Links for Keyword: Biological Rhythms

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COLUMBUS , Ohio –- The brains of one species of mouse actually shrink during the winter, causing the mice to have more difficulty with some types of learning, a new study found. The results showed that, during the short days of winter, white-footed mice had impaired spatial memory – the mental map that helps them remember important places in their environment. This is one of the first studies to show seasonal changes in the structure and the functioning of brains of mammals, said Randy Nelson, co-author of the study and professor of psychology and neuroscience at Ohio State University. The changes in the brain may help the mice conserve energy to survive during the cold winter season when food is scarce and conditions are harsh. “The brain uses a lot of energy relative to its weight,” Nelson said. “Like many mammals, mice need to reduce their energy costs during winter, and the brain is a good place to do that.” And while there are obviously many differences between mice and humans, studies like this may one day help researchers gain insight into seasonal brain dysfunctions in humans such as seasonal affective disorder, Nelson said. Nelson conducted the study with Leah Pyter, a graduate student in neuroscience at Ohio State , and Brenda Reader, an undergraduate psychology major at Ohio State . The findings were published in the May 4 issue of the Journal of Neuroscience.

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: 7345 - Posted: 06.24.2010

A cluster of brain cells less than half the size of a pencil eraser tells you when to wake up, when to be hungry and when it's time to go to sleep. The same cells also cause you to be disoriented after you've flown across multiple time zones. The human circadian clock, comprised of about 20,000 time-keeping cells, has mystified scientists since it was pinpointed in the brain about 30 years ago. Now, a researcher at the University of Calgary is getting a little bit closer to understanding how it ticks. Dr. Michael Antle, a neuroscientist in the U of C's Department of Psychology, has conclusively shown that the 20,000 cells are organized in a complex network of groups that perform different functions – contrary to the previously held belief that each cell did the same thing. Antle, an emerging leader in the field, has two new papers on the subject: one is featured on the March cover of the prestigious Trends in Neurosciences, and another is due out in a forthcoming issue of the Journal of Neurosciences. "There are enormous health, safety and economic benefits to figuring out how the circadian clock works," Antle says. "We are probably still at least 10 years away from developing a pill that could reset your circadian clock to eliminate jet lag, but this new perspective in how the cells are organized definitely improves our understanding."

Related chapters from BP7e: Chapter 14: Biological Rhythms, Sleep, and Dreaming
Related chapters from MM:Chapter 10: Biological Rhythms and Sleep
Link ID: 6993 - Posted: 06.24.2010

HOUSTON, – If you crammed for tests by pulling 'all nighters' in school, ever wonder why your memory is now a bit foggy on what you learned? A University of Houston professor may have the answer with his research on the role of circadian rhythms in long-term learning and memory. Arnold Eskin, the John and Rebecca Moores Professor of Biology and Biochemistry at UH, was recently awarded two grants totaling $2,472,528 from the National Institutes of Health (NIH) to continue pursuing his investigations of memory formation and the impact of the biological clock on learning and memory. Scientists have known for a while that the brain's biological (or circadian) clock influences natural body cycles, such as sleep and wakefulness, metabolic rate and body temperature. New research from Eskin suggests the circadian clock also may regulate the formation of memory at night. This new research focuses on "Circadian Modulation of Long-term Memory Formation" and "Long-term Regulation of Glutamate Uptake in Aplysia," with NIH funding to be disbursed over four years. "There is a lot of research going on in memory," Eskin said. "How do we remember things given that we don't have a camera in our brain to record events? What changes take place in our brains that allow us to remember? These grants are about fundamental learning and memory and about modulation of memory."

