The body surface potential mapping of the heart during the period of ventricular depolarization and the inotropic function of the ventricles were studied in rats under conditions of a translational model of post-infarction chronic heart failure developed by us. We revealed a statistically significant (p<0.001) correlation between the left-ventricular ejection fraction and the values of the maximum positive and negative extrema of the cardioelectric field on the body surface of rats with post-infarction chronic heart failure caused by anterior transmural myocardial infarction. The calculated linear regression equations have high predictive efficiency, which makes it possible to use the amplitude characteristics of the heart cardioelectric field as a marker of the development of chronic heart failure.

Cardiac remodeling in rats with post-infarction chronic heart failure caused by anterior transmural myocardial infarction leads to an atypical location of areas of positive and negative cardioelectric potentials on the body surface before the onset of the PII-wave on the ECG in the limb leads, which is a sign of increased heterogeneity of atrial depolarization associated with the appearance of additional excitation focus in the left atrium. A course of therapy with fabomotizole leads to a decrease in the heterogeneity of atrial depolarization at the initial stages of the formation of the cardioelectric field of the atria on the body surface before the onset of the PII-wave, thereby producing an antiarrhythmic effect.

Relevance. Alcoholic cardiomyopathy (ACMP) is the leading cause of mortality in chronic disease, which is largely associated with an increased risk of developing malignant diseases of the cardiovascular disease. Search for new drugs, including those exhibiting pronounced antiarrhythmic activity, supposed relevance. Objective. To study the effect of combination therapy with fabomotizole and ALM-802 on atrial depolarization in a translational model of alcoholic cardiomyopathy in rats. Methods. The sequence of depolarization of the atrial epicardium was studied in rats in a translational model of alcoholic cardiomyopathy, which received a combination of fabomotizole and compound ALM-802 daily for 28 days after the end of 24 weeks of alcoholization, or pyrogen-free water intraperitoneally. Results. As a result of the 28-day combined action of fabomotizole and the compound ALM-802 in animals with alcoholic cardiomyopathy, additional areas of early activation in the area of lacunae of the pulmonary veins that form during the 24-week period of alcoholization disappear, the risk of atrial arrhythmias is minimized, and sequential propagation.

In model experiments reproducing the holiday heart syndrome in rats, a discrepancy between the depolarization of the right and left atria has been revealed, which manifested by an atypical arrangement of positive and negative cardiopotentials in the cardioelectric field on the body surface during the P wave and the absence of inversion of the areas of cardioelectric potentials before the onset of P waves in lead II ECG from the limbs.

The similarity of porcine coronary circulation with humans [15], hemodynamic parameters [16] is suitable for using the porcine heart as an experimental model of cardiovascular diseases specific to humans. Pigs are a source of human valve bioprostheses [12]. Studies of pigs as donors for xenotransplantation have shown that it is impossible to unequivocally consider the heart of a pig to be identical to a human heart. The topography of the conducting system of the pig leads to significant differences in the sequence of depolarization of the heart ventricles, which must be taken into account when conducting electrocardiographic studies [3, 4].The aim of the study was to study the amplitude-temporal characteristics of the ECG in a normal pig. ECG in pigs was recorded in sagittal bipolar trunk leads according to Roshchevsky [7]. Animals were anesthetized with 1% solution of ventranquil (0,02 ml/kg), urethane (1,5 g/kg) intramuscularly. Heart rate in anesthetized pigs varied from 74 to 194 beats/min, the animals were divided into three groups. In the first group, animals with heart rate less than 100 beats/min, in the second from 100 to 150 beats/min, in the third more than 150 beats/min.In the course of the study, it was shown that in bipolar sagittal leads, the P-wave is positive single-phase; the most common configuration of the initial ventricular activity complex is rS; The T-wave is mostly positive. In animals from groups with significant differences in heart rate on the ECG in three bipolar sagittal leads, the shape and duration of the Q, R, S waves did not differ, the duration of the PQ and QT intervals differed significantly. The duration of the corrected QTc interval in animals with different heart rates practically did not differ.

