Morphometric studies on lipid inclusions in Sertoli cells during the spermatogenic cycle in the rat

Summary The volume and surface area of lipid inclusions often present in the cytoplasm of rat Sertoli cells was measured directly from semi-thin sections of perfusion-fixed testicular tissues using an image analyser linked to a light microscope. Sertoli cell nuclei were used as a reference for comparing any variations in the measured parameters of lipid inclusions during the rat spermatogenic cycle. Volume density of Sertoli cell lipid inclusions was assessed by morphometric analysis of Sertoli cells photographically reconstructed from electron micrographs. Maximum lipid content in Sertoli cells occurred during stages IX–XIV of the spermatogenic cycle, then declined at stages I–III and remained low from stages IV–VIII. The persistence and increase in number of many large Sertoli cell lipid inclusions beyond the stage where spermatid residual bodies are phagocytosed within the Sertoli cells (stage IX) suggests that the synthesis and lipolysis of Sertoli cell lipid inclusions represents an intrinsic functional cycle of the Sertoli cells. Stage-dependent variations in the lipid content of rat Sertoli cells offers morphological evidence that the metabolic duties of the Sertoli cells are synchronised with the spermatogenic cycle to provide local coordination of the proliferation and maturation of the germ cells.     

Proceedings: The role of the Sertoli cell in phagocytosis of the residual bodies of spermatids

The fate of residual bodies which form as spermatids are released from the seminiferous epithelium has been studied as part of a cytological investigation of the Sertoli cells during the stages of rat spermatogenesis. Testes from normal adult rats were fixed by whole body perfusion. All 14 stages of rat spermatogenesis were identified and studied by light and electron microscopy. Residual bodies are released at Stage 8 and are found in the luminal spaces of the seminiferous epithelium. During Stage 9 they appear to migrate peripherally in channels of the Seroli cell cytoplasm. During this migration, lysosomal-like bodies surround the residual bodies and appear to be involved in the degradative process. A considerable proportion of the lipid material persists and forms basal collections in the Sertoli cells. The lipid inclusions reach a peak at Stages 13 and 14 of the cycle and persist until Stage 2 and 3. Some lipid inclusions persist until Stage 4 to 7 when noticeable decrease occurs corresponding to the peripheral migration of maturing spermatids.     

Role of sulfated glycoprotein-1 (SGP-1) in the disposal of residual bodies by sertoli cells of the rat

Sulfated glycoprotein-1 (SGP-1) is a polypeptide secreted by Sertoli cells in the rat. Sequence analysis revealed a 76% sequence similarity with human prosaposin produced by various cell types. Human prosaposin is a 70 kDa protein which is cleaved in the lysosomes into four 10–15 kDa polypeptides termed saposins A, B, C, and D. The function of lysosomal saposins is to either solubilize certain membrane glycolipids or to form complexes with lysosomal enzymes and/or their glycolipid substrate to facilitate their hydrolysis. The present investigation dealt with the delivery of SGP-1 into the phagosomes of Sertoli cells; these phagosomes contain the residual bodies which detach from the late spermatids at the time of spermiation. Immunogold labeling with anti-SGP-1 antibody was found over Sertoli cell lysosomes, but was absent from phagosomes formed after phagocytosis of spermatid residual bodies in the apical Sertoli cell cytoplasm in stages VIII and early IX of the cycle of the seminiferous epithelium. The phagosomes found later in the basal Sertoli cell cytoplasm in stages IX and X of the cycle became labeled with the antibody as the components of the residual bodies rapidly underwent lysis and disappeared from the Sertoli cells. Sertoli cell lysosomes isolated by cell fractionation (estimated purity of 80%) were found to contain a 65 kDa form of SGP-1 or prosaposin, as well as the 15 kDa polypeptides or saposins. Thus, it appears that this unique lysosomal form of SGP-1 reached the Sertoli cell phagosomes and that their derived polypeptides, the saposins, must play a role in the hydrolysis of membrane glycolipids found in phagocytosed residual bodies. © 1995 Wiley-Liss, Inc.     

Relative volume of Sertoli cells in monkey seminiferous epithelium: a stereological analysis.

Techniques of quantitative stereology have been utilized to determine the relative volume occupied by the Sertoli cells and germ cells in two particular stages (I and VII) of the cycle of the seminiferous epithelium. Sertoli cell volume ranged from 24% in stage I of the cycle to 32% in stage VII. Early germ cells occupied 3.4% in stage I (spermatogonia) and 8.7% in stage VII (spermatogonia and preleptotene spermatocytes). Pachytene spermatocytes occupied 15% (Stage I) and 24% (stage VII) of the total volume of the seminiferous epithelium. In stage I the two generations of spermatids comprised 58% of the total epithelium by volume, whereas in stage VII, after spermiation, the acrosome phase spermatids occupied 35% of the total seminiferous epithelial volume.     

