scholarly journals ON THE STRUCTURAL CONTINUITIES OF THE TRANSVERSE TUBULAR SYSTEM OF RABBIT AND HUMAN MYOCARDIAL CELLS

1963 ◽  
Vol 16 (2) ◽  
pp. 297-313 ◽  
Author(s):  
Douglas A. Nelson ◽  
Ellis S. Benson
Keyword(s):  
Extracellular Fluid ◽  
Sartorius Muscle ◽  
Electron Microscopic ◽  
Transverse Tubular System ◽  
Tubular System ◽  
Time Distance ◽  
Kinetics Of ◽  
Frog Sartorius ◽  
Human Myocardial Cells ◽  
Physiologic Data

An electron microscopic study of rabbit and human myocardium provides further evidence of the existence of two distinct components of the sarcoplasmic reticulum. A thin-walled tubular system (termed longitudinal system) is arranged in anastomosing channels sur-surrounding each sarcomere and has transverse and possibly also longitudinal connections with the tubules of adjacent sarcomeres. A thick-walled tubular system traverses the myofiber transversely at the level of the Z lines of the myofibrils. The structure of these tubules very closely resembles that of deep sarcolemmal invaginations. Indeed, the membranes of the tubules appear to be continuous with the sarcolemma in favorable sections so that there seems to be an extension of the cell membrane and extracellular fluid to all depths of the myocardial fiber. Certain physiologic data which support this concept are discussed. The calculations of A. V. Hill comparing the kinetics of diffusion and the time-distance relationships between excitation and activation in frog sartorius muscle are reconsidered for cardiac muscle.

scholarly journals The Relation Between the Late After-Potential and the Size of the Transverse Tubular System of Frog Muscle

1964 ◽  
Vol 48 (2) ◽  
pp. 235-263 ◽  
Author(s):  
W. H. Freygang ◽  
D. A. Goldstein ◽  
D. C. Hellam ◽  
L. D. Peachey
Keyword(s):  
Experimental Data ◽  
Calculated Data ◽  
Frog Muscle ◽  
Free Solution ◽  
Electron Microscopic ◽  
Chloride Solutions ◽  
Transverse Tubular System ◽  
Tubular System ◽  
Low Potassium ◽  
Frog Sartorius

This is an investigation of the effects on the late after-potential of immersing frog sartorius muscles in three kinds of modified Ringer's fluid; hypertonic, low chloride, and potassium-free. The late after-potential has been attributed to the depolarizing effect of an accumulation of potassium, during a preceding train of impulses, in the intermediary space of the model of a muscle fiber proposed by Adrian and Freygang. Both the hypertonic and low chloride solutions prolonged the late after-potential reversibly and the potassium-free solution shortened it. The effect of the low potassium solution fitted those data calculated from the model, but the effect of the hypertonic and low chloride solutions required an increase in size of the intermediary space of the model in order to fit the calculated data. An electron microscopic study of the muscles showed that the size of the transverse tubular system changed reversibly in the hypertonic and low chloride solutions in almost the amount necessary to fit the experimental data to the calculated data. This agreement between the change in size of the transverse tubular system and that of the intermediary space indicates that the intermediary space may be the transverse tubular system.

scholarly journals Some Relations between Changes in the Linear Electrical Properties of Striated Muscle Fibers and Changes in Ultrastructure

1967 ◽  
Vol 50 (10) ◽  
pp. 2437-2458 ◽  
Author(s):  
W. H. Freygang ◽  
S. I. Rapoport ◽  
L. D. Peachey
Keyword(s):  
Electrical Properties ◽  
Time Constant ◽  
Striated Muscle ◽  
Sartorius Muscle ◽  
Transverse Tubular System ◽  
Tubular System ◽  
In Series ◽  
Striated Muscle Fibers ◽  
Frog Sartorius ◽  
Good Agreement

