Carbendazim generates symplasts in rat spermatogenic clones.

In order to find non-microtubular targets in the seminiferous epithelium for the fungicide and reproductive toxicant carbendazim, it was administered to 90 days old male Wistar rat in a single bolus dose of 400 mg/kg body weight through an oral intubation. A parallel control group was maintained. Rats were sacrificed 48 days after the treatment and the testes were analysed for histopathological changes adopting routine histological methods, when symplasts were localised. The maximum diameter of five largest symplasts was measured, and the number of nuclei in these symplasts was also determined. As it is known that symplasts of spermatogenic cells are produced due to opening up of the intercellular bridges between cells in a clone consequent upon disruption of actin microfilaments, the present study shows that actin microfilaments would also be targets in the seminiferous epithelium for carbendazim toxicity.     

Transcriptional and translational control of the message for transition protein 1, a major chromosomal protein of mammalian spermatids

The spermatid transition proteins comprise a set of basic chromosomal proteins that appear during the period when spermatids are undergoing nuclear elongation and condensation, about midway between the end of meiosis and the release of spermatozoa from the seminiferous tubule. The transition proteins replace the histones but are themselves subsequently replaced by protamines, and they are not found in sperm nuclei. We have used a cDNA clone for the smallest transition protein (TP1, 54 amino acids) to show that its message first appears postmeiotically in late round spermatids. Thus production of TP1 is an example of haploid gene expression. The message remains translationally inactive for some 3-4 days before translation occurs in early elongating spermatids. While translationally repressed, TP1 message is nonpolysomal and has a discrete size of about 590 bases, including a 140 residue poly(A) tail. In contrast, polysome-associated message is of heterogeneous size due to variability of poly(A) lengths.     

Testis structure in the sys (symplastic spermatids) mouse.

Testes of mice with the recessive insertional mutation termed symplastic spermatids (sys) were assessed for structural and developmental abnormalities. Homozygous (sys/sys) males are infertile due to an abnormality in spermatogenesis leading to azoospermia. The major interruption to spermatogenesis occurs when the intercellular bridges that connect round spermatids open prematurely resulting in the formation of symplasts. Symplasts contain as many as 285 nuclei. Development of spermatids within symplasts is arrested just before, or just after, elongation of the spermatid nuclei begins. Symplasts degenerate and appear to be phagocytized by Sertoli cells and by intratubular macrophages. In addition, degeneration of young round spermatids and also spermatocytes occasionally is observed. Spermatocyte degeneration is substantial in some tubules and leaves them depleted of cells other than basal compartment cells. Sertoli cell abnormalities are prominent and include intracellular vacuolation, absence of apical processes surrounding round spermatids, degeneration, and occasional sloughing. Although reduplication and infolding of the basal lamina is also seen, this does not appear as a common phenomenon. The sys phenotype is first manifest in animals between 19 days and 22 days of age. Considerable variability is seen in testis histology of prepubertal animals; some display degenerating pachytene spermatocytes and virtually no Sertoli cell vacuoles, while others display vacuoles without apparent elevated numbers of degenerating spermatocytes. Although this study has not revealed the primary cell type(s) affected by the insertional inactivation event, it is possible that the abnormalities in the Sertoli cells are responsible for germ cell degeneration as it is generally recognized that deficits in the Sertoli cell can result in major germ cell abnormalities but not vice versa.     

Separation of mouse spermatogenic cells by sedimentation velocity. A morphological characterization.

A method utilizing sequential enzymatic incubation in collagenase (1 mg/ml) and trypsin (2.5 mg/ml) has been developed for the dissociation of the seminiferous epithelium. A significant advantage of this method is that, following collagenase incubation and washings in an enriched Krebs-Ringer bicarbonate buffer solution, isolated seminiferous tubules are obtained which are free of interstitial cells. The “purified” seminiferous epithelium is then dissociated with trypsin. A further advantage of this dissociation technique has been a reduction in the number of symplasts (multinucleate cells) which form by the opening up of the intercellular bridges that occur between synchronously differentiating clusters of germ cells. Both the elimination of the interstitial cells and the reduction in the number of symplasts have made possible the recovery of more highly enriched germ cell fractions. The homogeneity of the cell fractions was determined by light and electron microscopy. Integrity of the isolated cells was verified by Trypan blue exclusion and measurement of oxygen consumption.     

