An overview of dioxin-like compounds, PCB, and pesticide exposures associated with sexual differentiation of neuroendocrine systems, fluctuating asymmetry, and behavioral effects in birds

Sublethal effects of early-life exposure to common and emerging contaminants in birds

The plight of wild birds is becoming critical due to exposure to environmental contaminants. Although laboratory studies have provided insights into the developmental effects of chemical exposures, less is known about the adverse effects of environmental chemicals in developing wild birds. Early life stages are critical windows during which long-term organization of physiological, behavioral, and neurological systems can occur. Thus, contaminant exposure at early life stages can directly influence survival and reproductive success, with consequences for population stability and resilience in wild species. This review synthesizes existing knowledge regarding both short- and long-term effects of early-life exposure to widespread contaminants in birds. We focus especially on wild birds and on contaminants of concern within the Gulf of Mexico as an example of a habitat under anthropogenic stress from exposure to a complex mixture of chemicals and changing land uses that exacerbate existing vulnerabilities of wildlife in this region. Chemical contaminants for discussion in this review are based on avian mortality records from the Wildlife Health Information Sharing Partnership (WHISPers) database and on additional review of the literature regarding avian contaminants of concern for the northern Gulf of Mexico, and include oil and associated polycyclic aromatic hydrocarbons, dioxin and dioxin-like compounds, flame retardants, pesticides, heavy metals, and plastics. We provide an overview of effects in bird species at both the pre-hatching and post-hatching early life stages, discuss differences in sensitivities by route of exposure, life stage, and life history, and provide recommendations for future research. We find that additional research is needed on altricial species, post-hatching early-life exposure, long-term effects, and on ecologically relevant contaminant concentrations and routes of exposure. Given the increasing frequency and intensity of anthropogenic stressors encountered by wild animals, understanding both lethal and sublethal impacts of contaminants on the health of individuals and populations will be critical to inform restoration, management, and mitigation efforts.

Levels of persistent organic pollutants in cane toads (Rhinella marina) differ among sites with varying industrial and agricultural activities

In this study, we captured cane toads (Rhinella marina) in four sites located in different regions affected by anthropogenic activities in Mexico. Subsequently we analyzed liver tissue for the presence of organochlorine pesticides (OCs) and polychlorinated biphenyls (PCBs) The levels of these POPs in the toads' livers ranged from 863.2 to 3109.6 ng/g of lipid weight across all sites. A multivariate statistical analysis highlighted two sites with the highest POPs levels, with the most polluted site displaying a high level of PCBs, suggesting influence of industrial activities. The second most polluted site displayed significant amounts of OCs, linking this location to agricultural activity. Additionally, we found pesticide metabolites and isomers that allowed us to distinguish past and recent exposure events. Our observations indicate that R. marina is suitable bioindicator of sites impacted by anthropogenic activities.

Feeding on grains containing pesticide residues is detrimental to offspring development through parental effects in grey partridge

Numerous toxicological studies have shown that ingestion of pesticides can induce physiological stress in breeding birds, with adverse consequences on egg laying parameters and offspring quality through parental effects. However, previous studies do not mimic current levels of pesticide residues in typical landscapes, and they do not consider potential cocktail effects of pesticides as they occur in the wild. Herein, we explored whether realistic pesticide exposure affected reproduction parameters and offspring condition through parental effects in Grey partridge. We fed 24 breeding pairs with either seeds from conventional agriculture crops treated with various pesticides during cropping, or organic grains without pesticide residues as controls. The conventional and organic grain diets mimicked food options potentially encountered by wild birds in the field. The results showed that ingesting low pesticide doses over a long period had consequences on reproduction and offspring quality without altering mortality in parents or chicks. Compared with organic pairs, conventional pairs yielded smaller chicks at hatching that had a lower body mass index at 24 days old. Additionally, these chicks displayed lower haematocrit when body mass index was higher. Therefore, ingestion of conventional grains by parents resulted in chronic exposure to pesticide residues, even at low doses, and this had detrimental consequences on offspring. These results demonstrate a sublethal effect of pesticide residues through parental effects. The consequences of parental exposure on chicks might partly explain the decline in wild Grey partridge populations, which raises questions for avian conservation and demography if current agrosystem approaches are continued.

