[Analysis of ECG in ventricular fibrillation in man and animals based on chaos theory]. / Analiz EKG pri fibrilliatsii zheludochkov u cheloveka i zhivotnykh na osnove teorii khaosa.

The methods of the chaos theory were used to estimate the degree of irregularity of ventricular fibrillation in human and experimental animals. To verify the hypothesis that the degree of chaos depends on the species of the living organisms, the parameters characterizing the degrees of irregularity of ventricular fibrillation were estimated and compared. The comparative analysis was performed using 32 fragments of electrocardiographic records from five patients with sudden ventricular fibrillation bouts and 215 episodes of induced fibrillation in 17 animals. It was shown that fibrillation in human and animals has a different degree of regularity and different values of the chaotic component. The highest values of chaos were recorded in dogs, the lowest degree of chaos was observed in human. Rabbits and rats are intermediate, between dogs and humans. The fractuality of the structure-function organization of myocardium is discussed.

[Effect of emotional stress on the cardiac rhythm variability in rats]. / Vliianie émotsional'nogo stressa na variabel'nost' serdechnogo ritma u krys.

A degree of irregularities of the heart rhythm was studied by two methods: chaos-analysis and the HRV (heart rate variability) analysis. Our study shows an individual response in 3 groups of animals: 1--animals with low initial level of chaos (correlation dimension (PD2 < 2); 2--animals with high level of chaos (PD2 > 4); and animals with middle level of chaos (2 < PD2 < 4). The first two groups proved to be more sensitive to stress than the third group. Moreover we found that the electrical stability of the heart as measured by the fibrillation threshold, was higher for the chaos third group. The animals of the first two groups had low cardiac stability and high risk of stress-induced cardiac disturbances.

[Nitrogen monoxide in the mechanisms of cardiovascular functional resistance to emotional stress]. / Monooksid azota v mekhanizmakh ustoichivosti serdechno-sosudistykh funktsii pri émotsional'nom stresse.

The paper presents the results of examination of the mechanisms of development of different physiological dysfunctions (diminished cardiac electrical stability, fibrillation threshold fall) under emotional stress. Search was made for their drug correction (nitric oxide precursor L-arginine, the NO synthase blocker Ng-methyl-L-arginine and sodium nitrate). Experiments have indicated that L-arginine and sodium nitrate restore cardiac electrical stability. The normalizing effects of NO donors depended on the stage of cardiac disorders.

[Delta sleep-inducing peptide as a modulator of mediators acting on the heart]. / Peptid del'ta-sna kak moduliator deistviia mediatorov na serdtse.

Experiments on 51 isolated rabbit hearts have documented, that delta sleep-inducing peptide (6 X 10(-6) M/l) has a modulating effect on the mediators influencing the heart. This peptide enhances negative chronotropic effect of acetylcholine (1 X 10(-6) M/l) and decreases positive chronotropic effect of noradrenaline (1 X 10(-6) M/l). Such effect may be one of mechanisms of changes in the extracardiac regulation on the heart influenced by this peptide.

[Parasympathetic regulation of cardiac rhythm in delta sleep-inducing peptide deficiency]. / Parasimpaticheskaia reguliatsiia serdechnogo ritma v usloviiakh defitsita peptida del'ta-sna v organizme.

The effect of delta-sleep peptide (DSP) deficiency on the parasympathetic regulation of the heart rate was studied on 35 rabbits. It was established that the injection of an-serum (titer-1:2000-1:3000) leads to the attenuation of parasympathetic influences: heart rate increase in freely behaving animals and a decrease in negative chronotropic effect with direct vagus irritation. Antiserum, like DSP, administration causes practically no damage of the myocardial ultrastructure.

[Mechanisms of the development of the terminal state in experimental emotional stress]. / O mekhanizmakh razvitiia terminal'nogo sostoianiia pri eksperimental'nom emotsional'nom stresse.

The development of ventricular fibrillation associated with experimental emotional stress was studied in chronic rabbit experiments. Changes in myocardial-fibre action potentials, thresholds for ventricular fibrillation and its precursors, blood and myocardial catecholamine levels and heart-muscle ultrastructure were examined. Emotional stress was shown to increase, via sympathoadrenal activation, functional and structural heterogeneity of the myocardium, leading, alongside other causes, to arrhythmias and death from ventricular fibrillation. Moderately prevailing parasympathetic effects on the heart during stress exposure contribute to the elevation of fibrillation and fibrillation precursor thresholds and prevent catecholamine rise and myocardial structural damage.

