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Biomedical subjects

T R Fukuto

Publications and source records attributed to T R Fukuto.

At least 37 records · Page 2Linked to original sources
PubMed1980

Properties and inhibition of rat malathion carboxylesterases.

Two malathion carboxylesterase fractions, designated as esterase fraction A and esterase fraction B, that hydrolyze malathion were purified 13- and 18-fold, respectively, from rat liver microsomes. The two enzymes could not be distinguished kinetically, but fraction A contained at least one electrophoretic species not present in fraction B. The molecular weight of fraction A was estimated as 50,000-60,000; the molecular weight of fraction B was about twice this value. Incubation of [methoxy-14C]malathion with fraction A or fraction B resulted in a mixture of malathion alpha and beta monoacids, but the composition of the mixture produced by fraction A (alpha/beta = 1.5) differed from that produced by fraction B (alpha/beta = 0.2), indicating the presence of multiple species of carboxylesterases in mammalian liver microsomes. Isomalathion was substantially more potent as an inhibitor of both rat liver and rat serum malathion carboxylesterases than O,S,S-trimethyl phosphorodithioate. Isomalathion appeared to be equipotent in inhibiting the rat liver carboxylesterase-catalyzed reactions leading to either alpha or beta-monoacid. O,S,S-Trimethyl phosphorodithioate, on the other hand, preferentially diminished the reactions leading to alpha monoacid. In contrast, the rat serum carboxylesterase-catalyzed reactions leading to either alpha or beta monoacid were inhibited to approximately on equal degree by isomalathion and O,S,S-trimethyl phosphorodithioate.

Animals↗
PubMed1980

Ecotoxicology of phenylphosphonothioates.

The phenylphosphonothioate insecticides EPN and leptophos, and several analogs, were evaluated with respect to their delayed neurotoxic effects in hens and their environmental behavior in a terrestrial-aquatic model ecosystem. Acute toxicity to insects was highly correlated with sigma sigma of the substituted phenyl group (regression coefficient r = -0.91) while acute toxicity to mammals was slightly less well correlated (regression coefficient r = -0.71), and neurotoxicity was poorly correlated with sigma sigma (regression coefficient r = -0.35). Both EPN and leptophos were markedly more persistent and bioaccumulative in the model ecosystem than parathion. Desbromoleptophos, a contaminant and metabolite of leptophos, was seen to be a highly stable and persistent terminal residue of leptophos.

Animals↗
PubMed1976

Alteration of O,O-dimethyl S-[alpha-(carboethoxy)benzyl] phosphorodithioate (phenthoate) in citrus, water, and upon exposure to air and sunlight.

The fate of 32P- and 14C-labeled O,O-dimethyl S-[alpha-(carboethoxy)benzyl] phosphorodithioate (phenthoate) was determined in citrus, water, and upon exposure to air and sunlight. The products recovered from citrus and glass plates exposed to sunlight were unchanged phenthoate, phenthoate oxon, demethyl phenthoate, mandelic acid, bis-[alpha-(carboethoxy)benzyl] disulfide, O,O-dimethyl phosphorothioic and phosphorodithioic acid. Similar products generally were found in citrus leaf and fruit extracts. Phenthoate was fairly stable in phosphate buffered water with a half-life of approximately 12 days at pH 8.0. The major hydrolysis products were phenthoate acid, demethyl phenthoate and demethyl phenthoate oxon.

Air↗
PubMed1976

Penetration and comparative metabolism of leptophos in susceptible and resistant houseflies.

The metabolism and rate of penetration of leptophos (O-methyl O-4-bromo-2,5-dichlorophenyl phenylphosphonothioate) was determined in a susceptible strain and a strain of housefies which was 50-fold resistant to leptophos. Penetration of leptophos into resistant flies was substantially slower than into susceptible flies but large differences in metabolism, both quantitatively and qualitatively, were not observed. No difference was observed in the sensitivity of flyhead and thorax acetylcholinesterase to leptophos-oxon in vitro, and tolerance to leptophos by the resistant strain is explained in terms of decreased rates or penetration and minor differences in metabolism.

Animals↗
PubMed1976

Absorption and metabolism of a selective insecticide, 2,2-dimethyl-2,3-dihydrobenzofuranyl-7 N-dimethoxyphosphinothioyl-N-methylcarbamate, in bean plants.

The absorption and metabolism of 2,2-dimethyl-2,3-dihydrobenzofuranyl-7 N-dimethoxyphosphinothioyl-N-methylcarbamate (PSC), a selective, insecticidally active carbofuran derivative, was studied in red kidney bean plants. PSC was absorbed from hydroponic culture media and was translocated throughout the plants. PSC was metabolized to carbofuran, 3-hydroxycarbofuran, and 3-ketocarbofuran and these materials accounted for 25% of the recovered radioactivity. Each of these compounds are more toxic to mice than the parent compound. Additionally at least four other oxidized, hydroxylated and/or hydrolyzed metabolites were formed.

Absorption↗
PubMed1976

Blocking of valinomycin-mediated bilayer membrane conductance by substituted benzimidazoles.

Valinomycin selectively transports alkali cations, e.g. potassium ions, across lipid bilayer membranes. The blocking of this carrier-mediated transport by four substituted benzimidazoles has been investigated. The compounds are 4,5,6,7-tetrachloro-2-trifluoromethylbenzimidazole, (TTFB); 4,5,6,7,-tetrachloro-2-methylbenzimidazole, (TMB); 2-trifluoromethylbenzimidazole, (TFB); and 2-methylbenzimidazole, (MBM). Because of its low acidic dissociation constant (pKa = 5.04), the blocking efficiency of TTFB in both neutral and anionic forms in the aqueous phase could be studied. The compounds exhibit the blocking efficiency sequence, TTFB- greater than TTFB0 greater than TMB0 greater than TFB0 greater than MBM0. The corresponding scale of decreasing lipophilicity, as determined by octanol/water partitioning, is TTFB0 greater than TMB0 greater than TTFB- greater than TFB0 greater than MBM0. Comparison of neutral species establishes a positive correlation of blocking efficiency with lipophilicity, with the latter being conferred primarily by chlorination of the benzenoid nucleus. Anionic TTFB, on the other hand, is the most effective blocking agent studied in spite of the fact that its dissociation in the aqueous phase markedly impedes its entry (presumably as a neutral species) into a bulk hydrocarbon phase. This observation suggests that the blocking of valinomycin-mediated bilayer membrane conductance takes place at the membrane/solution interface.

Benzimidazoles↗
PubMed1975

Attraction of the oriental fruit fly, Dacus dorsalis, to methyl eugenol and related olfactory stimulants.

The attraction of male oriental fruit flies to methyl eugenol and 34 analogues was investigated quantitatively using the characteristic feeding response. Methyl eugenol was the most active compound studied, with a feeding response to 0.01 mug, but saturation of the allyl side chain or replacement of allyl by allyloxy produced compounds almost as effective. Replacement of the methoxy groups by methylenedioxy, methyl, or chloro groups abolished all response. The ring geometry of the methoxy groups was critical, with orthodimethoxy most active and meta-dimethoxy inactive. Replacement of methoxy with hydroxy, methylthio, or amino groups did not abolish the response. The failure of the oriental fruit fly to respond to the methyl and chloro isosteres of methyl eugenol was contrasted with the response of a human odor panel which perceived these compounds as having weak floral odors.

Animals↗