Showing papers by "University of Zimbabwe published in 2003"

A novel mutant variant of the CYP2D6 gene (CYP2D617) common in a black African population: association with diminished debrisoquine hydroxylase activity

Abstract: 1. The debrisoquine hydroxylase (CYP2D6) is polymorphically distributed. Not only are there differences in the proportions of extensive metabolisers to poor metabolisers in various ethnic groups, but there are also pronounced variations in the metabolic capacity among those classified as extensive metabolisers. 2. The mean debrisoquine metabolic ratio of Caucasian extensive metabolisers is lower than that for a number of African populations. In the present study, we have searched for novel CYP2D6 mutations to explain the diminished enzyme activity in African populations. 3. Three Zimbabwean Shona subjects with EM phenotypes (metabolic ratios for debrisoquine of 0.4, 1.5 and 10.5 respectively) were selected and the open reading frame of the CYP2D6 gene of each was sequenced. 4. The subject with metabolic ratio of 10.5 was found to be homozygous for an allele with a nucleotide exchange in exon 2, 1111C-->T causing a 107Thr-->Ile amino acid exchange in a conserved region of the enzyme. In addition, he was homozygous for the 2938C-->T and 4268G-->C mutations causing 296Arg-->Ser and 486Ser-->Thr amino acid substitution found in the CYP2D6*2 allele. 5. Seventy-six Zimbabwean Shona subjects were subsequently genotyped for the 1111C-->T mutation and for the intron 1 gene conversion present in the CYP2D6*2 gene. The 1111C-->T mutation was found at an allele frequency of 34% and was only present in alleles carrying the gene conversion in intron 1 indicative for the CYP2D6*2 gene. 6. This allele (CYP2D6*17), containing the 1111C-->T, 2938C-->T and 4268G-->C mutations, was found to be strongly associated with lower capacity for debrisoquine hydroxylation. We therefore postulate that the CYP2D6*17 allele might contribute to the molecular basis of the previously established diminished debrisoquine hydroxylase activity in African Bantu populations.

Iron overload in Africans and African-Americans and a common mutation in the SCL40A1 (ferroportin 1) gene.

Abstract: The product of the SLC40A1 gene, ferroportin 1, is a main iron export protein. Pathogenic mutations in ferroportin 1 lead to an autosomal dominant hereditary iron overload syndrome characterized by high serum ferritin concentration, normal transferrin saturation, iron accumulation predominantly in macrophages, and marginal anemia. Iron overload occurs in both the African and the African-American populations, but a possible genetic basis has not been established. We analyzed the ferroportin 1 gene in 19 unrelated patients from southern Africa (N = 15) and the United States (N = 4) presenting with primary iron overload. We found a new c. 744 C-->T (Q248H) mutation in the SLC40A1 gene in 4 of these patients (3 Africans and 1 African-American). Among 22 first degree family members, 10 of whom were Q248H heterozygotes, the mutation was associated with a trend to higher serum ferritin to amino aspartate transferase ratios (means of 14.8 versus 4.3 microg/U; P = 0.1) and lower hemoglobin concentrations (means of 11.8 versus 13.2 g/dL; P = 0.1). The ratio corrects serum ferritin concentration for alcohol-induced hepatocellular damage. We also found heterozygosity for the Q248H mutation in 7 of 51 (14%) southern African community control participants selected because they had a serum ferritin concentration below 400 microg/L and in 5 of 100 (5%) anonymous African-Americans, but we did not find the change in 300 Caucasians with normal iron status and 25 Caucasians with non-HFE iron overload. The hemoglobin concentration was significantly lower in the African community controls with the Q248H mutation than in those without it. We conclude that the Q248H mutation is a common polymorphism in the ferroportin 1 gene in African populations that may be associated with mild anemia and a tendency to iron loading.

