Arina V. Tankanag

Wavelet phase coherence analysis of the skin blood flow oscillations in human

The wavelet phase coherence of oscillations in the peripheral blood flow of contralateral skin sites was studied in 20 healthy subjects. Skin perfusion was registered simultaneously on similar regions of the outer sides of the right and left forearms by the laser Doppler flowmetry technique. To estimate the reliability of the obtained wavelet phase coherence values we applied the comparative method using amplitude-adjusted Fourier transform surrogates. High median values (0.63 and 0.59) of the wavelet phase coherence were obtained for the frequency intervals of respiratory (0.145-0.6Hz) and cardiac (0.6-2Hz) rhythms in 18 and 20 participants, respectively. In all the 20 participants we detected high and reliable values (Ме=0.72) of the wavelet phase coherence for skin blood flow oscillations in the myogenic interval (0.052-0.145Hz). Additionally, we demonstrated high wavelet phase coherence in the neurogenic (0.021-0.052Hz) and endothelial (0.0095-0.021Hz) intervals in 8 and 7 participants, respectively. The corresponding medians of the reliable wavelet phase coherence values for these intervals were 0.74 and 0.82. The obtained results suggest that the microvascular blood flow possesses not only the local mechanisms of generating low-frequency blood flow oscillations, but also a central mechanism, which is likely to synchronize low-frequency oscillations throughout the whole cardiovascular system.

Age-related changes of skin blood flow during postocclusive reactive hyperemia in human

The objective was to study age‐related alterations in the time‐amplitude characteristics of the oscillatory components of peripheral blood flow in healthy humans during postocclusive reactive hyperemia.

To Break or to Brake Neuronal Network Accelerated by Ammonium Ions

Purpose The aim of present study was to investigate the effects of ammonium ions on in vitro neuronal network activity and to search alternative methods of acute ammonia neurotoxicity prevention. Methods Rat hippocampal neuronal and astrocytes co-cultures in vitro, fluorescent microscopy and perforated patch clamp were used to monitor the changes in intracellular Ca2+- and membrane potential produced by ammonium ions and various modulators in the cells implicated in neural networks. Results Low concentrations of NH4Cl (0.1–4 mM) produce short temporal effects on network activity. Application of 5–8 mM NH4Cl: invariably transforms diverse network firing regimen to identical burst patterns, characterized by substantial neuronal membrane depolarization at plateau phase of potential and high-amplitude Ca2+-oscillations; raises frequency and average for period of oscillations Ca2+-level in all cells implicated in network; results in the appearance of group of «run out» cells with high intracellular Ca2+ and steadily diminished amplitudes of oscillations; increases astrocyte Ca2+-signalling, characterized by the appearance of groups of cells with increased intracellular Ca2+-level and/or chaotic Ca2+-oscillations. Accelerated network activity may be suppressed by the blockade of NMDA or AMPA/kainate-receptors or by overactivation of AMPA/kainite-receptors. Ammonia still activate neuronal firing in the presence of GABA(A) receptors antagonist bicuculline, indicating that «disinhibition phenomenon» is not implicated in the mechanisms of networks acceleration. Network activity may also be slowed down by glycine, agonists of metabotropic inhibitory receptors, betaine, L-carnitine, L-arginine, etc. Conclusions Obtained results demonstrate that ammonium ions accelerate neuronal networks firing, implicating ionotropic glutamate receptors, having preserved the activities of group of inhibitory ionotropic and metabotropic receptors. This may mean, that ammonia neurotoxicity might be prevented by the activation of various inhibitory receptors (i.e. by the reinforcement of negative feedback control), instead of application of various enzyme inhibitors and receptor antagonists (breaking of neural, metabolic and signaling systems).

Age-related differences in the dynamics of the skin blood flow oscillations during postocclusive reactive hyperemia

Age-related changes in peripheral microcirculation were studied using laser Doppler flowmetry in 60 apparently healthy subjects. The response of microcirculation to short-term ischemia was studied using the occlusion test. Changes in the amplitude of the peripheral blood flow oscillations were determined using time-amplitude analysis based on continuous adaptive wavelet filtration. The oscillation amplitude in the frequency range of the heart rate was found to reach the maximum with a delay after the removal of the occlusion, whereas in the range of the respiratory rhythm, no delay was observed. The hyperemic response to short-term ischemia is assumed to develop under the predominant influence of the arterial-arteriolar component, whereas the dynamics of amplitude oscillations in the range of the respiratory rhythm is a result of the devastation of the venular component after removal of occlusion. In response to short-term ischemia, the maximum oscillation amplitudes of myogenic, neurogenic, and endothelial rhythms decreased with age, which demonstrates the restriction of the regulatory control of the peripheral blood flow by the corresponding systems.

