Colin Pittendrigh

Colin Pittendrigh (October 13, 1918 - March 19, 1996)^[1] was a US-American biologist of English parentage. He is a co-founder of modern chronobiology along with Jürgen Aschoff and Erwin Bünning.

Life

Colin Pittendrigh was born in 1918 in northeastern England (today Tyne and Wear) and received his first degree in botany at King's College, Newcastle upon Tyne, University of Durham, now University of Newcastle upon Tyne.^[2] He married and had two children, Robin and Colin Jr. (Sandy).^[3] During World War II the British Government sent him to Trinidad, where he studied the epidemiology of malaria transmitted by mosquitoes breeding in the bromeliad ponds ("tanks" formed by overlapping leaves), making acute observations on bromeliad distribution within forest canopies and between contrasting forest formations.^[4] His work with the biting rhythms of these mosquitoes piqued his interest in biological rhythms.^[2]

After the war, Pittendrigh attended Columbia University to study for his Ph.D. under the evolutionary geneticist Theodosius Dobzhansky.^[3] In 1947 he joined the faculty at Princeton,^[1] where he began his work on on circadian rhythm. He became a U.S. citizen in 1950; in 1969 he joined the faculty of Stanford where he helped found the program in Human Biology and later became the director of the Hopkins Marine Station.^[1] He died of cancer on March 19, 1996 in his home in Bozeman, Montana.^[1] His favorite hobby was fly-fishing.^[5]

Work

After his work in Trinidad, he continued to pursue his interest in animals' orientation to time at Princeton University. Together with Jürgen Aschoff he laid the groundwork for today's understanding of chronobiology; investigating such topics as human wake/sleep cycles, hibernation, the navigation of animals, and jetlag. Pittendrigh became close friends with Aschoff when the latter visited the United States in 1958.^[6] Aschoff's visit inspired the two to organize the 1960 Cold Spring Harbor symposium,^[7] which marked the recognition of the new field of chronobiology.^[6]

Pittendrigh also established the concept of teleonomy, a quality determined through objective principles as described in the book Behavior and Evolution (1958, edited by Anne Roe and George Gaylord Simpson).^[2] A teleonomic act or characteristic is one which owes its usefulness to the workings of a program. Pittendrigh applied this concept to knowledge of cellular control mechanisms. He purposefully positioned his concept of teleonomy against the concept of teleology, which he believed to be an unscientific and idealistic approach to the interpretation of biological control mechanisms.

Contributions to chronobiology

Pittendrigh was influential in establishing many of the key criteria a biological system must have in order to be considered a biological clock. His work studying the eclosion rhythms of Drosophila pseudoobscura demonstrated that 1) eclosion rhythms persist without environmental cues (i.e. in constant conditions),^[2] 2) unlike most chemical reactions, the period of eclosion remains relatively constant when exposed to changes in ambient temperature ("temperature compensation"),^[8] and 3) eclosion rhythms can be entrained by light cycles that are close to the flies' natural period.^[2]

Beginning in 1958,^[9] Pittendrigh developed the concept of the phase response curve or PRC.^[6] The PRC allowed chronobiologists to predict how a biological system would be affected by a change in its light schedule. Although biologists, including Pittendrigh himself, acknowledge that the PRC is a simplified model, it is still used today to teach the concept of non-parametric entrainment (see below).^[6]

Pittendrigh and Aschoff proposed two different models for the entrainment of the biological clock to external light cycles. Aschoff, noting that the internal clock's period depends on the length of the day, began with a parametric model in which the period of the internal clock shortens or lengthens in order to align with the external period. Pittendrigh's research with pulses of light and PRCs led him to propose a non-parametric model of entrainment in which pulses of light instantaneously shift the phase of the biological clock, while the intrinsic period remains constant.^[6]

Evidence for Pittendrigh's model was presented in his 1976 paper, "A Functional Analysis of Circadian Pacemakers in Nocturnal Rodents," ^[10] written in collaboration with Serge Daan. They showed that significant phase advances and delays could be induced in nocturnal rodents simply through the application of a single 15-minute light pulse at specific times of the rodents’ subjective night. Pittendrigh and Daan also demonstrated the history dependence of free running period, or the effects of prior light conditions on free running period in constant darkness (DD).^[11] Part II of the paper also develops certain observations regarding PRCs; Pittendrigh and Daan put forth that range of entrainment can be predicted by examination of the largest delay and the largest advance on a PRC. PRCs were found to have similar advance and delay zones, across species. However, species with a longer wake-sleep period tended to have larger advance zones as compared to delay zones whereas species with relatively short wake-sleep periods were found to have larger delay zones as compared to advance zones.^[11] Moreover, Pittendrigh and Daan argued that pacemaker accuracy was greater than rhythm accuracy.^[11] Part III demonstrated that various chemical stimuli can affect the period of mice, in this case ingestion of D₂O causes the period to lengthen by up to 1.8 hours.^[12] D₂O was later shown to lengthen the period of cockroaches as well.^[13] The use of chemicals to affect circadian periods and oscillations has led to the production of many new pharmaceutical drugs that aim to treat a variety of sleeping disorders.^[14] In part IV, Pittendrigh and Daan expanded their model to a two-pulse system (or “skeleton photoperiod”) with one flash at dawn and one at dusk to account for differences in day lengths. This model accurately predicts entrainment for photoperiods up to 12 hours, after which point a “Psi Jump” occurs (the organism switches which pulse is dawn and dusk). From these experiments, the concept of bistability was derived, showing that organisms are able to stably entrain to two different skeleton photoperiods each with a different phase relationship.^[15] In part V of the paper, "Pacemaker Structure: A Clock for All Seasons", Pittendrigh and Daan reported the phenomenon of alpha-splitting, in which animals develop two bouts of activity per 24 hour cycle, instead of one, in constant light (LL). Following these observations, they proposed a dual oscillator model, in which the pacemaker is composed of two mutually coupled oscillators, E and M, which regulate evening and morning activity peaks, respectively. ^[16]

