Article

Organochlorine pesticides directly regulate gonadotropin-releasing hormone gene expression and biosynthesis in the GT1-7 hypothalmic cell line

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Abstract

Environmental toxicants profoundly affect growth and developmental processes. In the present study, we hypothesized that hypothalamic gonadotropin-releasing hormone (GnRH) neurons, which regulate the reproductive axis, are targets of environmental endocrine disrupting chemicals. Two organochlorine pesticides (methoxychlor and chlorpyrifos) were tested for their effects on GnRH gene expression and biosynthesis in the immortalized hypothalamic GT1-7 cells, which synthesize and secrete GnRH. GT1-7 cells were treated with methoxychlor or chlorpyrifos for 24 h in dose-response experiments, and GnRH gene expression and peptide levels were quantified. In order to examine whether these pesticides affect GnRH biosynthesis through the estrogen receptor (ER), in other experiments their effects were compared to those of estrogen, or they were co-administered with the ER antagonist, ICI 182,780 (ICI). Both methoxychlor and chlorpyrifos had significant effects on GnRH gene transcription and GnRH mRNA levels. These effects were not consistently blocked by ICI, nor did the effects of these pesticides consistently mimic those of estrogen, suggesting a mechanism independent of the ER. Chlorpyrifos and methoxychlor slightly stimulated peptide levels, and this effect was blocked by ICI, suggesting that the ER may mediate effects of pesticides on GnRH release. These results indicate that chlorpyrifos and methoxychlor alter GnRH biosynthesis in this hypothalamic cell line in vitro, suggesting that they may have endocrine disrupting effects on GnRH neurons in vivo.

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... There are scarce studies performed to evaluate reproductive effects of CPF. In spite of the poor understanding of this action, CPF was postulated for the first time as an endocrine disruptor (ED) because it was found that this pesticide directly regulates gonadotropin-releasing hormone gene expression and biosynthesis in the GT1-7 hypothalamic cell line [12]. ...
... In the last years, many chemical compounds were described as EDs when they are found at low concentrations in the environment. CPF and methoxychlor were found toslightly stimulate GnRH peptide levels, and this effect was blocked by the irreversible inhibitor of ERα, ICI 182,780, suggesting that this receptor mediates the effects of the pesticides on GnRH post-translational biosynthetic mechanisms [12]. ...
Chapter
Organophosphate pesticides comprise a group of substances used in agriculture for insect and plague control, infestations in buildings, man or domestic animals. The use of insecticides represents an environmental risk due to the high mass of product applied annually. Chlorpyrifos (CPF) is a broad-spectrum-organophosphate pesticide. The primary target of CPF toxicity is the central and peripheral nervous system, due to its ability to inhibit the acetylcholinesterase activity. However, other actions of CPF as the effects on synthesis of macromolecule like DNA, RNA and proteins, interactions with neurotransmitter receptors and other neurochemical affections were described. Breast cancer is the most frequent malignant disease in women. Exposure to estrogens throughout woman's life is a risk factor for this malignancy. Estrogen receptor alpha (ERa) is the major regulator of breast cancer tumor behavior. In the mammary gland, 17ß-estradiol (E2) promotes cell proliferation in both normal and transformed epithelial cells by modifying the expression of hormone responsive involved genes. Endocrine disrupter (ED) is defined as a compound of industrial or natural origin that interferes with hormone biosynthesis, action and metabolism, resulting in a deviation from normal homeostatic control or reproduction. CPF was recognized as an ED since it has been demonstrated to possess the ability to interfere with the ERa responses. Moreover, CPF possesses antiandrogenic activity and significantly decreases testosterone biosynthesis. We demonstrated the ability of CPF environmental concentration to induce cell proliferation through ERa in hormone-dependent MCF-7 breast cancer cells. In contrast, higher doses of CPF promoted cell cycle arrest in S-phase modifying checkpoints proteins, through a mechanism that may involve changes in redox balance in MCF-7 cells. In hormone-non-dependent MDA-MB-231 cells, we demonstrated that CPF is not able to promote cell proliferation but induces G2/M cell cycle arrest. In breast cancer cells, CPF induces redox imbalance, which lead to the cell cycle arrest. In turn, redox imbalance was trigged by an increment of p-ERK1/2 levels which is a result of an increment of hydrogen peroxide production induced by CPF. In vivo, we have recently observed that virgin rats exposed to CPF present a proliferative mammary tissue similar to the pregnant state, lower estradiol circulating levels and a prolonged estrous cycle. These results point to CPF as an ED stimulating the mammary gland proliferation and altering the estrogenic balance at systemic levels. Taken all this into account, the use of CPF should be strictly controlled considering that this pesticide could affect human or animal health and environment.
... However, the effects of pesticides on neuroendocrine axes have been less of a focus. There is good evidence that pesticides are neuroactive in vertebrates, and these chemicals have been shown to affect the expression of neuropeptides (Gore, 2002), alter the reuptake of neurotransmitters such as dopamine (DA) (Miller et al., 1999), and bind to receptors that regulate neuroendocrine signaling (Gore, 2008). We present some of the evidence for neuroendocrine disrupting effects of organopesticides that includes both organochlorines (OCPs) and organophosphates (OPs). ...
... Perhaps the most notable example is the gonadotropin hormone-releasing hormone (GnRH) neuron. Several OCPs have been shown to affect GnRH1 biosynthesis in the GT1-7 immortalized hypothalamic cell line (Gore, 2002). After 24 h exposure, both methoxychlor and chlorpyrifos (CPF; 1-100 lM) significantly affected GnRH primary transcript levels. ...
... GT1-7 cells (kindly provided by Dr. Pamela Mellon;Mellon et al., 1990) were maintained in phenol red-free DMEM supplemented with 10% heat-inactivated fetal calf serum (FCS) and antibiotics (100 U/ml, penicillin, 100 mg/ml streptomycin). Cells were grown at 37°C with 5% CO 2 as described previously (Gore, 2002;Gore et al., 2002), and used between passages 15 -20. Cells were sub-cultured into six-well or 96-well tissue culture dishes 2-3 days before experiments in Dulbecco's minimum essential medium (DMEM) plus FCS and antibiotics, and grown to approximately 60-70% confluency. ...
... At the molecular level, the actions of PCBs on endocrine systems are thought to be mediated, at least in part, by nuclear estrogen receptors. Therefore, we tested PCBs together with ICI 182,780, a nuclear estrogen receptor antagonist that can act at both estrogen receptors α and β (Wijayaratne et al., 1999), and which has previously been shown to block some effects of estradiol in GT1-7 cells (Gore 2002) and other experimental models (Lee et al., 1999). In the current study, ICI 182,780 caused a partial reversal of the effects of the individual PCBs or their mixture on GnRH peptide secretion, suggesting potential involvement of an estrogen receptor-dependent mechanism, but also indicating that other mechanisms must be involved. ...
Article
Exposure to endocrine disrupting chemicals (EDCs) such as polychlorinated biphenyls (PCBs) causes functional deficits in neuroendocrine systems. We used an immortalized hypothalamic GT1-7 cell line, which synthesizes the neuroendocrine peptide gonadotropin-releasing hormone (GnRH), to examine the neurotoxic and endocrine disrupting effects of PCBs and their mechanisms of action. Cells were treated for 1, 4, 8, or 24 h with a range of doses of a representative PCB from each of three classes: coplanar (2,4,4′,5-tetrachlorobiphenyl: PCB74), dioxin-like coplanar (2′,3,4,4′,5′ pentachlorobiphenyl: PCB118), non-coplanar (2,2′,4,4′,5,5′-hexachlorobiphenyl: PCB153), or their combination. GnRH peptide concentrations, cell viability, apoptotic and necrotic cell death, and caspase activation were quantified. In general, GnRH peptide levels were suppressed by high doses and longer durations of PCBs, and elevated at low doses and shorter timepoints. The suppression of GnRH peptide levels was partially reversed in cultures co-treated with the estrogen receptor antagonist ICI 182,780. All PCBs reduced viability and increased both apoptotic and necrotic cell death. Although the effects for the three classes of PCBs were often similar, subtle differences in responses, together with evidence that the combination of PCBs acted slightly different from individual PCBs, suggest that the three tested PCB compounds may act via slightly different or more than one mechanism. These results provide evidence that PCB congeners have endocrine disrupting and/or neurotoxic effects on the hypothalamic GnRH cell line, a finding that has implications for environmental endocrine disruption in animals.
... Also, brain cholinergic activity increases prolactin secretion (Findling and Tyrrel, 1991). The OP pesticide chlorpyrifos may induce gene expression and biosynthesis of gonadotropin-releasing hormones (GnRH) " in vitro " (Gore, 2002) and can inhibit adrenal steroidogenesis as also do other OPs (Civen et al., 1977; Walsh et al., 2000). Inhibition of AChE in the hypothalamus may also alter the rate of GnRH secretion (Krsmanovic et al., 1998) and thus modify pituitary secretion of LH and FSH (Fig. 2 ). ...
Article
There is a growing concern about the endocrine effects of long-term, low-level exposure to organophosphate (OP) compounds. Studies on experimental animals have found that OP pesticides have an impact on the endocrine system and a few clinical and epidemiological studies have also shown that OPs may affect the male hormone profile, although results are inconsistent. We have evaluated the effect of exposure to OP pesticides, measured through urinary levels of six dialkylphosphate (DAP) metabolites, on male hormone profile in 136 floriculture workers from the State of Mexico and Morelos during two agricultural periods with different degree of pesticide exposure. Generalized estimated equations (GEE) models were developed and adjusted for several potential confounders, including PON1 enzyme activity, as a biomarker of susceptibility, and serum levels of p,p'-DDE, a metabolite of the pesticide DDT widely used in Mexico until 1999 for control of agricultural pests and malaria. Exposure of male floriculture workers to OP pesticides was associated with increased serum levels of follicle-stimulating hormone (FSH) and prolactin and with decreased serum testosterone and inhibin B levels. Among all DAPs tested, only DETP was inversely associated with luteinizing hormone (LH). Estradiol showed a marginally significant positive trend with DEP and DETP derivatives. In conclusion, OP pesticides may have an impact on the endocrine function because of their potential to modify the male hormone profile as a function of the type of pesticide used as well as the magnitude of exposure.
... In view of the fact that the adrenal gland induces production of a variety of cytokines, interactions between pesticides and HPA axis may result in change in the cytokine network (Marx et al., 1998). Moreover, since stimulatory effect of GnRH on immune system has been demonstrated in several studies, OC-and OP-mediated immunosuppression may partly attribute to dysregulation of pituitary gonadotropins (Gore, 2002; Sarkar et al., 2000; Tanriverdi et al., 2003). In the other hand, since the sex hormones play an important role in the modulation and development of immune responses, pesticides can disturb the normal function of the immune system via interference with secretion, metabolism and/or signaling of these hormones. ...
Article
Nowadays, in many communities, there is a growing concern about possible adverse effects of pesticides on human health. Reports indicate that during environmental or occupational exposure, pesticides can exert some intense adverse effects on human health through transient or permanent alteration of the immune system. There is evidence on the relation between pesticide-induced immune alteration and prevalence of diseases associated with alterations of the immune response. In the present study, direct immunotoxicity, endocrine disruption and antigenicity have been introduced as the main mechanisms working with pesticides-induced immune dysregulation. Moreover, the evidence on the relationship between pesticide exposure, dysregulation of the immune system and predisposition to different types of psychiatric disorders, cancers, allergies, autoimmune and infectious diseases are criticized.
... In the female reproductive system, diethylstilbestrol (DES) induces some morphological and functional changes [15]. In an in vitro study two organochlorine pesticides, methoxychlor and chlorpyrifos have caused alteration in the biosynthesis of gonadotropin hormone in hypothalamic GT1-7 cells [19]. So, toxicants target the whole system of hormone release in humans. ...
Article
Full-text available
Endocrine disrupting chemicals (EDC) are released into environment from different sources. They are mainly used in packaging industries, pesticides and food constituents. Clinical evidence, experimental models, and epidemiological studies suggest that EDC have major risks for human by targeting different organs and systems in the body. Multiple mechanisms are involved in targeting the normal system, through estrogen receptors, nuclear receptors and steroidal receptors activation. In this review, different methods by which xenobiotics stimulate signaling pathways and genetic mutation or DNA methylation have been discussed. These methods help to understand the results of xenobiotic action on the endocrine system. Endocrine disturbances in the human body result in breast cancer, ovarian problems, thyroid eruptions, testicular carcinoma, Alzheimer disease, schizophrenia, nerve damage and obesity. EDC characterize a wide class of compounds such as organochlorinated pesticides, industrial wastes, plastics and plasticizers, fuels and numerous other elements that exist in the environment or are in high use during daily life. The interactions and mechanism of toxicity in relation to human general health problems, especially endocrine disturbances with particular reference to reproductive problems, diabetes, and breast, testicular and ovarian cancers should be deeply investigated. There should also be a focus on public awareness of these EDC's risks and their use in routine life. Therefore, the aim of this review is to summarize all evidence regarding different physiological disruptions in the body and possible involved mechanisms, to prove the association between endocrine disruptions and human diseases.
