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Browsing by Author "Naik, Yogeshkumar S."

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Activities of glutamate dehydrogenase and aspartate and alanine aminotransferases in freshwater snails Helisoma duryi and Lymnaea natalensis exposed to copper.
(Biomarkers, 2003) Masola, B.; Chibi, M.; Naik, Yogeshkumar S.; Kandere, E.; Zaranyika, M.F.
In this paper we investigate the potential of glutamate dehydrogenase (GDH) and aspartate and alanine aminotransferases (AST and ALT) as biomarkers of water pollution due to copper in the freshwater snails Helisoma duryi and Lymnaea natalensis. Snails were dosed with copper(II) ion concentrations of 0.01, 0.1 and 1 mg kg(-1) breeding water for a period of 96 h, after which those surviving were shelled. The copper content in the breeding water, in whole snail tissue and in the snail shells was determined at the end of the period of exposure. For enzyme determinations, whole snail tissue was first homogenized and fractionated by centrifugation at 500 g to remove the nuclei. The resulting supernatant was then centrifuged at 10,000 g to give a pellet fraction representing the mitochondrial fraction and a supernatant representing the cytosolic fraction. Copper was very toxic to both snail species at concentrations above 0.2 mg l(-1), with only 3% of the Helisoma and 12% of the Lymnaea surviving at concentrations of approximately 1 mg l(-1). The copper content in the shells and tissues of snails rose with increasing copper concentration in the breeding water, and was 2.1- to 4.9-fold in snails exposed to copper ion at a dose of 1 mg kg(-1) water compared with undosed snails. Similarly, the activities of GDH and AST rose by up to 4.7-fold in the homogenate and the mitochondrial and cytosolic fractions with increasing concentrations of copper. These activities, however, fell at copper concentrations of approximately 1 mg l(-1), which coincided with massive death of snails. Mitochondrial ALT disappeared at copper ion concentrations of approximately 0.2 mg l(-1) for Lymnaea and 1 mg l(-1) for Helisoma, possibly indicating mitochondrial degeneration. These results show that GDH, AST and ALT have the potential to be biomarkers of sublethal copper pollution in these two snail species, since their activities were significantly altered by low copper concentrations.
Altered Esterase Activity Due To Pesticide Exposure In The Aquatic Snail Physa Acuta.
(2013-03-14) Maredza, Alice; Naik, Yogeshkumar S.
The effect ofpesticides on the xenobiotic metabolising enzymes of the aquatic snail Physa acuta was studied. Adult snails reared in the laboratory were exposed daily for three days to the following pesticides: 2,4-dichlorophenoxyacetic acid, deltamethrin, endosulphan, malathion and pirimiphos-methyl. Cytosolic fractions prepared from the snails showed that pesticide exposure had no effect on the glutathione or glutathione dependent enzyme activities. General esterase activity using two different substrates was reduced significantly by exposure to the organophosphate pesticides malathion and pirimiphos. Exposure to the other pesticides did not cause any substantial changes in the esterases activities. The nature of this inhibition is not yet apparent. It is likely, however, that the changes are due to a competitive type inhibition by the pesticides for the active site of the enzyme.
Altered esterase activity due to pesticide exposure in the aquatic snail Physa acuta.
(2013-09-24) Maredza, Alice; Naik, Yogeshkumar S.
The effect of pesticides on the xenobiotic metabolising enzymes of the aquatic snail Physa acuta was studied. Adult snails reared in the laboratory were exposed daily for three days to the following pesticides: 2,4-dichlorophenoxyacetic acid, deltamethrin, endosulphan,malathion and pirimiphos-methyl, Cytosolic fractions prepared from the snails showed that pesticide exposure had no effect on the glutathione or glutathione dependent enzyme activities. General esterase activity using two different substrates was reduced significantly by exposure to the organophosphate pesticides malathion and pirimiphos. Exposure to the other pesticides did not cause any substantial changes in the esterases activities. The nature of this inhibition is not yet apparent. It is likely, however, that the changes are due to a competitive type inhibition by the pesticides for the active site of the enzyme.
Antioxidant enzyme profiles in a species of ornamental fish (koi)
(2013-03-11) Naik, Yogeshkumar S.
