scholarly journals Effects of Caffeine on Crayfish Muscle Fibers

1970 ◽  
Vol 55 (5) ◽  
pp. 640-664 ◽  
Author(s):  
Dante J. Chiarandini ◽  
John P. Reuben ◽  
Philip W. Brandt ◽  
Harry Grundfest
Keyword(s):  
Time Course ◽  
Muscle Fibers ◽  
Resting Potential ◽  
Induced Responses ◽  
Single Muscle ◽  
Transverse Tubular System ◽  
Crayfish Muscle ◽  
Number Of Factors ◽  
Tubular System

Contractions are evoked in single muscle fibers of crayfish by intracellular as well as extracellular applications of caffeine. Responses to external applications in concentrations above 2 mM could be induced indefinitely. With concentrations above 5 mM the caffeine-induced responses were highly repeatable. Tensions were transient even when the caffeine remained in the bath. There was no change in resting potential, but during the contraction the effective resistance decreased about 10%. A number of factors (change in pH, Ca, K, and Cl) modified the responses. The time course of the tension was greatly prolonged when the transverse tubular system (TTS) was s swollen and was again shortened when the TTS was caused to shrink. An increased permeability to Ca induced by caffeine was evidenced by the transformation of the normally graded electrical responses to Ca spikes, which are insensitive to tetrodotoxin. The overshoot is a function of both external Ca and caffeine. A 10-fold change in Ca changed the overshoot by 19 mv in the presence of 10 mM caffeine and by 29 mv in 80 mM caffeine. The role of the increased permeability to Ca for caffeine-induced contractions will be analyzed in the accompanying paper.

scholarly journals Chloride currents from the transverse tubular system in adult mammalian skeletal muscle fibers

2010 ◽  
Vol 137 (1) ◽  
pp. 21-41 ◽  
Author(s):  
Marino DiFranco ◽  
Alvaro Herrera ◽  
Julio L. Vergara
Keyword(s):  
Skeletal Muscle ◽  
Time Course ◽  
Muscle Fibers ◽  
Optical Data ◽  
Mammalian Skeletal Muscle ◽  
Chloride Currents ◽  
Actual Distribution ◽  
Transverse Tubular System ◽  
Skeletal Muscle Fibers ◽  
Tubular System

Chloride fluxes are the main contributors to the resting conductance of mammalian skeletal muscle fibers. ClC-1, the most abundant chloride channel isoform in this preparation, is believed to be responsible for this conductance. However, the actual distribution of ClC-1 channels between the surface and transverse tubular system (TTS) membranes has not been assessed in intact muscle fibers. To investigate this issue, we voltageclamped enzymatically dissociated short fibers using a two-microelectrode configuration and simultaneously recorded chloride currents (ICl) and di-8-ANEPPS fluorescence signals to assess membrane potential changes in the TTS. Experiments were conducted in conditions that blocked all but the chloride conductance. Fibers were equilibrated with 40 or 70 mM intracellular chloride to enhance the magnitude of inward ICl, and the specific ClC-1 blocker 9-ACA was used to eliminate these currents whenever necessary. Voltage-dependent di-8-ANEPPS signals and ICl acquired before (control) and after the addition of 9-ACA were comparatively assessed. Early after the onset of stimulus pulses, di-8-ANEPPS signals under control conditions were smaller than those recorded in the presence of 9-ACA. We defined as attenuation the normalized time-dependent difference between these signals. Attenuation was discovered to be ICl dependent since its magnitude varied in close correlation with the amplitude and time course of ICl. While the properties of ICl, and those of the attenuation seen in optical records, could be simultaneously predicted by model simulations when the chloride permeability (PCl) at the surface and TTS membranes were approximately equal, the model failed to explain the optical data if PCl was precluded from the TTS membranes. Since the ratio between the areas of TTS membranes and the sarcolemma is large in mammalian muscle fibers, our results demonstrate that a significant fraction of the experimentally recorded ICl arises from TTS contributions.

scholarly journals Voltage Clamp Experiments on Single Muscle Fibers of Rana pipiens

