Applied Science

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Quantitative 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.
The 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.
Aflatoxin 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.
The Effect Of Three Species Of Schistosomes On Hepatic Drug Metabolism In Male BALB/ Mice
(Elsevier, 1990) Naik, Yogeshkumar S.; Basopo, N.
Schistosomiasis is a parasitic disease that affects over 200 million people in the world. S.mansoni and S.haematobium are of medical importance while S.mattheei is primarily of veterinary concern. It is important to know the effect that the disease has on elimination of xenobiotics. The effect of S.mansoni infection on thiopental sleeping times and zoxazolamine paralysis times has previously been reported by other workers as well as by us. Similar work on S.mattheei and S.haematobium infected animals, however, has not been reported in the literature. The effect of S.mattheei and S.haematobium on thiopental sleeping times was therefore studied and compared to results obtained for animals infected with S.mansoni. Thiopental sleeping times and egg loads of infected animals are shown in Table 1. Although S.haematobium infected animals did not have detectable levels of parasite eggs in their livers at 8 weeks post-infection, significant numbers of eggs were detectable at 12 weeks post-infection. This is in agreement with the observed delayed maturation of S.haematobium schistosomulae in rodents as compared to S.mansoni or S.mattheei. The number of worm pairs in each group was as follows: S.mattheei 20-25, S.mansoni 8-10, and S.haematobium (both 8 and 12 weeks post infection) 3-10 pairs. The sleeping times of all infected animals were prolonged when compared to their respective controls. The reasons for this are not clear but it is likely that the parasite egg-induced granulomas as well as the physical obstruction to portal blood flow caused by migration of•worms from mesenteric to portal veins play a significant role. Data obtained in this laboratory on drug metabolism in vitro in S.mansoni infected animals indicate that the activity of hepatic drug metabolising enzymes is also altered, but generlllly only in animals that have developed parasite egg-induced granulomas in their livers.
The 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.
Effects of phenobarbital and 3-methylcholanthrene pretreatment on the pharmacokinetics of praziquantel in rats.
(1992-06-25) Masimirembwa, Collen M.; Naik, Yogeshkumar S.; Hasler, Julia A.
The effects of phenobarbital (PB) and 3-methylcholanthrene (MC) pretreatment on the phannac~kinetics of praziquantel (PZQ), a schistosomicide were studied in Spnrgue-Dawley rats. Blood samples at different time intervals were obtained by severing the tail vein and were analyzed for unchanged PZQ by HPLC. The PB-pretreated rats showed a &fold decrtase in AUC, a 5-fold decrease in Cmax and an 8-fold increase in Ch compared to the saline treated controls. The MC-pretreated rats and their oliveoil treated controls did not show any statistically significant diffmnces in the above parameters. These results suggest that PZQ is extensively metabolised by PB-inducible cytochrome P-450 isoforms and not by MC-inducible isoforms. These findings also suggest that the bioavailability of praziquantel could be altered to a significant extent in humans taking drugs that are phenobarbital type inducers.
Xenobiotic metabolizing enzymes of the freshwater snails.Planorbella and lymnaea (RADIX)Natalensis.
(J. Med. and Appl. Malacol, 1994) Naik, Yogeshkumar S.; Magwere, Tapiwanashe; Matiyenga, M.; Hasler, Julia A.
Very little is known about the ability of snails to metabolise and remove xenobiotics such as molluscicides. The present study was conducted to determine whether the freshwater snails Planorbella duryi and Lymnaea (Radix) nntaIensis possess two of the major enzyme systems of detoxication, namely the P450 monooxygenase system and the glutathione Stransferases. We were able to measure microsomal cytochrome b5 and NADPH cytochrome c reductase activity, indicating a functional mixed function oxidase system. However, probing with three known substrates for the mammalian enzyme, we were unable to detect any cytochrome P450 mediated activity. Glutathione Stransferase activity was detectable in cytosolic fractions. In general, the activities detectable in snails were much lower than in mammalian liver preparations. The existence of these enzymes in snails suggests that studies should be undertaken to observe the interaction between these enzymes and xenobiotics such as candidate molluscicides. Key words: Planorbella duyi, Lyrnnaea (Radix) natalensis, cytochrome P450, glutathione
Combined 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.
