Comparison of elementary steps of the cross-bridge cycle in rat papillary muscle fibers expressing α- and β-myosin heavy chain with sinusoidal analysis

2016 ◽  
Vol 37 (6) ◽  
pp. 203-214 ◽  
Author(s):  
Masataka Kawai ◽  
Tarek S. Karam ◽  
John Jeshurun Michael ◽  
Li Wang ◽  
Murali Chandra
Keyword(s):  
Myosin Heavy Chain ◽  
Heavy Chain ◽  
Papillary Muscle ◽  
Muscle Fibers ◽  
Sinusoidal Analysis ◽  
Elementary Steps ◽  
Cross Bridge ◽  
The Cross ◽  
Rat Papillary Muscle

scholarly journals Cross-Bridge Kinetics in Rat Papillary Muscle Fibers that Carry α-MHC and β-MHC by Sinusoidal Analysis

2016 ◽  
Vol 110 (3) ◽  
pp. 294a-295a
Author(s):  
Tarek S. Karam ◽  
John J. Michael ◽  
Chandra Murali ◽  
Masataka Kawai
Keyword(s):  
Papillary Muscle ◽  
Muscle Fibers ◽  
Sinusoidal Analysis ◽  
Cross Bridge ◽  
Rat Papillary Muscle

Inotropic agent EMD-53998 weakens nucleotide and phosphate binding to cross bridges in porcine myocardium

1996 ◽  
Vol 271 (4) ◽  
pp. H1394-H1406 ◽  
Author(s):  
Y. Zhao ◽  
M. Kawai
Keyword(s):  
Equilibrium Constant ◽  
Isometric Tension ◽  
Association Constants ◽  
Phosphate Binding ◽  
Sinusoidal Analysis ◽  
Elementary Steps ◽  
Cross Bridge ◽  
The Cross ◽  
Cross Bridges ◽  
Emd 53998

The effect of EMD-53998 (EMD) on elementary steps of the cross-bridge cycle in skinned porcine myocardium was studied to understand the positive inotropic mechanisms of EMD. The kinetic constants of the elementary steps were obtained by sinusoidal analysis and compared in the presence and absence of 50 microM EMD. In the presence of 50 microM EMD, the equilibrium constant of the cross-bridge detachment step decreases three times, and the equilibrium constant of the cross-bridge attachment (force generation) step increases two times. Our results further show that, in the presence of 50 microM EMD, the association constants of MgATP and MgADP decrease to one-ninth and one-third, respectively, and the association constant of phosphate decreases to one-third. These results indicate that EMD suppresses the nucleotide binding to cross bridges and increases cross-bridge resistance to phosphate accumulation in myocardium. These results predict that EMD decreases the number of detached cross bridges and increases the number of attached cross bridges. This prediction is consistent with the twofold increase of isometric tension with 50 microM EMD.

scholarly journals Cardiomyopathy-related mutation (A30V) in mouse cardiac troponin T divergently alters the magnitude of stretch activation in α- and β-myosin heavy chain fibers

2017 ◽  
Vol 312 (1) ◽  
pp. H141-H149 ◽  
Author(s):  
Alexis V. Mickelson ◽  
Sampath K. Gollapudi ◽  
Murali Chandra
Keyword(s):  
Myosin Heavy Chain ◽  
Heavy Chain ◽  
Cardiac Troponin ◽  
Troponin T ◽  
Muscle Fibers ◽  
Cardiac Troponin T ◽  
Cross Bridge ◽  
Maximal Tension ◽  
Contractile Parameters ◽  
Functional Consequences

The present study investigated the functional consequences of the human hypertrophic cardiomyopathy (HCM) mutation A28V in cardiac troponin T (TnT). The A28V mutation is located within the NH2 terminus of TnT, a region known to be important for full activation of cardiac thin filaments. The functional consequences of the A28V mutation in TnT remain unknown. Given how α- and β-myosin heavy chain (MHC) isoforms differently alter the functional effect of the NH2 terminus of TnT, we hypothesized that the A28V-induced effects would be differently modulated by α- and β-MHC isoforms. Recombinant wild-type mouse TnT (TnTWT) and the mouse equivalent of the human A28V mutation (TnTA30V) were reconstituted into detergent-skinned cardiac muscle fibers extracted from normal (α-MHC) and transgenic (β-MHC) mice. Dynamic and steady-state contractile parameters were measured in reconstituted muscle fibers. Step-like length perturbation experiments demonstrated that TnTA30V decreased the magnitude of the muscle length-mediated recruitment of new force-bearing cross bridges ( ER) by 30% in α-MHC fibers. In sharp contrast, TnTA30V increased ER by 55% in β-MHC fibers. Inferences drawn from other dynamic contractile parameters suggest that directional changes in ER in TnTA30V + α-MHC and TnTA30V + β-MHC fibers result from a divergent impact on cross bridge-regulatory unit (troponin-tropomyosin complex) cooperativity. TnTA30V-mediated effects on Ca2+-activated maximal tension and instantaneous muscle fiber stiffness ( ED) were also divergently affected by α- and β-MHC. Our study demonstrates that TnTA30V + α-MHC and TnTA30V + β-MHC fibers show contrasting contractile phenotypes; however, only the observations from β-MHC fibers are consistent with the clinical data for A28V in humans. NEW & NOTEWORTHY The differential impact of α- and β-myosin heavy chain (MHC) on contractile dynamics causes a mutant cardiac troponin T (TnTA30V) to differently modulate cardiac contractile function. TnTA30V attenuated Ca2+-activated maximal tension and length-mediated cross-bridge recruitment against α-MHC but augmented these parameters against β-MHC, suggesting divergent contractile phenotypes.

Distribution of myosin heavy chain isoforms in non-weight-bearing rat soleus muscle fibers

1996 ◽  
Vol 81 (6) ◽  
pp. 2540-2546 ◽  
Author(s):  
Robert J. Talmadge ◽  
Roland R. Roy ◽  
V. Reggie Edgerton
Keyword(s):  
Myosin Heavy Chain ◽  
Soleus Muscle ◽  
Heavy Chain ◽  
De Novo ◽  
Weight Bearing ◽  
Muscle Fibers ◽  
Myosin Heavy Chain Isoforms ◽  
Hindlimb Suspension ◽  
Type I ◽  
Rat Soleus Muscle

Talmadge, Robert J., Roland R. Roy, and V. Reggie Edgerton.Distribution of myosin heavy chain isoforms in non-weight-bearing rat soleus muscle fibers. J. Appl. Physiol. 81(6): 2540–2546, 1996.—The effects of 14 days of spaceflight (SF) or hindlimb suspension (HS) (Cosmos 2044) on myosin heavy chain (MHC) isoform content of the rat soleus muscle and single muscle fibers were determined. On the basis of electrophoretic analyses, there was a de novo synthesis of type IIx MHC but no change in either type I or IIa MHC isoform proportions after either SF or HS compared with controls. The percentage of fibers containing only type I MHC decreased by 26 and 23%, and the percentage of fibers with multiple MHCs increased from 6% in controls to 32% in HS and 34% in SF rats. Type IIx MHC was always found in combination with another MHC or combination of MHCs; i.e., no fibers contained type IIx MHC exclusively. These data suggest that the expression of the normal complement of MHC isoforms in the adult rat soleus muscle is dependent, in part, on normal weight bearing and that the absence of weight bearing induces a shift toward type IIx MHC protein expression in the preexisting type I and IIa fibers of the soleus.

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