Browsing by Author "Siwela, Andrew H."
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- ItemAflatoxin Carryover during Large Scale Peanut Butter Production.(Scientific Research, 2011-04) Siwela, Andrew H.; Mukaro, Kudzayishe J.; Nziramasanga, NoziphoPeanut butter was monitored for aflatoxin contamination at different stages during its large-scale production starting from raw shelled peanuts up to the final product. Twenty five samples, weighing 2 kg each, were taken from each of the following stages: roasting at 160°C, blanching/de-skinning and grinding. The sub-samples were ground, thoroughly mixed and further reduced by the quartering technique until a 1 kg sub-sample was obtained. This was then analyzed for aflatoxins using reverse phase HPLC incorporating pre-column trifluoroacetic acid derivatization. The results showed a total aflatoxin percentage reduction of 51% after roasting, 27% after blanching/de-skinning followed by a further 11% after grinding to make peanut butter. This meant that there was a cumulative total reduction of 89% of aflatoxin concentration during the production process of peanut butter. These results show that there is a significant reduction of aflatoxin levels at the roasting and blanching stages in the process of producing peanut butter.
- ItemAflatoxin Contamination of Stored Groundnuts in Zimbabwe.(ICRISA T (International Crops Research Institute for the Semi-Arid Tropics)., 1989) Siwela, Andrew H.; Caley, A.D.Aflatoxins were analyzed in groundnuts stored for either local or export sales in the period 1982/83 to 1986/87. Four hundred and forty-one samples of seven groundnut varieties were collected for analysis. Sixty-eight percent of the samples had total concentrations of aIlatoxin BJ and OJ of up to 25 JIg kg-J. In the 1986/87 groundnut crop, the Flamingo and Makulu Red varieties, which constitute the bulk of export sales, had up to 25 JIgkg-J aIlatoxin BJin 79%of the samples, plus aIlatoxin OJ in 67% of the samples. Overall, the Egret variety was the most susceptible to aIlatoxin contamination during this period.
- ItemAlteration of some Hepatic Enzyme Activities by Gastrointestinal Helminth Parasites in Domesticated Ostritches.(Society of Education, 2013-05-05) Siwela, Andrew H.; Motsi, Leonah R.; Dube, S.Using the conventional methods for parasitological examinations of the salt floatation and direct smear, ten ostriches infected with internal parasites were identified. Ten birds that were without internal parasites were used as the controls. The metabolizing enzymes glutathione peroxidase (GPX), DT -diaphorase (DTD) and succinate dehydrogenase (SDH) were assayed accordingly using liver samples from the control and infected birds. Malondialdehyde (MDA), a marker of lipid peroxdation, was also assayed. Results showed that cestode eggs occurred at twice the amount of nematode eggs in the faeces of infected ostriches. Infected birds showed significantly higher DTD activity when compared to non-infected birds (Student’s t test, p < 0.05) whilst the activities of SDH and GPX were statistically not altered (Student’s t test p > 0.05). MDA levels were significantly elevated in infected birds compared to controls (Student’s t test, p < 0.001). These results suggest that infected birds are under oxidative stress due to the parasitic infection . Key words: Cestodes, nematodes, glutathione peroxidase, DT-diaphorase, Succinate dehydrogenase, malodialdehyde
- ItemCombined use of phenyl-bonded phase clean-up and HPLC for the determination of aflatoxins(Tropical Science, 1996) Siwela, Andrew H.Phenyl·bonded phase clean-up and HPLC were used to measure aflatoxins in groundnuts, peanut butter, beans, cowpeas and maize meant for human consumption. Of 277 samples, 84% were al or bleow the 20 pp.b. limil. Of 100 animal feed samples, 28% were at or below 5 p.p.b., the proposed limit infeedfor milk-producing animals.
