Events Occurring in the Region of the Threshold for Potassium-Induced Contractures of Frog Skeletal Muscle. Changes in Elasticity and Oxygen Consumption

1972 ◽  
Vol 50 (3) ◽  
pp. 179-187 ◽  
Author(s):  
E. C. Vos ◽  
G. B. Frank
Keyword(s):  
Oxygen Consumption ◽  
Striated Muscle ◽  
Ringer Solution ◽  
Continuous Change ◽  
Maximum Increase ◽  
Tension Development ◽  
Mechanical Threshold ◽  
Steady Level ◽  
Continuous Relaxation ◽  
Muscle Changes

Small bundles of fibers of the semitendinosus of Rana pipiens were subjected to rapid stretches in normal Ringer solution and solutions containing potassium in concentrations just below the mechanical threshold for tension development. The resistance to stretch (R.T.S.) increased with increasing [K+]0. The increase in R.T.S. was dependent on the duration of exposure; the maximum occurred after about 30 s while longer exposures led to a decrease in the R.T.S. The maximum increase in the R.T.S. varied from two to six times the normal R.T.S. The increase in the R.T.S was hyperbolically related to [K+]0. An attempt was made to correlate the mechanical activation and the increase in respiration in muscles exposed to elevated [K+]0 (Solandt effect) by continuously measuring the oxygen consumption [Formula: see text] of toe muscles. Following exposure to an elevated [K+]0 just below the mechanical threshold, the [Formula: see text] started to increase after about 30 s and took 2–3 min to reach a new steady level. The results suggest that: (a) a low level of activation of the contractile elements occurs just below the mechanical threshold for tension development, (b) the excitation–contraction coupling process of frog striated muscle is one of continuous change, i.e. without a sharply defined threshold, and (c) the Solandt effect is probably the expression of a continuous relaxation-type process.

The Threshold for Potassium-Induced Contractures of Frog Skeletal Muscle. Potentiation of Potassium-Induced Contractures by Preexposure to Subthreshold Potassium Concentrations

1972 ◽  
Vol 50 (1) ◽  
pp. 37-44 ◽  
Author(s):  
E. C. Vos ◽  
G. B. Frank
Keyword(s):  
Skeletal Muscle ◽  
Potassium Concentration ◽  
Ringer Solution ◽  
Frog Skeletal Muscle ◽  
Contractile Apparatus ◽  
Tension Development ◽  
Eventual Loss ◽  
Active Processes ◽  
Muscle Potentiation ◽  
Small Bundle

A brief exposure (about 10–30 s) of a frog's toe muscle or a small bundle of fibers from the semi-tendinosus muscle to just subthreshold potassium concentrations potentiated contractures subsequently produced by exposing the muscles to a potassium concentration slightly above the threshold. The contractures thus potentiated had greater maximum tensions, and greater rates of tension development and relaxation than control contractures elicited by the same final potassium concentration. The resistance to stretch (R.T.S.) in the first few seconds of the potentiated contractures was about twice that of control contractures. Maximum potentiation occurred with preexposures of about 30 s; longer preexposures led to a decrease of potentiation and eventually to a depression of the contracture. The potentiation was not immediately abolished when the muscle was reexposed to Ringer solution but persisted for 2 min or longer (the 'washout effect'). It was concluded that exposing a muscle to low subcontracture threshold concentrations of potassium for a few seconds primes the intracellular contractile apparatus, probably by causing an increased sarcoplasmic concentration of Ca2+ ions, resulting in a potentiation of subsequently induced submaximal potassium contractures. The increase in metabolism (or 'Solandt effect') seen under these conditions is temporally related to the decline and eventual loss of the potentiation and is probably a reflection of active processes involved in reducing the sarcoplasmic concentration of Ca2+ ions.

scholarly journals The duration of the recovery period following strenuous muscular exercise

1933 ◽  
Vol 113 (783) ◽  
pp. 327-344 ◽  
Keyword(s):  
Carbon Dioxide ◽  
Oxygen Consumption ◽  
Normal Values ◽  
Recovery Period ◽  
Oxygen Intake ◽  
Respiratory Metabolism ◽  
Carbon Dioxide Output ◽  
Steady Level ◽  
Made In

