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Isolated Sertoli cells were cultured on MatrigelTM-coated Millipore filters in bicameral chambers. The Sertoli cells form confluent epithelial sheets that, by virtue of the Sertoli cell tight junctions, form transepithelial permeability barriers between the apical and basal domains of the cells. These Sertoli cells secrete metabolically labeled proteins in a polarized manner. Three peptides, P1 (pI = 4.5-5.0, MW = 70,000), P2 (pI = 4.5-5.0, MW = 50,000), and P3 (pI = 4.0-4.7, MW = 34,000) are secreted apically from the epithelial sheets of Sertoli cells and are not found in basal secretions from the same Sertoli cells. Pachytene spermatocyte-conditioned medium contains proteins released from the germ cells that are uniquely different from the Sertoli cell-secreted proteins. Addition of the pachytene spermatocyte-conditioned medium to the apical reservoir of the bicameral chambers over an epithelial sheet of Sertoli cells stimulated the synthesis and secretion of total protein, transferrin, and specifically induced peptides S1 and S2 from Sertoli cells. As controls, conditioned medium from 3T3 fibroblasts and round spermatids did not stimulate the Sertoli cells. Hence, the ability of pachytene spermatocyte proteins to induce specific Sertoli cell secretion indicates that the pachytene spermatocytes are able to influence their surrounding milieu, and provides further support to the concept of a paracrine interaction between germ cells and Sertoli cells during spermatogenesis. Show less

Sertoli cells in vivo are believed to secrete androgen-binding protein (ABP) as well as other proteins in a polarized manner, primarily into the adluminal (apical) compartment of the seminiferous tubules. It is now possible to examine polarized secretion by Sertoli cells in vitro by growing them in dual environment (bicameral) culture chambers such that there is a separation of the apical and basal compartments of the cells. Sertoli cells obtained from 17-day-old rats were grown in these chambers on Millipore filters coated with a reconstituted basement membrane matrix. Within 3 days a confluent epithelial sheet of Sertoli cells (30-40 microns in height) is established, and these cells are joined along their baso-lateral plasma membranes by typical Sertoli-Sertoli tight junctions. We have previously shown that this epithelial sheet of Sertoli cells establishes an electrical resistance, as well as a permeability barrier to small molecules, between the basal and apical compartments of the culture chamber. In the absence of Sertoli cells, proteins equilibrate within 8 h across the matrix-coated filter support. Between 12 and 48 h of culture the Sertoli cell monolayers secrete approximately 4- and 2-fold more ABP and transferrin (Tf), respectively, into the apical compartment than into the basal compartment when grown in serum-free defined medium. ABP secretion is diminished 10-fold by the removal of testosterone from the serum-free defined medium. In addition, the apical/basal ratio of ABP secretion decreases from 4.1 to 1.7 in the absence of testosterone. In contrast, neither the amount nor the direction of Tf secretion is altered by the removal of testosterone. These results demonstrate the bidirectional secretion of ABP and Tf by Sertoli cells grown in bicameral chambers. In addition, the polarity of secretion of these two proteins by Sertoli cells appears to be under differential regulation by testosterone. Show less

The distribution of laminin, type IV collagen, heparan sulfate proteoglycan, and fibronectin was investigated in the rat testicular lamina propria by electron microscopic immunocytochemistry. Distinct patterns were observed for each antigen within the extracellular matrix (ECM) layers of the lamina propria. Laminin, type IV collagen, and heparan sulfate proteoglycan all localized to the seminiferous tubule basement membrane. Type IV collagen and heparan sulfate proteoglycan, but not laminin, localized to the seminiferous tubule side of the peritubular myoid cells. All four of the antigens were localized between the peritubular and lymphatic endothelial cells. Failure to localize fibronectin in the ECM layer between the Sertoli and peritubular myoid cells tends to support the concept that adult Sertoli cells do not produce this protein in vivo. Intracellular immunostaining was insufficient to allow unambiguous identification of the cellular source of any of the ECM molecules. Show less

