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PubMed2001

Shift in FTIR spectrum patterns in methomyl-exposed rat spleen cells.

Methomyl is a highly toxic carbamate insecticide which is widely used in many agricultural countries. We have applied the Fourier-transformed infrared (FTIR) spectroscopic method to study the toxicity of methomyl on cytoskeletal protein and the nucleic acid of rat spleen cells. Rats were given methomyl by gavage at 2, 6 and 8 mg/kg in single doses. Colchicine, a microtubule-disrupting agent, was given to rats at 2, 4, and 6 mg/kg in single doses and mitomycin C, an alkylating agent which acts as a DNA-cross-linking agent, was given by an intraperitoneal route to rats at 1 mg/kg. It was shown that the wavenumber of FTIR spectra at amide I and amide II in both methomyl- and colchicine-exposed rats shifted in dose response manner when compared with the control (P < 0.05). The amide I and II shifts in these regions have been proposed to be the result of an alpha-helix protein conformational change. Toxic doses of mitomycin C, a DNA-cross-linking agent, did not result in this pattern. Moreover, all exposed rats showed an increase in the absorbance ratios that were related to the vibrational mode of the phosphodiester group in nucleic acid (P < 0.05).

Animals↗
PubMed1982

Effect and mechanism of action of methomyl and cypermethrin insecticides on kynurenine metabolizing enzymes of mouse liver.

The effect of methomyl and cypermethrin insecticides on the B6-dependent kynurenine hydrolase (KH) and kynurenine aminotransferase (KATE) was studied. These insecticides induced pronounced inhibition on the (KH) and (KATE) enzymes after single dose treatment. Repeated doses of methomyl induced inhibition on the (KH) and (KATE) activities, whereas repeated treatment with cypermethrin had no effect on the activities of these enzymes. In vitro methomyl inhibited (KH) and (KATE) enzymes at 10(-6)M up to 10(-3)M, through a competitive mechanism. Methomyl and cypermethrin are capable of causing alterations in the kynurenine metabolizing enzymes of mouse liver.

Animals↗
PubMed1981

Degradation of methomyl residues in frozen strawberries.

14C-Methomyl (S-methyl N-[(methylcarbamoyl)-oxy]thioacetimidate) suspended in a commercial formulation was sprayed on strawberries. At 7 and 14 days post-application, mature berries were harvested in chopped. Fresh chopped berries were extracted with methanol using a Polytron homogenizer, and the crop marc was subsequently leached with methanol, freeze-dried, and re-extracted. Portions of the fresh chopped fruit were also frozen at-20 degrees C for 1, 30, and 102 days before extraction with methanol using a Polytron homogenizer, followed by subsequent leaching of the crop marc. For fresh berries, 93.7 and 88.9% of the 14C present at harvest was extractable at 7 and 14 days post-application, respectively. Based on thin layer chromatographic analysis, methomyl represented 83.5 and 68.2% of the 14C extracted from fresh berries at 7 and 14 days, respectively. Freezing of strawberries reduced extraction efficiency and appeared to degrade methomyl. At 7 and 14 days post-application, averages of 80.9 and 77.1%, respectively, of the 14C present were extractable after frozen storage regardless of storage time. Furthermore, only about 10% of the extracted 14C was methomyl; the remainder was of unknown composition.

Chromatography, Thin Layer↗
PubMed1995

Exposure evaluation is a crucial step for quantitative risk assessment of methomyl.

Methomyl, methyl N-[[(methylamino)carbonyl]oxy]ethanimidothioate is a carbamate insecticide with anticholinesterase activity. As a broad spectrum insecticide, it is one of the most frequently used pesticides in tangerine orchards in Thailand. Although methomyl is said to be rapidly eliminated from experimental animals (1) high incidence of acute poisonings was reported among patients occupationally exposed to a powder formulation of methomyl (2, 3). In this passive dosimetry study of tangerine growers, during mixing and overhead spraying of a 90% powder formulation of methomyl, ocular and nasal exposure was measured. Exposure data are discussed in terms of the "potentially absorbed" or "internal dose".

