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MHC Isoforms (mhc + isoform)

Distribution by Scientific Domains
Life Sciences100%

Selected Abstracts

Correlation of dystrophin,glycoprotein complex and focal adhesion complex with myosin heavy chain isoforms in rat skeletal muscle

ACTA PHYSIOLOGICA, Issue 4 2009
S. Masuda
Abstract Aim:, The dystrophin,glycoprotein complex (DGC) and focal adhesion complex (FAC) are transmembrane structures in muscle fibres that link the intracellular cytoskeleton to the extracellular matrix. DGC and FAC proteins are abundant in slow-type muscles, indicating the structural reinforcement which play a pivotal role in continuous force output to maintain posture for long periods. The aim of the present study was to examine the expression of these structures across fast-type muscles containing different myosin heavy chain (MHC) isoform patterns which reflect the fatigue-resistant characteristics of skeletal muscle. Methods:, We measured the expression of dystrophin and ,1 integrin (representative proteins of DGC and FAC respectively) in plantaris, extensor digitorum longus, tibialis anterior, red and white portions of gastrocnemius, superficial portion of vastus lateralis and diaphragm, in comparison with soleus (SOL) and cardiac muscle from rats. Results:, The expression of dystrophin and ,1 integrin correlated positively with the percentage of type I, IIa and IIx MHC isoforms and negatively with that of type IIb MHC isoform in fast-type skeletal muscles, and their expression was abundant in SOL and cardiac muscle. Conclusion:, Our results support the idea that DGC and FAC are among the factors that explain the fatigue-resistant property not only of slow-type but also of fast-type skeletal muscles. [source]

Differences in sodium voltage-gated channel properties according to myosin heavy chain isoform expression in single muscle fibres

THE JOURNAL OF PHYSIOLOGY, Issue 21 2009
F. Rannou
The myosin heavy chain (MHC) isoform determines the characteristics and shortening velocity of muscle fibres. The functional properties of the muscle fibre are also conditioned by its membrane excitability through the electrophysiological properties of sodium voltage-gated channels. Macropatch-clamp is used to study sodium channels in fibres from peroneus longus (PL) and soleus (Sol) muscles (Wistar rats, n= 8). After patch-clamp recordings, single fibres are identified by SDS-PAGE electrophoresis according to their myosin heavy chain isoform (slow type I and the three fast types IIa, IIx, IIb). Characteristics of sodium currents are compared (Student's t test) between fibres exhibiting only one MHC isoform. Four MHC isoforms are identified in PL and only type I in Sol single fibres. In PL, maximal sodium current (Imax), maximal sodium conductance (gNa,max) and time constants of activation and inactivation (,m and ,h) increase according to the scheme I,IIa,IIx,IIb (P < 0.05). ,m values related to sodium channel type and/or function, are similar in Sol I and PL IIb fibres (P= 0.97) despite different contractile properties. The voltage dependence of activation (Va,1/2) shows a shift towards positive potentials from Sol type I to IIa, IIx and finally IIb fibres from PL (P < 0.05). These data are consistent with the earlier recruitment of slow fibres in a fast-mixed muscle like PL, while slow fibres of postural muscle such as soleus could be recruited in the same ways as IIb fibres in a fast muscle. [source]

Correlation of dystrophin,glycoprotein complex and focal adhesion complex with myosin heavy chain isoforms in rat skeletal muscle

ACTA PHYSIOLOGICA, Issue 4 2009
S. Masuda
Abstract Aim:, The dystrophin,glycoprotein complex (DGC) and focal adhesion complex (FAC) are transmembrane structures in muscle fibres that link the intracellular cytoskeleton to the extracellular matrix. DGC and FAC proteins are abundant in slow-type muscles, indicating the structural reinforcement which play a pivotal role in continuous force output to maintain posture for long periods. The aim of the present study was to examine the expression of these structures across fast-type muscles containing different myosin heavy chain (MHC) isoform patterns which reflect the fatigue-resistant characteristics of skeletal muscle. Methods:, We measured the expression of dystrophin and ,1 integrin (representative proteins of DGC and FAC respectively) in plantaris, extensor digitorum longus, tibialis anterior, red and white portions of gastrocnemius, superficial portion of vastus lateralis and diaphragm, in comparison with soleus (SOL) and cardiac muscle from rats. Results:, The expression of dystrophin and ,1 integrin correlated positively with the percentage of type I, IIa and IIx MHC isoforms and negatively with that of type IIb MHC isoform in fast-type skeletal muscles, and their expression was abundant in SOL and cardiac muscle. Conclusion:, Our results support the idea that DGC and FAC are among the factors that explain the fatigue-resistant property not only of slow-type but also of fast-type skeletal muscles. [source]

Regional specialization of rat quadriceps myosin heavy chain isoforms occurring in distal to proximal parts of middle and deep regions is not mirrored by citrate synthase activity

JOURNAL OF ANATOMY, Issue 1 2007
Tertius Abraham Kohn
Abstract Myosin heavy chain (MHC) isoform content and citrate synthase (CS) activities were measured in the Quadriceps femoris (QF) muscle of 18 female rats. The muscle group was divided into superficial, middle and deep, distal, central and proximal parts. MHC IIb and IIx were more abundant in superficial regions (P < 0.05) with low CS activities compared with deeper parts. The deeper parts expressed all four isoforms (MHC IIb, MHC IIx, MHC IIa and MHC I), with a concomitantly higher CS activity. MHC I, MHC IIa and MHC IIb isoform content varied significantly along the length of the deep regions. Only MHC IIb and CS activity in the proximal middle part correlated (negatively) with each other. This study showed that the QF has regional specialization and that standardization of sampling site is important. Furthermore, CS activity and MHC isoforms are only loosely associated, or not at all. [source]

Differences in sodium voltage-gated channel properties according to myosin heavy chain isoform expression in single muscle fibres

THE JOURNAL OF PHYSIOLOGY, Issue 21 2009
F. Rannou
The myosin heavy chain (MHC) isoform determines the characteristics and shortening velocity of muscle fibres. The functional properties of the muscle fibre are also conditioned by its membrane excitability through the electrophysiological properties of sodium voltage-gated channels. Macropatch-clamp is used to study sodium channels in fibres from peroneus longus (PL) and soleus (Sol) muscles (Wistar rats, n= 8). After patch-clamp recordings, single fibres are identified by SDS-PAGE electrophoresis according to their myosin heavy chain isoform (slow type I and the three fast types IIa, IIx, IIb). Characteristics of sodium currents are compared (Student's t test) between fibres exhibiting only one MHC isoform. Four MHC isoforms are identified in PL and only type I in Sol single fibres. In PL, maximal sodium current (Imax), maximal sodium conductance (gNa,max) and time constants of activation and inactivation (,m and ,h) increase according to the scheme I,IIa,IIx,IIb (P < 0.05). ,m values related to sodium channel type and/or function, are similar in Sol I and PL IIb fibres (P= 0.97) despite different contractile properties. The voltage dependence of activation (Va,1/2) shows a shift towards positive potentials from Sol type I to IIa, IIx and finally IIb fibres from PL (P < 0.05). These data are consistent with the earlier recruitment of slow fibres in a fast-mixed muscle like PL, while slow fibres of postural muscle such as soleus could be recruited in the same ways as IIb fibres in a fast muscle. [source]