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Two independent research groups have established conclusively that prions are proteins, and that they do not depend on genes or other factors for transmission of their traits. According to the scientists, the studies answer a nagging question that had raised doubts among some researchers about the validity of the so-called “protein-only” hypothesis of prion infectivity. Scientists have grappled for years with one of the central tenets of the protein-only hypothesis, namely, that a single prion protein, when unaltered by genetic mutation, can give rise to different strains of prions with varying infectivity and other properties. The two research groups established that the strains could be accounted for by different misfolded conformations of the same protein. The researchers say this finding could contribute to better understanding of the functioning of disease-causing prions in animals and humans. Both groups published their findings in the March 18, 2004, issue of the journal Nature. Howard Hughes Medical Institute investigator Jonathan S. Weissman at the University of California at San Francisco led one group. The other effort was led by Chi-Yen King at Florida State University. ©2004 Howard Hughes Medical Institute

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Link ID: 5148 - Posted: 06.24.2010

Genetic technique may yield BSE-proof calves. MICHAEL HOPKIN Researchers in the United States and Japan claim to have created cow embryos that cannot produce the protein responsible for bovine spongiform encephalopathy (BSE). Without it, the animals should be immune to mad cow disease. A “handful" of the BSE-free cows will be born early next year, the researchers say. The calves will be tested with a small dose of mad cow protein to see whether they are truly resistant to the disease. The BSE-causing protein, called a prion, is present in both healthy and diseased cattle; it is only when it twists out of shape that it causes problems. When normal prion protein comes into contact with the disease-causing version it can flip into the malignant form, causing rogue prions to spread through the brain. This leads to coordination problems, behavioural changes and death. The US and Japanese researchers aimed to bypass this problem by creating genetically engineered cows that do not produce prions at all. This means that they should be safe from small doses of diseased prions, explains James Robl, president of biotechnology firm Hematech in Sioux Falls, South Dakota, and one of the leaders of the team. © Nature News Service / Macmillan Magazines Ltd 2003

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Link ID: 5579 - Posted: 06.24.2010

Scientists have firmed up the evidence that misshapen protein are responsible for brain-wasting diseases by showing how these infectious prions are created. Researchers from the United States and China have artificially created a disease-causing prion using proteins from mice. Prions are proteins that occur naturally in the cells of mammals. Infectious prions are abnormal, misshapen versions of this protein that cause neurodegenerative diseases such as Creutzfeldt-Jakob disease and bovine spongiform encephalopathy, also known as mad cow disease. The scientists used a mouse prion protein, called PrP, created through genetic engineering in bacterial cells in their experiments. They found that the protein interacts with lipids, the fatty molecules in the structures of cell membranes, and becomes contorted and improperly folded, changing it into a disease-causing prion. Jiyan Ma of Ohio State University said the experiment, published this week in Science, is the strongest evidence yet that prions are the cause of these brain-wasting diseases. "The major thing we showed in this study is that the infectious agent in these diseases is truly a misfolded protein," Ma said in a statement. © CBC 2010

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Link ID: 13727 - Posted: 06.24.2010

Jessica Hamzelou, reporter Prion proteins have a bad reputation. The misfolded forms of this brain protein are responsible for a host of neurological diseases including, notoriously, variant Creutzfeldt-Jakob Disease (vCJD), which has been linked to eating contaminated beef. But what about the normal, correctly folded version of prion protein? Surely it must have a function in the brain? Neurologists still haven't figured out exactly what this is, but several pieces of evidence suggest that prions aren't all bad. The latest study, published in Nature Neuroscience, suggests that prions are important in maintaining the myelin sheath that surrounds nerve cells, enabling them to transmit nerve impulses rapidly. Adriano Aguzzi and his team at University Hospital of Zurich, Switzerland, bred mice lacking prion protein. They found that these mice developed a condition where their peripheral nerves, which connect the limbs to the central nervous system, lost much of their myelin coating. Although it's too early to say whether the finding can be applied to human disease, Aguzzi told Asian News International that he thinks "it is going to be interesting to see if prions play any role in demyelinating diseases that stem from the brain". This isn't the first time prions have been caught doing some good. Over the past 15 years, researchers have been noting that although mice without the prion protein don't develop prion disease - and can even be rescued from it - they end up with all sorts of other problems. © Copyright Reed Business Information Ltd.

