Contribution of Hydrogen Sulfide to Dilation of Rat Cerebral Arteries after Ischemia/Reperfusion Injury.

The study examined the effect of H2S on the tone of cerebral arteries in rats after global cerebral ischemia/reperfusion injury and cooperation between NO and H2S in the control over cerebral circulation during the postischemic period. In control sham-operated and in experimental rats with ischemia/reperfusion injury, the diameter of pial arteries was repeatedly measured in vivo under a light microscope after removal of parietal bone and dura mater in 1 h and in 7 days after the surgery. The study established that H2S is an important signaling molecule in pial arteries, where it is responsible for vasodilation. Interaction of H2S and NO augmented dilation of pial arteries; in these arteries, H2S up-regulated the effect of NO/cGMP/sGC/PKG signaling pathways. Partially, the dilating effect of H2S is realized via activation of ATP-sensitive K+ channels in plasmalemma of smooth muscle cells. In the brain, ischemia/reperfusion injury degrades the ability of pial arteries to dilate via inhibition of NO-mediated signaling pathway.

Endothelium-dependent Hyperpolarization-Mediated Relaxation Pathway in Bovine Mesenteric Lymph Nodes.

Endothelium-dependent relaxation mechanisms have been studied in phenylephrine-precontracted capsules of bovine mesenteric lymph nodes studied in vitro. Tetraethylammonium chloride and TRAM-34 in a solution with L-NAME and Indomethacin, which suppress the production NO and prostacyclin of endothelium, increased the tone of the lymph nodes. We believe that in bovine mesenteric lymph nodes, the dilation mechanism is mediated by hyperpolarization of the endothelium, which is associated with activation of large- and intermedium conductance Ca2+-activated potassium channels.

Effect of Transplantation of Mesenchymal Stem Cells on the Density of Pial Microvascular Network in Spontaneously Hypertensive Rats of Different Age.

Using a TV device for studying microcirculation (×40), we analyzed the density of the whole microvascular network and the density of arterioles in the pia mater of the sensorimotor cortex in SHR rats of different ages (3-4 and 12 months) after intracerebral transplantation of human mesenchymal stem cells. We found that the density of pial microvascular network in SHR rats receiving transplantation of human mesenchymal stem cells increased to a level observed in young Wistar-Kyoto rats.

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.

Influence of High Blood Pressure on Microcirculation in Cerebral Cortex of Young Rats.

We studied the density and structure of the microvascular network of the pia mater, the blood flow rate and oxygen saturation in the sensorimotor cortex of young spontaneously hypertensive rats (SHR). The density of the microvascular network in hypertensive animals was by ~1.4 times lower than in normotensive Wistar-Kyoto rats (control) and arteriolar bed density was lower by ~1.9 times. The blood flow rate in tissue and oxygen saturation in the sensorimotor cortex in SHR rats were significantly lower than in control animals.

[THE AGING OF MICROVASCULAR NETWORK FORMED IN CORTEX FOLLOWING INTRACEREBRAL TRANSPLANTATION OF MESENCHYMAL STEM CELLS].

Using a TV device to study microcirculation in brain we found that intracerebral transplantation of mesenchymal stem cells to 12-months old rats led to a significant increase (circa 1,5-fold times) of microvascular density in pia tissue and to increased constriction reactions of pia arterioles in response to noradrenalin application on a brain surface. Both microvascular density and pia arterioles reactivity was completely preserved in aging until 22-24 months.

Postischemic Responsiveness of Pial Vessels to Hypercapnia.

Reactions of pial vessels to hypercapnia were studied in Wistar rats one week after global cerebral ischemia. In ischemic rats, the responsiveness of pial vessels to hypercapnia was diminished, which promoted a decrease in cerebral perfusion reserve. Changes in vascular responsiveness in the arterial and venous subdivisions of the vascular bed were observed and probably resulted from ischemia-provoked down-regulation of the vascular tone.

[Comparative analysis of the potentiative effect of noradrenaline on the neurogenic vasoconstriction diminished by various factors].

The effect of 0.03-1.0 µM noradrenaline on the neurogenic response to electrical field stimulation of the juvenile rat tail artery segment in control conditions, after cooling from 36 to 25 degrees C, and after solution pH decrease from 7.4 to 6.6 was studied. Noradrenaline was shown to potentiate neurogenic vasoconstriction diminished by low temperature or low pH. Decrease in neurogenic vasoconstriction being equal, low dose noradrenaline was most effective at low temperature and high dose noradrenaline was most effective at low pH. 1.0 µM noradrenaline was equally effective in both cases. Increase in the neurogenic tone of the rat tail artery evoked by noradrenaline at low temperature and acidosis may contribute to decrease in heat emission at low ambient temperature in vivo.

