Methamidophos Research Articles

Construction of an efficient molecular enrichment and magnetic separation flow with Fe3O4@Ag@COF for ratiometric SERS detection of methamidophos

As a typical organophosphorus pesticide widely utilized in agricultural production with its residue as enormous threat to human health and environment, methamidophos (MTD) has gained increasing attention in recent years, so, it is necessary to develop an effective strategy to detect MTD from complex matrix. Here, an efficient molecular enrichment and magnetic separation flow was constructed through Fe3O4@Ag@COF (covalent organic framework) for ratiometric SERS detection of MTD. Specifically, Fe3O4@Ag@COF is shown to have a high-density hot-spot region and optimal SERS performance by adjusting the particle size and addition volume of Fe3O4@Ag. COF endows Fe3O4@Ag@COF with a platform for enriching MTD molecules and isolating impurities, allowing the separation of Fe3O4@Ag@COF with MTD molecules from complex matrix by magnetism. More importantly, due to its natural core–shell structure, the Raman peaks of COF can be employed as an internal standard for ratiometric SERS sensing, thereby increasing its analysis accuracy and reliability. Under the optimal extraction method and solvent conditions, the developed detection flow exhibited a wide linear range from 10-4 M to 10-9 M and a low MTD detection limit of 8.3 × 10-5 mg/kg. Furthermore, the SERS sensor had excellent reproducibility and long-term stability with a low relative standard deviation (RSD). In practical application, this detection flow was tested for quantifying trace MTD in green tea samples, with recoveries of 89.54 % to 101.89 % and RSDs below 5 % (n = 5), comparable to the performance of gas chromatography mass spectrometry (GC–MS).

Removal of acephate and methamidophos from water: Coagulation and adsorptive treatment approaches

Pesticides has transformed the agricultural industry, primarily by enhancing productivity. However, the indiscriminate use of such compounds can adversely affect human health and disrupt ecosystem balance. Limited knowledge exists regarding the removal of these compounds from water, particularly for organophosphate pesticides when employing conventional treatment technologies. Therefore, this study aimed to assess the removal of acephate (ACE) and methamidophos (MET) - considered priority pesticides in Brazil - from waters with high and low turbidity during the clarification process carried out with aluminum sulfate (AS) and ferric chloride (FC), either alone or combined with powdered activated carbon (PAC) adsorption. All water samples were submitted to solid phase extraction (SPE C18 cartridges) prior to acephate and methamidophos analysis by HPLC MS/MS. The clarification process with either AS or FC coagulant did not efficiently remove acephate or methamidophos and maximum average removal (27 %) was observed with waters of high turbidity when using ferric chloride as coagulant. Addition of mineral PAC was also ineffective for removing both pesticides. However, the use of vegetable PAC (10 mg/L) resulted in better removal percentages, up to 80%, but only for methamidophos. The limited removal rates were attributed to the high hydrophilicity of acephate and methamidophos, along with their neutral charge at coagulation pH. These factors hinder the interaction of such organophosphorus pesticides with the flocs formed during coagulation as well as with PAC surface.

Gold nanoparticle-based selective and efficient spectrophotometric assay for the insecticidemethamidophos.

Areliable, rapid, and inexpensive nano-sized chemosensor is presentedfor methamidophos (MET)-an insecticide. Poly(lactic acid) (PLA)-stabilized gold nanoparticles (AuNPs) were synthesized by a simple one-pot, two-phase chemical reduction method. The synthesized PLA-AuNPs were subsequently employed for selective, efficient, and quantitative detection of MET. MET is one of the highly toxic pesticides used for eradication of agricultural and urban insects. Upon the addition of MET, the wine-red color of PLA-AuNPs swiftly transformed into greyish-blue, further corroborated by a significant bathochromic and hyperchromic shift in the SPR band. The presence of other interfering insecticides, metal salts, and drugs did not have any pronounced effect on quantitative MET detection. The detection limit, the quantification limit, and linear dynamic range of MET utilizing PLA-AuNPs were 0.0027µM, 0.005µM, and 0.005-1000µM, respectively. ThePLA-AuNP-based assay renders an efficient, rapid, accurate, and selective quantification of MET in food, biological, and environmental samples. The proposed sensor provides an appropriate platform for fast and on-the-spot determination of MET without requiring a well-equipped lab setup.

