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Wilderness & Environmental Medicine 2005Between 1960 and 2003, 13 Chinese expeditions successfully reached the summit of Chomolungma (Mt Everest or Sagarmatha). Forty-five of the 80 summiteers were Tibetan... (Review)
Review
Between 1960 and 2003, 13 Chinese expeditions successfully reached the summit of Chomolungma (Mt Everest or Sagarmatha). Forty-five of the 80 summiteers were Tibetan highlanders. During these and other high-altitude expeditions in Tibet, a series of medical and physiological investigations were carried out on the Tibetan mountaineers. The results suggest that these individuals are better adapted to high altitude and that, at altitude, they have a greater physical capacity than Han (ethnic Chinese) lowland newcomers. They have higher maximal oxygen uptake, greater ventilation, more brisk hypoxic ventilatory responses, larger lung volumes, greater diffusing capacities, and a better quality of sleep. Tibetans also have a lower incidence of acute mountain sickness and less body weight loss. These differences appear to represent genetic adaptations and are obviously significant for humans at extreme altitude. This paper reviews what is known about the physiologic responses of Tibetans at extreme altitudes.
Topics: Acclimatization; Asian People; Humans; Mountaineering; Tibet
PubMed: 15813148
DOI: 10.1580/pr04-04.1 -
Journal of Comparative Physiology. B,... Mar 2018To test the hypothesis of temperature-dependent deterioration of electrical excitability (TDEE) (Vornanen, J Exp Biol 219:1941-1952, 2016), the role of sodium (I ) and...
To test the hypothesis of temperature-dependent deterioration of electrical excitability (TDEE) (Vornanen, J Exp Biol 219:1941-1952, 2016), the role of sodium (I ) and calcium (I ) currents in heat tolerance of cardiac excitability was examined in a eurythermic fish, the roach (Rutilus rutilus). Densities of cardiac I and I and their acute heat tolerance were measured in winter-acclimatized (WiR) and summer-acclimatized (SuR) fish maintained in the laboratory at 4 ± 1 and 18 ± 1 °C, respectively. A robust L-type Ca current (I ), but no T-type Ca current, was present in roach atrial and ventricular myocytes. Peak density of I was smaller in atrial (- 1.97 ± 0.14 and - 1.75 ± 0.19 pA/pF for WiR and SuR, respectively) than ventricular myocytes (- 4.00 ± 0.59 and - 2.88 ± 0.47 pA/pF for WiR and SuR, respectively) (p < 0.05), but current density and heat tolerance of I did not change between seasons in either cell type. In contrast to I , marked differences appeared in I between WiR and SuR. I density was 38% higher in WiR than SuR atrial myocytes (- 80.03 ± 5.92 vs. - 49.77 ± 4.72 pA/pF; p < 0.05) and 48% higher in WiR than SuR ventricular myocytes (- 39.25 ± 3.06 vs. - 20.03 ± 1.79 pA/pF; p < 0.05). The winter increase in I density was associated with 55% (1.70 ± 0.27 vs. 0.77 ± 0.12) and 54% (1.08 ± 0.19 vs. 0.50 ± 0.10) up-regulation of the total Na channel (scn4 + scn5 + scn8) transcripts in atrium and ventricle, respectively (p < 0.05). Heat tolerance of atrial I was lower in WiR with a breakpoint temperature of 20.3 ± 1.2 °C than in SuR (23.8 ± 0.7 °C) (p < 0.05). The response of I to seasonal acclimatization conforms to the TDEE hypothesis. The lower heat tolerance of I in WiR is consistent with the lower heat tolerance of in vivo heart rate in WiR in comparison to SuR, but the match is not quantitatively perfect, suggesting that other factors in addition to I may be involved.
Topics: Animals; Cyprinidae; Myocytes, Cardiac; Thermotolerance
PubMed: 28942482
DOI: 10.1007/s00360-017-1126-1 -
European Journal of Applied Physiology... 1993The purpose of this study was to investigate the thermoregulatory mechanisms underlying artificial acclimatization to cold and to compare them with those of naturally...
