 14] The depolarizing response to FMRFamide was accompanied by an increase in input resistance. Potassium had some involvement in these responses. 15] The FMRFamide responses which were accompanied by a decreased input resistance showed a great variety of inversion potentials between neurones. These actions were dependent upon sodium and chloride ions. 16] Enkephalin and FMRFamide, when applied separately to the same spinal neurone, did not evoke the same response. 17] Responses evoked by neurotensin were hyperpolarizations associated with a decreased input resistance. These responses were dependent upon potassium and independent of chloride ions. 18] Glycyl L-glutamine evoked two types of hyperpolarizing response from the spinal neurones. These could appear separately or combined. 19] The faster responses to glycyl L-glutamine were apparently dependent on potassium ions. 20] The slower responses to glycyl L-glutamine were apparently insensitive to changes in extracellular potassium or chloride. However, these responses were sensitive to intracellular injection of chloride ions. 21] At concentrations of peptide which evoked a response from other spinal neurones, none of the peptides produced any measurable modulation of amino acid-evoked responses.
1985-01-01T00:00:00ZMcCarthy, Peter William1] Spinal cords from mouse embryos were successfully prepared and maintained in primary dissociated cell culture, for periods in excess of 10 weeks. 2] Stable intracellular recordings were made from spinal neurones which had been sustained in these cultures. 3] Experiments were made on these spinal neurones using various amino acids and peptides. Solutions of these compounds were discretely applied by pressure ejection. 4] L-Glutamate, GABA and glycine evoked responses which appeared the same as those documented previously. 5] Ethylene-diamine did not evoke a response from the spinal neurones tested. 6] Only a small percentage of the spinal neurones responded to met5- and leu5 - enkephalin, FMRFamide, neurotensin and glycyl L-glutamine. Supplementing the cultures with tissue from other organs did not increase the percentage of spinal neurones which were capable of responding to peptide. 7] Met5 -enkephalin and leu5 -enkephalin each evoked responses from the spinal neurones. 8] The enkephalin-evoked depolarizations accompanied by an increased input resistance were apparently voltage dependent. These responses were abolished at potentials more negative than -90mV and did not invert under normal recording conditions. 9] The enkephalin-evoked depolarizations associated with a decreased input resistance had extrapolated inversion potentials of -20mV. No voltage dependence was seen. 10] Enkephalins also evoked responses which had an inversion potential close to the resting membrane potential. These were accompanied by a decreased input resistance and were not desensitized by prolonged application of peptide. 11] None of these responses showed obvious desensitization with prolonged application, however, they were all attenuated by naloxone. 12] Met5 -enkephalin was apparently more potent than leu5 -enkephalin on a small number of neurones. Furthermore, met5 -enkephalin application, during the weaker response from those neurones to leu5 -enkephalin, evoked a attenuated response. 13] FMRFamide evoked two responses from these spinal neurones. These responses were seen separately and mixed. In the latter case they were referred to as biphasic responses. 14] The depolarizing response to FMRFamide was accompanied by an increase in input resistance. Potassium had some involvement in these responses. 15] The FMRFamide responses which were accompanied by a decreased input resistance showed a great variety of inversion potentials between neurones. These actions were dependent upon sodium and chloride ions. 16] Enkephalin and FMRFamide, when applied separately to the same spinal neurone, did not evoke the same response. 17] Responses evoked by neurotensin were hyperpolarizations associated with a decreased input resistance. These responses were dependent upon potassium and independent of chloride ions. 18] Glycyl L-glutamine evoked two types of hyperpolarizing response from the spinal neurones. These could appear separately or combined. 19] The faster responses to glycyl L-glutamine were apparently dependent on potassium ions. 20] The slower responses to glycyl L-glutamine were apparently insensitive to changes in extracellular potassium or chloride. However, these responses were sensitive to intracellular injection of chloride ions. 21] At concentrations of peptide which evoked a response from other spinal neurones, none of the peptides produced any measurable modulation of amino acid-evoked responses.Some aspects of the neurophysiology of the common whelk, Buccinum undatum L.Bailey, Donald F.https://hdl.handle.net/10023/147432019-03-29T10:29:45Z1964-01-01T00:00:00Z1964-01-01T00:00:00ZBailey, Donald F.Studies on the effects of drugs on the properties of synaptosomesBalfour, David John Kennedyhttps://hdl.handle.net/10023/147422019-03-29T10:41:56Z1971-01-01T00:00:00Z1. Synaptosomes have been isolated from guiuea-pig cerebral cortex and their appearance and enzymic and respiratory properties found to be similar to those reported for synaptosomes by other workers. 2. The effects of the convulsants, strychnine and pentamethylene tetrazol, and the anticonvulsants, phenobarbitone and acetazolamide, on some of the properties of synaptosomes have been examined. 3. The resting respiratory rate of synaptosomes was found to be insensitive to the convulsants and anticonvulaants and to a variety of other compounds which affect excitable neuronal membranes *in vivo*. The possible significance of these results has been discussed. 4. The incorporation of 14C in to synaptosomes from (U-14C)-glucose was inhibited by pentamethylene tetrazol and enhanced by phenobarbitone. 5. The uptake of xylose, which did not seem to occur by means of a simple diffusion process, was unaffected by phenobarbitone and pentamethylene tetrazol. 6. The concentration of xylose in the synaptosomes, once xylose uptake was complete, was unaffected by 2, 4-dinitroplienol. 7. The release of osmotically active constituents from synaptosomes suspended in warm sucrose was very much reduced by phenobsrbitone at relatively low concentrations and by acetaszolamide at concentrations which were substantially greater than those found 'in vivo'. 8. 45 per cent of the Na+ and 27 per cent of the K+ was lost to the medium if freshly prepared synaptosomes were incubated in sucrose at 25°C for 30 minutes, Phenobarbitone prevented the loss of these ions during the incubation. 9. Phenobarbitone had no effect on the release of xylose from synaptosomes which were suspended in warm sucrose.
1971-01-01T00:00:00ZBalfour, David John Kennedy1. Synaptosomes have been isolated from guiuea-pig cerebral cortex and their appearance and enzymic and respiratory properties found to be similar to those reported for synaptosomes by other workers. 2. The effects of the convulsants, strychnine and pentamethylene tetrazol, and the anticonvulsants, phenobarbitone and acetazolamide, on some of the properties of synaptosomes have been examined. 3. The resting respiratory rate of synaptosomes was found to be insensitive to the convulsants and anticonvulaants and to a variety of other compounds which affect excitable neuronal membranes *in vivo*. The possible significance of these results has been discussed. 4. The incorporation of 14C in to synaptosomes from (U-14C)-glucose was inhibited by pentamethylene tetrazol and enhanced by phenobarbitone. 5. The uptake of xylose, which did not seem to occur by means of a simple diffusion process, was unaffected by phenobarbitone and pentamethylene tetrazol. 6. The concentration of xylose in the synaptosomes, once xylose uptake was complete, was unaffected by 2, 4-dinitroplienol. 7. The release of osmotically active constituents from synaptosomes suspended in warm sucrose was very much reduced by phenobsrbitone at relatively low concentrations and by acetaszolamide at concentrations which were substantially greater than those found 'in vivo'. 8. 45 per cent of the Na+ and 27 per cent of the K+ was lost to the medium if freshly prepared synaptosomes were incubated in sucrose at 25°C for 30 minutes, Phenobarbitone prevented the loss of these ions during the incubation. 9. Phenobarbitone had no effect on the release of xylose from synaptosomes which were suspended in warm sucrose.The role of the basolateral amygdala in cocaine self-administration and cocaine-seeking behaviourWhitelaw, Rachel B.https://hdl.handle.net/10023/147412019-03-29T10:38:55Z1998-01-01T00:00:00ZThe experiments reported in this thesis have investigated the role of the basolateral amygdala (BLA) in the process by which conditioned stimuli (CS) acquire motivational salience and, as conditioned reinforcers, direct cocaine-seeking behaviour in the rat. Excitotoxic lesions of the BLA did not interfere with the reinforcing effects of cocaine in rats. Intra-peritoneal injections of cocaine produced similar locomotor responses in both lesioned and control animals and both groups also produced equivalent dose-response functions during a within- session dose-response test. Similarly, lesioned and control animals acquired cocaine self-administration under both continuous and progressive-ratio schedules of reinforcement. However, BLA-lesioned animals were (i) severely impaired in the acquisition of second-order schedules of cocaine self-administration; (ii) more sensitive than control animals to reductions in drug dose under a progressive-ratio schedule of cocaine self-administration and (iii) less sensitive than control animals to the omission of a drug-related CS, under a fixed-interval schedule of selfadministration. In vivo microdialysis showed that lesions of the BLA were associated with an impaired glutamatergic response to intra-nucleus accumbens infusions of cocaine, but that the dopaminergic response of lesioned and control animals of were identical. These findings suggest that drug-seeking behaviour in rats with lesions of the BLA is influenced more by the primary reinforcer and concomitantly less by secondary, conditioned reinforcers. This would indicate that the BLA is significantly involved in the development of cue-elicited drug-seeking behaviour and, by inference, this structure may also play an important role in the development of problem drug-use in humans.
1998-01-01T00:00:00ZWhitelaw, Rachel B.The experiments reported in this thesis have investigated the role of the basolateral amygdala (BLA) in the process by which conditioned stimuli (CS) acquire motivational salience and, as conditioned reinforcers, direct cocaine-seeking behaviour in the rat. Excitotoxic lesions of the BLA did not interfere with the reinforcing effects of cocaine in rats. Intra-peritoneal injections of cocaine produced similar locomotor responses in both lesioned and control animals and both groups also produced equivalent dose-response functions during a within- session dose-response test. Similarly, lesioned and control animals acquired cocaine self-administration under both continuous and progressive-ratio schedules of reinforcement. However, BLA-lesioned animals were (i) severely impaired in the acquisition of second-order schedules of cocaine self-administration; (ii) more sensitive than control animals to reductions in drug dose under a progressive-ratio schedule of cocaine self-administration and (iii) less sensitive than control animals to the omission of a drug-related CS, under a fixed-interval schedule of selfadministration. In vivo microdialysis showed that lesions of the BLA were associated with an impaired glutamatergic response to intra-nucleus accumbens infusions of cocaine, but that the dopaminergic response of lesioned and control animals of were identical. These findings suggest that drug-seeking behaviour in rats with lesions of the BLA is influenced more by the primary reinforcer and concomitantly less by secondary, conditioned reinforcers. This would indicate that the BLA is significantly involved in the development of cue-elicited drug-seeking behaviour and, by inference, this structure may also play an important role in the development of problem drug-use in humans.Exploratory accross-stimulus studies in event-related potentialsYoung, Malcolm Philiphttps://hdl.handle.net/10023/147402019-03-29T10:40:36Z1990-01-01T00:00:00ZEvent-related potentials (ERPs) were evoked by visually presented words in a number of experimental paradigms. The question of which linguistic factors, if any, underlie differences between visual word ERPs was addressed. These studies identified 3 factors as predictors of ERF variance. Studies of ERPs in language processing tasks are selectively reviewed, and methodological problems associated with ERPs evoked by non-identical stimuli are discussed. The importance of an understanding of the linguistic factors which underlie ERP differences is outlined, and a methodology for approaching this issue is set out. The statistical procedure necessary to address the question is developed and described in Chapter Two. This procedure was a quantitative modelling strategy, based on multidimensional scaling and PROCRUSTES rotation. Five quantitative modelling studies were undertaken. These experiments involved two experimental tasks, a passive exposure task in which the subjects attended but did not respond to the stimuli (experiment 1) and a category membership decision task (experiments 2 to 5). Words drawn from two semantic categories were employed. ERPs were evoked by individual members of the category of colour names (experiments 1 to 3) and by members of the category of furniture terms (experiments 4 and 5). The results of these studies suggested that word length was the important factor in the early part of the post-stimulus epoch and that this factor was followed by semantic similarity. A late positivity was present in the decision task ERPs whose modulation was related to word frequency. These results were validated by two conventionally analysed experiments which examined the relation between word length and repetition and that between word frequency and repetition. It is concluded that three factors underlie ERP variance in the experimental paradigms employed. These factors are word length (physical extent was not dissociated from length in letters), word frequency and semantic similarity. These results may inform issues of experimental control in future studies of ERPs and language processing, may suggest some reassessment of existing studies in which control was not effected for these factors and may have provided a method of wider utility in cognitive neuroscience. The results suggest that systematic information can be derived about the linguistic characteristics of individual words from single word ERPs.
1990-01-01T00:00:00ZYoung, Malcolm PhilipEvent-related potentials (ERPs) were evoked by visually presented words in a number of experimental paradigms. The question of which linguistic factors, if any, underlie differences between visual word ERPs was addressed. These studies identified 3 factors as predictors of ERF variance. Studies of ERPs in language processing tasks are selectively reviewed, and methodological problems associated with ERPs evoked by non-identical stimuli are discussed. The importance of an understanding of the linguistic factors which underlie ERP differences is outlined, and a methodology for approaching this issue is set out. The statistical procedure necessary to address the question is developed and described in Chapter Two. This procedure was a quantitative modelling strategy, based on multidimensional scaling and PROCRUSTES rotation. Five quantitative modelling studies were undertaken. These experiments involved two experimental tasks, a passive exposure task in which the subjects attended but did not respond to the stimuli (experiment 1) and a category membership decision task (experiments 2 to 5). Words drawn from two semantic categories were employed. ERPs were evoked by individual members of the category of colour names (experiments 1 to 3) and by members of the category of furniture terms (experiments 4 and 5). The results of these studies suggested that word length was the important factor in the early part of the post-stimulus epoch and that this factor was followed by semantic similarity. A late positivity was present in the decision task ERPs whose modulation was related to word frequency. These results were validated by two conventionally analysed experiments which examined the relation between word length and repetition and that between word frequency and repetition. It is concluded that three factors underlie ERP variance in the experimental paradigms employed. These factors are word length (physical extent was not dissociated from length in letters), word frequency and semantic similarity. These results may inform issues of experimental control in future studies of ERPs and language processing, may suggest some reassessment of existing studies in which control was not effected for these factors and may have provided a method of wider utility in cognitive neuroscience. The results suggest that systematic information can be derived about the linguistic characteristics of individual words from single word ERPs.Interactions between the pedunculopontine tegmental nucleus, mesencephalic dopamine neurones and the striatumInglis, Wendy Louisehttps://hdl.handle.net/10023/147382019-03-29T10:32:42Z1994-01-01T00:00:00ZThe role of the pedunculopontine tegmental nucleus (PPTg) in the control of behaviour is investigated in the experiments in this thesis through (1) the interactions between its ascending cholinergic neurones and dopamine neurones in the substantia nigra and ventral tegmental area; and (2) the involvement of its non- cholinergic neurones in modifying outflow from the striatum. (1) Stimulation of rat SN by carbachol produces an increase in behaviours for which the animal has a low current baseline rate and a positive predisposition (Winn et al, 1983). This was investigated further by examining first, whether consumption of a palatable food could also be stimulated by intranigral injections of nicotine or acetylcholinesterase inhibitors. Increased feeding was obtained dose- dependently from satiated rats following injection of carbachol, nicotine or neostigmine, but not eserine, into the substantia nigra. Second, it was demonstrated that spontaneous consumption by satiated rats could not be blocked by muscarinic or nicotinic antagonists, although eating stimulated by intranigral neostigmine were attenuated by these antagonists. These data suggest that the cholinergic innervation of substantia nigra is phasic in nature. Third, it was ascertained whether the excitation realised by neostigmine injections into the substantia nigra or ventral tegmental area could support the acquisition of responding for conditioned reinforcement. Injections of neostigmine into the substantia nigra, but not ventral tegmental area, assisted acquisition of the lever-press response and this resuh is discussed with respect to the significance of habit and expectation on responding. (2) The PPTg has been viewed as an important striatal output station for several years, primarily due to its proposed function as part of the mesencephalic locomotor region but more recently for its role in incentive behaviours. The validity of these perspectives was tested first by investigating the effects of ibotenate PPTg lesions on the well-known pattern of events which occur following systemic injections of d-amphetamine and apomorphine. The effects of lesions made in the deep mesencephalic nucleus were also investigated as this structure has also been linked with locomotor functions. Neither spontaneous nor drug-induced locomotion was affected by either lesion placement, but PPTg-lesioned rats exhibited abnormal stereotypies. At 3.0 and 5.0 mg-kg-1 d-amphetamine these included excessive biting behaviour, predominantly directed at their own forepaws, and they were the only group to score 6 (continuous biting) on the Creese-Iversen scale following apomorphine injections. The role of the PPTg in the mediation of reward-related behavior was investigated in the conditioned reinforcement paradigm. Ibotenate-lesioned rats responded as frequently as controls on the CR lever, but their pressing was equal on CR and NCR levers. These data are discussed with respect to a role for the non-cholinergic neurones in the PPTg in the mediation of stimulus-reward associations and a possible role for the cholinergic neurones in the integration of such associations back into basal ganglia and cortical circuitry. It is also suggested that the PPTg may have a role in the selection of appropriate and inhibition of inappropriate behaviours.
1994-01-01T00:00:00ZInglis, Wendy LouiseThe role of the pedunculopontine tegmental nucleus (PPTg) in the control of behaviour is investigated in the experiments in this thesis through (1) the interactions between its ascending cholinergic neurones and dopamine neurones in the substantia nigra and ventral tegmental area; and (2) the involvement of its non- cholinergic neurones in modifying outflow from the striatum. (1) Stimulation of rat SN by carbachol produces an increase in behaviours for which the animal has a low current baseline rate and a positive predisposition (Winn et al, 1983). This was investigated further by examining first, whether consumption of a palatable food could also be stimulated by intranigral injections of nicotine or acetylcholinesterase inhibitors. Increased feeding was obtained dose- dependently from satiated rats following injection of carbachol, nicotine or neostigmine, but not eserine, into the substantia nigra. Second, it was demonstrated that spontaneous consumption by satiated rats could not be blocked by muscarinic or nicotinic antagonists, although eating stimulated by intranigral neostigmine were attenuated by these antagonists. These data suggest that the cholinergic innervation of substantia nigra is phasic in nature. Third, it was ascertained whether the excitation realised by neostigmine injections into the substantia nigra or ventral tegmental area could support the acquisition of responding for conditioned reinforcement. Injections of neostigmine into the substantia nigra, but not ventral tegmental area, assisted acquisition of the lever-press response and this resuh is discussed with respect to the significance of habit and expectation on responding. (2) The PPTg has been viewed as an important striatal output station for several years, primarily due to its proposed function as part of the mesencephalic locomotor region but more recently for its role in incentive behaviours. The validity of these perspectives was tested first by investigating the effects of ibotenate PPTg lesions on the well-known pattern of events which occur following systemic injections of d-amphetamine and apomorphine. The effects of lesions made in the deep mesencephalic nucleus were also investigated as this structure has also been linked with locomotor functions. Neither spontaneous nor drug-induced locomotion was affected by either lesion placement, but PPTg-lesioned rats exhibited abnormal stereotypies. At 3.0 and 5.0 mg-kg-1 d-amphetamine these included excessive biting behaviour, predominantly directed at their own forepaws, and they were the only group to score 6 (continuous biting) on the Creese-Iversen scale following apomorphine injections. The role of the PPTg in the mediation of reward-related behavior was investigated in the conditioned reinforcement paradigm. Ibotenate-lesioned rats responded as frequently as controls on the CR lever, but their pressing was equal on CR and NCR levers. These data are discussed with respect to a role for the non-cholinergic neurones in the PPTg in the mediation of stimulus-reward associations and a possible role for the cholinergic neurones in the integration of such associations back into basal ganglia and cortical circuitry. It is also suggested that the PPTg may have a role in the selection of appropriate and inhibition of inappropriate behaviours.Examination of the role of the pedunculopontine tegmental nucleus in the control of behavioural processesKeating, Glenda Louisehttps://hdl.handle.net/10023/147372019-03-29T10:28:28Z1998-01-01T00:00:00ZThe role of the pedunculopontine tegmental nucleus (PPTg) in the control of behavioural processes was investigated in this thesis. This was achieved through examination of: (1) Conditioned place preference formation: PPTg lesioned rats were not impaired in forming an appropriate place preference, regardless of their deprivation state. (2) Reward-related responding: both food deprived and non-deprived lesioned rats displayed disinhibited intake across a gradient of sucrose rewards, the degree of disinhibition increasing as the reward became stronger. This disinhibited responding was disassociated from simple approach behaviour as shown by similar runway completion times across control and lesioned rats. (3) Radial arm maze performance: PPTg lesioned rats were impaired in their ability to retrospectively plan and forage in a random foraging task. This impairment was seen in both acquisition and retention tasks. PPTg lesioned rats were also impaired in the acquisition of a spatial working memory task in which they had to prospectively plan and execute responses. (4) These behavioural tasks are related to striatal output. To complement them anatomical experiments examining altered striatal outflow on neurotransmitter expression in the PPTg were conducted. Neither dopamine receptor blockade nor 6- hydroxydopamine (6-OHDA) lesions of striatal dopamine produced changes in nicotinamide adenine dinucleotide phosphate (NADPH)-diaphorase expression in the PPTg. This work did, however, lay the foundation for future experimentation to address this question. The combination of these findings extends current literature to outline a role for the PPTg in the control of complex behaviours that have been previously associated with sites higher up the neuraxis. This thesis demonstrates that removal of the PPTg results in behaviours that are inappropriate and disinhibited. In conclusion the PPTg is important for both accurate response selection and execution of goal directed behaviours, elements crucial for effective behavioural responding.
