The social transmission of social behaviours in nonhuman primates has been understudied, experimentally, relative to instrumental, food-related behaviours. This is disproportional in relation to the comparatively high percentage of potential social traditions reported in wild primates. I report a systematic survey of the social learning literature and provide quantitative evidence of the discrepancy (Watson and Caldwell, 2009). Addressing the identified deficit in experimental work on social behaviours, I also report three empirical studies investigating the contagious nature of affective states in captive, socially housed marmosets. I carried out an observational study, to determine whether marmosets are influenced by spontaneously produced neighbour calls to perform a range of behaviours associated with similar affect. My results supported a neighbour effect for anxiety in marmosets. Consistent with previous findings for chimpanzees (Baker and Aureli, 1996; Videan et al., 2005), I also found evidence for neighbour effects for aggression and affiliation (Watson and Caldwell, 2010). Through experimental playback, I investigated contingent social contagion in the auditory and visual modalities. The playback of pre-recorded affiliative (chirp) calls was found to be associated with marmosets spending increased time in a range of affiliative behaviours. Playback of video showing conspecifics engaged in a positive affiliative behaviour (allogrooming) also appeared to cause marmosets to spend longer performing various affiliative behaviours. My results indicate that social contagion of affiliation is a multi-modal phenomenon in marmosets and also represent the first evidence that allogrooming is visually contagious in primates. Sapolsky (2006) conceptualised culture as the performance of species-typical behaviours to an unusual extent, termed ‘social culture’. Researchers have yet to directly investigate a transmission mechanism. I investigated whether a social culture of increased affiliation could be initiated in marmosets through the long-term playback, of positive calls, or of video of positive behaviour. The results were consistent with a relatively long-lasting influence of the playback of affiliative calls across several affiliative behaviours. The effect appeared to last substantially beyond the specific hours of playback, between playbacks, and after playback had ceased, potentially indicating a temporary shift in social culture. These results are preliminary but provide some support for the proposal that auditory social contagion may be a transmission mechanism for social culture. The long-term video playback of allogrooming appeared to result in a transitory shift in performance of the identical behaviour (increased allogrooming) after playbacks had ceased. In addition to theoretical implications for social cognition and social culture, my findings have potential practical application for the enhancement of welfare in captive marmosets through sensory, and non-contact social, enrichment.

Campylobacter jejuni is the leading bacterial cause of gastrointestinal diarrheal disease in humans worldwide. This zoonotic pathogen has a complex epidemiology due to its presence in many different host organisms. The overall aim of this thesis was to explore the role of amoebae of the genus Acanthamoeba as an intermediate host and vector for survival and dissemination of C. jejuni. Earlier studies have shown that C. jejuni can enter, survive and replicate within Acanthamoebae spp. In this thesis, I have shown that C. jejuni actively invades Acanthamoeba polyphaga. Once inside, C. jejuni could survive within the amoebae by avoiding localization to degradative lysosomes. We also found that A. polyphaga could protect C. jejuni in acid environments with pH levels far below the range in which the bacterium normally survives. Furthermore, low pH triggered C. jejuni motility and invasion of A. polyphaga. In an applied study I found that A. polyphaga also could increase the survival of C. jejuni in milk and juice both at room temperature and at +4ºC, but not during heating to recommended pasteurization temperatures. In the last study we found that forty environmental C. jejuni isolates with low bacterial concentrations could be successfully enriched using the Acanthamoeba-Campylobacter coculture (ACC) method. Molecular genetic analysis using multilocus sequence typing (MLST) and sequencing of the flaA gene, showed no genetic changes during coculture. The results of this thesis have increased our knowledge on the mechanisms behind C. jejuni invasion and intracellular survival in amoebae of the genus Acanthamoeba. By protecting C. jejuni from acid environments, Acanthamoebae could serve as important reservoirs for C. jejuni e.g. during acid sanitation of chicken stables and possibly as vectors during passage through the stomach of host animals. Furthermore, Acanthamoeba spp. could serve as a vehicle and reservoir introducing and protecting C. jejuni in beverages such as milk and juice. Validation of the ACC method suggests that it is robust and could be used even in outbreak investigations where genetic fingerprints are compared between isolates. In conclusion, Acanthamoeba spp. are good candidates for being natural hosts and vectors of C. jejuni.

