The ejaculate is analyzed in the clinic primarily to obtain an estimation of sperm number, motion characteristics and cell morphology. Based on these data, conclusions are formulated as to the overall ‘fertility’ of the male. A major problem has been that the conclusions derived are often not (well) correlated with expected outcome, i.e., fertility. As a consequence, adjunct tests, e.g., sperm function tests, have been developed in an effort to uncover those defects/assets not revealed when measuring standard semen parameters. While some of these tests, e.g., hemizona assay, have helped to shed light on dysfunctional processes associated with fertilization, e.g., zona binding and penetration, individually they do not totally suffice for identifying fertile (defined as being capable of producing offspring) males.

The endometrium expresses many of the same integrins displayed by other tissues. Endometrial epithelial cells maintain the ‘classic’ epithelial integrins, including α2, α3, α6, and β4, while the stroma expresses the fibronectin receptor, α5β1. During the menstrual cycle, the endometrium undergoes dynamic changes in morphology in preparation for implantation. With these histological changes are concomitant alterations in integrin expression that appear to ‘frame’ the window of implantation, by the co-expression of glandular αvβ3 and α4β1 during days 20 to 24 of the menstrual cycle. The changes in integrin expression shift from epithelial to stroma predominance late in the menstrual cycle, extending into early pregnancy. Decidual integrins that appear upregulated in pregnancy include α1β1, α3β1, α6β1 and αvβ3. Markers of uterine receptivity hold promise for a better understanding of the implantation process and may help to explain many different types of infertility. These markers will be essential for monitoring and improving infertility therapies. The importance of integrins in the human endometrium now seems well established and promises to be an area of great clinical and basic science activity in the future.

Reproductive and developmental toxicology has existed, in some form, at least since the Middle Ages when women commonly used naturally derived abortifacients for birth control. Percival Pott was the first to observe that environmental exposures could detrimentally affect the male reproductive system. He noticed that chimney sweeps exposed to soot developed testicular cancer and infertility at unusually young ages. The formal investigation of male-mediated effects on offspring (germline mutagenesis) began with the pioneering studies of Muller, Hertwig, Snell, Brenneke, and others, who established X-rays as the first identified agent capable of inducing hereditary changes in mice. They showed that litters sired by irradiated males contained fewer pups than controls. Because sperm motility and density were not affected, but chromosome abnormalities were found in fertilized eggs, they concluded that irradiated sperm were the source of the abnormal chromosomes. Since that discovery, the mutagenic effects of radiation on the male germline have been studied extensively (see below). Later, Auerbach & Robson and Bock & Jackson were the first to demonstrate that exposing mice to chemicals decreases their fertility and induces chromosomal abnormalities and other mutations in the male germline. The subsequent five decades of work on chemical mutagens has resulted in a detailed biochemical and genetic characterization of chemical mutagenesis in the male germline and male-mediated developmental problems in laboratory animals (see below).

In trying to discern potential causes of male infertility, little investigation has been done to determine if there is predictive value in assessing acrosome reaction inducibility of human spermatozoa for clinical interpretation and application. The purpose of this review is to outline what is currently known in terms of the diagnostic significance of the induced acrosome reaction and to discuss what might be anticipated for the future. In constructing this review, every effort has been made to provide a comprehensive literature review for the reader and a number of review articles have been cited to serve as sources for additional related material. Regarding the aforementioned, it is essential to qualify that, with the exception of the Section entitled: ‘General characteristics of capacitation and the acrosome reaction’, only characteristics, properties and areas relevant to human spermatozoa will be addressed. Thus, in total, this review will: (1) provide a general description of capacitation and the acrosome reaction; (2) briefly characterize the acrosome and its properties; (3) address the signalling mechanism(s) by which the acrosome reaction occurs; (4) outline various methods for detecting the acrosome reaction; (5) define in vitro culture conditions that facilitate the acrosome reaction; (6) define agents, i.e., biological and chemical, that induce the reaction; (7) discuss the association of the acrosome reaction with fertilization; (8) discuss the clinical implications of the induced acrosome reaction; (9) discuss the relevance of sperm function assays in general; and lastly, (10) discuss future application of acrosome reaction assessment for the clinical diagnosis of male infertility.