1998-01-01T00:00:00ZKeating, Glenda LouiseThe role of the pedunculopontine tegmental nucleus (PPTg) in the control of behavioural processes was investigated in this thesis. This was achieved through examination of: (1) Conditioned place preference formation: PPTg lesioned rats were not impaired in forming an appropriate place preference, regardless of their deprivation state. (2) Reward-related responding: both food deprived and non-deprived lesioned rats displayed disinhibited intake across a gradient of sucrose rewards, the degree of disinhibition increasing as the reward became stronger. This disinhibited responding was disassociated from simple approach behaviour as shown by similar runway completion times across control and lesioned rats. (3) Radial arm maze performance: PPTg lesioned rats were impaired in their ability to retrospectively plan and forage in a random foraging task. This impairment was seen in both acquisition and retention tasks. PPTg lesioned rats were also impaired in the acquisition of a spatial working memory task in which they had to prospectively plan and execute responses. (4) These behavioural tasks are related to striatal output. To complement them anatomical experiments examining altered striatal outflow on neurotransmitter expression in the PPTg were conducted. Neither dopamine receptor blockade nor 6- hydroxydopamine (6-OHDA) lesions of striatal dopamine produced changes in nicotinamide adenine dinucleotide phosphate (NADPH)-diaphorase expression in the PPTg. This work did, however, lay the foundation for future experimentation to address this question. The combination of these findings extends current literature to outline a role for the PPTg in the control of complex behaviours that have been previously associated with sites higher up the neuraxis. This thesis demonstrates that removal of the PPTg results in behaviours that are inappropriate and disinhibited. In conclusion the PPTg is important for both accurate response selection and execution of goal directed behaviours, elements crucial for effective behavioural responding.Helisoma neurones in the construction of circuits in vitroMacfarlane, Scott R.https://hdl.handle.net/10023/147352019-03-29T10:39:01Z1995-01-01T00:00:00ZThe work described here used the invertebrate neurone culture methodology to study neurones from the pond snail Helisoma trivolvis. Isolated neurones were used to form small circuits, the input/output properties of which were investigated electrophysiologically. The activity of the circuits were then described with respect to the intrinsic properties of the individual neurones and the synaptic connections between them. Neurite extension from isolated neurones could be altered by making changes to the culture medium in which the neurones were maintained. Electrophysiological recordings made from pairs of neurones in culture revealed electrical, chemical and mixed connections. The purely chemical connections and the chemical component of the mixed connections were inhibitory in nature. Connections were not detected between all of the pairs. In many cases no connections at all were recorded between neurone pairs. Connections could also be obtained between neurone pairs if the two neurones were placed in culture on consecutive days. Connections were still obtained when three neurones were placed together to form circuits, although such connections were found to be weak. The three neurone circuits formed were unable to produce any rhythmic output, due both to the weak synaptic connections present and intrinsic membrane properties of the neurones. This study shows that invertebrate neurone culture is a viable way to study small circuits of neurones.
1995-01-01T00:00:00ZMacfarlane, Scott R.The work described here used the invertebrate neurone culture methodology to study neurones from the pond snail Helisoma trivolvis. Isolated neurones were used to form small circuits, the input/output properties of which were investigated electrophysiologically. The activity of the circuits were then described with respect to the intrinsic properties of the individual neurones and the synaptic connections between them. Neurite extension from isolated neurones could be altered by making changes to the culture medium in which the neurones were maintained. Electrophysiological recordings made from pairs of neurones in culture revealed electrical, chemical and mixed connections. The purely chemical connections and the chemical component of the mixed connections were inhibitory in nature. Connections were not detected between all of the pairs. In many cases no connections at all were recorded between neurone pairs. Connections could also be obtained between neurone pairs if the two neurones were placed in culture on consecutive days. Connections were still obtained when three neurones were placed together to form circuits, although such connections were found to be weak. The three neurone circuits formed were unable to produce any rhythmic output, due both to the weak synaptic connections present and intrinsic membrane properties of the neurones. This study shows that invertebrate neurone culture is a viable way to study small circuits of neurones.Cholinergic stimulation of the substantia negraParker, Graham Charleshttps://hdl.handle.net/10023/147332019-03-29T10:41:05Z1993-01-01T00:00:00ZConvergent lines of research suggest there exists an excitatory cholinergic input to the substantia nigra from the pedunculopontine tegmental nucleus and possibly the laterodorsal tegmental nucleus. Previous work has suggested that microinjection of cholinergic agonists into substantia nigra elicits behaviours performed with a high frequency but with a low current rate (Winn 1991). Experiments carried out during my PhD have demonstrated that: Microinjection of cholinergic agonists to anterior substantia nigra (SN) elicited increased consumption of palatable food such as spaghetti but not rat maintenance diet in pre-satiated rats. Stimulation of behaviour was achieved using direct agonists for either muscarinic or nicotinic cholinergic receptors (carbachol and nicotine respectively). Stimulation of behaviour was also achieved using the indirect cholinergic agonist neostigmine which blocks the de-activation of endogenous acetylcholine by AChE. Increased feeding elicited by cholinergic stimulation of the anterior SN was abolished by a selective lesion of ascending dopamine (DA) neurones which significantly depleted caudate DA levels but left accumbens DA levels unaltered. A behaviourally potent dose of carbachol caused a significant increase in the response to different doses of nicotine suggesting an additive effect of muscarinic and nicotinic stimulation at the doses used. Administration of cholinergic agonists to the VTA or SN caused indistinguishable effects on responding for conditioned reinforcement. Cholinergic stimulation caused increased responding for a conditioned reinforcer and also reinstated responding at the primary reward source. The functional significance of the cholinergic innervation of the DA- containing neurones of the substantia nigra is discussed with reference to its relationship to the neighbouring ventral tegmental area, and their innervation of the caudate-putamen and the nucleus accumbens. Cholinergic neurones in the PPTg and LDTN appear to exert a tonic control over the activity of midbrain DA-containing neurones. It is suggested that cholinergic control of midbrain DA-containing neurones facilitates the processing of information in the striatum and hence influence the selection of an appropriate behavioural response to a given situation.
1993-01-01T00:00:00ZParker, Graham CharlesConvergent lines of research suggest there exists an excitatory cholinergic input to the substantia nigra from the pedunculopontine tegmental nucleus and possibly the laterodorsal tegmental nucleus. Previous work has suggested that microinjection of cholinergic agonists into substantia nigra elicits behaviours performed with a high frequency but with a low current rate (Winn 1991). Experiments carried out during my PhD have demonstrated that: Microinjection of cholinergic agonists to anterior substantia nigra (SN) elicited increased consumption of palatable food such as spaghetti but not rat maintenance diet in pre-satiated rats. Stimulation of behaviour was achieved using direct agonists for either muscarinic or nicotinic cholinergic receptors (carbachol and nicotine respectively). Stimulation of behaviour was also achieved using the indirect cholinergic agonist neostigmine which blocks the de-activation of endogenous acetylcholine by AChE. Increased feeding elicited by cholinergic stimulation of the anterior SN was abolished by a selective lesion of ascending dopamine (DA) neurones which significantly depleted caudate DA levels but left accumbens DA levels unaltered. A behaviourally potent dose of carbachol caused a significant increase in the response to different doses of nicotine suggesting an additive effect of muscarinic and nicotinic stimulation at the doses used. Administration of cholinergic agonists to the VTA or SN caused indistinguishable effects on responding for conditioned reinforcement. Cholinergic stimulation caused increased responding for a conditioned reinforcer and also reinstated responding at the primary reward source. The functional significance of the cholinergic innervation of the DA- containing neurones of the substantia nigra is discussed with reference to its relationship to the neighbouring ventral tegmental area, and their innervation of the caudate-putamen and the nucleus accumbens. Cholinergic neurones in the PPTg and LDTN appear to exert a tonic control over the activity of midbrain DA-containing neurones. It is suggested that cholinergic control of midbrain DA-containing neurones facilitates the processing of information in the striatum and hence influence the selection of an appropriate behavioural response to a given situation.Dissociation of P300 brain potentials evoked by rare visual stimuliMatthews, Davidhttps://hdl.handle.net/10023/147322019-03-29T10:41:23Z1995-01-01T00:00:00ZThe P300 event related potential (ERP) has consistently been dissociated into separate components on the basis of scalp amplitude distribution within the auditory modality (for instance Squires et al. 1975). A parietally maximum P300 deflection being evoked in response to target stimuli in comparison with a more frontally maximum P300 deflection evoked in response to rare nontarget stimuli. Results obtained within experiment 1 and 6 demonstrated such a dissociation employing auditory stimuli within a three stimulus oddball paradigm. It did not prove possible to obtain such a dissociation of P300 deflections on the basis of scalp amplitude distribution within the visual modality. Across a number of experimental manipulations both target and rare nontarget stimuli evoked P300 deflections with similar amplitude distributions (centro-parietal maximum along the midline). Experiment 5 demonstrated that frequent stimuli similarly evoked a centro-parietal maximum amplitude distribution. It was demonstrated that both stimulus probability (Experiment 4) and the physical characteristics of the stimuli (Experiment 5) affected the mean amplitude of the evoked P300 deflection. However, the scalp amplitude distribution of the evoked deflections remained constant. Within Experiment 6 it was demonstrated that within both auditory and visual modalities P300 deflections, evoked in response to both target and rare nontarget stimuli, demonstrated an equipotential amplitude distribution within an elderly group of subjects. In addition across both modalities amplitude evoked in response to rare nontarget stimuli demonstrated an asymmetric distribution across lateral chains of electrodes. Amplitude evoked along the right chain was significantly reduced in comparison to that evoked along the left chain. It would appear that the same, or a similar combination of, underlying neural generators are responsible for the activity that may be recorded at the scalp as the P300 deflection within the visual modality.
1995-01-01T00:00:00ZMatthews, DavidThe P300 event related potential (ERP) has consistently been dissociated into separate components on the basis of scalp amplitude distribution within the auditory modality (for instance Squires et al. 1975). A parietally maximum P300 deflection being evoked in response to target stimuli in comparison with a more frontally maximum P300 deflection evoked in response to rare nontarget stimuli. Results obtained within experiment 1 and 6 demonstrated such a dissociation employing auditory stimuli within a three stimulus oddball paradigm. It did not prove possible to obtain such a dissociation of P300 deflections on the basis of scalp amplitude distribution within the visual modality. Across a number of experimental manipulations both target and rare nontarget stimuli evoked P300 deflections with similar amplitude distributions (centro-parietal maximum along the midline). Experiment 5 demonstrated that frequent stimuli similarly evoked a centro-parietal maximum amplitude distribution. It was demonstrated that both stimulus probability (Experiment 4) and the physical characteristics of the stimuli (Experiment 5) affected the mean amplitude of the evoked P300 deflection. However, the scalp amplitude distribution of the evoked deflections remained constant. Within Experiment 6 it was demonstrated that within both auditory and visual modalities P300 deflections, evoked in response to both target and rare nontarget stimuli, demonstrated an equipotential amplitude distribution within an elderly group of subjects. In addition across both modalities amplitude evoked in response to rare nontarget stimuli demonstrated an asymmetric distribution across lateral chains of electrodes. Amplitude evoked along the right chain was significantly reduced in comparison to that evoked along the left chain. It would appear that the same, or a similar combination of, underlying neural generators are responsible for the activity that may be recorded at the scalp as the P300 deflection within the visual modality.Properties and distribution of an active cerebellar factorMitchell, James Fabianhttps://hdl.handle.net/10023/147312019-03-29T10:33:45Z1957-01-01T00:00:00Z1. A technique for the introduction of substances into the cerebellum of the decerebrate rabbit was developed and the effects of drugs and brain extracts on the electrical activity of the cerebellum were studied using this method. 2. Extracts of cerebellar tissue were found to increase the electrical activity of the cerebellum and this action could not be attributed to Ach, histamine or to any other identified pharmacologically-active constituent of the nervous system, nor could it be attributed to a vascular action. The activity was not detected in similar concentrations in extracts of cerebral hemispheres or upper brain-stem. 3. The physical and chemical properties of the cerebellar excitatory substance were studied and attempts to purify it from crude brain extracts were made. 4. The enzymic destruction of the active factor was demonstrated and this destruction was shown to be inhibited by small amounts of strychnine. The active substance was found to be released from the cerebellum under various conditions of stimulation. 5. The active substance had no apparent effect on any of the common pharmecological preparations, not did it affect transmission at the neuromuscular junction and superior cervical ganglion. 6. The cerebellar factor was found to affect spinal reflexes and the electrical activity of the cerebral cortex. 7. Nervous tissue from six animal species was found to contain the active substance, but it was not detected in similar concentrations in tissues outside the nervous system. Its distribution in various regions of the nervous system of the dog was shown to bear an approximately inverse relationship to the distribution of choline acetylase activity and acetylcholine. 8. It has been suggested that the cerebellar factor has some claims to be considered as a non-colinergic transmitter of nerve impulses and experiments which might eventually confirm this hypothesis have been considered.
1957-01-01T00:00:00ZMitchell, James Fabian1. A technique for the introduction of substances into the cerebellum of the decerebrate rabbit was developed and the effects of drugs and brain extracts on the electrical activity of the cerebellum were studied using this method. 2. Extracts of cerebellar tissue were found to increase the electrical activity of the cerebellum and this action could not be attributed to Ach, histamine or to any other identified pharmacologically-active constituent of the nervous system, nor could it be attributed to a vascular action. The activity was not detected in similar concentrations in extracts of cerebral hemispheres or upper brain-stem. 3. The physical and chemical properties of the cerebellar excitatory substance were studied and attempts to purify it from crude brain extracts were made. 4. The enzymic destruction of the active factor was demonstrated and this destruction was shown to be inhibited by small amounts of strychnine. The active substance was found to be released from the cerebellum under various conditions of stimulation. 5. The active substance had no apparent effect on any of the common pharmecological preparations, not did it affect transmission at the neuromuscular junction and superior cervical ganglion. 6. The cerebellar factor was found to affect spinal reflexes and the electrical activity of the cerebral cortex. 7. Nervous tissue from six animal species was found to contain the active substance, but it was not detected in similar concentrations in tissues outside the nervous system. Its distribution in various regions of the nervous system of the dog was shown to bear an approximately inverse relationship to the distribution of choline acetylase activity and acetylcholine. 8. It has been suggested that the cerebellar factor has some claims to be considered as a non-colinergic transmitter of nerve impulses and experiments which might eventually confirm this hypothesis have been considered.Hemisphere differences and interhemispheric relations with special reference to the functions of the corpus callosumReynolds, Don McQuoidhttps://hdl.handle.net/10023/147302019-03-29T10:36:07Z1975-01-01T00:00:00ZThis thesis contains reports of behavioural investigations carried out on an acallosal girl and her brain-damaged sister. These patients were compared on tasks involving tactile, auditory, and visual perception with a group of control Subjects matched for sex, I.Q. and age, as well as with normal Subjects of the same sex and age. The general aim of the experiments was (a) to investigate and compare the functions of the cerebral hemispheres and (b) to study interhemispheric relationships. Using normal Subjects as well as the acallosal patient special attention was directed towards furthering our understanding of the functions of the corpus callosum. Our results were compared with previous findings in an effort to resolve conflicting findings in the agenesis literature and to explain differences between the previously reported acallosal and surgical-bisected patients' behaviour. The acallosal was found to perform less efficiently than control Subjects on some bimanual and unimanual motor coordination tasks. This finding is consistent with earlier reports on agenesis Subjects. Some evidence was found to indicate that acallosals do not efficiently transfer learning of a tactile formboard task from one hand to the other The acallosal patient did not show an anomia of the left hand as do surgical-bisected patients. There is, however, an inefficiency in tactile cross-localization of light touch stimuli. Dichotic listening experiments used verbal stimuli to test the hypothesis that the acallosal girl would demonstrate equipotentiality of language processes in both hemispheres. Tonal patterns were similar presented dichotically. The acallosal Subject exhibited a greater right-ear advantage than the controls on the recall of digits. Studies of reaction time to a simple visual stimulus replicated findings of greater pathway differences for acallosals than for normals. Another visual perception study supported the finding that acallosals do not show interocular transfer of movement aftereffects. Tachistoscopic recognition tasks of alphabetical and facial stimuli were used on the acallosal, her sister, and normal controls. A developmental study of normals was also carried out. Thirteen year old normals and adults were found to have a left-hemisphere superiority for letters and right-hemisphere for faces. The seven and eight year olds did not show significant lateralization of either faces or letters. The acallosal showed a left visual field superiority for letters, a finding opposite to that for normals. These findings suggest that processes involved in recognition of letters and faces develop with increasing age in childhood. The acallosal Subject appears to have bilateral representation of language processes across sensory modalities in opposite hemispheres, presumably the result of compensatory development arising from lack of a corpus callosum.