Not available / text

Mass spectrometry (MS) is a power analytical tool which is capable of analyzing biomolecules in great detail, both structurally and quantitatively. With regards to glycans, special considerations regarding sample preparation are necessary in order to achieve reproducible identification and relative quantification of these analytes. A workflow for isolation at the glycopeptide level and subsequent detection at the glycan level with phenylhydrazine, demonstrated that monoclonal antibodies (mAbs) containing a specific amino acid mutation were able to express approximately an additional 50% of the α2,6 disialylated glycan compared to their non-mutant analogues. In a second experiment using mAbs, an azide modified glycan (Ac4ManAz) was introduced both metabolically and enzymatically during mAb production. This glycan is a precursor in the sialic acid pathway and the azide moiety allows for specific chemistry post-production including the potential for highly specific enrichment. The results of this workflow demonstrated that [100 μM] of Ac4ManAz precursor added to the cell media was necessary for metabolic expression. More complex samples however, may contain multiple sites of glycosylation. To conserve the site of attachment, these molecules are often studied at the glycopeptide level, and require enrichment of glycopeptides to improve the lower signal intensity observed in the presence of co-eluting peptides. Carboxymethyl chitosan (CMCH) as well as amine-functionalized magnetic-nanoparticles (MNP) were developed as novel materials for this purpose. CMCH is naturally occurring, and therefore is cost-effective and readily available. In a 12 protein mixture CMCH demonstrated the bulk enrichment of glycopeptides yielding an approximately 20% higher enrichment of sialylated species as compared to a commercially available glycopeptide kit through the use of tandem mass tags for relative quantification. In the same approach, amine functionalized MNP were produced and used to enrich glycopeptides from tryptic digests. This approach was fast (about 10 mins) and quantitatively demonstrated improved retention for sialylated species. Examples of these techniques and their applications are reported in this work. / October 2015

The purpose of this study was to examine the effectiveness of Instrumental Enrichment, an educational program developed by Reuven Feuerstein, which attempts to improve an individual's ability to reason. A meta-analysis was performed on studies that had been conducted between the years 1979 to 1996. Thirty-six studies were analyzed according to their results from measurements in the cognitive/visual-perceptual, academic achievement and affective domains. The results from the meta-analysis were mixed. There were significant combined effect sizes of 0.24 for non-verbal ability, 1.41 for verbal ability, and 0.60 for one combination of full-scale ability. Significant effect sizes for measures of visual perception and visual-motor ability were 0.42, 0.71 and 1.68. There were also significant effect sizes for general achievement and for one combination of math achievement at 0.26 and 0.29 respectively. The intellectual achievement locus of control effect size was significant at 0.33. (Cohen (1988) considers an effect size of 0.20 to be small, that of 0.50 to be of medium size, and that of 0.80 to be large.) All effect sizes for reading were non-significant as was that for the Learning Potential Assessment Device. All other measures, such as those for self-confidence, self-concept, motivation and attitudes, in the affective domain were non-significant. One effect size for motivation and attitudes was significantly negative, indicating that the control group outperformed the treatment group. The results are discussed in terms of near- and far-transfer of learning.