Resumo Fundamento O exercício físico exaustivo pode causar alterações significantes nas propriedades elétricas do miocárdio. Objetivo Avaliar, através do mapeamento potencial de superfície corporal, a atividade elétrica do coração de ratos durante a despolarização ventricular após exercício exaustivo agudo. Métodos Ratos machos com doze semanas de idade foram submetidos a exercício agudo em esteira a 36 m/min até a exaustão. Eletrocardiogramas unipolares (ECGs) da superfície do tronco foram registrados em ratos anestesiados com zoletil três a cinco dias antes (Pré-Ex), 5 e 10 minutos após exercício exaustivo (Pós-Ex 5 e Pós-Ex 10, respectivamente) simultaneamente com ECGs nas derivações dos membros. Os mapas potenciais de superfície corporal instantâneos (BSPMs, body surface potential maps ) foram analisados durante a despolarização ventricular. Os valores de p <0,05 foram considerados estatisticamente significantes. Resultados Comparado com o Pré-Ex, uma conclusão precoce da segunda inversão de distribuições de potencial, uma conclusão precoce da despolarização ventricular, bem como uma diminuição na duração da fase média e a duração total da despolarização ventricular nos BSPMs foram reveladas no Pós-Ex5. Além disso, em comparação com o Pré-Ex, um aumento na amplitude do extremo negativo do BSPM no pico da onda R no ECG na derivação II (pico RII) e uma diminuição na amplitude do extremo negativo do BSPM a 3 e 4 ms após o pico RII foram demonstrados no Pós-Ex 5. No Pós-Ex 10, os parâmetros dos BSPMs não diferiram daqueles do Pré-Ex. Conclusão Em ratos, o exercício exaustivo agudo causa alterações reversíveis nas características temporais e de amplitude dos BSPMs durante a despolarização ventricular, provavelmente relacionadas a alterações na excitação da massa principal do miocárdio ventricular.

The article is focused on the evaluation of the electrical activity of the heart in rats during ventricular repolarization after a single bout of forced treadmill running until exhaustion. Electrophysiological properties of the myocardium were studied by conventional ECG and body surface potential mapping. Cardiac potentials were registered in zoletil-anesthetized rats 3–5 days before (baseline) and 5, 10, 20 and 30 min after exhaustive treadmill running. Compared with baseline, an increase in the duration of the QT II , JT II and Tpeak–Tend II intervals, an earlier onset and a later completion, as well as an increase in the duration of ventricular repolarization on body surface equipotential maps (BSPMs) were revealed in rats 5 min after exhaustive exercise. Ten min following treadmill running to exhaustion, the temporal parameters of the heart electrical activity returned to pre-exercise values. Changes in the amplitude characteristics of both ECG II (ST segment depression, a decrease in the T-wave amplitude) and BSPMs (a decrease in the maximum amplitudes of positive and negative extrema during ventricular repolarization) were showed after 5–10 min and persisted up to 20–30 min after running to exhaustion. A positive correlation was found between changes in the maximum amplitude of negative extremum of BSPMs and changes in the amplitude of the T II -wave in the analyzed time periods after exhausting exercise. It is assumed that the observed changes in the electrical properties of the heart in rats during ventricular repolarization after forced treadmill running were due to ischemic myocardial damage induced by exhaustive physical exercise.

Changes in lung bioelectric impedance were revealed in male Wistar rats exposed chronically to doxorubicin. Bioimpedance measurements were performed in rats two months after the first injection of doxorubicin (a cumulative dose of 10 mg/kg divided into 4 injections for 4 weeks) or saline. Bioimpedance was analysed at multiple frequencies (10, 30, 70 and 150 kHz) of electric current. Electrodes were placed on the surface of the lung. Significantly lower absolute values of the reactance and phase angle of bioelectrical impedance of the myocardium, liver (noted by us earlier) and lung in rats treated with doxorubicin compared with control animals indicated toxic damage to organs. Significantly higher amplitude (at a frequency of 70 kHz) of bioelectrical impedance of the rat’s lung may be associated with emphysematous changes and inflammation in the lung in the group with chronic exposure to doxorubicin compared to the rats in the control group.

