Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “Spermatogenesis”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 55 records · Page 3Linked to original sources
PubMed1999

[Human spermatogenesis: basic research and clinical issues].

Histological evaluation of human spermatogenesis suffers from the hazy border line between normal and pathological germ cell development. This border line needs better definition for histological fertility diagnosis and the early detection of germ cell tumors. Testicular biopsies from more than 2,900 patients with fertility disturbances and more than 1,900 patients with testicular tumors were investigated by means of semithin sectioning, different immunocytochemical methods and transmission electron microscopy. Cellular systems of the human testes possess a degree of autonomy from the body. Their morphological and functional heterogeneity reveals characteristics of cells that are not terminally differentiated. In the testis of an adult, fertile man not only the proliferation of spermatogonia, maturation divisions of spermatocytes and differentiation of spermatids take place, but also abortive germ cells, as well as apoptotic and degenerative cells appear. Disturbances of spermatogenesis are defined by the evaluation of quantity and quality of germ cell alterations. Compensatory and non compensatory defects of spermatogenesis may be distinguished. Deficiency of spermatogonial cell types, multilayered spermatogonia, megalospermatocytes, malformed spermatids and single tumor cells in the face of sufficient development of mature spermatids are considered compensatory defects of spermatogenesis. Dominating malformed germ cells or tumor cells accompanied by an arrest or lack of spermatogenesis, however, represent non-compensatory defects of spermatogenesis. In addition, normal organization and function of the microvasculature, Leydig cells and compartmentalizing cells in the intertubular space are prerequisites for spermatogenesis. The neuroendocrine function of Leydig cells may be responsible for regulating the blood flow rate and the permeability to hormones and nutritive substances. Finally, for patients a successful definition of the border line between normal and pathological events of germ cell development may be essential for early detection of germ cell tumors. Therefore, anatomical sciences not only contribute to basic research, advanced diagnostics and therapeutic concepts related to diseases of the male gonad, but also to the improvement of assisted reproduction.

Adult↗
PubMed2000

Microsurgical TESE and the distribution of spermatogenesis in non-obstructive azoospermia.

We wished to map the distribution of spermatogenesis in different regions of the testis in 58 men with non-obstructive azoospermia, and to develop a rational microsurgical strategy for the testicular sperm extraction (TESE) procedure. One goal was to maximize the chances for retrieving spermatozoa from such men, to minimize tissue loss and pain, and to preserve the chance for successful future procedures. Another goal was to expand upon the previously reported quantitative histological analysis of testicular tissue in 45 azoospermic men undergoing conventional TESE, this time using microsurgical as well as histological mapping. Tubular fullness observed at microsurgery and the presence of spermatozoa in the TESE specimen was compared with the quantitative histological analysis of spermatogenesis. Thus, our conclusions about the distribution of spermatogenesis are based on our experience with TESE in 103 consecutive cases of non-obstructive azoospermia. It was confirmed that men with non-obstructive azoospermia caused by germinal failure have a mean of 0 to 3 mature spermatids per seminiferous tubule in contrast to 17-35 mature spermatids per tubule in men with normal spermatogenesis and obstructive azoospermia. The former represented the threshold of quantitative spermatogenesis which must be exceeded in order for spermatozoa to 'spill over' into the ejaculate. Both testicular 'mapping' by multiple biopsy (n = 15) and microsurgical removal of contiguous strips of testicular tissue (n = 43) revealed a diffuse, rather than regional, quantitative distribution of spermatogenesis. A microsurgical approach resulted in the minimal amount of tissue loss and minimal-to-no pain (compared with the original 45 cases already reported). By this means it is often possible to immediately locate the few tubules with spermatogenesis at microsurgery, under local anaesthesia. But even in cases where greater amounts of tissue must be removed in order to find spermatozoa, the microsurgical TESE procedure prevents secondary testicular damage by protecting blood supply and preventing pain and atrophy from increased testicular pressure. Thus, future attempts at TESE-ICSI need not be compromised.

Biopsy↗
PubMed1999

Xenogeneic spermatogenesis following transplantation of hamster germ cells to mouse testes.

