Ultrastructural Myocardial Reorganization during Experimental Treatment with Doxorubicin and Atorvastatin.

We studied ultrastructural reorganization of the myocardium in Wistar rats treated with doxorubicin (single intraperitoneal injection in a dose of 15 mg/kg) and atorvastatin (daily intragastric administration in a dose of 20 mg/kg for 7 days) individually and in combination. It was found that doxorubicin administered alone or in combination with atorvastatin induces disturbances of varying severity in cardiomyocyte ultrastructure indicating the development of regenerative and plastic myocardial insufficiency. In case of isolated administration of atorvastatin, lytic changes in myofibrils, increased autophagic processes, and segregation of the fibrillar and granular components in the nucleoli appeared in the ultrastructure of some cardiomyocytes with increasing the observation period. Ultrastructural stereological analysis revealed a tendency to a decrease in the volume density of myofibrils and mitochondria in all experimental groups in comparison with the control.

Cardiotoxic and Dyslipidemic Effects of Doxorubicin and Betulinic Acid Amide.

Changes in the blood lipid spectrum and structural reorganization of the rat myocardium in response to injection of a single sublethal dose of doxorubicin (7 mg/kg) alone and in combination with course administration of betulonic acid amide (100 mg/kg/day for 14 days) were studied. Betulinic acid amide in the specified dose exhibited less pronounced cardiotoxic (necrobiotic impairment of cardiomyocytes) and dyslipidemic (increase of cholesterol and triglyceride levels) effects in comparison with doxorubicin. Combined treatment with betulinic acid amide and doxorubicin led to more pronounced remodeling of the myocardium, which was shown by a significant increase of the connective tissue/cardiomyocyte volume ratio detected by day 14 of the experiment.

Stimulation of Cardiomyocyte Regeneratory Reactions under Conditions of Cytopathic Hypercholesterolemia.

The regeneratory reactions of cardiomyocytes in the heart under conditions of cytopathic exposure to hypercholesterolemia and during verapamil treatment were studied by immunohistochemical detection of proliferation marker Ki-67 and evaluation of cardiomyocyte count. A 30-day exposure of rats to atherogenic diet led to an increase of Ki-67+ cardiomyocytes by 14.5-16.7 times (p<0.05). The Ki-67 label index in cardiomyocytes remained higher than normally (8-9-fold; p<0.05) after 64 days. It remained elevated (8-11-fold; p<0.05) after verapamil treatment. Evaluation of cardiomyocyte count and of their nuclear status detected various regeneratory strategies: increase of the total cardiomyocyte count, with increase of the percentage of mononuclear cardiomyocytes (particularly in response to verapamil in group 1 rats); decrease of total cardiomyocyte count with increase of the percentage of multinuclear cardiomyocytes (particularly in group 2 rats in response to verapamil).

Immunohistochemical Analysis of MMP-2 Expression in the Myocardium During the Postinfarction Period.

Immunohistochemical analysis revealed 2.5-fold increased of expression MMP-2 in myocardium samples during the early period (up to 3 days) of postinfarction reparative regeneration. During this period, MMP-2 was detected mainly in monocytes/macrophages circulating in the blood and migrating to the necrotic zone, while expression in the intermuscular and perivascular connective tissue was lower. At later terms, with development of large focal and diffuse cardiosclerosis, MMP-2 expression significantly decreased (to the initial level) and was detected mainly in the foci of intermuscular and perivascular fibrosis, its area in the sections increased by 1.8 times. Evaluation of MMP-2 expression in the blood vessels showed that the immunohistochemical reaction was the most pronounced in the walls of new sinusoidal vessels and the minimum in the intramural arteries of medium diameter. These results attest to an important role of MMP in connective tissue remodeling (proteolytic degradation) during the early period of postinfarction reparative regeneration. The decrease in MMP-2 expression observed at later terms correlated with myocardial fibrosis progression.

[Correlations of reproductive parameters of water vole females (Arvicola amphibius) with morphometric and hormonal characteristics].

