Vimentin expression in spermatogenic and Sertoli cells is stage-related in rat seminiferous epithelium

Inositol hexakisphosphate kinase 1 is essential for cell junction integrity in the mouse seminiferous epithelium

Inositol hexakisphosphate kinases (IP6Ks) are enzymes that catalyse the synthesis of the inositol pyrophosphate 5-IP7 which is involved in the regulation of many physiological processes in mammals. The IP6K paralog IP6K1 is expressed at high levels in the mammalian testis, and its deletion leads to sterility in male mice. Here, we show that the loss of IP6K1 in mice causes a delay in the first wave of spermatogenesis. Testes from juvenile Ip6k1 knockout mice show downregulation of transcripts that are involved in cell adhesion and formation of the testis-specific inter-Sertoli cell impermeable junction complex known as the blood-testis barrier (BTB). We demonstrate that loss of IP6K1 in the mouse testis causes BTB disruption associated with transcriptional misregulation of the tight junction protein claudin 3, and subcellular mislocalization of the gap junction protein connexin 43. In addition to BTB disruption, we also observe a loss of germ cell adhesion in the seminiferous epithelium of Ip6k1 knockout mice, ultimately resulting in premature sloughing of round spermatids into the epididymis. Mechanistically, we show that loss of IP6K1 in the testis enhances cofilin dephosphorylation in conjunction with increased AKT/ERK and integrin signalling, resulting in destabilization of the actin-based cytoskeleton in Sertoli cells and germ cell loss.

Aging affects gene expression in spermatids of Brown Norway rats

The effects of aging on the reproductive health of men and the consequences for their offspring are becoming more widely recognized. Correlative epidemiological studies examining paternal age and offspring health suggest there are more frequent occurrences of genetic disorders in the children of older fathers. Given the genetic basis for paternal age-related disorders, we aim to characterize gene expression in developing germ cells. Round spermatids (RS) were collected from young (mean = 5.3 months) and aged (mean = 19.5 months) Brown Norway rats, representative of humans aged 20-30 years and 55+ years, respectively. Gene expression data were obtained by mRNA sequencing (n = 5), and were analysed for differential expression. Sequencing data display 211 upregulated and 9 downregulated transcripts in RS of aged rats, compared to young (log2FC >1, p < 0.05). Transcripts with increased expression are involved in several processes including sperm motility/morphology, sperm-egg binding, capacitation, and epigenetic inheritance. In addition, there are numerous dysregulated transcripts that regulate germ cell epigenetic marks and Sertoli-germ cell binding and communication. These results show an overall increase in RS gene expression with age, with spermatogenic functions being perturbed. Taken together, these findings help identify the genetic origin of the fertility, germ cell niche, and epigenetic effects observed with advanced paternal aging.

Loss of Adgra3 causes obstructive azoospermia with high penetrance in male mice

The adhesion receptor ADGRA3 (GPR125) is a known spermatogonial stem cell marker, but its impact on male reproduction and fertility has not been examined. Using a mouse model lacking Adgra3 (Adgra3-/- ), we show that 55% of the male mice are infertile from puberty despite having normal spermatogenesis and epididymal sperm count. Instead, male mice lacking Adgra3 exhibited decreased estrogen receptor alpha expression and transient dilation of the epididymis. Combined with an increased estradiol production, this indicates a post-pubertal hormonal imbalance and fluid retention. Dye injection revealed a blockage between the ejaculatory duct and the urethra, which is rare in mice suffering from infertility, thereby mimicking the etiologies of obstructive azoospermia found in human male infertility. To summarize, male reproductive tract development is dependent on ADGRA3 function that in concert with estrogen signaling may influence fluid handling during sperm maturation and storage.

Testicular Localization and Potential Function of Vimentin Positive Cells during Spermatogonial Differentiation Stages

Simple Summary

Spermatogonia stem cells (SSCs) in the testis are responsible for transmitting genetic information to subsequent generations. During the differentiation of SSCs, various cytoskeletons are involved in giving the cell shape and internal organization. One of the essential cytoskeletons that play functions in these spermatogenic processes is vimentin. This study examined the vimentin expression in vivo and in vitro by immunocytochemistry (ICC), immunohistochemistry (IMH), Fluidigm real-time polymerase chain reaction, and bioinformatics analysis. IMH analysis demonstrated that the high vimentin expression was localized in the middle and central testicular cords cells of seminiferous tubules and low expression in the basal region under in vivo conditions. To evaluate the expression of vimentin in vitro, we first isolated SSCs and then cultured cells from the testis. Our results showed that vimentin plays important roles in the differentiation of testicular germ cells.

