where are stem cells in a human body

you're in line at the grocery store when, uh oh, someone sneezes on you. the cold virus is sucked inside your lungs and lands on a cell on your airway lining. every living thing on earth is made of cells, from the smallest one-celled bacteria to the giant blue whale to you. each cell in your body is surrounded by a cell membrane, a thick flexible layer made of fats and proteins,

that surrounds and protects the inner components. it's semipermeable, meaning that it lets some thing pass in and out but blocks others. the cell membrane is covered with tiny projections. they all have functions, like helping cells adhere to their neighbors or binding to nutrients the cell will need. animal and plant cells have cell membranes.

only plant cells have a cell wall, which is made of rigid cellulose that gives the plant structure. the virus cell that was sneezed into your lungs is sneaky. pretending to be a friend, it attaches to a projection on the cell membrane, and the cell brings it through the cell membrane and inside. when the virus gets through, the cell recognizes its mistake. an enemy is inside!

special enzymes arrive at the scene and chop the virus to pieces. they then send one of the pieces back through the cell membrane, where the cell displays it to warn neighboring cells about the invader. a nearby cell sees the warning and immediately goes into action. it needs to make antibodies,

proteins that will attack and kill the invading virus. this process starts in the nucleus. the nucleus contains our dna, the blueprint that tells our cells how to make everything our bodies need to function. a certain section of our dna contains instructions that tell our cells how to make antibodies. enzymes in the nucleus find the right section of dna,

then create a copy of these instructions, called messenger rna. the messenger rna leaves the nucleus to carry out its orders. the messenger rna travels to a ribosome. there can be as many as 10 million ribosomes in a human cell, all studded along a ribbon-like structure called the endoplasmic reticulum. this ribosome reads the instructions from the nucleus.

it takes amino acids and links them together one by one creating an antibody protein that will go fight the virus. but before it can do that, the antibody needs to leave the cell. the antibody heads to the golgi apparatus. here, it's packed up for delivery outside the cell. enclosed in a bubble made of the same material as the cell membrane, the golgi apparatus also gives the antibody directions, telling it how to get to the edge of the cell.

when it gets there, the bubble surrounding the antibody fuses to the cell membrane. the cell ejects the antibody, and it heads out to track down the virus. the leftover bubble will be broken down by the cell's lysosomes and its pieces recycled over and over again. where did the cell get the energy to do all this? that's the roll of the mitochondria.

to make energy, the mitochondria takes oxygen, this is the only reason we breathe it, and adds electrons from the food we eat to make water molecules. that process also creates a high energy molecule, called atp which the cell uses to power all of its parts. plant cells make energy a different way. they have chloroplasts that combine carbon dioxide and water

with light energy from the sun to create oxygen and sugar, a form of chemical energy. all the parts of a cell have to work together to keep things running smoothly, and all the cells of your body have to work together to keep you running smoothly. that's a whole lot of cells. scientists think there are about 37 trillion of them.

Read More »

where are stem cells found

neil degrasse tyson (host/astrophysicist,american museum of natural history): on this episode of nova sciencenow: the swamp creaturethat everyone fears... mark e. siddall (american museum of naturalhistory): he's not going to bite you. neil degrasse tyson: he started to bite me! mark siddall: come on. neil degrasse tyson: ...the slithery, slimyleech. mark siddall: he did not. neil degrasse tyson: he was hanging on. mark siddall: that was his back sucker, nothis mouth sucker.

uh, oh. neil degrasse tyson: but now these flexiblebloodsuckers are winning new fans in the world of microsurgery. thomas clark (accident victim): the leechessaved my finger. the part of my finger that was dying started coming back to life. neil degrasse tyson: and the big question... jill tarter (center for seti research): arewe alone? humans have been asking it forever. neil degrasse tyson: for more than 40 years,we've been trying to "tune in" to an alien station.

seth shostak (center for seti research): we'relooking for a signal somewhere on the radio dial that they might be broadcasting intospace. neil degrasse tyson: now, hundreds of newradio dishes... andrea kissack (correspondent): wow! thatis very flash gordon. neil degrasse tyson: ...are expanding thesearch for intelligent life somewhere else in the universe. jill tarter: the probability of success isdifficult to estimate, but if we never search, the chance of success is zero. neil degrasse tyson: also, if you're lookingto spy on life at the bottom of the sea, submarines

are not the answer. soenke johnsen (duke university): it's gotlights flashing, motors whirring, and then you come up to some animal, 5 inches away,and say, you know, "act natural." neil degrasse tyson: so this biologist cameup with a new kind of camera. and it's working, revealing some weird and wonderful creatures. edith widder (ocean research & conservationassociation, inc.): i was just wild. i couldn't believe it. every time we put this thing down we see somethingnobody's ever seen before. neil degrasse tyson: all that and more, onthis episode of nova sciencenow.

leechesneil degrasse tyson: hello, i'm neil degrasse tyson, your host of nova sciencenow. you know,in the old days, centuries ago, barbers were considered medical professionals. insteadof a shave and a haircut, for two bits, what you'd get was the cutting-edge treatment ofthe day, and that was bloodletting. and sometimes they did it, not with razors,but with a tiny little helper. modern medicine is not generally into bloodletting,but, strangely enough, in some cases, surgeons have come to rely once again on this talentedlittle creature. ladies and gentlemen, it turns out the leechis back! so how....you just look for ponds whereveryou find them and...

mark siddall: well, they have to have a certaincharacter. neil degrasse tyson: i wasn't quite sure whatto expect, when biologist mark siddall, my colleague from the american museum of naturalhistory, led me through the woods into a muddy swamp. mark siddall: it's not too bad. neil degrasse tyson: but i suspected it mightbe just kind of gross. this is nasty; let the record show. are wegetting sucked on right now? mark siddall: not likely to be being fed onjust yet. normally, it takes them a little while to realize we're here. they respondto movement in the water first.

neil degrasse tyson: within a few minutes,hungry leeches tracked us down and were swimming right towards us. mark siddall: there's one right there, rightthere, right there in the water. neil degrasse tyson: do i grab him? mark siddall: yup. it's a beautiful, beautifulmacrobdella decora, literally, "decorated leech." they have orange polka dots that godown the back. neil degrasse tyson: unlike mark, the squirmything's body decoration was the last thing on my mind. mark siddall: he's not going to bite you.

neil degrasse tyson: you can't blame me forgetting a little squeamish. after all, aren't these the bloodsucking creatures that turnup in movies to terrorize anybody who wanders into fresh water? humphrey bogart in african queen: if there'sanything in the world i hate, it's leeches, filthy little devils! neil degrasse tyson: once upon a time, peopleoften put leeches on their bodies on purpose. for centuries, people believed that intentionalbleeding was good for you, as a way to regulate what were called the body's "humors." mark siddall: if someone was sick, all youhad to do was rebalance the humors. you have

four humors: blood, yellow bile, black bileand phlegm. and what you needed to do was get the right balance of those, and then youwould be fine. neil degrasse tyson: in 19th century europe,the leech became the method of choice for all-purpose bloodletting. fever? try a leech.headache? stick one on your temple. overweight? never fear, leeches to the rescue. joseph upton (beth israel deaconess medicalcenter): leeching was kind of a panacea. if somebody had a black eye or a big shiner orsomething, they'd put a leech on it. that was commonplace. neil degrasse tyson: eventually, people beganto realize for a lot of the patients, all

this bloodletting wasn't really helping. andthe leech fell into disrepute, the poster child of medical ignorance. of course, it wasn't really the leeches' fault.they were just doing what they're good at, dining on your blood. mark siddall: uh, oh. neil degrasse tyson: he's got one. mark siddall: yup. neil degrasse tyson: for some reason, theleeches here seemed to prefer mark's legs to mine.

