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DALLAS – – Researchers from UT Southwestern Medical Center at Dallas and the Mayo Clinic have discovered a novel genetic mutation that leads to a debilitating muscle condition known as myasthenia. Myasthenia, a severe form of muscle weakness, usually results from an autoimmune attack against the nerve-muscle junction in which the nerve's communication to the muscle is broken down. In a study appearing this week in the online early edition of Proceedings of the National Academy of Sciences, researchers unveil a new cause discovered in a single patient: a genetic mutation leading to a shutdown in muscle responsiveness to the nerve's electrical impulses. "This was a surprise in that it's a totally different mechanism for a well-researched disease," said Dr. Stephen Cannon, chairman of neurology at UT Southwestern, who studied the consequences of the genetic mutation. "Until this study, every single case of myasthenia ever examined had been attributed to a reduction in what's called the safety factor of neurotransmission – or how reliably the nerve talks to the muscle."
An altered mouse model of Duchenne muscular dystrophy, developed to have high levels of insulin-like growth factor I (IGF-I), has shown increases in muscle mass of at least 40 percent and other changes that could herald a possible treatment for secondary symptoms of the disease in humans. The new mouse, developed with support from the National Institute of Arthritis and Musculoskeletal and Skin Diseases (NIAMS) and the Muscular Dystrophy Association, has also resulted in reduced amounts of muscle-replacing fibrous tissue and enhanced biological pathways associated with muscle regeneration. Duchenne muscular dystrophy, a genetic muscle-wasting disease caused by mutations in the gene for the protein dystrophin, results in repeated cycles of muscle damage and insufficient muscle regeneration, leading to gradual replacement of muscle by fibrous tissue. Since IGF-I is known to help regenerate muscle and enhance biological pathways for making proteins, the University of Pennsylvania's H. Lee Sweeney, M.D., and his colleagues tested its effects by creating a new mouse model – a cross between a strain with muscular dystrophy symptoms and another with high levels of IGF-I. The hybrid mouse showed not only increases in muscle mass and muscle force generation, but also reduced muscle cell death, a combination that could have significant treatment implications.
By JANE E. BRODY “Essential” usually means vital, necessary, indispensable. But in medicine, the word can assume a different cast, meaning inherent or intrinsic, not symptomatic of anything else, lacking a known cause. Since the mid-19th century, “essential tremor” has been the diagnosis for a disorder of uncontrollable shaking — usually of the hands but sometimes of the head and other body parts, or the voice — that is not due to some other condition. And without knowing what causes it, doctors have been slow to come up with treatments to subdue it. As a result, millions of individuals suffer to varying degrees with embarrassment and humiliation, social isolation and difficulties holding down a job or performing the tasks of daily life. When you cannot drink a glass of water or eat soup without spilling it because your hand shakes violently, you are unlikely to join others for a dinner out. When you have to depend on someone else to button your shirt or zip your jacket, you may not go out at all. Wherever those with essential tremor go, people are likely to stare at them and assume they have a drug or alcohol problem, said Catherine Rice, executive director of the International Essential Tremor Foundation in Lenexa, Kan. (Call it at 888-387-3667 or visit its Web site: www.essentialtremor.org.) Now, thanks to the devoted efforts of a few researchers here and abroad, all this may change. Recent studies have begun to unravel the mysteries of essential tremor, and “essential” may someday be dropped from its name. Copyright 2009 The New York Times Company
By RONI CARYN RABIN It may be hard to fathom, but in the haystack of government health statistics that track cancer, car accidents, twin births to women over 40, fat teenagers and people who quit smoking, there has been no reliable estimate of the number of Americans affected by paralysis. Until now. A study to be released on Tuesday by the Christopher and Dana Reeve Foundation reports that far more Americans than previously estimated are paralyzed to some degree: 5.6 million people, representing 1.9 percent of the population, or roughly 1 in 50 Americans. Previous estimates — or “guesstimates,” as some have called them — hovered around 4 million at most, and some were as low as 1.4 million. “Nobody had any idea what the numbers were, because no one ever tried to find out,” said Joseph Canose, vice president for quality of life at the Reeve Foundation’s Paralysis Resource Center, who led the study. “There were many different ways of counting it, and there was no common definition, and the numbers were all over the place.” But the figures, which could have enormous implications for public policy, research financing and health care, are already causing controversy, because the estimates for paralysis caused by certain diseases and conditions differ drastically from long-accepted numbers. Copyright 2009 The New York Times Company
