细胞运动、细胞迁移与细胞骨架研究进展

细胞定向运动与细胞骨架的动态循环密切相关。运动细胞在其伪足前沿依靠细胞骨架的不断聚合推动细胞膜的前进,在基部靠近细胞体部位通过细胞骨架的不断解聚收缩拖拉细胞体向前运动,细胞骨架的聚合与解聚通过伪足与支撑表面的吸附与解吸附而偶连。肌动蛋白组成的微丝骨架是大多数运动细胞的主要成分。外界刺激引起微丝细胞骨架动态变化的信号通路已逐步明了。线虫精子细胞的运动行为与阿米巴变形运动相似,但是在线虫精子细胞中没有肌动蛋白,而是以精子主要蛋白为基础形成细胞骨架驱动精子细胞的运动。与肌动蛋白不同,精子主要蛋白没有分子极性、ATP结合位点和马达蛋白。通过比较研究以上两种运动体系将有助于在分子水平上进一步阐明细胞运动的机理。     

优雅蝈螽精子形成期间微丝和微管蛋白的动态变化

【目的】分析微丝和微管蛋白在优雅蝈螽Gampsocleis gratiosa精子形成过程中的作用,为昆虫精子顶体复合体形成和细胞核重建机制研究奠定基础。【方法】应用免疫荧光、PAS-苏木精染色和透射电镜等方法,对优雅蝈螽成虫的精巢、雄性贮精囊和雌性受精囊内精子的发育以及微丝和微管蛋白在精子形成各个时期的分布进行了观察。【结果】精巢中,早期圆形精子细胞中微丝在精子细胞的某区域大量聚集,而微管蛋白随机分布在细胞质中。伸长的精子细胞中,顶体开始形成时,微丝首先在亚顶体区域出现,历经球形、短棒形,然后向细胞核的两侧扩展成倒"Y"形,接着形成箭头形;在顶体的外周即微丝的周围,细胞核周围以及鞭毛中发现微管蛋白。在雄虫贮精囊和雌虫受精囊中,精子和精子束中仅有微管存在,且仅存在于鞭毛中;精子头部的微丝和微管蛋白均消失。【结论】综合分析,我们认为微丝和微管作为"脚手架"结构在优雅蝈螽精子形成期间参与顶体复合体形成和细胞核重建,精子成熟形成精子束过程中"脚手架"结构拆除。     

中国石龙子雄性生殖腺的年周期变化

20 0 1年 3月至 2 0 0 2年 2月期间 ,通过每月捕捉浙江丽水中国石龙子 (Eumeceschinensis)雄性成体 ,解剖动物、观测性腺的形态和组织学特征 ,研究雄性生殖周期。睾丸重量和体积、附睾重、输精管重和曲细精管直径有显著的季节变化。睾丸 3月份最重 ,5-9月最轻。睾丸体积和重量的年周期变化规律一致。附睾 3月份最重 ,8-9月份最轻。输精管 4月最重 ,8-10月最轻。生精活动始于 9月下旬 ,翌年 4月最为活跃。 3月下旬曲细精管直径达全年最大值 ,管腔中开始出现呈穗状排列的精子。从基膜到管腔 ,各级生精细胞依次排列。 4月份生精上皮的生精活动最为活跃 ,5月下旬生精活动已近停止 ,7-8月份曲细精管管壁仅由精原细胞 (其间夹有支持细胞 )构成。根据曲细精管生精上皮的年周期变化规律 ,中国石龙子 8月份睾丸生精活动处于第Ⅰ期 ,9月至次年 2月份第Ⅱ期 ,3月上、中旬为Ⅲ期 ,3月底至 4月为Ⅳ期 ,5-6月份为Ⅴ期 ,7月份为Ⅵ期。 4月下旬附睾管腔中有大量的成熟精子 ,7月附睾管腔中已无精子。中国石龙子属于关联型繁殖周期     

原癌基因FOS蛋白、雌二醇及其受体在中国林蛙不同时期精巢中的表达

用免疫细胞化学方法检测了原癌基因FOS蛋白、17β-雌二醇(E2)和雌激素受体(ER)在中国林蛙生精周期中不同时期精巢内的表达定位。结果显示:在中国林蛙生精周期的Ⅰ—Ⅴ期,E2和ER在精原细胞、精母细胞、精子细胞、精子、支持细胞和间质细胞内均有表达。在不同时期的精巢中,E2和ER在生精细胞的定位具有一致性:在Ⅱ—Ⅲ期,精子细胞的E2和ER阳性表达最强;在Ⅲ期,精子中E2和ER阳性反应强度显著高于Ⅳ—Ⅴ期(P<0.01)。在生精周期的Ⅰ—Ⅴ期,支持细胞中,E2和ER表达强度经历由强减弱再增强的变化过程。在生精周期的Ⅲ期,间质细胞中E2和ER阳性反应强度高于其他各期。除精子外的生精细胞,支持细胞和间质细胞内均有FOS阳性反应,其表达强度呈现阶段性变化。     

