Pesticide exposure and decreased fertilisation rates in vitro

Organophosphorus pesticide quinalphos (Ekalux 25 E.C.) reduces sperm functional competence and decreases the fertilisation potential in Swiss albino mice

Quinalphos (QP) is one of the most commonly used organophosphate pesticide for agriculture. In this study, adult Swiss albino male mice were orally administered with 0.25, 0.5 and 1.0 mg/kg of QP (Ekalux 25 E.C.) for ten consecutive days and the reproductive function was assessed at 35 and 70 days after QP treatment. At highest dose (1.0 mg/kg), QP exposure resulted in significant decrease in motility and increase in sperm head defects and DNA damage. Pharmacokinetic data showed a threefold increase in concentration of QP in the testis as compared to serum. QP was detectable in testes even after 24 hr of administration indicating slow clearance from tissue. In addition, high oestradiol, low testosterone level with a parallel increase in aromatase and cytochrome P450 transcript levels was observed. Significant decrease in fertilisation, lower blastocyst rate and poor blastocyst quality was observed when spermatozoa collected from QP exposed mice were subjected to in vitro fertilisation. In conclusion, exposure of QP to male mice decreases the sperm functional competence and fertilising ability, which appears to be mediated through elevated oxidative stress and altered steroidogenesis in testes.

Effect of the herbicide atrazine and its major metabolite, DACT, on bovine sperm cryotolerance

During freezing and thawing procedures, sperm are exposed to chemical and/or physical stressors that may cause adverse and harmful changes to sperm membranes. Accurate evaluation of the structural and functional integrity of fresh as well as cryopreserved sperm is highly important in predicting sperm fertilization capacity and success of artificial insemination (AI). The herbicide atrazine (ATZ) and its major metabolite, diaminochlorotriazine (DACT) are considered a ubiquitous environmental contaminants and endocrine disruptors, which deleteriously effect sperm function. Taking into consideration possible damage caused by environmental contaminants to sperm membranes, additive effects during cryopreservation cannot be ruled out. The aim of the current study was to evaluate the effect of ATZ (0.1 or 1 μM) and DACT (1 or 10 μM) exposure during or after cryopreservation on bovine sperm cryotolerance. Sperm membrane integrity and functionality were evaluated using fluorimetric probes: (1) double-stranded DNA was examined by 4',6-diamidino-2-phenylindole; (2) plasma membrane integrity was examined by propidium iodide; (3) acrosome reaction (AR) was examined by fluorescein isothiocyanate-conjugated Pisum sativum agglutinin; mitochondrial membrane potential (ΔΨm) was examined by 5,5',6,6'-tetra-chloro-1,1',3,3'-tetraethylbenzimidazolyl carbocyanine iodide fluorescent probe. The findings demonstrate, that exposure of sperm to ATZ (0.1 or 1 μM) or DACT (1 or 10 μM) during cryopreservation increased the proportion of dead sperm relative to the control (P < 0.09); exposure to DACT (1 or 10 μM) increased ΔΨm (P < 0.03). Neither ATZ nor DACT affected spontaneous AR. In contrast, the proportion of sperm with Ca⁺⁺ ionophore-induced AR was lower after exposure to 1 μM DACT (P < 0.05). Following freezing and thawing procedures, exposing sperm to 1 μM ATZ increased the proportion of dead sperm relative to the control (P < 0.05), but had no significant effect on sperm ΔΨm or AR. In conclusion, exposing sperm to endocrine-disrupting chemicals such as ATZ or DACT during cryopreservation reduces sperm cryotolerance and resistance post-thawing.

Endocrine-disrupting effects and reproductive toxicity of low dose MCLR on male frogs (Rana nigromaculata) in vivo

Toxic cyanobacterial blooms are potential global threats to aquatic ecosystems and human health. The World Health Organization has set a provisional guideline limit of 1 μg/L microcystin-LR (MCLR) in freshwater. However, MCLR concentrations in several water bodies have exceeded this level. Despite this recommended human safety standard, MCLR-induced endocrine-disrupting effects and reproductive toxicity on male frog (Rana nigromaculata) were demonstrated in this study. Results showed that sperm motility and sperm count were significantly and negatively correlated with exposure time and concentration. By contrast, abnormal sperm rate was positively correlated with both parameters. Ultrastructural observation results revealed abnormal sperm morphologies, vacuoles in spermatogenic cells, cell dispersion, incomplete cell structures, and deformed nucleoli. These results indicated that MCLR could induce toxic effects on the reproductive system of frogs, significantly decrease testosterone content, and rapidly increase estradiol content. Prolonged exposure and increased concentration enhanced the relative expression levels of P450 aromatase and steroidogenic factor 1; thus, endocrine function in frogs was disrupted. This study is the first to demonstrate in vivo MCLR toxicity in the reproductive system of male R. nigromaculata. This study provided a scientific basis of the global decline in amphibian populations.

