scholarly journals A Fixed Charge Model of the Transverse Tubular System of Frog Sartorius

1969 ◽  
Vol 54 (2) ◽  
pp. 178-187 ◽  
Author(s):  
Stanley I. Rapoport
Keyword(s):  
External Solution ◽  
Fixed Charge ◽  
Transverse Tubular System ◽  
Charge Model ◽  
Tubular System ◽  
Charge Concentration ◽  
Frog Sartorius ◽  
System Volume ◽  
Osmotic Pressure Difference ◽  
T System

Volume changes of the transverse tubular system (T system) of frog sartorius in different solutions can be explained by a model which assumes fixed negative charges in the T system lumen, an open T system mouth, and a Donnan equilibrium between the T system and external solution. The T system volume is regulated by the osmotic pressure difference between the lumen and external solution, as well as by constraining forces whose nature is as yet unclear. The decreased swelling tendency produced by hypotonic solutions and increased tendency produced by some hypertonic solutions are ascribed to changes in the pressure constraint from the sarcoplasm. Fixed charge concentration was estimated tentatively from swelling and resistivity data to be between 0.1 and 0.4 M.

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 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 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 Swelling of the Transverse Tubular System in Frog Sartorius

1969 ◽  
Vol 54 (2) ◽  
pp. 166-177 ◽  
Author(s):  
Stanley I. Rapoport ◽  
L. D. Peachey ◽  
D. A. Goldstein
Keyword(s):  
Electron Microscopy ◽  
Ionic Strength ◽  
Sucrose Concentration ◽  
Time Dependent ◽  
Bathing Solution ◽  
Transverse Tubular System ◽  
Fixed Charges ◽  
Degree Of Swelling ◽  
Tubular System ◽  
Frog Sartorius

Electron microscopy shows that the transverse tubular system of frog sartorius swells in Ringer fluid in which NaCl is partially replaced by sucrose (sucrose isotonic solutions). At constant tonicity, the degree of swelling is roughly proportional to the decrease in ionic strength and to the sucrose concentration of the bathing solution. Swelling is time-dependent and reversible within 2 hr. The late after potential which follows a train of impulses is prolonged with swelling, but not to the extent expected from the model of Adrian and Freygang. This discrepancy remains unexplained, as does the mechanism of swelling of the transverse tubular system, although some suggestions are offered. One is that the transverse tubular system contains fixed charges and swells like a fixed charge gel.

Transverse tubular system depolarization reduces tetanic force in rat skeletal muscle fibers by impairing action potential repriming

2007 ◽  
Vol 292 (6) ◽  
pp. C2112-C2121 ◽  
Author(s):  
T. L. Dutka ◽  
G. D. Lamb
Keyword(s):  
Muscle Fibers ◽  
Force Output ◽  
Tetanic Force ◽  
Internal Solution ◽  
Transverse Tubular System ◽  
Tubular System ◽  
Fast Twitch Muscle ◽  
Fast Twitch ◽  
Pulse Stimulation ◽  
T System

When muscle fibers are repeatedly stimulated, they may become depolarized and force output decline. Excitation of the transverse tubular system (T-system) is critical for activation, but its role in muscle fatigue is poorly understood. Here, mechanically skinned fibers from rat fast-twitch muscle were used, because the sarcolemma is absent but the T-system retains normal excitability and its properties can be studied in isolation. The T-system membrane was fully polarized by bathing the skinned fiber in an internal solution with 126 mM K+ (control solution) or set at partially depolarized levels (approximately −63 and −58 mV) in solutions with 66 or 55 mM K+, respectively, and action potentials (APs) were triggered in the sealed T-system by field stimulation. Prolonged depolarization of the T-system reduced tetanic force proportionately more than twitch force, with greater effect at higher stimulation frequency (responses at 20 and 100 Hz reduced to 71 and 62% in 66 mM K+ and to 54 and 35% in 55 mM K+, respectively). Double-pulse stimulation showed that depolarization increased the repriming period (estimated minimum time before a second AP can be produced) from ∼4 ms to ∼7.5 and 15 ms in the 66 and 55 mM K+ solutions, respectively. These results demonstrate that T-system depolarization reduces tetanic force by impairing AP repriming, rather than by preventing AP generation per se or by inactivating the T-system voltage sensors. The findings also explain why it is advantageous to reduce the rate of motoneuron stimulation to muscles during repeated or prolonged periods of activity.

scholarly journals THE SARCOPLASMIC RETICULUM AND ITS ASSOCIATION WITH THE T SYSTEM IN AN INSECT

1967 ◽  
Vol 32 (3) ◽  
pp. 535-545 ◽  
Author(s):  
Martin Hagopian ◽  
David Spiro
Keyword(s):  
Fine Structure ◽  
Sarcoplasmic Reticulum ◽  
Cell Surface ◽  
Osmium Tetroxide ◽  
Surface Membrane ◽  
Transverse Tubular System ◽  
Leucophaea Maderae ◽  
Tubular System ◽  
Femoral Muscle ◽  
T System