Resilience building and water demand management for drought mitigation

Abstract: Doughts resulting in complete crop failure are common in Eastern and Southern Africa. We are at present experiencing a regional crisis, where crop failures related to drought are threatening the lives of millions of people in several countries in Southern Africa. A major challenge is to seek ways of mitigating and coping with droughts in small-holder farming systems, particularly in semi-arid regions which are most hardly hit by the effects of drought. An entry-point for drought mitigation is to build water resilience of present rainfed farming systems. The water balance is a good starting point to assess the options. As has been argued for decades, the term drought is very debated, and the boundaries between droughts being politically and biophysically defined is not sharp. Often crop failures and social suffering are blamed on drought, while in reality the causes are more complex than only a decline in rainfall. A challenge is to find management strategies to deal with the unreliable and extremely variable rainfall in savannah environments. In this paper examples of small-scale management practices to mitigate drought in semi-arid rainfed farming are presented. Focus is on water harvesting systems for supplemental irrigation. It is shown that with relatively simple and cheap means it is possible to build resilience to deal with water scarcity in semi-arid farming systems. If such measures are combined with efforts of maximising plant water availability and plant water uptake capacity, there are good chances of mitigating certain droughts. Conservation tillage systems have proven to maximise rainfall infiltration and storage of water in the soil, enabling even crops lacking supplemental irrigation to bridge severe dry spells. Interestingly, building resilience in rainfed farming systems is also a means of water demand management. More crop is produced per drop of water in resilient farming systems, which reduces the amount of water needed to produce food. Despite the opportunities to build resilience to mitigate droughts, it is impossible to escape from the severe drought years. This is where coping mechanisms are required, which involve social, economic and institutional preparedness to cope with the social effects of climatic droughts.

In vitro antiplasmodial evaluation of medicinal plants from Zimbabwe.

Abstract: In this study the in vitro antiplasmodial activities of extracts from Cussonia spicata (Araliaceae), Artemisia afra, Vernonia colorata, V. natalensis (Asteraceae), Parinari curatellifolia (Chrysobalanaceae), Clutia hirsuta, Flueggea virosa, (Euphorbiaceae), Adenia gummifera (Passifloraceae) and Hymenodictyon floribundum, (Rubiaceae) were evaluated. The lipophilic extracts from the aerial parts of Artemisia afra and Vernonia colorata proved to be the most active against the chloroquine-sensitive strain PoW and against the chloroquine-resistant clone Dd2 of Plasmodium falciparum. Bioassay-guided fractionation of the extract of A. afra yielded seven flavonoids, from which acacetin, genkwanin and 7-methoxyacacetin showed in vitro activity; the IC(50) values ranged from 4.3 microgram/mL to 12.6 microgram/mL. In addition, several sesquiterpene lactones could be obtained from the most active fractions. Whereas eudesmaafraglaucolide proved to be inactive, the guaianolides 1-desoxy-1alpha-peroxy-rupicolin A-8-O-acetate, 1alpha,4alpha-dihydroxybishopsolicepolide and rupicolin A-8-O-acetate revealed in vitro antiplasmodial activity. Evaluation of V. colorata gained four sesquiterpenes 11beta,13-dihydrovernodalin, vernodalol, 11beta,13-dihydrovernolide and 11beta,13,17,18-tetrahydrovernolide, from which the first two constituents exhibited the strongest antiplasmodial activity (IC(50) values: 1.1-4.8 microgram/mL).

Ungulate community structure and ecological processes: body size, hoof area and trampling in African savannas

Abstract: A wide range of bioenergetic, production, life history and ecological traits scale with body size in vertebrates. However, the consequences of differences in community body-size structure for ecological processes have not been explored. We studied the scaling relationships between body mass, shoulder height, hoof area, stride length and daily ranging distance in African ungulates ranging in size from the 5 kg dik-dik to the 5,000 kg African elephant, and the implications of these relationships on the area trampled by single and multispecies herbivore communities of differing structure. Hoof area, shoulder height and stride length were strongly correlated with body mass (Pearson's r >0.98, 0.95 and 0.90, respectively). Hoof area scaled linearly to body mass with a slope of unity, implying that the pressures exerted on the ground per unit area by a small antelope and an elephant are identical. Shoulder height and stride length scaled to body mass with similar slopes of 0.32 and 0.26, respectively; larger herbivores have relatively shorter legs and take relatively shorter steps than small herbivores, and so trample a greater area of ground per unit distance travelled. We compared several real and hypothetical single- and multi-species ungulate communities using exponents of between 0.1 and 0.5 for the body mass to daily ranging distance relationship and found that the estimated area trampled was greater in communities dominated by larger animals. The impacts of large herbivores are not limited to trampling. Questions about the ecological implications of community body-size structure for such variables as foraging and food intake, dung quality and deposition rates, methane production, and daily travelling distances remain clear research priorities.

Analysis of the sensitization profile towards allergens in central Africa.

