Alkylating properties of dichlorvos (DDVP)

Defensive proclivity of bacoside A and bromelain against oxidative stress and AChE gene expression induced by dichlorvos in the brain of Mus musculus

The objective of current study was to evaluate the neuroprotective effects of bacoside A and bromelain against dichlorvos induced toxicity. The healthy, 6-8 weeks old male Swiss mice were administered in separate groups subacute doses of dichlorvos (40 mg/kg bw), bacoside A (5 mg/kg bw) and bromelain (70 mg/kg bw). In order to determination of oxidative stress in different groups, thiobarbituric acid reactive substances (TBARS) and protein carbonyl content (PCC) were studied in the present investigation. Moreover, for toxic manifestation at molecular level the site-specific gene amplification of acetylcholinesterase (AChE) gene was studied in the brain. Nonetheless, the protective effects of bacoside A and bromelain were also evaluated on the TBARS, PCC and AChE gene. The exposure of dichlorvos leads to significant increase in TBARS level (p < 0.01, p < 0.001) and PCC. Besides, the decline in DNA yield, expression of amplified products of AChE gene was observed in the brain of dichlorvos treated group. The bacoside A and bromelain treatments significantly decreased the level of TBARS (p < 0.05, (p < 0.01) and PCC whereas, increase in the DNA yield and expression of amplified AChE gene products were observed in the brain compared to only dichlorvos treated mice. The overall picture which emerged after critical evaluation of results indicated that the dichlorvos induced oxidative stress and alteration in AChE gene expression showed significant improvement owing to the treatments of bacoside A and bromelain. Thus, bacoside A and bromelain are very effective in alleviating neurotoxicity induced by dichlorvos.

Guidance for the classification of carcinogens under the Globally Harmonised System of Classification and Labelling of Chemicals (GHS)

The United Nations Conference on Environment and Development (UNCED) has developed criteria for a globally harmonised system of classification and labelling of chemicals (GHS). With regard to carcinogenicity, GHS distinguishes between Category 1 ('known or presumed human carcinogens') and Category 2 ('suspected human carcinogens'). Category 1 carcinogens are divided into Category 1A ('known to have carcinogenic potential for humans'), based largely on human evidence, and 1B ('presumed to have carcinogenic potential for humans'), based largely on experimental animal data. Concerns have been raised that the criteria for applying these carcinogenicity classifications are not sufficiently well defined and potentially allow different conclusions to be drawn. The current document describes an attempt to reduce the potential for diverse conclusions resulting from the GHS classification system through the application of a series of questions during the evaluation of data from experiments with rodents; epidemiological data, which could lead to Category 1A, have not been considered. Answers to each question can lead either to a classification decision or to the next question, but this process should only be implemented in an environment of informed scientific opinion. The scheme is illustrated with five case studies. These questions are: (1) Has a relevant form of the substance been tested? (2) Is the study design relevant to human exposure? (3) Is there a substance-related response? (4) Is the target tissue exposure relevant to humans? (5) Can a mode of action be established? (6) Is the mode of action relevant to humans? (7) What is the potency?

Elevated frequency of sister chromatid exchanges in lymphocytes of victims of the Tokyo sarin disaster and in experiments exposing lymphocytes to by-products of sarin synthesis

More than 5000 passengers of Tokyo subway trains were injured with toxic chemicals including the nerve gas sarin. Most of the victims examined had marked miosis and decreased serum cholinesterase activity. To monitor the genetic aftereffects of sarin exposure, we measured sister chromatid exchanges (SCEs) of the victims using peripheral blood lymphocytes. The frequency of SCEs was significantly higher in the victims than in the control group. Analyzing results using samples of urine from the victims suggested that the victims were exposed to not only sarin per se, but by-products of sarin synthesis, i.e. diisopropyl methylphosphonate (DIMP), diethyl methylphosphonate (DEMP) and ethyl isopropyl methylphosphonate (EIMP). Thus, the in vitro SCE-inducing effect of DIMP, DEMP and EIMP was examined using human lymphocytes and we obtained positive results.

Brain involvement in organophosphate poisoning

Organophosphate poisonings cause substantial morbidity and mortality worldwide; however, the neurological effects have not been clearly established. We have studied cerebral perfusion to investigate neurotoxic effects. Clinical effects, plasma cholinesterase activity, and brain single photon emission computerization tomography (SPECT) data were investigated in 16 patients with organophosphate poisonings. The subjects were from an adult intensive care unit in a university hospital. Cholinesterase activity in plasma was determined upon admission and then every day in the morning. Brain SPECT studies were performed during the first week, at the end of therapy, and 3 months after discharge. Patients were classified into 3 groups using a modified Namba classification: latent poisoning (Group A); mild and moderate poisoning (Group B); or severe poisoning (Group C). None of the 6 patients in Group A showed any symptoms; 3 patients in Group B had muscarinic and nicotinic effects; 5 patients in Group C had muscarinic, nicotinic, and central nervous system symptoms. The average plasma cholinesterase for Groups A, B, and C were 54.16 +/- 9.10, 42.2 +/- 12.02, and 13 +/- 4.84 U/ml, respectively (normal range of plasma cholinesterase is 40-80 U/ml). Only 1 patient from Group A required treatment with oxime; 2 patients from Group B and all patients in Group C were given oxime, atropine sulfate, and mechanical ventilation. In the brain SPECT studies, the patients in Group A showed fewer perfusion defect areas than did Group B and C patients. All cases showed perfusion defects especially in the parietal lobe. In addition, perfusion improvement took more time for Group C than for the other groups. The intensive care unit stays of Group C were statistically longer than for Groups A and B. We concluded that brain SPECT is a highly sensitive diagnostic method, together with clinical symptoms and plasma cholinesterase activity, for monitoring the clinical prognosis of organophosphate poisonings.

Carcinogenesis studies of dichlorvos in Fischer rats and B6C3F1 mice

Dichlorvos (dichlorovinyl dimethyl phosphoric acid ester) is a cholinesterase inhibitor used widely as a contact and stomach insecticide for control of internal and external parasites. Carcinogenesis studies were conducted by administering dichlorvos in corn oil by gavage 5 times a week for 103 weeks to groups of 50 male and 50 female Fischer rats at 0, 4, or 8 mg/kg body weight, to groups of 50 male B6C3F1 mice at 0, 10, or 20 mg/kg, and to groups of 50 female B6C3F1 mice at 0, 20, or 40 mg/kg. During the course of the studies, body weights and survival rates of the male and female rats and mice were not different from those of their respective controls; females of both species appeared to gain more weight than controls. Neoplasms induced by dichlorvos included adenomas of the exocrine pancreas (male rats), mononuclear cell leukemia (male rats), and squamous cell papilloma of the forestomach (male and female mice; two other female mice had squamous cell carcinomas). Lesions observed in female rats that may have been due to dichlorvos administration included adenomas of the exocrine pancreas and fibroadenomas of the mammary gland. The results demonstrated that dichlorvos is carcinogenic for Fischer rats and B6C3F1 mice.