Survival studies using cell sorting techniques together with data averaging on asynchronously dividing V79-WNRE cells reveal statistically significant evidence of substructure in the radiation survival response at low dose (2 to 3 Gy) that cannot be adequately characterized by a single linear-quadratic function, S = exp( -αD -βD²). The data suggest a two-component response that is particularly evident when plotted in the linear form of the linear-quadratic equation, -ln(S)/D = α + βD. Application of other survival models (Single Hit + Multi Target and Repair-Misrepair) does not eliminate the substructure. The substructure may result from subpopulations of cells at different stages of the cell cycle, which differ in their radiosensitivity, giving rise to a two-component survival response. In order to explore this hypothesis, studies were carried out with populations of partially synchronized cells. The mitotic selection technique was employed alone or in combination with 12 hours exposure to 1 mM hydroxyurea or 1 μg/ml aphidicolin to obtain large numbers of synchronized cells. G1/S phase populations obtained by mitotic selection followed by hydroxyurea or aphidicolin do not show the substructure found for asynchronous cells, thus supporting the hypothesis. G1 phase populations obtained by mitotic selection alone revealed substructure which could be characterized by a single fit to the RMR or SH+MT models. Structure was also present in the response of heterogeneous S/G2 phase populations synchronized by mitotic selection followed by hydroxyurea, but may not be present in the response of S phase populations synchronized by mitotic selection alone. The data are consistent with the hypothesis that the substructure is a result of sensitive (G1, G2 or M) and resistant (S) subpopulations of cells. / Science, Faculty of / Physics and Astronomy, Department of / Graduate

The sensitivitiy of several species of marine phytoplankton to copper was investigated. No specific trends were found with respect to any general differences between diatoms and dinoflagellates or between different sized cells. Further investigation using a single bioassay species, Nitzschia lonqissima, indicate it to be very sensitive to cupric ion activity. Several physiological systems appear to be affected to different degrees, with cell division being more affected than photosynthetic pigment production or ¹⁴C uptake. The activity of the enzyme nitrate reductase is greatly increased by the addition of low concentrations of copper. / Science, Faculty of / Zoology, Department of / Graduate

Sub-acute ozone exposures (doses below the threshold for visible injury) have been found to affect plant growth, stomatal behavior, and the extent of visible injury in response to subsequent acute exposures (doses above the threshold for visible injury). The interrelationships of these effects varied according to the magnitude and timing of the pretreatment dose and the particular species and cultivar tested. When seedlings of bush bean (Phaseolus vulgaris L. cv Pure Gold Wax) were raised from seed in filtered air and then pretreated with 0.02 parts per million (ppm) ozone for six days (six hours per day), beginning at eight days after sowing, susceptibility to acute injury (the extent of visible injury after an acute exposure) was greater than that of controls maintained throughout in filtered air. Seedlings exposed to this low ozone treatment for an additional seven days became less susceptible to acute injury than controls maintained in filtered air. Treatment differences in acute susceptibility were found to correspond to differences in stomatal behavior. At the early stage of increased susceptibility, ozone-p're-treated plants and controls maintained in filtered air had the same stomatal resistance when measured in filtered air, but ozone-pretreated stomata had a reduced tendency, to close in response to an acute ozone exposure (0.4 ppm). At the later stage of decreased acute susceptibility, ozone-pretreated stomata still had this reduced sensitivity to ozone-induced closure, but ozone pretreatment also resulted in an overall increase in stomatal resistance in filtered air, prior to acute exposures. Stomatal entry of ozone may thus provide, in part, an explanation for the differences in susceptibility resulting from these treatments in bean. Exposure of mint cuttings (Mentha arvensis L.) to 0.02 ppm ozone increased their acute susceptibility slightly. The ozone tolerance of mint was approximately six times greater than that of bean seedlings raised in filtered air (based on the dosage required for equivalent degrees of visible injury). In experiments with potted grapevines (Vitis labruscana, Bailey) in open-top field chambers exposed to ambient air (containing "naturally ocurring" ozone) or charcoal-filtered air (containing reduced ozone levels) for an entire growing season, growth was found to be greater in ambient air in two of three cultivars tested. This growth stimulation was greatest in leaves, but occurred also in trunks and roots (both dry weight and fresh weight). Within the three cultivars ('Ives', 'Concord', and 'Delaware') the growth stimulation was directly related to the sensitivity of field-grown vines to ozone injury; the most sensitive cultivar, 'Ives', showed the greatest growth increase in ambient air as compared to filtered air. Only one of the grapevine cultivars. showed any statistically significant effect of chronic exposure to ambient ozone on acute susceptibility. In that case, 'Delaware', the cultivar most resistant to ozone injury in the field, was predisposed to acute injury by chronic pretreatment with low ozone. With grapevines, there were no statistically significant effects of low ozone pretreatment on stomatal behavior, but trends in the data indicated that ozone pretreatment tended to decrease both stomatal resistance when measured in filtered air and closure in response to acute ozone exposures (0.75 ppm). In experiments with grapevines, unlike those with beans, decreased susceptibility appeared to be more closely related to an increase in overall vigor, associated with a lower stomatal resistance in filtered air, rather than to a stomatal mechanism regulating ozone entry into the leaf. Although there were differences between species in the role that stomata play in the response to pretreatment with sub-acute ozone doses, there was the suggestion of a general pattern of increased tendencies toward a protective effect of ozone pretreatment in more ozone-sensitive species (bean versus mint) or cultivars ('Ives' and 'Concord' versus 'Delaware'). / Land and Food Systems, Faculty of / Graduate