Postnatal development of the connexion between tubulus seminiferus and tubulus rectus in the bovine testis

Summary Histology and ultrastructure of the connexion of seminiferous and straight testicular tubules were studied in 58 bovine testes of 29 animals ranging from 4 to 52 weeks of postnatal development. In the 4th and 8th week seminiferous tubules are solid. Their non-germinal supporting cells possess spherical nuclei in a basal location and a great amount of granular endoplasmic reticulum. The straight tubules have a narrow lumen and a stratified epithelium rich in intercellular canaliculi. Between 20 and 25 weeks the seminiferous tubules acquire a lumen and develop a terminal segment, the tip of which (terminal plug) protrudes into the cup-shaped modification of the adjacent straight tubule. At 30 weeks the structural differentiation between seminiferous tubule proper and its terminal segment has proceeded: in the former spermatocytes and spermatids make their first appearance, and the supporting cells have transformed to Sertoli cells. In the latter the morphology of the supporting cell preserves a more primitive state. Starting from the 16th week and proceeding through the 30th week and further, the epithelium of the tubulus rectus close to the connexion with the seminiferous tubule becomes monolayered by rearrangement of its cells and advances along the basal lamina into the area of the seminiferous tubule. Those cells of the seminiferous tubule that are cut off from the basal lamina by invading rectus cells degenerate. Between 40 and 52 weeks the adult situation is principally achieved. The terminal segment of the seminiferous tubule is tripartite consisting of transitional region, intermediate portion, and terminal plug. The terminal segment is surrounded by a vascular plexus. The straight testicular tubule adjacent to the terminal segment is modified into a cup region encompassing the terminal plug, followed by a narrow stalk region, which is lined by simple columnar epithelium. Mononuclear free cells are a constant feature of the tubulus rectus epithelium in all stages of postnatal development.Supported by grant Wr 7/6-6 from the Deutsche Forschungsge-meinschaft     

Rat spermatogenesis in vitro traced by quantitative flow cytometry

In vitro differentiation of germ cells in rat seminiferous tubule segments at stages II-III of the epithelial cycle was studied. DNA flow cytometry was used for quantitation of absolute cell numbers from the cultured tubule segments that were compared to freshly isolated stages of the cycle, as identified by transillumination stereomicroscopy of the seminiferous tubules and phase-contrast microscopy of live cell squashes. Spermatogonia and spermatocytes from stages II-III showed normal morphological differentiation during 7 days in vitro. Round spermatids differentiated to Step 7 of spermiogenesis but Step 16 spermatids failed to develop. Acid phosphatase activity in the spermatogenic cells changed normally during the culture. As compared with freshly isolated control tubule segments, 35% of round spermatids and 42% of pachytene spermatocytes were present in culture after 7 days. The cell numbers recovered from defined stages by DNA flow cytometry were close to those found in morphometric studies. Flow cytometry is an efficient quantitation method for cells liberated from seminiferous epithelium. Spermatogonia, spermatocytes, and early spermatids are able to differentiate in vitro, but spermatids approaching the elongation (acrosome) phase, and particularly the maturation phase, fail to differentiate under present culture conditions.     

