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PubMed2001

Purification and characterization of a dimethoate-degrading enzyme of Aspergillus niger ZHY256, isolated from sewage.

A dimethoate-degrading enzyme from Aspergillus niger ZHY256 was purified to homogeneity with a specific activity of 227.6 U/mg of protein. The molecular mass of the purified enzyme was estimated to be 66 kDa by gel filtration and 67 kDa by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. The isoelectric point was found to be 5.4, and the enzyme activity was optimal at 50 degrees C and pH 7.0. The activity was inhibited by most of the metal ions and reagents, while it was induced by Cu(2+). The Michaelis constant (K(m)) and V(max) for dimethoate were 1.25 mM and 292 micromol min(-1) mg of protein(-1), respectively.

Aspergillus niger↗
PubMed2005

Influence of dimethoate on acetylcholinesterase activity and locomotor function in terrestrial isopods.

Locomotor behavior in terrestrial organisms is crucial for burrowing, avoiding predators, food seeking, migration, and reproduction; therefore, it is a parameter with ecological relevance. Acetylcholinesterase (AChE) is a nervous system enzyme inhibited by several compounds and widely used as an exposure biomarker in several organisms. Moreover, changes in energy reserves also may indicate an exposure to a stress situation. The aim of this study is to link biomarkers of different levels of biological organization in isopods exposed to increasing doses of dimethoate in semifield conditions. Locomotor parameters, AChE activity, and energy reserves (lipid, glycogen, and protein contents) were evaluated in the isopod Porcellio dilatatus after 48-h and 10-d exposure to dimethoate-contaminated soil. Results showed a clear impairment of both locomotor and AChE activity during the entire study, although effects were more pronounced after 48 h. Most locomotor parameters and AChE activity showed a clear dose-response relationship. By contrast, no clear trend was observed on energetic components. A positive and significant relationship was found between AChE activity and those locomotor parameters indicating activity, and the opposite was observed with those locomotor parameters indicating confusion and disorientation. The results obtained in this study enhance the importance of linking biochemical responses to parameters with ecological relevance at individual level, the value of locomotor behavior as an important marker to assess effects of toxicants, and also the usefulness and the acquisition of ecological relevance by AChE as a biomarker, by linking it with ecologically relevant behavioral parameters.

Acetylcholinesterase↗
PubMed2001

The garden snail (Helix aspersa) as a bioindicator of organophosphorus exposure: effects of dimethoate on survival, growth, and acetylcholinesterase activity.

The garden snail (Helix aspersa) is currently used as bioindicator of metallic pollution. Our objective was to extend its use to organic chemicals by studying the effects and tissue concentrations of the organophosphorus pesticide dimethoate following dietary uptake. After exposure for four weeks to increasing doses of pesticide in the diet, the median lethal concentration (LC50) was determined to be 3,700 microg/g food. Clinical signs indicated a no-observed-effect concentration of 100 microg/g and a lowest-observed-effect concentration of 250 microg/g. The growth parameters were decreased with increasing exposure to the pesticide. The median effective concentration (EC50), which was evaluated based on both shell diameter and dry weight inhibitions, was 665 and 424 microg/g, respectively, and the EC10 was 180 and 145 microg/g, respectively. Accumulation in the viscera was related to the amount of dimethoate in the food. The bioconcentration factors were low (>6 x 10(-3)). Acetylcholinesterase (AChE) activity was strongly decreased (80% from 250 microg/g). In conclusion, we demonstrated that the species H. aspersa could be a useful sentinel organism for organophosphorus contamination surveys. Among the effects measured, the inhibition of AChE activities and clinical signs were the most sensitive, followed by the growth parameters. These results confirm the suitability of the garden snail for development of sublethal toxicity tests using primary consumers and aboveground organisms.

Acetylcholinesterase↗
PubMed2005

Early embryogenesis study on a dimethoate containing formulation and Cd-sulphate in chicken embryos.

