Applied Biology and Biochemistry Conference Papers

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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 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.
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.
A study of scavenging poultry gastrointestinal and ecto-parasites in rural areas of Matebeleland Province, Zimbabwe.
(Asian Network for Scientific Information, 2010) Dube, S.; Zindi, P.; Mbanga, J.; Dube, C.
A study was carried out to determine endo and ecto-parasites in Matebeleland North and South from free range chickens (Gallus domesticus). Only adult chickens were selected for determination of parasite. For intestinal parasites microscopic studies of eggs and faecal egg counts were done using the salt floatation technique. The endo parasites encountered in the study were Tetrameres americana, Acuaria hamulosa, Ascaridia galli, Heterakis gallinarum, H. dispar, Allodapa suctoria, Capillaria annulate, Raillietina echinobothrida and R. tetragona. A commercially prepared insecticide constituted as follows (0.02% Tetamethrin, 0.03% pramethrin and 0.034% Imiprothrin) was applied for 2 seconds and feathers were then gentle unruffled so that ectoparasites could be counted and identified. Ecto parasites recorded in this study were Menopon gallinae, Menacanthus stramineus, Dermanyssus gallinae, Argas persicus, Ornithonyssus bursa, Cnemidocoptes mutans, Echidnophaga gallinacean, Gonocoites gallinae and Gonocoites hologester.
Aflatoxin carryover during large scale peanut butter production.
(Scientific Research Publishing, 2011) Andrew H, S.; Kudzayishe J, M.; Nozipo, N.
Peanut 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.
Evaluation of test-kits for the detection of Escherichia coli O157 in raw meats and cattle faeces
(2012) Nyati, H.; Heuvelink, A.; Van Heerwaarden, C.; Zwartkruis, A.
Escherichia coli O157 detection limits in artificially contaminated beef and cattle faeces samples were determined using Dynabeads anti E. coli O157 immunomagnetic beads, VIDAS-UP, VIDAS-ICE, and real-time PCR (GeneDisc and LightCycler) systems. Dynabeads anti-E. coli O157 immunomagnetic separation (IMS) and the GeneDisc cycler were the most sensitive methods, and could detect an initial 1 CFU in 25g beef samples after 6h of incubation in modified tryptone soya broth with novobiocin (mTSB+n) or buffered peptone water (BPW). The VIDAS-UP method could detect an initial 10 CFU, while VIDAS-ICE and the LightCycler methods could only detect an initial 100 CFU. Higher detection rates were achieved with 18 hour incubations, where an initial 1 CFU in a 25g sample could be detected with all five methods. For cattle faeces enrichments, Dynabeads anti-E. coli O157 IMS could detect an initial 1 CFU after a 6 h incubation in mTSB+n, while the VIDAS-UP and VIDAS-ICE methods could detect an initial 10 CFU and both PCR methods could only detect an initial 100 CFU. Detection rates were lower in BPW, compared to mTSB+n, with thresholds of 100 CFU for VIDAS-ICE, VIDAS-UP and GeneDisc methods, and >100 CFU for the LightCycler method.
Glutathione Transferase of Schistoma Mansoni and its Interaction with Praziquantel.
(2013-03-11) Hasler, Julia A.
Glutathione S-transferases play an important role in the excretion of xenobiotics as well as in the antioxidant defence system of cells. The glutathione S-transferase of the parasitic' trematode Schistosoma mansoni has been studied. The results of preliminary experiments are presented here. The pH optimum of the enzyme was found to be 9.5 which is much higher than that of the mammalian liver enzyme. The apparent Km for the substrate 1 chloro 2,4 dinitrobenzene (CDNBL was 1.25 mN and for glutathione was 0.37 roM. The antischistosomal drug Praziquantel was found to inhibit the conjugation of CDNB in a competitive manner. The implications of these results will be discussed.
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.
In Vitro Effects of Carbaryl and Dimethoate on Esterases of Lymnaea Natalensis.
(2013-03-12) Basopo, N.; Naik, Yogeshkumar S.; Nyathi, C.B.
