Apical cytoplasm

About: Apical cytoplasm is a research topic. Over the lifetime, 1080 publications have been published within this topic receiving 36131 citations.

Ultrastructural localization of carbonic anhydrase II in subpopulations of intercalated cells of the rat kidney.

Abstract: At least two configurations of intercalated cells, type A and type B, are present in the cortical collecting duct. Intercalated cells are rich in carbonic anhydrase. However, it is not known whether there are differences in the level and subcellular distribution of this enzyme between type A and type B intercalated cells. The purpose of this study was to determine the relative content and intracellular distribution of carbonic anhydrase II in the various subpopulations of intercalated cells in the rat collecting duct. A rabbit polyclonal antibody directed against mouse erythrocyte carbonic anhydrase II was employed to localize carbonic anhydrase, II by light and electron microscopy by an indirect immunoperoxidase method. A Western immunoblot analysis of homogenates of rat kidney cortex and medulla with the carbonic anhydrase II antibody revealed a single polypeptide band at 29 kDa corresponding to the molecular size of carbonic anhydrase II. By both light and electron microscopy, carbonic anhydrase II immunoreactivity was present in all intercalated cells but the intensity of staining was much greater in type A than in type B cells. In addition, immunostaining in type A cells was especially pronounced in the apical cytoplasm and apical microprojections whereas in type B cells, immunostaining was more diffuse throughout the cytoplasm. A third configuration of intercalated cell with diffuse immunostaining for carbonic anhydrase II was occasionally observed in the connecting segment. Very weak immunostaining was present in principal cells, whereas connecting tubule cells and inner medullary collecting duct cells were negative for carbonic anhydrase II.(ABSTRACT TRUNCATED AT 250 WORDS)

Fine structure of the cytoplasm in salivary glands of Simulium.

Abstract: SUMMARY The salivary glands of 3rd or 4th instar larvae of Simulium niditifrons are about 5 mm long and up to 400 fi wide. They have a capacious lumen which is normally filled with secretion. The apical (luminal) plasmalemma of the gland cells is thrown into numerous microvilli. The basal plasmalemma is usually straight but is infolded in places. The infoldings may be complex near to cell junctions. There is a thick, uniform basement membrane. Contact surfaces of adjacent cells often interdigitate. A septate junction extends inwards from the lumen for onequarter the depth of the cells. Rough endoplasmic reticulum is distributed evenly throughout the cytoplasm. Many Golgi complexes with dark membrane-bounded granules are scattered throughout the cytoplasm. Solitary granules, often more than 1 fi in diameter, lie in the apical cytoplasm, especially near the apical border of the cell. These granules resemble the larger Golgi granules and the contents of the lumen. Solitary granules consisting of 2 components have been seen in various stages of passage through the cell membrane. The 2 components are present in roughly constant proportions and can be identified in the larger Golgi granules and in the secretion in the lumen. The nucleus is spherical. The nuclear envelope is smooth in the larger cells of a gland but may be folded in the smaller cells. There are 80-100 pores//* 2 of nuclear envelope. Each pore appears to have a small granule at its centre. Microtubules, about 180 A thick, are numerous in the apical cytoplasm, particularly near the luminal border. Tubules which lie deep in the cytoplasm are flanked by a clear area 100—200 A wide. The fine structure of a salivary gland cell of Simulium appears to indicate that the major components of the salivary secretion are synthesized in association with the ribosomes on the rough endoplasmic reticulum, concentrated in the Golgi regions, formed into secretion granules, and passed out of the cell into the lumen of the gland by reverse phagocytosis.

The fine structure of the follicular cells in growing and atretic ovarian follicles of the domestic goose.