Microplastics in the Gulf of Mexico: A Bird’s Eye View

Microplastic debris is a persistent, ubiquitous global pollutant in oceans, estuaries, and freshwater systems. Some of the highest reported concentrations of microplastics, globally, are in the Gulf of Mexico (GoM), which is home to the majority of plastic manufacturers in the United States. A comprehensive understanding of the risk microplastics pose to wildlife is critical to the development of scientifically sound mitigation and policy initiatives. In this review, we synthesize existing knowledge of microplastic debris in the Gulf of Mexico and its effects on birds and make recommendations for further research. The current state of knowledge suggests that microplastics are widespread in the marine environment, come from known sources, and have the potential to be a major ecotoxicological concern for wild birds, especially in areas of high concentration such as the GoM. However, data for GoM birds are currently lacking regarding typical microplastic ingestion rates uptake of chemicals associated with plastics by avian tissues; and physiological, behavioral, and fitness consequences of microplastic ingestion. Filling these knowledge gaps is essential to understand the hazard microplastics pose to wild birds, and to the creation of effective policy actions and widespread mitigation measures to curb this emerging threat to wildlife.

Impacts of endocrine disrupting chemicals on reproduction in wildlife and humans

Endocrine disrupting chemicals (EDCs) are ubiquitous in aquatic and terrestrial environments. The main objective of this review was to summarize the current knowledge of the impacts of EDCs on reproductive success in wildlife and humans. The examples selected often include a retrospective assessment of the knowledge of reproductive impacts over time to discern how the effects of EDCs have changed over the last several decades. Collectively, the evidence summarized here within reinforce the concept that reproduction in wildlife and humans is negatively impacted by anthropogenic chemicals, with several altering endocrine system function. These observations of chemicals interfering with different aspects of the reproductive endocrine axis are particularly pronounced for aquatic species and are often corroborated by laboratory-based experiments (i.e. fish, amphibians, birds). Noteworthy, many of these same indicators are also observed in epidemiological studies in mammalian wildlife and humans. Given the vast array of reproductive strategies used by animals, it is perhaps not surprising that no single disrupted target is predictive of reproductive effects. Nevertheless, there are some general features of the endocrine control of reproduction, and in particular, the critical role that steroid hormones play in these processes that confer a high degree of susceptibility to environmental chemicals. New research is needed on the implications of chemical exposures during development and the potential for long-term reproductive effects. Future emphasis on field-based observations that can form the basis of more deliberate, extensive, and long-term population level studies to monitor contaminant effects, including adverse effects on the endocrine system, are key to addressing these knowledge gaps.

Which factors influence the frequency of participation in longitudinal cohort studies? - An analysis of demographics, social factors, and medical preconditions in participants of the health effects in high level exposure to polychlorinated biphenyls (HELPcB) cohort

The continuous drop out of participants in longitudinal studies is a trend that may be observed in nearly all fields of medical research. A reduced participation rate might compromise the power of statistical analysis as well as lead to an attrition bias of the study. The aim of this analysis was to identify influencing factors on participation frequency in the monitoring program Health Effects in High Level Exposure to polychlorinated biphenyls (HELPcB) study, a cohort investigation of occupationally polychlorinated biphenyls (PCB) exposed individuals. The HELPcB study was initiated in 2010 and consisted of 7 study visits. At the last cross-section in 2019, less than one third of the included patients still actively participated. As possible influencing factors on study participation frequency, demographic, social, and medical characteristics of the participants were examined. In addition, a logistic regression model to predict study participation behavior was calculated. An overall higher frequency of participation was observed, if participants joined the program together with relatives or friends and had a higher age. For PCB plasma levels, an exceedance of the biological reference value (BAR) and further factors, such as (1) professional qualification, (2) later inclusion, (3) type of participant and (4) occupational-related disease notification, significant differences in the participation frequency were observed in the univariate analysis. Only age and joined study participation remained significant in the multivariate logistic regression. In conclusion, it was possible to identify several social and occupational-related factors that influence the frequency of participation of study attendees.

