Immunopathology of murine experimental allergic orchitis

Experimental allergic orchitis (EAO) was induced consistently in BALB/c mice by immunization with homologous testicular tissue homogenate emulsified in complete Freund's adjuvant (CFA) providing that the animals had received simultaneously at least 1 microgram of an extract of Bordetella pertussis rich in pertussigen. All animals thus treated developed orchitis and serum antibody to testicular antigens within 20 days after immunization. The lesions were located in testis (100%), rete testis (37%), cauda epididymis (21%), and vas deferens (37%). Ductus efferentes and caput epididymis were only rarely affected. Early lesions in the seminiferous tubules were characterized by peritubular and/or intratubular accumulation of eosinophils, neutrophils, lymphocytes, and macrophages. This was followed by aspermatogenesis. Late lesions included massive necrosis and extensive fibrosis of the seminiferous tubules. Disruption of blood-testis barrier on day 20 was evidenced by the detection of 1) perfused lanthanum deposits between Sertoli cells and surrounding inflammatory cells inside the seminiferous tubules, 2) deposits of endogenous mouse IgG in germinal epithelium, and 3) probable immune complexes (granular C3) surrounding seminiferous tubules. Murine EAO differed from that of the guinea pig in the lack of involvement of the ductus efferentes, the extensive necrosis, the abundant polymorphonuclear eosinophils in the lesion, and the exquisite requirement of concomitant injection of B. pertussis extract.     

In situ demonstration of both TUNEL-labeled germ cell and Sertoli cell in the cimetidine-treated rats

Cimetidine has caused dysfunction in the male reproductive system. In the rat testis, intratubular alterations and loss of peritubular tissue due to peritubular myoid cell death by apoptosis have been recently shown. Thus, the aim of this study is to evaluate which cells of the seminiferous epithelium have been affected and/or died by apoptosis after the treatment with cimetidine. For this purpose, an experimental group containing five male albino Wistar rats received intraperitoneal injections of cimetidine (50 mg/kg body weight) during 52 days. The testes were fixed with 4% buffered formaldehyde and were embedded in paraffin. For detection of DNA breaks (apoptosis) in the cells of the seminiferous epithelium, the testicular sections were treated by the TUNEL method (Apop-Tag Plus Peroxidase Kit). In the tubules affected by cimetidine, altered peritubular tissue, including the presence of TUNEL labeling in the myoid peritubular cells, were usually found. In these tubules, the seminiferous epithelium exhibited low density of germ cells and TUNEL-positive labeling in the germ cells of the basal compartment. The concomitant staining in both germ cells of the basal compartment and late spermatids suggest a sensitivity of these cells in the damaged tubules. Besides germ cells, TUNEL-positive Sertoli cells were also found in the injured seminiferous tubules. Thus, a relationship between dying germ cells and Sertoli cell damage and/or death must be considered in tubules where peritubular tissue has been affected by toxicants.     

Evaluation of single intratesticular injection of calcium chloride for nonsurgical sterilization of male Black Bengal goats (Capra hircus): a dose-dependent study

This study describes the induction of chemosterilization in three groups each of six adult male Black Bengal goats at 30 days after a single bilateral intratesticular injection of a calcium chloride (CaCl(2), 2H(2)O) solution at the doses of 10, 20 or 40 mg/kg body weight/testis, always in a 2 ml volume of normal saline. Another one group of animals received only 2 ml of normal saline per testis as a control. The induction of chemosterilization was measured using relative testicular weight as well as histomorphological parameters including seminiferous tubular architecture and germ cell association in seminiferous tubules along with morphology of the interstitial space. Biochemical markers included activities of testicular Delta(5), 3beta-hydroxysteroid dehydrogenase (Delta(5), 3beta-HSD), 17beta-hydroxysteroid dehydrogenase (17beta-HSD), catalase, glutathione peroxidase (GPx), glutathione S-transferase (GST) and superoxide dismutase (SOD) as well as monitoring the level of testicular thiobarbituric acid reactive substances (TBARS), conjugated dienes and reduced glutathione (GSH) content along with plasma concentrations of testosterone, LH and FSH. Histomorphological measures of testes showed total necrosis of testicular tissue at 30 days after an injection of either 20 or 40 mg CaCl(2) along with fibrosis in seminiferous tubules and interstitial spaces. Infiltration of leucocytes was observed with the 40 mg dose. Disintegration of germ cell arrangement in seminiferous tubules and washing out of germ cells from the tubules were noted with the 10mg dose. Relative organ weights, plasma concentrations of testosterone, testicular activities of Delta(5), 3beta-HSD, 17beta-HSD, catalase, GPx, GST, and SOD and testicular contents of GSH all were declined. Increases occurred in testicular TBARS, conjugated dienes and plasma concentrations of LH and FSH with each of the treatments by comparison with the control group. Plasma concentrations of cortisol and fasting blood sugar level as well as packed cell volume (PCV) and total plasma protein were recorded to monitor the changes of chronic stress in the experimental animals. Changes in these parameters were not significant. An intratesticular injection of calcium chloride at specified doses could be a suitable method of sterilization in preference to surgical castration of goats.     