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: 6898 - Posted: 06.24.2010

Researchers have discovered that individual fibroblast cells contain independent, self-sustaining circadian (ca. 24 hr) clocks. Circadian clocks are important for synchronizing many physiological and behavioral processes to the day/night cycle. For decades it has been known that a tiny cluster of brain cells known as the suprachiasmatic nucleus (SCN) is required for expression of circadian rhythms in mammals. When clock genes were identified in the late '90s, they were found to be expressed rhythmically not only in SCN but also in many other tissues. Some of these studies used the firefly luciferase gene, introduced into cells with regulatory elements from a clock gene, so that cell cultures emitted light with a circadian rhythm. However, peripheral tissue rhythms tended diminish after a few cycles in culture, suggesting that they might depend on the central nervous system's SCN to drive them. In the new work, performed by researchers at The Scripps Research Institute and Northwestern University, Dr. David Welsh and colleagues used bioluminescence imaging to monitor circadian rhythms of clock gene expression from individual rat or mouse fibroblasts. Robust rhythms of single cells persisted without diminishing for at least 1–2 weeks in culture. Cells were partially synchronized by medium change at the start of an experiment, but because of different circadian periods drifted out of phase after several days, leading the ensemble rhythm to diminish. Thus, even cells outside the brain contain bona fide circadian clocks.

Related chapters from BP7e: Chapter 14: Biological Rhythms, Sleep, and Dreaming
Related chapters from MM:Chapter 10: Biological Rhythms and Sleep
Link ID: 6474 - Posted: 06.24.2010

CHICAGO – Patients with deficit schizophrenia, a subtype of schizophrenia characterized by "negative" symptoms, such as blunted speech and expression, lack of emotional response, and apathy, are more likely to have been born in the summer months, according to an article in the October issue of The Archives of General Psychiatry, one of the JAMA/Archives journals. According to the article, winter birth was reported to be a risk factor for schizophrenia in 1929. Clinical aspects of patients with schizophrenia born in the winter include paranoia and a more benign course of illness. Additionally, the clinical features associated with winter birth are different from patients with deficit schizophrenia, defined by the presence of negative symptoms, including inability to experience pleasure, lack of interest in socializing, speech deficits, blunted emotional response, poor eye contact, and more severe course of illness. Nondeficit schizophrenia is characterized by symptoms including hallucinations, incoherent thinking, and prominent delusions. Erick Messias, M.D., M.P.H., of The Johns Hopkins University, Baltimore, Md., and colleagues analyzed published and unpublished data from the northern hemisphere on studies of season of birth with information on schizophrenia and its subtype- deficit or nondeficit. A total of 1,594 patients were included in the nine studies examined.

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: 6194 - Posted: 06.24.2010

(Santa Barbara, Calif.) –– Our biological clock, or circadian rhythm, is upset by travelling across time zones, but very soon the body adjusts to the new day/night cycle. New studies of the computational models of the circadian rhythm of fruit flies show that the internal clock is robust, that is, not easily perturbed. These studies may eventually lead to greater understanding of human jet lag as well as human disease states. Engineers at the University of California, Santa Barbara's new Institute for Collaborative Biotechnologies and the Max Planck Institute (MPI) for Dynamics of Complex Technical Systems, in Magdeburg, Germany have analyzed the mechanism of genetic circuits by which the fruit fly regulates its circadian rhythm. The results are published in the August 30 Proceedings of the National Academies of Science. The mechanism controlling the biological clock generates a complicated dynamic behavior, oscillating back and forth and making it difficult to study, but also making it a good prototypical dynamic cellular system. The circadian rhythm of the fruit fly is a regulatory system that takes its cues from the sun. When the sun rises it affects the light-sensitive neurons of the brain of the fruit fly, setting off reactions of proteins at a certain rate depending on the amount of light. The reactions set the clock. There are key proteins and two key feedback loops involved, making the system a hierarchical control scheme, a design tool often used in engineering.

