Circadian

After a time-shift, mixed signals from the circadian clock

Circadian rhythms in mammalian behavior, physiology, and biochemistry are controlled by the central clock within a brain structure known as the suprachiasmatic nucleus (SCN). The clock is synchronized to environmental cycles of light and dark. It is well known, from everyday experience, that adjusting to new light schedules takes several days, though the details of how this adaptation takes place...

The circadian clock: Understanding nature's timepiece

A cluster of brain cells less than half the size of a pencil eraser tells you when to wake up, when to be hungry and when it's time to go to sleep. The same cells also cause you to be disoriented after you've flown across multiple time zones. The human circadian clock, comprised of about 20,000 time-keeping cells, has mystified scientists since it was pinpointed in the brain about 30 year...

Gene controlling circadian rhythms linked to drug addiction

The gene that regulates the body's main biological clocks also may play a pivotal role in drug addiction, researchers at UT Southwestern Medical Center have found. The Clock gene not only controls the body's circadian rhythms, including sleep and wakefulness, body temperature, hormone levels, blood pressure and heart activity, it may also be a key regulator of the brain's reward system.</...

Temperature regulates circadian clock in zebrafish

The biological clock controls the circadian rhythms of a wide range of physiological and behavioral processes, from fluctuating hormone levels to sleep-wake cycles and feeding patterns. While it's well known that circadian clock elements sense and respond to light cycles, much less is known about how daily temperature cycles affect the clock's timing mechanism in vertebrates. In the open-access...

A novel method to measure circadian cycles

Everyone knows morning people and late-night owls. The variation in individual circadian rhythms is an anecdotal as well as experimentally verified fact. But, until now, to systematically study circadian differences (and thereby hope to rout out the underlying genetic causes), scientists have had to rely on prolonged behavioural observation. To screen for and identify circadian rhythm variation...

A resetting signal keeps circadian rhythm on track in Drosophila fruit flies

A Brandeis University study published this week in Nature shows for the first time that a molecular signal maintains coherence among brain clock cells that regulate daily activity of Drosophila melanogaster (fruit flies). The two key groups of neurons control morning and evening activity and are maintained in synch even when the flies are plunged into darkness for extended periods of time. <...

New fruit fly protein illuminates circadian response to light

Researchers at the University of Pennsylvania School of Medicine have identified a new protein required for the circadian response to light in fruit flies. The discovery of this protein ?named JET ?brings investigators one step closer to understanding the process by which the body's internal clock synchronizes to light. Understanding how light affects circadian (24-hour) rhythms will likely open...

Circadian gene helps the brain predict mealtime

By investigating how animals can predict the timing of food availability, researchers have identified the first gene critical for anticipation of mealtime. This gene, called Period 2, is a key component of the circadian time-keeping system. The findings are reported by Urs Albrecht of the University of Fribourg and Etienne Challet of the University Louis Pasteur/CNRS and colleagues in the October...

Research finds that circadian rhythms dominate all life functions

New research from Colorado State University shows that the function of all genes in mammals is based on circadian -- or daily -- rhythms. The study, publishing in PLoS Computational Biology on June 15, refutes the current theory that only 10 percent to 15 percent of all genes were affected by nature's clock. While scientists have long known that circadian rhythms regulate the behavior of the l...