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by Roger Highfield Before winning his Nobel prize, Stanley Prusiner was ridiculed for suggesting that something he called a prion caused spongiform brain diseases WHEN the evidence suggested that the baffling "spongiform" brain disorders Creutzfeldt-Jakob disease (CJD), kuru and scrapie could not be transmitted by a virus or bacterium, the neurologist Stanley Prusiner put forward a novel type of infectious agent as the cause: a rogue protein. It was an idea considered so outrageous that Prusiner was ridiculed. Prusiner first began to study these diseases in 1972, after one of his patients at the University of California, San Francisco, died of CJD. A decade later, in the journal Science (vol 216, p 136), he suggested that these diseases were caused by a "proteinaceous infectious particle", or prion. The idea built on the findings of British researchers. In 1967, Tikvah Alper of the Medical Research Council's Radiopathology Unit showed that whatever it was that caused CJD was unscathed by levels of ultraviolet radiation that would destroy any genetic material (Nature, vol 214, p 764). Shortly afterwards, mathematician John Stanley Griffith of Bedford College in London devised a protein-only hypothesis for scrapie propagation. His 1967 Nature paper (vol 215, p 1043) states there was no reason to fear that the idea "would cause the whole theoretical structure of molecular biology to come tumbling down". © Copyright Reed Business Information Ltd.

Related chapters from BP7e: Chapter 16: Psychopathology: Biological Basis of Behavior Disorders
Related chapters from MM:Chapter 12: Psychopathology: Biological Basis of Behavioral Disorders
Link ID: 14464 - Posted: 09.18.2010

By Caroline Parkinson A new form of brain disease, similar to Creutzfeld-Jakob Disease, could affect more people than previously thought, researchers in the US say. It had been thought that only people with one genetic profile were vulnerable to the prion disease VPSPr. But in an Annals of Neurology study, Case Western Reserve University experts found people with all three possible gene patterns are affected by VPSPr. They say the findings could help with the treatment of prion diseases. Although it is a prion disease like vCJD, VPSPr is not linked to eating infected meat. However, like CJD, the new condition happens sporadically. It was first identified because of the fast-advancing form of dementia seen in those affected. They were also unable to speak or move. But tests for CJD proved negative. Further molecular examination showed VPSPr was a prion disease, but one which looked very different to those already known. The human prion protein gene comes in three variants, depending on which amino acid the prion proteins contain - valine (V) or methionine (M). People can be VV, MM or MV. The first clutch of cases identified all had the VV variant. However, these latest cases included people with the other variants too. Despite extensive research, a relatively large group of neurodegenerative diseases associated with dementia remain undefined. (C)BBC

Related chapters from BP7e: Chapter 16: Psychopathology: Biological Basis of Behavior Disorders
Related chapters from MM:Chapter 12: Psychopathology: Biological Basis of Behavioral Disorders
Link ID: 14359 - Posted: 08.14.2010

Daniel Cressey After an epic series of experiments, a group of researchers has observed and reproduced what could be the spontaneous generation of prions — rogue misfolded proteins that have been implicated in the destruction of the central nervous system. These misfolded proteins, the culprits in Creutzfeldt–Jakob disease and scrapie, are highly infectious. Although famously transmitted by the ingestion of infected meats, prions are also thought to arise spontaneously in a tiny fraction of humans and other animals. Such de novo prion generation has previously been achieved with animal cells using a method called 'protein misfolding cyclic amplification' (PMCA), which involves repeated rounds of ultrasound and incubation. Now, a London-based team reports observing prions appearing from healthy mouse brain tissue1. (Human samples have traditionally proved less amenable to PMCA, and the misfolding of prion proteins is believed to occur at a much lower rate in humans than in mice.) "What we were doing was trying to develop a very sensitive assay for prion detection on a metal surface, so we could use that in prion decontamination," says co-author John Collinge, who heads up the Department of Neurodegenerative Disease at University College London. "It took a while before we could convince ourselves this was a real phenomenon." © 2010 Nature Publishing Group