Agrochemicals have adverse biochemical and physiological effects on organisms and can ultimately cause disturbances in ecosystems. It is therefore important that sensitive techniques are available to monitor their presence and persistence in the environment be monitored. We are pursuing the possibility of developing modified esterase activity in aquatic snails as a potential biomarker for the detection of organophosphate and carbamate pesticides in contaminated waters. We have previously reported that exposure in vivo of the aquatic snail Lymnaea natalensis to a number of organophosphorus and carbamate pesticides causes inhibition of esterase activity to varying degrees in a pesticide and esterase substrate specific manner. Here we report on the effects of two commonly used pesticides, dimethoate and carbaryl in vitro, on the esterase activity of an aquatic snail L. natalensis. Post mitochondrial fractions were prepared from adult L. natalensis bred in outdoor cement aquaria. Esterase activity was measured in the presence of various concentrations of dimethoate or carbaryl. Our results showed a non-linear, but dose dependent, inhibition of esterase activity with both pesticides using 5 different substrates which were used to differentiate (choline and non-choline) esterase activity. Esterase activity was reduced significantly, depending on the substrate used, in the presence of both dimethoate (11 "10 - 78'Yo) and carbaryl (l5'Yo-93"1o). Both dimethoate and carbaryl showed similar IC50 values but variations were noted depending on the substrate used to determine esterase activity. Dimethote was, however, the mor'e potent of the two pesticides as shown by the its lower IC50 values when compared to carbaryl. Our data suggests there is a potential for the use of esterase activity in L. natalensis as a biomarker of organophosphorus and carbamate pesticides
Molluscan Esterase Activity As a Biomarker of Aquatic Pollution Caused By Monocrotophos.
(2013-03-12) Naik, Yogeshkumar S.; Basopo, N.; Nyathi, C.B.
There are many analytical protocols for detecting levels of agrochemicals~inaquatic systems. Methods of analytical chemistry can provide information of the exact concentrations in water samples. However they do not provide information on the potentially harmful effects on the organisms in the aquatic environment as biological markers have been shown to. Biomarkers of environmental quality should be tested under field situations if they are to be accepted outside academic circles and become part of national policies in environmental monitoring programs. We have previously shown that exposure of Lymnaea natalensis to organophosphates caused dose and time dependent inhibition of esterase activity. Here we report on the effects of monocrotophos on esterase activity in L. natalensis under field simulated conditions.Juvenile snails reared outdoors were exposed to single dose (5, 12, 15, 20 and 25ppb) of monocrotophos dissolved in either Matopos (pristine) or Umguza (polluted)dam water for 1, 7 or 14 days. Water was not changed for the duration of exposure. Post mitochondrial supernatants of whole snail homogenates were used to measure esterase activity. Cholinesterase activity was measured using acetylcholine iodide while carboxylesterase activity was measured using a-naphthyl acetate and 4nitrophenyl acetate. Esterase activity was significantly reduced in a dose responsive manner for aIr substrates. The degree of inhibitioll. varied depen,ding on the water source. Our results also indicated a decrease with time in degree of inhibition of esterase activity, suggesting a recovery with time of the snails from pesticide poisoning. On comparing data from the two dams higher inhibitions were observed in snails exposed to Matopos dam water than those exposed to Umguza dam water. Umguza dam water is highly contaminated with industrial effluents and therefore expected to have a higher microbial load and increased pesticide decomposition rate when compared to Matopos dam water, which is relatively pristine. Our results have shown that esterase activity is very sensitive to presence of organophosphates with inhibitions of up to 92 % observed within 24 hours of exposure. Altered esterase activity therefore has a potential use as a biomarker for detecting organophosphatepollution in water samples.
Strain Dependant Variation In The Response Of Hepatic Drug Metabolizing Enzymes To Infection With Schistosoma Mansoni.
(2013-03-12) Naik, Yogeshkumar S.; Hasler, Julia A.