Abstract

Vimentin is a type of intermediate filament (IF) and one of the first filaments expressed in spermatogenesis. Vimentin plays numerous roles, consisting of the determination of cell shape, differentiation, cell motility, the maintenance of cell junctions, intracellular trafficking, and assisting in keeping normal differentiating germ cell morphology. This study investigated the vimentin expression in two populations of undifferentiated and differentiated spermatogonia. We examined vimentin expression in vivo and in vitro by immunocytochemistry (ICC), immunohistochemistry (IMH), and Fluidigm real-time polymerase chain reaction. IMH data showed that the high vimentin expression was localized in the middle of seminiferous tubules, and low expression was in the basal membrane. ICC analysis of the colonies by isolated differentiated spermatogonia indicated the positive expression for the vimentin antibody, but vimentin’s expression level in the undifferentiated population was negative under in vitro conditions. Fluidigm real-time PCR analysis showed significant vimentin expression in differentiated spermatogonia compared to undifferentiated spermatogonia (p < 0.05). Our results showed that vimentin is upregulated in the differentiation stages of spermatogenesis, proving that vimentin is an intermediate filament with crucial roles in the differentiation stages of testicular germ cells. These results support the advanced investigations of the spermatogenic process, both in vitro and in vivo.

ZnSO4 rescued vimentin from collapse in DBP-exposed Sertoli cells by attenuating ER stress and apoptosis

Sertoli cells (SCs) provide physical and nutritional support for spermatogenesis. Dibutyl phthalate (DBP) is a plasticizer that has male reproductive toxicity. The collapse of vimentin in DBP-exposed SCs is thought to induce the sloughing of spermatocytes from seminiferous tubules. In this study, we explored methods to rescue vimentin from collapse in DBP-exposed SCs. DBP not only induced the hyperphosphorylation of vimentin but also triggered endoplasmic reticulum (ER) stress and apoptosis in SCs. Treatment with BAPTA-AM, an antagonist of Ca²⁺, significantly decreased the level of phosphorylated vimentin, while LY294002, an inhibitor of Akt1, did not. ER stress and apoptosis remained at high levels, and the distribution of vimentin was not improved. ZnSO₄ treatment did not decrease the level of phosphorylated vimentin. However, after treatment, ER stress and apoptosis were obviously inhibited, and the distribution of vimentin was reconverted. These results indicated that ZnSO₄ could alleviate the collapse of vimentin by attenuating ER stress and apoptosis. This study suggested that an appropriate zinc supply might be a choice to alleviate DBP-induced adverse reproductive effects.

Influence of prolonged flaxseed ( Linum usitatissimum ) consumption over epididymis and testicle histoarchitecture of Wistar rats

ABSTRACT: Flaxseed is considered a functional food with several health benefits. However, because of its high phytoestrogen content, flaxseed influences hormone metabolism and affects the gonadal biomorphology. In this study, computerized histomorphometry was used to evaluate seminiferous and epididymal tubules, considering the different regions of the epididymis (head, body and tail) of rats subjected to a prolonged diet of flaxseed. Young adult male Wistar rats (n=20) were divided into 2 groups during their lactation period: Control Group (CG), fed casein-based meals and Flaxseed Group (FG), fed a 25% flaxseed meal. After 250 days of continuous ingestion, the animals were euthanized and a blood sample was collected. The testicles and epididymis were removed and fixed in buffered formalin solution. The samples were subjected to routine histological paraffin techniques and stained with hematoxilin and eosin. Immunostaining was performed using an antivimentin antibody for Sertoli cell identification. For morphometry, images of the slides were scanned and analyzed using Image J to determine the epithelial height, tubular and luminal diameter and tubular and luminal area. In the hormonal evaluation, FG had a higher serum concentration of estrogen (P=0.001), but no change was observed in the concentration of testosterone. The morphometric assay of seminiferous tubules and epididymal regions revealed no significant differences between the analyzed groups. Similarly, Sertoli cell quantification showed no significant differences in the FG (P=0.98). These results revealed that the continuous and prolonged intake of 25% flaxseed meals from gestation to 250 days of age, even with a significant increase in serum levels of estradiol, does not exert adverse effects on the testicular and epididymal structure or on the cells participating in the spermatogenesis of rats.

