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Plant bioassays are an important and integral part of the test battery used in detecting genotoxic/carcinogenic contamination in the environment. Highly sensitive biomonitoring of plant models have been developed, which enables the detection of hazards arising from pesticides, insecticides, industrial contamination, heavy metals and radiation. Root tips of Vicia faba ssp. minor were treated with 1-60 mM of the organophosphorus insecticide dichlorvos (DDVP) for 2 h, followed by a 20-h recovery period. Maleic acid hydrazide (MH) was used as a positive control for the mitotic index, micronucleus and chromosomal aberration assays performed on the Vicia model system. All treatments with DDVP significantly decreased the mitotic activity and increased the frequency of chromosomal aberrations at the metaphase. The frequency of micronuclei was significantly increased at DDVP concentrations starting from 10 mM. The results demonstrate clastogenic and mitodepressive effects of DDVP on Vicia faba cells.
Genotoxicity of pesticides is of a special significance because of the common presence of these agents in the environment and the long latent period between the exposure and effects becoming apparent. The DNA damaging effects of the commonly used organophosphorus insecticide malathion and its major metabolite malaoxon were evaluated. Freshly isolated human peripheral blood lymphocytes were incubated with 75 and 300 µM of malathion or malaoxon for 1 h. Sensitive alkaline microgel single cell electrophoresis (comet assay) was used to assess damage to the lymphocyte DNA. Possible lesions detected by this technique could be single- and double-strand DNA breaks as well as alkali-labile sites. Malaoxon, unlike malathion, induced DNA damage in a dose-dependent manner. The effect of malaoxon at 300 µM was comparable with the effect of hydrogen peroxide at 20 µM. Well recognized genotoxic effects of malathion may be a consequence either of the interaction of its major metabolite malaoxon with DNA or use of technical grade of malathion which contains impurities, including malaoxon. However, humans are exposed to the pesticide of technical grade and have the ability to metabolize malathion to malaoxon and in this regard malathion used as an organophosphorus insecticide can be considered as a genotoxic substance.
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