Cyclic endocytic activity and kinetics of lysosomes in Sertoli cells of the rat: a morphometric analysis

Native ferritin was injected into the rete testis of rats, and seminiferous tubules infused with the tracer were collected 6 h later and prepared for electron microscopic analysis. As a result of internalization of the tracer by Sertoli cells, label was found within 12-66% of the secondary lysosomes, depending on the stage of the cycle of the seminiferous epithelium. The Zeiss MOP-3 instrument was used on selected electron microscope photographs to measure a number of morphometric parameters. Applying appropriate formulae and a computerized program, it was possible to determine the absolute numbers of labeled and unlabeled secondary lysosomes per Sertoli cell for each one of the 14 stages of the cycle. Knowing the duration of these stages, it was also possible to evaluate the turnover kinetics and life span of lysosomes for each stage of the cycle. The percentage of ferritin-labeled lysosomes, regarded as an index of the endocytic activity of Sertoli cells, remained low in stages II to VIII, increased abruptly during stage IX, stayed high during stages X to XIV, and decreased to a low level during stage I of the following cycle. Correspondingly, the turnover of secondary lysosomes was relatively slow and their life span relatively long during stages II through VIII, while the turnover of lysosomes was faster and their life span shorter during stages X through XIV-I of the cycle. During stage IX, there was a sharp drop in the number of lysosomes per Sertoli cell associated with a fast rate of disappearance and a remarkably short life span of less than 4 h for the lysosomes. These features, characteristic of stage IX, are explained by the rapid fusion of lysosomes with residual bodies, which are phagocytosed by Sertoli cells at this particular stage of the cycle. The accelerated endocytosis taking place during stages IX through XIV of the cycle may explain the reduction of the surface area of the adluminal plasma membrane of Sertoli cells as well as the reduction in volume of the tubular lumen observed during these stages. Thus, the demonstrated cyclic endocytic activity of Sertoli cells and several other cyclical events taking place within seminiferous tubules correlate well.     

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.     

An ultrastructural and autoradiographic study of the immune response in Hyalophora cecropia pupae

Summary Membrane-bounded spherical vesicles found in rat Sertoli cells have been examined quantitatively during the cycle of the seminiferous epithelium. Most of the vesicles were localized to the basal and columnar portions of the Sertoli cell cytoplasm. The thin lateral projections of the Sertoli cells contained very few vesicles. Morphometric analysis of the basal portion of the Sertoli cell cytoplasm revealed that the volume density (V _v ) of the vesicles changed markedly during the cycle. The V _v was at its minimum (0.036) at stage VII and maximum (0.117) at stages XI-I. The vesicles were also smaller at stage VII compared to the vesicles at stages IX-V. The stage-dependent difference in the size of the vesicles was found both in the basal and the columnar portions of the Sertoli cells. At stage VII some of the vesicles appeared to be elongated much like the tubular elements of the smooth endoplasmic reticulum (SER) from which they are probably derived. The stage-dependent differences in volume density and size of the Sertoli cell vesicles may be related to cyclic biochemical variations in the Sertoli cells, and are further indications of a variation in Sertoli cell function during the cycle of the seminiferous epithelium. Whether or not this is due to an internal cycle of the Sertoli cell or to influences from adjacent germ cells remains to be determined.     

The structure and cytochemistry of the oocytes in the crab Xantho bidentatus Milne Edwards

In the development of the oocytes of xantho bidentatus four stages could be distinguished. In stage I the cytoplasm is homogenous, in state II a perinuclear ring is formed, in stage III oocytes round bodies which are carbohydrate-protein complexes appear near the peripheri. These bodies occupy the oocyte completely in the stage IV oocyte. There are two types of bodies in the oocyte, big oval or round bodies which are carbohydrate-protein complexes and smaller bodies in between the oval bodies. These smaller bodies are lipid bodies. In stage I and II the cytoplasm is rich in RNA and in stages III and IV the cytoplasm is full of carbohydrates, proteins and lipids.     

