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By Ashley Yeager Researchers led by Bert O’Malley of Baylor College of Medicine in Houston, Texas, identified a set of metabolism and stress genes in mouse liver cells that followed a pattern of expression on a 12-hour cycle—starting in the morning and again in the evening. O’Malley’s team also found that a 12-hour clock, distinct from the 24-hour circadian clock, drives this morning-evening rhythm in gene expression. The clock’s origin, the scientists suggest, may be rooted in organisms’ initial evolution in the ocean millions of years ago. “It’s a provocative argument,” Cambridge University biologist Michael Hastings tells The Scientist in a phone interview. He’s cautious about the claim of an evolutionary connection between the 12-hour clock in sea creatures and the 12-hour cycles seen in mammals. Still, he commends the team on taking a “cross-biology” approach toward exploring 12-hour gene-expression rhythms in a range of animals. In past studies, researchers have shown that coastal sea animals, such as the crustacean Eurydice pulchra have a dominant body clock driven by the 12-hour ebb and flow of the tides. Rhythms of gene expression every 12-hours have also been found in mammals, such as mice. Whether mammals’ 12-hour rhythms are driven by the body’s circadian clock or something else, however, has remained a mystery. Interested in that question and also observations that the time of day can affect humans’ ability to think clearly, handle stress, and respond to medicine, O’Malley and colleagues began to look more closely at mammals’ 12-hour gene-expression rhythms. In the new study, they analyzed gene-expression data of 18,108 mouse liver genes. Using a mathematical technique developed by researchers at Rice University, the team identified 3,652 genes that had 12-hour rhythms that didn’t appear to be associated with the mouse’s circadian clock. © 1986-2017 The Scientist

Related chapters from BP7e: Chapter 14: Biological Rhythms, Sleep, and Dreaming
Related chapters from MM:Chapter 10: Biological Rhythms and Sleep
Link ID: 23748 - Posted: 06.17.2017

By Amina Zafar, CBC News When men postpone meal times, it delays one of the body's clocks, British researchers say, a finding that sheds light on a potential way to overcome jet lag and health harms for shift workers. Our bodies run a roughly 24-hour cycle called the circadian or sleep/wake rhythm. It is controlled by a master "clock" in the brain that responds to light signals from the retina, synchronizing other clocks throughout the body. Now investigators have discovered that a five-hour delay in meal time causes a five-hour delay in blood glucose rhythms. "We think this is due to changes in clocks in our metabolic tissues but not the 'master' clock in the brain," said Jonathan Johnston of the University of Surrey, one of the authors of the study published in Thursday's issue of the journal Current Biology. "This work is important because it demonstrates for the first time that a relatively subtle change of standard human feeding pattern re-synchronizes key metabolic rhythms in the body." Currently, people disoriented by the sluggish time warp of jet lag may take melatonin supplements and time their light exposure to help synchronize their clocks. While the study introduces the idea of adding meal timing to the clock reset toolkit, the practical details of how to do so still need to be worked out. In the experiment, 10 healthy young men came to a specialized sleep lab for 13 days. At first, breakfast was set for 30 minutes after waking. Then, after the men got used ©2017 CBC/Radio-Canada.

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: 23695 - Posted: 06.02.2017

By Jyoti Madhusoodanan For three consecutive winters, starting in 2011, researchers at the University of Birmingham asked healthy men and women over the age of 65 to come in to clinics across the western Midlands in the U.K. for a seasonal influenza vaccination at specific times of day—either between 9 and 11 a.m., or between 3 and 5 p.m. Blood drawn a month later revealed that participants, who totaled nearly 300 over the three years, had higher levels of anti-flu antibodies if they’d received their vaccinations in the morning.1 The results suggested that daily rhythms of people’s bodies tweaked the vaccine’s effectiveness. Lead author Anna Phillips Whittaker had suspected as much, after observing similar trends in her studies on behavioral factors such as exercise that affect vaccination responses, and in the wake of a growing body of literature suggesting that a little timing can go a long way when it comes to health. Many hormones and immune signals are produced rhythmically in 24-hour cycles. Cortisol, for example, which is known to suppress inflammation and regulate certain T cell–mediated immune responses, peaks early in the morning and ebbs as the day progresses. Other facets of the immune system undergo similar cycles that could underlie the differences in antibody responses Phillips observed among people receiving the flu vaccine. Much more work is required to nail down the immune mechanisms responsible for such variation and exploit them appropriately, she says. But timing flu vaccine delivery would be straightforward to implement. “It’s such a simple, low-risk intervention that’s free to do, and could have massive implications for vulnerable populations.” © 1986-2017 The Scientist

