Surviving an Impossible Deep Freeze

the hearty animals found living north of the arctic circle live in a constant dance with death with a host of adaptations that help them battle the lethally cold temperatures creating more body heat hibernating and generally blocking the cold from getting into the body seem like the obvious approaches to survive such cold climates approaches taken by the large often furry animals you normally think of when you think of the arctic but there's one animal that seems to defy the logic that applies to most other cold weather animals an animal that almost certainly does not come to mind when thinking of the frost covered tundra it's the only amphibian found north of the arctic circle its body wet and cold blooded and if you came across it in the winter time you would undoubtedly think you had found a very dead frog its body frozen solid eyes glazed over motionless but if you waited until warmer conditions you would see that frozen frog thaw out gasp for air and bounce right back to life the wood frog doesn't survive in icy climates by resisting the cold but by embracing it it freezes and thaws with the environment with up to 70 of its body water freezing with every cold snap this is definitely a handy superpower for the frog but when it was discovered scientists immediately saw the bigger story utilizing these deep freeze abilities could mean a longer shelf life for human organs a quest that has been out of reach since the very first organ transplants human organs outside the body don't last very long and when lives are hanging in the balance even a few extra hours could make all the difference so how does the wood frog emerge from its frozen state completely unharmed what lessons can animals like this teach us and is this ability something we can harness for ourselves [Music] the wood frog is found across the forest of north america from the southern appalachian mountains up to the tree line above the arctic circle in places that freeze and freeze hard when winter starts to take hold the frogs take shelter in the leaf litter of the forest floor they assume a crouched position with the limbs drawn in close to the body and their head lowered this is the water holding position and helps to reduce the amount of water lost to evaporation over what could be months of being frozen ice formation begins in the extremities then spreads throughout the entire body cavity surrounding the abdominal organs eventually as much as 70 percent of the frog's body water is frozen and vital signs completely stop normally ice formation like this should shred tissue the crystals physically ripping cells apart freezing also normally wrecks cells by affecting the flow of fluids into and out of them before ice forms inside cells it forms in the spaces between them which reduces the volume of liquid there this increases the concentration of dissolved salts and other ions which causes water to rush out from the cells to compensate causing them to shrivel and die all of this leading to a frosty demise so to avoid this fate the wood frog's body carefully orchestrates the entire process to avoid ice crystallization and dehydration in vital parts of the body during the course of freezing they change over their metabolism they reorganize themselves they're not damaged by the physical ice they're not damaged by the anoxia they're not damaged by the dehydration to learn more about how the wood frog can survive such an ordeal i talked to dr ken story professor of biochemistry and wood frog expert at carleton university so what happens when a frog is wet and popping around yay and it goes below zero ice starts to penetrate into the frog so the frog can't generate heat itself it's a cold-blooded animal it's a poignant and so ice begins to push into the frog this ice goes down veins and arteries pushing blood ahead of it so eventually if you take a stone frozen frog and you cut off its legs and its arms which is cruel they have no blood the blood has all been pushed into the center of the frog where it's a huge lump of blood that then freezes solid so frogs are blood huge amounts of blood with large amounts of glucose 400 millimolar glucose in the middle of them this glucose acts as a protective molecule known as a cryoprotectant ice crystals are only made of pure water but the temperature at which they start to form depends on what else is in the solution anything suspended in water interferes with water's ability to form the hexagonal lattice work of ice crystals cryoprotectants are molecules such as alcohols or sugars that animals can use to lower water's freezing temperature inside their bodies essentially a biological antifreeze if i gave you a frozen frog whoa you would thaw it out you would taste ah and it would taste sweet you can measure the glucose of a frog by using a diabetes meter i don't know if you're diabetic but you just take a little test strip dip it in the frog and then it says oh my god you're dead go and see your doctor immediately because your blood glucose should be four and the blood glucose you measure out of the frog is 400. once the frog's body senses that the temperature is near freezing the frog's liver begins to dump massive amounts of glucose into its bloodstream then glycerol and alcohol and more glucose starts to be packed into the frog cells to prevent ice from forming there and to