Chapter 5. The Sensorimotor System

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Laurel Hamers Scientists have traced the sensation of itch to a place you can’t scratch. The discomfort of a mosquito bite or an allergic reaction activates itch-sensitive nerve cells in the spinal cord. Those neurons talk to a structure near the base of the brain called the parabrachial nucleus, researchers report in the Aug. 18 Science. It’s a region that’s known to receive information about other sensations, such as pain and taste. The discovery gets researchers one step closer to finding out where itch signals ultimately end up. “The parabrachial nucleus is just the first relay center for [itch signals] going into the brain,” says study coauthor Yan-Gang Sun, a neuroscientist at the Chinese Academy of Sciences in Shanghai. Understanding the way these signals are processed by the brain could someday provide relief for people with chronic itch, Sun says. While the temporary itchiness of a bug bite is annoying, longer term, “uncontrollable scratching behavior can cause serious skin damage.” Previous studies have looked at the way an itch registers on the skin or how neurons convey those sensations to the spinal cord. But how those signals travel to the brain has been a trickier question, and this research is a “major step” toward answering it, says Zhou-Feng Chen, director of the Center for the Study of Itch at Washington University School of Medicine in St. Louis. |© Society for Science & the Public 2000 - 2017.

Keyword: Pain & Touch
Link ID: 23972 - Posted: 08.18.2017

Researchers from the National Institutes of Health have identified a class of sensory neurons (nerve cells that electrically send and receive messages between the body and brain) that can be activated by stimuli as precise as the pulling of a single hair. Understanding basic mechanisms underlying these different types of responses will be an important step toward the rational design of new approaches to pain therapy. The findings were published in the journal Neuron. “Scientists know that distinct types of neurons detect different types of sensations, such as touch, heat, cold, pain, pressure, and vibration,” noted Alexander Chesler, Ph.D., lead author of the study and principal investigator with the National Center for Complementary and Integrative Health’s (NCCIH) Division of Intramural Research (DIR). “But they know more about neurons involved with temperature and touch than those underlying mechanical pain, like anatomical pain related to specific postures or activities.” In this study, Chesler and his colleagues used a novel strategy that combined functional imaging (which measures neuronal activity), recordings of electrical activity in the brain, and genetics to see how neurons respond to various stimuli. The scientists focused on a class of sensory neurons that express a gene called Calca, as these neurons have a long history in pain research. The scientists applied various stimuli to the hairy skin of mice cheeks, including gentle mechanical stimuli (air puff, stroking, and brushing), “high-threshold” mechanical stimuli (hair pulling and skin pinching), and temperature stimulation. They found that the target neurons belong to two broad categories, both of which were insensitive to gentle stimulation. The first was a well-known type of pain fiber—a polymodal nociceptor—that responds to a host of high intensity stimuli such as heat and pinching. The second was a unique and previously unknown type of neuron that responded robustly to hair pulling. They called this previously undescribed class of high-threshold mechanoreceptors (HTMRs) “circ-HTMRs,” due to the unusual nerve terminals these neurons made in skin. They observed that the endings of the fibers made lasso-like structures around the base of each hair follicle.

Keyword: Pain & Touch
Link ID: 23970 - Posted: 08.17.2017

By Kerry Grens The rare, severe effects of Zika infection in adults may go beyond Guillain-Barre syndrome. Doctors in Brazil report today in JAMA Neurology that among a group of hospitalized patients, those with the virus sometimes presented with other neurological problems—namely, an inflamed nervous system. The physicians tracked 40 patients who came to a hospital in Rio de Janeiro between December 2015 and May 2016 for acute neuroinflammation. Among them, 35 turned out to have been infected with Zika, and within this group, 27 had Guillain-Barre syndrome, which causes debilitating paralysis. Five patients had encephalitis, or inflammation of the brain, two had inflamed spinal cords, and one had nerve inflammation. Such symptoms are thought to indicate “post-infectious syndromes, where you have a viral infection, you clear the infection by mounting an antibody response, and the antibodies actually attack parts of the central and peripheral nervous system, causing these neurological symptoms,” Richard Temes, director of the Center for Neurocritical Care at North Shore University Hospital in Manhasset, New York, tells HealthDay. He was not involved in this study. Zika infection in adults is typically not dangerous, and many people won’t develop symptoms at all. Doctors have noticed an uptick in Guillain-Barre syndrome among those who have caught the virus. The authors note in their study that admissions to their hospital for both Guillain-Barre syndrome and encephalitis rose after May 2014, when the Zika outbreak hit Brazil.

