Integrating human health and environmental health into the DPSIR framework: a tool to identify research opportunities for sustainable and healthy communities

The U.S. Environmental Protection Agency has recently realigned its research enterprise around the concept of sustainability. Scientists from across multiple disciplines have a role to play in contributing the information, methods, and tools needed to more fully understand the long-term impacts of decisions on the social and economic sustainability of communities. Success will depend on a shift in thinking to integrate, organize, and prioritize research within a systems context. We used the Driving forces-Pressures-State-Impact-Response (DPSIR) framework as a basis for integrating social, cultural, and economic aspects of environmental and human health into a single framework. To make the framework broadly applicable to sustainability research planning, we provide a hierarchical system of DPSIR keywords and guidelines for use as a communication tool. The applicability of the integrated framework was first tested on a public health issue (asthma disparities) for purposes of discussion. We then applied the framework at a science planning meeting to identify opportunities for sustainable and healthy communities research. We conclude that an integrated systems framework has many potential roles in science planning, including identifying key issues, visualizing interactions within the system, identifying research gaps, organizing information, developing computational models, and identifying indicators.

Roles of reactive oxygen species and antioxidants in ovarian toxicity

Proper functioning of the ovary is critical to maintain fertility and overall health, and ovarian function depends on the maintenance and normal development of ovarian follicles. This review presents evidence about the potential impact of oxidative stress on the well-being of primordial, growing and preovulatory follicles, as well as oocytes and early embryos, examining cell types and molecular targets. Limited data from genetically modified mouse models suggest that several antioxidant enzymes that protect cells from reactive oxygen species (ROS) may play important roles in follicular development and/or survival. Exposures to agents known to cause oxidative stress, such as gamma irradiation, chemotherapeutic drugs, or polycyclic aromatic hydrocarbons, induce rapid primordial follicle loss; however, the mechanistic role of ROS has received limited attention. In contrast, ROS may play an important role in the initiation of apoptosis in antral follicles. Depletion of glutathione leads to atresia of antral follicles in vivo and apoptosis of granulosa cells in cultured antral follicles. Chemicals, such as cyclophosphamide, dimethylbenzanthracene, and methoxychlor, increase proapoptotic signals, preceded by increased ROS and signs of oxidative stress, and cotreatment with antioxidants is protective. In oocytes, glutathione levels change rapidly during progression of meiosis and early embryonic development, and high oocyte glutathione at the time of fertilization is required for male pronucleus formation and for embryonic development to the blastocyst stage. Because current evidence suggests that oxidative stress can have significant negative impacts on female fertility and gamete health, dietary or pharmacological intervention may prove to be effective strategies to protect female fertility.

Sperm DNA: organization, protection and vulnerability: from basic science to clinical applications--a position report

This article reports the results of the most recent in a series of EHSRE workshops designed to synthesize the current state of the field in Andrology and provide recommendations for future work (for details see Appendix). Its focus is on methods for detecting sperm DNA damage and potential application of new knowledge about sperm chromatin organization, vulnerability and repair to improve the diagnosis and treatment of clinical infertility associated with that damage. Equally important is the use and reliability of these tests to identify the extent to which environmental contaminants or pharmaceutical agents may contribute to the incidence of sperm DNA damage and male fertility problems. A working group (for workshop details, see Appendix) under the auspices of ESHRE met in May 2009 to assess the current knowledgebase and suggest future basic and clinical research directions. This document presents a synthesis of the working group's understanding of the recent literature and collective discussions on the current state of knowledge of sperm chromatin structure and function during fertilization. It highlights the biological, assay and clinical uncertainties that require further research and ends with a series of 5 key recommendations.

The effect of ambient air pollution on sperm quality

BACKGROUND

Research has suggested an association with ambient air pollution and sperm quality.

OBJECTIVES

We investigated the effect of exposure to ozone (O3) and particulate matter < 2.5 microm in aerodynamic diameter (PM2.5) on sperm quality.

METHODS

We reexamined a previous cohort study of water disinfection by-products to evaluate sperm quality in 228 presumed fertile men with different air pollution profiles. Outcomes included sperm concentration, total sperm per ejaculate (count), and morphology, as well as DNA integrity and chromatin maturity. Exposures to O3 and PM2.5 were evaluated for the 90-day period before sampling. We used multivariable linear regression, which included different levels of adjustment (i.e., without and with season and temperature) to assess the relationship between exposure to air pollutants during key periods of sperm development and adverse sperm outcomes.

RESULTS

Sperm concentration and count were not associated with exposure to PM2.5, but there was evidence of an association (but not statistically significant) with O3 concentration and decreased sperm concentration and count. Additionally, a significant increase in the percentage of sperm cells with cytoplasmic drop [beta = 2.64; 95% confidence interval (CI), 0.215.06] and abnormal head (beta = 0.47; 95% CI, 0.030.92) was associated with PM2.5 concentration in the base model. However, these associations, along with all other sperm outcomes, were not significantly associated with either pollutant after controlling for season and temperature. Overall, although we found both protective and adverse effects, there was generally no consistent pattern of increased abnormal sperm quality with elevated exposure to O3 or PM2.5.

CONCLUSIONS

Exposures to O3 or PM2.5 at levels below the current National Ambient Air Quality Standards were not associated with statistically significant decrements in sperm outcomes in this cohort of fertile men. However, some results suggested effects on sperm concentration, count, and morphology.

GSTM1 genotype influences the susceptibility of men to sperm DNA damage associated with exposure to air pollution

Previous studies have provided evidence for an association between exposure to high levels of air pollution and increased DNA damage in human sperm. In these studies DNA damage was measured using the sperm chromatin structure assay (SCSA) wherein the percentage of sperm with abnormal chromatin/fragmented DNA is determined and expressed as % DNA fragmentation index (%DFI). Here we extend these observations to address the following hypothesis: men who are homozygous null for glutathione-S-transferase M1 (GSTM1-) are less able to detoxify reactive metabolites of carcinogenic polycyclic aromatic hydrocarbons (c-PAHs) found in air pollution. Consequently they are more susceptible to the effects of air pollution on sperm chromatin. Using a longitudinal study design in which men provided semen samples during periods of both low (baseline) and episodically high air pollution, this study revealed a statistically significant association between GSTM1 null genotype and increased SCSA-defined %DFI (beta=0.309; 95% CI: 0.129, 0.489). Furthermore, GSTM1 null men also showed higher %DFI in response to exposure to intermittent air pollution (beta=0.487; 95% CI: 0.243, 0.731). This study thus provides novel evidence for a gene-environment interaction between GSTM1 and air pollution (presumably c-PAHs). The significance of the findings in this study with respect to fertility status is unknown. However, it is biologically plausible that increases in %DFI induced by such exposures could impact the risk of male sub/infertility, especially in men who naturally exhibit high levels of %DFI.

The healthy men study: an evaluation of exposure to disinfection by-products in tap water and sperm quality

BACKGROUND

Chlorination of drinking water generates disinfection by-products (DBPs), which have been shown to disrupt spermatogenesis in rodents at high doses, suggesting that DBPs could pose a reproductive risk to men. In this study we assessed DBP exposure and testicular toxicity, as evidenced by altered semen quality.

METHODS

We conducted a cohort study to evaluate semen quality in men with well-characterized exposures to DBPs. Participants were 228 presumed fertile men with different DBP profiles. They completed a telephone interview about demographics, health history, water consumption, and other exposures and provided a semen sample. Semen outcomes included sperm concentration and morphology, as well as DNA integrity and chromatin maturity. Exposures to DBPs were evaluated by incorporating data on water consumption and bathing and showering with concentrations measured in tap water. We used multivariable linear regression to assess the relationship between exposure to DBPs and adverse sperm outcomes.

RESULTS

The mean (median) sperm concentration and sperm count were 114.2 (90.5) million/mL and 362 (265) million, respectively. The mean (median) of the four trihalomethane species (THM4) exposure was 45.7 (65.3) microg/L, and the mean (median) of the nine haloacetic acid species (HAA9) exposure was 30.7 (44.2) microg/L. These sperm parameters were not associated with exposure to these classes of DBPs. For other sperm outcomes, we found no consistent pattern of increased abnormal semen quality with elevated exposure to trihalomethanes (THMs) or haloacetic acids (HAAs). The use of alternate methods for assessing exposure to DBPs and site-specific analyses did not change these results.

