Individual resistance of the organism and nerve cell to hypoxia

The correlation between the pattern of a neuron's reaction to acute hypoxia and individual resistance to oxygen deficit is studied on ratsin vivo as well as on surviving slices of their cerebellumin vitro. According to the survival time in a pressure chamber simulating an altitude of 11 km all the rats were divided into groups of high resistance, medium resistance, and low resistance to hypoxia. Survival time was 4.2 times longer in the high resistance group than in the low resistance group. In the cerebellar slices of high resistance animals 61.5% high-resistance neurons and 38.5% low-resistance neurons were recorded. On the other hand, in the high resistance animals the percentage of high-resistance neurons and low-resistance neurons was 31.2 and 68.8, respectively. The period of hypoxia development was 4.32 times longer in the high-resistance neurons as compared to low-resistance neurons. It is speculated that individual differences in the resistance to O₂ deficit are of a hereditary nature and manifest themselves not only on the level of the whole organism, but also in the individual nerve cell. Translated fromByulleten' Eksperimental'noi Biologii i Meditsiny, Vol. 118, N ^o 11, pp. 454–457, November, 1994     

Lipid peroxidation parameters in the internal organs of rats with different degrees of resistance to hypoxia

Lipid peroxidation and the antioxidant system of the heart, liver, and brain are studied in adult male Wistar rats with high and low resistance to hypoxia tested by “raising” to an altitude of 11.5 km and in intact outbred rats. These parameters are found to be the same in the brain of low- and high-resistance rats, while the brain content of lipid peroxidation products is higher in both groups of Wistar rats compared with outbred rats. The heart and liver parameters are coupled to the resistance to hypoxia. Antioxidant activity prevails over lipid peroxidation in the hearts and livers of high-resistance rats, confirming that oxidation plays a major role in the damaging and lethal effects of acute hypoxia. Translated fromByulleten' Eksperimental'noi Biologii i Meditsiny, Vol. 121, N ^o 1, pp 26–29, January, 1996 Presented by A. I. Archakov, Member of the Russian Academy of Medical Sciences     

Effects of adaptation to hypoxia on cytochrome levels in the brain and liver of rats

After a prolonged (for 30 days) adaptation of rats to intermittent hypoxia, their brains contained lowered levels of mitochondrial cytochromes, despite an increase in the number of mitochondria in the brain tissue mass, along with similar levels of high-energy compounds and more protein as compaired to the brains of unadapted controls. A mitochondrial population with novel properties presumably emerged in the brain. These effects were all more strongly marked in rats with an initially low resistance to hypoxia. In the liver of hypoxiaadapted animals, unlike in their brain, cytochrome levels in the mitochondrial and microsomal redox chains were lowered and the biogenesis of mitochondria was much less intensive. Translated fromByulleten' Eksperimental'noi Biologii i Meditsiny, Vol. 120, N ^o 12, pp. 576–579, December, 1995     

Effect of various oxygen concentrations on the ATP content in isolated hepatocytes of rats adapted and nonadapted to hypoxia

It is shown that isolated hepatocytes are capable of perceiving slight changes in the envioronmental oxygen concentration. A complicated phase dependence exists between adenosine triphosphate and partial oxygen pressure, which differs in cells from animals with high and low resistance to hypoxia, the former showing a more stable and resistant energy-synthesizing function than the latter. After long-term adaptation to periodic hypoxia, the resistance of the energy-synthesizing function rises in hepatocytes from high-resistant animals, and falls in low-resistant animals suggesting a fundamentally different organization of the emergency compensatory mechanisms of the energy-synthesizing function in hepatocytes of animals of these two types. Translated fromByulleten' Eksperimental'noi Biologii i Meditsiny, Vol. 118, N ^o 12, pp. 576–581, December, 1994     

Effects of adaptation to intermittent hypoxia on oxidative phosphorylation in brain mitochondria of rats with different sensitivities toward oxygen deficiency

