Effect of cordarone on the ultrastructure of cardiac muscle cells in experimental myocardial infarct

The effect of cordarone on the ultrastructure of cardiomyocytes of the periinfarction zone was studied in experiments on 30 cats. Cordarone was injected intramuscularly daily for 3.7 and 15 days in a dose of 10 mg/kg. Experimental myocardial infarction was induced by ligation of the left coronary artery at the border of its medium and inferior thirds. As compared with control, cordarone produced a more demonstrable reduction in the intracellular edema, more rapid recovery of the structure of myofibrils and greater accumulation of glycogen granules by the cytoplasm of cardiomyocytes. At the same time the structure of the mitochondria returned to normal more slowly as compared with control, with persistent widening of the cisternae of the sarcoplasmic reticulum being observed in addition. The changes described indicate that cordarone exerts different actions on the ultrastructure of cardiomyocytes, which is probably based on the drug influence on adrenergic processes and calcium turnover in the myocardium.     

Ultrastructure of cardiomyocytes in the peri-infarct zone during the treatment of experimental myocardial infarct in rats using the hexapeptide dalargin

The experiments on white rats with induced myocardial infarction have studied the influence of dalargin on the infarction size and peri-infarction zone ultrastructure. 24 hours later the decrease in the infarction zone size was detected in rats who had received dalargin in a dose of 50 and 100 micrograms/kg. In the peri-infarction zone the increase in glycogen quantity, the lower degree of lipid infiltration, the increase in mitochondrial number and mitochondrial energy effectiveness coefficient were noted, as compared to control animals. Sarcolemma of cardiomyocytes from the peri-infarction zone in rats on dalargin was impermeable for colloidal lanthanum. The decrease in the infarction size under the effect of dalargin is explained by its influence on the survival of cardiomyocytes in the peri-infarction zone.     

Ultrastructural stereological analysis of acute myocardial hypertrophy of hypertensive etiology

The myocardium of Wistar rats was studied by electron microscopy after ligation of the renal artery resulting in a stable elevation of blood pressure. The ultrastructural data on the development of heart hypertrophy were described within 5 to 35 days after operation using the morphometric and stereological methods and correlation analysis. The hypertrophied cardiomyocytes showed a reduction in the ratio of the total volume density of the mitochondria, sarcoplasmic reticulum and T system to the volume density of myofibrils. It was discovered that hypertrophy of cardiomyocytes is marked by an increase in the sarcoplasmic reticulum rather than in myofibrils and other cell compartments, whereas the relative volume of mitochondria decreases.     

Early ultrastructural changes in the myocardium following thyroxine-induced hypertrophy

The model of myocardial hypertrophy induced by thyroxine was studied with particular regard to the early ultrastructural changes in fractional volume of the mitochondria and myofibrils, and capillary distribution. Following injections of L-thyroxine (25 mg/kg IP) for 9 consecutive days, rats were sacrificed by vascular perfusion and cardiac tissue samples from the mid-wall zone of the left ventricle were processed routinely for electron microscopy. Heart weight/body weight ratios of thyroxine treated (T) rats showed a significant increase (P less than 0.001) over the ratios in control (C) rats. Likewise, the fractional volume of mitochondria (42%) was significantly increased (P less than 0.001) in the myocardium of T rats when compared with C rats (31%). However, the fractional volume of myofibrils was significantly decreased in the myocardium of T rats (P less than 0.001) and there was no significant difference between the hearts of T and C rats with respect to capillary luminal area/myocyte area. The mitochondria/myofibril ratio was increased in the hearts of T rats (0.82) over that found in control hearts (0.52). These results suggest that in the early stages of thyroxine-induced myocardial hypertrophy there is not an immediate increase in capillary area which may account for the ischemia and significant increase in mitochondrial volume which characterized myocardial hypertrophy in this model.     

Prevention of disorders of cardiomyocyte ultrastructure in experimental myocardial infarction in immobilization-induced stress by administration of thyroid hormones

In the experiment, carried out on 48 non-inbred male rats ultrastructural changes in cardiomyocytes in non-ischemized parts of the heart at experimental infarction of myocardium under conditions of immobilization stress have been studied, as well as possibility to correct these changes by means of thyroid hormones. The stress intensifies dystrophic processes, developed outside the infarction zone, increases the mass of the necrotized tissue, essentially decreases the areas occupied by mitochondria and myofibrils, as well as their ratio in the section area. Small doses of thyroid hormones prevent the heart from the damaging effect of the stressor: decreasing area; occupied by mitochondria, myofibrils and their relation in the section, as well as they stimulate intracellular regenerative processes (accumulation of polymorphous mitochondria with clearly manifested cristae, membranes of the endoplasmic reticulum) and decrease the myocardial necrotized zone). Thus, structural lesions, resulted from the effect of ischemic necrosis and stress, can be prevented by small doses of thyroid hormones+.     