Keyword: Movement Disorders
Link ID: 23960 - Posted: 08.15.2017

By GRETCHEN REYNOLDS Some types of exercise may be better than others at blunting appetite and potentially aiding in weight management, according to an interesting new study of workouts and hunger. It finds that pushing yourself during exercise affects appetite, sometimes in surprising ways. As anyone who has begun an exercise program knows, the relationships between exercise, appetite, weight control and hunger are complex and often counterintuitive. The arithmetic involved seems straightforward. You burn calories during exercise and, over time, should drop pounds. But the reality is more vexing. In both scientific studies and the world inhabited by the rest of us, most people who start exercising lose fewer pounds than would be expected, given the number of calories they are burning during workouts. Many people even gain weight. The problem with exercise as a weight-loss strategy seems to be in large part that it can make you hungry, and many of us wind up consuming more calories after a workout than we torched during it, a biological response that has led some experts and frustrated exercisers to conclude that exercise by itself — without strict calorie reduction — is useless for shedding pounds. But much of the past research into exercise and appetite has concentrated on walking or other types of relatively short or light activities. Some scientists have begun to wonder whether exercise that was physically taxing, either because it was prolonged or intense, might affect appetite differently than more easeful exercise. So for the new study, which was published recently in the Journal of Endocrinology, scientists from Loughborough University in Britain and other institutions who have been studying exercise and appetite for years recruited 16 healthy, fit young men. (They did not include women because this was a small, pilot study, the authors say, and controlling for the effects of women’s menstrual cycles would have been difficult.) © 2017 The New York Times Company

Keyword: Obesity
Link ID: 23934 - Posted: 08.09.2017

Nicola Davis A drug commonly used to treat diabetes could help those living with Parkinson’s disease, research has revealed. By 2020 it is predicted that 162,000 individuals in the UK will be living with the condition. While existing drugs help to control its symptoms, there are currently none available which slow or halt its progression. But now scientists say they have found that a drug commonly used to treat type 2 diabetes appears to improve movement-related issues. The benefit persisted even when the drug had not been taken for 12 weeks, suggesting it might be helping to slow the progression of the disease. “It is not ready for us to say ‘well, everyone needs to start this drug’,” said Thomas Foltynie, professor of neurology at University College London and co-author of the study. “[But] if we can replicate these findings in a multicentre trial, especially with longer follow-up, then this can change the face of our approach to treating Parkinson’s.” Writing in the Lancet, Foltynie and colleagues in the UK and US describe how they tested the impact of the drug, known as exenatide. With recent studies suggesting problems with insulin signalling in the brain could be linked to neurodegenerative disorders, hopes have been raised that diabetes drugs could also be used to tackle Parkinson’s, with previous research – including in cell cultures and animals, as well as a recent pilot study on humans by Foltynie and colleagues – backing up the notion.. But the latest study is the first robust clinical trial of the drug, randomly allocating 60 people with Parkinson’s to one of two treatments – either receiving injections of exenatide or a placebo once a week. © 2017 Guardian News and Media Limited

