Links for Keyword: Biological Rhythms

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By Susan Milius The first big study of daily rhythms in fruit flies outdoors doesn’t match some of the basic results from decades of lab tests. Fruit flies flittering in lab containers have revealed much about how light can set the master molecular clock that ticks out a daily beat in living organisms. Yet watching daily rhythms in fruit flies caged outdoors reveals regular surges in activity not seen in the lab, says geneticist Rodolfo Costa of the University of Padova in Italy. And certain patterns of activity seen in the lab don’t show up in the real world, he and his colleagues report online April 4 in Nature. A major difference, he says, is that the typical increase in fruit fly motion as day dawns doesn’t seem to need a built-in clock in the real world. Flies with genetic mutations that disable their biological clocks don’t join in the usual laboratory bustle of activity before lights-on. Yet outdoors they perk up and get moving just like clock-normal flies. “This was something really unexpected,” Costa says. “We are not saying that everything that has been done until now is useless,” he adds. But some of the assumptions based on laboratory experiments, he says, should be expanded to account for behavior in nature. “The new study very nicely illustrates the risks of extrapolating from laboratory studies to natural conditions,” says neuroscientist and chronobiologist F. Rob Jackson of Tufts University School of Medicine in Boston. © Society for Science & the Public 2000 - 2012

Related chapters from BP7e: Chapter 14: Biological Rhythms, Sleep, and Dreaming; Chapter 6: Evolution of the Brain and Behavior
Related chapters from MM:Chapter 10: Biological Rhythms and Sleep
Link ID: 16615 - Posted: 04.05.2012

By James Gallagher Health and science reporter, BBC News How the time of day can increase the risk of dying from an irregular heartbeat has been identified by researchers. The risk of "sudden cardiac death" peaks in the morning and rises again in the evening. A study published in the journal Nature suggests that levels of a protein which controls the heart's rhythm fluctuates through the day. A body clock expert said the study was "beautiful". The inner workings of the body go through a daily routine known as a circadian rhythm, which keeps the body in sync with its surroundings. Jet lag is the result of the body getting out of sync. As the chemistry of the body changes throughout the day, this can impact on health. US researchers say they have identified, in mice, how the time can affect the risk of sudden cardiac death, which kills 100,000 people a year in the UK. 'Insights' They identified a protein called kruppel-like factor 15 (Klf15), which was controlled by the body clock and whose levels in the body went up and down during the day. The protein influences ion channels which control heart beat. BBC © 2012

Related chapters from BP7e: Chapter 14: Biological Rhythms, Sleep, and Dreaming
Related chapters from MM:Chapter 10: Biological Rhythms and Sleep
Link ID: 16414 - Posted: 02.23.2012

By James Gallagher Health and science reporter, BBC News The time of the day could be an important factor in the risk of getting an infection, according to researchers in the US. They showed how a protein in the immune system was affected by changes in the chemistry of the body through the day. The findings, published in the journal Immunity, showed the time of an infection changed its severity. An expert said drugs were likely to take advantage of the body clock in the near future. Plants, animals and even bacteria go through a daily 24-hour routine, known as a circadian rhythm. Jet lag is what happens when the body gets out of sync with its surroundings after crossing time zones. It has been known that there are variations in the immune system throughout the day. Researchers are now drilling down into the details. The immune system needs to detect an infection before it can begin to fight it off. Researchers at Yale University School of Medicine were investigating one of the proteins involved in the detection process - Toll-like receptor nine (TLR9), which can spot DNA from bacteria and viruses. BBC © 2012

Related chapters from BP7e: Chapter 14: Biological Rhythms, Sleep, and Dreaming; Chapter 15: Emotions, Aggression, and Stress
Related chapters from MM:Chapter 10: Biological Rhythms and Sleep; Chapter 11: Emotions, Aggression, and Stress
Link ID: 16390 - Posted: 02.18.2012