Some of the linear electrical properties of frog sartorius muscle have been investigated in Ringer's fluid and in a Ringer fluid made hypertonic by the addition of sucrose or NaCl. Electrical constants were determined from measurements of the phase angle of the admittance of a fiber for an applied alternating current, from measurements of the voltage induced by an inward pulse of current, and from measurements of the conduction velocity of the action potential and the time constant of its foot. The dilation of the transverse tubular system induced by the sucrose hypertonic Ringer fluid was correlated with the change in the electrical constants. From this it is concluded that a two time constant equivalent circuit for the membrane, as proposed by Falk and Fatt, is in good agreement with our results. Both the area of the membrane of the transverse tubular system, and the capacity (ce) attributed to it, increased in the sucrose hypertonic Ringer fluid. The resistance re, which is in series with ce, did not fall when the transverse tubular system was dilated and probably is not located in that system.

The effect of nitrate ion on glycerol-treated frog skeletal muscle fibers

1970 ◽  
Vol 48 (12) ◽  
pp. 813-816 ◽  
Author(s):  
A. R. Luff ◽  
H. L. Atwood
Keyword(s):  
Time Constant ◽  
Surface Membrane ◽  
Muscle Fibers ◽  
Effective Resistance ◽  
Sartorius Muscle ◽  
Nitrate Ion ◽  
Transverse Tubular System ◽  
A Value ◽  
Tubular System ◽  
Frog Sartorius

The effect of nitrate ion on glycerol-treated, frog sartorius muscle fibers was investigated. Glycerol treatment alone (which has been shown to disrupt the transverse tubular system of the fiber) caused a considerable reduction in the time constant of the fiber membrane, but the effective resistance was virtually unchanged. Exposure of normal fibers to nitrate ion produced an increase in both the effective resistance and the time constant. Glycerol-treated fibers exposed to nitrate ion showed an increase in both the effective resistance and the time constant. The latter increased to a value in excess of that found in the normal fibers. The effect of nitrate ion on membrane electrical properties appeared to result from its action on the surface membrane as opposed to the transverse tubules.

scholarly journals Action Potentials, Afterpotentials, and Excitation-Contraction Coupling in Frog Sartorius Fibers without Transverse Tubules

1969 ◽  
Vol 53 (3) ◽  
pp. 298-310 ◽  
Author(s):  
Peter W. Gage ◽  
Robert S. Eisenberg
Keyword(s):  
Membrane Potential ◽  
Short Duration ◽  
Action Potentials ◽  
Sartorius Muscle ◽  
Transverse Tubules ◽  
Excitation Contraction Coupling ◽  
Transverse Tubular System ◽  
Contraction Coupling ◽  
Tubular System ◽  
Frog Sartorius

In frog sartorius muscle fibers in which the transverse tubular system has been disrupted by treatment with glycerol, action potentials which are unaccompanied by twitches can be recorded. These action potentials appear to be the same as those recorded in normal fibers except that the early afterpotential usually consists of a small hyperpolarization of short duration. After a train of action potentials no late afterpotential is seen even when the membrane potential is changed from the resting level. In fibers without transverse tubules hyperpolarizing currents do not produce a creep in potential. The interruption of excitation-contraction coupling, the changes in the afterpotentials, and the disappearance of creep are all attributed to the lack of a transverse tubular system.

scholarly journals Voltage dependence of desensitization. Influence of calcium and activation kinetics.

1980 ◽  
Vol 75 (5) ◽  
pp. 511-529 ◽  
Author(s):  
J F Fiekers ◽  
P M Spannbauer ◽  
B Scubon-Mulieri ◽  
R L Parsons
Keyword(s):  
Voltage Dependence ◽  
Kinetic Scheme ◽  
Sartorius Muscle ◽  
Voltage Sensitivity ◽  
Voltage Range ◽  
Rate Limiting Step ◽  
Rate Limiting ◽  
Kinetics Of ◽  
Frog Sartorius ◽  
Receptor Channel

