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Comparative Biochemistry and... 19911. Exposure of rats to an 8000 m altitude increased the hepatic tryptophan 2,3-dioxygenase (EC 1.13.1.12) activity. 2. Acclimatization to hypoxia by a repeated exposure...
1. Exposure of rats to an 8000 m altitude increased the hepatic tryptophan 2,3-dioxygenase (EC 1.13.1.12) activity. 2. Acclimatization to hypoxia by a repeated exposure to an altitude of 5000 m induced a marked decrease in liver tryptophan dioxygenase activity after the rats were subjected to an 8000 m altitude, but a pre-exposure to 4000 m altitude showed no effect on the enzyme activity. 3. Plasma tryptophan was rapidly decreased by exposure to 8000 m altitude to the same extent in the acclimatized and non-acclimatized rats. 4. Plasma tryptophan may be utilized as the substrate for tryptophan dioxygenase in liver of the non-acclimatized rats under highly hypoxic conditions; however, acclimatized rats can reserve tryptophan as the substrate for the alternative metabolism other than the degradation pathway in liver.
Topics: Acclimatization; Altitude; Animals; Hypoxia; Indoleamine-Pyrrole 2,3,-Dioxygenase; Liver; Male; Rats; Rats, Inbred Strains; Tryptophan; Tryptophan Oxygenase
PubMed: 1769205
DOI: 10.1016/0305-0491(91)90339-f -
European Journal of Applied Physiology Feb 2012We sought to determine if cold acclimatized men display higher economy (i.e. lower oxygen consumption at a given workload) during graded cycle ergometry in the cold...
We sought to determine if cold acclimatized men display higher economy (i.e. lower oxygen consumption at a given workload) during graded cycle ergometry in the cold (5°C). After completing a familiarization trial 1 week prior, five cold weather athletes (CWA) and eight physically active men (NON) underwent graded exercise tests to volitional fatigue in 5°C. The protocol always started at 60 W and increased by 20 W each minute. Oxygen consumption (VO(2)), respiration rate (RR), tidal volume (TV), and respiratory exchange ratio (RER) were determined via open circuit spirometry. Individuals were matched for body size and minutes of weekly physical activity. Repeated measures analyses of variance were conducted across time (workload) and cold acclimatization was entered as a between subjects factor. VO(2) peak was not different between groups but CWA had lower VO(2) at 60 and 240 W. CWA also had lower RR at 180 and 260 W as well as lower RER at 240 and 260 W. At submaximal workloads, cold acclimatized men have higher exercise economy than non-acclimatized men. This could have implications for those who work in this context.
Topics: Acclimatization; Cold Temperature; Energy Metabolism; Humans; Male; Oxygen Consumption; Physical Exertion; Respiratory Mechanics; Young Adult
PubMed: 21671101
DOI: 10.1007/s00421-011-2038-5 -
Acta Physiologica (Oxford, England) Apr 2022Ascent to high altitude is accompanied by a reduction in partial pressure of inspired oxygen, which leads to interconnected adjustments within the neuromuscular system.... (Review)
Review
Ascent to high altitude is accompanied by a reduction in partial pressure of inspired oxygen, which leads to interconnected adjustments within the neuromuscular system. This review describes the unique challenge that such an environment poses to neuromuscular fatigability (peripheral, central and supraspinal) for individuals who normally reside near to sea level (SL) (<1000 m; ie, lowlanders) and for native highlanders, who represent the manifestation of high altitude-related heritable adaptations across millennia. Firstly, the effect of acute exposure to high altitude-related hypoxia on neuromuscular fatigability will be examined. Under these conditions, both supraspinal and peripheral fatigability are increased compared with SL. The specific mechanisms contributing to impaired performance are dependent on the exercise paradigm and amount of muscle mass involved. Next, the effect of chronic exposure to high altitude (ie, acclimatization of ~7-28 days) will be considered. With acclimatization, supraspinal fatigability is restored to SL values, regardless of the amount of muscle mass involved, whereas peripheral fatigability remains greater than SL except when exercise involves a small amount of muscle mass (eg, knee extensors). Indeed, when whole-body exercise is involved, peripheral fatigability is not different to acute high-altitude exposure, due to competing positive (haematological and muscle metabolic) and negative (respiratory-mediated) effects of acclimatization on neuromuscular performance. In the final section, we consider evolutionary adaptations of native highlanders (primarily Himalayans of Tibet and Nepal) that may account for their superior performance at altitude and lesser degree of neuromuscular fatigability compared with acclimatized lowlanders, for both single-joint and whole-body exercise.