Keyword: Parkinsons
Link ID: 23918 - Posted: 08.05.2017

By Mitch Leslie Prions are insidious proteins that spread like infectious agents and trigger fatal conditions such as mad cow disease. A protein implicated in diabetes, a new study suggests, shares some similarities with these villains. Researchers transmitted diabetes from one mouse to another just by injecting the animals with this protein. The results don’t indicate that diabetes is contagious like a cold, but blood transfusions, or even food, may spread the disease. The work is “very exciting” and “well-documented” for showing that the protein has some prionlike behavior, says prion biologist Witold Surewicz of Case Western Reserve University in Cleveland, Ohio, who wasn’t connected to the research. However, he cautions against jumping to the conclusion that diabetes spreads from person to person. The study raises that possibility, he says, but “it remains to be determined.” Prions are misfolded proteins that can cause normally folded versions of the same protein to misfold themselves. When this conversion occurs in the brain, the distorted proteins bunch up inside cells and kill them. Although prion diseases are rare in people, they share some similarities with more common illnesses. In Alzheimer’s disease, for instance, globs of a misshapen protein known as β amyloid build up in the brain. Parkinson’s disease and Huntington disease, two other brain maladies, also feature aggregates, or lumps of misfolded proteins. © 2017 American Association for the Advancement of Science.

Keyword: Obesity; Prions
Link ID: 23910 - Posted: 08.02.2017

By DAVID C. ROBERTS Five years ago, I still lived a double life. I was 35, looking out over the Gulf of Thailand and a few weathered beach tenders. Inside, where dark suits filled the conference room, I could feel the eyes of my fellow diplomats. No doubt they were wondering why I was sitting on my briefcase. I joked to no one in particular “My nuclear codes,” trying to deflect awkwardness. The case actually concealed an orthotic sitting cushion that muffled the pain in my lower back; without it, silent shrieking was all I heard. Or maybe they had noticed I was the only one sweating. The air-conditioning tempered the tropical heat, but it was no match for the corset heat wrap that lay discreetly under my tailored suit. Over the previous decade I had become adept at hiding the unexplained pain that racked my back and joints. To all appearances, I was a fit 6-foot-3 man with an easy gait. No one in that conference room knew my suit pants disguised a lace-up ankle brace and a strap velcroed around my left knee. Nor did they know that during breaks I would sneak back to my hotel room where my wife, an artist who moonlighted as my one-person pit crew, waited to press my quadratus lumborum muscle back into submission. I lasted through that meeting as I had through countless others. But in the months that followed, sitting and walking became increasingly difficult. I started to stand during meetings, avoid plane travel, and take motorcycle taxis to go just a couple of buildings’ distance. Eventually, I let the doctors at the embassy in on my secret. They deemed me unfit for work and medevac’ed me from Bangkok back to the United States for treatment. I left quickly, without awkward explanations or goodbyes. © 2017 The New York Times Company

Keyword: Pain & Touch
Link ID: 23908 - Posted: 08.02.2017

Ashlie Stevens Ah, the brain freeze — the signature pain of summer experienced by anyone who has eaten an ice cream cone with too much enthusiasm or slurped down a slushie a little too quickly. But have you ever stopped mid-freeze to think about why our bodies react like this? Well, researchers who study pain have, and some, like Dr. Kris Rau of the University of Louisville in Kentucky, say it's a good way to understand the basics of how we process damaging stimuli. But first, a lesson in terminology. "There's a scientific medical term for ice cream headaches which is sphenopalatine ganglion neuralgia," Rau says. Try breaking that out at your next ice cream social. Anyway, to understand how brain freeze happens, it helps to think of your body and brain as a big computer where everything is hooked together. In this case, you see an ice cream truck. You get some ice cream. And then your brain gives you the go-ahead and you dive face-first into a double-scoop of mint chocolate chip. "Now on the roof of your mouth there are a lot of little blood vessels, capillaries," Rau says. "And there's a lot of nerve fibers called nociceptors that detect painful or noxious stimuli." The rush of cold causes those vessels to constrict. "And when that happens, it happens so quickly that all of those little pain fibers in the roof of your mouth — they interpret that as being a painful stimulus," Rau says. A message is then shot up to your brain via the trigeminal nerve, one of the major nerves of the facial area. The brain itself doesn't have any pain sensing fibers, but its covering — called the meninges — does. © 2017 npr

