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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
PubMed1995

Screening Young syndrome patients for CFTR mutations.

Young syndrome is characterized by obstructive azoospermia associated with chronic sinobronchial disease of an infectious nature, but normal sweat-gland and pancreatic function as well as normal nasal potential differences. Congenital bilateral absence of the vas deferens (CBAVD) in some patients arises from mutations within the cystic fibrosis (CF) transmembrane regulator (CFTR) gene. Because of some similarities between Young syndrome, CF, and CBAVD, we evaluated 13 patients with Young syndrome, including screening for more than 30 different mutations within the CFTR gene. The mean age of the patients was 43 yr (range, 32 to 50 yr), and all were of northern European extraction. The sweat chloride concentration was normal in all patients (mean = 29 mEq/L; range, 8 to 43 mEq/L). Most had intermittent bronchial and sinus infections, but none was chronically colonized with Staphylococcus aureus or Pseudomonas aeruginosa. The FEV1 was normal or only mildly reduced in most patients (mean = 74%; range, 48 to 100% predicted). Of 26 Young syndrome chromosomes, we identified one with the recognized CF mutation delta F508. The incidence of CFTR mutations (1 in 26) did not differ significantly from the expected carrier frequency in this population. In summary, it is unlikely that the typical Young syndrome patient has a clinical disease associated with CFTR mutation on both alleles.

Adult↗
PubMed1994

Testosterone effects on spermatogenesis in the gonadotropin-releasing hormone-immunized rat.

Active immunization of adult rats with a GnRH fusion protein was used to inhibit gonadotropin secretion and to establish an in vivo model for studying the hormonal control of spermatogenesis. The model was characterized in terms of the efficacy of the immunogen as well as the time course and nature of the immunological and biological responses. To study the reinitiation of spermatogenesis, testosterone (T) was chosen for this initial study as it is known to restore spermatogenesis in gonadotropin-deficient rats. Adult Sprague-Dawley rats were actively immunized with a proprietory GnRH immunogen (BA-11, 100 micrograms s.c.) every 4 wk. After 12 wk, 58% of animals showed markedly suppressed testicular size, as assessed by scrotal palpation, and were classed as responders. Serum LH, FSH, and T as well as the testicular elongated spermatid count (ESC) and epididymal sperm were undetectable in responding animals. Marked reductions in testicular (29% of control), prostatic (8% of control), and epididymal (32% of control) weights were seen. Spermatogenesis was severely disrupted with no evidence of progression beyond round spermatids. To study the action of T in GnRH-immunized animals, T (defined by lengths of s.c. silastic implant, T3-T24 cm) was given to responding animals. Animals were killed 2, 8, and 12 wk after T24 administration. In response to T24, serum T levels increased to 4 times control levels, serum FSH levels were restored to 65% of control levels by 2 wk, and serum LH remained undetectable. Testicular weight increased to 80% of control levels at 12 wk (p < 0.05 vs. control). Epididymal and prostatic weights were normalized by T. ESC increased to 82% of control values at 12 wk (110 +/- 10 vs. control 134 +/- 8 million/testis, p = 0.001). Spermatogenesis was histologically normal after 8 wk of T24 treatment. To study the time course and dose response of T action, animals were immunized with another GnRH immunogen (BA-17), which yielded an 87% response rate at 12 wk. Testicular weight increased by Day 5 of T24 treatment, and a clear dose-response effect was apparent. The restoration of ESC was delayed compared to that of testicular weight (no restoration at 2 wk) and required > or = T6 treatment. Rats immunized for 20 wk and then given T24 treatment showed a similar pattern of restoration in testicular weight and ESC. Serum FSH was normalized by Day 2 of T treatment by doses > or = 3 cm.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed1994

Effects of testosterone on spermatogenic cell populations in the adult rat.