CONCLUSIONS

The results of this study do not support an association between exposure to levels of DBPs near or below regulatory limits and adverse sperm outcomes in humans.

Assessing human germ-cell mutagenesis in the Postgenome Era: a celebration of the legacy of William Lawson (Bill) Russell

Birth defects, de novo genetic diseases, and chromosomal abnormality syndromes occur in approximately 5% of all live births, and affected children suffer from a broad range of lifelong health consequences. Despite the social and medical impact of these defects, and the 8 decades of research in animal systems that have identified numerous germ-cell mutagens, no human germ-cell mutagen has been confirmed to date. There is now a growing consensus that the inability to detect human germ-cell mutagens is due to technological limitations in the detection of random mutations rather than biological differences between animal and human susceptibility. A multidisciplinary workshop responding to this challenge convened at The Jackson Laboratory in Bar Harbor, Maine. The purpose of the workshop was to assess the applicability of an emerging repertoire of genomic technologies to studies of human germ-cell mutagenesis. Workshop participants recommended large-scale human germ-cell mutation studies be conducted using samples from donors with high-dose exposures, such as cancer survivors. Within this high-risk cohort, parents and children could be evaluated for heritable changes in (a) DNA sequence and chromosomal structure, (b) repeat sequences and minisatellites, and (c) global gene expression profiles and pathways. Participants also advocated the establishment of a bio-bank of human tissue samples from donors with well-characterized exposure, including medical and reproductive histories. This mutational resource could support large-scale, multiple-endpoint studies. Additional studies could involve the examination of transgenerational effects associated with changes in imprinting and methylation patterns, nucleotide repeats, and mitochondrial DNA mutations. The further development of animal models and the integration of these with human studies are necessary to provide molecular insights into the mechanisms of germ-cell mutations and to identify prevention strategies. Furthermore, scientific specialty groups should be convened to review and prioritize the evidence for germ-cell mutagenicity from common environmental, occupational, medical, and lifestyle exposures. Workshop attendees agreed on the need for a full-scale assault to address key fundamental questions in human germ-cell environmental mutagenesis. These include, but are not limited to, the following: Do human germ-cell mutagens exist? What are the risks to future generations? Are some parents at higher risk than others for acquiring and transmitting germ-cell mutations? Obtaining answers to these, and other critical questions, will require strong support from relevant funding agencies, in addition to the engagement of scientists outside the fields of genomics and germ-cell mutagenesis.

The healthy men study: design and recruitment considerations for environmental epidemiologic studies in male reproductive health

OBJECTIVE

To describe study design, conduct and response, and participant characteristics.

DESIGN

Prospective cohort study.

SETTING

Participants were male partners of women who were enrolled in a community-based prospective cohort study of drinking water disinfection by-products and pregnancy health.

PATIENT(S)

Two hundred thirty presumed fertile men recruited from 3 study sites in the United States.

INTERVENTION(S)

Men completed a telephone interview about demographics, health history, and exposures and provided a semen sample that was express mailed to the study laboratory.

MAIN OUTCOME MEASURE(S)

Response and participation rates, participant demographics, and lifestyle exposures.

RESULT(S)

We obtained a high participation rate (84%) among men who were located, but a low overall response rate (25%). Participants were more likely to be white, more highly educated, be married, and have a higher household income than the underlying study cohort.

CONCLUSION(S)

Our multisite study design may be applicable to the study of community environmental factors and reproductive health of men. Our design was efficient in that men from geographically disparate sites could be recruited, a semen sample was collected at home, and a telephone interview was conducted from a central study site. Despite these design features, the low response rates may suggest selection bias that can be addressed partially in the analysis.

Workgroup report: Implementing a national occupational reproductive research agenda--decade one and beyond

The initial goal of occupational reproductive health research is to effectively study the many toxicants, physical agents, and biomechanical and psychosocial stressors that may constitute reproductive hazards in the workplace. Although the main objective of occupational reproductive researchers and clinicians is to prevent recognized adverse reproductive outcomes, research has expanded to include a broader spectrum of chronic health outcomes potentially affected by reproductive toxicants. To aid in achieving these goals, the National Institute for Occupational Safety and Health, along with its university, federal, industry, and labor colleagues, formed the National Occupational Research Agenda (NORA) in 1996. NORA resulted in 21 research teams, including the Reproductive Health Research Team (RHRT). In this report, we describe progress made in the last decade by the RHRT and by others in this field, including prioritizing reproductive toxicants for further study; facilitating collaboration among epidemiologists, biologists, and toxicologists; promoting quality exposure assessment in field studies and surveillance; and encouraging the design and conduct of priority occupational reproductive studies. We also describe new tools for screening reproductive toxicants and for analyzing mode of action. We recommend considering outcomes such as menopause and latent adverse effects for further study, as well as including exposures such as shift work and nanomaterials. We describe a broad domain of scholarship activities where a cohesive system of organized and aligned work activities integrates 10 years of team efforts and provides guidance for future research.

Episodic air pollution is associated with increased DNA fragmentation in human sperm without other changes in semen quality

BACKGROUND

This study examined potential associations between exposure to episodes of air pollution and alterations in semen quality. The air pollution, resulting from combustion of coal for industry and home heating in the Teplice district of the Czech Republic, was much higher during the winter than at other times of year with peaks exceeding US air quality standards.

METHODS

Young men from Teplice were sampled up to seven times over 2 years allowing evaluation of semen quality after periods of exposure to both low and high air pollution. Routine semen analysis (sperm concentration, motility and morphology) and tests for sperm aneuploidy and chromatin integrity were performed, comparing measurements within each subject. Exposure was classified as high or low based on data from ambient air pollution monitoring.

RESULTS

Using repeated measures analysis, a significant association was found between exposure to periods of high air pollution (at or above the upper limit of US air quality standards) and the percentage of sperm with DNA fragmentation according to sperm chromatin structure assay (SCSA). Other semen measures were not associated with air pollution.

CONCLUSION

Exposure to intermittent air pollution may result in sperm DNA damage and thereby increase the rates of male-mediated infertility, miscarriage, and other adverse reproductive outcomes.

Individual variation in the frequency of sperm aneuploidy in humans

To examine interindividual differences in sperm chromosome aneuploidy, repeated semen specimens were obtained from a group of ten healthy men, aged 20-21 at the start of the study, and analyzed by multi-color fluorescence in situ hybridization (FISH) analysis to determine the frequencies of sperm aneuploidy for chromosomes X, Y, 8, 18 and 21 and of diploidy. Semen samples were obtained three times over a five-year period. Statistical analysis examining the stability of sperm aneuploidy over time by type and chromosome identified two men who consistently exhibited elevated frequencies of sperm aneuploidy (stable variants): one with elevated disomy 18 and one with elevated MII diploidy. Differences among frequencies of aneuploidy by chromosome were also seen. Overall, disomy frequencies were lower for chromosome X, 8 and 18 than for chromosomes 21 or Y and for XY aneuploidy. The frequency of chromosome Y disomy did not differ from XY sperm frequency. Also, the frequency of meiosis I (XY) and II (YY + XX) sex chromosome errors did not differ in haploid sperm, but the frequency of MII errors was lower than MI errors in diploid sperm. Frequencies of sperm aneuploidy were similar between the first sampling period and the second, two years later. However, the frequency of some types of aneuploidy (XY, disomy Y, disomy 8, total autosomal disomies, total diploidy, and subcategories of diploidy) increased significantly between the first sampling period and the last, five years later, while others remained unchanged (disomy X, 21 and 18). These findings confirm inter-chromosome differences in the frequencies of disomy and suggest that some apparently healthy men exhibit consistently elevated frequencies of specific sperm aneuplodies. Furthermore, time/age-related changes in sperm aneuploidy may be detected over as short a period as five years in a repeated-measures study.