Related chapters from BP7e: Chapter 14: Biological Rhythms, Sleep, and Dreaming
Related chapters from MM:Chapter 10: Biological Rhythms and Sleep
Link ID: 6045 - Posted: 06.24.2010

Development of a molecular timetable by analysis of circadian gene expression – A look inside a wristwatch reveals that timekeeping is a complex affair, involving the coordination of mechanical parts providing the impulses and feedback needed to achieve precisely recurring movement. Biological clocks are equally complex, regulated by a network of genes and transcriptional factors that interact to stabilize the rhythms of numerous physiological systems. Unlike the wristwatch, however, there is no visible readout or display showing an individual's body time, a lack which has stood as one of the major barriers to realizing the promise of chronotherapy, which seeks to deliver drug treatments at optimal body times. A new study by Hiroki R. Ueda (Laboratory for Systems Biology, RIKEN Center for Developmental Biology; Kobe, Japan) and colleagues has provided proof of principle that just such a display of individual body time may one day possible. The report, published in the August 3 issue of the Proceedings of the National Academy of Sciences, describes the analysis of the expression of more than 100 time-indicating genes in the mouse. The results of this genome-wide study enabled the authors to develop a "molecular timetable" that provides an accurate representation of the animal's body time based on the sampling of gene expression levels at a single point in time.

Related chapters from BP7e: Chapter 14: Biological Rhythms, Sleep, and Dreaming
Related chapters from MM:Chapter 10: Biological Rhythms and Sleep
Link ID: 5995 - Posted: 06.24.2010

HANOVER, NH – While picking apart the genetic makeup of the plant Arabidopsis, two Dartmouth researchers made a startling discovery. They found that approximately 36 percent of its genome is potentially regulated by the circadian clock, which is three and a half times more than had previously been estimated. The study, which appears in the June issue of Plant Physiology, was conducted by C. Robertson McClung, Dartmouth professor of biological sciences, and Todd Michael, a former Dartmouth graduate student who is now a postdoctoral fellow at the Salk Institute in La Jolla, Calif. Their research on circadian-controlled genes contributes to efforts to help improve plant productivity and can possibly lead to growing crops that are more resistant to stressful soil or climate conditions. McClung and Michael used a technique called "gene trapping" or "enhancer trapping" to measure how much mRNA is produced or synthesized by large sections in the genome. According to McClung, a great deal of gene regulation occurs in the gene's ability to synthesize mRNA, which then is translated into proteins that perform the critical metabolic activities of a cell.

Related chapters from BP7e: Chapter 14: Biological Rhythms, Sleep, and Dreaming
Related chapters from MM:Chapter 10: Biological Rhythms and Sleep
Link ID: 3982 - Posted: 06.24.2010

COLLEGE STATION, – It may be only pond scum, the sort of green gunk that clogs lakes and floats in on the tides. But inside, a clock is quietly ticking. Even this lowly one-celled bacterium has a biological clock, the sophisticated internal timing device that governs the daily rhythms of people, animals and plants, says Susan Golden, a biology professor at Texas A&M University. The university’s Department of Biology is a leader in unraveling the mysteries of biological clocks, research that eventually could lead to cures for sleep and mood disorders, as well as other medical problems. Golden and her colleagues also study the biological clocks of birds, rats and fungi, but it was the bacterium known as Synechococcus elongatus that yielded the latest revelation: the first structural model of part of the clockworks.

Related chapters from BP7e: Chapter 14: Biological Rhythms, Sleep, and Dreaming
Related chapters from MM:Chapter 10: Biological Rhythms and Sleep
Link ID: 3375 - Posted: 06.24.2010

WEST LAFAYETTE, Ind. – The biological clock – timekeeper for virtually every activity within living things, from sleep patterns to respiration – is a single protein, Purdue University researchers report. The husband and wife team of D. James and Dorothy Morré has discovered this protein, which is responsible for setting the length of periods of activity and inactivity within cells. If the protein is altered, an organism's body will experience "days" of different length – ranging from 22 to 42 hours in length in some cases. The discovery could have far-reaching implications for medicine. "We can now begin to understand the complex chain of events that connect the clock to events in the body," said James Morré ;, Dow Distinguished Professor of Medicinal Chemistry in Purdue's School of Pharmacy and Pharmacal Sciences. "Since the clock affects nearly every bodily activity, this discovery holds myriad potential applications, from minimizing jet lag to determining when best to administer cancer drugs."

