Katsuo Uchida

Rotational effects on fluorescence quantum yields of pyrazine and pyrimidine in the vapor phase

Abstract Fluorescence-excitation and quantum-yield spectra were measured along the rotational contours of the 0-0 and 10a o 1 bands of pyrazine and the 0-0 band of pyrimidine in the vapor phase at low pressure. A marked variation in quantum yield was observed. The yield spectra for the 0-0 bands exhibit a very sharp peak near the band origin. It is suggested that the S–T coupling is enhanced with increasing rotation.

Effects of methyl substitution on electronic relaxation processes of pyrimidine vapor

Abstract The pressure and excitation-energy dependence of the fluorescence quantum yields of pyrimidine, 5- and 4-methylpyrimidines and 4,6-dimethylpyrimidine in the vapor phase has been investigated in the pressure range 10 −3 –10 2 torr. The results indicate that not only pyrimidine but also its methyl derivatives give both fast and slow fluorescence emissions at low pressure, in conformity with the intermediate case of electronic relaxation. The total fluorescence quantum yields for the 0-0 transition, extrapolated to zero pressure, are 0. 17, 0.0079, 0.0057 and 0.0010 for pyrimidine, 5- and 4-methylpyrimidines and 4,6-dimethylpyrimidine, respectively. The methyl substitution significantly reduces the yield of the slow fluorescence component in essentially the same manner as the increase of excitation energy in the unsubstituted pyrimidine. The decrease of the slow-fluorescence yield resulting from the methyl substitution or the excitation-energy increase is interpreted as due to the increase of the number of triplet vibronic It is shown that there is a fairly good correlation between the number of the effectively coupled triplet levels and the vibrational state density in t

Phosphorescence from pyrimidine vapor

The phosphorescence from pyrimidine vapor has been observed by a method of time-resolved laser spectroscopy. The phosphorescence spectrum commences at 350.5 nm and consists mainly of three totally symmetric vibrations in the ground state, v6a, v12 and v9a as in the case of the zero-point vibrational level fluorescence of pyrimidine vapor. The phosphorescence quantum yield and lifetime are found to be about 1 × 10−4 and 50 μs.

Fast and slow fluorescence emissions from pyrimidine vapor

Abstract The pressure and excitation-energy dependence of the fluorescence quantum yield and lifetime of pyrimidine vapor has been investigated in the pressure range 10 −3 -10 torr. The results indicate that in conformity to the intermediate case the fluorescence of the isolated pyrimidine molecule consists of fast and slow components with lifetimes of the order of 1 ns and 10 μs, respectively. The total fluorescence quantum yield amounts to as high as 0.045. The yield of the slow fluorescence component decreases significantly with increasing excitation energy; this observation is interpreted as being due mainly to the lengthening of the radiative lifetime of that component.

Diffusion coefficient for O2 in plasma and mitochondrial membranes of rat cardiomyocytes

Oxygen diffusion in plasma membranes and mitochondrial (Mt) membranes of ventricular myocytes isolated from adult rat hearts was measured using O2-induced fluorescence quenching of pyrene-butyric acid. The diffusion coefficient for oxygen (DO2 in 10(-6).cm2 x s-1) of the plasma membrane was 2.91 +/- 0.05 (37 degrees C) in the control group, which was significantly higher than that of Mt membrane (2.23 +/- 0.11) (P < 0.001). The DO2 of the plasma membrane was reduced to 2.50 +/- 0.08 (P < 0.001) in myocytes isolated from heart after 15 min reperfusion following no-flow ischemia for 30 min, while that of the Mt membrane remained almost unchanged. Administration of hydrogen peroxide and hypochlorous acid to the isolated myocytes also reduced the plasma membrane DO2. The decrease in the plasma membrane DO2 correlated with that in the fraction of rod-shaped myocytes. We conclude that the plasma membrane is more susceptible to reperfusion injury than the Mt membrane, but these membranes do not limit O2 uptake in the heart because of the high absolute values of DO2.

Glycolysis vs. respiration as ATP source for the shape of quiescent cardiomyocytes

ATP concentration ([ATP]) and the fraction of rod-shaped myocytes (Rrod) were measured for quiescent ventricular cells isolated from the rat heart. The myocytes were gently shaken with metabolic inhibitors for 30 min at 37 degrees C, and then [ATP] was assayed enzymatically. [ATP] (mean +/- SE in nmol.(10(6) cells)-1) of the control group (80.2 +/- 6.3) was significantly reduced to 32.3 +/- 3.6 and 21.9 +/- 4.5 by inhibiting glycolysis with 2-deoxyglucose (DG, 10 mM) and iodoacetic acid (IAA, 2 mM), respectively. Inhibition of the oxidative phosphorylation by sodium cyanide (CN, 2 mM) or 2,4-dinitrophenol (DNP, 40 microM) did not induce significant [ATP] reduction (56.5 +/- 5.6 or 53.2 +/- 7.5). Rrod were 54.4 +/- 1.9, 47.3 +/- 5.1, 43.3 +/- 3.3, 28.5 +/- 3.6 and 11.6 +/- 1.8% for the control, CN, DNP, DG and IAA groups, respectively. Under glycolytic inhibition with DG, addition of pyruvate (5 mM) with a pyruvate dehydrogenase activator (dichloroacetate (DCA, 1 mM) or (-)isoproterenol (ISO, 10 microM)) restored [ATP] to 52.5 +/- 8.3 and 67.7 +/- 7.2, respectively, but Rrod still remained depressed (34.6 +/- 2.1 and 35.4 +/- 1.3%). We conclude that the normal shape of quiescent myocytes is maintained primarily by glycolytic ATP.

