Organophosphorus compounds may induce oxidative stress leading to generation of free radicals and alterations in antioxidant and scavengers of oxygen free radicals (OFRs). The effect of subchronic exposure to malathion in the production of oxidative stress was evaluated in male Wistar rats. Administration of malathion (100, 316, 1000, 1500 ppm) for 4 weeks increased catalase (CAT), superoxide dismutase (SOD) activities as well as malondialdehyde (MDA) concentration in red blood cells (RBC) and liver. However, acetylcholinesterase (AChE) and cholinesterase (ChE) activities were decreased in these samples. The increase in RBC and liver lipid peroxidation correlated well with the inhibition in RBC AChE and liver ChE activities. Elevation of MDA concentrations and increased activities of CAT and SOD showed significant correlations in both RBC and liver samples when different doses of malathion were used. The results of the present study suggest the usefulness of RBC AChE measurement as a good biomarker in the estimation of malathion-induced oxidative stress affecting blood and liver.

Context: In the present investigation, acute and subacute toxicity of the biogenic Se nanoparticles (Se NPs) has been reported. Objective: To characterize the Se NPs produced by a bacterium species and to evaluate their toxicity and impact on clinical chemistry and hematological parameters of NMRI mice. Materials and methods: The Se NPs were prepared by Bacillus sp. MSh-1 in a culture medium containing SeO₂ (1.26 mM) and their physiochemical properties investigated using TEM, XRD and FT-IR. The LD₅₀ of Se NPs and SeO₂ were determined and the subacute toxicity evaluated by orally administration of 0, 2.5, 5, 10 and 20 mg kg⁻¹ of Se NPs to male mice for 14 consecutive days. Parameters of blood cells, AST, ALT, ALP, creatinine, BUN, cholesterol, bilirubin, triglyceride and CPK were experimentally measured. Results: The XRD and TEM analyses showed that the spherical NPs were amorphous, in the size range of 80–220 nm. The toxicological evaluation showed that the LD₅₀ values of SeO₂ and Se NPs were 7.3 and 198.1 mg kg⁻¹, respectively. No biochemical changes were observed from the administration of 2.5, 5 and 10 mg kg⁻¹ of Se NPs, but a dose of 20 mg kg⁻¹ was accompanied with signs of toxicity including lower body weight and changes in clinical chemistry and hematological parameters. Conclusion: The biogenic Se NPs were less toxic than synthetic Se NPs and much less (26-fold) toxic than the SeO₂, which demonstrates the important role of Bacillus sp. MSh-1 in conversion of a highly toxic Se compound to the less toxic Se NPs.