Related chapters from BP7e: Chapter 14: Biological Rhythms, Sleep, and Dreaming
Related chapters from MM:Chapter 10: Biological Rhythms and Sleep
Link ID: 23484 - Posted: 04.13.2017

A gene variant may explain why some people prefer to stay up late and hate early mornings. The variant is a mutated form of the CRY1 gene, known to play a role in the circadian clock. Michael Young, at The Rockerfeller University, New York, and his team discovered the mutation in a person diagnosed with delayed sleep phase disorder – a condition that describes many so-called “night-owls”. The team found that five of this person’s relatives also had this mutation, all of whom had a history of sleep problems. They then studied six families in Turkey whose members included 39 carriers of the CRY1 variant. The sleep periods of those with the mutation was shifted by 2 to 4 hours, and some had broken, irregular sleep patterns. The mutation seems to slow the body’s internal biological clock, causing people to have a longer circadian cycle and making them stay awake later. The team have calculated that the variant may be present in as many as one in 75 people in some populations, such as Europeans of non-Finnish descent. But those who have a longer circadian cycle need not despair. Young says many people with delayed sleep phase disorder are able to control their sleep cycles by sticking to strict schedules. “It’s a bit like cigarette smoking in that there are things we can do to help the problem before turning to drugs,” he says. Journal reference: Cell, DOI: 10.1016/j.cell.2017.03.027 © 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: 23459 - Posted: 04.07.2017

By Jyoti Madhusoodanan The human body undergoes daily cycles in gene expression, protein levels, enzymatic activity, and overall function. Light is the strongest regulator of the central circadian rhythm. When light strikes a mammal’s eyes, it triggers an electrical impulse that activates neurons in the suprachiasmatic nucleus (SCN), the seat of the brain’s timekeeping machinery. The SCN sets the pace for neuronal and hormonal signals that regulate body temperature, feeding behavior, rest or activity, immune cell functions, and other daily activities, which in combination with direct signals from the SCN keep the body’s peripheral organs ticking in synchrony. Sunlight reaches the eyes, controls the central clock in the brain. The brain, in turn, controls different physiological processes, such as body temperature and rest-activity cycles, which then affect metabolites, hormones, the sympathetic nervous system, and other biological signals. These processes ensure that the different organ systems of the body cycle together. Timing Treatments to the Clock Regulated by peripheral clocks and interactions with other organs, many metabolic pathways in the body peak and ebb in specific circadian patterns. As a result, drugs targeting these pathways can work better when taken at particular times of day. Here are a few examples. © 1986-2017 The Scientist

Related chapters from BP7e: Chapter 14: Biological Rhythms, Sleep, and Dreaming
Related chapters from MM:Chapter 10: Biological Rhythms and Sleep
Link ID: 23458 - Posted: 04.07.2017

Katherine Whalley The mammalian suprachiasmatic nucleus (SCN) can autonomously generate circadian oscillations in gene expression and neuronal activity, enabling it to fulfil its role as the brain's 'master circadian clock'. Although the contributions of specific neuronal populations to SCN function have begun to be elucidated, the potential influences of SCN astrocytes are relatively unexplored. Brancaccio et al. now reveal an important role for astrocyte–neuron signalling in SCN timekeeping. SCN neurons exhibit circadian oscillations in their intracellular calcium level ([Ca2+]i), peaking during the circadian 'day'. To determine whether similar fluctuations in activity are observed in astrocytes, the authors expressed a genetically encoded reporter of astrocytic [Ca2+]i in organotypic SCN slices. Long-term imaging revealed the presence of circadian oscillations in astrocytic [Ca2+]i, which was at its highest during the circadian 'night' and thus was anti-phasic to that of neurons. Astrocytes release 'gliotransmitters', including glutamate, in response to an increase in [Ca2+]i. When the authors expressed a genetically encoded sensor of the extracellular glutamate concentration ([Glu]e) in SCN slices, they observed circadian oscillations in [Glu]e that were in phase with astrocytic [Ca2+]i. oscillations. That astrocytes were the source of the measured [Glu]e was supported by the fact that the pharmacological inhibition of astrocytic glutamate catabolism or the genetic ablation of astrocytes, respectively, increased or reduced [Glu]e. © 2017 Macmillan Publishers Limited,

