US researchers have found a link between working night shifts and the risk of ovarian cancer. A study of more than 3,000 women suggested that working overnight increased the risk of early-stage cancer by 49% compared with doing normal office hours. One possible explanation was disruption of the sleep hormone melatonin, the researchers said. But experts warned more work was needed and there might be other explanations. It does however follow an earlier association made between shift work and breast cancer. The International Agency for Cancer Research has previously identified working shift patterns that disrupt the body's natural "clock" as a probable cause of cancer. In the latest investigation, researchers looked at 1,101 women with advanced ovarian cancer, 389 with borderline or early disease and 1,832 women without the condition. Overall, a quarter with advanced cancer said they had worked night shifts, compared with a third of those with borderline disease and one in five of the control group. Analysis of the data showed a 24% increased risk of advanced cancer and 49% increased risk of early-stage disease for night workers compared with those who worked during the day. But the results were only significant for women over the age of 50, the researchers reported in Occupational and Environmental Medicine. And the risk did not seem to increase for those who had worked night shifts for the longest. BBC © 2013

Related chapters from BN: 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: 17913 - Posted: 03.18.2013

By Tina Hesman Saey Like the sun, insulin levels rise and fall in a daily rhythm. Disrupting that cycle may contribute to obesity and diabetes, a new study suggests. Many body systems follow a daily clock known as a circadian rhythm. Body temperature, blood pressure and the release of many hormones are on circadian timers. But until now, no one had shown that insulin — a hormone that helps control how the body uses sugars for energy — also has a daily cycle. Working with mice, researchers at Vanderbilt University in Nashville have found that rodents are more sensitive to insulin’s effects at certain times of day. Disrupting the animals’ circadian timers interferes with the hormone’s daily rise and fall and makes mice prone to obesity. If the findings hold up in humans, they could help explain why people who work night shifts tend to be overweight and suffer health problems. The discovery may also tie the obesity epidemic in part to staying up late and eating at the wrong time. Many people had thought that it was best for the body to maintain insulin at a relatively constant level, says Carl Johnson, a circadian biologist who led the new study. “But that’s not how organisms have adapted,” he says. Since the environment cycles through light and dark, body processes often coordinate with that rhythm. To uncover insulin’s natural rhythm, Johnson and his colleagues performed an “insulin clamp” procedure on mice. The clamp infuses glucose or insulin around the clock into mice that are moving freely in their cages. Measuring how much insulin or glucose the mice need to maintain constant blood sugar levels tells the researchers how responsive the animals are to the hormone at any given time of day. © Society for Science & the Public 2000 - 2013

Related chapters from BN: Chapter 13: Homeostasis: Active Regulation of the Internal Environment; Chapter 14: Biological Rhythms, Sleep, and Dreaming
Related chapters from MM:Chapter 9: Homeostasis: Active Regulation of the Internal Environment; Chapter 10: Biological Rhythms and Sleep
Link ID: 17831 - Posted: 02.23.2013

By Laura Hambleton, Winter often brings the flu, coughs, ski injuries and shoveling strains. Add to these ailments a more deadly one: heart attacks. A recent study has found that more fatal heart attacks and strokes occur during the winter than at other times of the year. And it doesn’t seem to matter if the winter is occurring in the warmer climes of Southern California or the frostier ones of Boston. After sifting through about 1.7 million death certificates filed between 2005 and 2008, cardiologists Bryan Schwartz of the University of New Mexico and Robert A. Kloner of the Heart Institute at the Good Samaritan Hospital in Los Angeles found a 26 to 36 percent greater death rate for heart attacks in winter than summer “despite different locations and climates,” Kloner says. The worst months are December, January, February and the beginning of March. The doctors analyzed the cause of death for people in Texas, Arizona, Georgia, Los Angeles, Washington state, Pennsylvania and Massachusetts. Of those who died of heart disease, the winter weather pattern was clear. In Los Angeles, for example, there were about 70 deaths per day from cardiac disease, Schwartz said. “In the summer, L.A. had an average circulatory death rate of about . . . 55 deaths per day.” The research uncovered patterns in cardiac deaths from “seven different climate patterns,” according to the study, and “death rates at all sites clustered closely together and no one site was statistically different from any other site.” An abstract of the study was published in the American Heart Association journal Circulation. © 1996-2013 The Washington Post

