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At least 955 records · Page 53Linked to original sources
PubMed1990

[The supramolecular organization of the keratinocyte cytoskeleton and extracellular matrix in human skin revealed by freezing-deep etching with rotary platinum-carbon shadow-casting].

The supramolecular organization of the keratinocyte cytoskeleton, the basal lamina and of the dermal extracellular matrix in the whole human skin revealed by freeze-deep etching with Pt/C rotary shadowing is presented. The routine equipment for this method and sample preparation are described. The resolution of the method is sufficient to visualize individual cytoskeleton elements and extracellular matrix. The presented cytoskeleton organization is very similar to the meshwork of strands or "microtrabeculae" seen in the cytoplasm of the whole cells by high voltage electron microscopy. Besides, the ultrathin section pattern of epidermis in human skin from patients with mycosis fungoides is described.

Biopsy↗
PubMed1990

rap1B, a cAMP-dependent protein kinase substrate, associates with the platelet cytoskeleton.

rap1B is a member of the ras superfamily of low molecular weight GTP binding proteins which constitutes a focal point of GTP and cAMP signal transduction systems. Like other members of this superfamily, rap1B is membrane-associated in resting platelets, presumably through polyisoprenylation. The studies presented here were undertaken to determine the subcellular changes in rap1B localization during cell activation. Activated and unactivated platelets were fractionated by Triton X-100 lysis followed by differential centrifugation to obtain a 10,000 x g cytoskeleton fraction, a 100,000 x g membrane skeleton fraction, and a 100,000 x g supernatant fraction containing solubilized proteins. In unactivated platelets, rap1B was present in the 100,000 x g supernatant fraction. In contrast, in platelets activated with 1 unit/ml alpha-thrombin or with the calcium ionophore, A23187, rap1B was quantitatively recovered in the 10,000 x g cytoskeleton fraction. rap1B was absent from the 100,000 x g fraction containing the membrane skeleton and could not be detected in the 100,000 x g supernatant containing cytosolic proteins and solubilized membrane components. These results indicate that rap1B associates with the cytoskeleton during cell activation.

Amino Acid Sequence↗
PubMed1987

Immunohistochemistry of the cytoskeleton of human prostatic epithelium. Evidence for disturbed organization in neoplasia.

An indirect immunoperoxidase technique was used to evaluate keratin, actin, tubulin, and calmodulin immunoreactivity in histologic sections of normal, hyperplastic, and neoplastic human prostate. Polyclonal as well as monoclonal keratin antibodies produced equivalent and intense staining of normal epithelium. The immunoreactivity of normal prostate with keratin antibodies was more pronounced than with antibodies to the other components of the cytoskeleton. Variation in staining for components of the cytoskeleton was minimal. The same findings applied to hyperplastic prostate. The immunoreactivity of prostate tumors with antibodies to these cytoskeletal proteins differed markedly from normal prostate. Prostatic carcinomas showed reduced keratin immunoreactivity with a panepithelial antibody, but unaltered or enhanced immunoreactivity with tubulin, actin, and calmodulin antibodies. Many tumors were unreactive with a monoclonal keratin antibody that was strongly reactive with tissues that contained cytokeratin 18 (45-kd) and which intensely stained normal and hyperplastic prostate. In addition, prostate carcinomas often yielded heterogeneous patterns of staining with actin, tubulin, and calmodulin antibodies in contrast to normal and hyperplastic prostate, which showed uniform staining. The results suggest that a disturbance in the organization of the cytoskeleton may accompany neoplastic transformation of human prostate.

Actins↗
PubMed1989

[The role of protein phosphorylation in mast cell secretion, stimulated by concanavalin A. Connection to the cytoskeleton].

The role of cytoskeleton and protein phosphorylation in concanavalin A and phorbol ester (PMA) induced mast cell secretion was investigated. It was shown that the receptor coupled with lectin interacts with the cytoskeleton. When the ligand-receptor complex is formed, an increased phosphorylation of some proteins is induced. The same proteins are phosphorylated under the influence of PMA, a protein kinase C activator, thus suggesting that protein kinase C is involved in the regulation of mast cell exocytosis. The results obtained testify to the effect that the mechanism of mast cell degranulation induced by concanavalin A is due to modification of the cytoskeleton.

