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Common mechanism of toxicity: a case study of organophosphorus pesticides.
A group of experts convened to examine scientific questions using the organophosphorus (OP) pesticides as the case study concluded that OP pesticides act by a common mechanism of toxicity if they inhibit acetylcholinesterase by phosphorylation and elicit any spectrum of cholinergic effects. Expand
Age-related differences in parathion and chlorpyrifos toxicity in male rats: target and nontarget esterase sensitivity and cytochrome P450-mediated metabolism.
Results indicate that target enzyme sensitivity is not responsible for age-related toxicity differences, nor is the potential for hepatic bioactivation, whereas lower levels of hepatic aliesterase-mediated protection and P450-mediated dearylation probably contribute significantly to the greater sensitivity of juveniles to phosphorothionate toxicity. Expand
Kinetic parameters of desulfuration and dearylation of parathion and chlorpyrifos by rat liver microsomes.
  • T. Ma, J. Chambers
  • Biology, Medicine
  • Food and chemical toxicology : an international…
  • 1994
A kinetic analysis of cytochrome P-450 mediated desulfuration (activation) and dearylation (detoxication) of the two insecticides indicated that rat hepatic microsomes have a higher capacity to activate and a lower capacity to detoxify parathion than chlorpyrifos; these capacities correspond to their acute toxicity levels. Expand
Kinetic analysis of the in vitro inhibition, aging, and reactivation of brain acetylcholinesterase from rat and channel catfish by paraoxon and chlorpyrifos-oxon.
The higher association constant (KA) of chlorpyrifos-oxon than paraoxon in both species and the lack of significant differences in the phosphorylation constants (kp) suggest that association of the inhibitor with AChE is the principal factor in the different potencies between these two inhibitors. Expand
Effects of repeated oral postnatal exposure to chlorpyrifos on open-field behavior in juvenile rats.
It is suggested that early postnatal chlorpyrifos exposures will depress locomotor activity in juvenile rats, with the effects most pronounced after brain ChE activity has substantially recovered. Expand
Biochemical mechanisms contributing to species differences in insecticidal toxicity.
Comparison of published LD50 or LC50 levels for a variety of insecticides in several vertebrate species indicate that a wide range of toxicity levels exist, and these cannot be easily predictedExpand
Organophosphates : chemistry, fate, and effects
(Section Headings): Introduction. Metabolic Fate. Toxic Effects--Noncholinergic Biochemical. Toxic Effects--Organismal. Summary and Conclusions.
Noncatalytic detoxication of six organophosphorus compounds by rat liver homogenates.
Abstract The ability of rat liver aliesterases to noncatalytically detoxify the oxons of six phosphorothionate insecticides was studied; the insecticides were methyl parathion, parathion,Expand
Developmental chlorpyrifos and methyl parathion exposure alters radial-arm maze performance in juvenile and adult rats.
Data show that repeated developmental exposure to OP insecticides can induce sex-selective alterations and long-lasting changes in spatial learning and memory formation when measured using a radial arm maze and that MPS and CPS induce different neurobehavioral outcomes. Expand
Time course of inhibition of cholinesterase and aliesterase activities, and nonprotein sulfhydryl levels following exposure to organophosphorus insecticides in mosquitofish (Gambusia affinis).
  • J. Boone, J. Chambers
  • Chemistry, Medicine
  • Fundamental and applied toxicology : official…
  • 1 February 1996
Hepatic aliesterases appear capable of affording some protection of ChE from inhibition following parathion or chlorpyrifos exposures, but considerably less protection against methylParathion. Expand