Adolescent↗
PubMed1984

Effects of Methomyl and Helminthosporium maydis Toxin on Matrix Volume, Proton Motive Force, and NAD Accumulation in Maize (Zea mays L.) Mitochondria.

Methomyl and Helminthosporium maydis race T toxin block oxidative phosphorylation in mitochondria isolated from maize plants with Texas male sterile cytoplasm (T) but not in mitochondria isolated from those with Normal cytoplasm (N) (Bednarski, Izawa, Scheffer 1977 Plant Physiol 59: 540-545). Moreover, they have been reported to cause specific swelling in T mitochondria (Miller, Koeppe 1971 Science 173: 67-69; Koeppe, Cox, Malone 1978 Science 201: 1227-1229). We could not detect, by direct volume measurements, any change induced by these compounds in the mitochondrial matrix space. We show here that the proton motive force, which in maize mitochondria is composed of a large transmembrane potential and of a low transmembrane pH difference, is absent in T mitochondria incubated in the presence of methomyl or of Helminthosporium maydis race T toxin, while it is unchanged in N mitochondria. Methomyl and Helminthosporium maydis race T toxin induce, independently of the collapse of the proton motive force, a release of the cofactors NAD and coenzyme A from the mitochondrial matrix space. In particular, we show that NAD is transported in maize mitochondria, and that this transport, which is not dependent on the proton motive force, is inhibited by methomyl or Helminthosporium maydis race T toxin.

Journal Article↗
PubMed1985

Mode of Methomyl and Bipolaris maydis (race T) Toxin in Uncoupling Texas Male-Sterile Cytoplasm Corn Mitochondria.

Bipolaris maydis race T toxin (BmT), and its functional analog, methomyl, uncoupled Texas male-sterile (T) cytoplasm mitochondria by decreasing the resistance of the inner membrane to protons. However, unlike protonophoric or ionophoric agents, BmT toxin and methomyl induced irreversible swelling. Packed volume measurements showed that mitochondrial volume was irreversibly increased by methomyl and BmT toxin indicating that mitochondria no longer functioned as differentially permeable osmometers. The decreased resistance of inner mitochondrial membranes to protons and the loss of osmotic volume regulation suggests that methomyl and BmT toxin induced the formation of hydrophilic pores in T mitochondrial inner membranes.

Journal Article↗
PubMed2002

An outbreak of food-borne illness associated with methomyl-contaminated salt.

