Secretory Vacuoles Research Articles

Immunoelectron Microscopical Demonstration of Egg-yolk Plasma Precursor Vitellogenin in the Hepatocyte of Oestradiol-treated Cockerels

Vitellogenin has been localized at the electron microscopical level in the liver of the cockerel using a colloidal gold technique. White leghorn cockerels were treated with 17 beta-oestradiol to induce vitellogenesis. Pieces of liver were removed from control and experimental birds on the 4th and 8th days following hormone treatment, and embedded in Lowicryl K4M. Vitellogenin was isolated from the plasma of oestradiol-treated cockerels, and the antibody to it elicited in rabbits and made vitellogenin-specific by affinity chromatography on lipovitellin-Sepharose columns. At the light microscopical level, the intensity of immunohistochemical staining was considerably above background levels in oestradiol-treated cockerels. At the electron microscopical level, gold particles indicating antigenic sites of vitellogenin were largely confined to the rough endoplasmic reticulum, Golgi apparatus, immature and lysosomes and phagosomes within hepatocytes and sinusoidal cells respectively. These observations strongly suggest that the intracellular pathway of vitellogenin secretion in chicken hepatocytes under the experimental conditions studied involves external stimuli and secretory vacuoles. The labelling of lysosomes may reflect catabolic turnover (crinophagy).

Histochemical localization of hydrolase activities in the alimentary canal of some parasitic copepods.

Using a freeze-substitution method, we examined light microscopic localizations of hydrolase activities in the alimentary canal of six species of parasitic copepods: Conchyliurus quintus, Modi-olicola bifidus, Ostrincola koe, Panaietis yamagutii, Neoergasilus japonicus and Ergasilus orientalis. Alkaline phosphatase activity was detected in the striated border of the non-vacuolar midgut cells. Acid phosphatase activity was detected in the secretary vacuoles of the vacuolar midgut cells and the striated border of the non-vacuolar midgut cells. Non-specific esterase, β-N-acetylglucosami-nidase and β-glucuronidase activities were detected only in the secretory vacuoles of the vacuolar midgut cells. No positive reactions were observed in the labral glands. These results suggest that digestive enzymes of these parasitic copepods are lysosomal enzymes secreted by the vacuolar midgut cells.

Ultrastructure of the Midgut Cells of Some Parasitic Copepods with Special Reference to the Secretion of Digestive Enzymes.

The ultrastructure of midgut cells of six species of parasitic copepods was observed. The anterior zone of the midgut of Conchyliurus quintus, Ostrincola koe, Panaietis yamagutii, Neo-ergasilus japonicus and Lernaea cyprinacea consisted of vacuolar cells and non-vacuolar cells. The vacuolar cells were characterized by sizable endocytotic and secretory vacuoles suggesting active absorptive and secretory functions, respectively. The secretory product containing digestive enzymes was discharged by holocrine secretion. The non-vacuolar cells were char-acterized by the well-developed microvilli suggesting an absorptive function of the cells. In Pseudomyicola spinosus, however, the anterior zone of the midgut consisted of non-vacuolar cells only containing numerous primary lysosome-like vacuoles. Such lysosome-like vacuoles situated just underneath the free surface and the well-developed microvilli of the non-vacuolar cells suggested their secretory and absorptive functions. Numerous bacteria occurred con-sistently in the anterior zone of the midgut of Ps. spinosus.

Localization of platelet-derived growth factor (PDGF) in CHO cells transfected with PDGF A- or B-chain cDNA: Retention of PDGF-BB in the endoplasmic reticulum and Golgi complex

Platelet-derived growth factor (PDGF) is a powerful mitogen for connective tissue cells. It is made up of two polypeptide chains (A and B) and exists in three dimeric forms (AA, AB, and BB). Transfection experiments have indicated that PDGF-AA and -AB are secreted as 30 x 10(3) Mr products, whereas PDGF-BB is processed into a 24 x 10(3) Mr product and remains associated with the cells. Here, CHO cells were transfected with PDGF B- or A-chain cDNA and the intracellular distributions of the respective gene products were compared by indirect immunofluorescence and immunoelectron microscopy, using primary antibodies specific for PDGF B- and A-chain homodimers. PDGF-BB was most conspicuous in stacked Golgi cisternae. It was also found in the endoplasmic reticulum and in lysosomes. Upon treatment of the cells with the microtubule-disruptive drug nocodazole, the Golgi complex was broken up and its stacks of cisternae were dispersed throughout the cytoplasm together with clusters of lysosomes. After this structural disorganization, the concentration of PDGF-BB to the Golgi stacks was even more prominent than before. Weak reactivity for PDGF-AA was detected in the endoplasmic reticulum and groups of vacuoles, both in control and nocodazole-treated cells, whereas Golgi stacks and lysosomes only seldom were positive. The observations suggest that PDGF-BB is processed and retained within the endoplasmic reticulum and Golgi complex. Eventually, it may also be transferred to lysosomes for degradation. In contrast, PDGF-AA is likely to follow a pathway for bulk flow, including rapid passage through the endoplasmic reticulum and Golgi complex, package in secretory vacuoles, and extracellular release by exocytosis.

