The heat of shortening and the dynamic constants of muscle
10 Oct 1938-Proceedings of The Royal Society B: Biological Sciences (The Royal Society)-Vol. 126, Iss: 843, pp 136-195
TL;DR: In this article, a more accurate and rapid technique for muscle heat measurement was proposed, and some astonishingly simple and accurate relations have been found, which determine the effect of load on speed of shortening, allow the form of the isometric contraction to be predicted, and are the basis of the so-called "visco-elasticity" of skeletal muscle.
Abstract: The hope was recently expressed (Hill 1937, p. 116) that with the development of a more accurate and rapid technique for muscle heat measurement, a much more consistent picture might emerge of the energy relations of muscles shortening (or lengthening) and doing positive (or negative) work. This hope has been realized, and some astonishingly simple and accurate relations have been found, relations, moreover, which (among other things) determine the effect of load on speed of shortening, allow the form of the isometric contraction to be predicted, and are the basis of the so-called “visco-elasticity” of skeletal muscle. This paper is divided into three parts. In Part I further developments of the technique are described: everything has depended on the technique, so no apology is needed for a rather full description of it and of the precautions necessary. In Part II the results themselves are described and discussed. In Part III the “visco-elastic” properties of active muscle are shown to be a consequence of the properties described in Part II.
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TL;DR: In this article, the basic building blocks are described, starting with the 20 amino acids and proceeding to polypeptides, polysaccharides, and polyprotein-saccharide.
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TL;DR: A role for the ATPase activity of myosin in determining the speed of muscle contraction is suggested and the F-actin-binding ability of myOSin from various muscles was rather constant.
Abstract: Myosin was isolated from 14 different muscles (mammals, lower vertebrates, and invertebrates) of known maximal speed of shortening. These myosin preparations were homogeneous in the analytical ultracentrifuge or, in a few cases, showed, in addition to the main myosin peak, part of the myosin in aggregated form. Actin- and Ca++-activated ATPase activities of the myosins were generally proportional to the speed of shortening of their respective muscles; i.e. the greater the intrinsic speed, the higher the ATPase activity. This relation was found when the speed of shortening ranged from 0.1 to 24 muscle lengths/sec. The temperature coefficient of the Ca++-activated myosin ATPase was the same as that of the speed of shortening, Q10 about 2. Higher Q10 values were found for the actin-activated myosin ATPase, especially below 10°C. By using myofibrils instead of reconstituted actomyosin, Q10 values close to 2 could be obtained for the Mg++-activated myofibrillar ATPase at ionic strength of 0.014. In another series of experiments, myosin was isolated from 11 different muscles of known isometric twitch contraction time. The ATPase activity of these myosins was inversely proportional to the contraction time of the muscles. These results suggest a role for the ATPase activity of myosin in determining the speed of muscle contraction. In contrast to the ATPase activity of myosin, which varied according to the speed of contraction, the F-actin-binding ability of myosin from various muscles was rather constant.
1,944 citations
TL;DR: Ca(2+) regulation of contraction in vertebrate striated muscle is exerted primarily through effects on the thin filament, which regulate strong cross-bridge binding to actin, and the physiological observations of steady-state and transient mechanical behavior are supported.
