Thursday, August 20, 2009

'BRAIN EXERCISES' MAY DELAY MEMORY DECLINE IN DEMENTIA

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People who engage in activities that exercise the brain, such as reading, writing, and playing card games, may delay the rapid memory decline that occurs if they later develop dementia, according to a study published in the August 4, 2009, print issue of Neurology®, the medical journal of the American Academy of Neurology.

The study involved 488 people age 75 to 85 who did not have dementia at the start of the study. They were followed for an average of five years; during that time 101 of the people developed dementia.

At the beginning of the study, people reported how often they participated in six leisure activities that engage the brain: reading, writing, doing crossword puzzles, playing board or card games, having group discussions, and playing music. For each activity, daily participation was rated at seven points, several days a week was rated at four points, and weekly participation was rated at one point.

The average was seven points total for those who later developed dementia, meaning they took part in one of the six activities each day, on average. Ten people reported no activities, and 11 reported only one activity per week.

The researchers then looked at the point when memory loss started accelerating rapidly for the participants. They found that for every additional activity a person participated in, the onset of rapid memory loss was delayed by 0.18 years.

"The point of accelerated decline was delayed by 1.29 years for the person who participated in 11 activities per week compared to the person who participated in only four activities per week," said study author Charles B. Hall, PhD, of Albert Einstein College of Medicine in Bronx, NY.

The results remained valid after researchers factored in the education level of the participants. "The effect of these activities in late life appears to be independent of education," Hall said. "These activities might help maintain brain vitality. Further studies are needed to determine if increasing participation in these activities could prevent or delay dementia."

American Academy of Neurology

BRAIN'S CENTER FOR PERCEIVING 3-D MOTION IS IDENTIFIED

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Ducking a punch or a thrown spear calls for the power of the human brain to process 3-D motion, and to perceive an object (whether it's offensive or not) moving in three dimensions is critical to survival. It also leads to a lot of fun at 3-D movies.

Neuroscientists have now pinpointed where and how the brain processes 3-D motion using specially developed computer displays and an fMRI (functional magnetic resonance imaging) machine to scan the brain.

They found, surprisingly, that 3-D motion processing occurs in an area in the brain—located just behind the left and right ears—long thought to only be responsible for processing two-dimensional motion (up, down, left and right).

This area, known simply as MT+, and its underlying neuron circuitry are so well studied that most scientists had concluded that 3-D motion must be processed elsewhere. Until now.

"Our research suggests that a large set of rich and important functions related to 3-D motion perception may have been previously overlooked in MT+," says Alexander Huk, assistant professor of neurobiology. "Given how much we already know about MT+, this research gives us strong clues about how the brain processes 3-D motion."

For the study, Huk and his colleagues had people watch 3-D visualizations while lying motionless for one or two hours in an MRI scanner fitted with a customized stereovision projection system.

The fMRI scans revealed that the MT+ area had intense neural activity when participants perceived objects (in this case, small dots) moving toward and away from their eyes. Colorized images of participants' brains show the MT+ area awash in bright blue.

The tests also revealed how the MT+ area processes 3-D motion: it simultaneously encodes two types of cues coming from moving objects.

There is a mismatch between what the left and right eyes see. This is called binocular disparity. (When you alternate between closing your left and right eye, objects appear to jump back and forth.)

For a moving object, the brain calculates the change in this mismatch over time.

Simultaneously, an object speeding directly toward the eyes will move across the left eye's retina from right to left and the right eye's retina from left to right.

"The brain is using both of these ways to add 3-D motion up," says Huk. "It's seeing a change in position over time, and it's seeing opposite motions falling on the two retinas."

That processing comes together in the MT+ area.

"Who cares if the tiger or the spear is going from side to side?" says Lawrence Cormack, associate professor of psychology. "The most important kind of motion you can see is something coming at you, and this critical process has been elusive to us. Now we are beginning to understand where it occurs in the brain."

(Photo: Brain rendering by Thadeus Czuba, Photo by Marsha Miller)

NATURAL BORN KILLERS - HOW THE BODY'S FRONTLINE IMMUNE CELLS DECIDE WHICH CELLS TO DESTROY

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The mechanism used by ‘Natural Killer’ immune cells in the human body to distinguish between diseased cells, which they are meant to destroy, and normal cells, which they are meant to leave alone, is revealed in new detail in research published today in PLoS Biology.

