SEARCH · PubMed Health

Results for “SARTORIUS MUSCLE”

Explore indexed PubMed citations for clinical trials, systematic reviews and public health research. Read source abstracts and follow each citation to its original PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 847 records · Page 47Linked to original sources

PubMed1970

Influence of polyvalent cations on the activation of muscle end plate receptors.

The influence of polyvalent cations on the activation of end plate receptors has been studied in vitro on the sartorius muscle of the frog. In the absence of extracellular calcium, the sensitivity of the receptors to depolarizing quaternary ammonium salts was markedly reduced. Maximum receptor activation occurred in those fibers equilibrated in 1.8 mM calcium Ringer solution, with the response being reduced as the calcium concentration was raised or lowered. Magnesium was less efficient than calcium in regulating the sensitivity of the end plate receptors, the maximum receptor response occurring in those fibers equilibrated in 8 mM magnesium Ringer solution. In the presence of lanthanum the end plate response to carbamylcholine or acetylcholine was enhanced. Lanthanum increased the conductance change produced by carbamylcholine both in polarized and in potassium-depolarized fibers. The application of 10(-2) mM lanthanum to the end plate increased MEPP's amplitude, rise time, and half-fall time by 19, 54, and 45%, respectively. The results suggest that polyvalent cations influence postjunctional membrane receptor processes in addition to their well-documented prejunctional action.

Acetylcholine↗

PubMed1977

[Effect of calcium channel blockaders (verapamil, D-600 and manganese ions) on mediator release from frog muscle motor nerve endings].

The reduction in the EPPs quantum content produced by manganese ions (0.4-5.0 mM) was observed in the frog sartorius muscle. In contrast to the inhibitory action on the evoked release, manganese ions increased a spontaneous transmitter release. Verapamil (1-10(-6)-5-10(-5) g/ml) and D-600 (2.5-10(-5) g/ml) did not inhibit the evoked release but increased the spontaneous one. All the calcium antagonists studied were able to prevent the facilitatory effect of imidazole (3 mM) on neuromuscular transmission. Verapamil (5-10(-6)-5-10(-5) g/ml) disturbed the action potential generation during the repetitive stimulation of the motor nerve. Manganese ions were ineffective in this respect. A conclusion is made that the calcium ionic channels in the nerve terminals differ from the calcium channels in some other tissues (heart, soma of neurons etc.).

Animals↗

PubMed1999

Time-resolved equatorial X-ray diffraction studies of skinned muscle fibres during stretch and release.

Equatorial X-ray diffraction patterns were recorded from small bundles of one to three chemically skinned frog sartorius muscle fibres (time resolution 250 microseconds) during rapid stretch and subsequent release. In the relaxed state, the dynamic A-band lattice spacing change as a result of a 2 % step stretch (determined from the positions of the 10 and 11 reflections) resulted in a 21 % increase in lattice volume, while static studies of spacing and sarcomere length indicated than an increase in volume of >/=50 % for the same length change. In rigor, stretch caused a lattice volume decrease which was reversed by a subsequent release. In activated fibres (pCa 4.5) exposed to 10 mM 2,3-butanedione 2-monoxime (BDM), stretch was accompanied by a lattice compression exceeding that of constant volume behaviour, but during tension recovery, compression was partially reversed to leave a net spacing change close to that observed in the relaxed fibre. In the relaxed state, spacing changes were correlated with the amplitude of the length step, while in rigor and BDM states, spacing changes correlated more closely with axial force. This behaviour is explicable in terms of two components of radial force, one due to structural constraints as seen in the relaxed state, and an additional component arising from cross-bridge formation. The ratio of axial to radial force for a single thick filament resulting from a length step was four in rigor and BDM, but close to unity for the relaxed state.

Animals↗

PubMed1977

Electrophysiological membrane properties of the frog muscle fibre: effects of detergents in the triton series.

