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Biomedical subjects

J Koyama

Publications and source records attributed to J Koyama.

At least 145 records · Page 8Linked to original sources
PubMed1980

Comparative studies on superoxide anion production by polymorphonuclear leukocytes stimulated with various agents.

Guinea-pig peritoneal polymorphonuclear leukocytes promoted superoxide anion (O2(-)) generation when stimulated with soluble antigen-antibody complex, concanavalin A or sodium dodecyl sulfate. The enhancement with antigen-antibody complex or concanavalin A was inhibited with diisopropyl fluorophosphate. On the other hand, the enhancement with sodium dodecyl sulfate was not affected by the inhibitor. L-1-pTosylamido-2-phenylethyl chloromethyl ketone (Tos-PheCH2Cl) and tetrahydrofuran also enhanced O2(-) generation even in the presence of diisopropyl fluorophosphate, while at low concentrations they inhibited O2(-) generation with antigen-antibody complex. These results indicate that a certain diisopropyl fluorophosphate-sensitive factor may be involved in the O2(-)-generating response of leukocytes to antigen-antibody complexes or concanavalin A, but not in that to sodium dodecyl sulfate, Tos-PheCH2Cl or tetrahydrofuran.

Animals↗
PubMed1980

Superoxide anion production from guinea pig macrophages stimulated with immune complexes of different IgG subclasses.

Guinea pig peritoneal macrophages produced superoxide anions (O2-) when reacted with ovalbumin complexes of homologous IgG1 and IgG2 antibodies. In this reaction, IgG2 complexes were about three times as active as IgG1 complexes. But the susceptibility of IgG1 complexes to phagocytosis by the cells appeared to be indistinguishable from that of IgG2 complexes. The avidity of IgG1 complexes in the antigen excess zone for Fc receptors on the cells was lower than that of the IgG2 counterparts. The amount of IgG1 complex bound to the cells, however, did not significantly differ from that of IgG2 complexes when compared using each complex at the equivalence zone which showed maximal effector functions on the cells. The binding of Clq to IgG2 complexes increased markedly the amounts of complexes bound to the cells, but it reduced O2- generation. These results suggest that the difference in abilities of IgG1 and IgG2 complexes to promote O2- generation may be caused by different structures of the Fc parts or their antigen complexes involved in priming macrophages for O2- generation.

Animals↗
PubMed1980

Proteolytic cleavage of an activated subcomponent of the first component of rabbit complement, C1s.

When rabbit C1 purified by affinity chromatography on IgG-Sepharose 6B was chromatographed on DEAE-cellulose in the presence of ethylenediaminetetraacetate, C1s was isolated as two forms, C1s(I) and C1s(II), having different molecular weights. On the other hand, incubation of the C1 with soybean trypsin inhibitor before the chromatography resulted in the isolation of C1s(I) alone, indicating that, during the purification, C1s(II) was derived from C1s(I) by proteolytic cleavage of C1s(I) by a contaminating protease, probably plasmin [EC 3.4.21.7]. In fact, C1s(I) was completely converted to C1s(II) or a C1s(II)-like fragment by highly purified plasmin. Analysis of the polypeptide chain structures revealed that C1s(I), which consisted of H and L chains with molecular weights of 70,000 and 36,000, respectively, was converted to C1s(II) by cleavage of the H chain, since C1s(II) consisted of two chains each with a molecular weight of 37,000. This conversion proceeded without any alteration in C1 esterase activity, but was accompanied by loss of the ability to form C1r-C1s complex.

Animals↗
PubMed1979

Purification and some properties of rabbit C1r.

C1r, an activated subcomponent of the first component of the complement system, was highly purified from rabbit serum by affinity chromatography on IgG-Sepharose 6B followed by column chromatography on CM-Sephadex C-50. The C1r thus purified had a molecular weight of 105,000, consisting of two polypeptide chains connected by disulfide bonds; the molecular weights of the chains were 60,000 and 45,000. The C1r was found to reconstitute C1 complex when it reacted with rabbit C1q and C1s in the presence of Ca2+, since C1s was able to bind to C1q bound on sensitized sheep erythrocytes only in the presence of C1r. On the other hand, and active C1s fragment derived by hydrolysis of the H chain without any loss of C1s activity [J. Biochem. 80, 1423--1427 (1976)] could not bind to C1q even in the presence of C1r. This result indicates that a part of the H chain of C1s not contributing to the structural integrity of an active site may be involved in the binding of C1s to C1r.

