Seasonal differences in the development of heightened resistance of the isolated heart during adaptation to physical exercise

Substantial seasonal differences are found in the development of the cardioprotective effect of adaptation to physical exercise: in winter such adaptation results in an increase of the resistance of the isolated heart to the contracture and arrhythmogenic effects of ischemia and reperfusion, while in summer the anticontracture effect is absent and the antiarrythmic effect is significantly lowered. Translated fromByulleten' Eksperimental'noi Biologii i Meditsiny, Vol. 120, N ^o 9, pp. 299–301, September, 1995 Presented by G. N. Kryzhanovskii, Member of the Russian Academy of Medical Sciences     

Effect of hemodilution and hemoconcentration on postischemic alterations of microvessels in rabbit paired auricles

Morphometric parameters of microvessels in paired rabbit ears and blood sampled from the internal vein were studied after ischemia reproduced under conditions of prior hemodilution and hemoconcentration. In hemodilution the postischemic alterations were found to be more pronounced in microvessels of the left ear, while for the right the same was true for rheological characteristics of the outflowing blood. Under conditions of hemoconcentration after ischemia the changes in rheological indexes were more marked on the left and in vasomotor indexes on the right. Translated fromByulleten' Eksperimental'noi Biologii i Meditsiny, Vol. 121, N ^o 3, pp. 352–354, March, 1996 Presented by V. V. Kupriyanov, Member of the Russian Academy of Medical Sciences     

Effect of substance P on neurological status and behavioral responses altered as a result of prolonged brain ischemia in rats with different types of behavior

Substance P administered 30 min after the onset of cerebral ischemia improved the neurological status and prevented postischemic hyperactivity in rats with a passive type of behavior; had no effect on the neurological status of rats with an intermediate type of behavior but reduced their postischemic hyperactivity; aggravated the neurological status of rats with an active type of behavior without exerting a significant effect on their behavioral responses; and averted a rise in the level of depression in rats of all three groups. The results of this study indicate that there is a relationship between the type of behavior, manifestations of cerebral ischemia, and the effects of substance P. Translated fromByulleten' Eksperimental'noi Biologii i Meditsiny, Vol. 120, N ^o 8, pp. 132–136, August, 1995 Presented by P. V. Simonov, Member of the Russian Academy of Medical Sciences     

On the involvement of endogenous μ- and δ-opiate receptor agonists in the antiarrhythmic effect of adaptation

Rats adapted to stress showed a decreased severity and incidence of cardiac arrhythmias induced by epinephrine, and these effects of adaptation were abolished by naloxone. It is suggested that stress adaptation mitigates arrhythmia by activating the endogenous opioid system and stimulating the μ-opiate receptors. Translated fromByulleten' Eksperimental'noi Biologii i Meditsiny, Vol. 121, N ^o 1, pp. 24–25, January, 1996 Presented by R. S. Karpov, Member of the Russian Academy of Medical Sciences     

Ca-transporting system of the left ventricular sarcoplasmic reticulum in the rat heart and damage to its membrane during ischemia and reperfusion

Ischemia and reperfusion of various duration are shown to result in a nonlinear increase in the level of free Ca in myocardial homogenates. A striking dissociation has been observed in the effect of ischemia and reperfusion on the rate of Ca transport in the sarcoplasmic reticulum, on the one hand, and the permeability of its membranes on the other. Translated fromByulleten' Eksperimental'noi Biologii i Meditsiny, Vol. 117, N ^o 2, pp. 130–135, February, 1994     

Protective effect of adaptation to hypoxia and its prolongation by pharmacological agents in rats prone to audiogenic epilepsy

Cytophotometric determination of RNA in various brain structures of hypoxia-adapted and unadapted epilepsy-prone rats at different times after an epileptic seizure shows much smaller decreases in RNA levels and their much more rapid return to normal in the adapted than in the unadapted rats. The adaptation to hypoxia produces a marked anticonvulsive effect, and this effect is enhanced and prolonged considerably by pharmacotherapy. Translated fromByulleten' Eksperimental'noi Biologii i Meditsiny, Vol. 117, N ^o 2, pp. 120–123, February, 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     

Lipid peroxidation level in the focus of compression ischemia in the cerebral cortex of rats

Pathomorphological changes in a focus of ischemia, the level of lipid peroxidation (as indicated by the content of products reacting with thiobarbituric acid), and the postischemic levels of adenyl nucleotides and tissue lipids were studied in rats with focal compression ischemia of the cerebral cortex. An increased level of the TBA-reactive products paralleled by a reduction of the concentrations of adenyl nucleotides and tissue lipids was found to be in clear-cut correlation with the processes of neuronal injury and death and with subsequent repair phenomena in the focus of cortical ischemia. Translated fromByulleten' Eksperimental'noi Biologii i Meditsiny, Vol. 118, N ^o 12, pp. 589–590, December, 1994 Presented by O. S. Adrianov, 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     

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     

Adaptation to periodic hypoxia and a diet supplemented with polyunsaturated class ω-3 fatty acids enhance the resistance of Ca2+ transport in the myocardial sarcoplasmic reticulum to free-radical oxidation