The effect of the nonionic detergent Triton X-100 on the membrane properties of frog sartorius muscle fibres was studied using intracellular microelectrode technique. The effect of Triton X-100 was compared with that of Triton X-45 and Triton N-101. At 40 muM Triton X-100 had little effect on the specific membrane resistance (Rm), membrane capacitance (Cm) and the resting membrane potential (Er) while the action potential (AP) was markedly reduced. At 160 muM AP was completely abolished and Er was diminished linearily with time. The effect on the maximum rate of rise (VA) of the AP was dose-dependent and the apparent dissociation constant (KD app) and K(D) were found to be about 40 muM. The Hill coefficient was 1.6 indicating a deviation from a first order reaction. The effect of Triton X-100 on Er may be accounted for by a reduction of the Na--K pumping activity. The effect of Triton X-100 on the AP is suggested to be due to a perturbation of a protein-system either by a drug-receptor interaction involving two or more sites, or an unspecific binding of Triton X-100 to hydrophobic loci on the protein.

Action Potentials↗

PubMed1983

The influence of the permeant ions thallous and potassium on inward rectification in frog skeletal muscle.

A three-electrode voltage-clamp method was used to investigate the inactivation of Tl currents through the inward rectifier of frog sartorius muscle fibres, and the interaction between the permeant ions Tl+ and K+. In 80 mM-Tl Ringer inward currents inactivated on hyperpolarization along an exponential time course, with time constants that initially increased and then fell with increasing hyperpolarization. Because of the inactivation process steady-state conductances were smaller than instantaneous conductances at all potentials in Tl Ringer. The steady-state conductance increased to a maximum value at around - 100 mV in 80 mM-Tl Ringer, and then fell with increasing hyperpolarization. In K Ringer the steady-state conductance was greater at all potentials than the instantaneous conductance because K currents activate (rather than inactivate) on hyperpolarization. Time constants of Tl inactivation were the same when measured from the decay of current during a single pulse, or from the rate of recovery from inactivation using either a two- or a three-pulse method, indicating that inactivation obeys first-order kinetics. In 80 mM-Tl Ringer steady-state inactivation increased with increasing hyperpolarization, e-fold every 48 mV. This would be consistent with the site at which inactivation occurs experiencing 0.5 of the membrane voltage field. Tl+ was more permeant than K+ through the inward rectifier, the permeability ratio PTl+/PK+ being 1.66. In solutions containing both Tl+ and K+ the membrane showed an anomalous mole-fraction dependence of conductance, the resting potential being more negative, and both instantaneous and steady-state conductances smaller than those recorded in solutions containing only Tl+ or only K+. The reduction in the amplitude of the instantaneous conductance in Tl-K mixtures was voltage-dependent, the block being initially increased and then falling with increasing hyperpolarization. Inward currents also inactivated on hyperpolarization in Tl-K mixtures. The time constants of inactivation, and the extent of inactivation which occurred, became less dependent on membrane potential in these solutions. When K+ is the major permeant ion in solution, Tl+ has a blocking effect on the currents carried by K+, and the degree of block is voltage-dependent. Increasing [Tl]o increased the block at all potentials. The results of our experiments in solutions containing both Tl+ and K+ are discussed in terms of an interaction between these ions within the channel.

Animals↗

PubMed1987

Red cell perfusion in skeletal muscle at rest and after mild and severe contractions.

The aim of this study was to evaluate the distribution of red cell perfusion in sartorius muscle of anesthetized frogs by analyzing simultaneously red cell velocity (VRBC), number of cells per unit capillary length (NRBC), and density of perfused capillaries (CD) in a 2.07 X 2.71-mm region of the muscle visualized microscopically at very low magnification. In the 16 muscles studied, a severe 1-min electrical stimulation induced statistically significant increases in the mean values, VRBC, NRBC, and CD, as well as significant decreases in heterogeneities (SD/mean) of these three parameters when going from rest to postcontraction hyperemia. A mild 3-s stimulation caused significant increases only in VRBC and NRBC. Red cell perfusion, computed as a product of the three parameters divided by the mean capillary length, increased significantly from 87.4 +/- 81.9 to 417.9 +/- 118.2 (SD) and from 96.9 +/- 75.7 to 192.5 +/- 190.2 (SD) cells X s-1 X mm-3, respectively. In both stimulations, the postcontraction increase of red cell supply to the muscle, expressed in cells per second per cubic millimeter, was larger than any individual increase in the three parameters. Based on pooled data from all muscles, both NRBC and CD were determined to be dependent on VRBC. The present study supports the view that VRBC, NRBC, CD, and heterogeneity of red cell distribution depend on vascular tone and demonstrates for the first time that these four dependencies can operate both concurrently and synergistically to increase O2 supply to muscle after contraction.