CONTEXT: On January 5, 1999, the California Department of Health Services was notified of the repeated occurrence (December 21, 1998, and January 2, 1999) of gastrointestinal tract illness among patrons at a Thai restaurant in central California. OBJECTIVE: To identify the source of the outbreak. DESIGN: Case-control study; microbiological and toxicological laboratory testing of samples of food, stool, and vomitus. SETTING: Thai food restaurant in central California. PARTICIPANTS: Patrons of the restaurant. A case (n = 107) was defined as dizziness, nausea, or vomiting occurring in a person who ate at the restaurant between December 20, 1998, and January 2, 1999, with onset of symptoms within 2 hours of eating. A control (n = 169) was a person who ate at the restaurant during the same period but reported no symptoms. MAIN OUTCOME MEASURES: Odds ratios (ORs) of illness associated with food exposures; ORs of shifts during which illness occurred associated with certain cooks; laboratory results. RESULTS: The median latency period was 40 minutes from beginning eating to first symptom and was 2 hours to onset of diarrhea. The median duration of symptoms was 6 hours. Twenty-six persons (24%) visited the emergency department or were treated by a physician; no person required hospitalization. Patients reported nausea (95%), dizziness (72%), abdominal cramps (58%), headache (52%), vomiting (51%), chills (48%), and diarrhea (46%). Fifty-one cases (48%) included dizziness, lightheadedness, or a feeling of disequilibrium as the initial symptom. Illness was statistically associated with several foods and ingredients, but no single dish or ingredient explained a substantial number of cases. The analysis of food exposures included salt added by cooks, as estimated by using the amount of salt in the recipe for each dish and the amount of each dish eaten by respondents. This association was stronger with increasing levels of salt: ORs for illness among persons who consumed more than 0.42 to 0.84, more than 0.84 to 1.25, and more than 1.25 tsp of salt added to foods in the kitchen were 1.9 (95% confidence interval [CI], 0.6-5.7), 3.0 (95% CI, 1.0-8.8), and 4.0 (95% CI, 1.3-13.5) compared with persons who consumed less than 0.42 tsp (P value for trend =.004). Methomyl, a highly toxic carbamate pesticide, was identified in a sample of vomitus (20 ppm) and in salt taken from containers in the storeroom (mean, 5600 ppm) and the stovetop (mean, 1425 ppm). The oral toxic dose causing illness in 50% of those exposed to methomyl was estimated to be 0.15 mg/kg of body weight (estimated range, 0.09-0.31 mg/kg of body weight). The presence of cook A was associated with shifts during which cases of illness occurred (OR, 10.4; 95% CI, 1.2-157.4). CONCLUSION: This outbreak of gastrointestinal illness was associated with the consumption of food seasoned with methomyl-contaminated salt. To allow rapid assessment for further investigational and control measures by health officials, physicians should report suspected outbreaks of illness to public health departments, however trivial the symptoms or cause may seem.

California↗
PubMed1990

Expression in yeast of the T-urf13 protein from Texas male-sterile maize mitochondria confers sensitivity to methomyl and to Texas-cytoplasm-specific fungal toxins.

The mitochondrial gene T-urf13 from maize (Zea mays L.) with Texas male-sterile (T) cytoplasm codes for a unique 13 kd polypeptide, T-URF13, which is implicated in cytoplasmic male sterility and sensitivity to the insecticide methomyl and to host-specific fungal toxins produced by Helminthosporium maydis race T (HmT toxin) and Phyllosticta maydis (Pm toxin). A chimeric gene coding for T-URF13 fused to the mitochondrial targeting peptide from the Neurospora crassa ATP synthase subunit 9 precursor was constructed. Expression of this gene in the yeast Saccharomyces cerevisiae yielded a polypeptide that was translocated into the membrane fraction of mitochondria and processed to give a protein the same size as maize T-URF13. Methomyl, HmT toxin and Pm toxin inhibited growth of yeast cells expressing the gene fusion on medium containing glycerol as sole carbon source and stimulated respiration with NADH as substrate by isolated mitochondria from these cells. These effects were not observed in yeast cells expressing T-URF13 without a targeting peptide. The results show that T-URF13 is sufficient to confer sensitivity to methomyl and the fungal toxins in a heterologous eukaryotic system, and suggest that mitochondrial localization of T-URF13 is critical for these functions.

Amino Acid Sequence↗
PubMed2001

Evaluation of chronic exposure of the male rat reproductive system to the insecticide methomyl.

Carbamate insecticides are widely used in industry, agriculture and for public health purposes. Numerous incidents of acute carbamate poisoning have resulted from inhalation of sprays or contamination of crops or food. This work was conducted to study the effect of chronic exposure to methomyl on hormonal, histopathological and histochemical changes in rat testes. The treated group received methomyl orally (17 mg kg(-1)in saline) daily for 2 months, while the control group received saline. A significant decrease in the level of testosterone was observed in the intoxicated animals, while the levels of FSH, LH and prolactin were significantly increased. Histopathological studies of the intoxicated rat testes revealed variable degrees of degenerative changes in the seminiferous tubules up to total cellular destruction. As regards the histochemical results, it was found that both acid phosphatase and alpha esterase enzyme activity was significantly increased compared to the control group. On the other hand succinic dehydrogenase enzyme activity was significantly reduced. No significant change was observed in alkaline phosphatase enzyme activity. The hormonal changes and testicular damage continued for 30 days after withdrawal of the insecticide indicating a persistent effect. From the above-mentioned findings, it has been concluded that chronic exposure to methomyl insecticide has deleterious effects on rat testes. Therefore application of such insecticide should be limited to a designed program with special care in handling to limit or minimize its hazards.

