Determinants of Unloaded Shortening Velocity in Striated Muscle

2002 ◽  
pp. 417-442
Author(s):  
Earl Homsher
Keyword(s):  
Striated Muscle ◽  
Shortening Velocity

scholarly journals Force: velocity relationship in single isolated toad stomach smooth muscle cells.

1987 ◽  
Vol 89 (5) ◽  
pp. 771-789 ◽  
Author(s):  
D M Warshaw
Keyword(s):  
Smooth Muscle ◽  
Smooth Muscle Cells ◽  
Striated Muscle ◽  
Muscle Cells ◽  
Length Change ◽  
Force Transducer ◽  
Cell Length ◽  
Shortening Velocity ◽  
Cross Sectional ◽  
Cross Bridges

The relationship between force and shortening velocity (F:V) in muscle is believed to reflect both the mechanics of the myosin cross-bridge and the kinetics of its interaction with actin. To date, the F:V for smooth muscle cells has been inferred from F:V data obtained in multicellular tissue preparations. Therefore, to determine F:V in an intact single smooth muscle cell, cells were isolated from the toad (Bufo marinus) stomach muscularis and attached to a force transducer and length displacement device. Cells were electrically stimulated at 20 degrees C and generated 143 mN/mm2 of active force per muscle cross-sectional area. At the peak of contraction, cells were subjected to sudden changes in force (dF = 0.10-0.90 Fmax) and then maintained at the new force level. The force change resulted in a length response in which the cell length (Lcell) rapidly decreased during the force step and then decreased monotonically with a time constant between 75 and 600 ms. The initial length change that coincided with the force step was analyzed and an active cellular compliance of 1.9% cell length was estimated. The maintained force and resultant shortening velocity (V) were fitted to the Hill hyperbola with constants a/Fmax of 0.268 and b of 0.163 Lcell/s. Vmax was also determined by a procedure in which the cell length was slackened and the time of unloaded shortening was recorded (slack test). From the slack test, Vmax was estimated as 0.583 Lcell/s, in agreement with the F:V data. The F:V data were analyzed within the framework of the Huxley model (Huxley. 1957. Progress in Biophysics and Biophysical Chemistry. 7:255-318) for contraction and interpreted to indicate that in smooth muscle, as compared with fast striated muscle, there may exist a greater percentage of attached force-generating cross-bridges.

scholarly journals The latch-bridge hypothesis of smooth muscle contraction

2005 ◽  
Vol 83 (10) ◽  
pp. 857-864 ◽  
Author(s):  
Richard A Murphy ◽  
Christopher M Rembold
Keyword(s):  
Smooth Muscle ◽  
Light Chain ◽  
Myosin Light Chain ◽  
Striated Muscle ◽  
Smooth Muscle Contraction ◽  
Myosin Light Chain Phosphatase ◽  
Shortening Velocity ◽  
General Applicability ◽  
Cross Bridge ◽  
Mechanical Transduction

In contrast to striated muscle, both normalized force and shortening velocities are regulated functions of cross-bridge phosphorylation in smooth muscle. Physiologically this is manifested as relatively fast rates of contraction associated with transiently high levels of cross-bridge phosphorylation. In sustained contractions, Ca2+, cross-bridge phosphorylation, and ATP consumption rates fall, a phenomenon termed "latch". This review focuses on the Hai and Murphy (1988a) model that predicted the highly non-linear dependence of force on phosphorylation and a directly proportional dependence of shortening velocity on phosphorylation. This model hypothesized that (i) cross-bridge phosphorylation was obligatory for cross-bridge attachment, but also that (ii) dephosphorylation of an attached cross-bridge reduced its detachment rate. The resulting variety of cross-bridge cycles as predicted by the model could explain the observed dependencies of force and velocity on cross-bridge phosphorylation. New evidence supports modifications for more general applicability. First, myosin light chain phosphatase activity is regulated. Activation of myosin phosphatase is best demonstrated with inhibitory regulatory mechanisms acting via nitric oxide. The second modification of the model incorporates cooperativity in cross-bridge attachment to predict improved data on the dependence of force on phosphorylation. The molecular basis for cooperativity is unknown, but may involve thin filament proteins absent in striated muscle.Key words: chemo-mechanical transduction, activation-contraction coupling, cross-bridge, myosin light chain kinase, myosin light chain phosphatase, phosphorylation, cooperativity.