mark siddall: you got any on you, by the way? neil degrasse tyson: i don't know. will ifeel it? mark siddall: yes, you will. you will feela pinch. neil degrasse tyson: and one really choweddown on the knee of mark's assistant, sara watson. mark siddall: so what the leech is doing rightnow is it's filling up with sara's blood. neil degrasse tyson: these leeches live exclusivelyon blood, and a huge stomach is key for their survival. mark siddall: so leeches can feed six to seven,maybe eight times their unfed body weight

in blood. and because of that, what they dois they hold onto that blood in the stomach, squeeze a little bit down into the intestinesas they need it after they've finished feeding, and digest it while they're hiding under arock or going off to find a mate. neil degrasse tyson: a leech can live formonths on one good blood meal, but a full stomach creates a potential risk. left alone,the blood would soon clot and thicken. so the leech produces a powerful anti-coagulant,a blood thinner. mark siddall: the importance of this is obvious,if you're a leech, because if you fill up with blood to, like, six or seven times yourbody weight, if that blood clots inside of you, you're going to turn into a brick andfall to the bottom of the water. you can't

swim; you can't mate; you can't have young.you can't get away from predators, and it's all over. so, these anti-coagulants are extremelyimportant in terms of the leeches' survival. neil degrasse tyson: and this blood thinner,so crucial to the creature's survival, is one reason the leech's reputation has recentlybeen rehabilitated. construction worker thomas clark had seensome leeches as a kid, but a few months ago, they played a major role in his life. thomas clark: that particular day, i was doingtree work. so i was in a little bobcat(r). it's pretty simple. neil degrasse tyson: clark was using a smallloader to lift a tree trunk into a dump truck

when things suddenly went wrong. thomas clark: as i was rolling the log off,the bobcat tilted forward, came off the rear wheels. my hand came out of the bobcat, andthis part of the bobcat kissed the side of the dump truck and crushed off all these fingers.exactly right here, chu, chu, chu, chu. it just looked like i put my hand in a meatgrinder 'cause it, like, it smushed. neil degrasse tyson: clark was rushed to thehospital where surgeons struggled to rebuild his hand. amir taghinia (beth israel deaconess medicalcenter): the middle finger had the worst injury, by far. it was really just hanging off byone tendon. and it was sort of twisted on

itself. and we had to do quite a bit of surgeryto get that finger to live. neil degrasse tyson: the next day, clark'smiddle finger was not doing well. thomas clark: it was turning black, and theysaid that it was dying. so they were going to take it off. neil degrasse tyson: too much blood was cominginto his finger, but not getting out. the veins that normally carry the blood away weretoo badly damaged. amir taghinia: if there's blood going intothe finger, but there's no blood coming out of the finger, pressure builds up, and thetissues can't tolerate that. if you were to leave that state and not doing anything torelieve that pressure, relieve that tension,

relieve that outflow, the finger would die. neil degrasse tyson: it didn't look like moresurgery would fix the problem. so, even though doctors usually want to stop bleeding afteran operation, in this case, it was just the opposite. amir taghinia: so your next option is to useleeches. thomas clark: i was actually kind of, like,"cool." you know, i was like, you know, "whatever works. i don't want to lose anything, youknow. so, if it's going to work, let's do it." neil degrasse tyson: leeches were broughtin to feed on his finger and suck out the

extra blood. thomas clark: every time my heart beat, itwas like the leech was sucking with the beat of my heart, and it was like a pump. it waslike "bum-bum, bum-bum." neil degrasse tyson: as the leech sucks, itreleases that powerful blood thinner into the finger, which prevents clotting. amir taghinia: the leech is interesting. itinjects a blood thinner, called herudin, into the soft tissues around that area. so whenthe leech gets full and falls off, the finger continues to bleed. that buys you time, thatprocess. neil degrasse tyson: with a few days of leeching,the finger can naturally grow new veins and

resume healthy blood circulation. thomas clark: it was almost instant. you couldtell that it was working, because my...the swelling was going down. the open wounds wereactually healing. and i could actually feel a pulse in my finger. and the blackness startedgoing away. and, like, the part of my finger that was dying started coming back to life. joseph upton: when you're in a situation whereyou've already done everything that you can technically do, and then you're still havingproblems, actually, the leeches are very valuable. they're incredibly valuable. neil degrasse tyson: thomas clark's leechtherapy worked. though he hasn't regained

full function of his hand, his fingers wereall saved. thomas clark: i definitely wanted to keepmy hand and all fingers, because the human body's got ten fingers, not nine. so it meansa lot. it does. the leeches saved my finger, no doubt about it. amir taghinia: they're really indispensablefor what we do. and there would be many a finger's lopped off if it weren't for leeches. neil degrasse tyson: the leech's comebackdelights biologist mark siddall, but his appreciation goes far beyond its medical usefulness. i don't mind him crawling on me, as long asi know when he's about to bite.

leeches are a kind of worm, and there arehundreds of different species living all over the world. mark siddall: he's trying to find a placeto feed on me. there are terrestrial leeches, there are freshwater leeches, there are marine leeches. there's just this huge diversity of form, color, patternand even of behavior. and most of them are not very specific, interms of what they'll feed on, but some of them are. some of them are very specific tofish, and there's even one in africa that lives exclusively in the rectum of hippopotamus. neil degrasse tyson: eww.

mark siddall: yes, well, there was a paperwritten called, "leeches ride the tunnel of love," because they mate there. neil degrasse tyson: you sure? leeches have been crawling and swimming aroundearth for hundreds of millions of years. for siddall, these graceful creatures are fascinating,even beautiful, despite their taste for blood. mark siddall: leeches are unnecessarily maligned.they don't take more blood than you can reproduce by yourself. and you know what? unlike a mosquitoor a black fly, they don't transmit any parasites. and quite frankly, if you took some time tohave a look at them, you'd see just how pretty they are. i know most people don't reallythink about conserving leeches, but just like

any group of organisms on the face of thisplanet, wouldn't it be just a little bit colder and darker without them? search for etneil degrasse tyson: ever wonder what the chances really are of finding a needle ina haystack? think they're about as good as finding space aliens? the search for intelligent life beyond earthhas been going on now for 40 years. some folks figure, "hey, if they haven't found it bynow, it's probably not there." but as correspondent andrea kissick reports, compared to needlehunting, looking for alien life in all the billions of possible places out there is much,much harder.

andrea kissack: okay, imagine you're at thebeach. in order to figure out if there are fish in the ocean, you dip an empty glassinto the water and look inside...no fish in the glass, well, there must be no fish inthe ocean. not too logical, is it? but that's exactly the type of reasoning that's plagueddr. jill tarter for years in her long search for intelligent life in our galaxy. astronomers like tarter began searching foralien intelligence about four decades ago. in that 40 years, they've only managed tosearch 1,000 star systemsã³1,000 glasses of waterã³while an unexplored cosmic ocean layright in front of them. jill tarter: forty years needs to be put inthe context of how big the universe is, how

enormous this cosmic haystack is that we'retrying to search through. and, so, we've just begun. andrea kissack: jill knows a little somethingabout seti, the search for extra-terrestrial intelligence. she's the current director ofthe center for seti research, in mountain view, california. like many seti scientists,she was drawn into the search by the early work of astronomer frank drake. drake looked at the makeup of our galaxy andcreated an equation to determine the likelihood that other intelligent life exists. the equationoffered a simple framework for modeling the problem, taking into account things like thefraction of stars with orbiting planets, the

percentage of planets that go on to developintelligent life, and the length of time that an intelligent race lasts. the results wereclear: scientifically, the odds are pretty good that we are not alone. but if you're hunting for e.t., where do youstart? what would the sign of a technically sophisticated alien culture look like? it could look something like this. these television and radio signals are examplesof the electromagnetic waves we've been leaking into space for over 80 years. that means anyplanet within 80 light years of earth is receiving them. but tv and radio are only a small part of the electromagneticspectrum.

although astronomers use the term "radio waves,"they're generally talking about any wavelength longer than a microwave. so the radio frequencyspectrum is huge, much wider than the visible light spectrum. and signals like this are simple to generate,easily pierce dust and atmospheres, and carry well over vast distances. that's why setiscientists believe alien cultures might be leaking them, just like we are. in 1979, as a young graduate student, jilltarter joined the hunt for these telltale signals. jill tarter: i was so enthralled by the ideathat i lived in the first generation, ever,

of human beings that could try and answerthe "are we alone" question by doing an experiment, rather than just asking the priests and thephilosophers what they believed. andrea kissack: by the early 1990s, with nasafunding, tarter was heading up the search at the largest facility in the world, thearecibo radio telescope, in puerto rico. tarter became the poster child for seti. even hollywoodembraced her. tarter is generally thought to be the inspiration for ellie arroway, thecharacter played by jodi foster in the classic science fiction movie contact. it seemed the golden age of seti had arrived.then, in 1993, congress abruptly shut off all federal seti funding. but that wasn'tthe end. today, nearly 15 years later, something

big is happening in this remote valley nearhat creek, california. seti's luck may be about to change. the radio telescope dishes behind me signalthe beginning of what many believe will be a seti renaissance. and if there is to bea breakthrough, the new allen telescope array is the best bet. the reversal of seti's fortune has largelybeen made possible by a $25 million grant from paul allen, one of the founders of microsoft.on october 11, 2007, allen "pushed the silver button," bringing the first 42 radio disheson-line. when completed, the allen telescope array will consist of 350 separate dishes.together they can operate as a single "virtual"

dish, over 2,700 feet across, making it oneof the largest and most sensitive radio telescopes in the world. it will be the fastest toolever built to hunt for signals of extra terrestrial intelligence. senior seti astronomer seth shostak tellsus how this new telescope will work. seth shostak: well, andrea, to understandhow we're trying to find e.t., you have to understand the technique we're using, andthat is to look for signals in what's called the electromagnetic spectrum. that's a lotof greek, but all it really means for us is the radio dial. we're looking for a signal,somewhere on the radio dial, that they might be broadcasting into space. let me show youhow this works. i'll just turn that on. okay.

