Saturation kinetics of the S0 to S2 optical transition in isolated diphenylhexatriene

1985 ◽  
Vol 82 (7) ◽  
pp. 2939-2941 ◽  
Author(s):  
Bryan E. Kohler ◽  
Thomas A. Spiglanin
Keyword(s):  
Optical Transition ◽  
Saturation Kinetics ◽  
Kinetics Of

Kinetics of hepatic alanine uptake and urea synthesis in pigs

1988 ◽  
Vol 254 (4) ◽  
pp. G602-G609
Author(s):  
H. Vilstrup ◽  
L. T. Skovgaard
Keyword(s):  
Maximum Rate ◽  
Maximum Likelihood Method ◽  
Blood Flow Rate ◽  
Likelihood Method ◽  
Synthesis Rate ◽  
Urea Synthesis ◽  
Half Maximum ◽  
Concentration Gradients ◽  
Saturation Kinetics ◽  
Kinetics Of

The kinetics of hepatic alanine uptake and urea synthesis in relation to sinusoid alanine concentration was investigated in seven anesthetized pigs weighing 63 kg, using liver vein catheterizations. Each experiment consists of four steady-state periods of 40 min with alanine concentrations in the range of 0.4-27 mmol/l. The process rates were measured as the products of transhepatic concentration gradients and hepatic blood flow rate, determined by indocyanine green. The data suggest that both processes follow saturation kinetics, that there exists a sinusoidal concentration of alanine below which net removal is limited, and that urea synthesis consists of two components: one alanine independent and one depending on alanine concentration according to Michaelis-Menten kinetics. The kinetic parameters were estimated iteratively by the maximum likelihood method. The maximum rate of alanine uptake was 1.13 +/- 0.74 mmol.min-1.kg liver wt-1 (mean +/- SD), the alanine concentration resulting in half-maximum alanine uptake rate was 1.69 +/- 0.99 mmol/l, and the removal-limiting alanine concentration was 0.27 +/- 0.09 mmol/l. The maximum rate of urea-N synthesis was 1.49 +/- 0.87 mmol.min-1.kg liver wt-1, the alanine concentration resulting in half-maximum urea-N synthesis rate was 2.32 +/- 1.11 mmol/l, and the alanine concentration-independent urea-N synthesis rate was 0.13 +/- 0.10 mmol.min-1.kg liver wt-1.

Kinetics of potassium uptake in red spruce seedlings

1985 ◽  
Vol 63 (3) ◽  
pp. 512-516
Author(s):  
J. R. Cumming ◽  
R. T. Eckert ◽  
L. S. Evans
Keyword(s):  
Nonlinear Least Squares ◽  
Theoretical Models ◽  
Potassium Uptake ◽  
Red Spruce ◽  
Saturation Kinetics ◽  
Potassium Absorption ◽  
Parameter Values ◽  
Kinetics Of ◽  
Diffusive Component ◽  
Nutrient Solutions

Potassium uptake by roots of 3-week-old red spruce (Picea rubens Sarg.) seedlings was measured in nutrient solutions ranging in K+ concentration from 0.01 to 10.0 mM. Nonlinear least squares analysis was used to estimate uptake parameters Vmax and Km. Analyses of residuals generated by several theoretical models of ion uptake were undertaken to choose the best mechanistic uptake model. Potassium absorption by red spruce seedlings was characterized by Michaelis–Menten behavior from K+ solutions in the range 0.01 to 1.0 mM. Above 1.0 mM, accumulation of potassium was most readily accounted for by a linear diffusive component superimposed on saturation kinetics. Uptake parameter values of Vmax = 1.17 μmol K∙g fresh weight−1∙h−1 and Km = 0.083 mM were similar to those reported for other species. The culture of seedlings in full-strength nutrient solution did not reduce the ability to resolve these uptake parameters in short-term experiments.

Increasing magnesium intakes in relation to magnesium absorption in dry cows

2004 ◽  
Vol 71 (3) ◽  
pp. 297-303 ◽  
Author(s):  
Surasak Jittakhot ◽  
J Thomas Schonewille ◽  
Hugo Wouterse ◽  
Anton WJ Uijttewaal ◽  
Chalermpon Yuangklang ◽  
...  
Keyword(s):  
Dairy Cow ◽  
Dry Matter ◽  
Rumen Fluid ◽  
Latin Square ◽  
Basal Diet ◽  
Apparent Absorption ◽  
Post Feeding ◽  
Saturation Kinetics ◽  
Kinetics Of

Earlier studies with temporarily isolated rumen of heifers show saturation kinetics of Mg efflux across the rumen wall. Therefore, we hypothesized that high Mg intakes would not further increase the rate of Mg absorption in cows. To test our hypothesis, six ruminally fistulated non-pregnant dry cows were given diets with different Mg concentrations in a 6×6 Latin square design. Desired concentrations of Mg were attained by adding MgO to the basal diet and the Mg concentrations in the total rations were 3·8, 6·4, 9·1, 11·8, 14·1 and 17·3 g Mg/kg dry matter, which provided Mg intakes of 27·1, 44·6, 64·6, 83·5, 100·4 and 124·3 g/d, respectively. Increasing Mg intakes were associated with increased (P<0·001) faecal Mg excretion. However, apparent Mg absorption expressed as g/d was not significantly different for Mg intakes from 100·4 to 124·3 g/d while Mg absorption expressed as a proportion of intake was not significantly different for Mg intakes ranging from 64·6 to 124·3 g/d. Mg concentrations in rumen fluid after feeding increased (P<0·001) with increasing Mg intakes. Apparent absorption of Mg appeared to become saturated at a ruminal Mg concentration of 17·5 mM (Mg intake of 83·5 g/d). Group-mean post-feeding concentrations of Mg and Na in rumen fluid were significantly correlated (Pearson's r=−0·96; P=0·003, n=6). This study showed that under conditions of practical dairy cow feeding, Mg absorption was maximal at Mg intakes [ges ]84 g/d.

