Biomedical subjects
Publications and source records attributed to M D Gaevyĭ.
The inhibitor of angiotensin-converting enzyme captopril does not change the tone of the brain vessels but decreases the blood pressure and the tone of peripheral vessels, increases the oxygen and glucose demand in the brain in intact cats. In animals with brain ischemia, captopril decreased the tone of the brain vessels and promoted normalising of metabolic and transcapillary exchange in the brain.
In anesthetized cats, comparative characteristics of hemodynamics and biochemical indications of postischemic period in respect to autohemoperfusion with stable blood volume and perfusion pressure, were determined. Cerebral ischemia was caused by the 15-min stop of the perfusing pump or flowmeter and a decrease of systemic arterial blood pressure to 40 ml Hg. In the autohemoperfusion of brain vessels in stable volume or stable arterial pressure, a phasic postischemic phenomenon becomes obvious. The regularity of modifications of the glucose and oxygen consumption by the brain, concentration of lactate and pyruvate under different conditions of autohemoperfusion, was found.
In acute experiments on anesthetized cats, the perfusion of dopamine (100 micrograms/kg.min) during 35 minutes after cerebral ischemia inhibited the development of postischemic phenomena. Dopamine was found to exert a considerable effect on the oxidative metabolism in the brain. The responses of cerebral, peripheral vessels and systemic arterial pressure to dopamine (25 and 75 micrograms/kg) in conditions of blood autoperfusion with cooled blood did not differ significantly from those in normothermia. The problem of dopamine participation in the organism adaptive responses to extreme conditions, is discussed.
Cerebral blood flow was measured in anesthetised white rats with the hydrogen clearance technique under different levels of arterial blood pressure before and after cerebral ischemia induced with the occlusion of the common carotid arteries during 12 min. The continuous i.v. infusion of dopamine improved the autoregulation of the cerebral blood flow in intact animals and restored it to the initial level in the rats with ischemia.
A disorder in the autoregulation of cerebral blood flow due to a drop of arterial blood pressure (shift to the right) occurred earlier in hypotensive rats than in normotensive ones. A beta-adrenergic blockade (obsidan) improved the autoregulation (shift to the left) in both normo- and hypertensive animals.
The dopamine effect on the tension of perfused vessels and the arterial BP depended on its doses in acute experiments on anesthetized cats. Dopaminergic vasodilatory components in perfused vessels responses and the BP were determined with joint blockade of alpha- and beta-receptors. Oxygen and glucose consumption increased in the brain during continuous i.v. infusion of various doses of dopamine (5 mg/kg/min and 100 mg/kg/min). The effect of dopamine on blood circulation and cerebral metabolism mediated through adrenergic (alpha- and beta-) and dopaminergic structures, is discussed.
Explore the source record for details and available documents.
The method of hydrogen clearance used for the registration of cerebral blood flow in acute experiments on anesthetized white rats with artificial respiration has shown that aminophylline had a biphasic effect (dilatation-constriction) on cerebral vessels, particularly with stable blood pressure. Systemic hypotension provoked an increase in dilatation response. With blood pressure reduced, autoregulation levels lowered.
Acute experiments were made on dogs under morphine analgesia and local novocaine anesthesia with extracorporeal respiration to determine autoregulatory reactions (AR) of brain vessels to different levels of arterial pressure (AP). The experiments indicated that 12 h after rausedyl injection (1 mg/kg s.c.) there occurred the relaxation of AR to the AP lowering without essential changes in AR to the AP elevation. Twenty to 40 minutes after pyrroxan injection (0.5 mg/kg i.v.) AR were reduced, while AP increased, whereas during AP fall, AR improved. Possible mechanisms of the evidence obtained are discussed.
Explore the source record for details and available documents.
