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At least 127 records · Page 7Linked to original sources
PubMed1976

Aquatic life at high altitude: respiratory adaptations in the Lake Titicaca frog, Telmatobius culeus.

Telmatobius culeus has a combination of behavioral, morphological and physiological adaptations which allows an aquatic life in cool (10 degrees C) O2-saturated (at 100 mm Hg) waters at high altitude (3812 m). The skin surgace area is increased by pronounced folds and the cutaneous capillaries penetrate to the outer layers of the skin. The erythrocyte volume (394 mu3) is the smallest reported for amphibians. The P50 (15.6 at ph 7.65 and 10 degrees C) is the lowest, and the erythrocyte count (729 - 103/mm3) the highest for an anuran. The O2 capacity (11.7 vol%), hemoglobin (8.1 g/100 ml), hemoglobin concentration (0.281 pg/mu3) and hematocrit (27.9%) measured at 18 degrees C and 3800 m are all elevated in comparison with most amphibians. The O2 dissociation curve is sigmoid (n = 2), the Bohr factor is small (deltalog P50/deltapH = -0.30) and the buffering capacity (-8.9 m M HCO3 - 1-1) is typical for an aquatic amphibian. The metabolic rate (14.1 mul -g-1-h-u) is the lowest reported for a frog and among amphibians only the giant salamanders (Amphiuma, Necturus and Siren) have lower values. If prevent from surfacing in hypoxic waters, the frogs ventilate the skin by "bobbing" behavior; if allowed to surface, they will ventilate the small lungs and the metabolic rate increases to 23 mul-g-1-h-1.

Adaptation, Physiological↗
PubMed1977

Reduction of pore area of the avian eggshell as an adaptation to altitude.

Standard measurements of water vapor conductance in units of mg of H(2)O . day(-1) . torr(-1) (SI equivalent is mg of H(2)O . day(-1) . pascal(-1)) of fresh eggs of the red-winged blackbird (Agelaius phoeniceus) and the native chicken of India (Gallus gallus) collected at altitude are significantly less than those of eggs of the same species collected near sea level. This decrease is caused by a reduction of the total effective pore area of the eggshell at altitude. It appears to be proportional to the reduction in barometric pressure and the simultaneous increase in the diffusion coefficient of water vapor. Thus, reduction in pore area offsets increased diffusivity at altitude, and water vapor loss through the eggshell at any altitude remains the same as at sea level. The data suggest a structural adaptation of the shell to altered diffusivity of gases at altitude in order to prevent excessive water loss of eggs during natural incubation.

Journal Article↗
PubMedDate not supplied

[Characteristics of energy metabolism and the effectiveness of muscular work in humans during adaptation to altitude].

The results obtained characterize changes in energy exchange and cardiovascular function that develop in exercising men in high mountains. At an early period of adaptation muscle performance decreased, indicating a new level of homeostatic regulation. The effectiveness of individual systems may differ from that of the whole body. Some of them (e. g., the cardiovascular system) may function very effectively, taking upon themselves additional functions. The final effect of adaptation to high mountains is an increase in the effectiveness of the whole body and an increase of aerobic reserves at sea level. Metabolic changes involve those that enhance lipid metabolism, including these that maintain active glycolysis. Structural rearrangements seem to be provided by a higher somatotropic activity of the hypothalamic-pituitary system.

Adaptation, Physiological↗
PubMed1993

High altitude tissue adaptation in Andean coots: capillarity, fibre area, fibre type and enzymatic activities of skeletal muscle.

Capillarity, fibre types, fibre area and enzyme activities of different skeletal muscles (pectoralis, extensor digitorum longus), tibialis anterior, plantaris and the myocardium) were compared in Andean coot (Fulica americana peruviana) native to high altitude (Junín, Perú, 4200 m) and the same species nesting at sea level. Numbers of capillaries per square millimeter were higher in all high-altitude muscles when compared with sea-level muscles (P < 0.0001). Moreover, values for capillaries per fibre and capillaries in contact with each fibre were higher in digitorum and tibialis high-altitude muscles. Muscle fibres were classified as Type I, Type IIA or Type IIB on the basis of their myofibrillar ATPase pH lability. Pectoralis muscle of high-altitude and sea-level coots presented only fibres of Type IIA. In contrast, all the leg muscles studied showed a mosaic pattern of the three fibre types. Fibre areas were determined using a Leitz Texture Analysis System. Significant differences in fibre area were observed (P < 0.01) between high-altitude and sea-level muscles. Mean muscle fibre diameters were also lower in the high-altitude group than in the sea-level group. The enzyme activities studied were hexokinase, lactate dehydrogenase, citrate synthase and 3-hydroxyacyl-CoA-dehydrogenase. The oxidative capacity, as reflected by citrate synthetase and hydroxyacyl-CoA-dehydrogenase activities, was greater for myocardial and pectoralis than for leg muscles. However, analysis of maximal enzyme activities showed that there were no significant differences between the glycolytic and oxidative enzyme activities of high-altitude and sea-level coots.(ABSTRACT TRUNCATED AT 250 WORDS)

Adaptation, Physiological↗
PubMed1999

High altitude living: genetic and environmental adaptation.