Related chapters from BN: Chapter 14: Biological Rhythms, Sleep, and Dreaming; Chapter 19: Language and Lateralization
Related chapters from MM:Chapter 10: Biological Rhythms and Sleep; Chapter 15: Language and Lateralization
Link ID: 17763 - Posted: 02.05.2013

By Stephani Sutherland If you have trouble sleeping, laptop or tablet use at bedtime might be to blame, new research suggests. Mariana Figueiro of the Lighting Research Center at Rensselaer Polytechnic Institute and her team showed that two hours of iPad use at maximum brightness was enough to suppress people's normal nighttime release of melatonin, a key hormone in the body's clock, or circadian system. Melatonin tells your body that it is night, helping to make you sleepy. If you delay that signal, Figueiro says, you could delay sleep. Other research indicates that “if you do that chronically, for many years, it can lead to disruption of the circadian system,” sometimes with serious health consequences, she explains. The dose of light is important, Figueiro says; the brightness and exposure time, as well as the wavelength, determine whether it affects melatonin. Light in the blue-and-white range emitted by today's tablets can do the trick—as can laptops and desktop computers, which emit even more of the disrupting light but are usually positioned farther from the eyes, which ameliorates the light's effects. The team designed light-detector goggles and had subjects wear them during late-evening tablet use. The light dose measurements from the goggles correlated with hampered melatonin production. On the bright side, a morning shot of screen time could be used as light therapy for seasonal affective disorder and other light-based problems. Figueiro hopes manufacturers will “get creative” with tomorrow's tablets, making them more “circadian friendly,” perhaps even switching to white text on a black screen at night to minimize the light dose. Until then, do your sleep schedule a favor and turn down the brightness of your glowing screens before bed—or switch back to good old-fashioned books. © 2013 Scientific American

Related chapters from BN: Chapter 14: Biological Rhythms, Sleep, and Dreaming
Related chapters from MM:Chapter 10: Biological Rhythms and Sleep
Link ID: 17743 - Posted: 02.02.2013

By Susan Milius Male European blackbirds monitored in a lab under simulated city lighting started secreting increased levels of testosterone and growing their sexual organs up to a month earlier in the spring than birds kept in country-style darkness, Davide Dominoni of the Max Planck Institute for Ornithology in Radolfzell, Germany, reported January 6 at the annual meeting of the Society for Integrative and Comparative Biology. Dominoni’s colleagues have found that, outside the lab, male blackbirds flying around Munich undergo this growth surge about three weeks earlier than counterparts in a forest just 40 kilometers out of town. Beginning in December 2010, the researchers exposed captive blackbirds to night light levels typical of urban settings. They estimated those levels by outfitting free-flying blackbirds with light-sensitive devices and averaging the urban light exposure. A winter of lab night light sped up the males’ molting and boosted testosterone levels as well as organ development in spring. Continuing the night light treatment through the next winter left the males reproductively shut down in the spring of 2012. The lab night lights probably kept the birds’ seasonal reproductive clocks from resetting at the end of the first breeding season, Dominoni says. That second-year suppression may not be common in the real world, where birds fly around and experience more variety in night lighting, he says. But he sees the lab breeding shutdown as a sign of how big of an impact artificial light might have. © Society for Science & the Public 2000 - 2013

Related chapters from BN: 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: 17664 - Posted: 01.10.2013