This is a speculative essay on the application of cybernetic concepts to the diagnosis and treatment of physical illness. The essay assumes that there is a unified biopsychosocial field in which the designation of illness as "physical" violates the ecological wholeness of the field. Although the field is complex, clinical intervention requires a degree of simplicity. This simplicity is sought by describing biopsychosocial experience in terms of recursive cycles. Clinical intervention is discussed as a disruption of recursive cycles. Show less

The minimal sequence required for biological activity of alpha-MSH (alpha-melanotropin, alpha-melanocyte stimulating hormone) was determined in the frog (Rana pipiens) skin bioassay. The sequence required to elicit measurable biological activity was the central tetrapeptide sequence, Ac-His-Phe-Arg-Trp-NH2 (Ac-alpha-MSH6-9-NH2), which was about 6 orders of magnitude less potent than the native tridecapeptide. Smaller fragments of this sequence (Ac-His-Phe-NH2, Ac-Phe-Arg-NH2, Ac-His-Phe-Arg-NH2) were devoid of melanotropic activity at concentrations as high as 10(-4) M. We were unable to demonstrate biological activity for the tetrapeptide, Ac-Phe-Arg-Trp-Gly-NH2 (Ac-alpha-MSH7-10-NH2), and for several carboxy terminal analogues including Ac-Lys-Pro-Val-NH2 (Ac-alpha-MSH11-13-NH2). We prepared a series of fragment analogues of alpha-MSH in an attempt to determine the contribution of each individual amino acid to the biological activity of the native hormone. The minimal potency of Ac-alpha-MSH6-9-NH2 could be enhanced about a factor of 16 by the addition of glycine to the C-terminus, yielding Ac-alpha-MSH6-10-NH2 (Ac-His-Phe-Arg-Trp-Gly-NH2). Addition of glutamic acid to the N-terminus provided the peptide, Ac-alpha-MSH5-10-NH2, which was only slightly more potent than Ac-alpha-MSH6-10-NH2, indicating that position 5 contributes little to the biological potency of alpha-MSH in this assay. Addition of methionine to the N-terminus of Ac-alpha-MSH5-10-NH2 resulted in the heptapeptide, Ac-alpha-MSH4-10-NH2, which was only about 4-fold more potent than Ac-alpha-MSH5-10-NH2. Addition of lysine and proline to the C-terminal of the Ac-alpha-MSH4-10-NH2 sequence yielded the peptide, Ac-alpha-MSH4-12-NH2 with a 360-fold increase in potency relative to Ac-alpha-MSH4-10-NH2. This peptide was only about 6-fold less potent than alpha-MSH. A series of Nle-4-substituted analogues also were prepared. Ac-[Nle4]-alpha-MSH4-10-NH2 was about 4 times more potent than Ac-alpha-MSH4-10-NH2. Ac-[Nle4]-alpha-MSH4-11-NH2 also was about 4 times more potent than Ac-alpha-MSH4-10-NH2, demonstrating that lysine-11 contributes somewhat to the biological activity of alpha-MSH on the frog skin melanocyte receptor.(ABSTRACT TRUNCATED AT 250 WORDS) Show less

Immature rat Sertoli cells were cultured for 7 to 14 days on Millipore filters impregnated with a reconstituted basement membrane extract in dual-environment (bicameral) culture chambers. Electron microscopy of the cultured cells revealed the presence of rod-shaped mitochondria, Golgi apparatus, rough endoplasmic reticulum, and Sertoli-Sertoli tight junctions, typical of these cells in vivo. The endocytic activity of both the apical and basal surfaces of the Sertoli cells was examined by either adding alpha 2-macroglobulin (alpha 2-M) conjugated to 20 nm gold particles to the apical chamber or by adding 125I labeled alpha 2-M to the basal chamber. During endocytosis from the apical surface of Sertoli cells, the alpha 2-M-gold particles were bound initially to coated pits and then internalized into coated vesicles within 5 minutes. After 10 minutes, the alpha 2-M-gold was found in multi-vesicular bodies (MVBs) and by 30 minutes it was present in the lysosomes. The proportion of alpha 2-M-gold found within endocytic cell organelles after 1 hour of uptake was used to estimate the approximate time that this ligand spent in each type of organelle. The alpha 2-M-gold was present in coated pits, coated vesicles, multivesicular bodies, and lysosomes for approximately 3, 11, 22, and 24 minutes, respectively. This indicates that the initial stages of endocytosis are rapid, whereas MVBs and lysosomes are relatively long-lived.(ABSTRACT TRUNCATED AT 250 WORDS) Show less