Effects of Silver Nanoparticles on Proliferation and Apoptosis in Granulosa Cells of Chicken Preovulatory Follicles: An In Vitro Study

The continuous development of poultry production related to the growing demand for eggs and chicken meat makes it necessary to use modern technologies. An answer to this demand may be the use of nanotechnology in poultry farming. One of the promising nanomaterials in this field are silver nanoparticles (AgNPs), which are used as disinfectants, reducing microbial pollution and the amounts of greenhouse gases released. This study aimed to evaluate the effect of AgNPs on the proliferation and apoptosis process in the granulosa cells of chicken preovulatory follicles. The in vitro culture experiment revealed that both 13 nm and 50 nm AgNPs inhibited the proliferation of the granulosa cells. However, a faster action was observed in 50 nm AgNPs than in 13 nm ones. A size-dependent effect of AgNP was also demonstrated for the caspase-3 activity. AgNPs 13 nm in size increased the caspase-3 activity in granulosa cells, while 50 nm AgNPs did not exert an effect, which may indicate the induction of distinct cell death pathways by AgNPs. In conclusion, our study reveals that AgNPs in vitro inhibit granulosa cell proliferation and stimulate their apoptosis. These results suggest that AgNPs may disrupt the final stage of preovulatory follicle maturation and ovulation.

Comparative Lethality of In ovo Exposure to PCB 126, PCB 77, and 2 Environmentally Relevant PCB Mixtures in Japanese Quail (Coturnix japonica)

The Japanese quail (Coturnix japonica) egg bioassay was used to directly compare the toxicity of 3,3',4,4',5-pentachlorobiphenyl (PCB 126), 3,3',4,4'-tetrachlorobiphenyl (PCB 77), and 2 environmentally relevant polychlorinated biphenyl (PCB) mixtures over specified dose ranges relative to vehicle and uninjected controls. Measures included lethality and deformities. Results showed clear dose-response relationships for PCB 126 and the 2 PCB mixtures by logistic analysis of covariance using a varying threshold model because there was a low but significant slope for mortality of vehicle controls over incubation. No dose-dependent increase in mortality was observed with PCB 77 treatment. Mortality increased above baseline for PCB 126 and the 2 mixtures after embryonic day 7 (ED07) to a stable slope from ED10. Median lethal doses and thresholds for response differed for PCB 126 and the 2 PCB mixtures, with the mixtures having lower initial toxicity and all showing progressively greater toxicity over the course of development. Further, the lethality of the PCB mixtures appeared to involve both aryl hydrocarbon receptor (AhR) and non-AhR mechanisms. Incidence of deformities was unrelated to treatments. In summary, complex mixtures of PCBs were lethal in a dose-related manner, with sublethal effects from exposure to PCB 77. Environ Toxicol Chem 2019;38:2637-2650. © 2019 SETAC.

Challenges to the parental brain: Neuroethological and translational considerations

Extending from research documenting adaptive parental responses in nonthreatening contexts, the influences of various neuroethological and physiological challenges on effective parenting responses are considered in the current review. In natural habitats, rodent family units are exposed to predators, compromised resources, and other environmental stressors that disrupt HPA axis functions. With the additional physiological demands associated with caring for offspring, alterations in stress-related neuroendocrine responsiveness contribute to adaptive responses in many challenging contexts. Some environmental contexts, however, such as restricted nesting resources, result in disrupted maternal responses that have a negative impact on offspring wellbeing. Additionally, parental dysregulation associated with exposure to environmental chemicals or pharmacological substances, also compromise maternal responses with effects that often extend to future generations. Continued preclinical and clinical research elucidating parental responses to various stressors and physiological disruptors is necessary to provide valuable translational information identifying threats to effective parenting outcomes.

