Speaker 1: Welcome to Stuff from the Science Lab from how stuff
Speaker 1: works dot com. Hey guys, and welcome to the podcast.
Speaker 1: This is Alison madam Ilk the science that are how
Speaker 1: stuff works dot com. And this is Robert Lamb, science
Speaker 1: writer at how stuff works dot com. Today we're talking
Speaker 1: about the process of regeneration. And this topic comes to
Speaker 1: you compliments of one Rob Chef, my colleague of ours
Speaker 1: at how stuff works, and Rob send us a story
Speaker 1: about a jellyfish, particular kind of jellyfish that can be
Speaker 1: immortal essentially. Yeah, it's like that old saying immortality was
Speaker 1: wasted on the jellyfish. Yeah, yeah, that old saying. Yeah. So,
Speaker 1: the definition of regeneration is um the ability to regrow
Speaker 1: lost tissue or destroyed organs or parts, and can be
Speaker 1: routine or it can be sustained after injury. And the
Speaker 1: regeneration is truly an amazing process. I mean, lest you
Speaker 1: not regarded such, let me just regalue with a quote.
Speaker 1: If there were no regeneration, there could be no life.
Speaker 1: If everything regenerated, then there could be no death. And
Speaker 1: that's the quote from the developmental biologist Richard Jay goss Um.
Speaker 1: And goss was a pioneer in the field of developmental
Speaker 1: biology and regeneration. Gossa taught up Brown for decades until
Speaker 1: his death ironically from cancer actually, and a lot of
Speaker 1: cellular and tissue growth. So that's pretty interesting. And Goss
Speaker 1: was actually interested in antler regeneration and he published a
Speaker 1: book called Deer Antlers in I was harping on this earlier,
Speaker 1: but it's like, this is the guy, this guy's life work,
Speaker 1: and he's just so passionate about and he just calls
Speaker 1: the book dear Antlers just dear Antlers. Just sometimes the
Speaker 1: topic speaks for itself, Robert, but not the complete Dear
Speaker 1: Antlers or amazing or my life with Dear Antlers something.
Speaker 1: I don't know. It just seems like a very gland title. Well,
Speaker 1: Gas was a scientist, perhaps he felt no need for embellishment.
Speaker 1: Unless the cover was a picture of himself with deer antlers,
Speaker 1: then I would forgive the title. So anyway, Goss was
Speaker 1: one of the main men in a pioneering regeneration um.
Speaker 1: But there are some other pioneers in the field as well. Yeah,
Speaker 1: I mean this is uh, the idea of regeneration is
Speaker 1: is not know people have been noticing this for a
Speaker 1: while Aristotle was writing about it, and if you go
Speaker 1: back to the Greek myths, you might remember a certain
Speaker 1: titan by the name of Prometheus, the firebringer um. And
Speaker 1: his punishment UM was that he was chained to a
Speaker 1: big rock and eagle would swoop down, eat his liver,
Speaker 1: fly off, and then what happens, liver grows right back.
Speaker 1: It's one of those eternal punishment type deals, but with
Speaker 1: the bonus of livery generation um. And then also in greeknests,
Speaker 1: you have the hydra, which is the multi headed serpent,
Speaker 1: and every time you cut off one of its heads,
Speaker 1: what happens, two of them grow back. That's correct, to
Speaker 1: grow back in its place, um. And Hercules killed the
Speaker 1: hydra correct, yeah, because he would, if I remember it correctly,
Speaker 1: he had he realized, Hey, I just need to bring
Speaker 1: a sword and a worch, and so every time he
Speaker 1: cut off a head, he'd he'd cauterized the wound, burn it,
Speaker 1: you know, shut. And so after a while you just
Speaker 1: had this monster that was nothing but stumps, and I
Speaker 1: guess it was dead. But it's a mythological creature, so
Speaker 1: who knows. Who knows how these things work? As it
Speaker 1: turns out, though, hydra eventually became a real thing, or
Speaker 1: rather we applied that name to a living creature. Yeah,
Speaker 1: it's a little tensicle microscopic animal. Yeah, I remember looking
Speaker 1: at him in science class. This was discovered by Abraham
Speaker 1: trimbley Um in seventeen forty and he picked the name
Speaker 1: for it because every time one of the heads is
Speaker 1: cut off, you can grow a new one, and as
Speaker 1: it turns out, the human liver can also regenerate itself.
