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At least 19 recordsLinked to original sources

PubMed1988

Stereospecificity in the oxidation of phorate and phorate sulphoxide by purified FAD-containing mono-oxygenase and cytochrome P-450 isozymes.

1. Both the cytochrome P-450-dependent mono-oxygenase system and the FAD-containing mono-oxygenase catalyse the sulphoxidation of thioether-containing organophosphate insecticides. Using purified FAD-containing mono-oxygenase and purified cytochrome P-450 isozymes isolated from mouse liver microsomes, the stereospecificity of the oxidation of phorate to (+)-and (-)-phorate sulphoxide and the further oxidations of the (+)-and (-)-phorate sulphoxides to the sulphone, the oxon sulphoxide and the oxon sulphone were examined. 2. The FAD-containing mono-oxygenase catalysed the formation of (-)-phorate sulphoxide, while two cytochrome P-450 isozymes (cytochrome P-450-B2, a constitutive form, and cytochrome P-450-PB, the principal form induced by phenobarbital) produced (+)-phorate sulphoxide. The other three constitutive cytochrome P-450 isozymes examined yielded racemic mixtures. 3. The FAD-containing mono-oxygenase had the lowest Km for the sulphoxidation reaction, 32 microM, while the Km values for the cytochrome P-450 isozymes ranged from 67 microM to 250 microM. No additional oxidation of phorate sulphoxide by the FAD-containing monooxygenase was detected using either (+)-phorate sulphoxide or (-)-phorate sulphoxide as substrates. 4. In contrast, all five cytochrome P-450 isozymes tested formed additional oxidation products; the (+)-phorate sulphoxide was the preferred substrate for all cytochrome P-450 forms. 5. The final oxidation product, phorate oxon sulphone, was derived by desulphuration of phorate sulphone, with the formation of the oxon sulphoxide being a terminal pathway.

Animals↗

PubMed2003

Persistence of phorate in soils: role of moisture, temperature, preexposure, and microorganisms.

In laboratory incubation studies with three soils of varying physicochemical characteristics, phorate was more persistent in nonflooded (60% water holding capacity) soils than in flooded soils. Phorate sulphoxide was recovered as the only metabolite of phorate in nonflooded soils while three metabolites (diethyl dithiophosphate, triethyl dithiophosphate and an unidentified metabolite) were formed in flooded soils. Study indicates that in nonflooded soils phorate is degraded via oxidation while in flooded soils hydrolysis is the major degradation process. Degradation of phorate was accelerated by an increase in incubation temperature. Preexposure or repeated application of soils to phorate slightly decreased the persistence of phorate or its metabolites. Decreased persistence of phorate and its metabolites formed in nonsterile soils compared to sterile soils suggested the role of microorganisms in their transformation.

Biodegradation, Environmental↗

PubMed1978

Pharmacological studies on the molluscicidal activity of phorate on Pila globosa (Gastropoda).

Amongst heart, rectum and radula protractor muscles of Pila globosa, the heart showed a negative inotropic and negative chronotropic response while the rectum and radula protractor showed a positive tonotropic response to exogenously applied acetycholine (ACh). The anti-cholinesterase pesticide phorate substantially increased the response to ACh; at high doses it could also evoke cholinomimetic response from the heart. The anti-cholinesterase property of phorate gradually increased with an increase in its contact period to the tissue. The extent of alteration in ACh response caused by prior treatment with low and high doses of phorate were very similar, indicating that the efficacy of phorate is by and large time-dependent rather than dose-dependent. The effect of phorate remained irreversible even after prolonged washing. The mode of action of phorate has been discussed in the light of the above findings.

Acetylcholine↗

PubMed2006

Phorate exposure and incidence of cancer in the agricultural health study.

BACKGROUND: We recently reported a link between use of the organophosphate pesticide phorate and risk of prostate cancer among applicators with a family history of prostate cancer in the Agricultural Health Study (AHS). OBJECTIVE: This finding, together with findings of associations between other organophosphate pesticides and cancer more broadly, prompted us to examine phorate exposure and overall cancer incidence in the AHS. Adding 3 years of follow-up and using more detailed exposure information allowed us to see whether the prostate cancer finding held. METHODS: The AHS is a prospective study of licensed restricted-use pesticide applicators from North Carolina and Iowa. To our knowledge, this is the largest examination of workers occupationally exposed to phorate. Pesticide exposure and other information was collected using two self-administered questionnaires completed from 1993 to 1997. Poisson regression was used to calculate rate ratios (RR) and 95% confidence intervals (CI), adjusting for potential confounders. RESULTS: Phorate use was not related to the incidence of all cancers combined or to any individual cancer, although we had insufficient numbers to study non-Hodgkin lymphoma or leukemia, which have been linked to organophosphates in other studies. Although prostate cancer risk was not significantly related to phorate use overall or among those without a family history, the risk tended to increase among applicators with a family history of prostate cancer. The interaction RR was 1.53 (95% CI, 0.99-2.37). CONCLUSION: The observed statistical interaction suggests a gene-environment interaction between family history and phorate exposure in the incidence of prostate cancer, but other explanations are also possible.

