scholarly journals Cross-Bridge Cycling Kinetics in Intact Multicellular Cardiac Muscle at Physiological Temperature: Impact of Muscle Length

2012 ◽  
Vol 102 (3) ◽  
pp. 351a
Author(s):  
Nima Milani-Nejad ◽  
Ying Xu ◽  
Jonathan P. Davis ◽  
Paul M.L. Janssen
Keyword(s):  
Cardiac Muscle ◽  
Muscle Length ◽  
Physiological Temperature ◽  
Cross Bridge ◽  
Temperature Impact

scholarly journals Effect of muscle length on cross-bridge kinetics in intact cardiac trabeculae at body temperature

2012 ◽  
Vol 141 (1) ◽  
pp. 133-139 ◽  
Author(s):  
Nima Milani-Nejad ◽  
Ying Xu ◽  
Jonathan P. Davis ◽  
Kenneth S. Campbell ◽  
Paul M.L. Janssen
Keyword(s):  
Body Temperature ◽  
Cardiac Muscle ◽  
Muscle Length ◽  
Ventricular Volume ◽  
Dynamic Force ◽  
Rabbit Muscle ◽  
Optimal Length ◽  
Rat Muscle ◽  
Cross Bridge ◽  
Cardiac Pumping

Dynamic force generation in cardiac muscle, which determines cardiac pumping activity, depends on both the number of sarcomeric cross-bridges and on their cycling kinetics. The Frank–Starling mechanism dictates that cardiac force development increases with increasing cardiac muscle length (corresponding to increased ventricular volume). It is, however, unclear to what extent this increase in cardiac muscle length affects the rate of cross-bridge cycling. Previous studies using permeabilized cardiac preparations, sub-physiological temperatures, or both have obtained conflicting results. Here, we developed a protocol that allowed us to reliably and reproducibly measure the rate of tension redevelopment (ktr; which depends on the rate of cross-bridge cycling) in intact trabeculae at body temperature. Using K+ contractures to induce a tonic level of force, we showed the ktr was slower in rabbit muscle (which contains predominantly β myosin) than in rat muscle (which contains predominantly α myosin). Analyses of ktr in rat muscle at optimal length (Lopt) and 90% of optimal length (L90) revealed that ktr was significantly slower at Lopt (27.7 ± 3.3 and 27.8 ± 3.0 s−1 in duplicate analyses) than at L90 (45.1 ± 7.6 and 47.5 ± 9.2 s−1). We therefore show that ktr can be measured in intact rat and rabbit cardiac trabeculae, and that the ktr decreases when muscles are stretched to their optimal length under near-physiological conditions, indicating that the Frank–Starling mechanism not only increases force but also affects cross-bridge cycling kinetics.

Morphological Basis of the Disparity Between Muscle Length and Sarcomere Length in the Myocardium

1973 ◽  
Vol 31 ◽  
pp. 422-423
Author(s):  
G.E. Adomian ◽  
L. Chuck ◽  
W.W. Pannley
Keyword(s):  
Cardiac Muscle ◽  
Sarcomere Length ◽  
Muscle Length ◽  
Contractile Force ◽  
Direct Function ◽  
Morphological Basis ◽  
Tension Curve

Sonnenblick, et al, have shown that sarcomeres change length as a function of cardiac muscle length along the ascending portion of the length-tension curve. This allows the contractile force to be expressed as a direct function of sarcomere length. Below L max, muscle length is directly related to sarcomere length at lengths greater than 85% of optimum. However, beyond the apex of the tension-length curve, i.e. L max, a disparity occurs between cardiac muscle length and sarcomere length. To account for this disproportionate increase in muscle length as sarcomere length remains relatively stable, the concept of fiber slippage was suggested as a plausible explanation. These observations have subsequently been extended to the intact ventricle.

