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An investigation into dopamine-melatonin interactions in the rat Corpus striatum and pineal gland: a possible pineal-striatal axis

  • Authors: Boyd, Clinton Shane
  • Date: 2000
  • Subjects: Pineal gland -- Research Melatonin Dopamine -- Physiological effect Dopamine Brain chemistry Rats -- Physiology
  • Language: English
  • Type: Thesis , Doctoral , PhD
  • Identifier: vital:3906 , http://hdl.handle.net/10962/d1003965
  • Description: Dysfunction of central dopaminergic systems has been implicated in neuroendocrine, neurodegenerative and psychiatric disorders. Monoamine oxidase and catechol-Omethyltransferase represent the key catabolic enzymes of dopamine, terminating neurotransmission following synaptic release of this catecholamine. Thus, both enzymes have been associated with the pathology of dopaminergic systems and represent therapeutic targets elf enormous clinical importance. Some neuroendocrine and circadian effects of melatonin have been attributed to an antidopamimetic effect of this pineal hormone in the hypothalamus and pituitary. Furthermore, both melatonin and dopamine modulate the behavioural output of the mesencephalic dopaminergic pathways of the basal ganglia, including movement disorders. However, the biochemical basis for the tonic inhibitory effect of melatonin in the nigro-striatal pathway has been poorly delineated. Thus, this study determined whether melatonin influences dopaminergic function in the corpus striatum of the Wistar rat by modulating monoamine oxidase and catecholO- methyltransferase activity. Reciprocally, the putative existence of an intrapineal dopaminergic system was investigated by determining the effect of selective dopaminergic agents, R-( -)apomorphine, haloperidol and dopamine, on indole metabolism of the pineal gland. The akinetic state of drug-induced catalepsy was employed as an animal model of Parkinson's disease to probe the neurotransmitter systems involved in the behavioural effects of melatonin. Indole metabolism was a reliable indicator of state-dependent metabolic fluxes in pineal gland function. These included a robust diurnal and seasonal variation in N-acetylserotonin and melatonin biosynthesis, and photoperiod- and drug-induced alterations of Inftabolism. The predominant changes could be attributed to an effect on serotonin N-acetyltransferase activity and/or the melatoninl5-methoxytryptophol ratio. Pineal 5-methoxyindole biosynthesis was determined primarily by the bioavailability of the corresponding 5-hydroxyindole and its affinity for hydroxyindole-O-methyltransferase. Evidence was found for the negative feedback or paracrine control of pineal indole metabolism by melatonin. A high inter-individual variability was observed in the biosynthesis of N-acetylserotonin and melatonin biosynthesis, and the weight of the pineal glands. Accordingly, the rats could be classified as either high or low capacity producers of these two indoles. R-(-)-apomorphine and dopamine in vitro, but not acute haloperidol in vivo, had dose- and phase-dependent effects on pineal indole metabolism. The predominant effect was a suppression of the scotophase-dependent induction ofN-acetylserotonin and melatonin biosynthesis by dopamine and R-( -)-apomorphine. It is postulated that these agonists inhibited nocturnal N-acetyltransferase activity via postsynaptic pineal D2 or D2-like receptors. The observed modulatory nature of the intrapineal dopaminergic system suggests that dopamine may be involved in the long-term regulation of pineal indole biosynthesis. Several lines of evidence are presented that the activity of striatal monoamine oxidase A and catechol-O-methyltransferase, represented predominantly by the soluble isoform, is statedependent and regulated in vivo by endogenous melatonin. Firstly, both enzymes showed a daynight variation in activity. Secondly, acute and subchronic administration and photoperiod manipulation studies indicated that both exogenous and endogenous melatonin inhibited each enzyme in a chronotypic fashion, with a more robust effect against catechol- -methyltransferase. The intensity of the in vivo effects was critically dependent on the dose, duration, route and the phase-timing of administration during the light dark cycle, and the length of the exposure to constant light. Melatonin in vitro had no effect on basal or Mg2+ -induced catechol-Omethyltransferase activity. Thus, it is proposed that the in vivo effects of the hormone can be attributed to a time-dependent change in the amount of active molecules of this enzyme. In contrast, melatonin and numerous other endogenous indolic compounds were found to be reversible inhibitors of striatal monoamine oxidase A in vitro. Structure-activity modeling revealed that the 5-methoxy moiety on the indole nucleus and substitution of the free primary amine of these compounds were the principal determinants of the potency and time-dependency of inhibition. Thus melatonin most likely has a direct inhibitory effect in vivo at the level of the active site of monoamine oxidase A. Exogenous melatonin alone had no cataleptogenic potential whereas a variety of behavioural responses were observed following intraperitoneal administration of y-hydroxybutyrate. The latter responses were state-dependent with day-night variations in intensity. Furthermore, yhydroxybutyrate stimulated melatonin biosynthesis during the photophase both in vitro and in vivo. These results point to a possible involvement of melatonin in the behavioural and neurochemical effects of y-hydroxybutyrate. Thus the general conclusion is that dopamine and melatonin display functional antagonism at the level of the pineal gland and corpus striatum of the Wistar rats. Therefore melatonin may be an important homeostatic modulator of dopaminergic neurotransmission throu~out the central nervous system. Furthermore, the putative existence of a functional pineal-striatal axis would greatly strengthen the argument for a holistic concept of brain homeostasis. The ability of endogenous melatonin to regulate monoamine oxidase A and catechol-O-methyltransferase may represent an alternative strategy for the treatment of disorders associated with these enzymes.
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  • Date Issued: 2000

