Showing papers on "Apical cytoplasm published in 1974"

Habitat, succession, attachment, and morphology of segmented, filamentous microbes indigenous to the murine gastrointestinal tract.

Abstract: Some indigenous microorganisms localize on epithelial surfaces in various areas of the digestive tracts of animals. One of these, a segmented, filamentous microbe, localizes on the epithelium in the small bowels of mice and rats. These filamentous microbes colonize mice at weaning time and persist in adult animals for at least 2 months. Results of the study of light and electron micrographs suggest that the microorganisms are procaryotic, and that they interact with small bowel epithelial cells to form an attachment site. This site consists of modified epithelial cell membrane and apical cytoplasm adjacent to the attached bacterium. The microbe fills the site with part of its first segment. This segment has a nipple-like appendage on the end inserted into the epithelial cell. The other segments, which compose the rest of the filament, are usually separated by septa. Many of the individual segments contain intrasegmental bodies that appear to be procaryotic cells. Some of these intrasegmental bodies are similar in morphology to the first segment of each filament inserted into an epithelial cell. These intracellular bodies may be components in the life cycle of the microorganism. The organism has not yet been cultured in recognizable form. Therefore, such a hypothesis cannot be proved as yet, nor can the microbe be classified with certainty. Because it localizes in an epithelial habitat in the small bowel, however, it may be a particularly important microbial type in the gastrointestinal ecosystem of laboratory rodents.

LOCALIZATION OF FREE AND BOUND SECRETORY COMPONENT IN HUMAN INTESTINAL EPITHELIAL CELLS A MODEL FOR THE ASSEMBLY OF SECRETORY IgA

Abstract: Antibody reagents were made specific for each of the two forms of human SC, FSC and BSC, which is an integral part of the sIgA molecule. With the fluorescent antibody method the cytological and histological localization of FSC, BSC, and α-chains has been studied in various human mucous membranes. SC was present in columnar epithelial cells of the intestines and in the cells of serous acini of bronchial and salivary glands. In contrast, SC was not found in intestinal goblet cells or cells of mucous acini of bronchial and salivary glands. In the columnar epithelial cells of the small and large bowel, FSC was present most prominently in the Golgi zone, and much less prominently in the apical cytoplasm. On the other hand, BSC and α-chains were located only in the apical cytoplasm in an overlapping manner. The results favor a model in which sIgA is assembled inside epithelial cells from SC, which was synthesized in the same cell, and IgA, which entered the epithelial cell after synthesis in and secretion by a plasma cell.

The nature of D-serine--induced nephrotoxicity.

Abstract: Renal structural changes were studied sequentially between 1 hour and 6 days in rats treated with D-serine. Extensive necrosis of proximal straight tubules was rapid in onset and was followed by complete tubular regeneration 6 days post-treatment. The apparent progression of cellular changes was initial shrinkage, followed either by swelling and loss of apical cytoplasm or immediate lysis of cytoplasmic and nuclear contents. Tubular damage left only the basement membrane as a barrier between interstitial and luminal fluids. In similarly treated rats, proteinuria and glucosuria developed at the onset of tubular necrosis and disappeared when the tubules were completely relined by epithelium suggesting that they are due to diffusion of protein and glucose from interstitium into tubular fluid across the denuded basement membranes and that epithelial cells, under normal conditions, act as a barrier to diffusion of certain substances between the interstitium and tubular fluid.

On the morphology of the human Sertoli cell.

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

Function of coated membranes and multivesicular bodies during membrane regulation in stimulated exocrine pancreas cells.

