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.     

Fine structural changes in Sertoli and Leydig cells during the reproductive cycle of the ground squirrel, Citellus lateralis

During spermatogenesis in sexually mature ground squirrels Leydig and Sertoli cells were morphologically well differentiated. For Leydig cells the most prominent organelles were lipid droplets, mitochondria with tubulo-vesicular cristae and abundant agranular reticulum organized as a mass of anastomosing tubules. These morphological criteria suggest that the Leydig cells were steroidogenically active. Sertoli cells exhibited a topographical distribution of certain organelles with basal regions containing stacks of granular reticulum, and large areas of agranular reticulum. The cytoplasm surrounding maturing germ cells contained numerous microtubules, and an adluminal layer of spermatids at a certain stage of spermiogenesis became enveloped by Sertoli cytoplasm containing an enormous proliferation of agranular reticulum. The presence of these organelles in Sertoli cells suggests that during spermatogenesis they are active in the synthesis of proteins and steroids. In particular the mass of agranular reticulum surrounding late stage spermatids indicates that steroids may be required for spermatid maturation and/or spermiation. By contrast Leydig and Sertoli cells observed during testicular regression, when only spermatogonia remain in the seminiferous tubules, had undergone structural changes. Leydig cells were still numerous and large with abundant agranular reticulum that was now organized as a loose assemblage of single unbranched tubules. Sertoli cells were drastically reduced in both cytoplasmic volume and content of organelles.     

Cyclic localization change of Golgi apparatus in Sertoli cells induced by mature spermatids in rats

Previously we reported that the intracellular localization of the Golgi apparatus of rat Sertoli cells changes during the seminiferous epithelial cycle, and that the cyclic changes seem to be correlated to specific generations of germ cells. To ascertain which generations of germ cells are responsible for the cyclic changes, we determined the relative volume of the Golgi apparatus within the basal, mid, and apical cytoplasm of Sertoli cells in testes with and without mature spermatids. In normal adult rats, the Golgi apparatus was usually localized exclusively in the basal cytoplasm, whereas at stages VII-IX it increased remarkably in mid and apical cytoplasm, with a concomitant decrease in the basal cytoplasm. In young adult testes without spermatids at steps 15-19 of spermiogenesis (2nd layer spermatids), the Golgi apparatus was localized in the basal cytoplasm throughout the seminiferous epithelial cycle. Orchiopexy maintained for 35 days following 60 days of cryptorchidism allowed germ cells to regenerate to spermatids at steps 1-14 of sperminogenesis (1st layer spermatids), but failed to change the intracellular localization of the Golgi apparatus in Sertoli cells. At 50 days after orchiopexy, when all generations of germ cells appeared in the tubules, the cyclic changes in localization of the Golgi apparatus were restored similar to those in normal adult testes. These findings indicate that the cyclic change in localization of the Golgi apparatus in Sertoli cells is evoked by the presence of 2nd layer spermatids.     

Changes in the lipid inclusion/Sertoli cell cytoplasm area ratio during the cycle of the human seminiferous epithelium

The area occupied by Sertoli cell lipid inclusions--electron-lucent lipid vacuoles (LLV) and electron-dense lipid droplets (DLD)--at each stage of the cycle of the seminiferous epithelium was measured on electron micrographs in young adults and elderly men, and expressed as the ratio "area occupied by lipid inclusions/area occupied by the Sertoli cell cytoplasm". For LLV this ratio increased from stage I to stage III, and decreased from stage IV to stage VI in young adults. These results suggest that the development of LLV is synchronized with the spermatogenic process: the residual bodies released in stages I and II are phagocytized by Sertoli cells and transformed into LLV; the amounts of LLV decrease in the subsequent stages of the cycle and increase again when new residual bodies appear. In elderly men the ratio LLV/Sertoli cell cytoplasm was 1.9-2.9 times higher than in young adults at each stage of the cycle. This increase may be related to the increased germ-cell degeneration observed in ageing testes, DLD were less abundant than LLV and the DLD/Sertoli cell cytoplasm ratio did not undergo cyclic changes in young adults or elderly men.     

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.     

