科学家从6千8百万年之久的恐龙骨中提取软组织（在线收听）

Scientists Extract Soft Tissue from 68-Million-Year-Old Dinosaur Bone

科学家从6千8百万年之久的恐龙骨中提取软组织

U.S. scientists have recovered soft tissue from the bones of a nearly 70-million-year-old dinosaur. If it proves to be original tissue not replaced by some other substance, it would be the first to show such material can last more than a few million years and could provide biological insights into the extinct animals.

When North Carolina State University biologist Mary Higby Schweitzer looked inside a thigh bone of a Tyrannosaurus rex excavated in the northern state of Montana recently, she was surprised by an unexpected find. Typically, only the hard parts of an animal, like the bones or shell, are preserved. But this dinosaur contained what appears to be well preserved soft tissue inside the bone where the marrow once was.

As Ms. Schweitzer reports in the journal Science, she isolated the tissue by dissolving the surrounding bone minerals in a weak acid. What remained appears to be blood vessels and cells still elastic after 68 million years.

Ms. Schweitzer: The thing that was so fascinating for us with this particular dinosaur was that they are transparent, they are flexible. The vessels are such that we can actually manipulate them with our probe. The bone matrix itself, once we removed the minerals from it, is stretchy and flexible. And then, of course, the microstructures that look like cells are preserved in every way. The cellular extensions are flexible. And they move in solution just like cells preserved in modern bones.

For comparison, the researchers analyzed soft tissue from an ostrich leg bone because birds are widely believed to have evolved from dinosaurs. The dinosaur vessels contained small, reddish-brown dots similar to the nuclei of cells lining ostrich blood vessels. The Tyrannosaurus rex bone also contained structures that looked virtually identical to ostrich bone cells.

There are few examples of prehistoric tissue that are not hard. Such soft material that is preserved is usually not more than a few million years old, such as insects trapped in amber or humans and mammoths in peat or ice. But Ms. Schweitzer says her discovery shows it is now possible to find soft tissue in animals many times older.

Ms. Schweitzer: This preservation to this extent, where you still have original flexibility and transparency has not been noted in dinosaurs before. So we're pretty excited about the find.

If the tissue consists of original material, experts say scientists might be able to extract new information about dinosaurs, especially if they can recover proteins and the genetic material DNA.

A deputy editor at the journal Science is Robert Hanson.

Robert Hanson: That is why the discovery described here is so interesting. These findings thus help us understand preservation in the fossil record and ultimately this study may pave the way towards new insights into dinosaur physiology and biochemistry.

But appearances can be deceiving. As a result, the scientists are not claiming their finding is actual proof that the dinosaur tissue is in its native, pristine condition. Ms. Schweitzer is conducting laboratory tests to determine whether it is still made of the molecules that existed in the living animal, or a pliable non-organic compound that has taken their place over the ages.

Ms. Schweitzer: Through further chemical analysis we can learn things like, are their protein fragments preserved? If so, how is the protein the same or different from animals that are alive today? As far as DNA goes, we don't know yet. We're doing a lot of stuff in the lab that looks promising right now.

The North Carolina State University researcher is secretive about those studies, awaiting their final outcome and publication.

David McAlary, VOA news, Washington.