Abstract: Stimulation of secretion by pilocarpine results in a 70% loss of zymogen granules from pancreatic acinar cell during the first hr after injection of the drug. In previous work (Geuze and Poort, 1973), we found that the amount of membrane stored in the surface of the microvilli and of the numerous infoldings present in highly stimulated cells, increases during the first 2 hr and then decreases again during the 3rd hr after stimulation, concurrently with maximal endocytosis of sorbitol-[su14C]. Further observations on the fine structure of stimulated cells at various time intervals after injection of pilocarpine showed that during the first hr numerous smooth vesicles and multivesicular bodies (mvb's) appear in the apical cytoplasm, while the number of coated vesicles and their relative total volume increase significantly 3 hr after stimulation. By infusion of ferritin in the pancreatic duct system in vivo and application of cytochemical techniques (osmium impregnation, electron microscope autoradiography and acid phosphatase cytochemistry) it could be established that after stimulated exocytotic secretion, redundant apical cell membrane is withdrawn by at least two routes: 1) During the initial rapid increase of the amount of apical cell membrane, withdrawal is accomplished by interiorization of luminal invaginations into smooth endocytotic vesicles, which in turn give rise to mvb's by infolding and subsequent fission of their limiting membrane. 2) Once the bulk of stored secretion granules has been discharged, endocytotic coated vesicles become gradually more prominent as carriers for redundant cell membrane. The contents of endocytotic structures ultimately become incorporated in residual bodies, suggesting lysosomal degradation of cell membrane prior to eventual reutilization. Coated vesicles also originate by pinching off from mature Golgi cisternae and condensing vacuoles. A possible function of the coated membranes in the concentration of exportable protein within forming secretory granules is discussed.

The vas deferens of the spider crab, Libinia emarginata.

Abstract: Sperm enter the anterior vas deferens individually in the spider crab male. There they become surrounded by secretion products from the cells of the vas deferens, and are compartmentalized into spermatophores of varying size. The anterior vas deferens can be divided into three regions. The epithelium of the anterior vas deferens varies regionally from low to high columnar. The cytoplasm contains vast arrays of rough endoplasmic reticulum and Golgi complexes but few mitochondria. Intercellular spaces contain septate junctions, gap junctions and vesicles. Once the spermatophores have been formed in the anterior vas deferens, they are moved posteriorly to the middle vas deferens where they are stored and surrounded by seminal fluids. The epithelial cells of the middle vas deferens contain large amounts of rough endoplasmic reticulum and Golgi complexes. Numerous micropinocytotic vesicles appear, forming at the cell surface and within the apical cytoplasm. Their suggested function is the resorption of secretion products of the anterior vas deferens which initiated compartmentalization of the spermatozoa into spermatophores. The posterior vas deferens functions primarily as a storage center for spermatophores until they are released at the time of copulation. Seminal fluid surrounding the spermatophores is produced in this region as well as in the middle vas deferens. The cells of this region contain vast arrays of vesicular rough endoplasmic reticulum and Golgi complexes. The cells are multinucleate. Microtubules are numerous throughout the length of the cells and appear to insert on the plasma membrane.

The morphology of the kidney of the atlantic hagfish, Myxine glutinosa (L.)

Abstract: The kidney of the Atlantic hagfish, Myxine glutinosa, consists of large, paired, segmentally arranged renal corpuscles connected to the archinephric ducts by short tubules The blood supply to the kidneys is arterial in origin; there is no renal portal system Each renal corpuscle is supplied by one afferent arteriole and drained by several efferent vessels which in turn supply the tubules and archinephric ducts Irregularly spaced renal veins drain blood from the ducts into the posterior cardinal veins The capillaries of the multilobed glomeruli are lined by thick endothelial cells which are rarely fenestrated These are coated by the short pedicels of the podocytes of the visceral layer of Bowman's capsule The mesangium is well developed between the endothelium and the glomerular basal lamina The epithelial cells of all regions of the tubules and archinephric ducts are characterized by a brush border, a complex system of lateral interdigitations, and a paucity of basal infoldings Pits, vesicles, large vacuoles, and single membrane-limited inclusion bodies (lysosomes?) are abundant in the apical cytoplasm It is suggested that these cells are specialized for the reabsorption of materials

Possible Precursors of Aminopeptidase and Alkaline Phosphatase in the Proximal Tubules of Kidney and the Crypts of Small Intestine of Mice

Abstract: Two hydrolytically inactive proteins, one having common antigenic determinants with aminopeptidase and the other with alkaline phosphatase, have been localised in the apical cytoplasm of crypt cells of small intestine and in the cytoplasm of proximal convoluted tubules. In addition, the two proteins are also differently heat labil. Although they could not be detected with mere histochemical stain methods, they were detected by the immunofluorescence sandwich technique using specific antibody directed against either of the solubilised enzymes. The findings were confirmed using the previously described immunohistochemical method (Wachsmuth, 1973). The cellular and subcellular localisation implies that these two proteins are precursors of the hydrolytically active brush border membrane enzymes.

