Prenatal lead exposure in the rat during the third week of gestation: long-term behavioral, physiological, and anatomical effects associated with reproduction

Lead in traditional and complementary medicine: a systematic review

Lead in the environment remains a matter of grave concern for public health. Lead has been associated with some traditional medicines and has been linked to cases of lead poisoning. A comprehensive compilation of these reports has not previously been conducted. The objective of this review is to explore how common is lead exposure after traditional medicine use, and which countries, systems and/or products are of most concern when it comes to lead contamination. A systematic search was conducted on PubMed, Ovid and EMBASE for studies published between 2005 and 2020. A grey literature search was conducted. Search terms related to lead and traditional medicine were developed for each database, and there were no limitations on language. Studies were included if they examined elevated lead in humans resulting from the use of traditional medicines reported in case reports, case-series, or observational studies. Of the papers discussing lead exposure, 85 case reports were identified and synthesized for the current review. Several themes were identified in the included studies. Traditional medicine has been used in the many parts of the world, however use is more common in South and Southeast Asian countries. The level of detectable lead in products varied widely by region and product types. Consumers of traditional medicines sought products for a wide variety of symptoms and ailments. The symptoms of lead poisoning from traditional medicine use reflected the typical symptom profile of lead poisoning, highlighting the need for awareness of traditional medicine products as a source of lead exposure. Traditional medicine usage remains an important part of health care in many regions, however there is a risk of lead exposure from several products. Health care practitioners in all regions of the world should be aware of the risk and explore the potential for traditional medicine use for patients presenting with elevated blood lead levels. Countries with a strong traditional medicine culture should explore policies for reducing lead exposure from traditional medicine products. JG, LO and MNBD are staff members of the World Health Organization. The authors alone are responsible for the views expressed in this publication and they do not necessarily represent the decisions, policy, or views of the World Health Organization.

Anxiety, aggression, reward sensitivity, and forebrain dopamine receptor expression in a laboratory rat model of early-life disadvantage

Despite early-life disadvantage (ELD) in humans being a highly heterogenous construct, it consistently predicts negative neurobehavioral outcomes. The numerous environmental contributors and neural mechanisms underlying ELD remain unclear, though. We used a laboratory rat model to evaluate the effects of limited resources and/or heavy metal exposure on mothers and their adult male and female offspring. Dams and litters were chronically exposed to restricted (1-cm deep) or ample (4-cm deep) home cage bedding postpartum, with or without lead acetate (0.1%) in their drinking water from insemination through 1-week postweaning. Restricted-bedding mothers showed more pup-directed behaviors and behavioral fragmentation, while lead-exposed mothers showed more nestbuilding. Restricted bedding-raised male offspring showed higher anxiety and aggression. Either restricted bedding or lead exposure impaired goal-directed performance in a reinforcer devaluation task in females, whereas restricted bedding alone disrupted it in males. Lead exposure, but not limited bedding, also reduced sucrose reward sensitivity in a progressive ratio task in females. D1 and D2 receptor mRNA in the medial prefrontal cortex and nucleus accumbens (NAc) were each affected by the early-life treatments and differently between the sexes. Most notably, adult males (but not females) exposed to both early-life treatments had greatly increased D1 receptor mRNA in the NAc core. These results illuminate neural mechanisms through which ELD threatens neurobehavioral development and highlight forebrain dopamine as a factor.

Progress on aptamer-based SERS sensors for food safety and quality assessment: methodology, current applications and future trends

It is well known that food safety has aroused extensive attentions from governments to researchers and to food industries. As a versatile technology based on molecular interactions, aptamer sensors which could specifically identify a wide range of food contaminants have been extensively studied in recent years. Surface-enhanced Raman spectroscopy integrated aptamer combines the advantages of both technologies, not only in the ability to specifically identify a wide range of food contaminants, but also in the ultra-high sensitivity, simplicity, portable and speed. To provide beneficial insights into the evaluation techniques in the field of food safety, we offer a comprehensive review on the design strategies for aptamer-SERS sensors in different scenarios, including non-nucleic acid amplification methods ("on/off" mode, sandwich mode, competition model and catalytic model) and nucleic acid amplification methods (hybridization chain reaction, rolling circle amplification, catalytic hairpin assembly). Meanwhile, a special attention is paid to the application of aptamer-SERS sensors in biological (foodborne pathogenic, bacteria and mycotoxins) and chemical contamination (drug residues, metal ions, and food additives) of food matrix. Finally, the challenges and prospects of developing reliable aptamer-SERS sensors for food safety were discussed, which are expected to offer a strong guidance for further development and extended applications.

In utero and peripubertal metals exposure in relation to reproductive hormones and sexual maturation and progression among girls in Mexico City

There is increasing evidence that several metals are endocrine disrupting chemicals (EDCs). In utero development and adolescence are critical windows of susceptibility to EDC exposure. With the exception of a few heavy metals, few human studies have evaluated the impact of metal exposure on pubertal development. Our aim was to investigate measures of in utero and peripubertal metal exposure in relation to reproductive hormone levels and sexual maturation and progression among girls from the Early Life Exposure in Mexico to Environmental Toxicants (ELEMENT) cohorts. We measured urinary concentrations of aluminum (Al), arsenic (As), barium (Ba), cadmium (Cd), cobalt (Co), copper (Cu), iron (Fe), manganese (Mn), molybdenum (Mo), nickel (Ni), antimony (Sb), selenium (Se), and zinc (Zn) in samples collected from women during their third trimester of pregnancy and from their female children at 8-13 years (n = 132). We measured serum testosterone, estradiol, dehydroepiandrosterone sulfate (DHEA-S), inhibin B, and sex hormone-binding globulin (SHBG) at age 8-13, and assessed Tanner stages for sexual maturation (breast, pubic hair development, and menarche status), at two time points (8-13, 14-18 years). We used linear regression to independently examine in utero and peripubertal metal concentrations as predictors of peripubertal hormones. In a longitudinal analysis using generalized estimation equations, we evaluated Tanner stage and menarche progression in relation to individual in utero and peripubertal metal concentrations. We found that higher in utero Zn was associated with increased inhibin B. Several metals at 8-13 years were associated with higher DHEA-S and estradiol, while Ni was positively but Cu was negatively associated with testosterone. In utero Ni, Al, and Cd were associated with slower progression of breast development after adjustment for child age and BMI z-score. For example, an IQR increase in in utero Al exposure was associated with 0.82 times lower odds of progressing to a higher Tanner stage for breast development per year (95% CI: 0.68, 0.99). Peripubertal concentrations of Ba and Al were also associated with being at a higher pubic hair Tanner stage and menarche at 8-13, but lower odds of progressing to the next stage at 14-18 years. We used Bayesian kernel machine regression (BKMR) to model the joint effect of multiple metals while accounting for correlated exposures, as well as potential non-linear relationships between metals and outcomes of interest, which yielded results similar to individual analyses. These findings suggest that female reproductive development may be vulnerable to the effects of metal exposure, and using both Tanner stages and hormone levels may provide clues about underlying mechanisms in two sensitive periods of development.

Environmental Mechanisms of Neurodevelopmental Toxicity

PURPOSE OF REVIEW

With the incidence of neurodevelopmental disorders on the rise, it is imperative to identify and understand the mechanisms by which environmental contaminants can impact the developing brain and heighten risk. Here, we report on recent findings regarding novel mechanisms of developmental neurotoxicity and highlight chemicals of concern, beyond traditionally defined neurotoxicants.

