Young Spermatids Research Articles

Comparative Proteome Analysis of Four Stages of Spermatogenesis in the Small-Spotted Catshark (Scyliorhinus canicula), Using High-Resolution NanoLC-ESI-MS/MS.

Spermatogenesis is a highly specialized process of cell proliferation and differentiation leading to the production of spermatozoa from spermatogonial stem cells. Due to its testicular anatomy, Scyliorhinus canicula is an interesting model to explore stage-based changes in proteins during spermatogenesis. The proteomes of four testicular zones corresponding to the germinative niche and to spermatocysts (cysts) with spermatogonia (zone A), cysts with spermatocytes (zone B), cysts with young spermatids (zone C), and cysts with late spermatids (zone D) have been analyzed by nanoLC-ESI-MS/MS. Gene ontology and KEGG annotations were also performed. A total of 3346 multiple protein groups were identified. Zone-specific protein analyses highlighted RNA-processing, chromosome-related processes, cilium organization, and cilium activity in zones A, D, C, and D, respectively. Analyses of proteins with zone-dependent abundance revealed processes related to cellular stress, ubiquitin-dependent degradation by the proteasome, post-transcriptional regulation, and regulation of cellular homeostasis. Our results also suggest that the roles of some proteins, such as ceruloplasmin, optineurin, the pregnancy zone protein, PA28β or the Culling-RING ligase 5 complex, as well as some uncharacterized proteins, during spermatogenesis could be further explored. Finally, the study of this shark species allows one to integrate these data in an evolutionary context of the regulation of spermatogenesis. Mass spectrometry data are freely accessible via iProX-integrated Proteome resources (https://www.iprox.cn/) for reuse purposes.

The Microtubule-Depolymerizing Kinesin-13 Klp10A Is Enriched in the Transition Zone of the Ciliary Structures of Drosophila melanogaster.

The precursor of the flagellar axoneme is already present in the primary spermatocytes of Drosophila melanogaster. During spermatogenesis each primary spermatocyte shows a centriole pair that moves to the cell membrane and organizes an axoneme-based structure, the cilium-like region (CLR). The CLRs persist through the meiotic divisions and are inherited by young spermatids. During spermatid differentiation the ciliary caps elongate giving rise to the sperm axoneme. Mutations in Klp10A, a kinesin-13 of Drosophila, results in defects of centriole/CLR organization in spermatocytes and of ciliary cap assembly in elongating spermatids. Reduced Klp10A expression also results in strong structural defects of sensory type I neurons. We show, here, that this protein displays a peculiar localization during male gametogenesis. The Klp10A signal is first detected at the distal ends of the centrioles when they dock to the plasma membrane of young primary spermatocytes. At the onset of the first meiotic prometaphase, when the CLRs reach their full size, Klp10A is enriched in a distinct narrow area at the distal end of the centrioles and persists in elongating spermatids at the base of the ciliary cap. We conclude that Klp10A could be a core component of the ciliary transition zone in Drosophila.

Male gonads morphology, spermatogenesis and sperm ultrastructure of the seahorse Hippocampus guttulatus (Syngnathidae)

AbstractTestes morphology, spermatogenetic process and mature sperm ultrastructure were analysed in Hippocampus guttulatus, using both light and transmission electron microscopy. Both testes were organized in a single large germinal compartment, with a central lumen. Spermatocysts only contained spermatogonia and primary spermatocytes. Inside the testis lumen, together with mature sperm, two types of large mono‐nucleate cells, flagellate and aflagellate, were present. Both types of cells were interpreted as developing germ cells precociously released inside the testis lumen, where their maturation was completed. According to the different morphological features of the nuclei, such as chromatin condensation degree, aspect of the nuclear fossa and others, the flagellate cells were unquestionably developing spermatids. On the contrary, the developmental stage of the aflagellate was more difficult to interpreted. They could be secondary spermatocytes or young spermatids. No dimorphic sperm were recognizable, the only sperm type observed have features typical of the intro‐sperm reports in other syngnathids species. They had a cylindrical head, a short midpiece, characterized by two mitochondrial rings housed inside a cytoplasmic collar, and a long flagellum. These and previous data about the same topic reported on other syngnathids species were compared and discussed.