Les différentes anomalies de la reproduction masculine sont-elles en augmentation ? Faits et controverses, possibles facteurs en cause: une analyse actualisée des données de la littérature et des registres

Au cours des dernières décennies, de nombreuses observations dans la faune sauvage d’anomalies relatives à l’appareil génital et à la fonction de reproduction mâle, certaines évoquant les données de la toxicologie expérimentale, ont conduit à s’interroger sur la toxicité de facteurs environnementaux pour la reproduction de l’homme. De plus, un certain nombre d’études suggère une augmentation de la prévalence des troubles de la reproduction de l’homme adulte au cours des dernières décennies dans de nombreux pays développés. Les données les mieux documentées concernent le cancer du testicule, son rythme de croissance suggérant le rôle de facteurs environnementaux et/ou de mode de vie. Toutefois, des différences régionales et ethniques considérables dans les taux d’incidence absolue pourraient impliquer des facteurs génétiques concomitants. Parallèlement, il semble que la qualité du sperme a diminué dans de nombreux pays, à en juger aussi bien par des méta-analyses que par des analyses statistiques de données d’un seul centre. Au début des années 2000, Skakkebæk et al. à Copenhague ont formulé l’hypothèse d’une origine commune à ces différentes anomalies lors du développement du testicule durant la gestation. Existe-t-il pour ces différentes conditions des données indiquant un lien de causalité avec une exposition environnementale/professionnelle à des composés reprotoxiques ? Ne serait-ce plutôt l’exposition chronique à de très nombreux composés chimiques à faible dose qui pourrait être impliquée ? Les facteurs de style de vie jouent-ils un rôle ? L’ensemble de ces questions se fondant sur une somme d’études, dont les résultats sont loin d’être univoques, a été la source de nombreux débats aussi bien au sein de la communauté scientifique que dans les médias. Les meilleures réponses possibles à ces questions complexes sont naturellement fondamentales pour les instances en charge de l’évaluation du risque et les politiques de santé publique qu’il convient d’adopter. La présente revue donne un état des lieux actualisé de ces questions.

Assessing human sperm morphology: top models, underdogs or biometrics?

The assessment of the percentage of spermatozoa having an 'ideal' morphology using so-called strict method is the method recommended in the latest edition of the World Health Organization (WHO) laboratory manual for semen analysis. This recommendation is a result of the statistical association between 'ideal' sperm morphology and fertility, and of the current general belief that sperm morphology assessment should be used primarily as a fertility tool. The notion of an 'ideal' sperm morphology has persisted despite the very low percentage of such spermatozoa in the semen of fertile men, a subject of intense controversy. The detailed categorization of each abnormal spermatozoon has thus, for a long time, been considered optional and partially redundant, an idea which is reflected in the earlier editions of the WHO manual. However, several recent studies have shown the importance of carefully assessing abnormal sperm morphology for use in the diagnosis of infertility, to determine fertility prognosis, and for basic or public health studies. One approach, which combines videomicroscopy and computer vision, and is the only approach able to assess the continuum of sperm biometrics, has been used successfully in several recent clinical, basic and toxicology studies. In summary, the visual assessment of detailed sperm morphology-including the categorization of anomalies allowing arithmetically derived indices of teratozoospermia-and the more modern computer-based approaches, although often considered to be redundant, are in fact complementary. The choice of the most appropriate method depends on the field of investigation (clinical, research, toxicology) and the problem being addressed. Each approach has advantages as well as certain limitations, which will be discussed briefly herein.