... This could be the main cause of the acute symptoms experienced after pesticide application. Thus, showing the health impact linked to their use, in fact such exposure can cause acute effects such as respiratory difficulties, skin irritation, headaches, blurred vision, fatigue (Zuskin et al., 2008), etc., and chronic effects such as endocrine disruption (reproduction) (Hirakawa et al., 2000; Gore, 2002 ), congenital malformation (teratogennicity ), induction of tumors and cancers (carcinogenesis) (Purdue et al., 2007; Bonner et al., 2005), gene mutation (mutagenesis), neuro-toxicity (central and peripheral nervous system) and immunosuppression (Lori et al., 2012). In this study, the association between pesticide exposure and the onset of symptoms showed that all the symptoms described by the gardeners and regularly observed were acute. ...
Article
Full-text available
Cameroon signed in 2001 and ratified in 2005, the Stockholm convention which aimed at restricting and eliminating the production, utilization and discharge of persistent organic pollutants (POPs). Since then, the implementation of this convention in countries is not effective despite the perceptive diffusion of this toxic chemical substance. Few studies on the diffusion of POPs and risks attached to it have been carried out in Yaounde. Thus, the aim of this study was to search the measures to limit sanitary and environmental impact which might result from the diffusion of these POPs in Yaounde VII sub-division. This descriptive, transversal and retrospective study was carried out from February to May, 2013. 100 Cameroonians aged 20 years and above took part in the study. A survey comprising globally of the sources of production of POPs and the identification of sanitary and environmental impact was performed. The results obtained were analysed using the STAT 11.0 software. The association between an exposition to a toxic chemical substance and the appearance of symptoms was measured through the estimation of the impact which corresponds to the calculation of the event rate. The proportion of participants aged more than 30 years was significantly higher than the proportion of participants aged 20 to 30 years (p<0.05). The participants did not follow any training for the use of pesticides. 70% of them did not know what is known as a POP pesticide, were ignorant and bought pesticides in the black market. An absence of the individual protection equipment was observed in the market-gardeners. The number of market gardeners having skin irritation and headaches daily after application of the pesticides was significantly higher as compared to the market gardeners not presenting any symptom, with respective risk of 0.9 and 0.8 for occurrence of each symptom after exposition. The number of users having headache, blurred vision and fatigue after manipulating paints was significantly higher as compared to users presenting no symptom, with respective risk of 0.9, 0.8 and 0.8 for occurrence of each symptom after exposition. It is worth noting that 15% of the study population was involved in the non-intentional production of POPs (dioxins and furans) through incineration of garbage. The sources of intentional production of POPs were: the wood transformation factory, the industry for production of plastic plates and cups as well as clandestine pastries. In conclusion, the diffusion of POPs in Yaounde VII sub-division could be associated with sanitary impact which varies from one individual to another. The assessment of the environmental risk was not exhaustive and therefore requires a more advanced study in which the POPs will be analysed in samples such as water, soil, air and food. Key words: Health, environment, risk, persistent organic pollutants (POPs), Yaounde.
... Preliminary observations [19] indicate that o,p ′ -dichlorodiphenyltrichloroethane could have stimulatory effects on GnRH secretion with involvement of oestrogen receptors and the glutamate receptor as well as the orphan dioxin receptor [32]. Two PCB mixtures, Aroclor 1221 (A1221) and A1254, have been shown to influence GnRH transcript and peptide levels after exposure of the hypothalamic neuronal GT1-7 cells in vitro [48]. Alternatively, some compounds such as DDT are known to interfere with brain aromatase, which converts testosterone into oestrogen in the immature brain [49]. ...
... A limited number of evidence is so far available exploring the endocrine disrupting potential of CPF, primarily exploring in vitro methods. CPF alters gonadotropin-releasing hormone biosynthesis in GT1-7 hypothalamic cell lines [57]; both anti-androgenic [58] and estrogenic effects, inducing growth in breast cancer cells [59,60], have been observed. Interestingly, still in vitro data from a wide screening study using cancer fibroblast cells (MCF-7BUS) evidenced that CPF selectively increases ERβ, but not ERα gene expression [61]. ...
... In view of the fact that the adrenal gland induces production of a variety of cytokines, interactions between pesticides and HPA axis may result in change in the cytokine network (Marx et al., 1998). Moreover, since stimulatory effect of GnRH on immune system has been demonstrated in several studies, OC-and OP-mediated immunosuppression may partly attribute to dysregulation of pituitary gonadotropins (Gore, 2002;Sarkar et al., 2000;Tanriverdi et al., 2003). ...
Article
Nowadays, in many communities, there is a growing concern about possible adverse effects of pesticides on human health. Reports indicate that during environmental or occupational exposure, pesticides can exert some intense adverse effects on human health through transient or permanent alteration of the immune system. There is evidence on the relation between pesticide-induced immune alteration and prevalence of diseases associated with alterations of the immune response. In the present study, direct immunotoxicity, endocrine disruption and antigenicity have been introduced as the main mechanisms working with pesticides-induced immune dysregulation. Moreover, the evidence on the relationship between pesticide exposure, dysregulation of the immune system and predisposition to different types of psychiatric disorders, cancers, allergies, autoimmune and infectious diseases are criticized.
... A limited number of evidence is so far available exploring the endocrine disrupting potential of CPF, primarily exploring in vitro methods. CPF alters gonadotropin-releasing hormone biosynthesis in GT1-7 hypothalamic cell lines [57]; both anti-androgenic [58] and estrogenic effects, inducing growth in breast cancer cells [59,60], have been observed. Interestingly, still in vitro data from a wide screening study using cancer fibroblast cells (MCF-7BUS) evidenced that CPF selectively increases ERβ, but not ERα gene expression [61]. ...
Article
Full-text available
Chlorpyrifos (CPF) is one of the most widely used organophosphate pesticides worldwide. Epidemiological studies on pregnant women and their children suggest a link between in utero CPF exposure and delay in psychomotor and cognitive maturation. A large number of studies in animal models have shown adverse effects of CPF on developing brain and more recently on endocrine targets. Our aim was to determine if developmental exposure to CPF affects social responsiveness and associated molecular neuroendocrine markers at adulthood. Pregnant CD1 outbred mice were fed from gestational day 15 to lactation day 14 with either a CPF-added (equivalent to 6 mg/kg/bw/day during pregnancy) or a standard diet. We then assessed in the offspring the long-term effects of CPF exposure on locomotion, social recognition performances and gene expression levels of selected neurondocrine markers in amygdala and hypothalamus. No sign of CPF systemic toxicity was detected. CPF induced behavioral alterations in adult offspring of both sexes: CPF-exposed males displayed enhanced investigative response to unfamiliar social stimuli, whereas CPF-exposed females showed a delayed onset of social investigation and lack of reaction to social novelty. In parallel, molecular effects of CPF were sex dimorphic: in males CPF increased expression of estrogen receptor beta in hypothalamus and decreased oxytocin expression in amygdala; CPF increased vasopressin 1a receptor expression in amygdala in both sexes. These data indicate that developmental CPF affects mouse social behavior and interferes with development of sex-dimorphic neuroendocrine pathways with potential disruptive effects on neuroendocrine axes homeostasis. The route of exposure selected in our study corresponds to relevant human exposure scenarios, our data thus supports the view that neuroendocrine effects, especially in susceptible time windows, should deserve more attention in risk assessment of OP insecticides.
... Neurodevelopmental effects have also been described (Auman et al. 2000;Campbell et al. 1997;Carr et al. 2001;Chakraborti et al. 1993;Chanda and Pope 1996;Crumpton et al. 2000;Dam et al. 1999;Dam et al. 1998Dam et al. , 2000Dam et al. , 2003Das and Barone 1999;Garcia et al. 2002;Gore 2001Gore , 2002Jett et al. 2001;Lassiter et al. 1998;Levin et al. 2002;Levin et al. 2001;Olivier et al. 2001;Qiao et al. 2002;Qiao et al. 2001;Qiao et al. 2003;Raines et al. 2001;Richardson and Chambers 2003;Roy et al. 1998;Sachana et al. 2001;Slotkin et al. 2001;Slotkin et al. 2002;Song et al. 1998;Tang et al. 1999;Whitney et al. 1995;Won et al. 2001). Some of these studies suggested that developmental neurotoxicity occurred at lower exposure levels than did acetylcholinesterase inhibition in adult animals, and developmental neurotoxicity may be worthy of consideration in future risk assessments (Abdel-Rahman et al. 2002). ...
Chapter
Introduction Physiologically Based Pharmacokinetic Modeling Pharmacodynamic Modeling Future Directions References
... The past 20 years have produced a great deal of new information from experimental studies focused on molecular, cellular, and animal experiments (6) to epidemiological studies demonstrating that a wide array of chemical structures-pharmaceuticals, personal care products, commercial chemicals, and environmental pollutants-can interfere with hormone action. Among the chemicals known to be EDCs are diethylstilbestrol (7), polychlorinated biphenyls, dioxins, perfluoroalkyl compounds, solvents, phthalates (8), BPA (9), dichlorodiphenyldichloroethylene (DDE) (10), organophosphate and organochlorine pesticides (11), and polybrominated diphenyl ethers (PBDEs) (12,13). These chemicals have been shown to interfere with a variety of endocrine pathways, including estrogen (14), androgen (14), thyroid (15,16), retinol (17), aryl hydrocarbon, and peroxisome proliferator-activated receptor pathways (18). ...
Article
Full-text available
A previous report documented that endocrine disrupting chemicals contribute substantially to certain forms of disease and disability. In the present analysis, our main objective was to update a range of health and economic costs that can be reasonably attributed to endocrine disrupting chemical exposures in the European Union, leveraging new burden and disease cost estimates of female reproductive conditions from accompanying report. Expert panels evaluated the epidemiologic evidence, using adapted criteria from the WHO Grading of Recommendations Assessment, Development and Evaluation Working Group, and evaluated laboratory and animal evidence of endocrine disruption using definitions recently promulgated by the Danish Environmental Protection Agency. The Delphi method was used to make decisions on the strength of the data. Expert panels consensus was achieved for probable (>20%) endocrine disrupting chemical causation for IQ loss and associated intellectual disability; autism; attention deficit hyperactivity disorder; endometriosis; fibroids; childhood obesity; adult obesity; adult diabetes; cryptorchidism; male infertility, and mortality associated with reduced testosterone. Accounting for probability of causation, and using the midpoint of each range for probability of causation, Monte Carlo simulations produced a median annual cost of €163 billion (1.28% of EU Gross Domestic Product) across 1000 simulations. We conclude that endocrine disrupting chemical exposures in the EU are likely to contribute substantially to disease and dysfunction across the life course with costs in the hundreds of billions of Euros per year. These estimates represent only those endocrine disrupting chemicals with the highest probability of causation; a broader analysis would have produced greater estimates of burden of disease and costs.
... These effects may be mediated by the oestrogen receptors. The effect was biphasic with lower doses stimulating and higher doses inhibiting mRNA levels (Gore 2002). found sex-selective elevated plasma cholesterol and triglycerides in adult rats exposed to 1 mg/kg chlorpyrifos on postnatal days 1-4. ...
... Evidences on the hormonal activity of CPF in different species are so far scant and not fully consistent, but an inverse link between CPF exposure and reproductive hormones in humans has been reported (Meeker et al., 2006b). Further studies which support CPF effects on hormones, directly involved in reproductive functions, come from hypothalamic GT1 cell lines, a validated model for the gonadotropin-releasing hormone neurons in vivo (Gore, 2002). Similarly to other classes of recognized EDC (PCB, PBDE, phthalates), CPF interferes with thyroid functions in humans (Fortenberry et al., 2012;Haviland et al., 2010;Meeker et al., 2006a) and in experimental rodents after developmental exposure (De Angelis et al., 2009). ...
Article
The complexity of the neuroendocrine level of investigation requires the assessment of behavioral patterns that extend beyond the reproductive functions, which are age- and sex-specific in rodents, described by defined clusters of behavioral items regulated by genetic, hormonal, and epigenetic factors. The study of social behavior in laboratory rodents reveals sex-dimorphic effects of environmental chemicals that may be undetected either by a traditional neurotoxicological approach or referring to the classical definition of endocrine disrupting chemicals. Here we review data on the neurobehavioral effects of developmental exposure to the non-persistent organophosphorus insecticide chlorpyrifos, whose neurotoxic activity at low doses is currently a matter of concern for children's health. In mice exposed to chlorpyrifos in utero and/or in early development social/emotional responses are differently affected in the two sexes in parallel with sex-dependent interference on hypothalamic neuroendocrine pathways regulating social behaviors (vasopressin, oxytocin, and steroid regulated systems). Through the analysis of complex sex-dimorphic behavioral patterns we show that neurotoxic and endocrine disrupting activities of CPF overlap. This widely diffused organophosphorus pesticide might thus be considered as a neuroendocrine disruptor possibly representing a risk factor for sex-biased neurodevelopmental disorders in children.
... However, this study also emphasizes that ecological implications may stem from the use of herbicides and affect non-target organisms. Similar cases were exemplified in the findings that the degradation products of the insect growth hormone, methoprene, affected amphibian differentiation [29], and some pesticides exhibit oestrogen activity [30]. ...
