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D M de Kretser

Publications and source records attributed to D M de Kretser.

At least 19 recordsLinked to original sources
PubMed2006

Histological evaluation of the human testis--approaches to optimizing the clinical value of the assessment: mini review.

Testicular biopsy is a crucial assessment in reproductive practice with diagnostic and prognostic importance for assisted reproductive technologies (ARTs) and risk of testicular neoplasia. Endocrine and genetic tests cannot reliably distinguish obstructive azoospermia (OA) from non-obstructive azoospermia (NOA) or predict recovery of mature spermatids by testicular sperm extraction (TESE). Currently, divergent histological reporting systems and the use of imprecise terminology seriously degrade the value of the literature on TESE recovery rates and hamper evaluation of treatments and research on genotype-phenotype relationships. The rising incidence of testis cancer and carcinoma in situ (CIS), especially in infertile populations, requires that every effort be made for its early detection. We provide a systematic approach to the histological classification of spermatogenic disorders and detection of CIS in adult patients. We evaluate a large consecutive series of bilateral biopsies from infertile men and report (i) the frequency of bilateral or discordant patterns that supports the use of bilateral biopsy for comprehensive evaluation and (ii) a high prevalence of mixed patterns, particularly within the hypospermatogenesis classification, that helps account for reported success of TESE. We propose a new diagnosis code for testicular biopsies that addresses the needs of ART clinicians and allows data storage and retrieval of value in clinical practice and research.

Azoospermia↗
PubMed2006

A repository of ENU mutant mouse lines and their potential for male fertility research.

Many of the proteins and their encoding genes involved in spermatogenesis are unknown, making the specific diagnosis and treatment of infertility in males difficult and highlighting the importance of identifying new genes that are involved in spermatogenesis. Through genome-wide chemical mutagenesis using N-ethyl-N-nitrosourea (ENU) and a three-generation breeding scheme to isolate recessive mutations, we have identified mouse lines with a range of abnormalities relevant to human male fertility. Abnormal phenotypes included hypospermatogenesis, Sertoli cell-only (SCO) seminiferous tubules, germ-cell arrest and abnormal spermiogenesis and were accompanied, in some, with abnormal serum levels of reproductive hormones. In total, from 65 mouse lines, 14 showed a reproductive phenotype consistent with a recessive mutation. This study shows that it is feasible to use ENU mutagenesis as an effective and rapid means of generating mouse models relevant to furthering our understanding of human male infertility. Spermatozoa and genomic DNA from all mouse lines, including those with abnormal reproductive tract parameters, have been cryopreserved for the regeneration of lines as required. This repository will form a valuable resource for the identification and analysis of key regulators of multiple aspects of male fertility.

Activins↗
PubMed2006

Follistatin is a candidate endogenous negative regulator of activin A in experimental allergic asthma.

BACKGROUND: Activin A is a member of the transforming growth factor-beta superfamily which is directly implicated in airway structural change and inflammation in asthma. In vitro, the biological effects of activin A are neutralized by the soluble binding protein follistatin. OBJECTIVE: To determine the potential of endogenous follistatin to suppress activin A in vivo by analysing their relative tissue and kinetic compartmentalization during the effector phase of subchronic Th2-driven mucosal inflammation in a murine model of allergic asthma. METHODS: Eosinophilic mucosal inflammation was elicited by triggering Th2 recall responses by antigen challenge in ovalbumin-sensitized BALB/c mice. The kinetics and distribution of activin A and follistatin protein were assessed in lung tissue and bronchoalveolar lavage fluid and measured in relation to airway eosinophilia, goblet cell metaplasia and Th2 cytokine production in mediastinal lymph nodes. RESULTS: Follistatin was released concurrently with activin A suggesting it acts as an endogenous regulator: peak BAL concentrations coincided with maximal airway eosinophilia, and frequency of IL-4, IL-5 and IL-13 producing cells in mediastinal lymph nodes but induction lagged behind the onset of inflammation. Follistatin and activin A immunoreactivity were lost in airway epithelial cells in parallel with goblet cell metaplasia. Exogenous follistatin inhibited the allergen-specific Th2 immune response in mediastinal lymph nodes and mucus production in the lung. CONCLUSION: Follistatin is preformed in the normal lung and released in concert with activin A suggesting it serves as an endogenous regulator. Disturbance of the fine balance between activin A and its endogenous inhibitor follistatin may be a determinant of the severity of allergic inflammation or tissue phenotypic shift in asthma.