RECENT FINDINGS

The perinatal window represents a critical and extremely vulnerable period of time during which chemical insult can alter the morphological and functional trajectory of the developing brain. Numerous chemical classes have been associated with alterations in neurodevelopment including metals, solvents, pesticides, and, more recently, endocrine-disrupting compounds. Although mechanisms of neurotoxicity have traditionally been identified as pathways leading to neuronal cell death, neuropathology, or severe neural injury, recent research highlights alternative mechanisms that result in more subtle but consequential changes in the brain and behavior. These emerging areas of interest include neuroendocrine and immune disruption, as well as indirect toxicity via actions on other organs such as the gut and placenta. Understanding of the myriad ways in which the developing brain is vulnerable to chemical exposures has grown tremendously over the past decade. Further progress and implementation in risk assessment is critical to reducing risk of neurodevelopmental disorders.

Early-life lead exposure results in dose- and sex-specific effects on weight and epigenetic gene regulation in weanling mice

AIMS

Epidemiological and animal data suggest that the development of adult chronic conditions is influenced by early-life exposure-induced changes to the epigenome. This study investigates the effects of perinatal lead (Pb) exposure on DNA methylation and bodyweight in weanling mice.

MATERIALS & METHODS

Viable yellow agouti (A(vy)) mouse dams were exposed to 0, 2.1, 16 and 32 ppm Pb acetate before conception through weaning. Epigenetic effects were evaluated by scoring coat color of A(vy)/a offspring and quantitative bisulfite sequencing of two retrotransposon-driven (A(vy) and CDK5 activator-binding protein intracisternal A particle element) and two imprinted (Igf2 and Igf2r) loci in tail DNA.

RESULTS

Maternal blood Pb levels were below the limit of detection in controls, and 4.1, 25.1 and 32.1 µg/dl for each dose, respectively. Pb exposure was associated with a trend of increased wean bodyweight in males (p = 0.03) and altered coat color in A(vy)/a offspring. DNA methylation at A(vy) and the CDK5 activator-binding protein intracisternal A-particle element was significantly different from controls following a cubic trend (p = 0.04; p = 0.01), with male-specific effects at the A(vy) locus. Imprinted genes did not shift in methylation across exposures.

CONCLUSION

Dose- and sex-specific responses in bodyweight and DNA methylation indicate that Pb acts on the epigenome in a locus-specific fashion, dependent on the genomic feature hosting the CpG site of interest, and that sex is a factor in epigenetic response.

Cross-species coherence in effects and modes of action in support of causality determinations in the U.S. Environmental Protection Agency's Integrated Science Assessment for Lead

The peer-reviewed literature on the health and ecological effects of lead (Pb) indicates common effects and underlying modes of action across multiple organisms for several endpoints. Based on such observations, the United States (U.S.) Environmental Protection Agency (EPA) applied a cross-species approach in the 2013 Integrated Science Assessment (ISA) for Lead for evaluating the causality of relationships between Pb exposure and specific endpoints that are shared by humans, laboratory animals, and ecological receptors (i.e., hematological effects, reproductive and developmental effects, and nervous system effects). Other effects of Pb (i.e., cardiovascular, renal, and inflammatory responses) are less commonly assessed in aquatic and terrestrial wildlife limiting the application of cross-species comparisons. Determinations of causality in ISAs are guided by a framework for classifying the weight of evidence across scientific disciplines and across related effects by considering aspects such as biological plausibility and coherence. As illustrated for effects of Pb where evidence across species exists, the integration of coherent effects and common underlying modes of action can serve as a means to substantiate conclusions regarding the causal nature of the health and ecological effects of environmental toxicants.

Evolution of DOHaD: the impact of environmental health sciences

Environmental exposures have a significant influence on the chronic health conditions plaguing children and adults. Although the Developmental Origins of Health and Disease (DOHaD) paradigm historically has focused on nutrition, an expanding body of research specifically communicates the effects of chemical exposures on early-life development and the propagation of non-communicable disease across the lifespan. This paper provides an overview of 20 years of research efforts aimed at identifying critical windows of susceptibility to environmental exposures and the signaling changes and epigenetic influences associated with disease progression. DOHaD grants funded by the National Institute of Environmental Health Sciences (NIEHS) in 1991, 2001 and 2011 are identified by grant-analysis software, and each portfolio is analyzed for exposures, disease endpoints, windows of exposure, study design and impact on the field based on publication data. Results show that the 1991 and 2001 portfolios comprised metals, PCBs and air pollutants; however, by 2011, the portfolio has evolved to include or expand the variety of endocrine disruptors, pesticides/persistent organic pollutants and metals. An assortment of brain-health endpoints is most targeted across the portfolios, whereas reproduction and cancer increase steadily over the same time period, and new endpoints like obesity are introduced by 2011. With mounting evidence connecting early-life exposures to later-life disease, we conclude that it is critical to expand the original DOHaD concept to include environmental chemical exposures, and to continue a research agenda that emphasizes defining sensitive windows of exposure and the mechanisms that cause disease.

Metals and female reproductive toxicity

Research into occupational exposure of metals and consequences of reproductive systems has made imperative scientific offerings in the preceding few decades. Early research works focused on possible effects on the reproductive functions rather than the complete reproductive health of the woman. Later, it was realized that metals, as reproductive toxins, may also induce hormonal changes affecting other facets of reproductive health such as the menstrual cycle, ovulation, and fertility. Concern is now shifting from considerations for the pregnant woman to the entire spectrum of occupational health threats and thus reproductive health among women.

Endocrine-disrupting chemicals: elucidating our understanding of their role in sex and gender-relevant end points

Endocrine-disrupting chemicals (EDCs) are diverse and pervasive and may have significant consequence for health, including reproductive development and expression of sex-/gender-sensitive parameters. This review chapter discusses what is known about common EDCs and their effects on reproductively relevant end points. It is proposed that one way that EDCs may exert such effects is by altering steroid levels (androgens or 17-estradiol, E₂) and/or intracellular E₂ receptors (ERs) in the hypothalamus and/or hippocampus. Basic research findings that demonstrate developmentally sensitive end points to androgens and E₂ are provided. Furthermore, an approach is suggested to examine differences in EDCs that diverge in their actions at ERs to elucidate their role in sex-/gender-sensitive parameters.

Binding mode investigations on the interaction of lead(II) acetate with human chorionic gonadotropin

Lead exposure could induce endocrine disruption and hormonal imbalance of humans, resulting in detrimental effects on the reproductive system even at low doses. However, mechanisms of lead actions remain unknown. This article investigated lead interactions with human chorionic gonadotropin (HCG) as a conceivable mechanism of its reproductive toxicity by spectroscopic technique, isothermal titration calorimetry (ITC), molecular docking study, and enzyme-linked immunosorbent assay (ELISA). Fluorescence measurements showed that lead acetate dynamically quenched intrinsic fluorescence of HCG through collisional mechanism with the association constant (KSV) in the magnitude of 10(3) L/mol at the detected temperatures (298, 303, and 310 K). ITC and molecular docking results revealed lead acetate could bind into 5 binding sites of HCG through electrostatic effects (ΔH < 0, ΔS > 0) and hydrophobic forces (ΔH > 0, ΔS > 0). The conformational investigation of HCG by UV-vis absorption spectroscopy, circular dichroism spectroscopy, and ELISA indicated lead acetate changed the secondary structure of HCG by loosening and destruction of HCG skeleton and increasing the hydrophobicity around Tyr residues and resulted in the decreased bioactivities of HCG. This work presents direct interactions of lead with sex hormones and obtains a possible mechanism on lead induced reproductive toxicity at the molecular level.