Ultrastructure and Cytochemistry of the Cell Types in the Larval Hematopoietic Organs and Hemolymph of Drosophila Melanogaster

The ultrastructure of the primordial blood cells in the first and second hematopoietic lobes of the late second and third instar larva and prepupa of Drosophila melanogaster was compared with the ultrastructure of the blood cells found freely in the larval hemolymph. Within the hematopoietic lobes two principal cell-types were detected: (i) the prohemocytes and proplasmatocytes, and (ii) different developmental stages of crystal cells., Prohemocytes are characterized by a ribsome-rich cytoplasm, showing small amounts of mitochondria, rough ER and Golgi complexes and few primary lyosomes. Prohemocytes differentiate into proplasmatocytes. When released into the hemolymph they transform further into plasmato-, podo-, and lamellocytes. This differentiation pathway is characterized by a gradual, numerical increase of cytoplasmic organelles, the development of the lysosomal system and the aquisition of the capacity for phagocytosis and melanin formation. The differentiation of a procrystal cell into a crystal cell involves a number of intermediate stages, during which the crystalline material is produced, accumulated, and crystallized. Primary and secondary lysosomes in the primordial blood cells of the hematopoietic organs as well as the free blood cells in the hemolymph were identified cytochemically with the help of the acid phosphatase test. The capacity for melanin synthesis was studied with the phenol- and polyphenol oxidase test.     

A quantitative analysis of the incidence of certain cytoplasmic structures in the ovum of the rat during cleavage

Summary The volumetric density of most cytoplasmic organelles in the segmenting ovum of the rat was determined by morphometric techniques described by Weibel, at the 1-, 2-, 4-, and 8-cell stages, and at the early and late blastocyst stages.During the course of cleavage, the volumetric density of mitochondria remained practically unchanged. The volumetric density of the Golgi complex was too small to permit assessment of the differences between the individual stages of development. Significant changes were found in both granular and agranular endoplasmic reticulum, secondary lysosomes, multivesicular bodies, lamellar structures and lipid droplets. Granular endoplasmic reticulum was first observed as late as the 8-cell ovum stage and its volumetric density increased further in the early and late blastocysts. The relative volume of agranular endoplasmic reticulum was highest in the 1-cell ovum and decreased during the course of cleavage. The same is true for multivesicular bodies. The volumetric density of secondary lysosomes increased during cleavage, reaching the highest values in the 8-cell ovum. Lamellar structures were the most voluminous part of the cytoplasm of the segmenting ovum at all stages. Their volumetric density, however, decreased during the course of cleavage. Lipid droplets occur in very small quantities in the 1- to 4-cell ova, but at later stages their volumetric density increased.Our findings underline the importance of acquiring quantitative information about changes in cell organelle populations for assessing morphological and functional relationships during the early stages of cleavage of the ovum.     

Testicular involution following optic enucleation

Summary The testes of adult male Syrian hamsters underwent involution within six weeks after optic enucleation. The diameter of the seminiferous tubules was 39% less than controls. Sertoli cells, spermatogonia, and primary spermatocytes were still present, but all steps of spermatids were completely absent from the involuted testes. Lipid droplets filled the Sertoli cell cytoplasm and often encroached upon the nucleus. Sertoli cells had sparse mitochondria and smooth endoplasmic reticulum, but Golgi cisternae were abundant. Typical SertoliSertoli junctions attached contiguous Sertoli cells. With lanthanum tracers it was demonstrated that these junctions were impenetrable; therefore, the bloodtestis barrier was deemed intact. Irregularly shaped protrusions often arose from the peritubular tissue and extended inward toward the seminiferous epithelium, often displacing the cytoplasm of the Sertoli cells and spermatogonia. The core of these protrusions consisted of irregular extensions of myoid cell cytoplasm surrounded by the myoid cells' basal lamina. External to the myoid cell basal lamina were bundles of collagen filaments with the basal lamina of the seminiferous epithelium forming the outermost layer of these protrusions. The apices of the Sertoli cells gave rise to numerous leaf-like processes that extended into and obliterated the lumen of the tubules. The Sertoli cell basal cytoplasm often contained phagocytized degenerating germ cells that appeared to give rise to the lipid droplets that filled the Sertoli cell cytoplasm. Acid phosphatase rich lysosome-like organelles were seen fusing with the degenerating germ cells and lipid droplets. The degenerating germ cells also were shown to contain acid phosphatase activity.     