Animals↗
PubMed1988

Role of tumor cytoskeleton and membrane glycoprotein IRGpIIb/IIIa in platelet adhesion to tumor cell membrane and tumor cell-induced platelet aggregation.

Components of the tumor cell cytoskeleton (i.e., microtubules, microfilaments, and intermediate filaments) have been reported to affect metastatic ability, since disruption of these components leads to a decrease in metastasis. One mechanism of metastasis which has not been previously considered is the decreased interaction of tumor cells with platelets. We present evidence that disruption of the tumor cell cytoskeleton decreases the ability of tumor cells to aggregate homologous platelets. This effect is dependent upon the disruption of microfilaments/intermediate filaments but not disruption of microtubules. In addition, tumor cell platelet interactions require the lateral mobility of specific receptors (i.e., clustering) on the tumor cell plasma membrane. A membrane glycoprotein immunologically related to the platelet glycoprotein IIb/IIIa complex was identified on Walker 256 carcinosarcoma cells using specific polyclonal and monoclonal antibodies and Northern blot analysis using complementary DNA probes for IIb and IIIa. Mobility of this receptor is dependent upon tumor cell microfilaments/intermediate filaments, but not microtubules. Furthermore, treatment of tumor cells with specific antibodies to the platelet glycoprotein IIb/IIIa complex inhibits tumor cell-platelet interaction at the macroscopic level (i.e., aggregation) and at the ultrastructural level (i.e., platelet adhesion to the tumor cell surface). These results suggest that this immunologically related glycoprotein IIb/IIIa is a receptor for platelet binding to the tumor cell surface, an event which precedes overt platelet aggregation and is dependent upon an intact tumor cell microfilament and intermediate filament network. Therefore, the decreased metastasis observed by others following disruption of the tumor cell cytoskeleton may be due, in part, to a decreased tumor cell-platelet interaction.

Animals↗
PubMed1986

Organization of the actin cytoskeleton of resting and activated platelets in suspension.

The present study has employed lysine, phalloidin, and a low concentration of osmic acid to protect the actin cytoskeleton of resting and thrombin-activated platelets during detergent extraction and fixation in suspension. Thin sections of resting platelets revealed a fine amorphous layer containing a few short actin filaments mimicking discoid shape and a randomly dispersed network of actin polymers in the cytoplasm. Following thrombin activation, the cytoskeleton consisted of a peripheral layer of submembrane actin filaments following the contour of shape change, a variable number of filaments in peripheral cytoplasm and extending into pseudopods, and a concentric mass of actin filaments with constricted microtubule rings in cell centers. Prior treatment with cytochalasin B (CB) appeared to reduce the number of actin filaments in resting platelets. Thrombin activation of CB-treated cells resulted in separation of actin filaments, which became concentrated in cell centers, from microtubule coils remaining at the cell periphery. The appearance of detergent-extracted cytoskeletons of platelet actin protected during fixation in suspension by lysine and phalloidin was remarkably similar to that of resting or CB-treated platelets before and after thrombin activation when viewed in conventionally prepared thin sections without exposure to detergent during fixation. The advantage of the new procedure is revelation of the actin filament organization in suspended platelets, which is obscured by the usual glutaraldehyde-osmic acid fixation technique.

Actins↗
PubMed1988

The role of cytoskeleton and nuclear matrix in virus replication.

In the light of the cytoarchitecture concept, the presented review attempts to cover what is known of the involvement of cytoskeletal and nucleoskeletal elements in the replication cycle of various viruses and in cell transformation. Our knowledge on the relationship of virus replication with cell architecture has rapidly progressed during the recent years in association with studies on composition of various filaments within cells, their spatial organization and possible functions which focussed much interest on the cytoskeleton and nuclear matrix. The new results indicated that highly specialized elements for normal cell function may be coopted for virus growth. Recently, using various methodical approaches it has been possible to obtain information about the association of virus-structural proteins with cytoskeletal and nucleoskeletal elements, about the reorganization of cytoskeleton during virus replication, about the role of tubulin in transcription and RNA synthesis of negative-strand viruses, about the involvement of cytoskeletal filaments in the transport of viral proteins, virus penetration, virus assembly and release from the infected cell. The role of cytoskeleton in cell transformation and in initiation of DNA synthesis and intracellular signaling to cell proliferation has been also investigated.