After long-term adaptation to intermittent hypoxia, rats with an initially low resistance to acute oxygen deficiency were 2 to 4 times more resistant to it, while highly resistant rats did not show a significant change in resistance. The adaptation was accompanied by weakening of the electron-transporting function of the respiratory chain and increasing efficiency of oxidative phosphorylation in the brain mitochondria oxidizing NAD-dependent substrates, indicating that energy was produced in a more economical way. The succinate oxidase pathway of oxidation was found to be utilized to only a limited extent as a compensatory mechanism in animals exposed to intermittent hypoxia over a prolonged period. The effects of adaptation were more marked in the brain mitochondria of rats initially highly sensitive to oxygen deficiency. Translated fromByulleten' Eksperimental'noi Biologii i Meditsiny, Vol. 120, N ^o 12, pp. 572–575, December, 1995     

Effects of adaptation to periodic hypoxia on kinetic parameters of respiratory chain enzymes in rat brain

A study of kinetic parameters of brain respiratory enzymes revealed that the maximal velocity and the Michaelis apparent constant for NADH-cytochrome C-reductase are significantly lower in low-resistant rats than in rats with a high resistance to hypoxia. Adaptation to periodic hypoxia increases total resistance only in low-resistant rats. It is accompanied by an increase in the values of kinetics parameters for NADH-cytochrome C-reductase and cytochrome oxidase. Kinetic parameters for these enzymes in the brain of high-resistant rats are either unaltered or even decreased. It is suggested that the first enzymatic complex of the respiratory chain is one of the limiting or regulating links in energy metabolism determining the brain's resistance to hypoxia. Translated fromByulleten' Eksperimental'noi Biologii i Meditsiny, Vol. 121, N ^o 3, pp. 252–255, March, 1996.     

Comparison of lipid peroxidation parameters in the heart,liver, and brain of rats with different degrees of resistance to hypoxia

The relationship between the intensity of lipid peroxidation and the activity of the antioxidant system in the heart, liver, and brain is studied in male Wistar rats with low and high resistance to hypoxia tested by being “raised” to an altitude of 11.5 km and in intact outbred rats. It is found that in all groups of rats the content of lipid peroxidation products is highest in the liver, lower in the heart, and lowest in the brain. In all groups, the rate of the ascorbate-induced lipid peroxidation is highest in the brain, lower in the liver, and lowest in the heart. The activity of the antioxidant system is highest in the brain, lower in the liver, and lowest in the heart of low-resistance and outbred rats, while in high-resistance rats it is the same in all the organs. Thus, the difference in the parameters of lipid peroxidation and, particularly, of the antioxidant system in the studied organs is most pronounced in rats with a low resistance to hypoxia. Translated fromByulleten' Eksperimental'noi Biologii i Meditsiny, Vol. 121, N ^o 2, pp. 138–143, February, 1996 Presented by A. I. Archakov, Member of the Russian Academy of Medical Sciences     

Content of 2,3-diphosphoglycerate and adenosine triphosphate in erythrocytes and the acid-base balance in adult and newborn rats during acute hypoxia

It is shown that in deep acute hypoxic hypoxia the 2,3-diphosphoglycerate content is reduced and the adenosine triphosphate content unchanged in the erythrocytes of newborn rats. Under the same conditions adult animals show an increase of 2,3-diphosphoglycerate and a drop in the adenosine triphosphate content in the erythrocytes. The importance of these changes is discussed in terms of the mechanisms regulating the oxygen-transporting function of erythrocytes during acute hypoxic hypoxia in newborn and adult animals. Translated fromByulleten' Eksperimental'noi Biologii i Meditsiny, Vol. 119, N ^o 6, pp. 631–633, June, 1995 Presented by M. Ya. Studenikin, Member of the Russian Academy of Medical Sciences     