Acute exposure to molinate alters neuroendocrine control of ovulation in the rat

Molinate, a thiocarbamate herbicide, has been reported to impair reproductive capability in the male rat and alter pregnancy outcome in a two-generation study. Published data are lacking on the effects of acute exposure to molinate in the female. Based on this work and our previous observations with related dithiocarbamate compounds, we hypothesized that a single exposure to molinate during the critical window for the neural trigger of ovulation on the day of proestrus (PRO) would block the luteinizing hormone (LH) surge and delay ovulation. To examine the effect of molinate on the LH surge, ovariectomized (OVX) rats were implanted with Silastic capsules containing estradiol benzoate to mimic physiological levels on proestrus. Doses of 25 and 50 mg/kg molinate significantly suppressed LH and prolactin secretion. Intact regularly cycling females gavaged with 0, 25, or 50 mg/kg molinate at 1300 h on PRO were examined on estrus or estrus +1 day for the presence of oocytes in the oviduct. All control females had oocytes in the oviduct on estrus. Molinate doses of 6.25 to 50 mg/kg delayed ovulation for 24 h. Estrous cyclicity was examined after daily exposure to 50 mg/kg (21 days). Estrous cyclicity was irregular in the molinate group, showing extended days in estrus. Two experiments were conducted to determine whether molinate blocked the LH surge via a central nervous system (CNS) mode of action or via an alteration in pituitary response. In the first experiment, we evaluated the release of LH in control and molinate-treated rats after a bolus dose of exogenous GnRH. Luteinizing hormone release was comparable in the two groups, suggesting that the effect of molinate is centrally mediated. To further examine the potential role of the CNS, we examined the pulsatile release of LH present in the long-term OVX females. In this model, the pulsatile pattern of LH secretion is directly correlated with GnRH release from the hypothalamus. A significant decrease in the LH pulse frequency was observed in molinate-treated females. These results indicate that molinate is able to delay ovulation by suppressing the LH surge on the day of proestrus and that the brain is the primary target site for the effects on pituitary hormone secretion.

Glyceraldehyde 3-phosphate dehydrogenase-S, a sperm-specific glycolytic enzyme, is required for sperm motility and male fertility

Although glycolysis is highly conserved, it is remarkable that several unique isozymes in this central metabolic pathway are found in mammalian sperm. Glyceraldehyde 3-phosphate dehydrogenase-S (GAPDS) is the product of a mouse gene expressed only during spermatogenesis and, like its human ortholog (GAPD2), is the sole GAPDH isozyme in sperm. It is tightly bound to the fibrous sheath, a cytoskeletal structure that extends most of the length of the sperm flagellum. We disrupted Gapds expression by gene targeting to selectively block sperm glycolysis and assess its relative importance for in vivo sperm function. Gapds(-/-) males were infertile and had profound defects in sperm motility, exhibiting sluggish movement without forward progression. Although mitochondrial oxygen consumption was unchanged, sperm from Gapds(-/-) mice had ATP levels that were only 10.4% of those in sperm from WT mice. These results imply that most of the energy required for sperm motility is generated by glycolysis rather than oxidative phosphorylation. Furthermore, the critical role of glycolysis in sperm and its dependence on this sperm-specific enzyme suggest that GAPDS is a potential contraceptive target, and that mutations or environmental agents that disrupt its activity could lead to male infertility.

Evaluation of chromosome breakage and DNA integrity in sperm: an investigation of remote semen collection conditions

Collection of ejaculated semen at a remote site (outside of the laboratory) would facilitate participation rates and geographic diversity in reproductive epidemiology studies. Our study addressed concerns that remote collection and overnight mail return might induce chromosome/DNA damage. We collected semen from 10 healthy men. Part of each sample was snap frozen in liquid nitrogen and the rest held at 22 +/- 1 degrees C for 24 hours in a transport container (simulating ambient temperature during overnight return) then snap frozen. DNA breakage and fragmentation were measured using tandem-label sperm-fluorescence in situ hybridization (FISH), terminal deoxynucleotidyl transferase-mediated dUTP nick end-labeling (TUNEL), and neutral comet assay. Tandem-label sperm-FISH and TUNEL detected no statistically significant difference between sperm fresh frozen (FF) and those frozen after 24 hours (F24). The mean frequency of chromosome breakage per 10 000 cells scored in sperm-FISH for FF and F24 was 10.5 +/- 1.3 breaks and 11.2 +/- 1.1 breaks, respectively (P =.69, Student's t test). The mean frequency of TUNEL-positive cells per 2000 cells scored in FF and F24 was 136 +/- 29 and 213 +/- 28 cells, respectively, which approached but did not reach statistical significance (P = 0.07, Student's t test). The neutral comet assay detected a statistically significant difference in DNA strand breakage between the 2 groups (percentage of DNA in the tail P = 0.037; tail moment P = 0.006; and tail length P = 0.033, all Student's t test). The mean frequency of damage denoted by tail length in micro m per 100 cells scored in FF and F24 was 175.0 +/- 15.5 and 152.2 +/- 17.6 micro m, respectively. Tandem-label sperm-FISH, TUNEL, and neutral comet assay are useful analytical techniques for laboratory-based studies of human sperm genomic integrity; however, for field studies incorporating the nonrefrigerated return of semen after 24 hours, only chromosome breakage at a level that can be detected using tandem-label sperm-FISH was unaffected. TUNEL and neutral comet assay need further study before they are used in specimens collected at remote sites and transported to a central laboratory.

The value of home-based collection of biospecimens in reproductive epidemiology

Detection, quantification, and prognosis of environmental exposures in humans has been vastly enhanced by the ability of epidemiologists to collect biospecimens for toxicologic or other laboratory evaluation. Ease of collection and level of invasiveness are commonly cited reasons why study participants fail to provide biospecimens for research purposes. The use of methodologies for the collection of biospecimens in the home offers promise for improving the validity of health effects linked to environmental exposures while maximizing the number and type of specimens capable of being collected in a timely and cost-effective manner. In this review we examine biospecimens (urine and blood) that have been successfully collected from the home environment. Related issues such as storage and transportation will also be examined as well as promising new approaches for collecting less frequently studied biospecimens (including hair follicles, breast milk, semen, and others). Such biospecimens are useful in the monitoring of reproductive development and function.

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

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

An occupational reproductive research agenda for the third millennium

There is a significant public health concern about the potential effects of occupational exposure to toxic substances on reproductive outcomes. Several toxicants with reported reproductive and developmental effects are still in regular commercial or therapeutic use and thus present potential exposure to workers. Examples of these include heavy metals, organic solvents, pesticides and herbicides, and sterilants, anesthetic gases, and anticancer drugs used in health care. Many other substances are suspected of producing reproductive or developmental toxicity but lack sufficient data. Progress has been limited in identifying hazards and quantifying their potencies and in separating the contribution of these hazards from other etiologic factors. Identifying the causative agents, mechanisms by which they act, and any potential target populations, present the opportunity to intervene and protect the reproductive health of workers. The pace of laboratory studies to identify hazards and to underpin the biologic plausibility of effects in humans has not matched the pace at which new chemicals are introduced into commerce. Though many research challenges exist today, recent technologic and methodologic advances have been made that allow researchers to overcome some of these obstacles. The objective of this article is to recommend future directions in occupational reproductive health research. By bridging interdisciplinary gaps, the scientific community can work together to improve health and reduce adverse outcomes.

Glutathione (GSH) concentrations vary with the cell cycle in maturing hamster oocytes, zygotes, and pre-implantation stage embryos

Glutathione (GSH) is thought to play critical roles in oocyte function including spindle maintenance and provision of reducing power needed to initiate sperm chromatin decondensation. Previous observations that GSH concentrations are higher in mature than immature oocytes and decline after fertilization, suggest that GSH synthesis may be associated with cell cycle events. To explore this possibility, we measured the concentrations of GSH in Golden Hamster oocytes and zygotes at specific stages of oocyte maturation and at intervals during the first complete embryonic cell cycle. Between 2 and 4 hr after the hormonal induction of oocyte maturation, GSH concentrations increased significantly (approximately doubling) in both oocytes and their associated cumulus cells. This increase was concurrent with germinal vesicle breakdown and the condensation of metaphase I chromosomes in the oocyte. GSH remained high in ovulated, metaphase II (MII) oocytes, but then declined significantly, by about 50%, shortly after fertilization, as the zygote progressed back into interphase (the pronucleus stage). GSH concentrations then plummeted by the two-cell embryo stage and remained at only 10% of those in MII oocytes throughout pre-implantation development. These results demonstrate that oocyte GSH concentrations fluctuate with the cell cycle, being highest during meiotic metaphase, the critical period for spindle growth and development and for sperm chromatin remodeling. These observations raise the possibility that GSH synthesis in maturing oocytes is regulated by gonadotropins, and suggest that GSH is more important during fertilization than during pre-implantation embryo development.