Cumulative lead exposure and age at menopause in the Nurses' Health Study cohort

BACKGROUND

Early menopause has been associated with many adverse health outcomes, including increased risk of cardiovascular disease morbidity and mortality. Lead has been found to be adversely associated with female reproductive function, but whether exposures experienced by the general population are associated with altered age at menopause has not been explored.

OBJECTIVE

Our goal was to assess the association between cumulative lead exposure and age at natural menopause.

METHODS

Self-reported menopausal status and bone lead concentration measured with K-shell X-ray fluorescence-a biomarker of cumulative lead exposure-were obtained from 434 women participants in the Nurses' Health Study.

RESULTS

The mean (± SD) age at natural menopause was 50.8 ± 3.6 years. Higher tibia lead level was associated with younger age at menopause. In adjusted analyses, the average age of menopause for women in the highest tertile of tibia lead was 1.21 years younger (95% CI: -2.08, -0.35) than for women in the lowest tertile (p-trend = 0.006). Although the number of cases was small (n = 23), the odds ratio for early menopause (< 45 years of age) was 5.30 (95% CI: 1.42, 19.78) for women in the highest tertile of tibia lead compared with those in the lowest tertile (p-trend = 0.006). There was no association between patella or blood lead and age at menopause.

CONCLUSIONS

Our results support an association between low-level cumulative lead exposure and an earlier age at menopause. These data suggest that low-level lead exposure may contribute to menopause-related health outcomes in older women through effects on age at menopause.

CITATION

Eum KD, Weisskopf MG, Nie LH, Hu H, Korrick SA. 2014. Cumulative lead exposure and age at menopause in the Nurses' Health Study Cohort. Environ Health Perspect 122:229–234; http://dx.doi.org/10.1289/ehp.1206399

Cognitive disparities, lead plumbing, and water chemistry: prior exposure to water-borne lead and intelligence test scores among World War Two U.S. Army enlistees

Higher prior exposure to water-borne lead among male World War Two U.S. Army enlistees was associated with lower intelligence test scores. Exposure was proxied by urban residence and the water pH levels of the cities where enlistees lived in 1930. Army General Classification Test scores were six points lower (nearly 1/3 standard deviation) where pH was 6 (so the water lead concentration for a given amount of lead piping was higher) than where pH was 7 (so the concentration was lower). This difference rose with time exposed. At this time, the dangers of exposure to lead in water were not widely known and lead was ubiquitous in water systems, so these results are not likely the effect of individuals selecting into locations with different levels of exposure.

The association between cadmium, lead and mercury blood levels and reproductive hormones among healthy, premenopausal women

BACKGROUND

Cadmium, lead and mercury have been identified in human follicular fluid and ovarian tissue, and have been associated with adverse reproductive outcomes in epidemiologic studies; however, few studies have examined the relationship between blood metal levels and reproductive hormones.

METHODS

Among 252 premenopausal women aged 18-44 years, we examined the association between blood metal levels (cadmium, lead and mercury), cycle length, and reproductive hormones [FSH, LH, estradiol (E(2)) and progesterone] measured at clinically relevant time points in the menstrual cycle. The association between metal levels (continuous) and hormone levels was assessed using linear regression with hormone levels (natural) log transformed and the results interpreted as the percentage difference in hormone level per unit increase in metal level.

RESULTS

Median (interquartile range) cadmium, lead and mercury levels were 0.30 µg/l (0.19, 0.43), 0.87 µg/dl (0.68, 1.20) and 1.10 µg/l (0.58, 2.10), respectively. Each 1 µg/l increase in cadmium levels was associated with a 21% [95% confidence interval (CI): -2.9, 49.9] increase in early follicular phase E(2) levels after adjusting for age, race/ethnicity, lead and mercury. This association decreased when restricted to never smokers (10%; 95% CI: -19.5, 51.3). Cadmium was also associated with a non-significant 9% (95% CI: -0.2, 19.9), or 2.7 day, increase in cycle length among never smokers. No associations were observed between lead or mercury and the outcomes in adjusted analyses.

CONCLUSIONS

Further evaluation of the association between cadmium, E(2) and cycle length is warranted, taking into consideration cigarette smoke and its multiple components.

Relationships of putative endocrine disruptors to human sexual maturation and thyroid activity in youth

Endocrine disruption has become a significant human health concern, but is difficult to study outside of the laboratory for several reasons including the multiplicity of exposures, the difficulty in assessing each exposure, and the variety of possible outcomes among human populations. This review summarizes our studies of the relationships of measured persistent organic pollutants (PCBs, p,p'-DDE, HCB and mirex), and heavy metals (lead and mercury), to outcomes directly related to thyroid function and sexual maturation. These studies were conducted in a sample of Native American youth from the Akwesasne Mohawk community. The participants were first studied during puberty (10-16.9 years of age) and then at approximately 18 years of age. Results from these studies show that PCB levels are positively related to TSH and negatively to free T4. Further, these effects are conditioned by breastfeeding history. Anti-thyroid peroxidase antibody levels also are related to PCB levels suggesting elevated risk of autoimmune disease among the exposed. Earlier age at menarche is associated with higher PCB levels while risk of delay is associated with higher lead levels. Some evidence that the timing of exposure produces different effects is presented, and the level of exposure in the participants suggests that effects observed may be relevant to a considerable proportion of the US population. Further investigations are warranted to determine effect thresholds and mechanisms.

Low doses of dietary lead are associated with a profound reduction in the time to the onset of puberty in female mice

We report results from a replication in second and third generation female mice of accelerated time to puberty associated with low Pb exposure levels . Mice in the 2nd generation study are offspring of mice from the initial study; the 3rd generation mice are offspring from mice in the 2nd generation study. For each generation the time to puberty onset was markedly influenced by exposure to dietary lead. Modest increases in blood lead concentration from a normal background of 2-3 to 8-13 micro g/dl delayed the onset of puberty by 10-20% from a normal of 33-35 days to about 40-43 days; reducing blood lead from 2-3 to 0.7 micro g/dl was associated with profound acceleration of puberty to 21 days, an enhancement by over 30%. This dose-response relationship, which replicates previous novel findings, has possible ecological as well as public health significance and indicates that lead is able to induce biologically significant changes at blood lead levels previously thought to be without effect.

IGF-1 administration to prepubertal female rats can overcome delayed puberty caused by maternal Pb exposure

Because prepubertal female rats maternally exposed to lead (Pb) exhibit suppressed serum levels of insulin-like growth factor-1 (IGF-1) and delayed puberty, we investigated the ability of centrally administered IGF-1 to stimulate luteinizing hormone (LH) release in vivo and LH-releasing hormone (LHRH) release in vitro from maternally Pb-exposed prepubertal female rats. Additionally, we assessed whether IGF-1 replacement could affect the timing of female puberty. Results demonstrated that IGF-1 stimulated significantly LH release in both control and Pb-exposed animals. When median eminences from control and Pb-exposed females were incubated with rat IGF-1 in vitro, they responded similarly with significant peptide-induced LHRH release. Lastly, we showed IGF-1 replacement reversed the delay in puberty caused by Pb. These results indicate the central LHRH response to IGF-1 is intact and that Pb-induced delayed puberty is due, at least in part, to suppressed circulating IGF-1 available to the hypothalamus.

