Cellular Cycles: The Body's Internal Clock

It's 3 a.m. You're asleep, your bronchial tubes are tightening and you may be snoring. Your temperature has dropped a couple of degrees. Twelve hours later, you yearn for a nap, your cholesterol level is hitting its daily peak and your blood pressure is up. The fluctuations are the work of a master clock in your brain, following the genetic orders passed down from your ancient ancestors. Scientists have found ways to shift the hands on that clock, but only a tinge. For the most part, humans cannot control when they feel drowsy, how frequently their eyes blink or how fast their hearts pump. "Research in the last century and this century suggested that biological functions were constant, not rhythmic," explains Dr. Michael Smolensky, director of the Hermann Hospital Clinical Chronobiology Center and Clinic in Houston. "We didn't have the technology to study (rhythms) in a 24-hour time span. Now we have ambulatory monitors and the body shows very clear and exact rhythms."A group of neurons in the brain serves as the taskmaster, commanding a fleet of thousands of smaller timepieces that do everything from renewing the lining of large blood vessels every six months to replacing stomach cells every three days. They are the mini-clocks that make scalp hair grow a half-inch a month, prompt small arteries to contract and relax every two to eight seconds and direct a quart of blood through the brain every minute. These chronometers make you spend two seconds inhaling and three exhaling."Just as the body is organized in space, the body is organized in time, in chronological rhythm," says Smolensky, in Detroit recently to speak to medical personnel at Riverview Hospital about timing drug dosages to take advantage of internal tempo.Although chronobiology, the study of body rhythms, is a new term, biological clocks daily, weekly, monthly and even annually have been observed for centuries. Hippocrates noted 24-hour fluctuations in his patients' symptoms and ancient people noticed that some plants opened their leaves and blossoms by day, then closed them at night. A French astronomer in the 1700s discovered the unfurling would continue if the plants were placed in a lightless room, indicating that an internal clock -- not light -- was the key. Most Detroiters' master clocks tick to the natural sunrise-sunset rhythms of the day, causing people to be active by day and sleepy at night. But a few are saddled with internal watches geared to some other time zone. They are the party poopers who conk out early, then rise, fresh and raring to go, when night fiends are just hitting the sack. "Most people are not extremes. Our biological clocks follow nicely the clock on the wall," says Smolensky. "But every once in a while you find someone who inherits a night clock."Jacquelin Carnegie is a classic night owl, giving up full-time employment for a part-time afternoon job and intentionally living in New York City because it has round-the-clock activities. "I am one of the few people who have made my life around circadian rhythm. I go to bed at 2 in the morning and I generally wake up around 10," says Carnegie, a magazine writer who works from 2 to 6 p.m. "I had no choice. The rhythm was too hard to fight." Carnegie says she attempted fitting into a traditional routine but "every single day I had full-time jobs in my entire life, I came in late. I never got anyplace before 10."They even threatened at one job to take my raise away. What could I do?" she adds. "You can't fight this thing." As a child, she hated going to bed and would lie awake for hours, sometimes sliding into the bathroom to read. When traveling to visit her mother, also a night owl, at a weekend home outside the city, she takes the train that arrives around midnight, never an early morning train. The best time she had with an early morning friend occurred when the friend lived on the West Coast. "I could call her at 11 p.m. and it would be 8 o'clock in California; she goes to bed at 9. She would call me at 7 a.m. in California and it would be 10 in the morning, which is when I was waking up."It is estimated 10 percent of the population is made up of night owls and another 10 percent of pre-dawn risers. Gonzo journalist Hunter S Thompson (He doesn't use a period after "S") hauls out of bed at midafternoon (with a Chivas Regal) and hits the sack at 8 a.m. Another night owl, Thomas Edison, hoped his invention of the electric light would help accommodate his schedule.Cynthia Eggleton, president of custom publishing firm Cerb Associates, could have socialized with either: she rises early and often goes to bed in the wee hours of the morning, making her one of the few people who can run on little sleep."I'm one of those people who live on four hours of sleep and I've always been that way," said Eggleton, of Ferndale. She rises before dawn and, although she sometimes goes to bed about 11 p.m or midnight, rarely sleeps more than an hour before she's up again, putting in a few more hours before she turns in for her three-hour night. "It's a joke amongst people who know me," Eggleton says. "I have clients who are very nocturnal, who work at 1 or 2 in the morning. They'll fax me and then we'll follow up immediately with phone