Review: Toxicants in reproductive fluid and in vitro fertilization (IVF) outcome

Some of the physical, chemical, dietary, occupational and environmental factors are having adverse effect on human reproduction. Increasing trend in reproductive disorders in recent years at least in part might be associated with these factors. The data available suggests less success rate of in vitro fertilization (IVF) outcome of parents exposed to some of the reproductive toxic chemicals as compared to parents who were not exposed to such chemicals. However, data are very meager and require more studies as some debatable data also exists. But existing positive findings encourage in advising that sub-fertile subjects, who are planning to go for the IVF, should reduce toxic exposure well in advance by adopting positive life style and work environment. Further, clinician ought to be aware of occupational and environmental exposure history of the participating couple.

Genital anomalies in boys and the environment

The prevalence of male reproductive disorders, such as testicular cancer and impaired semen quality, is increasing in many, albeit not all, countries. These disorders are aetiologically linked with congenital cryptorchidism and hypospadias by common factors leading to perinatal disruption of normal testis differentiation, the testicular dysgenesis syndrome (TDS). There is recent evidence that also the prevalence of genital malformations is increasing and the rapid pace of increase suggests that lifestyle factors and exposure to environmental chemicals with endocrine disrupting properties may play a role. Recent prospective studies have established links between perinatal exposure to persistent halogenated compounds and cryptorchidism, as well as between phthalates and anti-androgenic effects in newborns. Maternal alcohol consumption, mild gestational diabetes and nicotine substitutes were also identified as potential risk factors for cryptorchidism. It may be the cocktail effect of many simultaneous exposures that result in adverse effects, especially during foetal life and infancy.

Adverse health effects of children's exposure to pesticides: what do we really know and what can be done about it

Children may be exposed to pesticides in several ways, such as by transplacental transfer during foetal life, by intake of contaminated breast milk and other nutrients, or by contact with contaminated subjects and areas in the environment such as pets treated with insecticides, house dust, carpets and chemically treated lawns and gardens. Exposure early in life, and particularly during periods of rapid development, such as during foetal life and infancy, may have severe effects on child health and development by elevating the risk of congenital malformations, cancer, malabsorption, immunological dysfunction, endocrine disease, and neurobehavioural deficiencies. As pesticides can also interfere with parental reproductive health, exposure of parents may have consequences for the offspring leading to reduced chance of male birth and increased risk of childhood cancer.

CONCLUSIONS

Current knowledge about tolerable levels and consequences of toxic exposure to pesticides during human development is rather scarce. Owing to the high risk of exposure to pesticides, particularly in less developed countries, further elucidation by well-controlled epidemiological studies in this field it is urgently needed. The Policy Interpretation Network on Children's Health and Environment (PINCHE), which is financed by the EU DG research has suggested actions against pesticide exposure. They have been presented and discussed in this paper. Several suggestions of PINCHE concerning action needed regarding pesticides were presented in the paper.

Influence of tris(4-chlorophenyl)methanol, non-ortho PCB 77 and gamma-hexachlorocyclohexane on human sperm function in vitro

In recent years, there has been growing concern that environmental pollutants in general, and organochlorines in particular, adversely affect male fertility. Therefore, we investigated the effects of tris(4-chlorophenyl)methanol (TCPM), non-ortho PCB 77 and gamma-hexachlorocyclohexane (gamma-HCH, lindane) on human sperm functions in vitro. Human spermatozoa from healthy donors were washed in human tubular fluid medium containing 1% human serum albumin, filtered through glass wool and exposed to different concentrations of TCPM, PCB 77 or gamma-HCH. After incubation for 5 h at 37 degrees C and 5% CO(2), sperm vitality and the percentage of living acrosome-reacted spermatozoa were examined using triple stain technique. Total sperm motility was evaluated by computer-assisted sperm analysis (Stroemberg-Mika) after 5 h. For TCPM, total motility was additionally measured after 18 and 40 h. Different concentrations of PCB 77 and gamma-HCH did not alter the percentage of spontaneous living acrosome-reacted spermatozoa, vitality and total motility. TCPM dose-dependently altered sperm motility, vitality and acrosome reaction. The percentage of living acrosome-reacted spermatozoa was increased at overtly toxic concentrations. Therefore, it is suggested that unspecific acrosomal loss has been induced by degenerative processes. In conclusion, even high concentrations of PCB 77 and gamma-HCH did not affect human sperm functions in vitro. Only very high cytotoxic TCPM concentrations modulated spontaneous acrosome reaction and total motility. Therefore, in vivo effects on human sperm function seem to be unlikely. However, individual susceptibility has to be considered and little is known about additive and possible synergistic effects as other environmental pollutants with similar potencies have been found in the human male and female reproductive tract.