By Eric Niiler A new light bulb in the works could avoid tinkering with your body's sleep patterns. As late-night workers and long-distance travelers already know, shifting time zones or work periods throws the body's natural clock out of whack. Even regular folks often find it nearly impossible to get a restful sleep for several hours after sitting under bright lights after the sun has gone down (some call it the Fenway Park phenomena). Now a Florida inventor is testing a new LED bio-bulb that could regulate the body's circadian rhythm by helping control the production of melatonin, the body's sleep hormone that tells us when it's nighttime. This can be done by eliminating a small segment of the blue wavelength of light (around 465 to 485 nanometers) produced by the lightbulb, according to Fred Maxik, founder and chief technology officer of Lighting Science Group Corp., a Satellite Beach, Fla., firm. "We're looking at a way to filter out that part of the spectrum, and still have a white light," Maxik said. "Our ability to restore the natural position of where we were and natural hormonal secretions is an appealing one." Nearly 20 years ago, medical researchers discovered that the eye has a separate photoreceptor that picks up wavelengths of light, and then sends a signal to the hypothalamus which secretes melatonin. © 2011 Discovery Communications, LLC.

Related chapters from BP7e: Chapter 14: Biological Rhythms, Sleep, and Dreaming
Related chapters from MM:Chapter 10: Biological Rhythms and Sleep
Link ID: 16174 - Posted: 12.20.2011

by Chelsea Whyte Name an animal that is most active during the full moon, and even those of us untouched by the charms of the Twilight movies might think werewolf. Our subject today is no mythical beast, however. The Barau's petrel is one of a handful of tropical birds that uses the moon as a kind of alarm clock. During breeding season, the bird travels to mating sites on the aptly named Reunion Island off the shore of Madagascar to meet its mate. The monogamous birds synchronise their journeys using the full moon as a kind of Bat-Signal to indicate that it's time to mate. "First arrival at the colony is crucial in the mating system of colonial animals like seabirds," writes Patrick Pinet of the University of Réunion, France. It's not uncommon for birds to take cues from the intensity of sunlight or the length of the day to determine the seasons for migration and mating. Circadian clocks are influenced by melatonin secretions, which reflect the amount and intensity of daylight. But the Barau's petrel migrates longitudinally – that is, parallel to the equator – so there isn't much difference between the hours of sunrise and sunset in winter and summer. Still, the slight changes in daylight do affect the petrels. Daily and seasonal changes in melatonin secretion indicate time of day and the time of the year for these birds. But to migrate at the right time to ensure they meet their partners, they need something that varies more reliably. © Copyright Reed Business Information Ltd.

Related chapters from BP7e: Chapter 14: Biological Rhythms, Sleep, and Dreaming; Chapter 12: Sex: Evolutionary, Hormonal, and Neural Bases
Related chapters from MM:Chapter 10: Biological Rhythms and Sleep; Chapter 8: Hormones and Sex
Link ID: 16075 - Posted: 11.26.2011

By TARA PARKER-POPE Like most creatures on earth, humans come equipped with a circadian clock, a roughly 24-hour internal timer that keeps our sleep patterns in sync with our planet. At least until genetics, age and our personal habits get in the way. Even though the average adult needs eight hours of sleep per night, there are “shortsleepers,” who need far less, and morning people, who, research shows, often come from families of other morning people. Then there’s the rest of us, who rely on alarm clocks. For those who fantasize about greeting the dawn, there is hope. Sleep experts say that with a little discipline (well, actually, a lot of discipline), most people can reset their circadian clocks. But it’s not as simple as forcing yourself to go to bed earlier (you can’t make a wide-awake brain sleep). It requires inducing a sort of jet lag without leaving your time zone. And sticking it out until your body clock resets itself. And then not resetting it again. To start, move up your wake-up time by 20 minutes a day. If you regularly rise at 8 a.m., but really want to get moving at 6 a.m., set the alarm for 7:40 on Monday. The next day, set it for 7:20 and so on. Then, after you wake up, don’t linger in bed. Hit yourself with light. In theory, you’ll gradually get sleepy about 20 minutes earlier each night, and you can facilitate the transition by avoiding extra light exposure from computers or televisions as you near bedtime. (The light from a computer screen or an iPad has roughly the same effect as the sun.) “Light has a very privileged relationship with our brain,” says Dr. Jeffrey M. Ellenbogen, chief of sleep medicine at Massachusetts General Hospital and assistant professor of neurology at Harvard Medical School. While most sensory information is “processed” by the thalamus before being sent on its way, Ellenbogen says, light goes directly to the circadian system. © 2011 The New York Times Company

Related chapters from BP7e: Chapter 14: Biological Rhythms, Sleep, and Dreaming
Related chapters from MM:Chapter 10: Biological Rhythms and Sleep
Link ID: 16062 - Posted: 11.21.2011

