scholarly journals Effects of previous activity on the energetics of activation in frog skeletal muscle.

1980 ◽  
Vol 75 (6) ◽  
pp. 617-631 ◽  
Author(s):  
J A Rall
Keyword(s):  
Skeletal Muscle ◽  
Time Delay ◽  
Time Course ◽  
Frog Skeletal Muscle ◽  
Active Force ◽  
Force Development ◽  
Uptake Sites ◽  
Contractile Activation ◽  
Terminal Cisternae ◽  
Activation Heat

Effects of previous activity on the ability of frog skeletal muscle at 0 degrees C to liberate energy associated with contractile activation, i.e., activation heat (AH), have been examined. Earlier work suggests that activation heat amplitude (as measured from muscles stretched to lengths where active force development is nearly abolished) is related to the amount of Ca2+ released upon stimulation. After a twitch, greater than 2 s is required before a second stimulus (AHt) can liberate the same activation heat as a first stimulus (AH infinity), i.e., (AHt)/(AH infinity) = 1 -0.83 e-1.40t, where t is time in seconds. Caffeine introduces a time delay in the recovery of the ability to generate activation heat after a twitch. After a tetanus, the activation heat is depressed to a greater extent at any time than after a twitch. The activation heat elicited by a stimulus 1 s after a tetanus is depressed progressively with respect to tetanus duration up to 3 s. For tetani of 3, 40, and 80 s duration the postetanus activation heat is comparably depressed. The time-course of the recovery of the ability of the muscle to produce activation heat after a tetanus can be described as (AHt)/(AH infinity) = 1 -0.80 e-0.95t -0.20 e-0.02t. Greater than 90 s is required before the posttetanus activation heat is equal to the pretetanus value. The faster phase of recovery is similar to recovery after the twitch and the slower phase may be associated with the return of calcium to the terminal cisternae from uptake sites in the longitudinal sarcoplasmic reticulum.

scholarly journals The Intracellular Site of Calcium Activation of Contraction in Frog Skeletal Muscle

1970 ◽  
Vol 55 (1) ◽  
pp. 77-88 ◽  
Author(s):  
Saul Winegrad
Keyword(s):  
Skeletal Muscle ◽  
Room Temperature ◽  
Half Time ◽  
Frog Skeletal Muscle ◽  
Calcium Efflux ◽  
Transverse Tubules ◽  
Calcium Activation ◽  
Thin Filaments ◽  
Almost All ◽  
Terminal Cisternae

Radioautography has been used to localize 45Ca in isotopically labeled frog skeletal muscle fibers which had been quickly frozen during a maintained tetanus, a declining tetanus, or during the period immediately following a tetanus or a contracture. During a tetanus almost all of the myofibrillar 45Ca is localized in the region of the sarcomere occupied by the thin filaments. The amount varies with the tension being developed by the muscle. The movement of calcium within the reticulum from the tubular portion to the terminal cisternae during the posttetanic period has a half-time of about 9 sec at room temperature and a Q10 of about 1.7. Repolarization is not necessary for this movement. Evidence is given to support the notion that most calcium efflux from the cell occurs from the terminal cisternae into the transverse tubules.

Cooperative attachment of cross bridges predicts regulation of smooth muscle force by myosin phosphorylation

2004 ◽  
Vol 287 (3) ◽  
pp. C594-C602 ◽  
Author(s):  
Christopher M. Rembold ◽  
Robert L. Wardle ◽  
Christopher J. Wingard ◽  
Timothy W. Batts ◽  
Elaine F. Etter ◽  
...  
Keyword(s):  
Skeletal Muscle ◽  
Smooth Muscle ◽  
Time Course ◽  
Muscle Force ◽  
Regulatory System ◽  
Force Development ◽  
Cross Bridge ◽  
Cross Bridges ◽  
The Relationship ◽  
Cooperative Activation