Effects of single non-ortho, mono-ortho, and di-ortho chlorinated biphenyls on human sperm functions in vitro

Polychlorinated biphenyls (PCBs) are ubiquitous pollutants in the environment. They are present in body fluids associated with reproduction such as follicular fluid, seminal fluid and cervical mucus. Most PCB effects are mediated through the aryl hydrocarbon receptor, which is present in human spermatozoa. Additionally, PCBs may alter various biochemical reactions, such as calcium homeostasis. Therefore we investigated the effects of single non-ortho PCB 126, mono-ortho PCB 118, and di-ortho PCB 153 on human sperm motility, vitality, and calcium-dependent acrosome reaction (AR) in vitro. Human spermatozoa were either treated with different single PCB congeners or their combinations for 5 h at 37 degrees C (spontaneous AR), or for 16 h at room temperature and 4 degrees C (induced AR). Motility was measured after 5 h of incubation. Compared with the controls, PCB exposure had no effects on the percentage of living acrosome reacted spermatozoa, vitality, and motility. There was no difference in the inducibility of the AR between treatment groups and the respective controls after long term incubation. The PCB concentrations used were far higher than those found in cervical mucus or seminal fluid. In vivo effects of PCB congeners on human ejaculated spermatozoa seem to be unlikely. However these results cannot be easily transferred to the in vivo situation, because individual susceptibility has to be considered, and there is no information about synergistic or additive effects with other chemicals present in the male and female reproductive tract.

Paternal contribution: new insights and future challenges

It has been widely held that all that fathers essentially contribute to the next generation is half their genome. However, recent progress towards understanding biological processes such as sperm maturation and fertilization now indicates that the paternal contribution has been underestimated. To tackle some of the misconceptions surrounding the paternal contribution, the factors that are actually delivered by the sperm at fertilization and their potential developmental functions will be discussed using data from humans and animal models. Although still in their infancy, the practical applications of using sperm RNAs have already emerged in reproductive medicine as markers that are indicative of successful vasectomy. They are also beginning to appear in the forensic sciences and, within the next decade, might appear in the environmental sciences.

Spontaneous abortion in IVF couples—a role of male welding exposure

BACKGROUND

Fume from welding of stainless steel contains hexavalent chromium, which in animal studies can induce paternally mediated spontaneous abortion. Human studies have shown conflicting results. The best studies include early pregnancy experience, but these are expensive to conduct. In vitro fertilization (IVF) provides new design opportunities. Our aim was to study pregnancy survival in IVF treated women with respect to paternal welding exposure.

METHODS

We mailed a questionnaire to 5879 couples from the Danish IVF register that covers all IVF treatments after 1993 (response ratio 68.2%). A subgroup of male metal workers received a second questionnaire on exposure to welding (n = 319 men, response ratio 77%). Information on outcome was collected from national health registers. Survival of the first hCG-positive pregnancy was analysed using Cox regression.

RESULTS

The proportion of pregnancies terminated by spontaneous abortion before 28 gestational weeks was 18% (n = 91 pregnancies) and 25% (n = 128) in pregnancies with paternal exposure to stainless steel welding and mild steel welding, respectively. In the reference group of 2925 pregnancies the abortion ratio was 28%. The risk ratio for pregnancies with paternal exposure to stainless steel was 0.6 (95% CI 0.4-1.0).

CONCLUSIONS

We found no increased risk of spontaneous abortion in IVF treated women, who became pregnant by a man exposed to welding of any sort. Since the process of fertilization and selection of IVF pregnancies differs from natural pregnancies the negative results need not apply to other pregnancies.