Keyword: Pain & Touch
Link ID: 23901 - Posted: 08.01.2017

By Diana Kwon Like humans, some golden retrievers develop Duchenne muscular dystrophy (DMD), a hereditary muscle wasting condition that begins early in life. Using gene therapy, scientists were able to restore muscle function in dogs with the disease, according to a study published today (July 25) in Nature Communications. Researchers injected microdystrophin, a shortened version of the dystrophin gene that individuals with DMD lack, into 12 dogs with the disease. The treatment led to improved muscle function in those animals for more than two years. “This preclinical study demonstrates the safety and efficacy of microdystrophin, and makes it possible to consider developing a clinical trial in patients,” study coauthor Caroline Le Guiner of the Université de Nantes in France, says in a statement. “Indeed, this is the first time that it has been possible to treat the whole body of a large-sized animal with this protein.” Scientists have also used CRISPR to correct the disease-causing mutations in mouse models of DMD and in the cells of a human patient with the condition. “This [study] is very encouraging, as current treatments for muscular dystrophy are merely palliative and patients are under constant medical care throughout their life,” John Counsell, a research associate at University College London who was not involved in the study, in a statement published by the Science Media Center. “Further preclinical trials will be required to show that this treatment can be effective in patients.” © 1986-2017 The Scientist

Keyword: Movement Disorders; Muscles
Link ID: 23883 - Posted: 07.27.2017

By Andrew Wagner Although it’s a far cry from the exosuits of science fiction, researchers have developed a robotic exoskeleton that can help stroke victims regain use of their legs. Nine out of 10 stroke patients are afflicted with partial paralysis, leaving some with an abnormal gait. The exosuit works by pulling cords attached to a shoe insole, providing torque to the ankle and correcting the abnormal walking motion. With the suit providing assistance to their joints, the stroke victims are able to maintain their balance, and walk similarly to the way they had prior to their paralysis, the team reports today in Science Translational Medicine. The exosuit is an adaptation of a previous design developed for the Defense Advanced Research Projects Agency Warrior Web program, a Department of Defense plan to develop assistive exosuits for military applications. Although similar mechanical devices have been built in the past to assist in gait therapy, these were bulky and had to be kept tethered to a power source. This new suit is light enough that with a decent battery, it could be used to help patients walk over terrain as well, not just on a treadmill. The researchers say that although the technology needs long-term testing, it could start to decrease the time it takes for stroke patients to recover in the near future. © 2017 American Association for the Advancement of Science

Keyword: Robotics
Link ID: 23881 - Posted: 07.27.2017

By Aylin Woodward Keep your head up. Today, navigating the urban jungle can be challenging, with uneven sidewalks and errant kerbs presenting obstacles to easy walking. So why do we rarely trip up even though we hardly ever give walking our full attention? It seems that all we need is a brief glimpse of what’s coming next on the road in front of us, just one step ahead of time, to keep up upright. Humans have a unique kind of locomotion – we’re bipedal, meaning we move around on two legs rather than four. Scientists are still struggling to unravel the mystery behind our shift to two legs – for instance, some suggest it freed up our hands to carry food. Others point out that our human gait is much more energetically efficient. Our walking style exploits external forces like gravity and inertia to use as little muscular energy as possible so that we actually fall forward onto the lifted foot with each step. Jonathan Samir Matthis at the University of Texas at Austin wanted to know how we aim and control this forward motion – particularly since the way ahead is rarely level and obstacle-free. “We have to be much more careful about where we place our feet than we would if we had four legs on the ground,” he says. “Because if we do it wrong, there’s serious consequences like breaking your leg.” © Copyright New Scientist Ltd.