Force Maintenance with Reduced Ability to Shorten Actively in Barnacle Striated Muscle

1990 ◽  
Vol 148 (1) ◽  
pp. 281-291
Author(s):  
H. IWAMOTO ◽  
A. MURAOKA ◽  
A. GOTO ◽  
H. SUGI
Keyword(s):  
Electrical Stimulation ◽  
Mechanical Response ◽  
Striated Muscle ◽  
Isometric Force ◽  
Shortening Velocity ◽  
Cycling Rate ◽  
Quick Release ◽  
Mechanical Responses ◽  
Cross Bridge ◽  
Force Maintenance

1. Fibres from adductor scutorum muscle of a barnacle Tetraclita squamosa were made to contract isometrically by electrical stimulation, and the change in the ability to shorten actively during the mechanical responses was examined by suddenly allowing the fibres to shorten under a very small load (<3 % of the force immediately before shortening) at various times after the onset of stimulation. 2. The shortening velocity (Vsl) was nearly constant during stimulation. After the cessation of stimulation, shortening velocity decreased steeply while isometric force decayed slowly, indicating that isometric force was maintained with reduced ability to shorten actively. 3. Similar results were obtained when the maximum rate of force redevelopment following a quick release was measured at various times during the mechanical response to electrical stimulation. 4. In these fibres, but not in fibres from frog skeletal muscle, a quick restretch following a quick release could restore the force to a level similar to that observed without a quick release. These results, together with those above, indicated a reduced cross-bridge cycling rate during the relaxation phase of mechanical responses of barnacle fibres to electrical stimulation. 5. During electrical stimulation, Vsl showed less dependence on [Ca2+]o than was shown by isometric force. 6. These results are discussed in connection with the mechanism of force maintenance with reduced cross-bridge cycling rate.

scholarly journals The Huxley crossbridge model as the basic mechanism for airway smooth muscle contraction

2019 ◽  
Vol 317 (2) ◽  
pp. L235-L246 ◽  
Author(s):  
Ling Luo ◽  
Lu Wang ◽  
Peter D. Paré ◽  
Chun Y. Seow ◽  
Pasquale Chitano
Keyword(s):  
Smooth Muscle ◽  
Muscle Contraction ◽  
Airway Smooth Muscle ◽  
Time Course ◽  
Striated Muscle ◽  
Isometric Force ◽  
Smooth Muscle Contraction ◽  
Time Dependent ◽  
Shortening Velocity ◽  
Mlc20 Phosphorylation

The cyclic interaction between myosin crossbridges and actin filaments underlies smooth muscle contraction. Phosphorylation of the 20-kDa myosin light chain (MLC20) is a crucial step in activating the crossbridge cycle. Our current understanding of smooth muscle contraction is based on observed correlations among MLC20 phosphorylation, maximal shortening velocity ( Vmax), and isometric force over the time course of contraction. However, during contraction there are changes in the extent of phosphorylation of many additional proteins as well as changes in activation of enzymes associated with the signaling pathways. As a consequence, the mechanical manifestation of muscle contraction is likely to change with time. To simplify the study of these relationships, we measured the mechanical properties of airway smooth muscle at different levels of MLC20 phosphorylation at a fixed time during contraction. A simple correlation emerged when time-dependent variables were fixed. MLC20 phosphorylation was found to be directly and linearly correlated with the active stress, stiffness, and power of the muscle; the observed weak dependence of Vmax on MLC20 phosphorylation could be explained by the presence of an internal load in the muscle preparation. These results can be entirely explained by the Huxley crossbridge model. We conclude that when the influence of time-dependent events during contraction is held constant, the basic crossbridge mechanism in smooth muscle is the same as that in striated muscle.

scholarly journals The ATPase cycle of Human Muscle Myosin II Isoforms: Adaptation of a single mechanochemical cycle for different physiological roles

2019 ◽  
Author(s):  
Chloe A. Johnson ◽  
Jonathan Walklate ◽  
Marina Svicevic ◽  
Srboljub M. Mijailovich ◽  
Carlos Vera ◽  
...  
Keyword(s):  
Muscle Fiber ◽  
Striated Muscle ◽  
Fiber Type ◽  
Duty Ratio ◽  
Muscle Fiber Types ◽  
Fiber Types ◽  
Myosin Isoforms ◽  
Shortening Velocity ◽  
Load Dependence ◽  
Cross Bridge

AbstractStriated muscle myosins are encoded by a large gene family in all mammals, including human. These isoforms define several of the key characteristics of the different striated muscle fiber types including maximum shortening velocity. We have previously used recombinant isoforms of the motor domains of eight different human myosin isoforms to define the actin.myosin cross-bridge cycle in solution. Here, we use a recently developed modeling approach MUSICO to explore how well the experimentally defined cross-bridge cycles for each isoform in solution can predict the characteristics of muscle fiber contraction including duty ratio, shortening velocity, ATP economy and the load dependence of these parameters. The work shows that the parameters of the cross-bridge cycle predict many of the major characteristics of each muscle fiber type and raises the question of what sequence changes are responsible for these characteristics.

