Nature Podcast

This is a transcript of the 22nd January 2015 edition of the weekly Nature Podcast. Audio files for the current show and archive episodes can be accessed from the Nature Podcast index page (, which also contains details on how to subscribe to the Nature Podcast for FREE, and has troubleshooting top-tips. Send us your feedback to


Geoff Marsh: This week, the restorative power of the young blood.

Megan Scudellari: So almost everywhere they walked this young blood appears to have factors in it that heals and repairs organs that are ageing.

Kerri Smith: Plus increasing the safety of genetically modified organisms.

Elie Dolgin: This bug will only grow when you give it a non standard amino acid and in the wild it can't find it and so it won't grow.

Geoff Marsh: And decoding the solar system's early magnetism from meteorites. This is the Nature Podcast for the 22nd of January 2015. I'm Geoff Marsh.

Kerri Smith: And I'm Kerri Smith.


Geoff Marsh: In 1864, a French physiologist named Paul Bert stitched a pair of rats together. He wanted to show that these newly conjoined animals could form a shared circulatory system. I know it sounds pretty gross, but this technique called parabiosis is actually really useful and is still actually used today to study a number of things from cancer to immunity and a tantalizing result from a 1976 experiment in rats suggested that young blood pumped through an older sidekick might actually make the elder live longer. This effect on lifespan is controversial, but what's becoming clear is that young blood has some rejuvenating powers on various organs, most recently the brain. Neuroscientists at Stanford showed that blood plasma from young mice caused brain cells to grow in older mice. And actually now there's a human trial into the effects of young blood on Alzheimer's sufferers underway and the results are expected by the end of the year, don't worry nobody gets stitched to anybody else. Science writer, Megan Scudellari has written a feature about the uplifting effects of young blood and I gave her a call. Nature 517, 426–429 (22 January 2015)

Megan Scudellari: It's actually very simple. The researchers just make a thin cut along the backs of the mice or the rats and then sew that incision together and natural wound healing does the rest and the capillaries, this tiny little blood vessels connect through the skin and then through those capillaries the blood in the plasma can pass.

Geoff Marsh: Now these parabiosis experiments have led to major discoveries about immunity, hormones and cancer, but the recent hype has been around ageing, how has parabiosis been used to study ageing?

Megan Scudellari: Ageing, you know, is something that happens to a whole body. Your whole body at once ages, it's not like one organ starts to age and not the others and so they in the early 2000s at Stanford paired together old mice and young mice through this technique of parabiosis to see what will happen to their organs when the organs of the old mouse became awash in the blood of the young mouse.

Geoff Marsh: And the results of that study and in fact several studies like it seem to be suggesting that something in young blood has this rejuvenating effect on all these different organs of the body.

Megan Scudellari: It definitely seems like it. There are teams at Harvard and Stanford and Berkeley and they've all seen in different organs that young blood appears to activate the stem cells in the older mice and that results in a variety of rejuvenation across organs. They all appear to look younger and this is almost every organ they've looked at, in the heart, in the muscle, in the nervous system, in the spine, it can repair damaged spinal cords, in the brain it causes the growth of new brain cells. So almost everywhere they walked, this young blood appears to have factors in it that really through activating stem cells and causing the growth of new cells heals and repairs organs that are ageing.

Geoff Marsh: How do people take that this is acting on stem cells to reverse the ageing process?

Megan Scudellari: Yes, that was one of the first questions of the researchers doing this and so as soon as they saw this rejuvenation they went in and tried to isolate very specific factors out of the blood that were causing it. First they found out that if you take the blood cells out and just have the remaining liquid, that plasma is enough to also do the rejuvenation. So they started, you know, peeling through the plasma, trying to figure out what it was and they've identified a bunch of different factors. One of them is oxytocin, which is a hormone some of us know, it's involved in childbirth, induces labor in pregnant women, and it's also already an FDA approved drug which is promising. So that can, Oxytocin alone appears to regenerate muscles in older mice. Also at Harvard they identified this factor called Growth Differentiation Factor 11 that again on its own was sufficient to increase the strength and stamina of muscles to reverse DNA damage which we can think of is one of the causes of ageing. So it's most likely probably a combination of things in the blood, but slowly one by one they're figuring out what those things are.