Keyword: Movement Disorders; Attention
Link ID: 23872 - Posted: 07.25.2017

By Diana Kwon Using CRISPR, researchers have successfully treated congenital muscular dystrophy type 1A (MDC1A), a rare disease that can lead to severe muscle wasting and paralysis, in mice. The team was able to restore muscle function by correcting a splicing site mutation that causes the disorder, according to a study published today (July 17) in Nature Medicine. “Instead of inserting the corrected piece of information, we used CRISPR to cut DNA in two strategic places,” study coauthor Dwi Kemaladewi, a research fellow at the Hospital for Sick Children (Sick Kids) in Toronto, explains in a statement. “This tricked the two ends of the gene to come back together and create a normal splice site.” By targeting both the skeletal muscles and peripheral nerves, the team was able to improve the animals’ motor function and mobility. “This is important because the development of therapeutic strategies for muscular dystrophies have largely focused on improving the muscle conditions,” Kemaladewi says in the release. “Experts know the peripheral nerves are important, but the skeletal muscles have been perceived as the main culprit in MDC1A and have traditionally been the focus of treatment options.” “The robustness of the correction we see in animal models to me is very encouraging,” Amy Wagers, a biologist at Harvard University who was not involved in this study, tells the Toronto Star. © 1986-2017 The Scientist

Keyword: Muscles
Link ID: 23851 - Posted: 07.19.2017

Robin McKie Observer science editor Scientists at Cambridge University have co-opted an unusual ally in their battle to find treatments for an incurable degenerative ailment that affects thousands of people in the UK. They have taken charge of a flock of merino sheep that have been genetically modified to carry the gene for Huntington’s disease. The research, led by neuroscientist Professor Jenny Morton, aims to understand how to pinpoint early symptoms of the brain condition, which affects more than 6,700 people in the UK. The gene responsible for Huntington’s was isolated more then 30 years ago but scientists have yet to develop drugs that might halt or even slow its development in patients. The brain’s complexity has defied attempts to understand how the condition develops. “Until now, much of our effort has been based on research on mice or rats,” said Morton. “But sheep should make better research subjects. Not only do they live much longer than rodents, their brains are larger and closer in size and structure to humans.” Huntington’s disease, which affects men and women equally, is an inherited neurological condition whose symptoms manifest themselves in adulthood, usually between 35 and 55. Initially mood, personality, coordination and memory are affected but, as the disease progresses, speech, swallowing and motor function deteriorate until death occurs 10 to 25 years after symptoms first appear. There is no known cure for Huntington’s disease although there are treatments to manage symptoms. © 2017 Guardian News and Media Limited

Keyword: Huntingtons
Link ID: 23816 - Posted: 07.09.2017

By Meredith Wadman The hallmark brain damage in Parkinson’s disease is thought to be the work of a misfolded, rogue protein that spreads from brain cell to brain cell like an infection. Now, researchers have found that the normal form of the protein—α-synuclein (αS)—may actually defend the intestines against invaders by marshaling key immune cells. But chronic intestinal infections could ultimately cause Parkinson’s, the scientists suggest, if αS migrates from overloaded nerves in the gut wall to the brain. “The gut-brain immune axis seems to be on a cusp of an explosion of new insights, and this work offers an exceptionally exciting new hypothesis,” says Charles Bevins, an expert in intestinal immunity at the University of California, Davis, who was not involved with the study. The normal function of αS has long been a mystery. Though the protein is known to accumulate in toxic clumps in the brain and the nerves of the gut wall in patients with Parkinson’s disease, no one was sure what it did in healthy people. Noting that a region of the αS molecule behaves similarly to small, microbe-targeting proteins that are part of the body’s immune defenses, Michael Zasloff, an immunologist at Georgetown University Medical Center in Washington, D.C., set out to find whether αS, too, might help fend off microbial invaders. © 2017 American Association for the Advancement of Science

Keyword: Parkinsons
Link ID: 23784 - Posted: 06.28.2017

By Michael Price Contrary to popular lore that portrays chimpanzees as having “super strength,” studies have only found modest differences with humans. But our closest relatives are slightly stronger by several measures, and now a study comparing the muscle fibers of different primates reveals a potential explanation: Humans may have traded strength for endurance, allowing us to travel farther for food. To determine why chimpanzees are stronger than humans—at least on a pound-for-pound basis—Matthew O’Neill, an anatomy and evolution researcher at the University of Arizona College of Medicine in Phoenix, and colleagues biopsied the thigh and calf muscles of three chimps housed at the State University of New York at Stony Brook. They dissected the samples into individual fibers and stimulated them to figure out how much force they could generate. Comparing their measurements to known data from humans, the team found that, at the individual fiber level, muscle output was about the same. Given that different fibers throughout the muscle might make a difference, the researchers conducted a more thorough analysis of tissue samples from pelvic and hind limb muscles of three chimpanzee cadavers from various zoos and research institutes around the United States. Previous studies in mammals have found that muscle composition between trunk, forelimb, and hind limb muscles is largely the same, O’Neill says, so he’s confident the samples are representative across most of the chimp’s musculature. The team used a technique called gel electrophoresis to break down the muscles into individual muscle fibers, and compared this breakdown to human muscle fiber data. © 2017 American Association for the Advancement of Science.