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Link ID: 13709 - Posted: 06.24.2010

By Jennifer Couzin-Frankel In mad cow disease, misfolded proteins called prions punch holes in the brain, eventually destroying it. Inherited prion diseases, which are rare and passed through families, do the same thing. But it's long been a puzzle why prions attack neurons more than other types of cells, and how they do their damage. In a new study, researchers propose that prions deplete a poorly understood protein that normally keeps nerve cells healthy. The theory still has a ways to go before it's proven, but researchers are intrigued by this potential new twist on a mysterious disease. Prions are a faulty version of a healthy protein called PrP; when it misfolds, the results are disastrous. Yet researchers don't know exactly why. One argument suggests that whereas healthy PrP is normally located on the cell's surface, prions go astray and end up in the cytosol, the liquid found inside cells, somehow destroying them. The new study bolsters this theory. The first clues came in a paper published in 2003. In that work, researchers reported that mice lacking an obscure protein, Mahogunin, suffered a form of neurodegeneration much like prion disease. Cell biologists Ramanujan Hegde and Oishee Chakrabarti of the National Institute of Child Health and Human Development in Bethesda, Maryland, decided to probe deeper into the Mahogunin connection. © 2009 American Association for the Advancement of Science

Related chapters from BP7e: Chapter 16: Psychopathology: Biological Basis of Behavior Disorders
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Link ID: 12943 - Posted: 06.24.2010

By Rachel Zelkowitz Talk about Dr. Jekyll and Mr. Hyde. Misfolded proteins known as prions cause mad cow disease and other fatal neurodegenerative illnesses. But in their properly folded form, the proteins may be important to survival, helping mice and other animals keep their sniffing skills sharp, new research shows. Prions get the bad reputation--and the lion's share of research attention--but interest in the normal form of prion proteins is increasing. Brain tissue is particularly high in these proteins, and a growing body of research has shown that they help neurons conduct copper and may even protect them from destruction by rogue chemicals in the body. But no one had pegged prion proteins to a particular neurological function such as sight or smell. That's changed, thanks to an intriguing finding by electrophysiologist Stuart Firestein of Columbia University. Firestein and colleagues were studying the sense of smell in mice when they noticed high levels of normal prion protein (PrPc) in the cells that make up the animals' olfactory systems. Wondering whether the protein might play a role in this sense, the researchers hid bits of peanut butter cookies in the shredded bedding of a cage. They then timed how long it took both normal mice and rodents genetically engineered to not make PrPc to sniff out the snack. Normal mice spent an average of 73 seconds searching for the treat before they found it, three times faster than their PrPc-free counterparts. Six of the 20 PrPc-free mice never found the cookie at all, the team reports this week in Nature Neuroscience. © 2008 American Association for the Advancement of Science.

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Link ID: 12382 - Posted: 06.24.2010

Colin Barras More than a decade after the first reported cases of debilitating brain disease variant Creutzfeldt-Jakob disease (vCJD), the exact mode of infection remains controversial. Weird self-replicating proteins called prions are the prime suspect, but are yet to be found conclusively guilty. In an effort to solve the mystery biochemists have created the first complete synthetic prion and plan to discover if it can be as toxic as the real thing. The prion is the alter-ego of a protein that naturally exists in cells. But that harmless protein can undergo a Jekyll-and-Hyde transformation into a shape that clumps together into disease-causing plaques. Even worse, those prions convert any normal versions of the protein it meets into the malignant form. In 2005, Bruce Chesebro's team at the US National Institute of Allergy and Infectious Diseases, discovered that prions need a string of molecules that acts as an "anchor" to be toxic. Prions that usually cause the disease scrapie in sheep and goats proved unable to perform their usual toxic tricks in mice when stripped of their anchors (Science, DOI: 10.1126/science.1110837). © Copyright Reed Business Information Ltd.