Epididymal epithelial cells isolated from mature rats and Sertoli cells isolated from 10-day-old rats were cultured in serum-free defined media on extracellular matrix impregnated filters maintained in dual environment culture chambers. Epididymal epithelial cells had a polarized appearance only when plated at high density (greater than 1 X 10(6) cells/cm2). Confluent monolayers of these cells formed a permeability barrier to inulin. Sertoli cells were columnar and highly polarized when grown on extracellular matrix-impregnated filters, cuboidal when grown on filters alone, and squamous when grown on plastic. Confluent polarized monolayers of these cells excluded the electron-dense tracer lanthanum nitrate by way of basal-tight junctions. Therefore, polarized monolayers of epididymal epithelial cells and Sertoli cells can be obtained by growing the cells at high density on extracellular matrix-impregnated permeable supports. By maintaining the monolayers in specially constructed culture chambers, the cells can develop a permeability barrier, and are able to achieve the separation of apical from basal compartments so important for their function in vivo. Show less

The transferrin-mediated transcellular transport of 59Fe across confluent epithelial sheets of Sertoli cells grown on Millipore filters was investigated. These filters had been impregnated with reconstituted basement membrane and suspended in bicameral (two houses) culture chambers. After five days of culture, Sertoli cells from 10-day-old rats formed basally-located tight junctional complexes. Concomitantly, there was an increase in electrical resistance and the epithelial sheet became impermeable to lanthanum nitrate. The rate of passage of [3H]inulin across the epithelial sheet was considerably less than passage across a filter alone, a filter impregnated with reconstituted basement membrane or an epithelial sheet pretreated with 2 mM EGTA. We conclude from these permeability studies that the tight junctional complexes between Sertoli cells formed an effective transepithelial permeability barrier. Following addition of human serum [59Fe]transferrin to media bathing the basal cytoplasm of the cells, rat testicular [59Fe]transferrin was immunoprecipitated from apical media overlying the Sertoli cells. Cross-reactivity of the rabbit anti-rat transferrin antibody with human serum transferrin was less than 0.001%. Substitution of the primary antibody with normal rabbit serum reduced the amount of immunoprecipitable rat testicular [59Fe]transferrin to 20% of normal levels. Prior fixation of the Sertoli cell epithelial sheet in 2.5% glutaraldehyde, addition of a 100-fold excess of holotransferrin to the basal media, and incubation of the Sertoli cell epithelial sheet at 4 C all reduced the immunoprecipitable rat testicular [59Fe]transferrin in apical media to levels below that for the non-specific binding of the primary antibody. From these studies we conclude that 59Fe is shuttled across Sertoli cells by two different forms of transferrin. Serum transferrin delivers the 59Fe to the basal cytoplasm of the Sertoli cells. The 59Fe dissociates from the serum transferrin, is delivered to testicular transferrin, and is subsequently secreted from the apical surface of the epithelial sheet of Sertoli cells as testicular [59Fe]transferrin. Show less

The concentration of transferrin in fluids collected by micropuncture techniques from the rete testis and zones 1A, 2, 5A, and 6B of the rat ductus epididymidis was 44, 527, 113, and 49 ng/microliter, respectively. When changes in fluid volume were taken into account, it was found that transferrin was concentrated by the efferent ducts, whereas the amount of endogenous luminal transferrin declined from the caput to the cauda epididymidis. Using transferrin-gold as an electron dense marker, we showed that the decline in the concentration of transferrin along the epididymis could be attributed to its cumulative receptor-mediated endocytosis by the lining principal cells. No significant difference in the net receptor-mediated endocytosis of transferrin-gold was found between the proximal caput and corpus epididymidis in vivo. Show less

