Showing papers by "University of the Witwatersrand published in 1979"

Measuring Accessibility: A Review and Proposal

Abstract: An attempt is made to clarify some of the confusion about the notion of accessibility by examining the limitations, strengths, and conceptual bases of distance, topological, gravity, and cumulative-opportunity measures of accessibility. In their aggregate and disaggregate states the measures are practical, enabling measurement into the future and measurement with a minimum of data, but the assumptions that all nodes are potential destinations and that all origins are known severely restrict the meaning and uses of the measures. Time—space measures of accessibility do not make these assumptions although they are data hungry, retrospective, and share with the other measures the narrow conception of accessibility as a property of the built environment. It is proposed that accessibility be thought of as a vacancy in an activity routine and that it be measured in terms of the disruption involved in creating it.

Delta-aminolaevulinic acid is a potent agonist for GABA autoreceptors.

Abstract: ACUTE attacks of the hereditary hepatic porphyrias are frequently accompanied by neuropsychiatrie symptoms. The presentation of nervous system involvement varies; in decreasing order of frequency, there may be motor neuropathy, confusion, psychiatric manifestations, hyperexcitability and epileptic-type seizures1. Psychiatric manifestations include depression, anxiety, insomnia and an organic brain syndrome2. Although the aetiology of the neural dysfunction in the acute attack is unknown, several mechanisms have been suggested at a neurochemical level. It is possible that porphyrin precursors, which are produced in excess by the liver during acute episodes, gain access to the nervous system and exert direct neurotoxic effects3–5; alternatively, a metabolic defect in haem biosynthesis in nerve cells might result in a functional haemoprotein deficiency which becomes critical at the time of the acute attack6. The porphyrin precursor, δ-aminolaevulinic acid (δ-ALA), exhibits various effects in mammalian central nervous tissue preparations. It inhibits high-affinity uptake and increases efflux of γ-aminobutyric acid (GABA)3 and L-glutamate4 in rat cortical synaptosomes; it also inhibits the (Na+ + K+) ATPase isolated from rabbit brain and red blood cells7. These effects occur only at relatively high concentrations of δ-ALA (at least 10−4M), and it is very unlikely that such concentrations are reached in the brain during acute porphyric attacks8. Recently, there has been strong evidence that release of GABA is subject to negative feedback control through presynaptic receptors on GABAergic terminals9–11. Here we report that δ-ALA inhibits potassium-stimulated release of GABA from preloaded synaptosomes, probably by acting as an agonist at these presynaptic receptors. This effect is evident at concentrations of δ-ALA (10−6M) which are well within levels recorded in the cerebrospinal fluid of porphyric patients showing neuropsychiatrie symptomatology12.

The Effects of Job Enrichment on Employee Satisfaction, Motivation, Involvement, and Performance: A Field Experiment

Abstract: The effect of job enrichment on employee responses was investigated in a field experiment conducted in a federal agency among clerical employees, who were randomly assigned to either an enriched or unenriched condition. In the enriched condition, a systematic attempt was made to increase the extent to which the jobs of the employees possessed each of the dimensions of skill variety, task identity, task significance, autonomy, and feedback. In the unenriched condition, the employees performed their original duties and tasks. After a 6-month experimental period, the effect of enrichment was examined. The results showed that: (1) Employees in the enriched condition perceived their jobs as more enriched than before; (2) enrichment caused significant increases in employee job satisfaction, job involvement, and internal motivation; (3) enrichment led to significant decreases in absenteeism and turnover; but (4) enrichment had little impact on performance, whether assessed by superiors' ratings or by actual outp...

Early active motion following a beveled technique of flexor tendon repair: report on fifty cases.

Abstract: In an effort to overcome restrictive adhesions following flexor tendon repair, a technique involving beveling of the tendon ends and fine compressive suturing was used in 50 patients (110 tendons). Free early active motion was allowed. There were 70% good-to-excellent results, with a 10% rupture rate.

Transcutaneous electrical nerve stimulation and the reaction to experimental pain in human subjects

Abstract: The effect of peripheral transcutaneous electrical nerve stimulation (TENS) on the reaction to experimental pain in human volunteers has been assessed. Placebo stimulation and electrical stimulation at moderate intensities failed to modify the response to the pain produced by conducted thermal stimuli. TENS at very high intensities did however elevate both the thermal pain threshold and the tolerance temperature. TENS at moderate intensities failed completely to alter the response to graded mechanical stimuli. The subjective pain assessment and the maximum pain tolerance produced by ischaemic pain after a submaximal effort tourniquet test were significantly modified by peripheral electrical stimulation at non-noxious intensities. The response to experimental pain can therefore be altered in man by peripheral electrical stimulation in a manner partly dependent on the sensory modality used for producing the experimental pain and on the intensity of the electrical stimulation.