Stable variants of sperm aneuploidy among healthy men show associations between germinal and somatic aneuploidy

Repeated semen specimens from healthy men were analyzed by sperm fluorescence in situ hybridization (FISH), to identify men who consistently produced elevated frequencies of aneuploid sperm and to determine whether men who were identified as stable variants of sperm aneuploidy also exhibited higher frequencies of aneuploidy in their peripheral blood lymphocytes. Seven semen specimens were provided by each of 15 men over a 2-year period and were evaluated by the X-Y-8 multicolor sperm FISH method (i.e., approximately 1,050,000 sperm were analyzed from 105 specimens). Three men were identified as stable aneuploidy variants producing significantly higher frequencies of XY, disomy X, disomy Y, disomy 8, and/or diploid sperm over time. In addition, one man and three men were identified as sperm-morphology and sperm-motility variants, respectively. Strong correlations were found between the frequencies of sperm with autosomal and sex-chromosome aneuploidies and between the two types of meiosis II diploidy; but not between sperm aneuploidy and semen quality. A significant association was found between the frequencies of sex-chromosome aneuploidies in sperm and lymphocytes in a subset of 10 men (r2=0.67, P=.004), especially between XY sperm and sex-chromosome aneuploidy in lymphocytes (r2=0.70, P=.003). These findings suggest that certain apparently healthy men can produce significantly higher frequencies of both aneuploid sperm and lymphocytes. Serious long-term somatic and reproductive health consequences may include increased risks of aneuploidy-related somatic diseases and of having children with paternally transmitted aneuploidies, such as Klinefelter, Turner, triple-X, and XYY syndromes.

Aneuploidy and chromosome breakage in swim-up versus unprocessed semen from twenty healthy men

Toxicological and epidemiological studies have investigated several factors that are believed to induce cytogenetic damage in human sperm cells in an effort to estimate heritable risk to future generations. Most of these studies have not differentiated damage based on cell fertility or motility. In the clinical setting, intracytoplasmic sperm injection (ICSI) bypasses the natural process of sperm selection. Although practitioners attempt to select motile sperm for ICSI, the sperm may not always demonstrate motility, maturity, or even viability. Knowing whether cytogenetic damage differs in motile versus unselected sperm would improve our ability to estimate heritable risk and lead to improved ICSI procedures, and would expand the body of toxicology and epidemiology research. We divided semen samples from 20 healthy donors and compared aneuploidy and chromosome breakage in sperm cells gathered directly from the ejaculate (unprocessed semen) with cells enriched for motility using the swim-up assay. Sperm fluorescence in situ hybridization was used to detect aneuploidy for chromosomes 13, 18, 21, X, and Y. Tandem labeling probes were used to detect breakage in the 1cen-1q12 region of chromosome 1. The occurrence of disomy 18-18 and XY18 was significantly lower in specimens enriched for motility (P = .004 and P = .001, respectively). Sperm that carried duplication errors and diploid sperm were also seen less frequently in semen analyzed by the swim-up assay (P < .008). Chromosome 1 breakage did not differ between swim up-assayed and unprocessed specimens. Findings suggest that unprocessed semen may overestimate heritable aneuploidy risk in sperm biomarker studies, and may be biologically relevant to ICSI in disomy categories 18-18 and XY18, demonstrating 1.4-fold to 1.8-fold differences.

Localization of the sperm protein SP22 and inhibition of fertility in vivo and in vitro

We previously established that levels of the sperm membrane protein, SP22, are highly correlated with the fertility of sperm from the cauda epididymidis of rats exposed to both epididymal and testicular toxicants, and that a testis-specific SP22 transcript is expressed in postmeiotic germ cells. In this study, polyclonal and monoclonal antibodies were generated to study the expression of SP22 in the testis and epididymis, and to determine whether SP22 plays a coincidental or causal role in fertility. Polyclonal antiserum was raised in sheep against full-length recombinant rat SP22 (rSP22). Hybridoma clones were generated from mice immunized with rSP22 and boosted with native SP22; positive clones were used for ascites production. Immunoblots indicated that affinity-purified anti-rSP22 immunoglobulin (Ig) and ascites Ig recognized denatured and native SP22, respectively. Linear epitope mapping of the 189-amino acid SP22 sequence revealed 3 distinct peptide sequences recognized by anti-rSP22 Ig, and 1 sequence recognized by ascites Ig. Cytoplasm of round spermatids and heads of elongating/elongated spermatids immunostained with both anti-rSP22 and ascites antibodies. Isolated rete testis sperm revealed discrete staining over the cytoplasmic droplet, whereas staining was apparent over the equatorial segment of the head by the time sperm reached the caput epididymidis. Clear cells were, interestingly, immunostained along the length of the epididymis. Ascites Ig and anti-SP22 Ig each recognized the equatorial segment of sperm heads from rat, hamster, bull, rabbit, and human. Ascites Ig and affinity-purified anti-rSP22 Ig each significantly inhibited the fertility of cauda epididymal sperm from the rat in vivo, as well as the fertilization rates of cauda epididymal sperm in vitro. Moreover, affinity-purified anti-rSP22 significantly inhibited in vitro fertilization of both zona-intact and zona-free hamster oocytes, suggesting that SP22 may play a role in both the zona penetration and membrane fusion steps of fertilization.

Antiretroviral therapy effects on genetic and morphologic end points in lymphocytes and sperm of men with human immunodeficiency virus infection

Many human immunodeficiency virus (HIV)-infected persons receive prolonged treatment with DNA-reactive antiretroviral drugs. A prospective study was conducted of 26 HIV-infected men who provided samples before treatment and at multiple times after beginning treatment, to investigate effects of antiretrovirals on lymphocyte and sperm chromosomes and semen quality. Several antiretroviral regimens, all including a nucleoside component, were used. Lymphocyte metaphase analysis and sperm fluorescence in situ hybridization were used for cytogenetic studies. Semen analyses included conventional parameters (volume, concentration, viability, motility, and morphology). No significant effects on cytogenetic parameters, semen volume, or sperm concentration were detected. However, there were significant improvements in sperm motility for men with study entry CD4 cell counts >200 cells/mm(3), sperm morphology for men with entry CD4 cell counts < or =200 cells/mm(3), and the percentage of viable sperm in both groups. These findings suggest that nucleoside-containing antiretrovirals administered via recommended protocols do not induce chromosomal changes in lymphocytes or sperm but may produce improvements in semen quality.

Factor analytic models of clustered multivariate data with informative censoring

This article describes a general class of factor analytic models for the analysis of clustered multivariate data in the presence of informative missingness. We assume that there are distinct sets of cluster-level latent variables related to the primary outcomes and to the censoring process, and we account for dependency between these latent variables through a hierarchical model. A linear model is used to relate covariates and latent variables to the primary outcomes for each subunit. A generalized linear model accounts for covariate and latent variable effects on the probability of censoring for subunits within each cluster. The model accounts for correlation within clusters and within subunits through a flexible factor analytic framework that allows multiple latent variables and covariate effects on the latent variables. The structure of the model facilitates implementation of Markov chain Monte Carlo methods for posterior estimation. Data from a spermatotoxicity study are analyzed to illustrate the proposed approach.

Significance of incorporating measures of sperm production and function into rat toxicology studies

The rat is the preferred species for reproductive toxicity testing. The inclusion of measures of rat sperm quality, such as motility and morphology, into reproductive test protocols often increases the sensitivity of the test to detect effects, and provides the toxicologist and risk assessor with valuable information about the nature of the reproductive toxicity of the test substance. Technical advances in computer-aided sperm analysis have made it possible to evaluate motion characteristics of rat spermatozoa. This technology can provide an objective means of classifying the motion of rat spermatozoa as progressive or non-progressive, as required in test protocols. More specific tests of rat sperm function are being applied for the purpose of evaluating modes and mechanisms of toxicant action. Computer-aided sperm analysis can be used to evaluate sperm motion during cultures that support sperm capacitation and to identify hyperactivated spermatozoa. Under the same culture conditions, acrosome-specific stains can be used to identify effects of toxicants on the acrosome reaction. These approaches, in combination with in vitro fertilization in rats, can pinpoint sperm functional deficits and thereby assist the toxicologist in addressing hypotheses regarding the cellular-molecular bases of toxicant-induced male infertility.