Keyword: Muscles; Evolution
Link ID: 23782 - Posted: 06.27.2017

Carl Zimmer Mark D. Zabel wants to set some fires. Dr. Zabel and his colleagues are developing plans to burn plots of National Park Service land in Arkansas and Colorado. If the experiments turn out as the researchers hope, they will spare some elk and deer a gruesome death. Across a growing swath of North America, these animals are dying from a mysterious disorder called chronic wasting disease. It’s caused not by a virus or bacterium, but a deformed protein called a prion. When ingested, prions force normal proteins in the animal’s body to become deformed as well. Over the course of months, prions can gradually wreck the animal’s nervous system, ultimately killing it. This year is the 50th anniversary of the discovery of chronic wasting disease. In the September issue of Microbiology and Molecular Biology Reviews, Dr. Zabel, an immunologist at Colorado State University, and his former graduate student Aimee Ortega survey what scientists have learned about the slow-spreading plague. It makes for ominous reading. “There’s a lot that we still don’t know and don’t understand about the disease,” Dr. Zabel said in an interview. Once chronic wasting disease gets a foothold, it can spread relentlessly. It’s now documented in 24 states, and continues to expand into new ranges. In some herds, as many as half of the animals carry prions. It’s only been in recent years that scientists have gained crucial clues to how the disease spreads. Direct contact, it turns out, isn’t the only way that the prions get from one animal to another. © 2017 The New York Times Company

Keyword: Prions
Link ID: 23781 - Posted: 06.27.2017

By Natalie Grover (Reuters) - A handful of drugmakers are taking their first steps toward developing marijuana-based painkillers, alternatives to opioids that have led to widespread abuse and caused the U.S. health regulator to ask for a withdrawal of a popular drug this month. The cannabis plant has been used for decades to manage pain and there are increasingly sophisticated marijuana products available across 29 U.S. states, as well as in the District of Columbia, where medical marijuana is legal. There are no U.S. Food and Drug Administration (FDA)-approved painkillers derived from marijuana, but companies such as Axim Biotechnologies Inc, Nemus Bioscience Inc and Intec Pharma Ltd have drugs in various stages of development. The companies are targeting the more than 100 million Americans who suffer from chronic pain, and are dependent on opioid painkillers such as Vicodin, or addicted to street opiates including heroin. Opioid overdose, which claimed celebrities including Prince and Heath Ledger as victims, contributed to more than 33,000 deaths in 2015, according to the Centers for Disease Control and Prevention. Earlier this month, the FDA asked Endo International Plc to withdraw its Opana ER painkiller from the market, the first time the agency has called for the removal of an opioid painkiller for public health reasons. The FDA concluded that the drug's benefits no longer outweighed its risks. Multiple studies have shown that pro-medical marijuana states have reported fewer opiate deaths and there are no deaths related to marijuana overdose on record.(http://reut.rs/2r74Sbe) © 2017 Scientific American