- ItemA comparison of antibiotic resistance in microorganisms isolated from chicken and ostrich faeces in Bulawayo, Zimbabwe(International Formulae Group., 2007) Siwela, Andrew H.; Matsaure, Fradereck; Ncube, T.; Olonitola, Olayeni S.; Best, Geoffrey R.Samples of fresh faeces were obtained from a free-range chicken source, three commercial chicken farms and a commercial ostrich farm, all located around Bulawayo City, Zimbabwe, in order to determine the antibiotic resistance profile of selected bacterial isolates of interest in food-related human infections. Samples were prepared at various dilutions and plated on selective media for Coryneforms, Escherichia coli, Enterococcus faecalis and Pseudomonas. The targeted bacteria were isolated as pure cultures and tested for antibiotic resistance to ampicillin, chloramphenicol, oxytetracycline, sulphonamide, streptomycin and tetracycline. Isolates from the faeces of chickens and ostriches in the commercial farms were found to be generally more resistant to streptomycin, tetracycline and oxytetracycline as compared to those from the free- range chickens. This study emphasizes the need to monitor antibiotic resistance genes in the environment and to curb/curtail antibiotic use for growth promotion in farm animals, particularly in developing countries, as continued use will only add to the growing problem of microbial antibiotic resistance.
- ItemA comparison of metal levels and antioxidant enzymes in freshwater snails, Lymnaea natalensis, exposed to sediment and water collected from Wright Dam and Lower Mguza Dam, Bulawayo, Zimbabwe(Elsevier Inc., 2010-08) Siwela, Andrew H.; Nyathi, C.B.; Naik, Yogeshkumar S.We compared the bioaccumulation of lead (Pb), cadmium (Cd), zinc (Zn), copper (Cu), nickel (Ni) and iron (Fe) with antioxidant enzyme activity in tissues of the snails, Lymnaea natalensis, exposed to elements of two differently polluted dams. 45 snails were exposed to sediment and water collected from Wight Dam (reference) whilst another 45 snails were also exposed to sediment and water collected from Lower Mguza Dam (polluted dam). Except for Fe in sediment and Pb in water, metal concentrations were statistically higher in sediment and water collected from Lower Mguza Dam. Lead, Cd and Zn were two times higher in tissues of snails exposed to Lower Mguza Dam elements. On one hand, superoxide dismutase (SOD), diphosphotriphosphodiaphorase (DTD) and catalase (CAT) activities were significantly lower whilst malondialdehyde (MDA) levels were significantly higher in tissues of snails exposed to Lower Mguza Dam sediment and water. On the other hand, selenium-dependent glutathione peroxidase (Se-GPX) activity was significantly elevated in tissues of snails exposed to Lower Mguza Dam sediment and water. Snails exposed to Lower Mguza Dam elements seem to have responded to pollution by increasing CAT and Se-GPX specific activity in an effort to detoxify peroxides produced as a result of metal induced oxidative stress.
- ItemA comparison of metal levels and antioxidant enzymes in freshwater snails,Lymnaea natalensis, exposed to sediment and water collected from Wright Dam and Lower Mguza Dam, Bulawayo, Zimbabwe.(Elsevier Inc., 2010-08-02) Siwela, Andrew H.; Nyathi, C.B.; Naik, Yogeshkumar S.We compared the bioaccuniulation of lead (Pb), cadmium (Cd), zinc (Zn), copper (Cu), nickel (Ni) and iron (Fe) with antioxidant enzyme activity in tissues of the snails, Lymnaea natalensis, exposed to elements of two differently polluted dams. 45 snails were exposed to sediment and water collected from Wight Dam (reference) whilst another 45 snails were also exposed to sediment and water collected from Lower Mguza Dam (polluted dam). Except for Fe in sediment and Pb in water, metal concentrations were statistically higher in sediment and water collected from Lower Mguza Dam. Lead. Cd and Zn were two times higher in tissues of snails exposed to Lower Mguza Dam elements. On one hand, superoxide dismutase (SOD), diphosphotriphosphodiaphorase (DTD) and catalase (CAT) activities were significantly lower whilst malondialdehyde (MDA) levels were significantly higher in tissues of snails exposed to Lower Mguza Dam sediment and water. On the other hand, selenium-dependent glutathione peroxidase (Se-GPX) activity was significantly elevated in tissues of snails exposed to Lower Mguza Dam sediment and water. Snails exposed to Lower Mguza Dam elements seem to have responded to pollution by increasing CAT and Se-GPX specific activity in an effort to detoxify peroxides produced as a result of metal induced oxidative stress.
