Biomedical subjects

S Yamashoji

Publications and source records attributed to S Yamashoji.

5 recordsLinked to original sources

PubMed1992

Application of the chemiluminescent assay to cytotoxicity test: detection of menadione-catalyzed H2O2 production by viable cells.

Menadione-catalyzed H2O2 production by viable cells is proportional to viable cell number. The correlations between the viable cell number and the concentration of H2O2 produced are determined with the rapid chemiluminescent assay (S. Yamashoji, T. Ikeda, and K. Yamashoji, 1989, Anal. Biochem. 181, 149-152). This chemiluminescent assay of viable cells requires only 10 min and is much faster than NR (neutral red) inclusion and MTT (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide) reduction assays, which require 3-5 h. When viable cells are incubated with antitumor drugs, detergents, mycotoxins, and glycoalkaloids for 24-48 h, a decrease in menadione-catalyzed H2O2 production in a dose- or incubation time-dependent manner is observed. In general, the 50% inhibition concentration determined by the chemiluminescent assay is lower than that determined by NR inclusion and MTT reduction assays, and the order of relative cytotoxic effects of agents is the same among these assays. Furthermore, clear cytotoxic effects are observed by the chemiluminescent assay after 1 h exposure of trypsinized cells to toxic compounds. Therefore, the chemiluminescent assay is expected to be more useful for the rapid detection of cytotoxic compounds than NR inclusion and MTT reduction assays.

3T3 Cells↗

PubMed1991

Extracellular generation of active oxygen species catalyzed by exogenous menadione in yeast cell suspension.

Luminol chemiluminescence was observed by addition of menadione to yeast cell suspension and was amplified 1000-fold by further addition of Fe-complex. Catalase, superoxide dismutase and ceruloplasmin had inhibitory effects on luminol chemiluminescence, indicating the extracellular generation of active oxygens (H2O2 and O2-) and reduction of Fe-complex. The generation of H2O2 and reduction of Fe-complex were mainly dependent on the activity of NADH: menadione oxidoreductase in the plasma membrane and cytosol fractions. Both luminol chemiluminescence and H2O2 production were sensitive to the inhibitory effects of proton conductor, ionophorous antibiotics and ATPase inhibitor rather than the inhibitors of the mitochondria electron transport system. The incubation of glucose with yeast cells caused a parallel increase in luminol chemiluminescence, H2O2 production and intracellular NADH concentration. These facts suggest that menadione-catalyzed H2O2 production and chemiluminescence are used as the indicators of cell activity to keep the NADH concentration and NADH: menadione oxidoreductase activity which may be sensitive to the change in pH and ion concentrations.

Catalysis↗

PubMed1989

Chemiluminescent assay for determination of viable cell density of yeast, mammalian, and plant cells.

The production of H2O2 by intact cells is promoted in the presence of menadione and is proportional to the density of viable cells. The concentration of H2O2 produced is determined by the measurement of chemiluminescence which is generated in the mixture of H2O2, pyrene, and bis(2,4,6-trichlorophenyl)oxalate. This method is applied to the measurement of viable yeast, mammalian, and plant cells. For example, viable yeast cell density above 10(4) cells/ml is determined for 2 min, and mammalian cell density and the activity of plant tissues are determined for 10 and 5 min, respectively.

Animals↗

PubMed1986

Decrease of NADH in yeast cells by external ferricyanide reduction.

Ferricyanide reduction catalyzed by vitamin K-3 was accompanied by the decrease in intracellular (NAD(P)H concentration of yeast cells, and the rate of ferricyanide reduction depended on intracellular concentration of NADH rather than NADPH. The addition of glucose to the cell suspensions enhanced both ferricyanide reduction and intracellular NADH concentration. The catalytic action of vitamin K-3 on ferricyanide reduction was observed in the presence of NADH and plasma membrane preparations. As the toxic action of vitamin K-3 on cell growth of yeast was enhanced by addition of ferricyanide, ferricyanide reduction catalyzed by vitamin K-3 may inhibit cell growth by decreasing intracellular NADH concentration.

Ferricyanides↗

PubMed1984

Activation of yeast 6-phosphofructo-2-kinase by protein kinase and phosphate.

6-Phosphofructo-2-kinase (PFK2) is activated by a cAMP-dependent protein kinase, and inactivated by phosphatase, indicating the interconversion of PFK2. Inorganic phosphate also activates PFK2, and the optimum pH for the PFK2 activity varies with the concentration of phosphate. Phosphate also enhances the inactivation of PFK2 by citrate, suggesting that phosphate acts as a regulator of PFK2.

Alkaline Phosphatase↗