Alterations in systemic hemodynamics caused by electrostimulation of the ventral medulla oblongata

Alterations in arterial blood pressure induced in cats by electrostimulation of pressor or depressor points in the ventral part of the medulla oblongata did not, as a rule, differ in direction from those in other hemodynamic parameters, including cardiac output, total peripheral resistance, central venous pressure, maximal acceleration of aortic blood flow, heart rate, venous return, blood flow in the superior and inferior venae cavae, and arterial inflow to and venous outflow from the posterior part of the body. It is postulated that the ventral medulla exerts direct influences on both the venous and arterial hemodynamics. Translated fromByulleten' Eksperimental'noi Biologii i Meditsiny, Vol. 121, No. 6, pp. 613–618, June, 1996     

Correlation between blood pressure and parameters of systemic hemodynamics during pressor and depressor effects of the ventral medulla oblongata

Correlation between blood pressure and parameters of systemic hemodynamics was studied on cats using electrical stimulation of the ventral medulla oblongata. Changes in blood pressure induced by presoor activation were related to venous hemodynamics in the anterior rather than posterior vena cava. Venous blood flow is assumed to be involved in hemodynamic changes caused by stimulation of pressor centers but not depressor centers in the ventral medulla oblongata. Translated fromByulleten' Eksperimental'noi Biologii i Meditsiny, Vol. 129, No. 1, pp. 16–19, January, 2000     

Resistance and capacitance functions of veins in the gastrocnemius muscle during electrical stimulation of ventral subdivisions of medulla oblongata

Perfusion of blood vessels in the gastrocnemius muscle with autoblood under local electrostimulation of pressure zones of ventral part of the medulla oblongata revealed increments in resistance to blood flow in the muscle veins and arteries, which were respectively, 83 and 81% of the constrictor reactions of these vessels in response to a supramaximum electrostimulation of the sympathetic chains, while decrease in the venous blood filling was 33%. In response to electrostimulation of VMO depressor zones, the venous blood filling did not increase, while in the muscle arteries and veins the resistance to blood flow decreased by 60 and 130% in comparison with the dilator reactions of these vessels after dissection of sciatic nerve in the muscle preparation. Both quantitative and qualitative aspects of resistance and capacitance function of venous and resistive arterial vessels are shown to depend on individual features in the regulation of veins and arteries at the central and peripheral level. Translated fromByulleten' Eksperimental'noi Biologii i Meditsiny, Vol. 125, No. 5, pp. 493–496, May, 1998     

Alterations of phrenic nerve activity caused by stimulation of neuronal structures in rostral area of ventral surface of the medulla oblongata

Electrical stimulation of neuronal structures in a rostral area of the ventral bulbar surface alters central inspiratory activity in anesthetized rats, augmenting the amplitude and velocity of this activity during the periods of its increase and plateau. The reactions are more pronounced in rats with transected vagal nerves. Blockade of pulmonary mechanoreceptors eliminates the influence of rostral neuronal structures only on the temporal parameters of the plateau. Bilateral cooling of neuronal structures to 20°C results in complete block of central inspiratory activity. Translated fromByulleten' Eksperimental'noi Biologii i Meditsiny, Vol. 123, No. 6, pp. 617–619, June, 1997     

Cardiovascular effects elicited from the ventral surface of medulla oblongata in the cat

Cardiovascular adjustments induced by topical application of drugs on a restricted area on the ventral surface of the medulla oblongata, corresponding to the caudal part of the rostral chemoreceptor area and the intermediate area, have been studied in chloralose-anesthetized cats. Topical application of GABA or glycine on these structures resulted in blood pressure fall, bradycardia, vasodilatation in the kidney and the skeletal muscles and also depression of respiration. Similar responses except for a slight tachycardia occurred with application of physostigmine. Application of GABA resulted in a marked attenuation of the reflex vasoconstrictor responses to removal of arterial baroreceptor restraint (carotid occlusion), particularly in the kidney, and to disappearance of the reflex renal vasodilatation to baroreceptor stimulation. The findings suggest that GABA application leads to a general diminution of the tonic vasomotor neuron activity, and with regard to renal vasomotor neurons a virtual cessation. Atropine methylnitrate application induced blood pressure rise, increased peripheral resistance in both skeletal muscle and kidney and a strongly potentiated renal vasoconstrictor response to carotid occlusion. The results indicate that the studied superficial medullary structures play an important role for the maintenance of tonic vasomotor neuron activity, especially renal.Deceased January 1980     