The microwave dielectric constant and conductivity of MEM(TCNQ)₂ were studied in the neighbourhood of the monomer to dimer transition at 61°C using cavity-perturbation techniques at 9 GHz. The conductivity was found to be in general agreement with four-probe d.c. results. Thus, doubts about the reliability of the d.c. measurements above the destructive transition have been removed. The complex dielectric constant of TTF-TCNQ at liquid helium temperatures was studied using dielectric resonance techniques. Some anomalies regarding the interpretation of the dielectric resonance mode plots were resolved. Values for Є’ of (3.0±0.4)X10³ and for Є’of greater than 9 were implied by the results. Finally, preliminary results and proposed directions for a bolometric absorption measurement in TTF-TCNQ in the microwave bands are presented. This technique may prove useful for the direct observation of the pinned charge density wave in TTF-TCNQ. / Science, Faculty of / Physics and Astronomy, Department of / Graduate

M.Ed. (Curriculum Studies) / This study arises from the common perceptive of teachers and coaches that the pupil who actively participates in sport and other extramural activities, are the better academic achievers as well. Education is aimed at the total development of the child (this includes the physical, intellectual, spiritual and social aspects of his/her development.) Besides the everyday personal questions and problems that form part of a pupil's life, the pupil is also expected to develop his/her physical capabilities, build up self-confidence and in the process acquire dignity and a sense of self. At the same time it is also expected that the pupil achieve academically. The study was carried out in two ways. Firstly, a literary survey was undertaken, dealing with child development in a sosiopedagogic perspective, with the accent falling on the important role that sport plays in t~e child's quality of life. Secondly, the literature survey serves as a foundation for the empiric research that was done by means of a questionnaire, to establish whether there is any connection between activity/achievement in sport and other extramural activities and the pupil's educational progress which is the sole purpose of this study.

Most air pollutant investigations in controlled environments have utilized the conventional "steady state" exposure, yet air pollutant concentrations are rarely static in ambient conditions. Peak concentrations in air pollutant exposures vary in magnitude and occurrence despite equivalent doses and are likely to result in different degrees of injury to plants. The results of experiments involving 5 treatment regimes with a single peak concentration that varied in magnitude and occurrence while treatment doses remained equivalent, confirm this hypothesis and demonstrate that the levels of injury to bush beans (Phaseolus vulgaris)and radish (Raphanus sativus) may vary from 15 to 85% of the leaf area. An absolute injury assessment technique was developed for determining percent necrosis in the 5 treatments, with the same two crop species responding in a similar manner to the various constant dosage regimes. A simple workable model is presented that incorporates stomatal diffusive resistance along with the various exposure components, including cumulative dose, maximum concentration, and the interval of time during which the peak concentration was administered. Preliminary investigations failed to confirm an interaction between ozone and greenhouse whitefly in bush beans. / Land and Food Systems, Faculty of / Graduate