The aim of this study was to investigate the progression of germ cell populations through the rat spermatogenic cycle when spermatogenesis was suppressed by LH withdrawal through the use of a combination of testosterone (T) and estradiol (E) and then reinitiated by the administration of high doses of T. Adult Sprague-Dawley rats received 3-cm T and 0.4-cm E silastic implants for 6, 8, or 12 wk to suppress spermatogenesis followed by high-dose T (24-cm implants) for up to 12 wk to reinitiate spermatogenesis. The number of spermatogonia, primary spermatocytes, and round spermatids per testis was established by stereological techniques, and the elongated spermatid number was determined by the testicular content of nuclei resistant to homogenization in Triton X-100. Suppression for 6-12 wk resulted in moderate and significant (p < 0.05) reductions in the numbers of type A and type B spermatogonia (to 44-59% of control levels), preleptotene (68-72% of control), and leptotene/zygotene spermatocytes (62-79% of control) as well as in the numbers of stage I-VII (56-69% of control) and stage VIII-XIV (35-43% of control) pachytene spermatocytes. Round spermatids were suppressed to 29-45% of control levels (p < 0.05) while elongated spermatids were undetectable. The hourly production rates of germ cells (calculated using published time divisors) were used to study the cellular conversions through spermatogenesis (based on the ratios of the hourly production rates) and revealed that T withdrawal consistently abolished the conversion of round to elongated spermatids. The duration of suppression (6, 8, or 12 wk) had no effect on the degree to which germ cell populations or conversions were reduced. In response to high-dose T administration, spermatogonial and spermatocyte numbers and production rates (up to stage I-VII pachytene) remained suppressed, while stage VIII-XIV pachytene spermatocytes showed an increase of borderline significance. On the other hand, round and elongated spermatid numbers and production rates increased significantly (to 81% and 78% of control, respectively) and their conversion was normalized, i.e., the spermiogenic process was restored to a level consistent with the numbers of earlier germ cells proceeding through the cycle. These data suggest that, in the presence of low T levels, spermatogenesis proceeds at approximately 65% of normal levels between the spermatogonial and round spermatid stages, irrespective of the duration of T-induced suppression. This is followed by a precipitous decline in elongated spermatid number that is attributed to the disappearance of round spermatids.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed1993

Identification of receptor tyrosine kinases in the rat testis.

Evidence of receptor/ligand interactions that regulate testis cell function was sought in order to broaden the current understanding of the molecular basis of testis cell function. Using reverse transcription and the polymerase chain reaction, we have obtained novel evidence for the expression of three mRNAs encoding receptor tyrosine kinases in the adult rat testis: the platelet-derived growth factor type A receptor (PDGF-RA), the basic fibroblast growth factor receptor (flg), and fetal liver kinase 1 (Flk-1). A 6.8 kb transcript encoding the PDGF-RA was observed in RNA prepared from testes of rats aged day 5 through adult, with a decline in relative abundance with increasing age after day 17. Analysis of mRNA from isolated cell preparations (day 21 Sertoli cells, adult Leydig cells, round spermatids, and primary spermatocytes) and testes depleted of specific cell types [ethane dimethane sulfonate (EDS)-treated and cryptorchid] indicated that the Leydig cell was the predominant source of this mRNA in the adult testis. The addition of PDGF-BB to cultures of highly purified adult rat Leydig cell preparations resulted in a 40% increase in LH-stimulated testosterone production, confirming a role for this growth factor in regulation of Leydig cell function. These data indicate that the Leydig cell is a principal site of action of PDGF in the testis.

Amino Acid Sequence↗
PubMed1993

Human recombinant inhibin A suppresses plasma follicle-stimulating hormone to intact levels but has no effect on luteinizing hormone in castrated rams.

This study tested the hypothesis that inhibin is a major negative feedback regulator of FSH secretion but has minimal effects on LH secretion in rams. In experiment 1, castrated rams (wethers) were given either vehicle or human recombinant inhibin A (hr-inhibin) as three s.c. or three i.v. 50-micrograms injections 6 h apart or as one 50-micrograms i.v. injection followed by 100-micrograms infusion over 12 h. Human recombinant inhibin suppressed plasma FSH while the vehicle had no effect. The greatest suppression in plasma FSH was achieved following i.v. administration of hr-inhibin given either by repeated injection or by infusion. In experiment 2, wethers were given vehicle or a 50-micrograms i.v. injection followed by 800-micrograms infusion of hr-inhibin over 12 h. Infusion of hr-inhibin suppressed plasma FSH with a maximal suppression of 53.3% occurring between 15 and 24 h after the start of treatment. During this period, the plasma concentrations of FSH and inhibin were in the range of values for intact rams. Human recombinant inhibin did not influence plasma LH in either experiment. This study demonstrated that physiological treatment with inhibin, in the absence of testosterone, has the capacity to suppress plasma concentrations of FSH in wethers to the levels found in intact rams.

