[Electrolyte imbalance in the course of the postoperative period].

The article presents the results of an investigation aimed at the assessment of electrolyte balance in patients who underwent surgical treatment. The data demonstrate that in the patients from the control group there was increased blood concentration of Na+ during the preoperative period that remained in the course of the postoperative one. Hypernatriemia was associated with decreased level of K+. Besides, hyposalivation that was maximal on the days immediate after an operation and reduced Na+ excretion together with increased K+ excretion were revealed. On the postoperative day 3 and 5 the reduction of the amount of excreted K+ that did not reach baseline level was detected. In case of midazolam administration aimed at premedication and sedation minimal changes of electrolyte balance in the patients from the experimental group were noted. There was no significant increase of the secretion of K+ and its serum level was not reduced in the course of the preoperative and postoperative periods. At the same time moderate increase in Na+ secretion to the saliva associated with its normal serum concentration was detected.

[Effect of neutral muscle proteases on parameters of the contraction of isolated myocardial strips from albino rats during overload and during the period of readaptation]. / Deistvie neitral'nykh myshechnykh proteaz na parametry sokrashcheniia izolirovannoi poloski miokarda belykh krys pri peregruzkei v period readaptatsii.

The treatment of an isolated myocardial strip with Ca2+-activated neutral muscle proteases reduced the contraction amplitude and the relaxation rate of the myocardium by 21.0 +/- 1.7% and 25.0 +/- 1.6%, respectively, and the tension development rate--by 13.0 +/- 1.0%. In the animals exposed to +5 Gz (for 25 min daily during 15 days) the inhibitory effect of neutral proteases on the contractile function of an isolated myocardial strip increased from 23.0 +/- 1.7% to 34.0 +/- 4.3%. The initial sensitivity of the contraction apparatus to proteases did not return to the baseline after 30 days of readaptation.

[Cathepsin activity of skeletal muscle and myocardial myofibrils after exposure to weightlessness and G force]. / Katepsicheskaia aktivnost' miofibrill skeletnykh myshts i miokarda posle vozdeistviia nevesomosti i gravitatsionnoi peregruzki.

The rats flown on board Cosmos-605 and exposed to a synchronous experiment for 22 days showed an increased activity of myofibrillar cathepsins in skeletal muscles of different groups. In the flight rats the increase was greater than in the synchronous ground-based animals. This suggests a significant effect of weightlessness on the cathepsic activity. The parameter was partly normalized at R + 25 or 26. The exposure of rats to accelerations of 4 and 5 G for 20 min daily during 2 weeks also increased the cathepsic activity of skeletal and myocardial myofibers. The parameter returned to normal a month after completion of acceleration exposures. Thus, changes in the proteolytic activity of myofibers of different muscles induced by weightlessness and acceleration are reversible. The significance of changes in the muscle tension as related to the mechanism of stimulation of proteolytic reactions is discussed.

[Effect of simulated gravitational loading on chick embryo myocardium]. / Vliianie na miokard kurinogo émbriona modelirovannoi gravitatsionnoi peregruzki.

Daily centrifugation of 5--8-day embryos at 7 G for 20 min by means of a specially designed attachment to dlHP-1 decreased the amplitude and increased the rate of rhythmic activity of ventricular myocytes, the automatic activity of atrial pacemakers remaining unaltered. These changes were accompanied by a decrease of Ca2+-sensitivity of myocytes. Daily centrifugation of 11--20-day chick embryos led to myocardial hypertrophy and increase in the diameter of myocardiocytes as well as to decrease in the content of actin, troponin-T and the second light chain of myosin, increase in the content of tropomyosin and emergence of the third light chain of myosin in the electrophoregrams. It appears that the changes in the composition of protein subunits of the contractile system are induced by selective activation of proteolytic enzymes in the muscle tissue.

[1 of the molecular factors of development of compensatory myocardial hypertrophy]. / Ob odnom iz molekuliarnykh faktorov razvitiia kompensatornoi gipertrofii miokarda.

Using the method of tryptic digestion, the authors have found that myosin of a hypertrophied myocardium is characterized by a high resistance to proteolysis. At the final stage of compensatory hypertrophy of the myocardium an increased activity of the myofibril catherpsins is discovered. According to the authors, one of the important factors of the compensatory growth of myofibrils consists in the high resistance of the newly synthesized proteins to decay. In characterizing the subunit composition and kinetics of the tryptic decay the possibility of the synthesis of a new population of myosin in the process of compensatory hypertrophy has been postulated. This demonstrates the heterogeneity of the activation of the genetic segments that control the synthesis of protein myofibril subunites with due regard to the regimen ot the myocardium work.