- ItemA Comparison Of Organochlorine Pesticide Residues In Upper Ncema And Lower Umguza Dams, Zimbabwe.(Journal of Applied Science in Southern Africa, 1996) Siwela, Andrew H.; Marufu, G.; Mhlanga, A.T.This study examined the levels of chlorinated hydrocarbons (organochloride pesticides) in the ecosystem of Ncema and Umguza dams. Samples of water, water weeds, mud and fish were collected from each dam. The fish species collected from the two dams were river sardine (Mesobo/a brevianus), branded bream (Tilapia sparmanii), African catfish (e/arias gariepinus) and red-breasted bream (Tilapia rendelli). The samples were analysed for hexachlorocyclohexane, DDT, and its metabolites, DOE and DOD, aldrin and dieldrin. DDT was detected in all the samples, its concentration ranging from 1,12 J.l9 per kg in water weeds to 265 J.l9 per kg in mud from Upper Ncema dam. Aldrin was also detected in all the samples (except for branded bream from Upper Ncema dam), the highest level __being 223 ~g per kg in_ ~atdln~$'-rom Lower Umguza dam. Traces.of hexachlorocyclohexane were detected in some of the samples, the highest level of 20,1 ~g per kg in African catfish from Upper Ncema dam. Dieldrin was detected only in mud samples from Lower Umguza dam at a concentration of 80,5 ~g per kg. Overall, this study indicates that Upper Ncema dam has a higher pesticide load compared to Lower Umguza dam.
- ItemDecontamination of aflatoxin-contaminated maize by dehulling(Society of Chemical Industry., 2005) Siwela, Andrew H.; Siwela, Mthulisi; Matindi, Gibson; Dube, S.; Nziramasanga, NoziphoDehulling of maize grains as an aflatoxin decontamination method was investigated. Sixty kilograms of maize (whose average moisture content was 110 g kg−1) were thoroughly mixed and divided into two samples. The kernel moisture content of one sample was adjusted to 200 g kg−1 while the other (control) was left at 110 g kg−1. The two samples were kept at ambient temperature (25–30 ◦C) for 21 days. Twenty sub-samples, ten from each, were further divided into two so that one lot was dehulled while the other was not dehulled. These sub-samples were then milled to pass through a 1mm screen and the meal was evaluated for aflatoxin contamination. It was found that there was a 92% decrease in aflatoxin levels in dehulled maize meal compared with undehulled maize meal. We therefore suggest that dehulling the grain can be used to reduce aflatoxin levels in maize.
- ItemThe effect of schistosomiasis on the activation of aflatoxin B1(1986-03) Hasler, Julia A.; Siwela, Andrew H.; Nyathi, C.B.; Chetsanga, C.J.This study examined activation of aflatoxin Bl (AFB1) in livers of Schistosomamansoni-infected and noninfected mice by measuring covalent binding of ('H]AFBl to cellular macromolecules in vivo and in vitro. During a one week time period after AFB1 treatment of animals, maximal binding of ('H]AFB1 to DNA, RNA and protein in liver occured during the 1 - 6 hour period after treatment, with less binding throughout of AFB1 to macromolecules of infected mice. Experiments performed in vitro to determine the capacity of liver microsomes to mediate the binding of AFB1 to calf thymus DNA showed that microsomes from infected mice mediated the binding of less ('H]AFB1 to DNA than those from noninfected animals.
- ItemThe effect of schistosomiasis on the covalent binding of 2-acetylaminofluorene to mouse liver macromolecules in vivo and in vitro(Elsevier, 1990-07-15) Siwela, Andrew H.; Nyathi, C.B.; Chetsanga, C.J.; Hasler, Julia A.The covalent binding of [14C]acetylaminofluorene (AAF) to macromolecules in vivo and in vitro was measured in Schistosoma mansoni-infected and in non-infected mice. Liver microsomes from infected mice demonstrated a 42% decreased capacity to mediate covalent binding of AAF to DNA. In addition, the extent of binding of AAF to liver macromolecules in vivo was generally less in infected than non-infected mice.