Spermiogenesis in the bullfrog (Rana catesbeiana): a study of cytoplasmic events including cell volume changes and cytoplasmic elimination

The process by which spermatid cytoplasmic volume is reduced and cytoplasm eliminated during spermiogenesis was investigated in the bullfrog Rana catesbeiana. At early phases of spermiogenesis, newly formed, rounded spermatids were found within spermatocysts. As acrosomal development, nuclear elongation, and chromatin condensation occurred, spermatid nuclei became eccentric within the cell. A cytoplasmic lobe formed from the caudal spermatid head and flagellum and extended toward the seminiferous tubule lumen. The cytoplasmic lobe underwent progressive condensation whereby most of its cytoplasm became extremely electron dense and contrasted sharply with numerous electron-translucent vesicles contained therein. At the completion of spermiogenesis, many spermatids with their highly condensed cytoplasm still attached were released from their Sertoli cell into the lumen of the seminiferous tubule. There was no evidence of the phagocytosis of residual bodies by Sertoli cells. Because spermatozoa are normally retained in the testis in winter and are not released until the following breeding season, sperm were induced to traverse the duct system with a single injection of hCG. Some spermatids remained attached to their cytoplasm during the sojourn through the testicular and kidney ducts; however, by the time the sperm reached the Wolffian duct, separation had occurred. The discarded cytoplasmic lobe (residual body) appeared to be degraded with the epithelium of the Wolffian duct. It was determined that the volume of the spermatid was reduced by 87% during spermiogenesis through a nuclear volume decrease of 76% and cytoplasmic volume decrease of 95.3%.     

Morphological pattern of response after administration of procarbazine: Alteration of specific cell associations during the cycle of the seminiferous epithelium of the rat

Procarbazine, an anti-cancer agent, administered intraperitoneally to adult, male rats induced a characteristic morphological pattern of response in the seminiferous epithelium. Seminiferous tubules of rats receiving 100 mg/kg procarbazine and higher dosages displayed spermatids which were less mature than those normally found within seminiferous tubules which show a particular cell association. Early spermatids in steps 1–7 of spermiogenesis appeared arrested in their development and were present in cell associations which had advanced normally. The most probable cause of this apparent germ cell arrest was a retardation of acrosomal development since procarbazine is known to affect RNA and consequently protein synthesis. Other features which indicated defective RNA synthesis were the presence of abnormal spermatid nucleoli and abnormally configured chromatoid bodies. This study demonstrates, in contrast to what is indicated by present dogma, that apparent and temporary germ cell arrest may occur under certain deleterious conditions. It also illustrates that particular cell types within a cell association may be out of synchrony with the remainder of the cells in a cell association.     

An ultrastructural study on the occurrence of aberrant spermatids in the testis of the river sculpin,Cottus hangiongensis

The process of spermatogenesis and spermiogenesis in the river sculpin,Cottus hangiongensis, was observed ultrastructurally. During spermatogenesis, some germinal cysts in the seminal lobules were found to contain spermatocytes, which were provided with irregularly shaped nuclei, doughnut-shaped mitochondria, and atypical intercellular bridges with multiple disk-like cisternae. In addition, many cysts containing binuclear spermatids were observed in the testis. Within the condensed chromatin of the paired nuclei of the aberrant spermatids, highly electron-dense granules occurred, becoming the core of successively developing chromatin globules. The chromatin globules increased in size, resulting in an enlargement of the paired nuclei. These cells were finally released from the cyst into the lumen of the seminal lobules and underwent further degeneration, thus appearing as characteristic ‘spermatid masses’ in the mature testes.     

Ultrastructural changes of the intercellular relationship in impaired human spermatogenesis

Summary In seven hypo- or aspermic patients, electron microscopic investigations of the intercellular connections of the seminiferous tubule were performed. The analysis of cell junctions of Sertoli cells and germ cells revealed irregularities of the Sertoli-cell junctions, hypoplasias of occluding junctions, hypo- and hyperplasias of the Sertoli-spermatid cell junctions and abnormal formation of Sertoli cell junctions with early spermatids, spermatocytes, and spermatogonia. Gap junction-like cell membrane specializations were very rare. Intercellular cytoplasmic bridges of germ cells were always present together with these cells. One hypoplastic bridge connecting two spermatogonia was found.The results allow a preliminary classification of impaired spermatogenesia. The changes of intercellular connections might disturb the blood-testis barrier as well as the intercellular communication in the seminiferous tubule. Evidence is available to support the suggestion that genetic causes play a considerable role in the etiology of the germ cell aplasia and the spermatogenic maturation arrest.     