Introduction: Infection with S.mansoni has been shown to alter hepatic drug metabolising enzyme levels in mice although we have shown that hepatic drug metabolising enzymes of male hamsters are not significantly affected as a result of infection. Considerable specie and strain dependent variations do exist, however,' in the pathology of and immune response to S.mansoni infection in animals. It is not known if animals of the same specie but of different strains respond similarly to S.mansoni infection in terms of their hepatic drug metabolising enzymes. This study was therefore performed to assess the effect of S.mansoni infection on hepatic drug metabolism in vitro in male BALB/c and CBA/H mice. Results and Discussion: The results in Table 1 show that alterations in hepatic drug metabolism in vitro due to infection with S.mansoni vary between male BALB/c and CBA/H mice. Infected BALB/c and CBA/H mice both showed decreased concentrations of cytochromes P-450 and b5, and a decreased rate of ethoxyresorufin metabolism. Only infected BALB/c mice, however, showed decreases in their NADPHcytochrome c reduce activity and in the rate of ethoxycoumarin metabolism, and an increase in the rate of 4-nitroanisole metabolism. While the microsomal uridine diphosphate glucuronyl transferase activities were decreased in infected BALB/c and CBA/H mice, the cytosolic glutathione-S-transferase activities were decreased only in BALB/c mice as a result of infection. The reasons for the strain dependent difference observed here is not known. It is possible that various factors released in the circulation of animals infected with S.mansoni, such as interferons, interleukin-l, histamines etc, affect the activities of hepatic drug metabolising enzymes. Strain dependent alterations in microsomal drug metabolism have also been reported for animals pretreated with inducers of interferon synthesis. Interstrain differences among infected animals in the release of immune modulators such as those described above may be responsible for the varying effects on the hepatic drug metabolizing enzymes and their isozymes. Conclusions: It is concluded that the disposition of xenobiotics in experimental S.mansoni infected mice will vary depending on the mouse strain being used. Choice of an animal model for studies on the effect of schistosomiasis on drug metabolism should therefore be made carefully especially if extrapolation to humans is intended.
Esterase Activity of Two Aquatic Snail Species Helisoma Duryi And Lymnaea Natalensis
(2013-03-12) Nyathi, C.B.; Naik, Yogeshkumar S.; Basopo, N.
Previous work has shown that inhibition of esterase activity is likely to be a useful parafrieter to develop as a biomarker of organophosphate pollutants. We have extended our preliminary study and have now tested for esterase activity with two new substrates (five in total) while measuring the esterase activity in a newly established colony of the aquatic snails Lymnaea natalensis and Helisoma duryi. Post mitochondrial fractions prepared from whole body homogenates were used to measure esterase activity with the following 5 substrates: p-nitrophenyl acetate ( PNPA), (-naphthyl acetate (ANA), phenyl acetate (pHA), carboxylic esterase activity and acetylthiocholine iodide (Ach!) and S-butyrylthiocholine iodide (BthI) cholinesterase activity. Our data shows that the carboxylic esterase (CbE) activity measured in our new stock of snails was decreased (depending on the substrate used a range from 30% to 50%) compared to values obtained previously. Since the cholinesterase (ChE) activity was measured for the first time in these two species a comparison could not be made. In general, the esterase activity was found to be slightly higher in H. duryi than in L.natalensis. The reasons for the altered activity in the new snail colony is not clear but nutrient and climatic factors are likely to be responsible.
Pesticide Induced Alterations On Cellular Parameters In On-Target Species And Their Potential Effects On Ecosystems: A Review.
(2013-03-12) Naik, Yogeshkumar S.
Pesticide use has been associated with threats to human and ecosystem health. Inhibition of nerve function is usually the target for insect and pest control. In non-target species, there may be a: variety of additional effects of the pesticides besides nerve inhibition. Several studies have shown that pesticide exposure can cause a number of effects at the cellular level causing physiological and other disturbances in organisms. Amongst others, these include the following; endocrine disruption, oxidative stress, altered enzyme function or gene regulation. These cellular and physiological effects in individual species/organisms can manifest at higher levels within an ecosystem. Thus, reproductive and behavioural effects in organisms at a single trophic level can affect profoundly the entire ecosystem health and balance. This paper will provide an overview of these possible effects as well as show examples where they have been shown or known to operate.