Evaluation of aneuploidy and DNA damage in human spermatozoa: applications in field studies

With the goal of incorporating measures of sperm nuclear integrity in an epidemiology study, semen samples from young Czech men were analysed for sperm aneuploidy and sperm chromatin structure in addition to routine measures of sperm production and quality. The exposure in question was to high seasonal air pollution containing reactive polyaromatic hydrocarbons potentially capable of affecting spermatogenesis and damaging sperm DNA. The sperm aneuploidy assay uses fluorescence in situ hybridization to label selected sperm chromosomes; as applied in this study, the sex chromosomes (X,Y) and chromosome 8 were targeted. The sperm chromatin structure assay detects sperm nuclei with increased susceptibility to denaturation, a feature that is associated with DNA damage. Logistically, these assays were relatively easy to incorporate into the study design. The aneuploidy assay provided information suggesting that exposure to high levels of air pollution may increase the risk of sperm aneuploidy and that it is important to control for exposure to cigarette smoke and/or alcohol in such studies. The sperm chromatin structure assay provided valuable baseline information about Czech semen donors and data suggestive of an adverse effect of smoking and air pollution on spermatozoa that merits further investigation.

Semen quality and reproductive health of young Czech men exposed to seasonal air pollution

This study of male reproductive health in the Czech Republic resulted from community concern about potential adverse effects of air pollution. We compared young men (18 years of age) living in Teplice, a highly industrialized district with seasonally elevated levels of air pollution, to those from Prachatice, a rural district with relatively clean air. Surveys were scheduled for either late winter, after the season of higher air pollution, or at the end of summer, when pollution was low. Participation included a physical examination, donation of a semen sample, and completion of a questionnaire on health, personal habits, and exposure to solvents and metals through work or hobby. Analysis of data from 408 volunteers showed that the men from Teplice and Prachatice were similar in physical characteristics, personal habits, and work- or hobby-related exposures. Sixty-six percent (272) of these men donated a single semen sample for routine semen analysis, computer-aided sperm motion analysis, and sperm chromatin structure assay. The mean (median) sperm concentration and sperm count were 61. 2 (44.0) million/mL semen and 113.3 (81.5) million, respectively, and were not associated with district of residence or period of elevated air pollution. However, periods of elevated air pollution in Teplice were significantly associated with decrements in other semen measures including proportionately fewer motile sperm, proportionately fewer sperm with normal morphology or normal head shape, and proportionately more sperm with abnormal chromatin. These results suggest that young men may experience alterations in sperm quality after exposure to periods of elevated air pollution, without changes in sperm numbers.

Exposure to hazardous substances and male reproductive health: a research framework

The discovery in the mid-1970s that occupational exposures to pesticides could diminish or destroy the fertility of workers sparked concern about the effects of hazardous substances on male reproductive health. More recently, there is evidence that sperm quantity and quality may have declined worldwide, that the incidence of testicular cancer has progressively increased in many countries, and that other disorders of the male reproductive tract such as hypospadias and cryptorchidism may have also increased. There is growing concern that occupational factors and environmental chemical exposures, including in utero and childhood exposures to compounds with estrogenic activity, may be correlated with these observed changes in male reproductive health and fertility. We review the evidence and methodologies that have contributed to our current understanding of environmental effects on male reproductive health and fertility and discuss the methodologic issues which confront investigators in this area. One of the greatest challenges confronting researchers in this area is assessing and comparing results from existing studies. We elaborate recommendations for future research. Researchers in the field of male reproductive health should continue working to prioritize hazardous substances; elucidate the magnitude of male reproductive health effects, particularly in the areas of testicular cancer, hypospadias, and cryptorchidism; develop biomarkers of exposure to reproductive toxins and of reproductive health effects for research and clinical use; foster collaborative interdisciplinary research; and recognize the importance of standardized laboratory methods and sample archiving.

Workshop to identify critical windows of exposure for children's health: reproductive health in children and adolescents work group summary

This work group report addresses the central question: What are the critical windows during development (preconception through puberty) when exposure to xenobiotics may have the greatest adverse impact on subsequent reproductive health? The reproductive system develops in stages, with sex-specific organogenesis occurring prenatally and further maturational events occurring in the perinatal period and at puberty. Complex endocrine signals as well as other regulatory factors (genetics, growth factors) are involved at all stages. Evidence from animal models and human studies indicates that many specific events can be perturbed by a variety of toxicants, with endocrine-mediated mechanisms being the more widely studied. Prioritized research needs include basic studies on the cellular-molecular and endocrine regulation of sexual differentiation and development; increased efforts regarding potential adverse effects on development in females, including breast development; expanded animal studies on different classes of chemicals, comparing responses during development (prenatal and postnatal) with responses in adults; and, more extensive explorations regarding the reproductive biology and toxicology of puberty in humans.

Objective evaluation of hyperactivated motility in rat spermatozoa using computer-assisted sperm analysis

The aim of this study was to use computer-assisted sperm analysis (CASA) to examine changes in motion parameters of rat spermatozoa incubated under culture conditions that support IVF. Rat cauda epididymal spermatozoa were evaluated in six replicate experiments, at 0 and 4h of incubation. CASA was conducted at 60 Hz on digital 1s tracks ( approximately 100 spermatozoa/rat). Mean values of CASA parameters that describe the vigour of spermatozoa [curvilinear velocity (VCL), amplitude of lateral head displacement (ALH) and beat cross frequency (BCF)] increased, while those indicating progressiveness [straight line velocity (VSL), linearity (LIN) and straightness (STR)] decreased between 0 and 4 h. Visual inspection of sperm tracks after 4 h of incubation revealed classical hyperactivation patterns. Bivariate models were evaluated to objectively define the subpopulation of hyperactivated (HA) spermatozoa. Of all models considered, ALH and LIN, VCL and LIN, BCF and LIN, VCL and BCF, and VCL and ALH showed significant changes in the percentage of HA spermatozoa after the 4 h incubation period. The efficacy of detecting HA spermatozoa was evaluated using sperm tracks that were visually classified as HA or progressive. VCL and LIN provided the most accurate prediction of HA spermatozoa. It was concluded that analysis of CASA data using bivariate models could be used to detect and monitor hyperactivation in rat spermatozoa.

Evaluation of a container for collection and shipment of semen with potential uses in population-based, clinical, and occupational settings

Large, population-based studies of semen quality are encumbered by the logistics and expense of obtaining semen samples from men who live in a variety of locations. A prototype semen collection and transportation kit, the TRANSEM100, can be distributed to study participants and then directly shipped to a central laboratory for analysis. This study was designed to evaluate the ability of male volunteers to correctly use the kit. Thirty volunteers aged 20 to 44 years with no history of diabetes, recent chemotherapy, fertility problems, or vasectomy were recruited through a newspaper advertisement, interviewed to obtain demographic information, and instructed on the use of the kit. Twenty-six of the initial subjects provided at least 1 semen specimen using the kit and returned the specimens by overnight delivery to the laboratory for analysis, 25 completed a follow-up interview on the use of the collection kit, and 20 submitted a second semen sample using the same method. The average volunteer was white, 27.8 years old, and held at least a college degree. Forty percent of the volunteers were married. In general, participants correctly followed the instructions for collecting, packaging, and shipping the semen samples. Volunteers were instructed to collect samples after at least 2, but no more than 7 days of abstinence. For the first and second samples submitted, participants collected semen samples after an average of 3.3 and 3.9 days of abstinence, respectively. Seventeen (65%) of the samples from the first sampling period and 16 (80%) of the samples from the second period were received in the laboratory the day after they had been collected. In summary, the TRANSEM100 may prove to be useful for collecting human semen in field studies. Further testing of this method is warranted to evaluate preservation of sample quality and use of the kit by men among diverse socioeconomic groups.

Summarizing the motion of self-propelled cells: applications to sperm motility

Proper characterization of the motion of spermatozoa is an important prerequisite for interpreting differences in sperm motility that might arise from exposure to toxicants. Patterns of sperm movement can be extremely complex. On the basis of an exponential model that relates the discretely approximated curvilinear velocity to the tracking rate, we develop a statistic that indexes the predictability of the path for individual sperm. We summarize the path of each sperm using this and two other statistics: (1) the path displacement velocity and (2) linearity of movement. We apply the method to a set of rat sperm tracks representative of both normal and abnormal motion characteristics.

