Chapter 16. None
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By Maggie Fox Medical marijuana pills or an oral spray made from cannabis may help ease some of the painful spasms caused by multiple sclerosis that make day-to-day life hard for patients, according to new guidelines from the American Academy of Neurology. But the synthetic formulations of marijuana don’t change the course of the disease and might cause unpleasant side-effects, the experts at the academy caution. There is not enough evidence to make any recommendation on smoking marijuana for MS patients, stresses Dr. Vijayshree Yadav of Oregon Health & Science University, who led the team writing the guidelines. Synthetic marijuana in pill form, including the Marinol brand, is legal for use in treating nausea and loss of appetite in cancer. An oral spray called Sativex is approved for treating MS symptoms in Britain but not in the U.S. MS patients often seek alternative and complementary therapies because they have so few options for the chronic and incurable condition, caused when the immune system mistakenly attacks the nerves. A review of those therapies found there's no evidence most of them work. The review found that the herb Ginkgo biloba might help fatigue, but not thinking and memory problems. There’s also some evidence that magnetic therapy may help fatigue.
Keyword: Multiple Sclerosis
Link ID: 19402 - Posted: 03.25.2014
By ANNE EISENBERG People who strain to hear conversations in noisy places sometimes shun hearing appliances as telltale signs of aging. But what if those devices looked like wireless phone receivers? Some companies are betting that the high-tech look of a new generation of sound amplifiers will tempt people to try them. The new in-ear amps come with wireless technology and typically cost $300 to $500. The devices include directional microphones and can be fine-tuned by smartphone apps. Whatever you do, don’t call these amplifiers hearing aids. They are not considered medical devices like the ones overseen by the Food and Drug Administration and dispensed by professionals to aid those with impaired hearing. Rather, they are over-the-counter systems cleared by the F.D.A. for occasional use in situations when speech and other sounds are hard to discern — say, in a noisy restaurant or while bird-watching. “The market is proliferating with lots of devices not necessarily made for impaired hearing, but for someone who wants a boost in certain challenging conditions like lectures,” said Neil J. DiSarno, chief staff officer for audiology at the American Speech-Language-Hearing Association. Dr. DiSarno is among the many audiologists who strongly urge people to see a physician first, in order to rule out medical causes of hearing loss, which could vary from earwax to a tumor, rather than self-diagnosing and self-treating a condition. Carole Rogin, president of the Hearing Industries Association, a trade group, said the biggest problem with personal amplification products was that people might use them instead of seeking appropriate medical oversight. “Untreated hearing loss is not a benign condition,” she said. “We want people to do something about it as soon as they notice a problem,” rather than using these devices to mask a potentially dangerous condition. © 2014 The New York Times Company
Link ID: 19401 - Posted: 03.24.2014
By MATT RICHTEL A dangerous new form of a powerful stimulant is hitting markets nationwide, for sale by the vial, the gallon and even the barrel. The drug is nicotine, in its potent, liquid form — extracted from tobacco and tinctured with a cocktail of flavorings, colorings and assorted chemicals to feed the fast-growing electronic cigarette industry. These “e-liquids,” the key ingredients in e-cigarettes, are powerful neurotoxins. Tiny amounts, whether ingested or absorbed through the skin, can cause vomiting and seizures and even be lethal. A teaspoon of even highly diluted e-liquid can kill a small child. But, like e-cigarettes, e-liquids are not regulated by federal authorities. They are mixed on factory floors and in the back rooms of shops, and sold legally in stores and online in small bottles that are kept casually around the house for regular refilling of e-cigarettes. Evidence of the potential dangers is already emerging. Toxicologists warn that e-liquids pose a significant risk to public health, particularly to children, who may be drawn to their bright colors and fragrant flavorings like cherry, chocolate and bubble gum. “It’s not a matter of if a child will be seriously poisoned or killed,” said Lee Cantrell, director of the San Diego division of the California Poison Control System and a professor of pharmacy at the University of California, San Francisco. “It’s a matter of when.” © 2014 The New York Times Company