prevent any drastic loss in volume due to the dehydrating effects of ice formation at the same time water begins to move out of the vital organ cells and pools in the extracellular space ice nucleating proteins trigger the ice to freeze in these specific places in sheets between the skin and muscle layers in small spaces such as the lens of the eye or the ventricles of the brain everywhere except the critical organs and cells it can survive this period of no circulation by reducing the metabolic needs of cells so they don't need much if any nutrients and oxygen and then spring comes the frog thaws and all of its organs and bodily functions are restored nearly instantly and surprisingly the wood frog doesn't just withstand the cold but actually depends on it they're adapted to being frozen if you take a wood frog and you keep it in the lab and you don't freeze it it does it just uses up all of its fuel it uses up all of its muscle it uses up all of its fat it uses up all of its glycogen and it dies and even though frogs are amphibians and humans are mammals we have all of the same major organs so if a frog can freeze itself completely solid can we is there a way we can recreate this ability freezing organs and bringing them back to life in the big picture of history organ transplants are a relatively recent thing it wasn't until 1954 that the first human organ transplant was successfully completed a kidney transplanted from one identical twin brother to the other in 1967 the first liver and the first heart were transplanted and the era of organ transplants had begun in the u.s there are over a hundred thousand people on a waiting list to receive an organ transplant but only around forty thousand transplants are performed each year seventeen people die per day waiting for an organ that never came much of this is due to a challenging supply network constricted by the inherent lifespan of organs once they've been removed from the body with the standard cooling methods a liver or pancreas can survive for 12 hours outside the body a heart for only six when an organ is taken out it's a race against the clock as cells start dying from a lack of nutrients and oxygen but cooling them slows this process it reduces the metabolism of the cells so they need far less oxygen and nutrients than they would normally so the idea of freezing organs to slow this process even further making the organs last even longer became an immediate goal for doctors shortly after the first liver transplant researchers attempted the first frozen preservation of livers using glycerol as a cryoprotectant they froze canine livers at negative 20 degrees celsius for periods between 24 hours to 2 weeks but when the livers were then transplanted into healthy recipients the animals only survived for a few hours the livers had suffered serious damage to their cells most notably to their blood vessels years later researchers tried again this time armed with more knowledge of freeze tolerant animals like the wood frog mimicking how the wood frog undergoes freezing in nature researchers infused rat livers with glycerol and brought the temperature down to just negative three degrees celsius and did so slowly mirroring what happens to the frogs in the wild when these livers were transplanted back into the original donors they did produce bile and one animal even lived for five days but sadly none of the animals ultimately survived after decades of work in this field researchers are coming to the conclusion that ice is just too damaging to tissues even in the presence of cryoprotectants the frogs are able to withstand such freezing due to an amalgamation of multiple adaptive strategies anoxia tolerance dehydration tolerance metabolic rate suppression huge amounts of cryoprotectants targeted ice nucleating proteins we will struggle for a long time to recreate all of these elements working in perfect unison inside organs each with different sizes metabolic requirements and cell types i ask dr story if he thinks it will ever be possible to mimic the frozen frog's ability in organ preservation if we put in time energy and money on frozen frogs learned everything and then froze human organs yes of course it would be possible but it's not going to be done because it's not necessary if you discover that there are lemurs that are actually primates hi and they can hibernate perfectly you don't have to freeze a human you don't have to freeze an organ you have to turn off their metabolism like a freaking lemur and keep it warm dr story argues that perhaps looking at freeze tolerance was never the right place to look if the goal of freezing is simply to reduce the cellular needs of organs maybe there's a way to achieve this without the freeze [Music] when we think of hibernating animals we often think of cold weather animals like ground squirrels but the metabolic rate suppression that characterizes winter hibernation is not actually an adaptation to survive the cold but to survive periods of drought and periods with no food desert animals go through a nearly identical process called estivation and this then raises the obvious question if freezing temperatures aren't required for metabolic rate suppression can we bypass the ice altogether can we simply find a way to shut off the metabolism of organs to allow them to last longer this is the new line of thinking that ken's story