A bioassay of methyl parathion for possible carcinogenicity was conducted by administering the test chemical in feed to F344 rats and B6C3F1 mice. Groups of 50 rats of each sex were administered methyl parathion at one of two doses, initially either 62.5 or 125 ppm. These doses were maintained for 102 weeks for the females; however, due to decreased mean body weight gain in the dosed males, the...

Organophosphorus hydrolase (OPH, also known as phosphotriesterase) is a bacterial enzyme that is capable of degrading a wide range of neurotoxic organophosphate nerve agents. Directed evolution has been used to generate one variant (22A11) with up to 25-fold improved hydrolysis of methyl parathion. Surprisingly, this variant also degraded all other substrates (paraoxon, parathion and coumaphos)...

The role of glutathione S-transferase (GST, EC 2.5.1.18) in the degradation of and resistance to some insecticides of diamondback moth (DBM) larvae has been confirmed through the purification and characterization of its four isozymes from this notorious insect pest of cruciferous vegetables. Two immuno-related isozymes, GST-3 and GST-4, exhibit apparent substrate preference for 1,2-dichloro-4ni...

A consistent correlation between elevated esterase activity and methyl parathion resistance among Nebraska western corn rootworm, Diabrotica virgifera virgifera LeConte, populations has previously been documented. Characterization of general esterase activity using naphtholic esters as model substrates indicated that differences between resistant and susceptible strains could be maximized by op...

This work illustrates the toxicological impact of pesticide methyl parathion (MP) (dust—2 % active ingredient, a.i.) on growth and reproduction performance in tropical earthworms: Metaphire posthuma (endogeic), Lampito mauritii (anecic) and Allolobophora parva (epigeic). A total of three concentrations (a.i. g kg dry test soil), 1.00 (T1), 1.125 (T2) and 2.25 (T3) of MP, were applied in test su...

The western corn rootworm, Diabrotica virgifera virgifera LeConte (Coleoptera: Chrysomelidae), is a major pest of cultivated corn in North America and has recently begun to invade Europe. In addition to crop rotation, chemical control is an important option for D. v. virgifera management. However, resistance to chemical insecticides has evolved repeatedly in the USA. In Europe, chemical control...

Pseudomonas diminuta, P. putida and P. aeruginosa were established as a biodegrading agent for Methyl Parathion (MP) at 1200 mg/L, under basic growth parameters for mesophiles. In this study, the effects of process parameters, such as temperature, pH, salinity, carbon and nitrogen sources on the growth of those bacteria were studied and optimized to establish higher degradation of the target ch...

The objective of this study was to assess insecticide resistance in anopheline mosquito populations in agroecosystems with high and low insecticide use in a malaria endemic area in Chiang Mai province in northern Thailand. Anopheline mosquitoes were collected in May and June 2004 from two locations with different agricultural insecticide intensity (HIGH and LOW), but similar in vector control s...

Diverse organophosphate hydrolases have convergently evolved the ability to hydrolyse man-made organophosphates. Thus, these enzymes are attractive model systems for studying the factors shaping enzyme functional evolution. Methyl parathion hydrolase (MPH) is an enzyme from the metallo-β-lactamase superfamily, which hydrolyses a wide range of organophosphate, aryl ester and lactone substrates. ...

A remote electrochemical biosensor for ®eld monitoring of organophosphate nerve agents is described. The new sensor relies on the coupling of the effective biocatalytic action of organophosphorus hydrolase (OPH) with a submersible amperometric probe design. This combination results in a fast, sensitive, selective, and stable response at large sample-instrument distances. Such attractive perform...