scholarly journals Myosin Crossbridge, Contractile Unit, and the Mechanism of Contraction in Airway Smooth Muscle: A Mechanical Engineer's Perspective

2019 ◽  
Vol 2 (1) ◽  
Author(s):  
Chun Y. Seow
Keyword(s):  
Smooth Muscle ◽  
Muscle Contraction ◽  
Airway Smooth Muscle ◽  
Actin Filaments ◽  
Striated Muscle ◽  
Structural Data ◽  
Smooth Muscle Contraction ◽  
Shortening Velocity ◽  
Mathematical Analyses ◽  
Myosin Motors

Muscle contraction is caused by the action of myosin motors within the structural confines of contractile unit arrays. When the force generated by cyclic interactions between myosin crossbridges and actin filaments is greater than the average load shared by the crossbridges, sliding of the actin filaments occurs and the muscle shortens. The shortening velocity as a function of muscle load can be described mathematically by a hyperbola; this characteristic force–velocity relationship stems from stochastic interactions between the crossbridges and the actin filaments. Beyond the actomyosin interaction, there is not yet a unified theory explaining smooth muscle contraction, mainly because the structure of the contractile unit in smooth muscle (akin to the sarcomere in striated muscle) is still undefined. In this review, functional and structural data from airway smooth muscle are analyzed in an engineering approach of quantification and correlation to support a model of the contractile unit with characteristics revealed by mathematical analyses and behavior matched by experimental observation.

scholarly journals The Superfast Human Extraocular Myosin Is Kinetically Distinct from the Fast Skeletal IIa, IIb, and IId Isoforms

2013 ◽  
Vol 288 (38) ◽  
pp. 27469-27479 ◽  
Author(s):  
Marieke J. Bloemink ◽  
John C. Deacon ◽  
Daniel I. Resnicow ◽  
Leslie A. Leinwand ◽  
Michael A. Geeves
Keyword(s):  
Extraocular Muscle ◽  
Striated Muscle ◽  
Actin Binding ◽  
Myosin Isoforms ◽  
Shortening Velocity ◽  
Healthy Human ◽  
Sequence Comparisons ◽  
Human Muscles ◽  
The Individual ◽  
Actin Binding Site

Humans express five distinct myosin isoforms in the sarcomeres of adult striated muscle (fast IIa, IId, the slow/cardiac isoform I/β, the cardiac specific isoform α, and the specialized extraocular muscle isoform). An additional isoform, IIb, is present in the genome but is not normally expressed in healthy human muscles. Muscle fibers expressing each isoform have distinct characteristics including shortening velocity. Defining the properties of the isoforms in detail has been limited by the availability of pure samples of the individual proteins. Here we study purified recombinant human myosin motor domains expressed in mouse C2C12 muscle cells. The results of kinetic analysis show that among the closely related adult skeletal isoforms, the affinity of ADP for actin·myosin (KAD) is the characteristic that most readily distinguishes the isoforms. The three fast muscle myosins have KAD values of 118, 80, and 55 μm for IId, IIa, and IIb, respectively, which follows the speed in motility assays from fastest to slowest. Extraocular muscle is unusually fast with a far weaker KAD = 352 μm. Sequence comparisons and homology modeling of the structures identify a few key areas of sequence that may define the differences between the isoforms, including a region of the upper 50-kDa domain important in signaling between the nucleotide pocket and the actin-binding site.

Inorganic phosphate speeds loaded shortening in rat skinned cardiac myocytes

2004 ◽  
Vol 287 (2) ◽  
pp. C500-C507 ◽  
Author(s):  
Aaron C. Hinken ◽  
Kerry S. McDonald
Keyword(s):  
Cardiac Myocytes ◽  
Power Output ◽  
Inorganic Phosphate ◽  
Striated Muscle ◽  
Isometric Force ◽  
Force Transducer ◽  
Shortening Velocity ◽  
Cross Bridge ◽  
Force Peak ◽  
The Cross