by Joyce Gramza It’s been 20 years since the discovery of the gene that causes the most common type of Muscular Dystrophy — Duchenne MD — and patients are still waiting for a cure. "The mutation causes muscle fibers to pull away from each other and with progressive use of your muscles in these patients it eventually leads to muscle damage, severe muscle damage," explains Dean Burkin, assistant professor of pharmacology at the University of Nevada, Reno School of Medicine. Gene therapy to replace the faulty dystrophin gene might be a solution, but Burkin and his colleagues are excited about a simpler and potentially safer approach based on work they are publishing in this week’s Proceedings of the National Academy of Sciences. "This could be an IV drug for the patients if the work in the mouse models that we’ve been using translates to human studies," Burkin says. "That would allow a fair ease of treatment for the patients…. We’ve obviously got to do some safety tests and there’s still a few studies that we need to do. But in the field there are a number of drugs including ours that are being developed. "These patients, especially, have been waiting a long time for new therapies to come about and I think we’re at the cusp now." ©2009 ScienCentral
By DIANA MICHÈLE YAP In my dreams, I can walk. Awake, I lie in bed because I have to — on my back, or on my side. I shift positions. I’ve learned I’m lucky I can do that. Sometimes I’m so tired that simply lying in bed is not restful enough. Can I be any more horizontal? Can my atrophied limbs sink any lower into the sheets, the mattress that molds to my form? I imagine falling through the mattress, but realize it would probably hurt when I hit the floor. I never get bored, lying there. Just sad. Last year I lost my ability to walk. By the time I finally learned I had osteosclerotic myeloma, part of POEMS syndrome (a rare blood disorder whose initials stand for five of its features, including polyneuropathy, or nerve damage), I was weaker than I’d ever been. I was nearly unable even to use my hands. None of it registered as suffering, until this past spring, as I began to write these words. Perhaps I’ve been in shock. I recognize that I don’t live in a war zone, that there are more aggressive cancers. I’m told about others locked in their disabled bodies who produce great work, and even play sports. But I am not extraordinary; I’m no hero. The horror of my situation is the opposite of the happy ending I wished for in high school, half a lifetime ago. At 35, I’m mostly confined to the bed and the wheelchair. Twice a week I go to physical therapy. Copyright 2008 The New York Times Company
Related chapters from BP7e: Chapter 11: Motor Control and Plasticity; Chapter 15: Emotions, Aggression, and Stress
Related chapters from MM:Chapter 5: The Sensorimotor System; Chapter 11: Emotions, Aggression, and Stress
Link ID: 12394 - Posted: 06.24.2010
CHICAGO - U.S. scientists have created the first human model for studying a devastating nerve disease, which allows them to watch how the disease develops and could help researchers find a way to treat it. Using skin cells from a child with spinal muscular atrophy, a genetic disease that attacks motor neurons in the spinal cord, researchers grew batches of nerve cells with the same genetic defects. The finding allowed scientists to watch the nerve cells die off. "Now we can start from the beginning of development and replay the disease process in the lab dish," Clive Svendsen of the University of Wisconsin-Madison said in a telephone interview. The finding, reported on Sunday in the journal Nature, marks the latest advance in research that reprograms ordinary cells to look and act like embryonic stem cells — the master cells of the body that can produce any type of tissue or blood cell. Spinal muscular atrophy is the most common cause of childhood death caused by a genetic mutation, Svendsen said. It is caused by a deficiency of a protein called SMN, for survival of motor neurons. "That SMN protein is important for motor neuron survival. They are the cells that make muscles move," Svendsen said. Copyright 2008 Reuters.
