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- Frey, Urban, et al.
(författare)
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Proton NMR Kinetic Study of Ligand Exchange on Bis(1,4-dithiane)platinum(II), Bis(1,4-dithiane)palladium(II) and Tetrakis(dimethylsulfide)platinum(II) : High Presssure NMR Kinetics 51
- 1991
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Ingår i: Inorganic Chemistry. - : American Chemical Society (ACS). - 1520-510X .- 0020-1669. ; 30:26, s. 5033-5037
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Tidskriftsartikel (refereegranskat)abstract
- Ligand exchange on square-planar Pt(1,4-dithiane)2(2+), Pd(1,4-dithiane)2(2+), and Pt(Me2S)4(2+) has been studied as a function of temperature and pressure by H-1 NMR line-broadening, isotopic labeling, and magnetization transfer experiments with deuteriated nitromethane as solvent. Second-order rate constants and activation parameters are as follows: for 1,4-dithiane exchange on Pt(1,4-dithiane)2(2+), k2(298) = 28.8 +/- 4.8 m-1 s-1, DELTA-H double-ended dagger = 32.9 +/- 3.6 kJ mol-1, DELTA-S double-ended dagger = -106 +/- 11 J K-1 mol-1, and DELTA-V double-ended dagger = -12.6 +/- 1.1 cm3 mol-1; for 1,4-dithiane exchange on Pd(1,4-dithiane)2(2+), k2(298) = 9780 +/- 300 m-1 s-1, DELTA-H double-ended dagger = 22.9 +/- 0.6 kJ mol-1, DELTA-S double-ended dagger = -91.6 +/- 2.1 J K-1 mol-1, and DELTA-V double-ended dagger = -9.8 +/- 0.4 cm3 mol-1; for Me2S exchange on Pt(Me2S)4(2+), k2(298) = 1.54 +/- 0.07 m-1 s-1, DELTA-H double-ended dagger = 42.1 +/- 0.7 kJ mol-1, DELTA-S double-ended dagger = -100.2 +/- 2.2 J K-1 mol-1, and DELTA-V double-ended dagger = -22.0 +/- 1.3 cm3 mol-1. Second-order kinetics and negative entropies and volumes of activation indicate associative, I(a) or A, exchange mechanisms. For both metal centers, exchange of the chelated and strongly bound 1,4-dithiane, corrected for statistics, is faster than that of Me2S, probably due to steric factors. The ratio in reactivity for Pd/Pt is only ca. 1300 for Me2S and 340 for 1,4-dithiane, indicating a more pronounced sensitivity of Pt(II) to the electronic properties of the coordinated and entering ligands. Accordingly, activation volumes are more negative in the case of platinum. DELTA-V double-ended dagger for the Me2S exchange on Pt(II) is the most negative one reported so far for a square-planar solvent exchange.
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| 2. |
- Fuchi, Tokio, et al.
(författare)
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Microdialysis of rat skeletal muscle and adipose tissue : dynamics of the interstitial glucose pool.
- 1994
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Ingår i: Acta Physiologica Scandinavica. - 0001-6772 .- 1365-201X. ; 151:2, s. 249-60
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Tidskriftsartikel (refereegranskat)abstract
- Microdialysis was evaluated as a method for studying glucose metabolism in skeletal muscle. Dialysis probes (0.5 x 10 mm) were perfused at 0.5 or 1.0 microliter min-1. Based upon perfusion with glucose, the muscle interstitial glucose concentration was estimated to be 6.9 +/- 0.3 mM (n = 14), which was not significantly different from the blood glucose level. With insulin infusion (1200 mU kg-1 body wt i.v.), the insulin-induced change in the glucose concentration of the interstitial space of muscle was of equal magnitude to that of blood and adipose tissue. In spite of this, when the perfusion medium was not supplemented with glucose, the glucose concentration decreased more in skeletal muscle dialysates (to 36.7 +/- 4.9% of the initial level) than in blood (to 29.7 +/- 5.0%) but less than in adipose tissue (to 17.7 +/- 4.9% of the initial level) (P < 0.05). The results indicate that these differences are due to tissue-specific differences in the dynamic balance between the supply to, and removal from, the interstitial glucose pool. This balance is revealed as a result of the constant glucose drainage by the microdialysis probe. The present results show that, in skeletal muscle, increases in glucose uptake occur with a concomitant increase in tissue blood flow as revealed by the microdialysis ethanol technique, whereas in adipose tissue the glucose uptake increases in the absence of a corresponding increase in blood flow.
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| 3. |
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| 5. |
- Hickner, R C, et al.
(författare)
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The ethanol technique of monitoring local blood flow changes in rat skeletal muscle : implications for microdialysis.
- 1992
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Ingår i: Acta Physiologica Scandinavica. - 0001-6772 .- 1365-201X. ; 146:1, s. 87-97
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Tidskriftsartikel (refereegranskat)abstract
- We have investigated the feasibility of monitoring local skeletal muscle blood flow in the rat by including ethanol in the perfusion medium passing through a microdialysis probe placed in muscle tissue. Ethanol at 5, 55, or 1100 mM did not directly influence local muscle metabolism, as measured by dialysate glucose, lactate, and glycerol concentrations. The clearance of ethanol from the perfusion medium can be described by the outflow/inflow ratio ([ethanol]collected dialysate/[ethanol]infused perfusion medium), which was found to be similar (between 0.36 and 0.38) at all ethanol perfusion concentrations studied. With probes inserted in a flow-chamber, this ratio changed in a flow-dependent way in the external flow range of 5-20 microliters min-1. The ethanol outflow/inflow ratio in vivo was significantly (P less than 0.001) increased (to a maximum of 127 +/- 2.8% and 144 +/- 7.4% of the baseline, mean +/- SEM) when blood flow was reduced by either leg constriction or local vasopressin administration, and significantly (P less than 0.001) reduced (to 62 +/- 6.4% and 43 +/- 4.4% of baseline) with increases in blood flow during external heating or local 2-chloroadenosine administration, respectively. Dialysate glucose concentrations correlated negatively with the ethanol outflow/inflow ratio (P less than 0.01) and consequently decreased (to 46 +/- 7.6% and 56 +/- 5.6% of baseline) with constriction and vasopressin administration and increased (to 169 +/- 32.5% and 262 +/- 16.7% of baseline) following heating and 2-chloroadenosine administration. Dialysate lactate concentrations were significantly increased (approximately 2-fold, P less than 0.001) during all perturbations of blood flow. In conclusion, this technique makes it possible to monitor changes in skeletal muscle blood flow; however, methods of quantification remain to be established. The fact that blood flow changes were found to significantly affect interstitial glucose and lactate concentrations as revealed by microdialysis indicates that this information is critical in microdialysis experiments.
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