The Measurement of Potassium Efflux in Superfused Frog Sartorius Muscles

1972 ◽  
Vol 50 (2) ◽  
pp. 123-131 ◽  
Author(s):  
G. E. Lucier ◽  
G. W. Mainwood
Keyword(s):  
Gas Phase ◽  
Water Movement ◽  
Potassium Content ◽  
Sartorius Muscle ◽  
Detectable Change ◽  
Electrochemical Gradient ◽  
Potassium Efflux ◽  
Minimum Detectable Change ◽  
Potassium Flux ◽  
Frog Sartorius

A method of measuring net potassium flux in isolated frog sartorius muscles is described. The method depends on superfusing muscles at a slow rate in a gas phase so that a thin film of fluid is maintained on the surface. The effluent is analyzed and efflux determined by the product of flow rate and concentration change. Compartment volumes are measured and water movement is monitored by 14C-inulin. A mean resting net efflux of 25 nequiv/g/min or 0.9 pequiv/cm2/s is given in Ringers containing 2.5 mequiv/l potassium. Diffusion limits the response time of the system so that it is only possible to estimate mean flux rates over intervals of the order of 10–20 min. The minimum detectable change in potassium content of the muscle with this system is about 3.5 nequiv or approximately 0.04% of the average potassium content of the sartorius muscle. The increase in net efflux measured during activity (3.7 pequiv/cm2 per impulse) represents only about half the expected value. This is probably due to reentry of potassium with the electrochemical gradient resulting from the increased extracellular concentration. The addition of ouabain to the superfusion fluid results in an increase of potassium efflux to about four times the resting level (85 nequiv/g/min).

scholarly journals Tracer and Non-Tracer Potassium Fluxes in Frog Sartorius Muscle and the Kinetics of Net Potassium Movement

1964 ◽  
Vol 47 (4) ◽  
pp. 605-638 ◽  
Author(s):  
R. A. Sjodin ◽  
E. G. Henderson
Keyword(s):  
Specific Activity ◽  
Small Deviation ◽  
Sartorius Muscle ◽  
Potassium Efflux ◽  
Cellular Compartment ◽  
Ringer’S Solution ◽  
Frog Sartorius Muscle ◽  
Wide Range ◽  
Whole Muscle ◽  
Frog Sartorius

Experiments were performed to test the applicability of permeability kinetics to whole frog sartorius muscle using K42 ions as tracers of potassium flux. The whole muscle was found to obey closely the kinetic laws expected to hold for single cellular units in which the potassium fluxes are membrane-limited and intracellular mixing is rapid enough not to introduce serious error. In a 5 mM K Ringer's solution, potassium efflux was very nearly equal to influx when the rate constant for K42 loss was applied to the whole of the muscle potassium. Over a fairly wide range of external potassium concentration, the assumed unidirectional fluxes measured with tracer K42 showed good agreement with net potassium changes determined analytically. The specific activity of potassium lost from labeled muscles to an initially K-free Ringer's solution was measured as a test of the adequacy of intracellular mixing. The results were those expected for a population of cells with uniformly distributed intracellular K42. A small deviation was encountered which can be attributed either to a dispersion of fiber sizes in the sartorius or to a possible small additional cellular compartment in each individual fiber. The additional cellular compartment, should it exist, contains from 0.5 to 1 per cent of the muscle potassium. This is evidently not large enough to interfere seriously with the applicability of permeability kinetics to the whole muscle.

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.

scholarly journals The Potassium Flux Ratio in Skeletal Muscle As a Test for Independent Ion Movement

1965 ◽  
Vol 48 (5) ◽  
pp. 777-795 ◽  
Author(s):  
R. A. Sjodin
Keyword(s):  
Skeletal Muscle ◽  
Flux Ratio ◽  
Muscle Membrane ◽  
Sartorius Muscle ◽  
Potassium Ions ◽  
Theoretical Relation ◽  
Independence Principle ◽  
Potassium Flux ◽  
Frog Sartorius ◽  
Muscle Fiber Membrane

The flux ratio of potassium ions was measured on frog sartorius muscle under conditions in which a substantial net potassium loss occurs. Muscle fiber membrane potentials were measured under identical conditions. The observed flux ratios were compared with values calculated from a theoretical relation derived on the assumptions that the unidirectional fluxes are both passive and occur independently. The results favor the conclusion that the potassium fluxes across skeletal muscle membrane occur along passive electrochemical gradients and obey the independence principle.