An investigation into short course accreditation through the South African Qualification Authority

  • Authors: Mackenzie, Ian
  • Date: 2000
  • Subjects: Adult education -- South Africa Elementary education of adults -- South Africa School management and organization -- South Africa Guguletu Comprehensive School South African Qualifications Authority
  • Language: English
  • Type: Thesis , Masters , MEd
  • Identifier: vital:1600 , http://hdl.handle.net/10962/d1003482
  • Description: This research project offers an analysis of the Adult Basic Education and Training Directorate in the Eastern Cape Province. The Bush Models are described and critiqued and then used as a tool for analysis. Other organisational models are described and used to add depth to the analysis. The choice of analysing the Adult Basic Education and Training Directorate comes both from a professional desire to know and understand this organisation more fully, as well as the importance of stressing that the definition of education organisations does not stop at school, colleges and universities, but includes the government bodies which are a key part of the sector. This assignment therefore explores both the features of a government department as well as the appropriateness of using Bush’s models in this context and draws on other organisational theory--Introduction.
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  • Date Issued: 2000

An investigation into the effects of socio-economic and education factors on WAIS-III performance in a stratified South African sample

  • Authors: Kemp, Ryan
  • Date: 2000
  • Subjects: Wechsler Adult Intelligence Scale -- South Africa , Intelligence tests -- South Africa
  • Language: English
  • Type: Thesis , Masters , MA
  • Identifier: vital:3002 , http://hdl.handle.net/10962/d1002511 , Wechsler Adult Intelligence Scale -- South Africa , Intelligence tests -- South Africa
  • Description: The present study examined the effects of socio-economic status, quality and level of education on performance on the Wechsler Adult Intelligence Scale 3rd Edition r.:w AIS-III). The study was conducted within the context of the present Human Sciences Research Council (HSRC) W AIS-III standardisation process, cross-cultural psychometric research and the notion of test-wiseness. A South African sample (N = 68) comprising African first language (n = 40) and English first language (n = 28) participants, stratified for age (19 - 30 years), gender and educational attainment (Matric and Graduate) were utilised. Effects due to quality of education were determined by dividing the African language participants into those with private/model C schooling (n = 20) and those with DET schooling (n = 20). Effects due to level of education were determined by dividing the entire sample into those with Matric level education (n = 34) and those with Graduate level education (n = 34). Detailed demographic and socio-economic information were recorded for all participants, who completed the entire American version of the W AIS-III. Results revealed a highly significant positive correlation between high socio-economic status and W AIS-III Full Scale IQ. In addition the respective impact of the relatively poor quality of education and lower level of educational attainment on W AIS-III performance was substantial. These results were discussed in terms of their implications for cross-cultural research, the HSRC standardisation of the W AIS-III and the practical use of the W AIS-III in neuropsychological assessment.
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  • Date Issued: 2000