Dynamics of development of autoimmune myocarditis in rats

The development of autoimmune myocarditis in rats after a single subcutaneous injection of rat myosin mixed with a complete Freund’s adjuvant (CFA) (400 μg/kg in 200 μl) was studied. The rats from the control group were injected with only CFA. The titer of antibodies to myosin, infiltration of lymphocytes into the myocardium, ultrastructural damage of myofibrils, mitochondria, and nuclei of cardiomyocytes were maximally pronounced on days 14–21 after the immunization with myosin, which indicates a peak of the inflammatory reaction. The content of nitrites and nitrates in the blood serum and myocardium of immunized rats were also studied. A certain contribution to the development of the inflammation is made by CFA: in rats injected with only CFA, morphological signs of myocarditis were found, but to a much lesser degree than in the group immunized with myosin.     

Focal regeneration in the rat myocardium following cold injury

Summary The sequential cytological events in the myocardium of the rat were followed for 3 weeks after cold injury by light and electron microscopy. The traumatized area was initially filled with leukocytes and undifferentiated mononucleated cells and subsequently mainly with fibroblasts surrounded by collagen fibers. However, in the margins of the necrotic area repair processes of damaged myocardial cells and probably also the appearance of newly formed cells were evident. The ultrastructural features of these cells were characterized by clusters of ribosomes, numerous mitochondria that were dispersed in the cytoplasm and formation of junctional complexes and transverse tubular systems. Fibrillogenesis was also clearly evident in these cardiomyocytes. The myofibrillar material was initially dispersed in the cytoplasm and associated with clusters of ribosomes and thereafter with presumptive Z-bands and intercalated discs. The myofibrils became further organized in the shape and orientation of those of mature cells two to three weeks after injury. It is concluded that following cold injury regeneration in the mammalian myocardium takes place but is limited to the perinecrotic area. The process resembles the sequential cytological events which occur in cardiomyocytes during embryonic and postnatal development of the ventricular myocardium.     

Alterations in myocardial ultrastructure and protein expression after a single injection of isoproterenol

Immunochemical and electron microscopic characterization of rat myocardium was conducted 2 h and 3 weeks after a single injection of isoproterenol in rats. The relative content of several myospecific proteins (KRP – kinase-related protein, desmin), cytoskeletal proteins (tubulin, vinculin, myosin light chain kinase – MLCK) and extracellular matrix protein fibronectin was determined by immunoblotting. Two hours after injection of 50 mg/kg isoproterenol a destruction of some cardiomyocytes, contracture of myofibrils and mild edema of intercellular space was observed. The content of all the studied proteins except KRP decreased below control levels. This situation sustained 3 weeks after injection and paralleled alterations in cardiomyocyte ultrastructure. Areas of myofibrillar contracture and lysis were noted, glycogen granules were sparse; mitochondria contained arrow-like inclusions that are characteristic for calcium overload, also huge mitochondria contacting each other by specialized intermitochondrial contacts were detected. Clumps of unripe elastic fibers in enlarged intercellular space were combined with increased deposition of collagens type I and III forming areas of fibrosis. The smaller dosage of isoproterenol (10 mg/kg) rendered no significant damage in the acute postinjection period but 3 weeks later it induced the thickening of extracellular matrix around cardiac cells and the increase in KRP and tubulin content by 26 and 32%, correspondingly. MLCK levels remained depressed throughout the experiment. The rise in KRP expression was also observed after the addition of isoproterenol to cultured chicken embryo cardiomyocytes. Obtained results indicate that even a single injection of isoproterenol creates long lasting structural alterations in cardiac muscle accompanied by the increased expression of extracellular matrix proteins and several sarcoplasmic proteins apparently involved in hypertrophic response of cardiomyocytes.     

