Testicular development in cynomolgus monkeys

The testes from 136 male cynomolgus monkeys were examined histopathologically in order to investigate the relationship between the development of spermatogenesis and testis weight, age, and body weight. At Grade 1 (immature), Sertoli cells and spermatogonia were the only cell classes in the testis. At Grade 2 (pre-puberty), no elongated spermatids were observed in the testis, although a few round spermatids and small lumen formation were observed. At Grade 3 (onset of puberty), all classes of germ cells were observed in the testis, although seminiferous tubule diameters and numbers of germ cells were small. Slight debris in the epididymis was observed in almost all animals. At Grade 4 (puberty), almost complete spermatogenesis was observed in the seminiferous tubules and it was possible to ascertain the spermatogenesis stage as described by Clermont, although tubule diameters and numbers of germ cells were small. There was less debris in the epididymis than at Grade 3. At Grade 5 (early adult), complete spermatogenesis was observed in the seminiferous tubules. At Grade 6 (adult), complete spermatogenesis in the seminiferous tubules and a moderate or large number of sperm in the epididymis were observed. Moreover, sperm analysis using ejaculated sperm was possible. Logistic regression analysis showed that testis weight is a good indicator of testicular maturity.     

Carcinoma in situ of the testis in infertile men. A histological, immunocytochemical, and cytophotometric study of DNA content

Of 723 infertile men (128 with a history of cryptorchidism) whose testes were biopsied at the outer lateral face of the testis, five presented carcinoma in situ (CIS) in one testis. These testes were removed, serially sectioned, and examined by light microscopy. In order to evaluate whether only one or two biopsies are sufficient to diagnose CIS, before sectioning the testes four biopsies were taken at the anterior face, posterior face, superior pole, and inferior pole of the testis, respectively. Two of the five men had undergone orchiopexy in infancy and the testis contained tubules with Sertoli cells and isolated spermatogonia. CIS was also present in some tubules that were principally located near the rete testis. Of the four simulated biopsies, only that performed at the posterior face of the testis revealed CIS. The other three infertile men showed tubules with complete, although reduced, spermatogenesis, and tubules lined by Sertoli cells only. CIS was found in both types of tubules. These tubules with CIS formed lobules that extended throughout the testicular parenchyma. Most simulated biopsies performed in these three testes showed CIS. The average nuclear DNA content of CIS cells was about 4c in all testes. This content was similar both in tubules with complete spermatogenesis and in tubules with Sertoli cells only.     

Immunohistochemical study of flotillin-1 in the rat testis during postnatal development

The level and cellular localization of fotillin-1, a lipid raft protein, was examined in the testis of rats during postnatal development and spermatogenesis in order to determine if flotillin-1 is involved in testicular development. The testes of rats were sampled on postnatal days 7, 14, 21, 40, and 60, and analyzed by Western blot and immunohistochemistry. Western blot analysis detected flotillin-1 in the testes at days 7 and 14 after birth but the level decreased significantly at postnatal days 21, 40 and 60. At postnatal days 7, 14, 21, and 40, flotillin-1 immunolocalization was observed mainly in the Sertoli cells. However, there was little flotillin-1 immunolabeling in the spermatogenic cells from the seminiferous tubule of the testes. In the seminiferous tubule of the testes at postnatal day 60, flotillin-1 immunoreactivity in the Sertoli cells varied according to the stages of the spermatogenic cycle; intense immunoreactivity being observed in stages IX–III and less in stages IV–VIII. These results suggest that flotillin-1 participates in the developmental process of Sertoli cells and is involved in the regulation of spermatogenesis.     

A sertoli cell-specific knockout of connexin43 prevents initiation of spermatogenesis

The predominant testicular gap junctional protein connexin43 (cx43) is located between neighboring Sertoli cells (SCs) and between SCs and germ cells. It is assumed to be involved in testicular development, cell differentiation, initiation, and maintenance of spermatogenesis with alterations of its expression being correlated with various testicular disorders. Because total disruption of the cx43 gene leads to perinatal death, we generated a conditional cx43 knockout (KO) mouse using the Cre/loxP recombination system, which lacks the cx43 gene solely in SCs (SCCx43KO), to evaluate the SC-specific functions of cx43 on spermatogenesis in vivo. Adult SCCx43KO(-/-) mice showed normal testis descent and development of the urogenital tract, but testis size and weight were drastically lower compared with heterozygous and wild-type littermates. Histological analysis and quantitation of mRNA expression of germ cell-specific marker genes revealed a significant reduction in the number of spermatogonia but increased SC numbers/tubule with only a few tubules left showing normal spermatogenesis. Thus, SC-specific deletion of cx43 mostly resulted in an arrest of spermatogenesis at the level of spermatogonia or SC-only syndrome and in intratubular SC clusters. Our data demonstrate for the first time that cx43 expression in SCs is an absolute requirement for normal testicular development and spermatogenesis.     

