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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 -
International Journal of Molecular... Feb 2022Improvement of crop climate resilience will require an understanding of whole-plant adaptation to specific local environments. This review places features of plant form... (Review)
Review
Improvement of crop climate resilience will require an understanding of whole-plant adaptation to specific local environments. This review places features of plant form and function related to photosynthetic productivity, as well as associated gene-expression patterns, into the context of the adaptation of ecotypes to local environments with different climates in Sweden and Italy. The growth of plants under common cool conditions resulted in a proportionally greater emphasis on the maintenance of photosynthetic activity in the Swedish ecotype. This is compared to a greater emphasis on downregulation of light-harvesting antenna size and upregulation of a host of antioxidant enzymes in the Italian ecotype under these conditions. This differential response is discussed in the context of the climatic patterns of the ecotypes' native habitats with substantial opportunity for photosynthetic productivity under mild temperatures in Italy but not in Sweden. The Swedish ecotype's response is likened to pushing forward at full speed with productivity under low temperature versus the Italian ecotype's response of staying safe from harm (maintaining redox homeostasis) while letting productivity decline when temperatures are transiently cold. It is concluded that either strategy can offer directions for the development of climate-resilient crops for specific locations of cultivation.
Topics: Acclimatization; Arabidopsis; Cold Temperature; Ecotype; Photosynthesis
PubMed: 35216246
DOI: 10.3390/ijms23042129 -
American Journal of Physiology.... Jul 2011Comparative physiology offers powerful approaches for developing causal, mechanistic explanations of shifts in biogeographic patterning occurring in concert with global... (Review)
Review
Comparative physiology offers powerful approaches for developing causal, mechanistic explanations of shifts in biogeographic patterning occurring in concert with global change. These analyses can identify the cellular loci and intensities of stress-induced perturbation and generate predictions about ecosystem alterations in a changing world. Congeneric species adapted to different abiotic conditions offer excellent study systems for these purposes. Several findings have emerged from such comparative studies: 1) In aquatic and terrestrial habitats, the most heat-tolerant ectotherms may be most threatened by further increases in temperature, due to proximity of these species' thermal optima and tolerance limits to current maximal ambient temperatures and limited capacities for acclimatization to higher temperatures. 2) Cardiac function is a "weak link" in acute thermal tolerance. 3) Stress-induced changes in gene expression comprise a graded response involving genes linked to damage repair, lysis of irreversibly damaged molecules, and downregulation of cell proliferation. Transcriptomic and proteomic analyses provide "biomarkers" for diagnosing degrees of stress. 4) Different abiotic stresses may have synergistic or opposing effects on gene expression, a complexity needing consideration when developing integrated pictures of effects of global change. 5) Adaptation of proteins can result from one to a few amino acid substitutions, which can occur at many sites in a protein, a discovery with implications for rates of adaptive evolution. 6) Greater thermal tolerance of invasive species may favor their replacement of natives. 7) Losses of protein-coding genes and temperature-responsive gene regulatory abilities in stenothermal ectotherms of the Southern Ocean may lead to broad extinctions.
Topics: Acclimatization; Adaptation, Physiological; Animals; Body Temperature Regulation; Climate Change; Ecosystem; Physiology, Comparative; Stress, Physiological
PubMed: 21430078
DOI: 10.1152/ajpregu.00719.2010 -
The Journal of Experimental Biology Sep 2023In this study, Atlantic salmon were: (i) implanted with heart rate (fH) data storage tags (DSTs), pharmacologically stimulated to maximum fH, and warmed at 10°C h-1...
In this study, Atlantic salmon were: (i) implanted with heart rate (fH) data storage tags (DSTs), pharmacologically stimulated to maximum fH, and warmed at 10°C h-1 (i.e. tested using a 'rapid screening protocol'); (ii) fitted with Doppler® flow probes, recovered in respirometers and given a critical thermal maximum (CTmax) test at 2°C h-1; and (iii) implanted with fH DSTs, recovered in a tank with conspecifics for 4 weeks, and had their CTmax determined at 2°C h-1. Fish in respirometers and those free-swimming were also exposed to a stepwise decrease in water oxygen level (100% to 30% air saturation) to determine the oxygen level at which bradycardia occurred. Resting fH was much lower in free-swimming fish than in those in respirometers (∼49 versus 69 beats min-1) and this was reflected in their scope for fH (∼104 versus 71 beats min-1) and CTmax (27.7 versus 25.9°C). Further, the Arrhenius breakpoint temperature and temperature at peak fH for free-swimming fish were considerably greater than for those tested in the respirometers and given a rapid screening protocol (18.4, 18.1 and 14.6°C; and 26.5, 23.2 and 20.2°C, respectively). Finally, the oxygen level at which bradycardia occurred was significantly higher in free-swimming salmon than in those in respirometers (∼62% versus 53% air saturation). These results: highlight the limitations of some lab-based methods of determining fH parameters and thermal tolerance in fishes; and suggest that scope for fH may be a more reliable and predictive measure of a fish's upper thermal tolerance than their peak fH.