1972 ◽  
Vol 60 (1) ◽  
pp. 1-19 ◽  
Author(s):  
L. E. Moore
Keyword(s):  
Voltage Clamp ◽  
Rana Pipiens ◽  
Muscle Fibers ◽  
Petroleum Jelly ◽  
Single Muscle ◽  
Transverse Tubular System ◽  
Anomalous Rectification ◽  
Outward Currents ◽  
Delayed Rectification ◽  
Tubular System

A voltage clamp for single muscle fibers has been developed. Stability of the system was achieved when an artificial node was created by enclosing a single muscle fiber in a petroleum jelly seal which served as an analogue of the myelin sheath. Typical voltage clamp records were obtained with large inward transient currents followed by a delayed rectification of the outward currents. These currents looked qualitatively similar when the transverse tubular system was destroyed. Errors in current measurement, especially those due to anomalous rectification, are discussed.

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

1968 ◽  
Vol 38 (1) ◽  
pp. 115-129 ◽  
Author(s):  
Philip W. Brandt ◽  
John P. Reuben ◽  
Harry Grundfest
Keyword(s):  
Sarcoplasmic Reticulum ◽  
Current Flow ◽  
Muscle Fibers ◽  
Single Muscle ◽  
Unit Membrane ◽  
Membrane Phase ◽  
Transverse Tubular System ◽  
Contraction Coupling ◽  
Cytoplasmic Material ◽  
Tubular System

Living muscle fibers of crayfish become dark during efflux of Cl-. This change in appearance is correlated with occurrence of vacuolation in the fixed fibers. The vacuoles begin at and are mainly confined to the terminals of the transverse tubular system (TTS) which are in diadic contact with the sarcoplasmic reticulum (SR). In electron micrographs swellings more than 1 µ in diameter may be seen connected to the sarcolemma or sarcolemmal invaginations by relatively unswollen tubules about 300–500 A wide. Darkening of the living fibers can be reversed by causing an influx of Cl-. Vacuoles are then absent in the fixed preparations. These findings accord with the conclusion that the membrane of the TTS is anion permselective. Localization of the selectivity to the membrane of the terminals of the TTS strengthens the hypothesis that a channeling of current flow is responsible for initiation of excitation-contraction coupling. During the swelling, and upon its reversal, the area of the membrane of the terminals must change reversibly by about two to four orders of magnitude. The absence of changes in the dimensions of the unit membrane indicates that the expansion of the membrane and its subsequent shrinkage involve reversible incorporation of cytoplasmic material into the membrane phase.

scholarly journals The Mode of Transverse Spread of Contraction Initiated by Local Activation in Single Crayfish Muscle Fibers

1967 ◽  
Vol 50 (9) ◽  
pp. 2145-2166 ◽  
Author(s):  
Haruo Sugi ◽  
Rikuo Ochi
Keyword(s):  
Surface Membrane ◽  
Muscle Fibers ◽  
Fiber Surface ◽  
Large Area ◽  
Transverse Tubular System ◽  
Crayfish Muscle ◽  
Negative Current ◽  
Local Contraction ◽  
Tubular System ◽  
Long Time

Isolated single crayfish muscle fibers were locally activated by applying negative current pulses to a pipette whose tip was in contact with the fiber surface. The contraction initiated by a moderate depolarization spread inwards in a graded manner according to the magnitude and duration of depolarization. Increase of the depolarized area increased the distance of the inward spread for a given amount of depolarization. If a large area of the surface membrane was depolarized with a large pipette for a sufficiently long time, the contraction spread not only inwards, but further transversely passing through the center of the fiber. Successive brief depolarizations given at an appropriate interval could produce contraction more effectively for a given amount of total current than did a prolonged depolarization. On the other hand, the contraction initiated by a strong negative current was observed to spread around the whole perimeter but not through the center of the fiber. Each type of local contraction always spread along the striation pattern and not longitudinally. Possible mechanisms of these responses are discussed in connection with the transverse tubular system of the muscle fibers.