Molecular cloning and expression of a novel alternative splice variant of BRDT gene

In this study, a human adult testis cDNA microarray was constructed and hybridized with (33)P-labeled human adult testis, embryo testis and sperm cDNA probes, respectively. A novel alternative splice variant of BRDT gene, named BRDT-NY, presumably involved in testicular function was cloned. It was expressed 3.96-fold more in human adult than embryo testis and also expressed in human spermatozoa. Similarly, RT-PCR revealed a differential expression pattern of this gene in human adult testes and fetal testes. The full length of BRDT-NY was 3438 bp and contained a 2883 bp open reading frame, encoding a 960-amino-acid protein. Sequence analysis showed that it has two bromodomains in N-terminal of the protein. Multiple tissue RT-PCR results showed that BRDT-NY was exclusively expressed in testis. mRNA expression of BRDT-NY gene was deleted in some azoospermic patients' testes. These experiments suggested that BRDT-NY gene may have an important role in the process of spermatogenesis and may be correlated with male infertility.     

The testicular position and descent in developing human

AimThe present study aimed at reevaluating and providing a more comprehensive knowledge of position and descent of the testis.Materials and methodsThe position and descent of testis was studied on 104 male formalin fixed human fetuses in the Department of Anatomy, RIMS, Imphal. The fetuses were dissected and the location of the testes and the extent of the gubernaculum were noted. Special staining was done using Weigert's iron hematoxylin and Van Gieson's stain.ResultsThe testes were located, in the earliest specimen of the present series, retroperitoneally in the lower abdomen at L3–4 level. Left testis was usually at a lower level than the right. Testicular descent was observed earliest at 24 weeks of intra-uterine life (IUL) and 100% successful complete bilateral descent by 36 weeks IUL. Descent through the inguinal canal was rapid and no case of undescended testis was encountered. The testicular descent was symmetrical in majority of the cases except in 7 where the descent was asymmetrical with the left descending earlier. Structural changes in gubernaculum but not its contraction played a role in testicular descent.ConclusionThus, a comprehensive and thorough knowledge of the testicular descent will assist in management of cases related with testis, especially the undescended and ectopic testis.     

Reproduction in male swamp wallabies (Wallabia bicolor): puberty and the effects of season

This study describes pubertal changes in testes and epididymides and seasonal changes in the adult male reproductive organs and plasma androgen concentrations of the swamp wallaby (Wallabia bicolor). Pre-pubescent males had testes with solid seminiferous cords and spermatogenesis only to the stage of gonocytes. Their epididymides had empty lumina along their entire length. The testes of three males undergoing puberty had some lumen formation and mitotic activity. Their epididymides were similar in appearance to those of adult males but were entirely devoid of any cells within the lumen of the duct. Three other pubescent males showed full lumen formation in the testes and spermatogenesis up to the elongating spermatid stage. Their epididymides were similar in appearance to those of adult males but with no spermatozoa in the duct. However, cells of testicular origin were found in the lumen of the duct in all regions suggesting that testicular fluids and immature germ cells shed into the rete testes flow through the seminiferous tubules into the epididymis before the release of mature testicular spermatozoa. The weights of testes and epididymides of adult males showed no change throughout the year but prostate weight and plasma androgen concentrations varied significantly with season, with maximums in spring and summer and minimums in winter. The volume fraction of Leydig cells and seminiferous tubules was significantly lower in winter than in summer; but, despite this, maturing spermatozoa were found in the testes throughout the year. Females in the area conceived year-round, suggesting that seasonal changes in the male reproductive tract did not prevent at least some males from breeding throughout the year.     

Multinucleated spermatogonia in cryptorchid boys: A possible association with an increased risk of testicular malignancy later in life?