Understanding how this aspect of the body’s natural defences works could help medical researchers develop new ways of boosting these defences to treat disease.

The research was funded primarily by the Lister Institute for Preventative Medicine and the Medical Research Council, with additional support from the Biotechnology and Biological Sciences Research Council, the Royal Society and the Wellcome Trust.

Natural Killer (NK) cells – a type of white blood cell - are a major component of the human body’s innate immune system. Over 1,000 NK cells are found in every drop of blood. They provide a fast frontline defence against tumours, viruses and bacterial infections, by latching onto and killing cells in the human body that are cancerous or are infected with a virus or a bacterial pathogen.

On their journey round the human body NK cells regularly latch onto normal non-diseased cells too, before moving off, leaving them unharmed. Previously, the process by which NK cells made the right decision to kill or not kill another cell was unclear.

Now, a team of researchers from Imperial College London have used high speed microscopy imaging techniques to observe the NK cell decision making process in action. This has revealed striking differences in the behaviour of NK cells when interacting with healthy or diseased cells.

The outcome of the decision making process is determined by how receptors on the surface of the NK cell interact with proteins on the surface of the captured cell. Every NK cell has two types of surface receptors – activators, which turn the killing mechanism ‘on’ and inhibitors which turn the killing mechanism ‘off’.

Professor Davis and his colleagues discovered that if a captured cell is diseased or cancerous, it interacts with a large number of the NK cell’s activator receptors, which makes the NK cell stop dead in its tracks and spread out over the captured cell. During this spreading process the NK cell continuously reads the ‘on’ and ‘off’ signals from its surface contact with the captured cell. If the ‘on’ signals dominate, the NK cell remains in contact with the captured cell for a long time and eventually kills it.

Conversely if the captured cell is healthy, it interacts with more of the NK cell’s inhibitors – and fewer of its activators – meaning that the ‘off’ signals dominate and the ‘stopping and spreading’ process doesn’t occur, allowing the NK cell to quickly move off in search of a new target.

Principal investigator of the new study, Professor Dan Davis from Imperial College London’s Department of Life Sciences, explains: "Scientists have known for a long time that the proteins on the surface on Natural Killer cells are involved in answering the ‘to kill or not to kill?’ question, but we’ve not known exactly how these molecular cues are translated into the correct response. Our research has shown that information gleaned from its surface receptors tells the Natural Killer cell whether to stop patrolling and commence killing, or to move off quickly, and harmlessly, in search of another target."

Dr Fiona Culley, lead author of the study from the National Heart and Lung Institute at Imperial, says that finding out how NK cells use this process to sift out diseased cells from normal ones paints the clearest picture to date of how these cells do their vital work: "Considering that NK cells play such an important part in our immune response to cancer and disease, relatively little is known about their functionality – how exactly they work and how they interact with the cells they encounter inside us. This study adds significantly to our understanding of how Natural Killer cells distinguish between healthy and diseased cells."

The Biotechnology and Biological Sciences Research Council (BBSRC)

PILOT STUDY: WORKPLACE YOGA AND MEDITATION CAN LOWER FEELINGS OF STRESS

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Twenty minutes per day of guided workplace meditation and yoga combined with six weekly group sessions can lower feelings of stress by more than 10 percent and improve sleep quality in sedentary office employees, a pilot study suggests.

The study offered participants a modified version of what is known as mindfulness-based stress reduction (MBSR), a program established in 1979 to help hospital patients in Massachusetts assist in their own healing that is now in wide use around the world.

In this context, mindfulness refers in part to one’s heightened awareness of an external stressor as the first step toward relaxing in a way that can minimize the effects of that stress on the body.

While the traditional MBSR program practice takes up an hour per day for eight weeks supplemented by lengthy weekly sessions and a full-day retreat, the modified version developed at Ohio State University for this study was designed for office-based workers wearing professional attire.

The results of the pilot study are published in a recent issue of the journal Health Education & Behavior.