It was recently demonstrated that rat spermatogenesis can occur in the seminiferous tubules of an immunodeficient recipient mouse after transplantation of testis cells from a donor rat. In the present study, hamster donor testis cells were transplanted to mice to determine whether xenogeneic spermatogenesis would result. The hamster diverged at least 16 million years ago from the mouse and produces spermatozoa that are larger than, and have a shape distinctly different from, those of the mouse. In four separate experiments with a total of 13 recipient mice, hamster spermatogenesis was identified in the testes of each mouse. Approximately 6% of the tubules examined demonstrated xenogeneic spermatogenesis. In addition, cryopreserved hamster testis cells generated spermatogenesis in recipients. However, abnormalities were noted in hamster spermatids and acrosomes in seminiferous tubules of recipient mice. Hamster spermatozoa were also found in the epididymis of recipient animals, but these spermatozoa generally lacked acrosomes, and heads and tails were separated. Thus, defects in spermiogenesis occur in hamster spermatogenesis in the mouse, which may reflect a limited ability of endogenous mouse Sertoli cells to support fully the larger and evolutionarily distant hamster germ cell. The generation of spermatogenesis from frozen hamster cells now adds this species to the mouse and rat, in which spermatogonial stem cells also can be cryopreserved. This finding has immediate application to valuable animals of many species, because the cells could be stored until suitable recipients are identified or culture techniques devised to expand the stem cell population.

Acrosome↗
PubMed1994

The value of quantitative DNA flow cytometry of testicular fine-needle aspirates in assessment of spermatogenesis: a study of 137 previously maldescended human testes.

In order to assess the suitability of DNA flow cytometry of fine-needle aspirates for quantifying spermatogenesis, the results from DNA flow cytometry were compared to histological evaluation of testicular biopsies taken concomitantly from 171 previously maldescended testes. In 137 of 171 cases, sufficient material for flow cytometric as well as histological evaluation was obtained. Histological analysis of surgical biopsy specimens revealed spermatogenesis including the spermatid stage in 117 of the 137 gonads. In six of the 117 gonads no haploid cells were found using flow cytometry. On the other hand, surgical biopsies failed to reveal spermatogenesis in five cases in which the corresponding aspirates contained haploid cells. Both methods therefore seem equally sensitive in detection of spermatogenesis. Other types of histological patterns also corresponded to distinct DNA histograms. Thus, in 11 of 12 cases with Sertoli-cell-only pattern in all tubules, at least 95% of the cells had a diploid DNA content. Furthermore, predominance of tubules with maturation arrest at the primary spermatocyte level corresponded to an increased proportion of tetraploid cells. When compared to surgical biopsy, DNA flow cytometry of testicular fine-needle aspirates is a more objective, easy and rapid method, which is more convenient for the patient. This study has indicated that DNA flow cytometry is a suitable method of quantitative assessment of spermatogenesis. One of the first target groups might be men with azoospermia. In such men, DNA flow cytometric analysis of fine-needle aspirates and surgical biopsy are apparently of equal sensitivity in detecting gonads with spermatogenesis. We conclude that DNA flow cytometry may become an alternative method for the quantification of spermatogenesis.

Adult↗
PubMed1996

Moderate alcohol consumption and disorders of human spermatogenesis.

Environmental factors are suspected to be responsible in part for the deterioration in semen quality observed worldwide during the recent few decades. Alcohol might be one factor, considering the frequent changes in testicular function associated with heavy drinking. The dose-dependent effects of alcohol on human spermatogenesis are, however, not well known. We analyzed spermatogenesis and testicular tissue morphology of 195 men, aged 35-69 years, with computer-assisted microscopy in this autopsy study. The men were categorized into controls and four "consumption groups" according to the average daily alcohol consumption, which was determined on the basis of blind interviews with relatives and acquaintances. When the average daily alcohol consumption was 40 g or less, 59 (66%) of the 90 men showed normal spermatogenesis, whereas 31 (34%) had partial spermatogenic arrest (SA). Of the 31 men with average daily intake between 40 and 80 g, 17 (54%) showed normal spermatogenesis, 13 (42%) had partial or complete SA, and 1 man exhibited more severe testicular damage-"Sertoli cell only" (SCO) syndrome. Among men with daily intake between 80 and 160 g, only 13 of 35 men showed normal spermatogenesis (37%), 19 (54%) had partial or complete SA (odds ratio = 2.92), and 3 (9%) had the SCO syndrome (odds ratio = 16.85). The frequencies of spermatogenic disorders were similar in men drinking in excess of 160 g. Both SA and the SCO syndrome showed a clear dependence on daily dose; p < 0.0001 and p < 0.0004, respectively. We conclude that long-term average daily consumption of < 40 g of alcohol seems not to be associated with disorders of spermatogenesis. Consumption of moderate amounts of alcohol may affect semen quality more often than previously thought, whereas high alcohol consumption may even be associated with serious disorders of spermatogenesis.

