The effects of some divalent metals on cardiac and branchial Ca2+-ATPase in a freshwater fish Saccobranchus fossilis

The heart and gill of a freshwater fish Saccobranchus fossilis have been shown to contain a Ca2+-activated ATPase involved in Ca2+ transport. Enzyme showed optimal activity at 3 mM Ca2+ and 3 mM ATP for gills and at 3 mM Ca2+ and 1 mM ATP for heart. Mg2+ was equally effective in stimulating enzyme activity but was not essential for hydrolysis. Maximum activity was found in heart ventricular muscles as compared to gills. Among all the metals tested Hg2+ was the most toxic (IC50, 0.75 and 0.85 microM for heart and gill, respectively) followed by Pb2+, Mn2+, and Cd2+. The inhibition was concentration dependent and reached almost 100% with each metal at the highest concentration. Stimulation of enzyme activity was observed at lower concentrations of Mn2+ and Cd2+ but not with Pb2+ and Hg2+. Stimulation was more pronounced with Mn2+ than with Cd2+ in both heart and gills. The results indicated that the inhibitory effect of these metals might be through the Ca2+-ATPase which is a manifestation of the calcium pump in various tissues.     

Thein vivo effect of mercuric chloride on some digestive enzymes of a fresh water teleost fish,Channa punctatus

Summary Alterations in the activities of alkaline phosphatase, acid phosphatase, glucose-6-phosphatase amylase, trypsin, pepsin, aminotripeptidase, glycylglycine dipeptidase and carnosinase due to exposure ofChanna punctatus to a sublethal concentration (0.30 mg/L) of mercuric chloride by bath for 20 days have been studied in the different parts of the digestive system. A fall in the activities of the three phosphatases was recorded except for alkaline phosphatase which showed a slight elevation in activity in intestine and pyloric caeca. An increase in the activity of amylase and the two proteases was observed in all the portions of the digestive system. The three peptidases revealed a decrease in activity.     

Toxicity of the pyrethroid insecticide fenvalerate to a fresh water fish, Tilapia mossambica (Peters): changes in glycogen metabolism of muscle

Toxic effects of a pyrethroid insecticide, fenvalerate, on fish muscle glycogen metabolism were investigated. Estimations were made after 10 and 20 days of exposure, and altered muscle glycogen metabolism was observed. The changes included a significant (P less than 0.001) decrease in the levels of glycogen, pyruvate, maleate dehydrogenase (MDH), succinate dehydrogenase (SDH), and phosphorylase a, b, and ab activities, while elevated levels of lactic acid, aldolase, and lactate dehydrogenase (LDH) activity were observed under fenvalerate intoxication. There was a decrease in opercular movement and oxygen consumption with an increase in concentration of fenvalerate.     

Effects of chromium on humoral and cell-mediated immune responses and host resistance to disease in a freshwater catfish, Saccobranchus fossilis (Bloch).

The effects of subtoxic levels of Cr on humoral and cell-mediated immune responses, blood parameters, susceptibility to bacterial (Aeromonas hydrophila) infection, and macrophage activity in the freshwater air-breathing Asian catfish, Saccobranchus fossilis, during a 28-day exposure were examined by a static bioassay test procedure. At 0.1, 1.0, and 3.2 mg / liter Cr, dose-dependent Cr accumulation in kidney, liver, and spleen was observed at the end of the experiment. Chromium exposure caused a significant change in spleen to body weight ratio. Fish exposed to Cr concentrations had lower antibody titer values, reduced numbers of splenic and kidney plaque-forming cells, and higher counts of splenic lymphocytes but reduced counts of kidney cells when compared with the control group. At 0.1, 1.0, and 3.2 mg /liter Cr, dose-dependent decreases in red blood cell counts, hemoglobin content, and packed cell volume were observed. Differential leukocyte counts revealed that Cr exposure caused a significant decrease in large and small lymphocytes, whereas neutrophils and thrombocytes increased. Effects of Cr exposure to mitogen (Con A) on proliferation of splenic and pronephric lymphocytes suggests a decrease in mitogenic response. The eye-allograft rejection time, as a parameter of cell-mediated immunity, was statistically increased at 1.0 and 3.2 mg/liter Cr. Fish exposed to Cr for 28 days exhibited higher susceptibility to A. hydrophila infection than control fish. The results suggest that Cr exposure reduced the resistance of catfish to bacterial infections. The phagocytic activity of splenic and pronephros macrophages was examined in vitro and found to be significantly decreased.     

