Showing papers by "University of the Witwatersrand published in 1994"
TL;DR: Recently, resistance to and clinical failure of the extended-spectrum cephalosporins ceftriaxone and cefotaxime in the treatment of pneumococcal meningitis have been noted in Spain and the United States.
Abstract: The resistance of Streptococcus pneumoniae to penicillin and other antimicrobial agents is increasing in many parts of the world. The frequency of erythromycin resistance in parts of Europe1 and, to a lesser extent, in the United States2 limits the usefulness of macrolide antibiotics for the treatment of pneumonia, and resistance to trimethoprim-sulfamethoxazole, chloramphenicol, and tetracycline is an important problem in some other countries3,4. Recently, resistance to and clinical failure of the extended-spectrum cephalosporins ceftriaxone and cefotaxime in the treatment of pneumococcal meningitis have been noted in Spain5,6 and the United States7,8. In addition, there have . . .
547 citations
TL;DR: In this article, a new range of metallocene catalysts, Cp 2 MCl 2 (M = Ti, Zr, Hf) has been developed in the past decade, which, in the presence of alumoxanes are highly efficient at polymerizing α-olefins (ethene, propene, etc.).
464 citations
TL;DR: The atomic models define protein architectural relationships between the different gene classes in the superfamily, and reveal the molecular basis for substrate binding at the two adjacent subsites of the active site.
Abstract: Crystal structures of cytosolic glutathione S-transferases (EC 2.5.1.18), complexed with glutathione or its analogues, are reviewed. The atomic models define protein architectural relationships between the different gene classes in the superfamily, and reveal the molecular basis for substrate binding at the two adjacent subsites of the active site. Considerable progress has been made in understanding the mechanism whereby the thiol group of glutathione is destabilized (lowering its pKa) at the active site, a rate-enhancement strategy shared by the soluble glutathione S-transferases.
429 citations
TL;DR: The possible influence of plant cell wall glycoproteins on the process of lignification is discussed in the light of the observed affinity of phenolic substrates for prolyl residues in protein structures.
380 citations
TL;DR: This review covers the isolation, structure determination, synthesis, chemical transformations and biological activity of indolizidine and quinolIZidine alkaloids.
281 citations
TL;DR: In this paper, the factors which contribute to the chelate, macrocyclic and cryptate effects are described, including dilution effect, translational entropy, intrinsic basicities of donor atoms, coulombic attraction and repulsions of charged ions and groups, and covalent character of the coordinate bonds.
229 citations
TL;DR: The foraging responses of a browsing ruminant, the kudu, to changes in food abundance and quality over the seasonal cycle are documents and demonstrate that the foraging time and digestive capacity constraints assumed in optimal diet models are somewhat elastic.
Abstract: Foraging behavior provides the mechanistic link between species perfor- mance and food resources in the environment. I document the foraging responses of a browsing ruminant, the kudu (Tragelaphus strepsiceros), to changes in food abundance and quality over the seasonal cycle and interpret the results in the context of optimal foraging theory. The study was carried out on hand-reared but free-ranging animals in a savanna region with summer wet season and winter dry season in Transvaal, South Africa. During the dry season, kudus expanded their diet to include evergreen and unpalatable deciduous woody species neglected during the wet season. The acceptability rating of woody plants was correlated with food value expressed in terms of a protein-condensed tannin index, relative to handling time during ingestion or digestion. However, dietary expansion alone was inadequate to satisfy the daily energy requirement during this period. The animals also increased the fraction of trees of palatable species that was accepted for feeding, extended feeding duration at feeding stations, and increased encounter rate with evergreen trees still retaining leaves. Both total time active and proportion of active time spent foraging increased over the dry season. Digestive capacity was apparently increased to accommodate a higher daily food intake, which compensated for reduced diet quality. Only in September at the end of the dry season, when little foliage remained, were compensatory adjustments inadequate to meet energy requirements. The functional response relating consumption rate to seasonal changes in food abundance showed little variation, despite a decline in foliage biomass by more than an order of magnitude. The kudus were neither energy maximizers, nor time minimizers, but rather targeted on their energy requirements with least overall cost. Findings demonstrate that the foraging time and digestive capacity constraints assumed in optimal diet models are somewhat elastic. Dietary predictions obtained using average parameter settings may be misleading, because constraints may become effective only under extreme conditions. Further research is needed to establish the costs associated with stretching physiological constraints towards their upper tolerance limits.