Adult↗
PubMed1997

Incidence of disorders of spermatogenesis in middle aged finnish men, 1981-91: two necropsy series.

OBJECTIVE: To investigate if the incidence of disorders of spermatogenesis and testicular tissue morphology have changed in middle aged Finnish men over 10 years. DESIGN: Two necropsy series completed in 1981 and in 1991. SETTING: Department of Forensic Medicine, University of Helsinki, Finland. SUBJECTS: 528 men, aged 35 to 69 years, subjected to medicolegal necropsy. MAIN OUTCOME MEASURES: Scoring of spermatogenesis and morphometric analysis of testicular tissue components. Individual risk factors for testicular disorders obtained by postmortem blind interviews with acquaintances. RESULTS: Normal spermatogenesis was found in 41.7% of the men (mean age 53.1 years). Between 1981 and 1991, the ratio of normal spermatogenesis decreased significantly (odds ratio 3.5; 95% confidence interval 2.5 to 5.1) from 56.4% to 26.9%, with a parallel increase in the incidence of partial and complete spermatogenic arrest (2.1; 1.4 to 2.9 and 2.9; 1.7 to 5.0, respectively). During this period, the size of seminiferous tubules decreased, the amount of fibrotic tissue increased, and the weight of testicles decreased significantly. Alterations in testicular characteristics over time could not be explained by changes in body mass index, smoking, alcohol drinking, or exposure to drugs. CONCLUSIONS: The incidence of normal spermatogenesis decreased among middle aged Finnish men from 1981 to 1991, and the incidence of disorders of spermatogenesis and pathological alterations in testicles increased. Deteriorating spermatogenesis may thus be one important factor in the explanation of declining sperm counts observed worldwide.

Adult↗
PubMed2000

The effects of testicular denervation on spermatogenesis in the Sprague-Dawley rat.

In the rat, regression of spermatogenesis during the chronic stages of spinal cord injury (SCI) occurs in the presence of normal function of the pituitary-testis hormone axis, thus suggesting that nonendocrine mechanisms might be involved. The current study examined whether disruption of neural input to the testis contributes to the cascade that leads to the regression of spermatogenesis. Four weeks after denervation of the superior spermatic nerve (SSN), testis weight was 25% lower (p < 0.01) than that of the contralateral sham-operated testis. Defects in spermatogenesis including phagocytosis of mature spermatids, vacuolization of spermatid nuclei, delayed spermiation and incomplete cellular associations were observed in >60% of the tubules. In the remaining 30-40% of tubules, the seminiferous epithelium was severely regressed. While cutting the inferior spermatic nerve (ISN) alone did not affect spermatogenesis significantly, it enhanced the effect of SSN denervation on both spermatogenesis and testis weight (p < 0.01). Spermatogenesis was totally regressed in the SSN/ISN-denervated testes. At this time, quantitatively normal spermatogonial proliferation was maintained in SSN- or ISN-denervated testes. Twelve weeks after surgery, regression of the seminiferous epithelium characterized by absence of proliferating spermatogonia, while undifferentiating spermatogonia were present, was observed in all SSN-denervated testes. At this time, regression of the seminiferous epithelia also occurred in >30% of the tubules in ISN-denervated testes. At both times, serum follicle-stimulating hormone, luteinizing hormone and testosterone levels were normal and >60% of normal testicular testosterone concentrations were maintained in the denervated testes. These results indicate that disruption of neural input to the testis is not a cause for the decrease in spermatogonial proliferation during the acute phase of SCI, but may contribute to the chronic effects of SCI on spermatogenesis.

