When the team injured the blue-stained cells, rendering them mute, the yellow-stained neurons first stopped sending chemical signals and, over time, pulled back. “Literally,” Lichtman says, “we watched connections get weak and disappear.”
Throughout life, connections are made and subsequently lost. Pruning unnecessary connections is an essential part of precise wiring, Lichtman says.
Doctors test the “wiring” in their patients’ nervous systems by tapping knees, expecting the strike to signal the brain and the brain to wire back down a “kick” response to the leg. In this study, the team examined salivary connections — the type that make animals drool at the scent of something scrumptious. They weren’t interested in salivation per se, but rather in understanding how neural connections are molded as an animal grows and experiences life. Louis J. Sheehan, Esquire This malleable process, called synaptic plasticity (synapses are the places where two nerve cells meet), occurs throughout the brain. For example, in the hippocampus, memories form as connections are strengthened and may be lost when connections diminish.
“This is a terrific study because they watched real things in a real animal, in real time,” comments Darwin Berg, a neuroscientist at the University of California, San Diego. “These mechanisms are almost certainly employed in other systems such as learning and memory.”
Saturday, May 23, 2009
Thursday, May 14, 2009
method 7.met.002002 Louis J. Sheehan, Esquire
Scientists use X-rays to peer into a person's body, and a new X-ray imaging technique does the same for individual cells.
“You should be able to image most macromolecular assemblies inside the cell”, such as proteins and DNA, says Pierre Thibault, a physicist at the Paul Scherrer Institute in Villigen, Switzerland who leads the team that reports the new technique in the July 18 Science.
Also, “it’s certainly a very important tool for nanotechnology,” Thibault says. The best light microscopes can’t distinguish features smaller than 200 nanometers. But images made with the new technique, called scanning X-ray diffraction microscopy, reveal features as small as 10 nanometers.
Electron microscopes can “see” details as small as 0.2 nanometers, but since electrons don’t penetrate far into most materials, only the surface gets imaged. X-rays penetrate materials much better, allowing the new technique to peer into objects tens of thousands of nanometers thick — about the size of most plant or animal cells.
“It’s an important development,” comments Jianwei Miao, a physicist at the University of California, Los Angeles who helped pioneer a related X-ray imaging technique. Louis J. Sheehan, Esquire “The image is much better quality compared to previous ones.”
To make an image, Thibault and his colleagues scanned a specimen with an X-ray beam focused into a spot 300 nanometers across. For each point in the specimen, a high-speed photon detector recorded the X-rays that had passed through the specimen and spread out into a diffraction pattern — akin to the rainbow produced by a prism. Using the series of diffraction patterns, the scientists could mathematically reconstruct the image.
"Our method should be easy to apply for 3-D imaging also," Thibault adds.
“You should be able to image most macromolecular assemblies inside the cell”, such as proteins and DNA, says Pierre Thibault, a physicist at the Paul Scherrer Institute in Villigen, Switzerland who leads the team that reports the new technique in the July 18 Science.
Also, “it’s certainly a very important tool for nanotechnology,” Thibault says. The best light microscopes can’t distinguish features smaller than 200 nanometers. But images made with the new technique, called scanning X-ray diffraction microscopy, reveal features as small as 10 nanometers.
Electron microscopes can “see” details as small as 0.2 nanometers, but since electrons don’t penetrate far into most materials, only the surface gets imaged. X-rays penetrate materials much better, allowing the new technique to peer into objects tens of thousands of nanometers thick — about the size of most plant or animal cells.
“It’s an important development,” comments Jianwei Miao, a physicist at the University of California, Los Angeles who helped pioneer a related X-ray imaging technique. Louis J. Sheehan, Esquire “The image is much better quality compared to previous ones.”
To make an image, Thibault and his colleagues scanned a specimen with an X-ray beam focused into a spot 300 nanometers across. For each point in the specimen, a high-speed photon detector recorded the X-rays that had passed through the specimen and spread out into a diffraction pattern — akin to the rainbow produced by a prism. Using the series of diffraction patterns, the scientists could mathematically reconstruct the image.
