摘要:

AbstractSpermatogenesis appears to be a fairly conserved process throughout the vertebrate series. Thus, spermatogonia develop into spermatocytes that undergo meiosis to produce spermatids which enter spermiogenesis where they undergo a morphological transformation into spermatozoa. There is, however, variation amongst the vertebrates in how germ cell development and maturation is accomplished. This difference can be broadly divided into two distinct patterns, one present in anamniotes (fish, amphibia) and the other in amniotes (reptiles, birds, mammals). For anamniotes, spermatogenesis occurs in spermatocysts (cysts) which for most species develop within seminiferous lobules. Cysts are produced when a Sertoli cell becomes associated with a primary spermatogonium. Mitotic divisions of the primary spermatogonium produce a cohort of secondary spermatogonia that are enclosed by the Sertoli cell which forms the wall of the cyst. With spermatogenic progression a clone of isogeneic spermatozoa is produced which are released, by rupture of the cyst, into the lumen of the seminiferous lobule. Following spermiation, the Sertoli cell degenerates. For anamniotes, therefore, there is no permanent germinal epithelium since spermatocysts have to be replaced during successive breeding seasons. By contrast, spermatogenesis in amniotes does not occur in cysts but in seminiferous tubules that possess a permanent population of Sertoli cells and spermatogonia which act as a germ cell reservoir for succeeding bouts of spermatogenic activity. There is, in general, a greater variation in the organization of the testis and pattern of spermatogenesis in the anamniotes compared to amniotes. This is primarily due to the fact there is more reproductive diversity in anamniotes ranging from a relatively unspecialized condition where gametes are simply released into the aqueous environment to highly specialized strategies involving internal fertilization. These differences are obviously reflected in the mode of spermatogenesis and this is particularly true of the stage of spermiogenesis where the morphology of the species‐specific spermatozoon is determined. Moreover, unlike amniotes, many anamniotes display a spermatogenic wave manifest, depending upon the species, either at the level of the cyst or seminiferous lobule.This variation in the organization of the testis makes certain anamniotes perfect models for investigating germ cell development and maturation. For instance, the presence of a spermatogenic wave provides an opportunity to manually isolate discrete germ cell stages for analysis of specific Sertoli/germ cell interactions. Furthermore, for many anamniotes, germ cells mature in association with a morphologically poorly developed Sertoli cell. This seeming independence of Sertoli cell regulation allows the in vitro culture of isolated germ cells of some species of anamniotes through several developmental stages. Thus, due either to the anatomical organization of the testis, or structural simplicity of the germinal units, nonmammalian vertebrates can provide excellent experimental animal models for investigating many basic problems of male reproduction. © 1995 Wiley‐Liss,

ISSN:1059-910X    

DOI:10.1002/jemt.1070320602

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1995

数据来源: WILEY

摘要:

AbstractUsing testes fixed by perfusion with Bouin's fluid and embedded in paraffin wax, this study has established methods for combining in situ hybridization and immunocytochemistry on the same section to colocalize mRNA and protein for transition protein‐1 (TP‐1) and sulfated glycoprotein‐1 (SGP‐1), respectively. It was found that SGP‐1 could be detected in tissue sections subsequent to the detection of TP‐1 mRNA in situ. The finding that (1) the tissue pretreatments required to permeabilize the section and to allow access to the probe, and (2) the hybridization conditions themselves, had no adverse effect on the detection of antigen, eases the performance of this technique. On this basis, important information could be obtained on the transcriptional and translational activity of spermatogenic cells, if related probes and antibodies are utilized. © 1995 Wil

ISSN:1059-910X    

DOI:10.1002/jemt.1070320603

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1995

数据来源: WILEY

摘要:

AbstractSertoli cells are polarized epithelial cells of the seminiferous epithelium which provide structural and physiological support for differentiating germ cells. They establish different basal and adluminal environments for the selective nurturing of pre‐ and post‐meiotic germ cells within the seminiferous epithelium, segregated by the Sertoli‐Sertoli cell tight junctional complex, the blood‐testis barrier. Tight junction formation between epithelial cells in vitro is a critical polarizing event associated with changes in polarized targeting of membrane‐specific proteins and reorganization of microtubules, centrioles, and the Golgi apparatus. To investigate whether tight junction formation is associated with organelle reorganization in Sertoli cells in vivo, we have characterized distribution patterns of Sertoli cell microtubules, the mechanoenzymes kinesin and cytoplasmic dynein, and the Golgi apparatus during tight junction formation in developing rat testis. Immunocytochemistry on samples taken at 5, 10, 15, 20, and 25 days of age was used to examine the distribution of these proteins during the extensive cellular reorganization that culminates in the formation of the blood‐testis barrier at 19 days of age. Our data show that the distribution patterns reflect the extensive intercellular repositioning of tubule cells in developing seminiferous tubules, but that changes in intracellular organization are not temporally associated with formation of the blood‐testis barrier. © 1995 W