Article
Pheromones of nocturnal moths are derived from fatty acids produced as a result of the activity of acetyl-CoA carboxylase. This timely production is initiated in nocturnal moths by a tropic peptide, pheromone biosynthesis activating neuropeptide released into the hemolymph. In monocotyledonous plants, specific plastid acetyl-CoA carboxylase is inhibited by herbicides that target the eukaryotic form of the enzyme. We report evidence that these herbicides can also target pheromone biosynthesis by a moth, thereby implicating the acetyl-CoA carboxylase as a key regulatory enzyme in the pheromone biosynthetic pathway. These findings, whilst indicating the possible action of such herbicides on non-target organisms, also suggest a novel alternative method of insect pest management, which precludes sex-pheromone production and mating success, thereby reducing insect population growth.
... TCDD affected the levels of other hormones as well. For instance, Gore [8] showed methoxychlor to affect GnRH expression in hypothalamic GT1-7 cells. In a study from our laboratory, TCDD inhibited E2 secretion by follicular cells and P4 secretion by luteal cells dose-dependently. ...
Article
Full-text available
Persistent organic pollutants (POPs), such as polychlorinated dibenzo-p-dioxins (PCDDs) and dibenzofurans (PCDFs), polychlorinated biphenyls (PCBs), and polybrominated ethers (PBDEs), chloronaftalens (PCNs), and bisphenol A (BPA), are stable, lipophilic pollutants that affect fertility and cause serious reproductive problems, including ovotoxic action, lack of ovulation, premature ovarian failure (POF), or polycystic ovarian syndrome (PCOS). Most of the representatives of POPs influence the activation of transcription factors, not only activation of aromatic hydrocarbon receptor (AhR), but also the steroid hormone receptors. This minireview will focus on a variety of PAH activities in oocyte, ovary, placenta, and mammary gland. The complexity and diversity of factors belonging to POPs and disorders of the reproductive function of women indicate that the impact of environmental pollution as an important determinant factor in fertility should not be minimize.
... Moreover, these effects were reversed after a natural antioxidant administration to the animals, indicating the importance of oxidative damage in decreasing hormone levels [62]. Finally, Gore demonstrated that CPF greatly affects GT1-7 cell morphology, and gonadotropin-releasing hormone (GnRH) gene expression and biosynthesis [63]. Additionally, 3b-HSD and CYP17 steroidogenic enzymes are positively regulated by the hormone LH [64]. ...
... In view of the fact that the adrenal gland induces production of a variety of cytokines, interactions between pesticides and HPA axis may result in change in the cytokine network (Marx et al., 1998). Moreover, since stimulatory effect of GnRH on immune system has been demonstrated in several studies, OC-and OP-mediated immunosuppression may partly attribute to dysregulation of pituitary gonadotropins (Gore, 2002; Sarkar et al., 2000; Tanriverdi et al., 2003). In the other hand, since the sex hormones play an important role in the modulation and development of immune responses, pesticides can disturb the normal function of the immune system via interference with secretion, metabolism and/or signaling of these hormones. ...
Article
Nowadays, in many communities, there is a growing concern about possible adverse effects of pesticides on human health. Reports indicate that during environmental or occupational exposure, pesticides can exert some intense adverse effects on human health through transient or permanent alteration of the immune system. There is evidence on the relation between pesticide-induced immune alteration and prevalence of diseases associated with alterations of the immune response. In the present study, direct immunotoxicity, endocrine disruption and antigenicity have been introduced as the main mechanisms working with pesticides-induced immune dysregulation. Moreover, the evidence on the relationship between pesticide exposure, dysregulation of the immune system and predisposition to different types of psychiatric disorders, cancers, allergies, autoimmune and infectious diseases are criticized.
... The mRNA steady state abundance of neuropeptides in the vertebrate CNS has previously been shown to be affected by organochlorines. In PC12 cell lines, dieldrin increased mRNA levels from neurohormones that included, corticotropin releasing hormone, neuropeptide Y, and tachykinin 1 (Slotkin and Seidler, 2010) and methoxychlor, another OCP, has been shown to significantly suppress GnRH mRNA levels in GT1-7 cells (Gore, 2002). It has been pointed out that the fish neuroendocrine system is understudied in the context of environmental pollutants. ...
Article
Organochlorine pesticides (OCPs) such as dieldrin are a persistent class of aquatic pollutants that cause adverse neurological and reproductive effects in vertebrates. In this study, female and male largemouth bass (Micropterus salmoides) (LMB) were exposed to 3mg dieldrin/kg feed in a 2 month feeding exposure (August-October) to (1) determine if the hypothalamic transcript responses to dieldrin were conserved between the sexes; (2) characterize cell signaling cascades underlying dieldrin neurotoxicity; and (3) determine whether or not co-feeding with 17β-estradiol (E(2)), a hormone with neuroprotective roles, mitigates responses in males to dieldrin. Despite also being a weak estrogen, dieldrin treatments did not elicit changes in reproductive endpoints (e.g. gonadosomatic index, vitellogenin, or plasma E(2)). Sub-network (SNEA) and gene set enrichment analysis (GSEA) revealed that neuro-hormone networks, neurotransmitter and nuclear receptor signaling, and the activin signaling network were altered by dieldrin exposure. Most striking was that the majority of cell pathways identified by the gene set enrichment were significantly increased in females while the majority of cell pathways were significantly decreased in males fed dieldrin. These data suggest that (1) there are sexually dimorphic responses in the teleost hypothalamus; (2) neurotransmitter systems are a target of dieldrin at the transcriptomics level; and (3) males co-fed dieldrin and E(2) had the fewest numbers of genes and cell pathways altered in the hypothalamus, suggesting that E(2) may mitigate the effects of dieldrin in the central nervous system.
... The perimenopausal phase is characterized by increased levels of gonadotropins (hypergonadotropic condition) that are able to activate different molecular pathways involved in cellular growth and invasion and EDC exposure may enhance this process, further increasing gonadotropin levels and consequently the risk of OC 94 . It has been reported that chlorpyrifos and MXC might be able to alter gonadotropin-releasing hormone production 95,96 , and that DDT might disturb the normal functioning of gonadotropins via the expression of follicle stimulating hormone (FSH) and luteinizing hormone (LH) 97 . ...
Article
Purpose: Over the last two decades, increasing attention has been paid to environmental toxins and their effects on the female reproductive system. Endocrine disrupting chemicals (EDCs) are exogenous substances or mixtures that can mimic the action of steroid hormones and interfere with their metabolism. Advanced glycation end products (AGEs) are proinflammatory molecules that can interact with cell surface receptors and mediate the triggering of proinflammatory pathways and oxidative stress. The purpose of this review is to explore the effects of environmental toxins exposure in the pathogenesis of both polycystic ovary syndrome (PCOS) and OC (ovarian cancer), considered separately, and also to evaluate possible neoplastic ovarian repercussion after exposure in patients diagnosed with PCOS. Materials and methods: We searched PubMed for articles published in the English language with the use of the following MeSH search terms: “Polycystic Ovary Syndrome” and “Ovarian Cancer” combined with “endocrine disruptors”. Titles and abstracts were examined and full articles that met the selection criteria were retrieved. A manual search of review articles and cross-references completed the search. Results: Extensive data from different studies collected in recent years concerning the effects of EDCs/AGEs exposure have confirmed their role in the pathophysiology of both PCOS and OC. They favour PCOS/OC development through different mechanisms that finally lead to hormonal and metabolic disruption and epigenetic modifications. Conclusions: Environmental toxin exposure in PCOS women could favour neoplastic transformation by exacerbating and potentiating some PCOS features. Further research, although difficult, is needed in order to prevent further diffusion of these substances in the environment, or at least to provide adequate information to the population considered at risk.
... The neuroendocrine system of the hypothalamus-pituitarygonad (HPG) axis regulates reproduction in vertebrates and can be influenced by chemicals, therefore affecting the reproductive system. Neurotoxic environmental contaminants recognized as endocrine-disrupting chemicals (EDCs) have aroused considerable interest in the field of neuroendocrinology (Gore 2000;Pillai et al. 2003;Panzica et al. 2005;Gore 2008a, b). Among these pollutants, organochlorine pesticides are considered to be hazardous because they are very persistent, are nonbiodegradable, and are ubiquitously found in the environment (Palmer and Palmer 1995;Donohoe and Curtis 1996). ...
Article
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Endocrine-disrupting chemicals can influence the hypothalamus-pituitary-gonad axis and possibly affect reproduction in vertebrates. We analyzed the effect of 30-day endosulfan (ES) exposure in sexually undifferentiated larvae of the cichlid fish Cichlasoma dimerus. The number, area, mean cytoplasmic and nuclear diameter, and mean cytoplasmic optical density of gonadotropin-releasing hormone (GnRH) I, II, and III immunoreactive (ir-) neurons and β follicle-stimulating hormone (βFSH) ir-cells were measured. Animals exposed to the highest ES concentration (0.1 μg/l) showed a decrease in GnRH I nucleus/cytoplasm area ratio upon exposure. Nuclear area and mean nuclear diameter of βFSH ir-cells was higher in ES treated fish. βFSH nucleus/cytoplasm area ratio was high in exposed animals, and animals exposed to 0.1 μg/l ES showed smaller mean cytoplasmic optical density. These findings suggest that ES affects GnRH I and βFSH protein synthesis/release. However, these responses seem to be insufficient to affect gonadal differentiation at this stage of development.
... In this case, the endocrine disruption occurs at the level of the hypothalamus [137]. Similar studies using GT1-7 cell lines exposed to small doses of organochlorine pesticides demonstrated an increased expression of GnRH, whereas when exposed to high doses, the opposite effect was observed [138]. Although these works showed a positive response of GnRH cell lines to environmental obesogens, other studies demonstrated different outcomes. ...
Article
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The current scenario of male infertility is not yet fully elucidated; however, there is increasing evidence that it is associated with the widespread exposure to endocrine-disrupting chemicals (EDCs), and in particular to obesogens. These compounds interfere with hormones involved in the regulation of metabolism and are associated with weight gain, being also able to change the functioning of the male reproductive axis and, consequently, the testicular physiology and metabolism that are pivotal for spermatogenesis. The disruption of these tightly regulated metabolic pathways leads to adverse reproductive outcomes. The permanent exposure to obesogens has raised serious health concerns. Evidence suggests that obesogens are one of the leading causes of the marked decline of male fertility and key players in shaping the future health outcomes not only for those who are directly exposed but also for upcoming generations. In addition to the changes that lead to inefficient functioning of the male gametes, obesogens induce alterations that are “imprinted” on the genes of the male gametes, establishing a link between generations and contributing to the transmission of defects. Unveiling the molecular mechanisms by which obesogens induce toxicity that may end-up in epigenetic modifications is imperative. This review describes and discusses the suggested molecular targets and potential mechanisms for obesogenic–disrupting chemicals and the subsequent effects on male reproductive health.
... Chlorpyriphos alone showed weak estrogen-like effects on the ER␤ mRNA level, according to the reported weak estrogenic properties of the pesticide (Andersen et al., 2002). In vitro study concerning the hypothalamic gonadotropin-releasing hormone (GnRH) indicates that the effect of chlorpyrifos is mediated via the ERs (Gore, 2002). The organochlor and organophosphorous pesticides (prochloraz, fenarimol, endosulfan, dieldrin, and tolchlofos-methyl) exerted a further increase of the E2-induced ER␤ mRNA level. ...
... Liver transcriptomics studies have shed light on alterations to lipid metabolism and the hepatic transcriptome following EDC exposure (Santangeli et al., 2018;Zare et al., 2018). EDC alter neurotransmitter receptor pathways in brain as well as overall gene expression patterns (Martyniuk et al., 2006;Gore, 2010) and polychlorinated biphenyls were observed to affect GnRH gene expression in GT-1 cell lines (Gore, 2002). In gonad, BPA exhibits estrogenic and anti-androgenic properties (Takayanagi et al., 2006;Hatef et al., 2012). ...
Article
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Endocrine disrupting chemicals mimic or disrupt action of the natural hormones, adversely impacting hormonal function as well as cardiovascular, reproductive, and metabolic health. Goldfish are seasonal breeders with an annual reproductive cycle regulated by neuroendocrine signaling which involves allocation of metabolic energy to sustain growth and reproduction. We hypothesize that seasonal changes in physiology alter overall vulnerability of goldfish to metabolic perturbation induced by environmental contaminants. In this study, we assess effects of endogenous hormones, individual contaminants and their mixture on metabolism of goldfish at different reproductive stages. Exposure effects were assessed using 1H-NMR metabolomics profiling of male goldfish midbrain, gonad and liver harvested during early recrudescence (October), mid-recrudescence (February) and late recrudescence (June). Compounds assessed include bisphenol A, nonylphenol, bis(2-ethylhexyl) phthalate, fucosterol and a tertiary mixture (DEHP + NP + FS). Metabolome-level responses induced by contaminant exposure across tissues and seasons were benchmarked against responses induced by 17β-estradiol, testosterone and thyroid hormone (T3). We observe a clear seasonal dependence to metabolome-level alteration induced by hormone or contaminant exposures, with February (mid-recrudescence) the stage at which male goldfish are most vulnerable to metabolic perturbation. Responses induced by contaminant exposures differed from those induced by the natural hormones in a season-specific manner. Exposure to the tertiary mixture induced a functional gain at the level of biochemical pathways modeling over responses induced by individual components in select tissues and seasons. We demonstrate the importance of seasonally driven changes in physiology altering overall vulnerability of goldfish to metabolic perturbation induced by environmental contaminants, the relevance of which likely extends to other seasonally-breeding species.
