scholarly journals Effect of ATP on the Calcium Efflux in Dialyzed Squid Giant Axons

1974 ◽  
Vol 64 (4) ◽  
pp. 503-517 ◽  
Author(s):  
Reinaldo DiPolo
Keyword(s):  
Transport System ◽  
Calcium Transport ◽  
Artificial Seawater ◽  
Ionized Calcium ◽  
Calcium Efflux ◽  
Perfusion Technique ◽  
Virtual Absence ◽  
Giant Axons ◽  
The Mean

Dialysis perfusion technique makes it possible to control the internal composition of squid giant axons. Calcium efflux has been studied in the presence and in the virtual absence (<5 µM) of ATP. The mean calcium efflux from axons dialyzed with 0.3 µM ionized calcium, [ATP]i > 1,000 µM, and bathed in artificial seawater (ASW) was 0.24 ± 0.02 pmol·cm-2·s-1 (P/CS) (n = 8) at 22°C. With [ATP]i < 5 µM the mean efflux was 0.11 ± 0.01 P/CS (n = 15). The curve relating calcium efflux to [ATP]i shows a constant residual calcium efflux in the range of 1–100 µM [ATP]i. An increase of the calcium efflux is observed when [ATP]i is >100 µM and saturates at [ATP]i > 1,000 µM. The magnitude of the ATP-dependent fraction of the calcium efflux varies with external concentrations of Na+, Ca++, and Mg++. These results suggest that internal ATP changes the affinity of the calcium transport system for external cations.

scholarly journals Calcium Efflux from Internally Dialyzed Squid Giant Axons

1973 ◽  
Vol 62 (5) ◽  
pp. 575-589 ◽  
Author(s):  
Reinaldo Dipolo
Keyword(s):  
Calcium Ions ◽  
Initial Rate ◽  
Calcium Efflux ◽  
Perfusion Technique ◽  
Giant Axons ◽  
The Mean ◽  
Per Se ◽  
Internal Sources

Calcium efflux has been studied in squid giant axons under conditions in which the internal composition was controlled by means of a dialysis perfusion technique. The mean calcium efflux from axons dialyzed with 0.3 µM calcium and 5 mM ATP was 0.26 pmol/cm2·s at 22°C. The curve relating the Ca efflux with the internal Ca concentration had a slope of about one for [Ca]i lower than 0.3µM and a slope smaller than one for higher concentrations. Under the above conditions replacement of [Na]o and [Ca]o by Tris and Mg causes an 80% fall in the calcium efflux. When the axons were dialyzed with a medium free of ATP and containing 2 mM cyanide plus 5µg/ml oligomycin, analysis of the perfusion effluent gave values of 1–4 µM ATP. Under this low ATP condition, replacement of external sodium and calcium causes the same drop in the calcium efflux. The same effect was observed at higher [Ca]i, (80 µM). These results suggest that the Na-Ca exchange component of the calcium efflux is apparently not dependent on the amounts of ATP in the axoplasm. Axons previously depleted of ATP show a significant transient drop in the calcium efflux when ATP is added to the dialysis medium. This effect probably represents the sequestering of calcium by the mitochondrial system. The consumption of calcium by the mitochondria of the axoplasm in dialyzed axons was determined to be of the order of 6.0 x 10-7 mol Ca++/mg of protein with an initial rate of 2.6 x 10-8 mol Ca++/min·mg of protein. Axons dialyzed with 2 mM cyanide after 8–10-min delays show a rise in the calcium efflux in the presence of "normal" amounts of exogenous ATP. This effect seems to indicate that cyanide, per se, can release calcium ions from internal sources.