Abstract: Ca(2+) regulation of contraction in vertebrate striated muscle is exerted primarily through effects on the thin filament, which regulate strong cross-bridge binding to actin. Structural and biochemical studies suggest that the position of tropomyosin (Tm) and troponin (Tn) on the thin filament determines the interaction of myosin with the binding sites on actin. These binding sites can be characterized as blocked (unable to bind to cross bridges), closed (able to weakly bind cross bridges), or open (able to bind cross bridges so that they subsequently isomerize to become strongly bound and release ATP hydrolysis products). Flexibility of the Tm may allow variability in actin (A) affinity for myosin along the thin filament other than through a single 7 actin:1 tropomyosin:1 troponin (A(7)TmTn) regulatory unit. Tm position on the actin filament is regulated by the occupancy of NH-terminal Ca(2+) binding sites on TnC, conformational changes resulting from Ca(2+) binding, and changes in the interactions among Tn, Tm, and actin and as well as by strong S1 binding to actin. Ca(2+) binding to TnC enhances TnC-TnI interaction, weakens TnI attachment to its binding sites on 1-2 actins of the regulatory unit, increases Tm movement over the actin surface, and exposes myosin-binding sites on actin previously blocked by Tm. Adjacent Tm are coupled in their overlap regions where Tm movement is also controlled by interactions with TnT. TnT also interacts with TnC-TnI in a Ca(2+)-dependent manner. All these interactions may vary with the different protein isoforms. The movement of Tm over the actin surface increases the "open" probability of myosin binding sites on actins so that some are in the open configuration available for myosin binding and cross-bridge isomerization to strong binding, force-producing states. In skeletal muscle, strong binding of cycling cross bridges promotes additional Tm movement. This movement effectively stabilizes Tm in the open position and allows cooperative activation of additional actins in that and possibly neighboring A(7)TmTn regulatory units. The structural and biochemical findings support the physiological observations of steady-state and transient mechanical behavior. Physiological studies suggest the following. 1) Ca(2+) binding to Tn/Tm exposes sites on actin to which myosin can bind. 2) Ca(2+) regulates the strong binding of M.ADP.P(i) to actin, which precedes the production of force (and/or shortening) and release of hydrolysis products. 3) The initial rate of force development depends mostly on the extent of Ca(2+) activation of the thin filament and myosin kinetic properties but depends little on the initial force level. 4) A small number of strongly attached cross bridges within an A(7)TmTn regulatory unit can activate the actins in one unit and perhaps those in neighboring units. This results in additional myosin binding and isomerization to strongly bound states and force production. 5) The rates of the product release steps per se (as indicated by the unloaded shortening velocity) early in shortening are largely independent of the extent of thin filament activation ([Ca(2+)]) beyond a given baseline level. However, with a greater extent of shortening, the rates depend on the activation level. 6) The cooperativity between neighboring regulatory units contributes to the activation by strong cross bridges of steady-state force but does not affect the rate of force development. 7) Strongly attached, cycling cross bridges can delay relaxation in skeletal muscle in a cooperative manner. 8) Strongly attached and cycling cross bridges can enhance Ca(2+) binding to cardiac TnC, but influence skeletal TnC to a lesser extent. 9) Different Tn subunit isoforms can modulate the cross-bridge detachment rate as shown by studies with mutant regulatory proteins in myotubes and in in vitro motility assays. (ABSTRACT TRUNCATED)
1,637 citations
01 Feb 1996
TL;DR: Mechanical testing the modeling results for the McKibben artificial muscle pneumatic actuator, which contains an expanding tube surrounded by braided cords, and a linearized model of these properties for three different models is derived.
Abstract: This paper reports mechanical testing the modeling results for the McKibben artificial muscle pneumatic actuator. This device contains an expanding tube surrounded by braided cords. We report static and dynamic length-tension testing results and derive a linearized model of these properties for three different models. The results are briefly compared with human muscle properties to evaluate the suitability of McKibben actuators for human muscle emulation in biologically based robot arms.
1,410 citations
Cites background from "The heat of shortening and the dyna..."
...Human skeletal muscle also has its own particular characteristics: for example, the convex shape active tension-length relationship (Gordon et al. 1966), the non-linear passive tension-length relationship, and the hyperbolic tension-velocity relationship (Hill 1938)....
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...On the other hand, the hyperbolic tension-velocity curve of biological muscles indicates the viscosity decreases when the velocity increases (Hill 1938), and there is no Coulomb friction reported....
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...1966), the non-linear passive tension-length relationship, and the hyperbolic tension-velocity relationship ( Hill 1938 )....
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...viscosity decreases when the velocity increases ( Hill 1938 ), and there is no Coulomb friction...
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TL;DR: The equilibrium control hypothesis (λ model) is considered with special reference to the length-force invariant characteristic of the muscle together with central and reflex systems subserving its activity.