Effects of low doses of dietary lead on puberty onset in female mice

Female Swiss mice typically display signs of puberty at about 33-37 days of age. In the present investigation (96 female mice tested in 8 Pb exposure levels, n=12 per exposure level), the time to puberty onset was markedly influenced by exposure to dietary lead. While modest increases in blood lead concentrations from a normal background of 2-3 to 13.2 microg/dl delayed the onset of puberty by 15-20% to about 40-43 days, reducing blood lead from 2-3 to 0.7 microg/dl was associated with an acceleration of puberty to 21 days, an enhancement by over 30%. This dose-response relationship represents novel findings of possible ecological as well as public health significance and indicates that lead is able to induce biologically significant changes at blood lead levels previously thought to be without effect.

Relationship of lead, mercury, mirex, dichlorodiphenyldichloroethylene, hexachlorobenzene, and polychlorinated biphenyls to timing of menarche among Akwesasne Mohawk girls

BACKGROUND

Children are commonly exposed at background levels to several ubiquitous environmental pollutants, such as lead and persistent organic pollutants, that have been linked to neurologic and endocrine effects. These effects have prompted concern about alterations in human reproductive development. Few studies have examined the effects of these toxicants on human sexual maturation at levels commonly found in the general population, and none has been able to examine multiple toxicant exposures. The aim of the current investigation was to examine the relationship between attainment of menarche and levels of 6 environmental pollutants to which children are commonly exposed at low levels, ie, dichlorodiphenyldichloroethylene (p,p'-DDE), hexachlorobenzene (HCB), polychlorinated biphenyls (PCBs), mirex, lead, and mercury.

METHODS

This study was conducted with residents of the Akwesasne Mohawk Nation, a sovereign territory that spans the St Lawrence River and the boundaries of New York State and Ontario and Quebec, Canada. Since the 1950s, the St Lawrence River has been a site of substantial industrial development, and the Nation is currently adjacent to a US National Priority Superfund site. PCB, p,p'-DDE, HCB, and mirex levels exceeding the US Food and Drug Administration recommended tolerance limits for human consumption have been found in local animal species. The present analysis included 138 Akwesasne Mohawk Nation girls 10 to 16.9 years of age. Blood samples and sociodemographic data were collected by Akwesasne community members, without prior knowledge of participants' exposure status. Attainment of menses (menarche) was assessed as present or absent at the time of the interview. Congener-specific PCB analysis was available, and all 16 PCB congeners detected in >50% of the sample were included in analyses (International Union of Pure and Applied Chemistry numbers 52, 70, 74, 84, 87, 95, 99, 101 [+90], 105, 110, 118, 138 [+163 and 164], 149 [+123], 153, 180, and 187). Probit analysis was used to determine the median age at menarche for the sample. Binary logistic regression analysis was used to determine predictors of menarcheal status. Six toxicants (p,p'-DDE, HCB, PCBs, mirex, lead, and mercury) were entered into the logistic regression model. Age, socioeconomic status (SES), and BMI were tested as potential cofounders and were included in the model at P < .05. Interactions among toxicants were also evaluated.

RESULTS

Toxicant levels were measured in blood for this sample and were consistent with long-term exposure to a variety of toxicants in multiple media. Mercury levels were at or below background levels, all lead levels were well below the Centers for Disease Control and Prevention action limit of 10 microg/dL, and PCB levels were consistent with a cumulative, continuing exposure pattern. The median age at menarche for the total sample was 12.2 years. The predicted age at menarche for girls with lead levels above the median (1.2 microg/dL) was 10.5 months later than that for girls with lead levels below the median. In the logistic regression analysis, age was the strongest predictor of menarcheal status and SES was also a significant predictor but BMI was not. The logistic regression analysis that corrected for age, SES, and other pollutants (p,p'-DDE, HCB, mirex, and mercury) indicated that, at their respective geometric means, lead (geometric mean: 0.49 microg/dL) was associated with a significantly lower probability of having reached menarche (beta = -1.29) and a group of 4 potentially estrogenic PCB congeners (E-PCB) (geometric mean: 0.12 ppb; International Union of Pure and Applied Chemistry numbers 52, 70, 101 [+90], and 187) was associated with a significantly greater probability of having reached menarche (beta = 2.13). Predicted probabilities at different levels of lead and PCBs were calculated on the basis of the logistic regression model. At the respective means of all toxicants and SES, 69% of 12-year-old girls were predicted to have reached menarche. However, at the 75th percentile of lead levels, only 10% of 12-year-old Mohawk girls were predicted to have reached menarche; at the 75th percentile of E-PCB levels, 86% of 12-year-old Mohawk girls were predicted to have reached menarche. No association was observed between mirex, p,p'-DDE, or HCB and menarcheal status. Although BMI was not a significant predictor, we tested BMI in the logistic regression model; it had little effect on the relationships between menarcheal status and either lead or E-PCB. In models testing toxicant interactions, age, SES, lead levels, and PCB levels continued to be significant predictors of menarcheal status. When each toxicant was tested in a logistic regression model correcting only for age and SES, we observed little change in the effects of lead or E-PCB on menarcheal status.

CONCLUSIONS

The analysis of multichemical exposure among Akwesasne Mohawk Nation adolescent girls suggests that the attainment of menarche may be sensitive to relatively low levels of lead and certain PCB congeners. This study is distinguished by the ability to test many toxicants simultaneously and thus to exclude effects from unmeasured but coexisting exposures. By testing several PCB congener groupings, we were able to determine that specifically a group of potentially estrogenic PCB congeners affected the odds of reaching menarche. The lead and PCB findings are consistent with the literature and are biologically plausible. The sample size, cross-sectional study design, and possible occurrence of confounders beyond those tested suggest that results should be interpreted cautiously. Additional investigation to determine whether such low toxicant levels may affect reproduction and disorders of the reproductive system is warranted.

Detection of lead-induced oxidative stress in the rat epididymis by chemiluminescence

It has been shown that lead (Pb) is able to induce lipid peroxidation, one of the main manifestations of oxidative stress. In this study we examined the relationship between chronic Pb exposure and level of reactive oxygen species (ROS) in reproductive system tissues of sexually mature male Wistar rats. One group of animals (control, K) was allowed to drink distilled water, the second group (Pb) was allowed to drink freely 1% aqueous solution of lead acetate. Another groups had a following supplements: rats were allowed to drink distilled water containing vitamin C (vit C) at concentration of 500 mg/l or Trolox (a vitamin E analog) at concentration of 48 mg/l or vit C (500 mg/l) + Trolox (48 mg/l). The similar groups among Pb-treated animals were examined after treatment with the same vitamins and using the same vitamin doses, dissolved in 1% aqueous solution of lead acetate. In all cases the time of drinking was 6 months. It was found that lead content in samples of tissues from testis, epididymis and in a whole blood in Pb- and Pb with antioxidants treated rats was significantly elevated. Chemiluminescence (CL) emitted by the Pb-treated tissues was significantly higher when compared to the light emission by tissues isolated from the animals of control group. The increase in the CL caused by lead occurs in the following increasing order within the studied tissues: cauda of epididymis < testis < caput of epididymis (19%, 39% and 51%, respectively). Dietary vit C supplementation to the Pb-treated rats for 6 months period decreased the CL from caput of epididymis, cauda of epididymis and testis (by 43%, 24%, 39%, respectively) more effectively in comparison to the control group (35%, 17%, 33%, respectively). Also stronger quenching effect on the light emission from the above mentioned tissues after Trolox supplementation was observed in the Pb-treated group (42%, 21%, 35%, respectively) than in the control group (23%, 13%, 13% respectively). The combination of both antioxidants treatments (vit C and Trolox) did not give a higher significant quenching effect compared to the treatment with the vitamins separately. No ultrastructural changes were found in the seminiferous epithelium of Pb-treated animals. However, we found abnormalities in ultrastructure of epididymal epithelial cells and epididymal spermatozoa in rats of Pb-treated groups. These findings provide ex vivo evidence that Pb causes oxidative cellular damage in reproductive system tissues of adult male rats, which may be closely associated with the ROS production.