Effect of carbamylcholine on Harderian gland morphology in rats

To determine the effect of cholinergic secretagogue on the Harderian gland of rats, several light- and electron-microscopic parameters were morphometrically assessed at different time intervals after carbamylcholine injection. In controls, two types of glandular cells (type A cells having 40-55 large vacuoles per cell profile and type B cells containing 30-38 smaller vacuoles per cell profile) and myoepithelial cells were recognized. At 5 min after injection of carbamylcholine, when rats secreted "bloody tears", many alveoli showing narrower lumina and exocytotic figures in both types of cells were observed. Some vacuoles, which were covered by thin cytoplasmic sheets, protruded into the alveolar lumina. However, there was no evidence of apocrine or holocrine secretion. At 30 min and 120 min after injection, most of the alveolar lumina were dilated, and a pronounced decrease in the number of vacuoles in the glandular cells was observed. At 300 min after injection, the secretory vacuoles in both cell types reaccumulated. Transitional forms between the two cell types were not observed. The two types of Harderian gland cells can therefore be considered independent populations rather than different secretory stages of the same cell. It appears that the secretory process of the Harderian gland of rat is affected by cholinergic stimulation of the two types of glandular cells and of myoepithelial cells.

Ultrastructural analysis of collagen formation in the developing primate amnion

The amnion surrounding the mammalian embryo consists of the amniotic epithelium facing the amniotic cavity, a layer of extraembryonic mesoderm bordering the exocoelom and an intervening layer of extracellular matrix (Fig. 1). During gestation the amnion expands remarkably to acommodate the rapidly growing embryo. In this study we have examined the process of collagen fibril formation in the developing amnion of the rhesus monkey between 20 and 60 days of gestation.Most cytological evidence of collagen fibril formation was observed in association with the extraembryonic mesodermal cells rather than the amniotic epithelium. The mesodermal cells h ad abundant cisternae of rough endoplasmic reticulum and a prominent Golgi apparatus. Elongated secretory vacuoles were associated with the Golgi apparatus and often contained parallel aggregates of fine filaments (Fig. 2). In some secretory vacuoles, periodic densities also were observed. Some striated collagen fibrils were observed in an apparent intracellular location in long, membrane-limited compartments (Fig. 3). Still other striated fibrils were observed in dense bodies, presumably lysosomes (Fig. 4).

Cycles of F-actin redistribution in the dermal glands of an insect relate to secretion

ABSTRACT Cells of the dermal glands in Calpodes ethlius Stoll (Lepidoptera, Hesperiidae) survive without division but increase in size from moult to moult. The secretory cells become especially large, measuring up to 6 mm long in the fifth larval stadium. The nucleus in these giant cells has a sponge-like profile, with the nuclear envelope indented around cytoplasmic intrusions, each of which comes to contain several secretory vacuoles. The secretory vacuoles coalesce just before the glands discharge at ecdysis. Rhodaminyl phalloin labelling shows that F-actin redistributes in cycles corresponding to ecdysial secretion atlarval and pupal moults. Capsules of F-actin form around the vacuoles before ecdysis. After the vacuoles discharge, actin from the capsules survives in strands that aggregate into storage bundles during the intermoult as though the filamentous actin itself is redistributed and stored. The storage bundles disappear as the F-actin capsules re-form at the next moult

Localization of lysosomal and digestive enzymes in cytoplasmic vacuoles in caerulein-pancreatitis

