Posts Tagged Note Materials

The longer you’re awake, the slower you get


ScienceDaily (July 27, 2012) — Anyone that has ever had trouble sleeping can attest to the difficulties at work the following day. Experts recommend eight hours of sleep per night for ideal health and productivity, but what if five to six hours of sleep is your norm? Is your work still negatively affected? A team of researchers at Brigham and Women’s Hospital (BWH) have discovered that regardless of how tired you perceive yourself to be, that lack of sleep can influence the way you perform certain tasks.

This finding is published in the July 26, 2012 online edition of The Journal of Vision.

“Our team decided to look at how sleep might affect complex visual search tasks, because they are common in safety-sensitive activities, such as air-traffic control, baggage screening, and monitoring power plant operations,” explained Jeanne F. Duffy, PhD, MBA, senior author on this study and associate neuroscientist at BWH. “These types of jobs involve processes that require repeated, quick memory encoding and retrieval of visual information, in combination with decision making about the information.”

Researchers collected and analyzed data from visual search tasks from 12 participants over a one month study. In the first week, all participants were scheduled to sleep 10-12 hours per night to make sure they were well-rested. For the following three weeks, the participants were scheduled to sleep the equivalent of 5.6 hours per night, and also had their sleep times scheduled on a 28-hour cycle, mirroring chronic jet lag. The research team gave the participants computer tests that involved visual search tasks and recorded how quickly the participants could find important information, and also how accurate they were in identifying it. The researchers report that the longer the participants were awake, the more slowly they identified the important information in the test. Additionally, during the biological night time, 12 a.m. -6 a.m., participants (who were unaware of the time throughout the study) also performed the tasks more slowly than they did during the daytime.

“This research provides valuable information for workers, and their employers, who perform these types of visual search tasks during the night shift, because they will do it much more slowly than when they are working during the day,” said Duffy. “The longer someone is awake, the more the ability to perform a task, in this case a visual search, is hindered, and this impact of being awake is even stronger at night.”

While the accuracy of the participants stayed the fairly constant, they were slower to identify the relevant information as the weeks went on. The self-ratings of sleepiness only got slightly worse during the second and third weeks on the study schedule, yet the data show that they were performing the visual search tasks significantly slower than in the first week. This finding suggests that someone’s perceptions of how tired they are do not always match their performance ability, explains Duffy.

This research was supported by NIH grant P01 AG09975 and was conducted in the BWH CCI, part of the Harvard Catalyst Clinical and Translational Science Center (UL1 RR025758-01), formerly a GCRC (M01RR02635). Development and implementation of the visual search task was supported in part by NIH grant R21 AT002571. JFD was supported in part by the BWHBRI Fund to Sustain Research Excellence; MM was supported by fellowships from the La-Roche and Novartis Foundations (Switzerland) and Jazz Pharmaceuticals (USA); SWC was supported in part by a fellowship from the Natural Sciences and Engineering Research Council of Canada.

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The above story is reprinted from materials provided by Brigham and Women’s Hospital.

Note: Materials may be edited for content and length. For further information, please contact the source cited above.


Journal Reference:

  1. Marc Pomplun, Edward J. Silva, Joseph M. Ronda, Sean W. Cain, Mirjam Y. Münch, Charles A. Czeisler, and Jeanne F. Duffy. The effects of circadian phase, time awake, and imposed sleep restriction on performing complex visual tasks: Evidence from comparative visual search. The Journal of Vision, July 26, 2012 DOI: 10.1167/12.7.14

Note: If no author is given, the source is cited instead.

Disclaimer: This article is not intended to provide medical advice, diagnosis or treatment. Views expressed here do not necessarily reflect those of ScienceDaily or its staff.

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Do ovaries continue to produce eggs during adulthood?


ScienceDaily (July 26, 2012) — A compelling new genetic study tracing the origins of immature egg cells, or ‘oocytes’, from the embryonic period throughout adulthood adds new information to a growing controversy. The notion of a “biological clock” in women arises from the fact that oocytes progressively decline in number as females get older, along with a decades-old dogmatic view that oocytes cannot be renewed in mammals after birth.