Introduction: Chez les mammifères, la naissance de nouveaux neurones se poursuit à l’âge adulte dans deux régions du cerveau: 1) l’hippocampe et 2) la zone sous-ventriculaire du prosencéphale. La neurogenèse adulte n’est pas un processus stable et peut être affectée par divers facteurs tels que l’âge et la maladie. De plus, les modifications de la neurogenèse peuvent être à l’origine des maladies de sorte que la régulation ainsi que le rétablissement de la neurogenèse adulte doivent être considérés comme d’importants objectifs thérapeutiques. Chez la souris saine ou malade, la neurogenèse hippocampale peut être fortement régulée par l’enrichissement environnemental ainsi que par l’activité physique. Cependant, lors même que l’activité physique et l’enrichissement environnemental pourraient contribuer au traitement de certaines maladies, très peu d’études porte sur les mécanismes moléculaires et physiologiques responsables des changements qui sont en lien avec ces stimuli. Objectifs et hypothèses: Les principaux objectifs de cette étude sont de caractériser les effets de stimuli externes sur la neurogenèse et, par le fait même, d’élucider les mécanismes sous-jacents aux changements observés. En utilisant le modèle d’activité physique volontaire sur roue, cette étude teste les deux hypothèses suivantes: tout d’abord 1) qu’une période prolongée d’activité physique peut influencer la neurogenèse adulte dans le prosencéphale et l’hippocampe, et 2) que l’activité volontaire sur roue peut favoriser la neurogenèse à travers des stimuli dépendants ou indépendants de la course. Méthodes: Afin de valider la première hypothèse, nous avons utilisé un paradigme incluant une activité physique volontaire prolongée sur une durée de six semaines, ainsi que des analyses immunohistochimiques permettant de caractériser l’activité de précurseurs neuronaux dans la zone sous-ventriculaire et l’hippocampe. Ensuite, pour valider la seconde hypothèse, nous avons utlisé une version modifiée du paradigme ci-dessous, en plaçant les animaux (souris) soit dans des cages traditionnelles, soit dans des cages munies d’une roue bloquée soit dans des cages munies d’une roue fonctionnelle. Résultats: En accord avec la première hypothèse, l’activité physique prolongée volontaire a augmenté la prolifération des précurseurs neuronaux ainsi que la neurogenèse dans le gyrus dentelé de l’hippocampe comparativement aux animaux témoins, confirmant les résultats d’études antérieures. Par ailleurs, dans ce paradigme, nous avons aussi observé de la prolifération acrue au sein de la zone sous-ventriculaire du prosencéphale. De plus, en accord avec la seconde hypothèse, les souris placées dans une cage à roue bloquée ont montré une augmentation de la prolifération des précurseurs neuronaux dans l’hippocampe comparable à celle observée chez les souris ayant accès à une roue fonctionnelle (coureurs). Cependant, seuls les animaux coureurs ont présenté une augmentation de la neurogenèse hippocampale. Conclusions: Ces résultats nous ont permis de tirer deux conclusions nouvelles concernant les effets de l’activité physique (course) sur la neurogenèse. Premièrement, en plus de la prolifération et de la neurogenèse dans le gyrus dentelé de l’hippocampe, la prolifération dans la zone sous-ventriculaire du prosencéphale peut être augmentée par l’activité physique sur roue. Deuxièmement, l’environnement dans lequel l’activité physique a lieu contient différents stimuli qui peuvent influencer certains aspects de la neurogenèse hippocampale en l’absence d’activité physique sur roue (course). / Introduction: In mammals, new neurons continue to be produced throughout the adulthood in two brain regions: 1) the hippocampus and 2) the forebrain subventricular zone. Adult neurogenesis is not a stable process, and changes in response to diverse factors such as age and pathology. Furthermore, because changes in neurogenesis may in fact underlie pathogenesis, regulating or restoring neurogenesis is seen as an important therapeutic objective. In healthy and diseased mice, hippocampal neurogenesis can be robustly regulated by environmental enrichment. However, while physical activity and environmental enrichment are potentially important in the treatment of some pathologies, comparatively little is known about the molecular and physiological mechanisms underlying activity/environment-dependent changes in neurogenesis. Objectives and hypotheses: The primary objectives of this study are to characterize the neurogenesis-mediating effects of external stimuli and, in doing so, to elucidate the mechanisms that underlie observed changes. Using voluntary wheel running as a model, this study addresses two hypotheses: 1) that extended periods of physical activity can influence adult neurogenesis in the forebrain and the hippocampus and 2) that voluntary wheel running mediates neurogenesis through both running-dependent and running-independent stimuli. Methods: To address the first hypothesis, we used a prolonged six-week voluntary paradigm and immunohistochemical analyses to characterize neural precursor activity in the subventricular zone and hippocampus. To address the second hypothesis, we used a modified version of the above paradigm, where an additional group of mice were housed in cages with a locked running wheel. Results: With respect to the first hypothesis, prolonged voluntary wheel running was found to increase neural precursor proliferation and neurogenesis in the hippocampal dentate gyrus relative to control animals, confirming the results of previous studies. More importantly, in this paradigm, proliferation in the forebrain subventricular zone was also found to be increased. In keeping with the second hypothesis, mice that were housed in locked-running wheel cages showed an increase in hippocampal neural precursor proliferation comparable to that of running animals. However, only running animals displayed increased hippocampal neurogenesis. Conclusions: These results allow us to draw two novel conclusions regarding the effects of running on neurogenesis. First, proliferation in the forebrain subventricular zone, in addition to proliferation and neurogenesis in the hippocampus, is subject to regulation by wheel-running. Second, the wheel-running environment contains diverse stimuli which can influence some aspects of hippocampal neurogenesis in the absence of wheel running.

