Pharmacokinetics of antipyrine and isoniazid in rats during their adaptation to cold

The pharmacokinetics of the drugs antipyrine and isoniazid was studied in Wistar rats in the course of their adaptation to cold (+5°C) over 35 days. The significant increases recorded in the clearance of these drugs were mainly due to their accelerated elimination during the first week of cold and to their increased volume of distribution subsequently (on days 15–22). By the end of the 35-day observation period, the pharmacokinetic parameters of both drugs were close to the pre-exposure levels except that the clearance of isoniazid remained significantly elevated. For this animal model of adaptation to cold, no inhibition of the xenobiotic-metabolizing function of the liver was noted. Translated fromByulleten' Eksperimental'noi Biologii i Meditsiny, Vol. 118, N ^o 9, pp. 279–280, September, 1994     

Biotransformation of hepatic xenobiotics in rats with various resistance to hypoxia exposure to after cold

Hepatic monooxygenase activity was studied in rats with various resistance to hypoxia during adaptation to cold. Cold-induced change in the concentrations of cytochromes P-450 and b₅ and the activity of microsomals metabolism of amidopyrine and aniline were shown to be associated with individual resistance to hypoxia. The content of microsomal cytochromes in highly resistant rats did not change on the fifth day of cold exposure. However, the intensity of metabolic reactions decreased. In low-resistance rats, a cold-induced decrease in the concentration of the cytochromes was not accompanied by significant changes in metabolic rates of amidopyrine and aniline. Translated fromByulleten' Eksperimental'noi Biologii i Meditsiny, Vol. 126, No. 12, pp. 631–633, December, 1998     

Activity of liver monooxygenase system in rats with low and high resistance to hypoxia

Rats with low and high resistance to hypoxia are shown to differ in terms of the baseline activity of liver monooxygenases bothin vivo andin vitro. Low-resistance animals are characterized by a significantly higher rate of elimination of antipyrine, hexenal, and nifedipine, as evidenced by shorter half-elimination period and higher urinary concentration of metabolites. The concentration of microsomal cytochromes P-450 and b5 as well as the rates of N-demethylation of amidopyrine, p-hydroxylation of aniline, and hydroxylation of diazepam are considerably higher in rats with low resistance to hypoxia. Translated fromByulleten' Eksperimental'noi Biologii i Meditsiny, Vol. 122, No. 9, pp. 291–294, September, 1996     

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 hypoxia resistance in rats during daytime

The resistance to acute hypoxia in male Wistar rats was evaluated by the period of survival after exposure to high-altitude hypoxia (11.5 km above see level). The study was performed during daytime (13.00–21.00) in autumn. The fatal rat population was characterized by the log-normal distribution of survival periods. The rats with low and moderate resistance to hypoxia exhibited similar diurnal variations in it with gradual decrease by the end of daytime more pronounced in low-resistant rats. The rats with high resistance showed relatively constant resistance to hypoxia which decreased only at 21:00. All groups revealed a relatively stable resistance to hypoxia from 16:00 to 18:00. These variations in the resistance to hypoxia should be taken into consideration when planning experimental research. Translated fromByulleten' Eksperimental'noi Biologii i Meditsiny, Vol. 127, No. 3, pp. 256–260, March 1999     

Specific features in the behavior of rats with different genetic stability to stress

The effects of acute and chronic immobilization stress on the behavior of NISAG and outbred rats with different resistance to stress were evaluated. In the acute stress model, NISAG rats did not differ from stress-resistant outbred rats in the majority of the studied parameters. Chronic stress exhausted adaptive potential of NISAG rats, and their behavior became similar to that of rats with low resistance to stress. Translated fromByulleten' Eksperimental'noi Biologii i Meditsiny, Vol. 125, No. 4, pp. 420–424, April, 1997     

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     

A comparative study of generalized activation of the synthesis of stress proteins in adaptation to stress and hypoxia

Translated fromByulleten' Eksperimental'noi Biologii i Meditsiny, Vol. 116, N ^o 8, pp. 137–139, August, 1993.     

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     

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     

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     

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     

Resistance of the myocardium to adrenalin in rats adapted to hypoxia

The intensity of the changes produced by adrenalin in the myocardium of rats adapted to hypoxia was studied after its administration to the intact animal and perfusion of the isolated heart. The changes were revealed by histochemical reactions for succinate dehydrogenase activity and staining for lipids. After intramuscular injection of a cardiotoxic dose of adrenalin (2.0 mg/kg) into adapted rats no damage to the myocardium was found, whereas perfusion of the isolated heart with adrenalin (20 g/ml) caused the formation of micronecroses of the cardiocytes. However, their volume was statistically significantly smaller than in the isolated heart of intact rats under similar conditions. Differences in the sensitivity of the myocardium in vivo and in vitro indicate that the phenomenon of protection of the myocardium against the harmful effects of adrenalin in rats adapted to hypoxia is manifested at the level of the intact organism. The increase in the resistance of the myocardium itself is probably due to an increase in the power of the metabolic systems during adaptation.Department of Pathological Physiology, Patrice Lumumba Peoples' Friendship University. Department of Geographic Pathology, Research Institute of Human Morphology, Academy of Medical Sciences of the USSR, Moscow. (Presented by Academician of the Academy of Medical Sciences of the USSR A. P. Avtsyn.) Translated from Byulleten' Éksperimental'noi Biologii i Meditsiny, Vol. 84, No. 9, pp. 265–268, September, 1977.