1975-01-01T00:00:00ZReynolds, Don McQuoidThis thesis contains reports of behavioural investigations carried out on an acallosal girl and her brain-damaged sister. These patients were compared on tasks involving tactile, auditory, and visual perception with a group of control Subjects matched for sex, I.Q. and age, as well as with normal Subjects of the same sex and age. The general aim of the experiments was (a) to investigate and compare the functions of the cerebral hemispheres and (b) to study interhemispheric relationships. Using normal Subjects as well as the acallosal patient special attention was directed towards furthering our understanding of the functions of the corpus callosum. Our results were compared with previous findings in an effort to resolve conflicting findings in the agenesis literature and to explain differences between the previously reported acallosal and surgical-bisected patients' behaviour. The acallosal was found to perform less efficiently than control Subjects on some bimanual and unimanual motor coordination tasks. This finding is consistent with earlier reports on agenesis Subjects. Some evidence was found to indicate that acallosals do not efficiently transfer learning of a tactile formboard task from one hand to the other The acallosal patient did not show an anomia of the left hand as do surgical-bisected patients. There is, however, an inefficiency in tactile cross-localization of light touch stimuli. Dichotic listening experiments used verbal stimuli to test the hypothesis that the acallosal girl would demonstrate equipotentiality of language processes in both hemispheres. Tonal patterns were similar presented dichotically. The acallosal Subject exhibited a greater right-ear advantage than the controls on the recall of digits. Studies of reaction time to a simple visual stimulus replicated findings of greater pathway differences for acallosals than for normals. Another visual perception study supported the finding that acallosals do not show interocular transfer of movement aftereffects. Tachistoscopic recognition tasks of alphabetical and facial stimuli were used on the acallosal, her sister, and normal controls. A developmental study of normals was also carried out. Thirteen year old normals and adults were found to have a left-hemisphere superiority for letters and right-hemisphere for faces. The seven and eight year olds did not show significant lateralization of either faces or letters. The acallosal showed a left visual field superiority for letters, a finding opposite to that for normals. These findings suggest that processes involved in recognition of letters and faces develop with increasing age in childhood. The acallosal Subject appears to have bilateral representation of language processes across sensory modalities in opposite hemispheres, presumably the result of compensatory development arising from lack of a corpus callosum.On the action of noradrenaline microinjected into the paraventricular nucleus of rat hypothalamusClark, Andrew J. M.https://hdl.handle.net/10023/147042019-03-29T10:43:14Z1990-01-01T00:00:00ZThe microinjection of noradrenaline (NA) into the hypothalamic paraventricular nucleus (PVN) of the rat results in feeding. This response was shown; contrary to previous reports; to be mediated through both a-1 and a-2 NA receptors. Selective blockade of these two receptor sub-types, in conjunction with re-uptake blockade was used to examine the individual contributions of each receptor type to the whole response. It is suggested that the previously reported a-2 receptor specificity of the response to microinjected NA is a result of the location of these receptors. The post-synaptic a-1 receptor being located close to the pre-synaptic re-uptake mechanism, whilst the post-synaptic a-2 receptor is located outside the synapse and thus away from the re-uptake mechanism. The re-uptake mechanism acts to create a concentration difference of microinjected NA between the two receptor sub-types, resulting in a higher concentration and thus a preferential action at a-2 receptors. The involvement of the paraventricular NA system in stress induced eating was examined using a tail pinch procedure. Microinjection of NA antagonists into PVN prior to the onset of the pinch had no effect on the duration or latency of the eating response, thus there was no evidence for the involvement of this system in tail pinch elicited feeding. Further to the suggestion that the NA a-2 receptor is extra-synaptic whilst a-1 is intrasynaptic, the actions of NA were examined at a second site. NA microinjected into the ventral striatum elicited a vigorous locomotor response, although the origins of this showed a clear priming effect. However, this response was unaffected by prior microinjection of NA a-antagonists, preventing an analysis of receptor involvement comparable with that performed in PVN.
1990-01-01T00:00:00ZClark, Andrew J. M.The microinjection of noradrenaline (NA) into the hypothalamic paraventricular nucleus (PVN) of the rat results in feeding. This response was shown; contrary to previous reports; to be mediated through both a-1 and a-2 NA receptors. Selective blockade of these two receptor sub-types, in conjunction with re-uptake blockade was used to examine the individual contributions of each receptor type to the whole response. It is suggested that the previously reported a-2 receptor specificity of the response to microinjected NA is a result of the location of these receptors. The post-synaptic a-1 receptor being located close to the pre-synaptic re-uptake mechanism, whilst the post-synaptic a-2 receptor is located outside the synapse and thus away from the re-uptake mechanism. The re-uptake mechanism acts to create a concentration difference of microinjected NA between the two receptor sub-types, resulting in a higher concentration and thus a preferential action at a-2 receptors. The involvement of the paraventricular NA system in stress induced eating was examined using a tail pinch procedure. Microinjection of NA antagonists into PVN prior to the onset of the pinch had no effect on the duration or latency of the eating response, thus there was no evidence for the involvement of this system in tail pinch elicited feeding. Further to the suggestion that the NA a-2 receptor is extra-synaptic whilst a-1 is intrasynaptic, the actions of NA were examined at a second site. NA microinjected into the ventral striatum elicited a vigorous locomotor response, although the origins of this showed a clear priming effect. However, this response was unaffected by prior microinjection of NA a-antagonists, preventing an analysis of receptor involvement comparable with that performed in PVN.Examinations of the nature of the deficits induced by n-methyl-D-aspartic acid lesions of the rat lateral hypothalamusClark, Judithhttps://hdl.handle.net/10023/147032019-03-29T10:30:00Z1990-01-01T00:00:00ZThe lateral hypothalamic syndrome of aphagia, adipsia akinesia and sensorimotor impairments induced by electrolytic lesions of the lateral hypothalamus (LH) has been suggested to be due to the destruction of two components of a single system controlling feeding and drinking behaviour. While the "motor" component has been attributed to disruption of dopaminergic fibres, it has been suggested that destruction of intrinsic LH neurones induces a "motivational" deficit. The nature of this motivational deficit was investigated using the excitotoxin N-methyl-d~aspartic acid (NMDA) to lesion cell bodies and leave fibres of passage intact. Such lesions induced temporary reductions in body weight, food and water intake and residual deficits in response to some physiological challenges. Most animals recovered food and water intake and body weight gain after a short period of time. It was shown that LH lesioned rats were able to perceive and respond to the palatability of food/fluid; they responded physiologically to intracellular dehydration caused by hypertonic saline injections, although they did not respond behaviourally; they responded as controls to a battery of long-term, "positive" physiological challenges, but not to short-term, "negative" ones; and they displayed increased rate of development of schedule-induced polydipsia and tail pinch-induced eating, demonstrating that they had no motor impairments and that they did not have an "activational" deficit. These results indicate that the LH cannot be regarded as a feeding or drinking "centre" and that the motivational deficit following lesions of the LH is of a very complex nature. The implications of these data for the function of the LH are discussed in relation to electrophysiological and anatomical studies.
1990-01-01T00:00:00ZClark, JudithThe lateral hypothalamic syndrome of aphagia, adipsia akinesia and sensorimotor impairments induced by electrolytic lesions of the lateral hypothalamus (LH) has been suggested to be due to the destruction of two components of a single system controlling feeding and drinking behaviour. While the "motor" component has been attributed to disruption of dopaminergic fibres, it has been suggested that destruction of intrinsic LH neurones induces a "motivational" deficit. The nature of this motivational deficit was investigated using the excitotoxin N-methyl-d~aspartic acid (NMDA) to lesion cell bodies and leave fibres of passage intact. Such lesions induced temporary reductions in body weight, food and water intake and residual deficits in response to some physiological challenges. Most animals recovered food and water intake and body weight gain after a short period of time. It was shown that LH lesioned rats were able to perceive and respond to the palatability of food/fluid; they responded physiologically to intracellular dehydration caused by hypertonic saline injections, although they did not respond behaviourally; they responded as controls to a battery of long-term, "positive" physiological challenges, but not to short-term, "negative" ones; and they displayed increased rate of development of schedule-induced polydipsia and tail pinch-induced eating, demonstrating that they had no motor impairments and that they did not have an "activational" deficit. These results indicate that the LH cannot be regarded as a feeding or drinking "centre" and that the motivational deficit following lesions of the LH is of a very complex nature. The implications of these data for the function of the LH are discussed in relation to electrophysiological and anatomical studies.The effect of pedunculopontine tegmental nucleus and lateral hypothalamic excitotoxic lesions on motivational strength as measured by the progressive ratio paradigmRobertson, Alison Helenhttps://hdl.handle.net/10023/147022019-03-29T10:33:56Z1995-01-01T00:00:00ZMotivated behaviours are associated with the nucleus accumbens (NAS). For example, microinjection of J-amphetamine into the NAS results in increased motivated behaviours, and 6-hydroxydopamine lesions attenuate responding for a rewarding stimulus. Two efferent targets of the NAS are the pedunculopontine tegmental nucleus (PPTg) and lateral hypothalamus (LH). Excitotoxic lesions of the PPTg result in deficits in certain incentive-driven behaviours such as conditioned reinforcement. The LH, on the other hand, is involved in more subtle behaviours. LH excitotoxic lesions result in an apparent inability to suppress inappropriate behaviours with regard to food and water intake regulation. LH-lesioned rats do not respond to certain physiological challenges. Thus, both structures are apparently involved in different aspects of motivated behaviours. Motivational strength has not yet been examined in the PPTg and LH. Progressive Ratio (PR) schedules involve a systematic increase in the number of presses on a conditioned lever following each reinforcer delivery. The stage at which responding ceases is called the breaking point (BP) and it is an indicator of motivational strength. This study involved lesioning the PPTg and LH by excitotoxins and testing them on a PR5 schedule. Ibotenate PPTg lesioned rats produced a clear deficit in responding indicated by significantly lower BPs than quinolinate or sham lesioned rats, indicating the possibility that PPTg neurones mediated motivational strength. Ibotenate lesioned rats pressed the non-contingent lever and the panel significantly more often than the other groups. It was hypothesised that these rats were unable to dissociate between the two levers or the panel, and the reward. NMDA lesions of the LH had no effect on motivational strength. They did, however, continually fail to respond appropriately to hypertonic saline. Thus, it seems that by their connections to the NAS, the PPTg and the LH are implicated in motivated behaviours, with only the PPTg being involved in the expression of motivational strength.
1995-01-01T00:00:00ZRobertson, Alison HelenMotivated behaviours are associated with the nucleus accumbens (NAS). For example, microinjection of J-amphetamine into the NAS results in increased motivated behaviours, and 6-hydroxydopamine lesions attenuate responding for a rewarding stimulus. Two efferent targets of the NAS are the pedunculopontine tegmental nucleus (PPTg) and lateral hypothalamus (LH). Excitotoxic lesions of the PPTg result in deficits in certain incentive-driven behaviours such as conditioned reinforcement. The LH, on the other hand, is involved in more subtle behaviours. LH excitotoxic lesions result in an apparent inability to suppress inappropriate behaviours with regard to food and water intake regulation. LH-lesioned rats do not respond to certain physiological challenges. Thus, both structures are apparently involved in different aspects of motivated behaviours. Motivational strength has not yet been examined in the PPTg and LH. Progressive Ratio (PR) schedules involve a systematic increase in the number of presses on a conditioned lever following each reinforcer delivery. The stage at which responding ceases is called the breaking point (BP) and it is an indicator of motivational strength. This study involved lesioning the PPTg and LH by excitotoxins and testing them on a PR5 schedule. Ibotenate PPTg lesioned rats produced a clear deficit in responding indicated by significantly lower BPs than quinolinate or sham lesioned rats, indicating the possibility that PPTg neurones mediated motivational strength. Ibotenate lesioned rats pressed the non-contingent lever and the panel significantly more often than the other groups. It was hypothesised that these rats were unable to dissociate between the two levers or the panel, and the reward. NMDA lesions of the LH had no effect on motivational strength. They did, however, continually fail to respond appropriately to hypertonic saline. Thus, it seems that by their connections to the NAS, the PPTg and the LH are implicated in motivated behaviours, with only the PPTg being involved in the expression of motivational strength.The function of the lateral hypothalamus with regard to gustatory and reward related processesScollon, Jennifer Margarethttps://hdl.handle.net/10023/147012019-03-29T10:40:23Z1999-01-01T00:00:00ZThe lateral hypothalamus (LH) has been shown to be involved in consummatory behaviour by a number of different experimental techniques including behavioural and electrophysiological methods. Lesion studies indicate that loss of the LH does not significantly alter normal feeding and drinking in the home cage, responding to food and water deprivation or responding to glucose or salt adulteration of the diet. However, when injected with dehydrating, dipsogenic or glucoprivic agents, the so called needle challenges, LH lesioned rats failed to respond as sham lesioned rats. This is despite the fact that the injections described induced the same deficits in homeostasis as food and water deprivation. Both sets of challenges are cued by internal visceral signals but only deprivation has additional environmental cues; animals are aware that their food or water are missing and may even anticipate its return. These different types of cues may be conveyed by different neural pathways and it has been proposed that lesioning the LH removes a pathway whereby visceral signals reach higher neural structures thus accounting for why LH lesioned rats responded appropriately to deprivation but not needle challenges. The present study examined the hypothesis that the LH acts as a gateway for signals concerning internal state to reach structures involved in behavioural planning and action. This was tested by the use of tests known to be susceptible to damage or change in the paraventricular system, responsible for monitoring the internal milieu, and frontostriatal systems responsible for behavioural planning and execution. The functions known to be dependent on the paraventricular system which were tested were conditioned taste aversion, benzodiazepine induced hyperphagia and taste perception but no deficits were found in responding in any of these procedures as a result of lesioning the LH. The functions known to be dependent on frontostriatal systems that were examined with LH lesioned rats were conditioned reinforcement and conditioned place preference but again few deficits were found. Hence, the present study failed to provide evidence to substantiate the hypothesis that the LH stands as an interface between the paraventricular system and frontostriatal systems. However, it did provide evidence that lesioning the LH induces deficits in consummatory responses dependent on the circumstances of the tests.
1999-01-01T00:00:00ZScollon, Jennifer MargaretThe lateral hypothalamus (LH) has been shown to be involved in consummatory behaviour by a number of different experimental techniques including behavioural and electrophysiological methods. Lesion studies indicate that loss of the LH does not significantly alter normal feeding and drinking in the home cage, responding to food and water deprivation or responding to glucose or salt adulteration of the diet. However, when injected with dehydrating, dipsogenic or glucoprivic agents, the so called needle challenges, LH lesioned rats failed to respond as sham lesioned rats. This is despite the fact that the injections described induced the same deficits in homeostasis as food and water deprivation. Both sets of challenges are cued by internal visceral signals but only deprivation has additional environmental cues; animals are aware that their food or water are missing and may even anticipate its return. These different types of cues may be conveyed by different neural pathways and it has been proposed that lesioning the LH removes a pathway whereby visceral signals reach higher neural structures thus accounting for why LH lesioned rats responded appropriately to deprivation but not needle challenges. The present study examined the hypothesis that the LH acts as a gateway for signals concerning internal state to reach structures involved in behavioural planning and action. This was tested by the use of tests known to be susceptible to damage or change in the paraventricular system, responsible for monitoring the internal milieu, and frontostriatal systems responsible for behavioural planning and execution. The functions known to be dependent on the paraventricular system which were tested were conditioned taste aversion, benzodiazepine induced hyperphagia and taste perception but no deficits were found in responding in any of these procedures as a result of lesioning the LH. The functions known to be dependent on frontostriatal systems that were examined with LH lesioned rats were conditioned reinforcement and conditioned place preference but again few deficits were found. Hence, the present study failed to provide evidence to substantiate the hypothesis that the LH stands as an interface between the paraventricular system and frontostriatal systems. However, it did provide evidence that lesioning the LH induces deficits in consummatory responses dependent on the circumstances of the tests.Functional roles of the rat nucleus accumbens: further investigations using microinjection, lesion and electrochemical techniquesWeissenborn, Ruthhttps://hdl.handle.net/10023/146992019-03-29T10:37:22Z1993-01-01T00:00:00ZThe nucleus accumbens (N.Acc.) has been ascribed an important role in mediating locomotor activity and exploration, as well as more complex processes such as reinforcement, reward and the acquisition of displacement activities. Previous investigations of N.Acc. functions have primarily been based on pharmacological manipulations of activity of one of the main neurotransmitters in the N.Acc., dopamine (DA), either through administration of dopaminergic agonists or antagonists or through depletion of DA terminal fields in the N.Acc.. In the present thesis, the functional role of the N.Acc. in a number of different forms of behaviour has been investigated further using specific, fibre-sparing excitotoxic lesions of intrinsic neurones, intra-accumbens injections of DA and in vivo electrochemical measurements of extracellular levels of DA in the N.Acc.. Excitotoxic lesions in the N.Acc. were found to enhance spontaneous locomotion and exploratory behaviours while leaving intact the locomotor- stimulating effects of an indirect dopaminergic agonist, displacement drinking in response to intermittent food-reinforcement (SIP) and amphetamine-induced conditioned place preference (CPP). Thus, fibre-sparing excitotoxic lesions induced a pattern of behaviour distinct from that observed following terminal depletion in the N.Acc.. Further, microinjection and in vivo electrochemical experiments showed no direct relationship between DA activity in the N.Acc. and SIP. Overall, these results are discussed in terms of a theoretical model proposing that the N.Acc. may function as an interface between sensory input and locomotor output and that inhibitory activity in the N.Acc. is needed to channel activity levels appropriately in response to cortical input about the direction of change. It is suggested that rather than viewing it as a unitary structure with specific functions, the N.Acc. should be considered as a heterogeneous part of the striatal complex with a number of distinct subsystems that exist within a complex framework of interactive processes, where changes in one structure can only be understood by taking into account other, related structures.
1993-01-01T00:00:00ZWeissenborn, RuthThe nucleus accumbens (N.Acc.) has been ascribed an important role in mediating locomotor activity and exploration, as well as more complex processes such as reinforcement, reward and the acquisition of displacement activities. Previous investigations of N.Acc. functions have primarily been based on pharmacological manipulations of activity of one of the main neurotransmitters in the N.Acc., dopamine (DA), either through administration of dopaminergic agonists or antagonists or through depletion of DA terminal fields in the N.Acc.. In the present thesis, the functional role of the N.Acc. in a number of different forms of behaviour has been investigated further using specific, fibre-sparing excitotoxic lesions of intrinsic neurones, intra-accumbens injections of DA and in vivo electrochemical measurements of extracellular levels of DA in the N.Acc.. Excitotoxic lesions in the N.Acc. were found to enhance spontaneous locomotion and exploratory behaviours while leaving intact the locomotor- stimulating effects of an indirect dopaminergic agonist, displacement drinking in response to intermittent food-reinforcement (SIP) and amphetamine-induced conditioned place preference (CPP). Thus, fibre-sparing excitotoxic lesions induced a pattern of behaviour distinct from that observed following terminal depletion in the N.Acc.. Further, microinjection and in vivo electrochemical experiments showed no direct relationship between DA activity in the N.Acc. and SIP. Overall, these results are discussed in terms of a theoretical model proposing that the N.Acc. may function as an interface between sensory input and locomotor output and that inhibitory activity in the N.Acc. is needed to channel activity levels appropriately in response to cortical input about the direction of change. It is suggested that rather than viewing it as a unitary structure with specific functions, the N.Acc. should be considered as a heterogeneous part of the striatal complex with a number of distinct subsystems that exist within a complex framework of interactive processes, where changes in one structure can only be understood by taking into account other, related structures.A comparative study of proprioception in the appendages of decapod crustaceansWales, Williamhttps://hdl.handle.net/10023/146452019-03-29T10:31:02Z1971-01-01T00:00:00ZThe number and structure of the chordotonal organs present at all joints between the coxopodite and dactylopodite of the pereiopods and 3rd maxilliped of the Macruran gammarus L are described. As the form of the receptors depends to some degree upon the structure of the joint I have included details of musculature, planes of movement and degrees of freedom at each joint. 2 The 3rd maxilliped has a smaller number of chordotonal organs than the pereiopod, in particular at the merocarpopodite and cargo-propodite joints where only one organ is present. The response of these receptors shows considerable differences from the corresponding receptors in the pereiopoth 3. The structure of the carpo-propodite joint of both limbs is discussed in detail as this joint differs greatly from that of the Brachyura as a third muscle is present. In the pereiopod this joint is capable of rotation about the longitudinal axis but the additional muscle does not appear to produce this rotation. A small number of units in the CP2 receptor respond to rotation. 4. Cuticular sensilla (CAP organs) are described at the mero-carpopodite and carpo-propodite joints in both limbs and at the I-N joint of the pereiopod. 5. Situated in the basi-isehiopodite of the brachyuran Carcinus maenas are two receptors which resemble the chordotonal receptors of the limb articulations but are obviously not part of the series associated with the joints. The receptors have large numbers of bipolar neurones with their dendrites embedded in distinct connective tissue strands which insert onto discrete areas of thin or soft cuticle. The receptor strands do not span a limb joint nor do they attach to a muscle or its tendon. The receptors are referred to as cuticular stress detectors (CSD). CSD.1 lies proximal to the preformed breakage plane and the area of cuticle, onto which the strand inserts, lies close to the attachment of the anterior levator muscle tendon (autotomiser muscle). CSD.2 which lies distal to the breakage plane is located in the ventral ischiopodite. 6. Because of the proximity of the receptors to the preformed breakage plane the external cuticular features of the basi-ischiopodite and the musculature of the coxo-basipodite joint are described in some detail. 7. Comparative details are given for representative species of the Macrura and Anomurn. The nephropsideans, Macrura, are particularly interesting as only the 1st pereiopod, chela, exhibits true autotomy but both receptors are present in all the pereiopods. 8. A third group of bipolar neurones is described in Palinurus vulgaris where they innervate the membrane that seals the aperture after breakage. 9. The dual role of the two levator muscles in both posture control and autotomy and possible functions of the CSDs are discussed at length. 10. The CSD organs respond to pressure applied to the basi-ischiopodite and upon deformation of the discrete areas of soft cuticle onto which the connective tissue strands of the receptors insert. The CSDs exhibit a wide range of unit activity and both receptors have a similar population of unit types. Some units are active only on application or removal of a force applied to the soft cuticle but a large number of phaso-tonic and tonic units respond to a constant pressure applied to the soft cuticle. The majority of the units respond during application of the stimulus (ON units) but a small proportion of the units increase activity on removal, of the stimulus (OFF units). 11. Passively produced tension in the anterior levator (autotomiser) muscle and depressor muscle tendons of the C-B joint is a potent stimulus to both receptors. 12. Both receptors respond to movement of the B-I joint of the Nephropsidean walking leg and to movement of the I-M joint in the pereiopods of other reptantian decapods where the basipodite and ischiopodite have fused. The degree of activity is not directly related -to the joint position or direction of movement.