An investigation into the influence of the environment on spawning aggregations and jig catches of chokka squid Loligo Vulgaris reynaudii off the south coast of South Africa

  • Authors: Schön, Pieter-Jan
  • Date: 2000
  • Subjects: Squids -- Spawning , Squid fisheries -- South Africa , Squids , Shellfish fisheries -- South Africa
  • Language: English
  • Type: Thesis , Masters , MSc
  • Identifier: vital:5378 , http://hdl.handle.net/10962/d1016369
  • Description: Erratic and highly variable catches in the South African chokka squid Loligo vulgaris reynaudii fishery, cause socio-economic hardship for the industry and uncertainty for resource managers. Catch forecasting can reduce this problem as it is believed that catch variability is strongly influenced by environmental factors. In this study, data were collected at varying temporal and spatial scales. Data for the hourly time-scale study were collected from 1996-1998, aboard commercial vessels, whilst for the longer time-scales, data were extracted for Kromme Bay (a single fishing area) from existing databases (1991-1998) that were comprised of compulsory catch returns and oceanographic data. The environment-catch relationship for chokka squid on the inshore spawning grounds was then investigated using multiple correlation and regression analysis, analysis of variance, contingency table analysis and cross-correlation statistical techniques. This simple, direct, 'black box' statistical approach was relatively successful in developing a predictive capability. On a short time-scale (hourly), the regression model accounted for 32% of the variability in catch, with turbidity the main determinant (13%). On a daily monthly time-scale, the best prediction model was on a monthly scale, accounting for 40% of the variability in catch. The principal determinant, bottom temperature anomaly (11 %), was found to lag one month forward. Seasonal and diel catch variations induced changes in the relative importance of turbidity, water temperature and wind direction on catches. A strong, positive relationship was found between easterly winds (which cause upwelling) and catch, particularly in summer. Catch rates, however, decreased with an increase in turbidity. The correlation between temperature and catch was generally negative, however, higher catches were associated with a temperature range of 13-18°C. Highest catch rates were associated with easterly winds, zero turbidity conditions and sea surface temperatures from 15.0-16.9°C. Selected case studies (in situ observations) suggested that upwelling and turbidity events act as environmental triggers for the initiation or termination of the spawning process, respectively. A holistic approach is required to improve predictive capability of chokka squid abundance. Although short-term predictability remains essential (i.e. hourly-scale), future research should concentrate on long-term prediction models (e.g., monthly time-scales) involving greater spatial variation, which are the most important for management.
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  • Date Issued: 2000

An investigation into the neuroprotective properties of ibuprofen

  • Authors: Lambat, Zaynab Y , Conrad, Natasha , Anoopkumar-Dukie, Shailendra , Walker, Roderick B , Daya, Santylal
  • Date: 2000
  • Subjects: To be catalogued
  • Language: English
  • Type: text , article
  • Identifier: http://hdl.handle.net/10962/184335 , vital:44209 , xlink:href="https://doi.org/10.1023/A:1011115006856"
  • Description: There is increasing evidence suggesting a protective role for anti-inflammatory medications in neurological disorders such as Alzheimer's disease (AD). While there has not been any direct evidence for this, a number of clinical studies indicate that those patients who have had a history of nonsteroidal anti-inflammatory use, have a lower incidence of AD. Since there is currently no evidence on the mechanism by which these agents offer possible neuroprotection, we investigated the potential neuroprotective properties of the nonsteroidal anti-inflammatory drug, ibuprofen, by examining whether this agent could reduce lipid peroxidation and superoxide radical generation. Quinolinic acid and cyanide, known neurotoxins, were used to induce lipid peroxidation and superoxide anion formation respectively, in rat brain homogenate. The results show that ibuprofen significantly (p more than 0.05) reduced quinolinic acid-induced lipid peroxidation and cyanide-induced superoxide production. The results of the present report therefore suggest a possible mechanism for the neuroprotective effect of ibuprofen.
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  • Date Issued: 2000

