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Biomedical subjects

G S Sukhova

Publications and source records attributed to G S Sukhova.

At least 19 recordsLinked to original sources
PubMed2006

[Reversible inhibitory action of adenosine diphosphate ribose on isolated rat heart and rat heart in vivo].

Cardiotropic effects of endogenous regulator of intracellular ionic balance adenosine diphosphate ribose (ADP-ribose) was studied on isolated rat heart using standard retrograde perfusion and on rat heart in vivo by means of implanted arterial catheters. Parameters registered were heart rate, pressure developed in left ventricle of isolated heart and blood pressure of rats in vivo. It was shown that ADP-ribose exerted cardiotropic action on isolated rat heart and that its effects did not depend on effects of its metabolite AMP. In concentrations 10-70 microM ADP-ribose caused negative dose dependent chronotropic effect. Amplitude of contraction of isolated heart changed equivocally. In concentration 70 microM ADP-ribose in 50% of cases produced biphasic action: negative inotropic effect was preceded by positive inotropic effect. In other cases this concentration exerted negative inotropic effect. In concentration 10 microM only negative inotropic effect was observed. Contrary to ADP-ribose its metabolite AMP exerted only monophasic positive inotropic effect on isolated heart. The preparations studied differed in dynamics of cardiotropic action. In experiments in vivo ADP-ribose and AMP caused monophasic negative chronotropic and monophasic positive inotropic effects.

Adenosine Diphosphate Ribose↗
PubMed2006

[Peculiarities of regulation of cardiac function in some mammals].

We studied acetylcholine induced changes of action potentials (AP) in ventricles and atria of bat, hedgehog, yakut ground squirrel, and laboratory mice. In atria of all these species of mammals acetylcholine caused pronounced dose dependent shortening of AP. However sensitivity of ventricles of studied animals to acetylcholine was different. Acetylcholine induced AP shortening was 29.4, 42.1, 6.6 and 11% in ventricles of bat, hedgehog, laboratory mice and ground squirrel, respectively. Ventricles of none of previously studied mammals had sensitivity to acetylcholine comparable by magnitude to acetylcholine sensitivity which we found in hedgehog and bat. It is suggested that these animals have unique nervous regulation of cardiac action, principally different from that of other mammals, which do not require parasympathetic regulation of ventricles.

Acetylcholine↗
PubMed2004

Preclinical study of the effect of cardiotropic agents on isolated heart.

Direct effects of cardiotropic preparations on the hearts isolated from Wistar rats were examined. Deenergization of cardiomyocytes was modeled under conditions of hypoxic perfusion. Recovery of cardiac function during reperfusion was assessed by changes in the heart rate and contraction amplitude.

Animals↗
PubMed1999

[The action of ADP ribose on the mechanical and bioelectrical activity of the frog heart].

In the frog isolated heart, cyclic perfusion of ADP-ribose induced a dose-dependent decrease in the heart rate and the contraction force, a decrease in the AP duration as well as in the rate of rise in the sinus node. It also shortened the atrial AP and exerted no significant effect upon multicellular ventricular preparations. In conditions of systemic administration in unanesthetised frogs, the ADP-ribose induced a reversible increase in the heart rate due, probably, to a sympathetic effect.

Adenosine Diphosphate Ribose↗
PubMed1991

[The synchronizing interaction and mechanism of the formation of the common rhythm of the cardiac pacemaker. I. The modeling of the interaction of 2 pacemaker elements].

The main physiologic hypotheses in establishing a common rhythm of the heart sino-atrial node (SAN) have been considered. A mathematical model of SAN which takes into account the interaction between pace-makers in pairs has been proposed. A quantitative description of common rhythm establishing taking into account interaction in pairs has been obtained, the expressions for the period of common rhythm, a delay and the rate of stimulation distribution have been found. A comparison of calculated and experimental data is given.

Action Potentials↗
PubMed1990

[Dynamics of the rythm of the isolated and intact frog heart].

This study was designed to examine the changes of the isolated frog's heart rate as a function of the time in the two time intervals: 20-95 min and 95-170 min after hearts were prepared. The heart rate decreased in these intervals quite linear but average slope between 20-75 min was significantly steeper than in the time interval 95-170 min. It was shown that the difference in the heart rate response induced by the increasing temperature in intact animals and isolated hearts partly might be explored by this decrease in the isolated frog's heart rate with time.

Animals↗
PubMed1985

[Possible participation of slow Na+--Ca++ channels in realizing cholinergic effects on the cardiac pacemaker].

The effect of the Ca++-permeability inhibitors (Mn ions, Verapamil, D-600) on the bioelectrical activity and cholinergic responses of isolated sinus node involved reduction of the pacemaker rhythm within 30-40 min and a complete inhibition of the bioelectrical discharge as well as a diminished amplitude of the AP and a reduced slope of the slow diastolic and the fast depolarization. The findings seem to be due to an inhibiting of the slow Na+-Ca++ influx by Ca++-antagonists. The prolonged APs and the reduced rate of terminal repolarization might be due to effect of the inhibition on potassium permeability. After electrical stimulation of the efferent nerve or acetylcholine application, the cholinergic reactions were markedly reduced with Mn++ D-600 and Verapamil. The participation of slow Na+-Ca++ channels in cholinergic reactions of pacemaker cells is discussed.

