Here's a question for you: how many different scents do you think you can smell, and maybe even identify with accuracy?
请先思考一个问题：你认为自己可以分别多少种不同的气味？或者精确地识别多少种？
100? 300? 1,000? One study estimates that humans can detect up to one trillion different odors.
100种？300种？还是1000种？一项研究估计人类可以识别多达一万亿种不同的味道。
A trillion. It's hard to imagine, but your nose has the molecular machinery to make it happen.
一万亿种。这很难想象，但是你的鼻子的分子机制让它成为了现实。
Olfactory receptors -- tiny scent detectors -- are packed into your nose,
嗅觉受体，你的鼻子里充满了微小的气味检测器，
each one patiently waiting to be activated by the odor, or ligand, that it's been assigned to detect.
每一个都耐心地等待被气味激活，换句话说，被指定来探测配位体。
It turns out we humans, like all vertebrates, have lots of olfactory receptors.
其实我们人类和所有的脊椎动物一样，有许许多多的气味受体。
In fact, more of our DNA is devoted to genes for different olfactory receptors than for any other type of protein.
事实上，我们的DNA中被用来表达气味受体的基因多于任何一种用于制造其它蛋白质的基因。
Why is that? Could olfactory receptors be doing something else in addition to allowing us to smell?
为什么会这样？气味受体除了给我们嗅觉，还有其它的功能吗？
In 1991, Linda Buck and Richard Axel uncovered the molecular identity of olfactory receptors
在1991年，琳达·巴克和理查德·阿克塞尔揭示了气味受体的分子识别机制。
work which ultimately led to a Nobel Prize.
这一成果最终获得了诺贝尔奖。
At the time, we all assumed that these receptors were only found in the nose.
在那时，我们都设想这些气味受体都只能在鼻子里被发现。
However, about a year or so later, a report emerged of an olfactory receptor expressed in a tissue other than the nose.
然而，大约一年以后，一份报告指出气味受体也存在于不是鼻子的另一组织里。
And then another such report emerged, and another.
然后另一份这样的报告也出现了，接着又是一份。
We now know that these receptors are found all over the body,
现在我们知道在我们身体的每一处都可以找到这些气味受体，
including in some pretty unexpected places -- in muscle, in kidneys, lungs and blood vessels.
包括一些意想不到的部位--肌肉组织，肾脏，肺部以及血管。
But what are they doing there? Well, we know that olfactory receptors act as sensitive chemical sensors in the nose
但是它们为什么存在于那些部位？我们知道气味受体在鼻子中扮演一种敏感的化学传感器的角色，
that's how they mediate our sense of smell.
这是它们传出嗅觉（信号）的方法。
It turns out they also act as sensitive chemical sensors in many other parts of the body.
其实它们也在我们身体的许多其它部位扮演灵敏的化学传感器的角色。
Now, I'm not saying that your liver can detect the aroma of your morning coffee as you walk into the kitchen.
当然，我不是在说你的肝脏可以在你走进厨房的时候闻出早晨的咖啡香气。
Rather, after you drink your morning coffee,
而是当你喝过早餐咖啡后，
your liver might use an olfactory receptor to chemically detect the change in concentration of a chemical floating through your bloodstream.
你的肝脏可能使用一个气味受体通过化学机制检查在你血液中流动的化学物质浓度的变化。
Many cell types and tissues in the body use chemical sensors, or chemosensors,
身体中的许多细胞种类和身体组织使用化学感应器，
to keep track of the concentration of hormones, metabolites and other molecules,
来追踪激素和代谢物以及其它分子的浓度，
and some of these chemosensors are olfactory receptors.
这些化学感应器中的一部分就是气味受体。
If you are a pancreas or a kidney
如果你是一个胰腺或者肾脏，
and you need a specialized chemical sensor that will allow you to keep track of a specific molecule, why reinvent the wheel?
而当你需要一个特殊的可以帮助你追踪某个特定分子的化学传感器的时候，为什么要白费力气做重复工作呢？
One of the first examples of an olfactory receptor found outside the nose showed that human sperm express an olfactory receptor,
最早在鼻子以外发现气味受体的其中一个例子，告诉我们人类的精子就恰恰配备了气味受体，拥有了这个受体，
and that sperm with this receptor will seek out the chemical that the receptor responds to -- the receptor's ligand.