The isolation and culture of ciliated and nonciliated cells from rat ductuli efferentes is described. Fragments of epithelium obtained after two collagenase digestions attached to plastic and to extracellular matrix and could be maintained in culture for at least 2 weeks. Ciliary beating in cells grown on epididymal extracellular matrix-coated plastic could be observed for up to 7 days in culture. Although cells maintained on this substrate retained organelles characteristic of cells in vivo, they assumed a flattened, squamous appearance. In contrast, cells growing on the surface of permeable supports impregnated with extracellular matrix were polarized and exhibited a cuboidal/columnar appearance. Androgen binding protein conjugated to colloidal gold was taken up by these cells via coated pits and was found sequentially in uncoated endosomes, multivesicular bodies and lysosomes. Show less

Micropuncture techniques were used to study receptor-mediated endocytosis of alpha 2-macroglobulin bound to colloidal gold (alpha 2M-gold) by principal cells in the proximal caput epididymidis of control and efferent duct-ligated rats. The pathway of receptor-mediated endocytosis of alpha 2-macroglobulin-gold in vivo was similar to that which occurs in vitro. Alpha 2-macroglobulin-gold was taken up and internalized in coated pits and coated vesicles and was localized sequentially in uncoated vesicles (endosomes), tubular-vesicular structures, multivesicular bodies, and lysosomes. However, a 100-fold excess of alpha 2-macroglobulin did not displace the uptake of alpha 2-macroglobulin-gold in principal cells from control rats. In contrast, uptake of alpha 2-macroglobulin-gold by principal cells from efferent duct-ligated rats was six-fold greater than in control rats, and could be displaced to control levels by a 100-fold excess of alpha 2-macroglobulin. It is suggested that the inability of a 100-fold excess of alpha 2-macroglobulin to displace uptake of alpha 2-macroglobulin-gold in control rats was due to the normal saturation of apparent alpha 2-macroglobulin receptors on principal cells. The effect of efferent duct ligation was to remove the high levels of endogenous alpha 2-macroglobulin, which depleted the receptors of alpha 2-macroglobulin, thereby allowing a higher uptake of alpha 2-macroglobulin-gold in the efferent duct-ligated rats. Show less

A morphometric analysis of coated and uncoated structures found in the apical portion of principal cells from both the proximal and distal caput epididymidis has been carried out. Almost all endocytic, coated vesicles are found within 1 micron of the luminal surface of principal cells and the volume fraction of these and of uncoated vesicles is much greater in the proximal caput epididymidis. A serial section analysis indicated that many coated "vesicles" are tangentially sectioned coated pits and that a complex network of interconnected vesicular and tubular structures exists in the apical cytoplasm. Efferent duct ligation has no effect on the number of size of large coated and uncoated vesicles in either the proximal or distal caput epididymidis, indicating that substances delivered to principal cells from the lumen are not required to maintain the endocytic machinery. However, this treatment does result in a considerable increase in the number of large coated vesicles associated with the basal surface of principal cells from the proximal but not the distal caput epididymidis. The volume fraction of small, presumably exocytic, coated vesicles is significantly greater in the apical cytoplasm of cells from the distal caput epididymidis in control animals. Efferent duct ligation results in a significant increase in the volume fraction of these vesicles in the proximal but not distal caput epididymidis. These results show that there are marked differences in structure among principal cells from these two regions of the epididymis and that this may reflect differences in control and function. Show less

To determine whether there are any deleterious changes in the human testis after vasectomy, we obtained testicular biopsy specimens from 31 healthy men undergoing vasectomy reversal and from 21 healthy, fertile volunteers. Morphometric analyses of these specimens revealed a 100 per cent increase in the thickness of the seminiferous tubular walls (P less than 0.001), a 50 per cent increase in the mean cross-sectional tubular area (P less than 0.001), and a significant reduction in the mean number of Sertoli cells (P less than 0.01) and spermatids (P less than 0.01) per tubular cross section in the post-vasectomy group, as compared with the control group. Focal interstitial fibrosis was observed in 23 per cent of the specimens from the post-vasectomy group and in none from the control group. There was a significant correlation (P less than 0.01) between interstitial fibrosis and infertility in patients who underwent a surgically successful vasectomy reversal (sperm in the ejaculate). None of the other measured characteristics correlated with infertility after vasectomy reversal. We conclude that significant morphologic changes occur in the human testis after vasectomy. The presence of focal interstitial fibrosis was associated with a high incidence of infertility in this series. Show less