I investigated effects of environmental change on disease, and effects of disease on ecosystems, using a freshwater zooplankton host and its fungal parasite. This research involved lake surveys, manipulative experiments, and mathematical models. My results indicate that ecosystem characteristics such as habitat structure, nutrient availability, and quality of a host’s resources (here, phytoplankton) can affect the spread of disease. For example, a survey of epidemics in lakes revealed direct and indirect links between habitat structure and epidemic size, where indirect connections were mediated by non-host species. Then, in a mesocosm experiment in a lake, manipulations of habitat structure and nutrient availability interactively affected the spread of disease, and nutrient enrichment increased densities of infected hosts. In a separate laboratory experiment, poor quality resources were shown to decrease parasite transmission rate by altering host foraging behavior. My experimental results also suggest that disease can affect ecosystems through effects on host densities and host traits. In the mesocosm experiment, the parasite indirectly increased abundance of algal resources by decreasing densities of the zooplankton host. Disease in the experimental zooplankton populations also impacted nutrient stoichiometry of algae, which could entail a parasite-mediated shift in food quality for grazers such as the host. Additionally, I showed that infection dramatically reduces host feeding rate, and used a dynamic epidemiological model to illustrate how this parasite-mediated trait change could affect densities of resources and hosts, as well as the spread of disease. I discuss the implications of these ecosystem–disease interactions in light of ongoing changes to habitat and nutrient regimes in freshwater ecosystems.

The anterior thalamic nuclei (ATN) are a critical part of an extended hippocampal system that supports key elements of episodic memory. Damage or disconnection of the ATN is a component of clinical conditions associated with severe anterograde amnesisa such as the Korsakoff’s syndrome, thalamic stroke, and neurodegenerative disorders. Previous studies have demonstrated that the ATN and hippocampus are often interdependent, and that ATN damage can result in ‘covert pathology’ in ostensibly healthy distal regions of the extended hippocampal system. Adult male rats with neurotoxic bilateral ATN lesions or sham surgery were post-operatively housed in an enriched environment or standard housing after a lesion-induced spatial working memory deficit had been established. These rats were retested on cross-maze and then trained in radial-arm maze spatial memory tasks. Other enriched rats received pseudo-training only after the enrichment period. The detailed neuromorphology of neurons was subsequently examined in the hippocampal CA1. Soma characteristics were also examined in the retrosplenial granular b cortex and the prelimbic cortex. In Experiment 1, ATN lesions produced clear deficits in both the cross-maze and radial-arm maze tasks and reduced hippocampal CA1 dendritic complexity, length, and spine density, while increasing the average diameter of the dendrites. Post-operative enrichment reversed the ATN lesion-induced deficits in the cross-maze and radial-arm maze, and returned CA1 basal and apical spine density to a level comparable to that of sham standard housed trained rats. The sham enriched rats exhibited improved radial-arm maze performance and increased CA1 branching complexity and spine density in both basal and apical arbors compared to sham standard housed rats. The neuromorphological changes observed in the enriched ATN and sham rats may be in part responsible for the spatial working memory improvements observed. Experiment 2 provided support for this contention by demonstrating that the CA1 spine changes were explicitly relevant to spatial learning and memory, because trained enriched sham and ATN rats had increased spines, particularly in the basal tree when compared to closely comparable pseudo-trained enriched rats. Interestingly, spatial memory training increased the numbers of both thin and mushroom spines, whereas enrichment was only associated with an increase in thin spines. In Experiment 3, ATN lesions increased cell body size in layer II of the retrosplenial granular b cortex, whereas enrichment decreased cell body size in layer V of this region. Neither ATN lesions nor enrichment had any effect on cell body morphology in the prelimbic cortex. The current research provides some of the strongest evidence to date of ATN and hippocampal interdependence within the extended hippocampal system, and provides the first evidence of neuromorphological correlates of recovery after ATN lesions.

