Metabolic and thermal responses of the rat to a helium-oxygen environment

Rhoades, Rodney A.; Ra, Wright; Ep, Hiatt; Hs, Weiss

doi:10.1152/ajplegacy.1967.213.4.1009

Cited by 11 publications

(4 citation statements)

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“…1, A-E). Our measurement of thermal and metabolic variables for ash-grey mice in air and heliox did not differ significantly at thermoneutrality, consistent with previous studies for V O 2 (19,23,35,38) but not with a previous suggestion that V CO 2 may be affected by heliox (38). Our data support the assumption that animal metabolism is unaffected by replacing the nitrogen component of air with helium at atmospheric pressures.…”

Section: Discussionsupporting

confidence: 89%

Physiological responses of a rodent to heliox reveal constancy of evaporative water loss under perturbing environmental conditions

Cooper

Withers

2014

American Journal of Physiology-Regulatory, Integrative and Comp

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Total evaporative water loss of endotherms is assumed to be determined essentially by biophysics, at least at temperatures below thermoneutrality, with evaporative water loss determined by the water vapor deficit between the animal and the ambient air. We present here evidence, based on the first measurements of evaporative water loss for a small mammal in heliox, that mammals may have a previously unappreciated ability to maintain acute constancy of total evaporative water loss under perturbing environmental conditions. Thermoregulatory responses of ash-grey mice (Pseudomys albocinereus) to heliox were as expected, with changes in metabolic rate, conductance, and respiratory ventilation consistent with maintaining constancy of body temperature under conditions of enhanced heat loss. However, evaporative water loss did not increase in heliox. This is despite our confirmation of the physical effect that heliox augments evaporation from nonliving surfaces, which should increase cutaneous water loss, and increases minute volume of live ash-grey mice in heliox to accommodate their elevated metabolic rate, which should increase respiratory water loss. Therefore, mice had not only a thermoregulatory but also a hygroregulatory response to heliox. We interpret these results as evidence that ash-grey mice can acutely control their evaporative water loss under perturbing environmental conditions and suggest that hygroregulation at and below thermoneutrality is an important aspect of the physiology of at least some small mammals.

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Section: Discussionsupporting

confidence: 89%

Physiological responses of a rodent to heliox reveal constancy of evaporative water loss under perturbing environmental conditions

Cooper

Withers

2014

American Journal of Physiology-Regulatory, Integrative and Comp

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“…Values for MR and C wet were equivalent in both air and helox for ningauis at T a =30°C, consistent with the results of previous studies (e.g. Leon and Cook, 1960;Rhoades et al, 1967;Holloway and Geiser, 2001;Cooper and Withers, 2014) that there is no helox effect on C wet or MR in thermoneutrality. Below the TNZ, normothermic responses to T a were typical for this and other very small dasyurids (Dawson and Wolfers, 1978;Geiser and Baudinette, 1988;Warnecke et al, 2010).…”

Section: Discussionsupporting

confidence: 90%

Two lines of evidence for physiological control of insensible evaporative water loss by a tiny marsupial

Cooper

Withers

2020

Journal of Experimental Biology

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We present two independent lines of evidence that a tiny dasyurid marsupial, the ningaui (Ningaui spp.), has acute physiological control of its insensible evaporative water loss below and within thermoneutrality. Perturbation of the driving force for evaporation by varying relative humidity, and therefore the water vapour pressure deficit between the animal and the ambient air, does not have the expected physical effect on evaporative water loss. Exposure to a helox atmosphere also does not have the expected physical effect of increasing on evaporative water loss for live ningauis (despite it having the expected effect of increasing heat loss for live ningauis), and increasing evaporative water loss for dead ningauis. We discuss the relative advantages and disadvantages of both experimental approaches for demonstrating physiological control of insensible evaporative water loss. An appreciation of physiological control is important because insensible evaporative water loss contributes to both water and heat balance, is clearly under environmental selection pressure, and potentially impacts the distribution of endotherms and their response to environmental change.

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“…The five sites and the gross mechanisms likely to operate there a re: (a) The external body surface o f the animal, mediated through differ ences in thermal conductivity which appear to be one means by which major effects on metabolism arc produced [23,25,35].…”

Section: Discussionmentioning

confidence: 99%