At birth, undescended testes contain germ cells, but after 1 year of life, a reduced number of germ cells is generally found. Microlithiasis and carcinoma-in-situ-testis occur in cryptorchid boys. Multinucleated germ cells, including at least 3 nuclei in the cell, exist in impaired spermatogenesis and in the senescent testis. AIM OF THE STUDY: We investigated whether multinucleated spermatogonia were present in undescended testes of cryptorchid boys, and if such a pattern is associated with special clinical features. RESULTS: Multinucleated spermatogonia occurred in 13/168 (8%) of 163 consecutive cryptorchid boys, who underwent surgery for cryptorchidism with simultaneous testicular biopsy showing seminiferous tubules. The patients with multinucleated spermatogonia more often exhibited a normal germ cell number (Fisher's exact test, p<0.0005), and were younger at surgery (Mann Whitney, p<0.005) than the rest of the patients. Before surgery, 3 patients underwent treatment with Erythropoietin because of renal failure. An intra-abdominal testis underwent clipping and division of the spermatic vessels, and a biopsy at final surgery 7 months later, exhibited multinucleated spermatogonia. In 1 case the undescended testicular position, a fixed retraction, was acquired after surgery for an inguinal hernia. Multinucleated spermatogonia were found in cases of carcinoma-in situ-testis in 2 cryptorchid boys. No case of multinucleated germ cells appeared in our normal material. CONCLUSION: Multinucleated spermatogonia are a further abnormality present in cryptorchidism. The cryptorchid boys with multinucleated spermatogonia in general exhibited rather many germ cells. This feature may be associated with an increased risk of testicular malignancy later in life, and we propose a careful follow up regime in these cases including ultrasound examination and a testicular biopsy in cases of symptoms or clinical findings.     

Development, structure and function of the cranial suspensory ligaments of the mammalian gonads in a cross-species perspective; their possible role in effecting disturbed testicular descent

The present review aims to present a perspectiveon a relatively unknown part of the mammalian internal genitalia: their cranial suspensory apparatus.This apparatus shows wide divergence of development when examined during the fetal period or during adulthood, in males or females, or in individuals across a variety of species. In rats and other mamalian species the apparatus undergoes a distinct patern of sexually dimorphic development and fetal testicular androgens are proposed to play a key role in this process. Extensive development of this suspensory apparatus in females is argued to be a part of the anatomical adaptations of the genital apparatus to support the internal genitalia throughout pregnancy, including the relatively enormous growth towards the time of parturition. Minor development of this apparatus in males is judged to be a part of the anatomical requirements allowing developing testes to become displaced from the dorsal abdominal wall during the first stage of testicular descent. Extensive development of this suspensory apparatus in males generally seems to hinder testicular descent. Accordingly, the apparatus is well developed in so-called testicond species which do not show testis descent as a part of their normal male genital development. Furthermore, arguments are adduced that inappropriate and extensive development in species with testis descent may be a key aetiological factor in the disturbance of this process. Diagnosis and treatment of human cryptorchidism might profit from including an analysis of the development and function of (remnants of) the cranial testicular and epididymal suspensory apparatus.     

Neonatal exposure of male rats to estradiol benzoate causes rete testis dilation and backflow impairment of spermatogenesis

Estrogens administered to perinatal rodents cause spermatogenesis impairment; this study was undertaken to determine the mechanisms by which estrogens exert this effect. Neonatal male Wistar rats received estradiol benzoate (either 0.5 mg/5g BW or 1 mg/5g BW) and were killed at days 10, 22, 33, 45, and 60. Controls received vehicle. In tubule cross-sections of transverse sections of the right testes, 1) tubular diameter (TD) and seminiferous epithelium height (SEH) were measured, 2) normal and impaired spermatogenesis were classified in terms of the most advanced germ cell type present, including tubules lined by Sertoli cells only. A significant dose-dependent rise in the tubule percentage lined by Sertoli cells only at day 60 reflected spermatogenesis impairment. This was evidenced by the presence of multinucleated germ cells in a thin epithelium and sloughed into an enlarged tubular lumen, which was reflected in a significant dose-dependent increase in TD/SEH values from day 22 onward. TD was significantly greater and SEH significantly lower in tubular segments located at the cranial than the caudal halves of rat testes treated with the high (days 22, 33, and 60) and the low dose (day 33). This indicated distension in cranial tubular segments, perhaps due to the fact that these segments were the closest to the dilated rete testis. Consequently, they showed the highest TD/SEH values and the most regressive features of spermatogenesis (tubules lined by Sertoli cells only). In contrast, caudal segments in rat testes treated with the low dose showing TD/SEH values similar to controls displayed a delayed maturation of spermatogenesis coinciding with the late appearance of mature Leydig cells. Anat. Rec. 252:17–33, 1998. © 1998 Wiley-Liss, Inc.     