Expression and localization of cathepsin k in adult rat sertoli cells

The cathepsins are a family of cysteine proteases that have been broadly implicated in proteolytic processes during cell growth, cell development, and normal adult cellular function. Cathepsin L is a major secretory product of rat and mouse Sertoli cells, the absence of which in furless mice is associated with atrophy of some seminiferous tubules. However, furless mice produce viable sperm, suggesting the possibility that other members of the cathepsin family of proteases may complement cathepsin L action in the testis. Our objective herein was to begin to test this hypothesis. To this end, we first utilized cDNA microarray technology to identify the members of the cathepsin gene family expressed by freshly isolated adult rat Sertoli cells. This approach, complemented by Northern blot analyses, showed that in addition to cathepsin L, cathepsin K is highly and specifically expressed in Sertoli cells. As is also true of cathepsin L, cathepsin K mRNA was found to be expressed by Sertoli cells at specific stages of the cycle of the seminiferous epithelium, with maximal expression at stages VI-VII. The use of immunocytochemical methods revealed that cathepsin K protein localizes to the cytoplasm of Sertoli cells at stages VI-VIII, to small punctuate lysosomes at stages I-VIII and XIII-XIV, and to early and late residual bodies at stages IX-XII. This localization was found to be similar to that of cathepsin L. The similarity in the expression and localization of cathepsin K and cathepsin L suggest that the two proteases may have similar functions. If true, this might explain the fertility of furless mice. Further, the results suggest that cathepsin K, in both its secreted and lysosomal forms, may play a role in the degradation of Sertoli cell residual bodies.     

Ultrastructure of the Budgerigar testis during a photoperiodically induced cycle

Summary Spermatogenesis in the Budgerigar can be arrested by reducing the birds' photoperiod to 8 hours of daylight or less. When this occurs, Sertoli cell cytoplasm shows a great increase in the size and number of residual bodies, while the smooth endoplasmic reticulum is reduced. If the bird is kept at 8 hours of daylight for some weeks large lipid droplets are seen in Sertoli cytoplasm, and degenerated spermatids are apparently phagocytosed. The interstitium shows fewer active Leydig cells, a paucity of lipids and occasional ovoid mitochondria. The basal lamellae of the tubule which are thick and convoluted before and during spermatogenesis become thinner and straighter. It is thought that these morphological changes reflect changes in metabolic activity.This work was partly supported by a grant from the World Health Organisation for investigation of testicular carcinogenesis.I am grateful to Professor D. Bellamy for provision of laboratory facilities and to A. Stevenson, C. Winter and S. Jones for technical assistance.     

Morphometrical analysis of Sertoli cell ultrastructure during the seminiferous epithelial cycle in rats

Stage-dependent variations of Sertoli cell organelles during the seminiferous epithelial cycle were analyzed morphometrically in rats by use of a point-counting method. Cyclic changes in volume and surface area of various organelles were observed. Mitochondria and rough endoplasmic reticulum increased at stages VII-VIII and stage VII, respectively. Lipid droplets accumulated markedly after spermiation, decreased rapidly after meiotic division, and remained at low levels for stages IV-VIII. The most prominent change was a topographic alteration of the Golgi apparatus. It was usually located exclusively in the basal cytoplasm, but shifted upwards to the mid and apical cytoplasm at stages VII-VIII. This shift may be implicated in an increase of plasma membrane and lysosomes in these regions. Consecutive increases of primary and secondary lysosomes were observed twice in the basal and mid cytoplasm. The first peak of the primary lysosomes at stage IV was followed by the first peak of the secondary lysosomes at stage VI; and the second peak of the primary lysosomes at stages VII-IX was followed by the second peak of the secondary lysosomes at stage IX. These consecutive increases may indicate that Sertoli cells anticipate the increase of structures to be removed and accordingly produce primary lysosomes before their appearance.     

Regulated expression and ultrastructural localization of galectin-1, a proapoptotic beta-galactoside-binding lectin,during spermatogenesis in rat testis

Galectin-1, a highly conserved beta-galactoside-binding protein, induces apoptosis of activated T cells and suppresses the development of autoimmunity and chronic inflammation. To gain insight regarding the potential role of galectin-1 as a novel mechanism of immune privilege, we investigated expression and ultrastructural localization of galectin-1 in rat testis. Galectin-1 expression was assessed by Western blot analysis and immunocytochemical localization in testes obtained from rats aged from 9 to 60 days. Expression of this carbohydrate-binding protein was developmentally regulated, and its immunolabeling exhibited a stage-specific pattern throughout the spermatogenic process. Immunogold staining using the anti-galectin-1 antibody revealed the typical Sertoli cell profile in the seminiferous epithelium, mainly at stages X-II. During spermiation (stages VI-VIII), a strong labeling was observed at the luminal pole of seminiferous epithelium, localized on apical stalks of Sertoli cells, on heads of mature spermatids, and on bodies of residual cytoplasm. Moreover, spermatozoa released into the lumen showed a strong immunostaining. Following spermiation (stage VIII), galectin-1 expression was restored at the basal portion of Sertoli cells and progressively spread out through the whole cells as differentiation of germinal cells proceeded. Immunoelectron microscopy confirmed distribution of galectin-1 in nuclei and cytoplasmic projections of Sertoli cells and on heads and tails of late spermatids and residual bodies. Surface localization of galectin-1 was evidenced in spermatozoa from caput epididymis. Thus, the regulated expression of galectin-1 during the spermatogenic cycle suggests a novel role for this immunosuppressive lectin in reproductive biology.     