Effect of acute hypoxia on resistance to hypoxia in rats

The resistance of rats to hypoxia was measured by survival time after exposure to high-altitude (11.5 km) hypoxia. The first exposure to acute hypoxia caused phasic changes in the survival time: short-term in high-resistant rats (about 24 h) and long-term in moderate- and lowresistant rats (38–39 days) starting from 1 h and 6–7 days after the first exposure, respectively. Adaptive reactions were more pronounced in low- and moderate-resistant rats, while disadaptation was typical of high-resistant animals. In all rats, the adaptive effect dominated until days 22–23. Throughout the testing, the initial type of resistance was retained in 79% of high-resistant rats, in 41% of low-resistant and in 33% of moderate-resistant rats, i. e., the initially homogenous groups formed after the first exposure in accordance with the type of resistance became mixed, which reduced the intergroup differences. Translated fromByulleten' Eksperimental'noi Biologii i Meditsiny, Vol. 127, No. 6, pp. 625–628, June, 1999     

Role of glycolysis in the maintenance of the energy-synthesizing function of hepatocytes from rats adapted and nonadapted to hypoxia at different oxygen concentrations

It is demonstrated that the lactate-Po₂ dependence is the same in hepatocytes of rats with high and low resistance to hypoxia and does not correlate with phasic changes in the ATP concentration in the 890–50 μM O₂ region. Strong activation of lactate formation against the background of ATP decrease indicates that glycolysis is not the major mechanism determining the steady-state ATP level in the cell and affecting the ATP-Po₂ relationship in a wide range of oxygen concentrations. The intensity of glycolysis in hepatocytes of rats with high resistance to hypoxia is markedly increased after periodic adaptation to hypoxia but remains practically unchanged in the hepatocytes of low-resistance rats. This indicates that fundamentally different compensatory mechanisms are involved in this process in the liver of high- and low-resistance rats. Translated fromByulleten' Eksperimental'noi Biologii i Meditsiny, Vol. 119, N ^o 1, pp. 28–32, January, 1995     

Effect of prenatal hypoxia on DNA synthesis in the tracheal epithelium and LPO-AOD system in the lungs of newborn rats

Newborn rats euthanized 24 h after birth were examined. The rats were born to females exposed to chronic hypobaric hypoxia on days 14–19 of gestation. The index of nuclei labeled with³H-thymidine in the tracheal epithelium of newborn rats exposed to prenatal hypoxia was 3 times lower than in the control. The LPO level was higher in posthypoxic animals than in intact rats. Prenatal hypoxia led to the suppression of antioxidant defense in the lungs of newborn rats. Translated fromByulleten' Eksperimental'noi Biologii i Meditsiny, Vol. 117, N ^o 5, pp. 531–533, May, 1994     

Adaptation to altitude hypoxia limits lipid peroxidation during inflammation and stress

Preadaptation of rats to altitude hypoxia results in reduced activation of lipid peroxidation during subsequent stress, inflammation, or both, as compared to hypoxiaunadapted animals, with the result that secondary changes in organs and tissues of adapted rats are much less pronounced and conditions are created for alleviating the acute inflammation and the stress reaction. Translated fromByulleten' Eksperimental'noi Biologii i Meditsiny, Vol. 119, N ^o 6, pp. 590–593, June, 1995 Presented by E. D. Gol'dberg, Member of the Russian Academy of Medical Sciences     

Development of aseptic inflammation during the adaptation of the organism to high altitude hypoxia

The dynamics of lipid peroxidation and of the aseptic inflammatory process is studied in rats adapted to high altitude hypoxia. A greater activity and shorter duration of the acute period of inflammation are found in these animals, while in the reparative period stimulation of the proliferative processes and slowed formation of the fibroblast capsule are noted. Translated fromByulleten' Eksperimental'noi Biologii i Meditsiny, Vol. 118, N ^o 9, pp. 243–246, September, 1994 Presented by E. D. Gol'dberg, Member of the Russian Academy of Medical Sciences     

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     

Physiological concentrations of endothelin-1 cause only coronary vasodilatation in anesthetized rats

Various concentrations of the peptide endothelin-1 were tested for their effect on coronary vascular resistance in anesthetized rats. Intracoronary infusion of this peptide over 4 min in a total dose that gave rise to blood concentrations of 0.002–0.003 or 0.2–0.3 fmol/ml elicited only a decrease in the estimated coronary vascular resistance. It is suggested that only supraphysiological doses of endothelin are likely to exert a powerful vasoconstrictive effect on coronary vessels and cause myocardial ischemia. Translated fromByulleten' Eksperimental'noi Biologii i Meditsiny, Vol. 120, N ^o 7, pp. 16–19, July, 1995 Presented by I. P. Ashmarin. Member of the Russian Academy of Medical Sciences     