now, you notice that, if i just turn the dialhere, you hear static everywhere? andrea kissack: yeah, like white noise. seth shostak: that's just all natural noise.i mean, galaxies and hot gas between the galaxies, and pulsars and quasars, they all make radionoise, and it's everywhere on the dial. but here...wait a minute...hear that squeal?and then there's the station. all that energy...it's at one spot on the dial. nature does not makesignals that are restricted to one spot on the dial, in general. it just doesn't do that. andrea kissack: so that's intelligent life? seth shostak: that's intell...

andrea kissack: ...depending on your musicaltaste. seth shostak: it's definitely intelligence. andrea kissack: since the cosmos just don'tmake narrow, focused signals like this, finding one would be an almost certain sign of analien culture. so what is it about this new array that makesit more likely to succeed? jill tarter: the allen telescope array, basically,is all about speed. we can look at more than one star at once. and so, whereas, in thelast decade, we looked at about a thousand stars, in the next decade, we'll look at amillion. andrea kissack: that's because the allen array'sfield of view, the area of sky it sees at

one time, is much larger than any other telescope.and it can capture millions of frequencies from multiple star systems, simultaneously.basically, the allen telescope array is a seti hot rod with seti astronomers at thecontrols, 24/7. seth shostak: so here you can see where therubber really meets the road for the individual antennas. andrea kissack: wow! that is very flash gordon. seth shostak: indeed it is. in fact, the waythis thing works...it's really dead simple. the radio waves from the sky come in, theybounce off that 20-foot diameter reflector, and then they bounce off this somewhat smallerone here, in the front of the antenna, and

then they come into this feed. so this isthe thing that actually collects the radio waves and turns them into electrical signals,and in fact, down the pedestal, under the ground and back to the control room. andrea kissack: so a huge swath of the universecomes right into this room. seth shostak: yeah, it does, actually. theantennas send everything they collect from the cosmos into this room. it comes in rightback here. so all those data come in here, and then we put it together. andrea kissack: so how is this different thanthe seti of old? seth shostak: well, the fundamental differencehere is simply the amount of data you can

handle, and that's just the march of technology.the first seti experiment, back in 1960, one channel of the radio. here we've got 100 millionchannels coming in. andrea kissack: the sheer scale of the searchis almost impossible to imagine. remember, in our galaxy alone, there are about 300 billionother suns, many with orbiting planets. and beyond that, lie a hundred billion other galaxiesjust like our own. even in its current configuration, the array'svirtual dish gathers nine times more information than present-day processor technology candecode. that means 90 percent of what the telescope observes is simply thrown away,at least for now. so for the next decade or two, the technology in this little room willbe playing catch-up with the dishes outside.

seth shostak: all this stuff will be replaced,in another five years, by yet faster machines, which allow us to look at more star systems,more channels, in other words: to speed up the seti search. andrea kissack: and as that search accelerates,tarter and other seti scientists are thinking about the consequences of success. jill tarter: if we detect a signal, we'lldo everything that we can at this site to make sure that it isn't our own technologythat's fooling us or that it isn't a deliberate hoax. if we get an independent confirmation,then we will, in fact, tell the world. because a signal isn't being sent to the allen telescopearray, it's being sent to the planet earth,

and the planet earth deserves to know aboutit. andrea kissack: for jill tarter, it's a scenarioshe's imagined for almost 30 years. detecting even the accidental noise, the "dial tone"of an alien culture, would finally answer one of the most ancient questions of all. jill tarter: are we alone? humans have beenasking it forever. the probability of success is difficult toestimate, but if we never search, the chance of success is zero. stem cells breakthroughneil degrasse tyson: what if i made fettucini alfredo and then decided what i really wantedwas cheesecake? could i turn one into the

other? well, maybe i could. if i could turnback time and go back to the original ingredients, then i could make something else, entirely. this idea, of turning back the clock and rebuildingsomething from scratch is the basic premise behind stem cell research, which aims to transformone kind of cell into another. correspondent chad cohen reports recent groundbreakingdiscoveries seem to be bringing them that much closer to their goal. amiel reid (sickle cell anemia patient): itfeels like a lot of people are stabbing me with knives, from the inside of my body, allthe way down to my bone. sometimes i couldn't catch my breath it was so intense.

stephanie termitus (sickle cell anemia patient):i'm in tears, basically. it's just pain everywhere, it's going through your head, your back, yourlegs, and you can't do anything about it. chad cohen (correspondent): stephanie termitusand amiel reid know the inside of children's hospital boston better than any teenager should.they both suffer from sickle cell anemia. instead of the plump, doughnut-shaped bloodcells most of us have delivering oxygen to our organs, their blood cells are sickle-shaped,"banana," as stephanie likes to say. these cells can't deliver oxygen very well, whichcauses the kids excruciating pain. amiel's mom is on a first-name basis with the hospitalstaff. lynnie reid (mother of sickle cell anemiapatient): they've given amiel pain medication,

and it doesn't take the pain completely away.it sort of numbs it. i mean, that's happened, where he's ended up in the intensive careunit for four months. so it's pretty serious. george daley (children's hospital boston):the misshapen, stiff red blood cells get sludged and clogged into the blood vessels that feedtheir organs and their muscles and their bones. and this is intensely painful. chad cohen: it's been 50 years since researchersfound the cause for those misshapen blood cells, a single change in a single faultygene. sickle cell was the first genetic disease ever identified. george daley: give me a big, deep breath.

chad cohen: yet despite decades of searchingfor cures, all we can do is treat the symptoms, or in rare cases, perform bone marrow transplants,which are dangerous and carry a high risk of rejection. george daley: and so this is a condition thatwe need a new approach for. chad cohen: lately, that new approach hasinvolved embryonic stem cells, cells that are "pluripotent," meaning they can grow intojust about any cell in the body. when they were discovered, more than a decade ago, itwas thought that stem cells could fix, not just sickle cells, but the damaged cells ofcountless diseases: parkinson's, diabetes, a.l.s. that's what's driven george daley,who also heads a stem cell lab, right across

the street from his patients. george daley: thinking about the potentialthat this has for changing the way that we not only study disease, but one day treatdisease, is really very, very exciting. chad cohen: but there's a problem. stem cells,for the most part, come from human embryos, from that time, just after sperm meets egg,when we're made up of just a few dozen cells, and the function of those cells has yet tobe determined. the main sources for the embryos are i.v.f. clinics, where surplus embryosare often discarded as medical waste. still, harvesting the stem cells destroys the embryoand for many, that's morally wrong. others believe that holding back medical progressis also wrong.

george daley: here we are, at the dawn ofthis whole new field, all this excitement, all this possibility, and yet we're workingwith one hand tied behind our back. chad cohen: but in 2007, some experimentswere conducted that many believe will finally bring the fighting to an end. japanese researchershinya yamanaka figured out a way to take an ordinary skin cell from an adult, turnback its genetic clock and transform it into the equivalent of an embryonic stem cell,no embryos required. yamanaka's motivation came when he first glimpsed human embryosunder a microscope about 10 years ago. shinya yamanaka (gladstone institute, universityof california, san francisco): i have two daughters. and i thought, "the differencesbetween those small embryos and my own daughters

are very small." chad cohen: the realization presented someconflict for him, since, as a physician, he believed that embryonic stem cells were hisbest shot at treating disease. shinya yamanaka: to me, treating patientsand saving patients is the most important thing to do. but if we can avoid the usageof human embryos, we should avoid. chad cohen: ironically, yamanaka had to useembryonic stem cells in order to find a way to do without them. he started by exploringone of their fundamental properties. virtually every cell in the human body has the samed.n.a. heart cells, liver cells, skin cells, all share the same 20,000 genes. during ourdevelopment as embryos, though, different

genes in different cells get switched on andoff, in different ways, and that's what creates all the different types of cells in our bodies.it's called cell programming. yamanaka believed if he could find the gene switches responsiblefor programming stem cells, he could flip those same switches in adult cells, like skincells, and re-program them back to the moment before their destinies were determined. shinya yamanaka: each cell has at least 20,000genes, so that means we have to find those important switches from the 20,000 candidates. chad cohen: with so many genes to choose from,so many potential combinations, the search could have been infinitely complex.

george daley: yamanaka's insight was to appreciatethat it was a very limited set of genes. and he set out to identify them. chad cohen: first he reduced 20,000 possiblegene candidates down to 100, using on-line databases. but then, the work got harder. shinya yamanaka: we spent, like, three yearsto study the function of those 100 genes. chad cohen: were there people saying, "giveup, there's no use in this?" shinya yamanaka: yeah, many people told methat this is going to be very difficult. "you will fail." chad cohen: using specially engineered mice,called knockouts, he tested each gene's ability

to make pluripotent stem cells, eliminatingthem, one by one. after more than three years, culturing hundreds of thousands of cells,yamanaka narrowed the gene pool down to 24 genes, and finally four. then came the momentof truth: getting these four painstakingly selected genes to make stem cells. he tooksome skin cells from an adult mouse, then used a virus to insert the four genes insidethem. two weeks later the skin cells in the petri dish had completely transformed. shinya yamanaka: we saw cells which lookedlike stem cells. so it was...at the moment, you know we were very, very excited, and wewere very surprised. chad cohen: yamanaka dubbed the cells "inducedpluripotent stem cells," or i.p.s. cells,

and found they were virtually indistinguishablefrom embryonic stem cells. i can't see a difference; i wouldn't expectto be able to see a difference, but... shinya yamanaka: no, we can't see differenceseither. so these embryonic stem cells and induced pluripotent stem cells are indistinguishable.they are the same cells. chad cohen: it's amazing. george daley: yamanaka's experiment was bold,some might say foolhardy. i think it's the type of experiment that would be laughed outof the room in a standard peer review study section. you would never have gotten yourgrant funded with that experiment. chad cohen: really?

