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PubMed1980

[Effect of calcium ions on bimodal parameters of mediator liberation in frog sartorius muscle neuromuscular junctions].

In synaptic junctions of the frog sartorius muscle, the dependence of the power index of the EPPs quantum content (m) on external Ca ions concentration [Ca]0 is directly proportional to the initial miniature EPP frequency and can range from 2 to 5. The increase of m due to the action of Ca ions was accompanied by the growth of P and n binomial parameters. The P parameter depended upon the first power of (Ca)0 and n parameter - upon the second power of [Ca]0. Various dynamics of m under the influence of Ca ions in sartorius neuromuscular junctions seems to be due to different increases in power of available transmitter release store.

Animals↗

PubMed1960

Radiocalcium release by stimulated and potassium-treated sartorius muscles of the frog.

Stimulation of frog (Rana pipiens) sartorius muscle accelerates release of Ca(45), but only during the period of stimulation. No appreciable difference is obtained in the calcium released per impulse whether stimulation is at a rate of 20/sec. or 0.5/sec. However, prior stimulation may appreciably increase the loss per impulse. In unfatigued muscles, the minimum amount of calcium liberated during an isotonic twitch is estimated to be about that previously calculated to enter, viz. 0.2 micromicromole/cm(2). The time course of radiocalcium release during potassium depolarization depends on the nature of the contracture. When contracture is isometric, the rate of escape is doubled and declines only slowly; if isotonic, the rate is quadrupled but declines in a few minutes to a level maintained at about double that before potassium. The minimal calcium release during the first 10 minutes of potassium treatment is estimated to be about the same in both cases and about one-half to one-third the uptake. This, and especially the close equality of calcium entry and exit during electrical stimulation, are pointed out as not necessarily inconsistent with a transitory net entry of calcium, comparable to the influx, into restricted regions of the individual fibers.

Animals↗

PubMed1981

Local movement in stimulated frog sartorius muscle.

Local movement was recorded in tetanically contracting frog sartorius muscle to estimate the nonuniformity in the distribution of compliance in the muscle preparation and the compliance that resides in the attachments of the preparation to the measuring apparatus. The stimulated muscle was also subjected to rapid length changes, and the local movements and tension responses were recorded. The results indicate that during tension development at resting length the central region of the muscle shortens at the expense of the ends. After stimulation the "shoulder" in the tension, which divided the relaxation into a slow decline and a subsequent, rather exponential decay toward zero, was accompanied by an abrupt increase in local movement. We also examined the temperature sensitivity of the two phases of relaxation. The results are consistent with the view that the decrease in tension during relaxation depends on mechanical conditions. The local movement brought about by the imposed length changes indicates that the peak value of the relative length change of the uniformly acting part was approximately 20% less than the relative length change of the whole preparation. From these observations, corrections were obtained for the compliance data derived from the tension responses. These corrections allow a comparison with data in the literature obtained from single fiber preparations. The implications for the stiffness measured during the tension responses are discussed.

Animals↗

PubMed1979

The resting membrane potential of frog sartorius muscle.

1. The absolute resting membrane potential of the frog sartorius muscle was determined in Ringer solution at 20 degrees C. 2. Membrane potentials were measured with 0.03, 0.1, 0.3, 1.0 and 3.0 M-KCl electrodes; potentials, including the micro-electrode-tip potentials, were -62.4, -75.7, -83.0, -87.7 and -90.7 mV respectively. 3. Membrane potentials were corrected for the liquid junction potentials between the Ringer and KCl solutions, and the myoplasm and the KCl solutions of the micro-electrodes, using the Henderson's liquid junction equation. 4. The cation (U) and anion (V) conductances of the myoplasm were adjusted to give a constant membrane potential after correction for liquid junction potentials. The final values for U and V were 5.6 and 1.3 mmho/cm respectively, resulting in a membrane potential of -93.0 mV. 5. The correction for the liquid junction potential was -2.6 mV when a 3 M-KCl micro-electrode was used.

Animals↗

PubMed1988

Recurrent primary hydatidosis of sartorius muscle. Case report.

A case of recurrent primary hydatidosis of sartorius muscle is reported. Initially an intact cyst was enucleated and the cavity irrigated with hypertonic saline, but 41 months later the cyst had recurred. Cysto-pericystectomy and saline irrigation were now performed, followed by mebendazole for 21 days. The patient is recurrence-free after 19 months.

Aged↗

PubMed2003

The cranial sartorius muscle undergoes true hypertrophy in dogs with golden retriever muscular dystrophy.

