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is due to reduction in response to infectious agents because 25D is rate-limiting
是因为25D有限导致对病原反应的减少
And one of the speakers this morning commented
今天早上有位发言者
that it was known by the old-time pediatricians that principle cause of death in kids records was in fact respiratory infection
说从前儿科医生都知道小孩死亡的主要原因是呼吸道感染
So this is not so much a new observation
所以，这并不是什么新观测
It's a fact that we just had failed to connect the dots recently
只是到最近才把事情联系起来
And the greater TB susceptibility of blacks is probably due to their low vitamin D status
黑人更高的结核病易感性，某种程度上同低维生素D相关
You have to do a lot of head scratch yourself to try to make sense out of all this
研究中要多抓抓脑袋把问题搞明白
We've known for many, many years that all cells contain all of the information need to make a human being
我们已经知道很多很多年，所有细胞都包含构造人体的所有信息
and it wasn't entirely clear why
不过为什么这样，还没完全弄明白
Well we know that epithelial cells had to reproduce themselves
我们知道，上皮细胞能够自行繁殖
You cut your skin, you gotta grow new cells over the top of that Intestine mucosa turns over every 4 or 5 days
皮划破了，其上会生出新的肠粘膜，四五天一个周期
you're constantly making new cells
总在繁殖出新细胞
So it made sense to you
这很重要
You need to have the instructions to make a new cell in the nucleus and that seemed to make sense
细胞核内需要对繁殖新细胞发出指令，这说得通
and that's kind of where we left it; that was the old model
这是原来的老式模型
but the cell biologist have realized that that's not really an accurate way of looking at it
不过细胞生物学界开始意识到这样看问题并不完全准确
It turns out that ourselves are specialized primarily in the extent to which certain genes are kept and can't be expressed any more
我们体内的一些细胞已经特化到特定基因无法被表达的地步
So that a muscle cell doesn't express the genes that a white blood cell might express or a memory ductal cell might express
比如肌肉细胞无法表达白细胞等其它细胞表达的基因
And that's what the specialization means
这就是特化的含义
