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Chemistry and Physics of Lipids Feb 1999Perturbations induced by ethylazinphos on the physical organization of dipalmitoylphosphatidylcholine (DPPC) and DPPC/cholesterol membranes were studied by differential...
Perturbations induced by ethylazinphos on the physical organization of dipalmitoylphosphatidylcholine (DPPC) and DPPC/cholesterol membranes were studied by differential scanning calorimetry (DSC) and fluorescence polarization of 2-, 6-, 12-(9-anthroyloxy) stearic acids and 16-(9-anthroyloxy) palmitic acid. Ethylazinphos (50 and 100 microM) increases the fluorescence polarization of the probes, either in the gel or in the fluid phase of DPPC bilayers, and this concentration dependent effect decreases from the surface to the bilayer core. Additionally, the insecticide displaces the phase transition to a lower temperature range and broadens the transition profile of DPPC. A shifting and broadening of the phase transition is also observed by DSC. Furthermore at insecticide/lipid molar ratios higher than 1/7, DSC thermograms, in addition to the normal transition centered at 41 degrees C, also display a new phase transition centered at 45.5 degrees C. The enthalpy of this new transition increases with insecticide concentration, with a corresponding decrease of the main transition enthalpy. Ethylazinphos in DPPC bilayers with low cholesterol (< or = 20 mol%) perturbs the membrane organization as described above for pure DPPC. However, cholesterol concentrations higher than 20 mol% prevent insecticide interaction, as revealed by fluorescence polarization and DSC data. Apparently, cholesterol significantly modulates insecticide interaction by competition for similar distribution domains in the membrane. The present results strongly support our previous hypothesis that ethylazinphos locates in the cooperativity region, i.e. the region of C1-C9 atoms of the acyl chains, and extends to the lipid-water interface, where it increases lipid packing order sensed across all the thickness of the bilayer. Additionally, and, on the basis of DSC data, a lateral regionalization of ethylazinphos is here tentatively suggested.
Topics: 1,2-Dipalmitoylphosphatidylcholine; Azinphosmethyl; Calorimetry, Differential Scanning; Cholesterol; Fluorescence Polarization; Fluorescent Dyes; In Vitro Techniques; Insecticides; Lipid Bilayers; Membrane Lipids; Palmitic Acids; Stearic Acids
PubMed: 10192930
DOI: 10.1016/s0009-3084(98)00105-4 -
Biochimica Et Biophysica Acta May 1996The interaction of ethylazinphos with the physical organization of model and native membranes was investigated by means of fluorescence polarization of...
The interaction of ethylazinphos with the physical organization of model and native membranes was investigated by means of fluorescence polarization of 1,6-diphenyl-1,3,5-hexatriene (DPH) and of its propionic acid derivative (DPH-PA). Ethylazinphos shifts the phase transition midpoint to lower temperature values and broadens the phase transition profile of bilayers reconstituted with dimyristoyl-, dipalmitoyl- and distearoylphosphatidylcholines (DMPC, DPPC, DSPC), as detected by DPH and DPH-PA. Additionally, both probes detect significant effects of ethylazinphos in the fluid phase of the above lipid bilayers. The insecticide perturbations are more pronounced in bilayers of short-chain lipids, e.g., DMPC, in correlation with the higher partition in these membranes. On the other hand, the insecticide increases to some extent the ordering promoted by cholesterol in the fluid phase of DMPC, but high cholesterol concentrations (> or = 30 mol%) almost prevent insecticide interaction, as revealed by DPH and DPH-PA. In agreement with the results in models of synthetic lipids, the increase of intrinsic cholesterol in fluid native membranes depresses the partition values of ethylazinphos and consequently its effects.
Topics: Azinphosmethyl; Cell Membrane; Cholesterol; Diphenylhexatriene; Fluorescence Polarization; Fluorescent Dyes; Insecticides; Lipid Bilayers; Phospholipids
PubMed: 8652607
DOI: 10.1016/0005-2736(96)00012-0 -
Journal of AOAC International 1995A novel procedure is described for simple removal of coextractives prior to analysis of fruits and vegetables for azinphos-methyl and azinphos-ethyl residues. The...