Intracellular localization and enzymatic activities of lysosomal enzymes (cathepsin B, N-acetyl-beta-glucosaminidase, and beta-glucuronidase) were studied in control rats and after induction of caerulein pancreatitis. In control rats high enzymatic activities were found in the postnuclear 1000 g fraction (purified zymogen granules). The corresponding subcellular fraction in pancreatitis animals additionally contained larger secretory vacuoles and autophagosomes and revealed a marked increase in lysosomal enzyme activities. Immunolabelling studies at the ultrastructural level for trypsinogen and cathepsin B demonstrated a colocalization of lysosomal and digestive enzymes in zymogen granules in healthy controls. After induction of pancreatitis immunolabelling still demonstrated a colocalisation of cathepsin B and trypsinogen in secretory granules and newly formed Golgi-derived secretory vacuoles. Concomitantly appearing autophagosomes were, however, only labelled for cathepsin B. It is concluded that segregation of lysosomal and digestive enzymes is incomplete in normal acinar cells resulting in a colocalization in zymogen granules. In pancreatitis colocalization in secretory granules is maintained, whereas only lysosomal enzymes were sufficiently transferred into autophagic vacuoles. No indication for impaired mechanisms of molecular sorting of lysosomal and digestive enzymes in caerulein-induced pancreatitis was found.

Morphologic characterization of early prostatic carcinomas in the ACI rat: A light and electron microscopic study

The ACI rat constitutes a unique model for human prostatic carcinogenesis. A high percentage of these animals spontaneously develop prostatic carcinomas in the ventral lobe as they age. The light microscopic appearance of these tumors is similar to the cribriform pattern of adenocarcinoma in human prostate. In order to further characterize this useful model, we carried out light and electron microscopy studies of the morphology of carcinomatous lesions developing in these animals. Sixteen rats ranging in age from 25 to 43 months were examined histologically, and ultrastructural studies were performed on eight of these cases. The neoplastic cells showed features of well-developed secretory epithelium including prominent Golgi apparatus, abundant rough endoplasmic reticulum, and numerous secretory vacuoles. Microvilli were numerous in some cells and focal apocrine secretory activity was present. Intraluminal crystals similar to those associated with human prostate carcinoma were observed in one of our cases. Prostate carcinomas developing in the ACI rat share many of the ultrastructural features of human prostatic carcinoma.

Abnormal protein translocation as the elusive cause of cystic fibrosis: an hypothesis

Despite the recent rapid advances in isolation of the abnormal gene responsible for cystic fibrosis, there remains the need to explain the mechanism by which a single gene mutation causes the widespread clinical effects seen in this disease. Careful review of the otherwise unexplained abnormalities of cystic fibrosis from the perspective of cell biology reveals the following common features: (1) all these abnormalities involve proteins which are either (A) inserted into cell membranes in the RER and arrested after partial translocation or (B) inserted into RER membranes and fully translocated to be compartmentalized away from the cytosol in secretory vacuoles, lysosomes or peroxisomes; (2) all the involved proteins have minor abnormalities in their physicochemical properties or activity functions; (3) none of the involved proteins are missing or totally deficient in function; (4) final compartmentalization of the involved proteins is unaffected. These observations have directed our attention to the process by which most proteins are inserted into and translocated across lipid bilayer membranes, namely the signal peptide mechanism. This mechanism, not previously examined in cystic fibrosis, is reviewed in detail. Of the major proteins controlling signal peptide translocation, deficiencies in the function of signal peptidase activity appear most capable of causing the effects seen in cystic fibrosis.

Redistribution and recycling of internalized membrane in seminal vesicle secretory cells

This study was performed to clarify the fate of membrane constituents internalized from the apical domain in secretory cells, in particular their possible recycling and the compartments involved in it. Glycoproteins of the apical membrane of seminal vesicle secretory cells from guinea-pig were covalently labeled in vitro (0°C, 20 min) with 3H-galactose and the epithelium incubated for 15 min (37°C, first incubation) to allow endocytosis. The label which was not internalized was then exposed to enzymatic hydrolysis (0°C, 30 min) and the epithelium re-incubated to allow membrane movement for 15 and 30 min (37°C, 2nd incubation). After each step of the protocol, tissue pieces were fixed and processed for electron microscope autoradiography and the results studied by morphometric analysis. Following labeling, 99% of the silver grains were associated with the apical domain of the cell membrane (AD). After the 1st incubation at 37°C, 30° of the grains were inside the cells in association with the cytoplasmic vesicles (Cyt ves), secretory vacuoles (SV), Golgi vesicles (GV), Golgi cisternae (GC), multivesicular bodies (MVB), lysosomes (LYS), and the cell membrane basolateral domain (BLD). About 58% of non-internalized radioactivity was removed by hydrolysis. During the 2nd incubation at 37°C the concentration of label increased in BLD and LYS, decreased in SV and MVB, and fluctuated in GC, GV and AD. The distribution of grains observed at 15 min, as compared using the χ-square test, was highly significantly different from that expected without recycling. The results show that cell membrane glycoproteins internalized at the cell apex recycle back to the membrane apical domain and are consistent with the involvement of GC and SV in the recycling pathway. Membrane shuttle between the apical and basolateral domains of the cell membrane is also suggested by these observations.