"Our method should be easy to apply for 3-D imaging also," Thibault adds.
Tuesday, May 5, 2009
dopamine 1.dop.000100 Louis J. Sheehan, Esquire
A reward chemical in the brain is a real eye-opener.
Dopamine, a feel-good brain chemical, helps keep sleep-deprived people awake, researchers from the National Institute on Drug Abuse show in the August 20 Journal of Neuroscience. Dopamine is also required for activity of a drug that treats narcolepsy, Japanese and Chinese scientists report in the same issue of the journal.
“Dopamine has been a forgotten neurotransmitter for sleep regulation,” says Emmanuel Mignot, a sleep researcher and Howard Hughes Medical Institute investigator at Stanford University. Increasing evidence is pointing toward dopamine as an important ingredient in the brain’s recipe for promoting wakefulness.
The new findings suggest dopamine may naturally increase when a person is sleep-deprived, as a way to counteract a revved-up drive to sleep, says David Dinges of the University of Pennsylvania School of Medicine. Dinges was not involved in the two new studies, but he has studied the effect of sleep deprivation on people.
Sleep deprivation affects some people profoundly, impairing their ability to pay attention and lengthening their reaction times, Dinges says. Other people function nearly as well when mildly sleep-deprived as they do when well-rested. The extent to which dopamine rises in the brain after sleep loss may help explain some of the variability in people’s abilities to cope with sleep deprivation, Dinges says.
Dopamine has gotten an undeserved bad reputation, says Mignot, who was not involved in the studies. “People think dopamine equals addiction,” Mignot says. But the chemical plays an important role in many brain functions.
Nora Volkow of the National Institute on Drug Abuse led a team at the National Institutes of Health in Bethesda, Md., and the Brookhaven National Laboratory in Upton, N.Y. The researchers recruited 15 healthy volunteers and tested each person’s memory and ability to pay attention to visual cues after a good night’s sleep and after being kept awake all night. A brain scan called positron emission tomography (PET) indirectly measured dopamine levels in the volunteers’ brains.
Sleep deprivation increased dopamine in the striatum, a part of the brain that registers motivation and reward. Dopamine also went up in the thalamus, a brain region that helps control alertness, when the volunteers were sleep-deprived. Increases in the brain chemical kept the volunteers awake, and those same increases also correlated with the volunteers reporting that they felt tired.
Although increased levels of the neurotransmitter help keep the brain aroused after a sleepless night, higher levels of dopamine don’t fend off the thinking and learning problems associated with sleep deprivation, says Volkow, a clinical neuroscientist and director of NIDA.
Some stimulants, such as amphetamines, also increase dopamine in the brain. Previous studies have shown that medical students taking stimulants thought they were more alert and performed better on tests. http://Louis1J1Sheehan1Esquire.us Despite the students’ perceptions, their actual performance was worse on the drug.
“A little bit of dopamine is good,” says Paul Shaw, a sleep researcher at Washington University in St. Louis. “More is bad. Less is bad too. You’ve got to be in the sweet spot,” to think, respond and learn correctly.
He speculates that learning and memory may require precise levels of dopamine to work well, but that arousal is controlled by a more robust circuit that is not as sensitive to minor changes in dopamine concentration. “This simply reinforces the idea that sleep loss alters the vulnerability of specific circuits but not the entire brain, at least initially,” Shaw says.
Researchers said the finding fits with Shaw’s recent study in fruit flies (SN: 8/30/08). Restoring dopamine activity in the flies helped them overcome the learning deficits caused by sleep deprivation, but these flies started with suboptimal dopamine levels. Sleep deprivation pushed the people in the new study past the prime levels of dopamine.