Speaker 1: But that was an old Abraham different Abraham was main
Speaker 1: really interested in the hydas. Then seventeen twelve you had
Speaker 1: another guy that was really interested in this. So with
Speaker 1: the last name renew and I can't say the rest
Speaker 1: of it. You're gonna have to jump in with your French. Yeah,
Speaker 1: I believe his name is a renee Antoine Fair. So
Speaker 1: he made the first scientific observations of regeneration in crayfish,
Speaker 1: which I was kind of surprised to hear that they
Speaker 1: could regenerate because my wife's um of Cajun descent, so
Speaker 1: I've never seen a crayfish have really a good chance
Speaker 1: at surviving anything, just right in the pot. Yeah, So
Speaker 1: back then a regeneration actually caught on with the public,
Speaker 1: and according to Bruce Carlson, who published a textbook on
Speaker 1: regenerative biology, the public just you know, went wild for
Speaker 1: this concept. And so all of a sudden you have
Speaker 1: members of the French nobility wandering out into their gardens
Speaker 1: and chopping the heads off snails just to see the
Speaker 1: poor snails grow new one. And I'm glad that's where
Speaker 1: that story went, because when you first told me about it,
Speaker 1: I had this vision of, um, you know, a French
Speaker 1: noble has been getting all excited about regeneration, just hacking
Speaker 1: off loombs, willy nilly, you know. Yeah, the French evidently
Speaker 1: have a propensity for hacking off stuff, the poor snails.
Speaker 1: So there are other examples of limb regeneration among animals. There's,
Speaker 1: of course, the aforementioned hydra, which is that you know,
Speaker 1: small to of their freshwater polyp, and the crayfish, which
Speaker 1: we just talked about. There's the starfish. Do you remember
Speaker 1: that scene in life that we just read about, Yeah,
Speaker 1: where the crab snatches one of the limbs away. Yeah,
Speaker 1: the starfish is just sitting there and minding its own
Speaker 1: business and along comes this kid king crab. Don't don't,
Speaker 1: don't do, and he just wrenches off the appendage. Well
Speaker 1: you should. I mean, he's got he's got plenty to spare,
Speaker 1: so I might as well grab one. Yeah, especially since
Speaker 1: the starfish can can regrow them. Yeah, and this is um,
Speaker 1: you can. You can kind of hack a starfish to
Speaker 1: pieces as I recall, and each one will become a
Speaker 1: new starfish pretty much. Did you do this in science class? Um? No,
Speaker 1: but I remember hearing about it. We didn't have access
Speaker 1: to starfish. But it's just like the SORCER's a press,
Speaker 1: you know, SORCER's apprentice. Tell me Walt Disney Fantasia, Mickey
Speaker 1: Mouse in a wizard costume. Mickey Mouse is practicing your generation. No,
Speaker 1: he's practicing sorcery. But he has a there's like a
Speaker 1: broom that gets chopped to pieces. Then all the little
Speaker 1: they've turned all these little brooms and start marching everywhere. Yeah, yeah, yeah,
Speaker 1: I do you remember that? Now? That's magical regeneration. That's
Speaker 1: a whole different can of worms. Speaking of worms, yeah,
Speaker 1: the ability to regenerate, that's a that's a good example.
Speaker 1: And so regeneration is common among invertebrates, or at least
Speaker 1: more common than it is among vertebrates like us, like
Speaker 1: as humans, but a mind. Vertebrates. Salamanders are the kings
Speaker 1: of regeneration. Yeah, they can like regenerate things like their
Speaker 1: retina's right, I mean, it's just yeah, they can regenerate
Speaker 1: a ton of stuff like their limbs and their tail,
Speaker 1: their jaws there, and then yeah, eye tissues that you're saying,
Speaker 1: that's one they had to move underground because the French
Speaker 1: people were just trying to chop them up like crazy. Yeah,
Speaker 1: they can even regenerate parts of the heart. And then
Speaker 1: frogs they can they can survive from a broken heart then, right,
Speaker 1: I guess I guess right, Yeah, his heart and he's
Speaker 1: back out on the scene the next night. I'm sorry,
Speaker 1: I'm getting a stuft topic, but anyway, you're to other animals, um.
Speaker 1: And then, according to Scientific American, the embryos of some
Speaker 1: mammals may be able to replace developing limb buds. But
Speaker 1: this happens way, way, way way before the mammals are born,
Speaker 1: right and then after they're born. That's so we humans
Speaker 1: are capable of regeneration to just not necessarily limb regeneration.