Estrogen receptor independent rapid non-genomic effects of environmental estrogens on [Ca2+]i in human breast cancer cells

The aim of this study was to identify and characterize an alternative pathway through which environmental estrogenic compounds may mediate their intracellular effects. Three human breast cancer cell lines were employed including MCF-7 cells, which express both ERalpha and ERbeta; MDA-MB-231 cells, which express ERbeta but not ERalpha; and SKBR-3 cells, which express neither ERalpha nor ERbeta. The effect of environmental estrogenic compounds on intracellular calcium ion concentration ([Ca(2+)](i)) was measured and compared to that of 17beta-estradiol (E2). A rapid and maintained increase in [Ca(2+)](i) was observed following the application of nanomolar concentrations of environmental estrogens and E2 regardless of the expression of ERalpha and ERbeta. Removal of extracellular Ca(2+) completely abolished the steroid-induced [Ca(2+)](i) increase. Pre-treatment of cells with the estrogen receptor (ER) antagonist ICI 182,780 had no effect on either basal [Ca(2+)](i) or the steroid-triggered [Ca(2+)](i) response. In summary, we have demonstrated ER independent rapid non-genomic effects of environmental estrogenic compounds, at nanomolar concentrations, on [Ca(2+)](i). The results of this study demonstrate an alternative pathway to explain potent intracellular effects of endocrine disrupting chemicals.

Environmental and occupational factors affecting fertility and IVF success

Reproductive function has been shown to be sensitive to changes in the physical, psychosocial and chemical environments. Although reproductive effects of occupational exposure to hazardous chemicals have been well documented in the literature, the potential effects of chemical contaminants at levels representative of contemporary exposures in the general population are much less certain. Evidence for adverse effects of exposure to environmental contaminants is more conclusive among the lower animals than for humans where considerable controversy remains. In addition to potential reproductive hazards of exposure to environmental contaminants, there is also evidence for adverse reproductive effects of the physical and psychosocial environments. In this review we focus on the difficulties involved in linking exposure to putative hazardous substances in environmental and occupational settings to adverse reproductive outcomes, especially success of IVF procedures. We highlight the plausibility of adverse events through animal and cell studies and the application of these results to the interpretation of human data. We consider both the male and female partners since it is essentially their combined contributions of gametes which may be affected by chemicals, which lead to successful outcomes.

The male reproductive system and its susceptibility to endocrine disrupting chemicals

In the past years, there has been increased interest in assessing the relationship between impaired male fertility and environmental factors. Human male fertility is a complex process and therefore a great variety of sites may be affected by exogenous noxae. Lifestyle factors as well as various environmental and occupational agents may impair male fertility. Many studies have been published reporting on reproductive dysfunctions in male animals and humans. Especially environmental pollutants with endocrine activity are discussed as a possible cause of this detrimental development. Evidence from animal experiments show that substances with oestrogenic and antiandrogenic properties may cause hypospadia, cryptorchidism, reduction of sperm density and an increase of testicular tumours. Many adverse effects on animal male fertility have been documented for phthalates and some chlorinated hydrocarbons such as polychlorinated biphenyls and polychlorinated dibenzo-p-dioxins. For other chemicals such as bisphenol A and nonylphenols animal data are conflicting. Environmental pollutants may mediate their effects by receptor binding, modulation of hormone-regulated mechanisms or direct toxic effects. Data on environmental chemicals and human male fertility are scarce, and risk assessment is mostly based on the results of animal studies. However, there are indications that exposure to endocrine active chemicals during early development may alter hormone responsiveness in adulthood. Furthermore, some of the chemicals are found in fluids that are associated with human reproduction, such as follicular fluid, seminal fluid and cervical mucus. Recent studies suggest a correlation between pesticide exposure and standard semen parameters as well as in vitro fertilization rates.

New evidence of the influence of exogenous and endogenous factors on sperm count in man

OBJECTIVE

To examine the association between individual exposures due to occupation, environment and lifestyle on sperm count, we conducted a case-control study among 92 fertile and 73 sub-fertile Caucasian males.

STUDY DESIGN

Data from questionnaires were analysed using simple univariate and multivariate logistic regression models.

RESULTS

At risk for oligozoospermia are men exposed to pesticides (odds ratio (OR) 8.4; 95% confidence interval (CI) 1.3-52.1), welding (OR 2.8; CI 0.9-8.7), antibiotic use (OR 15.4; CI 1.4-163), a history of mumps (OR 2.9; CI 1.3-6.7), gastrointestinal complaints (OR 6.2; CI 1.4-26.8), decreased intake of fruits (OR 2.3; CI 1.0-5.1), vegetables (OR 1.9; CI 0.7-5.0), or with female fertility disorders in their families (OR 8.4; CI 1.7-41.9). Unlike other studies, no associations were observed between oligozoospermia and exposure to paint or heat.

