all circadian rhythm stories

Researchers discover second light-sensing system in human eye

404132862 — Thu, 13 Dec 2007 12:51:32 -0500

New research on blind subjects has bolstered evidence that the human eye has two separate light-sensing systems — one that perceives the familiar visual signals that allow us to see and a second, separate system that tells our body when it is day or night.

Researchers have long known that the eye performed both functions but until recent years it had been thought that both vision and the management of the circadian rhythm that tells us when to be sleepy and when to be alert had been done all at once through the retina’s rods and cones that enable us to see.

Basic understanding of biological clock advances

404132862 — Tue, 16 Oct 2007 20:54:53 -0400

Writing this week in the journal Science, researchers at Harvard describe what causes a trio of proteins, if placed in a test tube with the common biochemical fuel ATP as a source of phosphate, to function as a minimalist biological clock of sorts, maintaining an accurate circadian rhythm for long periods of time.

The new Harvard work builds upon research reported in 2005 by biologist Takao Kondo and colleagues at Nagoya University in Japan. That team initially reported that a circadian clock could be reconstituted in a test tube solely with three proteins and ATP.

Peripheral 'Swatch' watches are powerful force in modulating body's circadian rhythms

70652986 — Mon, 26 Mar 2007 05:20:42 -0400

Clinicians have known for years that organs function at different rates -- the heart beats, kidneys transport ions and electrolytes, the liver metabolizes lipids, sugars, and amino acids differently over the course of the day -- and have used this knowledge to design more effective drug regimens for patients. A better understanding of what drives those local rhythms, and how they go wrong, could aid physicians' efforts. Now a study, among the first to explore timing mechanisms outside the brain, could have a broad impact on the burgeoning fields of circadian medicine and postgenomic science.

Link found between body rhythms and circadian clock, light

70652986 — Mon, 26 Mar 2007 05:17:45 -0400

The brain's circadian clock is a tiny cluster of neurons behind the eyes. This cluster of cells sends out signals that control the body's daily rhythms. New research from Harvard Medical School has started us on the path to understanding better how this process works. The possible implications of understanding how the circadian clock works are obvious. "If you could figure out the factors that promote wakefulness and sleep, that could in principle be turned into better drugs for particular sleep disorders," said Charles Weitz, Harvard Medical School professor of neurobiology. So his research team began investigating the molecular pathway that transmits sleep and wakefulness signals. His team's findings appeared in the Dec. 21, 2001, Science.

Are you an 'early bird' or a 'night owl'?

70652986 — Mon, 26 Mar 2007 07:09:34 -0400

Harvard researchers working at Brigham and Women's Hospital have found that whether someone is a morning person or an evening person depends on a basic aspect of the circadian timing system that is known as intrinsic period. The study was published in the August 2001 issue of "Behavioral Neuroscience. "While some have argued that extremes in sleep-wake timing are personality characteristics, this study reveals that there is a biological basis for morning or evening patterns,” said Charles A. Czeisler, senior author of the study, chief of division at Brigham and Women's Hospital and professor of medicine at Harvard Medical School. “In this study, we found that differences in a fundamental property of the circadian timing system, its intrinsic period, will determine whether someone is a ‘early bird' who awakes before dawn or a ‘night owl' who tends to stay up at night but sleeps in late.” The study was funded by the National Institute on Aging, Air Force Office of Scientific Research, and National Institutes of Health Division of Research Resources.

Circadian rhythms may distinguish Alzheimer's disease

70652986 — Mon, 26 Mar 2007 05:10:33 -0400

Researcher David Harper and his colleagues monitored two key components of the circadian system -- the rise and fall of core body temperature and the waxing and waning of spontaneous motor activity -- in 38 dementia patients with either Alzheimer's disease or another form of dementia, frontotemporal degeneration. They found that body temperature reached its peak much later in the day in the Alzheimer patients than it did in control subjects. People with frontotemporal degeneration exhibited a much different pattern. Their activity levels reached a peak earlier in the day than in control subjects while their body temperature rhythms appeared normal.