Genetic variation within two pulmonate limpet species, Siphonaria capensis and S. serrata along the South African coast
- Authors: Seaman, Jennifer Ann
- Date: 2003
- Subjects: Limpets -- South Africa Pulmonata Siphonaria Limpets -- Genetics
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:5800 , http://hdl.handle.net/10962/d1006155
- Description: Dispersal rates are known to play a fundamental role in establishing the genetic structure found within a species. Dispersal in marine benthic invertebrates is largely dependent on life history strategy. The presence of pelagic larvae will potentially result in high dispersal within a species, while direct development limits dispersal. This study used two intertidal pulmonate limpet species to investigate the relationship between dispersal potential and genetic structure of populations. Siphonaria capensis produces benthic egg masses, which release pelagic larvae. These float in ocean currents before settling and metamorphosing into adults. S. serrata reproduces by direct development. The larvae hatch as completely metamorphosed juveniles after developing in an egg case not far from the parent. The high dispersal capacity of S. capensis pelagic larvae should result in high levels of within-population variation since individuals within a particular population may originate from several different populations. This should lead to high levels of gene flow along the coast and to low genetic differentiation among populations. On the other hand, the low dispersal potential of S. serrata should cause low levels of genetic variation within populations, as relatives will remain close to one another. Low levels of gene flow and high genetic differentiation among populations are expected in this species. In dealing with the relationship between life history strategy and population genetic structure in these two species, a series of indirect techniques was utilised. Multivariate analyses of the morphological variation within each species showed that variation in size was similar between the two species and largely governed by environmental factors. Variation in shell shape was largely under genetic control and supported the predictions made for each species. Variation in total proteins was relatively uninformative in terms of examining the differences between the two species. Allozyme analysis and mtDNA sequencing clearly showed differences between the species in terms of their population genetic structure. High levels of gene flow were found within S. capensis. This was strongly influenced by ocean currents, with the close inshore Agulhas current along the Transkei coast contributing to high levels of dispersal and hence gene flow. Low levels of gene flow occurred within S. serrata, resulting in low within-population variation and high among-population differentiation.
- Full Text:
- Date Issued: 2003
- Authors: Seaman, Jennifer Ann
- Date: 2003
- Subjects: Limpets -- South Africa Pulmonata Siphonaria Limpets -- Genetics
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:5800 , http://hdl.handle.net/10962/d1006155
- Description: Dispersal rates are known to play a fundamental role in establishing the genetic structure found within a species. Dispersal in marine benthic invertebrates is largely dependent on life history strategy. The presence of pelagic larvae will potentially result in high dispersal within a species, while direct development limits dispersal. This study used two intertidal pulmonate limpet species to investigate the relationship between dispersal potential and genetic structure of populations. Siphonaria capensis produces benthic egg masses, which release pelagic larvae. These float in ocean currents before settling and metamorphosing into adults. S. serrata reproduces by direct development. The larvae hatch as completely metamorphosed juveniles after developing in an egg case not far from the parent. The high dispersal capacity of S. capensis pelagic larvae should result in high levels of within-population variation since individuals within a particular population may originate from several different populations. This should lead to high levels of gene flow along the coast and to low genetic differentiation among populations. On the other hand, the low dispersal potential of S. serrata should cause low levels of genetic variation within populations, as relatives will remain close to one another. Low levels of gene flow and high genetic differentiation among populations are expected in this species. In dealing with the relationship between life history strategy and population genetic structure in these two species, a series of indirect techniques was utilised. Multivariate analyses of the morphological variation within each species showed that variation in size was similar between the two species and largely governed by environmental factors. Variation in shell shape was largely under genetic control and supported the predictions made for each species. Variation in total proteins was relatively uninformative in terms of examining the differences between the two species. Allozyme analysis and mtDNA sequencing clearly showed differences between the species in terms of their population genetic structure. High levels of gene flow were found within S. capensis. This was strongly influenced by ocean currents, with the close inshore Agulhas current along the Transkei coast contributing to high levels of dispersal and hence gene flow. Low levels of gene flow occurred within S. serrata, resulting in low within-population variation and high among-population differentiation.
- Full Text:
- Date Issued: 2003
Geographical races of the honeybees (Apis Mellifera L.) of the Northern regions of Ethiopia
- Authors: Mohammed, Nuru Adgaba
- Date: 2003
- Subjects: Honeybee -- Ethiopia Honeybee -- Behavior -- Ethiopia Honeybee -- Ethiopia -- Morphology Honeybee -- Ecology -- Ethiopia
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:5827 , http://hdl.handle.net/10962/d1007671
- Description: The ideal climatic conditions and diversity of floral resources allow Ethiopia to sustain millions of honeybee colonies. Beekeeping is widely practiced and plays a significant role in the livelihood of the farming community of the country. Despite this, information on the types of geographical races of honeybees, their behavioural characters and the related ecological factors are not established. In this work an attempt was made to characterise the honeybee populations of the northern parts of Ethiopia based on the analyses of morphological, behavioural and ecological characteristics. For morphological analysis, 155 honeybee colony samples from 31 localities were collected. 20 worker honeybees per colony sample totalled 3100 individual worker honeybees and thirteen morphological characters per bee, a total of 40 300 measurements were recorded following Ruttner's (1988) protocols. The behavioural characters such as reproductive swarming, migration, temperament and colony seasonal cycles were assessed based on survey work of a pre-structured questionnaire. Various univariate and multivariate statistical methods were employed to analyse the data. The principal components and step-wise linear discriminant analyses revealed the existence of four discrete morphoclusters or geographical races: A. m. jemenitica from eastern, northwestern and northern arid and semi-arid lowlands, A. m. scutellata from the western humid midlands, A. m. bandasii from sub-moist central highlands and A. m. monticola from the northern mountainous parts of the study areas. These different geographical races were found to be distinctively distributed in the different ecological parts of the study area. High intercolonial and intracolonial variances were observed in all localities, however particularly high values were obtained in areas of transitions between ecological zones indicating a region of gene flow or zones of hybridisation among the statistically defined populations. Such high variances were observed mostly in areas where A. m. jemenitica borders the other geographical races. Moreover. distinct behavioural variations were also noted among these geographical races. Generally. the highland and mountainous honeybees A. m. bandasii and A. m. monticola are relatively larger in body size. have less tendency to swarm. less inclination to migrate and are relatively gentle while the converse traits were noted for the lowlands and midlands honeybees A. m. jemenitica and A. m. scutellata. Both morphological and behavioural variations were highly correlated with environmental factors and the variations seem to be the result of long adaptation to the interrelated ecological factors in their respective areas. Variations in reproductive swarming periods were also noted among these honeybee populations as a result of variations in rainfall pattern. altitude and temperature in their respective ecological areas which are believed to alter the honeybee colonies' seasonal cycles and leads to partial temporal reproductive isolation among these different honeybee populations.
- Full Text:
- Date Issued: 2003
- Authors: Mohammed, Nuru Adgaba
- Date: 2003
- Subjects: Honeybee -- Ethiopia Honeybee -- Behavior -- Ethiopia Honeybee -- Ethiopia -- Morphology Honeybee -- Ecology -- Ethiopia
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:5827 , http://hdl.handle.net/10962/d1007671
- Description: The ideal climatic conditions and diversity of floral resources allow Ethiopia to sustain millions of honeybee colonies. Beekeeping is widely practiced and plays a significant role in the livelihood of the farming community of the country. Despite this, information on the types of geographical races of honeybees, their behavioural characters and the related ecological factors are not established. In this work an attempt was made to characterise the honeybee populations of the northern parts of Ethiopia based on the analyses of morphological, behavioural and ecological characteristics. For morphological analysis, 155 honeybee colony samples from 31 localities were collected. 20 worker honeybees per colony sample totalled 3100 individual worker honeybees and thirteen morphological characters per bee, a total of 40 300 measurements were recorded following Ruttner's (1988) protocols. The behavioural characters such as reproductive swarming, migration, temperament and colony seasonal cycles were assessed based on survey work of a pre-structured questionnaire. Various univariate and multivariate statistical methods were employed to analyse the data. The principal components and step-wise linear discriminant analyses revealed the existence of four discrete morphoclusters or geographical races: A. m. jemenitica from eastern, northwestern and northern arid and semi-arid lowlands, A. m. scutellata from the western humid midlands, A. m. bandasii from sub-moist central highlands and A. m. monticola from the northern mountainous parts of the study areas. These different geographical races were found to be distinctively distributed in the different ecological parts of the study area. High intercolonial and intracolonial variances were observed in all localities, however particularly high values were obtained in areas of transitions between ecological zones indicating a region of gene flow or zones of hybridisation among the statistically defined populations. Such high variances were observed mostly in areas where A. m. jemenitica borders the other geographical races. Moreover. distinct behavioural variations were also noted among these geographical races. Generally. the highland and mountainous honeybees A. m. bandasii and A. m. monticola are relatively larger in body size. have less tendency to swarm. less inclination to migrate and are relatively gentle while the converse traits were noted for the lowlands and midlands honeybees A. m. jemenitica and A. m. scutellata. Both morphological and behavioural variations were highly correlated with environmental factors and the variations seem to be the result of long adaptation to the interrelated ecological factors in their respective areas. Variations in reproductive swarming periods were also noted among these honeybee populations as a result of variations in rainfall pattern. altitude and temperature in their respective ecological areas which are believed to alter the honeybee colonies' seasonal cycles and leads to partial temporal reproductive isolation among these different honeybee populations.
- Full Text:
- Date Issued: 2003
Intercohort cannibalism and parturition-associated behaviour of captive-bred swordtail, Xiphophorus helleri (Pisces: Poeciliidae)
- Jones, Clifford Louis Wilshire
- Authors: Jones, Clifford Louis Wilshire
- Date: 2003
- Subjects: Poeciliidae -- Behavior Xiphophorus helleri Fish culture
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:5351 , http://hdl.handle.net/10962/d1007812
- Description: Adult fish that belong to the family Poeciliidae cannibalise juveniles, both in the wild and under captive conditions, but this behaviour has only been partly investigated in the Poeciliidae in some of the commercially valuable species. The objective of the research is to develop an understanding of intercohort cannibalism and parturition-associated behaviour in captive-bred swordtail (Xiphophorus helleri), with applications to industry and future research of other poeciliids. Experiments investigating the effect of adult stocking density and sex ratio on the production of juveniles were used to determine if cannibalism occurs under culture conditions. The average rate of intercohort cannibalism ranged from (5.5 to 53.9%), and was positively density dependent and independent of sex ratio, indicating that males and females were probably equally cannibalistic. The highest number of juveniles (1725.7±141.4) produced per tank over 70 days was obtained from two males and eight females. To develop a better understanding of adult and juvenile behaviour during parturition, fish were observed under controlled laboratory conditions using video and behaviours such as attack (burst of speed by an adult in the direction of a juvenile), escape (avoidance of cannibalism after attack) and cannibalism (predation of a live juvenile by an adult), for example, were identified. Under laboratory conditions most young escaped in downward direction after attack (49%) and most utilised the refuge made that was made available. Furthermore, most attacks (62-65%) and cannibalism (57-84%) occurred at the bottom. Since the presence of refuge significantly increased the rate of juvenile survival under culture conditions, it was hypothesised that the rate of cannibalism could be reduced under farming conditions if juveniles were protected when they escaped downwards. This hypothesis was accepted as it was found that refuge at the bottom of the water column or the inclusion of a false-bottom reduced the rate of cannibalism by 49% and 72%, respectively. Similarly, the hypothesise that the rate of cannibalism could be reduced if juveniles where given protection when escaping sideways (32% of juveniles escaped sideways in the laboratory) was also accepted when tested under farm-scale conditions because a false-side reduced the rate of cannibalism by an average of 45%. Since males and females were equally responsible for cannibalising juveniles in the laboratory, it was hypothesised that the rate of cannibalism would decrease proportionately with the removal of males (Le. 20% of the cannibals) from the population; the removal of males under farming conditions resulted in a 19.5% reduction in the rate of cannibalism. Since older juveniles were better able to escape cannibalism than neonates and since adults habituate to stimuli that previously resulted in attack behaviour, it was hypothesised that the rate of cannibalism would remain unaffected by the length of time that juveniles were exposed to adults in the breeding tanks. This hypothesis was also accepted when tested under farm conditions. However, some hypotheses based on laboratory observations were not accepted. For example, a constant low light intensity did not appear to decrease the rate of cannibalism under farm conditions; also, the occurrence of dead and deformed juveniles went unnoticed in the laboratory, and under farm conditions, where adults did not have access to the bottom of the tank, 10% of the harvest consisted of dead and deformed juveniles. It is concluded that technologies, such as bottom-refuge or a false-side, that increase the size of the liveharvest and allow for the removal of potentially less viable offspring are recommended for the commercial production of poeciliids. The overall similarity of X. helleri behaviour between the laboratory experiments and the farm-scale trials suggests that the post-partum behaviour of X. helleri remains consistent under these different conditions; thus, behaviour under one set of conditions may be used to predict behaviour under other conditions. The application and significance of extrapolations to industry and future research of X. helleri and possibly other poeciliids were discussed and the most applicable laboratory observations with the highest extrapolation capacity were proposed. Furthermore, techniques were developed to aid industry and future researchers in making predictions relating to behaviour of X. helleri under different conditions based on laboratory observations. The results were used to develop a model indicating that selection pressures against cannibalism are not likely to exist at the rate of cannibalism observed here since the potential genetic gain through kin survival and inclusive fitness was shown to be greater than any potential genetiC loss experienced by a victim of cannibalism. The model was successfully tested under a range of social conditions. Other possible explanations for cannibalism in poeciliids, such as parental manipulation, nutritional advantages, opportunistic predation and the recovery of energy are discussed. It is suggested that the most likely proximate cause of cannibalism under captive conditions is opportunistic predation. The theory that cannibalism ensures that only viable genes of the victim are expressed, through inclusive fitness, is a possible ultimate cause of cannibalism, which may have been inherited from feral ancestors of captive-bred X. helleri.
- Full Text:
- Date Issued: 2003
- Authors: Jones, Clifford Louis Wilshire
- Date: 2003
- Subjects: Poeciliidae -- Behavior Xiphophorus helleri Fish culture
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:5351 , http://hdl.handle.net/10962/d1007812
- Description: Adult fish that belong to the family Poeciliidae cannibalise juveniles, both in the wild and under captive conditions, but this behaviour has only been partly investigated in the Poeciliidae in some of the commercially valuable species. The objective of the research is to develop an understanding of intercohort cannibalism and parturition-associated behaviour in captive-bred swordtail (Xiphophorus helleri), with applications to industry and future research of other poeciliids. Experiments investigating the effect of adult stocking density and sex ratio on the production of juveniles were used to determine if cannibalism occurs under culture conditions. The average rate of intercohort cannibalism ranged from (5.5 to 53.9%), and was positively density dependent and independent of sex ratio, indicating that males and females were probably equally cannibalistic. The highest number of juveniles (1725.7±141.4) produced per tank over 70 days was obtained from two males and eight females. To develop a better understanding of adult and juvenile behaviour during parturition, fish were observed under controlled laboratory conditions using video and behaviours such as attack (burst of speed by an adult in the direction of a juvenile), escape (avoidance of cannibalism after attack) and cannibalism (predation of a live juvenile by an adult), for example, were identified. Under laboratory conditions most young escaped in downward direction after attack (49%) and most utilised the refuge made that was made available. Furthermore, most attacks (62-65%) and cannibalism (57-84%) occurred at the bottom. Since the presence of refuge significantly increased the rate of juvenile survival under culture conditions, it was hypothesised that the rate of cannibalism could be reduced under farming conditions if juveniles were protected when they escaped downwards. This hypothesis was accepted as it was found that refuge at the bottom of the water column or the inclusion of a false-bottom reduced the rate of cannibalism by 49% and 72%, respectively. Similarly, the hypothesise that the rate of cannibalism could be reduced if juveniles where given protection when escaping sideways (32% of juveniles escaped sideways in the laboratory) was also accepted when tested under farm-scale conditions because a false-side reduced the rate of cannibalism by an average of 45%. Since males and females were equally responsible for cannibalising juveniles in the laboratory, it was hypothesised that the rate of cannibalism would decrease proportionately with the removal of males (Le. 20% of the cannibals) from the population; the removal of males under farming conditions resulted in a 19.5% reduction in the rate of cannibalism. Since older juveniles were better able to escape cannibalism than neonates and since adults habituate to stimuli that previously resulted in attack behaviour, it was hypothesised that the rate of cannibalism would remain unaffected by the length of time that juveniles were exposed to adults in the breeding tanks. This hypothesis was also accepted when tested under farm conditions. However, some hypotheses based on laboratory observations were not accepted. For example, a constant low light intensity did not appear to decrease the rate of cannibalism under farm conditions; also, the occurrence of dead and deformed juveniles went unnoticed in the laboratory, and under farm conditions, where adults did not have access to the bottom of the tank, 10% of the harvest consisted of dead and deformed juveniles. It is concluded that technologies, such as bottom-refuge or a false-side, that increase the size of the liveharvest and allow for the removal of potentially less viable offspring are recommended for the commercial production of poeciliids. The overall similarity of X. helleri behaviour between the laboratory experiments and the farm-scale trials suggests that the post-partum behaviour of X. helleri remains consistent under these different conditions; thus, behaviour under one set of conditions may be used to predict behaviour under other conditions. The application and significance of extrapolations to industry and future research of X. helleri and possibly other poeciliids were discussed and the most applicable laboratory observations with the highest extrapolation capacity were proposed. Furthermore, techniques were developed to aid industry and future researchers in making predictions relating to behaviour of X. helleri under different conditions based on laboratory observations. The results were used to develop a model indicating that selection pressures against cannibalism are not likely to exist at the rate of cannibalism observed here since the potential genetic gain through kin survival and inclusive fitness was shown to be greater than any potential genetiC loss experienced by a victim of cannibalism. The model was successfully tested under a range of social conditions. Other possible explanations for cannibalism in poeciliids, such as parental manipulation, nutritional advantages, opportunistic predation and the recovery of energy are discussed. It is suggested that the most likely proximate cause of cannibalism under captive conditions is opportunistic predation. The theory that cannibalism ensures that only viable genes of the victim are expressed, through inclusive fitness, is a possible ultimate cause of cannibalism, which may have been inherited from feral ancestors of captive-bred X. helleri.
