Blockade of ovulation in the rat by the fungicide sodium N-methyldithiocarbamate: relationship between effects on the luteinizing hormone surge and alterations in hypothalamic catecholamines

Mechanistic investigation of the differential synergistic neurotoxicity between pesticide metam sodium and copper or zinc

Epidemiological studies suggest neurological disorders have been associated with the co-exposure to certain pesticides and transition metals. The present study aims to investigate whether co-exposure to the widely-used pesticide metam sodium and copper (Cu²⁺) or zinc ion (Zn²⁺) is able to cause synergistic neurotoxicity in neural PC12 cells and its possible mechanism(s). We found that both metam/Cu²⁺ and metam/Zn²⁺ synergistically induced apoptosis, intracellular Cu²⁺/Zn²⁺ uptake, reactive oxygen species (ROS) accumulation, double-strand DNA breakage, mitochondrial membrane potential decrease, and nerve function disorder. In addition, metam/Cu²⁺ was shown to release cytochrome c and apoptosis-inducing factor (AIF) from mitochondria to cytoplasm and nucleus, respectively, and activate the caspase 9, 8, 3, 7. However, metam/Zn²⁺ induced caspase 7 activation and AIF translocation and mildly activated cytochrome c/caspase 9/caspase 3 pathway. Furthermore, metam/Cu²⁺ activated caspase 3/7 by the p38 pathway, whereas metam/Zn²⁺ did so via both the p38 and JNK pathways. These results demonstrated that metam/Cu²⁺ or metam/Zn²⁺ co-exposure cause synergistic neurotoxicity via different mechanisms, indicating a potential risk to human health when they environmentally co-exist.

Chronic exposure to metam sodium-based pesticide in mice during adulthood elevated anxiety and depression-like behaviors: Involvement of serotoninergic depletion and gut microbiota dysbiosis

Metam sodium-based pesticide (MS-BP) is widely used in agriculture and public health. We have previously demonstrated that maternal exposure to MS-BP resulted in sensorimotor alterations in mice offspring with long-lasting deficits including anxiety- and depression-like behaviors. Here, we project to verify whether these two neurobehavioral effects occur during adulthood following direct exposure to MS-BP and whether it results in changes in the serotoninergic system and gut microbiota. Our findings showed that chronic exposure to MS-BP increased anxiety- and depression-like behaviors, accompanied by a depletion of serotonin-like neurons within the dorsal raphe nucleus and a reduction in serotoninergic terminals in the infralimbic cortex and the basolateral amygdala. In addition, all MS-BP-exposed animals exhibited a reduced total bacterial number and diversity of gut microbiota. Taken together, our data demonstrated that MS-BP-induced behavioral changes could be related to the impairment of the serotoninergic system and gut microbiota dysbiosis.

Metam sodium exposure during pregnancy and lactation in mice caused behavioral abnormalities and oxidative stress in offspring

Metam sodium (MS) is a widespread biocide with a broad-spectrum activity. Here, we addressed the behavioral impact of MS by exposing female mice to 50, 100 and 150 mg/kg of MS during both pregnancy and lactation, and evaluated the oxidative stress as a potential mechanism of MS-induced neurotoxicity. The results showed that MS affected fertility and reproduction parameters as well as some aspects of maternal behavior, especially at high doses. In offspring, MS caused a significant delay in the ontogeny of sensorimotor functions. In addition, treated mice exhibited during adulthood an increase of anxiety-like, depression-like behaviors as well as learning and memory impairment. These alterations were accompanied by an increase of the superoxide dismutase activity, and a significant decreased catalase and malondialdehyde activities in specific brain areas. The present work revealed that early exposure to MS induced sensorimotor and behavioral impairments in offspring likely associated with onset of oxidative stress.

Prenatal exposure to the pesticide metam sodium induces sensorimotor and neurobehavioral abnormalities in mice offspring

The present study has investigated developmental neurotoxicity of Metam sodium (MS), from gestational day 6 and throughout the gestation period until delivery. Therefore, mated female mice were orally exposed on a daily basis to 0 (control), 50, 100 or 150 mg of MS/kg of body weight and their standard fertility and reproductive parameters were assessed. The offspring were examined for their sensorimotor development, depression and cognitive performance. Our results showed that MS exposure during pregnancy led to one case of mortality, two cases of abortion and disturbed fertility and reproductive parameters in pregnant dams. In offspring, MS induced an overall delay in innate reflexes and sensorimotor performances. Furthermore, all prenatally treated animals showed an increased level of depression-like behavior as well as a pronounced cognitive impairment in adulthood. These results demonstrated that prenatal exposure to MS causes a long-lasting developmental neurotoxicity and alters a wide range of behavioral functions in mice.