Identification of 5-bromo-2'-deoxyuridine-labeled cells during mouse spermatogenesis by heat-induced antigen retrieval in lectin staining and immunohistochemistry

DNA replication occurs during S-phase in spermatogonia and preleptotene spermatocytes during spermatogenesis. 5-Bromo-2'-deoxyuridine (BrdU) is incorporated into synthesized DNA and is detectable in the nucleus by immunohistochemistry (IHC). To identify BrdU-labeled spermatogenic cells, the spermatogenic stages must be determined by visualizing acrosomes and detecting cell type-specific marker molecules in the seminiferous tubules. However, the antibody reaction with BrdU routinely requires denaturation of the DNA, which is achieved by pretreating tissue sections with hydrochloric acid; however, this commonly interferes with further histochemical approaches. Therefore, we examined optimal methods for pretreating paraffin sections of the mouse testis to detect incorporated BrdU by an antibody and, at the same time, visualize acrosomes with peanut agglutinin (PNA) or detect several marker molecules with antibodies. We found that the use of heat-induced antigen retrieval (HIAR), which consisted of heating at 95C in 20 mM Tris-HCl buffer (pH 9.0) for 15 min, was superior to the use of 2 N hydrochloric acid for 90 min at room temperature in terms of the quality of subsequent PNA-lectin histochemistry with double IHC for BrdU and an appropriate stage marker protein. With this method, we identified BrdU-labeled spermatogenic cells during mouse spermatogenesis as A1 spermatogonia through to preleptotene spermatocytes.

Altered phosphorylation and distribution status of vimentin in rat seminiferous epithelium following 17β-estradiol treatment

Vimentin, type III intermediate filament, has stage-specific localization in the Sertoli cell. In the rat, during stages I-V and XI-XIV of the seminiferous epithelium, vimentin is localized in the perinuclear area with filaments projecting into the apical region toward the developing germ cells. These filaments decrease in length at stages VI-VII with perinuclear staining in stages VIII-IX, when spermiation occurs. Our earlier studies following 17β-estradiol treatment to adult male rats demonstrated an increase in germ cell apoptosis, spermiation failure and disruption of Sertoli cell microfilaments and microtubules. The present study was undertaken to determine the stage-specific distribution of vimentin and its involvement in spermiation failure and germ cell apoptosis. Immunofluorescence studies revealed that in contrast to the perinuclear localization with small extensions in control stages VII-IX, long extensions radiating apically to the spermatids in deep recess were observed in the treated group. Immunoprecipitation studies showed marked absence of phosphorylated vimentin in stages VII-VIII in the treated group. Further, localization of plectin, cytoskeletal linker protein, showed decrease in all the stages of spermatogenesis following estradiol treatment. Interestingly, for the first time the localization of plectin in the tubulobulbar complex was observed. In conclusion, the study suggests that estradiol treatment leads to an effect on vimentin phosphorylation, which could have inhibited the disassembly of vimentin leading to retention of apical projection in stages VII-VIII. These effects could be presumably due to a decrease in plectin, affecting the reorganization of vimentin and therefore the apical movement of spermatids, leading to spermiation failure.

Vimentin expression during altered spermatogenesis in rats

The collapse of vimentin caused by some xenobiotics correlates with the loss of structural integrity of the seminiferous epithelium. In this study, we investigated the effect of busulphan (an anticancer drug with toxic effects on dividing germ cells) on vimentin filament distribution in rat seminiferous epithelium and compared it with changes found in testes of unilaterally cryptorchid rats. In the seminiferous epithelium, the vimentin labelling was observed only in the Sertoli cells, showing a stage-specific arrangement of the filaments. Both busulphan treatment and cryptorchism caused altered distribution of vimentin filaments in the Sertoli cells. In both models, the apical vimentin filaments collapsed towards the nuclei and were disorganized in the basal region of the Sertoli cells while the germ cells were diminished in the epithelium. After the busulphan effect subsided (4 weeks after administration), spermatogenesis began to restore and vimentin filaments began to organize in basal and perinuclear regions of Sertoli cells among the spermatogonia and spermatocytes. Vimentin labelling of the sloughed material in the lumen of cryptorchid testes (but not in busulphan treated animals) was observed. We conclude that the Sertoli cell vimentin filaments play an important role in the maintenance of spermatogenesis, their damage is associated with the seminiferous epithelium disintegration and their restoration with a recovery of spermatogenesis after the unfavourable conditions subside.

