Effect of intermittent high altitude hypoxia on the structure and enzymatic activity of cardiac myosin

The time course of structural and enzymatic changes in cardiac myosin was studied in the right and left ventricle of rats exposed to intermittent high altitude (IHA) hypoxia. In the controls, ATPase activity and myosin structure in both ventricles was the same. After the third exposure to simulated high altitude (2 600 m), myosin enzymatic activity rose significantly in the left ventricle and a significant right-left difference appeared. In the next phase of adaptation (11 exposures, 6 000 m), myosin ATPase activity fell in both ventricles and the right-left difference disappeared. After the 16th exposure (7 000 m), enzymatic activity increased again in both ventricles and attained control values. IHA also produced significant structural changes in cardiac myosin, particularly in the rigaht ventricle. The changes were characterized by the formation of myosin aggregates with significantly lower ATPase activity that the myosin monomer. The time course and localization of structural and enzymatic changes in cardiac myosin corresponded to the morphological damage to the heart fibres.     

The formation of the right and left heart ventricles from the ventricular part of the cardiac tube during embryogenesis

It has been generally assumed that the initial rudiment of the heart ventricle is divided by the longitudinal interventricular septum into the right and left ventricles. This paper presents evidence for the hypothesis that the right and the left ventricles are produced during normal development from different sequentially located segments of the cardiac tube. These segments yielding rudiments of the right and left ventricles could be detected even during early embryogenesis. This hypothesis requires a new explanation for the process of the formation of two separate outlets from the heart ventricles.     

CHANGES IN ADRENALS AND SYMPATHETIC NERVE TERMINALS FOLLOWING COLD EXPOSURE

Abstract— Rats kept at 3°C for 24 h show no significant change in the catecholamine content of the adrenals, although the protein content is raised. Whole heart ventricles show no change in noradrenaline content, but the vesicular pellet isolated from heart ventricles has a decreased noradrenaline concentration and DBH activity and an increased protein content.     

The formation of the right and left heart ventricles from the ventricular portion of the heart tube in embryogenesis

It has been generally assumed that the initial rudiment of the heart ventricle is divided by the longitudinal interventricular septum into the right and left ventricles. This paper presents evidence for the hypothesis that the right and the left ventricles are produced during normal development from different sequentially located segments of the cardiac tube. These segments yielding rudiments of the right and left ventricles could be detected even during early embryogenesis. This hypothesis requires a new explanation for the process of the formation of two separate outlets from the heart ventricles.     

Action potentials of the heart atria and ventricles of Rana temporaria frogs and Cyprinus carpio carp]

Using microelectrode technique, studies have been made on electrophysiological indices (amplitude of AP, amplitude of the plateau, latent period of AP, duration of maximal depolarization, duration of repolarization at different levels) of cells of isolated atrium and ventricles of the carp during both the spontaneous activity and electrical stimulation. The obtained amplitude-temporal parameters were compared to those of the heart in the frog R. temporaria. It was found that the amplitude of AP, the amplitude of the plateau and the duration of the latent period of AP in both the atrium and ventricles of the carp significantly (p less than 0.01) differ from the corresponding indices of the frog. On the contrary, the duration of maximal depolarization and repolarization in cells from homologous parts of the heart is very close in the species investigated.     

Thyroxine influences on contractile proteins from atrial and ventricular myocardium

When thyroxine is administered to rats or rabbits, both heart ventricles eventually undergo hypertrophy. Both atria and ventricles show a relative weight increase and this mainly involves sarcoplasmic proteins. Ventricular myosin from thyrotoxic rabbits has higher Ca2+-ATPase activity when compared with euthyroid rabbits, the hyperthropied atria however, show no change in myosin ATPase after thyroxine administration.     