Intercellular transport of steroids in the infused rabbit testis

Tritiated-pregnenolone and tritiated-testosterone were infused via the testicular artery into the rabbit testis in situ, in order to determine if steroids can pass the "blood-testis barrier". After various periods of infusion (5-60 minutes) the testis were frozen cryostat sections were cut and freeze-dried. Interstitium and tubules were isolated by micro dissection and radioactivity per mcg dry weight was measured in both tissue compartments. Radioactive steroids could be isolated from the interstitial tissue as well as from the seminiferous tubules. Levels of radioactivity in the testes after infusion of tritiated-pregnenolone varied from 4 to 50% of the infused dose and were found to be dependent on the type of perfusion medium and the duration of the perfusion. Separation and identification of the radioactive steroids after infusing tritiated prognenolone showed that pregnenolone and testosterone were the major radioactive steroids in both interstitium and seminiferous tubules. After infusion with tritiated-testosterone, both tritiated-testosterone (77%) and tritiated-androstenedione (23%) were dound in the seminiferous tubules. It is concluded that steroids can be transported from the Leydig cells to the seminiferous tubules.     

Serum and testis selenium concentrations and testis morphology in ram lambs of varying ages

Serum and testis selenium (Se) concentrations, body and testes weights, seminiferous tubule height and width measurements and percent of tubules containing luminal spermatozoa were determined in Se-treated (SSe) and control (NSe) crossbred ram lambs at 60, 90, 120, 150 and 180 days of age. With IM injections, SSe lambs received 3 mg of Se as selenite and NSe lambs received 0.9% saline at 30-day intervals throughout the study. For each age group, lambs were weighed, jugular vein blood collected and testes removed at the designated age. Serum and testis tissue samples for each lamb were assayed for Se, and testis tissue was also evaluated for histological parameters. For all parameters, only serum Se concentrations were affected (P<0.0001) by Se treatment; however, all other parameters were affected (P<0.0001) by age. For combined groups, mean testis Se concentration (0.33 ppm), testes weights, seminiferous tubule measurements and percent of tubules (82.2) containing luminal spermatozoa were greatest (P<0.05) at 180 days of age, and mean testis Se concentrations were significantly correlated with these testicular parameters. These data lend support to the hypothesis that the increase in concentration of testicular Se to adult concentrations (>0.3 ppm) around the time of puberty is associated with rapid testicular development and production of spermatozoa.     

Testosterone immunoreactivity in the seminiferous epithelium of rat testis: effect of treatment with ethane dimethanesulfonate

Androgens drive spermatogenesis by processes that are largely unknown. Direct effects on germ cells and indirect effects mediated via testicular somatic elements are currently under consideration, and specific localization of androgens in seminiferous tubules may provide information as regards this. Adult male rats were injected with ethane dimethanesulfonate (EDS; 75 mg/kg body weight) or vehicle. Testes were fixed and paraffin-embedded for localization of testosterone immunoreactivity 1 and 2 weeks after treatment, using the unlabeled antibody (PAP) technique. Plasma testosterone dropped from a pre-treatment level of 2.3 ng/ml to below 0.2 ng/ml 3 days after EDS injection and remained at low levels until the end of observation, accompanied by a progressive decrease in testicular weight. In the seminiferous tubules of vehicle-injected males, testosterone immunoreactivity was found in nuclei of spermatocytes and spermatids and in nuclei and the cytoplasm of Sertoli cells, and showed typical variations according to the stage of spermatogenesis. One week after EDS treatment, immunoreactivity had disappeared from the seminiferous epithelium. Two weeks after treatment, staining of germ cells was detected in two out of four males. The disappearance and reappearance of immunoreactivity coincided with the time course of EDS effects on rat Leydig cells, and we conclude that it corresponds to androgen specifically localized in fixed, paraffin-embedded tissue. Because staining of germ cell nuclei varied with the stage of spermatogenesis, the technique may detect a physiologically relevant androgen fraction; its location suggests that androgens may also directly affect certain germ cell stages.     