The fine structure of the sarcoplasmic reticulum and the transverse tubular system of the femoral muscle of the cockroach, Leucophaea maderae, was studied after prefixation in glutaraldehyde, postfixation in osmium tetroxide, and embedding in Epon. The sarcoplasmic reticulum in this muscle reveals features not previously reported. The sarcoplasmic reticulum is abundant, consisting mainly of a fenestrated envelope which surrounds each myofibril at all levels in the sarcomere. This sarcoplasmic reticulum envelope is continuous transversally as well as longitudinally along the myofibrils. Dyadic junctions are formed by a single T system element which contacts the unfenestrated sarcoplasmic reticulum of adjacent myofibrils in an alternating manner at the ends of the A band. At the dyads, regularly spaced thickenings of the sarcoplasmic reticulum membranes bordering the dyadic spaces are noted. These thickenings, however, do not contact the T tubule membrane. Typical dyadic contacts also are seen between the cell surface membrane and sarcoplasmic reticulum. Z line-like material is seen in contact with the membranes of the cell surface and longitudinal branches of the T systems.

scholarly journals CORRELATED MORPHOLOGICAL AND PHYSIOLOGICAL STUDIES ON ISOLATED SINGLE MUSCLE FIBERS

1965 ◽  
Vol 25 (3) ◽  
pp. 233-262 ◽  
Author(s):  
Philip W. Brandt ◽  
John P. Reuben ◽  
Lucien Girardier ◽  
Harry Grundfest
Keyword(s):  
Single Muscle ◽  
Transverse Tubular System ◽  
Contraction Coupling ◽  
Permselective Membrane ◽  
Leg Muscles ◽  
Thick Filaments ◽  
Vertebrate Muscle ◽  
Tubular System ◽  
Ca 50 ◽  
T System

Single fibers isolated from walking leg muscles of crayfish have 8- to 10-µ sarcomeres which are divided into A, I, and Z bands. The H zone is poorly defined and no M band is distinguishable. Changes in the width of the I band, accompanied by change in the overlap between thick and thin myofilaments, occur when the length of the sarcomere is changed by stretching or by shortening the fiber. The thick myofilaments (ca. 200 A in diameter) are confined to the A band. The thin myofilaments (ca. 50 A in diameter) are difficult to resolve except in swollen fibers, when they clearly lie between the thick filaments and run to the Z disc. The sarcolemma invaginates at 50 to 200 sites in each sarcomere. The sarcolemmal invaginations (SI) form tubes about 0.2 µ in diameter which run radially into the fiber and have longitudinal side branches. Tubules about 150 A in diameter arise from the SI and from the sarcolemma. The invaginations and tubules are all derived from and are continuous with the plasma membrane, forming the transverse tubular system (TTS), which is analogous with the T system of vertebrate muscle. In the A band region each myofibril is enveloped by a fenestrated membranous covering of sarcoplasmic reticulum (SR). Sacculations of the SR extend over the A-I junctions of the myofibrils, where they make specialized contacts (diads) with the TTS. At the diads the opposing membranes of the TTS and SR are spaced 150 A apart, with a 35-A plate centrally located in the gap. It appears likely that the anion-permselective membrane of the TTS which was described previously is located at the diads, and that this property of the diadic structures therefore may function in excitation-contraction coupling.

scholarly journals THE SARCOPLASMIC RETICULUM, THE T SYSTEM, AND THE MOTOR TERMINALS OF SLOW AND TWITCH MUSCLE FIBERS IN THE GARTER SNAKE

1965 ◽  
Vol 26 (2) ◽  
pp. 467-476 ◽  
Author(s):  
Arthur Hess
Keyword(s):  
Sarcoplasmic Reticulum ◽  
Muscle Fibers ◽  
Postsynaptic Membrane ◽  
Slow Muscle ◽  
Garter Snake ◽  
Transverse Tubular System ◽  
Physiological Reaction ◽  
Slow Fiber ◽  
Tubular System ◽  
T System

Twitch and slow muscle fibers, identified morphologically in the garter snake, have been examined in the electron microscope. The transverse tubular system and the sarcoplasmic reticulum are separate entities distinct from each other. In twitch fibers, the tubular system and the dilated sacs of the sarcoplasmic reticulum form triads at the level of junction of A and I bands. In the slow fibers, the sarcoplasmic reticulum is severely depleted in amount and the transverse tubular system is completely absent. The junctional folds of the postsynaptic membrane of the muscle fiber under an "en grappe" ending of a slow fiber are not so frequent or regular in occurrence or so wide or so long as under the "en plaque" ending of a twitch fiber. Some physiological implications of these differences in fine structure of twitch and slow fibers are discussed. The absence of the transverse tubular system and reduction in amount of sarcoplasmic reticulum, along with the consequent disposition of the fibrils, the occurrence of multiple nerve terminals, and the degree of complexity of the post junctional folds of the sarcolemma appear to be the morphological basis for the physiological reaction of slow muscle fibers.

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