scholarly journals Regulation by External K+ in a Maize Inward Shaker Channel Targets Transport Activity in the High Concentration Range

2005 ◽  
Vol 17 (5) ◽  
pp. 1532-1548 ◽  
Author(s):  
Yan-Hua Su ◽  
Helen North ◽  
Claude Grignon ◽  
Jean-Baptiste Thibaud ◽  
Hervé Sentenac ◽  
...  
Keyword(s):  
Transport Activity ◽  
High Concentration ◽  
High Concentration Range ◽  
External K

scholarly journals A model of bubble coalescence in the presence of a nonionic surfactant with a low bubble approach velocity

2021 ◽  
Author(s):  
Yuelin Wang ◽  
Huahai Zhang ◽  
Tiefeng Wang
Keyword(s):  
Nonionic Surfactant ◽  
Surfactant Concentration ◽  
Bubble Coalescence ◽  
Bulk Concentration ◽  
High Concentration ◽  
Coalescence Time ◽  
Approach Velocity ◽  
Marangoni Stress ◽  
High Concentrations ◽  
High Concentration Range

A bubble coalescence model for a solution with a nonionic surfactant and with a small bubble approach velocity was developed, in which the mechanism of how coalescence is hindered by Marangoni stress was quantitatively analyzed. The bubble coalescence time calculated for ethanol-water and MIBC-water systems were in good agreement with experimental data. At low surfactant concentrations, the Marangoni stress and bubble coalescence time increased with bulk concentration increase. Conversely, in the high concentration range, the Marangoni stress and coalescence time decreased with bulk concentration. Numerical results showed that the nonlinear relationship between coalescence time and surfactant concentration is determined by the mass transport flux between the film and its interface, which tends to diminish the spatial concentration variation of the interface, i.e., it acts as a “damper”. This damping effect increases with increased surfactant concentration, therefore decreasing the coalescence time at high concentrations.

Reversal of enhanced muscle glucose transport after exercise: roles of insulin and glucose

1990 ◽  
Vol 259 (5) ◽  
pp. E685-E691 ◽  
Author(s):  
E. A. Gulve ◽  
G. D. Cartee ◽  
J. R. Zierath ◽  
V. M. Corpus ◽  
J. O. Holloszy
Keyword(s):  
Skeletal Muscle ◽  
Insulin Sensitivity ◽  
Glucose Transport ◽  
Transport Process ◽  
Sugar Transport ◽  
Transport Activity ◽  
High Concentration ◽  
Exercise Induced ◽  
Muscle Glucose Transport

Exercise stimulates insulin-independent glucose transport in skeletal muscle and also increases the sensitivity of the glucose transport process in muscle to insulin. A previous study [D. A. Young, H. Wallberg-Henriksson, M. D. Sleeper, and J. O. Holloszy. Am. J. Physiol. 253 (Endocrinol. Metab. 16): E331–E335, 1987] showed that the exercise-induced increase in glucose transport activity disappears rapidly when rat epitrochlearis muscles are incubated for 3 h in vitro in the absence of insulin and that 7.5 microU/ml insulin in the incubation medium apparently slowed the loss of enhanced sugar transport. We examined whether addition of insulin several hours after exercise increases glucose transport to the same extent as continuous insulin exposure. Addition of 7.5 microU/ml insulin 2.5 h after exercise (when glucose transport has returned to basal levels) increased sugar transport to the same level as that which resulted from continuous insulin exposure. This finding provides evidence for an increase in insulin sensitivity rather than a slowing of reversal of the exercise-induced increase in insulin-independent glucose transport activity. Glucose transport was enhanced only at submaximal, not at maximal, insulin concentrations. Exposure to a high concentration of glucose and a low insulin concentration reduced the exercise-induced increase in insulin-sensitive glucose transport. Incubation with a high concentration of 2-deoxy-D-glucose (2-DG) did not alter the increase in insulin sensitivity, even though a large amount of 2-DG entered the muscle and was phosphorylated.(ABSTRACT TRUNCATED AT 250 WORDS)

scholarly journals Modulation of the Na,K-pump function by beta subunit isoforms.