Serine 19 phosphorylation of the myosin regulatory light chain (MRLC) appears to be the primary determinant of smooth muscle force development. The relationship between MRLC phosphorylation and force is nonlinear, showing that phosphorylation is not a simple switch regulating the number of cycling cross bridges. We reexamined the MRLC phosphorylation-force relationship in slow, tonic swine carotid media; fast, phasic rabbit urinary bladder detrusor; and very fast, tonic rat anococcygeus. We found a sigmoidal dependence of force on MRLC phosphorylation in all three tissues with a threshold for force development of ∼0.15 mol Pi/mol MRLC. This behavior suggests that force is regulated in a highly cooperative manner. We then determined whether a model that employs both the latch-bridge hypothesis and cooperative activation could reproduce the relationship between Ser19-MRLC phosphorylation and force without the need for a second regulatory system. We based this model on skeletal muscle in which attached cross bridges cooperatively activate thin filaments to facilitate cross-bridge attachment. We found that such a model describes both the steady-state and time-course relationship between Ser19-MRLC phosphorylation and force. The model required both cooperative activation and latch-bridge formation to predict force. The best fit of the model occurred when binding of a cross bridge cooperatively activated seven myosin binding sites on the thin filament. This result suggests cooperative mechanisms analogous to skeletal muscle that will require testing.

Parvalbumin relaxes frog skeletal muscle when sarcoplasmic reticulum Ca(2+)-ATPase is inhibited

1996 ◽  
Vol 270 (2) ◽  
pp. C411-C417 ◽  
Author(s):  
Y. Jiang ◽  
J. D. Johnson ◽  
J. A. Rall
Keyword(s):  
Skeletal Muscle ◽  
Sarcoplasmic Reticulum ◽  
Relaxation Rate ◽  
Time Course ◽  
Muscle Fibers ◽  
Peak Force ◽  
Half Time ◽  
Frog Skeletal Muscle ◽  
Twitch Force ◽  
Total Failure

Inhibition of sarcoplasmic reticulum (SR) Ca(2+)-adenosinetriphosphatase (ATPase) with 2,5-di-(tert-butyl)-1,4-benzohydroquinone (TBQ) in frog skeletal muscle fibers at 10 degrees C prolonged the half time of the fall of the Ca2+ transient by 62% and twitch force by 100% and increased peak force by 120% without increasing the amplitude of the Ca2+ signal. In the presence of TBQ the rate of relaxation and the rate of fall of Ca2+ became progressively slower in a series of twitches until relaxation failed. Relaxation rate decreased with a time course (approximately 2 s-1) similar to the Mg2+ off rate from purified parvalbumin (PA; 3.6 s-1). TBQ slowed the rate of fall of Ca2+ (5-fold) and force (8-fold) in a 0.3-s tetanus so that the rate of fall of Ca2+ (approximately 2.5 s-1) was similar to the Mg2+ off rate from PA. TBQ caused a near total failure of both Ca2+ sequestration and relaxation in a 1.1-s tetanus, during which PA would be saturated with Ca2+ and could not contribute to relaxation. Thus, when the SR Ca(2+)-ATPase is inhibited, Mg(2+)-PA can sequester Ca2+ and produce relaxation at a rate that is defined by the Mg2+ off rate from PA.

Effects of 2-n-butyl-methylenedioxyindene on skeletal muscle mechanics and energetics

1982 ◽  
Vol 242 (5) ◽  
pp. C347-C352 ◽  
Author(s):  
D. M. Burchfield ◽  
J. A. Rall ◽  
R. G. Rahwan
Keyword(s):  
Skeletal Muscle ◽  
Sarcoplasmic Reticulum ◽  
Heat Production ◽  
Muscle Mechanics ◽  
Stimulus Frequency ◽  
Energy Liberation ◽  
Force Development ◽  
Unit Energy ◽  
Kinetics Of ◽  
Activation Heat

Mechanical and energetic effects of 2-n-butyl-3-dimethylamino-5,6-methylenedioxyindene (2-butyl-MDI) were investigated in isolated frog semitendinosus muscles at 0 degrees C. Previous research on various tissues suggested that this compound functions as an intracellular Ca2+ antagonist. The effects of 2-butyl-MDI (2 X 10(-4) M) with respect to time were progressive and reversible with exposures of 30 min or less. A 30-min exposure to the agent significantly decreased twitch and tetanus force and energy liberation, increased the twitch-to-tetanus ratio, prolonged kinetics of force development, induced a stimulus frequency-dependent tetanic fatigue, and decreased contractile economy (measured as force per unit energy liberation). Energy associated with Ca2+ cycling, activation heat, was depressed by 31 +/- 4%. The significant reduction of activation heat production by 2-butyl-MDI suggests that the quantity of Ca2+ released by the sarcoplasmic reticulum upon stimulation is reduced. However, the complexity of the results summarized above suggests multiple sites and/or modes of action for the agent.

