Browsing by Author "VIAL, JD"

Now showing 1 - 11 of 11
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    ACTIN AND MYOSIN IN OXYNTIC CELL - GELATION AND CONTRACTION OF CRUDE EXTRACTS INVITRO
    (1981) KOENIG, CS; DABIKE, M; VIAL, JD
    Extracts prepared from purified toad [Bufo spinulosus] oxyntic cells undergo temperature-dependent, cytochalasin B (CB)-sensitive gelation. In the presence of ATP, the interaction between gelled actin and myosin produces a contracted gel. Such association ceases spontaneously after shrinkage is completed. A stable myosin-actin interaction takes place in the absence of ATP, but no contraction of the gel is observed. A correlation between this actomyosin system present in oxyntic cells and the high mobility of the secretory pole, resulting in the changes in shape observed during the onset of HCl secretion, is proposed.
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    ACTIN-LIKE FILAMENTS AND MEMBRANE REARRANGEMENT IN OXYNTIC CELLS
    (1976) VIAL, JD; GARRIDO, J
    The secretory pole of vertebrate oxyntic cells possesses 2 distinct membrane systems: the apical plasma membrane which presents numerous infoldings, microvilli and processes and a complex tubulovesicular system located in close proximity to the plasma membrane. These 2 membrane systems are generally believed to be interconvertible in relation to the functional state of the cell. To determine the role that filaments may play in the interconversion process, the secretory pole of rat and toad [Bufo spinulosus] oxyntic cells was examined by EM under conditions designed to demonstrate filamentous structures, i.e., slight cellular swelling and incubation with heavy meromyosin. Filaments 50-80 .ANG. in diameter are present in close association with the plasma membrane to which they are connected by regularly spaced bridges. Heavy meromyosin-treated material reveals decorated filaments in topographically corresponding locations. No filaments are seen in association with membranes of the tubulovesicular system. Association with actin-like filaments may be a step in the translocation of membranes from the tubulovesicular system to the plasma membrane.
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    AXONS SPROUT AND MICROTUBULES INCREASE AFTER LOCAL INHIBITION OF RNA-SYNTHESIS, AND MICROTUBULES DECREASE AFTER INHIBITION OF PROTEIN-SYNTHESIS - A MORPHOMETRIC STUDY OF RAT SURAL NERVES
    (1991) BUSTOS, J; VIAL, JD; FAUNDEZ, V; ALVAREZ, J
    Drugs that inhibit RNA or protein synthesis are known to affect some functional properties of axons. In this context, we studied the ultrastructural effects of actinomycin-D, an inhibitor of RNA synthesis, and cycloheximide and emetine, inhibitors of protein synthesis, in rat sural nerves. A silicone sleeve (4 mm long) loaded with drug was placed around the nerves and left for about a week. The ultrastructural alterations of axons and Schwann cells progressed over this period. After cycloheximide and emetine, the cytoplasm of Schwann cells was enlarged and the rough endoplasmic reticulum was prominent. After actinomycin-D, the Schwann cells reached the stage of lysis. Nonmedullated were more affected than myelinated axons. After cycloheximide and emetine, the axoplasmic matrix decreased substantially but reversibly. Microtubules of nonmedullated fibres decreased by about 50%. Actinomycin-D determined sprouting of axons and a rise of axonal microtubules; in nonmedullated axons, the normal inverse correlation between microtubular density and calibre gave way to a high and constant density for all axonal sizes. A few millimetres proximal and distal to the sleeve, the nerve tissue and the axonal microtubular content were close to normal, i.e. the effects of drugs were local. Present results suggest that the local turnover of amino acids in the axon is necessary to maintain the integrity of microtubule and neurofilament proteins. We propose that the Schwann cell down-regulates the axonal cytomatrix.
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    CYTOCHEMICAL STUDY OF DISTRIBUTION OF ADENOSINE-TRIPHOSPHATASE IN PANCREAS OF DOG
    (1976) KOENIG, CS; SANTELICES, LC; VIAL, JD
    Dog pancreatic tissue, incubated in a modified Wachstein-Meisel medium, showed 2 different ATPase activities. One of them was located at the apical border of the cells lining the intralobular ducts and of the centroacinar cells and was stimulated by HCO3-, depressed by SCN- and OCN- and completely abolished by CN-. The other was located at the intracellular clefts of the epithelium lining the interlobular ducts and was stimulated by Mg2+. These findings correlated well with the results of incubation of homogenates of fresh and fixed tissues. Their significance with respect to the role of different segments of the duct system in the formation of the pancreatic juice was discussed.
