The diffusion potentials in electrolytic mixtures. II. The system “concentrated KCl/dilute HCl”

2010 ◽  
Vol 58 (2) ◽  
pp. 99-106 ◽  
Author(s):  
J. J. Hermans
Keyword(s):  
Diffusion Potentials

scholarly journals Excitation of skinned muscle fibers by imposed ion gradients. I. Stimulation of 45Ca efflux at constant [K][Cl] product.

1985 ◽  
Vol 86 (6) ◽  
pp. 813-832 ◽  
Author(s):  
E W Stephenson
Keyword(s):  
Isometric Force ◽  
Muscle Fibers ◽  
Water Flux ◽  
Skinned Muscle ◽  
Skinned Muscle Fibers ◽  
Diffusion Potentials ◽  
45Ca Efflux ◽  
Osmotic Effects ◽  
45Ca Release ◽  
And Diffusion

45Ca efflux from skinned muscle fibers is stimulated transiently, by a highly Ca2+-dependent mechanism, by KCl replacement of K propionate. In the present studies, Cl replaced the much less permeant anion methanesulfonate (Mes) either (a) at constant [K], in which increased [K][Cl] permits net KCl and water flux across internal membranes, or (b) at constant [K][Cl] (choline substitution), in which the imposed gradients and diffusion potentials should dissipate slowly. 45Ca efflux and isometric force were measured simultaneously on segments of frog semitendinosus fibers skinned by microdissection. EGTA was applied to chelate released 45Ca either (a) shortly after high [Cl] (interrupted response), to minimize reaccumulation, (b) before high [Cl] (pretreated response), to evaluate Ca2+ dependence, or (c) under control conditions in KMes. KCl replacement of KMes stimulated release of 65% fiber 45Ca within 1 min in interrupted responses; EGTA pretreatment was only moderately inhibitory with substantial residual stimulation. In contrast, choline Cl replacement of KMes induced release of 26-35% fiber 45Ca in interrupted responses; EGTA pretreatment was strongly inhibitory, but release significantly exceeded control with a small, sustained increase in Ca2+-insensitive efflux. These differences in 45Ca release and EGTA inhibition suggest that Cl replacement of Mes at constant [K] stimulates efflux by osmotic effects as well as imposed diffusion potentials; at least half the stimulated 45Ca loss (above control) in interrupted KCl responses is attributable to an osmotic component with low Ca2+ sensitivity. In the highly Ca2+-sensitive stimulation at constant [K][Cl], 45Ca release (above control) in interrupted responses correlated well with that in the pretreated responses of segments from the same fiber, with a slope of 8.4. This relationship suggests that imposed diffusion potentials stimulate a small Ca2+-insensitive component that gradates a much larger Ca2+-dependent efflux. The Ca2+-insensitive component apparently reflects intermediate steps in the excitation-contraction coupling that require positive feedback to result in sufficient Ca release for contraction.

scholarly journals Membrane potentials and resistances of giant mitochondria. Metabolic dependence and the effects of valinomycin.

1978 ◽  
Vol 78 (1) ◽  
pp. 199-213 ◽  
Author(s):  
B L Maloff ◽  
S P Scordilis ◽  
C Reynolds ◽  
H Tedeschi
Keyword(s):  
Membrane Potential ◽  
Membrane Potentials ◽  
The Other ◽  
Metabolic State ◽  
Giant Mitochondria ◽  
Internal Concentration ◽  
Diffusion Potentials ◽  
K Concentration ◽  
Metabolic Dependence

The membrane potentials and resistances of giant mitochondria from mice fed cuprizone have been studied. They were found to correspond approx. 10-20 mV, positive inside, and 2 M omega, respectively. These properties were found to be independent of the metabolic state. The microelectrodes were in the inner mitochondrial space since (a) the potentials in the presence of valinomycin depended on the K+ concentration of the medium and magnitude of the K+ diffusion potentials was consistent with the presence of a high internal concentration of K+, (b) almost identical results were obtained with mitochondria from which the external membrane had been removed and the cristae were evaginated, and (c) punch-through experiments, in which the microelectrodes were advanced until they emerged through the other side of the mitochondria, showed an identical membrane potential both in the presence and in the absence of valinomycin. The potentials were stable under a variety of conditions and showed no sign of decay of membrane leakiness. Detailed evidence that the impaled mitochondria are metabolically viable will be presented in a separate publication.

