scholarly journals Changes in the Membrane Permeability of Frog's Sartorius Muscle Fibers in Ca-Free EDTA Solution

1963 ◽  
Vol 47 (2) ◽  
pp. 379-392 ◽  
Author(s):  
H. Kimizuka ◽  
K. Koketsu
Keyword(s):  
Membrane Permeability ◽  
Chloride Content ◽  
Chloride Ions ◽  
Sartorius Muscle ◽  
Constant Field ◽  
Sodium Influx ◽  
Sodium Potassium ◽  
Edta Solution ◽  
Frog Sartorius ◽  
Sodium And Potassium

The changes in the membrane permeability to sodium, potassium, and chloride ions as well as the changes in the intracellular concentration of these ions were studied on frog sartorius muscles in Ca-free EDTA solution. It was found that the rate constants for potassium and chloride efflux became almost constant within 10 minutes in the absence of external calcium ions, that for potassium increasing to 1.5 to 2 times normal and that for chloride decreasing about one-half. The sodium influx in Ca-free EDTA solution, between 30 and 40 minutes, was about 4 times that in Ringer's solution. The intracellular sodium and potassium contents did not change appreciably but the intracellular chloride content had increased to about 4 times normal after 40 minutes. By applying the constant field theory to these results, it was concluded that (a) PCl did not change appreciably whereas PK decreased to a level that, in the interval between 10 and 40 minutes, was about one-half normal, (b) PNa increased until between 30 and 40 minutes it was about 8 times normal. The low value of the membrane potential between 30 and 40 minutes was explained in terms of the changes in the membrane permeability and the intracellular ion concentrations. The mechanism for membrane depolarization in this solution was briefly discussed.

Resting membrane potentials: a student test of alternate hypotheses.

1995 ◽  
Vol 269 (6) ◽  
pp. S37 ◽  
Author(s):  
C L Thurman
Keyword(s):  
Hypothesis Testing ◽  
Membrane Permeability ◽  
Channel Blocker ◽  
Membrane Potentials ◽  
Membrane Voltage ◽  
K Channel ◽  
Sartorius Muscle ◽  
Student Test ◽  
Physiology Students ◽  
Frog Sartorius

The frog sartorius muscle is a model tissue for demonstrating to physiology students the principles underlying both membrane phenomena and hypothesis testing. Myocytes can be impaled with conventional glass microelectrodes to measure membrane voltage (Vm). Further, Vm is observed as extracellular K+ is altered and a K+ channel blocker is added. After the experiment, students examine the underlying assumptions of the Nernst equilibrium and the Goldman-Hodgkin-Katz equation. They ultimately determine which of the two algorithms best predicts the measured Vm. In addition, students learn micromanipulation and impalement techniques. This experiment facilitates the student's understanding of membrane permeability, ionic gradients, and membrane voltage.

Frusemide-Sensitive Sodium and Potassium Transport by Human Leucocytes

1985 ◽  
Vol 68 (1) ◽  
pp. 89-91 ◽  
Author(s):  
Valerie E. Johnson ◽  
P. J. Hilton
Keyword(s):  
Potassium Transport ◽  
Sodium Influx ◽  
Potassium Efflux ◽  
Sodium Potassium ◽  
External Potassium ◽  
Normal Human ◽  
Potassium Influx ◽  
Net Flux ◽  
Sodium And Potassium

1. Frusemide-sensitive sodium and potassium transport by normal human leucocytes has been studied in vitro by both isotopic and net flux techniques. 2. In physiological media the leucocyte exhibits a frusemide-sensitive influx of sodium and potassium of equal magnitude compatible with a 1:1 co-transport system. 3. Cells exposed to zero external sodium and potassium (osmolality maintained with choline) demonstrated a frusemide-sensitive sodium and potassium efflux. 4. Frusemide-sensitive potassium influx was dependent on the presence of external sodium but frusemide-sensitive sodium influx persisted unchanged in the absence of external potassium. 5. Frusemide-sensitive potassium influx was dependent on external chloride but frusemide-sensitive sodium influx was chloride-independent. 6. These last two observations make it likely that the frusemide-sensitive pathway is capable of operating in modes other than sodium-potassium co-transport.