scholarly journals The Changes in Ca2+ Sparks Associated with Measured Modifications of Intra-store Ca2+ Concentration in Skeletal Muscle

2006 ◽  
Vol 128 (1) ◽  
pp. 45-54 ◽  
Author(s):  
Bradley S. Launikonis ◽  
Jingsong Zhou ◽  
Demetrio Santiago ◽  
Gustavo Brum ◽  
Eduardo Ríos
Keyword(s):  
Skeletal Muscle ◽  
Cardiac Muscle ◽  
Confocal Imaging ◽  
Frog Skeletal Muscle ◽  
Average Increase ◽  
Global Level ◽  
Event Frequency ◽  
Average Change ◽  
Contractile Activation

In cardiac muscle and amphibian skeletal muscle, the intracellular Ca2+ release that signals contractile activation proceeds by discrete local packets, which result in Ca2+ sparks. The remarkably stereotyped duration of these release events requires a robustly timed termination mechanism. In cardiac muscle the mechanism of spark termination appears to crucially involve depletion of Ca2+ in the lumen of the sarcoplasmic reticulum (SR), but in skeletal muscle, the mechanism is unknown. We used SEER (shifted excitation and emission ratioing of fluorescence) of SR-trapped mag-indo-1 and confocal imaging of fluorescence of cytosolic rhod-2 to image Ca2+ sparks while reversibly changing and measuring [Ca2+] in the SR ([Ca2+]SR) of membrane-permeabilized frog skeletal muscle cells. Sparks were collected in cells immersed in a solution promoting production of events at moderate frequency. Just after permeabilization, event frequency was zero, and in 10 minutes it reached close to a steady value. Controlled interventions modified [Ca2+]SR reversibly between a low value (299 μM on average in 10 experiments) and a high value (433 μM, a 45% average increase). This change increased sparks frequency by 93%, spatial width by 7%, rise time by 10%, and peak amplitude by 38% (provided that it was calculated in absolute terms, rather than normalized by resting fluorescence). The changes in event frequency and amplitude were statistically significant. The “strength” of the effect of [Ca2+]SR on frequency, quantified by decomposition of variance, was <6%. While the average change in [Ca2+]SR was limited, it reached up to 200% in individual fibers, without causing massive Ca2+ release or an increase of >3.5-fold in event frequency. Taken together with existing evidence that depletion is modest during Ca2+ sparks or release elicited by an action potential, the mild effects of [Ca2+]SR reported here do not support a major role of depletion in either the termination of sparks or the strong inactivation that terminates Ca2+ release at the global level in frog skeletal muscle.

scholarly journals Kinetics of contractile activation in voltage clamped frog skeletal muscle fibers

1997 ◽  
Vol 73 (4) ◽  
pp. 1999-2011 ◽  
Author(s):  
P. Szentesi ◽  
Z. Papp ◽  
G. Szücs ◽  
L. Kovács ◽  
L. Csernoch
Keyword(s):  
Skeletal Muscle ◽  
Muscle Fibers ◽  
Frog Skeletal Muscle ◽  
Skeletal Muscle Fibers ◽  
Contractile Activation ◽  
Kinetics Of

scholarly journals Sizes of components in frog skeletal muscle measured by methods of stereology.

1975 ◽  
Vol 66 (1) ◽  
pp. 31-45 ◽  
Author(s):  
B A Mobley ◽  
B R Eisenberg
Keyword(s):  
Skeletal Muscle ◽  
Sarcoplasmic Reticulum ◽  
Surface Area ◽  
Volume Ratio ◽  
Sartorius Muscle ◽  
Morphological Parameters ◽  
Frog Skeletal Muscle ◽  
Fiber Volume ◽  
Transverse Tubules ◽  
Terminal Cisternae