Activins↗
PubMed2006

Spermatogenesis does not require the local production of follistatin.

It has been proposed that follistatin can modulate the actions of activins and/or other members of the transforming growth factor-beta superfamily of proteins on testicular function, since mice overexpressing follistatin showed spermatogenic disruption. However, since mice with targeted disruption of the follistatin gene die soon after birth, it is not feasible to determine the effect of the absence of follistatin on testicular function using this model. To further understand the role of follistatin on the development and maintenance of spermatogenesis, fetal testes, collected by Caesarean section at day 18 of gestation from follistatin null mice, were transplanted to the external ear of castrated recombination activating gene 1 immunocompromised male mice. The testicular grafts were then analysed 7-8 weeks after transplantation and showed that full spermatogenesis developed in both the testes of wild-type and follistatin null mice. This study indicates that, if follistatin is required to modulate spermatogenic development, it is not supplied by local testicular production but by circulating follistatin from the host mouse.

Animals↗
PubMed2006

Regulated production of activin A and inhibin B throughout the cycle of the seminiferous epithelium in the rat.

Production and regulation of activin A and inhibin B during the cycle of the seminiferous epithelium were investigated in adult rats. Immunohistochemistry localised the activin beta(A)-subunit to the Sertoli cell cytoplasm, with much weaker expression in spermatocytes and spermatids. Both activin A and inhibin B, measured by ELISA were secreted by, seminiferous tubule fragments over 72 h in culture. Activin A was secreted in a cyclic manner with peak secretion from tubules isolated at stage VIII. Tubules collected during stage VI produced the least activin A. Inhibin B secretion was highest from stage IX-I tubules and lowest from stage VII tubules. Addition of interleukin-1beta (IL-1beta) had relatively little effect on activin A or inhibin B secretion in culture. In contrast, the peak secretion of activin A by stage VIII tubules was blocked by co-incubation with an excess of human recombinant IL-1 receptor antagonist, whereas inhibin B secretion increased slightly. Dibutyryl cAMP stimulated activin A secretion by late stage VII and VIII tubules and stimulated inhibin B across all stages. These data indicate that activin A and inhibin B are cyclically regulated within the seminiferous epithelium, with endogenous IL-1 (presumably IL-1alpha produced by the Sertoli cells), responsible for a peak of activin A production subsequent to sperm release at stage VIII. These data provide direct evidence that production of activin A and inhibin B by the Sertoli cell is locally modulated by IL-1alpha , in addition to FSH/cAMP, under the influence of the developing spermatogenic cells.

Activins↗
PubMed2005

Sexual activity, fertility and contraceptive use in middle-aged and older men: Men in Australia, Telephone Survey (MATeS).

BACKGROUND: With limited information regarding fertility and sexual activity in the older population, men's behaviour, attitudes and concerns were explored in a representative population of middle-aged and older men using the Men in Australia, Telephone Survey (MATeS). METHODS: A stratified random national sample of 5990 men participated in a standardized computer-assisted telephone interview. Equal numbers in the age strata 40-49, 50-59, 60-69 and >or=70 years were surveyed with findings census-standardized to the national population. Broad aspects of men's health and well-being, including reproductive health, were explored. RESULTS: The majority of men were sexually active in the last 12 months (age-standardized proportion, 78.3%) with approximately 37% of men aged >or=70 years still continuing sexual activity. Overall, 12.2% of men had never fathered children, of whom most (7.7%) had chosen not to have children. Questioning on failed attempts to produce a pregnancy suggested an involuntary infertility rate of 7.6%. The age-standardized vasectomy rate was 25.1%, with 5.6% of vasectomized men having no children. Although 9.2% of vasectomized men regretted sterilization, only 1.4% had undergone vasectomy reversal. CONCLUSIONS: Continuing sexual activity, fertility and contraception needs in middle-aged and older men suggests that education and service delivery must be more appropriately directed to an ageing population.