Related chapters from BP7e: Chapter 16: Psychopathology: Biological Basis of Behavior Disorders
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Link ID: 12117 - Posted: 06.24.2010

Amber Dance Infectious prion proteins from hamsters can change normal proteins from mice into new, infectious forms of prion - simply by mixing the proteins together in a test tube. Researchers at the University of Texas Medical Branch in Galveston suggest their discovery could be turned into a useful test for whether a given prion strain is transmissible from one species to another. Prion proteins are responsible for Creutzfeld-Jakob disease and "mad cow" disease. But they also found that when a prion jumps species, it produces a new kind of prion. "This is very worrisome," says Claudio Soto, who led the research, published in Cell1. "The universe of possible prions could be much larger than we thought." Normal prion protein, or PrP, is found throughout the body but is concentrated in the brain. Its exact role is not known, although it has been linked to cell signalling2, metal-ion transport3, and blood-cell manufacture4. The protein can adopt malformed shapes that cause disease. Those proteins, which are resistant to degradation, bind and convert normal protein to their troublesome conformation. Over time, the diseased protein builds up and forms fibrils in the brain, causing neurodegeneration and ultimately death. © 2008 Nature Publishing Group

Related chapters from BP7e: Chapter 16: Psychopathology: Biological Basis of Behavior Disorders
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Link ID: 12015 - Posted: 06.24.2010

By MATT APUZZO WASHINGTON -- The Bush administration can prohibit meat packers from testing their animals for mad cow disease, a federal appeals court said Friday. The dispute pits the Agriculture Department, which tests about 1 percent of cows for the potentially deadly disease, against a Kansas meat packer that wants to test all its animals. Larger meat packers opposed such testing. If Creekstone Farms Premium Beef began advertising that its cows have all been tested, other companies fear they too will have to conduct the expensive tests. The Bush administration says the low level of testing reflects the rareness of the disease. Mad cow disease has been linked to more than 150 human deaths worldwide, mostly in Great Britain. Only three cases have been reported in the U.S., all involving cows, not humans. ad_icon A federal judge ruled last year that Creekstone must be allowed to conduct the test because the Agriculture Department can only regulate disease "treatment." Since there is no cure for mad cow disease and the test is performed on dead animals, the judge ruled, the test is not a treatment. The U.S. Court of Appeals for the District of Columbia Circuit overturned that ruling, saying diagnosis can be considered part of treatment. © Copyright 1996-2008 The Washington Post Company

Related chapters from BP7e: Chapter 16: Psychopathology: Biological Basis of Behavior Disorders
Related chapters from MM:Chapter 12: Psychopathology: The Biology of Behavioral Disorders
Link ID: 11996 - Posted: 06.24.2010

Researchers in the U.S. have identified the emergence of a new type of brain-wasting disease that resembles Creutzfeld-Jakob, the human form of mad cow disease. Similarly to Creutzfeld-Jakob disease (CJD), the human variant of bovine spongiform encephalopathy, the new disease causes the brains of sufferers to fill with tiny holes, robbing them of the ability to think, speak and move. In the U.S., it has been found in 16 people since 2002, 10 of whom have died of it. Cases of the disease were first described in the Annals of Neurology in 2006 and are discussed in an article in the June 20 issue of the journal and in a July 9 article in New Scientist. "I believe the disease has been around for many years, unnoticed," Pierluigi Gambetti, director of the U.S. National Prion Disease Pathology Surveillance Center at Case Western Reserve University in Cleveland, Ohio, said in a news release Wednesday. It's believed that excessive amounts of prions, misfolded forms of a brain protein, lead to breakdown of brain tissue in both types of brain-wasting diseases. In the case of CJD, prions are not broken down by enzymes, but in the new disease, they are. © CBC 2008

Related chapters from BP7e: Chapter 16: Psychopathology: Biological Basis of Behavior Disorders
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Link ID: 11804 - Posted: 06.24.2010

