scholarly journals Mechanical Responses of a Crustacean Slow Muscle

1983 ◽  
Vol 107 (1) ◽  
pp. 367-383 ◽  
Author(s):  
WILLIAM D. CHAPPLE
Keyword(s):  
Short Range ◽  
Motor Nerve ◽  
Maximum Velocity ◽  
Isometric Tension ◽  
Muscle Stiffness ◽  
Gradual Transition ◽  
Active Muscle ◽  
Cross Bridge ◽  
Reference Length ◽  
Activation Level

1. Mechanical properties of the abdominal ventral superficial muscle of the hermit crab, Pagurus pollicarus, were examined under isometric and iso-velocity conditions. The muscle was activated by stimulating its motor nerve at different frequencies. 2. Length-isometric tension relations were measured. Peak tension, P0, was 0.16–0.2MNm−2 and the sarcomere length of the muscle at the optimum length, L0, was 10.8+1.0 μm. Passive tension was high at L0. Correlated measurements of the operating length of the muscle and L0 indicate that the operating length is at a point on the ascending limb of the length-tension curve approximately 0.77 L0. 3. The relationship between activation level of the muscle and the length-tension relation indicates that the curve is not substantially displaced along the length axis by increasing activation level; increased force is primarily due to an increase in the slope of the ascending limb of the curve. 4. The force-velocity relation was obtained by measuring the force at a reference length during iso-velocity shortening of an active muscle. Hill constants of a/P0 = 0.11 + 0.02 and b = 1.07 = 0.24 mm s−1 were obtained. The maximum velocity of shortening per half sarcomere was approximately 4.2μms−1. 5. Stretch of an active muscle did not produce an abrupt short range yield but a gradual transition between short range and terminal stiffness. This behaviour is shown to be due not to differences in cross bridge stiffness between VSM and other muscle but to a non cross bridge stiffness with a value that is one-fifth that of vertebrate muscle. 6. Such a low stiffness may provide an intrinsic mechanism for simplifying load compensation in the absence of rapid proprioceptive reflexes for the control of muscle stiffness.

scholarly journals Effect of an ADP analog on isometric force and ATPase activity of active muscle fibers

2003 ◽  
Vol 284 (4) ◽  
pp. C816-C825 ◽  
Author(s):  
Christina Karatzaferi ◽  
Kathryn H. Myburgh ◽  
Marc K. Chinn ◽  
Kathleen Franks-Skiba ◽  
Roger Cooke
Keyword(s):  
Creatine Kinase ◽  
Simple Model ◽  
Atpase Activity ◽  
Isometric Force ◽  
Psoas Muscle ◽  
Isometric Tension ◽  
Active Muscle ◽  
Absolute Value ◽  
Cross Bridge ◽  
Skinned Muscle

The role played by ADP in modulating cross-bridge function has been difficult to study, because it is hard to buffer ADP concentration in skinned muscle preparations. To solve this, we used an analog of ADP, spin-labeled ADP (SL-ADP). SL-ADP binds tightly to myosin but is a very poor substrate for creatine kinase or pyruvate kinase. Thus ATP can be regenerated, allowing well-defined concentrations of both ATP and SL-ADP. We measured isometric ATPase rate and isometric tension as a function of both [SL-ADP], 0.1–2 mM, and [ATP], 0.05–0.5 mM, in skinned rabbit psoas muscle, simulating fresh or fatigued states. Saturating levels of SL-ADP increased isometric tension (by P′), the absolute value of P′ being nearly constant, ∼0.04 N/mm2, in variable ATP levels, pH 7. Tension decreased (50–60%) at pH 6, but upon addition of SL-ADP, P′ was still ∼0.04 N/mm2. The ATPase was inhibited competitively by SL-ADP with an inhibition constant, K i, of ∼240 and 280 μM at pH 7 and 6, respectively. Isometric force and ATPase activity could both be fit by a simple model of cross-bridge kinetics.