Adult↗
PubMed2005

The Y chromosome gr/gr subdeletion is associated with male infertility.

Men with Y chromosome (Yq) AZFc deletions lack all copies of the DAZ gene and have severe spermatogenic failure. A recently described gr/gr subdeletion of AZFc removes two of four copies of DAZ. To better understand the relative frequencies of AZFc and gr/gr deletions and their associated phenotypes, we analysed two large groups of infertile men. A total of 788 men from the Monash Male Infertility (MMI) database with a range of fertility disorders showed similar overall prevalences of AZFc (2.5%) and gr/gr deletions (3.4%). There was no association of gr/gr deletions with sperm density. In 234 control men of known or presumed fertility, only one gr/gr deletion was found. In a further 599 consecutive men presenting for assisted reproductive technologies, we detected 13 (2.2%) AZFc deletions and 28 (4.7%) gr/gr deletions. All AZFc deletions were seen with sperm densities <5 million/ml but again the gr/gr deletion occurred with similar frequency across all sperm density categories. These data show that gr/gr deletions are significantly associated with infertility in the Australian population (P = 0.0015) but not exclusively with reduced sperm density suggesting a complex interaction with other factors important for male fertility. Vertical transmission of gr/gr deletions from father to son by ICSI was demonstrated in four cases. Analysis of 130 ICSI-conceived sons revealed no de novo gr/gr deletions indicating that ICSI is not a risk factor. The data suggest that testing for gr/gr deletions should be considered in the routine genetic assessment of men with idiopathic infertility.

Chromosome Deletion↗
PubMed2005

Reciprocal regulation of activin A and inhibin B by interleukin-1 (IL-1) and follicle-stimulating hormone (FSH) in rat Sertoli cells in vitro.

In several biological systems, the inhibin beta(A) homodimer activin A is stimulated by, and in turn, inhibits the action of interleukin (IL)-1 (both IL-1alpha and IL-1beta) and IL-6. The possibility that a similar regulatory relationship operates within the testis was investigated. Sertoli cells from immature (20-day-old) rats were cultured with human IL-1alpha or IL-1beta, human IL-6 and/or ovine FSH or dibutyryl cAMP. Activin A and the inhibin dimers, inhibin A and inhibin B, were measured by specific ELISA. Immunoreactive inhibin (ir-inhibin) was measured by RIA. Activin/inhibin subunit mRNA expression was measured by quantitative real-time PCR. Both IL-1 isoforms, but not IL-6, stimulated activin A secretion through increased synthesis of beta(A)-subunit mRNA. IL-1 also stimulated activin A secretion by testicular peritubular cells. In contrast to the effect on activin A, IL-1 suppressed inhibin beta(B)-subunit and, to a lesser extent, alpha-subunit mRNA expression, thereby reducing basal and FSH-stimulated inhibin B secretion by the Sertoli cells. Conversely, FSH inhibited basal activin A secretion and antagonised the stimulatory effects of IL-1. Dibutyryl cAMP partially inhibited the action of IL-1 on activin A secretion, but had no significant effect on basal activin A secretion. Secretion of inhibin A was low in all treatment groups. These data demonstrate that IL-1 and FSH/cAMP exert a reciprocal regulation of activin A and inhibin B synthesis and release by the Sertoli cell, and suggest a role for activin A as a potential feedback regulator of IL-1 and IL-6 activity in the testis during normal spermatogenesis and in inflammation.