The toxic effects of a widely used organophosphate insecticide (BI 58 EC containing 38% dimethoate as active ingredient) applied alone or in combination with cadmium sulphate modelling the heavy metal load of the environment were studied on chicken embryos in the early phase of development. Solutions and emulsions of different concentrations were made from the test materials and injected in 0.1 ml volume into the air space of eggs on the first day (day 0) of incubation. Subsequently, on days 2 and 3 of incubation permanent preparations were made from the embryos in order to study the early developmental stage. Embryos fixed on slides and stained with osmium tetroxide solution were studied under light microscope. Summarising the findings, it can be established that the embryotoxicity increased after the simultaneous administration of Cd-sulphate and 38% dimethoate containing insecticide formulation compared to the control or the individually treated groups.

Abnormalities, Drug-Induced↗
PubMed1989

Haematological changes induced by dimethoate in rat.

Chronic effects of a sublethal dose (150 mg/kg body weight) of dimethoate, an organophosphorus insecticide, on blood constituents were investigated in rats after exposure of 15 and 30 days. A significant decrease was observed in haemoglobin concentration, total RBC and WBC counts and in haematocrit values. After 30 days of exposure, the levels of blood glucose, cholesterol, urea, total bilirubin and the activities of glutamic-oxalacetic transaminase, glutamic- pyruvic transaminase and amylase markedly increased, but the activities of acid phosphatase and cholinesterase significantly decreased. There was no effect on total plasma protein content. The rats exposed to dimethoate for 30 days showed more prominent changes in all the blood constituents than those exposed for 15 days.

Animals↗
PubMed1994

Changes of brain evoked potentials caused by dimethoate treatment in three generations of rats.

Wistar rats were continuously treated with 7.0, 10.5, 14.0, and 28.0 mg/kg (1/100, 1/70, 1/50 and 1/25 LD50) of dimethoate per os including the pregnancy and lactation periods for three subsequent generations. The somatosensory, visual and auditory evoked brain potentials of male rats of each generation were registered at the age of 12-13 weeks with silver electrodes placed on the primary somatosensory, visual and auditory cortex. The measured parameters were the latency and duration of the evoked potentials. There were differences in the changes among the various evoked potentials in all of the generations. The strongest effect caused by dimethoate was seen in the case of the somatosensory evoked potentials compared to the control. The changes of the visual and auditory evoked potentials were milder. Comparing the changes of the evoked potentials of the three generations it was found that there were no significant changes between the data of the three populations.

Animals↗
PubMed1988

Uptake of dieldrin, dimethoate and permethrin by cyanobacteria, Anabaena sp. and Aulosira fertilissima.

Blue-green algae showed a poor ability to pick up and concentrate dieldrin and dimethoate. However, the uptake and bioconcentration factor for permethrin was very high. The uptake of dieldrin by Anabaena and Aulosira ranged from 5.1 to 73.2 and 5.5 to 17.4 microg g(-1) (ppm), respectively. The uptake of permethrin was from 9.0 to 249.7 and 4.6 to 1422.5 microg g(-1) by Anabaena and Aulosira, respectively. The highest bioconcentration factors for permethrin in Anabaena and Aulosira were 813 and 2373, respectively. This was followed by the bioconcentration factor of dieldrin (620) and dimethoate (119) in Aulosira fertilissima.

Journal Article↗
PubMed1992

Dermal and inhalation exposure to dimethoate.

Dermal and respiratory exposure and plasma acetylcholinesterase (ChE) activity were monitored on six workers spraying tomato crops under plastic houses with dimethoate [O,O-dimethyl S-(N-methylcarbamoylmethyl) phosphorodithoate]. The mean dermal exposure was 914 mg/day and the mean respiratory exposure was 17 mg/day. The maximum dose received by the spraymen was 18.2 mg/day. It was estimated that 84% of the dermal exposure was to the forearms and hands. Of the body areas monitored, the back of the neck received the least rate of exposure. The results also show a reduction in plasma ChE among spraymen. The mean difference was 37.1% less than the preexposure values, which exceeds the limits set by the World Health Organization.

Administration, Inhalation↗
PubMed1994

Changes of some serum parameters and amino acids content in rats after chronic sublethal doses of dimethoate.

An intraperitoneal repeated dose of dimethoate (O,O-dimethyl S-[N-methylcarbamoyl methyl] phosphorodithioate) was injected to male Wistar rats for 8 successive days. Body weight and liver weight decreased significantly while liver/body weight ratio and mg protein/g liver remained unchanged. Twenty serum amino acids were assayed in blood samples collected from hepatic vein, portal vein, and aorta. Most of the measured amino acids showed a tendency of decrease compared to control. The decrease was significant only for taurine, serine, threonine, methionine, tyrosine, histidine, and arginine but not for the rest of the amino acids measured. Glucose, 3-hydroxybutyrate, urea, ammonia, and lactate were measured in the same serum samples. These serum parameters showed a tendency of decrease (except urea) of them from control but the decrease was not significant.

