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Biomedical subjects

T Osawa

Publications and source records attributed to T Osawa.

At least 343 records · Page 19Linked to original sources
PubMed1983

Induction of increased calcium uptake in liposomes having membrane proteins of chicken erythrocytes by S-adenosylmethionine.

Liposomes having membrane proteins of chicken erythrocytes were prepared and the effect of S-adenosylmethionine on 45Ca2+ uptake into the liposomes was investigated. S-Adenosylmethionine, a donor of methyl groups in enzymatic methylation, induced an increase of 45Ca2+ uptake into the proteoliposomes with membrane proteins but not into the liposomes without membrane proteins. Increased release of 45Ca2+ from the inside of the proteoliposomes was also induced by S-adenosylmethionine. These increases of uptake and release of 45Ca2+ were inhibited by S-adenosylhomocystein, an inhibitor of enzymatic methylation. Furthermore, membrane proteins from chicken erythrocytes showed protein and phospholipid methyltransferase activities. The uptake of other materials, 3-0-[methyl-3H]glucose, alpha-[1-14C]aminoisobutyric acid, 42K+ and 54Mn2+, into the proteoliposomes was not increased by S-adenosylmethionine. These results suggest that enzymatic methylation of membrane components may have an important role in the regulation of calcium transport in the chicken erythrocyte membrane and this regulation is rather specific for calcium.

Animals↗
PubMed1983

The carbohydrate moiety of human platelet glycocalicin.

Glycocalicin, a predominant glycoprotein on the human platelet surface, has been purified from a platelet suspension by sonication, ammonium sulfate precipitation and acid treatment followed by chromatography on columns of wheat germ agglutinin-Sepharose and Sephacryl S-300. Ser/Thr-linked (O-linked) oligosaccharides were released by alkaline borohydride treatment, and fractionated by high performance liquid chromatography with an anion-exchange resin. The structure of a major oligosaccharide alditol separated by high performance liquid chromatography was investigated by a combination of compositional analyses, methylation and glycosidase treatments, and proposed to be a hexasaccharide alditol, NeuAc alpha 2-3Gal beta 1-4GlcNAc beta 1-6(NeuAc alpha 2-3Gal beta 1-3) N-acetylgalactosaminitol. We also found some sugar units which appeared to be intermediates in the biosynthetic pathway of the major hexasaccharide.

Blood Platelets↗
PubMed1983

Human T-cell hybridomas producing lymphokines. II. Enhancement of lymphotoxin secretion from human T-cell hybridomas by phorbol myristate acetate.

Human lymphotoxin (LT)-producing T-cell hybridomas were constructed by fusing concanavalin A-activated human peripheral blood lymphocytes with emetine-actinomycin D-pretreated human acute lymphatic leukemia cells. LT secretion from these hybridomas was considerably enhanced by stimulation with phorbol-12-myristate-13-acetate (PMA) and concanavalin A or PMA alone. A study using cloned hybrid lines revealed that PMA/Con A acted directly on the LT-producing clones. Furthermore, PMA/Con A stimulated A-B9-24, one of the cloned hybridomas, and secreted fourfold larger amounts of LT under serum-free conditions than under serum-containing conditions. However, MIF/MAF and LT-producing cloned hybrid line E10-20 secreted rather decreased amounts of MIF/MAF when stimulated with PMA, while the LT secretion from the same hybridoma was enhanced with PMA.

Clone Cells↗
PubMed1983

Accessory functions and mutual cooperation of murine macrophages and dendritic cells.