An investigation into tools and protocols for commercial audio web-site creation

  • Authors: Ndinga, S'busiso Simon
  • Date: 2000
  • Subjects: Web sites -- Design , Digital libraries , Internet -- Security measures
  • Language: English
  • Type: Thesis , Masters , MSc
  • Identifier: vital:4621 , http://hdl.handle.net/10962/d1006488 , Web sites -- Design , Digital libraries , Internet -- Security measures
  • Description: This thesis presents a feasibility study of a Web-based digital music library and purchasing system. It investigates the current status of the enabling technologies for developing such a system. An analysis of various Internet audio codecs, streaming audio protocols, Internet credit card payment security methods, and ways for accessing remote Web databases is presented. The objective of the analysis is to determine the viability and the economic benefits of using these technologies when developing systems that facilitate music distribution over the Internet. A prototype of a distributed digital music library and purchasing system named WAPS (for Web-based Audio Purchasing System) was developed and implemented in the Java programming language. In this thesis both the physical and the logical component elements of WAPS are explored in depth so as to provide an insight into the inherent problems of creating such a system, as well as the overriding benefits derived from the creation of such a system.
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  • Date Issued: 2000

An investigation of learners' perceptions of homework in relation to the learning of mathematics : case studies in the northern townships of Port Elizabeth

  • Authors: Wendt, Gabriele Erika
  • Date: 2000
  • Subjects: Homework -- South Africa -- Port Elizabeth Mathematics -- Study and teaching -- South Africa -- Port Elizabeth Mathematics -- Study and teaching -- South Africa -- Case studies Education and state -- South Africa Education -- South Africa
  • Language: English
  • Type: Thesis , Doctoral , PhD
  • Identifier: vital:1635 , http://hdl.handle.net/10962/d1003517
  • Description: Matriculation pass rates in South Africa, especially in Mathematics, have been poor. The literature and personal experience suggests that a problem with homework may be a factor in this. In order to discover how Port Elizabeth learners from ex-DET schools perceived and experienced Mathematics homework, and the nature of such homework, ten case studies of Grade 11 learners were done. While conducting and analyzing the case studies, a pattern emerged from the findings, which together with some new questions, needed to be explored on a larger sample population. In order to do this and to be able to generalize the findings, four follow-up studies in the form of surveys on Mathematics homework were conducted at nine schools. These studies involved a learner questionnaire, a teacher questionnaire, the timing of learners as they did set Mathematical problems and the analysis of common errors made by the learners while doing the problems. The findings revealed that learners received too little homework too infrequently and did it inefficiently and ineffectively. The learners worked too slowly, did not complete the homework, left out the difficult problems and made numerous unnecessary mistakes. However, most of the learners claimed to have enough time available to do their homework and spent approximately one hour on Mathematics homework when it had been assigned. Many of the misconceptions and the resultant errors originated from work that should have been well covered in previous grades. However, parts of the syllabi were omitted in previous grades and completion of the syllabus and homework was only seriously considered in Grade 12. Some implications of the findings for educational practice and further research are discussed.
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  • Date Issued: 2000

