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T Osawa

Publications and source records attributed to T Osawa.

At least 451 records · Page 25Linked to original sources
PubMed1977

Isolation and characterization of membrane receptors for pokeweed mitogens from mouse lymphocytes.

The major glycoproteins that bind pokeweek B-cell mitogen (Pa-1) and pokeweed T-cell mitogen (Pa-2) were isolated and identified from bone-marrow-derived lymphocytes (B-cells) and thymus-derived lymphocytes (T-cells) of C3H/He mice. The surfaces of the cells were 125I-labelled by using the enzyme lactoperoxidase, and the plasma membranes were isolated from the 125I-labelled cells. These membranes were solubilized with Triton X-100 and subjected to affinity chromatography on the affinity adsorbent prepared by coupling mitogen Pa-1 or Pa-2 to activated Sepharose 4B. The glycoproteins specifically eluted with di-N-acetylchitobiose from the affinity adsorbents were analysed according to their mobility on polyacrylamide-gel electrophoresis in sodium dodecyl sulphate. These glycoproteins were further identified by immunoprecipitation with specific antisera. Immunoglobulins, possibly immunoglobulins M and D, were identified in the eluate from the B-cell membranes, but they were not detected in the eluate from the T-cell membranes. The histocompatibility-2-complex proteins (H-2D, H-2K and Ia antigens) were found to be major receptor sites for the pokeweed mitogens on both B-cells and T-cells. However, mitogen Pa-1 (B-cell) has a stronger affinity to Ia antigens than does mitogen Pa-2 (T-cell).

Animals↗
PubMed1977

The structure of unit B-type glycopeptides from porcine thyroglobulin.

The structure of Unit B-type glycopeptides (monosialo-type and disialo-type) was investigated by Smith degradation, methyllation, and mass spectral analysis. These glycopeptides contain three peripheral sugar chains. Two are composed of D-galactose residues linked at C-6 and 2-acetamido-2-deoxy-D-glucose residues linked at C-4, and the other is composed of a D-galactose residues linked at C-6, a 2-acetamido-2-deoxy-D-glucose residues linked at C-4, and a D-mannose residue linked at C-2. Most of these peripheral sugar chains are linked to two inner D-mannose residues which are substituted at C-3 and C-6, and constitute branching points. L-Fucose and N-acetyl-neuraminic acid residues are nonreducing terminal groups, and a di-N-acetylchitobiose moiety is linked to an asparagine residue in the peptide moiety. By methylation analysis of the oligosaccharide obtained by hydrazinolysis of the disialoglycopeptide, the L-fucose residues was found to be linked to C-6 of the 2-acetamido-2-deoxy-D-glucose residue linked to the asparagine residue. From these results, and from the previously reported data on the sugar sequence and the anomeric configurations of the linkages between sugar residues, structures for these glycopeptides are proposed.

Animals↗
PubMed1977

Chromosomal location of a structural gene for the RNA polymerase sigma factor in Escherichia coli.

A set of F' strains of Escherichia coli K-12 partially diploid for various chromosomal segments has been examined for possible gene dosage effects in the synthesis of sigma factor of the DNA-dependent RNA polymerase (RNA nucleotidyltransferase; nucleoside-triphosphate:RNA nucleoti-dyltransferase, EC 2.7.7.6). It was found that all F' strains diploid for the dnaG region synthesize sigma at rates two to three times higher than other F' or F- strains. Moreover, strains of Salmonella typhimurium harboring these F' plasmids produce E. coli sigma in addition to Salmonella sigma. This has been shown on the basis of the finding that Salmonella sigma can be precipitated with antiserum against E. coli RNA polymerase but is distinguishable from E. coli sigma in its mobility in sodium dodecyl sulfate/polyacrylamide gel electrophoresis. E. coli sigma polypeptides thus produced seem to be stable in cells of S. typhimurium. These results indicate that a structural gene for sigma (rpoD) is located at the metC-argG region, probably near the dnaG locus (66 min on the current genetic map of E. coli).

Alleles↗
PubMed1977

Effect of various reagents on the susceptibility of target cells to the cytotoxicity of guinea pig lymphotoxin (GLT).