Abstract: The structure of follicular layer of growing and atretic follicles in the ovary of the domestic goose, was studied by electron microscopy In small follicles, the wall is lined with a narrow layer of tightly packed small, cuboidal cells separated from the thecal tissue by the basal lamina During growth, they transform into tall, columnar cells arranged in a single row The cells display several peculiar ultrastructural features First, annulate lamellae are commonly observed Second, cytoplasmic dense-cored granules accumulate in close association with fenestrated cisternae and networks of tubuli derived from the RER They consist of spheres and strands of amorphous substance of unknown origin Third, the cells contain many transosomes, a unique organelle of the avian follicle cell consisting of a dense plaque associated with ribosome-like particles The mature forms of transosomes are located at the tips of lateral and apical cell projections, while bodies thought to be their precursors, are found in the apical cytoplasm In follicles larger than 8 mm in diameter, most of the transosomes and their precursors have disappeared Follicular atresia occurs in all of the size-classes of follicles investigated A loss of transosomes (in follicles up to 8 mm in diameter) and an accumulation of lipid droplets are the first atretic events detectable by electron microscopy Morphologic features, including deep nuclear indentations, accumulation of lipid droplets frequently encireled by membrane whorls, dilation and disintegration of RER cisterns, swelling of mitochondria and accumulation of dense irregular masses of unknown origin in the cytoplasm, are taken as evidence for advanced degradation We conclude that necrosis is the dominant type of cell death of the follicular cells during atresia However, a small fraction of cells, characterized by dark condensed cytoplasm, seems to die by apoptosis

Immunocytological responses in porcine proliferative enteropathies.

Abstract: The ileum, colon, and mesenteric lymph nodes of pigs naturally affected by either of the two major forms of proliferative enteropathy, namely, intestinal adenomatosis or hemorrhagic enteropathy, were examined for immunocytological responses to infection by immunocytochemistry, using antibodies directed against elements of the porcine immune system. In both forms, there was mucosal proliferation of immature enterocytes which lacked substantial major histocompatibility complex class II expression and a marked accumulation of immunoglobulin A (IgA) at the apical cytoplasm of affected enterocytes in association with intracellular Campylobacter-like organisms. In intestinal adenomatosis, there was only a mild infiltration of CD8+ and CD25+ T cells in the intestinal lamina propria. In hemorrhagic enteropathy, there was a moderate infiltration of CD8+ and CD25+ T cells and IgM+ B cells in the lamina propria. In rats and humans, villous enterocytes are thought to act as antigen-presenting cells, with major histocompatibility complex class II molecules present on their surface, capable of initiating a T-cell response (particularly of CD8+ T cells) in response to bacterial antigens. Therefore, the selection of immature crypt cells by the intracellular Campylobacter-like organisms for entry and multiplication may represent a remarkable microbial adaptation associated with local immunomodulation and enhanced bacterial survival. The accumulation of IgA within affected enterocytes may represent a reduced capability of the cells to process nonspecific IgA or an accumulation of specific IgA.

Ultrastructure of Paneth cells in the intestine of various mammals.

Abstract: Paneth cells in the following species were observed under an electron microscope: human, rhesus monkey, hare, guinea pig, rat, nude rat, mouse, golden hamster, and insect feeder bat. Secretory granules containing homogeneous electron-dense materials were observed in the Paneth cells of humans, monkeys, hares, guinea pigs, and bats; mouse Paneth-cell granules were bipartite (central core and peripheral halo), and the Paneth cells in rats and golden hamsters had secretory granules showing various electron densities. In humans, monkeys, and bats, immature granules near the Golgi apparatus sometimes showed bipartite substructure. The number and size of secretory granules were also diverse among various animal species. Some lysosome-like bodies were commonly observed in peri- or supranuclear regions, though the size and shape of the bodies differed from cell to cell. In apical cytoplasm, small clear vesicles (100-200 nm diameter) were more-or-less observed in all species examined, and it was especially note that rat Paneth cells contained many clear vesicles. Small dense-cored vesicles (150-200 nm diameter) were rare. It is unlikely that the various ultrastructural features of Paneth cells correlate with the phylogenetical classification.