Topics: Acclimatization; Altitude; Altitude Sickness; Fatigue; Humans; Hypoxia; Oxygen
PubMed: 35007386
DOI: 10.1111/apha.13788 -
Molecular Biology Reports Aug 2023Environmental variation is the most crucial problem as it is causing food insecurity and negatively impacts food availability, utilization, assessment, and stability.... (Review)
Review
Environmental variation is the most crucial problem as it is causing food insecurity and negatively impacts food availability, utilization, assessment, and stability. Wheat is the largest and extensively cultivated staple food crop for fulfilling global food requirements. Abiotic stresses including salinity, heavy metal toxicity, drought, extreme temperatures, and oxidative stresses being the primary cause of productivity loss are a serious threat to agronomy. Cold stress is a foremost ecological constraint that is extremely influencing plant development, and yield. It is extremely hampering the propagative development of plant life. The structure and function of plant cells depend on the cell's immune system. The stresses due to cold, affect fluid in the plasma membrane and change it into crystals or a solid gel phase. Plants being sessile in nature have evolved progressive systems that permit them to acclimatize the cold stress at the physiological as well as molecular levels. The phenomenon of acclimatisation of plants to cold stress has been investigated for the last 10 years. Studying cold tolerance is critical for extending the adaptability zones of perennial grasses. In the present review, we have elaborated the current improvement of cold tolerance in plants from molecular and physiological viewpoints, such as hormones, the role of the posttranscriptional gene, micro RNAs, ICE-CBF-COR signaling route in cold acclimatization and how they are stimulating the expression of underlying genes encoding osmoregulatory elements and strategies to improve cold tolerance in wheat.
Topics: Triticum; Cold Temperature; Oxidative Stress; Plants; Cold-Shock Response; Gene Expression Regulation, Plant; Acclimatization; Plant Proteins
PubMed: 37378744
DOI: 10.1007/s11033-023-08584-1 -
Respiration Physiology Dec 1988One of the most important factors in the acclimatization of lowlanders to high altitude is hyperventilation which helps to defend the alveolar PO2. However, how rapidly...
One of the most important factors in the acclimatization of lowlanders to high altitude is hyperventilation which helps to defend the alveolar PO2. However, how rapidly this occurs at very high altitude is poorly understood. Information can be obtained by comparing the alveolar gas values reported from the extended low pressure chamber studies, Operation Everest I and II, and the American medical research expedition to Everest (AMREE) of 1981. Rahn and Otis (1949) reported the alveolar PO2 and PCO2 values for non-acclimatized and well-acclimatized man on an O2-CO2 diagram, and pointed out that the Operation Everest I data fell approximately halfway between the two curves. The AMREE data agree well with the fully-acclimatized curve, and the Operation Everest II values are intermediate. The differences can be partly, though not wholly, attributed to the different periods of acclimatization. The conclusion is that 31 and 36 days are inadequate periods of acclimatization for altitudes over 8000 m, but that 77 days is sufficient. However, other factors are also involved.
Topics: Acclimatization; Adult; Altitude; Humans; Male; Mountaineering; Respiration
PubMed: 3222564
DOI: 10.1016/0034-5687(88)90040-0 -
Nature Apr 2014
Topics: Acclimatization; Animals; Anthozoa; Awards and Prizes; Coral Reefs; Directed Molecular Evolution; Global Warming; Hydrogen-Ion Concentration; Samoa; Seawater; Symbiosis; Temperature
PubMed: 24759396
DOI: 10.1038/508444a -
Journal of Plant Research Jan 2012Photosynthetic organisms have evolved various acclimatory responses to high-light (HL) conditions to maintain a balance between energy supply (light harvesting and... (Review)
Review
Photosynthetic organisms have evolved various acclimatory responses to high-light (HL) conditions to maintain a balance between energy supply (light harvesting and electron transport) and consumption (cellular metabolism) and to protect the photosynthetic apparatus from photodamage. The molecular mechanism of HL acclimation has been extensively studied in the unicellular cyanobacterium Synechocystis sp. PCC 6803. Whole genome DNA microarray analyses have revealed that the change in gene expression profile under HL is closely correlated with subsequent acclimatory responses such as (1) acceleration in the rate of photosystem II turnover, (2) downregulation of light harvesting capacity, (3) development of a protection mechanism for the photosystems against excess light energy, (4) upregulation of general protection mechanism components, and (5) regulation of carbon and nitrogen assimilation. In this review article, we survey recent progress in the understanding of the molecular mechanisms of these acclimatory responses in Synechocystis sp. PCC 6803. We also briefly describe attempts to understand HL acclimation in various cyanobacterial species in their natural environments.
