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CHRONOBIOLOGY For Everything There is a Season and a Time for Every Matter Under Heaven The above quotation from Ecclesiastes appears on the cover of a recent monograph – Chronobiology – A science in tune with the rhythms of life. Chronobiology is a relatively new science, new to most clinicians and other students of the life sciences, and only a few papers dealing with it have appeared in the clinical literature. Much of the following is taken from the monograph by Boger Publications made possible through the interest and support of Mr. Carl Bakken of Medtronics, Inc. Proper credit should also be given to author, Barbara Murdoch, who, quoting from Mr. Bakken, "has done an outstanding job in making this complex material more accessible and understandable." Chronobiology is the study of the relation of time to and its influence on biologic phenomena and functions. Various environmental entities, including the sun, moon, tides, light and darkness, seasons, temperature, atmospheric pressure, humidity, and drought may be factors in this influence, but there is, in addition, a built-in time-clock peculiar to types of cells, organisms, and species. The first recorded recognition of this built-in rhythm in living organisms was that of the French scientist J. J. Mairan in 1729. He placed a heliotrope plant in utter darkness and was surprised to see that it continued to turn its face in a 24-hour rhythm as it had done in and to the sun all of its life. There are variations of these rhythms – from about 24 to 26 hours (circadian), seven days (circaseptan), 29 to 30 days (circatrigintan – the human menstrual interval) to yearly or seasonal rhythms (circaannual). Over long periods of time these rhythms may and do change as adaptation to environment requires.
Recent studies have shown that these rhythms are genetically imprinted and are part of the DNA of all creatures. Dr. Ronald Konopka of Clarkson University (Science, December 1985) has found genes that affect two prominent rhythms of the fruit fly. One involves the time that the new fly emerges from the pupa, and a second the pattern of the mating song which in normal flies is repeated every 60 seconds. Michael Young of Rockefeller University, together with Konopka, has shown that these patterns can be altered by snipping certain strands of the fly’s DNA. Young and his research team have found similar coding in mice, chickens, and human beings. Work in recent years has demonstrated the importance of these rhythms in the diagnosis and treatment of disease. It has been observed that human blood pressures have a circadian rhythm that peaks in most persons studied between noon and 4 PM. It also may have a 48-hour pattern. It becomes important then that a number of readings of elevated pressure be taken at varying times over a 48-hour period before a patient is diagnosed as hypertensive. Quoting Dr. Franz Halberg, Chairman of the Departments of Pathology and Chronobiology at the University of Minnesota, and one of the pioneers in the latter field, "using a single measure of blood pressure or even a series taken at arbitrary times in a physician’s office is like taking snapshots of a roller coaster" (Chronobiology, 1986). As recently as November of last year an article in The New England Journal of Medicine reported that the incidence of coronary thrombosis is greater at 9 o’clock in the morning than at 11:00 at night. Monday morning is also a bad time of the week for this type of heart attack. The most common malignant tumor of the testicle (seminoma) in men under 35 is diagnosed more often in winter than in summer. The body temperature cycle of a depressed person is different from that of a "healthy" one. Most of us are familiar with the monitoring of a heart patient for abnormal rhythms.
The study of the relation of time to the drug treatment of patients is probably one of the most fertile fields for clinical research. Halberg has found that "a long list of drugs can be tolerated without obvious effects but twelve hours earlier or later, the same dose may kill most animals exposed to it" (Chronobiology, 1986). Growth hormones stimulate cell division if given at one time, but have no effect when given at another. Penicillin is effective by interfering with the building of the bacterium’s cell wall and only destroys actively growing bacterial colonies. It is important then, to give an antibiotic at the optimum time for its maximum therapeutic effect. Hopefully, this young, vigorously growing science will before long pervade all disciplines of the life sciences as well as all specialties of clinical medicine to improve our life styles and enhance our diagnostic and therapeutic abilities. Article from NOHA NEWS, Vol. XI, No. 4, Fall 1986, page 2. |