Related chapters from BP7e: Chapter 16: Psychopathology: Biological Basis of Behavior Disorders
Related chapters from MM:Chapter 12: Psychopathology: Biological Basis of Behavioral Disorders
Link ID: 14298 - Posted: 07.27.2010

By Laura Sanders Prion protein, notorious for causing the brain-wasting mad cow and Creutzfeldt-Jakob diseases, may also be a coconspirator in Alzheimer’s disease, a new study in mice suggests. In mad cow and Creutzfeldt-Jakob diseases, misshapen prion proteins do the damage. But the new paper, appearing February 26 in Nature, offers evidence that the harmless version of the prion protein assists the amyloid-beta protein responsible for brain cell death in Alzheimer’s disease. “It’s pretty sensational,” comments Adriano Aguzzi, a neuropathologist at the University of Zurich. “What’s tremendously electrifying is that prion protein may be a genetic sensor for extremely toxic, small concentrations of A-beta.” A-beta proteins can travel alone or in groups in the brain. On their own, A-beta proteins are harmless. Massive, insoluble clumps of A-beta, known as plaques, are probably harmless, too, says study coauthor Stephen Strittmatter, a neuroscientist at Yale University. These plaques may be a gravestone marker of dead brain cells but are probably not the killer. Instead, smaller, soluble clumps of 50 to 100 A-beta proteins, known as oligomers, are the most likely suspect, Strittmatter says. Earlier studies have shown that mice with A-beta oligomers can’t remember how to get through a maze as quickly as mice without A-beta oligomers. Such oligomers prevent cross-talk between certain brain cells in the hippocampus of mice, which helps explain the loss of learning and memory functions in Alzheimer’s disease. © Society for Science & the Public 2000 - 2009

Related chapters from BP7e: Chapter 7: Life-Span Development of the Brain and Behavior; Chapter 16: Psychopathology: Biological Basis of Behavior Disorders
Related chapters from MM:Chapter 13: Memory, Learning, and Development; Chapter 12: Psychopathology: Biological Basis of Behavioral Disorders
Link ID: 12594 - Posted: 06.24.2010

The US has found its second case of mad cow disease in a cow suspected, but cleared, of having BSE in November 2004. Although meat from the cow did not enter the food chain, the finding calls into question the accuracy of the country’s BSE surveillance programme. The cow might also be the first case born in the US. The first US case was in a cow imported from Canada in 2003. In 2004 the country started testing “high-risk” cattle - those that show neurological symptoms, are found dead or are “downers” (unable to stand). Since then it has tested 375,000 cattle. None were declared positive. In contrast, Canada has tested 30,000 cattle and found three positives. The rate at which the tests uncover positive cattle depends on the sample size, stresses Marcus Doherr of the University of Bern in Switzerland, who helped develop Swiss BSE surveillance. This means either that BSE is less evenly distributed in North America than thought, or that the US is missing cases. Unlike Canada, which uses the rapid “western blot” test, the US uses a test called ELISA, which is more prone to false positives. In 2004 the ELISA test detected three BSE positive cattle in the US. When these brains were re-tested, the ELISA was negative. Then they were subjected to immunohistochemistry (IHC) testing - a thin slice of brain is stained with antibodies for the prion protein that causes BSE. All were negative, and the cattle were declared BSE-free. “But if the prion is diffuse enough in the brain tissue, you can get a weak signal with the ELISA, and a negative with IHC,” says Doherr. Another test is needed to be certain, he says. © Copyright Reed Business Information Ltd

Related chapters from BP7e: Chapter 16: Psychopathology: Biological Basis of Behavior Disorders
Related chapters from MM:Chapter 12: Psychopathology: Biological Basis of Behavioral Disorders
Link ID: 7487 - Posted: 06.24.2010

