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.     

Prostaglandins and cyclic nucleotides in the dynamic development of an experimental poisoning syndrome caused by Yersinia pestis lipopolysaccharide

This work deals with the influence of Y. pestis lipopolysaccharide (LPS), introduced intraperitoneally in a dose of 2 LD50, on the content of prostaglandins (PG), such as PGE, PGF2 alpha and 6-keto-PGF1 alpha, thromboxane, cAMP and cGMP in the liver, lungs and blood plasma of guinea pigs in the process of the development of experimental intoxication. The content of thromboxane in blood plasma increased 2.4-fold in 2 hours after intoxication and remained elevated for as long as 5 hours. Other parameters of blood plasma remained unchanged. The data obtained in this investigation indicate that thromboxane, known as a regulator of thrombogenesis, may induce early disturbances in microcirculation. A change in the content of PG was shown to occur in pulmonary tissue 2 and 5 hours after the beginning of intoxication. The content of PG in liver tissue was found to occur at a later period of the toxic action. The concentration of cyclic nucleotides (CN) in the tissues under study sharply increased even at the initial stage of the development of shock in guinea pigs. The effect of LPS on the metabolism of PG and CN, revealed in this investigation, resembles the effect produced by the thermostable fraction of "mouse" toxin.     

DNA changes in a nonischemic area of the rat myocardium in experimental myocardial infarct and its prevention

DNA damage and repair in the nonischemic area of the heart were analyzed after experimental myocardial infarction to evaluate the effect on these processes of the beta-blocker inderal and lipid peroxidation inhibitor ionol. It was found that in the nonischemic area of the heart, DNA damage was manifested by the decreased polymerism averted to a significant degree by inderal and ionol which interfered with postinfarction activation of lipid peroxidation. Accordingly, inderal and, to a greater degree, ionol reduced postinfarction activation of DNA repair synthesis in the nonischemic area of the heart.     

Saturation of anti cyclic nucleotides antibodies by endogenous cyclic nucleotides.

Rabbits immunized against cyclic AMP or cyclic GMP produce antibodies which are fully saturated by their respective endogenous cyclic nucleotides. This was proved a) in comparing radioimmunological measurements of cyclic nucleotides in antiserum and the binding site concentration determined by equilibrium dialysis, b) in showing the ineffectiveness of serum phosphodiesterase to hydrolyze the cyclic AMP present in the anti-cyclic AMP antiserum. Immunological and radioimmunological implications of this phenomenon are discussed.     

Ultrastructure of the sinus and atrioventricular nodes in experimental myocardial infarct

The ultrastructure of sinus and atrioventricular nodes was studied in white rats with experimental myocardial infarction. 24 hours after the induction of the disease mitochondrial enlargement characterized by the increase in their area, decrease in the number of cristae and the decline in the rate of mitochondrial energy effectiveness was detected. Different degrees of nuclear chromatin aggregation and membrane permeability for colloidal lanthanum were observed. Characteristic types of conduction cellular lesions were revealed in experimental myocardial infarction.     

Effect of adaptation to short-term stress exposure on the fibrillation threshold and ectopic activity of the heart in experimental myocardial infarct

Preliminary adaptation to short-term stress was shown to prevent the decrease in the heart fibrillation threshold and an increase in ectopic activity which is usually observed in experimental myocardial infarction. This protective effect involves an enhanced activity of the antioxidant system. Therefore, a synthetic antioxidant ionol was applied to prevent disturbances of the heart electrical stability in infarction. It was established that ionol completely prevents the decrease in the electrical threshold and the increase in ectopic activity of the heart in experimental infarction. Thus, it can be concluded that ionol possesses an antiarrhythmic effect.     

Effect of enkephalins on vasopressin and aldosterone levels in acute experimental myocardial ischemia

It has been demonstrated in experiments on rats that acute myocardial ischemia gives rise to a decrease in diuresis, elevation of antidiuretic activity of blood plasma and the blood concentration of immunoreactive aldosterone. Intraperitoneal injection of a synthetic enkephalin analog D-ala2-leu5-arg6-enkephalin in a dose of 1.25 nmol/kg bw resulted in partial normalization of diuresis, reduction in antidiuretic activity of blood plasma and blood aldosterone level to the control values. Naloxone eliminated the effects described. It is concluded that enkephalins have an inhibitory action on aldosterone and vasopressin secretion, with this action being mediated via opiate receptors.     

Changes in the cyclic nucleotides of rat thyroid, pituitary and plasma caused by methylthiouracil treatment.

Changes in the content of cyclic nucleotides (cAMP and cGMP) and related enzyme activities were observed in the rat thyroid, pituitary and plasma during the prolonged increase of endogenous TSH produced by treatment with methylthiouracil (MTU). Experiments were performed after 4 weeks treatment with MTU. The wet weight and cAMP content per wet weight of the thyroid increased 3 and 1.4 times respectively, but cGMP showed a slight decrease. Pituitary weight increased 1.3 times, but cAMP and cGMP content did not change. The cAMP level in plasma also increased about 1.3 times, but cGMP did not increase. The cAMP-phosphodiesterase activity in the thyroid, pituitary and plasma was increased 1.9, 1.4 and 1.3 times respectively after MTU treatment, while cGMP-phosphodiesterase showed no significant change. ATPase activity in the thyroid and pituitary was also increased more than 1.5 times after MTU treatment, while 5'-nucleotidase activitity decreased remarkably. These data indicate that the metabolism of the cyclic nucleotide system in the thyroid is stimulated by TSH.     

Protein-synthesizing function of the liver of rabbits in experimental myocardial infarct

The content of serum albumin in rabbit blood was found to be lowered within the first day after reproduction of experimental myocardial infarction. The rate and the level of translation of endogenous mRNA were studied in cell-free systems from normal rabbit liver and 6-12-24 h after experimental myocardial infarction. The decrease of the total protein synthesis in the crude cell-free system from the liver of experimental animals was shown to depend on the lack of energy supply rather than on the reduced activity of the protein-synthesizing apparatus. The relative drop of protein synthesis in the cell-free system with saturating concentration of ATP, GTP and creatine phosphate is likely to be connected with a decrease in the proportion of membrane-bound polysomes.     

Functioning of the monooxygenase system of the liver in experimental myocardial infarct

The experiments on rats have shown that coronary artery ligation reduces the content of microsomal cytochromes P-450 and b5 and causes amidopyrine-N-demethylation and aniline-p-hydroxylation disturbances that persist throughout a 3-week period of myocardial infarction. The investigation of spontaneous lipid peroxidation of microsomal membranes in myocardial infarction has shown that concentration of malonic dialdehyde in microsomal fraction significantly increased by the 7th day after coronary artery ligation, as compared to sham-operated rats.     

Participation of histamine and cyclic nucleotides in the regulation of gastric secretion in experimental thyrotoxicosis

Experiments on 48 Wistar rats evidence that in early times of hyperthyroidism, the action of thyroxine on parietal cells is mediated by histamine and cAMP, while in prolonged hyperthyroidism, its action on parietal cells refractory to endogenous histamine and cAMP is found to be unmediated and direct.     

Reaction of the nodose ganglion neurons to myocardial ischemia complicated by ventricular fibrillation

Standard microelectrode techniques were used to study the impulse activity of different types of nodosal ganglion neurons. Differences in electrical activity of cardiovascular neurons were observed in myocardial ischemia both complicated and not complicated by fibrillation. In these conditions rhythmic activity of cardiopulmonary, late inspiratory and inspiratory-expiratory neurons is quite similar.