Metal Coordination-Driven Supramolecular Nanozyme as an Effective Colorimetric Biosensor for Neurotransmitters and Organophosphorus Pesticides.

Analytical methods for detecting neurotransmitters (NTs) and organophosphorus (OP) pesticides with high sensitivity are vitally necessary for the rapid identification of physical, mental, and neurological illnesses, as well as to ensure food safety and safeguard ecosystems. In this work, we developed a supramolecular self-assembled system (SupraZyme) that exhibits multi-enzymatic activity. SupraZyme possesses the ability to show both oxidase and peroxidase-like activity, which has been employed for biosensing. The peroxidase-like activity was used for the detection of catecholamine NTs, epinephrine (EP), and norepinephrine (NE) with a detection limit of 6.3 µM and 1.8 µM, respectively, while the oxidase-like activity was utilized for the detection of organophosphate pesticides. The detection strategy for OP chemicals was based on the inhibition of acetylcholine esterase (AChE) activity: a key enzyme that is responsible for the hydrolysis of acetylthiocholine (ATCh). The corresponding limit of detection of paraoxon-methyl (POM) and methamidophos (MAP) was measured to be 0.48 ppb and 15.8 ppb, respectively. Overall, we report an efficient supramolecular system with multiple enzyme-like activities that provide a versatile toolbox for the construction of sensing platforms for the colorimetric point-of-care detection of both NTs and OP pesticides.

The Role of Brain Methamidophos in Acephate Poisoning in Mice.

We gave mice a 540 mg/kg dose of LD50 acephate, followed by an assessment of acephate, methamidophos (MP), and choline esterase (ChE) activity for up to 4 hours (hr) in order to investigate the time course of acephate intoxication. At 1 hr, the blood acephate and MP levels were 428 ± 90 µg/ml (mean ± SEM) and 4.2 ± 0.4 µg/ ml, respectively. The liver acephate levels were similar to those in the blood, but the liver MP levels were approximately 3.5 times that of the blood at 1 hr. The brain MP level tended to be higher than the blood MP at 1 hr. These levels decreased gradually over 4 hr, but the brain acephate and MP levels surpassed the blood levels significantly at 4 hr, and after 2 hr, respectively. Serum, liver, cerebrum, cerebellum, and brainstem cholinesterase activity (ChE) were inhibited at 1 hr, and remained inhibited in all but the cerebellum until the end of the experiment. The obtained data were applied to previously reported autopsy cases of acephate intake. Experimental data suggest that brain MP is involved in acute acephate-induced poisoning, even after a reduction in blood acephate. In autopsy cases with suspected acephate poisoning, the MP level in the brain should be considered in addition to the ChE activity to diagnose the cause of death.

Simultaneous degradation of triazophos, methamidophos and carbofuran pesticides in wastewater using an Enterobacter bacterial bioreactor and analysis of toxicity and biosafety

