Functional, morphologic and histochemical changes in the myocardium and their role in the development of cor pulmonale following pulmonary resection]

Functional, morphological and histochemical alterations were studied in 32 dogs within the period of 5 days--18 months after resection of 32-80% of the pulmonary tissue. According to the presence of hypertrophy of the heart right ventricle wall, morphological changes of the myocardium and disorders in the functional features of the cardiovascular activity all the animals were divided into 4 groups: 1--control animals; 2--experimental animals without hypertrophy of the right ventricle wall; 3--experimental animals with hypertrophy of the right ventricle wall in the stage of compensation; 4--experimental animals with hypertrophy of the right ventricle wall in the stage of decompensation. In the myocardium of the second group animals a decrease of aerobic processes and an increase of anaerobic ones were found to take place. The aerobic processes increased and the anaerobic processes decreased in the myocardium of dogs having hypertrophy of the right ventricle wall in the stage compensation. In the muscle of the decompensated pulmonary heart there occurred a pronounced decrease of aerobic and anaerobic processes, a disturbance of the protein and fat metabolism. All this resulted in a decreased contractive function of the myocardium with distrubed hemodynamics. The investigations have shown the interrelationships of morphological, histochemical and ECG alterations in the dynamics of the pulmonary heart development after resection of lungs.     

Compensatory and adaptive changes in the heart after pulmonary resection (morphometric analysis)

The experiment has been performed in 124 non-inbred dogs by means of a complex of morphometrical methods in order to study compensatory-adaptive processes in the heart after pulmonary resection various in its volume. After 58% resection, and especially after 67-75% resection of the lung mass, a stable pulmonary arterial hypertension appears; it results in development of a chronic cor pulmonale and terminates in its decompensation. Application of extrapulmonary arterio-venous anastomosis, before 67-75% of the pulmonary parenchyma is resected, decreases hypertension in the pulmonary circulation, improves adaptive changes of the heart in the newly formed conditions of hemodynamics, preventing development of its failure.     

Cytological mechanisms of the growth and regeneration of the parathyroid glands

Contribution of proliferation and hypertrophy of the epitheliocytes to the growth and regeneration of the rat parathyroid glands was estimated using organo- and cytometry, cytophotometry of DNA content in the nuclei and determination of mitotic index. During postnatal development and in the case of hypertrophy of the adult glands following a moderate resection (50%), the gland growth is provided by mitotic divisions of the parathyroid cells, rather than by the increase in cell size. When up to 75 and 90% of the gland volume is removed, cell hyperplasia is accompanied by stable hypertrophy of the parathyroid cells unrelated to their polyploidization. The contribution of nonmitotic cell hypertrophy to the total increment of the organ volume amounts to 40-50%.     

Myocardial reaction of the right ventricle to lung resection

Right-sided pulmonectomy (resection of 63-65% of the lung parenchyma) in white noninbred rats resulted in development of chronic cor pulmonale, that develops according to the stages: I--from the time of the operation up to the 10th-15th days after the operation--the stage of acute disturbances and mobilization forces of the organism; II--from the 11th-15th up to the 90th day is the stage of a relative steady compensatory hypertrophy of the cardiac right ventricle; III--after the 90th day--the stage of decompensation. The hypertrophy of the right ventricle myocardium transfers into its dilatation. Amount of cardiomyocytes and their nuclei in 1 mg of the right ventricle tissue progressively decreases, quantity of multinuclear cardiomyocytes increases, ploidy of the nuclei changes: number of tetraploid nuclei decreases, octaploid nuclei appear. Lethality among the animals is 56%.     