The relationship between the level of accumulation of lipid peroxidation products and the status of the Ca²⁺-transporting system in the sarcoplasmic reticulum of the rat myocardium is studied against the background of two cardioprotective factors, namely adaptation to periodic hypoxia and a diet enriched in polyunsaturated fatty acids of the ω-3 class. It is shown that the diet leads to an increase of level of lipid peroxidation products by 1.8 times in the heart and by 19 times in the liver, whereas a adaptation has no effect on the level of lipid peroxidation products in either of these organs. At the same time, the combined action of both factors considerably enhances the resistance of the myocardial Ca²⁺-transporting system to free radical-induced oxidation. Inin vitro experiments it is shown that adaptation to periodic hypoxia results in a more than twofold deceleration of Ca²⁺ transport inhibition during the oxidation induction by the Fe²⁺/ascorbate system; the diet causes a 3.5-fold deceleration of such inhibition. The results show that the accumulation of a high level of lipid peroxidation products is not always followed by damage to the Ca²⁺-transporting system in the myocardial sarcoplasmic reticulum. Translated fromByulleten' Eksperimental'noi Biologii i Meditsiny, Vol. 120, N ^o 7, pp. 42–45, July, 1995 Presented by G. N. Kryzhanovskii, Member of the Russian Academy of Medical Sciences     

Reactivity of the basilar artery in Krushinsky-Molodkina rats 24 hours after an audiogenic epileptic seizure

Examination of the reactivity exhibited by the basilar artery of the brain in Krushinsky-Molodkina rats before and after an induced epileptiform seizure accompanied by subarachnoid hemorrhages showed increased contractility of this artery in response to endothelin-1 and its reduced sensitivity to ATP 24 h after the seizure. Such changes in the reactivity of brain vessels may contribute to the development of vasospasm and secondary ischemia of the brain after an epileptic seizure. Translated fromByulleten' Eksperimental'noi Biologii i Meditsiny, Vol. 121, N ^o 2, pp. 131–134, February, 1996 Presented by M. Ya. Studenikin, Member of the Russian Academy of Medical Sciences     

Effect of adaptation to moderate physical loads on the increased resistance of the isolated heart to ischemia and reperfusion

Adaptation to physical loads elicits pronounced anti-ischemic and antireperfusion effects on the isolated heart. By the 20th min of total ischemia contracture in the hearts of adapted animals is much less than that in the control group. During reperfusion of hearts from adapted animals the degree of restoration of the contractile force was 6-fold higher, contracture was lesser, and the total period of tachycardia and fibrillation were 3-fold shorter than in the control. Translated fromByulleten' Eksperimental'noi Biologii i Meditsiny, Vol. 119, N ^o 1, pp. 25–27, January, 1995 Presented by S. S. Debov, Member of the Russian Academy of Medical Sciences     

Ammonium succinate is an effective corrector of cerebral circulatory hypoxia

It is demonstrated that ammonium succinate is capable of increasing the survival of rats with acute brain ischemia. In transient brain ischemia therapeutic injection of ammonium succinate prevents the development of postischemic hypoperfusion and hypooxygenation of the brain. The antiischemic effect of ammonium succinate is due to a decrease of the oxygen affinity of hemoglobin and to limitation of the accumulation of malonic dialdehyde, a secondary product of lipid peroxidation, in the brain. No vasotropic activity of ammonium succinate is revealed. Translated fromByulleten' Eksperimental'noi Biologii i Meditsiny, Vol. 118, N ^o 9, pp. 276–278, September, 1994 Presented by E. D. Gol'dberg, Member of the Russian Academy of Medical Sciences     

Endothelial function and nitric oxide production in rats adapted to intermittent hypoxia

Adaptation to intermittent hypoxic hypoxia did not affect the endothelium-dependent relaxation of the aorta in rats, but significantly increased the relaxation of their tail artery. Following the adaptation, the NO level fell in the liver, intestine, and kidneys and remained unchanged in the spleen. Adaptation to hypoxia presumably limits NO synthesis and/or release in the vascular endothelium or enhances the capacity of this oxide to bind in a physiologically active depot. Translated fromByulleten' Eksperimental'noi Biologii i Meditsiny, Vol. 120, N ^o 11, pp. 495–498, November, 1995 Presented by Yu. A. Vladimirov, Member of the Russian Academy of Medical Sciences     

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     

Structural and functional changes in the brain of rats with different behavioral types at later stages of circulatory hypoxia

Structural changes in the brain were studied at later (one and three months) stages of cerebral hypoxia caused by occlusion of the common carotid arteries, which were indicative of the development of recovery and destructive processes. Brain ultrastructure was found to be better preserved in rats with an active type of behavior one month after the onset of ischemia than in rats of the other groups; motor activity was restored to the baseline level, thus demonstrating a higher rate of recovery processes. Significant ultrastructural damage to the brain at the same stage of ischemia was observed in rats with a passive type of behavior (especially in rats of the middle group), while motor activity was increased. Translated fromByulleten' Eksperimental'noi Biologii i Meditsiny, Vol. 118, N ^o 11, pp. 529–534, November, 1994 Presented by P. V. Simonov, Member of the Russian Academy of Sciences     

Effect of adaptation to intermittent normobaric hypoxia on the ultrastructure of cardiac myocytes in pregnant rats

A comparative ultrastructural study of organelles involved in supplying cardiac myocytes with energy (nucleus, mitochondria, microbodies, and lysosomes) in pregnant rats that had been exposed to intermittent normobaric hypoxia and in rats not so exposed showed no significant differences between these two groups of animals. In both groups, glycogen granules were present in the nucleus, mitochondria, lysosomes, and microbodies (peroxisomes) of cardiac myocytes, and many of their mitochondria had a dense matrix and appeared hyperplastic. Translated fromByulleten' Eksperimental'noi Biologii i Meditsiny, Vol. 119, N ^o 6, pp. 597–602, June, 1995 Presented by A. V. Smol'yannikov, Member of the Russian Academy of Medical Sciences     

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     

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