Topics: Acclimatization; Cyanobacteria; Gene Expression Profiling; Gene Expression Regulation, Bacterial; Light; Transcription Factors
PubMed: 22006212
DOI: 10.1007/s10265-011-0454-6 -
Journal of Applied Physiology... Oct 2001Women living at low altitudes or acclimatized to high altitudes have greater effective ventilation in the luteal (L) compared with follicular (F) menstrual cycle phase... (Clinical Trial)
Clinical Trial Comparative Study
Women living at low altitudes or acclimatized to high altitudes have greater effective ventilation in the luteal (L) compared with follicular (F) menstrual cycle phase and compared with men. We hypothesized that ventilatory acclimatization to high altitude would occur more quickly and to a greater degree in 1) women in their L compared with women in their F menstrual cycle phase, and 2) in women compared with men. Studies were conducted on 22 eumenorrheic, unacclimatized, sea-level (SL) residents. Indexes of ventilatory acclimatization [resting ventilatory parameters, hypoxic ventilatory response, hypercapnic ventilatory response (HCVR)] were measured in 14 women in the F phase and in 8 other women in the L phase of their menstrual cycle, both at SL and again during a 12-day residence at 4,300 m. At SL only, ventilatory studies were also completed in both menstrual cycle phases in 12 subjects (i.e., within-subject comparison). In these subjects, SL alveolar ventilation (expressed as end-tidal PCO(2)) was greater in the L vs. F phase. Yet the comparison between L- and F-phase groups found similar levels of resting end-tidal PCO(2), hypoxic ventilatory response parameter A, HCVR slope, and HCVR parameter B, both at SL and 4,300 m. Moreover, these indexes of ventilatory acclimatization were not significantly different from those previously measured in men. Thus female lowlanders rapidly ascending to 4,300 m in either the L or F menstrual cycle phase have similar levels of alveolar ventilation and a time course for ventilatory acclimatization that is nearly identical to that reported in male lowlanders.
Topics: Acclimatization; Altitude; Blood Gas Analysis; Carbon Dioxide; Female; Follicular Phase; Humans; Luteal Phase; Male; Menstrual Cycle; Oxygen Consumption; Respiratory Function Tests; Respiratory Mechanics; Sex Characteristics
PubMed: 11568164
DOI: 10.1152/jappl.2001.91.4.1791 -
Comparative Biochemistry and... Oct 2023The fields of biological anthropology and exercise physiology are closely related and can provide mutually beneficial insights into human performance. These fields often... (Review)
Review
The fields of biological anthropology and exercise physiology are closely related and can provide mutually beneficial insights into human performance. These fields often use similar methods and are both interested in how humans function, perform, and respond in extreme environments. However, these two fields have different perspectives, ask different questions, and work within different theoretical frameworks and timescales. Biological anthropologists and exercise physiologists can greatly benefit from working together when examining human adaptation, acclimatization, and athletic performance in the extremes of heat, cold, and high-altitude. Here we review the adaptations and acclimatizations in these three different extreme environments. We then examine how this work has informed and built upon exercise physiology research on human performance. Finally, we present an agenda for moving forward, hopefully, with these two fields working more closely together to produce innovative research that improves our holistic understanding of human performance capacities informed by evolutionary theory, modern human acclimatization, and the desire to produce immediate and direct benefits.
Topics: Humans; Acclimatization; Adaptation, Physiological; Altitude; Anthropology; Extreme Environments
PubMed: 37423419
DOI: 10.1016/j.cbpa.2023.111476 -
Respiration Physiology Jul 2000Studies of ventilatory response to high altitudes have occupied an important position in respiratory physiology. This review summarizes recent studies in Tibetan... (Comparative Study)
Comparative Study Review
Studies of ventilatory response to high altitudes have occupied an important position in respiratory physiology. This review summarizes recent studies in Tibetan high-altitude residents that collectively challenge the prior consensus that lifelong high-altitude residents ventilate less than acclimatized newcomers do as the result of acquired 'blunting' of hypoxic ventilatory responsiveness. These studies indicate that Tibetans ventilate more than Andean high-altitude natives residing at the same or similar altitudes (PET[CO(2)]) in Tibetans=29.6+/-0.8 vs. Andeans=31.0+/-1.0, P<0.0002 at approximately 4200 m), a difference which approximates the change that occurs between the time of acute hypoxic exposure to once ventilatory acclimatization has been achieved. Tibetans ventilate as much as acclimatized newcomers whereas Andeans ventilate less. However, the extent to which differences in hypoxic ventilatory response (HVR) are responsible is uncertain from existing data. Tibetans have an HVR as high as those of acclimatized newcomers whereas Andeans generally do not, but HVR is not consistently greater in comparisons of Tibetan versus Andean highland residents. Human and experimental animal studies demonstrate that inter-individual and genetic factors affect acute HVR and likely modify acclimatization and hyperventilatory response to high altitude. But the mechanisms responsible for ventilatory roll-off, hyperoxic hyperventilation, and acquired blunting of HVR are poorly understood, especially as they pertain to high-altitude residents. Developmental factors affecting neonatal arterial oxygenation are likely important and may vary between populations. Functional significance has been investigated with respect to the occurrence of chronic mountain sickness and intrauterine growth restriction for which, in both cases, low HVR seems disadvantageous. Additional studies are needed to address the various components of ventilatory control in native Tibetan, Andean and other lifelong high-altitude residents to decide the factors responsible for blunting HVR and diminishing ventilation in some native high-altitude residents.
Topics: Acclimatization; Altitude; Altitude Sickness; Animals; Asia; Female; Fetal Growth Retardation; Humans; Infant, Newborn; Male; North America; Respiratory Physiological Phenomena; South America
PubMed: 10963780
DOI: 10.1016/s0034-5687(00)00133-x