Low level lead (Pb) exposure during gestation and lactation: assessment of effects on pubertal development in Fisher 344 and Sprague-Dawley female rats

Studies using both Fisher 344 and Sprague-Dawley (SD) rat lines have shown that gestational and/or lactational maternal lead (Pb) exposure causes delayed reproductive maturation in their respective female offspring. Because these studies utilized different experimental regimens for dosing and for monitoring Pb levels, it has not been possible to determine which rat line provides the best model for low level Pb toxicity studies. This study was designed to address this issue. Adult Fisher and SD female rats were dosed with either a solution of PbAc containing 12 mg of Pb/ml or sodium acetate (NaAc) for controls. Dosing began 30 days prior to breeding and continued until their pups were weaned at 21 days of age. At the time of breeding and through weaning the blood lead (BPb) levels in the Fisher dams averaged 37.3 microg/dl and the SD dams averaged 29.9 microg/dl. Pb delayed the timing of puberty (p < 0.01) in Fisher offspring, and suppressed serum levels of luteinizing hormone (LH, p < 0.001) and estradiol (E2, p < 0.01). These effects did not occur in the SD offspring. Doubling the dose given to the SD rats increased their BPb levels to 62.6 microg/dl, yet there were still no effects noted. These results indicate that Fisher offspring are more sensitive to maternal Pb exposure with regard to puberty related insults than are SD rats, suggesting that the Fisher line may be a more reliable rodent model to study the effects of low level Pb toxicity.

Lead-induced cell signaling cascades in GT1-7 cells

The effects of lead on the signal transduction pathways that may be involved in the release of gonadotropin-releasing hormone (GnRH) from neurons in the hypothalamus have not been well defined. Using the GT1-7 cell line, an in vitro model for GnRH-secreting neurons, we examined signal transduction pathways directly affected by lead. We found that lead-induced phosphorylation of extracellular signal-regulated kinase 1 and 2 (ERK1 and ERK2), as well as p90RSK and cAMP response element-binding protein (CREB), but did not induce IkappaB degradation. MEK1/2 inhibitor (PD98059) suppressed lead-induced ERK and p90RSK activation. Neither PKC inhibitors (Go6983, Go6976) nor CaMKII inhibitor (KN-62) had a pronounced effect on lead-induced ERK1 and ERK2 phosphorylation. However, MEK1/2 inhibitor, CaMKII inhibitor, and PKC inhibitor significantly suppressed lead-induced CREB phosphorylation. These results indicate that lead-activated PKC, CaMKII and MEK/ERK/p90RSK pathways simultaneously, all of which contributed to CREB phosphorylation. Our results also indicate that lead-induced p90RSK and CREB activation does not alter expression of early response genes like c-fos. We conclude that lead activates PKC, CaMKII or MEK-ERK-p90RSK pathways in GT1-7 cells, leading to CREB phosphorylation and modulation of gene expression.

Lead intoxication in gestational and lactation periods alters the development of male reproductive organs

The effect of lead (Pb) intoxication during pregnancy and lactation on the male reproductive system was studied to evaluate the alterations caused by Pb in the development of pups. The investigations covered the effect of lead on the course of spermatogenesis and the development of the epididymis and reproductive glands. For this purpose, dams were intoxicated with 300 mg/L Pb during the gestational period and through lactation. Pups were sacrificed on Postnatal (PN) Days 12 and 21. Blood lead (PbB) and plasma iron concentrations were measured, and blood cells counted. Biochemical studies as well as histochemical analyses were performed on testes and accessory glands of the reproductive system. Lead intoxication resulted in a decrease in testis and seminal vesicle weights and an increase in DNA and RNA levels on PN Day 21. Total protein was significantly decreased by the toxicant, and alkaline and acid phosphatase levels of the gonads were reduced. Effects were also reflected in the reduction of the thickness of epithelium and of seminiferous tubule diameter (STD) as a consequence of the action of lead in the reduction in numbers of prospermatogonia and spermatocytes. Results indicate that the reproductive system targets of lead intoxication are not only the testes; lead intoxication results in the inhibition of testicular, epididymal, and seminal vesicle function, altering the biochemical composition of these organs, and consequently, affecting the normal development of germinal cells.

Effects of lead (Pb) exposure during gestation and lactation on female pubertal development in the rat

Lead (Pb) can delay sexual maturation; however, the mechanism and critical time of insult are not clearly defined. Therefore, we assessed maternal Pb levels during low-level gestational and/or lactational exposure, as well as blood and tissue Pb in developing fetuses in relation to the subsequent detrimental effects of Pb on puberty-related hormones and the onset of female puberty. Adult Fisher 344 female rats were gavaged daily with either a 1-ml solution of PbAc containing 12 mg/ml Pb or an equal volume of sodium acetate (NaCl), for the controls, from 30 days prior to breeding until their pups were weaned at 21 days. By cross-fostering at the time of birth, the pups were either exposed to PbAc or NaAc during gestation only, lactation only, or during both gestation and lactation. Pb delayed the timing of puberty and this delay was associated with suppressed serum levels of insulin-like growth factor-1 (IGF-1), luteinizing hormone (LH), and estradiol (E(2)). Liver IGF-1 mRNA was not affected, suggesting that Pb altered translation and/or secretion of IGF-1. We reported previously that peripherally derived IGF-1 acts at the hypothalamic level to facilitate LH release at puberty; hence, we suggest that the action of Pb in decreasing circulating IGF-1 contributes to the delayed puberty. The detrimental effects occurred regardless of the developmental time of exposure, although gestational exposure appeared more sensitive to the effects of Pb. Also, the effects noted were with blood Pb levels less than previously reported and these levels are relevant to human health concerns.

Role of early GnRH administration in sexual behavior disorders of rat pups perinatally exposed to lead

The effects of maternal exposure to lead (Pb) during the perinatal (1% and 0.1% Pb) periods of sexual brain differentiation were studied in adult male offspring. Maternal Pb levels were measured after treatment. Behavioral (open field and sexual behavior), physical (sexual maturation, body and organ weights), and biochemical (testosterone levels and hypothalamic monoamine and respective metabolite levels) data were assessed in perinatally exposed offspring. The effects of gonadrotopin-releasing hormone (GnRH) administration to pups at birth on puberty and sexual behavior were also investigated in offspring postnatally exposed to the metal. Results showed that perinatal administration of the two Pb concentrations did not modify maternal weight gain; 1% Pb exposure reduced offspring body weight during the 7 days of treatment while no changes were observed after 0.1% Pb exposure; neither Pb concentration altered offspring sexual maturation; the higher Pb concentration improved sexual behavior while the 0.1% concentration reduced it; exposure to 0.1% Pb caused decrease in testis weight, an increase in seminal vesicle weight and no changes in plasma testosterone levels; hypothalamic VMA levels were increased compared to the control group; GnRH administration reversed the effects of 0.1% Pb administration on male sexual behavior. These results show that perinatal exposure to Pb had a dose-dependent effect on the sexual behavior of rats and that a decrease in GnRH source in the offspring was probably involved in the reduction of their sexual performance.