george daley: and now it's probably goingto win shinya yamanaka a nobel prize. chad cohen: creating stem cells without anembryo in mice certainly made headlines in the scientific community, but less than ayear later came the news that caught the world's attention. based on yamanaka's work, threeindependent scientists, james thomson in wisconsin, george daley in boston and yamanaka, himself,transformed human skin cells into i.p.s. stem cells. it was a monumental breakthrough, andin george daley's case, the doctor even experimented on himself. dermatologist: so what we're going to be doingis just obtaining a small biopsy of the skin and...

george daley: we have a protocol where wecan have anyone walk in, roll up their sleeve...we take a very small skin biopsy, smaller thanthe eraser at the end of a pencil. dermatologist: we'll just snip this, and we'regood to go. george daley: fantastic. and those skin cells are then put right intoa petri dish, and then, within a week, all of a sudden, this huge bloom of cells appears.and then you bring into them the three or four genes that do the re-programming. what's really remarkable is that just simplyputting those genes into the cell and making them work, starts this whole process. it takesthose stable, specialized skin cells and erases

all the skin functions, and reactivates, enlivensthe embryonic functions and turns that skin cell back into a pluripotent embryonic cell.that's really... chad cohen: back in time, basically. george daley: it's back in time, i mean, it'slike a whole altered universe. i mean, it's really changed the fundamental nature of thatcell. how many times would you say you've been inthe hospital your whole life? stephanie termitus: i can't even say it'sso many; ten times a year? chad cohen: so, how long before this technologyactually helps patients like stephanie? well, some serious challenges will have to be overcomefirst.

for one thing, that virus to shovel yamanaka'sfour genes into adult cells can mutate a patient's d.n.a. and cause cancer. at least one of thefour genes is an actual oncogene; it definitely causes cancer. and a high percentage of themice created with these stem cells did develop cancer. but the promise of these cells faroutweighs their problems, and, as we speak, researchers around the world are figuringout how to safely use them. late in 2007, rudolph jaenisch, of the whitehead instituteat m.i.t, demonstrated a powerful application of i.p.s. cells. he used them to cure sicklecell anemia in mice. to do it, he first had to give the mice the disease. so you were able, basically, to give the micesickle cell disease, and use that as a model?

rudolph jaenisch (whitehead institute, massachusettsinstitute of technology): yes. these mice were highly anemic. they had just stoppedgrowing. they were very...rather small. they wouldn't gain weight, they would die early.i mean it was...it's a very faithful model of this major human disease. you would take then a skin cell from thismouse and re-program it to i.p.s. cells. chad cohen: jaenisch made the stem cells usingyamanaka's same four gene switches, but this time he removed that nasty oncogene once ithad done its job. rudolph jaenisch: so now these i.p.s. cellsthey didn't need anymore, they didn't have that oncogene. so that was useful. and thenthe next thing was we repaired the genetic

defect by gene targeting. chad cohen: jaenisch targeted that singlesickle cell mutation, fixed it, then prompted the stem cells to become blood cells and injectedthem back into the mice. since these cells came from the very same mice, they were aperfect match; there was no chance of rejection. rudolph jaenisch: and to ourã³reallyã³delight,the blood of the mouse totally normalized, and they begin to, began to gain weight. theyhave lived. as far as we know, they have no problem, so that they're totally cured, thesemice, from the sickle cell condition. chad cohen: so have these new stem cells madeembryonic stem cells obsolete? well, until we know for sure whether they can faithfullygrow into all the different cell types, the

answer is definitely no. george daley: i'm not willing to concede thati.p.s. cells will ever fully replace human embryonic stem cells. the embryonic stem cellline remains the gold standard. could you take a big deep breath? it has been the most exciting past few yearsi could imagine, in my career. and i hope that it is translated into real treatmentsfor my kids. amiel reid: my favorite subject is science. george daley: that's good! that's very good.we like to hear that. amiel reid: the fact that they can take yourown skin and turn it into something that can

cure a disease like that, it's incredible. profile: edith widderneil degrasse tyson: the bottom of the ocean is a dark and secretive place. but if youcome down here to take a look around, once you turn on a light, of course, all the interestingstuff disappears. well, in this episode's profile, we'll meetone of the world's most determined undersea spies, who's engineering new and ingeniousways to behold the mysteries of the deep. she's clearly a woman on the go. and whenher feet are not firmly on the ground, she's perfecting her sea legs out here. edie widder is a marine biologist and explorer.her quest? to understand ocean creatures and

help save their undersea world. edie widder: i think i have the best job inthe world. seventy-one percent of the planet is covered by water, we've explored less thanfive percent of the ocean, and there are so many fabulous discoveries that have yet tobe made. neil degrasse tyson: she's working on discoveringhow animals communicate using light. it's called bioluminescence. edie widder: they use it to attract food,to ward off predators, to attract mates. it's vital to their existence. neil degrasse tyson: but there's a problem.there are only two ways to study these creatures,

in their environment or in ours. both havetheir limitations. bringing them up, well, they're not exactly themselves. going to themin a submersible also has its drawbacks. soenke johnsen: it's got lights flashing,motors whirring. and then you come up to some animal, five inches away, and say, you know,"act natural." and it's not going to happen. neil degrasse tyson: so edie came up witha new kind of camera she calls the "eye in the sea." it's basically a highly sensitivewaterproof security camera on a timer. its lights are red, which most underwater creaturescannot see. to entice animals in front of the camera,edie uses smelly fish guts inside a bait box and an electronic light show that mimics theway certain animals attract prey.

peter girguis (harvard university): thereis no doubt that edie is at the forefront of her field. and this is, again, sort ofa tribute to her capacity as a scientist and, let's say, her closet engineering tendencies. neil degrasse tyson: the eye gets droppedoff on the ocean floor, via submersible. today, edie is deploying it in the bahamas. edie widder: so we're just looking for a niceflat piece of terrain that we can set it down on safely. phil: topside, our depth is 1,585, one, five,eight, five feet. we're going to attempt to deploy it here.

edie widder: now, you've got to let go atthe right moment. neil degrasse tyson: new revelations pop upevery time edie uses it. edie widder: the payoffs have been huge. imean, every time we put this thing down, we see something nobody's ever seen before. neil degrasse tyson: in the gulf of mexico,the eye recorded an amazing first: a squid, over six feet long, that is so new to science,it cannot be placed in any known family. edie widder: i screamed so loud; and i'm nota screamer. but i was just wild. i couldn't neil degrasse tyson: most recently, the eyerevealed previously unknown feeding behavior of six-gilled sharks.

edie widder: they were doing something nobody'sever seen before. they were rooting on the bottom and apparently sucking up, in the sand,these little pill bugs, these isopods. and it's a possible explanation for how thesebehemoths survive in what seems like a desert sometimes. neil degrasse tyson: the eye has allowed marinebiologists to study creatures only a mother could love, or a human like edie. she's beendrawn to other species since she was a kid. edie widder: i loved anything to do with animalsfrom a very early age. neil degrasse tyson: school, on the otherhand, wasn't quite as much fun. edie widder: i was so bored that i just tunedout everything that was being said.

neil degrasse tyson: then edie got a new leaseon learning. her parents, both mathematics professors, whisked her away on a magicalglobetrotting adventure. first stop: europe. edie widder: ...went to all these magnificentart museums, and i decided i wanted to be an artist. then we went to egypt, and i decidedi wanted to be an archeologist. and then we went to australia and saw all of these fabulousanimals, and i decided i had to be a biologist. neil degrasse tyson: one of the last stops?a fateful trip to the teeming reefs in fiji. edie widder: i just was mesmerized by allof this life everywhere i looked. and so i wanted to be a marine biologist. neil degrasse tyson: edie had found her element.

