Positive effect of green tea extract on reproductive toxicity induced by dimethoate in male mice.

Background: Dimethoate (DM) is one of the most organophosphorus pesticides used all over the world to control insect pests, the extensive use of this insecticide causes a health hazard to animals and humans. Aim: This study was conducted to evaluate the positive effect of green tea extract on sperm quality and testicular cytoarchitecture in male mice treated with DM and on its reproductive performance. Methods: Mice were divided into three groups, each group contained nine mice, the first group (control) was given distilled water only, the second group received DM at a dose (0.1 ml DM/100 ml distilled water) while the third group was given DM at a dose (0.1 ml DM/ 100 ml distilled water) and the green tea extract at a dose (100 mg/kg). After 20 days of the treatment, six mice from each group were killed, sperm quality (sperm count, morphology motility) and histopathological lesions of testis were evaluated. Results: The results showed that DM significantly affected sperm quality a decrease in sperm motility and an increase in abnormal sperm morphology and caused marked alterations in the microstructures of testicular tissues. When treated males were mated with untreated females, a decline in the number of live embryos was found, while the green tea extract revealed an effective role by reducing those negative influences. Conclusion: This study revealed that DM has detrimental effects on sperm quality, testicular tissues, and the embryos, while treatment with green tea revealed a positive role in improving those negative influences of DM without causing any harmful side effects.

Effects of selenium treatment on endogenous antioxidant capacity in signal crayfish (Pacifastacus leniusculus).

Selenium is an essential element that plays a role in numerous physiological processes and is critical for the maintenance of a strong endogenous antioxidant system. Previous work by our research group reported that the organophosphate pesticide dimethoate decreased glutathione S-transferase activity (GST) in signal crayfish (Pacifastacus leniusculus) collected from the Boise River (Idaho, USA). The goals of this study were to examine whether: 1) sodium selenite modulated the endogenous antioxidants glutathione (GSH), metallothionein (MT), and glutathione S-transferase (GST), thus suggesting a mechanism of antioxidant activity, 2) dimethoate exposure (pro-oxidant stressor) decreased GST activity in a localized population of signal crayfish collected from the Snake River (Idaho, USA), and 3) investigate whether selenium cotreatment ameliorated the adverse effects of dimethoate on GST activity due to the antioxidant properties associated with selenium. Selenium and dimethoate treatments (and co-treatments) did not modulate GSH or MT concentrations at the doses tested in this study. Furthermore, neither selenium nor dimethoate was factors influencing GST activity, and no interaction was found between the treatments. While our results did not support our predictions, they are suggestive and future studies examining the protective role of selenium in pro-oxidant exposure in this species are warranted. Population-specific responses as well as seasonal variations in endogenous antioxidant expression should be considered in future experiments.

Concentration- and time-dependent toxicity of commonly encountered pesticides and pesticide mixtures to honeybees (Apis mellifera L.).

Honeybees are exposed to a wide range of pesticides for long periods via contaminated water, pollen and nectar. Some of those pesticides might constitute health hazards in a time- and dose-dependent manner. Time-dependent toxicity profiles for many applied pesticides are lacking, despite the fact that such profiles are crucial for toxicological evaluations. Therefore, we sought to determine the time-dependent toxicities of pesticides/pesticide metabolites frequently found in Israeli beehives, namely, amitraz metabolites, N'-(2,4-dimethylphenyl)-N-methylformamidine (DMPF) and N-(2,4-dimethylphenyl)-formamide (DMF), coumaphos, imidacloprid, thiacloprid, acetamiprid and dimethoate (toxic reference). By applying accepted methodological approaches such as the modified Haber's rule (product of concentration and exposure duration leads to a constant effect) and comparisons between cumulative doses at different time points, we determined the time-dependent toxicities of these pesticides. We also studied the mixture toxicities of frequently occurring pesticide combinations and estimated their potential contributions to the overall toxicities of neonicotinoids. Thiacloprid was the only pesticide that complied with Haber's rule. DMPF, dimethoate and imidacloprid exhibited time-diminished -toxicities. In contrast, DMF and acetamiprid exhibited time-reinforced toxicities. Neither the binary mixtures nor the tertiary mixtures of DMF, DMPF and coumaphos at 10 times their environmentally relevant concentrations potentiated the neonicotinoids' toxicities. DMPF and imidacloprid were found to present the greatest hazard to honeybees, based on their 50% lethal cumulative dose and 50% lethal time. Amitraz's instability, its low detection frequency and high toxicity profile of its metabolite, DMPF, lead us to the conclusion that DMPF constitutes the actual toxic entity responsible for amitraz's toxic effect.