Toxicity and bioconcentration of selected organophosphorus pesticides in Mytilus galloprovincialis and Venus gallina

A study on toxicity and bioconcentration of the organophosphorus pesticides dimethoate, methidathion, chlorfenvinphos, chlorpyrifos, and phosmet has been carried out for two species of mollusc (Mytilus galloprovincialis and Venus gallina). The LC50 (96-h) and NOLC (not observable lethal concentration) values were determined and some sublethal effects (the development of functional byssus for M. galloprovincialis and response speed at mechanical stimulation for both) were recorded at nominal pesticide concentrations of 1, 3.2, 5.6, 10, and 32 mg/L; and 56 mg/L only in M. galloprovincialis. Methidathion, chlorfenvinphos, and chlorpyrifos produced mortality and sublethal effects on M. galloprovincialis, but no effect was observed on V. gallina at the concentrations tested. Dimethoate and phosmet did not cause appreciable effects on either of the two species tested. Toxicity of the organophosphorus pesticides tested varied from moderate toxicity to no-effect (in acute tests), depending on the compound and organism that was tested.Pesticides residue analyses of the soft tissue of exposed molluscs showed that toxic pesticides can be bioconcentrated in short time periods. The levels of chlorpyrifos and methidathion in the two molluscs are related to the concentration in water and are also somewhat related to the percentage of mortality in M. galloprovincialis. V. gallina concentrated large amounts of pesticides in its tissues in short time periods with no observable toxic effects after 96-h. Bioconcentration of pesticide residues could produce serious risks to public health due to the consumption of these contaminated organisms.     

Environmental impact of mosquito pesticides: Toxicity and anticholinesterase activity of chlorpyrifos to fish in a salt marsh habitat

Chlorpyrifos was tested for its influence on thein vitro andin vivo brain acetylcholinesterase (AChE) activity ofFundulus heteroclitus under laboratory as well as field conditions. The concentration required for a 50% reduction in the mvitro enzyme activity (I₅₀) was 7.2 × 10^–2 mM for the parent compound and 4.1 × 10^–6 mM for its oxygen analog. A 96-hr exposure of live fish to 1.0g/L chlorpyrifos resulted in a maximum AChE inhibition of 24%. At a concentration of 2.1g/L or higher, a 100% enzyme inhibition was observed after a 24-hr exposure period, followed by varying degrees of recovery during the next 24 hr. A second peak of AChE inhibition, proportional to the concentration of the insecticide, was observed 72 hr after the initial exposure and this was followed by a second phase of recovery during the next 24 hr. In spite of an initial 100% AChE inhibition at test concentrations of 2.1g/L and above, the fish mortality was less at lower concentration of the insecticide than at the higher levels. The 96-hr TL₅₀ and TL₅ (tolerance limit for 50% and 5% fish survival) of chlorpyrifos forF. heteroclitus were 4.7g/L and 12.2g/L, respectively. The LT₅₀ (lethal time in which 50% of the fish died) at a concentration of 5.6g/L was 49.5 hr.Fish exposed to 4 successive field applications of chlorpyrifos granules showed AChE inhibition ranging from 56 to 100% and the insecticide effect was cumulative in nature. By 24 hr after the second application, 18.6% of the treatment fish had died; live fish collected at this time showed a 96% depression of AChE activity. AChE inhibition was still evident (62%) in fish 69 days after the final application of chlorpyrifos.Paper of the Journal Series, New Jersey Agricultural Experiment Station, Rutgers-The State University of New Jersey, New Brunswick, New Jersey 08903, USA. Supported by a grant from N. J. State Mosquito Commission.