科学美国人60秒 SSS Genetics of longevity, diaper-free movement, possible plane problems from personal electronics（在线收听）

Welcome to the Scientific American Podcast for the seven days starting March 8th. I am Steve Mirsky. This week on the podcast, M.I.T. biologist Lenny Guarente talks about the genetics of longevity and what the findings mean for healthy lives in general. Cornell University anthropologist Meredith Small discusses some cross-cultural issues at the other end of the age spectrum in babies, and Carnegie Mellon electrical and computer engineer M. Granger Morgan tells us about a startling new study of personal electronic devices on airplanes. Plus, we'll test your knowledge of some recent science in the news.

First up, M.I.T.'s Lenny Guarente. He spent the last 15 years studying the genes that regulate ageing and he and David Sinclair wrote the cover story in the March issue of Scientific American about genes and ageing and the implications of his research. I called him at his office in Cambridge, Massachusetts.

Steve: Dr. Guarente, thanks for talking to us today.

Guarente: It's my pleasure.

Steve: You have the article, the cover article, in the March issue of Scientific American, "Unlocking the Secrets of Longevity Genes." Let's talk about the genetics of longevity. Conventional wisdom always had it that ageing was a function of normal maintenance mechanisms going awry as you got older.

Guarente: Well! I think there is some truth to that idea, but what one has to keep in mind is that there are times in which ageing is regulated and this was really first known from the time people started varying the diet in laboratory animals and they noticed that calorie restriction could make rodents live up to twice as long.

Steve: And we've seen calorie restriction also have a profound effect on lifespan in other organisms as well?

Guarente: That's right! I believe this is a universal in nature that low-calorie diets promote longevity. In humans we can at least say that some of the markers, the physiological markers for longevity, are affected by the diet. A study to look at lifespan, of course, are [is] difficult in very long terms, so there is no information yet on that, but there is every reason to think that the effect of calorie restriction will be universal. The important thing about it is to ask the question, how does it work? And that's where the genes come in.

Steve: Okay, so let's talk about that. What's the genetics that wind up coming into play with calorie restriction?

Guarente: Well! We encountered a gene in a study in yeast some 15 years ago called S-I-R 2 or SIR2, and what we found is that that gene was an anti-ageing gene, so the more active it was, the longer the lifespan. It turns out that this gene is universal, all critters have it, we have it and what we think the gene does is respond to the environment and in particular to food and exert[s] [an] effect on cells that will determine how long the organism as a whole will survive.

Steve: Okay, a lot of the calorie restriction conventional wisdom was that you slow down metabolism and you didn't have the waste products of metabolism, but you don't think that's what's happening.

Guarente: That's not true. Calorie restriction does not slow down metabolism. What it does is it alters the metabolic strategy and it alters it in a way that this gene, SIR2 and its cousins—there are seven of these genes in total in mammals—these genes can recognize that alteration in metabolism, and exert effects on cells that make them survive longer.

Steve: Can you talk a little bit about what SIR2 actually does?

Guarente: Well! We were really amazed to find that the SIR2 gene product, which is a protein, has an enzymatic activity that has never been observed before. It can modify a protein by removing acetyl groups, so, it's so called deacetylate. And there are other deacetylates that have been found, but what was unique about SIR2 deacetylate is that it requires a cofactor for its activity. The cofactor is a molecule called NAD, which is a small molecule itself involved in metabolism. So, it's that fact that SIR2 requires NAD, a metabolic conduit, and has an ability to modify protein that told us that it might be the connector, the nexus between metabolism and that is diet and regulation of cell biology. So, I think that the activity was really a critical discovery along the path of SIR2 biology.

Steve: By the way what does SIR2 stand for?

Guarente: SIR stands for silent information regulator and 2, it was the second gene in yeast of this type, so it's involved in yeast in a process that's called silencing.

Steve: And can you explain that real briefly?

Guarente: Silencing is the turning off of specific genes in the genome. SIR2 in yeast has the ability of turning off regions of the yeast genome and one of those regions in yeast is involved in dictating how long cells live.

Steve: So, what do you think the future can hold in terms of what we're going to do with this knowledge?

Guarente: Well! Let me talk about that for a minute. So, I think that if one understands the mechanism—the genes and how they work—then one has a path to developing drugs that could deliver the same benefits of calorie restriction without the difficulty of the diet itself and I think that's a goal. Now, that said, you might ask the question, why do we want to do that? And I think that the compelling reason for doing it is not to make people live longer. But the thing about calorie restriction [that] is not appreciated, is [that] in the rodents in which it's been studied, calorie restriction not only extends lifespan, but it prevents or mitigates many different diseases of ageing including cardiovascular disease, cancer, neurodegenerative disease, diabetes – the major diseases of ageing. So, it's my belief that if we could harness the benefits of calorie restriction in people, it wouldn't simply be an act of making people live longer, but it would provide a new strategy to attack the major diseases of ageing. I hope that the article conveyed how excited we the scientists who are doing this work are, the fact that there are these genes that nature has tailored to do this, that is to say, to convey information about the environment to setting the lifespan of the organism. I think it's a wonderful opportunity for us as scientists and as a society to really develop new strategies to look for cures or at least palliatives for human diseases.