Potency of testicular somatic environment to support spermatogenesis in XX/Sry transgenic male mice

The sex-determining region of Chr Y (Sry) gene is sufficient to induce testis formation and the subsequent male development of internal and external genitalia in chromosomally female mice and humans. In XX sex-reversed males, such as XX/Sry-transgenic (XX/Sry) mice, however, testicular germ cells always disappear soon after birth because of germ cell-autonomous defects. Therefore, it remains unclear whether or not Sry alone is sufficient to induce a fully functional testicular soma capable of supporting complete spermatogenesis in the XX body. Here, we demonstrate that the testicular somatic environment of XX/Sry males is defective in supporting the later phases of spermatogenesis. Spermatogonial transplantation analyses using XX/Sry male mice revealed that donor XY spermatogonia are capable of proliferating, of entering meiosis and of differentiating to the round-spermatid stage. XY-donor-derived round spermatids, however, were frequently detached from the XX/Sry seminiferous epithelia and underwent cell death, resulting in severe deficiency of elongated spermatid stages. By contrast, immature XY seminiferous tubule segments transplanted under XX/Sry testis capsules clearly displayed proper differentiation into elongated spermatids in the transplanted XY-donor tubules. Microarray analysis of seminiferous tubules isolated from XX/Sry testes confirmed the missing expression of several Y-linked genes and the alterations in the expression profile of genes associated with spermiogenesis. Therefore, our findings indicate dysfunction of the somatic tubule components, probably Sertoli cells, of XX/Sry testes, highlighting the idea that Sry alone is insufficient to induce a fully functional Sertoli cell in XX mice.     

细胞松弛素E对大鼠生精细胞发育的影响

本文采用微丝抑制剂——细胞松弛素E对大鼠生精细胞发育的影响作了形态学观察,特别对支持细胞骨架复合体的作用进行了较为详细的研究。结果表明睾丸内注射0.1ml,1000μmol/L～2000μmol/L,细胞松弛素E,6-14小时后,光镜下可见曲细精管上皮排列疏松,组合紊乱,有的生精上皮基底部出现双核和三核的圆形细胞和多核巨精子细胞,管腔内出现未成熟的精子;在第ⅤⅢ～Ⅸ期曲细精管上皮中,有许多第8、第9期的精子细胞顶体不指向基底方向,属定向不正的精子。电镜下,实验组动物可见一些面向第8-18期精子细胞顶体的支持细胞骨架复合体出现不同程度的缺如,有的断裂成小段;有的破坏仅发生在顶体上方;有的几乎全部丢失,并有类管球复合体的形成。另外,在高渗液处理下,可见精子细胞顶体和支持细胞间的间隙扩大。最后对微丝在精子发育中的作用进行了讨论。     

免不1号和2号治疗免疫性不育雄鼠的组织学和免疫组织化学研究

用中药复方免不1号,免不2号治疗免疫性不育雄鼠,观察睾丸,附睾组织学和免疫组化的变化。用精子抗原免疫昆明种雄性小白鼠,建立免疫性不育动物模型。同时分别饲喂中药复方免不1号,免不2号,醋酸强的松,生理盐水;从组织学和免疫组化等方面观察免疫性不育症的变化。结果显示免疫性不育雄鼠血清,精囊液抗精子抗体高,睾丸间质,睾丸曲细精管界膜,精原细胞,附睾管上皮细胞免疫复合物沉积多,睾丸每曲细精管精子和晚期精子细胞减少,中药免不1号和2号能降低抗精子抗体,清除免疫复合物的沉积,恢复曲细精管精子和晚期精子细胞数。结果表明：免不1号和2号通过调节全身免疫系统,清除循环和局部的抗精子抗体,免疫复合物,提高精子和精子细胞数,从而提高小鼠的受孕率。     