Visual illusions, such as the rabbit-duck (shown above) and café wall (shown below) are fascinating because they remind us of the discrepancy between perception and reality. But our knowledge of such illusions has been largely limited to studying humans. That is now changing. There is mounting evidence that other animals can fall prey to the same illusions. Understanding whether these illusions arise in different brains could help us understand how evolution shapes visual perception. For neuroscientists and psychologists, illusions not only reveal how visual scenes are interpreted and mentally reconstructed, they also highlight constraints in our perception. They can take hundreds of different forms and can affect our perception of size, motion, colour, brightness, 3D form and much more. Artists, architects and designers have used illusions for centuries to distort our perception. Some of the most common types of illusory percepts are those that affect the impression of size, length or distance. For example, Ancient Greek architects designed columns for buildings so that they tapered and narrowed towards the top, creating the impression of a taller building when viewed from the ground. This type of illusion is called forced perspective, commonly used in ornamental gardens and stage design to make scenes appear larger or smaller. As visual processing needs to be both rapid and generally accurate, the brain constantly uses shortcuts and makes assumptions about the world that can, in some cases, be misleading. For example, the brain uses assumptions and the visual information surrounding an object (such as light level and presence of shadows) to adjust the perception of colour accordingly. © 2014 Guardian News and Media Limited
Link ID: 19398 - Posted: 03.22.2014
Jessica Morrison The human nose has roughly 400 types of scent receptors that can detect at least 1 trillion different odours. The human nose can distinguish at least 1 trillion different odours, a resolution orders of magnitude beyond the previous estimate of just 10,000 scents, researchers report today in Science1. Scientists who study smell have suspected a higher number for some time, but few studies have attempted to explore the limits of the human nose’s sensory capacity. “It has just been sitting there for somebody to do,” says study co-author Andreas Keller, an olfactory researcher at the Rockefeller University in New York. To investigate the limits of humans' sense of smell, Keller and his colleagues prepared scent mixtures with 10, 20 or 30 components selected from a collection of 128 odorous molecules. Then they asked 26 study participants to identify the mixture that smelled differently in a sample set where two of three scents were the same. When the two scents contained components that overlapped by more than about 51%, most participants struggled to discriminate between them. The authors then calculated the number of possible mixtures that overlap by less than 51% to arrive at their estimate of how many smells a human nose can detect: at least 1 trillion. Donald Wilson, an olfactory researcher at the New York University School of Medicine, says the findings are “thrilling.” He hopes that the new estimate will help researchers begin to unravel an enduring mystery: how the nose and brain work together to process smells. © 2014 Nature Publishing Group,
Keyword: Chemical Senses (Smell & Taste)
Link ID: 19394 - Posted: 03.21.2014
by Simon Makin How much can environmental factors explain the apparent rise in autism spectrum disorders? Roughly 1 per cent of children in the US population are affected by autism spectrum disorder (ASD). Rates in many countries, including the US, have risen sharply in recent years but no one is sure why. It is still not clear whether this is prompted by something in the environment, increased awareness of the condition and changes in diagnoses, or a result of people having children later. The environmental case is hotly debated. There is some evidence that maternal infections during pregnancy can increase the risk. Other studies have pointed to a possible link with antidepressants while others have looked at elevated levels of mercury. But determining prenatal exposure to any substance is difficult because it is hard to know what substances people have been exposed to and when. To get around this, Andrey Rzhetsky and colleagues at the University of Chicago analysed US health insurance claims containing over 100 million patient records – a third of the population – dating from 2003 to 2010. They used rates of genital malformations in newborn boys as a proxy of parents' exposure to environmental risk factors. This is based on research linking a proportion of these malformations to toxins in the environment, including pesticides, lead and medicines. Toxic environment? The team compared the rates of these malformations to rates of ASD county by county. After adjusting for gender, income, ethnicity and socio-economic status, they found that a 1 per cent increase in birth defects – their measure for environmental effects - was associated with an average increase of 283 per cent in cases of ASD. © Copyright Reed Business Information Ltd.