The cilium like region of theDrosophilaspermatocyte: an oncoming flagellum?

Primary cilia and flagella are distinct structures with different functions in eukaryotic cells. Despite the fact that they share similar basic organization and architecture, a direct developmental continuity among them has not been reported until now. The primary cilium is a dynamic structure that typically assembles and disassembles during mitotic cell cycles, whereas the sperm axoneme is nucleated by the centriole inherited by the differentiating spermatid at the end of meiosis. Fruit flies display a remarkable exception to this general rule. Drosophila spermatocytes have an unusual axoneme-based structure reminiscent of primary cilia (the cilium-like region, or CLR). This structure persists through the meiotic divisions when it is internalized with the centriole to organize the centrosome and is finally inherited by young spermatids. Examination of elongating spermatids by transmission electron microscopy (EM) and cold regrowth experiments suggests that the motile axoneme derives directly from the elongation and remodelling of the immotile CLR. Both the CLR and elongating spermatid flagella have incomplete C-tubules that form longitudinal sheets associated with the B-tubule wall, unlike axonemes of other organisms in which C-tubules stop growing at the transition between the basal body and the axonemal doublets. Moreover, both the CLR and spermatid flagella lack a structured transition zone, a characteristic feature of ciliated cells. Uncoordinated (unc) mutants that lack C-remnants have short centrioles, suggesting that the C-sheets play a role in the elongation of the centriole after it docks to the cell membrane. The structural similarities between CLR and sperm axoneme suggest that the CLR can be considered as the basal region of the future axoneme and could represent the start point for its elongation.

Heterochromatin and histone modifications in the germline-restricted chromosome of the zebra finch undergoing elimination during spermatogenesis

In the zebra finch (Taeniopygia guttata) a germline-restricted chromosome (GRC) is regularly present in males and females. While the GRC is euchromatic in oocytes, in spermatocytes this chromosome is cytologically seen as entirely heterochromatic and presumably inactive. At the end of male meiosis, the GRC is eliminated from the nucleus. By immunofluorescence on microspreads, we investigated HP1 proteins and histone modifications throughout male meiotic prophase, as well as in young spermatid stages after the GRC elimination. We found that in prophase spermatocytes the GRC chromatin differs from that of the regular chromosome complement. The GRC is highly enriched in HP1 beta and exhibits high levels of di- and tri-methylated histone H3 at lysine 9 and tri- and di-methylated histone H4 at lysine 20. The GRC does not exhibit neither detectable levels of di- and tri-methylated histone H3 at lysine 4 nor acetylated histone H4 at lysine 5 and 8. The results prove the heterochromatic organization of the GRC in male germline and strongly suggest its transcriptional inactive state during male prophase. Following elimination, in young spermatids the GRC lacks HP1 beta signals but maintains high levels of methylated histone H3 at lysine 9 and methylated histone H4 at lysine 20. The release of HP1 from the GRC with respect to its elimination is discussed.

Spermatological characters of the caryophyllidean cestode Khawia sinensis Hsü, 1935, a carp parasite