- ItemEstablishment of baseline values of copper, zinc and manganese in ostriches in Zimbabwe: a preliminary study.(Zimbabwe Vet Journal, 2000) Siwela, Andrew H.; Shonhai, A.; Foggin, C.M.; Revol, B.Ostrich (Struthio came/us) sera from apparently 302 healthy birds on 32 different fanns around the country were analysed for three essential trace elements (copper, zinc and manganese) by atomic absorption spectrometry with the objective establishing baseline values which could be used as guidelines in the diagnosis of deficiency or toxicity of the trace elements in ostriches. Trace elements levels in ostrich sera were also detennined according to age groups i.e chicks, growers and b~eeders. Comparisons were also done to determine whether the geographical regions had any influence on the levels of the trace elements in the different categories of birds. Results indicated significant variations with regard to age and geographical region variations in the level of copper. No significant age variations were evident for manganese levels but regional differences were noted. Zinc levels did not show significant geographical differences but variation in the concentration of the trace element according to age was strongly evident.
- ItemMetal Accumulation and Antioxidant Enzyme Activity in C. gariepinus, Catfish, and 0. mossambicus, Tilapia, Collected from Lower Mguza and Wright Dams, Zimbabwe(Springer Science+Business Media, 2009-08-28) Siwela, Andrew H.; Nyathi, C.B.; Naik, Yogeshkumar S.The aim of this study was to measure antioxidant enzyme activities as biological indicators of pollution in tissues of two species of fish. Five Clarius gariepinus and three Oreochromis mossambicus were collected from Umguza Dam (polluted dam) whilst seven C. gariepinus and eight 0. mossambicus were collected from Wright Dam (relatively pristine dam). Diphosphotriphoshodiaphorase and catalase activities were consistently lower (42 f 2% and 78 f 20%, respectively) in liver whilst malondialdehyde levels were two times higher in muscles of both species of fish collected from Umguza Dam. However, seleniumdependent glutathione peroxidase (Se-GPX) activity was elevated four-fold in liver and gills of 0. mossambicus collected from Umguza Dam. Metal levels were two to five times higher in muscles of both species of fish collected from Umguza Dam. Fish from Umguza Dam seem to have responded to pollution by increasing Se-GPX specific activity in an effort to detoxify peroxides produced as a result of metal induced oxidative stress. Keywords Antioxidant enzymes . Heavy metals . 0. mossambicus . C. gariepinus High levels of trace metals in freshwater may occur as a result of natural weathering of minerals in the sediments and bed rocks or as a result of anthropogenic activities such as mining, industrial, municipal and agricultural discharges (Winston 1991). Most trace metals are essential in small concentrations for normal metabolic processes in mammals including fish and humans. At abnormally high concentrations, metals can cause death in fish. Metals such as lead (Pb), cadmium (Cd), copper (Cu) mercury (Hg), silver (Hg) and cobalt (Co) have been shown to be extremely toxic when they bind to fish gills (Tao et al. 2000). Fish are exposed to metals through contaminated food and the water column in chronically contaminated aquatic ecosystems, the main routes of accumulation being through gills (Tao et al. 2000). Sublethal and chronic concentration of metals exerts their toxicity on fish by generating free radicals such as the hydroxyl radical ('OH), peroxyl-radical (Roo2) and superoxide (Oo2-) and some non-radical ROS such as hydrogen peroxide (H202). These ROS can trigger oxidative damage to proteins, nucleic acids and lipids (Winston 1991). However, defensive antioxidant enzymes, which detoxify reactive oxygen species, are present in the liver, kidneys, gills and intestine (Buhler and Williams 1988). Antioxidant enzymes have been used as biomarkers of pollution by metals and organic compounds that generate oxidative stress in molluscs (Cossu et al. 2000) whilst MDA levels have also been shown to be affected by oxidative stress (Rodrigues-Ariza et al. 1993). As antioxidant enzyme activities and MDA levels can be used as biomarkers of pollution, this study was undertaken to determine the relat~ onship between concentration of metals, antioxidant enzyme activities and MDA levels in two species of fish collected from Mguza Dam (which receives domestic and industrial effluent from Bulawayo City sewage works) and from Wright Dam with no history of pollution.