Participants attended one-hour weekly group meetings during lunch and practiced 20 minutes of meditation and yoga per day at their desks. After six weeks, program participants reported that they were more aware of external stressors, they felt less stressed by life events, and they fell asleep more easily than did a control group that did not experience the intervention.

“Because chronic stress is associated with chronic disease, I am focusing on how to reduce stress before it has a chance to contribute to disease,” said Maryanna Klatt, lead author of the study and an assistant professor of clinical allied medicine at Ohio State.

“My interest is to see whether or not we can get people to reduce their health care utilization because they’re less stressed. I want to deliver something low cost at the work site, something practical that can be sustained, that can help reduce health care costs,” Klatt said.

Klatt and colleagues are building on these preliminary findings and continuing to study the broader impact of the intervention in various populations, such as cancer survivors, intensive-care nurses and inner-city schoolchildren. In addition to gathering self-reported data from research participants, the scientists plan to collect biological samples to determine whether the intervention can lead to lower levels of stress hormones.

For the pilot study, the researchers recruited 48 adult office workers with body mass index scores lower than 30 who exercised less than 30 minutes on most days of the week. Half were randomized to the intervention and half were wait-listed to receive the intervention later. Forty-two people completed the study.

Those who received the intervention participated in weekly one-hour group sessions during which breathing, relaxation and gentle yoga movement were designed to coax participants toward a meditative state. Participants also discussed work-related stress. As part of the pursuit of mindfulness, they were coached to contemplate a specific topic in each session that explored their response to a specific type of stress over the past week.

“It doesn’t matter what the stress is, but how you change the way you perceive the stress,” Klatt noted. “I like to describe mindfulness as changing the way you see what’s already there. It’s a tool that teaches people to become aware of their options. If they can’t change the external events in their life, they can instead change the way they view the stress, which can make a difference in how they experience their day-to-day life.”

The weekly sessions were supplemented by 20 minutes each day of movement and meditation guided by verbal cues and music provided on compact discs that Klatt designed and recorded. The entire intervention lasted six weeks.

The study analyzed participants’ responses to the intervention using data from established research questionnaires that measured perceived stress, or the degree to which situations in life are considered stressful; a number of components of sleep quality; and what is called mindful attention awareness, which refers to how often a person is paying attention to and is aware of what is occurring in the present.

All participants completed the questionnaires before and after the intervention. Twenty-two adults completed the intervention. Their pre- and post-test results were compared to those reported by the 20 control participants.

Mindful attention awareness increased significantly and perceived stress decreased significantly among the intervention group when compared to the control group’s responses. Overall sleep quality increased in both groups, but three of seven components of sleep were more affected in the intervention group.

On average, mindfulness increased by about 9.7 percent and perceived stress decreased by about 11 percent among the group that experienced the intervention. These participants also reported that it took them less time to fall asleep, they had fewer sleep disturbances and they experienced less daytime dysfunction than did members of the non-intervention group.

The researchers also took saliva samples to test for the presence of cortisol, a stress hormone, but found no significant changes in average daily levels of the hormone over time for participants in both groups. Klatt said the design of this part of the pilot study could have affected the result, and the sample collection technique will be changed in subsequent studies.

Klatt said mindfulness-based stress reduction, developed by Jon Kabat-Zinn at the University of Massachusetts Medical Center, has been studied widely and determined to be useful in lowering symptoms ranging from depression and anxiety to chronic pain. But the time commitment required in the program makes it impractical for busy working professionals, and adding a stress-reduction class outside of work could add stress to these people, she said.

So Klatt set out to develop what she calls a “low dose” of the program that is suitable for the workplace and still offers stress-reduction benefits. She specifically scheduled weekly sessions during lunch to avoid interfering with work time or home time, and combined movement with verbal prompts and music that are cues for participants to relax.

“As I’ve been working on the program, I heard so many of the participants say they wish they had learned this earlier,” Klatt said.

Because the low-dose program remains a work-in-progress that is still under investigation, it is not available for public use, Klatt noted.

(Photo: OSU)

Ohio State University

NEW EVIDENCE SUPPORTS POSSIBILITY OF LIFE ON MARS

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The presence of perchlorates—a naturally occurring salt of perchloric acid—was detected in the polygon-patterned plains of northern Mars.

