Aneuploidy in sperm and exposure to fungicides and lifestyle factors. ASCLEPIOS. A European Concerted Action on Occupational Hazards to Male Reproductive Capability

The mutagenic effect of tobacco smoke on male fertility

Despite the association between tobacco use and the harmful effects on general health as well as male fertility parameters, smoking remains globally prevalent. The main content of tobacco smoke is nicotine and its metabolite cotinine. These compounds can pass the blood-testis barrier, which subsequently causes harm of diverse degree to the germ cells. Although controversial, smoking has been shown to cause not only a decrease in sperm motility, sperm concentration, and an increase in abnormal sperm morphology, but also genetic and epigenetic aberrations in spermatozoa. Both animal and human studies have highlighted the occurrence of sperm DNA-strand breaks (fragmentation), genome instability, genetic mutations, and the presence of aneuploids in the germline of animals and men exposed to tobacco smoke. The question to be asked at this point is, if smoking has the potential to cause all these genetic aberrations, what is the extent of damage? Hence, this review aimed to provide evidence that smoking has a mutagenic effect on sperm and how this subsequently affects male fertility. Additionally, the role of tobacco smoke as an aneugen will be explored. We furthermore aim to incorporate the epidemiological aspects of the aforementioned and provide a holistic approach to the topic.

The environmental and occupational influence of pesticides on male fertility: a systematic review of human studies

BACKGROUND

Environment plays a key role in male infertility, changing the incidence in various populations, and pesticides are one of the most studied hazards. The use of the latter has never decreased, jeopardizing the safety of workers and the general population.

OBJECTIVE

Our purpose was to summarize the results of studies discussing the association between pesticides and male fertility.

METHODS

A comprehensive literature search was performed through MEDLINE via PubMed, Scopus, and Web of Science. Only human studies were considered. Semen parameters, and DNA integrity were considered to evaluate the effect of pesticides on men.

RESULTS

A total of 64 studies that investigated their impact in terms of semen parameters (51 studies), chromatin and DNA integrity (25 studies), were included. The most frequently affected parameters were total sperm count sperm motility and morphology, although a reduction in ejaculate volume and concentration occur in several cases. A tangible worsening of semen quality was associated with organochlorines and organophosphates. Furthermore, pesticide exposure, especially pyrethroids, was related to a higher DNA fragmentation index and chromosome aneuploidy in most articles.

CONCLUSION

The epidemiological evidence supports the association between pesticides and male fertility for workers and the exposed population in terms of semen quality, DNA fragmentation and chromosome aneuploidy. This article is protected by copyright. All rights reserved.

From sperm to offspring: Assessing the heritable genetic consequences of paternal smoking and potential public health impacts

Individuals who smoke generally do so with the knowledge of potential consequences to their own health. What is rarely considered are the effects of smoking on their future children. The objective of this work was to review the scientific literature on the effects of paternal smoking on sperm and assess the consequences to offspring. A literature search identified over 200 studies with relevant data in humans and animal models. The available data were reviewed to assess the weight of evidence that tobacco smoke is a human germ cell mutagen and estimate effect sizes. These results were used to model the potential increase in genetic disease burden in offspring caused by paternal smoking, with specific focus on aneuploid syndromes and intellectual disability, and the socioeconomic impacts of such an effect. The review revealed strong evidence that tobacco smoking is associated with impaired male fertility, and increases in DNA damage, aneuploidies, and mutations in sperm. Studies support that these effects are heritable and adversely impact the offspring. Our model estimates that, with even a modest 25% increase in sperm mutation frequency caused by smoke-exposure, for each generation across the global population there will be millions of smoking-induced de novo mutations transmitted from fathers to offspring. Furthermore, paternal smoking is estimated to contribute to 1.3 million extra cases of aneuploid pregnancies per generation. Thus, the available evidence makes a compelling case that tobacco smoke is a human germ cell mutagen with serious public health and socio-economic implications. Increased public education should be encouraged to promote abstinence from smoking, well in advance of reproduction, to minimize the transmission of harmful mutations to the next-generation.

The association between environmental exposure to pyrethroids and sperm aneuploidy

The aim of the present study is to determine whether the environmental exposure to pyrethroids was associated with males sperm chromosome disomy. The study population consisted of 195 men who attended the infertility clinic for diagnostic purposes and who had normal semen concentration of 20-300×10(6) mL(-1) or slight oligozoospermia (semen concentration of 15-20×10(6) mL(-1)) (WHO, 1999). Participants were interviewed and provided a semen sample. The pyrethroids metabolites: 3-phenoxybenzoic acid (3PBA), cis-3-(2,2-dichlorovinyl)-2,2-dimethylcyclopropane carboxylic acid (CDCCA), trans-3-(2,2-dichlorovinyl)-2,2-dimethylcyclopropane carboxylic acid (TDCCA) and cis-2,2-dibromovinyl-2,2-dimethylcyclopropane-1-carboxylic acid (DBCA) were analysed in the urine using a validated gas chromatography ion-tap mass spectrometry method. Sperm aneuploidy was assessed using multicolor FISH (DNA probes specific for chromosomes X, Y, 18, 13, 21). Our results showed that CDCCA >50th percentile was associated with disomy of chromosome 18 (p=0.05) whereas the level of TDCCA in urine >50th percentile was related to XY disomy (p=0.04) and disomy of chromosome 21 (p=0.05). Urinary 3PBA level ⩽50 and >50 percentile was related to disomy of sex chromosomes: XY disomy (p=0.05 and p=0.02 respectively), Y disomy (p=0.04 and 0.02 respectively), disomy of chromosome 21 (p=0.04 and p=0.04 respectively) and total disomy (p=0.03 and p=0.04 respectively). Additionally disomy of chromosome 18 was positively associated with urinary level of 3PBA >50 percentile (p=0.03). The results reported here are found that pyrethroids may be a sperm aneugens. These findings may be of concern due to increased pyrethroid use and prevalent human exposure.

Sperm aneuploidy in infertile male patients: a systematic review of the literature

Males with abnormal karyotypes and subgroups of fertile and infertile males with normal karyotypes may be at risk of producing unbalanced or aneuploid spermatozoa. Biological, clinical, environmental and other factors may also cause additional sperm aneuploidy. However, increased risk of sperm aneuploidy is directly related to chromosomally abnormal embryo production and hence to poor reproductive potential. This systemic literature review focuses on the identification of these males because this is an essential step in the context of assisted reproduction. This research may allow for a more personalised and, hence, more accurate estimation of the risk involved in each case, which in turn will aid genetic counselling for affected couples and help with informed decision-making.