Mancozeb impaired male fertility in rabbits with trials of glutathione detoxification

The study aims to evaluate the potential reproductive toxicity induced by mancozeb fungicide in male rabbits and to examine the ameliorative effect of glutathione (GSH), a non-enzymatic antioxidant, against mancozeb reproductive toxicity. Mancozeb is a member of the dithiocarbamates group currently in use in the management of fungal diseases of plants. To achieve these aims, mature male White New-Zealand rabbits of 4-5 months old were randomly assigned to four groups of 9 animals each: control, mancozeb only, mancozeb and GSH, and GSH only. This study discovered a significant reduction in serum FSH, LH, testosterone and testicular LDH, ACP, and ALP levels in the groups of mancozeb-treated rabbits compared with control. The mancozeb-treated groups also showed significant losses in sperm viability, along with a significant increase in the number of abnormal sperms. Finally, an upregulation in steroidogenic 3β-HSD enzyme activity was noted in mancozeb-treated rabbits. Histopathological inspection of the testicles established disruption of the germinal epithelium with vacuolization of Leydig cells and reduced spermatogenic cells. GSH co-administration increased serum concentrations of FSH, LH, testosterone, and levels of the testicular enzymes: LDH, ACP, and ALP. Improved steroidogenesis was indicated in this group by a significant improvement in the testicular 3β-HSD enzyme, by a significant increase in sperm viability, and by a significant decrease in the number of abnormal sperms. The findings of this study suggest that mancozeb exposure has anti-spermatogenic and anti-steroidogenic adverse effects in rabbits and administration of GSH may alleviate the reproductive toxicity.

Pesticide use in the U.S. and policy implications: A focus on herbicides

This article examines herbicide use in the United States, providing estimates of poundage, land surface covered, distribution, and recent trends based on federal and state figures. Herbicides are by far the most widely used class of pesticide in the US, where 556 million lbs of herbicide active ingredients (AIs) were applied in 1995. Agriculture accounts for the majority of herbicide use, totaling 461 million lbs of AIs in 1995. Over 60% of the poundage of all agricultural herbicides consist of those that are capable of disrupting the endocrine and/or reproductive systems of animals. In addition, at least 17 types of `inert ingredients,' which can equal 90% or more of a pesticide product, have been identified as having potential endocrine-disrupting effects. Atrazine is the predominant herbicide used according to poundage, with 68-73 million lbs of AIs applied in 1995. However, 2,4-D is the most widespread herbicide, covering 78 million acres for agricultural uses alone. Both of these herbicides are reported endocrine disruptors. Acetolactate synthase (ALS) inhibitors, namely the sulfonylureas and imidazolinones, are one of the fastest growing classes of herbicides. Many of these herbicides are 100 times more toxic to select plant species than their predecessors, so they can be applied at rates approximately 100 times lower. Consequently, they can affect plant species at concentration levels so low that no standard chemical protocol can detect them. Due in part to these more potent herbicides, the poundage of herbicides used in the US has decreased since the mid-1980s; however, the available data suggest that the number of treated acres has not significantly declined. A thorough assessment of potential exposure to herbicides by wildlife and humans is limited due to the inaccessibility of production and usage data.

The effects of permethrin on rat ovarian tissue morphology

All organisms are exposed to chemical agents during their lifetime. One of these agents is a pesticide that is used as fly killer. In this study we investigated the effects of permethrin on rat ovaries using light and electron microscopy. We used 24 Wistar albino female rats and divided them into 3 groups. Dosages 20 and 40 mg/kg/day permethrin were administered by gavage for 14 days. Normal saline was given to control rats. After treatment, ovarian tissues were collected and prepared for light and electron microscopy evaluation. Negative effects of permethrin were detected on follicular and corpus luteum cell morphology in a dose dependent manner when compared with the control group. Picnotic cellular appearance and condensed chromatin were detected as evidence of apoptotic cell death. Furthermore, degenerative changes were seen in the ultrastructure of mitochondria and endoplasmic reticulum. Thus, these findings suggested that permethrin caused degenerative effects on ovarian morphology in a dose dependent manner.

