Developmental toxicity of orally administered technical dimethoate in rats

Prenatal exposure to ethion caused maternal and foetal toxicity in rats

Ethion is a class II moderately toxic organothiophosphate pesticide. The main objective of this study was to evaluate the maternal and foetal toxicity of ethion in rats. Pregnant rats were divided into 5 groups. Group I served as control. Group II, III, IV, and V were orally administered with 0.86, 1.71, 3.43, and 6.9 mg/kg of ethion respectively, from gestational day (GD) 6-19. Dams were sacrificed on GD 20. Maternal toxicity was assessed by body weight gain, foetal resorptions, oxidative stress, liver and kidney function tests, and histopathology. Foetal toxicity was assessed by physical status, gross, teratological and histopathological examination. Ethion caused dose-dependent reduction in maternal body weight gain, increased resorptions, and reduced gravid uterine weights. Elevated MDA levels and altered levels of GSH, SOD and catalase were recorded in pregnant dam serum and tissues. SGOT, SGPT, total bilirubin, urea, uric acid, and creatinine were elevated in ethion groups indicating liver and kidney toxicity. Histology of uterus revealed myometrial degeneration and mucosal gland atrophy in uterus of pregnant dams and degenerative changes in placenta. It showed histological alterations in liver, kidney, and lungs. There was reduction in the foetal body weights and placental weights, and degenerative changes in the foetal liver and kidney. Gross evaluation of foetuses showed subcutaneous hematoma. Skeletal evaluation showed partial ossification of skull bones, costal separation, and agenesis of tail vertebrae, sternebrae, metacarpals and metatarsals. The findings reveal that prenatal exposure to ethion caused maternal and foetal toxicity in rats.

Residential proximity to pesticide application as a risk factor for childhood central nervous system tumors

BACKGROUND

Pesticide exposures have been examined previously as risk factors for childhood brain cancers, but few studies were able to assess risk from specific agents.

OBJECTIVE

To evaluate risks for childhood central nervous system tumors associated with residential proximity to agricultural pesticide applications.

METHODS

Using the California Cancer Registry, we identified cancer cases less than 6 years of age and frequency matched them by year of birth to 20 cancer-free controls identified from birth certificates. We restricted analyses to mothers living in rural areas and births occurring between 1998 and 2011, resulting in 667 cases of childhood central nervous system tumors and 123,158 controls. Possible carcinogens were selected per the Environmental Protection Agency's (US. EPA) classifications, and prenatal exposure was assessed according to pesticides reported by the California Department of Pesticide Regulation's (CDPR) Pesticide Use Reporting (PUR) system as being applied within 4000m of the maternal residence at birth. We computed odds ratios for individual pesticide associations using unconditional logistic and hierarchical regression models.

RESULTS

We observed elevated risks in the hierarchical models for diffuse astrocytoma with exposure to bromacil (OR: 2.12, 95% CI: 1.13-3.97), thiophanate-methyl (OR: 1.64, 95% CI: 1.02-2.66), triforine (OR: 2.38, 95% CI: 1.44-3.92), and kresoxim methyl (OR: 2.09, 95% CI: 1.03-4.21); elevated risks for medulloblastoma with exposure to chlorothalonil (OR: 1.78, 95% CI: 1.15-2.76), propiconazole (OR: 1.60, 95% CI: 1.02, 2.53), dimethoate (OR: 1.60, 95% CI: 1.06, 2.43), and linuron (OR: 2.52, 95% CI: 1.25, 5.11); and elevated risk for ependymoma with exposure to thiophanate-methyl (OR: 1.72, 95% CI: 1.10-2.68).

CONCLUSION

Our study suggests that exposure to certain pesticides through residential proximity to agricultural applications during pregnancy may increase the risk of childhood central nervous system tumors.

Lufenuron induces reproductive toxicity and genotoxic effects in pregnant albino rats and their fetuses