Scientists have taken a big step towards a quick, sensitive test for the proteins that go haywire in mad-cow disease. Because people or animals can be infected for years without showing symptoms, the researchers say developing a better test will be key to preventing a silent epidemic. Right now, the only method that blood banks have for keeping deadly mad cow disease (called variant Creutzfeldt Jakob Disease, or vCJD ) out of the blood supply is with donor questionnaires. National Institutes of Health researcher Byron Caughey has been searching for a better way for more than a decade. "There have been several examples now where it's documented that humans who've received blood transfusions from other people, who unbeknownst to anyone had CJD, have actually come down with CJD themselves," Caughey says. By the time prion diseases cause sickness and death, huge amounts of the infectious misfolded proteins can be easily found in the brain. Yet the infection can start off with only tiny amounts of prions. "It can take from months to decades depending on the particular prion disease and the species, but during that time, infected individuals can serve as carriers of the disease," says Caughey. "It really is key to be able to pick up those otherwise invisible infections, prion infections before any potential transmissions to others can occur." © ScienCentral, 2000-2007

Related chapters from BP7e: Chapter 16: Psychopathology: Biological Basis of Behavior Disorders
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Link ID: 10596 - Posted: 06.24.2010

By Sarah C. P. Williams Researchers have developed a way to vaccinate mice against deadly prion diseases, which include scrapie, kuru, mad cow disease, and Creutzfeldt-Jakob disease. The findings, presented today at the annual American Academy of Neurology meeting in Boston, suggest that these degenerative brain diseases can be stopped if caught early enough. Prion proteins, expressed in neurons, are found in one form in healthy individuals. But when even one protein becomes misfolded--or a misfolded protein enters the body through food, such as infected beef--it changes the conformation of all the prions around it (ScienceNOW, 21 April 2005). The misfolded proteins clump and destroy neurons, creating tiny holes in the brain. Prion diseases have no known cure. Previous attempts at vaccines have delayed the onset of prion diseases, but never prevented them. Searching for a more effective vaccine, a team led by neuropathologist Thomas Wisniewski of the New York University School of Medicine in New York City took a new approach. They genetically modified a strain of Salmonella bacteria to express prion proteins. When researchers fed these bacteria to mice, the bugs multiplied in the rodents' guts, and the animals developed antibodies against the prions. © 2007 American Association for the Advancement of Science

Related chapters from BP7e: Chapter 16: Psychopathology: Biological Basis of Behavior Disorders
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Link ID: 10260 - Posted: 06.24.2010

Debora MacKenzie THE discovery that a rare brain disease in cows can mutate into BSE has given new life to the theory that mad cow disease started out in cattle, rather than crossing over from sheep. When BSE emerged in British cattle in the mid-1980s, the leading theory was that they had initially contracted the disease by eating feed containing the remains of sheep infected with scrapie. Both BSE and scrapie are caused by infectious prions, misshapen forms of a normal brain protein. Having made this species jump, BSE would have spread as cattle carcasses were processed into animal fodder and fed back to cows. Yet attempts to duplicate BSE by deliberately giving scrapie to cows have failed, and many countries included sheep remains in cattle feed without creating BSE. This has led some scientists to speculate that BSE arose as a rare spontaneous condition in cattle, which spread to other cows when they ate these animals' remains. The new twist to the story comes from studies of a disease called bovine amyloidotic spongiform encephalopathy, or BASE. It was discovered in 2003, when two Italian cows, out of tens of thousands of European cattle screened for BSE at slaughter, were found to have a prion disease that seemed different from BSE. The BASE prion had a lower molecular weight and one, rather than two, sugars bound to it. The brains of cows with BASE were also damaged in different places from those with BSE, and had dense protein deposits called amyloid that are not seen in BSE. Similar prions have also turned up in France, Germany and Japan. © Copyright Reed Business Information Ltd

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Link ID: 10095 - Posted: 06.24.2010