Ovarian tissue freezing has been used successfully in animals and it has recently begun to be offered clinically to young women who have medical conditions with a high risk of sterility. Although no frozen human ovarian grafts have yet been returned to the donor and resulted in a pregnancy, there are many indications that this procedure should be feasible. Although live young have been derived from frozen grafts in several species, research should aim to make further improvements to the cryopreservation and grafting procedures to optimize follicle survival, and hence minimize the amount of tissue that needs to be collected, stored and returned. Ovarian tissue freezing, particular if used in combination with egg and embryo freezing, should allow a patient to safeguard their chance of becoming a parent later (Table 1). In cases where the patient has a systemic cancer or infection and malignant cells or viruses may be present in the systemic circulation and the gonadal tissue, ovarian tissue could be collected and frozen, but grafting is not currently recommended (Table 3).

Consideration of the function of the epididymis has undergone profound changes over the last century during which it has moved from a largely neglected male reproductive organ to one that is an increasingly exploited source of sperm for assisted reproduction strategies. From histological studies in the lizard1 it was considered that, ‘…the cells lining the epididymal canal produce a material necessary for the spermatozoa during their passage through the organ …’ whereas a fertility study with guinea-pigs stated boldly that, ‘… changes undergone [by spermatozoa in the epididymis] are not conditioned by some specific action of epididymal secretion …’. The former view found favour in a review of the literature which concluded that, ‘… there are specific epididymal secretions necessary for sperm maturation and survival …’, although the nature of the secretions were not then known. However, this concept, currently held by most of those studying the epididymis of animals, was again contradicted on the basis of clinical work: ‘… it certainly is possible for sperm that have never passed through any length of the epididymis at all to mature on their own …’.

Cytokines were first recognized as factors involved in the immune responses. However, emerging evidence suggests that cytokines serve as the unanimous language through which cells in organ systems as diverse as hypothalamus to endometrium communicate. Evidence for the participation of these factors in the normal function of the endometrium and uteroplacental unit and development of the embryo is being recognized. This review will highlight the significant insight gained over the past several years for the role of cytokines in the field of reproductive biology. Major emphasis will be placed on interleukins, tumour necrosis factor-α, transforming growth factors, colony stimulating factors and interferon-gamma.

The diagnosis of inherited disease in affected embryos before implantation is now possible using in vitro fertilization (IVF), embryo biopsy and DNA analysis. This enables pregnancies to be established with unaffected embryos following transfer to the uterus avoiding the possibility of terminating a pregnancy diagnosed as affected later in gestation. Pregnancies have been established with female embryos in women carrying X-linked recessive genetic defects affecting boys by identifying the sex of embryos either by DNA amplification of Y-specific sequences or by dual fluorescent in situ hybridization (FISH) with X- and Y-specific probes to interphase nuclei. The predominant ΔF508 deletion causing cystic fibrosis (CF) has also been detected by DNA amplification from single cells and the first pregnancy and birth of a child successfully screened for a single gene defect achieved. The prospects for applying preimplantation diagnosis to other chromosomal and single gene defects are reviewed.

The process whereby a fertilized egg develops into more than 200 different cell types and forms a new individual is both intriguing and fundamental to developmental biology. The systematic pathway of cellular differentiation is generally thought to confer a restriction whereby differentiated cells lose the capacity to change into other cell types. However, the substitution of nuclear material from one cell type (egg) with that of another, in a process known as nuclear transfer or cloning, can reverse this restriction by removing epigenetic modifications to the chromatin structure. The ability to clone new individuals using this procedure was achieved some 30 years ago in amphibia in an effort to understand cellular differentiation. More recently, with the advent of improved embryo micromanipulation techniques, the technology has been applied to domestic and laboratory animals.

The pathogenetic role of oestrogen deficiency in osteoporosis was first postulated by Fuller Albright in 1941 and has subsequently become well established. Hormone replacement therapy prevents menopausal bone loss and is the only treatment which has convincingly been shown to reduce fracture risk at both the spine and hip. The mechanisms by which oestrogens affect bone, however, are poorly understood and many aspects of treatment remain ill-defined, in particular with respect to the duration of therapy and its long-term risks and benefits.

The formation of adhesions is a significant clinical problem. Complications like bowel obstruction and chronic pelvic pain are known to be related to adhesion formation. Besides these complications, adhesions do play an additional role in the gynaecological patient. Interference with the functioning of the fallopian tubes and ovaries disturbs ovum pickup and sperm transport and may compromise the fertility of patients.