Researchers at the Howard Hughes Medical Institute are unveiling a new resource that they say will speed scientists' understanding and treatment of a group of inherited disorders called ataxias that kill cells in the brain, causing loss of balance, coordination and often death. The scientists are making new data available on hundreds of interacting proteins that are involved in dozens of inherited forms of ataxia. The approach to mapping the global set of interacting proteins—called an “interactome”—could also be applied to disorders as diverse as Parkinson's disease, diabetes, and hypertension. Howard Hughes Medical Institute investigator Huda Y. Zoghbi and her colleagues reported on their studies in an article published in the May 18, 2006, issue of the journal Cell. Zoghbi and her colleagues at the Baylor College of Medicine collaborated on the studies with researchers from Harvard Medical School and the University of Notre Dame. Since proteins are the major machines that work inside cells, understanding how they interact may give researchers an opportunity to learn how they can go awry and cause disease. Furthermore, understanding these interactions offers scientists targets for drugs that can help restore normal function to such malfunctioning machinery. © 2006 Howard Hughes Medical Institute.
We all teeter and tip while first learning to walk but, for adults like retired electrical engineer Fred Kawabata — whose sense of balance was damaged when a childhood disease flared up as an adult — a simple stroll becomes something to learn all over again. "When it first struck me I was flat on my back," explains 65-year-old Kawabata from Beaverton, Oregon. "I had vertigo, I was dizzy, I could hardly get out of bed." Almost ten years ago the chicken pox he had suffered as a kid came back in the form of shingles. The virus that lay dormant for all those years in his nerves attacked the vestibular nerves of Kawabata's the inner ear, leaving him rather unsteady on his feet because of a balance disorder. "In about a month, I could get up and walk around although it was still very uncomfortable. It took a couple months before I could be reasonably comfortable walking around," he recalls. "[Now], when I'm walking on a flat surface, I generally don't have to think about it very much. But if I'm on an uneven surface like when I'm hiking and the trail is rough, then I really have to think about it. © ScienCentral, 2000-2006.
Related chapters from BP7e: Chapter 9: Hearing, Vestibular Perception, Taste, and Smell; Chapter 11: Motor Control and Plasticity
Related chapters from MM:Chapter 6: Hearing, Balance, Taste, and Smell; Chapter 5: The Sensorimotor System
Link ID: 8729 - Posted: 06.24.2010
By Aaron J. Sender John Donoghue is building a brain decoder that could transform the lives of people paralyzed by injury or disease. Those who have lost the ability to move their limbs often have perfectly intact brains, so Donoghue hopes to implant a chip that can monitor their brain activity and convert their intentions into computer commands. In its current version, the chip’s 100 hair-thin electrodes listen to neurons firing in an area that controls arm movement and translate the activity into electronic signals. A program then decodes the brain signals into commands that direct a cursor on a computer screen. Donoghue hopes the chip can eventually control appliances or even robotic limbs. “We’re effectively rewiring the nervous system—not biologically but with real wires,” says Donoghue. So far, more than 20 monkeys have been equipped with the implanted chip, and four of them have successfully willed a cursor to follow a moving target. Now Cyberkinetics, the company Donoghue cofounded to develop the device they call BrainGate, is preparing to test it in five paralyzed humans. “People with these kinds of injuries are perfectly capable of leading full and productive lives,” says Donoghue. “They just can’t get their signals out.” Give me the big picture first. How did the idea originate and what problem were you looking to solve? D: I’ve had a long-standing basic science research program that has really been directed at how the brain computes information. In a simpler sense, how do you turn thoughts into action? The way you get at the fundamental activity is by recording with electrodes in the brain. And since it’s a procedure that requires you to introduce that electrode, you have to use a monkey or an experimental animal. A monkey has a motor cortex like ours, and its behaviors are a lot like ours, so we use it as a model. © 2004 The Walt Disney Company.