Origin of electrical PD's in hamster thin ascending limbs of Henle's loop

1977 ◽  
Vol 232 (4) ◽  
pp. F348-F357 ◽  
Author(s):  
D. J. Marsh ◽  
C. M. Martin
Keyword(s):  
Ionic Transport ◽  
Mineral Oil ◽  
Ringer Solution ◽  
Transport Numbers ◽  
High Impedance ◽  
Perfusion Solution ◽  
Henle's Loop ◽  
Vasa Recta ◽  
Diffusion Potentials

Microelectrodes with 2-micronm-tip diameters arranged to record differentially between this ascending limbs (ALH) and ascending vasa recta (AVR), gave values of 1.95 +/- 0.17 mV, ALH positive, in hydropenia with mineral oil bathing the kidney. Average values remained in the range of 1-2 mV when the ALH and AVR values were obtained sequentially, when the kidney was bathed in Ringer solution, when 5-8 Momega Ling-Gerard microelectrodes were used in the ALH, or when the hamsters were in saline diuresis. These results contradict reports of earlier studies with high impedance Ling-Gerard electrodes that the PD was -9 mV, ALH negative. Perfusion of ALH in saline diuresis with solutions of various compositions provided estimates of ionic transport numbers: tNa+ = 0.33 +/- 0.01, tK+ = 0.00 +/- 0.02, tC1- = 0.67 +/- 0.02. When the perfusion solution was designed to have the same Na+, K+, and C1- concentrations as AVR plasma, the PD was 1.36 +/- .20 mV; when ouabain or furosemide were included (10(-5) M), the PD declined 1.35 +/- 0.21 mV and 1.41 +/- 0.28 mV, respectively. The results suggest that active C1- transport is mainly responsible for the PD, but that diffusion potentials can contribute.

Permeability of the Isolated Atlantic Salmon (Salmo salar) Chorion to Ions as Estimated by Diffusion Potentials

1987 ◽  
Vol 44 (9) ◽  
pp. 1635-1639 ◽  
Author(s):  
R. H. Peterson ◽  
D. J. Martin-Robichaud
Keyword(s):  
Atlantic Salmon ◽  
Salmo Salar ◽  
Ion Pairs ◽  
Atlantic Salmon Salmo Salar ◽  
Environmental Perturbations ◽  
Hen’S Egg ◽  
Anions And Cations ◽  
Potential Impact ◽  
Diffusion Potentials ◽  
The Difference

The properties of the teleost chorion and perivitelline fluid may allow the embryo to develop in an ionic medium which differs from ambient. A knowledge of these properties facilitates assessment of the potential impact of environmental perturbations (e.g. low-pH episodes) on the developing embryo. Diffusion potentials are created when differing concentrations of a salt solution are imposed upon the opposite sides of isolated Atlantic salmon (Salmo salar) chorions. These diffusion potentials are related to the mobilities of the cations and anions. The magnitude of the diffusion potentials were measured with NaCl, CaC2, H2SO4, and HCl solutions. The results indicate that both anions and cations permeate the chorion. Chloride appears to have greater mobility through the chorion than does sodium, although the difference in mobility of such ion pairs moving through the chorion is not as great as the difference in their mobilities in aqueous solution. Diffusion potentials obtained with CaCl2 solutions, on the other hand, indicate reduced calcium mobility through the chorion relative to chloride. The decreased mobility of Ca2+ is probably due to adsorption to fixed negative charges on the chorion. The properties of the perivitelline potential of the intact egg could be simulated qualitatively by placing a solution of negatively charged colloid (hen's egg albumin) inside the isolated chorion.

Reducing Activity and the Formation of Base in the Shore Crab, Carcinus Maenas

1985 ◽  
Vol 65 (2) ◽  
pp. 505-530 ◽  
Author(s):  
Peter S. B. Digby
Keyword(s):  
Outer Surface ◽  
Biological Material ◽  
Sea Water ◽  
Carcinus Maenas ◽  
Water Salinity ◽  
Shore Crab ◽  
Calcareous Deposits ◽  
Reducing Activity ◽  
Diffusion Potentials ◽  
Active Processes

Crustacean cuticle consists essentially of chitin impregnated and coated with protein which is tanned with quinone (Dennell, 1947a). The outer surface is most heavily tanned, and the cuticle is further strengthened by calcification. The various theories as to the mechanism of calcification in crustacean and other biological material have been reviewed briefly by Digby (1967). Most appear unsatisfactory for various reasons, and evidence was outlined that calcification might arise from the formation of base by processes which are essentially electrochemical in origin. The quinone-tanned protein of the cuticle is electrically semiconducting and supports electrode action in suitable gradients of potential (Digby, 1965), and small potential differences may arise by diffusion or by active processes. Thus the deposition of calcareous salts might arise partly at least by action comparable to that which takes place at a metallic cathode. In support of this, the position of the initial calcareous deposits in Carcinus maenas (L.) was found to change with the gradient of sea-water salinity in the manner expected if some control were exercised by diffusion potentials, acting across a thin semiconducting layer to generate small changes of pH (Digby, 1968).

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