High altitude (HA) living produces physiological changes for adaptation to chronic hypobaric-hypoxemic conditions. Although much is known about these physiologic adaptations, no clear separation has been made regarding what is "native" or "genetic" adaptation and what is "acquired." In this review, we describe the genetic vs. acquired adaptation and only include studies performed in a population native to HA and not in an acclimatized population or trekkers. The changes encountered in animals and humans living at HA in terms of hematology, muscular, respiratory, cerebral, cardiovascular, hormonal, fluid and electrolytes and reproduction, strongly suggest that genetics play a very important role in HA adaptation. Unfortunately, the characteristic physiology of HA natives has not been systematically defined to established specific measurable parameters of adaptation in comparison to the acquired ambient adaptation of the non-native population. Once the parameters are established, we can compare non-native populations exposed to HA that must emulate the HA physiology for a definite adaptation to be present. With measurable parameters, especially in the management of fluids and electrolytes, we can define how long it will take for a sea level native to adapt to an HA altitude. Until these studies are performed, speculation will continue and no rational medical intervention can be offered to HA newcomers who may experience HA difficulties.

Adaptation, Physiological↗
PubMed1982

[Learning of animals during adaptation to altitude and its relations with serotonin metabolism in the brain].

The influence of high altitude (3 200 m) on learning was studied on 104 non-linear male rats weighing 120 to 140 g, along with biochemical analysis of serotonin content (5-HT) and noradrenaline (NA) in brain structures. A drastic deterioration in the animals' learning has been established in conditions of high altitude, both with alimentary and pain reinforcement attended with a considerable suppression of the 5-HT and NA brain systems activity. Systematic administration of 5-HTP resulting in an enhanced serotonin level in the cortex and the caudal part of the brainstem, improved the learning process, regardless of the emotional sign of the reinforcing stimulus. The prospect, is being substantiated, of evolving methods preventing pathological implications of external influences of high altitudes on the organism by means of pharmacological actions on monoamines' metabolism.

5-Hydroxytryptophan↗
PubMed1995

Enhanced cardiac metabolism of plasma glucose in high-altitude natives: adaptation against chronic hypoxia.

The metabolism of glucose in mammalian heart is 25-50% more O2 efficient than the metabolism of free fatty acids. To assess the role of substrate preference in adaptations to chronic hypoxia, positron emission tomographic measurements of heart regional glucose uptake rates after an overnight fast were made in volunteer Quechua subjects and in Sherpa subjects, both indigenous to altitudes of over 3,000 m, and in a group of lowlander volunteers. Highest uptake rates were found in the Quechuas on arrival and in the Sherpas after a 3-wk period at low altitude, intermediate rates in Quechuas after a 3-wk period at low altitude and in the lowlanders, and lowest rates in Sherpas on arrival. These low values were probably related to the stress of travel to the site of the experiments. Measured plasma catecholamines, hormones, and substrates indicated that glucose concentrations correlated best with observed variations in glucose uptake, with a negative correlation for the control subjects and a positive correlation for the Quechuas and Sherpas. Uptake values in Quechuas declined significantly after a 3-wk period at low altitude, but the positive correlation with glucose levels persisted. We conclude that an elevated glucose preference in heart is a true metabolic adaptation in humans adapted over generations to chronic hypoxia.

Adaptation, Physiological↗
PubMed2005

A mitochondrial genome sequence of the Tibetan antelope (Pantholops hodgsonii).

To investigate genetic mechanisms of high altitude adaptations of native mammals on the Tibetan Plateau, we compared mitochondrial sequences of the endangered Pantholops hodgsonii with its lowland distant relatives Ovis aries and Capra hircus, as well as other mammals. The complete mitochondrial genome of P. hodgsonii (16,498 bp) revealed a similar gene order as of other mammals. Because of tandem duplications, the control region of P. hodgsonii mitochondrial genome is shorter than those of O. aries and C. hircus, but longer than those of Bos species. Phylogenetic analysis based on alignments of the entire cytochrome b genes suggested that P. hodgsonii is more closely related to O. aries and C. hircus, rather than to species of the Antilopinae subfamily. The estimated divergence time between P. hodgsonii and O. aries is about 2.25 million years ago. Further analysis on natural selection indicated that the COXI (cytochrome c oxidase subunit I) gene was under positive selection in P. hodgsonii and Bos grunniens. Considering the same climates and environments shared by these two mammalian species, we proposed that the mitochondrial COXI gene is probably relevant for these native mammals to adapt the high altitude environment unique to the Tibetan Plateau.

Amino Acid Sequence↗