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.
Metal 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.
Species and Sex Related Differences in Antioxidant Enzymes in Fish Collected From Umguza and Auchmacoy Wright Dams, Bulawayo, Zimbabwe.
(2013-03-12) Nyathi, C.B.; Siwela, Andrew H.; Naik, Yogeshkumar S.
Agricultural and industrial activity results in the pollution of our environment by pesticides and metals usually causing deleterious effects on both humans and other animals in the environment. We are interested in the effects of pesticides and metals on non-human targets, such as fish, in the environment. Literature reports suggest that there are species and sex differences amongst fish in the metabolism of foreign compounds (xenobiotics) on the detoxifying enzymes of aquatic organisms. The aim of this study was to assess whether there are any species and sex differences in antioxidant enzyme activities of local fish. Catfish (Clarius gariepinus) and bream (Oreochromis mossambicus) collected from two dams, one polluted (Umguza) and one pristine (Auchmacoy Wright) in the Bulawayo area. Gills, liver and kidneys from captured (gill netted) fish were excised, homogenized and centrifuged to obtain S-9 fractions. The S-9 fraction was used to assay for activities of the antioxidant enzymes, catalase, glutathione peroxidase and DT- diaphorase. Significant sex-related differences in the activity of catalase in liver and gill but not in kidney of catfish collected from Umguza Dam were noted (Student t test, P< 0.05). No sex-related differences in catalase activity were observed in bream tissues collected from Umguza Dam. Catalase activity in female bream collected from Umguza Dam was/significantly higher when compared to female catfish catalase from the same dam. Glutathione peroxidase activity in catfish collected from Umguza Dam were Seen to be sex dependent in gill and liver but not in kidney (Student t test, P < 0.05) whilst species differences were noted only in liver, with higher activities in catfish. Umguza bream showed significant sex differences in glutathione peroxidase activity onfy in the gills. DT- diaphorase activity in catfish collected from Umguza Dam was shown to be sex dependent in gill and kidney but not in liver. In Umguza bream, DT-diaphorase activity was seen to be sex dependent only in gills. Species differences in DT-diaphorase activity were only seen when male catfish and male bream were compared. DT-diaphorase activity was shown to be significantly higher in male catfish compared to male bream but there were no differences in activity when female catfish were compared to female bream in all the tissues. For fish collected from Auchmacoy Wright Dam, significant differences in bream catalase activity was seen in all the three tissues studied. Species difference in catalase activity were noted in liver and gill but not in kidney. Significant sex differences in the activity of glutathione peroxidase were noted only in the kidneys of the bream. Species differences in glutathione peroxidase activity were noted only in the gills of female fish. No significant diffe.rences in DT-diaphorase activity either by sex or species were noted in all the tissues of fish collected from Auchmacoy Wright Dam. Our data indicates that enzyme activity is species, sex and tissue dependent in fish and that enzyme activity is also affected by the presence of pollutants.
Potential Use of Esterases As Markers of Aquatic Pollution By Organophosphate and Carbamate Pesticides
(2013-03-12) Naik, Yogeshkumar S.; Basopo, N.
Potential Use of Esterases As Markers of Aquatic Pollution By Organophosphate and Carbamate Pesticides Pesticides are used to widely in agriculture in Southern Africa. Many of these pesticides fall into the category of either organochlorines, pyrethroids, organophosphates or carbamates. We have been interested in the possible use of esterase is as biomarkers of environmental water pollution. Amongst the compounds we have studied are dimethoate, pirirniphos, malathione and monocrotophos. We have studied the effects of these pesticides on the esterase of aquatic molluscan species such as Lymnaea natalensis and Helisoma duryi and Physa acuta. The esterases studied include choline and non-choline esterases and activity was measured using different substrates namely, a-naphthyl acetate, phenyl acetate, 4-nitrophenyl acetate, acetyl thiocholine and S-butyryl thiocholine. Our data indicates that there is a marked species difference in the response to these pesticides. In addition we have found that carbamate pesticides inhibit esterase activity to a lesser extent than do organophosphates and that this inhibition is time and dose dependent. In general esterase activity has been shown to be inhibited by as little as one ppm within eight hours of exposure. Our date supports the results of studies conducted elsewhere in freshwater, estuarine, as well as marine organisms that suggest inhibition of esterase activity in aquatic organisms is a potential biomarker of water pollution. A review of the literature will be provided in addition to data generated in our laboratory.