The long-held view that a full moon or even a new moon triggers psychological problems has been debunked by a study from Montreal. Researchers at the University of Laval's School of Psychology evaluated patients visiting Montreal's Sacré-Coeur Hospital and Hôtel-Dieu de Lévis between March 2005 and April 2008 and found no correlation between anxiety disorders and the phases of the moon — despite, it seems, what 80 per cent of nurses and 64 per cent of doctors surveyed believe. These researchers analyzed 771 individuals who had shown up at the emergency room with chest pains for which no medical cause could be determined. Psychological evaluations indicated many were suffering anxiety, panic attacks, mood disorders or suicidal thoughts. The time of their visit was then correlated with the phase of the moon at that moment. "We observed no full-moon or new-moon effect on psychological problems," said lead researcher Genevieve Belleville whose study is published in General Hospital Psychiatry. The study went on to suggest that health professionals may think there are more mental problems during a full-moon phase due to "self-fulfilling prophecies." © CBC 2012

Related chapters from BN: 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: The Biology of Behavioral Disorders
Link ID: 17541 - Posted: 11.27.2012

By Laura Sanders Devoid of any external time cues, monkeys can still tell time. Animals learned to move their eyeballs once every second, a completely internal timing feat made possible by the rhythmic behavior of small groups of nerve cells, researchers propose online October 30 in PLOS Biology. Time is often measured with clues from the environment, says study coauthor Geoffrey Ghose of the University of Minnesota in Minneapolis. A quick glance at a clock indicates that your meeting will start soon, and a look outside at a low sun tells you that it’s time to leave work. But some time-telling abilities rely on purely internal processes — just a feeling that minutes, hours or days have ticked by, Ghose says. Ghose and Blaine Schneider, also of the University of Minnesota, studied this internal sensation of time by creating a situation in which two monkeys had to generate their own pattern without any outside help. The animals were trained to switch their gaze rhythmically between a red dot and a blue dot on a computer screen once every second, a job that looks like “they’re watching an extremely boring tennis match,” Ghose says. After a while, the monkeys got good, on average just tens of milliseconds off their tempo. Meanwhile, the researchers used electrodes to eavesdrop on the behavior of neurons in a part of the brain called the lateral intraparietal area. Earlier monkey studies found that neurons there build up activity with time, firing messages more and more frequently as the milliseconds tick by. © Society for Science & the Public 2000 - 2012

Related chapters from BN: 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 Higher Cognition
Link ID: 17442 - Posted: 11.03.2012

by Douglas Heaven Timing is everything. But exactly how the brain keeps time, which it does very well, has been something of a mystery. One widely held theory suggests that a single brain region acts as a centralised timekeeper – possibly in the basal ganglia or cerebellum. However, a study now suggests that timekeeping is decentralised, with different circuits having their own timing mechanisms for each specific activity. The finding could help explain why certain brain conditions affect our sense of timing, and even raise the possibility of artificially manipulating time perception. Geoffrey Ghose and Blaine Schneider, at the University of Minnesota in Minneapolis, investigated timing in the brain by training two rhesus macaques to perform tasks in which they moved their eyes between two dots on a screen at regular 1-second intervals. There were no external cues available to help them keep track of time. After three months, the monkeys had learned to move their eyes between the two dots with average intervals of 1.003 and 0.973 seconds, respectively. The researchers then used electrodes to record brain activity across 100 neurons in the lateral intraparietal cortex – associated with eye movement – while the monkeys performed the task. The activity of these neurons decreased during the interval between each eye movement, and the rate of decrease correlated with the monkeys' timing. Using this information, Ghose and Schneider were able to predict the interval between eye movements by measuring the preceding decay rate. © Copyright Reed Business Information Ltd.

Related chapters from BN: Chapter 14: Biological Rhythms, Sleep, and Dreaming
Related chapters from MM:Chapter 10: Biological Rhythms and Sleep
Link ID: 17438 - Posted: 10.31.2012