The degree of atrophy or hypertrophy of selected pelvic limb muscles was determined in the canine homologue of Duchenne muscular dystrophy. While most muscles were atrophied, the caudal and cranial sartorius were hypertrophied. Cranial sartorius weights were corrected for body weight and endomysial space to determine true muscle weights (g/kg; mean+/-SD) in three golden retriever muscular dystrophy age groups, 4-10 (Group 1; n=15), 13-26 (Group 2; n=4), and 33-66 (Group 3; n=4) months and grouped normal dogs (6-20 months; n=12). Group 1 golden retriever muscular dystrophy weights (2.2063+/-0.6884) were greater than those of normal dogs (1.2699+/-0.1966), indicating that young golden retriever muscular dystrophy dogs have true cranial sartorius muscle hypertrophy. Values of Group 2 (1.3758+/-0.5078) and Group 3 (0.5720+/-0.2423) golden retriever muscular dystrophy dogs were less than those of Group 1, suggesting that the cranial sartorius muscle atrophies over time. Given that cranial sartorius muscle weight correlated with tarsal joint angle in affected dogs (r=-0.817), the hypertrophied muscle may play a role analogous to iliotibial band tightness in Duchenne muscular dystrophy.

Animals↗

PubMed1983

Ultrastructural configuration of sarcomeres in passive and contracted frog sartorius muscle.

The structural configuration of passive and contracted sarcomeres from frog sartorius muscle was determined for sarcomere lengths between 1.4 and 3.07 microns. Sarcomeres fixed with glutaraldehyde, without detectable contractile activity, were invariably rectangular in shape in longitudinal section regardless of sarcomere length. The structure of sarcomeres excited by osmium tetroxide and contracted depended upon sarcomere length. For lengths greater than 1.6 microns, longitudinally sectioned sarcomeres were convexoconvex (or barrel-shaped). At 1.6 microns, contracted sarcomeres were invariably rectangular in shape. Below 1.6 microns, sarcomeres were compressed and appeared concavoconcave. The results of this study provide models for isovolumetrically contracted sarcomeres which differ significantly from those previously reported.

Animals↗

PubMed1970

Effects of sulphydryl inhibitors on frog sartorius muscle: p-chloromercuribenzenesulphonic acid.

1. Experiments were done on frog sartorius muscles to study the effects and mechanisms of action of the -SH inhibitors, p-chloromercuribenzoic acid (PCMB) and p-chloromercuribenzenesulphonic acid (PCMBS).2. Both organomercurials produce a depolarization of the surface membrane which is associated with a period of asynchronous twitching and followed by inexcitability.3. Only PCMB produces a unique fractionation of the electrically evoked twitch into an initial rapid and later slow phase.4. PCMB and PCMBS increase the rate of (45)Ca efflux from whole muscle. Ethylenediamine tetraacetic acid (EDTA, 5 mM) causes only limited antagonism of the enhancement of (45)Ca efflux produced by PCMB whereas it completely antagonizes this same effect of PCMBS. EDTA selectively removes superficial calcium without penetrating into the intracellular space.5. The results suggest that PCMB inhibits -SH groups in the terminal cisternae causing a fractionation of the twitch. PCMBS acts primarily at surface sites with limited access to the cisternae and sarcoplasmic reticulum.

Action Potentials↗

PubMed1967

The break-down of adenosine triphosphate in the contraction cycle of the frog sartorius muscle.

1. It is confirmed that a fluorodinitrobenzene (FDNB)-treated frog sartorius muscle does not split phosphorylcreatine in the course of its contraction cycle, but does use adenosine triphosphate (ATP).2. Good stoicheiometric relations between the diminution of ATP and the formation of adenosine diphosphate (ADP), adenosine monophosphate (AMP) and phosphate are obtained, and in a 0.2 sec tetanus at 0 degrees C the net break-down of ATP amounts to 0.27, the total equivalent break-down to 0.34 mumoles/g.3. There is no difference in this quantity between muscles interrupted at the height of contraction and those that have also relaxed, and, in experiments specifically designed to determine relaxation metabolism separately, no such metabolism is found. Thus, all the ATP-break-down occurs in the contraction phase.

Adenine Nucleotides↗

PubMed1975

The effects of extracellular pH and buffer concentration on the efflux of lactate from frog sartorius muscle.