Sensitivity of mouse,rat, and human embryonic lungs to the action of nitrosomethylurea in organ culture

In response to the direct action of nitrosomethylurea (NMU) in a concentration of 0.05 mg/ml on organ cultures of embryonic lungs of strain A mice, Wistar rats, and man, a varied degree of degenerative changes and hyperplastic proliferation of the epithelium developed in the cultures. In the early stages of the experiment the toxic effect of the cultures predominated. Tissue of rat embryonic lungs was most sensitive to the toxic action of NMU, mouse lung tissue least sensitive. The frequency of hyperplastic proliferation, on the other hand, was highest in cultures of mouse lungs and lowest in cultures of rat lungs. During culture the sensitivity of the human and rodent embryonic lungs to the toxic action of NMU decreased when the substance was repeatedly added to the nutrient medium. Meanwhile an increase in the survival of the experimental cultures was observed compared with the intact control.Department of Carcinogenic Agents, Oncologic Scientific Center, Academy of Medical Sciences of the USSR, Moscow. (Presented by Academician of the Academy of Medical Sciences of the USSR L. M. Shabad.) Translated from Byulleten' Éksperimental'noi Biologii i Meditsiny, Vol. 84, No. 9, pp. 349–352, September, 1977.     

Role of ultrastructural changes in the lungs of suckling rabbits in the pathogenesis of experimental cholera

Type II alveolocytes are destroyed in suckling rabbits during adhesion ofVibrio cholerae, whereas in type I alveolocytes no ultrastructural disorders are detected. The number of lipid granules is increased in the lipofibroblast cytoplasm. Transendothelial micropinocytosis and endothelial edema and destruction are increased in pulmonary capillaries, and plasmatic impregnation of the stroma is observed. The development of experimental cholera is associated with progressive disorders of the regional circulation, degranulation of platelets and basophils, destruction of polymorphonuclear leukocytes and endotheliocytes, and a marked increase of vascular permeability. Translated fromByulleten' Eksperimental'noi Biologii i Meditsiny, Vol. 120, No. 8, pp. 173–177, August, 1995 Presented by P. V. Sergeev, Member of the Russian Academy of Medical Sciences     

Relationship of changes in the central hemodynamics to the development of posthypoxic cerebral edema in the postresuscitation period

A syndrome of low cardiac output developed between the first and third hours after resuscitation in 16 dogs subjected to circulatory arrest for 15 min. In half of the cases its development was preceded by an increase in the cardiac output in the initial period of resuscitation. Without hyperperfusion at the beginning of resuscitation, the animals died 9–23 h after the beginning of the experiment. Among the surviving animals, edema of the cerebral cortex always developed in dogs with a reduced cardiac output 24 h after resuscitation, but no cerebral edema was observed in dogs with a high cardiac output.Laboratory of Experimental Physiology of Resuscitation, Academy of Medical Sciences of the USSR, Moscow. (Presented by Academician of the Academy of Medical Sciences of the USSR V. A. Negovskii.) Translated from Byulleten' Éksperimental'noi Biologii i Meditsiny, Vol. 83, No. 3, pp. 266–268, March, 1977.     

Changes in expired air composition during electrical stimulation of the ventral medulla

Department of Physiology of Visceral Systems, Institute of Experimental Medicine, Academy of Medical Sciences, Saint Petersburg. Translated from Byulleten' Éksperimental'noi Biologii i Meditsiny, Vol. 113, No. 4, pp. 339–340, April, 1992.     