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 Muscle Length is a Determinant of Cross-Bridge Cycling Rate in Intact Cardiac Trabeculae: Studies from Rodents to Humans

2013 ◽  
Vol 104 (2) ◽  
pp. 315a-316a
Author(s):  
Nima Milani-Nejad ◽  
Ying Xu ◽  
Jonathan P. Davis ◽  
Kenneth S. Campbell ◽  
George S. Billman ◽  
...  
Keyword(s):  
Muscle Length ◽  
Cycling Rate ◽  
Cross Bridge

scholarly journals The Frank-Starling mechanism involves deceleration of cross-bridge kinetics and is preserved in failing human right ventricular myocardium

2015 ◽  
Vol 309 (12) ◽  
pp. H2077-H2086 ◽  
Author(s):  
Nima Milani-Nejad ◽  
Benjamin D. Canan ◽  
Mohammad T. Elnakish ◽  
Jonathan P. Davis ◽  
Jae-Hoon Chung ◽  
...  
Keyword(s):  
Heart Failure ◽  
Right Ventricular ◽  
Muscle Length ◽  
Human Myocardium ◽  
Force Frequency ◽  
Heart Failure Patients ◽  
Cycling Rate ◽  
Physiological Conditions ◽  
Cross Bridge ◽  
The Right

Cross-bridge cycling rate is an important determinant of cardiac output, and its alteration can potentially contribute to reduced output in heart failure patients. Additionally, animal studies suggest that this rate can be regulated by muscle length. The purpose of this study was to investigate cross-bridge cycling rate and its regulation by muscle length under near-physiological conditions in intact right ventricular muscles of nonfailing and failing human hearts. We acquired freshly explanted nonfailing ( n = 9) and failing ( n = 10) human hearts. All experiments were performed on intact right ventricular cardiac trabeculae ( n = 40) at physiological temperature and near the normal heart rate range. The failing myocardium showed the typical heart failure phenotype: a negative force-frequency relationship and β-adrenergic desensitization ( P < 0.05), indicating the expected pathological myocardium in the right ventricles. We found that there exists a length-dependent regulation of cross-bridge cycling kinetics in human myocardium. Decreasing muscle length accelerated the rate of cross-bridge reattachment ( ktr) in both nonfailing and failing myocardium ( P < 0.05) equally; there were no major differences between nonfailing and failing myocardium at each respective length ( P > 0.05), indicating that this regulatory mechanism is preserved in heart failure. Length-dependent assessment of twitch kinetics mirrored these findings; normalized dF/d t slowed down with increasing length of the muscle and was virtually identical in diseased tissue. This study shows for the first time that muscle length regulates cross-bridge kinetics in human myocardium under near-physiological conditions and that those kinetics are preserved in the right ventricular tissues of heart failure patients.

The Frank-Starling mechanism is not mediated by changes in rate of cross-bridge detachment

1997 ◽  
Vol 273 (5) ◽  
pp. H2428-H2435 ◽  
Author(s):  
Thomas Wannenburg ◽  
Paul M. L. Janssen ◽  
Dongsheng Fan ◽  
Pieter P. De Tombe
Keyword(s):  
Cardiac Muscle ◽  
Maximum Rate ◽  
Sarcomere Length ◽  
Myosin Head ◽  
Isometric Force ◽  
Force Development ◽  
Cross Bridge ◽  
Average Slope ◽  
The Cross ◽  
Kinetics Of

We tested the hypothesis that the Frank-Starling relationship is mediated by changes in the rate of cross-bridge detachment in cardiac muscle. We simultaneously measured isometric force development and the rate of ATP consumption at various levels of Ca2+ activation in skinned rat cardiac trabecular muscles at three sarcomere lengths (2.0, 2.1, and 2.2 μm). The maximum rate of ATP consumption was 1.5 nmol ⋅ s−1 ⋅ μl fiber vol−1, which represents an estimated adenosinetriphosphatase (ATPase) rate of ∼10 s−1 per myosin head at 24°C. The rate of ATP consumption was tightly and linearly coupled to the level of isometric force development, and changes in sarcomere length had no effect on the slope of the force-ATPase relationships. The average slope of the force-ATPase relationships was 15.5 pmol ⋅ mN−1 ⋅ mm−1. These results suggest that the mechanisms that underlie the Frank-Starling relationship in cardiac muscle do not involve changes in the kinetics of the apparent detachment step in the cross-bridge cycle.