Animals↗
PubMed1988

Induction of precocious maturation of spermatogenesis in infant rats by human menopausal gonadotropin and inhibition by simultaneous administration of gonadotropins and testosterone.

This study was undertaken to determine if the initiation of spermatogenesis could be modified by the administration of gonadotropins and sex hormones in infant rats. Five-day-old rats were injected daily between the 5th and 11th days of life with test substances and killed on day 15. Administration of testosterone propionate (TP; 2.5 mg daily), human menopausal gonadotropin (hMG; 7.5 IU daily), or coadministration of both of these substances (TP + hMG) or administration of estradiol benzoate (15 micrograms daily) caused quantitative changes in premeiotic spermatogenesis, as measured by the mean cell counts per tubule cross-section. hMG caused an increased yield of type A1 spermatogonia (SgA1) from undifferentiated type A spermatogonia (UnA) and increased the yield of type B spermatogonia from SgA1. TP was not effective in stimulating first premeiotic spermatogenesis, and in contrast to hMG, it had a negative influence on the numbers of UnA and SgA1 and on the volume of Sertoli cell nucleus. Administration of TP + hMG or estradiol benzoate resulted in a significant increase in the numbers of UnA and SgA1, but inhibited cell differentiation. TP + hMG significantly reduced the rate of premeiotic spermatogenesis. The results demonstrate that precocious numerical stabilization of premeiotic spermatogenesis can be achieved by the application of hMG. TP applied alone was able to induce peripheral androgenic effects (seminal vesicle weight) 100% greater than those produced by administration of hMG, but was not able to stimulate seminal tubule function. TP applied together with hMG produced inhibition of spermatogenesis. This effect might be due to the inhibition of Sertoli cell function by the direct influence of testosterone. In contrast to testosterone, estradiol may play a stimulatory role in the multiplication of the reserve stem cells of the first spermatogenesis of the rat.

Animals↗
PubMed1996

Relationship among hormonal treatments, suppression of spermatogenesis, and testicular protection from chemotherapy-induced damage.

To further elucidate the mechanism by which hormonal pretreatment protects the rat testis from damage by procarbazine, we investigated the relationship between the suppression of hormone levels and spermatogenesis and the recovery of spermatogenesis from stem spermatogonia. LBNF1 rats were implanted with capsules containing testosterone or testosterone plus estradiol. After hormone treatment, rats were injected with procarbazine, and recovery of spermatogenesis was assessed. Testosterone (2 cm) plus estradiol (0.5-cm) reduced serum LH levels causing intratesticular testosterone (ITT) to fall to 3% of control levels within 2 weeks, but testis weights and sperm head counts were not appreciably suppressed until 4 weeks. Two weeks' hormone pretreatment, only slightly enhanced spermatogenesis recovery, but 4 weeks markedly increased it. Testosterone (2 cm) alone produced slower suppression of spermatogenesis and less protection from procarbazine than did testosterone plus estradiol implants, despite equivalent suppression of LH and ITT. Long testosterone implants (24-cm) partially maintained ITT at 14% of control despite undetectable LH levels, prevented any decline in sperm counts, and nearly completely abrogated the protective effect of the hormone treatment. Protection appeared to be best correlated with the testis weight reduction by hormone treatment. Thus, recovery of spermatogenesis after chemotherapy is dependent on the degree of suppression of spermatogenesis caused by the reduction of ITT levels at the time of chemotherapy and likely involves cells, such as the Sertoli cells, that are both androgen-responsive and affected by the numbers of germ cells present.

Animals↗
PubMed1993

Failure of combined follicle-stimulating hormone-testosterone administration to initiate and/or maintain spermatogenesis in men with hypogonadotropic hypogonadism.

