[CORRELATIONS BETWEEN EEG AND RHEOGRAPHIC INDICES OF CEREBRAL BLOOD FLOW IN CHILDREN ON NORTH-EAST OF RUSSIA].

The purpose of the work was an estimation of correlations between EEG spectral parameters and rheoencephalogram (REG) indicators of cerebral blood flow (CBF) in the group of children of 7-18 years old living in the North-East of Russia. Well-known data were confirmed about age-dependent EEG and REG-CBF indicators dynamics. It was not revealed strong coordination between EEG and REG age-dependent changes in this period of life.

[Reflection of reserves of the brain energy mechanisms in cerebral blood flow dynamics in human under acute hypoxia].

Results of experimental researches of the cerebral blood flow (CBF) dynamics in human under acute hypoxia have been analyzed in the paper. It was found that changes of CBF under severe acute hypoxia are of nonlinear character and have several phases--the primary growth in the first minutes of hypoxia, relative stabilization and secondary growth. Secondary growth has no relation to changes of the hypoxemia level.

[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.

[Individual systemic reactions of human organism under acute hypoxia].

Results of physiological and biochemical study including analysis of brain electrical activity dynamics, volumetric and linear parameters of cerebral blood flow, plasma stress hormones levels (adrenaline, noradrenaline, cortisol) and energy metabolism markers (glucose, lactate) at different stages of acute normobaric hypoxia are presented. The correlations are shown between alterations of main cerebral arteries tone and resistivity type vessels, as well as between changes in linear and volumetric cerebral blood flow providing a compensation of the oxygen deficit. Features of EEG dynamics were investigated that characterized CNS regulatory functions and brain electrogenesis disturbance under deep stages of hypoxia.

[Nitric oxide metabolites level in human serum in acute normobaric hypoxia].

The influence of acute normobaric hypoxia on NO metabolites level of the blood serum in volunteers at respiration of hypoxic gas mixture containing 8 % of O2 during 25 min was investigated. Health status of participants and the hypoxia intensity were monitored with a complex of indexes: EEC, ECG, blood pressure, oxygen saturation of haemoglobin, cardiac output, gas composition of exhaled air. Cluster analysis (k-means clustering) conducted among volunteers that have successfully passed the test has shown presence of two groups differing in NO metabolites level during experiment.

[Changes of external respiration, brain circulation and the EEG in acute hypoxia in the subjects with different hypoxic resistance].

Two groups of individuals were distinguished in experiments with acute hypoxic action (respiration of oxygen-nitrogen mixture with 8 % oxygen content) - with low (LHR) and high (HHR) resistance to hypoxia. In subjects of the LR group, slowing down of the pulse rate and lowering of arterial pressure in the shoulder artery were observed on the 5th-10th minute of hypoxia. In the HHR subjects, primary growth of the pulse rate was followed by its stabilization; no significant changes of the arterial pressure were observed.

[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.

[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.

Cortical-subcortical interactions and the regulation of the functional state of the brain in acute hypoxia in humans.

The mechanisms regulating the functional state (FS) of the brain were studied in humans in conditions of dosed acute hypoxia (breathing a mixture of 8% oxygen in nitrogen for 15-25 min). The dynamics of the FS of the brain due to changes in the balance of the activities of brain regulatory structures in hypoxia were reflected in rearrangements of EEG spatial relationships (factor and cluster analysis of EEG crosscorrelation matrixes) and the redistribution of intracerebral locations of electrically equivalent dipole sources (EEDS), with increases in EEDS density in the projections of the medial and basal parts of the temporal lobes of the hemispheres (EEDS tomography data). Changes in cortical-subcortical interactions were characterized by a decrease in the tone of the activatory brain system, a decrease in the inhibitory control of subcortical structures by neocortical formations, and activation of limbic system and hypothalamic structures.

Interaction of hypocapnia, hypoxia, brain blood flow, and brain electrical activity in voluntary hyperventilation in humans.

Changes in various physiological measures in voluntary hyperventilation lasting three minutes or more in humans were studied and compared. Three-minute hyperventilation, in which the rate of external ventilation increased by an average factor of 4.5-5, produced similar phasic changes in central and brain hemodynamics.

[Cortical-subcortical interactions and the brain functional state regulation under acute hypoxia in man].

Regulation mechanisms of the brain functional state (FS) were studied in man during acute hypoxic conditions (inhalation of 8% O2 hypoxic air for 15-25 minutes). Changes in balance of the brain regulatory structures activities caused by hypoxia determine FS dynamics that is reflected in the reorganization of the EEG spatial interrelations (by data of factor and cluster analysis of EEG cross-correlation matrices), as well as translocation of intracerebral position of electrical equivalent dipole sources (EEDS) coupled with EEDS density rising in medial and basal regions of the cerebral hemisphere temporal lobes (by EEDS-tomography data). Alterations of the cortical-sub-cortical interactions show a decline in the brain activating system tone, a decrease in the neocortical inhibitory control of subcortical processes, and activation of structures of limbic and hypothalamic regions.