Cardiac myocyte hypertrophy and proliferating cell nuclear antigen expression in Wistar rats infected with Trypanosoma cruzi

Chagasic cardiomyopathy is a major life-threatening complication of Trypanosoma cruzi infection in human beings. This study focuses on the hypertrophic and hyperplastic mechanisms underlying the structural changes of the heart during experimental infection. Proliferating cell nuclear antigen (PCNA) expression, transversal diameter, nuclear area, and number of nuclei per unit volume were determined in the ventricular myocytes of T. cruzi-infected Wistar rats. PCNA expression was enhanced throughout the inflamed myocardium and in the spared areas of the left ventricular wall and the septum. Myocyte width increased from 26 to 75% at the inflammation-free myocardium (P < 0.0001), whereas it decreased 25% at the inflamed left ventricular wall areas (P < 0.001). Nuclear size increased in the inflammation-free myocardium of the left ventricle and the septum (> 10-36%, P < 0.01 and >0.2-32%, P < 0.03, respectively) and decreased at the inflamed areas of the left ventricular wall (10-22%. P < 0.02) with respect to the controls. The number of nuclei per unit volume decreased at the inflamed myocardium regardless of topographical location (36-65%) with respect to the controls (P < 0.0001) and in the inflammation-free myocardium of the right ventricle and the septum (<21-37%, P < 0.002 and <8-39%, P < 0.002, respectively). These results show that the heart responds to T. cruzi infection with DNA repair and cell multiplication in the inflamed sites and with hypertrophy of the unaffected myocardium.     

A sharp increase in the density of pulmonary and pericardial mast cells under monocrotaline-induced pulmonary hypertension in rats

Multifunctional granular mast cells (MCs) are involved in various pathological processes. The response of MC populations of myocardium, pericardium and lung to pulmonary hypertension (PH) has been studies 8 weeks after injection of monocrotaline. Five intact and five experimental rats were used. The density of MCs of different maturity was estimated on paraffin sections stained with Alcian blue and Safranin. Expressiveness of PH was estimated by functional parameters with the help of echocardiograms and by morphological markers. The MC density in myocardium of the intact and experimental rats was relatively low: 2 to 4 cells/mm2. MC density in the pericardium of intact rats was 14 times higher than in myocardium and increased 3 times for PH. The mature Safranin-positive cells predominated (70-80%) in myocardium and pericardium of intact and experimental rats. The MC density in the lungs of intact rats was about 30 cells/mm2; 98% of these cells were immature Alcian-positive cells. The mean density of MCs in the lungs of rats with PH increased 5.6 times. The mature Safranin-positive cells appeared in the lungs of rats with severe pathology. The greatest number of MCs in lungs was in the rats with the most pronounced disorders of myocardium function and marked histological damages (injuries) of myocardium and lungs. The finding show active response of MC population to monocrotaline-induced PH that stimulates migration of immature MCs into pericardium and lungs from the outside. Our data indicate the important role of MCs in the pathogenesis of PH.     

Induction of hypertrophy in vitro by mechanical loading in adult rabbit myocardium

To study myocardial hypertrophy under in vitro conditions, we developed an experimental system and protocol in which mechanical conditions of isolated multicellular myocardium can be controlled while function can be continuously assessed. This in vitro culture system now allows us to investigate how mechanical overload impacts on cardiac hypertrophy in the absence of systemic factors. In this system, small right ventricular rabbit trabeculae were subjected to different modes of mechanical load, while being electrically stimulated to contract at 1 Hz at 37 degrees C. Muscles subjected to prolonged isometric contractions at high, but physiological, pre- and afterload showed a rapid induction of cardiac hypertrophy; overall muscle diameter increased by 4.3 +/- 1.4 and 17.9 +/- 4.0% after 24 and 48 h, respectively. This finding was confirmed at the cellular level; individual myocyte width significantly increased after 24 and 48 h. In muscles subjected to a low preload, or in the absence of afterload, this hypertrophic response was absent. Functionally, after 24 h of isometric contractions at high load, active developed tension had gradually increased to 168 +/- 22% of starting values. Proteomic analysis of this cultured myocardium demonstrated reproducible changes in the protein expression pattern and included an upregulation of myofilament proteins, myosin light chain isoforms, alpha-b crystalline, and breast cancer 1 protein, and a downregulation of myoglobin. We conclude that multicellular myocardium can be stressed to undergo rapid hypertrophy in vitro, and changes in function and protein expression can be investigated during the transition from healthy myocardium to early hypertrophy.     