Contribution of galaninergic structures of the brain to reaction to lipopolysaccharide

Relationship between blocking of galanine receptors in the brain and lipopolysaccharide-induced two-wave reaction and changes in neurotransmitter metabolism in the anterior and posterior hypothalamus, caused by provision of this reaction, are studied in rats. Intraventricular administration of the galanine receptor antagonist M-15 prevented the decrease in rectal temperature 3 h after intraperitoneal injection of lipopolysaccharide, thus rendering the pyrogenic reaction a prolonged single-wave pattern. Neurotransmitter changes, specifically, a decrease in the dopamine content in the anterior and increase in the posterior hypothalamus during reaction to endotoxin, are blocked by specific antagonist of the galanine receptor. These data indicate the participation of galaninergic mechanisms of the brain in central reactions to lipopolysaccharide. Translated fromByulleten' Eksperimental'noi Biologii i Meditsiny, Vol. 124, No. 4, pp. 430–433, April, 1998     

Changes in the systemic hemodynamics produced by vasopressin in dogs during individual development

Indices of the central hemodynamics were studied in puppies aged 18–22 days and 2–3 months and in dogs aged 3–5 years after intravenous injection of synthetic vasopressin (0.8 unit/kg body weight). The pressor effect was strongest in the adult dogs and bradycardia in the puppies aged 18–22 days. The cardiac output was reduced in all animals and the peripheral resistance considerably increased. In adult dogs the external work of the left ventricle and the energy consumption of the heart were increased. In puppies a reduction in the volume velocity of ejection of blood and in the external work of the heart was combined with a smaller increase in energy consumption.Department of Pathological Physiology, Rostov Medical Institute. (Presented by Academician of the Academy of Medical Sciences of the USSR, N. N. Sirotinin.) Translated from Byulleten' Éksperimental'noi Biologii i Meditsiny, Vol. 83, No. 3, pp. 261–263, March, 1977.     

Effect of prostaglandin B1 on the systemic and regional hemodynamics

The effect of prostaglandin B₁ (PGB₁) on the cardiovascular system was studied in experiments on anesthetized dogs. After intravenous injection of PGB₁ (40 g/kg in a single dose) arterial hypotension tachycardia, increased myocardial contractility, an increased cardiac output, and a rise of pressure in the pulmonary artery were observed. The total peripheral resistance and total pulmonary resistance were reduced. The work of the right and left ventricles was increased. The coronary blood flow was increased by 29%. The mean velocity of the volume blood flow in the renal and femoral arteries was appreciably increased after administration of PGB₁, but in the common carotid and superior mesenteric arteries the increase was not significant. Changes in the systemic and regional hemodynamics were of short duration.Department of Pharmacology, I. M. Sechenov First Moscow Medical Institute. Department of Anesthesiology, Institute of Clinical and Experimental Surgery, Ministry of Health of the USSR, Moscow. (Presented by Academician of the Academy of Medical Sciences of the USSR V. V. Zakusov.) Translated from Byulleten' Éksperimental'noi Biologii i Meditsiny, Vol. 83, No. 2, pp. 131–133, February, 1977.     

Changes in hemodynamics and respiration in animals with different resistance to acute hypoxia

We studied the effects of acute hypoxia on hemodynamics and respiration in cats. The animals were divided into high-, low- and medium-resistant to hypoxia by the time of respiratory arrest after breathing with 3% O₂ gas mixture. In high-resistant animals, hemodynamic indices remained at a high level throughout the hypoxic episode, while in low-resistant cats they decreased shortly after the onset of hypoxia. It is suggested that the peculiarities of hemodynamic regulation play an important role in individual resistance to acute hypoxia. Translated fromByulleten' Eksperimental'noi Biologii i Meditsiny, Vol. 128, No. 9, pp. 286–290, September, 1999     

Changes in phospholipid composition of mitochondria in the medulla oblongata and frontal lobes of the cerebral hemispheres in hemorrhagic shock in cats

Considerable regional differences in the phospholipid composition of mitochondrial membranes are found in the brain of cats in the terminal phase of hemorrhagic shock. The most prominent alteration is noted in the medulla oblongata and consists in a progressive elimination of phosphatidylcholine. Changes in the main phospholipids in mitochondrial membranes of the cerebral hemispheres are less pronounced and consist in a drop of phosphatidylinositol and phosphatidylethanolamine. Accumulation of lysophosphatidylcholine and lysophosphatidylethanolamine is a regular feature of the studied mitochondria. Accumulation of lysophosphatidylserine is found primarily in mitochondrial membranes of the medulla oblongata. Translated fromByulleten' Eksperimental'noi Biologii i Meditsiny, Vol. 121, No. 4, pp. 387–391, April, 1996     