Embryonic effects of an environmentally relevant PCB mixture in the domestic chicken

Studies were conducted to develop methods to assess the effects of a complex mixture of polychlorinated biphenyls (PCBs) in the domestic chicken (Gallus domesticus). Treatments were administered by egg injection to compare embryonic effects of an environmentally relevant PCB congener mixture in the domestic chicken over a range of doses. Chicken eggs were injected with the PCB mixture with a profile similar to that found in avian eggs collected on the upper Hudson River, New York, USA, at doses that spanned 0 to 98 μg/g egg. Eggs were hatched in the laboratory to ascertain hatching success. In the domestic chicken, the median lethal dose was 0.3 μg/g. These data demonstrate adverse effects of an environmentally relevant PCB mixture and provide the basis for further work using in vitro and other models to characterize the potential risk to avian populations. Environ Toxicol Chem 2018;37:2513-2522. © 2018 SETAC.

Differential expression of hepatic genes with embryonic exposure to an environmentally relevant PCB mixture in Japanese quail (Coturnix japonica)

The upper Hudson River was contaminated with polychlorinated biphenyls (PCB) Aroclor mixtures from the 1940s until the late 1970s. Several well-established biomarkers, such as induction of hepatic cytochrome P450 monooxygenases, were used to measure exposure to PCBs and similar contaminants in birds. In the present study, Japanese quail eggs were injected with a PCB mixture based upon a congener profile found in spotted sandpiper eggs at the upper Hudson River and subsequently, RNA was extracted from hatchling liver tissue for hybridization to a customized chicken cDNA microarray. Nominal concentrations of the mixture used for microarray hybridization were 0, 6, 12, or 49 μg/g egg. Hepatic gene expression profiles were analyzed using cluster and pathway analyses. Results showed potentially useful biomarkers of both exposure and effect attributed to PCB mixture. Biorag and Ingenuity Pathway Analysis® analyses revealed differentially expressed genes including those involved in glycolysis, xenobiotic metabolism, replication, protein degradation, and tumor regulation. These genes included cytochrome P450 1A5 (CYP1A5), cytochrome b5 (CYB5), NADH-cytochrome b5 reductase, glutathione S-transferase (GSTA), fructose bisphosphate aldolase (ALDOB), glycogen phosphorylase, carbonic anhydrase, and DNA topoisomerase II. CYP1A5, CYB5, GSTA, and ALDOB were chosen for quantitative real-time polymerase chain reaction confirmation, as these genes exhibited a clear dose response on the array. Data demonstrated that an initial transcriptional profile associated with an environmentally relevant PCB mixture in Japanese quail occurred.

Animal models of endocrine disruption

Endocrine disrupting chemicals (EDCs) are compounds that alter the structure and function of the endocrine system and may be contributing to disorders of the reproductive, metabolic, neuroendocrine and other complex systems. Typically, these outcomes cannot be modeled in cell-based or other simple systems necessitating the use of animal testing. Appropriate animal model selection is required to effectively recapitulate the human experience, including relevant dosing and windows of exposure, and ensure translational utility and reproducibility. While classical toxicology heavily relies on inbred rats and mice, and focuses on apical endpoints such as tumor formation or birth defects, EDC researchers have used a greater diversity of species to effectively model more subtle but significant outcomes such as changes in pubertal timing, mammary gland development, and social behaviors. Advances in genomics, neuroimaging and other tools are making a wider range of animal models more widely available to EDC researchers.

Uptake of radiolabeled 3,3',4,4'-tetrachlorobiphenyl into Japanese quail egg compartments and embryo following air cell and albumen injection

The avian embryo is an excellent model for testing adverse developmental effects of environmental chemicals as well as uptake and movement of xenobiotics within the egg compartments. Before incubation at embryonic day 0, ¹⁴ C 3,3',4,4'-tetrachlorobiphenyl (¹⁴ C PCB 77) was injected into Japanese quail eggs either onto the air cell or into the albumen. All egg components were collected on embryonic day 1, 5, or 10, and concentrations of ¹⁴ C PCB 77 were measured in various egg components (shell, membrane, yolk, albumen, and embryo). The results showed measurable ¹⁴ C PCB 77 in all egg components, with changing concentrations in each egg component over the course of embryonic development. Specifically, concentrations in the shell content decreased between embryonic days 1 and 10, increased in albumen from embryonic days 1 to 5 and then decreased at embryonic day 10, and increased in both yolk and embryo from embryonic days 1 to 10. Vehicle and injection site both influenced ¹⁴ C PCB 77 allantoic fluid concentrations, with little effect on other egg components except for the inner shell membrane. The fatty acid vehicle injected into the albumen yielded the highest ¹⁴ C PCB 77 recovery. These findings demonstrate dynamic movement of toxicants throughout the egg components during avian embryonic development and a steady increase of relatively low levels of ¹⁴ C PCB 77 in the embryo compared with the yolk, albumen, and shell, suggesting that embryonic uptake (i.e., exposure) mirrors utilization of egg components for nutrition and growth during development. Environ Toxicol Chem 2018;37:126-135. © 2017 SETAC.

