Thursday, August 20, 2009

Chronobiology: Rhythms in life

I was already teaching for eight years when I decided to temporarily leave the Philippines for a Ph.D position here in The Netherlands. It was a difficult decision to make not only because I already had then a six-month old daughter, but also and more importantly, because of my active role in AGHAM, a national organization of advocates of science and technology for the people.

Working for AGHAM means believing that the current backward state of science and technology in the country can only be improved by working closely with the Filipino people especially those from poor communities. Leaving the country for a Ph.D position abroad meant leaving behind the people whom our science and technology must serve. It cannot be denied that my decision is comparable to those seeking greener pastures abroad—a selfish decision that puts the individual over the society.

Whatever my specific justification, I still carry the same dream of contributing to the uplifting of the state of science in our country. I can list many ways of how this dream can be made real even by Filipino scientists like me who are away: I know many Filipinos overseas, scientists and not, who are helping the country in their own way. Let me do my part by writing about the science that I am studying.

Chronobiology is a branch of biology, which is not widely known, perhaps, even among Filipino biologists. It is the study of rhythms observed in plants, animals, and other organisms. An example of these rhythms is our sleep-wake cycle which takes place within a period of around 24 hours. This is the reason why such rhythms are called circadian (“circa” = around, “diem” = day).

Other rhythms observed in nature are called circatidal, circalunar, and circannual; each type of rhythm corresponds to a cyclic behavior of the Earth. Circatidal rhythm includes, for instance, hatching behavior of some species of crabs: they tend to synchronize with the cycle of alternating low and high tides. Menstruation cycles exemplify a circalunar rhythm. For circannual rhythms, we can cite a four-year study in the 1980s, which revealed that testosterone in boys at prepuberty peaks around July, suggesting a circannual hormonal rhythm. As you can see, circannual rhythms are the most difficult to study and thus least understood among the four biological rhythms mentioned—your experimental data for one year is not enough statistically to conclude that there is indeed a rhythm. Besides these four Earth-synchronized biological rhythms, there are also biological rhythms that have periods ranging from milliseconds to decades.

A practical question about chronobiology: what is the use of knowing these biological rhythms? There are several practical uses of chronobiology ranging from biological timers to drug administration. Linnaeus’s flower clock is based on the difference in timing of opening and closing of different plants. Imagine a garden with plants whose flowers open at 6 a.m. and at 9 a.m., at 12 noon, and at 3 p.m. and at 6 p.m. Besides the difficulty of maintaining such a garden, this may also be not of much use to many people since we can buy cheap China-made watches nowadays, which may be of the same precision as flower clocks but are definitely more portable.

In medicine, chronobiology can help in determining the right timing of drug administration. As an example, studies have shown that our blood pressure is not really constant, but follow cycles throughout the day which peak around 6 p.m. This also varies per individual depending on circumstances. Thus, it is also very likely that blood-pressure-lowering medicines have different efficacy across the day, and it would be wise for doctors to determine the correct timing for a specific individual. Chronopharmacology is the field of medicine that deals with how the effects of drugs vary with biological rhythms.

A scan of scientific journals in chronobiology and conversation with chronobiologists will give you an idea how wide-ranging the topics are in this not-so-popular field in biology: detection of mood disorders based on sleep patterns; the link between night-shift work and cancer; zoo management (there was a study on the feeding schedule of koalas in a zoo); physiological effects of low-gravity; timing in the brain, etc.

Chronobiology can also be applied in the agriculture sector. For fisherfolk, it would be very useful to know the abundance of fish and their types at a given time, day, or month. For farmers, knowing when pests thrive would save precious time for other activities. It is possible that fisherfolks and farmers actually have these knowledge in crude form that local scientists might help refine. After all, science is the product of the accumulated experience of the people throughout history.

An active member of Agham, Kim obtained his physics bachelors and masters degrees at MSU-IIT and UP-Diliman, respectively. He is now pursuing doctoral research in chronobiology at the University of Groningen, Netherlands.


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