Adenoviridae↗
PubMed1985

Association of nerve growth factor receptors with the triton X-100 cytoskeleton of PC12 cells.

Triton X-100 solubilizes membranes of PC12 cells and leaves behind a nucleus and an array of cytoskeletal filaments. Nerve growth factor (NGF) receptors (10% of those found in intact cells) are associated with this Triton X-100-insoluble residue. Two classes of NGF receptors are found on PC12 cells which display rapid and slow dissociating kinetics. Although rapidly dissociating binding is predominant (greater than 75%) in intact cells, the majority of binding to the Triton X-100 cytoskeleton is slowly dissociating (greater than 75%). Rapidly dissociating NGF binding on intact cells can be converted to a slowly dissociating form by the plant lectin wheat germ agglutinin (WGA). This lectin also increases the number of receptors which associate with the Triton X-100 cytoskeleton by more than 10-fold. 125I-NGF bound to receptors can be visualized by light microscopy autoradiography in Triton X-100-insoluble residues of cell bodies, as well as growth cones and neurites. The WGA-induced association with the cytoskeleton, however, is not specific for the NGF receptor, since greater than 90% of cell surface glycoprotein receptors for WGA become associated with Triton X-100-insoluble material at lectin concentrations greater than 33 micrograms/ml. Concentrations of WGA which change the Triton X-100 solubility of membrane glycoproteins are similar to those required to alter the kinetic state of the NGF receptor. Both events may be related to the crossbridging of cell surface proteins induced by this multivalent lectin.

Adrenal Gland Neoplasms↗
PubMed1986

Receptor-cytoskeleton interactions and membrane traffic may regulate chemoattractant-induced superoxide production in human granulocytes.

When dihydrocytochalasin (dhCB) was added either prior to or after CHO-Met-Leu-Phe (fMLP), the rate and duration of superoxide production in human granulocytes stimulated by fMLP was augmented. This effect was maximal when dhCB was added before fMLP, increasing the rate 1.5-3-fold. The effect of dhCB was progressively diminished for later additions and was undetectable after 6-10 min. The effects of dhCB could be blocked by the additional presence of 10 microM t-Boc-Phe-Leu-Phe-Leu-Phe (where t-Boc is t-butoxycarbonyl) indicating a requirement for receptor occupancy. In the presence of dhCB, the reversible binding of fML[3H]P was elevated and the formation of slowly dissociating surface complexes of occupied receptor and cytoskeleton was inhibited. Myeloperoxidase and lactoferrin release from fMLP-stimulated cells was induced by dhCB but was only partially correlated with the potentiating effects of dhCB on superoxide production and receptor expression. To circumvent the complicating effects of degranulation on the analysis of the functional consequences of receptor-cytoskeletal associations, cells were also preincubated with 100 nM fMLP at 15 degrees C. Under these conditions, the majority of the surface receptors became irreversibly occupied and coisolated with the cytoskeletal fraction of the cell. Subsequent exposure of the cells to fMLP at 37 degrees C resulted in no superoxide production. This desensitization was blocked by dhCB which also inhibited coisolation of the ligand and cytoskeletons. Conversion of receptor to a slowly dissociating state may represent its trapping in an inactive form and would provide a role for receptor-cytoskeleton interactions in the termination of the granulocyte response to chemoattractants. The inhibition of such receptor "sequestration" and the induction of new receptor expression could, therefore, partially account for dhCB-induced potentiation of the fMLP response.

Biological Transport↗
PubMed1986

Association of synapsin I with neuronal cytoskeleton. Identification in cytoskeletal preparations in vitro and immunocytochemical localization in brain of synapsin I.

