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Biomedical subjects

N N Orlova

Publications and source records attributed to N N Orlova.

At least 19 recordsLinked to original sources
PubMed1992

[Specific features of the regulation of coronary circulation during reperfusion after coronary insufficiency of different degrees].

Coronary insufficiency of various degrees was reproduced in experiments with anesthetized dogs by using coronary artery catheterization by progressively limiting the regional blood flow by 30, 50, 70, and 90%, the dog chest being closed. The specific features of regulatory reactions of cardiac vessels were also studied under subsequent reperfusion. It was shown that regulation of coronary circulation became changed in most cases after markedly limited coronary blood flow, as manifested by impaired reperfusion hyperemia and its rapid cessation that prevented the "payment" of blood flow debt and a secondary increase of cardiac vascular resistance above the preocclusive level. There was a significant relationship between the detected disorders and the degree of prior limited coronary perfusion.

Animals↗
PubMed1991

[Characteristics of the regulation of coronary circulation in progressive disorders of coronary perfusion].

Coronary failure was demonstrated to be followed by impaired coronary circulation regulation in the hypoperfused area, as manifested by quantitative (incomplete realization of dilator reserve) or qualitative (greater coronary resistance) alterations of coronary responses to ischemia. The disorders detected were shown to be directly related to the manifestations of limited coronary flow, predominant with its 70% decrease and represent an essential mechanism of further progression of coronary failure.

Animals↗
PubMed1986

[Characteristics of coronary vasodilation reserve in partial restriction and subsequent recovery of the coronary blood flow].

The studies were performed on anesthetized dogs using the model of partial controlled blood flow restriction in the left circumflex coronary artery with intact thorax. 70% of blood flow restriction were compensated by coronary vasodilation reserve, evaluated in hyperemia reaction. No rapid reperfusion hyperemia reaction was observed in reperfusion period, while moderate reduction in heart contractility was maintained. Alterations in coronary vessel reactivity could have a certain depressing effect on reperfusion hyperemia reaction. The observed changes were reversible, as coronary vessels retained their dilatation ability in response to an additional ischemic stimulus.

Animals↗
PubMed1986

[Correlation between coronary dilatation reserve and cardiac contractile function after marked disorders of coronary circulation].

Relationship between the realization of the coronary dilatation reserve and cardiac contractility was investigated in acute dog experiments with the intact thoracic cage under partially limited and rationed flow through a major coronary artery (a 30-minute 70% reduction), and during subsequent reperfusion. Limited coronary flow was seen in combination with moderately depressed cardiac contractility that did not improve significantly during the reperfusion period of equal duration. Inadequate realization of the coronary dilatation reserve that fails to restore the balance between blood supply and myocardial oxygen requirement may be a cause of incomplete recovery during the early reperfusion period.

Adaptation, Physiological↗
PubMed1982

[Relationship between anaerobic energy formation and myocardial contractile function in disturbed cardiac blood supply].

Graded 70 and 90% restrictions of the coronary blood flow were reproduced in dogs with closed chest upon catheterization and autoperfusion of the circumflex branch of the left coronary artery. Interrelations between shifts in anaerobic carbohydrate metabolism and the main parameters of myocardial contractility were explored. An increase in glycolytic and phosphorylase activities, lactic acid concentration and a drop in the glycogen level were disclosed. The alterations were most pronounced in the ischemic area upon 90% restriction of coronary perfusion, whereas in the left ventricular myocardium outside the ischemic area, they were less detectable. There was a significant negative correlation between the lactate level and glycolysis intensity in both the heart areas under study and the contractility rate parameters dp/dt max, Vpm. dp/dt/p, etc. Lactic acid accumulation in the ischemic myocardium is an important factor inhibiting contractility. This may be caused by acidosis as well as by the mechanisms which are independent of pH changes.

Anaerobiosis↗
PubMed1982

Contractile function, energy metabolism and myocardial structure at graded restriction of coronary blood flow.

In closed-chest dogs, 30, 50 and 70% restriction of coronary blood flow was carried out by catheterization and autoperfusion of the circumflex branch of the left coronary artery. At 70% restriction, a mild decrease in most contractility indices was observed, without simultaneous impairment of the indices of systemic haemodynamics. Changes in energy metabolism appeared already in the initial stage of coronary insufficiency. A characteristic features at suppression of aerobic oxidation was an increase of the cAMP level of glycolytic activity of the pentoso-phosphate cycle, which ensured a sufficiently high ATP level in the myocardium. A limiting factor were disturbances in the system of energy transport (creatine phosphate, creatine phosphokinase) and of the calcium pump (Ca++-ATPase of the sarcoplasmic reticulum, SPR), which evidently led to a decrease of the inotropic properties of the myocardium at 70% restriction of coronary blood flow. Signs were found of structural lesions of the myofibrils and the SPR.