Animals↗
PubMed1978

Failure of the usual anti-Ig antibody method for quantitative measurement of low affinity antibodies.

The usual anti-Ig antibody method, consisting of the precipitation of soluble antigen-antibody complexes by heterologous anti-Ig antibody, was applied for quantitative estimation of guinea pig IgG2 anti-ovalbumin and anti-2,4-dinitrophenyl (DNP) antibodies by measuring the maximum amounts of antibody-bound antigens. However, the amounts of antibodies estimated were less than those obtained by other methods: the precipitin reaction, the precipitation of antigen-antibody complexes with 50% saturated ammonium sulfate, and equilibrium dialysis. In particular, the anti-Ig antibody method greatly underestimated the amount of anti-DNP antibody with low affinity for epsilon-DNP-L-lysine. Thus, it was concluded that partial dissociation of the antigen-antibody complexes occurring upon precipitation with anti-Ig antibody made the anti-Ig antibody method unsuitable for quantitative determination of antibodies.

Animals↗
PubMed1977

Immunochemical studies on non-precipitating guinea pig antibody produced by administration of an excessive dose of Bacillus subtilis alpha-amylase.

Administration of an excessive dose of Bacillus subtilis alpha-amylase [EC 3.2.1.1, alpha-1,4-glucan 4-glucanohydrolase] (BalphaA) induced the production of non-precipitating (non-ppt) IgG2 antibody in guinea pigs, whereas immunization with a normal dose produced precipitating (ppt) IgG1 and IgG2 antibodies. The non-ppt IgG2 antibody thus produced could be isolated from the coexisting ppt IgG2 antibody by means of the precipitin reaction at maximum precipitation. The non-ppt antibody was incapable of forming a precipitin arc with BalphaA in a conventional agar plate. In the presence of 4% polyethylene glycol (PEG), however, it formed a single arc which fused completely with those of the ppt IgG1 and IgG2 antibodies. The non-ppt antibody could not fix complement, but inhibited BalphaA activity, though with less efficiency than the ppt antibodies. These properties of the non-ppt IgG2 antibody may be due to a low affinity for BalphaA, since both gel filtration and precipitation of soluble antigen-antibody complexes with 20% PEG showed that the antibody was easily dissociable from BalphaA.

Amylases↗
PubMed1977

Purification and some properties of rabbit C1 inactivator.

C1 inactivator (C1 INA) was highly purified from rabbit serum. C1 INA thus purified was a single polypeptide chain with a molecular weight of 105,000 or 140,000, as estimated by SDS-polyacrylamide gel electrophoresis or gel filtration on Sephadex G-200, respectively. It inhibited rabbit and also human C1, when the C1 activities were measured in terms of hydrolyses of acetylglycyl-L-lysine methylester, N-alpha-acetyl-L-arginine methylester and N-alpha-acetyl-L-tyrosine ethylester. These properties showed that rabbit C1 INA bears a marked structural similarity to human C1 INA. Furthermore, rabbit C1 INA was capable of inhibiting similarly both rabbit C1s and its active fragment lacking a half of the H chain of C1s, indicating that deletion of a half of the H chain did not affect the susceptibility of C1s to the inhibitory activity of C1 INA.

Animals↗
PubMed1977

Sequential IgM and IgG2 anti-DNP antibody responses against DNP-E. coli and DNP-lipopolysacchardies in guinea-pigs.

When 2,4-dinitrophenylated cells (DNP-E. coli) and lipopolysaccharides (DNP-LPS) of Escherichia coli were injected i.p. into guinea-pigs, they were capable of inducing sequential production of IgM and IgG2 anti-DNP antibodies, both of which were substantially thymus-independent, but only a trace of IgG1 anti-DNP antibody was produced. On the other hand, thymus-dependent DNP-bovine serum albumin (DNP-BSA) induced concomitantly both the IgG1 and IgG2 antibody responses in the presence of LPS. Therefore, the preferential IgG2 antibody response against DNP-LPS seems to be elicited with DNP-LPS itself and not by a combination of mitogenic stimulation with LPS and haptenic stimulation with other contaminating substances carrying DNP residues. Furthermore, it may not be related to affinity of the antibodies produced since there was no significant difference in the affinity for DNP residue between the IgG2 and IgG1 anti-DNP antibodies produced with DNP-E. coli and DNP-BSA, respectively.

Animals↗