conversations." She has another group of clients, early risers, who begin their daily phone calls to her at about 6 a.m.Although studies show that 90 percent of Americans sleep from six to nine hours each night, Eggleton isn't unique. Napoleon reportedly slept only four hours a night. Although scientists aren't yet sure what purpose sleep serves, they are certain that humans need it. A desire to sleep is linked to the rhythmic release of some hormones. Some adjustments in the biological clock can be engineered using bright lights and rigid activity and rest schedules, but most people are slaves to the evolutionary clocks passed down by their ancestors who hunted by day and slept by night.Scientists say a human schedule is just more than 24 hours long, but environmental cues like sunlight and work schedules bring it into harmony with the earth's cadence. That daily, or circadian, rhythm explains why most heart attacks occur around 9 a.m., why women tend to go into labor and deliver babies between midnight and 6 a.m. and why blood clots best earlier in the day.There are other biological beats. It takes about a week for blood pressure and heart rates to return to normal after an upheaval, a week-based fluctuation appears in the sodium levels in urine and colds generally last a week. The heart attack rate on Mondays is 40 percent higher than on other days and the risk of organ rejection after a kidney transplant is highest seven days after surgery.Monthly rhythms, most notably menstrual cycles, join circannual, or yearly, patterns in the body's complicated system of clocks. The World Health Organization found that Northern Hemisphere births are most likely to occur the last week in July. Death from cardiovascular and respiratory diseases is highest in winter, even in warm weather states like Hawaii. And annual clock cycles are key to Big Eye, Arctic hysteria and Seasonal Affective Disorder.Big Eye is the Arctic monicker for insomnia during midwinter where it is dark nearly 24 hours a day. Arctic hysteria is another mood disorder linked to a lack of sunlight, which confuses humans' internal clocks. In Arctic climes, December and January see the highest number of suicides among non-native folks.Some Michiganians suffer from SAD, characterized by depression, tiredness and weight gain when the days grow shorter in the fall and winter. Scientists link the disorder to abnormal rhythms in the body's release of the hormone melatonin, normally secreted at night. Despite unproven claims that synthetic melatonin supplements lower blood pressure, boost one's sex life and increase longevity, SAD-afflicted folks awash in the hormone feel only sleepy and lethargic. Exposing SAD sufferers to bright fluorescent light, imitating springtime sun, can reduce symptoms, prompting chronobiology fans to predict bright light will be the wonder drug of the future, a cure-all for everything from infertility to low work productivity. Researchers are already using bright light to treat jet lag, which besets travelers who blast across several time zones in a short time, throwing their biological clocks out of whack."I had no sickness but I was in a slight daze and only wanted to sleep," explains Northern Ireland resident Maureen Miskelly, describing her arrival in Detroit earlier this month after an eight-hour flight from London. "I was sleepy for a few days and I was rising about 4 a.m., which would have been 9 a.m. for me, my usual time." Detroiter Amy Rose fights jet lag on her every-other-year vacation trips to New Zealand."Not only is that seven hours different, but it's a whole day before and you're in another hemisphere and another season," Rose explains. "I always have difficulty adjusting to the new sleep schedule and I wake up at odd hours of the night." The symptoms experienced by Rose and Miskelly are mild. Severe jet lag includes hazy vision, headaches and flulike symptoms. Illness appears tightly linked to times when a mini-clock or two jumps out of synchronization."The rhythms still exist, but they're ongoing incorrectly," says Smolensky, explaining that familiarity with body tempos can help in the diagnosis of ailments and their treatment. "The risk of disease worsening from one part of the day to another is a very real possibility."In people who have asthma, very often their symptoms are suffered most strongly at nighttime. We know that people with arthritis wake up in the morning complaining of more marked symptoms and they get better in the daytime even if they don't take medicine," he notes. "People with hay fever get most sneezing bouts when they first awaken. In the evening hours, peptic ulcer problems show up."Physicians have begun coordinating medication times and doses with those rhythms. The American Medical Association has a free pamphlet, Taking your medication, a question of timing. (To order it, call toll-free, 888-MY-CLOCK.) A website (www.chrono therapy.com) slated to come online at the end of the month also addresses so-called chronotherapy. Is there anyone who doesn't have an internal clock? "Infants," Smolensky says. "Babies go at their own pace, every four to six hours, wetting their diapers, wanting to eat --until their biological systems mature."


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