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Biomedical subjects

T Osawa

Publications and source records attributed to T Osawa.

At least 433 records · Page 24Linked to original sources
PubMed1979

Activation of membrane phospholipase A by guinea pig lymphotoxin (GLT).

The effect of GLT on target cells (L.P3 cells) labeled with radioactive fatty acids was examined. After incubation for 1 or 2 hr, no change in the survival ratio was observed, but radioactive fatty acid was released from phospholipids of the cells. When incubation was continued for 4 or 5 hr, the survival ratio was decreased with a concomitant increase of the radioactivity of triglyceride of the target cells and enhancement of calcium uptake into the target cells. These results could be explained by activation of membrane-bound phospholipase A after the binding of GLT to cell surface receptors.

Animals↗
PubMed1979

Kinetics of B-lymphocytes stimulation by pokeweed Pa-1 mitogen and bacterial lipopolysaccharide.

The presence of two subpopulations in mouse B lymphocytes responding to pokeweed Pa-1 mitogen or bacterial lipopolysaccharide (LPS) in terms of DNA synthesis was demonstrated. The analysis of surface markers of these two subpopulations revealed that one of the subpopulations carried the complement receptor (CR+) and the other lacked the complement receptor (CR-). The kinetics of stimulation by Pa-1 and LPS differed between these two subpopulations. CR+ -B cells exhibited the first peak of DNA synthesis 27 h after the addition of the mitogen, whereas CR- -B cells showed the first maximal response after 39 h. When the responses of CR+ -B cells 27 h and of CR- -B cells 39 h after various pulsed exposures to the mitogen were compared with those after continuous exposures to the mitogen, two successive 3 h exposures (0-3 and 12-15 h for CR+ -B cells; 0-3 and 21-24 h for CR- -B cells) yielded the same level of response as continuous exposure for 27 h (CR+ -B cells) or 39 h (CR- -B cells). These results indicate that both B-cell subpopulations require two signals for maximal stimulation.

Animals↗
PubMed1979

The collaboration of T-cell subsets in the mitogenic stimulation of purified B-cell subpopulations.

A highly purified preparation of mouse B cells showed greatly decreased incorporation of [6-3H]-thymidine when stimulated with pokeweed Pa-1 mitogen or bacterial lipopolysaccharide compared with mouse splenic lymphocytes. This decreased stimulation was restored by the addition of purified T cells, but not macrophages. Nylon-adherent T cells exerted this helper activity only toward complement receptor-positive B cells (CR+B cells). whereas the helper activity of nylon-non-adherent T cells was effective only on complement receptor-negative B cells (CR-B cells). Since the helper activity of nylon-adherent T cells was completely abolished by the treatment with anti-Ia antiserum and complement but that of nylon-non-adherent T cells was not, it was assumed that Ia+T cells were helper cells for CR+B cells and Ia-T cells helper cells for CR-B cells. Moreover, these helper activities of both T-cell subsets were mediated by soluble factors, which were effective just before the onset of DNA synthesis of the corresponding B-cell subpopulations.

Animals↗
PubMed1979

Covalently cross-linked monovalent, divalent, and tetravalent derivatives of concanavalin A.

Dimeric succinyl-concanavalin A was cross-linked with ethylenediamine using 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide a condensing agent. Thus, a divalent dimer and a tetravalent tetramer composed mostly of covalently cross-linked subunits bearing altered net charges were obtained. Photoaffinity labeling of the cross-linked dimer with p-azidophenyl alpha-D-mannopyranoside resulted in a specific label for its saccharide-binding site and yielded a nonvalent dimer and a monovalent dimer (showing no subunit exchange). However, hemagglutination and glycogen precipitation data suggested that the labeled binding site is shielded but not destroyed by the label and can still bind weakly an external saccharide ligand possibly due to unsteadiness of the shielding label. Although nonvalent and monovalent derivatives were mitogenic as well as divalent and tetravalent derivatives for mouse splenic lymphocytes, binding and stimulation experiments indicated that their stimulating efficiencies after binding to the cells were far lower than those of the multivalent counterparts. Their activities were inhibited by methyl alpha-D-mannopyranoside, suggesting that the weak activities of nonvalent and monovalent derivatives were due to the labeled sites entirely and partly, respectively. We suggest that the triggering of lymphocyte mitogenesis by concanavalin A may depend on cross-linkage of cell surface receptors.