Geoff Marsh: And we haven't honed in on what it is that had the regenerating effects on brain cells, but you mentioned in your feature that there's already human trial set up for Alzheimer's patients.

Megan Scudellari: Yeah, it's pretty amazing that so quickly a lot of this work has been done since, you know, between 2005 and now in the lab and already we've moved into human clinical trials, which is very fast to go from the laboratory into the clinic. And what's happening is that one of the experiments show that young blood causes this growth of new brain cells in older mice and Alzheimer's disease, we know, which is one of the diseases of ageing is characterized by the loss of neurons of these brain cells. So, they are hypothesizing that if we were to use young blood or in this case young plasma, just the plasma alone again not the red blood cells, that that might be enough to cause new brain cell growth and may be treat Alzheimer's. So, right now at Stanford they are getting blood and plasma from young men, actually men under 30 and then they're injecting that plasma into Alzheimer's patients. It's going to be right now just a small trial, 18 people to start to see if that young plasma will actually reduce the symptoms of Alzheimer's.

Geoff Marsh: Is anyone kind of worried about injecting, you know, different people's blood into older patients?

Megan Scudellari: What we do know from blood transfusions and plasma transfusions, that this is a very safe procedure, I mean, millions of people have received blood and plasma transfusions and just like those transfusions in the hospital, they're being very careful to match the blood and their plasma to the right patients. What scientists are, some have raised few concerns about is that if that if say we started using young blood regularly to try to treat some of the diseases of ageing and maybe not just Alzheimer's, maybe other types of dementia, maybe heart disease, since we know it works by activating stem cells, some folks are wary and want to do a lot more research to make sure that the cause of activation of stem cells over time, wouldn't result in too many cells growing which is the hallmark of cancer when your cells grow out of control.

Geoff Marsh: Over the next 10 years, can you imagine the younger generations helping out their grandparents by giving them some of their blood?

Megan Scudellari: I could, I don't know if it can happen over the next decade, but luckily blood is not hard to come by, we can donate it easily and our body makes more for us. So, if we really show in humans that young blood or plasma can be helpful, can be a drug or treatment for the disease of ageing, it will not be very hard to gather and use it even within one's own family, you know, maybe bank some blood of your kids or your grand kids in case you need it.

Geoff Marsh: That was Megan Scudellari. Her feature is at

Kerri Smith: In just a moment, we'll be talking ancient scrolls and a lost and found spacecraft with Richard van Noorden, but slipping in before that reporter Elie Dolgin visits a genetics lab in Boston to meet some unnatural creatures. Nature (2015)

Elie Dolgin: Dan Mandell reaches into the incubator and pulls out a Petri plate of E. coli. They look like any old bacteria, just a mass of little white spots, but these microbes are special. Their lives depend on a protein building block, an amino acid not found anywhere in nature.

Daniel Mandell: So, this synthetic amino acid to the best of our knowledge doesn't resemble anything that is just in nature and you can see that in the presence of the synthetic amino acid it grows fine, but not at all in the absence.

Elie Dolgin: It's the perfect pet for a control freak. Keep it supplied with its synthetic amino acid and it's happy, without that it can't survive.

Daniel Mandell: And so if this stream were to escape from the lab, it wouldn't grow.

Elie Dolgin: These bacteria at Harvard Medical School could hold the key to one of the biggest challenges in synthetic biology. It would be bad news if genetically modified organisms could spread into the environment and contaminate wild populations. The E. coli in this Harvard Lab have been designed to prevent just that. It's a culmination of decade of work of famed Harvard geneticists, George Church and his former postdoc Farren Isaacs. First the researchers devised a way to repurpose all the TAG triplets in the genetic code. These usually signal for protein production to stop but Church and Isaacs swapped all the TAGs with TAA another stop codon that frees up the TAG codon so that the researchers can assign it a new function. In this case, they made TAG into a dedicated code for a synthetic amino acid and then incorporated this codon into the recipe for various essential proteins. Church explained to me how his operations will help limit the spread of GMOs.