Calmodulin-dependent protein kinase II (CaM kinase II) is associated with microtubule preparations and phosphorylates several endogenous proteins including microtubule-associated protein 2, tubulin, and an 80,000-dalton protein doublet (pp80). We now report that pp80 is identical to synapsin I by all criteria studied including molecular weight, isoelectric point, phosphopeptide mapping of cAMP- and calmodulin-dependent phosphorylated protein, comigration with authentic synapsin I, and sensitivity to digestion with collagenase. Synapsin I and CaM kinase II were found in association with both microtubule preparations and preparations enriched in neurofilaments. Antibodies to synapsin I specifically labeled neurofilaments prepared in vitro. Immunocytochemical studies on rat brain tissue demonstrated synapsin I immunoreactivity specifically associated with the neuronal cytoskeleton as well as synaptic vesicles. The observed synapsin I staining on cytoskeletal elements was considerably diminished or abolished by the inclusion of Triton X-100 in the staining solutions. These results indicate that synapsin I is associated with the cytoskeleton and may be an important link between cytoskeletal elements as well as between the cytoskeleton and membrane.

Antibodies↗
PubMed1985

Heparan sulfate proteoglycans of rat embryo fibroblasts. A hydrophobic form may link cytoskeleton and matrix components.

Heparan sulfate proteoglycans (HSPGs) synthesized in cultures of rat embryo fibroblasts have been isolated and characterized. Cells grown in the presence of [35S]sulfate secreted a large amount of radiolabeled macromolecules into the culture medium of which only a small proportion was identified as HSPG. However, the majority of radiolabeled proteoglycans isolated from the cell layer were HSPGs. Here, two types of HSPG were detected. One type had an Mr of 5-8 X 10(5) as estimated by gel chromatography on Sepharose CL-4B in the presence of 0.1% sodium dodecyl sulfate and lacked hydrophobic properties in that it showed no affinity for octyl-Sepharose and could not be inserted into liposomes. The other HSPG type had an estimated Mr of 3-5 X 10(5), was retained on octyl-Sepharose, and could be inserted into liposomes. In addition, the cells contained low molecular weight heparan sulfate oligosaccharides. Treatment of living cells with 0.2% Triton X-100, which retained stress fibers and extracellular matrix but solubilized cell membranes, released a proportion of the smaller HSPG together with the heparan sulfate oligosaccharides. The cytoskeleton-matrix residue remaining after detergent extraction of the cell contained the larger species of HSPG in addition to the smaller HSPG. The presence of the smaller hydrophobic HSPG in the detergent-treated cytoskeleton-matrix preparations suggests that it may form part of a transmembrane cytoskeleton-matrix linkage.

Animals↗
PubMed1986

The teleost cone cytoskeleton. Localization of actin, microtubules, and intermediate filaments.

This laboratory has been using the teleost retinal cone as a model for studying the mechanisms and regulation of retinal cell motility. In previous inhibitor studies, the authors have shown that dark-induced cone elongation requires microtubules, whereas light-induced contraction requires actin filaments. This study examines the distributions of actin filaments, microtubules, and intermediate filaments in the cone cytoskeleton. Actin filaments have been localized in isolated cones by labeling with fluorescent derivatives of phalloidin; microtubules were localized by immunofluorescent labeling with anti-tubulin. Actin, microtubule, and intermediate filament distributions have also been examined in detergent-lysed motile cell models of cones fixed with a new method that enhances preservation of the cytoskeleton. Longitudinal bundles of actin filaments extend from the cone's calycal processes through the ellipsoid and into the myoid. No actin filaments are detectable in the perinuclear region and axon, but filaments are present in both pre- and post-synaptic components of the synapse. Intermediate filaments are numerous in the perinuclear region and cone axon but relatively sparse in the myoid. In contrast, microtubule distribution is more uniform: numerous longitudinally oriented microtubules are present throughout the length of the cell. Thus the cone cytoskeleton reflects the highly polarized shape and function of the cell, with actin filaments localized to the distal movable part of the cell and intermediate filaments localized to the proximal part of the cell, which is anchored in the retina.

Actins↗
PubMed1986

[Characteristics of the cytoskeleton structure of podocytes in vertebrates].

Using transmission electron microscopy a study was made of the cytoskeleton of the renal glomerulus visceral epithelium cells (-podocytes) in representatives of all classes of vertebrates. An obvious tendency of microtubules in the cytoskeletons of the investigated cells is disclosed. This process is accompanied by the intense intracellular development of microfilaments. The role the podocyte cytoskeleton in renal ultrafiltration, and possible mechanisms of its functioning are discussed.

