Administration Proposes

Higher Fuel-Use Standards

The Bush administration proposed higher fuel economy standards for SUVs and minivans with a new regulatory system that sets different mileage goals for six sizes of vehicles, replacing the current single standard for all light trucks.

Administration officials say the regulations would result in more fuel savings than any previous increase in efficiency standards for larger vehicles. Transportation Secretary Norman Y. Mineta said the rules would save 10 billion gallons of gasoline.

But environmentalists say the complex proposal adds up to little real change and continues to reward Detroit for building bigger vehicles.

Eric Haxthausen, an economist with Environmental Defense of Washington, called the 10 billion gallons of fuel savings a "weak yardstick" because it would be spread over as many as 15 years. Last year, for instance, U.S. drivers consumed nearly 140 billion gallons of gas, according to federal Energy Information Administration.

The new regulations would start affecting light trucks in the 2008 model year, and all such vehicles would have to comply by 2011 models.

-- Margaret Webb Pressler

Uranium in Iran Tied

To Pakistani Equipment

Traces of bomb-grade uranium found two years ago in Iran came from contaminated Pakistani equipment and are not evidence of a clandestine nuclear weapons program, a group of U.S. government experts and other international scientists has determined.

Scientists from the United States, France, Japan, Britain and Russia met in secret during the past nine months to pore over data collected by inspectors from the International Atomic Energy Agency, according to U.S. and foreign officials. Recently, the group, whose existence had not been previously reported, definitively matched samples of the highly enriched uranium -- a key ingredient for a nuclear weapon -- with centrifuge equipment turned over by the government of Pakistan.

Iran has long contended that the uranium traces were the result of contaminated equipment bought years ago from Pakistan. But the Bush administration had pointed to the material as evidence that Iran was making bomb-grade ingredients.

The conclusions will be shared with IAEA board members in a report due out the first week in September, according to U.S. and European officials.

-- Dafna Linzer

Chinese Web Sites Are Used

To Target U.S. Federal Networks

Web sites in China are being used heavily to target computer networks in the Defense Department and other U.S. agencies, successfully breaching hundreds of unclassified networks, according to several U.S. officials.

Classified systems have not been compromised, the officials added. But U.S. authorities remain concerned because, as one official said, even seemingly innocuous information, when pulled together from various sources, can yield useful intelligence to an adversary.

"The scope of this thing is surprisingly big," said one of four government officials.

Some in the Pentagon are said to be convinced of official Chinese involvement; others see the electronic probing as the work of other hackers using Chinese networks to disguise the origins of the attacks.

-- Bradley Graham

Harvard Team Converts

Skin Cells to Stem Cells

Scientists for the first time have turned ordinary skin cells into what appear to be embryonic stem cells -- without having to use human eggs or make new human embryos in the process, as has previously always been required, a Harvard research team announced in the journal Science.

The new technique uses laboratory grown human embryonic stem cells -- such as the ones President Bush has already approved for use by federally funded researchers -- to "reprogram" the genes in a person's skin cell, turning that skin cell into an embryonic stem cell itself.

Moreover, since the new stem cells made this way are essentially rejuvenated versions of a person's own skin cells, the DNA in those new stem cells matches the DNA of the person who provided the skin cells. In theory at least, that means that any tissues grown from those newly minted stem cells could be transplanted into the person to treat a disease without much risk that they would be rejected, since they would constitute an exact genetic match.

Until now, the only way to turn a person's ordinary cell into a "personalized" stem cell such as this was to turn that ordinary cell into an embryo first and later destroy the embryo to retrieve the new stem cells growing inside -- a process widely known as "therapeutic cloning."

-- Rick Weiss

Mouse Researchers Find

Hormone That Extends Life

Scientists have identified a hormone that significantly extends the life span of mice, a discovery that could mark a crucial step toward developing drugs that boost longevity in people.

The hormone is the first substance identified that is produced naturally in mammals, including humans, and can extend life span -- a goal in the intense effort to help people live longer.

Much more work is needed to study the substance, and investigate whether the hormone or a similar compound would be effective and safe in people, experts cautioned.

"This is a significant discovery," said Anna McCormick of the National Institute on Aging, which helped fund the new research, published online by the journal Science.

The discovery was triggered by a study Makoto Kuro-o and his colleagues at the University of Texas's Southwest Medical Center published in 1997. That study identified a gene in mice that, when damaged, caused the animals to experience all the hallmarks of aging in humans -- hardening of the arteries, thinning bones, withered skin, weak lungs -- and to die prematurely. They dubbed the gene Klotho, for the Greek goddess who spins the thread of life.

Suspecting the gene may play a role in regulating life span, Kuro-o and his colleagues genetically engineered mice with overactive Klotho genes. In the latest experiments, they found that these animals lived an average of 20 percent to 30 percent longer than normal -- 2.4 to 2.6 years vs. a normal life span of about two years -- without ill effects.

-- Rob Stein

Role of Daydreaming

In Alzheimer's Is Studied

The brain areas involved in daydreaming, musing and other stream-of-consciousness thoughts appear to be the same regions targeted by Alzheimer's disease, researchers reported in an unusual study that offers new insights into the roots of the deadly illness.

The strong correlation between the two suggests there might be a link between the sort of thinking that people regularly do when not involved in purposeful mental activity and the degenerative disease that is characterized by forgetfulness and dementia, said scientists who conducted the federally funded study that was published in the Journal of Neuroscience.

Randy Buckner, a neuroscientist at Washington University in St. Louis, said the implications of the finding are far from clear. It is too early to suggest that daydreaming is dangerous, he said, or that avoiding such musings could make a difference to the risk of Alzheimer's disease. Rather, he and others said, the study adds to the evidence that everyday mental and physical activities play an important role in the course of neurological disease.

-- Shankar Vedantam