Jim Schnabel Of all the ways that proteins can go bad, becoming an amyloid is surely one of the worst. In this state, sticky elements within proteins emerge and seed the growth of sometimes deadly fibrils. Amyloids riddle the brain in Alzheimer's disease and Creutzfeldt–Jakob disease. But until recently it has seemed that this corrupt state could threaten only a tiny fraction of proteins. Research is now hinting at a more unsettling picture. In work reported in February, a team led by David Eisenberg at the University of California, Los Angeles, sifted through tens of thousands of proteins looking for segments with the peculiar stickiness needed to form amyloid1. They found, says Eisenberg, that "effectively all complex proteins have these short segments that, if exposed and flexible enough, are capable of triggering amyloid formation". Not all proteins form amyloids, however. The 'amylome', as Eisenberg calls it, is restricted because most proteins hide these sticky segments out of harm's way or otherwise keep their stickiness under control. His results and other work suggest that evolution treats amyloids as a fundamental threat. Amyloids have been found in some of the most common age-related diseases, and there is evidence that ageing itself makes some amyloid accumulation inevitable. It now seems as though the human body is perched precariously above an amyloidal abyss. "The amyloid state is more like the default state of a protein, and in the absence of specific protective mechanisms, many of our proteins could fall into it," says Chris Dobson, a structural biologist at the University of Cambridge, UK. © 2010 Nature Publishing Group,

Related chapters from BP7e: Chapter 7: Life-Span Development of the Brain and Behavior; Chapter 16: Psychopathology: Biological Basis of Behavior Disorders
Related chapters from MM:Chapter 13: Memory, Learning, and Development; Chapter 12: Psychopathology: Biological Basis of Behavioral Disorders
Link ID: 13964 - Posted: 06.24.2010

Prions, the mis-folded proteins best known for causing diseases such as bovine spongiform encephalopathy in cows, scrapie in sheep and Creutzfeldt–Jakob disease in humans, could also help yeast survival, according to a study in the journal Cell1. "We think prions are really important," says co-author Simon Alberti of the Whitehead Institute for Biomedical Research in Cambridge, Massachusetts. "When environmental conditions are harsh, they might allow a species to survive." The work, led by Susan Lindquist of the Whitehead Institute, bolsters the theory that prions might confer an evolutionary advantage, says Alberti. Lindquist first broached that idea nine years ago, after finding that a prion called PSI+ in the yeast Saccharomyces cerevisiae triggered heritable changes that could provide a way of adapting to fluctuating environments2. More recent work also suggests prions might play a role in memory in sea slugs and smell in mice. In the new work, a scan of the S. cerevisiae genome yielded 24 potential prion-forming proteins. Only five prions were known to exist in yeast before this study. The team focused on a protein called Mot3 and found that it can twist into a prion form. When in its normal shape, Mot3 suppresses yeast genes involved in building the cellular wall. But when Mot3 kinks into a prion, it loses this function and the wall-building genes activate. Hence, yeast carrying the Mot3 prions grew thicker, more robust cell walls. © 2009 Nature Publishing Group,

Related chapters from BP7e: Chapter 16: Psychopathology: Biological Basis of Behavior Disorders
Related chapters from MM:Chapter 12: Psychopathology: Biological Basis of Behavioral Disorders
Link ID: 12716 - Posted: 06.24.2010

Debora McKenzie Viruses, not prions, may be at the root of diseases such as scrapie, BSE and variant Creutzfeldt-Jakob disease (vCJD), researchers say. If true, the new theory could revolutionise our understanding of these so-called transmissible spongiform encephalopathies (TSEs), and potentially lead to new ways of treating them. The widely accepted theory of what causes infectious prion diseases – such as vCJD, scrapie and “mad cow disease” – is that deformed proteins called prions corrupt other brain proteins, eventually clogging and destroying brain cells. However, this theory has not been definitively proven. Laura Manuelidis at Yale University in New Haven, Connecticut, US, has insisted for years that tiny virus-like particles observed in TSE-infected brains may be the culprits. But such brains are degenerating, so the particles had been dismissed as general debris. When Manuelidis studied cultures of neural cells infected with two particular strains of scrapie and CJD, she found that these virus-like particles were clustered in regular arrays within the cells – in a pattern that viruses regularly form in cells – and she saw no apparent prions in the cells. © Copyright Reed Business Information Ltd.