Animals↗

PubMed1983

Effects of physostigmine on the voltage dependent ionic conductances of skeletal muscle fibres.

The voltage dependent ionic conductances were studied by analysing the phase plane trajectories of action potentials evoked by electrical stimulation of the sartorius muscles of the frog (Rana esculenta). The delayed outward potassium current was measured also under voltage clamp conditions on muscle fibres of either the frog (Rana esculenta) or Xenopus laevis. On analysing the effect of physostigmine decreasing the peak amplitude, the rate of both the rising and falling phases of the action potentials, it was revealed that the alkaloid at a concentration of 1 mmol/l reduced significantly both the delayed potassium conductance and the outward ionic current values during the action potentials. The inhibition of sodium conductance and inward ionic current was less expressed. The maximum value of delayed potassium conductance measured under voltage clamp conditions was decreased by 1 mmol/l physostigmine. The time constant determined from the development of delayed potassium conductance was increased at a given membrane potential. The voltage vs. n relationship describing the membrane potential dependence of the delayed rectifier was not influenced by physostigmine. It has been concluded that physostigmine changes the time course of the action potentials by decreasing the value of both voltage dependent ionic conductances and by slowing down their kinetics. It is discussed that results obtained from the phase plane analysis of complex pharmacological effects can only be accepted with some restrictions.

Action Potentials↗

PubMed1971

Ionic permeability changes induced by some cholinergic agonists on normal and denervated frog muscles.

1. The reversal potential of responses to iontophoretic application of acetylcholine, carbamylcholine and decamethonium has been measured at junctional and extrajunctional sensitive areas of the normal sartorius muscle of the frog.2. The values obtained with any one of the drugs at junctional spots were similar to those previously reported for the end-plate potential (about - 16 mV).3. On the other hand, at extrajunctional areas the reversal potential of responses to these agonists was found to have a mean value of - 42 mV. The muscle-tendon responses to acetylcholine reversed at - 51 mV.4. The response to decamethonium was used to determine the nature of the ionic permeability changes mediated by the extrajunctional receptors. The results obtained show that extrajunctional responses are due to an increase in conductance to Na(+) and K(+) but not to Cl(-).5. The reversal potential of acetylcholine responses in denervated frog sartorius was - 42 mV both at former junctional spots and at non-neural sensitized regions.6. These different values of the reversal potential can be due either to effects of receptor density on the ionic selectivity of the membrane or to regional variations in the extracellular ionic accumulation during the transmitter action.

Acetylcholine↗

PubMed1980

High-voltage electron microscopy of crossbridge interactions in striated muscle.

In order to investigate the geometry of the interactions which myosin molecules make with actin filaments we have studied thick (0.2--0.5 micrometer) transverse sections of striated muscles in the 1 Me V electron microscope at Imperial College. Sections obtained from fixed relaxed frog sartorius muscle and both fixed relaxed and fixed rigor insect flight muscles, show regular electron opaque features between the thick and thin filament profiles. These are thought to be the overlapping images of the many levels of myosin heads that occur in such sections. From the appearances of these images, together with studies of thin transverse sections, it appears that of the possible interactions which one myosin molecule can make, namely that its two component heads interact with the same thin filament or with two different thin filaments, it is the former interaction (both heads on the same filament) which is predominant. Nevertheless appearances have been seen similar to those expected if an interaction of one molecule with two thin filaments occurs. It is concluded that both single filament and two filament interactions can occur depending on the steric convenience of the available actin subunits, but that the single filament interaction occurs in the majority of cases in the muscle states we have studied. Finally it is shown that the myosin filament profiles seen in thick transverse sections may be a very misleading guide to thick filament structure because of the influence which the myosin crossbridge have on the appearance of the profiles.

