[Conformity between atmospheric pressure and blood hemoglobin content during adaptation to higher altitudes].
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Adaptation, Physiological↗
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[Mechanical activity of the papillary muscles of the rat heart under high altitude conditions].
Mechanical activity of isolated papillary muscles in the left ventricle of rats was studied during permanent high altitude adaptation. The main computer parameters were: maximal developing tension, force of contraction, and capacity of papillary muscles at different periods of mountain adaptation (3, 15, 30 and 45 days). On the 15th day of mountain exposure, a statistically significant increase of maximal developing tension and papillary muscles activity was observed, which remained until the 45th day. Capacity was considerably increased on the 30th--45th day of adaptation. The data suggest positive effect of high altitude hypoxia on inotropic function of intact myocardium.
Actomyosin↗
[Tolerance for hypokinesia in persons adapted to high mountains].
After a 26-day exposure to an altitude of 3200 m test subjects were kept in bed for 10 and 24 days. Each experimental group consisted of 6 test subjects. Physiological effects of the exposure were measured with respect to changes in the respiration, circulation and red blood systems as well as in the orthostatic and exercise tolerance. High altitude adaptation which preceded bed rest did not arrest the development of orthostatic intolerance or the decrease of physical performance that resulted from the bed rest experiment.
Adaptation, Physiological↗
[Effect of adaptation to continuous and intermittent hypoxia on heart resistance to ischemic and reperfusion arrhythmias].
The effect of adaptation to intermittent hypoxia in a pressure chamber (5.000 m daily for 6 hours for 30 days) on arrhythmias occurring in occlusion of the coronary artery and subsequent reperfusion in rats was compared with the effect of adaptation to continuous hypoxia at middle-mountain altitudes. Adaptation to intermittent hypoxia reduced the duration of severe ventricular arrhythmias in acute ischemia and reperfusion to a great measure. Adaptation to continuous hypoxia at middle-mountain altitudes has a similar effect only in ischemic arrhythmias but at the same time promotes the development of reperfusion arrhythmias. The possible mechanisms of these effects are discussed.
Adaptation, Physiological↗
Myoglobin content and enzymatic activity of human skeletal muscle--their relation with the process of adaptation to high altitude.
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Acclimatization↗
The genome of Thesium ramosoides (Santalales) reveals evolutionary dynamics associated with parasitism and alpine adaptation.
Plant species adapting to complex environments experience contrasting selection pressures that drive the expansion and contraction of different gene families. However, few studies have investigated simultaneous genomic responses to such diverse selective forces. Here, we generate a high-quality genome assembly for the hemiparasitic plant Thesium ramosoides, the first for the largest genus in the Santalales, and explore the genomic basis underlying the evolution of parasitism and alpine adaptation. Unlike many other parasitic plants, the Thesium genome has not undergone additional rounds of whole-genome duplication, making it particularly tractable for studying gene family evolution. Our analyses reveal substantial loss of photosynthesis-related genes and contraction of biotic defense gene families, likely reflecting adaptation to a hemiparasitic lifestyle and reduced pathogen pressure at high altitudes. The absence of key root hair development genes correlates with the degenerate root hair phenotype observed in this species. Furthermore, hallmarks of high-altitude adaptation include the expansion of gene families involved in responses to hypoxia. Notably, expansion of gene families associated with meristem development is consistent with the presence of below-ground crown buds that enable rapid regeneration after mountain fires. Unexpectedly, we detected tandem duplication and diversification of the strigolactone receptor gene D14, which regulates secondary shoot formation, but not of its ancestral paralog KAI2, which mediates seed germination in response to the smoke-derived compound karrikin. This finding suggests divergent signaling mechanisms underlying fire adaptation across different parasitic plant lineages. By integrating time-series transcriptomic data, we propose a post-fire "defense first, repair later, recovery last" model, in which resources are reallocated from immediate defense to rapid repair and ultimately to long-term recovery, to explain the adaptation of T. ramosoides to fire-prone habitats. Our study provides critical insights into the complex and contrasting genomic dynamics that drive adaptation to multiple co-occurring selection pressures.
Genome, Plant↗
[Maximum respiratory work in adaptation to high altitude].
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Acclimatization↗
[On the behavior of some functional entities in Alpine high speed skiing in the framework of adaptation to high altitude].
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Adaptation, Physiological↗
[Vitamins in the process of adaptation to high altitude].
The data obtained show that adaptation to a high altitude environment is accompanied by various metabolic changes. It is recommended to use essential nutrients--vitamins to optimize adaptation to this environment and to maintain adequate work capacity and good health.
Acclimatization↗
Are Tibetans better adapted?