1971-01-01T00:00:00ZWales, WilliamThe number and structure of the chordotonal organs present at all joints between the coxopodite and dactylopodite of the pereiopods and 3rd maxilliped of the Macruran gammarus L are described. As the form of the receptors depends to some degree upon the structure of the joint I have included details of musculature, planes of movement and degrees of freedom at each joint. 2 The 3rd maxilliped has a smaller number of chordotonal organs than the pereiopod, in particular at the merocarpopodite and cargo-propodite joints where only one organ is present. The response of these receptors shows considerable differences from the corresponding receptors in the pereiopoth 3. The structure of the carpo-propodite joint of both limbs is discussed in detail as this joint differs greatly from that of the Brachyura as a third muscle is present. In the pereiopod this joint is capable of rotation about the longitudinal axis but the additional muscle does not appear to produce this rotation. A small number of units in the CP2 receptor respond to rotation. 4. Cuticular sensilla (CAP organs) are described at the mero-carpopodite and carpo-propodite joints in both limbs and at the I-N joint of the pereiopod. 5. Situated in the basi-isehiopodite of the brachyuran Carcinus maenas are two receptors which resemble the chordotonal receptors of the limb articulations but are obviously not part of the series associated with the joints. The receptors have large numbers of bipolar neurones with their dendrites embedded in distinct connective tissue strands which insert onto discrete areas of thin or soft cuticle. The receptor strands do not span a limb joint nor do they attach to a muscle or its tendon. The receptors are referred to as cuticular stress detectors (CSD). CSD.1 lies proximal to the preformed breakage plane and the area of cuticle, onto which the strand inserts, lies close to the attachment of the anterior levator muscle tendon (autotomiser muscle). CSD.2 which lies distal to the breakage plane is located in the ventral ischiopodite. 6. Because of the proximity of the receptors to the preformed breakage plane the external cuticular features of the basi-ischiopodite and the musculature of the coxo-basipodite joint are described in some detail. 7. Comparative details are given for representative species of the Macrura and Anomurn. The nephropsideans, Macrura, are particularly interesting as only the 1st pereiopod, chela, exhibits true autotomy but both receptors are present in all the pereiopods. 8. A third group of bipolar neurones is described in Palinurus vulgaris where they innervate the membrane that seals the aperture after breakage. 9. The dual role of the two levator muscles in both posture control and autotomy and possible functions of the CSDs are discussed at length. 10. The CSD organs respond to pressure applied to the basi-ischiopodite and upon deformation of the discrete areas of soft cuticle onto which the connective tissue strands of the receptors insert. The CSDs exhibit a wide range of unit activity and both receptors have a similar population of unit types. Some units are active only on application or removal of a force applied to the soft cuticle but a large number of phaso-tonic and tonic units respond to a constant pressure applied to the soft cuticle. The majority of the units respond during application of the stimulus (ON units) but a small proportion of the units increase activity on removal, of the stimulus (OFF units). 11. Passively produced tension in the anterior levator (autotomiser) muscle and depressor muscle tendons of the C-B joint is a potent stimulus to both receptors. 12. Both receptors respond to movement of the B-I joint of the Nephropsidean walking leg and to movement of the I-M joint in the pereiopods of other reptantian decapods where the basipodite and ischiopodite have fused. The degree of activity is not directly related -to the joint position or direction of movement.The dorsal organ and other cuticular structures in larval and adult crustacea : an ultrastructural studyBarrientos Chacon, Yolandahttps://hdl.handle.net/10023/146442019-03-29T10:40:54Z1985-01-01T00:00:00ZSEM observations on the integument of larvae and adult Crustacea Malacostraca indicated differences in setal armature, and in types and frequency of occurrences, which seem to be related with development and sensilla body position. The Amphipoda and Isopoda species studied share a common type of articulated conical spine on the pereiopod segments. In each species, the conical spine has a modified apex which contains sub-apical setules whose tips are provided with ventrally positioned pores or bifid ends. The epimeral and lateral body plates are covered by short articulated pegs with modified hair bases: asymmetrical lip-like extensions, knobs or vesicle-like projections around the hair rim. An unusual type of aesthetasc sensillum is present on the male Cumacea antennal flagellum. A sub-terminal and ventrally positioned pore is present in these aesthetascs whose tips are divided. Companion and guard hair sensilla are absent. A number of cuticular out/ingrown structures are described in both Decapoda and non-Decapoda Crustacea which cannot be related with any previous classification schemes. Crustacea Decapoda larvae (Macrura, Anomura, and Brachyura) have a common trichoid sensillum, whose numbers and distributional patterns are specific for each group. There is a tendency for the trichoid sensilla to be arranged in clusters rather than describing ramdon patterns. Setal organization changes according to developmental instars: larva and post-larval forms have small numbers and types of sensilla, or in some cases they possess the incipient forms of receptors such as the funnel-canal organs known to be present in the pereiopods of adult animals. Juvenile stages exhibit a more complex and sophisticated setal arrangement. Brachyura stage IX-X embryos and hatchling larvae are equipped with well anatomically organized (TEM) sensory hairs. According to their ultrastructural features potential mechano-, and chemoreceptive hairs can be differentiated in the antennules and maxillipeds. In the dorsal median anterior region of the head, Decapoda larvae possess a discrete organ: glandular-sensory complex. Its external topography reveals the presence of one or two central pores (Brachyura, Anomura) or a poreless central area (Macrura) surrounded by four equidistant plate-pits which contain a central pimple or cone. The Macrura plate-pits lack the central cone but develop a row of diminutive pegs. The dorsal organ ultrastructure reveals several components: a gland cell, a ductule cell, two supporting cells and eight sensory cells. The gland cell components allow it to be categorized it as an excretory class 3 gland cell; and the presence of two biciliary sensory cells per plate pit, without scolopale matrix and thick dendritic sheath may identify them as potential chemoreceptors or as bimodal sensitive units. SEM observations indicated that the organ is not present in the integument when juvenile stages are reached. The organ might degenerate or internalize. No definitive function can yet be ascribed to the organ.
1985-01-01T00:00:00ZBarrientos Chacon, YolandaSEM observations on the integument of larvae and adult Crustacea Malacostraca indicated differences in setal armature, and in types and frequency of occurrences, which seem to be related with development and sensilla body position. The Amphipoda and Isopoda species studied share a common type of articulated conical spine on the pereiopod segments. In each species, the conical spine has a modified apex which contains sub-apical setules whose tips are provided with ventrally positioned pores or bifid ends. The epimeral and lateral body plates are covered by short articulated pegs with modified hair bases: asymmetrical lip-like extensions, knobs or vesicle-like projections around the hair rim. An unusual type of aesthetasc sensillum is present on the male Cumacea antennal flagellum. A sub-terminal and ventrally positioned pore is present in these aesthetascs whose tips are divided. Companion and guard hair sensilla are absent. A number of cuticular out/ingrown structures are described in both Decapoda and non-Decapoda Crustacea which cannot be related with any previous classification schemes. Crustacea Decapoda larvae (Macrura, Anomura, and Brachyura) have a common trichoid sensillum, whose numbers and distributional patterns are specific for each group. There is a tendency for the trichoid sensilla to be arranged in clusters rather than describing ramdon patterns. Setal organization changes according to developmental instars: larva and post-larval forms have small numbers and types of sensilla, or in some cases they possess the incipient forms of receptors such as the funnel-canal organs known to be present in the pereiopods of adult animals. Juvenile stages exhibit a more complex and sophisticated setal arrangement. Brachyura stage IX-X embryos and hatchling larvae are equipped with well anatomically organized (TEM) sensory hairs. According to their ultrastructural features potential mechano-, and chemoreceptive hairs can be differentiated in the antennules and maxillipeds. In the dorsal median anterior region of the head, Decapoda larvae possess a discrete organ: glandular-sensory complex. Its external topography reveals the presence of one or two central pores (Brachyura, Anomura) or a poreless central area (Macrura) surrounded by four equidistant plate-pits which contain a central pimple or cone. The Macrura plate-pits lack the central cone but develop a row of diminutive pegs. The dorsal organ ultrastructure reveals several components: a gland cell, a ductule cell, two supporting cells and eight sensory cells. The gland cell components allow it to be categorized it as an excretory class 3 gland cell; and the presence of two biciliary sensory cells per plate pit, without scolopale matrix and thick dendritic sheath may identify them as potential chemoreceptors or as bimodal sensitive units. SEM observations indicated that the organ is not present in the integument when juvenile stages are reached. The organ might degenerate or internalize. No definitive function can yet be ascribed to the organ.Distribution, localisation and functional significance of biologically active monoamines in gastropod molluscsOsborne, Neville N.https://hdl.handle.net/10023/146432019-03-29T10:35:05Z1970-01-01T00:00:00ZAn outline of our present knowledge concerning the occurrence, distribution and possible function of monoamines in the animal kingdom. The purpose of the present study was to investigate the localisation of monoamines in gastropod molluscs so as to gain insight into their functional significance.
1970-01-01T00:00:00ZOsborne, Neville N.An outline of our present knowledge concerning the occurrence, distribution and possible function of monoamines in the animal kingdom. The purpose of the present study was to investigate the localisation of monoamines in gastropod molluscs so as to gain insight into their functional significance.Relationships between the nudibranch 'Adalaria proxima' and its prey, the bryozoan 'Electra pilosa'White, Helen Judithhttps://hdl.handle.net/10023/146422019-03-29T10:28:45Z1993-01-01T00:00:00ZThe cosmopolitan distribution of the anascan bryozoan Electra pilosa manifests itself in the phenotypic plasticity of growth morphology expressed. Longterm field observations of the bryozoan on the essentially ephemeral substrata of the marine macroalgae, Fucus serratiis and Laminaria digitata, at two contrasting sites in Scotland, confirm this. Despite its potential for exponential indeterminate growth, Electra pilosa rarely realises this in the field. Observations show that any pattern of growth is complicated and distorted by the influences of physical (colony abrasion and the dynamics of the substratum) and biotic disturbance (predation by the nudibranch Adalaria proxima). Rather than effect a visible induced defensive response after sustaining injury from mechanical damage or Adalaria proxima, Electra pilosa was demonstrated to maintain a high specific growth rate. It is suggested that this would preclude the settlement of potential competitors and ensure the fitness of this competitively weak, opportunistic species. Adoption of a stellate colony morphology was not concomittant with higher predation susceptibility but rather represented a plastic adaptive response to an ephemeral, dynamic environment. The lack of a metamorphic response to anything other than the presence of live Electra pilosa clearly demonstrated that metamorphosis of Adalaria proxima is by some component of the live, intact bryozoan. This component is neither water- soluble or extractable, and the inductive property is eliminated by homogenisation and freezing. Although hypotheses for this are evaluated, the mechanism of induction and the reasons for this relationship remain unclear. Adaptations to this close nudibranch-bryozoan association are therefore evident in the life history strategies of both species.
1993-01-01T00:00:00ZWhite, Helen JudithThe cosmopolitan distribution of the anascan bryozoan Electra pilosa manifests itself in the phenotypic plasticity of growth morphology expressed. Longterm field observations of the bryozoan on the essentially ephemeral substrata of the marine macroalgae, Fucus serratiis and Laminaria digitata, at two contrasting sites in Scotland, confirm this. Despite its potential for exponential indeterminate growth, Electra pilosa rarely realises this in the field. Observations show that any pattern of growth is complicated and distorted by the influences of physical (colony abrasion and the dynamics of the substratum) and biotic disturbance (predation by the nudibranch Adalaria proxima). Rather than effect a visible induced defensive response after sustaining injury from mechanical damage or Adalaria proxima, Electra pilosa was demonstrated to maintain a high specific growth rate. It is suggested that this would preclude the settlement of potential competitors and ensure the fitness of this competitively weak, opportunistic species. Adoption of a stellate colony morphology was not concomittant with higher predation susceptibility but rather represented a plastic adaptive response to an ephemeral, dynamic environment. The lack of a metamorphic response to anything other than the presence of live Electra pilosa clearly demonstrated that metamorphosis of Adalaria proxima is by some component of the live, intact bryozoan. This component is neither water- soluble or extractable, and the inductive property is eliminated by homogenisation and freezing. Although hypotheses for this are evaluated, the mechanism of induction and the reasons for this relationship remain unclear. Adaptations to this close nudibranch-bryozoan association are therefore evident in the life history strategies of both species.Reproduction, larval growth and metamorphosis of the nudibranch molluscs "Onchidoris bilamellata" (L.) and "Goniodoris nodosa" (Montagu)Lafuente, Isabelhttps://hdl.handle.net/10023/146412019-03-29T10:39:07Z1997-01-01T00:00:00ZThis study investigated the reproduction, larval growth and metamorphosis of the nudibranchs Onchidoris bilamellata (L.) and Goniodoris nodosa (Montagu) under controlled laboratory conditions. In addition, the rare occurrence of spawning events of O. bilamellata taking place in the field outwith the winter and spring reproductive period was studied. Onchidoris bilamellata and Goniodoris nodosa differ in the size and number of eggs produced per spawning event. In the present study O. bilamellata does not exhibit a clear spawning pattern, whereas G. nodosa lays increasingly smaller eggs and larvae as the season progresses. The diameter of the eggs of O. bilamellata is not correlated with the organic content per egg. The data available for G. nodosa were insufficient to analyse this relationship. The rates of larval growth and development are reported for Onchidoris bilamellata and Goniodoris nodosa. These variables do not differ significantly for O. bilamellata between cultures maintained under various light regimes, ranging from continuous darkness to continuous illumination, and are comparable to those of G. nodosa. The shell growth pattern exhibited by larvae of G. nodosa is sigmoid, similar to that of other opisthobranchs. Spawn masses laid during the winter and spring months were collected fresh from the field and compared to spawn masses collected from the field in July and September, outwith the typical spawning period of Onchidoris bilamellata in the British Isles. The shell size of the July and September hatchlings was significantly smaller than that of the winter and spring hatchlings. Furthermore, the larvae hatched from spawn masses laid in September cultured in the laboratory exhibited high mortality rates and the overwhelming majority did not survive through metamorphosis. The significance of the spawning activity of O. bilamellata past the typical spawning period of this species is discussed. The induction of metamorphosis of Onchidoris bilamellata was investigated using seawater containing elevated concentrations of potassium ion, and the results indicate that the optimal concentration inductive of metamorphosis is 19 mM K+ ASW, Metamorphosis experiments were also performed with the natural prey of O. bilamellata, the acorn barnacle Semibalanus balanoides (L.). The results suggest that pediveligers can be induced to metamorphose at a distance from the inductive substrata. Attempts were made to identify the natural inductive cue of Goniodoris nodosa, but this was not successful.
1997-01-01T00:00:00ZLafuente, IsabelThis study investigated the reproduction, larval growth and metamorphosis of the nudibranchs Onchidoris bilamellata (L.) and Goniodoris nodosa (Montagu) under controlled laboratory conditions. In addition, the rare occurrence of spawning events of O. bilamellata taking place in the field outwith the winter and spring reproductive period was studied. Onchidoris bilamellata and Goniodoris nodosa differ in the size and number of eggs produced per spawning event. In the present study O. bilamellata does not exhibit a clear spawning pattern, whereas G. nodosa lays increasingly smaller eggs and larvae as the season progresses. The diameter of the eggs of O. bilamellata is not correlated with the organic content per egg. The data available for G. nodosa were insufficient to analyse this relationship. The rates of larval growth and development are reported for Onchidoris bilamellata and Goniodoris nodosa. These variables do not differ significantly for O. bilamellata between cultures maintained under various light regimes, ranging from continuous darkness to continuous illumination, and are comparable to those of G. nodosa. The shell growth pattern exhibited by larvae of G. nodosa is sigmoid, similar to that of other opisthobranchs. Spawn masses laid during the winter and spring months were collected fresh from the field and compared to spawn masses collected from the field in July and September, outwith the typical spawning period of Onchidoris bilamellata in the British Isles. The shell size of the July and September hatchlings was significantly smaller than that of the winter and spring hatchlings. Furthermore, the larvae hatched from spawn masses laid in September cultured in the laboratory exhibited high mortality rates and the overwhelming majority did not survive through metamorphosis. The significance of the spawning activity of O. bilamellata past the typical spawning period of this species is discussed. The induction of metamorphosis of Onchidoris bilamellata was investigated using seawater containing elevated concentrations of potassium ion, and the results indicate that the optimal concentration inductive of metamorphosis is 19 mM K+ ASW, Metamorphosis experiments were also performed with the natural prey of O. bilamellata, the acorn barnacle Semibalanus balanoides (L.). The results suggest that pediveligers can be induced to metamorphose at a distance from the inductive substrata. Attempts were made to identify the natural inductive cue of Goniodoris nodosa, but this was not successful.Aspects of the life history and physiological ecology of long-lived nudibranch molluscsDavies, Jonathanhttps://hdl.handle.net/10023/146392019-03-29T10:36:43Z1993-01-01T00:00:00ZNudibranchia is the major Order of the gastropod Sub-class Opisthobranchia. Nudibranchs demonstrate a considerable evolutionary departure from the typical shelled gastropod and have achieved wide morphological and ecological diversity. Most species are recorded from nearshore rocky habitats where they are primary macrobenthic predators; most species are stenophagous limited to a single, or a few, prey species. Previous investigations had shown that most nudibranch species have evolved to an annual semelparous life history strategy and adopt a planktotrophic larval development strategy which would appear to be the ancestral conditions. Reviews of published data had drawn attention to some species which demonstrated an evolutionary departure from these ancestral modes and had evolved extended life history strategies combined with more advanced larval development strategies. Archidoris pseudoargus and Cadlina laevis are sponge-grazing dorid nudibranchs, and Tritonia hombergi, which feeds on an alyconarean soft coral, appeared to have extended life cycles. The aim of the present study was to investigate the life history and larval development strategies of these species and, via a study their physiological ecology, attempt to determine the selective forces which may have driven any evolutionary departure away from the ancestral condition. Archidoris pseudoargus was found to have a biennial semelparous life history strategy and a planktotrophic larval development strategy; the planktotrophic lai'vae were found to have some characteristics of the more advanced lecithotrophic laeval form. Cadlina laevis was found to have a perennial iteropalous life history strategy and a direct mode of larval development; this was the first observation of perennial iteroparity in the Order Nudibranchia. Archidoris pseudoargus and Cadlina laevis had markedly seasonal growth patterns with a high growth rate in spring and early summer, followed by a period of reduced growth, or even degrowth in late summer and over the winter. An allometric relationship was determined between body size and feeding rate for A. pseudoargus; the exponent was less than unity. For both species, a significant allometric relationship was determined between body size and respiration rate with an exponent less than unity indicating an increase in metabolic efficiency with body size. Both species displayed an acclimatization of respiration rate with increasing temperature; the acclimatization was more pronounced in C. laevis. Fecundity of both species was shown to have a significant allometric relationship body size with an exponent less than unity. Insufficient numbers of T. hombergi were collected and kept alive in the laboratory to undertake any experiments to generate meaningful data to answer these principal questions for this species. Results of the present study together with data published from previous investigations have been interpreted to suggest that the extension of the life cycle is a consequence of seasonal variations in prey quality and quantity. Rather than being an exception to the rule, it is suggested that extended life cycles could be the ancestral condition and the more common annual/sub annual life cycles would be a more adapted condition. These conclusions are based on the results obtained from laboratory investigations which are discussed in their application to the field situation.