scholarly journals Osmotic Compression Influences Cross-Bridge Detachment Rate in Transgenic Hypertrophic Cardiomyopathy Variant Hctnt-I79N and Non-Transgenic Mouse Cardiac Muscle

2020 ◽  
Vol 118 (3) ◽  
pp. 596a
Author(s):  
Maicon Landim Vieira ◽  
Bjorn C. Knollmann ◽  
Hyun S. Hwang ◽  
Coen A. Ottenheijm ◽  
J. Renato D. Pinto ◽  
...  
Keyword(s):  
Hypertrophic Cardiomyopathy ◽  
Cardiac Muscle ◽  
Transgenic Mouse ◽  
Cross Bridge ◽  
Detachment Rate ◽  
Osmotic Compression

Regulation of energy consumption in cardiac muscle: analysis of isometric contractions

1999 ◽  
Vol 276 (3) ◽  
pp. H998-H1011 ◽  
Author(s):  
Amir Landesberg ◽  
Samuel Sideman
Keyword(s):  
Energy Consumption ◽  
Cardiac Muscle ◽  
Feedback Mechanism ◽  
Isometric Contractions ◽  
Cross Bridge ◽  
Time Integral ◽  
Length Relationship ◽  
Cross Bridges ◽  
Force Time ◽  
Force Time Integral

The well-known linear relationship between oxygen consumption and force-length area or the force-time integral is analyzed here for isometric contractions. The analysis, which is based on a biochemical model that couples calcium kinetics with cross-bridge cycling, indicates that the change in the number of force-generating cross bridges with the change in the sarcomere length depends on the force generated by the cross bridges. This positive-feedback phenomenon is consistent with our reported cooperativity mechanism, whereby the affinity of the troponin for calcium and, hence, cross-bridge recruitment depends on the number of force-generating cross bridges. Moreover, it is demonstrated that a model that does not include a feedback mechanism cannot describe the dependence of energy consumption on the loading conditions. The cooperativity mechanism, which has been shown to determine the force-length relationship and the related Frank-Starling law, is shown here to provide the basis for the regulation of energy consumption in the cardiac muscle.

Isotonic relaxation in cardiac muscle

1975 ◽  
Vol 229 (3) ◽  
pp. 646-651 ◽  
Author(s):  
JE Strobeck ◽  
AS Bahler ◽  
EH Sonnenblick
Keyword(s):  
Cardiac Muscle ◽  
Isometric Force ◽  
Muscle Length ◽  
Constant Load ◽  
Papillary Muscles ◽  
Initial Length ◽  
Total Load ◽  
Relaxation Velocity ◽  
Force Velocity ◽  
Maximum Isometric Force

The force-velocity-length determinants of isotonic relaxation were studied in 12 cat papillary muscles. Isotonic relaxation velocity (VL) was found to be a function of total load (preload + afterload), with peak VL increasing to a maximum at loads approximately .3 to .4 Po(L') (Po(L') defined as maximum isometric force developed during a twitch at the experimental length) and falling with increasing loads. Initial muscle length (ML) had no effect on the peak VL with constant load. Increasing the initial length at which isotonic relaxation occurred (LL) decreased peak VL but did not alter the unique length-velocity trajectory at constant load. This unique length-velocity trajectory occurred, despite a wide variation in time during the contraction when peak VL was measured. Increasing Ca++ from 2.5 to 7.5 mM increased peak VL (1.73 +/- .16 to 2.32 +/- .20 ML/s) and shifted the entire length-velocity trajectory toward higher velocities of lengthening. The addition of 10 mM caffeine increased peak VL also (1.67 +/- .18 to 2.54 +/- .20 ML/s) and had a similar effect on the length-velocity trajectory during lengthening as Ca++. Both increased Ca++ and caffeine (10 mM) augmented the maximum VL measured on addition of load.

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.

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