Effects of postnatal maturation on energetics and cross-bridge properties in rat diaphragm

2002 ◽  
Vol 92 (3) ◽  
pp. 1074-1082 ◽  
Author(s):  
Gilles Orliaguet ◽  
Olivier Langeron ◽  
Belaid Bouhemad ◽  
Pierre Coriat ◽  
Yves LeCarpentier ◽  
...  
Keyword(s):  
Mechanical Efficiency ◽  
Total Force ◽  
Rat Diaphragm ◽  
Shortening Velocity ◽  
Cross Sectional ◽  
Muscle Energetics ◽  
Postnatal Maturation ◽  
Cross Bridge ◽  
Velocity Relationship ◽  
Force Velocity

The effects of maturation on cross-bridge (CB) properties were studied in rat diaphragm strips obtained at postnatal days 3, 10, and 17 and in adults (10–12 wk old). Calculations of muscle energetics and characteristics of CBs were determined from standard Huxley equations. Maturation did not change the curvature of the force-velocity relationship or the peak of mechanical efficiency. There was a significant increase in the total number of CBs per cross-sectional area (m) with aging but not in single CB force. The turnover rate of myosin ATPase increased, the duration of the CB cycle decreased, and the velocity of CBs decreased significantly only after the first week postpartum. There was a linear relationship between maximum total force and m ( r = 0.969, P < 0.001), and between maximum unloaded shortening velocity and m ( r = 0.728, P < 0.001). When this study in the rat and previous study in the hamster are compared, it appears that there are few species differences in the postnatal maturation process of the diaphragm.

scholarly journals Power fatigue of the rat diaphragm muscle

2000 ◽  
Vol 89 (6) ◽  
pp. 2215-2219 ◽  
Author(s):  
Bill T. Ameredes ◽  
Wen-Zhi Zhan ◽  
Y. S. Prakash ◽  
Rene Vandenboom ◽  
Gary C. Sieck
Keyword(s):  
Diaphragm Muscle ◽  
Fiber Types ◽  
Rat Diaphragm ◽  
Shortening Velocity ◽  
Reduction In Force ◽  
Novel Technique ◽  
Velocity Relationship ◽  
Stimulus Train ◽  
Force Velocity

We hypothesized that decrements in maximum power output (W˙max) of the rat diaphragm (Dia) muscle with repetitive activation are due to a disproportionate reduction in force (force fatigue) compared with a slowing of shortening velocity (velocity fatigue). Segments of midcostal Dia muscle were mounted in vitro (26°C) and stimulated directly at 75 Hz in 400-ms-duration trains repeated each second (duty cycle = 0.4) for 120 s. A novel technique was used to monitor instantaneous reductions in maximum specific force (Po) andW˙max during fatigue. During each stimulus train, activation was isometric for the initial 360 ms during which Po was measured; the muscle was then allowed to shorten at a constant velocity (30% V max) for the final 40 ms, and W˙max was determined. Compared with initial values, after 120 s of repetitive activation, Po andW˙max decreased by 75 and 73%, respectively. Maximum shortening velocity was measured in two ways: by extrapolation of the force-velocity relationship ( V max) and using the slack test [maximum unloaded shortening velocity ( V o)]. After 120 s of repetitive activation, V max slowed by 44%, whereas V o slowed by 22%. Thus the decrease inW˙max with repetitive activation was dominated by force fatigue, with velocity fatigue playing a secondary role. On the basis of a greater slowing of V max vs. V o, we also conclude that force and power fatigue cannot be attributed simply to the total inactivation of the most fatigable fiber types.

