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Biomedical subjects

N I Losev

Publications and source records attributed to N I Losev.

At least 19 recordsLinked to original sources
PubMed1992

The mechanisms of free-radical lipids and antioxidant heart protection in experimental ischaemia and infarction.

Free-radical lipid peroxidation (FRLP) during experimental myocardial ischaemia and infarction was studied on the first author's model using coronary occlusion in more than 1500 albino rats. FRLP was tested at various intervals after coronary occlusion (from the 20th minute to 14--30 days) in myocardial lipid extracts using various methods: 1) chemiluminescent method determining the intensity of free radical reactions, 2) diene conjugate production, 3) malone dialdehyde reaction, 4) Schiff bases fluorometric determination. The severity of ischaemia and infarction was assessed according to electrocardiographic, light and electron microscopic findings and morphometry of the damaged area. Intensified FRLP was registered in all four indicators at most tests performed within the first 14 days after production of ischaemia and infarction. The severity of ischaemic lesion could be reduced by FRLP inhibition using antioxidative agents of sharply differing chemical nature (sodium selenite, alpha-tocopherol a.o.). The authors conclude that FRLP intensification plays a role in the pathogenesis of myocardial ischaemia and infarction, and recommend to include antioxidative drugs in comprehensive heart protection.

Animals↗
PubMed1989

[The generation of active microbicidal forms of oxygen by leukocytes transiting the vascular bed of the lungs].

In experiments on dogs using the chemiluminescent method and nitroblue-tetrazole reaction the authors found out that leucocytes while passing through the pulmonary vessels bed, in contrast to the spleen increase the generation of active microbicidal forms of oxygen. Due to this fact we suppose that the lungs may take part in the formation of free radical status and phagocytic antiinfectious defence of the organism.

Animals↗
PubMed1989

[Acid hydrolase activity and cyclic nucleotide contents in the rat heart during myocardial ischemia and postischemic reperfusion].

The acid phosphatase and cathepsin D activities and cAMP and cGMP levels in isolated perfused rat heart were investigated during various periods of ischaemic myocardial injury and postischaemic reperfusion. The effect of phosphodiesterase inhibitor--caffeine was also studied. Free acid hydrolases activities and cyclic nucleotide content were increased under 40 and 60 min ischemia and 20 min postischaemic reperfusion. Addition of 50 microM caffeine to perfusion solution after 30 min of ischaemia resulted in increase of cAMP level, cAMP/cGMP ratio, lysosomal bound activities of acid hydrolase and decrease of free acid hydrolase activities. The obtained results suggested that defect in cAMP synthesis might be present in lysosomal membranes labilization in cardiomyocytes injured during ischaemic conditions. Addition of such agents, as caffeine, which increased heart cAMP level, may be effective in lysosomal membranes stabilization under reversible heart ischaemia and reperfusion.

Acid Phosphatase↗
PubMed1986

[Formation of the marginal "pro-oxidant" zone and its role in the enhancement of lipid peroxidation in the area of myocardial ischemia and infarction].

The formation of peripheral zone devoid of dehydrogenase activity but possessing vessels connected with the normal myocardium was demonstrated in the area of fresh myocardial infarction 2 h after coronary occlusion. A direct correlation between the changes of the zone area and the intensity of free radical lipid peroxidation in the area of fresh myocardial infarction was established.

Animals↗
PubMed1986

[Characteristics of the "no-reflow" phenomenon in reperfusion of the myocardium depending upon the duration of ischemia].

The dynamics of changing dimensions of "no reflow" area following reperfusion after 30 min-1 h-long ischemia is characterized by three basic phases. The reperfusion following and hour-long ischemia altered considerably the character of phases of "no reflow" phenomenon. The data obtained suggest that the therapy of transitory ischemia must be directed not only to ischemia itself, but also to postischemia reperfusion-induced "no reflow" phenomenon.

Animals↗
PubMed1984

[Effect of naloxone and thyroliberin on respiration in acute hypoxia].

Experiments on 48 adult rats anesthetized with urethane were made to study the effects of naloxone and thyrotropin-releasing hormone on respiration after acute hemorrhage. The drugs were injected intravenously in doses 0.25-0.30 mg/kg. The changes found in the electromyogram of the diaphragm, blood pressure and ECG demonstrated naloxone and thyrotropin-releasing hormone to stimulate the respiratory center at different stages of respiratory disorders (dyspnea, apnea, gasping) induced by hemorrhage.

Acute Disease↗
PubMed1984

[Changes in the size of the myocardial damaged area in postischemic reperfusion].

The changes in the size of the myocardial injury area during reperfusion after the coronary occlusion-induced ischemia lasting 30 minutes are phasic in nature. Until 3.5 h the injured area increases and after 23.5 h relatively diminishes. After a more prolonged ischemia such manifestations are either unmarked or absent. Ischemia lasting from 30 min to 4 hours followed by reperfusion, as compared with ischemia of the same duration without reperfusion, normally gives rise to the formation of an area of injury, which is less or occasionally equal in size. The data obtained and reported indicate that in the area of coronary occlusion there are groups of cardiomyocytes that differ as regards the resistance to ischemia.

Animals↗
PubMedDate not supplied

[The role of the lungs in regulating the generation of active forms of oxygen by the phagocytes, the concentration of immunoglobulins and the complement activity].

Experiments on 25 intact dogs, 2 calves and clinical tests in 45 patients have shown that in the blood of the aorta or pulmonary vein leaving the lungs there is a rise in generation of active oxygen forms by leukocytes, their phagocytic activity, the activity of myeloperoxidase, NADPN-oxidase, complement, immunoglobulins content. As to the liver, kidneys, spleen, no such increased generation of active oxygen forms by leukocytes was registered. The results suggest an important role of the lungs in regulation of free radical activity of leukocytes, their phagocytic ability and thus in anti-infection defense of the body.

Animals↗
PubMedDate not supplied

[Study of contractile properties of muscles of curarized animals by the method of stimulation impedancography].

The effect of relaxation doses of tubocurarine on the stimulation and contractile properties of muscles in complete synaptic block was studied in experiments on laboratory rats by means of a previously developed method of stimulation impedancography. During intramuscular electrostimulation the stimulus threshold for short 0.01 mc test impulses increased, while the steepness of the characteristic "force of action--contractile effect" curve, registered at 1 mc impulses, reduced. The reduction was caused by loss of the function of synaptic nerve structures which take part in recruiting the contractile elements. Nonsynaptic mechanisms of recruiting through direct stimulation of the muscle fibres ensure 45% of recruitment. Changes of the duration of the contraction were not detected in the first 20 minutes of the effect. After 60-80 minutes of relaxation there was a tendency to prolongation of the time of the contraction act, which may be caused by prolonged immobilization of the animals.

Animals↗
PubMedDate not supplied

[Role of the lungs in the regulation of the generation of active oxygen forms by leukocytes under normal and pathological conditions].

Studies conducted in the clinic (in patients with cardiac diseases) and experiments (performed on intact dogs) by means of the hemiluminescent method and the nitroblue tetrazolium test showed that the lungs, in distinction to other organs (heart and others), have a stimulating effect on the generation of active oxygen forms (AOF) by the leukocytes. In this way the lungs may probably play a double role in the organism: potentiate its defence (by intensifying the microbicidal activity of the phagocytes) and facilitate damage (by secretion of AOF by the phagocytes beyond them--into the tissues); the resultant effect depends on the balance of these two types of action. In carcinoma of the lung the stimulating effect of its involved lobe (part) on the leukocytes diminishes.

Animals↗