Muscle type

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... 

Nicotinic receptors (nicotinic acetylcholine receptors, nACHR) exist not only in the membrane of vertebrate skeletal muscle at the synapse between nerve and muscle (muscle-type nAChR) but also at various synapses throughout the brain, mainly at presynaptic positions (neuronal-type nAChR). Whereas the muscle-type nAChR is precisely composed of two a 1-subunits, one (3 -subunit, one y -subunit and one y -subunit (adult)... 

Some researchers reject the explanation that caffeine inhibits glycogen depletion during short term exercise54 but there is an increasing abundance of research supporting the notion of variable sensitivity to caffeine by muscle type. Muscles with higher ratios of type I fibers appear more sensitive than type II fibers, both in animal55-56 and human models.57... 

Phosphofructokinase (PFK) is a key regulatory enzyme of glycolysis that catalyzes the conversion of fructose-6-phosphate to fructose-1,6-diphosphate. The active PFK enzyme is a homo- or heterotetrameric enzyme with a molecular weight of 340,000. Three types of subunits, muscle type (M), liver type (L), and fibroblast (F) or platelet (P) type, exist in human tissues. Human muscle and liver PFKs consist of homotetramers (M4 and L4), whereas red blood cell PFK consists of five tetramers (M4, M3L, M2L2, ML3, and L4). Each isoform is unique with respect to affinity for the substrate fructose-6-phosphate and ATP and modulation by effectors such as citrate, ATP, cAMP, and fructose-2,6-diphosphate. M-type PFK has greater affinity for fructose-6-phosphate than the other isozymes. AMP and fructose-2,6-diphosphate facilitate fructose-6-phosphate binding mainly of L-type PFK, whereas P-type PFK has intermediate properties. 

Somljo It all depends on the fixation method. We use osmium ferricyanide to selectively infiltrate the SR. If we use intermediate high-voltage electron microscopy, we can look at thicker specimens, and this technique provides more extensive views than obtained from the usual thin sections. This is the same information we get when we infiltrate the SR with Fluo-3. These pictures are pretty reliable. Furthermore, if you want to confirm without chemical fixation, methods such as rapid freezing are available. All these techniques give the same pictures, which vary according to the smooth muscle type. 

To date, all smooth muscle types examined display characteristic Ca2+ release events known as Ca2+ sparks (Fig. 1 see Jaggar et al 2000 for review). Ca2+ sparks are localized Ca2+ release events through RyRs in the SR located very close (10—20nm) to the surface membrane. Ca2+ sparks can activate Ca2+ -dependent ion channels in the cell surface, and the physiological response of the particular cell type will reflect the type of ion channels involved (Fig. 1). 

Young In the myometrium, the Ca2+ waves are from the deep cytoplasmic Ca2+ to the plasma membrane. The intracellular Ca2+ waves should be considered separately from either phasic or tonic smooth muscle types. The myometrium is phasic smooth muscle. And intercellular Ca2+ waves are an entirely different phenomenon altogether. 

Beside fat, the content and distribution of connective tissue in the meat is also considered to be of importance as these contribute to meat toughness. Based on differences in magnetic susceptibility compared with the surrounding muscle tissue, Bonny et al 23 succeeded in visualizing the distribution of connective tissue in beef muscles. Clear differences in the organisation of connective tissue were demonstrated between two different muscle types. 

In conclusion, 31P NMR spectroscopy has already displayed metabolic differences between the muscle types, which could contribute to a better understanding of observed variations in properties among different muscle types and the significance of muscle type for meat quality. 

The anatomical unit of muscle is an elongated cell called a fibre. Each individual fibre cell consists of myofibrils which are bundles of contractile protein filaments composed of actin and myosin (Figure 7.1). Differences in structure indicate that muscles have evolved to perform particular functions. Although the structure of fibres, myofibrils and filaments of actin and myosin, is similar in all muscle types, their arrangement, action and control allow identification of three tissue types ... 

All muscle types require ATP to achieve contraction. Glucose, fatty acids and amino acids may all be used as oxidizable substrates to produce ATP and all three energy sources may be obtained from stored intracellular sources (glycogen, triglyceride and protein) or imported from the blood stream. In quantitative terms, skeletal muscle is... 

The present work focuses on examinations in skeletal muscle, which makes up the bulk of the body s muscle and is the tissue we use for physical activity. For this reason features of this muscle type are reported in more detail in the following. 

Spectral series for determination of MTR in TA is shown in Fig. 20a, indicating a strong signal decrease caused by MT preparation, dependent on the MT-prepulse amplitude. However, no significant differences in MTRw were found between the two muscle types examined (see Fig. 20b). 

Chow ESH, Cheng SH (2003) Cadmium affects muscle type development and axon growth in zebrafish embryonic somitogenesis. Toxicol Sci 73 149-159... 

Only in a few muscle types (e.g., extraocular muscle) are muscle fibers supplied with multiple endplates. Here succinylcholine causes depolarization distributed over the entire fiber, which responds with a contracture. Intraocular pressure rises, which must be taken into account during eye surgery. 

The aptamers obtained against the nAChR either are biologically active by themselves and inhibit the muscle-type nAChR activity as cocaine does or are by them biologically inactive and, therefore, protect the receptor against inhibition by cocaine (25). 

For the electrophysiological assay, BCjHl cells that express the muscle-type nAChR are plated in cell culture dishes. 

Their actions on smooth muscle, in particular, can be complex. For example, both PGEs and PGFs induce contraction of uterine and gastrointestinal smooth muscle. On the other hand, PGEs stimulate dilation of vascular and bronchial smooth muscle, whereas PGFs induce constriction of these muscle types. 

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