[Effect of the delta-sleep peptide on parasympathetic regulation of the cardiac rhythm]. / Vliianie peptida del'ta-sna na parasimpaticheskuiu reguliatsiiu serdechnogo ritma.

Effect of delta-sleep peptide (60 nM/kg) on the parasympathetic regulation of cardiac activity has been studied in the experiments on rabbits. It has been established that intravenous administration of this peptide to voluntary-behaving animals results in heart rate reduction by an average of 16%, that can be eliminated by atropine. Delta-sleep peptide has been demonstrated to intensify negative chronotropic effect in the case of directly irritated wandering nerve. The data obtained explain a protective effect of delta-sleep peptide on the heart under emotional stress.

[Spread of excitation through the heart upon electrical stimulation of the atrioventricular valves]. / Rasprostranenie vozbuzhdeniia v serdtse pri élektricheskoi stimuliatsii atrioventrikuliarnykh klapanov.

Experiments were conducted on the isolated hearts of rabbits and dogs. Synchronous recording of the electrical activity of the right auricle, the right ventricle, and tricuspid valve demonstrated the existence of definite functional associations between the auricular, ventricular and valvular depolarization. The spread of excitation in the heart in electrical stimulation of the atrio-ventricular valves was investigated. The impulses from the heterotopic excitation focus localized in these valves could be conducted to the other parts of the heart and thus lead to cardiac arrhythmias.

[Automatic activity of the pacemaker cells of the atrioventricular valves under the action of parasympathetic and sympathetic mediators]. / Avtomaticheskaia aktivnost' peismekernykh kletok atrio-ventrikuliarnyhk klapanov pri deistvii parasimpaticheskogo i simpaticheskikh mediatorov.

Effects of neorpinephrine, epinephrine, and acetylcholine 4.5.10(-7) M--2.9.10(-6)M on the automatic activity of the pace-maker cells of the rabbit atrioventricular valves were studied. The sympathetic mediators accelerated spontaneous beating by increasing the rate of slow diastolic depolarization or by the inducing additional subthreshold potentials converted in action potentials. Acetylcholine (1.1.10(-6)M) reduced the rate of the spontaneous beating and in concentrations 2.7.10(-6)M eliminated automatic activity either by suppression of AP when subthreshold potentials gradually disappeared or by gradual decrement of AP rate and amplitude. Simultaneous application of equal doses of acetylcholine and sympathetic mediators revealed a predominant effect of acetylcholine as well as intensification of the acetylcholine effect under the influence of sympathetic mediators. Sympathetic-parasympathetic interactions can be explained by their influence on permeability of membrane of the pace-maker cells through the slow Na-Ca channel.

[Morphofunctional characteristics of pacemaker formations situated in the atrioventricular valves of the heart]. / Morfofunktsional'naia kharakteristika peismekernykh obrazovanii, raspolozhennykh v atrioventrikuliarnykh klapanakh serdtsa.

By the microelectrode technique and the method of electron microscopy multicellular formations responsible for generation of the automatic pacemaker activity were found in the cusps of the atrioventricular valves in the rabbit heart. Cells of different morphological structure were revealed: P-cells, cells of the Purkinje type and transitional cells. These formations have rich innervation, mainly of cholinergic nature. A certain correlation was established between the morphological and electrophysiological characteristics of these cells.

[Automatic activity of pacemaker cells in the atrioventricular valves of the rabbit heart]. / Avtomaticheskaia aktivnost peimekernykh kletok atrio-ventrikuliarnykh klapanov serdtsa krolika

The microelectrode technique applied revealed an automatic activity of the pacemaker cells with slow diastolic depolarization in the cusps of the atrioventricular valves obtained from 34 rabbit hearts. Electrophysiological characteristics of the action potentials of these cells were investigated. Inhibitors of slow sodium-calcium canal (Mn++, Co++, and Mg++ ions) proved to eliminate the automatic activity of the pacemaker cells. When the content of potassium ions was elevated in the perfusion solution, no suppression occurred. It is suggested that the automatic activity of the pacemaker cells in the atrioventricular values depended mainly on the functioning of the slow sodium-calcium canal.