Smoking-induced chromosomal segregation anomalies identified by FISH analysis of sperm

Background

Numerical chromosome aberrations in gametes are directly related to infertility and aneuploid embryos. Previous studies have shown that toxic substances from cigarette smoke induce structural and numerical chromosomal aberrations in vitro and could potentially increase levels of aneusomy in sperm. Moreover, increased levels of aneusomy in sperm are correlated with low implantation rates, spontaneous abortions and fetal losses. Studies of chromosome 3 in sperm suggest it may be more prone to segregation anomalies than other autosomes, but there has been no systematic investigation of the incidence of disomy for chromosome 3 in sperm derived from donor male smokers. The objective of this study was to use FISH to evaluate the influence of smoking on the levels of disomy for chromosomes X and Y, and to determine whether disomy levels for chromosome 3 were elevated in sperm derived from male smokers.

Results

FISH analysis was used to evaluate the frequency of disomies of chromosomes 3, X, and Y in sperm of 10 smokers, compared to a control group of 7 non-smoking fertile men. All the subjects presented a normal somatic karyotype. There was a significant increase in the overall frequency of disomies in sperm derived from the smoking group (P< 0.0001). When each chromosome pair was analyzed individually, disomy of chromosome 3 in smokers was found to be more than twice that observed in the matched non-smoker control group. In addition we observed a higher frequencies of disomy of the X and Y chromosomes, indicating elevated levels of diploidy in the sperm from the smoking group.

Conclusions

In this study we have shown that chromosome 3 may be susceptible to smoking-related segregation anomalies. Our results also suggest that errors can occur in both meiosis I and II, confirming the emerging literature that the male meiotic process may generally be affected by the genotoxic damage from tobacco use. Collectively, these findings provide additional evidence for enhancing tobacco control measures, and suggest that FISH analysis of chromosome 3 in sperm may be useful for monitoring smoking–induced segregation damage as part of the evaluation of infertile males.

Lifestyle factors and sperm aneuploidy

Different environmental and lifestyle factors may interfere with the normal disjunction of sister chromatids/chromosomes during meiosis and may cause aneuploidy. The aim of the study was to examine the association between lifestyle factors and sperm aneuploidy. The study population consisted of 212 healthy men under 45 years of age attending an infertility clinic for diagnostic purposes and who had a normal semen concentration of 20-300×10⁶mL or slight oligozoospermia (semen concentration of 15-20×10⁶/mL). All participants were interviewed and provided a semen sample. Sperm aneuploidy was assessed using multicolor FISH (DNA probes specific for chromosomes X, Y, 18, 13, 21). Results from the study suggest that lifestyle factors are related to sperm aneuploidy. A positive relationship was found between coffee drinking everyday and the lack of chromosome X or Y, as well as coffee drinking 1-6 times per week and additional chromosome 18. Wearing boxer shorts decrease the copy number changes in the whole chromosome 18, the number of additional chromosome 18 and the lack of chromosome 13. Additionally, obesity (BMI 30-40 kg/m²) was positively associated with additional chromosome 21 after being adjusted for potential confounders. These findings demonstrate that changing the men's lifestyle habits may contribute to reduction of the incidence of sperm aneuploidy. It is necessary that men continue to follow sensible health advice concerning excess weight, coffee drinking and wearing tight fitting underwear. As this is the first such study to examine different lifestyle factors and sperm aneuploidy, the results need to be confirmed on larger population.

Environmental exposure to pyrethroids and sperm sex chromosome disomy: a cross-sectional study

BACKGROUND

The role of environmental pesticide exposures, such as pyrethroids, and their relationship to sperm abnormalities are not well understood. This study investigated whether environmental exposure to pyrethroids was associated with altered frequency of sperm sex chromosome disomy in adult men.

METHODS

A sample of 75 subjects recruited through a Massachusetts infertility clinic provided urine and semen samples. Individual exposures were measured as urinary concentrations of three pyrethroid metabolites ((3-phenoxybenzoic acid (3PBA), cis- and trans- 3-(2,2-Dichlorovinyl)-1-methylcyclopropane-1,2-dicarboxylic acid (CDCCA and TDCCA)). Multiprobe fluorescence in situ hybridization for chromosomes X, Y, and 18 was used to determine XX, YY, XY, 1818, and total sex chromosome disomy in sperm nuclei. Poisson regression analysis was used to examine the association between aneuploidy rates and pyrethroid metabolites while adjusting for covariates.

RESULTS

Between 25-56% of the sample were above the limit of detection (LOD) for the pyrethroid metabolites. All sex chromosome disomies were increased by 7-30% when comparing men with CDCCA and TDCCA levels above the LOD to those below the LOD. For 3PBA, compared to those below the LOD, those above the LOD had YY18 disomy rates 1.28 times higher (95% CI: 1.15, 1.42) whereas a reduced rate was seen for XY18 and total disomy (IRR = 0.82; 95% CI: 0.77, 0.87; IRR = 0.93; 95% CI: 0.87-0.97), and no association was seen for XX18 and 1818.

CONCLUSIONS

Our findings suggest that urinary concentrations of CDCCA and TDCCA above the LOD were associated with increased rates of aneuploidy. However the findings for 3BPA were not consistent. This is the first study to examine these relationships, and replication of our findings is needed before the association between pyrethroid metabolites and aneuploidy can be fully defined.

Occupational causes of male infertility

PURPOSE OF REVIEW

To highlight and discuss the new evidence on occupational and environmental risk to male reproductive function.

RECENT FINDINGS

Semen quality following occupational exposure to boron (an acknowledged experimental reproductive toxicant) and benzene, and new evidence on low-level environmental exposure to widespread xenobiotics with endocrine actions.