by Paul Austin The patient was lying placidly on the stretcher with her eyes closed when I introduced myself. “I’m Paul Austin, one of the ER doctors. Can you open your eyes and talk with me?” She raised her eyebrows a few millimeters, not even enough to wrinkle her forehead. Her right eye remained shut, and her left eye opened just enough to expose a narrow sliver of white. She turned her face toward me, her eyes still closed. I looked at her paperwork. She was a 63-year-old woman who said she couldn’t keep her eyes open, had difficulty swallowing, and had fallen four times the day before. She also had complaints of general weakness for about two years. That bothered me. The possible causes of overall weakness could fill a textbook. Yet in cases that have gone on for two years without a diagnosis, doctors often find no physical cause. Her chart noted that she had recently been hospitalized for schizo-affective disorder, which causes symptoms of both schizophrenia and a mood disorder, and had recently been discharged. That concerned me as well. When a psychiatric diagnosis is present, it can distract doctors from looking for an organic cause of symptoms. “Can you open your eyes for me?” I asked again. Her eyebrows moved a millimeter up. “Open them all the way.” Using her index fingers she raised both her upper eyelids. She stared at me, holding her eyelids up with her fingers, her elbows sticking out at her sides.
By BEN DAITZ, M.D. ALBUQUERQUE, In 1598, Joyce Gonzalez’s great- great- great- great -great -great -great -great -great -great -grandfather followed the famous conquistador Juan de Oñate from Spain to Mexico, then north on the Camino Real, the Royal Road to Santa Fe. In the 1800s, one of Mary Ann Chavez’s distant relatives, possibly a French fur trapper and trader from Quebec, also made his way into northern New Mexico. Mrs. Chavez and Mrs. Gonzalez, though not related, share a Hispanic heritage and a fascination with genealogy. They also share the burden of having forebears with genetic diseases that, like the remote mountain villages in this region, have remained largely hidden from medical diagnosis and treatment. Now, thanks to the efforts of patient advocates and the work of a clinic here at the University of New Mexico Medical School, these illnesses are finally being confronted and studied. “We call it the family curse,” said Mrs. Chavez, 73, “and you don’t know you’ve got it until you’re 40 or 50 when your eyelids start to droop, and you begin to have trouble swallowing and get muscle weakness.” The illness is called oculopharyngeal muscular dystrophy, or OPMD, and the largest group of Americans affected are Hispanics living in northern New Mexico. They are descendants of the wandering French-Canadian or, perhaps, early Spanish colonists. Mrs. Chavez’s son, her brother and innumerable aunts, uncles and cousins have all inherited the disease. Copyright 2007 The New York Times Company
ITHACA, N.Y. -- Using a state-of-the-art technique to map neurons in the spinal cord of a larval zebrafish, Cornell University scientists have found a surprising pattern of activity that regulates the speed of the fish’s movement. The research may have long-term implications for treating injured human spinal cords and Parkinson’s disease, where movements slow down and become erratic. The study, "A Topographic Map of Recruitment in Spinal Cord," published in the March 1 issue of the journal Nature, maps how neurons in the bottom of the fish’s spinal cord become active during slow movements, while cells further up the spinal cord activate as movements speed up. By removing specific neurons in the lower spinal cord with laser beams, the researchers rendered the fish incapable of slow movements. By removing nerves further up the backbone, the fish had difficulty moving fast. "No one had any idea that organization like this existed in a spinal cord," said Joseph Fetcho, a Cornell professor of neurobiology and behavior and an author of the study. "Now that we know the pattern, we can begin to ask how that changes in disease states." David McLean, Cornell postdoctoral researcher in Fetcho’s laboratory, was the first person to discover the pattern of neural activation and how it was associated with speed of movement. He is the lead author on the study.
Drug therapy can extend survival and improve movement in a mouse model of spinal muscular atrophy (SMA), new research shows. The study, carried out at the NIH’s National Institute of Neurological Disorders and Stroke (NINDS), suggests that similar drugs might one day be useful for treating human SMA. "This study shows that treatment can be effective when started after the disease appears," says Kenneth H. Fischbeck, M.D., of the NINDS, who helped lead the new study. The finding is important because most children with SMA are diagnosed after symptoms of the disease become obvious, he adds. The report appears in the February 22, 2007, advance online publication of The Journal of Clinical Investigation. SMA is the most common severe hereditary neurological disease of childhood, affecting one in every 8,000-10,000 children. Babies with the most common form of the disease, called SMA type I, develop symptoms before birth or in the first few months of life and have severe muscle weakness that makes it difficult for them to breathe, eat, and move. They usually die by age two. Other forms of SMA are not as severe, but still cause significant disability. While some symptoms of SMA can be alleviated, there is currently no treatment that can change the course of the disease. SMA is caused by mutations in a gene called SMN1. Investigators studying the genetics of SMA have found that there is another gene, called SMN2, on the same chromosome. While the normal form of SMN1 produces a full-length functional protein, most of the protein produced by SMN2 is truncated and unable to function. The relatively small amount of normal SMN protein produced by the SMN2 gene can reduce the severity of the disease. Therefore, investigators are searching for drugs that can increase the amount of normal protein produced by this gene.