Neural and behavioral teratological evaluation of rats exposed to ultra-wideband electromagnetic fields

Several investigators have reported teratologic effects of electromagnetic field exposure. The majority of these studies have been performed at levels of exposure that could produce substantial heating of the animals. New and unique sources of ultra-wideband (UWB) electromagnetic fields are currently being developed and tested that are capable of generating nonthermalizing, high-peak-power, microwave (MW) pulses with nanosecond (ns) pulse widths, picosecond (ps) rise times, and an UWB of frequencies. Our study was performed to determine if teratological changes occur in rat pups as a result of (i) daily UWB exposures during gestation days 3-18, or (ii) as a result of both prenatal and postnatal (10 days) exposures. Dams were exposed either to (i) UWB irradiation from a Kentech system that emitted a 55 kV/m-peak E field, 300 ps rise time, and a 1.8 ns pulse width, average whole-body specific absorption rate 45 mW/kg; (ii) sham irradiation; or (iii) a positive control, lead (Pb) acetate solution (2000 microg/ml) continuously available in the drinking water. Offspring were examined for ontogeny (litter size, sex-ratios, weights, coat appearance, tooth-eruption, eye-opening, air-righting, and ultrasonic stress vocalizations). Male pups were tested on various performance measures (locomotor, water-maze learning, and fertilization capabilities). The pups postnatally exposed were examined for hippocampal morphology and operant behavior. Behavioral, functional, and morphological effects of UWB exposure were unremarkable with these exceptions: (i) The UWB-exposed pups emitted significantly more stress vocalizations than the sham-exposed pups; (ii) the medial-to-lateral length of the hippocampus was significantly longer in the UWB-exposed pups than in the sham-exposed animals; (iii) male offspring exposed in utero to UWB mated significantly less frequently than sham-exposed males, but when they did mate there was no difference in fertilization and offspring numbers from the sham group. There does not appear to be a unifying physiological or behavioral relationship among the significant differences observed, and our findings could be due to the expected spurious results derived when a large number of statistical comparisons are made. Significant effects found between our positive-controls and other groups on numerous measures indicates that the techniques used were sensitive enough to detect teratological effects. Bioelectromagnetics 21:524-537, 2000. Published 2000 Wiley-Liss, Inc.

Lead effects on protamine-DNA binding

BACKGROUND

Lead impairs male fertility and may affect offspring of exposed males, but the mechanisms for this impairment are not completely clear. Protamine P1 and P2 families pack and protect mammalian sperm DNA. Human HP2 is a zinc-protein and may have an important role in fertility. As lead has affinity for zinc-containing proteins, we evaluated its ability in vitro to bind to HP2 and its effects on HP2-DNA binding. Methods and Results UV/VIS spectroscopic data indicated that HP2 binds both Pb(2+) and Zn(2+)(as chloride salts). They also provided evidence that thiol groups mainly participate for Zn(2+)-binding; however, HP2 has additional binding sites for Pb(2+). The mobility shift assay showed that lead interaction with HP2 caused a dose-dependent decrease on HP2 binding to DNA, suggesting that lead may alter chromatin stability.

CONCLUSIONS

These in vitro results demonstrate that lead can interact with HP2 altering the DNA-protamine binding. This chemical interaction of lead with protamines may result in chromatin alterations, which in turn may lead to male fertility problems and eventually to DNA damage.

Endocrine-disrupting chemicals: prepubertal exposures and effects on sexual maturation and thyroid activity in the female rat. A focus on the EDSTAC recommendations

In 1996, the US Environmental Protection Agency was given a mandate by Congress to develop a screening program that would evaluate whether variously identified compounds could affect human health by mimicking or interfering with normal endocrine regulatory functions. Toward this end, the Agency chartered the Endocrine Disruptor Screening and Testing Advisory Committee in October of that year that would serve to recommend a series of in vitro and in vivo protocols designed to provide a comprehensive assessment of a chemical's potential endocrine-disrupting activity. A number of these protocols have undergone subsequent modification by EPA, and this review focuses specifically on the revised in vivo screening procedure recommended under the title Research Protocol for Assessment of Pubertal Development and Thyroid Function in Juvenile Female Rats. Background literature has been provided that summarizes what is currently known about pubertal development in the female rat and the influence of various forms of pharmaceutical and toxicological insult on this process and on thyroid activity. Finally, a section is included that discusses technical issues that should be considered if the specified pubertal endpoints are to be measured and successfully evaluated.

Study of alterations produced by cadmium and cadmium/lead administration during gestational and early lactation periods in the reproductive organs of the rat

Administration of cadmium (10 mg/liter) and cadmium+lead (300 mg/liter) via drinking water to Wistar rats during gestation and early lactation until delivery and (5 days after parturition) damaged pup reproductive systems. The effects are additive in the decreased gonad weight and additive or even synergistic in the reduced DNA gonadal content. The effects on protein reduction are similar for both cations. In the testes, the effects of cadmium are more important in the reduction of seminiferous tubule diameter, whereas the effects of lead are more overt in the reduction of the number of prospermatogonia.

Effects of vitamin E and/or C on reactive oxygen species-related lead toxicity in the rat sperm

This study was undertaken to investigate whether treatment with vitamin E (VE) and/or vitamin C (VC) protects rat sperm by inhibiting reactive oxygen species generation induced by lead (Pb) exposure. Male Sprague-Dawley rats were assigned to the following five groups: vitamin-unsupplemented; 150 mg VE/kg chow supplemented; 300 mg VE/kg chow supplemented; 500 mg VC/l drinking water supplemented and 150 mg VE/kg chow + 500 mg VC/l drinking water supplemented group. Rats in each group were divided into Pb-unexposed and Pb-exposed subgroups, received weekly intraperitoneal injection of 10 mg sodium acetate or 10 mg Pb acetate/kg for 6 weeks, respectively. The blood and sperm Pb levels were analyzed by graphite furnace atomic absorption spectrophotometer. Chemiluminescence was measured to evaluate the generation of sperm reactive oxygen species (ROS). Motility and sperm-oocyte penetration rate (SOPR) were measured. In Pb-unexposed rats, epididymal sperm counts, motility, ROS, and SOPR were not different in the five supplemented groups. Lead exposure might decrease the defense capacity of sperm to the oxidative stress and therefore elevate the ROS generation, reduce sperm motility, and reduce SOPR. Supplementation with VE and/or VC reduced ROS generation, prevented loss of motility and capacity of oocyte penetration in Pb-exposed rats. This study suggests that supplementation with VE and/or VC inhibits Pb-related ROS generation, protects spermatozoa from loss of motility and oocyte penetration capability.

Effect of perinatal lead exposure on rat behaviour in open-field and two-way avoidance tasks

In view of conflicting results in literature concerning lead exposure associated with behavioural alterations, this study investigated behaviour in the open-field and shuttle avoidance, for as well as tissue lead burdens of pre- and postnatally lead-exposed rats. Rats were exposed to the metal from conception to weaning by giving the dams 0.5, 2.0 or 4.0 mM lead acetate in drinking water. This regimen did not affect body weight gain of dams or offspring development and had no effect on cerebral weights nor on haematological parameters of 23-day-old rats. In 1-day-old rats, lead accumulated in the blood but not in the brain, whereas both in 23-day-old rats and in dams lead accumulated in blood, kidney and cerebral cortex. In the open-field, lead-exposed groups showed higher locomotor activity in the test session as compared to controls and did not show any decrease in rearing responses in the test, indicating less habituation. Lead-treated rats subjected to a shuttle avoidance task showed no significant increase in avoidance responses between sessions as compared to control, indicating less retention. Moreover, only the control group presented a significant reduction of the footshock escape latency along testing session, suggesting a lead effect on footshock escape acquisition. In the shuttle box, intertrial crossing responses were not affected by lead treatment. The behavioural alterations occurred in animals with blood lead levels in the range 11-50.6 micrograms/dl.