Staying awake and alert is a problem for people with the sleeping disorder narcolepsy. The drug modafinil is used to treat the condition, but no one is entirely sure how it works. Previous research has suggested that the drug acts on a wide variety of brain chemicals including serotonin, glutamate, orexin and histamine. But the second new study, by researchers at the Osaka Bioscience Institute in Japan and at the Fudan University in Shanghai, China, shows that two proteins sensitive to dopamine’s action are essential for the arousal effect of modafinil.
The research is the most direct evidence that dopamine plays a role in the drug’s action, Dinges says. Louis J. Sheehan, Esquire Dopamine could be the drug’s direct target, but there is not enough data to rule out the possibility that dopamine may just be a key link in a cascade set off by other excitatory molecules.
Other molecules are almost certainly involved in the brain’s response to sleep loss, Volkow says. “Sleep is so important that it would be over-simplistic to say that sleep deprivation is only going to change the dopamine system.”
Dopamine, a feel-good brain chemical, helps keep sleep-deprived people awake, researchers from the National Institute on Drug Abuse show in the August 20 Journal of Neuroscience. Dopamine is also required for activity of a drug that treats narcolepsy, Japanese and Chinese scientists report in the same issue of the journal.
“Dopamine has been a forgotten neurotransmitter for sleep regulation,” says Emmanuel Mignot, a sleep researcher and Howard Hughes Medical Institute investigator at Stanford University. Increasing evidence is pointing toward dopamine as an important ingredient in the brain’s recipe for promoting wakefulness.
The new findings suggest dopamine may naturally increase when a person is sleep-deprived, as a way to counteract a revved-up drive to sleep, says David Dinges of the University of Pennsylvania School of Medicine. Dinges was not involved in the two new studies, but he has studied the effect of sleep deprivation on people.
Sleep deprivation affects some people profoundly, impairing their ability to pay attention and lengthening their reaction times, Dinges says. Other people function nearly as well when mildly sleep-deprived as they do when well-rested. The extent to which dopamine rises in the brain after sleep loss may help explain some of the variability in people’s abilities to cope with sleep deprivation, Dinges says.
Dopamine has gotten an undeserved bad reputation, says Mignot, who was not involved in the studies. “People think dopamine equals addiction,” Mignot says. But the chemical plays an important role in many brain functions.
Nora Volkow of the National Institute on Drug Abuse led a team at the National Institutes of Health in Bethesda, Md., and the Brookhaven National Laboratory in Upton, N.Y. The researchers recruited 15 healthy volunteers and tested each person’s memory and ability to pay attention to visual cues after a good night’s sleep and after being kept awake all night. A brain scan called positron emission tomography (PET) indirectly measured dopamine levels in the volunteers’ brains.
Sleep deprivation increased dopamine in the striatum, a part of the brain that registers motivation and reward. Dopamine also went up in the thalamus, a brain region that helps control alertness, when the volunteers were sleep-deprived. Increases in the brain chemical kept the volunteers awake, and those same increases also correlated with the volunteers reporting that they felt tired.
Although increased levels of the neurotransmitter help keep the brain aroused after a sleepless night, higher levels of dopamine don’t fend off the thinking and learning problems associated with sleep deprivation, says Volkow, a clinical neuroscientist and director of NIDA.
Some stimulants, such as amphetamines, also increase dopamine in the brain. Previous studies have shown that medical students taking stimulants thought they were more alert and performed better on tests. http://Louis1J1Sheehan1Esquire.us Despite the students’ perceptions, their actual performance was worse on the drug.
“A little bit of dopamine is good,” says Paul Shaw, a sleep researcher at Washington University in St. Louis. “More is bad. Less is bad too. You’ve got to be in the sweet spot,” to think, respond and learn correctly.
He speculates that learning and memory may require precise levels of dopamine to work well, but that arousal is controlled by a more robust circuit that is not as sensitive to minor changes in dopamine concentration. “This simply reinforces the idea that sleep loss alters the vulnerability of specific circuits but not the entire brain, at least initially,” Shaw says.