Correlation between testicular biopsies (prepubertal and postpubertal) and spermiogram in cryptorchid men

Twenty-one young men who underwent testicular biopsy and orchidopexy in infancy consulted owing to infertility and had biopsies again. The first and second biopsy specimens from these patients were compared by means of a semiquantitative study of the seminiferous tubules to evaluate the evolution of germ cells and to correlate these data with spermatozoon numbers. The infant testes showing lesions were classified into 3 types according to the mean tubular diameter and tubular fertility index: (1) slight lesions, (2) marked germinal hypoplasia, and (3) severe germinal hypoplasia. In the adult testes, spermatogenesis was evaluated by calculating the average numbers of spermatogonia, primary spermatocytes, young spermatids, and mature spermatids. These testes were classified as (1) normal; (2) having lesions in the adluminal compartment; (3) having lesions in the basal compartment; and (4) mixed atrophy. The number of differentiated spermatids was correlated with the expected number of spermatozoa in the ejaculate by a power regression curve. The observation of certain histologic lesions in the seminiferous tubules was assumed to indicate excretory duct obstruction: ectasia, indented outline of the seminiferous epithelium, intratesticular spermatocele, apical cytoplasmic vacuolation of Sertoli cells, and mosaic distribution of testicular lesions. There was a correlation between the prepubertal lesions and the degree of spermatogenesis in postpubertal biopsy specimens. The evolution of the 40 testes without regard to their location in infancy (cryptorchid or scrotal) was as follows. The 14 infant testes with a normal histologic pattern (5 testes) or minor lesions (9 testes) evolved to testes with lesions of the adluminal compartment (8 testes), mixed atrophy (4 testes), or lesions of the basal and adluminal compartments (2 testes). The 6 testes with marked germinal hypoplasia evolved to testes with mixed atrophy. The 20 testes with severe germinal hypoplasia evolved to testes with mixed atrophy (17 testes), Sertoli-cell-only tubules (2 testes), or lesions in the basal compartment (1 testis). In the 9 patients with a histologic pattern of obstruction bilaterally (6 men) or unilaterally (3 men), the expected number of spermatozoa according to the correlation curve was much higher than the actual number in the spermiogram. This means that the testes of many azoospermic men produce spermatozoa, and this finding corroborates the importance of testicular biopsy in infertility studies.     

Cell-cell interactions in the control of spermatogenesis as studied using leydig cell destruction and testosterone replacement

This review centers around studies which have used ethane dimethane sulphonate (EDS) selectively to destroy all of the Leydig cells in the adult rat testis. With additional manipulations such as testosterone replacement and/or experimental induction of severe seminiferous tubule damage in EDS-injected rats, the following questions have been addressed: (1) What are the roles and relative importance of testosterone and other non-androgenic Leydig cell products in normal spermatogenesis and testicular function in general? (2) What are the factors controlling Leydig cell proliferation and maturation? (3) Is it the Leydig cells or the seminiferous tubules (or both) which control the testicular vasculature? The findings emphasize that in the normal adult rat testis there is a complex interaction between the Leydig cells, the Sertoli (and/or peritubular) cells, the germ cells, and the vasculature, and that testosterone, but not other Leydig cell products, plays a central role in many of these interactions. The Leydig cells drive spermatogenesis via the secretion of testosterone which acts on the Sertoli and/or peritubular cells to create an environment which enables normal progression of germ cells through stage VII of the spermatogenic cycle. In addition, testosterone is involved in the control of the vasculature, and hence the formation of testicular interstitial fluid, presumably again via effects on the Sertoli and/or peritubular cells. When Leydig cells regenerate and mature after their destruction by EDS, it can be shown that both the rate and the location of regenerating Leydig cells is determined by an interplay between endocrine (LH and perhaps FSH) and paracrine factors; the latter emanate from the seminiferous tubules and are determined by the germ cell complement. Taken together with other data on the paracrine control of Leydig cell testosterone secretion by the seminiferous tubules, these findings demonstrate that the functions of all of the cell types in the testis are interwoven in a highly organized manner. This has considerable implications with regard to the concentration of research effort on in vitro studies of the testis, and is discussed together with the need for a multidisciplinary approach if the complex control of spermatogenesis is ever to be properly understood.     