The aim of this work was to determine whether, and at what levels, antioxidant enzymes are expressed in the various organs of the koi. The activity of the antioxidant enzymes catalase (CAT), glutathione peroxidase (GPX), NAD(P)H: :' quinone oxidoreductase (NQOR) and malondialdehyde (MDA) content were determined in tissue homogenates of liver, kidney, pectoral muscle, gills, eggs, blood, heart and intestine. There was a marked variability (up to tenfold difference) in enzyme activity in the various organs, but much less individual variability ( - three fold difference). NQOR activity was highest in eggs (- 5.56(A/min/mg). Catalase activity also found heterogeneously in all organs had its highest activity in the liver ( - 5.02(A/min/mg). GPX (selenium dependent) activity was highest in the liver (5.14(A/min/mg). Thiobarbituric acid reactive substances (MDA) content, a measure of lipid peroxidation was, significantly low in all organs and tissues with an A535/mg of 0.00145(0.0027. The results suggest that antioxidant enzymes are expressed in most organs of the koi and that this species of fish is likely to be protected when exposed to compounds that either undergo redox cycling or that exerl a direct oxidative stress.
Biological oxidants and antioxidants
(2013) Naik, Yogeshkumar S.
The generation of reactive oxygen species, such as the supcroxideanionradical and hydroxyl radical, is known to lead to a variety of pathological conditions. Antioxidants such as vitamins A, C, Eand antioxidant enzymes are known to prevent the deleterious elfects of these toxic radicals. THe role of free radicals in disease may be most familiar to readers of the literature on postischacmic organ reperfusion injury. However, recent studies have shown that these radicals may also play a role in the ageing process, artherosclerosis, carcinogenesisa and even Diabetes mellitus
Biomarkers of Environmental Pollution
(2013-03-14) Naik, Yogeshkumar S.
The threat to our environment due to human activity continues as the need for increased agricultural and industrial output continues. Agrochemicals currently used include pesticides such as organochlorines, organophosphates (OP's), neonicotinoids and pyrethroids. Industrial activity continues to generate an increasing diversity and volume of chemicals, such as PCB's and dioxins, that find their way into our natural and manmade water bodies. Metals such as lead, chromium and cadmium are either mined or are discharged as by-products of human activity. When used safely or disposed of properly these compounds are not always hazardous. However, their improper disposal or use poses a hazard to the health of humans, wildlife and the ecosystem as a whole. They are known to cause a variety of toxic effects such as genetic damage, organ toxicity and several physiological changes such as endocrine disruption. There is.a need to identify such toxic compounds and also to monitor their presence particularly in water bodies of Southern Africa where freshwater is scarce. Some of the methods, currently available to detect such toxins, include the measurement of parameters such as esterase activity (or its inhibition) for OP's, the extent of DNA damage (using the COMET assay) and induction/inhibition of detoxication enzymes (cytochrome P-450, glutathione S-transferase, antioxidant enzymes etc.) and induction of vitellogin synthesis (in fish). However, all these methods are not reliable or sufficiently sensitive. A summary of the data presented in the literature as well as that generated in our own laboratory will be presented.
Carbaryl and Dimethoate Induced Alterations of the Antioxidant Defense System in Two Freshwater Pulmonate Snails Helisoma Duryi and Lymnaea Natalensis
(Scholars Research Library, 2016) Basopo, N.; Naik, Yogeshkumar S.
Organophosphates and carbamates are extensively used to increase the quality and quantity of field crops. These pesticides may indirectly enter water bodies where they affect aquatic organisms. Once absorbed by aquatic organisms the pesticides are metabolised and normal metabolic processes may produce reactive oxygen species that have adverse effects on the aquatic organisms. The effects of exposure to carbaryl and dimethoate pesticides on antioxidant enzymes of two freshwater snail species Helisoma duryi and Lymanea natalensis were evaluated. Groups of snails were exposed to 25 ppb of carbaryl and/or dimethoate for 72 hours. After the exposure duration they were then analysed for their effects on the oxidative defense systems of the snails. Increased thiobarbituric acid reactive substances levels and activities of catalase, superoxide dismutase, glutathione peroxidase and glutathione S-transferase in both snail species were observed, probably as a means of combating oxidative stress due to pesticide poisoning. Increased lipid peroxidation, coupled with altered levels of oxygen free radical scavenging enzymes in snail homogenates are discussed in relation to oxidative stress.
A 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.
A 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.
Cytosolic glutathione s-transferases of ostrich liver.
(2015-04-09) Naik, Yogeshkumar S.; Kanyepi, R.; Ndiweni, N.; Hasler, Julia A.; Nyathi, C.B.
Chemicals consummumed by the ostrich are likely to be metabolised by liver detoxifying enzymes such as the cytosolic glutathione Stransferases (GST). We have studied the affinity purified GST from male and female ostrich livers. 1-chloro-2, 4-dinitrobenzene (CDNB) proved to be the best of several substrates tested to measme activity. Activity with this substrate was inhibited by sulphobromoptgnalein and cibamon blue which are well established inhibitors for the m ammalian enzyme. A number of pesticides and environmentai pollutants were also found to be strong inhibitors of the enzymes. Our data indicates that ostrich liver enzymes behave similarly to the mammalian liver enzyme in terms of substrate requirements and inhibition characteristics.
