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Toxicology Dec 2012This work evaluated the potential of the isoforms of methamidophos to cause organophosphorus-induced delayed neuropathy (OPIDN) in hens. In addition to inhibition of... (Comparative Study)
Comparative Study
Biochemical, histopathological and clinical evaluation of delayed effects caused by methamidophos isoforms and TOCP in hens: ameliorative effects using control of calcium homeostasis.
This work evaluated the potential of the isoforms of methamidophos to cause organophosphorus-induced delayed neuropathy (OPIDN) in hens. In addition to inhibition of neuropathy target esterase (NTE) and acetylcholinesterase (AChE), calpain activation, spinal cord lesions and clinical signs were assessed. The isoforms (+)-, (±)- and (-)-methamidophos were administered at 50mg/kg orally; tri-ortho-cresyl phosphate (TOCP) was administered (500mg/kg, po) as positive control for delayed neuropathy. The TOCP hens showed greater than 80% and approximately 20% inhibition of NTE and AChE in hen brain, respectively. Among the isoforms of methamidophos, only the (+)-methamidophos was capable of inhibiting NTE activity (approximately 60%) with statistically significant difference compared to the control group. Calpain activity in brain increased by 40% in TOCP hens compared to the control group when measured 24h after dosing and remained high (18% over control) 21 days after dosing. Hens that received (+)-methamidophos had calpain activity 12% greater than controls. The histopathological findings and clinical signs corroborated the biochemical results that indicated the potential of the (+)-methamidophos to be the isoform responsible for OPIDN induction. Protection against OPIDN was examined using a treatment of 2 doses of nimodipine (1mg/kg, i.m.) and one dose of calcium gluconate (5mg/kg, i.v.). The treatment decreased the effect of OPIDN-inducing TOCP and (+)-methamidophos on calpain activity, spinal cord lesions and clinical signs.
Topics: Acetylcholinesterase; Administration, Oral; Animals; Brain; Calcium; Calcium Gluconate; Calpain; Carboxylic Ester Hydrolases; Chickens; Female; Homeostasis; Insecticides; Neurotoxicity Syndromes; Nimodipine; Organothiophosphorus Compounds; Spinal Cord; Time Factors; Tritolyl Phosphates
PubMed: 22974967
DOI: 10.1016/j.tox.2012.08.002 -
Brazilian Journal of Otorhinolaryngology Jun 2012Pesticides are widely used in agriculture, despite the risk of hearing loss related to the exposure to their chemical components. This study looks into protective drugs...
UNLABELLED
Pesticides are widely used in agriculture, despite the risk of hearing loss related to the exposure to their chemical components. This study looks into protective drugs to counteract the ototoxicity of pesticides.
OBJECTIVE
This study aims to analyze the effect ginkgo biloba extract may have in protecting against possible cochlear damage caused by organophosphate pesticides (methamidophos). Anatomic changes are assessed through surface and electron microscopy.
MATERIALS AND METHODS
This is a prospective experimental study. Twenty-one guinea pigs were given saline solution, pesticide, and ginkgo biloba alone or combined for seven consecutive days. Then their cochleas were removed and examined in a scanning electron microscope.
RESULTS
Pesticide-exposed guinea pigs had morphological alterations in their cochleas and injuries in the three turns analyzed through electron microscopy. Injury intensity varied according to the dosages of the agents given to the test subjects. Guinea pigs treated with pesticide and ginkgo biloba maintained the architecture of their outer hair cells in all cochlear turns.
CONCLUSION
The antioxidant properties found in the ginkgo biloba extract protected guinea pigs from pesticide ototoxicity.
