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From: TSS ()
Subject: Computer model may hold mad cow key
Date: June 15, 2005 at 8:12 am PST

Computer model may hold mad cow key

By DON THOMPSON - Associated Press Writer - 06/15/05

DAVIS, Calif. — Researchers at the University of California Davis are trying to explain how mad cow disease acts so frighteningly fast using an unconventional tool — mathematical modeling.

The disease is caused when proteins in the body bend into misfolded shapes called ‘‘prions,'' eventually forming clumps that kill brain cells and leave spongy holes in the brain.

It takes years to incubate in an infected animal or human. But once it becomes active, the researchers found the flawed proteins grow exponentially and replicate in two dimensions, not merely growing end-to-end as previously thought. They're still studying why the disease acts as it does.

Most research into mad cow disease is being conducted through experiments on animal tissue, not computer modeling.

‘‘Certainly, this research could help to answer some of the key questions we have about the disease,'' says Benjamin Higgins, executive vice president of the California Cattlemen's Association. ‘‘We know the disease is dormant in that animal somewhere. We know that later in life, something causes an exponential growth in those prions in that animal."


UC Davis physicists have been studying the disease at the molecular level for nearly five years, including investigating the role — and possible preventive measures — that metal ions play in bonding to the proteins. Their findings, some drawn from mathematical simulations using Lawrence Livermore National Laboratory's supercomputer, dovetail with what other scientists are discovering through laboratory experimentation.

In 2001, they published the first of several papers. It disclosed that flooding a diseased mouse with flawed hamster protein can actually slow the spread of the mouse's illness.

‘‘It extended the incubation time dramatically,'' physics professor Daniel Cox said.

The findings come as U.S. Department of Agriculture officials examine the possibility of a second case of the disease in the United States. They said the suspect animal, possibly from Texas, never entered the food supply.

American cattlemen still are recovering from the first such instance, a cow imported from Canada into Washington state in December 2003 — a breach that led more than 50 countries to ban U.S. beef.

On Monday, officials in the Czech Republic confirmed a 19th case of an infected cow in that country. The worst human outbreak has claimed more than 100 lives in Britain since the 1990s.

‘‘This is a disease that in Europe has proven itself to be insidious and long-lasting,'' Higgins said.

Understanding the role proteins play, and how they go wrong, might also help scientists understand far more prevalent neurological disorders such as Alzheimer's, Parkinson's, Lou Gehrig's and Huntington's diseases. They can take years to develop and mainly affect older adults.

For those diseases, ‘‘it's an act of God and it's an old-age thing,'' said Rajiv Singh, another UC Davis physics professor involved in the research.

By contrast, the human form of mad cow disease ‘‘can happen to young people and it's a really rapid death once it happens. So in that sense, it's scary, even though the chances of getting it are very low.''

And unlike Alzheimer's and similar diseases, mad cow is transferrable.

‘‘The probability isn't high, but it's scary because you can catch it'' by eating infected animal parts, Singh said.

The disease, formally known as bovine spongiform encephalopathy, attacks an animal's nervous system and is similar to scrapies in sheep and chronic wasting disease in deer and elk. It can cause a variant of Creutzfeldt-Jakob disease in humans who eat contaminated food.

About one in a million humans will spontaneously develop Creutzfeldt-Jakob disease, while other versions are passed down through generations. But scientists believe the human body usually rejects misfolded proteins without harm; it's when a microscopic ‘‘seed'' of flawed proteins is consumed from another animal that the disease can take hold in a person or animal who otherwise would never develop the disease.

A cow that consumes contaminated feed at an early age may not show symptoms for several years, making diagnosis difficult. And even now it is uncertain how many Britons will ultimately die from the contamination there years ago.

The UC Davis research is being supported by a $175,000-a-year grant from the U.S. Army that lasts for three years. Cox said the Army fears troops could be exposed overseas.

Higgins hopes researchers can develop a test for live animals instead of examining the brains of dead ones, a test he thinks eventually could help eradicate the disease.

Cox said a better understanding of how animals fold proteins into many shapes could one day have other applications as well, including perhaps the production of exotic materials using microscopic protein ‘‘nanotubes.'' The researchers explore that potential in an article this month in the Materials Research Society Bulletin.

On the Net:

University of California, Davis: http://www.ucdavis.edu

USDA mad cow information: http://www.aphis.usda.gov/lpa/issues/bse/bse.html

http://www.helenair.com/articles/2005/06/15/national_top/a01061505_04.txt

TSS



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