Abstract: Summary Background Almost no information is available regarding the prevalence of IgE-mediated allergies and the disease-eliciting allergens in tropical Africa. Objective To study IgE-mediated allergies and the allergen profile in allergic patients from Zimbabwe. Methods The frequency of sensitization to common environmental allergen sources was determined by skin prick testing in 650 allergic patients from Zimbabwe. Fifty representative sera were analysed for IgE reactivity to 20 respiratory and 20 food allergen extracts by multiallergen extract testing. The IgE reactivity profiles to recombinant pollen and mite allergens were compared between grass pollen- and mite-sensitized patients from Zimbabwe and central Europe. Sera from grass pollen-allergic patients were also analysed for IgE reactivity to nitrocellulose-blotted natural timothy grass and Bermuda grass pollen allergens. Results IgE-mediated allergies were found to be common in Zimbabwe. Similar to the situation in central Europe, mites and grass pollens represented the most prevalent allergen sources. However, the IgE reactivity profiles determined with single recombinant pollen and mite allergens revealed interesting differences between the European and African patients, which most likely reflect the local allergen exposure. Conclusions The striking differences regarding sensitization to grass pollen and mite allergens between African and European patients revealed by recombinant allergen-based testing emphasize the need for component-resolved allergy testing to optimize allergy prevention and therapy in different populations.

High frequency of syncytium-inducing and CXCR4-tropic viruses among human immunodeficiency virus type 1 subtype C-infected patients receiving antiretroviral treatment.

Abstract: Human immunodeficiency virus type 1 (HIV-1) subtype C viruses have been found to almost exclusively use the chemokine receptor CCR5 as a coreceptor for entry, even in patients with advanced AIDS. We have characterized subtype C virus isolates from 28 patients from Harare, Zimbabwe, 20 of whom were receiving antiretroviral treatment. Virus from 10 of the treated patients induced syncytium formation (SI virus) when cultured with MT2 cells. Only non-syncytium-inducing (NSI) virus was cultured from the peripheral blood mononuclear cells of the eight patients who had not received treatment. The majority of these subtype C SI viruses were capable of using both CCR5 and CXCR4 as coreceptors for viral entry, and the consensus V3 loop sequences from the SI viruses displayed a high net charge compared to those of NSI viruses. While those on treatment had reverse transcriptase (RT) and protease mutations, there was no clear association between RT and protease drug resistance mutations and coreceptor tropism. These results suggest that CXCR4-tropic viruses are present within the quasispecies of patients infected with subtype C virus and that antiretroviral treatment may create an environment for the emergence of CXCR4 tropism.

Fertilizer use efficiency and nitrate leaching in a tropical sandy soil.

Abstract: Maize (Zea mays L.) production in the smallholder farming areas of Zimbabwe is based on both organic and mineral nutrient sources. A study was conducted to determine the effect of composted cattle manure, mineral N fertilizer, and their combinations on NO3 concentrations in leachate leaving the root zone and to establish N fertilization rates that minimize leaching. Maize was grown for three seasons (1996-1997, 1997-1998, and 1998-1999) in field lysimeters repacked with a coarse-grained sandy soil (Typic Kandiustalf). Leachate volumes ranged from 480 to 509 mm yr-1 (1395 mm rainfall) in 1996-1997, 296 to 335 mm yr-1 (840 mm rainfall) in 1997-1998, and 606 to 635 mm yr-1 (1387 mm rainfall) in 1998-1999. Mineral N fertilizer, especially the high rate (120 kg N ha-1), and manure plus mineral N fertilizer combinations resulted in high NO3 leachate concentrations (up to 34 mg N L-1) and NO3 losses (up to 56 kg N ha-1 yr-1) in 1996-1997, which represent both environmental and economic concerns. Although the leaching losses were relatively small in the other seasons, they are still of great significance in African smallholder farming where fertilizer is unaffordable for most farmers. Nitrate leaching from sole manure treatments was relatively low (average of less than 20 kg N ha-1 yr-1), whereas the crop uptake efficiency of mineral N fertilizer was enhanced by up to 26% when manure and mineral N fertilizer were applied in combination. The low manure (12.5 Mg ha-1) plus 60 kg N ha-1 fertilizer treatment was best in terms of maintaining dry matter yield and minimizing N leaching losses.