Ultrastructural changes in the seminiferous epithelium of two seasonally reproducing bats (Mammalia: Chiroptera)

The Sertoli cells of the Cape horseshoe bat (Rhinolophus capensis) and Schreiber's long-fingered bat (Miniopterus schreibersii) undergo marked changes in ultrastructure related to stages in the spermatogenic cycle. The amount of lipid stored in the Sertoli cells varies annually and is at a maximum from just after spermiation to early in the following spermatogenic cycle. During spermatogenesis, the diameter of the lipid droplets decreases, reaching a minimum prior to spermiation. Sertoli cells exhibit a marked apicobasal differentiation, particularly in the vicinity of developing late spermatids, where the cytoplasm of the Sertoli cell is packed with smooth endoplasmic reticulum. The possible roles of lipid droplets and smooth endoplasmic reticulum. The possible roles of lipid droplets and smooth endoplasmic reticulum in steroidogenesis by Sertoli cells are discussed. Junctional complexes occur between Sertoli cells and spermatogonia, are apparently absent from between Sertoli cells and spermatocytes, and are restricted to the region of the developing acrosome in the spermatids. Annulate lamellae, which occur commonly in the developing germinal cells and less frequently in the Sertoli cells, may be associated with the production of microtubules, which are present in both spermatids and Sertoli cells.     

Active Hydrocarbon Biosynthesis and Accumulation in a Green Alga,Botryococcus braunii (Race A)

Among oleaginous microalgae, the colonial green alga Botryococcus braunii accumulates especially large quantities of hydrocarbons. This accumulation may be achieved more by storage of lipids in the extracellular space rather than in the cytoplasm, as is the case for all other examined oleaginous microalgae. The stage of hydrocarbon synthesis during the cell cycle was determined by autoradiography. The cell cycle of B. braunii race A was synchronized by aminouracil treatment, and cells were taken at various stages in the cell cycle and cultured in a medium containing [¹⁴C]acetate. Incorporation of ¹⁴C into hydrocarbons was detected. The highest labeling occurred just after septum formation, when it was about 2.6 times the rate during interphase. Fluorescent and electron microscopy revealed that new lipid accumulation on the cell surface occurred during at least two different growth stages and sites of cells. Lipid bodies in the cytoplasm were not prominent in interphase cells. These lipid bodies then increased in number, size, and inclusions, reaching maximum values just before the first lipid accumulation on the cell surface at the cell apex. Most of them disappeared from the cytoplasm concomitant with the second new accumulation at the basolateral region, where extracellular lipids continuously accumulated. The rough endoplasmic reticulum near the plasma membrane is prominent in B. braunii, and the endoplasmic reticulum was often in contact with both a chloroplast and lipid bodies in cells with increasing numbers of lipid bodies. We discuss the transport pathway of precursors of extracellular hydrocarbons in race A.     

The role of sertoli cells in spermatid maturation in the testis of the crayfish, Procambarus paeninsulanus

With the onset of spermiogenesis, many changes become apparent in the crayfish spermatid during its transition to mature sperm. The nucleus passes through a series of stages, excess cytoplasm is removed, the acrosome develops, and nuclear arms form and become wrapped around the sperm prior to its enclosure in a capsule. Changes are also apparent in the Sertoli cells surrounding the germ cells in the crayfish testis. The amount of cytoplasm of individual Sertoli cells appears to increase in quantity and changes in the intracellular organelles become apparent. As spermiogenesis commences, the cytoplasm along one side of Sertoli cells adjacent to the spermatids is devoid of obvious organelles. Numerous finger/like projections of Sertoli cytoplasm penetrate into the spermatid and appear to isolate portions of the sperm cytoplasm. During later stages of spermiogenesis, several vesicles in the Sertoli cells which appear to contain droplets of this isolated sperm cytoplasm. appear to undergo lytic changes, As the amount of cytoplasm of the spermatid is reduced, contact is maintained between the spermatid and Sertoli cell in the area of the acrosome. The nuclear arms of the sperm extend into the Sertoli cell during their formation and later become wrapped around the acrosomal area of the sperm. At this time, very little space exists between the Sertoli cell and its many sperm. Large vesicles of electron dense material appear to be released by the Sertoli cells into the space between the sperm and Sertoli cell. This material completely surrounds the sperm and forms the sperm capsule. Spermiation involves the gradual dissolution of the points of contact between the sperm capsule and the Sertoli cell.     