Related chapters from BP7e: Chapter 14: Biological Rhythms, Sleep, and Dreaming; Chapter 3: Neurophysiology: The Generation, Transmission, and Integration of Neural Signals
Related chapters from MM:Chapter 10: Biological Rhythms and Sleep; Chapter 3: Neurophysiology: The Generation, Transmission, and Integration of Neural Signals
Link ID: 23436 - Posted: 04.01.2017

By STEPH YIN For animals that hibernate, making it to spring is no small feat. Torpor — the state of reduced bodily activity that occurs during hibernation — is not restful. By the time they emerge, hibernating animals are often sleep-deprived: Most expend huge bursts of energy to arouse themselves occasionally in the winter so their body temperatures don’t dip too low. This back-and-forth is exhausting, and hibernators do it with little to no food and water. By winter’s end, some have shed more than half their body weight. But just because it’s spring doesn’t mean it’s time to celebrate. Spring means getting ready for the full speed of summer — and after spending a season in slow motion, that requires some ramping up. Here’s a look at what different animals have on the agenda after coming out of winter’s slumber. Black bears emerge from their dens in April, but stay lethargic for weeks. During this so-called walking hibernation, they sleep plenty and don’t roam very far. Though they have lost up to one-third of their body weight over winter, they don’t have a huge appetite right away — their metabolism is not yet back to normal. They snack mostly on pussy willows and bunches of snow fleas. In January or February, some females give birth, typically to two or three cubs. New mothers continue to hibernate, but they go in and out of torpor, staying alert enough to respond to their cubs’ cries. When they emerge from their dens, mama bears find trees with rough bark that her cubs can easily climb for safety. “Slowly, the bears’ metabolism gears up to normal, active levels,” said Lynn Rogers, a bear expert and principal biologist at the Wildlife Research Institute, a nonprofit in Minnesota. “When plants start sprouting on the forest floor, that’s when they start really moving around.” © 2017 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: 23406 - Posted: 03.25.2017

By Diana Kwon Astrocytes, star-shape glial cells in the brain, were once simply considered support cells for neurons. However, neuroscientists have recently realized they have many other functions: studies have shown that astrocytes are involved in metabolism, learning, and more. In the latest study to investigate astrocytes’ roles in the brain, researchers confirmed these cells played a key role in regulating mouse circadian rhythms. The team’s results were published today (March 23) in Current Biology. “Recent results have indicated that [glia] are actively modulating synaptic transmission, the development of the nervous system, and changes in the nervous system in response to changes in the environment,” said coauthor Erik Herzog, a neuroscientist at Washington University in St. Louis. “So circadian biologists recognized that the system that we study in the brain also had astrocytes and have wondered what role that they might play.” In 2005, Herzog’s team published a seminal study linking glia to mammalian circadian rhythms. By investigating rat and mouse astrocytes in a dish, the researchers discovered that these glial cells showed circadian rhythms in gene expression. Since then, several independent groups have reported evidence to suggest that astrocytes help regulate daily rhythms. However, linking astrocytes to circadian behaviors in mice remained difficult. “I had several folks in the lab over many years [who] were unable to find the tools that would allow us to answer the question definitively: Do astrocytes play a role in scheduling our day?” Herzog recalled. “Then, within the last year or so, some new tools . . . became available for us.”. © 1986-2017 The Scientist

Related chapters from BP7e: Chapter 14: Biological Rhythms, Sleep, and Dreaming
Related chapters from MM:Chapter 10: Biological Rhythms and Sleep
Link ID: 23405 - Posted: 03.25.2017