Animals↗
PubMed1979

A lectin-like substance from bovine spleen.

A lectin-like substance was isolated and purified from bovine spleen. This protein was named bovine spleen binding protein (BSBP). BSBP has binding activity for sialidase-treated bovine erythrocytes but not for normal erythrocytes. It specifically recognizes terminal galactose residues of sugar moieties of the bovine erythrocyte cell surface. BSBP shows an apparent molecular weight of 240,000. It is an acidic protein having a pI value of 4.8 and containing 13% carbohydrates. It has mitogenic activity against human peripheral lymphocytes. The physiological role of BSBP has not been clarified yet, but it may play a significant role in the clearance of aged erythrocytes which have a decreased amount of sialic acid on the cell surface.

Animals↗
PubMed1978

Isolation and partial characterization of the major sialoglycoprotein of human T-lymphoblastoid cells of a MOLT-4B cell line.

A sialoglycoprotein with an approx. mol.wt. of 95000 was isolated from human lymphoblastoid cells of a MOLT-4B cell line, which was of human T-lymphocyte origin, by ion-exchange chromatography, affinity chromatography on a column of wheat-germ agglutinin-Sepharose and preparative slab-gel electrophoresis. The localization of this glycoprotein on the cell surface was indicated by surface labelling by the periodate/NaB3H4 and lactoperoxidase-catalysed iodination methods. Carbohydrate analyses of this glycoprotein revealed that its total carbohydrate content is 28% (w/w), and it contains fucose, galactose, mannose, N-acetylglucosamine, N-acetylgalactosamine and sialic acid in molar proportions 1.0:4.0:3.7:3.5:1.2:2.5, suggesting that it has two types of sugar chain, i.e. sugar chains like those of serum glycoproteins and sugar chains of the type found in mucins. Actually, alkaline borohydride treatment of this glycoprotein yielded tri- and tetra-saccharide, the latter containing 1 molecule of fucose in addition to each molecule of galactose, N-acetylgalactosamine and sialic acid. This glycoprotein bound to Ricinus communis agglutinin and concanavalin A as well as to wheat-germ agglutinin.

Borohydrides↗
PubMed1978

Carbohydrate-binding specificity of pokeweed mitogens.

The carbohydrate-binding specificity of two pokeweed (Phytolacca americana) mitogens (Pa-1 and Pa-2) was investigated by means of hemagglutination inhibition assays and the quantitative inhibition of the binding of 125I-labeled lectins to human erythrocytes using various oligosaccharides, glycopeptides and glycoproteins as hapten inhibitors. Among the inhibitors employed in this study, chitin oligosaccharides and the glycopeptides and glycoproteins which bear sugar chains of the type found in serum glycoproteins, particularly PAS-1 glycoprotein and band-3 glycoprotein of human erythrocyte membranes, exerted strong inhibitory activity. The inhibitory constants of band-3 glycoprotein toward the binding of both mitogens to human erythrocytes were found to be very close to the association constants of the mitogens to the cells. Furthermore, the results of competitive binding studies between Pa-1 and Pa-2 indicated that these mitogens share a common oligosaccharide chains on the erythrocyte surface. To isolate the membrane receptors for these two mitogens, the solubilized membranes of human erythrocytes were subjected to affinity chromatographies using Pa-1-Sepharose 4B and Pa-2-Sepharose 4B as specific adsorbents. In both cases of these two specific adsorbents, band-3 glycoprotein was found to bind most strongly. These results suggest that two pokeweed mitogens have essentially the same carbohydrate-binding specificity and they bind primarily to the sugar chains of band-3 glycoprotein, possibly to the core structure of the sugar chains containing a di-N-acetylchitobiose moiety, on human erythrocytes.

