Masami Tsuchiya

Spectroscopic evidence for an energy minimum at the cis geometry of the triplet state of a butenylanthracene. Further insight into across-a-ridge isomerization of anthrylethylenes

The triplet energy surface of 2-(3,3-dimethyl-1-butenyl)anthracene (1) was investigated in detail on the basis of isomerization quantum yields, phosphorescence and transient absorption spectra, and emission-absorption study. There exists an energy minimum at the cis geometry as well as at the trans geometry of the triplet state of 1; this olefin undergoes “across-a-ridge” one-way isomerization from the cis to the trans isomer.

Transonic solutions of isothermal galactic winds in a cold dark matter halo

We study fundamental properties of steady, spherically symmetric, isothermal galactic outflow in appropriate gravitational potential models. We aim at constructing a universal scale free theory not only for galactic winds, but also for winds from clusters/groups of galaxies. In particular, we consider effects of mass-density distribution on the formation of transonic galactic outflows under several models of the density distribution profile predicted by cosmological simulations of structure formation based on the cold dark matter (CDM) scenario. In this study, we have clarified that there exists two types of transonic solutions: outflows from the central region and from distant region with a finite radius, depending upon the density distribution of the system. The system with sufficiently steep density gradient at the center is allowed to have the transonic outflows from the center. The resultant criterion intriguingly indicates that the density gradient at the center must be steeper than that of the prediction of conventional CDM model including Navarro, Frenk & White (1997) and Moore et al. (1999). This result suggests that an additional steeper density distribution originated by baryonic systems such as the stellar component and/or the central massive black hole is required to realize transonic outflow from the central region. On the other hand, we predict the outflow, which is started at the outskirts of the galactic center and is slowly-accelerated without any drastic energy injection like starburst events. These transonic outflows may contribute secularly to the metal enrichment of the intergalactic medium.

In vivo inhibition of the rate of de novo purine synthesis in rat liver by glucagon

The rates of de novo purine and protein synthesis were assessed in vivo in rat liver after bolus administration of glucagon. The specific activity of hepatic purines and the specific activity ratio of hepatic purine/protein were used as an index of the rate of de novo purine synthesis and the rate relative to protein. Glucagon at doses of 0.01 mg to 0.1 mg/200 g body weight (BW), administered as an intravenous bolus, inhibited dose-dependently the rate of de novo purine synthesis and the rate relative to protein although it increased dose-dependently the hepatic concentration of 5-phosphoribosyl 1-pyrophosphate (PRPP). The inhibition of the rate of de novo purine synthesis recovered to control levels during the period between 60 and 90 minutes after glucagon administration. Dibutyryl cyclic AMP (Bt2 cAMP) partially mimicked this effect of glucagon in that it did not increase the rate of de novo purine synthesis in spite of increased concentrations of PRPP. These results suggest that an intravenous bolus of glucagon inhibits the rate of de novo purine synthesis through increasing cAMP concentration. The data are consistent with inhibition of amidophosphoribosyltransferase (ATase) in spite of increased PRPP concentrations.

Increase of amidophosphoribosyltransferase activity and phosphoribosylpyrophosphate concentration as the basis for increased de novo purine biosynthesis in the regenerating rat liver.

The labeling of hepatic purines with [ 14C]glycine increased in the regenerating rat liver 12 hours after a 70% hepatectomy and it reached the 2.4 folds higher peak 12 hours after the surgical operation in comparison to sham-operated control. These observations suggest that the rate of de novo biosynthesis increases in the regenerating rat liver to supply purine ribonucleotides to the cells. In the regenerating rat liver the activity of amidophosphoribosyltransferase (ATase) significantly increased and reached the 1.8 folds higher peak than control 18 hours after surgery. Hepatic 5-phosphoribosyl 1-pyrophosphate (PRPP) concentration significantly increased and reached the 3.0 folds higher peak 12 hours after surgery. Although the mean hepatic concentration of ATP and GTP showed a 13 and 15% decrease respectively in the regenerating rat liver 12 hours after surgery, they were counterbalanced by the increased concentrations of AMP and GMP by 13 and 44% respectively. These results suggest that the increased rate of de novo purine biosynthesis in the regenerating rat liver is mediated by the increased enzymatic activity of ATase and by the increased concentration of PRPP.

Increased adenylate energy charges in rat liver or primary cultured rat hepatocytes by diisopropyl 1,3-dithiol-2-ylidenemalonate.

Six hours after oral administration in rat liver, diisopropyl 1,3-dithiol-2-ylidenemalonate (malotilate) decreased AMP concentrations by 60% with unchanged total adenine nucleotide concentrations and significantly increased adenylate energy charges of 0.87 in comparison to those of 0.81 in vehicle administered control animals. Twelve hours after incubation in primary cultured rat hepatocytes, malotilate decreased AMP concentrations by 18% and increased ATP and GTP concentrations by 13 and 18% respectively with significantly increased adenylate energy charges of 0.89 in comparison to 0.87 in vehicle control. Increased adenylate energy charges by malotilate coincided with the initiation of increases in protein and de novo purine synthesis in vivo, and are associated with the increased rate of de novo purine synthesis in vitro.

INCREASE OF AMIDOPHOSPHORIBOSYLTRANSFERASE ACTIVITY AND PHOSPHORIBOSYLPYROPHOSPHATE CONCENTRATION AS THE BASIS FOR INCREASED DE NOVO PURINE BIOSYNTHESIS IN THE REGENERATING RAT LIVER: 91

The rate of de novo purine biosynthesis assayed by the specific activity of hepatic purines in the pulselabeling with radioactive glycine significantly increased in the regenerating rat liver in the time course after a 70% hepatectomy and it peaked 12 hours post-surgery by 2.4 folds above sham-operated control without associated change of the glycine pool sizes. In the regenerating rat liver in comparison to sham-control, the activity of amidophosphoribosyltransferase(ATase) significantly increased with its peak 1.8 folds higher than control 18 hours post-surgery and hepatic 5-phosphoribosyl 1-pyrophosphate(PRPP) concentration significantly increased with its peak 3.0 folds higher than control 12 hours post-surgery. Although there was a 17 and 24% decrease of hepatic ATP and GTP concentration respectively in the regenerating rat liver 12 hours post-surgery, they were counter-balanced by the increased concentration of AMP, ADP, GMP and GDP. Results of these studies suggest that the increased ATase activity and PRPP concentration lead to the increased rate of de novo purine biosynthesis in the regenerating rat liver.

The Mechanism of Insulin-Induced Increase of the Rate of De Novo Purine Biosynthesis in Primary Cultured Rat Hepatocytes

The effect of insulin on the rate of de novo purine biosynthesis was studied in freshly isolated hepatocytes from adult male rats. Insulin started to increase the rate of de novo purine biosynthesis at 1.5 X 10(-10) M and plateaued at 1.5 X 10(-8) M with the magnitude of increase of about 280%. Insulin at 1.5 X 10(-9) M or the higher concentration increased the 5-phosphoribosyl 1-pyrophosphate (PRPP) availability for purine ribonucleotide synthesis to about 230%. Insulin increased ATP concentration to 127% and decreased AMP, ADP, GMP and GDP concentration to 73, 69, 73 and 69% in association with the increased adenylate energy charge of 0.90 in comparison to the control level of 0.83. But the total adenine and guanine nucleotide concentration in the cell was not significantly changed. In addition insulin increased the specific activity of amidophosphoribosyltransferase (ATase) with the increased Vmax and the unchanged Km for PRPP.