Involvement of the sympatho-vagal balance in the formation of respiration-dependent oscillations in the human cardiovascular system

The effect of deep breathing controlled in both rate and amplitude on the heart rate variability (HRV) and respiration-dependent blood flow oscillations was studied in the forearm and finger-pad skin of healthy 18- to 25-year-old volunteers. In order to reveal the effects of the divisions of the autonomic nervous system on the amplitudes of respiratory sinus arrhythmia (RSA) and skin blood flow oscillations, we studied the indices of the cardiovascular system in two groups of subjects with respectively lower and higher values of the sympatho-vagal balance. This index was calculated as a ratio of low frequency and high frequency HRV spectral power (LF/HF) under the conditions of spontaneous breathing. It was found that, in subjects with a predominant parasympathetic tone, the amplitudes of RSA and the rate of blood flow in the finger-pad skin were higher compared to subjects with a predominant sympathetic tone during respiration with the frequency lower than 4 cycle/min. In the forearm skin, where sympathetic innervation is weaker compared to the finger-pad skin, there were no significant differences in respiration-dependent oscillations of the rate of blood flow in two groups of subjects.

Role of additive stochastic modulation of the heart activity in the formation of 0.1-Hz blood flow oscillations in the human cardiovascular system

In the framework of our previous hypothesis about the participation of structural and hydrodynamic properties of the vascular bed in the formation of the 0.1-Hz component of blood flow oscillations in the human cardiovascular system and on the basis of the reduced hydrodynamic model, the role of additive stochastic perturbations of the operation of the single-chamber pump that simulates the heart was investigated. It was shown that aperiodic noise modulation of the rigidity of the walls of the pump or its valves generates low-frequency oscillations of pressure and blood flow velocity of arterial vascular bed with the maximum amplitude at a frequency close to 0.1 Hz.

THE IN VITRO ASSESSMENT OF POTENTIAL GENOTOXICITY OF HIGH POWER MICROWAVE PULSES

Till the present time, the potential genotoxicity of high power microwave pulses (HPMP) is not clear. Using the alkaline single cell gel electrophoresis assay, known as the alkaline comet assay, we studied the effects of HPMP (8.8 GHz, 180 ns pulse width, peak power 65 kW, repetition rate 50 Hz) on DNA of erythrocytes of Xenopus laevis frog, human whole-blood leukocytes and isolated human lymphocytes. The cell suspensions were exposed to HPMP for 40 min in a rectangular waveguide. To determine the temperature changes in the cell suspension produced by HPMP exposure, we provided an accurate dosimetry of HPMP under our exposure conditions. The

Anesthesia effects on the low frequency blood flow oscillations in mouse skin

When laboratory animals are used one needs to anesthetize them before recording. However, the influence of anesthesia on animal blood flow oscillations has not been studied. The effects of two ways of anesthesia, zoletil‐xylazine, and zoletil‐nitrous oxide mixtures, on mouse skin perfusion using laser Doppler flowmetry (LDF) technique were studied.

A Study of the Oscillatory Components of the Skin Microhemodynamics in Mice by Laser Doppler Flowmetry

A skin blood flow was studied by laser doppler flowmetry. Fourteen male BALB/c mice were used. The skin blood flow was registered in the left hind paw. To measure the skin microhemodynamics, we proposed a protocol of animal immobilization with two types of anesthesia, injection with zoletil and inhalation with nitrous oxide. The borders of low-frequency intervals of oscillations of the microhemodynamics in mice have been determined; they coincided with those for humans and rats that were determined earlier.

Phase synchronization of oscillations in cardiovascular and respiratory systems in humans

Phase synchronization between blood flow oscillations of left and right forearm skin sites, heart rate variability (HRV) and breath rate were studied from healthy volunteers at rest. The degree of synchronization between the phases of the analyzed signals was estimated from the value of the wavelet phase coherence. High medians of values of phase wavelet coherence function were obtained for the endothelial, neurogenic, myogenic and cardiac intervals. Significant phase synchronization were demonstrated between HRV and skin blood flow oscillations in both left and right forearms in a wide frequency range from 0.04 to 0.4 Hz. Six participants exhibited low phase synchronization (< 0.5) between the breath rate and HRV, while nine participants had high phase synchronization (> 0.5). This distribution was not affected by the sex or sympathovagal status of volunteers. Participants with low phase synchronization between breath rate and HRV featured low phase synchronization (< 0.5) between breath rate and blood flow oscillations in both forearms. Contrariwise, in subjects with high phase synchronization between respiratory rhythm and HRV both low and high phase synchronization between breath rate and blood flow oscillations in both forearms was observed. The results obtained allow us to suggest that the organism possesses a mechanism mediating the synchronization of blood flow oscillations in the skin microvasculature with all other periodical processes across the cardiovascular system, in particular, with HRV and breath rate over a wide frequency range.