Immunohistochemical localization of parathyroid hormone-related protein in the lesions of breast disease

Parathyroid hormone-related protein (PTHrP) is a major contributing factor in the aetiology of humoral hypercalcaemia of malignancy (HHM). HHM is often a complication of squamous cell carcinoma of the bronchus but may occur with tumours of other epithelial surfaces. Hypercalcaemia occurs in 10% of patients with advanced breast cancer and a breast rumour cell line has been a source of PTHrP (Stewart el al., 1987, BBRC 146:672-8). Polyclonal antibodies have been raised in rabbits against synthetic (1-34) peptides. This antiserum is highly specific and does not cross-react with PTH on Western blot, in radioimmunoassay or at high concentrations to block adenylate cyclase in PTH responsive cells. Using this antiserum and peroxidase antiperoxidase procedures PTHrP has been identified in breast lesions. A range of normal and lactating breast tissues and pathological lesions of the breast have been examined. PTHrP staining is absent from normal resting and lactating breast tissue, from the lesions of fibrocystic disease, absent in gynaecomastia and in most fibroadenomas. It has been shown to be present in one fibroadenoma with evidence of secretory activity, where the protein appeared to be associated with secretory vacuoles. In a patient with hypercalcaemia occurring with giant hypertrophy of both breasts the protein was present in myoepithelial cells and so called “clear” or stem cells of the ducts. In duct carcinoma the protein has been shown to be present within clumps or cords of tumour cells, particularly in those areas which have foci of microcalcification. In medullary carcinoma PTHrP staining occurs within the “crushed” cells, described by Azzopardi, occurring around the margin of tumour cords. Demonstration of the PTHrP antigen in malignant breast tumour tissue provides an explanation for the association of HHM with these tumours. It is possible that the hormone may also be at least in part responsible for the ability of these tumours to resorb and to metastasise to bone Parathyroid hormone-related protein (PTHrP) is a major contributing factor in the aetiology of humoral hypercalcaemia of malignancy (HHM). HHM is often a complication of squamous cell carcinoma of the bronchus but may occur with tumours of other epithelial surfaces. Hypercalcaemia occurs in 10% of patients with advanced breast cancer and a breast rumour cell line has been a source of PTHrP (Stewart el al., 1987, BBRC 146:672-8). Polyclonal antibodies have been raised in rabbits against synthetic (1-34) peptides. This antiserum is highly specific and does not cross-react with PTH on Western blot, in radioimmunoassay or at high concentrations to block adenylate cyclase in PTH responsive cells. Using this antiserum and peroxidase antiperoxidase procedures PTHrP has been identified in breast lesions. A range of normal and lactating breast tissues and pathological lesions of the breast have been examined. PTHrP staining is absent from normal resting and lactating breast tissue, from the lesions of fibrocystic disease, absent in gynaecomastia and in most fibroadenomas. It has been shown to be present in one fibroadenoma with evidence of secretory activity, where the protein appeared to be associated with secretory vacuoles. In a patient with hypercalcaemia occurring with giant hypertrophy of both breasts the protein was present in myoepithelial cells and so called “clear” or stem cells of the ducts. In duct carcinoma the protein has been shown to be present within clumps or cords of tumour cells, particularly in those areas which have foci of microcalcification. In medullary carcinoma PTHrP staining occurs within the “crushed” cells, described by Azzopardi, occurring around the margin of tumour cords. Demonstration of the PTHrP antigen in malignant breast tumour tissue provides an explanation for the association of HHM with these tumours. It is possible that the hormone may also be at least in part responsible for the ability of these tumours to resorb and to metastasise to bone

Caerulein-induced acute pancreatitis in rats: changes in glycoprotein-composition of subcellular membrane systems in acinar cells