Animals↗
PubMed1989

Testicular enlargement and elevated serum inhibin concentrations occur in patients with pituitary macroadenomas secreting follicle stimulating hormone.

We studied four male patients with pituitary macroadenomas. Before treatment all had high serum FSH concentrations, but LH and testosterone were normal or subnormal; all patients were found to have large testes. All had had normal sexual function, and three patients had fathered children. After pituitary surgery there were decreases in serum gonadotrophins and testosterone, which were accompanied by decreases in testicular volumes. hCG stimulation tests in two patients showed normal responses of testosterone and oestradiol, confirming normal Leydig cell function. Inhibin levels were increased in two patients studied when FSH levels were high, suggesting a defect in gonadal-pituitary feedback control. Later, as FSH concentrations decreased to normal, so did inhibin levels. Histology showed that increased testicular size was due to increased lengths of seminiferous tubules. The association of pituitary macroadenomas, large testes and increased serum inhibin has not been reported previously. Assessment of testicular size in patients with raised serum FSH is important, since enlarged testes suggest the likely pathogenesis is that of a pituitary gonadotrophinoma, rather than primary gonadal failure. Increased inhibin levels may then confirm this, and be a biochemical marker for these tumours.

Adenoma↗
PubMed1989

Determination of Sertoli cell numbers in the developing rat testis by stereological methods.

Stereological studies were performed to determine the number of Sertoli cells present during the postnatal development of the rat testes. Sprague-Dawley rats aged from 1 to 70 days were used in two experiments, and in each were fixed by vascular perfusion and embedded in Epon-Araldite, subsequent to which 1 micron sections stained with Toluidine blue were prepared. In the first experiment, rats aged from 1 to 20 days were used in groups of three, and number estimates were made using a direct counting method. In the second, which used groups of four rats aged from 20 to 70 days, a point sampled intercept was used to estimate nuclear volume and thence number. The results of the experiments indicate that the newborn rat testis contains 1.3 +/- 0.2 x 10(6) Sertoli cells and that this number increases to 38.4 +/- 2.7 x 10(6) at day 15. No further increase in Sertoli cell number occurred thereafter up to day 70 of age.

Animals↗
PubMed1989

Inhibin secretion is influenced by Leydig cells: evidence from studies using the cytotoxin ethane dimethane sulphonate (EDS).

Adult male rats given a single intraperitoneal injection of the Leydig cell cytotoxin ethane dimethane sulphonate (EDS) show a significant decrease in testosterone from 7 to 14 days, and elevation of serum FSH and LH levels commencing 7 days after treatment, returning to normal at 28 days for LH and 49 days for FSH. A significant rise in serum inhibin levels was seen at day 14 after EDS treatment with levels returning to normal at day 49. In a second series of experiments, silastic implants of testosterone, either 2.5 cm or 22.5 cm in length, were introduced subcutaneously into adult male rats which were treated with EDS 10 days later. Both doses of testosterone suppressed basal LH levels but did not significantly change FSH levels. The rise in FSH and LH levels seen in normal rats after EDS treatment did not occur in either group of testosterone-implanted rats. However, serum inhibin levels rose significantly in both groups after EDS treatment, suggesting that the rise in serum inhibin levels was not due to stimulation arising from the increase in FSH levels after EDS treatment. The data suggest that the rise in serum inhibin levels after EDS treatment is linked to destruction of the Leydig cells through mechanisms that require further investigation.

Animals↗
PubMed1989

Immunoreactive inhibin concentrations in serum throughout the menstrual cycle of the macaque: suppression of inhibin during the luteal phase after treatment with an LHRH antagonist.

