[Modification of the thiobarbituric method for determining sialic acids in biological material].

The authors have examined the possibility of replacing sodium arsenite with acetyl thiourea and of using butanol acidified with phosphoric acid in measuring sialic acids in biologic material. The results evidence a sufficient specificity, reproducibility, higher sensitivity and lower toxicity of the modification as compared to the routine technique, for this modification does not involve the use of highly toxic sodium arsenite and of highly volatile aggressive butanol/hydrochloric acid mixture.

[Role of sialic acid loss in the myocardium in depressing the contractile function of the heart muscle during stress].

Under conditions of stress a time-dependent decrease in content of sialic acids was found in adult rats; within 9 hrs of the animal immobilization the sialic acid content was decreased by 40% as compared with controls. At the same time, activities of trypsin and LDHI were increased in blood serum. The data obtained suggest that activation of proteases occurring during the stress led to increased hydrolysis of base components of glycocalyx and to impairment of the cardiomyocyte sarcolemma.

[Effect of emotional and pain stress on the contractile function of the hypertrophied heart muscle].

Rats with compensatory hypertrophy of the heart and control animals were subjected to emotional painful stress (EPS). It was established that EPS led to the lowering of the main indicators of the contractile function of an isolated papillary muscle and reduced the resistance of the function under study to excess/Na+ and H+ forcing out Ca2+ from the binding sites on the sarcolemma. Compensatory hypertrophy of the heart itself was accompanied by a reduction of the myocardial contractility but the increase of the concentration of Na+ and H+ in the perfusate led to a far greater depression of the contractile parameters than in the myocardium of the control animals.

[Effect of the age of animals on disorders of the contractile function of the heart muscle under stress].

During intensive growth of animals, the main parameters of myocardial contractility were reduced. Poststressor depression of the contraction of isolated papillary muscles was more marked in adult than in young animals. Thus, aging of animals was accompanied by reduced cardiac muscle contraction.

[Effect of emotional-pain stress on myocardial contraction in prolonged hypokinesia].

Prolonged restriction of rat mobility resulting in stoppage of the body and heart mass growth was accompanied by the increased contraction and relaxation velocity of isolated papillary muscles. Absolute values of the poststressor decrease in the main parameters of myocardial contractility in prolonged hypokinesia-exposed animals did not substantially differ from those in controls. The resultant functional significance of such a depression was less dangerous.