Activins↗
PubMed2005

Regulation of activin A and inhibin B secretion by inflammatory mediators in adult rat Sertoli cell cultures.

The regulation of Sertoli cell activin A and inhibin B secretion during inflammation was investigated in vitro. Adult rat Sertoli cells were incubated with the inflammatory mediators, lipopolysaccharide (LPS), interleukin-1beta (IL-1beta), IL-6 and the IL-1 receptor antagonist (IL-1ra) over 48 h in culture. Activin A, inhibin B and IL-1alpha were measured in the culture medium by specific two-site ELISAs. Both IL-1beta- and LPS-stimulated activin A and inhibited inhibin B secretion. LPS also stimulated the production of IL-1alpha in the cultures. In contrast to IL-1beta, IL-6 had no effect on activin A, although it did have a significant inhibitory effect on inhibin B secretion. Ovine follicle-stimulating hormone (FSH) and the cAMP analogue dibutyryl cAMP opposed the actions of IL-1 and LPS by suppressing activin A and IL-1alpha secretion and by stimulating inhibin B. Blocking IL-1 activity in the cultures by addition of an excess of IL-1ra completely prevented the response of activin A to exogenous IL-1beta, and reduced the response to LPS by 50%. In the presence of IL-1ra, basal secretion of inhibin B was increased, but IL-1ra was unable to reverse the suppression of inhibin B by LPS. These data indicate the importance of both IL-1 isoforms in regulating secretion of activin A and inhibin B by mature Sertoli cells during inflammation. The data also establish that inflammation exerts its effects on activin A and inhibin B secretion via other pathways in addition to those mediated by IL-1, and that hormonal stimulation by FSH and cAMP moderates the Sertoli cell response to inflammation. Interference with the complex interactions between these cytokines and hormones may contribute to the disruption of reproductive function that can accompany infection and illness in men.

Activins↗
PubMed2004

The role of activin, follistatin and inhibin in testicular physiology.

The role of the inhibins, activins and follistatins in testicular function are being more clearly defined following studies describing the cellular localisation of these proteins to the testis and the availability of specific assay systems enabling measurement of these proteins. Taken together with the results of targetted gene inactivation experiments, several concepts emerge. Inhibin B is predominantly produced by the Sertoli cell in many adult male mammals whereas there is a perinatal peak of inhibin A in the rat. In contrast, activin A has its highest concentrations in the immediate post-natal period during which it is involved in the developmental regulation of both germ cells and Sertoli cells being modulated by follistatin. Activin A levels are considerably lower in the adult testis but Sertoli cell production is stimulated by interleukin-1 and inhibited by FSH. Little is known about the production of activin B due to the absence of a suitable assay but the beta(B) subunit mRNA is expressed in germ cells and Sertoli cells and is stage-dependent. This pattern of expression suggest that it may be involved in autocrine or paracrine actions within the seminiferous epithelium.

Activins↗
PubMed2004

Effect of graded hypoxia on activin A, prostaglandin E2 and cortisol levels in the late-pregnant sheep.

The aim of the present study was to determine whether activin A concentrations are dependent on feto-placental oxygen availability and to investigate the temporal relationship of activin A with prostaglandin (PG) E(2) and cortisol. Nine fetal sheep (six hypoxic and three control) were instrumented and catheterised at 0.8 gestation. Reduced uterine blood flow was used to achieve three levels of hypoxia (mild = fetal SaO(2) 40-50%; moderate = fetal SaO(2) 30-40%; severe = fetal SaO(2) 20-30%), for 4 h on 3 consecutive days. Activin A, PGE(2) and cortisol levels were determined in maternal and fetal blood and amniotic fluid. Moderate and severe hypoxia produced a significant (P < 0.05) increase in fetal plasma activin A concentrations. The amniotic fluid activin A concentrations were 15-fold higher than those in the fetal circulation, but were unchanged by hypoxia. The fetal PGE(2) response reflected the degree of hypoxia over the 3 days, with moderate and severe hypoxia producing a significant (P < 0.05) increase in PGE(2) concentrations. Fetal plasma cortisol concentrations were increased ( P < 0.05) during all levels of hypoxia. Fetal arterial activin A was increased in response to moderate and severe hypoxia, but levels were not maintained over the hypoxic period. The increases in activin A and cortisol concentrations preceded the increase in PGE(2).

