Effects of exposure to oxamyl, carbofuran, dichlorvos, and lindane on acetylcholinesterase activity in the gills of the Pacific oyster Crassostrea gigas.

Acetylcholinesterase (AChE) activity has been used to test the exposure of mollusk bivalves to pesticides and other pollutants. The Pacific oyster Crassostrea gigas is a species with a worldwide distribution, and it has a high commercial value. The use of this species as a bioindicator in the marine environment, and the use of measurements of AChE activity in tissues of C. gigas require prior evaluation of organisms exposed to several toxic compounds in the laboratory. In our study, the effects of pesticides on AChE activity in the gills and mantle tissues of C. gigas were analyzed by exposing animals to organophosphate (dichlorvos), carbamate (carbofuran and oxamyl), and organochlorine (lindane) pesticides. Adult Pacific oysters were exposed to several concentrations (0.1-200 microM) of dichlorvos, carbofuran, and oxamyl for 96 h, and lindane (1.0 and 2.5 microM) was applied for 12 days. In gill tissues, all pesticides analyzed caused a decrease in AChE activity when compared to the control unexposed group. The mean inhibition concentration (IC(50)) values were determined for dichlorvos, carbofuran, and oxamyl pesticides. Dichlorvos had the highest toxic effect, with an IC(50) of 1.08 microM; lesser effects were caused by oxamyl and carbofuran, with IC(50)s of 1.67 and 3.03 microM, respectively. This study reports the effects of pesticides with several chemical structures and validates measurement of AChE activity in the gill tissues of C. gigas for use in environmental evaluations or food quality tests.

Glutathione S-transferase activity and genetic polymorphisms associated with exposure to organochloride pesticides in Todos Santos, BCS, Mexico: a preliminary study.

The objective of this study was to identify and evaluate the impact of exposure to mixtures of organochloride pesticides (OCPs) in agricultural workers by detecting their effects on the activity of the enzyme glutathione S-transferase (GST) and the presence of polymorphisms of the GSTT1 and GSTM1 genes. The presence of OCPs was identified and quantified by gas chromatography, while spectrophotometry was used to measure enzymatic GST activity. The frequencies of the GSTM1 genotypes were analyzed by multiplex PCR. A total of 18 metabolites of OCPs were identified in the workers' blood, most of which are either prohibited (DDT and its metabolites p, p'DDD and p, p'DDE, dieldrin, endrin, aldrin) and/or restricted (δ hexachlorocyclohexane, cis chlordane, methoxychlor, and endosulfan). The results obtained indicate lower levels of GST activity at higher OCPs concentrations detected in blood from exposed workers, together with an increase in OCP levels in individuals who presented the GSTT1*0 and GSTM1*0 genotypes. These conditions place the detoxification process in agricultural workers with null polymorphisms in the GST genes and high concentrations of OCPs in the blood (especially DDT and its metabolites, DDD and DDE) at risk, and increase their susceptibility to develop serious diseases.

Subchronic organismal toxicity, cytotoxicity, genotoxicity, and feeding response of Pacific oyster (Crassostrea gigas) to lindane (gamma-HCH) exposure under experimental conditions.

This study evaluated organismal toxicity, cytotoxicity, and genotoxicity and the filtration rate in response to different concentrations of subchronic lindane (gamma-hexachlorocyclohexane [gamma-HCH]), exposure (12 d) in adult Pacific oysters Crassostrea gigas. Oysters were exposed in vivo in laboratory aquaria to 10 different concentrations (0.0-10.0 mg/L) of gamma-HCH. The median lethal concentration (LC50) after 12 d was calculated as 2.22 mg/L. Cytotoxic effects were observed in hemocytes, where the mean cell viability was significantly decreased at 1.0 mg/L of gamma-HCH after 12 d. Genotoxicity of gamma-HCH measured by single cell gel electrophoresis assay, in hemocytes was evident at 0.7 mg/L of gamma-HCH after 12 d. After 4 h of exposure to gamma-HCH, filtration rates were reduced compared with controls to 65.8 and 38.2% at concentrations of 0.3 and 0.7 mg/L, respectively, and after 11 d of exposure, filtration rates were reduced to 60.4 and 30.9% at concentrations of 0.1 mg/L and higher. These results show the subchronic effects of gamma-HCH at different concentrations and effect sensitivities are categorized as filtration rate < genotoxicity < cytotoxicity < mortality. The relevance of integral toxicity evaluation, considering different endpoints from molecular, cellular, and individual levels is discussed.

A study of DNA damage in buccal cells of consumers of well- and/or tap-water using the comet assay: Assessment of occupational exposure to genotoxicants.

Because of concerns that natural aquifers in the region of Todos Santos (Baja California Sur, Mexico) might be contaminated by organochlorine pesticides and heavy metals, a case-control study was conducted among consumers and non-consumers of well- and/or tap-water to determine risks to human health. This study was based on a genotoxic evaluation of buccal cells using the Comet assay technique. Levels of DNA damage in the consumers group were significantly higher than those of the control group. However, occupational exposure to genotoxicants showed to be the critical factor rather than water consumption. Taking into account the professions of well- and/or tap-water consumers, agricultural workers exposed directly (those who fumigated) or indirectly (those not involved in fumigating) to agrochemicals showed greater genetic damage than controls. This difference persisted even when age, and whether the person smoked or consumed alcoholic drinks were considered. These factors were not associated with the level of genetic damage observed. Chemical analyses of organochlorine pesticides and heavy metals were carried out to evaluate the water quality of wells, faucets, and surface water of canals consumed by the population and/or used for irrigation. High concentrations of α and ß endosulfan were detected in water of surface canals. Although our inventory of agrochemicals employed in the region showed the use of products considered carcinogenic and/or mutagenic, they were not detected by the analytical techniques used. Heavy metals (arsenic, mercury, and lead) were detected in water of some wells used for irrigation and human consumption. Environ. Mol. Mutagen. 58:619-627, 2017. © 2017 Wiley Periodicals, Inc.

Analysis of the immune response induced by a scorpion venom sub-fraction, a pure peptide and a recombinant peptide, against toxin Cn2 of Centruroides noxius Hoffmann.

Three different immunogens from the venom of the Mexican scorpion Centruroides noxius Hoffmann were used to study protective antibody response in mice and rabbits, challenged with toxin Cn2, one of the most abundant toxic peptide of this venom. The immunogens were: Cn5, a crustacean specific toxin; a recombinant protein containing the peptide Cn5 linked to the maltose transporter and a sub-fraction (F.II.5) containing 25 distinct peptides, among which is Cn5. Mice immunized with these three preparations, when directly challenged with Cn2 presented no apparent protection, whereas anti-sera produced in rabbits with these three immunogens were capable of partially neutralizing the effect of Cn2, when injected into naive mice. Cn5 rabbit anti-serum showed a better protective effect on mice, than the rabbit sera obtained against the two other antigens. The subcutaneous route of challenging mice was shown to be better than intraperitoneal injections. Comparative structural analysis of Cn5 with other toxins of this venom showed that our results are important to be taken into consideration, when choosing appropriate immunogens aimed at the production of better anti-venoms or for the rational design of possible vaccines.