Specialized cilia of the byssus attachment plaque forming region in Mytilus californianus

Abstract: The distal depression of the ventral pedal groove of Mytilus californianus was investigated by scanning and transmission electron microscopy. This part of the byssus forming system is responsible for the formation of the attachment plaque of the byssus thread. The longitudinal pedal ducts open into this area and the floor of the distal depression is covered by specialized cilia which terminate as biconcave flattened discs or “paddles.” The disc is formed by a 360° curvature of the axoneme tip within the ciliary membrane. The diameter of the disc is about 1.33 μ while that of the shaft portion is 0.24 μ. There are about 11 cilia per square micron of surface area and the necks of the cilia are separated from each other by a web-like extension of apical cytoplasm extending from the epithelial cells. It is proposed that these specialized cilia function as microscopic spatulas for the application of the adhesive plaque material to substrate surfaces. The pattern of surface convection currents seen in vivo tends to support this hypothesis.

Degeneration of mouse pancreatic acinar cells during fasting

Abstract: Ultrastructural changes in mouse pancreas were studied after 1, 2, and 3 days of fasting. The number of zymogen granules markedly decreased after 1 day of fasting. Numerous small secretory granules, approximately 0.2–0.3 μ in diameter, appeared in the apical cytoplasm. There was increased autophagic activity but signs of intracellular degradation of zymogen granules were not found. After a 3 day fast, focal cytoplasmic degeneration was marked and many acinar cells were necrotic. Pancreatic amylase levels were also significantly reduced by this time. These extensive degenerative changes occurring after modest periods of fasting, emphasize the need for careful interpretation of results of experimental studies where fasting is used to establish a baseline for studies on the exocrine pancreas.

Secretory processes in follicular cells of the bat thyroid. III. The occurrence of extracellular vesicles and colloid droplets during arousal from hibernation

Abstract: Ultrastructural changes that occur in follicular cells of the bat thyroid gland just prior to, and immediately after arousal from hibernation are discussed in relation to the known changes which occur in thyroid function during arousal from hibernation. The most distinctive ultrastructural change that takes place just before emergence from hibernation is the occurrence, extracellularly, of concentrations of small vesicles lying in the colloid near the cell's apical plasma membrane. Similar accumulations of vesicles are absent in the apical cytoplasm of the follicular cell. Other principal changes from the early hibernating state found at this time are an increase in the number of apical vacuoles, dense granules and multivesicular bodies. These changes are followed at arousal itself by the appearance of large numbers of intracytoplasmic colloid droplets, often intimately associated with dense granules. An unusual feature of these follicular cells is that although they are rich in colloid droplets, apical pseudopods cannot be found.