- Full Text:
- Date Issued: 2003
Isolation of antigenic peptides of Cowdria ruminantium and their encoding genes using a genome-derived phage display library
- Authors: Fehrsen, Jeanni
- Date: 2003
- Subjects: Bacteriophages -- Genetics Ruminants -- Diseases Heartwater
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:3920 , http://hdl.handle.net/10962/d1003979
- Description: The development of new and effective vaccines and immunodiagnostic reagents requires the characterisation of antigenically relevant proteins and their interactions with the products of the immune system. Phage display technology was investigated as a means of elucidating some of the antigenic properties of the rickettsial parasite, Cowdria ruminantium (Cowdria). Randomly fragmented gene-derived libraries have been useful in elucidating viral and other epitopes, but only limited work has been done with entire genomes. A phage display library expressing a repertoire of Cowdria peptides was constructed. It was sufficiently large to represent the organism's genome, but lacked phages displaying peptides coded for by genes containing a Pvu II restriction enzyme site, including the one coding for the major antigenic protein 1 (MAP1). This was considered advantageous since MAP1 is immunodominant and has already been well characterised. Affinity selection with antibodies against Cowdria proteins other than MAP1 allowed several antibody-reactive peptides to be isolated. These selected sequences were placed in the context of the genome by screening a lambda bacteriophage library and by comparison with Cowdria DNA sequences. Apart from showing that antigenic mimics were present in the phage display library, six open reading frames encoding putative Cowdria proteins were identified. All had similarities to, or motifs in common with, membrane proteins and are thus likely to be exposed to the host's humoral immune system. Some of the proteins identified were larger than the antigens used to elicit the antibodies used for selection, probably as a result of the presence of cross-reactive epitopes. Despite limitations experienced when extending a fragmented-gene approach for epitope location to genomes, it was possible to identify an antigenic region on MAP1 by comparison with selected mimics. In addition, binding peptide sequences were identified with two monoclonal antibodies that had been raised against non-Cowdria antigens. An epitope on the VP7 protein of bluetongue virus was identified and peptides were found that reacted with a monoclonal antibody directed against malignant catarrhal fever virus. Thus, apart from being able to identify several potentially important Cowdria epitopes and genes, the fragmented-genome library holds promise as a universal reagent for identifying useful mimics.
- Full Text:
- Date Issued: 2003
- Authors: Fehrsen, Jeanni
- Date: 2003
- Subjects: Bacteriophages -- Genetics Ruminants -- Diseases Heartwater
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:3920 , http://hdl.handle.net/10962/d1003979
- Description: The development of new and effective vaccines and immunodiagnostic reagents requires the characterisation of antigenically relevant proteins and their interactions with the products of the immune system. Phage display technology was investigated as a means of elucidating some of the antigenic properties of the rickettsial parasite, Cowdria ruminantium (Cowdria). Randomly fragmented gene-derived libraries have been useful in elucidating viral and other epitopes, but only limited work has been done with entire genomes. A phage display library expressing a repertoire of Cowdria peptides was constructed. It was sufficiently large to represent the organism's genome, but lacked phages displaying peptides coded for by genes containing a Pvu II restriction enzyme site, including the one coding for the major antigenic protein 1 (MAP1). This was considered advantageous since MAP1 is immunodominant and has already been well characterised. Affinity selection with antibodies against Cowdria proteins other than MAP1 allowed several antibody-reactive peptides to be isolated. These selected sequences were placed in the context of the genome by screening a lambda bacteriophage library and by comparison with Cowdria DNA sequences. Apart from showing that antigenic mimics were present in the phage display library, six open reading frames encoding putative Cowdria proteins were identified. All had similarities to, or motifs in common with, membrane proteins and are thus likely to be exposed to the host's humoral immune system. Some of the proteins identified were larger than the antigens used to elicit the antibodies used for selection, probably as a result of the presence of cross-reactive epitopes. Despite limitations experienced when extending a fragmented-gene approach for epitope location to genomes, it was possible to identify an antigenic region on MAP1 by comparison with selected mimics. In addition, binding peptide sequences were identified with two monoclonal antibodies that had been raised against non-Cowdria antigens. An epitope on the VP7 protein of bluetongue virus was identified and peptides were found that reacted with a monoclonal antibody directed against malignant catarrhal fever virus. Thus, apart from being able to identify several potentially important Cowdria epitopes and genes, the fragmented-genome library holds promise as a universal reagent for identifying useful mimics.
- Full Text:
- Date Issued: 2003
Language and value : the place of evaluation in linguistic theory
- Authors: Kilpert, Diana Mary
- Date: 2003
- Subjects: Linguistics -- Philosophy Systemic grammar Discourse analysis English language -- Standardization Linguistic analysis (Linguistics) Functionalism (Linguistics) Halliday, M. A. K. (Michael Alexander Kirkwood), 1925- Chomsky, Noam Labov, William Pinker, Steven, 1954- Harris, Roy, 1931-
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:2353 , http://hdl.handle.net/10962/d1002635
- Description: It is a central claim of modern linguistic theory that linguists do not prescribe, but describe language as it is, without pronouncing on correctness or judging one variety better than another. This attempt to exclude evaluation is motivated by a desire to be ' politically correct', which hinders objective analysis of language, and by an ill-advised imitation of the natural sciences, which obstructs the discipline's progress towards becoming a science in its own right. It involves linguists, as users of a valued variety, in self-deception and disingenuousness, distances them from the concerns of the ordinary language user, and betrays a failure to understand the involvement of social values in language, the nature of language itself, and the limits of linguistic science. On a wider scale, linguistics reflects society's devaluing and mechanisation of language. Despite growing concern expressed in the literature, and the incoherence that becomes apparent when linguists attempt to address social problems using a theory that regards language as an autonomous object, newcomers to the discipline continue to be taught that anti-prescriptivism is the natural corollary of a scientific approach to language. This thesis suggests that the way out of these difficulties is to rethink the meaning of ' theory' in linguistics. If we take the reflexivity of language seriously, building on M.A.K. Halliday's notion of 'linguistics as metaphor', we are reminded that a linguistic theory is made of language. Metalanguage must use the experiential and interpersonal meaning-making resources of everyday language. It follows that a linguistic theory cannot escape being evaluative, because evaluation is an inherent part of interpersonal meaning. If we fail to notice our own metalinguistic evaluation, this is because language disguises its evaluative meanings, or perhaps we are just not used to thinking of them as part of the grammar. To achieve clarity about the involvement of value in language, we need to turn our metalanguage back on itself - 'using the grammar to think with about the grammar' . Some ways of doing this are demonstrated here, turning the resources of systemic functional linguistics on linguists' own language. The circularity of this process should be seen not as a drawback but as a salutary reminder that linguistics is an interpretive rather than a discovery process. This knowledge should help us revalue language and make a place for evaluation in linguistic theory, paving the way for a socially responsible and productive linguistics.
- Full Text:
- Date Issued: 2003
- Authors: Kilpert, Diana Mary
- Date: 2003
- Subjects: Linguistics -- Philosophy Systemic grammar Discourse analysis English language -- Standardization Linguistic analysis (Linguistics) Functionalism (Linguistics) Halliday, M. A. K. (Michael Alexander Kirkwood), 1925- Chomsky, Noam Labov, William Pinker, Steven, 1954- Harris, Roy, 1931-
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:2353 , http://hdl.handle.net/10962/d1002635
- Description: It is a central claim of modern linguistic theory that linguists do not prescribe, but describe language as it is, without pronouncing on correctness or judging one variety better than another. This attempt to exclude evaluation is motivated by a desire to be ' politically correct', which hinders objective analysis of language, and by an ill-advised imitation of the natural sciences, which obstructs the discipline's progress towards becoming a science in its own right. It involves linguists, as users of a valued variety, in self-deception and disingenuousness, distances them from the concerns of the ordinary language user, and betrays a failure to understand the involvement of social values in language, the nature of language itself, and the limits of linguistic science. On a wider scale, linguistics reflects society's devaluing and mechanisation of language. Despite growing concern expressed in the literature, and the incoherence that becomes apparent when linguists attempt to address social problems using a theory that regards language as an autonomous object, newcomers to the discipline continue to be taught that anti-prescriptivism is the natural corollary of a scientific approach to language. This thesis suggests that the way out of these difficulties is to rethink the meaning of ' theory' in linguistics. If we take the reflexivity of language seriously, building on M.A.K. Halliday's notion of 'linguistics as metaphor', we are reminded that a linguistic theory is made of language. Metalanguage must use the experiential and interpersonal meaning-making resources of everyday language. It follows that a linguistic theory cannot escape being evaluative, because evaluation is an inherent part of interpersonal meaning. If we fail to notice our own metalinguistic evaluation, this is because language disguises its evaluative meanings, or perhaps we are just not used to thinking of them as part of the grammar. To achieve clarity about the involvement of value in language, we need to turn our metalanguage back on itself - 'using the grammar to think with about the grammar' . Some ways of doing this are demonstrated here, turning the resources of systemic functional linguistics on linguists' own language. The circularity of this process should be seen not as a drawback but as a salutary reminder that linguistics is an interpretive rather than a discovery process. This knowledge should help us revalue language and make a place for evaluation in linguistic theory, paving the way for a socially responsible and productive linguistics.
- Full Text:
- Date Issued: 2003
Metal interactions with neural substrates and their role in neurodegeneration
- Authors: Lack, Barbara Anne
- Date: 2003
- Subjects: Nervous system -- Degeneration Neurotoxicology Chemical reactions Metals -- Physiological effect Melatonin -- Physiological effect
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:4391 , http://hdl.handle.net/10962/d1005709
- Description: "Life" may be characterized as a controlled stationary flow equilibrium, maintained by energy consuming chemical reactions. The physiological functioning of these life systems include at least 28 of the elements isolated on the periodic table thus far, most of which are metals. However, as with Paracelsus Principle: "The dose makes the poison", there exists a definite link between metal levels, essential and toxic, and the onset of neurodegenerative diseases. The economic costs of brain dysfunction are enormous, but this pales in comparison to the staggering emotional toll on the victims themselves and their families. In an attempt to improve the understanding of the causes of neurodegeneration, this study focuses on one potential aspect: the possible link between metals and neurotransmitter homeostasis utilising a variety of electronanalytical techniques. Adsorptive cathodic stripping voltammetry was employed to investigate the binding affinities and complex formation of melatonin and its precursor serotonin with calcium, potassium, sodium, lithium and aluminium. The results showed that all the metals studied formed complexes with both pineal indoleamines. However, the stability and affmity of the ligands toward the various metals varied greatly. The study suggests a further role for melatonin, that of metalloregulator and possible metal detoxifier in the brain, the in vivo studies which followed will further substantiate this notion. This research additionally focused on the cholinergic system, in particular acetylcholine complex formation studies with mercury, lead, cadmium, copper and zinc using the adsorptive cathodic stripping voltammetry method. The formation and characterisation of a solid mercury-acetylcholine complex lent further strength to the in situ electrochemical complex formation observed. The results showed the preference of acetylcholine for environmentally toxic heavy metals (such as Cd²⁺) over those divalent cations that occur naturally in the body. The possible metalloregulatory role melatonin played in the three brain regIOns: cerebellum, cortex and corpus striatum of male Wistar rats was studied as an in vivo extension of the earlier in vitro studies. Anodic stripping voltammetry was employed to detect metal levels present. The results showed that daily injections of melatonin was responsible for significantly decreasing copper(I), cadmium(II) and lead(II) levels in various regions of the rat brain of those animals that had undergone a pinealectomy in comparison to the saline injected group having undergone the same treatment. Histological and electrochemical stripping techniques were applied to investigate the implications of high A1³⁺ levels in the brain regions, particularly the hippocampus. Melatonin showed signs of promise in indirect symptom alleviation and by significantly decreasing A1³⁺ levels in rats that had been dosed with melatonin prior to A1³⁺ treatments in comparison with the control groups. Finally a preliminary study outlining a method for the production of a calcium selective microelectrode was undertaken. Further work is still needed to optimise the microelectrode production as well as its possible applications. However, whilst the overall conclusions of this entire multidisciplinary study may indeed only be in effect one piece of a very large puzzle on neurodegenerative diseases, this piece will no doubt serve as a building block for further ideas and work in this field.
- Full Text:
- Date Issued: 2003
- Authors: Lack, Barbara Anne
- Date: 2003
- Subjects: Nervous system -- Degeneration Neurotoxicology Chemical reactions Metals -- Physiological effect Melatonin -- Physiological effect
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:4391 , http://hdl.handle.net/10962/d1005709
- Description: "Life" may be characterized as a controlled stationary flow equilibrium, maintained by energy consuming chemical reactions. The physiological functioning of these life systems include at least 28 of the elements isolated on the periodic table thus far, most of which are metals. However, as with Paracelsus Principle: "The dose makes the poison", there exists a definite link between metal levels, essential and toxic, and the onset of neurodegenerative diseases. The economic costs of brain dysfunction are enormous, but this pales in comparison to the staggering emotional toll on the victims themselves and their families. In an attempt to improve the understanding of the causes of neurodegeneration, this study focuses on one potential aspect: the possible link between metals and neurotransmitter homeostasis utilising a variety of electronanalytical techniques. Adsorptive cathodic stripping voltammetry was employed to investigate the binding affinities and complex formation of melatonin and its precursor serotonin with calcium, potassium, sodium, lithium and aluminium. The results showed that all the metals studied formed complexes with both pineal indoleamines. However, the stability and affmity of the ligands toward the various metals varied greatly. The study suggests a further role for melatonin, that of metalloregulator and possible metal detoxifier in the brain, the in vivo studies which followed will further substantiate this notion. This research additionally focused on the cholinergic system, in particular acetylcholine complex formation studies with mercury, lead, cadmium, copper and zinc using the adsorptive cathodic stripping voltammetry method. The formation and characterisation of a solid mercury-acetylcholine complex lent further strength to the in situ electrochemical complex formation observed. The results showed the preference of acetylcholine for environmentally toxic heavy metals (such as Cd²⁺) over those divalent cations that occur naturally in the body. The possible metalloregulatory role melatonin played in the three brain regIOns: cerebellum, cortex and corpus striatum of male Wistar rats was studied as an in vivo extension of the earlier in vitro studies. Anodic stripping voltammetry was employed to detect metal levels present. The results showed that daily injections of melatonin was responsible for significantly decreasing copper(I), cadmium(II) and lead(II) levels in various regions of the rat brain of those animals that had undergone a pinealectomy in comparison to the saline injected group having undergone the same treatment. Histological and electrochemical stripping techniques were applied to investigate the implications of high A1³⁺ levels in the brain regions, particularly the hippocampus. Melatonin showed signs of promise in indirect symptom alleviation and by significantly decreasing A1³⁺ levels in rats that had been dosed with melatonin prior to A1³⁺ treatments in comparison with the control groups. Finally a preliminary study outlining a method for the production of a calcium selective microelectrode was undertaken. Further work is still needed to optimise the microelectrode production as well as its possible applications. However, whilst the overall conclusions of this entire multidisciplinary study may indeed only be in effect one piece of a very large puzzle on neurodegenerative diseases, this piece will no doubt serve as a building block for further ideas and work in this field.
