Applied Biology and Biochemistry Conference Papers
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- ItemEffects of chronic exposures of selected heavy metals on the glutathione S-transferase activity of freshwater snails Lymnaea natalensis in Zimbabwe(Taylor & Francis, 2019) Mnkandla, S.M.; Siwela, A.H.; Basopo, N.The effect of the heavy metals (cadmium, copper, mercury and lead) on snail glutathione S-transferase (GST) was investigated in 2015. Groups of Lymnaea natalensis snails were exposed to heavy metals for 28 days at concentrations reportedly found in the Mguza Dam. Water and food were changed daily. Samples were collected at days 1, 7, 14, 21 and 28 post exposure. Inhibition of GST activity, following cadmium exposures, ranged between 58 and 60%, with a decrease of 30% on day 28. When snails were exposed to copper, inhibition significantly decreased by 16%, 29%, 49% and 72% inhibition when tested on days 1, 7, 14 and 21, respectively. Inhibition on day 28 was 44%. Mercury exposures resulted in significant increases in GST inhibition, namely, 47%, 62% and 79% inhibition on days 1, 7 and 14, respectively. Inhibition on day 21 was 82%, whereas on day 28 it was significantly lower, at 29%. Concerning lead exposures, inhibition levels on day 1, 7 and 21 had mean inhibition of 60%. Inhibition on days 14 and 28 was significantly lower, with a mean inhibition of 30%. These results suggest that chronic exposures could inhibit GST activity for a certain period, after which inhibition is reduced, possibly as a result of adaptation.
- ItemAssessing the impact of coal mining activities on soils and terrestrial organisms using land snail Achatina fulica as a bioindicator(2022) Ndebele, D.A lack of evaluation of soil quality in Zimbabwe's coal mining regions threatens the soil's ability to support biological productivity. Reports from the Environmental Management Agency of Zimbabwe and the Centre for Natural Resources Governance showed that the river (Deka) that flows through the study area was polluted. Pollutants in the Deka River were possibly emanating from land, but there was no scientific evidence. Hence it was important to evaluate pollution on land in the coal mining area. The biochemical response of the land snail Achatina fulica, exposed to soils collected from the coal mining area, was used to assess soil health. The level of selected heavy metals and polyaromatic hydrocarbon (PAH) levels were determined in soil samples obtained from 7 different sites at a coal mining area over a 2-year period (2018 to 2019). Soils obtained from the coal mining area were used to expose land snails acquired from a comparatively pure environment and acclimated to laboratory settings (for 1 year). The coal mining region's soils were determined to be mildly acidic (pH 5.53). Solubility of some metal elements increases when soils are acidic thus making such metals bioavailable and possibly increasing metal toxicity. The concentrations of heavy metals in soil samples from the coal mining area were significantly higher than in control soils (p < 0.05). The concentrations of zinc and cadmium were found to be above the World Health Organisation maximum permissible limits of 50 and 0.8 mg/kg respectively in the study period. Zinc and cadmium had mean concentrations of 164.40±81.82 and 0.97±0.27 mg/kg respectively. Results of regression analysis indicated that cadmium, lead and zinc were highly bioaccumulated with regression coefficients of 0.90, 0.94 and 0.95 respectively. Metallothionein induction in snail tissue often happen upon exposure of snails to certain metals such as cadmium. The highest levels of metallothioneins were observed in snail tissue exposed to soils with the highest concentration of heavy metal levels. The concentrations of naphthalene, acenaphthene, phenanthrene, anthracene, flouranthene, pyrene, benzo(k)fluoranthene, benzo(a)pyrene and indeno(1,2,3-c,d)pyrene in soils from the thermal power plant area were higher compared to soil from the control site (p < 0.05). High molecular weight (HMW) polycyclic aromatic hydrocarbons were predominant in soil samples from the coal mining area compared to low molecular weight polyaromatic hydrocarbons. High molecular weight polyaromatic hydrocarbons are carcinogenic and benzo(a)pyrene is the most potent. The thermal power plant area had the highest proportion of HMW polyaromatic hydrocarbons thus organisms around the area were likely to be at high risk of cancer and mutations. The sum of 14 polyaromatic hydrocarbons (Σ14 PAHs) at all sites was significantly higher than the 1000 µg/kg allowable in soil by United States Environmental Protection Agency. The ratio of anthracene to the sum of anthracene and phenanthrene was above 1 in soils from the disused coal processing area (Site C), active coal processing area (Site E) and thermal power plant area (Site F). This indicated that polyaromatic hydrocarbons in soils from Site C, E and F mostly emanated from wood, grass and coal combustion. There was a general increase in heavy metal and PAH levels from 2018 to 2019. This was probably because the study area is semi-arid hence leaching and runoff was minimal in soils from the coal mining area. Antioxidant enzyme (superoxide dismutase, catalase, glutathione peroxidase and NAD(P)H quinone reductase) and xenobiotic metabolising enzyme (glutathione S-transferase and ethoxyresorufin O-deethylase) activities were significantly increased in snails exposed to soils from the coal mining area compared to the control soil (p < 0.05). The high antioxidant enzyme activities showed that the snails were adapting to the effects of reactive oxygen species or experiencing oxidative stress. The highest xenobiotic metabolising enzyme activities were observed in snails exposed to soil from the coal tailing and power plant area. Persistent exposure (45 days) of land snails to contaminated soils markedly increased biomarker responses in land snails. Results showed ii that land snails are sensitive bioindicators and may be used to monitor pollution on land. Further more, results showed that combining biomarker measurements and chemical analysis can be a useful approach in evaluating the health of invertebrates in terrestrial ecosystems and the soil quality. The data obtained in this study can be included in soil ecotoxicological data and used in formulating soil quality management frameworks of the area.
