وبلاگ خانه تبدیل شباهنگ مرکز تخصصی تبدیل صدا و تصویر
Mammalian skeletal muscle exhibits enormous variability in its functional characteristics such as the rate of force production, fatigue resistance, and energy metabolism, with a wide range from slow aerobic physiology to rapid anaerobic physiology. In addition, skeletal muscle has a high plasticity based on the potential of muscle fibers to undergo changes in their cytoarchitecture and the composition of specific muscle protein isoforms. Adaptive changes in muscle fibers occur in response to a variety of stimuli such as. B growth and differentiation factors, hormones, nerve signals or movement. In addition, muscle fibers are arranged in compartments, which often function as largely independent muscle subunits. All muscle fibers use Ca2+ as the most important regulatory and signaling molecule. Therefore, the contractile properties of muscle fibers depend on the variable expression of proteins involved in Ca2+ signaling and manipulation. The molecular diversity of the main proteins of the Ca2+ signaling apparatus (the calcium cycle) largely determines the contraction and relaxation properties of a muscle fiber. The Ca2+ signaling apparatus includes 1) the ryanodine receptor, which is the channel of release of the sarcoplasmic reticulum Ca2+, 2) the protein complex of troponin, which mediates the Ca2+ effect on the myofibrillar structures that lead to contraction, 3) the Ca2+ pump, which is responsible for the reuptake of Ca2+ in the sarcoplasmic reticulum, and 4) calequesterin, the Ca2+ storage protein in the sarcoplasmic reticulum.
In addition, a variety of Ca2+ binding proteins are present in muscle tissue, including parvalbumin, calmodulin, S100 proteins, adnexins, sorcin, myosin light chains, actinin β, calcineurin and calphaine. These Ca2+ binding proteins can either play an important role in Ca2+-induced muscle contraction under certain conditions, or modulate other muscle activities such as metabolism, differentiation and protein growth. Recently, several Ca2+ signaling and manipulation molecules have been shown to be altered in muscle diseases. Functional changes in Ca2+ manipulation appear to be responsible for the pathophysiological conditions observed in dystrophinopathies, Brody`s disease and malignant hyperthermia. These also highlight the importance of the affected molecules for proper muscle performance. The muscle contraction cycle is triggered by calcium ions that bind to the troponin protein complex and expose the active binding sites on actin. Once the actin binding sites are exposed, the high-energy myosin head closes the gap and forms a transverse bridge. Once the myosin binds to the actin, the pi is released and the myosin undergoes a conformational change at a lower energy state. When myosin consumes energy, it moves through the “force snap” and pulls the actin filament towards the M line. When the actin is pulled about 10 nm in the direction of the M line, the sarcomere shortens and the muscle contracts. At the end of the strength race, the myosin is in a low-energy position. Myocytes: Skeletal muscle cell: A skeletal muscle cell is surrounded by a plasma membrane called a sarcolemma, along with a cytoplasm called a sarcoplasm.
A muscle fiber consists of many myofibrils, which are packed in ordered units. Muscle tissue can be functionally classified as voluntary or involuntary and morphologically as striated or untried. Voluntary refers to whether the muscle is under conscious control, while striping refers to the presence of visible bands in the myocytes caused by the organization of myofibrils to create constant tension. This article focuses mainly on the complexity of the ca2+ manipulation system in the skeletal muscle of mammals, although on several occasions reference is made to the heart and smooth muscles and, if applicable, to the muscles of other vertebrates. The diversity of muscle fiber types analyzed at the histological level and the functional consequences of the composition of fiber types are described in detail (see section ii) to emphasize the importance of morphological studies to understand muscle plasticity in response to a given stimulus and its dependence on the Ca2+ manipulation apparatus. Contraction and relaxation of bovine muscles. Beef Quality Research on behalf of The Beef Checkoff, National Cattlemen`s Beef Association. Created by the Center for Meat Safety and Quality, Department of Animal Science, Colorado State University. Describe how calcium, tropomyosin and troponin complex regulate actin binding by myosin Recent findings on the role of laminin, a component of the extracellular skeletal muscle matrix, and dystrophin-associated glycoproteins (DAGs), dystroglycans α and β, and sarcomas α, β, γ and Î` (۴۹۹) have provided new information on the function of dystrophin. Mutations in these proteins can also cause muscular dystrophy (Table 2). An autosomal recessive form of muscular dystrophy (severe autosomal recessive muscular dystrophy in childhood, SCARMD) is associated with mutations in the α-sarcoglycan gene (former name: adhaline) (429, 499).
The genes that code for β, γ and Î`-sarcoglycans (Fig. 13), cause various forms of limb belt muscular dystrophy (LGMD) when affected by mutations [LGMD2C, I³-sarcoglycan (374); LGMD2E, β sarcoglycan (35); LGMD2F, Î`-Sarcoglycan (372)]. Congenital muscular dystrophy (CMD) is a clinically heterogeneous group of muscular dystrophies that often set in at the beginning of the crisis. .