by Dennis Normile Are you a morning lark or a night owl? Scientists use that simplified categorization to explain that different people have different internal body clocks, commonly called circadian clocks. Sleep-wake cycles, digestive activities, and many other physiological processes are controlled by these clocks. In recent years, researchers have found that internal body clocks can also affect how patients react to drugs. For example, timing a course of chemotherapy to the internal body time of cancer patients can improve treatment efficacy and reduce side effects. But physicians have not been able to exploit these findings because determining internal body time is, well, time consuming. It's also cumbersome. The most established and reliable method requires taking blood samples from a patient hourly and tracking levels of the hormone melatonin, which previous research has tied closely to internal body time. Now a Japanese group has come up with an alternative method of determining internal body time by constructing what it calls a molecular timetable based on levels in blood samples of more than 50 metabolites—hormones and amino acids—that result from biological activity. The researchers established a molecular timetable based on samples from three subjects and validated it using the conventional melatonin measurement. They then used that timetable to determine the internal body times of other subjects by checking the levels of the metabolites in just two blood samples from each subject per day. © 2010 American Association for the Advancement of Science.

Related chapters from BN: Chapter 14: Biological Rhythms, Sleep, and Dreaming
Related chapters from MM:Chapter 10: Biological Rhythms and Sleep
Link ID: 17211 - Posted: 08.28.2012

By Alyssa A. Botelho, Melanie Brunson, who has been blind since birth, suddenly awoke and found herself standing at 15th and K streets in Northwest Washington. She had stopped at the corner on her way home from work to await a safe time to cross and had dozed off. Even on awakening, she was so groggy she couldn’t focus well enough to hear passing cars and judge when it was safe to cross. The incident was a startling reminder of the sleep problems that had plagued her since birth. “Who knows how long I had been standing there,” she said. “I realized then that my safety was in jeopardy, and I began searching for remedies with a vengeance.” But years after that 2005 traffic scare and many subsequent visits to doctors and sleep clinics, Brunson still lies awake in bed night after night and then is desperately sleepy during the day. Although doctors have not definitively identified her disorder, researchers believe she suffers from non-24-hour sleep-wake disorder, or “non-24.” The chronic and little-known sleep condition is characterized by a body clock that is not aligned with a 24-hour day. Though non-24 can affect those with normal vision, it is especially prevalent among blind people who cannot sense light, the strongest environmental signal that synchronizes the brain’s internal sleep-wake pattern to the 24-hour cycle of the Earth day. © 1996-2012 The Washington Post

Related chapters from BN: 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: 17132 - Posted: 08.07.2012

Shift workers are slightly more at risk of having a heart attack or stroke than day workers, research suggests. An analysis of studies involving more than 2m workers in the British Medical Journal said shift work can disrupt the body clock and have an adverse effect on lifestyle. It has previously been linked to an increased risk of high blood pressure and diabetes. Limiting night shifts would help workers cope, experts said. The team of researchers from Canada and Norway analysed 34 studies. In total, there were 17,359 coronary events of some kind, including cardiac arrests, 6,598 heart attacks and 1,854 strokes caused by lack of blood to the brain. These events were more common in shift workers than in other people. The BMJ study calculated that shift work was linked to a 23% increased risk of heart attack, 24% increased risk of coronary event and 5% increased risk of stroke. But they also said shift work was not linked to increased mortality rates from heart problems and that the relative risks associated with heart problems were "modest". The researchers took the socioeconomics status of the workers, their diet and general health into account in their findings. BBC © 2012

Related chapters from BN: 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: 17103 - Posted: 07.30.2012

Analysis by Emily Sohn Have a birthday in September, October, or November? Lucky you. You may have above-average chances of living an extra-long life. In a recent study, researchers from the University of Chicago looked at data from more than 1,500 people who were born between 1880 and 1895 and who lived to be 100 or older. The researchers compared that data with the birth months and life spans of nearly 12,000 of the centenarians’ siblings and spouses. The majority of people who lived an extra-long life were born between September and November, the researchers reported in the Journal of Aging Research http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3236478/. Birthdays in March, May, and July produced 40 percent fewer centenarians. The findings support a growing body of evidence that the conditions we experience extremely early in life may influence our health and survival many decades later, the researchers say. By comparing centenarians to their siblings, the study aimed to take into account living conditions early in life. By comparing spouses, the idea was to consider living conditions later in life. The study didn’t offer a definitive explanation for the birth and death patterns, though the researchers offered some theories. It’s possible, for example, that pregnant mothers had access to different levels of nutrition at different times of year in the late 1800s. Seasonal rates of infection may have also influenced fetuses in the womb, with vulnerability peaking during certain developmental periods. © 2012 Discovery Communications, LLC.

