The Experts below are selected from a list of 21531 Experts worldwide ranked by ideXlab platform
Neng Zhu - One of the best experts on this subject based on the ideXlab platform.
-
Influence of the temperature and relative humidity on human heat Acclimatization during training in extremely hot environments
Building and Environment, 2015Co-Authors: Dandan Shen, Neng ZhuAbstract:Abstract Heat-related disorders, decreases in productivity and security risks are common phenomena when people live in extremely hot environments. To a certain extent, humans can adapt to extremely hot environments, but few studies have examined the causes of and factors influencing the aforementioned phenomena, especially in hot environments. In this paper, a climate chamber was built to simulate an extremely hot environment. Sixteen healthy male university students were asked to simulate manual labour by running. The physiological indexes (rectal temperature, heart rate and sweat production) were measured. The effects of human heat Acclimatization in extremely hot environments were determined via paired sample t -tests. The time required to acclimate to the heat (in days) was determined based on the standard of thermal adaptation improvement. A Cox regression method was adopted to quantify the development of heat Acclimatization and to rank the effects of several variables on heat Acclimatization to determine the relationship between thermal parameters and heat Acclimatization. The effects of heat Acclimatization are significant, and heat Acclimatization training can improve the adaptability of humans to extremely hot environments. The Cox regression method can be used to analyse heat Acclimatization effectively. Both the dry bulb temperature and the relative humidity significantly affect heat Acclimatization, with the effect of the former being more significant.
-
Experimental study on physiological and psychological effects of heat Acclimatization in extreme hot environments
Building and Environment, 2011Co-Authors: Zhe Tian, Neng Zhu, Guozhong Zheng, Huijiao WeiAbstract:Abstract Extreme hot environments are prevalent in many industries. Exposed to extreme hot environments, people are at great risk of a variety of heat-related disorders and safety problems. In this paper, a climate chamber was built to simulate the extreme hot environment. The dry bulb temperature in the chamber was 37.0 ± 1.0 °C, the relative humidity was 20–40%, and the black bulb temperature was 41.0 ± 1.0 °C. Eleven healthy male university students were asked to do stair stepping in prescriptive speeds to simulate manual work. The physiological indexes (oral temperature, heart rate, blood pressure and sweating rate) and the psychological effects (comprehensive thermal sensation and fatigue feeling) were measured. The effects of heat Acclimatization in extreme hot environments were determined by paired sample t-tests. The results demonstrate that the effects of heat Acclimatization are significant and the heat Acclimatization training can improve adaptability of human body to extreme hot environments.
Peter J Edmunds - One of the best experts on this subject based on the ideXlab platform.
-
Effect of Acclimatization to low temperature and reduced light on the response of reef corals to elevated temperature
Marine Biology, 2009Co-Authors: Peter J EdmundsAbstract:This study tested the effects of Acclimatization on the response of corals to elevated temperature, using juvenile massive Porites spp. and branching P. irregularis from Moorea (W149°50′, S17°30′). During April and May 2006, corals were acclimatized for 15 days to cool (25.7°C) or ambient (27.7°C) temperature, under shaded (352 μmol photons m^−2 s^−1) or ambient (554 μmol photons m^−2 s^−1) natural light, and then incubated for 7 days at ambient or high temperature (31.1°C), under ambient light (659 μmol photons m^−2 s^−1). The response to Acclimatization was assessed as biomass, maximum dark-adapted quantum yield of PSII ( F _v/ F _m), and growth, and the effect of the subsequent treatment was assessed as F _v/ F _m and growth. Relative to the controls (i.e., ambient temperature/ambient light), massive Porites spp. responded to Acclimatization through increases in biomass under ambient temperature/shade, and low temperature/ambient light, whereas P. irregularis responded through reduced growth under ambient temperature/shade, and low temperature/ambient light. Acclimatization affected the response to thermal stress for massive Porites spp. (but not P. irregularis ), with an interaction between the Acclimatization and subsequent treatments for growth. This interaction resulted from a lessening of the negative effects of high temperature after acclimatizing to ambient temperature/shade, but an accentuation of the effect after acclimatizing to low temperature/shade. It is possible that changes in biomass for massive Porites spp. are important in modulating the response to high temperature, with the taxonomic variation in this effect potentially resulting from differences in morphology. These results demonstrate that corals can acclimatize during short exposures to downward excursions in temperature and light, which subsequently affects their response to thermal stress. Moreover, even con-generic taxa differ in this capacity, which could affect coral community structure.