支持细胞在生精细胞凋亡过程中的重要作用

精子的生成过程是一个连续的周期性的过程,这包括二倍体的精原细胞进行一系列的有丝分裂,减数分裂最后分化成为成熟的单倍体精子的过程。支持细胞(Sertoli cell)是生精上皮的一种大细胞,它从管周肌样细胞所处的基底膜延伸出去,直到生精小管的管腔内。它的底部与精原细胞相连,胞质的侧面则形成许多突起将互相联系的生精细胞包围起来,成熟的精子就从这儿释放出去。在复杂的动态生精过程中,支持细胞作为精曲小管的重要组成部分指挥着生精细胞的一系列动态过程,包括有丝分裂、减数分裂以及以后的分化。支持细胞通过给生精细胞提供激素、营养以及生理支持来完成它的功能。     

FXR1通过相分离激活后期精子细胞中mRNA的翻译

<正>减数分裂后的单倍体精子细胞经过一系列剧烈形态及结构变化,包括细胞质丢弃、细胞核压缩、顶体和鞭毛形成等,最终发育为高度特化的精细胞或精子,此过程被称为精子形成(spermiogenesis)[1～3]。基于精子细胞的形态变化,研究人员将小鼠的精子形成过程划分为16个步骤：第1～8步球形精子细胞期,第9～11步延长形精子细胞期,第12～14步长形精子细胞期,第15～16步精子细胞则基本发育完成,呈现典型的弯钩状[4]。     

血管内皮生长因子蛋白在大鼠睾丸和附睾的表达和定位研究

为探讨血管内皮生长因子(VEGF)在雄性生殖系精子发生发育和成熟过程中的调控作用,应用免疫组化、Periodic acid-Schiff(PAS)染色及蛋白质免疫印迹技术,检测VEGF蛋白在成年大鼠睾丸和附睾的表达和定位情况。Western-blots显示,在大鼠睾丸和附睾内均有VEGF蛋白(约45kD)的表达;免疫组化显示,睾丸内VEGF见于圆形和长形精子细胞、Sertoli细胞和Leydig细胞,免疫阳性产物位于细胞质内。精子细胞的VEGF表达伴随精子细胞顶体发育的全过程,精子残余体呈强阳性。附睾内VEGF表达于附睾管上皮,且有区域和细胞特异性。附睾起始段的所有上皮主细胞内都有VEGF阳性颗粒;头、体、尾各段的VEGF阳性细胞多数与含PAS阳性颗粒的细胞重合,证明为亮细胞;近端附睾的管腔内可见精子头部呈VEGF阳性染色。睾丸、附睾间质血管内皮为VEGF阴性。上述结果表明,VEGF蛋白可由生殖细胞和附睾管上皮细胞直接产生,它可能以自分泌和/或旁分泌的形式共同作用于睾丸和附睾的生殖细胞和血管内皮,直接或间接影响精子的发生、发育和成熟过程,特别是精子顶体的形成过程,并可能与精子在附睾内的成熟有关。     

中华蟾蜍精子的发生和形成

中华蟾蜍精子的发生可以分为精原细胞期、初级精母细胞期、次级精母细胞期、精子细胞期和精子期5个时期,精子的形成过程包括核固缩、细胞质丢失、鞭毛形成等阶段.曲细精管中可以分出4种形态的精原细胞,其中有3种为增殖型精原细胞,另1种形态的精原细胞通过分裂形成1个精原干细胞和1个增殖型精原细胞,前者分裂以维持精原细胞的数量,后者发育分裂成精母细胞.Mallory三色法染色能清晰的区分精原干细胞和增殖型精原细胞.毕特氏器是异性生殖腺的残余,与精巢以被膜为界.性成熟个体的毕特氏器之卵母细胞圆形或椭圆形,多处于Ⅲ时相;滤泡细胞扁平或矮立方状;卵母细胞间富含微血管、间质细胞、嗜苦味酸细胞等.     