SUMMARY

The naturally occurring semimetal boron is an experimental reproductive toxicant, but now a Turkish semen study corroborates earlier evidence that high-level occupational exposure is not toxic to human spermatogenesis. It seems that human exposure levels are below the levels that cause reproductive toxicity in rodents. On the contrary, there is now ample evidence that the carcinogenic substance benzene may cause chromosomal aberrations in sperm at very low exposure levels. This includes chromosomal deletions that are known to cause infertility, mental retardation and congenital malformations. This research highlights the need to scrutinize the chemicals for possible male-mediated developmental toxicity. Several occupational studies are addressing adult testicular function in men exposed to chemicals that may interfere with endocrine signalling such as bisphenol A and phthalates, but findings are rather inconsistent and it remains to be established whether these widespread chemicals have any impact on male fertility.

Male-mediated infertility in sons of building painters and gardeners: a nationwide register-based follow-up study

AIM

To investigate whether sons of gardeners and building painters have increased risk of infertility in comparison with sons of bricklayers, carpenters and electricians.

METHODS

Participants were men born 1965-1984 in Denmark whose fathers the year before birth had worked as gardeners, painters, bricklayers, carpenters or electricians (N=22,978). Cases of infertility were identified by Danish registers, and participants were followed-up for up to 24 years after their 20th birthday.

RESULTS

Sons of gardeners did not have increased risk of infertility. Hazard ratios for sons of painters fluctuated around the null in main analyses but were 1.6 (98% CI: 1.0-2.5) and 1.7 (95% CI: 0.9-3.2) in the subset of participants with smallest risk of paternal exposure misclassification.

CONCLUSIONS

Working as gardener or building painter was not related to increased risk of infertility among the next generation of males in main analyses. However, inherent limitations in data may have attenuated true associations.

The genotoxic effect of nicotine on chromosomes of human fetal cells: the first report described as an important study

CONTEXT

Recent studies have suggested a direct contribution of nicotine--the addictive component of tobacco and tobacco smoke--to human carcinogenesis, and it remains the most common harmful substance to which pregnant women are exposed. Also, it has deleterious effects on the fetus. The sperm of smoking fathers and newborns of smoking mothers have elevated frequencies of chromosome translocations and DNA strand breaks.

OBJECTIVE

We tried to understand the genotoxic effect of nicotine in pregnancies of active or passive smoking mothers. For this reason, we provide the evidence that nicotine exposure in vitro has detrimental effects on fetal cells.

MATERIALS AND METHODS

We examined the effect of nicotine sulphate on amniotic cells by designing an experimental setting consisting fetal cells grown in nicotine containing medium (25 ng/mL) in study group and fetal cells grown in control medium, which did not contain nicotine.

RESULTS

According to our findings, there is a significant difference of chromosomal aberrations (CAs) between nicotine containing medium grown cells and control medium grown cells, determined by the χ² test (P <0.001). We found CAs in 21.5% of cells analyzed. The 19.4% of the all cells had numerical aberrations. Chromosomes 21, 22, 8, 15 and 20 related numerical abnormalities were found to be the most frequent numerical abnormalities.

CONCLUSION

Results of this study confirm that the nicotine leads to significant direct genotoxic effects in human fetal cells in vitro. We speculate that there is an association between prenatal exposure to cigarette smoke and in utero aneuploidies.

Aneuploidy in human spermatozoa

We reviewed the frequency and distribution of disomy in spermatozoa obtained by multicolor-FISH analysis on decondensed sperm nuclei in (a) healthy men, (b) fathers of aneuploid offspring of paternal origin and (c) individuals with Klinefelter syndrome and XYY males. In series of healthy men, disomy per autosome is approximately 0.1% but may range from 0.03 (chromosome 8) to 0.47 (chromosome 22). The great majority of authors find that chromosome 21 (0.18%) and the sex chromosomes (0.27%) have significantly elevated frequencies of disomy although these findings are not universal. The total disomy in FISH studies is 2.26% and the estimated aneuploidy (2× disomy) is 4.5%, more than double that seen in sperm karyotypes (1.8%). Increased disomy levels of low orders of magnitude have been reported in spermatozoa of some normal men (stable variants) and in men who have fathered children with Down, Turner and Klinefelter syndromes. These findings suggest that men with a moderately elevated aneuploidy rate may be at a higher risk of fathering paternally derived aneuploid pregnancies. Among lifestyle factors, smoking, alcohol and caffeine have been studied extensively but the compounding effects of the 3 are difficult to separate because they are common lifestyle behaviors. Increases in sex chromosome abnormalities, some autosomal disomies, and in the number of diploid spermatozoa are general features in 47,XXY and 47,XYY males. Aneuploidy of the sex chromosomes is more frequent than aneuploidy of any of the autosomes not only in normal control individuals, but also in patients with sex chromosome abnormalities and fathers of paternally derived Klinefelter, Turner and Down syndromes.

Association between socio-psycho-behavioral factors and male semen quality: systematic review and meta-analyses

OBJECTIVE

To identify the factors associated with male semen quality from many socio-psycho-behavioral factors.

DESIGN

Medline/PubMed, EMBASE, and CNKI were searched to identify relevant publications for systematic review and meta-analysis.

PATIENT(S)

None.

INTERVENTION(S)

None.

MAIN OUTCOME MEASURE(S)

Thirteen socio-psycho-behavioral factors in 57 cross-sectional studies with 29,914 participants from 26 countries/regions were involved in this review. Six factors (age, body mass index [BMI], psychological stress, smoking, alcohol, and coffee consumption) were included in meta-analyses.

RESULT(S)

Smoking can deteriorate all of the sperm parameters of both fertile and infertile men, but it is not risk factor for semen volume in Switzerland and Iran and for sperm density in the United States, Denmark, and Brazil; higher age and alcohol consumption are risk factors for lower semen volume; and psychological stress can lower sperm density and sperm progressive motility and increase abnormal sperm.

CONCLUSION(S)

This review further suggested that higher age, smoking, alcohol consumption, and psychological stress were risk factors for semen quality. These results indicated that health programs focusing on lifestyle and psychological health would be helpful for male reproductive health. Well-designed studies are needed to further identify the role of more socio-psycho-behavioral factors in male semen quality.