Richard A. Friedman Jet lag makes everyone miserable. But it makes some people mentally ill. There’s a psychiatric hospital not far from Heathrow Airport that is known for treating bipolar and schizophrenic travelers, some of whom are occasionally found wandering aimlessly through the terminals. A study from the 1980s of 186 of those patients found that those who’d traveled from the west had a higher incidence of mania, while those who’d traveled from the east had a higher incidence of depression. I saw the same thing in one of my patients who suffered from manic depression. When he got depressed after a vacation to Europe, we assumed he was just disappointed about returning to work. But then he had a fun trip out West and returned home in what’s called a hypomanic state: He was expansive, a fount of creative ideas. It was clear that his changes in mood weren’t caused by the vacation blues, but by something else. The problem turned out to be a disruption in his circadian rhythm. He didn’t need drugs; he needed the right doses of sleep and sunlight at the right time. It turns out that that prescription could treat much of what ails us. Clinicians have long known that there is a strong link between sleep, sunlight and mood. Problems sleeping are often a warning sign or a cause of impending depression, and can make people with bipolar disorder manic. Some 15 years ago, Dr. Francesco Benedetti, a psychiatrist in Milan, and colleagues noticed that hospitalized bipolar patients who were assigned to rooms with views of the east were discharged earlier than those with rooms facing the west — presumably because the early morning light had an antidepressant effect. The notion that we can manipulate sleep to treat mental illness has also been around for many years. Back in the late 1960s, a German psychiatrist heard about a woman in Tübingen who was hospitalized for depression and claimed that she normally kept her symptoms in check by taking all-night bike rides. He subsequently demonstrated in a group of depressed patients that a night of complete sleep deprivation produced an immediate, significant improvement in mood in about 60 percent of the group. © 2017 The New York Times Company

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: The Biology of Behavioral Disorders
Link ID: 23350 - Posted: 03.13.2017

By Julia Shaw We all have times of day when we are not at our best. For me, before 10am, and between 2-4pm, it’s as though my brain just doesn’t work the way it should. I labor to come up with names, struggle to keep my train of thought, and my eloquence drops to the level expected of an eight-year-old. In an effort to blame my brain for this, rather than my motivation, I reached out to a researcher in the area of sleep and circadian neuroscience. Andrea Smit, a PhD student working with Professors John McDonald and Ralph Mistlberger at Simon Fraser University in Canada, was happy to help me find excuses for why my memory is so terribly unreliable at certain times of day. Humans have daily biological rhythms, called circadian rhythms, which affect almost everything that we do. They inform our bodies when it is time to eat and sleep, and they dictate our ability to remember things. According to Smit, “Chronotype, the degree to which someone is a “morning lark” or a “night owl,” is a manifestation of circadian rhythms. In a recent study, Smit used EEG, a type of brain scan, to study the interaction between chronotypes and memory. “Testing extreme chronotypes at multiple times of day allowed us to compare attentional abilities and visual short term memory between morning larks and night owls. Night owls were worse at suppressing distracting visual information and had a worse visual short term memory in the morning as compared with the afternoon,” she says. “Our research shows that circadian rhythms interact with memories even at very early stages of processing within the brain.” © 2017 Scientific American

Related chapters from BP7e: Chapter 14: Biological Rhythms, Sleep, and Dreaming; Chapter 17: Learning and Memory
Related chapters from MM:Chapter 10: Biological Rhythms and Sleep; Chapter 13: Memory, Learning, and Development
Link ID: 23194 - Posted: 02.07.2017

Aylin Woodward Fearful, flighty chickens raised for eating can hurt themselves while trying to avoid human handlers. But there may be a simple way to hatch calmer chicks: Shine light on the eggs for at least 12 hours a day. Researchers at the University of California, Davis bathed eggs daily in light for different time periods during their three-week incubation. When the chickens reached 3 to 6 weeks old, the scientists tested the birds’ fear responses. In one test, 120 chickens were randomly selected from the 1,006-bird sample and placed one by one in a box with a human “predator” sitting visibly nearby. The chickens incubated in light the longest — 12 hours — made an average of 179 distress calls in three minutes, compared with 211 from birds incubated in complete darkness, animal scientists Gregory Archer and Joy Mench report in January in Applied Animal Behaviour Science. Chickens exposed to lots of light as eggs “would sit in the closest part of the box to me and just chill out,” Archer says. The others spent their time trying to get away. How light has its effect is unclear. On commercial chicken farms, eggs typically sit in warm, dark incubation rooms. The researchers are now testing light's effects in large, commercial incubators. Using light exposure to raise less-fearful chickens could reduce broken bones during handling at processing plants, Archer says. It might also decrease harmful anxious behaviors, such as feather pecking of nearby chickens. G. S. Archer and J. A. Mench. Exposing avian embryos to light affects post-hatch anti-predator fear responses. Applied Animal Behaviour Science. Vol. 186, January 2017, p. 80. doi: 10.1016/j.applanim.2016.10.014. © Society for Science & the Public 2000 - 2016

