النتائج (
العربية) 1:
[نسخ]نسخ!
هو زيادة 80% في التمثيل الغذائي كثيرا أو قليلاً؟In the study of Ouellet et al. (2), the subjects exposed to cold stress increased their metabolism by, on average, 80% over “warm” levels. Some of the heat production undoubtedly emanated from shivering. Ouellet et al. found that shivering in those subjects with the most brown adipose tissue was about half the magnitude of those with less. An interpretation of this would be that about half of the increased heat production resulted from shivering, and about half would be the true contribution of brown adipose tissue (thus, about a 40% increase over basal). This is slightly higher than but close to results obtained some 30 years ago, in which estimates were made of nonshivering thermogenesis capacity in adult humans, following the strictest protocol for this phenomenon: curarized subjects (i.e., on artificial respiration), who although unable to shiver could still increase their metabolism by some 25% when exposed to cold (15). Similarly, an increase in metabolism was observed in cold-exposed men, before any shivering was detectable (16). Furthermore, mild cold exposure increases metabolism in men without leading to observable spontaneous physical activity (non-exercise activity thermogenesis [NEAT]) or to shivering (17). At the time when those experiments were performed, the site of the cold-induced nonshivering thermogenesis was unknown and was definitely not considered to be attributable to brown adipose tissue (since it was believed at that time that adult humans did not possess brown adipose tissue). Today, we can reasonably ascribe all these demonstrations of nonshivering thermogenesis to activation of brown adipose tissue in the examined adult humans
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