Animals↗
PubMed1981

[Relation between myocardial contractility and systemic hemodynamics in the early stages of severe blood flow disorders in a major coronary artery].

In the course of the initial observation period, a 70 and 90% controlled restriction of the coronary blood flow was not the solely mechanism by which there occurred changes in myocardial contractility. The circulatory alterations consequent on the ischemic focus formation influenced by the feedback mechanism the development of different varieties of hemodynamic supply through the changes in preload and afterload.

Animals↗
PubMed1980

[Functional state characteristics of the heart in measured coronary blood flow limitation to varying degrees].

The consequences of three different degrees of restricted circulation (by 30%, 50%, and 70%) in the circumflex branch of the left coronary artery were studied in experiments on dogs in which partial strictly dosed reduction of coronary blood flow was reproduced without opening the thoracic cavity. In most cases, the first two degrees of blood flow restriction were not attended by the natural changes in the contractile function of the heart, its decrease in particular, in the first 30 minutes. In 70% restriction of blood flow, on the contrary, moderate diminution of the contractile function of the heart begins to be manifested in most of the cases despite the fact that there is no progressive deterioration in general hemodynamics.

Animals↗
PubMed1979

[Modelling of measured restriction of the coronary blood flow].

Experiments were conducted on dogs under conditions of closed chest catheterization and autoperfusion of the coronary vessels to study the methods and manipulations providing reliable reproduction of previously planned direct restriction of coronary blood flow, strictly dosed in degree and duration, simulating coronary insufficiency of various severity. The use of this complex of methods and manipulations makes it possible to avoid the shortcomings and undesirable consequences of denervation of the coronary arteries and their extravascular mechanical compression and the need to open the chest. The simulated restriction of coronary blood flow is reversible owing to which it may be reproduce many time in one experiment.

Animals↗
PubMed1978

[Coronary circulation under alpha-adrenergic blockade].

In canine experiments with coronary catheterization and perfusion, catheterization of the heart cavities and great vessles, and with thermodilution it was demonstrated that the alpha-adrenergic blocker Phentolamine causes a regular flow resistance in the coronary vessels. The maximal depressor effect was observed with 0.3 mg/kg (intravenously), and it did not grow under higher doses of the drug. The reduction of coronary resistance under the effect of Phentolamine was realized, firstly, by way of a moderate activation of myocardial beta-receptors, and secondly, by way of a specific block of alpha-adrenergic receptors of the heart vessels. Phentolamine inhibited the pressor reactions of the coronaries to mesatone, adrenalin, noradrenalin, and limited the manifestations of the pressor effects in the coronary vessels during systemic sinocarotid reflexes.

Adrenergic alpha-Antagonists↗
PubMed1976

[Mechanism of the cardiotonic effect of alpha-adrenoblockade by phentolamine].

In canine experiments with recording intraventricular pressure and its first derivative, with electromagnetic flowmetry and thermodilution it has been demonstrated that controlled Phentolamine-induced alpha-adrenergic block results in an increase of the cardiac output, heart rate, myocardial contractility index, and, at the same time, in a reduction of the total vascular resistance, arterial pressure, intraventricular pressure and heart work. The beneficial chronotropic effect of Phentolamine was shown not to depend on its suggested "central" action, to be not determined by reflex stimulation of the cardiac activity due to systemic hypotension, but to be brought about by a block of the myocardial alpha-adrenergic receptors and a moderate activation of beta-adrenergic receptors. The concept of the untoward chronotropic effects being mediated by myocardial alpha-adrenoreceptors is being substantiated. The mechanism of the beneficial inotropic effect of Phentolamine may be based on the stimulation of beta-receptors, concomitant tachycardia, and, probably, the effect of the "centrai" action of the drug.

Animals↗
PubMed1975

[Comparative characteristics of the effect of curanthil on blood vessels of different organs].

In experiments on dogs conducted by means of resistography Curanthil (Dipyridamol) was shown to produce a consistent fall in the resistance to the blood flow in the cardiac vessels due to their active depressor reaction. Besides, Curanthil helps a distinct fall in the resistance of the vessels of the small intestine, sceletal muscles and, to a lower degree, of the brain. These data do not support those of a selective coronary-dilating action of this drug. The reaction of the renal vessels to Curanthil was not uniform and was predominantly of a pressor nature.

Animals↗