George Church: So this organism has one or more proteins that are essential to the life of the organism that are dependent upon those synthetic amino acids which is not available in the wild and when you don't provide that amino acid, other amino acids cannot replace it.

Elie Dolgin: So the bug will basically only grow when you give it this non standard amino acid and if it finds itself out in the wild, where it doesn't exist it's toast?

George Church: Right this bug will only grow when you give it a non standard amino acid and in the wild it can't find it, it can't scrounge it out from other dying organisms and so it won't grow.

Elie Dolgin: One problem is that genetically modified organisms getting out and escaping into the wild. Another problem is it actually contaminating natural organisms through some kind of gene transfer or what not, do we see that in the laboratory experiments that you've done with your bug?

George Church: Any gene that we make, if that gene gets into another organism, it will be a read as a stop, and even it was read as anything other than a stop, it won't have the right amino acid to have the gene function, so it's got a double barrier to functioning outside of industrially useful organism.

Elie Dolgin: I think when a lot of people hear the word, genetically modified organisms, they think of GM Crops that will be planted in the wild and those worries about those spreading and contaminating wild populations. In theory could this strategy be used to limit the growth of these kind of plants to just the field where we want them?

George Church: You know I think that one of the suggestions or complaints about GM crops is the uncertainty about them spreading and this directly addresses, you know I'm not predicting whether this is going to satisfy everybody but it certainly attempts to address some of the concerns.

Elie Dolgin: Beyond agriculture, the new biocontainment strategy could be useful in medicine, environmental cleanup and the energy sector. Farren Isaacs, who now runs his own lab at Yale University, explains.

Farren Isaacs: It's gonna be a very important technology for example biofuels or not thinking about deploying engineered GMOs into environmental settings to counter challenges in bioremediation, toxic buildup as well as looking at opportunities in medicine using these engineered organisms, for example as probiotics that can really alter the composition of the microbial gut. So thinking now about how we're going to be able to do that really is rooted in establishing safety and security from the get-go to really enable more broad and open use of engineered organisms.

Elie Dolgin: What we've got then is a microbe that could be engineered for these various applications and one that it has its own genetic safeguards built-in and that says Todd Kuiken, a policy researcher at the Wilson Center in Washington D.C. that is unlike any GMO in the world today.

Todd Kuiken: What we're now starting to talk about is really completely synthetic organisms that are going to look nothing like what a natural sort of comparative one that's put out into the environment. So what that organism is treated as under different regulatory statutes, I think, is going to be an interesting question.

Elie Dolgin: One thing is for certain though life as we know it just got a little less like we know it. For the Nature Podcast, I'm Elie Dolgin in Boston.


Geoff Marsh: But Geoff wait, what can meteorites tell us about the early solar system's magnetic field, I hear you ask don't worry that's coming up after these micro stories from the world of research with Noah Baker.Jingle

Noah Baker: Flex your wrists and you'll feel your arm muscles contract. Muscle bundles that can do the same thing have been grown in a lab. This is the first 3-D model of human muscle tissue. A US team took living human muscle cells and grew them using a scaffold. The muscles could spontaneously twitch. When prodded with electrical pulses similar to nerve signals the muscles contracted. The tissues also respond to drugs like steroids meaning that the set up could be used to test other drugs for muscle disorders. That's in the Journal E Life. Nature 517, 414 (22 January 2015)The increasing price of gold is threatening tropical forests. Gold prices have risen steadily over the last decade and it's become worthwhile for mining companies to extract it from more remote places. A ten-year study of forests in South America finds that almost 2000 square kilometers of forest was cleared for gold mining, that's an area the size of London, England or Toronto, Canada, worse, these areas often coincide with biodiversity hotspots and only a tiny portion is replanted. It's not a lot of land compared to the clearing for agriculture say, but it's accelerating. Find the study in Environmental Research Letters. Nature 517, 415 (22 January 2015)


Kerri Smith: The early solar system was a turbulent place. Lots of matter bashed around and formed planets, as well as smaller bodies like dwarf planets and asteroids. Tiny chunks of these bodies have since made their way to earth, where we know them as meteorites. These meteorites are like cosmic hard drives, within them tiny gem like shards of metal called pallasites can carry information about the magnetic history of the parent bodies they came from, data that was saved four and a half billion years ago. James Bryson at the University of Cambridge spoke to reporter, Lizzie Gibney about what these ancient rocks can teach us about the early solar system and how the asteroids and dwarf planets they came from might be much more earth like than we believed. Nature 517, 472–475 (22 January 2015)

Elizabeth Gibney: What did we already know about the bodies where these meteorites seem to have come from?