Variation in antiinfectious nonspecific resistance of the organism caused by cholinergic stimulation

Cholinergic stimulation (acetylcholine, aceclidine, armin) is found to improve antiinfectious nonspecific resistance in mice. The effect depends on the dose of cholinomimetic (armin), is maximal during the first 18 hours of the infectious process, and is determined by serum antibacterial activity, lysozyme activity, and the function of neutrophils and natural killers. Translated fromByulleten' Eksperimental'noi Biologii i Meditsiny, Vol. 120, N ^o . 8, pp. 164–166, August, 1995 Presented by Yu. A. Romanov, Member of the Russian Academy of Medical Sciences     

The mechanism of pulmonary hypertension in rats with high-altitude hypoxia

Morphofunctional examinations of the lungs of rats exposed to high-altitude conditions for 3 to 300 days revealed that systolic pulmonary hypertension observed during the entire period of study is caused by a total increase of the elastic resistance of pulmonary arteries. Adequate bloodflow in such a case is provided by intensive work of the right-ventricular myocardium against this resistance. Translated fromByulleten' Eksperimental'noi Biologii i Meditsiny, Vol. 121, N ^o 3, pp. 324–327, March, 1996 Presented by V. A. Trufakin, Member of the Russian Academy of Medical Sciences     

Opiatergic mechanisms of the cardiotropic effect of acute cooling

Changes in myocardial contractility after an acute cold exposure following intracerebroventricular administration of opiate receptor agonists were studied in rat hearts isolated after Langendorff. Cold exposures were carried out individually for each animal in chambers at −10°C for 4 h. Thirty min before being exposed to cold the animals were administered in a brain ventricle 10 μl of μ- or δ-opiate receptor agonists (DAGO or DADLE, respectively). Isolation and perfusion of the hearts were performed directly after the cold exposure was over. The mechanism of reduction of myocardial contractility and coronary flow induced by an acute cold exposure is believed to include stimulation of μ-opiate receptors as one of its main components, and the effect of intracerebral hypertension on hemodynamic parameters is partially mediated through activation of δ-opiate receptors. Translated fromByulleten' Eksperimental'noi Biologii i Meditsiny, Vol. 118, N ^o 12, pp. 582–584, December, 1994 Presented by R. S. Karpov, Member of the Russian Academy of Medical Sciences     

Rat brain gangliosides during hypoxia

The content and composition of rat brain gangliosides in various forms of hypoxia is studied. The content of lipid-bound sialic acid is found to be considerably elevated in the earliest stages of hypoxia combined with hypercapnia and cooling. The content of gangliosides remains elevated over the hypoxia period and returns to control values 48 hours after its discontinuation. Repeated hypoxia results in the same changes in rat brain gangliosides. Hemic sodium nitrite-induced hypoxia also leads to a reliable elevation of these lipids. Hypoxia also causes changes in the content of individual ganglioside fractions: a decreased content of mono- and an increased content of polysialogangliosides. Translated fromByulleten' Eksperimental'noi Biologii i Meditsiny, Vol. 118, N ^o 7 pp. 19–21, July, 1994 Presented by A. N. Klimov, Member of the Russian Academy of Medical Sciences     

Individual differences in responses to acute stress associated with type of behavior (Prediction of stress resistance)

On the basis of the initial parameters of behavior in the “open field,” “forced swimming,” and “emotional resonance” tests, the main behavioral parameters — the number of squares crossed, the number of standing postures, and the time of passive swimming — are shown to be predictable for stress in rats with different types of behavior. Translated fromByulleten' Eksperimental'noi Biologii i Meditsiny, Vol. 117, N ^o 1, pp. 89–92, January, 1994 Presented by P. V. Simonov, Member of the Russian Academy of Medical Sciences