Differential sensitivity of plasma carboxylesterase-null mice to parathion, chlorpyrifos and chlorpyrifos oxon, but not to diazinon, dichlorvos, diisopropylfluorophosphate, cresyl saligenin phosphate, cyclosarin thiocholine, tabun thiocholine, and carbofuran

Abiotic transformation of chlorpyrifos to chlorpyrifos oxon in chlorinated water.

In vivo transformation of chlorpyrifos to chlorpyrifos oxon is believed to be a prerequisite for this insecticide to display acute toxicity to organisms. We discovered that active chlorine dispersed in water causes the rapid abiotic transformation of chlorpyrifos to chlorpyrifos oxon. The proposed mechanism for the transformation is an electrophilic attack by hypochlorous acid (HOCl) on the thi...

Comparative toxicity of chlorpyrifos, diazinon, malathion and their oxon derivatives to larval Rana boylii.

Organophosphorus pesticides (OPs) are ubiquitous in the environment and are highly toxic to amphibians. They deactivate cholinesterase, resulting in neurological dysfunction. Most chemicals in this group require oxidative desulfuration to achieve their greatest cholinesterase-inhibiting potencies. Oxon derivatives are formed within liver cells but also by bacterial decay of parental pesticides....

Nonenzymatic Functions of Acetylcholinesterase Splice Variants in the Developmental Neurotoxicity of Organophosphates: Chlorpyrifos, Chlorpyrifos Oxon, and Diazinon

BACKGROUND Organophosphate pesticides affect mammalian brain development through mechanisms separable from the inhibition of acetylcholinesterase (AChE) enzymatic activity and resultant cholinergic hyperstimulation. In the brain, AChE has two catalytically similar splice variants with distinct functions in development and repair. The rare, read-through isoform, AChE-R, is preferentially induced...

In vitro age-dependent enzymatic metabolism of chlorpyrifos and chlorpyrifos-oxon in human hepatic microsomes as well as chlorpyrifos-oxon in plasma

Relative inhibitory potencies of chlorpyrifos oxon, chlorpyrifos methyl oxon, and mipafox for acetylcholinesterase versus neuropathy target esterase.

The relative inhibitory potency (RIP) of an organophosphorus (OP) inhibitor against acetylcholinesterase (AChE) versus neuropathy target esterase (NTE) may be defined as the ratio [k(i)(AChE)/k(i)(NTE)], where k(i) is the bimolecular rate constant of inhibition for a given inhibitor against each enzyme. RIPs greater than 1 correlate with the inability of ageable OP inhibitors or their parent co...