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Tomoyuki Yamaguchi

Scientists Grow Mouse Organs Inside Rats, Then Transplant Them Into Mice

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Tomoyuki Yamaguchi

Researchers from Stanford University and the University of Tokyo have pioneered a technique to grow organs from one species inside another, then transplant them back into individuals of the first species. The technique, described this week in the journal Nature, suggests that we might someday be able to grow desperately needed human organs inside other animals.

The field of organ transplantation is no stranger to interspecies interactions. Surgeons have been giving patients heart valves from pigs for decades—a situation that speaks to the fundamental shortage of viable human organs available today. Researchers are currently attacking that issue from a number of different angles, including recycling used organs and 3-D printing new ones.

The latest study focused on the pancreas, an organ essential for digestion and regulating blood sugar. Pancreas transplants are very effective in combating Type 1 diabetes, but as with hearts and lungs, there just are not enough organs to go around.

To see if they could grow new, viable pancreata from scratch, researchers bred a type of rat that could not grow its own pancreas. They then implanted mouse stem cells into the rats while they were still embryos. The stem cells took, and grew successfully into mouse pancreatic cells. Next, the scientists removed these cells and transplanted them into diabetic mice.

Yamaguchi et al. in Nature

 
The new organs worked beautifully, as though the mice had grown them themselves, co-author Hiromitsu Nakauchi said in a statement: “We found that the diabetic mice were able to normalize their blood glucose levels for over a year after the transplantation of as few as 100 of these islets.”

Rejection of new organs is a substantial risk with any transplant, but the mice’s new pancreata made themselves right at home. The mice only needed a five-day course of immunosuppressive drugs to keep their bodies from attacking the new organs, as opposed to having to take those drugs for the rest of their lives.

“We examined them closely for the presence of any rat cells, but we found that the mouse’s immune system had eliminated them,” said Nakauchi. “This is very promising for our hope to transplant human organs grown in animals because it suggests that any contaminating animal cells could be eliminated by the patient’s immune system after transplant."

Further research and ethical discussions will be required before the technique can be used in other animals.

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Big Questions
Why Do Cats Freak Out After Pooping?
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Cats often exhibit some very peculiar behavior, from getting into deadly combat situations with their own tail to pouncing on unsuspecting humans. Among their most curious habits: running from their litter box like a greyhound after moving their bowels. Are they running from their own fecal matter? Has waste elimination prompted a sense of euphoria?

Experts—if anyone is said to qualify as an expert in post-poop moods—aren’t exactly sure, but they’ve presented a number of entertaining theories. From a biological standpoint, some animal behaviorists suspect that a cat bolting after a deposit might stem from fears that a predator could track them based on the smell of their waste. But researchers are quick to note that they haven’t observed cats run from their BMs in the wild.

Biology also has a little bit to do with another theory, which postulates that cats used to getting their rear ends licked by their mother after defecating as kittens are showing off their independence by sprinting away, their butts having taken on self-cleaning properties in adulthood.

Not convinced? You might find another idea more plausible: Both humans and cats have a vagus nerve running from their brain stem. In both species, the nerve can be stimulated by defecation, leading to a pleasurable sensation and what some have labeled “poo-phoria,” or post-poop elation. In running, the cat may simply be working off excess energy brought on by stimulation of the nerve.

Less interesting is the notion that notoriously hygienic cats may simply want to shake off excess litter or fecal matter by running a 100-meter dash, or that a digestive problem has led to some discomfort they’re attempting to flee from. The fact is, so little research has been done in the field of pooping cat mania that there’s no universally accepted answer. Like so much of what makes cats tick, a definitive motivation will have to remain a mystery.

Have you got a Big Question you'd like us to answer? If so, let us know by emailing us at bigquestions@mentalfloss.com.

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Animals
Listen to the Impossibly Adorable Sounds of a Baby Sloth
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RODRIGO ARANGUA/AFP/GettyImages

Sometimes baby sloths seem almost too adorable to be real. But the little muppet-faced treasures don't just look cute—turns out they sound cute, too. We know what you're thinking: How could you have gone your whole life without knowing what these precious creatures sound like? Well, fear not: Just in time for International Sloth Day (today), we have some footage of how the tiny mammals express themselves—and it's a lot of squeaking. (Or maybe that's you squealing?)

The sloths featured in the heart-obliterating video below come from the Sloth Sanctuary of Costa Rica. The institution rescues orphaned sloths, rehabilitates them, and gets them ready to be released back into the wild.

[h/t The Kid Should See This]

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