A novel procedure is described for simple removal of coextractives prior to analysis of fruits and vegetables for azinphos-methyl and azinphos-ethyl residues. The solvent extract is concentrated, placed in a polymeric membrane tube, and then dialyzed in cyclohexane. Both azinphos-methyl and azinphos-ethyl diffuse into the surrounding solvent while coextractants remain inside the membrane. The dialyzing solvent is exchanged during concentration with n-hexane and analyzed without further cleanup by gas-liquid chromatography with a specific thermionic detector. The detection limit for a 25 g grape sample with final volume of extract made to 15 mL was 0.01 mg/kg. Recoveries of both residues from grapes averaged 107% (spike levels of 0.3 to 2.0 mg/kg). From a 20 g spinach sample, recoveries averaged 82% for azinphos-methyl and 72% for azinphos-ethyl when final volume of extract was made to 5 mL (spike levels of 0.1 to 1.0 mg/kg). Recoveries from 20 types of fruits and vegetables (20 g sample spiked at 1 mg/kg for both azinphos-methyl and azinphos-ethyl) were consistently greater than 70%, except for strawberries (61-67%) and avocado (28-34%). The high lipid content of avocado may impede diffusion of azinphos-methyl and azinphos-ethyl through the polymeric membrane. A field evaluation of the procedure showed a strong correlation (r = 0.957) between azinphos-methyl residues on grapes and treatments with 2 spray formulations. The membrane cleanup procedure is a simple and cost-effective alternative to other column or liquid-liquid partitioning procedures for azinphos-methyl and azinphos-ethyl residue analysis.
Topics: Azinphosmethyl; Chromatography, Gas; Diffusion; Food Contamination; Fruit; Insecticides; Membranes, Artificial; Pesticide Residues; Solubility; Solvents; Vegetables
PubMed: 8664581
DOI: No ID Found -
Archives of Biochemistry and Biophysics Apr 1995The extensive use of organophosphorothioate insecticides in agriculture has resulted in the risk of environmental contamination with a variety of broadly based... (Comparative Study)
Comparative Study
The extensive use of organophosphorothioate insecticides in agriculture has resulted in the risk of environmental contamination with a variety of broadly based neurotoxins that inhibit the acetylcholinesterases of many different animal species. Organophosphorus hydrolase (OPH, EC 3.1.8.1) is a broad-spectrum phosphotriesterase that is capable of detoxifying a variety of organophosphorus neurotoxins by hydrolyzing various phosphorus-ester bonds (P-O, P-F, P-CN, and P-S) between the phosphorus center and an electrophilic leaving group. OPH is capable of hydrolyzing the P-X bond of various organophosphorus compounds at quite different catalytic rates: P-O bonds (kcat = 67-5000 s-1), P-F bonds (kcat = 0.01-500 s-1), and P-S bonds (kcat = 0.0067 to 167 s-1). P-S bond cleavage was readily demonstrated and characterized in these studies by quantifying the released free thiol groups using 5,5'-dithio-bis-2-nitrobenzoic acid or by monitoring an upfield shift of approximately 31 ppm by 31P NMR. A decrease in the toxicity of hydrolyzed products was demonstrated by directly quantifying the loss of inhibition of acetylcholinesterase activity. Phosphorothiolate esters, such as demeton-S, provided noncompetitive inhibition for paraoxon (a P-O triester) hydrolysis, suggesting that the binding of these two different classes of substrates was not identical.
Topics: Aryldialkylphosphatase; Azinphosmethyl; Binding Sites; Biodegradation, Environmental; Disulfoton; Environmental Pollutants; Esterases; Flavobacterium; Hydrolysis; Insecticides; Kinetics; Malathion; Molecular Structure; Organothiophosphorus Compounds; Paraoxon; Phosphoramides; Pseudomonas; Recombinant Proteins; Substrate Specificity
PubMed: 7726573
DOI: 10.1006/abbi.1995.1204 -
Hua Xi Yi Ke Da Xue Xue Bao = Journal... Mar 1993A total of 22 organophosphorus pesticides (OPPs), including 8 ethyl-, 9 methyl-, and 5 other OPPs, were tested for mutagenicity in micronucleus assay system both in 615...