By Tina Hesman Saey Broken biological clocks in blood vessels may contribute to hardened arteries, even if the main timer in the brain works fine. The finding, from transplant experiments with mice, suggests that throwing off the daily rhythms of the body’s organs can have serious health consequences. A wealth of evidence shows that skimping on sleep and working against the body’s natural daily, or circadian, rhythms can raise the risk of developing illnesses such as heart disease and diabetes. Scientists assumed that the diseases resulted from malfunctions in a master clock in the brain, which synchronizes sleeping, waking and other body functions with the rising and setting of the sun. But recently, scientists have discovered that the liver and other organs have their own internal clocks that may work independently of the brain clock and are set by meal times or other cues (SN: 4/10/10, p. 22). It wasn’t clear until now whether disrupting these body clocks could also contribute to disease, says Satchidananda Panda, a circadian rhythm researcher at the Salk Institute for Biological Studies in La Jolla, Calif. The finding may help explain why shift workers, people with sleep disorders and others who disrupt their circadian rhythms by staying up late or eating meals at the wrong time tend to be more vulnerable to heart disease.“If you want to prevent people from getting heart attacks, you have to know whether to treat the clock in the brain or the clock in the heart,” Panda says. © Society for Science & the Public 2000 - 2011

Related chapters from BP7e: Chapter 14: Biological Rhythms, Sleep, and Dreaming
Related chapters from MM:Chapter 10: Biological Rhythms and Sleep
Link ID: 15883 - Posted: 10.06.2011

By Bora Zivkovic So, why do I say that it is not surprising the exposure to bright light alleviates both seasonal depression and other kinds of depression, and that different mechanisms may be involved? In mammals, apart from visual photoreception (that is, image formation), there is also non-visual photoreception. The receptors of the former are the rods and cones that you all learned about in middle school. The receptors for the latter are a couple of thousand Retinal Ganglion Cells (RGCs) located in the retina in each eye. Each of these cells expresses a photopigment melanopsin (the cryptochrome challenger apparently lost the contest about a year ago after several years of frantic research by proponents of both hypotheses). The axons – nerve processes – from these cells go to and make connections in three parts of the brain. One is the brain center that controls pupillary reflex – when the light is bright the pupils constrict, while in the dark the pupils dilate. The second is the brain center involved in the control of mood. There is still a lot to work out about this center, but that is probably the place where exposure to light helps alleviate regular, i.e., non-seasonal depression. The third place where these RGCs project is the suprachiasmatic nucleus (SCN) – the main circadian pacemaker in the mammalian circadian system. The first light of dawn perceived by the eyes tells the SCN that it is day. Likewise, at dusk, the gradual decrease in light intensity perceived by these RGCs signals to the SCN that night is about to start. © 2011 Scientific American,

Related chapters from BP7e: Chapter 14: Biological Rhythms, Sleep, and Dreaming; Chapter 16: Psychopathology: Biological Basis of Behavior Disorders
Related chapters from MM:Chapter 10: Biological Rhythms and Sleep; Chapter 12: Psychopathology: Biological Basis of Behavioral Disorders
Link ID: 15843 - Posted: 09.27.2011

by Michael Marshall People will do almost anything if they think it will help them cheat death. The futurist Ray Kurzweil has utterly transformed his lifestyle in a bid to live until 2050, by when he thinks technology will allow his consciousness to be uploaded into a computer, making him immortal. His anti-ageing regimen is based on established research that has identified ways to slow the process. Cutting your intake of calories and getting plenty of exercise both seem to help. One of Kurzweil's ploys is to get lots of sleep too. In this, he is unwittingly emulating the Djungarian hamster. These rodents use short hibernatory naps to reverse the ageing process. Djungarian hamsters suffer from a Chaucerian degree of uncertainty over how to spell their name. Because the word has been transliterated from Mongolian, they can be called "Djungarian", "Dzungarian" or "Dzhungarian", not to mention "Siberian" and "Russian winter white dwarf". Popular as pets, they're only distantly related to the golden hamsters most commonly kept. Each Djungarian hamster lives alone in an underground burrow. When conditions are good it seeks out seeds and insects, which it brings back to the nest in its cheek pouches. It only meets other hamsters to mate. © Copyright Reed Business Information Ltd.