Insecticides and other agrochemicals have become indispensable components of the agricultural system to ensure a notable increase in crop yield and food production. As a natural consequence, chemical residues result in significantly increased contamination of both terrestrial and aquatic ecosystems. The present study evaluated the teratogenic, genotoxic, and oxidative stress effects of residual-level lufenuron exposure on pregnant rats during the organogenesis gestational period of both mother and fetus. The tested dams were divided into three groups; control (untreated), low-dose group (orally administered with 0.4 mg/kg lufenuron) and high-dose group (orally administered with 0.8 mg/kg lufenuron). The dams of the two treatment groups showed teratogenic abnormalities represented by the asymmetrical distribution of fetuses in both uterine horns, accompanied by observed resorption sites and intensive bleeding in the uterine horns, whereas their fetuses suffered from growth retardation, morphologic malformations, and skeletal deformations. Histologic examination of the liver and kidney tissues obtained from mothers and fetuses after lufenuron exposure revealed multiple histopathologic changes. DNA fragmentation and cell cycle perturbation were also detected in the liver cells of lufenuron-treated pregnant dams and their fetuses through comet assay and flow cytometry, respectively. Moreover, lufenuron-induced oxidative stress in the liver of mothers and fetuses was confirmed by the increased malondialdehyde levels and decreased levels of enzymatic antioxidants (glutathione peroxidase and superoxide dismutase). Taken together, it can be concluded that lufenuron has a great potential in exerting teratogenic, genotoxic, and oxidative stresses on pregnant rats and their fetuses upon chronic exposure to residual levels during the organogenesis gestational period. The obtained results in the present study imply that women and their fetuses may have the same risk.

Repeated exposure of pyriproxyfen to pregnant female mice causes developmental abnormalities in prenatal pups

The continuous exposure to conventional pesticides leads to severe health and environmental issues especially at prenatal stage during developmental period. Herein, we aimed to investigate the anomalies due to repeated exposure of pyriproxyfen in pregnant female mice and their neonates. Twenty-four pregnant female mice were repeatedly administered with pyriproxyfen at 30, 100, 300, and 1000 mg/kg by oral gauge from gestation day (GD) 7 to gestation day 17 and six females were given distilled water in the control group. All the live pups were euthanized at postnatal day (PND) 7 and their organs (heart, liver, kidney, and brain) were dissected out, weighed, and assessed for further histopathological examinations. The results exhibited a significant (P < 0.001) decrease in the body weight gain of all treated pregnant mice in comparison to the controls and a significant increase in the gestational length was observed in group IV (P < 0.01) and group V (P < 0.001). In addition, no live pups were born in groups IV and V and one pregnant female mouse was also found dead in both treatments. The body weights of the pups were significantly decreased in group II (P < 0.05) and group III (P < 0.001) and the relative organ (liver, heart, and kidney) weight of the pups was increased significantly (P < 0.001, P < 0.01, P < 0.05) due to prenatal exposure in group II as compared to group I. The relative brain weights of the pups were decreased significantly (P < 0.001) in groups II and III as compared to group I. The liver, kidney, heart, and brain sections exhibited various histological alterations in groups II and III by hematoxylin and eosin staining. Furthermore, immunohistochemical staining of the coronal sections of pup's brain showed significant (P < 0.001) reduction in cortical radial thickness and total neural count in group II and III as compared to group I. Therefore, the prenatal exposure to pyriproxyfen provoked the damage to various organs in mice offspring and an increase in fetal death at higher doses.

Environmental Fate and Toxicology of Dimethoate

The insecticide dimethoate, an organophosphate, was first introduced in 1962 for broad spectrum control of a wide range of insects including mites, flies, aphids, and plant hoppers. It inhibits AChE activity, resulting in nerve damage, which may lead to death. It is considered highly toxic to insects although dimethoate resistance has been observed. Dimethoate has both a low vapor pressure (0.247 mPa) and Henry's law constant (l.42x10(-6) Pa m3/mol), thus volatilization is not a major route of dissipation from either water or moist soils. Photolysis is considered a minor dissipation pathway. However, studies have shown that in the presence of a catalyst, the rate of photolysis does increase. The insecticide has high water solubility (39,800 mg/L) and under alkaline conditions, hydrolysis predominates representing a major degradation pathway. It has a low soil sorption capacity (Koc=20) which varies by soil type and organic matter content. Dimethoate is degraded by microbes under anaerobic conditions and bacterial species have been identified that are capable of using dimethoate as a carbon source. Although many intermediate by-products have been identified by abiotic and biotic processes, the major degradation product is omethoate. Dimethoate has been found to adversely impact many organisms. In plants, photosynthesis and growth are highly impacted, whereas birds exhibit inhibition in brain enzyme activity, thus sublethal effects are apparent. Furthermore, aquatic organisms are expected to be highly impacted via direct exposure, often displaying changes in swimming behavior. Toxicity results include inhibition in growth and more importantly, inhibition of acetylcholinesterase activity.

Proteomic analysis of dimethoate-responsive proteins in the oyster (Saccostrea cucullata) gonad

INTRODUCTION

The organophosphorus pesticide dimethoate (DM) has been widely used in agriculture, and its extensive use could still have left many environmental problems.

METHODS

In the present study, the oyster (Saccostrea cucullata) was subjected to acute DM toxicity (2 mg/L), and gas chromatographic analysis revealed and quantified residues of DM in the oyster gonad.