Temporal trends of mercury and organohalogen contaminants in great blue heron eggs from the St. Lawrence River, Québec, Canada, 1991-2011, and relationships with tracers of feeding ecology

Since 1991, great blue heron (Ardea herodias) eggs have been collected and analyzed for mercury (Hg), persistent organic contaminants (OCs), brominated and non-brominated flame retardants (FRs) as well as stable isotopes δ¹³C and δ¹⁵N. In the present study, temporal trends of contaminants were analyzed in eggs sampled in four regions along the St. Lawrence River (Quebec, Canada) and inland sites using new and previously published data. Most contaminants declined significantly over time in most regions. Globally, the highest annual change, -17.5%, was found for pp'-DDD, while the smallest annual decline, -0.54%, was observed for Hg. Concentrations of ΣDDT and ΣFR₈ (sum of 8 congeners) decreased by -11.6% and -7.3%, respectively. Declines in ΣPCBs differed among regions, from -5.6% in the fluvial section to -14.7% in the inland region. The highest concentration of ΣFR₈ was measured in eggs from Grande Ile in the fluvial section of the river in 1996 (2.39μg/g). Stable isotope ratios also showed temporal trends in some regions: δ¹³C decreased in the fluvial section and increased in Gulf region, while δ¹⁵N decreased in the fluvial section and increased in the upper estuary. Significant positive relationships were found between ΣDDT, ΣPCBs and ΣFRs and δ¹⁵N and δ¹³C in freshwater colonies, but not in estuarine or marine colonies. These results suggest that changes in trophic level and foraging areas over time were influential factors with respect to contaminant burden in great blue heron eggs in the fluvial section, but not in the other regions.

Exposures of zebrafish through diet to three environmentally relevant mixtures of PAHs produce behavioral disruptions in unexposed F1 and F2 descendant

The release of polycyclic aromatic hydrocarbons (PAHs) into the environment has increased very substantially over the last decades. PAHs are hydrophobic molecules which can accumulate in high concentrations in sediments acting then as major secondary sources. Fish contamination can occur through contact or residence nearby sediments or though dietary exposure. In this study, we analyzed certain physiological traits in unexposed fish (F1) issued from parents (F0) exposed through diet to three PAH mixtures at similar and environmentally relevant concentrations but differing in their compositions. For each mixture, no morphological differences were observed between concentrations. An increase in locomotor activity was observed in larvae issued from fish exposed to the highest concentration of a pyrolytic (PY) mixture. On the contrary, a decrease in locomotor activity was observed in larvae issued from heavy oil mixture (HO). In the case of the third mixture, light oil (LO), a reduction of the diurnal activity was observed during the setup of larval activity. Behavioral disruptions persisted in F1-PY juveniles and in their offspring (F2). Endocrine disruption was analyzed using cyp19a1b:GFP transgenic line and revealed disruptions in PY and LO offspring. Since no PAH metabolites were dosed in larvae, these findings suggest possible underlying mechanisms such as altered parental signaling molecule and/or hormone transferred in the gametes, eventually leading to early imprinting. Taken together, these results indicate that physiological disruptions are observed in offspring of fish exposed to PAH mixtures through diet.