Foliar persistence and residual activity of four insecticides of different mode of action on the predator Engytatus varians (Hemiptera: Miridae).

A greenhouse study was conducted to investigate the degradation kinetics of spinosad, flufenoxuron, dimethoate and imidacloprid in tomato (Solanum lycopersicum L.) foliage and their residual toxicity on Engytatus varians (Distant) (Hemiptera: Miridae), a predator of the tomato psyllid Bactericera cockerelli (Sulcer) (Hemiptera: Triozidae). Insecticides were sprayed at 100% and 50% of their maximum field-registered concentrations (MFRC). Starting 6 h after spraying, leaf samples were taken every 10 d for 40 d and analyzed while E. varians adults were exposed to treated leaves to evaluate residual toxicity. Immediately after application at 100% MFRC, the residue concentrations were 73.34 µg g-1 spinosyn A and 59.2 µg g-1 spinosyn D, 9.21 µg g-1 flufenoxuron, 71.49 µg g-1 dimethoate and 31.74 µg g-1 imidacloprid. At 50% MFRC, initial residue concentrations were between 75% and 90% those at 100% MFRC. The estimated half-life (DT50) of spinosyns A and D, flufenoxuron, and dimethoate was between 34 and 40 d, while that of imidacloprid was 112 d. Flufenoxuron caused no mortality, while mortality due to spinosad was less than 10%, and only during the first 10 d. Mortality caused by either imidacloprid or dimethoate was around 100% up to 10 d after application, then decreased to around 30% after 40 d. Dimethoate toxicity was approximately proportional to residue concentration, while for imidacloprid there was an apparent threshold around 15 µg g-1. These results can be used to establish periods harmless for release of E. varians in the control of B. cockerelli on tomato crops under greenhouse conditions.

Ethanolic extract of fenugreek seeds moderates dimethoate-induced pancreatic damage in male rats.

Dimethoate is a widely used organophosphate insecticide known to be toxic to the pancreas. The aim of this study is to detect the possible protective effects of the fenugreek seed ethanolic extract on the biochemical, histological, and ultra-structural abnormalities induced by dimethoate chronic exposure in the pancreas of adult male rats. The study was conducted on 50 adult male albino rats that were divided equally into 5 groups: (group I) negative control, (group II) vehicle control group, (group III) fenugreek-treated group that was given 400 mg/kg ethanolic fenugreek seed extract once daily, (group IV) dimethoate group received 20 mg/kg/day dimethoate, and (group V) dimethoate- + fenugreek-treated group received a combination of dimethoate and fenugreek in the same previous doses. Dimethoate treatment caused a significant increase in serum glucose, amylase, and lipase levels and a significant decrease in serum insulin. A significant increase in lipid peroxidation and pro-fibrotic cytokine (TGF-ß1) together with a significant reduction of the antioxidant {reduced glutathione (GSH), catalase (CAT), superoxide dismutase (SOD)} activities and the anti-inflammatory (IL-4) in pancreatic tissues was also recorded. There was a histological and ultra-structural evidence of pancreatic acinar and islet cell injury. The recorded abnormalities were reversed in dimethoate+fenugreek treated group indicating that fenugreek ethanolic extract can serve as an antidote for dimethoate-induced pancreatic insult.

Protective Role of Achillea biebersteinii Pretreatment on Dimethoate Induced Oxidative Stress in Guinea Pigs Liver.