After careful assessment of data from a recent study published in PLoS Genetics, scientists from Massachusetts General Hospital and the University of Edinburgh argue that the findings support formation of new eggs during adult life; a topic that has been historically controversial and has sparked considerable debate in recent years.

Eggs are formed from progenitor germ cells that exit the mitotic cycle, thereby ending their ability to proliferate through cell division, and subsequently enter meiosis, a process unique to the formation of eggs and sperm which removes one half of the genetic material from each type of cell prior to fertilization.

While traditional thinking has held that female mammals are born with all of the eggs they will ever have, newer research has demonstrated that adult mouse and human ovaries contain a rare population of progenitor germ cells called oogonial stem cells capable of dividing and generating new oocytes. Using a powerful new genetic tool that traces the number of divisions a cell has undergone with age (its ‘depth’) Shapiro and colleagues counted the number of times progenitor germ cells divided before becoming oocytes; their study was published in PLoS Genetics in February this year.

If traditional thinking held true, all divisions would have occurred prior to birth, and thus all oocytes would exhibit the same depth regardless of age. However, the opposite was found — eggs showed a progressive increase in depth as the female mice grew older.

In their assessment of the work by Shapiro and colleagues — published recently in a PLoS Genetics Perspective article — reproductive biologists Dori Woods, Evelyn Telfer and Jonathan Tilly conclude that the most plausible explanation for these findings is that progenitor germ cells in ovaries continue to divide throughout reproductive life, resulting in production of new oocytes with greater depth as animals age.

Although these investigations were performed in mice, there is emerging evidence that oogonial stem cells are also present in the ovaries of reproductive-age women, and these cells possess the capacity, like their mouse counterparts, to generate new oocytes under certain experimental conditions. While more work is needed to settle the debate over the significance of oocyte renewal in adult mammals, Woods and colleagues emphasize that “the recent work of Shapiro and colleagues is one of the first reports to offer experimental data consistent with a role for postnatal oocyte renewal in contributing to the reserve of ovarian follicles available for use in adult females as they age.”

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The above story is reprinted from materials provided by Public Library of Science.

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Journal Reference:

  1. Woods DC, Telfer EE, Tilly JL. Oocyte Family Trees: Old Branches or New Stems? PLOS Genet, 2012 DOI: 10.1371/journal.pgen.1002848

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Disclaimer: This article is not intended to provide medical advice, diagnosis or treatment. Views expressed here do not necessarily reflect those of ScienceDaily or its staff.

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Modeling of new enzymes helps develop therapies for cocaine abuse


ScienceDaily (July 26, 2012) — Researchers from the University of Kentucky have designed and discovered a series of highly efficient enzymes that effectively metabolize cocaine. These high-activity cocaine-metabolizing enzymes could potentially prevent cocaine from producing physiological effects, and could aid in the treatment of drug dependency.

The results of this study by Chang-Guo Zhan et al are published in the journal PLOS Computational Biology.

The effectiveness of the enzymes’ work was evaluated through modeling cocaine pharmacokinetics, the study of the body’s action on administered external substances, such as cocaine, when the enzyme exists in the body. As there is no FDA-approved anti-cocaine medication, the medical and social consequences of cocaine abuse have made the development of anti-cocaine medication a high priority.

Administration of an enzyme to enhance cocaine metabolism has been recognized as a promising treatment strategy for overdose and abuse. A remarkable feature of the enzyme-based therapeutic approach is that one enzyme molecule can degrade many thousands of drug molecules per minute.

This pharmacokinetic modelling is a crucial step of enzyme-based therapy development for cocaine abuse. Furthermore, the general insights of the research should also be valuable for future development of an enzyme therapy for any addictive drug, as the general methodology of the modelling may be used to develop valuable models for evaluating the effectiveness of metabolic enzymes in detoxifying other drugs.

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The above story is reprinted from materials provided by Public Library of Science.

