Chronobiology An Internal Clock for All Seasons. Part 1.
The Development of the Science of Biological Rhythms
Institute for Scientific Institution 3501 Market St., Philadelphia, PA
The lives of virtually all plants and animals, from the simplest one-celled organisms to humans, are governed by a variety of internal biological rhythms. This essay (the first of two parts) discusses chronobiology, the study of these biological clocks. Biological periodicities may range from ultradian and circadian to circahmar and circasrnualcycles. Using ISI” data, we trace the development of the field from its earliest underpismirrgsin botany and zoology and identify the authors of Citation Ck.rsics”, such as Jurgen Aschoff, Erwin Burming, and Colin S. Phtendrigh.
Essays of an Information Scientist: Science Literacy, Policy, Evaluation, and other Essays, Vol:11, p.1, 1988 Current Contents, #1, p.3-9, January 4, 1988
Living organisms exhibit myriad cycles. Annually, the leaves of deciduous trees in the temperate zones turn brilliant hues of yellow, orange, and red as the days shorten and winter approaches. Each year, anirnrds go through cycles related to reproduetion; most of those in the temperate zones also experience rhythms that prepare them for the period of inactivity that comes with winter.
Cycles that take less than a year to complete are also plentiful. Daily rhythms include the folding and unfolding of the leaves of certain plants, such as the “sensitive plant” (Mimosa pudica) and the tamarind tree (Thnrars”ndusindicus), and the rise and fall of the body temperature of animals (including humans). 1(p. 5, 14) Numerous organisms inhabiting the earth’s tidal zones, from plankton and diatoms to crabs and aeabirds, exhibit cycles of physical and behavioral change ranging from 12 hours to two weeks to a month in length, matching the complex, interacting effeets of the sun and the moon on the tides.2 In fact, even cells exhibit some type of periodicity in their activities, often in cycles lasting fractions of a second.3-5
The importance of rhythms in nature has been appreciated for thousands of years:6 people plant their crops in tune with the cycle of the seasons and eat and sleep according to the daily rise and fall of the sun. Indeed, so familiar are these rhythms that, according to pharmacologists Joseph S. Takahashi and Martin Zatz, Laboratory of Clinical Science, National Institute of Mentaf Health, Bethesda, Maryland, they did not elicit systematic, scholarly investigation until the 1700s.7 Since that time, however, the study of these biological rhythms has slowly coalesced into the science of chronobiology.
Some of the foundations of chronobiology were laid in the 1930s. But as the first part of this essay shows, activity in this field remained fairly constant at a relatively low level until the 1950s and 1960s. Since then, according to a review by Akin Reinberg, director of research, National Center of Scientific Research, Paris, France, and Michael H. Smolensky, associate professor of envirorunental sciences, University of Texas Herdth Sciences Center, Houston, chronobiology has been art active, rapidly growing, multidisciplinary field.6 The second part of this essay focuses on the latest research in this dynamic science.