Related chapters from BP7e: Chapter 14: Biological Rhythms, Sleep, and Dreaming
Related chapters from MM:Chapter 10: Biological Rhythms and Sleep
Link ID: 15810 - Posted: 09.17.2011

By Tina Hesman Saey A fish that swims in limestone caverns under the Somalian desert has something to tell scientists about keeping time. Despite living in permanent darkness, with no difference between day and night, this blind cave-dweller still has its own quirky sense of rhythm. The Somalian cave fish, Phreatichthys andruzzii, has an inner timekeeper that ticks out a roughly 47-hour cycle set by food rather than sunlight, scientists from Italy, Germany and Spain report online September 6 in PLoS Biology. This odd biological clock may teach scientists more about the molecular pathways that govern such clocks, why clocks are important to organisms and how living things adapt when their clocks are no longer tied to cycles set by the rising and setting of the sun. Most animals, plants and some kinds of bacteria follow the sun’s cue in setting their own daily clocks. These biological, or circadian, clocks help govern sleeping, waking and feeding times, the rise and fall of blood pressure and other daily rhythms. Generally, circadian clocks follow an approximately 24-hour cycle and are reset largely by sunlight. When people’s circadian clocks aren’t set correctly, jet lag and even long-term health problems can result. Researchers study fish and other organisms to learn how circadian clocks’ gears mesh. Somalian cave fish have been cut off from the sun for up to 2.6 million years. Adapting to life in the dark has not only caused the fish’s eyes (as well as its scales and skin coloring) to disappear, but also altered its clock, say study authors Nicholas S. Foulkes of the Karlsruhe Institute of Technology in Germany, Cristiano Bertolucci of the University of Ferrara in Italy and their colleagues. © Society for Science & the Public 2000 - 2011

Related chapters from BP7e: Chapter 14: Biological Rhythms, Sleep, and Dreaming
Related chapters from MM:Chapter 10: Biological Rhythms and Sleep
Link ID: 15781 - Posted: 09.08.2011

By Nadia Drake Beware the full moon, for as it fades, hungry lions emerge to reclaim the night — and prowl for human flesh. Scientists studying lion attack trends in Tanzania found that predation peaks in the evenings after a full moon. The finding is the first to link lunar cycles with predation on humans, long a source of superstition and lore. The study, led by Craig Packer of the University of Minnesota Twin Cities campus, looked at the relationship between lunar cycles, lion attacks and lion feeding behavior. Researchers used records of more than 1,000 lion attacks on Tanzanian villagers that occurred between 1988 and 2009. Of these, nearly two-thirds were fatal, and most occurred after dark. Researchers were able to pinpoint a precise time of day for 474 attacks, and found that attacks clustered between 6 p.m. and 9:45 p.m. They also found that attack rates were two to four times higher in the 10 days after a full moon. But periods of waxing lunar light were not similarly bloody. That's because lions hunt best in darkness, the researchers report, and are hungry after nights of blazing, brilliant moonlight. Measuring lions' belly sizes — and relative fullness — reveals a dip in food consumption during the full moon. So, as the lunar cycle wanes and nights slip toward inky darkness, lions compensate for their full moon fast by attacking humans. © Society for Science & the Public 2000 - 2011

Related chapters from BP7e: Chapter 14: Biological Rhythms, Sleep, and Dreaming
Related chapters from MM:Chapter 10: Biological Rhythms and Sleep
Link ID: 15585 - Posted: 07.21.2011

By LAURA BEIL Just as the ear has two purposes — hearing and telling you which way is up — so does the eye. It receives the input necessary for vision, but the retina also houses a network of sensors that detect the rise and fall of daylight. With light, the body sets its internal clock to a 24-hour cycle regulating an estimated 10 percent of our genes. The workhorse of this system is the light-sensitive hormone melatonin, which is produced by the body every evening and during the night. Melatonin promotes sleep and alerts a variety of biological processes to the approximate hour of the day. Light hitting the retina suppresses the production of melatonin — and there lies the rub. In this modern world, our eyes are flooded with light well after dusk, contrary to our evolutionary programming. Scientists are just beginning to understand the potential health consequences. The disruption of circadian cycles may not just be shortchanging our sleep, they have found, but also contributing to a host of diseases. “Light works as if it’s a drug, except it’s not a drug at all,” said George Brainard, a neurologist at Thomas Jefferson University in Philadelphia and one of the first researchers to study light’s effects on the body’s hormones and circadian rhythms. Any sort of light can suppress melatonin, but recent experiments have raised novel questions about one type in particular: the blue wavelengths produced by many kinds of energy-efficient light bulbs and electronic gadgets. © 2011 The New York Times Company