Related chapters from BP7e: Chapter 16: Psychopathology: Biological Basis of Behavior Disorders
Related chapters from MM:Chapter 12: Psychopathology: Biological Basis of Behavioral Disorders
Link ID: 9956 - Posted: 06.24.2010

Stu Hutson The curative properties of stem cells may rely on prions, a new study suggests, the type of protein made infamous by mad cow disease. Prions are a special class of protein that can change the shape and function of other proteins around them. While these are found throughout any mammal’s body, the understanding of their biological role is limited. What is known is that prions that become misshapen, through some unknown process, can result in BSE (bovine spongiform encephalopathy) – mad cow disease – and its equivalents in other animals. Researchers at the Whitehead Institute in Cambridge, Massachusetts, US, have now found that adult stem cells in bone marrow gradually lose their ability to regenerate without their normal complement of membrane-bound prions. Stem cells are primitive cells which have the potential to divide endlessly, and the ability to differentiate into any cell type in the body – offering hope for future therapies. Andrew Steele, Cheng Cheng Zhang and colleagues used radiation to deplete the bone marrow of mice genetically engineered to not produce the prion proteins. The animals’ marrow regenerated quickly at first, but eventually slowed to a stop. The marrow also lost its regenerative abilities when transplanted into normal mice. © Copyright Reed Business Information Ltd

Related chapters from BP7e: Chapter 16: Psychopathology: Biological Basis of Behavior Disorders; Chapter 7: Life-Span Development of the Brain and Behavior
Related chapters from MM:Chapter 12: Psychopathology: Biological Basis of Behavioral Disorders; Chapter 13: Memory, Learning, and Development
Link ID: 8461 - Posted: 06.24.2010

Debora MacKenzie The infectious prions that cause Chronic Wasting Disease, an infection similar to BSE that afflicts North American deer and elk have been found in the parts of the animals that people eat. No one knows if CWD can jump to humans, but if it does hunters in affected areas might be at risk. CWD was first diagnosed as a spongiform encephalopathy in captive deer and elk in Colorado in the 1970s, and in wild deer and elk in the region in the 1980s. But in the 1990s it spread widely within the elk farming industry, jumped to wild deer, and now affects two provinces of Canada and 13 US states. Like the related sheep disease scrapie – though unlike BSE – CWD spreads from animal to animal, says Glenn Telling of the University of Kentucky at Lexington, US. Deer housed with infected animals, or fed infected brain experimentally, contract the disease. Because of this there are fears that the CWD prion might be distributed widely in the deer’s tissues – as scrapie is in sheep. Efforts to find the infectious prion in the muscle of infected animals, by seeing whether antibodies to the prion could find any and bind on, have previously failed. But Telling’s lab has now shown that diseased prions can reside in muscle of deer infected with CWD, by using transgenic mice. © Copyright Reed Business Information Ltd.

Related chapters from BP7e: Chapter 16: Psychopathology: Biological Basis of Behavior Disorders
Related chapters from MM:Chapter 12: Psychopathology: Biological Basis of Behavioral Disorders
Link ID: 8450 - Posted: 06.24.2010

Study reveals antibodies can kill brain cells. HELEN PEARSON Antibody therapies designed to treat the human form of mad cow disease could backfire, warn US scientists. The group investigated the proteins called prions that cause the rare brain disorder variant Creutzfeldt–Jakob disease (vCJD) and its farmyard equivalent, bovine spongiform encephalopathy (BSE). Prions cause disease when they take on a misshapen form, accumulate in the brain and kill off nerve cells. Some research groups are trying to prevent this by using antibodies that grab hold of normal prions and prevent them from transforming into the harmful configuration. © Nature News Service / Macmillan Magazines Ltd 2003

Related chapters from BP7e: Chapter 16: Psychopathology: Biological Basis of Behavior Disorders
Related chapters from MM:Chapter 12: Psychopathology: Biological Basis of Behavioral Disorders
Link ID: 4888 - Posted: 06.24.2010