scholarly journals RUBIDIUM AND CESIUM FLUXES IN MUSCLE AS RELATED TO THE MEMBRANE POTENTIAL

1959 ◽  
Vol 42 (5) ◽  
pp. 983-1003 ◽  
Author(s):  
Raymond A. Sjodin
Keyword(s):  
Field Theory ◽  
Membrane Potential ◽  
Low Temperatures ◽  
Resting Potential ◽  
Sartorius Muscle ◽  
Potassium Ions ◽  
Constant Field ◽  
Cesium Ions ◽  
Potassium Flux ◽  
Frog Sartorius

The reduction of membrane potential in frog sartorius muscle produced by rubidium and cesium ions has been studied over a wide concentration range and compared with depolarization occasioned by potassium ions. The constant field theory of passive flux has been used to predict the potential changes observed. The potential data suggest certain permeability coefficient ratios and these are compared with ratios obtained from flux data using radioactive tracers. The agreement of the flux with the potential data is good if account is taken of the inhibition of potassium flux which occurs in the presence of rubidium and cesium ions. A high temperature dependence has been observed for cesium influx (Q10 = 2.5) which is correlated with the observation that cesium ions depolarize very little at low temperatures. The observations suggest that cesium ions behave more like sodium ions at low temperatures and more like potassium ions at room temperature with respect to their effect on the muscle cell resting potential. The constant field theory of passive ion flux appears to be in general agreement with the experimental results observed if account is taken of the dependence of permeability coefficients on the concentrations of ions used and of possible interactions between the permeabilities of ions.

Sodium permeability of frog skeletal muscle in absence and presence of veratridine

1987 ◽  
Vol 252 (2) ◽  
pp. C190-C196 ◽  
Author(s):  
L. C. McKinney ◽  
R. W. Ratzlaff
Keyword(s):  
Sodium Channels ◽  
Sartorius Muscle ◽  
Constant Field ◽  
Dependent Manner ◽  
Sodium Permeability ◽  
Voltage Range ◽  
Flux Measurements ◽  
Dose Dependent ◽  
Frog Sartorius ◽  
External Ph

The effect of veratridine on the Na permeability of frog sartorius muscle was studied by means of ion flux measurements using radiolabeled sodium. Veratridine increases Na influx in a dose-dependent manner (apparent Kd = 160 +/- 7 microM when Vm congruent to -40 mV). The increase can be completely inhibited by tetrodotoxin (TTX) (apparent Ki = 8 +/- 2 nM), indicating that all veratridine-induced Na influx occurs via sodium channels. The time constant for the rate of onset of veratridine action is 1 h. Raising external pH one unit to 8.3 causes the rate of action of veratridine and the final level of Na influx to increase. The apparent Kd for veratridine depends on membrane voltage. Values obtained in 2.5 and 5 mM K Ringer (Vm congruent to -95 and -80 mV) were 579 +/- 279 and 35 +/- 8 microM, respectively. Veratridine-induced Na influx obeys the Goldman constant field flux equation and when veratridine concentration is 1 mM, sodium permeability is 1.5 X 10(-7) cm/s. This is much less than the maximum PNa (1.6 X 10(-3) cm/s) obtained from voltage-clamp measurements of peak Na conductance. Mg (52 mM) inhibits veratridine-induced influx by about half. Aspects of resting Na influx in the absence of veratridine (but in the presence of ouabain) were also characterized. Steady-state Na influx is unaffected by tetrodotoxin over the voltage range -90-0 mV, suggesting that no sodium channels are open in the resting state. Na influx is also insensitive to curare. It is linearly dependent on external sodium and larger at more negative membrane potentials.