ISSN:1059-910X    

DOI:10.1002/jemt.1070320604

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1995

数据来源: WILEY

摘要:

AbstractThe perinuclear theca (PT) is a unique cytoskeletal element that encapsulates the mammalian sperm nucleus. It is divided into subacrosomal and postacrosomal regions. The objective of this study was to analyze and stage the intracellular distribution of several promiment bull PT proteins during spermatogenesis. For this purpose, polyclonal antibodies raised and affinitypurified against the 15.5‐, 25‐, 28‐, 32‐, 36‐, and 60‐kDa bull PT polypeptides were used as probes on sections of aldehyde‐fixed testes. Immunoperoxidase staining revealed that the PT polypeptides first appeared early in spermiogenesis, concomitant with early steps of development of the acrosomic system. Immunogold labeling further showed that these polypeptides were peripherally associated with the entire acrosomal membrane, before and during the attachment of the acrosomic vesicle onto the spermatid's nucleus. Once the acrosome had capped the nucleus the labeling resided mainly in the subacrosomal region of the spermatid, between the inner acrosomal membrane and nuclear envelope. Later, during the elongation of the spermatid's nucleus, the labeling with all antibodies except the anti‐15.5‐kDa antibody extended caudally over the assembling postacrosomal sheath. This study suggests that the perinuclear theca proteins play an instrumental role in the attachment, spreading, and binding of the acrosome onto the nucleus of spermatids. © 19

ISSN:1059-910X    

DOI:10.1002/jemt.1070320605

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1995

数据来源: WILEY

摘要:

AbstractIn this paper we present the state of knowledge on cell‐cell interactions in the testis of two groups of anamniote vertebrates—teleosts and elasmobranchs—which include most fish. In these fish, the structural organization of the testis differs fundamentally from that which characterizes amniotes in which the germinal tissue is located in tubules open at both ends and consists of a permanent population of Sertoli cells associated with successive stages of germ cell development. In fish, the spermatogenic unit of testis is the spermatocyst, which corresponds to one germ cell or to a clone of isogenetic germ cells, enclosed by one or several Sertoli cells, which form the wall of the cyst. In fish testis, the Sertoli cells do not represent a permanent population of cells. Although both are of the cystic type, the teleost and elasmobranch testes are differently organized. In elasmobranchs, primary spermatogonia and Sertoli cells lie initially free within the interstitial tissue, before becoming sequestered by a basement membrane; the testis is then composed of a mass of spermatocysts which contain many Sertoli cells, each being associated with a clone of germ cells. In contrast, in teleosts, the cysts are confined to large elongated structures limited by a basement membrane. These structures are either lobules originating under the albuginea or tubules which, in contrast to those of mammals, are anastomosed. In the lobules, the spermatocysts start to develop at the blind end of the lobules and migrate towards the efferent system, whereas in the tubules, the spermatocysts are located against the basement membrane, all along the tubules and do not migrate. In elasmobranchs, unlike teleosts, Leydig cells are either absent from the interstitial tissue or rare and undifferentiated and their role in steroid production is at best marginal.While many studies have focused on topographical and functional interactions between the diverse cell types present in mammalian testis, only a few studies have brought particular attention to these aspects in fish. In fish, like in mammals, testicular cell‐cell interactions are based on structural elements and chemical factors. Occasionally, various adhering junctions have been observed, essentially in teleosts, between Sertoli cells, between Sertoli cells and germ cells, between germ cells themselves, and interstitial cells. Furthermore, in some teleost species, using horseradish peroxidase or lanthanum salts, the presence of tight junctions between Sertoli cells has been correlated to the occurrence of a Sertoli barrier. In these species, the barrier develops after meiosis so that only haploid germ cells are shielded from the vascular system. In fish, recent development of techniques which enable the preparation and in vitro culture of enriched populations of testicular cells and of spermatocysts, has allowed investigations on functional aspects of cell‐cell interactions. In particular, data have been obtained, in the trout, on the control of spermatogonia proliferation by Sertoli cell‐conditioned media and, in the dogfish, on the steroidogenic activity of Sertoli cells, in relation to the differentiation stage of the associated germ cells. Furthermore information exists, in the trout, showing that intratubular macrophages may participate in the re‐initiation of spermatogonial proliferation.In conclusion, the cytoarchitecture of fish testis, as compared to that of mammals, presents original feátures which provide unique opportunities to develop fruitful studies for a better understanding of the complex control mechanisms underlying testicular function in vertebrates. © 1995

ISSN:1059-910X    

DOI:10.1002/jemt.1070320606

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1995

数据来源: WILEY

ISSN:1059-910X    

DOI:10.1002/jemt.1070320601

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1995

数据来源: WILEY