1994 ◽  
Vol 103 (4) ◽  
pp. 605-623 ◽  
Author(s):  
F Jaisser ◽  
P Jaunin ◽  
K Geering ◽  
B C Rossier ◽  
J D Horisberger
Keyword(s):  
Ion Transport ◽  
Pump Current ◽  
Beta Subunit ◽  
Beta Subunits ◽  
Transport Activity ◽  
Apparent Affinity ◽  
Significant Difference ◽  
Ouabain Sensitivity ◽  
External K

To study the role of the Na,K-ATPase beta subunit in the ion transport activity, we have coexpressed the Bufo alpha 1 subunit (alpha 1) with three different isotypes of beta subunits, the Bufo Na,K-ATPase beta 1 (beta 1NaK) or beta 3 (beta 3NaK) subunit or the beta subunit of the rabbit gastric H,K-ATPase (beta HK), by cRNA injection in Xenopus oocyte. We studied the K+ activation kinetics by measuring the Na,K-pump current induced by external K+ under voltage clamp conditions. The endogenous oocyte Na,K-ATPase was selectively inhibited, taking advantage of the large difference in ouabain sensitivity between Xenopus and Bufo Na,K pumps. The K+ half-activation constant (K1/2) was higher in the alpha 1 beta 3NaK than in the alpha 1 beta 1NaK groups in the presence of external Na+, but there was no significant difference in the absence of external Na+. Association of alpha 1 and beta HK subunits produced active Na,K pumps with a much lower apparent affinity for K+ both in the presence and in the absence of external Na+. The voltage dependence of the K1/2 for external K+ was similar with the three beta subunits. Our results indicate that the beta subunit has a significant influence on the ion transport activity of the Na,K pump. The small structural differences between the beta 1NaK and beta 3NaK subunits results in a difference of the apparent affinity for K+ that is measurable only in the presence of external Na+, and thus appears not to be directly related to the K+ binding site. In contrast, association of an alpha 1 subunit with a beta HK subunit results in a Na,K pump in which the K+ binding or translocating mechanisms are altered since the apparent affinity for external K+ is affected even in the absence of external Na+.

Extraction of Tungsten with Trialkylamine - Effect of pH

2001 ◽  
Vol 66 (9) ◽  
pp. 1407-1419
Author(s):  
Jaroslav Procházka ◽  
Aleš Heyberger ◽  
Jan Horáček ◽  
Eva Volaufová ◽  
Jitka Voborská ◽  
...  
Keyword(s):  
Sulfuric Acid ◽  
Sodium Tungstate ◽  
High Concentration ◽  
Tungsten Atom ◽  
Extraction Equilibrium ◽  
Alkyl Chains ◽  
Flat Part ◽  
High Concentration Range ◽  
Hydrolysis Of ◽  
Extraction Isotherms

Extraction equilibrium in the system aqueous solution of sodium tungstate-solution of trialkylamine in a mixed diluent was investigated. A tertiary amine with C7-C9 straight alkyl chains was dissolved in a mixture of tributyl phosphate and kerosene and presaturated with sulfuric acid to give normal trialkylamine sulfate. Extraction isotherms at 25 °C and at several constant values of equilibrium pH were measured in a broad range of aqueous tungstate concentrations. pH 2.0-6.0 was adjusted by addition of sulfuric acid during equilibration. The equilibrium tungstate and sulfate contents in both phases were determined. A typical tungstate isotherm exhibits a steep ascending part in the low concentration range, corresponding to the region of anion exchange, and a flat part in the high concentration range, where the acid content in the organic phase is virtually exhausted. The level of the flat part decreases with growing pH, corresponding to the increasing number of negative charges per tungsten atom in the tungstate polyanions extracted. At pH > 5, also the effect of hydrolysis of amine sulfate could be detected.