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: 23193 - Posted: 02.07.2017

Ian Sample Science editor As an antidote to one of the ills of modern life, it may leave some quite cold. When the lure of the TV or fiddling on the phone keep you up late at night, it is time to grab the tent and go camping. The advice from scientists in the US follows a field study that found people fell asleep about two hours earlier than usual when they were denied access to their gadgets and electrical lighting and packed off to the mountains with a tent. A weekend in the wilds of the Rocky Mountains in Colorado helped reset people’s internal clocks and reversed the tendency of artificial light to push bedtime late into the night. A spell outdoors, the researchers conclude, could be just the thing for victims of social jetlag who find themselves yawning all day long. “Our modern environment has really changed the timing of our internal clocks, but also the timing of when we sleep relative to our clock,” said Kenneth Wright, director of the sleep and chronobiology lab at the University of Colorado in Boulder. “A weekend camping trip can reset the clock rapidly.” To explore the sleep-altering effects of the natural environment, Wright sent five hardy colleagues, aged 21 to 39, on a six day camping trip to the Rocky Mountains one December. They left their torches and gadgets behind, and had only sunlight, moonlight and campfires for illumination. The campers went to bed on average two and a half hours earlier than they did at home, and racked up nearly 10 hours of sleep per night compared with their usual seven and a half hours. Monitors showed that they were more active in the daytime and were exposed to light levels up to 13 times higher than they typically received at home.

Related chapters from BP7e: Chapter 14: Biological Rhythms, Sleep, and Dreaming
Related chapters from MM:Chapter 10: Biological Rhythms and Sleep
Link ID: 23183 - Posted: 02.03.2017

By Rachael Lallensack Jet lag can put anyone off their game, even Major League Baseball (MLB) players. Long-distance travel can affect specific—and at times, crucial—baseball skills such as pitching and base running, a new study finds. In fact, jetlag's effects can even cancel out the home field advantage for some teams returning from away games. Jet lag is known for its fatigue-inducing effects, most of which stem from a mismatch between a person’s internal clock and the time zone he or she is in, something called “circadian misalignment.” This misalignment is especially strong when a person’s day is shorter than it should be—which happens whenever people travel east—previous research has shown. Just how that affects sports teams has long been debated. A 2009 study of MLB, for example, found that jet lag did decrease a team’s likelihood of winning, if only slightly. But no prior study has ever been able to pinpoint exact areas of game play where the effects of jet lag hit hardest—data that could help coaches and trainers better prepare players for games following travel. To figure out how that might happen, “adopted” Chicago Cubs fan and study author Ravi Allada, a neurobiologist at Northwestern University in Evanston, Illinois, looked at 20 years’ worth of MLB data from 1992 to 2011. He and his team narrowed their data set from 46,535 games to the 4919 games in which players traveled at least two time zones. Then, they broke down offensive and defensive stats from each of those games, including home runs allowed, stolen bases, and sacrifice flies. Finally, they compared how the numbers changed for teams that had traveled east versus those that had traveled west. © 2017 American Association for the Advancement of Science.

Related chapters from BP7e: Chapter 14: Biological Rhythms, Sleep, and Dreaming
Related chapters from MM:Chapter 10: Biological Rhythms and Sleep
Link ID: 23140 - Posted: 01.24.2017

by Laura Sanders Most nights I read a book in bed to wind down. But when I run out of my library supply, I read articles on my phone instead. I suspect that this digital substitution messes with my sleep. That’s not good for me — but it’s probably worse for the many children who have screens in their rooms at night. A team of researchers recently combed through the literature looking for associations between mobile devices in the bedroom and poor sleep. Biostatistician Ben Carter of King’s College London and colleagues found that kids between ages 6 and 19 who used screen-based media around bedtime slept worse and were more tired in the day. That’s not surprising: Phones, tablets and laptops make noise and emit blue light that can interfere with the sleep-inducing melatonin. But things got interesting when the researchers compared kids who didn’t have screens in their bedrooms with kids who did have phones or tablets in their rooms but didn’t use them. You might think there wouldn’t be a sleep difference between those groups. None of these kids were up all night texting, gaming or swiping, so neither sounds nor blue light were messing with any of the kids’ sleep. Yet Carter and colleagues found a difference: Kids who had screen-based media in their bedroom, but didn’t use it, didn’t sleep as much as kids without the technology. What’s more, the sleep they did get was worse and they were more tired during the day, the researchers reported in the December JAMA Pediatrics. |© Society for Science & the Public 2000 - 2017

