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Biomedical subjects

I M Rodionov

Publications and source records attributed to I M Rodionov.

At least 55 records · Page 3Linked to original sources
PubMed1985

[Systemic hemodynamic changes during the development of DOCA-salt hypertension. The effect of neonatal sympathectomy].

The elevation of the cardiac index was discovered at the initial stage of DOCA-salt hypertension in rats. The blood pressure rise at the stage of stable hypertension was caused by an increase in the total peripheral vascular resistance. Neonatal sympathectomy prevented the development of DOCA-salt hypertension and elevation of the cardiac index revealed in control sympathectomized rats.

Animals↗
PubMed1984

[Role of sympathetic nervous system in the pathogenesis of spontaneous hypertension in rats].

The structural component of resistance and vascular reactivity in posterior half of the rat body were studied in intact normotensive animals as well as in rats with hereditary hypertension. Chemical desympathization in the spontaneously hypertensive rats reduced the arterial pressure, cardiac outflow, structural component of the resistance and reactivity to noradrenaline, these parameters remaining, however, higher than in normal intact rats. 2-week hypoxic adaptation of young spontaneously hypertensive rats hinders increasing of the arterial pressure and structural component of resistance. The augmented sympathetic activity along with other factors (genetic, humoral) seem to increase the structural component of resistance and arterial pressure in spontaneously hypertensive rats.

Animals↗
PubMed1984

[Changes in osmolarity of arterial blood in intensive muscle exercise].

Acute experiments in cats demonstrated that a prolonged rhythmic muscle contraction of four limbs induced by stimulation of transected motor nerve endings is concomitant with an increase in osmotic pressure of arterial and venous blood plasma both in blood vessels and in the heart. The increase in osmolarity is parallel to an increase in the minute volume of the heart, a fall in the arterial pressure and an enhanced blood flow through the exercising limbs. Muscle hyperemia is related to osmotic shifts in venous blood and the increased minute volume of the heart--to those in arterial blood. The osmotic factor seems to be involved in adaptation of the cardiovascular system to intensive physical exercise.

Animals↗
PubMed1984

[Changes in the morphometric indices of the microvascular bed of the brain in experimental hypertension].

Brain stem microvessels up to 15 microns in diameter of spontaneously hypertensive rats and rats with experimental renal hypertension were investigated in histological sections with the aid of a texture analysis system. Hypertensive animals showed a reduction in the vascular diameter per unit volume of cerebral tissue, in the mean vascular diameter as well as in the area occupied by the vessels, thus attesting to the lessened density of brain vascularization. The proportion of the vessels measuring from 6 to 15 microns in diameter per unit volume of cerebral tissue decreased whereas the proportion of the vessels measuring up to 5 microns in diameter remained unchanged. The characteristics under study demonstrated the same line of changes in both spontaneous and experimental renal hypertension.

Animals↗
PubMed1982

Increase in osmolality of venous blood from skeletal muscle during cholinergic vasodilatation.

The arterio-venous difference in the osmolality of blood plasma of cat m. triceps surae was studied during sympathetic cholinergic nerve excitation. The vasodilatation was induced by stimulation of hypothalamus or the sympathetic chain, the latter after alpha-adrenoceptor blockade. The vasodilator effect induced by intraarterial injection of acetylcholine was also tested. In all cases studied the vasodilatation was associated with an increase in osmolality (on the average by 10 mOsm/kg H2O with a maximum at the 30-40th s after the beginning of stimulation). Atropine (0.1 mg/kg) considerably decreased the vasodilator effect elicited by hypothalamic stimulation. The increase in osmolality was much smaller after atropine, a small peak remaining at the 50-60th s after the beginning of stimulation. The latter effect was blocked by propranolol (0.5 mg/kg). Atropine similarly almost completely abolished the vasodilator effect and the increase in osmolality produced by lumbar sympathetic stimulation and acetylcholine. The increase in osmolality was caused by a rise in the contents of Na+ (7.4%), lactate (8.2%) and K+ (13.2%); Ca2+, inorganic phosphate and total protein concentrations remained unchanged. Our data indicate that acetylcholine released by sympathetic endings activates muscle fibre metabolism via the muscarin-receptors. The increase in tissue osmolality resulting from activation of metabolism causes, at least partly, the vasodilator effect.

