[System for effecting the action of cyclic adenosine monophosphate in skeletal muscle during chicken ontogeny]. / Sistema realizatsii deistviia tsiklicheskogo adenozinmonofosfata v skeletnykh myshtssakh v ontogeneze kury.

Studies have been made on the possibility of realization of cAMP regulatory action on carbohydrate and calcium metabolism of skeletal muscles in chick embryos. It was shown that during embryonic period cAMP does not activate phosphorylase system and does not inhibit glycogen synthetase. It was found that the absence of any influence of cAMP on these enzymes of carbohydrate metabolism in embryonic muscles does not depend on the state of cAMP-dependent protein kinase, since this enzyme is functionally active. In contrast to the enzymes of carbohydrate metabolism, Ca2+, Mg2+-ATPase of sarcoplasmic reticulum is sensitive to stimulation by cAMP at least from the 2nd week of embryonic development. It is concluded that embryonic skeletal muscles of chicks exhibit all the conditions which are necessary for realization of the regulatory effect of cAMP. Yet the realization of any effect of the nucleotide depends on the maturity of the given effector link.

Effects of prolonged space flight on rat skeletal muscle.

The effect of a 20-day space flight on water, Na+, K+, Mg2+, Ca2+ and glycogen contents as well as on activities of glycogen metabolism enzymes--glycogen synthetase and glycogen phosphorylase--of rat skeletal muscles was studied. This data is regarded as an integral test characterizing the state of contractile tissue of the animals at the final stage of flight aboard biosatellites. The measurements indicate that there were no significant changes of cations and glycogen contents nor of the enzymic activities in fast-twitch muscles during the 20-day spaceflight. At the same time dehydration in these muscles was observed, which disappeared on the 25th postflight day. In slow-twitch antigravitational skeletal muscle (m. soleus) there was a decrease of K+ and increase of Na+ in the tissue contents. The changes disappeared at the end of the on-earth readaptation period. From the pattern of these observations, we can conclude that the 20-day space flight leads to some reversible biochemical changes of the rat skeletal muscles. A conclusion can be drawn about necessity of creating, aboard the spaceship, an artificial load on antigravitational skeletal muscles.

[Role of phospholipids in the realization of catecholamine action]. / Znachenie fosfolipidov v realizatsii deistviiv katekholaminov.

The involvement of phospholipids into the function of the hormonoreactive system realizing the catecholamine action on the skeletal muscle metabolism was studied at different stages of chicken ontogenetic development. The phospholipase "D" treatment of the chicken muscle homogenate removed the epinephrine activating effect on phosphorylase. Phosphatidylserine and phosphatidylinositol not only completely restore the epinephrine responsiveness of this system but also slightly intensify it. The cAMP and Ca2+ effects on muscle phosphorylase are also removed after the phospholipase "D" treatment. But they are not restored by phosphatidylserine and phosphatidylinositol. It is shown that these membrane phospholipids do not accelerate the origination of catecholamine reactivity of the above-mentioned hormonecompetent system in the process of embryonic development.

[Reaction between cGMP and cAMP in their effect on muscle carbohydrate metabolism]. / O vzaimodeistvii tsGMF i tsAMF v ikh vliianii na uglevodnyi metabolizm myshts.

cGMP (10(-4)-10(-7) M) did not affect the activity of phosphorylase and glycogen synthetase from chicken sceletal muscles; but the cGMP prevented completely an effect of cAMP on the enzymes. This blocking effect was specific for cGMP (GMP did not exhibit the effect) and for cAMP (influence of calcium on the enzyme was not eliminated by cAMP). Possible mechanisms of the cGMP effects studied are considered: 1) stimulation of cAMP hydrolysis, 2) antagonism at the level of proteinkinase system. cGMP (10(-4)-10(-7) M) did not stimulate the phosphodiesterase activity at millimolar concentration of its substrate--cAMP.