Triazophos (TAP), methamidophos (MAP) and carbofuran (CF) pesticides are highly toxic, soluble and absorbable. Efficient co-degradation of multi-pesticides is rare reported. The objectives of this study were to investigate TAP, MAP and CF co-degradative ability of Enterobacter sp. Z1 and study the degradation mechanisms. Strain Z1 was shown to efficiently co-degrade TAP, MAP and CF when they were used as primary carbon sources. The degradation occurred over a wide range of temperatures, pH values and pesticide concentrations and followed first-order kinetics. Under the optimum conditions (37 °C, pH 7 and 100 mg/L of each pesticide), the degradation efficiencies were 100%, 100%, and 95.3% for TAP, MAP and CF, respectively. In addition, strain Z1 could simultaneously degrade TAP, MAP, CF and total nitrogen in wastewater in a batch bioreactor, with high removal efficiencies of 98.3%, 100%, 98.7% and 100%, respectively. Genomics, proteomics, qRT-PCR and gene overexpression analyses revealed that the degradation mechanisms involved the activities of multiple proteins, among which, organophosphorus hydrolase (Oph) and 3-hydroxyacyl-CoA dehydrogenase (PaaC) are primarily responsible for TAP and MAP degradation, while carbofuran hydrolase (Mcd) and amidohydrolase (RamA) primarily degrade CF. Among these enzymes, PaaC and RamA are newly identified pesticide-degrading enzymes. Toxicity assays of strain Z1 using reporter recombinase gene (recA) and zebrafish showed that there was no accumulation of toxic metabolites during the degradation process. Biosafety test using zebrafish showed that the strain was nontoxic toward zebrafish. Strain Z1 provides a good purification effect for pesticides-containing wastewater and novel microbial pesticide-degrading mechanisms were discovered.

Short- and long-term exposure to methamidophos impairs spermatogenesis in mice

Methamidophos (MET) is a pesticide that has toxic properties, including effects on fertility. This study aimed to assess the joint action of treatment time and exposure to methamidophos on the male reproductive system. MET was orally administered to adult male Swiss mice at a dose of 0.004 mg.kg−1 for 15 and 50 consecutive days. The following parameters were evaluated: weight of reproductive organs, spermatogenesis, sperm and Sertoli cell count, daily sperm production and sperm transit time. Short-term exposure to methamidophos induced a decrease in epididymal weight. The frequency of stages V–VI of spermatogenesis increased and the frequency of stage IX decreased. In the epididymis, sperm transit time (caput/corpus) was reduced and the relative sperm number (cauda) increased. Long-term exposure induced an increase in the frequencies of stages I–IV and V-VI and decreased the stages VII-VIII and IX. The number of Sertoli cells with evident nucleoli was reduced in both exposures. These results confirm the reproductive toxicity of MET.

A fast room temperature single step nano-gold synthesis in organic phase for rapid detection of methamidophos in water

The study claims to exploit nanomaterials based fast sensing strategy at liquid-liquid interface for pesticide residues in short analytical time. Herein, a rapid extractive spectrometric platform for the trace levels determination of methamidophos (MET) in water has been established. It was based on the room temperature formation of nano-gold particles (AuNPs(org)) in organic phase (CHCl3) by ascorbic acid as a reducing agent and hexadecyl trimethyl ammonium bromide (HTAB) as a phase transfer agent at pH 10–11. The method employs response surface methodology (RSM) based on central composite design (CCD) for selecting appropriate conditions for optimal reagent functioning and liquid microextraction pretreatment factors. Traces of MET influences the surface plasmon absorbance of the formed AuNPs(org) at λmax = 520 nm with consequent lowering of the color. The stability for the formed AuNPs(org), influence of temperature (298–338 K), TEM and EDS analysis were carefully performed. Under the optimized CCD experimental conditions, the obtained linear calibration range was 0.01–0.25 μg mL−1 with a limit of detection (LOD) 3.30 × 10−3 μg mL−1 and limit of quantification (LOQ) 0.011 μg mL−1. A relative standard deviation (RSD) of 2.29 (n = 5) at 0.20 μg mL−1 of MET was obtained. The developed method was successfully applied for the analysis of trace concentrations of MET in environmental water samples with satisfactory recovery percentages (95.14 ± 3.99–103.00 ± 2.78). The suitability of the proposed method was further validated in terms of student t- and F tests at 95% confidence.