Stereological techniques of point and intersection counting were used to measure morphological parameters from light and electron micrographs of frog skeletal muscle. Results for sartorius muscle are as follows: myofibrils comprise 83% of fiber volume; their surface to volume ratio is 3.8 mum-1. Mitochondria comprise 1.6% of fiber volume. Transverse tubules comprise 0.32% of fiber volume, and their surface area per volume of fiber is 0.22 mum-1. Terminal cisternae of the sarcoplasmic reticulum comprise 4.1% of fiber volume; their surface area per volume of fiber is 0.54 mum-1. Longitudinal sarcoplasmic reticullum comprises 5.0% of fiber volume, and its surface area per volume of fiber is 1.48 mum-1. Longitudinal bridges between terminal cisternae on either side of a Z disk were observed infrequently; they make up only 0.035% of fiber volume and their surface area per volume of fiber is 0.009 mum-1. T-SR junction occurs over 67% of the surface of transverse tubules and over 27% of the surface of terminal cisternae. The surface to volume ratio of the caveolae is 48 mum-1; caveolae may increase the sarcolemmal surface area by 47%. Essentially the same results were obtained from semitendinosus fibers.

scholarly journals Intracellular Calcium Movements of Frog Skeletal Muscle during Recovery from Tetanus

1968 ◽  
Vol 51 (1) ◽  
pp. 65-83 ◽  
Author(s):  
Saul Winegrad
Keyword(s):  
Skeletal Muscle ◽  
Electrical Stimulation ◽  
Skeletal Muscles ◽  
Room Temperature ◽  
Complete Recovery ◽  
Mechanical Activity ◽  
Tetanic Stimulation ◽  
Frog Skeletal Muscle ◽  
Fixation Techniques ◽  
Terminal Cisternae

Radioautographs of 45Ca-labeled frog skeletal muscles have been prepared using freeze-dry and vapor fixation techniques to avoid displacement of the isotope during the preparation of the radioautographs. 45Ca has been localized in resting muscles exposed to 45Ca Ringer's for 5 min or 5 hr and in isotopically labeled muscles recovering from tetanic stimulation at room temperature or at 4°C. In muscles soaked at rest for 5 min 45Ca was present almost exclusively in the terminal cisternae. In all other muscles there were three sites at which the isotope was concentrated: (a) the terminal cisternae, (b) the intermediate cisternae and the longitudinal tubules, and (c) the A band portion of the myofibrils. The terminal cisternae were labeled more rapidly than the myofibrils, but both exchanges were accelerated by electrical stimulation. The amount of 45Ca in the longitudinal tubules and the intermediate cisternae decreased with time after a tetanus as the amount in the terminal cisternae increased. It is proposed that electrical stimulation releases calcium from the terminal cisternae and that relaxation occurs from the binding of the released calcium by the longitudinal tubules and the intermediate cisternae. Complete recovery from mechanical activity involves the transport of this bound calcium into the reticulum and its subsequent binding by the terminal cisternae. Resting exchange of calcium occurs primarily between the terminal cisternae and the transverse tubules.

Force development and metabolism in skeletal muscle of euthyroid and hypothyroid rats

1981 ◽  
Vol 97 (2) ◽  
pp. 221-225 ◽  
Author(s):  
M. E. Everts ◽  
C. van Hardeveld ◽  
H. E. D. J. Ter Keurs ◽  
A. A. H. Kassenaar
Keyword(s):  
Skeletal Muscle ◽  
Oxygen Consumption ◽  
Muscle Metabolism ◽  
Glucose Consumption ◽  
Triceps Surae ◽  
Active Force ◽  
Muscle Preparation ◽  
Force Development ◽  
Contraction Process ◽  
Triceps Surae Muscles

Abstract. The effects of thyroid hormone depletion on skeletal muscle metabolism in relation to force development were studied. For this purpose, the triceps surae muscles were perfused and stimulated at 5 Hz. The basal oxygen consumption of the skeletal muscle preparation was 50% lower in hypothyroid rats as compared with euthyroid rats. The results show that: 1. Active force development was the same in euthyroid and hypothyroid rats during 30 min of stimulation. 2. The increase in oxygen consumption during contraction was twice as high in the euthyroid group compared with the hypothyroid group. 3. Lactate release and glucose consumption were considerably higher in the euthyroid group than in the hypothyroid group during the last 15 min of stimulation. The data show that force development is not impaired in hypothyroid rats but, on the contrary, indicate that the contraction process proceeds more economically in hypothyroid rats than in euthyroid rats.

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