Acid Phosphatase↗
PubMed2000

Reduction of azinphos-methyl, chlorpyrifos, esfenvalerate, and methomyl residues in processed apples.

McIntosh, Red Delicious, and Golden Delicious from two years of experimental spray programs using azinphos-methyl, chlorpyrifos, esfenvalerate, and methomyl were processed into frozen apple slices, applesauce, single-strength juice, and juice concentrate. Residue levels were expressed as micrograms per 150 g of apple or the equivalent amount of apple product to calculate the percentage change in these pesticides brought about by processing. Producing single-strength apple juice reduced azinphos-methyl, chlorpyrifos, esfenvalerate, and methomyl residues by 97.6, 100, 97.8, and 78.1%, respectively. Production of applesauce reduced all four compounds by >/=95%. Azinphos-methyl, chlorpyrifos, esfenvalerate, and methomyl residues were reduced in apple slices by 94.1, 85.7, 98.6, and 94.7%, respectively. Processing is shown to be very effective in reducing the levels of these pesticides.

Azinphosmethyl↗
PubMed2006

Photocatalytic degradation of pesticide methomyl: determination of the reaction pathway and identification of intermediate products.

The degradation of pesticide methomyl in aqueous solution by UV-irradiation in the presence of TiO2 "Degussa P-25" has been studied. It was found that mineralisation to carbon dioxide, water, sulfate and ammonia took place during the process. The rate of photodecomposition of methomyl was measured using high performance liquid chromatography (HPLC), while its mineralization was followed using ion chromatography (IC), and total organic carbon (TOC) analysis. The identification of reaction intermediate products was carried out using coupled techniques HPLC-MS (electrospray ionization in positive mode) and a degradation pathway was proposed. Under our conditions, complete disappearance of 1.23 x 10(-4) mol l(-1) of pure pesticide occurred within 45 min of illumination and 80% TOC removal occurred in less than 4 h. Three main intermediates were identified resulting from (i) the rupture of the ester bond (or the N-O bond), (ii) the hydroxylation of methyl group borne by the nitrogen atom and (iii) the product resulting from the decarboxylation of the oxidized hydroxylated methyl group (photo-Kolbe reaction). In order to be sure that the photocatalytic results were consistent, hydrolysis and photolysis tests were performed. Photocatalysis proved to be an excellent new advanced oxidation technology (AOT) to eliminate methomyl present in water.

Biodegradation, Environmental↗
PubMed2003

An outbreak of food-borne illness due to methomyl contamination.