OBJECTIVE: The present study investigated the influence of Achillea biebersteinii (Ab), a medicinal herb used widely in Yemeni's folk medicine as analgesic, antipyretic, against diarrhea and flatulence and for liver diseases, on the liver antioxidant potential of guinea pigs acutely intoxicated with dimethoate pesticide (DM). MATERIALS AND METHODS: Animals were administered with Ab aqueous extract (50 and 100 mg kg-1 b.wt., orally) or silymarin (100 mg kg-1 b.wt., orally) for 2 weeks followed by single acute DM administration (80 mg kg-1 b.wt., 1/4 of the LD50 orally). Data were analyzed by one-way ANOVA using SPSS. RESULTS: The results showed that the treatment with Ab extract significantly lowered the DM induced serum levels of hepatic marker enzymes (AST, ALT and ALP). Liver histopathology also showed that Ab extract reduced the incidence of lesions including the swelling of cells, lymphocytes infiltration, nucleus fragmentation and condensation and necrosis induced by DM treatment in guinea pigs. CONCLUSION: The results of this study suggest that Ab aqueous extract could protect the liver against DM-induced oxidative damage.

Dimethoate modifies enhanced UV-B effects on growth, photosynthesis and oxidative stress in mung bean (Vigna radiata L.) seedlings: implication of salicylic acid.

The present study is aimed to investigate implication of salicylic acid (SA) in regulation of dimethoate (30 and 150 ppm designated as D1 and D2, respectively) and enhanced UV-B radiation (ambient + supplemental; ambient + 4.0 kJ m(-2) and ambient + 8.0 kJ m(-2), designated as UV-B1 and UV-B2, respectively) induced responses in mung bean seedlings. Seeds of Vigna radiata L. cv. Narendra 1 were surface sterilized, washed thoroughly and soaked for 24 h in sterilized distilled water. Soaked seeds were sown in acid washed sterilized sand filled in plastic trays, and incubated in dark at 26 ± 2 °C for 2 days. The seedlings were grown in growth chamber at 26 ± 2 °C with 12 h photoperiod (350 µmol photons m(-2 )s(-1), PAR) and watered regularly. Six day old seedlings of equal size were gently transferred in 0.2 strength Rorison nutrient medium (pH 6.8) for acclimatization. Thereafter, dimethoate (30 and 150 ppm designated as D1 and D2, respectively) and enhanced UV-B radiation treatments were given. On the 12th day, seedlings of each set were harvested and various parameters related to growth, pigments, photosynthesis, oxidative stress and antioxidant system were analyzed. The D2 dose of dimethoate and UV-B1 and UV-B2 alone and together significantly (P < 0.05) declined growth, photosynthetic pigments and photosynthesis (Fv/Fm and qP except NPQ) which were accompanied by significant decrease in SA level. Similarly, D2 and UV-B also enhanced (P < 0.05) accumulation of reactive oxygen species and concomitantly damaging effects on lipids, proteins and membrane stability were observed. In contrast, in SA-pretreated seedlings damaging impacts of D2, UV-B1 and UV-B2 alone and together were significantly (P < 0.05) alleviated. Besides this, interestingly D1 dose of dimethoate alone had stimulatory effect on growth and it also ameliorated damaging effects of both the doses of UV-B. The activity of superoxide dismutase was stimulated by all the combinations. However, catalase, glutathione reductase and dehydroascorbate reductase activities were significantly (P < 0.05) inhibited by D2, UV-B1 and UV-B2 while SA-pretreatment ameliorated D2 and UV-B-induced inhibitions in activities of these enzymes. Total ascorbate and glutathione pools also decreased by D2 and both doses of UV-B; however, in SA-pretreated seedlings their amounts were significantly (P < 0.05) higher than D2, UV-B1 and UV-B2 alone. Interestingly, D1 also alleviated damaging impact of UV-B1 and UV-B2 on total ascorbate and glutathione pools. Results revealed that D2, UV-B1 and UV-B2 might alter SA biosynthesis that results into declined SA level which might be related with their toxicity. However, SA-pretreatment might act as a signal that reduces oxidative stress by triggering up-regulation of antioxidants hence improved growth and photosynthesis noticed. Alleviation of UV-B toxicity by D1 suggests about hormesis that triggers SA biosynthesis and hence protection against both doses of UV-B was observed.

Protective effects of vitamin E and selenium against dimethoate-induced cardiotoxicity in vivo: biochemical and histological studies.