... Observações preliminares (Rasier et al., 2006) indicam que o diclorodifeniltricloroetano pode ter efeito estimulante sobre a secreção de GnRH com o envolvimento de receptores de estrogênio e receptor de glutamato, bem como receptores órfãos (Ohtake et al., 2003). Constatou-se que duas misturas de PCB, Aroclor 1221 (A1221) e A1254 influenciam a transcrição de GnRH e os níveis de peptídeo após a exposição das células neuronais hipotalâmicas GT1-7 in vitro (Gore, 2002). Por outro lado, sabe-se que alguns compostos como o DDT interferem na aromatase no cérebro, que converte a testosterona em estrogênio no cérebro imaturo (Kuhl Manning e Brouwer, 2005). ...
... Ces données ont montré que les neurones à GnRH sont sensibles aux polychlorobiphényles (PCB). En effet, ces molécules classées comme écotoxiques et reprotoxiques induisent une modification de l'expression du gène GnRH-1(Gore, 2002), une modification de la sécrétion du peptide GnRH par lesGT1-7 (McGarvey et al., 2001) et des modifications de la morphologie cellulaire. ...
... Despite the agricultural benefits from the use of pesticides, a number of issues surrounding their use have been identified; in particular, (i) environmental concerns involving contamination of soil, water and air [14] , impacts to ecological systems [15,16] and (iii) effects on human health [17][18][19][20] . For example, the insecticide chloropyrifos, which is an organophosphorus pesticide, has been found to be highly toxic with effects on the nervous system [21] . Likewise, the pesticide dichlorodiphenyltrichloroethane (DDT), which has now been banned in numerous countries, is a known endocrine disruptor with its effects influencing the human reproductive, cardiovascular and metabolic systems [22] . ...
Article
Pesticide residue analysis in cannabis has become a subject of growing interest in North America since recent legalization in Canada and decriminalization for medicinal or recreational use in most US states. To meet regulatory and quality control standards, cannabis products should be tested for both authorized and unauthorized pesticides. In Canada, testing requirements mandated by Health Canada stipulate pesticide contaminant limits of quantification values of 0.02-3.0 μg/g, 0.01-2.5 μg/g and 0.01-1.5 μg/g for cannabis dried flowers, oil and fresh plants, respectively. Sample preparation and clean up methods reported in the literature for pesticide analysis in cannabis products include liquid-liquid extraction, solid-phase extraction, solid-phase microextraction and QuEChERS whereas separation and detection methods include thin-layer chromatography, capillary electrophoresis, high-performance liquid chromatography and gas chromatography in combination with various detectors such as UV and mass spectrometers. Advantages and disadvantages of the various analytical methods used in pesticide analysis of cannabis products are evaluated in this review. Furthermore, challenges ahead and future directions are discussed.
... 29,30 They can also lead to endocrine disorders, and their capacity for blocking male hormones and thus affecting human reproduction is well documented. 31,32 Pesticides can cause brain damage and have been implicated in several brain disorders, such as mild cognitive impairment or dysfunction (MCD), which manifests as compromised ability to talk and identify words, colors and numbers. 33,34 Other side-effects of pesticide exposure are respiratory disorders, including chronic bronchitis, asthma and lung diseases that primarily affect farm workers. ...
... Increased plasma E2 level in IMI-might be due to its estrogenic potential [47]. Some estrogenic organochlorine pesti- cides (endosulfan, methoxychlor and chlorpyrifos) and pyrethroid (tefluthrin) have been reported to disrupt the GnRH neurons and impair its pulsatile release [48][49][50]. Pesticides-induced disruption of GnIH has not been studied so far. ...
Article
The effect of two thyroid disrupting pesticides (TDPs) mancozeb (MCZ) and imidacloprid (IMI) on the hypothalamic-pituitary-gonadal/testicular (HPG) axis of a seasonally breeding bird, Amandava amandava has been evaluated. Male birds (n = 8/group) were exposed to each of the pesticide (0.25% LD50 of respective pesticide) as well as to their two equimixture doses (0.25% of LD50 of each and 0.5% LD50 of each) through food for 30d during pre-breeding stage of the reproductive cycle. Reduction in weight, volume and other histopathological features revealed testicular regression. Suppression of gonadotropin releasing hormone, increased expression of gonadotropin inhibitory hormone in the hypothalamus of exposed groups as well as impairment of plasma levels of the reproduction related hormones indicated the disruption of the HPG axis. The pesticides interference of the thyroid function during the critical phase of reproductive development impaired the HPG axis; more significantly in co-exposed groups suggesting the cumulative toxicity
... Chlorpyrifos and MXC may alter the synthesis of gonadotropin-releasing hormones. 105,106 Ventura et al indicated that exposure to chlorpyrifos may further cause endocrine imbalance thereby posing a risk factor in reproductive cancer. 106 Owing to structural homology to hormone receptors, DDT and its metabolites are believed to disturb the normal functioning of gonadotropin hormones. ...
Article
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Ovarian cancer (OC) is a relatively fatal female reproductive malignancy. Since the underlying causes are uncertain, it brings us to believe that both genetic and external factors contribute toward development of this lethal disorder. Exposure to endocrine-disrupting chemicals (EDCs) in the form of occupational usage of pesticides, fungicides, herbicides, plasticizers, cosmetics, and so on is potentially carcinogenic and their ability to cause epigenetic modifications has led us to hypothesize that they may play a catalytic role in OC progression. In response to synthetic chemicals, animal models have demonstrated disturbances in the development of ovaries and steroid hormonal levels but in humans, more research is required. The present review is an attempt to address the impact of EDCs on the hormonal system and gene methylation levels that may lead to malfunctioning of the ovaries which may consequently develop in the form of cancer. It can be concluded that endocrine disruptors do have a potential carcinogenicity and their high proportions in human body may cause epigenetic modifications, prompting ovarian surface epithelium to grow in an abnormal manner.
... GnRH-peptide release from GT1-7 cells was also stimulated by Aroclor 1221, a PCB cocktail (Gore et al., 2002). In a similar study on organochlorine pesticides, treatment with methoxychlor or chlorpyrifos affected GnRH mRNA levels with an inverted U-shaped dose-response curve: low doses stimulated GnRH mRNA while higher doses suppressed this endpoint (Gore, 2002b). The methoxychlor metabolite 2,2-bis-(phydroxyphenyl)-1,1,1-trichloroethane (HPTE) suppressed both GnRH transcription and mRNA levels (Roy et al., 1999). ...
... It has also been shown in the hypothalamic GT1-7 cell line that organochlorine pesticides such as methoxychlor and chlopyrifos altered gonadotropin-releasing hormone (GnRH) gene expression and biosynthesis (Gore, 2002) suggesting that EDCs could affect the different levels or reproductive axis. Interestingly, it has been revealed that the BPA-mediated inhibition of GnRH neuronal activity occurred independent of estrogen receptors via a non-canonical unknown pathway (Klenke et al., 2016). ...
Article
Full-text available
Endocrine-disrupting chemicals (EDCs) are diverse natural and synthetic chemicals that may alter various mechanisms of the endocrine system and produce adverse developmental, reproductive, metabolic and neurological effects in both humans and wildlife. Research on EDCs has revealed that they use a variety of both nuclear receptor-mediated and non-receptor-mediated mechanisms to modulate different components of the endocrine system. The molecular mechanisms underlying the effects of EDCs are still under investigation. Interestingly, some of the effects of EDCs have been observed to pass on to subsequent unexposed generations, which can be explained by the gametic transmission of deregulated epigenetic marks. Epigenetics is the study of heritable changes in gene expression that occur without a change in the DNA sequence. Epigenetic mechanisms, including histone modifications, DNA methylation and specific micro-RNAs (miRNAs) expression, have been proposed to mediate transgenerational transmission and can be triggered by environmental factors. MiRNAs are short noncoding RNA molecules that post-transcriptionally repress the expression of genes by binding to 3′-untranslated regions of the target mRNAs. Given that there is mounting evidence that miRNAs are regulated by hormones, then clearly it is important to investigate the potential for environmental EDCs to deregulate miRNA expression and action.
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IntroductionEndocrine Disruption by Organophosphate Pesticides In VitroEndocrine-Disrupting Activity of Organophosphate Pesticides In Vivo in AnimalsEffect of Organophosphate Pesticides as Endocrine Disruptors on Central Nervous SystemInfluence of Organophosphate Pesticides on HumansConclusions References
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Many endocrine-disrupting agents, including industrial materials, pesticides, pharmaceuticals and phytochemicals, have been identified with their use by in vitro assay systems and in vivo studies in laboratory animals. These chemicals are widely distributed in the environment, and are able to mimic or antagonize the biological functions of natural hormones. Indeed, abnormalities thought to be due to such agents have been found in animals throughout the world. There is also thought to be a risk to humans, for example, DES syndrome. Xenoestrogens can accumulate in our environment, and may play a role in the increasing incidences of breast cancer, testicular cancer and other problems of the reproductive system in humans. Risks due to endocrine disruptors in the environment are discussed in this chapter.
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Public concern about the potential effects of endocrine disrupting chemicals (EDCs) on wildlife and human health has heightened experimental paradigms to assess the mechanistic effects of exposure to these compounds. The worry stems from the known effects caused in humans by exposure of pregnant mothers to the synthetic estrogen, diethylstilbestrol (DES) to help them avoid miscarriage (Milhan, 1992). The effects were observed 20 years after the initial exposure of the mothers and resulted in a higher than normal chance of inducing rare endocrine-related cancers as well as other reproductive abnormalities in their progeny.
Article
Background Evidence indicated the possibility of non-persistent pesticides disrupting the homeostasis of sex hormones. However, few studies have focused on this relationship in females. We aimed to explore the relationship between non-persistent pesticide exposure and sex hormones among the US females from the National Health and Nutrition Examination Survey 2013–2014. Methods A total of 790 females, including girls (6–11 years), female adolescents (12–19 years), and adult females (>19 years), were enrolled in this study. Age stratified associations of individual non-persistent pesticide metabolites and their mixtures with sex hormone were analyzed by weighted multiple linear regression and Bayesian kernel machine regression (BKMR) using spot urinary non-persistent pesticide measurement, including 2,4-dichlorophenoxyacetic acid (2,4-D), 3,5,6-trichloropyridinol (TCPY), para-nitrophenol (PNP) and 3-phenoxybenzoic acid (3-PBA), and three serum sex hormones [total testosterone (TT), estradiol (E2) and sex hormone binding globulin (SHBG)]. Results In girls, weighted multivariate linear regression indicated that both 2,4-D and PNP were negatively associated with TT, and TCPY was inversely associated with SHBG. In female adolescents, TCPY was negatively associated with TT and E2, and 3-PBA was negatively associated with SHBG; positive associations were detected both in 2,4-D with SHBG, and in PNP with TT. In adult females, a higher concentration of 3-PBA was associated with higher levels of TT. The BKMR model showed that in female adolescents, the concentrations of pesticide metabolite mixtures at or above the 55th percentile were negatively related to the levels of E2 compared with their mixtures at 50th percentile, and an inverse U-shaped exposure-response function between PNP and E2 was found. Conclusions Associations between the four non-persistent pesticide metabolites and serum sex hormones were identified in the US females from NHANES 2013–2014 and these associations were age dependent, especially in adolescents. Large-scale cohort studies are needed to confirm these findings and elucidate the potential biological mechanism.
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Recent scientific evidence has advanced our understanding of how exogenous environmental chemicals influence developing organisms. The documented effects of industrial compounds introduced into the environment by humans include actions on hormonal systems, including the reproductive, growth, thyroid, and lactotrophic axes. The central focus of this chapter is the impact of environmental endocrine-disrupting chemicals (EDCs) on the developing reproductive neuroendocrine axis. Because the developing brain and reproductive organs are sculpted via processes that are largely influenced by steroid hormones, organisms are particularly vulnerable to the actions of EDCs during the period of life spanning late gestation and early postnatal life. A review of the literature regarding the effects of five classes of EDCs on the developing mammal is provided, with specific regard to sexual differentiation of the reproductive hypothalamic-pituitary-gonadal axis. Although the majority of the studies summarized herein focus on laboratory animals, epidemiological information regarding the known effects of EDCs on humans will be presented when available. We conclude that the available experimental animal and epidemiological data are supportive of a potential role of EDCs on alterations of neuroendocrine development, and on pubertal onset.
Article
During the past decade, possible advancement in timing of puberty has been reported in the United States. In addition, early pubertal development and an increased incidence of sexual precocity have been noticed in children, primarily girls, migrating for foreign adoption in several Western European countries. These observations are raising the issues of current differences and secular trends in timing of puberty in relation to ethnic, geographical, and socioeconomic background. None of these factors provide an unequivocal explanation for the earlier onset of puberty seen in the United States. In the formerly deprived migrating children, refeeding and catch-up growth may prime maturation. However, precocious puberty is seen also in some nondeprived migrating children. Attention has been paid to the changing milieu after migration, and recently, the possible role of endocrine- disrupting chemicals from the environment has been considered. These observations urge further study of the onset of puberty as a possible sensitive and early marker of the interactions between environmental conditions and genetic susceptibility that can influence physiological and pathological processes.
