Muscles structure

Huxley A F 1957 Muscle structure and theories of contraction Prog. Biophys. Biophys. Chem. 7 255... 

In addition to the major proteins of striated muscle (myosin, actin, tropomyosin, and the troponins), numerous other proteins play important roles in the maintenance of muscle structure and the regulation of muscle contraction. Myosin and actin together account for 65% of the total muscle protein, and tropomyosin and the troponins each contribute an additional 5% (Table 17.1). The other regulatory and structural proteins thus comprise approximately 25% of the myofibrillar protein. The regulatory proteins can be classified as either myosin-associated proteins or actin-associated proteins. 

This chapter discusses drug s used to treat urinary tract infections (UTIs) and certain miscellaneous drag > used to relieve the symptoms associated with an overactive bladder (involuntary contractions of the detrusor or bladder muscle). Structures of the urinary system that may be affected include the bladder (cystitis), prostate gland (prostatitis), the kidney, or the urethra (see Pig. 47-1). These drug s also help control the discomfort associated with irritation of the lower urinary tract mucosa caused by infection, trauma, surgery, and endoscopic procedures. 

Somlyo AV, Franzini-Armstrong C 1985 New views of smooth muscle structure using freezing, deep-etching and rotary shadowing. Experientia 41 841-856 Somlyo AP, Somlyo AV 1994 Signal transduction and regulation in smooth muscle. Nature 372 231-236... 

The muscle is a highly organized tissue, built up of individual cells known as fibres, which are held together by connective tissue. Each muscle fibre consists of a high number of single strands of myofibrils. The myofibrils are again comprised of myofilaments. The myofilaments are divided into thin and thick filaments, which mainly contain two filamentary proteins, actin and myosin, respectively. The myofibrils occupy approximately 80% of the muscle cell volume, and the majority of the water, which makes up about 75% of the muscle, is located in the spaces between thin and thick filaments. A schematic drawing of muscle structure is shown in Fig. 1. 

Analysis of muscle structure began about the middle of the last century. Microscopists reported a transverse striated appearance when muscle fibers were examined by ordinary light microscopy. With the... 

Huxley, A.F. (1957). Muscle structure and the theories of contraction. Prog, in Biophy. 7, 255-318. 

Wang K. Titin/connectin and nebulin giant protein rulers of muscle structure and function. Adv Biophys 1996 33 123-134. 

Succinylcholine acts primarily at the skeletal neuromuscular junction and has little effect at autonomic ganglia or at postganglionic cholinergic (muscarinic) junctions. Actions at these sites attributed to succinylcholine may arise from the effects of choline. Succinylcholine has no direct action on the uterus or other smooth muscle structures. It does not enter the CNS and does not cross the placental barrier. It may, however, release histamine from mast cells. Because succinylcholine works by stimulating rather than blocking end plate receptors, anti-AChEs will not reverse muscle paralysis and may actually prolong the block. 

Any dialogue on meat flavor development and deterioration requires a brief discussion of muscle structure. Muscle has a highly compact and complex multicellular structural organization (Figure 2). Individual muscle cells contain numerous mitochondria and nuclei. They also contain contractile elements as the bulk of their structure. While the sarcoplasm of muscle (the aqueous non-organellar component) is small compared to the cytoplasm of non-muscle cells, it does have a highly evolved system of membranes called the SR/L representing an acronym for sarcoplasmic reticulum/lysosomal membrane system (11). The SR/L surrounds each contractile element (Fig. 9-13 in 12 Fig. 7-10 in 13). The close proximity of the SR/L to the contractile proteins situates the proteins in a location that is optimal for their hydrolysis by lysosomal hydrolases (12, 13). 

The top spectrum is the result of subtracting the female s from the male s response. In this upper spectrum, one can readily observe a relatively large amount of lactate and pyruvate at 87 and 89 . These acids are products of metabolism males generally have more muscle structure and hence more metabolism than females, therefore the evolution of these compounds in quantitites significantly greater from males than from females is not surprising. The other peaks in this top spectrum can be ascribed to reagent ions and some remain unidentified. 

A molecular view of muscle structure, (a) Segment of actin-tropomyosin-troponin. 

Halton, D.W. and Maule, A.G. (2004) Flatworm nerve-muscle structural and functional analysis. Canadian Journal of Zoology 82, 31 6-333. 

Lazarides, E., and Burridge, K. (1975). Alpha-actinin Immunoflourescent localisation of a muscle structural protein in nonmuscle cells. Cell 6, 289-298. 

Multiminicore disease may also result from mutations in another protein found in the lumen of the ER/SR, selenoprotein N (Ferreiro 2002b). The function of selenoprotein N is currently unknown but may be to participate in regulation of redox homeostasis. An intriguing question is the relationship between RyRl and selenoprotein N such that mutations in either protein can produce similar changes in muscle structure and function. 

The background ideas about muscle structure and the crossbridge cycle, together with some historical perspectives, are discussed in this volume in Squire et al. (2005) and Geeves and Holmes (2005) and also, for example, in Huxley (1969, 2004), Holmes (1997), Geeves and Holmes (1999), and the special Royal Society issue on Myosin, Muscle and Motility (Phil. Trans. Roy. Soc. B. volume 359, pp 1811-1964). 

Clearly there is a still much to learn about the contractile mechanism, force production, the strain dependence of the crossbridge cycle and, indeed, how force and movement are actually generated. As shown in Squire et al., Granzier and Labeit, Brown and Cohen, and Geeves and Holmes (all in this volume), and in this article, a great deal is already known about muscle structure and function. However, there is also little doubt that the sarcomere still has some major surprises in store for us. 

Labeit, S., and Kolmerer, B. (1995). Titins Giant proteins in charge of muscle structure and elasticity. Science 270, 293-296. 

Johnston, I.A. and Camm, J.-P. (1987). Muscle structure and differentiation in pelagic and demersal stages of the Antarctic teleost Notothenia neglecta. Marine Biology 94,183-190. 

Targeted deletion of the muscular dystrophy gene myotilin does not perturb muscle structure or function in mice. Mol Cell Biol 27, 244-252. 

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