The organophosphate pesticide methamidophos opens the blood-testis barrier and covalently binds to ZO-2 in mice

Methamidophos (MET) is an organophosphate (OP) pesticide widely used in agriculture in developing countries. MET causes adverse effects in male reproductive function in humans and experimental animals, but the underlying mechanisms remain largely unknown. We explored the effect of MET on mice testes (5 mg/kg/day/4 days), finding that this pesticide opens the blood-testis barrier and perturbs spermatogenesis, generating the appearance of immature germ cells in the epididymis. In the seminiferous tubules, MET treatment changed the level of expression or modified the stage-specific localization of tight junction (TJ) proteins ZO-1, ZO-2, occludin, and claudin-3. In contrast, claudin-11 was barely altered. MET also modified the shape of claudin-11, and ZO-2 at the cell border, from a zigzag to a more linear pattern. In addition, MET diminished the expression of ZO-2 in spermatids present in seminiferous tubules, induced the phosphorylation of ZO-2 and occludin in testes and reduced the interaction between these proteins assessed by co-immunoprecipitation. MET formed covalent bonds with ZO-2 in serine, tyrosine and lysine residues. The covalent modifications formed on ZO-2 at putative phosphorylation sites might interfere with ZO-2 interaction with regulatory molecules and other TJ proteins. MET bonds formed at ZO-2 ubiquitination sites likely interfere with ZO-2 degradation and TJ sealing, based on results obtained in cultured epithelial cells transfected with ZO-2 mutated at a MET target lysine residue. Our results shed light on MET male reproductive toxicity and are important to improve regulations regarding the use of OP pesticides and to protect the health of agricultural workers.

Molecularly imprinted fluorescent probe based on hydrophobic CdSe/ZnS quantum dots for the detection of methamidophos in fruit and vegetables

AbstractIn this study, a molecularly imprinted polymer (MIP)‐fluorescent probe based on hydrophobic CdSe/ZnS quantum dots (CdSe/ZnS@MIP) was designed and synthesized by bulk polymerization for detecting methamidophos (MAP). The CdSe/ZnS@MIP was characterized by Fourier‐transform infrared spectroscopy, thermo‐gravimetric analysis and adsorption properties, and it exhibited good adsorption capacity and fluorescent stability, and excellent selectivity. Under optimal conditions, the fluorescence showed a good linear decrease in the range of 3.50 × 10−7–0.71 × 10−3 mol/L with a correlation coefficient of 0.995. The limit of detection of the fluorescent probe was 9.16 × 10−8 mol/L, and the relative standard deviation of the method for nine replicate analyses of 4.0 × 10−6 mol/L MAP was 4.1%. Apple and pear samples spiked with MAP at three levels were extracted and determined by the presented method with good recoveries (89.7%–94.9%). The accuracy of the method was verified by gas chromatography for the detection of kidney beans, leek and cucumber samples, and no significant difference was observed for the results of two methods.

Structure and mode of action of organophosphate pesticides: A computational study

Six organophosphate pesticides of high to moderate toxicity (dichlorvos (DCV), dicrotophos (DTP), ethoprophos (EPP), methamidophos (MAP), mevinphos (MVP) and omethoate (OMT)) are computationally studied to determine their structure and up to 12 different mechanisms of reaction with methanol. Methanol is chosen as a surrogate molecule to represent the serine residue and imidazole to represent histidine in the active site of acetylcholinesterase, the target enzyme in the central nervous system of organisms. Transition states (first order saddle points) and intermediates along several plausible reaction pathways are computed, along with activation enthalpies, entropies, and free energies. Pathways for different leaving groups are also analyzed. All geometry optimizations of products, reactants, intermediate complexes, and saddle points were performed using hybrid density functional theory method mPW1B95-44 in conjunction with the 6-31+G(d,p) basis set, with and without a polarized continuum model of implicit solvation. Composite rate constants were calculated using a steady-state analysis for mechanisms with more than one activation barrier. Mechanisms explored fall into two main categories, direct and indirect, all involving proton transfer from the methanol hydroxyl group to the oxygen or sulfur of the leaving group. The indirect proton-transfer mechanism is a Wright-type mechanism (Wright and White, 1998) which relays the proton through the phosphinyl oxygen, and the leaving group is positioned on the opposite side to the incoming hydroxyl nucleophile in a distorted trigonal bipyramidal transition state. We explored mechanisms in which one or two water molecules and/or an imidazole molecule assisted in the proton transfer. Generally speaking, whether direct or indirect, the lowest activation energies were obtained for mechanisms in which the phosphinyl oxygen plays a role in transfer, and additionally water assistance (ubiquitous in the enzyme active site) lowers activation barriers.

