Association of Serotonin Receptor Gene Polymorphisms with Regulatory and Adaptive Capacities of Medical Students.

Molecular genetic analysis of polymorphic variants of serotonin receptor genes (HTR2C and HTR2A) was performed in 89 healthy medical students and regulatory and adaptive capacities were determined by cardiorespiratory synchronism. The relationship of serotonin receptor gene polymorphisms and the regulatory and adaptive capabilities of the body were revealed. The highly active *G allele and *G/*G genotype of the serotonin receptor HTR2C gene and the heterozygous *A/*G genotype of the serotonin receptor HTR2A gene are associated with "good" regulatory and adaptive capacities. The low-active *C allele of the serotonin receptor HTR2C gene is associated with "low" regulatory and adaptive capacities.

Mathematical description of human body constitution and fatness.

Using mathematical modeling of human body, we demonstrated logical drawbacks of body mass index (BMI1 = M/H(2); A. Quetelet, 1832) and proposed more precise body mass index (BMI2 = M/H(3)) as well as body constitution index (BCI = (M/H(3))(1/2)) and fatness index (FI = M/HC(2)), where M, H, and C are body weight, height, and wrist circumference of the individual.

[Resonance hypothesis of heart rate variability origin].

A hypothesis is advanced of the heart rate variability being subjected to beat-to-beat regulation of cardiac cycle duration in order to ensure the resonance interaction between respiratory and own fluctuation of the arterial system volume for minimization of power expenses of cardiorespiratory system. Myogenic, parasympathetic and sympathetic machanisms of heart rate variability are described.

[The sino-atrial node as an indicator of oscillatory processes in the cardiovascular system].

The spectrogram of heart rate in denervated (vagotomy + propranolol) and artificially ventilated cats always contains the true respiratory peak and 1-3 resonance ones pacing at intervals equivalent to frequency of breathing. Hypothermic decrease of heart rate periodically draws the splitting of respiratory peaks and generation of supplementary rate-dependent peaks reflecting the interference of heart and breathing rhythms. The functional base for detection of mentioned peaks is myogenic reaction of sino-atrial node to its extension by fluctuations of venous inflow.

[The spectrogram of heart rate in cats following burst stimulation of the vagus nerve].

Denervation of the heart (bilateral vagotomy and propranolol) in artificially ventilated cats didn't remove respiratory peaks on the spectrogram of heart rate, while burst stimulation of vagus nerve increased or decreased them several times by synchronization of the heart and vagus rhythms, which in its turn was observed under the bradycardia only. At the same time, the desynchronization of rhythms provoked severe sinus arrhythmia which had a distinct periodic character. Under these conditions, there were high non-respiratory peaks appearing at the spectrogram of the heart rate that indicated existence of two vagus chronotropic effects: a well known tonic one and special intracycle synchronizing effect correcting duration of every cardiac cycle.

Comparative assessment of conduction anesthesia produced by procaine, marcaine, richlocaine, and RU-353.

Conduction anesthesia of the vagus nerve produced by procaine (0.5%), marcaine (0.25%), richlocaine (0.5%), and imidazobenzoimidazole derivative RU-353 (0.25%) was compared in acute experiments on cats. RU-353 produced the most long-term local anesthesia (assessed by inhibition of cardiochronotropic effect of vagus nerve).

A method for evaluation of conduction anesthesia.

We propose a new method for evaluation of conduction anesthesia in animals: by the degree of prolongation of cardiac cycle during vagus nerve stimulation by solitary electric discharges synchronous to the dominant ECG wave, proximally from the site of anesthetic application on the nerve.

Structural analysis of heart rhythm spectrogram in narcotized cats.

Eight types of peaks were revealed in the cardiac rhythm spectrum during acute experiments on vagotomized cats. Some peaks had no physiological nature and resulted from specificity of ECG processing by Fourier analysis, while others reflected myogenic reaction of the sinoatrial node (length-dependence of automaticity) to changes in venous return caused by respiratory-induced and other variations of the blood flow in the cardiovascular system.

Atrial fibrillation: a new explanation of the old phenomenon.

We propose a new mechanism of atrial fibrillation basing on the results of 30 series of acute experiments on anesthetized cats. In brief, combination of two or more arrhythmogenic factors shortens the interval between the inward and outward ionic currents in cardiomyocytes to a critical value. Under these conditions repolarization of cardiomyocyte membrane reaches the excitation threshold before complete inactivation of the depolarizing currents. This inevitably results in autoexcitation of myocytes (or extrasystole), that in turn promotes repolarization. Once occurred, autoexcitation turns into self-triggering activity resembling tachyarrhythmia paroxysm.

Sympathetic modulation of vagal chronotropic and arrhythmogenic influences on the heart.

In acute experiments on cats, stimulation of the caudal cardiac nerve inhibited tonic and synchronizing components of the vagal chronotropic effects and suppressed arrhythmogenic effect of vagal stimulation. By contrast, stimulation of ansa subclavia potentiated the effects of vagal stimulation. A novel model of vagosympathetic interactions in the heart of mammals is proposed.

Peculiarities of cardiotropic effect of aconitine.

In experiments on anesthetized cats, aconitine produced direct arrhythmogenic and cardiotoxic effects on the myocardium combined with indirect cardiotropic effects mediated via activation of extracardial nerves. Aconitine demonstrated pronounced cholinolytic properties and blocked vagal arrhythmogenic effect.