Binding, Competitive↗
PubMed1978

The nature of human blood group A3 erythrocytes.

A population of human erythrocytes (free A3 cells) which was entirely unagglutinable with anti-A hemagglutinins was successfully separated from human blood group A3 erythrocytes by affinity chromatography on a column of lima bean anti-A hemagglutinin (LBH)-Sepharose. The hemagglutinating and the binding properties of free A3 cells with purified LBH and purified eel serum anti-H hemagglutinin (ESH) were investigated. It has been revealed that there exists a bulk of H antigens on free A3 cells, whereas the number of A antigens on a free A3 cell is only 9% of that on an A1 cell. However, no appreciable difference was observed in the binding constants of A1 and free A3 cells to LBH and ESH. From these results it is assumed that the structure of the A antigens on free A3 cells is identical with, or at least similar to, that on A1 cells, but the density of the antigens on the surface of free A3 cells is too low to induce the agglutination of the cells with LBH or anti-A serum.

ABO Blood-Group System↗
PubMed1978

Lymphocyte-potentiating factor from human peripheral blood adherent cells.

Low-molecular-weight factor, which can restore the diminished concanavalin A (Con A) response of adherent-cell-depleted human peripheral blood lymphocytes, was partially purified from the culture supernatant of human peripheral blood adherent cells by ion-exchange column chromatography, gel filtration and preparative paper chromatography. This factor apparently has a mechanism of action distinct from that of 2-mercaptoethanol. It affects the cells just before the onset of DNA synthesis possibly as one of the second signals in the Con-A-induced activation of human peripheral blood lymphocytes. However, it was demonstrated that the effective activation of lymphoyctes also required the presentation of Con A by adherent cells to lymphocytes at the triggering stage of the activation, indicating that adherent cells have two distinct functions in the Con-A-induced activation of lymphocytes, i.e. the the presentation of Con A to lymphoyctes and the elaboration of soluble factors.

Animals↗
PubMed1978

Secondarily generalized convulsive seizures induced by daily amygdaloid stimulation in rhesus monkeys.

Amygdaloid kindling in rhesus monkeys resulted in development of secondarily generalized convulsive seizures in an average of 196 days. Prior pharmacologic (bemegride) kindling accelerated this seizure development in one animal. None of the animals reached the stage 5 primary generalized seizure of baboons (Papio papio), even after 400 daily amygdaloid stimulations. Seizure stage instability, with frequent regression to an earlier stage, and the difficulty of establishing a generalized seizure triggering threshold in most of the rhesus monkeys, contrasts with our experiences in Papio papio. Thus, differences in the speed of kindling and in the quality of kindled convulsion between rhesus monkeys and epileptic baboons probably reflect the presence or absence of an epileptogenic predisposition in these two species. The difficulty of developing convulsive seizure in rhesus monkeys suggests that this species is particularly suited for the study of partial complex seizure. These studies indicate that the abrupt onset of human epilepsy with a fully developed convulsive seizure must represent and overwhelming central pathophysiologic event resulting from an endogenous, exogenous or a combined insult interacting with a genetically predisposed seizure susceptibility.

Amygdala↗
PubMed1978

Membrane receptors of human erythrocytes for bacterial lipopolysaccharide (LPS).

The binding specificity of bacterial lipopolysaccharide (LPS) was investigated by inhibition experiments of the binding of 3H-labelled Escherichia coli lipopolysaccharide (LPS) AND 3H-labelled Salmonella minnesota R595 glycolipid and lipid A to human erythrocytes using various glycoproteins as inhibitors. PAS-1 glycoprotein and band-3 glycoprotein of human erythrocyte membranes exerted strong inhibitory activity. To characterize membrane receptors for LPS, solubilized membranes of human erythrocytes were subjected to affinity chromatography with an affinity adsorbent prepared by coupling S. minnesota R595 glycolipid to activated Sepharose 4B. Band-3 and PAS-1 glycoproteins were identified as major receptor sites.

Binding Sites↗