Elderly Men Have Low Levels of Anti-Müllerian Hormone and Inhibin B,but with High Interpersonal Variation: A Cross-Sectional Study of the Sertoli Cell Hormones in 615 Community-Dwelling Men

The Sertoli cells of the testes secrete anti-Müllerian hormone (Müllerian inhibiting Substance, AMH) and inhibin B (InhB). AMH triggers the degeneration of the uterine precursor in male embryos, whereas InhB is part of the gonadal-pituitary axis for the regulation of sperm production in adults. However, both hormones are also putative regulators of homeostasis, and age-related changes in these hormones may therefore be important to the health status of elderly men. The levels of AMH in elderly men are unknown, with limited information being available about age-related changes in InhB. We have therefore used ELISAs to measure Sertoli cell hormone levels in 3 cohorts of community-dwelling men in New Zealand. In total, 615 men were examined, 493 of which were aged 65 or older. Serum AMH and InhB levels inversely correlated with age in men older than 50 years (p<0.001) but not in the younger men. A minority of elderly men had undetectable levels of AMH and InhB. The variation in hormone levels between similarly aged men increased with the age of men. AMH and InhB partially correlated with each other as expected (r = 0.48, p<0.001). However, the ratio of the two Sertoli hormones varied significantly between men, with this variation increasing with age. Elderly men selected for the absence of cardiovascular disease had AMH levels similar to those of young men whereas their InhB levels did not differ from aged-matched controls. These data suggests that Sertoli cell number and function changes with age, but with the extent and nature of the changes varying between men.     

On the morphology of the human sertoli cell

Summary As revealed by light microscopical investigations the human Sertoli cell presents different appearances according to the pattern of infranuclear cytoplasmic inclusions. Although two or three stages of spermatogenesis are seen in a single cross section of a seminiferous tubule the Sertoli cells all show virtually the same features in such a cross sectioned tubule.The different appearances are also evident under the electron microscope. Although no obvious correlation was found with the stages of spermatogenesis in the seminiferous epithelium, the Sertoli cell appearances described here may be assumed to represent different metabolic situations.Other features of Sertoli cell ultrastructure are discussed such as the presence of residual bodies in the apical cytoplasm, glycogen-rich areas protruding towards the tubular lumen or the extracellular space, and membrane bound, round structures, found between the membranes of the smooth endoplasmic reticulum and resembling the microbodies of steroid producing cells.Presented in part at the 69^th Versammlung der Anatomischen Gesellschaft, Kiel, 1974.     

Distribution of insoluble polysaccharides, neutral lipids, and proteins in the developing anthers of Campsis radicans (L.) Seem. (Bignoniaceae)

In this study, distribution of polysaccharides, lipids, and proteins in the developing anthers of Campsis radicans (L.) Seem. was examined from sporogenous cell stage to mature pollen, using cytochemical methods. To detect the distribution and dynamic changes of insoluble polysaccharides, lipid bodies, and proteins in the anthers through progressive developmental stages, semi-thin sections of anthers at different developmental stages were stained with periodic-acid-Schiff (PAS) reagent, Sudan black B, and Coomassie brilliant blue, respectively, and examined under light microscope. Ultrastructural observations with TEM were also carried out to determine the storage form of starch in the connective tissue, and storage form of lipids in the tapetal cells. In sporogenous cell stage, anther wall contains numerous insoluble polysaccharides. However, from the sporogenous cell stage to the vacuolated microspore stage, the amount of insoluble polysaccharides in the anther wall decreases gradually. At bicellular pollen stage, tapetum degenerates completely and polysaccharides are not seen in the anther wall. Lipid bodies are observed in the cytoplasm of both middle layer and tapetal cells at tetrad stage, whereas they disappear in the vacuolated microspore stage. Compared with polysaccharides, proteins are limited in the anther wall at early stages of development. During pollen development, polysaccharides, proteins, and lipid bodies are scarce in the cytoplasm of sporogenous cells, but their amount increases at premeiotic stage. From tetrad stage to bicellular pollen stage, microspore cytoplasm contains variable amount of insoluble polysaccharide grains, lipid and protein bodies. At bicellular pollen stage, plentiful amount of starch granules are stored in the cytoplasm of the pollen grains. Proteins and lipid bodies are also present in the cytoplasm.     

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.