1. The rate of efflux of lactate from isolated frog sartorius muscles is measured with a superfusion technique. Efflux curves are followed after raising the internal lactate level of the muscles by repetitive electrical stimulation over a 200 sec period.2. With an external pH of 7.0 or below the measured efflux rates following stimulation reach 100-150 n-mole/g.min. Increasing the pH of the superfusion fluid to 8.0 results in a two or threefold increase in the peak efflux rate. The effect is independent of the buffer system used and occurs fairly rapidly when the pH of the superfusion fluid is changed. This suggests that the effect of pH on lactate efflux is extracellular.3. The increase in efflux rate due to an increase in pH is dependent on buffer concentration. This fact together with measurements of surface pH changes in muscles following arrest of superfusion indicates that a pH gradient exists through the muscle thickness during lactate efflux.4. The low lactate efflux rate seen at a low buffer concentration (1 mM) is reduced to an even lower level by depolarization with potassium sulphate suggesting a membrane potential dependent component. At pH 8.0 with a high buffer concentration (25 mM) potassium sulphate only reduces efflux rate slightly.The observations are interpreted as indicating that a fraction of lactate lost is in the form of undissociated acid and that this fraction increases with increasing external pH.5. Conditions which favour loss of hydrogen ions and lactate from muscle are also associated with improved recovery of twitch tension.

Journal Article↗

PubMed1976

Properties of motor units of the frog sartorius muscle.

1. The mechanical properties of single motor units in the sartorius muscle of the frog Litoria aurea were examined during single shock and repetitive stimulation of motor axons. 2. The tetanic tension developed by motor units lay in the range 1-40% of whole muscle tension with two peaks in the distribution, in the range 5-10% and 25-30%. The large units had briefer times-to-peak for the twitch than the small units and were more readily fatigued during prolonged repetitive stimulation. 3. Histological examination of the muscle gave a count of 620 muscle fibres with a diameter range of 28-128 mum. Cholinesterase stained preparations showed that the majority of muscle fibres had several nerve terminals (mean 3, range 1-5). 4. Muscle fibres received their multiple innervation from different axons (polyneuronal) or branches of the same axon (multiterminal). The presence of polyneuronal innervation of muscle fibres was confirmed by a comparison of the tensions when each of a pair of motor units was stimulated alone and when they were stimulated together. The tension excess, or overlap, was up to 60% when expressed in terms of the tension developed by either unit alone. Motor units developing similar amounts of tension tended to show more overlap in their innervation than units with very different tensions. 5. An estimate of the amount of multiterminal innervation gave variable results but could account for up to 60% of a motor unit's tension. No correlation could be detected between the values for multiterminal innervation and any other measured parameter. However, it is argued that because of the limitations of the measurements the existence of a relationship between the extent of multiterminal or polyneuronal innervation and the mechanical properties of the motor unit cannot be excluded.

Action Potentials↗

PubMed1985

Effect of gramicidin A and thallium ions on cation effluxes in frog sartorius muscle.

The effluxes of potassium, rubidium, sodium and lithium from the sartorius muscle of Rana temporaria in magnesium-Ringer solution free of sodium and potassium have been studied with the flame-emission technique. The channel-forming antibiotic gramicidin A (2.5 X X10(-7)-1 X 10(-6) mol/l) enhanced the efflux of potassium and rubidium and increased the rate constants of these effluxes. Gramicidin had small if any effect on sodium and lithium effluxes and rate constants. After 60-100 min in a gramicidin-containing medium, the potassium efflux and the corresponding rate constant reached a steady-state level. This steady-state value depended on gramicidin concentration. Effect of gramicidin on both the potassium efflux and the rate constant was partially reversible. Thallium ions (2.5 X 10(-3) and 5 X 10(-3) mol/l) in sodium- and potassium- free magnesium Ringer solution caused a large increase in effluxes of all the cations examined (K+, Rb+ and Na+) both in presence and absence of gramicidin. Possible mechanisms of gramicidin and thallium effects are discussed.

Animals↗

PubMed1979

[Effect of low-molecular nonelectrolytes and hypotonia on the contractile responses of frog sartorius muscles].

The potentiation of contractile responses during prolonged incubation of frog sartorius muscles in a conventional Ringer solution and in a calcium-free Ringer solution which contained 400 mM of urea, acetamide or ethylene glycol was observed when stimulation with single electric impulses and with caffeine was carried out. When the muscles were exposed to a hypotonic solution the reduction in the amplitude of caffeine contractures or their complete disappearance were registered, whereas the electrical stimulation of muscles in the same medium exerted an increase in the amplitude of contractile responses. The addition of 400 mM glycerol to the hypotonic solution caused an increase in the amplitude of contractions under both types of stimulation.

Acetamides↗

PubMed1978

[Inhibition of the process of sugar transport stimulation in the frog sartorius muscles by amines and amides].