The purpose of this study was to investigate the thermoregulatory mechanisms underlying artificial acclimatization to cold and to compare them with those of naturally acclimatized men. Six white men were cooled, nude, in air at 10 degrees C for 2 h before and after they had been acclimatized by ten daily cold (15 degrees C) baths of 30-60 min followed by rapid rewarming in hot (38-42 degrees C) water, and again 4 months later after acclimatization had decayed. Six control subjects also underwent the same tests, providing an opportunity to discriminate between changes caused by the immersions and those caused by extraneous influences. Acclimatization significantly reduced heat production and heat loss (P < 0.05) but did not change heat debt. The reduced heat production was accompanied by reductions in shivering (P < 0.10) and in cold-induced muscle tenseness; no evidence of nonshivering thermogenesis or active brown fat was found. These findings are attributed to increased tissue insulation, mediated by an enhanced vascular response to cold that did not involve the cutaneous circulation and was probably located in skeletal muscle. Thermal sensation and discomfort did not change, although perceived strain tended to increase (P = 0.08). Acclimatization was accompanied by, but was unrelated to, slower cooling of the finger and toe. The main conclusions, and many specific findings, agree with those of two previous studies made by the same techniques in naturally acclimatized men wintering in Antarctica. Other significant findings included changes--in particular reduced thermoneutral rectal temperature and a delayed onset of shivering--that are commonly regarded as evidence of acclimatization but were in fact unrelated to it as they also occurred in the control group. They are attributed to extraneous influences, in particular the relaxation of heightened arousal ('first-time effects') found in the baseline tests.
Topics: Acclimatization; Adult; Air; Antarctic Regions; Baths; Blood Pressure; Body Temperature Regulation; Cardiovascular Physiological Phenomena; Cold Temperature; Expeditions; Heart Rate; Humans; Male; Middle Aged; Muscle Contraction; Oxygen Consumption; Physical Fitness; Skin Temperature; Skinfold Thickness; Water
PubMed: 8299616
DOI: 10.1007/BF00376461 -
The Journal of Veterinary Medical... Mar 2023The Marabou stork (Leptoptilos crumenifer) is a typical scavenging bird and adapted to the Savannah environment, where they show a carnivorous feeding style. However,...
The Marabou stork (Leptoptilos crumenifer) is a typical scavenging bird and adapted to the Savannah environment, where they show a carnivorous feeding style. However, Marabou stork recently penetrated into the city areas and acclimatized to the urban environment, where they modified their feeding habits to an omnivorous type toward more carbohydrate. To reveal their adaptation to the variable feeding customs, this study compared the gut microbiomes and chemical compositions of feces of Marabou storks inhabiting two different locations in peri urban Kampala: one is a slaughter house floc that predicted their original carnivorous feeding, and the other is a landfill floc that adapted more to the omnivorous feeding. 16S rRNA gene sequencing analysis revealed more diverse gut microbiome, more enriched Lactobacilli, and less abundant Peptostreptococci in the landfill flock comparing to the slaughter house flock. Isolation work and predicted metagenome analysis confirmed more diverse Lactobacilli and more enriched functions for carbohydrate metabolism in the landfill flock. In addition, chemical composition of feces revealed higher ammonia in the former, which is consisting with higher Peptostreptococci and their practice of carnivorous feeding. These results highlighted their adaptation to the variable feeding environment, which presumably protects their health and ensure survival of species.
Topics: Animals; Uganda; RNA, Ribosomal, 16S; Birds; Acclimatization; Microbiota; Feces
PubMed: 36792209
DOI: 10.1292/jvms.22-0580 -
Respiratory Physiology & Neurobiology Aug 2002The mechanisms responsible for altering cardioventilatory control in vertebrates in response to chronic hypoxia are not well understood but appear to be mediated through...
