[Changes in the efficacy of vasoconstrictor stimuli in acute and chronic hypotension in the microcirculatory bed of rat skeletal muscle]. / Izmeneniia v éffektivnosti vazokonstriktornykh stimulov pri ostroi i khronicheskoi gipotenzii v mikrotsirkuliatornom rusle skeletnoi myshtsy krysy.

Microvascular diameters in m. extensor hallucis proprius of rats were measured by the image split method. The baseline diameters and responses to the electrical stimulation (20 Hz, 10 s) of the sympathetic tract were obtained in arterioles i. d. 7.8-88 microns. Measurements were made under baseline pressure into the right femoral artery, 1 min after local blood pressure drop (LBPD) produced by inflation of the cuff around descending aorta and in the rats with the chronic (1-2 months) regional hypotension (CRH) produced by implantation of a metal coil narrowing the aorta. Thirty five arterioles out of 45 showed reduction of responsiveness to sympathetic stimulation after LBPD (mean-19.1 +/- 2.1%), 6 arterioles reacted by insignificant enhancing of the constrictor responses and the reactions of 3 vessels were more pronounced (mean-21.1 +/- 9.1%). The responsiveness to sympathetic stimulation of the skeletal muscle arterioles i. d. 10-20 microns exposed to CRH did not differ from that in the sham-operated rats (11.6 +/- 1.3% vs 10.4 +/- 0.1%).

[Constrictor reaction to transmural electric stimulation of the isolated femoral artery and its branches in chronic arterial hypotension]. / Konstriktornye reaktsii na transmural'nuiu élektricheskuiu stimuliatsiiu izolirovannykh bedrennykh arterii s vetviami, dlitel'no nakhodivshikhsia v usloviiakh arterial'noi gipotenzii.

Chronic regional arterial hypotension in the hind limbs of rats was produced by narrowing of the abdominal aorta. 14-19 days later the femoral artery and its main branches were isolated and perfused in vitro with oxygenated Krebs' solution. It was shown that constrictor responses to transmural electrical stimulation decreased 14-30 days after the constriction of the aorta, however, 90 days after the operation the responses were identical to those in the control. Guanethidine (1.10(-5) mol/l) decreased significantly the responses to stimulation in all the cases, while phentolamine (3.5.10(-5) mol/l) inhibited completely those reactions. The constriction of femoral arteries in response to noradrenaline infusion was the same in control and hypotensive vessels.

[Changes in the microcirculatory bed and tissue metabolism in chronic regional arterial hypotension]. / Izmeneniia mikrotsirkuliatornogo rusla i tkanevogo obmena pri khronicheskoi regionarnoi arterial'noi gipotenzii.

Blood pressure was reduced in the hind part of rats by narrowing the aorta in regions distal to renal artery ostium. Resetting of microcirculatory bed (m. extensor hallicis propius) was revealed in arterial hypotension, characterized by resistance vessel dilatation ensuring the decrease in hydravlic resistance, thus facilitating blood supply and tissue metabolism normalization, irrespective of marked reduction in perfusion pressure.

[Effect of long-term arterial hypotension on the relative volume of functioning capillaries in working skeletal muscles]. / Vliianie dlitel'noi arterial'noi gipotonii na otnositel'nyi ob"em funktsioniruiushchikh kapilliarov v rabotaiushchikh skeletnykh myshtsakh.

In control rats, the relative red cell volume, mirroring the number of the functioning capillaries, was substantially greater in the soleus than in the gastrocnemius muscle, while the rise of this parameter seen during contraction of both the muscles, provoked by stimulation of the sciatic nerve, amounted to 37 and 54%, respectively. Fourteen days and 3-4 months after abdominal aorta constriction by a metal spiral, that produced a 30-50% lowering of the blood pressure in the vessels of the animal's body posterior, contractions of the gastrocnemius muscle did not provoke any increase in the relative red cell volume, whereas contractions of the soleus muscle were accompanied by a marked elevation of the relative red cell volume. It is assumed that the mechanisms underlying the working hyperemia of the gastrocnemius and soleus muscles are different.

[Relative volume of open capillaries in the skeletal muscles of rats with chronic local arterial hypotension]. / Otnositel'nyi ob"em otkrytykh kapilliarov v skeletnykh myshtsakh krysy pri khronicheskoi mestnoi arterial'noi gipotenzii.