There is considerable interest in the study of free radical-mediated damage to biological systems due to pesticide exposure. However, there is a lack of consensus as to which determinations are best used to quantify future risks arising from xenobiotic exposure and natural antioxidant interventions. Our study investigated the potential ability of selenium and/or vitamin E, used as nutritional supplements, to alleviate cardiotoxicity induced by dimethoate. Female Wistar rats were exposed for 30 days either to dimethoate (0.2 g L⁻¹ of drinking water), dimethoate+selenium (0.5 mg kg⁻¹ of diet), dimethoate+vitamin E (100 mg kg⁻¹ of diet), or dimethoate+selenium+vitamin E. The exposure of rats to dimethoate promoted oxidative stress with a rise in malondialdehyde, advanced protein oxidation, and protein carbonyl levels. An increase of glutathione peroxidase, superoxide dismutase, and catalase activities was also noted. A fall in acetylcholinesterase and Na⁺ K⁺-ATPase activities, glutathione, nonprotein thiols, vitamins C and E levels was observed. Plasma levels of cholesterol, triglycerides, and low density lipoprotein-cholesterol increased and those of high density lipoprotein-cholesterol decreased. Coadministration of selenium or vitamin E to the diet of dimethoate-treated rats ameliorated the biochemical parameters cited above. The histopathological findings confirmed the biochemical results and the potential protective effects of selenium and vitamin E against cardiotoxicity induced by dimethoate.

Hepato-protective potential of methanol extract of leaf of Ziziphus mucronata (ZMLM) against dimethoate toxicity: biochemical and histological approach.

BACKGROUND: The leaves of Ziziphus mucronata are used locally as food and a health drink; the leaf paste can also be used in the treatment of boils. The root of the plant is usually used in the treatment of a wide range of pains. OBJECTIVE: The study was carried out to evaluate the hepatoprotective potential of the methanol leaf extract of Ziziphus mucronata (ZMLM). METHOD: The extract was prepared by soaking in 70% methanol/water and rotary evaporation. The phenol content of extract was then estimated. Twenty five adult male Sprague dawley rats (aged 21 weeks) were divided into five groups of five rats each and treated as follows; normal control (NC) received distilled water. Dimethoate control (DC) (received 6 mg/kg.bw.day(-1) dimethoate dissolved in distilled water). Experimental Groups (E1) received dimethoate (6mg/kg.bw) + ZMLM (100 mg/kg.bw(-1)); (E2) received dimethoate (6 mg/kg.bw) + ZMLM (200 mg/kg.bw(-1)) and (E3) received dimethoate (6 mg/kg.bw) + ZMLM (300 mg/kg.bw(-1)). In both the cases a normal control and dimethoate control were kept to compare the results. After 90 days, blood was collected and rats were sacrificed to collect the liver tissue for biochemical assays and histological estimations. RESULTS: The results of E1 did not show much change from the normal control group but was significantly different from the dimethoate control group (P≤ 0.05). The preventive effect which was tested in E2 and E3 proved that the extract could almost retain the normal condition in 90 days time. Histological observations also agreed with the results obtained in biochemical parameters. CONCLUSIONS: Ziziphus mucronata methanol leaf extract possesses a preventive effect against dimethoate induced oxidative stress as observed in male albino Sprague Dawley rats.

[Impacts that dimethoate inhibited the benchmark dose of acetylcholinesterase based on experimental designs].

OBJECTIVE: To obtain the impacts of experimental design on benchmark dose (BMD), and the result was applied to test the computer simulation by software Slob (optimal method to calculate the BMD: for a certain sample capacity, to add the experimental groups by reducing the amount of animals in each group) , consequently, this method can be widely used in the future. METHODS: Eighty adult female SD rats were ig given dimethoate 0.5, 1, 2, 4, 8, 16 and 32 mg/kg for 21 d, respectively. Rats were sacrificed, and acetylcholinesterase (AChE) activity in the hippocampus, cerebral cortex and serum of rats was determined after dimethoate was ig given to rats for 21 d. And then, the software package PROAST28.1 was applied to calculate the BMD. The four does groups of 10 animals (4 x 10 design) and 8 x 5 design were selected from 8 x 10 design to study the impacts of experimental design on BMD. RESULTS: Comparing with the normal control, the significant decline of AChE in hippocampus was observed in 2, 4, 8, 16 and 32 mg/kg groups (P < 0.05), whereas the significant decrease was obtained in 0.5, 1, 2, 4, 8, 16 and 32 mg/kg groups (P < 0.05). Taking the 8 x 10 design as the standard, the confidence interval of BMD calculated by both of 4 x 10 design and 8 x 5 design covered the BMD by 8 x 10 design. And also, confidence interval of BMD, calculated by design scheme 1, 2, 3, 4 and 6 of 4 x 10 design, wider than that of 8 x 5 design, but its scheme 5 narrower than 8 x 5 design. CONCLUSION: To add experimental groups in a certain sample capacity was the optimal method to calculate BMD, but was not the common toxicity experimental design (e. g. set four groups including control, low-dose, moderate-dose, high-dose group).

