Muscles classification

Elucidation of the stmctural requirements for dmg interaction at the recognition site is by the study of stmcture—activity relationships (SAR), in which, according to a specific biologic response, the effects of systematic molecular modification of a parent dmg stmcture are determined. Such studies have permitted the classification of discrete classes of pharmacological receptors. For example, the neurotransmitter acetylcholine acts at both peripheral and central receptors which are of at least three distinct types. The effects of acetylcholine are mimicked in smooth and cardiac muscles and secretory... 

The distinction between a- and P-adrenergic receptors was first proposed by Ahlquist in 1948 based on experiments with various catecholamine derivatives to produce excitatory (a) or inhibitory (P) responses in isolated smooth muscle systems. Initially, a further subdivision into presynaptic a2- and postsynaptic oq-receptors was proposed. However, this anatomical classification of a-adrenergic recqrtor subtypes was later abandoned. 

Different types of fibers have been detected in skeletal muscle. One classification subdivides them into type I (slow twitch), type IIA (fast twitch-oxidative), and type IIB (fast twitch-glycolytic). For the sake of simphcity, we shall consider only two types type I (slow twitch, ox-... 

The individual subtypes of receptors often show discrete anatomical locations in the peripheral nervous system, and this has facilitated their classification. Nicotinic receptors are found in peripheral ganglia and skeletal muscle. Upon innervation of skeletal muscle, receptors congregate in the junctional or postsynaptic endplate area. Upon denervation or in noninnervated embryonic muscle, the receptors are distributed across the surface of the muscle,... 

Tubocurarine was the first muscle relaxant used in clinical anaesthesia, although it is now rarely used and is not available in many countries. The ED95 of tubocurarine is approximately Table 6.3 Classification of non-depolarising relaxants... 

Both adrenaline and noradrenaline stimulate smooth muscles throughout the body and have a hypertensive effect. Their postsynaptic receptors are 7-helix transmembrane proteins (Fig. 11-6). A comparison of the effects of various analogs led to the classification of these receptors into classes a, a2, P, and P2, which are discussed briefly on pp. 553-555. The a receptors, which are structurally closely related to rhodopsin,753/754 are coupled via Gq /11 proteins to a phosphoinositide-activated phospholipase C (Figs. 11-9, 30-19).755 They usually provoke an excitatory response. However, in intestinal smooth muscles they are inhibitory. Adrenaline is usually more active at a receptors than is noradrenaline. A specific antagonist... 

The classification of proteins as IFs has been debated over the years, with much discussion as to whether certain IFs are bona fide IFs or IFAPs then, if they are IFs, how should they be classified In the end, the classification has been based primarily on sequence homology and protein structure. Thus, synemin and paranemin, which were originally identified as IFAPs, have now been dubbed IFs (Beilin et al., 1999 Hemken et al., 1997). In spite of sequence similarities, however, they differ from classical IFs in that these proteins require other IFs (such as desmin) for incorporation into the polymer. In this respect, synemin and paranemin are similar to several other IFs including nestin, NF-H, tanabin in the nervous system (for review, see Coulombe et al., 2000) and syncoilin in muscle (Blake and Martin-Rendon, 2002). 

Respiratory smooth-muscle cells contain the beta-2 subtype of adrenergic receptors.76 (See Chapter 18 for a discussion of adrenergic receptor classifications.) Stimulation of these beta-2 receptors results in relaxation of bronchiole smooth muscle. Lienee, drugs that stimulate these beta-2 adrenergic receptors (i.e., beta-adrenergic agonists) produce bronchodilation and can be used to prevent or inhibit airway obstruction in bronchospastic diseases.22,99... 

Fig. 28. Classification of crossbridge configurations in myosin filaments in different muscles. In each case, the axial separation is 143-145 A and the lateral separation is 120-150 A. There are three main classes (A) Class I, where the interaction is between heads of the same molecule as in vertebrate striated muscles (B) Class II, where interaction occurs between heads of adjacent myosin molecules in the same crown, as seen in insect (Lethocerus) flight muscles and (C) Glass III, where the interaction appears to be between heads in different crowns, as seen in tarantula and Limulus.

STREET NAMES Legal steroid, muscle candy, ergogenic aid, performance-enhancing substance DRUG CLASSIFICATIONS Not scheduled, dietary supplement... 

B. P. LefF, G. R. Martin, and J. M. Morse. Differential classification of vascular smooth muscle and cndoihenai ceil 5-KT receptors by use of irypiaminc analogues, fie J. Pharm. 97 321-331 (1987). 

Suppliers. BCR, Institute for Reference Materials and Measurements (IRMM), Belgium NIST, National Institute of Standards and Technology, United States NRCC, National Research Council of Canada. Classifications CRM, Certified Reference Material DORM, Dogfish Muscle Reference Materials for Trace Metals LUTS, Nondefatted Lobster Hepatopancreas Reference Material for Trace Metals SRM, Standard Reference Material TORT, Lobster Hepatopancreas Marine Reference Material for Trace Metals. 

Active site selective reagents can be classified in various manners. One way is to divide them according to how they react (Table IX). In such a classification one finds substrates that can be covalently attached by chemical treatment of the enzyme while it is catalyzing some change in the substrate. An example is the reaction of functional amino groups by the enzyme muscle aldolase acting on glyceraldehyde and reduced by cyanoboro-hydride (16). 

---