In Part I, a modified synthesis of radio-labelled secodine (68) and its incorporation into vindoline (7) is described. In a model study, for the synthesis of side-chain labelled 3-ethylpyridine (74), [2-² H]-(3'-pyridyl)-ethane was achieved from the correspondingly labelled 3-acetylpyridine by desulphurization of the intermediate thioketal (93). In a second study, [1- ³H]-(3'-pyridyl)- ethane was synthesized by treating 3-acetylpyridine with sodium borohydride-³H. The resulting alcohol (95) was acetylated, and hydrogenolysis achieved the desired product. The ester alcohol (74) was coupled to [1- ³H]-(3'-pyridyl)-ethane and the resulting pyridinum salt (90) was reduced to the corresponding piperdeine ester (80) in a "one-pot" synthesis. The conversion of (80) to [19-³H]-secodine was achieved by a known procedure. In two experiments, [19-³H, ¹⁴C0₂CH₃]-secodine (68)(³H/¹³C ratios = 3.00 and 1.54) was administered to Catharanthus roseus plants. The vindoline (7) which was isolated was shown to have been biosynthesized from the entire secodine molecule (³H/¹³C = 3.31 and 1.35 respectively). In Part II, a degradation scheme designed to achieve the isolation of the N-methyl group of uleine (1) is described as well as preliminary results from an investigation into the biosynthesis of uleine (1) and olivacine (4). Variously radio-labelled forms of tryptophan (15), anthranilic acid and secodine (18) were administered to Aspidosperma pyricollum root segments and whole plants. The uleine (1) which was isolated was found to be inactive in all experiments. Variously radio-labelled forms of tryptophan (15), anthranilic acid and secodine (18) as well as ¹⁴CH₃-methionine (30) was administered to Aspidosperma australe plants. Uleine (1) and olivacine (4) was isolated. The only incorporation that could be demonstrated was that of ¹⁴CH₃ methionine (30) into uleine (1) to the extent of 0.168% and 0.147%. The isolation of the N-methyl group from (1) showed that it contained 97% and 98% of the activity. In Part III, the attempted synthesis of compounds of the preakuammicine- and stemmadenine-series is described. A new method for the C-18 deoxygenation of curan derivatives using Birch reduction conditions was achieved. Also, a modification of the Oppenauer oxidation of the curenol (36) to achieve improved yields of the aldehyde (37) and nor-fluorocurarine (39) was developed. The introduction of a carbomethoxy group into the C-16 position of the curan aldehyde derivatives (44) and (50) using a base and methylchloroformate was unsuccessful. Also, the introduction of cyanide into position C-16 of the indole alcohol (52) or indole acetate (57) via the corresponding chloroindolenines was unsuccessful. The synthesis of product (60), which is believed to be identical with preakuammicine aldehyde (7), was achieved. This material could not be converted into akuammicine (5) or stemmadenine (4). Only the dehydrated indolenine (72) could be obtained. The ring-opening reaction of the corresponding thioacetal derivative (73) yielded the decarboxylated indole thioacetals (75) and (76). / Science, Faculty of / Chemistry, Department of / Graduate

This study looked at effects of organic solvents dimethylsulfoxide, dimethylformamide and acetone at 0.01%, 0.05% and 0.1% concentration on germination and seedling development wetland plants. Even at 0.01% level, all solvents affected some aspect of seed germination or seedling growth. Acetone at 0.01% was least toxic. Root morphological characteristics were most sensitive compared to shoot morphological characteristics. This study also looked at bioconcentration patterns of antimicrobial compounds triclosan, triclocarban and methyl-triclosan in wetland plants exposed to Denton Municipal Waste Water Treatment Plant effluent. Bioconcentration patterns of antimicrobial compounds varied among species within groups as well as within organs of species. The highest triclocarban, triclosan and methyltriclosan concentration were in shoot of N. guadalupensis, root of N. lutea and in shoots of P. nodous respectively.