3-Hydroxybutyric Acid↗
PubMed2005

Apoptosis and biochemical biomarkers of stress in spiders from industrially polluted areas exposed to high temperature and dimethoate.

The aim of this study was to evaluate the relations between apoptosis and the activity of antioxidant enzymes (superoxide dismutase; catalase) and quantitative changes in stress protein positive cells (Hsp70; metallothionein) in midgut glands of funnel web spiders Agelena labyrinthica (Agelenidae) and wolf spiders Pardosa lugubris (Lycosidae) exposed to high temperature and pesticide under laboratory conditions. The spiders were collected from two meadow ecosystems differently polluted with metals (Olkusz and Pilica, southern Poland). Under stress conditions, P. lugubris had fewer apoptotic cells in the midgut glands than A. labyrinthica. In P. lugubris from both sites, the observed increase in the percentage of metallothionein and Hsp70-positive cells, simultaneous with intensification of superoxide dismutase and catalase activity, suggests an anti-apoptotic function of those proteins in representatives of wandering spiders. In the midgut glands of A. labyrinthica, heat shock and dimethoate increased the number of Annexin V-positive cells as well as the amounts of mitochondria with low transmembrane potential (DeltaPsi(m)) versus the control. The changes in the percentage of MT- and Hsp70-positive cells in funnel web spiders were less than in wolf spiders. The absence of change in SOD and CAT activity in A. labyrinthica shows that the participation of those enzymes in antioxidant reactions is minimal in this species.

Animals↗
PubMed2005

High concentrations of pralidoxime are needed for the adequate reactivation of human erythrocyte acetylcholinesterase inhibited by dimethoate in vitro.

Due to the current controversy about the real effectiveness of the oximes in the treatment of organophosphate poisoning, the reactivation capacity of pralidoxime has been evaluated in vitro on human erythrocyte acetylcholinesterase inhibited by dimethoate. In the in vitro model, a partial recovery of acetylcholinesterase activity was observed with concentrations from 0.066 mM pralidoxime, probably useful enough to prevent death in most cases in vivo. However, much more effectiveness was observed with concentrations up to 0.70 mM pralidoxime. Although pralidoxime should be applied as soon as possible after organophosphate exposure, the application of the antagonist can be useful even 24h after, particularly for organophosphates with biological half-life longer than one day. The protective capacity of pralidoxime after the application was reduced up to 50% in 6h and disappeared almost completely in 24h. Furthermore, the pesticide and its metabolites remained active and were able to inhibit the enzyme as soon as pralidoxime reduced its antagonist capacity. Our results in conjunction with the short half-life of pralidoxime suggest that the maintenance of higher plasmatic concentrations than the currently used should be considered in the management of severe poisoned patients, although adverse effects could be expected.

Acetylcholinesterase↗
PubMed2005

Use of benchmark dose and meta-analysis to determine the most sensitive endpoint for risk assessment for dimethoate.