Acetylcholine↗
PubMed1984

[Mechanical action of the atria during stimulation on the work of the sinus node].

The cardiac pacemaker and atria were removed from the frog heart and placed into a chamber with Ringer solution. Atrial pacing was performed at a suprathreshold milliamperage. The mechanism of changes in the cardiac pacemaker during atrial pacing was studied both under the conditions of the blockade of the intracardiac nervous system and elimination of the bioelectrical and mechanical effects of the atria on the cardiac pacemaker. It is inferred that the change in the rate of pacemaker stimulation during atrial pacing is largely determined by the mechanical activity of the atria.

Animals↗
PubMed1983

[Role of the atrium in the functional organization of the sinoatrial node].

The automatic activity of the venous sinus was studied in respect to the atrial bioelectrical activity in frogs. Each of the two parts of the divided venous sinus had different rhythms. Extra-cellular recording revealed that the APs of both parts of the sinus were closely synchronized if the parts were connected with the atrium. The data obtained suggests that this synchronization was due to atrial bioelectrical activity.

Action Potentials↗
PubMed1982

[Changes in the rate of sinoatrial node after high-frequency stimulation of the heart atrium].

Variations in the sinus node rate of the frog heart isolated together with the atria were studied during suprathreshold atrial stimulation at a frequency exceeding the intrinsic sinus node rate. If the stimulation frequency surpassed the intrinsic sinus node rate by 20%, the sinus node rate became equal to the pacing rate. Provided the pacing rate was increased, the sinus node rhythm became irregular. If the pacing rate exceeded the sinus node rate more than two-fold, the latter became half the pacing rate. Variations in the sinus node rate during suprathreshold atrial stimulation were also observed after blockade of possible retrograde conduction by application of the necrotic tissue on the sinoatrial border. The results allow the conclusion that variations in the sinus node rate seen during high-frequency suprathreshold atrial stimulation are not connected with retrograde conduction.

Action Potentials↗
PubMed1981

[Effect of iontophoretic application of acetylcholine on the discharge rate and action potential shape of pacemaker cells].

A study was made of the action of iontophoretic application of acetylcholine to the limited number of pacemaker cells with a simultaneous recording of the activity of one of them. It was shown that both generalized and strictly localized action of acetylcholine is capable of exerting different chronotropic effects. Acceleration of the rhythm was normally accompanied by an increase in the rate of accretion of slow diastolic depolarization (SDD) and by a decrease in the action potential. The same pacemaker cell was demonstrated to modulate the direction of the chronotropic reaction for an opposite one depending on acetyl-choline concentration. Low concentration of the mediator induced rhythm acceleration and an increase in the accretion rate of SDD whereas high concentration led to rhythm deceleration and SDD lowering.

Acetylcholine↗
PubMed1978

[Effect of acetylcholine on the firing rate and action potential shape of pacemaker cells].

A study was made of the action of exogenous acetylcholine on the isolated pacemaker of the Rana temporaria heart. Bioelectrical activity of individual cells and sum total activity of the preparation were recorded. Exogenous acetylcholine was found not only to inhibit, but also to accelerate the rhythm of pacemaker cells' discharge. As a rule, positive chronotropic effects were observed when relatively low acetycholine concentrations were used. Parasympathetic acceleration was accompanied by an increase in the rate of slow diastolic depolarization; this is in favour of the active mechanism of this process. It is suggested that low and high concentrations of acetylcholine could change the transmembrane ionic currents in a different way.

Acetylcholine↗
PubMed1977

[Changes in pacemaker cell activity during parasympathetic acceleration of the heart rate].

Acceleration of the heart rate can be elicited by stimulation of the extracardiac paraysmpathetic pathways (previous investigations). In this study, changes of the pacemaker APs were continually recorded with microelectrode in the sinus node cell. The data showed acceleration of the slope of slow diastolic depolarization (distolic prepotential) of the pace-maker AP during the parasympathetic positive chronotrct. The parasympathetic acceleration of the slow diastolic depolarization and of the heart rate was shown to be cholinergic by its nature.

Action Potentials↗
PubMed1977

[Bioelectrical activity and automatic properties of different parts of a two-chambered heart].

Two pacemakers localized in sinoatrial and atrioventricular valves were revealed in the tench heart. In their absence, the ventricular and sometimes the atrial myocardium are capable of initiating the automaticity. Pacemaker's cells of the sinoatrial valve are surrounded by specific area similar to sinoauricular ring in amphibia or sino-caval region in mammals. Characteristics of the action potential in different parts of the tench heart are presented.

Animals↗