Sexual transmission is the most common route of spread of human immunodeficiency virus (HIV), with heterosexual transmission of HIV infection accounting for 90% of those infected in 1992 and over 75% of the 10–12 million of those infected to date worldwide. Yet, heterosexual transmission is poorly understood. Since HIV can be transmitted from HIV-infected people who are asymptomatic as well as from those who have the acquired immunodeficiency syndrome (AIDS), we must better define the potential for transmission of HIV from HIV-infected individuals as well as the factors which influence the susceptibility of HIV-uninfected individuals.

The notion of an oxytocic principle residing within the ovary is not new. In as early as 1910, Ott and Scott showed that an extract of bovine corpus luteum could induce milk letdown and uterine contraction. However, it took a further 70 years before the identification of this principle with the nonapeptide hormone oxytocin (OT) was made at the peptide and mRNA levels. This was followed by the identification of the peptide in ovarian tissues and ovarian venous blood from a wide variety of species, including humans, monkeys, pigs and ruminants (reviewed in 7, 8). For the majority of non-ruminant species the levels of expression of the peptide and its specific mRNA are relatively low, implying that whatever function the ovarian hormone has in these species, it is most likely to be at the local, paracrine level. Ruminants are an exception. Cows and sheep both produce very high levels of OT and OT-mRNA – the latter attaining concentrations of approximately 1% of all transcripts – within the corpus luteum of the early oestrous cycle. In ruminants, evolution has culminated in a systemic link between ovarian OT production and OT receptors in the endometrium of the uterus, inducing there the production of prostaglandin-F2∞ (PGF2∞) which completes a positive feedback loop to the ovary by stimulating further OT release (reviewed in 10). It is important to note, however, that natural selection can only act on a preexisting system. In this case, it has developed a systemic endocrine pathway in ruminants from a local ovarian OT system present probably in all mammals. There is even evidence for OT-related peptides, such as mesotocin and vasotocin, within the ovaries of marsupials and chicken, though their function is not known.

Ovarian hyperstimulation syndrome (OHSS) is an iatrogenic complication induced by exogenous administration of substances that are used to stimulate follicular growth and ovulation. There has only been one reported incidence of a spontaneous occurrence of OHSS and that was in 1992. The crucial event in the development of the syndrome is the administration of human chorionic gonadotropin (HCG), although several studies have reported the onset of OHSS after gonadotropin stimulation despite withholding HCG. OHSS is represented by a broad spectrum of clinical and laboratory manifestations which, in the severest form, can induce a life-threatening condition.

For more than a decade in vitro fertilization (IVF) has been successful in the treatment of couples with long-standing infertility due to various aetiologies such as tubal disease, male-factor infertility, unexplained infertility and endometriosis. The usual fertilization rate in IVF for nonmale infertility cases is 60–70% of the inseminated cumulus-oocyte complexes and in andrological infertility it is only 20–30%. The lower the number of normally fertilized oocytes, the less chance there is of available embryos, so that patients may have no embryos to transfer. It has been the experience of all centres for reproductive medicine, including our own, that a certain number of couples with male-factor infertility cannot be helped by standard IVF treatment. After insemination with progressively motile spermatozoa the number of two-pronuclear oocytes was either zero or less than 5%. Furthermore, a sizeable number of couples cannot be accepted for IVF if the number of progressively motile spermatozoa in the ejaculate is below a certain threshold number such as 500 000. In the past five years, assisted fertilization procedures have been developed to circumvent the barriers that prevent sperm access to the ooplasma, namely the zona pellucida and the ooplasmic membrane. Pregnancies and births have been reported after partial zona dissection (PZD) and subzonal insemination (SUZI). The success rate of PZD and SUZI has remained moderate: the normal fertilization rate (two-pronuclear oocytes) has never exceeded 20–25% of the micromanipulated oocytes; only two-thirds of the patients have had embryo transfers of, usually, a low number of embryos, resulting in a reduced pregnancy and take-home baby rate.

Sexual reproduction in the ocean necessitates only the combination of gametes, followed by absorption of nutrients and oxygen from the surrounding watery medium. As life moved from the sea to the land, reproductive strategies required compensation for the loss of this aquatic environment. For the mammals, and scattered other animals, the solution to this problem was the development of the placenta, the means by which the fetus extracts nutrients from its environment. As the animals that utilized the placenta evolved from small rodent-like creatures with short gestations to larger animals with prolonged gestations, the demands of the developing fetus grew. Whereas the placenta of the fetal pig, with a gestational period of a little less than four months, can extract sufficient nutrients from the mother by simple diffusion across the uterus to the placenta, the human fetus needs a far more complex uteroplacental relationship.