“No one expected to find perchlorates,” said Dr. John Hoffman, a member of the Phoenix Mars Lander research team and professor of physics at UT Dallas. Hoffman designed and built the spectrometer that definitively confirmed the presence of water on Mars. “It’s not yet been determined how this stuff was formed, but perchlorates store a great deal of energy that could have been a food source for tiny living organisms.”

Hoffman co-authored three articles related to the Martian surface in a recent issue of Science. The research articles examined detection of perchlorates and provided an overview of the Mars water discovery and the discovery of calcium carbonate.

“Discovering what the surface of Mars consists of is particularly fascinating,” Hoffman said. “We found calcium carbonate, or limestone, which precipitates out of water over time. Because we found water, we expected to find calcium carbonate, but the perchlorate was a big surprise. And what it means is that millions, or even a billion years ago, life could have existed on Mars. No one knows for sure at this time, but it’s possible.”

Hoffman said that while Mars is an extremely cold planet today, just a few tens of millions of years ago the planet’s axis of rotation of the planet was quite different. Mars pointed more directly toward the sun during Martian summers, and that could have boosted surface temperatures enough for life to flourish.

(Photo: UT Dallas)

UT Dallas

RODENT SIZE LINKED TO HUMAN POPULATION AND CLIMATE CHANGE

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You probably hadn't noticed -- but the head shape and overall size of rodents has been changing over the past century. A University of Illinois at Chicago ecologist has tied these changes to human population density and climate change.

The finding is reported by Oliver Pergams, UIC research assistant professor of biological sciences, in the July 31 issue of PLoS One.

Pergams said that such size-and-shape changes in mammals, occurring around the world in less than a century, are quite substantial.

He had done earlier studies on a century's worth of anatomic changes between two geographically isolated rodents -- Channel Island deer mice from coastal California and white-footed mice northwest of Chicago -- and noted fast change among both.

"I suspected they weren't unique examples," he said. "I wondered whether these changes were occurring elsewhere, whether they were global in nature, and what some of the causes may be."

Pergams examined specimen rodents from museums around the world, including the big collections held at Chicago's Field Museum and the Smithsonian in Washington. Altogether, he recorded more than 17,000 body and skull measurements from 1,300 specimens from 22 locations in Africa, the Americas and Asia. The animals were collected from 1892 to 2001, and Pergams compared those from before 1950 to those collected after.

He also compared specimens gathered from sparsely populated islands to those from the mainland, where human populations were denser.

Pergams found both increases and decreases in the 15 anatomic traits he measured, with changes as great as 50 percent over 80 years. Ten of the 15 traits were associated with changes in human population density, current temperature, or trends in temperature and precipitation.

"Rapid change, contrary to previous opinion, really seems to be happening quite frequently in a number of locations around the world," Pergams said. "There seem to be significant correlations with 'people-caused' parameters, such as population density and anthropologically-caused climate change."

While Pergams' study was by no means comprehensive, it was the first attempt of its kind to examine data on mammals from many global locations to find links between morphological change and variables such as population density and changing climate.

"Species can adapt quickly to rapid environmental changes -- quicker than many people have thought, especially for mammals," said Pergams. "Those mammals that can adapt quickly have a much higher chance to survive big environmental changes caused by humans. Understanding which species and populations have the greatest ability to change has a crucial impact on being able to conserve biodiversity."

University of Illinois

COLUMBIA RESEARCHERS LEAD RACE TO FIND DARK MATTER

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Inside a mountain range in central Italy, Columbia researchers are trying to solve one of the most pressing questions in modern physics: What is dark matter?

The riddle has obsessed astronomers and physicists since the 1930s, when Caltech professor Fritz Zwicky first predicted its existence. Because dark matter neither emits nor reflects light and cannot be directly observed, no one has ever proven that it exists; yet theories show it makes up as much as a quarter of the universe. Columbia physics professor Elena Aprile, with collaborators from universities around the world, including Rice University and UCLA, is leading the race to find and identify dark matter for the first time.

“Sometimes I think of dark matter as a mysterious woman with her face covered by one of those beautiful Venetian masks,” said Aprile, who is also co-director of Columbia’s Astrophysics Lab. “All of us experimentalists are driven by one desire: to uncover that face.”

