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Biomedical subjects

L M Lobanok

Publications and source records attributed to L M Lobanok.

At least 19 recordsLinked to original sources
PubMed2006

Dose-rate dependent effects of ionizing radiation on vascular reactivity.

This study was designed to investigate the dose-rate dependent effects of ionising radiation on endothelium- and NO-mediated reactivity of aorta and coronary vessels. Rats were exposed to acute ((137)Cs, 9 x 10(-4) Gy s(-1), 18 min) and chronic ((137)Cs, 2.8 x 10(-7) Gy s(-1), 41 days) radiation in 1 Gy dose. Acute irradiation transiently increased coronary flow in eNOS-activity-dependent manner on day 3 after exposure. In striking contrast, chronic irradiation caused a significant depression of coronary flow even on day 90 after irradiation and abolished the effects of NO-synthase inhibitor N-nitro-L-arginine methyl ester (10 micromol l(-1)). Furthermore, low intensity radiation strongly diminished the vasodilator properties of NO-donor sodium nitroprusside (5 micromol l(-1)). A similar pattern was observed in aortic rings. Endothelium-dependent vasodilation was increased on days 3 and 10 after acute irradiation, but strongly inhibited following chronic exposure for the entire post-radiation period. This was accompanied by a diminished vasodilator response to NO-donor on days 3, 10 and 30 of post-radiation but not on day 90. The data suggest that ionising radiation in 1 Gy induces changes of aortic and coronary vessels reactivity depending on the dose-rate and the interval after exposure.

Animals↗
PubMed2005

The effects of acute and chronic radiation on endothelium- and no-dependent vascular reactivity.

Endothelium- and NO-dependent relaxation of aortic segments and basal coronary flow and response of coronary vessels to exogenous NO in the Langendorff-perfused rat hearts were examined on the 3rd, 10th, 30th and 90th days following whole body irradiation in 1 Gy dose with different dose rate. NO-mediated elevation of coronary flow and increased aortic endothelium-dependent vasodilation were found at the early stage after acute irradiation (137Cs, 9 x 10(-4) Gy/s), while vascular reactivity to exogenous NO was not changed. Chronic irradiation (137Cs, 2.3 x 10(-7) Gy/s) significantly impaired endothelium-dependent relaxation within whole experimental period and decreased NO component of basal coronary flow at the 3rd, 10th and 90th day. It was associated with attenuated reactivity to NO-donor in aorta one month after irradiation and in the coronary vessels--shortly after irradiation. In the delayed period endothelial dysfunction and the diminution of NO-dependent coronary flow were mediated by selective impairment of NO synthesis/release. Decreased survival rate of the lethally-irradiated Nwnitro-L-arginine methyl ester-treated animals revealed radiosensitizing properties of NO synthase inhibition. The data obtained indicate the involvement of NO in the alterations of vascular reactivity depending on the dose rate and on the interval after the irradiation.

Animals↗
PubMed1999

[The effect of stimulation of the adrenergic receptors on the frequency depression of the temporal parameters of the action potential in the right atrium of rats].

At a stimulation rate of 1 Hz, activation of alpha-adrenoreceptors prolonged the AP duration at 10%, 50%, and 90% repolarisation at 10(-7), 10(-6) M in the rat isolated right atria, but shortened it at a higher concentration of 10(-5) M. The frequency-induced depression of the AP duration became more evident in cardiomyocytes stimulated by 10(-7), 10(-6) M and less obvious at 10(-5) M of alpha-adrenoagonist. Activation of alpha-adrenoreceptors by isoprenalin shortened the AP duration and enhanced the stimulation-rate-dependent changes in the atrial AP configuration.

Action Potentials↗
PubMed1999

[The aspects of adenylate cyclase activity regulation in myocardium cell membranes during hypokinesia].

Nonstimulated and isoproterenol, GTF, GITF, NaF stimulated activities of the adenylate cyclase in sarcolemma in white rats' myocardium was studied after two weeks of hypokinesia. As was established, in restrained animals the sensitivity of adenylate cyclase to the specified agents was increased and transition to the bimodal GTF regulation took place. It is hypothesised that involvement of membrane-bound Gi-proteins in the adrenergic effects on cardiomyocytes is one of mechanisms of the cardiotropic effects of restraint and heart distresses.

