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Biomedical subjects

Y Miyake

Publications and source records attributed to Y Miyake.

At least 649 records · Page 36Linked to original sources
PubMed1981

Theophylline reduces poly (ADP-ribose) synthetase from chick embryo liver nuclei.

The effect of theophylline on poly(ADP-ribosyl)ation was investigated. The poly(ADP-ribose) synthetase activity in vitro was markedly reduced in the liver nuclei prepared from theophylline-treated chick embryo. This reduction was not due to the enzyme inhibition by theophylline contamination in the nuclear fraction. The hydroxyapatite column chromatographic analysis of [3H]adenosine-labelled poly(ADP-ribose)molecules formed in vivo revealed that the in vivo formation of poly(ADP-ribose)molecules was also decreased by theophylline administration. The theophylline-induced reduction of poly(ADP-ribose) synthesis was not due to either low NAD levels or to a decrease in the chain length of the poly(ADP-ribose) molecule, rather this reduction was derived from a decrease in the number of poly(ADP-ribose) molecule. Possible mechanisms related to reduction of poly(ADP-ribose) synthesis in vivo are discussed.

Animals↗
PubMed1981

Effect of polyamines on purified poly(ADP-ribose) synthetase from rat liver nuclei.

Using the purified enzyme system, we investigated the spermine-induced stimulation of poly(ADP-ribose) formation. In the presence of 2 microgram DNA and 10 mM Mg2+ in a reaction mixture of 0.2 ml, the optimal concentrations of spermine, spermidine and putrescine were 10, 12.5 and 35 mM, respectively. With the omission of Mg2+, there was an increase in optimal concentrations of polyamines without changes in the rate of poly(ADP-ribose) formation. The concentrations of spermine required for maximum synthesis of poly(ADP-ribose) were increased in proportion to the increase in the amount of DNA. Kinetic analysis of poly(ADP-ribose) formation showed a decrease in Km values for NAD with the addition of spermine. The possible relationship of polyions with regard to DNA, spermine and histone in the purified enzyme system was discussed.

Animals↗
PubMed1981

Homozygous familial hypercholesterolemia mutant with a defect in internalization of low density lipoprotein.

During studies on binding of low density lipoprotein (LDL) to fibroblasts from patients with the homozygous form of familial hypercholesterolemia (FH), a unique line was derived from subject M.N. This line could bind as much LDL as normal cells, or even more. However, like fibroblasts from other patients with the homozygous form of FH, it failed to show regulation of cholesterol synthesis. Analyses of the LDL receptors showed that this line could not mediate internalization of receptor-bound LDL. Studies on the fibroblasts of the parents of this subject showed that the inability to internalize LDL was hereditary and that the subject was a pure homozygote for this defect. The plausibility of this finding was supported by the fact that her parents were first cousins. The possible existence of a homozygous state of this defect was predicted by Goldstein et al. [Goldstein, J. L., Brown, M. S. & Stone, N. J. (1977) Cell 12, 629-41], but an actual case of the internalization defect in a pure homozygous form had not been found. There were no differences from normal cells in the nature of the LDL binding activity of this line, such as in its specificity, affinity, or Ca2+ requirement.

Adult↗
PubMed1981

Purification and characterization or porcine kidney cathepsin B.

Three types of cathepsin B were purified from porcine kidney by a procedure involving ammonium sulfate fractionation, acetone fractionation, pH-gradient elution from CM-cellulose, gel filtration, salt gradient elution chromatography of CM-cellulose and finally preparative isoelectric focusing. The isoelectric points for the three types of cathepsin B were at pH 5.5 (Type I), pH 5.9 (Type II), and pH 6.2 (Type III). The molecular weights were estimated at 24,000 (Types I and II), and 29,000 (Type III) by SDS-polyacrylamide gel electrophoresis. The preparations were all unstable above pH 7.0 when compared with the stability at their optimal pH of around pH 6.0. The isozymes cleaved benzyloxycarbonyl-phenylalanyl-arginine-4-methyl-7-coumarylamide at pH 6.0 and at 40 degrees C with Km values of 0.225 mM (Types I and III) and 0.204 mM (Type II) and with kcat values of 71 s-1 (Types I and II) and 63 s-1 (Type III). They were strongly inhibited by iodoacetate, leupeptin and antipain, but not by DFP, PMSF, or pepstatin. The values of apparent inhibition constant for leupeptin were 15 nM (Types I and II) and 17 nM (Type III).

Animals↗
PubMed1981

Transformed phenotypes in long-term cultures persistently infected with bovine leukemia virus.

Two cell lines, 3178 and FLK, were established respectively from calf form bovine lymphosarcoma and from fetal lamb kidney cells inoculated in vitro with bovine leukemia virus. These two cell lines persistently infected with bovine leukemia virus were maintained for more than 150 passages over three years. They exhibited the characteristics of transformed cell lines in vitro: 1) anchorage independence, 2) increased saturation density and decreased population doubling time, 3) increased uptake of 2-deoxy-D-glucose and 4) tumorigenicity in athymic nude mice.

Animals↗