Coordinated expression of UT-A and UT-B urea transporters in rat testis

The blood-seminiferous tubule barrier is responsible for maintaining the unique microenvironment conducive to spermatogenesis. A key feature of the blood-testis barrier is selective permeability to solutes and water transport, conferred by the Sertoli cells of the seminiferous tubules (SMTs). Movement of fluid into the lumen of the seminiferous tubule is crucial to spermatogenesis. By Northern analysis, we have shown that 4.0-, 3.3-, 2.8-, and ~1.7-kb UT-A mRNA transcripts and a 3.8-kb UT-B mRNA transcript are detected within rat testis. Western analysis revealed the expression of both characterized and novel UT-A and UT-B proteins within the testis. Immunolocalization studies determined that UT-A and UT-B protein expression are coordinated with the developmental stage of the SMT. UT-A proteins were detected in Sertoli cell nuclei at all stages of tubule development and in residual bodies of stage VIII tubules. UT-B protein was expressed on Sertoli cell membranes of stage II-III tubules. Using in vitro perfusion, we determined that a phloretin-inhibitable urea pathway exists across the SMTs of rat testis and conclude that UT-B is likely to participate in this pathway.

Plectin is concentrated at intercellular junctions and at the nuclear surface in morphologically differentiated rat Sertoli cells

Intermediate filaments in Sertoli cells have a well-defined pattern of distribution. They form a basally situated perinuclear network from which filaments extend peripherally to adhesion plaques at the plasma membrane and to sites of codistribution with other major elements of the cytoskeleton, particularly with microtubules. Although the general pattern of intermediate filament distribution is known, the molecular components involved with linking the filaments to organelles and attachment plaques in these cells have not been identified. One candidate for such a linking element is plectin. In this study we test for the presence of, and determine the distribution of, plectin in Sertoli cells of the rat testis. Fixed frozen sections and fixed epithelial fragments of rat testis were probed for plectin and vimentin using antibodies. Tissue was evaluated using standard fluorescence microscopy and confocal microscopy. Plectin in Sertoli cells was concentrated in a narrow zone surrounding the nucleus, and at focal sites, presumably desmosome-like plaques, at interfaces with adjacent cells. Plectin was also concentrated at sites where intermediate filament bundles project into specialized actin-filament containing plaques at sites of attachment to elongate spermatids. Plectin in Sertoli cells is concentrated at the nuclear surface and in junction plaques associated with the plasma membrane. The pattern of distribution is consistent with plectin being involved with linking intermediate filaments centrally (basally) to the nucleus and peripherally to intercellular attachment sites.

Spermatogenic cell apoptosis induced by mitomycin C in the mouse testis

Spermatogenic cell degeneration in the mature mammalian testis occurs both spontaneously during normal spermatogenesis and in response to cytotoxic agents. Mitomycin C (MC) is an antibiotic that affects DNA synthesis. In the present study, we examined the induction of mouse spermatogenic cell apoptosis by MC, using TdT-mediated dUTP-biotin nick end labeling (TUNEL) to detect high levels of DNA fragmentation in situ, transmission electron microscopy (TEM) to observe nuclear chromatin condensation, and molecular methods to detect DNA ladders. This study shows that in the testis of MC-treated mice: (i) apoptotic cell death with fragmentation of nuclear DNA is induced by MC dose-dependently, (ii) apoptotic cell death is most commonly found in the spermatogonia and less frequently in spermatocytes, and (iii) apoptotic cell death induced by MC is not specific for the seminiferous stage of the tubules. The present study suggests that the spermatogenic cell apoptosis induced by MC might be involved in its testicular toxicity.

Changes in the distribution of intermediate filaments in rat Sertoli cells during the seminiferous epithelium cycle and postnatal development

BACKGROUND

Intermediate filaments (IFs) are components of the cytoskeleton. In mammalian Sertoli cell, IFs are formed by vimentin. Previous studies have shown some characteristics of its distribution in Sertoli cells, however, very little is known of its distributional changes during the seminiferous epithelium cycle and during postnatal development.

METHODS

Immunohistochemical and electron microscopic methods were used to determine the distribution of vimentin-type IFs in rat Sertoli cells during the seminiferous epithelium cycle and postnatal development.

