[Effect of caffeine on the Ca2+-transport function of sarcoplasmic reticulum vesicles in the rat myocardium]. / Vliianie kofeina na Ca2+-transportiruiushchuiu funktsiiu puzyr'kov sarkoplazmaticheskogo retikuluma iz miokarda krysy.

The effects of caffeine on active transport of Ca2 by heavy and light fractions of rat myocardial microsomes were investigated with the use of a Ca2+-selective electrode and nephelometry. It was found that under the effect of caffeine (5 mM) the rate of Ca2 transport in the presence of oxalate decreased by 30 to 40%. The caffeine-induced inhibition was prevented by ruthenium and tetracaine, thus suggesting the inhibitor specificity. Since caffeine is a specific blocker of Ca2 transport to the terminal cisterns of the skeletal muscle sarcoplasmic reticulum, it is assumed that the microsomal fraction of rat myocardium contains terminal cistern fragments.

[Effect of acidosis on Ca2+ binding by the sarcoplasmic reticulum and on relaxation of the cardiac muscle]. / Vliianie atsidoza na pogloshchenie Ca2+ sarkoplazmaticheskim retikulumom i rasslablenie serdechnoi myshtsy.

A value of Ca2+ binding in 1 second by sarcoplasmic reticulum fragments from guinea pig hearts increased proportionally to elevation of Ca2+ concentration from 0.1 to 3.0(-6) M at pH 7.2. Decline of pH to 6.8 and 6.2 decreased the Ca2+ bound in 1 second, but increased the Ca2+ bound in 30 seconds when membrane permeability has become a crucial factor in determining Ca2+ bound. In experiments on guinea pig papillary muscles, a decline of pH from 7.35 to 6.83 resulted in a nearly equal fall in velocities of isometric contraction and relaxation (27 and 21%, respectively), but during isotonic shortening when the relaxation proceeds much faster, a fall in relaxation velocity (44 +/- 3%) was significantly more profound as compared to the fall in contraction velocity (29 +/- 4%). This effect as well as a decrease in initial rate of Ca2+ binding by sarcoplasmic reticulum suggest a direct inhibitory effect of acidosis on Ca2+ removal from myofibrils in myocardial cells.

[Metabolism of rat brain nonhistone proteins following alteration of nervous system function and training]. / Obmen negistonovykh belkov golovnogo mozga krys pri izmenenii funktsii nervnoi sistemy i obuchenii.

Metabolism of total nonhistone nuclear proteins (NNP) of the rat brain was studied in three groups of animals: trained, pseudotrained and control. Protein synthesis and degradation were estimated by determining NNP specific radioactivity 1, 3, 6 and 9 weeks after the precursor, 14C-lysine, injection. The experimental results indicate that there are two fractions of NNP which differ in their metabolic rates. The half-life of the first "short-living" group of proteins is 5-10 days and that of the second "long-living" one is 18-21 days. It is shown that there is a significant difference in specific radioactivity and metabolic rate between the "short-living" fractions of NNP isolated from the brains of trained or pseudotrained rats, on the one hand, and control rats, on the other hand. Possible participation of the brain total nonhistone nuclear proteins in the mechanisms of alterations of the central nervous system function and learning is discussed.