Scientists first developed the theory of dark matter to explain how galaxies keep from breaking apart as they spin. Like merry-go-rounds, galaxies generate centripetal force as they rotate. Gravity is the glue that counteracts that force and holds stars and planets together, but there isn’t enough visible matter in the universe to generate the amount of gravity needed to keep galaxies from being torn to shreds. That’s why scientists believe there must be additional, unseen matter out there. Finding it will give them a deeper understanding of the laws of nature.

Aprile and many other physicists believe that dark matter is made up of WIMPS, or weakly interacting massive particles. As their name suggests, WIMPS very rarely bump into each other or into anything else; otherwise, scientists would have discovered them a long time ago.

Aprile and her colleagues are looking for WIMPS beneath 5,000 feet of rock in Italy’s Gran Sasso mountains in an experiment known as XENON. The project, which recently won $2.5 million of additional funding from the National Science Foundation, consists of a hatbox-sized container of liquid xenon—an element that occurs naturally in the atmosphere as a gas—sandwiched between two detectors. Should a dark matter particle come into contact with a xenon atom, it will trigger a flash of bluish light that the detectors will pick up. The particle is also expected to generate a small electrical charge—weaker than that of any other known radioactive particle. If one of the cameras registers such a charge, it will be a strong indication that Aprile’s team has found dark matter.

The Columbia researchers use xenon because it is one of the heaviest elements in the periodic table; at three times the density of water, it has many atoms per square kilogram, maximizing the chances that a WIMP will collide with it. “It’s like a densely woven fishing net,” said Rafael Lang, a postdoctoral research scientist in Aprile’s lab.

The experiment was set up underground to shield it from as many known atoms and particles as possible, including cosmic rays in the atmosphere. “The number of these cosmic rays keeps going down as you get deeper and deeper in the ground,” said Aprile, who travels frequently between New York and Gran Sasso. A coating of lead around the xenon vat keeps out X-rays and gamma rays; rock inside the mountain acts as a shield against muons, a type of heavy electron. “Gran Sasso is the best place in the world for doing this science,” she says.

The region is home to Italy’s Laboratori Nazionali del Gran Sasso, one of the world’s largest underground physics labs, which hosts a handful of dark matter experiments. Aprile’s experiment is recognized as a leader in the field because it is one of the largest and most sensitive, and it's expanding at the fastest rate. The new funding will allow her team to begin gathering data later this year and, soon, to expand the amount of xenon they use tenfold, to one ton. The experiment will run in phases through 2012.

(Photo: Guillaume Plante)

University of Columbia

EXTRATERRESTRIAL PLATINUM WAS STIRRED INTO THE EARTH

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A research program aimed at using platinum as an exploration guide for nickel has for the first time been able to put a time scale on the planet’s large-scale convection processes.

The research is reported in a Nature paper titled “Progressive mixing of meteoritic veneer into the early Earth’s deep mantle”.

Report author CSIRO Minerals Down Under Flagship researcher Dr Stephen Barnes said the study group collected a large body of data on the platinum content of lava flows called komatiites, which host some of the world’s major nickel deposits.

“We found that the oldest komatiites have the lowest platinum content,” Dr Barnes said.

“The platinum content gradually increases from about 3.5 billion years to 2.9 billion years ago.

“This tells us that the deep source where the komatiite came from, down near the boundary between the Earth’s core and mantle, was gradually gaining platinum over time”.

The paper’s authors now think they know why.

“When the Earth’s core formed, it took all the available platinum with it, leaving the mantle and crust with none,” Dr Barnes said.

“Following that, a steady rain of meteorites created the so-called Late Veneer – a thin surface layer of meteorite debris rich in platinum.”

With time through large-scale convection processes, which now cause plate tectonics, this material was stirred down into the interior of the Earth.

We are seeing the signal of that stirring, which took about 1.5 billion years to occur.

This is the first time a time scale has been put on the stirring, which has important implications for the people who study the dynamics of mantle processes and the mechanisms that cause plate tectonics, earthquakes and volcanoes.

Combined with some other work by the researchers on sister elements to platinum, iridium and osmium, we also now have a new framework for understanding the variations in isotopic ratios of osmium with time.