Lysozyme in the paneth cells of man

Abstract: Human lysozyme was localized immunocytochemically at the uitrastructural level within Paneth cells of man by use of the unlabeled antibody enzyme method. Specific staining for lysozyme was observed over secretion granules in the apical cytoplasm, within the region of the Golgi apparatus and within some, but not all, lysosomes. No staining was observed within the cisternae of the rough endoplasmic reticulum or other cellular organelles. In control experiments comparing semiadjacent sections of the same Paneth cell, substitution of either normal rabbit serum for rabbit antihuman lysozyme antiserum (specificity control) or normal sheep serum for sheep antirabbit immunoglobulinG antiserum (method control) completely eliminated specific staining for lysozyme. The intensity of staining for lysozyme was related to both the titer and length of exposure to antilysozyme antiserum. Specific staining was obtained in tissue embedded in Araldite or Epon and was facilitated by etching with hydrogen peroxide. No staining was observed after prolonged fixation in giutaraldehyde or treatment with uranyi acetate in block. Paneth cells are serozymogenic cells located in the base of the intestinal crypts of LieberkUhn in a number of animal species including man. Although initially described by Schwalbe (52) over a century ago, the physiologic significance of Paneth cells, which number almost 200 million in man (10), and their contribution to intestinal function have not yet been determined. A number of functions have been attributed to the secretory product of the Paneth cell (see reviews by Merzel (32), Moe (34), and Trier (67)). such as the production of trophic factors related to crypt cell turnover (10), the secretion of free amino acids (19) and the secretion of dipeptidases for the digestion of food protein (70); however, convincing experimental evidence necessary to support these hypotheses is lacking. Recent investigations in rodents suggest that Paneth cells may contribute to the regulation of the intestinal flora by several mechanisms. Cell fractionation (11) and substrate film studies (20, 21, 55) suggest that lysozyme, a bacteriolytic enzyme capable of degrading a glycopeptide layer in most bacteria (8), may be the secretory product of Paneth cells. In addition, ultrastructural studies by

An electron microscopic investigation of the surface coat of visceral yolk sac endoderm cells in the guinea pig

Abstract: Guinea pig visceral yolk sac endoderm cells are known to absorb proteins from the uterine lumen by the process of pinocytosis. Since previous studies have shown that the first step in protein absorption is the binding of the protein to an extracellular material on the surface of pinocytotic invaginations, it was thought that the surface coat might possess receptor sites for molecules which are subsequently absorbed. This study investigates the nature of the surface coat of the endoderm cells using ruthenium red, alcian blue/cetylpyridynium chloride-lanthanum and concanavalin A-peroxidase procedures. Results using these methods showed the presence of a surface coat on both the microvilli and pinocytotic invaginations. The coat on the pinocytotic invaginations was thicker than that on the microvilli. Concanavalin A receptor sites were separated from one another on the cell surface. Since only those pinocytotic invaginations which were open to the surface at the time of fixation would be “stained” by these methods, the procedures also show that the numerous tubules and vesicles in the apical cytoplasm do not all form an intercommunicating labyrinth open to the surface, even though most of them are part of a related functional system. The results indicate that the surface coat contains mucopolysaccharide components. In addition, concanavalin A receptor sites are present which are probably oligosaccharides associated with a glycoprotein component of the apical cell membrane.

Localized Organic Binding of Radioiodine in Hydra

Abstract: Radioiodine, given as the iodide, localized in protein-bound form in the ectoderm of Hydra fusca and H. littoralis. The radioiodine was shown by autoradiography to be: (1) diffusely distributed in the ectoderm over the gonads and (2) precisely localized in the apical cytoplasm of cnidoblasts that carry stenotele nematocysts. The meaning of such precise cellular localization of iodoprotein in Hydra remains to be determined.

Electron microscopic demonstration of nonspecific esterases in the small intestine of the rat

Abstract: The nonspecific esterase activity was investigated at the electron microscopic level, by means of azo dye technique applied to the duodenal, jejunal and ileal mucosae of living rats. After perfusion of a medium containing 1-naphthyl acetate and hexazonium pararosaniline into the lumen of the small intestine, the enzyme reaction product of electron opaque grains (50-100nm in diameter) was localized on the limiting membrane of microvilli of epithelial cells, and on the vesicles and the granular endoplasmic reticulum in the apical cytoplasm of epithelial cells. When the medium was perfused intravascularly, electron opaque grains were localized on the basal cell membrane and the basal lamina of epithelial cells as well as on the vesicles present in the basal cytoplasm of epithelial cells. Localizations of the esterase activity were essentially alike whether naphthyl propionate or butyrate was used as a substrate. The esterase activity in the duodenal and jejunal mucosae was higher than that in the ileal mucosa, judging from the results of inhibition test and reactivation test.