ST. PAUL, MN -- An anticonvulsant drug typically used to control seizures and neuropathic pain may reduce symptoms among those who suffer from restless legs syndrome (RLS), a movement disorder that affects up to 10 percent of the population. A study published in the November 26 issue of Neurology, journal of the American Academy of Neurology, concludes, “Gabapentin may be a potent agent for treatment of even severe RLS, without the disadvantages of long-term complications of previously favored treatments,” according to study author Diego Garcia-Borreguero, MD, of the Fundacion Jimenez Díaz in Madrid, Spain. RLS is characterized by: an urge to move the legs, generally accompanied by unpleasant sensations; an increase of symptoms during rest and a partial, temporary relief of symptoms through activity; and worsening of symptoms in the evening or at night. Symptoms tend to progress with age. RLS is usually treated with dopaminergic drugs, such as those used with Parkinson’s disease patients. However, the side effects and likelihood of long-term complications have driven the search for RLS treatment options.
Researchers have discovered how the abnormal repetition of a genetic sequence can have disastrous consequences that lead to the death of neurons that govern balance and motor coordination. The studies bolster the emerging theory that neurodegenerative disorders can be caused by having extra copies of a normal protein, not just a mutated one. People who are afflicted with the rare neurodegenerative disorder spinocerebellar ataxia type 1 (SCA1) suffer damage to cerebellar Purkinje cells caused by a toxic buildup of the protein Ataxin-1. Researchers knew that SCA1, Huntington's disease and other related disorders arise because of a “genetic stutter,” in which a mutation causes a particular gene sequence to repeat itself. These abnormal genetic repeats cause the resulting proteins to contain unusually long repetitive stretches of the amino acid glutamine. The new findings, which are published in the August 26, 2005, issue of the journal Cell, provide a molecular explanation for Ataxin-1's assault on cerebellar Purkinje cells. The findings should help to understand a range of diseases, including Huntington's disease, which are caused by an abnormal number of repetitive gene sequences. The discovery may also offer a new conceptual approach to understanding the pathology of Parkinson's disease and Alzheimer's disease, according to Huda Y. Zoghbi, a Howard Hughes Medical Institute investigator at the Baylor College of Medicine. © 2005 Howard Hughes Medical Institute.
Rossella Lorenzi, Discovery News -- The remains of a man who could be the world's oldest known paralysis victim have been unearthed by Australian bio-archaeologists in northern Vietnam. Found at the Neolithic cemetery site of Man Bac, some 100 kilometers (62 miles) south of Hanoi, the remains are between 3,500 and 4,000 years old and belong to an adult male who died around age 25. Called Man Bac Burial 9, or simply M9, the young man suffered from paraplegia or possibly quadriplegia due to a rare disorder called Klippel-Feil Syndrome, a condition involving congenital fusion of the spine. The disorder, which can make sufferers look as if they have a short neck, is also often associated with various complications. In the case of M9, posture-related complications forced his head to tilt to his right side, a condition known as torticollis. M9 also likely had problems chewing. spine surgery "Amazingly, this man survived in a subsistence Neolithic economy with total lower body paralysis, and at best minimal upper body mobility for at least a decade prior to death," Lorna Tilley, the Australian National University Ph.D. candidate who excavated the remains with lead researcher Marc Oxenham, told Discovery News. © 2009 Discovery Communications, LLC. Inc.
