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Industrial Health Jul 2009Nowdays, occupational and recreational activities in cold environments are common. Exposure to cold induces thermoregulatory responses like changes of behaviour and...
Nowdays, occupational and recreational activities in cold environments are common. Exposure to cold induces thermoregulatory responses like changes of behaviour and physiological adjustments to maintain thermal balance either by increasing metabolic heat production by shivering and/or by decreasing heat losses consecutive to peripheral cutaneous vasoconstriction. Those physiological responses present a great variability among individuals and depend mainly on biometrical characteristics, age, and general cold adaptation. During severe cold exposure, medical disorders may occur such as accidental hypothermia and/or freezing or non-freezing cold injuries. General cold adaptations have been qualitatively classified by Hammel and quantitatively by Savourey. This last classification takes into account the quantitative changes of the main cold reactions: higher or lower metabolic heat production, higher or lesser heat losses and finally the level of the core temperature observed at the end of a standardized exposure to cold. General cold adaptations observed previously in natives could also be developed in laboratory conditions by continuous or intermittent cold exposures. Beside general cold adaptation, local cold adaptation exists and is characterized by a lesser decrease of skin temperature, a more pronounced cold induced vasodilation, less pain and a higher manual dexterity. Adaptations to cold may reduce the occurrence of accidents and improve human performance as surviving in the cold. The present review describes both general and local cold adaptations in humans and how they are of interest for cold workers.
Topics: Acclimatization; Adaptation, Physiological; Cold Temperature; Humans; Occupational Exposure
PubMed: 19531907
DOI: 10.2486/indhealth.47.221 -
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 -
Free Radical Biology & Medicine Apr 2012This review summarizes published information on the levels of nitric oxide gas (NO) in the lungs and NO-derived liquid-phase molecules in the acclimatization of visitors... (Review)
Review
This review summarizes published information on the levels of nitric oxide gas (NO) in the lungs and NO-derived liquid-phase molecules in the acclimatization of visitors newly arrived at altitudes of 2500 m or more and adaptation of populations whose ancestors arrived thousands of years ago. Studies of acutely exposed visitors to high altitude focus on the first 24-48 h with just a few extending to days or weeks. Among healthy visitors, NO levels in the lung, plasma, and/or red blood cells fell within 2h, but then returned toward baseline or slightly higher by 48 h and increased above baseline by 5 days. Among visitors ill with high-altitude pulmonary edema at the time of the study or in the past, NO levels were lower than those of their healthy counterparts. As for highland populations, Tibetans had NO levels in the lung, plasma, and red blood cells that were at least double and in some cases orders of magnitude greater than other populations regardless of altitude. Red blood cell-associated nitrogen oxides were more than 200 times higher. Other highland populations had generally higher levels although not to the degree shown by Tibetans. Overall, responses of those acclimatized and those presumed to be adapted are in the same direction, although the Tibetans have much larger responses. Missing are long-term data on lowlanders at altitude showing how similar they become to the Tibetan phenotype. Also missing are data on Tibetans at low altitude to see the extent to which their phenotype is a response to the immediate environment or expressed constitutively. The mechanisms causing the visitors' and the Tibetans' high levels of NO and NO-derived molecules at altitude remain unknown. Limited data suggest processes including hypoxic upregulation of NO synthase gene expression, hemoglobin-NO reactions, and genetic variation. Gains in understanding will require integrating appropriate methods and measurement techniques with indicators of adaptive function under hypoxic stress.
Topics: Acclimatization; Altitude; Altitude Sickness; Humans; Hypertension, Pulmonary; Nitric Oxide
PubMed: 22300645
DOI: 10.1016/j.freeradbiomed.2011.12.028 -
Journal of Applied Physiology... Jan 2016In 1875, Paul Bert linked high altitude danger to the low partial pressure of oxygen when 2 of 3 French balloonists died euphorically at about 8,600 m altitude. World... (Review)
Review
In 1875, Paul Bert linked high altitude danger to the low partial pressure of oxygen when 2 of 3 French balloonists died euphorically at about 8,600 m altitude. World War I fatal crashes of high altitude fighter pilots led to a century of efforts to use oximetry to warn pilots. The carotid body, discovered in 1932 to be the hypoxia detector, led to most current physiologic understanding of the body's respiratory responses to hypoxia and CO2. The author describes some of his UCSF group's work: In 1963, we reported both the brain's ventral medullary near-surface CO2 (and pH) chemosensors and the role of cerebrospinal fluid in acclimatization to altitude. In 1966, we reported the effect of altitude on cerebral blood flow and later the changes of carotid body sensitivity at altitude and the differences in natives of high altitude. In 1973, pulse oximetry was invented when Japanese biophysicist Takuo Aoyagi read and applied to pulses a largely forgotten 35-year-old discovery by English medical student J. R. Squire of a method of computing oxygen saturation from red and infrared light passing through both perfused and blanched tissue.
Topics: Acclimatization; Altitude; Animals; Humans; Oximetry; Oxygen; Partial Pressure
PubMed: 26251514
DOI: 10.1152/japplphysiol.00476.2015 -
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 -
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 -
The Journal of Physiology Dec 2022
Topics: Humans; Altitude; Adrenergic Agents; Acclimatization; Hemodynamics; Hypoxia; Regional Blood Flow
PubMed: 36314729
DOI: 10.1113/JP283688 -
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 -
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