210 citations
TL;DR: In this paper, the demographic, pathologic, and hemodynamic profiles of patients with severe rheumatic mitral valve disease in a developing country and assess their relation to uncontrol control were described.
Abstract: Objective: To describe the demographic, pathologic, and hemodynamic profiles of patients with severe rheumatic mitral valve disease in a developing country and to assess their relation to uncontrol...
177 citations
TL;DR: In this article, the infrared absorption spectra of a suite of twenty-one type Ib synthetic diamonds have been recorded, and the concentrations of nitrogen in the form of single substitutional N atoms in these specimens determined by electron spin resonance measurements.
Abstract: The infrared absorption spectra of a suite of twenty-one type Ib synthetic diamonds have been recorded, and the concentrations of nitrogen in the form of single substitutional N atoms in these specimens determined by electron spin resonance measurements. It is found that an absorption coefficient, at 1130 wave-numbers, of 1 cm−1 is produced by 250 ±2at. p.p.m. of nitrogen in this form, a. result identical to that of Chrenko, Strong and Tuft and consistent also with that of Woods, van Wyk and Collins. Seventeen of these specimens were heated at temperatures between 1800 and 2050°C, under a stabilizing pressure, to bring about an appreciable degree of aggregation of the single N defects into A centres, or nitrogen pairs. For each specimen the residual, unaggregated single N defect concentration was then determined by electron spin resonance. The difference between this and the original value gave the concentration of nitrogen in the form of A defects. The infrared absorption strength of the A centr...
169 citations
TL;DR: A bridge to where? Introducing the Interim Bill of Rights (IBR) as mentioned in this paper was the first attempt to introduce the concept of a bridge between South Africa and the international community.
Abstract: (1994). A Bridge to Where? Introducing the Interim Bill of Rights. South African Journal on Human Rights: Vol. 10, No. 1, pp. 31-48.
169 citations
TL;DR: This review paper reports recent advances in the subject of developmental odontogenic cysts, essentially those of the past decade, starting with reference to the new WHO classification.
Abstract: This review paper reports recent advances in the subject of developmental odontogenic cysts, essentially those of the past decade, starting with reference to the new WHO classification (1). On keratocysts, the latest reported recurrence rates are assessed as are their mode of growth, immunocytochemistry, immunology, genetic studies, and work on specific keratocyst antigens. There is a critical account of the group of lesions which includes the gingival cyst of adults, lateral periodontal cyst, botryoid odontogenic cyst and glandular odontogenic cyst, and their possible relationship to one another. On dentigerous cysts, reference is made to the relationship between them and deciduous teeth, as well as to their immunocytochemistry and immunology. Recent work on the unicystic ameloblastomas, their classification and prognosis, is assessed, as is the calcifying odontogenic cyst and its relationship with solid odontogenic tumours.
TL;DR: The incidence of port/extraction site recurrence following laparoscopically resected colon cancer surgery is low, and there was diffuse peritoneal carcinomatosis in two of the three cases, suggesting that port/ Extraction Site recurrence may be attributable to the advanced nature of the disease rather than the laparoscopic technique.