Epididymal epithelial fragments, free of stromal elements were isolated from mature rats using two sequential collagenase digestions. Within 24 h these attached efficiently to a variety of substrates including glass, plastic, placental collagen, type IV collagen and epididymal extracellular matrix material. Cells spreading away from the fragments rapidly assumed a flattened, overlapping, monolayer appearance typical of epithelial cells in culture. Cells still associated with the fragments or adjacent to them remained more polarized and more closely resembled epididymal principal cells in vivo than did cells that had migrated to the periphery of the monolayer. Apical microvilli characteristic of these cells in vivo were common during the first 4 days in culture but diminished in number and size thereafter. Cultured cells maintained many of the structural features characteristic of principal cells in vivo, including a well developed Golgi apparatus, coated pits and vesicles, and many multivesicular bodies. An extensive filamentous network, shown immunocytochemically to consist of keratin, was present in the cytoplasm of all cells but was more obvious in flattened cells at the periphery of the monolayer. Rhodamine phalloidin labelling of filamentous actin showed that concentrations of actin occurred corresponding to microvilli on the apical surface, in a continuous ring just below the apical surface, and also in stress fibres at the base of the cells. Cells isolated and cultured from the distal caput epididymidis possessed lobulated nuclei, in contrast to the round or oval nuclei found in cells cultured from the proximal caput epididymidis. Cells from the distal caput epididymidis were also characterized by the presence of many lipid droplets in their cytoplasm. Autofluorescent granules were observed in epithelial cells from both regions but were larger and more numerous in cells isolated from the distal caput epididymidis. Tritiated thymidine incorporation by the cells after 4 days in culture showed that cells adjacent to the parent epithelial fragment were dividing at a greater rate than cells that had migrated to the periphery of the monolayer. Show less

Sertoli cell preparations isolated from 10-day-old rats were cultured on three different substrates: plastic, a matrix deposited by co-culture of Sertoli and peritubular myoid cells, and a reconstituted basement membrane gel from the EHS tumor. When grown on plastic, Sertoli cells formed a squamous monolayer that did not retain contaminating germ cells. Grown on the matrix deposited by Sertoli-myoid cell co-cultures, Sertoli cells were more cuboidal and supported some germ cells but did not allow them to differentiate. After 3 wk however, the Sertoli cells flattened to resemble those grown on plastic. In contrast, the Sertoli cells grown on top of the reconstituted basement membrane formed polarized monolayers virtually identical to Sertoli cells in vivo. They were columnar with an elaborate cytoskeleton. In addition, they had characteristic basally located tight junctions and maintained germ cells for at least 5 wk in the basal aspect of the monolayer. However, germ cells did not differentiate. Total protein, androgen binding protein, transferrin, and type I collagen secretion were markedly greater when Sertoli cells were grown on the extracellular matrices than when they were grown on plastic. When Sertoli cells were cultured within rather than on top of reconstituted basement membrane gels they reorganized into cords. After one week, tight junctional complexes formed between adjacent Sertoli cells, functionally compartmentalizing the cords into central (adluminal) and peripheral (basal) compartments. Germ cells within the cords continued to differentiate. Thus, Sertoli cells cultured on top of extracellular matrix components assume a phenotype and morphology more characteristic of the in vivo, differentiated cells. Growing Sertoli cells within reconstituted basement membrane gels induces a morphogenesis of the cells into cords, which closely resemble the organ from which the cells were dissociated and which provide an environment permissive for germ cell differentiation. Show less

