( Go a few nights without enough sleep an...)Sleepless for science: Flies show link between sleep, immune system in Stanford study

What they have learned thus far is that illness and sleep disruption may be a two-way street: sick flies can't sleep, and losing sleep makes them more susceptible to infection.

"When flies get sick, they stop sleeping," said David Schneider, PhD, assistant professor of microbiology and immunology. "Disrupting sleep in turn disrupts the immune system, which makes them even more infected and it's downhill from there in a 'spiral of death.'" Schneider is the senior author of a study on the sleep patterns of flies that will be published in the May 15 issue of Current Biology.

Schneider worked with postdoctoral scholar Mimi Shirasu-Hiza, PhD, who is the study's first author, to examine the connection between illness and sleep patterns by infecting fruit flies with one of two bacteria - Streptococcus pneumoniae or Listeria monocytogenes.

The infected flies lost their "day" and "night" patterns of activity, which are part of the regular changes that occur in the course of a day, called circadian rhythm. Uninfected flies alternate between 12 hours of high activity and 12 hours of low activity. The researchers found the sick flies had fewer sleep sessions and shorter periods of continuous sleep than did healthy flies. They basically just didn't sleep well, concluded the researchers.

The researchers can't say for sure say whether a disruption of the brain's central clock, which is the area of the fly brain that exhibits circadian gene activity, was responsible for the changes seen in the sick flies. But the behavior of the ill flies looked a lot like that of flies known to have disruptions in their genes controlling circadian rhythm.

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Source:Stanford University Medical Center