Showing papers on "Altitude Hypoxia published in 1981"

Time course of plasma growth hormone during exercise in humans at altitude.

Abstract: Several studies (5,6) tend to demonstrate that hypoxic conditions enhance the release of growth hormone (GH). However, results obtained in highlanders in Peru suggest that stimulation of GH release during exercise is not increased by altitude hypoxia (4). The present study was designed to define more accurately the time course of plasma GH concentration and that of other metabolites related to muscular exercise and to compare them in lowlanders at sea level, in subjects fully adapted to altitude hypoxia, and in lowlanders acutely exposed to hypoxia either by breathing a low pressure O2 gas mixture or by a process of acclimatization after translocation to high altitude.

Comparative study of ultrastructure and function of the rat heart hypertrophied by exercise or hypoxia.

Abstract: Summary Comparative ultrastructural morphometric and physiological studies of the left ventricle of the rat were made with the aim to obtain information on the adaptation process of the rat heart to physical training and high altitude. For this purpose animals were subjected to mild swimming exercise (up to 1 hour per day for a total duration of 40 hours), a second group was subjected to hypoxia in a hypobaric chamber (6,000 m, 5 hours per day). The ultrastructural examinations were carried out in accordance with stereological principles using the conventional point counting technique, whilst examinations of the contraction function were performed on the isolated papillary muscle. Physical training leads to a left ventricular hypertrophy with a significant increase in wet weight by 21%. Morphometric analysis of myocardial cells showed an increase in the volume density of mitochondria, which is attributed to an increase in their number. There is an increase in the surface density of the sarcoplasmic reticulum (SR). The surface density of the SR per unit volume of myofibrils (SR/myofibrils ratio) is enlarged by 55%. The Golgi apparatus shows pronounced hyperplasia. Hypoxia results in a slight left ventricular hypertrophy, which is only 50% of that of the right ventricle. The mitochondria are enlarged, but diminished in number, so that their volume density remains constant. The SR/myofibrils ratio is enlarged only by 8%. Hyperplasia of the Golgi apparatus is slight. Unlike in the case of exercised animals, the T-tubuli are reduced in number and dilated. In comparison with the non-adapted animals, most parameters of the contractile function of the myocardium conditioned through exercise are significantly increased, but no such increase is observed in the case of altitude hypoxia. The changes in the cardiac contractile function observed after adaptation to physical training are based on biogenesis of mitochondria and on structural changes of the SR. The increased relaxation velocity after physical training could, for instance, be attributed to the significant increase in the SR/ myofibrils ratio. The studies admit the conclusion that physical training and chronic altitude hypoxia in the left heart result in different structural patterns which correspond to different responses of the contractile function. These findings can be explained by differences in the cell's adaptation mechanism, the phosphorylation potential probably being a key factor in the biogenesis of cellular structures.

Adaptation to chronic hypoxia at various altitudes

Abstract: A comparison is made between the results obtained and the examinations carried out in the study of adaptation to chronic altitude hypoxia at 2500 m (19th Olympic Games, Mexico City), and 5350 m (base camp, 1973 Italian Mt. Everest Expedition). An assessment is made of circulation, respiration, and blood changes, and their influence on maximum aerobic effort capacity per unit of time, i.e. VO2max (maximum oxygen consumption). The fall in this capacity is greater than might be supposed from the compensatory mechanisms. Lastly, a comparison is made between recently acclimatised chronically hypoxic subjects and high-altitude natives, and suggestions are put forward to explain the better muscle performance of the latter.

The oxygen consuming systems of the liver of mice exposed to simulated high altitude

Abstract: Altitude hypoxia does not induce any changes in the enzymatic systems related to oxygen consumption in guinea pigs native of the Peruvian high altitudes. The biochemical changes frequently found in high altitude animals are the result of exposure to the low temperature of this environment rather than to hypoxia. In the present work, mice were chronically exposed to hypobaric hypoxia and maintained at equal temperature as the sea level control group, and measurements of enzymatic activities of the three major oxygen consuming systems of the liver were carried out, i.e., mitochondria, microsomes and peroxisomes. The results obtained have confirmed that hypoxia has no apparent influence on these enzymatic systems.