In men with hypogonadotropic hypogonadism, prolonged treatment with LH and FSH induces spermatogenesis. To compare the respective role of exogenous testosterone and intratesticular testosterone on the induction and maintenance of spermatogenesis, 10 men with hypogonadotropic hypogonadism and without history of cryptorchidism were studied. They were treated with human gonadotropins (hMG; 150 IU FSH and LH and 1500 IU hCG, im, three times weekly) or pure FSH (150 IU, im, three times a week) and testosterone (T: 250 mg, im, once a week). Five men were treated first with hMG-hCG and then with pure FSH plus T. The other five men started with pure FSH plus T. Each treatment period lasted 24 months. In all men, hMG-hCG induced spermatogenesis after 24 months, with normal motility and quality. The combination of pure FSH and T was not able to induce spermatogenesis after 24 months. In addition, sperm count dropped dramatically to 0.3 +/- 0.1 x 10(6)/mL within 3 months and to 0 after 6 months when pure FSH and T followed [corrected] hMG-hCG. Plasma T levels were increased by both treatments, but significantly more after pure FSH and T (35.3 +/- 5.2 nmol/L) than after hMG-hCG (20.4 +/- 5.2 nmol/L; P < 0.05). Plasma estradiol levels after treatment with pure FSH and T were also increased, but the difference from those obtained during hMG-hCG treatment was not significant. In conclusion, in men with complete gonadotropin deficiency, FSH and exogenous T are not able to induce spermatogenesis. Furthermore, spermatogenesis induced by LH plus FSH (hMG-hCG) cannot be maintained when exogenous T replaced LH in the regimen. Thus, exogenous T is unable to replace LH (and intratesticular T) to induce spermatogenesis. These data are noteworthy in the prospect of male contraception after a complete blockade of gonadotropin activity.

Adult↗
PubMed2002

Maintenance of spermatogenesis in hypogonadotropic hypogonadal men with human chorionic gonadotropin alone.

OBJECTIVE: It is generally accepted that both gonadotropins LH and FSH are necessary for initiation and maintenance of spermatogenesis. We investigated the relative importance of FSH for the maintenance of spermatogenesis in hypogonadotropic men. SUBJECTS AND METHODS: 13 patients with gonadotropin deficiency due to idiopathic hypogonadotropic hypogonadism (IHH), Kallmann syndrome or pituitary insufficiency were analyzed retrospectively. They had been treated with gonadotropin-releasing hormone (GnRH) (n=1) or human chorionic gonadotropin/human menopausal gonadotropin (hCG/hMG) (n=12) for induction of spermatogenesis. After successful induction of spermatogenesis they were treated with hCG alone for maintenance of secondary sex characteristics and in order to check whether sperm production could be maintained by hCG alone. Serum LH, FSH and testosterone levels, semen parameters and testicular Volume were determined every three to six Months. RESULTS: After spermatogenesis had been successfully induced by treatment with GnRH or hCG/hMG, hCG treatment alone continued for 3-24 Months. After 12 Months under hCG alone, sperm counts decreased gradually but remained present in all patients except one who became azoospermic. Testicular Volume decreased only slightly and reached 87% of the Volume achieved with hCG/hMG. During treatment with hCG alone, FSH and LH levels were suppressed to below the detection limit of the assay. CONCLUSION: Once spermatogenesis is induced in patients with secondary hypogonadism by GnRH or hCG/hMG treatment, it can be maintained in most of the patients qualitatively by hCG alone, in the absence of FSH, for extended periods. However, the decreasing sperm counts indicate that FSH is essential for maintenance of quantitatively normal spermatogenesis.

Adult↗
PubMed2002

Comparative studies between in vivo and in vitro spermatogenesis of Japanese eel (Anguilla japonica).

