Adaptive changes in sections of the myocardium of experimental animals undergoing physical loading of a static nature

Adaptation of the parts of myocardium of 18 white rats to the physical static loadings during two months have been studied by means of morphometric and histological methods. Physical loadings cause hyperfunction and hypertrophy of all chambers of the heart with a predominant hypertrophy of the right ventricle, right auricle and dilatation of these cavities. The heterogeneous changes of the myocardium were found on the organic level.     

Variations in morphologic alterations in the hearts of white rats during adaptation to different types of physical loads

While adapting to physical loadings various in their character, most of rats develop a moderate hypertrophy in the right cardiac ventricle without any noticeable changes in the organ's mass. ECG dynamics is positive. Myocardial hypertrophy, at the expense of increasing mass of the left ventricle, is most regularly observed in animals subjected to forced endurance training (daily swimming); less regularly--if the loading is applied with intervals (swimming every other day) and is practically absent in rats performing work with force application. Pathological ECG changes occur more often on the background of myocardial hypertrophy and are brought about by dystrophic disorders in muscular fibres, their focal micronecrosis, by edema of the interstitial and perivascular tissue.     

Valvular apparatus of the cardiac veins in the pig]

The valvular apparatus of the subepicardial venous network has been studied in reflected light of the diaphragmated source. Structure, form and variations of the valvular apparatus have been determined in different parts of the coronary sinus, in the large cardiac vein, in the median cardiac and in the posterior veins of the left ventricle and their main branches.     

Isoproterenol-induced responses in the regional polyamine metabolism of the rat heart

Rats were treated with a single dose of isoproterenol (25 mg/kg s.c.) and the levels of polyamines determined in various parts (right ventricle, basis, medial part and apex of the left ventricle) of the heart 24, 48 and 72 hours after the injection. The isoproterenol treatment produced marked alterations in the concentrations of cardiac polyamines. The most apparent changes were seen in the apex and medial part of the left ventricle where spermidine concentration exhibited a biphasic response with peaks at 24 and 72 hours. In the basis of the heart the spermidine concentration was significantly elevated only at 24 hours. In the right ventricle the spermidine level was significantly higher than control at 72 hours. Spermidine/spermine ratio was augmented in all cardiac tissues examined over the 72-hour period. Results appear to show that the isoproterenol-induced alterations in cardiac polyamine metabolism were not uniformly distributed in the various regions of the heart.     

Morphometric research on the cardiomyocytes in cardiac hyperfunction]

By means of a complex morphometrical method special quantitative parameters of cardiomyocytes have been studied in the cardiac parts of 37 dogs, 6 months after right-sided pulmonectomy, and of 12 control dogs. The cardiac hyperfunction is accompanied with an increased mass of the heart's parts, hypertrophy of the right ventricle and right atrium dominating. Hypertrophy of myocardial parts takes place mainly at the expense of the increasing length and width of cardiomyocytes. This causes disorganization and disorder of morphological systems and an essential decrease in compensatory possibilities of the hyperfunctioning heart parts.     

Non-invasive evaluation of the kinematic activity of the intact left ventricle of the heart

Vector analysis of the movement of the epicardium has been used to calculate the energy efficiency of different parts of the left cardiac ventricle. The protocol based on the results of these calculations would allow the calculation of the potential power of myocardial contraction.     

Stretch of contracting cardiac muscle abruptly decreases the rate of phosphate release at high and low calcium

The contractile performance of the heart is linked to the energy that is available to it. Yet, the heart needs to respond quickly to changing demands. During diastole, the heart fills with blood and the heart chambers expand. Upon activation, contraction of cardiac muscle expels blood into the circulation. Early in systole, parts of the left ventricle are being stretched by incoming blood, before contraction causes shrinking of the ventricle. We explore here the effect of stretch of contracting permeabilized cardiac trabeculae of the rat on the rate of inorganic phosphate (P(i)) release resulting from ATP hydrolysis, using a fluorescent sensor for P(i) with millisecond time resolution. Stretch immediately reduces the rate of P(i) release, an effect observed both at full calcium activation (32 μmol/liter of Ca(2+)), and at a physiological activation level of 1 μmol/liter of Ca(2+). The results suggest that stretch redistributes the actomyosin cross-bridges toward their P(i)-containing state. The redistribution means that a greater fraction of cross-bridges will be poised to rapidly produce a force-generating transition and movement, compared with cross-bridges that have not been subjected to stretch. At the same time stretch modifies the P(i) balance in the cytoplasm, which may act as a cytoplasmic signal for energy turnover.     