Decreased endurance to cold water swimming and delayed sexual maturity in the rat following neonatal lead exposure

The effects of neonatal lead (Pb) exposure on ability to endure stress and on the onset of sexual maturity were investigated using rats. Sprague-Dawley dams (n = 17/treatment) were treated with or without lead acetate (0.3%) in drinking water from parturition until postnatal day (PND) 21, at which time the pups were weaned. A set of sex-balanced pairs of pups (24 male and 24 females/treatment) from randomly selected control and Pb-treated dams was tested for cold water (4 degrees C) swimming-endurance on PND 15, 21, 25 and 30. Lead treated-female pups showed significantly (P < 0.05) lower endurance on PND 21 and 30, while Pb-treated males exhibited lower (P < 0.05) endurance on PND 21 compared to their respective controls. The results of this study indicate that neonatal exposure to Pb decreased cold water swimming-endurance. Neonatal exposure to either Pb or swimming stress delayed (P < 0.002) the onset of sexual maturity in both sexes. However, exposure to both treatments masked the effect of swimming stress on the onset of maturity in females but not in males.

Lead effects on the brain stem auditory evoked potential in monkeys during and after the treatment phase

Rhesus monkeys were pre- and postnatally exposed to either 0, 350, or 600 mg lead acetate/kg diet continuously until the age of about 9.75 years. At the age of 8-8.25 years (Experiment 1) and 9.25-9.5 years (Experiment 2) brain stem auditory evoked potentials (BAEPs) were recorded. Blood lead levels at the time of testing were about 5, 35, or 55 micrograms/dl for controls, the 350-mg group and the 600-mg group, respectively. There were no clinical signs of intoxications. Clicks varying in sound pressure level (SPL) and rate were used to elicit BAEPs. In addition, the influence of different levels of masking noise was explored in Experiment 1. Four early prominent waves were detected in accordance with other studies of the monkey BAEP. The most reliable wave was No. II. Latencies in the BAEP exhibited the known dependencies on parametric variation for SPL, stimulus rate, and masking level. The 600-mg group exhibited the longest latencies at all stimulus conditions. Analysis of wave II and IV latencies revealed a significant main effect for lead on wave II. At the rate condition there were also signs of latency decreases in the 350-mg group that did not reach significance. Therefore, repetition rate was varied on all SPLs in Experiment 2 to assess the reliability of this effect because similar observations were reported in lead-exposed children. There was no indication of reduced latencies using this extended design. In contrast, significant lead-induced increases in latencies of waves I, II, and IV were revealed by multivariate ANOVA. The purpose of Experiment 3 was to examine whether these results were dependent on current exposure or persisted after cessation of lead treatment. It started 18 months after the end of lead feeding, when blood lead levels had declined to nearly normal values. The same lead-related effects were detected as in the previous experiments. Taken together, these results indicate consistent prolongations of latencies in the BAEP due to subtoxic lead exposure that are not dependent on current treatment. The results are compared to the effects found in epidemiological studies in lead-exposed children.

Reproductive toxicity of chronic lead exposure in male and female mice

The reproductive toxicity of lead was investigated in NMRI mice exposed to 0.5% lead acetate in drinking water from day 1 of intra-uterine life until 60 days after birth. Compared with control mice, the weights of lead-exposed fetuses and subsequently of the lead-exposed weaned pups, male and female, diminished by 11 and 13% respectively. The lead-exposed male and female offspring of lead-exposed dams were mated with unexposed females and males, to examine the effect of lead exposure on reproductive function. Male fertility was not affected but reduced female fertility was observed: litters were smaller and a smaller number of implantation sites was found in lead-exposed females. In lead-exposed males, the weights of the body, testes and epididymes diminished by about 13%, and seminal vesicle and ventral prostate weights, by about 29%. Testicular histology and the number and morphology of epididymal spermatozoa were normal. The levels of plasma FSH, LH and testosterone, and of testicular testosterone, were not modified. These results suggest that the hypothalamic-pituitary-testicular axis is not adversely affected by the above lead exposure, and that therefore the decreased seminal vesicle and ventral prostate weights might not be the consequence of reduced testosterone levels. The hypothesis that lead has a direct effect on these organs as well as a secondary effect resulting from possibly reduced food consumption by lead-exposed mice cannot be excluded. Consequently, in male NMRI mice, exposure to lead might affect reproductive function by acting directly and/or indirectly on accessory sex organs.

Testicular alterations in rats due to gestational and early lactational administration of lead

A solution of lead acetate (300 mg/L) was administered via drinking water to pregnant Wistar rats from day 1 of pregnancy to delivery (Pb-treated day 0 group) or throughout gestation and early lactation (from day 1 to day 5 postnatal) (Pb-treated day 5 group). When the pups were born, four dams and their offspring in each group (control day 0, Pb-treated day 0, control day 5, and Pb-treated day 5) were sacrificed on day 0 (day 0 groups) or on day 5 (day 5 groups). Relative testicular weight and gross testicular structure were not altered by the treatment. The seminiferous tubule diameter and the number of prospermatogonia were reduced by the treatment. Determination of the n-ploidy stage of prospermatogonia indicates that these cells have more proliferative activity in Pb-treated rats than in control rats. On the other hand, the total DNA, RNA, and protein content of the testes in treated rats was significantly reduced, but the DNA: RNA ratio remained unaltered.

Loss of reproductive competence at an earlier age in female rats exposed prenatally to ethanol

Previous studies have shown that prenatal ethanol exposure can partially masculinize or defeminize neurobehavioral development of female rats. An early age of onset of anovulation is one of the primary characteristics of partial defeminization. Consequently, we examined the occurrence of anovulation in fetal alcohol-exposed (FAE) female rats at 2, 6, and 12 months of age using both vaginal cytology as well as wheel-running behavior. We assessed the ability of estrogen and progesterone to elicit proprioceptive behaviors and lordosis at 2 and 17 months of age. Female subjects were derived from Sprague-Dawley dams administered an ethanol liquid diet (35% ethanol-derived calories), a pair-fed isocaloric liquid diet, or fed lab chow from days 14 to 22 of gestation. Litter representatives were placed in a computer-monitored wheel-running apparatus under a 12-hr lighting schedule from 49 to 60 days of age. Vaginal smears were taken from littermates during this same period. This same procedure was conducted again from 180 to 196 and from 380 to 396 days of age, except that vaginal cytology was examined in the same animals immediately after wheel-running behavior was studied. At approximately 2 months of age, a normal cyclical pattern of wheel-running, characteristic of 4- to 5-day estrus cycles, was observed in all animals. No differences were detected in mean activity levels during the wheel-running period. This was accompanied by normal cyclic vaginal cytology and normal proprioceptive behaviors and lordosis. At 6 months of age, FAE females exhibited significantly reduced wheel-running.(ABSTRACT TRUNCATED AT 250 WORDS)

Adrenalectomy reverses stress-induced suppression of luteinizing hormone secretion in long-term ovariectomized rats

An inhibitory effect of stress on reproductive function is well established. This inhibition involves activation of the hypothalamic-pituitary-adrenal (HPA) axis, which leads to a suppression of LH secretion. It has been proposed that this suppression is mediated by a direct effect of CRF that is independent of glucocorticoid actions. We tested this proposition by examining plasma LH levels in adult rats that were both ovariectomized (OVX) and adrenalectomized (ADX). Each animal was surgically implanted with an indwelling atrial cannula and exposed to intermittent foot shock for 100 min. Blood samples were drawn just prior to putting the animals into the test cage and then at 20-min intervals. Results revealed normal castrate levels of plasma LH in both ADX and ADX/OVX animals prior to shock. A significant shock-induced suppression of LH was observed in OVX animals within 20 min after the onset of shock and remained throughout the duration of the session. In contrast, no evidence was obtained for a suppression of LH in OVX/ADX animals at any time point. Additional studies demonstrated a marked suppression of LH in experimentally naive OVX/ADX females implanted with corticosterone capsules for 2 weeks prior to blood sampling. Overall, these results support a primary role for glucocorticoid actions in the stress-induced inhibition of reproductive function.