Evaluation of the OECD (Q)SAR Application Toolbox for the profiling of estrogen receptor binding affinities

The determination of binding affinities for the estrogen receptor (ER) is used extensively to assess potential hazards to human health and the environment arising from chemicals that can interfere with natural hormone homeostasis. Given the great number of chemicals to which humans and wildlife are exposed, (quantitative) structure-activity relationship (Q)SAR models for the characterization of ER disruptors represent a fast and cost-efficient alternative to experimental testing. In this toxicological context, the freely available Organisation for Economic Co-operation and Development (OECD) (Q)SAR Application Toolbox provides a profiler for the categorical profiling of chemicals according to their ER binding propensities. The aim of this study was to evaluate the predictive performances of this profiler. To achieve such a purpose, prediction results with the ER-profiler were compared with experimental binding affinities relative to two large datasets of chemicals (rat and human). The resulting Cooper statistics indicated that the binding affinities of the majority of chemicals included in the retained datasets could be correctly predicted.

Effects of carbosulfan administration schedules on estrous cycle and follicular dynamics in albino mice

Carbosulfan an acaricide was orally administrated at 48 mg/kg body weight/day to female swiss albino mice for 5, 10, 20 and 30 d. Daily vaginal smear and body weight was recorded. The mice were sacrificed by cervical dislocation after 24 h of terminal exposure to carbosulfan. The results of the present study indicated that there was a significant decrease in the number of estrous cycle and phases with a concomitant increase in the length of the estrous cycle and diestrus phase with carbosulfan treatment for 10, 20, and 30 d. There was a significant decrease in the weight of the ovary, uterus, number of healthy follicles and increase in the number of atretic follicles with 20 and 30 d carbosulfan treatment when compared with the control. There was a significant decrease in the level of sialic acid with an increase in the level of cholesterol by carbosulfan treatment for 20 and 30 d. The decreased level of sialic acid indicates the decreased level of circulating FSH/LH. The ovary 3beta HSD activity decreased significantly with 20 and 30 d carbosulfan exposure mice indicating its effect on steroidogenesis, when compared to controls. The above findings may be due to direct effect on the ovary or on the gonadotrophins secretion via central nervous mechanism in mice.

Reproductive functions and hypothalamic catecholamines in response to the soil fumigant metam sodium: Adaptations to extended exposures

Metam sodium (MS) is a soil fumigant and Category II pesticide with a relatively low toxicity in mammals. Previous data have shown an ability to impair reproductive mechanisms in ovariectomized, estradiol-primed rats. A single i.p. injection blocked the luteinizing hormone (LH) surge that in gonadal-intact females initiates the final stages of follicular and oocytic maturation and serves as the trigger for ovulation. The effect paralleled a fall in hypothalamic norepinephrine (NE) and rise in hypothalamic dopamine (DA) that was likely due to a suppression in dopamine-beta-hydroxylase activity. In addition to determining the influence on catecholamine (CA) concentrations from a single oral exposure to MS, the present study explored effects of longer, 3-week treatments on estrous cyclicity, the LH surge, ovulation and hypothalamic CAs. Normally cycling 90 d S-D rats were administered MS (0-200 mg/kg/d, oral) and cyclicity was monitored daily. At the end of the 3rd week, proestrous blood was sampled over the afternoon from regular 4-day cyclers for a determination of LH. These animals were then killed on the following day of estrus (treatment days 21-26) for oocyte retrieval and assessment of hypothalamic CAs. Results showed that shortly after treatment began there occurred a dose-related period of persistent diestrus that typically lasted 8-16 d before regular cycles were reinstated. After 3 weeks, no effects were seen on the magnitude/timing of the LH surge or ovulated oocyte numbers. Anterior and posterior hypothalamic NE and DA were not significantly different from controls, although DA turnover (reflected by the ratio of DOPAC {3,4-dihydroxy-phenylacetic acid} to DA) in both anterior hypothalamic and caudate regions was decreased at all dosages. The data indicate that a 3 week oral exposure to MS induced an initial period of extended diestrus before the resumption of apparently normal reproductive activity, with previously reported CA alterations (apart from a persistent alteration in the DOPAC/DA ratio) being normalized by the end of dosing.

