Dear Doctor: Apparently, wounds that occur at night don't heal as well as those that occur in the daytime. Why would that be -- and what can people do if they're hurt at night?

Dear Reader: An intriguing study that looked at wounds and the rates at which they healed reinforces the idea that the circadian clock, the inner timekeeper in virtually every living thing, is even more complex than was realized. Considering the circadian clock in humans is already known to manage sleep-wake cycles, hormone production, brain wave activity, body temperature and mood, to name just a few of its functions, that's pretty impressive.

The circadian cycle is a period of approximately 24 hours. During that time, and keyed to the daily shift from light to dark and back again, the circadian clock influences rhythmic changes in both physiology and behavior. Disruption to these cycles, whether short- or long-term, is known to adversely affect health and well-being. Research has shown that the cycle of sleep and wakefulness in mammals is keyed to visible light. A specific region of the brain receives and interprets the visual input from the eyes and sends out the appropriate cues of whether to sleep or wake up.

But recent studies have surprised scientists by suggesting that certain parts of the body, including the liver and lungs, have circadian rhythms that are independent of patterns of dark and light, and of the brain center that interprets those patterns. All of which (finally!) leads us to your question. According to research published in the journal Science Translational Medicine, burns that were sustained during the day took about 17 days to heal. The same types of injuries that were sustained at night required an additional 11 days -- or 28 days total -- to heal.

The reason for this turns out to be the behavior of fibroblasts, which are among the first cells to rush to the rescue at the site of an injury. These take various forms, depending on their location within the body. But what fibroblasts have in common is the ability to generate a matrix of specialized proteins that help a wound to contract and heal. How quickly they get to work depends on whether it's day or night.

When researchers looked at cells grown in a petri dish, at wounds in mice and at data from the International Burn Injury Database, which includes the time that a patient was injured, they discovered that daytime wounds healed a startling 60 percent faster than the same types of wounds when sustained at night. Because fibroblasts obey their own circadian clocks, which are independent of a person's own master clock, it turns out that they work harder and more efficiently during the daytime hours.

At this time there's no known way to override the fibroblasts' circadian clock. When you become injured during the nighttime hours, the healing process will be slower. However, researchers are already looking into how these insights might be used to improve medical care -- surgical outcomes, for example -- and to explore the impact on other forms of treatment.

(Send your questions to askthedoctors@mednet.ucla.edu, or write: Ask the Doctors, c/o Media Relations, UCLA Health, 924 Westwood Blvd., Suite 350, Los Angeles, CA, 90095. Owing to the volume of mail, personal replies cannot be provided.)

Dear Doctor: Please inform your readers about polymyalgia rheumatica. I thought I was experiencing arthritis, until my doctor informed me otherwise.

Dear Reader: Polymyalgia rheumatica is a common disorder that generally occurs in adults over the age of 50, with peak incidence occurring between the ages of 70 to 80. PMR causes stiffness and aching in both shoulders and both sides of the neck; it also affects the hips and lower back. The symptoms are worse first thing in the morning, and ease over the course of the day.

The condition is two to three times more common in women than in men and is also more prevalent among people of northern European ancestry. In fact, among those over 50 in one Minnesota county, the prevalence of PMR is 1 in 140 people. The rate appears to be lower in parts of the country with greater African-, Asian- and Latin-American populations.

The causes of PMR are unknown. It's possible that an environmental factor leads to the production of inflammatory molecules. Note, however, that although the word polymyalgia implies muscle inflammation, no muscle damage has been linked to the condition. What does appear to happen is inflammation of the tendons, bursa and joints in the hips and shoulders.

This inflammation leads to severe stiffness and pain. The stiffness often occurs suddenly, causing significant movement problems. An affected person can have difficulty getting out of a chair or putting on socks or a shirt. Half the time, the symptoms occur beyond the hips and shoulders, such as the wrists, hands and the knees. Often, patients with PMR also experience fatigue, weight loss and low-grade fever.

