[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.

[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.

[Myocardial electrogenesis in laboratory rats under conditions of acute nitrite intoxication].

In anesthetized male rats the arterial blood pressure in femoral artery and electrocardiogram in standard leads were recorded uninterruptedly for 1-1.5 h under conditions of acute nitrite intoxication produced by a subcutaneous injection of water solution of sodium nitrite (donor of nitric oxide) at concentrations of 10, 30, and 50 mg/kg body mass. Results of the study have shown dose-dependent changes of arterial pressure as well as of time and amplitude characteristics of electrocardiogram under effect of NaNO2. At the threshold hypoxic dose, an increase of amplitude of R and S waves was observed by the 30-45th min, while at the maximal NaNO2 dose, amplitude of all waves rose by the 15th min of intoxication. High nitric doses often caused an increase of the ST segment above the isoelectric line and a rise of the amplitude of the T wave, on which a notch appeared in some cases. The change of the ECG time parameters was expressed in the dose-dependent development of bradycardia for the first 4-7 min; its level correlated with the progressively decreasing arterial pressure in the beginning (the 2-4th min) of nitrite intoxication. Variation analysis of heart rate spectral characteristics by Baevskii has revealed a rise of the total spectral power of pulse oscillations. Under effect of nitrite, in the spectrum of cardiointervals, quent recovery of the normal ECG spectrum in the end of the experimental period. The maximal nitrite dose produced more pronounced shifts of the heart rate spectrum towards the LF and VLF diapasons that were not restored for 1 h of experiment. Transitory processes of readjustment of the cardiac rhythm had discrete character. The nitrite dose of 50 mg/kg body mass increased the RR-interval after 4-7 min with amplitude steps of 3-5 imp/s and the time constant of 20-40 s. The revealed ECG changes had the reflex (enhancement of parasympathetic tonus) and metabolic (the hypoxic and histotoxic damage of myocardium) nature.

[Effect of nitrite-induced methemoglobinemia on the kinetics of blood deoxygenation].

Kinetics of blood deoxygenation was studied during acute hypoxia induced by subcutaneous administration of sodium nitrite using polarographic method. Plasma oxygen tension remained unaltered as the dose of sodium nitrite increased, while the dynamics of oxygen release was dose-dependent. The constant of oxyhemoglobin deoxygenation rate proved to vary with blood deoxygenation. The nitrite-induced deceleration of oxyhemoglobin deoxygenation was due to the inactivation of a fraction of hemoglobin as well as to the increased hemoglobin oxygen affinity and possible changes in the oxygen permeability of erythrocyte membranes during acute methemoglobinemia.

[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.

[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.

[Activation of the antioxidant system as a factor in increasing the body resistance during combined adaptation]. / Aktivatsiia antioksidantnoi sistemy kak faktor povysheniia rezistentnosti organizma pri kombinirovannoi adaptatsii.

In semi-aquatic mammals (minks and muskrats) significant changes were found to occur in the leukocyte formula during adaptation to hypoxia, as compared with non-adapted rats and mice, although no increase in lipid peroxidation was found in any of their organs. This latter finding seems to be due to simultaneously enhanced activities of superoxide dismutase and catalase. In humans under professional stress, treatment with combined technology of adaptation: cold-and-hypoxic exposure, yields a positive therapeutic result accompanied by a decrease in lipid peroxidation and increase in superoxide dismutase and catalase activities in the blood. The data obtained suggest that the strategy of formation of protection against hypoxia and toxic free radical oxidation is common for the animals and humans.

[Cardiovascular system reactions and bioenergy metabolism in relation to adaptation to apnea]. / Reaktsii serdechno-sosudistoi sistemy i bioénergeticheskii metabolizm v sviazi s adaptatsiei k apnoé.

Responses of the cardio-vascular system and bioenergetic metabolism were studied in the heart tissue in apnoea in naturally adapted to diving musk-rats and unadapted rats and mice. A sharp bradycardia was shown to develop in former animals in arresting a breathing as well an increase in the neutrophils contents in the blood. The data obtained suggest that release of the necessary oxygen and antiradical defence functions can be related to the catalase activity.

[Adaptation to short-term acute hypoxia as a factor in enhancing resistance]. / Adaptatsiia k kratkovremennoi ostroi gipoksii kak faktor povysheniia rezistentnosti.

The responses of cortical neurons to multiple short-term hypoxic influences were studied in immobilised cats. ARs were recorded. To produce hypoxia, artificial respiration was switched off for a period of 3-5 min every 60-90 min. Cortical neurons, hypothalamus, cerebellum were shown to increase their tolerance to oxygen deficiency. There was a significant (P = 0.05) increase in the duration of background impulse activity at the 2nd and 3rd exposures to hypoxia. Metabolic rearrangements maintaining neuron electrogenesis, seem to be of great importance in this process.

[The action of amtizol and gutimin on the respiratory metabolism of the neuron]. / Deistvie amtizola i gutimina na dykhatel'nyi metabolizm neirona.

The effects of antihypoxants gutimine and amtisole on oxygen consumption by the intact nerve cell of the invertebrate and the activity of NADN-DH and SDH-dependent ways of oxidation in the cell were studied. Under normoxia gutimine inhibited the nerve cell respiration and decreased the activity of NADN-DN and SDH-dependent ways of oxidation by 15% and 5% respectively. Amtisole activated the neuron respiration increasing the activity of NADN-DH-dependent way of oxidation. Both antihypoxants, despite the fact that they refer to the same class of compounds, have different mechanisms of action on the neuron metabolism. Gutimine appears to be a pharmacological agent, protector, amtisole as an initiator of the active adaptative reorganization of the intracellular metabolism.

[The neuronal electrical activity of the cerebellar cortex in hypoxia]. / Elektricheskaia aktivnost' neironov kory mozzhechka pri gipoksii.

The dynamics of impulse activity of the cerebellar cortex neurons demonstrated in acute experiments on nembutal-anesthetized and diplacinum-immobilized cats bore evidence that the cerebellum participates in the organism's response to hypoxia. The Purkinje cells proved to be more resistant to hypoxia than the neurons of the neopallium, archipallium, and some other structures of the brain stem.

[Action of gutimine on the redox status of flavin and pyridine nucleotides in intact neurons]. / Deistvie gutimina na redoks-sostoianie flavinovykh i piridinovykh nukleotidov intaktnykh neironov.

Redox-reactions of flavine (FN) and pyridine (PN) nucleotides of the cell to guthimine were studied by the method of fluorescent microscopy without using any stains. The comparison was made of the kinetics of fluorescence intensity of FN and PN of the Retzius intact neuron under the action of guthimine, oxaloacetate, nembutal and succinate. It is suggested that guthimine may activate the switching of oxidative metabolism of the cell over to a more energitically profitable way.