Changes in persistent organic pollutant levels from adolescence to young adulthood

Elimination rates and their corresponding half-lives are conceptually important and intuitively accessible pharmacokinetic measures of toxicant elimination, but regression-based estimates are biased proportional to the degree of continuing (background) exposure. We propose an alternative estimator, the censored normal regression model, which uses all observations, but treats individuals whose initial level failed to exceed their follow-up level as censored observations to weight the regression estimates from those that declined between blood draws. In this manner, we derive the intrinsic elimination rate, the elimination rate free from ongoing exposure, as a parameter in a regression with an unobserved, latent dependent variable. We utilize sequential measurements of persistent organic pollutants (POPs) levels from adolescence to adulthood, a period of intense change in size and body composition, to quantify individual-level change within a community exposed to significant quantities of contaminants over an extended period of time. Although much research has been conducted on effects of POPs, far less attention has been given to vectors of intake and changes in toxicant levels during the life course. We apply exploratory factor analysis (EFA) to types and timing of consumption, along with physical behavioral characteristics, to identify a structure of seven underlying factors. Although several variables show factorial complexity, the latent constructs included an age/maturation and period-related factor, a nutritional composite, consumption prior to pregnancy, fish and fowl consumed during pregnancy, factors distinguishing body mass and weight from height, and bottom-feeding fish consumption. Unadjusted and adjusted half-lives using the censored normal regression estimator, as well as estimated half-lives from conventional log concentration regressions, are reported for PCB groupings, specific congeners, p,p'-DDE, and HCB.

Assessing effects of environmental chemicals on neuroendocrine systems: potential mechanisms and functional outcomes

Environmental pollutants encompass a vast array of compounds. Most studies in birds have focused on toxicological effects, with little attention to non-lethal effects. Consequently, it has proven difficult to assess potential risk associated with exposure to endocrine disrupting chemicals (EDCs). Assessing potential adverse effects due to exposure is further complicated by the great variation that occurs across avian species. These include variations in reproductive strategies, life span, sexual differentiation, and migration. Differences in reproductive strategies, particularly in the developmental patterns and mechanisms for precocial and altricial chicks, predispose birds to wide variations in response to steroids and steroid-like EDCs. We have investigated the effects of EDCs in precocial birds including Japanese quail (Coturnix japonica) and mallard ducks (Anas platyrhynchos) as well as in wild altricial songbirds. Studies in Japanese quail characterized endogenous steroid hormone changes during development and have demonstrated that the developing embryo uses the yolk as a 'steroid hormone depot'. It appears that actual embryonic exposure is quantitatively lower than indicated by the treatment in egg injections and that the true amount of compound necessary for bioactivity may be quite low relative to the actual dosage delivered. Additionally, embryonic exposure to specific EDCs adversely affected sexual differentiation in quail, especially impacting male sexual behavior as well as neural systems, immune response, and thyroid hormones. Many of these studies considered single compounds; however, wild birds are exposed to complex mixtures and multiple compounds. We tested complex mixtures of polychlorinated biphenyls (PCBs) at concentrations that bracketed those found in eggs in contaminated regions. Results indicated that the predictive value of the toxic equivalency (TEQ), based on comparative activation of the aryl hydrocarbon receptor (AhR) relative to dioxin was not as accurate as expected. We discuss the potential of developing an endocrine disruption index (EDI) to bridge the inconsistencies observed between responses predicted by the TEQ and those observed in vivo following exposure to EDCs. Further, we will discuss how an EDI would complement the adverse outcome pathways analyses to consider the range of effects of endocrine disruptors in birds.

Endocrine disrupters: a review of some sources, effects, and mechanisms of actions on behaviour and neuroendocrine systems