Topics: Animals; Temperature; Salmo salar; Acclimatization; Bradycardia; Hypoxia; Oxygen
PubMed: 37622446
DOI: 10.1242/jeb.246227 -
PloS One 2015Studies on thermal acclimation in insects are often performed on animals acclimated in the laboratory under conditions that are not ecologically relevant. Costs and...
Studies on thermal acclimation in insects are often performed on animals acclimated in the laboratory under conditions that are not ecologically relevant. Costs and benefits of acclimation responses under such conditions may not reflect costs and benefits in natural populations subjected to daily and seasonal temperature fluctuations. Here we estimated costs and benefits in thermal tolerance limits in relation to winter acclimatization of Drosophila melanogaster. We sampled flies from a natural habitat during winter in Denmark (field flies) and compared heat and cold tolerance of these to that of flies collected from the same natural population, but acclimated to 25 °C or 13 °C in the laboratory (laboratory flies). We further obtained thermal performance curves for egg-to-adult viability of field and laboratory (25 °C) flies, to estimate possible cross-generational effects of acclimation. We found much higher cold tolerance and a lowered heat tolerance in field flies compared to laboratory flies reared at 25 °C. Flies reared in the laboratory at 13 °C exhibited the same thermal cost-benefit relations as the winter acclimatized flies. We also found a cost of winter acclimatization in terms of decreased egg-to-adult viability at high temperatures of eggs laid by winter acclimatized flies. Based on our findings we suggest that winter acclimatization in nature can induce strong benefits in terms of increased cold tolerance. These benefits can be reproduced in the laboratory under ecologically relevant rearing and testing conditions, and should be incorporated in species distribution modelling. Winter acclimatization also leads to decreased heat tolerance. This may create a mismatch between acclimation responses and the thermal environment, e.g. if temperatures suddenly increase during spring, under current and expected more variable future climatic conditions.
Topics: Acclimatization; Animals; Cold Temperature; Denmark; Drosophila melanogaster; Ecosystem; Seasons
PubMed: 26075607
DOI: 10.1371/journal.pone.0130307 -
Experimental Physiology May 2014Cerebral hypoxaemia associated with rapid ascent to high altitude can be life threatening; yet, with proper acclimatization, cerebral function can be maintained well...
Cerebral hypoxaemia associated with rapid ascent to high altitude can be life threatening; yet, with proper acclimatization, cerebral function can be maintained well enough for humans to thrive. We investigated adjustments in global and regional cerebral oxygen delivery (DO2) as 21 healthy volunteers rapidly ascended and acclimatized to 5260 m. Ultrasound indices of cerebral blood flow in internal carotid and vertebral arteries were measured at sea level, upon arrival at 5260 m (ALT1; atmospheric pressure 409 mmHg) and after 16 days of acclimatization (ALT16). Cerebral DO2 was calculated as the product of arterial oxygen content and flow in each respective artery and summed to estimate global cerebral blood flow. Vascular resistances were calculated as the quotient of mean arterial pressure and respective flows. Global cerebral blood flow increased by ∼70% upon arrival at ALT1 (P < 0.001) and returned to sea-level values at ALT16 as a result of changes in cerebral vascular resistance. A reciprocal pattern in arterial oxygen content maintained global cerebral DO2 throughout acclimatization, although DO2 to the posterior cerebral circulation was increased by ∼25% at ALT1 (P = 0.032). We conclude that cerebral DO2 is well maintained upon acute exposure and acclimatization to hypoxia, particularly in the posterior and inferior regions of the brain associated with vital homeostatic functions. This tight regulation of cerebral DO2 was achieved through integrated adjustments in local vascular resistances to alter cerebral perfusion during both acute and chronic exposure to hypoxia.