Concentrations of immunoreactive inhibin in serum samples collected daily from six adult stumptailed female macaques during normal menstrual cycles were measured with a heterologous radioimmunoassay. Serum inhibin concentrations were low during the follicular phase of the cycle. After ovulation they began to rise, reaching a plateau between 8 and 11 days, before falling in parallel with the decline in luteal progesterone secretion. The dependence of the inhibin secretion by the corpus lutem on pituitary gonadotrophins was investigated by the administration of an LHRH antagonist [N-Ac-D-Nal(2)1,D-pCl-Phe2,D-Trp3,D-hArg(Et2)6,D-Ala10 ]LHRH once daily for 3 days beginning on day 8 of the luteal phase in six macaques. LHRH antagonist treatment markedly suppressed serum levels of inhibin and progesterone and these remained at the level found in the follicular phase for the remainder of the luteal phase. These results show that inhibin in the macaque is secreted into the peripheral blood almost exclusively during the luteal phase, being highest when FSH is at its nadir. Suppression of serum inhibin concentrations during the luteal phase by LHRH antagonist suggests that its secretion is integrated with the LH control of the corpus luteum.

Animals↗
PubMed1988

Plasma inhibin levels in men with chemotherapy-induced severe damage to the seminiferous epithelium.

Immunoreactive plasma inhibin levels and free testosterone index (FTI) were estimated in 17 patients who had previously received combination chemotherapy for Hodgkin's disease and in 16 age-matched controls. In the same patients we had previously found significantly raised FSH and LH levels in the presence of normal basal and HCG-stimulated total testosterone levels. Mean plasma inhibin levels were not different between the patients (601 +/- 321 U/l) and controls (530 +/- 174 U/l) nor were FTI values (81.5 +/- 35 vs 91 +/- 47 respectively). There was a positive correlation (r = 0.53, P less than 0.05) between FSH and inhibin levels and a negative correlation between FSH and FTI (r = -0.51, P less than 0.05) in the patients but not in the controls. No such correlations with inhibin or FTI existed for LH but there was a positive correlation between LH and FSH levels in the patients. In four patients inhibin levels were pathologically raised and in this group mean FSH values (21.7 +/- 4.7 IU/l) were higher (P less than 0.001) and mean FTI (59.1 +/- 22.6) lower (P less than 0.001) than respective values (13.6 +/- 5.3 IU/l and 88.4 +/- 35) for the remainder of the patients. These data are not compatible with the hypothesis that inhibin is the major negative feedback signal for the control of FSH secretion.

Adolescent↗
PubMed1987

Male-factor infertility and in vitro fertilization.

In vitro fertilization (IVF) was developed primarily as a treatment for female and idiopathic infertility. However, with the discovery that relatively few sperm are required to achieve fertilization in vitro, it was proposed that IVF could be used also as an effective treatment for male-factor infertility. This review deals with the work that has been carried out by various groups in this area of male-factor infertility. As the standards of classification and the presentation of results vary from group to group, this also shows that there is a need for some standardization of how patient selection and the presentation of results are carried out in the area of male-factor infertility.

Cell Separation↗
PubMed1986

Kartagener's syndrome with motile cilia and immotile spermatozoa: axonemal ultrastructure and function.

A 35-yr-old infertile man with chronic sinobronchial disease and dextrocardia (Kartagener's syndrome) was found to have immotile sperm and motile nasal cilia in vitro. Ciliary beat frequency in vitro was normal, but in vivo nasal mucociliary clearance was markedly prolonged. Quantitative electron microscopy demonstrated a severe reduction in spermatozoal outer and inner dynein arms compared with normal (p less than 0.001) but normal numbers of outer doublets, central microtubules, and radial spokes were seen. In 2 samples of nasal cilia collected 14 months apart, the number of inner dynein arms was significantly reduced from normal (p less than 0.001), but normal numbers of radial spokes and microtubule structures were seen. Ciliary outer dynein arms were slightly reduced in 1 specimen (p less than 0.001) but were normal in the other. It is suggested that the reduction in the number of ciliary inner dynein arms does not affect ciliary motility in vitro but that, under the increased load of mucus in vivo, this defect prevents the cilia from functioning normally. The difference in axonemal ultrastructure between cilia and spermatozoa from the same patient further suggests a separate genetic control of their structural components.

Adult↗