Concentrations, sources and pollution characteristic of organic pesticide in soil from typical Chinese Bamboo forest

Concentrations, pollutant characteristics and sources apportionment of organic pesticides (OPs) of fifty one soils from bamboo forest in Zhejiang province, China were investigated. Ten organochlorine(OCPs), three organophosphorus(OPPs), and one pyrethroids (OPYs) were detected. The detection rate (DR %) ranged from 27.27% to 100%, and descended in the order: OCPs>OPPs>OPYs. Concentrations of all OCPs and OPPs were <150 μg.kg−1, while the concentrations of hexachlorocyclohexane (HCH) and 1,1,1‐trichloro‐2,2‐di(4‐chlorophenyl)ethane (DDT) were <50 μg.kg−1, and no recent usage. However, fenvalerate(FEN) had a concentration of 1227 μg.kg−1, the maximal value of all OPs. OPs residue in soil with pH 3.10 ‐ 4.50 was nearly higher than those of soil with pH 4.51 ‐ 5.90. OCPs residue was positive correlated with soil TOC, while OPPs and OPYs residue were influenced markedly by usage and management intensity. The DR %, peak value and ratio of excess standard for methamidophos (MEA) was 82.35%, 33.62 μg.kg−1 and 82.35%, respectively. The residue levels of MEA accounted for 70.87% of the σ‐OPPs and significantly positively correlated with σ‐OPPs. All results was summarized that OPPs, OPYs and partial of OCPs such as Chlorothalonil (CHL), Dicofol (DIC) was main pollutant and potential to jeopardize the human health, bamboo forest environment and shoot production. © 2016 American Institute of Chemical Engineers Environ Prog, 35: 729–736, 2016

Cytogenotoxicity of selected organophosphate insecticides on HaCaT keratinocytes and NL-20 human bronchial cells.

Organophosphate insecticides (OI) are widely used. To humans the main routes of exposure are skin and inhalation. For this, keratinocytes (HaCaT) and bronchial cells (NL-20) were used as cell culture models to evaluate the effects of OI. The aim of this study was to evaluate the effect of four OI on HaCaT and NL-20 cells: azinphos-methyl, (AM); parathion-methyl (PM); omethoate (OM); and methamidophos (MET). Cells were exposed to 0.1, 1 and 10 μg/μL of each. Results showed a decrease in cell viability in both cell lines. Viability of the NL-20 cell line decreased with the three concentrations of OM. All differences were significant (p < 0.05). Genotoxic damage, evaluated through the comet assay, was observed in both cell lines with AM. NL-20 cell line was more sensitive than HaCaT. Higher concentrations of the insecticides except MET, induced cell death. MET caused DNA damage in HaCaT cells at all concentrations. Differences were significant (p < 0.05). Both cell lines revealed the presence of single membrane vacuoles of different sizes when exposed to 1 μg/μL of each insecticide. Quantitative real time-polymerase chain reaction (RT-qPCR) showed an increase of BN1 gene in HaCaT by effect of AM and MET at 1 μg/μL. In conclusion, all the insecticides induced different levels of cyto and genotoxic effects in both cell lines.

Methamidophos induces cytotoxicity and oxidative stress in human peripheral blood mononuclear cells.

