SCIENCE
Notebook

Monday, April 30, 2007

Drug May Reverse Dementia

Might there one day be a drug that restores memory to people with dementia?

An extraordinary set of experiments published yesterday by the journal Nature suggests that the answer could be yes.

Li-Huei Tsai and Andre Fischer at the Massachusetts Institute of Technology used a strain of mice in which a gene that causes the brain to atrophy can be turned on by adding a chemical to their diet.

After six weeks, the animals lose their memory of a frightening task that causes normal animals to freeze when they encounter it again. The gene-activated mice also have trouble learning new activities, and their brains actually shrink.

The researchers first showed that "enriched environments" -- cages with two running wheels, tunnels and hidden caches of food -- increased the animals' ability to learn and restored much of the normal reaction to the frightening task.

Subsequent examination of the still-atrophied brains revealed high concentrations of proteins that help lay down new synapses, or connections, between neurons. Further, it appeared that a complex program of brain rewiring had been triggered by changes, called acetylation, in proteins called histones that are part of the nerve cells' chromosomes.

In the final step, the scientists gave the mice daily injections of a drug that stimulated acetylation.

Remarkably, many of the animals gained the ability to learn new tasks, recovered the memory of the frightening task and began once again to freeze when confronted with it. In all, the research suggests that at least some memories appearing to be lost as the brain degenerates may still be present, but inaccessible. Rewiring the surviving neurons may get some of those memories back.

-- David Brown

Babies Exposed to Chemicals

A study of 300 newborn babies has shown that virtually all were exposed in the womb to two ubiquitous chemicals used to make protective coatings, nonstick products and insecticides. Past studies have tied the compounds -- at lower levels than observed in the Johns Hopkins study -- to tumors and developmental toxicity in lab animals.

Researchers at the Johns Hopkins Bloomberg School of Public Health found perfluorooctane sulfonate (PFOS) and perfluorooctanoate (PFOA) in the infants' umbilical-cord blood. They published the results April 20 in the online edition of Environmental Science & Technology.

Co-author Lynn Goldman said researchers are concerned that they are learning how prevalent the compounds are just as they are getting a sense of their toxicity. The chemicals are used to make Teflon and a stain repellent for carpets.

"By the time we're becoming aware of the potential effect on public health, nearly everyone's exposed," Goldman said in an interview. "Once they're in the environment, we can't take them out of the environment."

Eight U.S. companies, including DuPont Co., agreed last year to virtually eliminate PFOA from consumer products by 2015.

Goldman said the scientists are trying to determine how the two compounds, which come from different sources, got in the babies' blood. "What we don't know about these products is how they're getting into people's bodies," she said.

-- Juliet Eilperin

Planet in 'Habitable' Zone Seen

Astronomers have identified the first planet outside our solar system that appears to be within the "habitable" zone of the star it orbits. While they did not find evidence of water to support life on the planet, which is about 130 trillion miles away, they concluded that liquids could exist there based on the power of its star and the planet's distance from it.

European astronomers who discovered the planet, named Gliese 581 C, said it orbits its star every 13 days, and so is quite close to it. But because the star is a red dwarf, smaller and less hot than the sun, the planet could have many, if not all, of the components that make up the Earth's water cycle -- including oceans, rivers, clouds and polar caps.

"On the treasure map of the universe, one would be tempted to mark this planet with an X," said Xavier Delfosse, a member of the European Southern Observatory team. Its paper has been submitted to the journal Astronomy & Astrophysics.

Astronomers found the new planet -- one of about 230 identified outside our solar system -- by observing the wobble its gravity causes in the star it orbits, using a 141-inch-diameter telescope at the European observatory in La Silla, Chile.

While detection by "wobble" can tell astronomers the mass of a planet, they have to catch it passing in front of its star to determine its size and density and whether it has an atmosphere. Astronomers estimated that Gliese 581 C is about half as large as the Earth. Two years ago, the same team discovered a Neptune-size planet orbiting closer to the same star.

-- Marc Kaufman