Differential Effects Of Some Quinoline Antimalarial Drugs On Rat Antioxidant Enzyme Activities
(2013-03-12) Naik, Yogeshkumar S.; Magwere, Tapiwanashe; Hasler, Julia A.
Quinoline-based antimalarial drugs have played a crucial role in the fight against malaria for decades. However, with the resurgence in drug tolerance among malaria parasites worldwide. The onus is on drug designers to synthesize more effective and less toxic drugs. In this study we sought to determine the effects of quinine, and the synthetic quinolines primaquine and chloroquine, on antioxidant enzymes so as to gain a better understanding of their effects on various enzyme systems which might be of value in the development of new, safe and more effective drugs. We used the Sprague-Dawley rat as a model to study the effects of these drugs on various hepatic and renal antioxidant enzymes. Our results show that primaquine administration increased the activities of some antioxidant enzymes (superoxide dismutase, glutathione peroxidase, and catalase), whereas chloroquine increased the activity of only superoxide dismutase while decreasing that of glutathione peroxidase and catalase. These results indicate a predisposition of the organs towards oxidative damage as evidenced by increases in parameters of lipid peroxidation in the same organs. Unlike the two synthetic drugs, however, quinine did not appear to cause any significant alterations in the activities of the antioxidant enzymes and neither did it cause any oxidative damage in rat organs. From these results, we conclude that since quinoline is still an effective drug against some chloroquine-resistant strains of malaria,the renewed interest in quinoline drugs should aim to design and synthesize quinine analogues which are less toxic and have enhanced antimalarial activity.
Effect Of Cadmium On The Activltes Of Glutamate Dehydrogemase, Alanine And Aspartate Aminotransferase In Fresh Water Snails, Helisoma Duryi And Lymnea Natalensis
(2013-03-14) Naik, Yogeshkumar S.; Masola, B.; Chibi, M.; Kandere, E.; Zaranyika, M.F.
Snails are known to accumulate metal ion pollutants in their tissues this being attributed to induction of metal binding proteins (Petering and Fowler. 1986). A consequence of the presence of pollutants in water inhabited by aquatic organisms may be the induction of enzymes required to metabolise or degrade the pollutants in such organisms. Other enzymes may also be induced in response to toxic effects of these pollutants on metabolic pathways in which these enzymes are involved. We are investigating the potential use of key enzymes of amino acid metabolism as markers of pollution due to metal ions in fresh water snails. Helisoma dllryi and Lnnl1ea natalensis. Experimental snails were drawn from concrete breeding tanks where they were regularly fed on lettuce. The snails were exposed for 96 hours to 0.0 1. 0.1 and I ppm concentrations of cadmium ion as a chloride salt. After exposure. snails were shelled excluding any dead snails. The tissue was homogenised and centrifuged at 500 x g for 10 minutes at 4PC to pellet nuclei and unbroken cells. The post nuclear supernatant was centrifuged at 10 000 x g for 10 minutes at 4uC. After suspension of the resulting pellet in buffer. both the pellet fraction ("mitochondria'" fraction) and the supernatant (cytosolic fraction) were aliquoted and stored at -82uC. The samples \vere assayed for the activities of glutamate dehydrogenase. and aspartate and alanine aminotransferases. The concentration of cadmium in breeding waters and in shells and tissues (not homogenised) was also determined. The concentration of cadmium in tissues rose with increasing concentTation the metal ion in breeding waters. In the absence of Cd added i.e. 0.03 and 0.02 1lg./ml Cd concentration in the breeding waters of Helisoma and Ll'lIlI1t!a respectively. the concentration of Cd was 0.08Ilg/g. in Helisvma and Ln7lnea tissues. This concentration rose to 0.47 and 0.37 Ilg/g. at I ppm added Cd for Helisoma and L.1'ml1ea respectively. showing 5.9 and 4.6 fold increases over initial concentration. Cadmium was also found to accumulate in shells of the two snail species. In general the activities of glutamate dehydrogenase (GDH). aspartate and alanine aminotransferases (AST and ALT) increased with concentration of cadmium but then decreased at Ippm added metal for GDH and AST. and at 0.1 ppm for ALT. In both snails consistent changes in GDH activity were seen in the homogenate and 10 000 x g pellet. At 0.1 ppm added cadmium the increased activity of GDH in the 10 000 x g pellet was 2.5 and 3.6 fold over initial activities for Helisol11a and Ll'Il1l1ea respectively. AST however showed consistent changes in the homogenates and 10 000 x g supernatants for both snails. At 0.1 ppm added cadmium the increased activity of AST in the 10 000 x g sup ematant was 3.4 and 1.8 over initial activities for Helisol11o and (1'IIlI1ea respectively. ALT also showed a similar pattern of activity change in the homogenate and 10 000 x g supernatant although decrease in activity staned much earlier at 0.1 ppm added metal. In the 10 000 x g pellets ALT activity progressively declined froin the initial values to reach 3-t°'0 and 43% of these values at I ppm added Cd for Helisol11a and (Hl/l1ea respectively. Since alanine and aspanate aminotransferases are known to be dually localised in the mitochondria and cy10so1 in a number of species. a possibility that enzyme could have redistributed due to organelle damage is unlikely in view of the low initial activities in the pellets. Funher the increase in enzyme activit. with metal ion concentration also occurred in the homogenates. The increases in enzyme activities were therefore likely to be due to induction of enzymes. Homogenate enzyme activities as well as those of pellet GDH and ALT. and supernatant AST could be sensitive indicators of Cd pollution
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.