In order to check the quality of in vitro spermatogenesis of Japanese eel, in vitrol 1-ketotestosterone (11-KT) induced spermatogenesis was compared with in vivo spermatogenesis induced by a single injection of human chorionic gonadotropin (hCG) in detail. DNA contents of germ cells from in vitro and in vivo testicular fragments were compared using flow cytometry. Since the in vitro result of flow cytometry showed prominent 1C peak including spermatozoa and spermatids, the reduction of DNA by meiosis was assumed to progress normally, (i.e., haploid spermatozoa were produced in this in vitro system). In the testes of in vitro culture, however, spermatozoa were not released into lumen. Furthermore, the number of mitotic divisions of the in vitro experiment (6 divisions) was fewer than that of in vivo (10 divisions). In electron microscopy observations, both of in vivo and in vitro spermatozoon had a crescent-shaped nucleus with a flagellum, and a single large spherical mitochondrion. However, the elongation of the sperm head was not sufficient and the mitochondrion was not always located at the anterior end as is observed for the spermatozoa obtained from hCG injected eels. Eel spermatogenesis related substance-11 (eSRS11) is homologue of histone H1 which is up-regulated during spermatogenesis. Using this probe, in vitro spermatogenesis was also evaluated in molecular levels. In Northern blot analysis, eSRS11 mRNA was detected in both in vivo and in vitro testes. However, the expression of in vitro was much weaker than that of in vivo. These differences indicate that the stimulation of 11-KT is not sufficient, and another factors are needed to induce complete spermatogenesis in vitro.

Amino Acid Sequence↗
PubMed2005

Expression of mucin genes in the human testis and its relationship to spermatogenesis.

In this study we investigate the expression pattern of mucin genes in the human testis and evaluate the relationship between the expression of mucin genes and impaired spermatogenesis in the human testis. Thirty human testis tissues were collected from patients undergoing diagnostic testicular biopsy to investigate the cause of infertility. One part of the tissue underwent histological observation, and the other part of the tissue was subjected to semiquantitative RT-PCR of mucin genes, that is, mucin1, 2, 3, 4, and 9. The relative amount of mucin mRNAs was calculated by densitometry using glyceraldehydes-3-phosphate dehydrogenase (GAPDH) as an internal control. The samples were histologically diagnosed as either obstructive azoospermia with normal spermatogenesis (n = 13) or non-obstructive azoospermia with impaired spermatogenesis (n = 17). In the human testis with normal spermatogenesis, mRNA expression of mucin1, 9, 13 and GAPDH were found, but RT-PCR products of mucin 2, 3 and 4 were not detected. In the testis with impaired spermatogenesis, however, RT-PCR product of mucin1 was not found. There was no difference in the other mucin mRNA expression patterns between the testis with either normal or impaired spermatogenesis. To our knowledge, this study is the first that has detected the mRNA of mucin9 and 13 in human testis. This study also shows that mucin1 expression might be closely related to spermatogenesis. Our findings should be substantiated by more direct evidence, such as mucin protein expression and localization.

Adult↗
PubMedDate not supplied

Suppression of growth hormone does not affect ongoing spermatogenesis in rats.

Recent evidence suggests that growth hormone (GH) may enhance physiologic processes, such as spermatogenesis, in addition to causing classical anabolic effects. We have previously shown that testosterone restores spermatogenesis in rats that were made azoospermic by immunization against gonadotropin-releasing hormone (GnRH). In this study, we investigated whether suppression of GH affects spermatogenesis and the ability of testosterone to restore spermatogenesis following immunization against GnRH and/or growth hormone-releasing hormone (GHRH). Twelve rats were actively immunized against GnRH (anti-GnRH), twelve rats were actively immunized against GHRH (anti-GHRH), six rats were immunized against both GnRH and GHRH (anti-GnRH/GHRH), and six rats served as controls. Two weeks after the second booster, six rats each from the anti-GnRH and anti-GHRH groups as well as the six anti-GnRH/GHRH rats received 24-cm testosterone-filled Silastic implants (T), and the remaining six rats from each of these groups received empty Silastic implants. All rats were euthanized 2 months later. Weights of testes and testicular sperm counts were determined. Serum testosterone, luteinizing hormone (LH), follicle-stimulating hormone (FSH), growth hormone (GH), and insulin-like growth factor-1 (IGF-1) concentrations were determined by radioimmunoassays. Serum GH and IGF-1 were suppressed in anti-GHRH rats. IGF-1 was partially restored by testosterone in anti-GHRH and in anti-GnRH/GHRH rats, but GH was restored to control value in anti-GnRH/GHRH rats. Serum LH and FSH were suppressed in anti-GnRH and anti-GnRH/GHRH rats, but only FSH was partially restored by testosterone. Suppression of GH did not affect maintenance of spermatogenesis. However, because T partially restored GH and IGF-1 levels in anti-GnRH/GHRH rats and because spermatogenesis was found to be restored in these rats, we conclude that GH does not play a role in the maintenance of spermatogenesis in adult rats, but it may be required for the replenishment of germ cells in experimentally induced regressed rat testes.