[Individual specifics of oxygen consumption by the human organism in hypoxia].

Influence of hypoxia on a human organism was studied with the help of hypoxic gas mixtures (HGM) in the first series with 14 % content of oxygen in nitrogen (n = 6), in the second one--with 12 % (n = 10) in the third one--with 8 % (n = 14). Hypoxic exposition in all the series was 25 min. In 6 subjects engaged in all the 3 series, physical working capacity was assessed in two-step test on a veloergometer.

[Interrelations of hypocapnia, hypoxia, cerebral blood flow and electrical activity of the brain under voluntary hyperventilation in humans].

Changes of different physiological parameters in human caused by hyperventilation of 3-min and longer duration were investigated and correlated. It was found that during 3-min hyperventilation, resulting in 4.5-5 fold increase of the respiration velocity, similar phasing changes of the central and cerebral haemodynamics occurred.

Characteristics of the formation of systems activity in the brain and autonomic functions in children in conditions of the European North (discussion paper).

Results obtained from complex medical-physiological investigations performed during 10 scientific expeditions in the Arkhangel'sk Region in 2003-2005 are presented. The effects of climatological-geographic, biogeochemical, and social conditions of the conditions obtaining in the Far North region of Russia on sexual maturation, formation of the structural-functional organization of the brain, autonomic functions, and immunological and biochemical status of schoolchildren were studied using state-of-the-art neurophysiological methods (computerized electroencephalography, computerized rheoencephalography, computerized electric dipole origin tomography, etc.), psychophysiological and psychometric methods (assessment of the state of cognitive and memory functions, Wechsler intellectual scale), along with biochemical assay of monoamine oxidase (MAO, the key enzyme in adrenergic neurotransmitter metabolism) and the liver enzyme butyrylcholinesterase (BuChE) and physicochemical analysis of the levels of macroelements and trace elements in the body.

[Characteristics of the brain system activity and vegetative function formation in children under conditions of the European north (a problem study)].

Results of complex medical-physiological research performed during 10 scientific expeditions in Arkhangelsk region in 2003-2005 are presented. Influence of climatic-geographic, biogeochemical and social conditions of North-West region of Russia on sexual maturation, formation of the brain structural-functional organization, vegetative functions, immunological and biochemical status of schoolchildren was studied with the aid of modern neurophysiologic (computer electroencephalography, computer rheoencephalography, computed electric dipole origin tomography, etc.), psychophysiological and psychometric methods (evaluation of cognitive and mnestic functions, Vechsler 1Q estimation), biochemical assessment of monoamine oxidase and butyrylcholinesterase activity, physical-chemical analysis of macro- and microelements in the organism.

Interaction between changes in local and temporospatial spectral EEG characteristics during exposure of humans to hypoxia.

The temporospatial and local characteristics of the EEG were studied in healthy subjects during the respiration of a hypoxic oxygen-nitrogen gas mixture containing 8% oxygen. Analysis of the spectral power density, coherence, phase shift, similarity of dominant frequencies in the EEG in different leads was performed separately for epochs containing and not containing visually apparent patterns of EEG spatial synchronization. In addition, assessment of spectral measures took account of the fact of the dominance of the frequency being analyzed in the EEG spectrum of the corresponding lead.

Age-related characteristics of brain development in children living in the north.

The morphofunctional age-related development of the brain was studied in schoolchildren living in the difficult climatological-geographic and socioeconomic conditions of the north (Arkhangel'sk region). Of the 62 students in country middle schools, EEG amplitude-frequency, time, and spatial measures corresponded to age norms (European norms) in only 10 cases (16%). A further 26 children (53%) showed minor abnormalities in the form of an inadequate degree of organization of the temporospatial EEG pattern, mainly in the frontal and temporal lobes of the brain, with increases in the levels of the theta and delta rhythms, and the absence of any marked "functional nucleus" in the alpha rhythm.

[Relations of the EEG local and spatialtemporal spectral characteristics changes under hypoxia in humans].

Spatial temporal and local EEG characteristics were studied in healthy subjects during inhalation of hypoxic oxygen-nitrogen gas mixture with 8 % content of oxygen. Analysis of spectra power density, coherence, phase shift, similarity of dominant frequencies in the EEGs of different derivations was performed separately for the EEG epochs with and without visually detected patterns of spatial synchrony of the EEG. Apart from this, a fact of dominance of the frequency in the EEG spectra of corresponding derivation was taken into account when estimating spectral parameters.

[Special features of age development of the brain in children living in the north].

Special features of morphological functional age development of the brain in children living in difficult climatic-geographical and social-economical conditions of the North (Archangelsk region) were studied. It was found that among 62 examined pupils of middle country school only in 10 persons (16%) amplitude-frequency and temporal-spatial EEG parameters are in accordance with passport age (European standards). 38 pupils (61%) have insignificant deviations such as insufficient regularity of EEG spatial-temporal pattern in frontal and temporal parts of the brain, increased theta- and delta-rhythms, absence of distinct "functional nuclear" in alpha range.