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PubMed1979

Effects of methomyl and ethanol on behavior in the Sprague-Dawley rat.

Emotional behavior and activity levels were studied following administration of ethanol and/or a carbamate pesticide, methomyl, to rats via a ground chow diet. Acetylcholinesterase levels were lowered following the experimental diets. The group having the greatest reduction in AChE, the methomyl group, showed less evidence for habituation in an open-field test. No differences relative to control subjects were noted on handling and muricide tests.

Aggression↗
PubMed1998

Sensitive determination of methomyl in blood using gas chromatography-mass spectrometry as its oxime tert.-butyldimethylsilyl derivative.

A sensitive, selective and reliable method was developed to determine methomyl ¿methyl-N-[(methylcarbamoyl)oxy]-thioacetimidate¿, a carbamate insecticide in human blood, using gas chromatography-mass spectrometry. Dimethylglyoxime served as an internal standard (I.S.). Methomyl in the blood was converted to its oxime form by sodium hydroxide. The solution made acidic with hydrochloric acid was poured into a column packed with Extrelut. Methomyloxime and I.S. were eluted from the column with a mixture of dichloromethane-ethyl acetate-chloroform (65:25:10), transformed to tert.-butyldimethylsilyl derivatives, and analyzed by gas chromatography-mass spectrometry in the electron impact mode. The calibration curves were linear in the concentration range from 1 ng/g to 100 ng/g and 100 ng/g to at least 5000 ng/g. The lower limit of detection was 0.5 ng/g. The absolute recoveries were 72-93% and within-day coefficients of variation were 3.1-5.6% at blood concentrations of 10 and 1000 ng/g. Two practical forensic applications are described.

Acetamides↗
PubMed2006

Rate of degradation of lambda-cyhalothrin and methomyl in grapes (Vitis vinifera L.).

Rates of degradation of lambda-cyhalothrin and methomyl residues in grape are reported. The dissipation behavior of both insecticides followed first-order rate kinetics with similar patterns at standard and double-dose applications. Residues of lambda-cyhalothrin were lost with pre-harvest intervals (PHI) of 12.0-12.5 and 15.0-15.5 days, corresponding to the applications at 25 and 50 g a.i. ha-1, respectively. In the case of methomyl, residues were lost with PHI of 55.0 and 61.0 days, following applications at 1 and 2 kg a.i. ha-1, respectively. The PHI, recommended on the basis of the experimental results, was shown to be effective in minimizing residue load of these insecticides below their maximum residue limits (MRLs) in vineyard samples.

Food Analysis↗
PubMedDate not supplied

Methomyl in the blood of a pilot who crashed during aerial spraying.

An aerial-spray pilot died when his aircraft crashed while he was spraying methomyl. We measured the pesticide in his blood by gas chromatography with flame photometric detection and confirmed the results by mass spectrometry with direct liquid injection through a liquid chromatography interface. The whole blood methomyl concentration was 570 ng/mL.

Accidents, Aviation↗
PubMed1990

Management of methomyl poisoning.

Eleven patients who suffered methomyl poisoning were admitted to the intensive care unit. All of them showed cholinergic symptoms similar to that produced by organophosphate insecticides but of lesser intensity. Plasma cholinesterase activity was normal in four patients and moderately lower in the remainder (always above 32%). All of the patients showed miosis and none presented with bradycardia. No complications were detected in the acute stage or on further examination a month later. The treatment applied was: (1) gastric lavage or washing the skin; (2) the administration of activated charcoal; (3) small doses of atropine according to symptoms (average of total dose 4.3 mg). All of the patients recovered within 24-48 h. In conclusion, we can assume that methomyl poisoning does not produce serious complications if moderate surveillance is assumed. Only small doses of atropine are required to counteract symptoms.

Adolescent↗
PubMed1992

Cardiac toxicity following short-term exposure to methomyl in spraymen and rabbits.

A health surveillance study in 22 healthy spraymen showed significant T-wave changes (including inversion) in most of the limb leads and chest leads following 5 d exposure to methomyl, a carbamate pesticide. Significant changes in plasma cholinesterase and lactic dehydrogenase activities were also noticed. The ECG changes could be reproduced in rabbits and were dose dependent. This type of ECG change following exposure to a carbamate compound is reported for the first time in occupationally-exposed subjects. The study results indicate that these changes are probably directly related to methomyl rather than its toxicity through cholinesterase inhibition. The significance of these changes remain to be investigated.

Administration, Inhalation↗
PubMed1979

Propanil-chloracne and methomyl toxicity in workers of a pesticide manufacturing plant.