Animals↗
PubMed2000

Spermatogenesis and testicular tumours in ageing dogs.

Spermatogenesis was examined in testes from 74 dogs of various breeds without clinically detected testicular disease. A modified Johnsen score system was used to determine whether spermatogenesis deteriorates with ageing. The diameter of seminiferous tubules was measured in dogs without testicular disease to examine other possible effects of ageing on tubular performance. There appeared to be no relation between age and these variables. The influence of testicular tumours on spermatogenesis was also investigated in both affected and unaffected testes. The testes of 28 dogs with clinically palpable tumours and 21 dogs with clinically non-palpable tumours were investigated. In cases of unilateral occurrence of a tumour, impairment of spermatogenesis was observed only in the affected testis of dogs with clinically detected tumours. Bilateral occurrence of tumours, whether detected clinically or non-clinically, was associated with severe impairment of spermatogenesis. The prevalence of tumours increased during ageing. Eighty-six per cent of the clinically detected and 57% of the non-clinically detected tumours were found in old dogs. Multiple types of tumour and bilateral occurrence were very common. Seminomas and Leydig cell tumours were more frequent than Sertoli cell tumours. It was concluded that spermatogenesis per se did not decrease during ageing in dogs but the occurrence of testicular tumours increased with ageing and affected spermatogenesis significantly, as reflected by a lower Johnsen score.

Aging↗
PubMed1991

Reinitiation of spermatogenesis by exogenous gonadotropins in a seasonal breeder, the woodchuck (Marmota monax), during gonadal inactivity.

The present study was undertaken (1) to document structural and functional changes in the testes of seasonally breeding woodchuck during active and inactive states of spermatogenesis and (2) to evaluate the ability of exogenous gonadotropins to reinitiate spermatogenesis outside the breeding season. During seasonal gonadal inactivity, there were significant (P less than 0.05) reductions in volumes of several testicular features (testis, seminiferous tubules, tubular lumen, interstitial tissue, individual Leydig cells, Leydig cell nuclei, and Leydig cell cytoplasm) as compared with gonadally active animals. The diameter of the seminiferous tubules was decreased by 26%, and Leydig cell numbers also declined in the regressed testes. These changes were accompanied by a decline in testosterone (T) levels in both plasma and testis, and reduction in epithelial height of accessory reproductive organs. A hormonal regimen was developed that would reinitiate spermatogenesis in captive, sexually quiescent woodchucks. A combination of PMSG and hCG markedly stimulated testicular growth and function and restored spermatogenesis qualitatively. Quantitatively normal spermatogenesis was restored in 2 of 6 treated males. Morphometric analyses revealed substantial increases in seminiferous tubular diameter and in the volume of seminiferous tubules, tubular lumen, total Leydig cells, and individual Leydig cells in the hormone-treated animals. These increased values corresponded to 99, 75, 68, 51, and 200%, respectively, of the values measured in naturally active woodchucks. Leydig cell numbers, however, remained unchanged and approximated only 31% of the number found in naturally active testes. Hormonal stimulation also resulted in a significant rise in serum T as well as in the total content of testicular T, and a marked increase in epithelial height in various accessory reproductive glands. The most effective hormonal protocol for stimulating spermatogenesis was treatment with 12.5 IU of PMSG twice a week for 4 weeks followed by 12.5 IU of PMSG + 25 IU of hCG twice a week for 4 weeks.

Animals↗
PubMed1989

Quantitative assessment of the biological effects of follicle regulatory protein on dihydrotestosterone-maintained spermatogenesis in hypophysectomized rat.