Adenylyl Cyclases↗
PubMed1992

[The adrenergic regulation of cardiomyocyte electrophysiological activity, cardiac biochemical function and coronary blood flow in rats with incorporated 131I].

The study was made of the rat heart isolated according to Langendorf and right auricles. Intraperitoneal injections of 2.5 MBq/kg 131I were performed. Electrophysiological and biomechanical myocardium response to stimulation of alpha and beta-adrenoreceptors with isoprenalin and phenylephrine hydrochloride was analyzed. Postradiation modification of adrenergic control in animals with incorporated 131I appeared as reduced functional response of cardiomyocytes and intact heart to beta-adrenoagonist and enhanced response to alpha-agonist was detected.

Animals↗
PubMed1987

[Mechanism of self-regulation and the inotropic reaction of the rat myocardium during aging].

The experiments on rat papillary muscles revealed that in ageing rats myocardium has a decreased distension ability. The curves of shortening value/length and force/velocity for the myocardium of old animals are shifted downwards. The alterations in isotonic contraction parameters had a distinct age differentiation, while the age did not affect the inotropic effects of increased frequency, paired stimulation and external calcium. It is suggested that changes in biomechanical properties of ageing myocardium are associated with alterations in calcium transport in sarcoplasmic reticulum.

Aging↗
PubMed1986

[Effect of calcium on the force-frequency ratio and resting potentiation in the myocardium of mature and old rats].

The studies on the isolated papillary muscles have shown age-dependent differences in the tension developed, the rate of its development and decline in adult (10 months) and old (27 months) rats at 0.1 Hz stimulation frequency and different concentrations of external calcium (0.3, 1.25, 5.0). With 0.3 mM of Ca2+ in the solution, the negative inotropic frequency effect, and resting potentiation of contractions (interstimulus interval 30 s) in the myocardium of old rats were considerably lower than those in adult animals. Calcium level elevation (5.0 mM) resulted in elimination of frequency inotropic effect and resting potentiation in the rat myocardium in both age groups. The abnormalities of chronoinotropic relations in the myocardium during aging can probably be explained by the changes in Ca2+ transport.

Aging↗
PubMedDate not supplied

[The biomechanical function of the heart and its adrenergic regulation after long-term gamma radiation exposure].

The study of heart isolated by Langendorf's method has shown that the prolonged gamma irradiation of rats with 1.0 Gy dose (2.8 x 10(-7) Gy/sec) causes the decrease in contraction and relaxation ability, of myocardium, reduces functional response of heart to the stimulation of beta-adrenergic receptors, and increases of myocardium reaction to the stimulation of alpha-adrenergic receptors.

Adrenergic alpha-Agonists↗
PubMedDate not supplied

[Effect of prolonged gamma-irradiation on the functional state of heart and its adrenergic regulation at hypothyroidism].

The study of heart isolated by Langendorf's method has shown that the prolongated gamma-irradiation of euthyroid rats in 1.0 Gy dose (2.8 x 10(-7) Gy/sec) causes the decrease in contraction ability, myocardium relaxation and functional response of heart to the stimulation of beta-adrenergic receptors, and the increase in myocardium reaction to the stimulation of alpha-adrenergic receptors. The irradiation of hypothyroid animals leads to more significant and long changes in contraction function of heart and its adrenergic regulation.

Animals↗
PubMedDate not supplied

[Influence of hypoxia and anoxia on endothelium-dependent dilatation response of rat's aorta exposed to low-intensity gamma irradiation].

The study of isolated segments of aorta has shown that prolongated exposure of rats to gamma-radiation with 50 cGy dose (with a dose rate of 2.8 x 10(7) Gy/s) causes the decrease in endothelium-dependent dilatation responses to M-cholinoreceptors stimulation. During oxygenation the post-radiation changes are displayed within one month, and under functional loads, specifically, during perfusion by hypoxic and anoxic solutions--in more remote terms of the post-radiation period.