Evidence is reviewed from our recent (1987-1991) investigations which demonstrate better high-altitude adaptation among Tibetans than in acclimatized newcomers or other lifelong high-altitude residents. Characteristics of oxygen transport contributing to the Tibetans' remarkable exercise performance are described.
Acclimatization↗
Human adaptability approach to nutritional assessment: a Bolivian example.
Recent interest in the functional correlates of mild to moderate malnutrition has provided an opportunity for anthropologists to collaborate in research with nutritional scientists. Physical anthropological studies of human adaptability have developed the methodology and theory to examine the importance of general and specific functional areas of individual and population adaptations. This anthropological approach to human adaptability corresponds well with the functional approach to nutritional sciences. Examples are presented from recent physical anthropological research on high-altitude adaptation to demonstrate how this integration of disciplinary methodology can contribute to a better understanding of human nutritional status. The functional areas of child growth and female reproductive performance are examined in relation to the multistress environment of the Peruvian-Bolivian high Andes. Knowledge of how nutritional variation affects the adaptability of high-altitude populations provides a better basis for the identification of protein-energy malnutrition during childhood and iron deficiency anemia during pregnancy.
Adaptation, Physiological↗
[Role of thyroid gland hormones in thermoregulatory reactions during adaptation to high altitude].
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.
Adaptation, Physiological↗
Thoracic adaptation to high altitude.
Growth in the thoracic region and its adaptation to higher altitude was investigated in boys between 5 to 18 years of Rajput origin at two altitudes, i. e. Rampur Bushahr (800 m above sea level) and Kinnaur (3,000 m above sea level). Both places are located in Himachal Pradesh. The sample includes 405 individuals From Bushahr and 676 individuals from Kinnaur. The results of this study reveal that as the higher altitudes are attained the vital capacity also increases relatively more, and these differences become more pronounced after adolescence, indicating longer time of apnoea. The population living at higher altitudes is also characterised by a significant greater chest length.
Adaptation, Physiological↗
Patterns of O2-dependence of metabolism.
1. In O2 regulating systems, mitochondrial O2 uptake is stabilized as O2 availability declines by means of metabolite signals that simultaneously activate glycolysis; the consequent Pasteur effect is an attempt to make up the energy deficit arising from O2 limitation. 2. In O2 conforming systems, the regulatory link between the ETS and glycolysis is seemingly lost. The advantage of O2 conformity is that it avoids the Pasteur effect; the cost is an exaggerated dependence of mitochondrial respiration on O2 availability. 3. The VO2(max) of man and other low-altitude adapted animals follows the O2 conforming pattern; at altitudes equivalent to the peak of Everest, the VO2(max) is only slightly greater than RMR. Again, key regulatory interactions between the ETS and glycolysis seem to be missing, so the energy deficit is tolerated (lactate production during exercise to exhaustion is less in hypobaric hypoxia than in normoxia). 4. The O2 conformity of VO2(max) in mammals may be explained by inherently inefficient O2 delivery systems in which low Km and low kcat cytochrome oxidase function would be selected. O2-limited maximum mitochondrial respiration helps to explain what would otherwise be a perplexing observation: why over a 10(4) range of mass-specific muscle metabolic rates, the peak O2 uptake rates per unit mitochondrial volume are always the same at VO2(max). 5. The concept of O2-limited mitochondrial respiration predicts that more efficient O2 delivery systems, such as tracheoles found in insect flight muscles, should support much higher in vivo cytochrome oxidase turnover rates. As far as can be currently evaluated, this prediction is realized.(ABSTRACT TRUNCATED AT 250 WORDS)
Aerobiosis↗
Physiological changes induced by pre-adaptation to high altitude.
To study the physiological effects of pre-adaptation to high altitude, seven subjects were submitted to acclimatization at 4350 m followed by intermittent acclimation in a low barometric pressure chamber (5000 m to 8500 m). The subjects then spent 25 days in the Himalayas. Ventilatory and cardiac responses were studied during a hypobaric poikilocapnic hypoxic test performed both at rest and during exercise (100 W) in normoxia and in hypoxia (barometric pressure: 589 hPa, altitude: 4500 m). Haemoglobin, erythrocytes, reticulocytes, packed cell volume, 2,3-diphosphoglycerate (2,3-DPG) and erythropoietin (EPO) were measured. All variables were studied before pre-adaptation to high altitude (A), after the acclimatization period (B), after the acclimation period (C) and after the expedition (D). The ventilatory and cardiac responses were characterized by an increased tidal volume in hypoxia (+33% during exercise in B, P < 0.05; +100% at rest and +33% during exercise in C, P < 0.05) without any change in respiratory frequency, whereas an increased systolic blood pressure was only observed in C during exercise in hypoxia [+23 mmHg (3.07 kPa), P < 0.01]. Arterial O2 saturation was higher in hypoxia in C and D, both at rest (+8.2% and +4.7%, P < 0.01, respectively), and during exercise (+6.3% and +6.3%, P < 0.01, respectively). Erythrocytes, haemoglobin and packed cell volume did not vary significantly. The number of reticulocytes was higher in B (+172%, P < 0.05) and in C (+249%, P < 0.05). EPO and 2,3-DPG increased only in C (+770%, P < 0.01 and +23%, P < 0.05, respectively).(ABSTRACT TRUNCATED AT 250 WORDS)
Acclimatization↗
Effects of adaptation to high altitude hypoxia on the contractile function and adrenoreactivity of the heart.