RESULTS

Two-dimensional gel electrophoresis showed 12 differentially expressed proteins in the DM-exposed oyster gonad in comparison to the control. Among these 12 protein spots, nine were down-regulated, and three were up-regulated. Both matrix-assisted laser desorption/ionization time-of-flight tandem mass spectrometry and database searching were utilized to identify these differential proteins, and revealed five proteins previously described as being related to DM toxicity. In addition, the levels of mRNA expression corresponding to these differential proteins were further proved in part by real-time PCR. The functions of these proteins were summarized as: carrying out energy metabolism, DNA repair, DNA transcriptional regulation, and oxidative protection. The remaining seven protein spots were of particular interest in terms of their responses to DM, which have seldom been reported.

CONCLUSION

These data might point to a number of novel and significant biomarkers for evaluating the contamination levels of DM and provide useful insight into the mechanisms of DM toxicity in vivo.

Evaluation of developmental toxicity induced by anticholinesterase insecticide, diazinon in female rats

Developmental toxicities, including birth defects, are significant public health problems. This study was planned to assess the cholinergic and developmental potentials of diazinon that is widely used as an organophosphate insecticide. Pregnant female Sprague-Dawley rats were given diazinon orally at doses of 0, 1.9, 3.8, and 7.6 mg/kg body weight (b.w.)/day on gestation days 6 to 15. Maternal brain acetylcholinesterase activities, measured on gestation day20, were significantly decreased at 3.8 and 7.6 mg/kg b.w./day, but fetal acetylcholinesterase activity was not altered. Maternal toxicities, as evidenced by cholinergic symptoms including diarrhea, tremors, weakness, salivation, and decreased activities, were observed at the 3.8 and 7.6 mg/kg b.w./day dose groups. Net gravid uterine weight was decreased at a dose of 7.6 mg/kg b.w./day. No maternal effects were apparent in the 1.9 mg/kg b.w./day dose group. Maternal toxicity at a dose of 3.8 mg/kg b.w./day did not induce fetotoxicity or teratogeneicity. However, 7.6 mg/kg b.w./day doses significantly resulted in fetal toxicity and malformations in addition to maternal toxicity in animals. In conclusion, teratogenic disorders only outlined by doses that produced marked maternal toxicity. Since the malformations were not morphologically related, they were considered to be secondary to maternal toxicity; hence, the malformations were not related to cholinesterase inhibition.

Comparative effects of dimethoate and deltamethrin on reproductive system in male mice

The effects of dimethoate (5, 15 and 28 mg kg(-1) day(-1)), deltamethrin (5 mg kg(-1) day(-1)) and their mixture (5 mg kg(-1) day(-1)) on male reproduction in mice were studied. The insecticides were given orally by gavage to male mice for 21 days. At the end of the treatment period, body, testes and epididymides weights and sperm parameters were determined. Alone mixture treatment has significantly decreased body weights. Dimethoate at 28 mg kg(-1) day(-1), deltamethrin at 5 mg kg(-1) day(-1) and their mixture at 5 mg kg(-1) day(-1) were associated with a significantly decreased sperm count, motility and viability and significantly increased percent morphologically abnormal spermatozoa compared with the controls. This study demonstrated the adverse effects of dimethoate at high dose, deltamethrin and their combining at 5 mg kg(-1) day(-1) on reproductive system and sperm parameters in male mice.

Reproductive Toxicity Evaluation of Pestban Insecticide Exposure in Male and Female Rats

Sexually mature male and female rats were orally intubated with the organophosphorus insecticide, Pestban at a daily dosage of 7.45 or 3.72 mg/kg bwt, equivalent to 1/20 and 1/40 LD50, respectively. Male rats were exposed for 70 days, while the female rats were exposed for 14 days, premating, during mating and throughout the whole length of gestation and lactation periods till weaning. The results showed depressed acetylcholinesterase (AChE) activity in the brain of parents, fetuses and their placentae in a dose-dependent manner. The fertility was significantly reduced with increasing the dose in both treated groups, with more pronounced suppressive effects in the male treated group. The number of implantation sites and viable fetuses were significantly reduced in pregnant females of both treated groups. However, the number of resorptions, dead fetuses, and pre-and postimplantation losses were significantly increased. The incidence of resorptions was more pronounced in treated female compared to male group and was dose dependant. The behavioral responses as well as fetal survival and viability indices were altered in both treated groups during the lactation period. The incidence of these effects was more pronounced in the treated female group and occurred in a dose-related manner. The recorded morphological, visceral, and skeletal anomalies were significantly increased with increasing the dose in fetuses of both treated groups, with more pronounced effects on fetuses of treated females. In conclusion, the exposure of adult male and female rats to Pestban would cause adverse effects on fertility and reproduction.

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.