The endocytic activity of epithelial cells from the rat epididymis in vitro has been examined by following the uptake of tracer compounds conjugated to proteins. Transferrin-gold and alpha 2-macroglobulin-gold were taken up initially in coated pits, internalized and sequestered into tubular-vesicular structures, multivesicular bodies and, in the case of alpha 2-macroglobulin, into lysosomes. Uptake could be prevented by an excess of unlabeled protein. Studies using 125I-alpha 2-macroglobulin and 125I-transferrin also showed that the uptake of these proteins was specific and could be displaced with increasing amounts of unlabeled protein. In addition, binding of 125I-transferrin to cells was saturable at 4 degrees C. These studies indicate that transferrin and alpha 2-macroglobulin are taken up by receptor-mediated endocytosis. In contrast, a fluid phase marker, bovine serum albumin-gold (BSA-gold), was initially taken up predominantly in uncoated caveolae rather than coated pits, and could not be displaced with excess BSA. By virtue of their charge, polycationized ferritin and unlabeled colloidal gold were taken up and internalized by adsorptive endocytosis, a pathway which is similar to fluid phase endocytosis. The uptake and internalization of alpha 2-macroglobulin and transferrin differed in a number of respects. Uptake and internalization of alpha 2-macroglobulin but not of transferrin was dependent on extracellular calcium. Only alpha 2-macroglobulin was transferred into lysosomes, whereas transferrin was recycled to the cell surface. Although the proton ionophore, monensin, and the transglutaminase inhibitor, dansylcadaverine, did not stop uptake and internalization of either alpha 2-macroglobulin or transferrin, they did prevent the transfer of alpha 2-macroglobulin to lysosomes. Show less

The immunocytochemical localization of the milk protein alpha-lactalbumin in the male reproductive tract is described. Using a primary antiserum raised against highly purified rat milk alpha-lactalbumin, specific staining was consistently shown in the supranuclear Golgi region of the principal cells of the proximal caput epididymidis but only occasionally in epithelial cells from other regions of the duct. Staining was also found in the epididymal lumen and associated with spermatozoa. This luminal staining persisted throughout the distal caput, corpus and cauda epididymidis. Staining was rarely associated with spermatozoa in the efferent ducts and initial segment. Alpha-lactalbumin immunoreactivity was also detected in the seminiferous epithelium. Staining was confined to the Golgi-acrosome region of spermatids. These results indicate that an alpha-lactalbumin-like molecule, or molecules, is present in the male reproductive tract and that it is localized specifically in principal cells from the proximal caput epididymidis and germ cells from the seminiferous epithelium. Show less

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. Show less

Study of Sertoli cells of the ground squirrel provides a unique opportunity to examine cell structure and function. The cells are large, have an elaborate cytoskeleton, and undergo dramatic changes in organization during spermatogenesis. Microtubules (MTs) are prominent elements of the cytoskeleton and appear to be associated structurally with many of the events that occur during sperm production. To investigate the function of MTs, animals were injected subcutaneously with colchicine, and their seminiferous epithelia examined by light and electron microscopy. Some animals were injected with 30--80 mg of the drug per kg body weight and sacrificed 3 to 5 hr later. Others were given 0.3 mg/kg/day for 6 days and processed on day 7. Virtually no MTs were seen in Sertoli cells after short-term treatments, and their numbers were greatly reduced after the long-term injections. Intermediate filaments were very evident throughout the cytoplasm of treated cells, particularly in the short-term studies. Moreover, a close association of some of these filaments with centrioles was observed. In all cases, elongate spermatids which normally move apically did not do so. Indeed, some spermatids appear to have been pulled to a basal position after having moved apically prior to treatment. Also, smooth endoplasmic reticulum (SER) accumulated basally in the Sertoli cell, unlike controls, and the acrosomes of late spermatids developed abnormally or did not complete their shape changes. Cell junctions appeared normal and sperm release was observed. In conclusion, our data suggest that Sertoli cell MTs are necessary for the normal development and translocation of spermatids in the seminiferous epithelium and are involved with positional changes in Sertoli cell SER. They do not appear essential for the maintenance of cell junctions. Show less

The seminiferous epithelium in mature vasectomized Macaca fascicularis was examined quantitatively to assess spermatogenesis. Monkeys were bilaterally vasectomized and controls were bilaterally sham operated. At postoperative periods of 10 and 18 months, groups of monkeys were castrated and their testes prepared for morphologic analysis. Diameters were measured in 100 cross sections of seminiferous tubules from each animal. Numbers of spermatogonia (Ad and Ap), preleptotene spermatocytes, pachytene spermatocytes, and step 7 spermatids, relative 10 Sertoli cell nucleoli, were counted in stage VII tubules. Tubule diameter and germ cell numbers per Sertoli cell nucleoli were not altered by vasectomy. Our study demonstrates quantitatively that spermatogenesis in the monkey is not inhibited up to 18 months following vasectomy. Show less