Background: Exhaustive physical exercise can cause substantial changes in the electrical properties of the myocardium. Objective: To evaluate, using body surface potential mapping, the electrical activity of the heart in rats during ventricular depolarization after acute exhaustive exercise. Methods: Twelve-week-old male rats were submitted to acute treadmill exercise at 36 m/min until exhaustion. Unipolar electrocardiograms (ECGs) from the torso surface were recorded in zoletil-anesthetized rats three to five days before (Pre-Ex), 5 and 10 minutes after exhaustive exercise (Post-Ex 5 and Post-Ex 10, respectively) simultaneously with ECGs in limb leads. The instantaneous body surface potential maps (BSPMs) were analyzed during ventricular depolarization. P values <0.05 were considered statistically significant. Results: Compared with Pre-Ex, an early completion of the second inversion of potential distributions, an early completion of ventricular depolarization, as well as a decrease in the duration of the middle phase and the total duration of ventricular depolarization on BSPMs were revealed at Post-Ex 5. Also, compared with Pre-Ex, an increase in the amplitude of negative BSPM extremum at the R-wave peak on the ECG in lead II (R-II-peak) and a decrease in the amplitude of negative BSPM extremum at 3 and 4 ms after R-II-peak were showed at Post-Ex 5. At Post-Ex 10, parameters of BSPMs did not differ from those at Pre-Ex. Conclusion: In rats, acute exhaustive exercise causes reversible changes in the temporal and amplitude characteristics of BSPMs during ventricular depolarization, most likely related to alterations in the excitation of the main mass of the ventricular myocardium.

Studies on experimental animals allow us to approach the understanding of the mechanisms of changes in the electrical activity of the heart during morphofunctional rearrangements that occur as a result of the development of arterial hypertension (AH). Aim of the study was to investigate body surface potential mapping in young ISIAH rats with genetically determined stress-induced AH during ventricular depolarization. Material and methods. The study was carried out on 3-month-old ISIAH males ( n = 10) weighing 250–300 g. Body surface potential mapping was performed using 64 electrodes evenly distributed around the chest of the animal. Results. Significantly higher systolic blood pressure was shown in ISIAH rats compared to Wistar rats (203 ± 14 and 125 ± 5 mm Hg, respectively), as well as heart relative mass, thickness of the left ventricle, right ventricle, and interventricular septum were significantly higher compared to Wistar. During the period of ventricular depolarization, a shift of the zone of negative cardiopotentials to the left-lateral region of the chest is shown in the period corresponding to the time the positive extremum reaches its maximum value in ISIAH rats compared to Wistar. An earlier time of formation, a significantly longer time to achieve the first and second inversion of cardiopotentials, a later time for the positive and negative extrema to reach their maximum values, a greater amplitude of the absolute value of the negative extremum, and a significantly longer total ventricular duration in ISIAH rats compared to Wistar rats were shown. Conclusions. The study give perspective to the use of body surface potential mapping for diagnosing the initial stages of the formation of myocardial hypertrophy in AH.

The aim of the work is non-invasive identification of the features of the initial atrial activity by the dynamics of the cardioelectric field on the surface of the chest of experimental animals under chronic exposure to doxorubicin. Materials and methods . The distribution and dynamics of changes in cardioelectric potentials on the surface of the chest of rats under chronic exposure to doxorubicin during the period of initial atrial activity were investigated. Doxorubicin was administered intraperitoneally 1.5 mg/kg once a week for a month. The cumulative dose was 6 mg/kg animal weight. Results . It has been shown that chronic exposure to doxysubicin leads to changes in the positional dynamics of positive and negative cardiopotentials cardioelectric field of heart on the chest surface during the ascending and descending P-wave on the ECG in the II limb leads. It is observed significantly earlier the beginning of cardioelectric field formation, characteristic of atrial depolarization, on the body surface, the beginning, the peak and the end of the P-wave on the ECG in the II limb leads compared to the initial state. Conclusion . Chronic exposure to doxorubicin causes significant changes in the initial atrial activity, which leads to a significant change in the corresponding period of atrial depolarization in the dynamics of the cardioelectric field on the surface of the thorax of animals.

Using an experimental model of pulmonary hypertension in rats (monocrotaline in a dose of 60 mg/kg), we revealed an additional focus of early excitation in the zone where the pulmonary veins enter the left atrium, in addition to the main focus in the sinoatrial node. Pulmonary hypertension leads to the formation of regions of early activation in the right and left atria and a significant change in the sequence of atrial depolarization. Propagation of independent excitation waves in the right and left atria increases heterogeneity of depolarization and leads to the formation of atrial arrhythmias.

Проведено исследование влияния доксорубицина на электрическую активность сердца крыс в период деполяризации желудочков методом множественного поверхностного картирования. Доксорубицин применяли в дозе 1,5 мг/кг внутрибрюшинно 1 раз в неделю на протяжении 4-х недель. Курсовая доза составила 6 мг/кг. Через 2 мес после первого введения доксорубицина выявляли изменения амплитудно-временных характеристик электрического поля сердца в период деполяризации желудочков — абсолютных значений амплитуд экстремумов (уменьшение положительного на 19,8 % (p < 0,007) и увеличение отрицательного — на 34,9 % (p < 0,01); увеличение общей длительности деполяризации желудочков за счет начального этапа на 9,7 % (p < 0,0001), по сравнению с исходным состоянием, при сохранении пространственного распределения кардиопотенциалов.