Steve: Thank you very much, Dr. Guarente.

Guarente: Thank you.

Steve: There's a lot more on genes, ageing and health in Guarente and Sinclair's article called, "Unlocking the Secrets of Longevity Genes." It's in the March issue of Scientific American and is available free for a limited time at our Web site, www.sciam.com. And also check out Lenny Guarente's book about his work. It's called, Ageless Quest.

Now it's time to play TOTALL…….Y BOGUS. Here are four science stories, three are true. See if you know which one is TOTALL…….Y BOGUS.

Story number 1: Japanese researchers have developed a technique to extract the sweet-smelling substance vanillin from cow dung.

Story number2: Blondes are almost done having more fun. A World Health Organization study led researchers to conclude that there are fewer and fewer blondes, well, natural blondes, and that the last natural blonde will likely be born in Finland around the year 2202.

Story number 3: A cosmonaut wants to hit a golf ball from the International Space Station. The ball would zip around the earth for about four years until its orbit decayed and it burned up.

Story number 4: A study of Dutch men found that those who ate a lot of cocoa actually cut their risk of dying from cardiovascular disease in half.

We'll be back with the answer. But first, Cornell University anthropologist Meredith Small generated a great deal of buzz with a recent op-ed piece. I called Small at her home in Ithaca, New York.

Steve: Professor Small, thanks for being with us.

Small: It's great to be here, Steve.

Steve: So you had an op-ed piece in the New York Times so a few weeks ago that I remember reading and you got some interesting reaction to that, I understand. Tell us about the piece and the reaction you got.

Small: The Times came to me and asked me if I would write in a comment[ary] on its[a] growing movement in the United States that takes babies as soon as they are born and start putting them on the toilet instead of wearing diapers, and it's called the diaper-free movement. It has a Web site. It has, I don't know how many people doing this, and the idea is that you train your kids right away, never have to put them in any kind of diapers. So, I wrote the op-ed from an anthropologist’s point of view saying [that] it doesn't surprise me at all because if you look around in other cultures, they don't have diapers, they don't have cloth, they don't have disposable diapers and these kids are trained right away and by the time they can walk and talk, they know exactly where to go, to go to the bathroom. So, the article was published and to my great surprise, it caused a flurry of e-mails. It was the number one e-mailed article that week. It was one of the top e-mailed [articles], one of the month. It was just crazy and I got all kinds of e-mails from people and telephone calls and strangely enough, when I walked up to pick up my daughter at school, all these parents wanted to talk about it. The one that I found most interesting was a friend of mine, a guy, and he said, "When I went to a cocktail party on Friday, it's what everybody was talking about," and I started laughing.

Steve: Are you sure that they didn't think you were talking about the movement-free diaper?

Small: (laughs)

Steve: Okay, it's the diaper-free movement.

Small: That's right! (laughs)

Steve: Alright!

Small: So, it turns out it was a big discussion at the cocktail party and, I don't know, this seems to have hit the hearts of many people who are parents and nonparents: the idea of having little kids who are able to sleep through the night and not wear a diaper, get up in the morning, put them on the pot and then they can run around half naked the rest of the day.

Steve: And you came across this kind of interesting cross-cultural difference in the course of researching a general book on the subject?

Small: Yeah! For about the past almost 10 years, I've been working as an anthropologist on parenting in different cultures and I've written a couple of books, Our Babies, Ourselves, and Kids, and now I'm working on a parenting advice book. But I'm doing it from the voice of these other people and other cultures, so, I'm going to ask the same questions that you see in books like What to Expect When You're Expecting, and then I'm going to answer them from other cultures.

Steve: Thanks a lot, Meredith.

Small: You're very welcome.

Steve: Meredith Small's last book was called Kids: How Biology and Culture Shape the Way We Raise Our Children.

Now it's time to find out which story was TOTALL…….Y BOGUS. Let's review the four stories, three of which are real.

Story number 1: You can get perfume vanillin from cow dung.

Story number 2: The last blonde will be born in Finland in about 200 years.

Story number 3: A cosmonaut wants to whack a golf ball into orbit.

And story number 4: Dutch chocolate-eating men cut their cardiovascular disease deaths in half.

The first story is true. Japanese researchers can get vanillin from cow dung. Vanillin is a common ingredient in candles and shampoo.

The fourth story is true. Dutch men who ate a lot of cocoa cut their risk of dying from all diseases in half. You can read the details of that study on our Web site, www.sciam.com.

The third story is true. A cosmonaut does want to drive a golf ball from the space station. A Canadian golf club company would sponsor the stunt, but NASA would have to give the green light and some scientists are worried that the ball might actually hit something important like a satellite and put a hole in one, which means that the story about blondes going extinct is TOTALL…….Y BOGUS. Now, if you think you saw this story in the news recently, you did. A study on the evolution of blondes got some attention recently and some versions mentioned the "WHO Blonde Extinction Report," but that report was a hoax, perpetuated in 2002, according to the Web site museumofhoaxes.com. Yes, there is a Web site, museumofhoaxes.com, and yes there will be blondes for, well, presumably for a long, long time.

