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  • 1
    ISSN: 1749-6632
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Natural Sciences in General
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 0886-1544
    Keywords: platelet ; platelet adhesion ; cytoskeleton ; high voltage electron microscopy ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Adhesion of platelets in vitro resulted in rapid polymerization of the amorphous cytoplasmic ground substance into an organized cytoskeletal superstructure. This cytoskeleton, characterized through the use of whole-mount and stereo (3-D), high-voltage microscopy in conjunction with morphometrics and cytochemistry, comprised four major size classes of filaments organized in distinctive zones. The central matrix, or granulomere, at the center of the cell mass, was an ill-defined meshwork of 80-100-Å filaments which enshrouded granules, dense bodies, and elements of the dense tubular system as identified through peroxidase cytochemistry. Demarcasting this central matrix was a trabecular zone containing 30-50, 80-100, and 150-170 Å filaments in an open and rigid-appearing lattice. Circumscribing the trabecular zone and extending to the margins of the hyalomere was the third region, the peripheral web, in which 70-Å filaments were arranged in a tight honeycomb lattice. This organizational pattern was retained in cytoskeletons prepared by Triton x-100 extraction of the adherent cells, and was observed in basally located cells of aggregates which formed subsequent to adhesion. Our observations are consistent with biochemical studies of cytoskeletons prepared from suspended platelets and suggest a contractile protein composition for the superstructure during adhesion.
    Additional Material: 11 Ill.
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 0275-3723
    Keywords: adhesion ; microfilaments ; thrombocytes ; whole mount ; cytochalasin B ; Chemistry ; Molecular Cell Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Thrombocyte adhesion following activation by a Formvar surface involves a morphologic transition resulting in a fully spread cell. Correlative SEM and whole mount TEM were used to study the cytoskeletal alterations that accompany changes in surface morphology during adhesion. Following initial adhesion, thrombocytes extend slender pseudopods containing longitudinally oriented bundles of filaments that are 13-22 nm in diameter. Concomitant with pseudopod extension, a cytoplasmic hyalomere, consisting of a dense filamentous network, extends between the pseudopods and ultimately results in a fully spread cell. Treatment of thromboyctes with cytochalasin B (10-5 M) caused clumping of the hyalomere filament network and retraction of the hyalomere. Examination of partially retracted cells revealed that pseudopod filament bundles were continuous with the contracting filamentous network. It is concluded that pseudopod filament bundles and cytoplasmic hyalomere filaments are interconvertible and that their organizational relationship changes in accordance with gross morphologic changes.
    Additional Material: 13 Ill.
    Type of Medium: Electronic Resource
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  • 4
    ISSN: 0886-1544
    Keywords: lipoprotein ; receptor-mediated endocytosis ; nonspecific endocytosis ; microvilli ; membrane ruffles ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Endocytosis of pigeon beta migrating very-low-density lipoprotein (βVLDL) by monocyte-derived macrophages (monocyte/macrophages), cultured from Random Bred White Carneu (RBWC) pigeons, occurs by both coated and non-coated regions of the plasma membrane (Henson et al.: Exp. Mol. Pathol. 51:243-263, 1989). Secondary to binding, the βVLDL is translocated to lysosomes for degradation. Ultimately these events lead to foam cell formation in vitro. Utilizing video-enhanced contrast light microscopy in conjunction with whole mount intermediate-voltage transmission electron microscopy (IVEM) and high-resolution scanning EM, the dynamics of βVLDL binding have been correlated with ultrastructure. Beta VLDL conjugated to gold colloids was visualized at the surface of living cells by using Allen video-enhanced contrast-differential interference contrast microscopy (AVEC-DIC). Subsequent to AVEC-DIC, direct observation of the identical cells by IVEM and SEM was facilitated through the use of gold finder grids, and these EM observations confirmed identification of the videoobserved βVLDL particles.Upon addition of βVLDL, pigeon monocyte/macrophages underwent gross morphological changes. These changes were recorded by video as movements at the cytoplasmic periphery, and the movements involved extension of microvilli, expression of retraction fibers, and elaboration of membrane ruffles. When secondarily observed by stereo (3-D) IVEM and SEM, the identification of microvilli, retraction fibers, and membrane ruffles was confirmed and the lipoprotein-gold conjugates were associated with these ligand-induced membrane structures. Beta VLDL-gold conjugates were also associated with pit-like regions at the base of microvilli, while at the base of ruffles, βVLDL-gold conjugates were located in membrane invaginations and cytoplasmic vesicles.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
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