Topography of the respiratory and circulatory responses to acetylcholine and nicotine on the ventral surface of the medulla oblongata

The effects of different [Ca²⁺]₀ in the presence of variable [Na⁺]₀ (100 to 37 mM) on the slow action potentials were studied in isolated rat atria in the presence of 25 mM K⁺ plus 10^–6 M isoproterenol. Two modes of electrical stimulation were used, sustained stimulation at 0.5 Hz (steady-state mode), and stimulation by a single stimulus after rest periods of 2 to 5 min (1st response mode). With the first type of stimulation, and for [Ca²⁺]₀ between 0.5 and 10 mM and [Na⁺]₀ between 100 and 65 mM, the slow action potential overshoot increased linearly with the logarithm of the [Ca²⁺]₀ (28.4 mV per 10-fold change in [Ca²⁺]₀). However, elevation of [Ca²⁺]₀ above 10 mM caused depression of the overshoot. This overshoot depression by high [Ca²⁺]₀ was accentuated if [Na⁺]₀ was decreased to 37 mM. With the 1st response mode of stimulation, the overshoot — log [Ca²⁺]₀ relationship was linear within a wider [Ca²⁺]₀ range (0.5 to 25 mM), and was less sensitive to further decreases in [Na⁺]₀. It is suggested that rat atria slow action potentials are generated by selective influx of Ca²⁺ but not Na⁺, and that the depression of amplitudes observed a high [Ca²⁺]₀ and low [Na⁺]₀ is due to a decrease in the Na²⁺ exchange mechanism which results in a higher [Ca²⁺]_i, and not to a decrease in the inward Na⁺ current. Adenosine produced a parallel downward displacement of the overshoot to log [Ca²⁺]₀ relationship. This adenosine effect was concentration dependent, independent of [Ca²⁺]₀ and the frequency of stimulation. In contrast, the effects of 0.4 mM La³⁺ were dependent on the [Ca²⁺]₀ and on the frequency of stimulation. Adenosine also produced a downward shift of the relationship between maximal rate of rise of the slow action potential and membrane resting potential in such a manner that its effects cannot be attributed to changes in inactivation potential of the slow channels. Hence, adenosine and La³⁺ depress the slow Ca²⁺ action potentials by two different mechanisms. Adenosine may act by 1) decreasing the number of functional slow channels, 2) decreasing the conductance of the individual channels, or 3) altering the kinetic properties of these channels. La³⁺ may act by competing with Ca²⁺ for membrane binding sites. These membrane binding sites appear to be characterized by frequency dependence.Supported by Grants NHLBI 10384 and AHA 74-942.Dr. Luiz Belardinelli is the recipient of a fellowship No. 1112. 1273/75 from Conselho Nacional de Desenvolvimento Cientifico e Technologico (CNPq) and Fundacao Universitaria de Cardiologia do Rio Grande do Sul, Brasil.     

Histological structures in the chemosensitive regions on the ventral surface of the cat's medulla oblongata

Summary The region on the ventral surface of the medulla oblongata (see preceding communication) responding maximally to both electrical and chemical stimulation by inducing an increase of ventilation was marked electrolytically and examined histologically. A characteristic group of large multipolar nerve cells was always found at the spot marked by electrolysis.These cells are located medial to the hypoglossal roots and ventral to the inferior olive which separates them from the respiratory centers. The cells are distributed at a distance of 8–450 m from the ventral surface of the medulla oblongata, the greatest concentration being located at 150–200 m beneath the surface.The possible role of these cells in the central chemical respiratory drive is discussed.Im Rahmen des Programms des Sonderforschungsbereiches 114 (Bionach) der Deutschen Forschungsgemeinschaft.     

Effect of intravenous infusion of Polyosm on diuresis and parameters of systemic and cerebral hemodynamics

The effect of 30-min infusion of Polyosm (a polyethylene oxide 400 solution) is studied on anesthetized cats. The preparation stimulates diuresis and has no effect on arterial and venous pressure and cardiac and stroke indices. By the 30th min of infusion, the total peripheral and cerebral vascular resistance significantly decrease, while cerebral blood flow increases. Translated fromByulleten' Eksperimental'noi Biologii i Meditsiny, Vol. 123, No. 3, pp. 299–301, March, 1997