Structural and functional characteristics of myocardial capillaries after resection of the lungs

In the experiment performed on 107 dogs, after resection of 33-75% of the pulmonary volume, it has been stated that considerable disturbances take place in the myocardial microcirculatory bed. At early stage after the operation the amount of capillaries per 1 mm2 of the section increases, their lumens become wide. With elapse of time after the operation, as a result of myocardial hypertrophy, density in arrangement of the capillaries decreases, and the transversal section area of the cardiomyocyte per one capillary increases. In the capillary walls destructive changes are also noted; they result in myocardiodistrophy and in development of cardiac failure.     

Vessels of the heart and lung in some experimental defects]

Under study were changes of intraorganic blood vessels of the heart and lungs in some experimental defects (open arterial defect, coarctation of the aorta, simultaneous existence of these two defects, stenosis of the pulmonary trunk, defect of the interatrial septum, triad of Fallot, syndrom of Lutembachet). Morphological data correlated with blood pressure in the pulmonary circulation and cardiac chambers. The complex of compensatory-adaptational mechanisms consisting of comparatively active and passive zones is formed in the heart and lungs. In most cases the changes develop in the vessels already existing. In hypertrophy of the myocardium when there is hypertension and hypervolemia in coronary vessels, sinusoids perform the function of blood reservoir, to a certain degree balancing the blood pressure, and luminar ducts relieve the muscle from excessive blood. The changes in the vascular system of the lung are directly dependent upon the pressure in the pulmonary circulation and the duration of observation. The closing arteries are the most active link in the chain of compensatory-adaptational mechanisms.     

Down-regulation of mitofusin-2 expression in cardiac hypertrophy in vitro and in vivo

Mitofusin-2 (Mfn2) suppresses smooth muscle cell proliferation through inhibition of the Ras-extracellular signal-regulated kinases (ERK1/2) pathway. Since the ERK1/2 pathway is implicated in mediating hypertrophic signaling, we studied the changes in Mfn2 in cardiac hypertrophy using in vitro and in vivo models. Phenylephrine was used to induce hypertrophy in neonatal rat ventricular myocytes (NRVMs). In vivo hypertrophy models included spontaneously hypertensive rats (SHR), pressure-overload hypertrophy by transverse aortic constriction (TAC), hypertrophy of non-infarcted myocardium following myocardial infarction (MI), and cardiomyopathy due to cardiac-restricted overexpression of beta(2)-adrenergic receptors (beta(2)-TG). We determined hypertrophic parameters and analysed expression of atrial natriuretic peptide (ANP) and Mfn2 by real-time PCR. Phosphorylated-ERK1/2 (phospho-ERK) was measured by Western blot. Mfn2 was downregulated in phenylephrine treated NRCMs (by approximately 40%), hypertrophied hearts from SHR (by approximately 80%), mice with TAC (at 1 and 3 weeks, by approximately 50%), and beta(2)-TG mice (by approximately 20%). However, Mfn2 was not downregulated in hypertrophied hearts with 15 weeks of TAC, nor in hypertrophied non-infarcted myocardium following MI. phospho-ERK1/2 was increased in hypertrophied myocardium at 1 week post-TAC, but not in non-infarcted myocardium after MI, indicating that downregulated Mfn2 may be accompanied by an increase of phospho-ERK1/2. This study shows, for the first time, downregulated Mfn2 expression in hypertrophied hearts, which depends on the etiology and time course of hypertrophy. Further study is required to examine the causal relationship between Mfn2 and cardiac hypertrophy.     