A modification of Pickworth's method for detection of open capillaries was used. The modification is based on freezing an organ in situ with liquid propane, cooled with liquid nitrogen, followed by lyophilization of the preparation and its fixation in gaseous formaldehyde. It was shown in rat experiments that the number of functioning capillaries in m. gastrocnemius and m. soleus 14 and 90-12 days after reduction of pressure in the hindquarter of the body with the narrowing of the abdominal aorta lumen was practically the same as that in the control animals. The data support the view that reduction of the hydraulic resistance in the area of regional hypotension does not correlate with increase in the number of parallel-functioning vessels.

[Orthostatic circulatory instability: role of deconditioning of resistance vessels]. / Ortostaticheskaia neustoichivost' krovoobrashcheniia: rol' detrenirovannosti rezistivnykh sosudov.

One of the effects of weightlessness on the circulatory system, i.e. reduction of the tension distending resistance vessels due to the loss of hydrostatic pressure, was simulated. For this purpose the abdominal aorta of rats was constricted by a wire spiral. As a result, the arterial pressure in the posterior body decreased by 30-50%. Beginning with postoperation day 7 the hydraulic resistance of resistance vessels of hindlimbs was decreased progressively and the myogenic regulation of their lumen was inhibited. The response to the stimulation of vasoconstrictive fibers of the sciatic nerve that was reduced 7-14 days after operation returned to normal 90 days later. An examination of the tail arteries demonstrated that the ability of their muscular layer to withstand the distending effect of the physiologically normal pressure was impaired. The magnitude of the constrictor reactions to norepinephrine (particularly to its moderate concentrations) was lowered. These changes may play an important role in the orthostatic disorders of circulation that occur after exposure to weightlessness.

[Neurohistochemical and ultrastructural study of the adrenergic innervation of the wall of the rat posterior vena cava during chronic venous hypertension caused by experimental oleothorax]. / Neirogistokhimicheskoe i ul'trastrukturnoe izuchenie adrenergicheskoi innervatsii stenki zadnei poloi veny krys pri khronicheskoi venoznoi gipertenzii, vyzvannoi éksperimental'nym oleotoraksom.

Chronic venous hypertension in rats was provoked by injection of polymethyloxane into the pleural cavity. Hypertrophy of muscular tissue was accompanied by reconstitution of adrenergic nervous structures. In the early stages (up to 40 days), the changes in the latter are reactive in nature: first there occurs a weakening of luminescence, rare-fraction of the network and then "hyperneuria". Pulmonary heart formation was followed by marked hypertrophy of SMC, increased density of adrenergic fibers, convergence of SMC and nerve terminals (synapse formation).

[Ultrastructure of the wall of the femoral artery in rats with chronic regional arterial hypotension]. / Ul'trastruktura stenki bnedrennoi arterii krys pri khronicheskoi regionarnoi arterial'noi gipotenzii.

In experiments on rats a lowering of the arterial pressure in the vessels of the body posterior was attained by occlusion of the aorta distally to the ostia of renal arteries. Twelve days after the operation there occurred a significant thinning out of the muscle layer and intermuscular septa in the wall of the femoral artery. Also, there was a disappearance of extracellular matrix vesicles usually seen in great numbers in tunica media of the artery. The animals with arterial hypotension of one- and three-month standing manifested a negligible number of extracellular vesicles; the thickness of the muscle layers and intermuscular septa increased but remained far less than normal.

[Improvement in the histochemical method of detecting open capillaries]. / Usovershenstvovannyi gistokhimicheskii metod vyiavleniia otkrytykh kapilliarov.

A modification of Pickworth's method for detection of open capillaries is described. The special feature of this method consists in freezing the organ in situ with liquid propane, cooled with liquid nitrogen, with the subsequent lyophilization of the preparation and its fixing in gazeous formaldehyde. The slides were stained strictly according to Pickworth.

[Relative volume of functioning capillaries in the skeletal muscle in regional hypotension]. / Otnositel'nyi ob"em funktsioniruiushchikh kapilliarov v skeletnoi myshtse pri regionarnoi gipotenzii.

Experiments on rats demonstrated that one month after the reduction of pressure in the vessels of the hind part of the body caused by narrowing of the abdominal aorta lumen the number of functioning capillaries in the gastrocnemius and the soleus muscles was practically the same as in control animals. These results allowed the authors to assume that a decrease of the hydraulic resistance of the resistive vessels in the area of chronic local arterial hypotension was not connected with an increase in the number of parallelly functioning vessels.

[Volume rigidity of the capacitance vessels of rats in local arterial hypotension]. / Ob'menaia zhestkost' emkostnykh sosudov krysy pri mestnoi arterial'noi gipotonii

It was shown in experiments on rats that reduction of arterial pressure in the vessels of the posterior extremity for a period of up to three months was accompanied by a decrease of the volume stiffness of the capacitance vessels of this area.