Spermatological characters of the caryophyllidean tapeworm Khawia sinensis (Lytocestidae), a carp parasite, have been investigated for the first time. The process of the spermatozoon formation corresponds in basic pattern to that of Khawia armeniaca (Brunanská and Poddubnaya, Parasitol Res 99: 449-454, 2006). The presence of dense material at the early stages of spermiogenesis, the intercentriolar body, flagellar rotation (free flagellum plus flagellar bud), and a complete proximodistal fusion have been reported. In addition, it was shown that the developing spermatids may exhibit a free flagellum distally. The unipartite young spermatid and/or mature spermatozoon of K. sinensis consist of one axoneme of the 9 + "1" trepaxonematan pattern, nucleus, and cortical microtubules. These components are situated in cytoplasm, which is either electrolucent (young spermatid) or moderately electrodense (mature spermatozoon). The crested body is absent. The proximal extremity of the male gamete of K. sinensis contains a centriole and a few (up to six) cortical microtubules arranged in a semicircle. The number of cortical microtubules increases distally and reaches maximum (up to 15) in the middle part of the filiform cell, which contains the nucleus. The posterior extremity of the mature spermatozoon exhibits elements of the disorganized axoneme. The ultrastructural characteristics of spermiogenesis and the mature spermatozoon of K. sinensis support basal position of the Caryophyllidea (and Spathebothriidea) relative to other eucestode orders.

Antifertility effects of sulfapyridine on male hamsters

Sulfapyridine was administered to mature male golden hamsters either by impregnation in feed pellets, or by subcutaneous injection as a solution in dimethylsulfoxide. The average litter size for control males was 8.3 +/- 3.3 (n = 13) vs. 4.2 +/- 2.7 (n = 11) for sulfapyridine-fed treated animals. Histology of the testis and epididymis was normal and sperm were normal in morphology and motility. Subcutaneous injection of sulfapyridine caused much more dramatic inhibition of male fertility than was achieved by feeding the drug. Sulfapyridine (750 mg/kg body weight in 0.2 ml DMSO) injected subcutaneously for 60 days was effective in reducing testis size and sperm quality. Histology of testes showed spermatogenic arrest at young spermatids. Two classes of animals were found in both sulfapyridine-fed and -injected treatment groups. One class was relatively resistant to the antifertility effects of the drugs. This difference may reflect differing abilities of the animals to convert sulfapyridine to an active form or to excrete its metabolites.

Ultrastructure of Testicular Cells in Rats Treated with Dibromochloropropane (DBCP)/Ultrastruktur von Hodenzellen der Ratte nach Therapie mit Dibromchlorpropan

Three days after a single injection of rats with dibromochloropropane (DBCP) the testicular seminiferous tubules displayed focal damage, which became more pronounced six days after the treatment. Severely damaged tubules exhibited an almost complete exfoliation of the germ cells, while the Sertoli cells' lining remained mostly intact. The most affected germ cells were the spermatids. The mitochondrial sheath of the midpiece was often incomplete, vacuolated and/or broken into several pieces. In many cases the mitochondrial sheath protruded towards the interior, thus partially separating dense fibers 1, 2 and 9 from 3 to 8. In addition, cross sections revealed several midpieces of different flagellae surrounded by a single plasmalemma. In young spermatids, an atypical acrosome formation was noted concomitantly with a progressive emptying of the central nuclear region. This resulted in nuclei with electron lucent center surrounded by a chromatin belt. Sertoli cells displayed intense phagocytotic activity, their cytoplasm containing increased numbers of lysosomes, cellular debris and axonemal fragments.

The effect of clomiphene citrate and its Zu or En isomers on the reproductive system of the immature male rat.

The effect of clomiphene citrate (CC) and of its Zuclomiphene (ZuC) and Enclomiphene (EnC) isomers on the reproductive organs of immature male rats under different experimental conditions is reported. CC, ZuC, and EnC were administered daily to groups of either intact or castrated rats between the age of 21-44 d. This led to inhibition of weight increase of testis and accessory glands in the intact group. Spermatogenesis was arrested at the stage of primary spermatocyte following CC and ZuC treatment, and at the stage of young spermatids by EnC treatment. In the castrated group clomiphenes significantly stimulated weight increase of seminal vesicles (SV) compared with castrated control animals, but the former group were unable to achieve organ weight gain comparable to that in normal controls. Administration of human Chorionic Gonadotropin (hCG) together with CC or each of its isomers to intact animals, abolished the drug effect on spermatogenesis and on reproductive organ growth. Administration of CC, ZuC, and EnC together with testosterone to castrated animals, abolished the drug effect on growth inhibition of accessory glands. In intact treated rats LH and testosterone secretion were suppressed by all forms of clomiphenes. In the castrated group ZuC proved to be the most potent inhibitor of LH secretion. Therefore, it is inferred that ZuC and EnC have different potencies as far as their biological activity in the immature male rat is expressed.