Effects of lead poisoning of rats during pregnancy on the reproductive system and fertility of their offspring

1. The effects of lead poisoning during pregnancy were tested on female Sprague-Dawley rats that inhaled 5 mg m-3 lead oxide for 13 days during gestation. At the end of gestation, the respective blood lead levels of dams and fetuses were 71.1 and 83.2 micrograms 100 ml-1, indicating lead poisoning. 2. In the 90 day-old male offspring of the exposed dams, testis weight and histology, and epididymal weight and sperm reserve, were all similar to those of control males. Spermatozoa mobility and morphology were normal. 3. Also similar to control values were the pituitary weight in these male offspring, their plasma FSH, LH and testosterone levels, and the weight of their ventral prostate and seminal vesicles, the targets of the sexual hormones. 4. When male and female offspring of exposed dams were mated, their fertility was normal, with no increase in prenatal death or malformations, and no changes in the size or sex ratio of litters. 5. These results indicate that, under our experimental conditions, lead oxide inhalation by rats during pregnancy did not perturb reproductive function in their male offspring.

Developmental profiles of ornithine decarboxylase activity in the hippocampus, neocortex and cerebellum: modulation following lead exposure

Ornithine decarboxylase (ODC) is a growth-associated enzyme which is critical for cell growth and transformation. ODC activity follows a specific ontogenetic pattern of activity in distinct brain regions according to their developmental stage. Perturbations in the pattern of ODC activity have been associated with brain damage including arrested cerebral growth. Modulations in the pattern of ODC activity were examined in the hippocampus, neocortex and cerebellum of neonatal rats (PND 3, 6, 9, 15) exposed via the dam to 0.2% lead-acetate (Pb2+ prenatally (gestational day 13 to birth), postnatally (PND 1-15) or perinatally (gestational day 13 to PND 15). Prenatal exposure to Pb2+ perturbed the profile of ODC activity in all three brain regions examined, while postnatal exposure to Pb2+ resulted in prolonged stimulations of ODC activity in the cerebellum. Following prenatal exposure, these effects were manifested as a stimulation of ODC activity in the hippocampus, a repression of activity in the neocortex and a combination of these effects in the cerebellum. Perinatal exposure to Pb2+ transiently modulated the pattern of ODC activity similarly in all three brain regions, in a characteristic manner irrespective of their developmental stage. These Pb(2+)-induced modulations of ODC activity suggest that polyamine-dependent processes may play a significant role in the manifestation of Pb(2+)-induced neurotoxicity dependent upon developmental factors at specific exposure periods.

Predicting ecotoxicological impacts of environmental contaminants on terrestrial small mammals

This review examines whether the effects of environmental contaminants on wild small mammals can be predicted from the results of single-species, laboratory toxicity studies. Heavy metals, organochlorines, chlorinated aromatic hydrocarbons, and OP/carbamate pesticides were identified as the groups of xenobiotics for which there are toxicity data for terrestrial small mammals and that, on the basis of persistence, acute toxicity, and bio-accumulation potential, present the greatest hazard to wild mammals. Laboratory-generated toxicity data, which used lethality and reproduction as measurable endpoints, were reviewed and intake and residue LOAELs estimated for representative chemicals (lead, endrin, PCBs) from the heavy metal, organochlorine, and chlorinated aromatic hydrocarbon substance groups; the OPs and carbamates were reviewed as a whole. Intakes and residues of these compounds in wild small mammals were compared with laboratory-defined LOAELs and the likelihood of effects predicted. The accuracy of these predictions was examined and the efficacy of extrapolating toxicity data from laboratory to wild species assessed. Qualitative extrapolation from laboratory to wild species was good for all the chemicals considered, laboratory tests correctly identifying the types of effects chemicals had on a wide range of wild mammals. In contrast, the quantitative extrapolation of dose-response data was either poor or largely unvalidated. This is because interspecies variation in sensitivity to xenobiotics and the effects on toxicity of differences in exposure pattern between laboratory and wild species are largely unquantified. Based upon the limited evidence available, errors in the direct extrapolation of dose-response data from laboratory to field may be as large as three orders of magnitude. Direct extrapolation of residue-response data from laboratory to wild mammals is good both for the effects of heavy metals on specific organs and for residues and acetylcholinesterase inhibition associated with pesticide-induced mortality. The use of organ residues or biomarkers to predict the severity of sublethal effects on reproductive output may be possible, although large residues or biomarker responses are not necessarily indicative of the severity of wider physiological effect. Appropriate residues/biomarkers may differ for various xenobiotics and even between species for the same xenobiotic. Further research is required to identify suitable markers that can be correlated with the occurrence and magnitude of ecologically important effects. Xenobiotics likely to have a direct effect on population dynamics are those that are persistent and adversely affect survival and reproduction. At present, this weak correlation is the only one that can be made between single-species laboratory tests and population effects.(ABSTRACT TRUNCATED AT 400 WORDS)

Comparison of two weeks versus one week of prenatal ethanol exposure in the rat on gonadal organ weights, sperm count, and onset of puberty

Sprague-Dawley dams from Harlan Ind. (Indianapolis, IN) were administered a fortified ethanol liquid diet containing 35% ethanol derived calories for two weeks (E-2) beginning on day 7 or one week (E-1) beginning on day 13 of gestation and continuing through parturition. Control dams were pair-fed an isocaloric liquid diet containing no ethanol during these periods or remained on lab chow and water. E-2 dams consumed an average of 13.52 g ethanol/kg bwt during the first week of exposure (days 8-14) and 12.50 g ethanol/kg bwt the second week (days 14-20). E-1 dams consumed significantly less than E-2 dams during the second week (9.75 g/kg; p < 0.0001). Although the lower consumption in E-1 dams led to a significant decrease in maternal weight gained during the few days of pregnancy compared to E-2 dams, birthweights of E-1 offspring were significantly heavier than those of E-2 offspring (p < 0.05). No effect of ethanol was detected on anogenital distance at birth in either sex. Puberty was delayed in female offspring of both E-1 and E-2 dams (p < 0.01) as measured by age of vaginal opening. These data suggest that the primary teratogenic actions of ethanol in the rat on fetal growth, as well as delayed puberty in females, occur in the last week of gestation. In adult E-2 males, testis weight was significantly heavier than all other groups when indexed to body weight. No effect of prenatal ethanol exposure was observed on the indexed weights of prostate, epididymis, or seminal vesicles.(ABSTRACT TRUNCATED AT 250 WORDS)