Scoring of sperm chromosomal abnormalities by manual and automated approaches: qualitative and quantitative comparisons

It is now well known that levels of sperm disomy correlate to levels of infertility (as well as other factors). The risk of perpetuating aneuploidy to the offspring of infertile males undergoing intracytoplasmic sperm injection (ICSI) has become a hotly debated issue in assisted reproduction; however, there remain barriers to the practical implementation of offering sperm disomy screening in a clinical setting. The major barrier is the operator time taken to analyze a statistically meaningful (sufficient) number of cells. The introduction of automated 'spot counting' software-hardware combinations presents a potential solution to this problem. In this preliminary validation study, we analyzed 10 patients, both manually and using a commercially available spot counter. Results show a statistically significant correlation between both approaches for scoring of sperm disomy, but no correlation is found when scoring for diploid sperm. The most likely explanation for the latter is an apparent overscoring of two closely associated sperm heads as a single diploid cell. These results, and similar further studies that will ensue, help to inform cost-benefit analyses that individual clinics need to carry out in order to decide whether to adopt sperm aneuploidy screening as a routine tool for the assessment of sperm from men requiring ICSI treatment.

Gender effects on the incidence of aneuploidy in mammalian germ cells

Aneuploidy occurs in 0.3% of newborns, 4% of stillbirths, and more than 35% of all human spontaneous abortions. Human gametogenesis is uniquely and gender-specific susceptible to errors in chromosome segregation. Overall, between 1% and 4% of sperm and as many as 20% of human oocytes have been estimated by molecular cytogenetic analysis to be aneuploid. Maternal age remains the paramount aetiological factor associated with human aneuploidy. The majority of extra chromosomes in trisomic offspring appears to be of maternal origin resulting from nondisjunction of homologous chromosomes during the first meiotic division. Differences in the recombination patterns between male and female meiosis may partly account for the striking gender- and chromosome-specific differences in the genesis of human aneuploidy, especially in aged oocytes. Nondisjunction of entire chromosomes during meiosis I as well as premature separation of sister chromatids or homologues prior to meiotic anaphase can contribute to aneuploidy. During meiosis, checkpoints at meiotic prophase and the spindle checkpoint at M-phase can induce meiotic arrest and/or cell death in case of disturbances in pairing/recombination or spindle attachment of chromosomes. It has been suggested that gender differences in aneuploidy may result from more permissive checkpoints in females than males. Furthermore, age-related loss of chromosome cohesion in oocytes as a cause of aneuploidy may be female-specific. Comparative data about the susceptibility of human male and female germ cells to aneuploidy-causing chemicals is lacking. Increases of aneuploidy frequency in sperm have been shown after exposure to therapeutic drugs, occupational agents and lifestyle factors. Conversely, data on oocyte aneuploidy caused by exogenous agents is limited because of the small numbers of oocytes available for analysis combined with potential maternal age effects. The vast majority of animal studies on aneuploidy induction in germ cells represent cause and effect data. Specific studies designed to evaluate possible gender differences in induction of germ cell aneuploidy have not been found. However, the comparison of rodent data available from different laboratories suggests that oocytes are more sensitive than male germ cells when exposed to chemicals that effect the meiotic spindle. Only recently, in vitro experiments, analyses of transgenic animals and knockdown of expression of meiotic genes have started to address the molecular mechanisms underlying chromosome missegregation in mammalian germ cells whereby striking differences between genders could be shown. Such information is needed to clarify the extent and the mechanisms of gender effects, including possible differential susceptibility to environmental agents.

Addressing the linkage between exposure to pesticides and human health effects--research trends and priorities for research

In recent years, there has been escalating concern over the possible association between exposure to pesticides and adverse human health effects by a number of non-governmental organizations, professional and public interest groups. Recognizing the need to document the scientific basis of these concerns as a foundation for initiating a research theme devoted to linkages between exposures to pesticides and human health effects, the Canadian Institutes of Health Research (CIHR) requested a summary of recent research trends that address these linkages. Experts across Canada in the field of pesticide regulation and research were invited to participate in the review. The review summarizes the limitations of past and current studies related to pesticides and human health effects research and makes suggestions for future research priorities and proposed study designs that will improve the assessment of pesticide exposure, the associated health risks, and improved methodology for regulatory decision making.

Is smoking a risk factor for decreased semen quality? A cross-sectional analysis

BACKGROUND

Previous studies suggest a deleterious effect of cigarette smoking on semen quality, but their results have not been consistent. We studied the association between current smoking and semen characteristics and hormonal levels in a large group of healthy men.

METHODS

From 1987 to 2004, seven separate occupational or environmental semen quality studies were co-ordinated by our department. A total of 2562 men participated, each providing semen and blood sample and answering a questionnaire about lifestyle and factors related to health. Appropriate semen and smoking data were available for 2542 men.

RESULTS

Adjusting for study, age and other covariates, we observed an inverse dose-response relation between smoking and semen volume, total sperm count and percentage motile sperm. Heavy smokers had a 19% lower sperm concentration than non-smokers. We found a positive dose-response relationship between smoking and testosterone, LH and the LH/free testosterone ratios.

CONCLUSION

Current smoking in adult life moderately impairs the semen quality. It is well known that semen quality is associated to fecundity. Therefore, it would be sensible to advise men to abstain from smoking to avoid decreased fecundity.

Meiotic chromosome abnormalities in human spermatogenesis

The last few years have witnessed an explosion in the information about chromosome abnormalities in human sperm and the meiotic events that predispose to these abnormalities. We have determined that all chromosomes are susceptible to nondisjunction, but chromosomes 21 and 22 and, especially, the sex chromosomes have an increased frequency of aneuploidy. Studies are just beginning on the effects of potential mutagens on the chromosomal constitution of human sperm. The effects of pesticides and cancer therapeutic agents have been reviewed. In the last decade, there has been a great impetus to study chromosome abnormalities in sperm from infertile men because the advent of intracytoplasmic sperm injection (ICSI) made it possible for these men to father pregnancies. A large number of studies have demonstrated that infertile men have an increased frequency of chromosomally abnormal sperm and children, even when they have a normal somatic karyotype. Meiotic studies on the pachytene stage of spermatogenesis have demonstrated that infertile men have impaired chromosome synapsis, a significantly decreased frequency of recombination, and an increased frequency of chromosomes completely lacking a recombination site. Such errors make these cells susceptible to meiotic arrest and the production of aneuploid gametes.