An investigation of male and female cognitive ability on the WAIS-III

  • Authors: Muirhead, Joanne
  • Date: 2000
  • Subjects: Wechsler Adult Intelligence Scale , Sex differences (Psychology) , Intelligence tests -- South Africa
  • Language: English
  • Type: Thesis , Masters , MA
  • Identifier: vital:3028 , http://hdl.handle.net/10962/d1002537 , Wechsler Adult Intelligence Scale , Sex differences (Psychology) , Intelligence tests -- South Africa
  • Description: This study, which formed part of a larger research project, investigated the effect of gender on test performance on the Wechsler Adult Intelligence Scale - Third Edition (WAIS-III). The WAIS-III was administered to a sample of 68 participants in the Eastern Cape following the initiative of the Human Sciences Research Council to standardise the WAIS-III for a South African population. The participants, aged 19 to 30, were stratified according to language of origin (African or English First Language), educational attainment (matriculant or graduate), quality of education (Department of Education and Training or private/"Model C" school) and gender. Analyses of variance and two sample t tests were used to compare male and female test performance. For the total sample, no significant difference between males and females on Verbal, Performance and Full Scale IQ were found. On the factor indices, females scored marginally higher than males on Processing Speed at a level which was approaching significance (p = 0.105), but no significant differences were found. On subtest performance, females significantly outperformed males on Digit Symbol (p = 0.020). Differences which were approaching significance were found on Information (p = 0.133) in favour of males, and on Matrix Reasoning (p = 0.092) in favour of females. For subgroups of the total sample, the most significant differences in test performance were found for the African First Language private/"Model C" school cohort in favour of females. Thus the overriding implication that emerged from this research was that on this relatively highly educated sample, no significant gender differences in cognitive ability were apparent.
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  • Date Issued: 2000

An investigation of parental non-involvement in the governance of a Duncan Village school and its implications for the management of the school : a case study

  • Authors: Ndlazi, Sibongile Mandisa
  • Date: 2000
  • Subjects: School management and organization -- South Africa -- Eastern Cape Education -- Parent participation -- South Africa Education -- Parent participation -- Case studies
  • Language: English
  • Type: Thesis , Masters , MEd
  • Identifier: vital:1639 , http://hdl.handle.net/10962/d1003521
  • Description: This study explores the perceptions that parents have about their non-involvement in the governance of a Duncan Village High School, and considers the implications of such perceptions for the management of the school. Recent discussions on Radio Talk Shows and articles written in local newspapers indicate that Black parents have generally not been involved in the education of their children at the traditionally Black schools. Parental non-involvement also emerges as a strong theme in recent research. However, most of the research and media coverage focuses on school management's perceptions of the reasons and consequences of such non-involvement. The parents' voices have rarely been heard. Against this background, as well as the fact that the South African Schools Act presents a strong case for the involvement of parents in school governance and management, a phenomenological investigation was conducted at a traditionally Black Duncan Village High School. I chose phenomenology because I believed this approach has the potential for revealing my respondents' attitudes and perceptions. The sample consisted of four parent members of the school governing body who were key informants. The respondents were subjected to unstructured interviews which were held at their homes. The interviews probed the background and reasons for their lack of involvement, and the possible implications ofthis non-involvement for school management. The most significant of the wealth of findings is that parental non-involvement is linked to the historical background of the culture of non-participation of Black people which was created and encouraged by the successive White Governments in South Africa.
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  • Date Issued: 2000

An investigative case study of the introduction of democratic decision-making within an East London secondary school

  • Authors: Carelse, Garth Craig
  • Date: 2000
  • Subjects: School management and organization -- South Africa Decision making -- Cast studies Education and state Ebenezer Majombozi High
  • Language: English
  • Type: Thesis , Masters , MEd
  • Identifier: vital:1920 , http://hdl.handle.net/10962/d1007404
  • Description: The move towards greater democracy and participation in our education system is legislated quite succinctly in our South African Schools Act. The Act furthermore, and more importantly for this case study, posits that decision-making should be democratic in nature and our schools should eventually become governed in a collaborative and co-operative manner. Other policy texts such as the Labour Relations Act and the South African Constitution canonise the demand for a democratic South African society. This study investigates how democratic decision-making practices are taking place in an East London Secondary School namely Ebenezer Majombozi High. Even though distinct links exist between management and governance arms of schools, this study concentrates predominantly on decision-making within the school governing body and touches briefly on management thinking trends as a theoretical background to the kind of management at the school. What makes the school interesting as a case study is its rich history and its location in a deprived and impoverished township environment. The school was also part of the ex-Department of Education and Training, the black educational department of the past apartheid state. The kind of research undertaken was in the form of unstructured personal interviews with influential stakeholders at the school. Some of these stakeholders fonn part of the school governing body and the questions asked probed forms of governance at the school and how decision-making impacted on the overall school governance. The research findings acknowledges that decision-making does occur democratically at the school but that the practical implementation of positive consensual decisions are rarely realized. The school governing body only meets to deal with crises underpinned by a lack of learning and teaching and has not even debated the policies within the South African Schools Act. The study also argues that only by building capacity within the school and empowering the stakeholders, can constructive participation by all become a reality.
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  • Date Issued: 2000