Activins↗
PubMed2004

Characterisation of the rapid release of activin A following acute lipopolysaccharide challenge in the ewe.

A series of experiments were conducted in adult ewes to delineate the release profile of activin A and its relationship to other cytokines following an i.v. injection of the bacterial cell wall component, lipopolysaccharide (LPS). Following this challenge, plasma activin A increased rapidly and appeared to be released in a biphasic manner, slightly preceding the release of tumour necrosis factor-alpha (TNFalpha) and before elevation of interleukin (IL)-6 and follistatin levels. The concentration of activin A was correlated with body temperature during the response to LPS. A second experiment compared cytokine concentrations in matched blood and cerebrospinal fluid (CSF) samples. This revealed that activin A was not released centrally in the CSF following a peripheral LPS injection, nor was TNFalpha or the activin binding protein, follistatin, but IL-6 showed a robust elevation. In a third experiment, the stimulus for activin A release was examined by blocking prostaglandin synthesis. Flurbiprofen, a prostaglandin synthesis inhibitor, effectively attenuated the fever response to LPS and partly inhibited cortisol release, but the cytokine profiles were unaffected. Finally, the bioactivity of TNFalpha and/or IL-1 was blocked using soluble receptor antagonists. These treatments did not affect the initial release of activin A, but blockade of TNFalpha depressed the second activin peak. These studies define more rigorously the release of activin A into the circulation following acute inflammatory challenge. The response is rapid and probably biphasic, independent of prostaglandin- mediated pathways and does not depend upon stimulation by TNFalpha or IL-1. The data suggest that activin A release is an early event in the inflammatory cascade following the interaction of LPS with its cellular receptor.

Activins↗
PubMed2002

Expression of monocyte chemoattractant protein-1 and macrophage colony-stimulating factor in normal and inflamed rat testis.

Macrophages are numerous in the testicular interstitial tissue under normal conditions and increase during inflammation. The mechanisms involved are poorly characterized. Expression of the macrophage-regulating cytokines monocyte chemoattractant protein (MCP)-1 and macrophage colony-stimulating factor (M-CSF) was examined in the adult rat testis before and after an i.p. injection of an inflammatory stimulus, lipopolysaccharide (LPS). In the normal testis, M-CSF was readily observed using Northern blot and Western blot analysis. In contrast, MCP-1 was not detectable by Northern blot in the normal testis, but was detected using RT-PCR amplification and a sensitive ELISA. After LPS treatment, testicular MCP-1 mRNA and protein expression increased dramatically (up to 400-fold). In-situ hybridization for MCP-1 revealed that production was confined to the interstitium of the inflamed testis, in Leydig cells, peritubular cells, perivascular cells and monocyte-like macrophages, but not in tissue-resident macrophages. Unlike MCP-1, M-CSF mRNA and protein expression in the testis increased only marginally, if at all, after LPS treatment. These results suggest that MCP-1 stimulates the increase in intratesticular macrophages that accompanies LPS-induced inflammation in vivo. Together with M-CSF, MCP-1 may also play a role in maintaining the resident macrophage population of the normal testis.

Animals↗
PubMed2002

Genetic follow-up of male offspring born by ICSI, using a multiplex fluorescent PCR-based test for Yq deletions.