- Full Text:
- Date Issued: 2003
Metallophthalocyanine derivatives as catalysts for the detection of sulphur dioxide, cyanide, nitrite and amino acids
- Authors: Thamae, Mamothibe Amelia
- Date: 2003
- Subjects: Cyanides Nitric oxide Electrochemistry Nitrites Suplhur dioxide Amino acids
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:4295 , http://hdl.handle.net/10962/d1004542
- Description: Electrocatalytic reduction and oxidation of nitrite using cobalt phthalocyanine derivatives was studied. The detection limit of 1 x 10⁻¹° mol dm⁻³ was achieved when these molecules were employed as catalysts for nitrite detection. The mechanisms for nitrite catalysis were proposed. The position of the peripheral substituents on cobalt porphyrazines (related to cobalt phthalocyanines) affected the catalytic activity of these complexes. The highest activity for nitrite reduction was observed on the cobalt(II) 2,3-tetramethyltetrapyridinoporphyrazine ([CoTm-2,3-tppa]⁴⁺), with cobalt phthalocyanine showing the lowest activity, and the cobalt(II) 3,4- tetramethyltetrapyridinoporphyrazine ([CoTm-3,4-tppa]⁴⁺), showing intermediate behaviour. A mixture of a negatively charged cobalt(II) tetrasulfophthalocyanine ([Co¹¹TSPc]⁴⁻) and a positively charged [CoTm-3,4-tppa]⁴⁺ showed better activity for nitrite reduction than did the individual components. Cobalt porphyrazines lowered the potentials for nitrite reduction in that peaking was observed, as opposed to cobalt phthalocyanine, where only the increase in currents was observed without peaking. Using the cobalt phthalocyanine derivatives, nitrite can be reduced to ammonia with high current efficiency. A glassy carbon electrode modified with [Co¹¹TSPc]⁴⁻ was employed for the determination of nitrite. Nitrate had an insignificant effect on nitrite oxidation on these modified electrodes. Electrocatalytic determination of S0₂ was studied as a function of pH at a glassy carbon electrode modified with iron(II) tetrasulfophthalocaynine. It was found that depending on pH, S0₂.xH₂0, HS0₃⁻ and/or SO₃²⁻ are the main compounds in solution and that these compounds behave differently at the electrode surface. Detection limits ranging from 4.0 ± 0.1 x 10⁻⁵ to 7.5 ± 0.1 x 10⁻⁵ mol dm⁻³ depending on pH were observed. Similar results were obtained when cobalt(II) tetrasulfophthalocaynine was employed for S0₂ catalysis under the same experimental conditions. Cysteine and histidine determination using oxidation currents was performed on glassy carbon electrodes modified with [CoTm-3,4-tppa]⁴⁺ (represented as [CoTm-3,4-tppa]⁴⁺-GCE) in pH 7 Tris buffer. The detection limit of 1.0 x 10⁻⁵ mol dm⁻³ for cysteine and 2.24 x 10⁻⁷ mol dm⁻³ for histidine were obtained. Cyanide can be detected down to 1 x 10⁻¹¹ mol dm⁻³ using [CoTm-3,4-tppa]⁴⁺-GCE in pH 10.8 buffer. Cyanide and S0₂ coordinate to the [CoTSPc]⁴⁻ species. The coordination is accompanied by oxidation of the central Co(II) metal, forming a [Co¹¹¹CoTSPc]³⁻ species. The rate constants for cyanide coordination to the [Co¹¹TSPc]⁴⁻ complex are larger than those reported for the coordination of cyanide to FePc and RuPc complexes in non-aqueous media. Autoreduction of [Co¹¹Tmtppa]⁴⁺ occurred in the presence of either histidine or cysteine, with the formation of metal reduced species, [Co¹Tmtppa(-2)]³⁺. Nitric oxide and nitrite coordinate to the [Co¹¹Tmtppa]⁴⁺ species, without auto-reduction of this species, which was observed for cysteine or histidine. The use of [Co¹¹TSPc]⁴ resulted in improved rate of interaction with nitrite when compared to the [Co¹¹Tmtppa]⁴⁺ species.
- Full Text:
- Date Issued: 2003
- Authors: Thamae, Mamothibe Amelia
- Date: 2003
- Subjects: Cyanides Nitric oxide Electrochemistry Nitrites Suplhur dioxide Amino acids
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:4295 , http://hdl.handle.net/10962/d1004542
- Description: Electrocatalytic reduction and oxidation of nitrite using cobalt phthalocyanine derivatives was studied. The detection limit of 1 x 10⁻¹° mol dm⁻³ was achieved when these molecules were employed as catalysts for nitrite detection. The mechanisms for nitrite catalysis were proposed. The position of the peripheral substituents on cobalt porphyrazines (related to cobalt phthalocyanines) affected the catalytic activity of these complexes. The highest activity for nitrite reduction was observed on the cobalt(II) 2,3-tetramethyltetrapyridinoporphyrazine ([CoTm-2,3-tppa]⁴⁺), with cobalt phthalocyanine showing the lowest activity, and the cobalt(II) 3,4- tetramethyltetrapyridinoporphyrazine ([CoTm-3,4-tppa]⁴⁺), showing intermediate behaviour. A mixture of a negatively charged cobalt(II) tetrasulfophthalocyanine ([Co¹¹TSPc]⁴⁻) and a positively charged [CoTm-3,4-tppa]⁴⁺ showed better activity for nitrite reduction than did the individual components. Cobalt porphyrazines lowered the potentials for nitrite reduction in that peaking was observed, as opposed to cobalt phthalocyanine, where only the increase in currents was observed without peaking. Using the cobalt phthalocyanine derivatives, nitrite can be reduced to ammonia with high current efficiency. A glassy carbon electrode modified with [Co¹¹TSPc]⁴⁻ was employed for the determination of nitrite. Nitrate had an insignificant effect on nitrite oxidation on these modified electrodes. Electrocatalytic determination of S0₂ was studied as a function of pH at a glassy carbon electrode modified with iron(II) tetrasulfophthalocaynine. It was found that depending on pH, S0₂.xH₂0, HS0₃⁻ and/or SO₃²⁻ are the main compounds in solution and that these compounds behave differently at the electrode surface. Detection limits ranging from 4.0 ± 0.1 x 10⁻⁵ to 7.5 ± 0.1 x 10⁻⁵ mol dm⁻³ depending on pH were observed. Similar results were obtained when cobalt(II) tetrasulfophthalocaynine was employed for S0₂ catalysis under the same experimental conditions. Cysteine and histidine determination using oxidation currents was performed on glassy carbon electrodes modified with [CoTm-3,4-tppa]⁴⁺ (represented as [CoTm-3,4-tppa]⁴⁺-GCE) in pH 7 Tris buffer. The detection limit of 1.0 x 10⁻⁵ mol dm⁻³ for cysteine and 2.24 x 10⁻⁷ mol dm⁻³ for histidine were obtained. Cyanide can be detected down to 1 x 10⁻¹¹ mol dm⁻³ using [CoTm-3,4-tppa]⁴⁺-GCE in pH 10.8 buffer. Cyanide and S0₂ coordinate to the [CoTSPc]⁴⁻ species. The coordination is accompanied by oxidation of the central Co(II) metal, forming a [Co¹¹¹CoTSPc]³⁻ species. The rate constants for cyanide coordination to the [Co¹¹TSPc]⁴⁻ complex are larger than those reported for the coordination of cyanide to FePc and RuPc complexes in non-aqueous media. Autoreduction of [Co¹¹Tmtppa]⁴⁺ occurred in the presence of either histidine or cysteine, with the formation of metal reduced species, [Co¹Tmtppa(-2)]³⁺. Nitric oxide and nitrite coordinate to the [Co¹¹Tmtppa]⁴⁺ species, without auto-reduction of this species, which was observed for cysteine or histidine. The use of [Co¹¹TSPc]⁴ resulted in improved rate of interaction with nitrite when compared to the [Co¹¹Tmtppa]⁴⁺ species.
- Full Text:
- Date Issued: 2003
Metallophthalocyanines as photocatalysts for transformation of chlorophenols and self-assembled monolayers for electrochemical detection of thiols and cyanides
- Authors: Ozoemena, Kenneth Ikechukwu
- Date: 2003
- Subjects: Electrochemistry Cyanides Thiols Chlorophenols Photocatalysis
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:4089 , http://hdl.handle.net/10962/d1007709
- Description: Photochemical properties of sulphonated phthalocyanine complexes of aluminium, zinc, tin and silicon, and octa-carboxyphthalocyanine complexes of aluminium and zinc have been investigated. These water-soluble metallophthalocyanine (MPc) complexes, especially the sulphonated aluminium and zinc phthalocyanines, were found to be good photosensitisers for the transformation of the toxic mono-, tri- and penta-chlorophenols in aqueous solutions. The efficiency of MPc sensitiser towards photo-transformation of chlorophenols depends on its effectiveness to generate singlet oxygen as well as its photostability. Octa-substituted thiol-derivatised phthalocyanine complexes of cobalt, iron and zinc were synthesized and their spectral and electrochemical properties investigated. The photochemical properties ofthe zinc phthalocyanine complexes in non-aqueous solutions were comparable to those in literature. Ultrathin films of the octasubstituted thiol-derivatised phthalocyanine complexes of cobalt, iron and zinc were, for the first time, immobilized onto gold electrodes using the self-assembling technique. Surface electrochemistry indicates that the ultrathin films are surface-confined self-assembled monolayer (SAM) species. Gold electrodes modified with the redox-active SAMs of cobalt and iron phthalocyanine complexes proved to be potential electrochemical sensors for the detection of thiols (L-cysteine, homocysteine and penicillamine) and thiocyanate in aqueous solutions (pH 4). The limits of detection for the thiols and thiocyanate were in the range of ∼ 10⁻⁷ and 10⁻⁶ mol dm⁻³, respectively. The modification process was reproducible and the modified electrodes showed good stability and, if stored in pH 4 buffer solutions, could be used for the analysis of thiols and thiocyanate for about a month without the need for recalibration. Etching of gold marred electrochemical detection of cyanide with the MPc-SAM-modified gold electrodes. Interestingly, however, kinetic and equilibria studies revealed strong interaction of octabutylthiophthalocyaninatoiron (II), FeOBTPc, with cyanide in both DMF and DMSO solutions.
- Full Text:
- Date Issued: 2003
- Authors: Ozoemena, Kenneth Ikechukwu
- Date: 2003
- Subjects: Electrochemistry Cyanides Thiols Chlorophenols Photocatalysis
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:4089 , http://hdl.handle.net/10962/d1007709
- Description: Photochemical properties of sulphonated phthalocyanine complexes of aluminium, zinc, tin and silicon, and octa-carboxyphthalocyanine complexes of aluminium and zinc have been investigated. These water-soluble metallophthalocyanine (MPc) complexes, especially the sulphonated aluminium and zinc phthalocyanines, were found to be good photosensitisers for the transformation of the toxic mono-, tri- and penta-chlorophenols in aqueous solutions. The efficiency of MPc sensitiser towards photo-transformation of chlorophenols depends on its effectiveness to generate singlet oxygen as well as its photostability. Octa-substituted thiol-derivatised phthalocyanine complexes of cobalt, iron and zinc were synthesized and their spectral and electrochemical properties investigated. The photochemical properties ofthe zinc phthalocyanine complexes in non-aqueous solutions were comparable to those in literature. Ultrathin films of the octasubstituted thiol-derivatised phthalocyanine complexes of cobalt, iron and zinc were, for the first time, immobilized onto gold electrodes using the self-assembling technique. Surface electrochemistry indicates that the ultrathin films are surface-confined self-assembled monolayer (SAM) species. Gold electrodes modified with the redox-active SAMs of cobalt and iron phthalocyanine complexes proved to be potential electrochemical sensors for the detection of thiols (L-cysteine, homocysteine and penicillamine) and thiocyanate in aqueous solutions (pH 4). The limits of detection for the thiols and thiocyanate were in the range of ∼ 10⁻⁷ and 10⁻⁶ mol dm⁻³, respectively. The modification process was reproducible and the modified electrodes showed good stability and, if stored in pH 4 buffer solutions, could be used for the analysis of thiols and thiocyanate for about a month without the need for recalibration. Etching of gold marred electrochemical detection of cyanide with the MPc-SAM-modified gold electrodes. Interestingly, however, kinetic and equilibria studies revealed strong interaction of octabutylthiophthalocyaninatoiron (II), FeOBTPc, with cyanide in both DMF and DMSO solutions.
- Full Text:
- Date Issued: 2003
Molecular characterization of the tetratricopeptide repeat-mediated interactions of murine stress-inducible protein 1 with major heat shock proteins
- Authors: Odunuga, Odutayo Odutola
- Date: 2003
- Subjects: Plants -- Effect of stress on Proteins -- Purification Electrophoresis Heat shock proteins
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:4091 , http://hdl.handle.net/10962/d1007724
- Description: Murine stress-inducible protein 1 (mSTI1) is a co-chaperone that is homologous with the human heat shock protein 70 (Hsp70)/heat shock protein 90 (Hsp90)-organizing protein (Hop). The two proteins are homologues of the highly conserved stress-inducible protein 1 (STI1) family of co-chaperones. The STI1 proteins interact directly and simultaneously at some stage, with Hsp70 and Hsp90 in the formation of the hetero-multi-chaperone complexes that facilitate the folding of signal transducing kinases and functional maturation of steroid hormone receptors. The interactions of mSTI1 with both Hsp70 and Hsp90 is mediated by a versatile structural protein-protein interaction motif, the tetratricopeptide repeat (TPR). The TPR motif is a degenerate 34-amino acid sequence a-helical structural motif found in a significant number of functionally unrelated proteins. This study was aimed at characterizing the structural and functional determinants in the TPR domains of mSTI1 responsible for binding to and discriminating between Hsp70 and Hsp90. Guided by data from Hop's crystal structures and amino acid sequence alignment analyses, various biochemical techniques were used to both qualitatively and quantitatively characterize the contacts necessary for the N-terminal TPR domain (TPR1) of mSTI1 to bind to the C-terminal EEVD motif of heat shock cognate protein 70 (Hsc70) and to discriminate between Hsc70 and Hsp90. Substitutions in the first TPR motif of Lys⁸ or Asn¹² did not affect binding of mSTI1 to Hsc70, while double substitution of these residues abrogated binding. A substitution in the second TPR motif of Asn⁴³ lowered but did not abrogate binding. Similarly, a deletion in the second TPR motif coupled with a substitution of Lys⁸ or Asn¹² reduced but did not abrogate binding. Steady state fluorescence and circular dichroism spectroscopies revealed that the double substitution of Lys⁸ and Asn¹² resulted in perturbations of inter-domain interactions in mSTl1. Together these results suggest that mSTI1-Hsc70 interaction requires a network of electrostatic interactions not only between charged residues in the TPR1 domain of mSTI1 and the EEVD motif of Hsc70, but also outside the TPR1 domain. It is proposed that the electrostatic interactions in the first TPR motif collectively made by Lys⁸ and Asn¹² define part of the minimum interactions required for successful mSTI1-Hsc70 interaction. In the first central TPR domain (TPR1A), single substitution of Lys³°¹ was sufficient to abrogate the mSTI1-Hsp90 interaction. Using a truncated derivative of mSTI1 incapable of binding to Hsp90, residues predicted by crystallographic data to determine Hsp70 binding specificity were substituted in the TPR1 domain. The modified protein had reduced binding to Hsc70, but showed significant binding capacity for Hsp90. In contrast, topologically equivalent substitutions on a truncated derivative of mSTI1 incapable of binding to Hsc70 did not confer Hsc70 specificity on the TPR2A domain. These data suggest that binding of Hsc70 to the TPR1 domain is more specific than binding of Hsp90 to the TPR2A domain. In addition, residues C-terminal of helix A in the second TPR motif of mSTI1 were shown to be important in determining specific binding to Hsc70. Binding assays using surface plasmon resonance spectroscopy showed that the affinities of binding of mSTI1 to Hsc70 and Hsp90 were 2 μM and 1.5 μM respectively. Preliminary in vivo studies revealed differences in the dynamics of binding of endogenous and exogenous recombinant mSTI1 with Hsc70 and Hsp90. The outcome of this study poses serious implications for the mechanisms of mSTI1 interactions with Hsc70 and Hsp90 in the cell.