Related chapters from BP7e: Chapter 14: Biological Rhythms, Sleep, and Dreaming; Chapter 10: Vision: From Eye to Brain
Related chapters from MM:Chapter 10: Biological Rhythms and Sleep; Chapter 7: Vision: From Eye to Brain
Link ID: 15527 - Posted: 07.05.2011

By RANDOLPH E. SCHMID WASHINGTON — Reports of sleeping air traffic controllers highlight a long-known and often ignored hazard: Workers on night shifts can have trouble concentrating and even staying awake. "Government officials haven't recognized that people routinely fall asleep at night when they're doing shift work," said Dr. Charles Czeisler, chief of sleep medicine at Brigham and Women's Hospital in Boston. Czeisler said studies show that 30 percent to 50 percent of night-shift workers report falling asleep at least once a week while on the job. So the notion that this has happened only a few times among the thousands of controllers "is preposterous," he said in a telephone interview. In a sign of growing awareness of the problem, the Federal Aviation Administration said Saturday it was changing air traffic controllers' work schedules most likely to cause fatigue. The announcement comes after the agency disclosed another incident in which a controller fell asleep while on duty early Saturday morning at a busy Miami regional facility. According to a preliminary review, there was no impact to flight operations, the FAA said. Czeisler said the potential danger isn't limited to air traffic controllers, but can apply to truck and bus drivers, airline pilots and those in the maritime industry. Who else? Factory workers, police, firefighters, emergency workers, nurses and doctors, cooks, hotel employees, people in the media and others on night or changing shifts. Copyright 2011 The Associated Press.

Related chapters from BP7e: Chapter 14: Biological Rhythms, Sleep, and Dreaming; Chapter 15: Emotions, Aggression, and Stress
Related chapters from MM:Chapter 10: Biological Rhythms and Sleep; Chapter 11: Emotions, Aggression, and Stress
Link ID: 15231 - Posted: 04.18.2011

Having the lights on before bedtime could result in a worse night's sleep, according to a study to be published in the Journal of Endocrinology and Metabolism. The research shows that the body produces less of the sleep hormone melatonin when exposed to light. Sleep patterns have been linked to some types of cancer, blood pressure and diabetes. The US researchers also found lower melatonin levels in shift workers. Lifestyles may have moved on from a day/night rhythm, but it seems the human body has not. The pineal gland produces melatonin through the night and starts when darkness falls. Researchers have shown that switching on lights in the home switches off the hormone's production. In the study, 116 people spent five days in room where the amount of light and sleep was controlled. They were awake for 16 hours and asleep for eight hours each day. Initially the patients were exposed to 16 hours of room light during their waking hours. They were then moved onto eight hours of room light in the morning and eight hours of dim light in the evening. The researchers found that electrical light between dusk and bedtime strongly suppressed melatonin levels. With dim light, melatonin was produced for 90 minutes more a day. BBC © MMXI

Related chapters from BP7e: Chapter 14: Biological Rhythms, Sleep, and Dreaming; Chapter 5: Hormones and the Brain
Related chapters from MM:Chapter 10: Biological Rhythms and Sleep; Chapter 8: Hormones and Sex
Link ID: 14880 - Posted: 01.17.2011

By Susan Milius SALT LAKE CITY — As summer heats up, the sight of blooming thistles may give male goldfinches a testosterone kick. Thistle flowers could signal to American goldfinches that the seeds the songbirds prize for baby food and parent food will soon be abundant, proposes Thomas Luloff of the University of Western Ontario in London, Canada. And in lab setups, male goldfinches housed among blooming Canadian thistles underwent physiological changes that indicate the birds got the “breed now” message from the combination of summery heat and thrilling thistles, Luloff reported January 6 at the annual meeting of the Society for Integrative and Comparative Biology. What particularly impressed George Bentley of the University of California, Berkeley was that the birds “don’t eat the flower — they eat the seeds,” he says. Yet the precursor to food still appeared to have an effect. Biologists still have much to learn about what tips off birds that it’s time to breed, says Bentley, who was not part of the research project. Yet, he says, the need to understand those cues is growing as climate change threatens to knock signals out of sync. Many birds lose what they don’t use during the winter, letting hormone concentrations dwindle and reproductive organs shrink. When the breeding season returns, both males and females typically have to recharge and regrow. Much of the earlier work on breeding signals has focused on the broad role of day length or temperature, yet birds can react to other cues too. Species differ in what cues or mixes of cues rev up their breeding biology again. © Society for Science & the Public 2000 - 2011

