Apical cytoplasm

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

Cytodifferentiation of the rat Paneth cell: an immunocytochemical investigation in suckling and weanling animals.

Abstract: The cytodifferentiation of the intestinal Paneth cell was investigated in 2- to 50-day-old rats by evaluating the phenotypic expression of bacteriolytic lysozyme. Samples of duodenum, jejunum, and ileum were exposed to anti-lysozyme antiserum and treated by the periodic-acid Schiff (PAS) technique for the demonstration of carbohydrate moieties. The distribution of the Paneth cell population was then assessed. At days 3-6, Paneth cells were present in ≤ 1% of intestinal crypts and exhibited (a) location in the bases of crypts, (b) apical granules positive for lysozyme, and (c) a slender truncated shape extending to the crypt lumen. By days 6-8, Paneth cells had acquired their typical broad, truncated shape and prominent secretory apparatus. Between 1 and 7 weeks postpartum, the frequency of Paneth cellcontaining crypts in duodenum rose from 9% to 79%; in jejunum and ileum the frequency increased through the third week of life and stabilized at 77%–93% thereafter. At all ages, a rostro-caudal gradient of crypts containing Paneth cells was observed, and greater numbers of paneth cells per crypt were seen caudally. In both suckling and weanling animals, two intermediate cell types were encountered. The first predominated at crypt bases through the fourth week of life and contained lysozyme-positive supranuclear granules, concomitant with an apical aggregation of PAS-positive material. The second type, identical to goblet cells in size and shape, predominated along the walls of intestinal crypts and at the bases of villi, and manifested both lysozyme-positive granules and PAS-positive mucigen droplets in the apical cytoplasm. This cell type appeared by day 12 and persisted through day 50. The results of this study provide further evidence that Paneth cells differentiate from a subpopulation of multipotent stem cells residing at crypt bases. The observation of Paneth cell-goblet cell transitional forms supports the view that these two cell types share a common lineage.

Protein transport in mouse kidney utilizing tyrosinase as an ultrastructural tracer.

Abstract: The morphological basis of glomerular filtration and protein reabsorption in mouse kidney was examined by using mushroom tyrosinase subunits (mol wt 34,500), as an ultrastructural tracer. Almost immediately after injection tyrosinase reaction product was visualized in the glomerulus, and within the capillary lumen extending into the endothelial fenestrae. The entire basement membrane showed accumulations of tyrosinase in the subendothelial and subepithelial layers. The urinary space contained considerable amounts of reaction product, some of which was adsorbed to the cell coat of the podocytes. Reaction product could also be seen in the brush border region of the proximal tubule cells. By 30 min after injection, no tyrosinase reaction product was demonstrable in the glomerulus except for dense vesicles in mesangial cells. Most of the reaction product was localized in absorption droplets in the apical cytoplasm of proximal tubule cells. Occasionally, some tyrosinase reaction product was present within the basal infoldings of these cells. The behavior of tyrosinase in the mouse kidney is in accordance with that of other low molecular weight tracers. The pattern of localization within the basement membrane provides additional support for the presence of two filtration barriers in the glomerulus. The adherence of tyrosinase to the cell coat of the glomerular epithelial cells suggests that this may be an additional mechanism whereby protein is removed from the glomerular filtrate. Tyrosinase subunits may prove to be a useful new tracer for the study of protein transport.

Zymogen granules of the pancreas and the parotid gland and their role in cell secretion.

Abstract: Publisher Summary This chapter highlights zymogen granules (ZGs) of pancreas and the parotid gland. It describes the overall variations of the ZG compartment and the variations of the granule size under a variety of physiological conditions. The chapter also examines the origin and fate of ZGs as observed by cytochemical methods and summarizes the contribution of freeze–fracture techniques to the definition of the ZG membrane architecture. The electrophysiological properties of ZGs and the influence of the cytoskeleton on secretion are discussed. The pancreas and the parotid gland process their macromolecular products by cisternal packaging and exocytosis. The size distribution of the ZGs in the parotid gland cells shows some points of similarity with that observed in the pancreas. During exocytosis the ZG membrane fuses with the luminal plasmalemma, allowing the discharge of granule content. The cytoskeleton controls the movement of ZGs toward the cell apex. The nature of these interactions may be much more complex than a simple ZG alignment in the apical cytoplasm. The life of a ZG starts in the trans-Golgi saccule, in the form of condensing vacuole (CV). Both size and electron opacity of the forming CV are highly variable.

The fine structure of Brunner's glands in the rabbit.

Abstract: The fine structure of the duodenal glands of Brunner in the rabbit has been examined. The glands, which are concentrated within the submucosa, are composed of tubules that open into the bases of the intestinal glands. Unlike most species, in the rabbit two distinct cell types are present within the tubules. Serous cells, which occur in small groups in the blind endings to the tubules, contain a concentration of ergastoplasm in the basal cytoplasm and the apical cytoplasm is occupied principally by discrete secretory droplets. Intercellular secretory canaliculi occur between opposed serous cells and between serous and mucous cells. The latter cells possess little ergastoplasm but exhibit an extensive development of the Golgi apparatus in the supranuclear region. Secretory droplets are pale and show a tendency to fuse into complexes. No intercellular canaliculi occur between mucous cells. The cytological features are discussed in relation to previous observations on duodenal glands of other species, where only mucous cells are present. It is apparent that there are species differences with regard to mucous cells. These structural differences may reflect physiological and biochemical differences in the glands. The significance of the presence of serous cells in rabbit duodenal glands is unknown.

Ultrastructural analysis of the integument during the moult cycle in Ligia italica (Crustacea, Isopoda)

Abstract: The formation of the cuticle was investigated during moulting of the isopod crustaceanLigia italica. The intermoult cuticle is a four-layered lamellar structure composed of chitin-protein fibrils and mineralized in its upper half. The distribution of calcium carbonate in cuticle during moult cycle was determined by cytochemical methods and X-ray microanalysis. Epi-and exocuticle are secreted during premoult. Calcium is resorbed from the old cuticle and accumulates in the ecdysal gap as calcium granules. Endocuticle is secreted after moult when the mineralization of exocuticle starts. The shape and ultrastructure of epithelial cells change during cuticle secretion and mineralization. Mitochondria, bundles of filaments, calcium granules and large amounts of glycogen accumulate in the apical cytoplasm of cells in premoult animals.