The Blue Tier Batholith, Northeastern Tasmania

Abstract: The Blue Tier Batholith is one of a number of high-level, essentially postkinematic, composite granitoid bodies occurring at the southern end of the Tasman orogenic belt of Eastern Australia. An integrated study of the structure, texture, and geochemistry of the batholith suggests that it has a cumulate-like character. In particular, the trace element (Ba, Rb, Sr) data, when constrained by textural features of the granitiods, indicate that the batholith formed by fractional crystallization of a single magma which underwent crystallization in situ by progressive nucleation and solidification from the roof, walls, and floor inwards. Progressive changes in liquids (cumulate) mineralogy during crystallization led to the observed sequence of early biotite and/or hornblende granodiorites followed by biotite adamellites and late muscovite biotite granites. Progressive in situ crystallization led in some instances to gradational boundaries between granitoid types whereas periodic tectonic distrubances caused the rest magma to reintrude earlier crystallizates in places: thus emplacement and crystallization sequences are parallel. The ultimate product of fractional crystallization was a water-saturated melt, enriched in incompatible elements, whose crystallization resulted in significant tin mineralization. The chemistry of the rocks comprising the batholith is in many respects analogous to that of basic cumulate rocks, although an origin by outward growth of crystals and expulsion of interstitial melt, coupled with convective mixing, rather than by crystal settling, is favoured for the granitoid suite. It is suggested that the Blue Tier Batholith is not an isolated example of a granitoid body with cumulate-like character, but that such bodies may be more common than is recognized.

Mammalian lung development: the possible role of cell proliferation in the formation of supernumerary tracheal buds and in branching morphogenesis.

Abstract: During the development of the lung, branching morphogenesis of the epithelium requires the presence of bronchial mesenchyme. Although it has been demonstrated that continuing morphogenesis is dependent upon growth through proliferation, there is no direct evidence to suggest that the specific pattern of branching is a consequence of differential mitotic activity which is influenced by the appropriate mesenchymal tissue. The induction of supernumerary buds in the tracheal epithelium of the mouse by transplantations of bronchial mesenchyme provides a means for analysing the role of cell proliferation in the formation of bronchial buds. We have addressed the problem by examining the ability of the tracheal epithelium, at different stages of development, to respond to bud induction by bronchial mesenchyme, and attempted to correlate this with the labeling index and 3H-thymidine uptake in the trachea at the respective stages. It has been found that both the 11-day-old and 12-day-old tracheal epithelia initiate supernumerary buds in response to bronchial mesenchyme although the initiation in 12-day-old embryonic trachea occurred somewhat later than in the 11-day-old explants. The 13-day-old trachea failed to elicit buds after the tracheal mesenchyme had been stripped following treatment with 3% trypsin-pancreatin. A decrease in cell proliferation in the tracheal epithelium (as revealed by autoradiography and scintillation counting following 5-hour labeling with tritiated thymidine) between 11 and 13 days of development could contribute to these varying responses to bud induction. Further autoradiographic studies whereby the labeling index in the induced bud and the tracheal epithelium of the same explant have been compared, have revealed a continued high level of labeling in the branching bud and a concomitant decrease in labeling of the trachea. These data suggest that the bronchial mesenchyme either acts as a mitotic stimulator or provides conditions permissive to continued mitotic activity.

Evidence for a widespread late Pleistocene humid period in the Kalahari

Abstract: THE nature and extent of late Quaternary environmental changes in the interior of southern Africa are obscure, in part because of a lack of absolutely dated sediments, and landforms of clear palaeoenvironmental significance. Here I present evidence to show that, during the period 17,000–15,000 BP, the Kalahari, now a semi-arid area with little or no surface drainage, was a region of widely distributed small lakes, as a result of a substantial increase in rainfall.

Effect of the chronic administration of nitrous oxide 0.5% to gravid rats

Abstract: Twenty-four gravid Wistar rats (12 experimental and 12 control) were studied. From day 1 to day 19 of gestation the experimental group was exposed day and night to nitrous oxide 0.5%, while the control group was exposed to air. On day 19 the rats were killed and a detailed examination of the uterus, ovaries and fetuses was undertaken. The fetuses were fixed, cleared and stained with alizarin red, examined for skeletal anomalies and their crownrump lengths measured. There was a significant decrease in litter size of the dams exposed to nitrous oxide as compared with control (P

Indigenous Healing in South Africa: A Neglected Potential

Abstract: The incidence of indigenous healing, recognition of the spiritual and emotional dimension in the lives of our population, lack of ‘professionally’ qualified mental health workers, inadequacy of imposing Western approaches on other cultures, proven effectiveness of nonprofessional workers in the mental health area, shortcomings in and disenchantment with Western models of healing and the holistic nature of indigenous healing compel cognisance. The similarity between certain Western approaches, such as that of Jung, and indigenous healing, development in brain research, humanistic and transpersonal psychology, arguments by the World Health Organization (WHO), and the call to integrate indigenous and Western approaches to healing, necessitates a closer look at the area. South African academics and professionals have urged for the recognition of indigenous healing in order to provide a comprehensive mental health service. It is felt that indigenous healing can teach us and offer unique opportunities in the ap...