Analysis of strategies used by an organisation to manage conflict

  • Authors: Lourens, Ann Sharon
  • Date: 2000
  • Subjects: Conflict management , Negotiation in business , Mediation
  • Language: English
  • Type: Thesis , Masters , MTech
  • Identifier: vital:10828 , http://hdl.handle.net/10948/18 , Conflict management , Negotiation in business , Mediation
  • Description: This research study addresses the problem of determining the strategies that can be used to manage conflict effectively. To achieve this objective a comprehensive literature study was performed to determine the views on conflict and various models of conflict. The study also included the reasons for and sources of conflict and the effects of conflict on an organisation. The next step was to identify the conflict management strategies that were revealed by the literature study. The appropriate conflict handling styles, how to improve organisational practices and special rules and structures were discussed as well as various suggestions from different authors on how to resolve a conflict situation. Based on the information obtained from the literature study a model was developed to serve as a guide to organisations to manage conflict effectively. Managers from a specific organisation were requested to complete questionnaires in order to determine the strategies used by their organisation to manage conflict. The questionnaire was developed in accordance with the findings from the research. The answers of the respondents were analysed and compared to the findings of the literature study. The information obtained from the literature study and from the respondents resulted in various recommendations and conclusions. The previously mentioned model that was developed was applied to the organisation, specifically addressing the pertinent issues as indicated by the respondents.
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  • Date Issued: 2000

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Application of the Minolta chromameter to the assessment of corticosteroid-induced skin blanching

Aspects of reproduction in the four-striped field mouse, Rhabdomys pumilio

  • Authors: Jackson, Claire
  • Date: 2000
  • Subjects: Microtus , Mice , Mice -- Reproduction
  • Language: English
  • Type: Thesis , Masters , MSc
  • Identifier: vital:5637 , http://hdl.handle.net/10962/d1005319 , Microtus , Mice , Mice -- Reproduction
  • Description: Rhabdomys pumilio, in the Eastern Cape of South Africa, does not use short day length as an inhibitory cue for reproductive activity, and, despite previous records indicating that these mice are strictly seasonal in their reproduction, litters have been found during the winters of some years,both in the Eastern Cape and in the Western Cape. This led me to believe that the reproductive activity of Rhabdomys pumilio is more opportunistic and that the cue or cues used to control reproduction are less predictable and, or more variable than the photoperiod cue used by many seasonally reproducing rodents. Two experiments were conducted, investigating the influence of low ambient temperature (15⁰C)and reduced food availability on the reproductive activity of both male and female four striped field mice. Mice were maintained in one of four conditions (food restricted at 15⁰C, food restricted at 26⁰C, ad lib. food at 15⁰C, and ad lib. food at 26⁰C) for 4 (males) and 8 weeks (females)(photoperiod 12L:12D, humidity 40%). Results indicated that the males reduced their reproductive activity slightly when exposed to either low temperature or low food availability and that maximum inhibition of reproduction occurred when mice were exposed to both low temperature and low food availability. However, female reproductive activity was inhibited when exposed to low food availability, irrespective of the temperature. Both sexes of mice showed varying abilities to resist fat loss and, in the males, the size of the fat store had a significant effect on reproduction. This varying ability to resist fat loss could be related to levels of activity and in the females (where activity was quantified), high activity scores were significantly associated with reproductive inhibition. These results support the hypothesis that reproduction in Rhabdomys pumilio is opportunistic and controlled by the availability of energy. I propose that the females will be more sensitive to reproductive inhibition due to their far greater post-fertilization responsibilities, where the reproductive activity of the females is rapidly inhibited by a reduction in food availability, while the males are less readily inhibited by low food availability or low temperature, unless the change in the controlling factors is severe enough, or prolonged, at which stage their reproductive activity will cease. The significance of opportunistic reproduction in the seasonal but unpredictable climate of the study area is discussed.
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  • Date Issued: 2000