- ItemMetal accumulation and antioxidant enzyme activity in C. gariepinus, Catfish, and O. mossambicus, Tilapia, collected from lower Mguza and Wright dams, Zimbabwe(Springer Science+Business Media, LLC, 2009-08) Siwela, Andrew H.; Nyathi, C.B.; Naik, Yogeshkumar S.The aim of this study was to measure antioxidant enzyme activities as biological indicators of pollution in tissues of two species of fish. Five Clarius gariepinus and three Oreochromis mossambicus were collected from Umguza Dam (polluted dam) whilst seven C. gariepinus and eight O. mossambicus were collected from Wright Dam (relatively pristine dam). Diphosphotriphoshodiaphorase and catalase activities were consistently lower (42 ± 2% and 78 ± 20%, respectively) in liver whilst malondialdehyde levels were two times higher in muscles of both species of fish collected from Umguza Dam. However, seleniumdependent glutathione peroxidase (Se-GPX) activity was elevated four-fold in liver and gills of O. mossambicus collected from Umguza Dam. Metal levels were two to five times higher in muscles of both species of fish collected from Umguza Dam. Fish from Umguza Dam seem to have responded to pollution by increasing Se-GPX specific activity in an effort to detoxify peroxides produced as a result of metal induced oxidative stress.
- ItemMetal Accumulation and Antioxidant Enzyme Activity in C. gariepinus, Catfish, and O. mossambicus, Tilapia, Collected from Lower Mguza and Wright Dams, Zimbabwe.(Springer Science+Business Media, 2009) Siwela, Andrew H.; Nyathi, C.B.; Naik, Yogeshkumar S.The aim of this study was to measure antioxidant enzyme activities as biological indicators of pollution in tissues of two species of fish. Five Clarius gariepinus and three Oreochromis mossambicus were collected from Umguza Dam (polluted dam) whilst seven C. gariepinus and eight O. mossambicus were collected from Wright Dam (relatively pristine dam). Diphosphotriphoshodiaphorase and catalase activities were consistently lower (42 ± 2% and 78 ± 20%, respectively) in liver whilst malondialdehyde levels were two times higher in muscles of both species of fish collected from Umguza Dam. However, seleniumdependent glutathione peroxidase (Se-GPX) activity was elevated four-fold in liver and gills of O. mossambicus collected from Umguza Dam. Metal levels were two to five times higher in muscles of both species of fish collected from Umguza Dam. Fish from Umguza Dam seem to have responded to pollution by increasing Se-GPX specific activity in an effort to detoxify peroxides produced as a result of metal induced oxidative stress.
- ItemMetal Levels and Antioxidant Enzyme Activities in Freshwater Snails Exposed to Sediments From Polluted and Pristine Dams in Zimbabwe(2013-03-12) Naik, Yogeshkumar S.; Nyathi, C.B.; Siwela, Andrew H.The aim of this study was to determine the metal and antioxidant enzyme activities (AGE's) in the freshwater snail Lymnaea natalensis, exposed to sediments form a polluted (Umguza) and pristine (Wright) dams around Bulawayo City, Zimbabwe with a view to developing a biomarker of freshwater pollution. Adult lab reared snails (10-15 mm) were exposed for 4 weeks to water and sediment cofiected from 4 different sites of Umguza Dam (a sink of domestic and industrial effluent) and Wright Dam (privately owned -and considered to be relatively pristine). Antioxidant. enzymes, heavy metals and malondia1dehyde (MDA) analyses were performed using the S-9 fraction of whole snail soft tissue. Catalase and glutathione peroxidase activities were significantly elevated in snails exposed to Umguza Dam water and sediment (Student t-test, p < 0.01 and p < 0.001) when compared to snails exposed to Wright Dam. DT- diaphorase activity was significantly reduced in snails exposed to Umguza Dam water and sediment (p < 0.001) when compared to snails exposed to Wright Dam water and sediment. Snails exposed to Umguza Dam water and sediment bad a higher total metal load compared to those exposed to Wright Dam elements and the MDA levels were correspondingly elevated in snails exposed to polluted water and sediment (p < 0.01). The higher MDA levels and altered AGE activities suggest that the snails exposed to Umguza Dam elements are under higher oxidative stress.