Fabricating Necklace-, Tower-, and Rod-Shaped In2O3 Nanostructures by Controlling Saturation Kinetics of Catalyst Droplets in a Vapor–Liquid–Solid Process

2017 ◽  
Vol 17 (9) ◽  
pp. 4596-4602 ◽  
Author(s):  
J. Alberto Ramos Ramón ◽  
Ana Cremades ◽  
David Maestre ◽  
Rutilo Silva González ◽  
Umapada Pal
Keyword(s):  
Vapor Liquid Solid ◽  
Saturation Kinetics ◽  
Kinetics Of ◽  
In2o3 Nanostructures ◽  
Vapor Liquid

scholarly journals Saturation kinetics of magnesium efflux across the rumen wall in heifers

1983 ◽  
Vol 49 (1) ◽  
pp. 153-158 ◽  
Author(s):  
H. Martens
Keyword(s):  
Active Process ◽  
Saturation Kinetics ◽  
Kinetics Of ◽  
Menten Constant

1. Absorption of magnesium from the temporarily-isolated, emptied and washed rumen of four 10–12-month-old heifers was measured at five different Mg concentrations (2·5, 5·0, 7·5, 12·5 and 20 mmol/l).2. Net absorption of Mg was observed at all concentrations. Saturation occurred at a concentration of 12·5 mmol Mg/l.3. Using an Eadie–Hofstee plot, the Michaelis–Menten constant (Km; 11·43 mmol/l) and maximal efflux (Vmax; 120·3 μmol/min) were estimated.4. The phenomenon of saturation supports the assumption that Mg transport across the rumen wall of heifers is an active process.

Tubular reabsorption rates for myoglobin in the isolated perfused rat kidney

1986 ◽  
Vol 70 (6) ◽  
pp. 595-599 ◽  
Author(s):  
P. J. Ratcliffe ◽  
M. P. Esnouf ◽  
J. G. G. Ledingham
Keyword(s):  
Rat Kidney ◽  
Tubular Reabsorption ◽  
Renal Tubules ◽  
Immunoglobulin Light Chain ◽  
Renal Handling ◽  
Water Excretion ◽  
Isolated Perfused Rat Kidney ◽  
Saturation Kinetics ◽  
Perfused Rat Kidney ◽  
Kinetics Of

1. The renal handling of myoglobin has been studied in the isolated perfused rat kidney. 2. Myoglobin was freely filtered. Reabsorption by the renal tubules showed saturation kinetics with a relatively low maximum rate of reabsorption (Tmax) of 27-30 μg min−1 g−1 wet wt. at a perfusate concentration of 70-80 μg/ml. Myoglobin reabsorption is therefore much less than that reported for immunoglobulin light chain or lysozyme in this model. 3. Large increases in sodium and water excretion produced by omission of oncotic agent from the perfusate did not alter the kinetics of myoglobin reabsorption. 4. The use of bovine serum albumin as oncotic agent in the perfusate prevented the tubular reabsorption of myoglobin. Small amounts of albumin are filtered by the isolated perfused kidney and it is postulated that this albumin interferes with tubular reabsorption of myoglobin.

The role of divalent cations in the activation of the NADP+-specific isocitrate dehydrogenase from Pisum sativum L.

1977 ◽  
Vol 55 (9) ◽  
pp. 928-934 ◽  
Author(s):  
Robert J. Maloney ◽  
David T. Dennis
Keyword(s):  
Ionic Strength ◽  
Stability Constants ◽  
Isocitrate Dehydrogenase ◽  
Divalent Cations ◽  
Free Form ◽  
Saturation Kinetics ◽  
The Difference ◽  
The Stability ◽  
Kinetics Of

A divalent cation electrode was used to measure the stability constants (association constants) for the magnesium and manganese complexes of the substrates for the NADP+-specific isocitrate dehydrogenase (EC 1.1.1.42) from pea stems. At an ionic strength of 26.5 mM and at pH 7.4 the stability constants for the Mg2+–isocitrate and Mg2+–NADP+ complexes were 0.85 ± 0.2 and 0.43 ± 0.04 mM−1 respectively and for the Mn2+–isocitrate and Mn2+–NADP+ complexes they were 1.25 ± 0.07 and 0.75 ± 0.09 mM−1 respectively. At the same ionic strength but at pH 6.0 the Mg2+–NADPH and Mn2+–NADPH complexes had stability constants of 0.95 ± 0.23 and 1.79 ± 0.34 mM−1 respectively. Oxalosuccinate and α-ketoglutarate do not form measureable complexes under these conditions. Saturation kinetics of the enzyme with respect to isocitrate and metal ions are consistent with the metal–isocitrate complex being the substrate for the enzyme. NADP+ binds to the enzyme in the free form. Saturation kinetics of NADPH and Mn2+ indicate that the metal–NADPH complex is the substrate in the reverse reaction. In contrast the pig heart enzyme appears to bind free NADPH and Mn2+. A scheme for the reaction mechanism is presented and the difference between the reversibility of the NAD+ and NADP+ enzyme is discussed in relation to the stability of the NADH and NADPH metal complexes.

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