The cytotoxic activity of guinea pig lymphotoxin (GLT) was increased when the target cells were treated with the following metabolic inhibitors: puromycin, actinomycin D, NaN3, NaF, and 2,4-dinitrophenol, whereas calf serum, N-acetyl-D-galactosamine, colchicine, and vinblastin inhibited GLT-cytotoxicity. Puromycin, an inhibitor of protein synthesis, exhibited the most potent enhancing effect on GLT-cytotoxicity. It seems likely that there are certain cellular metabolic processes depending on cellular protein synthesis which antagonize GLT-cytotoxicity. Taking advantage of this effect of puromycin, a time-saving assay method for GLT-cytotoxicity was developed.

Animals↗
PubMed1977

Morphological microassay and kinetics of the cytotoxicity of guinea pig lymphotoxin.

The kinetics of guinea pig lymphotoxin (GLT)-cytotoxicity on three L cell sublines were studied in detail by a micromethod using morphological distinctions between intact cells and dead cells. The reduction of the intact cell number and increase of the dead one concurrently occurred after a lag time, its length depending upon the GLT concentration ([GLT]). Although different patterns of the changes in the survival ratio (S) were discerned with different sublines, under appropriate conditions, --ln S was proportional to [GLT] and the reciprocal of the initial target cells number. Furthermore, it was shown that the S value at 24 hr was dependent upon the absolute amount of GLT.

Animals↗
PubMed1977

The effect of pulse treatment of target cells with guinea pig lymphotoxin and the nature of its binding to target cells.

In order to investigate the binding of guinea pig lymphotoxin (GLT) to target cells, the reduction of survival ratio (S) after the pulsed exposure of target cells to GLT at 4 degrees C and subsequent incubation at 37 degrees C for 24 hr was examined in detail. The dose response of GLT, and the relation between the S value and the length of pulse treatment demonstrated the saturation and equilibrium of the GLT-binding. It was also shown that the GLT once bound to the target cells dissociated very slowly. Several sugars possessing a terminal beta-galactosyl residue had an inhibitory activity against the effect of pulse treatment. This suggests that GLT binds to receptors on the target cell surface, probably glycoproteins having beta-galactosyl residues as terminal sugar residues. The trypsin treatment of GLT-pulsed target cells restored survival ratios and this restoration was dependent upon the time of trypsin treatment. This suggests that the stage of the association of GLT to target cells changes from trypsin-sensitive into trypsin-insensitive.

Animals↗
PubMed1977

[Lymphokines].

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Animals↗
PubMed1977

Isolation of glycopeptides from the lectin-stimulated human peripheral lymphocyte cell surface.

Three radioactive glycopeptides were isolated from human peripheral lymphocytes stimulated with Wistaria floribunda mitogen in the presence of D-[14C]glucosamine hydrochloride by mild trypsin digestion followed by gel filtration and preparative high-voltage paper electrophoresis. The carbohydrate compositions of these glycopeptides suggest that one has a sugar chain of the type found in serum glycoproteins, consisting of sialic acid, galactose, N-acetylglucosamine, mannose, and fucose in a molar ratio of 2:2:4:2:1, and the other two have sugar chains like those of mucins, consisting of sialic acid, galactose, and N-acetylgalactosamine in a molar ratio of 1 or 2:1:1. The results of enzymic degradation with purified glycosidases indicate that these sugar chains are similar in structure to their counterparts in human erythrocyte membranes.

Carbohydrates↗
PubMed1976

Elucidation of lectin receptors by quantitative inhibition of lectin binding to human erythrocytes and lymphocytes.

The binding to normal and sialidase-treated human erythrocytes and lymphocytes of four 125I-labeled lectins [Maackia amurensis hemagglutinins (MAM and MAH), Ricinus communis hemagglutinin (RCH), and Bauhinia purpurea hemagglutinin (BPH)] was studied in detail. The quantitative inhibition assays against the lectin binding to the cells were also performed with various glyco-proteins and glycopeptides as inhibitors. The comparison of the inhibition constants of the inhibitors thus obtained with the association constants of the lectins to the cells permitted estimation of the relative receptor activities of cell surface glyco-proteins toward the lectins.

Binding Sites↗