Raindrop kinetic energy and sheet flow can disintegrate aggregates during interrill erosion, a process responsible for non point source pollution. Also, the dissolution process during aggregate wetting can affect interrill erosion. These factors can be responsible for changes in particle size distribution in the sediment, especially when different tillage systems are compared. The effect of soil tillage and management on soil properties is not uniform, which determine a wide range of runoff and sediment delivery rate. Variety in these rates can be associated with pore functions and their interactions with aggregate stability. One of the objectives of this study was to analyze the wetting behavior of soil aggregates from soils under conventional tillage compared with soils under no tillage. It was expected that the wetting rate is a function of pore system and that different tillage systems would affect the soil wetting behavior based on their impact on soil structure and shape. The second objective was to analyze the relationships among soil wetting rate, particle movement, organic carbon (OC) and iron release with the sediment produced via interrill erosion. A rainfall simulation experiment was performed in the field to determine the effect of low and fast soil wetting on total soil loss through high and low kinetic rainfall energy, sediment particle size distribution and OC loss. Two soils that differed in soil textural composition and that were under conventional and no tillage were investigated. Soil loss depended largely on soil characteristics and wetting rate. Particle size distribution of sediment was changed by treatment and the proportion of particles smaller than 0.053 mm increased over time, at any kinetic energy wetting level. Temporal OC and iron release were constant, which required a continuous source principally due to aggregate slaking. An empirical model was proposed to improve an interrill erosion equation by using a bond-dissolution mechanism that identified soil as a regulator of particle release.

The realisation of the objectives of the South African Schools Choral Eisteddfod (SASCE) is influenced by the national education system and the environment it operates in. This thesis accordingly studies the SASCE within the organisational framework of the Department of National Education. It provides a comprehensive description of the factors that influence the achievement of the objectives of the SASCE in the FET band in the Motheo district of the Free State Province. South African national education policy provides for a single unified democratic system for the organisation, governance and funding of schools. The Department of National Education formulates policy and provinces are responsible for its implementation by means of district offices. In this respect the education system is regarded as an organisation consisting of different sub–organisations that must provide effective education in line with the educational needs of the country. A generic five–point model of effective organisational structure accordingly was applied to determine the factors impacting on the realisation of the objectives of SASCE. Data were gathered and analysed by means of personal observations, document analysis and semi–structured interviews with education officials, school principals and choir conductors. The challenges of the national education system with regard to appropriate facilities, equipment, funding, appropriately trained officials and educators, support staff and effective policy implementation are consistent with the challenges facing the Department of National Education’s enrichment programmes, of which the SASCE forms part. Findings and recommendations are offered for all research questions. A general recommendation pertains to a proposed restructuring of the provincial enrichment programmes sub–directorate in order to address some of its organisational shortcomings and also the challenges facing the SASCE. / Thesis (Ph.D (Music))--North-West University, Potchefstroom Campus, 2011.