Osmium isotopes are widely used as tracers of mantle processes, but there has been a mismatch between signals from osmium and from other important isotopic tracer systems which has eluded explanation until now.

Co-authors Dr Marco Fiorentini and Dr Wolfgang Maier from the University of Western Australia are delighted that this is a completely academic outcome which came out of an industry-funded project.

“It is a nice example of an unexpected fundamental discovery arising from a practical applied science study and demonstrates the very positive collaborations that exist between CSIRO and the University of Western Australia,” Dr Fiorentini said.

(Photo: CSIRO)

CSIRO

SCARY ANCIENT SPIDERS REVEALED IN 3D MODELS, THANKS TO NEW IMAGING TECHNIQUE

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Scientists at Imperial College London have created detailed 3D computer models of two fossilised specimens of ancient creatures called Cryptomartus hindi and Eophrynus prestvicii, closely related to modern-day spiders. The study reveals some of the physical traits that helped them to hunt for prey and evade predators.

The researchers created their images by using a CT scanning device, which enabled them to take 3,000 x-rays of each fossil. These x-rays were then compiled into precise 3D models, using custom-designed software.

Both Cryptomartus hindi and Eophrynus prestivicii were around the size of a 50 pence piece and they roamed the Earth during the Carboniferous period, 359 – 299 million years ago. This was a time before the dinosaurs, when life was emerging from the oceans to live on land. During this period, the world’s continents were merging together near the equator to form one supercontinent and the first tropical rainforests were playing host to a diverse range of species.

Previous studies of the fossilised remains of Cryptomartus hindi allowed scientists to see some features of the creature, which had four pairs of legs and looked similar to a spider.

In the new study, the researchers' computer models reveal that Cryptomartus hindi's first two legs were angled towards the front of the body, which suggests that it used its legs to grab its prey before killing them. The researchers believe this find suggests the Cryptomartus hindi was an ambush predator, living in logs and fronds, waiting for prey such as insects to walk by before catching and killing them. This stance is seen in modern day crab spiders, which sit on the edge of flowers and wait for insects to land so that they can grab them.

The scientists also discovered that Cryptomartus hindi had ball-like growths at the base of its limbs, called coxal endites. The scientists believe the coxal endites could be an evolutionary hang-over from their last common ancestor, who probably used the growths at the base of their limbs to help them grind their food. These coxal endite-type growths can still be seen today in species such as horseshoe crabs, which use them to grind up their prey before pushing it into their backward-facing mouths.

The computer models also revealed that Cryptomartus hindi's mouth appendages, called pedipalps, had tiny ‘tarsal’ claws attached at the end to help the creature to manipulate its prey. These claws are seen in rare modern-day arachnids such as the Ricinulei. The researchers say that the existence of this common physical feature, shared by the Cryptomartus hindi and the Ricinulei, lends further weight to the theory that they are closely related.

The models also reveal new information about Eophrynus prestivicii. Previous studies of fossilised remains of this creature suggested that it could have hunted on the open forest floor. It had long legs that enabled it to run through leaf litter to chase, catch and kill its prey.

The new models reveal, for the first time, that Eophrynus prestivicii had defensive spikes on its back. The researchers say that the spikes may have been a defensive adaption by Eophrynus prestivicii, to make them a less tempting meal for the amphibians that would have recently emerged from the oceans onto land.

The study’s lead author, Mr Russell Garwood, PhD student from the Department of Earth Science and Engineering at Imperial College London, says:

“Our models almost bring these ancient creatures back to life and it’s really exciting to be able to look at them in such detail. Our study helps build a picture of what was happening during this period early in the history of life on land. We think one creature could have responded to increasing predation from the amphibians by growing spikes, while the other responded by becoming an ambush predator, hiding away and only exposing itself when it had to come out to eat.”

At present, most palaeontologists analyse fossils by splitting open a rock and looking at the creatures encased inside. This means that scientists can often only see part of the fossil and cannot explore all of the fossil’s physical features.

The researchers believe their new technique could be used to re-explore previously analysed fossils to provide a much clearer picture of how ancient extinct species survived on early Earth.

(Photo: Imperial College London and the Natural History Museum)

Imperial College London

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