Antioxidant-rich date palm fruit extract inhibits oxidative stress and nephrotoxicity induced by dimethoate in rat

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Recent investigations have proved the crucial role of nutritional antioxidants to prevent the damage caused by toxic compounds. In this study, the antioxidant effect of date palm fruit extract on dimethoate-induced oxidative stress and nephrotoxicity in rat is investigated and compared with the effect of the well-known antioxidant vitamin C. Male Wistar rats were randomly divided into six groups of ten each: a control group (C), a group that received dimethoate (20 mg/kg body weight) (D), a group given Deglet Nour extract (DNE), a group treated with DNE 30 min before the administration of dimethoate (DNE + D), a group which received VitC (100 mg/kg body weight) plus dimethoate (Vit C + D), and a group given dimethoate for the first month and DNE 30 min after administration of dimethoate, during the second month (D + DNE). These components were daily administered by gavage for 2 months. After completing the treatment period, blood samples from rats were collected under inhaled diethyl ether anesthesia for serum (..) (AU)

Antioxidant supplementations in vitro improve rat sperm parameters and enhance antioxidant enzyme activities against dimethoate-induced sperm damages.

Organophosphorus compounds are currently among the most frequently used pesticides worldwide, and therefore, the potential for human exposure to man is considerable. Their toxicity results in negative effects on many organs and systems such as the male reproductive system. So, vitamins that can offer spermatozoa protection are of great importance. This study was designed to investigate (i) the possibility of dimethoate, an organophosphate insecticide, to induce oxidative stress response in rat spermatozoa in vitro and its effect on antioxidant defence system and (ii) the role of vitamin C and vitamin E in alleviating the cytotoxic effects of dimethoate Epididymal spermatozoa were incubated for 3 h at 37 °C with different concentrations of dimethoate (50, 100 and 200 µm) without vitamins or pre-incubated with 20 mm of vitamin C or 2 mm of vitamin E. Sperm parameters, malondialdehyde (MDA), superoxide dismutase (SOD), catalase (CAT) and glutathione peroxidase (GPx) levels were performed. Dimethoate caused a significant induction of oxidative damage in spermatozoa at different concentrations as evidenced by increased MDA levels. However, a significant decrease in sperm mobility, viability and activities SOD, CAT and GPx was observed. Vitamins pre-treated spermatozoa showed a significant protection against the cytotoxic effects induced by dimethoate on studied parameters.

Dimethoate-induced oxidative damage in erythrocytes of female adult rats: possible protective effect of vitamin E and selenium supplemented to diet.

Pesticide hazards have been accentuated by the sharp rise in their agricultural, industrial and domestic use. Acute exposure to pesticides can cause oxidative damage. Our study investigated the potential ability of selenium (Se) and/or vitamin E, used as nutritional supplements, to alleviate erythrocyte oxidative damage induced by dimethoate (DM), an organophosphate pesticide. Female Wistar rats were exposed to DM (0.2g/L(-1) of drinking water), DM + Se (0.5 mg/kg of diet), DM + vitamin E (100 mg/kg of diet), or DM + Se + vitamin E. Rats exposed to DM for 30 days showed an increase in malondialdehyde levels, superoxide dismutase and glutathione peroxidase activities in their erythocytes, while Na(+),K(+)-ATPase and catalase activities, glutathione, non-protein thiol, vitamin E and vitamin C levels decreased. We also noted an increase in lactate dehydrogenase activity, marker of haemolysis and a decrease in acetylcholinesterase, the principal mode of organophosphorus action. Co-administration of Se or vitamin E to the diet of DM-treated rats ameliorated the biochemical parameters cited above. But the combined effect of Se and vitamin E was more powerful in antagonizing DM-induced oxidative stress. Therefore, our investigation revealed that both Se and vitamin E were useful elements in preventing DM-induced erythrocytes damage.