Atrazine and reproductive function: mode and mechanism of action studies

Atrazine, a chlorotriazine herbicide, is used to control annual grasses and broadleaf weeds. In this review, we summarize our laboratory's work evaluating the neuroendocrine toxicity of atrazine (and related chlorotriazines) from an historic perspective. We provide the rationale for our work as we have endeavored to determine: 1) the underlying reproductive changes leading to the development of mammary gland tumors in the atrazine-exposed female rat; 2) the cascade of physiological events that are responsible for these changes (i.e., the mode of action for mammary tumors); 3) the potential cellular mechanisms involving adverse effects of atrazine; and 4) the range of reproductive alterations associated with this pesticide.

The rodent estrous cycle: characterization of vaginal cytology and its utility in toxicological studies

While an evaluation of the estrous cycle in laboratory rodents can be a useful measure of the integrity of the hypothalamic-pituitary-ovarian reproductive axis, it can also serve as a way of insuring that animals exhibiting abnormal cycling patterns are disincluded from a study prior to exposure to a test compound. Assessment of vaginal cytology in regularly cycling animals also provides a means to establish a comparable endocrine milieu for animals at necropsy. The procedure for obtaining a vaginal smear is relatively non-invasive and is one to which animals can become readily accustomed. It requires few supplies, and with some experience the assessments can be easily performed in fresh, unstained smears, or in fixed, stained ones. When incorporated as an adjunct to other endpoint measures, a determination of a female's cycling status can contribute important information about the nature of a toxicant insult to the reproductive system. In doing so, it can help to integrate the data into a more comprehensive mechanistic portrait of the effect, and in terms of risk assessment, may provide some indication of a toxicant's impact on human reproductive physiology.

Pesticide exposure: the hormonal function of the female reproductive system disrupted?

Some pesticides may interfere with the female hormonal function, which may lead to negative effects on the reproductive system through disruption of the hormonal balance necessary for proper functioning. Previous studies primarily focused on interference with the estrogen and/or androgen receptor, but the hormonal function may be disrupted in many more ways through pesticide exposure. The aim of this review is to give an overview of the various ways in which pesticides may disrupt the hormonal function of the female reproductive system and in particular the ovarian cycle. Disruption can occur in all stages of hormonal regulation: 1. hormone synthesis; 2. hormone release and storage; 3. hormone transport and clearance; 4. hormone receptor recognition and binding; 5. hormone postreceptor activation; 6. the thyroid function; and 7. the central nervous system. These mechanisms are described for effects of pesticide exposure in vitro and on experimental animals in vivo. For the latter, potential effects of endocrine disrupting pesticides on the female reproductive system, i.e. modulation of hormone concentrations, ovarian cycle irregularities, and impaired fertility, are also reviewed. In epidemiological studies, exposure to pesticides has been associated with menstrual cycle disturbances, reduced fertility, prolonged time-to-pregnancy, spontaneous abortion, stillbirths, and developmental defects, which may or may not be due to disruption of the female hormonal function. Because pesticides comprise a large number of distinct substances with dissimilar structures and diverse toxicity, it is most likely that several of the above-mentioned mechanisms are involved in the pathophysiological pathways explaining the role of pesticide exposure in ovarian cycle disturbances, ultimately leading to fertility problems and other reproductive effects. In future research, information on the ways in which pesticides may disrupt the hormonal function as described in this review, can be used to generate specific hypotheses for studies on the effects of pesticides on the ovarian cycle, both in toxicological and epidemiological settings.

Norman Cousins Lecture. The uses and abuses of psychoneuroimmunology: a global overview

Studies of interactions between the nervous and immune systems that effect immunological and behavioral changes are relevant to our understanding biological issues pertinent to evolution, ethology, ecology, and aging, in addition to our understanding the immune and nervous systems per se. Psychoneuroimmunology also relates to homeland security, science education, and the practice of conventional as well as complementary and alternative medicine. This paper will highlight just some of these global implications of psychoneuroimmunology.