RESULTS

The distribution of IFs in adult rat Sertoli cell showed distinct cyclic changes during the seminiferous epithelium cycle. At stages I-VI, bundles of IFs extend from the perinuclear region to the supranuclear and apical regions of the Sertoli cell. These apical extensions became shorter at stage VII, and at stages VIII-X IFs were observed only in the perinuclear region. Short apical extensions reappeared at stages XI-XII; and at stages XIII-XIV, they extended again into the apical region. During this cycle, IFs were always closely associated with the heads of elongate spermatids. IFs were also shown to be in close apposition to some specialized structures on the cell membrane, such as the ectoplasmic specialization between adjacent Sertoli cells. During postnatal (p.n.) development, IFs were mainly observed at the basal nuclear region on p.n. day 7. The IFs in the supranuclear or apical regions first appeared at p.n. day 14 and gradually increased during the development. The perinuclear IFs network was fully established by p.n. day 28 and the adult distribution pattern of the IFs was established by p.n. day 42.

CONCLUSIONS

Vimentin-type IFs in rat Sertoli cells are a delicate endocellular network, which is centered in the perinuclear region and extends to the apical region of the cell. During the seminiferous epithelium cycle, the distribution of IFs changes in a stage-dependent manner and is closely related to the location of the heads of elongate spermatids. During postnatal development, IFs gradually increase in numbers and the main distribution area is transferred from the basal nuclear to the perinuclear and supranuclear regions.

Morphological analysis of germ cell apoptosis during postnatal testis development in normal and Hsp 70-2 knockout mice

The present study examined the occurrence of apoptotic cell death in the testis of wild-type mice from postnatal days 3 to 26 and in juvenile Hsp 70-2 knockout mice. Adult Hsp 70-2 knockout males are infertile and lack spermatids and spermatozoa (Dix et al. [1996a] Proc. Natl. Acad. Sci. U.S.A. 93:3264-3268). To identify the cell types undergoing apoptosis, we also examined the relationship between the occurrence of apoptotic cell death and the expression pattern of the Hsp 70-2 gene product (heat-shock protein 70-2 [HSP70-2]; marker for spermatocytes and spermatids), germ cell nuclear antigen 1 (GCNA1;marker for spermatogonia and spermatocytes), and vimentin (marker for Sertoli cells). This study shows that during postnatal development of the wildtype mouse testis (1) the percentage of apoptotic cell death detected by the TdT-mediated dUTP-biotin nick end labeling (TUNEL) method is higher in mice from days 8 to 22 than in younger or older mice, (2) the majority of apoptotic cells are spermatogonia and less frequently are spermatocytes, and (3) the degenerative cell death of spermatogonia and primary spermatocytes involves apoptosis with fragmentation of DNA. The analysis of apoptotic cell death in the testes of juvenile Hsp 70-2 knockout mice showed an additional increased level of apoptosis at day 17, during the first wave of spermatogenesis, in pachytene spermatocytes.

Testicular cell cytoskeleton in the newt, Triturus marmoratus marmoratus, during the annual cycle

Light and electron microscopy immunohistochemical studies and Western blotting analysis of cytoskeletal proteins have been carried out in the testis of the marbled newt (Triturus marmoratus marmoratus) during the annual testicular cycle. The present findings revealed homologies and differences with regard to those reported in the testes of mammals and other vertebrates. Changes in immunohistochemical expression have also been detected in the course of the annual cycle. Actin and tubulin, which were scanty and diffusely located in spermatogonia and spermatocytes, increased their expression and reorganized during spermiogenesis. Vimentin and keratin, undetected in spermatogonia and spermatocytes, were expressed in differentiating spermatids and spermatozoa. In these cells, actin might be related with the connection of the axial fiber to the undulating membrane and the coordination of movement by both structures, while vimentin might be involved in the maintenance of the spatial relationship between the axoneme and the marginal fiber. During the first stages of spermatogenesis, the cytoplasm of Sertoli cells (follicular cells) showed a diffuse immunoreaction to actin, myosin, and tubulin and no vimentin immunolabeling. In advanced spermiogenesis, the follicular cells showed an intense immunoreaction to actin, myosin, tubulin, and vimentin in the apical projections that surrounded the spermatid heads. These apical cytoskeletal components might be involved in spermatid elongation, since the spermatids display no manchette, and in spermatozoon positioning and grouping. The colocalization of myosin and actin in the follicular cells suggests that actin filaments from contractile bundles and that contraction might be involved in changes in the Sertoli cell shape that accompany germ cell development during spermatogenesis. The interstitial cells immunostained to actin, myosin, tubulin, and vimentin. These cells, together with follicular cells, seemed to form the glandular tissue cells which showed a similar immunophenotype. The cells that surrounded the efferent duct epithelium immunostained to desmin, and they are probably contractile cells involved in sperm evacuation.

