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Biomedical subjects

J Styk

Publications and source records attributed to J Styk.

At least 37 records · Page 2Linked to original sources
PubMed1991

[Right-sided mechanical circulatory support in acute right ventricular failure in the dog].

The technique of surgically induced acute progressive right ventricular failure in experimental animals is described. It sumultates the hemodynamic situation of right ventricular failure in some patients after termination of extracorporeal circulation applied for carrying out procedures on the left ventricle. The described technique consists of rightsided longitudinal ventriculotomy, destruction of the tricuspid valve, and ligation of the right coronary artery. Nine control dogs died within two hours after induction of failure due to low stroke volume caused by low pulmonary and left atrial pressure. The use of rightsided support appliance draining blood from the right atrium in systole and pumping it into the trunk of the pulmonary artery in diastole by means of a membrane pump resulted in further 12 dogs in the restoration of left ventricular diastolic pressure, significant increase of aortal pressure (p less than 0.003) and stroke volume (p less than 0.003) and in a decrease of right atrial pressure (p less than 0.003). The study demonstrated that by using the described mechanical support the circulation can be adequately assisted so that the failing right side of the heart can get restored. (Tab.1,Fig.5,Ref.25.).

Acute Disease↗
PubMed1990

Mechanism of action of estradiol on sodium pump in sarcolemma from the myocardium.

Today it is accepted that estrogens mitigate the consequences of ischemic heart disease. Preliminary experiments revealed an increase in heart sarcolemmal (Na+ + K+)-ATPase activity after application of estradiol in vivo. It is also well known the key role of latter enzyme for heart function. The facts mentioned above indicate that estradiol may act on the heart just via modulation of the (Na+ + K+)-ATPase activity. In present paper it is confirmed that 17-beta-estradiol stimulates the activity of sarcolemmal (Na+ + K+)-ATPase by allosteric manner, particularly by increasing positive cooperativity between the K(+)-binding sites of the enzyme. This effect is manifested by enhancement in functional capacity of the sodium pump in sarcolemma. Stimulatory effect of estradiol is bound to integrated myocytes: neither is it manifested in isolated sarcolemma in vitro nor exhibits any influence on the affinity of binding sites for cardiac glycosides or on total capacity of the sarcolemma to bind ouabain. Basing on the data obtained it was assumed that estradiol acts on the (Na+ + K+)-ATPase not directly but by means of a mediator released within the myocyte.

Animals↗
PubMed1990

[Extracorporeal circulation with auto-oxygenation in cardiac surgery].

The authors describe briefly the historical development of the method of biventricular bypass without the use of and oxygenator and its technique. With regard to the favourable influence on physiological parameters of the organism, the reduced number of complications and the economic factor, the authors consider its wider use in contemporary coronary surgery justified.

Cardiac Surgical Procedures↗
PubMed1990

[Analysis and study of factors in ischemia-reperfusion heart damage].

Specific features of myocardial damage induced by overload and the very action of reactive oxygen species were analyzed and characterized. The experiments were performed on the isolated perfused heart of the rat (according to Langendorff). Overload of the heart by calcium ions was studied on the model of calcium paradox; damage of the heart by reactive oxygen species was induced by a single application of a free radicals generating system. Functional, biochemical, and ultrastructural parameters were studied. Several of the examined parameters (lactate accumulation, drop of total adenine nucleotides, transmural heterogeneity in the histochemical reactivity of enzymes) are of a certain value in recognizing the participation of individual factors involved in reperfusion induced damage of the myocardium.

Animals↗
PubMed1989

Protective effect of oestradiol on the heart of rats exposed to acute ischaemia.

Sex-related differences in mortality from ischaemic heart disease are attributed chiefly to difference in the incidence of atherosclerosis. Little attention has been paid to the influence of sex hormones on resistance of the myocardium itself to acute ischaemia. Experiments on rats showed that isolated female hearts were more resistant than male hearts. A period of eight weeks spent at an altitude of 1,350 m raised heart resistance only in males. Conversely, gonadectomy abruptly reduced the resistance of the male heart to ischaemia, especially under conditions of mild altitude hypoxia. The administration of oestradiol to gonadectomized male rats largely abolished the disturbance caused by isolated gonadectomy. Since coronary vasoconstriction and vasospasm lead to temporary ischaemia and even to infarction, the above effect of the sex hormones may play a role in the increased incidence of heart attacks after the gonads have ceased to function.

Animals↗
PubMed1989

The influence of exaprolol upon the ischaemic rat heart and its interaction with sarcolemmal (Na+ + K+)-ATPase.

The capability of cyclohexylphenol exaprolol of protecting the ischaemic myocardium during ischaemic cardiac arrest was assessed in the isolated working rat heart. Exaprolol added to the perfusion medium in a dose of 10(-7) mol.l-1 only minimally influenced the left ventricular function (reduced the stroke volume by 18.84% and cardiac output by 14.63%). The hearts were subjected to global ischaemia for 75 min at 26 degrees C and subsequently reperfused for 60 min at 37 degrees C. The recovery of left ventricular function following reperfusion, expressed as a percentage of preischaemic functional performance was used as an indicator of the ischaemic tolerance of the heart. The effect of exaprolol on sarcolemmal (Na+ + K+)-, Mg2+- and Ca2+-ATPase activities was also examined. Exaprolol-pretreated hearts revealed better postischaemic recovery of the left ventricular dP/dt max and stroke volume as well as improved efficiency in the transformation of chemical energy to mechanical work. Exaprolol in 10(-4) mol.l-1 concentration significantly stimulated the specific activity of sarcolemmal (Na+ + K+)-ATPase. Possible mechanisms of the salutary effect of exaprolol on the ischaemic heart are discussed.

Adrenergic beta-Antagonists↗
PubMed1988

[Assisted circulation for volume relief of the right heart ventricle].

The model of the failure of the right ventricle was formed in dog experiments. The animals were connected with the right mechanically assisted circulation. The blood was pumped synchronously with the heart action from the right atrium directly to the pulmonary artery by temporary bypass of the right ventricle. The right volume relief improved (p less than 0.03) the decisive hemodynamic parameters. The value of assisted circulation in case of the hitherto only difficulty to controlled failure of the right ventricle is proved with that.

Animals↗