Immunolocalization of albumin and transferrin in germ cells and Sertoli cells during rat gonadal morphogenesis and postnatal development of the testis

The localization of albumin and transferrin was examined immunohistochemically in germ cells and Sertoli cells during rat gonadal morphogenesis and postnatal development of the testis. These proteins appeared as early as the 13th day of gestation in migrating primordial germ cells before Sertoli cell differentiation. In the fetal testis, strong immunoreactivity was only detected in the gonocytes. In the prepubertal testis, spermatogonia, primary spermatocytes, and some Sertoli cells accumulate albumin and transferrin. At puberty, different patterns of immunostaining of the germ cells were observed at the various stages of the cycle of the seminiferous epithelium. Diplotene spermatocytes at stage XIII, spermatocytes in division at stage XIV, and round spermatids at stages IV–VIII showed maximal staining. Labeling was evident in the cytoplasm of adult Sertoli cells. Albumin and transferrin staining patterns paralleled each other during ontogenesis.     

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 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.     

Cytochemical reaction for cationic proteins as a marker of primary granules during development in chick heterophilis.

The ammoniacal silver reaction (ASR) for cationic proteins was used as a cytochemical marker for the primary or A granules in the cytoplasm of developing heterophils of chick bone marrow. The presence of the electron-dense particulate reaction product of silver, which is localized in the fully formed rod-shaped A granules, provides a marker by which the A granules could be distinguished from the B granules of similar size and by which the formation and maturation of both granule types could be followed through the developmental stages. Progressive developmental stages were ascertained on the basis of decreasing cell size, increasing condensation and margination of the chromatin, and the number and morphology of the granules; the stages were divided into promyelocyte, myelocyte, metamyelocyte and heterophil. During the promyelocyte stage, the first appearance of the electron-dense, membrane-bound, spherical granules (0.3--1.0 micrometer in diameter) is observed in the vicinity of an extensive Golgi complex. They occur in a cytoplasm containing rough-surfaced endoplasmic reticulum, ribosomal clusters, centrioles, mitochondria, microtubules, as well as the membranes, saccules, vesicles and vacuoles of the Golgi complex. These granules are considered as primary but their presence as the only granule type appears very brief. The ASR reaction product is first detected on the surface of these primary granules in late promyelocytes or myelocytes. The secondary or B granule, devoid of reaction for cationic protein at all stages, appears as a condensing vacuole in promyelocytes, but after some A granules are already present. The vacuole contents condense to form the B granules which are 0.1--0.6 micrometer in diameter, often oval-shaped, and contain a loose filamentous material surrounded by a membrane. Tertiary C granules or lysosomes appear during the myelocyte stage as dense core vesicles (0.1--0.2 micrometer in diameter) negative for cationic protein.     

Ultrastructure of the choroid plexus epithelium of pigeons treated with drugs: II. Effect of cytochalasin D and colchicine

A remarkable projection of bleblike protrusions, the expulsion of organelles into the protrusions formed on the apical surface, and the separation into the ventricular lumen of these protrusions was the general cellular response of choroidal epithelial cells to intravenous injection of cytochalasin D (CD). The compact microfilament mass and agglomeration of microtubules at the base of the cluster of protrusions reflect the results of cell contraction and displacement of microfilaments induced by CD. In earlier stages after intravenous injections of colchicine, an obvious increase in the number of various-sized vesicles, vacuoles, and lysosomes in the Golgi region was detected. In the later stages, these organelles were seen to accumulate in the basal portion of the epithelial cells. These changes were accompanied by an increase in vacuoles and the disorganization and displacement of the Golgi complex, and they coincided with a decrease in the number of microtubules in apical and basal cytoplasm. These findings suggest that the action of colchicine results in destruction of the three-dimensional architecture between cytoskeletal network and cell organelles. The present results suggest that the cytoskeletal network plays a role in the spatial coordination of the three-dimensional architecture of cell organelles. The study also indicates that the structural differences in the ventricles of the choroid plexus in drug-treated pigeons are manifestations of regional functional specialization in different parts of the ventricular system.     