Acetylcholine↗
PubMed1982

[Morphofunctional characteristics of the myocardium in chronically sympathectomized rats].

Experiments on rats weighing 110 g exposed to sympathectomy induced by guanethidine injections during 4 weeks after the birth were made to examine the morphological characteristics of cardiomyocytes, ultrastructure of heart tissue mitochondria, heart contractility under relative physiological rest, and the pressure in the ascending aorta. It was shown that the chronic absence of the sympathetic system leads to changes in the structure of the heart tissue proved by hypertrophy of the left ventricle and disturbances of the cell mitochondrial system. Under continuous high pressure the sympathectomized rats manifest suppression of the heart contractile function. It is suggested that the changes discovered are a consequence of the disorders in the myocardial energy balance in the sympathectomized animals.

Animals↗
PubMed1982

[Age-related changes in the sympathetic innervation of effector organs in the rat after partial sympathectomy with guanethidine].

Guanethidine (30 mg/kg daily for first 15 days of life) decreased by 85% the amount of cells in the rat upper cervical sympathetic ganglion for 4 months. In ageing, the volume of the ganglion's cells, the density of adrenergic fibers and the noradrenaline content in the heart, intestine and ductus deferens increased in the desympathized animals. The neural cells remaining after desympathization seem to develop a growth of axons and to restore to some extent the density of sympathetic innervation of the periphery. The firing rate of single preganglionic fibers of the cervical sympathetic nerve is increased in the desympathized animals. The increased firing rate seems to be the cause of changes in the surviving neurons.

Adrenergic Fibers↗
PubMed1981

Growth of sympathetic postganglionic axons after partial chemical destruction with guanethidine.

Partial sympathectomy of neonatal rats was produced by treatment with guanethidine. The number of neurons of the superior cervical ganglion decreased to 15% of control values and remained constant throughout the subsequent observation period of 4 months. The volume of the remaining neuronal perikarya increased faster than that of control animals during the observation period, and the density of adrenergic innervation of the iris and the noradrenaline content of the heart were found to partially recover after the initial decrease produced by the guanethidine treatment, reaching 33% and 30% of control values, respectively, after 4 months. The noradrenaline content of the duct of the vas deferens was greatly reduced by guanethidine treatment, but almost recovered after 4 months. The frequency of sympathetic preganglionic impulses was elevated throughout the 4 months observation period, and it is suggested that this increase is responsible for the compensatory changes in cell volume, terminal density and terminal noradrenaline content of the remaining neurons.

Aging↗
PubMed1981

Arterial pressure, cardiac output and exercise hyperemia in chemically sympathectomized rats.

This study showed that arterial blood pressure of chemically sympathectomized rats (SR) was decreased, whereas heart rate was increased relative to controls. The cardiac output in SR was higher than that in intact animals (by 36% under urethane anaesthesia and by 80% without anaesthesia). The total peripheral resistance of SR was 1.7 times less than normal, although the magnitude of the structural component of resistance was increased. The half-time clearance of 133Xe from skeletal muscle during motor nerve stimulation was greater in SR than in intact rats by a factor of 2. It is concluded that the number of small resistance vessels in SR is low, while the lumen of individual vessels is greater than in controls, thus giving rise to an insufficient "vasodilator reserve".

Animals↗
PubMed1981

Efficacy of sympathetic influences as related to initial vascular tonicity.

