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Biomedical subjects

T Yasuda

Publications and source records attributed to T Yasuda.

At least 955 records · Page 53Linked to original sources
PubMed1977

Immunogenicity of liposomal model membranes in mice: dependence on phospholipid composition.

This investigation demonstrated that antigenic expression in liposomal model membranes may be markedly influenced by phospholipid composition. Incorporation of dinitrophenylaminocaproylphosphatidylethanolamine (Dnp-Cap-PE) into egg lecithin/cholesterol/dicetylphosphate bilayers did not significantly enhance the response of AKR mice to this synthetic amphipathic antigen. In contrast, the immunogenicity of Dnp-Cap-PE was increased (as measured by either plaque-forming cell frequency of hemagglutination titer) after its insertion into liposomes prepared with beef sphingomyelin instead of egg lecithin. We also show that the response to the Dnp-Cap determinant can be stimulated by the presence of lipid A in the same bilayers without altering the relative immunogenic potency of the sphingomyelin and lecithin liposomes; similarly, incorporation of this mitogen into sphingomyelin liposomes produced a greater polyclonal (nonspecific) response. The response to Dnp-Cap-PE-sensitized liposomes (with or without lipid A) prepared with a series of synthetic phosphatidylcholines (distearoyl-, dipalmitoyl-, dimyristoyl-, dilauroyl-, dioleoyl-) suggests a direct correlation between liposomal immunogenicity and transition temperature of the phospholipid.

Animals↗
PubMed1977

Detection of nucleoside Q precursor in methyl-deficient E.coli tRNA.

32P-Labeled tRNAAsn was isolated from methyl-deficient E. coli tRNA. Nucleotide sequence analysis showed that tRNAAsn contains three derivatives of the Q nucleoside, possibly Q precursors, in addition to guanosine in the first position of the anticodon. One of the Q precursors was isolated on a large scale. Its UV spectra were identical with those of normal Q, indicating that 7-deazaguanosine structure having a side chain at position C-7 is complete in the Q precursor. No radioactivity was incorporated into Q or Q precursors from either [methyl-14C]methionine, [1-14C]methionine or [U-14C]methionine, showing that methionine was not directly involved in the formation of Q.

Asparagine↗
PubMed1977

In vitro and in vivo antibacterial activity of T-1220, a new semisynthetic penicillin.

T-1220, sodium 6-[d-(-)-alpha-(4-ethyl-2,3-dioxo-1-piperazinylcarbonyl-amino)- alpha-phenylacetamido] penicillanate, is a new semisynthetic penicillin derivative that possesses a broad spectrum of in vitro antibacterial activity against gram-positive and gram-negative bacteria. T-1220 is more effective than carbenicillin (CB-PC) against Pseudomonas aeruginosa, Klebsiella pneumoniae, Proteus species, and Serratia marcescens. Addition of human serum to culture media did not significantly alter the antibacterial activity of T-1220. Greater bactericidal activity toward various strains of gram-negative bacteria was demonstrated with T-1220 than with CB-PC. T-1220, like penicillin G, was hydrolyzed by penicillinase, but was sable to a type IV penicillinase produced by P. aeruginosa strains. In vivo antibacterial activities of T-1220, ampicillin (AB-PC), and CB-PC were compared, using systemic infections of mice with P. aeruginosa, K. pneumoniae, and Escherichia coli. The 50% effective doses (milligrams per kilogram) of T-1220 were consistently lower than those of AB-PC and CB-PC.

Ampicillin↗
PubMed1977

Deficiency of S-adenosylmethionine-homocysteine methyltransferase activity in hepatoma cells.

S-Adenosylmethionine-homocysteine methyltransferase, which catalyzes synthesis of methionine from homocysteine, with the use of S-adenosylmethionine as the methyl donor, is absent in tumor tissue such as rat ascites hepatoma and Morris hepatoma but is present in rat liver homogenate. Absence of the enzymatic activity in tumor cells is not due to the action of an inhibitor. S-Adenosylhomocysteine hydrolase, however, is present in both rat liver and hepatoma tissue.

Animals↗
PubMed1977

Immunogenic properties of liposomal model membranes in mice.

Liposomal model membranes, which were prepared with sphingomyelin, cholesterol, and dicetylphosphate, and sensitized by incorporation of either dinitrophenyl-epsilon-aminocaproylphosphatidylethanolamine (DNP-Cap-PE) or fluoresceinthiocarbamylphosphatidylethanolamine (Fl-PE), can induce a hapten-specific humoral response when administered to AKR mice in saline. The magnitude of the response (as measured by the appearance of direct plaque forming cells in the spleen and/or serum antibody titer) is dependent on liposomal dose, the epitope density of the PE derivative in the liposomes, and the time after immunization. In the case of DNP-Cap-PE sensitized liposomes, only a minor IgG response (as measured by the production of indirect plaques or mercaptoethanol-resistant antibody) could be detected after either primary or secondary immunization. Together with the finding that mice deficient in, or depleted of, thymus-derived (T) lymphocytes respond to liposomes containing DNP-Cap-PE, the available data indicate that these liposomes are primarily T cell-independent immunogens. The liposomes are also immunogenic in other inbred mice strains (differing in H-2 haplotype), although the magnitude of the response varies sufficiently to suggest the existence of high, intermediate, and low responders. On the basis of this preliminary survey, further examination of the possibility that the immunogenicity of liposomes may be under genetic control seems warranted.

Animals↗