安得爱胜蚓精子及精子形成的超微结构

利用透射电镜研究了安得爱胜蚓（Eisenia anderi)精子的超微结构及其形成过程,精子呈纤毛状,由顶体,核,中段和鞭毛四部分组成,全长92μm左右,储精囊中可见成束的各种发育阶段的生精细胞。文中详细描述了从精子细胞到成熟精子的精子形成过程。     

大鼠睾丸曲细精管组织支持细胞/生殖细胞长期共培养与精子发生分析

睾丸体外生殖模型的发展为体外研究睾丸的精子发生分子机制和睾丸毒理学提供了实验工具。很多报道的模型都无法真正地模拟体内复杂的生化分子及功能性相互作用从而导致研究价值有限。该实验拟建立一个体外长期维持睾丸生殖细胞存在,并能持续产生精子细胞的支持细胞/生殖细胞共培养体系。体系中的支持细胞和生殖细胞均由曲细精管组织块迁移到培养皿上,在不添加任何生长因子的情况下维持体外精子发生至圆形精子细胞超过2个月。RT-PCR分析显示,共培养细胞稳定表达cdh1、scp3、tnp2;免疫荧光染色结果显示,CDH1、PLZF、SCP3以及SOX9阳性细胞存在。这些结果例证了体系中同时存在精原干细胞、精母细胞、精子细胞和支持细胞。简单高效的支持细胞/生殖细胞体外共培养体系可用于雄性生殖的分子机制和毒理学研究。     

Cytoskeletal involvement in spermiation and sperm transport

The process of spermiation and sperm transport was studied using specific inhibitors of cytoskeletal elements. Within 12-24 hr after the intratesticular injection of taxol, a compound that acts to stabilize microtubules and inhibit microtubule-related processes, an unusually large number of microtubules was seen within the body of the Sertoli cell. At the same time, transport of elements within the seminiferous epithelium was affected. At the end of stage VI of the cycle, step 19 spermatids were maintained in the deep recesses of the Sertoli cell and not transported to the rim of the seminiferous tubule lumen. At stage VIII, residual bodies remained at, or near, the rim of the tubule and were not transported to the base of the tubule. They underwent only partial degradation at this site, indicating that there may have been two phases involved in their dissolution--one autophagic and one phagocytic, but the latter did not occur since the residual bodies were not transported to Sertoli lysosomes at the base of the tubule. The observations suggest that microtubules are involved in transport processes within the seminiferous epithelium. Within 1-12 hr after the intratesticular injection of 500 microM cytochalasin D, a compound which interferes with actin-related processes, normal appearing tubulobulbar complexes were not present. The tubular portion (distal tube) of the complex did not initiate development. It was assumed that filaments (which were identified as such using NBD-phallacidin and the S-1 fragment of myosin) played an important role in the development of this portion of the complex. Cells did not eliminate cytoplasm normally, as evidenced by an enlarged cytoplasmic droplet, further emphasizing the published role for tubulobulbar complexes in cytoplasmic elimination. Although sperm were released normally from stage VIII tubules, many remained within the tubular lumen and did not traverse the duct system. Cytochalasin did not inhibit fluid secretion by the Sertoli cell, as demonstrated by efferent duct ligation, but did alter myoid cell actin cytoskeletal organization, suggesting that myoid cell contractility is primarily responsible for transport of sperm. Overall, the observations suggest that cytoskeletal activity of the Sertoli cell is important for several aspects of the spermiation process as well as sperm transport.     

Seminiferous tubule involution in elderly men

The observation of different types of seminiferous tubules (from tubules with normal spermatogenesis to sclerosed tubules) in aging human testes points to the progressive stages of tubular involution in elderly men. The tubules with hypospermatogonesis (reduced number of elongated spermatids) show numerous morphological anomalies in the germ cells, including multinucleated cells. Abnormal germ cells degenerate, causing Steroli cell vacuolation. These vacuoles correspond to dilations of the extracellular spaces resulting from the premature exfoliation of germ cells. Degenerating cells that are phagocytized by Sertoli cells lead to an accumulation of lipid droplets in the Sertoli cell cytoplasm. The loss of germ cells begins with spermatids, but progressively affects the preceding germ cell types, and tubules with maturation arrested at the level of spermatocytes or spermatogonia are observed. Simultaneously, an enlargement of the tunica propria occurs. This leads to the formation of sclerosed tubules, some of which display a low seminiferous epithelium consisting of a few cells--including lipid-loaded Sertoli cells and both Ap and Ad spermatogonia--and others, showing complete sclerosis, are devoid of seminiferous epithelium. The development of tubular involution is similar to that reported after experimental ischemia, which also seems to cause nonspecific effects on the testis such as multinucleate cells, vacuoles, and increased lipids in Sertoli cells.     

