Changes in Cerebral Blood Flow in the Postischemic Period.

Experiments on Wistar rats showed that blood flow in the cortex and subcortical brain structures was not completely restored within 21 days after transient ischemia caused by bilateral carotid artery occlusion with controlled hypotension. After 7 days of reinfusion, the end-diastolic blood flow velocity increases with simultaneous decrease in pulsation index, which indicates the decrease in peripheral vascular resistance. During the following 14 days, peripheral blood resistance increases, as was seen from the increased peak systolic blood flow velocity, mean blood flow velocity over the heart cycle, and pulsation index. These changes are likely a delayed manifestation of ischemic reperfusion injury to brain microvessels (no-reflow phenomenon) and are determined by changes in blood rheologiy and pial vessel lumen.

[THE INFLUENCE OF SHORT-TIME CEREBRAL ISCHEMIA ON PIAL VESSELS ADRENOREACTIVITY IN RATS].

Reactivity of pial vessels in response to a brain surface irrigation by norepinephrine solution in rats, subjected to transient global cerebral ischemia (2VO+hypo model), was investigated. Four different groups of rats at 2, 7, 14 or 21 days after ischemia were subjected to microvascular studies using in vivo video microscopy method. The diameter changes of pial arteries and veins in response to norepinephrine were measured. It was established that cerebral ischemia led to increase the number of the constrictions to norepinephrine mainly at the vessels to relating to a group of small pial arteries and arterioles and pial veins of the 3rd generation. Reactivity changes were observed in all time points studied. These changes probably is connected with caused by ischemia the increase in reactivity and sensitivity of pial vessels adrenoceptors. The greatest changes are noted in 14 days after ischemia.

Role of nitric oxide in responses of pial arterial vessels to low-intensity red laser irradiation.

The responses of rat pial vessels to red laser irradiation can be mediated by NO. NO mainly affects major arteries and did not contribute to reactivity of small pial arteries and precortical arterioles.

Adrenoreactivity of rat pial arteries under conditions of stabilized systemic blood pressure.

Segment-specific characteristics of the reactions of pial arteries of different generations to intravenous injection of norepinephrine were studied under conditions of instrumental stabilization of systemic blood pressure in rats with blocked α- and ß-adrenoceptors.

Effect of laser irradiation on adrenoreactivity of pial arterial vessels in rats.

Experiments on WKY and SHR rats showed that low-intensity laser irradiation reduced the tone of pial arterial vessels thereby potentiating the subsequent constrictor effect of norepinephrine. Irradiation in the red region of the spectrum produced a more pronounced effect in the blue region. The observed effects were less pronounced in SHR rats compared to normotensive WKY rats.

Effect of low-intensity laser radiation of the red spectrum on some properties of erythrocytes in Wistar rats.

Laser radiation of different power had various effects on the properties of erythrocytes. An increase in the radiation power from 2.2 to 25 mW/cm2 was accompanied by a decrease in the erythrocyte sedimentation rate and an increase in erythrocyte filtration index. Radiation of 50 mW/cm2 induced abnormal erythrocyte aggregation. Increasing the time of irradiation at power intensity of 2.2 mW/cm2 did not potentiate its effect on the blood.

Adrenergic reactions in microcirculatory bed of pia mater in rat brain.

Differential characteristic of the reaction of pial arteries of various generations to intravenous administration of norepinephrine was obtained in experiments on rats under artificially stabilized systemic blood pressure.

Neurogenic vasoconstriction of pial arterial vessels of various branching orders in normotensive and spontaneously hypertensive rats.

Intravital television microscopy was employed to study the reaction of pial arteries in normotensive and spontaneously hypertensive rats to stimulation of the superior cervical ganglion. The amplitude of constrictor response was similar in WKY and SHR animals. Under conditions of normal arterial pressure and arterial hypertension, the maximum constrictor effect was attained due to equal involvement of the arteries from all generations in the normotensive rats and predominant constriction of the precortical arterioles in SHR animals.

Effect of alveolar hypoxia on reactivity of pial vessels in normotensive and spontaneously hypertensive rats.

Intravital television microscopy revealed reduced reactivity of pial arterioles in response to alveolar hypoxia in spontaneously hypertensive rats (SHR) compared to normotensive (WKY) rats, which manifested in decreased number of dilatory reactions and in less pronounced vascular dilation.

[Response of pial arterioles to alveolar hypercapnia in normotensive and hypertensive rats]. / Reaktivnost' k al'veoliarnoi giperkapnii pial'nykh arteriol normotenzivnykh i gipertenzivnykh krys.

In the WKY rats, a large number of vessels were dilated in response to alveolar hypercapnia, the rest of the vessels remaining unchanged, whereas both vasodilation and vasoconstriction occurred under the same conditions in the SHR rats. The difference seems to be due to biophysical and/or biochemical specifics of the SHR vascular walls and to partially depend on specific features of haemodynamics in pial vascular micromodules in both strains of rats.

