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     

Wall thickness and constrictive responses of the caudal artery in rats with renovascular hypertension

In rats with hypertension modeled by the one kidney-one clamp method, constrictory responses of the isolated caudal artery to norepinephrine differed under various perfusion conditions. Vascular reactions in hypertensive rats were more potent at a constant flow rate, and less potent at a constant pressure compared to those in normotensive rats. Previous experiments demonstrated similar changes in constrictory responses of the caudal artery in spontaneously hypertensive rats. It is assumed that these peculiarities of the vascular reactivity during hypertension are determined by thickening of the smooth muscle layer of the vascular wall. Translated fromByulleten' Eksperimental'noi Biologii i Meditsiny, Vol. 130, No. 8, pp. 159–162, August, 2000     

Indications for radical correction of the common arterial trunk with high pulmonary hypertension

Thirty-nine patients with a diagnosis of common arterial trunk and high pulmonary hypertension were examined. Radical correction of the anomaly was performed in 22 patients with a hospital lethality of 36%. Residual pulmonary hypertension was the cause of death in all cases. Results of surgical treatment as well as the indexes of hemodynamics and biopsy and autopsy data were analyzed during the investigation. Translated fromByulleten' Eksperimental'noi Biologii i Meditsiny, Vol. 118, N ^o 11, pp. 540–543, November, 1994 Presented by V. I. Burakovskii Member of the Russian Academy of Medical Sciences     

Cytological changes in the myocardium of rats adapted to high-altitude hypoxia

During adaptation of rats to high-altitude hypoxia evidence of stimulation of both formative and lytic processes was observed, and either one process or the other was predominant in different cells. The ratios between volumes of mitochondria and myofibrils were substantially unchanged. The relative volume of the microcirculation was increased on account of dilatation of the small vessels with no increase in their number.Laboratory of Pathomorphology, Institute of Cytology and Genetics, Siberian Branch, Academy of Sciences of the USSR, Novosibirsk. (Presented by Academician of the Academy of Medical Sciences of the USSR N. N. Zhukov-Verezhnikov.) Translated from Byulleten' Éksperimental'noi Biologii i Meditsiny, Vol. 82, No. 11, pp. 1380–1382, November, 1976.     

Adaptation to periodic high-altitude hypoxia inhibits baroreflex vagal bradycardia in rats

A 3-week course of adaptation to high-altitude hypoxia (4500 m above sea level) inhibited baroreflex avagal bradycardia induced by a rapid rise of systemic blood pressure in conscious rats. Bradycardic responses to electrical stimulation of peripheral end of the right vagus nerve and methacholine (M₂ muscarinic receptor agonist) in hypoxia-adapted rats did not differ from the control. It is concluded that hypoxia inhibits baroreflex vagal bradycardia by acting on a central element of the baroreceptor reflex arch Translated fromByulleten' Eksperimental'noi Biologii i Meditsiny, Vol. 129, No. 4, pp. 386–389, April, 2000     

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     

Effect of the season on lipid peroxidation in the myocardium of rats with different resistance to hypoxia

Lipid peroxidation and the antioxidant system of the myocardium of adult male Wistar rats with low and high resistance to acute hypoxia tested by “raising” to an altitude of 11.5 km are studied in winter and in summer. It is found that the winter season is a mild stressor inducing changes in the myocardial antioxidant system and lipid peroxidation which are similar to those observed at the early stages of catecholamine stress in the summer season. In both cases alterations are more pronounced in low-resistance than in high-resistance rats. In winter, in low-resistance rats the intensity of lipid peroxidation and the activity of the antioxidant system are lower, while the ratio of their parameters (chemiluminescence data) is higher. At the same time, the levels of thiobarbituric acid-reactive substances are higher in winter in both groups. The relationship between the studied parameters and the resistance of rats to hypoxia is more obvious in winter than in summer, i.e., it is season-dependent and is also more pronounced in catecholamine stress. Translated fromByulleten' Eksperimental'noi Biologii i Meditsiny, Vol. 120, N^olo 7, pp. 87–90, July, 1995 Presented by N. A. Agadzhanyan, Member of the Russian Academy of Medical Sciences     