- Full Text:
- Date Issued: 2003
- Authors: Odunuga, Odutayo Odutola
- Date: 2003
- Subjects: Plants -- Effect of stress on Proteins -- Purification Electrophoresis Heat shock proteins
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:4091 , http://hdl.handle.net/10962/d1007724
- Description: Murine stress-inducible protein 1 (mSTI1) is a co-chaperone that is homologous with the human heat shock protein 70 (Hsp70)/heat shock protein 90 (Hsp90)-organizing protein (Hop). The two proteins are homologues of the highly conserved stress-inducible protein 1 (STI1) family of co-chaperones. The STI1 proteins interact directly and simultaneously at some stage, with Hsp70 and Hsp90 in the formation of the hetero-multi-chaperone complexes that facilitate the folding of signal transducing kinases and functional maturation of steroid hormone receptors. The interactions of mSTI1 with both Hsp70 and Hsp90 is mediated by a versatile structural protein-protein interaction motif, the tetratricopeptide repeat (TPR). The TPR motif is a degenerate 34-amino acid sequence a-helical structural motif found in a significant number of functionally unrelated proteins. This study was aimed at characterizing the structural and functional determinants in the TPR domains of mSTI1 responsible for binding to and discriminating between Hsp70 and Hsp90. Guided by data from Hop's crystal structures and amino acid sequence alignment analyses, various biochemical techniques were used to both qualitatively and quantitatively characterize the contacts necessary for the N-terminal TPR domain (TPR1) of mSTI1 to bind to the C-terminal EEVD motif of heat shock cognate protein 70 (Hsc70) and to discriminate between Hsc70 and Hsp90. Substitutions in the first TPR motif of Lys⁸ or Asn¹² did not affect binding of mSTI1 to Hsc70, while double substitution of these residues abrogated binding. A substitution in the second TPR motif of Asn⁴³ lowered but did not abrogate binding. Similarly, a deletion in the second TPR motif coupled with a substitution of Lys⁸ or Asn¹² reduced but did not abrogate binding. Steady state fluorescence and circular dichroism spectroscopies revealed that the double substitution of Lys⁸ and Asn¹² resulted in perturbations of inter-domain interactions in mSTl1. Together these results suggest that mSTI1-Hsc70 interaction requires a network of electrostatic interactions not only between charged residues in the TPR1 domain of mSTI1 and the EEVD motif of Hsc70, but also outside the TPR1 domain. It is proposed that the electrostatic interactions in the first TPR motif collectively made by Lys⁸ and Asn¹² define part of the minimum interactions required for successful mSTI1-Hsc70 interaction. In the first central TPR domain (TPR1A), single substitution of Lys³°¹ was sufficient to abrogate the mSTI1-Hsp90 interaction. Using a truncated derivative of mSTI1 incapable of binding to Hsp90, residues predicted by crystallographic data to determine Hsp70 binding specificity were substituted in the TPR1 domain. The modified protein had reduced binding to Hsc70, but showed significant binding capacity for Hsp90. In contrast, topologically equivalent substitutions on a truncated derivative of mSTI1 incapable of binding to Hsc70 did not confer Hsc70 specificity on the TPR2A domain. These data suggest that binding of Hsc70 to the TPR1 domain is more specific than binding of Hsp90 to the TPR2A domain. In addition, residues C-terminal of helix A in the second TPR motif of mSTI1 were shown to be important in determining specific binding to Hsc70. Binding assays using surface plasmon resonance spectroscopy showed that the affinities of binding of mSTI1 to Hsc70 and Hsp90 were 2 μM and 1.5 μM respectively. Preliminary in vivo studies revealed differences in the dynamics of binding of endogenous and exogenous recombinant mSTI1 with Hsc70 and Hsp90. The outcome of this study poses serious implications for the mechanisms of mSTI1 interactions with Hsc70 and Hsp90 in the cell.
- Full Text:
- Date Issued: 2003
Multivariate morphometric analysis and behaviour of honeybees (Apis Mellifera L.) in the southern regions of Ethiopia
- Authors: Amssalu, Argaw Bezabeh
- Date: 2003
- Subjects: Honeybee -- Ethiopia -- Behavior Honeybee -- Ethiopia
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:5616 , http://hdl.handle.net/10962/d1003130
- Description: Morphometric and behavioural characteristics of honeybees, Apis mellifera were analysed using multivariate and bivariate statistical methods to characterise honeybees of southern Ethiopian region. A total of 33800 morphometric character measurements were taken from 2600 individual worker honeybees of 130 honeybee colonies collected at 26 sampling localities with an average inter-locality distance of 89km to determine the occurrence of morphoclusters. 117 experienced farmer beekeepers and beekeeping experts were interviewed on pre-tested questionnaire to investigate the behavioural characteristics of these honeybees in their respective areas. Morphometric characters associated with pigmentation and body size exhibited a higher discriminant power while forewing venation angles (B4, N23 and 026) lack discriminatory power to segregate honeybees in the southern Ethiopian region. Principal components and discriminant analyses using the most discriminatory morphological characters delineated four statistically distinct morphoclusters in the southern Ethiopian region: the smallest and yellow honeybees, A. m. woyi-gambella which are different from all African honeybees, occur in the western and southern lowlands; the small and yellowiest honeybees, Apis mellifera jemenitica in the eastern escarpment; the largest and darkest honeybees, Apis mellifera bandasii in the central and eastern highlands; and dark honeybees, Apis mellifera scutellata in the wet tropical forests. High intracolonial and intercolonial variances within and between the boundaries of the honeybee groups were detected. The former suggests areas of ecological instability, while the latter areas of transitional or natural hybridisation zones. These areas are characterised by transitional ecological zones having intermediate climate and physiography. Even though honeybees of the southern Ethiopian region are generally dark and small, they show a high tendency to reproductive swarming, migration and aggressiveness, great variation in pigmentation, size and behaviour were observed both within and between the groups. A. m. jemenitica honeybees have a high propensity to migration and less a tendency for reproductive swarming. A. m. bandasii and A. m. scutellata have a high inclination to reproductive swarming and the former has a lesser and the later intermediate propensity to migration. A. m. woyi-gambella honeybees have intermediate swarming and migration tendencies. These results revealed that reproductive swarming and migration are higher in resource-rich and resource-poor areas respectively. Honey plants of the central highlands of Ethiopia are predominantly herbaceous in nature and mainly grow on open and cultivated lands. The bulk of pollen collected came comparatively from few genera. Strong correlation was observed between the intensities of flowering and rainfall. Reproductive swarming and migration occur during high and low intensity of flowering respectively.
- Full Text:
- Date Issued: 2003
- Authors: Amssalu, Argaw Bezabeh
- Date: 2003
- Subjects: Honeybee -- Ethiopia -- Behavior Honeybee -- Ethiopia
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:5616 , http://hdl.handle.net/10962/d1003130
- Description: Morphometric and behavioural characteristics of honeybees, Apis mellifera were analysed using multivariate and bivariate statistical methods to characterise honeybees of southern Ethiopian region. A total of 33800 morphometric character measurements were taken from 2600 individual worker honeybees of 130 honeybee colonies collected at 26 sampling localities with an average inter-locality distance of 89km to determine the occurrence of morphoclusters. 117 experienced farmer beekeepers and beekeeping experts were interviewed on pre-tested questionnaire to investigate the behavioural characteristics of these honeybees in their respective areas. Morphometric characters associated with pigmentation and body size exhibited a higher discriminant power while forewing venation angles (B4, N23 and 026) lack discriminatory power to segregate honeybees in the southern Ethiopian region. Principal components and discriminant analyses using the most discriminatory morphological characters delineated four statistically distinct morphoclusters in the southern Ethiopian region: the smallest and yellow honeybees, A. m. woyi-gambella which are different from all African honeybees, occur in the western and southern lowlands; the small and yellowiest honeybees, Apis mellifera jemenitica in the eastern escarpment; the largest and darkest honeybees, Apis mellifera bandasii in the central and eastern highlands; and dark honeybees, Apis mellifera scutellata in the wet tropical forests. High intracolonial and intercolonial variances within and between the boundaries of the honeybee groups were detected. The former suggests areas of ecological instability, while the latter areas of transitional or natural hybridisation zones. These areas are characterised by transitional ecological zones having intermediate climate and physiography. Even though honeybees of the southern Ethiopian region are generally dark and small, they show a high tendency to reproductive swarming, migration and aggressiveness, great variation in pigmentation, size and behaviour were observed both within and between the groups. A. m. jemenitica honeybees have a high propensity to migration and less a tendency for reproductive swarming. A. m. bandasii and A. m. scutellata have a high inclination to reproductive swarming and the former has a lesser and the later intermediate propensity to migration. A. m. woyi-gambella honeybees have intermediate swarming and migration tendencies. These results revealed that reproductive swarming and migration are higher in resource-rich and resource-poor areas respectively. Honey plants of the central highlands of Ethiopia are predominantly herbaceous in nature and mainly grow on open and cultivated lands. The bulk of pollen collected came comparatively from few genera. Strong correlation was observed between the intensities of flowering and rainfall. Reproductive swarming and migration occur during high and low intensity of flowering respectively.
- Full Text:
- Date Issued: 2003
NeGPAIM : a model for the proactive detection of information security intrusions, utilizing fuzzy logic and neural network techniques
- Authors: Botha, Martin
- Date: 2003
- Subjects: Computer security , Fuzzy logic , Neural networks (Computer science)
- Language: English
- Type: Thesis , Doctoral , DTech (Computer Studies)
- Identifier: vital:10792 , http://hdl.handle.net/10948/142 , Computer security , Fuzzy logic , Neural networks (Computer science)
- Description: “Information is the lifeblood of any organisation and everything an organisation does involves using information in some way” (Peppard, 1993, p.5). Therefore, it can be argued that information is an organisation’s most precious asset and as with all other assets, like equipment, money, personnel, and so on, this asset needs to be protected properly at all times (Whitman & Mattord, 2003, pp.1-14). The introduction of modern technologies, such as e-commerce, will not only increase the value of information, but will also increase security requirements of those organizations that are intending to utilize such technologies. Evidence of these requirements can be observed in the 2001 CSI/FBI Computer Crime and Security Survey (Power, 2001). According to this source, the annual financial losses caused through security breaches in 2001 have increased by 277% when compared to the results from 1997. The 2002 and 2003 Computer Crime and Security Survey confirms this by stating that the threat of computer crime and other related information security breaches continues unabated and that the financial toll is mounting (Richardson, 2003). Information is normally protected by means of a process of identifying, implementing, managing and maintaining a set of information security controls, countermeasures or safeguards (GMITS, 1998). In the rest of this thesis, the term security controls will be utilized when referring to information protection mechanisms or procedures. These security controls can be of a physical (for example, door locks), a technical (for example, passwords) and/or a procedural nature (for example, to make back-up copies of critical files)(Pfleeger, 2003, pp.22-23; Stallings, 1995, p.1). The effective identification, implementation, management and maintenance of this set of security controls are usually integrated into an Information Security Management Program, the objective of which is to ensure an acceptable level of information confidentiality, integrity and availability within the organisation at all times (Pfleeger, 2003, pp.10-12; Whitman & Mattord, 2003, pp.1-14; Von Solms, 1993). Once the most effective security controls have been identified and implemented, it is important that this level of security be maintained through a process of continued control. For this reason, it is important that proper change management, measurement, audit, monitoring and detection be implemented (Bruce & Dempsey, 1997). Monitoring and detection are important functions and refer to the ability to identify and detect situations where information security policies have been compromised and/or breached or security violations have taken place (BS 7799, 1999; GMITS, 1998; Von Solms, 1993). The Information Security Officer is usually the person responsible for most of the operational tasks in the control process within an Information Security Management Program (Von Solms, 1993). In practice, these tasks could also be performed by a system administrator, network administrator, etc. In the rest of the thesis the person responsible for these tasks will be referred to as system administrator. These tasks have proved to be very challenging and demanding. The main reason for this is the rapid advancement of technology in the discipline of Information Technology, for example, the modern distributed computing environment, the Internet, the “freedom” of end-users, the introduction of e-commerce, and etc. (Whitman & Mattord, 2003, p.9; Sundaram, 2000, p.1; Moses, 2001, p.6; Allen, 2001, p.1). As a result of the importance of this control process, and especially the monitoring and detection tasks, it is vital that the system administrator has proper tools at his/her disposal to perform this task effectively. Many of the tools that are currently available to the system administrator, utilize technical controls, such as, audit logs and user profiles. Audit logs are normally used to record all events executed on a system. These logs are simply files that record security and non-security related events that take place on a computer system within an organisation. For this reason, these logs can be used by these tools to gain valuable information on security violations, such as intrusions and, therefore, are able to monitor the current actions of each user (Microsoft, 2002; Smith, 1989, pp. 116-117). User profiles are files that contain information about users` desktop operating environments and are used by the operating system to structure each user environment so that it is the same each time a user logs onto the system (Microsoft, 2002; Block, 1994, p.54). Thus, a user profile is used to indicate which actions the user is allowed to perform on the system. Both technical controls (audit logs and user profiles) are frequently available in most computer environments (such as, UNIX, Firewalls, Windows, etc.) (Cooper et al, 1995, p.129). Therefore, seeing that the audit logs record most events taking place on an information system and the user profile indicates the authorized actions of each user, the system administrator could most probably utilise these controls in a more proactive manner.
- Full Text:
- Date Issued: 2003
- Authors: Botha, Martin
- Date: 2003
- Subjects: Computer security , Fuzzy logic , Neural networks (Computer science)
- Language: English
- Type: Thesis , Doctoral , DTech (Computer Studies)
- Identifier: vital:10792 , http://hdl.handle.net/10948/142 , Computer security , Fuzzy logic , Neural networks (Computer science)
- Description: “Information is the lifeblood of any organisation and everything an organisation does involves using information in some way” (Peppard, 1993, p.5). Therefore, it can be argued that information is an organisation’s most precious asset and as with all other assets, like equipment, money, personnel, and so on, this asset needs to be protected properly at all times (Whitman & Mattord, 2003, pp.1-14). The introduction of modern technologies, such as e-commerce, will not only increase the value of information, but will also increase security requirements of those organizations that are intending to utilize such technologies. Evidence of these requirements can be observed in the 2001 CSI/FBI Computer Crime and Security Survey (Power, 2001). According to this source, the annual financial losses caused through security breaches in 2001 have increased by 277% when compared to the results from 1997. The 2002 and 2003 Computer Crime and Security Survey confirms this by stating that the threat of computer crime and other related information security breaches continues unabated and that the financial toll is mounting (Richardson, 2003). Information is normally protected by means of a process of identifying, implementing, managing and maintaining a set of information security controls, countermeasures or safeguards (GMITS, 1998). In the rest of this thesis, the term security controls will be utilized when referring to information protection mechanisms or procedures. These security controls can be of a physical (for example, door locks), a technical (for example, passwords) and/or a procedural nature (for example, to make back-up copies of critical files)(Pfleeger, 2003, pp.22-23; Stallings, 1995, p.1). The effective identification, implementation, management and maintenance of this set of security controls are usually integrated into an Information Security Management Program, the objective of which is to ensure an acceptable level of information confidentiality, integrity and availability within the organisation at all times (Pfleeger, 2003, pp.10-12; Whitman & Mattord, 2003, pp.1-14; Von Solms, 1993). Once the most effective security controls have been identified and implemented, it is important that this level of security be maintained through a process of continued control. For this reason, it is important that proper change management, measurement, audit, monitoring and detection be implemented (Bruce & Dempsey, 1997). Monitoring and detection are important functions and refer to the ability to identify and detect situations where information security policies have been compromised and/or breached or security violations have taken place (BS 7799, 1999; GMITS, 1998; Von Solms, 1993). The Information Security Officer is usually the person responsible for most of the operational tasks in the control process within an Information Security Management Program (Von Solms, 1993). In practice, these tasks could also be performed by a system administrator, network administrator, etc. In the rest of the thesis the person responsible for these tasks will be referred to as system administrator. These tasks have proved to be very challenging and demanding. The main reason for this is the rapid advancement of technology in the discipline of Information Technology, for example, the modern distributed computing environment, the Internet, the “freedom” of end-users, the introduction of e-commerce, and etc. (Whitman & Mattord, 2003, p.9; Sundaram, 2000, p.1; Moses, 2001, p.6; Allen, 2001, p.1). As a result of the importance of this control process, and especially the monitoring and detection tasks, it is vital that the system administrator has proper tools at his/her disposal to perform this task effectively. Many of the tools that are currently available to the system administrator, utilize technical controls, such as, audit logs and user profiles. Audit logs are normally used to record all events executed on a system. These logs are simply files that record security and non-security related events that take place on a computer system within an organisation. For this reason, these logs can be used by these tools to gain valuable information on security violations, such as intrusions and, therefore, are able to monitor the current actions of each user (Microsoft, 2002; Smith, 1989, pp. 116-117). User profiles are files that contain information about users` desktop operating environments and are used by the operating system to structure each user environment so that it is the same each time a user logs onto the system (Microsoft, 2002; Block, 1994, p.54). Thus, a user profile is used to indicate which actions the user is allowed to perform on the system. Both technical controls (audit logs and user profiles) are frequently available in most computer environments (such as, UNIX, Firewalls, Windows, etc.) (Cooper et al, 1995, p.129). Therefore, seeing that the audit logs record most events taking place on an information system and the user profile indicates the authorized actions of each user, the system administrator could most probably utilise these controls in a more proactive manner.
