Exercise delays the hypoxic thermal response in rats

2003 ◽  
Vol 95 (1) ◽  
pp. 272-278 ◽  
Author(s):  
A. D. Ray ◽  
A. J. Roberts ◽  
S. D. Lee ◽  
G. A. Farkas ◽  
C. Michlin ◽  
...  
Keyword(s):  
Body Temperature ◽  
Ambient Temperature ◽  
Small Mammals ◽  
Tissue Damage ◽  
Acute Mountain Sickness ◽  
Thermal Response ◽  
Lung Damage ◽  
Mountain Sickness ◽  
Water Contents

Exercise exacerbates acute mountain sickness. In infants and small mammals, hypoxia elicits a decrease in body temperature (Tb) [hypoxic thermal response (HTR)], which may protect against hypoxic tissue damage. We postulated that exercise would counteract the HTR and promote hypoxic tissue damage. Tb was measured by telemetry in rats ( n = 28) exercising or sedentary in either normoxia or hypoxia (10% O2, 24 h) at 25°C ambient temperature (Ta). After 24 h of normoxia, rats walked at 10 m/min on a treadmill (30 min exercise, 30 min rest) for 6 h followed by 18 h of rest in either hypoxia or normoxia. Exercising normoxic rats increased Tb (°C) vs. baseline (39.68 ± 0.99 vs. 38.90 ± 0.95, mean ± SD, P < 0.05) and vs. sedentary normoxic rats (38.0 ± 0.09, P < 0.05). Sedentary hypoxic rats decreased Tb (36.15 ± 0.97 vs. 38.0 ± 0.36, P < 0.05) whereas Tb was maintained in the exercising hypoxic rats during the initial 6 h of exercise (37.61 ± 0.55 vs. 37.72 ± 1.25, not significant). After exercise, Tb in hypoxic rats reached a nadir similar to that in sedentary hypoxic rats (35.05 ± 1.69 vs. 35.03 ± 1.32, respectively). Tb reached its nadir significantly later in exercising hypoxic vs. sedentary hypoxic rats (10.51 ± 1.61 vs. 5.36 ± 1.83 h, respectively; P = 0.002). Significantly greater histopathological damage and water contents were observed in brain and lungs in the exercising hypoxic vs. sedentary hypoxic and normoxic rats. Thus exercise early in hypoxia delays but does not prevent the HTR. Counteracting the HTR early in hypoxia by exercise exacerbates brain and lung damage and edema in the absence of ischemia.

Body Temperature, Autonomic Responses, and Acute Mountain Sickness

2003 ◽  
Vol 4 (3) ◽  
pp. 367-373 ◽  
Author(s):  
Jack A. Loeppky ◽  
Milton V. Icenogle ◽  
Damon Maes ◽  
Katrina Riboni ◽  
Pietro Scotto ◽  
...  
Keyword(s):  
Body Temperature ◽  
Acute Mountain Sickness ◽  
Autonomic Responses ◽  
Mountain Sickness

scholarly journals Responding to the weather: energy budgeting by a small mammal in the wild

2019 ◽  
Vol 66 (1) ◽  
pp. 15-20 ◽  
Author(s):  
Taylor Hume ◽  
Fritz Geiser ◽  
Shannon E Currie ◽  
Gerhard Körtner ◽  
Clare Stawski
Keyword(s):  
Body Temperature ◽  
Ambient Temperature ◽  
Small Mammals ◽  
Barometric Pressure ◽  
Breeding Period ◽  
Daily Torpor ◽  
Entire Study ◽  
Fat Reserves ◽  
In The Wild ◽  
Antechinus Stuartii

Abstract Energy conservation is paramount for small mammals because of their small size, large surface area to volume ratio, and the resultant high heat loss to the environment. To survive on limited food resources and to fuel their expensive metabolism during activity, many small mammals employ daily torpor to reduce energy expenditure during the rest phase. We hypothesized that a small terrestrial semelparous marsupial, the brown antechinus Antechinus stuartii, would maximize activity when foraging conditions were favorable to gain fat reserves before their intense breeding period, but would increase torpor use when conditions were poor to conserve these fat reserves. Female antechinus were trapped and implanted with small temperature-sensitive radio transmitters to record body temperature and to quantify torpor expression and activity patterns in the wild. Most antechinus used torpor at least once per day over the entire study period. Total daily torpor use increased and mean daily body temperature decreased significantly with a reduction in minimum ambient temperature. Interestingly, antechinus employed less torpor on days with more rain and decreasing barometric pressure. In contrast to torpor expression, activity was directly related to ambient temperature and inversely related to barometric pressure. Our results reveal that antechinus use a flexible combination of physiology and behavior that can be adjusted to manage their energy budget according to weather variables.