精子可以寻找一种化学物质，即令这种受体做出反应的化学物质，也就是受体的配位体。
That is, the sperm will swim toward the ligand. This has intriguing implications.
也就是说，精子会游向这个配位体。这里有一个有趣的暗示。
Are sperm aided in finding the egg by sniffing out the area with the highest ligand concentration?
精子寻找卵子的过程当中是否是靠嗅探拥有最高配位体浓度的区域呢？

I like this example because it clearly demonstrates that an olfactory receptor's primary job is to be a chemical sensor,
我喜欢这个例子，因为它清晰地说明了一个气味受体的首要工作是做一个化学传感器，
but depending on the context, it can influence how you perceive a smell,
但是结合情境，它还可以影响你感受气味，
or in which direction sperm will swim, and as it turns out, a huge variety of other processes.
或者引导精子游向的方向，而且事实上还拥有各种各样的功能。
Olfactory receptors have been implicated in muscle cell migration,
气味受体帮助肌肉细胞的移动，
in helping the lung to sense and respond to inhaled chemicals, and in wound healing.
帮助肺部感应和回应吸入的化学物质，以及手部创伤的痊愈。
Similarly, taste receptors once thought to be found only in the tongue,
同样的，味觉受体曾经被认为只存在与舌头中，
are now known to be expressed in cells and tissues throughout the body.
现在我们知道它们存在于身体各处的细胞和组织中。
Even more surprisingly, a recent study found that the light receptors in our eyes also play a role in our blood vessels.
更令人惊奇的是，最近的一个研究表明，眼睛中的光受体在血管中居然也能发挥某种功能。
In my lab, we work on trying to understand the roles of olfactory receptors and taste receptors in the context of the kidney.
在我的实验室里，我们致力于尝试推断气味受体和味觉受体在肾脏中的功能。
The kidney is a central control center for homeostasis.
肾脏在体内平衡中扮演着核心角色。
And to us, it makes sense that a homeostatic control center would be a logical place to employ chemical sensors.
对于我们来说，作为体内平衡的核心控制器的部位，拥有化学传感器是完全合乎情理的。
We've identified a number of different olfactory and taste receptors in the kidney, one of which, olfactory receptor 78,
我们已经在肾脏中识别出许多不同的气味受体和味觉受体，气味受体78号就是其中之一，
is known to be expressed in cells and tissues that are important in the regulation of blood pressure.
据了解它已经存在于重要的控制血压的细胞和组织中。
When this receptor is deleted in mice, their blood pressure is low.
当我们在老鼠体内清除这种受体时，它们的血压会变低。
Surprisingly, this receptor was found to respond to chemicals called short-chain fatty acids
令人惊奇的是，这些受体曾被发现是用来回应一种被称作短链脂肪酸的化学物质，
that are produced by the bacteria that reside in your gut -- your gut microbiota.
这种物质由肠道中的一种细菌产生--具体地说是肠道菌群。
After being produced by your gut microbiota,
这些化学物质在被肠道菌群产生后，
these chemicals are absorbed into your bloodstream where they can then interact with receptors like olfactory receptor 78,
直接被体内循环的血液吸收，在血液里它们与受体发生反应，比如气味受体78号，
meaning that the changes in metabolism of your gut microbiota may influence your blood pressure.
也就是说，你的肠道菌群的新陈代谢的变化可能会影响你的血压。
Although we've identified a number of different olfactory and taste receptors in the kidney,
尽管我们已经在肾脏中识别出了许多不同的气味受体和味觉受体，
we've only just begun to tease out their different functions and to figure out which chemicals each of them responds to.
我们还是刚开始梳理它们不同的功能，以及它们分别会对哪些化学物质做出回应。
Similar investigations lie ahead for many other organs and tissues -- only a small minority of receptors has been studied to date.
类似的针对其它器官和组织的调查研究即将开展--迄今为止人们仅仅研究了很小一部分受体。
This is exciting stuff. It's revolutionizing our understanding of the scope of influence for one of the five senses.
这是一件令人激动的事。它对我们理解人类五感之一的作用范围有着革命性的影响。
And it has the potential to change our understanding of some aspects of human physiology.
而且它具有巨大的潜质来改变我们对于人类生理机能的某些方面的理解。
It's still early, but I think we've picked up on the scent of something we're following. Thank you.
尽管这项研究尚未成熟，但是我相信我们嗅到了一种寻觅已久的气味。谢谢大家。