scholarly journals Tension in Skinned Frog Muscle Fibers in Solutions of Varying Ionic Strength and Neutral Salt Composition

1973 ◽  
Vol 62 (5) ◽  
pp. 550-574 ◽  
Author(s):  
A. M. Gordon ◽  
R. E. Godt ◽  
S. K. B. Donaldson ◽  
C. E. Harris
Keyword(s):  
Ionic Strength ◽  
Muscle Fiber ◽  
Muscle Fibers ◽  
Isometric Tension ◽  
High Ionic Strength ◽  
Frog Muscle ◽  
Hypertonic Solution ◽  
Base Line ◽  
Neutral Salt ◽  
Skinned Muscle

The maximal calcium-activated isometric tension produced by a skinned frog single muscle fiber falls off as the ionic strength of the solution bathing this fiber is elevated declining to zero near 0.5 M as the ionic strength is varied using KCl. When other neutral salts are used, the tension always declines at high ionic strength, but there is some difference between the various neutral salts used. The anions and cations can be ordered in terms of their ability to inhibit the maximal calcium-activated tension. The order of increasing inhibition of tension (decreasing tension) at high ionic strength for anions is propionate- ≃ SO4-- < Cl- < Br-. The order of increasing inhibition of calcium-activated tension for cations is K+ ≃ Na+ ≃ TMA+ < TEA+ < TPrA+ < TBuA+. The decline of maximal calcium-activated isometric tension with elevated salt concentration (ionic strength) can quantitatively explain the decline of isometric tetanic tension of a frog muscle fiber bathed in a hypertonic solution if one assumes that the internal ionic strength of a muscle fiber in normal Ringer's solution is 0.14–0.17 M. There is an increase in the base-line tension of a skinned muscle fiber bathed in a relaxing solution (no added calcium and 3 mM EGTA) of low ionic strength. This tension, which has no correlate in the intact fiber in hypotonic solutions, appears to be a noncalcium-activated tension and correlates more with a declining ionic strength than with small changes in [MgATP], [Mg], pH buffer, or [EGTA]. It is dependent upon the specific neutral salts used with cations being ordered in increasing inhibition of this noncalcium-activated tension (decreasing tension) as TPrA+ < TMA+ < K+ ≃ Na+. Measurements of potentials inside these skinned muscle fibers bathed in relaxing solutions produced occasional small positive values (<6 mV) which were not significantly different from zero.

scholarly journals Nonparallel isometric tension response of rabbit soleus skinned muscle fibers to magnesium adenosine triphosphate and magnesium inosine triphosphate.

1979 ◽  
Vol 74 (2) ◽  
pp. 261-274 ◽  
Author(s):  
B Krasner
Keyword(s):  
Steady State ◽  
Ionic Strength ◽  
Adenosine Triphosphate ◽  
Soleus Muscle ◽  
Muscle Fibers ◽  
Isometric Tension ◽  
Maximum Tension ◽  
Skinned Muscle ◽  
Tension Response ◽  
Skinned Muscle Fibers

The isometric tension response of single "skinned' rabbit soleus muscle fibers to MgATP and McITP in the absence of calcium was studied. [MgATP] or [MgITP] was varied in solutions of ionic strength 0.30 and temperature 20 degrees C. Steady-state tension that developed in MgATP or MgITP solutions was a biphasic bell-shaped function of log [MgATP] or log [MgITP] which increased from zero to maximum tension and then declined again to zero. Analysis of the data showed that, under comparable ionic conditions, percent tension vs. log [MgATP] and percent tension vs. log [MgITP] curves are not parallel. Instead, the percent tension vs. log [MgITP] curve is much broader. Additionally, under comparable ionic conditions maximum tension in MgITP solutions was higher than in MgATP solutions. In addition, in MgATP solutions, pH, [K+], and excess ATP were varied. Raising pH from 7 to 8, [K+] from 46 mM to 200 mM, or decreasing excess ATP from 2 to 0.5 mM all increased maximum tension. None of these factors, however, influenced the shape or position of the percent tension vs. log [MgATP] curve.