1993-01-01T00:00:00ZDavies, JonathanNudibranchia is the major Order of the gastropod Sub-class Opisthobranchia. Nudibranchs demonstrate a considerable evolutionary departure from the typical shelled gastropod and have achieved wide morphological and ecological diversity. Most species are recorded from nearshore rocky habitats where they are primary macrobenthic predators; most species are stenophagous limited to a single, or a few, prey species. Previous investigations had shown that most nudibranch species have evolved to an annual semelparous life history strategy and adopt a planktotrophic larval development strategy which would appear to be the ancestral conditions. Reviews of published data had drawn attention to some species which demonstrated an evolutionary departure from these ancestral modes and had evolved extended life history strategies combined with more advanced larval development strategies. Archidoris pseudoargus and Cadlina laevis are sponge-grazing dorid nudibranchs, and Tritonia hombergi, which feeds on an alyconarean soft coral, appeared to have extended life cycles. The aim of the present study was to investigate the life history and larval development strategies of these species and, via a study their physiological ecology, attempt to determine the selective forces which may have driven any evolutionary departure away from the ancestral condition. Archidoris pseudoargus was found to have a biennial semelparous life history strategy and a planktotrophic larval development strategy; the planktotrophic lai'vae were found to have some characteristics of the more advanced lecithotrophic laeval form. Cadlina laevis was found to have a perennial iteropalous life history strategy and a direct mode of larval development; this was the first observation of perennial iteroparity in the Order Nudibranchia. Archidoris pseudoargus and Cadlina laevis had markedly seasonal growth patterns with a high growth rate in spring and early summer, followed by a period of reduced growth, or even degrowth in late summer and over the winter. An allometric relationship was determined between body size and feeding rate for A. pseudoargus; the exponent was less than unity. For both species, a significant allometric relationship was determined between body size and respiration rate with an exponent less than unity indicating an increase in metabolic efficiency with body size. Both species displayed an acclimatization of respiration rate with increasing temperature; the acclimatization was more pronounced in C. laevis. Fecundity of both species was shown to have a significant allometric relationship body size with an exponent less than unity. Insufficient numbers of T. hombergi were collected and kept alive in the laboratory to undertake any experiments to generate meaningful data to answer these principal questions for this species. Results of the present study together with data published from previous investigations have been interpreted to suggest that the extension of the life cycle is a consequence of seasonal variations in prey quality and quantity. Rather than being an exception to the rule, it is suggested that extended life cycles could be the ancestral condition and the more common annual/sub annual life cycles would be a more adapted condition. These conclusions are based on the results obtained from laboratory investigations which are discussed in their application to the field situation.Intra-specific variations in the life-history traits of two lacunids (Gastropoda : Prosobranchia)Cashmore, Deborahhttps://hdl.handle.net/10023/146362019-03-29T10:40:26Z1997-01-01T00:00:00ZWithin life-history trait variations for two herbivorous intertidal lacunids, Lacuna pallidula, a direct developer and Lacuna vincta a planktotroph, were compared and related to their ecology and to marine invertebrate life-history theory. Aspects of life-history theory covered included; reproductive investment, the relationship between egg size and egg fecundity, the Egg-Juvenile-Period (EJP), the implications of egg size for offspring status and maternal effects. Similar patterns of growth and reproductive investment were observed for adult females of both species, although absolute rates of growth and reproduction were differently affected by macroalgal diet. Further, differences in response to the favourability of macroalgal diet were observed for the two species, notably in the manner in which eggs were packaged. Variations in both egg size and egg numbers in spawn masses were observed for the two species, among populations within both species and within Lacuna pallidula populations. For Lacuna pallidula, these variations were shown to be mediated by both maternal macroalgal diet and population source. Maternal diet directly affected the size of hatching offspring but not the size of eggs produced. Consequently, egg size was not a good indicator of hatching size for either species. The EJP was determined for both species for a range of temperatures. Greater variations in the EJP and juvenile size were observed in Lacuna vincta. This was attributed to the ability of the larvae of this species to delay metamorphosis and to display positive growth during the delay phase. Both temperature and microalgal diet were shown to affect patterns of growth and development in Lacuna vincta larvae. Sources of naturally occurring cues for inducing settlement and metamorphosis in Lacuna vincta larvae were investigated to understand further the distribution patterns of this species on macroalgal types. Extension of the work investigated the suitability of various artificial cues for inducing metamorphosis and the effects of larval age and nutritional status of larvae upon latency of response to established inducing cues. Overall, L. pallidula displayed greater variation in traits and was more sensitive to environmental change than L. vincta. This finding is discussed in light of the two species larval strategy.
1997-01-01T00:00:00ZCashmore, DeborahWithin life-history trait variations for two herbivorous intertidal lacunids, Lacuna pallidula, a direct developer and Lacuna vincta a planktotroph, were compared and related to their ecology and to marine invertebrate life-history theory. Aspects of life-history theory covered included; reproductive investment, the relationship between egg size and egg fecundity, the Egg-Juvenile-Period (EJP), the implications of egg size for offspring status and maternal effects. Similar patterns of growth and reproductive investment were observed for adult females of both species, although absolute rates of growth and reproduction were differently affected by macroalgal diet. Further, differences in response to the favourability of macroalgal diet were observed for the two species, notably in the manner in which eggs were packaged. Variations in both egg size and egg numbers in spawn masses were observed for the two species, among populations within both species and within Lacuna pallidula populations. For Lacuna pallidula, these variations were shown to be mediated by both maternal macroalgal diet and population source. Maternal diet directly affected the size of hatching offspring but not the size of eggs produced. Consequently, egg size was not a good indicator of hatching size for either species. The EJP was determined for both species for a range of temperatures. Greater variations in the EJP and juvenile size were observed in Lacuna vincta. This was attributed to the ability of the larvae of this species to delay metamorphosis and to display positive growth during the delay phase. Both temperature and microalgal diet were shown to affect patterns of growth and development in Lacuna vincta larvae. Sources of naturally occurring cues for inducing settlement and metamorphosis in Lacuna vincta larvae were investigated to understand further the distribution patterns of this species on macroalgal types. Extension of the work investigated the suitability of various artificial cues for inducing metamorphosis and the effects of larval age and nutritional status of larvae upon latency of response to established inducing cues. Overall, L. pallidula displayed greater variation in traits and was more sensitive to environmental change than L. vincta. This finding is discussed in light of the two species larval strategy.The reproductive and larval ecology of the intertidal nudibranch mollusc 'Adalaria proxima' (Alder & Hancock) (Gastropoda : opisthobranchia)Jones, Helen Lucyhttps://hdl.handle.net/10023/146332019-03-29T10:42:41Z1996-01-01T00:00:00ZThis study concerns the reproductive and larval ecology of the nudibranch Adalaria proxima. Attainment of competence is demonstrated to be cue specific. Embryos metamorphose in response to choline, yet remain precompetent to elevated potassium and the natural cue until after hatching. It is hypothesized that the choline-mediated metamorphic pathway (or choline-sensitive portion of the natural pathway) becomes functionally complete ontogenetically earlier than do larval chemoreceptors. Larvae metamorphose in response to sea water 'conditioned' (CSW) by the bryozoan Electra pilosa. A range of littoral organisms failed to induce metamorphosis and it is suggested that A. proxima displays a high degree of cue specificy. It is reported that CSW-mediated metamorphosis is dose dependent and effected in a disparate manner to that of potassium. No evidence for a bacterial role in metamorphosis was found. These results are intended to facilitate future isolation of the natural cue. Both starved (lecithotrophic) and fed (facultatively planktotrophic) larvae may successfully delay metamorphosis for 28-31d post-hatching (at 10-C). Larval fitness appeared to be unaffected by nutritional status, which is suggested to reflect the transitional evolutionary nature of facultative planktotrophy. The lowered fitness commensurate with an extended pelagic period is hypothesized to confer a lowered dispersal potential. A. proximais semelparous, producing up to eleven spawn before dying. Significant variation in reproductive traits is demonstrated within and between six U.K. populations of A. proxima Intrapopulation decreases in egg size, fecundity and hatching success with spawn laying sequence are suggested to reflect phylogenetic constraints. Interpopulation differences in egg size and fecundity are considered consistent with the predicted limited larval dispersal potential. Population egg size was correlated to larval size but not latitude or fecundity. Possible causative factors of the observed interpopulation variation in reproductive traits are discussed, and most probable causes hypothesized.
1996-01-01T00:00:00ZJones, Helen LucyThis study concerns the reproductive and larval ecology of the nudibranch Adalaria proxima. Attainment of competence is demonstrated to be cue specific. Embryos metamorphose in response to choline, yet remain precompetent to elevated potassium and the natural cue until after hatching. It is hypothesized that the choline-mediated metamorphic pathway (or choline-sensitive portion of the natural pathway) becomes functionally complete ontogenetically earlier than do larval chemoreceptors. Larvae metamorphose in response to sea water 'conditioned' (CSW) by the bryozoan Electra pilosa. A range of littoral organisms failed to induce metamorphosis and it is suggested that A. proxima displays a high degree of cue specificy. It is reported that CSW-mediated metamorphosis is dose dependent and effected in a disparate manner to that of potassium. No evidence for a bacterial role in metamorphosis was found. These results are intended to facilitate future isolation of the natural cue. Both starved (lecithotrophic) and fed (facultatively planktotrophic) larvae may successfully delay metamorphosis for 28-31d post-hatching (at 10-C). Larval fitness appeared to be unaffected by nutritional status, which is suggested to reflect the transitional evolutionary nature of facultative planktotrophy. The lowered fitness commensurate with an extended pelagic period is hypothesized to confer a lowered dispersal potential. A. proximais semelparous, producing up to eleven spawn before dying. Significant variation in reproductive traits is demonstrated within and between six U.K. populations of A. proxima Intrapopulation decreases in egg size, fecundity and hatching success with spawn laying sequence are suggested to reflect phylogenetic constraints. Interpopulation differences in egg size and fecundity are considered consistent with the predicted limited larval dispersal potential. Population egg size was correlated to larval size but not latitude or fecundity. Possible causative factors of the observed interpopulation variation in reproductive traits are discussed, and most probable causes hypothesized.Aspects of the biology and ecology of the nudibranch mollusc 'Aeolidia papillosa (L.)'Hall, Stephen Johnhttps://hdl.handle.net/10023/146292019-03-29T10:42:10Z1984-01-01T00:00:00ZIn this study particular attention has been paid to the foraging biology and ecology of Aeolidia papillosa (L.); an anemone-eating nudibranch mollusc. 'Prey-value', derived in its current biological sense from optimal foraging models, is expected to be an important determinant of prey-selection behaviour. In the present study 'prey-values', or more specifically, food or tissue-values (because intact anemones were not used in the analyses), have been investigated for a range of anemone species. Analysis of the biochemical composition of anemone tissues and their consumption and assimilation by nudibranchs did not reveal any marked interspecific differences. S.troglodytes, however, is indicated as being somewhat different from the other species studied, possibly being assimilated more efficiently and consumed at a faster rate. These factors, in conjunction with the strong preferences shown for S.troglodytes in switching experiments and the apparent preponderance of field associations with this species, do Indicate that S.troglodytes may be a more valuable food item for A.papillosa. Analysis of the canposite estimates of fitness (growth and reproduction), however, did not reveal any contrasts in performance which could be related to diet. This was almost certainly a result of the marked variability in the performance of nudibranchs within each diet group obscuring any dietary effects which may have obtained. In the latter part of this study a series of behavioural experiments were conducted which investigated specific aspects of prey-selection behaviour. Using a variety of multiple-prey species choice experiments, data have been collected which show the effects of previous dietary experience on prey-species selection. The results of these experiments suggest that at least some of the contradictions in previous reports of prey-species preference by A.papillosa may be accounted for by "ingestive conditioning". "Ingestive conditioning" concerns the modification of a predator's behaviour such that it continues to choose that prey species which it has most recently or most frequently encountered. Such alterations of prey preference may exert considerable effects on the control of local anemone prey populations and their relative abundances. A variant of this experiment was ccmpleted during a five week investigation at the Friday Harbor Marine Laboratories, University of Washington, in the summer of 1982. Experiments showed that ingestive conditioning occurs for both U.K. and N.W Pacific A.papillosa. However, the modified experimental design used in Friday Harbor, and in corroborative experiments in St Andrews, also indicate that there is a significant "carry-over" effect from the previous conditioning diet. In the light of these results it was predicted that A.papillosa might exhibit frequency-dependent (i.e. switching) prey selection. Experiments undertaken to test this hypothesis were unable to demonstrate such behaviour due to persistent preference for one particular prey species. Field observations of A.papillosa-anemone associations are discussed in relation to the laboratory investigations.
1984-01-01T00:00:00ZHall, Stephen JohnIn this study particular attention has been paid to the foraging biology and ecology of Aeolidia papillosa (L.); an anemone-eating nudibranch mollusc. 'Prey-value', derived in its current biological sense from optimal foraging models, is expected to be an important determinant of prey-selection behaviour. In the present study 'prey-values', or more specifically, food or tissue-values (because intact anemones were not used in the analyses), have been investigated for a range of anemone species. Analysis of the biochemical composition of anemone tissues and their consumption and assimilation by nudibranchs did not reveal any marked interspecific differences. S.troglodytes, however, is indicated as being somewhat different from the other species studied, possibly being assimilated more efficiently and consumed at a faster rate. These factors, in conjunction with the strong preferences shown for S.troglodytes in switching experiments and the apparent preponderance of field associations with this species, do Indicate that S.troglodytes may be a more valuable food item for A.papillosa. Analysis of the canposite estimates of fitness (growth and reproduction), however, did not reveal any contrasts in performance which could be related to diet. This was almost certainly a result of the marked variability in the performance of nudibranchs within each diet group obscuring any dietary effects which may have obtained. In the latter part of this study a series of behavioural experiments were conducted which investigated specific aspects of prey-selection behaviour. Using a variety of multiple-prey species choice experiments, data have been collected which show the effects of previous dietary experience on prey-species selection. The results of these experiments suggest that at least some of the contradictions in previous reports of prey-species preference by A.papillosa may be accounted for by "ingestive conditioning". "Ingestive conditioning" concerns the modification of a predator's behaviour such that it continues to choose that prey species which it has most recently or most frequently encountered. Such alterations of prey preference may exert considerable effects on the control of local anemone prey populations and their relative abundances. A variant of this experiment was ccmpleted during a five week investigation at the Friday Harbor Marine Laboratories, University of Washington, in the summer of 1982. Experiments showed that ingestive conditioning occurs for both U.K. and N.W Pacific A.papillosa. However, the modified experimental design used in Friday Harbor, and in corroborative experiments in St Andrews, also indicate that there is a significant "carry-over" effect from the previous conditioning diet. In the light of these results it was predicted that A.papillosa might exhibit frequency-dependent (i.e. switching) prey selection. Experiments undertaken to test this hypothesis were unable to demonstrate such behaviour due to persistent preference for one particular prey species. Field observations of A.papillosa-anemone associations are discussed in relation to the laboratory investigations.Characterization of 5-hydroxytryptamine receptors in the snail, 'Helix aspersa'Cadogan, Anna-Karinahttps://hdl.handle.net/10023/146272019-03-29T10:43:17Z1992-01-01T00:00:00ZThe aim of this investigation was to characterize those 5-HT receptors present in three different tissues of the common garden snail. Helix aspersa, into one or more of the categories already described for vertebrate 5-HT receptors. Specific 5-HT receptor agonists and antagonists which had been developed and used to help characterize, and subsequently classify, the various types of 5-HT receptor in vertebrates, were utilized in this study. The three preparations from Helix included: i) identified neurones in the visceral ganglion ii) the heart and iii) the pharyngeal retractor muscle (PRM). The action of 5-HT on identified neurones in the visceral ganglion was studied using the electrophysiological techniques of both voltage- and current- damp. Under voltage-clamp conditions the response of the identified neurones to iontophoretic application of 5-HT was seen to be an inward current of approximately 3-10 nA. Under current-clamp conditions the response to 5-HT was an excitatory depolarization leading to the firing of action potentials of approximately 3-15 mV. Both responses showed rapid desensitization to repetitive applications of 5-HT and were blocked by tubocurarine. No specific 5-HT receptor antagonist to this 5-HT response in Helix neurones was found. The action of 5-HT was mimicked by 5-CT and a- Me-5-HT both of which showed similar-sized responses to 5-HT, whereas sumatriptan gave smaller responses than those of 5-HT. 5-HT had a positive inotropic effect on the heart. The excitatory action of 5-HT on the heart was studied using an organ bath methodology with application of the 5-HT receptor agonists and antagonists at suitable concentrations. No specific 5-HT receptor antagonist was found for the cardioexcitatory effect of 5-HT. The full rank order of potency for the 5-HT receptor agonists tested was 5-HT > methylergometrine = ergotamine = 5-CT > -Me-5-HT = sumatriptan > methysergide = 2-Me-5-HT = tryptamine 8-OH-DPAT. 5-HT caused relaxation in the PRM and was found to inhibit, in a dose- dependent manner, acetylcholine (ACh)-induced contraction in the muscle. This inhibition of ACh-induced contraction by 5-HT in the PRM was studied using an organ bath methodology with application of 5-HT receptor agonists and antagonists at suitable concentrations. No specific 5-HT receptor antagonist for the inhibition of ACh-induced contraction was found. The rank order of 5-HT receptor agonist potency was 5-HT > 5-CT > sumatriptan = ergotannine = methysergide >> -Me-5-HT = 2-Me-5-HT. The effect of 5-HT on cyclic adenosine 3',5'-monophosphate (cAMP) levels within Helix heart and pharyngeal retractor muscle (PRM) tissue were monitored in this investigation. 5-HT caused a dose-dependent increase in cAMP both in Helix heart and PRM tissue. The 5-HT receptors within Helix are not readily characterized into any of the categories of 5-HT receptor that have been already classified in vertebrates: Helix 5-HT receptors appear to be unique in the fact that they are unclassifiable in terms of the vertebrate 5-HT receptor classification. The evidence presented in this investigation is discussed in terms of the molecular biology of receptors: this includes the hypothesis that the 5-HT receptors particularly in Helix heart and PRM tissue could be related to a family of G-protein-coupled receptors whereas the neuronal 5-HT receptors in Helix are more likely to be integral to an ion channel.
