ASP Annual Meeting to Focus On Circadian Biology.

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The American Society for Photobiology is holding its annual meeting to present the latest findings in photobiology at the Fairmont Le Chateau Frontenac, Quebec City, Canada, July 13-17, 2002.

The ASP is a scientific society whose members carry out research into the effects of light on living systems and whose interests range from skin cancer, phototherapy, vision, photosynthesis and circadian rhythms to photochemistry and phototechnology.

The meeting will focus this year is on circadian biology. Light exposure influences alertness and also the timing of rhythmic functions such as digestion, sleep, mood and performance. These intrinsic rhythms, called the circadian clock, are entrained or reset by the daily light cycle. This is most familiarly experienced as jet lag where the circadian clock is no longer synchronized with the daylight cycle because of rapid jet travel across time zones. Until recently, the mechanisms by which light controls the circadian clock were obscure.

Recent findings (Provencio I, Rollag MD, Castrucci AM. Nature 2002 Jan 31;415.:493; Hattar S, Liao HW, Takao M, Berson DM, Yau KW Science 2002 Feb 8;295, 1065-70.) have demonstrated that a photoreceptive "net" of specialized cells in the eye called retinal ganglion cells, which are distinct from the cells responsible for vision, are the site of the primary circadian pacemaker. The pigment, melanopsin in these cells, (unrelated to the skin pigment melanin) which was first described in frogs, appears to be the responsible photoreceptor.

New findings will be presented at this meeting using approaches from genomics, photobiology and investigations of signal transduction pathways to further understand this mechanism. It will be shown that, in humans, the most effective wavelengths that control circadian rhythms are in the blue light region. Understanding the mechanisms of control of human circadian rhythms by light is critical for light therapy for jet lag sufferers and for shift workers. Understanding the signal transduction pathways by which the circadian signal is transmitted to the brain may allow the development of drugs to block or alter these signals and allow more rapid adaptation to new light exposure patterns.

In non-mammalian vertebrates including birds, reptiles, fish and amphibians there is another method of control of circadian responses by extra retinal photoreception in which light directly impacts on the brain instead of indirectly via the retina and the nerves which supply the pineal gland as in mammals. Dr. Michael Menaker, founding member of the ASP, will be given a lifetime achievement award for his discovery of the importance of extra-retinal photoreception in circadian rhythms and Dr. Toshiyuki Okano will be awarded a new investigator award for his discovery of pinopsin, one of the photoreceptors responsible and for elucidating the signal transduction pathways leading to the secretion of melatonin, the hormone which influences circadian responses.