Actins↗

PubMed1997

Active and passive forces of isolated myofibrils from cardiac and fast skeletal muscle of the frog.

1. Force measurements in isolated myofibrils (15 degrees C; sarcomere length, 2.10 microns) were used in this study to determine whether sarcomeric proteins are responsible for the large differences in the amounts of active and passive tension of cardiac versus skeletal muscle. Single myofibrils and bundles of two to four myofibrils were prepared from glycerinated tibialis anterior and sartorius muscles of the frog. Skinned frog atrial myocytes were used as a model for cardiac myofibrils. 2. Electron microscope analysis of the preparations showed that: (i) frog atrial myocytes contained a small and variable number of individual myofibrils (from 1 to 7); (ii) the mean cross-sectional area and mean number of myosin filaments of individual cardiac myofibrils did not differ significantly from those of single skeletal myofibrils; and (iii) the total myofibril cross-sectional area of atrial myocytes was on average comparable to that of bundles of two to four skeletal myofibrils. 3. In maximally activated skeletal preparations, values of active force ranged from 0.45 +/- 0.03 microN for the single myofibrils (mean +/- S.E.M.; n = 16) to 1.44 +/- 0.24 microN for the bundles of two to four myofibrils (n = 9). Maximum active force values of forty-five cardiac myocytes averaged 1.47 +/- 0.10 microN and exhibited a non-continuous distribution with peaks at intervals of about 0.5 microN. The results suggest that variation in active force among cardiac preparations mainly reflects variability in the number of myofibrils inside the myocytes and that individual cardiac myofibrils develop the same average amount of force as single skeletal myofibrils. 4. The mean sarcomere length-resting force relation of atrial myocytes could be superimposed on that of bundles of two to four skeletal myofibrils. This suggests that, for any given amount of strain, individual cardiac and skeletal sarcomeres bear essentially the same passive force. 5. The length-passive tension data of all preparations could be fitted by an exponential equation. Equation parameters obtained for both types of myofibrils were in reasonable agreement with those reported for larger preparations of frog skeletal muscle but were very different from those estimated for multicellular frog atrial preparations. It is concluded that myofibrils are the major determinant of resting tension in skeletal muscle; structures other than the myofibrils are responsible for the high passive stiffness of frog cardiac muscle.

Animals↗

PubMed1978

Bound potassium in muscle.

Joining to the debate on "bound" or "freely diffusible" muscle potassium, which is still going on nowadays, direct current was perfused through couples of semimembranous and sartorius muscles of frog for 0.5 to 1 hour. It was done in normal, fresh condition on one muscle, and on the other after having it over-stimulated with ac of 110 V supposing that a part of K is immobilly bound in fresh muscles, but in the overtired muscles a part of K is released and becomes mobile. As mobile K+ migrates to the negative electrode, we could really find a difference between the behavior of the K+ content of fresh and over-stimulated muscles, in so far as there was much more K in the overstimulated muscle near the negative electrode than near the positive one, as compared with the K content of the corresponding parts of normal muscle.

Animals↗

PubMed1987

Contractile properties of fast and slow twitch muscles of the rat at temperatures between 6 and 42 degrees C.

The effect of a wide range of temperature on the development of twitch and tetanic tension was investigated in directly stimulated rat fast (EDL) and slow (SOL) twitch muscle preparations. When increasing the temperature from 6 to 30 degrees C the maximum tetanic tension rose steadily. The Q10 was 2.3 (EDL) and 2.7 (SOL) for temperatures between 12 and 22 degrees C. The twitch tension output of SOL muscle increased up to 36-38 degrees C, whereas the EDL muscle exhibited a distinct maximum at 22 degrees C followed by a 50% decrease at 34 degrees C. Post-tetanic potentiation was observed in EDL muscle at temperatures higher than 20 degrees C. In SOL muscle neither posttetanic potentiation nor cold potentiation could be observed. The twitch/tetanus ratio was 0.2-0.3 at 35 degrees C but 0.7-0.8 at 6 degrees C. In both muscle types the most characteristic effect of temperature was the prolongation of the time to peak and the relaxation time in parallel to cooling. The tension rise of fast twitch rat muscle during cooling from 35 degrees C downwards can be compared to the cold potentiation of frog sartorius muscle. It is suggested that the main effect of temperature on muscle function concerns the process of Ca2+ release and of Ca2+ uptake. The different response of SOL muscle may be related to the less developed sarcoplasmic reticulum and the lower Ca2+ ATPase activity.