edie widder: so the family joke is, "if we'dgone from west to east instead of east to west, would i have ended up as an artist?"but i think the total lack of talent might have been somewhat of a drawback. neil degrasse tyson: and then she found asoul mate. she was in high school, when she caught husband dave's eye. dave smith (edie widder's husband): therewas an assembly, and i was sitting in there, and i saw her come down the aisle with someof her girlfriends. and she was wearing a leather skirt. and she just looked reallyhot. she was definitely fantasy stuff. edie widder: i think the leather skirt isa figment of his imagination. but, okay, we'll

keep it in the mythology. but he was a boy with a brain. he was thefirst one i'd ever met. then one of my girlfriends pointed out to me, "wow, he's got great shoulders."shoulders? really? and so we started dating. and i hate to admit it, but i married thefirst boy i ever dated. neil degrasse tyson: and they lived happilyever after...well, almost. edie widder: it turns out my poor husbandgets seasick if there's a heavy dew on the lawn. in fact, he has declared he will neverbe going to sea with me again. neil degrasse tyson: that's okay. there'slots for him to do on land. dave's an expert in high tech instruments and is pitching inwith edie's newly-founded ocean research & conservation

association, orca. edie widder: you were talking about stormwater runoff. you have to have that meteorological data. a lot of what we want to do with our new organizationis make people aware of the value of the ocean for our existence on this planet. neil degrasse tyson: to do this, edie cameup with another invention she calls kilroy. it's a monitoring device equipped with sensorsthat can track salinity, temperature, wave height, direction and speed of the current. edie widder: we can send out commands to itas well as receive information from it.

neil degrasse tyson: to send the data backto shore, kilroy just makes a call, via standard cell phone technology. they'll keep addingsensors, including some that will measure certain pollutants. edie widder: and suddenly, now, we're startingto understand what's going on. so it's not just this placid blue surface that...everythinglooks fine. we can start telling people what's really happening. neil degrasse tyson: edie is diving into anythingthat will help people understand the oceans, including a children's book series on bioluminescence. the originality of her work and her determinationto share it with the public have earned her

the prestigious macarthur award. edie widder: i never, ever would have imaginedthe kind of career i've had. it just wouldn't have occurred to me that anything like thiscould have been possible. i didn't have any such aspirations. and i still can't believemy good fortune. cosmic perspective ã± seti neil degrasse tyson: and now for some finalthoughts on the search for life in the universe. i've always wondered how we would fare, ifthe search for intelligent life in the universe were conducted by intelligent aliens in anotherstar system. suppose they used radio waves to observe us.and suppose they had super-sensitive detectors

with specially designed decoders. imaginewhat they would find. if they fell within our radio bubble, thatexpanding sphere of waves from the dawn of our broadcast technology, then the alienswould first hear our early radio programs like amos 'n' andy, as these signals passedthem by. some years later, they might decode tv programssuch as the howdy doody show. then comes the beverly hillbillies, followed by graphic imagesfrom the vietnam and gulf wars. the aliens might then look at technology markersin our atmosphere, and find high radiation areas from nuclear test blasts and globalgreenhouse warming from the burning of fossil fuels.

after all that, what else could the alienspossibly conclude, but that earth shows no signs of intelligent life? meanwhile, with the growth of internet radioand cable television, earth may one day fall silent to eavesdropping aliens, with no broadcastsignals for them to decode. they might wonder if we'd disappeared completely.but, more likely, they will conclude, as do those on earth who search elsewhere for intelligence,that the absence of evidence is not the same as the evidence of absence. and that is the cosmic perspective. and now, we'd like to hear your perspectiveon this episode of nova sciencenow. log on

to our web site and tell us what you think.you can watch any of these stories again, download audio and video podcasts, hear fromexperts and much more. find us at pbs.org. that's our show. we'll see you next time.

Read More »

when were stem cells discovered

â there are many christians throughout the americas opposed to the use of stem cells, which could prevent human suffering and potentially save billions of lives. nowhere in the bible, just as in galileo’s age, does it state upon what grounds christians have in taking this controversial stance. however, the use of stem cells is being lumped together with the pro-life argument, stating that because stem cells are taken from a fertilized egg, it means the egg has the potential to become a person and therefore it would be murder to use this embryofor any other purpose than to begin another human life. if you enjoy this video please subscribe.

the majority of stem cells are made from frozenembryos leftover from fertility treatments that will never be taken to term. and although using these cells for scientific research is somewhat controversial, the cloning of stems cells, which allows for a much more responsive therapy, has unfortunately resulted in even greater resistance from the religious community. the process of cloning stem cells works byremoving the dna from an unfertilized human egg. next, dna from a patient’s cell, such as a pancreatic cell, is transferred into the egg -- a process known as nuclear transfer. scientists add a few chemicals, and the egg begins to divide,

just as if the egg had been fertilized through traditional means. after a few days the egg becomes a blastocyst, a ball of about 50-200 cells. in order for this blastocyst to develop into anything beyond a ball of cells it would have to be placed into a woman’s uterus. however, scientists need the cells from the blastocyst, which is why the next step is so controversial. scientists breakdown the outer layer of the blastocyst and use the remaining cells as embryonic stem cells,

which contain the exact genetic makeup as the patient. these cells can be given to patients withoutfear of rejection from their immune system and many childhood diseases could be cured by using stem cell research. for instance, type i juvenile diabetes requires constant vigilanceof blood sugar and the amount of carbohydrates being consumed. there are also many patients, both childand adult, in need of bone marrow transplants that would greatly benefit from the use of stem cells in addition to saving lives with customized transplants, scientist are excited about stem cell researchbecause of the ability to create “sick cells.” the reason for this being, if cloned stem cells of a patient are purposely infected,

scientists could follow these cells as they developin a culture dish to discover the root cause of disease. if scientists could learn how a disease initially starts,they have a much better chance of finding a cure. this could work with a lot of diseases that invisibly developinside patients, such as in parkinson’s and alzheimer's disease. the problem is with the cells we are not using. that are being wasted. hundreds of thousands of cell that are leftoverfrom in vitro fertilization are being thrown away, they are not going to become life. they are being thrown away. so, in that sense people say "protect the unborn",but they are going to be destroyed anyway. so lets use those cells to protect the unborn that are going to be born with diabetes. that are going to be born with a genetic predisposition to alzheimer's.

or parkinson's. or that are going to be injured as children and have spinal cord injury. i mean, that’s the pro-life position. because those cells are going to be wasted.that’s what people need to understand. the catholic church, as well as many pro-life groups, have been the major opponents of stem cell cloning. even the previous president of the united states, george w. bush, actively fought to prevent the advancement of stem cell technology. in july of 2006 the senate passed a bill that would haveexpanded federal funding for embryonic stem-cell research,

a bill that had already passed the house in 2005. however, president bush vetoed the bill, the very first use of this executive powerin what was at the time his 6th year in office. one year later in june 2007 bush used his vetopower for the second time in his presidency to once again, stop the passage of a bill that would allow federalfunding to be allocated for embryonic stem cell research and to prevent what he called "the growing of life to destroy it.” research cloning on the other hand. involves the creation of cloned human embryos, which are then destroyed.

to derive stem cells. i believe all human cloning is wrong. and both forms of cloning ought to be banned for the following reasons. first, anything other than a total ban on human cloning would be unethical. research cloning would contradict the most fundamental principles of medical ethics. that no human life should be exploited or extinguished for the benefit of another. (applause) the election of barak obama in 2008 ushered in a new era of scientific advancement. on march 9th 2009, president obama abolishedthe contentious restraints on stem-cell research

implemented by bush over his two terms in office. today, with the executive order i am about to sign, we will bring the change that so manyscientists and researchers, doctors and innovators, patients and loved ones have hoped for an fought for the past eight years. we will lift the ban on federal funding for promising embryonic stem cell research. but the question remains. when does the significance of human life begin? many argue that, biologically, it begins at conception. but is a human blastocyst, smaller than a grain of sand,

whether cloned or made from the union of sperm and egg, really the same as a person? what rights does this blastocyst have? is this issue based on when life begins, or when a person begins?â  the chronic consumption of alcohol has the possibility of destroying liver cells, smoking tobacco is known to kill brain cells, and the consumption of antibiotics during aninfection effectively murders thousands of bacterial cells. cancer patients undergoing chemotherapy are not only destroyingneoplasms but many healthy cells throughout their body as well. therefore, by what standard are we to judge the value of a living cell? whether it be a liver, brain, bacterial or embryonic stem cell.

