[Antagonism effect of MK801 on apoptosis of primary-cultured cortical neuron caused by dimethoate].

OBJECTIVE: To explore the antagonism effect of MK801 on apoptosis of primary-cultured cortical neurons caused by dimethoate. METHODS: Cortical neurons were isolated and cultured in serum free medium for 6 days in vitro, then treated with 100 micromol/L dimethoate for 48h. 50 and 100 micromol/L MK801, a N-methyl-D-aspartic acid receptor (NMDAR) blocker, were used to intervene 100 micromol/L dimethoate group. HPLC-FLD was taken to measure the concentration of excitatory amino acid. RT-PCR was used to detect transcription level of NR2B. Florescence probe DCFH-DA kit was used to detect ROS level. TUNEL staining was used to determine apoptosis. RESULTS: When neurons were treated with 50 and 100 micromol/L MK801 to 100 micromol/L dimethoate group, Apoptosis decreased to 79.6% of 100 micromol/L dimethoate group in higher intervention group (P < 0.01). Concentration of EAA decreased in both intervention groups (P < 0.01). The level of ROS decreased to 88.9% and 74. 8% of 100 micromol/L dimethoate group (P < 0.01), while still higher than that of control group (P < 0.01). Transcription level of NR2B increased to 1.59 and 2.22 folds of 100 micromol/L dimethoate group (P < 0.01) and had big differences with control group (P < 0.01). CONCLUSION: Excitatory amino acid system and ROS both contribute to the apoptosis of neurons caused by dimethoate. MK801 not only decrease the ROS level but also diminish the elevated excitatory amino acid concentration caused by dimethoate, thus abolish apoptosis of neuron.

Evaluation of medical countermeasures against organophosphorus compounds: the value of experimental data and computer simulations.

Despite extensive research for more than six decades on medical countermeasures against poisoning by organophosphorus compounds (OP) the treatment options are meagre. The presently established acetylcholinesterase (AChE) reactivators (oximes), e.g. obidoxime and pralidoxime, are insufficient against a number of nerve agents and there is ongoing debate on the benefit of oxime treatment in human OP pesticide poisoning. Up to now, the therapeutic efficacy of oximes was mostly evaluated in animal models but substantial species differences prevent direct extrapolation of animal data to humans. Hence, it was considered essential to establish relevant experimental in vitro models for the investigation of oximes as antidotes and to develop computer models for the simulation of oxime efficacy in different scenarios of OP poisoning. Kinetic studies on the various interactions between erythrocyte AChE from various species, structurally different OP and different oximes provided a basis for the initial assessment of the ability of oximes to reactivate inhibited AChE. In the present study, in vitro enzyme-kinetic and pharmacokinetic data from a minipig model of dimethoate poisoning and oxime treatment were used to calculate dynamic changes of AChE activities. It could be shown that there is a close agreement between calculated and in vivo AChE activities. Moreover, computer simulations provided insight into the potential and limitations of oxime treatment. In the end, such data may be a versatile tool for the ongoing discussion of the pros and cons of oxime treatment in human OP pesticide poisoning.

Effect of ascorbic acid in the detoxification of the insecticide dimethoate in the bone marrow erythrocytes of mice.

The antimutagenic potential of ascorbic acid in the detoxification of the organophosphorus insecticide dimethoate was evaluated in female Swiss albino mice using the in vivo bone marrow micronucleus test. Groups of three mice were treated with distilled water (control), 1% dimethyl sulphoxide (solvent control), or 86, 129.5 or 259 mg ascorbic acid/kg body weight, with or without the concurrent administration of 150 mg dimethoate/kg. There was a statistically significant increase in the frequency of micronuclei in dimethoate-treated mice. However, in mice that were given dimethoate and ascorbic acid simultaneously, the numbers of micronuclei did not differ significantly from control values, thus indicating the protective role of ascorbic acid.

Vitamin C-mediated minimisation of Rogor-induced genotoxicity.

The genotoxic effect of Rogor (an organophosphorous pesticide) at concentrations used in agriculture was studied in terms of mitotic index in onion root-tip cells, chromosome abnormalities and meiotic index in mice and lastly, lethal mutation rate in Drosophila. It was observed that the pesticide could (i) cause mitotic as well as meiotic inhibition, (ii) increase the clastogenicity rate and (iii) induce lethal mutations. The modificatory role, if any, of L-ascorbic acid (vitamin C) was studied after administering the vitamin concurrently with the pesticide. It was observed that the cytogenetic toxicity of Rogor can be appreciably minimised by vitamin C. The possible mode of antigenotoxic action of vitamin C was discussed.

Modificatory effect of vitamin C and vitamin B-complex on meiotic inhibition induced by organophosphorus pesticide in mice Mus musculus.

Administration of organophosphorous pesticide Malathion and Rogor (both @ 0.2 micrograms/kg body wt/day) upto ten days was found to decrease the division rate in the primary spermatocytes of mice. The concurrent administration of vitamin B-complex (0.3 ml of 1% polybion) or ascorbic acid (0.25 ml of 1% Redoxon) with the pesticide could nullify the meiotic inhibition caused by the pesticides. The vitamins were not found to produce any significant effect on the division rate. Possible mechanism(s) behind this vitamin mediated nullification of meiotic inhibition are discussed.