A total of 22 organophosphorus pesticides (OPPs), including 8 ethyl-, 9 methyl-, and 5 other OPPs, were tested for mutagenicity in micronucleus assay system both in 615 mouse marrow cells in vivo with multi-intraperitoneal administrations and in cultured Chinese hamster lung (CHL) cells in vitro; and structure-mutagenicity relationship of OPPs was analyzed. Among the OPPs tested in vivo, 5 ethyl-(diazinon, chlorpyrifos, disulfoton, ethion, and parathion), and only 1 methyl-(dimethoate) were found mutagenic, while the other OPPs were negative. Six ethyl- (azinphos ethyl, chlorpyrifos, ethion, parathion, phosaione, and quinaphos), 8 methyl- (azinophos methyl, chlorpyrifos methyl, dichlorvos, dimethoate, fenitrothion, malathion, parathion methyl, and trimethyl phosphate), and 2 other OPPs (EII and MIA), however, induced micronucleus in CHL cells in vitro. The results indicated that most of the ethyl-OPPs tested showed the ability to induce micronucleus both in vivo and in vitro, and that most of the methyl-OPPs were positive only in vitro. The mechanism for the adversity of mutagenic activity in micronucleus assay in vivo and in vitro produced by different kinds of OPPs was also discussed.
Topics: Animals; Bone Marrow Cells; Cells, Cultured; Cricetinae; Cricetulus; Female; Fibroblasts; Insecticides; Lung; Male; Mice; Micronucleus Tests; Mutagenesis; Organophosphorus Compounds
PubMed: 8340099
DOI: No ID Found -
The Science of the Total Environment Aug 1992The use of gel permeation chromatography (GPC) and capillary gas chromatography (GC) with thermionic detection (NPD) is described as a routine methodology for the...
The use of gel permeation chromatography (GPC) and capillary gas chromatography (GC) with thermionic detection (NPD) is described as a routine methodology for the determination of organophosphorus pesticides in biota samples. Confirmatory analysis is done by capillary GC with mass spectrometry in the negative chemical ionization mode (NCI-MS). As an example, the use of GPC is described as trace-enrichment technique and clean-up to remove coextractive lipids in samples of mosquito fish Gambussia affinis collected during periods of 1987-1989 in the rice crop fields of the Ebro Delta (Spain). Recoveries of dioxathion, fenitrothion, malathion, tetrachlorvinphos, azinphos-ethyl, ronnel and coumaphos varied between 60% and 80% depending on the compound.
Topics: Animals; Bivalvia; Chromatography, Gas; Chromatography, Gel; Cyprinodontiformes; Fresh Water; Insecticides; Organophosphorus Compounds; Perciformes; Spain
PubMed: 1439741
DOI: 10.1016/0048-9697(92)90131-b -
Analytical Biochemistry Jan 1992A flow injection system, incorporating an acetylcholinesterase (AChE) single bead string reactor (SBSR), for the determination of some organophosphorous (azinphos-ethyl,...
A flow injection system, incorporating an acetylcholinesterase (AChE) single bead string reactor (SBSR), for the determination of some organophosphorous (azinphos-ethyl, azinphos-methyl, bromophos-methyl, dichlorovos, fenitrothion, malathion, paraoxon, parathion-ethyl and parathion-methyl) and carbamate insecticides (carbofuran and carbaryl) is presented. The detector is a simple pH electrode with a wall-jet entry. Variations in enzyme activity due to inhibition are measured from pH changes when the substrate (acetylcholine) is injected before and after the passage of the solution containing the insecticide. The percentage inhibition of enzyme activity is correlated to the insecticide concentration. Several parameters influencing the performance of the system are studied and discussed. The detection limits of the insecticides ranged from 0.5 to 275 ppb. The determination of these compounds was conducted in Hepes buffer and a synthetic sea water preparation. The enzyme reactor can be regenerated after inhibition with a dilute solution of 2-PAM and be reused for analysis. The immobilized enzyme did not lose any activity up to 12 weeks when stored at 4 degrees C.
Topics: Acetylcholine; Acetylcholinesterase; Carbamates; Cholinesterase Inhibitors; Enzyme Activation; Enzymes, Immobilized; Flow Injection Analysis; Hydrogen-Ion Concentration; Hydrolysis; Insecticides; Organophosphorus Compounds; Substrate Specificity; Temperature
PubMed: 1595894
DOI: 10.1016/0003-2697(92)90297-k -
Journal of Analytical Toxicology 1990Azinphos-ethyl concentrations in the blood, urine, and gastric lavage liquid from medical examiner cases are reported. In all cases, there was ingestion of the...