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: 23139 - Posted: 01.24.2017

By Krystnell A. Storr This one goes out to the head bobbers, the window seat sleepers, and the open-mouth breathers — there is no shame in being able to fall asleep anywhere, and at any time. Be proud, and, if you can’t help it, snore loud. Scientists have come to a consensus that our bodies definitely need sleep, but we don’t all need the same amount. The next step for them is to figure out where the process of sleep starts and ends in the body. And, like a good movie, one revelation about sleep only leads to another. Think of yourself as a very minor character in the scientific story of fatigue. The real star of this cozy mystery is the fruit fly, an A-lister in sleep science. Thanks to fruit flies, we understand two of the basic factors that govern sleep: a biological clock, which scientists know a lot about, and a homeostatic switch, which they only just discovered and are beginning to understand. Let’s start with this biological clock. The clock that is connected to sleep is controlled by a circadian rhythm and uses environmental cues such as sunlight to tell the body when to wake up. This sun-sleep connection in humans and flies alike got scientists like Russell Foster, a professor at Oxford University in the United Kingdom, asking questions such as: What happens when we don’t have the mechanisms in our eye to distinguish dawn from dusk and send that message to the brain? Why can we still fall asleep according to the circadian rhythm? The answer, Foster said, is that mammals have a third layer of photoreceptors in the eye. It used to be that scientists thought rods and cones, cells that help us process images, were the only ones in the eye that worked to detect light. But when they removed these cells in mice, they noticed that the mice could still keep up with the circadian rhythm. The hidden cells, they found, were intrinsically sensitive to light and acted as a backup measure to keep us on our sleep schedule, whether we can see that the sun is up or not.

Related chapters from BP7e: Chapter 14: Biological Rhythms, Sleep, and Dreaming
Related chapters from MM:Chapter 10: Biological Rhythms and Sleep
Link ID: 22656 - Posted: 09.15.2016

By Sunpreet Singh Every day people are exposed to hours of artificial light from a variety of sources – computers, video games, office lights and, for some, 24-hour lighting in hospitals and nursing homes. Now new research in animals shows that excessive exposure to “light pollution” may be worse for health than previously known, taking a toll on muscle and bone strength. Researchers at Leiden University Medical Center in the Netherlands tracked the health of rats exposed to six months of continuous light compared to a control group of rats living under normal light-dark conditions — 12 hours of light, followed by 12 hours of dark. During the study, the rats exposed to continuous light had less muscle strength and developed signs of early-stage osteoporosis. They also got fatter and had higher blood glucose levels. Several markers of immune system health also worsened, according to the report published in the medical journal Current Biology. While earlier research has suggested excessive light exposure could affect cognition, the new research was surprising in that it showed a pronounced effect on muscles and bones. While it’s not clear why constant light exposure took a toll on the motor functions of the animals, it is known that light and dark cues influence a body’s circadian rhythms, which regulate many of the body’s physiological processes. “The study is the first of its kind to show markers of negatively-affected muscle fibers, skeletal systems and motor performances due to the disruption of circadian clocks, remarkably in only a few months,” said Chris Colwell, a psychiatry professor and sleep specialist at the University of California, Los Angeles, who was not part of the study. “They found that not only did motor performance go down on tests, but the muscles themselves just atrophied, and mice physically became weaker under just two months under these conditions.” © 2016 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: 22556 - Posted: 08.13.2016

By JOANNA KLEIN Jet lag may be the worst part of traveling. And it hits many people harder traveling east than west. Why they feel this way is unclear. But scientists recently developed a model that mimics special time-keeping cells in the body and offers a mathematical explanation for why traveling from west to east feels so much worse. It also offers insights on recovering from jet lag. Deep inside the brain, in a region called the hypothalamus (right above where our optic nerves cross) the internal clock is ticking. And approximately every 24 hours, 20,000 special pacemaker cells that inhabit this area, known as the superchiasmatic nucleus, synchronize, signaling to the rest of the body whether it’s night or day. These cells know which signal to send because they receive light input from our environments — bright says wake, dark says sleep. But when you travel across multiple time zones, like flying from New York to Moscow, those little pacemaker cells that thought they knew the routine scramble around confused before they can put on their show. The whole body feels groggy because it’s looking for the time and can’t find it. The result: jet lag. Most of our internal clocks are a little bit slow, and in the absence of consistent light cues — like when you travel across time zones — the pacemaker cells in your body want to have a longer day, said Michelle Girvan, a physicist at the University of Maryland who worked on the model published in the journal Chaos on Tuesday. “This is all because the body’s internal clock has a natural period of slightly longer than 24 hours, which means that it has an easier time traveling west and lengthening the day than traveling east and shortening the day,” Dr. Girvan said. © 2016 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: 22446 - Posted: 07.16.2016