Related chapters from BP7e: Chapter 14: Biological Rhythms, Sleep, and Dreaming; Chapter 12: Sex: Evolutionary, Hormonal, and Neural Bases
Related chapters from MM:Chapter 10: Biological Rhythms and Sleep; Chapter 8: Hormones and Sex
Link ID: 14862 - Posted: 01.13.2011

By RONI CARYN RABIN Antidepressants like Prozac and Paxil are widely used to treat depression, but a much less costly alternative called bright light therapy, in which a patient sits under an artificial light for a set period of time each day, is not. Light therapy is typically recommended for seasonal affective disorder, the “winter blues” brought on by shorter days and limited sun. Some psychiatrists prescribe it for this condition, often as a last resort when patients fail to respond to drugs. One reason light therapy hasn’t been used in more people with depression is that there aren’t many good clinical trials of the therapy in depressed patients without seasonal affective disorder. There isn’t much money to be made from the treatment — all it involves is a one-time purchase of a special lamp. The upside is that it has few, if any, side effects (though, doctors note, it should always be done in consultation with a physician). Now a new, carefully designed randomized controlled trial — of the kind considered the gold standard in medicine — suggests bright light therapy deserves a closer look. The study was small, involving only 89 patients ages 60 and older, but the results were remarkable. Compared with a placebo, light therapy improved mood just as well as conventional antidepressant medications, said Dr. Ritsaert Lieverse, the paper’s lead author and a psychiatrist at the VU University Medical Center in Amsterdam. © 2011 The New York Times Company

Related chapters from BP7e: Chapter 16: Psychopathology: Biological Basis of Behavior Disorders; Chapter 14: Biological Rhythms, Sleep, and Dreaming
Related chapters from MM:Chapter 12: Psychopathology: Biological Basis of Behavioral Disorders; Chapter 10: Biological Rhythms and Sleep
Link ID: 14848 - Posted: 01.10.2011

by Nathan Collins Add this to your list of worries, high schoolers: daylight savings time might mess with your college admissions. For decades, scientists have debated whether spring and fall time changes affect everything from seasonal affective disorder to traffic accidents. The idea is that resetting clocks by "springing forward" and "falling back" can upset sleep patterns and with them the ability to concentrate. Now, it appears that these time changes might just muck up performance on the SAT, the U.S. college admissions exam, which is administered five times a year, including two dates that fall after daylight savings transitions. Using data from Indiana, where until recently individual counties could opt in or out of daylight savings, researchers found that scores in counties that changed their clocks were consistently 16.34 points—or 2%—lower than in counties that did not, they report online this month in the Journal of Neuroscience, Psychology, and Economics. That may not sound like a lot, but it may be enough to keep you out of Harvard. So choose your test dates carefully, kids. Springing forward could land you in your fall-back school. © 2010 American Association for the Advancement of Science.

Related chapters from BP7e: Chapter 14: Biological Rhythms, Sleep, and Dreaming; Chapter 18: Attention and Higher Cognition
Related chapters from MM:Chapter 10: Biological Rhythms and Sleep; Chapter 14: Attention and Consciousness
Link ID: 14702 - Posted: 11.23.2010