Effect of lifestyle exposures on sperm aneuploidy

Lifestyle exposures including cigarette smoke, alcohol, and caffeine have all been studied in relationship to male reproductive health. Over the years the focus has primarily been on semen quality and/or fertility. More recently, literature evaluating direct adverse effects of lifestyle exposures on sperm chromosomes and chromatin has grown due to concern that induced damage could be transmitted to offspring causing transgenerational health effects. In this paper we present a new analysis that summarizes published studies of smoking effects on sperm chromosome number and demonstrates a statistically significant increase in sperm disomy among smokers compared to nonsmokers (P < 0.001). In addition, new data on the effect of alcohol intake on sperm chromosome number are presented showing a rate ratio of 1.38 (95% CI 1.2, 1.6) for XY frequency in sperm of alcohol drinkers compared to nondrinkers.

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.

Pesticides and the induction of aneuploidy in human sperm

Pesticides are some of the most frequently released toxic chemicals into the environment. Exposure to them has been associated with reproductive dysfunction, but the knowledge of the genotoxic risks of these substances is still limited. In vitro and in vivo, many pesticides are shown to induce aneuploidy. Analysis of sperm chromosomes by fluorescence in situ hybridization (FISH) with chromosome-specific probes has obtained increasing popularity in genetic toxicology. Sperm-FISH studies on men exposed to pesticides have yielded conflicting results: in men exposed to multiple pesticides during spraying no increased disomy frequencies in sperm were observed, although one study reported an increased rate of sex chromosome nullisomy. In contrast the two studies conducted in pesticide factories showed increased frequencies of sperm aneuploidy in exposed men compared to controls. The available data indicates that at least some of the commonly used pesticides are capable of inducing aneuploidy in human sperm when the exposure level is high enough.

Differential induction of micronuclei in peripheral lymphocytes and exfoliated urothelial cells of workers exposed to 4,4'-methylenebis-(2-chloroaniline) (MOCA) and bitumen fumes

Cytogenetic end-points used to estimate risk of genotoxic events in workers include the measurement of micronuclei (MN) in exfoliated cells, lymphocytes, and other tissues. Micronuclei are chromatin-containing bodies outside the cell nucleus resulting from contaminant-induced DNA damage. A review of 71 reports of human genotoxic responses to chemical or physical agents published between 1999 and 2001 revealed that 14% of such studies measured genotoxicity endpoints in specific target tissues relevant to the site of disease for the agent examined; 18% used endpoints in surrogate or non-target tissues but considered the relations between endpoints in surrogate and disease target tissues, and 68% measured genotoxicity endpoints in accessible tissues without reference to specific targets for disease. Methylenebis-(2-chloroaniline) (MOCA), used in polyurethane manufacture, is a suspected bladder carcinogen. Bitumen, used in road surfacing, contains skin and lung carcinogens. In this study, we aimed to compare genotoxicity in urothelial cells and in lymphocytes of workers exposed to these materials. Twelve men employed in polyurethane manufacture, twelve bitumen road layers, and eighteen hospital stores personnel (controls) were recruited and all provided blood and urine samples on the same day. Blood cultures were prepared using a cytochalasin B-block method. Exfoliated urothelial cells were collected from urine and stained for light microscopy. The number of MN in urothelial cells was higher in MOCA-exposed (14.27 +/- 0.56 MN/1000, 9.69 +/- 0.32 MN cells/1000) than in bitumen exposed workers (11.99 +/- 0.65 MN/1000, 8.66 +/- 0.46 MN cells/1000) or in control subjects (6.88 +/- 0.18 MN/1000, 5.17 +/- 0.11 MN cells/1000). Conversely, in lymphocytes, MN were higher in bitumen-exposed (16.24 +/- 0.63 MN/1000, 10.65 +/- 0.24 MN cells/1000) than in MOCA-exposed workers (13.25 +/- 0.48 MN/1000, 8.54 +/- 0.14 MN cells/1000) or in control subjects (9.24 +/- 0.29 MN/ 1000, 5.93 +/- 0.13 MN cells/1000). The results of this study suggest that genotoxins can cause different rates of micronuclei formation in different tissues. Thus, the sensitivity and relevance to cancer risk may be greater if the tissues selected for genotoxicity studies reflect the target tissue for the chemicals concerned.

Genotoxic Effects on Spermatozoa of Carbaryl-Exposed Workers

Carbaryl, one of the most important insecticides, is widely produced and used. To explore carbaryl-induced genotoxic effects of spermatozoa, particularly DNA damage and chromosome aberrations (CA), we first examined conventional semen parameters, the progression and motion parameters of the spermatozoa among 16 carbaryl-exposed workers and 30 internal and external control individuals. Sperm DNA damage represented as positive percentage of DNA fragmentation was detected by a modified terminal deoxy-nucleotidyl transferase-mediated dUTP-biotin nick end-labeling (TUNEL) assay. Then numerical CA of chromosome X, Y, and 18 were investigated by multicolor fluorescence in situ hybridization (FISH). The results showed significant differences in the percentage of sperm abnormality between carbaryl-exposed group and the external control group (p = 0.008). Mean (+/-SD) percentage of spermatozoa with fragmented DNA in carbaryl-exposed group (21.04 +/- 8.88%) was significantly higher than those in the internal (13.36 +/- 12.17%) and external control groups (13.92 +/- 7.15%), respectively (p = 0.035 and p = 0.030). Using FISH, we observed the frequency of sperm sex chromosome disomy was 0.661 +/- 0.238% in the exposed group, which was significantly higher than that in the external control group (0.386 +/- 0.140%) (p = 0.001), and the carbaryl-exposed group (0.276 +/- 0.126%) had an elevated chromosome 18 disomy compared with the internal (0.195 +/- 0.094%) and external control groups (0.124 +/- 0.068%), respectively (p < 0.05 and p < 0.01). In addition, carbaryl-exposed donors had significantly higher sperm nullisomic frequencies of sex chromosomes and chromosome 18 than the external controls (p < 0.01) but not the internal controls. In summary, the frequencies of aneuploidy and numerical CA showed significant differences between exposed group and control groups (p < 0.05 and/or p < 0.01). Moreover, positive correlations were found between sex chromosome disomy, aneuploidy rate, and morphologic abnormalities in spermatozoa of all donors (r = 0.564 and r = 0.555, p < 0.01). Our findings suggested that carbaryl might induce morphologic abnormalities and genotoxic defects of spermatozoa among exposed workers by causing DNA fragmentation and numerical CA in spermatogenesis as a potential genotoxicant. The evidence also indicated that the spermatotoxicity induced by carbaryl exposure might be related to adverse reproductive outcomes.