- ItemOxidative stress associated with nematode infections in sheep: a preliminary study(International Formulae Group, 2010-02) Siwela, Andrew H.; Mambvura, Chiedza Isabel; Masanganise, K.E.; Dube, S.A hundred and seven sheep slaughtered at the Cold Storage Company (CSC) in Bulawayo, were examined for nematode parasite infections using coporological methods. Direct smear and salt floatation methods were used to observe nematode parasite eggs. Nine sheep were found to be infested with nematode eggs only. Nine uninfected sheep were used as controls. Liver samples collected from the infected and noninfected sheep were used for assays of the antioxidant enzymes, glutathione peroxidase (GPX) and diphosphotriphosho-diaphorase (DTD) as well as the intermediary metabolic enzyme,succinate dehydrogenase (SDH). Lipid peroxidation was assayed by determining malondialdehyde (MDA) levels. Significantly higher GPX activities were observed in infected sheep when compared with non- infected sheep (p < 001). No difference in the activity of DTD was observed in both infected and non-infected sheep (p>0.05). Parasitic infection resulted in significant reduction in SDH activity (p <0.05) and significantly higher MDA levels (p < 0.01). This study suggests that parasitic infections induce oxidative stress.
- ItemParamphistome species infecting cattle in Matabeleland North province in Zimbabwe(University of Zambia Press, 2005-11-20) Dube, S.; Siwela, Andrew H.; Dlamini, N.R.; Masanganise, K.E.Two thousand five hundred and eighty three cattle originating fromvarious localities in Matabeleland North province were examined for adult paramphistomes in wet season and two thousand two hundred and twenty in dry season. On slaughter, the rumen and reticulum of each amimal were cut open and inner walls examined for attached paramphistomes. About 37% were infected by paramphistomes in the wet season and 39% in the dry season. Applying t-test showed no significant differences at p<0.05 between infected cattle in the dry and wet seasons. In the wet season proximity to the dry season did not significantly influence the prevalence at p<0.05. Morphological structures and measurement of diagnostic features were me i median sagittal sections. Analysis of the structures of acetabulum, pharnyx, and genital atrium revealed the following parasites in the area: paramphistomum microbothrium, paramphostomum clavula, calicophoron calicophorum, calicophoron raja, and Gigantocolye symmeri in 20%, 2%, 10%, 2% and 5% of cattle examined respectively. The visible damage by adult parasites on the host's tissue was a result of sucking the rumen and reticulum mucosa into the acetabulum, which eventually nipped off, leading to slightly hardened areas devoid of ruga due to necrosis. In a few severe casesthe papillae was damaged and catarrhal pus like exudate was noticed on the mucosa.
- ItemPrevalence of Paramphistomes in Mashonaland West, Central, and East, and Midlands Provinces, Zimbabwe(Acta ZoologicaTaiwanica, 2002) Dube, S.; Siwela, Andrew H.; Masanganise, K.E.; Dube, C.Paramphistomes were collected from cattle from various localities in Mashonaland West, Central, and East and Midlands Provinces. After slaughter, their rumens and reticulum were cut open and examined for paramphistomes. Identifications were based on the morphological structuresand measurementsof diagnosticfeaturesfrom flattened and median sagittal sections. Analysis of the structures of the acetabulum, pharynx, and genital atrium revealed the following parasites in the area, Paramphistomum microbothrium, P. clavula, Calicophoron calicophorum, C. raja, and Gigantocotyle symmeri. The average number of cattle found infected annually was 29.39% with an upper limit of the range of around 69%. Parasite loads and damage to tissues were not serious in most cases, except in a few severe cases where the papillae were damaged and a catarrhal pus-like exudate was noticed on the mucosa
- ItemQuantitative Amino Acid Analysis of Extracted Soyabean Meal Hydrolysates by Ion Exchange Chromatography(Zimbabwe agriculture Journal., 1985) Siwela, Andrew H.Although there are tables of amino acids In foods and feeding stuffs written by authorities in the field, it is felt that there is a need for such tables appertaining to Zimbabwean conditions. As a first step to this objective a survey was undertaken to determine the amino acid cr;mtent, and its variability, of extracted soyabean meal which in this country is used as a majO'/' source of protein in feedstuffs in common with worldwide practice. The variability from batch to batch Wlm' found. t,o be very low.