Fertility of rat epididymal sperm after chemically and surgically induced sympathectomy

Guanethidine, a chemical that selectively blocks sympathetic noradrenergic neurons, was used to investigate the role of sympathetic innervation in the fertility of rat epididymal sperm, using both natural mating and in utero insemination protocols. This animal model correlates, at least in part, with spinal cord injury (SCI) in men. Adult male rats were treated daily by i.p. injections, for 21 or 42 days, with 0 or 6.25 mg/kg guanethidine. To compare the effects of guanethidine-induced sympathectomy with those following surgically induced sympathectomy, the inferior mesenteric ganglion and the proximal hypogastric nerves were removed in another group of rats. Both chemically and surgically induced sympathectomy increased the weight of the epididymis and seminal vesicles/coagulating glands as well as the number and the transit time of cauda epididymal sperm. Neither serum testosterone levels nor LH was affected by treatment with guanethidine. Using natural mating, no litters were produced by guanethidine-treated rats. Chemically denervated rats failed to produce copulatory plugs or ejaculate into the uterus. However, distal cauda epididymal sperm from chemically or surgically denervated rats displayed normal fertilization ability (80%) using in utero inseminations. In addition, the sperm of denervated rats did not show abnormal sperm chromatin structure using an assay that detects DNA damage. We conclude that sympathectomy delays the transit of sperm through the cauda epididymidis and produces ejaculatory dysfunction but does not compromise sperm quality in the distal cauda epididymidis. Moreover, these data provide compelling evidence that there is no association between the prolonged transit time of sperm within the epididymis, i.e., pre-ejaculatory sperm aging, and the fertility of those sperm, which has important implications for artificial insemination using sperm from men with SCI.

Glutathione oxidation is associated with altered microtubule function and disrupted fertilization in mature hamster oocytes

We hypothesized that depletion of glutathione (GSH) with diamide, a relatively specific GSH oxidant, may alter the meiotic spindle apparatus in mature hamster oocytes. Immunofluorescent analysis of oocytes exposed to diamide for 1.5 or 3 h revealed time- and concentration-dependent disruption of spindle morphology accompanied by chromosome clumping. In oocytes first cultured in diamide for 1.5 h and then in diamide-free medium for 1.5 or 3 h, microtubules appeared to repolymerize, but normal spindle structure was not regained. HPLC confirmed that diamide oxidized oocyte GSH under conditions identical to those associated with spindle-related abnormalities. Exposure of oocytes to 25 or 50 microM diamide before in vitro fertilization did not affect their ability to undergo fertilization. A significant proportion of the fertilized oocytes that had been exposed to 50 microM diamide before insemination exhibited abnormal multiple female pronuclei with an apparently normal male pronucleus. These observations indicate that mature hamster oocytes are susceptible to oxidative stress during the critical period that precedes fertilization and provide further evidence that GSH plays important roles in oocyte spindle function and pronucleus development.

Sperm motion predicts fertility in male hamsters treated with alpha-chlorohydrin

An understanding of the relationship between altered sperm motion and sperm function (fertility) is important when interpreting the biological significance of toxicant-induced changes in sperm velocity in rodent test species. Previous studies showed that a brief (4-day) exposure of male hamsters to the model chemical alpha-chlorohydrin (ACH) results in significant deficits in epididymal and uterine sperm velocity, which are associated with both a delay and a failure of fertilization in vivo. To characterize this effect in terms of fertility, similarly treated male hamsters were bred to untreated females and pups were counted the day before parturition. ACH treatment resulted in a dose-dependent decline in the percentage of sperm-positive females that were pregnant at the end of gestation (100, 78, 67, 22, and 0 where males were treated with 0, 33, 49, 66, and 83 mg ACH/kg/day, respectively). Cauda epididymal sperm from the same males were assayed for motion characteristics using computer-assisted sperm analysis (CASA), and for fertilizing ability in vitro. While the percentage of motile sperm was unaffected by ACH treatment, sperm velocity declined in a dose-dependent manner at all ACH treatment levels. Furthermore, the velocity of sperm from infertile males was shifted downward consistently across the entire velocity distribution. Since treated males tended to either be infertile (no pups) or have near normal litter size, the correlation between sperm velocity and litter size was nonlinear. Therefore, logistic regression models using velocity cut-off values were the most useful models for predicting fertility. These results support the contention that fertility relies on there being a sufficient number of sperm that exceed a velocity threshold. Sperm from treated males were also less likely to support in vitro fertilization (IVF), providing further evidence of impaired sperm function associated with acute exposure to ACH.

Assessment of reproductive disorders and birth defects in communities near hazardous chemical sites. III. Guidelines for field studies of male reproductive disorders

Exposures to environmental toxicants can have detrimental effects on several aspects of human male reproduction: fertility, sexual function, hormone status, and pregnancy/birth outcomes. However, no simple prescreening methods are available for reliably identifying potential hazards; questionnaires alone are relatively imprecise and inefficient in the absence of field data. Multidisciplinary field studies are required that include detailed exposure information, health and reproductive histories, physical examinations, semen analyses, and possibly, hormone analyses. Semen analysis is a critical component of field studies for evaluating two aspects of male reproduction: 1) changes in sperm or seminal content, which may be indicative of adverse effects on the male reproductive system with possible implications for fertility potential; and 2) defects in sperm DNA or chromosomes, which may be associated with subsequent changes in viability during embryonic development and health risks to the offspring. Semen analyses may be tiered: 1) initially, each semen study may include conventional semen assays (concentration, motility, and morphology) as well as specific biomarkers indicated by the health effect of concern in the study cohort: and 2) archived samples (i.e., frozen, videotaped, or smeared) may be utilized in later second-tier analyses to further characterize specific findings. Before initiating any field study, it is cost effective to critically evaluate the suitability of the cohort by confirming exposure and determining that there are adequate numbers of male participants in each exposure category. Such evaluations must be based on the statistical sensitivities of the specific tissue biomarkers and health endpoints for detecting changes. This article summarizes the components of the ideal field study and identifies research needs for improving field studies of male effects and for understanding the mechanisms of male reproductive toxicity. Several promising semen methods currently under development are also discussed.

Comparison of rat epididymal sperm counts by IVOS HTM-IDENT and hemacytometer

Epididymal sperm counts, a common measurement in male reproductive toxicity studies, are routinely determined using a hemacytometer. Recently, computer assisted methods for automated sperm counts have been developed. In the present study we evaluated an automated system, the TOX IVOS (Hamilton Thorne Research, Beverly, MA) HTM-IDENT option, that utilizes a DNA-specific stain and fluorescence illumination to identify sperm for enumeration. Cauda and caput epididymal sperm counts were determined in 48 adult male Sprague-Dawley rats, using both the hemacytometer and HTM-IDENT. The mean hemacytometer and HTM-IDENT counts (+/- SD) were 250 +/- 43 and 254 +/- 52 million, respectively, for cauda sperm, and 123 +/- 13 and 127 +/- 18 million, respectively, for caput sperm. The average coefficient of variation using the hemacytometer was 13.8% as compared to 17.3% for the HTM-IDENT. Comparison of the machine count and a visual count from the Display Statics screen of the HTM-IDENT indicated that when two or more sperm heads touched or overlapped, the machine counted them as one. Manual (visual) and machine counts when compared over a range of nine concentrations from 3.7 to 47.8 million/mL differed by 4 to 12% at the lowest to highest concentration. The concentration of epididymal sperm samples used in comparing the two counting methods ranged from 5.8 to 17.7 million/mL. Therefore, the HTM-IDENT undercounting error attributable to sperm heads touching was less than 6%. Overall the data indicate good agreement between the HTM-IDENT and the hemacytometer counts. Furthermore, both counting time and technician fatigue were markedly reduced. Thus the HTM-IDENT option improves the efficiency of epididymal sperm counting without loss of precision.

Teplice program--the impact of air pollution on human health

The aim of the Teplice Program is to investigate and assess the impact of air pollution on the health of the population in the district of Teplice, Czech Republic. Characterization of the air pollutants demonstrated unusually high concentrations during winter inversions of fine particles dominated by acidic sulfates, genotoxic organic compounds, and toxic trace elements. The major source of airborne fine particles is the burning of coal for heating and power. Human exposure and biomarker studies demonstrated large seasonal variations in air pollution within the Teplice District and higher seasonal average pollution levels than the comparative district, Prachatice. Personal exposures to fine particles and organic carcinogens [e.g., polycyclic aromatic hydrocarbons (PAH)] were correlated with excretion of PAH metabolites in urine, several trace metals in blood, and DNA adducts in white blood cells. Respiratory and neurobehavioral studies of school children were conducted using questionnaires and clinical measures. A significantly higher prevalence of adverse respiratory symptoms and decreased lung function were found in the Teplice district than in Prachatice. The neurobehavioral studies indicated significantly higher teacher referrals for clinical assessment in Teplice, but the majority of objective performance measures did not differ. Reproductive studies were conducted in both males and females. A study of the effects of exposure on pregnancy and birth found an excess prevalence of low birth weight and premature births in Teplice; these adverse effects were more common in infants conceived in the winter and whose mothers were smokers. Based on questionnaires and medical examination, the reproductive development of young men was not different between districts and seasons, however, measures of semen quality suggest that exposure to high levels of air pollution are associated with transient decrements in semen quality.