Abstract: Purpose: To quantify the magnitude of the risk for port/extraction site recurrence of laparoscopically resected colon cancer in a defined study population. Methods: The data from a prospective laparoscopic bowel surgery registry was used to identify cases of colon cancer that were resected laparoscopically, with a minimum follow-up of 1 year. A questionnaire was sent to the surgeons who performed the procedures. Results: A total of 252 cases were identified from the registry. Questionnaires were returned in 208 of those cases, a response rate of 82.5%. Three cases of port or extraction site recurrence were noted, two of them associated with diffuse peritoneal carcinomatosis. All the patients had a Dukes' stage C tumor at the time of initial surgery. Conclusions: The incidence of port/extraction site recurrence following laparoscopic colon cancer surgery is low. All the recurrences were in patients with Dukes' stage C tumors, and there was diffuse peritoneal carcinomatosis in two of the three cases, suggesting that port/extraction site recurrence may be attributable to the advanced nature of the disease rather than the laparoscopic technique. Longer follow-up and more cases are required to confirm these findings. (Arch Surg. 1994;129:897-899)
TL;DR: This study examined survival of fixed implant-supported prostheses using different cantilever lengths and offers clinical support for the contention that longer cantilevers lead to increased risk of failure.
Abstract: Various lengths of cantilevers for fixed implant-supported prostheses have been recommended in the literature. No scientific data are available for selecting specific lengths, and different views are reported. Authors contend that longer cantilevers lead to increased risk of failure. This study examined survival of fixed implant-supported prostheses using different cantilever lengths and offers clinical support for the contention.
Journal Article•
TL;DR: The data extend previous cytogenetic findings and suggest that, in addition to the known involvement of chromosome I, one or more genes on chromosome 17 also play a role in neuroblastoma development.
Abstract: We report on the finding of a t(1;17) in two primary neuroblastomas. Subsequent fluorescence in situ hybridization (FISH) analysis revealed the presence of 1; 17 transfocations in four out of nine neuroblastoma cell lines. The chromosome 1 short arm breakpoints were determined using region-specific probes. FISH screening also demonstrated or confirmed the presence of 11;17 translocations in three cell lines and other chromosome 17 rearrangements in those cell lines that did not carry a t(1; 17) or t(11; 17). Our data extend previous cytogenetic findings and suggest that, in addition to the known involvement of chromosome I, one or more genes on chromosome 17 also play a role in neuroblastoma development. Genes Chromosom Cancer 10:103–114 (1994). © 1994 Wiley-Liss, Inc.
TL;DR: In this paper, acid-and alkali-catalyzed polyflavonoid tannin-based rigid foams were prepared and the fluid polymer phase was based on a mimosa tANNIN-formaldehyde resin with a minor addition of a fortifier resin, whereas dimensional stabilization was achieved through cross-linking at the desired density.
Abstract: Acid- and alkali-catalyzed polyflavonoid tannin-based rigid foams were prepared. These foams have comparable physical and mechanical properties to the synthetic phenolic rigid foam used as a comparative standard. The fluid polymer phase was based on a mimosa tannin-formaldehyde resin with a minor addition of a fortifier resin. Expansion of the fluid phase was brought about by a physical blowing agent, whereas dimensional stabilization was achieved through cross-linking at the desired density. In the case of the acid-catalyzed foam, a heat-generating agent in the form of furfuryl alcohol was employed. The polymer composition of tannin–formaldehyde/urea–formaldehyde systems as a function of pH was predicted from the respective gel times and rate constants, i.e., above pH 7, the copolymer proportion will tend to 100% and, that at pH 3.4, the polymer blend proportion will tend to a maximum. © 1994 John Wiley & Sons, Inc.
TL;DR: In this article, the defect microstructures in quartz grains from different lithologies sampled at various places at the Vredefort structure were investigated by optical and transmission electron microscopy (TEM).
TL;DR: This unique human carcinoid tumor cell line should provide the opportunity for new insight into the biology of carcinoid tumors and of specific intracellular mechanisms for secretagogue action in the release of amines and peptides.