The ionic composition of rainwater at Katherine, NT. and its part in the cycling of plant nutrients

1963 ◽  
Vol 14 (3) ◽  
pp. 319 ◽  
Author(s):  
R Wetselaar ◽  
JT Hutton
Keyword(s):  
Ionic Composition ◽  
Correlation Coefficients ◽  
Chloride Content ◽  
Particulate Material ◽  
Chloride Ions ◽  
Nitrate Content ◽  
Wet Season ◽  
Sodium Potassium ◽  
Annual Total ◽  
Soluble Material

Rainwater was collected from individual showers at Katherine, Northern Territory, Australia, during the 1958–59 wet season, and again in 3.4 mm portions of individual showers during the 1959–60 wet season. Strict precautions were taken during rainless periods to prevent particulate material from accumulating in the rain collector. The laboratory examination of the samples included determinations of nitrate, ammonium, sodium, potassium, magnesium, and chloride ions, and of insoluble silica. Soil and plant material samples collected in the surroundings of Katherine were also analysed for a number of elements. In spite of a total annual average rainfall of 925 mm the annual total amount of soluble material in the rainwater was less than 6–7 kg 'ha. The concentration of all ions decreased during the progress of a shower, and from shower to shower, during the progress of the season. Correlation coefficients between the different ions were all positive and generally high. No relation could be detected between the nitrate content in the rainwater and the incidence of lightning. The correlation between chloride content and amount of insoluble silica was high (+ 0.73). It is argued that most of the material in the rainwater is part of a terrestrial cycle and cannot be regarded as a true accession.

Influence of Ouabain, Strophanthidin and Dihydrostrophanthidin on Sodium and Potassium Transport in Frog Sartorii

1956 ◽  
Vol 187 (2) ◽  
pp. 328-332 ◽  
Author(s):  
John A. Johnson
Keyword(s):  
Inhibitory Action ◽  
Potassium Transport ◽  
Resting Potential ◽  
Sartorius Muscle ◽  
Frog Sartorius Muscle ◽  
Frog Sartorius ◽  
Sodium And Potassium

Ouabain and strophanthidin at a concentration of about 10–6 molar appear to inhibit the net transport of sodium out of and of potassium into the cells of the frog sartorius muscle under conditions where transport would otherwise occur. This inhibition occurs without significant effect on the resting potential. Dihydrostrophanthidin, also at a concentration of 10–6 m, failed to show the inhibitory action displayed by ouabain and strophanthidin.

scholarly journals Sodium and Potassium Influx into Citrus Leaf Slices

1971 ◽  
Vol 24 (4) ◽  
pp. 861 ◽  
Author(s):  
FA Smith ◽  
JB Robinson
Keyword(s):  
Chloride Ions ◽  
External Concentration ◽  
Sodium Influx ◽  
Citrus Leaf ◽  
Potassium Influx ◽  
Citrus Leaves ◽  
Sodium And Potassium

The influxes of sodium and potassium have been measured in slices of mature citrus leaves, using 22Na and 42K as tracers. External concentrations were 0�03-100 mM (sodium) and 0�I-100 mM (potassium). The sodium influx was always less than the potassium influx, for any given external concentration. In neither case was the influx increased by light. There was no effect on the influxes when chloride ions in the experimental solutions were replaced by sulphate ions.

Prepotentials and unidirectional propagation in myocardium

1961 ◽  
Vol 201 (5) ◽  
pp. 873-880 ◽  
Author(s):  
T. Hoshiko ◽  
Nick Sperelakis
Keyword(s):  
Current Flow ◽  
Reverse Direction ◽  
Sartorius Muscle ◽  
Potential Response ◽  
Ringer’S Solution ◽  
Current Pulses ◽  
Negative Current ◽  
Reversed Polarity ◽  
Bidirectional Propagation ◽  
Frog Sartorius

In frog ventricular strips bathed in Ca-free Ringer's solution containing 6–30 mm/liter Mg and treated with conditioning current pulses, propagation became impaired. An exaggerated foot, or prepotential, was consistently more prominent when the conditioned strip was stimulated from one end than from the other. Occasionally a prepotential in isolation alternated with a prepotential plus action potential response. After further treatment with current pulses, propagation failed in the direction of negative current flow. Thresholds of impaled cells were identical. Bidirectional propagation was restored in Ringer's solution. Conditioning pulses of reversed polarity induced unidirectional propagation in the reverse direction. Propagation in frog sartorius muscle was not blocked under similar conditions. Prepotentials and unidirectional propagation may be explained by junctional transmission from cell to cell.

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