Action Potentials↗

PubMed1981

A comparative study of charge movement in rat and frog skeletal muscle fibres.

1. The middle of the fibre voltage--clamp technique (Adrian & Marshall, 1977), modified where necessary for electrically short muscle fibres, has been used to measure non-linear charge movements in mammalian fast twitch (rat extensor digitorum longus), mammalian slow twitch (rat soleus) and frog (sartorius) muscles. 2. The maximum amount of charge moved in mammalian fast twitch muscle at 2 degrees C in hypertonic solution, was 3--5 times greater than in slow twitch muscle. The voltage distribution of fast twitch charge was 10--15 mV more positive when compared to slow twitch. 3. In both mammalian muscle types hypertonic Ringer solution negatively shifted the voltage distribution of charge some 6 mV. The steepness of charge moved around mechanical threshold was unaffected by hypertonicity. 4. The amount of charge in frog sartorius fibres at 2 degrees C in hypertonic solution was about half of that in rat fast twitch muscle; the voltage distribution of the frog charge was similar to rat soleus muscle. 5. Warming between 2 and 15 degrees C had no effect on either the amount of steady-state distribution of charge in mammalian or frog muscles. 6. At 2 degrees C, the kinetics of charge movement in fast and slow twitch mammalian muscles were similar and 2--3 times faster than frog muscle at the same temperature. In fast and slow mammalian fibres at 2 degrees C similar times were taken to shift the same fractions of the total amount of charge. The Q10 of charge movement kinetics was between 1.2 and 2.0 in the three muscles studied.

Animals↗

PubMed1959

Muscle: a three phase system. The partition of divalent ions across the membrane.

The partition of sulfate, Ca(++), and Mg(++) across the membrane of the sartorius muscle has been studied, and the effect of various concentrations of these ions in the Ringer solution on the cellular level of Na(+), K(+), and Cl(-) has been determined. The level of the three divalent ions in toad plasma and muscle in vivo has been assayed. Muscle was found to contain an almost undetectable amount of inorganic sulfate. Increases in the external level of these ions brought about increases in intracellular content, calculated from the found extracellular space as determined with radioiodinated serum albumin or inulin. Less of the cell water is available to sulfate than to Cl(-), and the Mg(++) space is less than the Na(+) space. An amount of muscle water similar to that found for Li(+) and I(-) appears to be available to these divalent ions. Sulfate efflux from the cell was extremely rapid, and it was not found possible to differentiate kinetically between intra- and extracellular material. These results are consistent with the theory of a three phase system, assuming the muscle to consist of an extracellular phase and two intracellular phases. Mg(++) and Ca(++) are adsorbed onto the ordered phase, and increments in cellular content found on raising the external level are assumed to occur in the free intracellular phase.

Calcium↗

PubMedDate not supplied

[Response of the isolated muscle tissue of frog species to the successive effects of subtoxic and toxic chloral hydrate solutions].

Time-related changes in the mean resistance of sartorius muscle from individual common frogs to the toxic effect of chloral hydrate (0.05 and 0.08 M) were observed. The correlation coefficient between the initial muscle resistance and the value and direction of its changes as well as between the resistance of the paired muscle under the influence of subtoxic chloral hydrate solution (0.005 M) was calculated. A biphase pattern of change of almost all the above indices depending on the dose of pretreatment was observed. Time-related changes in the correlation coefficient between muscle resistance and its changes and between the resistance of the paired muscle and variability of the resistance proved to be much more informative than the mean resistance concerning both the muscle response to the stimulus and functional state of the muscle cells.