Genotoxicity of tobacco smoke and tobacco smoke condensate: a review

This report reviews the literature on the genotoxicity of mainstream tobacco smoke and cigarette smoke condensate (CSC) published since 1985. CSC is genotoxic in nearly all systems in which it has been tested, with the base/neutral fractions being the most mutagenic. In rodents, cigarette smoke induces sister chromatid exchanges (SCEs) and micronuclei in bone marrow and lung cells. In humans, newborns of smoking mothers have elevated frequencies of HPRT mutants, translocations, and DNA strand breaks. Sperm of smokers have elevated frequencies of aneuploidy, DNA adducts, strand breaks, and oxidative damage. Smoking also produces mutagenic cervical mucus, micronuclei in cervical epithelial cells, and genotoxic amniotic fluid. These data suggest that tobacco smoke may be a human germ-cell mutagen. Tobacco smoke produces mutagenic urine, and it is a human somatic-cell mutagen, producing HPRT mutations, SCEs, microsatellite instability, and DNA damage in a variety of tissues. Of the 11 organ sites at which smoking causes cancer in humans, smoking-associated genotoxic effects have been found in all eight that have been examined thus far: oral/nasal, esophagus, pharynx/larynx, lung, pancreas, myeoloid organs, bladder/ureter, uterine cervix. Lung tumors of smokers contain a high frequency and unique spectrum of TP53 and KRAS mutations, reflective of the PAH (and possibly other) compounds in the smoke. Further studies are needed to clarify the modulation of the genotoxicity of tobacco smoke by various genetic polymorphisms. These data support a model of tobacco smoke carcinogenesis in which the components of tobacco smoke induce mutations that accumulate in a field of tissue that, through selection, drive the carcinogenic process. Most of the data reviewed here are from studies of human smokers. Thus, their relevance to humans cannot be denied, and their explanatory powers not easily dismissed. Tobacco smoke is now the most extreme example of a systemic human mutagen.

Genotoxic effects on human spermatozoa among pesticide factory workers exposed to fenvalerate

Fenvalerate, a synthetic pyrethroid insecticide, is widely produced and used worldwide. To explore fenvalerate-induced genotoxic effects, particularly numerical chromosome aberration (CA), we firstly examined conventional semen parameters, the progression and motion parameters of the spermatozoa among 12 fenvalerate-exposed workers and 30 donors of the internal and external control groups. Then numerical CA of chromosome X, Y and 18 were investigated by multicolor fluorescence in situ hybridization (FISH). The results showed the significant differences in the percentage of sperm abnormality between fenvalerate-exposed group and the external control group (P = 0.024). In aneuploid parameters, the frequency (mean +/- S.D.) of sex chromosome disomy was 0.742 +/- 0.131% in fenvalerate-exposed group, which was significantly higher than those in the internal (0.563 +/- 0.135%) and external control group (0.386 +/- 0.140%) (P < 0.01), and the frequency of chromosome 18 disomy in fenvalerate-exposed group (0.326 +/- 0.069%) was significantly higher than those in the internal and external control groups (0.195 +/- 0.094% and 0.124 +/- 0.068%), respectively (P < 0.01). We also found the nullisomies of sex chromosomes and chromosome 18 were significantly higher than those in the external control group and two control groups, respectively (P < 0.01). The frequencies of aneuploidy and numerical CA we detected also showed significant differences between exposed group and control groups (P < 0.05 and/or P < 0.01). Moreover, we found the positive correlation not only between nullisomic frequencies of these chromosomes and numerical CA rate (r > 0.70, P < 0.01) but also between disomic frequency of sex chromosomes, aneuploidy rate and sperm abnormality in all donors (r = 0.530 and r = 0.536, P < 0.01). Our findings suggest that fenvalerate or its metabolites induced morphologic abnormality and genotoxic defects of spermatozoa among fenvalerate-exposed workers by causing numerical CA in spermatogenesis as a special and potential genotoxic agent.

Human sperm aneuploidy after exposure to pesticides

This study examined the effect of paternal environmental exposure to pesticides on the frequency of aneuploidy in human sperm. To determine if the chromosome number in germ cells was altered by paternal exposure, multicolor fluorescence in situ hybridization (FISH) analysis was utilized to measure aneuploidy frequencies in the sperm of 40 men (20 exposed, 20 controls). Samples were coded for "blind analysis" to eliminate scorer bias. Aneuploidy and diploidy frequencies were assessed for chromosomes 13, 21, X, and Y. A minimum of 10,000 sperm was scored per donor per chromosome probe with a total of 809,935 sperm scored. Hybridization efficiency was 99%. There were no significant differences in aneuploidy or diploidy frequencies between exposed and control groups, suggesting that the pesticides did not increase the risk of numerical chromosomal abnormalities in these men.

A survey of semen indices in insecticide sprayers

This study aims at clarifying the semen indices of insecticide sprayers who are exposed mainly to organophosphorus and pyrethroid insecticides. Eighteen male sprayers out of 54 working for 9 companies in central Japan and 18 age-matched students or medical doctors as unexposed controls participated in detailed reproductive check-ups conducted in summer and the following winter. The sprayers were exposed to insecticides more in summer, the busiest season, than winter, the off-season (p<0.05). Erythrocyte true cholinesterase activities in the sprayers were lower than in the controls in summer (p<0.05), and decreased in significant association with the increase in exposure frequency. Testicular volumes in the sprayers tended to be smaller than in the controls (p=0.06). The serum testosterone concentration in winter in the sprayers was higher than in the controls (p<0.05), though luteinizing hormone and follicle stimulating hormone concentrations were not significantly different. The sperm counts and vitality were comparable between the groups, but detailed sperm motility analysis in summer revealed that the percentages of slow progressive and nonprogressive motile sperm were twice as high in the sprayers (p<0.05), and that of rapid progressive sperm tended to be lower (p=0.06). Such differences were not observed in winter. Differential sperm morphology counts showed that interaction of group and abstinence effects were significant in sperm with normal morphology and with head deformity only in the summer check-up. Despite possible inherent differences between the groups, the above season-dependent differences suggested that the observed lower semen quality in the sprayers was associated with pesticide spraying work.

