Apical cytoplasm

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

Study of the olfactory epithelium in the developing sturgeon. Characterization of the crypt cells.

Abstract: In acipenserids, crypt cells (CCs) have only been observed in juvenile specimens, and it has not been clarified whether they differentiate along with olfactory receptor neurons (ORNs) during the lecithotrophic stage or during later development stages. Furthermore, no detailed optical microscopy (OM) or electron microscopy study on the development of CCs has been published to date. In the present study, we used OM and electron microscopy to follow the development of CCs in Acipenser naccarii from hatching to the establishment of exogenous feeding. Based on these observations, we can affirm that CCs are present from the first few posthatching (PH) days. CCs appear with their nucleus close to the basal lamina of the epithelium and enveloped by supporting cells. In addition, from the beginning of day 2 PH, we observed cells with highly similar characteristics to those of CCs (absence of knob, abundant mitochondria and filamentous material in apical cytoplasm, numerous microtubules, and envelopment by supporting cells) but with cilia still remaining on their noninvaginated apical surface. We conclude that these cells may correspond to immature CCs in which the crypt, the final feature of their morphological differentiation, has not yet formed.

Ultrastructural markers of colonic adenocarcinoma.

Abstract: A mixed population of 96 adenocarcinomas was examined by electron microscopy to establish the presence of organ specific features. This resulted in the identification of fine structural characteristics, occurring consistently in colorectal adenocarcinomas but not in other epithelial tumors. The colorectal "ultrastructural profile" consists of microvilli with dense cores of microfilaments extending as long rootlets into a clear zone of apical cytoplasm, apical electron dense bodies, and abundant glycocalyceal bodies. Of these features, the long rootlets constitute the best morphologic marker for large intestinal type adenocarcinoma. Using these characteristics in another series of 58 adenocarcinomas studied in a double-blind manner, it was possible to distinguish colorectal adenocarcinomas from other carcinomas on ultrastructural grounds alone.

Starvation induces apoptosis in the midgut nidi of Periplaneta americana : a histochemical and ultrastructural study

Abstract: The effects of starvation on cell death in the midgut of Periplaneta americana were studied histochemically and ultrastructurally TUNEL assays showed that cell death began to increase in the columnar cells and nidi, the nests of stem cells and newborn cells from 2 weeks of starvation A significant increase in cell death occurred in the nidi after 4 weeks of starvation Cockroaches starved for 4 weeks showed active-caspase-3-like immuno-reactivity both in the columnar cells and nidi, whereas control cockroaches that were fed for 4 weeks showed this reactivity only in the apical cytoplasm of columnar cells Electron microscopy revealed no chromatin condensation in the nucleus of columnar cells of cockroaches, whether fed or starved for 4 weeks Starved cockroaches exhibited many small vacuoles in the cytoplasm of some columnar cells and “floating” organelles including nuclei in the lumen A 4-week starvation induced the appearance of cytoplasmic fragmentation and secondary lysosomes in the nidi Each fragment contained nuclear derivatives with condensed chromatin, ie apoptotic bodies Mitotic cells were found in some, but not all nidi, even within the same starved sample Fragmentation was not observed in the nidi of control cockroaches Thus, starvation increases cell death not only in the columnar cells, but also in the nidi The cell death in the nidi is presumably apoptosis executed by caspase 3

RAB26 coordinates lysosome traffic and mitochondrial localization

Abstract: As they mature, professional secretory cells like pancreatic acinar and gastric chief cells induce the transcription factor MIST1 (also known as BHLHA15) to substantially scale up production of large secretory granules in a process that involves expansion of apical cytoplasm and redistribution of lysosomes and mitochondria. How a scaling factor like MIST1 rearranges cellular architecture simply by regulating expression levels of its transcriptional targets is unknown. RAB26 is a MIST1 target whose role in MIST1-mediated secretory cell maturation is also unknown. Here, we confirm that RAB26 expression, unlike most Rabs which are ubiquitously expressed, is tissue specific and largely confined to MIST1-expressing secretory tissues. Surprisingly, functional studies showed that RAB26 predominantly associated with LAMP1/cathepsin D lysosomes and not directly with secretory granules. Moreover, increasing RAB26 expression – by inducing differentiation of zymogen-secreting cells or by direct transfection – caused lysosomes to coalesce in a central, perinuclear region. Lysosome clustering in turn caused redistribution of mitochondria into distinct subcellular neighborhoods. The data elucidate a novel function for RAB26 and suggest a mechanism for how cells could increase transcription of key effectors to reorganize subcellular compartments during differentiation.