- Full Text:
- Date Issued: 2003
On the use of metabolic rate measurements to assess the stress response in juvenile spotted grunter, Pomadasys commersonnii (Haemulidae, Pisces)
- Authors: Radull, John
- Date: 2003
- Subjects: Fishes -- Metabolism Fishes -- Physiology Pomadasys -- Physiology Grunts (Fishes) -- Physiology Stress (Psychology) Stress (Physiology)
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:5350 , http://hdl.handle.net/10962/d1007564
- Description: Quantitication of stress requires the use of a stress indicator that is easy to measure, and which can be readily interpreted in terms of the potential long-term effects to an organism. This study evaluates the suitability of metabolic rate as an indicator of the stress response in fish. By comparing the metabolic with the cortisol stress response, the most commonly used indicator of stress in fish, it was possible to assess the suitability of metabolic rate as a stress indicator. Changes in metabolic rate were used to predict the long-term effects of transport-related stressors. This study also detennined the baseline metabolic rates of the tish. The standard and the active metabolic rates of juvenile P. cummersonnii were 0.16 ± 0.02 (mean ± S.D, n = 6) mg O₂g⁻¹h⁻¹, and 0.56 ± 0.04 mg O₂g⁻¹h⁻¹, respectively, whereas the routine metabolic rate for the fish was 0.25 ± 0.03 mg O₂g⁻¹h¹. The relationship between metabolic rate and body weight was described by the equation ϺO₂ = 0.64 W⁻°·³⁸. 24-h oxygen consumption measurements showed that juvenile P. commersonnii exhibited diel rhythmicity in oxygen consumption rate, the higher rates occurring at night and the lower rates during the daytime. The higher nocturnal metabolic activity may have been due to increased activity induced by an endogenous rhythm related to feeding. Diel rhythmicity has direct implications for the measurement of baseline metabolic rates since it could result in overestimation or underestimation of these rates. 24-h continuous oxygen consumption measurements enabled the detection of the rhythmicity in oxygen consumption rate, and thereby ensured a greater degree of accuracy in the estimation of these parameters. The metabolic stress response in juvenile P. commersonnii was best described by the equation, y = -0.0013 x² + 0.0364 x ÷ 0.3052, where x = time after application of stressor, and y = oxygen consumption rate. Using the derivative of this equation, the metabolic stress response was estimated to peak approximately 14 min after application of a simulated capture and handling stressor. Oxygen consumption increased by about 300 % as a result of the stress. Approximately 15 min after application of a similar stressor, plasma cortisol levels in stressed fish was 200 % higher than baseline levels. However, cortisol levels in fish sampled 30 min after the disturbance was similar to the baseline cortisol levels, indicating that full recovery had occurred. Although the patterns in the metabolic and cortisol stress responses were similar, metabolic rate could be measured continuously, thereby ensuring accurate interpretation of the data. Furthermore, increases in metabolic rate during the stress response are a culmination of physiological events from the primary to the tertiary levels of biological organization and are, therefore, easier to interpret in terms of long-term effects on the fish. Different transportation procedures elicited variable degrees of stress in juvenile P. commersonnii. The cost of metabolism attributed to the effects of capture and handling was twice as much as that attributed to acute temperature elevation. Acute temperature decrease resulted in a signiticant reduction in the oxygen consumption rate (ANOVA, P < 0.05). Oxygen consumption by the fish was not affected by fish density (ANOVA: F = 2.002, P = 0.5), or by oxygen depletion at dissolved oxygen concentrations above the critical level. Below this level, however, oxygen consumption decreased linearly with further decrease in dissolved oxygen concentration. These results showed that the highest energetic cost to juvenile P. commersonnii was incurred as a result of capture and handling. The results also showed that by subjecting fish to different stressors, it was possible to categorize them according to their relative metabolic costs to the fish. At 25º C, the effective concentration of 2-phenoxyethanol to fully anaesthetize (Stage IV, McFarland 1960) juvenile P. commersonnii was 0.4 ml l⁻¹ and the most appropriate concentration for deep sedation (Stage II, McFarland 1960) of the fish for at least 24 h was 0.2 ml l⁻¹. A maximum of 3 minutes was required by the fish to recover from the effects of the anaesthetic. There was no correlation between fish weight and the rate of induction of anaesthesia (r² = 0.001, p = 0.3). At the peak of the metabolic stress response, oxygen consumption was twice as high in the un-anaesthetized fish compared to the fish anaesthetized after the application of the simulated capture and handling stressor, suggesting that anaesthetization with 2-phenoxyethanol may have reduced the effect of the disturbance on the fish. Similar oxygen consumption rates for the fish anaesthetized prior to capture and the non-stressed fish suggested that the increases in metabolic rate could be linked to the struggling associated with attempts by fish to escape from the perceived stressor. Anaesthetization of juvenile P. commersonnii with 0.3 ml l⁻¹ 2-phenoxyethanol resulted in a more than 200 % increase in plasma cortisol concentration. The elevated levels of plasma cortisol in the anaesthetized fish suggested a manifestation of 2-phenoxyethanol as a stressor. At the time of capture, cortisol levels in fish that were anaesthetized prior to capture were the same as those measured in the disturbed fish at the peak of the stress response (ANOVA, p = 0.95), suggesting that the anaesthetized fish were already experiencing considerable stress at the time they were captured. Undisturbed juvenile P. commersonnii that were anaesthetized for 1 h also had cortisol levels that were five times higher than those measured in undisturbed-unanaesthetized fish, indicating that the duration of exposure to the anaesthetic had a significant effect on plasma cortisol levels. The results presented in this study demonstrate the usefulness of metabolic rate as an indicator of acute stress in fish. This was achieved by comparing the metabolic and the cortisol stress responses. The ease and accuracy with which oxygen consumption of fish could be measured made it possible to measure the stress response more accurately than by plasma cortisol concentration. It was also possible to monitor metabolic rate continuously over a long duration using polarographic oxygen sensors, thus enabling a better evaluation of the stress response. These results, thus, suggest that metabolic rate measurements could be a more practical way to quantify the effects of acute stressors on juvenile fishes. By detailing the profile of the metabolic stress response in P. commersonnii, this study makes a contribution towards understanding the physiological effects of stress in fishes. The study also contributes towards the quantification of baseline metabolic rates of this species under captivity. This study also contributes towards understanding the effects of 2-phenoxyethanol on the stress physiology of fish. By anaesthetizing fish under different conditions of stress, it was possible to evaluate the effect of 2-phenoxyethanol on the metabolic stress response. The ability of 2-phenoxyethanol to reduce physical activity of the fish, and thereby reduce the impact of acute stress on the metabolic stress response, makes it a good agent for the mitigation of stress during the capture and handling of fish. However, the increase in plasma cortisol concentration during prolonged anaesthetization using this drug suggests that the anaesthetic might be a stressor to fish and may, therefore, not be suitable for long-term sedation.
- Full Text:
- Date Issued: 2003
- Authors: Radull, John
- Date: 2003
- Subjects: Fishes -- Metabolism Fishes -- Physiology Pomadasys -- Physiology Grunts (Fishes) -- Physiology Stress (Psychology) Stress (Physiology)
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:5350 , http://hdl.handle.net/10962/d1007564
- Description: Quantitication of stress requires the use of a stress indicator that is easy to measure, and which can be readily interpreted in terms of the potential long-term effects to an organism. This study evaluates the suitability of metabolic rate as an indicator of the stress response in fish. By comparing the metabolic with the cortisol stress response, the most commonly used indicator of stress in fish, it was possible to assess the suitability of metabolic rate as a stress indicator. Changes in metabolic rate were used to predict the long-term effects of transport-related stressors. This study also detennined the baseline metabolic rates of the tish. The standard and the active metabolic rates of juvenile P. cummersonnii were 0.16 ± 0.02 (mean ± S.D, n = 6) mg O₂g⁻¹h⁻¹, and 0.56 ± 0.04 mg O₂g⁻¹h⁻¹, respectively, whereas the routine metabolic rate for the fish was 0.25 ± 0.03 mg O₂g⁻¹h¹. The relationship between metabolic rate and body weight was described by the equation ϺO₂ = 0.64 W⁻°·³⁸. 24-h oxygen consumption measurements showed that juvenile P. commersonnii exhibited diel rhythmicity in oxygen consumption rate, the higher rates occurring at night and the lower rates during the daytime. The higher nocturnal metabolic activity may have been due to increased activity induced by an endogenous rhythm related to feeding. Diel rhythmicity has direct implications for the measurement of baseline metabolic rates since it could result in overestimation or underestimation of these rates. 24-h continuous oxygen consumption measurements enabled the detection of the rhythmicity in oxygen consumption rate, and thereby ensured a greater degree of accuracy in the estimation of these parameters. The metabolic stress response in juvenile P. commersonnii was best described by the equation, y = -0.0013 x² + 0.0364 x ÷ 0.3052, where x = time after application of stressor, and y = oxygen consumption rate. Using the derivative of this equation, the metabolic stress response was estimated to peak approximately 14 min after application of a simulated capture and handling stressor. Oxygen consumption increased by about 300 % as a result of the stress. Approximately 15 min after application of a similar stressor, plasma cortisol levels in stressed fish was 200 % higher than baseline levels. However, cortisol levels in fish sampled 30 min after the disturbance was similar to the baseline cortisol levels, indicating that full recovery had occurred. Although the patterns in the metabolic and cortisol stress responses were similar, metabolic rate could be measured continuously, thereby ensuring accurate interpretation of the data. Furthermore, increases in metabolic rate during the stress response are a culmination of physiological events from the primary to the tertiary levels of biological organization and are, therefore, easier to interpret in terms of long-term effects on the fish. Different transportation procedures elicited variable degrees of stress in juvenile P. commersonnii. The cost of metabolism attributed to the effects of capture and handling was twice as much as that attributed to acute temperature elevation. Acute temperature decrease resulted in a signiticant reduction in the oxygen consumption rate (ANOVA, P < 0.05). Oxygen consumption by the fish was not affected by fish density (ANOVA: F = 2.002, P = 0.5), or by oxygen depletion at dissolved oxygen concentrations above the critical level. Below this level, however, oxygen consumption decreased linearly with further decrease in dissolved oxygen concentration. These results showed that the highest energetic cost to juvenile P. commersonnii was incurred as a result of capture and handling. The results also showed that by subjecting fish to different stressors, it was possible to categorize them according to their relative metabolic costs to the fish. At 25º C, the effective concentration of 2-phenoxyethanol to fully anaesthetize (Stage IV, McFarland 1960) juvenile P. commersonnii was 0.4 ml l⁻¹ and the most appropriate concentration for deep sedation (Stage II, McFarland 1960) of the fish for at least 24 h was 0.2 ml l⁻¹. A maximum of 3 minutes was required by the fish to recover from the effects of the anaesthetic. There was no correlation between fish weight and the rate of induction of anaesthesia (r² = 0.001, p = 0.3). At the peak of the metabolic stress response, oxygen consumption was twice as high in the un-anaesthetized fish compared to the fish anaesthetized after the application of the simulated capture and handling stressor, suggesting that anaesthetization with 2-phenoxyethanol may have reduced the effect of the disturbance on the fish. Similar oxygen consumption rates for the fish anaesthetized prior to capture and the non-stressed fish suggested that the increases in metabolic rate could be linked to the struggling associated with attempts by fish to escape from the perceived stressor. Anaesthetization of juvenile P. commersonnii with 0.3 ml l⁻¹ 2-phenoxyethanol resulted in a more than 200 % increase in plasma cortisol concentration. The elevated levels of plasma cortisol in the anaesthetized fish suggested a manifestation of 2-phenoxyethanol as a stressor. At the time of capture, cortisol levels in fish that were anaesthetized prior to capture were the same as those measured in the disturbed fish at the peak of the stress response (ANOVA, p = 0.95), suggesting that the anaesthetized fish were already experiencing considerable stress at the time they were captured. Undisturbed juvenile P. commersonnii that were anaesthetized for 1 h also had cortisol levels that were five times higher than those measured in undisturbed-unanaesthetized fish, indicating that the duration of exposure to the anaesthetic had a significant effect on plasma cortisol levels. The results presented in this study demonstrate the usefulness of metabolic rate as an indicator of acute stress in fish. This was achieved by comparing the metabolic and the cortisol stress responses. The ease and accuracy with which oxygen consumption of fish could be measured made it possible to measure the stress response more accurately than by plasma cortisol concentration. It was also possible to monitor metabolic rate continuously over a long duration using polarographic oxygen sensors, thus enabling a better evaluation of the stress response. These results, thus, suggest that metabolic rate measurements could be a more practical way to quantify the effects of acute stressors on juvenile fishes. By detailing the profile of the metabolic stress response in P. commersonnii, this study makes a contribution towards understanding the physiological effects of stress in fishes. The study also contributes towards the quantification of baseline metabolic rates of this species under captivity. This study also contributes towards understanding the effects of 2-phenoxyethanol on the stress physiology of fish. By anaesthetizing fish under different conditions of stress, it was possible to evaluate the effect of 2-phenoxyethanol on the metabolic stress response. The ability of 2-phenoxyethanol to reduce physical activity of the fish, and thereby reduce the impact of acute stress on the metabolic stress response, makes it a good agent for the mitigation of stress during the capture and handling of fish. However, the increase in plasma cortisol concentration during prolonged anaesthetization using this drug suggests that the anaesthetic might be a stressor to fish and may, therefore, not be suitable for long-term sedation.
- Full Text:
- Date Issued: 2003
Predictive modelling of species' potential geographical distributions
- Authors: Robertson, Mark Peter
- Date: 2003
- Subjects: Alien plants -- South Africa -- Geographical distribution Species -- Geographical distribution -- Mathematical models Cicadas -- South Africa -- Geographical distribution Scaevola plumieri -- South Africa -- Geographical distribution
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:5816 , http://hdl.handle.net/10962/d1007189
- Description: Models that are used for predicting species' potential distributions are important tools that have found applications in a number of areas of applied ecology. The majority of these models can be classified as correlative, as they rely on strong, often indirect, links between species distribution records and environmental predictor variables to make predictions. Correlative models are an alternative to more complex mechanistic models that attempt to simulate the mechanisms considered to underlie the observed correlations with environmental attributes. This study explores the influence of the type and quality of the data used to calibrate correlative models. In terms of data type, the most popular techniques in use are group discrimination techniques, those that use both presence and absence locality data to make predictions. However, for many organisms absence data are either not available or are considered to be unreliable. As the available range of profile techniques (those using presence only data) appeared to be limited, new profile techniques were investigated and evaluated. A new profile modelling technique based on fuzzy classification (the Fuzzy Envelope Model) was developed and implemented. A second profile technique based on Principal Components Analysis was implemented and evaluated. Based on quantitative model evaluation tests, both of these techniques performed well and show considerable promise. In terms of data quality, the effects on model performance of false absence records, the number of locality records (sample size) and the proportion of localities representing species presence (prevalence) in samples were investigated for logistic regression distribution models. Sample size and prevalence both had a significant effect on model performance. False absence records had a significant influence on model performance, which was affected by sample size. A quantitative comparison of the performance of selected profile models and group discrimination modelling techniques suggests that different techniques may be more successful for predicting distributions for particular species or types of organism than others. The results also suggest that several different model design! sample size combinations are capable of making predictions that will on average not differ significantly in performance for a particular species. A further quantitative comparison among modelling techniques suggests that correlative techniques can perform as well as simple mechanistic techniques for predicting potential distributions.
- Full Text:
- Date Issued: 2003
- Authors: Robertson, Mark Peter
- Date: 2003
- Subjects: Alien plants -- South Africa -- Geographical distribution Species -- Geographical distribution -- Mathematical models Cicadas -- South Africa -- Geographical distribution Scaevola plumieri -- South Africa -- Geographical distribution
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:5816 , http://hdl.handle.net/10962/d1007189
- Description: Models that are used for predicting species' potential distributions are important tools that have found applications in a number of areas of applied ecology. The majority of these models can be classified as correlative, as they rely on strong, often indirect, links between species distribution records and environmental predictor variables to make predictions. Correlative models are an alternative to more complex mechanistic models that attempt to simulate the mechanisms considered to underlie the observed correlations with environmental attributes. This study explores the influence of the type and quality of the data used to calibrate correlative models. In terms of data type, the most popular techniques in use are group discrimination techniques, those that use both presence and absence locality data to make predictions. However, for many organisms absence data are either not available or are considered to be unreliable. As the available range of profile techniques (those using presence only data) appeared to be limited, new profile techniques were investigated and evaluated. A new profile modelling technique based on fuzzy classification (the Fuzzy Envelope Model) was developed and implemented. A second profile technique based on Principal Components Analysis was implemented and evaluated. Based on quantitative model evaluation tests, both of these techniques performed well and show considerable promise. In terms of data quality, the effects on model performance of false absence records, the number of locality records (sample size) and the proportion of localities representing species presence (prevalence) in samples were investigated for logistic regression distribution models. Sample size and prevalence both had a significant effect on model performance. False absence records had a significant influence on model performance, which was affected by sample size. A quantitative comparison of the performance of selected profile models and group discrimination modelling techniques suggests that different techniques may be more successful for predicting distributions for particular species or types of organism than others. The results also suggest that several different model design! sample size combinations are capable of making predictions that will on average not differ significantly in performance for a particular species. A further quantitative comparison among modelling techniques suggests that correlative techniques can perform as well as simple mechanistic techniques for predicting potential distributions.
