[The function of the heart changes in implementation of the diving reactions in humans].

The changes of chronotropic function of the heart and of the myocardium in the implementation of the diving response in humans were studied by the electrocardiographic method. The study involved 80 students aged 18-20 years. Diving simulation was performed by immersing the face in cold water during breath-hold exhale. When the water temperature was 12.3 +/- 2.3 degrees C, average duration of apnea was 31 +/- 11 s. The oxygen content in the exhaled air after apnea was 98.8 +/- 8.7 mm Hg, carbon dioxide--49.1 +/- 3.5 mm Hg. It was observed slowing of the heart rate, mainly due to the increasing of diastole in 41 of the 80 surveyed during simulating diving. But it also can be observed symptoms of conduction deterioration: atrioventricular block type I (22% of reactive type and 29% of the highly reactive type subjects), and exceeds standards QTc-interval prolongation (at 7.5% of the subjects). These responses are adaptive in nature and disappear in the recovery process. But the fact abnormalities of conduction in the myocardium must be considered when using the diving reflex in medical practice, as may be due to a predisposition to a certain pathology of the cardiovascular system.

[Effect of exhaustive weightlifting exercise on EMG, biochemical markers of muscle damage and performance capacity in young male subjects].

The aim of this study was to examine the effect of exhaustive weightlifting exercise on electrical and biochemical variables and performance capacity in young male subjects. The onset of exercise (80-50% 1RM) was associated with a decrease in the amount of work performed, which was followed by a steady performance capacity at 40-10% 1RM. There were no significant changes of m. rectus femoris EMG maximal amplitude though it tended to be increased during the first half of exercise. A significant blood lactate concentration increase indicated that an anaerobic metabolism was a predominant mechanism of muscle contraction energy-supply. CK level in blood plasma did not change but plasma myoglobin concentration doubled immediately post-exercise. The data presented here suggest that decrease in performance capacity was likely due to progressive "refusal of work" of the fast motor units and work prolongation of weaker, intermediate and slow motor units. Unchangeable CK activity and relatively small increase in myoglobin concentration in plasma suggest that used weightlifting exercise did not induced substantial damage in myocytes' membranes in our subjects.

[Changes of cerebral blood flow during diving reactions in humans].

The characteristics of human cerebral blood flow were estimated during the implementation of the diving response, simulated by complex cold-hypoxic-hypercapnic exposure (CHHE), and under the influence of separate cold, hypercapnic and hypoxic stimuli. Was studied 18 people aged 18-22 years who had no special training. Cerebral blood flow was recorded by transcranial Doppler. It is shown that in the CHHE with the respect initial state to observe a marked increase in cerebral blood flow linear velocity (BFV) to 82.3 ± 15.2%, as well as reducing characterizing the tone of resistance vessels of the brain pulsatility index (PI) to 77.2 ± 13.1%. During cold and tactile stimulation of facial skin BFV and PI did not change significantly, with a single breath hold (Genchi test) BFV increased by 52.3 ± 12.5%, PI at 64.5 ± 15%. The latent period of cerebral blood flow (14-43) allow suppose metabolic (chemical) nature of regulatory influences, which provide changes of considered indicators.

[Acute and remote biochemical and physiological effects of exhaustive weightlifting exercise].

The goal of the work was a study of exhaustive weightlifting exercise effect on prolonged changes in physiological and biochemical variables characterized functional status of skeletal muscles. An exercise gave rise to significant blood lactate concentration increase that was indicative of an anaerobic metabolism to be a predominant mechanism of muscle contraction energy supply. A reduction of m. rectus femoris EMG activity (amplitude and frequency), tonus of tension and an increase in tonus of relaxation were found immediately after exercise. Both EMG amplitude and frequency were increased 1 day post-exercise. However, after 3 days of recovery, EMG amplitude and frequency were decreased again and, in parallel, blood serum creatine kinase (CK) activity was significantly increased. After 9 recovery days, all measured variables with the exception of CK were normalized. A significant reverse correlation was found between blood serum lactate concentration and m. rectus femoris EMG activity at the same time points. Blood serum CK activity and m. rectus femoris EMG and tonus variables were observed to be significantly reversely correlated on the 3rd post-exercise day. Presented data demonstrate that exhaustive exercise-induced muscle injury resulted in phase alterations in electrical activity and tonus which correlated with lactate concentration and CK activity in blood serum.

[Dynamics of parameters of energy metabolism at adaptation to diving in human].