Separation of active and passive components of short-range stiffness of muscle

1977 ◽  
Vol 232 (1) ◽  
pp. 45-49 ◽  
Author(s):  
D. L. Morgan
Keyword(s):  
Short Range ◽  
Muscle Tension ◽  
Isometric Tension ◽  
Incomplete Fusion ◽  
Low Frequencies ◽  
Passive Components ◽  
Stimulus Rate ◽  
Straight Line ◽  
Wide Range ◽  
Tendon Compliance

The short-range stiffness of smoothly but submaximally contracting isometric soleus muscles of anesthetised cats was measured by applying small fast stretches. The ratio of isometric tension to stiffness was plotted against tension over a wide range of muscle lengths and stimulus rates. The results fitted a straight line well, as predicted from crossbridge theory, showing the stiffness to be a function of tension only, independent of the combination of length and stimulus rate used to generate the tension. The major deviation from this line was attributed to incomplete fusion at low frequencies of stimulation. Values believed to be tendon compliance and crossbridge tension per unit of stiffness were found from the graph, and the tendon compliance correlated with the maximum muscle tension. Shortening the tendon by attaching nearer to the muscle changed the results in a manner consistent with the theory, provided that appropriate precautions were taken against slippage.

The effects of pH on force and stiffness development in mouse muscles

1987 ◽  
Vol 65 (8) ◽  
pp. 1798-1801 ◽  
Author(s):  
J. M. Renaud ◽  
R. B. Stein ◽  
T. Gordon
Keyword(s):  
High Frequency ◽  
Small Amplitude ◽  
Force Production ◽  
Muscle Length ◽  
Low Ph ◽  
Muscle Stiffness ◽  
Average Force ◽  
Cross Bridge ◽  
Effects Of Ph ◽  
Cross Bridges

Changes in force and stiffness during contractions of mouse extensor digitorum longus and soleus muscles were measured over a range of extracellular pH from 6.4 to 7.4. Muscle stiffness was measured using small amplitude (<0.1% of muscle length), high frequency (1.5 kHz) oscillations in length. Twitch force was not significantly affected by changes in pH, but the peak force during repetitive stimulation (2, 3, and 20 pulses) was decreased significantly as the pH was reduced. Changes in muscle stiffness with pH were in the same direction, but smaller in extent. If the number of attached cross-bridges in the muscle can be determined from the measurement of small amplitude, high frequency muscle stiffness, then these findings suggest that (a) the number of cross-bridges between thick and thin filaments declines in low pH and (b) the average force per cross-bridge also declines in low pH. The decline in force per cross-bridge could arise from a reduction in the ability of cross-bridges to generate force during their state of active force production and (or) in an increased percentage of bonds in a low force, "rigor" state.

scholarly journals Phosphate has dual roles in cross-bridge kinetics in rabbit psoas single myofibrils

2021 ◽  
Vol 153 (3) ◽  
Author(s):  
Masataka Kawai ◽  
Robert Stehle ◽  
Gabriele Pfitzer ◽  
Bogdan Iorga
Keyword(s):  
Rate Constants ◽  
Striated Muscle ◽  
Intrinsic Rate ◽  
Isometric Tension ◽  
Force Generation ◽  
Skinned Fibers ◽  
Sinusoidal Analysis ◽  
Rabbit Psoas ◽  
Cross Bridge

In this study, we aimed to study the role of inorganic phosphate (Pi) in the production of oscillatory work and cross-bridge (CB) kinetics of striated muscle. We applied small-amplitude sinusoidal length oscillations to rabbit psoas single myofibrils and muscle fibers, and the resulting force responses were analyzed during maximal Ca2+ activation (pCa 4.65) at 15°C. Three exponential processes, A, B, and C, were identified from the tension transients, which were studied as functions of Pi concentration ([Pi]). In myofibrils, we found that process C, corresponding to phase 2 of step analysis during isometric contraction, is almost a perfect single exponential function compared with skinned fibers, which exhibit distributed rate constants, as described previously. The [Pi] dependence of the apparent rate constants 2πb and 2πc, and that of isometric tension, was studied to characterize the force generation and Pi release steps in the CB cycle, as well as the inhibitory effect of Pi. In contrast to skinned fibers, Pi does not accumulate in the core of myofibrils, allowing sinusoidal analysis to be performed nearly at [Pi] = 0. Process B disappeared as [Pi] approached 0 mM in myofibrils, indicating the significance of the role of Pi rebinding to CBs in the production of oscillatory work (process B). Our results also suggest that Pi competitively inhibits ATP binding to CBs, with an inhibitory dissociation constant of ∼2.6 mM. Finally, we found that the sinusoidal waveform of tension is mostly distorted by second harmonics and that this distortion is closely correlated with production of oscillatory work, indicating that the mechanism of generating force is intrinsically nonlinear. A nonlinear force generation mechanism suggests that the length-dependent intrinsic rate constant is asymmetric upon stretch and release and that there may be a ratchet mechanism involved in the CB cycle.