Rebecca Boyle Eliane Lucassen works the night shift at Leiden University Medical Center in the Netherlands, beginning her day at 6 p.m. Yet her own research has shown that this schedule might cause her health problems. “It’s funny,” the medical resident says. “Here I am, spreading around that it’s actually unhealthy. But it needs to be done.” Lucassen and Johanna Meijer, a neuroscientist at Leiden, report today in Current Biology1 that a constant barrage of bright light prematurely ages mice, playing havoc with their circadian clocks and causing a cascade of health problems. Mice exposed to constant light experienced bone-density loss, skeletal-muscle weakness and inflammation; restoring their health was as simple as turning the lights off. The findings are preliminary, but they suggest that people living in cities flooded with artificial light may face similar health risks. “We came to know that smoking was bad, or that sugar is bad, but light was never an issue,” says Meijer. “Light and darkness matter.” Disrupted patterns Many previous studies have hinted at a connection between artificial light exposure and health problems in animals and people2. Epidemiological analyses have found that shift workers have an increased risk of breast cancer3, metabolic syndrome4 and osteoporosis5, 6. People exposed to bright light at night are more likely to have cardiovascular disease and often don’t get enough sleep. © 2016 Macmillan Publishers Limited,

Related chapters from BP7e: Chapter 14: Biological Rhythms, Sleep, and Dreaming
Related chapters from MM:Chapter 10: Biological Rhythms and Sleep
Link ID: 22442 - Posted: 07.15.2016

By Clare Wilson One day, you might be seeing in blue for 24 hours before you have an operation ­– to prevent organ damage. A study in mice suggests that exposure to blue light reduces a form of organ damage that is common during surgery. Reperfusion injury can happen when blood vessels are temporarily tied off during surgery, or when blocked arteries are surgically widened after a heart attack or stroke. Some damage is caused by a lack of oxygen, and further harm results when oxygen levels rebound, causing cells to become overactive, and triggering an attack by the immune system. But blue light seems to reduce this, in mice at least. Matthew Rosengart of the University of Pittsburgh, Pennsylvania, and his team have found that when mice are exposed to blue light for 24 hours before the blood supply to their liver or kidney is temporarily tied off, there is less reperfusion injury than if the mice are exposed to other types of light. “That’s pretty remarkable,” says Jack Pickard, a reperfusion researcher at University College London. Further tests showed that blue light seems to dampen down the sympathetic nervous system, which is involved in mammal stress responses. In turn, this reduced the activity of immune cells called neutrophils, which are involved in inflicting the damage of a reperfusion injury. © 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: 22145 - Posted: 04.26.2016

By Lisa L. Lewis On Tuesday, U.S. News and World Report released its annual public high-school rankings, with the School for the Talented and Gifted in Dallas earning the top spot for the fifth year in a row. The rankings are based on a wealth of data, including graduation rates and student performance on state proficiency tests and advanced exams, as well as other relevant factors—like the percentage of economically disadvantaged students the schools serve. But there’s one key metric that isn’t tracked despite having a proven impact on academic performance: school start times. First-period classes at the School for the Talented and Gifted start at 9:15 a.m. That’s unusually late compared to other schools but is in keeping with the best practices now recommended by public health experts. Teens require more sleep than adults and are hardwired to want to sleep in. Eight hours a night may be the goal for adults, but teens need between 8.5–9.5 hours, according to the American Academy of Pediatrics. Unfortunately, few teens meet that minimum: Studies show that two out of three high school students get less than eight hours of sleep, with high school seniors averaging less than seven hours. Sure, kids could go to bed earlier. But their bodies are set against them: Puberty makes it hard for them to fall asleep before 11 p.m. When combined with too-early start times, the result is sleep deprivation.

Related chapters from BP7e: 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 13: Memory, Learning, and Development
Link ID: 22133 - Posted: 04.23.2016