Related chapters from BN: Chapter 14: Biological Rhythms, Sleep, and Dreaming; Chapter 7: Life-Span Development of the Brain and Behavior
Related chapters from MM:Chapter 10: Biological Rhythms and Sleep; Chapter 4: Development of the Brain
Link ID: 17081 - Posted: 07.24.2012

Content provided by Jennifer Welsh, LiveScience Night owls often wake up for work or school with a scowl on their faces and wishing for an IV drip of coffee, while morning people come skipping in 15 minutes early. However, morning people aren't chipper just as the sun is coming up; they are happier and more satisfied with life overall, a new study suggests. Teenagers' night owl tendencies fade as they age, and the study says this switch to a morning-focused schedule could be why older adults are happier than younger ones. "Past research has suggested that morning-type people report feeling happier than evening-type people, and this research was only on young adults," study researcher Renee Biss, a graduate student at the University of Toronto, told LiveScience. The new study looked across the lifespan to see if the morning habits of older individuals contributed to their overall life outlook. The researchers studied two populations: a group of 435 adults ages 17 to 38, and a group of 297 older adults, ages 59 to 79. Both groups filled out questionnaires about their emotional state, how healthy they feel and their preferred "time of day." [Life's Extremes: Early Birds vs. Night Owls] By age 60, most people are morning types, the researchers found. Only about 7 percent of young adults are morning larks, but as the population ages, this switches — in the older years only about 7 percent of the population are still night owls. © 2012 Discovery Communications, LLC.

Related chapters from BN: 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: 16899 - Posted: 06.12.2012

By Tina Hesman Saey WASHINGTON — A protein famous for slowing aging and increasing life span also acts as a metronome, helping coordinate metabolism and the body’s daily rhythms. SIRT1, one of a group of proteins called sirtuins, plays roles in many cellular processes, including aging. Researchers hope that activating the protein with drugs such as resveratrol can extend life span and improve health for people, as it does in animal studies. Now, researchers at MIT have evidence that SIRT1 may not only help determine long-term health and longevity, but it also has a hand in setting the body’s daily or “circadian” clock. The finding, reported May 31 at the Metabolism, Diet and Disease meeting, could be important for understanding how metabolism and life span are linked. Studies of cells in laboratory dishes had suggested that SIRT1 might work with certain gears of the circadian clock in liver cells. But until now no one has shown that the protein could influence the body’s master clock in the brain, says Raul Mostoslavsky, a molecular biologist at Harvard Medical School. In the new study, scientists led by Leonard Guarente of MIT monitored the natural activity patterns of mice. Normally, mice’s circadian clocks run just shy of a 24-hour day, at about 23.5 hours. Mice that lack SIRT1 in their brains have a longer internal day, closer to 24 hours, Guarente said. And mice that made twice as much SIRT1 as normal in their brains had a shorter-than-usual day. Mice making five times as much SIRT1 as normal had even shorter natural days. © Society for Science & the Public 2000 - 2012

Related chapters from BN: Chapter 14: Biological Rhythms, Sleep, and Dreaming; Chapter 7: Life-Span Development of the Brain and Behavior
Related chapters from MM:Chapter 10: Biological Rhythms and Sleep; Chapter 4: Development of the Brain
Link ID: 16866 - Posted: 06.02.2012