Establishment of spermatogenesis in neonatal bovine testicular tissue following ectopic xenografting varies with donor age

Ectopic testicular xenografting can be used to investigate spermatogenesis and as an alternative means for generating transgenic spermatozoa in many species. Improving the efficiency of spermatogenesis in xenografted testicular tissue will aid in the application of using this approach. The present study was conducted to evaluate age-related differences in the establishment of spermatogenesis in grafted testicular tissue from bulls between 2 and 16 wk of life. Testicular tissue was ectopically xenografted under the skin on the backs of castrated nude mice and subsequently evaluated for growth, testosterone production, and establishment of spermatogenesis 24 wk after grafting. The greatest weight increases occurred in donor tissue from calves of the ages 2, 4, and 8 wk compared with the ages of 12 and 16 wk. Recipient mouse serum testosterone concentration was at normal physiological levels 24 wk after grafting and no significant differences were detected between recipients grafted with testicular tissue from bull calves of different ages. The development of germ cells to elongated spermatids were observed in seminiferous tubules of grafts from donor calves of the ages 4, 8, 12, and 16 wk but not observed in grafts from 2-wk donors, which contained round spermatids as the most advanced germ cell stage. Grafts from 8-wk donors contained a significantly higher (10-fold) average percentage of seminiferous tubules with elongated spermatids than all other donor ages. These data demonstrate differences in the ability of testicular tissue from donor animals of different ages to establish spermatogenesis following ectopic testicular xenografting.     

Real-time observation of transplanted 'green germ cells': proliferation and differentiation of stem cells

To elucidate the mechanism of proliferation and differentiation of testicular germ cells, donor testicular germ cells labeled with enhanced green fluorescent protein (eGFP) were transplanted to recipient seminiferous tubules. The kinetics of colonization as well as of differentiation of the donor cells was followed in the same transplanted tubules (alive) under ultraviolet light. One week after transplantation, clusters of fluorescent cells were randomly spread as dots in the recipient seminiferous tubule, whereas non-homed cells flowed out from the testis to the epididymis. By 4 weeks after transplantation, green germ cells were observed with weak and moderate fluorescence along the recipient seminiferous tubule. By 8 weeks, proliferation and differentiation of the germ cells occurred, resulting in strong fluorescence in the middle part of the seminiferous tubule but in weak and moderate fluorescence at both terminals. The length of the fluorescent positive seminiferous tubule became longer. Detailed histological analyses of the recipient tubules indicated that the portions of the seminiferous tubule in weak, moderate, and strong fluorescence contained the spermatogonia, spermatogonia with spermatocytes, and all types of germ cells including spermatids, respectively. Thus, testicular stem cells colonized first as dots within 1 week, and then proliferated along the basement membrane of the seminiferous tubules followed by differentiation.     

A testis-mediated germline chimera production based on transfer of chicken testicular cells directly into heterologous testes

In this study, we proposed a testis-mediated germline chimera production system based on the transplantation of testicular cells directly into heterologous testes. The testicular cells of juvenile (4-wk-old) or adult (24-wk-old) Korean Ogol chickens with a recessive pigmentation inhibitory gene, with or without prior culture, were injected (2 x 10(7) cells/head) into the seminiferous tubules of juvenile or adult recipients with White Leghorn with a dominant pigmentation inhibitory gene in a 2 x 2 factorial arrangement. The localization of transplanted cells into the inner space of the seminiferous tubules was confirmed within 24 h after injection. Subsequent testcross analyses showed that 7.8% (5/64) of the recipients had chimeric status in their testes. The periods of time from transfer to hatching of the first progeny with black feathers were 38 and 45 days for adult cells transplanted into an adult recipient, 188 days for adult cells into a juvenile recipient, and 137 days for juvenile cells into a juvenile recipient. Culture of the testicular cells derived both colony-forming and monolayer-forming cells. The colony-forming cells were stained positively for periodic acid Schiff solution, and further reacted with anti-SSEA-1, anti-SSEA-3, and anti-SSEA-4 antibodies both before and after culture for 15 days. In conclusion, it may be possible to develop the testis-mediated germline chimera production technique, which extends the feasibility of genetic manipulations in avian species.     

