Cells muscle

Small, 1989] Small, J. V. Microfilament-based motility in non-muscle cells. Curr. Opinion Cell Biol. 1 (1989) 75-79... 

Contraction of muscle follows an increase of Ca " in the muscle cell as a result of nerve stimulation. This initiates processes which cause the proteins myosin and actin to be drawn together making the cell shorter and thicker. The return of the Ca " to its storage site, the sarcoplasmic reticulum, by an active pump mechanism allows the contracted muscle to relax (27). Calcium ion, also a factor in the release of acetylcholine on stimulation of nerve cells, influences the permeabiUty of cell membranes activates enzymes, such as adenosine triphosphatase (ATPase), Hpase, and some proteolytic enzymes and facihtates intestinal absorption of vitamin B 2 [68-19-9] (28). 

Long-lasting vasoconstriction is produced by the ETs in almost all arteries and veins and several studies have shown that ET-1 causes a reduction in renal blood flow and urinary sodium excretion. ET-1 has been reported to be a potent mitogen in fibroblasts and aortic smooth muscle cells and to cause contraction of rat stomach strips, rat colon and guinea pig ileum. In the central nervous system, ETs have been shown to modulate neurotransmitter release. 

Proteoglycans (from cultured human muscle cells). Separated by ion-exchange HPLC using a Biogel TSK-DEAE 5-PW analytical column. [Harper et al. Anal Biochem 159 150 1986.]... 

Maintenance of electrical potential between the cell membrane exterior and interior is a necessity for the proper functioning of excitable neuronal and muscle cells. Chemical compounds can disturb ion fluxes that are essential for the maintenance of the membrane potentials. Fluxes of ions into the cells or out of the cells can be blocked by ion channel blockers (for example, some marine tox-... 

If the internal pH of a muscle cell is 6.8, what is the [HP04 ]/[H2P04 ] ratio in this cell ... 

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... 

FIGURE 17.10 The four classes of muscle cells iu mammals. Skeletal muscle and cardiac muscle are striated. Cardiac muscle, smooth muscle, and myoepithelial cells are mononucleate, whereas skeletal muscle is multinucleate. 

FIGURE 17.11 The structure of a skeletal muscle cell, showing the mauuer iu which t-tubules enable the sarcolemmal membrane to contact the ends of each myofibril iu the muscle fiber. The foot structure is shown iu the box. 

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. 

Muscle cells contain two different isozymes of creatine kinase, one in the mitochondria and one in the sarcoplasm. Explain. 

The plasnialogens are a group of lipids found in nerve and muscle cells. How do plasma I oge ns differ from fats ... 

The lactic acid (C3H603(flg), AG = —559 kj) produced in muscle cells by vigorous exercise eventually is absorbed into the bloodstream, where it is metabolized back to glucose (AG = —919 kj) in the liver. The reaction is... 

Fabiato, A., and Fabiato, F. (1979). Calculator program for computing the composition of the solutions containing multiple metals and ligands used for experiments in skinned muscle cells. J. Physiol., Paris 75 463-505. 

In the vasculature, ANG H not only increases contraction of smooth muscle cells, but is also able to induce vascular injury. This can be prevented by blocking NFkB activation [3] suggesting a link between ANG II and inflammation processes involved in the pathogenesis of arteriosclerosis (see below). Thus, ACE inhibitors not only decrease vascular tone but probably also exert vasoprotective effects. 

Bradykinin stimulates natriuresis and, through stimulation of prostaglandin synthesis, inhibits the actions of antidiuretic hormone (ADH), thereby inhibiting water retention. Bradykinin further improves insulin sensitivity and cellular glucose utilization of skeletal muscle cells in experimental models. This, however, appears not to be relevant in the clinical context. 

Acetylcholine serves as a neurotransmitter. Removal of acetylcholine within the time limits of the synaptic transmission is accomplished by acetylcholinesterase (AChE). The time required for hydrolysis of acetylcholine at the neuromuscular junction is less than a millisecond (turnover time is 150 ps) such that one molecule of AChE can hydrolyze 6 105 acetylcholine molecules per minute. The Km of AChE for acetylcholine is approximately 50-100 pM. AChE is one of the most efficient enzymes known. It works at a rate close to catalytic perfection where substrate diffusion becomes rate limiting. AChE is expressed in cholinergic neurons and muscle cells where it is found attached to the outer surface of the cell membrane. 

The calcification of atherosclerotic plaques may be induced by osteopontin expression, since osteopontin is a protein with a well-characterized role in bone formation and calcification. Vascular smooth muscle cell migration on osteopontin is dq endent on the integrin av 33 and antagonists of av 33 prevent both smooth muscle cell migration and restenosis in some animal model [8]. 

Ca2+ is an important intracellular second messenger that controls cellular functions including muscle contraction in smooth and cardiac muscle. Ca2+ channel blockers inhibit depolarization-induced Ca2+ entry into muscle cells in the cardiovascular system causing a decrease in blood pressure, decreased cardiac contractility, and antiarrhythmic effects. Therefore, these drugs are used clinically to treat hypertension, myocardial ischemia, and cardiac arrhythmias. 

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