PMR causes a decreased range of motion in the shoulders and hips and sometimes swelling at the wrist and hands. A doctor's diagnosis is solidified with blood tests that show elevations in the inflammatory markers, Erythrocyte sedimentation rate (ESR) and C-reactive protein (CRP). Moreover, people with PMR may have mild anemia, which may be a reason for the fatigue.

Treatment consists of medication to decrease the inflammation, often with a low dose of the steroid prednisone. In fact, a significant rapid improvement of symptoms with a 15- to 20-milligram dose of prednisone helps to differentiate PMR from other disorders.

Because long-term use of oral steroids like prednisone can increase the risk of osteoporosis, high blood pressure and elevations of blood sugar, the medication should be tapered off after a while. This must be done slowly, however, so that the symptoms of PMR don't return. In total, oral steroids need to be continued from six months to potentially more than two years. Other therapies that suppress the immune system could also be used, but they have not shown the same benefits.

On a last note, people with PMR are at increased risk of having giant cell arteritis, which causes headaches and a transient or irreversible loss of vision in one eye. If you have PMR and notice these symptoms, seek medical attention immediately.

(Send your questions to askthedoctors@mednet.ucla.edu, or write: Ask the Doctors, c/o Media Relations, UCLA Health, 924 Westwood Blvd., Suite 350, Los Angeles, CA, 90095. Owing to the volume of mail, personal replies cannot be provided.)

Dear Doctor: I know I need to eat more vegetables, but because I have dentures, I can't chew them well enough to swallow easily. I have particular problems with celery, lettuce, oranges and tomato skins. If I were to "masticate" them in a food processor, would I still get the benefits, or would the processor blade destroy too many cells?

Dear Reader: We see you're familiar with two indisputable facts when it comes to living with dentures: First, the way they function is different from our original teeth. Dentures rely on a seal to stay in place, so you have to be careful about the types of foods you eat. Texture (think nuts or steak or seeded breads) and the angle of attack (like an apple or corn on the cob) can wreak havoc on both the seal that keeps the dentures in place, and sometimes the dentures themselves. Second, these challenges don't have to be a barrier to the foods you want to eat. As your question illustrates, a bit of creative problem solving can add to the diversity of the foods in your diet.

While there's a certain logic to the idea that using a food processor to chop or mince or emulsify a food can adversely affect its nutritional content, the good news is that's not the case. What appliances like food processors and blenders do first and foremost is to alter a food's texture and, of course, its appearance. And let's agree that we're not talking about juicing here. That's the process in which the liquid content of a food is extracted and the resulting pulp, the food's fiber content, is left behind. That's an entirely different process with outcomes that merit a separate discussion. (Drop us a line if you're interested.)

Digestion begins the minute food enters the mouth. Teeth pulverize the bite into smaller pieces and particles and mix it with saliva, all of which jump-starts the process of dismantling the food on a chemical level. The lion's share of the work of breaking down the bonds between food molecules takes place after you swallow, carried out by powerful enzymes in the stomach, and trillions of friendly bacteria in the intestines. What you're proposing is to get a head start on the chewing process with the help of a food processor. Depending on the blade you use, you can slice, chop, pulverize or puree.

The act of slicing, chopping or pureeing food doesn't change its nutritional value. However, once a food is broken down, the nutritional clock does start ticking. That's because a wide range of nutrients found in vegetables and fruit are sensitive to air and light, as well as to heat. When you put an item through the food processor, it's a good idea to eat it the same day. Wrap any leftovers tightly and refrigerate.

In general, remember to chew on both sides of your mouth when you're living with dentures. Dental adhesives can help when a saliva seal proves inadequate. As you've shown, with preparation and imagination, dentures needn't be an impediment to a balanced and interesting diet.

(Send your questions to askthedoctors@mednet.ucla.edu, or write: Ask the Doctors, c/o Media Relations, UCLA Health, 924 Westwood Blvd., Suite 350, Los Angeles, CA, 90095. Owing to the volume of mail, personal replies cannot be provided.)