Adult↗

PubMed2003

Influence and persistence of phorate and carbofuran insecticides on microorganisms in rice field.

An experiment was conducted in microplots (4 m x 4 m) with two insecticides, phorate and carbofuran at rates of 1.5 and 1.0 kga.i.ha(-1) respectively, to investigate its effect on the population and distribution of bacteria, actinomycetes and fungi as well as the persistence of the insecticidal residues in rhizosphere soils of rice (Oryza sativa L., variety IR-50). Application of the insecticides stimulated the population of bacteria, actinomycetes and fungi in the rhizosphere soils, and the stimulation was more pronounced with phorate as compared to carbofuran. Both the insecticides did not have marked effect on the numbers of Streptomyces and Nocardia in the rhizosphere soils. However, the growth of Bacillus, Escherichia, Flavobacterium, Micromonospora, Penicillium, Aspergillus and Trichoderma with phorate and that of Bacillus, Corynebacterium, Flavobacterium, Aspergillus and Phytophthora with carbofuran were increased. On the other hand, the numbers of Staphylococcus, Micrococcus, Fusarium, Humicola and Rhizopus under phorate and Pseudomonas, Staphylococcus, Micrococcus, Klebsiella, Fusarium, Humicola and Rhizopus under carbofuran were inhibited. Both the insecticides persisted in the rhizosphere soil for a short period of time and the rate of dissipation of carbofuran was higher than that of phorate in the soil depicting the half-life (T1/2) 9.1 and 10.4 days, respectively.

Bacteria↗

PubMed1997

Phorate-induced enzymological alterations in mouse olfactory bulb.

The organophosphate pesticide, phorate, is an extremely hazardous insecticide. Not much experimental study is available on effects of phorate on different brain areas. We report in this study the alterations induced by phorate on enzyme profile of mouse olfactory bulb. Olfactory bulb, the first processing centre after the sensory cells in the olfactory pathway, has connections with the other higher centres of the brain like hippocampus and hypothalamus. Phorate was administered orally in the diet at the doses of 1.0 mg and 1.5 mg/kg body weight to adult albino mice. After 32 weeks of exposure animals were sacrificed and cryosections were processed for acetylcholinesterase and butyrylcholinesterase (AChE and BChE, respectively) enzyme localization. Significant reduction occurs in AChE and BChE activity at higher dose level, whereas reduced BChE activity was found at both dose levels. Our results shows an obvious effect on cholinesterase enzyme profile of olfactory bulb of mice after systemic administration of low doses of phorate for long terms.

Acetylcholinesterase↗

PubMed1983

The effects of phorate and some of its metabolites incorporated in an artificial diet on liquid uptake by Aphis fabae scop.

[14C]Phorate and some of its metabolites were incorporated in an artificial diet and their effects on liquid uptake by Aphis fabae were studied. At sublethal and very low toxicity levels of phorate there was a tendency for a reduction in feeding with increasing concentrations. [14C]Phorate sulphone, [14C]phorate sulphoxide and [14C]phoratoxon sulphoxide at high concentrations gave very low mortality figures, but a significant drop in liquid uptake occurred with increasing concentrations. The results demonstrate that the presence of the insecticide rendered the diet less acceptable to the aphids which exhibited a wandering behaviour that might promote transmission of virus diseases.

Animals↗

PubMed2002

Decomposition of phorate in aqueous solution by photolytic ozonation.

The degradation of phorate, a highly toxic organic phosphate pesticide, in aqueous solution by photolytic ozonation was studied under various experimental conditions. The rate constants of phorate decomposition and formation of various anions by photolytic ozonation were roughly independent of the solution's pH value. The initial step of the photolytic decomposition of phorate is considered to be the breakage and subsequent oxidation of the P=S double bond on the phorate molecule, followed by isomerization and consequent oxidation of various organic intermediates.

