听力文本

So they kind of scratched their heads
他们有些不解
This is one of those studies that evolved
这时研究就要改进了
You do something. You see how it works and you wonder why it didn't and so you do something different and soforth
做实验，看如何工作，不行就要尝试其它办法
So they scratched their heads and then they realize that fetal calf serum in which they were incubating their macrophages is low in the vitamin D metabolites
他们很不解，然后意识到自己在胎牛血清中培育巨噬细胞，这里维生素D代谢物很低
Not much 25D, certainly not much 1,25D
没有很多25D，也没很多1,25D
So thinking in the old model that 1,25 was what was important
老模型中 1,25D非常重要
They added 1,25D to the system
他们于是加入1,25D
It got in there to bind with the vitamin D receptor and lo and behold, it worked as what it was supposed to
1,25D同维生素D受体结合，这时，结果就对了
Cathelicidin messenger RNA was expressed and the defense in protein was made and you know all worked just fine
抗菌肽信使RNA得以表达，形成蛋白质防御，一切都很顺利
Notice that Cyp24 gene also gets expressed
注意到，这里还表达了Cyp24基因

That's the 24-hydroxylase
这是24-羟化酶
That's the enzyme that chews up 1,25D
是破坏1,25D的酶
So it's no longer active
让它不再有活性
So it acts just once, rifle shot and then it's done
只活动一次，用完了就完了
but then these guys asked once again and said what is the cell doing expressing the one alpha hydroxylase?
之后他们还问，细胞干什么表达1α-羟化酶
It must have been looking for 25D
必然是在找25D
So they said well, let's add 25D to the system instead of 1,25 and lo and behold, that work perfectly
于是他们加入25D而不是1,25D，结果非常完美
The 1,25D was synthesized into the system and the whole system played itself out
1,25D得以合成，整个系统运作良好
It's absolutely beautiful experiment
非常漂亮的实验
And in fact, they could do this with circulating levels of 25D
实际上，用循环水平的25D就行了
They're physiological whereas the 1,25 they had to add to the system was higher than you would achieve physiologically
他们加入到系统的1,25D显然比生理上得到的要高
So clearly, this is how the system was designed to be operating
显然，这就是系统的工作方式

视频及简介

维生素D，是一类脂溶性维生素，属类固醇化合物。在人类所需的维生素中，维生素D非常特殊，它是一种激素的前体，而且在阳光充足的情况下，人体自身可以合成。这一讲教授着重讲了维生素D同DNA作用，参与到蛋白质合成的原理，以及维生素D对癌症、糖尿病、骨质疏松、高血压等诸多疾病的预防及辅助治疗作用。