Internal Clocks Keep Everything From Humans To Algae Ticking

Vanderbilt University biologist Carl Johnson, who studies circadian (biological) rhythms, says that the biological clocks of lower organisms and humans are "entrained" by both artificial and natural light.

For humans, man-made alarm clocks and artificial light help set our internal clock, which naturally runs at a daily rate slightly longer than 24 hours.

Johnson says there are certain constants about the human biological clock. For example, the older we are, the faster our internal clock tends to run.

This may be the reason why older people wake up early in the morning and therefore experience sleep disruptions - their internal "alarm clock" goes off too early. Also, most humans would benefit from an afternoon nap, because napping is an innate biological function.

"The human internal clock has become entrained by man-made clocks," Johnson said. "For lower organisms, light is usually the factor that sets the timing of the internal clock."

Johnson is currently working on several research projects related to biological clocks, including the role of circadian rhythms in blue-green algae in which he and researchers from Japan and Texas A & M University have developed "mutant" blue-green algae to determine the adaptive significance of biological clocks.

The mutant algae and natural algae are subjected to light in two different cycles - 24 hours, the "natural day," and 30 hours. The two algae groups start out the same, but the mutant algae adapt to the 30-hour light cycle, while the natural blue-green algae does not.

Johnson is also researching the regulatory role of calcium in and melatonin's role in plants, such as how it may affect seasonal functions, such as flowering. His research is funded by the National Science Foundation, the Human Frontier Science Program and the National Institute of Mental Health.

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