Speaker 1: But if you think about it, we're i mean human
Speaker 1: limbs aren't really all that different from a salamanders, according
Speaker 1: to the Scientific American story that I read. I mean,
Speaker 1: they both have bones and muscles and tendons and nerves
Speaker 1: and blood vessels and all this kind of things that
Speaker 1: make a limb necessary. Um, mine are pretty pasty and
Speaker 1: are a little freckled. Yeah, but if a salamander were
Speaker 1: to lose a limb, it can regrow over and over
Speaker 1: and over again. In fact, they think that this process
Speaker 1: of regrowth can happen indefinitely, which is kind of crazy.
Speaker 1: Whereas we just form a scar and that's the end
Speaker 1: of the process by a peg lag and we're good
Speaker 1: to go. So, yeah, what are the types of regeneration? Yeah,
Speaker 1: as exciting as getting a whole new limb is as
Speaker 1: exciting as getting a whole new limb, Maybe regeneration and
Speaker 1: compasses is a lot more. In fact, you're probably doing
Speaker 1: um little or a lot of regeneration right now while
Speaker 1: you're listening to this. And I don't just mean the
Speaker 1: salamanders out there. Um. So, here are a few different
Speaker 1: ways that regeneration occurs in animals. Um, do you want
Speaker 1: to take the first time? Yeah? Okay, So, according to Carlson. Um,
Speaker 1: there's physiological regeneration, and that's just you know, think of
Speaker 1: it as your body replacing worn out body parts. Yeah,
Speaker 1: wearing out and building itself back up again. Yeah. It
Speaker 1: can be as simple as replacing blood. You know, so
Speaker 1: you just give blood, you know, you have to replace
Speaker 1: the blood, right. Yeah. It's like they're you know, people
Speaker 1: often you know, point that it's like you're not even
Speaker 1: like the same person after a certain amount of time,
Speaker 1: you know, because you've replaced so many different cells. Al Right,
Speaker 1: I remember you talking about this. This is fascinating and uh,
Speaker 1: and some people even take the extra mile and like
Speaker 1: sort of talk about the how the mind changes and
Speaker 1: about how you're not even the same you're not the
Speaker 1: same person physically anymore after a certain amount of time,
Speaker 1: and you're not the same person, uh you know mentally, uh,
Speaker 1: constantly changing, constantly regenerating. Right, So the regeneration kind of
Speaker 1: leading to this whole new composition of the body, and
Speaker 1: that's the whole new person. Yeah. Yeah, that's really interesting.
Speaker 1: Like I like to point out to you sort of
Speaker 1: in a way, you're sort of building that new body
Speaker 1: out of the things you buy the grocery store. So
Speaker 1: which is my whole argument for why would you buy
Speaker 1: a whole bunch of crappy food? You know, why don't
Speaker 1: you buy a whole bunch of you know whatever kind
Speaker 1: of crappy food is not in some way you know,
Speaker 1: right right right? Well food food arguments aside. Um regeneration
Speaker 1: also happens, you know, just on a very basic level
Speaker 1: with your skin cells. You know, think about it. You're
Speaker 1: constantly shedding skin cells. Did you forgear that fact about?
Speaker 1: You know, if you have a mattress for a couple
Speaker 1: of years, what percentage of that mattress is basically just
Speaker 1: your dead skin cells filling it up? Yeah, well there's
Speaker 1: a crazy fact out there, but I can't remember exactly
Speaker 1: what percentages, Like your mattress just becomes your skin cells
Speaker 1: or you might you need to check when you buy
Speaker 1: a mattress because it's not composed only of skin cells.
Speaker 1: Before we're not the ladder um. There's another form of
Speaker 1: regeneration called hypertrophy, and this one is when an oregan
Speaker 1: gets bigger to compensate for um. So you lost a
Speaker 1: kidney or donated to kidney, so then you just have
Speaker 1: one and it's got a whole lot more work to
Speaker 1: do so it gets bigger. UM. They've also documented this
Speaker 1: taking place with the lungs. UM livers. Pancreas can also
Speaker 1: experience some regeneration if they're damaged. This reminds me a
Speaker 1: little bit of that phenomena they've talked about in UM.
Speaker 1: People who lose the sense, you know, visually impaired people,
Speaker 1: and you know the other senses compensating for that. I
Speaker 1: wonder like you you go blind, you're hearing gets better. UM,
Speaker 1: you go deaf, you're smelling gets better. So the final
Speaker 1: kind of regeneration is called reparative regeneration. And you might
Speaker 1: find this happening and your muscle, bone, and your skin,
Speaker 1: your heart, tissues, anything along those lines. And this is
Speaker 1: also where that handy ability to form new limbs would fall.