- ItemMolecular Identification of Mycobacterium Species of Public Health Importance in Cattle in Zimbabwe by 16S rRNA Gene Sequencing(2015) Padya, L.; Chin’ombe, N.; Magwenzi, M.; Mbanga, J.; Ruhanya, V.; Nziramasanga, P.Mycobacterium species are naturally found in the environment as well as in domestic animals such as cattle. So far, more than 150 species of Mycobacterium, some of which are pathogenic, have been identified. Laboratory isolation, detection and identification of Mycobacterium species are therefore critical if human and animal infections are to be controlled. The objective of this study was to identify Mycobacterium species isolated in cattle in Zimbabwe using 16S ribosomal RNA gene amplification and sequencing. A total of 134 cow dung samples were collected throughout Zimbabwe and mycobacteria were isolated by culture. Only 49 culture isolates that were found to be acid-fast bacilli positive by Ziehl-Neelsen staining. The 16S rRNA gene was successfully amplified by PCR in 41 (84%) of the samples. There was no amplification in 8 (16%) of the samples. Out of the 41 samples that showed amplification, 26 (63%) had strong PCR bands and were selected for DNA sequencing. Analysis of the DNA sequences showed that 7 (27%) belonged to Mycobacterium neoaurum, 6 (23%) belonged to Mycobacterium fortuitum, 3 (12%) to Mycobacterium goodii, 2 (1%) to Mycobacterium arupense, 2 (1%) to Mycobacterium peregrinum or M. septicum and 1 isolate (0.04%) to Mycobacterium elephantis. There were 5 (19%) isolates that were non-mycobacteria and identified as Gordonia terrae, a close relative of Mycobacterium. The study therefore provided a molecular basis for detection and identification of Mycobacterium species in animals and humans
- ItemGenotyping Human Papillomavirus in Women Attending Cervical Cancer Screening Clinic in Harare, Zimbabwe(2023) Matuvhunye, T.; Dube-Mandishora, R.S.; Chin’ombe, N.; Chakafana, G.; Mbanga, J.; Zumbika, E.; Stray-Pedersen, B.Aim: To determine the prevalence of human papillomavirus genotypes in women attending a cervical cancer screening VIAC (visual inspection with acetic acid) clinic. Study Design: Cross-sectional studyPlace and Duration of Study: VIAC clinic at Parirenyatwa Referral Hospital in Harare in Zimbabwe between February and April 2015. Methodology: Sexually active women were recruited and they provided their socio-demographic data and self-collected vaginal swabs. HIV status of the participants was determined. DNA was extracted from the swabs using the standard phenol-chloroform method. HPV DNA was detected using the standard consensus MY09/11-GP5+/GP6+ nested polymerase chain reaction. Amplicons were sequenced and sequences analyzed using bioinformatics tools to identify the HPV genotypes. Results: Sixty women were recruited. Their age ranged from 21-83 years, with a mean of 40.1 years. Most of the women were married and resided in the urban areas. Of the 60 participants, 50% (30/60) were HIV-positive. The prevalence of HPV genotypes in the study subjects was 56.7% (34/60). HPVs were most prevalent in women aged 30 years and below, and became less prevalent as the age increased. The predominant genotypes detected were HPV-16, -58, -52, -45, 18, -33, -51, -6, -81, -11, -70, -62, -32 and -40. Conclusion: A number of HPV genotypes were detected in half of women tested. There was no significance association between risk-factors (parity, level of education, residence, history of STI, contraceptive use and sexual debut) and HPV infection. The findings of this study showed that consensus nested PCR and DNA sequencing could be used to detect HPV genotypes in women in cervical cancer screening programs. Although this method is sensitive, it is inefficient at detecting multiple HPV infections.
- ItemCurrent Status of Mycotoxin Contamination of Food Commodities in Zimbabwe(MDPI, 2018) Nleya, N.; Adetunji, M.C.; Mwanza, M.Agricultural products, especially cereal grains, serve as staple foods in sub-Saharan Africa. However, climatic conditions in this region can lead to contamination of these commodities by moulds, with subsequent production of mycotoxins posing health risks to both humans and animals. There is limited documentation on the occurrence of mycotoxins in sub-Saharan African countries, leading to the exposure of their populations to a wide variety of mycotoxins through consumption of contaminated foods. This review aims at highlighting the current status of mycotoxin contamination of food products in Zimbabwe and recommended strategies of reducing this problem. Zimbabwe is one of the African countries with very little information with regards to mycotoxin contamination of its food commodities, both on the market and at household levels. Even though evidence of multitoxin occurrence in some food commodities such as maize and other staple foods exist, available published research focuses only on Aspergillus and Fusarium mycotoxins, namely aflatoxins, deoxynivalenol (DON), trichothecenes, fumonisins, and zearalenone (ZEA). Occurrence of mycotoxins in the food chain has been mainly associated with poor agricultural practices. Analysis of mycotoxins has been done mainly using chromatographic and immunological methods. Zimbabwe has adopted European standards, but the legislation is quite flexible, with testing for mycotoxin contamination in food commodities being done voluntarily or upon request. Therefore, the country needs to tighten its legislation as well as adopt stricter standards that will improve the food safety and security of the masses.