Simulation of the contraction of the ventricles in a human heart model including atria and pericardium

During the contraction of the ventricles, the ventricles interact with the atria as well as with the pericardium and the surrounding tissue in which the heart is embedded. The atria are stretched, and the atrioventricular plane moves toward the apex. The atrioventricular plane displacement (AVPD) is considered to be a major contributor to the ventricular function, and a reduced AVPD is strongly related to heart failure. At the same time, the epicardium slides almost frictionlessly on the pericardium with permanent contact. Although the interaction between the ventricles, the atria and the pericardium plays an important role for the deformation of the heart, this aspect is usually not considered in computational models. In this work, we present an electromechanical model of the heart, which takes into account the interaction between ventricles, pericardium and atria and allows to reproduce the AVPD. To solve the contact problem of epicardium and pericardium, a contact handling algorithm based on penalty formulation was developed, which ensures frictionless and permanent contact. Two simulations of the ventricular contraction were conducted, one with contact handling of pericardium and heart and one without. In the simulation with contact handling, the atria were stretched during the contraction of the ventricles, while, due to the permanent contact with the pericardium, their volume increased. In contrast to that, in the simulations without pericardium, the atria were also stretched, but the change in the atrial volume was much smaller. Furthermore, the pericardium reduced the radial contraction of the ventricles and at the same time increased the AVPD.     

The inotropic action of adrenergic agonists on the heart ventricles of the chick embryo]

The effects of adrenergic drugs on the twitch tension of the electrically driven (1.2-1.5 Hz) ventricular preparations from 2-20-day old chick embryos and hatched chicks were studied. Agonists evoked positive inotropic responses of 3-day embryonic ventricles and of ventricles from older animals. 2-day embryonic ventricles were unresponsive. 5-day embryonic ventricles were most sensitive to agonists (EC50 value of adrenaline = 4.5 x 10(-9) M), while ventricles from 14-20-day old embryos had a minimal sensitivity (1-2 x 10(-9) M), while ventricles from 14-20-day old embryos had a minimal sensitivity (1-2 x 10(-7) M). The order of agonists activity (isoproterenol greater than noradrenaline greater than adrenaline much greater than phenylephrine) and the high potency of propranolol as antagonist of adrenaline indicate that responses are mediated with beta-adrenoceptors. The role of GTP-binding protein for the regulation of adrenoreactivity in embryonic chick heart during ontogenesis is discussed.     

Effect of the autonomic nervous system on the resistance of heart ventricles to fibrillation

Effects of vagus stimulation and cutting on the tolerance of heart ventricles to fibrillation in cats have been studied. The parasympathetic effects increased the tolerance of heart ventricles to fibrillation while sympathetic ones--decreased it.     

Lipid peroxidation in the myocardium in experimental infarct

Changes in the content of lipid peroxidation (LP) products and activities of antioxidant enzymes--superoxide dismutase, glutathione peroxidase and catalase in myocardium of rats after experimental infarction as well as after pretreatment with antioxidant ionol, beta-adrenoblocker inderal and verapamil, an inhibitor of slow Ca2+-channels have been studied. In the left ventricles of the control animals decreased levels of LP-products (Schiff bases and lipid hydroperoxides) have been registered as compared with right ventricles, accompanied by increased activity of antioxidant enzymes in the left ventricles. In experimental infarction the level of LP products increases and activity of antioxidant enzymes decreases both in ischemic and nonischemic regions of the heart. In nonischemic zone these changes can be prevented by pretreatment with inderal and ionol but not with verapamil.     

Relationship of the maximum QRS vector with the left ventricular myocardial mass during the development of hypertrophy: Computer simulation and empirical data

A model of electrical activity of the heart has been used to demonstrate that, all other conditions remaining the same, the spatial vector of the heart changes, as a first approximation, proportionally to the increase in the surface area of the heart ventricles (rather than the myocardial mass) during proportional homothetic changes in the sizes of the heart and His-Purkinje system. In contrast, the electrocardiosignal (ECS) amplitude is determined, at any given moment, by the area of depolarized regions of the epicardium and endocardium, which agrees with the model of a double electrical layer on the surface of an electrically active myocardium.     