CONCLUSION

This study suggests new risk factors oligozoospermia in man and confirms previously reported results from others.

Risk factors for female infertility in an agricultural region

BACKGROUND

Recent studies have suggested that agricultural occupations or exposure to pesticides may impair female fertility.

METHODS

The Fertility Risk Factor Study retrospectively examined agricultural and residential exposures and the risk of female infertility. Cases and controls (N = 322 each) came from women who sought treatment at a large group medical clinic in Wisconsin. Women and their male partners provided information on health, occupational and lifestyle exposures in response to a telephone interview during 1997-2001.

RESULTS

Mixing and applying herbicides 2 years before attempting conception was more common among infertile women (odds ratio [OR] = 27; 95% confidence interval [CI] = 1.9-380), as was the use of fungicides (OR = 3.3; CI = 0.8-13). Residing on a farm, ranch or in a rural area during this time period was protective of female fertility. Households supplied with central Wisconsin groundwater were at less risk for infertility than households using municipal sources (OR = 0.6; CI = 0.4-0.9). Behavioral risk factors included alcohol consumption (OR = 1.8; 1.2-2.5), smoking (1.6; 0.9-2.9), passive smoke exposure (1.8; 1.2-2.5), steady weight gain in adult life (3.5; 2.0-6.1), and having a male partner over the age of 40 (4.5; 1.2-16.3). Drinking 3 or more glasses of milk per day was protective of female fertility (0.3; 0.1-0.7).

CONCLUSION

These results suggest that certain agricultural, residential and lifestyle choices may modify the risk of female infertility.

The presence of environmental pollutants in the semen of farm animals (bull, ram, goat, and boar)

Organochlorine pesticides and polychlorinated biphenyls are widely used in agriculture and industry, respectively, and may affect male reproduction function. Although several pollutants have been detected in human semen, similar studies in farm animals have not appeared. In the present study, the semen of bulls, rams, goats, and boars was assayed for the organochlorine pesticides hexachlorobenzene (HCB), hexachlorocyclohexane (HCH, alpha-, beta-, and gamma-isomers), dieldrin, and heptachlor epoxide, for DDT-related chemicals (o,p'-DDE, p,p'-DDE, p,p'-DDD, p,p'-DDT), and for the PCBs congeners (PCB-52, -101, -138, -150, and -180). In all species of farm animals, the most frequently detected pollutants were p,p'-DDE (80-100% of samples), HCB (73.9-100%), and gamma-HCH (69.6-100%). Species differences in the concentrations of HCB, alpha-, beta-, and gamma-HCH, dieldrin, p,p'-DDE, p,p'-DDD, and PCBs were noted as well as differences in the concentrations of some isomers of HCH, DDT-related chemicals, and PCB congeners in the same species.

Steroid hormone receptors and dietary ligands: a selected review

Members of the nuclear steroid hormone superfamily mediate essential physiological functions. Steroid hormone receptors (SHR) act directly on DNA, regulate the synthesis of their target genes and are usually activated by ligand binding. Both endogenous and exogenous compounds and their metabolites may act as activators of SHR and disruptors of endocrine, cellular and lipid homeostasis. The endogenous ligands are generally steroids such as 17beta-oestradiol, androgens, progesterone and pregnenolone. The exogenous compounds are usually delivered through the diet and include non-steroidal ligands. Examples of such ligands include isoflavanoids or phytooestrogens, and food contaminants such as exogenous oestrogens from hormone-treated cattle, pesticides, polychlorinated biphenyls and plasticisers. Certain drugs are also ligands; so nuclear receptors are also important drug targets for intervention in disease processes. The present review summarises recent reports on ligand-activated SHR that describe the selective regulation of a tightly-controlled cross-talking network involving exchange of ligands, and the control of major classes of cytochrome P450 (CYP) isoforms which metabolise many bioactive exogenous compounds. Many CYP have broad substrate activity and appear to be integrated into a coordinated metabolic pathway, such that whilst some receptors are ligand specific, other sensors may have a broader specificity and low ligand affinity to monitor aggregate levels of inducers. They can then trigger production of metabolising enzymes to defend against possible toxic nutrients and xenobiotic compounds. The influence of dietary intakes of nutrients and non-nutrients on the human oestrogen receptors (alpha and beta), the aryl hydrocarbon receptor, the pregnane X receptor, the constitutive androstane receptor, and the peroxisome proliferator-activated receptors (alpha and gamma), can be examined by utilising computer-generated molecular models of the ligand-receptor interaction, based on information generated from crystallographic data and sequence homology. In relation to experimental and observed data, molecular modelling can provide a scientifically sound perspective on the potential risk and benefits to human health from dietary exposure to hormone-mimicking chemicals, providing a useful tool in drug development and in a situation of considerable public concern.