Previous studies have shown that organophosphate pesticide (OP) exposure is associated with oxidative stress. Methamidophos (MET) is an OP widely used in agriculture, which is regarded as a highly toxic pesticide and it is a potent inhibitor of acetylcholinesterase. The aim of this study was to evaluate whether MET can induce oxidative stress at low concentrations in primary cultures of human peripheral blood mononuclear cells (PBMCs). PBMCs from healthy individuals were exposed to MET (0-80 mg/L) for 0-72 h. We performed the MTT and neutral-red assays to assess the cytotoxicity. As indicators of oxidative stress, the levels of reactive oxygen species (ROS) were assessed using flow cytometry, and the malondialdehyde (MDA) and reduced glutathione (GSH) levels were determined. MET decreased the viability of PBMCs in a dose-dependent manner. At concentrations of 3, 10, or 20 mg/L for 24 h, MET increased the ROS production significantly compared with the vehicle control. Similarly, MET increased the levels of MDA at the same concentrations that increased ROS (10 and 20 mg/L); however, no changes in GSH levels were observed. These results suggest that MET increased the generation of oxidative stress in PBMCs. © 2015 Wiley Periodicals, Inc. Environ Toxicol 32: 147-155, 2017.

Theoretical study on the degradation mechanism of methamidophos and chloramine phosphorus with OH radicals

Theoretical investigation on the gas-phase degradation reaction mechanism of methamidophos (MAP) and chloramine phosphorus (CHP) with OH radicals is performed. The equilibrium geometries and the harmonic vibration frequencies of the stationary points are obtained at M06-2x/6-31+G(d,p) level, and the higher-level energetic information is further refined at M06-2x/6–311++G(3df,2p) level. The rate constants for the 14 reaction channels are calculated by the improved canonical variational transition state theory with small-curvature tunneling correction over the temperature range 200–2000 K. The three-parameter expressions of k1(T) = 1.53 × 10−19T2.74exp(−1005.12/T), k2(T) = 1.36 × 10−20T3.02exp(−1259.56/T) are given. The total rate constants of all reaction channels of MAP with OH radicals are in good agreement with the available experimental data. Our results indicate that the H-abstraction reactions on methyl are the major channels for the reaction of MAP and CHP with OH radicals. © 2015 Wiley Periodicals, Inc.

Identification of differentially expressed proteins of brain tissue in response to methamidophos in flounder (Paralichthys olivaceus)

Methamidophos (MAP), an organophosphorus pesticide used around the world, has been associated with a wide spectrum of toxic effects on organisms in the environment. In this study, the flounder Paralichthys olivaceus was subjected to 10 mg/L MAP for 72 h and 144 h, and the morphological and proteomic changes in the brain were observed, analyzed and compared with those in the non-exposed control group. Under the light microscope and transmission electron microscope, MAP had evidently induced changes in or damage to the flounder tissues. Gas chromatography analysis demonstrated that the MAP residues were significantly accumulated in the flounder brain tissues. Proteomic changes in the brain tissue were revealed using two-dimensional gel electrophoresis and 27 protein spots were observed to be significantly changed by MAP exposure. The results indicated that the regulated proteins were involved in immune and stress responses, protein biosynthesis and modification, signal transduction, organismal development, and 50% of them are protease. qRT-PCR was used to further detect the corresponding change of transcription. These data may be beneficial to understand the molecular mechanism of MAP toxicity in flounder, be very useful for MAP-resistance screening in flounder culture. According to our results and analyzing, heat shock protein 90 (HSP90) and granzyme K (GzmK) had taken important part in immune response to MAP-stress and could be biomarkers for MAP-stress in flounder.

Effects of ultrasound combined with ozone on the degradation of organophosphorus pesticide residues on lettuce

Methamidophos (MDP) and dichlorvos (DDVP) are organophosphorous pesticides which are commonly used for pest control in agriculture to obtain better yields.

Toxic effects of methamidophos on paraoxonase 1 activity and on rat kidney and liver and ameliorating effects of alpha-tocopherol.