BACKGROUND: On December 26, 2002, 124 dinners took ill while eating lunch at a seafood restaurant in the town of Chiching in Kaohsiung municipality of Taiwan. Sixty-nine people were sent to the emergency departments of the Municipal Chiching Hospital and Yuan's General Hospital. METHODS: We analyzed the clinical symptoms, detailed food history, and ingested amount of each food from 59 hospitalized adult patients and identified the source of the outbreak. RESULTS: The median latency period from beginning eating to first symptoms was 5 min. Twenty-six symptoms and signs were recorded. The most commonly reported clinical effects were general weakness (84%), ataxia (82%), dizziness (82%), vomiting (80%), sweating (75%), floating sensation (71%), headache (69%), dyspnea (69%), and blurred vision (67%). Thirty-one patients had residual symptoms 7 days after ingestion. Of the six residual symptoms reported, the most frequent ones were dizziness (40%), poor appetite and dry mouth (11%), and gastrointestinal disturbance (11%). The presence of residual symptoms correlated with the severity of the initial complaints (p < 0.01). Almost all patients ate cooked rice (93%) and leaf vegetable stir-fried with crab claw (93%). The amount of each food eaten by the patients was not associated with the severity of symptoms (p > 0.05). High levels of methomyl in leaf vegetables of "leaf vegetables stir-fried with crab claws" (380 ppm) and fried mussels (1113 ppm) were found by the Food Inspection Center at the Department of Health. The food history and chemical analysis of the poison indicated methomyl was the cause of this outbreak. Twenty-four patients recovered completely within 7 days. CONCLUSION: Food-related methomyl intoxication produced a rapid onset of significant clinical toxicity in 124 individuals. Based on the analysis of 55 adult patients, the most common effects were gait ataxia, dizziness, generalized weakness, and vomiting.

Adult↗
PubMed1979

A fatal episode of accidental methomyl poisoning.

Three fatalities from the accidental ingestion of methomyl, a carbamate pesticide, are reported. The methomyl had been stored in an unlabeled tin can and was accidentally used in preparing "roti," an Indian dish. The identification of the source of the poison through animal tests and further chemical identification is described. The lethal dose of methomyl was estimated to have been between 12 and 15 mg/kg body weight.

Accidents↗
PubMed2005

Methomyl-induced severe acute pancreatitis: possible etiological association.

CONTEXT: N-methyl carbamate insecticides are widely used in homes, gardens and agriculture. They share the capacity to inhibit cholinesterase enzymes with organophosphates and therefore share similar symptomatology during acute and chronic exposures. One of the serious effects of organophosphate and carbamate intoxication is the development of acute pancreatitis and subsequent intrapancreatic fluid formation. CASE REPORT: An 18-year old Caucasian man was admitted to our Intensive Care Unit with cholinergic crisis symptomatology, after the ingestion of an unknown amount of a carbamate insecticide (methomyl). Pseudocholinesterase levels were 2 kU/L on the day of admission (reference range: 5.4-13.2 kU/L). Two days after admission, an abdominal CT scan revealed blurring of the peripancreatic fat planes, inflammation and swelling of the pancreas, and a substantial amount of ascitic fluid in the left anterior pararenal space and pelvis. Paracentesis and analysis of the ascitic fluid demonstrated findings diagnostic of pancreatic ascites. There had been no other evident predisposing factors for acute pancreatitis, other than methomyl intoxication. Eleven days after admission, pseudocholinesterase levels returned to normal, while a new abdominal CT scan revealed the formation of intrapancreatic fluid collection. The patient was discharged in good physical condition two weeks after admission. A follow up abdominal CT scan performed one month later showed a significant reduction in the size of the intrapancreatic fluid. DISCUSSION: Acute pancreatitis is not uncommon after organophosphate intoxication and carbamates share the same risk as organophosphorus pesticides. The development of acute pancreatitis and subsequent intrapancreatic fluid collection after methomyl intoxication has not previously been reported. This is the first case reported of acute pancreatitis and pancreatic ascite formation after anticholinesterase insecticide ingestion.

Acute Disease↗
PubMed1982

Influence of various solvent-water mixtures on the extraction of dieldrin and methomyl residues from radishes.