Assessment of pubertal development of boars derived from ultrasonographic determination of testicular diameter

At the onset of puberty, seminiferous tubules rapidly increase in diameter, thereby occupying a greater proportion of the testis, resulting in a rapid increase in testicular size. The objective of the current studies was to evaluate ultrasonography for assessing testicular diameter, as a basis for ranking boars relative to their extent of pubertal development. In the initial study, prior to castration at 4, 5, 6, or 7 mo of age, testicular length and diameter were assessed by ultrasonography in 160 anesthetized boars. After castration, testes were weighed. Mean diameter of seminiferous tubules and percentage of the testis occupied by tubules were determined by histological evaluations of all testes. Testicular volume was calculated from length and diameter and was correlated with testicular weight (P < 0.001; r ≧ 0.78) within each of the four age groups. At 4 and 5 mo of age, testicular diameter correlated positively (P < 0.001) with diameter of seminiferous tubules; this relationship was not significant at older ages. In two subsequent studies, testicular diameter determined ultrasonographically in conscious boars was highly correlated (r > 0.8) when assessed twice on the same day, or when diameter of the right was compared with diameter of the left testis. Similarly, testicular diameter obtained initially at 92 d of age correlated positively (P < 0.001) with the diameter observed at older ages, but the magnitude of the relationship decreased as time between evaluations increased. These findings supported ultrasonographic determination of testicular diameter during early pubertal development, as a means to rank boars of similar chronological age for extent of pubertal development.     

Early stages of testicular differentiation in the rat

Summary The initial phases of the development of the seminiferous cords (future seminiferous tubules) were studied with histological techniques and with electron microscopy. On day 14 after fertilization, seminiferous cords are well differentiated in the anterior part of the testis near the mesonephric tubules. They comprise Sertoli cells which encompass the primordial germ cells. The Sertoli cells show an expanded clear cytoplasm and microfilaments beneath the outer surface; they differentiate complex contact zones. On day 13 a few cells localized near the mesonephric tubules display the characteristics of the Sertoli cells. These cells become more and more numerous. They aggregate and they form the seminiferous cords.The primordia of male gonads explanted in vitro on the mesonephros, realize testicular organogenesis in a synthetic medium. Adding 15% fetal calf serum to the medium prevents the morphogenesis of the testicular cords, although the Sertoli cells seem to differentiate morphologically and physiologically. In these gonads differentiation of the Sertoli cells was obtained but their aggregation and the morphogenesis of the seminiferous cords were prevented. This gives new insights into testicular morphogenesis and probably provides an experimental model for a new type of gonadal anomaly.     

Testicular histological examination of spermatogenetic activity in captive gorillas (Gorilla gorilla)

To clarify the reproductive state of male gorillas, we performed histological examinations on the testicles of 10 male gorillas (Gorilla gorilla). The testicular samples were obtained by autopsy, and ordinal histological preparations were made for light microscopy. The poor spermatogenesis of this species was characterized by the following findings: First, spermatogenesis was evident in only four samples. Meiosis progressed in two samples, but they lacked spermatogenesis. In the remaining four specimens, seminiferous tubules hyalinized without any sign of spermatogenesis. Second, seminiferous epithelia were thin even in the males in which spermatogenesis was observed. Third, degenerated seminiferous tubules were found in all specimens. Fourth, abnormally large syncytial cells were found in the tubules. Six stages in the epithelial cycle of the seminiferous tubules were identified. Testosterone staining made it clear that there were many Leydig cells with spherical or fusiform nuclei in an abundance of interstitial tissue. The relevance of the testicular architecture of gorillas to the mating system is discussed.     