In acute experiments on anesthetized cats with artificial respiration and isolated autohemoperfusion of the cerebral vessels by the pump of stabilized capacity (heparin was injected intravenously), cerebral ischemia was evoked by the stopping of the perfusion pump for 15 minutes. In the postischemic period (after perfusion resumption), 2 phases of the perfusion pressure (PP) changes were noted: at the beginning the PP lowering followed by the long-term increase (above the basic level). It is assumed that the PP changes reflect the time course of the development of suggestive postischemic cerebrovascular phenomena: hyper- and hypoperfusion. Preliminary intravenous injection (40-90 min before ischemia) of strophanthine and celanide (0.05 and 0.1 mg/kg) enhanced and extended the first phase and hampered the development of the second phase PP changes. Administration of strophanthine 90-120 min after ischemia (during the PP increase phase) did not alter the cerebrovascular resistance to the blood flow. Under these conditions the response of the cerebral vessels to strophanthine decreased as compared to that in intact (non-ischemized) cats.
Autoregulation of cerebral blood flow (ACBF) under orthostatic tests (OT) was estimated in acute experiments on rabbits and cats under local anesthesia according to changes of perfusion pressure (PP) in carotid arteries, cerebral blood flow, pressure in the venous system of the brain, and resistance of cerebral vessels. OT was modeled by turning a special table with animal fixed stop of it from horizontal position to head up or down position for 40--80 degrees. In most experiments ACBF correlated with the changes of PP. Different variations of ACBF and its possible mechanisms are discussed.
Blood pressure in the common carotid artery, the tone of the cerebral and femoral vessels were recorded by resistography in acute experiments on nonanesthetized cats (local anesthetics, listenon) with artificial respiration. The increased pressure in isolated carotid sinuses was accompanied by a decrease in arterial pressure and in the tone of the cerebral and femoral vessels. In both cases the reaction of the cerebral vessels was less pronounced as compared to that shown by the femoral vessels. The blocking of alpha-adrenoreceptors with phentolamine reduced or abolished completely the reactions noted. After beta-adrenergic blockade with obsidan these reactions persisted. The role of carotid baroceptors in the regulation of cerebral circulation under orthostatic collapse is discussed.
Explore the source record for details and available documents.
Acute experiments were conducted on anesthetized cats; verapamil in a dose of 0.05, 0.1, 0.5, and 1 mg/kg, injected intravenously, caused a reduction of the tone of the cerebral vessels and of the general arterial pressure. Changes in the volume velocity of the cerebral circulation were phasic in character and depended on the tone of the cerebral vessels and the arterial pressure level. The circulation increased more in the cerebral cortex than in the reticular formation; PO2 correlated with the circulation in the cerebral cortex. The diameter of the pial arteries became greater both in case of the intravascular verapramil administration and its local application. The block of beta-adrenoceptors, M-cholinoreceptors, histamine receptors and preliminary administration of the sympatholytic failed to eliminate the vasodilatory action of verapamil. It is supposed that vasodilation was myotropic in character, and was possible connected with the electrolyte metabolism.
Explore the source record for details and available documents.
The effect of phentolamine and anapriline on the cerebral blood flow autoregulation (CBFA) under the orthostatic test (OT) was studied in experiments on locally anesthetized rabbits. Cerebral blood flow (CBF) in the carotids, venous pressure in the cerebral vessels, perfusion pressure (PP) in the carotid arteries were measured, the resistance of cerebral vessels was calculated. OT was modeled by tilting a special table with the animal (with its head upwards or a special table with the animal (with its head upwards or downwards) by 40--80 degrees from the horizontal level. The results showed adrenergic block in most of OT cases to disturb CBFA; phentolamine promoted passive increase of CBF when PP was increased; on the contrary, anapriline promoted passive CBF reduction when PP was decreased.
It was established in acute experiments on anesthetised and nonanesthetised cats by means of resistography that methylapogalanthamine decreased the total arterial pressure, the tone of cerebral vessels, extracranial and femoral vessels. The effect of the latter was more pronounced. A two-phase reaction (dilatation-constriction) was not rare. Methylapogalanthamine diminished the constriction reaction of intra- and extracranial vessels in response to st mulation of the cervical sympathetic nerves. The vasodilator action of methylapogalanthamine was enhanced by anesthesia and decreased by rausedyl.