Smad2和Smad4在家猫睾丸发育和精子发生中的表达与定位

目的 研究转化生长因子β(TGF-β)超家族的下游信号转导分子Smad2和Smad4蛋白,在不同发育阶段家猫睾丸中的表达和定位,探索Smad2和Smad4蛋白与家猫睾丸发育和精子发生的关系. 方法 应用免疫组织化学技术,研究Smad2和Smad4蛋白在幼年(n=3)、青春期(n=3)和性成熟(n=18)睾丸中的定位,并通过Western blotting技术对免疫组织化学中所用抗体的特异性进行了检测. 结果 免疫组织化学结果显示,Smad2和Smad4蛋白定位于各发育阶段家猫睾丸的生殖细胞、支持细胞和间质细胞的胞质中;Western blotting结果显示,多克隆兔抗Smad2和Smad4抗体与家猫睾丸蛋白提取物中分子量约为58kD、66kD的蛋白条带发生免疫阳性反应. 结论 Smad2和Smad4蛋白在家猫睾丸发育和精子发生的各个阶段均有表达,提示其参与睾丸发育和精子发生的调节.     

Development and Morphogenesis of Testis in Human Fetuses

Development and maturation of prenatal testis was studied on 104 human male fetuses. At 9 weeks, the testes were seen as elongated yellowish tissue superolateral to the developing urinary bladder and medial to mesonephros. The testis assumed ellipsoidal shape at 13 weeks. At about 16 weeks, the testes developed convexity on its anterior aspect. Epididymis and testis were at the same level until 20 weeks thereafter the upper testicular pole was encroached upon by the epididymis, with complete encroachment till its anterior aspect at 24 week. The sinus was also distinctly present between the two. The testis assumed miniature adult testis at term, but its size was approximately 1/15th of the adult. Cytoarchitecture of the testis at 9 weeks revealed radially disposed sex cords. At 13 weeks, tunica albuginea,tubular organization in the parenchyma and the Leydig cells were identifiable. At 17 weeks, tunica vasculosa and incomplete lobules were apparent. At 24 weeks, testis was marked by more but solid seminiferous tubules lined by 4–5 germ layers. Leydig cells were also identifiable till 24 weeks. Spermatogenic cells, both pale and dark type were distinguishable although pale spermatogonia were more numerous than dark cells. 28 weeks onwards tunica vaginalis and complete septa in the testicular parenchyma were evident. Moreover, the seminiferous tubules developed central vacuolation. By 30 weeks, seminiferous tubules became more complex as evident by their increase in number and coiled and tortuousity. At term, the fetal testis had not yet attained the cytoarchitecture of the adult testis suggesting that testicular maturation continues postnatally.     

Focal orchitis in undescended testes: discussion of pathogenetic mechanisms of tubular atrophy.

OBJECTIVE: To evaluate seminiferous epithelium lesions in adult cryptorchid testes showing lymphoid infiltrates in seminiferous tubules and interstitium (i.e., focal orchitis). Also, to consider the possible role of this lesion in the etiology of tubular atrophy. METHODS: We performed a histopathologic study of the cryptorchid testes and adjacent epididymides removed from 50 adult men who had not been previously treated for cryptorchidism. The study included morphologic and semiquantitative evaluation of seminiferous tubule pathology (according to germ cell numbers), Sertoli cell morphology, tubular lumen dilation, rete testis pattern (normal, hypoplastic, or cystic), and epididymal pattern (normal or epididymal duct hypoplasia). The study also included immunohistochemical evaluation of immune cell markers. The results were compared with clinical and laboratory findings. RESULTS: Focal lymphoid infiltrates (mainly lymphocytes) in seminiferous tubules and interstitium were found in 22 patients (44%), all of whom had unilateral cryptorchidism. The course of orchitis was asymptomatic, and laboratory data were normal. According to the seminiferous tubule pathology, a variety of histopathologic diagnoses, were made: (1) mixed atrophy consisting of Sertoli cell-only tubules intermingled with tubules showing maturation arrest of spermatogonia (11 testes, 4 of which also showed hyalinized tubules); (2) Sertoli cell-only tubules plus hyalinized tubules (4 testes); (3) Sertoli cell-only tubules (3 testes); (4) intratubular germ cell neoplasia (2 testes, 1 of which also showed hyalinized tubules); (5) complete tubular hyalinization (1 testis); and (6) tubular hyalinization plus some groups of tubules with hypospermatogenesis (all germ cell types were present although in lower numbers, 1 testis). Dysgenetic Sertoli cells, that is, Sertoli cells that had undergone anomalous, incomplete maturation, were observed in all nonhyalinized seminiferous tubules with inflammatory infiltrates. Tubular ectasia was observed in 13 cases. The rete testis was hypoplastic and showed cystic transformation in 18 testes, and the epididymis was hypoplastic in 15 testes. CONCLUSIONS: The causes of these focal inflammatory infiltrates are unknown. It is possible that tubular ectasia and Sertoli cell dysgenesis are involved and that these alterations cause a disruption of the blood-testis barrier and allow antigens to enter the testicular interstitium, giving rise to an autoimmune process.     

