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The Journal of Physiology Feb 2023In recent years, there has been an explosion of new approaches (technological, methodological, pharmacological, etc.) designed to improve physical performance for... (Review)
Review
In recent years, there has been an explosion of new approaches (technological, methodological, pharmacological, etc.) designed to improve physical performance for athletes, the military and in other applications. The goal of the present discussion is to review and quantify several ways in which physiology can provide important insights about which tools may lead to improved performance (and may therefore be worth resource investment) and which tools are less likely to provide meaningful enhancement. To address these objectives, we review examples of technological solutions/approaches in terms of the magnitude of their potential (or actual) influences: transformational, moderate, ineffective or undetermined. As one example, if there were a technology which significantly increased arterial oxygen partial pressure by 10%, this would be relatively meaningless in healthy people resting at sea level, where it would have a minimal effect on arterial oxygen content. However, there might be specific situations where such an effect would be very helpful, including at high altitude or in some patient populations. We discuss the importance of quantitative evaluation of putative approaches to performance enhancement and highlight the important role of integrative physiologists in the development and critical appraisal of these approaches.
Topics: Humans; Altitude; Hypoxia; Acclimatization; Oxygen Consumption; Oxygen; Physical Endurance
PubMed: 36518016
DOI: 10.1113/JP283975 -
Biochimica Et Biophysica Acta.... Apr 2020The higher plant chloroplast thylakoid membrane system performs the light-dependent reactions of photosynthesis. These provide the ATP and NADPH required for the... (Review)
Review
The higher plant chloroplast thylakoid membrane system performs the light-dependent reactions of photosynthesis. These provide the ATP and NADPH required for the fixation of CO into biomass by the Calvin-Benson cycle and a range of other metabolic reactions in the stroma. Land plants are frequently challenged by fluctuations in their environment, such as light, nutrient and water availability, which can create a mismatch between the amounts of ATP and NADPH produced and the amounts required by the downstream metabolism. Left unchecked, such imbalances can lead to the production of reactive oxygen species that damage the plant and harm productivity. Fortunately, plants have evolved a complex range of regulatory processes to avoid or minimize such deleterious effects by controlling the efficiency of light harvesting and electron transfer in the thylakoid membrane. Generally the regulation of the light reactions has been studied and conceptualised at the microscopic level of protein-protein and protein-ligand interactions, however in recent years dynamic changes in the thylakoid macrostructure itself have been recognised to play a significant role in regulating light harvesting and electron transfer. Here we review the evidence for the involvement of macrostructural changes in photosynthetic regulation and review the techniques that brought this evidence to light.
Topics: Acclimatization; Light; Photosynthesis; Thylakoids
PubMed: 31228404
DOI: 10.1016/j.bbabio.2019.06.011 -
The Plant Journal : For Cell and... Jan 2021Each year, abiotic stress conditions such as drought, heat, salinity, cold and particularly their different combinations, inflict a heavy toll on crop productivity... (Review)
Review
Each year, abiotic stress conditions such as drought, heat, salinity, cold and particularly their different combinations, inflict a heavy toll on crop productivity worldwide. The effects of these adverse conditions on plant productivity are becoming ever more alarming in recent years in light of the increased rate and intensity of global climatic changes. Improving crop tolerance to abiotic stress conditions requires a deep understanding of the response of plants to changes in their environment. This response is dependent on early and late signal transduction events that involve important signaling molecules such as reactive oxygen species (ROS), different plant hormones and other signaling molecules. It is the integration of these signaling events, mediated by an interplay between ROS and different plant hormones that orchestrates the plant response to abiotic stress and drive changes in transcriptomic, metabolic and proteomic networks that lead to plant acclimation and survival. Here we review some of the different studies that address hormone and ROS integration during the response of plants to abiotic stress. We further highlight the integration of ROS and hormone signaling during early and late phases of the plant response to abiotic stress, the key role of respiratory burst oxidase homologs in the integration of ROS and hormone signaling during these phases, and the involvement of hormone and ROS in systemic signaling events that lead to systemic acquired acclimation. Lastly, we underscore the need to understand the complex interactions that occur between ROS and different plant hormones during stress combinations.
Topics: Acclimatization; Plant Growth Regulators; Plant Physiological Phenomena; Plants; Reactive Oxygen Species; Signal Transduction; Stress, Physiological
PubMed: 33015917
DOI: 10.1111/tpj.15010 -
Proceedings. Biological Sciences Mar 2023How does the brain maintain an accurate visual representation of external space? Movement errors following saccade execution provide sufficient information to...