Receptor-mediated endocytosis of transferrin by Sertoli cells of the rat

Binding of 125I-transferrin (125I-Tf) to the plasma membrane of Sertoli cells and its endocytosis were analyzed by means of light- and electron-microscope quantitative radioautography. Five minutes after 125I-Tf was injected into the interstitial space of the testis, a strong labeling of the basal aspect of the seminiferous epithelium was observed in light-microscope radioautographs. Injection of the same dose of 125I-Tf plus a 200-fold excess of cold transferrin resulted in a marked diminution of the radioautographic reaction, indicating that the initial strong labeling with radiolabeled transferrin was specific. These results were consistent with the localization of immunoreactive fluorescence of transferrin receptor at the base of the seminiferous epithelium. In electron-microscope radioautographs of tubules collected at 5 min after injection, the membrane of Sertoli cells facing the basement membrane was well labeled with 125I-Tf. At 15 and 30 min, the plasma membrane was less intensely labeled, but the silver grains were then seen overlying multivesicular bodies with an electron-lucent matrix, identified as endosomes. This population of endosomes was always seen at a short distance from the basal membrane of Sertoli cells. At 90 min, no more labeling of the plasma membrane, endosomes, or any other cytoplasmic component was observed. Isolated seminiferous tubules and Sertoli cells labeled with 125I-Tf at 4 degrees C were rinsed and reincubated in a label-free medium at 37 degrees C for various periods of time from 5 to 90 min. A radioactive protein precipitated by trichloroacetic acid, presumably intact transferrin, was released from the tubules into the incubating medium; when measured, it was found to increase rapidly from 5 to 45 min and stabilize thereafter. These results suggest that transferrin was internalized by receptor-mediated endocytosis, reached endosomes, and then was released to the extratubular space. When native ferritin (NF), a tracer for fluid-phase endocytosis, was infused within the lumen of seminiferous tubules and 125I-Tf was simultaneously injected into the interstitial space, both markers rapidly reached different populations of endosomes. Endosomes labeled with NF, scattered throughout the cytoplasm, evolved with time into dense multivesicular bodies and secondary lysosomes, whereas radiolabeled transferrin reached only the endosomes located in the basal cytoplasm of Sertoli cells. The latter thus appeared to be principally involved in the uptake and recycling of transferrin.     

Interrelationships between Sertoli cells and germ cells in the Syrian hamster

The interrelationships of the Sertoli cells and germ cells in the Syrian hamster were examined using the electron microscope. Demosome-like junctions were observed attaching Sertoli cells to spermatogonia and spermatocytes. In the region of the junctions dense plaques lay on the cytoplasmic surfaces of the plasmalemma of the opposing cells. Sertoli cell cytoplasmic filaments converged in the area of the junctions and inserted into the subsurface densities. Filaments were not observed associated with the subsurface densities of the germ cells. In the region of the junctions a 15...20 nm gap, filled with an attenuate amorphous substance, separated the plasmalemmata. Another attachment device termed "junctional specialization" occurred between Sertoli cells, and preleptotene spermatocytes and all successive developmental steps in the germ cell line in the hamster. The junctional specializations consisted of a mantel of Sertoli cell cytoplasmic filament lying subjacent to the Sertoli cell plasmalemma and an opposed cisterna of the endoplasmic reticulum. In stages VII-VIII preleptotene supermatocytes were observed in transit from the basal compartment to the adluminal compartment. While Sertoli-Sertoli junctions adluminal to the spermatocytes remained intact, typical Sertoli-Sertoli junctions formed between opposed Sertoli cell processes basal to the spermatocytes. It is proposed that, during the passage of spermatocytes in to the adluminal compartment, junctional specializations associated with preleptotene spermatocytes in the basal compartment migrate basal to the spermatocytes and contribute to formation of Sertoli-Sertoli junctions. Treatment of seminiferous tubules with hypertonic media was used to demonstrate that the junctional specializations function in cell-to-cell adhesion. Data indicated that these junctions function to retain the developing spermatids within the seminiferous epithelijm until the time of spermiation. At spermination the junctional specializations disappear and the spermatids drift off into the tubule lumen.     