A 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.
Effects of chloroquine treatment on antioxidant enzymes in rat liver and kidney.
(Elsevier Inc., 1996-05-09) Magwere, Tapiwanashe; Naik, Yogeshkumar S.; Hasler, Julia A.
The effect of chloroquine (CHQ) administration on antioxidant enzymes in rat liver and kidney was studied. Male Sprague-Dawley rats were administered 20 mglkg CHQ once a week for 4 weeks (chronic treatment) or a single dose at 10 or 20 mglkg (acute treatment). Antioxidant enzyme activities were determined in cytosolic fractions of liver and kidney, whereas reduced glutathione (GSH) and malondialdehyde (MDA) were determined in tissue samples. Results indicate minimal effects of acute CHQ treatment, whereas chronic treatment with CHQ differentially affected antioxidant enzymes in the two organs. Superoxide dismutase activity was increased nearly twofold, while activities of selenium glutathione peroxidase (GPX), catalase, and NAD (P) H: quinone oxidoreductase were decreased in livers of CHQ-treated rats compared to controls. No significant effects of CHQ on glutathione reductase, GSH, and MDA levels were seen in the liver. Fewer effects of CHQ were observed in the kidney where a decrease in GPX activity and an increase in MDA levels was seen. Lowering of antioxidant enzymes activities in the liver by CHQ could render the organ more susceptible to subsequent oxidative stress; while increased MDA production after CHQ treatment in the kidney indicate that the organ is being subjected to oxidative stress. This could have implications for prolonged chloroquine intake.
Phenotyping of the glutathione S-transferase M1 polymorphism in Zimbabweans and the effects of chloroquine on blood glutathione S-transferases M1-A
(Elsevier, 1997-05-31) Mukanganyama, Stanley; Masimirembwa, Collen M.; Naik, Yogeshkumar S.; Hasler, Julia A.
The frequency of the null allele phenotype of glutathione S-transferase (GST) M1 was investigated in 114 Zimbabweans and results for a subset of 63 subjects were compared with genotyping by PCR. In addition, the effect of the antimalarial chloroquine on blood levels of GSTMl and GSTA in 19 subjects was studied. Quantification of GSTs was by enzyme linked immunosorbent assays (ELISA). Thirty percent of the subjects were of the GSTMl null phenotype. Comparison of results of phenotyping by ELISA and genotyping by PCR showed that 16% of samples were in discordance; unknown mutations in the GSTMl gene in the Zimbabwean population may explain this observation. Chloroquine decreased levels of blood GSTM1 and GSTA by 50% or more. In populations treated with chloroquine, these decreases in GST activities might lead to compromised ability to detoxify xenobiotics, could confound GSTMl phenotyping and might invalidate use of GSTA as an indicator of liver damage. O 1997 Elsevier Science B.V. Keywords: Glutathione S-transferases; Phenotype; Black Zimbabweans; Chloroquine
The Effect of Schistosoma Mansoni Infection on the Hepatic Drug Metabolizing Enzymes of Mice and Hamsters
(South African Journal of Science, 1998) Naik, Yogeshkumar S.; Hasler, Julia A.
Discusses the effect of schistosome infection on hepatic drug metabolizing enzymes. Examples of drug metabolizing enzymes; Effect of liver disease of drug metabolism; Alterations in enzyme activity caused by infection; Perturbations in hepatic drug metabolizing enzyme activity with S. mansoni infection.
Effect of schistosome infection on hepatic drug metabolising enzymes
(South African Journal of Science, 1998-06) Naik, Yogeshkumar S.; Hasler, Julia A.
