Cytogenetic studies on the effect of feeding mice with stored wheat grains treated with malathion

The cytogenetic effect of malathion residues in wheat grains stored for different periods of time (4, 12, 24 weeks) was evaluated in Swiss mice. The studies included: (1) chromosomal aberrations analysis in bone-marrow and spermatocyte cells; (2) chromosomal aberrations and sister chromatid exchange (SCE) analysis in spleen cell culture from mice fed with stored wheat grains. The tested doses were 8.36 (applied dose), 25.08 and 41.80 mg malathion kg −1 wheat grains. The results demonstrated that the cytogenetic effect induced in different mouse tissues by malathion residues was dose-dependent and increased with increasing of both feeding and storage periods. Feeding mice with wheat grains stored for 4 weeks had a non-significant effect with respect to the induction of chromosomal aberrations or SCEs. Significant chromosome damage and increase of SCEs were observed in mice fed with wheat grains stored for 12 weeks. The maximum effect was recorded in mice fed for 12 weeks with the grains treated with the highest tested dose and stored for 24 weeks. However, mitomycin C i.p.-injected in mice at 1 mg kg −1 body weight (b.w.) (positive control) induced a higher effect. The percentage of chromosome aberrations reached 13.60±0.98, 13.60±0.77 and 11.73±0.98 ( P