Browsing by Author "Masola, B."

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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.
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    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
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    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.
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    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.