Timeline of accomplishments

• 1940: Graduation from University of Durham in England
• 1940-1945: Stationed in Trinidad working on Malaria for the Rockefeller Foundation
• 1945-1946: Doctoral thesis at Columbia University (Graduated 1948)
• 1947: Assistant Professor of Biology at Princeton University
• 1950: Became U.S. citizen
• 1960: Chaired organizing committee for Cold Spring Harbor Symposium on biological clocks
• 1969: Began his work at Stanford University
• 1976-1984: Director of the Hopkins Marine Station

Positions and honors

• Member of Senior Staff of NASA
• National Academy of Sciences study: "Biology and the Exploration of Mars"
• National Academy of Sciences
• American Academy of Arts and Sciences
• Guggenheim Fellowship
• Alexander von Humboldt Prize
• Gold Medal of the Czech Academy of Science
• Director of the Hopkins Marine Station
• President of the American Society of Naturalists
• Vice-President of the American Association for the Advancement of Science

References

1. ^ ^{a b c d} [1] "Colin Pittendrigh, 'Father of biological clock,' dies at 77", March 25, 1996, accessed April 9, 2011.
2. ^ ^{a b c d e} Menaker, M (May 1996). "Colin S. Pittendrigh (1918-96)". Nature 381 (6577): 24. doi:10.1038/381024a0. http://www.nature.com/nature/journal/v381/n6577/pdf/381024a0.pdf. 
3. ^ ^{a b} [2] "Memorial Resolution: Colin S. Pittendrigh" accessed April 26, 2011
4. ^ Pittendrigh, Colin (March 1948). "The Bromeliad-Anopheles-Malaria Complex in Trinidad. I-The Bromeliad Flora". Evolution 2 (1): 58–89. JSTOR 2405616. 
5. ^ Donald Kennedy, Albert Hastorf, David Epel, David Perkins (March 2008). "Colin S. Pittendrigh". Proceedings of the American Philosophical Society 152 (1): 158–161. 
6. ^ ^{a b c d e} Daan, Serge. [3] "Colin Pittendrigh, Jürgen Aschoff, and the Natural Entrainment of Circadian Systems." The Colin S. Pittendrigh Lecture, May 9, 1998, accessed April 9, 2011.
7. ^ [4] "Biological Clocks, Vol XXV." accessed April 9, 2011.
8. ^ Pittendrigh, Colin S. (1954), "On Temperature Independence in the Clock System Controlling Emergence Time in Drosophila", Proc Natl Acad Sci USA 40 (10): 1018–1029, doi:10.1073/pnas.40.10.1018, PMC 534216, PMID 16589583, http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=534216 
9. ^ Pittendrigh, CS. "Perspectives in the study of biological clocks." Perspectives in Marine Biology, AA Buzati-Traverso, ed, 239-268, University of California Press, Berkeley.
10. ^ Daan, S & CS Pittendrigh (1976). "A Functional Analysis of Circadian Pacemakers in Nocturnal Rodents". Journal of Comparative Physiology A 106 (3): 223–355. 
11. ^ ^{a b c} Daan, S & CS Pittendrigh (1976). "A Functional Analysis of Circadian Pacemakers in Nocturnal Rodents - II. The Variability of Phase Response Curves". Journal of Comparative Physiology A 106 (3): 253–266. 
12. ^ Daan, S & CS Pittendrigh (1976). "A Functional Analysis of Circadian Pacemakers in Nocturnal Rodents - III. Heavy water and constant light". Journal of Comparative Physiology A 106 (3): 267–290. 
13. ^ Caldarola, PC & CS Pittendrigh (1974). "A Test of the Hypothesis That D20 Affects Circadian Oscillations by Diminishing the Apparent Temperature". Proc Natl Acad Sci USA 71 (11): 4386–4388. doi:10.1073/pnas.71.11.4386. 
14. ^ Jan, J. E., Espezel, H. and Appleion, R. E. (1994). "THE Treatment of Sleep Disorders with Melatonin". Developmental Medicine & Child Neurology 36 (2): 97–107. doi:10.1111/j.1469-8749.1994.tb11818.x. 
15. ^ Daan, S & CS Pittendrigh (1976). "A Functional Analysis of Circadian Pacemakers in Nocturnal Rodents - IV. Entrainment: Pacemaker as Clock". Journal of Comparative Physiology A 106 (3): 291–331. 
16. ^ Daan, S & CS Pittendrigh (1976). "A Functional Analysis of Circadian Pacemakers in Nocturnal Rodents - V. Pacemaker Structure: A Clock for All Seasons". Journal of Comparative Physiology 106 (3): 333–355. 

External links

• Colin S. Pittendrigh, 77, Biologist and Expert in Internal 'Clocks', The New York Times, March 26, 1996
• Cold Spring Harbor
• Dictionary of Circadian Physiology

Persondata
Name	Pittendrigh, Colin
Alternative names	Pitt
Short description
Date of birth	October 13, 1918
Place of birth	Whitley Bay, England
Date of death	March 19, 1996
Place of death	Bozeman, Montana