The efficacy of vasoconstrictor influences as dependent on the initial vascular tone (initial rate of perfusion) and perfusion pressure was investigated in rat and frog hindlimb preparations perfused with saline solution. Efficacy was determined as the ratio of the preparation resistance (R) induced by sympathetic stimulation to the initial resistance R0. At a pressure normal for the experimental animal, the relationship between R/R0 and flow is expressed by a dome-shaped curve. At a pressure twice the normal, it is low at all points; at a pressure half the normal, different responses were obtained from the two species used in the experiment: in rats elevation of vascular tone induced by sympathetic stimulation resulted in a complete cessation of flow, whereas in frogs the initial high efficacy diminished with increasing vascular tone. A mathematical model devised to study the dependence of the efficacy of sympathetic stimulation on initial tonicity is described. The good consistency of experimental and calculated results is regarded as evidence that the prerequisites stipulated in the model, i.e., the capacity of closure and the heterogeneity of arterioles, in regard to the effort developed by their smooth muscle, are actually inherent in the vascular system of organs.

Animals↗
PubMed1981

[Morphological characteristics of the capillary network in the rat brain in experimental DOCA-salt and renal hypertension].

The capillary network of nuclei n. reticularis pontis caudalis and n. ventralis thalami of the brain of the normal rats and animals with DOCA-salt and renal forms of experimental hypertension have been studied. It is shown that in 91 92% of the visual fields the number of capillary fragments is statistically significantly decreased as compared to the controls. 8-9% of the visual fields did not show statistically significant difference from the normal as to the density of the capillaries.

Animals↗
PubMed1981

[Circulatory features of "chemically" desympathized rats].

Desympathized rats developed a lower arterial pressure, a higher heart rate and a greater one--minute blood volume heart output as compared to intact rats. The total peripheral resistance in the major circulation of desympathized rats is by 1.7 times lesser although their structural component of the resistance is higher. The latter finding seems to be due to a reduce density of vessels per unit of tissue volume. The time of half--washing of Xe33 out of intramuscular depot in working hyperemia during motor nerve stimulation is nearly twofold in desympathized rats. The humber of small resistance vessels seems to be lessened per unit of tissue volume in desympathized animals whereas the lumen of separate vessels in them is larger than in normal animals. This accounts for considerable reduction of the range of vasomotor vascular regulation in desympathized animals.

Animals↗
PubMed1981

[Changes in plasma composition resulting in an increase in the osmotic pressure of venous blood during the cholinergic dilatation effect].

Stimulation of the sympathetic chain in the presence of alpha-receptor blocking agents caused cholinergic vasodilatation of the cat hind-limb vessels. The arterial-venous difference with respect to osmotic pressure (Posm), as well as to the content of K+, Na+, Ca2+, lactate, total protein, and inorganic phosphate was determined in blood samples collected during vasodilatation. Sympathetic stimulation in the presence of alpha-receptor-blocking agents agents increased the conductance of the hind-limb vessels and Posm of the venous blood (7.6 +/- 0.8 mOsm/l); both effects were abolished by atropine. During vasodilatation the content of K+, Na+ and lactate in venous blood plasma was increased, while that of total protein, inorganic phosphate and Ca2+ remained unchanged. The increase in Posm (73.7%) was found to be due to the rise in Na+. The data obtained suggest an increased intensity of metabolism in skeletal muscle during cholinergic vasodilatation.

Animals↗
PubMed1980

The content of cyclic nucleotides (3',5'-cGMP and 3',5'-cAMP) in cat skeletal muscle during sympathetic cholinergic vasodilatation.

Phosphorylase activity and content of cyclic GMP and AMP were investigated in the gastrocnemius muscle of the cat during the development of cholinergic vasodilatation evoked by stimulation of the hypothalamus. Samples of muscle tissue were taken during an early stage of the vascular effect. One of the hindlimbs was denervated and served as control. With the development of the dilator response the conductance in the bed of the femoral artery increased by 143 +/- 12%, phosphorylase "a" activity reached 76.1 +/- 2.1% of the total phosphorylase activity as compared with 49.2 +/- 1.9% in the control, the content of cGMP increased approximately 2-fold. The content of cAMP remained unchanged. All these effects - the increase in blood flow, phosphorylase activation and the increase in cGMP content - were abolished by atropine. It is suggested that acetylcholine, released by sympathetic endings during hypothalamic stimulation, has the effect of increasing the level of intracellular cGMP and that the vasodilatation is secondary to the metabolic changes.

Acetylcholine↗