Follicle regulatory protein (FRP) isolated from porcine ovarian follicles influences folliculogenesis through a paracrine mechanism. A similar protein has been found in the testes and seems to have some inhibitory effects on spermatogenesis when administered to intact male experimental animals. On the basis of female and male studies, it has been ascertained that the effects of FRP are at the level of gonads and not the pituitary or the hypothalamus. In the studies with intact males it was not possible to determine the exact site of FRP action on the testes. Dihydrotestosterone (DHT) has been shown to maintain spermatogenesis in hypophysectomized rats. In order to determine if the inhibitory effects of FRP are at steps prior to the formation of DHT, FRP was administered to hypophysectomized rats that were injected with DHT. Groups of adult rats were hypophysectomized and treated daily with FRP, DHT, FRP + DHT, or vehicle alone for 30 days. At necropsy, body, testes, prostate glands, and seminal vesicle weights were recorded. One testis and sexual accessory glands were fixed for histological evaluation. The contralateral testis was decapsulated, six 2 mm segments of seminiferous tubules, representing defined stages of spermatogenesis, were isolated by transillumination-assisted microdissection, and spermatogenic cells were quantified by DNA flow cytometry. Histologically, the seminiferous tubules of vehicle-treated hypophysectomized controls showed advanced regression. Rats treated with FRP alone showed similar degeneration. On the other hand, rats treated with DHT showed maintenance of spermatogenesis comparable to normal controls. The testes of rats treated with FRP + DHT were indistinguishable from those treated with DHT only. Flow cytometric quantification of germinal cells from all groups confirmed the histological findings. In this study FRP did not exert deleterious effects on DHT-maintained spermatogenesis. This finding suggests that the inhibitory effects of FRP on spermatogenesis in intact animals may not be a direct effect on spermatogenic cells but may impair androgen action or production or DHT formation.

3-Hydroxysteroid Dehydrogenases↗
PubMed1995

Regulation of beta-tubulin function and expression in Drosophila spermatogenesis.

In this study we examined two aspects of beta-tubulin function in Drosophila spermatogenesis: 1) beta-tubulin structural requirements for assembly of different categories of microtubules and 2) regulatory requirements for production of the correct tubulin protein level. In normal Drosophila spermatogenesis, the testis-specific beta 2-tubulin isoform supports multiple microtubule functions. Our previous work showed that another Drosophila isoform, beta 3, cannot support spermatogenesis, whereas a carboxyl-truncated form of beta 2, beta 2 delta C, can at least to some extent provide all of beta 2's normal functions, save one: beta 2 delta C cannot support organization of axonemal microtubules into the supramolecular architecture of the axoneme. Here, to test whether beta 2 carboxyl sequences can rescue the functional failure of the beta 3 isoform in spermatogenesis, we constructed a gene encoding a chimeric protein, beta 3 beta 2C, in which beta 3 sequences in the carboxyl region are replaced with those of beta 2. Unlike either beta 3 or beta 2 delta C, beta 3 beta 2C can provide partial function for both assembly of axonemal microtubules and their organization into the supramolecular architecture of the axoneme. In particular, the beta 2 carboxyl sequences mediate morphogenesis of the axoneme doublet tubule complex, including accessory microtubule assembly and attachment of spokes and linkers. However, our data also reveal aspects of beta 2-specific function that require structural features other than the primary sequence of the isotype-defining variable regions, the C terminus and the internal variable region. Tests of fecundity in males that coexpress beta 2 and the chimeric beta 3 beta 2C protein showed that in Drosophila there are differential requirements for sperm motility in the male and in the female reproductive tract. Since some aspects of microtubule function in spermatogenesis are sensitive to the tubulin pool size, we examined the mechanisms for control of tubulin protein levels in the male germ cells. We found that both beta 2-tubulin mRNA accumulation and protein synthesis are dependent on gene dose, and that the level of expression is regulated by 3' noncoding sequences in the beta 2 gene. Our data show that the regulatory mechanisms that control tubulin pool levels in the Drosophila male germ line differ from those observed in cultured animal somatic cells. Finally, expression of transgenic constructs is consistent with early cessation of X chromosome expression in Drosophila spermatogenesis.

Amino Acid Sequence↗