Involvement of a gelsolin-related protein in spermatogenesis of the earthworm Lumbricus terrestris

A gelsolin-related protein was isolated from seminal vesicles of the annelid Lumbricus terrestris. Compared with the isoforms of the gelsolin-related protein previously found in the muscle of the annelid body wall, the isolated protein was assigned to the first isoform (EWAM-P1) because of its electrophoretic mobility, chromatographic elution behaviour, immunological cross-reactivity and identical nucleotide sequence of segments obtained by reverse transcription/polymerase chain reaction. Immunofluorescence studies with smear preparations of developing male germ cells revealed characteristic changes of the local distribution of actin and EWAM-P1 during spermatogenesis. These changes were correlated with the developmental transport processes and structural alterations. F-actin, as revealed by rhodamine-phalloidin staining, formed a toroid-shaped structure in cytoplasmic bridges connecting the germ cells to a central cytophore during the developmental stages. An actin antibody reacting with both G- and F-actin demonstrated that actin was concentrated at the proximal and distal parts of the spermatocytes. EWAM-P1 was also localized in these regions, with intense staining in the distal part of spermatocytes and young spermatids in which the Golgi complex and proacrosome resided. The anti-actin antibody further stained the periphery of the nucleus. This staining gradually reduced during sperm maturation and covered about half of the length of the nucleus in elongated spermatids. Co-localization of EWAM with actin implied a functional significance of this gelsolin-related protein for the rearrangement of the actin cytoskeleton during earthworm spermiogenesis.

Upregulation of AP1 by tertiary butyl hydroperoxide induced oxidative stress and subsequent effect on spermatogenesis in mice testis

Oxidative stress is detrimental to sperm function and a significant factor in the etiology of male infertility. Present study evaluates the effect of ter butyl hydroperoxide (TBHP)-induced oxidative stress on the spermatogenic process and cell number in the seminiferous tubules. Intraperitoneal injection of TBHP (84 mumol TBHP/100 g body weight) for 2 weeks to male Balb/c mice resulted in enhanced lipid peroxidation (P < 0.0001) decrease in reduced glutathione (P < 0.0001) and increase in the oxidized glutathione levels (P = 0.007) in the testis. Status of spermatogenesis after the treatment was assessed by the quantitative methods of germ cell evaluation in the seminiferous tubules. A significant decrease in the number of young spermatids (P = 0.0003) and pachytene cells (P = 0.022) was observed. A marked reduction was also seen in the mature spermatid number (P < 0.0001). An increase in testicular mRNA levels of redox-regulated cjun (P = 0.008) and cfos (P = 0.0006) subunits of activator protein 1 (AP1) was observed after TBHP treatment. Evaluation of AP1 regulated antioxidant enzymes in the testis revealed an increase in gamma-glutamyl cysteine synthetase (GCS) mRNA expression (P = 0.001). These results suggest a potential role of AP1 in oxidative stress-mediated meiotic and post meiotic changes in the spermatogenic process and regulation of cell number in male reproductive system.