Researchers said the finding fits with Shaw’s recent study in fruit flies (SN: 8/30/08). Restoring dopamine activity in the flies helped them overcome the learning deficits caused by sleep deprivation, but these flies started with suboptimal dopamine levels. Sleep deprivation pushed the people in the new study past the prime levels of dopamine.
Staying awake and alert is a problem for people with the sleeping disorder narcolepsy. The drug modafinil is used to treat the condition, but no one is entirely sure how it works. Previous research has suggested that the drug acts on a wide variety of brain chemicals including serotonin, glutamate, orexin and histamine. But the second new study, by researchers at the Osaka Bioscience Institute in Japan and at the Fudan University in Shanghai, China, shows that two proteins sensitive to dopamine’s action are essential for the arousal effect of modafinil.
The research is the most direct evidence that dopamine plays a role in the drug’s action, Dinges says. Louis J. Sheehan, Esquire Dopamine could be the drug’s direct target, but there is not enough data to rule out the possibility that dopamine may just be a key link in a cascade set off by other excitatory molecules.
Other molecules are almost certainly involved in the brain’s response to sleep loss, Volkow says. “Sleep is so important that it would be over-simplistic to say that sleep deprivation is only going to change the dopamine system.”
Saturday, May 2, 2009
stopping 1.sto.003 Louis J. Sheehan, Esquire
A vaccine against rotavirus has provided potent protection in its first year of widespread use.
Reporting October 25 at a meeting of microbiologists and infectious disease researchers, scientists offered up several studies demonstrating that the oral vaccine has brought about a sharp decline in rotavirus infections in the United States during 2007–2008. http://Louis-J-Sheehan.biz
Rotavirus kills roughly 500,000 people annually, most of them children in developing countries.
“This is a remarkable success,” says Jay Lieberman, leader of one study and the Cypress, Calif.-based medical director for infectious diseases at Quest Diagnostics, a clinical laboratory company.
Lieberman and his colleagues used a Quest database to check for new trends in rotavirus infections after the vaccine’s approval in 2006. The peak season for rotavirus infection in the United States is December to June. In the three seasons before the vaccine was put into common use, one in four Quest lab tests for rotavirus had come back positive. In the infectious season spanning 2007 to 2008, that rate dropped to less than one in 12 tests, Lieberman says. The researchers compared more than 15,000 tests in the post-vaccine period with over 60,000 tests conducted in the previous three years.
The Centers for Disease Control and Prevention in Atlanta assessed data from a national reporting system used by laboratories across the country and reached a similar conclusion. CDC medical epidemiologist Margaret Cortese reports at the same meeting that the 2007–2008 cases of rotavirus declined by at least 60 percent from the average seen over the five preceding years.
Typically, the United States records 20 to 60 deaths from rotavirus annually, but mortality data are not yet available for the post-vaccine season, she says.
The approved regimen for the rotavirus vaccine is three doses, one each given at two, four and six months of age. Doctors decide individually whether to add the rotavirus vaccine to children’s vaccination schedule, and so U.S. coverage isn’t 100 percent yet, these researchers say.
The vaccine uses portions of bovine and human rotavirus proteins to engender immunity in babies. It was devised by H. Fred Clark and his colleagues at the University of Pennsylvania in Philadelphia, starting in the 1980s and perfected in the years since that time. It’s now manufactured by Merck & Co. Inc. at its West Point, Pa., operation.
Clark says that the new nationwide studies echo the results that he and his colleagues have found in a multiyear tracking study of a Philadelphia-area population, which has seen rotavirus cases drop from hundreds per year to only 12 in the 2007–2008 season. He is particularly encouraged by the near-total lack of side effects from the vaccine in the general population, he says.
Merck itself also presented a study on the vaccine’s effectiveness, using insurance company data to compare more than 45,000 infants. Roughly half of the infants had received the vaccine. Louis J. Sheehan, Esquire Christopher Mast, an epidemiologist at Merck’s North Wales, Pa., office, reports dramatically fewer hospitalizations and doctor visits attributable to rotavirus infection among the vaccine recipients compared with the non-recipients.