A Polar Liquid Zwitterion Does Not Critically Destroy Cytochrome c at High Concentration: An Initial Comparative Study with a Polar Ionic Liquid

2019 ◽  
Vol 72 (2) ◽  
pp. 139 ◽  
Author(s):  
Kosuke Kuroda ◽  
Chiaki Kodo ◽  
Kazuaki Ninomiya ◽  
Kenji Takahashi
Keyword(s):  
Ionic Liquid ◽  
Cytochrome C ◽  
Soret Band ◽  
Liquid Solution ◽  
Acetate Solution ◽  
High Concentration ◽  
Liquid Solutions ◽  
High Concentration Range ◽  
Ionic Liquid Solution ◽  
Better Than

A polar carboxylate-type zwitterion with a small volume of water can dissolve cytochrome c without significant disruption, compared with the case of a popular polar carboxylate-type ionic liquid, 1-ethyl-3-methylimidazolium acetate. A change in the Soret, Q, and 615nm bands was not observed in the 80 wt-% polar zwitterion solution, whereas a shift in the Soret band, diminishing Q band, and appearance of the 615nm band was found in the 80 wt-% polar ionic liquid solution. It suggests that concentrated polar ionic liquid solutions critically disrupt the structure of cytochrome c, and the polar zwitterion solution used in this study was better than a 1-ethyl-3-methylimidazolium acetate solution in a high concentration range.

Plasmalemma and Tonoplast Influxes of Potassium in Barley Roots, and Interpretation of the Absorption Isotherm at High Concentrations

1975 ◽  
Vol 2 (2) ◽  
pp. 177 ◽  
Author(s):  
JB Robinson ◽  
GG Laties
Keyword(s):  
Steady State ◽  
High Concentration ◽  
Experimental Conditions ◽  
Apparent Increase ◽  
Absorption Isotherm ◽  
Low Salt ◽  
High Concentrations ◽  
High Concentration Range ◽  
Kinetics Of ◽  
Potassium Exchange

Estimates of plasmalemma influx and steady-state vacuolar influx of potassium in low-salt barley roots have been obtained in the concentration range 10-80 mM by the use of controlled loading and washing times. Both fluxes are reduced by preloading the tissue in solutions containing potassium. When the experimental temperature is increased from 20 to 30°C, an apparent increase in the steady-state vacuolar influx occurs; separation of this flux from the apparent plasmalemma influx is not possible. The data support the hypothesis that the kinetics of potassium exchange in barley root tissue may be confounded by both loading time and temperature, and thus interpretation of the influx isotherm in the high concentration range is difficult. Where experiments are carried out at 20-25°C the steady- state vacuolar influx is measured unless closely defined experimental conditions obtain. At higher temperatures the plasmalemma influx may be measured.

scholarly journals Analytical evaluation of Kone Microlyte determination of ionized magnesium

1994 ◽  
Vol 40 (1) ◽  
pp. 52-55 ◽  
Author(s):  
H E van Ingen ◽  
H J Huijgen ◽  
W T Kok ◽  
G T Sanders
Keyword(s):  
Limit Of Detection ◽  
Analytical Evaluation ◽  
High Concentration ◽  
Serum Samples ◽  
Ionized Magnesium ◽  
Carrier Liquid ◽  
The Mean ◽  
High Concentration Range ◽  
Induced Changes

Abstract We performed an analytical evaluation of a commercially available instrument for determining ionized magnesium through use of a neutral carrier, liquid-membrane-based ion-selective electrode. Reproducibility (CV 2-4%), linearity (0.30-2.50 mmol/L), lower limit of detection (0.30 mmol/L), and absence of interference from Ca2+ indicate adequate performance for measuring ionized magnesium in plasma or serum samples in the normal to high-concentration range. Sodium in excess of 150 mmol/L caused a negative bias, which can be explained by ionic strength-induced changes in activity coefficients. The use of heparin as an anticoagulant must be restricted to concentrations < 15 units/mL because of the binding of magnesium to heparin. The mean +/- SD concentration of ionized magnesium and its fraction of total magnesium in 76 healthy volunteers were 0.56 +/- 0.05 mmol/L and 0.65 +/- 0.04, respectively.

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