Antioxidant effect of vitamin E and selenium on hepatotoxicity induced by dimethoate in female adult rats.

Acute exposure to pesticides can cause hepatotoxicity. Our study pertains to the potential ability of selenium and/or vitamin E, used as nutritional supplements, to alleviate oxidative stress induced by dimethoate. Female Wistar rats were randomly divided into seven groups of six each: group I served as controls; group II received in their drinking water dimethoate (2 g L(-1)); group III received both dimethoate and selenium (0.5 mg/kg of diet); group IV was treated with dimethoate and vitamin E (100 mg/kg of diet); group V received dimethoate+selenium+vitamin E and groups VI and VII received either selenium or vitamin E. The exposure of rats to dimethoate for 30 days promoted oxidative stress with an increase in malondialdehyde and a decrease in glutathione and non-protein thiol levels. A decrease in glutathione peroxidase, superoxide dismutase and catalase activities was also observed. While, plasma transaminases, lactate dehydrogenase activities and bilirubin levels increased. Co-administration of selenium and/or vitamin E through diet improved the biochemical parameters cited above. Liver histological studies confirmed biochemical parameters and the beneficial roles of selenium and vitamin E.

Protective effect of date palm fruit extract (Phoenix dactylifera L.) on dimethoate induced-oxidative stress in rat liver.

Nowadays, people's exposure to chemical compounds such as organophosphorus insecticides is continuously on the rise more and more. Theses compounds have induced an excessive production of free radicals which are responsible for several cell alterations in the organism. Recent investigations have proved the crucial role of nutritional antioxidants to prevent the damage caused by toxic compounds. In this study, we investigate the role of date palm fruit extract (Phoenix dactylifera L.) in protection against oxidative damage and hepatotoxicity induced by subchronic exposure to dimethoate (20mg/kg/day). Oral administration of dimethoate caused hepatotoxicity as monitored by the increase in the levels of hepatic markers enzymes (transaminases, alkaline phosphatase, gamma-glutamyl transferase and lactate dehydrogenase), as well as in hepatic malondialdehyde thus causing drastic alteration in antioxidant defence system. Particularly, the activities of superoxide dismutase (SOD) and glutathione peroxidase (GPx) were found increased by dimethoate while catalase (CAT) activity was reduced significantly. These biochemical alterations were accompanied by histological changes marked by appearance of vacuolization, necrosis, congestion, inflammation, and enlargement of sinusoids in liver section. Pretreatment with date palm fruit extract restored the liver damage induced by dimethoate, as revealed by inhibition of hepatic lipid peroxidation, amelioration of SOD, GPx and CAT activities and improvement of histopathology changes. The present findings indicate that in vivo date palm fruit may be useful for the prevention of oxidative stress induced hepatotoxicity.

Protective effects of Danshensu on liver injury induced by omethoate in rats.

This study was to evaluate the protective effects of Danshensu on liver injury induced by omethoate in Sprague Dawley rats. The acute omethoate poisoning model was established by administrating subcutaneously with omethoate at a single dose of 60 mg/kg. Danshensu treatment markedly inhibited the increases of aspartate aminotransferase, alanine aminotransferase, cyclooxygenase-2, tumor necrosis factor-alpha, thromboxane B(2), and thromboxane B(2)/6-keto-PGF1alpha ratio induced by omethoate. The histopathological examination further confirmed that administration with Denshensu ameliorated liver injury. The results demonstrated that Danshensu possesses protective action on hepatic injury induced by omethoate and the pharmacological mechanism was related to the anti-inflammatory effect and circulation improvement of Danshensu, at least in part.

Development of tolerance of egg plant (Solanum melangena L.) to field application of dimethoate.

