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Frozen in Time

May 8, 2006
Julie Feinstein is a biologist at the American Museum of Natural History. She manages the Museum's Frozen Tissue Collection, which has room for a million DNA specimens. (Photo by Craig Chesek / AMNH)
Julie Feinstein is a biologist at the American Museum of Natural History. She manages the Museum's Frozen Tissue Collection, which has room for a million DNA specimens. (Photo by Craig Chesek / AMNH)

A museum biologist keeps animal tissues frozen for years

Donning a lab apron, gloves, and safety goggles, Julie Feinstein stands next to one of seven freezers located in the American Museum of Natural History's Frozen Tissue Lab. Her attire may seem unnecessary for a peek into a freezer. But unlike kitchen-variety freezers, these stainless steel cauldrons, called cryovats, get their chill from liquid nitrogen. When kept at sub-zero temperatures, the liquid nitrogen stored at the bottom of each cryovat turns into a frigid vapor. This swirling cloud keeps the freezer at a frosty -160°C (-256°F). Without proper safety gear, temperatures that low could give Feinstein frostbite, or even freeze her hands solid.

As Feinstein opens the lid to a cryovat, puffs of cold nitrogen vapor envelop her. She pulls out one of the cryovat's precious contents: a frozen sample of animal tissue that had been sent to her by a scientist that was working in Asia.

GLOBAL FREEZER

As the collection manager of one of the world's largest frozen-tissue labs, Feinstein receives tissue samples from all over the globe. Recently, museum scientists who had been working in Cambodia sent Feinstein tiny, circular tissue samples that they had clipped from the wings of fruit-eating bats called flying foxes. The scientists who mailed the samples probably won't get a chance to analyze them right away. But there's no rush. Feinstein can keep the samples in tip-top condition for decades by storing them inside one of the museum's cryovats.

Feinstein seals the samples in a plastic vial and keeps it in a tray inside the cryovat. Under natural conditions, when an organism dies, chemical reactions cause the body's tissues and DNA, or genetic codes, to decay. The vats' glacial conditions put the brakes on these destructive chemical reactions. As a result, the flying foxes' tissues-including the DNA-will stay "frozen in time."

Why is this important? Most populations of these fruit-eating bats are declining in number due to habitat destruction and hunting by humans. Currently, scientists are analyzing the DNA from different populations of flying foxes. With this genetic information, scientists can learn if a particular population of these bats-such as one living in Cambodia-is genetically diverse. The variety of genes passed down from parents to infant bats is important for the health of a population. If this variety dwindles in a group of animals, the group is more susceptible to disease. By knowing if this has happened in a population, conservation scientists can work to protect the animals.

The genetic codes will also help scientists pinpoint once-unrecognized species-for instance, members of a group of elephants in Africa may look identical to each other. But their genes may indicate that the group contains two separate elephant species. So environmental scientists would need to find ways to protect the two genetically distinct groups of elephants.

FUTURISTIC THINKING

The museum's cryovats hold more than just bat tissues. "We have samples of many species of animals that are on the brink [of extinction]," explains Feinstein. These include groups of lemurs, whales, birds, and insects. With many species tipping toward extinction, Feinstein suspects that the samples in her care could one day be all that's left of some species. "[The lab] has been referred to as a Noah's Ark of genetic resources for the future," she says.

But this doesn't mean the lab hopes to revive animals in Jurassic Park fashion. The purpose of the cryovats is to preserve animal tissues for research. Also, Feinstein explains, protecting organisms before they die out is a safer bet. 9

-Jeanna Bryner

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