Intercellular organelle traffic through cytoplasmic bridges in early spermatids of the rat: mechanisms of haploid gene product sharing

Stable cytoplasmic bridges (or ring canals) connecting the clone of spermatids are assumed to facilitate the sharing of haploid gene products and synchronous development of the cells. We have visualized these cytoplasmic bridges under phase-contrast optics and recorded the sharing of cytoplasmic material between the spermatids by a digital time-lapse imaging system ex vivo. A multitude of small (ca. 0.5 microm) granules were seen to move continuously over the bridges, but only 28% of those entering the bridge were actually transported into other cell. The average speed of the granules decreased significantly during the passage. Immunocytochemistry revealed that some of the shared granules contained haploid cell-specific gene product TRA54. We also demonstrate the novel function for the Golgi complex in acrosome system formation by showing that TRA54 is processed in Golgi complex and is transported into acrosome system of neighboring spermatid. In addition, we propose an intercellular transport function for the male germ cell-specific organelle chromatoid body. This mRNA containing organelle, ca. 1.8 microm in diameter, was demonstrated to go over the cytoplasmic bridge from one spermatid to another. Microtubule inhibitors prevented all organelle movements through the bridges and caused a disintegration of the chromatoid body. This is the first direct demonstration of an organelle traffic through cytoplasmic bridges in mammalian spermatogenesis. Golgi-derived haploid gene products are shared between spermatids, and an active involvement of the chromatoid body in intercellular material transport between round spermatids is proposed.     

Dynamic of VE-cadherin-mediated spermatid–Sertoli cell contacts in the mouse seminiferous epithelium

Spermatids are haploid differentiating cells that, in the meantime they differentiate, translocate along the seminiferous epithelium towards the tubule lumen to be just released as spermatozoa. The success of such a migration depends on dynamic of spermatid–Sertoli cell contacts, the molecular nature of which has not been well defined yet. It was demonstrated that the vascular endothelial cadherin (VEC) is expressed transitorily in the mouse seminiferous epithelium. Here, we evaluated the pattern of VEC expression by immunohistochemistry first in seminiferous tubules at different stages of the epithelial cycle when only unique types of germ cell associations are present. Changes in the pattern of VEC localization according to the step of spermatid differentiation were analysed in detail using testis fragments and spontaneously released germ cells. Utilizing the first wave of spermatogenesis as an in vivo model to have at disposal spermatids at progressive steps of differentiation, we checked for level of looser VEC association with the membrane by performing protein solubilisation under mild detergent conditions and assays through VEC-immunoblotting. Being changes in VEC solubilisation paralleled in changes in phosphotyrosine (pY) content, we evaluated if spermatid VEC undergoes Y658 phosphorylation and if this correlates with VEC solubilisation and spermatid progression in differentiation. Altogether, our study shows a temporally restricted pattern of VEC expression that culminates with the presence of round spermatids to progressively decrease starting from spermatid elongation. Conversely, pY658-VEC signs elongating spermatids; its intracellular polarized compartmentalization suggests a possible involvement of pY658-VEC in the acquisition of spermatid cell polarity.     

