Chronobiology An Internal Clock for All Seasons Part 1

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organism from single celled plants and an Environmental Influences on. imals to such complex creatures as human Biological Rhythms. beings s These rhythms are intrinsic to the For centuries it was believed that biolog. organism and enable it to measure the pas ical periodicities were cuused by the envi. sage of time For many organisms the most ronmental rhythms with which they were. important interval measured by their inter synchronized b But in 1729 French astron. nal clocks is the 24 hour cycle of light and omer Jean Jacques d Ortous de Mairan. dark Rhythms that coincide with this cycle 1678 1771 conducted an experiment show. are called circadian from the Latin cir ing that even in total darkness the leaves. ca about and dies day g p 2 10 of a sensitive heliotropic plant probably. Other important biological periodicities Mimosa pudical p f continue to fold. include circatidal rhythms matching the and unfold in a 24 hour cycle that was pre. period of daily high and low tides and cir viously thought to be in response to day. casyzygic rhythms which match the cy light 10, cle of unusually high and low tides occur The idea that the circadian movements of. ring each fortnight when the sun and moon plants are indepmdent of the daily light dark. are in the proper alignment Circahmar cycle was confirmed by a series of experi. rhythms are synchronized with the monthly ments performed by the Oerman botanist. waxing and waning of the moon Circan Wilhelm F P Pfeffer 1845 1920 6 1 I. nual periodicities are cycles of about a p 61 2 in the late 1800slz and early. year g p 9 10 It should be noted 1900s 13As Reinberg and Smolens note. however that circannual rhythms are not the however it was not until the 1950s that. end of the story for example the 7 year and Pfeffer s findings were clearly understood. 17 year locusts that emerge from their long and appreciated 6. puprd incubation in the ground are cycles It was another Oerman botanist Erwin. that span longer periods Bihming University of Ttibingen who first. An innate ability to measure the passage conclusively established the accepted foun. of time has adaptive significance A sense dations of chronobiology that organisms use. of time helps birds to accurately use the sun their biological rhythms to measure the pas. moon and stars as navigational aids during sage of time and that these rhythms are in. migration Internal clocks also enable orgrm herent to the organism Bunning proved the. isms to synchronize their breeding behav genetic origin of biological rhythms in the. iors with one another as well as with the mid 1930s while working at the BotardcaJ. most favorable environmental conditions for Institute of the University of Jena He found. raising young In fact biologicrd rhythms that circadian rhythms persisted in the. help organisms match a number of activities bean plant Phaseolus14 and the fmit fly. to the times when those activities can be car Drosophila 15 even though generation after. ried out most effectively For example as generation had km raised in environments. noted by zoologist David S Saunders Uni completely lacking cues to the passage of. versity of Ediiburgh ScotJand circadian time b 11 p 146 8 The 1936 paper on fruit. rhythms allow animals of different spexies flies has been cited over 180 times accord. tosharethe same foodsources without direct ing to the Science Citation Index SCF. competition because some animals are ac A Citation Ckz rsic 16 it is the most cited. tive ordy during hours of darkness i e they paper ever published by Berichre der. are nocturnaf while others are active only Deutschen tlotanischen Gesellschq the. during the day diwnuf The advantage to journal of the Oerman Society of Botanists. having a built in methcd of responding to Bunrting s work with Drosophila eventu. light and darkness rather than relying on ally led him to conclude that the fruit fly. actual changes in light as a cue is that in knew when to emerge from the pupal. effect the organism is prevented from stage of its development because its circa. sleeping late and missing the optimal time dian rhythm had cycled a given number of. of day for foraging g p 12 times indicating that a season had passed. His work has been extensively cited A de To describe the environmental cues from. finitive German language edition of Bun which biological rhythms are derived. ning s work in this area entitled Die Aschoff coined the word Zeitgeber. physiologische Uhr The Physiological meaning time giver z Colin S Pit. Clock 17 was originally published in 1958 tendrigh Stanford University California. and reprinted in 1963 Using the 1955 1964 later introduced the term entraining. SCI 18 we determined that the former has agent Z6still later Halberg and colleagues. received