Cysteinyl Leukotriene Blockade Does Not Prevent Acute Mountain Sickness

2004 ◽  
Author(s):  
S. R. Muza ◽  
D. Kaminsky ◽  
C. S. Fulco ◽  
L. E. Banderet ◽  
A. Cymerman
Keyword(s):  
Acute Mountain Sickness ◽  
Cysteinyl Leukotriene ◽  
Mountain Sickness

Optic nerve sheath diameter changes at high altitude and in acute mountain sickness: meta-regression analyses

2020 ◽  
pp. bjophthalmol-2020-317717
Author(s):  
Tou-Yuan Tsai ◽  
George Gozari ◽  
Yung-Cheng Su ◽  
Yi-Kung Lee ◽  
Yu-Kang Tu
Keyword(s):  
Optic Nerve ◽  
High Altitude ◽  
Acute Mountain Sickness ◽  
Optic Nerve Sheath Diameter ◽  
Optic Nerve Sheath ◽  
Cochrane Library ◽  
Regression Analyses ◽  
Spline Regression ◽  
Nerve Sheath ◽  
Mountain Sickness

Background/aimsTo assess changes in optic nerve sheath diameter (ONSD) at high altitude and in acute mountain sickness (AMS).MethodsCochrane Library, EMBASE, Google Scholar and PubMed were searched for articles published from their inception to 31st of July 2020. Outcome measures were mean changes of ONSD at high altitude and difference in ONSD change between subjects with and without AMS. Meta-regressions were conducted to investigate the relation of ONSD change to altitude and time spent at that altitude.ResultsEight studies with 248 participants comparing ONSD from sea level to high altitude, and five studies with 454 participants comparing subjects with or without AMS, were included. ONSD increased by 0.14 mm per 1000 m after adjustment for time (95% CI: 0.10 to 0.18; p<0.01). Restricted cubic spline regression revealed an almost linear relation between ONSD change and time within 2 days. ONSD was greater in subjects with AMS (mean difference=0.47; 95% CI: 0.14 to 0.80; p=0.01; I2=89.4%).ConclusionOur analysis shows that ONSD changes correlate with altitude and tend to increase in subjects with AMS. Small study number and high heterogeneity are the limitations of our study. Further large prospective studies are required to verify our findings.

Torpor and hibernation

2017 ◽  
Author(s):  
Andrew Clarke
Keyword(s):  
Body Temperature ◽  
Small Mammals ◽  
Energy Input ◽  
The Arctic ◽  
Arid Areas ◽  
Daily Torpor ◽  
High Latitudes ◽  
Small Species ◽  
Universal Feature ◽  
Deep Hibernation

A diurnal (circadian) rhythm in body temperature is a widespread, and possibly universal, feature of endotherms. Some mammals and birds down-regulate their metabolic rate significantly by night, allowing their body temperature to drop sufficiently that they become inactive and enter torpor. Both the minimum temperature achieved and the duration of torpor are highly variable. Daily torpor is principally a response to reduced energy intake, and a drop in ambient temperature. Hibernation is essentially an extreme form of torpor. Small mammals hibernating at high latitudes have regular arousals during which they urinate and may feed. Bears hibernate with relatively high body temperature, and do not undergo arousal. Only one bird, the poorwill, is known to hibernate. Rewarming during arousal may be fuelled exclusively by metabolism (for example in small mammals in the Arctic) or with significant energy input from basking (for example in subtropical arid areas). The capacity for torpor appears to be an ancestral character in both mammals and birds, possibly related to the origin of endothermy in small species subject to marked diurnal and/or seasonal variation in body temperature. Both deep hibernation and strict endothermy are probably derived characteristics.

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