Related chapters from BP7e: Chapter 14: Biological Rhythms, Sleep, and Dreaming
Related chapters from MM:Chapter 10: Biological Rhythms and Sleep
Link ID: 3268 - Posted: 06.24.2010

New method shows electrical activity to be a central component of molecular clocks governing circadian rhythms Electrical excitability is harnessed by the body for a myriad of physiological functions including communication between nerve cells and regulation of heartbeat. Diseases caused by pathological electrical over-excitability, such as epilepsy and cardiac arrhythmia, can be catastrophic. A team of biologists at New York University has discovered a new and efficient method of “silencing” neurons – effectively blocking their electrical excitability – by introducing a new twist on a standard genetic technique. The new method sheds light on the central role electrical activity in neurons plays in governing the body’s circadian rhythms, or internal clock. It may also help in the future development of more effective treatments for diseases that are caused by aberrant electrical activity in neurons and other electrically excitable cells and tissues. The findings were published in the May 17 issue of Cell. Led by Todd C. Holmes, Assistant Professor of Biology at NYU, the team developed an experimental test case to control the electrical activity of a specific neural circuit in Drosophila by directing the expression of modified potassium channel genes. Potassium channels act as the “brakes” for electrical excitability.

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: 2085 - Posted: 06.24.2010

PHILADELPHIA – Working with sleep-deprived fruit flies, scientists at the University of Pennsylvania have uncovered the first molecular pathway, in any species, implicated in the shift between rest and wakefulness. The findings, from a team led by Joan C. Hendricks of Penn's Center for Sleep and Respiratory Neurobiology, are reported in the November issue of the journal Nature Neuroscience. The work indicates that a Drosophila melanogaster gene known as CREB – evolutionarily conserved in species from flies to humans – plays a role in rest's rejuvenating effects, apparently permitting sustained wakefulness. Anyone who's ever pulled an all-nighter knows by the next morning that sleep is essential, and sleep's status as a behavior found in organisms ranging from fruit flies to frogs to humans underscores its importance as a biological process. But 50 years after the discovery of REM sleep, scientists still know little, on a molecular level, about why sleep is needed and the exact benefits conferred by a daily period of rest

Related chapters from BP7e: Chapter 14: Biological Rhythms, Sleep, and Dreaming
Related chapters from MM:Chapter 10: Biological Rhythms and Sleep
Link ID: 1022 - Posted: 06.24.2010

Neuroscientists at Jefferson Medical College have clarified how the human eye uses light to regulate melatonin production, and in turn, the body's biological clock. They have discovered what appears to be a fifth human "photoreceptor," and which is the main one to regulate the biological – and non-visual – effects of light on the body. They have identified a novel photopigment in the human eye responsible for reacting to light and controlling the production of melatonin, which plays an important role in the body's circadian rhythms. They also discovered that wavelengths of light in the blue region of the visible spectrum are the most effective in controlling melatonin production. ©2001 Thomas Jefferson University Hospital

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: 429 - Posted: 06.24.2010

Charles Q. Choi Networks of brain cells in a petri dish can be trained to keep time like hourglasses, a new study says. The discovery may help scientists reveal how our brains track time, an ability fundamental to how humans interact with each other and the world. It's also key to how we recognize speech patterns and song rhythms.cn "One issue that's been long debated regarding timing is whether there's a central clock in the brain or whether timing is a general ability in many different circuits of the brain," said study leader Dean Buonomano, a neuroscientist at University of California, Los Angeles. Buonomano and colleagues kept networks of rat brain cells alive in petri dishes and stimulated them with two electrical pulses separated by intervals ranging from a twentieth of a second to a half-second in length. After the cell networks received two hours of "training," a single electrical pulse was given to them to see how the cells would react. In networks trained with short intervals, the communication between cells lasted for only a short while—say, 50 to 100 milliseconds in networks trained on 50-millisecond intervals. However, in networks trained with long intervals, network activity lasted for much longer, according to the study, published June 13 in Nature Neuroscience. When networks trained on half-second intervals were probed, the networks essentially talked to each other for 500 to 600 milliseconds. © 1996-2010 National Geographic Society