Azinphos-ethyl concentrations in the blood, urine, and gastric lavage liquid from medical examiner cases are reported. In all cases, there was ingestion of the organophosphate pesticide. They are presented under three categories of intoxication: less serious, more serious, and fatal intoxications. The results of this study indicate that it was not possible to determine the blood levels that show the correct degree of intoxication and of lethal dose. Fast methods are given for identification and quantification of azinphos-ethyl in human biological fluids.
Topics: Acute Disease; Azinphosmethyl; Chromatography, Gas; Chromatography, Thin Layer; Drug Stability; Female; Humans; Insecticides; Male; Predictive Value of Tests
PubMed: 2395348
DOI: 10.1093/jat/14.4.243 -
Journal - Association of Official... Mar 1983Several fruits and vegetables were fortified at a low (0.02-0.5 ppm) and at a high (0.1-5 ppm) level with pesticides and with a synergist, and recoveries were...
Several fruits and vegetables were fortified at a low (0.02-0.5 ppm) and at a high (0.1-5 ppm) level with pesticides and with a synergist, and recoveries were determined. Analyses were performed by using 3 steps of a multiresidue method for determining N-methylcarbamates in crops: methanol extraction followed by removal of plant co-extractives by solvent partitioning and chromatography with a charcoal-silanized Celite column. Eleven compounds were determined by using a high performance liquid chromatograph equipped with a reverse phase column and a fluorescence detector. Twelve additional compounds were determined by using a gas-liquid chromatograph equipped with a nonpolar packed column and an electron capture or flame photometric detector. Recoveries of 10 pesticides (azinphos ethyl, azinphos methyl, azinphos methyl oxygen analog, carbaryl, carbofuran, naphthalene acetamide, naphthalene acetic acid methyl ester, napropamide, phosalone, and phosalone oxygen analog) and the synergist piperonyl butoxide, which were determined by high performance liquid chromatography, averaged 100% (range 86-117) at the low fortification level and 102% (range 93-115) at the high fortification level. Quantitative recovery of naphthalene acetamide through the method required that an additional portion of eluting solution be passed through the charcoal column. Recoveries of 7 additional pesticides (dimethoate, malathion, methyl parathion, mevinphos, parathion, phorate oxygen analog, and pronamide), which were determined by gas-liquid chromatography (GLC), averaged 108% (range 100-120) at the low fortification level and 107% (range 99-122) at the high fortification level. DDT, diazinon, dieldrin, phorate, and pirimiphos ethyl, which were determined by GLC, were not quantitatively recovered.
Topics: Carbamates; Chromatography, Gas; Chromatography, High Pressure Liquid; Fruit; Insecticides; Microchemistry; Pesticide Residues; Spectrometry, Fluorescence; Vegetables
PubMed: 6853408
DOI: No ID Found -
Journal - Association of Official... May 1980A method intended for regulatory purposes is described for the determination of organophosphorus insecticide residues in fruits and vegetables. Eighteen organophosphorus...
A method intended for regulatory purposes is described for the determination of organophosphorus insecticide residues in fruits and vegetables. Eighteen organophosphorus insecticides, azinphos-ethyl, chlorpyrifos, diazinon, dichlorvos, dimethoate, ethion, ethoate-methyl, fenitrothion, fenthion, formothion, malathion, methidathion, mevinphos, parathion, phosalone, phosphamidon, thiometon, and trichlorphon, and 7 metabolites, fenitrooxon, fenthion sulfoxide, fenthion sulfone, malaoxon, desethylphosphamidon, thiometon sulfoxide, and thiometon sulfone, were extracted from different crops with acetone and partitioned into hexane or ethyl acetate, according to their polarities. The hexane extract was cleaned up by eluting from a Florisil column with acetone-hexane (4+96). The ethyl acetate extract needs no cleanup. The concentrated extracts were analyzed by gas-liquid chromatography using thermionic detectors. Recoveries conducted at fortification levels ranging from 0.1 to 2 mg/kg were in most cases above 80%. The limit of sensitivity is less than 0.1 mg/kg.
Topics: Chromatography, Gas; Food Contamination; Fruit; Insecticides; Organophosphorus Compounds; Pesticide Residues; Vegetables
PubMed: 7430038
DOI: No ID Found