Topics: Animals; Cochlea; Ginkgo biloba; Guinea Pigs; Microscopy, Electron, Scanning; Organothiophosphorus Compounds; Pesticides; Plant Extracts; Prospective Studies
PubMed: 22714857
DOI: 10.1590/S1808-86942012000300020 -
Basic & Clinical Pharmacology &... Dec 2012Methamidophos is one of the most toxic organophosphorus (OP) compounds. It acts via phosphorylation of a serine residue in the active site of acetylcholinesterase (AChE)... (Comparative Study)
Comparative Study
Methamidophos is one of the most toxic organophosphorus (OP) compounds. It acts via phosphorylation of a serine residue in the active site of acetylcholinesterase (AChE) and butyrylcholinesterase (BChE), leading to enzyme inactivation. Different oximes have been developed to reverse this inhibition. Thus, our work aimed to test the protective or reactivation capability of pralidoxime and obidoxime, as well as two new oximes synthesised in our laboratory, on human and rat cholinesterases inhibited by methamidophos. In addition, we performed molecular docking studies in non-aged methamidophos-inhibited AChE to understand the mechanisms involved. Our results suggested that pralidoxime protected and reactivated methamidophos-inhibited rat brain AChE. Regarding human erythrocyte AChE, all oximes tested protected and reactivated the enzyme, with the best reactivation index observed at the concentration of 50 μM. Concerning BChE, butane-2,3-dionethiosemicarbazone oxime (oxime 1) was able to protect and reactivate the methamidophos-inhibited BChE by 45% at 50 μM, whereas 2(3-(phenylhydrazono)butan-2-one oxime (oxime 2) reactivated 28% of BChE activity at 100 μM. The two classical oximes failed to reactivate BChE. The molecular docking study demonstrated that pralidoxime appears to be better positioned in the active site to attack the O-P moiety of the inhibited enzyme, being near the oxyanion hole, whereas our new oximes were stably positioned in the active site in a manner similar to that of obidoxime. In conclusion, our work demonstrated that the newly synthesised oximes were able to reactivate not only human erythrocyte AChE but also human plasma BChE, which could represent an advantage in the treatment of OP compounds poisoning.
Topics: Acetylcholinesterase; Animals; Butyrylcholinesterase; Cholinesterase Inhibitors; Cholinesterase Reactivators; Erythrocytes; Humans; Insecticides; Male; Obidoxime Chloride; Organothiophosphorus Compounds; Pralidoxime Compounds; Rats; Rats, Wistar
PubMed: 22703537
DOI: 10.1111/j.1742-7843.2012.00912.x -
Toxicology in Vitro : An International... Sep 2012Organophosphates (OPs), which are widely used as pesticides, are acetylcholinesterase (AChE) and butyrylcholinesterase (BChE) inhibitors. The inactivation of AChE...
Isatin-3-N4-benzilthiosemicarbazone, a non-toxic thiosemicarbazone derivative, protects and reactivates rat and human cholinesterases inhibited by methamidophos in vitro and in silico.
Organophosphates (OPs), which are widely used as pesticides, are acetylcholinesterase (AChE) and butyrylcholinesterase (BChE) inhibitors. The inactivation of AChE results in the accumulation of acetylcholine at cholinergic receptor sites, causing a cholinergic crisis that can lead to death. The classical treatment for OP poisoning is administration of oximes, but these compounds are ineffective in some cases. Here we determined whether the new compound isatin-3-N(4)-benzilthiosemicarbazone (IBTC), which in our previous study proved to be an antioxidant and antiatherogenic molecule, could protect and reactivate AChE and BChE. Toxicity of IBTC after subcutaneous injection in mice was measured using assays for oxidized diclorofluoresceine (DCF), thiobarbituric acid reactive substances (TBARS), non-protein thiol (NPSH) levels, and catalase (CAT), sodium potassium (Na(+)/K(+)) ATPase, delta-aminolevulinic acid dehydratase (ALA-D), and glutathione peroxidases (GPx) enzyme activities. The cytotoxicity was evaluated and the enzymatic activity of cholinesterase was measured in human blood samples. Molecular docking was used to predict the mechanism of IBTC interactions with the AChE active site. We found that IBTC did not increase the amount of DCF-RS or TBARS, did not reduce NPSH levels, and did not increase CAT, (Na(+)/K(+)) ATPase, ALA-D, or GPx activities. IBTC protected and reactivated both AChE and BChE activities. Molecular docking predicted that IBTC is positioned at the peripheral anionic site and in the acyl binding pocket of AChE and can interact with methamidophos, releasing the enzyme's active site. Our results suggest that IBTC, besides being an antioxidant and a promising antiatherogenic agent, is a non-toxic molecule for methamidophos poisoning treatment.
