Apical cytoplasm

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

Histochemistry of human urethral glands.

Abstract: Human urethral glands were reacted histochemically and immunohistochemically to identify glycopro-teins, some androgen metabolic enzymes, and VIP-like immunoreactivity. Neutral/acid mucosubstances were detected mainly in the apical cytoplasm of the principal cells. 3β-, 17β-, and 3α-hydroxysteroid dehydrogenase, G6PD, and 6PGD reactivity were intense in all the glandular epithelium. Small amounts of VIP-positive fibers were noted around the secretory elements.

Development of the hamster submandibular gland. II. The ductal system.

Abstract: The major secretory duct is differentiated from the SMG anlage in early embryogenesis and undergoes minor morphologic changes from its inception until full maturation. Structurally, the ducts appear to be suited for a conduit function. At birth, the extralobular and intralobular ducts arise directly from the major duct or indirectly from the primary and secondary branches, respectively. They are distinguishable from each other by their topography only. However, developmentally, intralobular ducts give rise to 'terminal tubule' complexes but no such function is performed by the extralobular ducts. Both duct types first show distinct evidence of striation of their cells at one week after birth. Their lateral and basal infoldings, interdigitations and close association with mitochondria provide them with increased surface area and a source of energy for exchange of ions and fluids. The differentiation of convoluted granular ducts begins at 2 weeks of age with the appearance of membrane-bound and dense secretory granules in the apical cytoplasm of the luminal cells. The changes start in the proximal segment of the intralobular striated duct, and extend to occupy a large part of it in a mature 6-week old animal. These ducts comprise the bulk of the ductal system. The distribution of the granules is size-gradient dependent, the small granules being near the lumen and the large ones being close to the nucleus. The morphologic features of CGD are in keeping with absorptive and secretory functions.

The ommatidia of Arca noae: a three-tier structure with a central light-guiding element for the receptor cell.

Abstract: The compound eyes of ark clams appear to function as an optical system to trigger shell closure against predators. We have analyzed the structure of the ommatidia of Arca noae by thin section electron microscopy and serial sectioning, Concanavalin A–gold labeling and acid phosphatase cytochemistry. Our results demonstrate that the ommatidia are a three-tier structure composed of a central single receptor cell, surrounded and covered by proximal pigment cells followed by rows of distal pigment cells. The receptor cells of Arca noae have no lens and the disks of their receptive segment are derived from sensory cilia. The distal mitochondrial segment in the cytoplasm between the nucleus and the receptive segment is surrounded by a mass of Concanavalin A-reactive glycogen particles. Although both, proximal and distal pigment cells have numerous microvilli, only those of the proximal pigment cells form a well-aligned brush border. The microvilli of the latter are ≈9–11 μm long and have a diameter of ≈70–80 nm. Numerous microlamellar bodies cover them. The microlamellar bodies are stored in acid phosphatase-negative secretory granules of the pigment granule-free apical cytoplasm of proximal pigment cells before their secretion. Observation of living compound eyes indicated that the apex of proximal pigment cells transmitted significantly more light than the surrounding distal pigment cells. Hence, the regular geometry of the brush border seems to be a light-guiding structure for receptor cells similar to an optical fiber.

Sodium bicarbonate secretion indicated by ultrastructural cytochemical localization of HCO3−, Cl−, and Na+ ions on rat bile duct brush cells

Abstract: Brush cells are widely distributed in the digestive and respiratory apparatus, but their function is still unknown. Because brush cells (BC) are found in organs secreting NaHCO3, it was hypothesized that these cells may secrete NaHCO3. To test this possibility, rat common bile duct epithelia were examined by ultrastructural cytochemical methods for localizing HCO3(-), Cl-, and Na+ ions. All three ion precipitates were few in or on BCs of rats without stimulation. Lead carbonate precipitates, which localized HCO3(-) ions by the lead nitrate-osmium method, increased markedly on the surface of the microvilli (MV) of BCs after secretin or meal stimulation, but similar precipitates were few on the luminal surface of principal cells (PCs). Silver chloride precipitates, which indicate the presence of Cl- ions by the silver-osmium method, increased in the apical cytoplasm and in MV of BCs after secretin or meal stimulation, but they were few in PCs. Sodium pyroantimonate precipitates, which localize Na+ ions by the potassium pyroantimonate-osmium method, increased on the surface of the MV, along the basolateral membrane, and in the apical cytoplasm of BCs after secretin or meal stimulation, but they were few in PCs. These results strongly suggest that BCs may be a significant source of NaHCO3 secretion.