[Effect of caffeine on various regulatory mechanisms, rhythmogenesis and contractile function of the isolated rat heart in ischemia and post-ischemic reperfusion].

The rat hearts isolated and perfused by the Langendorf method were used to examine the effects of caffeine-induced increase in cAMP levels on the contractility, rhythmogenesis, some mechanisms of myocardial autonomic regulation in ischemia and resultant reperfusion. The caffeine-induced elevated intracellular cAMP resulted in normalization of myocardial contractility in reperfusion, as well as in stabilization of norepinephrine levels and cardiac adrenoreactivity during ischemia and reperfusion. The positive action of higher cardiomyocyte cAMP levels on the performance of the heart and its sympathetic and parasympathetic control was followed by a reduction in myocardial sensitivity to the induced lipid peroxidation.

[Soluble guanyl cyclase of blood platelets and heart of rats with experimental myocardial ischemia].

The activity of soluble guanylate cyclase (GC) and its regulation in the platelets and heart of normal rats and rats with experimental acute myocardial ischemia provoked by coronary ligation was examined. There was a synchronous reduction in platelet and heart GC activity immediately following 15 minutes after surgery along with a drastically marked drop in genuine baseline activity (with Mg2+) to 19 and 40% in the platelets and heart (both ischemic and intact areas), respectively. Following 24 hours, GC activity insignificantly rose (up to 35.

[Effect of ischemia and postischemic reperfusion on some mechanisms of regulation, rhythmogenesis, and contractile function of the heart in rats].

Isolated rat hearts were perfused with Krebs' solution after Langendorff's method. Decrease of the perfusion rate from 8.8 to 2.

[Soluble guanylate cyclase from rat platelets during experimental myocardial ischemia].

Activity of soluble guanylate cyclase and regulation of the enzyme were studied in thrombocytes of intact rats and under conditions of acute myocardial ischemia caused by ligation of left coronary artery. Distinct decrease in the enzymatic activity was detected already within 15 min after the operation: down to 19% and 46%, in presence of Mg2+ and Mn2+, respectively, as compared with control values. Within 24 hrs of the ischemia the guanylate cyclase activity was slightly increased up to 33.

[Cardiac guanylate cyclase in rats with ischemic damage to the myocardium].

The activity of soluble guanylate cyclase (GC) of rat heart and the regulatory activity of dithiothreitol (DTT) and sodium nitroprusside under ischemic myocardium damage caused by ligation of left coronary artery has been investigated. After coronary occlusion the GC activity in the presence of Mn2+ or Mg2+ decreases both in ischemic and in intact zones (40% from normal) in 15 min, in 24 h it more diminishes (up to 30%) in the ischemic zone, in intact zone it partially normalizes (up to 70%). The stimulatory effect of DTT on the GC activity in studied heart zones doesn't differ from control.

[Kinetics of the oxidative deamination reaction in the preconvulsive period of oxygen-induced epilepsy].

Kinetic parameters of monoamine oxidative deamination in compensatory and preconvulsive periods of oxygen epilepsia were studied. It was shown that in rat brain MAO's affinity for serotonin reduced from the 5th minute of exposure to hyperbaric oxygen and went on reducing on the 15th minute. In rat heart the affinity of MAO for serotonin firstly decreased and then returned to normal meaning.

[Changes in the balance of biogenic monoamines and their metabolites in the organs of rats with oxygen-induced epilepsy].

The content of some biogenic monoamines and their metabolites in rat brain and heart in different periods of oxygen epilepsia was studied using high performance liquid chromatography with electrochemical detection. It was shown that already at the 5th minute of exposure to oxygen adrenaline, DOPA and some noradrenaline metabolites disappeared in the brain and noradrenaline level reduced. At this period in rat heart the reduction of catecholamine content was the most distinct and serotonin level was unchanged.

[Use of hyperbaric oxygenation in the therapy of experimental hypothyroidism].

In animal experiments on rabbits the effect of hyperbaric oxygen was studied on the functional state of the myocardium, the cardiac resistance to induced peroxide lipid oxidation, the structural and functional changes in the thyroid gland and the state of microcirculation in the conditions of experimentally induced hypothyrosis. It was demonstrated that hyperbaric oxygen has a favourable effect on the state of myocardium and microcirculation.

[Reaction of deamination of monoamines in the brain and heart of rats under the toxic action of hyperbaric oxygenation].

Kinetic parameters of monoamine deamination processes in the rat brain and heart after hyperbaric oxygenation (HBO) in toxic conditions (6 ata) were studied. HBO was shown to cause a substantial reduction in MAO affinity to serotonin in the brain, but not in the heart. Contrastingly, MAO affinity to dopamine was found to decrease in the heart, but not in the brain in response to HBO.

[Effect of benzamide derivatives on convulsions induced by the toxic action of oxygen in rats].

The reversible MAO-A inhibitor moclobemide (5 mg/kg) was shown to prevent seizures in rats during exposure to toxic oxygen (6 ata). Benzamide derivatives increased the latent period of oxygen seizures and decreased the lethality following hyperbaric oxygenation. The range of anti-MAO activity of moclobemide and clorgyline in the rat brain and heart after toxic oxygenation was studied.