Topics: Animals; Cell Line; Cell Survival; Cells, Cultured; Cholinesterase Inhibitors; Cholinesterase Reactivators; Cholinesterases; Humans; Insecticides; Isatin; Lymphocytes; Male; Mice; Molecular Docking Simulation; Organothiophosphorus Compounds; Sodium-Potassium-Exchanging ATPase
PubMed: 22542756
DOI: 10.1016/j.tiv.2012.04.008 -
PloS One 2012An aerobic bacterium capable of breaking down the pesticide acephate (O,S-dimethyl acetyl phosphoramidothioic acid) was isolated from activated sludge collected from a...
An aerobic bacterium capable of breaking down the pesticide acephate (O,S-dimethyl acetyl phosphoramidothioic acid) was isolated from activated sludge collected from a pesticide manufacturing facility. A phylogenetic tree based on the 16 S rRNA gene sequence determined that the isolate lies within the Pseudomonads. The isolate was able to grow in the presence of acephate at concentrations up to 80 mM, with maximum growth at 40 mM. HPLC and LC-MS/MS analysis of spent medium from growth experiments and a resting cell assay detected the accumulation of methamidophos and acetate, suggesting initial hydrolysis of the amide linkage found between these two moieties. As expected, the rapid decline in acephate was coincident with the accumulation of methamidophos. Methamidophos concentrations were maintained over a period of days, without evidence of further metabolism or cell growth by the cultures. Considering this limitation, strains such as described in this work can promote the first step of acephate mineralization in soil microbial communities.
Topics: Calcification, Physiologic; Carbon; Environment; Hydrolysis; Insecticides; Nitrogen; Organothiophosphorus Compounds; Pesticide Residues; Phosphoramides; Phylogeny; Pseudomonas; Pseudomonas Infections; RNA, Ribosomal, 16S; Soil Microbiology; Sulfur; Tandem Mass Spectrometry
PubMed: 22496729
DOI: 10.1371/journal.pone.0031963 -
Journal of Zhejiang University.... Apr 2012The widespread use of organophosphorus pesticides (OPs) poses a great threat to human health and has made the detection of OP residues in food an important task,...
The widespread use of organophosphorus pesticides (OPs) poses a great threat to human health and has made the detection of OP residues in food an important task, especially in view of the fact that easy and rapid detection methods are needed. Because OPs have inhibitory effects on the activity of α-naphthyl acetate esterase (ANAE) in plants, in this work we evaluated the possibility of detecting OPs in vegetables with ANAE extracted from commercial flour. The limits of detection (LODs) obtained for methamidophos, dichlorvos, phoxim, dimethoate, and malathion in lettuce samples with crude ANAE were 0.17, 0.11, 0.11, 0.96, and 1.70 mg/kg, respectively. Based on the maximum residue limits (MRLs) for OPs in food stipulated by Chinese laws which are 0.05, 0.20, 0.05, 1.00, and 8.00 mg/kg for methamidophos, dichlorvos, phoxim, dimethoate, and malathion, respectively, the esterase inhibition method with crude ANAE had sufficient sensitivity to detect the residues of dichlorvos, dimethoate, and malathion in lettuce, but it could not be used to guarantee the safety of the same samples if methamidophos or phoxim residue was present. The sensitivity of the method was improved by the use of esterase purified by ammonium sulfate salting-out. The LODs obtained for methamidophos and phoxim with purified esterase were lower than the MRLs for these OPs in food. This is a very promising method for the detection of OP residues in vegetables using crude or purified esterase because of its cheapness, sensitivity, and convenience.
Topics: Flour; Food Analysis; Food Contamination; Naphthol AS D Esterase; Organophosphorus Compounds; Pesticides; Plant Extracts; Triticum; Vegetables
PubMed: 22467368
DOI: 10.1631/jzus.B11a0180 -
Journal of Toxicologic Pathology Sep 2011Organophosphates such as methamidophos, usually used in the agricultural field, have harmful effects on humans. Exposures to insecticides has been associated with many...