Carbofuran induced block of compensatory ovarian growth in hemicastrated albino mice

Carbofuran, a systemic N-methyl carbamate pesticide was orally administered at doses of 0.4, 0.7, 1 and 1.3 mg/(kg day) to normal hemicastrated (HC) mice for 15 consecutive days to investigate the effects on compensatory ovarian growth. Sham-operated and hemicastrated control mice were administered a similar quantity of olive oil. The vaginal smear and body weight of the mice were recorded daily and mice were sacrificed on day 16. The results revealed that the HC control mice showed 54.58% increase in the ovary weight of the remaining left ovary and many follicles, corpora lutea and showed normal estrous cycle as compared to Sham-operated control mice. The remaining left ovaries of the mice treated with 1.3 mg carbofuran showed 0.82% increase in the ovary weight and significant decrease in the number of developing follicles, corpora lutea, increase in many atretic follicles, the estrous cycle and its phases were affected when compared to HC control mice. In HC mice treated with 1 mg/(kg day) carbofuran resulted in 12.63% increase in the ovary weight and showed significant decrease in follicles, corpora lutea and many increased atretic follicles. The estrous cycle was affected with significant decrease in estrus phase and increase in diestrus phase. In HC mice treated with 0.7 mg/(kg day) carbofuran showed 26.30% increase in ovary weight and showed normal number of follicles and the mice showed normal number of estrous cycles but the estrus and diestrus phases were affected significantly. However, HC mice treated with 0.4 mg/(kg day) carbofuran revealed 33.09% increase in the ovary weight with no significant change in the follicles and estrous cycle as compared with that of HC control mice. There was no significant change in the body weight gain and weight of the organs such as uterus, kidney, adrenals, liver, spleen, thymus and thyroid in all the carbofuran treated mice. These observed effects of carbofuran on ovary, follicles and estrous cycle are considered to be hormonal imbalance.

Temporal effect of carbofuran on estrous cycle compensatory ovarian hypertrophy and follicles in hemiovariectomized albino mice

Carbofuran, a systemic N-methyl carbamate pesticide was administered orally with an effective dose of 1.3mg/kg per day to hemiovariectomized (HOVX) mice for 5, 10, and 15 days. Sham-operated and HOVX control mice were administered a similar quantity of olive oil. The vaginal smear and body weight of the mice were recorded daily and mice were sacrificed on day 16. The results of the present study indicate that there is a significant decrease in the duration of the estrus with a concomitant significant increase in the duration of the diestrus with carbofuran treatment for 10 days. In the HOVX mice treated with carbofuran for 15 days there was a significant decrease in the length of the estrous cycle and the duration of the estrus and metestrus with a concomitant significant increase in the diestrus. There was a significant increase in the ovarian weight in HOVX control mice when compared to that of the sham operated control mice. HOVX mice treated with carbofuran for 10 and 15 days showed a significant decrease in the relative ovarian weight with a concomitant inhibition of compensatory ovarian hypertrophy in HOVX mice. There was also a significant decrease in the ovarian growth rate in relation to the contralateral ovary of the same animal. There was a significant decrease in the number of small and total number of healthy follicles with a concomitant significant increase in the number of medium, large and total number of atretic follicles in HOVX mice treated with carbofuran for 10 days. There was a significant decrease in the number of small, medium, large, and total number of healthy follicles with a concomitant significant increase in the number of medium, large, and total number of atretic follicles in HOVX mice treated with carbofuran for 15 days. The administration of carbofuran in the present study showed that there is no significant change in the body and organs weight such as uterus, kidney, adrenals, liver, spleen, thymus and thyroid in all the carbofuran-treated mice. The above findings such as disruption in the estrous cycle, inhibition of compensatory ovarian hypertrophy, and follicular toxicity may be due to a direct effect on the ovary or through the hypothalamo-hypophysial-ovarian axis.

Temporal effects of mancozeb on testes, accessory reproductive organs and biochemical constituents in albino mice