in his lab are investigating we discovered that primates primates little tiny monkeys look called lemurs they hibernate and turn off their metabolism completely but they're not cold they're warm and adorable so then we said look why cool down a human why cool down a human organ why freeze a human organ why not just do what a lemur does the gray mouse lemur is the particular animal model that the story lab is currently researching they are one of a few primate species that have recently been discovered to hibernate and they do so in warm weather every hibernator you know of hibernates in the cold oh my god the bears the ground squirrels the balls the mice lemurs hibernating madagascar it has never been cold in madagascar for 60 million years but madagascar has two sides the two sides are summer and winter but they're wet and dry dry and wet wet and dry so the lemurs run out of food for six months of the year so they lower their metabolic rate and as primates they are the closest relatives to humans that hibernate making them the best models for identifying and applying the mechanism of metabolic rate suppression to human needs the story lab is now focusing on understanding the biochemistry involved in warm bodied metabolic rate suppression when a lemur finally turns off its metabolism its body temperature goes down from your body temperature 37 down to 35. that's not cold that's warm they turn off their metabolism with known molecular mechanisms known because we study them they turn it off with microrna they turn it off by taking message rnas and putting them in prison so they develop parts of their cells which are prisons for mrna so they can't make any proteins they do it by phosphorylating and turning off metabolic pathways and reorganizing transcription and translation and they turn it off by reaching into the nucleus and making certain dna can't be developed any further and while complicated applying these genetic mechanisms to human organ transplants could very well be the thing that saves tens of thousands of lives every year the animal kingdom has answers to some of our biggest problems hidden within countless species we just need to ask the right questions talking with dr story was definitely the highlight of my week for some obvious reasons yes watch this oh look at this yay watch this hi hi or my personal thing would be just to put up pictures of brad pitt and facebook and because talking with experts like this gives a whole new perspective to the story i'm trying to tell every science story is driven because of the people behind it the ones in the lab or in the field asking the complicated questions and these human stories to me are just as fascinating as the science ones and this is why we decided to start a podcast to explore just this modulus hosted by me and brian from real engineering is a podcast about the people behind the scientific stories we tell you here on youtube we talk to the scientists who are on the cutting edge of research and the people who are affected by the topics we discuss the second episode of modulus launched yesterday it's an episode where i talked to two pioneers of the ocean some of the world's first saturation divers they discuss the physiological and psychological effects of living at the bottom of the ocean for weeks at a time they're two of the most interesting people i've ever had the chance to talk to and their stories will give you insight to a whole world that exists at the bottom of the ocean this episode of modulus launched yesterday on nebula the streaming platform made by me and several other educational youtube content creators it's a place to watch and listen to our videos and podcasts ad free along with original content that's not available anywhere else like the real engineering series the logistics of d-day or tom scott's game show money we can take more risks on nebula where we don't have to worry about the youtube algorithm there is so much original content there with more being added all the time and to make it even better nebula has partnered with curiosity stream the streaming platform with thousands of high budget high quality documentaries there are loads of documentaries about extraordinary animal behavior like this one called nature's weirdest events made by the bbc it explores a parasite that can use mind control on a snail in order to reproduce the massive amounts of slime made by a very strange fish or the incredible architectural structures made by huge ant colonies it's a fun 50-minute documentary with several of these wild animal stories if you've hesitated before to get curiosity stream and never quite pulled the trigger now is definitely the time to do it for a very limited time curiosity stream is still offering 41 off their annual plans making a yearly subscription just 11.79 that's less than a dollar per month there's only a day or so left on this deal so get it while it's hot so by signing up at curiositystream.com real science you'll get a subscription to curiosity stream and a subscription to nebula for just 1179 for the entire year signing up is also the best way to support this channel and all of your favorite 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Channel: Real Science

Views: 136,671

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Id: eoJWQNg7egc

Length: 17min 56sec (1076 seconds)

Published: Tue Jan 19 2021