粗糙沼虾精巢发育的组织学

利用光镜技术,对粗糙沼虾精巢发育进行了研究,根据精子发生过程中每种生殖细胞所占的比例和发生的次序,并结合精巢的形态特征,把精巢发育过程分为五个时期,即精原细胞期,精母细胞期,精细胞期,成熟精子期及退化期,精原细胞期,精巢小,透明乳白色,生精小管内的生殖细胞以精原细胞为主;精母细胞期;精巢体积增大,半透明乳白色,主要由处于初级精母细胞的次级精母细胞阶段的生殖细胞组成;精细胞期,精巢体积继续增大,颜色加深,生精小管内的生殖细胞以精细胞为主;成熟精子期,精巢体积可达最大,紫红色,生精小管内充满着成熟的精子,退化期;精巢体积减小,半透明乳白色,生精小管内的成熟精子几乎排空。     

Ultrastructural study of the Sertoli cell and the limiting membrane in the seminiferous tubule of the adult cryptorchid rat

Cryptorchidism was simulated in 13-15-day-old rats by severing the gubernaculum testis and fixing the testis to the abdominal wall. Ultrastructural examination of the testis was made 100 days after birth when a number of modifications to the seminiferous tubules were noted. Germ cells were scanty, with only occasional spermatogonia and primary spermatocytes persisting. The nuclei of Sertoli cells were regular and oval or indented in shape. Their cytoplasm was characterized by a rich smooth endoplasmic reticulum, lipid inclusions and mitochondria with tubulo-vesicular cristae indicative of stero?dogenic activity. The decrease in the number of the germ cells induced a membrane rearrangement with numerous tight junctions and interdigitations between the Sertoli cells. Sertoli cell-specific junctional complexes were very extensive. The lamina propria of the seminiferous tubule appeared thickened and folded and the multilayered basal lamina had complex folds. After fixation with glutaraldehyde containing lanthanum, the latter substance was identified in the basal intercellular spaces of the seminiferous tubules indicating that the blood-testis barrier remains functional in the intra-abdominal testis.     

Rat testis motor proteins associated with spermatid translocation (dynein) and spermatid flagella (kinesin-II)

In this study, we report sites in the seminiferous epithelium of the rat testis that are immunoreactive with antibodies to the intermediate chain of cytoplasmic dynein and kinesin II. The study was done to determine whether or not microtubule-dependent motor proteins are present in Sertoli cell regions involved with spermatid translocation. Sections and epithelial fragments of perfusion-fixed rat testis were probed with an antibody (clone 74.1) to the intermediate chain of cytoplasmic dynein (IC74) and to kinesin-II. Labeling with the antibody to cytoplasmic dynein was dramatically evident in Sertoli cell regions surrounding apical crypts containing attached spermatids and known to contain unique intercellular attachment plaques. The antibody to kinesin II reacted only with spermatid tails. The levels of cytoplasmic dynein visible on immunoblots of supernatants collected from spermatid/junction complexes treated with an actin-severing enzyme (gelsolin) were greater than those of controls, indicating that at least some of the dynein may have been associated with Sertoli cell junction plaques attached to spermatids. Results are consistent with the conclusion that an isoform of cytoplasmic dynein may be responsible for the apical translocation of elongate spermatids that occurs before sperm release. Also, this is the first report of kinesin-II in mammalian spermatid tails.     

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.     

Spontaneous degeneration of germ cells in normal rat testis: assessment of cell types and frequency during the spermatogenic cycle.

The occurrence of degenerating germ cells in the cycle of the seminiferous epithelium was measured in testicular tissues from eight normal adult rats. Testes were perfusion fixed, embedded in epoxy resin and, after sectioning a total of 180 randomly selected blocks at 1 microns, stained sections were examined by light microscopy; all cross-sectioned seminiferous tubules were categorized into one of 14 stages of the spermatogenic cycle. The number of degenerating cells per tubule was recorded in 2103 tubules. Degenerating germ cells were not detected at stages II-VI, and only rarely at stage VII (n = 366 tubules) in which one primary spermatocyte and one step 19 spermatid degenerated. All other stages exhibited a greater incidence of degenerative germ cells, particularly at stage XIV where, on average, the frequency of degenerating cells per round seminiferous tubule was about 40 times greater than at stage VII. The results indicated that, in the normal adult rat testis, the germ cells are least at risk of degeneration as they pass through stage VII.