[Efficacy of mesenchymal stem cells intracerebral transplantation for the correction of age-related cerebral microcirculation alterations in rats].

Using a television-based vital microscopy method and immunohystochemical analysis, we have assessed the effect of intracerebral transplantation of syngeneic mesenchymal stem cells (MSC) on the brain cortex structure and the microcirculation in the pia mater of old rats. Using "open field" system, we have studied the effect of MSC transplantation on position-finding and discovery behavior of older animals. We have found that density of microvascular network of the pia mater increased ca. 1.9-fold in MSC recipients, compared to age-matched intact animals. Density of the arteriolar area of microvascular network of the pia mater increased ca. 2-fold. Reactivity of the newly formed arterioles was nearly equal to that of native microvessels. Intracerebral transplantation procedure itself was traumatic for brain cortex of rats, but it had no effect on the microcirculation in the contralateral hemisphere. Intracerebral transplantation of MSC did not improve locomotor behavi- or and emotional stage of old rats, did not increase their position-finding and discovery activity.

Effect of intracerebral transplantation of mesenchymal stem cells on reactivity of pial arterioles in old rats.

Using a TV device for studying microcirculation (×160), we analyzed the responses of arterioles in the pia mater of the sensorimotor cortex in young (2-3 months) and old (22-24 months) rats after local application of a vasoconstrictor (norepinephrine, 10(-6) M) or vasodilator (acetylcholine, 10(-6) M). The responses of the arterioles were evaluated by changes in their diameter and by the number of responding vessels in the field of view. The constrictor responses of the pial arteries to norepinephrine did not significantly differ in intact young and old rats. The number and degree of dilatory responses to acetylcholine in old rats were lower than in young animals by 14 and 30%, respectively. Intracerebral transplantation of mesenchymal stem cells to old rats had practically no effect on reactivity of pial arterioles to acetylcholine, while the number of constricted vessels in response to norepinephrine increased by ~20%.

[Mesenchymal stem sell donor age effect on the cerebral cortex microvascular net density in old age rats-recipients of transplant].

Male Wistar-Kyoto rats aged 22-24 months were intracerebrally transplanted with syngenic bone marrow mesenchymal stem cells (BM MSC) established from the donor aged 3-4 months and 20-22 months, respectively. Using a TV device to study microcirculation in vivo, we have established that transplantation of BM MSC from young donors increased a density of the microvascular network in the pia mater of the sensorimotor cortex in old rats approximately 1.9-fold, comparing to age-matched controls, while a density of the arteriolar compartment increased approximately 2.1-fold. Transplantation of BM MSC from old donors did not lead to the significant increase in the density of the microvascular network in the pia mater, while a density of the arteriolar compartment increased approximately 1.5-fold.

[Potentiative effects of noradrenaline on the neurogenic vasoreactivity diminished by cooling].

The effect of 0.03--1.0 µM noradrenaline on the response to electrical field stimulation of the juvenile rat tail artery segment at 36 degrees C and after cooling to 25 degrees C was studied. At 25 degrees C, the neurogenic vasoconstriction was inhibited, but low dose noradrenaline potentiate the constriction. This potentiation was greater at 25 degrees C than at 36 degrees C, following spontaneous decline in the constriction counteracted by noradrenaline. At low temperature, the potentiative effects of noradrenaline were greater at high frequency of electrical field stimulation. The phenomenon of increase in the noradrenaline-evoked potentiation of neurogenic vasoconstriction inhibited by cold may be of importance for thermoregulation. It could provide restoration of diminished effectiveness of the neurogenic contractile signal thus leading to low heat emission at low temperature.

[Age-related changes of microcirculation in pia mater of rats' sensorimotor cortex].

We studied the density of whole microvascular network and separately the density of arterioles in the pia mater of sensorimotor cortex of rats of different ages. Also pial arteriolar reactivity on exposure to norepinephrine or acetylcholine chloride was evaluated. The microvascular density and the arteriolar reactivity in the pia mater were not significantly changed before the age of 12 months. In the age of 22-24 months the density of whole microvascular network decreased 1,7 times at the mean and the density of arterioles decreased 1,2 times. There were no significant changes of pia arterioles constriction during the animals life but dilatation was noticeably worse in senility. Orientation and exploratory behavior got worse to the age of 22-24 months: the number of behavioral acts in the "open field" test decreased 1,5-2,3 times in comparison with young animals.

[The effect of intracerebral mesenchymal stem cells transplantation on the density of microvascular network of the pial matter of the rat brain cortex].