Article
A magnetic solid-phase extraction (MSPE) method based on a novel magnetic sorbent was proposed for the extraction of target compounds from large-volume water samples. First, magnetic hypercrosslinked microspheres (NAND-1) were prepared via membrane emulsification-suspension polymerization and post crosslinking reaction. To ensure that the Fe3O4 nanoparticles could completely pass through the membrane without blocking the pores, oleic acid was used to modify the Fe3O4 nanoparticles, which enhanced lipophilicity and monodispersity of the magnetite nanoparticles. The obtained NAND-1 microspheres exhibited super paramagnetic characteristics and excellent magnetic responsiveness with a saturation magnetization of 2.53emu/g. In addition, a uniform particle size (∼8μm) and a large average surface area (1303.59m(2)/g) were also observed, which were both beneficial for the extraction of the target compounds. Thus, NAND-1 has the potential to simultaneously exhibit good extraction efficiencies toward different types of organic micropollutants (OMPs), including triazines, carbamazepine and diethyl phthalate. The conditions of the MSPE based on NAND-1 were optimized by single factor and orthogonal design experiments. This MSPE method needed only a small amount of sorbent (50mg/L) for the extraction of OMPs from a large-volume aquatic sample (5L) and reached equilibrium in a short amount of time (30min). Moreover, the solution volume, the pH, and the salinity had insignificant influences on the extraction of the eight target OMPs. Under the optimum conditions, the recoveries of the eight OMPs calculated by analyzing the spiked samples were from 91.7% to 99.4%. The NAND-1 could be recycled ten times and still achieve recoveries of the eight OMPs higher than 86%. The limits of detection of the eight OMPs ranged from 1.76 to 27.56ng/L, and the limits of quantification were from 5.71 to 92.05ng/L. These results indicated that the proposed method, based on the use of NAND-1 as a magnetic sorbent, has the advantages of convenience and high efficiency and can be successfully applied to analyze the OMPs in real water samples.
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Introduction “Epigenetics” has been described as the study of changes in gene expression that occur not due to changes in DNA sequence, but rather due to remodeling of the chromatin or modifications in DNA such as methylation, a process by which methyl groups are added to the base cytosine in DNA. Waddington defined “epigenetics” as “… the interactions of genes with their environment which bring the phenotype into being.” In those days, the gene as the unit of heritable material was a theoretical concept without a physical identity. Holliday and Pugh proposed that covalent chemical DNA modifications, including methylation of cytosine–guanine (CpG) dinucleotides, were the molecular mechanisms behind Waddington's hypothesis. Developmental processes are regulated largely by epigenetics, because different cell types maintain their fate during cell division even though their DNA sequences are essentially the same. The further revelations that X chromosome inactivation in mammals and genomic imprinting are regulated by epigenetic mechanisms highlighted the heritable nature of epigenetic gene-regulation mechanisms. The genomics revolution inspired the investigation of global, rather than local, gene analyses, and the term “epigenomics” was coined as the study of the “ … effects of chromatin structure, including the higher order of chromatin folding and attachment to the nuclear matrix, packaging of DNA around nucleosomes, covalent modifications of histone tails (acetylation, methylation, phosphorylation, ubiquitination), and DNA methylation”. The resistance of some gene loci to methylation reprogramming during embryogenesis revealed the possibility that epigenetic modifications are inherited not only during somatic-cell division, but also in subsequent generations.
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Endocrine-disrupting chemicals (EDCs) are artificial and natural substances that can perturb endocrine and/or reproductive systems through their actions on hormonally sensitive pathways. Exposures to environmental EDCs may have devastating effects on the individual, its offspring, and even populations. Reproductive neuroendocrine systems, hormones, and sexual behaviors are especially vulnerable to endocrine-disruptive exposures that occur during key periods of development. The vertebrate brain may be perturbed by even very low-level, subtoxic EDC exposures during the critical period of brain sexual differentiation (particularly embryonic and early postnatal developmental stages) because of its extremely high sensitivity to hormones or hormonally active compounds at these life stages. Often, these effects of EDCs are not manifested at birth, enabling the organism to develop, mature, and even potentially to reproduce. This is of serious concern since these animals compete with healthy conspecifics, and may pass on genetic or epigenetic traits to subsequent generations, thereby proliferating the problem. Here, we review the scientific evidence for effects of EDCs on hormones, the brain, and sexual behaviors in vertebrates.
Article
Recently, pest control has become a very interesting research topic because it is closely associated with agricultural and economic loss. Empirical evidence shows that pest insects are responsible for lower crop production and many other adverse effects on the farming sector. There are several biological, physical and chemical control mechanisms. However, the biological control of pest populations by using natural enemies is one of the most important ecosystem services adopted in agriculture around the world. In the present study, we consider an ecological model consisting of prey (pest) and its natural enemy as the predator. Different system equilibria are obtained, their stability is analyzed, and Hopf bifurcation of the system around the interior equilibrium is discussed. The sufficient permanence criteria of the system are also derived. Moreover, we perform bifurcation analysis to explore the existence of limit cycle. We also investigate the stability property of the positive periodic solution when the interior equilibrium loses its stability. Our analytical results are further verified through numerical simulations. Our findings suggest that, in the absence of a super predator, pest and natural enemy show stable coexistence. However, in the presence of super predator, if the natural enemy is killed at a lower rate, both pest and natural enemy coexist. Finally, above a threshold value, the natural enemy is eradicated from the system and pest outbreak occurs.
Chapter
Puberty is a crucial developmental stage marked by the gradual transition from childhood to adulthood, initiated by the activation of the hypothalamus–pituitary–gonadal axis, and gonadal stimulation by rising levels of gonadotropins in response to an increased pulsatility of hypothalamic gonadotropin-releasing hormone, terminating with attainment of sexual maturity and accompanied by growth spurt, changes in physical aspect and behavior, and appearance of secondary sexual characteristics. Interconnections between genetic, endocrine, environmental, lifestyle-related and nutritional cues are involved in the complex control of the normal onset and/or progression of puberty; nevertheless, although risk factors of aberrant pubertal development have been widely investigated in girls, studies in boys are scarce. Sparse and uncertain associations between prenatal to adolescent exposure to polychlorinated biphenyls, dioxin and dioxin-like compounds, phthalates, bisphenol A, pesticides and lead and delayed genital and pubertal development have been provided, but no definitive causal inferences may be drawn at present. An equivocal relationship of obesity with pubertal timing has been reported in boys, partly explained by the paucity of studies and methodological drawbacks, as well as by contrasting actions on the hypothalamus–pituitary–gonadal axis exerted by hormonal changes occurring in obesity. Indeed, despite a beneficial effect of physiological increase of leptin levels on pubertal onset, obesity-induced leptin resistance at the hypothalamic–pituitary level determines central inhibition of the hypothalamus–pituitary–gonadal axis; moreover obesity-related hyperleptinemia might directly inhibit testicular steroidogenesis therefore potentially further delaying pubertal progression. On the other hand, reduced adiponectin levels might favor earlier pubertal onset and/or accelerate pubertal progression. Although increased adrenal androgens might accelerate the androgenic manifestations of puberty irrespective of the activation of the hypothalamus-pituitary-gonadal axis, excessive obesity-induced greater peripheral conversion of adrenal androgens to estrogens after pubertal onset might result in the inhibition of hypothalamus–pituitary–gonadal axis and delayed pubertal completion. Defective growth hormone-insulin-like growth factor 1 system signaling might also be called into question with a potential role of increased insulin-like growth factor 1 in anticipating pubertal onset and progression. A tendency to an earlier or a delayed onset of puberty has been associated with maternal cigarette smoking and alcohol consumption during pregnancy, in line with evidence suggesting delayed appearance of pubertal signs in boys consuming alcohol in pre-pubertal stage. Lastly, very scant evidence seems to suggest an association of higher animal protein dietary intake with earlier puberty in boys, whereas a potential malnutrition-related and negative energy balance-related delay in pubertal development might be speculated, based on evidence from girls suffering from anorexia nervosa or practicing vigorous physical activity, respectively.
Article
Pesticides, including organophosphate (OP), organochlorine (OC), and carbamate (CB) compounds, are widely used in agricultural and indoor purposes. OP and CB act as acetyl cholinesterase (AChE) inhibitors that affect lots of organs such as peripheral and central nervous systems, muscles, liver, pancreas, and brain, whereas OC are neurotoxic involved in alteration of ion channels. There are several reports about metabolic disorders, hyperglycemia, and also oxidative stress in acute and chronic exposures to pesticides that are linked with diabetes and other metabolic disorders. In this respect, there are several in vitro and in vivo but few clinical studies about mechanism underlying these effects. Bibliographic databases were searched for the years 1963-2010 and resulted in 1652 articles. After elimination of duplicates or irrelevant papers, 204 papers were included and reviewed. Results indicated that OP and CB impair the enzymatic pathways involved in metabolism of carbohydrates, fats and protein within cytoplasm, mitochondria, and proxisomes. It is believed that OP and CB show this effect through inhibition of AChE or affecting target organs directly. OC mostly affect lipid metabolism in the adipose tissues and change glucose pathway in other cells. As a shared mechanism, all OP, CB and OC induce cellular oxidative stress via affecting mitochondrial function and therefore disrupt neuronal and hormonal status of the body. Establishing proper epidemiological studies to explore exact relationships between exposure levels to these pesticides and rate of resulted metabolic disorders in human will be helpful.
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Polychlorinated biphenyls (PCBs), a family of global environmental contaminants, have been shown to disrupt a wide array of physiological and behavioral systems, including reproduction and brain development. Some PCBs such as the commercial PCB mixture, Aroclor 1221 (A1221), act as endocrine disrupters because of their affinity for estrogen receptors (Bitman and Cecil 1970). Other PCBs, such as Aroclor 1254 (A1254), exhibit minimal binding to estrogen receptors, and some of their metabolites may even have antiestrogenic activity (Bitman and Cecil 1970; Moore et al 1997). Since estrogen has profound effects on sexual differentiation (MacLusky and Naftolin 1981) these two commercial PCB mixtures may have different effects on the development of sexual behavior. PCBs also exhibit neurotoxic effects on dopaminergic neurons (Brouwer et al. 1995) which are important in controlling sexual behavior. Based on the position of their chlorine substitutes, PCBs can be categorized into coplanar (position 3, 4, 5 on the benzene ring) or ortho-substituted (position 2, 6 on the benzene ring) noncoplanar PCBs. With regard to their effects on dopaminergic systems, noncoplanar, ortho-substituted PCBs have been shown to reduce dopamine levels in the brain and in PC-12 cells, while the coplanar PCBs increase dopamine or have no effect (Seegal et al. 1990, 1997). Coplanar congeners, in addition to their ability to alter brain dopamine concentration, also exhibit estrogenic or antiestrogenic function (Gierthy et al. 1988; Spink et al. 1990). Since female sexual behavior can be disrupted by exposure to estrogen during perinatal development (MacLusky and Naftolin 1981) and since brain dopaminergic systems are involved in adult female sexual behavior (Carter and Davis 1977; Mani et al. 1994) the likelihood that developmental exposure to PCBs could disrupt feminine sexual behavior by disrupting dopaminergic systems seems high. In addition, lesions or dopamine administration into the medial preoptic area altered female paced sexual behavior (Whitney 1986) and A11 and A13 dopaminergic neurons appeared to be the major dopaminergic input into the medial preoptic area (Lindvall and Björklund 1983). In this report we compare the effect of two commercial PCB mixtures on female sexual behavior and All and A13 dopaminergic systems. A1221, an estrogenic PCB mixture composed of about 40% coplanar PCBs and 60% ortho-substituted PCBs (Webb and McCall 1972; Willis and Addison 1972) and A1254 a non-estrogenic, mainly ortho-substituted PCB mixture (Sissons and Welti 1971; Webb and McCall 1972) were used to examine the possible risks of PCB exposure during sexual differentiation on female sexual behavior and A11 and A13 dopaminergic systems.
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On the basis of results of studies using high doses of estrogens, exposure to estrogen during fetal life is known to inhibit prostate development. However, it is recognized in endocrinology that low concentrations of a hormone can stimulate a tissue, while high concentrations can have the opposite effect. We report here that a 50% increase in freeserum estradiol in male mouse fetuses (released by a maternal Silastic estradiol implant) induced a 40% increase in the number of developing prostatic glands during fetal life; subsequently, in adulthood, the number of prostatic androgen receptors per cell was permanently increased by 2-fold, and the prostate was enlarged by 30% (due to hyperplasia) relative to untreated males. However, as the free serum estradiol concentration in male fetuses was increased from 2- to 8-fold, adult prostate weight decreased relative to males exposed to the 50% increase in estradiol. As a model for fetal exposure to man-made estrogens, pregnant mice were fed diethylstilbestrol (DES) from gestation days 11 to 17. Relative to controls, DES doses of 0.02, 0.2, and 2.0 ng per g of body weight per day increased adult prostate weight, whereas a 200-ng-per-g dose decreased adult prostate weight in male offspring. Our findings suggest that a small increase in estrogen may modulate the action of androgen in regulating prostate differentiation, resulting in a permanent increase in prostatic androgen receptors and prostate size. For both estradiol and DES, prostate weight first increased then decreased with dose, resulting in an inverted-U dose-response relationship.