蛋白激酶Cδ可能参与肥大心肌细胞转向凋亡

为了探讨肥大心肌细胞对凋亡刺激的易感性及蛋白激酶Cδ(protein kinase Cδ,PKCδ)在其中的作用,以内皮素-1 (endothelin-1,ET-1)处理原代培养的新生大鼠心肌细胞,诱导心肌细胞肥大;再用血管紧张素Ⅱ(angiotensin II,Ang II)作为细胞凋亡诱导因子,采用鬼笔环肽(phalloidin)荧光染色与细胞面积测量两种方法检测心肌肥大,Hoechst 33258荧光染色检测细胞凋亡。结果显示：(1)1与10 nmol/L ET-1作用48h,心肌细胞肌原纤维排列整齐、染色增浓,随ET-1浓度增加而愈加明显,心肌细胞表面积分别增加42．5%和67．3%,以此作为轻度和中度心肌细胞肥大模型。(2)正常、轻度肥大与中度肥大心肌细胞受1nmol/L AngⅡ处理24h后,凋亡率分别为(15．54±1．32)%、(20．65±1．40)%与(29．33±3．52)%,三组之间有显著差异(P＜0．05)。(3)受AngⅡ刺激后,PKCδ特异性抑制剂rottlerin不影响正常心肌细胞的凋亡率,却有效抑制了轻度和中度肥大心肌细胞的凋亡。肥大心肌细胞凋亡易感性明显高于正常心肌细胞,抑制PKCδ可以抑制肥大心肌细胞凋亡,提示PKCδ参与肥大心肌细胞凋亡过程。     

Increased number of beta-adrenergic receptors in the hypertrophied myocardium.

Development of cardiac hypertrophy is associated with depletion of endogenous catecholamine stores and increased inotropic response to exogenous catecholamines. A biochemical basis for these changes is provided by the observation that the number of cardiac beta-adrenergic receptors - as reflected in specific [3H]dihydroalprenolol binding - is increased in hypertrophy without a change in the affinity of dihydroalprenolol for the binding sites or in the capacity of isoproterenol to displace dihydroalprenolol. This change in beta-receptor numbers may be an important adaptive mechanism for preserving the contractile performance of the hypertrophied myocardium.     

Myotrophin: purification of a novel peptide from spontaneously hypertensive rat heart that influences myocardial growth

Mechanisms involved in the development or the regression of myocardial hypertrophy cannot be fully explained as responses to blood pressure control alone. We had hypothesized that the development of hypertrophy is initiated by a signal (mechanical or humoral) to the myocardium, which in turn produces a soluble factor that triggers protein synthesis and initiates myocardial growth. Using the stimulation of protein synthesis in isolated cardiac myocytes obtained from normal rat hearts as an assay system, we have identified a soluble factor from the hypertrophied myocardium of spontaneously hypertensive rats. This factor, which has been purified to apparent homogeneity, is a protein of 12 kDa. The sequence of three internally liberated peptides containing 7-24 residues was determined. Based on the determined amino acid sequences of these peptides, this factor (designated myotrophin) appears to be a novel protein that shows no homology with any previously described growth factors. Myotrophin is present in human, dog, and rat hypertrophied hearts (28-35% stimulation of protein synthesis over control) and in small amounts in normal hearts (5-6% stimulation). Myotrophin causes two dose-dependent effects in neonatal cardiac myocytes: an increase in the surface area of the myocyte and the appearance of organized myofibrils, which become apparent within 48 h. Myotrophin may play an important role in the pathogenesis of cardiac hypertrophy as well as in the normal development of cardiac myocytes.     

Evaluation of the effectiveness of the long-term use of obzidan in experimental myocardial infarct

The authors performed a comprehensive study of the recovery processes in the myocardium after occlusion of the coronary artery in 126 white rats under the effect of a long-term treatment with propranolol (0.5 mg/kg). The drug reduced the size of necrosis by 2.6 times, significantly decreased the S-T segment rise on the ECG (up to 0.86 +/- 0.09 mV versus 1.85 +/- 0.15 mV, in untreated animals with myocardial infarction, P less than 0.001). The treated animals manifested the improvement of the morphologic status of the perinecrotic area and the myocardium of the posterior wall of the left ventricle. Cardiomyocytes preserved to a considerable degree the ultrastructure of the mitochondria, demonstrating an increase in DK and protein biosynthesis (up to 296.1%, P less than 0.001). At the same time the long-term treatment with propranolol led to an appreciable activation of intracellular reparative regeneration, acceleration of the renewal of organelles, thereby promoting a decrease in the hypertrophy of cardiomyocytes (by 22.1%, P less than 0.001) as compared with control. It is concluded that propranolol administered in a dose of 0.05 mg/kg favours rapid recovery of the functional structures of the myocardium.     