[Comparative characteristics of myogenic responses in pial arterioles in normotensive and spontaneously hypertensive rats]. / Sravnitel'naia kharakteristika miogennykh realtsii pial'nykh arteriol normotenzivnykh i spontanno gipertenzivnykh krys.

In acute experiments on SHR and WKY rats, the pial arterioles' myogenic responses to a drop in systemic blood pressure (SBP) were studied. The SHR seem to be more capable of keeping the myogenic activity in low SBP. It might depend on structural changes in the vascular wall under these conditions wall in the SHR.

[The effect of high-molecular compounds on the rheological properties of the blood and on the reactivity of the skeletal muscle vessels]. / Vliianie vysokomolekuliarnykh soedinenii na reologicheskie svoistva krovi i reaktivnost' sosudov skeletnoi myshtsy.

The administration of polymers into the vascular bed of the m. gastrocnemius and in vitro did not affect the postocclusion hyperemia but in changed the venous outflow from the muscle, the change having a phasic character. The effects of concentrations and molecular mass of the polymers on the blood rheological properties were more obvious in vitro. Dextran-20 thousand most favourably affects the blood viscosity whereas the least favourable one belongs to polyoxyethylene-20 thousand. The polymers with molecular mass about 500 thousand in small concentrations reduce the viscosity of the blood, in larger concentrations they enhance it increasing the erythrocytes aggregation.

[Nocigenic changes in the blood viscosity indices of rats]. / O notsigennykh izmeneniiakh pokazatelei viazkosti krovi u krys.

One-minute subcutaneous nociceptive stimulation increased arterial pressure by 15-20 mm Hg in Wistar rats. The 20-min. stimulation altered rheological properties of the blood: the hematocrit, the plasma viscosity and protein concentration, the erythrocyte aggregation velocity, the utmost tension of shift, and the viscosity of the blood standardized by hematocrit--all these parameters increased. These changes are rather unfavourable for flowing properties of the blood. The changes of the blood rheological properties were reflex-based, the problem of compensatory shifts is discussed.

[Aggregation of erythrocytes placed in macro- and micro-cuvettes]. / Agregatsiia éritrotsitov v krovi, pomeshchennoi v makro- i mikrokiuvety.

Changes of the intensity of light reflected or passing through cuvette with the blood specify the degree of blood aggregation. The parameters of light reflection by the surface of blood in macro-cuvette are compared with those of light passage through a thin micro-cuvette with preliminarily stirred blood. The latter technique enables a direct microscopy of the erythrocytes aggregation. Virtually similar results were obtained with blood of different animals and with different values of hematocrit. The data suggest a correlation between velocity of the aggregation and increase of the hematocrit value. Causes of discrepancies of the absolute values of parameters under study are discussed.

[Effect of stretching of the cat gastrocnemius muscle on its tetany, postcontraction hyperemia and energy metabolism indices]. / Vliianie rastiazheniia ikronozhnoi myshtsy koshki na ee tetanusy, postkontraktsionnuiu giperemiiu i pokazateli énergeticheskogo metabolizma.

Longitudinal stretch of the muscle in the range E = 0.11-0.17 (111-117% of the initial length) is followed by increase in passive strength and in mechanical displays of the 15-sec isometric Blood flow in the muscle vessels decreases at rest in the longitudinal stretching whereas O2 extraction from the blood increases; O2 consumption and ration of arterio-venous differences in the lactate and pyruvate concentration do not change. Additional posttetanic blood supply in the muscle, posttetanic alteration of the O2 consumption in it and the lactate/pyruvate ratio in longitudinal stretch do not differ from the analogous parameters in the initial--length muscle. The data obtained are in accordance with the metabolic theory of the hyperemia mechanisms but can hardly be explained from the standpoint of the histomechanical theory.

[Blood supply and oxygen consumption in cat musculus gastrocnemius during isometric tetanus and intra-arterial infusion of norepinephrine]. / Krovosnabzhenie i potreblenie kisloroda ikronozhnoi myshtsei koshki pri izometricheskom tetanuse v usloviiakh vnutriarterial'noi infuzii noradrenalina.

In anesthetized cats with maximal isometric tetanus induced by the n. ischiadicus stimulation, the initial oxygen consumption depended on the 2--fold reduction of initial blood flow, the anaerobic metabolism index remaining the same, at that. Stimulation of the nerve induces practically the same mechanical activity of the muscle in control and after i. a. administration of noradrenaline, but the working hyperemia with concomitant changes of the metabolism indices becomes weaker than in control. A correlation of muscle blood supply changes with oxygen consumption changes was revealed whereas there was no correlation between changes of these indices and changes of oxygen extraction from the blood. A possibility of effects of the primary increase in blood flow occurring in hyperemia following the mechanical factor action, on the oxygen consumption is discussed as well as effect of willed decrease in blood flow within non-hypoxic range upon the oxidated metabolism.