European journal of applied physiology
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Eur. J. Appl. Physiol. · Sep 2008
Non-evaporative effects of a wet mid layer on heat transfer through protective clothing.
In order to assess the non-evaporative components of the reduced thermal insulation of wet clothing, experiments were performed with a manikin and with human subjects in which two layers of underwear separated by an impermeable barrier were worn under an impermeable overgarment at 20 degrees C, 80% RH and 0.5 ms(-1) air velocity. By comparing manikin measurements with dry and wetted mid underwear layer, the increase in heat loss caused by a wet layer kept away from the skin was determined, which turned out to be small (5-6 W m(-2)), irrespective of the inner underwear layer being dry or wetted, and was only one third of the evaporative heat loss calculated from weight change, i.e. evaporative cooling efficiency was far below unity. ⋯ Accordingly, total clothing insulation calculated over the walking period from heat balance equations was reduced by 0.02 m(2) degrees C W(-1) (16%), while for the standing period the same decrease in insulation, representing 9% reduction only showed up after allowing for the lower evaporative cooling efficiency in the calculations. As evaporation to the environment and inside the clothing was restricted, the observed small alterations may be attributed to the wet mid layer's increased conductivity, which, however, appears to be of minor importance compared to the evaporative effects in the assessment of the thermal properties of wet clothing.
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Eur. J. Appl. Physiol. · Sep 2008
HIF-1alpha subunit and vasoactive HIF-1-dependent genes are involved in carbon monoxide-induced cerebral hypoxic stress response.
Hypoxia-inducible transcription factor-1 (HIF-1) is the most important component of cellular and molecular adaptive responses to hypoxia. We aimed to analyze effects of systemic hypoxia and CO exposure on the oxygen-regulated alpha-subunit of HIF-1 and HIF-1-dependent vasoactive target genes in rat brain. Brains of adult Sprague-Dawley rats were investigated after incubation for 3 and 12 h under normoxia, hypoxia (8% O(2)) and CO 0.1% (n = 10 per group). ⋯ Hypoxia increased ADM (P < 0.05) and VEGF mRNA levels within 3 h (P < 0.01) which persisted up to 12 h of exposure (ADM, P < 0.05; VEGF, P < 0.001). Similarly, CO inhalation led to early up-regulation of VEGF (3 h: P < 0.05; 12 h: P < 0.01), but a more delayed increase of ADM mRNA levels (3 h: n.s., 12 h: P < 0.01). We suggest that CO-induced oxygen deprivation is a potent stimulus to cerebral HIF-1-regulated hypoxic stress responses even though its effects are more transient than exposure to hypoxia.