Mancozeb, a fungicide of ethylenebisdithiocarbamate group was orally administered at 800 mg/kg body weight to male Swiss albino mice for 5, 10, 20 and 30 days. Daily body weight of the mice were recorded. The mice were sacrificed by cervical dislocation after 24 h of terminal exposure of mancozeb. Testes weight decreased significantly in 20 and 30 days mancozeb treated mice. However, there was a significant decrease in the number of spermatogonia, diameter of spermatocytes and spermatids in 20 days and number of spermatids in 10 days mancozeb treated mice. Histologic studies of the testis of the mice treated with mancozeb for long duration revealed spermatogenesis inhibition reflected by significant decrease in the number of spermatogenic cells and sperms, when compared with that of controls. In the mice treated with mancozeb for 20 and 30 days showed significant decrease in the weight of the prostate gland. However weight of Cowper's glands decreased significantly in 30 days mancozeb treated mice. There was significant decrease in the kidney, spleen and liver weight, where as thyroid weight increased significantly in mice treated with mancozeb for 30 days. However, thymus weight increased significantly only in the mice treated with mancozeb for 10, 20 and 30 days. In mice treated with mancozeb for 20 days caused significant decrease in the level of protein and a significant increase in the level of total lipids in the testis. However, there was significant decrease in the level of glycogen in the kidney. In mice treated with mancozeb for 30 days caused significant decrease in the levels of protein and glycogen and significant increase in the level of total lipids in the testis and liver and a significant decrease in the protein, glycogen and total lipids in the kidney. These observed effects of mancozeb on testis and biochemical constituents may be due to hormonal imbalance in any of the stages in the hypothalamo-hypophysial-testicular axis.

Potential mechanisms responsible for chlorotriazine-induced alterations in catecholamines in pheochromocytoma (PC12) cells

Chlorotriazines interact with undifferentiated PC12 cells in vitro to modulate catecholamine synthesis and release, but the mechanism(s) responsible for this effect had not been determined. In this study we evaluated the effect of atrazine, simazine and cyanazine on the protein expression of the enzymes responsible for the synthesis of dopamine [tyrosine hydroxylase (TH)] and norepinephrine [dopamine-beta-hydroxylase (DbetaH)]. We also examined the possible intracellular pathway associated with chlorotriazine-induced changes in catecholamine synthesis and release. Incubating PC12 cells in the presence of 100 microM atrazine and simazine decreased intracellular dopamine (DA), norepinephrine (NE) concentration and NE release, and the protein expression of TH (approximately 20%) and DbetaH (approximately 50 and 25%, respectively) after 12-24 h exposure. In contrast, cyanazine (100 microM) stimulated intracellular and released NE concentration, and the protein expression of TH (approximately 20%) and DbetaH (approximately 225%) after 12-36 h exposure. Simultaneous exposure to the essential TH co-factors (iron and tetrahydrobiopterine) was ineffective in altering cellular DA. Agents known to enhance TH and DbetaH transcription, phosphorylation or activity (e.g., 8-bromo cAMP, forskolin or dexamethasone) reversed the inhibitory effects of atrazine and simazine on the NE. Again, in contrast to atrazine and simazine, cyanazine attenuated catecholamine-depleting effect of alpha-Methyl-p-tyrosine (alphaMpT) on NE. Both DA and NE synthesis can be altered by the chlorotriazines and suggest these occur via an alteration of the synthetic enzymes TH and DbetaH.

Abnormal fertilization is responsible for reduced fecundity following thiram-induced ovulatory delay in the rat

Brief exposure to some pesticides, applied during a sensitive window for the neural regulation of ovulation, will block the preovulatory surge of LH and, thus, delay ovulation. Previously, we have shown that a single i.p. injection of 50 mg/kg of thiram, a dithiocarbamate fungicide that decreases norepinephrine synthesis, on proestrus (1300 h) suppresses the LH surge and delays ovulation for 24 h without altering the number of oocytes released. However, when bred, the treated dams had a decreased litter size and increased postimplantation loss. We hypothesized that the reduced litter size in thiram-delayed rats was a consequence of altered oocyte function arising from intrafollicular oocyte aging. To test this hypothesis, we examined delayed oocytes, zygotes, and 2-cell embryos for evidence of fertilization and polyspermy. In addition, we used confocal laser-scanning microscopy to evaluate and characterize cortical granule localization in oocytes and release in zygotes, because the cortical granule response is a major factor in the normal block to polyspermy. Our results demonstrate that a thiram-induced, 24-h delay in ovulation alters the fertilizability of the released oocyte. Although no apparent morphological differences were observed in the unfertilized mature oocytes released following the thiram-induced delay, the changes observed following breeding include a significant decrease in the percentage of fertilized oocytes, a significant increase in polyspermic zygotes (21%), and a 10-fold increase in the number of supernumerary sperm in the perivitelline space. Importantly, all the polyspermic zygotes exhibited an abnormal pattern of cortical granule exudate, suggestive of a relationship between abnormal cortical reaction and the polyspermy in the delayed zygotes. Because polyspermy is associated with polyploidy, abnormal development, and early embryonic death, the observed polyspermy could explain the abnormal development and decreased litter size that we observed previously following thiram-delayed ovulation.