The mechanisms responsible for altering cardioventilatory control in vertebrates in response to chronic hypoxia are not well understood but appear to be mediated through the oxygen-sensitive chemoreceptor pathway. Little is known about the effects of chronic hypoxia on cardioventilatory control in vertebrates other than mammals. The purpose of this study was to determine how cardioventilatory control and the pattern of response is altered in channel catfish (Ictalurus punctatus) by 1 week of moderate hypoxia. Fish were acclimatized for 7 days in either normoxia (P(O(2)) approximately 150 Torr) or hypoxia (P(O(2)) approximately 75 Torr). After acclimatization, cardioventilatory, blood-gas and acid/base variables were measured during normoxia (P(O(2)) 148+/-1 Torr) then at two levels of acute (5 min) hypoxia, (P(O(2)) 72.6+/-1 and 50.4+/-0.4 Torr). Ventilation was significantly greater in hypoxic acclimatized fish as was the ventilatory sensitivity to hypoxia (Delta ventilation/Delta P(O(2))). The increase in ventilation and hypoxic sensitivity was due to increases in opercular pressure amplitude, gill ventilation frequency did not change. Heart rate was greater in hypoxic acclimatized fish but decreased in both acclimatization groups in response to acute hypoxia. Heart rate sensitivity to hypoxia (Delta heart rate/Delta P(O(2))) was not affected by hypoxic acclimatization. The ventilatory effects of hypoxic acclimatization can be explained by increased sensitivity to oxygen but the effects on heart rate cannot.
Topics: Acclimatization; Animals; Blood Pressure; Carbon Dioxide; Chemoreceptor Cells; Gills; Hematocrit; Hydrogen-Ion Concentration; Hypoxia; Ictaluridae; Oxygen
PubMed: 12126923
DOI: 10.1016/s1569-9048(02)00019-8 -
Human Biology Aug 1999The effects of climate and altitude on casual blood pressure are examined from the perspectives of initial exposure, acclimatization, long-term residence, and... (Review)
Review
The effects of climate and altitude on casual blood pressure are examined from the perspectives of initial exposure, acclimatization, long-term residence, and birthplace. Hot arid and hot humid climates seem to have little effect on blood pressure, although a slight reduction may be found in some naturally acclimatized groups. Exposure of the total body to mild cold likewise has little apparent effect. Local exposure of the extremities to severe cold occasions significant increases in blood pressure during exposure but not at other times. Acclimatization reduces but does not eliminate that response. The effects of altitude on blood pressure are variable. There is initial hypertension, followed by gradual normalization. After years of residence at high altitude blood pressure may actually be lower than that observed among residents at sea level.
Topics: Acclimatization; Altitude; Blood Pressure; Climate; Humans; Native Hawaiian or Other Pacific Islander; Racial Groups; Seasons
PubMed: 10453102
DOI: No ID Found -
American Journal of Physiology.... Nov 2022Acclima(tiza)tion to heat or hypoxia enhances work capacity in hot and hypoxic environmental conditions, respectively; an acclimation response is considered to be... (Review)
Review
Acclima(tiza)tion to heat or hypoxia enhances work capacity in hot and hypoxic environmental conditions, respectively; an acclimation response is considered to be mediated by stimuli-specific molecular/systemic adaptations and potentially facilitated by the addition of exercise sessions. Promising findings at the cellular level provided the impetus for recent studies investigating whether acclimation to one stressor will ultimately facilitate whole body performance when exercise is undertaken in a different environmental condition. The present critical Mini-Review examines the theory of cross-adaptation between heat and hypoxia with particular reference to the determinants of aerobic performance. Indeed, early functional adaptations (improved exercise economy and enhanced oxyhemoglobin saturation) succeeded by later morphological adaptations (increased hemoglobin mass) might aid acclimatized humans perform aerobic work in an alternative environmental setting. Longer-term acclimation protocols that focus on the specific adaptation kinetics (and further allow for the adaptation reversal) will elucidate the exact physiological mechanisms that might mediate gains in aerobic performance or explain the lack thereof.