- Full Text:
- Date Issued: 2003
Pyrroloiminoquinone metabolites from South African Latrunculid sponges
- Authors: Antunes, Edith Martins
- Date: 2003
- Subjects: Sponges -- South Africa PQQ (Biochemistry) Marine metabolites -- South Africa
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:4340 , http://hdl.handle.net/10962/d1005001
- Description: An in depth chemical investigation of the major and minor pyrroloiminoquinone metabolites produced by four species of endemic South African Latrunculid sponges, collected from Algoa Bay and the Tsitsikamma Marine Reserve off the south eastern coast of South Africa, yielded eleven new and twelve known pyrroloiminoquinone metabolites. The structures of the new metabolites were determined using standard spectroscopic techniques. Tsitsikamma pedunculata was shown to contain 7,8-dehydro-3-dihydro-discorhabdin C (2.1), 14-bromo-7,8-dehydro-3-dihydro-discorhabdin C (2.2), discorhabdin S (2.3), 14-bromo-1-hydroxy-discorhabdin S (2.4), 1-bromo-2-hydroxy-4-debromo-discorhabdin S (2.5), and 2,4-debromo-3-dihydro-discorhabdin C (2.6), together with the known compounds 14-bromo-discorhabdin C (1.51), 14-bromo-3-dihydro-discorhabdin C (1.52) and 3-dihydro-discorhabdin C. The metabolites from T. pedunculata were characterised by the presence of a reduced C-3 carbonyl and bromination at C-14. Compounds isolated from a second Latrunculid sponge, Latrunculia lorii, ranged from a substituted bicyclic pyrrolecarboxylic acid, makaluvic acid A (1.47), to the simple tricyclic known pyrroloiminoquinones makaluvamine C (1.33) and damirone B (1.20) and the more complex discorhabdin D type metabolites, discorhabdin M (3.2), 1-amino discorhabdin D (3.3), 1-methoxy discorhabdin D (3.4) and 1-alanyl discorhabdin D (3.5). Discorhabdin G* (3.1) was also isolated and characterised. This is the first reported occurrence of the known compounds 1.20, 1.33 and 1.47 in a Latrunculia sponge. Discorhabdin and bis-pyrroloiminoquinone type compounds predominated in Tsitsikamma favus. Three known, tsitsikammamines A (1.71) and B (1.72), 1.52, and five new pyrroloiminoquinones, tsitsikammamine N-oxime (4.1), tsitsikammamine B N-oxime (4.2), 2.1, 2.4 and 2.6, were isolated from this sponge. A fourth Latrunculid sponge (Strongylodesma sp.) yielded three known compounds, discorhabdins A (1.57), D (1.61) and 1.53, and one new pyrroloiminoquinone 3.3. The dual role of these metabolites as cytotoxic agents and pigments resulted in an attempt to relate the photochemical properties of these metabolites to their cytotoxicity. The pyrroloiminoquinone metabolites studied exhibited moderate singlet oxygen quantum yields, while three compounds (1.57, 4.1 and 4.2) were shown to be capable of producing radicals at a wavelength of 532 nm. The possibility of a correlation between the electrochemical properties and anti-cancer (HCT-116) activity of selected pyrroloiminoquinones was explored. A study of the oesophageal and ovarian cytotoxicities of two pyrroloiminoquinones (1.57 and 1.72), together with an investigation into the intercalation and topoisomerase I inhibitory activity of the bis-pyrroloiminoquinones (1.71, 1.72, 4.1 and 4.2), are presented.
- Full Text:
- Date Issued: 2003
- Authors: Antunes, Edith Martins
- Date: 2003
- Subjects: Sponges -- South Africa PQQ (Biochemistry) Marine metabolites -- South Africa
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:4340 , http://hdl.handle.net/10962/d1005001
- Description: An in depth chemical investigation of the major and minor pyrroloiminoquinone metabolites produced by four species of endemic South African Latrunculid sponges, collected from Algoa Bay and the Tsitsikamma Marine Reserve off the south eastern coast of South Africa, yielded eleven new and twelve known pyrroloiminoquinone metabolites. The structures of the new metabolites were determined using standard spectroscopic techniques. Tsitsikamma pedunculata was shown to contain 7,8-dehydro-3-dihydro-discorhabdin C (2.1), 14-bromo-7,8-dehydro-3-dihydro-discorhabdin C (2.2), discorhabdin S (2.3), 14-bromo-1-hydroxy-discorhabdin S (2.4), 1-bromo-2-hydroxy-4-debromo-discorhabdin S (2.5), and 2,4-debromo-3-dihydro-discorhabdin C (2.6), together with the known compounds 14-bromo-discorhabdin C (1.51), 14-bromo-3-dihydro-discorhabdin C (1.52) and 3-dihydro-discorhabdin C. The metabolites from T. pedunculata were characterised by the presence of a reduced C-3 carbonyl and bromination at C-14. Compounds isolated from a second Latrunculid sponge, Latrunculia lorii, ranged from a substituted bicyclic pyrrolecarboxylic acid, makaluvic acid A (1.47), to the simple tricyclic known pyrroloiminoquinones makaluvamine C (1.33) and damirone B (1.20) and the more complex discorhabdin D type metabolites, discorhabdin M (3.2), 1-amino discorhabdin D (3.3), 1-methoxy discorhabdin D (3.4) and 1-alanyl discorhabdin D (3.5). Discorhabdin G* (3.1) was also isolated and characterised. This is the first reported occurrence of the known compounds 1.20, 1.33 and 1.47 in a Latrunculia sponge. Discorhabdin and bis-pyrroloiminoquinone type compounds predominated in Tsitsikamma favus. Three known, tsitsikammamines A (1.71) and B (1.72), 1.52, and five new pyrroloiminoquinones, tsitsikammamine N-oxime (4.1), tsitsikammamine B N-oxime (4.2), 2.1, 2.4 and 2.6, were isolated from this sponge. A fourth Latrunculid sponge (Strongylodesma sp.) yielded three known compounds, discorhabdins A (1.57), D (1.61) and 1.53, and one new pyrroloiminoquinone 3.3. The dual role of these metabolites as cytotoxic agents and pigments resulted in an attempt to relate the photochemical properties of these metabolites to their cytotoxicity. The pyrroloiminoquinone metabolites studied exhibited moderate singlet oxygen quantum yields, while three compounds (1.57, 4.1 and 4.2) were shown to be capable of producing radicals at a wavelength of 532 nm. The possibility of a correlation between the electrochemical properties and anti-cancer (HCT-116) activity of selected pyrroloiminoquinones was explored. A study of the oesophageal and ovarian cytotoxicities of two pyrroloiminoquinones (1.57 and 1.72), together with an investigation into the intercalation and topoisomerase I inhibitory activity of the bis-pyrroloiminoquinones (1.71, 1.72, 4.1 and 4.2), are presented.
- Full Text:
- Date Issued: 2003
Reader-response approaches to literature teaching in a South African OBE environment
- Authors: Van Renen, Charles Gerard
- Date: 2003
- Subjects: Reader-response criticism -- South Africa , Literature -- Study and teaching -- South Africa , Competency-based education -- South Africa
- Language: English
- Type: Thesis , Doctoral , DEd
- Identifier: vital:11013 , http://hdl.handle.net/10948/297 , Reader-response criticism -- South Africa , Literature -- Study and teaching -- South Africa , Competency-based education -- South Africa
- Description: This research is based on the hypothesis that response-based approaches to teaching literature and an outcomes-based system of education (OBE) are conceptually incompatible. This thesis claims that reader response involves processes that cannot be accommodated pedagogically within a system based on pre-determined outcomes. Furthermore, the kind of assessment prescribed by OBE is inappropriate to the nature of reader response. The hypothesis is based on three main premises. The first is that each reader brings a highly individual and complex set of personal schemata to the reading of imaginative texts, and these schemata have a decisive influence on the nature of a reader’s response. This means that response during imaginative engagements with literary texts tends to be idiosyncratic, and therefore largely unpredictable. Because of this, it would be inappropriate for a teacher, working within an OBE system, to try to teach towards pre-selected outcomes and to attempt to ensure that these outcomes, based on responses to literary texts, are in fact achieved. The second premise is that readers’ imaginative engagements with literary texts are essentially hidden events, which even the individual reader cannot fully bring to the surface and articulate. Because they are complex, and to some extent inaccessible, it would be inappropriate to assess the processes of response in the form of tangible evidence that a particular kind of response has taken place, or an outcome achieved. The third premise is that responses need time to grow and develop and do not merely happen quickly and cleanly. Consequently, aesthetic response, already a complex and inaccessible process, has no clearly distinguishable beginnings or endings. It would therefore be inappropriate to try to pinpoint the exact nature and parameters of a particular response or fragment it into a discrete unit of competence or knowledge. A two-dimensional problem emerges. The first is a conceptual one: whether there is an inherent tension between encouraging response to imaginative literature on the one hand, and accepting the rationale for OBE, on the other. The second dimension of the problem is empirical: whether teachers of literature experience any tension of either a conceptual or a practical nature when following response based approaches within the OBE system of Curriculum 2005, and if so, what they do in order to cope. In exploring the conceptual problem, the argument of this thesis is supported by reception theory and reader response criticism. The former provides key theoretical principles and insights that illuminate the nature of aesthetic reading, while the latter describes and analyses the nature, extent and manifestations of response in educational contexts, underpinned by both reception theory and empirical research. Together they offer evidence that personal response is determined by a complex range of processes, and is the core activity in reading for aesthetic purposes. This thesis also examines the conceptual basis and the structure of OBE as interpreted in both Curriculum 2005 and the revised National Curriculum Statement. The purpose of this is to establish the extent to which the philosophy and modus operandi of these curricula are rooted in notions of competence, and the requirement that learners give tangible demonstrations of pre-determined outcomes being achieved. If it is found that the curricula do lean heavily on pre-determined outcomes in regard to competencies that must be demonstrated, it may be concluded that 1) reader response activities are incompatible with OBE in a South African context, and 2) the potential exists for such incompatibility to create obstacles to creative and effective literature teaching. This can lead to difficulties for the teacher, who will then have to adopt acceptable strategies to cope with the situation. These strategies may ultimately be to the detriment of the pupils, particularly if the teacher seeks a compromise between genuine response and the kinds of activities that would yield precise, palpable measures of attainment that can be easily demonstrated. Exploring the empirical dimension of the problem involves investigating the responses of both teachers and teacher trainers to the experience of promoting response-based literature teaching and learning in an OBE environment. In order firstly investigated whether the practitioners do encourage reading response as a core activity in reading for aesthetic purposes. The extent to which practitioners have a sound grasp of the conceptual issues relevant to this research is also investigated. Insight into such issues depends on teachers and teacher trainers understanding the nature of reader response, on the one hand, and the rationale and structures of the relevant OBE curricula, on the other. Whether, and to what extent, practitioners experience tensions through their awareness of conceptual incompatibilities is also investigated. It should be borne in mind that practitioners work in real contexts in which a variety of complex factors play a role in determining how they respond to pressures from the environment. It cannot therefore be expected that teachers and others involved in delivering the curriculum will be able to reflect on purely conceptual issues without being influenced to an extent by more practical or logistical considerations. However, this study argues that the extent to which they are able to identify the relevant factors that affect the conceptual underpinnings of their practice will determine the degree to which their responses support the argument of this thesis. Together, the empirical and the theoretical findings offer qualitative evidence that should illuminate the nature and extent of the problem.
- Full Text:
- Date Issued: 2003
- Authors: Van Renen, Charles Gerard
- Date: 2003
- Subjects: Reader-response criticism -- South Africa , Literature -- Study and teaching -- South Africa , Competency-based education -- South Africa
- Language: English
- Type: Thesis , Doctoral , DEd
- Identifier: vital:11013 , http://hdl.handle.net/10948/297 , Reader-response criticism -- South Africa , Literature -- Study and teaching -- South Africa , Competency-based education -- South Africa
- Description: This research is based on the hypothesis that response-based approaches to teaching literature and an outcomes-based system of education (OBE) are conceptually incompatible. This thesis claims that reader response involves processes that cannot be accommodated pedagogically within a system based on pre-determined outcomes. Furthermore, the kind of assessment prescribed by OBE is inappropriate to the nature of reader response. The hypothesis is based on three main premises. The first is that each reader brings a highly individual and complex set of personal schemata to the reading of imaginative texts, and these schemata have a decisive influence on the nature of a reader’s response. This means that response during imaginative engagements with literary texts tends to be idiosyncratic, and therefore largely unpredictable. Because of this, it would be inappropriate for a teacher, working within an OBE system, to try to teach towards pre-selected outcomes and to attempt to ensure that these outcomes, based on responses to literary texts, are in fact achieved. The second premise is that readers’ imaginative engagements with literary texts are essentially hidden events, which even the individual reader cannot fully bring to the surface and articulate. Because they are complex, and to some extent inaccessible, it would be inappropriate to assess the processes of response in the form of tangible evidence that a particular kind of response has taken place, or an outcome achieved. The third premise is that responses need time to grow and develop and do not merely happen quickly and cleanly. Consequently, aesthetic response, already a complex and inaccessible process, has no clearly distinguishable beginnings or endings. It would therefore be inappropriate to try to pinpoint the exact nature and parameters of a particular response or fragment it into a discrete unit of competence or knowledge. A two-dimensional problem emerges. The first is a conceptual one: whether there is an inherent tension between encouraging response to imaginative literature on the one hand, and accepting the rationale for OBE, on the other. The second dimension of the problem is empirical: whether teachers of literature experience any tension of either a conceptual or a practical nature when following response based approaches within the OBE system of Curriculum 2005, and if so, what they do in order to cope. In exploring the conceptual problem, the argument of this thesis is supported by reception theory and reader response criticism. The former provides key theoretical principles and insights that illuminate the nature of aesthetic reading, while the latter describes and analyses the nature, extent and manifestations of response in educational contexts, underpinned by both reception theory and empirical research. Together they offer evidence that personal response is determined by a complex range of processes, and is the core activity in reading for aesthetic purposes. This thesis also examines the conceptual basis and the structure of OBE as interpreted in both Curriculum 2005 and the revised National Curriculum Statement. The purpose of this is to establish the extent to which the philosophy and modus operandi of these curricula are rooted in notions of competence, and the requirement that learners give tangible demonstrations of pre-determined outcomes being achieved. If it is found that the curricula do lean heavily on pre-determined outcomes in regard to competencies that must be demonstrated, it may be concluded that 1) reader response activities are incompatible with OBE in a South African context, and 2) the potential exists for such incompatibility to create obstacles to creative and effective literature teaching. This can lead to difficulties for the teacher, who will then have to adopt acceptable strategies to cope with the situation. These strategies may ultimately be to the detriment of the pupils, particularly if the teacher seeks a compromise between genuine response and the kinds of activities that would yield precise, palpable measures of attainment that can be easily demonstrated. Exploring the empirical dimension of the problem involves investigating the responses of both teachers and teacher trainers to the experience of promoting response-based literature teaching and learning in an OBE environment. In order firstly investigated whether the practitioners do encourage reading response as a core activity in reading for aesthetic purposes. The extent to which practitioners have a sound grasp of the conceptual issues relevant to this research is also investigated. Insight into such issues depends on teachers and teacher trainers understanding the nature of reader response, on the one hand, and the rationale and structures of the relevant OBE curricula, on the other. Whether, and to what extent, practitioners experience tensions through their awareness of conceptual incompatibilities is also investigated. It should be borne in mind that practitioners work in real contexts in which a variety of complex factors play a role in determining how they respond to pressures from the environment. It cannot therefore be expected that teachers and others involved in delivering the curriculum will be able to reflect on purely conceptual issues without being influenced to an extent by more practical or logistical considerations. However, this study argues that the extent to which they are able to identify the relevant factors that affect the conceptual underpinnings of their practice will determine the degree to which their responses support the argument of this thesis. Together, the empirical and the theoretical findings offer qualitative evidence that should illuminate the nature and extent of the problem.