In a survey of occupationally acquired disease in workers at a pesticide plant, we found that 11 (11%) of 102 workers had been hospitalized for illness related to chemical exposures; highest hospitalization rates occurred in packaging (27%), production (22%), and maintenance (9%) workers. Commonest causes of hospitalization were intoxication by the carbamate pesticide methomyl [1-(methylthio)ethylideneamino methyl carbamate], a reversible cholinesterase inhibitor, and methemoglobinemia following exposure to 3,4-dichloroaniline. On clinical evaluation, five (46%) of 11 packaging workers, the group with the highest exposure to methomyl, had experienced blurred vision or pupillary constriction. Seventeen (61%) of 28 production workers with exposure to dichloroaniline and propanil (3'4'-dichloropropionanilide) had chloracne, an acne-form dermatosis caused by the contaminant tetrachlorazobenzene in propanil and dichloroaniline. The chloracnegenic potentials of propanil and dichloroaniline were verified by rabbit ear tests. These findings reemphasize the hazards inherent in the the manufacture and formulation of pesticides and herbicides.

Acne Vulgaris↗
PubMed2001

[Acute poisoning with methomyl and other pesticides in the province of Ragusa, Sicily].

In 1995-96, the Occupational Medicine Service of the province of Ragusa, Sicily, examined all cases of pesticide poisonings among persons seen in two local emergency departments, identifying 86 cases due to unintentional pesticide exposure. Methomyl, a highly toxic carbamate, was indicated for 51% of all cases. The most frequently reported symptoms included nausea and vomiting (48%), excessive perspiration (33%), and dyspnea (16%). Fifty-nine cases (69%) were hospitalized, 5 in intensive care. The methomyl cases occurred more frequently during summer months while the cases from all other pesticides showed no seasonal patterns. These observations point out the relevance of identifying acute pesticide poisonings in the province of Ragusa and suggest that ongoing registration of these events should be a public health priority.

Acute Disease↗
PubMed1994

Energy related metabolic alterations in diaphragm muscle resulting from acute methomyl toxicity.

Male Sprague-Dawley rats receiving an acute dose of methomyl (5 mg/Kg, sc) developed overt signs of toxicity within 2 min. The maximum severity, including muscle fasciculations and convulsions, was attained within 7-10 min and lasted for about 30 min. A very rapid recovery followed and by 90 min rats were free from obvious toxicity. During intoxication, the body temperature was significantly below normal. In diaphragm, when the activity of acetylcholinesterase (AChE) was markedly depressed (82%), the levels of high-energy phosphates, adenosine triphosphate (ATP) and phosphocreatine (PCr) were also significantly lowered (27% and 54%, respectively). Significant decreases in the levels of adenosine diphosphate (ADP, 19%), total adenine nucleotides (TAN, 27%), creatine (Cr, 27%), and total creatine compounds (TCrC, 29%) were noted at various intervals. The ratio of PCr/Cr was reduced by 53%. The adenylate energy charge [(ATP + 1/2 ADP)/(ATP + ADP + AMP)], an indicator of high-energy phosphate bond availability, remained unchanged throughout the time course. More than twofold elevation in the activity of Mg(2+)-facilitated creatine kinase (reverse Lohmann reaction) in diaphragm (CK-MM) and more than twofold increase in the levels of glucose in serum, were suggestive of greater synthesis of ATP. Higher activity of CK-MM was also noted in the serum. That high-energy phosphates were partially depleted suggested that the rate of ATP utilization was far greater than its synthesis. Methomyl intoxication also resulted in higher activity of LDH and its isoenzymes in muscle as a result of induced greater synthesis. Elevation of CK and LDH and their isoenzymes in the serum was probably a result of their leakage from the tissues due to loss of membrane permeability caused by significant depletion of ATP and PCr.

Acetylcholinesterase↗
PubMed1997

Assessment of the ability of propoxur, methomyl, and aldicarb, three carbamate insecticides, to induce micronuclei in vitro in cultured Chinese hamster ovary cells and in vivo in BALB/c mice.

Three carbamate insecticides (propoxur, methomyl, and aldicarb) were evaluated for their ability to induce micronuclei (MN) in vitro using cultured Chinese hamster ovary (CHO) cells, and in vivo in mouse bone marrow erythrocytes. In vitro, all three insecticides induced a significant increase in micronucleated binucleate cells, which was generally both dose and sample time dependent. The in vivo studies involved treating male BALB/c mice by different routes, either once or on 3 consecutive days, followed by multiple or single sampling. Treatment by intraperitoneal injection or oral gavage induced a significant increase in micronucleated reticulocytes (MNRETs) in peripheral blood. For all three chemicals, the MN response depended on sample time and the number of treatments, while for aldicarb, the response depended also on the route of exposure. These positive results demonstrate that propoxur, methomyl, and aldicarb are capable of inducing structural and/or numerical chromosomal aberrations in mammalian cells either in vitro or in vivo. Furthermore, based on the results obtained, on optimal in vivo MN protocol for carbamate insecticides is a single treatment followed by blood sampling at 24 and 48 hr after treatment.