scholarly journals Double Sucrose-Gap Method Applied to Single Muscle Fiber of Xenopus laevis

1974 ◽  
Vol 63 (2) ◽  
pp. 235-256 ◽  
Author(s):  
Shigehiro Nakajima ◽  
Joseph Bastian
Keyword(s):  
Electrical Properties ◽  
Action Potential ◽  
Muscle Fiber ◽  
Time Course ◽  
Muscle Fibers ◽  
Membrane Conductance ◽  
Frog Muscle ◽  
Muscle Twitch ◽  
Sucrose Gap ◽  
Isotonic Shortening

Passive electrical properties (internal conductance, membrane conductance, low frequency capacity, and high frequency capacity obtained from the foot of the action potential) of normal and glycerol-treated muscle of Xenopus were determined with the intracellular microelectrode technique. The results show that the electrical properties of Xenopus muscle are essentially the same as those of frog muscle. Characteristics of the action potential of Xenopus muscle were also similar to those of frog muscle. Twitch tension of glycerol-treated muscle fibers of Xenopus recovered partially when left in normal Ringer for a long time (more than 6 h). Along with the twitch recovery, the membrane capacity increased. Single isolated muscle fibers of Xenopus were subjected to the double sucrose-gap technique. Action potentials under the sucrose gap were not very different from those obtained with the intracellular electrode, except for the sucrose-gap hyperpolarization and a slight tendency toward prolongation of the shape of action potential. Twitch contraction of the artificial node was recorded as a change of force from one end of the fiber under the sucrose gap. From the time-course of the recorded force and the sinusoidal stress-strain relationship at varying frequencies of the resting muscle fiber, the time-course of isotonic shortening of the node was recovered by using Fourier analysis. It was revealed that the recorded twitch force can approximately be regarded as isotonic shortening of the node.

Stabilization and rectification of muscle fiber membrane by tetrodotoxin

1960 ◽  
Vol 198 (5) ◽  
pp. 934-938 ◽  
Author(s):  
Toshio Narahashi ◽  
Takehiko Deguchi ◽  
Norimoto Urakawa ◽  
Yoshio Ohkubo
Keyword(s):  
Muscle Fiber ◽  
Muscle Fibers ◽  
Membrane Resistance ◽  
Frog Muscle ◽  
Resting Potential ◽  
Fiber Membrane ◽  
Delayed Rectification ◽  
Intracellular Microelectrodes ◽  
Cathodal Current ◽  
Muscle Fiber Membrane

The mode of action of tetrodotoxin on the frog muscle fiber membrane has been analyzed with the aid of intracellular microelectrodes. Tetrodotoxin of 10–7 concentration made the applied cathodal current ineffective in producing action potential, whereas the resting potential and resting membrane resistance underwent little or no change. With 10–8 tetrodotoxin the muscle fibers responded with the small action potentials at high critical depolarizations. These results can be explained on the basis of the membrane being stabilized by inactivation of the sodium-carrying mechanism. Although delayed rectification was not observed in normal muscle fibers, it became apparent in the fibers rendered inexcitable by tetrodotoxin. This finding, together with other evidence in the existing literature, supports an applicability of the sodium theory to the frog muscle fibers.

scholarly journals Loss of muscle strength during sepsis is in part regulated by glucocorticoids and is associated with reduced muscle fiber stiffness

2012 ◽  
Vol 303 (10) ◽  
pp. R1090-R1099 ◽  
Author(s):  
Nima Alamdari ◽  
Gianluca Toraldo ◽  
Zaira Aversa ◽  
Ira Smith ◽  
Estibaliz Castillero ◽  
...  
Keyword(s):  
Muscle Strength ◽  
Muscle Weakness ◽  
Muscle Fiber ◽  
Muscle Fibers ◽  
Cecal Ligation ◽  
Treatment Strategies ◽  
Skinned Muscle ◽  
Cross Bridges ◽  
New Treatment