Calculation of muscle maximal shortening velocity by extrapolation of the force–velocity relationship: afterloaded versus isotonic release contractions

2010 ◽  
Vol 88 (10) ◽  
pp. 937-948 ◽  
Author(s):  
Sharon R. Bullimore ◽  
Travis J. Saunders ◽  
Walter Herzog ◽  
Brian R. MacIntosh
Keyword(s):  
Shortening Velocity ◽  
Experimental Conditions ◽  
Activation Kinetics ◽  
Cross Bridge ◽  
Bridge Model ◽  
Velocity Relationship ◽  
Model Predictions ◽  
Force Velocity ◽  
Single Fibres ◽  
Lumbrical Muscles

The maximal shortening velocity of a muscle (Vmax) provides a link between its macroscopic properties and the underlying biochemical reactions and is altered in some diseases. Two methods that are widely used for determining Vmax are afterloaded and isotonic release contractions. To determine whether these two methods give equivalent results, we calculated Vmax in 9 intact single fibres from the lumbrical muscles of the frog Xenopus laevis (9.5–15.5 °C, stimulation frequency 35–70 Hz). The data were modelled using a 3-state cross-bridge model in which the states were inactive, detached, and attached. Afterloaded contractions gave lower predictions of Vmax than did isotonic release contractions in all 9 fibres (3.20 ± 0.84 versus 4.11 ± 1.08 lengths per second, respectively; means ± SD, p = 0.001) and underestimated unloaded shortening velocity measured with the slack test by an average of 29% (p = 0.001, n = 6). Excellent model predictions could be obtained by assuming that activation is inhibited by shortening. We conclude that under the experimental conditions used in this study, afterloaded and isotonic release contractions do not give equivalent results. When a change in the Vmax measured with afterloaded contractions is observed in diseased muscle, it is important to consider that this may reflect differences in either activation kinetics or cross-bridge cycling rates.

scholarly journals Effects of cross-bridge compliance on the force-velocity relationship and muscle power output

PLoS ONE ◽  
2017 ◽  
Vol 12 (12) ◽  
pp. e0190335 ◽  
Author(s):  
Axel J. Fenwick ◽  
Alexander M. Wood ◽  
Bertrand C. W. Tanner
Keyword(s):  
Power Output ◽  
Muscle Power ◽  
Cross Bridge ◽  
Velocity Relationship ◽  
Force Velocity ◽  
Muscle Power Output

Force-velocity relationship of expiratory muscles in normal subjects

1982 ◽  
Vol 52 (4) ◽  
pp. 930-938 ◽  
Author(s):  
Y. Kikuchi ◽  
H. Sasaki ◽  
K. Sekizawa ◽  
K. Aihara ◽  
T. Takishima
Keyword(s):  
Respiratory Muscles ◽  
Normal Subjects ◽  
Contractile Element ◽  
Shortening Velocity ◽  
Mean Values ◽  
Significant Difference ◽  
Velocity Relationship ◽  
Force Velocity ◽  
Expiratory Muscles ◽  
Relationship Of

We examined the force-velocity relationship of the respiratory muscles in normal subjects under nearly isotonic conditions, taking into consideration the pleural pressure (Ppl) changes during maximum forced expirations (MFE). We used an electromagnetic valve (EMV) to select the Ppl value at the onset of mouth flow; and both a pressure reservoir and a variable resistance to control the Ppl changes after the opening of the EMV during MFE. To simulate isotonic conditions and to obtain the shortening velocity of the contractile element (CE), we mathematically corrected the velocity of the series elastic component (SEC), using a modified version of Hill's equation. Although the maximum tension at total lung capacity (TLC) [1,156 +/- 215 (SD) g/cm] was larger than that at functional residual capacity (FRC) (782 +/- 97 g/cm) there was no significant difference in the maximum shortening velocity, 3.4 +/- 1.0 and 3.2 +/- 0.8 circumference/s at TLC and FRC, respectively. The mean values of k (slope) for the SEC at TLC and FRC were 19 +/- 4 and 18 +/- 5 circumference-1, respectively, and they were not significantly different. We concluded that the force-velocity relationship of the expiratory muscles exhibited the same mechanical properties as that of the other skeletal muscles.