scholarly journals THE STRUCTURE OF INTERSEGMENTAL MUSCLE FIBERS IN AN INSECT, PERIPLANETA AMERICANA L

1966 ◽  
Vol 29 (3) ◽  
pp. 449-459 ◽  
Author(s):  
David S. Smith
Keyword(s):  
Periplaneta Americana ◽  
Flight Muscle ◽  
Muscle Fibers ◽  
Structural Features ◽  
Mitochondrial Content ◽  
Thin Filaments ◽  
Transverse Tubular System ◽  
Thick Filaments ◽  
Tubular System ◽  
Contraction And Relaxation

The organization of intersegmental muscle fibers associated with the dorsal abdominal sclerites of the cockroach is described. These fibers correspond closely, in the disposition and derivation of the membranes of the transverse tubular system and sarcoplasmic reticulum cisternae, with insect synchronous flight muscle fibers, but differ markedly from these in their fibrillar architecture and mitochondrial content. The mitochondria are small and generally aligned alongside the prominent I bands of the sarcomere, and, in the best-oriented profiles of the A bands, thick filaments are associated with orbitals of twelve thin filaments, a configuration that has also been observed in striated fibers of insect visceral muscle. These structural features of insect muscles are compared and discussed in terms of possible variations in the control of contraction and relaxation, and in the nature of their mechanical role.

Hyperpolarization of mammalian skeletal muscle fibers in K-free media

1982 ◽  
Vol 242 (1) ◽  
pp. C12-C18 ◽  
Author(s):  
N. Akaike
Keyword(s):  
Time Course ◽  
Muscle Fibers ◽  
Resting Potential ◽  
Mammalian Skeletal Muscle ◽  
Krebs Solution ◽  
Free Medium ◽  
Metabolic Potential ◽  
Rat Soleus Muscle ◽  
K Concentration ◽  
Free Media

Time course of changes in resting potential following removal of K ions from Krebs solution was studied in the isolated rat soleus muscle. In K+-free Krebs solution the muscle fibers hyperpolarized to a peak within 60 min followed by a variable, gradual depolarization over the next few hours. A significant decrease of the intracellular K+ concentration ([K]i) occurred within 30 min in K+-free Krebs. Compensatory increase of the intracellular Na+ concentration ([Na]i) lagged behind [K]i change. Both hyperpolarization and successive depolarization were modified in K+-free medium containing different [Na]o, [Ca]o, or osmotic strength. A part of the hyperpolarization was reduced by adding ouabain. Therefore, ouabain-sensitive potential of the fibers in K+-free medium was attributed to the activation of electrogenic Na pump by K+ leaked out continuously from the fibers and accumulated just outside of cell membranes but not to changes of membrane Na+ and Cl- permeabilities. It is concluded that hyperpolarization of muscles exposed to K+-free medium is the sum of the diffusional K+ potential and ouabain-sensitive metabolic potential. Interestingly, the time course of changes of membrane response to K+-free krebs was identical for contralateral soleus muscles in the same rat, though it varied among different rats.

Effect of dinitrophenol on phosphorylation and bioelectric phenomena of excitable tissues

1961 ◽  
Vol 200 (3) ◽  
pp. 431-436 ◽  
Author(s):  
L. G. Abood ◽  
K. Koketsu ◽  
K. Noda
Keyword(s):  
Energy Metabolism ◽  
Muscle Fibers ◽  
Resting Potential ◽  
Sartorius Muscle ◽  
Nerve Roots ◽  
Intracellular Potassium ◽  
Frog Sartorius Muscle ◽  
Anodal Polarization ◽  
Frog Sartorius

The effect of 2, 4-dinitrophenol (DNP) was investigated on the phosphorylation of frog sartorius muscle and ventral nerve roots, using P32 as a tracer. It was possible almost completely to inhibit phosphorylation without significantly altering excitability, although the resting potential and intracellular potassium decreased over 30%. The addition of 0.01 mm DNP to a sodium-free hydrazinium system completely blocked excitability, despite the fact that this concentration of DNP produced no further inhibition of phosphorylation. It was possible to restore the excitability of frog sartorius muscle fibers by anodal polarization after the fibers were rendered inexcitable by immersion in 1 mm DNP. The results were discussed in terms of the role of energy metabolism in excitability and other bioelectric phenomena of muscle and nerve.

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