Sepsis is associated with impaired muscle function but the role of glucocorticoids in sepsis-induced muscle weakness is not known. We tested the role of glucocorticoids in sepsis-induced muscle weakness by treating septic rats with the glucocorticoid receptor antagonist RU38486. In addition, normal rats were treated with dexamethasone to further examine the role of glucocorticoids in the regulation of muscle strength. Sepsis was induced in rats by cecal ligation and puncture, and muscle force generation (peak twitch and tetanic tension) was determined in lower extremity muscles. In other experiments, absolute and specific force as well as stiffness (reflecting the function of actomyosin cross bridges) were determined in isolated skinned muscle fibers from control and septic rats. Sepsis and treatment with dexamethasone resulted in reduced maximal twitch and tetanic force in intact isolated extensor digitorum longus muscles. The absolute and specific maximal force in isolated muscle fibers was reduced during sepsis together with decreased fiber stiffness. These effects of sepsis were blunted (but not abolished) by RU38486. The results suggest that muscle weakness during sepsis is at least in part regulated by glucocorticoids and reflects loss of contractility at the cellular (individual muscle fiber) level. In addition, the results suggest that reduced function of the cross bridges between actin and myosin (documented as reduced muscle fiber stiffness) may be involved in sepsis-induced muscle weakness. An increased understanding of mechanisms involved in loss of muscle strength will be important for the development of new treatment strategies in patients with this debilitating consequence of sepsis.

scholarly journals Ionic Strength and the Contraction Kinetics of Skinned Muscle Fibers

1974 ◽  
Vol 63 (4) ◽  
pp. 509-530 ◽  
Author(s):  
Marc D. Thames ◽  
Louis E. Teichholz ◽  
Richard J. Podolsky
Keyword(s):  
Ionic Strength ◽  
Muscle Fibers ◽  
Bathing Solution ◽  
Shortening Velocity ◽  
Skinned Muscle ◽  
Cross Bridges ◽  
Low Ionic Strength ◽  
Contraction Cycle ◽  
Kinetics Of ◽  
Contraction Kinetics

The influence of KCl concentration on the contraction kinetics of skinned frog muscle fibers at 5–7°C was studied at various calcium levels. The magnitude of the calcium-activated force decreased continuously as the KCl concentration of the bathing solution was increased from 0 to 280 mM. The shortening velocity at a given relative load was unaffected by the level of calcium activation at 140 mM KCl, as has been previously reported by Podolsky and Teichholz (1970. J. Physiol. [Lond.]. 211: 19), and was independent of ionic strength when the KCl concentration was increased from 140 to 280 mM. In contrast, the shortening velocity decreased as the KCl concentration was reduced below 140 mM; the decrease in velocity was enhanced when the fibers were only partially activated. In the low KCl range, the resting tension of the fibers increased after the first contraction cycle. The results suggest that in fibers activated at low ionic strength some of the cross bridges that are formed are abnormal in the sense that they retard shortening and persist in relaxing solution.

scholarly journals Calcium-Activated Tension of Skinned Muscle Fibers of the Frog

1974 ◽  
Vol 63 (6) ◽  
pp. 722-739 ◽  
Author(s):  
Robert E. Godt
Keyword(s):  
Thin Filament ◽  
Muscle Fibers ◽  
Creatine Phosphate ◽  
Isometric Tension ◽  
Skinned Fibers ◽  
University Of Wisconsin ◽  
Skinned Muscle ◽  
Physiology And Biochemistry ◽  
Calcium Affinity ◽  
Similar Solutions