There are a variety of ways in which the duration of the recovery period after exercise can be determined. The method most frequently employed depends upon observations of the respiratory metabolism. This method has been chosen because the respiratory changes due to exercise can be followed with reasonable ease and accuracy, and because these changes are among the last of the more obvious effects of the exercise to disappear during recovery. In addition, interesting data concerning the effects of exercise on respiratory metabolism can be collected during the determination of the duration of the recovery period when this method is used. In determining the duration of the recovery period by observation of the respiratory metabolism, it is necessary to decide when the carbon dioxide output and oxygen intake have returned to their normal values and are no longer affected by the process of recovery from the exercise. This decision has been made in a variety of ways by different investigators. Some have made one or more pre-exercise determinations of the subject's basal oxygen intake and carbon dioxide output. Recovery was said to be complete when the carbon dioxide output and oxygen consumption returned to these values after exercise. Others found that the oxygen consumption did not return to the pre-exercise level within a reasonable length of time, but remained above normal for several hours. They considered that recovery was complete when the carbon dioxide output and oxygen intake returned to a steady level after exercise, even if the level was not the same as that before exercise.

Active state plateau and latency in mammalian striated muscle

1961 ◽  
Vol 200 (4) ◽  
pp. 667-671 ◽  
Author(s):  
Forbes H. Norris
Keyword(s):  
Latent Period ◽  
Striated Muscle ◽  
Muscle Length ◽  
Single Stimulus ◽  
Active State ◽  
Tension Development ◽  
Maximum Tension ◽  
Tension Curves ◽  
Tetanic Tension

The active state plateau in rat striated muscle was studied by superimposition of tension curves resulting from one and two stimuli. The plateau ends 4.0 ± 0.1 msec. after stimulation in rat striated muscle at 36°C. The time to the end of the plateau is 3.4 ± 0.1 times the latent period. During the plateau, response to a second stimulus appears after increased mechanical latency. The second stimulus can also result in tension development at rates nearly twice those reached after a single stimulus. This effect has a peak which about corresponds to the end of the active state plateau, but precedes the peak of the curve for maximum tension. Correct timing of the second stimulus can result in about 60% of tetanic tension. The use of thiopental, gallamine, tubocurarine and changes in muscle length did not affect these results.

scholarly journals Poorly Understood Aspects of Striated Muscle Contraction

2015 ◽  
Vol 2015 ◽  
pp. 1-28 ◽  
Author(s):  
Alf Månsson ◽  
Dilson Rassier ◽  
Georgios Tsiavaliaris
Keyword(s):  
Muscle Contraction ◽  
Structural Changes ◽  
Striated Muscle ◽  
Three Dimensional ◽  
Skeletal Muscle Function ◽  
Tension Development ◽  
Atomic Structures ◽  
Molecular Events ◽  
Physiological Properties

Muscle contraction results from cyclic interactions between the contractile proteins myosin and actin, driven by the turnover of adenosine triphosphate (ATP). Despite intense studies, several molecular events in the contraction process are poorly understood, including the relationship between force-generation and phosphate-release in the ATP-turnover. Different aspects of the force-generating transition are reflected in the changes in tension development by muscle cells, myofibrils and single molecules upon changes in temperature, altered phosphate concentration, or length perturbations. It has been notoriously difficult to explain all these events within a given theoretical framework and to unequivocally correlate observed events with the atomic structures of the myosin motor. Other incompletely understood issues include the role of the two heads of myosin II and structural changes in the actin filaments as well as the importance of the three-dimensional order. We here review these issues in relation to controversies regarding basic physiological properties of striated muscle. We also briefly consider actomyosin mutation effects in cardiac and skeletal muscle function and the possibility to treat these defects by drugs.

scholarly journals An Analysis of the Leakages of Sodium Ions into and Potassium Ions out of Striated Muscle Cells

1973 ◽  
Vol 61 (2) ◽  
pp. 222-250 ◽  
Author(s):  
R. A. Sjodin ◽  
L. A. Beaugé
Keyword(s):  
Steady State ◽  
Striated Muscle ◽  
Ringer Solution ◽  
Intracellular Sodium ◽  
Sodium Ion ◽  
Ion Concentration ◽  
Sodium Ions ◽  
Sodium Influx ◽  
Potassium Efflux ◽  
Steady State Balance