Schistosomiasis is a parasitic disease that affects over 200 million persons worldwide.' The disease is caused by infection with any one of several species that are known to affect humans. Infected persons are likely to be consuming a wide spectrum of xenobiotics such as drugs and environmental toxins. The drugs consumed would not only include praziquantel and other schistosomicides, but also those used for the treatment of other parasitic diseases such as antimalarials, anthelmintics and antibiotics. Experiments involving humans and experimental animals suggest that infection with schistosomes causes a reduction in the host's ability to metabolise and remove drugs from the body.
Effect of schistosome infection on hepatic drug metabolising enzymes
(1998-06) Naik, Yogeshkumar S.; Hasler, Julia A.
Schistosomiasis is a parasitic disease that affects over 200 million persons worldwide.' The disease is caused by infection with any one of several species that are known to affect humans. Infected persons are likely to be consuming a wide spectrum of xenobiotics such as drugs and environmental toxins. The drugs consumed would not only include praziquantel and other schistosomicides, but also those used for the treatment of other parasitic diseases such as antimalarials, anthelmintics and antibiotics. Experiments involving humans and experimental animals suggest that infection with schistosomes causes a reduction in the host's ability to metabolise and remove drugs from the b~dy.~.~ The metabolic fate of drugs is dependent to a large extent on the expression and activity of the microsomal drug metabolising enzyme^.^^^ These enzymes include the microsomal cytochrome P-450 dependent monooxygenase system and the uridine diphosphate glucuronosyl transferases as well as other cytosolic enzymes such as glutathione S-transferases. This article reviews the effects of experimental Schistosoma mansoni infection on hepatic drug metabolising enzyme activity.
Regulatory aspects of aflatoxin control in Zimbabwe - a review
(JASSA, 1999) Siwela, Andrew H.; Nziramasanga, Nozipho
Aflatoxins are highly toxic and carcinogenic chemicals produced by fungi of the Aspergillus family. As the fungi may be found growing on virtually all stored agricultural commodities and foodstuffs, many countries have put in place regulations to control the levels of afJatoxins and other mycotoxins that may be found contaminating foodstuffs and stock feeds. Current regulations and aflatoxin control in Zimbabwe is based on a voluntary code of conduct drawn in 1971 which putthe action limit at between 4f,glkg to 20!.glkg aflatoxin G, (AFG,J or Sf,glkg to 2Sf,glk9 aflatoxin B, (AFB1) for human consumption. Any commodity contaminated by Aflatoxin greater than these limits should be used for stock feed and those below these limits could be used for the export market. The 2Sfl9/kg AFB, action limit has been levi sed to 20f'9/kg by the statutory instrument of 1990 under the Food Standard Act of 1971. This paper reviews work that has been done in the past ten years in the monitoring and control of aflatoxin in foodstuffs and feeds. Aflatoxin levels in foods, stock feeds, urine and human milk from a cross section of the population have shown that the population and livestock are exposed to aflatoxin. Disease outbreaks in livestock have also been linked to aflatoxins and other mycotoxins. It is recommended that aflatoxin monitoring be intensified in support of the Food Standards Act and the voluntary code of conduct be made into a legal instrument to control transmission of aflatoxin in the food chain.
Seismic hazard assessment in Eastern and Southern Africa.
(ANNALI DI GEOFISICA,, 1999-12) Midzi, Vunganai; Hlatywayo, Dumisani J.; Chapola, Lostina S.; Kebede, Fekadu; Atakan, Kuvvet; Lombe, Daniel K.; Turyomurugyendo, Gadi; Tugume, Fred Alex
Seismic hazard assessment for the Eastern and Southern Africa region was done using the probabilistic approach. Seismic hazard maps for 10% exceedance in 50 years, 10% exceedance in 100 years, as well as for 50 and 100 years return periods were prepared using the FRISK88M software. The area involved covers a wide region bounded by latitudes 400 S-25°N and longitudes 100E and 55°E. Input parameters for the computations were obtained using the recent earthquake catalogue compiled by Turyomurugyendo. The catalogue which covers the time period 627-1994, contains earthquakes within the area bounded by 400 S-25°N and 100 E-55°E, with homogeneous magnitudes (M). Since a Poisson model of earthquake occurrence is assumed, dependent events were cleaned from the catalogue. Attenuation relations for the Eastern and Southern Africa region based on the strong motion data are virtually non-existent. However, attempts have been made recently by Jonathan 'and Twesigomwe to establish an average attenuation relation for the region. These relations were used in the computations. Possible uncertainties in the attenuation relations were accounted for using the logic-tree formalism. The results are presented in seismic hazard maps in terms of Peak Ground Acceleration (PGA) for the mean and the 85th percentile. The distribution ofPGA values indicate relatively high hazard along the EastAfrican rift system. In the northern segments of the rift system, they exceed 250 gals for 10% probability of exceedence in 50 years.