Studies of the diving reaction in the comparative-evolutionary aspect have shown that a complex of reactions providing the oxygen-saving effect during diving is inherent in human like in the secondary-aquatic mammals. This is confirmed by results of study of peculiarities of energy metabolism during imitation of diving (hold-up of respiration with immersion of face into the cold water--the cold-hypoxic-hypercapnic action) (CHHA). Data of gas analysis have shown that during the diving imitation the oxygen consumption rate is statistically significantly lower than during the usual hold-up of respiration (Genche's test). As shown by the study, this is due to the greater degree to vasoconstriction of peripheral vessels and selective redistribution of blood flow than to slowing down of the blood flow caused by reflex bradycardia during diving. It has been revealed that under effect of adaptation to CHHA, on the background of a decrease of the total energy consumption by the organism there occurs some increase of contribution of aerobic processes to its energy provision. Adaptation to CHHA has been shown to be accompanied by a decrease of reactivity of the parasympathetic chain of regulation of the heart chronotropic function and by an increase of duration of apnea. The duration of apnea is directly correlated with level of insulin--the hormone stimulating the anaerobic pathway of energy provision. Under effect of adaptation to CHHA there has been established an increase of the organism resistance to stress actions, which is confirmed by the lower levels of cortisol and thyroid hormones in representatives of the experimental group as compared with the control one.

[Psychosomatic factors of resistance to hypoxia]. / Psikhosomaticheskie faktory gipoksicheskoi ustoichivosti.

During formation of human long-term adaptation to cold-hypoxic influence, the some dynamics of psychological mechanisms contribution was revealed. On the first step of adaptation process, emotional-volitional personal peculiarities are significantly contributing; on further steps, communicability and general learning abilities are gaining importance. Anxiety, tenseness, diffidence and too strong self-control limit the hypoxic resistance far before restriction of physiological markers of the organism's functional abilities. Adaptation to cold-hypoxic effect contributing to organism stress-limiting system is believed to help experiencing extreme somatic and psychic loads by the people from psychological risk group.

[Characteristics of the human cardiovascular system in the human diving response]. / Ob osobennostiakh serdechno-sosudistoi sistemy pri nyriatel'noi reaktsii u cheloveka.

Comparative-evolutional research of diving response showed that mechanisms of its expression had much in common in humans and in animals. Firstly, it involves a reflex bradycardia, vasoconstriction of peripheral vessels, and blood flow centralization. But, unlike animals whose diving response has some typical species peculiarities, human diving response is rather diverse. Four types of cardiovascular system response to face submersion were revealed: over-reactive, reactive, paradoxical, and nonreactive. These types were chosen according to the bradycardia character. It is also supposed that the occurrence of individual maximal R--R-interval, while serving as a signal to apnea stopping, is among the reasons of apnea activity limitation.

[New methods of evaluation of the human-operator reliability]. / Novye sposoby otsenki nadezhnosti cheloveka-operatora.

New methods to evaluate the human operator reliability were tested with participation of 27 students of the Air Traffic Control Faculty at the Civil Aviation Academy. One of the proposed criteria is reactivity of the sympathetic cardiovascular regulation as determined during a cold hypoxic-hypercapnic exposure. By this criterion, the subjects divided into a reactive and a super-reactive group. Subjects of the "reactive " group demonstrated much better efficiency on a simulator, whereas subjects of the "super-reactive" group developed an inadequate sympathetic reaction to the rest-to-work transition revealed by a high activation of the parasympathetic component. Information perception was rated with the method of competing fields of vision aimed at evaluating the plasticity of the higher nervous system.

[Mechanisms of human adaptation to hypoxia]. / O mekhanizmakh adaptatsii cheloveka k gipoksicheskomu vozdeistviiu.

The effects of adaptation to cold-and-hypoxic exposure on the cardiovascular system, lipid peroxidation and concentrations of adaptogenesis involved hormones were studied in male students. The two weeks cold- and hypoxic training was shown to be accompanied by a significant increase of apnea duration, reduced velocity of bradycardia development and a more rapid ECG post-cold and- hypoxic exposure normalization, as well as by inhibition of activation of adrenal cortex and thyroid gland after stress of different nature. The changes of the character of influences between the indices under study, were demonstrated. The correlation analysis showed an increase of the human's adaptive potential and a decrease of its dependence on the adrenal cortex hormones.

[Levanase from Fusarium solani-68]. / O levanaze Fusarium solani 68.

Extracellular levanase was isolated from the culture of Fusarium solani-68 by ammonium sulfate precipitation at 0.8 saturation and purified in part by Sephadex G-150 gel chromatography. Levanase showed maximum activity at pH = 6.0 and t = 45 degrees C. The levanase reaction (hydrolysis of high molecular levane with a molecular weight of 1--5 min) reached a maximum rate at a polysaccharide concentration of 6.7 mg/ml, Michaelis constant being 1.5 X 10(-6) M. Levanase remained stable at pH 5.4--7.5 and temperature 40--45 degrees C.