Effect of lead on the calcium transport in human erythrocyte

1999 ◽  
Vol 18 (3) ◽  
pp. 146-153 ◽  
Author(s):  
J V Calderón-Salinas ◽  
M A Quintanar-Escorza ◽  
C E Hernández-Luna ◽  
M T González-Martínez
Keyword(s):  
Intracellular Calcium ◽  
Transport System ◽  
Human Erythrocyte ◽  
Calcium Transport ◽  
Calcium Uptake ◽  
Calcium Influx ◽  
Passive Transport ◽  
Calcium Efflux ◽  
Excitable Cell ◽  
Physiological Conditions

In this paper we study the calcium uptake in the erythrocyte, a non-excitable cell. This uptake is performed through a passive transport system with two kinetic components (Michaelis-Menten and Hill). The uptake of calcium seems to be driven by voltage through its electrophoretical effect. Lead is capable of inhibiting calcium uptake in a non-competitive manner. As it has been described in other systems, lead is also capable of inhibiting calcium efflux by inhibiting Ca(Mg)-ATPase. Under physiological conditions, the function of ATPase reduces the effect of lead on calcium influx. However, in chronic intoxication a small increment of intracellular calcium is observed, indicating that lead is affecting calcium efflux mainly. We discuss the effects of lead on calcium equilibrium in erythrocytes.

scholarly journals Stoichiometry and ion dependencies of the intracellular-pH-regulating mechanism in squid giant axons.

1983 ◽  
Vol 81 (3) ◽  
pp. 373-399 ◽  
Author(s):  
W F Boron ◽  
J M Russell
Keyword(s):  
Intracellular Ph ◽  
Transport System ◽  
Extrusion Rate ◽  
Giant Axons ◽  
Constant Ph ◽  
Absolute Dependence ◽  
Standard Set ◽  
Series Of Experiments ◽  
The Mean ◽  
Acid Extrusion

The ion transport system responsible for intracellular pH (pHi) regulation in squid giant axons was examined in experiments with pH-sensitive microelectrodes and isotopic fluxes of Na+ and Cl-. In one study, axons were acid-loaded and the rate of the subsequent pHi recovery was used to calculate the acid extrusion rate. There was an absolute dependence of acid extrusion on external Na+, external HCO-3 (at constant pH), and internal Cl-. Furthermore, the dependence of the acid extrusion rate on each of these three parameters was described by Michaelis-Menten kinetics. Acid extrusion was stimulated by an acid pHi, required internal ATP, and was blocked by external 4-acetamido-4'-isothiocyanostilbene-2,2'-disulfonate (SITS). Under a standard set of conditions (i.e., [HCO-3]o = 12 mM, pHo = 8.00, [Na+]o = 425 mM, [Cl-]i = 150 mM, [ATP]i = 4 mM, pHi = 6.5, and 16 degrees C), the mean acid extrusion rate was 7.5 pmol X cm-2 X s-1. In a second study under the above standard conditions, the unidirectional Na+ efflux (measured with 22Na) mediated by the pHi-regulating system was found to be approximately 0, whereas the mean influx was about 3.4 pmol X cm-2 X s-1. This net influx required external HCO-3, internal Cl-, and acid pHi, internal ATP, and was blocked by SITS. In the final series of experiments under the above standard conditions, the unidirectional Cl- influx (measured with 36Cl) mediated by the pHi-regulating system was found to be approximately 0, whereas the mean efflux was approximately 3.9 pmol X cm-2 X s-1. This net efflux required external HCO-3, external Na+, an acid pHi, internal ATP, and was blocked by SITS. We conclude that the pHi-regulating system mediates the obligate net influx of HCO-3 (or equivalent species) and Na+ and the net efflux of Cl- in the stoichiometry of 2:1:1. The transport system is stimulated by intracellular acid loads, requires ATP, and is blocked by SITS.

scholarly journals Effects of Temperature on the Flow and Heat Transfer in Gel Fuels: A Numerical Study

Energies ◽  
2020 ◽  
Vol 13 (4) ◽  
pp. 821
Author(s):  
Qin-Liu Cao ◽  
Wei-Tao Wu ◽  
Wen-He Liao ◽  
Feng Feng ◽  
Mehrdad Massoudi
Keyword(s):  
Heat Transfer ◽  
Low Temperature ◽  
Transport System ◽  
Apparent Viscosity ◽  
Thermal Design ◽  
Straight Pipe ◽  
Heating Wall ◽  
Supply Pressure ◽  
Flow And Heat Transfer ◽  
The Mean

