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Biomedical subjects

A A Lebedev

Publications and source records attributed to A A Lebedev.

At least 127 records · Page 7Linked to original sources
PubMedDate not supplied

[Mechanism of the diuretic effect of eufillin].

In acute experiments on rats the xanthine diuretic euphylline did not block the short-circuited current in the proximal tubule, nor did it lower the transtubular potential and the transepithelial resistance of the nephron wall. The diuretic speeded up significantly the passage of the tubular fluid along the proximal region of the nephron and Henle's loop. The dihydroergotoxin and inderal blocking of adrenoreceptors did not produce any influence on the renal effects of the xanthine agent. Reserpine totally blocked the diuretic and saluretic effects of euphylline, whereas other sympatholytics, such as alpha-methyl-dofa, anthabus and hemedin, did not modify the action of the diuretic.

Aminophylline↗
PubMedDate not supplied

[Hematoma of the cerebral peduncle].

The paper presents a rare case of surgical treatment for hematoma of the cerebral peduncle in a 30-year-old woman found to have progressive neurological focal disorders due to mesaticephalic and thalamic lesions. Computed tomography and magnetic resonance imaging (MRI) revealed a round mass (26 x 3 x 25 mm) in the left cerebral peduncle and thalamus without surrounding edema. The focus showed characteristic signs of subacute parenchymatous hematoma. The interpeduncular cistern was explored via transsylvian approach and hematoma was removed by making a small incision of the left cerebral peduncle. Histological examination of a surgical specimen demonstrated no vascular malformation. The postoperative period was complicated by left oculomotor nerve palsy which regressed following several months. A small slit-like cyst communicating with the interpeduncular cistern was detected in the left cerebral peduncle by MRI at follow-up.

Adult↗
PubMedDate not supplied

[A comparison of the self-stimulation reaction and of conditioned place preference with fenamine administration in rats].

The reinforcing properties of different doses of amphetamine (1 and 5 mg/kg) were examined using two variants of self-stimulation reaction (in the Skinner box and locomotor self-stimulation in a shuttle box) and place preference test. Amphetamine in dose of 1 mg/kg increased the frequency of self-stimulation in the Skinner box and prolonged the time of rat staying in active zone of a shuttle box to a greater degree than 5 mg/kg of the drug. On the contrary, the aversive phase of self-stimulation, determined by a coefficient of "disagreement", grew higher after 5 mg/kg amphetamine than following 1 mg/kg. The study of effects by place preference test revealed the other regularity: the most positive reinforcing properties possessed the drug in a dose of 5 mg/kg. Thus, there are dissociation between the two doses of amphetamine (1 and 5 mg/kg) in their action on different physiological conditioned responses. The mechanisms of this dissociation are discussed.

Amphetamine↗
PubMedDate not supplied

[Comparative study of the effects of amphetamine and dimethoxymethamphetamine on brain self-stimulation in rats after perinatal administration of 6-hydroxydopamine].

The effects of amphetamine and its analog dimethoxymethamphetamine (DMA) on self-stimulation of the lateral hypothalamus was studied in adult rats treated with the neurotoxin 6-hydroxydopamine in the prenatal and early postnatal periods. Both compounds administered in a dose of 1 mg/kg produced similar activation of the brain self-stimulation suppressed by 6-hydroxydopamine. DMA, in contrast to amphetamine, did not produce such activation in intact rats and in the animals treated with 6-hydroxydopamine in the prenatal period.

DOM 2,5-Dimethoxy-4-Methylamphetamine↗
PubMedDate not supplied

[Norepinephrine-induced pressor diuresis blockade as a possible cause of hypertension].

