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Biomedical subjects

J Nagai

Publications and source records attributed to J Nagai.

At least 109 records · Page 6Linked to original sources
PubMed1982

Kinetic studies on inhibition of aminopropyltransferases by aurintricarboxylic acid in vitro.

Activities of aminopropyltransferases (spermidine synthase and spermine synthase) were inhibited by aurintricarboxylic acid (ATA). Spermidine synthase was slightly more sensitive to the inhibitor than spermine synthase. These inhibitions were not prevented by 0.15 M NaCl. Inhibition by ATA of spermidine synthase was 'uncompetitive' with respect to putrescine and that of spermine synthase was 'non-competitive' with respect to spermidine. When the amount of spermidine synthase or spermine synthase was varied, inhibition ratio hardly changed on either case implying no appreciable interaction between ATA and these enzymes.

Animals↗
PubMed1982

Effect of DNA-binding drugs on the activity of DNA methylase from Ehrlich's ascites tumour cells.

DNA methylase from Ehrlich's ascites tumour cells preferentially methylates DNA with high GC content. The methylase activity was not affected by the presence of the oligonucleotides, dCdG or dCdCdGdG, which are known to be part of the methyl-acceptor sequence for mammalian DNA methylase. DNA from 5-azacytidine-treated ascites cells was a good methyl acceptor. Actinomycin D, ethydium bromide and quinacrine inhibited the methylase activity. Distamycin A also inhibited the methylation of DNA from 5-azacytidine-treated ascites cells, but did not inhibit the methylation of (dG,dC)n. The inhibitory effect of all these drugs was overcome by increasing the DNA concentration. Non-competitive type inhibition in regard to S-adenosylmethionine was observed with all the DNA-binding drugs.

Animals↗
PubMed1981

Increased proportion of medium chain fatty acids in nystatin-resistant yeast mutants.

Fatty acid composition of phospholipids and steryl esters from four nystatin-resistant mutants of Saccharomyces cerevisiae was compared to that from the wild strain. All the mutant strains which produce several ergosterol intermediates incorporated two- to three-fold as much medium chain fatty acids, especially 14:1 in phospholipids, and 12:0, 14:0 and 14:1 in steryl esters as the wild strain did. The increase in the relative amount of medium chain fatty acids in these mutants was found at all the growth temperatures and the growth phases examined, and in all the phospholipid species.

Cell Division↗
PubMed1981

Inhibition of oxidative hemolysis and lipid peroxidation by mepacrine.

Mepacrine at 50 microM completely protected vitamin E-deficient rat erythrocytes from peroxidative hemolysis induced by dialuric acid or reduced glutathione under the standard experimental conditions. Malondialdehyde formation, which precedes the hemolysis, was also inhibited by mepacrine. These effects of mepacrine were observed when it was added after incubating the cells with dialuric acid before the malondialdehyde formation reached 50% of its maximal value. Mepacrine also inhibited NADPH-dependent lipid peroxidation in rat liver microsomes. The degree of inhibition by mepacrine of lipid peroxidation and hemolysis was dependent on the amount of red blood cells or microsomes in the reaction mixture.

Animals↗
PubMed1980

DNA methylation in isolated nuclei during development of chick embryos.

5-Methylcytosine content of chick embryo DNA was almost constant, independent of the age of embryos. Labelling experiments with isolated nuclei revealed that 5-methylcytosine was only the methylated product and the rate of DNA methylation in nuclei decreased with the age of embryos. The enzyme activity of nuclear extract paralleled the decrease. DNA from the 4 and 10-day embryos were methylated at the same rate by solubilized DNA methylase, indicating that the degree of DNA methylation does not vary with the age of embryos.

Animals↗
PubMed1980

Effect of 5-azacytidine on DNA methylation in Ehrlich's ascites tumor cells.

5-Azacytidine inhibited in vivo DNA methylation in Ehrlich's ascites tumor cells depending upon the dose at which 5-azacytidine did not inhibit DNA synthesis significantly. This drug did not inhibit DNA methylation in vitro. The DNA methylase activity in ascitic cells decreased with the increasing dose of 5-azacytidine. Hypomethylated DNA was obtained from the 5-azacytidine treated ascitic cells.

Animals↗
PubMed1980

Effect of litter size at birth on lactation in mice.

The relative influence of litter size at birth and dam body weight at parturition on lactational performance was determined with five among-line crossfostering experiments involving 17 populations of mice. Included were lines selected for postweaning growth and maternal performance, and unselected controls. Twelve-day litter weight of a crossfostered litter standardized to six or eight pups was used as the criterion of lactational performance. Litter size at birth had a small positive correlation with 12-day litter weight when pooled within lines in each crossfostering experiment (.06 to .30, with mean of .17). The correlation between dam body weight at parturition and her crossfostered 12-day litter weight was consistently higher (.13 to .51, with mean of .35). Litter size was positively correlated with dam body weight at parturition (.33 to .56, with mean of .47). The partial correlation between litter size and 12-day litter weight, with dam body weight at parturition held constant, was reduced (-.07 to .18, with mean of .02) compared to the simple correlation. Multiple regression analyses indicated that dam body weight at parturition consistently accounted for more of the variation in 12-day litter weight than litter size. The data provide no evidence to support the hypothesis that increased fetal number or mass results in a greater lactational output by the dam.

Animals↗
PubMed1978

Quantitative aspects of free and esterified sterols in Saccharomyces cerevisiae under various conditions.

For extraction of free and esterified sterols from yeast cells, a method was devised in which both forms of sterols were extracted with light petroleum after the treatment of the cells with acetone, and then with dimethylsulfoxide. The content of sterol esters in the cells under aerobic conditions markedly increased with time, amounting to 95% of the total sterols under some conditions. However, the formed sterol esters were decreased, accompanied with an increase of free sterols, when the cells were put under anaerobic conditions. Variations of radioactivities of both sterols which had been labeled in the side chain by incubation of the cells with [Me[-14C]methionine were examined on the cells grown under various conditions. No variation was observed on the cells under aerobic conditions. On the other hand, the labeled esters were hydrolyzed to yield free sterols in the cells under anaerobic conditions. In the cells under aerobic conditions, the free sterols were found to consist mainly of ergosterol, whereas the esterified sterols contained considerable amounts of zymosterol, lanosterol, and other intermediate sterols besides ergosterol.

Aerobiosis↗