Aspects of the ecology and reproductive biology of the limpet, Helcion pruinosus (Gastropoda : prosobranchia)

  • Authors: Henninger, Tony Oskar
  • Date: 2000
  • Subjects: Prosobranchia , Limpets -- Reproduction , Limpets -- Ecology , Prosobranchia -- Ecology
  • Language: English
  • Type: Thesis , Masters , MSc
  • Identifier: vital:5641 , http://hdl.handle.net/10962/d1005323 , Prosobranchia , Limpets -- Reproduction , Limpets -- Ecology , Prosobranchia -- Ecology
  • Description: Helcion pruinosus, the rayed limpet, is found in the midshore region of the intertidal zone, (i.e. the Balanoid zone) of rocky shores, from Saldanha Bay to Sodwana Bay along the coast of South Africa. At Gonubie (32°57'S/25°01'E) this species of limpet was found under boulders, (when not feeding), and could reach average densities of 85/ m². The limpets prefer smooth boulders, avoiding those encrusted by coralline algae or boulders with a rough texture. There was no habitat segregation between adult and juvenile H. pruinosus, i.e. there was no sign of up-shore migration by larger individuals. Males out-numbered females by, on average 1.4 : 1, which was a similar sex ratio to that of the congeneric species, H. pectunculus (Gray, 996). Unlike H. pectunculus, there were no differences in shell lengths between males and females (p = 0.946 at Gonubie, south-east coast and p = 0.961 at Kommetjie, south-west coast; t-test). Shell height could also not be used as a criterion to differentiate between the sexes. The average maximum shell length of H. pruinosus at Gonubie and Kommetjie was 25 mm, but the maximum shell lengths found were 30 mm, (one individual in each case), on both the southeast coast and west coast. Growth occurred most rapidly in the first year of life, with individuals reaching 15 mm after 1 year. In the second year limpet growth slowed to only 7 mm. Sexual maturity was reached at a shell length of between 11 to 14 mm (at an age of 8 months to 1 year). The life-span of H. pruinosus was determined at 2.55 years on the south-east coast and 2.9 years on the south-west coast. Micro-growth bands were produced tidally. Growth occurred allometrically, i.e. shell length increased at a faster rate than shell height. The limpets foraged during low tide, at night, presumably feeding on epilithic algae on the boulders. A second smaller peak of limpet activity was often recorded during the day, when low tide coincided with dawn). More limpets (up to ten times more) were active at spring tides compared to neap tides. Limpet activity was greatest during the spring tides of autumn. During all seasons limpet activity peaked 30 minutes before low water, after which numbers decreased rapidly. All limpets had retreated beneath the boulders before being covered by the flooding tide. It was concluded that the limpets were responding to both endogenous and exogenous cues, but the actual stimulus for retreat could not be determined. The limpets did not return to a fixed scar nor did they return rigidly to a home site. H. pruinosus was found to be gonochoristic. Sexes could be separated, on dissection, according to the colour of their gonads (males had white gonads, whilst that of the females was olive-green). Gonads were present throughout the year in most individuals, i.e. totally spent animals were never observed. Reproductive seasonality was similar in west coast and south-east coast animals. The gonad indices of the west coast limpets were higher, (maximum of 35%), compared to that on the southeast coast, (25%). The animals were probably trickle spawners, with some individuals liberating gametes throughout the year. There was however synchrony in gametogenesis between male and female limpets on both the west coast and south-east coast lines. Gonad indices peaked in the summer months (October to December) with a second minor peak in April/May. These peaks occurred before the release of the gametes in spawning events. The gonad index was lowest in winter, (July). The ovaries were full of mature eggs (oocytes having a diameter of 200 to 250 ~) prior to spawning. The acinal wall thickness had been decreasing prior to spawning. After spawning there was an increase in previtellogenic eggs « 100 μm) in females, and an increase in the acinal wall thickness to indicate spermatogenesis. The two populations are subjected to different environmental conditions and the actual cue for stimulating the release of gametes could not be determined. Finally, a table of differences between H pruinosus and its sister species, H pectunculus was created to show the life-style of H pruinosus.
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  • Date Issued: 2000