Morphology of the bovine Sertoli cell during the spermatogenetic cycle

Summary The morphology of the bovine Sertoli cell was studied during 6 different phases of the spermatogenetic cycle. Tubular dimensions do not vary significantly during the phases. Sertoli cells occupy 27.0% (phase 4) to 38.4% (phase 8) of the tubular epithelium. Sertoli cells of phase 1 are approximately 20% larger than during the other phases. 30–35% of Sertoli cell volume consists of organelles. Mitochondrial (about 5.0%) and nuclear (about 5.7%) volume densities remain remarkably stable during the cycle, irrespective of changes in Sertoli cell size. Phagocytic capacity of bovine Sertoli cells is only moderate. Elimination of excess spermatid cytoplasm occurs to a large extent prior to spermiation. The majority of spermatid residual bodies undergoes autolytic decay while attached to the Sertoli cell apical surface. Aggregates of densely packed cisternae of the smooth endoplasmic reticulum (ER) located in a basal position and associated with the acrosome-phase and maturation-phase spermatids contribute between 14 and 17% to Sertoli cell volume. During phase 3 the ER pinches off a large number of small, smooth-walled vesicles filled with flocculent content. The contact area between Sertoli cells and other tubular constituents changes considerably during the different phases. It is concluded that the blood-testis barrier is particularly impassable during phases 1 and 8. A lipid cycle does not exist in the bovine testicular tubular epithelium.     

The consequences of actin disruption at Sertoli ectoplasmic specialization sites facing spermatids after in vivo exposure of rat testis to cytochalasin D

Cytochalasin D (CD) was used to perturb actin filaments of the Sertoli ectoplasmic specialization (ES)--a cytoskeletal complex of the Sertoli cell related to spermatids. CD (500 microM for 6 h) produced a loss of 88% of the ES facing the head region of early (Step 8) elongating spermatids as compared to vehicle (dimethylsulfoxide:saline) controls. Nitrobenzoxadiazole-phallacidin staining of F-actin revealed a CD-related loss of uniform fluorescence over the head of elongated spermatids. To examine for a possible relationship between the presence of actin and cell attachment at ES sites, hypertonic fixatives were introduced to provoke cell shrinkage and stress ES-associated junctions. After osmotic stress, cell-to-cell adhesion at ES sites remained intact in vehicle-treated animals. CD treatment caused Sertoli cells to separate from elongating spermatids at sites where ES had been lost from the Sertoli cell surface. It is suggested that actin of the ES plays a role in cell-to-cell interaction analogous to its possible role at the Sertoli cell barrier. In CD-treated animals, structures resembling tubulobulbar complexes frequently developed at sites where ES was lost, suggesting that the loss of ES has a facilitatory role in tubulobulbar complex formation. It is hypothesized that tubulobulbar complexes are devices that rid the cells of ES-associated junctional links to effect dissociation of the spermatid from the Sertoli cell during spermiation. Spermatids at Step 8 of development are known to become oriented with their acrosomes facing the base of the Sertoli cell. After CD treatment, a 5.8-fold increase in malorientation of Step 8 spermatids was noted. A role for the ES cytoskeletal complex in orienting the spermatid acrosome toward the basal aspect of the Sertoli cell is also suggested.     

Male sterility in mice lacking retinoic acid receptor alpha involves specific abnormalities in spermiogenesis

The severe degeneration of the germinal epithelium and subsequent male sterility observed in mice null for the retinoic acid receptor alpha (RARalpha) gene suggested its critical role in spermatogenesis, although the etiology and progression of these abnormalities remain to be determined. Previous studies have revealed that elongated spermatids in RARalpha(-/-) testes were improperly aligned at the tubular lumen and did not undergo spermiation at stage VIII(*). We now report a distinctive failure of step 8-9 spermatids to orient properly with regard to the basal aspect of Sertoli cells, resulting in stage VIII(*)-IX(*) tubules with randomly oriented spermatids. By in situ terminal deoxynucleotidyltransferase-mediated deoxy-UTP nick end labeling (TUNEL), we noted that elongating spermatids frequently underwent apoptosis. Immunohistochemical analysis revealed that while activated caspase-3, the primary effector caspase in the apoptotic cell death machinery, was detected in the nuclei of primary spermatocytes in the first wave of spermatogenesis and occasionally in spermatogonia of both normal and mutant testes, it was not involved in the death of elongating spermatids in RARalpha(-/-) testes. Thus, sterility in RARalpha(-/-) males was associated with specific defects in spermiogenesis, which may correlate with a failure in both spermatid release and spermatid orientation to the basal aspect of Sertoli cells at stage VIII(*) in young adult RARalpha(-/-) testis. Further, the resulting apoptosis in elongating spermatids appears to involve pathways other than that mediated by activated caspase-3.     