about 100 citations The reprint has proposed the word synchronizer 27A1. been cited at least 120 times An English though these authors each give a somewhat. translation appeared in 19649 and has been different definition of their terms it has be. reprinted twice since then The various edi come common practice in the field to use. tions have been explicitly cited in almost 700 them interchangeably b. publications making l re Physiological,Clock a Citation Ckmsic 20. Aithough biological rhythms are innate The Emergence of the Diacipiine of. they nevertheless function to k p organisms Chronobiohgy. in tune with their environment and are thus Despite the discoveries of Pfeffer Bun. responsive to various environmental or ex ting Aschoff and others chronobiology. ogenous cues In 1954 Jiirgen Aschoff pro did not really begin to coalesce as a distinct. fessor of physiology and director Max discipline until the 1960s 6 in part accord. Phmck Institute for Behavioral Physiology ing to Reinberg and Smolens this was be. Seewiesen iiber Starnberg Federal Republic cause chronobiology lacked some of the at. of Gemmny zl and Franz Halberg Univer tributes that help a field establish its own. sity of Minnesota Medcal School Minne identity For example until recently chro. apolis and Cambridge State School and nobiology was not taught in schools as a sub. Hospital Minnesota and colleagueszz in ject in its own right and no departments or. dependently and aimost simultaneously de chairs of chronobiology existed This meant. veloped an explanation of the role that en that those who studied chronobiology nec. vironmental factors play in the functioning essarily came to the subject from other. of internal clocks 6 fields often by accident As a result the au. These environmentai factors such as thors write the number of active and weii. light and dark ambient temperature noise trained chronobiologists was quite small b. and even interactions with other members Again until recently there were few. of the same species wt to keep biological scholarly societies devoted to chronobiolo. cycles in phase with periodic fluctuations in gy which may have hampered communi. the environment in the absence of such cues cation between the widely scattered mem. which owurs when plants and anirnais are bers of the chronobiologicai community. removed to controlled laboratory condi It is otlen beiieved that the true emergence. tions the cycles continue but begin to drift of a specialty is hampered by a lack of jour. out of phase with clock time and become nais focused on that field Untii recently no. free running Within their own free run joumais devoted exclusively to chronobiol. ning cycles though they are remarkably re ogy were being published In this respect. sistant to perturbation 6 In fact several it is worth quoting Victor A McKusick2s. studies by Aschoff demonstrated that be and Frank H Ruddle editors in chief of Ge. yond certain narrow Mnits the presence or nomics on their justification for launching. lack of environmental cues has no effect on a new journal In an editoriai in the first is. biological rhythms zs zs One of these pa sue they said that they viewed the journal. pers entitled Exogenous and endogenous as a common meeting ground for molee. components in circadian rhythms 24 is uiar biologists and biochemists human and. Aschoff s most cited paper published in somatic cd geneticists cytogeneticists pop. 1960 this Citation Ciassic has been cited ulation and evolutionary biologists genetic. over 470 times epidemiologists clinical geneticists thtm. Table 1 Selected list of joumds reponingonbasicand journals the smaller new journals will have. appliedstudyof physiologicalrhythms A title and a tough time. publisher B 19S6impsct factor,Since the 1960s however several. A B changes have begun to take place that have,American Journal of Physiology 3 29. enabled chronobiology to gain recognition, American Physiological Society and intluence as a discipline in its own right.
Bctheada MD Three journals that report solely on chro. Brain Research 2 86 nobiological research the Internutioncd. Elsevier Science Polishers Journal of Chronobiofogy Chrorwbiologia. Ammerdam The Netherlands,and Chronobiology Itiemutional have been. Chronobiologia 0 72 founded Table 1 lists these and other jour. Casa Editrice, Mifrm hfy nals in which chronoblologists publish The. Chronoblology Intemationsl,Society for the Study of Biological Rhythm. Pergamon Press Inc founded in 1937 but relatively dormant un. Ehrrsford NY til 1953 changed its name to the Intern. International Jourmd of Chronoblology ational Society for Chronobiology in 1971. Gordon Breach Science publishers Ltd and has been highly active ever since Other. London United Kingdom,scholarly societies and associations that pro. JoumaJ of Biological Rhythms,mote chronoblological research are listed in.