Potential Use of Superoxide Dismutase As A Biomarker of Metal Pollution In Two Species of Freshwater Snails Lymnaea Natalensis And Helisoma Duryi.
(2013-03-12) Naik, Yogeshkumar S.; Masola, B.; Sakala, K.T.; Zaranyika, M.F.
Toxic metals such as lead and cadmium are widely found in our environment. Humans and animals are exposed to these metals from numerous sources through contaminated air, water, soil and food. Exposure to these metals has been shown to cause an increase in the production of reactive oxygen species (ROS) such as hydroxyl radical COIr), superoxide anion radical C02-) or hydrogen peroxide (H202). These ROS are toxic to the cell and usually cause apoptosis. A number of enzymes are responsible for the removal of these ROS and include superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GPX) and quinone oxidoreductase (QOR). At times exposure to metals results in the induction, repression or inhibition of these enzymes. We have prevsiously reported on the effect of metals on CAT, GPX and QOR. However, it has been shown that SOD can be induced as a result of exposure to metals. This study was therefore conducted to assess the possibility of using metal exposure related induction of SOD as a potential biomarker of water pollution. The study was performed using two species of aquatic snails found in Southern Africa, namely Lymnaea natalensis and Helisoma duryi. Adult snails reared in outdoor cement aquaria were exposed daily for three days to three concentrations (0.01 ppm, 0.1 ppm and 1.0 ppm) of copper (Cu), cadmium (Cd), lead (Ph) or zinc (Zn) individually. SOD activity was measured in post-mitochondrial fractions. Although not statistically significant, our data indicates a trend in hoth species of snails where Cu, Cd and Pb caused dose related increases in SO..p activity. However, Pb caused a dose related change only in L natalensis and not in H. ~ryi. The activity was increased several fold at 1 ppm while the lower concentrations seemed to have little or no effect. These results suggest that metal exposure results in an increased SOD activity in aquatic invertebrates. Furthermore, induction of SOD activity as a result of exposure to metal is a potential biomarker of water pollution. However, further studies are required using other metals and a wider concentration range in order to test the reliability of this enzyme as a biomarker.
Recovery Of Choline And Non-Cholinesterase Activity Of The Freshwater Snail Lymnaea Natalensis Following Exposure To Six Pesticides
(2013-03-12) Naik, Yogeshkumar S.; Basopo, N.; Nyathi, C.B.
Organophosphates and carbamates are the most widely used insecticides mainly because they are readily biodegradable in the environment. We investigated the recovery of esterase activity of an aquatic snail L. natalensis following a 24-hour exposure to 6 different pest.icides. A third of the snails were sacrificed after 24 hours while another third was allowed to recover in clean water for 14 days and the remainder for 28 days. All pesticides caused significant inhibition of esterase activity. Aldicarb caused the highest inhibition in esterase activity 98 % while thiamethoxam caused the least 61 %. Esterase activity improved significantly in the recovery period and 14 days in the recovery period, aldicarb and thiamethoxam exposed snails had recovered to 57 % and 67 % of control. After 28 days of recovery, aldicarb exposed snails had only 62 % esterase activity in comparison to controls. The results show that even after 28 days of recovery, esterase activity was still reduced by up to 38 % depending on the pesticide, an indication that recovery of the snails depends on the pesticide. From the results we suggest that where pesticides need to be applied more than once, a time gap between applications should be allowed to enable non-target organisms in soil and aquatic systems to recover from effects of previous applications thereby ensuring the good health of non-target organisms.
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.

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