In the experiments on isolated frog sartorius muscles, amines and amides were found to inhibit the process of stimulation of D-xylose transport induced by insulin, 2,4-dinitrophenol or potassium contracture. The inhibitory action was produced by urea, acetamide, guanidine, NH4Cl, mono-, di- and trimethyl- or ethylamines, some diamines (all the substances being, applied in the concentration range equal to 100 mM). The similar effect was obtained when cystamine (20 mM), tryptamine, 5-methoxytryptamine (2 mM) and adenine, adenosine, guanosine (1-10 mM) were used. There was no inhibitory effect of acetone, glycerol, tetraethylammonium, propilamine, butylamine, aminoacids, spermine, spermidine, ATP, AMP or cAMP. It has been suggested that the inhibitory substances may interact by producing hydrogen bonds from NH-groups with the neutrally or negatively charged groups at the external surface of the muscle membrane in the region with a slow hydrophobicity. As a result, no structural changes required for activation of the sugar transport system occur in the membrane.

Amides↗

PubMed1966

A study on the electrical resistance of the frog sartorius muscle.

Four different methods of measuring the resistance of a muscle fiber have been applied to the frog sartorius muscle. The methods, in which the resistance of the microelectrode entered the calculation of the effective resistance of the fiber, resulted in values which were 8 times higher than the resistance values obtained with methods independent of the electrode resistance. A simple cable model of a muscle fiber could not account for the discrepancy in the effective resistance found in these measurements; therefore, an enlarged cable model for a muscle fiber has been proposed, and its biological implications have been discussed. The effective resistance (measured with the two different groups of methods) decreased when the potassium concentration in the bath increased. Using the proposed enlarged cable model for the interpretation of these results, it is shown that not only the membrane resistance but also the myoplasmic resistance decreases with an increasing potassium concentration in the Ringer solution.

Animals↗

PubMed1988

Effect of pH and stimulus phase on work done by isolated frog sartorius muscle during cyclical contraction.

Work per cycle was calculated in isolated frog sartorius muscle by measuring force as the activated muscle was subjected to sinusoidal length changes. Work per cycle was calculated from the area of the loop formed when force was plotted against length. Measurements were made at 20 degrees C using physiological solutions with high pHe (7.9 or low pHe (6.6). Net work done per cycle was positive when the muscle was activated during the shortening phase of the length cycle. Maximum work done increased as excursion amplitude increased and was about 17Jkg-1 at a strain of 12% (i.e. Lo +/- 6%) at a cycle frequency of 2 Hz. Maximum power was 35 W kg-1 and was about 25% less at the lower pHe. Power measured in this way is much less than the value calculated from force-velocity curves. However, power calculated from force-velocity curves neglects the time that the muscle must be inactive during locomotion. Thus the measurements of the present study are realistic relative to actual mechanical power output during locomotion.

Animals↗

PubMed1970

Potassium exchange and afterpotentials in frog sartorius muscles treated with glycerol.

The potassium exchange properties of glycerol-treated sartorius muscles of the frog were determined. Potassium ((42)K) uptake, efflux, and net flux were measured in the presence of glycerol and at various times after exposure to glycerol and return to isotonic Ringer solution. Potassium uptake was not altered by the presence of glycerol but was reduced on the average 53% after glycerol treatment. Efflux transiently increased in the presence of glycerol and was reduced 37% after glycerol removal. Consequently, there was a net loss of intracellular potassium as well as a gain of sodium. In contrast to the irreversible alterations of potassium exchange induced by glycerol treatment, action potentials with normal negative afterpotentials (N.A.P.) were elicited 4-5 hr after glycerol removal. The reappearance of the N.A.P. was associated with a return of the membrane potential to normal values (90 +/- 2 mv). However, the response of these muscles to reduced extracellular potassium was anomalous. In K(+)-free Ringer solution the average resting membrane potential was 74 +/- 3 mv and a positive afterpotential of 11 +/- 3 mv was associated with the action potential.

Action Potentials↗

PubMed1985

The interactive effects of fatigue and pH on the ionic conductance of frog sartorius muscle fibers.

The effects of fatigue on the membrane conductance of frog sartorius muscle at the resting potential and during an action potential were studied. When muscles were exposed to an extracellular pH of 8.0 the membrane conductance at the resting potential increased during fatigue by about 20% and returned to prefatigue level in about 20 min. The membrane conductance of muscle fibers exposed to pH 6.4 was about three times less than that of pH 8.0 and decreased further during fatigue. Furthermore, the recovery of a normal membrane conductance was slow at pH 6.4. Both the inward, depolarizing and the outward, repolarizing currents during the action potential are reduced in fatigue. In each case the effect is greater at pH 6.4 than at 8.0 and recovery towards normal values is slower at pH 6.4. It is concluded that the ionic conductance of the sarcolemmal membrane at the resting potential and during an action potential are modified by fatigue and that these changes are modulated by pHo.

Action Potentials↗