Topics: Acclimatization; Altitude; Cerebrovascular Circulation; Female; Humans; Male; Middle Cerebral Artery; Oxygen; Regional Blood Flow; Young Adult
PubMed: 24243839
DOI: 10.1113/expphysiol.2013.075184 -
Physiology (Bethesda, Md.) May 2016Large numbers of people visit, work, or reside at high altitude. The inevitable hypoxia reduces physical performance and, in many instances, impairs neuropsychological... (Review)
Review
Large numbers of people visit, work, or reside at high altitude. The inevitable hypoxia reduces physical performance and, in many instances, impairs neuropsychological function. The new technique of oxygen conditioning raises the oxygen concentration in the air of buildings such as homes, schools, and hospitals. The result is to decrease the equivalent altitude and improve both physical and cognitive performance.
Topics: Acclimatization; Altitude; Altitude Sickness; Animals; Humans; Hypoxia; Life; Oxygen
PubMed: 27053735
DOI: 10.1152/physiol.00057.2015 -
British Journal of Sports Medicine Apr 1974
Topics: Acclimatization; Altitude; Sports Medicine
PubMed: 4462946
DOI: 10.1136/bjsm.8.1.2 -
Annals of the New York Academy of... Sep 2020Convergent evolution, where independent lineages evolve similar phenotypes in response to similar challenges, can provide valuable insight into how selection operates... (Review)
Review
Convergent evolution, where independent lineages evolve similar phenotypes in response to similar challenges, can provide valuable insight into how selection operates and the limitations it encounters. However, it has only recently become possible to explore how convergent evolution is reflected at the genomic level. The overlapping outlier approach (OOA), where genome scans of multiple independent lineages are used to find outliers that overlap and therefore identify convergently evolving loci, is becoming popular. Here, we present a quantitative analysis of 34 studies that used this approach across many sampling designs, taxa, and sampling intensities. We found that OOA studies with increased biological sampling power within replicates have increased likelihood of finding overlapping, "convergent" signals of adaptation between them. When identifying convergent loci as overlapping outliers, it is tempting to assume that any false-positive outliers derived from individual scans will fail to overlap across replicates, but this cannot be guaranteed. We highlight how population demographics and genomic context can contribute toward both true convergence and false positives in OOA studies. We finish with an exploration of emerging methods that couple genome scans with phenotype and environmental measures, leveraging added information from genome data to more directly test hypotheses of the likelihood of convergent evolution.
Topics: Acclimatization; Adaptation, Physiological; Animals; Animals, Wild; Biological Evolution; Evolution, Molecular; Genome; Genomics
PubMed: 31241191
DOI: 10.1111/nyas.14177 -
Insect Science Dec 2022In nature, insects concurrently face multiple environmental stressors, a scenario likely increasing with climate change. Integrated stress resistance (ISR) thus often...
In nature, insects concurrently face multiple environmental stressors, a scenario likely increasing with climate change. Integrated stress resistance (ISR) thus often improves fitness and could drive invasiveness, but how physiological mechanisms influence invasion has lacked examination. Here, we investigated cross-tolerance to abiotic stress factors which may influence range limits in the South American tomato pinworm-a global invader that is an ecologically and socially damaging crop pest. Specifically, we tested the effects of prior rapid cold- and heat-hardening (RCH and RHH), fasting, and desiccation on cold and heat tolerance traits, as well as starvation and desiccation survivability between T. absoluta life stages. Acclimation effects on critical thermal minima (CT ) and maxima (CT ) were inconsistent, showing significantly deleterious effects of RCH on adult CT and CT and, conversely, beneficial acclimation effects of RCH on larval CT . While no beneficial effects of desiccation acclimation were recorded for desiccation tolerance, fasted individuals had significantly higher survival in adults, whereas fasting negatively affected larval tolerances. Furthermore, fasted and desiccation acclimated adults had significantly higher starvation tolerance, showing strong evidence for cross-tolerance. Our results show context-dependent ISR traits that may promote T. absoluta fitness and competitiveness. Given the frequent overlapping occurrence of these divergent stressors, ISR reported here may thus partly elucidate the observed rapid global spread of T. absoluta into more stressful environments than expected. This information is vital in determining the underpinnings of multistressor responses, which are fundamental in forecasting species responses to changing environments and management responses.
Topics: Animals; Introduced Species; Acclimatization; Thermotolerance; Larva; Stress, Physiological; Starvation
PubMed: 35290720
DOI: 10.1111/1744-7917.13035