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Chlorpyrifos, one of the most widely used pesticides, exhibits greater toxicity during development than in adulthood. We administered chlorpyrifos to neonatal rats in apparently subtoxic doses that caused no mortality and little or no weight deficits and examined developing brain regions (cerebellum, forebrain, brainstem) for signs of interference with cell development. One-day-old rats given 2 mg/kg sc of chlorpyrifos showed significant inhibition of DNA synthesis in all brain regions within 4 hr of treatment; equivalent results were obtained when a small dose (0.6 microgram) was introduced directly into the brain via intracisternal injection, indicating that the actions were not secondary to systemic toxicity. Inhibition of DNA synthesis was also seen at 8 days of age; however, at this point, there was regional selectivity, with sparing of the cerebellum. Between 1 and 8 days of age, brain regions develop wide disparities in cholinergic innervation; accordingly, we tested whether the effect of chlorpyrifos was mediated through cholinergic actions on nicotinic receptors known to mediate inhibition of DNA synthesis. Pretreatment with mecamylamine caused a decline in DNA synthesis by itself, but nevertheless prevented the effect of chlorpyrifos. Additionally, chlorpyrifos administration at 1 day of age caused an even larger inhibition of protein synthesis throughout the brain; the effect was distinct from that on DNA synthesis, as it diminished substantially by 8 days of age and did not develop any regional selectivity. The effects of chlorpyrifos on DNA and protein synthesis were not secondary to generalized cell damage or suppression of cell metabolism, as evidenced by maintenance of normal ornithine decarboxylase activities. These results indicate that low doses of chlorpyrifos target the developing brain during the critical period in which cell division is occurring, effects which may produce eventual cellular, synaptic, and behavioral aberrations after repeated or prolonged subtoxic exposures.
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The increase in the number of reports of abnormalities in male sex development in wildlife and humans coincided with the introduction of 'oestrogenic' chemicals such as DDT (1,1,1-trichloro-2,2-bis(p-chlorophenyl)ethane) into the environment. Although these phenotypic alterations are thought to be mediated by the oestrogen receptor, they are also consistent with inhibition of androgen receptor-mediated events. Here we report that the major and persistent DDT metabolite, p,p'-DDE (1,1-dichloro-2,2-bis(p-chlorophenyl)ethylene), has little ability to bind the oestrogen receptor, but inhibits androgen binding to the androgen receptor, androgen-induced transcriptional activity, and androgen action in developing, pubertal and adult male rats. The results suggest that abnormalities in male sex development induced by p,p'-DDE and related environmental chemicals may be mediated at the level of the androgen receptor.
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In a previous review of the literature related to the toxicity of polychlorinated biphenyls (PCBs), one of the present authors1 reviewed the experimental evidence demonstrating that one of the major classes of PCBs—the ortho-substituted congeners—were capable of altering neurological function in a wide variety of experimental preparations. In this chapter we broaden the review to include a discussion of the behavioral effects of exposure as well as contributions that coplanar PCBs, dioxins (PCDDs), and di-benzofurans (PCDFs) make to the overall neurotoxic risk to humans from exposure to complex environmental mixtures.
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Hypothalamic GnRH secretory neurons are precisely regulated by circulating gonadal steroids. However, the question of whether these cells are directly responsive to steroid hormones remains a central and controversial issue in reproductive science. In the present study, we demonstrate the expression of androgen receptor (AR) in a mouse hypothalamic GnRH-secreting cell line, GT1–7. AR messenger RNA was detected by Northern blot analysis of 10 μg total cellular RNA. Western blot analysis revealed a 110K AR immunoreactive band, and saturation binding analysis confirmed the presence of a high affinity low capacity androgen binding entity (Kd = 0.06 nm; Bmax = 12.4 fmol/mg protein). In addition, GT1–7 cells were found to express ARA70, an AR-specific coactivator that has been reported to enhance transactivational activity of the AR. GT1–7 cells transiently transfected with an androgen responsive MMTV-luciferase reporter construct displayed a 4.2-fold induction of luciferase reporter gene activity by 1 nm 5α-dihydrotestosterone (DHT), further demonstrating the presence of a functional AR. Treatment of GT1–7 cells with 1 or 10 nm DHT resulted in approximately 55% reduction in GnRH messenger RNA measured at 24 and 36 h after treatment. This repression was completely blocked by hydroxyflutamide, an AR antagonist. These results provide the first demonstration that androgen acts directly through an AR-mediated pathway to repress GnRH gene expression in hypothalamic GnRH-secreting neurons.
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The immortalized GT1–7 cell line synthesizes and secretes GnRH, the key hormone of reproduction. However, GT1–7 cells lack the normal inputs from neurotransmitters, growth factors, and steroids, which are involved in the maturation and maintenance of GnRH neurons in the brain. We examined the effects of the neurotrophic factor insulin-like growth factor-I (IGF-I) on GnRH gene expression and the mechanism for these changes. Initially, effects of IGF-I on GnRH gene expression were determined by ribonuclease protection assay. In time-course experiments, IGF-I treatment caused significant increases in nuclear GnRH primary transcript levels, an index of GnRH gene transcription, 4 and 8 h after initiation of IGF-I treatment. GnRH messenger RNA (mRNA) levels in the cytoplasm were stimulated by IGF-I at 24 h of treatment. IGF-I also affected GT1–7 cell morphology, with an increase in process extension and cell-cell contacts. In contrast, GnRH peptide levels in the medium were initially stimulated and then suppressed by IGF-I, indicating an uncoupling of biosynthesis and secretion. The increase in GnRH mRNA levels induced by IGF-I is probably caused by a transcriptional mechanism, as evidenced by the increase in GnRH primary transcript levels before a change in GnRH mRNA levels, as well as our finding of a similar GnRH mRNA half-life for both control and IGF-I-treated cells. Interestingly, GT1–7 cells themselves were observed to express IGF-I immunoreactivity, suggesting the possibility of autoregulation by this neurotrophic factor. It is concluded that IGF-I is an important modulator of GnRH gene expression and release in the GT1–7 cell line. The reported stimulatory effects of IGF-I in vivo, and its hypothesized role in the development of GnRH neurons in the brain, suggest that IGF-I may make the GT1–7 cells line more like a mature GnRH neuron, as a model for future studies.
Article
It is well known that young animals are generally more sensitive to lethal effects of cholinesterase-inhibiting pesticides, but there are sparse data comparing less-than-lethal effects. We compared the behavioral and biochemical toxicity of chlorpyrifos in young (postnatal Day 17; PND17) and adult (about 70 days old) rats. First, we established that the magnitude of the age-related differences decreased as the rat matures. Next, we evaluated the time course of a single oral dose of chlorpyrifos in adult and PND17 male and female rats. Behavioral changes were assessed using a functional observational battery (with age-appropriate modifications for pre-weanling rats) and an evaluation of motor activity. Cholinesterase (ChE) activity was measured in brain and peripheral tissues and muscarinic receptor binding assays were conducted on selected tissues. Rats received either vehicle (corn oil) or chlorpyrifos (adult dose: 80 mg/kg; PND17 dose: 15 mg/kg); these doses were equally effective in inhibiting ChE. The rats were tested, and tissues were then taken at 1, 2, 3.5, 6.5, 24, 72, 168, or 336 h after dosing. In adult rats, peak behavioral changes and ChE inhibition occurred in males at 3.5 h after dosing, while in females the onset of functional changes was sooner, the time course was more protracted and recovery was slower. In PND17 rats, maximal behavioral effects and ChE inhibition occurred at 6.5 h after dosing, and there were no gender-related differences. Behavioral changes showed partial to full recovery at 24 to 72 h, whereas ChE inhibition recovered markedly slower. Blood and brain ChE activity in young rats had nearly recovered by 1 week after dosing, whereas brain ChE in adults had not recovered at 2 weeks. Muscarinic-receptor binding assays revealed apparent down-regulation in some brain areas, mostly at 24 and 72 h. PND17 rats generally showed more receptor down-regulation than adults, whereas only adult female rats showed receptor changes in striatal tissue that persisted for 2 weeks. Thus, compared to adults (1) PND17 rats show similar behavioral changes and ChE inhibition although at a five-fold lower dose; (2) the onset of maximal effects is somewhat delayed in the young rats; (3) ChE activity tended to recover more quickly in the young rats; (4) young rats appear to have more extensive muscarinic receptor down-regulation, and (5) young rats show no gender-related differences.
Article
Having used the cingulate cortex to demonstrate the validity of our methods for detecting hitherto unrecognized oestrogen receptor alpha (ERα)-immunoreactive neurones, we have now employed immunoprecipitation and double-label immunohistochemistry to investigate whether the ERα protein is present in gonadotrophin-releasing hormone (GnRH)-containing cells. The immortalized GnRH cell line GT1–7 and GnRH neurones within the rat preoptic area were found to possess ERα-immunoreactivity (ERα-IR). These observations indicate that oestrogen may regulate the synthesis and release of GnRH by direct actions on GnRH neurones.
Article
The behavior of the gonadotropin-releasing hormones (GnRH) neu- rons controlling fertility is dependent upon cyclic fluctuations in cir- culating concentrations of estrogen. However, the nature of estrogen action upon these cells has remained controversial due to their dis- persed distribution within the brain, and evidence indicating that they do not express nuclear estrogen receptors (ERs) in vivo .W e report here an acute brain slice preparation that enables individual living GnRH neurons to be identified within the mouse brain and show, using single cell multiplex RT-PCR, that the greater than 50% of GnRH neurons in adult and prepubertal females contain ERa messenger RNA. Approximately 10% of GnRH neurons contained ERb transcripts that were always coexistent with ERa. Single cell RT-PCR analysis of nonGnRH cells located in the medial preoptic area revealed a similar coexpression pattern of ERa and ERb transcripts. In contrast, single striatal cells were not found to contain ERb despite ERa being present in approximately 25% of cells. The analysis of single GnRH neurons in cycling female mice revealed that the de- tection of ERa and ERb transcripts was lowest on proestrus (ERa, 18% of all GnRH neurons; ERb, 0%) compared with diestrus (44% and 6%) and estrus (75% and 19%, respectively). Using a novel approach that enables single cell RT-PCR analysis of GnRH neurons, we present here evidence for the cyclic expression of ERa and ERb mes- senger RNAs within prepubertal and adult female GnRH neurons. (Endocrinology 140: 5195-5201, 1999)
Article
This study examined the effects of the xenoestrogen methoxychlor (Mxc) on messenger RNA (mRNA) concentrations of two estrogen- responsive uterine genes, lactoferrin (LF) and glucose-6-phosphate dehydrogenase (G6PD). Ovariectomized wild-type (WT) and estrogen receptor (ER)a-knockout (ERaKO) mice were treated with Mxc or estradiol-17b (E2) to determine whether Mxc acts via pathways that involve ERa. In WT mice, both E2 and Mxc stimulated increases in uterine LF and G6PD mRNA concentrations in a dose-dependent manner. Competitive pretreatment with the pure antiestrogen ICI 182,780 dramatically reduced E2-stimulated increases in mRNA con- centrations but had no effect on Mxc-induced effects. Competitive pretreatment with E2 had only a partially inhibitory effect on Mxc- induced responses. In the ERaKO mouse, E2 had little effect on uter- ine LF or G6PD mRNA concentrations, whereas Mxc stimulated marked increases in both LF and G6PD mRNAs. The Mxc-induced increases in LF and G6PD mRNAs in the ERaKO mouse were not suppressed by competitive pretreatment with either E2 or ICI 182,780. Fold increases in mRNA concentrations for both genes in- duced by Mxc were similar for WT and ERaKO mice. The results surprisingly indicate that a xenoestrogen, Mxc, can increase LF and G6PD mRNA concentrations by a mechanism that is not mediated through ERa or ERb, and acts through another pathway. (Endocri- nology 140: 3526 -3533, 1999)
Article
Estrogen has wide-ranging and complex effects on the reproductive axis, which are often difficult to interpret from in vivo studies. Es- trogen negatively regulates tonic GnRH synthesis and also plays a pivotal role in the positive regulation of GnRH necessary for the preovulatory surge. To dissect the mechanisms by which these di- vergent effects occur, we attempted to observe the direct action of estrogen on the regulation of GnRH messenger RNA (mRNA) levels using the well characterized, GnRH-secreting, hypothalamic cell line, GT1-7. Using RT-PCR, we first investigated estrogen receptor tran- script expression in GT1-7 neurons. We found that the GT1-7 cells express both estrogen receptor-a (ERa) and the recently described ERb mRNAs. We also detected the presence of both receptor subtypes in the GT1-7 neurons by Western blot analysis using specific ER antibodies. By Northern blot analysis of total GT1-7 RNA, we found that 17b-estradiol (1 nM) down-regulates GnRH mRNA levels to ap- proximately 55% of basal levels over a 48-h time course. This effect appears to occur specifically through an ER-mediated mechanism, as ICI 182,780, a complete ER antagonist, blocks the repression of GnRH mRNA levels by estradiol. The recently reported ERa-specific agonist/ ERb-specific antagonist 2,2-bis-(p-hydroxyphenyl-1,1,1-trichloroeth- ane (HPTE), a methoxychlor metabolite, also down-regulated GnRH gene expression. The repression of GnRH mRNA levels appears to occur at the transcriptional level, as simian virus 40 T antigen mRNA expression, which is under the control of 2.3 kb of the rat GnRH 59-regulatory region, mimics the down-regulation of GnRH after treatment with estradiol. As the rat GnRH regulatory region in GT1-7 neurons does not appear to harbor a classic estrogen response element, the mechanism involved in the repression of GnRH has yet to be determined. These results suggest that estradiol directly reg- ulates GnRH gene expression at the level of the GnRH neuron and may exert its neuroendocrine control through direct interaction with specific receptors expressed in these cells. (Endocrinology 140: 5045- 5053, 1999)
Article
Ovariectomized rats were pretreated with intravenous estradiol-17β (E2), coumestrol or genisteinand were challenged 2 h later with GnRH (50 ng/kg BW, i.v.). Blood samples, drawn at the time of GnRH administration and 15 min afterwards, were assayed for luteinizing hormone (LH). While low-dose E2 pretreatment (10 ng/kg BW) significantly enhanced GnRH-induced LH release, high dose E2 pretreatment (1000 ng/kg BW) blocked the GnRH-induced rise. Intermediate-dose E2 pretreatment (100 ng/kg BW) yielded a GnRH response that did not differ from that in the vehicle pretreatment group. At all doses studied, coumestrol pretreatment (10 ng/kg BW, 100 ng/kg BW, and 1000 ng/kg BW) appeared to diminish but not abrogate GnRH-induced LH release. While intermediate-dose genistein pretreatment (100 ng/kg BW) significantly enhanced GnRH-induced LH release, high-dose genistein pretreatment (1000 ng/kg BW) yielded a GnRH response that did not differ from that in the vehicle pretreatment group. Both low-dose (10 ng/kg BW) and very high-dose (10,000 ng/kg BW) genistein pretreatment appeared to inhibit GnRH-induced LH release.The results demonstrate that acute exposure to phytoestrogens alters GnRH-induced LH release in ovariectomized rats. The dose-response pattern of enhanced GnRH-induced LH release at lower pretreatment doses but inhibited GnRH-induced LH release at higher pretreatment doses was observed for E2 and genistein. The potency of genistein appears to be approximately 1/10 that of E2 in this system. Phytoestrogens acutely perturb reproductive neuroendocrine function.