scholarly journals Kinetics of a Ca(2+)-sensitive cross-bridge state transition in skeletal muscle fibers. Effects due to variations in thin filament activation by extraction of troponin C.

1991 ◽  
Vol 98 (2) ◽  
pp. 233-248 ◽  
Author(s):  
J M Metzger ◽  
R L Moss
Keyword(s):  
Steady State ◽  
Direct Effect ◽  
Thin Filament ◽  
Near Neighbor ◽  
Troponin C ◽  
Isometric Tension ◽  
Cross Bridge ◽  
Filament Activation ◽  
Kinetics Of ◽  
Partial Extraction

The rate constant of tension redevelopment (ktr; 1986. Proc. Natl. Acad. Sci. USA. 83:3542-3546) was determined at various levels of thin filament activation in skinned single fibers from mammalian fast twitch muscles. Activation was altered by (a) varying the concentration of free Ca2+ in the activating solution, or (b) extracting various amounts of troponin C (TnC) from whole troponin complexes while keeping the concentration of Ca2+ constant. TnC was extracted by bathing the fiber in a solution containing 5 mM EDTA, 10 mM HEPES, and 0.5 mM trifluoperazine dihydrochloride. Partial extraction of TnC resulted in a decrease in the Ca2+ sensitivity of isometric tension, presumably due to disruption of near-neighbor molecular cooperativity between functional groups (i.e., seven actin monomers plus associated troponin and tropomyosin) within the thin filament. Altering the level of thin filament activation by partial extraction of TnC while keeping Ca2+ concentration constant tested whether the Ca2+ sensitivity of ktr results from a direct effect of Ca2+ on cross-bridge state transitions or, alternatively, an indirect effect of Ca2+ on these transitions due to varying extents of thin filament activation. Results showed that the ktr-pCa relation was unaffected by partial extraction of TnC, while steady-state isometric tension exhibited the expected reduction in Ca2+ sensitivity. This finding provides evidence for a direct effect of Ca2+ on an apparent rate constant that limits the formation of force-bearing cross-bridge states in muscle fibers. Further, the kinetics of this transition are unaffected by disruption of near-neighbor thin filament cooperativity subsequent to extraction of TnC. Finally, the results support the idea that the steepness of the steady-state isometric tension-calcium relationship is at least in part due to mechanisms involving molecular cooperativity among thin filament regulatory proteins.

scholarly journals Mavacamten Decreases Maximal Force and Ca2+-sensitivity in the N47K-Myosin Regulatory Light Chain Mouse Model of Hypertrophic Cardiomyopathy

2020 ◽  
Author(s):  
Peter O Awinda ◽  
Marissa Watanabe ◽  
Yemeserach M. Bishaw ◽  
Anna M Huckabee ◽  
Keinan B Agonias ◽  
...  
Keyword(s):  
Heart Disease ◽  
Hypertrophic Cardiomyopathy ◽  
Light Chain ◽  
Isometric Force ◽  
Regulatory Light Chain ◽  
Isometric Tension ◽  
Myosin Regulatory Light Chain ◽  
Cardiac Myosin ◽  
Cross Bridge ◽  
Obstructive Hypertrophic Cardiomyopathy