Methods for assessing sperm motility, morphology, and counts in the rat, rabbit, and dog: a consensus report. ILSI Risk Science Institute Expert Working Group on Sperm Evaluation

Reproductive toxicity studies are increasingly including assessments of sperm parameters including motility, morphology, and counts. While these assessments can provide valuable information for the determination of potential reproductive toxicity, the methods for conducting the assessments have not been well developed in all laboratories and are continually evolving. The use of different methods in different laboratories makes comparison of data among laboratories difficult. To address the differences in methods, a working group was convened to discuss methods currently in use, share data, and try to reach consensus about optimal methods for assessing sperm parameters in rats, rabbits, and dogs. This article presents the consensus report, as well as future research needs, with the hope that optimized common methods will aid in the detection of reproductive effects and enhance interlaboratory comparisons.

Acute exposure of female hamsters to carbendazim (MBC) during meiosis results in aneuploid oocytes with subsequent arrest of embryonic cleavage and implantation

A single oral dose of the fungicide and microtubule poison, MBC, administered to female hamsters at proestrus, results in infertility and early pregnancy loss (1). To characterize the site and mode of action of this effect, direct assessments of oocyte chromosomes, fertilization, and preimplantation embryo development were made. Female hamsters were given a single dose of MBC (1,000 mg/kg) on the afternoon of proestrus (to coincide with meiotic maturation of the oocytes) and either killed shortly after ovulation (day 1) to recover oocytes, or bred and killed on gestation day (gd) 1 to 5 of pregnancy to assess fertilization and preimplantation embryo development and enumerate early implantation sites. Chromosome analysis in unfertilized oocytes revealed an MBC-induced increase in aneuploidy (37 vs. 14% in controls). When animals were bred after dosing, MBC had no effect on the number of oocytes recovered or fertilized. However, significant increases were found in the proportion of embryos that failed to reach the expected stage of development, namely, the eight-cell stage on the afternoon of gd 3, the morula stage by the morning of gd 4, and the blastocyst stage by the afternoon of gd 4 (a time when some embryos have implanted). The mean number of implantation sites, revealed by Evans Blue staining, was also significantly lower in treated females on the afternoon of gd 4 and the morning of gd 5. These simple direct assessments elucidated a mechanism of MBC-induced early pregnancy loss, induction of aneuploidy in oocytes. They also ruled out an effect on fertilization, but demonstrated a subsequent arrest of preimplantation embryonic development accompained by a decrease in the likelihood of implantation.

Synchronous assessment of sperm motility and fertilizing ability in the hamster following treatment with alpha-chlorohydrin

To investigate the relationship between sperm motion parameters and fertilizing ability, a model was developed to assess both of these endpoints synchronously using a toxicant that inhibits sperm motion. alpha-Chlorohydrin (ACH) was administered daily for 4 days to male hamsters at 0, 33, 49, 66, and 83 mg/kg body weight. These males were then allowed a 45-minute breeding period with untreated estrus females on the morning of day 5. One hour after breeding, sperm samples were surgically recovered from the uteri of the females for motility analysis. Six hours later, eggs were flushed from the oviducts and evaluated for fertilization. Cauda epididymal sperm were also collected from the males shortly after breeding. Proportions of motile and progressively motile sperm were manually quantified, and overall sperm velocity and the velocity of representative vigorously swimming sperm in both the uterine and epididymal samples were measured by computer-aided sperm analysis. Significant decreases in in vivo fertilization rates and epididymal sperm motion parameters were observed at 66 and 83 mg/kg ACH, whereas uterine sperm motion was adversely affected at all ACH dosages used. All sperm motion parameters except the percentage of motile sperm in the epididymis were significantly correlated with fertilization rates by both linear and logistic regression. Overall, uterine and epididymal sperm endpoints predicted fertilizing ability comparably well. Stepwise multiple linear regression gave a model containing epididymal sperm velocity (EVCL) and uterine sperm percent motility (UMOT) with an R2 value of 0.649. Stepwise multiple logistic regression gave models containing EVCL alone and EVCL and UMOT in binary (fertile/infertile) and quantal models, respectively.

Dibromoacetic acid affects reproductive competence and sperm quality in the male rat

Recently, we demonstrated with short-duration tests that dibromoacetic acid (DBAA), a commonly occurring by-product of water disinfection, alters sperm morphology and motility in the male rat. These results suggested that the effects of DBAA on sperm quality were likely to compromise reproductive competence of the male rat early in subchronic exposure. The present studies were undertaken to investigate the dose response and time course of alterations in fertility and sperm quality. Proven breeder male rats were gavaged daily with 0, 2, 10, 50, or 250 mg DBAA/kg for up to 79 days; interim and terminal measurements of sperm quality and reproductive outcome were made. Because of the known neurotoxicity of the analogue, dichloroacetic acid, both natural breeding and artificial inseminations were evaluated in untreated females to distinguish between possible behavioral and spermatogenic effects. DBAA compromised male fertility during the second treatment week in naturally bred rats dosed with 250 mg/kg. The early antifertility effect appeared to be the result of behavioral changes since females artificially inseminated with sperm collected on Day 9 successfully produced offspring. However, sperm morphology and motility also were rapidly affected by DBAA treatment so that no offspring via natural insemination and only one litter via artificial insemination were produced subsequent to Day 15. Through 31 days, substantial effects on sperm motility, sperm morphology, and epididymal sperm numbers were observed, but there was no demonstrable effect on serum testosterone or sperm production. Because severe toxicity developed in the group given 250 mg/kg, exposure of these animals was prematurely terminated after 42 doses and their recovery was monitored through a 6-month posttreatment period; decreased testis weights and only limited recovery of reproductive performance were observed. Exposure to 50 mg/kg resulted in moderate changes in sperm morphology and motility and moderate decreases in epididymal sperm counts in rats dosed for 31 or 79 days. However, these males remained fertile, litter size was unaffected, and no paternally mediated developmental defects were noted in their offspring. No effects on sperm quality were detected at dosages of 2 or 10 mg/kg. However, compared to controls, naturally bred DBAA-treated rats tended to have fewer inseminations, fewer copulatory plugs, and fewer multiple litters, suggesting that DBAA may have altered mating behavior at dosages as low as 10 mg/kg.

Carbendazim (MBC) disrupts oocyte spindle function and induces aneuploidy in hamsters exposed during fertilization (meiosis II)

Peri-fertilization exposure to Carbendazim (MBC; a microtubule poison) induces infertility and early pregnancy loss in hamsters. Presently, both in vivo and in vitro techniques were employed to characterize the effects of MBC on cellular aspects of fertilization in hamsters. Exposure to MBC during either in vivo or in vitro fertilization (IVF) induced identical morphological abnormalities in the maternal chromatin of zygotes and embryos. These abnormalities included either multiple second polar bodies (PB2), and/or multiple small female pronuclei (PN), or meiotic arrest. Multiple PB2, multiple female PN, multiple PB2 with multiple female PN, or meiotic arrest were exhibited by approximately 31%, 15%, 12%, and 2% of the in vivo zygotes; and 3%, 16%, 36%, and 20% of IVF zygotes, respectively. The effects of MBC persisted to day 2 of pregnancy as indicated by decreased (P < 0.05) embryo development to the two-cell stage and the presence of micronuclei in 6% of two-cell embryos from MBC-treated females. Immunofluorescence analysis of microtubules (MTs) confirmed that MBC disrupted spindle MTs during IVF. Numerical chromosome analysis revealed that a single dose of MBC administered during in vivo fertilization induced aneuploidy in the resulting pronuclear-stage zygotes. The present data point to two mechanisms by which peri-fertilization MBC exposure may induce early pregnancy loss: 1) arrested meiosis with no zygotic cleavage; or 2) induction of zygotic aneuploidy with subsequent developmental arrest.