if the concern were truly based on the destruction of cellular life, then should we not conceder chemotherapy, smoking,and the use of antibiotics as a forms of murder as well? to put it another way, imagine you are in afertility clinic with a young child sitting next to you. suddenly, the fire alarm sounds. you must get out of the building as fast as possible butyou only have enough time to do one of the following. you can either run to the freezer and grab a container full of fertilized eggs. or, you can take the child sitting next to you into yourarms and rush her to safety, leaving the embryos behind. the answer is obvious. no one in their right mind would leave a child toburn in a fire in order to save a test tube full of eggs,

no matter how many "potential lives" it might contain. this emphasizes the difference between a real life, of aperson who exists, and a potential life, which does not exist. both the blastocyst and the child are alive,but we as a society must decide who to rescue. do we save the child with type i diabetes, or do we save the cloned embryo sitting somewherein a peetree dish, which will never be taken to term. what life do we value most?â  christians claim the motivation to outlaw stemcell research and to restrict a woman right to choose is rooted in god's commandment "thou shall not kill." their argument might have some substance if christians were notso inconsistent with their perception of the sanctity of human life

which is evidenced by widespread christian support of capital punishment. the following men are some most prominent evangelical christian leaders that have vocalized their opposition to the use of stem cell, yet support the death penalty as a viablemeans of punishing criminals and deterring crime. there is also a total of 36 states that practice capitalpunishment and currently have inmates on death row. the largely christian conservative state of texas holds the record at 462 state executions, 152 of which were conducted under the governorship of george w. bush. more than any other governor in modern american history

and the same man that twice vetoed federal funding for stem cell research. there are various reasons given for why someone would support the death penalty. one, for example, is that by executing someone convicted of murder you reduce the possibility they could ever be released on parole and hence you reduce the risk of a repeat offence. in addition, legislators believe that crimes carrying apenalty of death also act as a deterrent against violent crimes. therefore, when it comes to capital punishment many christians are willing to accept the death of one humanlife in order to preserve the innocent lives of potential victims. yet, when it comes to stem cell research

they are not willing to sacrifice a ball of cells in order tosave the countless innocent lives of sick and dying children it may be true that the life christians are willingto sacrifice is that of a vicious murder or rapist, but the sixth commandment was not provided with a list exceptions. however, not every single person convicted of a heinous crime is guilty. wife-killing banker. why'd you do it? i didn't since you ask. (laughs) you gonna fit right in. everybody in here is innocent. didn't you know that?

heywood, what you in for? didn't do it, lawyer fucked me. there are countless instances all over the world where people have been wrongly imprisoned for decades and later acquitted upon the discovery of new evidence. this is not to say capital punishment should be permanently outlawed, and in extreme cases the death penalty is appropriate, but if every person convicted of a serious crimewere put to death within a few years of sentencing thousands of innocent people would have unjustly lost their lives.

do christians believe these are acceptable lossesin order to maintain the current penalty system? and if so, why is less value placed on the life of someonefalsely convicted of a crime verses a frozen embryonic stem cell? we are of course products of our environment, and those with a religious upbringing will no doubt be influenced by the teachings of their faith. but all too often the only way for someone to reevaluate their stance on a topic is to be placed in a difficult situation thatdirectly conflicts with one's long-held views. for example, take dick cheney, former vice president of the bush administration. the republican party is infamous for their passage of anti-homosexual legislature, preventing tax-paying gay and lesbian citizens of the unitedstates from enjoying the same rights and liberties as everyone else.

however, recently cheney came out in publicsupport of not only civil unions, but gay marriage itself. this is an issue that directly affects cheney's family and his lesbian daughter. well i think freedom means freedom for everyone. as many of you know, one of my daughters is gay. something that we have lived with for a long time in our family. i think people ought to be free to enter into any kind of union they wish. any kind of arrangement they wish. for a moment, imagine someone very important in your life, such as a parent, a child, or sibling.

given the opportunity, wouldn't you do anything inyour power to support this loved one in a time of need? would you fail to appeal the death sentence of familymember if there was any possibility of their innocence? would you prevent your child suffering with aspinal cord injury access to embryonic stem cells, declining them a fighting chance at life? would you reject someone you dearly care for, such a brother, sister or close friend, after they've come out to you about their homosexuality. it is very easy to form opinions on topics that donot personally affect you or anyone you even know. but for a moment place yourself in each of thesedifficult positions and honestly reevaluate your stance. if you would provide assistance to a loved one in any of these situations,

why shouldn’t this standard be applicable to all people in similar times of need? christians are treading on very thin ice by engaging in politicalrhetoric that in most instances can be observed as unconstitutional. at what point should religious dogma be restrained from tramplingthe governing principles of a nation and the rights of its citizens? to what end will the ideologies of religious philosophy continue todictate the aims of scientific discovery and the rights of the individual?

Read More »

when did stem cell research became known

can you imagine a world where one day if youneed a new heart you could just order one made just for you? sound like science fiction?well we’re not so far off. hey guys, julia here for dnews dudes, so something pretty cool just happenedin the wonderful world of science. researchers grew beating hearts from human stem cells.okay fine hyperbole, it’s not the whole heart just a few beating cells. but it’sso cool. in a study published in the journal nature,the researchers used human skin cells, turned them into pluripotent cells and used physicaland chemical signals to coax the cells into forming little cardiac microchambers. whichcould be important for studying how the heart

grows in an embryo or how drugs might affecta fetus’s heart. or… looking way into the future, for growing hearts in a dish.it could be a great way to replace organs. no more waiting for a donor and since it wouldbe perfect match to your body, no more terrible drugs to prevent rejection.so far smaller organs like tracheas and bladders have been grown in a lab using a person’sown stem cells, but a heart is a little more complicated. so let’s take a little lookinto how we got here. first off, what are stem cells? stem cellsare pluripotent, meaning they are undifferentiated cells that can develop into any kind of cell.skin, heart, liver etc. so alright, but what’s the big deal? why do researchers love to studystem cells? even from the earliest inklings

of stem cells, there have been big dreams.researchers have hoped that one day they could be able to grow entire new organs from stemcells that would be a perfect match for the recipient. we’ve come a long way from the early daysof stem cell research. human stem cells were first isolated in 1998 by two independentresearch teams led by james a. thomson of the university of wisconsin and another byjohn d. gearhart of johns hopkins university school of medicine. these early stem celllines were derived from early embryos, which are destroyed in the process and thus stirreda little controversy. okay a lot of controversy. because of the debate that raged in the ussurrounding embryonic stem cell research,

scientists looked to find stem cells in otheradult tissues. so a few years later in 2001 adult stem cells were found in fat tissue.now adult stem cells can be found from almost any tissue. but they are tricky, they takea while to coax into growing in a dish. so they’re not ideal. but in 2007, in a paper published in the journalnature biotechnology, dr. anthony alata discovered that amniotic fluid also contains stem cells.which of course added more fuel to the debate. and the same year, two independent teams ofresearchers pioneered a process to turn adult somatic cells into pluripotent stem cells,naturally called induced pluripotent stem cells. the process involves introducing 4different genes into the cells using a virus

as a carrier. the team from japan led shinya yamanaka, publishedtheir work in the journal cell and the team from by james thomson at university of wisconsin–madisonpublished their work in the journal nature. and it was such a huge deal that, yamanakaactually won the 2012 nobel prize for discovering ips cells. which of course this discovery held a lotof promise, it would sidestep some of the controversy with embryonic stem cells. butthere are more than a few issues with their technique, like low efficiency, it’s difficultto do and when done, only a few cells are reprogrammed. plus there’s weird problemswith rejection and also a problem with tumors

developing. but problems aside, tons of studies have beenand are being done with this technology. with lofty goals, like attempting to cure blindnessand diabetes. the federation of american societies for experimental biology says that ips cellswill also “allow scientists to study complex human diseases in petri dishes, a step towardanalyzing the conditions and developing therapies.” some researchers like dr. alata don’t carewhere the cells come from, just that they work well. no matter where stem cells comefrom, it’s clear that we’re on the road to organs grown in a dish. well i certainlyhope so. but it’s also clear that more research is needed.

and really, lab grown organs can’t comesoon enough! if you wanna know the challenges of living with an organ transplant & why theyfail, check out this recent video i did:

Read More »

what's a stem cell

voiceover: i'm gonna startby drawing a blood vessel. inside the blood vessel i'm gonna draw in some of the cells that you'dexpect to see in normal blood. i'm gonna put in a few red blood cells. i'm gonna draw in a couple of platelets which are just fragments of cells and then i'm gonna put ina few white blood cells. even though all of thesecells are found in the blood they're actually not made there.

the cells in the bloodare made inside the bone. if you were to take across section of bone, if you were to take a slice like this and you looked at it, you'd see that on the inside of bone there's a central cavity. this is the outside part of the bone. the hard part and thisis the central cavity. inside that cavity there'sthis red spongy tissue.

that stuff is called bone marrow. bone marrow. bone marrow is where all ofthese blood cells are made. it's the site of hematopoiesis. hemato means blood and poiesis means to form or to make. hematopoiesis is just a scary greek word that means to make blood. let's take a look at what goeson inside the bone marrow.

what's interesting is that as different as all of the blood cells are they all actually originatefrom the same cell and that cell is called ahematopoietic stem cell. this stem cells gives rise to all of the different cellsthat you see in the blood. it gives rise first to twodifferent cell lineages or two different cell groups. first there is the myeloid group.

myeloid group. which is different fromthe lymphoid group. the lymphoid group. all of the cells that you see in the blood belong to either the myeloid group or the lymphoid group. the lymphoid group includes two different types of blood cells. first there is the t cell

or actually that's too big because this is a very little cell. that seems about right. there's a t cell andthe majority of the cell is taken up by the cell's nucleus, and that's what i'm shading in over here. so much so that this cell has a nickname. it's often referred to as a naked nucleus because it looks like the nucleus

isn't surrounded by very much cytoplasm. this is a t cell or a t-lymphocyte. t-lymphocyte. it's very similar in appearance to the other type of lymphoid cell. this cell also has a nucleus that takes up the majority of the cell and this cell is a bcell or a b-lymphocyte. b-lymphocyte, lymphocyte.

