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Biomedical subjects

N A Novikova

Publications and source records attributed to N A Novikova.

At least 37 records · Page 2Linked to original sources
PubMed1988

[Relation of cardiac diastolic elasticity to its adaptation to loading].

The pump function of the isolated rat or guinea pig hearts was assessed at various functional loads. The diastolic left ventricular (LV) stiffness was determined by a ratio of a rise in LV pressure for a diastole to LV filling volume for a diastole. This index was several times lower for guinea pig's hearts as compared to the rat hearts at equal heart rate. It was associated with a higher cardiac output of guinea pig hearts at low left atrium filling pressure. The rat hearts, however, having a higher diastolic stiffness adapted better to increased resistance or elevated heart rate, preserved the cardiac output and markedly increased cardiac work. The data obtained suggest that LV diastolic stiffness is an important factor determining cardiac adaptation to various functional loads; its influence seems to be actualized through changes in the LV filling.

Adaptation, Physiological↗
PubMed1988

[Cardiac relaxation and distensibility in energy deficit].

Changes in the cardiac pump function, contractility, relaxation and distensibility in progressive metabolic blockade induced with dinitrophenol, were compared in the guinea pig isolated heart. A fall in relaxation and distensibility occurred first and was more obvious than a fall in contractility or the cardiac output. The same relationships were observed in isolated hearts of rats with myocardial phosphocreatine deficiency. The fall in relaxation and distensibility seem to be the necessary sign of acute or chronic myocardial energy deficiency.

Animals↗
PubMed1987

The role of phosphocreatine and ATP in contraction of normal and ischemic heart.

The effect of cellular creatine (Cr) and adenine nucleotides (AdN) deficiency on cardiac work, ATP turnover rate and flux through creatine kinase (CK) has been investigated. Depletion of 60-65% of total heart AdN by 2-deoxyglucose treatment in the presence of pyruvate and subsequent washout resulted in only 25% decrease in contractile activity and phosphocreatine level. Substitution of 80-90% of heart Cr (and PCr) by guanidinopropionic acid (GP) by feeding of rats with 1% GP diet reduced maximal values of cardiac work, ATP turnover and flux through CK by 40-50% and elevated end diastolic pressure and index of diastolic stiffness. Hearts depleted of AdN or glycogen showed better post-ischemic recovery of mechanical function that can be attributed to restriction of accumulation of ischemic catabolytes (lactate, H+, Pi). These data imply that in myocardium PCr is an essential high energy phosphate and contractile function stays unchanged at significantly reduced ATP levels.

Adenosine Triphosphate↗
PubMed1987

[Contractile function of the isolated heart in chronic adriamycin-induced myocardial lesions].

Adriamycin, administered to rats for 4 weeks, caused insufficiency of isolated heart contractility with a twofold reduction of cardiac output in surviving animals. The same cumulative dose of adriamycin, administered to rats over 10 weeks, was not associated with any significant reduction of the heart's pumping function. However, heart rate increase by atrial electrostimulation that shortened the diastolic pause to a control level, also reduced the minute and stroke volumes by 38%, as compared to the controls. All animals showed increased diastolic stiffness of the left ventricle that must have interfered with its filling, particularly so in case of low inflow pressure, and disturbed atrial automaticity, as reflected in bradicardia in rats and supraventricular arrhythmia in guinea pigs.

Animals↗
PubMed1986

[Isovolumic and auxovolumic constants of cardiac relaxation in evaluating its inotropism].

The left ventricular pressure curve was registered in experiments on isolated guinea pig heart performing external work. An analysis of initial diastolic portion of the curve in logarithmic scale has revealed for the first time that the time course of the pressure fall is accelerated during transition from isovolumic to auxovolumic phase. The constant of pressure fall rate in auxovolumic phase (ACPFR) has been approximately 1.5-fold higher than isovolumic constant. The former also changed significantly more than the latter one during elevation in Ca2+ perfusate concentration or EGTA addition. A parallel reduction in ACPFR and rate of left ventricular filling during EGTA addition was observed in special experiments with elimination of left atrium distension. Thus, inotropic changes in myocardial relaxation seem to determine left ventricular filling rate.

Animals↗
PubMed1986

[Compensatory factors in acute failure of the isolated heart].