Fluctuations in water vole population size depend on abiotic and intra-population factors affecting the physiological condition of females. The relationship between variability in reproductive success and morpho-physiological characteristics of female during pregnancy is studied quite poorly. In standard vivarium conditions, the morphometric and hormonal characteristics of female were assessed at different stages of pregnancy (first trimester--days 4-7, second trimester--days 8-14, third semester--days 15-20), and their relationship with potential and actual fecundity and the level of embryonic lethality was elucidated. The general regression model was used in the data analysis. Positive correlations were found between potential fecundity and the female body mass at mating, body mass index and blood testosterone level. The reproductive parameters under study were independent of the blood thyroxin level. A positive correlation was established between the level of embryonic loss and the indices of liver and lung functions. Liver and spleen are essential for the maintenance of the female body mass homeostasis during the reproductive period.

Expression of ryanodine receptor mRNA and sarcoplasmic Ca²âº-ATPase mRNA in the myocardium and intracellular reorganization of cardiomyocytes in dyslipidemia and during verapamil treatment.

In experiments on rats, atherogenic diet led to hypercholesterolemia, while addition of verapamil to the diet led to the development of hypertriglyceridemia in these animals. Dyslipidemia induced significant changes in the cardiomyocyte ultrastructure (lytic changes in myofibrils and sarcoplasmic matrix and aggravation of autophagocytosis) that were most pronounced after addition of mercazolyl alone to the diet. After 30-day atherogenic diet, we observed a decrease in the relative content of RyR2 mRNA (by 67-73%, p<0.01) and SERCA2a mRNA (by 75-91%, p<0.01) in the myocardium. In 64 days these parameters remained reduced: by 64-72% (p<0.05) and 54-62% (p<0.05), respectively. Verapamil treatment reduced the severity and number of lytic lesions in cardiomyocytes, induced considerable glycogen accumulation in the sarcoplasm and its sequestration, promoted normalization, and prevented pronounced decrease of the relative RyR2 mRNA and SERCA2a mRNA in rat myocardium.

Remodeling of myocardium in rat with chronic dyslipidemia and under conditions of verapamil treatment.

The type and intensity of remodeling (structural reorganization) of the myocardium in Wistar rats were studied under conditions of experimental chronic dyslipidemia and verapamil treatment. Long (64 days) atherogenic diet caused dyslipidemia and led to reduction of the heart percent weight. The cytopathic effect of dyslipidemia manifested in more intense lytic injuries of cardiomyocytes, development of diffuse and small focal cardiosclerosis under conditions of manifest circulatory disorders. Remodeling of the myocardium during various periods of the experiment manifested in a higher connective tissue/cardiomyocyte volume ratio (by 74% after 30 days and by 58-62% after 64 days of experiment). Verapamil injection promoted attenuation of lytic changes in cardiomyocytes and in fibroplastic reactions of the stroma, but failed to prevent them completely.

Proliferative activity of cadriomyocytes in chronic hypercholesterolemia.

We studied proliferative activity of cardiomyocytes (using proliferation marker Ki-67) and compared it with their total number in the heart under conditions of experimental chronic hypercholesterolemia and its combination with hypothyroidism. It was found that Ki-67-positive cells are primarily located in the subepicardial layer near the heart base in both intact and experimental animals. Replicative cardiomyocyte pool in intact rats constituted 1.67 ± 0.33‰ of the total cardiomyocyte population; after 68-day atherogenic diet with exogenous cholesterol alone, the replicative cardiomyocyte pool decreased by 16 % (to 1.40 ± 0.24‰). Treatment with mercazolil against the background of exogenous cholesterol increased this parameter by 40 % (to 2.33 ± 0.88‰). Changes in replicative activity of cardiomyocytes correlated with their total number in the heart and organ weight. We conclude that replicative cardiomyocyte pool primarily includes non-terminally differentiated cardiomyocytes (small mononuclear cardiomyocytes) and their proliferation maintains the total number of cardiomyocytes in the heart under conditions of cytopathic influences and provides the basis for physiological and reparative regeneration of the myocardium.