SCIENCE
Notebook

Monday, February 5, 2007

New Pollution Effects Observed

Here is one more reason to dread the rat race.

Rats exposed to highway pollution for several hours in an experiment by University of Rochester researchers experienced a drop in heart rate and impairment of the nervous system. The rats, old and prone to high blood pressure, rode in a mobile laboratory for six hours on a New York interstate, inhaling vehicle emissions that motorists would be exposed to along the 320-mile route.

Tests showed that the creatures experienced up to a 10 percent decline in their heart rate and that the effect of the pollution lasted up to 14 hours.

The researchers said the findings, published in January's issue of Inhalation Toxicology, help explain why on smoggy days hospitals in urban areas typically see a spike in visits to the emergency room because of heart attacks.

The findings also are in line with a recent European study that showed that people who are exposed to air pollution while riding a bus or riding a bicycle to work are more likely to have a heart attack within an hour of their commute.

"The fact that exposure to air pollution can change the heart rate, independent of other factors, is a cause for concern," said Alison Elder, the lead researcher. "It's important to understand that these changes are taking place outside of the lung. Air pollution is either having a direct effect on the heart in rats or is altering something within the circulatory system."

-- Christopher Lee

Smelling Food Could Speed Aging

Plug your nose, live a little longer. That's the take-home message from a study showing that mere whiffs of food can shorten a fly's life.

Studies in worms, flies, mice and monkeys have shown that aging can be slowed by cutting way back on calories consumed. Loosely organized experiments in humans are ongoing.

But is it food itself that shortens life? Or might it be the mere perception of food -- the biochemical stimulation that occurs when food odors tickle olfactory nerves?

Scott Pletcher, a geneticist at the Huffington Center on Aging at Baylor College of Medicine in Houston, knew that the mere scent of food could block some of the life-extending effects of caloric restriction in tiny, soil-dwelling worms. So he and his colleagues conducted similar tests in flies.

Sure enough, when calorie-restricted flies -- which tend to live about 50 percent longer than normal -- were housed in containers with the smell of fresh yeast (a favorite food of flies) wafting in, the life-extending benefits of their diet were reduced by about 20 percent.

In separate tests, mutant flies with defective senses of smell lived 56 percent longer than their smell-enabled counterparts, even though they ate all they wanted.

Because odor has the same effect in worms and flies, it may affect people the same way, Pletcher said. He noted that food smells alone trigger a raft of biochemical and hormonal changes in people that, while not as intense as those that occur when eating, nonetheless appear to be implicated in the aging process.

Pletcher doubts that people can do much about the life-shortening effects of being well-fed by blocking their sense of smell alone. But exposure to food smells might blunt the life-extending effects of limiting calories, he speculated.

Further work may reveal the mechanisms that link olfaction and longevity, he said, and point the way to effective anti-aging drugs.

-- Rick Weiss

A Deeper Probe of Life on Mars

Scientists probing for life on Mars should look a little deeper, say British researchers.

Current probes might turn up evidence that life once existed on the red planet, but they have little chance of finding anything alive now because they do not drill to depths where cellular life could escape the deadly cosmic radiation that bathes the surface, according to a study published last week in the journal Geophysical Research Letters.

Researchers from University College London created a model of cosmic radiation levels at various depths on Mars, accounting for geographical differences in surface conditions. They concluded that a probe would have to dig several meters down to have any hope of finding life. Mars, unlike Earth, is not shielded from radiation by a thick atmosphere and a global magnetic field.

"It just isn't plausible that dormant life is still surviving in the near-subsurface of Mars," said lead author Lewis Dartnell. "Finding life on Mars depends on liquid water surfacing on Mars, but the last time liquid water was widespread on Mars was billions of years ago. Even the hardiest cells we know of could not possibly survive the cosmic radiation levels near the surface of Mars for that long."

The best places to look for life, he said, are in a frozen sea beneath the surface in the equatorial Elysium region and in recently formed craters.

-- Christopher Lee