Selected contribution: mechanisms that may stimulate the resolution of alveolar edema in the transplanted human lung.

Pulmonary edema is common in organ donors and lung transplant recipients. Therefore, we assessed the responsiveness of human donor lungs to pharmacological agents that stimulate clearance of alveolar edema. Organ donors whose lungs were rejected for transplantation were studied. After resection, transport (4 degrees C), and rewarming (37 degrees C) of lungs, alveolar fluid clearance was measured with (n = 8 donors) or without (n = 23 donors) beta-adrenergic stimulation. Terbutaline-stimulated clearance (10(-4) M) was higher than unstimulated clearance (7.1 +/- 1.3 vs. 4.8 +/- 2.4%/h, P < 0.01). Second, we determined whether medications given to the organ donor were associated with the extent of pulmonary edema or the rate of alveolar fluid clearance in the harvested lung. Preharvest administration of dopamine in low to moderate doses was associated with faster alveolar fluid clearance (r = 0.62, P < 0.01). Preharvest administration of diuretics was associated with lower extravascular lung water-to-dry weight ratios. This study provides the first evidence that a beta(2)-adrenergic agonist stimulates alveolar fluid clearance in the human donor lung. Aerosolized beta(2)-adrenergic agonists may have therapeutic value for hastening the resolution of alveolar edema during the management of donors before resection of lungs for transplantation or in the posttransplant setting.     

Increased generation of hydroxyl radicals in the rat hypertrophied myocardium: in vivo study by microdialysis

A comparative study of the generation of hydroxyl radicals (OH*) in the hypertrophic myocardium of SHR-SP rats (n = 8) and in the myocardium of WKY (n = 5) and Wistar (n = 12) rats was performed using the microdialysis technique. The experiments were carried out on anesthetized open-chest male rats (ketamine intraperitoneally, 10 mg/kg) with artificial ventilation. The amount of OH* produced was estimated by high-performance liquid chromatography with electrochemical detection using as a marker 2,3-dihydroxybenzoic acid (2,3-DHBA), a product of the reaction of the hydroxyl radical with salicylic acid added to the perfusate. The quantity of 2,3-DHBA in the dialysate was estimated by the external standard method and expressed in percent of the 2,3-DHBA concentration in the perfusion fluid. The mean baseline value of 2,3-DHBA in dialysate samples in SHR-SP rats (157 +/- 22%, n = 8) was significantly higher than in Wistar (90 +/- 15%, n = 12, p = 0.0001) and Wistar-Kyoto rats (106 +/- 12%, n = 5, p = 0.005). The basal 2,3-DHBA level in SHR-SP rats was positively correlated (r = 0.831, n = 7, p < 0.05) with the degree of hypertrophy of the left ventricle expressed as the ratio of the left ventricle weight to the body weight. The data presented demonstrate that the hypertrophy of the left ventricle in SHR-SP rats is accompanied by the elevation of the level of free oxygen radicals.     

