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Biomedical subjects

A Asano

Publications and source records attributed to A Asano.

At least 109 records · Page 6Linked to original sources
PubMed1983

[Regulatory proteins of the cytoskeleton system and their changes associated with carcinogenesis].

Microfilaments are known to participate in several cellular functions. Proteins which cross-link, sever or cap F-actin filaments, and those inhibit polymerization of G-actin may regulate intracellular distribution, length and amount of F-actin to cope with wide varieties of cellular functions of microfilaments. Actinogelin, a calcium-regulated crosslinking protein of F-actin, was discovered in and purified from Ehrlich tumor cells. Native molecule of the protein was found to be consisted of two 110,000-115,000 dalton subunits. Gelation of F-actin can be induced by the addition of the purified protein, and this can be inhibited by Ca2+ (half maximal inhibition, 2 microM). Actinogelin is distributed in several types of cells including fibroblasts, epithelial cells, macrophages and lymphocytes. This protein is found to localize at crossing or converging points of stress fibers (bundle of microfilaments) by immunofluorescence staining using anti-actinogelin antibody. Adhesion plaques of fibroblasts are also stained. Since oncogene product of Rous sarcoma virus, pp 60src, is also present in adhesion plaques, possible phosphorylation of actinogelin in a RSV-transformed cells was studied by the immunoblotting technique. It was found that phosphorylation of actinogelin occurred only at permissive temperature. This modification of the protein might be a cause of disappearance of stress fibers from cancer cells.

Actins↗
PubMed1983

[Clinical evaluation of serum CEA levels in uterine cervix cancer].

Serum CEA levels were measured in the blood of 98 patients with uterine cervix cancer before, during, and after treatment to investigate the relationship among the CEA level, the extent of the disease, and recovery. The CEA level rose as the disease progressed. Although there was no significant difference in the survival rates of patients with various CEA levels, those who returned to normal levels after treatment recuperated better. There was not clear evidence that CEA levels are clinically significant. However, it can be concluded that CEA levels at pre- and post-treatment times are helpful in the early detection of disease, prognosis, and in predicting recurrence or metastasis.

Carcinoembryonic Antigen↗
PubMed1982

Characterization and localization of actinogelin, a Ca2+ - sensitive actin accessory protein, in nonmuscle cells.

Actinogelin, which induces gelation of F-actin at Ca2+ concentrations below micromolar concentrations but not at higher concentrations, was isolated in the pure state from Ehrlich tumor cells. The protein consists of subunits of 112,000-115,000 daltons and under physiological conditions is present mostly as a dimer. Up to 1 mol of actinogelin (dimer) binds to 10-12 mol of actin monomer. The binding was slightly decreased by the presence of 50 microM Ca2+ and almost completely inhibited by 300 mM KCl. Antibodies against actinogelin giving a single precipitation line with Ehrlich cell extract and with pure actinogelin were raised in rabbits. Antibody preparations were purified before use in an affinity column containing purified actinogelin. In mouse embryo fibroblasts and 3T3 cells, staining of actin bundles by the antiactinogelin antibody usually was discontinuous or gave a striated appearance. Most of the crossing points of the actin bundles were intensively stained. In epithelial cells from mouse small intestine, actinogelin was distributed throughout the cell, with the exception of the microvilli, which were devoid of staining. In mouse peritoneal cells, the antibody staining patterns were similar to those of tetramethylrhodamine isothiocyanate-labeled heavy meromyosin, but the former usually were sharper than the latter. Intracellular localization of actinogelin was drastically altered by cytochalasin D treatment at 10 microgram/ml. We conclude that actinogelin is present in a wide variety of cell types and discuss the possible participation of actinogelin in the Ca2+-dependent regulation of microfilament distribution.

Actins↗
PubMed1982

Purification and characterization of actinogelin, a calcium-sensitive actin-accessory protein, from rat liver.

Although cell-free extracts prepared from several types of free-living cells, including Ehrlich tumor cells, macrophages and sea-urchin eggs, readily form gels under low Ca2+ conditions, no such ability to induce actin-related gel has been detected in tissue-cell extracts. Ca2+ -insensitive gelation activity was discovered, however, in several tissue-cell extracts, including liver and brain, provided that the extracts were supplemented with skeletal muscle actin. Based on sodium dodecylsulfate/polyacrylamide gel electrophoretic analysis of the gel, these extracts seem to contain both a Ca2+ -insensitive gelation factor and Ca2+ -sensitive one, actinogelin. A procedure for purification of actinogelin from rat liver was developed, and the properties of actinogelin thus purified were compared with those of Ehrlich tumor cell actinogelin. No appreciable difference was found in these two proteins, and Ca2+ sensitivity (50% inhibition of gelation at 1 microM) was very similar. Some of the molecular characteristics are described, and the importance of the presence of actinogelin in tissue cells is discussed.

Actins↗
PubMed1982

Viral proteins in cell fusion.