A meta-analysis of several rat toxicity studies for dimethoate was conducted to determine the most sensitive endpoint for use in risk assessment. The analysis was motivated by a recent developmental neurotoxicity (DNT) study, which identified the same no observed adverse effect level (NOAEL) for pup mortality and cholinesterase inhibition. The pup mortality NOAEL was lower than that determined in a range-finding study for the DNT and other reproduction studies, and was highly influenced by a single total litter loss in the middle dose group, which made interpretation difficult. First, a meta-analysis was conducted of four recent studies by gavage dosing with very similar designs, including the DNT. Benchmark dose (BMD) modeling was used to determine the appropriate point of departure for regulatory purposes, the lower limit of the BMD for a 5% incidence for pup mortality (BMDL(5)) and the lower limit of a 10% inhibition of brain cholinesterase (BMDL(10)*), the asterisk denotes that the BMD is based on continuous response variable as opposed to an incidence level. For pup mortality, the BMDL(5) for post-natal days (PND) 1-4 was 0.64 mg/kg/day. For cholinesterase inhibition, the lowest BMDL(10)* was 0.19 mg/kg/day for the dams at gestation day 20. These results show that the regulatory point-of-departure for cholinesterase inhibition is more than threefold lower than pup mortality. Thus, risk assessments protecting against cholinesterase inhibition are likely to also be protective of pup mortality. In addition, cholinesterase inhibition and pup mortality were evaluated in two 2-generation reproduction studies by dietary exposure. Also, cholinesterase inhibition was evaluated in a 28-day dietary study. Dietary exposure is more relevant than gavage exposures for many human risk assessment scenarios. There was no consistent pup mortality at the highest doses of the two 2-generation dietary studies (6.0 and 6.5mg/kg/day). The average BMD(10)s for brain cholinesterase inhibition for the 2-generation studies was 0.65 mg/kg/day, with a range of 0.49--0.96 mg/kg/day. This suggests that cholinesterase inhibition is at least a 10-fold more sensitive endpoint than pup mortality for dietary exposures. For the 28-day dietary study, the BMD(10) for brain cholinesterase inhibition was 1.1mg/kg/day for males and 0.70 mg/kg/day for females. The exposure duration in the 28-day dietary study is closest to the durations in the gavage studies. Compared to the dams in the gavage studies, which had a BMDL(10) of 0.19 mg/kg/day, the animals were more than threefold more sensitive to cholinesterase inhibition by gavage compared to dietary exposure.

Age Factors↗
PubMed2005

Photo-fenton assisted reaction of dimethoate in aqueous solutions.

The photo-Fenton reaction of an organophosphorus insecticide, dimethoate (O,O-dimethyl methylcarbamoylmethyl phosphorodithioate), was studied by following the identification and determination of the decomposition products and the total carbon removal rate. The reactions were performed in a batch recycle reactor, at room temperature, using UV radiation, H2O2 as oxidant, and FeCl3 x 6H2O as catalyst. The oxidation results were determined with a total organic carbon (TOC) analyzer and ion chromatography. The presence of reaction products was identified by gas chromatography-mass spectrometry (GC-MS). Apart from the sulfate, phosphate, and ammonium ions, the presence of dimethyl phosphite, N-methyl-acetamide, and formic acid was also detected. Excess of H2O2 concentration did not influence the reaction rate. The expression for the total carbon removal was assessed and the TOC removal rate constants were calculated.

Dimethoate↗
PubMed2001

Gas chromatographic method for assessing the dermal exposure of greenhouse applicators to dimethoate and malathion.

An analytical method is developed to determine potential and actual dermal exposure to dimethoate and malathion for agricultural workers using whole body dosimetry. The methodology described includes three different aspects: the validation of the analytical method incorporating a matrix effect for establishing performance parameters such as recovery rates (between 92% and 103% for both pesticides), limits of detection and quantitation, and precision of measurements (RSD < 10%); a field sampling strategy developing a procedure for collecting samples and carrying out field spikes and field blanks in order to ensure the stability of samples during transport, storage, and analysis; and finally, a quality control procedure for ensuring that data are under statistical control. The method is applied to evaluate the potential and actual dermal exposure as well as its distribution for a pesticide applicator and the applicator's assistant after a greenhouse application. Operator exposure levels of approximately 68 mL/h, and 25 mL/h in the case of the assistant, are found. The body areas most exposed are the lower body and hands.

Agriculture↗
PubMed1990

A case of unusual suicidal poisoning by the organophosphorus insecticide dimethoate.

A 20-year-old male who attempted suicide by injecting subcutaneously 10 ml of Sistemin 40 (40% dimethoate) was admitted 16 h later. General weakness, muscular fibrillations and a marked inhibition of red blood cell and serum cholinesterases were the prominent signs of intoxication. The antidotal treatment of intermittent boluses of atropine, oxime HI-6 and diazepam was combined with symptomatic therapy. Cholinesterase activity decreased within the next 3 d. In contrast to the marked general improvement of the patient, the return of cholinesterase activities was very slow. The patient was discharged 24 d after the poisoning with no notable consequences which could be ascribed to the intoxication.

Adult↗
PubMed1995

Immunotoxicity study of repeated small doses of dimethoate and methylparathion administered to rats over three generations.