Hydrogen-Ion Concentration↗

PubMed2000

Pathways for the hydrolysis of phorate: product studies by (31)P NMR and GC-MS.

A new intramolecular mechanism is proposed for the hydrolysis of phorate. (31)P NMR was used to study the formation of P-containing products of phorate hydrolysis in situ. When hydrolysis was followed by (31)P NMR, a dominant P-containing product was found and was identified to be diethyl dithiophosphate using methylation and GC-MS. Combining the data from phorate hydrolysis at three different temperatures, thermodynamic parameters were calculated. The contributions of various possible pathways to phorate hydrolysis are discussed.

Gas Chromatography-Mass Spectrometry↗

PubMed2004

S-oxygenation of the thioether organophosphate insecticides phorate and disulfoton by human lung flavin-containing monooxygenase 2.

Phorate and disulfoton are organophosphate insecticides containing three oxidizable sulfurs, including a thioether. Previous studies have shown that only the thioether is oxygenated by flavin-containing monooxygenase (FMO) and the sole product is the sulfoxide with no oxygenation to the sulfone. The major FMO in lung of most mammals, including non-human primates, is FMO2. The FMO2*2 allele, found in all Caucasians and Asians genotyped to date, codes for a truncated, non-functional, protein (FMO2.2A). Twenty-six percent of individuals of African descent and 5% of Hispanics have the FMO2*1 allele, coding for full-length, functional protein (FMO2.1). We have here demonstrated that the thioether-containing organophosphate insecticides, phorate and disulfoton, are substrates for expressed human FMO2.1 with Km of 57 and 32 microM, respectively. LC/MS confirmed the addition of oxygen and formation of a single polar metabolite for each chemical. MS/MS analysis confirmed the metabolites to be the respective sulfoxides. Co-incubations with glutathione did not reduce yield, suggesting they are not highly electrophilic. As the sulfoxide of phorate is a markedly less effective acetylcholinesterase inhibitor than the cytochrome P450 metabolites (oxon, oxon sulfoxide or oxon sulfone), humans possessing the FMO2*1 allele may be more resistant to organophosphate-mediated toxicity when pulmonary metabolism is an important route of exposure or disposition.

Animals↗

PubMed2003

Isolation and characterization of phorate degrading soil bacteria of environmental and agronomic significance.

Phorate [O,O-diethyl-S-(ethylthio)methyl phosphoradiothioate] degrading bacteria were isolated from agricultural soil and characterized based on their morphological and biochemical characteristics. The selected isolates PS-1, PS-2 and PS-3 were presumptively identified as Rhizobium, Pseudomonas and Proteous species, respectively. The HPLC analysis of phorate in bioaugmented soil revealed its complete disappearance within 40 days. The degradation isotherms of the isolates PS-1, PS-2 and PS-3 suggested time-dependent disappearance of phorate following the first order rate kinetics at the corresponding rate constants of 0.04, 0.05 and 0.04 days-1. Besides, the isolates concurrently exhibited substantial phosphate solubilization, indole acetic acid, and siderophore production. The isolate PS-3 also showed anti-fungal activity against a phytopathogen Fusarium oxysporum. As a result of the multifarious biological properties, the isolates have been suggested to be important bioresource for efficient bioinoculant development.

Agriculture↗

PubMed1984

Persistence and movement of phorate at high concentrations in soil.

The entrance of a large number of chemicals into the agricultural market has caused concern to both cultivators and scientists because of their effectiveness at the target site, possibility of underground water contamination, and other undesirable effects such as phytotoxicity and effects on nontarget species. The persistence and movement of phorate--a systemic granular insecticide--were studied at high concentrations (4 and 8 kg a.i./ha) in field soil in two seasons, i.e., winter and summer. Periodic sampling for total phorate residues (TPR) at various vertical depths showed that it leached more efficiently at the higher dose (i.e., 8 kg a.i./ha) in both seasons. The horizontal mobility was also higher at this dose. Irrespective of the treatments, TPR leaching was significantly greater in winter with the higher dose, whereas its movement in the horizontal plane was comparatively greater in summer with this dose. The TPR concentration peaks remained stationary at 7.5 cm depth at all the redistribution times until the pesticide was nearly dissipated under both treatments and in both seasons. TPR persistence was higher at the higher dose. Its persistence was comparatively greater in winter than in summer. The present findings show that there seems to be no threat of underground water contamination by this pesticide even at a rate as high as 8 kg a.i./ha.