James Bryson: So, we know that they're in the asteroid belt at the present day most of them and we know a certain amount about their composition and their structure from looking at their geochemistry, but principally in my research what people in the last 10 years have been looking at is the magnetism that these meteorites carry and what that means in term of the large scale structures of these planets.

Elizabeth Gibney: So, how is it that these meteorites actually record something about their parent body's magnetic field?

James Bryson: So, these meteorites, they're composed of the rocky part and the metal part and in the metal part are these very small scale just a couple of hundred nanometer islands of a very good magnetic recorder, similar to what you see in your computer or phone in a hard drive. So in hard drives, you've got these are the small magnetic, very stable particles that record whatever data you're saving and the islands within the metal parts on meteorites are actually very similar and they record these magnetic fields billions of years ago and because of their stability, they've been able to preserve that to the present day which allowed us to investigate what happened billions of years ago in the lab through measurement.

Elizabeth Gibney: And, what do these pallasites actually look like, I understand they're quite stunning?

James Bryson: Yeah, they have gem quality olivine crystals that are about a centimetre big and they're embedded in these continuous iron matrix and you have these big slabs of these meteorites that maybe a meter across they contain hundreds of thousands of these crystals in this continuous metal that runs all the way through.

Elizabeth Gibney: And so from looking at these meteorites in particular you studied, what were you able to tell about the magnetic history of these meteorites and where they came from?

James Bryson: So we were able to tell that they must have recorded a very late field in the planet history, so most previous studies have found early fields and people have kind of suggested that these fields can't really be created after 10 million years after the solar system was formed, but we're seeing field created hundreds of millions of years later and the only way that we can explain is through a different type of motion in the core of this planet or asteroid which hasn't really been considered on bodies of this size before.

Elizabeth Gibney: So, how did we previously think that they would've created their magnetic fields and how is that changing now with your research?

James Bryson: So, previously people thought that the magnetic fields could only be generated through the motion in the core of these asteroids to thermal effects, so if there's hot liquid it would move up and there is cold liquid it's moving down and this resulting motion creates a magnetic field, but that's not the case on the earth the present day, it's actually due to the crystallization and growth of the inner core in our earth in the earth, which is causing the convection magnetic fields and what I've showed in my research is that exactly the same process happened billions of years ago on small planets. And the important point is that this convection is much more efficient than thermal conduction, so it could have lasted for much longer and generated more intense magnetic field.

Elizabeth Gibney: If these fields would last a lot longer and these were happening a lot later after the initial formation of the solar system, does that mean that there would have been a whole period then when lots of these little planets would have been magnetically active?

James Bryson: I think so, that's one of the main points I'm trying to get across in my research but given the efficiency of this mechanism at creating magnetic field, it was probably very widespread among small bodies, so asteroids that solidified in this manner.

Elizabeth Gibney: So ones that we've now we have heard off, Ceres or Vesta or Pluto in fact as a dwarf planet, would they all have had magnetic fields, do we think?

James Bryson: There's definitely evidence of Vesta creating magnetic fields, we have some meteorites from Vesta and it looks like it was magnetically active, so that definitely could have generated in the same way. Recent suggestions have also said that the moon probably created a magnetic field in the same way a very long lived late stage magnetic activity on the moon. Whether Pluto has the core has never been observed with the New Horizons mission that's about to fly past it we might be able to look at its shape and say whether it has a core, because if you've got a core, you normally have a very spherical planet, so we might be able to say some stuff about Pluto's interior just some images that New Horizons Machine can get as it passes by it.

Elizabeth Gibney: And if protoplanets probably had magnetic fields and had cores does that make them all that different then from planets, they essentially seem to have a lot of the same characteristics?