Immunotoxic effects of chronic, equitoxic doses (1/50, 1/75, and 1/100 LD50) of two organophosphorus pesticides dimethoate (DM) and methylparathion (MPT) (14.1, 9.39, and 7.04 mg kg-1 DM; and 0.436, 0.291, and 0.218 mg kg-1 MPT) were investigated in a three generation study in outbred Wistar rats. Treatment of the first generation (G1) with these doses began in animals 4 weeks of age; the parental males were dosed until separation of females, and after mating the females were treated until separation of their G2 offspring (at the age of 4 weeks), and the G3 generation was produced in the same way from treated parental G2 animals. Selected 4 week old males from each generation were also treated with DM and MPT for 4 weeks (experimental groups) before determination of certain conventional toxicological (body weight gain, birth weight and number, organ weights), haematological (absolute and differential WBC, RBC, Ht, MCV, nucleated cell content of femoral bone marrow), and immune function parameters (IgM-PFC number of spleen, DTH reaction). Effects of both substances on immunological variables were detectable at the 1/75 LD50 dose level, but different parameters were affected in the three consecutive generations.

Animals↗
PubMed1999

Immunotoxicological examination of repeated dose combined exposure by dimethoate and two heavy metals in rats.

The immunotoxicity of 28 days combined oral exposure by dimethoate (DM) and two heavy metals (Pb or Cd) was investigated in male Wistar rats. Immunotoxic and no-effect doses of DM (28.2 and 7.04 mg/kg) were combined with immunotoxic and no-effect doses of CdCl2 (6.43 and 1.61 mg/kg) or lead acetate (80.0 and 20.0 mg/kg) in such a way that the high dose of each substance was given in combination with the no-effect dose of the other. To examine the interactions of these agents, general toxicological (body weight gain, organ weights), haematological (absolute and differential WBC, RBC, MCV, Ht. cell content of the femoral bone marrow), and immune function (splenic PFC number. DTH reaction) parameters were measured. Treatment with the combination of Pb or Cd and DM did not result in a reduction of humoral (PFC) and cellular (DTH) immune responses, whereas treatment with the substances alone did result in immune suppression. This protecting effect can probably be attributed to an effect on the kinetics of the compounds tested rather than on the immune system itself. Further interactions were found in both combinations, DM-Cd and DM-Pb, in the body weight gain and in the relative liver weight; the DM-Pb combination also affected the relative thymus weight and the MCV value. These findings show that the immunotoxic effects of the investigated materials, including their detectability and health consequences, can be modified in case of combined exposure.

Animals↗
PubMed2001

Immunotoxicological investigations on rats treated subacutely with dimethoate, As3+ and Hg2+ in combination.

Effects of combined exposure with dimethoate (DM), HgCl2 (Hg), and NaAsO2 (As) were investigated following a 28 - day oral exposure in male Wistar rats. In preliminary experiments, the LOEL (Lowest Observed Effect Level) and NOEL (Non Observed Effect Level) doses of the substances were determined using the same experimental system [determination of body weight gain, organ weights of brain, thymus, heart, lung, kidneys, adrenals, spleen, testicles, popliteal lymph node, white blood cell (WBC) and red blood cell (RBC) count, haematocrit (Ht), mean cell volume (MCV) of RBCs, cell content of the femoral bone marrow, IgM-plaque forming cell (PFC) content of the spleen, delayed type hypersensitivity (DTH) reaction] and animal strain. In the combination studies, LOEL dose of DM (28.2 mg/kg) was combined with NOEL doses of the heavy metals ( HgCl2 = 0.40 mg/kg, NaAsO2 = 3.33 mg/kg), and vice versa (DM = 7.04 mg/kg, HgCl2 = 3.20 mg/kg, NaAsO2 = 13.3 mg/kg). In the DM-Hg combinations, significant alterations were found versus the corresponding high- dose internal control in the body weight gain, relative liver and kidney weights, and in the PFC response. When DM was combined with As, interactions were indicated by changes of relative liver weight, MCV value, and the PFC content of the spleen. These results support the theory that the interactions between pesticides and heavy metals may modify the toxic effects of the single substances, and may also change the functional detection limits of the exposure. The changes in the functional detection limits, if they occur, can lead to false-positive and false-negative results in human epidemiological studies.

Animals↗