Link ID: 19393 - Posted: 03.21.2014
By Dominic Basulto In last weekend’s Wall Street Journal, two leading brain researchers conjectured that as a result of rapid breakthroughs in fields such as molecular biology and neuroscience, one day “brain implants” will be just about as common as getting a bit of plastic surgery is today. In short, today’s tummy tucks are tomorrow’s brain tucks. Similar to what you’d expect from watching science fiction films such as “The Matrix,” these brain implants would enable you to learn foreign languages effortlessly, upgrade your memory capabilities, and, yes, help you to know Kung Fu. Vinton Cerf argues that today’s Internet (think Google) is already a form of cognitive implant, helping us to learn the answer to just about anything within seconds. If computing power continues to increase at the same rate as it has for the past 50 years, it is likely that a single computer will have the computing capacity of a human brain by 2023. By 2045, a single computer could have the processing capability of all human brains put together. Just think what you’d be able to use Google to do then. You wouldn’t even need to type in a search query, your brain would already know the answer. Of course, the ability to create these brain implants raises a number of philosophical, ethical and moral questions. If you’re a young student having a tough time in a boring class, why not just buy a brain module that simulates the often repetitive nature of learning? If you’re a parent of a child looking to get into a top university, why not buy a brain implant as a way to gain an advantage over children from less privileged backgrounds, especially when it’s SAT time? Instead of the digital divide, we may be talking about the cognitive divide at some point in the next two decades. Some parents would be able to afford a 99 percent percentile brain for their children, while others wouldn’t. © 1996-2014 The Washington Post
Link ID: 19391 - Posted: 03.21.2014
Neuroscientist Bevil Conway thinks about color for a living. An artist since youth, Conway now spends much of his time studying vision and perception at Wellesley College and Harvard Medical School. His science remains strongly linked to art--in 2004 he and Margaret Livingstone famously reported that Rembrandt may have suffered from flawed vision--and in recent years Conway has focused his research almost entirely on the neural machinery behind color. "I think it's a very powerful system," he tells Co.Design, "and it's completely underexploited." Conway's research into the brain's color systems has clear value for designers and artists like himself. It stands to reason, after all, that someone who understands how the brain processes color will be able to present it to others in a more effective way. But the neuroscience of color carries larger implications for the rest of us. In fact, Conway thinks his insights into color processing may ultimately shed light on some fundamental questions about human cognition. Step back for a moment to one of Conway's biggest findings, which came while examining how monkeys process color. Using a brain scanner, he and some collaborators found "globs" of specialized cells that detect distinct hues--suggesting that some areas of the primate brain are encoded for color. Interestingly, not all colors are given equal glob treatment. The largest neuron cluster was tuned to red, followed by green then blue; a small cell collection also cared about yellow. © 2014 Mansueto Ventures, LLC.
Link ID: 19390 - Posted: 03.21.2014
By JAMES GORMAN There are lots of reasons scientists love fruit flies, but a big one is their flying ability. These almost microscopic creatures, with minimalist nervous systems and prey to every puff of wind, must often execute millisecond aerial ballets to stay aloft. To study fly flight, scientists have to develop techniques that are almost as interesting as the flies. At Cornell University, for instance, researchers have been investigating how the flies recover when their flight is momentarily disturbed. Among their conclusions: a small group of fly neurons is solving calculus problems, or what for humans are calculus problems. To do the research, the members of Cornell team — Itai Cohen and his colleagues, including Z. Jane Wang, John Guckenheimer, Tsevi Beatus and Leif Ristroph, who is now at New York University — glue tiny magnets to the flies and use a magnetic pulse to pull them this way or that. In the language of aeronautics, the scientists disturb either the flies’ pitch (up or down), yaw (left or right) or roll, which is just what it sounds like. The system, developed by Dr. Ristroph as a graduate student in Dr. Cohen’s lab, involves both low and high tech. On the low end, the researchers snip bits of metal bristle off a brush to serve as micromagnets that they glue to the flies’ backs. At the high end, three video cameras record every bit of the flight at 8,000 frames per second, and the researchers use computers to merge the data from the cameras into a three-dimensional reconstruction of the flies’ movements that they can analyze mathematically. © 2014 The New York Times Company
Link ID: 19388 - Posted: 03.20.2014