Structural Changes of Yolk Platelets and Related Organelles during Development of the Newt Embryo

Structural changes in yolk platelets and related organelles in the cytoplasm of the presumptive ectodermal region up to the stage of gastrulation were studied by light and electron microscopies using full-grown oocytes, mature eggs descending the oviduct and embryos of the newt, Cynops pyrrhogaster . Yolk platelets with a superficial layer are first observed in mature eggs descending the oviduct. During the cleavage and early morula stages, the superficial layer increases in thickness and the main bodies become more slender. The superficial layer decreases in thickness in the blastula stage, and many yolk platelets lose this layer in the gastrula stage.
The amount of rough-surfaced endoplasmic reticulum (r-ER) increases rapidly in the morula stage, while Golgi complexes gradually increase in number between the cleavage and gastrula stages. In the cleavage and early morula stages, most of the r-ER is closely adherent to yolk platelets and is associated with several mitochondria. Two types of free vesicles, large (0.5–4.0 μm diameter) and small (0.15–0.3 μm diameter), were seen in abundance from the early morula stage to the early gastrula stages.
Changes in the structure of yolk platelets are discussed in relation to changes in other cytoplsmic organelles.     

Distribution of the microtubule-dependent motors cytoplasmic dynein and kinesin in rat testis.

To examine the possible role of microtubule-based transport in testicular function, we used immunofluorescent techniques to study the presence and localization of the microtubule mechanoenzymes cytoplasmic dynein (a slow-growing end-directed motor) and kinesin (a fast-growing end-directed motor) within rat testis. Cytoplasmic dynein immunofluorescence was observed in Sertoli cells during all stages of spermatogenesis, with a peak in apical cytoplasm during stages IX-XIV. Cytoplasmic dynein immunofluorescence was also localized within Sertoli cells to steps 9-14 (stages IX-XIV) germ cell-associated ectoplasmic specializations. In germ cells, cytoplasmic dynein immunofluorescence was observed in manchettes of steps 15-17 (stages I-IV) spermatids, and small, hollow circular structures were seen in the cytoplasm of step 17 and step 18 spermatids during stages V and VI. Kinesin immunofluorescence was observed in manchettes of steps 10-18 spermatids (stages X-VI). The stage-dependent apical Sertoli cell cytoplasmic dynein immunofluorescence, in conjunction with the previously reported orientation of Sertoli cell microtubules (slow-growing ends toward the lumen) and peak secretion of androgen-binding protein and transferrin, is consistent with the hypothesis that cytoplasmic dynein is involved in Sertoli cell protein transport and secretion. Further, the localization of cytoplasmic dynein and kinesin to manchettes is consistent with current hypotheses concerning manchette function.     

泥螺卵子发生的超微结构研究

利用透射电镜观察了泥螺卵子发生过程。结果表明 ,泥螺的卵子发生可划分为卵原细胞、卵黄发生早期、卵黄发生中期及卵黄发生后期卵母细胞 4个时期。卵原细胞核大而圆 ,胞质内分布有少量的线粒体和高尔基囊泡 ,细胞表面具微绒毛。卵黄发生早期的卵母细胞 ,胞质中各类细胞器发达 ,并出现数量较多的类朦胧子。卵黄发生中期的卵母细胞胞体迅速增大 ,核伸出伪足状突起 ,卵质中各种细胞器活动活跃 ,并参与形成卵黄粒和脂滴。此期还可观察到卵母细胞与滤泡细胞间的物质交换现象。卵黄发生后期的卵母细胞体积增至最大 ,细胞器数量减少。本文就卵黄发生前后卵母细胞内部构造的变化、意义及滤泡细胞与卵母细胞蛋白来源间的关系作了探讨     

Short- and long-term exposure to methamidophos impairs spermatogenesis in mice

Methamidophos (MET) is a pesticide that has toxic properties, including effects on fertility. This study aimed to assess the joint action of treatment time and exposure to methamidophos on the male reproductive system. MET was orally administered to adult male Swiss mice at a dose of 0.004 mg.kg⁻¹ for 15 and 50 consecutive days. The following parameters were evaluated: weight of reproductive organs, spermatogenesis, sperm and Sertoli cell count, daily sperm production and sperm transit time. Short-term exposure to methamidophos induced a decrease in epididymal weight. The frequency of stages V–VI of spermatogenesis increased and the frequency of stage IX decreased. In the epididymis, sperm transit time (caput/corpus) was reduced and the relative sperm number (cauda) increased. Long-term exposure induced an increase in the frequencies of stages I–IV and V-VI and decreased the stages VII-VIII and IX. The number of Sertoli cells with evident nucleoli was reduced in both exposures. These results confirm the reproductive toxicity of MET.