Stereological ultrastructural study of myocardial atrophy in hypokinesia

The myocardium of Wistar rats immobilized for 5, 15 and 30 days was examined by morphometry and stereological methods for evaluating the volumetric and surface density of myofibrils, mitochondria, T system, sarcoplasmic reticulum and for the measurement of the volumetric ratio of different ultrastructures to the density of myofibrils and the surface-volumetric ratio of the main organelles of the cardiomyocyte. Myocardial atrophy was shown to develop in the course of hypokinesia. The 30-day hypokinesia entailed changes in ultrastructural organization of cardiomyocytes, attesting to the tension of intracellular systems responsible for energy supply, of ionic membrane transport and the contractile apparatus.     

An ultrastructural stereological analysis of the myocardium in homoiothermal animals during cooling]

By methods of electron microscopy and stereology the ultrastructural cardiomyocyte reorganization of rats exposed to influence of low temperatures (exposure during 16 days at -7 degrees C) was studied. It was shown, that with this regime of cooling the disturbance of intracellular regeneration in cardiomyocytes occurred and the complex of morphological changes typical for the syndrome of regenerative-plastic deficiency was developed. The most essential changes were seen in myofibrils and mitochondria. According to the stereologic data a change in spatial reorganization of cardiomyocytes was connected largely with these organelles. With the increase in cooling duration an increase in the volume density of myofibrils and a decrease in this parameter for mitochondria were marked. As a result of these changes the mitochondria/myofibrils volume ratio was essentially decreased. As a whole, ultrastructural reorganization of cardiomyocytes under the influence of low temperatures on rats was characterized by a decrease in the ratio of the organelle volume to myofibrillar volume. The same quantitative reorganization was revealed in atrophied cardiomyocytes under the conditions of the decreased inflow of plastic substances to cells.     

Effect of chronic stress on the ultrastructure of the myocardium and hypothalamus of "emotional" and "nonemotional" rats

The influence of chronic stress on the ultrastructure of the myocardium and hypothalamus was studied in experiments on male rats with different levels of emotional-behavioral reactivity. "Emotional" rats manifested a pronounced increase in glycogen granules in myocytes and intercellular space, appearance of the areas of overcontraction of myofibrils, conglomerates of aggregated platelets in myocardial capillaries, and red cell egress from myocardial and hypothalamic capillaries. Alterations in the ultrastructure of the myocardium and hypothalamus in "nonemotional" rats were less marked and consisted in the appearance of the areas of overcontraction of myofibrils, enlargement of sarcoplasmic reticulum caverns, and in an increase in the lipid content in cardiomyocytes. The ultrastructural changes in the myocardium and hypothalamus of "emotional" and "nonemotional" rats indicate different reactivity of the animals and are likely to be accounted for by different levels of activation of their adrenergic systems.     

Stereological analysis of the ultrastructural organization of the cardiomyocytes in the red-cheeked suslik in different seasons of the year

The myocardium of red-cheeked sousliks was studied at different seasons with the use of stereological analysis. The volume and surface densities of the myofibrils, mitochondria, T system, sarcoplasmic reticulum as well as the surface-volume ratios of the main organelles were measured. Pronounced seasonal changes in physiological activity of the heterothermal animals were accompanied by marked reorganization of the spatial ultrastructure of the cardiomyocytes. The seasonal regression of the heart weight and diminution of the cardiomyocyte diameter were recorded during hibernation. The authors believe that the increased volume ratio of the cytoplasmic organelles to the myofibrils forms the basis for a rapid adaptive reaction of the heart during hibernation and waking up.     

Photon radiation-induced structural and functional changes in the myocardium of hypertensive spontaneously hypertensive rats

Hypertensive SHR rates were irradiated with orange-red light using a Korobkov photon light-emitting diode matrix with a maximum radiation at 612 nm; irradiation was performed daily for 1 h for 13 days. After the course of irradiation, the rhythmoinothropic characteristics of the cardiac papillary muscle significantly improved. Morphological analysis revealed active rearrangement in myocytes, which were observed primarily in the structure of the sarcoplasmic reticulum (SR), whose relative area increased more than twice compared to the control. Apparently, photon therapy of hypertensive rats normalizes calcium homeostasis in myocytes and improves the calcium-transport function of SR. The normalization of structural and functional characteristics of the myocardium with hypertensive rates may result from an increase in the SR buffer capacity and activation of SR Ca²⁺-ATPase. Furthermore, qualitative and quantitative changes in the proportion of capillaries, myofibrils, and mitochondria in myocytes indicate the development of adaptive-compensatory processes leading to the activation of biosynthetic processes and an increase in the energy potential of the myocardium.     