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     

Criteria of individual and population-wide resistance to acute hypoxia

It is shown that the geometric mean of survival time and the deviation of σ from τ are measures of a population's resistance to acute hypoxia; that a measure of the individual resistance of an animal to such hypoxia is Student's parameter for that animal; that the distribution of Student's parameter in a population is a lognormal distribution under any conditions; and that the number of animals with low resistance is always equal to the number of highly resistant animals. The procedure described makes it possible to limit the number of animals used in an experiment by recording with the requisite accuracy the proposed measures of resistance to acute hypoxia at the population and individual levels. Translated fromByulleten' Eksperimental'noi Biologii i Meditsiny, Vol. 120, N ^o 9, pp. 239–241, September, 1995     

Content of HSP70 in rats with hereditary stress-induced arterial hypertension

Sensitivity of normotensive Wistar rats and NISAG rats (with hereditary arterial hypertension) to heat stress is compared at the organism and cell levels. High temperature sensitivity of NISAG rats correlates with a low content of the main heat shock protein HSP70. This relationship can serve as a biochemical marker of predisposition to arterial hypertension. Translated fromByulleten' Eksperimental'noi Biologii i Meditsiny, Vol. 124, No. 8, pp. 171–173, August, 1997     

Morphological peculiarities of juxtaglomerular apparatus of the kidney in rats with hereditary stress-induced arterial hypertension (NISAG rats)

Structure of juxtaglomerular apparatus of the kidney in NISAG rats and morphometric parameters of renin-producing juxtaglomerular, cells of afferent arterioles attest to its activation. Translated fromByulleten' Eksperimental'noi Biologii i Meditsiny, Vol. 127, No. 5, pp. 576–579, May, 1999     

Plasma and lymph electrolyte and endocrine parameters in rats with genetically-determined arterial hypertension

Hemolymphatic interactions of electrolytes and plasma contents of aldosterone and insulin are studied in rats with genetically-determined stress-induced arterial hypertension (NISAG) and in normotensive rats (Wistar). Correlation analysis shows that alterations in electrolyte metabolism in NISAG are strongly determined by endocrine influences. These alterations are regarded, on the one hand, as a mechanism responsible for generically-determined arterial hypertension, and, on the other hand, as a variant of “adaptation disease” accompanied by transformation of primarily adaptive reactions into a pathogenic factor of arterial hypertension. Translated fromByulleten' Eksperimental'noi Biologii i Meditsiny, Vol. 124, No. 7, pp. 36–38, July, 1997     

Alterations in cardiac function in response to epinephrine in rats with hereditary hypertension (An ECG study)

A comparative electrocardiographic evaluation of changes in cardiac function in rats with hereditary arterial hypertension (NISAG strain) and normotensive (Wistar) rats in response to a single epinephrine injection revealed much more pronounced changes in NISAG rats, including an unfavorable time course of electrocardiographic waves (left ventricle overload) and impaired conduction (blockade) and excitability (extrasystoles). The results indicate that the myocardium of NISAG rats is much more responsive to the acute stimulation of adrenergic receptors by epinephrine than is the myocardium of normotensive rats. Translated fromByulleten' Eksperimental'noi Biologii i Meditsiny, Vol. 120, N ^o 10, pp. 372–375, October, 1995 Presented by V. A. Trufakin, Member of the Russian Academy of Medical Sciences     

Vascular reactivity in NISAG hypertensive rats

In vitro experiments on isolated segments of abdominal aorta of NISAG hypertensive rats with assessment of³²P incorporation showed that hypertension in these rats is developed as due to enhanced metabolism of phosphatidylinositol phosphates under the effect of norepinephrine resulting in higher vascular reactivity to norepinephrine. Translated fromByulleten' Eksperimental'noi Biologii i Meditsiny, Vol. 126, No. 8, pp. 136–138, August, 1998     

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     

Behavioral peculiarities and reactions of brain dopaminergic systems in rats with different resistance to acute hypobaric hypoxia

Locomotor activity in the open field test did not correlate with rat resistance to acute hypobaric hypoxia; there was a correlation between this resistance and rat behavior during acute stress. Immobility was characteristic of rats with low and particularly medium resistance to hypoxia; this reaction can be abolished by antidepressants. By contrast, highly resistant rats were mainly hyperactive. The resistance to hypoxia was associated with extreme parameters of dopaminergic neuron functioning. In low-resistant rats locomotor stereotypia was maximal, while perioral stereotypia was the minimal; highly resistant rats were characterized by an opposite pattern, and medium-resistant rats occupied an intermediate position. Translated fromByulleten' Eksperimental'noi Biologii i Meditsiny, Vol. 130, No. 9, pp. 275–278, September, 2000