In general, rheological properties of gelled fuels change dramatically when temperature changes. In this work, we investigate flow and heat transfer of water-gel in a straight pipe and a tapered injector for non-isothermal conditions, which mimic the situations when gelled fuels are used in propulsion systems. The gel-fluid is modeled as a non-Newtonian fluid, where the viscosity depends on the shear rate and the temperature; a correlation fitted with experimental data is used. For the fully developed flow in a straight pipe with heating, the mean apparent viscosity at the cross section when the temperature is high is only 44% of the case with low temperature; this indicates that it is feasible to control the viscosity of gel fuel by proper thermal design of pipes. For the flow in the typical tapered injector, larger temperature gradients along the radial direction results in a more obvious plug flow; that is, when the fuel is heated the viscosity near the wall is significantly reduced, but the effect is not obvious in the area far away from the wall. Therefore, for the case of the tapered injector, as the temperature of the heating wall increases, the mean apparent viscosity at the outlet decreases first and increases then due to the high viscosity plug formed near the channel center, which encourages further proper design of the injector in future. Furthermore, the layer of low viscosity near the walls plays a role similar to lubrication, thus the supply pressure of the transport system is significantly reduced; the pressure drop for high temperature is only 62% of that of low temperature. It should be noticed that for a propellent system the heating source is almost free; therefore, by introducing a proper thermal design of the transport system, the viscosity of the gelled fuel can be greatly reduced, thus reducing the power input to the supply pressure at a lower cost.

Calcium efflux in giant axons

1967 ◽  
Vol 135 (2) ◽  
pp. 368-370 ◽  
Author(s):  
M. Luxoro ◽  
S. Rissetti
Keyword(s):  
Calcium Efflux ◽  
Giant Axons

Lead and calcium transport in human erythrocyte

1999 ◽  
Vol 18 (5) ◽  
pp. 327-332 ◽  
Author(s):  
J V Calderón-Salinas ◽  
M A Quintanar-Escorcia ◽  
M T González-Martínez ◽  
C E Hernández-Luna
Keyword(s):  
Transport System ◽  
Human Erythrocyte ◽  
Calcium Transport ◽  
Human Erythrocytes ◽  
The Other ◽  
Erythrocyte Ghosts ◽  
Passive Transport ◽  
Ca Uptake

In this paper we report the lead (Pb) and calcium (Ca) uptake by erythrocyte ghosts. In both cases the transport was carried out by a passive transport system with two kinetic components (Michaelis-Menten and Hill). Pb and Ca were capable of inhibiting the transport of the other metal in a non-competitive way. Under hyperpolarization, the uptakes of Ca and Pb were enhanced and the Michaelis-Menten component prevailed. Both Ca and Pb uptakes were inhibited by N-ethyl-maleimide to the same extent. These results indicate that Pb and Ca share the same permeability pathway in human erythrocytes and that this transport system is electrogenic.

scholarly journals Metabolic evaluation of Crioulo horses participating in competitions of 750 km

2013 ◽  
Vol 33 (12) ◽  
pp. 1471-1477 ◽  
Author(s):  
Lorena Alvariza Amaral ◽  
Millie Marchiori ◽  
Charles Ferreira Martins ◽  
Marcio Nunes Correa ◽  
Carlos Eduardo Wayne Nogueira
Keyword(s):  
Inflammatory Process ◽  
Ionized Calcium ◽  
Metabolic Responses ◽  
Total Calcium ◽  
Blood Cell Count ◽  
Metabolic Evaluation ◽  
Sodium Potassium ◽  
Blood Samples ◽  
Mean Values ◽  
The Mean