Computed ventricular acoustic frequency

A mathematical model of the left ventricle is constructed. This model is a spherical thinwalled chamber with a radius and wall density approximately that of the left ventricle and enclosing a fluid whose pressure is that noted when heart sounds occur. The solution for the natural frequency of vibration is of the same value as that noted physiologically. Substitution of the values for the right ventricle yields similar results. The lowest natural frequencies of the idealized cardiac chamber possessing physical properties similar to a real cardiac chamber are of the same order of magnitude as the lowest significant observed cardiac frequencies. Such observation reinforces the likelihood that cardiac sounds are generated by the vibrating cardiac walls.     

Accumulation of messenger RNA of the atrial natriuretic factor in the rat left ventricle at the compensatory hypertrophy stage in pressure overload

The atria produce several peptides that have natriuretic and vasoactive properties, collectively called atrial natriuretic factor. All these peptides share a single messenger ribonucleic acid, the amount of which greatly increases in the rat left ventricle when the latter is submitted to chronic volume overload. Using the molecular hybridization technique and a desoxyribonucleic acid probe complementary to the atrial natriuretic factor messenger ribonucleic acid, we now report that a very important increase in the amount of this messenger ribonucleic acid is also observed in rat ventricle at at the compensatory stage of a pressure overload induced cardiac hypertrophy. This result suggests that the pressure overload hypertrophied rat ventricle also has the potential to itself regulate it's loading conditions via the regulation of extracellular fluid volume and vascular resistance.     

Features of the contour of the inner surface of the cardiac ventricles and Thebesius-Vieussens vessels

Using certain morphological methods, relief peculiarities of the cardiac ventricle chambers, form and extent of the intertrabecular spaces, connections with the myocardial blood bed have been studied in 92 human hearts. Foramina, fissurae and excavations on the internal surface of the ventricles are the beginnings of the intertrabecular spaces, in their deep parts elements of the microcirculatory blood bed of the myocardium have openings. As demonstrate serial sections, there are not any immediate anastomoses between the myocardial arteries, veins and the intertrabecular spaces. This fact does not confirm the existing opinion that the smallest cardiac veins (Viessen-Thebesian vessels) belong to the arterio-venous anastomoses. A propose is made to use the term "the smallest cardiac veins" only to the veins that directly open into the auricular chambers.     

Cardiac taurine levels during endotoxemia

Three hours after dogs were given an intravenous injection of Escherichia coli endotoxin significant decreases in cardiac taurine levels were observed in the apex and epicardial regions of the right ventricle and in all regions sampled from the left ventricle. A decrease in taurine was seen in all regions of the heart (including the atria) by 90 min after endotoxin treatment but the results were not statistically significant. Echocardiography and left ventricular cannulation were used in a separate group to confirm that the dose of endotoxin used was adequate to produce depression of cardiac output and force of contraction.     

房室间期对双腔起搏器患者心功能影响的研究进展

房室间期在双腔起搏器患者中具有重要意义,不仅对心房收缩及心室充盈产生影响,且与右心室起搏比例有关联,给心脏血液动力学及心功能带来一系列影响,合适的房室间期,才能使双腔起搏器患者心脏血液动力学及心功能获益更多。     

Spread of excitation through the heart upon electrical stimulation of the atrioventricular valves]

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.     

State of the capillary network of rat myocardium in the presence of hypertrophy and physical loading

Morphofunctional state of the capillary network in various myocardial parts was studied in white rats under normal conditions, myocardial hypertrophy of different degree and under physical loading. It was demonstrated that density, metabolic surface and capacity of the capillary bed is larger in the right ventricle than in the left one. The capillary blood supply in hypertrophied myocardium, increasing simultaneously with hypertrophy, at the state of rest corresponds to its increasing mass. On the contrary, under maximal physical loading functioning of the capillary part in the myocardium becomes unadequate that is evident from a decreasing activity of the test animals.     