James Bryson: Not really no, they appear to be or the evidence is gathering that suggests that they are, to many intents and purposes, just small versions of earth and other rocky bodies which is really interesting because they are so small, they're cooled very quickly so they're essentially sped up small versions of earth or the moon which allows us to look at the whole history of the thermal activity on these planets. So, one of the aspects of my research is we're able to look at what happens as the core completely solidifies which obviously hasn't happened on earth till the present day. We're able to predict the kind of behaviour we'd expect to see when the earth's core does completely solidify in billions of year's time.

Elizabeth Gibney: So like little microcosms of our own future perhaps.

James Bryson: Exactly yeah.

Geoff Marsh: That was James Bryson talking to Lizzie Gibney, fascinating discussion. And as you maybe think how much Kerri reminds me of a dwarf planet?

Kerri Smith: Yeah, well your core looks to be molten.

Geoff Marsh: Well, that explains my magnetism.

Kerri Smith: Get back in your orbit. You're falling right off your axis there, aren't you?

Geoff Marsh: That was below the asteroid belt.

Kerri Smith: If you don't come up with some more good jokes, you're going to so an exo-presenter of this show.

Geoff Marsh: Got any good ones, share them with us on Twitter @NaturePodcast. News time now and joining me in the studio is Nature reporter Richard van Noorden. Hi Richard.

Richard van Noorden: Hello Geoff.

Geoff Marsh: So today, we are first of all going to discuss some very old Roman papyri that have now been able to read, what's this?

Richard van Noorden: When Mount Vesuvius famously erupted in 79 AD, it destroyed everybody nearby in Pompeii and Herculaneum but in 1873, about 250 years ago, we uncovered an entire library of scrolls that had been carbonized by the volcano, turned to a kind of black charcoaly log and twisted up, closed impossible to decipher and for the next 200 years, people tried to unroll them, cut them up, use a machine to read what was written and they had some success, but about half of this library remains unreadable. Nature

Geoff Marsh: So if unrolling these scrolls is so impossible how have the scientists cracked it?

Richard van Noorden: They've done it with x-rays and it sounds simple in a way, you think well when someone takes an x-ray of my body and shows up my skeleton well that's how x-rays work, isn't it? Unfortunately the ink in the scrolls which is carbon based absorbs x-rays in exactly the same way as the papyrus on which the ink sits so that didn't work, when scientists tried that six years ago. But today they say they tried another technique using x-rays called x-ray phase contrast tomography. So inside these scrolls, there's hundreds of rolls of skewed twisted papyrus and the letters are raised about 0.1 of a millimetre above the papyrus and it's that, that we're detecting when we shoot the x-rays through.

Geoff Marsh: Did they work this technique on just one scroll?

Richard van Noorden: So, they put one scroll into a synchrotron in Grenoble and have just deciphered a few letters, a whole Greek alphabet in fact for what's written inside, which is amazing, when you consider they will never be able to unroll this papyrus.

Geoff Marsh: So, do we now have a clear understanding of what the papyrus actually said at this point?

Richard van Noorden: Well, we can decipher the handwriting apparently and we know that the letters are the same hands as a scribe that wrote some of the other texts that have been unrolled and that means it's likely based on the other texts that this papyrus contains writing by philosopher called Philodemus, who lived in the first century B.C. about the same time as these papyrus actually date from.

Geoff Marsh: Why did they leave it at just a few letters, is the assumption that we can read the whole papyrus?

Richard van Noorden: It's very very slow, they just got some beam time at the synchrotron which they needed for the x-rays and just to decipher these mangled letters took a lot of work and it was completely manual. Now what they want to do is get a computer program to be able to speed this up, may be digitize all of these images, maybe put them online and crowd-source the reading of each letter. There are thousands of letters in each scroll, each scroll would unroll to about 15 metres long, so you've got a lot to read and if they can speed all that up, then we can have hopes of reading much of this scroll and all the other scrolls.

Geoff Marsh: Okay. Well we'll all be eagerly waiting to hear what secrets those scrolls have to offer. Next up, there's been argument about when to officially start what geologists are calling the anthropocene. Nature

Richard van Noorden: The idea is that we are in a new geological epoch when humans influence the geological structure of our planet and the term that's been coined for that is the Anthropocene. Geologists are now arguing should we really call a new epoch an Anthropocene, anyway when we start this era from. Now a working paper last week from a group of international scientists that's thrown their weight behind the idea that the first atomic bomb blast in 1945 should be the start of a new unit of geologic time but some people don't agree with them.