Speaker 1: And Um, this happens with courtesy of a blastema. And
Speaker 1: the blastema is just a grouping of undifferentiated cells that
Speaker 1: are capable of growth and later differentiation. And so by
Speaker 1: differentiation we just mean you know it's going to go on.
Speaker 1: It starts off life, maybe without a purpose, it's a
Speaker 1: blank slate, and then it goes on to become a
Speaker 1: heart cell. Say that's all we mean by differentiation. Well,
Speaker 1: let's bring it all back to jellyfish. What about Tatopsis ah.
Speaker 1: Tatopsis s. Neutricula is a particular species of jellyfish that
Speaker 1: maybe the only animal in the world that's a maybe
Speaker 1: has something in common with vampires, and that is it's
Speaker 1: a it may live forever and how many do that? Well,
Speaker 1: it's capable of cycling, uh, from an adult to to
Speaker 1: an immature stage, the polyp stage, like a frog being
Speaker 1: able to rewind to tadpole form and then advance into
Speaker 1: frog again then rewinded the tadpole form, that kind of thing. Yeah,
Speaker 1: So as you can imagine, if you have this kind
Speaker 1: of ability, your numbers, your population numbers of this particular
Speaker 1: species would probably spike, as they are. In fact with
Speaker 1: Totopsis neutricula they were found originally in the Caribbean, I believe,
Speaker 1: but now they've spread to waters all over the world.
Speaker 1: And so the key in this process that allows um
Speaker 1: a mature adult to cycle back into this immature poly
Speaker 1: up stage lies in a cellular process called trends differentiation,
Speaker 1: which we've just kind of touched on a little bit. So, yeah,
Speaker 1: differentiation is the process by which an unspecified imbryonic cell
Speaker 1: acquires the features of a specialized cell, such as a
Speaker 1: hard liver or muscle cell, all right, and it's controlled
Speaker 1: by an interaction of the cells genes with physical or
Speaker 1: chemical properties. Trans Differentiation is a little different in this
Speaker 1: adult stem cells can differentiate into cell types of scene
Speaker 1: and organs or tissues other than those expected from the
Speaker 1: cells predicted lineage. So like brains, like brain stem cells
Speaker 1: might differentiate into blood cells or blood forming cells, um
Speaker 1: into brain cells, et cetera. Yeah, I mean it's kind
Speaker 1: of amazing. Jellyfish typically die after the propagate, but this
Speaker 1: particular jellyfish can just i mean, keep on reproducing and
Speaker 1: you know, carrying on its life forever. I mean, as
Speaker 1: a mom, I find that prospect a little horrifying, the
Speaker 1: fact that, you know, perhaps you might have to go
Speaker 1: through childbirth numerous times. Not the jellyfish in fact go
Speaker 1: through childbirth, but just comparing it to my own human
Speaker 1: perspective on the reproduction cycle, Yeah, it's kind of like
Speaker 1: it's almost like they're going through just repetitive midlife crisis.
Speaker 1: You know. It's like, oh, I'm getting old, I'm gonna
Speaker 1: act like a young jellyfish again. But they actually become
Speaker 1: a young jellyfish. But the interesting thing is they have
Speaker 1: no idea what how this happens. They don't know the
Speaker 1: mechanism behind the life cycle. They know that cells are
Speaker 1: able to turn from one type into another, from general
Speaker 1: to specific, from specific to general, and keep going back
Speaker 1: and forth, but if they don't know why, and it's
Speaker 1: not very I mean, ultimately, it's not like a sustainable thing.
Speaker 1: Like you mentioned the vampires um our own. Josh Clark
Speaker 1: did a blog post a while back where some scientists
Speaker 1: like sit down and look at the whole vampire thing,
Speaker 1: and they're like, look, it could never happen because obviously
Speaker 1: you'd end up with more vamps, so many more vampires
Speaker 1: than humans. It wouldn't be any humans to feed on,
Speaker 1: and you just have vampires and they'd starve or whatever. Right,
Speaker 1: It's not so immortality is just not sustainable. Sustainable. Yeah, So, I,
Speaker 1: for one, I'm very interested in regeneration and its prospects
Speaker 1: for medicine and stem cells in the lake in the future.
Speaker 1: So I would love to do a follow up podcast
Speaker 1: on this. Let us know if you guys are interested
Speaker 1: um in a in a podcast also on regeneration in
Speaker 1: the meantime, come check out our blogs, where we'll keep
Speaker 1: you up to date on whatever we're podcasting about for
Speaker 1: the week and uh any other interesting scientific tidbits that
Speaker 1: cross our desk. And if you guys have a question
Speaker 1: about immortality, vampires, jellyfish, or regeneration in fact, send us
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