How does the brain maintain an accurate visual representation of external space? Movement errors following saccade execution provide sufficient information to recalibrate motor and visual space. Here, we asked whether spatial information for vision and saccades is processed in shared or in separate resources. We used saccade adaptation to modify both, saccade amplitudes and visual mislocalization. After saccade adaptation was induced, we compared participants' saccadic and perceptual localization before and after we inserted 'no error' trials. In these trials, we clamped the post-saccadic error online to the predicted endpoints of saccades. In separate experiments, we either annulled the retinal or the prediction error. We also varied the number of 'no error' trials across conditions. In all conditions, we found that saccade adaptation remained undisturbed by the insertion of 'no error' trials. However, mislocalization decreased as a function of the number of trials in which zero retinal error was displayed. When the prediction error was clamped to zero, no mislocalization was observed at all. The results demonstrate the post-saccadic error is used separately to recalibrate visual and saccadic space.
Topics: Humans; Saccades; Acclimatization; Brain; Movement; Retina
PubMed: 36855869
DOI: 10.1098/rspb.2022.2566 -
International Journal of Environmental... Feb 2023This report aims to summarise the scientific knowledge around hydration, nutrition, and metabolism at high altitudes and to transfer it into the practical context of... (Review)
Review
This report aims to summarise the scientific knowledge around hydration, nutrition, and metabolism at high altitudes and to transfer it into the practical context of extreme altitude alpinism, which, as far as we know, has never been considered before in the literature. Maintaining energy balance during alpine expeditions is difficult for several reasons and requires a deep understanding of human physiology and the biological basis for altitude acclimation. However, in these harsh conditions it is difficult to reconcile our current scientific knowledge in sports nutrition or even for mountaineering to high-altitude alpinism: extreme hypoxia, cold, and the logistical difficulties intrinsic to these kinds of expeditions are not considered in the current literature. Requirements for the different stages of an expedition vary dramatically with increasing altitude, so recommendations must differentiate whether the alpinist is at base camp, at high-altitude camps, or attempting the summit. This paper highlights nutritional recommendations regarding prioritising carbohydrates as a source of energy and trying to maintain a protein balance with a practical contextualisation in the extreme altitude environment in the different stages of an alpine expedition. More research is needed regarding specific macro and micronutrient requirements as well as the adequacy of nutritional supplementations at high altitudes.
Topics: Humans; Altitude; Mountaineering; Hypoxia; Altitude Sickness; Acclimatization
PubMed: 36833880
DOI: 10.3390/ijerph20043186 -
The Journal of Physiological Sciences :... Oct 2023Heat acclimation/acclimatisation (HA) mitigates heat-related decrements in physical capacity and heat-illness risk and is a widely advocated countermeasure for... (Review)
Review
Heat acclimation/acclimatisation (HA) mitigates heat-related decrements in physical capacity and heat-illness risk and is a widely advocated countermeasure for individuals operating in hot environments. The efficacy of HA is typically quantified by assessing the thermo-physiological responses to a standard heat acclimation state test (i.e. physiological biomarkers), but this can be logistically challenging, time consuming, and expensive. A valid molecular biomarker of HA would enable evaluation of the heat-adapted state through the sampling and assessment of a biological medium. This narrative review examines candidate molecular biomarkers of HA, highlighting the poor sensitivity and specificity of these candidates and identifying the current lack of a single 'standout' biomarker. It concludes by considering the potential of multivariable approaches that provide information about a range of physiological systems, identifying a number of challenges that must be overcome to develop a valid molecular biomarker of the heat-adapted state, and highlighting future research opportunities.
Topics: Humans; Hot Temperature; Acclimatization; Biomarkers; Phenotype; Heart Rate
PubMed: 37848829
DOI: 10.1186/s12576-023-00882-4 -
International Journal of Molecular... Feb 2022The demand for agricultural crops continues to escalate with the rapid growth of the population. However, extreme climates, pests and diseases, and environmental... (Review)
Review
The demand for agricultural crops continues to escalate with the rapid growth of the population. However, extreme climates, pests and diseases, and environmental pollution pose a huge threat to agricultural food production. Silica nanoparticles (SNPs) are beneficial for plant growth and production and can be used as nanopesticides, nanoherbicides, and nanofertilizers in agriculture. This article provides a review of the absorption and transportation of SNPs in plants, as well as their role and mechanisms in promoting plant growth and enhancing plant resistance against biotic and abiotic stresses. In general, SNPs induce plant resistance against stress factors by strengthening the physical barrier, improving plant photosynthesis, activating defensive enzyme activity, increasing anti-stress compounds, and activating the expression of defense-related genes. The effect of SNPs on plants stress is related to the physical and chemical properties (e.g., particle size and surface charge) of SNPs, soil, and stress type. Future research needs to focus on the "SNPs-plant-soil-microorganism" system by using omics and the in-depth study of the molecular mechanisms of SNPs-mediated plant resistance.
Topics: Acclimatization; Animals; Humans; Nanoparticles; Plants; Silicon Dioxide; Stress, Physiological
PubMed: 35216062
DOI: 10.3390/ijms23041947 -
Journal of Applied Physiology... Jun 2021Rapid ascent to high altitude imposes an acute hypoxic and acid-base challenge, with ventilatory and renal acclimatization countering these perturbations. Specifically,...