Peak power output is maintained in rabbit psoas and rat soleus single muscle fibers when CTP replaces ATP

1998 ◽  
Vol 85 (1) ◽  
pp. 76-83 ◽  
Author(s):  
Philip A. Wahr ◽  
Joseph M. Metzger
Keyword(s):  
Muscle Contraction ◽  
Peak Power ◽  
Muscle Length ◽  
Peak Power Output ◽  
Fiber Types ◽  
Rabbit Psoas ◽  
Cross Bridge ◽  
Chemomechanical Coupling ◽  
Velocity Relationship ◽  
Force Velocity

The chemomechanical coupling mechanism in striated muscle contraction was examined by changing the nucleotide substrate from ATP to CTP. Maximum shortening velocity [extrapolation to zero force from force-velocity relation ( V max) and slope of slack test plots ( V 0)], maximum isometric force (Po), power, and the curvature of the force-velocity curve [ a/Po(dimensionless parameter inversely related to the curvature)] were determined during maximum Ca2+-activated isotonic contractions of fibers from fast rabbit psoas and slow rat soleus muscles by using 0.2 mM MgATP, 4 mM MgATP, 4 mM MgCTP, or 10 mM MgCTP as the nucleotide substrate. In addition to a decrease in the maximum Ca2+-activated force in both fiber types, a change from 4 mM ATP to 10 mM CTP resulted in a decrease in V max in psoas fibers from 3.26 to 1.87 muscle length/s. In soleus fibers, V max was reduced from 1.94 to 0.90 muscle length/s by this change in nucleotide. Surprisingly, peak power was unaffected in either fiber type by the change in nucleotide as the result of a three- to fourfold decrease in the curvature of the force-velocity relationship. The results are interpreted in terms of the Huxley model of muscle contraction as an increase in f 1and g 1 coupled to a decrease in g 2(where f 1 is the rate of cross-bridge attachment and g 1 and g 2 are rates of detachment) when CTP replaces ATP. This adequately accounts for the observed changes in Po, a/Po, and V max. However, the two-state Huxley model does not explicitly reveal the cross-bridge transitions that determine curvature of the force-velocity relationship. We hypothesize that a nucleotide-sensitive transition among strong-binding cross-bridge states following Pi release, but before the release of the nucleotide diphosphate, underlies the alterations in a/Poreported here.

Task-dependent control of the jaw during food splitting in humans

2014 ◽  
Vol 111 (12) ◽  
pp. 2614-2623 ◽  
Author(s):  
Anders S. Johansson ◽  
Karl-Gunnar Westberg ◽  
Benoni B. Edin
Keyword(s):  
Masseter Muscle ◽  
Task Demands ◽  
Shortening Velocity ◽  
Anteroposterior Axis ◽  
Food Items ◽  
Velocity Relationship ◽  
Closing Force ◽  
Force Velocity ◽  
Study Participants ◽  
Relationship Of

Although splitting of food items between the incisors often requires high bite forces, rarely do the teeth harmfully collide when the jaw quickly closes after split. Previous studies indicate that the force-velocity relationship of the jaw closing muscles principally explains the prompt dissipation of jaw closing force. Here, we asked whether people could regulate the dissipation of jaw closing force during food splitting. We hypothesized that such regulation might be implemented via differential recruitment of masseter muscle portions situated along the anteroposterior axis because these portions will experience a different shortening velocity during jaw closure. Study participants performed two different tasks when holding a peanut-half stacked on a chocolate piece between their incisors. In one task, they were asked to split the peanut-half only (single-split trials) and, in the other, to split both the peanut and the chocolate in one action (double-split trials). In double-split trials following the peanut split, the intensity of the tooth impact on the chocolate piece was on average 2.5 times greater than in single-split trials, indicating a substantially greater loss of jaw closing force in the single-split trials. We conclude that control of jaw closing force dissipation following food splitting depends on task demands. Consistent with our hypothesis, converging neurophysiological and morphometric data indicated that this control involved a differential activation of the jaw closing masseter muscle along the anteroposterior axis. These latter findings suggest that the regulation of jaw closing force after sudden unloading of the jaw exploits masseter muscle compartmentalization.

