[Effect of the heart electric stimulation on repolarization of fish and amphibian ventricular myocardium].

By the method of synchronous multielectrode cartography (24-unipolar leads), distribution of durations and time of end of repolarization were studied on ventricular epicardium of pikes (Esox lucius) and frogs (Rana esculenta) and in ventricular intramural layers of toads (Bufo bufo) at the ectopic heart excitation. The time of arrival of the excitation wave and of the end of repolarization in each lead was determined from the minimum of time derivative of potential at the period of the QRS complex and by minimum of the T wave, respectively. It has been established that at the ventricle electrostimulation, alongside with deceleration and a change of sequence of the myocardium activation, there occurs redistribution of local repolarization durations: in areas of late activation the repolarization being longer than in zones of early activation (p < 0.05). At stimulation, the apicobasal gradient of repolarization is predominantly changed due to electrophysiological processes in the apical areas. In all studied species. at ectopical excitation of the heart ventricle the sequence of its repolarization repeats the depolarization sequence due to delay of activation (in fish) and redistribution of repolarization durations (in amphibians).

[Repolarization pattern of the ventricular myocardium in pikes].

The study aimed at investigation into the repolarization pattern in the myocardium of fish. Activation times, activation-recovery intervals and repolarization times were determined in the intramural layers of the heart ventricle in eight pikes with multiple plunge electrodes. In the heart ventricle of the pike, the earliest end of repolarization was found in the subendocardium of the base and the subepicardium of the apex, the areas corresponding to the earliest and latest depolarization, respectively. The latest repolarization was observation on the anterior epicardial surface of the base. Endocardialto-epicardial repolarization sequence at the base corresponded to the activation sequence in this area with the transmural gradient of the end of repolarization times being 54 +/- 23 ms (p < 0.001). The transmural difference in activation-recovery interval durations and end of repolarization times decreased as one moved from the base to apex with the maximal apex-to-base end of repolarization gradient being 133 +/- 98 ms (p < 0.10).

[Cardiac electric field at the period of depolarization and repolarization of the frog heart ventricle].

Multichannel mapping of electrical field on heart ventricle epicardium and the body surface in frogs Rana esculenta and Rana temporaria was performed at periods of the ventricular myocardium depolarization and repolarization. The zone of the epicardium early depolarization is located on epicardium of the ventricle base posterior wall, while the late depolarization zone--on its apex and on the base anterior wall. The total vector of sequence of the ventricle epicardium depolarization is directed from the base to the apex. The zone of the early repolarization is located in the apical area, while that of the late one--in the area of the base. On the frog body surface the cardioelectric field with the cranial zone of negative and the caudal zone of positive potentials is formed before the appearance of the QRS complex on ECG. At the period of the heart ventricle repolarization the zone of the cardioelectric field negative potentials is located in the cranial, while that of the positive ones--in the body surface caudal parts. The cardioelectric field on the frog body surface at the periods of depolarization and repolarization of the ventricle myocardium reflects adequately the projection of sequence of involvement with excitation and of distribution of potentials on epicardium.

[Structure of the cardiac systole in mammals and birds].

The comparative analysis of the contractile function of the heart left ventricle in four species of homoeothermic tetrapods (chicken, quail, rat, sheep) who differ in their spatio-temporal pattern of ventricular excitation, heart rate, and heart weight was performed. The analysis of cardiac cycle structure was performed on the basis of synchronous recording of ECG, phonocardiogram, and apex cardiogram. Indices of myocardial contractility of the left ventricle calculated on the basis of the analysis of the cardiac dynamics indicate disadvantageous contractile function of the left ventricle in rodents and non-flying birds in comparison with sheep. The functioning of the left ventricle in male rats is more strained than in female rats. One fundamental factor determining a more strained functioning of the left ventricle in birds in comparison with mammals is the heart rate. The relative weight and activation pattern of the left ventricular myocardium govern the contractile function of the left ventricle to a lesser extent.

[Sequence of ventricular repolarization under body cooling in the frog].

Lowering the temperature is known to prolong the repolarization of cardiomyocytes. However, whether the prolongation of action potentials is uniform throughout the myocardium, and whether this prolongation is obvious in ECG, remains unclear. Ventricular repolarization sequences and body surface potential distributions were studied in 20 frogs Rana temporaria using epicardial and body surface potential mapping. An apex-to-base ventricular repolarization sequence corresponded to the distribution of local repolarization durations was demonstrated at the temperature of 18 degrees C. The body surface potential distribution during the ST-T complex was characterized by the cranial negative and caudal positive potential areas. Under the body cooling to 10 degrees C, repolarization prolonged to a greater extent at the apex that resulted in the base-to-apex repolarization sequence, which, in turn, caused an inversion in the body surface potential distribution with cranial portion of the body being positive and caudal portion being negative.

[Cardiac electric field on the epicardial and body surfaces during the period of depolarization and repolarization of ventricular myocardium in pikes].

Body surface and ventricular epicardial potential distributions during the electrocardiographic QRST interval were studied in pikes with the aid of potential mapping. The earliest epicardial activation was observed at the posterior base near the atrioventricular orifice. The areas of the earliest repolarization were found at the apex and the posterior base, whereas the area of the latest repolarization was detected at the anterior base. In the initial period of the QRS, the minimum was developed in the middle third of the right lateral body surface, and the maximum in the middle third of the ventral body surface. The body surface potential distribution during the ST-Twas characterized by the clear-cut negative potential zone in the cranial ventral area with the rest of the body surface having positive potentials, a pattern being largely unchanged throughout the period of the T-wave. The ventricular epicardial repolarization sequence differed from the activation sequence. The ventricular epicardial depolarization and repolarization sequences as well as epicardial potential distributions are expressed in the cardiac electric field on the body surface during the QRS and ST-T complexes.

[Correlation in the of the process of cardiac ventricle intramural depolarization and distribution of cardioelectric field potentials of the dog Canis familiaris].

Based on a multichannel synchronous mapping of heart electric potentials, the sequence in time of the ventricle myocardium depolarization was compared with dynamics of distribution of cardioelectric potentials on the body surface in a dog. The cardioelectric field on the dog body surface at the period of the initial ventricular activity has been shown to be characterized by the presence of two inversions of the mutual disposition of areas of positive and negative potentials. Contribution to formation of distribution of the cardioelectric potentials on the body surface at each moment of the period of initial ventricular activity was made by all myocardial layers involved by excitation.

[Effect of hypothermia on sequence of the ventricle epicardium repolarization in rabbits]. / Vliianie gipotermii na posledovatel'nost' repoliarizatsii épikarda zheludochkov krolika.

In anaesthetised rabbits at normal body temperature, the earliest ventricles' epicardial recovery occurs at the heart apex and adjacent left ventricle's surface whereas the latest one occurs at the epicardium of the right ventricle's base. A decrease in the mediastinum temperature to 32 degrees C reversed the recovery sequence. Following the cooling of the heart, the longest prolongation of the activation-recovery interval occurred at the heart apex area and the lowest one--at the right ventricle base.

[The acid-base properties of hemoglobin in the laboratory mouse after gamma irradiation]. / Kislotno-osnovnye svoistva gemoglobina laboratornoi myshi posle gamma-oblucheniia.

Direct and indirect gamma-irradiation of blood in laboratory mice was followed by acidic changes of hemoglobin measured by ionic equilibrium method.