The effect of norepinephrine infusion at a constant rate (0.8 or 2.5 microg/kg/min), i.v.) on the diuiresis, sodium excretion with urine, glomerular filtration, and arterial pressure (AP) was studied in acute experiments on dogs. The sodium excretion was calculated as percentage relative to the filtration charge. Norepinephrine infusion at a constant rate of 0.8 microg/kg/min led to an increase in the urine volume, in the amount of excreted sodium with increased AP (pressor diuresis effect), and glomerular filtration with increasing AP, while the level of reabsorption remained unchanged. An increase in the infusion rate to 2.5 microg/kg/min, led to a decrease in the urine volume, the level of sodium excretion, and the rate of glomerular filtration. In this case, the AP level was higher than that in the first series of experiments, and the level of sodium reabsorption was increased.

Animals↗
PubMedDate not supplied

[Astressin blockade of amygdaloid corticoliberin receptors eliminates the stimulating effects of amphetamine, morphine and leu-enkephalin on brain self-stimulation].

Amphetamine (1 mg/kg), morphine (1 mg/kg), and ethaminal sodium (5 mg/kg) activated self-stimulation reaction of lateral hypothalamus in rats. In contrast, intraamygdalary injections of astressin (1 microg/microl), which is a nonselective antagonist of corticoliberin receptors, inhibited this reaction. The astressin blockade of extrahypothalamic corticoliberin receptors in the central nucleus of amygdala modified the effects of various narcogens on self-stimulation reaction. On this background, amphetamine did not activate self-stimulation, ethaminal sodium retained significant psychoactivating effect, whereas the effect of morphine switched from stimulant to depressant. Leu-enkephalin exhibited a stable depressant effect, thus potentiating the action of astressin. The astressin-induced enhancement of the inhibiting action of leu-enkephalin on cerebral self-stimulation is probably related to a temporary switch-off of the activating influence of the central nucleus of amygdala on hypothalamus.

Action Potentials↗
PubMedDate not supplied

[Effects of antidepressants in models of brain self-stimulation and place preference after prolong social isolation and alcoholization].

In rats rearing in social isolation since 17th day of life and treated with 5-15% ethanol solution within 3 months, the effects of antidepressants on self-stimulation of lateral hypothalamus and place preference were studied. The comparative study of seven antidepressants with different mechanism of action (fluoxetine, maprotiline, tianaptine, pyrazidol, sertraline, citalopram, mianserin) was shown that pyrazidol and tianeptine and in a less degree sertraline and citalopram possessed the significant antidepressant activity in the model of social isolation and maprotiline and tianeptine did in model of alcoholization. It is concluded that antidepressants studied activate the reinforcing properties of the brain, that is associated with the involvement of both the catecholamine and serotonin system, working reciprocally.

Animals↗
PubMedDate not supplied

[Effect of peptides introduced into the central nucleus of amygdala on the hypothalamic self-stimulation in chronically alcoholized rats].

The reinforcing properties of neuropeptides (substance P, corticoliberin, leu-enkephalin, alaptide) and 70 kDa heat shock protein (HSP) administered into the extended amygdala were studied on the hypothalamic self-stimulation model in rats reared in community or social isolation since the 17th day after birth. Since that time (17th day) half of rats were given 5 - 15 % ethanol solution instead of water (semiforced alcoholization). In the age of 90 - 100 days, all rats were implanted electrodes into lateral hypothalamus and cannulas into the central nucleus of amygdala. In the group of alcohol-dependent rats, the alcohol administration was continued. In rats reared in community, corticoliberin, leu-enkephalin and substance P increased the reinforcing properties of self-stimulation in dose-dependent manner, but alaptide and HSP decreased self-stimulation moderately. In rats reared in social isolation, the vector of neuropeptide effects was retained, although the magnitude of the effects was lower. Therefore, the neuropeptides differently participate in the reinforcing mechanisms of hypothalamus. It is suggested that the extended amygdala modulates the reinforcing properties of lateral hypothalamus, probably by means of extrahypothalamic corticoliberin-containing neurons.

Alcoholism↗
PubMedDate not supplied

[Anxiogenic and mnestic effects of corticoliberin and its analogs introduced into the brain ventriculi of rats].