Research by North Carolina State University scientists, in conjunction with scientists from the Netherlands and BioResource International, an NC State spin-off biotechnology company, has shown that, under proper conditions, an enzyme can fully degrade the prion – or protein particle – believed to be responsible for mad cow disease and other related animal and human diseases. These transmissible prions – believed to be the cause of bovine spongiform encephalopathy (BSE), the technical name for mad cow disease, as well as the human and sheep versions, called Creutzfeldt-Jakob disease and scrapie, respectively – are highly resistant to degradation, says Dr. Jason Shih, professor of biotechnology and poultry science at NC State. But the new research, which tested the effects of a bacterial enzyme keratinase on brain tissues from cows with BSE and sheep with scrapie, showed that, when the tissue was pretreated and in the presence of a detergent, the enzyme fully degraded the prion, rendering it undetectable. The research was published in the Dec. 1 edition of The Journal of Infectious Diseases.

Related chapters from BP7e: Chapter 16: Psychopathology: Biological Basis of Behavior Disorders
Related chapters from MM:Chapter 12: Psychopathology: Biological Basis of Behavioral Disorders
Link ID: 4757 - Posted: 06.24.2010

CAMBRIDGE, Mass. – Scientists have discovered a new process for how memories might be stored, a finding that could help explain one of the least-understood activities of the brain. What's more, the key player in this process is a protein that acts just like a prion – a class of proteins that includes the deadly agents involved in neurodegenerative conditions such as mad cow disease. The study, published as two papers in the Dec. 26 issue of the journal Cell, suggests that this protein does its good work while in a prion state, contradicting a widely held belief that a protein that has prion activity is toxic or at least doesn't function properly. "For a while we've known quite a bit about how memory works, but we've had no clear concept of what the key storage device is," says Whitehead Institute for Biomedical Research Director Susan Lindquist, who coauthored the study with neurobiologist Eric Kandel at Columbia University. "This study suggests what the storage device might be – but it's such a surprising suggestion to find that a prion-like activity may be involved."

Related chapters from BP7e: Chapter 16: Psychopathology: Biological Basis of Behavior Disorders; Chapter 18: Attention and Higher Cognition
Related chapters from MM:Chapter 12: Psychopathology: Biological Basis of Behavioral Disorders; Chapter 14: Attention and Consciousness
Link ID: 4739 - Posted: 06.24.2010

Old epidemic sheds new light on vCJD XAVIER BOSCH New evidence from an old epidemic could help those trying to estimate how many people may be incubating variant Creutzfeldt–Jakob disease (vCJD) - the human form of mad cow disease. So say scientists in the United States who have studied DNA extracted from victims of the first documented prion disease, kuru1. Like vCJD, kuru is a neurodegenerative disease caused by infection with a rogue 'prion' protein. The disease spread among the Fore people of Papua New Guinea in the 1940s and 1950s as a result of their cannibalistic funerary rituals. 1.Lee, H.-S. et al. Increased susceptibility to kuru of carriers of the PRNP 129 methionine/methionine genotype. Journal of Infectious Diseases 183, 192–196 (2001). © Macmillan Magazines Ltd 2001 - NATURE NEWS SERVICE Nature © Macmillan Publishers Ltd 2001 Reg. No. 785998 England.

Related chapters from BP7e: Chapter 16: Psychopathology: Biological Basis of Behavior Disorders
Related chapters from MM:Chapter 12: Psychopathology: Biological Basis of Behavioral Disorders
Link ID: 189 - Posted: 06.24.2010

By Tina Hesman Saey Sea slugs make memories with a twist. Screwing a normal nerve cell protein into a distorted shape helps slugs, and possibly people, lock in memories, new research shows. Notably, the shape change also brings a shift in the protein’s behavior, leading it to form clumps. That kind of behavior is the sort seen in prions, the misshapen, infectious proteins that cause mad cow disease, scrapie and other disorders (SN: 7/31/04, p. 67). But the new study, published February 5 in Cell, shows a possible normal function for the shape-shifting, suggesting that twists and clumps don’t necessarily make prions monsters. In one sense, prions are machines of “molecular memory,” says Yury Chernoff, a biologist at the Georgia Institute of Technology in Atlanta and editor in chief of the journal Prion. The proteins remember what happened to them — changing shapes — and then transmit that change to other proteins. “But the notion of these machines being used for cellular, and therefore organismal, memory is truly amazing,” he says. If further research shows the process works the same way in humans as it does in sea slugs, prionlike proteins might eventually be used in memory-enhancing treatments, Chernoff says. Prions have a bad reputation due to the most famous of the shape-changing proteins, called prion protein or PrP. When PrP switches from its harmless form, which is normally present in nerve cells, into a prion form, it corrupts other PrP molecules that then assemble themselves into nearly indestructible plaques known as amyloids. © Society for Science & the Public 2000 - 2010