The germ-line-restricted chromosome in the zebra finch: recombination in females and elimination in males

In the zebra finch (Taeniopygia guttata), there is a germ-line-restricted chromosome regularly present in males and females. A reexamination of male and female meiosis in the zebra finch showed that this element forms a euchromatic bivalent in oocytes, but it is always a single, heterochromatic element in spermatocytes. Immunostaining with anti-MLH1 showed that the bivalent in oocytes has two or three foci with a localized pattern, indicating the regular occurrence of recombination. In male meiosis, the single restricted chromosome forms an axis that contains the cohesin subunit SMC3, and the associated chromatin is densely packed until late pachytene. Electron microscopy of thin-sectioned seminiferous tubules shows that the restricted chromosome is eliminated in postmeiotic stages in the form of packed chromatin inside a micronucleus, visible in the cytoplasm of young spermatids. The selective condensation of the restricted chromosome during early meiotic prophase in males is interpreted as a strategy to avoid the triggering of asynaptic checkpoints, but this condensation is reversed prior to the final condensation that leads to its (ulterior) elimination. Recombination during female meiosis may prevent the genetic attrition of the restricted chromosome and, along with the elimination in male germ cells, ensures its regular transmission through females.

Reproductive potential of male Portan rats exposed to various levels of lead with regard to zinc status.

The present study was designed to elucidate the mechanisms accounting for disruption of the normal function of the testis exposed to various levels of Pb. Three different doses of Pb (10, 50, 200 mg Pb/kg body weight per d) were given orally to male Portan rats (groups 2, 3, 4). Zn (1 mg Zn/kg body weight per d) was also given with Pb (50 mg Pb/kg body weight per d) in group 5. Treatments continued for 3 months. Plasma luteinizing hormone and follicle-stimulating hormone concentrations were found to be decreased in Pb-exposed rats. This was in turn reflected in the appreciable decline in fertility status. In cell kinetic studies, significant declines in various cell populations (preleptotene, pachytene, young (step 7) spermatids and mature (step 19) spermatids) were seen. However, in group 5 after Zn supplementation, hormone levels, cell numbers and fertility status were found to be close to normal. It is concluded that Pb might act at maturation level to cause conspicuous degenerative changes in the testis; Zn supplementation protected against these effects.

Diagnostic value of differential quantification of spermatids in obstructive azoospermia.

Testicular biopsies from 80 azoospermic young men were revised and the average numbers per cross-sectioned tubule of each germ cell type were calculated and compared with those of control normal testes. In 53 patients, azoospermia had an obstructive cause, and in 22 of those 53 patients more adult spermatids were found by testicular biopsy than young spermatids (over 100% in some testes), in one or both testes. However, in normal testes fewer mature spermatids than young spermatids (23.3%) were found. In the 22 patients, the causes of azoospermia were: vasectomy (7 patients), bilateral agenesis of the vas deferens (3 patients), Young syndrome (3 patients), bilateral cysts in the caput epididymidis (1 patient), bilateral inguinal herniorrhaphy (1 patient), left varicocele (1 patient), and unknown causes (6 patients). Biopsies were bilateral except for 3 cases (a vasectomized patient, a patient with Young syndrome, and a patient with obstruction due to an unknown cause). Hormonal levels were normal in the 22 patients. In addition, testicular biopsies of 3 twisted testes from 3 young adult men showing a number of adult spermatids higher than that of young spermatids were also included in the study. All testicular biopsies-including those of the twisted testes-showed an obstructive histologic pattern, consisting of a mosaic distribution of testicular lesions: mainly tubular ectasis and germ cell sloughing into the adluminal compartment of seminiferous tubules. The increase in the number of adult spermatids was bilateral in 1 of the 6 vasectomized men who underwent bilateral biopsy, and in 7 of the 11 bilaterally biopsied patients with obstructive azoospermia due to other causes. The most probable explanation for the increased number of adult spermatids is stagnation of testicular fluid, caused by sperm excretory duct obstruction. The unilateral increase in the number of adult spermatids in vasectomized men might be related to the occurrence of a spermatic granuloma (a frequent finding in vasectomy) in the proximal end of the sectioned ductus deferens ipsilateral to the testis with nonincreased adult spermatid numbers, and the absence of spermatic granuloma in the ductus deferens ipsilateral to the testis with increased adult spermatid numbers. This granuloma would produce, in addition to spermatozoon destruction, reabsorption of the testicular and epididymal fluids. The higher rate of bilateral increase, in the number of young spermatids observed in the patients with congenital lesions of the ductus deferens or the ductus epididymidis, might be related to the absence of spermatic granulomas in congenital obstructions.