Adaptation, Physiological↗

PubMed1995

The force-velocity curve in passive whole muscle is asymmetric about zero velocity.

The force-velocity property of passive muscle was investigated to determine if a discontinuity of slope occurred at zero velocity. Isolated, unstimulated whole frog sartorius muscles were subjected to constant-velocity stretches and releases using a servo-controlled lever. The force due to damping (delta T) was calculated by subtracting the tension measured at a very low speed (1.0 mm s-1) from the tension measured at the same length while the muscle was shortening or lengthening at a particular test speed. The experiments were performed over a range of speeds at each of several lengths and at two temperatures. For comparison, the same experiments were performed using a strip of pure latex rubber and a steel spring. Curves showing the magnitude of delta T vs velocity were nearly symmetric about the zero-velocity axis for the steel spring and the rubber strip, but were markedly asymmetric for passive muscle, showing a positive delta T for lengthening at all speeds that was between four and 11 times the negative delta T for shortening at the same speed, depending on the temperature and initial stretch length. The force due to damping at a given speed increased with extension above the rest length in passive muscle but decreased with increasing length in experiments using the latex strip. Predictions obtained from a mathematical model based on a damping element in series with a lightly damped spring were fitted to the experimental measurements of delta T vs velocity. The damping parameter provisionally representing interfilamentary sliding was between six and 12 times larger for lengthening than for shortening.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed1986

TMB-8 can block twitches without blocking high K+ or caffeine induced contractures in frog's skeletal muscle.

TMB-8 [8-(diethylamino)-octyl-3,4,5-trimethoxybenzoate] is known to inhibit calcium ion dependent processes in several tissues by stabilizing some intracellular stores of membrane-bound calcium. TMB-8 was used to study the excitation-contraction (E-C) coupling process in frog's skeletal muscle. TMB-8 (5 X 10(-5) - 10(-4) M) blocked electrically evoked twitches but not high K+ (123 mM)- or caffeine (2.36 mM)-induced contractures in isolated, curarized toe muscles. TMB-8 (10(-4) M) produced a small decrease (16%) in the action potential of frog's sartorius muscle fibres. However, reducing extracellular Na+ to 44.7 mM produced a similar reduction (17%) in action potential amplitude but did not suppress the twitch; i.e. it produced only a small increase (about 10%) in twitch amplitude. It is known that potassium contractures are produced by extracellular Ca++ ions which enter through calcium channels in the t-tubules and that caffeine produces contractures by sensitizing the sarcoplasmic reticulum to Ca++-induced Ca++ release. The present results suggest that TMB-8 blocks twitches by preventing the release of Ca++ ions bound to the intracellular surface of the t-tubular membrane which is often called the store of 'trigger-calcium' ions.

Action Potentials↗

PubMed1972

Potassium conductance changes in skeletal muscle and the potassium concentration in the transverse tubules.

1. When one hyperpolarizes a muscle fibre by passing electric current, the K conductance declines with time. Voltage-clamp experiments on frog sartorius muscle fibres showed that two components contribute to this decline.2. A rapid component operates when the fibre is hyperpolarized to potentials more negative than -120 mV. Decline by this mechanism is reversed completely within 200 msec. The large effect of temperature on the kinetics of this process indicates that it represents a time-dependent membrane permeability change.3. A slow component operates also at less negative potentials. Recovery at -65 mV takes place with half-times of about 0.4 sec. The Q(10) for the rate of recovery is 1.3, indicating that this process is diffusion limited.4. After prolonged hyperpolarization to potentials positive to -120 mV, membrane current at the resting potential is outward and persists for several seconds. At that time, the potential measured in the absence of membrane current is shifted in the negative direction by 3-5 mV.5. This shift and the time course of currents near the resting potential after hyperpolarization as well as the Q(10) of 1.3 indicate that the slow process is due to changes in tubular K concentration and not to a time-dependent membrane permeability change.6. At potentials less negative than -120 mV, tubular depletion can satisfactorily account for the decline of K conductance. At more negative potentials, the decline appears to be due to both depletion and a permeability change.

Animals↗