Africa’s conservation areas have vast road networks as a result of motorized vehicle game viewing. In conservation areas these roads provide increased accessibility to previously inaccessible areas, often with negative ecological impacts, such as wildlife fatalities and decreased habitat quality and connectivity. Additionally, tar roads often have a greater negative effect on mammal species than dirt roads, altering their spatial distribution and behaviour to a greater extent. The Kruger National Park, South Africa, has 2294 km of public roads within the park, of which 850 km is tarred – carrying a higher traffic density than dirt roads – and 1444 km is dirt. The aim of this study was to compare the ecological impacts of tar and dirt roads on medium to large mammal species in the Kruger National Park, hypothesizing that the tar roads within the park have greater negative impacts on the park’s mammal species. I focused on three response variables: 1. observation likelihoods; 2. species group sizes and 3. distances to the road, comparing tar to dirt roads. Sampling was done at 1 km intervals, for 430 km of tar and 430 km of dirt roads, in savanna vegetation during the Austral winter of 2017 and 2019. In total 476 sampling points were on tar roads (401 systematic and 75 ad hoc) and 451 on dirt roads (369 systematic and 82 ad hoc). At each sampling point, all observed medium to large mammals, their group size, distance of the closest individual to the road, GPS coordinates, traffic volume and percentage cloud cover were recorded. Chi-square analyses were used to identify associations between species presence and road type. To determine the relationship between group size and road type, as well as the observed distance from the road and road type, Generalised Linear Models (GLMs) were used. The results refute the hypothesis of increased ecological impacts associated with tar roads, as the majority of the commonly occurring mammal species were not disproportionately associated with a specific road type. My results indicated that, as a tourist, one has an equal likelihood of observing the majority of the common mammal species from either road type. The results suggest that the increased traffic intensity of tar roads does not decrease one’s chances of viewing game, as hypothesized. The commonly occurring species were also observed at similar distances from both road types, and all were observed on the road, suggesting a limited barrier effect, if any. Previous studies on the impacts of road type on mammals both support and contradict my results. Elephant (Loxodonta africana) was the only species that was associated with a road type, although the complete opposite was found to what was hypothesized. Elephant occurred more often alongside tar roads (albeit only in the north of the park) than dirt roads, in larger groups next to tar roads and closer to tar roads. Potential reasons that are discussed are higher quality forage, plant species richness, group vigilance and predator avoidance. My results can have an influence on park management decisions and communication with tourists. Tourists can be informed that they do not need to make use of dirt roads, which are often less accessible, to view game. In terms of road management, my results suggest that the temporary closure of dirt roads for rehabilitation should not affect game viewing. It is, however, suggested that further research is needed to compare the influence of public to private road areas on animal ecology within the Kruger National Park, as well as to compare the influence of road areas to completely natural areas. / Mini Dissertation (MSc (Environmental Ecology))--University of Pretoria, 2020. / Thuthuka programme - National Research Foundation (NRF) of South Africa (Grant no. 94103). / Zoology and Entomology / MSc (Environmental Ecology) / Restricted

The neuroanatomical consequences of chronic ethanol ingestion were investigated using neuropsychological tests selectively sensitive to damage in circumscribed brain areas-~~~ The performance of a group of male alcoholics (N=15) with a self-reporte?- drinking history less than ten years, and a group of male alcoholics (N=15) with a self-reported drinking history of ten or more years was compared to a group of male nqnalcoholic controls (N=15). l.A--multiple covariate analysis was done prior to analyzing group differences to determine what influence three covariates (age, education and socioeconomic status) had on the group performances. Results from this analysis indicated that some of the tests were significantly influenced by age or education but no significant Group x Covariate interactions were observed. /JCn agreement with numerous neuropathological findings, the late stage alcoholics were found to be principally deteriorated on the tests of frontal lobe functioning, followed by lesser impairment on the tests of temporal lobe functioning, with no evidence of impairment on the tests of parietal lobe functioning~ No significant group differences were found betv1een the early stage alcoholics and the controls~ Small but negative correlations were found between both the duration of alcoholism and the average amount of alcohol consumed with each of the neuropsychological measures given in this study.