In this study the antigen-presenting functions of murine splenic dendritic cells (DC) and macrophages (M phi) have been compared. DC and M phi were pulsed with keyhole limpet hemocyanin (KLH) and found to contain approximately 92% and 50% Ia-positive cells, respectively. The two KLH-pulsed cell populations had almost equal ability to stimulate KLH-immune T cells. The antigen-presenting functions of DC and M phi were compared by measuring the capacity of KLH-pulsed, UV-irradiated cells, which failed to secrete interleukin 1 (IL 1), to stimulate KLH-immune T cells when each culture was supplemented with an equal amount of exogenous IL 1. The antigen-presenting capacity of DC was always greater than that of M phi. Coculturing of the two kinds of accessory cells upon KLH pulsing resulted in enhanced antigen-presenting capacity of the mixture relative to the same number of each accessory cell type. That is, collaboration between them in antigen presentation was clearly observed. However, direct contact between DC and M phi was not obligatory for this collaboration. Furthermore, we found that different types of soluble factors released by each of them might be responsible for the collaboration. In addition, supernatants of concanavalin A-stimulated spleen cells augmented the antigen-presenting function of only M phi. Finally, the antigen-presenting function of DC and M phi from athymic mice was almost the same as that from control mice.

Animals↗
PubMed1983

Intragenic localization of amber and temperature-sensitive rpoD mutations affecting RNA polymerase sigma factor of Escherichia coli.

A set of multi-copy plasmids carrying part or all of the rpoD gene of Escherichia coli have been used to localize several amber and temperature-sensitive mutations affecting RNA polymerase sigma factor. In contrast to the plasmid carrying a complete rpoD sequence, plasmids carrying part of rpoD could not complement any of the rpoD mutations tested. However, the mutants harboring some of the latter plasmids produced wild-type recombinants at high frequency, provided that they carry the recA+ gene. The results permitted us to localize the rpoD mutations into one of the three intragenic segments. Thus, the rpoD285(ts) mutation (Harris et al. 1978) was located on the 0.8 kilobase segment defined by the Bg/II and BamHI sites in the middle segment, and the amber mutation rpoD40 (Osawa and Yura 1980) in the N-terminal 0.8 kilobase segment. Four additional amber mutations were also identified and classified into one of the segments of rpoD. It was further revealed that plasmids carrying certain amber mutations (rpoD47 or rpoD63) in the C-terminal segment of rpoD render all rpoD mutants tested (including rpoD47 and rpoD63 mutants themselves) able to grow at the restrictive condition. It is suggested that the enhanced synthesis of incomplete sigma polypeptides encoded by rpoD47 or rpoD63 phenotypically suppresses the defects in sigma function at least partially.

Bacterial Proteins↗
PubMed1983

Human T-cell hybridomas producing migration inhibitory factor and macrophage activating factors.

Studies were carried out to determine the heterogeneity of factors that affect macrophage functions using human hybridomas constructed by fusing PHA-activated human peripheral blood lymphocytes with emetine-actinomycin D-pretreated cloned human acute lymphatic leukemia cells (CEM). Three assay systems were used to investigate the activity of the macrophage migration inhibitory factor and of the macrophage activation factors for glucose consumption (MAF-G) and for O2- formation. In the culture supernatant of hybridomas and other cells, various combinations of these activities were detected. The results indicate that at least three molecules are concerned in each of these activities.

Animals↗
PubMed1983

Enrichment of IL-2-producer T cells from mouse spleen by use of Bauhinia purpurea lectin.

Bauhinia purpurea agglutinin (BpA) was used to enrich the interleukin 2 (IL 2)-producing T-cell subset from mouse spleen. IL 2 was found to be produced by the BpA-non-agglutinated (BpA-) T cells of mouse spleen on stimulation with concanavalin A (Con A). The degree of IL 2 production by BpA-agglutinated (BpA+) T cells was significantly low. The proliferative response to Con A of BpA- T cells was not influenced by the addition of exogenous IL 2, whereas BpA+ T cells were partially dependent on the exogenous addition of IL 2 in the proliferative response.

Animals↗
PubMed1983

The reactivities of Bauhinia purpurea and Lens culinaris lectins to mouse B Lymphocytes and their subsets.

