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 回骆驼：我什么时候说过芦笛是种族歧视？ |
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请教非文人和芦笛 -- 芒种 - (226 Byte) 2008-4-11 周五, 上午6:15 (470 reads) |
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作者：非文人 在 驴鸣镇 发贴, 来自 http://www.hjclub.org
至于藏人在低海拔地区出生及生活会发生什么改变，Beall这篇文章中也有论述，是用Sherpas(500年前移居到低海拔地区的一个藏人群体)做的研究：
A denser capillary network could potentially improve perfusion and oxygen delivery, because each capillary would supply a smaller area of tissue, and oxygen would diffuse a shorter distance. Tibetans (the study sample were Sherpas, an ethnic group that emigrated from Tibet to Nepal 500 years ago) who are born and raised at high altitude have higher capillary density in muscles as compared with Andean high-altitude natives, Tibetans born and raised at low altitude, or lowlanders (Fig. 5) (40). Those findings suggest that another route used particularly by Tibetans to overcome profoundly low arterial oxygen content is a high rate of diffusion. Diffusion could be further enhanced by easier dissociation of oxygen from hemoglobin. However, oxygen dissociation is normal in both Tibetan and Andean populations (25, 41, 42).
The last potential point of adaptation is at the level of the mitochondrion itself. Acutely exposed lowlanders lose mitochondria in leg muscles during the first 3 weeks at altitude. Similarly, both Tibetan (Sherpas) and Andean high-altitude natives have a lower mitochondrial volume in leg muscle tissue than sea-level natives at sea level (Fig. 5) (40). However, Tibetans born and raised closer to sea level (at 1,200 m) also have few mitochondria, indicating that, for them, expression of this trait does not require exposure to high altitude. The functional implications of fewer mitochondria are unclear, because overall oxygen-requiring metabolism is not lower. Among Tibetans, a smaller mitochondrial volume somehow supports a relatively larger oxygen consumption, perhaps by higher metabolic efficiency (12, 43, 44).
作者：非文人 在 驴鸣镇 发贴, 来自 http://www.hjclub.org |
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