Biomedical subjects
Publications and source records attributed to R S Orlov.
Four versions of lymphangions contractions were revealed in a single isolated bovine mesentery: longitudinal, total circular, partial circular and uniform. Authentic distinctions in realisation by lymphangions of their pump function depending on a type of the contraction, were absent. The type of contraction seems to be determined by an orientation of the smooth muscle cell bunches in the lymphangion's wall.
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Lymphangions were found to possess a considerable ability for temperature adaptation under modelled stressful effects on humans. The minute volume of lymphangions was found to linearly depend on the temperature of bathing solution within the range of 22-41 degrees C. Aspirin and other non-steroid analgetic agents were found to exert an obvious dose-dependent negative inotropic effect on electric potentials and contractile activity of a lymphangion. Clinical-experimental assessment and physiological justification of action of a new perfusion solution: polyvisoline, was given.
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The modules of elasticity of circular stripes of lymphangion wall were 3.5.10(4) N.m-2, and those of longitudinal stripes were 1.5.10(5) N.m-2. The module of elasticity of intact lymphangions ranged from 1.2.10(4) to 5.2.10(4) N.m-2. The volume-pressure relationship in intact lympangions were similar to length-force relationship in circular stripes. Spontaneous contractions were only evoked by distention of circular stripes. These findings suggest that smooth muscle of circular layer of lymphangion's wall seems to play a basic role in pumping function of lymphangions.
A combined clinico-morpho-physiologic investigation was conducted in 98 patients with primary and secondary lymphatic edema. All patients underwent lymphography by means of electron and light microscopy; biopsy specimens obtained from a lymphatic vessel at lymphography were investigated histologically, and contractility records were made. Pronounced disorders were demonstrated in the lymphatic vessels and their myocytes. New rational schedules of pathogenetic treatment for lymphedema of the lower limbs are outlined on the basis of the reported findings.
The pump function was studied in single isolated lymphangions of the bovine mesenteric vessels 2.5-3.5 mm in diameter. The lymphangion was found to be able to self-regulate the pump function. The terminal diastolic pressure 0.5-1.0 kPa was found to be optimal for the pump function. The ratio of the lymphangion power to its weight is 0.2 Wt/N at the pressure 1 kPa. i.e. the lymphangion is near to the heart of warm-blooded animals by this parameter. Mainly the myocytes of circular layer contribute to the lymphangion pump function, the myocytes carrying out the function of stretch receptors enabling the lymphangion to alter its efficacy in accordance with the level of lymph production.
APs of smooth muscles of isolated lymphatic vessels were recorded by means of the single sucrose-gap method. Plateau APs with sharp spikes on the plateau were recorded in Krebs' solution. Low-sodium solutions led to discontinuation of the plateau phase whereas calcium-free solution eliminated the sharp spikes. Increase of the intravascular pressure during the action of D-600 blocking agent activated the electrical activity which suggests that smooth muscle cells have channels of mechanical sensitivity. Intracellular Ca2+ seems to participate in the contractile mechanism.
Increased intravessel pressure resulted in depolarization of the smooth muscle cell membrane in lymphatic vessels, elongation of APs, augmentation of oscillatory potentials plateau and in increased steadiness of the smooth muscle cells in Ca--free solution, D-600 and Mn2+. The membrane of smooth muscle cells of lymphatic vessels seems to have Na-Ca channels with mechanical sensitivity.
The electrical activity of smooth muscle of isolated lymphangiomas revealed spontaneous APs about 3.8 +/- 1.3 mV for 200-250 ms preceding the contractions. In Ca-free solution the APs and the contractions disappeared. The blockade of calcium channels suppressed electrical activity of smooth muscle cells. The increase of amplitude and time of the APs increased the amplitude and time of the contractions. The data suggest that spontaneous APs play a part in activation and coordination of the phasic contractions, and show that automaticity of lymphangiomas is revealed in smooth muscle cells of the circular layers of the valves, and that tonic and phasic contractions have a special type of membrane activating mechanisms.
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An inhibitory effect of hypoxia (Po2 less than 5 mmHg) on electrical and mechanical activity of the smooth muscle of the rat portal vein has been described by Hellstrand, Johansson & Norberg (1977). The present study using the sucrose gap method confirmed their finding that spontaneous activity was completely (or almost completely) abolished by the low Po2. Increased [K+]0 from 6 to 24 mM or decreased [Na+]0 from 137.5 to 76.5 mM reinitiated electrical and mechanical activity during hypoxia. If muscle activity had already been increased by 24 mM K+ or 76.5 mM Na+ solutions in the aerobic situation, switching to hypoxia caused only partial inhibition. In hypoxic solutions of such altered ionic composition a gradual increase in muscle activity with time was seen especially in the low Na+-solution. Stimulating agents such as noradrenaline, acetylcholine, 4-aminopyridine, and Ba2+ could reinitiate spike activity and contractions under hypoxic conditions. Ouabain stimulated the activity in normoxia but no effect was seen in hypoxia. Uptake and washout of 42K+ was studied. No difference in uptake was found between normoxic and hypoxic conditions. The rate of 42K+ efflux was decreased under hypoxia. A similar decrease was produced by Mn2+ (0.4 mM) which, like hypoxia abolished phasic muscle activity. In both cases the reduction in 42K+ efflux may just reflect the elimination of action potentials. It is concluded from these results that profound hypoxia exerts its inhibitory effect on the smooth muscle to a large extent through membrane mechanisms responsible for pacemaker activity or spike generation. The electrophysiological response may be secondary to change in intracellular [Na+] or [Ca2+].
In isolated segments of the dog and cat renal arteries alkalization of the bathing solution at pH from 6.5 to 8.0 increased the amplitude of contraction and the sensitiveness to noradrenaline. A sharp rise of O2 content induced some increase in reactivity of muscle cells and caused spontaneous rhythmic activity. The results suggest a direct effect of pH and pO2 on the functional characteristics of renal arterial muscles. The effect seems to occur due to reversible changes in intracellular pH.
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Effect of gamma-aminobutyric acid (GABA) and its agonists, phenibut, phenylpyrrolidone and LGPI-29, on contractility of smooth muscle cells was studied on an isolated rat vena porta. The contractility was recorded by a rapidly operating 6MH-1B mechanotrone to show that the solutions of GABA and those of phenibut (to a less extent) exert a distinct inhibitory effect on smooth muscle cells of the rat vena porta at a concentration of 10--20 mM. Phenylpyrrolidone and LGPI-29 did not decrease vascular tone. Depolarization of the cell membrane did not interfere with the inhibitory effect of GABA and its agonists on smooth muscle cell contractility of the rat vena porta.
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Epinephrine, norepinephrine, and isoproterenol induced circular contraction of isolated segments of canine intracerebral internal carotid artery. The alpha--and beta-antagonists inhibited the effects of catecholamines. Acetylcholine showed dual effects involving both dilation (5.10(-12)--5.10(-9) g/ml) and contraction 5.10(-8) g/ml and higher). Atropine inhibited both effects. The K+ depolarization abolished the contractile effects of norepinephrine and acetylcholine. The blockade of calcium permeability by Mn++ abolished the contractile effects of sympathetic and parasympathetic mediators.