F (fusion) and HANA (hemagglutinin and neuraminidase) glycoproteins of HVJ (Sendai virus) were purified and characterized. The NH2-terminal hydrophobic region of the F1 (larger) subunit of F (fusion)-glycoprotein seems to be required for the hemolytic and cell fusion-inducing activity of the virus for the following reasons. (1) Selective splitting off of a 2,500-3,500 dalton segment from the NH2-terminal region of F1 by chymotrypsin or thermolysin resulted in inactivation of the biological activities of HVJ. (2) At least a part of this region may be exposed to the surrounding medium, since it is preferentially iodinated and is easily split by aminopeptidase M, chymotrypsin, and thermolysin. Tryptic digestion, which does not remove the NH2-terminal region but produce nicking of F1 subunit to subfragments F1a (larger one) and F1b (smaller one), resulted in substantial structural changes evidenced by circular dichroism measurement and iodination by lactoperoxidase method. Trypsin-digested F seems to have the NH2-terminal hydrophobic region buried within hydrophobic interior of the protein (or in the lipid bilayers). Based on these and other results, we propose a hypothesis featuring direct interaction of the hydrophbic region with the lipid bilayers of the target-cell membrane as an important step in fusion reactions between the viral envelope and cell membranes.

Animals↗
PubMed1981

Virus-induced fusion of human erythrocyte ghosts. I. Effects of macromolecules on the final stages of the fusion reaction.

Human erythrocyte ghosts prepared by hypotonic hemolysis can be fused by Sendai virus, provided that certain macromolecules (bovine serum albumin, dextran and others) are sequestered in the ghosts. Since fusion of the ghosts is dependent on intactness of the F(fusion)-glycoprotein of the virion, and since the other requirements for this reaction are also similar to those for the Sendai virus-induced fusion of intact erythrocytes, this system can be used as a model for the Sendai virus-induced cell fusion reaction. Sequestered macromolecules seem to be required for rounding of locally fused ghosts. Under low osmotic swelling conditions, such as use of ghosts sealed without macromolecules or using bovine serum albumin-loaded ghosts sealed in the presence of external macromolecules, no apparently complete cell fusion (large spherical polyghost formation) could be observed. Even under these conditions, however, occurrence of local cell fusion could be demonstrated either by transfer of fluorescent-labeled albumin from one ghost to an other, or by observation of polyghost formation after osmotic swelling in the cold. Thus, final stages of the fusion reaction can be divided into local cell-cell fusion which could not be observed by phase-contrast microscopy, and rounding (i.e. formation of spherical polyghosts). For the observation of fusion of ghosts, the last step seems to be important.

Albumins↗
PubMed1981

The preparation of cell fusion-inducing proteoliposomes from purified glycoproteins of HVJ (Sendai virus) and chemically defined lipids.

Cell fusion-inducing (fusogenic) proteoliposomes of defined chemical composition were reconstituted from purified glycoproteins of hemagglutinating virus of Japan (Sendai virus) either with lipids extracted from the virus particles or with a chemically defined lipid mixture. Cell fusion reactions induced by the reconstituted system have several important characteristics similar to the virus-induced fusion reaction: fusogenic activity of the proteoliposomes depends on the presence of active fusion protein in the vesicles and, in the case of Ehrlich tumor cells, the fusion is almost completely inhibited by adding cytochalasin D to a final concentration of 4 microgram/ml. The only known difference between the original and reconstituted systems is that a greater amount of the latter is necessary for the same degree of fusogenic activity. Thus, the reconstituted system can be used as a model for the Sendai virus-induced fusion reaction. A lipid mixture (phosphatidylcholine:phosphatidylethanolamine:phosphatidylserine:sphingomyelin = 1:2:1:1, by weight, and cholesterol equimolar to the total phospholipids) similar to that of the virion was active for reconstitution, whereas a mixture containing the same composition of phospholipids but no cholesterol, and ones containing cholesterol with only a single species of phospholipid were not reconstitutively active.

Animals↗
PubMed1981

Rheological studies on calcium-sensitive gelation of actin filaments by actinogelin.

Actinogelin, a regulatory protein of cell motility, enhanced gelation of actin filaments in the absence of calcium ions, only on standing still or with very low velocity gradients ( less than 0.1 s-1). The Ca2+-sensitive action of actinogelin on action filaments was dependent on a weak external force. In the presence of a micromolar level of Ca2+, actinogelin did not affect the network formation of actin filaments at all.

Actins↗
PubMed1978

Redistribution of intramembrane particles of human erythrocytes induced by HVJ (Sendai virus): a prerequisite for the virus-induced cell fusion.

Aggregation of intramembrane particles of human erythrocytes was found to be induced by HVJ (Sendai virus) under conditions which lead to cell fusion. Degree of polyerythrocyte formation was compared under a variety of conditions with extent of cluster formation observed with the same preparations. Both structural changes of the membranes, ie, fusion and clustering of the particles, behaved very similarly under widely different virus-to-cell ratios and over the time course of cell fusion. Furthermore, by inclusion of high concentrations of antispectrin antibodies within the ghosts, inhibition of clustering of intramembrane particles and hindrance of virus-induced cell fusion were found to occur simultaneously. Antibodies by themselves did not induce aggregation of particles under isotonic conditions, whereas particle clustering could be induced under hypotonic conditions at antibody concentrations causing partial cross-linking of spectrin molecules. In conclusion, clustering of intramembrane particles seems to be required for virus-induced fusion of human erythrocytes.

Antigen-Antibody Reactions↗