Biomedical subjects
Publications and source records attributed to Iu I Bazhenov.
Morphofunctional conditions of hypophysealadrenal axis and placenta following hypoxis hypoxia and an infrared treatment, were studied in rats. The data obtained involved high levels of the DNA, RNA, and lipidogenesis. Probable mechanisms of structural changes are discussed.
Physiological adaptation to cold increased the activity of the rat red bone marrow. Possible reasons and factors inducing a proliferation and amplification of the rat CFU-E under conditions of hypothermia, are discussed.
The total contents of the myocardium water was increased by beta-adrenergic stimulation at swimming in water at 33 degrees C in rats. Both total and intracellular contents of water remained unchanged in beta-adrenergic blockade. A beta-adrenergic activating agent increased the intracellular water content.
A method has been developed for measuring the rates of rotenone-sensitive oxidation of NADH and oligomycin-sensitive hydrolysis of ATP in rat skeletal muscle homogenates. The method is based on the use of alamethicin which increases the permeability of the inner mitochondrial membrane for NADH and ATP. It has been shown that prolonged cold adaptation of rats (4 weeks, 4 degrees) does not change the activity of rotenone-sensitive NADH-oxidase in rat skeletal muscle homogenates which is equal to 12.4 +/- 4.4 nmol NADH/min/mg protein, but increases threefold that of F0F1-ATPase--from 31.8 +/- 7.4 up to 93.1 +/- 14.3 nmol P(i)/min/mg protein. It is suggested that prolonged cold adaptation induces structural-and-functional changes in the H(+)-ATP-synthetase complex of skeletal muscle mitochondria.
Noradrenaline injected into cerebral lateral ventricles was found to change the temperature homeostasis in white rats. The fall of rectal temperature, the rise of brown adipose tissue temperature and oxygen consumption occurred within 25-30 min after the injection. Preliminary adaptation to cold increased the effect of noradrenaline. The beta-adrenergic blockade of cerebral structures by propranolol altered the noradrenaline effect: both the rise of brown adipose tissue temperature and the oxygen consumption increase do not occur. This effect is more obvious in cold-adapted animals. The adaptation to cold seems to increase the sensitivity of central adrenergic structures to noradrenaline, central beta-adrenoreceptors being mainly responsible for the effect of noradrenaline (the rise of brown adipose tissue temperature and the oxygen consumption increase) on the thermoregulation.
The role of paraventricular hypothalamic nuclei (PVN) in the development of cold adaptation was studied in chronic experiments on white rats. Animals with the PVN lesions revealed a low resistance against cooling, a small increase of brown adipose tissue mass and no calorigenic effect of noradrenaline after long-lasting cold exposure. The data obtained suggest that the PVN lesions delayed the development of specific mechanisms of adaptation to low temperature.
The influence of thyroid hormone in thermogenesis of animals adapting to high altitude for different periods were studied in white rats. The adaptation to high altitude hypoxia decreased reaction of the organism to cold. The antithyroid injection of mercazolil potentiated the hypoxia action in cold thermogenesis and lowered sharply the body temperature stability in cooling. The analogous injection of triiodthyronine reduced the hypoxia influence on the thermogenesis and increased the contribution of the contractile heat production in the thermoregulative metabolism. The data suggest that one of the reasons of the low heat effect of the muscle contraction in adaptation to hypoxia may be the functional weakening of the thyroid gland.
The temperature range for specific thermoregulatory responses (shivering, sweat secretion) of the high altitude residents is narrower than in the lowland inhabitants, as well as the sensitivity of temperature centres of the formers is lower than in the latters. The absolute level of heat emission of the respiratory tract, internal and external gradients of temperature, are the important parts in mechanisms of shivering. The average level of body temperature domineers in the response of thermal sweat secretion.
The authors studied the working capacity and heat formation of the skeletal muscles during contraction in rats--control and those adapted to hypoxia. The force of contraction, the work and fatigueability of the muscles, as well as elevation of the muscle temperature as a result of contraction were determined under conditions of indirect muscle electrostimulation. Hypoxia adaptation failed to influence the force of muscle contraction and the work performed. However, hypoxia led to reduction of the temperature effect of the muscle contraction per unit of the work performed. This pointed to increase of the efficiency of the muscle work in hypoxia adaptation. Fatigueability of the muscles in "hypoxic" rats was elevated. Changes in the energy of the muscle contraction in hypoxia and cold adaptation were different.
During the hypoxia muscular work revealed an augmented electrical activity of the working muscles, a lesser increase in their and body's temperature. Rats adapted to hypoxia developed a higher level of muscular activity and a lesser increase of temperature indices. This suggests that hypoxia and adaptation to hypoxia decrease thermoregulatory effects of arbitrary activity of skeletal muscles. The additional thermogenesis formed during the muscular work seems to be depressed during hypoxia.
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