Helen Shen For Frank Donobedian, sitting still is a challenge. But on this day in early January, he has been asked to do just that for three minutes. Perched on a chair in a laboratory at Stanford University in California, he presses his hands to his sides, plants his feet on the floor and tries with limited success to lock down the trembling in his limbs — a symptom of his Parkinson's disease. Only after the full 180 seconds does he relax. Other requests follow: stand still, lie still on the floor, walk across the room. Each poses a similar struggle, and all are watched closely by Helen Bronte-Stewart, the neuroscientist who runs the lab. “You're making history,” she reassures her patient. “Everybody keeps saying that,” replies the 73-year-old Donobedian, a retired schoolteacher, with a laugh. “But I'm not doing anything.” “Well, your brain is,” says Bronte-Stewart. Like thousands of people with Parkinson's before him, Donobedian is being treated with deep brain stimulation (DBS), in which an implant quiets his tremors by sending pulses of electricity into motor areas of his brain. Last October, a team of surgeons at Stanford threaded the device's two thin wires, each with four electrode contacts, through his cortex into a deep-seated brain region known as the subthalamic nucleus (STN). But Donobedian's particular device is something new. Released to researchers in August 2013 by Medtronic, a health-technology firm in Minneapolis, Minnesota, it is among the first of an advanced generation of neurostimulators that not only send electricity into the brain, but can also read out neural signals generated by it. On this day, Bronte-Stewart and her team have temporarily turned off the stimulating current and are using some of the device's eight electrical contacts to record abnormal neural patterns that might correlate with the tremors, slowness of movement and freezing that are hallmarks of Parkinson's disease. © 2014 Nature Publishing Group,
by Ashley Yeager Owl monkeys don't sleep around, genetic tests show. That could be a result of the amount of care males provide for their young, a new study suggests. Infidelity appears to be common in mammals that live in pairs. But new genetic tests suggest that Azara's owl monkeys are unusually faithful. Scientists studied 35 infants born to 17 owl monkey pairs and found that in all cases the youngsters were being raised by their biological parents. Data from the owl monkeys and 14 other species showed that the more involved the males were in raising an infant, the more likely the males were to be faithful, the team reports March 18 in Proceedings of the Royal Society B. Owl monkeys are the only primates and one of five mammal species, including coyotes and California mice, that don’t seem to cheat, according to genetic studies. The evolution of animals’ sexual fidelity is probably linked to the intensity of male care, the researchers suggest. © Society for Science & the Public 2000 - 2013.
Keyword: Sexual Behavior
Link ID: 19386 - Posted: 03.20.2014
By Lenny Bernstein When your name is Leonard Bernstein, and you can’t play or sing a note, people are, understandably, a bit prone to noting this little irony. But now I have an explanation: My lack of musical aptitude is mostly genetic. Finnish researchers say they have found genes responsible for auditory response and neuro-cognitive processing that partially explain musical aptitude. They note “several genes mostly related to the auditory pathway, not only specifically to inner ear function, but also to neurocognitive processes.” The study was published in the March 11 issue of the journal “Molecular Psychiatry.” In an e-mail, one of the researchers, Irma Jarvela, of the University of Helsinki’s department of medical genetics, said heredity explains 60 percent of the musical ability passed down through families like Bach’s. The rest can be attributed to environment and training. Genes most likely are responsible for “better perception skills of different sounds,” Jarvela said. Feel free to cite this research at your next karaoke night. © 1996-2014 The Washington Post
Sara Reardon The US brain-research programme aims to create tools to image and control brain activity, while its European counterpart hopes to create a working computational model of the organ. It seems a natural pairing, almost like the hemispheres of a human brain: two controversial and ambitious projects that seek to decipher the body's control center are poised to join forces. The European Union’s €1-billion (US$1.3-billion) Human Brain Project (HBP) and the United States’ $1-billion Brain Research through Advancing Innovative Neurotechnologies (BRAIN) Initiative will launch a collaboration later this year, according to government officials involved in both projects. Representative Chaka Fattah (Democrat, Pennslyvania) hinted at the plan in a speech on 12 March. The brain, he says, ”is something that has defied understanding. You can't imagine a more important scientific cooperation”, says Fattah, the highest-ranking Democratic member of a House of Representatives panel that oversees funding for several US science agencies. Details about how closely the US and European programmes will coordinate are still nebulous, but US government officials say that the effort will include all of the BRAIN Initiative's government partners — the US National Institutes of Health (NIH), the National Science Foundation and Defense Advanced Research Projects Agency. Henry Markram, a neuroscientist at the Swiss Federal Institute of Technology in Lausanne (EPFL), who directs the HBP, says that Israel's brain initiative will also be involved. © 2014 Nature Publishing Group