- Full Text:
- Date Issued: 2003
Sandy beach morphodynamics and macrobenthic communities in temperate, subtropical and tropical regions : a macroecological approach
- Authors: Soares, Alexandre Goulart
- Date: 2003
- Subjects: Seashore ecology , Intertidal ecology , Benthos
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:11077 , http://hdl.handle.net/10948/293 , Seashore ecology , Intertidal ecology , Benthos
- Description: A comprehensive study involving 52 microtidal beaches spanning from reflective to dissipative states and located in tropical, subtropical and temperate regions in the Atlantic, Pacific and Indian oceans was carried out to unravel the relative roles of latitude and beach morphodynamics in determining beach macrobenthic species richness, abundance, biomass and mean individual body sizes. Since beach slope is one of the most important factors controlling beach fauna, a model based on beach geometry was applied to the sub-aerial beach deposit to understand the role of physical factors in predicting equilibrium beach slopes. Additionally, it was tested if the occurrence of beach types is related to latitude, and how physical factors change with morphodynamics and latitude. The beach morphometric model makes three assumptions: 1) that the cross-section of a beach deposit is equivalent to a right-angled triangle, 2) that the physical hydrodynamic factors (wave height and spring tide amplitude) and the beach deposit characteristics (sand grain size, beach slope and width) are interchangeable with their geometric counterparts producing an equation to explain beach geometry, and 3) that the predicted beach slope is in equilibrium with the hydrodynamic and sedimentological forces. The equation for predicting beach slope was derived and then tested against field data collected over 52 beaches. The predicted slopes were not significantly different from the observed slopes of the studied natural beaches. However some estimated slopes were different than observed ones. Possible sources of deviation between calculated and observed slopes may be the systematic sampling errors associated with field data. Alternatively, observed slopes could be the result of past hydrodynamic conditions, explaining the differences with the slopes calculated by the beach morphometric model, which assumes a state of equilibrium between beach slope and hydrodynamic conditions. A higher correlation of beach faunal structure with observed slopes rather than with present hydrodynamic conditions could then be indicative of faunal responses to previous hydrodynamic conditions in the same way was the observed slopes. The beach morphometric model could therefore be also useful in predicting faunal responses to changing hydrodynamic conditions. Since the model does not consider wave period, it is concluded that further tests should be done using laboratory and time-series field data and incorporating the role of wave period and beach permeability to ascertain its predictive value. Tropical regions had significantly more beaches in a reflective state than temperate and subtropical regions. Some tropical beaches were fronted by coral reefs, which not only provided coarse carbonate particles, but also additionally dissipated the low wave energy present in these climatic areas. Only one dissipative beach with high energy was found in the tropics, in southeast Madagascar. Temperate and subtropical regions, on the other hand, were dominated by dissipative beaches with medium to fine sands. Open oceanic reflective beaches were non-existent in the subtropics and rare in temperate regions, only occurring in estuaries, enclosed bays or on islands facing the continent. Intermediate beaches were more common in the subtropics but also occurred frequently in the other two regions, having higher energy in temperate regions. Reflective beaches had significantly steeper slopes, coarser sands, smaller waves and shorter swash lengths when compared to dissipative beaches. Additionally, reflective beaches were narrower, had deeper water tables and in consequence shorter saturation zones. Wave periods and surfzone widths were on average larger on dissipative than on reflective beaches. The frequency of occurrence of beach types is therefore related to the climatic signature of each latitude. Mid latitudes would be predicted to have more dissipative beaches with large and long waves because of their proximity to the storm generating belt around 50-60° S - these beaches will have a predominantly finer sands because of the input by rivers in rainy areas. Lower latitudes will have more reflective beaches due to a modal low energy wave climate and also because of the presence of inshore and offshore biotic structures such as coral reefs that dissipate even more the energy from the waves. Tropical and subtropical regions had larger marine species pools than temperate regions. After controlling for biogeographical differences in total species pool, dissipative beaches were on average significantly richer than intermediate and reflective beaches. Crustaceans were also more diverse on dissipative beaches, this difference being not significant for either molluscs or polychaetes. Significant relationships were found between total beach species richness (with or without terrestrial species), crustacean and mollusc species richness with beach morphodynamics as represented by the Dean’s index. Indices incorporating the role of tide, such as BSI, were less important in predicting species richness on the microtidal beaches studied here. Several other physical factors were also significantly correlated with species richness, the most important being the Beach Deposit Index, i.e. BDI, a composite index of beach slope and grain size. The highest correlation was between BDI and relative species richness, i.e. local beach species richness / regional species richness. Total regional marine species richness was higher in Madagascar and North Brazil (tropical beaches) than in Southeast Brazil (subtropical), or the West Coast of South Africa and South-Central Chile (temperate beaches). Not only was the pool of species capable of colonizing beaches richer in tropical and subtropical regions, but also local diversity of each morphodynamic beach type was higher among tropical beaches than their temperate counterparts. Although the results of this study agree with the predictions of the swash exclusion hypotheses, several reflective and intermediate beaches had higher species richness than predicted before and this seems to be linked to the presence of finer sediments and a less turbulent flow for larvae to settle. It is concluded that beach species richness is not necessarily controlled by one major morphodynamic parameter; this control is complex and probably involves multiple interacting biotic (biological interactions) and abiotic (e.g. grain size, wave height, beach slope and width, water table) factors. Species richness seems to be controlled on two different scales: on an evolutionary one where tropical and subtropical regions have higher regional and local diversity due to higher speciation rates; and on an ecological scale, where fine grained sand beaches have their carrying capacity enhanced by higher larval settlement rates and survival of recruits towards adulthood. On average dissipative beaches had higher total densities and macrofaunal abundances than reflective ones. Crustaceans, terrestrial species and cirolanid isopods such as Excirolana spp. were also more abundant on dissipative beaches. The difference was not significant for molluscs and polychaetes. Significant relationships were found between total abundance, crustacean species richness and beach morphodynamics as represented by the Dean’s index. Again, BSI was less important than individual physical factors in determining faunal abundance on the studied microtidal beaches. Several other physical factors were also significantly correlated with abundance, the most important being the Beach Deposit Index (BDI). The highest correlation was between BDI and total macrofaunal abundance. Factors related to surf zone processes, and possibly productivity, were highly correlated with total community, crustaceans, Excirolana spp. and terrestrial species abundances. The abundances of polychaetes and molluscs were better correlated with factors related to the beach deposit (BDI, slope, grain size and water table depth). Significant differences were observed between latitudinal regions for the average beach and also for each beach type. In general temperate beaches harboured larger community densities and abundances, and also crustacean, Excirolana spp. and terrestrial abundances. Mollusc and polychaete abundances were larger on subtropical and tropical beaches. The control of abundance on a sandy beach is complex and involves multifactorial processes at evolutionary and ecological scales. At evolutionary scales animals seem to attain higher abundances in the region where they first evolved, e.g. amphipods and isopods in temperate regions. At ecological scales they attain higher abundances where productivity is higher (total macrofaunal, crustaceans, Excirolana spp., terrestrial spp.) or where the settlement environment is more benign (molluscs and polychaetes). Dissipative beaches supported larger average and total community biomass than reflective beaches. Crustaceans, terrestrial species and cirolanid isopods such as Excirolana spp. also had larger biomass on dissipative beaches. The difference was not significant for molluscs and polychaetes. Significant relationships were found between the biomass of community and taxonomic groups with beach morphodynamics as represented by the Dean’s morphodynamic index. On the microtidal beaches studied here, BSI was less important than other morphodynamic indices and single physical factors in determining faunal biomass and mean individual body size. Surf zone characteristics such as wave height, period and surf zone width had the highest correlations with community, crustacean.
- Full Text:
- Date Issued: 2003
- Authors: Soares, Alexandre Goulart
- Date: 2003
- Subjects: Seashore ecology , Intertidal ecology , Benthos
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:11077 , http://hdl.handle.net/10948/293 , Seashore ecology , Intertidal ecology , Benthos
- Description: A comprehensive study involving 52 microtidal beaches spanning from reflective to dissipative states and located in tropical, subtropical and temperate regions in the Atlantic, Pacific and Indian oceans was carried out to unravel the relative roles of latitude and beach morphodynamics in determining beach macrobenthic species richness, abundance, biomass and mean individual body sizes. Since beach slope is one of the most important factors controlling beach fauna, a model based on beach geometry was applied to the sub-aerial beach deposit to understand the role of physical factors in predicting equilibrium beach slopes. Additionally, it was tested if the occurrence of beach types is related to latitude, and how physical factors change with morphodynamics and latitude. The beach morphometric model makes three assumptions: 1) that the cross-section of a beach deposit is equivalent to a right-angled triangle, 2) that the physical hydrodynamic factors (wave height and spring tide amplitude) and the beach deposit characteristics (sand grain size, beach slope and width) are interchangeable with their geometric counterparts producing an equation to explain beach geometry, and 3) that the predicted beach slope is in equilibrium with the hydrodynamic and sedimentological forces. The equation for predicting beach slope was derived and then tested against field data collected over 52 beaches. The predicted slopes were not significantly different from the observed slopes of the studied natural beaches. However some estimated slopes were different than observed ones. Possible sources of deviation between calculated and observed slopes may be the systematic sampling errors associated with field data. Alternatively, observed slopes could be the result of past hydrodynamic conditions, explaining the differences with the slopes calculated by the beach morphometric model, which assumes a state of equilibrium between beach slope and hydrodynamic conditions. A higher correlation of beach faunal structure with observed slopes rather than with present hydrodynamic conditions could then be indicative of faunal responses to previous hydrodynamic conditions in the same way was the observed slopes. The beach morphometric model could therefore be also useful in predicting faunal responses to changing hydrodynamic conditions. Since the model does not consider wave period, it is concluded that further tests should be done using laboratory and time-series field data and incorporating the role of wave period and beach permeability to ascertain its predictive value. Tropical regions had significantly more beaches in a reflective state than temperate and subtropical regions. Some tropical beaches were fronted by coral reefs, which not only provided coarse carbonate particles, but also additionally dissipated the low wave energy present in these climatic areas. Only one dissipative beach with high energy was found in the tropics, in southeast Madagascar. Temperate and subtropical regions, on the other hand, were dominated by dissipative beaches with medium to fine sands. Open oceanic reflective beaches were non-existent in the subtropics and rare in temperate regions, only occurring in estuaries, enclosed bays or on islands facing the continent. Intermediate beaches were more common in the subtropics but also occurred frequently in the other two regions, having higher energy in temperate regions. Reflective beaches had significantly steeper slopes, coarser sands, smaller waves and shorter swash lengths when compared to dissipative beaches. Additionally, reflective beaches were narrower, had deeper water tables and in consequence shorter saturation zones. Wave periods and surfzone widths were on average larger on dissipative than on reflective beaches. The frequency of occurrence of beach types is therefore related to the climatic signature of each latitude. Mid latitudes would be predicted to have more dissipative beaches with large and long waves because of their proximity to the storm generating belt around 50-60° S - these beaches will have a predominantly finer sands because of the input by rivers in rainy areas. Lower latitudes will have more reflective beaches due to a modal low energy wave climate and also because of the presence of inshore and offshore biotic structures such as coral reefs that dissipate even more the energy from the waves. Tropical and subtropical regions had larger marine species pools than temperate regions. After controlling for biogeographical differences in total species pool, dissipative beaches were on average significantly richer than intermediate and reflective beaches. Crustaceans were also more diverse on dissipative beaches, this difference being not significant for either molluscs or polychaetes. Significant relationships were found between total beach species richness (with or without terrestrial species), crustacean and mollusc species richness with beach morphodynamics as represented by the Dean’s index. Indices incorporating the role of tide, such as BSI, were less important in predicting species richness on the microtidal beaches studied here. Several other physical factors were also significantly correlated with species richness, the most important being the Beach Deposit Index, i.e. BDI, a composite index of beach slope and grain size. The highest correlation was between BDI and relative species richness, i.e. local beach species richness / regional species richness. Total regional marine species richness was higher in Madagascar and North Brazil (tropical beaches) than in Southeast Brazil (subtropical), or the West Coast of South Africa and South-Central Chile (temperate beaches). Not only was the pool of species capable of colonizing beaches richer in tropical and subtropical regions, but also local diversity of each morphodynamic beach type was higher among tropical beaches than their temperate counterparts. Although the results of this study agree with the predictions of the swash exclusion hypotheses, several reflective and intermediate beaches had higher species richness than predicted before and this seems to be linked to the presence of finer sediments and a less turbulent flow for larvae to settle. It is concluded that beach species richness is not necessarily controlled by one major morphodynamic parameter; this control is complex and probably involves multiple interacting biotic (biological interactions) and abiotic (e.g. grain size, wave height, beach slope and width, water table) factors. Species richness seems to be controlled on two different scales: on an evolutionary one where tropical and subtropical regions have higher regional and local diversity due to higher speciation rates; and on an ecological scale, where fine grained sand beaches have their carrying capacity enhanced by higher larval settlement rates and survival of recruits towards adulthood. On average dissipative beaches had higher total densities and macrofaunal abundances than reflective ones. Crustaceans, terrestrial species and cirolanid isopods such as Excirolana spp. were also more abundant on dissipative beaches. The difference was not significant for molluscs and polychaetes. Significant relationships were found between total abundance, crustacean species richness and beach morphodynamics as represented by the Dean’s index. Again, BSI was less important than individual physical factors in determining faunal abundance on the studied microtidal beaches. Several other physical factors were also significantly correlated with abundance, the most important being the Beach Deposit Index (BDI). The highest correlation was between BDI and total macrofaunal abundance. Factors related to surf zone processes, and possibly productivity, were highly correlated with total community, crustaceans, Excirolana spp. and terrestrial species abundances. The abundances of polychaetes and molluscs were better correlated with factors related to the beach deposit (BDI, slope, grain size and water table depth). Significant differences were observed between latitudinal regions for the average beach and also for each beach type. In general temperate beaches harboured larger community densities and abundances, and also crustacean, Excirolana spp. and terrestrial abundances. Mollusc and polychaete abundances were larger on subtropical and tropical beaches. The control of abundance on a sandy beach is complex and involves multifactorial processes at evolutionary and ecological scales. At evolutionary scales animals seem to attain higher abundances in the region where they first evolved, e.g. amphipods and isopods in temperate regions. At ecological scales they attain higher abundances where productivity is higher (total macrofaunal, crustaceans, Excirolana spp., terrestrial spp.) or where the settlement environment is more benign (molluscs and polychaetes). Dissipative beaches supported larger average and total community biomass than reflective beaches. Crustaceans, terrestrial species and cirolanid isopods such as Excirolana spp. also had larger biomass on dissipative beaches. The difference was not significant for molluscs and polychaetes. Significant relationships were found between the biomass of community and taxonomic groups with beach morphodynamics as represented by the Dean’s morphodynamic index. On the microtidal beaches studied here, BSI was less important than other morphodynamic indices and single physical factors in determining faunal biomass and mean individual body size. Surf zone characteristics such as wave height, period and surf zone width had the highest correlations with community, crustacean.
- Full Text:
- Date Issued: 2003
Stability studies on some substituted aminobenzoic acids
- Authors: Rotich, Moses Kipngeno
- Date: 2003
- Subjects: Aminobenzoic acids Aminobenzoic acids -- Stability Salicylic acid
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:4347 , http://hdl.handle.net/10962/d1005012
- Description: he thermal behaviour in the solid state of various substituted aminobenzoic acids (3-aminobenzoic acid (3-ABA), 4-aminobenzoic acid (4-ABA), 3-aminosalicylic acid (3-ASA), 4-aminosalicylic acid (4-ASA), and 5-aminosalicylic acid (5-ASA), as well as the "parent" benzoic acid (BA) and salicylic acid (SA) as reference substances, and possible decomposition products: 2-aminophenol (2-AP), 3-aminophenol (3-AP) and 4-aminophenol (4-AP), has been examined. The various sets of isomers studied showed considerable and interesting differences. Most sublimed well before melting, generally with an increasing rate of mass loss beyond their very different melting points. The existence of ranges of isomers allows for the comparison of their behaviour, including such aspects as melting, vaporisation, and the influence of products on the course of decomposition of initially-solid reactants. The differences in behaviour of 4-ASA and 5-ASA were the most remarkable, with 5-ASA being far more stable and apparently not decarboxylating readily, while 4-ASA sublimed at temperatures below the melting point, becoming less stable and decarboxylating in the liquid form. There is also a marked difference in the thermal behaviour of 3-ASA, as compared with 4-ASA and 5-ASA. It decarboxylated at higher temperatures (260°C) than 4-ASA (150°C). The addition of the possible decomposition products to these compounds showed faster decomposition for 4-ASA mixed with 3-AP. The sodium salts of 3-ASA and 4-ASA decarboxylate while that of 5-ASA did not. Binary mixtures of the substances listed above with beta-cyclodextrin (BCD), hydroxypropylbeta-cyclodextrin (HPBCD) and gamma-cyclodextrin (GCD) were prepared (by simple physical mixing or by kneading with a solvent) and were then examined for possible interactions using DSC, TG-FTIR, HSM, XRD and NMR. Generally, kneaded mixtures showed greater changes in thermal behaviour from that of the individual components than the physical mixtures, but changes in the physical mixtures were also significant. Comparison of the effects of the different CDs on the thermal behaviour of individual ASA isomers showed that HPBCD has the greatest interaction with 3-ASA and 5-ASA, followed by GCD, while BCD generally showed the least interactions. For 4-ASA, the effect of GCD is more marked than for 3-ASA and 5-ASA. GCD has the largest molecular cavity.
