The cycle of dawn and dusk changes with the seasons everywhere in the world (except at the equator, where there is always 12 hours of daylight and 12 hours of darkness). In order to compensate for the seasonal variations of light, mammals likely have an adjustable daily program under the regulation of a biological clock.
But how do mammals in the Arctic which is characterized by months of full light followed by months of full darkness -- retain their sleep and awake habits in such unusual circumstances? After analyzing the reactions of certain mammals following 82 days of continuous daylight in the summer and 82 days of continuous darkness in the winter, a team of researchers may have begun to identify a clue.
A New Study
The research is captured in a presentation entitled, "Cardiac Physiology of Mammals in Arctic Light Cycle: Heart Rates and Biological Clocks." The authors, G. Edgar Folk, Diana L. Thrift, James B. Martins, and Miriam B. Zimmerman, all from the University of Iowa, Iowa City, IA, will present their findings at the American Physiological Society's (APS)(www.the-aps.org) annual scientific conference, Experimental Biology 2004, being held April 17-21, 2004, at the Washington, D.C. Convention Center.
Methodology and Results
The researchers analyzed the biological clocks using cardiac physiology. They recorded the mammals' daily circadian rhythm using heart rate to show the rhythm of sleep and wakefulness.
Control laboratory rats (N=4) w
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Contact: Donna Krupa
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703-527-7357
American Physiological Society
19-Apr-2004