Testicular torsion and its effects on the spermatogenic cycle in the contralateral testis of the rat

The aim of the present study was to evaluate the effects of unilateral testicular torsion on the contralateral testis with respect to the stages of the cycle of the seminiferous epithelium (CSE). Fifty-five male Wistar rats, 60 days old, were used. The animals were divided into 11 groups. Groups 1-5 were subjected to unilateral testicular torsion from 3 to 48 h, followed by detorsion. Groups 6-10 had unilateral orchiectomies after unilateral testicular torsion for 3 to 48 h. Animals constituting group 11 served as the control sham-operated group. All animals were killed after 2 months. The percentage of affected tubules (tubules showing pathological changes) in the contralateral testis was estimated based on the CSE stages. In the torsion/detorsion group, the percentage of affected tubules was significantly greater (58.6%) than in torsion/orchiectomy group (48.0%). Stages VI-XI of the spermatogenic cycle were the most affected when compared with the rest of the stages in each experimental group (P <0.05). These results show that stages VI-XI of the spermatogenic cycle, the stages associated with low antioxidant capacities, are the most sensitive to the effects of testicular torsion on the contralateral testis.     

Genetic variation in testicular development in mice of the C57BL/10ScSn, C57BL/6By and BALB/cBy strains and the CXB recombinant-inbred lines

When compared with C57BL/6By mice, BALB/cBy mice had testes that were 41% heavier at 60 days of age and seminiferous tubules that were 41% greater in cross-sectional area at 120 days. Absolute testicular weight did not increase between 60 and 120 days of age in either C57BL/6By or C57BL/10ScSn mice but did in BALB mice, paralleling changes in the size of the seminiferous tubules. Significant testicular growth took place over this age period in mice of all seven of the CXB recombinant-inbred (RI) strains of mice derived from a cross of the BALB/cBy and C57BL/6By strains. The wide range of phenotypes shown by adult recombinant mice, which ranged from those with significantly heavier testes than BALB to those with testes the same size (at 60 days) as those of C57BL/10ScSn mice, implied the existence of several separable factors affecting testicular size in adults. At 30 days of age the RI lines fell into two groups; one with small testes like C57BL/6By and the other with larger testes like BALB/cBy mice. The segregation pattern for prepubertal testicular weight was identical to that for the H-2 histocompatibility locus.     

Testicular development in Chinese Meishan boars

The developmental process of the testis and age-related changes in the morphology of rete testicular spermatozoa were investigated in Meishan boars at 1 to 364 days of age. Testicular weight and the diameter of seminiferous tubules increased rapidly until 150 to 180 days of age. Leptotene stage spermatocytes, round spermatids and spermatozoa were first found in the section of seminiferous tubules at 30 to 45, 60 and 75 days of age, respectively. However, after 105 to 120 days of age, most rete testicular spermatozoa were morphologically normal. These results indicate that Meishan boars reach puberty as early as 75 days of age, though the testes acquire the ability to produce morphologically normal spermatozoa at about 120 days.     

Evaluation of the safety and efficacy of testicular biopsies in llamas

Evaluation of the reproductive function of Lama glama is generally considered to be a challenging task due to the difficulty of obtaining representative semen samples. One method that has been proposed for evaluation of testicular function in these animals is histologic examination of testicular needle biopsies. This study was undertaken to examine the safety and efficacy of using needle biopsies to assess testicular function in this species. One randomly selected testicle from each of 16 sexually mature llamas was biopsied with a 14-gauge self-firing biopsy instrument. The llamas were evaluated over a 6-week period with thermography for temperature changes of the scrotum. At the end of the 6-week trial, the llamas were castrated and sections of each testis were fixed in Bouin's solution for histologic examination. Immediately prior to castration, an additional biopsy was taken from each testis to compare the tissue obtained via biopsy with sections from the corresponding testis obtained after castration. A qualitative grading scale was used to compare the seminiferous tubules from each testis. No difference was found between the biopsied and the nonbiopsied testes (P = 0.69). The percentage of normal tubules between the biopsied and the nonbiopsied sides also did not differ (P = 0.70). Furthermore, the percentage of normal seminiferous tubules did not differ between the needle biopsy samples and the corresponding tissue samples obtained at castration (P = 0.48). The number of round seminiferous tubules counted in each biopsy section ranged from 3 to 67. There was no significant difference in the thermographic images of the scrotum between the biopsied and the nonbiopsied testes. This study supports testicular biopsies as a safe and useful procedure in the evaluation of testicular function.     