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. H UM P ATHOL 31:1022-1030.

Testicular biopsy in patients with obstructive azoospermia.

The present report studies the testicular biopsy lesions (histologic and semiquantitative) in a series of 48 patients with obstructive azoospermia of known etiology (vasectomy, congenital absence of vas deferens, herniorrhaphy, hydrocelectomy, Young's syndrome, and ejaculatory duct obstruction) in order to establish objective testicular data that permit the pathologist to diagnose an obstructive process, which should not be mistaken with a primary testicular lesion. The semiquantitative study included determinations of the average numbers of spermatogonia, primary spermatocytes, young spermatids (Sa + Sb), and differentiated spermatids (Sc + Sd). According to this study, the testes were classified into the following groups: (1) normal testes whose germ cell numbers were within normal limits (27 testes); (2) testes with lesions in the adluminal compartment; these lesions comprise two subgroups: (2a) late sloughing of primary spermatocytes (both spermatid types were greatly reduced in number while the other germ cell types were in normal numbers) (45 testes); and (2b) early sloughing of primary spermatocytes (normal spermatogonial number, reduced number of spermatocytes, and scanty spermatids) (9 testes); and (3) lesions in the basal compartment; these lesions comprise two subgroups: (3a) pure hypospermatogenesis (a proportionate decrease in the numbers of all germ cell types) (8 testes); and (3b) hypospermatogenesis associated with sloughing of primary spermatocytes (decreased numbers of all germ cell types with a very scanty number spermatids) (4 testes). Two testes appeared hyalinized and one testis was removed owing to cryptorchidism. The most frequent testicular lesion observed (alteration in the adluminal compartment of seminiferous tubules) seems to be related to the increase in hydrostatic pressure in the tight compartment formed by seminiferous tubules, rete testis, efferent ducts, the epididymal duct, and the initial portion of the vas deferens. The severity of the lesions is probably related to the cause and span of the obstruction. In addition, two azoospermic men without obstructive azoospermia and whose testicular biopsy study revealed meiotic anomalies (with the subsequent bad prognosis) were also studied for comparison. The semiquantitative study of these patients permitted the differential diagnosis between two lesion types. Testes with meiotic anomalies had a disproportionately elevated number of primary spermatocytes, and an extremely low number of young spermatids.

Spermatogenesis and Spermiogenesis in Microcotyle sp. (Microcotylidae, Monogenea)

Ultrastructural observations of spermatogenesis and spermiogenesis in Microcotyle sp. a microcotylid monogenean parasite from the gills of Hypostomus sp., are described. The spermatogonia were irregularly shaped, forming a peripheral layer of cells; spermatocytes were larger than spermatogonia and a nuclear synaptonemal complex was observed; young spermatids were joined by a central cytophore forming rosettes. Spermiogenesis was characterized by the outgrowth of a cytoplasmic protuberance, the zone of differentiation, containing the basal bodies, separated by an intercentriolar body, from which flagella grow out and fuse posteriorly with the median process. Cross sections of the anterior and the middle regions of spermatozoa revealed nuclei, mitochondria, peripheral microtubules, and paired axonemes each with a 9+1 pattern.

Histological characterization of defective spermatogenesis in mice lacking the basigin gene.