Antimicrobial Susceptibility Testing of Pneumococci: Determination of Kirby-Bauer Breakpoints for Penicillin G, Erythromycin, Clindamycin, Tetracycline, Chloramphenicol, and Rifampin

Abstract: Antimicrobial susceptibility testing of pneumococci is now essential to monitor for the presence of resistance to agents such as the penicillins, macrolides, lincomycins, chloramphenicol, and tetracycline. In this study, clinical isolates of a selection of resistant South African strains were tested for antimicrobial susceptibility by minimal inhibitory concentration (MIC) determination and by a modified Kirby-Bauer disk diffusion technique, using Mueller-Hinton medium supplemented with 5% horse blood. Disk diffusion breakpoints were determined for penicillin G, erythromycin, clindamycin, tetracycline, chloramphenicol, and rifampin. Reliable results were obtained on disk diffusion for all these agents except for penicillin G. With 6-mug penicillin G disks, zones of strains with intermediate penicillin susceptibility overlapped those of sensitive and resistant strains. With 5-mug methicillin disks, clearer separation of strains based on susceptibility to penicillin G occurred. Strains with zones of <35 mm around penicillin G disks and <25 mm around methicillin disks should have penicillin G MICs determined to confirm their resistance to penicillin G. In view of the potential for pneumococci to be resistant to the agents used in this study, antimicrobial susceptibility of all clinically significant isolates should be determined.

Opportunistic fungal infection by Fusarium oxysporum in a renal transplant patient

Abstract: A white female with chronic glomerular nephritis received a renal transplant in 1971. After 1 year, Livido Reticularis (LR) developed and in 1976 erythematous, painful nodules formed on the LR and ulcerated. The patient also suffered diffuse calcification of the major blood vessels and small arterioles of the extremities with progressive necrosis and gangrene of the fingers. Hyperparathyroidism was evident. The necrotic ulcers yielded Candida albicans and Fusarium oxysporum; both organisms were seen in histological preparations. The ulcers were excised and grafted; no specific antifungal therapy was given.

Re-appraisal of lithostratigraphy of Makapansgat Limeworks hominid site

Abstract: A new lithostratigraphic classification is proposed for the Makapansgat Limeworks hominid site. The Makapansgat Formation is defined in terms of constituent members and beds. The new terminology is correlated with that used previously and hominid finds are linked to the newly defined lithostratigraphic units.

Rainfall along the east coast of southern Africa, the southern oscillation, and the latitude of the subtropical high pressure belt

Abstract: Eighteen rainfall series within a latitude belt 28°08′S to 30°25′S are inspected for relationships with Pittock's L index for the latitude of the subtropical high pressure belt (eastern Australia), and the southern oscillation index Principal components analysis is used to reduce the dimensions of each of the three data sets, and the components for the pressure systems are used as independent variables in a step-wise regression analysis; rainfall components are taken as the dependent variables Useful relationships exist between rainfall and Pittock's L, but there is no evidence to suggest that the same situation applies for the southern oscillation index The results agree with those recently obtained for Mauritius by M D Dennett

Resistance Mechanisms of Multiply Resistant Pneumococci: Antibiotic Degradation Studies

Abstract: Strains of Streptococcus pneumoniae resistant to penicillin have been reported from several countries around the world. Many South African isolates, in addition, exhibit resistance to tetracycline, chloramphenicol, erythromycin, clindamycin, and cotrimoxazole in varying patterns. A qualitative test of the ability of antibiotic-resistant pneumococci to inactivate penicillin, oxacillin, cephalothin, cefoxitin, chloramphenicol, tetracycline, minocycline, erythromycin, clindamycin, streptomycin, gentamicin, and cotrimoxazole revealed that only chloramphenicol was degraded. This finding was confirmed in a quantitative test in which the residual antimicrobial activity of broth containing chloramphenicol in subinhibitory concentrations was determined after incubation with antibiotic-resistant bacteria. Chloramphenicol resistance was shown to be associated with the production of inducible chloramphenicol acetyltransferase. No beta-lactamase activity was demonstrated. Plasmid deoxyribonucleic acid was not demonstrable in partially purified lysates of antibiotic-resistant strains of S. pneumoniae.

Some subjective-experiential parameters in experimental tooth clenching in man.

Abstract: Summary Experimental tooth clenching was performed by fourteen human subjects in order to determine the onset of the subjective sensations of jaw muscle fatigue and jaw muscle pains, the ability to endure jaw muscle pains, and other discomforts. During production of maximal voluntary isometric tension by the elevator jaw muscles the fatigue threshold (x= 31 s), the pain threshold (x= 55 s), and the pain tolerance (x= 118 s) of tooth clenching did not vary significantly intraindividually, whereas this was so interindividually. There might have existed psychological relationships between the three parameters, but they might also have been influenced by the same physiological cause. The weak to intense discomforts were localized to the face, and primarily to the jaw muscles, and after determination of the pain tolerance they disappeared in about 90 s.