Morbidity and mortality associated with heart disease is a growing threat to the global population and novel therapies are needed. Mavacamten (formerly called MYK-461) is a small molecule that binds to cardiac myosin and inhibits myosin ATPase. Mavacamten is currently in clinical trials for the treatment of obstructive hypertrophic cardiomyopathy (HCM), and it may provide benefits for treating other forms of heart disease. We investigated the effect of mavacamten on cardiac muscle contraction in two transgenic mouse lines expressing the human isoform of cardiac myosin regulatory light chain (RLC) in their hearts. Control mice expressed wild-type RLC (WT-RLC), and HCM mice expressed the N47K RLC mutation. In the absence of mavacamten, skinned papillary muscle strips from WT-RLC mice produced greater isometric force than strips from N47K mice. Adding 0.3 µM mavacamten decreased maximal isometric force and reduced Ca2+-sensitivity of contraction for both genotypes, but this reduction in pCa50 was nearly twice as large for WT-RLC vs. N47K. We also used stochastic length-perturbation analysis to characterize cross-bridge kinetics. The cross-bridge detachment rate was measured as a function of [MgATP] to determine the effect of mavacamten on myosin nucleotide handling rates. Mavacamten increased the MgADP release and MgATP binding rates for both genotypes, thereby contributing to faster cross-bridge detachment, which could speed myocardial relaxation during diastole. Our data suggest that mavacamten reduces isometric tension and Ca2+-sensitivity of contraction via decreased strong cross-bridge binding. Mavacamten may become a useful therapy for patients with heart disease, including some forms of HCM.

Effect of temperature of resistance to stretch of tortoise muscle

1976 ◽  
Vol 231 (5) ◽  
pp. 1349-1355 ◽  
Author(s):  
WS Fowler ◽  
A Crowe
Keyword(s):  
Isometric Contraction ◽  
Isometric Tension ◽  
Effect Of Temperature ◽  
Active Muscle ◽  
Muscular Tension ◽  
Tension Change ◽  
Effects Of Temperature ◽  
Gastrocnemius Muscles

The effects of temperature over the range 5-30 degrees on isometric contraction and resistance to mechanical stretches of the ramp and hold type applied to active muscle have been studied in isolated tortoise gastrocnemius muscles. The isometric tension decreases as the temperature is lowered but, when expressed as a proportion of the isometric tension, the change in tension at the end of the ramp phase of the stretch is increased at the lower temperatures. The proportionate tension change at the end of the hold phase of the stretch could not be directly related to the temperature. An attempt is made to interpret the results in terms of current opinions on the mechanism of the generation of muscular tension.

Short-range stiffness of slow fibers and twitch fibers in reptilian muscle

1976 ◽  
Vol 231 (2) ◽  
pp. 449-453 ◽  
Author(s):  
U Proske ◽  
PM Rack
Keyword(s):  
Short Range ◽  
Motor Nerve ◽  
Nerve Fibers ◽  
Repetitive Stimulation ◽  
Fiber Types ◽  
Cross Links ◽  
Stimulation Of Nerve ◽  
Limiting Value ◽  
Stimulation Of

The semitendinous muscle of the lizard Tilique contains both slow and twitch fibers; by subdivision of its motor nerve, fibers of each type may be stimulated separately. When, during repetitive stimulation of nerve filaments, the muscle was lengthened or shortened, the tension changes included an initial short-range stiffness, followed by a later compliance. With increasing velocities of movement, the short-range stiffness increased toward a limiting value. For slow fibers this limiting value was reached with lower velocities of movement than for the twitch fibers. Provided that the same velocity of movement was used and the movements began from similar initial isometric tensions, the slow fibers resisted the movements with a greater stiffness than the twitch fibers. It is suggested that not all of the observed differences between the two fiber types can be interpreted simply in terms of differences in rates of formation and breakdown of cross-links.