Related chapters from BP7e: Chapter 16: Psychopathology: Biological Basis of Behavior Disorders; Chapter 17: Learning and Memory
Related chapters from MM:Chapter 12: Psychopathology: Biological Basis of Behavioral Disorders; Chapter 13: Memory, Learning, and Development
Link ID: 13747 - Posted: 06.24.2010

By Carina Storrs When prions are transferred from one species to another—like from sheep and cows to mice in the laboratory or to humans in the case of the fatally neurodegenerative variant Creutzfeldt-Jakob disease—new forms of the infectious proteins can emerge over time that make them deadly to the new host. A new study examines the emergence and persistence of prion mutations, which allow prions to grow in infected cells in the presence of anti-prion compounds. In the classic sense, prions, which are misfolded versions of the brain protein PrP, cannot mutate because they do not contain DNA or RNA. They can, however, give rise to variants with different properties, possibly due to differences in the folding, or shape, of the proteins. In the study, published December 31 in Science Express, researchers estimated the rate at which prion mutants can appear in cultured human nerve cells. In addition, the study suggests that once variants appear, they persist at low levels, giving rise to a heterogeneous prion population. "On the face of it, you have exactly the same process of mutation and adaptive change in prions as you see in viruses," said Dr. Charles Weissmann in a prepared statement. Weissmann, who is the head of the Scripps Florida Department of Infectology in Jupiter, Fla., led the study. To track prion mutation, Weissmann's team mixed one prion-infected human nerve cell with 1,000 uninfected human nerve cells in each petri dish. The infected cell contained a single prion that was susceptible to a drug called swainsonine, or swa. © 1996-2010 Scientific American

Related chapters from BP7e: Chapter 16: Psychopathology: Biological Basis of Behavior Disorders
Related chapters from MM:Chapter 12: Psychopathology: Biological Basis of Behavioral Disorders
Link ID: 13621 - Posted: 06.24.2010

A group of German researchers may have figured out why a protein that can turn rogue and cause fatal illnesses such as mad cow disease exists in large quantities inside cows, humans and other animals. The protein — known as the "prion" protein or PrP — appears to help cells communicate with each other when an embryo is developing, said a paper published Monday in the journal PloS Biology by a group of researchers at University of Konstanz in Germany. "What we see PrP doing in the fish embryo may be analogous to what it does in the mammalian brain, which is what may go wrong during prion diseases," biologist Edward Malaga-Trillo, who led the study, said in an email to CBCNews.ca. Diseases such as mad cow disease in cows and Creutzfeldt-Jakob disease in humans have been traced back to rogue, altered versions of the prion protein. But up until now, researchers have been unsure what normal versions of the protein are supposed to do. Those normal proteins are the "starting ingredient" for prion diseases. When prion proteins fold abnormally, they clump together into groups called plaques that lead to brain damage. The misfolded prions multiply by turning normal prions "bad." In previous studies, mice engineered so they were unable to produce the normal prion protein seemed mostly normal. However, in the recent study led by University of Konstanz biologist Edward Malaga-Trillo, zebrafish embryos that could not make the prion protein didn't develop normally and eventually died. © CBC 2009

Related chapters from BP7e: Chapter 16: Psychopathology: Biological Basis of Behavior Disorders
Related chapters from MM:Chapter 12: Psychopathology: Biological Basis of Behavioral Disorders
Link ID: 12634 - Posted: 06.24.2010