In Vivo sup 31 P Magnetic Resonance Spectroscopy for Evaluation of Testicular Function in Cryptorchid Rats

PURPOSE To assess in vivo metabolism of rat testicles in experimental cryptorchidism, we used 31P magnetic resonance (MR) spectroscopy and compared testicular MR spectroscopic parameters with flow cytometric DNA analysis. MATERIALS AND METHODS In vivo 31P MR spectroscopy and flow cytometric DNA analysis of rat testis were performed before and during 14 days of experimental cryptorchidism. RESULTS The testicular phosphomonoester (PM)/ATP ratio showed a transient increase when multinuclear giant cells appeared in the seminiferous tubules. However, the ratio returned to the preoperative level when these cells disappeared. The phosphodiester (PD)/ATP ratio gradually decreased and the inorganic phosphate (Pi)/ATP ratio slowly increased. DNA flow cytometry showed a decrease in the percentage of haploid cells and an increase in the percentage of diploid cells from 7 days after cryptorchidism. The percentage of tetraploid cells did not change before and during cryptorchidism. CONCLUSION This study indicates that in vivo 31P MR spectroscopy in combination with flow cytometric DNA analysis provides useful biochemical and histological information for evaluation of testicular function.

Effects of lower-leg rhythmic cuff inflation on cardiovascular autonomic responses during quiet standing in healthy subjects.

To determine the effects of muscle pump function on cardiac autonomic activity in response to quiet standing, we simulated the muscle pump effect by rhythmic lower-leg cuff inflation (RCI) with four cuff pressures of 0 (sham), 40, 80, and 120 mmHg at 5 cycles/min. The R-R interval (RRI) and beat-to-beat blood pressure (BP) were acquired in healthy subjects (6 males and 5 females, aged 21-24 yr). From the continuous BP measurement, stroke volume (SV) was calculated by a pulse-contour method. Using spectral and cross-spectral analysis, RRI and systolic BP variability as well as the gain of spontaneous cardiac baroreflex sensitivity (sBRS) were estimated for the low- and high-frequency (HF) bands. Compared with the sham condition, RCI with cuff pressures of 80 and 120 mmHg led to increases in the mean RRI (P < 0.01) and HF power of RRI fluctuation (P < 0.05 for 80 mmHg and P < 0.01 for 120 mmHg) during quiet standing. Reduction in SV during standing was suppressed, and the sBRS of the HF band for standing were increased by RCI for either cuff pressure (P < 0.05 for 80 mmHg and P < 0.01 for 120 mmHg). However, at 40 mmHg RCI, these remained unchanged. These results suggest that, during standing, RCI of the lower leg increases cardiac vagal outflow when the cuff pressure is raised enough to oppose the hydrostatic-induced venous pressure in the calf.

Relation between the contact time and venous and alveolar PCO2 at rest.

The simultaneous partial differential equations for diffusions of O2, CO2, and HCO 3 − ions in the red blood cell (RBC) were solved numerically, taking chemical reactions of Bohr- and Haldane-effects into account. The diffusion equations and the chemical reactions were computed alternatively in an increment time of 2 msec. After solving each of the three diffusion equations, the Po2, O2 saturation (S), Pco2, pH and HCO 3 − content were corrected by using the equations of Bohr- and Haldane-effects, and a modified Henderson-Hasselbalch equation (Kagawa and Mochizuki, 1984). The Bohr-shift was calculated from Hill’s equation by assuming its K value to be a function of the intracellular pH. The change in intracellular Pco2 due to the Haldane effect was also evaluated by means of the modified Henderson-Hasselbalch equation, in which the buffer value was taken as 44 mmol · 1(RBC)−1 · pH c −1 . The computed Pco2 profiles during the Haldane effect in a closed vessel was compatible wit the experimental data of Klocke (1973). The extracellular Po2 profile computed during the Bohr-off-shift in a closed system coincided well with the experimental data of Nakamura and Staub (1964) and Forster and Steen (1968).

Quantitative Relations between Gas Exchange Parameters including Contact Time at Rest and during Treadmill Exercise

Studies on quantitative relations between gas exchange parameters at rest and during exercise have provided many reports on the relation between oxygen uptake (\(\dot V{o_2}\)), arterio-venous 02 differenc.