Changes in the activity of some metabolic enzymes in the heart of SHR rat incurred by transgenic expression of CD36

Hypertension, dyslipidemia, and insulin resistance in the spontaneously hypertensive rat (SHR) can be alleviated by rescuing CD36 fatty acid translocase. The present study investigated whether transgenic rescue of CD36 in SHR could affect mitochondrial function and activity of selected metabolic enzymes in the heart. These analyses were conducted on ventricular preparations derived from SHR and from transgenic strain SHR-Cd36 that expresses a functional wild-type CD36. Our respirometric measurements revealed that mitochondria isolated from the left ventricles exhibited two times higher respiratory activity than those isolated from the right ventricles. Whereas, we did not observe any significant changes in functioning of the mitochondrial respiratory system between both rat strains, enzyme activities of total hexokinase, and both mitochondrial and total malate dehydrogenase were markedly decreased in the left ventricles of transgenic rats, compared to SHR. We also detected downregulated expression of the succinate dehydrogenase subunit SdhB (complex II) and 70 kDa peroxisomal membrane protein in the left ventricles of SHR-Cd36. These data indicate that CD36 may affect in a unique fashion metabolic substrate flexibility of the left and right ventricles.     

Enzymatic heterogeneity of the rat myocardium]

The histoenzymatic method was applied to the study of distribution of the activity of the redox enzymes in the myocardium of the ventricles in rats; distribution of the activity of lactic and malic dehydrogenase and of alpha-glycerophosphate proved to be the most manifest near the apex of the heart and was expressed in the presence of "spotty" areas of increased activity against the general homogeneous background of formazan deposits. The activity of mitochondrial upsilon-glycerophoric dehydrogenase was seen in all the portions of the ventricles and was characterized by an uneven distribution in the sarcoplasm with increase in the direction from the interdisc to the nucleus. Unevenness of distribution of the beta-oxybutyric dehydrogenase activity was detected in some of the animals and was pronounced in all the portions of the myocardium. The intensity of the reaction in detection of succinic dehydrogenase, NAD- and NADP-diaphorases varied but insignificantly.     

大鼠心脏的雌激素受体免疫组织化学研究

观察雌激素受体在雌性与雄性大鼠心脏中的表达.取大鼠心房与心室组织制作冰冻切片,应用抗雌激素受体单抗进行免疫组织化学(SP法)染色并进行图像分析.结果显示,雌性与雄性大鼠心脏都存在雌激素受体,且受体的表达无性别差异(P＞0.05);心房与心室都存在雌激素受体阳性表达,其表达也无明显差异(P＞0.05);阳性反应见于心肌细胞和成纤维细胞.结果表明,大鼠心脏存在雌激素受体,心房与心室都可能是雌激素的靶组织;心血管疾病的性别差异与雌性、雄性的受体含量无关,可能与生理条件下受体的活性及功能状态有关.     

Effect of ectopic excitation on the ventricular pump function in chicken

The pump function of the heart ventricles was studied in chest-open anaesthetized adult female chickens under sinus rhythm and ectopic excitation of different localization. The intraventricular pressure in the right and left heart ventricles was measured by insertion of catheters through the ventricular free walls. Maximum systolic pressure, end-diastolic pressure, contractility (dP/dtmax) and relaxation (dP/dtmin) of both heart ventricles, and duration of the asynchronous contraction time of the left ventricle were analyzed. It was revealed that reduction of the pump function of the left ventricle tends to be greater under right ventricular ectopic excitation compared with left ventricular one. In comparison with the sinus rhythm, the pump function of the right ventricle was preserved to a greater extent under stimulation of the left ventricular apex and was significantly impaired under right ventricular ectopic excitation. Relaxation of both heart ventricles was more susceptible to ventricular ectopic excitation than contractility, and was more vulnerable in the right ventricle than in the left one. The direction of changes of the pump function of the heart ventricles in chickens under ventricular ectopic excitation was similar to changes of the pump function of mammalian hearts.     