The influence of MgATP on the Ga++-activated isometric tension of skinned frog muscle fibers was examined in solutions containing: Mg++ = 5 mM, creatine phosphate (CP) = 14.5 mM, creatinephosphokinase (CPK) = 1 mg/ml, total EGTA = 7 mM, CaCl2, KCl, imidazole ≥ 20 mM so that ionic strength = 0.15, pH = 7.00, and MgATP = 2 mM, 0.1 mM, or 20 µM. CP and CPK were necessary for these experiments as determined experimentally by their effect on the tension-Ca++ relation, which was saturated for CP ≥ 14.5 mM. This was interpreted to mean that sufficient CP was present to effectively buffer MgATP intracellularly. Decreasing MgATP shifts the tension-pCa curve to higher pCa (-log Ca++) so that, for half-maximal tension: pCa1/2 = 4.5 for MgATP = 2 mM, pCa1/2 = 5.1 for MgATP = 0.1 mM, and pCa1/2 = 5.8 for MgATP = 20 µM; maximum isometric tension is the same in all cases, however. If MgATP was decreased to 1 µM, tension at Ga++ > 10–8 M was 84% of the maximum Ca-+-activated tension in 2 mM MgATP and increased only slightly to 90% for pCa = 4.5. Weber (1970, In The Physiology and Biochemistry of Muscle as Food, Volume 2, E. J. Briskey, R. G. Cassens, and B. B. Marsh, University of Wisconsin Press, Madison, Wis.), using similar solutions, observed similar shifts in half-maximal calcium activation of rabbit myofibril ATPase rates. In explanation, Weber and Bremel (1971, In Contractility of Muscle Cells and Related Processes, R. J. Podolsky, editor, Prentice-Hall, Inc., Englewood Cliffs, N.J.; Bremel and Weber, 1972, Nat. New Biol., 238:97) have described a mechanism whereby, at low ATP, "rigor complexes" are formed between myosin and thin filament actin and, in turn, alter the calcium affinity of one class of the two Ca++-binding sites on troponin, so that the thin filament is "turned on" for contraction at lower Ca++ levels. Tension data from skinned fibers substantially supports this hypothesis. A stability constant for CaEGTA of 2.62 x 1010 M–1 was determined, with the help of F. N. Briggs, in solutions similar to those used for skinned fibers and was the same for 100 and 300 mM KCl.

scholarly journals Contraction transients of skinned muscle fibers: effects of calcium and ionic strength.

1978 ◽  
Vol 72 (5) ◽  
pp. 701-715 ◽  
Author(s):  
J Gulati ◽  
R J Podolsky
Keyword(s):  
Ionic Strength ◽  
Muscle Fibers ◽  
Kinetic Properties ◽  
Cross Bridge ◽  
Skinned Muscle ◽  
The Cross ◽  
Cross Bridge Mechanism ◽  
Low Ionic Strength ◽  
Bridge Number ◽  
Steady Force

Calcium and ionic strength are both known to modify the force developed by skinned frog muscle fibers. To determine how these parameters affect the cross-bridge contraction mechanism, the isotonic velocity transients following step changes in load were studied in solutions in which calcium concentration and ionic strength were varied. Analysis of the motion showed that calcium has no effect on either the null time or the amplitude of the transients. In contrast, the transient amplitude was increased in high ionic strength and was suppressed in low ionic strength. These results are consistent with the idea that calcium affects force in skeletal muscle by modulating the number of force generators in a simple switchlike "on-off" manner and that the steady force at a given calcium level is proportional to cross-bridge number. On the other hand, the effect of ionic strength on force is associated with changes in the kinetic properties of the cross-bridge mechanism.