Sertoli cell ectoplasmic specializations in the seminiferous epithelium of the testosterone-suppressed adult rat

The Sertoli cell ectoplasmic specialization is a unique junctional structure involved in the interaction between elongating spermatids and Sertoli cells. We have previously shown that suppression of testicular testosterone in adult rats by low-dose testosterone and estradiol (TE) treatment causes the premature detachment of step 8 round spermatids from the Sertoli cell. Because these detaching round spermatids would normally associate with the Sertoli cell via the ectoplasmic specialization, we hypothesized that ectoplasmic specializations would be absent in the seminiferous epithelium of TE-treated rats, and the lack of this junction would cause round spermatids to detach. In this study, we investigated Sertoli cell ectoplasmic specializations in normal and TE-treated rat testis using electron microscopy and localization of known ectoplasmic specialization-associated proteins (espin, actin, and vinculin) by immunocytochemistry and confocal microscopy. In TE-treated rats where round spermatid detachment was occurring, ectoplasmic specializations of normal morphology were observed opposite the remaining step 8 spermatids in the epithelium and, importantly, in the adluminal Sertoli cell cytoplasm during and after round spermatid detachment. When higher doses of testosterone were administered to promote the reattachment of all step 8 round spermatids, newly elongating spermatids associated with ectoplasmic specialization proteins within 2 days. We concluded that the Sertoli cell ectoplasmic specialization structure is qualitatively normal in TE-treated rats, and thus the absence of this structure is unlikely to be the cause of round spermatid detachment. We suggest that defects in adhesion molecules between round spermatids and Sertoli cells are likely to be involved in the testosterone-dependent detachment of round spermatids from the seminiferous epithelium.     

Actin-related intercellular adhesion junctions in the germinal compartment of the testis in the hagfish (Eptatretus stouti) and lamprey (Lampetra tridentatus)

The germinal epithelium of male vertebrates consists of Sertoli cells and spermatogenic cells. Intercellular junctions formed by Sertoli cells assume critical roles in the normal functions of this epithelium. While Sertoli cell junctions have been well characterized in mammals, similar junctions in nonmammalian vertebrates have received little attention. We examined the intercellular junctions found within the germinal epithelium of the hagfish (Eptatretus stouti) and lamprey (Lampetra tridentatus). Ultrastructurally, Sertoli cells were seen to form filament-associated junctions in both species. Adjacent Sertoli cells formed microfilament-related junctions near their apices. Filaments of these junctions were arranged in loose networks and were not associated with cisterns of endoplasmic reticulum. In fixed, frozen sections of hagfish testis, similar areas labeled with rhodamine phalloidin, indicating the filament type is actin. In the lamprey, desmosomes were observed immediately below the microfilament-related junctions. In appearance and location, the Sertoli cell junctions observed in these species resembled those of the typical junctional complex of other epithelial cell types. No junctions were observed between Sertoli cells and elongating spermatids. In the hagfish, but not the lamprey, an additional zone of microfilaments occurred near the base of Sertoli cells in areas of association with the basal lamina. Our observations are consistent with the proposal that the unique forms of intercellular attachment found in the testes of higher vertebrates evolved from a typical epithelial form of intercellular junction.     

Light and electron microscopic localization of ATPase in normal and degenerating testes of Syrian hamsters.

The distribution of Mg++-activated ATPase was determined with light and electron microscopy in normal and degenerating seminferous tubules. In the normal animals ATPase was localized in the interface between spermatids and Sertoli cells, in association with the cytoplasmic filaments contained within Sertoli cell processes, and in the lymphatic endothelium. ATPase activity increased in degenerating tubules as observed by light microscopy. Electron microscopic investigations of the degenerating tubules which contained only spermatogonia and Sertoli cells revealed reaction product on the outer surface of the Sertoli cell processes and within the interface between adjacent Sertoli cells. Reactaction product was also observed in the Sertoli cell processes between the cytoplasmic filaments and the cell membrane. Where filaments were absent in Sertoli cell processes, no reaction product was observed. These electron microscopic studies indicate that the increase in ATPase activity in testicular degeneration is probably a relative increase due to a loss of the germinal elements of the tubular epithelium and subsequent apposition of the Sertoli cell processes. We speculate that the ATPase activity localized within the Sertoli cell processes may be involved in providing an energy source for filament motility.     