scholarly journals Mechanical model of muscle contraction. 6. Calculations of the tension exerted by a skeletal fiber during a shortening staircase

2019 ◽  
Author(s):  
Louvet S.
Keyword(s):  
Myosin Head ◽  
Myosin Ii ◽  
Velocity Curve ◽  
Shortening Velocity ◽  
Velocity Relationship ◽  
Length Step ◽  
Force Velocity ◽  
Uniform Law ◽  
Slope Line ◽  
Constant Slope

AbstractAccompanying Paper 1 tests a theoretical relationship between force and shortening velocity of a muscle fiber without justifying its validity. Paper 2 determines the kinematics and dynamics of a myosin II head during the working stroke (WS). Paper 3 imposes the Uniform law as a density representative of the orientation of the levers belonging to the WS heads. By support of these works, Papers 4 and 5 put into equation the evolution of the tension during the four phases of a length step. The present paper closes all six articles by imposing two tasks on itself. The first purpose is to apply the theoretical elements developed for a length step to a succession of identical length steps, otherwise known as shortening staircase. With the values of the geometric and temporal parameters assigned to a myosin head in Papers 1 to 5, a correct adjustment is established between the theoretical tension deduced from our model and the experimental tension published in 1997 by a team of Italian researchers relating to nine shortening staircases performed on the same fiber. In particular, we obtain the equation of the tension reached at the time end of the step (T*) which remains constant step by step as soon as the shortening of a half-sarcomere exceeds 17 nm. The second objective is to find and explain the equation of the Force-Velocity curve introduced ex abrupto into Paper 1: by decreasing the size and duration of the steps, the staircase tends towards a constant slope line corresponding to a continuous speed shortening. By applying the methods of infinitesimal calculus to the different formulations leading to T*, we deduce the Force-Velocity relationship (see Supplement S6.L). And the circle is complete.

scholarly journals The effects of inorganic phosphate on muscle force development and energetics: challenges in modelling related to experimental uncertainties

2019 ◽  
Author(s):  
Alf Månsson
Keyword(s):  
Inorganic Phosphate ◽  
Muscle Force ◽  
Isometric Force ◽  
Shortening Velocity ◽  
Apparent Contradiction ◽  
Sequence Of Events ◽  
Velocity Relationship ◽  
Force Velocity ◽  
Cross Bridges ◽  
Experimental Findings

Abstract Muscle force and power are developed by myosin cross-bridges, which cyclically attach to actin, undergo a force-generating transition and detach under turnover of ATP. The force-generating transition is intimately associated with release of inorganic phosphate (Pi) but the exact sequence of events in relation to the actual Pi release step is controversial. Details of this process are reflected in the relationships between [Pi] and the developed force and shortening velocity. In order to account for these relationships, models have proposed branched kinetic pathways or loose coupling between biochemical and force-generating transitions. A key hypothesis underlying the present study is that such complexities are not required to explain changes in the force–velocity relationship and ATP turnover rate with altered [Pi]. We therefore set out to test if models without branched kinetic paths and Pi-release occurring before the main force-generating transition can account for effects of varied [Pi] (0.1–25 mM). The models tested, one assuming either linear or non-linear cross-bridge elasticity, account well for critical aspects of muscle contraction at 0.5 mM Pi but their capacity to account for the maximum power output vary. We find that the models, within experimental uncertainties, account for the relationship between [Pi] and isometric force as well as between [Pi] and the velocity of shortening at low loads. However, in apparent contradiction with available experimental findings, the tested models produce an anomalous force–velocity relationship at elevated [Pi] and high loads with more than one possible velocity for a given load. Nevertheless, considering experimental uncertainties and effects of sarcomere non-uniformities, these discrepancies are insufficient to refute the tested models in favour of more complex alternatives.