Aldicarb↗
PubMed1997

New treatment regimens in organophosphate (diazinon) and carbamate (methomyl) insecticide-induced toxicosis in fowl.

The objective of this work was to determine optimal treatment regimens for organophosphate (OP) or carbamate insecticide toxicoses in fowl using the antidotes atropine sulfate and pralidoxime chloride (2-PAM). Broiler chicks in treatment groups, each comprising 3 replicates of 6-7 birds/replicate, were gavaged on a body weight (BW) basis with the OP and carbamate insecticides, diazinon and methomyl, respectively, at lethal dosages. Treatment groups were injected with either or both of the antidotes at various dosages as soon as clinical signs appeared. Birds appearing healthy 24 h thereafter were regarded as having been treated successfully. At a dosage of 100 mg/kg BW, atropine was mildly toxic and at 200 mg/kg 2-PAM was severely toxic (but not lethal), whereas at dosages of 50 and 100 mg/kg BW, respectively, the antidotes were at their most effective. With diazinon, atropine alone was only partially effective (12/20 survivors), whereas 2-PAM was extremely efficacious. (20/20 survivors); the combination of the 2 antidotes at 2 dosages was slightly less effective (19/20 survivors) than 2-PAM alone. For methomyl toxicity, atropine was largely successful (18/20 survivors), whereas 2-PAM was mostly unsuccessful (10/20 survivors); the combination at high dosage was less effective (15/20 survivors) than atropine alone, but at a low dosage the combination was the most successful (20/20 survivors). The results indicate that anticholinesterase insecticide toxicoses in fowl should not be treated according to textbook recommendations, and antidotal dosage with atropine should be up to 100 times greater than is commonly recommended. The specific cause of the toxicoses should ideally be determined before treatment is given, but as this is often unknown, a combination of antidotes may be the optimal treatment protocol.

Animals↗
PubMed2006

Time course of cholinesterase inhibition in adult rats treated acutely with carbaryl, carbofuran, formetanate, methomyl, methiocarb, oxamyl or propoxur.

To compare the toxicity of seven N-methyl carbamates, time course profiles for brain and red blood cell (RBC) cholinesterase (ChE) inhibition were established for each. Adult, male, Long Evans rats (n=4-5 dose group) were dosed orally with either carbaryl (30 mg/kg in corn oil); carbofuran (0.5 mg/kg in corn oil); formetanate HCl (10 mg/kg in water); methomyl (3 mg/kg in water); methiocarb (25 mg/kg in corn oil); oxamyl (1 mg/kg in water); or propoxur (20 mg/kg in corn oil). This level of dosing produced at least 40% brain ChE inhibition. Brain and blood were taken from 0.5 to 24 h after dosing for analysis of ChE activity using two different methods: (1) a radiometric method which limits the amount of reactivation of ChE activity, and (2) a spectrophotometric method (Ellman method using traditional, unmodified conditions) which may encourage reactivation. The time of peak ChE inhibition was similar for all seven N-methyl carbamate pesticides: 0.5-1.0 h after dosing. By 24 h, brain and RBC ChE activity in all animals returned to normal. The spectrophotometric method underestimated ChE inhibition. Moreover, there was a strong, direct correlation between brain and RBC ChE activity (radiometric assay) for all seven compounds combined (r(2)=0.73, slope 1.1), while the spectrophotometric analysis of the same samples showed a poor correlation (r(2)=0.09). For formetanate, propoxur, methomyl, and methiocarb, brain and RBC ChE inhibitions were not different over time, but for carbaryl, carbofuran and oxamyl, the RBC ChE was slightly more inhibited than brain ChE. These data indicate (1) the radiometric method is superior for analyses of ChE activity in tissues from carbamate-treated animals (2) that animals treated with these N-methyl carbamate pesticides are affected rapidly, and recover rapidly, and (3) generally, assessment of RBC ChE is an accurate predictor of brain ChE inhibition for these seven pesticides.

Animals↗
PubMed1989

Heat Shock Protein Synthesis Induced by Methomyl in Maize (Zea mays L.) Seedlings.

Exposure of plumules of intact maize seedlings (Zea mays L.) to S-methyl-N-[(methylcarbamoyl)-oxy]thioacetimidate (methomyl) represses synthesis of several polypeptides normally made under control conditions and induces synthesis of polypeptides similar to maize heat shock polypeptides (HSPs). Three of the methomyl-induced polypeptides (18 kilodaltons) are recognized by antibodies raised against 18 kilodalton maize heat shock polypeptides.

Journal Article↗
PubMed1979

Determination of residues of methomyl and oxamyl and their oximes in crops by gas-liquid chromatography of oxime trimethylsilyl ethers.