Abstract: The equilibrium control hypothesis (λ model) is considered with special reference to the following concepts: (a) the length-force invariant characteristic (IC) of the muscle together with central and reflex systems subserving its activity; (b) the tonic stretch reflex threshold (λ) as an independent measure of central commands descending to alpha and gamma motoneurons; (c) the equilibrium point, defined in terms of λ, IC and static load characteristics, which is associated with the notion that posture and movement are controlled by a single mechanism; and (d) the muscle activation area (a reformulation of the “size principle”)— the area of kinematic and command variables in which a rank-ordered recruitment of motor units takes place. The model is used for the interpretation of various motor phenomena, particularly electromyographic patterns. The stretch reflex in the λ model has no mechanism to follow-up a certain muscle length prescribed by central commands. Rather, its task is to bring the system to an ...
1,287 citations
References
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TL;DR: The behaviour under sudden stress, or under sudden extension, of all visco-elastic substances (rubber, gelatin jellies, etc.) suggests a system partly damped, partly undamped.
Abstract: IN a perfectly elastic body, to each length should correspond a certain tension, and to each tension a certain length. When a given change in length, or tension, is applied the body should immediately take the corresponding tension or length. Many elastic substances, however, behave differently, e.g. rubber. When extended by a sudden increase in tension they show at first an instantaneous extension followed by a slow further extension(5, 6, 7). Under a sudden increase in length the tension shows a large instantaneous increase, followed by a slow decrease; when suddenly released the reverse occurs. The mechanical work absorbed by a sudden extension is greater than that liberated by a sudden shortening(8, 9, 10). This phenomenon called visco-elasticity, or elastic hysteresis (elastische Nachwirkung), can be observed in nearly all substances. Crystals alone show no appreciable elastic hysteresis, all other substances show it more or less. That a muscle in the excited state shows a series of properties corresponding to those of a visco-elastic system has been shown by Gasser and Hill(l). The behaviour under sudden stress, or under sudden extension, of all visco-elastic substances (rubber, gelatin jellies, etc.) suggests a system partly damped, partly undamped. A precise dynamical model behaving in the same way is, for instance, a spring carrying at some point in its length a disc which can move vertically in a cylindrical vessel without touching the sides (Fig. 1). One end of the spring is anchored to the bottom of the vessel, and a load, or an extension, can be applied vertically to the other. The vessel is filled with viscous fluid. The visco-elastic properties of muscle suggest the same model. Levin and Wyman(2), investigating the tensionlength curve of the excited muscle for stretches and releases at different
27 citations
TL;DR: The great improvement in myothermic technique achieved in recent years suggested a re-investigation of the problem, and this is described below, where the coefficient of linear expansion of muscle is negative when its initial extension is less than 35 p.c. of its unloaded length and with greater initial extension the coefficient becomes positive.
Abstract: THE thermo-elastic properties of muscle have been sti*lied by various workers since the first attempt by Heidenhain [1863] and by Meyerstein and Thiry [1863]. Some have measured the thermal effects of stretch and release, others the actual change of length with alteration of temperature. Considerable disagreement, however, exists among both groups of investigators (see Wohlisch and Clamann [1931] for a brief review). Hill and Hartree [1920] with the best myothermic technique then available obtained a negative thermal coefficient of linear expansion for muscle, whether living or dead. The great improvement in myothermic technique achieved in recent years suggested a re-investigation of the problem, and this is described below. During the course of it, a paper by Wohlisch and Clamann appeared [1931] who, with the former's optical linear dilatometer, measured the variation with temperature of the length of a muscle. Their most important conclusions are: (a) the coefficient of linear expansion of muscle is negative when its initial extension is less thani 35 p.c. of its unloaded length, and (b) with greater initial extension the coefficient becomes positive. Dead muscle always gave a positive coefficient. These conclusions are only in partial agreement with those of Hill and Hartree and made a repetition of their work the more necessary.
27 citations
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