By Bora Zivkovic The biannual meeting of the Society for Research on Biological Rhythms happened last week. Unfortunately, I could not attend, so will have to wait another two years for the next opportunity. I am not sure how this stuff happens, but there was a flurry of new papers in the circadian field just preceding the event. Several of them have already received quite a lot of attention in both old and new media, and rightfully so, but I decided not to cover them one at a time just as the embargo lifted for each one of them. Instead, I will just very briefly describe and explain the main take-home messages of each one of them, link to the best coverage for those who want more detail (“Cover what you do best. Link to the rest.“), and then try to come up with more of a ‘big picture’ summary of the current state of the field. I apologize in advance for covering and linking to some of the papers that are not published in Open Access journals. I am not as strict about this policy as some other bloggers are (“if my readers cannot access it, they cannot fact-check me”), and will occasionally cover non-OA papers. Even if most of my readers cannot access them, I gather that a miniscule proportion can access and, if I got something wrong, can alert the other readers in the comments. And speaking of Open Access, I am not one to sign many online petitions, but this one is worth it so please sign if you have not done it already. So, let’s see what new and exciting in chronobiology these days… © 2012 Scientific American,

Related chapters from BN: 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: 16857 - Posted: 05.31.2012

By Susan Milius Throughout the world, climate change is causing age-old ecological partners to miss their cues as seasons shift. The trend may be so strong at higher latitudes that researchers now propose that some species’ ranges could actually shrink away from the poles. This idea comes from studying broad-tailed hummingbirds that migrate north from Central America each spring to high-altitude breeding sites in the western United States. With only brief mountain summers to raise chicks, male hummingbirds typically arrive in the region before the first flowers bloom and scout for territories. Around the Rocky Mountain Biological Laboratory in Gothic, Colo., near the upper limit of the broad-tailed hummingbird breeding range, the gap between the first hummingbird arrival and the first bloom has narrowed by roughly 13 days during the last four decades. Amy McKinney of the University of Maryland in College Park and her colleagues report the discovery online May 14 in Ecology. Glacier lilies start blooming roughly 17 days earlier than they did in the 1970s, but birds haven’t sped up nearly as much. In a few extreme years, lilies have already started blooming before the first hummingbird showed up. Researchers calculate that if the timing trends continue, in about two more decades the males will routinely miss the first flowers. © Society for Science & the Public 2000 - 2012

Related chapters from BN: 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: 16822 - Posted: 05.22.2012

by Debora MacKenzie OUR core physiology relies on subtle organic timers: disrupt them, and effects range from jet lag to schizophrenia. Exactly how and when life began keeping time is unclear, but a candidate for the original biological clock may solve the mystery. Biological clocks are ubiquitous in nature, so the first clock should pre-date the evolutionary parting of the ways that led to modern groups of organisms. All the clocks found so far are unique to different groups of organisms, though. Not so the clock discovered by Akhilesh Reddy at the University of Cambridge and colleagues. In an enzyme called peroxiredoxin (PRX), they seem to have found a grandfather clock - one that is common to nearly all life. PRX gets rid of poisonous, highly reactive oxygen (ROS), which is produced by oxygen-based metabolism. And the enzyme oscillates: it flits between an active and inactive state, depending on whether oxygen is bound to the active site. Using antibodies that bind only to the oxidised enzyme, the team found that PRX oxidation keeps cycling independently on a 24-hour cycle, even when organisms were kept in constant light or constant dark. Moreover, they found this PRX cycle in mice, fruit flies, a plant, a fungus, an alga, bacteria and even in archaea - the most primitive of all cellular life (Nature, DOI: 10.1038/nature11088). That suggests PRX evolved early in life's history. A gene sequence analysis suggests it did so 2.5 billion years ago, during the Great Oxygenation Event (GOE) - a critical interval when the oxygen released by photosynthesis began to accumulate in the atmosphere. © Copyright Reed Business Information Ltd.

