Myocyte, muscle cell

Rhabdomyolysis is disintegration and death of muscle cells (myocytes). It is an important but rare side effect of treatment with statins. 

Conversion of AF to NSR can also be accomplished with a subset of antiarrhythmic drugs (including 2-7) that act directly on cardiac muscle cells (myocytes) and antagonize either the sodium channel-mediated propagation currents (procainamide 2, flecainide 3, propafenone 4), or the inwardly rectifying (7 ) potassium channel currents (ibutilide 5, dofetilide 6). Some of the antiarrhythmics have actions at both potassium and sodium channels (i.e., dronedarone 7 and its close structural progenitor... 

Muscle cells Myocytes are electrically excitable and are popular in cell-based biosensors [44]. Primary myocytes isolated from adult or neonatal rat hearts have been used to study the effect of microtopography on cell functions [45], Murine skeletal muscle cells have been patterned in line... 

The main experimental use of barium is in electrophysiology where it can be used as a charged probe for metal ion-dependent processes. The isolation and identification of individual ion fluxes which contribute to the electric currents flowing through cell membranes often requires techniques to block specific components of electrical activity. This can sometimes be achieved by the use of the soluble salts of divalent cations such as barium and manganese which may block potassium and calcium and currents in, for example, the cardiac pacemaker [4]. Barium can also be used to identify potassium-conducting channels in isolated membrane vesicles [S,6] or calcium charmels in isolated heart muscle cells, myocytes [7], and adrenal gland chromaffin cells [8]. 

The cells of the latter three types contain only a single nucleus and are called myocytes. The cells of skeletal muscle are long and multinucleate and are referred to as muscle fibers. At the microscopic level, skeletal muscle and cardiac muscle display alternating light and dark bands, and for this reason are often referred to as striated muscles. The different types of muscle cells vary widely in structure, size, and function. In addition, the times required for contractions and relaxations by various muscle types vary considerably. The fastest responses (on the order of milliseconds) are observed for fast-twitch skeletal... 

The myocytes of smooth muscle are approximately 100 to 500 p,m in length and only 2 to 6 p,m in diameter. Smooth muscle contains very few t-tubules and much less SR than skeletal muscle. The Ca that stimulates contraction in smooth muscle cells is predominantly extracellular in origin. This Ca enters the cell through Ca channels in the sarcolemmal membrane that can be opened by electrical stimulation, or by the binding of hormones or drugs. The contraction response time of smooth muscle cells is very slow compared with that of skeletal and cardiac muscle. 

Sites of endothelin-receptor expression. ETA receptors are expressed in the smooth muscle cells of the vascular medial layer and the airways, in cardiac myocytes, lung parenchyma, bronchiolar epithelial cells and prostate epithelial cells. ETB receptors are expressed in endothelial cells, in bronchiolar smooth muscle cells, vascular smooth muscle cells of certain vessels (e.g. saphenous vein, internal mammary artety), in the renal proximal and distal tubule, the renal collecting duct and in the cells of the atrioventricular conducting system. 

NFAT proteins are expressed in skeletal, cardiac, and smooth muscle and play important roles in the regulation of the development and differentiation of these tissues. In skeletal muscle, NFAT isoforms are expressed at different stages of development and regulate progression from early muscle cell precursors to mature myocytes. NFAT proteins have also been shown to control the expression of the myosin heavy chain and positively regulate muscle growth [1, 2]. 

Plasma membrane channels. The most common mechanism for the movement of into smooth muscle cells Ifom the extracellular space is the electrodiffusion of Ca " ions through highly selective channels. This movement can be significant in two quite different ways. First, Ca ions carry two positive charges and, in fact, most of the inward charge movement across the plasma membrane of smooth muscle myocytes is carried by Ca. Most smooth muscle action potentials are known to be Ca " action potentials. And second, the concentration of intracellular free calcium, the second messenger, is increased by inward calcium movement. 

FIG. 3. Tight coupling in cardiac but not smooth muscle myocytes. Cells dialysed with 17 nM mobile Ca2+ buffer (EGTA). When depolarized, brief Ca2+ release events are seen in ventricular myocytes, indicating RyR gating occurs before the mobile buffer can scavenge the gating Ca2+ ions. Conversely, in smooth muscle cells CICR is completely blocked. The simplest interpretation of these data is that Ca2+ ions must traverse a distance of at least lOOnm, the distance beyond which the mobile buffer can prevent a rise in Ca2+. (From Collier et al 2000.)... 

Gordienko DV, Greenwood IA, Bolton TB 2001 Direct visualization of sarcoplasmic reticulum regions discharging Ca2+ sparks in vascular myocytes. Cell Calcium 29 13—28 Imaizumi Y, Torii Y, Ohi Y et al 1998 Ca2+ images and K+ current during depolarization in smooth muscle cells of the guinea-pig vas deferens and urinary bladder. J Physiol (Lond) 510 705-719... 

Wang Q, Hogg RC, Large WA 1992 Properties of spontaneous inward currents recorded in smooth muscle cells isolated from the rabbit portal vein. J Physiol 451 525—537 ZhuGe R, Sims SM, Tuft RA, Fogarty KE, Walsh JV 1998 Ca2+ sparks activate K+ and Cl-channels, resulting in spontaneous transient currents in guinea-pig tracheal myocytes. J Physiol 513 711-718... 

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