An ultrastructural study of the effect of a diabetogenic dose of alloxan on the secretory ameloblasts of the rat incisor

Sertoli cells of the ground squirrel (Spermophilus lateralis), a seasonal breeder, were examined by light and electron microscopy and their structure, particularly the organization of the cytoskeleton, was related to events that occur in the seminiferous epithelium during spermatogenesis. Among the events considered and described are the apical movement of elongate spermatids, withdrawal of residual cytoplasm from germ cells, transport of smooth endoplasmic reticulum (SER) between the base and apex of the Sertoli cells, and sperm release. These events are dramatically evident in this species because the seminiferous epithelium is thin, i.e., there are few germ cells, and both the germ cells and Sertoli cells are large. Sertoli cells of the ground squirrel have a remarkably well developed cytoskeleton. Microfilaments occur throughout the cell but are most evident in ectoplasmic specializations associated with junctions. Intermediate filaments occur around the nucleus, as a layer at the base of the cell, and adjacent to desmosome-like junctions with germ cells. Intermediate filaments, together with microtubules, are also abundant in regions of the cell involved with the transport of SER, in cytoplasm associated with elongate spermatids, and in processes that extend into the residual cytoplasm of germ cells. Our observations of ultrastructure are consistent with the hypothesis that Sertoli cell microtubules are involved with the movement of germ cells within the seminiferous epithelium, and further implicate these structures as possibly playing a role in the retraction of residual cytoplasm from germ cells and the intracellular transport of SER. The abundance and organization of intermediate filaments suggest that these cytoskeletal elements may also be involved with events that occur during spermatogenesis.     

A comparative study in twelve mammalian species of volume densities, volumes, and numerical densities of selected testis components, emphasizing those related to the Sertoli cell

Morphometric studies were performed on 12 mammalian species (degu, dog, guinea pig, hamster, human, monkey, mouse, opossum, rabbit, rat, stallion, and woodchuck) to determine volume density percentage (Vv%), volume (V), and numerical density (Nv) of seminiferous tubule components, especially those related to the Sertoli cell, and to make species comparisons. For most species, measurements were taken both from stages where elongate spermatids were deeply embedded within the Sertoli cell and from stages near sperm release where elongate spermatids were in shallow crypts within the Sertoli cell. Montages, prepared from electron micrographs, were used to determine Vv% of Sertoli cell components in seminiferous tubules. Excluding the tubular lumen, the Sertoli cell occupied from a high of 43.1% (woodchuck) to a low of 14.0% (mouse) of the tubular epithelium. There was a strong negative correlation (r = -0.83; P less than 0.005) of volume occupancy of Sertoli cells with sperm production. Nuclear volume, as determined by serial reconstruction using serial thick sections, ranged from a high of 848.4 microns 3 (opossum) to a low of 273.8 microns 3 (degu). There was no correlation (r = 0.02) of nuclear volume with volume occupancy (Vv%) in the tubule. Sertoli cell volume was determined by point-counting morphometry at the electron-microscope level as the product of the nuclear size and points determined over the entire cell divided by points over the nucleus. Sertoli cell V ranged from 2,035.3 microns 3 (degu) to 7,011.6 microns 3 (opossum) and was highly correlated (r = 0.85; P less than 0.001) with nuclear size. However, there was no significant correlation between the Sertoli cell size (V) and volume occupancy (Vv%; r = 0.13) or sperm production (r = -0.21). Stereological estimates of the numerical density (Nv) of Sertoli cells ranged from a high of 101.9 x 10(6) (monkey) to a low of 24.9 x 10(6) (rabbit) cells per cm3 of testicular tissue. There was no correlation of numerical density of Sertoli cells with sperm production (r = 0.002). A negative correlation was, however, observed between the numerical density of the Sertoli cells and the Sertoli cell size (r = -0.79; P less than 0.002). Data from the present study are compared with those previously published. This is the first study to compare Sertoli cell morphological measurements using unbiased sampling techniques. Morphometric data are provided which will serve as a basis for other morphometric studies.