By Nicholette Zeliadt Our sleep patterns, eating habits, body temperature and hormone levels are driven by the rhythmic activity of body's circadian clock. Travel across time zones or shift work can knock those rhythms out of whack, possibly leading to sleep problems, bipolar disorder, metabolic syndrome and even cancer. The lack of convenient and reliable methods to monitor the internal clock's activity has severely limited the study of circadian-related disease, but now, scientists report that they can easily track the circadian rhythms by analyzing a person's plucked hairs. The finding could one day help doctors diagnose and treat patients suffering from circadian dysfunction. The body's master clock, located in the brain region called the hypothalamus, is set by light, which activates clock genes that are responsible for keeping this timekeeper ticking correctly. Within the past decade, scientists have discovered that organs outside the brain (such as the skin, liver and pancreas) also keep track of time with 24-hour fluctuations in clock gene expression. Previous studies have attempted to monitor molecular timekeeping in blood cells or in cells lining the mouth, but these approaches are technically challenging. In an attempt to develop a simpler, noninvasive method to clock circadian rhythms, researchers led by Makoto Akashi of the Research Institute for Time Studies at Yamaguchi University in Japan obtained hairs plucked from volunteers' heads or chins and analyzed clock gene expression in hair follicle cells. They report online this week in the Proceedings of the National Academy of Sciences that the patterns of circadian gene expression in the hair follicle cells accurately reflected the subjects' behavioral rhythms, "demonstrating that this strategy is appropriate for evaluating the human peripheral circadian clock." © 2010 Scientific American

Related chapters from BP7e: Chapter 14: Biological Rhythms, Sleep, and Dreaming
Related chapters from MM:Chapter 10: Biological Rhythms and Sleep
Link ID: 14391 - Posted: 08.24.2010

By Katherine Harmon Having a mixed up body clock has been linked to a vast array of ailments, including obesity and bipolar disorder. And researchers are still trying to understand just how these cyclical signals influence aspects of our cellular and organ system activity. Now, a study published online August 3 in Cell Metabolism shows that in mice, a disrupted circadian rhythm spurs an increase in triglycerides—heightened levels of which have been linked to heart disease and metabolic syndrome in humans. To find this link, researchers compared normal lab mice to those bred to have dysfunctional sleep-wake cycles. As nocturnal animals, the control mice had the lowest levels of triglycerides at night, when they were most active, and higher levels during the daytime rest period. The mice with out-of-whack cycles kept confused hours, fed longer and were less active overall. These mutant mice also had far less fluctuation in their triglyceride levels. "We show that the normal up and down [of triglycerides] is lost in clock mutants," M. Mahmood Hussain, of the Department of Cell Biology and Pediatrics at the State University of New York Downstate Medical Center in Brooklyn and coauthor of the paper, said in a prepared statement. The mutant mice had "high triglycerides all the time," he noted. © 2010 Scientific American,

Related chapters from BP7e: Chapter 14: Biological Rhythms, Sleep, and Dreaming; Chapter 13: Homeostasis: Active Regulation of the Internal Environment
Related chapters from MM:Chapter 10: Biological Rhythms and Sleep; Chapter 9: Homeostasis: Active Regulation of the Internal Environment
Link ID: 14322 - Posted: 08.05.2010

by Sujata Gupta WHAT happens when you take blind mice and see how they run? It turns out they can identify objects using receptors in the eye that were previously thought to have no role in forming images. Since humans possess the same receptors, the finding could point the way to giving blind people some ability to see. Mice, and humans, have three types of light-detecting receptor in the eye. Rods and cones detect light, darkness, shape and colour, and make normal sight possible. Receptors of the third type, the melanopsin-containing ganglion cells (MCGCs), were until now thought only to respond to light over longer periods of time, to help moderate patterns of sleep and wakefulness. To investigate their role in vision, Samer Hattar of the Krieger School of Arts and Sciences at Johns Hopkins University in Baltimore, Maryland, and colleagues engineered mice to lack rods and cones. When these mice were placed in a maze, they were able to identify a lever with a visible pattern on it which allowed them to escape. Mice that lacked rods, cones and MCGCs could not find the lever. In another task, the team found that the MCGC mice could follow the movement of a rotating drum (Neuron, DOI: 10.1016/j.neuron.2010.05.023). This suggests MCGCs can form "low-acuity yet measurable images", Hatter says. Tom Cronin at the University of Maryland notes that the mice in the experiment behave like people with "blindsight", who can navigate round objects without consciously perceiving them. "It's mind-boggling but I suspect that the mice are doing something like that," he says. © Copyright Reed Business Information Ltd.

Related chapters from BP7e: Chapter 14: Biological Rhythms, Sleep, and Dreaming; Chapter 10: Vision: From Eye to Brain
Related chapters from MM:Chapter 10: Biological Rhythms and Sleep; Chapter 7: Vision: From Eye to Brain
Link ID: 14284 - Posted: 07.24.2010