Links for Keyword: Biological Rhythms

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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 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: 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 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: 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 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: 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 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: 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 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: 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 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: 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 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: 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 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: 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 BP7e: 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 BP7e: 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 4: The Chemistry of Behavior: Neurotransmitters and Neuropharmacology
Link ID: 16660 - Posted: 04.17.2012

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