Keyword: Pain & Touch; Drug Abuse
Link ID: 23774 - Posted: 06.26.2017

By Sam Wong People who have had amputations can control a virtual avatar using their imagination alone, thanks to a system that uses a brain scanner. Brain-computer interfaces, which translate neuron activity into computer signals, have been advancing rapidly, raising hopes that such technology can help people overcome disabilities such as paralysis or lost limbs. But it has been unclear how well this might work for people who have had limbs removed some time ago, as the brain areas that previously controlled these may become less active or repurposed for other uses over time. Ori Cohen at IDC Herzliya, in Israel, and colleagues have developed a system that uses an fMRI brain scanner to read the brain signals associated with imagining a movement. To see if it can work a while after someone has had a limb removed, they recruited three volunteers who had had an arm removed between 18 months and two years earlier, and four people who have not had an amputation. While lying in the fMRI scanner, the volunteers were shown an avatar on a screen with a path ahead of it, and instructed to move the avatar along this path by imagining moving their feet to move forward, or their hands to turn left or right. The people who had had arm amputations were able to do this just as well with their missing hand as they were with their intact hand. Their overall performance on the task was almost as good as of those people who had not had an amputation. © Copyright New Scientist Ltd.

Keyword: Robotics
Link ID: 23770 - Posted: 06.24.2017

By KATIE THOMAS Nolan and Jack Willis, twins from upstate New York, and just 10 other boys took part in a clinical trial that led to the approval last fall of the very first drug to treat their rare, deadly muscle disease. Now the Willis boys are again test cases as a different type of medical question comes to the fore: whether insurers will cover the controversial drug, Exondys 51, which can cost more than $1 million a year even though it’s still unclear if it works. The boys’ insurer, Excellus BlueCross BlueShield, refused to cover the cost of the drug because the twins, who are 15, can no longer walk. Their disease, Duchenne muscular dystrophy, overwhelmingly affects boys and causes muscles to deteriorate, killing many of them by the end of their 20s. “I’m cycling between rage and just sadness,” their mother, Alison Willis Hoke, said recently, on the day she learned that an appeal for coverage had been denied. For now, the company that sells the drug, Sarepta Therapeutics, is covering the treatment’s costs, but Mrs. Hoke does not know how long that will last. The desperation in Mrs. Hoke’s voice reflects a sobering reality for families of boys with the disease since their elation last fall over the drug’s approval. Because the Food and Drug Administration overruled its own experts — who weren’t convinced the Exondys 51 had shown sufficiently good results — and gave the drug conditional approval, many insurers are now declining to cover it or are imposing severe restrictions that render patients ineligible. The story of Exondys 51 raises complex and emotionally charged questions about what happens when the F.D.A. approves an expensive drug based on a lower bar of proof. In practice, health insurers have taken over as gatekeeper in determining who will get the drug. © 2017 The New York Times Company

Keyword: Muscles; Movement Disorders
Link ID: 23768 - Posted: 06.23.2017

By Alice Klein EVIDENCE that Parkinson’s disease may be an autoimmune disorder could lead to new ways to treat the illness. Parkinson’s begins with abnormal clumping of a protein called synuclein in the brain. Neighbouring dopamine-producing neurons then die, causing tremors and difficulty moving. The prevailing wisdom has been that these neurons die from a toxic reaction to synuclein deposits. However, Parkinson’s has been linked to some gene variants that affect how the immune system works, leading to an alternative theory that synuclein causes Parkinson’s by triggering the immune system to attack the brain. An argument against this theory has been that brain cells are safe from immune system attack, because most neurons don’t have antigens – the markers immune cells use to recognise a target. But by studying postmortem brain tissue samples, David Sulzer at Columbia University and his team have discovered that dopamine-producing neurons do display antigens. The team has now conducted blood tests to reveal that people with Parkinson’s show an immune response to these antigens, while people who don’t have the condition do not (Nature, DOI: 10.1038/nature22815). These findings suggest Parkinson’s may be an autoimmune disorder, in which the immune system mistakenly attacks part of the body. There have been hints before that the immune system is involved in Parkinson’s, but this is the first evidence that it plays a major pathological role, says Roger Barker at the University of Cambridge. “It would be an attractive target for therapeutic intervention,” he says. However, it isn’t clear yet if the immune response directly causes neuron death, or if it is merely a side effect of the disease. Sulzer’s team plans to try blocking the autoimmune response in Parkinson’s, to see if this can stop the disease progressing. © Copyright New Scientist Ltd.

Keyword: Parkinsons; Neuroimmunology
Link ID: 23760 - Posted: 06.22.2017