[HR AND DURATION OF ECG ELEMENTS OF AN ADULT DURING PHYSICAL EXERCISES].

The degree of heart rate (HR) and of duration PP, PT and TP elements electrocardiogram (ECG) before and after physical exercises (PE) depends on their value in the control, in healthy young girls (n = 21), aged 18.1 ± 0.7 years, body weight 56.5 ± 4.0 kg. The 300 cardiocycles by ECG at II standard lead were registered. Рower of PE was 1 W/kg. The growth of the HR after PE at the time of depolarization and repolarization (PT interval) remains practically unchanged, whereas the duration of the isopotential state of the myocardium (segment TP) is revealed. The PP intervals of long duration are shortened by 60%, low duration - by 30 %. The variability of PP interval in control due to the variability of the TP segment, in the experience of the PT interval was found.

[Spectral parameters of heart rate variability in man under the acute normobaric hypoxia conditions].

Spectral parameters (SP) of heart rate variability (HRV) and a duration of cardiointervals (RR) in 14 healthy male volunteers at the age of 23-36 years under the influence of acute normobaric hypoxia by respiratory gas oxygen-nitrogen mixture (9% O2, 25 min) were studied. The 300 cardiocycles at each of six experimental time points by ECG at II standart lead were registered. The parameters before hypoxia were (M ± m): RR (s) 0.90 ± 0.03; SP powers (ms2) TP 13 553 ± 2789; VLF 3885 ± 902; LF 4724 ± 1062; HF 4945 ± 1165. All parameters were about 21-25% less as compared to background in the 5th min of hypoxia. The decreasing was about 17% (RR) and 34-38% (SP) in the 10th min of hypoxia. At the 20th min of hypoxia all parameters but RR were increased to the background level. At last after hypoxia in the 5th min parameters RR were at the background level, SP were to 1.5-2 times higher. In the 15th min all parameters returned to initial levels.

[Effects of acute normobaric hypoxia on free plasma amino acids metabolism in humans].

We demonstrated significant changes in levels of several plasma free amino acids--proline, hydroxyproline, glycine, and phenylalanine--in healthy volunteers in response to severe acute normobaric hypoxia (breathing nitrogen-oxygen mixture with 9% of O2). We assume that demonstrated an increase of free proline, hydroxyproline, and glycine in plasma in the 10th minute of hypoxia was caused by increased collagenolysis due to hypoxic activation of matrix metalloproteinases. Significantly increased levels of free phenylalanine in the 10th and 20th minutes of hypoxia were the consequences of autophagy activation. Our results suggest that acute severe normobaric hypoxia has specific effects on plasma free amino acids in healthy humans.

[Serum glucose level in acute severe hypoxia in human at rest].

Study of the effects of acute normobaric hypoxia was performed on a group of young healthy males (age 19-23, n = 10). Conditions of acute normobaric hypoxia were modeled by using oxygen-nitrogen mixture containing 8% of oxygen as a breath gas. That level of oxygen corresponds with its partial pressure at 7000 meters above sea level. A number of different analyses were conducted during experiment: levels of glucose, pyruvate, lactate in peripheral venous blood, hemoglobin, pH, hematocrit, partial pressures of 02 and CO2, hemoglobin saturation. It was shown that on 5th minute of hypoxia serum glucose level decreased significantly (p < 0.05). The average decrease was about 0.76 mmol/l in its maximum and lowest individual glucose levels were 4.0 mmol/l or higher. Serum glucose level returned to background values (assessed before the test) at 10th minute of experiment. In our opinion results of the study suggest that syncopal form of height hypoxia may be caused by the reasons other than hypoglycemia.

[Fatty acid of human plasma under the influence of acute strong normobaric hypoxia].

The influence of acute normobaric hypoxia on total pool of human plasma fatty acids was studied in experiment (respiration of hypoxic gas mixture containing 8% of O2, during 25 min). Health status of participants-volunteers and the hypoxia intensity were monitored with a complex of electrophysiological methods: EEC, ECG, measurement of blood pressure, SpO2, evaluation of cardiac output, gas analysis of exhaled air. Using gas chromatography we studied plasma fatty acids total profile (esterificated and non-esterificated) before hypoxia exposure, on 2nd, 5th, 10th, 20th minutes of acute hypoxia and on 5th and 15th minutes of recovery. It was shown that blood saturation value dropped to 52.1 +/- 7.1 % on 25th minute of hypoxia exposure. There were no statistically significant changes in concentrations of total fatty acids, saturated fatty acids, monounsaturated palmitoleic acid, polyunsaturated linoleic and linolenic acids. Significant (p < 0.05) decrease of concentration of oleic and arachidonic acids was displayed that persisted after 15 minutes of recovery period. It is possible to assume that these changes in unsaturated fatty acid concentration were caused by activation of free radical oxidation processes and production of oleic acid derivatives. The performed hypoxic test seemed to be sufficient in order to reveal hypoxia effects on metabolism of individual unsaturated fatty acids.

[Blood lactate dehydrogenase activity in newborn children].

Arterial and venous blood samples from babies' umbilical cord vessels before lung breath beginning were used to measure arterial-venous difference between lactate dehydrogenase activity, pH and oxygen blood saturation (sO2). Enzyme activity was 735.4 +/- 90.8 U/L in venous blood and 672.0 +/- 108.1 U/L in arterial one, pH 7.21 +/- 0.06 and 7.32 +/- 0.06, sO2 32.9 +/- 12.7 and 56.5 +/- 18.3%, respectively. Reverse correlation between enzyme activity, pH and sO2 was found.

[Interrelationships among cardiohaemodynamic parameters in human postnatal ontogenesis].

In one-day old humans and to 20 years of age, the stroke volume (SV) increases from 5.4 +/- 0.4 to 70 +/- 5 ml, the arterial systolic pressure (ASP)--from 60 +/- 5 to 120 +/- 10 mm Hg. Heart rate decreases to 70 +/- 4/min from 136 +/- 10/min at birth. The N coefficient as the SV/ASP ratio parameter grows from 0.1 in children to 0.6 by 20 years of age. The peripheral resistance in the arterial system scope from the left ventricle exit tract to the middle of the humeral artery amounts up to 76 mm Hg x ml(-1) x min(-1) in newborn infants and in adults it is reduced to 28. Reduction of post-load decreases 6-fold the total amount of the heart mechanical work of pumping the SV into the vascular system.

Temperature dependence of H+ transport across erythrocyte membrane of Rana temporaria grass frog in media containing Cl- and SO4(2-).

H+ transport across the erythrocyte membrane was studied in Rana temporaria grass frog. The temperature coefficients and activation energy of H+ transport were calculated in media containing Cl- and SO4(2-). Our results show that kinetic characteristics of H+ transport depend on function of band 3 protein in the erythrocyte membrane.

Relationship between H+ transfer through human erythrocyte membrane and temperature.

The parameters of thermal dependence of H+ transport into human erythrocytes in the presence of furosemide were measured. The relationship between these changes and function of band 3 protein of the erythrocyte membrane is discussed.

[Mechanical work of the left ventricle of the human heart]. / Mekhanicheskaia rabota levogo zheludochka serdtsa cheloveka.

By means of the echocardiographic techniques, morphometric and functional parameters of the heart left ventricle (HLV) were studied in male humans aged 20 to 23, in resting and under the effect of a physical load. The total ventricle work was found to be about 1 J, the relative one (per 100 g of the LV mass)--0.6 J. The total working power was found to be about 70 Watt, the relative one--about 40 Watt. The physical load resulted in increase of the LV mechanical work parameters due to the heart rate and systolic arterial pressure.