Chemical composition and physical characteristics of cowpea haulms as forage for ruminants
(South African Society of Animal Science, 2000) Mokoboki, H.K.; Ayisi, K.K.; Ndlovu, Lindela R
Cowpea ( Vigna unguiculata) is a major grain legume grown by small- scale farmers in the Northern Province of South Africa. The crop is indigenous to Africa and is used extensively in many cropping systems throughout Africa (Eaglesham et al., 1981). Cowpea straws are potential supplementary feed for ruminants in the dry season. Cowpea straws are likely to have higher crude protein than cereal straws and may thus improve digestibility of cereal straws if used together. However, cowpea straws may contain anti-nutritional factors such as tannins and total phenols which affect animal performance. The protein and tannin content of cowpea straws is likely to be affected by variety and growth environment. Straws of varieties adapted to Northern Province have not been evaluated for their content of these constituents. Whilst animal intake and utilisation are the ultimate test of forage suitability, the procedures are unsuitable when large number of forage germ-plasm are to be screened. Chemical and physical characteristics that are known to affect intake and utilisation are often used in such circumstances. The main aim of this research was to determine the effect of variety on physical and chemical characteristics of straws of long season cowpeas and also to determine if haulms of varieties that retain greenness longer will have a better nutritional value than those that dry early.
Establishment 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.
In vitro monitoring of rabbit anterior cruciate ligament damage by acoustic emission.
(Medical Engineering Physics, 2000-06) Azangwe, Godfrey
Anterior cruciate ligament (ACL) rupture is a major clinical problem leading to instability and degeneration of the knee joint. The problem is compounded by the limited ability of the ACL to heal when ruptured. The existing knowledge regarding the way the ACL ruptures is limited, and this investigation is an attempt to understand the nature of the ruptures using the rabbit as a model. A total of 16 rabbit tibia–ACL–femur complexes were stretched in tension to complete rupture. Four specimens were stretched to failure at a displacement rate of 0.5 mm/min and 12 specimens at 10 mm/min. Acoustic emission (AE) transducers were placed on both the tibia and the femur, and stress wave signals generated during the tensile test were recorded. Fibre fractures produced the highest amplitude signals with a relatively longer rise time. Other failure modes such as matrix failure and debonding produced lower amplitude signals with shorter rise times. We also noted that few events were recorded during the initial period of tensile loading (the elastic phase). The activity then increased significantly after maximum load was reached. The location information provided by the acoustic emission system was consistent with the final site of rupture. We have shown that AE can be used to characterise ligament damage, with fibre pull-outs and fibre fracture producing the highest signal amplitudes.
The effect of air sparging on the electrical resolution of water-in-oil emulsions
(Elsevier Science Ltd., 2001) Bailes, P.J.; Kuipa, Pardon K.
A novel process is described in which the resolution of a stable water-in-oil emulsion is augmented by the simultaneous use of pulsed DC electric 1elds and mild bubbling of the emulsion with air. The work has indicated that there is a synergistic effect of air sparging on demulsi1cation in the electric 1eld and that the maximum emulsion resolution requires the voltage to be pulsed with optimum frequency. Emulsion resolution was found to increase steadily with increasing air 5ow rate until a maximum value is reached after which the extent of phase separation starts to fall rapidly with further increase in the air 5ow rate. The electrical resolution was best (79% resolution) when the ratio of air to emulsion 5ow rate (volumetric) in the coalescer was about 120 : 1.

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