Dimethoate, at field concentration (1.419 mg g(-1) fr wt), caused inhibition of photosynthesis, transpiration and stomatal conductance of Solanum melangena L. on first treatment but subsequent treatments caused adaptation and recovery of these parameters. The variable fluorescence (F(v)), dissipation (DI(0)/RC), 2 ms relative variable fluorescence (V(j)), net rate of PS II closure (M(0)), and maximum trapping rate of active PS II (TR(0)/RC) increased initially but reduced to the control value with repetition of treatment. However, fluorescence yield (TR(0)/Abs), electron transport probability (ET(0)/TR(0)) and activity of RC (ET(0)/RC) increased with each treatment. With each subsequent treatment there was enhancement of activities of esterases and decrease of insecticide content of leaves.

Assessment of reproductive toxicity of orally administered technical dimethoate in male mice.

The effect of organophosphate insecticide dimethoate at three dosage levels (7, 15, and 28 mg/kg/day) on male reproduction in mice was studied. Dimethoate was given orally by gavage to male mice for 20 days before mating with untreated females. Signs of cholinergic effects were observed in the 15 and 28 mg/kg/day treated groups. Brain and skeletal muscle acetylcholinesterase activities were inhibited in both the middle and high dose groups. Dimethoate was associated with a decreased number of implantations and live fetuses, and an increased number of dead and early resorptions at 28 mg/kg/day treated group. The percent morphologically normal spermatozoa were unaffected in any of dose groups. However, sperm production and percent motile sperm were decreased in the 15 and 28 mg/kg/day treated groups compared to the control. Histological changes in testis were observed in the middle and high treated groups. The current study demonstrated the adverse effects of dimethoate on the reproductive performance of male mice and pregnancy outcomes following mating with untreated female mice at dose levels of 15 and 28 mg/kg/day. The No Observed Effect Level (NOEL) in the present study for reproductive performance was 7 mg/kg/day.

Evaluation of dimethoate toxicity on pregnancy in albino mice.

We investigated whether dimethoate, an organophosphorus insecticide, causes abortion or fetal resorption in pregnant albino mice. Graded doses of 16, 20, 24, and 28 mg/kg body weight/d were administered orally from days 7 to day 15 of pregnancy. Laparotomy was performed on day 8 of pregnancy to note the number of implantations, and the animals were autopsied on day 19. The results revealed no inhibition of pregnancy in all dimethoate treated mice relative to a suitable control group. Treatment with 24 or 28 mg dimethoate caused a significant decrease in the number of implantations, live fetuses, and corpora lutea, but a decreased percent fetal survival and increased percent post-implantation loss and gestation length were not significant when compared with control mice. In all mice treated with 28 mg dimethoate, a significant decrease occurred in the body weight of the ovaries, uterus, and liver when compared with control mice. Following treatment with 16 or 20 mg dimethoate, however, no significant change was found in body and organ weights or in the number of implantations, live fetuses, and corpora lutea, percent post-implantation loss, and fetal survival, or gestation length compared with the corresponding parameters in control mice. The results of this study clearly indicate that dimethoate does not cause abortion or fetal resorption in pregnant mice. A significant decrease in the number of corpora lutea and percent fetal survival observed at higher doses of dimethoate could be due to a toxic effect on the embryo or to a hormonal imbalance.

Leaf surfaces and the bioavailability of pesticide residues.

Laboratory bioassays were carried out to determine the toxicity to Folsomia candida Willem (Collembola: Isotomidae) of residues of a pyrethroid insecticide, deltamethrin, and an organophosphorus insecticide, dimethoate, on different leaf surfaces. The test leaves included a range of species and leaves of different ages. Dose-response relationships were estimated for F candida walking over the various treated leaf substrates. Probit analysis was used to estimate the means and standard deviations of the associated tolerance distributions expressed as gAIha-1. Parallelism tests were undertaken to compare the susceptibilities of F candida to the two compounds applied to the different leaf surfaces. On deltamethrin-treated leaf surfaces, the LD50 values for F candida varied from 6.36 to 77.14 gAIha-1. F candida was least susceptible to deltamethrin residues when applied to leaves of dwarf bean (Phaseolus vulgarus L) and the highest susceptibility was observed following application to leaves of seedlings of barley (Hordeum vulgare L). In contrast, the LD50 values observed for dimethoate treatments did not differ significantly between leaf types, ranging from 1.35 to 8.69 gAIha-1. The laboratory data on susceptibility of F candida on different leaf types for different pesticides can be used to investigate the role of leaf surface properties in modifying the toxicity of applied pesticides to exposed invertebrates.