The use of lectins for the separation of murine spleen lymphocyte subsets was examined. Bauhinia purpurea agglutinin was found to be effective for the enrichment of B cells by differential agglutination. When the differential agglutination technique using lectins was applied to the separation of B cell subsets, Lens culinaris agglutinin was found to be able to fractionate B cells into high responding and low responding subsets for dextran sulfate. A different expression of cell surface IgD was also observed between the cell populations showing different agglutinability with Lens culinaris agglutinin.

Animals↗
PubMed1983

The effect of concanavalin A on the incorporation of fatty acids into lymphocyte phospholipids.

The incorporation of radioactively labeled palmitic, stearic, oleic, linoleic and arachidonic acid into the phospholipids of lymphocytes was studied. When concanavalin A (Con A) was added a gradual increase in the incorporation was found over the period investigated (0-4 h). Changes were not detected over the first 15 min. The increased incorporation at 4 h was shown to be Con A dose dependent and the Con A concentrations for the maximum effect on fatty acid incorporation (at 4 h) and on [3H]thymidine incorporation (at 72 h) were the same. With the exception of stearic acid all the other fatty acids showed an increased incorporation into phosphatidyl choline on addition of Con A, linoleic and oleic acids also had an increased incorporation into phosphatidyl ethanolamine.

Animals↗
PubMed1983

Purification and characterization of two types of Cytisus multiflorus hemagglutinin by affinity chromatography.

Two hemagglutinins were separated from extracts of Cytisus multiflorus seeds by successive affinity chromatographies on columns of galactose- and di- N-acetylchitobiose-Sepharose 4B. One was found to be inhibited by di- N-acetylchitobiose or tri- N-acetylchitotriose and shown to possess anti-H(O) activity [Cytisus-type anti-H(O) hemagglutinin designated as Cytisus multiflorus hemagglutinin I]. The other, which was not a blood group-specific hemagglutinin, was inhibited by galactose or lactose (hemagglutinin II). Hemagglutinins I and II were further purified by gel filtration on Sephacryl S-300. These preparations were homogeneous as judged by polyacrylamide gel electrophoresis and gel filtration. The molecular weights of the purified hemagglutinins I and II were found to be 86000 by sedimentation equilibrium analysis and 80000 by gel filtration. On disc gel electrophoresis in the presence of sodium dodecyl sulfate and dithiothreitol, both hemagglutinins gave a single component of a molecular weight of 42000 +/- 2000, suggesting that these hemagglutinins are dimeric proteins of two identical subunits. Hemagglutinins I and II contain 2.7% and 1.5% carbohydrate, respectively, and only very small amounts of cystine and methionine were detected, but they are rich in aspartic acid and serine. Treatment of human O erythrocytes with a purified H-decomposing enzyme (alpha-L-fucosidase from Bacillus fulminans abolished the agglutinability of the cells with hemagglutinin I. This indicates that the L-fucosyl residue is important even for the H-specificity detected by this di-N-acetylchitobiose-specific hemagglutinin I.

Amino Acids↗
PubMed1983

Establishment and characterization of continuous murine non-specific suppressor T cell lines.

Normal mouse spleen cells were activated by Con A and suppressor T cells were enriched by the use of peanut agglutinin (PNA). Cells of the enriched suppressor T cell fraction were further cultured in a medium containing T cell growth factor (TCGF) and the suppressor T cell lines were established. These cell lines have been growing in culture for more than one year and retained surface characteristics of Thy-1+, Lyt-1-, 2- and bear receptor sites for PNA. The suppressor clones exerted an inhibitory effect on in vitro antigen specific and antigen nonspecific PFC responses. The culture supernatant of these clones had a suppressive effect on the in vitro humoral responses, indicating that a soluble factor mediates at least partly the suppressive activity of the antigen nonspecific suppressor T cells. Moreover, it was revealed that the suppressor cells must exist at an early stage of PFC culture to exert their activity.

Animals↗