Organophosphates such as methamidophos, usually used in the agricultural field, have harmful effects on humans. Exposures to insecticides has been associated with many disorders, including damage to the central and peripheral nervous system. Chronic exposure to organophosphates may lead to persistent neurological and neurobehavioral effects. This study was conducted to determine the effect of methamidophos on [(3)H]-dopamine (DA) and gamma aminobutyric acid (GABA) release from different brain regions after chronic exposure to it for 3, 6 or 9 months. After a six-month methamidophos treatment, the mice showed high susceptibility to convulsive seizures and a reduction in stimulated gamma aminobutyric acid release from the cerebral cortex and hippocampal slices, whereas stimulated (DA) release was slightly decreased from the striatum after three months of methamidophos exposure. The results indicate changes in gamma aminobutyric acid and dopamine neurotransmission, suggesting a specific neuronal damage.
PubMed: 22272056
DOI: 10.1293/tox.24.163 -
Applied and Environmental Microbiology Mar 2012De-esterification is an important degradation or detoxification mechanism of sulfonylurea herbicide in microbes and plants. However, the biochemical and molecular...
De-esterification is an important degradation or detoxification mechanism of sulfonylurea herbicide in microbes and plants. However, the biochemical and molecular mechanisms of sulfonylurea herbicide de-esterification are still unknown. In this study, a novel esterase gene, sulE, responsible for sulfonylurea herbicide de-esterification, was cloned from Hansschlegelia zhihuaiae S113. The gene contained an open reading frame of 1,194 bp, and a putative signal peptide at the N terminal was identified with a predicted cleavage site between Ala37 and Glu38, resulting in a 361-residue mature protein. SulE minus the signal peptide was synthesized in Escherichia coli BL21 and purified to homogeneity. SulE catalyzed the de-esterification of a variety of sulfonylurea herbicides that gave rise to the corresponding herbicidally inactive parent acid and exhibited the highest catalytic efficiency toward thifensulfuron-methyl. SulE was a dimer without the requirement of a cofactor. The activity of the enzyme was completely inhibited by Ag(+), Cd(2+), Zn(2+), methamidophos, and sodium dodecyl sulfate. A sulE-disrupted mutant strain, ΔsulE, was constructed by insertion mutation. ΔsulE lost the de-esterification ability and was more sensitive to the herbicides than the wild type of strain S113, suggesting that sulE played a vital role in the sulfonylurea herbicide resistance of the strain. The transfer of sulE into Saccharomyces cerevisiae BY4741 conferred on it the ability to de-esterify sulfonylurea herbicides and increased its resistance to the herbicides. This study has provided an excellent candidate for the mechanistic study of sulfonylurea herbicide metabolism and detoxification through de-esterification, construction of sulfonylurea herbicide-resistant transgenic crops, and bioremediation of sulfonylurea herbicide-contaminated environments.