[Contractile function and antioxidative system of the myocardium of the intact rabbit during hyperbaric oxygenation].

Daily exposures of rabbits to the HBO (2 ata, 1 hr) enhanced activity of glutathione-peroxidase for all 28 days of exposure. Other parameters of the antioxidative defence and the contractile function remained unchanged. The 2.

[Increased levels of transferrin in the rabbit heart muscle in experimental myocardial infarction].

Concentration of transferrin was distinctly increased in the infarction zone of heart muscle of rabbits with experimental myocardium infarction within 24 hrs and 168 hrs after coronary occlusion. Under conditions of cell lysis apotransferrin appears to bind free iron in rabbit heart muscle. The data obtained suggest that apotransferrin may serve as a screening agent of free iron, while caeruloplasmin is able to exhibit the superoxide dismutase activity.

[Effect of hyperbaric oxygenation on paramagnetic centers in the rabbit myocardium during experimental myocardial infarction].

Changes in paramagnetic centres (PC) concentration in rabbit's myocardial muscle were studied under experimental myocardial infarction during 168 hours by means of ESR-spectroscopy. PC characterized by ESR signal with g = 3.0 was found.

[Superoxide dismutase inhibition as a prerequisite for disordered myocardial function under oxygen loading].

Changes in the contractility of rabbit myocardium following administration of diethyl dithiocarbamate were studied to determine the role of superoxide dismutase (SOD) in cardiac support function. It was observed that in healthy rabbits, a 50% decrease in the left ventricle SOD level induced by the inhibitor was not followed by any considerable disturbances in myocardial contractility as determined without additional stimulation and load. HBO sessions caused appreciable disorders in heart contractility which could be partly prevented by SOD administration.

[Effect of guanyl nucleotides and hyperbaric oxygenation on the adenylate cyclase activity of the heart in rabbits with myocardial hypertrophy].

The authors studied the role of guanyl nucleotides and hyperbaric oxygenation (HBO) in desensitization and resensitization of adenylate cyclase of the heart during hypertrophy which was induced by aorta stenosing. The basal activity of the enzyme and the rate of its activation with adrenaline and guanyl nucleotides were discovered to be reduced. In the presence of guanyl nucleotides, HBO gave rise to the recovery of enzyme sensitivity to the hormone.

[Effect of hyperbaric oxygenation on the cyclic nucleotide and catecholamine content, energy and carbohydrate metabolism and on cardiac contractile function in acute focal myocardial ischemia].

Two hours after the ligation of the descending branch of the left coronary artery in rabbits the contractile function of the heart decreased, concentration of phosphocreatine, ATP, glycogen dropped, and the content of lactic acid in the ischaemic and intact areas of the left ventricle elevated. Two-hour ischaemia of the myocardium was accompanied by increase of the cAMP and decrease of cGMP levels in the ischaemic and intact areas. Hyperbaric oxygenation (HBO, 2 at.

[Changes in the activity of cyclic adenosine monophosphate metabolism enzymes in myocardial hypertrophy and after exposure to hyperbaric oxygenation].

Hypertrophy of myocardium, developed within 4 weeks after aorta stenosis, led to alteration in content of adrenaline in heart tissue as well as in some pathways of cAMP turnover: decrease in content of cAMP, an increase in the basal activity of adenylate cyclase, decrease in activation of the enzyme by adrenaline; activity of phosphodiesterase was not distinctly altered. Under conditions of hyperbaric oxygenation hypertrophy of myocardium became less distinct, content of cAMP was increased up to the normal value, the increased basal activity of adenylate cyclase was slightly decreased, whereas sensitivity of the enzyme to adrenaline did not reduce, content of adrenaline was increased.

[Patholphysiological aspects of hyperbaric oxygenation exposure on the heart in compensatory hypertrophy].

Chronic interrupted effect of hyperbaric oxygenation applied for 4 weeks reduces the rate of the development of myocardial hypertrophy in rabbits and is thus conducive to stabilization of myocardial contractile function on a sufficiently high level and increases the reliability of the circulation system in emergency situations. In the dangerous stage of compensatory cardiac hyperfunctions, hyperbaric oxygenation protects the myocardium from destructive changes and activates bionergetic processes, whereas in the stage of marked hypertrophy it inhibits the development of cardiosclerosis. Hyperbaric oxygenation prevents the development of functional isolation of the hypertrophied myocardium from the neurohormonal effects and contributes to the preservation of the reserve capacity of the neuroeffector mechanisms of heart regulations.

[Effect of hyperbaric oxygenation on several functional and morphologic properties of the heart and catecholamine metabolism in the presence of compensatory myocardial hypertrophy].

Rabbits subjected to hyperbaric oxygenation (HBO) for one month following ascending aorta stenosis developed less distinct hypertrophy and signs of myocardial dystrophy with a more distinct enhancement of the left ventricular contractility than animals with aortic stenosis kept under normal pressure. In rabbits with heart hypertrophy developing under HBO the increasing adaptive capacity of the myocardium was accompanied by an elevation in functional reserve of the sympathetic regulation apparatus. Apparently HBO aided the development of the optimum cardiac adaptation to a high afterload.