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Moonsleeping bad for spacewalking

Day three of the Society for Neuroscience annual meeting offered news about Down syndrome and sleep cycles.

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3:47pm, November 17, 2008
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Day three of the Society for Neuroscience annual meeting offered news about Down syndrome and sleep cycles

Melatonin by moonlight

Moonlight may interrupt astronauts’ sleep cycles by messing with their melatonin, a new study shows.

Sleep cycles are regulated by the type and amount of light that people encounter. When a person goes to sleep, the hormone melatonin circulates through the body to maintain a drowsy state. But if a light comes on, the body’s melatonin levels drop, causing the person to wake up.

Astronauts are notoriously bad sleepers, says Benjamin Warfield of Thomas Jefferson University in Philadelphia. They average just four to six hours of sleep a night when they’re on a mission and amass a huge sleep deficit. But no one knew how moonlight might be affecting this chronic lack of sleep.

To figure it out, the researchers built a piece of equipment they call the Moonlight Machine — a complicated series of lights, mirrors, lenses, and filters — to mimic light conditions on the moon. Subjects sat inside the Moonlight Machine between 2 and 3:30 a.m., a time when melatonin levels in the body are normally high. The researchers found that melatonin levels were diminished after moonlight exposure. The team’s next step is to repeat the experiments at all points during the night. Ultimately, Warfield would like to design visors and window blocks that could regulate the amount of moonlight for astronauts. “We’re really excited to see where this goes,” says Warfield. The team plans to begin studying how the lighting conditions on Mars might affect the human sleep cycle.

These kinds of studies aren’t just important for sweetening astronauts’ dreams. Understanding how different kinds of light influence the body could lead to new ways to treat diseases like seasonal affective disorder and insomnia. Astronauts have a lot of problems to deal with, but a lack of sleep should not be one of them, says Warfield. — Laura Sanders

Four genes possible culprits for early Alzheimer’s in people with Down syndrome

Four genes may help explain why people with Down syndrome are particularly at risk for Alzheimer’s disease, new research has shown. Down syndrome is a genetic disease caused by inheriting an extra copy of chromosome 21. People who have the disease are likely to get Alzheimer’s — a debilitating brain disease that normally affects only the elderly — in their 30s and 40s.

In the 1920s, the life expectancy of a person with Down syndrome was around nine years, says Ralf Schmid of Duke University in Durham, N.C., author of the new study. But today, improved healthcare allows many more people with Down syndrome to survive into middle age. Doctors examining these older patients saw that many of them were succumbing to the debilitating effects of Alzheimer’s at much earlier ages than regular patients. “It’s well established that the majority of Down syndrome kids will get Alzheimer’s,” says Schmid.

A critical region of chromosome 21 is known to be responsible for Down syndrome because, when a third copy of the chromosome is present, its genes produce proteins at excessive levels. Schmid and his colleagues added genes from that region to rat neurons. Four of those genes caused early death of the neurons, suggesting that those genes may be responsible for the early neurodegeneration of Alzheimer’s in Down syndrome patients. — Laura Sanders

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