Effect of endosulfan on ovarian compensatory hypertrophy in hemicastrated albino mice

Endosulfan, a chlorinated cyclodiene insecticide, was administered orally at 1.5, 3, 6, and 9 mg/kg per day to normal hemicastrated virgin mice for 15 consecutive days to examine the effect on ovarian function. Sham-operated and hemicastrated control mice were administered a similar volume of olive oil. The vaginal smear and body weight of the mice were recorded daily and mice were sacrificed on day 16. The remaining left ovary, uterus, kidney, adrenal, liver, thymus, and thyroid were removed and weighed. The left ovary from each animal was serially sectioned and stained for histologic studies. The hemicastrated control mice had a 40.5% increase in weight of the remaining left ovary and a significant increase in healthy and atretic follicles when compared with sham-operated controls. The remaining left ovaries of mice treated with 1.5mg endosulfan had a 37.2% increase in weight with no significant difference in ovarian weight and or in the healthy and atretic follicles when compared with hemicastrated olive oil-treated controls. However, treatment with 3, 6, and 9 mg endosulfan resulted in weight increases in the remaining left ovary of only 14.9, 7.4, and 0.8% and a significant decrease in healthy follicles with a concomitant increase in the number of atretic follicles compared to the olive oil-treated controls. There was no significant change in the number of estrous cycles or the duration of each phase of the estrous cycle with 1.5 and 3mg/kg per day endosulfan. However, there was a significant decrease in the number of estrous cycles, and the duration of estrus and metestrus with a concomitant significant increase in the duration of the diestrus phase with 6 and 9 mg/kg per day endosulfan treatment when compared with hemicastrated olive oil-treated controls. There were no significant change in body weight or the weights of the uterus, kidney, adrenal, liver, thymus, or thyroid after endosulfan treatment. These observations show that endosulfan treatment caused a significant decrease in compensatory ovarian hypertrophy. An increase in the number of atretic follicles and disruption of the estrous cycle may have been due to a direct effect on the ovary or to effects on the hypothalamo-hypophysial-ovarian axis.

Neuroendocrine and reproductive effects of contemporary-use pesticides

Work in our laboratory has focused on the hypothesis that certain environmental contaminants will interfere with reproductive function because they disrupt the neuroendocrine regulation of gonadal function. In this article, we review the evidence that certain classes of contemporary-use pesticides alter gonadotropin secretion through a disruption of hypothalamic mechanisms. Specifically, we discuss the effect of formamidine and dithiocarbamate pesticides on the noradrenergic control of pituitary hormone secretion, ovarian function, and pregnancy in the rat. This is followed by a review of studies evaluating the effect of a chlorotriazine herbicide, atrazine, on the hormonal control of ovulation and lactation. We also discuss the physiological consequences of these endocrine alterations in the female, how toxicant-induced endocrine alterations may differ in physiological outcome in the male and female, and the fact that the reproductive risk assessment of some pesticides that act on the central nervous system (CNS) may be influenced by the development of tolerance.

Characterization of pregnancy outcome following thiram-induced ovulatory delay in the female rat

A single injection of the dithiocarbamate fungicide, thiram, suppresses the proestrous surge of LH and delays ovulation for 24 h. In this study, we examined fertility after a thiram-induced delayed ovulation. Females were injected with thiram (50 mg/kg, IP) on proestrus (1300 h) and mated on the following evening. Control and thiram-treated, but nondelayed, females were injected and mated on the same day. The number of females in the thiram-delayed group that became pregnant was reduced and litter size on GD 20 was reduced: however, no obvious morphological anomalies were seen. The number of pregnant females and litter size was not altered in the thiram-nondelayed rats, indicating that it is the thiram-induced delay in ovulation and not the exposure to thiram per se that was responsible for altered pregnancy outcome. On GD 7 and 11, the number of live fetuses per litter was reduced in the delayed females, but the number of implantation sites was not different from controls. On GD 11 the mean developmental score, head length, crown-rump length, and somite number in the delayed group were also reduced, indicating retarded development of live embryos. These results demonstrate that delayed ovulation induced by a single thiram exposure does not alter the number of oocytes released or the number that implant. However, the concept from these females are compromised during midgestation.