Apical cytoplasm

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

Focal adhesion proteins associated with apical stress fibers of human fibroblasts.

Abstract: Human fibroblasts stained with fluorescently labeled phalloidin revealed many stress fibers within the apical cytoplasm in addition to those located along the basal plasma membrane and associated with focal adhesions. The staining patterns of these apical stress fibers with fluorescent phalloidin, anti-alpha-actinin, and antimyosin were identical to those of the basal stress fibers, suggesting the same macromolecular organization for both types of stress fibers. There were two types of apical stress fibers that clearly interacted with the apical plasma membrane, those extending between the basal and the apical plasma membrane and those having both ends on the basal membrane forming arches whose top interacted with the apical plasma membrane. By electron microscopy, we observed that apical stress fibers were associated with the apical plasma membrane via electron-dense plaques reminiscent of the focal adhesion. Since several proteins have been specifically localized to the focal adhesion site, we examined whether they were also present at the apical stress fiber-membrane association site by using immunocytochemical methods and image reconstruction techniques. We found that vinculin, talin, paxillin, a fibronectin receptor protein, several integrin subunits including beta 1, fibronectin, and proteins with phosphorylated tyrosine were also components of the apical plaque. These observations indicate that apical stress fibers are attached to the plasma membrane by using principally the same molecular assembly as the focal adhesion associated with the basal stress fiber. We suggest that the complex molecular organization of the focal adhesion is not demanded by cell adhesion, but rather it is needed for anchoring stress fibers to the plasma membrane. Apical plaques did not stain with the anti-integrin alpha v subunit or anti-focal adhesion associated kinase (FAK), although these antibodies stained focal adhesions. These results suggest that the apical stress fiber-membrane contact has some important functions different from those of the focal adhesion.

The mechanism of spermiation in the toad

Abstract: The present paper is the first demonstration, at the ultrastructural level, of the mechanism of sperm release from the Sertoli cells. The main target of the immediate effect of LH is the cytoplasm of the Sertoli cells. Three main stages are recognized in the cellular response: (1) swelling of the endoplasmic reticulum, (2) swelling of the apical cytoplasm, (3) the apical detachment. The preservation of the nucleated basal portion of the Sertoli cells after the stage of apical detachment is assured by a mechanism of protective overlapping of residual membranes. It has also been shown that LH is able to increase water and sodium content in the toad testis. It is postulated that water enters after the injection of the LH into the channels of the endoplasmic reticulum, then the water moves into the apical cytoplasm attracted by hydrophilic products derived from enzymatic splitting of cytoplasmic mucoproteins. Finally water passes into the lumen of the seminiferous tubules simultaneously with cell debris and the liberated spermatozoa. The lysosomes present in the cytoplasm of the Sertoli cell in this mucolytic action may be involved.

Uteroglobin in the rabbit. I. Intracellular localization in the oviduct, uterus, and preimplantation blastocyst.

Abstract: The localization and release of uteroglobin (UGL) were investigated immunohistologically in the oviducts and uteri of female rabbits from oestrus through the 7th day post coitum and the blastocyst on the 7th day post coitum. UGL was detected within Fallopian tube cells even during oestrus. Granules of UGL appeared toward the bases of these cells. Subsequently, the cells became almost entirely filled with UGL. Drop-like protrusions of the apical cytoplasm suggest a mechanism of apocrine extrusion. All stages of filling and extrusion were visible during the entire preimplantation period. During oestrus, synthesis of UGL within uterine cells becomes sufficiently advanced so that extrusion has either already begun or is about to begin. UGL positive material first appears in the supranuclear regions. Later the entire cytoplasm shows a positive reaction. An uneven distribution of UGL cells is observed in the endometrium. Since only the glands adjacent to the myometrium and cells of the cavum epithelium contain UGL, a striking mosaic of UGL positive and negative cells results. The present report is the first detecting UGL in single cells of the blastocyst. Both entodermal and ectodermal cells proved to be UGL positive. The synthesis and section of UGL in the oviduct and uterus and the possible origins of UGL in the blastocyst are discussed.

Mitochondria-rich (chloride) cells in the gill epithelia from four species of stenohaline fresh water teleosts

Abstract: The mitochondria-rich (chloride) cells have been found to be present in the gill epithelia of four species of stenohaline fresh water teleosts. The cytoplasm of these chloride cells contains an extensive network of cytoplasmic tubules which communicate with intercellular spaces bordering the lateral and basal cell surfaces. Numerous vesicles with fairly electron-dense interiors are also present in the apical cytoplasm of chloride cells. The apical surface of a chloride cell forms an apical pit, but the lumen of the pit does not appear to be in continuity with the interior of the apical vesicles and tubules inside the cell. When Carassius auratus were kept in 100, 200, 300, and 400 mOsm-diluted sea water for a month, no appreciable changes occurred in the number and fine structure of the chloride cells, except for a dilation of the apical vesicles and a slight decrease in diameter of the cytoplasmic tubules in these cells in the fishes kept in 300 and 400 mOsm. These results suggest that chloride cells may be a rather common occurrence in the gill epithelia of stenohaline fresh water teleosts, and may function in ion-transport in these fishes in fresh water environments.