Modified testicular expression of stress-associated "readthrough" acetylcholinesterase predicts male infertility

Male infertility is often attributed to stress. However, the protein or proteins that mediate stress-related infertility are not yet known. Overexpression of the "readthrough" variant of acetylcholinesterase (AChE-R) is involved in the cellular stress response in a variety of mammalian tissues. Here, we report testicular overexpression of AChE-R in heads, but not tails, of postmeiotic spermatozoa from mice subjected to a transient psychological stress compared with age-matched control mice. Transgenic mice overexpressing AChE-R displayed reduced sperm counts, decreased seminal gland weight, and impaired sperm motility compared with age-matched nontransgenic controls. AChE-R was prominent in meiotic phase spermatocytes and in tails, but not heads, of testicular spermatozoa from AChE-R transgenic mice. Head-localized AChE-R was characteristic of human sperm from fertile donors. In contrast, sperm head AChE-R staining was conspicuously reduced in samples from human couples for whom the cause of infertility could not be determined, similar to the pattern found in transgenic mice. These findings indicate AChE-R involvement in impaired sperm quality, which suggests that it is a molecular marker for stress-related infertility.

Paternal occupational exposures and embryo implantation rates after IVF

OBJECTIVE

To investigate any influence of paternal occupational exposures on implantation rates after IVF.

DESIGN

Cohort study of couples who sought IVF treatment.

SETTING

University Hospital Utrecht, The Netherlands.

PATIENT(S)

The study population was composed of 726 couples pursuing IVF treatment.

INTERVENTION(S)

Only the earliest IVF treatment cycle with ET was selected for the analysis. All couples filled in a generic questionnaire on lifestyle factors and details about their occupation. In addition, more detailed exposure information was obtained for pesticides with use of job-specific questionnaires and a subsequent telephone interview.

MAIN OUTCOME MEASURE(S)

The implantation rate was defined as the number of gestational sacs seen with ultrasound at 6-7 weeks of pregnancy, divided by the number of embryos replaced.

RESULT(S)

A significantly reduced implantation rate was seen among couples with male partners working in occupations with presumably high levels of organic solvent exposure. Conversely, paternal pesticide exposure was significantly associated with an increased implantation rate. Paternal exposures to metal dust or fumes and welding fumes were not related to the probability of implantation.

CONCLUSION(S)

The findings suggested that paternal organic solvent exposure decreased the implantation rate among couples undergoing IVF-ET treatment.

Effects of chlorinated hydrocarbons on sperm function in vitro

For the past few years there has been controversial discussion of whether environmental pollutants in general, and chlorinated hydrocarbons in particular, may impair male fertility. Organochlorine compounds, e.g. dichlorodiphenyltrichlorothane (DDT) and metabolites, polychlorinated biphenyls (PCBs), dibenzo-p-dioxins (PCDDs) and dibenzofurans (PCDFs) are highly persistent in the environment and there is therefore some concern about human exposure. These chlorinated compounds are universally found in human body fluids. Substantial amounts are detected in human body fluids associated with reproduction such as follicular fluid, seminal fluid and cervical mucus. The available data on male fertility and organochlorines are scarce and controversial. Fertilization rates in in vitro fertilization procedures were found to be decreased in couples in whom the male partner was exposed to pesticides. Data on the effects of PCBs on human sperm motility and acrosome reaction in vitro are controversial. Various PCDD congeners had no effect on human sperm motility in vitro. Effects of chlorinated hydrocarbons on sperm function in vivo seem to be unlikely since the concentrations used in vitro were far higher than those found in fluids of the human reproductive tract. However, negative effects on human spermatozoa in vivo cannot be totally excluded because other organohalogen compounds can be identified in the genital tract and little is known about their synergistic effects.