In 1997 a cloned sheep named Dolly brought the issue of cloning to the public's attention. Then it was quickly proven that other animals, including pigs and cows, could also be cloned. But, it still had to be proven that it was safe to consume products from cloned animals. In a study published in 2005 in Proceedings of the National Academy of Sciences, Xiangzhong "Jerry" Yang, director of the Center for Regenerative Biology at the University of Connecticut, found that meat from two cloned bulls and a thousand samples of milk from cloned Holstein Dairy Cows meet industry standards for beef and milk from naturally produced cattle. The study was more than just curiosity, because as Yang points out, "One of the applications for cloning farmed animals, including cattle, pigs is really for improving agriculture, for better milk production, for better meat production." But, until the FDA approval, no country had allowed consumption or marketing of products from cloned animals. Yang says cloning cattle could improve agricultural efficiency. "If we can clone highly producing top genetic cows in the U.S. or for developing countries, we actually can increase the number of animals for high-level production. Or, if you have enough milk already, you can reduce the number for the same amount of milk production." © ScienCentral, 2000-2007.

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Link ID: 9803 - Posted: 06.24.2010

Michael Hopkin A US-led research team has developed a technique to filter potentially deadly prion proteins from blood. They suggest that the method should be used routinely in attempts to remove prions, which can cause variant Creutzfeldt-Jakob disease (vCJD), from blood products used for transfusions. The method could offer better protection than the current practice of removing white blood cells from donated blood, say the researchers, led by Robert Rohwer of the University of Maryland, Baltimore. Previous studies have shown that around a half of the abnormal, infective prion proteins are in white blood cells, so removing these can help reduce the risk of infection. But infective prions are also found in the blood plasma. Of the 200 vCJD cases recorded worldwide, only a few have involved contaminated blood transfusions, but health officials are still worried about this possible transmission route. Several countries have banned blood donations from people who have lived in Britain, where many people have potentially eaten meat containing infective prions. Despite the relatively few cases of this devastating, untreatable disease, researchers worry that many other people might be carriers. According to a survey of samples from tonsil and appendix removals, as many as 4,000 British people may be harbouring the disease, which can remain dormant for decades, without showing symptoms. There is currently no test to detect abnormal prions in humans, meaning that it is impossible to identify these people. ©2006 Nature Publishing Group

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Link ID: 9780 - Posted: 06.24.2010

By Katherine Unger The proteins that, when mangled, cause "Mad Cow" and similar diseases also help regulate how yeast cells metabolize metals, biochemists report. Exposure to high levels of metals can coax proteins called prions to adopt an abnormal disease-causing conformation, the researchers found. That could explain why outbreaks of prion diseases have popped up in Iceland, Slovakia, and Colorado--regions with soils high in manganese. Mad Cow disease in cattle, scrapie in sheep, and Creutzfeldt-Jakob disease in humans are all deadly and transmissible conditions in which the brain degenerates. All seemed to be caused by prion proteins that have changed shape so that enzymes can no longer break them down. This altered conformation is widely thought to be responsible for the diseases, because the tangled and essentially indestructible proteins collect in brain tissue (ScienceNOW, July 29 2004). Studies have shown that some metals bind to prion proteins, leading some scientists to wonder whether metals are involved in the shape shift. Now, biochemist Gerd Multhaup of the Free University of Berlin and colleagues have shown that prions alter metal metabolism in yeast. As a first step, they took a species of yeast that does not normally make prions and added prions that don't cause disease. Copper levels increased 1.6-fold inside these cells while manganese decreased by half compared to yeast without prion proteins, the researchers report in a paper to be published 13 June in Biochemistry. The researchers then added copper or manganese to the growth medium to form 1 to 5 millimolar concentrations; both additions transformed the prions to the indestructible form. © 2006 American Association for the Advancement of Science

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Link ID: 8995 - Posted: 06.24.2010