Abstract: The study of functioning human endocrine tumors has been hampered by a lack of suitable in vitro models. We have established the first permanent cell line of a human pancreatic carcinoid tumor (BON) in culture. BON cells grow in monolayer culture and form colonies in soft agar. Injection of BON cells into nude mice produces transplantable tumors in a dose-dependent fashion. The histology of tumors in athymic mice from injection of dispersed, cultured BON cells is similar to the original histology of the resected tumor. Significant amounts of neurotensin, pancreastatin, and serotonin (5-HT) are demonstrated in the cells by radioimmunoassay (RIA) and the presence of chromogranin A, bombesin, and 5-HT is confirmed by immunocytochemistry. Numerous round and pleomorphic dense-core neurosecretory granules are present on electron microscopy. Functional receptors for acetylcholine, 5-HT, isoproterenol, and somatostatin are present on cultured cells. BON cells possess a specific transport system for uptake of 5-HT from the medium; this uptake system may be a route for regulation of autocrine effects of 5-HT on carcinoid cells. This unique human carcinoid tumor cell line should provide the opportunity for new insight into the biology of carcinoid tumors and of specific intracellular mechanisms for secretagogue action in the release of amines and peptides.
TL;DR: No significant difference was observed between any of the treatment groups with respect to emesis, nausea or drug-related adverse events, and no severe or unexpected drug- related adverse events were observed with ondansetron or granisetron.
Abstract: This is the first international, multi-centre, double-blind, randomised, parallel group study to directly compare the efficacy and safety profile of a single intravenous dose of ondansetron (8 or 32 mg) with granisetron (3 mg) in the control of cisplatin-induced acute emesis. A total of 496 patients were randomised to receive one of three anti-emetic treatments prior to cisplatin chemotherapy (> or = 50 mg/m2). Of these, 165 and 162 patients received 8 and 32 mg of ondansetron, respectively, and 169 patients received 3 mg of granisetron. Complete control of emesis (0 emetic episodes) over 24 h was reported in 59% of patients in the 8-mg ondansetron group, 51% of patients in the 32-mg ondansetron group and 56% of patients in the granisetron group. Complete or major control (< or = 2 emetic episodes) was achieved in 76 and 74% of patients in the 8- and 32-mg ondansetron group, respectively, compared with 78% of patients in the granisetron group. Nausea graded none or mild 24 h after the start of cisplatin infusion was reported in 71 and 69% of patients in the 8- and 32-mg ondansetron groups, respectively, and in 73% of patients in the granisetron group. There were no significant differences between the treatment groups when global satisfaction scores were compared. Logistic regression models were fitted to assess any interaction between treatments and prognostic factors (age, gender, alcohol use, cisplatin dose or concomitant chemotherapy) on complete or major response, but there was no evidence of interaction for any factor. All three anti-emetic treatments were well tolerated and no severe or unexpected drug-related adverse events were observed with ondansetron or granisetron. Headache, the most reported drug-related adverse event for all three treatment groups, occurred in 9% of all patients. In summary, no significant difference was observed between any of the treatment groups with respect to emesis, nausea or drug-related adverse events.
TL;DR: In this paper, the authors show that islands act as sinks for dissolved solids during intense evapotranspirational loss from the swamps, and that calcite and amorphous silica occur beneath island fringes.
TL;DR: In this article, a new role for rock art in the writing of southern African history is outlined, and the old view of the art as a pictorial record of Stone Age life needs to be discarded.
Abstract: This paper outlines a new role for rock art in the writing of southern African history. The old view of the art as a pictorial record of Stone Age life needs to be discarded. What has been learned about southern African rock art has raised the status of its images from objects in need of explanation to evidence for historically situated social processes. These processes implicated not only the makers of the art but also neighbouring peoples with whom they interacted. The art became a site of struggle as ‘egalitarian’ values were eroded and shamans assumed political roles that included control of resources.
TL;DR: In this paper, an image processing system was used to identify different copper levels in the froth down a rougher bank and extract global features from the visual characteristics of the surface froth.
TL;DR: The authors investigated change in Zulu naming practices as a reflection of wider social changes, taking historical accounts as the source of traditional name giving, and an analysis of rural, farm, and urban names showed quantitative and qualitative differences in naming practices.