1992-01-01T00:00:00ZCadogan, Anna-KarinaThe aim of this investigation was to characterize those 5-HT receptors present in three different tissues of the common garden snail. Helix aspersa, into one or more of the categories already described for vertebrate 5-HT receptors. Specific 5-HT receptor agonists and antagonists which had been developed and used to help characterize, and subsequently classify, the various types of 5-HT receptor in vertebrates, were utilized in this study. The three preparations from Helix included: i) identified neurones in the visceral ganglion ii) the heart and iii) the pharyngeal retractor muscle (PRM). The action of 5-HT on identified neurones in the visceral ganglion was studied using the electrophysiological techniques of both voltage- and current- damp. Under voltage-clamp conditions the response of the identified neurones to iontophoretic application of 5-HT was seen to be an inward current of approximately 3-10 nA. Under current-clamp conditions the response to 5-HT was an excitatory depolarization leading to the firing of action potentials of approximately 3-15 mV. Both responses showed rapid desensitization to repetitive applications of 5-HT and were blocked by tubocurarine. No specific 5-HT receptor antagonist to this 5-HT response in Helix neurones was found. The action of 5-HT was mimicked by 5-CT and a- Me-5-HT both of which showed similar-sized responses to 5-HT, whereas sumatriptan gave smaller responses than those of 5-HT. 5-HT had a positive inotropic effect on the heart. The excitatory action of 5-HT on the heart was studied using an organ bath methodology with application of the 5-HT receptor agonists and antagonists at suitable concentrations. No specific 5-HT receptor antagonist was found for the cardioexcitatory effect of 5-HT. The full rank order of potency for the 5-HT receptor agonists tested was 5-HT > methylergometrine = ergotamine = 5-CT > -Me-5-HT = sumatriptan > methysergide = 2-Me-5-HT = tryptamine 8-OH-DPAT. 5-HT caused relaxation in the PRM and was found to inhibit, in a dose- dependent manner, acetylcholine (ACh)-induced contraction in the muscle. This inhibition of ACh-induced contraction by 5-HT in the PRM was studied using an organ bath methodology with application of 5-HT receptor agonists and antagonists at suitable concentrations. No specific 5-HT receptor antagonist for the inhibition of ACh-induced contraction was found. The rank order of 5-HT receptor agonist potency was 5-HT > 5-CT > sumatriptan = ergotannine = methysergide >> -Me-5-HT = 2-Me-5-HT. The effect of 5-HT on cyclic adenosine 3',5'-monophosphate (cAMP) levels within Helix heart and pharyngeal retractor muscle (PRM) tissue were monitored in this investigation. 5-HT caused a dose-dependent increase in cAMP both in Helix heart and PRM tissue. The 5-HT receptors within Helix are not readily characterized into any of the categories of 5-HT receptor that have been already classified in vertebrates: Helix 5-HT receptors appear to be unique in the fact that they are unclassifiable in terms of the vertebrate 5-HT receptor classification. The evidence presented in this investigation is discussed in terms of the molecular biology of receptors: this includes the hypothesis that the 5-HT receptors particularly in Helix heart and PRM tissue could be related to a family of G-protein-coupled receptors whereas the neuronal 5-HT receptors in Helix are more likely to be integral to an ion channel.A study of the neurosecretory system associated with the vena cava in the cephalopod, Eledone Cirrosa (Lamarck)Berry, Cynthia F.https://hdl.handle.net/10023/146262019-03-29T10:35:22Z1974-01-01T00:00:00Z1. The nervous system of cephalopod molluscs provides many unusual features which puzzle the biologist. Among these features is a system of nerves passing to the vena cava. Alexandrowicz proposed that this is a neurosecretory system. 2. Examination of the fine structure of the system in Eledone cirrosa shows that the nerves contain many types of vesicle, the most numerous being electron-dense vesicles of 80 - 150 nm diameter. The vesicles are concentrated in the nerve terminals which lie adjacent to the basement membrane found on the inner side of the blood vessel wall. The appearance of the nerves is similar to that of neurosecretory neurons found in both invertebrate and vertebrate nervous systems. Examination of the fine structure of the system in Sepia officinalis demonstrates that a similar arrangement is also present in this cephalopod. 3. Extracts of the vena cava of E. cirrosa exhibit potent pharmacological activity. This activity may be due to one or more active substances. When assayed on the isolated systemic heart of E. cirrosa the active substance causes an increase in amplitude and a prolonged increase in frequency of heartbeat. The regions of the blood vessel demonstrating this activity exactly parallel the distribution of the nerve terminals within the vena cava wall. 4. Structures within the nerve terminals may be isolated on a discontinuous sucrose gradient. It is found that the cardio-excitatory activity is associated with the electron-dense vesicles of 80 - 150 nm diameter. 5. Gel-filtration of vena cava extracts on Sephadex columns indicates that at least two active substances are present, one with a molecular weight less than 5,000 and one with a molecular weight greater than 5,000. 6. Various techniques, i.e. fluorescence histochemistry, spectro- photofluorimetry, and bioassay, reveal that the activity present in the extracts cannot be attributed to the presence of 5-hydroxy- tryptamine or catechol amines. 7. The active substance resists heating at an acid or alkaline pH, is unaffected by evaporation to dryness, and is extractable in organic solvents e.g. acetone. Further analysis is required before the chemical nature of the substance can be determined. 8. Release of the active substance could not be demonstrated to occur after electrical stimulation of the nerve trunks, or by changing the ionic environment of the nerve trunks. 9. The above results support Alexandrowicz' proposal that the nerves passing to the vena cava in Eledone citrosa form a neurosecretory system. The possible functions of this system are discussed.
1974-01-01T00:00:00ZBerry, Cynthia F.1. The nervous system of cephalopod molluscs provides many unusual features which puzzle the biologist. Among these features is a system of nerves passing to the vena cava. Alexandrowicz proposed that this is a neurosecretory system. 2. Examination of the fine structure of the system in Eledone cirrosa shows that the nerves contain many types of vesicle, the most numerous being electron-dense vesicles of 80 - 150 nm diameter. The vesicles are concentrated in the nerve terminals which lie adjacent to the basement membrane found on the inner side of the blood vessel wall. The appearance of the nerves is similar to that of neurosecretory neurons found in both invertebrate and vertebrate nervous systems. Examination of the fine structure of the system in Sepia officinalis demonstrates that a similar arrangement is also present in this cephalopod. 3. Extracts of the vena cava of E. cirrosa exhibit potent pharmacological activity. This activity may be due to one or more active substances. When assayed on the isolated systemic heart of E. cirrosa the active substance causes an increase in amplitude and a prolonged increase in frequency of heartbeat. The regions of the blood vessel demonstrating this activity exactly parallel the distribution of the nerve terminals within the vena cava wall. 4. Structures within the nerve terminals may be isolated on a discontinuous sucrose gradient. It is found that the cardio-excitatory activity is associated with the electron-dense vesicles of 80 - 150 nm diameter. 5. Gel-filtration of vena cava extracts on Sephadex columns indicates that at least two active substances are present, one with a molecular weight less than 5,000 and one with a molecular weight greater than 5,000. 6. Various techniques, i.e. fluorescence histochemistry, spectro- photofluorimetry, and bioassay, reveal that the activity present in the extracts cannot be attributed to the presence of 5-hydroxy- tryptamine or catechol amines. 7. The active substance resists heating at an acid or alkaline pH, is unaffected by evaporation to dryness, and is extractable in organic solvents e.g. acetone. Further analysis is required before the chemical nature of the substance can be determined. 8. Release of the active substance could not be demonstrated to occur after electrical stimulation of the nerve trunks, or by changing the ionic environment of the nerve trunks. 9. The above results support Alexandrowicz' proposal that the nerves passing to the vena cava in Eledone citrosa form a neurosecretory system. The possible functions of this system are discussed.Genetic determinism, inducible morphology and phenotypic plasticity in the marine bryozoan Èlectra pilosa' (L.)Bayer, Michahttps://hdl.handle.net/10023/146232019-03-29T10:41:25Z1998-01-01T00:00:00ZThe marine bryozoan Electra pilosa typically inhabits ephemeral substrata in the intertidal and shallow subtidal, and is probably the ecologically most successful bryozoan species in British waters. Modular organisms like E. pilosa frequently evolve pronounced phenotypic plasticity to cope with the ecological challenges resulting from passive larval dispersal into unpredictable habitats, and temporal variability of the environment colonized by the immobile adult stage. E. pilosa colonies on wave-exposed shores differ morphologically from those found on sheltered shores in possessing numerous long-spined zooids. The present study demonstrates that spine formation in E. pilosa is environmentally inducible by wave-related abrasion by macroalgae; additionally, the spines also have a fortuitous anti-predator effect in discouraging predation by the nudibranchs Adalaria proxima and Polycera quadrilineata. It is suggested that the inducible spines of E. pilosa constitute an adaptation for the protection of feeding polypides in high-energy environments, and that plasticity for the trait is of adaptive value in this organism which exploits a diverse range of habitats. Although a number of traits in this species clearly are subject to considerable phenotypic plasticity, other attributes apparently are highly deterministic, heritable and genotype-specific. Electra pilosa displays pronounced among-genotype variation in colony growth rate, and the present study shows that this variation is due to proximate factors which affect growth rate and covary with genotype. This study also presents the first evidence of senescence at the zooid level in E. pilosa: Zooids deteriorate systematically over time, as indicated by decreasing polypide life spans and increasing polypide regeneration times, but in contrast to this, whole-organism senescence does not appear to occur in this species.
1998-01-01T00:00:00ZBayer, MichaThe marine bryozoan Electra pilosa typically inhabits ephemeral substrata in the intertidal and shallow subtidal, and is probably the ecologically most successful bryozoan species in British waters. Modular organisms like E. pilosa frequently evolve pronounced phenotypic plasticity to cope with the ecological challenges resulting from passive larval dispersal into unpredictable habitats, and temporal variability of the environment colonized by the immobile adult stage. E. pilosa colonies on wave-exposed shores differ morphologically from those found on sheltered shores in possessing numerous long-spined zooids. The present study demonstrates that spine formation in E. pilosa is environmentally inducible by wave-related abrasion by macroalgae; additionally, the spines also have a fortuitous anti-predator effect in discouraging predation by the nudibranchs Adalaria proxima and Polycera quadrilineata. It is suggested that the inducible spines of E. pilosa constitute an adaptation for the protection of feeding polypides in high-energy environments, and that plasticity for the trait is of adaptive value in this organism which exploits a diverse range of habitats. Although a number of traits in this species clearly are subject to considerable phenotypic plasticity, other attributes apparently are highly deterministic, heritable and genotype-specific. Electra pilosa displays pronounced among-genotype variation in colony growth rate, and the present study shows that this variation is due to proximate factors which affect growth rate and covary with genotype. This study also presents the first evidence of senescence at the zooid level in E. pilosa: Zooids deteriorate systematically over time, as indicated by decreasing polypide life spans and increasing polypide regeneration times, but in contrast to this, whole-organism senescence does not appear to occur in this species.On various aspects of reproduction and early development in Arenicola marinaHowie, David Ian Dicksonhttps://hdl.handle.net/10023/146202019-03-29T10:27:25Z1957-01-01T00:00:00Z1957-01-01T00:00:00ZHowie, David Ian DicksonParasitological studies: post-embryonic development in the polycercus of paricterotaenia paradoxa (Rudolphi, 1802) in allolobophora terrestris (Savigny, 1826)Scott, James Stuarthttps://hdl.handle.net/10023/146182019-03-29T10:33:38Z1963-01-01T00:00:00Z1. Metchnikov's discovery of Polycerus lubrici in the Earthworm, made in 1867, is confirmed for the first time. 2. The conclusion of Joyeux and Baer that Polycercus lumbrici is the larval form of Paricterotaenia paradoxa (= Amoebotaenia lumbrici) is confirmed. 3. The intermediate host is identified as Allolobophora terrestris and the principal final host as the Woodcock (Scolopax rusticola). 4. The polycercus has been found only in immature specimens of A. terrestris. The implications of this are discussed. 5. Earthworms were experimentally infested with Polycercus lumbrici by feeding them with mature proglottides of Paricterotaenia Paradoxa from the Woodcock. 6. The incidence and habits of the Woodcock are discussed. 7. The degree and site of infestation of Paricterotaenia paradoxa in the Woodcock are discussed. 8. The development of Polycerous lumbrici in the Earthworm, from the earliest form of the larva to the cysticercoid, is described in detail for the first time. 9. MetchniRov's outline of the development of Polvcercus lumbrici is amended to include a retroversion of the larva prior to the differentiation of the primordia of the scolex, retention of the side-walls of the larva and the appearance of an axial column of cells. His account is also extended to give, for the first time, a complete description of the development of the scolex. The rostellum is formed, as in Cysticercus fasciolars, from a bulb and prebulb, the former supplying the hook-elevator muscles and the glandular elements, the latter the muscles of the walls of the rostellum and the hook-retractor muscles. The remainder of the muscles of the scolex are modifications of the parenchymal and peripheral musculature. 10. The muscular, excretory, nervous and glandular systems are described and discussed. 11. A description is given of experiments to determine: (i) suitable media for keeping the larvae alive in vitro; (ii) agents for freeing the cysticercoids from the cyst; (iii) agents which induce evagination of the scolex; (iv) suitable media for culture and development of the evaginated tapeworms. The results of the experiments indicate that: (i) the larvae can be kept alive for periods of up to five days in simple physiological solutions such as Locke's (ii) the larvae are freed from the cyst in the gizzard of the final host by a purely mechanical process; (iii) the larvae are induced to evaginate in the final host by the action of gastric juice followed by pancreatic juice, the effective agents being pepsin in the first and pancreatin in the second, (iv) the tapeworm will not develop to maturity in any of the media used. 12. The discovery of a second polycercus, the larval form of Paricterotaenla burti Sandeman, 1959 is recorded from the Earthworm Allolophora terrestris. 13. Hook development in Paricterotaenia burti is described it follows the same general pattern as that of P. paradoxa. 14. An unidentified species of Amoebotaenia is described. 15. Evidence is offered which elucidates the life-cycles of the following cestodes: (i) Paricterotaenia paradoxa: intermediate host, the Earthworm Allolobophora terrestris; final host, the Woodcock (Scolopax rusticola). (ii) Parieterotaenia burti; intermediate host, the Earthworm Allolobophora terrestris; final host, the Woodcock (Scolopax rustlcola). (iii) Paricterotaenia stelliferai: final host, various charadrriform birds; intermediate host, Tubifex. Cysticercus pachycanthus is identified as the larval form of Valipora skrjabini a parasite of the Common Snipe (Gallinago gallinago). An unrecorded cyrsticercoid from Tubifox is noted.
1963-01-01T00:00:00ZScott, James Stuart1. Metchnikov's discovery of Polycerus lubrici in the Earthworm, made in 1867, is confirmed for the first time. 2. The conclusion of Joyeux and Baer that Polycercus lumbrici is the larval form of Paricterotaenia paradoxa (= Amoebotaenia lumbrici) is confirmed. 3. The intermediate host is identified as Allolobophora terrestris and the principal final host as the Woodcock (Scolopax rusticola). 4. The polycercus has been found only in immature specimens of A. terrestris. The implications of this are discussed. 5. Earthworms were experimentally infested with Polycercus lumbrici by feeding them with mature proglottides of Paricterotaenia Paradoxa from the Woodcock. 6. The incidence and habits of the Woodcock are discussed. 7. The degree and site of infestation of Paricterotaenia paradoxa in the Woodcock are discussed. 8. The development of Polycerous lumbrici in the Earthworm, from the earliest form of the larva to the cysticercoid, is described in detail for the first time. 9. MetchniRov's outline of the development of Polvcercus lumbrici is amended to include a retroversion of the larva prior to the differentiation of the primordia of the scolex, retention of the side-walls of the larva and the appearance of an axial column of cells. His account is also extended to give, for the first time, a complete description of the development of the scolex. The rostellum is formed, as in Cysticercus fasciolars, from a bulb and prebulb, the former supplying the hook-elevator muscles and the glandular elements, the latter the muscles of the walls of the rostellum and the hook-retractor muscles. The remainder of the muscles of the scolex are modifications of the parenchymal and peripheral musculature. 10. The muscular, excretory, nervous and glandular systems are described and discussed. 11. A description is given of experiments to determine: (i) suitable media for keeping the larvae alive in vitro; (ii) agents for freeing the cysticercoids from the cyst; (iii) agents which induce evagination of the scolex; (iv) suitable media for culture and development of the evaginated tapeworms. The results of the experiments indicate that: (i) the larvae can be kept alive for periods of up to five days in simple physiological solutions such as Locke's (ii) the larvae are freed from the cyst in the gizzard of the final host by a purely mechanical process; (iii) the larvae are induced to evaginate in the final host by the action of gastric juice followed by pancreatic juice, the effective agents being pepsin in the first and pancreatin in the second, (iv) the tapeworm will not develop to maturity in any of the media used. 12. The discovery of a second polycercus, the larval form of Paricterotaenla burti Sandeman, 1959 is recorded from the Earthworm Allolophora terrestris. 13. Hook development in Paricterotaenia burti is described it follows the same general pattern as that of P. paradoxa. 14. An unidentified species of Amoebotaenia is described. 15. Evidence is offered which elucidates the life-cycles of the following cestodes: (i) Paricterotaenia paradoxa: intermediate host, the Earthworm Allolobophora terrestris; final host, the Woodcock (Scolopax rusticola). (ii) Parieterotaenia burti; intermediate host, the Earthworm Allolobophora terrestris; final host, the Woodcock (Scolopax rustlcola). (iii) Paricterotaenia stelliferai: final host, various charadrriform birds; intermediate host, Tubifex. Cysticercus pachycanthus is identified as the larval form of Valipora skrjabini a parasite of the Common Snipe (Gallinago gallinago). An unrecorded cyrsticercoid from Tubifox is noted.Studies on the helminth parasites of some marine birdsShelswell, Eileen Margarethttps://hdl.handle.net/10023/146142019-03-29T10:35:00Z1954-01-01T00:00:00Z1. This thesis describes the investigations and tests carried these have been directed towards solving the problem of the identity of the adult stage of C. patellae, a digenetic trematode parasite of the limpet, Patella vulgate. 2. Morphological descriptions of the trematode parasites (Cercaria patellae and Cercaria B) of the limpet are given and brief comments of those found in the American mud-snail, Naasa obsoleta, have been included. An ecological arid statistical survey on the occurrence and distribution of the parasites of the limpet has indicated that the final host of Cercaria patellae is a bird; in addition, evidence has been presented to show that the metacercariae found probably develop from Cercaria B. 3. A brief survey is reported of flukes found in the birds examined - those likely to harbour the adult form of Cercaria patellae. 4. The serological methods used in this investigation are reviewed historically, and, the chief technique for measuring the precipitin, reaction - photo - electric estimation and the ring test - are described. 5. Antigens used for the purposes of injections and teats have been prepared variously and the role of lipoids in the specificity of the reaction is discussed briefly. Some of the methods, used toy other workers, to estimate the strength of an antigen have been compared, and the moat suitable used here for standardisation of the ring test. The methods used for preparation, of antisera to a variety of cercariae are described. Rabbits and domestic fowl were used, and it appears that domestic fowl are the more efficient antibody-producers in this particular field of serology. It has also been shown, although, not conclusively that better antisera are produced during an active infection, than by a series of injections of dead material. 6. The tests carried out are divided into qualitative and quantitative techniques. The former include observations on living carcariae in normal sera and antisera, employment of the anaphylactic reaction and, finally, use of the ring test. These tests were employed for the purpose of judging the efficiency of different methods of producing antisera. 7. Quantitative tests were applied to two adult trematodes against two selected antisera to cercariae. In an attempt to apply the ring test technique to the ontogeny of C.patellae.