Related chapters from BP7e: Chapter 14: Biological Rhythms, Sleep, and Dreaming
Related chapters from MM:Chapter 10: Biological Rhythms and Sleep
Link ID: 14179 - Posted: 06.24.2010

By Robert Roy Britt The moon holds a mystical place in the history of human culture, so it's no wonder that many myths — from werewolves to induced lunacy to epileptic seizures — have built up regarding its supposed effects on us. "It must be a full moon," is a phrase heard whenever crazy things happen and is said by researchers to be muttered commonly by late-night cops, psychiatry staff and emergency room personnel. It's been a long time since the Big Cheese revealed any new secrets as important as this week's announcement that traces of water exist all across its surface. Coincidentally, a study this week found zero connection between the full moon and surgery outcomes. In fact a host of studies over the years have aimed at teasing out any statistical connection between the moon — particularly the full moon — and human biology or behavior. The majority of sound studies find no connection, while some have proved inconclusive, and many that purported to reveal connections turned out to involve flawed methods or have never been reproduced. Reliable studies comparing the lunar phases to births, heart attacks, deaths, suicides, violence, psychiatric hospital admissions and epileptic seizures, among other things, have over and over again found little or no connection. © 2009 Space.com

Related chapters from BP7e: Chapter 14: Biological Rhythms, Sleep, and Dreaming
Related chapters from MM:Chapter 10: Biological Rhythms and Sleep
Link ID: 13305 - Posted: 06.24.2010

By Siri Carpenter Early birds may get the best worms—or at least the best garage sale deals—but they also tire out more quickly than night owls do. In a new study researchers Christina Schmidt and Philippe Peigneux, both at the University of Liège in Belgium, and their colleagues first asked 16 extreme early risers and 15 extreme night owls to spend a week following their natural sleep schedule. Then subjects spent two nights in a sleep lab, where they again followed their preferred sleep patterns and underwent cognitive testing twice daily while in a functional MRI scanner. An hour and a half after waking, early birds and night owls were equally alert and showed no difference in attention-related brain activity. But after being awake for 10 and a half hours, night owls had grown more alert, performing better on a reaction-time task requiring sustained attention and showing increased activity in brain areas linked to attention. More important, these regions included the suprachiasmatic area, which is home to the body’s circadian clock. This area sends signals to boost alertness as the pressure to sleep mounts. Unlike night owls, early risers didn’t get this late-day lift. Peigneux says faster activation of sleep pressure appears to prevent early birds from fully benefiting from the circadian signal, as evening types do. © 1996-2009 Scientific American Inc.

Related chapters from BP7e: Chapter 14: Biological Rhythms, Sleep, and Dreaming
Related chapters from MM:Chapter 10: Biological Rhythms and Sleep
Link ID: 13268 - Posted: 06.24.2010

By Janet Raloff To stay healthy, the body needs its zzz’s. But independent of slumber, human health also appears to require plenty of darkness — especially at night. Or so suggests a pair of new cancer studies. One found that among postmenopausal women, the lower the overnight production of melatonin — a brain hormone secreted at night, especially during darkness — the higher the incidence of breast cancer. The second study correlated elevated prostate cancer incidence around the world with places that have the brightest signatures of light in satellite imagery. Trends seen in both studies bolster animal data indicating that natural nighttime peaks in blood concentrations of melatonin, which tend to occur during sleep, depress the growth of the hormonally sensitive cancers. Light will depress the body’s natural secretion of that hormone, whether someone is awake or asleep. In 2001, Eva S. Schernhammer of Brigham and Women's Hospital in Boston and her colleagues found an elevated risk of breast cancer among women who worked night shifts. The data, gleaned from participants in the long-running Nurses’ Health Study, fit with the idea that the light encountered while working nocturnal hours would have suppressed the women’s melatonin production. © Society for Science & the Public 2000 - 2009