Three‐dimensional structure of seminiferous tubules in the adult mouse

Seminiferous tubules develop from sex cords, which are embryonic structures with simple C‐shaped arches. Histologically, the epithelium of adult mouse seminiferous tubules has been divided into 12 stages based on the associations of spermatogenic cells in four cycles of spermatogenesis. However, the gross characteristics of the seminiferous tubules themselves, including their number, length, run, and mutual relationships remain largely unknown. In the present study, we analyzed all seminiferous tubules in a single adult mouse testis with high resolution using serial paraffin sections and high‐perfomance three‐dimensional reconstruction software. There were 11 seminiferous tubules with an average length of 140 mm. Each tubule ran along circular paths within the testis while making convolutions with cranial and caudal hairpin turns. The cranial turns of all tubules were in contact with the tunica albuginea, whereas the caudal turns were not, resulting in funnel‐shaped networks of these tubules with tapered caudal portions. The caudally located networks surrounded the preceding cranially located networks from the bottom and outside, similar to stacked paper cups. Five out of the 11 seminiferous tubules were continuous from one end to the other both connected with the rete testis (10 connection points). Nine branching points, one blind end, and 18 more connection points with the rete testis were detected in the remaining six seminiferous tubules, making the paths of these tubules complicated to various degrees. The present study revealed that the 3D structures of seminiferous tubules were highly regular as a whole in the adult mouse testis.     

Atypical development of Sertoli cells and impairment of spermatogenesis in the hypogonadal (hpg) mouse

Testes of hypogonadal (hpg) mice show arrested postnatal development due to congenital deficiencies of gonadotrophin-releasing hormone (GnRH) and gonadotrophin synthesis and secretion. Follicle-stimulating hormone (FSH), androgen or oestrogen treatment restore qualitatively normal spermatogenesis in hpg testes. Understanding the cellular and molecular changes accompanying hormone-induced spermatogenesis in hpg mice requires detailed morphological analyses of the germ cells and Sertoli cells in the untreated hpg testis. We compared seminiferous epithelial cytology in adult hpg, immature and adult wild-type mice using unbiased optical disector-based stereology, immunolocalization of Sertoli cell microtubules (MT), espin (a component of the blood-testis barrier), markers of Sertoli cell maturity (p27(kip1) and WT-1), and electron microscopy. Hpg testes had marked reductions in weight, seminiferous cord volume and length, and severe spermatogenic impairment with germ cells per testis < 1% of adult wild-type testes. Sertoli cell nuclei expressed WT-1 in hpg testes, but often were centrally located, similar to 9-14-day-old wild-type testes, and they expressed p27(kip1), indicating that hpg Sertoli cells were post-mitotic. Hpg testes had significantly (P < 0.05) reduced Sertoli cells per testis (0.56 million) compared with 10-day wild-type (1.15 million) and adult wild-type testes (2.06 million). Immunofluorescence labelling of normal adult Sertoli cells showed supranuclear MT columns and basally located espin, but these features were absent in 10-day-old and hpg Sertoli cells. Hpg Sertoli cells showed pleomorphic nuclear ultrastructure with mature-type nucleoli, similar to normal adult-type Sertoli cells, but hpg Sertoli cells exhibited incomplete tight junctions that lacked ectoplasmic specializations. We conclude that in hpg mice, chronic gonadotrophin insufficiency restrains Sertoli cell proliferation and maturation, forming pseudo-adult-type Sertoli cells that are incapable of supporting germ cell proliferation and maturation.