Rapid ascent to high altitude imposes an acute hypoxic and acid-base challenge, with ventilatory and renal acclimatization countering these perturbations. Specifically, ventilatory acclimatization improves oxygenation, but with concomitant hypocapnia and respiratory alkalosis. A compensatory, renally mediated relative metabolic acidosis follows via bicarbonate elimination, normalizing arterial pH(a). The time course and magnitude of these integrated acclimatization processes are highly variable between individuals. Using a previously developed metric of renal reactivity (RR), indexing the change in arterial bicarbonate concentration (Δ[HCO]a; renal response) over the change in arterial pressure of CO (Δ[Formula: see text]; renal stimulus), we aimed to characterize changes in RR magnitude following rapid ascent and residence at altitude. Resident lowlanders ( = 16) were tested at 1,045 m ( []) prior to ascent, on within 24 h of arrival, and during residence at 3,800 m. Radial artery blood draws were obtained to measure acid-base variables: [Formula: see text], [HCO]a, and pHa. Compared with , [Formula: see text] and [HCO]a were lower on ( < 0.01) and ( < 0.01), whereas significant changes in pHa ( = 0.072) and RR ( = 0.056) were not detected. As pHa appeared fully compensated on and RR did not increase significantly from to , these data demonstrate renal acid-base compensation within 24 h at moderate steady-state altitude. Moreover, RR was strongly and inversely correlated with ΔpHa on and ( -0.95; < 0.0001), suggesting that a high-gain renal response better protects pHa. Our study highlights the differential time course, magnitude, and variability of integrated ventilatory and renal acid-base acclimatization following rapid ascent and residence at high altitude. We assessed the time course, magnitude, and variability of integrated ventilatory and renal acid-base acclimatization with rapid ascent and residence at 3,800 m. Despite reductions in [Formula: see text] upon ascent, pHa was normalized within 24 h of arrival at 3,800 m through renal compensation (i.e., bicarbonate elimination). Renal reactivity (RR) was unchanged between and , suggesting a lack of plasticity at moderate steady-state altitude. RR was strongly correlated with ΔpHa, suggesting that a high-gain renal response better protects pHa.
Topics: Acclimatization; Altitude; Bicarbonates; Humans; Hypocapnia; Hypoxia
PubMed: 33703943
DOI: 10.1152/japplphysiol.00973.2020 -
British Journal of Sports Medicine Jan 2023This document presents the recommendations developed by the IOC Medical and Scientific Commission and several international federations (IF) on the protection of...
This document presents the recommendations developed by the IOC Medical and Scientific Commission and several international federations (IF) on the protection of athletes competing in the heat. It is based on a working group, meetings, field experience and a Delphi process. The first section presents recommendations for event organisers to monitor environmental conditions before and during an event; to provide sufficient ice, shading and cooling; and to work with the IF to remove regulatory and logistical limitations. The second section summarises recommendations that are directly associated with athletes' behaviours, which include the role and methods for heat acclimation; the management of hydration; and adaptation to the warm-up and clothing. The third section explains the specific medical management of exertional heat stroke (EHS) from the field of play triage to the prehospital management in a dedicated heat deck, complementing the usual medical services. The fourth section provides an example for developing an environmental heat risk analysis for sport competitions across all IFs. In summary, while EHS is one of the leading life-threatening conditions for athletes, it is preventable and treatable with the proper risk mitigation and medical response. The protection of athletes competing in the heat involves the close cooperation of the local organising committee, the national and international federations, the athletes and their entourages and the medical team.
Topics: Humans; Hot Temperature; Sports; Acclimatization; Heat Stroke; Athletes
PubMed: 36150754
DOI: 10.1136/bjsports-2022-105942 -
The New Phytologist Mar 2023The physiological challenges posed by climate change for seasonal, perennial plants include increased risk of heat waves, postbudbreak freezing ('false springs'), and... (Review)
Review
The physiological challenges posed by climate change for seasonal, perennial plants include increased risk of heat waves, postbudbreak freezing ('false springs'), and droughts. Although considerable physiological work has shown that the traits conferring tolerance to these stressors - thermotolerance, cold hardiness, and water deficit stress, respectively - are not static in time, they are frequently treated as such. In this review, I synthesize the recent literature on predictable seasonal - and therefore, phenological - patterns of acclimation and deacclimation to heat, cold, and water-deficit stress in perennials, focusing on woody plants native to temperate climates. I highlight promising, high-throughput techniques for quantifying thermotolerance, cold hardiness, and drought tolerance. For each of these forms of stress tolerance, I summarize the current balance of evidence regarding temporal patterns over the course of a year and suggest a characteristic temporal scale in these responses to environmental stress. In doing so, I offer a synthetic framework of 'phenological physiology', in which understanding and leveraging seasonally recurring (phenological) patterns of physiological stress acclimation can facilitate climate change adaptation and mitigation.
Topics: Seasons; Plants; Acclimatization; Water; Climate Change; Cold Temperature
PubMed: 36372992
DOI: 10.1111/nph.18617