Related chapters from BN: 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: 16811 - Posted: 05.17.2012

by Erin Loury As if you needed another reason to despise your alarm clock. A new study suggests that, by disrupting your body's normal rhythms, your buzzing, blaring friend could be making you overweight. The study concerns a phenomenon called "social jetlag." That's the extent to which our natural sleep patterns are out of synch with our school or work schedules. Take the weekends: many of us wake up hours later than we do during the week, only to resume our early schedules come Monday morning. It's enough to make your body feel like it's spending the weekend in one time zone and the week in another. But is social jetlag actually bad for your health? To investigate, chronobiologist Till Roenneberg at the University of Munich in Germany and colleagues compiled data from tens of thousands of responses to an internet survey on sleep patterns and other behaviors. Previous work with such data has already yielded some clues. "We have shown that if you live against your body clock, you're more likely to smoke, to drink alcohol, and drink far more coffee," says Roenneberg. In the new study, the team measured the social jetlag of people ages 16 to 65 by calculating how offset sleep times were on workdays and non-workdays. They then constructed a mathematical model that gauged how well biological factors, such as age, gender, sleep duration, and social jet lag could predict body weight. They found that the first three factors were important predictors of body weight for all people. In addition, for people who are already on the heavy side, greater social jet lag corresponded to greater body weight. However, social jet lag was not a good predictor for people with normal body weights, the team reports online today in Current Biology. © 2010 American Association for the Advancement of Science.

Related chapters from BN: 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: 16780 - Posted: 05.12.2012

By Rebecca Cheung The settings for a person’s biological clock might provide clues to when, during the day, he or she will be more active. What’s more, these same settings could be linked to what time of day a person might die, a new study finds. Understanding the biological basis of these built-in, or circadian, clocks “could lead to products that eventually allow us to shift the clock forwards or backwards,” says Philip De Jager, a neurologist with Harvard Medical School in Boston. He and his colleagues describe their work online April 26 in Annals of Neurology. Being able to alter these clocks could prove useful for shift workers, such as pilots, who might face trouble working against their intrinsic daily rhythms, De Jager adds. And patients can be better cared for if doctors know what times of day are most critical. Previously, scientists have shown that many genes are involved in regulating people’s inherent daily wake and sleep patterns. Disruptions to this natural circadian rhythm are often linked to serious health conditions, including diabetes. In the new work, De Jager’s team took a close look at common subtle tweaks that occur in a circadian clock-regulating gene called PER1. By mostly focusing on DNA samples collected from a group of 537 older adults of European ancestry, the team found that there were three different variations of PER1. The researchers also found these variations in another smaller group of 38 people between 18 and 72 years old. © Society for Science & the Public 2000 - 2012

Related chapters from BN: Chapter 14: Biological Rhythms, Sleep, and Dreaming
Related chapters from MM:Chapter 10: Biological Rhythms and Sleep
Link ID: 16779 - Posted: 05.12.2012

by Jane J. Lee Waking up from surgery can be disorienting. One minute you're in an operating room counting backwards from 10, the next you're in the recovery ward sans appendix, tonsils, or wisdom teeth. And unlike getting up from a good night's sleep, where you know that you've been out for hours, waking from anesthesia feels like hardly any time has passed. Now, thanks to the humble honeybee (Apis mellifera), scientists are starting to understand this sense of time loss. New research shows that general anesthetics disrupt the social insect's circadian rhythm, or internal clock, delaying the onset of timed behaviors such as foraging and mucking up their sense of direction. Putting insects to sleep is nothing new. Researchers have used the animals for decades to figure out how anesthetics work, because the drugs elicit the same effects, at the same concentrations, in many different organisms. "You can give the anesthetic to a monkey and a snail, and they'll fall over and stop moving," says study co-author Guy Warman, a chronobiologist at the University of Auckland in New Zealand. The circadian rhythm's daily cycles are also common across organisms. So-called clock genes help regulate the rhythms that make us feel awake during the day and tired at night, while also prompting honeybees to search for nectar at certain times of day. External inputs, such as light, fine-tune those cycles. In our case, they keep us on a roughly 24-hour schedule. © 2010 American Association for the Advancement of Science

Related chapters from BN: Chapter 14: Biological Rhythms, Sleep, and Dreaming; Chapter 4: The Chemistry of Behavior: Neurotransmitters and Neuropharmacology
Related chapters from MM:Chapter 10: Biological Rhythms and Sleep; Chapter 3: The Chemistry of Behavior: Neurotransmitters and Neuropharmacology
Link ID: 16660 - Posted: 04.17.2012