Intermediate filaments in the testis of the teleost mosquito fish Gambusia affinis holbrooki: a light and electron microscope immunocytochemical study and western blotting analysis

A light and electron microscope immunocytochemical study and Western blotting analysis has been performed on intermediate filaments (vimentin, desmin and cytokeratins) in the testis of the teleost fish Gambusia affinis holbrooki. An immunoreaction to vimentin was observed in the epithelium of the efferent ducts, testicular canal and their surrounding peritubular cells. Positive vimentin immunostaining was also observed in the cells located around seminiferous tubules (boundary cells), Leydig cells, interstitial fibroblasts, chromatophores, and blood vessel endothelial cells. In contrast to mammals, no vimentin immunoreactivity was found in the Sertoli cells. Immunoreactivity to desmin was weak in the epithelial cells of the efferent ducts and testicular canal and intense in the peritubular cells that surrounded these ducts. Desmin immunoreactivity was also observed in the seminiferous tubule boundary cells. The immunoreactivity was weak in the boundary cells that surrounded germ cell cysts containing spermatogonia or spermatocytes and intense in the boundary cells around cysts with elongated or mature spermatids. Immunoreactivity towards cytokeratins was observed only in testicular blood vessels. Cytokeratin immunolabelling was intense in the endothelium and weak in the vascular smooth muscle cells. No cytokeratin immunoreactivity was found in the Sertoli cells, germ cells, interstitial cells or in the efferent duct epithelium. The absence of intermediate filaments in the Sertoli cells, the absence of cytokeratins in the epithelium of the sperm excretory ducts, and the presence of desmin filaments in these epithelial cells are the most important differences with regards to the intermediate filament phenotype in mammalian testes.

Cytoskeleton in Sertoli cells of the mosquito fish (Gambusia affinis holbrooki)

BACKGROUND

There is little information about the distribution of cytoskeletal components in the testes of teleost fish. The aim of this paper was to know the distribution of some major cytoskeletal proteins (tubulin, actin, vimentin, desmin, and cytokeratins) in the Sertoli cells of Gambusia affinis holbrooki and in their efferent duct epithelial cells which are possibly originated from the Sertoli cells.

METHODS

Light and electron microscopic immunocytochemical studies and Western blotting analysis were performed in G. affinis testis.

RESULTS

Actin immunoreaction was observed in the Sertoli cells at all spermatogenic stages, although the intensity of this reaction varied from one stage to another. Sertoli cells that support spermatogonia or spermatocytes showed a weak immunoreaction which was uniformly distributed throughout the cytoplasm and somewhat more concentrated at the level of the inter-Sertoli specialized junctions. Immunoreaction to actin increased during the first stages of spermiogenesis and was mainly localized beneath the plasma membrane. This immunoreaction was more intense in the basal than in the apical cytoplasm of Sertoli cells. In a more advanced stage of spermiogenesis, actin immunoreaction become stronger in the apical cytoplasm where Sertoli cells displayed cytoplasmic projections around each spermatid. After sperm release, the apical Sertoli cell cytoplasm still showed an intense actin immunoreaction. Intense immunoreaction to actin was also observed in the epithelial cells lining the efferent ducts. Immunoreaction to tubulin was diffuse throughout the Sertoli cell cytoplasm. No immunoreaction to vimentin or desmin was observed in the Sertoli cells during the spermatogenic process. Immunoreaction to both vimentin and desmin was observed in the efferent duct cells. Desmin immunoreaction was also observed in the seminiferous tubule boundary cells, mainly in the sections showing germ cell cysts at the last stages of spermiogenesis and in the peritubular cells that surrounded the efferent duct epithelium. Immunoreaction to cytokeratins was found in the endothelium of testicular blood vessels but not in the Sertoli cells or in the efferent duct epithelium.

CONCLUSIONS

Immunoreaction pattern to cytoskeletal proteins in the Sertoli cells of G. affinis differs from that reported in mammalian Sertoli cells. These differences include the distribution of actin filaments and the absence of detectable vimentin immunoreaction in G. affinis Sertoli cells.