Changes in the ultrastructure of muscle fibers of the diaphragm in response to physical loading (morphometric analysis)

Red and white fibers have been investigated in the diaphragm of white rats, normal and under effect of physical loadings, various in intensity and duration. Relative volume and amount of lipid inclusions and mitochondria and their profiles and amount of glycogen granules have been estimated per one unit of the fiber section area. In unadapted animals acute physical loadings result in exhaustion of the reserves in the areas with a high volumetric density of mitochondria. These changes are mostly pronounced in the red fibers. Under a prolonged effect of the physical loadings of the training regimen, muscle fibers of both types have similar ultrastructural changes, demonstrating certain increase in their oxidative potential.     

Anatomic features of postmortem experimental ruptures of the human heart

Comparison of postmortem performed experimental cardiac ruptures with post-infarction lesions reveals uniformity of their localization. The ruptures are found to occur at places of a sharp change in the relief of the cardiac internal surface. These areas should be considered as concentrators of strain, promoting cardiac ruptures. In the left ventricle six concentrators of strain are revealed. They are: the place where the anterior part of the interventricular septum passes into the anterior wall of the left ventricle, the right edge of the papillary muscle, the left edge of the anterior papillary muscle, the left edge of the posterior papillary muscle, the right edge of the posterior papillary muscle, the place where the posterior part of the interventricular septum passes into the posterior wall of the left ventricle. Frequency of the experimental ruptures of the interventricular septum, under loading of the left ventricle, is demonstrated to depend on pressure in the right cardiac part.     

Novel salmon cardiac peptide hormone is released from the ventricle by regulated secretory pathway

We used the secretion of the novel salmon cardiac peptide (sCP) as a model to examine the mechanisms of ventricular hormone release. Mechanical load increased dose dependently the secretion of immunoreactive sCP from isolated perfused salmon ventricle, with 3. 3-fold increase when a load of 13 cmH(2)O was applied. Endothelin-1 (5 nmol/l) was also able to rapidly increase the secretion of sCP. The released peptide corresponded to the biologically active sCP-29, whereas the large ventricular storage consisted of pro-sCP-sized material. With the use of immunoelectron microscopy, a large number of granules containing immunoreactive sCP could be detected in salmon ventricle. As judged by RNA blot analysis, there was very active basal expression of the sCP gene in the ventricle, which was not increased by mechanical load of up to 2-h duration. Our results show that the ventricle actively expresses the gene of sCP, stores the prohormone in secretory granules, and releases the peptide in response to mechanical load and endothelin-1. Thus the salmon ventricle uses the regulated pathway to produce and release a hormone structurally related to the mammalian natriuretic peptides.     

Combined experimental and numerical analysis of the flow structure into the left ventricle

Fluid dynamics is used for diagnosis in cardiology only to a partial extent. Indeed several aspects of cardiac flows and their relation with pathophysiology are unknown. The flow that develops into the left ventricle is here studied by using a combination of numerical and experimental models. The former allows a detailed three-dimensional analysis, the latter can be used in conditions, like in presence of turbulence, that are out of reach of the current computational power. The three-dimensional flow dynamics is analyzed in terms of its vortical structure. The study, within its limitations, provides further physical understanding about the intraventricular flow structure. This could eventually support the development of cardiac diagnostic indicators based on fluid dynamics.     

Afferentation of the heart in pathological states of the myocardium

The state of afferent connections between sinoatrial node zone (SNZ) in the normal and affected myocardium (reversible ischemia, necrosis) and rostral parts of the brain cortex (RPC) was studied with the help of evoked potentials in acute experiments on cats. Interruption of afferent connections (SNZ-RPC) during reversible ischemia and experimental myocardial necrosis of the right ventricle was revealed. Ultramicroscopic data of SNZ studies as well as electrophysiologic changes registered in RCP during irritation of the peripheral part of the right vagus nerve and local application of GABA on SNZ suggest possible interruption of cardiac afferentation at the level of SNZ due to the mechanism of presynaptic inhibition.