Effects of adaptation to mountain altitude of 3200 m on the contractile function and adrenoreactivity of the heart in rats have been investigated. It was shown that adaptation to altitude increased the contractile force and contraction and relaxation velocities of the left ventricle as compared to the controls. Simultaneously, a significant increase in cardiac response to noradrenaline developed in the course of adaptation. The increased response was accompanied by its more rapid disappearance. These changes may be explained by the increase in the activity of myocardial adenylate cyclase and phosphodiesterase. It was also shown that the decrease in cardiac function produced by cardiac denervation was less pronounced in adapted rats. This fact may be explained by increased effectiveness of cardiac autoregulatory mechanism. The comparison of these results with the data of other investigators suggests that in well adapted animals the strength of interaction between the levels of the regulatory hierarchy of the whole organism changes, i.e., the capacity of autoregulatory cell mechanisms and their reactivity to neurohumoral stimuli increase. As a result, control of the organism's reactions by higher levels of the regulatory system is more economical in adapted animals.
Adaptation, Physiological↗
Pain perception under chronic high-altitude hypoxia.
Following studies of respiratory sensory functions during high-altitude adaptation, pain perception investigations were carried out on European lowlanders during an expedition on the Bhrikuti peak, Himalaya (first ascent). Perception thresholds and discrimination performances of electrical stimuli applied to the skin were determined with a constant stimulus method. Additionally, Clark's Situational Pain Questionnaire was used to measure discriminability and response bias of the subjects' reports of pain. The tests were performed in the field under normoxic conditions, before and after ascent, and under hypoxic conditions at altitudes of 3500 and 5600 m. The tests were also performed in a control group under normoxic conditions and similar ambient temperatures. Under normoxic conditions, the expedition group differed from the control group and demonstrated a more stoic attitude and a lower pain threshold. At high altitudes, pain thresholds decreased through improved sensory discrimination performances. Hypoxia is supposed to be the main cause of this sensory adaptive reaction to altitude as psychological attitude remained unchanged and a decrease in ambient temperature was without effect on pain perception in the control group. Increased discrimination in pain perception may be a component of a general improvement in sensory processing during the early stages of altitude acclimatization.
Adult↗
Geriatric men at altitude: hypoxic ventilatory sensitivity and blood dopamine changes.
BACKGROUND: Short-term exposure to high-altitude hypoxia increases hypoxic ventilatory sensitivity (HVS) in healthy humans. Dopamine (DA) is the implicated neurotransmitter in carotid body (CB) chemoreceptor response, and the microenvironmental conditions in CB tissue are comparable to blood. Continuous DA infusion affected ventilation in animals and humans. Age-related oscillations in blood DA levels may influence peripheral chemoreflexes. OBJECTIVE: Hypoxic ventilatory responses (HVR) relative to blood DA concentration and its precursor, dihydroxyphenylalanine (DOPA) was measured in young and elderly men during short-term altitude adaptation. METHODS: Nine elderly climbers (group 1:61+/-1.4 years) and 7 young healthy subjects (group 2: 23+/-2 years) were tested at sea level on day 0, on day 3 after passive transport to 2,200 m, and on day 14 after climbing to 4,200 and 5,642 m. RESULTS: Sea level HVR in group 1 was 47% lower than in group 2, accompanied by higher blood DOPA (300%) and DA (37%) content. Initial DA and DOPA concentrations showed a negative correlation with initial HVR but a positive correlation with age. Passive transport to middle altitude (2,200 m) increased HVS, doubling HVR slopes in groups 1 and 2 and producing increased maximum expired minute ventilation during isocapnic rebreathing (29 and 28%, respectively). Day 3 2,200-meter blood DOPA content decreased by 22% in group 1 and increased by 300% in group 2. DA increased in both groups. CONCLUSION: The relationship between HVR and the reciprocal DA and DOPA values seen in both groups is associated with age, producing decreased DA receptor sensitivity and enhanced DA reuptake during adaptation to high altitude.
Adaptation, Physiological↗