The quantitative relationship between longitudinal and radial function in left, right, and total heart pumping in humans

The total heart volume variation (THVV) during systole has been proposed to be caused by radial function of the ventricles, but definitive data for both ventricles have not been presented. Furthermore, the right ventricle (RV) has been suggested to have a greater longitudinal pumping component than the left ventricle (LV). Therefore, we aimed to compare the stroke volume (SV) generated by radial function to the volume variation of the left, right, and total heart. To do this, we also needed to develop a new method for measuring the contribution of the longitudinal atrioventricular plane displacement (AVPD) to the RVSV (RVSV(AVPD)). For our study, 11 volunteers underwent cine MRI in the short- and long-axis planes and MRI flow measurement in all vessels leading to and from the heart. The left, right, and total heart showed correlations between volume variation from flow measurements and radial function calculated as SV minus the longitudinal function (r = 0.81, P < 0.01; r = 0.80, P < 0.01; and r = 0.92, P < 0.001, respectively). Compared with the LV, the RV had a greater AVPD (23.4 +/- 0.8 vs. 16.4 +/- 0.5 mm), center of volume movement (13.0 +/- 0.7 vs. 7.8 +/- 0.4 mm), and, RVSV(AVPD) (82 +/- 2% vs. 60 +/- 2%) (P < 0.001 for all). We found that THVV is predominantly caused by radial function of the ventricles. Longitudinal AVPD accounts for approximately 80% of the RVSV, compared with approximately 60% for the LVSV. This difference explains the larger portion of THVV found on the left side of the heart.     

Effect of hypoxia on pig heart short-chain acylcarnitines

The right ventricles of pig heart were perfused with hypoxic blood and the left ventricles were perfused with normally ventilated arterial blood. Free carnitine and short-chain acylcarnitines in hypoxic ventricles were lower than in perfused controls, and much lower than in non-perfused heart. Acetylcarnitine levels decreased and the branched-chain acylcarnitines and propionylcarnitine were elevated in the hypoxic perfused ventricles. These data indicate that both hypoxia and anaesthesia caused loss of carnitine and short-chain acylcarnitines from the heart and hypoxia also changed the distribution of short-chain acylcarnitines in the heart.     

The contractile function and electrical stability of the heart in different regimens of physical exercise

Adaptation to moderate duration of physical loading causes identical levels of increase in threshold fibrillation of ventricles in wide range of their intensity. Rise of contractile heart function increases with prolonged adaptation regimen of heavy loading exercise. With hypokinesia and excessive physical load the sinking of threshold of fibrillation of ventricles occurs in lacking of alterations and with high contractile function of the heart respectively.     

Effects of temperature on rat and mouse cardiac myosin ATPase activity during development

Myosin was isolated from rat and mouse ventricular myocardium and examined during development at stages with known composition of myosin isoenzymes. The ATPase activity and its temperature dependence is the same in one-week-old and adult mouse ventricles. In rat heart myosin, the ATPase activity is low 18 days prenatally, high in 3-week-old animals and declines towards adulthood. ATPase activity of heart myosin from rat foetuses is more temperature dependent than that of three-week-old animals. These results strongly suggest that adaptation of the heart to development differs in the mouse and the rat and that the properties of mouse V1 isoenzyme do not change at the studied periods.     

Electrical activity of the heart in anti-ischemic protection of the myocardium

The paper studies electrical activity of the heart during the anti-ischemic protection by cool high-potassium cardioplegic solution based on the blood. Parametres characterising automatism function and the myocardial state of the ventricles practically did not differ from the control data obtained during the experiments without ischemia. Atrioventricular conduction and the atrium myocardium were worse preserved. The positive effects of the papaverine addition to the cardioplegic perfusate has been also shown. The author came to the conclusion that it is necessary to pay special attention to the electrical activity of the supraventricular area of the heart for the adequate evaluation of the cardioplegia.