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Journal Reference:

  1. Zheng F, Zhan C-G. Modeling of Pharmacokinetics of Cocaine in Human Reveals the Feasibility for Development of Enzyme Therapies for Drugs of Abuse. PLoS Comput Biol, 2012 DOI: 10.1371/journal.pcbi.1002610

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Disclaimer: This article is not intended to provide medical advice, diagnosis or treatment. Views expressed here do not necessarily reflect those of ScienceDaily or its staff.

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Decoding the secrets of balance


ScienceDaily (July 26, 2012) — If you have ever looked over the edge of a cliff and felt dizzy, you understand the challenges faced by people who suffer from symptoms of vestibular dysfunction such as vertigo and dizziness. There are over 70 million of them in North America. For people with vestibular loss, performing basic daily living activities that we take for granted (e.g. dressing, eating, getting in and out of bed, getting around inside as well as outside the home) becomes difficult since even small head movements are accompanied by dizziness and the risk of falling.

We’ve known for a while that a sensory system in the inner ear (the vestibular system) is responsible for helping us keep our balance by giving us a stable visual field as we move around. And while researchers have already developed a basic understanding of how the brain constructs our perceptions of ourselves in motion, until now no one has understood the crucial step by which the neurons in the brain select the information needed to keep us in balance.

The way that the brain takes in and decodes information sent by neurons in the inner ear is complex. The peripheral vestibular sensory neurons in the inner ear take in the time varying acceleration and velocity stimuli caused by our movement in the outside world (such as those experienced while riding in a car that moves from a stationary position to 50 km per hour). These neurons transmit detailed information about these stimuli to the brain (i.e. information that allows one to reconstruct how these stimuli vary over time) in the form of nerve impulses.

Scientists had previously believed that the brain decoded this information linearly and therefore actually attempted to reconstruct the time course of velocity and acceleration stimuli. But by combining electrophysiological and computational approaches, Kathleen Cullen and Maurice Chacron, two professors in McGill University’s Department of Physiology, have been able to show for the first time that the neurons in the vestibular nuclei in the brain instead decode incoming information nonlinearly as they respond preferentially to unexpected, sudden changes in stimuli.

It is known that representations of the outside world change at each stage in this sensory pathway. For example, in the visual system neurons located closer to the periphery of the sensory system (e.g. ganglion cells in the retina) tend to respond to a wide range of sensory stimuli (a “dense” code), whereas central neurons (e.g. in the primary visual cortex at the back of the head tend to respond much more selectively (a “sparse” code). Chacron and Cullen have discovered that the selective transmission of vestibular information they were able to document for the first time occurs as early as the first synapse in the brain. “We were able to show that the brain has developed this very sophisticated computational strategy to represent sudden changes in movement in order to generate quick accurate responses and maintain balance,” explained Prof. Cullen. “I keep describing it as elegant, because that’s really how it strikes me.”

This kind of selectivity in response is important for everyday life, since it enhances the brain’s perception of sudden changes in body posture. So that if you step off an unseen curb, within milliseconds, your brain has both received the essential information and performed the sophisticated computation needed to help you readjust your position. This discovery is expected to apply to other sensory systems and eventually to the development of better treatments for patients who suffer from vertigo, dizziness, and disorientation during their daily activities. It should also lead to treatments that will help alleviate the symptoms that accompany motion and/or space sickness produced in more challenging environments.

The research was conducted by Corentin Massot a Postdoctoral fellow in the Department of Physiology, and Adam Schneider a Ph.D. Student in the Department of Physics.

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The above story is reprinted from materials provided by McGill University.

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Journal Reference:

  1. Corentin Massot, Adam D. Schneider, Maurice J. Chacron, Kathleen E. Cullen. The Vestibular System Implements a Linear–Nonlinear Transformation In Order to Encode Self-Motion. PLoS Biology, 2012; 10 (7): e1001365 DOI: 10.1371/journal.pbio.1001365

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Disclaimer: This article is not intended to provide medical advice, diagnosis or treatment. Views expressed here do not necessarily reflect those of ScienceDaily or its staff.

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