Topics: Cations, Divalent; Cloning, Molecular; DNA, Bacterial; Enzyme Inhibitors; Escherichia coli; Esterases; Esterification; Gene Deletion; Herbicides; Metals; Methylocystaceae; Molecular Sequence Data; Open Reading Frames; Organothiophosphorus Compounds; Protein Multimerization; Saccharomyces cerevisiae; Sequence Analysis, DNA; Sodium Dodecyl Sulfate; Substrate Specificity; Sulfonylurea Compounds
PubMed: 22247165
DOI: 10.1128/AEM.07440-11 -
Toxicology Feb 2012The current Organisation for Economic Co-operation and Development (OECD) guidelines for evaluating organophosphorus-induced delayed neuropathy (OPIDN) require the... (Comparative Study)
Comparative Study
The current Organisation for Economic Co-operation and Development (OECD) guidelines for evaluating organophosphorus-induced delayed neuropathy (OPIDN) require the observation of dosed animals over several days and the sacrifice of 48 hens. Adhering to these protocols in tests with enantiomers is difficult because large quantities of the compound are needed and many animals must be utilized. Thus, developing an in vitro screening protocol to evaluate chiral organophosphorus pesticides (OPs) that can induce delayed neuropathy is important. This work aimed to evaluate, in blood and brain samples from hens, human blood, and human cell culture samples, the potential of the enantiomeric forms of methamidophos to induce acetylcholinesterase (AChE) inhibition and/or delayed neurotoxicity. Calpain activation was also evaluated in the hen brain and SH-SY5Y human neuroblastoma cells. The ratio between the inhibition of neuropathy target esterase (NTE) and AChE activities by the methamidophos enantiomers was evaluated as a possible indicator of the enantiomers' abilities to induce OPIDN. The (-)-methamidophos exhibited an IC(50) value approximately 6 times greater than that of the (+)-methamidophos for the lymphocyte NTE (LNTE) of hens, and (+)-methamidophos exhibited an IC(50) value approximately 7 times larger than that of the (-)-methamidophos for the hen brain AChE. The IC(50) values were 7 times higher for the human erythrocyte AChE and 5 times higher for AChE in the SH-SY5Y human neuroblastoma cells. Considering the esterases inhibition and calpain results, (+)-methamidophos would be expected to have a greater ability to induce OPIDN than the (-)-methamidophos in humans and in hens.
Topics: Acetylcholinesterase; Animals; Brain; Calpain; Cell Line, Tumor; Chickens; Cholinesterase Inhibitors; Female; Humans; Inhibitory Concentration 50; Insecticides; Least-Squares Analysis; Neurotoxicity Syndromes; Organothiophosphorus Compounds; Stereoisomerism
PubMed: 22198100
DOI: 10.1016/j.tox.2011.12.004 -
Exposure to methamidophos at adulthood adversely affects serotonergic biomarkers in the mouse brain.Neurotoxicology Dec 2011Epidemiologic studies describe a potential risk of depression and suicide in farm workers exposed to organophosphates (OPs). In a previous study we observed an increase...
Epidemiologic studies describe a potential risk of depression and suicide in farm workers exposed to organophosphates (OPs). In a previous study we observed an increase in depressive-like behavior in adult mice exposed to the OP pesticide methamidophos. Considering the association between depression and the serotonergic (5HT) system, in the present study we investigated whether a subchronic exposure to methamidophos affects the serotonergic system of adult mice. From postnatal day 60 to 89 (PN60 to PN89), one of two concentrations of methamidophos (higher dose: 5.25 μg/ml; lower dose: 1.31 μg/ml) or vehicle was administered in the drinking water of male Swiss mice. We evaluated three serotonergic biomarkers during (PN89) and after (PN100) the exposure period: 5HT(1A) receptor binding with [(3)H]OH-DPAT, 5HT(2) receptor binding with [(3)H]ketanserin and 5HT transporter binding with [(3)H]paroxetine. Methamidophos elicited robust decreases in binding for all 5HT markers. These decreases were evident in brain regions containing 5HT cell bodies and dendritic arbors (midbrain, brainstem) as well as in the cerebral cortex, which contains 5HT projections. In the cerebral cortex, effects were identified in mice exposed to the higher dose of methamidophos while in the midbrain and brainstem, both doses elicited significant effects. Overall, effects were present both during and after exposure, even though there were some regional disparities regarding the persistence of effects. Our results indicate that exposure to methamidophos affects synaptic transmission promoting decreases of specific serotonergic biomarkers. These data suggest a mechanism of action of this pesticide that might explain the increased depressive-like behavior in adult mice.
Topics: Age Factors; Animals; Biomarkers; Brain; Depression; Down-Regulation; Insecticides; Male; Mice; Organothiophosphorus Compounds; Receptor, Serotonin, 5-HT1A; Receptors, Serotonin, 5-HT2; Risk Assessment; Risk Factors; Serotonin; Serotonin Plasma Membrane Transport Proteins; Synaptic Transmission; Time Factors
PubMed: 21871486
DOI: 10.1016/j.neuro.2011.08.002