- Full Text:
- Date Issued: 2003
- Authors: Rotich, Moses Kipngeno
- Date: 2003
- Subjects: Aminobenzoic acids Aminobenzoic acids -- Stability Salicylic acid
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:4347 , http://hdl.handle.net/10962/d1005012
- Description: he thermal behaviour in the solid state of various substituted aminobenzoic acids (3-aminobenzoic acid (3-ABA), 4-aminobenzoic acid (4-ABA), 3-aminosalicylic acid (3-ASA), 4-aminosalicylic acid (4-ASA), and 5-aminosalicylic acid (5-ASA), as well as the "parent" benzoic acid (BA) and salicylic acid (SA) as reference substances, and possible decomposition products: 2-aminophenol (2-AP), 3-aminophenol (3-AP) and 4-aminophenol (4-AP), has been examined. The various sets of isomers studied showed considerable and interesting differences. Most sublimed well before melting, generally with an increasing rate of mass loss beyond their very different melting points. The existence of ranges of isomers allows for the comparison of their behaviour, including such aspects as melting, vaporisation, and the influence of products on the course of decomposition of initially-solid reactants. The differences in behaviour of 4-ASA and 5-ASA were the most remarkable, with 5-ASA being far more stable and apparently not decarboxylating readily, while 4-ASA sublimed at temperatures below the melting point, becoming less stable and decarboxylating in the liquid form. There is also a marked difference in the thermal behaviour of 3-ASA, as compared with 4-ASA and 5-ASA. It decarboxylated at higher temperatures (260°C) than 4-ASA (150°C). The addition of the possible decomposition products to these compounds showed faster decomposition for 4-ASA mixed with 3-AP. The sodium salts of 3-ASA and 4-ASA decarboxylate while that of 5-ASA did not. Binary mixtures of the substances listed above with beta-cyclodextrin (BCD), hydroxypropylbeta-cyclodextrin (HPBCD) and gamma-cyclodextrin (GCD) were prepared (by simple physical mixing or by kneading with a solvent) and were then examined for possible interactions using DSC, TG-FTIR, HSM, XRD and NMR. Generally, kneaded mixtures showed greater changes in thermal behaviour from that of the individual components than the physical mixtures, but changes in the physical mixtures were also significant. Comparison of the effects of the different CDs on the thermal behaviour of individual ASA isomers showed that HPBCD has the greatest interaction with 3-ASA and 5-ASA, followed by GCD, while BCD generally showed the least interactions. For 4-ASA, the effect of GCD is more marked than for 3-ASA and 5-ASA. GCD has the largest molecular cavity.
- Full Text:
- Date Issued: 2003
Structural and synthetic investigations of diterpenoid natural products from southern African marine invertebrates
- Authors: Gray, Christopher Anthony
- Date: 2003
- Subjects: Ethyl acetoacetate Diterpenes Limpets -- South Africa Natural products -- South Africa
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:4349 , http://hdl.handle.net/10962/d1005014
- Description: This thesis is divided into two parts. The first part (Chapter Two) documents a bioassay guided investigation of the ethyl acetate extracts of four marine invertebrates from Mozambique (an Irciniid sponge, a Haliclona sp. sponge, an ascidian tentatively identified as Diplosoma sp., and the soft coral Cladiella kashmani). Eight known compounds [ilimaquinone (2.1), renierone (2.7), N-formyl-1,2-dihydrorenierone (2.8), 1,6-dimethyl-7-methoxy-5,8-dihydroisoquinoline-5,8-dione (2.9), mimosamycin (2.10) 7Z-allylidene-5-hydroxy-7,7a-dihydro-2H-cyclopenta[b]pyran-6-one (2.11), flaccidoxide (2.18) and 11S,12S-epoxycembra-1Z,3E,7E-trien-14S-ol (2.19)] and a new diterpene [13S,14R-diacetoxy-11S,12R-epoxycembra-1Z,3E,7E-triene (2.20)] were isolated and identified using standard spectroscopic techniques. Anomalies in the published spectral data of 2.1 and 2.8 were exposed and corrected, and the absolute stereochemistry of the cembrane diterpenes 2.18 and 2.20 established using the modified Mosher’s method. The comparative activities of the nine natural products against four cancer cell lines (A549, LOX, OVCAR3, SNB19) are reported. The second part of the thesis (Chapter Three – Chapter Six) is concerned with an ecological, structural and synthetic study of diterpenes from the endemic South African pulmonate limpet Trimusculus costatus. Two new labdane diterpenes [6b,7a-diacetoxylabda-8,13E-dien-15-ol (3.10) and 2a,6b,7a-triacetoxylabda-8,13E-dien-15-ol (3.11)] were isolated from T. costatus and evaluated for anti-feeding activity against the common predatory fish Pomadasys commersonnii. A strategy for the semi-synthesis of 3.10 from rhinocerotinoic acid (4.14), a diterpene reportedly present in the ubiquitous South African shrub Elytropappus rhinocerotis, was devised in order to allow further bioactivity tests to be performed and unequivocally assign the unknown absolute stereochemistry of the T. costatus metabolites. Attempts to isolate rhinocerotinoic acid from local specimens of Elytropappus rhinocerotis were unsuccessful, and as the repetition of a published synthesis of 4.14 from (-)-sclareol (4.15) gave rhinocerotinoic acid in unacceptably low yields with poor stereoselectivity, an improved synthesis of 4.14 is presented. Comprehensive studies using hispanone (5.1) as a model compound showed that 6,7-dioxygenated labda-8-enes could be prepared from compounds possessing a 7-oxo-labda-8-ene skeleton with some degree of stereocontrol. In the process, fourteen new hispanone analogues were prepared and most of these were tested for activity in a suite of ten agro-chemical assays. The novel compound 7b-hydroxy-9a-carbonitrile-15,16-epoxylabda-13(16),14-dien-6-one (5.34) exhibited significant activity against the crop fungus Phytophthora infestans and is currently being subjected to further agro-chemical tests. Unfortunately, the results from the oxygenation study performed on the model compound 5.1 could not be directly extrapolated to rhinocerotinoic acid. Attempts to prepare the naturally occurring 3.10 from 4.14 via an alternative route were unsuccessful but yielded an analogue of 3.10 in which the substituents at C-6 and C-7 are in a diequatorial rather than a diaxial configuration.
- Full Text:
- Date Issued: 2003
- Authors: Gray, Christopher Anthony
- Date: 2003
- Subjects: Ethyl acetoacetate Diterpenes Limpets -- South Africa Natural products -- South Africa
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:4349 , http://hdl.handle.net/10962/d1005014
- Description: This thesis is divided into two parts. The first part (Chapter Two) documents a bioassay guided investigation of the ethyl acetate extracts of four marine invertebrates from Mozambique (an Irciniid sponge, a Haliclona sp. sponge, an ascidian tentatively identified as Diplosoma sp., and the soft coral Cladiella kashmani). Eight known compounds [ilimaquinone (2.1), renierone (2.7), N-formyl-1,2-dihydrorenierone (2.8), 1,6-dimethyl-7-methoxy-5,8-dihydroisoquinoline-5,8-dione (2.9), mimosamycin (2.10) 7Z-allylidene-5-hydroxy-7,7a-dihydro-2H-cyclopenta[b]pyran-6-one (2.11), flaccidoxide (2.18) and 11S,12S-epoxycembra-1Z,3E,7E-trien-14S-ol (2.19)] and a new diterpene [13S,14R-diacetoxy-11S,12R-epoxycembra-1Z,3E,7E-triene (2.20)] were isolated and identified using standard spectroscopic techniques. Anomalies in the published spectral data of 2.1 and 2.8 were exposed and corrected, and the absolute stereochemistry of the cembrane diterpenes 2.18 and 2.20 established using the modified Mosher’s method. The comparative activities of the nine natural products against four cancer cell lines (A549, LOX, OVCAR3, SNB19) are reported. The second part of the thesis (Chapter Three – Chapter Six) is concerned with an ecological, structural and synthetic study of diterpenes from the endemic South African pulmonate limpet Trimusculus costatus. Two new labdane diterpenes [6b,7a-diacetoxylabda-8,13E-dien-15-ol (3.10) and 2a,6b,7a-triacetoxylabda-8,13E-dien-15-ol (3.11)] were isolated from T. costatus and evaluated for anti-feeding activity against the common predatory fish Pomadasys commersonnii. A strategy for the semi-synthesis of 3.10 from rhinocerotinoic acid (4.14), a diterpene reportedly present in the ubiquitous South African shrub Elytropappus rhinocerotis, was devised in order to allow further bioactivity tests to be performed and unequivocally assign the unknown absolute stereochemistry of the T. costatus metabolites. Attempts to isolate rhinocerotinoic acid from local specimens of Elytropappus rhinocerotis were unsuccessful, and as the repetition of a published synthesis of 4.14 from (-)-sclareol (4.15) gave rhinocerotinoic acid in unacceptably low yields with poor stereoselectivity, an improved synthesis of 4.14 is presented. Comprehensive studies using hispanone (5.1) as a model compound showed that 6,7-dioxygenated labda-8-enes could be prepared from compounds possessing a 7-oxo-labda-8-ene skeleton with some degree of stereocontrol. In the process, fourteen new hispanone analogues were prepared and most of these were tested for activity in a suite of ten agro-chemical assays. The novel compound 7b-hydroxy-9a-carbonitrile-15,16-epoxylabda-13(16),14-dien-6-one (5.34) exhibited significant activity against the crop fungus Phytophthora infestans and is currently being subjected to further agro-chemical tests. Unfortunately, the results from the oxygenation study performed on the model compound 5.1 could not be directly extrapolated to rhinocerotinoic acid. Attempts to prepare the naturally occurring 3.10 from 4.14 via an alternative route were unsuccessful but yielded an analogue of 3.10 in which the substituents at C-6 and C-7 are in a diequatorial rather than a diaxial configuration.
- Full Text:
- Date Issued: 2003
Structures and struggles of rural local government in South Africa: the case of traditional authorities in the Eastern Cape
- Authors: Ntsebeza, Lungisile
- Date: 2003
- Subjects: Local government -- South Africa -- Eastern Cape Tribal government -- South Africa -- Eastern Cape Political leadership -- South Africa -- Eastern Cape Tribal government -- South Africa -- History South Africa -- Politics and government
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:3304 , http://hdl.handle.net/10962/d1003092
- Description: This thesis is about the political implications of the constitutional recognition of the hereditary institution of traditional leadership in post-1994 South Africa for the democratization process in the rural areas of the former Bantustans. The thesis is organized around three related conceptual, historical and political questions. The conceptual question deals with the meaning of democracy in rural areas under the jurisdiction of traditional authorities. The historical question traces how the institution and traditional authorities have survived to the present post-colonial period. Lastly, this study investigates the political issue of why an ANC-led government came to recognize the institution. The focus of the thesis is the sphere of rural local government in the Xhalanga district, where these issues are best illustrated. The thesis argues that the institution of traditional leadership and its officials survived precisely because they were incorporated into the colonial and apartheid administrative structures in the project of indirect rule. Traditional authorities were central to the apartheid policy of retribalisation, which was essentially a form of control of Africans in the Bantustans. Rural residents engaged in fierce struggles against the imposition of rural local government structures such as the District Council and Tribal Authorities. In so far as traditional authorities were part of government structures, they could not avoid being targets in these struggles. In explaining the recognition of the institution of traditional leadership, the thesis focuses on the policies of the ANC, the majority party in the Government of National Unity, towards traditional authorities. Organisationally weak on the rural grounds, the ANC operated through what they considered to be “good/progressive/comrade chiefs”. The ANC had hoped that these traditional authorities would accept a non-political ceremonial role. However, traditional authorities have rejected this ceremonial role. Their refusal, coupled with the ANC’s ambivalence in resolving the tension imply, the study concludes, that the (political) citizenship rights of rural people are partial: they are neither citizens nor subjects.
- Full Text:
- Date Issued: 2003
- Authors: Ntsebeza, Lungisile
- Date: 2003
- Subjects: Local government -- South Africa -- Eastern Cape Tribal government -- South Africa -- Eastern Cape Political leadership -- South Africa -- Eastern Cape Tribal government -- South Africa -- History South Africa -- Politics and government
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:3304 , http://hdl.handle.net/10962/d1003092
- Description: This thesis is about the political implications of the constitutional recognition of the hereditary institution of traditional leadership in post-1994 South Africa for the democratization process in the rural areas of the former Bantustans. The thesis is organized around three related conceptual, historical and political questions. The conceptual question deals with the meaning of democracy in rural areas under the jurisdiction of traditional authorities. The historical question traces how the institution and traditional authorities have survived to the present post-colonial period. Lastly, this study investigates the political issue of why an ANC-led government came to recognize the institution. The focus of the thesis is the sphere of rural local government in the Xhalanga district, where these issues are best illustrated. The thesis argues that the institution of traditional leadership and its officials survived precisely because they were incorporated into the colonial and apartheid administrative structures in the project of indirect rule. Traditional authorities were central to the apartheid policy of retribalisation, which was essentially a form of control of Africans in the Bantustans. Rural residents engaged in fierce struggles against the imposition of rural local government structures such as the District Council and Tribal Authorities. In so far as traditional authorities were part of government structures, they could not avoid being targets in these struggles. In explaining the recognition of the institution of traditional leadership, the thesis focuses on the policies of the ANC, the majority party in the Government of National Unity, towards traditional authorities. Organisationally weak on the rural grounds, the ANC operated through what they considered to be “good/progressive/comrade chiefs”. The ANC had hoped that these traditional authorities would accept a non-political ceremonial role. However, traditional authorities have rejected this ceremonial role. Their refusal, coupled with the ANC’s ambivalence in resolving the tension imply, the study concludes, that the (political) citizenship rights of rural people are partial: they are neither citizens nor subjects.
- Full Text:
- Date Issued: 2003
Studies of the environmental and endocrine control of reproduction in the four striped field mouse, Rhabdomys pumilio
- Authors: Jackson, Claire
- Date: 2003
- Subjects: Microtus Microtus -- South Africa -- Reproduction Mice -- Reproduction
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:5777 , http://hdl.handle.net/10962/d1005465
- Description: Previous studies of the control of reproduction in Rhabdomys pumilio have shown that day length alone does not inhibit spermatogenesis, that a reduction in food availability and ambient temperature results in an inhibition of gametogenesis, that females are more susceptible to inhibition than are males, and that mice that are able to maintain a body fat store in the face of an energetic challenge, are less likely to show reproductive inhibition than those that lose their fat store. In the present study, field and laboratory experiments were conducted to examine the effects of winter food supplementation on reproduction and population dynamics, and the effects of exogenous GnRH, leptin and mercaptoacetate (MA) on reproductive activity of Rhabdomys pumilio exposed to an energetic challenge. In the field food supplementation experiments in Thomas Baines Nature Reserve (2000, 2001), there was no winter inhibition of reproduction and provision of supplementary food had little effect. While at Mountain Zebra National Park (2002) winter was harsher, females became reproductively inactive, spermatogenesis continued and the provision of extra food resulted in higher rates of individual growth and larger reproductive organs. Treatment of mice that had been exposed to a prolonged energetic challenge, with exogenous GnRH (1µg/mouse/treatment) resulted in an increase in the masses of the testes and epididymides, and in the activity of the reproductive organs. Treatment with exogenous leptin (40µg/mouse/treatment), concurrently with an energetic challenge, countered the negative effects of the energetic challenge, and treated males had larger reproductive organs. MA (600µmol/kg body mass), given concurrently with an energetic challenge, did not inhibit fat metabolism, although the high-fat diet countered the effects of the energetic challenge. Results suggest that the first response of male Rhabdomys pumilio to an energetic challenge is a reduction in the size of the reproductive organs, without an inhibition of spermatogenesis. It is likely that this effect is mediated via white fat and leptin, and leptin’s influence on the hypothalamic-pituitary-gonad axis. Results of the study support the suggestion that females are more sensitive to reproductive inhibition than males and that reproduction in Rhabdomys pumilio is truly opportunistic.
- Full Text:
- Date Issued: 2003
- Authors: Jackson, Claire
- Date: 2003
- Subjects: Microtus Microtus -- South Africa -- Reproduction Mice -- Reproduction
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:5777 , http://hdl.handle.net/10962/d1005465
- Description: Previous studies of the control of reproduction in Rhabdomys pumilio have shown that day length alone does not inhibit spermatogenesis, that a reduction in food availability and ambient temperature results in an inhibition of gametogenesis, that females are more susceptible to inhibition than are males, and that mice that are able to maintain a body fat store in the face of an energetic challenge, are less likely to show reproductive inhibition than those that lose their fat store. In the present study, field and laboratory experiments were conducted to examine the effects of winter food supplementation on reproduction and population dynamics, and the effects of exogenous GnRH, leptin and mercaptoacetate (MA) on reproductive activity of Rhabdomys pumilio exposed to an energetic challenge. In the field food supplementation experiments in Thomas Baines Nature Reserve (2000, 2001), there was no winter inhibition of reproduction and provision of supplementary food had little effect. While at Mountain Zebra National Park (2002) winter was harsher, females became reproductively inactive, spermatogenesis continued and the provision of extra food resulted in higher rates of individual growth and larger reproductive organs. Treatment of mice that had been exposed to a prolonged energetic challenge, with exogenous GnRH (1µg/mouse/treatment) resulted in an increase in the masses of the testes and epididymides, and in the activity of the reproductive organs. Treatment with exogenous leptin (40µg/mouse/treatment), concurrently with an energetic challenge, countered the negative effects of the energetic challenge, and treated males had larger reproductive organs. MA (600µmol/kg body mass), given concurrently with an energetic challenge, did not inhibit fat metabolism, although the high-fat diet countered the effects of the energetic challenge. Results suggest that the first response of male Rhabdomys pumilio to an energetic challenge is a reduction in the size of the reproductive organs, without an inhibition of spermatogenesis. It is likely that this effect is mediated via white fat and leptin, and leptin’s influence on the hypothalamic-pituitary-gonad axis. Results of the study support the suggestion that females are more sensitive to reproductive inhibition than males and that reproduction in Rhabdomys pumilio is truly opportunistic.
- Full Text:
- Date Issued: 2003