-
the physiological mechanisms of Acclimatization in tropical reef corals
Integrative and Comparative Biology, 1999Co-Authors: Ruth D Gates, Peter J EdmundsAbstract:SYNOPSIS. The ability of scleractinian corals to survive changes that are predicted in the global environment over the next century will lie in their physiological mechanisms of Acclimatization. Corals display rapid modifications in behavior, morphology and physiology enabling them to photoacclimate to changing light conditions, a scenario that demonstrates considerable biological flexibility. Here we argue that the Acclimatization mechanisms in corals are fundamentally similar to those exhibited by other invertebrate taxa. We discuss protein metabolism as a mechanism underlying Acclimatization responses in reef corals, and explore the relationship between protein turnover, metabolic rate, growth rate, and Acclimatization capacity. Our preliminary analyses suggest that corals with low growth rates ([micro]Ca/mgN/h) and high metabolic rates ([micro][O.sub.2]/cm2/hr), such as the massive species, acclimatize more effectively than those with high growth rates and low metabolic rates, a feature that is characteristic of branching species. We conclude that studies of protein turnover, combined with temporally relevant investigations into the dynamic aspects of coral dinoflagellate symbioses will provide considerable insight into why corals exhibit such a high level of variation in response to the same environmental challenge. Furthermore, a more detailed understanding of Acclimatization mechanisms is essential if we are to predict how a coral assemblage will respond to present and future environmental challenges.
Andrew W Subudhi - One of the best experts on this subject based on the ideXlab platform.
-
altitudeomics resetting of cerebrovascular co2 reactivity following Acclimatization to high altitude
Frontiers in Physiology, 2016Co-Authors: Juilin Fan, Andrew W Subudhi, James Duffin, Andrew T Lovering, Robert C Roach, Bengt KayserAbstract:Previous studies reported enhanced cerebrovascular CO2 reactivity upon ascent to high altitude using linear models. However, there is evidence that this response may be sigmoidal in nature. Moreover, it was speculated that these changes at high altitude are mediated by alterations in acid-base buffering. Accordingly, we reanalyzed previously published data to assess middle cerebral blood flow velocity (MCAv) responses to modified rebreathing at sea level (SL), upon ascent (ALT1) and following 16 days of Acclimatization (ALT16) to 5,260 m in 21 lowlanders. Using sigmoid curve fitting of the MCAv responses to CO2, we found the amplitude (95% vs. 129%, SL vs. ALT1, 95% confidence intervals (CI) [77, 112], [111, 145], respectively, P=0.024) and the slope of the sigmoid response (4.5 vs. 7.5 %/mmHg, SL vs. ALT1, 95% CIs [3.1, 5.9], [6.0, 9.0], respectively, P=0.026) to be enhanced at ALT1, which persisted with Acclimatization at ALT16 (amplitude: 177%, 95% CI [139, 215], P<0.001; slope: 10.3 %/mmHg, 95% CI [8.2, 12.5], P=0.003) compared to SL. Meanwhile, the sigmoidal response midpoint was unchanged at ALT1 (SL: 36.5 mmHg; ALT1: 35.4 mmHg, 95% CIs [34.0, 39.0], [33.1, 37.7], respectively, P=0.982), while it was reduced by ~7 mmHg at ALT16 (28.6 mmHg, 95% CI [26.4, 30.8], P=0.001 vs. SL), indicating leftward shift of the cerebrovascular CO2 response to a lower arterial partial pressure of CO2 (PaCO2) following Acclimatization to altitude. Sigmoid fitting revealed a leftward shift in the midpoint of the cerebrovascular response curve which could not be observed with linear fitting. These findings demonstrate that there is resetting of the cerebrovascular CO2 reactivity operating point to a lower PaCO2 following Acclimatization to high altitude. This cerebrovascular resetting is likely the result of an altered acid-base buffer status resulting from prolonged exposure to the severe hypocapnia associated with ventilatory Acclimatization to high altitude.
-
altitudeomics effect of ascent and Acclimatization to 5260 m on regional cerebral oxygen delivery
Experimental Physiology, 2014Co-Authors: Andrew W Subudhi, Nicolas Bourdillon, Oghenero Evero, Juilin Fan, Andrew T Lovering, Bengt Kayser, Colleen G Julian, Robert C RoachAbstract: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.