Mechanical regulation of cardiac muscle by coupling calcium kinetics with cross-bridge cycling: a dynamic model

1994 ◽  
Vol 267 (2) ◽  
pp. H779-H795 ◽  
Author(s):  
A. Landesberg ◽  
S. Sideman
Keyword(s):  
Cardiac Muscle ◽  
Calcium Binding ◽  
Mechanical Activity ◽  
Free Calcium ◽  
Shortening Velocity ◽  
Cross Bridge ◽  
Mechanical Constraints ◽  
Force Velocity ◽  
Cross Bridges ◽  
Reported Data

This study describes the regulation of mechanical activity in the intact cardiac muscle, the effects of the free calcium transients and the mechanical constraints, and emphasizes the central role of the troponin complex in regulating muscle activity. A “loose coupling” between calcium binding to troponin and cross-bridge cycling is stipulated, allowing the existence of cross bridges in the strong conformation without having bound calcium on the neighboring troponin. The model includes two feedback mechanisms: 1) a positive feedback, or cooperativity, in which the cycling cross bridges affect the affinity of troponin for calcium, and 2) a negative mechanical feedback, where the filament-sliding velocity affects cross-bridge cycling. The model simulates the reported experimental force-length and force-velocity relationships at different levels of activation. The dependence of the shortening velocity on calcium concentration, sarcomere length, internal load, and rate of cross-bridge cycling is described analytically in agreement with reported data. Furthermore, the model provides an analytic solution for Hill's equation of the force-velocity relationship and for the phenomena of unloaded shortening velocity and force deficit. The model-calculated changes in free calcium in various mechanical conditions are in good agreement with the available experimental results.

Regulation of energy liberation during steady sarcomere shortening

2005 ◽  
Vol 289 (5) ◽  
pp. H2176-H2182 ◽  
Author(s):  
Oren Tchaicheeyan ◽  
Amir Landesberg
Keyword(s):  
Energy Liberation ◽  
Free Calcium ◽  
Relative Role ◽  
Shortening Velocity ◽  
Velocity Relationship ◽  
Intracellular Free Calcium Concentration ◽  
Free Calcium Concentration ◽  
Strong Transition ◽  
Force Velocity

Energy liberation rate ( Ė) during steady muscle shortening is a monotonic increasing or biphasic function of the shortening velocity ( V). The study examines three plausible hypotheses for explaining the biphasic Ė-V relationship (EVR): 1) the cross-bridge (XB) turnover rate from non-force-generating (weak) to force-generating (strong) conformation decreases as V increases; 2) XB kinetics is determined by the number of strong XBs (XB -XB cooperativity); and 3) the affinity of troponin for calcium is modulated by the number of strong XBs (XB -Ca cooperativity). The relative role of the various energy-regulating mechanisms is not well defined. The hypotheses were tested by coupling calcium kinetics with XB cycling. All three hypotheses yield identical steady-state characteristics: 1) hyperbolic force-velocity relationship; 2) quasi-linear stiffness-force relationship; and 3) biphasic EVR, where Ė declines at high V due to decrease in the number of cycling XBs or in the weak-to-strong transition rate. The hypotheses differ in the ability to describe the existence of both monotonic and biphasic EVRs and in the effect of intracellular free calcium concentration ([Ca2+]i) on the EVR peak. Monotonic and biphasic EVRs with a shift in EVR peak to higher velocity at higher [Ca2+]i are obtained only by XB -Ca cooperativity. XB -XB cooperativity provides only biphasic EVRs. A direct effect of V on XB kinetics predicts that EVR peak is obtained at the same velocity independently of [Ca2+]i. The study predicts that measuring the dependence of the EVR on [Ca2+]i allows us to test the hypotheses and to identify the dominant energy-regulating mechanism. The established XB -XB and XB -Ca mechanisms provide alternative explanations to the various reported EVRs.

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