Article
Gonadotropin-releasing hormone (GnRH), having a highly conserved structure across mammalian species, plays a pivotal role in the control of the neuroendocrine events and the inherent sexual behaviors essential for reproductive function. Recent advances in molecular genetic technology have contributed greatly to the investigation of several aspects of GnRH physiology, particularly steroid hormone and neurotransmitter regulation of GnRH gene expression. Behavioral studies have focused on the actions of GnRH in steroid-sensitive brain regions to understand better its role in the facilitation of mating behavior. To date, however, there are no published reports which directly correlate GnRH gene expression and reproductive behavior. The intent of this article is to review the current understanding of the way in which changes in GnRH gene expression, and modifications of GnRH neuronal activity, may ultimately influence reproductive behavior.
Article
1. Sex differences in the control of gonadotropin secretion and reproductive functions are a distinct characteristic in all mammalian species, including humans. Ovulation and cyclicity are among the most distinct neuroendocrine markers of female brain differentiation, along with sex behavioral traits that are also evident in different species. 2. The luteinizing hormone-releasing hormone (LHRH) neuronal system is the prime regulator of neuroendocrine events leading to ovulation and hormonal changes during the menstrual cycle and, as such, is the potential site where many of these sex differences may be expressed or, at the very least, integrated. However, until recently, no significant differences were seen in LHRH neurons between male and female brains, including cell number, pattern of distribution, and expression of message or peptide (LHRH) levels. 3. Recently, we reported that galanin (GAL), a brain-gut peptide, is coexpressed in LHRH neurons and that this coexpression is sexually dimorphic. When GAL is used as a marker for this neuronal system, it is clear that estradiol as well as progesterone profoundly affects the message and expression of the peptide and that this regulation, at least in rodents, is neonatally predetermined by gonadal steroid imprinting. 4. Changes in GAL expression and message can also be seen at puberty, during pregnancy and lactation, and in aging, all situations that affect the function of the LHRH neuronal system. Using an immortalized LHRH neuronal cell line (GT1) we have recently observed that these neurons express estrogen receptor (ER) and GAL and that estradiol can increase the expression of GAL, indicating functional activation of the endogenous ER.
Article
The current investigation was designed to determine if the pesticide methoxychlor (M) mimicked the effects of estrogen in the brain and on behavior. Running wheel activity (RWA) and sex behaviors were evaluated in this study because the role of estrogen in the regulation of these behaviors has been thoroughly established. M exposure at 400 mg/kg/day (90% pure) induced high levels of acyclic RWA and persistent vaginal estrus in the female rats. Following ovariectomy (ovx), RWA declined precipitously in controls but remained at high levels in M-treated-ovx females. M also produced estrogen-like alterations of the uterine endometrial epithelium, the ovary, and growth after ovx. In another study, ovx female rats were dosed with M at 200 mg/kg/day and then with progesterone (P). P acts as an antiestrogen and specifically suppresses estrogen-induced RWA. P blocks the synthesis of estrogen receptors in the CNS and reproductive tract but does not lower RWA induced by nonestrogenic mechanisms. After 14 days of M administration RWA was increased fourfold over the ovx-oil-treated females. Subsequently, P injections reduced RWA levels far below those seen when the ovx-M-treated rats were injected with oil. The P-induced decline represents a 95% inhibition of the M-induced increase in RWA. Subsequently, M-treated-ovx rats and hamsters were injected with P and tested for their ability to display reproductive behaviors when paired with a stud male. Female sexual behaviors are induced by the administration of estrogen followed by progesterone. In this study the M-treated females displayed reproductive behaviors, in contrast to the oil-treated rats and hamsters. The observation that the high levels of RWA induced by methoxychlor treatment in ovx rats can be suppressed by concurrent progesterone injections demonstrates that the increase in RWA is due to the estrogenic effects of methoxychlor on the CNS. The fact that methoxychlor, followed by P injections, induces behavioral estrus in the rat and hamster extends this estrogenicity to other areas in the CNS.
Article
We have compiled a protocol for simultaneous quantitation of a variety of gene transcripts in multiple individual brain and pituitary gland dissections for studying pretranslational regulation of neuroendocrine systems in vivo, using experimental designs compatible with meaningful statistical power. To facilitate collection of many samples at a time, the tissue was snap-frozen in chilled liquid Freon and stored at -80 °C until further processing. In this way, as many as five different brain and pituitary gland dissections per rat could be collected from eight rats in about an hour. The snap-frozen tissue was suitable for isolation of separate cytoplasmic and nuclear RNA fractions using homogenization in the presence of detergents. To facilitate homogenization of many samples at a time, we devised a method in which the tissue was repeatedly expelled through a 22 gauge hypodermic needle attached to a 1-ml plastic syringe used as a disposable, ready-to-use homogenizer. In order to promote dissolution of lipid membrane structures which are prevalent in the brain, the lysis buffer has been optimized to include the detergent sodium deoxycholate in addition to Nonidet P-40. Specific RNA transcripts were analyzed using a quantitative solution hybridization-ribonuclease protection assay coupled with polyacrylamide gel electrophoresis. The value of this highly sensitive assay has been expanded by including several molecular probes against a variety of neuroendocrine mRNA sequences simultaneously (e.g. progonadotropin-releasing hormone, proopiomelanocortin, tyrosine hydroxylase, dopamine D2 receptor, prolactin), thus increasing the amount of information obtained from each sample in one assay. Furthermore, each sample was routinely co-assayed for cyclophilin mRNA, an abundant, generally non-regulated mRNA whose levels reflected the individual variability in sample processing, thus serving as an internal reference. Once stored in hybridization solution, as many as 100 samples could be analyzed simultaneously for several different RNA transcripts in one assay. This protocol provides a powerful tool for studying regulation of neuroendocrine systems at the molecular level in vivo, using sample sizes suitable for applying statistical analysis of meaningful statistical power.
Article
DURSBAN (DB; active ingredient chlorpyrifos) is a widely-used organophosphate insecticide. The teratogenic and neurotoxic potential of DB was evaluated in rats in utero by exposing embryos on days 0-7 or days 7-21 of development. These prenatal exposures to DB (0.03, 0.1 or 0.3 mg chlorpyrifos/kg, ip) induced physical abnormalities and embryotoxicity. Rat pups which had been exposed to 0.3 mg chlorpyrifos/kg prenatally demonstrated significant behavioral neurotoxicity on postnatal day 16 in the rotorod test compared to time-matched saline-infused litters. Exposure to DB on postnatal day 3, 10 or 12 also caused neurotoxicity as evaluated by the rotorod test. Our studies suggest prenatal exposure to relatively low concentrations of DB may be associated with embryotoxicity, fetal lethality and behavioral neurotoxicity.
Article
The neurochemical identity of preoptic neurons containing oestrogen receptors was investigated in the male and female rat using a sequential double-staining immunocytochemistry procedure. Single-immunostaining revealed large populations of cells with nuclear immunoreactivity to the oestrogen receptor in the medial preoptic area of the male and female rat. Optimal double-staining of sections for the oestrogen receptor and one of several neuropeptides or tyrosine hydroxylase, was achieved with short-term (two- to four-day) gonadectomized rats treated with colchicine where necessary. Neurotensin-immunoreactive cells were distributed in a sexually dimorphic manner in the region of the anteroventral preoptic nucleus and exhibited oestrogen receptor immunoreactivity in both sexes. Double-labelled cells in this area of the female rat comprised 50% and 11% of the total neurotensin- and oestrogen receptor-containing cell populations, respectively, compared with 25% and 4% in the male (P <0.01). The numbers of neurotensin-immunoreactive cells in the region of the medial preoptic nucleus were similar in male and female rats with double-labelled cells making up 20–38% and 3–5% of the total numbers of cells containing neurotensin and oestrogen receptors, respectively, in both sexes.
Article
Gonadotropin-releasing hormone (GnRH) cell lines were developed by genetically targeted tumorigenesis in transgenic mice. The cell lines designated GT1 cells have a neuronal phenotype, express neuronal but not glial markers and express the GnRH gene at high levels. The GnRH prohormone is processed in the cells to multiple molecular forms including biologically active GnRH and GnRH-associated peptide. Basal secretion of GnRH from the cells is regulated in part by fast Na+ channels necessary for propagated action potentials. In many instances, basal GnRH release is pulsatile with an interpulse frequency similar to that seen in castrated rodents, suggesting that GnRH neurons are the pulse generator and are capable of synchronizing their secretion in vitro. The secretion of GnRH is stimulated by depolarization and by the neurotransmitter norepinephrine. In related studies we have demonstrated that expression of Simian virus 40 T antigen in GnRH neurons of transgenic mice leads to hypothalamic hypogonadism due to the inability of GnRH nerve terminals to organize in the median eminence. These findings support the use of genetically-directed tumorigenesis to establish highly differentiated GnRH neuronal cell lines that are a valuable model to study the cell biology and regulation of the neurons.
Article
Ultrastructural effects of 17 beta-estradiol were compared with technical pesticide methoxychlor in uterus and vagina of young mice. Neonates received 14 daily ip injections of either sesame oil, 10.0 micrograms 17 beta-estradiol, or 0.05, 0.1, 0.5, or 1.0 mg methoxychlor. Estradiol accelerated vaginal opening to 11 days, increased reproductive tract weight gain, and induced vaginal cornification, the cells of which exhibited complex surface microridge patterns. The hypertrophied uterine cells were covered with dense, enlarged microvilli with bulbous expansions or clumps. The highest three methoxychlor doses were stimulatory. Exposure to 0.5 or 1.0 mg methoxychlor increased reproductive tract weights threefold due to excessive fluid accumulation, and induced vaginal cornification and opening by 10 days. The cornified cells lacked complex surface microridges, while uterine cells exhibited dense microvilli growth, atypical morphology, and separation. Although 0.5 and 1.0 mg methoxychlor were highly stimulatory, the surface alterations in uterus and vagina appeared different from estradiol.
Article
The rat preoptic area-anterior hypothalamic continuum (POA-AH) contains about 400-800 neurons that express the decapeptide GnRH and the 56-amino-acid GnRH-associated peptide. Originating from the olfactory placode, these neurons migrate and establish their final distribution and connections in the POA-AH several days before birth. The aim of the present study was to examine whether the biosynthesis of the mRNA encoding the precursor (proGnRH) common to GnRH and GnRH-associated peptide undergoes postnatal changes corresponding to the development of sexual maturation. The POA-AH content of proGnRH messenger RNA (mRNA) was followed from postnatal day 1 to day 90 in female and male Sprague-Dawley rats killed by decapitation between 1000-1200 h. Cytoplasmic RNA fractionated from individual POA-AH homogenates was purified using proteinase K digestion. Cytoplasmic proGnRH mRNA was quantitated simultaneously with cyclophilin mRNA (an internal standard control) using solution hybridization-RNase protection assay, with the protected fragments separated through polyacrylamide gel electrophoresis. In the POA-AH, the concentrations of proGnRH mRNA (femtograms mRNA per microgram total RNA) increased significantly with age in both sexes (P less than 0.001). In males, proGnRH mRNA levels increased by day 30 some 2-fold over the values of days 5 and 10, and the levels established on day 30 were maintained through adulthood. In females, the first rise in proGnRH mRNA levels occurred on day 30, followed by an additional increase on day 45 to levels seen in adulthood. Levels of proGnRH mRNA established in adulthood were significantly higher in females than in males (P less than 0.03). The concentrations of cyclophilin mRNA (picograms mRNA per microgram total RNA) remained essentially unchanged in both sexes during the same period of time when proGnRH mRNA levels were increasing. These results provide evidence for postnatal sex-related increases in the levels of proGnRH mRNA in the rat POA-AH, which are likely to reflect differential regulation by gonadal steroids.