The deadly human form of mad cow disease, vCJD, may have infected far more people than previously thought, suggests a new study. The assumption that most people are genetically shielded from the devastating disease could be wrong, said the research published on Friday. But it cautions that the evidence for this remains sketchy. Variant Creutzfelt-Jakob disease (vCJD) is linked to eating meat infected with bovine spongiform encephalopathy (BSE), also known as mad-cow disease. A rogue version of a prion protein proliferates in the brain, leading to distressing mental deterioration, loss of motor control, and eventually death. After vCJD was first identified in March 1996, some experts calculated it could inflict a death toll in the tens of thousands, especially in the UK, where the outbreak began. But these calculations were swiftly revised downwards to a few hundred or even fewer when it was realised that the toll was rising far slower than expected. At present, the UK has recorded 161 definite and probable cases of vCJD, six of whom are still alive. One reason for optimism about the potential extent of the vCJD epidemic has been the assumption that it is genetic. © Copyright Reed Business Information Ltd.

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Link ID: 8939 - Posted: 06.24.2010

Andreas von Bubnoff The inflamed mammary glands of sheep have been found to contain protein particles that cause scrapie, a sickness similar to mad cow disease. This suggests that the suspect proteins, called prions, may also be present in the milk of infected animals. If prions exist in the milk of cows infected with both an inflammatory illness and mad cow disease, formally known as bovine spongiform encephalopathy (BSE), this raises concerns for human health. Consumption of prion-contaminated meat from cows with BSE is believed to cause the fatal variant Creutzfeldt-Jakob disease (vCJD) in people; so might contaminated milk. Adriano Aguzzi, the lead researcher on the study, has not detected prions in milk itself, because it is difficult to analyse for the abnormal proteins. But he says he expects to find them. "It is unlikely that the prions are not in the milk," says Aguzzi, a pathologist at the University of Zurich Hospital, Switzerland. "And the prospect is not a pleasant one." ©2005 Nature Publishing Group

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Link ID: 8108 - Posted: 06.24.2010

Andreas von Bubnoff The protein particles that cause illnesses such as mad cow disease can be found in the urine of infected mice, researchers report. Their study may solve the mystery of how such 'prion' diseases spread among animals such as sheep, elk and deer. But it also raises concerns that the urine of humans with new-variant Creutzfeldt-Jakob disease (vCJD) may contain dangerous proteins. Prions are primarily found in the brain, the spinal cord and the immune system. British cows are thought to have developed the prion disease bovine spongiform encephalopathy (BSE) by eating ground-up brains, spleens and similar material. Other body parts were thought to be relatively safe for consumption. Then, in 2003, Adriano Aguzzi's group at the University Hospital of Zurich, Switzerland, found prions in the muscle tissue of people who had died from a brain wasting disease. And this January, the team showed in mice that prions also spread to the pancreas, kidneys and liver if there is inflammation in these organs. Together, these findings suggested that the brain and lymphatic organs might not be the only dangerous ones. ©2005 Nature Publishing Group

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Link ID: 8031 - Posted: 06.24.2010

CBC News A new and disturbing theory about the possible origin of "mad cow" disease has been published, and a Canadian scientist said it is "plausible." In a report in the British medical journal, The Lancet, Professor Alan Colchester of the University of Kent in England says BSE (bovine spongiform encephalopathy) may have been caused by the tonnes of animal bones and other tissue imported in the '60s and '70s from India for animal feed which also may have contained the remains of humans infected with Creutzfeldt-Jakob disease (CJD). Colchester, and his daughter Nancy, from the college of medicine and veterinary medicine at the University of Edinburgh in Scotland, said the practice may still be taking place elsewhere. They said it is important to discover whether other countries are importing animal byproducts contaminated with human remains that are destined for feed mills. The authors admitted their hypothesis is based on a compilation of circumstantial evidence. They wrote: "We do not claim that our theory is proved, but it unquestionably warrants further investigation." It had previously been thought that the brain-wasting mad cow disease passed to cattle through remains of sheep infected with scrapie -- the sheep equivalent of BSE -- that were added to cattle feed. Copyright © CBC 2005

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Link ID: 7871 - Posted: 06.24.2010