The behavioral effects of native human corticotropin-releasing hormone (CRH) and its agonists D-Glu-20 (R1) and D-Pro-5 (R2) introduced (0.01 - 1 microg) into the lateral brain ventriculi of Sprague-Dowley rats have been studied in the open field, dark - light, Y-maze, and place preference tests. The different effects of CRH and its agonists on the anxiety level and short-term memory were revealed. D-Glu-20 (an R1 agonist of CRH) acted as an anxiogen in the open field and dark - light tests. D-Pro-5 (an R2 agonist of CRH) did not cause the typical anxiogenic effect, but produced a nonspecific suppression of behavior. D-Pro-5 only in high doses decreased the number of visits into the light box in the dark - light test. At the same time, this compound enhanced the short-term memory to a maximum degree and prevented the memory loss induced by diazepam. The data obtained are in agreement with the published data about differential participation of R1 and R2 receptor systems of CRH in the regulation of emotional and mnestic components of behavior. The anxiogenic action of CRH is connected with the activation of R1 receptors of CRH.

Animals↗
PubMedDate not supplied

[Electrolyte and water content in the kidney cortical sections of rats exposed to catecholamine action].

Functional significance of alpha and beta-adrenoreceptors and also possible involvement of the cyclic 3', 5'-AMP in the catecholamines regulation mechanism of the sodium and potassium ions transport in renal cortex slices of rats were studied. Epinephrine did not change the intracellular sodium and water content, but increased that of potassium in the cells. Phentolamine-a blocking agent of the alpha-adrenoreceptors--did not change the reaction of slices to epinephrine, while inderal--a beta-adrenoblocking agent-prevented accumulation of potassium by the cells occurring under the action of epinephrine. Isopropyl-nore-pinephrine reproduced the action of epinephrine on the electrolytes composition of the renal tissue. It is suggested that accumulation of postassium by the cells of the rats' renal cortex slices is consequent upon excitation of the beta-adrenoreceptors.

Animals↗
PubMedDate not supplied

[New concepts of nephron function and the mechanisms of action of diuretics].

The hypothesis of gate charges of intracellular junctions of nephron wall is proposed. According to the hypothesis, negative charges at the entrance of the channel fixed on the lumenal side of nephron epithelium permit cation entry and block anion flow in the channel. The interaction of ions and fixed charges with sodium leads to increased reabsorption of various cations including sodium and also enhanced excretion of chloride and hydrogen ions in the urine resulting from osmotic fluid and ion diffusion through intracellular junctions. Mercurial diuretics, ethacrynic acid and osmotic agents but not furosemide enhance permeability of intracellular junctions for ions and eliminate the selective function of the fixed charges.

Animals↗
PubMedDate not supplied

[Furosemide-induced changes in the inhibiting action of urea and lactate dehydrogenase isoenzyme].

Experiments on rat tissues in vitro showed that the effect of furosemide on the activity of lactate dehydrogenase significantly changes against the background of the action of 2M urea. Furosemide decreases the activity of urea-stable fractions of lactate dehydrogenase in the kidney tissues at concentrations of 10(-6) and 10(-7) M, whereas in the liver and heart tissues this effect occurs at the concentration of 10(-3) M. However the introduction of furosemide in the incubation mixture before the addition of urea eliminates its inhibitory effect on lactate dehydrogenase activity in the kidney and its cortical layer at the concentration of 10(-6) M, in the medulla at 10(-5) M and in the liver and heart tissues only at 10(-3) M.

Animals↗
PubMedDate not supplied

[Study of the binding of diuretics by serum proteins according to changes in tryptophan fluorescence].

The effect of diuretics on tryptophan fluorescence of blood serum proteins divided by electrophoresis was studied. It was shown that ethacrynic acid produces the most significant extinction of tryptophan fluorescence in albumin fraction and novurit in globulin fraction. Furosemide possessing a high affinity for all three obtained fractions of protein does not exhibit a preferential binding to one or another of these fractions. It was also found that furosemide and ethacrynic acid by binding to human serum albumin molecule produce its conformational alterations. Mercury diuretic does not possess such effect.

Alkylmercury Compounds↗