Apical cytoplasm

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

Electron microscopic and histochemical identification of lipofuscin in the human inner ear.

Abstract: Normal inner ears of 14 individuals ranging from 2 days to 91 years of age were studied with electron microscopic and histochemical techniques for the distribution of lipofuscin and lysosomal enzymes (acid phosphatase, beta-glucuronidase and N-acetyl-beta-glucosaminidase). The electron microscope revealed in the cochlea large membrane-limited inclusions in the apical cytoplasm of all epithelial cells lining the endolymphatic space. Similar inclusions were also seen in the vestibular apparatus; the apical zone of the sensory and supporting cells, as well as the transitional epithelium and dark cells contained numerous lipofuscin granules. In the same locations where these structures occurred, we have observed intracytoplasmic granules with the histochemical characteristics of lipofuscin, including yellow to green autofluorescence. The sites of lipofuscin accumulation also displayed strong acid phosphatase activity. Lipofuscin could not be demonstrated histochemically in the newborn and was only sparse in c...

Intracellular crystal-bearing vesicles in the epidermis of scleractinian corals, Astrangia danae (Agassiz) and Porites porites (Pallas).

Abstract: Orthorhombic aragonitic crystals, embedded with a granular lipo-protein matrix and surrounded by a trilaminar membrane, are localized in the apical cytoplasm of epidermal cells of Scleractinian corals. Adult specimens of Astrangia danae (Agassiz) and settled planulae of Porites porites (Pallas) contain crystals averaging 0.7 mu by 0.1 mu by 0.3 mu within Golgi-derived vesicles. Short-term labelling with 45Ca reveals distribution of radioactivity amont a basic tissue fraction (92%) an acid tissue fraction (5%) and a skeletal fraction (3%). Identification of the primordial crystal population within membrane-bound visicles provides overwhelming evidence for the intracellular mode of calcification in Scleractinia. Moreover, it permits development of a novel concept of cellular regulation over these dynamic events. The membrane-bound vesicel is a miniature crystal fabrication station and a vehicle responsible for transportation of seed crystals and an organic matrix material to sites of discharge from the cell. The vesicle membrane becomes a probable locus of active transport and enzymatic activity as well as a physical barrier to be penetrated for release of vesicle contents into the extracellular milieu. Contact between the vesicle membrane and the plasmalemma would result in exocytosis and the onset of skeletogenesis. Principles governing crystal growth would prevail from then on. The released crystal becomes a nucleation catalyst and the organic matrix, a supply of ionic calcium for self-limiting crystallization. Crystals are produced by the organism spontaneously and continuously from shortly after larval attachment throughout the life of the polyp. Therefore, these membrane-bound vesicles signal the dynamic process by which initiation, differentiation, growth and limitation of the coral skeleton is regulated.

Intracellular transport of horseradish peroxidase in the absorptive cells of goldfish hindgut in vitro, with special reference to the cytoplasmic tubules

Abstract: This study was undertaken to determine whether the numerous cytoplasmic tubules (CT) in the apical cytoplasm of goldfish hindgut absorptive cells are directly involved in the endocytotic transport of macromolecules into the cells, or whether they are derived from the intracellular membrane components. The absorptive cells were exposed to horseradish peroxidase (HRP)-containing medium in organ culture and subsequently fixed and prepared for electron microscopy. Analysis revealed that 5 sec after exposure, many vesicular structures, including coated vesicles, were labelled with reaction product whereas almost all CT were negative. After a 1-min exposure, reaction product was detected in about 11 % of the CT, and thereafter, the percentage increased to about 95% after 15 min exposure. As labelled CT increased in number, the number of densely labelled vacuoles with attached CT also increased. CT connected to vacuoles with a peripheral margin of dense reaction product were always HRP-positive, whereas those connected to vacuoles which were not distinctly labelled were themselves also devoid of HRP reaction product. This indicated that the labelling of CT was closely associated with the labelling of the inner surface of the vacuolar membrane. These results indicate that CT are probably formed by a budding off from these vacuoles, rather than being directly involved in endocytosis.

Electron microscopic studies on the differentiation of the ependymal cells and the glioblast in the spinal cord of domestic fowl

Abstract: Using 3H-thymidine autoradiography and electron microscopy the authors studies the differentiation of the ependymal cells and glioblasts in the embryonic spinal cord of the chick. 1. Ependymal cells are differentiated from the matrix cells at 8 days of incubation. Signs of differentiation are increase in number of basal bodies (blepharoblasts), and appearance of immature cilia and rough-surfaced endoplasmic reticulum in the apical cytoplasm. 2. After 8 days of incubation remaining matrix cells lose the potency to produce neuroblasts and change into glioblasts. They lie beneath the immature ependymal layer, i.e., subependymal layer in sensu stricto. The fine structure of the immature glioblast is fairly similar to that of the matrix cell; characteristic are a small nucleus and numerous aggregates of free ribosomes throughout the cytoplasm. Some glioblasts migrate through the mantle layer toward the periphery and reach the neuropil region. At this stage the fine structure of this migrating glioblast is not remarkably different from that of glioblasts in the subependymal layer.