Amphibians↗
PubMed1985

Immunochemical analysis of the supramolecular structure of myosin in contractile cytoskeletons of Dictyostelium amoebae.

A collection of monoclonal antibodies against Dictyostelium myosin was screened to identify an antibody that could distinguish monomeric from polymeric myosin. An antibody was found that reacted only with monomeric myosin, provided that the antigen-antibody reaction was carried out in solution. This antibody was used in competition radioimmunoassays to probe the supramolecular structure of myosin in Triton-extracted cell models, or cytoskeletons, of Dictyostelium amoebae. The competition assay showed that, as isolated, cytoskeletal myosin was entirely filamentous, but could be converted to monomeric form by increasing the ionic strength of the surrounding buffer. As monomer, it remained associated with the cytoskeleton and could be cycled back to filament form by a second change of buffer. The ability of cytoskeletons to carry out ATP-dependent contraction was examined as a function of the assembly state of myosin. The results suggested that filamentous myosin is responsible for contraction of the cortical filament matrix.

Adenosine Triphosphate↗
PubMedDate not supplied

[Scanning electron microscopy of the cytoskeleton of the aortic endothelial cells of mature and aged rats].

The aortic endothelial cells' cytoskeleton was visualized using scanning electron microscopy of detergent-extracted cells. It is shown that the aortic endothelial cells' cytoskeleton undergoes structurization during aging. The cytoskeleton structurization is supposed to be an adaptive reaction which increases stability of intracellular contacts and cell adhesion with the underlying substrate.

Aging↗
PubMed1984

The effects of X irradiation on the cytoskeleton of rat alveolar macrophages in vitro.

The three-dimensional visualization of Triton X-100 resistant cytoskeletons has been used to demonstrate that an absorbed dose of 120 Gy from X rays causes a distinctive and reproducible alteration of the cytoskeleton of intact rat alveolar macrophages in vitro. The alteration has also been shown to be rapidly and completely "repaired" and to be apparently similar to alterations caused by colchicine but dissimilar to those caused by cytochalasin B. From these observations and those of other workers who have studied the irradiation of extracted microtubular proteins in vitro, we think it likely that microtubules rather than microfilaments are the radiosensitive component of the macrophage cytoskeleton.

Animals↗
PubMed1981

Sodium and calcium regulation and the role of the cytoskeleton in the pathogenesis of disease: a review and hypothesis.

Recent years have seen a rapid development in knowledge concerning ion regulation and the cytoskeleton and their roles in many normal and abnormal cell processes. The structure and function of the cytoskeleton plays a key part in a number of cell properties including cell shape, potential mobility of intracellular proteins including receptors, cell to cell adhesion, and many other phenomena such as secretion, phagocytosis and autophagocytosis. Although earlier studies have emphasized the roles of sodium and calcium ion modification following acute and chronic cell injury, it has not been until recently that volume regulation and sodium modification have been found to be intimately linked through mechanisms such as sodium-calcium exchange and that the interaction of these regulations are associated with the cytoskeleton and the cell membrane. Therefore, it is the purpose of this review not only to summarize the vast amount of data which has rapidly accumulated in this field, and to put it into perspective, but also to advance a hypothesis which, we hope, will eventually establish that a wide variety of pathological phenomena ranging from acute cell death to chronic processes such as neoplasia, hypertension and aging are all a common series of cellular reactions.

Animals↗
PubMed1994

Helical structure of the cytoskeleton in the axoplasm and dendroplasm of olfactory bulb neurons after functional re-innervation in goldfish.

An ultrastructural study was carried out of the cytoskeleton arrangement of neuronal and glial processes in the olfactory bulbs and the olfactory tracts of intact and operated goldfish. Ripple patterns of bundles formed by both microtubules and intermediated filaments (neurofilaments and glial filaments) suggest that the cytoskeleton of olfactory cell processes has a helical arrangement. One year after bilateral olfactory tract transection complete recovery in the ultrastructure of the medial and lateral subtracts was observed. The obtained results are interpreted as reflecting the inherent helicity of the cytoskeleton of the olfactory cell processes.

Animals↗