Lab Report: Health, Science and Medicine

SLEEP

Key to a Good Night's Sleep Is in Your Brain

An uninterrupted night of sleep is a rare commodity--what with TVs blaring, toilets flushing and the occasional plane flying overhead. The sleeping brain is designed to tune out these auditory distractions, but some people's brains do so a lot better than others'. Now researchers have the first clues to understanding why.

Scientists at Massachusetts General Hospital analyzed the brain waves of 12 self-described healthy sleepers during a three-night study in a sleep lab. The volunteers were given cozy beds, but throughout the night they were assaulted with 14 sounds--including car traffic, airplane noise and slamming doors--piped through speakers at varying volumes.

It turned out that those who dozed through the loudest noises were those whose brains recorded the most "sleep spindles" on an EEG. Scientists say the spindles, produced by activity in the thalamus (a region deep in the brain that processes incoming stimuli), can be used as a measure of how well the brain blocks out sound during sleep. And someday, they say, they may be able to manipulate spindle activity to help light sleepers catch more zzz.

SEXUAL HEALTH

Are Girls Entering Puberty Too Soon?

A new report finds that girls in the U.S. are more likely than they were a decade ago to develop breasts as early as age 7. The study is the latest in a growing body of research that suggests girls may be hitting puberty at ever earlier ages, prompting experts to wonder, How young can you go?

The report, which examined girls from 2004 to 2006, found the trend particularly striking among white girls, who were nearly twice as likely as girls in 1997 to show breast development by age 7. But the study also hinted that some girls have reached the minimum age for sexual maturity: African-American girls were no more likely to show early breast development than they were a decade ago, possibly because they can't begin puberty any younger.

Early puberty can be worrisome because estrogen, the hormone responsible for breast development and sexual maturity, also contributes to breast cancer. The longer a girl's body is exposed to estrogen, the greater her risk of cancer may be as an adult.

What's prompting the shift? The authors speculate that a major cause of early puberty is obesity, since fat deposits produce sex hormones and trigger sexual development. But exposure to environmental sources of estrogen-mimicking chemicals like food additives and endocrine disrupters like BPA may also play a role.

FROM THE LABS

Reviving Old Cells

Newts and salamanders may sit lower on the evolutionary tree than mammals, but they can do something mammals can't: regrow damaged or missing limbs. Researchers have now found a way to coax muscle cells in mice to perform the same regenerative trick, by turning off genes that limit cell growth. Scientists still need to ensure that they can deactivate those genes only temporarily; otherwise the muscle cells may start to divide uncontrollably, leading to cancer.

Alzheimer's Test?