Assessing alternative assessment: students' experiences of the different forms of assessment in a Bachelor of Education course

  • Authors: Hendricks, Monica
  • Date: 2000
  • Subjects: Education, Higher -- South Africa -- Evaluation Educational tests and measurements -- South Africa
  • Language: English
  • Type: Thesis , Masters , MEd
  • Identifier: vital:1424 , http://hdl.handle.net/10962/d1003305
  • Description: In this study I examine the current alternative forms of assessment that were employed in the foundation year of the Bachelor of Education course at Rhodes University in 1998. Since assessment is concerned with ascertaining the amount, and kind, of learning that has taken place, it links learning and teaching. As my role in the course was academic development, I was interested in the nature ofthe development that the course promoted, for lecturers and students. My main intention was to gain insight into students' experiences of the assessment practices. To this end I selected six students, photocopied all their academic writing for the year and interviewed them. In addition, to provide a holistic picture of assessment and marking, I interviewed the six lecturers who team-taught the course. The data thus included the course assignments of the six students and an interview with each student as well as with the course lecturers. The findings show that though policy documents advocate alternative forms of assessment, implementing such assessment is a complex matter for both teachers and students.
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  • Date Issued: 2000

Assessing the potential for biological invasion - the case of Ammophila arenaria in South Africa

  • Authors: Hertling, Ursula M , Lubke, Roy
  • Date: 2000
  • Language: English
  • Type: Article
  • Identifier: vital:6518 , http://hdl.handle.net/10962/d1005947
  • Description: Many plants, especially woody species, introduced into South Africa for ornamental or commercial purposes, have become invasive in a number of habitats. Because of the risk of an invasion of coastal dunes by yet another species, the European dune grass Ammophila arenaria, used as a dune stabilizer, is assessed using lists of attributes of invasive species and invasible ecosystems. It is impossible to predict plant invasions, but both invasive species as well as invaded ecosystems are often characterized by certain attributes which facilitate invasions. Many of the species attributes connected with invasion appear to apply to A. arenaria. Above all, the grass is characterized by ecological tolerance and vigorous rhizomatous reproduction. An important site attribute connected with invasion is an evolutionary history with isolation patterns, which applies to the South African Cape coast. We conclude also on the basis of the overseas experience, that the potential for A. arenaria to become invasive needs urgent investigation in the South African context.
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  • Date Issued: 2000

Assessment of the potential contribution of the Coega industrial development initiative to the Eastern Cape Economy

  • Authors: Bibby, Ray Russ
  • Date: 2000
  • Subjects: Harbors -- Environmental aspects -- South Africa -- Port Elizabeth , Industrial development projects -- South Africa -- Port Elizabeth
  • Language: English
  • Type: Thesis , Masters , MTech
  • Identifier: vital:10830 , http://hdl.handle.net/10948/20 , Harbors -- Environmental aspects -- South Africa -- Port Elizabeth , Industrial development projects -- South Africa -- Port Elizabeth
  • Description: The research problem addressed in this study was to analyse and report on the development of the Coega Industrial Development Zone as an infrastructure for renewed entrepreneurial activity and profitable management of existing firms in the Eastern Cape. To achieve this objective, a literature study was undertaken to assess the potential benefits achieved at similar industrial development zones around the world and what could be learnt from these developments which will make the Coega Industrial Development Zone workable. The Empirical results obtained, indicate that most local companies are confident that the Coega industrial Development Zone will be beneficial to the region. In conclusion, various recommendations have been made with regard to the findings ascertained in the Empirical Study.
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  • Date Issued: 2000
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