Some environmental contaminants interact with hormones and may exert adverse consequences as a result of their actions as endocrine disrupting chemicals (EDCs). Exposure in people is typically a result of contamination of the food chain, inhalation of contaminated house dust or occupational exposure. EDCs include pesticides and herbicides (such as dichlorodiphenyl trichloroethane or its metabolites), methoxychlor, biocides, heat stabilisers and chemical catalysts (such as tributyltin), plastic contaminants (e.g. bisphenol A), pharmaceuticals (i.e. diethylstilbestrol; 17α-ethinylestradiol) or dietary components (such as phytoestrogens). The goal of this review is to address the sources, effects and actions of EDCs, with an emphasis on topics discussed at the International Congress on Steroids and the Nervous System. EDCs may alter reproductively-relevant or nonreproductive, sexually-dimorphic behaviours. In addition, EDCs may have significant effects on neurodevelopmental processes, influencing the morphology of sexually-dimorphic cerebral circuits. Exposure to EDCs is more dangerous if it occurs during specific 'critical periods' of life, such as intrauterine, perinatal, juvenile or puberty periods, when organisms are more sensitive to hormonal disruption, compared to other periods. However, exposure to EDCs in adulthood can also alter physiology. Several EDCs are xenoestrogens, which can alter serum lipid concentrations or metabolism enzymes that are necessary for converting cholesterol to steroid hormones. This can ultimately alter the production of oestradiol and/or other steroids. Finally, many EDCs may have actions via (or independent of) classic actions at cognate steroid receptors. EDCs may have effects through numerous other substrates, such as the aryl hydrocarbon receptor, the peroxisome proliferator-activated receptor and the retinoid X receptor, signal transduction pathways, calcium influx and/or neurotransmitter receptors. Thus, EDCs, from varied sources, may have organisational effects during development and/or activational effects in adulthood that influence sexually-dimorphic, reproductively-relevant processes or other functions, by mimicking, antagonising or altering steroidal actions.

Endocrine disrupting chemicals: Multiple effects on testicular signaling and spermatogenesis

In the past 200 years, an enormous number of synthetic chemicals with diverse structural features have been produced for industrial, medical and domestic purposes. These chemicals, originally thought to have little or no biological toxicity, are widely used in our daily lives as well as are commonly present in foods. It was not until the first World Wildlife Federation Wingspread Conference held in 1994 were concerns about the endocrine disrupting (ED) effects of these chemicals articulated. The potential hazardous effects of endocrine disrupting chemicals (EDCs) on human health and ecological well-being are one of the global concerns that affect the health and propagation of human beings. Considerable numbers of studies indicated that endocrine disruption is linked to "the developmental basis of adult disease," highlighting the significant effects of EDC exposure on a developing organism, leading to the propensity of an individual to develop a disease or dysfunction in later life. In this review, we intend to provide environmental, epidemiological and experimental data to associate pollutant exposure with reproductive disorders, in particular on the development and function of the male reproductive system. Possible effects of pollutant exposure on the processes of embryonic development, like sex determination and masculinization are described. In addition, the effects of pollutant exposure on hypothalamus-pituitary-gonadal axis, testicular signaling, steroidogenesis and spermatogenesis are also discussed.

Perinatal exposure to polychlorinated biphenyls alters social behaviors in rats

Perinatal exposure to polychlorinated biphenyls (PCBs) leads to significant alterations of neural and hormonal systems. These alterations have been shown to impair motor and sensory development. Less is known about the influence of PCB exposure on developing emotional and motivational systems involved in social interactions and social learning. The present study examined the impact of perinatal PCB exposure (mixture of congeners 47 and 77) on social recognition in juvenile animals, conspecific-directed investigation in adults and on neural and hormonal systems involved in social functions. We used a standard habituation-dishabituation paradigm to evaluate juvenile recognition and a social port paradigm to monitor adult social investigation. Areal measures of the periventricular nucleus (PVN) of the hypothalamus were obtained to provide correlations with related hormone and brain systems. PCB exposed rats were significantly impaired in social recognition as indicated by persistent conspecific-directed exploration by juvenile animals regardless of social experience. As adults, PCB exposure led to a dampening of the isolation-induced enhancement of social investigation. There was not a concomitant alteration of social investigation in pair-housed PCB exposed animals at this stage of development. Interestingly, PVN area was significantly decreased in juvenile animals exposed to PCB during the perinatal period. Shifts in hypothalamic regulation of hormones involved in social behavior and stress could be involved in the behavioral changes observed. Overall, the results suggest that PCB exposure impairs context or experience-dependent modulation of social approach and investigation. These types of social-context deficits are similar to behavioral deficits observed in social disorders such as autism and other pervasive developmental disorders.