Using a TV installation for studying the microcirculation (with 30-160-fold magnification), the density of microvascular network in the pia matter of the rat brain sensomotor cortex was determined after intracerebral transplantation of mesenchymal stem cells (MSC) or (as control) of the MSC cultivation nutrition medium, or of saline. The results have shown that intracerebral transplantation does not change density of microvascular network in the pia mater of the ipsilateral hemisphere. Transplantation of the MSC led to a 1.8-fold increase of density of the pia matter of the contralateral hemisphere as compared with control animals; the number of arterioles in the same zone was 2.5-fold higher than in intact rats.

[The effect of noradrenaline on the neurogenic vasoreactivity at various frequencies of the electrical field stimulation].

The effect of 0.03-10.0 microM noradrenaline on the response to electrical field stimulation (EFS) of the juvenile rat tail artery segment was studied. At frequencies of the EFS equal to 10 or 40 Hz, noradrenaline was shown to cause much more pronounced potentiation or--at higher concentration--much less pronounced inhibition of the EFS-evoked constriction in arteries characterized by spontaneous decrease in the constriction value in the course of experiments as compared with arteries which were not characterized by such a decrease. At frequencies of the EFS equal to 3 or 5 Hz, the value and/or direction of the change in the neurogenic vasoconstriction in the presence of noradrenaline depends on the presence of the spontaneous decrease in the constriction evoked by EFS at 10 Hz, rather than at 3 or 5 Hz. It is concluded that the character of the change in the neurogenic vasoreactivity is a factor of a great importance for the prediction of the further change in the reactivity in the presence of noradrenaline.

[The effect of low-intensity red and infrared laser radiation on the rat arterial and deoxygenated blood].

In vitro experiments the effect of low-intensity red or near-infrared laser irradiation on the blood samples (1.5 ml from abdominal aorta of Wistar rats) were studied. The diode laser light (lambda = 650 nm or 808 nm, power density 15.6 mW/cm2, duration 15 min) were used. In some experiments the deoxygenated blood as object for comparison with arterial blood was chosen. Under red laser irradiation we observed a significant increase of average volume of erythrocytes as well as mean amount of free (disaggregated) leukocytes especially in case of the deoxygenated blood. At the same time the concentration of Ca2+ and Na+ were decreased. The effects of infrared laser irradiation on indices mentioned above were not significant. We believe that red low-intensity laser irradiation on the blood is an important factor for theological properties in the field of microcirculation.

Noradrenaline can restore decreased neurogenic vasoreactivity.

Experiments on isolated segments of the tail artery from young (aged 4-6 weeks) rats addressed the effects of noradrenaline (0.01-1.0 microM) on the reactions of these segments to stimulation with an electric field in isometric conditions. These studies showed that noradrenaline increases this reaction after spontaneous or acidosis (pH 6.6)-induced decreases and that the extent of this increase was proportional to the magnitude of the previous reduction in the reaction. The increase in the decrease in the reaction to electrical stimulation was accompanied by widening of the range of potentiating noradrenaline concentrations and an increase in the noradrenaline concentration at which potentiation was maximal. The nitric oxide synthesis blocker NG-nitro-L-arginine did not eliminate the potentiating effect of noradrenaline. These data led to the conclusion that noradrenaline produces a concentration-dependent recovery of decreased neurogenic reactivity of blood vessels and that this effect is not associated with changes in nitric oxide synthesis.

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.

[Restoring effect of noradrenalne on diminished neurogenic vasoreactivity].

The effect of 0.01-1.0 microM noradrenali on response to electrical field stimulation (EFS) of the juvenile rat tail artery segment was studied. Noradrenali was shown to potentiate the EFS-evoked constriction decreased in the course of experiments or in the acidic solution (pH 6.6) and this potentiation was proportional to the extent of the preceding decrease of the constriction. The more decreased was the EFS-evoked constriction the higher was the noradrenali concentration which produced the maximal potentiation and the wider was the potentiative noradrenali concentration range. The potentiative effect of noradrenali was not prevented by the NO synthase inhibitor NG-nitro-L-arginine. The results suggest that noradrenali can restore the diminished neurogenic reactivity of blood vessels, and this effect is not connected with the change in the NO production.

Differences in adrenoreception in the microcirculatory bed of the pia mater in normotensive and spontaneously hypertensive rats.

Adrenoceptors in pial vascular bed of normotensive Wistar-Kyoto rats are distributed unevenly during stimulation of the superior cervical ganglion, their density was maximum in the 5th-generation arteries. In spontaneously hypertensive rats (SHR) the density of adrenoceptor is lower than in normotensive rats and their number is maximum in the 1st-generation arteries.