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: 12486 - Posted: 06.24.2010

Rachel Courtland Does the body make sure we're awake when it's time to eat?PunchstockYour stomach may truly have a mind of its own. A tiny area of the brain may switch sleep schedules to match up with mealtimes. It's been known for a long time that nocturnal creatures such as mice and bats flip their sleep schedules if food is only available during the day. But finding the parts of the brain responsible for the switch has proved difficult. In a paper published today in Science 1, a team led by Clifford Saper from Harvard Medical School in Boston, Massachusetts suggests they have found the region of the brain responsible for the sleep-rhythm adjustment — a clump of cells known as the dorsomedial hypothalamic nucleus (DMH). This region sits close to the area of the brain that manages ordinary circadian responses to light and dark. The study shows that mice lacking a particular gene that acts in the DMH do not adjust to changes in feeding schedule. Reinstating the gene restored the behaviour. But some researchers in the field have serious concerns about the work. “On the face of it, it’s almost the final nail in saying DMH is the pacemaker, but under the surface there are people who strongly disagree,” says neuroscientist Masashi Yanagisawa of University of Texas Southwestern Medical Center in Dallas, who was not involved in the work. © 2008 Nature Publishing Group

Related chapters from BP7e: Chapter 14: Biological Rhythms, Sleep, and Dreaming
Related chapters from MM:Chapter 10: Biological Rhythms and Sleep
Link ID: 11657 - Posted: 06.24.2010

James Owen Those who struggle to get out of bed in the morning may be able to hold their genes responsible, new research suggests. Scientists have discovered that a person's waking habits are mirrored by body cells that are equipped with their own daily alarm clocks. The work represents the first internal look at the biological clocks of those suffering from sleeping disorders, said study leader Steven A. Brown of the Institute for Pharmacology and Toxicology at the University of Zurich, Switzerland. "One of the big surprises was that so much of our daily behavior was genetically encoded," Brown said. "The idea that skin cells are telling us anything about our behavior was, for me, quite fascinating," he added. The study investigated the circadian rhythm—the brain-controlled phenomenon that governs various body functions over a 24-hour period—of extreme late and early risers. Suitable volunteers were recruited by the study team using TV advertisements shown between 3 a.m. and 4 a.m. "We got both our early types and our late types that way," Brown said. "Some had not yet gone to bed, while others were already up." Skin cells taken from the volunteers were cultured in the lab and injected with a bioluminescence gene found in fireflies. © 1996-2008 National Geographic Society

Related chapters from BP7e: Chapter 14: Biological Rhythms, Sleep, and Dreaming
Related chapters from MM:Chapter 10: Biological Rhythms and Sleep
Link ID: 11295 - Posted: 06.24.2010

CBC News Cockroaches, like humans, have dramatic daily variations in their ability to learn, say biologists at Vanderbilt University in Nashville. More pointedly, cockroaches could use a strong cup of coffee in the morning, but appear to need no boost in the evening, according to their study, published this week in the Proceedings of the National Academy of Sciences. Professor Terry Page holds one of the cockroaches that he used in his research. (Daniel Dubois, Vanderbilt University) "This is the first example of an insect whose ability to learn is controlled by its biological clock," Terry Page, professor of biological sciences, said in a release. Most studies on learning and circadian rhythms have focused on mammals. For example, recent experiments with humans have found that people's ability to acquire new information is reduced when their biological clocks are disrupted. In the current study, the researchers taught individual cockroaches to associate peppermint — a scent they normally find slightly distasteful — with sugar water, causing them to favour it over vanilla, a scent they like very much. The researchers trained individual cockroaches at different times in the 24-hour day/night cycle and then tested them to see how long they remembered the association. © CBC 2007

Related chapters from BP7e: Chapter 14: Biological Rhythms, Sleep, and Dreaming
Related chapters from MM:Chapter 10: Biological Rhythms and Sleep
Link ID: 10795 - Posted: 06.24.2010