The voltage dependence of carbachol-induced desensitization has been analyzed in potassium-depolarized frog sartorius muscle preparations with voltage clamp techniques over a wide voltage range (-120 to +40 mV). Desensitization developed exponentially at all voltages with tau, the time constant of desensitization onset, varying as a logarithmic function of membrane voltage. The voltage dependence of tau remained in calcium-deficient solutions and was not altered by elevating either the level of extracellular or intracellular calcium. We have analyzed our results according to a simple sequential kinetic scheme in which the rate-limiting step in the development of desensitization is a transition of the receptor channel complex from the activated conducting state to a desensitized, nonconducting state. We conclude (a) that the observed voltage sensitivity of desensitization primarily resides in the voltage dependence of this transition, and (b) the kinetics of activation appear to have a greater influence on the observed rate of desensitization than on its voltage dependence. The magnitude of the voltage dependence suggests that a greater change in free energy is required for the transition to the desensitized state than for the transition between the open and closed states of the receptor channel complex.

scholarly journals SELECTIVE DISRUPTION OF THE SARCOTUBULAR SYSTEM IN FROG SARTORIUS MUSCLE

1968 ◽  
Vol 39 (2) ◽  
pp. 451-467 ◽  
Author(s):  
Brenda Eisenberg ◽  
Robert S. Eisenberg
Keyword(s):  
Extracellular Space ◽  
Skeletal Muscles ◽  
Muscle Fibers ◽  
Ringer Solution ◽  
Sartorius Muscle ◽  
Normal Muscle ◽  
Tubular System ◽  
Sarcotubular System ◽  
Reliable Marker ◽  
Frog Sartorius

Skeletal muscles which have been soaked for 1 hr in a glycerol-Ringer solution and then returned to normal Ringer solution have a disrupted sarcotubular system. The effect is associated with the return to Ringer's since muscles have normal fine structure while still in glycerol-Ringer's. Karnovsky's peroxidase method was found to be a very reliable marker of extracellular space, filling 98.5% of the tubules in normal muscle. It was interesting to note that only 84.1% of the sarcomeres in normal muscle have transverse tubules. The sarcotubular system was essentially absent from glycerol-treated muscle fibers, only 2 % of the tubular system remaining connected to the extracellular space; the intact remnants were stumps extending only a few micra into the fiber. Thus, glycerol-treated muscle fibers provide a preparation of skeletal muscle with little sarcotubular system. Since the sarcoplasmic reticulum is not destroyed and the sarcolemma and myofilaments are intact in this preparation, of the properties of the sarcolemma may thus be separated from those of the tubular system.

Potassium exchange in frog sartorius muscle

1964 ◽  
Vol 206 (6) ◽  
pp. 1340-1346 ◽  
Author(s):  
D. R. H. Gourley
Keyword(s):  
Extracellular Fluid ◽  
Sartorius Muscle ◽  
Ringer’S Solution ◽  
Frog Sartorius Muscle ◽  
Energy Stores ◽  
Low K ◽  
Potassium Exchange ◽  
Frog Sartorius ◽  
High Phosphate

Under normal conditions, the fibers of frog sartorius muscle contain two K compartments. About two-thirds of the muscle K is in a compartment which readily exchanges with K in the extracellular fluid; the remainder of the muscle K is relatively nonexchangeable. Compartmentalization of the muscle K is not a result of high phosphate or low [K] in the Ringer's solution or previous equilibration at low temperature, but occurs also in vivo. By means of K42, the average muscle K influx and efflux in 2.5 K-Ringer's solution at 20 C were found to be (in µEq g–1 hr–1) 6.41 and 5.81, respectively (different muscles). In the steady state, K moves into the exchangeable compartment of muscle K by a process that can be described by a single exponential equation, but this mechanism fails when the energy stores of the muscle become low. K influx increases with the [K] of the Ringer's solution but reaches a maximum at high external levels of K. It is inferred from these results that the influx of K in frog muscle involves a saturable intermediate, or carrier, system.

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