Insecticides↗

PubMed2004

Study of Serum Cholinesterase levels in fish Clarias batrachus (Linn.) exposed to pesticides carbaryl and phorate.

Study of the Serum Cholinesterase levels (SchE) in the freshwater catfish Clarias batrachus when exposed to sub lethal dose of pesticides phorate and carbamate, was attempted in this paper. SchE levels decreased in the fish exposed to both the pesticides, the depletion being more pronounced with phorate. These results can be due to impairment of nervous system, liver damage as well as myocardial infarction. Similar findings were not only reported in experimental organisms but also found in human beings working in agricultural fields and pesticide manufacturing plants. Hence it is imperative that suitable occupational health and preventive measures need to be undertaken.

Animals↗

PubMed1979

Phorate intoxication at an insecticide formulating plant.

The use of phorate requires precautions similar to those taken with other organophosphate pesticides, as demonstrated by the case histories and environmental concentrations found in a formulating plant using phorate. Routine supply of personal protective equipment is not necessarily adequate to prevent poisoning.

Adolescent↗

PubMedDate not supplied

Clinical effects and cholinesterase activity changes in workers exposed to Phorate (Thimet).

Phorate (Thimet), an aliphatic derivative of phosphorus is a highly toxic insecticide. In order to implement the safety measures, the clinical manifestations and cholinesterase (ChE) activity were evaluated before and after 2 weeks of exposure to this insecticide in 40 male formulators. The 2 week's exposure reveal signs and symptoms of toxicity in 60% of the formulators. Gastrointestinal symptoms and lowering of heart rate (bradycardia) were more prominent as compared to the neurological symptoms. A significant depression in plasma ChE activity was observed at the end of 1st week (55%) and 2nd week (71%) as compared to the respective pre-exposure values. A recovery up to 79% of the pre-exposure activity of this enzyme was noticed 10 days after cessation of the above exposure.

Adult↗

PubMed1980

Feeding behaviour and susceptibility of Myzus persicae (Sulz) and Brevicoryne brassicae (L.) to [14C] phorate in artificial diet.

The effect of artificial diet on the growth and reproduction of the aphids Myzus persicae (Sulz) and Brevicoryne brassicae (L) was studied. Following the application of [14C] phorate to the diet, the results showed that B. brassicae was more susceptible than M. persicae. In these experiments the dead and live aphids and their honeydew were also analysed. The dead aphids contained more toxic 14C than the live ones with a direct correlation between the amount of insecticide in the diet and the insecticide extracted from the aphids. The total amount of 14C imbided by aphids was calculated but it bore no correlation with the insecticide applied. The amounts of honeydew produced before and after application of the insectide were measured. In both the species the honeydew production was increased as the insecticide was increased from sublethal doses until the toxic range was reached when honeydew production fell gradually. The results obtained from foliar application of the insecticide were compared with those following treatment of the diet. It was found that the aphids were more susceptible to insecticide applied to the diet.

Animals↗

PubMed1980

Toxicity of [14C] phorate applied systemically to the aphids Myzus persicae (Sulz) and Brevicoryne brassicae (l.) grown on brussels sprout plants.

The effect of foliar application of [14C] phorate on the larvae of M. persicae and B. brassicae was studied. Regression analysis of the toxic components in the foliage and the probit kill showed that B. brassicae was more susceptible to the insecticide than M. persicae. The level of radioactivity extracted from the leaves, aphids and their honeydew shows that there was no correlation between the applied dose and the mortality. The amounts of honeydew produced by colonies before and after application of the insecticide were measured. The ratio of honeydew calculated shows that in M. persicae there was a slight increase in the honeydew production as the insecticide was increased from sublethal doses. At higher doses over the lethal range of the insecticide, honeydew production declined gradually in both the species.

Animals↗

PubMed2001

Effect of pesticides carbaryl and phorate on serum cholesterol level in fish, Clarias batrachus (Linn).

Freshwater edible catfish Clarias batrachus (Linn.) was treated with sublethal concentration of two different groups of pesticides- carbaryl, a carbamate and phorate, an organophosphate for 24 ,72 ,120 and 168 h. The disorders of lipid metabolism were observed in serum. Cholesterol levels in the serum decreased significantly throughout the exposure period with both the pesticides. These results indicate one significant manifestation of the toxic response from the fish under the stress of pesticide exposure.

Animals↗