The studies were presented in Washington, D.C., at a combined meeting of the Infectious Diseases Society of America and the Interscience Conference on Antimicrobial Agents and Chemotherapy.
The findings set the stage for a worldwide assault on this diarrhea-causing virus. Merck is distributing the vaccine, called RotaTeq, in Latin America and the Caribbean as part of public health programs and is conducting clinical trials to test its effects in Africa and Asia.
GlaxoSmithKline is also marketing a new rotavirus vaccine, dubbed Rotarix. The oral, two-dose vaccine gained U.S. regulatory approval earlier this year.
Reporting October 25 at a meeting of microbiologists and infectious disease researchers, scientists offered up several studies demonstrating that the oral vaccine has brought about a sharp decline in rotavirus infections in the United States during 2007–2008. http://Louis-J-Sheehan.biz
Rotavirus kills roughly 500,000 people annually, most of them children in developing countries.
“This is a remarkable success,” says Jay Lieberman, leader of one study and the Cypress, Calif.-based medical director for infectious diseases at Quest Diagnostics, a clinical laboratory company.
Lieberman and his colleagues used a Quest database to check for new trends in rotavirus infections after the vaccine’s approval in 2006. The peak season for rotavirus infection in the United States is December to June. In the three seasons before the vaccine was put into common use, one in four Quest lab tests for rotavirus had come back positive. In the infectious season spanning 2007 to 2008, that rate dropped to less than one in 12 tests, Lieberman says. The researchers compared more than 15,000 tests in the post-vaccine period with over 60,000 tests conducted in the previous three years.
The Centers for Disease Control and Prevention in Atlanta assessed data from a national reporting system used by laboratories across the country and reached a similar conclusion. CDC medical epidemiologist Margaret Cortese reports at the same meeting that the 2007–2008 cases of rotavirus declined by at least 60 percent from the average seen over the five preceding years.
Typically, the United States records 20 to 60 deaths from rotavirus annually, but mortality data are not yet available for the post-vaccine season, she says.
The approved regimen for the rotavirus vaccine is three doses, one each given at two, four and six months of age. Doctors decide individually whether to add the rotavirus vaccine to children’s vaccination schedule, and so U.S. coverage isn’t 100 percent yet, these researchers say.
The vaccine uses portions of bovine and human rotavirus proteins to engender immunity in babies. It was devised by H. Fred Clark and his colleagues at the University of Pennsylvania in Philadelphia, starting in the 1980s and perfected in the years since that time. It’s now manufactured by Merck & Co. Inc. at its West Point, Pa., operation.
Clark says that the new nationwide studies echo the results that he and his colleagues have found in a multiyear tracking study of a Philadelphia-area population, which has seen rotavirus cases drop from hundreds per year to only 12 in the 2007–2008 season. He is particularly encouraged by the near-total lack of side effects from the vaccine in the general population, he says.
Merck itself also presented a study on the vaccine’s effectiveness, using insurance company data to compare more than 45,000 infants. Roughly half of the infants had received the vaccine. Louis J. Sheehan, Esquire Christopher Mast, an epidemiologist at Merck’s North Wales, Pa., office, reports dramatically fewer hospitalizations and doctor visits attributable to rotavirus infection among the vaccine recipients compared with the non-recipients.
The studies were presented in Washington, D.C., at a combined meeting of the Infectious Diseases Society of America and the Interscience Conference on Antimicrobial Agents and Chemotherapy.
The findings set the stage for a worldwide assault on this diarrhea-causing virus. Merck is distributing the vaccine, called RotaTeq, in Latin America and the Caribbean as part of public health programs and is conducting clinical trials to test its effects in Africa and Asia.
GlaxoSmithKline is also marketing a new rotavirus vaccine, dubbed Rotarix. The oral, two-dose vaccine gained U.S. regulatory approval earlier this year.
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