Caerulein-induced acute pancreatitis is characterized by the occurrence of two membrane-bound vacuolar systems in acinar cells. Beside digestive enzymes containing secretory vacuoles, lysosomal autophagic structures can be identified at the ultrastructural level. In the present study glycoconjugate patterns of the surrounding membranes were characterized by ultrastructural lectin-binding experiments using five colloidal-gold labeled lectins with distinct sugar specificities. Furthermore, the profile of membrane glycoproteins of isolated vacuolar fractions was studied by SDS-PAGE and lectin-blotting. In pancreatitis, membranes of secretory vacuoles showed a significant lower degree of lectin-binding compared to normal zymogen granules. In contrast, newly appearing autophagic vacuoles in pancreatitis revealed a strong membrane labelling for most lectins used. The pattern of membrane glycoproteins of secretory and autophagic vacuoles as determined by SDS-PAGE and lectin-blotting differed from those of normal zymogen granules resembling the protein profile of smooth microsomes. Since this pattern requires a previous passage through Golgi stacks, it is assumed that the two types of vacuoles derive from Golgi elements. For the pathogenesis of caerulein pancreatitis these vacuolar post-Golgi structures seem to play an important role.

Histological and clinical features of menstruation induced by the antiprogestin mifepristone (RU486) compared to menstruation occurring spontaneously.

The clinical and histological features of menstruation induced by a single oral dose of mifepristone were compared to those in normal spontaneous menstruation to aid understanding of the mechanism of endometrial shedding. 30 healthy volunteers, sterilized or seeking sterilization, were given a single oral dose, ranging from 5-200 mg mifepristone (RU-486) in the 1st half of the luteal phase, timed by the LH surge. Endometrial biopsies were taken on that day or the day after the 1st episode of bleeding for histological examination. Quantitative histological features on a 15 item scale were compared to those seen in women having spontaneous menses. 7 of 15 features differed between the 2 groups. Bleeding induced by mifepristone was associated with the following endometrial characteristics: increased gland cell height, reduced secretion in gland lumen, increased volume fraction of gland occupied by cells and nuclei, increased pseudostratification of gland cells, reduced stromal predecidual reaction, as judged by glycogen and fat content, and reduced leukocyte infiltration in the stroma. Thus there was less gland activity and an appearance of more cell packing, taller and more pseudostratified cells. The features in common with normal menses were mitotic activity in both glands and stroma, secretory vacuoles, edema and extravasation. Clinically the amount and duration of menstrual flow induced by mifepristone was similar to normal menses, suggestive of a similar hemostatic process.

Histologic Effects of Oral Contraceptives on the Uterine Corpus and Cervix

The progestogenic component of combination oral contraceptives (OCs) intervenes in the negative feedback on pituitary luteinizing hormone secretion thereby inhibiting ovulation. Further combined OCs inhibit early growth and differentiation of glandular epithelium of the endometrium. During the 1st several cycles of the beginning of combined OC therapy secretory vacuoles appear in endometrial glands earlier than they do in untreated women. Histologists observe pronounced shedding of the endometrium more often in OCs of >5mg of progestogen with 10- nortestosterone derivatives than the low dose OCs. Therefore histologic characteristics of the endometrial glands and stroma may be at different stages of maturity that do not coincide to the actual day of the cycle on which a biopsy is taken. Prolonged sequential OC therapies promotes irregular proliferative or deficient secretory endometrium which often induces simple hyperplasia and/or adenomatous hyperplasia. Sequential OCs were removed from the US and Canada markets due to studies associating them with adenocarcinoma of the endometrium. Continuous low dose progestogen OC therapy causes endometrial atrophy to occur earlier in women who take them tan does other combined OC therapies. This may occur because of the induced suppression of pituitary gonadotropin secretion. Combined OCs cause 2 changes in the endometrium that inhibit the implantation of the blastocyst. They include atypical proliferative changes of blood vessels and the absence of normal spiral arteriolar development. Progestational and combination OCs foster microglandular hyperplasia of the cervix but low doses of these OCs apparently do not stimulate the growth of leiomyomas.

Secretion of Lamellar Bodies in Type II Pneumocytes in Organoid Culture: Effects of Colchicine and Cytochalasin B

Lamellar bodies are the morphological correlate to the alveolar surface-active agent. Diminished synthesis of this surfactant in newborns results in the respiratory distress syndrome. Secretion of lamellar bodies and its dependence on the cytoskeleton are not yet well understood and are still controversially discussed in the literature. We therefore used an organoid culture system of fetal mouse lung cells to investigate electron microscopically secretion of lamellar bodies and influence of both colchicine and cytochalasin B on the secretion process. Secretion of lamellar bodies is to be considered as an eccrine secretion, because no other cytoplasmic components were extruded. It includes a very fast component in opening of the secretory vacuole. Synthesis, but not secretion, was inhibited by colchicine; secretion, but not synthesis, was inhibited by cytochalasin B. Furthermore, formation of the histotypic structures in vitro and deposition of the basal lamina were disturbed by cytochalasin B, but not altered by colchicine. After short-term treatment, these effects turned out to be reversible. The results indicate that synthesis of lamellar bodies depends on an intact microtubular system, whereas secretion requires actin filaments in a functional state.