The Crioulo breed of horses performs in one of the most physically demanding equestrian competitions, the Marcha de Resistência, which is a contest in which the horses run 750 km in 15 days. The study's aim was to characterize the metabolic responses during this period. We evaluated eleven Crioulo horses in the competition, specifically, two males and nine females. Blood samples were collected 24 hours before the contest and on the 4th, 9th, 11th, 14th and 15th days of competition. We evaluated CK, AST, LDH, glucose, lactate, urea, creatinine, sodium, potassium, chloride, magnesium, total calcium, ionized calcium, total protein, hematocrit and the white blood cell count. At the end of the competition, the mean values of serum AST were 1151±358 IU/ L the mean LDH values were 7418±1695 IU/L and CK was 13,867±3998UI /L. There was a significant increase in urea, creatinine and lactate (p<0.0001). A decrease in the mean values of chloride, sodium, potassium, and total and ionized calcium was observed (p≤0.0002). An evaluation of the total leukocytes and segmented neutrophils (p≤0.0002) revealed their increased values, and decreased values were observed for hematocrit, plasma protein and total lymphocytes (p≤0.0003). The values of glucose, on average, remained constant. Based on these data, we conclude that the Marcha de Resistência competition necessitated a high muscular demand and the depletion of energy and electrolytes, suggesting an inflammatory process in the animals evaluated.

Effect of 1,25-(OH)2D3 on jejunal absorption of magnesium in patients with chronic renal disease

1980 ◽  
Vol 238 (4) ◽  
pp. G349-G352 ◽  
Author(s):  
A. C. Schmulen ◽  
M. Lerman ◽  
C. Y. Pak ◽  
J. Zerwekh ◽  
S. Morawski ◽  
...  
Keyword(s):  
Vitamin D ◽  
Renal Disease ◽  
Chronic Renal Disease ◽  
Normal Subjects ◽  
Mean Value ◽  
Normal Serum ◽  
Perfusion Technique ◽  
Dihydroxyvitamin D3 ◽  
Jejunal Absorption ◽  
The Mean

These studies were performed to see if jejunal malabsorption of magnesium in patients with chronic renal disease was influenced by therapy with 1 alpha, 25-dihydroxyvitamin D3 [1,25-(OH)2D3; 2 microgram/day by mouth for 7 days]. This treatment restored normal serum concentrations of the vitamin D metabolite from 0.9 +/- 0.2 to 4.2 +/- 0.6 ng/dl. Jejunal absorption of magnesium, measured by a triple-lumen constant-perfusion technique, was enhanced in each of the seven patients by this therapy. The mean value rose from 0.04 +/- 0.02 to 0.13 +/- 0.02 mmol . 30 cm-1 . h-1. This last value is similar to the magnesium absorption rate in untreated normal subjects. These results demonstrate that magnesium absorption in the human jejunum is dependent on vitamin D, and they show that 1 alpha,25-dihydroxyvitamin D3 therapy in patients with chronic renal failure is associated with an enhanced jejunal absorption of magnesium.

Rate of uptake of carbon monoxide at different inspired concentrations in humans

1982 ◽  
Vol 52 (1) ◽  
pp. 109-113 ◽  
Author(s):  
H. A. Jones ◽  
J. C. Clark ◽  
E. E. Davies ◽  
R. E. Forster ◽  
J. M. Hughes
Keyword(s):  
Carbon Monoxide ◽  
Transport System ◽  
Human Lung ◽  
Normal Subjects ◽  
Facilitated Transport ◽  
Diffusing Capacity ◽  
Normal Human ◽  
The Mean ◽  
Co Concentrations

The rate of uptake of carbon monoxide (CO) in the lungs of normal subjects were measured at inspired concentrations of less than 1, 300, and 3,000 ppm (less than 0.0001–0.3%) using radioactive CO (11CO). In nine subjects the rate of uptake was monitored at the mouth during rebreathing. At inspired CO concentrations of approximately 1, 300, and 3,000 ppm and a mean alveolar O2 fraction of 0.15, the mean lung diffusing capacity was 25.8, 26.4, and 25.3 ml . min-1. Torr-1, respectively. In seven subjects the measurements were repeated after a period of O2 breathing, giving a mean alveolar O2 fraction of 0.78. The calculated membrane diffusing capacity was 31.9, 33.7, and 32.0 ml . min-1. Torr-1 at less than 1, 300, and 3,000 ppm inspired CO. We conclude that there is no difference in the rate of uptake of CO over the range of concentrations studied in these experiments. No evidence for the presence of a facilitated transport system for CO in the normal human lung was found.

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