Austempered ductile iron: an alternative material for earth moving components

Abstract: Traditionally steels have enjoyed some kind of monopoly in earth movement applications like ripper tips and grader blades. Earth movement demands that the material possesses both wear resistance and toughness. Ironically, the limitation of steels is that it is difficult to get a good combination of these properties. Recent research efforts in earth movement have focused on austempered ductile iron (ADI) as an alternative material, which exhibits both these properties. ADI is obtained when ductile cast iron is accorded a special heat treatment known as austempering. Before the usage of ADI can flourish, there is a need to thoroughly understand its mechanical and tribological behaviour. This paper details the heat treatment of ductile iron to yield ADI and also examines its mechanical and abrasive wear properties. These properties are compared with those of a proprietary quenched and tempered (Q&T) steel used in applications requiring wear resistance. Typically, when a load of 0.25 N mm−2 is used, the relative abrasion resistance (RAR) of ADI austempered at 375 °C with an initial hardness of 315 Hv is 2.01, while that of a Q&T steel, of hardness 635 Hv is 2.02. The good wear resistance exhibited by ADI despite the low initial hardness can be attributed to the surface transformation of retained austenite to martensite during abrasion. This phenomenon has been positively confirmed by XRD.

Long-term consequences of early childhood malnutrition

Abstract: "This paper examines the impact of preschool malnutrition on subsequent human capital formation in rural Zimbabwe using a maternal fixed effects-instrumental variables (MFE-IV) estimator with a long-term panel data set. Representations of civil war and drought 'shocks' are used to identify differences in preschool nutritional status across siblings. Improvements in height-for-age in preschoolers are associated with increased height as a young adult and number of grades of schooling completed. Had the median preschool child in this sample had the stature of a median child in a developed country, by adolescence, she would be 4.6 centimeters taller and would have completed an additional 0.7 grades of schooling." Authors' Abstract

Untying the Kibaran knot: A reassessment of Mesoproterozoic correlations in southern Africa based on SHRIMP U-Pb data from the Irumide belt

Abstract: The Irumide belt is part of a network of late Mesoproterozoic Kibaran-age orogens in south-central Africa. Sensitive high-resolution ion microprobe (SHRIMP) U-Pb zircon ages for gneisses, migmatites, and granitoids indicate that peak Irumide metamorphism was ca. 1020 Ma and that this was associated with widespread granitic magmatism at 1050–950 Ma. Pre-Irumide protoliths are dominated by 1650–1519 Ma granitic gneisses. These data provide the first robust constraint on the timing of Irumide tectonism and show that previous estimates of ca. 1350 and 1100 Ma are incorrect, thereby negating previously proposed correlations of the Irumide belt with nearby Kibaran-aged tectonism. The correlation between the Irumide belt and Choma-Kalomo block of southern Zambia has had a major influence on models for the tectonic assembly of southern Africa because it required that the intervening Neoproterozoic Zambezi belt was intracratonic and associated with minimal horizontal displacements. Our data indicate that both terranes have distinct histories, consistent with lithologic and metamorphic evidence of Neoproterozoic ocean closure along the Zambezi belt. This implies that the Kalahari and Congo cratons assembled during the Neoproterozoic and not during Kibaran-age tectonism, as previously believed. This new outlook on regional African tectonics supports a configuration of the Rodinia supercontinent that places the Congo craton well away from the Kalahari craton ca. 1000 Ma.

International survey on variations in practice of the management of the third stage of labour

Abstract: OBJECTIVE: To determine the use of the active management of the third stage of labour in 15 university-based obstetric centres in ten developing and developed countries and to determine whether evidence-based practices were being used. METHODS: From March 1999 to December 1999, the Global Network for Perinatal and Reproductive Health (GNPRH) conducted an observational, cross-sectional survey to assess the use of the practice and its components. Prospective data on patient characteristics and the interventions used in the management of the third stage of labour were collected using standardized methods. Data on approximately 30 consecutive vaginal deliveries in each centre (452 in total) were included. FINDINGS: Significant intracountry and intercountry variation in the practice of the active management of the third stage of labour was found (111/452 deliveries used active management), which confirmed the existence of a large gap between knowledge and practice. CONCLUSION: Areas identified for improvement are the urgent implementation of the evidence-based clinical management practice defined as the active management of the third stage of labour; increased accessibility to systematic reviews in developing countries; and the conduction of clinical trials that assess the impact of this intervention in other settings.

Effects of seed priming, aggregate size and soil matric potential on emergence of cotton (Gossypium hirsutum L.) and maize (Zea mays L.)

Abstract: Poor crop establishment, due to poor land preparation methods and inadequate soil moisture, continues to be a major constraint to crop production for smallholder farmers in the semi-arid tropics. On-farm seed priming (soaking seed in water) has been offered as a solution to this problem, but the ways in which this technology interacts with soil conditions are not well understood. The interactions between seed priming and soil physical conditions on cotton ( Gossypium hirsutum L.) and maize ( Zea mays L.) emergence and seedling growth were determined in laboratory pot experiments. The treatments included seed treatment (primed and non-primed), initial soil matric potential (−10, −50, −100, −200 and −1500 kPa) and aggregate size (

Canine transmissible venereal tumour: cytogenetic origin, immunophenotype, and immunobiology. A review.

