Apical cytoplasm

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

Ultrastructural distribution of Class II MHC molecules in mucosal antigen presenting cells and their relationship to antigen uptake and processing

Abstract: Expression of Class II MHC molecules by potential antigen presenting cells in the gut mucosa and afferent lymph has been examined at light microscope and ultrastructural levels by an indirect immunoperoxidase technique. Mature enterocytes in rat and human small intestine express cytoplasmic as well as cell surface Class II molecules. In rats, surface Class II molecules are restricted to the basolateral cell membranes of enterocytes in the midvillus region. Cytoplasmic Class II molecules are associated with multivesicular bodies and lysosomes in the apical cytoplasm. The pattern is essentially similar in human jejunal enterocytes, with the important exception that the brush borders also express Class II molecules. Large mononuclear cells in the lamina propria also contain Class II molecules in association with lysosomal bodies, but intracellular Class II molecules have not been detected in veiled cells in intestinal afferent lymph. We have failed to show uptake of horseradish peroxidase (HRP) from the lumen by enterocytes in normal gut but immature enterocytes absorb the marker from the extracellular fluid. The results are discussed in relation to antigen transport and presentation in the gut.

Carbohydrate cytochemistry of the endothelium lining the splenic blood vessels in the rat

Abstract: In the endothelial cells lining the rat splenic blood vessels, neutral carbohydrates were studied by means of combined periodic acid-thiocarbohydrazide-silver protein (PA-TCH-SP) and alpha-amylase digestion methods. In the endothelial cells lining the central and follicular arteries of the spleen, the neutral glycoconjugate-containing surface coat of the luminal plasma membrane and related pinocytotic invaginations and vesicles in the apical cytoplasm were strikingly distinguished, as compared with those in the cells lining the splenic sinuses. In contrast, cytoplasmic glycogen particles in the sinus endothelial cells were apparently larger in amount than those in the arteriolar endothelial cells. Such cytochemical variations of neutral carbohydrates with the arteriolar and venous vessels of the rat spleen were discussed with special reference to varying cytophysiological functions of the endothelial cells with the different segments of the splenic blood vessels.

A minimal WLE2 element is not sufficient to direct apical localization in the absence of RNAs containing the full length wingless 3'UTR.

Abstract: The mRNAs encoded by the Drosophila Wnt-1 homologue, wingless, are localized to a small region of the apical cytoplasm in early embryonic epithelial cells. This requires the activity of cis-acting sequences within the 3’ untranslated region called wingless localization elements (WLEs). One of these, WLE2, was identified initially as a cis-acting sequence that directed apical localization of in vivo expressed mRNAs in 4-5 hr Drosophila embryos. To determine the precise activity of WLE2 during wingless apical localization, we performed an in-depth mutagenesis of this sequence. Using both direct-injection and in vivo transgenic assays we determined that WLE2, by itself, is not sufficient to direct binding of trans-acting factors that mediate apical RNA transport in embryonic cells. Rather, RNAs containing only WLE2 are transported apically only in the presence of a second RNA containing other cis-acting localization sequences of the wingless 3’ untranslated region. This co-requirement for WLE2 and additional...

Ultrastructural and cytochemical characterization of cultured dogfish shark rectal gland cells.

Abstract: The dogfish shark rectal gland (SRG) is histologically complex, containing connective, nerve, and smooth muscle tissue and at least three types of epithelial cells: secretory tubule, central duct, and endothelial. This cellular heterogeneity precludes studies of the intact SRG from distinguishing direct tubular effects of mediators that modulate chloride secretion from their indirect effects on nonepithelial cells such as neurons. Primary SRG cultures express high levels of secretagogue-stimulated chloride secretion, suggesting that SRG cells retain a significant level of cytodifferentiation in vitro. However, because nontubular cells could contaminate these cultures, the question of whether secretagogues activate chloride secretion through direct or indirect effects on tubular epithelial cells remains unresolved. To address this issue, detailed ultrastructural and cytochemical analyses of SRG cultures were carried out to assess the level of cellular heterogeneity and the degree of cytodifferentiation expressed by SRG cells in vitro. The results demonstrate that, after 15 days, primary SRG monolayer cultures are composed exclusively of tubular epithelial cells with no detectable contamination by central duct cells, fibroblasts, smooth muscle cells, endothelial cells, or neurons. Tubular epithelial cells express most of the structural features of native SRG cells, including numerous mitochondria, massive basolateral surface amplification, complex tight junctions, and an extensive tubulovesicular system in the apical cytoplasm. Cultured SRG cells also display a striking level of polarization of cytoplasmic organelles and plasma membrane secretagogue receptors. These results account for the exceptionally high rates of electrogenic chloride secretion by SRG tubular epithelial cells in vitro and confirm that the effects of secretagogues on transport activity reflect their direct interaction with tubular epithelial cells.