Animals↗
PubMedDate not supplied

[Adrenergic control of myocardial contractile function in rats with incorporated 137Cs].

It was shown on isolated myocardium preparations that internal gamma irradiation of rats with 137Cs (1.6 MBq/kg) decreased the contractile function of ventricles and had no essential effect on the auricle contractility. The inotropic response of myocardium to activation of alpha-adrenergic receptors decreased, and of beta-adrenergic receptors decreased.

Animals↗
PubMedDate not supplied

[Age related features of postradiation changes of functional activity of local vascular renin-angiotensin system].

The postradiation changes of constriction effects of angiotensin II (Ang II) and angiotensin I (Ang I) on isolated preparations of thoracic aorta young and old rats which underwent gamma-irradiation in dose 1 Gy (137Cs, 9 x 10(-4) Gy/s) were investigated. It has been found, that the aging leads to the alteration of angiotensin receptors, which appears as changes in their density and/or sensitivity to action of agonist. With increase of age the activity of angiotensin-converting enzyme (ACE) in the wall of aorta is oppressed, and as a result, the level of local formation of Ang II and the constriction, caused by it are reduced. The inhibitory influence of endothelium on vasoconstriction effects of Ang II and Ang I in ontogenesis does not change. The influence of gamma-radiation in a dose of 1 Gy modifies the functional activity of the local vascular renin-angiotensin system (RAS): the sensitivity and/or density of angiotensin receptors and the activity of ACE increased the dilatation influences of endothelium were oppressed mainly for account of easing the synthesis of NO. The duration of postradiation infringements of functional activity of local vascular RAS in many respects are determined by the stage of ontogenic development of irradiated organism.

Aging↗
PubMedDate not supplied

[Systemic approach to radiobiological studies].

The principles of information theory were applied for analysis of radiobiological effects. The perception of ionizing radiations as a signal enables living organism to discern their benefits or harm, to react to absolute and relatively small deviations, to keep the logic and chronicle of events, to use the former experience for reacting in presence, to forecast consequences. The systemic analysis of organism's response to ionizing radiations allows explaining the peculiarities of effects of different absorbed doses, hormesis, apoptosis, remote consequences and other post-radiation effects.

Adaptation, Physiological↗
PubMedDate not supplied

[Role of NO-mediated mechanisms in post-irradiation changes of neurohormonal regulation of the heart function].

Investigations on isolated Langendorff-perfused rat heart have shown that after the impact of ionizing radiation in 1 Gy dose the myocardial contractility and relaxation are decreased. The inhibition of NO synthesis attenuates chrono- and inotropic responses of the heart and reaction of coronary vessels to norepinephrine (NE), increases negative inotropic and vasoconstrictor effects of carbamylcholine (CCh). In the irradiated animals the reaction of isolated heart to NE and CCh is decreased. The post-irradiation changes in adreno- and cholinoreactivity caused not only by changes in receptor sensitivity and density, but also by impairment of NO-mediated regulation of coronary flow and biomechanical heart function.

Adrenergic alpha-Agonists↗
PubMedDate not supplied

[Modification of the chronotropic-inotropic relations in the atrial and ventricular myocardium during external gamma-irradiation].

It has been shown of isolated muscle preparations of rat heart that external gamma-irradiation with a dose of 6 Gy reduces the contractile capacity of myocardium and changes the chronoinotropic relationships: in the auricle, the rate/power relationship and the potentiating effect of the passive interval increase, and in the ventricles, the potentiating effect decreases. Modification of the chronoinotropic relationships may be associated with changes in the calcium ion transport in the heart cells.

Animals↗
PubMedDate not supplied

[The effect of low doses of gamma radiation on the structural-functional status of the membranes of aortic smooth muscle cells in rats].

Using the fluorescent probe and membrane filtration methods it has been shown that 3 days after gamma-irradiation of rats with a dose of 1 Gy microviscosity of membranes increases and their Ca2(+)-transport function decreases with a simultaneous increase in the affinity of Ca2(+)-pump for calcium. In 15 days, the characteristics under study do not differ from those of the intact controls.

Animals↗