The cardiac output of isolated guinea-pig hearts fell during progressive infusion of Ca2+-complexon, EGTA, or oxidative phosphorylation inhibitor dinitrophenol. Moderate doses of EGTA (0.3-0.6 mM) caused an apparent diminution of the left-ventricular +dP/dt and aortic pressure amplitude but did not influence cardiac output, which was maintained due to a prolongation of the contraction time. When the left-atrial cavity was greatly reduced by ligation, cardiac output fell by 40 per cent while left-ventricular systolic pressure and +dP/dt remained unchanged. In these conditions, EGTA in the same concentration reduced cardiac output by 30 per cent thus proving the important role of the left atrium in the compensation of hypocalcemic heart failure. On the contrary, the infusion of dinitrophenol shortened contraction time and increased myocardial rigidity. The latter change facilitated force development thus contributing to a lesser fall of +dP/dt and aortic pressure amplitude at equal diminution of cardiac output as compared to EGTA action. However, this compensation required a higher elevation of the filling pressure for inflow maintenance.

2,4-Dinitrophenol↗
PubMed1986

[Effect of corinfar on the dynamic function and various indices of glycolysis and glycogenolysis in the thrombocytes of patients with unstable stenocardia].

An increase in the aggregation properties of platelets accompanied by the activation of glycogenolysis and glycolysis was established in patients with unstable angina as compared to a control group of healthy persons. In most cases corinfar therapy resulted in a positive time course of the main platelet indices and a marked improvement of the patients' status. The correlation between the platelet aggregation index and phosphorylase A activity and their association with a course of disease indicated an opportunity of using these indices as accessory diagnostic criteria and control over therapeutic efficacy in unstable angina.

Adult↗
PubMed1985

[Comparative analysis of the action of 2 calmodulin inhibitors on the contractile function of the isolated heart].

Ca2+-complexon EGTA and two calmodulin inhibitors: metaphenazine and trifluoperazine, induced similar effects on the cardiac contractile function: they diminished cardiac output, decelerated left ventricle pressure fall and increased both minimal--and end-diastolic pressure. Changes in the left ventricular pressure and its time course were more obvious during calmodulin inhibitor action as compared to EGTA at equal diminution of cardiac output. Trifluoperazine decreased left ventricular systolic pressure and resistance of coronary arteries to a greater extent than metaphenazine. The findings suggest participation of calmodulin in the regulation of myocardial relaxation mainly.

Animals↗
PubMed1983

[Effect of increased mechanical loading on the relation between the contraction of isolated cardiac muscle and the concentration of Ca++ in the perfusate].

The distension of isolated papillary muscles working isotonically or a transition to isometric working entailed an increased sensitivity of the contractile velocity to changes in perfusate Ca++ concentration. After sudden fall in Ca++ concentration, a more rapid decline of the contractile velocity in isometric mode was observed as compared to isotonic mode of working. The similar difference was found in experiments on isolated guinea pig heart working in isovolumic or auxotonic modes, though the rate of Ca++ loss by the heart was the same. The results suggest that an increased mechanical load may diminish the ability of myocardial cells to compensate for the changes in external Ca++.

Animals↗
PubMed1983

[Protective effect of extracellular K+ in the myocardium in disorders of energy metabolism].

In an experimental study on isolated isovolumetric guinea-pig hearts, a 2.2-fold reduction of the coronary duct combined with metabolic block caused by dinitrophenol (0.05 mM) resulted in an eleven-fold drop in the attained pressure, and a shorter electric systole, a smaller P wave, and an ST displacement on the ECG. Deep suppression of mechanical and electric activity was combined with reduced glycogen content, and greater K+ and Na+ withdrawal from the heart. Quantitatively, the drop in contractility correlated with K+ withdrawal and ST displacement. A sudden increase in coronary perfusion rate was accompanied by a rapid increase in the rate of K+ elimination from the heart which was proportionate to the rate of hyperfusion, with a simultaneous transitory rise in attained pressure, a great increment in diastolic pressure and the emergence of arrhythmia and fibrillation, the severity of the changes correlating with the degree of K+ loss. A moderate increase in K+ concentration of the perfusate prevented the development of fibrillation and drastically reduced the degree of contracture and glycogen drop during hyperfusion. The obtained results suggest that moderate accumulation of extracellular K+ during the early phase of energy generation disorder can be of a protective nature, as it contributes to a sharp reduction in contractility and energy spending to improve cell survivability in critical conditions.

Animals↗
PubMed1982

[Coronary perfusion rate as a factor determining the degree of heart contractile function decrease in an energy formation disorder].

Experiments on the isolated hearts of guinea pigs have shown that administration of dinitrophenol in the concentrations of 0.01-0.10 mmol elicited, depending on the dose given, a decrease in pressure of a latex balloon, placed into the cavity of the left ventricle and an increase in the displacement of the SI segment on the ECG, recorded from the subendocardial layer of the apex. It is established that the rate of the coronary flow, limiting washing out of K+ and other metabolites determines the degree of depression of the contractile function with energy formation disorders and also its restoration during reoxygenation.

Animals↗