Histological, Genotoxic, and Biochemical Effects on Cnesterodon decemmaculatus (Jenyns 1842) (Cyprinodontiformes, Poeciliidae): Early Response Bioassays to Assess the Impact of Receiving Waters.

In the present study, the toxicity of receiving waters from a highly polluted urban watercourse, the Reconquista River, Argentina, collected at a dam in the upstream part of the river was evaluated. Cnesterodon decemmaculatus, a widely distributed fish species in Pampasic rivers proposed for use in ecotoxicological evaluations, was used as a test organism. A 96-h acute toxicity bioassay with river water quality which has been characterized as moderately contaminated was performed. The treatment groups were (1) whole surface river water; (2) whole surface river water with 2 mg Cd/L added as a simulated metal contaminant pulse; (3) a negative control using reconstituted moderately hard water (MHW); (4) a metal positive control, MHW + 2 mg Cd/L; and (5) a positive genotoxicity control, MHW + 5 mg Cyclophosphamide/L (CP). The condition factor rate, micronuclei frequency, and comet assay from peripherical blood, structural changes of the gill arrangement by scanning electron microscope (SEM) analysis, histopathological changes in the liver and the glutathione-S-transferase, catalase, superoxide dismutase, glutathione, and protein content from the body midsection (viscera) were evaluated. According to our results, for short term exposure, SEM analyses of gills and liver histopathological analyses could be useful tools for the evaluation of target organ damage as well as comet assays for DNA damage. We propose that the 96-h laboratory bioassay protocol described is useful for monitoring the deterioration of water quality employing the teleost C. decemmaculatus and that the microscope analysis of gills and liver as well as the comet assay methodology could be sensitive endpoint indicators.

Antivenom against Crotalus durissus terrificus venom: Immunochemical reactivity and experimental neutralizing capacity.

The venom of Crotalus durissus terrificus produces a neurotoxic and myotoxic syndrome that can lead to the death. Specific antivenom is the only treatment to neutralize the toxicity of the venom and the precocity in applying the antivenom is crucial for the efficiency of the treatment. We studied the variation of the immunochemical reactivity and neutralizing capacity of the specific antivenom on this venom in pre-incubation and rescue experiments, at different times. ELISA titers increased with longer venom-antivenom incubation times (p < 0.05) nevertheless incubation times had no effect on the neutralizing capacity of the antivenom. The antivenom dose necessary to rescue mice injected with 1.5 MMD (minimal mortal dose) 30 min after venom inoculation was over ten folds the dose of antivenom theoretically required to neutralize the same dose of venom according values obtained from pre-incubation experiments. Results showed that the in vitro immunochemical reactivity is not directly related to the neutralizing capacity. These observations underline the need for a rapid antivenom administration. Although preincubation experiments in mice are a powerful tool for the validation of the potency of the antivenoms in the productive process, it is clear that the nominal neutralization of the antivenoms must not be considered as a "stoichiometric" value regarding the venom to be neutralized in case of natural envenomation and emphasize the need of realization of clinical trials in order to evaluate the adequate doses of antivenom to be therapeutically used.