Effect of selenium on cadmium-induced oxidative stress and esterase activity in rat organs
(South African Journal of Science, 2013) Dzobo, Kelvin; Naik, Yogeshkumar S.
Metal toxicity is a threat mainly in the industrialised world where industry discharges many toxic metals into the environment. We investigated the effects of two metals – cadmium and selenium – on the cytosolic antioxidant enzymes and esterases in the liver, kidneys and testes of rats. Male Sprague-Dawley rats (n=28) were divided equally into four groups: control, cadmium, selenium and cadmium/selenium. Salts of the metals were administered intraperitoneally for 15 days. In the liver, cadmium treatment (1.67 mg/kg per day) resulted in a decrease in catalase activity and an increase superoxide dismutase (SOD) activity. Selenium treatment (0.23 mg/kg per day) resulted in increases in glutathione s-transferase, catalase and DT-diaphorase activities. Treatment with both cadmium and selenium resulted in an increase in glutathione peroxidase (GPx) activity. Esterase activities were significantly lower in the presence of cadmium. In the kidney, cadmium treatment caused a decrease in catalase, DT-diaphorase, and SOD activities and selenium supplementation reversed the cadmium-induced decrease in these enzyme activities. Selenium treatment increased catalase and SOD activities in the kidney. In the testis, cadmium treatment decreased GPx and SOD activities, but at the same time increased catalase and DT-diaphorase activities. Esterase activities increased in the presence of selenium in both the kidney and testis. These results suggest that selenium might be toxic to the liver while at the same time play a protective role against cadmium-induced oxidative stress and toxicity in the kidney and testis.
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.
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.
Effects Of Exposure To Lead And Zinc On Antioxidant Enzyme Activity In Lymnaea Natalensis And Helisoma Duryi.
(2013-03-14) Masola, B.; Zaranyika, M.F.; Naik, Yogeshkumar S.
Metals such as Zinc (Zn) are is found in high concentrations in mine drainage, while lead, as tetra-ethyl lead in petrol, causes contamination of water, soil and air can lead to severe health consequences. Zinc has been shown to reduce the efficiency of oxygen transport across the gill membrane of fish, as well as the respiration and ammonia excretion rates of freshwater shrimp. Molluscs have been shown to accumulate a wide variety of pollutants and have, in some instances, proposed as indicators of environmental pollution by metals. The effect of lead (Pb) and Zn on the antioxidant enzymes (AOE's) of two aquatic snail species, namely Lymnaea natalensis and Helisoma duryi was studied with a view to developing a biomarker of freshwater metal pollution. Adult snails reared in the laboratory were exposed daily for three days to 0.01 ppm, 0.1 ppm and 1.0 ppm of either Pb or Zn S-9 fractions were prepared form whole snails. The S-9 fractions were used to measure the activity of AOE's such as DT-diaphorase, catalase and glutathione-S-transferase as well as reduced glutathione (GSH) and the product of lipid peroxidation, malondialdehyde (MDA). Lead exposure tended to increase enzymatic activity several fold. Significant changes were observed after exposure to 0.01 ppm and 0.1 ppm in L. natalensis. Zinc also increased activity of the enzymes but to a lesser extent. Levels of markers of oxidative stress, MDA and glutathione GSH were also altered, with MDA generally decreased in L. natalensis. In H duryimetal exposure resulted in an increased GSH levels when exposed to 0.1 ppm and 1.0 ppm of Pb as well as by all three concentrations of Zn but not in a dose dependent manner. In H duryi, but not L. natalensis metal exposure resulted in an increased (up to 75'7'0) MDA level. Our data suggest that antioxidant status, as a result of exposure to heavy metals in aquatic snails metals is not altered in a dose dependent or manner and is also species specific. Thus, the alterations in AOE's using either L. natalensisor H duryi, are not sufficiently reliable to develop a biomarker of heavy metal pollution in aquatic systems.
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.

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