1954-01-01T00:00:00ZShelswell, Eileen Margaret1. This thesis describes the investigations and tests carried these have been directed towards solving the problem of the identity of the adult stage of C. patellae, a digenetic trematode parasite of the limpet, Patella vulgate. 2. Morphological descriptions of the trematode parasites (Cercaria patellae and Cercaria B) of the limpet are given and brief comments of those found in the American mud-snail, Naasa obsoleta, have been included. An ecological arid statistical survey on the occurrence and distribution of the parasites of the limpet has indicated that the final host of Cercaria patellae is a bird; in addition, evidence has been presented to show that the metacercariae found probably develop from Cercaria B. 3. A brief survey is reported of flukes found in the birds examined - those likely to harbour the adult form of Cercaria patellae. 4. The serological methods used in this investigation are reviewed historically, and, the chief technique for measuring the precipitin, reaction - photo - electric estimation and the ring test - are described. 5. Antigens used for the purposes of injections and teats have been prepared variously and the role of lipoids in the specificity of the reaction is discussed briefly. Some of the methods, used toy other workers, to estimate the strength of an antigen have been compared, and the moat suitable used here for standardisation of the ring test. The methods used for preparation, of antisera to a variety of cercariae are described. Rabbits and domestic fowl were used, and it appears that domestic fowl are the more efficient antibody-producers in this particular field of serology. It has also been shown, although, not conclusively that better antisera are produced during an active infection, than by a series of injections of dead material. 6. The tests carried out are divided into qualitative and quantitative techniques. The former include observations on living carcariae in normal sera and antisera, employment of the anaphylactic reaction and, finally, use of the ring test. These tests were employed for the purpose of judging the efficiency of different methods of producing antisera. 7. Quantitative tests were applied to two adult trematodes against two selected antisera to cercariae. In an attempt to apply the ring test technique to the ontogeny of C.patellae.Helminth parasites of marine fishes: the biology of diclidophora denticulata a monogenetic trematodeFrankland, Helga Maud Toynbeehttps://hdl.handle.net/10023/146122019-03-29T10:31:26Z1953-01-01T00:00:00Z1953-01-01T00:00:00ZFrankland, Helga Maud ToynbeeCalcium and ageing in the Rotifer Mytilina Brevispina Var ReduncaSincock, A. M.https://hdl.handle.net/10023/146092019-03-29T10:35:12Z1973-01-01T00:00:00ZRotifers of the species Mytilina brevispina var redunca were cultured at 24°C under standard and aseptic culture conditions in artificial saline media of three calcium concentrations. 1. All populations were homologated with respect to maternal age by a process of egg selection carried out over three generations. 2. Observations on survival, growth and egg production were made on populations cultured on the three media containing a-full and reduced diet, while the effects of transfer between culture media, periodic washing in chelating agents, and constant exposure to antioxidants were tested on survival and egg-laying in Control cultures. 3, The calcium content of rotifers was investigated by continual exposure to the radionuclide 45 calcium in the three culture media, while the 45 calcium accumulated and withdrawn from rotifers cultured on Control 45 calcium medium and subjected to treatment with the chelating agent sodium citrate, and the 45 calcium accumulated in rotifers cultured on Control 45 calcium medium containing the antioxidant B.H.T., were also investigated. The 45 calcium intake of algae cultured for one day on Control 4-5 calcium medium at the concentration normally employed for experiments was noted. 4. In the case of rotifers cultured on a full diet in the three calcium media the greatest longevity, egg' total, and reproductive period was recorded in the Low calcium cultured population, while the lowest longevity value and total number of eggs laid was recorded in the High calcium group. Continual exposure to 4-5 calcium in each of the three media, revealed an accumulation of calcium that began in all cases at the end of the period of growth in size. This accumulation occurred at a rate that was inverse.ly related to longevity and directly related to the level of radionuclide in each medium in the manner predicted by the Lansing hypothesis. The total 45 calcium taken up in the daily intake of algae in 4 day old rotifers cultured on Control medium approximately the same order as the maximum rate of 45 calcium accumulation in untreated rotifers cultured on the same medium, suggesting a possible source of calcium accumulation in the event of a breakdown in the mechanism of excretion. 5. Rotifers cultured on a reduced diet in each of the three media showed an increase in longevity, egg total and reproductive period compared with rotifers cultured in the corresponding media on a full diet. However, the relative differences with respect to these characteristics were approximately similar between populations cultured on the same dietary level, with the Low calcium cultured population showing the greatest increase in longevity, total egg production and reproductive period. No execution in the growth period or difference in final size was noted in the case of the dietary restricted groups (cf McCay's starvation studies). 6. The results of the culture transfer experiments in which rotifers were transferred to another of the three media at the end of the growth period, revealed that it was the medium on which rotifers were cultured after growth that exerted the major influence on longevity value, total egg production and length of reproductive period. This result is in agreement with the appearance of an ageing factor at the end of the period of growth size postulated in the Lansing ageing theory.
1973-01-01T00:00:00ZSincock, A. M.Rotifers of the species Mytilina brevispina var redunca were cultured at 24°C under standard and aseptic culture conditions in artificial saline media of three calcium concentrations. 1. All populations were homologated with respect to maternal age by a process of egg selection carried out over three generations. 2. Observations on survival, growth and egg production were made on populations cultured on the three media containing a-full and reduced diet, while the effects of transfer between culture media, periodic washing in chelating agents, and constant exposure to antioxidants were tested on survival and egg-laying in Control cultures. 3, The calcium content of rotifers was investigated by continual exposure to the radionuclide 45 calcium in the three culture media, while the 45 calcium accumulated and withdrawn from rotifers cultured on Control 45 calcium medium and subjected to treatment with the chelating agent sodium citrate, and the 45 calcium accumulated in rotifers cultured on Control 45 calcium medium containing the antioxidant B.H.T., were also investigated. The 45 calcium intake of algae cultured for one day on Control 4-5 calcium medium at the concentration normally employed for experiments was noted. 4. In the case of rotifers cultured on a full diet in the three calcium media the greatest longevity, egg' total, and reproductive period was recorded in the Low calcium cultured population, while the lowest longevity value and total number of eggs laid was recorded in the High calcium group. Continual exposure to 4-5 calcium in each of the three media, revealed an accumulation of calcium that began in all cases at the end of the period of growth in size. This accumulation occurred at a rate that was inverse.ly related to longevity and directly related to the level of radionuclide in each medium in the manner predicted by the Lansing hypothesis. The total 45 calcium taken up in the daily intake of algae in 4 day old rotifers cultured on Control medium approximately the same order as the maximum rate of 45 calcium accumulation in untreated rotifers cultured on the same medium, suggesting a possible source of calcium accumulation in the event of a breakdown in the mechanism of excretion. 5. Rotifers cultured on a reduced diet in each of the three media showed an increase in longevity, egg total and reproductive period compared with rotifers cultured in the corresponding media on a full diet. However, the relative differences with respect to these characteristics were approximately similar between populations cultured on the same dietary level, with the Low calcium cultured population showing the greatest increase in longevity, total egg production and reproductive period. No execution in the growth period or difference in final size was noted in the case of the dietary restricted groups (cf McCay's starvation studies). 6. The results of the culture transfer experiments in which rotifers were transferred to another of the three media at the end of the growth period, revealed that it was the medium on which rotifers were cultured after growth that exerted the major influence on longevity value, total egg production and length of reproductive period. This result is in agreement with the appearance of an ageing factor at the end of the period of growth size postulated in the Lansing ageing theory.Light and electron microscopical studies on the trochophore larva of harmothoe imbricata, Polynoid PolychaeteHolborow, Patricia L.https://hdl.handle.net/10023/146072019-03-29T10:33:41Z1972-01-01T00:00:00ZThe trochophore larva of Harmothoe imbricata was examined by both light and electron microscopy. Light microscopy of living trochophores was limited to a study of the action of cilia and muscles, and observations on trochophores at various stages from the egg to the fully formed trochophore. The observations on the developing trochophore revealed the presence of apparently uniquely acting cilia. Fixed, sectioned trochophores were examined under the light microscope as an adjunct to electron microscopy to give the gross anatomy. Scanning electron microscopy was used to determine the arrangement of cilia and glands on the surface of the trochophore. This demonstrated that previous views, at least on the apical array of cilia, were erroneous, and that there is considerable asymmetry in the positions of both cilia and gland pores. Transmission electron microscopy of the fully formed trochophore afforded the first information at an ultrastructural level on all the organ systems of a trochophore, and revealed the presence of previously unknown structures such as modified cilia and a probable photoreceptor which is additional to the pigmented eyespot. Certain general issues of contention in electron-microscopical work were able to be resolved in the course of this work. This included the finding of neuro-ciliary synapses, and certain significant features in the development of trochophores from the egg to the fully formed trochophore. The suitability of this animal for experimental investigation became clear as the fine structural analysis proceeded. Accordingly, preliminary studies were made on pepsin digestion of thin sections and the testing of drugs on whole- animals before fixation.
1972-01-01T00:00:00ZHolborow, Patricia L.The trochophore larva of Harmothoe imbricata was examined by both light and electron microscopy. Light microscopy of living trochophores was limited to a study of the action of cilia and muscles, and observations on trochophores at various stages from the egg to the fully formed trochophore. The observations on the developing trochophore revealed the presence of apparently uniquely acting cilia. Fixed, sectioned trochophores were examined under the light microscope as an adjunct to electron microscopy to give the gross anatomy. Scanning electron microscopy was used to determine the arrangement of cilia and glands on the surface of the trochophore. This demonstrated that previous views, at least on the apical array of cilia, were erroneous, and that there is considerable asymmetry in the positions of both cilia and gland pores. Transmission electron microscopy of the fully formed trochophore afforded the first information at an ultrastructural level on all the organ systems of a trochophore, and revealed the presence of previously unknown structures such as modified cilia and a probable photoreceptor which is additional to the pigmented eyespot. Certain general issues of contention in electron-microscopical work were able to be resolved in the course of this work. This included the finding of neuro-ciliary synapses, and certain significant features in the development of trochophores from the egg to the fully formed trochophore. The suitability of this animal for experimental investigation became clear as the fine structural analysis proceeded. Accordingly, preliminary studies were made on pepsin digestion of thin sections and the testing of drugs on whole- animals before fixation.Motion parallax and the perception of three-dimensional surfacesGraham, Maureen E.https://hdl.handle.net/10023/145792019-07-15T10:15:13Z1983-01-01T00:00:00ZThis thesis presents an empirical analysis of the depth cue of motion parallax. The history of research in this area is described and some recent computational models are outlined which show that parallax information can theoretically provide accurate information about the depth structure of the environment. In contrast to previous empirical work, which failed to demonstrate that motion parallax could be used effectively, the experiments reported in this thesis show that it can be an accurate source of information about depth structure. The characteristics of the processing underlying the use of motion parallax were investigated. Sensitivity to depth surfaces specified by relative motion was high, and it varied as a function of the spatial rate of change of depth. Moreover, the sensitivity function was similar to that measured for stereoscopic depth surfaces. The finding of close similarities between motion parallax and stereoscopic depth was a major theme of the thesis. Strong negative aftereffects followed prolonged viewing of depth surfaces specified by either cue and, in addition, large simultaneous contrast effects were also found. Here, the perceived depth of one area was affected by the depth of the surrounding area. These findings suggest that depth processing from both parallax and stereopsis involves extensive spatial interactions. A model of depth processing was suggested where the basic mechanisms had extended receptive fields which extracted changes in depth, specified either by relative motion or disparity, across local areas. The presence of anisotropies in the perception of depth surfaces showed that there was a differential sensitivity to particular local patterns of relative motion or disparity, which might be due to an asymmetric organisation within depth receptive fields. Finally, the motion parallax and stereoscopic depth processing systems were found to interact, indicating that information from the two sources might come together at some stage. Overall, the empirical findings emphasised the importance of extracting information about the local structure of depth surfaces rather than the depths of individual points.
1983-01-01T00:00:00ZGraham, Maureen E.This thesis presents an empirical analysis of the depth cue of motion parallax. The history of research in this area is described and some recent computational models are outlined which show that parallax information can theoretically provide accurate information about the depth structure of the environment. In contrast to previous empirical work, which failed to demonstrate that motion parallax could be used effectively, the experiments reported in this thesis show that it can be an accurate source of information about depth structure. The characteristics of the processing underlying the use of motion parallax were investigated. Sensitivity to depth surfaces specified by relative motion was high, and it varied as a function of the spatial rate of change of depth. Moreover, the sensitivity function was similar to that measured for stereoscopic depth surfaces. The finding of close similarities between motion parallax and stereoscopic depth was a major theme of the thesis. Strong negative aftereffects followed prolonged viewing of depth surfaces specified by either cue and, in addition, large simultaneous contrast effects were also found. Here, the perceived depth of one area was affected by the depth of the surrounding area. These findings suggest that depth processing from both parallax and stereopsis involves extensive spatial interactions. A model of depth processing was suggested where the basic mechanisms had extended receptive fields which extracted changes in depth, specified either by relative motion or disparity, across local areas. The presence of anisotropies in the perception of depth surfaces showed that there was a differential sensitivity to particular local patterns of relative motion or disparity, which might be due to an asymmetric organisation within depth receptive fields. Finally, the motion parallax and stereoscopic depth processing systems were found to interact, indicating that information from the two sources might come together at some stage. Overall, the empirical findings emphasised the importance of extracting information about the local structure of depth surfaces rather than the depths of individual points.The development and evaluation of a microprocessor-controlled bioreactor for use in developing countriesLima Filho, Jose Luiz dehttps://hdl.handle.net/10023/145722019-07-15T10:12:11Z1987-01-01T00:00:00ZA laboratory scale fermenter control system, based on a Z80 microprocessor operating at 4 MHz, has been developed. The system has the following features: 1 -" 8 Kbytes of RAM and 4 Kbytes of EPROM (with extra space for another 4 Kbytes); 2 -" Two serial links (RS232c);3-" An analog/digital converter with an 8 channel multiplexer and an opto-triac system for switching control devices (heater, peristaltic pumps); 4 -" Four interface cards to connect the parameter sensors. This system has the advantage that it is based on well established (though not state-of-the-art) microelectronic technology (Z80 chips) widely available in the world at reasonable prices. This, plus the fact that both hardware and software were locally designed, means that it is truly 'portable' in the sense that, with limited resources, copies can easily be constructed in developing countries (the idea is that Mark-II will be built in North East Brazil to support research into yeast fermentation technology). The control system was evaluated in batch and chemostatic growth modes. Both modes were used to investigate the growth kinetics of a genetically engineered Saccharomyces cerevisiae strain (BC55) carrying the plasmid pCYG4 which directs 10 fold more NADP-GDH activity than wild type cells. Batch culture experiments showed that the presence of plasmid increased ammonia uptake by the cells but did not improve biomass or ethanol yield compared to wild type cells. Under carbon-limitation NADP-GDH activity was in phase with GOGAT and penicillinase activity. NADP-GDH and GOGAT activities were inversely proportional to intracellular ammonia concentration and proportional to intracellular L-glutamate concentration. Under nitrogen limitation (using ammonia as limiting substrate) GOGAT activity increased, but NADP-GDH and penicillinase activity remained at the same level as under carbon limitation. Using L-glutamate as nitrogen source NADP-GDH activity was very low and GOGAT and penicillinase activities were undetectables with an increase in NAD-GDH activity. Oscillations found in enzyme activities and intracellular metabolite concentration under carbon and nitrogen limitation experiments are a consequence of a mixed culture (the presence of cells with plasmid GDH (gdh+ cells) and cells without plasmid GDH (gdh- cells)) with changing concentrations of the 2 populations.
1987-01-01T00:00:00ZLima Filho, Jose Luiz deA laboratory scale fermenter control system, based on a Z80 microprocessor operating at 4 MHz, has been developed. The system has the following features: 1 -" 8 Kbytes of RAM and 4 Kbytes of EPROM (with extra space for another 4 Kbytes); 2 -" Two serial links (RS232c);3-" An analog/digital converter with an 8 channel multiplexer and an opto-triac system for switching control devices (heater, peristaltic pumps); 4 -" Four interface cards to connect the parameter sensors. This system has the advantage that it is based on well established (though not state-of-the-art) microelectronic technology (Z80 chips) widely available in the world at reasonable prices. This, plus the fact that both hardware and software were locally designed, means that it is truly 'portable' in the sense that, with limited resources, copies can easily be constructed in developing countries (the idea is that Mark-II will be built in North East Brazil to support research into yeast fermentation technology). The control system was evaluated in batch and chemostatic growth modes. Both modes were used to investigate the growth kinetics of a genetically engineered Saccharomyces cerevisiae strain (BC55) carrying the plasmid pCYG4 which directs 10 fold more NADP-GDH activity than wild type cells. Batch culture experiments showed that the presence of plasmid increased ammonia uptake by the cells but did not improve biomass or ethanol yield compared to wild type cells. Under carbon-limitation NADP-GDH activity was in phase with GOGAT and penicillinase activity. NADP-GDH and GOGAT activities were inversely proportional to intracellular ammonia concentration and proportional to intracellular L-glutamate concentration. Under nitrogen limitation (using ammonia as limiting substrate) GOGAT activity increased, but NADP-GDH and penicillinase activity remained at the same level as under carbon limitation. Using L-glutamate as nitrogen source NADP-GDH activity was very low and GOGAT and penicillinase activities were undetectables with an increase in NAD-GDH activity. Oscillations found in enzyme activities and intracellular metabolite concentration under carbon and nitrogen limitation experiments are a consequence of a mixed culture (the presence of cells with plasmid GDH (gdh+ cells) and cells without plasmid GDH (gdh- cells)) with changing concentrations of the 2 populations.Computer applications in bioinorganic chemistryMay, Peter Michaelhttps://hdl.handle.net/10023/145692019-03-29T10:28:51Z1981-01-01T00:00:00ZNowadays, computers play an indispensable role in the determination of metal-ligand formation constants and in their application to various situations of analytical, industrial or biological interest. The development of programs and simulation techniques to meet some current problems in bioinorganic chemistry constitutes the broad objective of the present research. Consideration is given to the thermodynamic calculation of complex species concentrations in biological fluids. New methods of solving the mathematical relationships for metal-ligand solution equilibria, particularly in the simulation of large multicomponent systems, are investigated. The ways in which computer simulations are involved in the determination of formation constants are discussed. Principles are developed and applied to problems concerning (i) the calibration of glass electrodes and (ii) the choice of complex species to describe metal-ligand systems under experimental investigation. The function of transition elements in biological systems is briefly reviewed. Emphasis is given to the significance of low-molecular-weight complexes and how a knowledge of their in vivo behaviour can affect bioinorganic drug design. The relationship between copper and rheumatoid arthritis and the importance of equilibria in the regulation of iron metabolism are treated in some detail. New simulation techniques are developed for blood plasma. The results successfully rationalise many bioinorganic phenomena. In particular, the relative ability of a series of chelating agents to compete with proteins for metal ions in plasma is correlated with the urinary excretion of trace elements that they cause. Further simulations extend the approach to other biofluids and to medical solutions intended for intravenous infusion.
