WRONG NUMBER FILE NAME: DINODNA1.ZIP [From The New York Times, July 1, 1993] CELLS OF DINO
WRONG NUMBER FILE NAME: DINODNA1.ZIP
[From _The New York Times_, July 1, 1993]
CELLS OF DINOSAUR APPARENTLY FOUND
Scientists Believe Blood Cells
in Tyrannosaurus Rex May
Lead to Traces of DNA
By MALCOLM W. BROWNE
A Montana paleontologist and his colleagues believe they have found red
blood cells in the fossilized leg bone of a Tyrannosaurus Rex and say they
have high hopes of extracting DNA from the dinosaur's cells.
The discovery of the putative dinosaur blood cells has not yet been
submitted to a scientific journal or independently confirmed but was
reported two weeks ago by the National Science Foundation, which has
financed the exploratory project. Jack Horner, a paleontologist at Montana
State University who directed the investigation, said in an interview
yesterday that his group hoped to find matches between gene fragments left
in the preserved blood cells with comparable DNA segments from modern
crocodiles or birds.
"If we're lucky enough to find matches," he said, "they could go a long way
toward showing what the relationship between dinosaurs and birds might be.
We're not there yet, but we think we're getting close."
The femur, or leg bone, that Mr. Horner's group is studying is part of an
unusually well-preserved tyrannosaur fossil, more than 65 million years
old, which they found and excavated from the Hell Creek Formation in
eastern Montana three years ago. The apparent blood cells were discovered
by Mary Schweitzer, Mr. Horner's graduate student who was investigating the
cell structure of fossilized bone and marrow tissue
New Climate of Belief
In the past, few paleontologists or molecular biologists believed that
biological material could survive for millions of years without becoming
mineralized, thus losing its organic molecular structure. The survival of
any intact DNA, which ordinarily decays with time, seemed even less likely.
But the recent discovery of organic material and even fragments of DNA in
ancient plant and animal fossils has changed opinions.
"Two years ago I would have called this baloney," said Dr. Raul J. Cano of
California Polytechnic State University at San Luis Obispo, a molecular
biologist who has himself extracted DNA fragments from fossilized insects
and plants millions of years old.
Told of Mr. Horner's belief that blood cells have survived in a tyrannosaur
bone - and that they may contain dinosaur DNA fragments - Dr. Cano said:
"It's certainly plausible. We have seen similar things ourselves, and
there are reports from other investigators of the finding of surviving
biological material inside fossil dinosaur bones, especially in the deep
bone cortex, which seems to be somewhat protected from mineralization."
Earlier this month, Dr. Cano and his associates reported in the British
journal Nature that they had extracted DNA from a weevil that had been
entombed in amber for 120 million to 135 million years.
Doubter Grants Possibility
A molecular biologist who has strongly questioned the premise that
appreciable quantities of DNA could survive for very long periods is Dr.
Russell Higuchi of Roche Molecular Systems in Alameda, Calif. But Dr.
Higuchi said yesterday that it seemed possible that Mr. Horner's group,had
actually seen dinosaur blood cells.
Although Dr. Higuchi said he remained doubtful about the survival of
dinosaur DNA, particularly in a fossil that was probably exposed to water,
"we ourselves speculated 10 years ago that if dinosaur DNA survived at all,
it might be found" deep inside a fossil bone.
Mr. Horner said that microscopic examination of a thin slice through the
dinosaur bone revealed that although its outer layers were mineralized the
bone itself, brown in color, remained more or less intact in the interior
of the marrow cavity.
"Mary found spherical structures that appear to be nucleated red cells
inside the blood vessels running through the bone, right where you'd expect
to find blood, if it's there," he said. "Since then we've been trying
everything we can think of to show that they're not blood cells, but they
still seem to be the real thing."
Fears of Contamination
Part of the science foundation's grant to Mr. Horner's group went for
laboratory equipment to conduct a polymerase chain reaction, a technique
that can single out a lone molecular fragment of DNA and make enough copies
so it can be analyzed using standard methods.
"The biggest problem is contamination of the fossil by foreign DNA, "Mr,
Horner said. "There's lots of it there, The real trick is in identifying
some thing that is not a contaminant. This is why we are looking for
matches with crocodile DNA, which is not a likely contaminant."
Mr. Horner says he is certain that at least some original tissue remains in
the fossil because his group has positively identified collagen in the
bone. Collagen is a fibrous protein found in the connective tissue of
animals, which ordinarily decays rapidly except under special
Cheryl Dybas, a spokeswoman for the National Science Foundation,
acknowledged that her agency had intentionally released its report of Mr.
Horner's progress to coincide with the opening of "Jurassic Park," a
science fiction movie based on the premise that dinosaurs might one day be
cloned from their surviving DNA.
"We thought it would be a good opportunity to get the word out on 4 of the
10 dinosaur research projects the N.S.F. is funding this year, including
that of Mr. Horner," Ms. Dybas said.
WRONG NUMBER FILE NAME: DINODNA1.TXT
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