Ultrastructural stereological analysis of the absolute parameters of the cardiomyocytes in myocardial hypertrophy

Arterial hypertension was produced in male Wistar rats by abdominal aorta ligation. By the 35th day of experiment the animals had developed myocardial hypertrophy. The subcellular organization of cardiomyocytes was studied by electron microscopy and stereology (computation of relative and absolute parameters). In myocardial hypertrophy, the absolute volume of myofibrils, sarcoplasmic reticulum and T system in the left ventricle of the heart was increased, whereas the absolute volume of the mitochondria remained unchanged. The general surface area of all organelles was noticeably increased. The myofibrils and sarcoplasmic reticulum experienced greater changes, which may reflect the features of compensatory processes under the experimental conditions described.     

The effect of insulin on plasma-membrane and mitochondrial-membrane potentials in isolated fat-cells.

1. A recently developed technique for the measurement of plasma-membrane and mitochondrial-membrane potentials in intact cells by using the distribution of 86Rb+ and [3H]methyltriphenylphosphonium+ has enabled us to characterize a novel insulin effect on fat-cell mitochondria. For control cells the plasma-membrane and mitochondrial-membrane potentials were 75 mV and 152 mV respectively. Insulin (10 mu units/ml) caused a 9 mV hyperpolarization of the plasma membrane and a 19 mV depolarization of the mitochondrial membrane. 2. The insulin-dependent mitochondrial depolarization was observed at physiological insulin concentrations (10 mu units/ml) and was apparent when the cells metabolized a wide variety of substrates. 3. Evidence from the uptake of the weak acid 5,5-dimethyloxazolidine-2,4-dione by fat-cells was interpreted as indicating that the mitochondrial pH gradient was increased by insulin. 4. Insulin alters the balance between the electrical and pH-gradient components that form the mitochondrial protonmotive force. A model is proposed.     

HSP25 in isolated perfused rat hearts: Localization and response to hyperthermia

Recent investigations concentrate on the correlation between the myocardial expression of the inducible 70-kDa heat shock protein (HSP70i) by different stress conditions and its possible protective effects. Only few studies have focused on the involvement of small heat shock proteins in this process. We analyzed the location of the small heat shock protein HSP25 in isolated cardiomyocytes as well as its location and induction in isolated perfused hearts of rats. By immunofluorescence microscopy HSP25 was found to colocalize with actin in the I-band of myofibrils in cardiomyocytes of isolated perfused hearts as well as in isolated neonatal and adult cardiomyocytes. Hyperthermic perfusion of isolated hearts for 45 min resulted in modulation of different parameters of heart function and in induction of HSP25 and HSP70i. Temperatures higher than 43°C (44–46°C) were lethal with respect to the contractile function of the hearts. Compared to control hearts perfused at 37°C, significant increases during hyperthermic perfusion at 42°C and 43°C were obtained for heart rate, contraction velocity and relaxation velocity. In response to hyperthermia at 43°C and after subsequent normothermic perfusion for 135 min at 37°C, left ventricular pressure, contraction velocity and relaxation velocity remained significantly elevated. However, heart rate returned to control values immediately after the period of heat treatment. HSP25 is constitutively expressed even in normothermic perfused hearts as shown by Western blotting. Hyperthermia increased the content of HSP25 only in the left ventricular tissue. In contrast, HSP70i was strongly induced in all analyzed parts of the myocardium (left ventricle, right ventricle, septum). Our findings suggest a differential regulation of HSP25 and HSP70i expression in response to hyperthermia in isolated perfused hearts. The constitutively expressed HSP25 seems to be located adjacent to the myofibrils which implies a specific role of this protein even under unstressed conditions for the contractile function of the myocardium.     