The ethane dimethanesulfonate-induced decrease in the fertilizing ability of cauda epididymal sperm is independent of the testis

Several decades ago it was reported that when adult male rats were exposed to a single injection of 50 mg/kg body weight ethane dimethanesulfonate (EDS) and mated with untreated females, average litter size was significantly reduced as early as 2 weeks later. Recently, we demonstrated that EDS exerts multiple effects in the epididymis of adult rats. Some of these effects were independent of reduced serum testosterone (T) levels. Later we found that EDS has direct effects on epididymal epithelial cells in vitro. Herein, we sought to determine whether EDS perturbs the fertilizing ability of cauda epididymal sperm. Four days after exposure to 50 mg/kg EDS, sperm from the proximal cauda epididymidis were inseminated into adult receptive females in utero; on the next day the percentage of fertilized eggs was determined. Exogenous T administration and castration were used to determine what role, if any, androgen deprivation and the testis had on the fertilizing ability of proximal cauda epididymal sperm. Sperm motion parameters, serum T, T in the caput/corpus epididymidis, and detergent-extracted sperm protein were evaluated and correlated with fertilizing ability. We found that both castration and EDS exposure significantly compromised the fertilizing ability of sperm in proximal cauda epididymidis 4 days after exposure. Exogenous T, sufficient to maintain serum T, completely restored the fertilizing ability of sperm following castration, but not after EDS exposure. Moreover, exogenous T failed to restore fertilizing ability when castrated animals were exposed to EDS. Thus, the effects that EDS exerts on sperm maturation in vivo are independent of the testis. Finally, the only endpoint that was well correlated with fertilizing ability was the relative amount of an acidic 18-kDa sperm protein.

Optimization of the Hamilton-Thorn computerized sperm motility analysis system for use with rat spermatozoa in toxicological studies

To optimize the Hamilton-Thorn Motility Analyzer (HTM; Hamilton-Thorn Research, Beverly, MA) for use in reproductive toxicology studies with rat spermatozoa, the accuracy and precision of the instrument were assessed under a variety of instrument settings. Videotapes of both fast- and slow-swimming sperm were analyzed repeatedly to obtain data across a range of sperm velocities as might be encountered as a consequence of exposure to reproductive toxicants. Acquisition rates were varied across the HTM menu choices (30, 19, 10, or 7 frames/sec) as were the number of frames analyzed (5 to 20) at each framing rate. For fast-swimming samples (mean straight-line velocity (VSL) approximately 130 microns/sec) generally good agreement between computer-assisted sperm analysis (CASA) and manually obtained data was found for percentage of motile sperm and straight-line velocity; i.e., CASA values were within 10% of manual values for most frame/rate combinations. The accuracy of these measures held true over a wide range of sperm concentrations and percentage motilities. However, CASA measures were less accurate for sperm samples of lower velocities (mean VSL approximately 50 microns/sec and mean VSL approximately 30 microns/sec) in that the velocity of very slow sperm was overestimated (particularly at 30 frames/sec). A soft-ware change (6.5R) and performing analyses at 19 instead of 30 frames/sec improved straight-line accuracy for the slow sperm and enhanced the discrimination between fast (presumably control) and slow (presumably treated) sperm samples. These data show that this motility analyzer could be successfully configured to evaluate rodent sperm samples. The use of such CASA systems in toxicology studies will provide valuable information that may improve human reproductive risk assessment.

Influence of the formamidine pesticide chlordimeform on ovulation in the female hamster: dissociable shifts in the luteinizing hormone surge and oocyte release

The formamidine pesticide chlordimeform (CDF) has been found to interfere with the hormonal control of ovulation in the rat by a presumptive disruption in the catecholaminergic regulation of the midcycle surge of luteinizing hormone (LH). While the brain hypothalamic mechanisms underlying generation of the hamster surge have not been as well-defined, there is evidence for an adrenergic component. The present experiments were designed to investigate the effects of CDF on ovulation in the golden hamster and whether any observed alterations are associated with differences in the appearance of the surge. Intraperitoneal CDF injections (0, 75, 150, or 200 mg/kg) at 1400 hr on proestrus caused a dose-related reduction in oocytes retrieved at 0700 hr on the day of estrus. Additional experiments demonstrated that this effect was due to a delay in ovulation and not a decrease in the complement of oocytes released. Doses of 150 or 200 mg/kg at 1100 hr or 200 mg/kg at 1600 hr were without a comparable ovulatory effect. Characterization of the LH surge indicated that there was a dose-related delay, but that this effect was not sufficient to account for the delay in ovulation. Animals dosed at 1100 hr (150 or 200 mg/kg) exhibited shifts in the surge identical to those animals injected at 1400 hr, but did not show any such detectable effects on the time of oocyte release. CDF administered at 1100 or 1400 hr also caused alterations in serum estradiol and progesterone, even at a relatively low dose of 37.5 mg/kg. The results indicate that CDF given at a time just prior to the preovulatory rise in LH is able to impede ovulation in the hamster by possibly influencing some ovulatory event(s) triggered by the surge. Also, the ability of CDF to alter the timing of LH release is consistent with catecholaminergic participation in the generation of the gonadotropin signal stimulating the final events leading to ovulation. Under the present conditions, this perturbation can be characterized as a delay in the LH trigger, rather than a blockade.

Chromatin remodeling in mammalian zygotes

With sperm-egg fusion at the time of fertilization the gamete nuclei are remodeled from genetically quiescent structures into pronuclei capable of DNA synthesis. Features of this process that are critical to insure the genetic integrity of the zygote and the success of subsequent embryonic development include: oocyte responses that prevent polyspermy; completion of the 2nd meiotic division by the oocyte; exchange of proteins in the sperm nucleus; and, remodelling of the oocyte chromosomes and sperm nucleus into functional pronuclei. Elucidation of the biological and molecular mechanisms underlying zygote formation and chromatin remodeling should enhance our understanding of the potential vulnerability of the zygote to toxicant-induced damage.

Use of the fungicide carbendazim as a model compound to determine the impact of acute chemical exposure during oocyte maturation and fertilization on pregnancy outcome in the hamster

Early pregnancy loss due to acute chemical exposure is difficult to detect and essentially impossible to characterize in humans. Here we use a hamster animal model to identify early pregnancy loss due to an acute chemical exposure to the female during the perifertilization interval. The fungicide carbendazim (methyl 1H-benzimidazole-2-carbamate), a microtubule poison with antimitotic activity, was selected as a model compound because it would be expected to perturb microtubule-dependent events occurring in the oocyte during meiotic maturation and fertilization. Such effects would likely lead to aneuploidy in the zygote with subsequent early pregnancy loss. Female hamsters were given a single oral dose of carbendazim during meiosis I (the afternoon of proestrus) prior to breeding, or during meiosis II (the morning of estrus) following overnight breeding. Pregnancy outcome was assessed on Day 15 (the afternoon before parturition). When given during during meiosis I, carbendazim treatment (750 or 1000 mg/kg body weight) significantly reduced the percentage of pregnant hamsters. In those animals that became pregnant, the average number of live pups was significantly lower at all dosages of carbendazim used (250, 500, 750, and 1000 mg/kg), an effect attributable to both preimplantation and early postimplantation losses. When given early on the morning of estrus, shortly before and during fertilization (0500 or 0600 hr), carbendazim treatment (1000 mg/kg) produced a similar decrease in litter size. This effect disappeared when carbendazim was administered at a slightly later time (0800 or 0900 hr), after the microtubule-dependent events of fertilization have occurred. These results demonstrate that a single exposure to a microtubule poison such as carbendazim at critical times, coincident with microtubule-dependent meiotic events, can result in very early pregnancy loss. Such loss was readily measurable in this animal model and serves as the basis for further mechanistic studies which would be impossible to conduct in humans.

Methods for assessing rat sperm motility

Computer-assisted sperm analysis (CASA) systems are becoming more widely used. With this spread of technology come more data from toxicology studies, designed to determine if treatment with putative toxicants affects sperm motion parameters. While these CASA methods provide us with more ways to evaluate toxicity and thus perhaps increase our chances of successfully protecting human health, there is also a greater likelihood that different laboratories will use different methods of collecting data on sperm motility. Different systems used with different methods in different laboratories will inevitably generate data that are difficult to compare. In a prospective attempt to address this issue of comparability and limit the problems, a group of individuals using CASA systems to analyze rat sperm motility convened to discuss methodologic issues, share data, and try to reach a consensus about methods for performing these studies. This article shares those meetings and data in the hope that common methods will enhance interlaboratory comparisons.