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    DISTRIBUTION OF INTERMEDIATE FILAMENTS IN AMPHIBIAN OXYNTIC CELLS - BIOCHEMICAL AND IMMUNOLOGICAL CHARACTERIZATION
    (1981) DABIKE, M; KOENIG, CS; VIAL, JD
    Intermediate filaments of toad oxyntic cells were isolated and analyzed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. The major proteins of the residue were identified as actin and a 51,000 dalton polypeptide. Immunological crossreactivity between toad oxyntic cell intermediate filament components and antiprekeratin was shown by double immunodiffusion tests and indirect immunofluorescence. The immunofluorescent decoration of oxyntic cells and the EM images are coincident in locating the intermediate filaments mainly at the cortical and perinuclear basal zones. The cortical zone appears especially rich in prekeratin-like material at its adluminal 3rd. This results in a cup-like structure that encloses the cell portion occupied by the tubulovesicular system, which does not contain intermediate filaments. The translocation of membranes occurring during the secretory cycle of the oxyntic cell was attributed to a system of contractile proteins. The disposition of the prekeratin-like material suggests a role for intermediate filaments in the generation of movement produced by actin and myosin interaction, by providing a fixed plane for the anchoring of actin microfilaments.
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    EFFECT OF BILE-DUCT LIGATION ON ULTRASTRUCTURAL MORPHOLOGY OF HEPATOCYTES
    (1976) VIAL, JD; SIMON, FR; MACKINNON, AM
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    EPIDERMAL GROWTH-FACTOR INHIBITS CYTOSKELETON-RELATED CHANGES IN THE SURFACE OF PARIETAL-CELLS
    (1981) GONZALEZ, A; GARRIDO, J; VIAL, JD
    The effect of epidermal growth factor (EGF) on gastric acid secretion was correlated with the morphological changes of the apical pole of rat parietal cells studied by transmission electron microscopy. Gastric acid secretion was stimulated by histamine, carbachol, pentagastrin and insulin-induced hypoglycemia and estimated by continuous recording of pH variations of gastric luminal perfusate. EGF inhibits acid secretion in these conditions. The action of the hormone also results in the arrest or reversal of the changes in shape undergone by parietal cells as they go into secretion. In view of the evidence involving cytoskeletal elements in the generation of these structural alterations, the action of EGF on gastric acid secretion may be a consequence of a general effect of this hormone on cytoskeletal function.
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    FINE-STRUCTURE OF THE OXYNTICOPEPTIC CELL IN THE GASTRIC GLANDS OF AN ELASMOBRANCH SPECIES (HALAELURUS-CHILENSIS)
    (1979) REBOLLEDO, IM; VIAL, JD
    Gastric mucosa of an elasmobranch species was examined by EM. The gastric glands contain 1 form of cell whose fine structure is similar to the cell that secretes HCl and pepsinogen of the amphibian gastric glands proper. These oxynticopeptic cells are characterized by a luminal surface with long projections of cytoplasm having dilatations in their thickness, a tubulo-vesicular system in the apical cytoplasm, a great number of mitochondria, some of which are of great length, a well developed granular endoplasmic reticulum and a conspicuous Golgi apparatus, and a large nucleus with a conspicuous nucleolus. A 4th part of the cells are binucleated. Physiological implications of some of these ultrastructural features are discussed.
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    THE EARLY CHANGES OF PARIETAL-CELL STRUCTURE IN THE COURSE OF SECRETORY ACTIVITY IN THE RAT
    (1985) VIAL, JD; GARRIDO, J; GONZALEZ, A
    The fine structure of the rat parietal cell was studied, at rest and after stimulation by refeeding or insulin administration. Experiments on fixation procedures showed that whenever the fixative contained sucrose at a concentration higher than 0.2 M, the system of cytoplasmic membranes was clearly tubular in arrangement, whereas the omission of sucrose in the fixative usually resulted in a vesicular structure. High-voltage EM of thick sections prepared by conventional techniques or by impregnation with zinc iodide-osmium (ZIO) revealed that the tubules were grouped into fascicles and these formed a feltwork that was especially thick toward the cell apex. The development of the secretory canaliculus after stimulation appeared to take place by an in situ remodeling of the cytoplasmic domain occupied by the tubular system. Cells examined after short periods of stimulation (5-15 min) showed images of the tubular system and of the canalicular structure which differed both from the nonstimulated and from the fully active (30-45 min of stimulation) cell. These features included the formation of wide cisternae and of pericanalicular cytoplasmic trabeculae or laminae, whose fine structure beared close resemblance to the intracanalicular processes in the same cells. These images can be ordered into a hypothetical sequence which may be a model to explain the transformation of the tubular system and intervening cytoplasmic matrix into secretory canaliculus.
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