Geoff Marsh: What other competing candidates are there for a date or month beginning of the Anthropocene?

Richard van Noorden: We have to think of future geologists digging up layers of earth and seeing a marked change and describing that to human influence. So another idea is perhaps the industrial revolution, one further idea is perhaps the transition between a deposit that's completely natural and one that's been altered by humans like a layer of pottery filled debris in a plowed field and of course that layer would be different around the world but that's going thousands of years back, so should it be thousands of years ago or then 19th century or perhaps as recently as the atomic bomb. Because the people that put this idea forward are lead by Jan Zalasiewicz at the University of Leicester who is the lead author of this paper. This looks like a very influential suggestion that's going to go forward to The International Commission on Stratigraphy which has to set whether they're going to announce a new geologic time unit. Now none of this settled and to be honest this process of defining new epochs normally happens at a glacial pace it can take decades. So they're really hurrying forward on this, but we won't know anything until 2016 when a subcommittee on Quaternary Stratigraphy will formally recommend this and then we won't know for a few years after that but this is actually a very, very fast discussion for geologists, they're used to waiting decades to define new epochs.

Geoff Marsh: And once they do define this new epoch if you'll excuse the pun will it then it be set in stone.

Richard van Noorden: Once the International Commission of Stratigraphy says it, it is law, that body has the authority so perhaps by 2020 this is going to be in text books

Geoff Marsh: Okay, and finally we got a quite happy story then about a British lander that we lost contact within 2003 that has been papped on Mars. Nature

Richard van Noorden: Listeners might remember Beagle 2, the shoestring budget craft that Britain launched and on Christmas day it was supposed to hit the Martian surface but it disappeared. Well it is there, it did land successfully, it was spotted by NASA's Mars Reconnaissance orbiter in a rather blurry picture, but it does seem to show that the craft landed but failed to open its antenna and phone home, which is exciting for the people in the mission who thought they had failed although perhaps bitter sweet since nothing can be got from the mission.

Geoff Marsh: So we're confident that this blurry picture is indeed Beagle 2.

Richard van Noorden: Yeah, the mission manager Mark Sims says he's very confident that the picture is Beagle 2, it's consistent with a shape of its open some but not all of its solar panels, and we're talking about 2-metre wide craft on Mars which is why it's taken so long for orbiting cameras to spot it.

Geoff Marsh: Almost 11 years.

Richard van Noorden: Exactly and it was only really with the Mars Reconnaissance orbiter's high rise camera which has a pixel resolution of about 25 centimetres came online about a decade ago was there any chance of finding it. Sims said there are an awful lot of rocks on Mars the size of Beagle 2 so it was a needle in a haystack job.

Geoff Marsh: Have we learnt any lessons from this fuzzy pick?

Richard van Noorden: Well good question because of course the mission failed. Now Sims says well I know that I am in this mission again, I would use crushable airbags that deflates on landing because he thought the airbags might have gone all the way. He would have put the antenna on the outside, so the mission could've have phoned home but most of all I think it's a victory for British science because the whole project was panned by the European Space Agency. He wrote a report in 2004 absolutely slating the enthusiasm and management of the project. Listeners might remember that Colin Pillinger this very charismatic guy was leading the project and sadly he died in May 2014. So, he never lived to see this news. But you know his enthusiasm and eccentricity was seen by some as amateurism but in fact the mission worked very well. It was probably just bad luck that the craft hit a rock or somehow just didn't quite succeed that final hurdle but it got almost all the way there. So, it is bitter sweet as I say, but it is probably vindication for Pillinger and his work.

Geoff Marsh: Okay thanks Richard. If you'd like to read those stories in full. Why not mosey on over to our news site,

Kerri Smith: And there you have it, another Nature Podcast comes to a close. Thanks for joining us and we'll see you next week. I'm Kerri Smith.

Geoff Marsh: And I'm Geoff Marsh.