Electron microscopic results on the ventral prostate of the rat after CdCl2 administration. A contribution towards etiology of the cancer of the prostate

The prostate epithelium of rats which received repeated cadmium chloride (CdCl2) injections showed a gradual disruption of structural differentiation. Electron microscopy studies revealed severe changes in the ultrastructure affecting all epithelial cell organelles, particularly the nuclei, rough endoplasmatic reticulum, the golgi apparatus, and mitochondria. The cells infiltrating the stroma contained secretory vacuoles and their nuclear evaginations on the invasion front showed similarities to ultrastructural pathological changes in man. Examinations of the ventral prostate following oral CdCl2 administration revealed changes ranging in severity up to dysplasia, but there was no evidence of carcinoma.

Collagen fibril and matrix assembly during morphogenesis

The morphogenesis of the extracellular matrix requires the synthesis, assembly and deposition of collagen in a tissue specific manner. Collagen synthesis and molecular assembly occur within a series of well defined cytoplasmic compartments, while the assembly and deposition of collagen fibrils, fibril bundles and collagen macroaggregates occurs within a series of extracellular compartments. In the studies described here we focus our attention on the assembly of collagen molecules into fibrils, bundles and tissue specific macroaggregates.The fibroblast has a complex topography which serves to partition the extracellular space into distinct domains where the hierarchical stages in matrix assembly occur. The first recognizable extracytoplasmic domain is a narrow channel which originates deep within the cytoplasm and is open to the extracellular space. These narrow spaces contain single or sometimes 2-3 collagen fibrils and are intimately associated with secretory vacuoles. These channels fuse with each other and with the cell surface giving rise to the second level of compartmentalization and matrix hierarchy where fibrils coalesce to form bundles.

Organization of the internal membrane system in the principal cells of the mouse epididymis after osmium impregnation

The ultrastructure of the principal cells of the mouse epididymis was studied using osmium impregnation techniques which have the advantage that the endoplasmic reticulum (ER) content displays a positive reactivity after glutaraldehyde fixation whereas the Golgi condensing vacuoles are negative. In the proximal part (caput) of the epididymis, the Golgi apparatus formed a large supranuclear area filled with electronluscent secretory vacuoles while, in the medial (corpus) and distal (cauda) parts, dictyosomes were small and sparse with few secretory vacuoles. In all the principal cells of the caput, the supranuclear ER cisternae were heterogeneously impregnated. In the corpus and cauda, the ER appeared as an extensive continuous network of canaliculi and saccules which were fenestrated when surrounding mitochondria. The ER content was homogeneously stained but impregnation intensity varied from cell to cell. In the apex of the caput cells, numerous impregnated or electronluscent vesicles were seen in close apposition to the plasma membrane, while in the corpus and cauda some Golgi vacuoles and extensions of ER canaliculi were observed in the terminal webb region. Thus, in the epididymal caput, osmium impregnation suggested that two distinct secretory pathways were functioning continuously. The first corresponded to the transport of proteins to the cell membrane by the Golgi condensing vacuoles. The second might only affect the small impregnated vesicles of the ER, through which proteins bypassed the Golgi apparatus and were exported towards the lumen. In the corpus and cauda, the network organization of the ER and the association of fenestrated cisternae with mitochondria (also found in absorptive epithelial cells) supported the view of a predominant absorptive function in these epididymal parts.

Primary culture of epithelial cells derived from the rat ventral prostate: formation of three-dimensional acinus-like structure in collagen gel.

Rat ventral prostate epithelial cells were cultured in collagen gel after collagenase digestion. The primary cultures were mainly composed of single and spherical cells. After 10 days incubation in growth medium containing insulin, transferrin, and cholera toxin, there was a 3.8-fold increase in cell numbers, aggregates of which formed three-dimensional acinus-like structures. These structures consisted of one layer of cells surrounding the lumen. The cells were joined together with a junctional complex and had microvilli on the luminal surface and secretory vacuoles in the cytoplasm facing the lumen. The ultrastructural features of the cells were not altered by growth medium containing steroids. This culture system may prove to be very useful in elucidating proliferation, organization, and differentiation of prostatic epithelial cells in relation to the extracellular matrix and stromal cells.