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Biomedical subjects

T Koike

Publications and source records attributed to T Koike.

At least 793 records · Page 44Linked to original sources
PubMed1980

Stacking properties of a highly hydrophobic dinucleotide sequence, N6, N6-dimethyladenylyl(3' leads to 5')N6, N6-dimethyladenosine, occurring in 16--18-S ribosomal RNA.

The thermal denaturation ultraviolet absorption spectra of N6,N6-dimethyladenylyl(3' leads to 5')-N6,N6-dimethyladenosine (m2(6)Apm2(6)A), which is a common sequence in 16--18-S ribosomal RNA, in aqueous buffer at pH 7 have been measured over the temperature range 3-90 degrees C. These data have been used to determine the thermodynamic quantitites associated with the intramolecular stacking equilibria. At 25 degrees C in neutral aqueous solution m2(6)Apmw(6)A exists mainly (about 81%) as a stacked form, so that the stacking interactions are stronger than those in the parent unmethylated adenylyl-(3'-5')adenosine (ApA), where about 52% is stacked. From the parameters of delta H and delta S, it is concluded that 'hidden' hydrophobic inteactions are of prime importance in the enhanced stability of m2(6)Apm2(6)A. Transphosphorylation reaction of ApA and m2(6)Apm2(6)A to form the corresponding cyclic 2',3'-phosphates has been studied. First-order rate constants at 25 degrees C for the reactions, which are base-catalyzed, have been obtained. Insertion of two methyl groups at N-6 of ApA reduces the rate of transphosphorylation. Effects of stacking on rates are discussed in the light of reaction mechanisms.

Adenosine↗
PubMed1979

Differential sensitivity of functional subsets of T cells to the cytotoxicity of natural T-lymphocytotoxic autoantibody of systemic lupus erythematosus.

A naturally occurring T-lymphocytotoxic autoantibody (Hu-NTA) in serum from a patient with systemic lupus erythematosus (SLE) showed a differential cytotoxic effect on functionally different T cell subsets as did natural thymocytotoxic autoantibody (NTA) of NZB mice. When the normal peripheral blood lymphocytes were treated, in the presence of complement, with Hu-NTA at a dilution that eliminated 25 to 30% of Hu-NTA-sensitive T cells, there was a marked reduction or a total depletion in the ability of resultant cells to show Con A-activated suppression on the proliferative response of responder cells in mixed lymphocyte reaction. The treatment of PBL in the same manner also resulted in a marked reduction in its responsiveness to Con A and PHA. However, the responder cells to allogeneic stimulator cells in MLR were found to be much more resistant to the cytotoxicity of Hu-NTA than other functional T cell subsets tested. These results suggest that Hu-NTA is responsible for the selective loss of certain functional T cell subsets including suppressor T cells in patients with SLE.

Antilymphocyte Serum↗
PubMed1979

Erythrocyte rosette inhibition as an assay for naturally occurring T lymphocytotoxic antibody in systemic lupus erythematosus.

By means of a modified sheep erythrocyte rosette inhibition assay, we were able to detect naturally occurring lymphocytotoxic antibodies in sera from patients with systemic lupus erythematosus (SLE). The incidence of lymphocytotoxic antibodies was 86% in all SLE patients, and 100% in patients with active disease. Since this assay detects only the antibodies that react with the determinants on T cells or on both T and B cells, it has a great advantage of demonstrating in combination with appropriate absorptions the antibodies specific for T cells. When an appropriate panel of target cells was used, most of the antibodies in SLE sera as detected by this assay appeared to be analogous to a natural thymocytotoxic autoantibody (NTA) of New Zealand mice in its specificity and nature. The changes in the antibody titer of a patient with SLE during the course of disease correlated well with those in the total number of T cells in the blood, the antinuclear antibody titer, and some delayed skin hypersensitivities.

Absorption↗
PubMed1979

Carboxymethyl cellulose stimulation of neurite outgrowth of neuroblastoma cells in culture.

The addition of 1% (w/v) carboxymethyl cellulose to the culture medium induces the formation of neurites of clone N18 neuroblastoma cells even in the presence of normal (5-10%) serum supplement concentrations, which rivals that previously observed by growth in low 0.1% serum. Heavy metal ions associated with the carboxymethyl cellulose were responsible for small increases in the sizes of cell bodies during treatment. Pretreatment of the PC12 pheochromocytoma line of neuroblasts with carboxymethyl cellulose for 1 day prior to their stimulation with nerve growth factor resulted in an acceleration in the rate, but not extent, of neurite outgrowth.

Animals↗