Guilford Publications,New York NY Table 2,Journalnf ClinicslEndwrinologysod 4 20. A favorable intellectual climate also, Metabolism played a role in helping to establish chro. EndncrineSnciety nobiology as a distinct discipline Reinberg. Bsftimore MD and Smolensky refer to the 19 Os as the. Jourmd of Comparative Physiology A 0 90 golden age of molecular biology and note. Sensory Neural and J3efraviomJ Physiology,Springer Verlag New York hrc. that it coincided with a flowering of chro, New York NY nobiological research 6 In part they say. Joumaf of Insect Physiology 1 60 the emergence of cbronobiology was aided. Pergarnon Press inc by the burgeoning interest of molecular bi. Oxford United Kingdom ologists in cellular periodicities At the same. Jnurnaf of fnterdiaciplinary Cycle Research 1 46 time as both a cause and an interactive re. Swets Zeitlinger BV,sult of this heightened interest new statis.
Lisse The Netherlands,tical approaches for detecting and measur. Journal of Pkwal Research 1 25,Alan R Liss Inc,ing biological periodicities were being de. New York NY veloped These were especially useful in. Physiology and Behavior 1 43 studying ultradian rhythms which include. Pergrmron Press Jnc cycles that range from a fraction of a second. Elms ford NY to a fraction of a day, Psychiatry Research 2 30 Pittendrigh organized a symposium at. Elaevier Scientific publishers Irehmd Ltd,CoId Spring Harbor New York in 1960 to. Shannon Irclsnd,address the standards that chronobiology had.
sleep 1 50,to meet to develop further as a modem,Raven Press. New York NY quantitative biological science b Among the. topics discussed were more rigorous meth, retical biologists and computational scien ods of data sampling and gathering and sta. tists all interested in the biology and genet tistical amdysis zq zb l e 1960 paper Pit. ics of human and other complex ge tendrigh wrote for the symposium entitled. nomes 29 However not every field best Circadian rhythms and the circadian or. serves itself by jumping into separate pub ganization of living systems 26 is hk. lication As long as the most important ar most cited work This Citation Classic has. ticles remain in the bigger mukidiseiplinary been cited in over 450 works. Table Z Selectedlist, of aasnciations promoting research greatly increased since the 1960s This has. and providing information on various aspezts of,chronobiology and circadian rhytbma. enabled chronobiologists to produce what,Reinberg and Smolens call a critical.
International Commission on Circadian Rhythms and mass of experimental evidence that has. Department of Physiology,overcome previous theories that slowed or. Harvard Medical School inhibited the advance of chronobiologic hy. 25 Shattuck Street potheses and concepts e,Boston MA 02115. These theories included the idea taught, International Snciety of Mathematical Biology to generations of students as Reinberg. 11 bk avenue de la Providence,F 92 160 Arremry,and Smolensky note that the regulatory. F mechanisms of biological systems are pro, Intemational Society for Chronobiology cesses that attempt to maintain a constant.
Chronobiology Laboratories or steady state called homeostasis. University of Minnesota Schnol of Medicine Although Reinberg and Smolens do not. 380 Lyon Laboratories,Mirmeapnlis MN 55455,discount the importance of homeostatic. regulatory mechanisms they point out that,the body s set points fluctuate within a. This symposium and the subsequent ac narrow range in a distinct rhythm Such. tivity and debate that surrounded the estab physiological phenomem as the levels of. lishment of chronobiology as a discipline plasma cortisol testosterone circulating. have been the objects of considerable interest Iymphoeytes and blood pressure and body. Chronobiology An Internal Clock L for All Seasons Part 1 The Development of the Science k of Biological Rhythm Number 1 January 4 1988 The lives of virtually all plants and animals from the simplest one celledorganisms 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

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