Related chapters from BP7e: Chapter 11: Motor Control and Plasticity; Chapter 6: Evolution of the Brain and Behavior
Related chapters from MM:Chapter 5: The Sensorimotor System
Link ID: 13211 - Posted: 06.24.2010
By Michael Price People with muscular dystrophy tire after even light exercise. Now a study suggests that the exhaustion is caused by an enzyme that is missing from the muscle cell membrane, and the results point to a possible treatment for the condition: Viagra. Every year, about 500 boys in the United States are born with Duchenne muscular dystrophy, the disease's most common form. All forms of muscular dystrophy, which cause skeletal muscles to gradually weaken, result from mutations that overload the body with the enzyme creatine kinase, which breaks down muscle tissue. Researchers have long known that even in milder types of the disease, such as Becker's muscular dystrophy, and in the early stages of Duchenne muscular dystrophy, patients tend to fatigue after relatively minor activities. The briefest walk can leave them far more worn out than would be expected from just having weak muscles. These effects show up in mouse models of the disease, too. About 3 years ago, Kevin Campbell, a biophysicist at the University of Iowa in Iowa City, showed a video of the tired muscular dystrophy mice in his lab at a conference. A chance comment inspired a possible solution. "One of the physicians in the audience said, 'That looks just like my Becker's [muscular dystrophy] patients,' " Campbell recalls. One of the hallmarks of Becker's muscular dystrophy is the loss of an enzyme, neuronal nitric oxide synthase (nNOS), from muscle cell membranes. Campbell wondered whether the deficiency of nNOS might be the source of fatigue. © 2008 American Association for the Advancement of Science.
Kerri Smith A monkey's paralysed wrist can be moved and controlled by electrical signals artificially routed from its brain, according to scientists who say that their experiment is a step towards helping paralysed people to regain the use of their limbs. Previously, scientists have been able to train monkeys to move robotic arms using signals routed from electrodes in their brains1. This involved decoding the activity of tens of neurons at a time to replicate actions such as grasping, and required considerable computing power. Now, Chet Moritz and his colleagues at the University of Washington in Seattle have used similar signals to deliver direct electrical stimulation from just one neuron to a paralysed muscle. They first implanted a number of electrodes in the motor cortex of two macaque monkeys. Each electrode picked up signals from a single neuron, and those signals routed through an external circuit to a computer. The neuronal signals controlled a cursor on a screen, and the monkeys were trained to move the cursor using only their brain activity. The scientists then temporarily paralysed the monkeys' wrist muscles using a local anaesthetic. They re-routed the signals from the electrodes to deliver electrical stimulation to the wrist muscles, and found that the monkeys could control their previously paralysed limbs using the same brain activity. The monkeys learnt to do this in less than an hour, the team report in Nature2. © 2008 Nature Publishing Group
By Sandra G. Boodman Bruce Munro wonders how things might have turned out if he hadn't lost it and dialed 911. The retired obstetrician had watched with mounting alarm as his wife, Bettie, seemed to get sicker by the day. For decades her health had been stable, regulated by medicines she took to control her cholesterol, blood pressure, Type 2 diabetes, a thyroid condition and a mood disorder. But in March 2006, Bettie Munro had developed a tremor that became very bad very fast. Doctors assumed she was suffering from a rapidly progressive case of Parkinson's disease, but the neurologist treating her was baffled about why the increasingly potent drugs he prescribed didn't seem to help. On Dec. 22, 2006, while Munro was getting his wife dressed for the day, he snapped. She had fallen three times and could no longer feed herself. "I thought, 'This is it, I can't handle this at home,' " Munro recalled. He picked up the phone and called for help. An ambulance whisked Bettie Munro from their house in a Loudoun County retirement community to Inova Loudoun Hospital. © 2008 The Washington Post Company
Related chapters from BP7e: Chapter 11: Motor Control and Plasticity; Chapter 16: Psychopathology: Biological Basis of Behavior Disorders
Related chapters from MM:Chapter 5: The Sensorimotor System; Chapter 12: Psychopathology: The Biology of Behavioral Disorders
Link ID: 11596 - Posted: 06.24.2010