The role of alpha-tocopherol on nephrotoxicity and hepatotoxicity induced by methamidophos (MT) was investigated in wistar rats. Animals were given via gavage, for four weeks, a low dose of MT (MT1), a high dose of MT (MT2), vitamin E (200 mg/kg of bw) or both MT2 plus vitamin E (Vit E) and control group was given distillate water. MT treatment resulted in a significant decrease in the body weight of MT2-treated group. Moreover, MT-treated groups had significantly lower butyrylcholinesterase (p < 0.01) and paraoxonase 1 (PON1) activities compared with the control group (p < 0.05). However, MT2-treated group had significantly higher alkaline phosphatase activity compared with untreated rats (p < 0.05). Both MT-treated groups had significantly higher urea (p < 0.01) and uric acid levels (p < 0.05) compared with the control group. However, significant low uric acid level (p < 0.05) was noted in MT2 plus vit E-treated rats compared with MT2-treated group. Histopathological changes in organ tissues were observed in both MT-treated groups and MT2 plus vit E-treated rats. However, the damage was reduced in MT2 plus vit E-treated rats. Therefore, this study deduces that alpha-tocopherol administration may ameliorate the adverse effects of subacute exposure to MT on rat liver and kidney and this antioxidant can protect PON1 from oxidative stress induced by this organophosphorus pesticide. © 2014 Wiley Periodicals, Inc. Environ Toxicol 31: 842-854, 2016.

Methamidophos alters sperm function and DNA at different stages of spermatogenesis in mice

Methamidophos (MET) is a highly toxic organophosphate (OP) pesticide that is widely used in developing countries. MET has male reproductive effects, including decreased fertility. We evaluated MET effects on sperm quality, fertilization and DNA integrity, exploring the sensitivity of different stages of spermatogenesis. Adult male mice received MET (3.75 or 5mg/kg-bw/ip/day/4days) and were euthanized 1, 28 or 45days post-treatment (dpt) to evaluate MET's effects on epididymal maturation, meiosis or mitosis, respectively. Spermatozoa were obtained from the cauda epididymis–vas deferens and were evaluated for sperm quality, acrosome reaction (AR; Coomassie staining), mitochondrial membrane potential (by JC-1), DNA damage (comet assay), oxidative damage (malondialdehyde (MDA) production), in vitro fertilization and protein phosphorylation (immunodetection), and erythrocyte acetylcholinesterase (AChE) activity. At 1-dpt, MET inhibited AChE (43–57%) and increased abnormal cells (6%). While at 28- and 45-dpt, sperm motility and viability were significantly reduced with an increasing MET dose, and abnormal morphology increased at 5mg/kg/day/4days. MDA and mitochondrial activity were not affected at any dose or time. DNA damage (OTM and %DNA) was observed at 5mg/kg/day/4days in a time-dependent manner, whereas both parameters were altered in cells from mice exposed to 3.75mg/kg/day/4days only at 28-dpt. Depending on the time of collection, initial-, spontaneous- and induced-AR were altered at 5mg/kg/day/4days, and the fertilization capacity also decreased. Sperm phosphorylation (at serine and tyrosine residues) was observed at all time points. Data suggest that meiosis and mitosis are the more sensitive stages of spermatogenesis for MET reproductive toxicity compared to epididymal maturation.

Isolation and Characterization of Three Bacterium Strains for Biodegradation of Methamidophos

In this study, three bacterium strains capable of degrading methamidophos (MAP) were isolated from the soil samples contaminated with organophosphorus pesticides (OPs). According to morphological characteristics, physiological properties, and 16S rDNA sequence analysis, the isolates HS-A32, HS-D36, and HS-D38 were identified as Acinetobacter sp., Pseudomonas stutzeri and Pseudomonas aeruginosa, respectively. They could utilize MAP as the sole carbon and nitrogen source, and the degradation ratio upon 500 mg/L MAP could reach 80% in 3 days under optimal conditions (pH 7.0, 30-35 °C). The strains could use glucose, fructose, ethanol, and galactose as carbon and energy sources, and the favorable nitrogen source included organic and inorganic nitrogen. Further studies showed that the three strains could degrade various OPs. The characterized strains with broad-spectrum OP-degrading activities could be useful for the biodegradation of MAP and the other OPs.