By DONALD G. McNEIL Jr. D. Carleton Gajdusek, a virologist who won the 1976 Nobel Prize in medicine for his work on the mysterious epidemics now known as prion diseases, died last week in Tromso, Norway. The cause of death is unknown, but Dr. Gajdusek (pronounced GUY-dah-shek) was 85 and had long had congestive heart failure, said Dr. Robert Klitzman, his biographer, who said he had spoken to him about a week ago. He was found in his Tromso hotel room on Friday morning about 24 hours after a manager saw him at breakfast. In later life, Dr. Gajdusek became notorious when he was charged with molesting the many young boys he had adopted in New Guinea and Micronesia and brought to live with him in Maryland. He pleaded guilty to one charge, served a year in prison and left the United States in 1998, dividing his time between Paris, Amsterdam and Tromso. Dr. Gajdusek won the Nobel for his work on kuru, which was slowly wiping out the Fore tribe of New Guinea. Victims descended into trembling and madness before death and, after an autopsy, were found to have brains shot through with spongy holes. In 1957, Dr. Gajdusek — who had searched the Hindu Kush, the Amazon jungle and finally the mountain valleys of New Guinea hoping to find remote tribes with unique diseases to study — realized that the victims had all participated in “mortuary feasts” in the decades before the custom was suppressed in the 1940s by missionaries and the Australian police. Copyright 2008 The New York Times Company

Related chapters from BP7e: Chapter 16: Psychopathology: Biological Basis of Behavior Disorders
Related chapters from MM:Chapter 12: Psychopathology: Biological Basis of Behavioral Disorders
Link ID: 12338 - Posted: 06.24.2010

Prions have traditionally been linked with the development of Creutzfeld-Jakob Disease (CJD), the brain-wasting equivalent of mad cow disease (also known as bovine spongiform encephalopathy). (CBC)Prions — infectious agents that cause diseases like the human variant of mad cow disease — also have protective properties, new research suggests. When functioning normally, prion proteins protect neurons in the brain from becoming overstimulated and dying, indicates the study, published in the May 5 issue of the Journal of Cell Biology. Prions have traditionally been linked with the development of neurodegenerative diseases like Creutzfeld-Jakob Disease (CJD), the brain-wasting equivalent of mad cow disease (also known as bovine spongiform encephalopathy, or BSE). In this role, abnormal prions cause plaques to form on the neurons preventing them from functioning properly. Researchers at Rockefeller University discovered that when they removed prion proteins from the brain cells of mice, their neurons overreacted to electrical and drug-induced stimulation, eventually dying. The authors believe that prion proteins only turn deadly when they are physically altered, as they can no longer regulate the behaviour of the neurons and offer a neuroprotective effect. Researchers aren't sure how this transformation occurs. © CBC 2008

Related chapters from BP7e: Chapter 16: Psychopathology: Biological Basis of Behavior Disorders
Related chapters from MM:Chapter 12: Psychopathology: Biological Basis of Behavioral Disorders
Link ID: 11611 - Posted: 06.24.2010

Nathan Seppa Mad cow disease and other brain disorders stemming from prion proteins have long resisted cure. Now, in a test in mice, a prion disease caught early has been reversed. Prions—misfolded versions of a natural protein called PrP—trigger normal PrP to misfold in the same way. Over time, prion infection kills so many neurons that the brain becomes riddled with holes. In the new study, neurologist Giovanna R. Mallucci of the Institute of Neurology in London and her colleagues tested whether shutting off the prions' supply of PrP could alter the course of disease. They worked with genetically engineered mice that make PrP only for the first 9 weeks of life and normal mice that make PrP indefinitely. The researchers infected both groups, shortly after birth, with prions that cause scrapie in sheep. At 8 weeks of age, mice in both groups showed cognitive deficits. For example, mice normally spend more time exploring unfamiliar sets of objects than known ones. But the infected mice spent the same time examining strange or familiar arrangements of blocks, indicating that the animals had forgotten familiar arrangements. The mice also lost some of their natural inclination to gather food pellets. ©2007 Science Service.

Related chapters from BP7e: Chapter 16: Psychopathology: Biological Basis of Behavior Disorders
Related chapters from MM:Chapter 12: Psychopathology: Biological Basis of Behavioral Disorders
Link ID: 9918 - Posted: 06.24.2010