-
altitudeomics the integrative physiology of human Acclimatization to hypobaric hypoxia and its retention upon reascent
PLOS ONE, 2014Co-Authors: Andrew W Subudhi, Nicolas Bourdillon, Jenna Bucher, Christopher Davis, Jonathan E Elliott, Morgan Eutermoster, Oghenero Evero, Juilin Fan, Sonja Jamesonvan HoutenAbstract:An understanding of human responses to hypoxia is important for the health of millions of people worldwide who visit, live, or work in the hypoxic environment encountered at high altitudes. In spite of dozens of studies over the last 100 years, the basic mechanisms controlling Acclimatization to hypoxia remain largely unknown. The AltitudeOmics project aimed to bridge this gap. Our goals were 1) to describe a phenotype for successful Acclimatization and assess its retention and 2) use these findings as a foundation for companion mechanistic studies. Our approach was to characterize Acclimatization by measuring changes in arterial oxygenation and hemoglobin concentration [Hb], acute mountain sickness (AMS), cognitive function, and exercise performance in 21 subjects as they acclimatized to 5260 m over 16 days. We then focused on the retention of Acclimatization by having subjects reascend to 5260 m after either 7 (n = 14) or 21 (n = 7) days at 1525 m. At 16 days at 5260 m we observed: 1) increases in arterial oxygenation and [Hb] (compared to acute hypoxia: PaO2 rose 9±4 mmHg to 45±4 while PaCO2 dropped a further 6±3 mmHg to 21±3, and [Hb] rose 1.8±0.7 g/dL to 16±2 g/dL; 2) no AMS; 3) improved cognitive function; and 4) improved exercise performance by 8±8% (all changes p<0.01). Upon reascent, we observed retention of arterial oxygenation but not [Hb], protection from AMS, retention of exercise performance, less retention of cognitive function; and noted that some of these effects lasted for 21 days. Taken together, these findings reveal new information about retention of Acclimatization, and can be used as a physiological foundation to explore the molecular mechanisms of Acclimatization and its retention.
Huijiao Wei - One of the best experts on this subject based on the ideXlab platform.
-
Experimental study on physiological and psychological effects of heat Acclimatization in extreme hot environments
Building and Environment, 2011Co-Authors: Zhe Tian, Neng Zhu, Guozhong Zheng, Huijiao WeiAbstract:Abstract Extreme hot environments are prevalent in many industries. Exposed to extreme hot environments, people are at great risk of a variety of heat-related disorders and safety problems. In this paper, a climate chamber was built to simulate the extreme hot environment. The dry bulb temperature in the chamber was 37.0 ± 1.0 °C, the relative humidity was 20–40%, and the black bulb temperature was 41.0 ± 1.0 °C. Eleven healthy male university students were asked to do stair stepping in prescriptive speeds to simulate manual work. The physiological indexes (oral temperature, heart rate, blood pressure and sweating rate) and the psychological effects (comprehensive thermal sensation and fatigue feeling) were measured. The effects of heat Acclimatization in extreme hot environments were determined by paired sample t-tests. The results demonstrate that the effects of heat Acclimatization are significant and the heat Acclimatization training can improve adaptability of human body to extreme hot environments.
D V Abramochkin - One of the best experts on this subject based on the ideXlab platform.
-
thermal acclimation and seasonal Acclimatization a comparative study of cardiac response to prolonged temperature change in shorthorn sculpin
The Journal of Experimental Biology, 2019Co-Authors: Tatiana S Filatova, D V Abramochkin, Holly A ShielsAbstract:ABSTRACT Seasonal thermal remodelling (Acclimatization) and laboratory thermal remodelling (acclimation) can induce different physiological changes in ectothermic animals. As global temperatures are changing at an increasing rate, there is urgency to understand the compensatory abilities of key organs such as the heart to adjust under natural conditions. Thus, the aim of the present study was to directly compare the Acclimatization and acclimatory response within a single eurythermal fish species, the European shorthorn sculpin (Myoxocephalus scorpio). We used current- and voltage-clamp to measure ionic current densities in both isolated atrial and ventricular myocytes from three groups of fish: (1) summer-caught fish kept at 12°C (‘summer-acclimated’); (2) summer-caught fish kept at 3°C (‘cold acclimated’); and (3) fish caught in March (‘winter-acclimatized’). At a common test temperature of 7.5°C, action potential (AP) was shortened by both winter Acclimatization and cold acclimation compared with summer acclimation; however, winter Acclimatization caused a greater shortening than did cold acclimation. Shortening of AP was achieved mostly by a significant increase in repolarizing current density (IKr and IK1) following winter Acclimatization, with cold acclimation having only minor effects. Compared with summer acclimation, the depolarizing L-type calcium current (ICa) was larger following winter Acclimatization, but again, there was no effect of cold acclimation on ICa. Interestingly, the other depolarizing current, INa, was downregulated at low temperatures. Our further analysis shows that ionic current remodelling is primarily due to changes in ion channel density rather than current kinetics. In summary, Acclimatization profoundly modified the electrical activity of the sculpin heart while acclimation to the same temperature for >1.5 months produced very limited remodelling effects.