Article
By genetically targeting tumorigenesis to specific hypothalamic neurons in transgenic mice using the promoter region of the gonadotropin-releasing hormone (GnRH) gene to express the SV40 T-antigen oncogene, we have produced neuronal tumors and developed clonal, differentiated, neurosecretory cell lines. These cells extend neurites, express the endogenous mouse GnRH mRNA, release GnRH in response to depolarization, have regulatable fast Na+ channels found in neurons, and express neuronal, but not glial, cell markers. These immortalized cells will provide an invaluable model system for study of hypothalamic neurosecretory neurons that regulate reproduction. Significantly, their derivation demonstrates the feasibility of immortalizing differentiated neurons by targeting tumorigenesis in transgenic mice to specific neurons of the CNS.
Article
Effects of estradiol-17 beta and the estrogenicity of different doses of the technical grade pesticide methoxychlor were compared in the vagina, uterus, and oviducts of neonatal mice. Beginning within 24 h of birth, neonates received 10 daily i.p. injections of sesame oil vehicle, 10.0 micrograms estradiol, or 0.05, 0.1, 0.5, or 1.0 mg methoxychlor. Estradiol injections induced precocious vaginal opening, complete vaginal cornification, and increased total reproductive tract weight and its DNA content. In comparison to the controls, the three highest methoxychlor doses also significantly increased the weights of the reproductive tracts and stimulated their development. The two highest doses (0.5 and 1.0 mg) also induced precocious vaginal opening and complete vaginal cornification. In addition, the same two doses produced atypical cells in the uterus and oviducts that may be indicative of early dysplasia; similar atypia were not recorded following estradiol treatments. Total DNA content in various reproductive organs increased with increased methoxychlor dosages. Dose-response changes were observed in the oviduct and uterus but not vagina. In summary, methoxychlor stimulated the development of neonatal female reproductive tracts, even at concentrations not previously reported to be biologically active. Furthermore, the higher doses induced abnormalities that were not seen following estradiol treatment; these abnormalities may represent precursors of pathological changes.
Article
The determination that a chemical poses a reproductive risk to man typically relies upon fertility studies using rodents. However, fertility in rodents is often difficult to disrupt and more sensitive indicators of reproductive function should be included in the risk assessment process. The present discussion compares the sensitivity of fertility to other endpoints following exposure to known reproductive toxicants. In our studies rats were dosed from weaning through puberty , gestation, and lactation. The reproductive function of the male, the female, and the offspring was assessed. The effects of methoxychlor, carbendazim (MBC), dibutyl phthalate (DBP), and lindane are discussed and compared to fertility. For each compound a ratio (SR = sensitivity ratio) of the lowest effect level (LEL) for infertility or reduced fecundity to the LEL for the most sensitive physiologic endpoint was calculated. The SR should be large when a compound produces effects over a wide range of doses, but should equal unity when the dose-response curve is very steep. For methoxychlor, which blocked implantation, pubertal landmarks and estrous cyclicity provided rapid and sensitive indicators of the subsequent reproductive failure. The SR = 8 (100/12) for methoxychlor using data from females. In contrast, DBP and MBC directly altered testicular function, and for these compounds, sperm and testicular measures provided sensitive indicators of toxicity. The SR for MBC was 2 (100/50), while DBP had a SR of 1 (500/500). In the lindane study, fertility was not reduced but most of the pups (F1) died shortly after birth. The SR for lindane is equal to 0.5 (10/20). At 20 mg/kg the treated females were larger and their estrous cycles were erratic.(ABSTRACT TRUNCATED AT 250 WORDS)
Article
To determine the regulatory mechanism of the LHRH release associated with puberty, episodic release of LHRH from the stalk-median eminence was measured using a push-pull perfusion technique in conscious prepubertal and peripubertal female monkeys. After insertion of a push-pull cannula into the stalk-median eminence, a modified Krebs-Ringer phosphate buffer solution was infused through the push-cannula, and perfusates were collected through the pull-cannula at 200 microliters/10 min. LHRH in perfusates was determined by RIA. Two 6-h sampling sessions, in the morning (0600-1200 h; lights on 0600 h) and in the evening (1800-2400 h; lights off 1800 h) were performed in each animal. LHRH release patterns were analyzed in prepubertal (15.7 +/- 0.7 months of age; mean +/- SEM, n = 6) early pubertal (premenarcheal; 26.1 +/- 1.0 months, n = 7), and midpubertal (40.0 +/- 1.4 months, n = 6) monkeys. Results were as follows: 1) LHRH release was pulsatile in all age groups. While LHRH release in five of six prepubertal animals consisted of small (amplitude less than 2.5 pg/ml) pulses, in all peripubertal animals LHRH release was a mixture of small and large (amplitude greater than 2.5 pg/ml) pulses. 2) There was a significant developmental increase in mean LHRH release (P less than 0.02), and this was particularly apparent in the evening. Mean LHRH release in the early and midpubertal groups was higher than that in the prepubertal group (P less than 0.05 for morning and P less than 0.01 for evening). The mean release in the evening of the midpubertal group further increased over that of the early pubertal group (P less than 0.05). 3) Similarly, LHRH pulse amplitude increased developmentally (P less than 0.01). Pulse amplitudes in early and midpubertal groups were higher than those in the prepubertal group (P less than 0.05 for morning and P less than 0.02 for evening). Again the amplitude in the evening further increased from the early pubertal to the midpubertal period (P less than 0.05). 4) There was also a developmental increase in basal LHRH release (P less than 0.01). The evening values in the early pubertal and midpubertal groups were higher than those in the prepubertal group (P less than 0.05). 5) The interpulse interval decreased developmentally (P less than 0.001). Interpulse intervals in early and midpubertal groups were shorter than those in the prepubertal group (P less than 0.01 for morning and P less than 0.025 for evening).(ABSTRACT TRUNCATED AT 400 WORDS)
Article
Kallmann syndrome inherited hypogonadotropic hypogonadism with anosmia, is associated with an X-chromosome deletion at Xp 22.3. In a Kallmann fetus, we have found an absence of luteinizing hormone-releasing hormone (LHRH)-expressing cells in the brain despite dense clusters of LHRH cells and fibers in the nose. LHRH-containing cells and neurites end in a tangle beneath the forebrain, within the dural layers of the meninges, on the dorsal surface of the cribriform plate of the ethmoid bone. Normal fetal brains, matched for age and sex, had LHRH cells and fibers, as expected, in the hypothalamus and preoptic area. Since LHRH-expressing cells recently were discovered to migrate from the olfactory placode into the brain, it appears that the hypogonadotropism of the Kallmann syndrome can be accounted for by a failure of LHRH cells to migrate into the brain.
Article
The pesticide methoxychlor (MXC) is known to possess a weak estrogenic action and has been found to have a number of toxic effects on the rodent reproductive system, primarily at the gonadal level. The purpose of this study was to explore the influence of MXC on the pituitary and hypothalamic components of the male reproductive system at dose levels that were without detectable testicular effects. At 21 days, male Long-Evans rats were gavaged daily with 25 or 50 mg/kg MXC in corn oil. Controls received vehicle only. After 8 weeks of dosing, no significant changes were seen in serum LH, FSH, or prolactin, nor in the pituitary concentrations of LH or FSH. Pituitary prolactin was elevated for both doses, and pituitary fragments perifused in vitro released more prolactin than did controls. The concentration of gonadotropin-releasing hormone (GnRH) was higher in the mediobasal hypothalamus, but only for the 50-mg/kg group. At this dose, there was a corresponding increase in the KCl-stimulated release of GnRH. The data suggest that previously reported reproductive effects of MXC may be mediated, at least in part, through an elevation in prolactin concentration and release, which in turn is able to influence hypothalamic levels of GnRH. This prolactinemic effect may well represent an early component of the adverse action of MXC on the reproductive system.
Article
The widespread occurrence of 1,1,1-trichloro-2-2-bis (p-chlorophenyl) ethane (DDT) in our environment and the possibility that this insecticide may have adverse effects on animal fertility led us to investigate the influence of this chlorinated hydrocarbon on carbohydrate metabolism in uteri of ovariectomized rats. Administration of o,p′-DDT (10 mg/100 g) significantly enhanced uterine weights, glycogen content and the activities of hexokinase, phosphofructokinase, aldolase and pyruvate kinase as well as of glucose 6-phosphate and 6-phosphogluconate dehydrogenases. o,p′-DDT treatment, on the other hand, resulted in only minor increases in uterine aldolase, pyruvate kinase and glucose 6-phosphate dehydrogenase without exerting any appreciable effect on the other enzymes or on glycogen. Time-course studies demonstrated that, while significant increases in uterine weight and in the activities of most enzymes occurred within 4 hr after a single injection of o,p′-DDT, maximal increases were attained at 16 hr. Chronic treatment with o,p′-DDT (5.0 mg/100 g) for 3 days produced increases in uterine enzyme activities greater than those observed after a single dose of the pesticide. Administration of either actinomycin or cycloheximide to o,p′-DDT-treated animals effectively blocked the insecticide-stimulated increases in uterine glycloytic and hexose monophosphate shunt enzymes, suggesting that acceleration of the synthesis of both new RNA and protein may be associated with the observed augmented enzymatic activities. Whereas concomitant treatment with estradiol-17β and o,p′-DDT produced effects on uterine enzymes which were somewhat additive, administration of progesterone resulted in an almost complete inhibition of the insecticide-stimulated enzyme increases. The present investigation indicates that DDT analogs possess uterotrophic activity and that, analogous to the action of estrogens on uterine tissue, they are capable of inducing new synthesis of several carbohydrate-metabolizing enzymes.
Article
The intraperitoneal injection of 50 mg/kg of purified o,p′-DDT, technical grade DDT, purified methoxychlor, or purified p,p′-DDT increased the uterine wet weight by 49, 43, 37, and 28%, respectively, 6 hours after injection. o,p′-DDD, m,p′-DDD, p,p′-DDD, and p,p′-DDE exhibited little or no activity. The intraperitoneal injection of as little as 5 mg/kg or 1 mg/kg of technical grade DDT or o,p′-DDT, respectively, caused a significant increase in the uterine wet weight in immature female rats. The injection of technical grade DDT or o,p′-DDT into ovariectomized adult rats also increased uterine wet weight, indicating that the effect of the DDT analogs was not mediated through the ovaries. Treatment of immature female rats with a 50 mg/kg injection of technical grade DDT or purified o,p′-DDT caused a severalfold stimulation in the incorporation in vitro of glucose-U-14C into lipid, protein, RNA, and acid-soluble constituents in the uterus 6 hours after the dose of DDT. A smaller stimulatory effect was observed with purified p,p′-DDT. Treatment of rats with technical grade DDT, purified o,p′-DDT, methoxychlor or p,p′-DDT 2 hours before an injection of estradiol-17β-6,7-3H inhibited the uptake of estradiol-17β-6,7-3H by the uterus in vivo, possibly by competing for sites that bind estradiol-17β in the uterus. o,p′-DDD, p,p′-DDD, m,p′-DDD and p,p′-DDE did not inhibit the uptake of estradiol-17β-6,7-3H by the uterus. Pretreatment of rats with carbon tetrachloride inhibited the uterotropic action of o,p′-DDT and technical grade DDT. This suggests the possibility that the action of these substances on the uterus may depend on the conversion of the analogs of DDT to estrogenic metabolites.
Article
Pregnant CF-1 mice were given 0, 1, 10, or 25 mg/kg/day of chlorpyrifos by gavage on Days 6 through 15 of gestation. Severe maternal toxicity was observed among pregnant mice given 25 mg/kg of the test compound. Plasma and erythrocyte cholinesterase levels were significantly reduced among maternal mice at all dosages. Fetotoxicity was noted among litters of mice given 25 mg/kg of chlorpyrifos as evidenced by decreased fetal body measurements and an increased incidence of minor skeletal variants. An increase in the incidence of exencephaly was observed among litters of mice at the lowest dosage, 1 mg/kg/day, but not at 10 or 25 mg/kg. Additional groups of mice were given 0, 0.1, 1, or 10 mg chlorpyrifos/kg/day on Days 6 through 15 of gestation. Plasma and erythrocyte cholinesterase levels were significantly decreased among maternal mice at 1 and 10 mg/kg but not at the lowest dosage, 0.1 mg/kg. No evidence of a teratogenic response was observed in these mice. Thus, since exencephaly was not repeatable and was not found at 10- and 25-fold higher dose levels in the original study, chlorpyrifos was not teratogenic in mice at dose levels up to 25 mg/kg/day.
Article
Oestrogen, acting in both the brain and pituitary, has a critical role in regulating the reproductive cycle in most mammals. In the brain, oestrogen regulates the release of luteinizing hormone-releasing hormone (LHRH) partly through a mechanism that is blocked by inhibitors of DNA-dependent RNA synthesis or protein synthesis. The distributions of oestrogen-concentrating neurones and of LHRH neurones overlap. The present study was undertaken to determine whether genomic ef