The transfer of a blastocyst established the first human clinical pregnancy following in vitro fertilization (IVF). Nine years later Cohen et al. reported pregnancies resulting from the transfer of cryopreserved human blastocysts. However, it was another six years before the first report of births resulting from the transfer of human blastocysts produced in vitro appeared in the medical literature. In the intervening period clinics have opted to transfer embryos at the early cleavage stage to the uterus, despite the fact that in vivo the embryo does not enter the uterus until two to three days later at the morula to blastocyst stage of development. The viability and potential for implantation of blastocysts is high, as indicated by the finding that more than 60% of in-vivo-derived blastocysts, recovered by uterine lavage following artificial insemination of fertile donors, implant and develop into viable fetuses when transferred to recipients. This is in stark contrast to the 10–20% of in-vitro-produced embryos transferred at the early cleavage stage of development that result in a live-birth. This reduction in viability following transfer of in-vitro-derived early cleavage stage embryos may have several possible explanations: (1) a failure of implantation due to poor synchronization between the embryo and the uterine endometrium; (2) a hostile environment in the uterus for early cleavage stage embryos; (3) sub-optimal in vitro culture conditions which result in a reduction in embryo viability; (4) the assumption that all oocytes retrieved in an IVF cycle have an equal ability to develop into viable embryos; and (5) the failure to identify the most viable embryo in a cohort. Certainly, improving culture conditions and laboratory techniques for developing high quality blastocysts routinely in vitro will not only address many of the above questions but will also improve the quality and viability of earlier stages of embryo development.

Angiogenesis is defined as the formation of new blood vessels from the existing vasculature. Angiogenesis occurs regularly in the endometrium throughout the reproductive life of females as part of the rapid growth and regression of this tissue that occurs during the menstrual cycle. It is now clearly evident that angiogenesis plays a key role in reproductive processes such as embryo implantation, placentation, endometrial regeneration after menstruation, and in the ovary during folliculogenesis and corpus luteum formation. Given the complexity and continual change of the endometrial milieu, it seems highly likely that aberrations in the angiogenic process may contribute to various disorders, including endometrial cancer, endometriosis, menorrhagia and breakthrough bleeding – all significant and common gynaecological pathologies. This review provides an update on the mechanisms and regulation of endometrial angiogenesis, with particular reference to the role of angiogenesis in implantation and placentation, as well as two endometrial pathologies – endometriosis and breakthrough bleeding.

Amongst men who attend fertility problems clinics, just over 10% are diagnosed to be oligospermic (< 5 × 106 sperm per ml) or azoospermic, with no known aetiological explanation. Amongst the many possible causes of impaired sperm production there is a genetic component, a pointer to the possible location of some of the responsible genes being found in 1976 when Tiepolo and Zuffardi discovered six azoospermic individuals with a deleted Y chromosome. In each individual, the long arm of the Y chromosome had lost its distal fluorescent segment as well as part of the nonfluorescent euchromatin lying proximal to it (Figure 1). They hypothesized that factors important in spermatogenesis might lie at the interface between fluorescent and nonfluorescent material. The locus, AZFor ‘azoospermia factor’, was subsequently mapped, using collections of deleted Y chromosomes, to interval six of the long arm and it lies within cytological band Yq11.23 (Figure 2).

Of all the assisted reproductive technologies in current use, artificial insemination has by far the longest history. While the earliest verifiable reports using this technique date to the eighteenth century for nonhuman artificial insemination and to the nineteenth century for human artificial insemination, systematic use of this approach to assist reproduction did not occur until the early part of this century. During the early 1900s, in Russia, Ivanov developed methods for semen collection from and insemination of horses. These techniques were later modified to apply to other agriculturally important species so that by the 1930s, millions of horses, cattle and sheep were being bred using artificial insemination. The adaptation of widespread use of artificial insemination (primarily in cattle) in agriculture extended to Britain in the early 1940s and to the USA in the 1950s. Corresponding implementation of artificial insemination in human reproductive medicine closely followed these innovations in the animal husbandry field.