Cardiac ischemia and reperfusion in spontaneously diabetic rats with and without application of EGb 761: I. cardiomyocytes

Diabetic cardiomyopathy is known to result in increased mortality after ischemic events. Permanently increased oxidative stress with formation of oxygen-free radicals plays a key role in the development of specific heart muscle disease. Associated lesions include structural alterations to cardiomyocytes. Antioxidative treatment in addition to the usual insulin substitution would seem sensible in preventing or delaying long-term diabetic complications and protecting the myocardium against acute ischemic events. We investigated the effects of radical scavenger Ginkgo biloba extract EGb 761 against diabetes-induced damage to cardiomyocytes and additional ischemia/reperfusion injury in spontaneously diabetic BioBreeding/Ottawa Karlsburg (BB/OK) rats, as a model of diabetic myocardium infarction. Morphological and morphometric parameters of heart muscles were analyzed by light and electron-microscopic techniques. We used immunohistochemistry to evaluate parameters of oxidative stress (superoxide dismutase [SOD]) and inducible nitric oxide synthase (iNOS) protein expression. Our results indicated that A) Diabetic myocardium appears more vulnerable to ischemia/reperfusion damage concerning ultrastructure of cardiomyocytes (sarcomeres, vacuoles, mitochondria), expression of antioxidative enzymes (CuZnSOD, MnSOD), and iNOS than normal myocardium; B) Pre-treatment of diabetic myocardium with EGb and additional ischemia/reperfusion leads to a relative improvement in myocardial ultrastructure compared to unprotected myocardium. In summary, EGb appears to be promising as an adjuvant therapeutic drug in diabetics with respect to ischemic myocardium injury. It may contribute to the prevention of late diabetic complications in diabetic cardiomyopathy.     

Immunohistochemical determination of cytosolic cytochrome C concentration in cardiomyocytes.

Cytochrome c release from the intermembrane space of mitochondria is one of the triggers of apoptosis. There is no histochemical method available to demonstrate cytochrome c in cryostat sections, possibly because small cytosolic proteins diffuse readily into aqueous fixation media. This report shows that it is possible to demonstrate cytochrome c release in cardiomyocytes in failing myocardium using vapor fixation of cryostat sections and immunohistochemistry. The method is calibrated using sections from gelatin blocks containing known concentrations of cytochrome c. The method is applied to the hypertrophied right ventricular wall of rats in which pulmonary hypertension was induced by monocrotaline. Cytochrome c release is found in a fraction of the cardiomyocytes, leading to a mosaic-staining pattern. Cytochrome c release was found in myocytes over the full range of cross-sectional area (from 1 to 3.9 times control) in the hypertrophied myocardium. Cytosolic cytochrome c concentrations up to 0.4-0.5 mM occur frequently.     

Ultrastructural changes in cardiomyocytes and heart muscle capillaries after vagotomy and physical exertion

Electron microscopic studies of the changes in cardiomyocytes and capillaries of the cardiac muscle were performed in white mice after partial extracardiac parasympathectomy and graded physical exercise. It has been established that submaximum physical exercise leads to slight ultrastructural alterations in the left ventricular cardiomyocytes and capillaries. Maximum physical exercise in intact animals is followed by still greater ultrastructural changes in the heart muscle. Swelling of mitochondria with the focal destruction of crysts, widening of sarcoplasmic reticular cisterns, disturbance of sarcomer to mitochondrion ratio, endotheliocyte edema and narrowing of the capillary lumen are observed. In vagotomized animals fulfilling running exercises of submaximum load dystrophic changes in cardiomyocytes and capillaries are noted only at early stages (day 7). Maximum physical exercise in animals with disturbed integrated nerve influences promotes the development of focal destructive changes in the myocardium.     

Correction of stress-induced disorders of the ultrastructure of hypertrophied myocardium with thyroid hormones

In the experiment performed on 25 non-inbred male rats ultrastructural changes in cardiomyocytes of the hypertrophied heart have been studied under conditions of stress caused by immobilization and possibility to correct these changes by means of thyroid hormones. The stress intensifies destructive lesions in a number of organelles++, which develop at a prolonged hypertrophy, decreases essentially the ratio mitochondria/myofibrils in section area. Small doses of the thyroid hormones protect the hypertrophied heart from the damaging effect of the stress: prevent the stress-induced+ decrease in the ratio mitochondria/myofibrils, as well as stimulate development of the regenerative-adaptive processes (increase in size and number of mitochondria and their crists, elements of the sarcoplasmic reticulum, glycogen granules, increase in section areas of their nuclei and chromatin in them). The thyroid hormones restrict essentially decrease in correlation of organelles++, resulted from hypertrophy. Thus, the stress-induced disturbances in ultrastructure of the hypertrophied heart can be prevent by means of the thyroid hormones, administered in small doses.