those are the two differenttypes of lymphoid cells. what about the differenttypes of myeloid cells. for starters we have a red blood cell. i guess we should draw that in red. this is also very small cell. i'm gonna shade in this cell so that i can show you thatthe center of this cell is much lighter than the edges or the periphery of the cell.

this is not the cell's nucleus, guys because we know that red blood cells don't have nuclei. what i'm trying to show isthat the center of the cell is much lighter than theperiphery of the cell. i guess i could do a better job of that if i showed you what thiscell looks like on its side. this is what a red blood cell looks like when it's laid on its side.

it kind of looks like a dumbbell where the edges are much thicker or much wider than the center. the edges would since they're thicker they would be much moredensely packed with hemoglobin. since we know that hemoglobin is what gives red bloodcells their red color, the edges would then bedarker than the center. since the center is much thinner

it would have a lot less hemoglobin. it would be a lot paler in comparison. we said that this is a red blood cell but since in science we never use a plain andordinary name of things we call this an erythrocyte. erythrocyte which is just a fancy name for a plain old red blood cell. what are some of the othertypes of myeloid cells?

we have this one cell thati'm drawing in over here. you might say well, thatlooks nothing like a cell and you'd be totally right. this is a very odd-looking,very large cell and it's called a megakaryocyte. even if you never heardof a megakaryocyte before you may have heard ofwhat it gives rise to because a megakaryocyte gives off little blebs of its cytoplasm

to form this small cell fragments and these fragmentsare known as platelets. you may have heard ofthe platelets before. the rest of the myeloid cells are actually differenttypes of white blood cells. for example you have thisone type of white blood cell and the rest of these white blood cells are about twice thesize of a red blood cell so that looks like it's twice the size

of a red blood cell to me. this cell is called a monocyte. it's known for having this nucleus that's in the shape of a kidney bean. that kind of looks likea kidney bean to me. this is a really cool white blood cell because it protects us from bacteria and viruses and other invading organisms just like any other white blood cell does

but it does so in a very interesting way. let's say that this was a bacterium or actually, no i like the color pink so let's use a color i don't like. let's say that this was a bacterium. the monocyte would defend us against it. it would attack this bacterium by engulfing itself around the bacterium. when it does that it kind of looks like

it's eating the bacteria. it looks like its eating the bacterium. that's a very interesting way of dealing with these invading organisms. let's clear out that. mono actually refers to the fact that this cell has a nucleusthat's in one piece and i guess a lot ofthese cells have nuclei that are in one piece.

it makes us wonder what types of cells have nuclei that are not in one piece and that would bring us to a neutrophil. this is a neutrophil. a neutrophil. it has a nucleus like i'm drawing in that is broken up into severaldifferent pieces or segment. the segments are still held together by little pieces of string.

this is called a multi segmented nucleus. even if you've never heardof a neutrophil before i'm sure you've seen them before and how do i know that? it's because neutrophils are actually the main component of pus. if you like anybody elsehas ever popped a pimple you've looked at a bunch of neutrophils. what are the other types of myeloid cells?

well, we have this one cellthat's called a basophil. basophil. it looks something like this. you might say, well, that looks an awful lot like a monocyte and you'd be completely correct except this cell has a very unique feature that the monocyte doesn't have, and that is that it hasthese bright blue granules

in its cell's cytoplasm. that make it stick out. the way i like to thinkof a basophil is like a basophil is like a blueberry muffin and that reminds that it has these bright blue granules inits cell's cytoplasm. for the last type of myeloidcell we talked about. whoops. for the last type of myeloidcell that we talked about

is an eosinophil. it's an eosin-o-p-h,p-h-i-l, eosinophil, okay? it has a nucleus thatcan sometimes be found in two pieces. this is the first piece andthis is the second piece but that's not what makes it so unique. what it's really well known for is the fact that it has these bright, beautiful red granulesin its cell cytoplasm.

those are all of the different blood cells with all the lymphoid cells on this side and all the myeloid cells on this side. it turns out that all of these cells don't directly develop fromhematopoietic stem cell. instead they undergo multiplestages of development to mature into their adult form, but don't worry guyswe're not gonna hash out each of those differentforms and their names

and physical characteristics. instead we're gonna makea very general statement. i guess we could put that up here. we're gonna say that the immature forms. the immature forms of all these cells are called blasts. when the blast mature, they mature they are called cytes. let me show you what i mean.

to spare you guys the agony of having to watch me draw out all of those different forms i just pasted them in here. we can see here that what we said about the immature forms being called blasts and the more mature formbeing called cytes is true. the t-lymphocyte developsfrom a t lymphoblast just like an erythrocyte develops

from an erythroblast and a megakaryocyte developsfrom a megakaryoblast. you guys get the pattern. the only wrench i'm gonnathrow into this pattern is with the neutrophil,basophil and eosinophil which all actuallydevelop from the same cell and that cell is called a myeloblast. i think that that's a reasonable place to end our discussion on hematopoiesis.

Read More »

what is the stem cell

- [voiceover] so, let megive you an analogy, here. when you were still anadorable little baby, you were just bursting with potential. you could decide to be a pilot, or a doctor, or a journalist. you had the potential to specialize into all sorts of different careers, and as you got a bit older,you got more and more committed down a certain pathway,

and the decisions that you made moved you further and furtheralong this pathway, right? well, it turns out that stemcells operate in a similar way, going from unspecializedto more specialized as they get older. so, let me show you what i mean by that over the course of this video. and let's actually startback at the zygote, here, the cell that resultswhen sperm and egg fuse

because that's really where our stem cell story kinda begins. so, the zygote starts to divide, right, by mitosis until it reachesthe blastocyst stage, this hollow ball of cellshere is called a blastocyst. and here, things start to geta little bit more interesting. so, in a blastocyst, there'sthis little grouping of cells down in here, referred toas the inner cell mass. and this is a really speciallittle bunch of cells

that go on to become the embryo. so, these are called stem cells. and what they can do as stem cells is they can specialize intoseveral other cell types. so, we actually call thempluripotent stem cells. pluri meaning several and potent referring to these stem cells' ability to actually do this differentiation. so, during development,these inner cell mass

pluripotent stem cells can differentiate into any of the more than200 different cell types in the adult human body whengiven the proper stimulation. so, it's kind of incredible to think that every single cell in your body can trace its ancestry back to this little group of stem cells, here. and actually, if you ever hear anyone talking about embryonic stem cells,

these are the ones they're referring to, these icm stem cells. so, is this the only placewe can find stem cells, here in the developmental structures? we used to think so, but, it turns out that in mammals, there aretwo main types of stem cells. embryonic stem cells that we just saw and somatic stem cells whichare found in every person. so, the embryonic stem cellsare used to build our bodies,

to go from one cell totrillions of specialized cells, and the somatic stem cells are used as sort of a repair system for the body, replenishing tissuesthat need to be replaced. and they can't repair everything, but, there's a lot of every day repairs that can happen because of our stem cells. so, in skin, for example... this outside layer is the partof our skin that we can see

and that we can touch, right? and it's made of these waterproof, pretty rugged epithelialor skin cells and interestingly, althoughthey are pretty rugged, you're constantlyshedding these skin cells. they actually just sort offall off or get rubbed off during every day activities like when you're putting your clothes on. and then, the ones from underneath them

just sort of move up and take their place. so, you shed them and you lose almost 40,000 of them per hour. so, if we wanna have anyhope of keeping our skin, we kinda need a way toreplace these cells, and that's where stem cells that live in our skin come in. actually, our skin cells are shed and replaced so often,that it only takes a month

for us to have a completely new skin. like, literally onemonth, entirely new skin. it's outrageous. anyway, deep within our skin, there's this layer of stem cells called epidermal stem cells, and their job is to becontinually dividing. so, you can see themdividing, here, dividing, dividing, dividing, and makingnew skin cells that go on

to migrate upward as themultiple layers of our skin. and their goal is to eventually replace these ones up here on the outside that get damaged or worn out and fall off. so, it's this kind of activity here which show off our stem cells' role as our regenerative cells. now, lemme just highlighta few differences between our mature skin cells over here

and our stem cells down here. they are very different. mature cells are notthe same as stem cells, and this principle goesfor really any mature cell versus any stem cell. so, the mature cell isalready specialized, it already has a really specific function. for example, our outer layerof epithelial cells, here, they have a protective function

against the outside environment. and, you know, just thinkingof other adult cell types, right, like muscle cellshave a contractile function, and neurons have amessage sending function, and bones have a rigidstructural function. so, all these adult cells are already nice and specialized, they'vegrown up and decided what they wanna do for a living, whereas, stem cells arenot like that at all.