The gas-liquid chromatographic behavior of methomyl (methyl N-[(methyl-carbamoyl)oxy]thioacetimidate), oxamyl (methyl N',N'-dimethyl-N-[(methylcarbamoyl)oxyl]-1-thiooxamimidate), their respective oxime hydrolysis products and the trimethylsilyl (TMS) ethers of the oximes on 5% OV-1 was studied under isothermal conditions using a flame-photometric detector in the sulfur-selective mode. In contrast to the behavior of the parent carbamates and underivatized oximes, the oxime-TMS ethers readily produced symmetrical peaks of consistent size. Quantities of derivative equivalent to at least 0.25 ng of oxime were easily measurable. Derivative formation was reproducible for standards over the range 10.0 to 0.25 microgram/ml in benzene and at 10.0 and 0.50 microgram/ml in the presence of extractives from tomato, carrot and celery at concentrations equivalent to 10 g/ml of crop. Derivative yields from crop extract fotifications were 89% or better in most cases. Both the carbamates and oximes were simply and consistently recovered in high yield from crops fortified at 1.00 and 0.05 ppm using the procedures described. The inclusion of a second analytical step provided separate analysis for oximes and carbamates. The application of these observations to the analyses of residues in crops is discussed.

Carbamates↗
PubMed2001

Reduction of the carbamate pesticides oxamyl and methomyl by dissolved FeII and CuI.

The degradation of two oxime carbamate pesticides, oxamyl and methomyl, was investigated in anoxic solutions containing various metal ions and reducing agents. In reagent-free solutions, these carbamates degrade slowly via base-catalyzed elimination. Rates of carbamate degradation are accelerated by Fe(II), Cu(I), and Cu(II), but not by several other metal ions and reducing agents. In the presence of Fe(II), carbamates undergo a net two-electron reduction that is coupled to the sequential one-electron oxidation of two Fe(II) ions. The observed products are a substituted nitrile, methanethiol, and methylamine. A radical intermediate is inferred by polymerization of the radical scavenger acrylonitrile. Redox kinetics (i) vary with carbamate identity, (ii) exhibit first-order dependence on both Fe(II) and carbamate concentration, (iii) are relatively independent of pH, (iv) follow Arrhenius temperature dependence, and (v) are only indirectly influenced by the presence of O2. Coordinatively saturated Fe(II) complexes (Fe(II)EDTA2- and Fe(II)(CN)6(4-)) react with oxamyl at rates equal to and greater than hexaquo Fe(II), respectively, indicating that an inner-sphere Fe(II)-carbamate coordination complex is not required for electron transfer. Experimental results indicate that Cu(I) reduces the carbamates by the same mechanism as Fe(II) but at much higher rates. In contrast, Cu(II) acts as a catalyst for both elimination and reduction reactions.

Carbamates↗
PubMed2002

Reduction of the pesticides oxamyl and methomyl by FeII: effect of pH and inorganic ligands.

This work examines the effect that pH and selected inorganic ligands have on the kinetics of reactions between FeII and two structurally related oxime carbamate pesticides, oxamyl and methomyl. In anoxic solutions containing FeII, these compounds degrade by parallel elimination and reduction pathways. Rates of FeII-independent carbamate elimination (EIcb mechanism) are proportional to [OH-], increasing 10-fold for each unit increase in pH. In homogeneous solution, rates of carbamate reduction by 0.5 mM FeII are relatively constant at pH <7, but increase dramatically between pH 7 and pH 8.3. At pH >8.3, Fe(OH)2(s) precipitation occurs, and carbamates react with both solution-phase and solid-phase FeII. Carbamate reduction by FeII is not significantly affected by the presence of chloride, bromide, nitrate, perchlorate, and sulfate. In contrast, increased rates of carbamate reduction are observed in solutions containing fluoride, carbonate, and phosphate. Kinetic measurements are interpreted in terms of changing FeII speciation according to the expression kred = [FeII]sigmaikialphai, where k(red) is the pseudo-first-order rate constant for carbamate reduction, [FeII] is the total FeII concentration, and ki and alphai are the second-order rate constant and fractional concentration of each FeII species, respectively. It follows that the overall kinetics of carbamate reduction is a function of the identity and concentration of individual FeII species present in solution as well as the inherent reactivity of each species with carbamates. The magnitude of ki is related to the standard one-electron reduction potential (E(H) degrees) of the corresponding FeIII/FeII redox couple.

Carbamates↗
PubMed1985

Disappearance of dislodgable residues of methomyl from leaves and vegetables in Tamilnadu (India).

The dislodgable residues of methomyl from leaves and vegetables were determined by a single-step methanol extraction followed by reversed-phase HPLC. The residues on the bhendi vegetables and leaves were several times higher than on the brinjal vegetables and leaves. The pesticide, however, dissipates rapidly under the South Indian climatic conditions resulting in undetectable residues within three days of spraying.

Chromatography, High Pressure Liquid↗