Basigin is a transmembrane protein belonging to the immunoglobulin superfamily. In the light of the fact that knockout mice lacking the basigin gene (Bsg) are azoospermic, the phenotype in the male reproductive system was extensively examined in this study. Spermatogenesis in Bsg (-/-) mice was found to be disrupted, and arrested at the metaphase of the first meiotic division. A few germ cells differentiated into young spermatids, but they were exfoliated. The lumens of the male reproductive system were filled with round degenerated cells. Using the TUNEL method and electron microscopy, some of the degenerated cells in the testis and epididymal head were shown to be apoptotic. Crystalloids of fine tubules and unusual ectoplasmic specializations were also observed in the Sertoli cells of Bsg (-/-) mice. These specializations displayed unusual 'circular' structures. Furthermore, unusual ectoplasmic specializations covering the spermatocytes rather than the mature spermatids were found. These structures were formed as a result of the lack of mature spermatids in the Bsg (-/-) testis. Results from analyses of azoospermia in the Bsg (-/-) mice suggest that basigin, through the interactions between germ cells and Sertoli cells, is an essential factor in the growth and/or survival of spermatids.

Germ Cell Genotype Controls Cell Cycle during Spermatogenesis in the Rat1

Spermatogenesis is one of the most productive self-renewing systems in the body: on the order of 10(7) spermatozoa are produced daily per gram of testis tissue. In each mammalian species, the time required for completion of the process is unique and unalterable. Because the process is supported by somatic Sertoli cells, it has generally been thought that cell-cell interaction between germ and Sertoli cells controls the duration of cell cycles and cellular organization. We have used the newly developed technique of spermatogonial transplantation to examine which cell type(s) determines the rate at which germ cells proceed through spermatogenesis. Rat germ cells were transplanted into a mouse testis, and the mouse was killed 12.9-13 days after administration of a single dose of [3H]thymidine. The most advanced rat cell type labeled was the pachytene spermatocyte at stages VI-VIII of the spermatogenic cycle. In animals given only rat cells, some endogenous spermatogenesis of the mouse recovered. The most advanced labeled mouse cell types in recipients killed 12.9-13 days after administration of a single dose of [3H]thymidine were meiotic cells or young spermatids, which is consistent with a spermatogenic cycle length comparable to the 8.6 days reported for the mouse. The same results were obtained if a mixture of rat and mouse cells were transplanted. There existed two separate timing regimens for germ cell development in the recipient mouse testis; one of rat and one of mouse duration. Rat germ cells that were supported by mouse Sertoli cells always differentiated with cell cycle timing characteristic of the rat and generated the spermatogenic structural pattern of the rat, demonstrating that the cell differentiation process of spermatogenesis is regulated by germ cells alone.

Fine structure of spermiogenesis with special reference to the spermatid morulae of the freshwater mussel Prisodon alatus (Bivalvia, Unionoidea).

Within the testicular cysts of the mussel Prisodon alatus are numerous somatic host cells described as Sertoli cells (SC), each containing a variable number of young spermatid morulae. Among them, several free spermatid morulae, spermatids, and spermatozoa were observed. Each free spermatid morula is surrounded by an external membrane. The early spermatids enclosed within the morulae have dense and homogeneous chromatin, and the cytoplasm occupies little space around the nucleus. Later, during spermiogenesis, the SC show lysis and disrupt to liberate the spermatid morulae. The membrane of the free morula is then disrupted, releasing the young spermatids. The SC disappear just after the appearance in the testis of a large number of free young spermatids. The nucleus of each free spermatid becomes gradually smaller and denser by the appearance of a granular pattern of condensed chromatin. During the maturation phase of the spermatids, the cytoplasm becomes more voluminous, and mitochondria and centrioles are more evident. Then, flagellogenesis occurs, and the nucleus gradually condenses into thicker strands. In the mature sperm, the apical zone has a disc-shaped acrosomal vesicle and the midpiece contains five mitochondria and two centrioles located at the same level. The flagellum has the common 9+2 microtubular pattern. The results are discussed with particular reference to Sertoli cells and clusters of spermatid morulae with those of species of closely related taxa in the bivalves. J. Morphol. 238:63-70, 1998. © 1998 Wiley-Liss, Inc.