Next up, M. Granger Morgan, head of Carnegie Mellon University's Department of Engineering and Public Policy. He and three co-authors just published a study about possible problems from using cell phones and other electronic devices on airplanes. I called Morgan from a landline at his office in Pittsburgh.

Steve: Dr. Morgan, thanks for talking to us today.

Morgan: You're most welcome.

Steve: You have a study along with your co-authors in the issue of IEEE Spectrum that ran in March. As a nervous flyer to begin with, I wasn't particularly pleased with your results. So, you want to tell us a little bit about the study?

Morgan: Sure. Wireless technology is becoming ubiquitous and more and more of us are spending time on airplanes. And we began to wonder a few years ago whether the combination of those two might present some problems for avionics and navigation systems on airplanes. And as we began to look into it, we discovered that no one had actually ever measured the RF environment, that is, the radio emissions within the cabin of commercial airliners.

Steve: And that's due to all the electronic devices that people will typically use in a flight?

Morgan: Yeah! Computers and cell phones and game boards and all those sorts of things, and so, with the whole support from FAA and the several US Airlines and the TSA, we built a little box that looks just like an innocuous carry-on bag, but inside it is a spectrum analyzer that allows us to look at radio emissions in the cabin of the airplane. And so, we then flew it on 37 commercial flights, putting it under seats or in the overhead compartments just like any other luggage.

Steve: The results of that kind of monitoring are really startling.

Morgan: Yeah! Well! (laughs) We discovered that first of all, as you might suspect, a lot of people forget to turn off their cell phones and so you got regular little bleeps with their cell phones saying, "Here I am," or "Are you out there?". But then we also found regular use of cell phones, people making calls, including calls in flight protocol phases like during climb up and on final approach. That's troubling. We also, however, found emissions in the GPS band. Now, GPS is the Global Positioning System and it's increasingly being used for precision landing and other navigation purposes, and though we didn't study this, NASA has determined that there are at least some… there is at least one model of cell phone that can actually cause a GPS receiver to lose satellite block. If that happened in a foggy final approach, it could be really quite serious.

Steve: We should say that according to the study there are no accidents—commercial aircraft accidents—that can be directly traced to any kind of problem like this.

Morgan: Yes! And we also think that probably this is not at the moment a big risk, but on the other hand, as more and more people fly with wireless devices, it also says to us we need to start being careful. There are proposals afoot, for example, to start allowing cell phones on airplanes with a microcell on the aircraft. We think you shouldn't rush into that. We also think it would be a good idea if the FAA, the people who regulate airlines, and the FCC, the people who regulate radio emissions, would start cooperating on the standards. At the moment, standards set by the FCC aren't coordinated with the idea that a lot of these things might end up on airplanes. And finally, we think it would be good to start actually monitoring the environment in cabins, both to get a better sense than we've been able to produce of what the environment looks like, and also because if you ever do have an accident, if you don't have monitoring like that, you'd probably never figure out that it came from radio interference.

Steve: How can people be using their cell phones currently when you are warned or advised at any rate on every commercial flight to turn off your cell phone and not to use it in flight?

Morgan: Yeah! Well! It turns out a lot of people don't believe that that's a safety announcement. A lot of people think that this is the folks who put in the seat-back phones that are so expensive trying to enforce a monopoly. That's not the case. And you know, people know that occasionally our calls get made from the air and so they simply don't appreciate that this really is a significant safety issue and proceed to use their phones.

Steve: The article talks about one specific case of a DVD player and a GPS, a huge GPS error. You want to talk about that?

Morgan: Yeah! This is the one, where the 30-degree heading error?

Steve: Yes!

Morgan: And the flight crew went back and asked folks to turn off the device and the error went away and asked him to turn the device back on, something I think very probably couldn't do today, but did then and the error resumed. There have been a bunch of reports like this and there is actually a database maintained by NASA in which flight crews and others can report events. And we've done a fair amount of statistical analysis of that database trying to get a sense of how common these kinds of events are, and they are common enough to be troubling.

Steve: So for now, based on your study, you want the FAA and the FCC to get on the same page and what else?

Morgan: Yeah! Well! The other thing is that we would like some substantially more detailed analyses of what is going on in the cabins of airliners, and we would like folks to go slow on any proposals to introduce expanded use of wireless on aircraft until we know just exactly how big a problem we've got and what might be done to better deal with it.

Steve: Dr. Morgan, thank you very much.

Morgan: You are most welcome.

Steve: Morgan's article is currently available online at www.spectrum.ieee.org.

Well! That's it for this edition of the Scientific American podcast. Our e-mail address is [email protected]. That's [email protected]. And also remember that science news is updated daily on the Scientific American Web site, www.sciam.com. I am Steve Mirsky. Thanks for clicking on us.