Changes in bioelectrical impedance of the myocardium and liver were revealed in male Wistar rats chronically exposed to doxorubicin. Multi-frequency bioimpedance and echocardiographic studies were carried out before and two months after the first injection of doxorubicin (a cumulative dose of 10 mg/kg divided into 4 injections over 4 weeks) or saline (control), while histological examination of the left ventricular myocardium and liver was performed at the end of the experiment. Two months after the first doxorubicin injection, 56% of animals showed a 13 ± 2% decrease in the left ventricular ejection fraction. In 33% of doxorubicin-treated rats with, histological examination revealed hemorrhages, as well as intra- and intercellular vacuolization in the left ventricular myocardium. Morphological alterations in the liver were detected in all rats chronically exposed to doxorubicin. In the latter, the intercellular fluid was found to accumulate both in the left ventricular myocardium and liver due to impaired microcirculation and damage to vascular cell membranes, as evidenced by a change in the dependence of active resistance of bioelectrical impedance of the heart and liver on the alternating current (AC) frequency, and a statistically significant decrease in the ratio of low-frequency to high-frequency resistance compared to control animals. Histologically verified morphological alterations in both tissues led to significantly lower absolute values of the phase angle (myocardium and liver) and reactance (liver) of bioelectrical impedance compared to control rats. A statistically significant correlation was found between the phase angle of myocardial bioelectrical impedance at high AC frequencies and the left ventricular free wall thickness. A lower extracellular resistance of bioelectrical impedance of the liver in doxorubicin-treated rats compared to control animals indicates the expansion of the inter-hepatocytic extracellular space and cell destruction.

Although the pericentromeric regions of chromosomes that are enriched in tandemly repeated satellite DNA represent a significant part of eukaryotic genomes, they remain understudied, which is mainly due to interdisciplinary knowledge gaps. Recent studies suggest their important role in genome regulation, karyotype stability, and evolution. Thus, the idea of satellite DNA as a junk part of the genome has been refuted. The integration of data regarding molecular composition, chromosome behaviour, and the details of the in situ organization of pericentromeric regions is of great interest. The objective of this work was a cytogenetic analysis of the interactions between pericentromeric regions from non-homologous chromosomes in mouse spermatocytes using immuno-FISH. We analysed two events: the associations between centromeric regions of the X chromosome and autosomes and the associations between the centromeric regions of the autosomal bivalents that form chromocenters. We concluded that the X chromosome forms temporary synaptic associations with different autosomes in early meiotic prophase I, which can normally be found until the pachytene–diplotene, without signs of pachytene arrest. These associations are formed between the satellite-DNA-rich centromeric regions of the X chromosome and different autosomes but do not involve the satellite-DNA-poor centromeric region of the Y chromosome. We suggest the hypothetical model of X chromosome competitive replacement from such associations during synaptic correction. We showed that the centromeric region of the X chromosome in association remains free of γH2Ax-dependent chromatin inactivation, while the Y chromosome is completely inactivated. This finding highlights the predominant role of associations between satellite DNA-rich regions of different chromosomes, including the X chromosome. We suppose that X-autosomal transient associations are a manifestation of an additional synaptic disorder checkpoint. These associations are normally corrected before the late diplotene stage. We revealed that the intense spreading conditions that were applied to the spermatocyte I nuclei did not lead to the destruction of stretched chromatin fibers of elongated chromocenters enriched in satellite DNA. The tight associations that we revealed between the pericentromeric regions of different autosomal bivalents and the X chromosome may represent the basis for a mechanism for maintaining the repeats stability in the autosomes and in the X chromosome. The consequences of our findings are discussed.

The method of electrocardiography was used to study the electrical activity of the heart of purebred and crossbred young sheep of the Pechora Experimental Station at the age of 70-90 days. Statistically significant differences between groups of young sheep of different genotypes which were probably related to the constitutional features of animals were found in the amplitude of the R-wave and T-wave on the ECG in the III sagittal lead as well as in the position of the electrical axis of the heart. The results of the studies should be considered when assessing the functional state of the cardiovascular system of the offspring of sheep received from parents with different genetically determined constitutional productive qualities.