The effect of organic solvent/water ratios on the extraction of field-incurred residues of dieldrin and methomyl from radishes was determined. 14C-Dieldrin and 14C-methomyl were applied separately to radishes in commercial formulations at rates of 0.2 and 0.9 kg/ha, respectively. Fourteen days post-application, the radishes were harvested and fresh root tissues were extracted using a Polytron homogenizer. Acetone, acetonitrile, and methanol containing 0, 10, 20, 30, 40, and 50% water were used as extraction solvents. For methomyl residues, the optimum water content of acetonitrile-water extraction mixtures was 40-50%; less than 40% water reduced the ability of acetonitrile to extract carbon-14. Methanol and acetone were nearly as efficient as 50% acetonitrile-water and were apparently not influenced by solvent/water ratios. For dieldrin, low water content slightly reduced the extraction efficiency of acetonitrile, with the optimum water content also being 40-50%. Percentage of water appeared to have little overall effect on methanol extraction efficiency. The extraction efficiency of acetone was lower than that of the other 2 solvents, and this effect was independent of the acetone/water ratio. Approximately 20% of the 14C-dieldrin residue was bound to radish roots 14 days post-application.

Acetone↗
PubMed1977

Spectrophotometric determination of methomyl residues in selected vegetables, grains, and soil.

Methomyl (S-methyl-N-[(methylcarbamoyl) oxy] thioacetimidate) is converted to oxime and hydroxylamine by alkali and acid treatment, respectively. Hydroxylamine is oxidized with iodine in the presence of sulfanilic acid to yield p-diazoniumbenzenesulfonic acid which is coupled with alpha-naphthylamine to form a crimson p-benzenesulfonic acid-azo-alpha-naphthylamine with an absorption maximum at 520 nm. The relationship between absorbance and concentration of methomyl is linear in the range 0.5-10 microgram. The method is sensitive and specific; 0.625 ppm methomyl can be determined in a 40 g sample of selected vegetables, grains, and soil.

Edible Grain↗
PubMedDate not supplied

Determination and degradation of methomyl in tomatoes and green beans grown in greenhouses.

A liquid chromatographic (LC) method using UV detection at 233 nm was used to study the degradation of methomyl in tomatoes and green beans grown in greenhouses. A liquid-liquid extraction with CH2Cl2-methanol (90 + 10, v/v) and a cleanup step with Florisil were combined with LC to isolate, recover, and quantitate the pesticide. Average recoveries obtained at spike levels of 0.03 and 0.40 mg/kg were 83.2-84.7% for tomatoes and 83.3-87.5% for green beans. Determination limits were 0.03 mg/kg for tomatoes and 0.01 mg/kg for green beans. Levels of methomyl residues were studied in tomatoes and green beans grown in an experimental greenhouse to establish the effect of the kind of greenhouse, application dose, species grown, and climatic conditions on the degradation of this pesticide. Analysis of variance showed that doses did not affect the response. The half-life, however, is greater in a flat-roof greenhouse than in an asymmetric-roof greenhouse and is significantly longer for green beans than for tomatoes and longer in winter than in spring. A preharvest time of about 5 days may be suitable for green beans sprayed with methomyl. Tomatoes show residue levels at the time of application lower than Spanish minimum residue levels.

Agriculture↗
PubMed2004

Assessing insecticide resistance and aversion to methomyl-treated toxic baits in Musca domestica L (Diptera: Muscidae) populations in southern California.

Progeny of house flies (Musca domestica L) from ten California poultry operations, three dairies and one horse-riding facility were tested for methomyl- and muscalure-treated bait resistance using up to three different assays: a topical assay, a no-choice feeding assay and a choice feeding assay. LD50 resistance factors from the topical assay, compared with a locally-derived susceptible colony, ranged between 1 and 4. LC50 resistance factors from the no-choice feeding assay ranged mostly between 2 and 5, with one value of 18. Measurable LT50 resistance ratios for female flies in the choice feeding assay ranged from 43 to 159; two populations had <10% mortality at 48h and could not be measured. LT50 resistance ratios for male flies in the choice feeding assay ranged from 26 to 96, and one population was too resistant to measure. A behavioral assay tested the feeding preference of male and female flies provided a dish of sugar and a dish of methomyl- and muscalure-treated bait. Of eight strains tested, females from seven strains and males from six strains showed significant preference for sugar over bait. Behavioral factors appear to be important in the severe resistance of house flies to baits in California.

Alkenes↗