Abstract: Children in many African societies have meaningful names – unlike their Western counterparts, whose names are primarily labels. In Zulu, Xhosa, Sotho, Tswana, and many other cultures, namegivers traditionally chose personal names that pointed to a range of people and circumstances that were relevant at the time of the child's birth. These highly individual or unique names were part of particular social frameworks that have long been evolving with Western acculturation. Like the social frameworks within which they are embedded, naming practices are in the process of change.This article investigates change in Zulu naming practices as a reflection of wider social changes. Taking historical accounts as the source of traditional namegiving, an analysis of rural, farm, and urban names shows quantitative and qualitative differences in naming practices. Contemporary
names differ significantly from traditional ones, and provide evidence that the world view within which names are given is in the process of redefinition. (Anthropological linguistics, naming, South Africa, Zulu)
TL;DR: The lack of bone formation in the granular hydroxyapatite indicates the critical role of geometry of the substratum in bone differentiation in primates, and may have implications for the appropriate selection of porous bone substitutes for reconstructive craniofacial surgery in humans.
Abstract: Previous studies have shown the morphogenesis of bone in a porous hydroxyapatite substratum when implanted intramuscularly in baboons. This hydroxyapatite-induced osteogenesis model was used to study the effect of geometry and pore size of the substratum on bone differentiation. Two distinct geometric configurations of porous hydroxyapatite of different pore size were obtained after hydrothermal conversion of the calcium carbonate exoskeleton of corals (genera Porites and Goniopora). Substrata were blocks of hydroxyapatite in rod configuration of 200− and 500-μ pore size and granular hydroxyapatite (400 to 620 μ in diameter) of 200− and 500-μ pore size. A total of 64 granular hydroxyapatite implants and 32 hydroxyapatite rods were implanted intramuscularly in 8 subadult male baboons (Papio ursinus). Specimens were harvested on days 60 and 90 and subjected to histologic and histomorphometric analysis. With the exception of an island of bone that formed in two implants of granular hydroxyapatite of 500-μ pore size, bone differentiation occurred only in blocks of hydroxyapatite in rod configuration of either pore size at both observation periods. The lack of bone formation in the granular hydroxyapatite indicates the critical role of geometry of the substratum in bone differentiation. These results in primates may have implications for the appropriate selection of porous bone substitutes for reconstructive craniofacial surgery in humans. (Plast. Reconstr. Surg. 93: 959, 1994.)
TL;DR: In this paper, the woody and herbaceous vegetation was investigated around four rural settlements in the savanna area of the eastern Transvaal Lowveld, South Africa. At each settlement three transects radiating out from the settlement, representing a gradient from high to low disturbance, were sampled for community structure and species composition.
Abstract: The woody and herbaceous vegetation was investigated around four rural settlements in the savanna area of the eastern Transvaal Lowveld, South Africa. At each settlement three transects radiating out from the settlement, representing a gradient from high to low disturbance, were sampled for community structure and species composition. In general, attributes of woody community structure (density, height, biomass, basal area and diversity) were negatively related to increasing disturbance. Herbaceous cover responded positively. Although individual woody species exhibited a range of responses to disturbance, overall species compositional changes were not related directly to the intensity of disturbance. Individual woody species were classified into behavioural species response groups according to their response along the disturbance gradient. Local wood harvesters demonstrated marked selection for particular species and size classes, which should have disproportional impacts on community structure. However, proportional size class distributions were little altered along the gradient.
TL;DR: The experience with a subset of 30 patients with Stage III or Stage IV ovarian cancer who presented at initial laparotomy with advanced disease in whom large (greater than 10 cm) confluent nodules, plaques, or nodal metastatic deposits were found intraperitoneally is provided.
TL;DR: The Roter Kamm crater has been identified as an impact structure on the basis of crater morphology and the presence of impact melt breccias which contain metamorphosed quartz and lithic clasts as mentioned in this paper.
TL;DR: Na2EDTA added to meals with molar ratios of EDTA to iron between 1.0 and 0.25 significantly increases iron absorption provided the meal is of low iron bioavailability, according to standard double isotope techniques.
TL;DR: It was concluded that selected jaw-movement variables were significant determinations of chewing performance, and therefore could contribute to developing a baseline for normal masticatory function.