Skeletal muscle phosphorus

Mechanism of Action A polypeptide hormone that stimulates cartilaginous growth areas of long bones, increases the number and size of skeletal muscle cells, influences the size of organs, and increases RBC mass by stimulating erythropoietin. Influences the metabolism of carbohydrates (decreases insulin sensitivity), fats (mobilizes fatty acids), minerals (retains phosphorus, sodium, potassium by promotion of cell growth), and proteins (increases protein synthesis). Therapeutic Effect Stimulates growth. 

E. L. Lim, K. G. Hollingsworth, P. E. Thelwall and R. Taylor, Measuring the acute effect of insulin infusion on ATP turnover rate in human skeletal muscle using phosphorus-31 magnetic resonance saturation transfer spectroscopy. NMR Biomed., 2010, 23,952-957. 

Pralidoxime Very high affinity for phosphorus atom but does not enter CNS Regenerates active AChE can relieve skeletal muscle end plate block Usual antidote for early-stage (48 h) cholinesterase inhibitor poisoning Intravenous every 4-6 h Toxicity Can cause muscle weakness in overdose... 

I n this way we have shown that phosphoryl transfer catalysed by Bacillus stearothermophilus and rabbit skeletal muscle phosphofructokinase (6), and rabbit skeletal muscle pyruvate kinase occurs with inversion of configuration at phosphorus (7). The simplest interpretation of these stereochemical results is that phosphoryl transfer occurs by an in-line mechanism in the enzyme substrate ternary complexes. Stereochemical analysis is thus proving to be of considerable importance for delineating the mechanism adopted by phosphokinases. ... 

Skeletal muscle and yeast phosphofructokinases will catalyse the phosphorylation of 5-keto-D-fructose-l,6-bisphosphate (9). The latter has been isolated chromatographically and identified by its phosphorus content and the rather doubtful method of acid lability of the phosphate groups. The bis-phosphate is a competitive inhibitor of the reaction between aldolases and fructose-1,6-bisphosphate probably because of Schiff base formation with the enzyme. ... 

Any disorder that results in necrosis of skeletal muscle cells (i.e., rhabdomyolysis) can result in the release of large amounts of intracellular phosphorus into the systemic circulation. This condition is frequently associated with acute renal failure and thus severe hyperphosphatemia may develop due to increased endogenous phosphorus release coupled with decreased renal phosphorus excretion. Bowel infarction, malignant hyperthermia, and severe hemolysis are also conditions that may increase endogenous release of phosphorus. 

Phosphorus NMR is also used for vascularly perfused preparations, such as heart, skeletal muscle, bladder, or uterus. In these cases, the contributions to the spectra by the perfusate may be important. Phe-nylphosphonate or similar derivatives are often used for such experiments. PPA has a direct C-P bond, unlike phosphates that have O-P bonds. As a result, PPA resonates downfield (to the left) of the naturally occurring phosphorus compounds. In mechanical and NMR experiments, the effects of PPA on the isolated, perfused bladder were measured (Fisher and Dillon, 1987a). PPA in concentrations up to 20 mM did not produce a significant reduction in force generation. Its NMR peak position was shown to be pH sensitive with a pK of 7.09, making it ideal for measurements of extracellular pH. It did not produce any alteration in the natural phosphorus spectrum, and it was able to be washed into and out of the perfused tissue without measurable residue, indicating that it did not cross cell membranes. In addition to being a pH indicator, it is therefore also useful as a marker for extracellular space. 

Phospholipides.— Lecithin and other phospholipides of the diet are important nutritional somces of choUne and of phosphoric acid, and are resolved into their components by the esterases of the small intestine previous to absorption. Within the intestinal mucosa, a re-synthesis occiun, or a new phospholipide is assembled containing units derived from the saponified fats of the diet, and as such participates in the lipide transport in the lymph and the portal blood. By use of a phosphate containing a radioactive isotope of phosphorus as indicator, Artom and his colleagues (1937) have shown that phospholipides of the lecithin and cephalin type are synthesised in large quantities during fat absorption, and accumulate in the intestinal mucosa, the liver, and to a lesser extent, the kidney, but not in the spleen, heart or skeletal muscles. 

R22. Phosphorus nuclear magnetic resonance of cardiac and skeletal muscles Ingwal, J. S. Am. J. Physiol. 1982, 242, H729-H744. A review with 82 references on metabolism of phosphorus compounds in muscle. 

Only twenty minutes after an intravenous injection of labeled pho.s-phate, the creatine phosphorus, both of the rabbit s and the frog s (at 20°C.) skeletal muscle, was found to have a specific activity corresponding... 

Specific Activity of the Phosphorus Fractions Isolated from the Skeletal Muscle of the Rabbit (102)... 

In this chapter we discuss several clinical applications of P NMR. The main emphasis is placed on advances in skeletal muscle (since the review of Glonek et al., 1981), but advances in heart, kidney, brain, eye, and mammalian fluids are also covered. The resonances we deal with are from the phosphorus compounds soluble in the cytoplasm. At the time of this writing, the phospholipids in the membranes of intact tissues are not amenable for P-NMR analysis under the high-resolution conditions cus-... 

Phosphorus-31 MRS has been used widely to investigate mitochondria diseases in muscle. Trenell et al. measured an elevated ADP concentration and pHi in a group of mitochondrial myopathy (MM) patients, which is evidence of impaired oxidative ATP production in their skeletal mus-cle This study also showed that increased inspired oxygen concentration improves oxidative fimction in MM patients. In a separate study, Jeppesen et al. could not differentiate healthy subjects and MM patients using P MRS. ° They concluded the P MRS should not be a routine test in the diagnosis for MM patients. 

The many diverse components of milk have demonstrable effects on human health. Perhaps, the most commonly associated component of dairy food is that of dietary calcium. Dairy products provide the most significant contribution to dietary calcium intake in the modem Western diet. It has been estimated that dairy products contribute to >72% of dietary calcium in the United States (Huth et al., 2006). Calcium is an important mineral for maintenance of optimal bone health (Bonjour et al., 2009) and is an integral component of key metabolic pathways relating to, for example, muscle contraction both in skeletal and smooth muscle (Cheng and Lederer, 2008). Further, dairy products contribute other essential nutrients in the diet, such as proteins, phosphorus, potassium, zinc, magnesium, selenium, folate, riboflavin, vitamin B12, and vitamin A (Haug et al., 2007 Huth et al., 2006). Low-fat milk alternatives are fortified with vitamin A and vitamin D which is added to milk and fermented milk in many countries making it an important source for vitamin D (Huth et al., 2006). 

Of the total calcium in the body, 99% is contained in bones and teeth, and if the tendons and ligaments are included the complete skeletal structure contains 99.5% of the body s calcium. The remaining 0.5% is distributed among the blood, the lymph, and the soft tissues in which the concentration varies somewhat but in general that of the tissues and lymph approximates to the diffusible calcium concentration of plasma. Variable estimates of the distribution of phosphorus suggest that rather more than 85% of the total phosphorus is combined with calcium in the skeleton, about 10% is in muscle tissue, rather less than 1% in brain, and about 0.3% in blood, the remainder being in other tissues and tissue fluids. The... 

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