Epidemiology of male reproductive function: a field searching for tools

BACKGROUND

An increase in the frequency of disorders of the male human reproductive organs has been described over recent decades. Neither its causes nor its consequences on fecundity, the ability of the couples to produce a live child, are clearly known. This lack of knowledge may partly be due to methodological difficulties specific to reproductive epidemiology.

METHODS

We discuss the relevance and limits of some markers of the male aspects of human reproduction, focusing on semen parameters and fecundability, a measure of the probability of pregnancy.

RESULTS

Semen parameters are associated with fecundability, although they have a relatively low sensitivity to detect couples with low fecundability. The study of semen parameters proved central to describe the influence of environmental factors on the male side of reproductive function. The main limitation of semen studies is low participation rates and the possible selection biases ensuing. Fecundability can be estimated by collecting waiting time to pregnancy. Its assessment in retrospective studies often excludes the least fecund, those couples remaining childless, which entails a bias and a decrease in statistical power. The prospective approach and an approach relying on the enrollment of a cross-sectional sample of the couples currently trying to obtain a pregnancy (current duration approach) do not have these limitations. Although it has never been used, the assessment of fecundability using the current duration approach is promising both for aetiologic research and monitoring.

CONCLUSION

Most of the potential markers of male reproductive function are not assessed in the general population of France, with the exception of the incidence rate of testis cancer, which is currently increasing. We present some alternatives for a monitoring system of reproductive function.

Effects of male age on the frequencies of germinal and heritable chromosomal abnormalities in humans and rodents

OBJECTIVE

To review evidence regarding the effects of male age on germinal and heritable chromosomal abnormalities using available human and rodent studies and to evaluate possible underlying mechanisms.

DESIGN

Review of English language-published research using MEDLINE database, excluding case reports and anecdotal data.

RESULT(S)

There was little evidence from offspring or germ cell studies for a generalized male age effect on autosomal aneuploidy, except in rodents. Sex chromosomal nondisjunction increased with age in both human and rodent male germ cells. Both human and rodent data showed age-related increases in the number of sperm with chromosomal breaks and fragments and suggest that postmeiotic cells are particularly vulnerable to the effects of aging. Translocation frequencies increased with age in murine spermatocytes, at rates comparable to mouse and human somatic cells. Age-related mechanisms of induction may include accumulation of environmental damage, reduced efficiency of DNA repair, increased genomic instability, genetic factors, hormonal influences, suppressed apoptosis, or decreased effectiveness of antioxidants and micronutrients.

CONCLUSION(S)

The weight of evidence suggests that the increasing trend toward fathering at older ages may have significant effects on the viability and genetic health of human pregnancies and offspring, primarily as a result of structural chromosomal aberrations in sperm.

Sperm-FISH analysis and human monitoring: a study on workers occupationally exposed to styrene

Occupational exposure to styrene, a chemical extensively used worldwide, is under investigation for possible detrimental effects on human health, including male reproductive capacity. Aneuploidy in germ cells is the main cause of infertility, abortions and congenital diseases. Fluorescence in situ hybridisation (FISH), is the most efficient cytogenetic molecular technique to date to analyse numerical alterations of chromosomes in spermatozoa. We investigated the frequencies of aneuploidy and diploidy in individuals occupationally exposed to styrene and in healthy unexposed controls. We performed multicolour FISH, using DNA probes specific for the centromeric regions of sex chromosomes and chromosome 2, in decondensed sperm nuclei of samples with normal semen parameters for a total of 18 styrene-exposed subjects and 13 unexposed controls of the same age range. Exposed individuals had worked for at least 2 years during the last 5 years, and continuously for 6 months, in factories producing reinforced plastics. The incidence of aneuploidy and diploidy for the tested chromosomes did not show a statistically significant difference between workers and controls. The exposure to styrene was associated with increased frequencies of nullisomy for sex chromosomes in the group of non-smokers, although only a limited number of subjects belonged to this sub-group. Considering the whole study population, age was associated with an increased frequency of XX disomy, whereas smoking was associated with meiosis II non-disjunction of sex chromosomes. Overall, confounding factors appeared to exert a more important effect than exposure to styrene on numerical chromosome alterations in sperm nuclei of subjects selected for normal semen parameters.

How work-place conditions, environmental toxicants and lifestyle affect male reproductive function

Major temporal and geographical shifts in male reproductive function is presently an issue worldwide. The hormonal disruption hypothesis has achieved considerable attention but epidemiological evidence in support of the theory is lacking. Several occupational hazards to male reproductive function are known but exposure prevalences are hardly sufficient to play a role for reduced sperm count in the general male population. Sedentary work may be an exception. Perhaps prolonged time in the sedentary position exhausts the testicular heat regulation. But so far studies addressing implications of the heat hypothesis in the general population are few. Neither change of sexual behaviour nor reduced period of sexual continence seems to be a likely explanation. Tobacco smoking and consumption of caffeine and alcoholic beverages in adulthood have a rather marginal impact on spermatogenesis and can hardly explain major shifts or regional differences in male reproductive health. However, prenatal effects following smoking during pregnancy might play a role because we have witnessed a smoking epidemic among fertile women in some countries during the second half of the twentieth century. Moreover, if genetic factors play more than a marginal role for testicular function and sperm count, pregnancy planning resulting in reduced family size during the past 100 years could possibly explain a decline in semen quality because the most fertile part of the population reproduce less while the subfertile probably continue to get a limited number of children.

Sperm aneuploidy rates in younger and older men

BACKGROUND

In order to assess the possible risk of chromosomal abnormalities in offspring from older fathers, we investigated the effects of age on the frequency of chromosomal aneuploidy rates of human sperm.

METHODS AND RESULTS

Semen samples were collected from 15 men aged <30 years (24.8 +/- 2.4 years) and from eight men aged >60 years (65.3 +/- 3.9 years) from the general population. No significant differences in ejaculate volume, sperm concentration and sperm morphology were found, whereas sperm motility was significantly lower in older men (P = 0.002). For the hormone values, only FSH was significantly elevated in the older men (P = 0.004). Multicolour fluorescence in-situ hybridization was used to determine the aneuploidy frequencies of two autosomes (9 and 18); and of both sex chromosomes using directly labelled satellite DNA probes on decondensed sperm nuclei. A minimum of 8000 sperm per donor and >330 000 sperm in total were evaluated. The disomy rates per analysed chromosomes were 0.1-2.3% in younger men and 0.1-1.8% in older men. The aneuploidy rate determined for both sex chromosomes and for the autosomes 9 and 18 were not significantly different between the age groups.

