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[en] When an isotopic tracer is infused for the purpose of determining the rate of turnover or oxidation of a substrate, it is assumed that the resulting isotopic enrichment of the trace will reflect kinetics of only the pool of interest. However, this may not be the case when carbon-labeled lactate is infused, since rapid isotopic exchange with the intracellular pyruvate and alanine pools could potentially occur. Therefore the authors have determined the extent of isotopic exchange occurring during the infusion of [3-¹³C]lactate into six anesthetized dogs. In the steady state, pyruvate enrichment was 91 ± 2.2% of the lactate enrichment, and alanine enrichment was 81 ± 3.3% of the pyruvate enrichment and 72 ± 2.6% of the lactate enrichment. In contrast, when [3-¹³C]alanine was infused, pyruvate (and lactate) enrichment was 9.9% of the alanine enrichment. They therefore conclude that there is rapid isotopic equilibration between lactate and pyruvate but that interaction with alanine reflects the true metabolic flux rates, rather than isotopic exchange. Consequently, lactate kinetics, as traditionally determined, more accurately reflect whole body pyruvate kinetics

[en] The importance of the location of isotope infusion and blood sampling on calculating glucose kinetics was studied in five mongrel dogs in the basal state and when glucose turnover was increased during a hyperinsulinemic euglycemic clamp. [U-¹⁴C]glucose was infused into the pulmonary artery, unlabeled glucose was infused into a femoral vein to maintain euglycemia, and blood was sampled from the right atrium (AV mode) and the femoral artery (VA mode). In the basal state there was no difference between the AV or VA mode in plateau specific activity; hence, the calculated rate of appearance of glucose was the same with either mode. During the euglycemic clamp procedure, plateau specific activity of the AV mode was significantly lower than that of the VA mode (P less than 0.05). The rate of appearance of glucose calculated from the VA mode was almost identical to the rate of infusion of unlabeled glucose (13.0 +/- 1.4 vs. 12.6 +/- 1.4 mg.kg-1.min-1, respectively), but the rate of appearance of glucose calculated from the AV mode was 12% greater. This study demonstrates that the calculation of glucose kinetics is sensitive to differences in sampling site when the turnover rate is high relative to the mass flow rate (cardiac output times substrate concentration)

[en] The magnetic moment of ¹⁹N was measured by using a β-NMR method and a spin-polarized ¹⁹N beam from the fragmentation reaction. As a result, the g value for the ¹⁹N ground state, g=0.61±0.03(preliminary), was obtained. The value was compared with those of¹⁵N and ¹⁷N. Contrary to shell-mode predictions that the g value should increase with increasing number of neutrons in the sd shell, the obtained g for ¹⁹N_g.s. is significantly smaller than the g factor for ¹⁷N_g.s.. (author)

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[en] The magnetic moments for ³⁰Al and ³²Al have been measured by the β-NMR method with spin-polarized radioactive nuclear beams from the project ile- fragmentation reaction. The fragmentation processes that involved large numbers of removed nucleons, 10 and 8, from the projectiles ⁴⁰Ar were successfully utilized to produce polarized ³⁰Al and ³²Al fragments. The obtained magnetic moments, |μ(³⁰Al)| = (3.012 ± 0.021)μ_N and |μ(³²Al)| = (1.959 ± 0.019)μ_N, were reproduced well by shell model calculations within a model space of the full sd shell. (author)

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[en] Neutrons with energies E below the Fermi effective potential U_eff∼0.2 μeV are called ultracold neutrons (UCN), which are totally reflected from a surface of material and thus can be stored in a bottle. The UCN in a bottle are of a great advantage for high-precision measurements in fundamental physics with neutrons, where the UCN density ρ_UCN takes the key role. We have proposed a new method for the production of UCN, which is based on the repeated application of a field-gradient force on a magnetic moment realized with a spatially alternating field and the correlated spin flips. To evaluate the feasibility and performance of the method, a computer simulation of neutron decelerating and transporting processes has been performed. The result indicates that the UCN density ρ_UCN in a storage bottle in the present method reaches quite large values as ρ_UCN≅2.2x10³ n/cm³ in a realistic condition. An experiment to test the principle and to explore the technical ingredients of the present method is being conducted using the UCN beam from the supermirror turbine at KUR