stem cells are unspecialized. but, they still have areally important job, which is to give rise to ourmore specialized cell types, like these cells here, okay? and, actually, in order tobe considered a stem cell, and this goes for theembryonic stem cells we met previously and the somaticstem cells we're meeting now, to be a stem cell, you'd need to possess two main properties.

the ability to self renew,meaning you can divide and divide, and divide, but, at least one of your resultingcells remains a stem cell, it remains undifferentiated, and you'd need to have a high capacity to differentiate intomore specialized cells when the time comes. so, remember, this is also referred to as having some degree of potency.

and there's actually a few different types of stem cells, and someof them can turn into more types of cells than others. some are more potent than others. so, this epithelial stem cell we saw here is actually one of the lesspotent types of stem cell. in other words, thesestem cells can only divide and specialize into more epithelial cells. so, they're our source ofepithelial cells, sure,

but, only epithelial cellsand not any other cell type. so, we call them unipotent,referring to their ability to only create one type of cell. but, lemme show you another example here of a multipotent stem cell. let's look at this guy'sfemur, his thigh bone, which is where our blood cells are made inside bone marrow in our bones. so, you might know thatour red blood cells

have a life span of about four months. so, that means that we needto be constantly replacing our red blood cells orwe'll run out, right? well, in our bone marrow,we have what are called hematopoietic stem cells, which are our blood making stem cells. and these are pretty special, they're multipotent stem cells, which means they can giverise to many types of cells,

but, only ones within a specific family. in this case, blood cells,and not, for example, cells of the nervous systemor the skeletal system. so, our hematopoietic stem cells are always busy churningout new blood cells, red blood cells to carry oxygen for us, and white blood cells to keep our immune system nice and strong. and for a more clinical example,

with blood diseases like leukemia, certain blood cellswill grow uncontrollably within a patient's bone marrow, and it actually crowds out their healthy stem cells, here, from being able to produce enough blood cells. so, as part of treatment,once the leukemia cells are cleared from the bone marrowwith, usually, chemotherapy or radiation, doctors can actually put

more hematopoietic stem cellsback into the bone marrow that then go on to produce normal amounts of blood for the person again. so, this is probably the most common use of stem cells in medicine as of now. and you can actually findthese multipotent stem cells in most tissues and organs. so, for example, we havemultipotent neural stem cells that slowly give rise to neurons

and their supporting cells when necessary. and we have multipotentmesenchymal stem cells in a few different places in the body that give rise to bonecells and cartilage cells, and adipose cells. so, you might be wonderingafter seeing our epithelial and our hematopoietic stem cells dividing, why aren't these cells beingused up as they divide? and that's a really good question.

so, stem cells havetwo mechanisms in place to make sure that theirnumbers are maintained. so, their first trick isthat when they divide, they undergo what's calledobligate asymmetric replication where the stem cell dividesinto one so called mother cell identical to the original stem cell, and one daughter cellthat's differentiated. so, then, the daughtercell can go on to become more specialized while the mother cell

replaces the stem cellthat divided, initially. the other mechanism is calledstochastic differentiation. so, if one stem cellhappens to differentiate into two daughter cells insteadof a mother and a daughter, another stem cell will notice this and makes up for the lossof the original stem cell by undergoing mitosis andproducing two stem cells identical to the original. so, these two mechanisms make sure

their numbers remain nice and strong. so, we've looked at embryonic stem cells and we've looked at somatic stem cells. there's actually one more type called induced pluripotent stemcells, or ips cells. it turns out that youcan actually introduce a few specific genes intoalready specialized somatic cells like muscle cells, andthey'll sort of forget what type of cell they are,and they'll revert back,

they'll be reprogrammedinto a pluripotent stem cell just like an embryonic stem cell. and this is a huge discovery. i mean, the technique isstill being perfected, but, there's a lot ofmedicinal implications, here. for example, ips cellsare basically the core of regenerative medicine,which is a pretty new field of medicine where the goalis to repair damaged tissues in a given person by using stem cells

from their own body. so, with ips cells, each patient can have their own pluripotent stem cell line to theoretically replaceany damaged organs with new ones made out of their own cells. so, not only would apatient get the new organ they might need, but, there also won't be any immune rejection complications since the cells are their own.

so, there's still a ways to go here before this type of medicineis sort of mainstream, but, already, ips cells have helped to create the precursorsto a few different human organs in labs, suchas the heart and the liver. now, before we finish up here, i just wanna answer two questions that might have come up for you. so, one, what triggers ourstem cells to differentiate?

well, it turns out thatin normal situations, right, when the stemcell's just hangin' out, not doin' too much, it actually expresses a few different genes that helps to keep it undifferentiated. so, there are a few proteinsfloating around in the cell that prevents other genesfrom being activated and triggering differentiation. but, when put in certain environments,

this regulation can be overridden, and then, they can go on and differentiate into a more specialized cell. the type of which depends on what specific little chemical signals are hanging around in the stem cell's environment. so, for example, in the bone marrow, there are certain proteinsthat hang around stem cells and induce some to differentiate

into the specific blood cell types. and finally, what's all thisstuff you might have heard, maybe in the news, about cord blood? well, from cord blood,which is blood taken from the placenta and the umbilical cord after the birth of ababy, you can get lots of multipotent stem cells, and sometimes, some other stem cells that have been shown to be pluripotent.

so, this cord blood usedto just be discarded after a baby's birth, but now, there's a lot of interest in keeping it because now we know itcontains all these stem cells.

Read More »

what is stem cell

can you imagine a world where one day if youneed a new heart you could just order one made just for you? sound like science fiction?well we’re not so far off. hey guys, julia here for dnews dudes, so something pretty cool just happenedin the wonderful world of science. researchers grew beating hearts from human stem cells.okay fine hyperbole, it’s not the whole heart just a few beating cells. but it’sso cool. in a study published in the journal nature,the researchers used human skin cells, turned them into pluripotent cells and used physicaland chemical signals to coax the cells into forming little cardiac microchambers. whichcould be important for studying how the heart

grows in an embryo or how drugs might affecta fetus’s heart. or… looking way into the future, for growing hearts in a dish.it could be a great way to replace organs. no more waiting for a donor and since it wouldbe perfect match to your body, no more terrible drugs to prevent rejection.so far smaller organs like tracheas and bladders have been grown in a lab using a person’sown stem cells, but a heart is a little more complicated. so let’s take a little lookinto how we got here. first off, what are stem cells? stem cellsare pluripotent, meaning they are undifferentiated cells that can develop into any kind of cell.skin, heart, liver etc. so alright, but what’s the big deal? why do researchers love to studystem cells? even from the earliest inklings

of stem cells, there have been big dreams.researchers have hoped that one day they could be able to grow entire new organs from stemcells that would be a perfect match for the recipient. we’ve come a long way from the early daysof stem cell research. human stem cells were first isolated in 1998 by two independentresearch teams led by james a. thomson of the university of wisconsin and another byjohn d. gearhart of johns hopkins university school of medicine. these early stem celllines were derived from early embryos, which are destroyed in the process and thus stirreda little controversy. okay a lot of controversy. because of the debate that raged in the ussurrounding embryonic stem cell research,

scientists looked to find stem cells in otheradult tissues. so a few years later in 2001 adult stem cells were found in fat tissue.now adult stem cells can be found from almost any tissue. but they are tricky, they takea while to coax into growing in a dish. so they’re not ideal. but in 2007, in a paper published in the journalnature biotechnology, dr. anthony alata discovered that amniotic fluid also contains stem cells.which of course added more fuel to the debate. and the same year, two independent teams ofresearchers pioneered a process to turn adult somatic cells into pluripotent stem cells,naturally called induced pluripotent stem cells. the process involves introducing 4different genes into the cells using a virus

as a carrier. the team from japan led shinya yamanaka, publishedtheir work in the journal cell and the team from by james thomson at university of wisconsin–madisonpublished their work in the journal nature. and it was such a huge deal that, yamanakaactually won the 2012 nobel prize for discovering ips cells. which of course this discovery held a lotof promise, it would sidestep some of the controversy with embryonic stem cells. butthere are more than a few issues with their technique, like low efficiency, it’s difficultto do and when done, only a few cells are reprogrammed. plus there’s weird problemswith rejection and also a problem with tumors

developing. but problems aside, tons of studies have beenand are being done with this technology. with lofty goals, like attempting to cure blindnessand diabetes. the federation of american societies for experimental biology says that ips cellswill also “allow scientists to study complex human diseases in petri dishes, a step towardanalyzing the conditions and developing therapies.” some researchers like dr. alata don’t carewhere the cells come from, just that they work well. no matter where stem cells comefrom, it’s clear that we’re on the road to organs grown in a dish. well i certainlyhope so. but it’s also clear that more research is needed.

and really, lab grown organs can’t comesoon enough! if you wanna know the challenges of living with an organ transplant & why theyfail, check out this recent video i did:

Read More »