Abstract: Canine transmissible venereal tumour (CTVT) is the only known naturally occurring tumour that can be transplanted as an allograft across major histocompatibility (MHC) barriers within the same species, and even to other members of the canine family, such as foxes, coyotes and wolves. The progression of this tumour is unique in that, it follows a predictable growth pattern. In natural and experimental cases, the growth pattern includes progressive growth phase, static phase and regression phase, and this is followed by transplantation immunity in immunocompetent adults, while metastasis occurs in puppies and immunosuppressed dogs. Because of the uniqueness of CTVT transmission and progression, experimental investigations of various aspects of the biology of CTVT have been used to provide clues to the immunobiology of both animal and human tumours. This review examines the current state of knowledge of the aspects of the cytogenetic origin, immunophenotype, immunobiology and immunotherapy of CTVT.

Miombo woodland termite mounds: resource islands for small vertebrates?

Abstract: Macrotermes mounds are a significant feature of African woodland landscape, contributing to habitat heterogeneity. The mounds are massive, often many centuries old, and support dense vegetation and a suite of woody plant species scarce in surrounding woodland. The present study tested the hypothesis that Zimbabwean Macrotermes mounds, with their greater niche availability, were more heavily utilized by small vertebrates than the surrounding miombo woodland. We carried out a survey of amphibian, reptile and mammal species during early and late rains for 16 termite mounds and 16 adjacent woodland habitat sites, and compared numbers of individuals, species and diversity. For amphibians and reptiles, individual numbers and species did not differ significantly between habitats and their activity was more influenced by season. For mammals, however, significantly more individuals and species were captured on termite mounds, with three species captured only on mounds (most notably the musk shrew Crocidura hirta spp. complex) and all others showing marked preference for this habitat. The greater number of mammals on termite mounds contributed to total small vertebrate biomass being 800 g/ha for termite mounds compared with 380 g/ha in woodland. For mammals certainly, Macrotermes mounds provide significant food and habitat in miombo woodland.

Priority setting in a hospital critical care unit: qualitative case study.

Abstract: ObjectiveTo describe priority setting for admissions in a hospital critical care unit and to evaluate it using the ethical framework of “accountability for reasonableness.”DesignQualitative case study and evaluation using the ethical framework of accountability for reasonableness.SettingA medical/su

Gender differences in self-construal: how generalizable are Western findings?

Abstract: The authors used the Twenty Statements Test in 2 studies to investigate gender and country differences in the spontaneous self-descriptions of 811 college students from Hong Kong, India, Nepal, Nigeria, and Zimbabwe and 136 secondary school students from Taiwan and Hong Kong. The authors performed statistical analysis and found no significant gender differences in the percentage of responses classified as belonging to the idiocentric self in either study. However, the authors found significant Country effects in both studies for responses classified as representing the idiocentric self and some aspects of the collective self, and the authors found significant Country x Gender effects involving all 4 categories of the idiocentric self and the collective self for the college students. These findings raise questions about the generalizability of Western findings that males are more likely to espouse an independent conception of self than females. However, as the authors predicted, females were more likely to use small group self-descriptions than their male peers.

Stable Incidence Rates of Tuberculosis (TB) among Human Immunodeficiency Virus (HIV)–Negative South African Gold Miners during a Decade of Epidemic HIV-Associated TB

Abstract: During the last decade, annual tuberculosis (TB) case-notification rates increased 4-fold, to >4000 cases/100000 person-years, in the study workforce, among whom prevalence of human immunodeficiency virus (HIV) was 30% in 2000. Three separate cohort studies, totalling 6454 HIV-negative participants, were combined and analyzed for time trends. Observed incidence of TB varied between 962 (1991-1994) and 1589 (1999-2000) cases/100000 person-years (P=.17, test for trend). There was, however, a progressive increase in age, and, for each period, older age was associated with increased incidence rates of TB (P<.001). Having adjusted for age differences, there was no significant association between incidence of TB and calendar period (P=.81, test for trend). Relative to 1991-1994, multivariate-adjusted incidence-rate ratios were 0.94, for 1995-1997, 0.96, for 1998-1999, and 1.05, for 1999-2000. Preventing a secondary epidemic of TB among HIV-negative individuals may be achievable with conventional means, even in settings with a high burden of HIV-associated TB.