CONCLUSIONS

The results suggest that men of advanced age still wanting to become fathers do not have a significantly higher risk of procreating offspring with chromosomal abnormalities compared with younger men.

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.

Cigarette smoking and aneuploidy in human sperm

Cigarette smoke contains chemicals which are capable of inducing aneuploidy in experimental systems. These chemicals have been shown to reach the male reproductive system, increasing oxidative DNA damage in human sperm and lowering semen quality. We have examined the association between smoking and aneuploid sperm by studying 31 Chinese men with similar demographic characteristics and lifestyle factors except for cigarette smoking. None of the men drank alcohol. These men were divided into three groups: nonsmokers (10 men), light smokers (< 20 cigarettes/day, 11 men), and heavy smokers (> or = 20 cigarettes/day, 10 men). There were no significant differences in semen parameters or in age across groups. Two multi-color fluorescence in situ hybridizations (FISH) were performed: two-color FISH for chromosomes 13 and 21, and three-color FISH for the sex chromosomes using chromosome 1 as an internal autosomal control for diploidy and lack of hybridization. The mean hybridization efficiency was 99.78%. The frequency of disomy 13 was significantly higher in light and heavy smokers than in non-smokers, while no significant differences in the frequency of disomy 21, X or Y were observed across groups. Significant inter-donor heterogeneity in every category of disomic sperm examined was found in both light and heavy smokers, while in nonsmokers only XY disomy showed significant inter-donor differences. Thus, we conclude that cigarette smoking may increase the risk of aneuploidy only for certain chromosomes and that men may have different susceptibilities to aneuploidy in germ cells induced by cigarette smoking. Mol. Reprod. Dev. 59: 417-421, 2001.

Aneuploidy in spermatozoa of infertile men with teratozoospermia

Recent studies have shown that aneuploidy in spermatozoa of infertile men with poor semen quality is increased. The purpose of this study was to determine whether poor sperm morphology is associated with the incidence of spermatozoa with numerical chromosome abnormalities. Semen samples from 20 infertile teratozoospermic men were studied using multicolour fluorescence in situ hybridization (FISH). Men were divided into four groups according to the proportion of normal sperm morphology: infertile men with <10% (group A, n=7), 10-19% (group B, n=6), and 20-29% (group C, n=7) of morphologically normal spermatozoa, and controls (group D, n=5) with > or =30% normal forms. Two hybridizations were performed. All the samples were analysed using probes for chromosomes 1 and 7 and, in addition, in group A and in controls with normal semen parameters probes for chromosomes X, Y and 18 were also used. Ten thousand spermatozoa were scored per hybridization. Severely teratozoospermic men (<10% normal forms) had significantly higher frequency of disomy 7, 18, YY, XY and diploidy in their spermatozoa when compared with controls. The results suggest that poor sperm morphology is associated with numerical chromosome abnormalities of spermatozoa. Severely teratozoospermic men may be at an increased risk of producing aneuploid offspring.

Spontaneous frequencies of aneuploid and diploid sperm in 10 normal Chinese men: assessed by multicolor fluorescence in situ hybridization

Many studies have been published establishing the background frequencies of disomic and diploid sperm in normal men by fluorescence in situ hybridization (FISH) analysis, with highly significant variance among the reports. Besides interdonor heterogeneity and differences in the experimental protocols used, the question of inherent differences in chromosome malsegregation and meiotic arrest among different geographic and ethnic groups of donors has been raised. In this study, multicolor FISH analysis was carried out on semen samples from 10 nonsmoking, nondrinking Chinese men from the People's Republic of China. The results were compared to FISH data on 10 nonsmoking, nondrinking Canadians under the same experimental conditions, in the same laboratory. A total of 200,497 sperm was scored in the Chinese donors and compared to 202,320 sperm from Canadian donors. Approximately 10,000 sperm per chromosome probe per donor were analyzed. The mean hybridization efficiency was 99.99%. The frequencies of X-bearing and Y-bearing sperm were not significantly different from the expected 50% for each individual and for the combined data from all donors (49.73% vs. 49.46%, P = 0.3946). The mean disomy frequencies (range) were 0.07% (0.02%-0.12%) for chromosome 13, 0.18% (0.09%-0.19%) for chromosome 21, 0.05% (0. 01%-0.09%) for 24,XX, 0.02% (0.01%-0.06%) for 24,YY, and 0.29% (0. 13%-0.49%) for 24,XY. The mean diploidy frequency (range) was 0.38% (0.22%-0.73%) for 13-21 hybridizations and 0.32% (0.07%-0.70%) for XY hybridizations. Highly significant interdonor heterogeneity was found for diploidy (P = 0.0000) and for XY disomy (P = 0.0011), but no age effect was observed in any category of disomic or diploid sperm. The data reported here show no marked differences in disomy and diploidy frequencies between the mainland Chinese and Canadian groups, if donor heterogeneity is taken into account.

Aneuploidy in human sperm: a review of the frequency and distribution of aneuploidy, effects of donor age and lifestyle factors

Application of fluorescence in situ hybridization (FISH) analysis has opened the way for comprehensive studies on numerical chromosome abnormalities in human sperm. During the last decade, more than five million sperm from approximately 500 normal men were analyzed by a number of laboratories from around the world by this approach. Except for chromosome 19 which has been analyzed in only one study, all other chromosomes have been examined by two or more studies with considerable differences in disomy frequency for an individual chromosome among studies. The mean disomy frequency is 0.15% for each of the autosomes and 0.26% for the sex chromosomes. Most chromosomes analyzed have an equal distribution of disomy with the exception of chromosomes 14, 21, 22 and the sex chromosomes, which display significantly higher disomy frequencies. Slight but significant increases in disomy frequency with advancing paternal age were observed for some chromosomes, in particular for the sex chromosomes. Some lifestyle factors such as smoking, alcohol drinking and caffeine consumption have been investigated and no consistent association between disomy frequency and any type of lifestyle factors has been established. The question of whether different geographic and ethnic groups of men have inherent differences in frequency of disomic sperm has been investigated by two studies with conflicting results.

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.