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.

scholarly journals Minimum Detectable Change of Visual Acuity Measurements Using ETDRS Charts (Early Treatment Diabetic Retinopathy Study)

2021 ◽  
Vol 18 (15) ◽  
pp. 7876
Author(s):  
María Carmen Sánchez-González ◽  
Raquel García-Oliver ◽  
José-María Sánchez-González ◽  
María-José Bautista-Llamas ◽  
José-Jesús Jiménez-Rejano ◽  
...  
Keyword(s):  
Visual Acuity ◽  
Diabetic Retinopathy ◽  
Early Treatment ◽  
High Reliability ◽  
Minimal Detectable Change ◽  
High Contrast ◽  
Detectable Change ◽  
Low Contrast ◽  
Minimum Detectable Change ◽  
The Mean

In our work, we determined the value of visual acuity (VA) with ETDRS charts (Early Treatment Diabetic Retinopathy Study). The purpose of the study was to determine the measurement reliabilities, calculating the correlation coefficient interclass (ICC), the value of the error associated with the measure (SEM), and the minimal detectable change (MDC). Forty healthy subjects took part. The mean age was 23.5 ± 3.1 (19 to 26) years. Visual acuities were measured with ETDRS charts (96% ETDRS chart nº 2140) and (10% SLOAN Contrast Eye Test chart nº 2153). The measurements were made (at 4 m) under four conditions: Firstly, photopic conditions with high contrast (HC) and low contrast (LC) and after 15 min of visual rest, mesopic conditions with high and low contrast. Under photopic conditions and high contrast, the ICC = 0.866 and decreased to 0.580 when the luminosity and contrast decreased. The % MDC in the four conditions was always less than 10%. It was minor under photopic conditions and HC (5.83) and maximum in mesopic conditions and LC (9.70). Our results conclude a high reliability of the ETDRS test, which is higher in photopic and high contrast conditions and lower when the luminosity and contrast decreases.

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.

Minimum clinically important difference in pain, disability, and quality of life after neural decompression and fusion for same-level recurrent lumbar stenosis: understanding clinical versus statistical significance

2012 ◽  
Vol 16 (5) ◽  
pp. 471-478 ◽  
Author(s):  
Scott L. Parker ◽  
Stephen K. Mendenhall ◽  
David N. Shau ◽  
Owoicho Adogwa ◽  
William N. Anderson ◽  
...  
Keyword(s):  
Quality Of Life ◽  
Minimum Clinically Important Difference ◽  
Leg Pain ◽  
Lumbar Stenosis ◽  
Detectable Change ◽  
Calculation Methods ◽  
Recurrent Stenosis ◽  
Minimum Detectable Change ◽  
Clinically Important Difference

Object Spine surgery outcome studies rely on patient-reported outcome (PRO) measurements to assess treatment effect, but the extent of improvement in the numerical scores of these questionnaires lacks a direct clinical meaning. Because of this, the concept of a minimum clinically important difference (MCID) has been used to measure the critical threshold needed to achieve clinically relevant treatment effectiveness. As utilization of spinal fusion has increased over the past decade, so has the incidence of same-level recurrent stenosis following index lumbar fusion, which commonly requires revision decompression and fusion. The MCID remains uninvestigated for any PROs in the setting of revision lumbar surgery for this pathology. Methods In 53 consecutive patients undergoing revision surgery for same-level recurrent lumbar stenosis–associated back and leg pain, PRO measures of back and leg pain were assessed preoperatively and 2 years postoperatively, using the visual analog scale for back pain (VAS-BP) and leg pain (VAS-LP), Oswestry Disability Index (ODI), Physical and Mental Component Summary categories of the 12-Item Short Form Health Survey (SF-12 PCS and MCS) for quality of life, Zung Depression Scale (ZDS), and EuroQol-5D health survey (EQ-5D). Four established anchor-based MCID calculation methods were used to calculate MCID (average change; minimum detectable change; change difference; and receiver operating characteristic curve analysis) for 2 separate anchors (health transition index of the SF-36 and the satisfaction index). Results All patients were available for 2-year PRO assessment. Two years after surgery, a significant improvement was observed for all PROs assessed. The 4 MCID calculation methods generated a range of MCID values for each of the PROs (VAS-BP 2.2–6.0, VAS-LP 3.9–7.5, ODI 8.2–19.9, SF-12 PCS 2.5–12.1, SF-12 MCS 7.0–15.9, ZDS 3.0–18.6, and EQ-5D 0.29–0.52). Each patient answered synchronously for the 2 anchors, suggesting both of these anchors are equally appropriate and valid for this patient population. Conclusions The same-level recurrent stenosis surgery-specific MCID is highly variable based on calculation technique. The “minimum detectable change” approach is the most appropriate method for calculation of MCIDs in this population because it was the only method to reliably provide a threshold above the 95% confidence interval of the unimproved cohort (greater than the measurement error). Based on this method, the MCID thresholds following neural decompression and fusion for symptomatic same-level recurrent stenosis are 2.2 points for VAS-BP, 5.0 points for VAS-LP, 8.2 points for ODI, 2.5 points for SF-12 PCS, 10.1 points for SF-12 MCS, 4.9 points for ZDS, and 0.39 QALYs for EQ-5D.

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