1981-01-01T00:00:00ZMay, Peter MichaelNowadays, computers play an indispensable role in the determination of metal-ligand formation constants and in their application to various situations of analytical, industrial or biological interest. The development of programs and simulation techniques to meet some current problems in bioinorganic chemistry constitutes the broad objective of the present research. Consideration is given to the thermodynamic calculation of complex species concentrations in biological fluids. New methods of solving the mathematical relationships for metal-ligand solution equilibria, particularly in the simulation of large multicomponent systems, are investigated. The ways in which computer simulations are involved in the determination of formation constants are discussed. Principles are developed and applied to problems concerning (i) the calibration of glass electrodes and (ii) the choice of complex species to describe metal-ligand systems under experimental investigation. The function of transition elements in biological systems is briefly reviewed. Emphasis is given to the significance of low-molecular-weight complexes and how a knowledge of their in vivo behaviour can affect bioinorganic drug design. The relationship between copper and rheumatoid arthritis and the importance of equilibria in the regulation of iron metabolism are treated in some detail. New simulation techniques are developed for blood plasma. The results successfully rationalise many bioinorganic phenomena. In particular, the relative ability of a series of chelating agents to compete with proteins for metal ions in plasma is correlated with the urinary excretion of trace elements that they cause. Further simulations extend the approach to other biofluids and to medical solutions intended for intravenous infusion.Structure and function of the cerebral organs in 'Paranemertes peregrina', 'Tetrastemma candidum' and 'Amphiporus lactifloreus' (Hoplonemertea : Monostilifera)Amerongen, Helen M.https://hdl.handle.net/10023/145682019-03-29T10:28:37Z1984-01-01T00:00:00ZThe histology and ultrastructure of the cerebral organs have been studied in three species of monostiliferous hoplonemertean: Paranemertes penegnina Coe, Amphiporus lactifloreus (Johnston) and Tetrastemma candidum (O.F. Muller). The role of the cerebral organs in osmoregulation and behaviour has been investigated in Paranemertes. Based on the information obtained, it is concluded that the cerebral organs in these species are chemoreceptors. The structure of the cerebral organs is essentially the same in the three species studied. The cerebral organs consist of two groups of sensory cells, two groups of gland cells, and two groups of endocytic/lysosomal cells (vesicular cells), as well as ciliated cells and support cells, surrounding a ciliated, blind-ending canal. The canal is functionally divided into two channels, designated the major and minor canals. According to the orientation of ciliary basal feet in cells of the canal epithelium, the minor canal is an incurrent channel, and the major canal is an excurrent channel. The organization of cell types with respect to the direction of flow in the canal is such that along the minor canal; Type A gland cell processes are upstream from Type 2 sensory cell dendrites, and Type 2 vesicular cells are downstream from the dendrites. Similarly, in the major canal. Type B gland cell processes are upstream, and Type 1 vesicular cells are downstream, from Type 1 sensory cell dendrites. Based on this organization, and on the interpretation of cellular fine structure in the cerebral organs, it is proposed that the function of gland cells is to secrete a mucous coating over the sensory epithelium, and the function of vesicular cells is to remove this coating from the canal as the mucus is carried downstream from the dendrites by ciliary action. In gland cells, the amount of secretion product present may be regulated by autophagic breakdown of secretion granules (crinophagy), according to a variable demand for secretion in the canal. Crinophagy contributes to the amount of vesicular material (degraded secretion product) present in the cerebral organs. Although the dendrites are not innervated, dendrite sensitivity may be modulated by variation of the rate of flow through the canal, and the rate of mucous turnover across the two sensory epithelia. An efferent nerve fibre is present among the ciliated cells of the minor canal. The fibre is rare and its synapse has not been observed. It is thought that the fibre innervates a few cells which act as pacemakers, their cilia mechanically entraining the beat frequency of other cilia, thus determining the rate of flow through the canal. There is no indication that vesicular material is disposed of outside the cerebral organs. In Paranemertes and Amphiporus, but not in Tetrastemma, the cephalic blood vessel lies adjacent to the posterior glandular part of the cerebral organ, however, this association is not reflected in the internal structure of the cerebral organs. It is, therefore, unlikely that the cerebral organs in these species have an endocrine function. The function of the cerebral organs in Paranemertes has been investigated by comparing the behaviour of intact worms with the behaviour of worms from which the cerebral organs have been surgically removed. Cerebral organ removal did not affect trail following behaviour, which is associated with homing, but it abolished the response of Paranemertes to prey trails. It is concluded that the cerebral organs of Paranemertes are chemoreceptors responsible for the detection of prey. The behavioural physiology of Paranemertes has been investigated, using extracellular suction electrodes to record from the lateral nerve cords and the cerebral organ nerves. The results indicate that the cerebral organs are sensitive to prey extract and distilled water, but not to mechanical, thermal or photic stimuli. The role of the cerebral organs of Paranemertes in salinity stress tolerance has been investigated by measuring the effect of cerebral organ removal on volume regulation, and by observing the effects of hypo-osmotic media on the cytology of the cerebral organs. Removal of the cerebral organs decreases volume regulatory capacity, however, a similar change is seen in sham-operated worms, indicating that the decreased capacity for regulation is due to the operation itself and not to interference with a physiological role of the cerebral organs. Cytological changes caused by exposure to dilute sea water are similar to those seen in worms fixed in hypo-osmotic fixative. It is unlikely, therefore, that these represent a co-ordinated response of the organs to salinity stress. No exchange of material between the cerebral organs and the vascular system was observed. It is concluded that in Paranemertes, the cerebral organs are not involved in osmoregulation.
1984-01-01T00:00:00ZAmerongen, Helen M.The histology and ultrastructure of the cerebral organs have been studied in three species of monostiliferous hoplonemertean: Paranemertes penegnina Coe, Amphiporus lactifloreus (Johnston) and Tetrastemma candidum (O.F. Muller). The role of the cerebral organs in osmoregulation and behaviour has been investigated in Paranemertes. Based on the information obtained, it is concluded that the cerebral organs in these species are chemoreceptors. The structure of the cerebral organs is essentially the same in the three species studied. The cerebral organs consist of two groups of sensory cells, two groups of gland cells, and two groups of endocytic/lysosomal cells (vesicular cells), as well as ciliated cells and support cells, surrounding a ciliated, blind-ending canal. The canal is functionally divided into two channels, designated the major and minor canals. According to the orientation of ciliary basal feet in cells of the canal epithelium, the minor canal is an incurrent channel, and the major canal is an excurrent channel. The organization of cell types with respect to the direction of flow in the canal is such that along the minor canal; Type A gland cell processes are upstream from Type 2 sensory cell dendrites, and Type 2 vesicular cells are downstream from the dendrites. Similarly, in the major canal. Type B gland cell processes are upstream, and Type 1 vesicular cells are downstream, from Type 1 sensory cell dendrites. Based on this organization, and on the interpretation of cellular fine structure in the cerebral organs, it is proposed that the function of gland cells is to secrete a mucous coating over the sensory epithelium, and the function of vesicular cells is to remove this coating from the canal as the mucus is carried downstream from the dendrites by ciliary action. In gland cells, the amount of secretion product present may be regulated by autophagic breakdown of secretion granules (crinophagy), according to a variable demand for secretion in the canal. Crinophagy contributes to the amount of vesicular material (degraded secretion product) present in the cerebral organs. Although the dendrites are not innervated, dendrite sensitivity may be modulated by variation of the rate of flow through the canal, and the rate of mucous turnover across the two sensory epithelia. An efferent nerve fibre is present among the ciliated cells of the minor canal. The fibre is rare and its synapse has not been observed. It is thought that the fibre innervates a few cells which act as pacemakers, their cilia mechanically entraining the beat frequency of other cilia, thus determining the rate of flow through the canal. There is no indication that vesicular material is disposed of outside the cerebral organs. In Paranemertes and Amphiporus, but not in Tetrastemma, the cephalic blood vessel lies adjacent to the posterior glandular part of the cerebral organ, however, this association is not reflected in the internal structure of the cerebral organs. It is, therefore, unlikely that the cerebral organs in these species have an endocrine function. The function of the cerebral organs in Paranemertes has been investigated by comparing the behaviour of intact worms with the behaviour of worms from which the cerebral organs have been surgically removed. Cerebral organ removal did not affect trail following behaviour, which is associated with homing, but it abolished the response of Paranemertes to prey trails. It is concluded that the cerebral organs of Paranemertes are chemoreceptors responsible for the detection of prey. The behavioural physiology of Paranemertes has been investigated, using extracellular suction electrodes to record from the lateral nerve cords and the cerebral organ nerves. The results indicate that the cerebral organs are sensitive to prey extract and distilled water, but not to mechanical, thermal or photic stimuli. The role of the cerebral organs of Paranemertes in salinity stress tolerance has been investigated by measuring the effect of cerebral organ removal on volume regulation, and by observing the effects of hypo-osmotic media on the cytology of the cerebral organs. Removal of the cerebral organs decreases volume regulatory capacity, however, a similar change is seen in sham-operated worms, indicating that the decreased capacity for regulation is due to the operation itself and not to interference with a physiological role of the cerebral organs. Cytological changes caused by exposure to dilute sea water are similar to those seen in worms fixed in hypo-osmotic fixative. It is unlikely, therefore, that these represent a co-ordinated response of the organs to salinity stress. No exchange of material between the cerebral organs and the vascular system was observed. It is concluded that in Paranemertes, the cerebral organs are not involved in osmoregulation.The biology of Phascolosoma minutum KefersteinStevens, John Loudonhttps://hdl.handle.net/10023/145672019-03-29T10:33:48Z1956-01-01T00:00:00Z1956-01-01T00:00:00ZStevens, John LoudonOocyte maturation, fertilization and post-fertilization development in two polychaete speciesWatson, Gordon Jameshttps://hdl.handle.net/10023/145662019-03-29T10:40:45Z1997-01-01T00:00:00ZPrevious studies on Arenicola marina suggest that oocyte maturation is induced by a hormone, from the prostomium, acting directly on the oocyte (Meijer and Durchon, 1977). Results presented here, from studies on British populations of Arenicola marina, show that in this species, oocyte maturation is controlled by two hormonal steps; a prostomial maturation hormone followed by a maturation inducing substance in the coelomic fluid, the Coelomic Maturation Factor (CMF). A reliable in vitro assay for oocyte maturation in A. marina has been adopted distinguishing immature from mature oocytes enabling CMF to be investigated; CMF has a molecular mass greater than 10 kDa, is thermolabile and inactivated by trypsin suggesting a proteinaceous nature. Production of CMF was also investigated; peak production occurs at approximately 2 hours after the injection of homogenised female prostomia. Oocytes require, on average, a minimum time of 20 minutes incubation in CMF to mature and preliminary results suggest calcium may not be necessary for maturation. Immunocytochemical techniques were used to characterise microtubule structures during oocyte maturation and post-fertilization development in Arenicola marina. Different regimes capable of bringing about maturation do not affect the morphology of the meiotic spindle. However, post-fertilization development is slower in oocytes matured in vitro when compared to mature oocytes obtained from naturally spawning females and females injected with homogenised prostomia which then spawn. Changes in microtubule structures in A. defodiens and Nereis virens during post-fertilization have also been partially characterised and these are compared and contrasted with A. marina. The development of a microinjection system will enable intracellular calcium and its role in maturation and fertilization within oocytes to be examined in these polychaetes.
1997-01-01T00:00:00ZWatson, Gordon JamesPrevious studies on Arenicola marina suggest that oocyte maturation is induced by a hormone, from the prostomium, acting directly on the oocyte (Meijer and Durchon, 1977). Results presented here, from studies on British populations of Arenicola marina, show that in this species, oocyte maturation is controlled by two hormonal steps; a prostomial maturation hormone followed by a maturation inducing substance in the coelomic fluid, the Coelomic Maturation Factor (CMF). A reliable in vitro assay for oocyte maturation in A. marina has been adopted distinguishing immature from mature oocytes enabling CMF to be investigated; CMF has a molecular mass greater than 10 kDa, is thermolabile and inactivated by trypsin suggesting a proteinaceous nature. Production of CMF was also investigated; peak production occurs at approximately 2 hours after the injection of homogenised female prostomia. Oocytes require, on average, a minimum time of 20 minutes incubation in CMF to mature and preliminary results suggest calcium may not be necessary for maturation. Immunocytochemical techniques were used to characterise microtubule structures during oocyte maturation and post-fertilization development in Arenicola marina. Different regimes capable of bringing about maturation do not affect the morphology of the meiotic spindle. However, post-fertilization development is slower in oocytes matured in vitro when compared to mature oocytes obtained from naturally spawning females and females injected with homogenised prostomia which then spawn. Changes in microtubule structures in A. defodiens and Nereis virens during post-fertilization have also been partially characterised and these are compared and contrasted with A. marina. The development of a microinjection system will enable intracellular calcium and its role in maturation and fertilization within oocytes to be examined in these polychaetes.Reinitiation of meiosis in polychaete (annelida) oocytesPaterson, Lesley Annhttps://hdl.handle.net/10023/145642019-03-29T10:38:46Z1999-01-01T00:00:00ZThis thesis presents ultrastructural and biochemical information on meiotic reinitiation during oocyte maturation in the polychaetes, Arenicola marina, A. defodiens and Nereis virens. The ultrastructural changes during meiotic maturation was characterised in the oocytes of Arenicola marina and Nereis virens using transmission electron microscopy in addition to germinal vesicle breakdown, release of the prophase I block was signified by major cortical changes in both species. The ultrastructure of fertilization in A. marina was independent of whether the oocytes were matured in vivo and spawned or matured in vitro by CMF. Oocyte maturation in Arenicola marina is controlled by a hormonal cascade that is initiated by the prostomial maturation hormone, PMH, and followed by the coelomic maturation factor, CMF (Watson and Bentley, 1997). Results presented here demonstrated that PMH has a molecular mass greater than 10 kDa, yet how this molecule triggers CMF activity remains unknown. M-phase promoting factor (MPF) consists of two subunits, cdkl and cyclin B, and is responsible for the control of mitosis and meiosis. The cytoplasmic "second messenger" that transduces the hormone signal to the activation of MPF in the oocyte cytoplasm was investigated in the two Arenicola species and is discussed. MPF regulation was investigated in Arenicola marina and Nereis virens oocytes. MPF activation was driven by the dephosphorylation of cdkl and phosphorylation of cyclin B. The results indicate that as with all other higher eukaryotes, the precursor of MPF in A. marina oocytes was maintained inactive by the phosphorylation of threonine 14 and tyrosine 15 (or equivalent residues) on the cdkl subunit. In contrast to other organisms, however, only a fraction of the cdkl present was complexed to cyclin B and utilised during meiotic reinitiation. All the cdkl in N. virens oocytes was joined with cyclin B but results suggest that the inactive complex contained tyrosine-only phosphorylated cdk1.
1999-01-01T00:00:00ZPaterson, Lesley AnnThis thesis presents ultrastructural and biochemical information on meiotic reinitiation during oocyte maturation in the polychaetes, Arenicola marina, A. defodiens and Nereis virens. The ultrastructural changes during meiotic maturation was characterised in the oocytes of Arenicola marina and Nereis virens using transmission electron microscopy in addition to germinal vesicle breakdown, release of the prophase I block was signified by major cortical changes in both species. The ultrastructure of fertilization in A. marina was independent of whether the oocytes were matured in vivo and spawned or matured in vitro by CMF. Oocyte maturation in Arenicola marina is controlled by a hormonal cascade that is initiated by the prostomial maturation hormone, PMH, and followed by the coelomic maturation factor, CMF (Watson and Bentley, 1997). Results presented here demonstrated that PMH has a molecular mass greater than 10 kDa, yet how this molecule triggers CMF activity remains unknown. M-phase promoting factor (MPF) consists of two subunits, cdkl and cyclin B, and is responsible for the control of mitosis and meiosis. The cytoplasmic "second messenger" that transduces the hormone signal to the activation of MPF in the oocyte cytoplasm was investigated in the two Arenicola species and is discussed. MPF regulation was investigated in Arenicola marina and Nereis virens oocytes. MPF activation was driven by the dephosphorylation of cdkl and phosphorylation of cyclin B. The results indicate that as with all other higher eukaryotes, the precursor of MPF in A. marina oocytes was maintained inactive by the phosphorylation of threonine 14 and tyrosine 15 (or equivalent residues) on the cdkl subunit. In contrast to other organisms, however, only a fraction of the cdkl present was complexed to cyclin B and utilised during meiotic reinitiation. All the cdkl in N. virens oocytes was joined with cyclin B but results suggest that the inactive complex contained tyrosine-only phosphorylated cdk1.Sperm activation and spawning in Arenicola marina (L) (Annelida:Polychaeta)Pacey, Allan Anthonyhttps://hdl.handle.net/10023/145622019-03-29T10:37:23Z1991-01-01T00:00:00ZThe spermatozoa of Arenicola marina are unlike those of most marine invertebrates, in that they become motile in the body cavity prior to spawning. This occurs in response to a Sperm Maturation Factor (SMF) which is released from the prostomium. Prior to activation, spermatozoa are held as morulae with several hundred spermatozoa connected by a common mass of cytoplasm called the cytophore. Sperm activation by SMF is characterised in vitro, in terms of the ultrastructural changes which occur as the sperm become motile, and an active role for the cytophore during sperm activation is suggested. The morphology of these spermatozoa is 'primitive', and ultrastructural observations show that they possess a discoid swelling at the distal end of the flagellum. It is suggested that this may aid in swimming efficiency. The chemical nature of SMF has been putatively identified as 8,11,14-eicosatrienoic acid from both in vitro and in vivo studies. Biochemical investigations demonstrate that sperm activation is linked to an increase in sperm respiration rate, and an elevation of intracellular pH in the order of 0.2 pH units. Levels of ATP in spermatozoa are higher than those reported in other species, and it is considered that quiescence of sperm is not mediated by the deprivation of ATP to the axoneme. It is reported that sperm activated in vitro display a motile life of less than one hour, sperm which has been spawned in vivo, however, can have a motile life of up to 48 hours. It is suggested that this extension in sperm motile life may result from capacitation-like events which occur during activation and release in vivo. A hypothesis for the synthesis of 8,11,14-eicosatrienoic acid, its release from the prostomium, its transportation and mode of action at the level of the spermatozoa is also developed.
1991-01-01T00:00:00ZPacey, Allan AnthonyThe spermatozoa of Arenicola marina are unlike those of most marine invertebrates, in that they become motile in the body cavity prior to spawning. This occurs in response to a Sperm Maturation Factor (SMF) which is released from the prostomium. Prior to activation, spermatozoa are held as morulae with several hundred spermatozoa connected by a common mass of cytoplasm called the cytophore. Sperm activation by SMF is characterised in vitro, in terms of the ultrastructural changes which occur as the sperm become motile, and an active role for the cytophore during sperm activation is suggested. The morphology of these spermatozoa is 'primitive', and ultrastructural observations show that they possess a discoid swelling at the distal end of the flagellum. It is suggested that this may aid in swimming efficiency. The chemical nature of SMF has been putatively identified as 8,11,14-eicosatrienoic acid from both in vitro and in vivo studies. Biochemical investigations demonstrate that sperm activation is linked to an increase in sperm respiration rate, and an elevation of intracellular pH in the order of 0.2 pH units. Levels of ATP in spermatozoa are higher than those reported in other species, and it is considered that quiescence of sperm is not mediated by the deprivation of ATP to the axoneme. It is reported that sperm activated in vitro display a motile life of less than one hour, sperm which has been spawned in vivo, however, can have a motile life of up to 48 hours. It is suggested that this extension in sperm motile life may result from capacitation-like events which occur during activation and release in vivo. A hypothesis for the synthesis of 8,11,14-eicosatrienoic acid, its release from the prostomium, its transportation and mode of action at the level of the spermatozoa is also developed.