De-novo deletions involving AZFa, b, c and d are one of the most common chromosomal aberrations in man resulting in defective spermatogenesis and male infertility. Currently, Yq deletion screening involves either single or multiplex PCR using Y-specific sequence tagged site markers and the subsequent analysis of the amplification products on ethidium bromide-stained agarose gels. To improve the practicality of routine and high throughput Yq testing, we have developed a more sensitive multiplex fluorescent (FL)-PCR screening system using genomic DNA extracted from cheek buccal cells as a readily available PCR template. For genetic follow-up studies of ICSI-conceived children, we also developed a DNA fingerprinting system based on the co-amplification of four highly polymorphic markers to validate family samples and detect any potential extraneous DNA contamination that could cause a misdiagnosis. Multiplex FL-PCR analysis of buccal cell DNA from two infertile men who conceived three sons by ICSI demonstrated that their Yq deletions were vertically transmitted. Fine mapping with additional Yq markers revealed identical deletion endpoints involving the loss of AZFdc sequences. This firstly indicates that the extent of the Yq deletion was unchanged on ICSI transmission and secondly supports the view that AZFdc deletions may arise by a common de-novo event. Analysis of paternal, maternal and sibling DNA fingerprints showed the co-inheritance of parental alleles by each male child and confirmed the expected relationship between each family member. The application of these new FL-PCR based screening tests in genetic follow-up studies will assist in confirming transmission of specific genetic defects to male offspring conceived by ICSI and provide a basis for genetic counselling and potential treatment options as these boys approach sexual maturity.

Adult↗
PubMed2002

Identification of specific sites of hormonal regulation in spermatogenesis in rats, monkeys, and man.

A detailed understanding of the hormonal regulation of spermatogenesis is required for the informed assessment and management of male fertility and, conversely, for the development of safe and reversible male hormonal contraception. An approach to the study of these issues is outlined based on the use of well-defined in vivo models of gonadotropin/androgen deprivation and replacement, the quantitative assessment of germ cell number using stereological techniques, and the directed study of specific steps in spermatogenesis shown to be hormone dependent. Drawing together data from rat, monkey, and human models, we identify differences between species and formulate an overview of the hormonal regulation of spermatogenesis. There is good evidence for both separate and synergistic roles for both testosterone and follicle-stimulating hormone (FSH) in achieving quantitatively normal spermatogenesis. Based on relatively selective withdrawal and replacement studies, FSH has key roles in the progression of type A to B spermatogonia and, in synergy with testosterone, in regulating germ cell viability. Testosterone is an absolute requirement for spermatogenesis. In rats, it has been shown to promote the adhesion of round spermatids to Sertoli cells, without which they are sloughed from the epithelium and spermatid elongation fails. The release of mature elongated spermatids from the testis (spermiation) is also under FSH/testosterone control in rats. Data from monkeys and men treated with steroidal contraceptives indicate that impairment of spermiation is a key to achieving azoospermia. The contribution of 5alpha-reduced androgens in the testis to the regulation of spermatogenesis is also relevant, as 5alpha-reduced androgens are maintained during gonadotropin suppression and may act to maintain low levels of germ cell development. These concepts are also discussed in the context of male hormonal contraceptive development.

Androgens↗
PubMed2001

Inhibins, activins and follistatin: actions on the testis.

While the early studies of the inhibins, activins and follistatins concentrated on their role as endocrine regulators of FSH secretion, recent data has emphasized the local actions of the activins and follistatin. Inhibin, through its capacity to suppress FSH secretion can modulate numerous processes within the testis. However, to date, evidence to support a local role for inhibin is limited. In contrast, activin and its binding protein follistatin are produced by a large number of cell-types within the testis raising the possibility of a range of paracrine and autocrine actions. These include the modulation of androgen production, influence on the proliferation of Sertoli cells and germ cells as well as the capacity to influence the structural and functional features of mitochondria within germ cells. Some of these actions are carefully controlled in a temporal relationship during the development of testicular function in the rat in which there is no separation in time between birth and the onset of spermatogenesis. Given the range of actions of activin in different cell-types, recognition of systems that are designed to modulate its actions are crucial in enhancing our understanding of how these many roles can be compartmentalized.

Activins↗