Age-related changes in cytoskeletal components of the BDF1 mouse Sertoli cell

Age-related changes in mouse Sertoli cell cytoskeletal components (F-actin, vimentin and cytokeratin) were investigated by light and transmission electron microscopy and immunofluorescence using BDF1 mice from 3-33 months of age. In old mice (30 and 33 months of age), the testicular seminiferous epithelia were extremely thin, containing scarce round spermatids and spermatocytes with no elongated spermatids. In these epithelia, the Sertoli cells had lost their polarity and had become flattened. F-actin was detectable at the junction between adjoining Sertoli cells and around the spermatid head in young mice. In old mice, F-actin was distributed at the junction between adjacent Sertoli cells, around the spermatid head, and at the luminal side of the Sertoli cell cytoplasm. Vimentin was detected around the Sertoli cell nucleus and extended into the Sertoli cell trunk towards the tubular lumen in young mice. In old mice testes, however, vimentin was recognized around the Sertoli cell nucleus, but not in the Sertoli cell trunk. Additionally, sheet-like reactions of vimentin, running parallel to the basement membrane, were detected near the luminal surface. Although cytokeratin was not detected in the Sertoli cells of mice until 27 months of age, it was obvious in the extremely thin seminiferous epithelia of older mice. Cytokeratin was randomly distributed within the Sertoli cell cytoplasm. In these Sertoli cells, the expression of vimentin was concurrently detected. Detection of cytokeratin in the extremely thin seminiferous epithelia is one of the most characteristic phenomena of age-related testicular changes in Sertoli cells of older mice.

Immunohistochemical distribution of vimentin, desmin, glial fibrillary acidic protein and neurofilament proteins in feline tissues

The immunohistochemical distribution pattern of vimentin, desmin, glial fibrillary acidic protein and neurofilaments intermediate filament proteins has been analyzed in a wide range of formalin fixed, paraffin embedded tissues using polyclonal and monoclonal antibodies raised against non-feline antigens. The vimentin antibody reacted with mesenchymal cells, the desmin antibody with striated and smooth muscle fibres, the glial fibrillary acidic protein antibody with glial cells in the central and peripheral nervous system, and the neurofilament proteins antibody with neuronal cell bodies and processes. In addition, some epithelial cells were vimentin positive, perisinusoidal liver cells were desmin positive, and basal/myoepithelial cells of the mammary gland, and luteinic cells were glial fibrillary acidic protein positive. These staining patterns of feline tissues are basically similar with respect to that of corresponding tissues in other mammalian species for each of the four intermediate filament proteins studied, but some differences have been also noticed. This study confirms the broad interspecies cross-reactivity of intermediate filament proteins antisera and demonstrates their capability to differentiate particular types of feline cells and tissues.

Intermediate filaments in Sertoli cells

Using immunohistochemical techniques both at light and electron microscopic levels, the arrangement and distribution of intermediate filaments in Sertoli cells of normal testis (in rat and human), during pre- and postnatal development (in rabbit, rat, and mouse) and under experimental and pathological conditions (human, rat), have been studied and related to the pertinent literature. Intermediate filaments are centered around the nucleus, where they apparently terminate in the nuclear envelope providing a perinuclear stable core area. From this area they radiate to the plasma membranes; apically often a close association with microtubules is seen. Basally, direct contacts of the filaments with focal adhesions occur, while the relationship to the different junctions of Sertoli cells is only incompletely elucidated. In the rat (not in human) a group of filaments is closely associated with the ectoplasmic specializations surrounding the head of elongating spermatids. Both in rat and human, changes in cell shape during the spermatogenic cycle are associated with a redistribution of intermediate filaments. As inferred from in vitro studies reported in the literature, these changes are at least partly hormone-dependent (vimentin phosphorylation subsequent to FSH stimulation) and influenced by local factors (basal lamina, germ cells). Intermediate filaments, therefore, are suggested to be involved in the hormone-dependent mechanical integration of exogenous and endogenous cell shaping forces. They permit a cycle-dependent compartmentation of the Sertoli cell into a perinuclear stable zone and a peripheral trafficking zone with fluctuating shape. The latter is important with respect to the germ cell-supporting surface of the cell which seems to limit the spermatogenetic potential of the male gonad.