Role of myofibrillogenesis regulator-1 in myocardial hypertrophy

Myofibrillogenesis regulator-1 (MR-1) is a novel homologous gene, identified from a human skeletal muscle cDNA library, that interacts with contractile proteins and exists in human myocardial myofibrils. The present study investigated MR-1 protein expression in hypertrophied myocardium and MR-1 involvement in cardiac hypertrophy. Cardiac hypertrophy was induced by abdominal aortic stenosis (AAS) in Sprague-Dawley rats. Left ventricular (LV) hypertrophy was assessed by the ratio of LV wet weight to whole heart weight (LV/HW) or LV weight to body weight (LV/BW). Rat MR-1 (rMR-1) expression in the myocardium was detected by immunohistochemical and Western blotting analysis. Hypertrophy was induced by ANG II incubation in cultured neonatal rat cardiomyocytes. The effect of rMR-1 RNA interference on ANG II-induced hypertrophy was studied by transfection of cardiomyocytes with an RNA interference plasmid, pSi-1, which targets rMR-1. Hypertrophy in cardiomyocytes was assessed by [3H]Leu incorporation and myocyte size. rMR-1 protein expression in cardiomyocytes was detected by Western blotting. We found that AAS resulted in a significant increase in LV/HW and LV/BW: 89% and 86%, respectively (P < 0.01). Immunohistochemistry and Western blot analysis demonstrated upregulated rMR-1 protein expression in hypertrophic myocardium. ANG II induced a 24% increase in [3H]Leu incorporation and a 65.8% increase in cell size compared with control cardiomyocytes (P < 0.01), which was prevented by treatment with losartan, an angiotensin (AT1) receptor inhibitor, or transfection with pSi-1. rMR-1 expression increased in ANG II-induced hypertrophied cardiomyocytes, and pSi-1 transfection abolished the upregulation. These findings suggest that MR-1 is associated with cardiac hypertrophy in rats in vivo and in vitro.     

Myocardial lysosomes in pressure-overload hypertrophy

Summary Combined electron microscopic and cytochemical studies were used to investigate the effects of chronic-pressure overload hypertrophy on myocardial lysosomes, mitochondria, and myofibrils in the left ventricle of the cat. Myocardial hypertrophy was induced by an 84% banding constriction of the ascending aorta. After one month of aortic constriction the experimental animals demonstrated a 51% increase in left ventricular mass. No qualitative ultrastructural differences were noted between the myocardial tissues of the hypertrophy and normal group. However, the cytochemical reaction product to acid phosphatase appeared more frequently in the myocardium of the hypertrophy group compared to that of the normal group. By use of quantitative morphometry the percentage of mitochondria, myofibrils and lysosomes per myocardial cell was determined in both hypertrophy and normal groups of animals. Despite significant increases in the left ventricular mass of hypertrophy animals, a normal balance of mitochondria and myofibrils was maintained within the myocardium. Further analysis indicated an enhanced lysosomal population in the hypertrophy group compared to the normal group.This research was supported by a grant from the California Affiliate of the American Heart Association     

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.     

Ultrastructural analysis of collagen fibers in the conductive and working myocardium of the sinoatrial region of the human heart

Qualitative and quantitative electron microscopic analysis of collagenous fibers has been performed in the sinusal node (SN) and perinodal working myocardium of the right atrium (RA) in the hearts of 22 men, died at the age of 23-63 years. Five of them died from alcoholic cardiomyopathy, 8--from coronary cardiac disease and 9--from noncardiac causes and craniocerebral trauma (group of comparison). In 21 cases seven types of ultrastructural changes of the collagenous fibers have been revealed in the SN (changes in the form, size and degree of their osmiophilia). As a whole the volumetric density of the collagenous fibers in the selection makes 24.4 +/- 1.6% from the volume of the SN conductive myocardium and 5.7 +/- 0.8% from the volume of the RA perinodal working myocardium. Content of the collagenous fibers in the SN does not depend on the death cause, age of the dead or on degree of the cardiac hypertrophy. Content of the collagenous fibers in the RA is 2.2 times higher at a sudden coronary death, than in the group of comparison. With age in the RA the volumetric density of the collagenous fibers increases by 1.9 times, and with rise in the cardiac mass, it increases by 2.2 times. The data obtained are discussed in order to understand the role of the collagenous fibers in functioning of the sinoauricular area both normal and at the cardiac pathology.