Response of compressed skinned skeletal muscle fibers to conditions that simulate fatigue

1997 ◽  
Vol 82 (4) ◽  
pp. 1297-1304 ◽  
Author(s):  
Kathryn H. Myburgh ◽  
Roger Cooke
Keyword(s):  
Skeletal Muscle ◽  
Lattice Spacing ◽  
Atp Hydrolysis ◽  
Muscle Fibers ◽  
Isometric Tension ◽  
Skinned Fibers ◽  
Skinned Muscle ◽  
Skeletal Muscle Fibers ◽  
Myosin Subunits ◽  
Osmotic Compression

Myburgh, Kathryn H., and Roger Cooke. Response of compressed skinned skeletal muscle fibers to conditions that simulate fatigue. J. Appl. Physiol. 82(4): 1297–1304, 1997.—During fatigue, muscles become weaker, slower, and more economical at producing tension. Studies of skinned muscle fibers can explain some but not all of these effects, and, in particular, they are less economical in conditions that simulate fatigue. We investigated three factors that may contribute to the different behavior of skinned fibers. 1) Skinned fibers have increased myofilament lattice spacing, which is reversible by osmotic compression. 2) A myosin subunit becomes phosphorylated during fatigue. 3) Inosine 5′-monophosphate (IMP) accumulates during fatigue. We tested the response of phosphorylated and unphosphorylated single skinned fibers (isometric tension, contraction velocity, and adenosinetriphosphatase activity) to changes in lattice spacing (0–5% dextran) and IMP (0–5 mM) in the presence of altered concentrations of Pi (3–25 mM), H+ (pH 7–6.2), and ADP (0–5 mM). The response of maximally activated skinned fibers to the direct metabolites of ATP hydrolysis is not altered by osmotic compression, phosphorylating myosin subunits, or increasing IMP concentration. These factors, therefore, do not explain the discrepancy between intact and skinned fibers during fatigue.

Muscle fiber capacity in low conductivity solution

1976 ◽  
Vol 54 (2) ◽  
pp. 107-112 ◽  
Author(s):  
D. Loo ◽  
P. C. Vaughan
Keyword(s):  
Membrane Potential ◽  
Muscle Fiber ◽  
Muscle Fibers ◽  
Circuit Theory ◽  
Frog Muscle ◽  
Constant Current ◽  
Effective Capacity ◽  
Injection Technique ◽  
Length Constant ◽  
Per Se

A method is described for computing the effective capacity of muscle fibers, C = Q/V where Q is the charge stored, and V is the membrane potential, using a standard two-microelectrode, constant current injection technique. The method is used to compare physical (or effective) capacity of frog muscle fibers bathed in a low conductivity, 2.5 mM K+ solution, with circuit-theory derived quantities in the same cells and in control fibers. No differences can be discerned and it is concluded that low conductivity of physiological solutions, per se, does not significantly reduce the length constant of frog muscle transverse tubules.

Importance of Protease Inhibition in Studies on Purified Factor VIII (Antihaemophilic Factor)

1976 ◽  
Vol 35 (01) ◽  
pp. 186-190 ◽  
Author(s):  
Eugen A. Beck ◽  
Peter Bachmann ◽  
Peter Barbier ◽  
Miha Furlan
Keyword(s):  
Ionic Strength ◽  
Factor Viii ◽  
Gel Filtration ◽  
High Ionic Strength ◽  
Procoagulant Activity ◽  
Carrier Protein ◽  
Protease Inhibition ◽  
Functional Sites ◽  
Molecular Weight Peak ◽  
Von Willebrand

SummaryAccording to some authors factor VIII procoagulant activity may be dissociable from carrier protein (MW~ 2 × 106) by agarose gel filtration, e.g. at high ionic strength. We were able to reproduce this phenomenon. However, addition of protease inhibitor (Trasylol) prevented the appearance of low molecular weight peak of factor VIII procoagulant activity both at high ionic strength and elevated temperature (37°C). We conclude from our results that procoagulant activity and carrier protein (von Willebrand factor, factor VIII antigen) are closely associated functional sites of native factor VIII macro molecule. Consequently, proteolytic degradation should be avoided in functional and structural studies on factor VIII and especially in preparing factor VIII concentrate for therapeutic use.

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