The Sertoli cell cytoskeleton: a target for toxicant-induced germ cell loss

Numerous studies in recent years have elucidated fundamental properties of axoplasmic structure, biochemistry, and function. The structural role of the cytoskeletal elements, the orientation of MTs within the axon, the phenomenon of MT-dependent transport, and the identity and direction of movement of two MT motors--kinesin and MAP-1C--have been revealed. For many years to come, researchers investigating the structure and function of the Sertoli cell cytoskeleton will be able to adapt techniques gleaned from work on the axonal cytoskeleton. Innovative thinking will be required to apply these techniques to the special circumstances of the male reproductive system; however, the underlying questions are similar. For example, knowledge of several fundamental properties of transport processes in the Sertoli cell would facilitate the toxicologic evaluation of this system. What is the orientation of MTs within the Sertoli cell cytoplasm? Are the fast-growing (+) ends of all MTs in the Sertoli cell cytoplasm directed toward the lumen? This is an important question because the direction of MT-dependent transport involving known MT motors is dependent upon the MT orientation. Which of the Sertoli cell transport pathways are MT-dependent pathways? What are the MT motors involved in these pathways? Ultrastructural examination following exposure to specific cytoskeleton-disrupting agents has highlighted the importance of AFs, IFs, and MTs in the Sertoli cell. Future research will focus on the nature of those molecules which integrate these cytoskeletal components into a dynamic whole, the regulatory systems which control this integration, and the role of an integrated cytoskeleton in Sertoli cell function and testicular homeostasis. Toxicology will be an active participant in this process of scientific discovery. The selective nervous system and testicular toxicants may be useful tools in revealing similarities in the cytoskeletal organization of these apparently disparate organ systems. By searching for common targets in the testis and nervous system, the mechanisms of action of these agents may be more easily, and more confidently, determined.

An immunohistochemical study of canine tissues with vimentin, desmin, glial fibrillary acidic protein, and neurofilament antisera

In a wide range of canine tissues the immunoreactivity with commercially available antisera against intermediate filament antigens viz. vimentin, desmin, glial fibrillary acidic protein (GFAP) and neurofilament proteins, was studied. In addition, the results of formalin and Carnoy fixation were compared. Carnoy fixation appeared to result in optimal reactivity for all antisera. Epithelial cells did not react with any of the antisera, with exception of ovarian surface epithelium, which showed staining with the vimentin and desmin antisera. The vimentin antiserum induced staining of several cell types viz. fibroblasts, endothelial cells, chondrocytes, Schwann cells, ependymal cells, astrocytes, Leydig cells, synovial cells, podocytes and some parietal cells of Bowman's capsule. Sertoli cells showed a faint staining reaction. Muscle cells in various tissues reacted with the desmin antiserum. In the kidney a varying number of parietal cells appeared to react as did a restricted number of epithelial cells of proximal tubules and loops of Henle. GFAP reactivity was confined to glial cells, predominantly fibrous astrocytes, Schwann cells and axons. Additionally, some neuronal cell bodies in peripheral ganglia showed staining of varying intensity. Neurofilament staining was restricted to axons and some neurons. The immunoreactivity of canine tissues with these antisera is compared to findings in other species. The results confirm a broad interspecies cross-reactivity of these antisera. They can be used in studying the nature of canine tissues.

Physiology of the male reproductive system: endocrine, paracrine and autocrine regulation

This presentation reviews the male reproductive system, concentrating on newer advances in our knowledge of its physiology, biochemistry, and regulation, and introduces the topic of male reproductive toxicology. GnRH is the hypothalamic peptide responsible for the stimulation of LH and FSH release from the pituitary. It is synthesized as a pro-hormone, processed in the hypothalamus and released into the portal system in a pulsatile fashion. The timing of these pulses is critical to the release of LH and FSH into the general circulation. While LH and FSH are the main trophic hormones for the testis, we now realize the importance of not only endocrine control, but also of paracrine and autocrine regulation. Specifically, the local control of Leydig cells, Sertoli cells, and germ cells appears to be modulated by numerous growth factors and local regulators arising from within the testis. This point is emphasized both during a discussion of the interaction of the various cell types in the testis and during a discussion of spermatogenesis, where techniques which show stage-specific secretions are highlighted. Newest advances in the mechanism of action of steroidal and peptide hormones are also emphasized with special reference to the possible interaction between toxicants and endocrine control of the reproductive system. This update of the reproductive system "sets the stage" for an in-depth examination of the site and mechanism of action of reproductive toxicants.