Topics: Humans; Hot Temperature; Oxyhemoglobins; Acclimatization; Exercise; Hypoxia
PubMed: 36094448
DOI: 10.1152/ajpregu.00339.2021 -
EMBO Reports Apr 2006The ability of psychrophiles to survive and proliferate at low temperatures implies that they have overcome key barriers inherent to permanently cold environments. These... (Review)
Review
The ability of psychrophiles to survive and proliferate at low temperatures implies that they have overcome key barriers inherent to permanently cold environments. These challenges include: reduced enzyme activity; decreased membrane fluidity; altered transport of nutrients and waste products; decreased rates of transcription, translation and cell division; protein cold-denaturation; inappropriate protein folding; and intracellular ice formation. Cold-adapted organisms have successfully evolved features, genotypic and/or phenotypic, to surmount the negative effects of low temperatures and to enable growth in these extreme environments. In this review, we discuss the current knowledge of these adaptations as gained from extensive biochemical and biophysical studies and also from genomics and proteomics.
Topics: Acclimatization; Antifreeze Proteins; Biodiversity; Heat-Shock Response; Membrane Fluidity; Microbiology
PubMed: 16585939
DOI: 10.1038/sj.embor.7400662 -
Physiologia Plantarum Feb 2008Plants possess inducible tolerance mechanisms that extend the temperature range for survival during acute temperature stress. The inducible mechanisms of cold... (Review)
Review
Plants possess inducible tolerance mechanisms that extend the temperature range for survival during acute temperature stress. The inducible mechanisms of cold acclimation and acquired thermotolerance involve highly complex processes. These include perception and signal transduction of non-optimal temperatures or their physical consequences on cellular components that program extensive modification of the transcriptome, proteome, metabolome and composition and physical structure of the cytoplasm, membranes and cell walls. Therefore, a systems biology approach will be necessary to advance the understanding of plant stress responses and tolerance mechanisms. One promise of systems biology is that it will greatly enhance our understanding of individual and collective functions and thereby provide a more holistic view of plant stress responses. Past studies have found that several metabolites that could functionally contribute to induced stress tolerance have been associated with stress responses. Recent metabolite-profiling studies have refocused attention on these and other potentially important components found in the 'temperature-stress metabolome'. These metabolomic studies have demonstrated that active reconfiguration of the metabolome is regulated in part by changes in gene expression initiated by temperature-stress-activated signaling and stress-related transcription factors. One aspect of metabolism that is consistent across all of the temperature-stress metabolomic studies to date is the prominent role of central carbohydrate metabolism, which seems to be a major feature of the reprogramming of the metabolome during temperature stress. Future metabolomic studies of plant temperature-stress responses should reveal additional metabolic pathways that have important functions in temperature-stress tolerance mechanisms.
Topics: Acclimatization; Computational Biology; Gene Expression Regulation, Plant; Plants; Temperature
PubMed: 18251863
DOI: 10.1111/j.1399-3054.2007.00999.x -
Bioresource Technology Dec 2017In this study, a multifarious microbial mix from different sources is acclimatized over a period of three months to digesting cowgrass, and the changes in the community...
Acclimatization of a mixed-animal manure inoculum to the anaerobic digestion of Axonopus compressus reveals the putative importance of Mesotoga infera and Methanosaeta concilii as elucidated by DGGE and Illumina MiSeq.
In this study, a multifarious microbial mix from different sources is acclimatized over a period of three months to digesting cowgrass, and the changes in the community structure are examined with both a traditional denaturing gradient gel electrophoresis method as well as a next generation sequencing MiSeq method. It is shown that the much more in depth analysis by Illumina gives more information about the relative abundance and thus putative importance of the role of various microbes, in particular the bacterium Mesotoga infera and the archaeon Methanosaeta concilii.
Topics: Acclimatization; Anaerobiosis; Animals; Bioreactors; Denaturing Gradient Gel Electrophoresis; High-Throughput Nucleotide Sequencing; Manure
PubMed: 28869126
DOI: 10.1016/j.biortech.2017.08.123