Pubertal development of the boar: age-related changes in testicular morphology and in vitro production of testosterone and estradiol-17 beta

The responsiveness of testicular tissue, in terms of testosterone (T) and estradiol-17 beta (E2) production, to human chorionic gonadotropin (hCG) stimulation in vitro was assessed during pubertal development of the boar. A morphometric investigation was conducted concurrently to quantitate Leydig cell and seminiferous tubule changes in the testes of developing boars. Testicular volume percentage of seminiferous tubules increased from 36% at 40 days of age to a maximum of 72% at 190 days of age. Increases in tubular diameter were from 65 micrometers at 40 days of age to 236 micrometers at 250 days of age. Testicular volume percentage of Leydig cells decreased from 40% at 40 days of age to 10% at 250 days of age. Leydig cell number increased rapidly to 130 days of age, remained constant through 160 days, and then increased steadily to 220 days of age. Volume per Leydig cell changed little from 40 to 130 days of age, increased by 75% at 160 days, and declined thereafter. Total Leydig cell weight increased steadily from 40 to 160 days of age and then declined slightly. The capacity of Leydig cells for T production and testicular tissue for E2 production was greatest (P less than 0.05) after hCG stimulation in boars that were 130 and 160 days of age. In addition, sensitivity, as judged by the regression coefficient of T or E2 production per Leydig cell on log dosage of hCG was greater (p less than 0.05) for T at 130 days of age and for E2 at 160 days of age. The data presented support the hypothesis that one factor in pubertal development of boars is an increased capacity and sensitivity of the testes to gonadotropin stimulation.     

Sexual dimorphism in the regulation of meiotic process in the rabbit

Meiosis, mitosis, and apoptosis during fetal and postnatal periods were investigated in order to explore mechanisms of sexual dimorphism in initiation of germ cell meiosis. Gonads were obtained from Japanese white rabbits from 23 to 51 days postcoitum (dpc). Gonadal thin sections were stained with hematoxylin and eosin. Germ cell alkaline phosphatase and apoptosis were detected with histochemical and immunohistochemical methods, respectively. In the ovary, meiotic germ cells were initially recognized at 29 dpc and arrested after enclosure within follicles. Similarly, meiotic germ cells were recognized outside seminiferous tubules at 29 dpc, but no meiotic figures were identified in intratubular spaces. Apoptotic germ cells were not recognized in the intratubular spaces before 35 dpc, and no apoptotic figures were recognized in the ovary during the period studied. In conclusion, the initiation of meiosis in testicular interstitial tissue at the time comparable to that in the ovary indicates that germ cells of both sexes have the ability to enter meiosis during the same stage of fetal development; and it appears most likely that delayed initiation of meiosis in the intratubular space is attributable to meiosis-inhibiting substance(s) present in seminiferous tubules.     

Thorium induced testicular changes in rats.

Daily intraperitoneal administration of thorium nitrate produced progressive morphological and biochemical alterations with the increase in thorium concentration in rat testis. The degenerative changes in the seminiferous tubules increased with the duration of treatment and after 90 days calcification occurred in about 25% of the tubules and in the connective tissue of the tunica albuginea. The activity of adenosine triphosphatase and alkaline phosphatase increased markedly as a result of thorium administration. An attempt has been made to interrelate histopathological and enzymatic changes and the metal concentration in the testicular tissue.     

Selective destruction and regeneration of rat Leydig cells in vivo

Summary The effect of a single i.p. administration of ethane dimethanesulphonate (EDS) upon rat testicular histology was studied by light microscopy and morphometry up to 4 weeks after treatment. One day after injection the interstitial tissue exhibited degenerating Leydig cells, abundant pyknotic interstitial cells, deposition of cellular debris and extensive networks of fibrillar material. Macrophages contained greatly increased numbers of cytoplasmic inclusion bodies. From 3 to 7 days morphometric analysis showed that Leydig cells and cellular debris had disappeared from the interstitial tissue, leaving only macrophages, fibroblasts and lymphatic endothelial tissue. A very small number of new Leydig cells were seen on day 14, often located in peritubular or perivascular positions. Regeneration of foetal-like Leydig cells occurred by 4 weeks, their cytoplasm containing large lipid inclusions and, numerous Leydig cells were often observed closely applied to the walls of the seminiferous tubules. The observations suggest that, after experimental destruction and depletion of Leydig cells, an interstitial precursor cell, as yet unidentified, gives rise to a new Leydig cell population. EDS thus offers a valuable opportunity to study further the interactions between the seminiferous tubules and the interstitial tissue following the destruction and subsequent regeneration of the Leydig cells.