Effect of denervation on ATP consumption rate of diaphragm muscle fibers

2007 ◽  
Vol 103 (3) ◽  
pp. 858-866 ◽  
Author(s):  
Gary C. Sieck ◽  
Wen-Zhi Zhan ◽  
Young-Soo Han ◽  
Y. S. Prakash
Keyword(s):  
Consumption Rate ◽  
Atp Hydrolysis ◽  
Maximum Velocity ◽  
Diaphragm Muscle ◽  
Single Type ◽  
Shortening Velocity ◽  
Cycling Rate ◽  
Cross Bridge ◽  
Atpase Reaction ◽  
The Difference

Denervation (DNV) of rat diaphragm muscle (DIAm) decreases myosin heavy chain (MHC) content in fibers expressing MHC2X isoform but not in fibers expressing MHCslow and MHC2A. Since MHC is the site of ATP hydrolysis during muscle contraction, we hypothesized that ATP consumption rate during maximum isometric activation (ATPiso) is reduced following unilateral DIAm DNV and that this effect is most pronounced in fibers expressing MHC2X. In single-type-identified, permeabilized DIAm fibers, ATPiso was measured using NADH-linked fluorometry. The maximum velocity of the actomyosin ATPase reaction ( Vmax ATPase) was determined using quantitative histochemistry. The effect of DNV on maximum unloaded shortening velocity ( Vo) and cross-bridge cycling rate [estimated from the rate constant for force redevelopment ( kTR) following quick release and restretch] was also examined. Two weeks after DNV, ATPiso was significantly reduced in fibers expressing MHC2X, but unaffected in fibers expressing MHCslow and MHC2A. This effect of DNV on fibers expressing MHC2X persisted even after normalization for DNV-induced reduction in MHC content. With DNV, Vo and kTR were slowed in fibers expressing MHC2X, consistent with the effect on ATPiso. The difference between Vmax ATPase and ATPiso reflects reserve capacity for ATP consumption, which was reduced across all fibers following DNV; however, this effect was most pronounced in fibers expressing MHC2X. DNV-induced reductions in ATPiso and Vmax ATPase of fibers expressing MHC2X reflect the underlying decrease in MHC content, while reduction in ATPiso also reflects a slowing of cross-bridge cycling rate.

Activation and Behavior. I: Relationship between Physiological “Indicants” of Activation and Performance during Memorization of Nonsense Syllables Using Differing Induced Tension Conditions

1964 ◽  
Vol 19 (1) ◽  
pp. 95-110 ◽  
Author(s):  
Robert G. Eason ◽  
M. Russell Harter ◽  
William F. Storm
Keyword(s):  
Heart Rate ◽  
Gradual Transition ◽  
Experimental Session ◽  
Nervous Systems ◽  
Physiological Variables ◽  
Tension Level ◽  
Activation Level ◽  
Increasing Functions ◽  
Forearm Flexor ◽  
Nonsense Syllables

This is the first of a series of studies oriented toward determining what physiological variables constitute the most reliable and valid indices of activation level; what is the minimal number of variables required to estimate accurately general activation level as well as patterns of activation, taking into account the activity of both the autonomic and somatic nervous systems; and how each variable relates to performance under specified conditions. The primary purpose of this study was to ascertain how four different “indicants” of activation level relate to one another and to verbal performance under different induced tension conditions. Sixteen Ss memorized 16 5-syllable lists of 3-letter nonsense syllables under 16 conditions in a single experimental session, using a balanced Latin square to control for order effects. The conditions were generated by various combinations of three independent variables: (1) mode of syllable presentation (visual vs auditory); (2) method of inducing tension (lifting weights vs squeezing hand dynamometer); and (3) amount of induced tension (5, 10, 15, and 20 lbs.). Each trial was 2 min. long, being followed by 2 min. of rest. Orderly within- and between-trial changes were noted in skin conductance, heart rate, and neck and forearm flexor tension level, but the changes varied, respectively, among the four variables from decreasing to increasing functions. This gradual transition was explained in terms of the relative degree of control the autonomic and somatic nervous systems exerted on each of the variables. The decreasing functions probably reflect a gradual reduction in the degree of anxiety or apprehensiveness experienced by Ss; the increasing functions probably reflect an increase in the amount of muscular effort exerted by Ss in order to maintain a specified amount of force on a hand grip device. Increasing amounts of induced tension caused performance to deteriorate and caused heart rate and forearm flexor tension level to increase. The manner in which the syllables were presented and method of inducing tension significantly affected performance but not the physiological variables.

Sign in / Sign up

Export Citation Format

Share Document