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ANDREA SEABROOK, host:

And now since we're in a very masculine state of mind here, a story about the very essence of masculinity. Freeze dried food is nothing new, but what about freeze drying sperm and then using it to make a baby? That's today's science out of the box.

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SEABROOK: A freeze-dryer basically uses super-cold temperatures and a change in pressure to dry things out. You're left with something you can store it for years. It's very convenient. And imagine how convenient it would be if labs could store sperm that way, turning a male's reproductive potential into an off-the-shelf product. NPR's Nell Greenfieldboyce has more.

NELL GREENFIELDBOYCE: Everybody's got to have a dream. This is Ryuzo Yanagimachi's...

Mr. RYUZO YANAGIMACHI (University of Hawaii): My dream is to keep sperm at room temperature.

GREENFIELDBOYCE: Room-temperature sperm. That may seem like an unusual dream. But Yanagimachi is an expert on reproduction, a pioneer in things like cloning. He says labs traditionally freeze and store sperm with the help of liquid nitrogen. This approach has drawbacks, though. For example, liquid nitrogen evaporates and has to be replaced, which costs money.

So about a decade ago, Yanagimachi freeze-dried mouse sperm at his lab at the University of Hawaii, creating a powder. Adding water didn't exactly bring the sperm back to life. They didn't wiggle around or swim. But, inject a freeze-dried mouse sperm into an egg, and it works just fine.

Mr. YANAGIMACHI: As far as the mouse is concerned, we can get a perfect baby, from freeze dried sperm.

GREENFIELDBOYCE: And he worked with another group and made a baby bunny using freeze-dried rabbit sperm. Other researchers have been looking into this as well. One team used freeze-dried sperm to make monkey embryos, but so far, no pregnant monkeys.

Now, in the journal Human Reproduction, Yanagimachi and his colleagues say they've freeze-dried human sperm from two men. Yanagimachi says he hasn't tried using the human sperm to fertilize an egg. But even if it works, don't expect sperm banks to ditch their liquid-nitrogen tanks.

Dale McClure is an infertility specialist at Virginia Mason Medical Center in Seattle. He says the regular old way of freezing sperm has a rock-solid reputation. It's safe and well understood.

Mr. DALE MCCLURE (Virginia Mason Medical Center): We have a pretty good technique right now. Frozen sperm is good for 15, 20, many, many years and is still very efficacious.

GREENFIELDBOYCE: And it's efficacious without always having to inject the sperm directly into an egg, which is what you'd have to do with freeze-dried sperm.

Still, Rob Taft thinks freeze-drying could someday be useful. He works at the Jackson Laboratory in Maine, which breeds mice for scientists. It has nitrogen tanks full of sperm from hundreds of different kinds of mice. Taft says this kind of storage is very reliable. But the freeze-drying approach might help protect sperm collections from major disasters like Hurricane Katrina.

Mr. ROB TAFT (Jackson Laboratory): With those types of disasters, you may not have access to electricity, to liquid nitrogen, and so your samples may be destroyed. Whereas if you could freeze-dry them, then you'd have much greater protection against their loss.

GREENFIELDBOYCE: Experts also say it would be easier to ship freeze-dried sperm around the world, for customers who want to get their male in the mail.

Nell Greenfieldboyce, NPR News.

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