Net sodium influx under K-free conditions was independent of the intracellular sodium ion concentration, [Na]i, and was increased by ouabain. Unidirectional sodium influx was the sum of a component independent of [Na]i and a component that increased linearly with increasing [Na]i. Net influx of sodium ions in K-free solutions varied with the external sodium ion concentration, [Na]o, and a steady-state balance of the sodium ion fluxes occurred at [Na]o = 40 mM. When solutions were K-free and contained 10-4 M ouabain, net sodium influx varied linearly with [Na]o and a steady state for the intracellular sodium was observed at [Na]o = 13 mM. The steady state observed in the presence of ouabain was the result of a pump-leak balance as the external sodium ion concentration with which the muscle sodium would be in equilibrium, under these conditions, was 0.11 mM. The rate constant for total potassium loss to K-free Ringer solution was independent of [Na]i but dependent on [Na]o. Replacing external NaCl with MgCl2 brought about reductions in net potassium efflux. Ouabain was without effect on net potassium efflux in K-free Ringer solution with [Na]o = 120 mM, but increased potassium efflux in a medium with NaCl replaced by MgCl2. When muscles were enriched with sodium ions, potassium efflux into K-free, Mg++-substituted Ringer solution fell to around 0.1 pmol/cm2·s and was increased 14-fold by addition of ouabain.

scholarly journals Control of myocardial oxygen consumption: relative influence of contractile state and tension development

1968 ◽  
Vol 47 (2) ◽  
pp. 375-385 ◽  
Author(s):  
Thomas P. Graham ◽  
James W. Covell ◽  
Edmund H. Sonnenblick ◽  
John Ross ◽  
Eugene Braunwald
Keyword(s):  
Oxygen Consumption ◽  
Myocardial Oxygen Consumption ◽  
Relative Influence ◽  
Tension Development ◽  
Contractile State

Ammonia production in the isolated working rabbit heart

1961 ◽  
Vol 200 (2) ◽  
pp. 238-242 ◽  
Author(s):  
H. Feinberg ◽  
Sister Mary Alma
Keyword(s):  
Blood Pressure ◽  
Heart Rate ◽  
Oxygen Consumption ◽  
Rabbit Heart ◽  
Ringer Solution ◽  
Heart Weight ◽  
Ammonia Production

Ammonia production, oxygen consumption, heart rate and blood pressure were observed in the isolated working rabbit heart perfused with Krebs-Ringer solution and with Krebs-Ringer solution containing dog hemoglobin. Oxygen consumption and an index to cardiac effort (heart rate x blood pressure) were shown to be correlated. There was a lesser correlation between ammonia production and cardiac effort. The ratio, ammonia production/oxygen consumption, when both are expressed as micromoles/minute/ gram of heart weight, averaged 0.064 ± .006. Perfusate pH was altered by alternately exposing the perfusate to 95%O2– 5%CO2 and 90%O2–10%CO2. No effect on the ratio ammonia production/oxygen consumption was noted. l-Epinephrine, 0.1–1.0 µg/ml, was continuously infused and resulted in an increase in cardiac effort, oxygen consumption, ammonia production and the ratio of ammonia production/ oxygen consumption.

Optical density changes of single muscle fibers in sodium-free solutions

1968 ◽  
Vol 46 (2) ◽  
pp. 247-260 ◽  
Author(s):  
S. G. A. McLaughlin ◽  
J. A. M. Hinke
Keyword(s):  
Optical Density ◽  
Striated Muscle ◽  
Muscle Fibers ◽  
Ringer Solution ◽  
Bathing Solution ◽  
Alkali Metal Cations ◽  
Initial Value ◽  
Striated Muscle Fibers ◽  
Exchange Resins ◽  
Normal Ringer

The optical density, O.D., of single striated muscle fibers from the giant barnacle, Balanus nubilus, was measured at 50-mμ intervals between 450 and 850 mμ. At all wavelengths, the O.D. decreased markedly when the normal Ringer bathing solution was replaced by sodium-free sucrose Ringer solution. For example, at 850 mμ the O.D. of the fibers, relative to the initial value in normal Ringer solution, decreased from 1 to 0.21 ± 0.06 in 25 min. The corresponding increase in the transmittance, T, (O.D. = −log T) was from 5% to 55%. This change in O.D. could be reversed by returning the normal Ringer bathing solution to the bath. Large, reversible decreases in O.D. were also observed when potassium and Tris were used as substitutes for sodium. These changes in O.D. are explained by the theory of light scattering if it is assumed that sodium is bound to macromolecules in the myoplasm. This assumption is supported by experiments with cation-sensitive microelectrodes, which indicate that most of the sodium in the muscle fibers is not free in the myoplasm. When the fibers were bathed in sodium-free, lithium-substituted Ringer solution, a small reversible increase in the O.D. was observed, which may indicate that lithium is complexed more strongly than sodium by macromolecules in the myoplasm. This conclusion is compatible with the known affinities of carboxylate ion exchange resins for the alkali metal cations.

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