Force generation in striated muscle is coupled with inorganic phosphate (Pi) release from myosin, because force falls with increasing Pi concentration ([Pi]). However, it is unclear which steps in the cross-bridge cycle limit loaded shortening and power output. We examined the role of Pi in determining force, unloaded and loaded shortening, power output, and rate of force development in rat skinned cardiac myocytes to discern which step in the cross-bridge cycle limits loaded shortening. Myocytes ( n = 6) were attached between a force transducer and position motor, and contractile properties were measured over a range of loads during maximal Ca2+ activation. Addition of 5 mM Pi had no effect on maximal unloaded shortening velocity ( Vo) (control 1.83 ± 0.75, 5 mM added Pi 1.75 ± 0.58 muscle lengths/s; n = 6). Conversely, addition of 2.5, 5, and 10 mM Pi progressively decreased force but resulted in faster loaded shortening and greater power output (when normalized for the decrease in force) at all loads greater than ∼10% isometric force. Peak normalized power output increased 16% with 2.5 mM added Pi and further increased to a plateau of ∼35% with 5 and 10 mM added Pi. Interestingly, the rate constant of force redevelopment ( ktr) progressively increased from 0 to 10 mM added Pi, with ktr ∼360% greater at 10 mM than at 0 mM added Pi. Overall, these results suggest that the Pi release step in the cross-bridge cycle is rate limiting for determining shortening velocity and power output at intermediate and high relative loads in cardiac myocytes.

Blebbistatin specifically inhibits actin-myosin interaction in mouse cardiac muscle

2007 ◽  
Vol 293 (3) ◽  
pp. C1148-C1153 ◽  
Author(s):  
Ying Dou ◽  
Per Arlock ◽  
Anders Arner
Keyword(s):  
Cardiac Muscle ◽  
Cardiac Tissue ◽  
Striated Muscle ◽  
Cardiac Myosin ◽  
Shortening Velocity ◽  
Isolated Cardiomyocytes ◽  
Cardiac Contractile ◽  
Contractile System ◽  
Myosin Interaction ◽  
Micromolar Range

Blebbistatin is a powerful inhibitor of actin-myosin interaction in isolated contractile proteins. To examine whether blebbistatin acts in a similar manner in the organized contractile system of striated muscle, the effects of blebbistatin on contraction of cardiac tissue from mouse were studied. The contraction of paced intact papillary muscle preparations and shortening of isolated cardiomyocytes were inhibited by blebbistatin with inhibitory constants in the micromolar range (1.3–2.8 μM). The inhibition constants are similar to those previously reported for isolated cardiac myosin subfragments showing that blebbistatin action is similar in filamentous myosin of the cardiac contractile apparatus and isolated proteins. The inhibition was not associated with alterations in action potential duration or decreased influx through L-type Ca2+ channels. Experiments on permeabilized cardiac muscle preparations showed that the inhibition was not due to alterations in Ca2+ sensitivity of the contractile filaments. The maximal shortening velocity was not affected by 1 μM blebbistatin. In conclusion, we show that blebbistatin is an inhibitor of the actin-myosin interaction in the organized contractile system of cardiac muscle and that its action is not due to effects on the Ca2+ influx and activation systems.

Myosin essential light chain in health and disease

2007 ◽  
Vol 292 (4) ◽  
pp. H1643-H1654 ◽  
Author(s):  
Olga M. Hernandez ◽  
Michelle Jones ◽  
Georgianna Guzman ◽  
Danuta Szczesna-Cordary
Keyword(s):  
Light Chain ◽  
Striated Muscle ◽  
Transgenic Animal ◽  
Familial Hypertrophic Cardiomyopathy ◽  
Fine Tuning ◽  
Phenotypic Characterization ◽  
Dependent Manner ◽  
Shortening Velocity ◽  
Essential Light Chain ◽  
Almost All

The essential light chain of myosin (ELC) is known to be important for structural stability of the α-helical lever arm domain of the myosin head, but its function in striated muscle contraction is poorly understood. Two ELC isoforms are expressed in fast skeletal muscle, a long isoform and its NH2-terminal ∼40 amino acid shorter counterpart, whereas only the long ELC is observed in the heart. Biochemical and structural studies revealed that the NH2-terminus of the long ELC can make direct contacts with actin, but the effects of the ELC on the affinity of myosin for actin, ATPase, force, and the kinetics of force generating myosin cross-bridges are inconclusive. Myosin containing the long ELC has been shown to have slower cross-bridge kinetics than myosin with the short isoform. A difference was also reported among myosins with long isoforms. Increased shortening velocity was observed in atrial compared with ventricular muscle fibers. The common findings suggest that ELC provides the fine tuning of the myosin motor function, which is regulated in an isoform and tissue-dependent manner. The functional importance of the ELC is further implicated by the discovery of ELC mutations associated with Familial Hypertrophic Cardiomyopathy. The pathological phenotypes vary in severity, but more notably, almost all ELC mutations result in sudden cardiac death at a young age. This review summarizes the functional roles of striated muscle ELC in normal healthy muscle and in disease. Transgenic animal models and phenotypic characterization of ELC-mediated remodeling of the heart are also discussed.

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