Keyword: Brain imaging
Link ID: 19384 - Posted: 03.19.2014
By Helen Briggs BBC News Sleep loss may be more serious than previously thought, causing a permanent loss of brain cells, research suggests. In mice, prolonged lack of sleep led to 25% of certain brain cells dying, according to a study in The Journal of Neuroscience. If the same is true in humans, it may be futile to try to catch up on missed sleep, say US scientists. They think it may one day be possible to develop a drug to protect the brain from the side-effects of lost sleep. The study, published in The Journal of Neuroscience, looked at lab mice that were kept awake to replicate the kind of sleep loss common in modern life, through night shifts or long hours in the office. A team at the University of Pennsylvania School of Medicine studied certain brain cells which are involved in keeping the brain alert. After several days of sleep patterns similar to those followed by night workers - three days of night shifts with only four to five hours sleep in 24 hours - the mice lost 25% of the brain cells, known as locus coeruleus (LC) neurons. The researchers say this is the first evidence that sleep loss can lead to a loss of brain cells. But they add that more work needs to be done to find out if people who miss out on sleep might also be at risk of permanent damage. Prof Sigrid Veasey of the Center for Sleep and Circadian Neurobiology, told BBC News: "We now have evidence that sleep loss can lead to irreversible injury. "This might be in a simple animal but this suggests to us that we are going to have to look very carefully in humans." BBC © 2014
Link ID: 19382 - Posted: 03.19.2014
by Andy Coghlan Burmese pythons can find their way home even if they are taken dozens of kilometres away. It is the first demonstration that big snakes can navigate at all, and far exceeds the distances known to have been travelled by any other snake. At over 3 metres long, Burmese pythons (Python molurus bivitattus) are among the world's largest snakes. For the last two decades they have been eating their way through native species of Florida's Everglades National Park, having been abandoned to the wild by former owners. "Adult Burmese pythons were able to navigate back to their capture locations after having been displaced by between 21 and 36 kilometres," says Shannon Pittman of Davidson College in North Carolina. Pittman and her colleagues caught 12 pythons and fitted them with radiofrequency tags (see video). She released half of them where they were caught, as controls, and transported the other six to distant locations before releasing them. Five pythons made it back to within 5 kilometres of their capture location, and the sixth at least moved in the right direction. The displaced snakes made progress towards their destination most days and seldom strayed more than 22 degrees from the correct path. They kept this up for 94 to 296 days. By contrast, the control snakes moved randomly. On average, displaced snakes travelled 300 metres each day, while control snakes averaged just 100 metres per day. © Copyright Reed Business Information Ltd.
Keyword: Animal Migration
Link ID: 19380 - Posted: 03.19.2014
The cancer gene BRCA1, which keeps tumors in the breast and ovaries at bay by producing proteins that repair damaged DNA, may also regulate brain size. Mice carrying a mutated copy of the gene have 10-fold fewer neurons and other brain abnormalities, a new study suggests. Such dramatic effects on brain size and function are unlikely in human carriers of BRCA1 mutations, the authors of the study note, but they propose the findings could shed light on the gene's role in brain evolution. Scientists have known for a long time that the BRCA1 gene is an important sentinel against DNA damage that can lead to ovarian and breast cancers. More than half of women with a mutated copy of the BRCA1 gene will develop breast cancer, a statistic that has led some who carry the mutation to get preventative mastectomies. But its roles outside the breast and ovaries are less clear, says Inder Verma, a geneticist and molecular biologist at the Salk Institute for Biological Studies in San Diego, California, who headed the new study. Mice bred without BRCA1 die soon after birth, so it’s clear that the gene is necessary to sustain life, but scientists are just starting to unravel its many functions, he says. Several years ago, one of the students in Verma’s lab noticed that BRCA1 is very active in the neuroectoderm, a sliver of embryonic tissue containing neural stem cells that divide and differentiate into the brain’s vast assortment of cell types and structures. Verma and his colleagues wondered why the gene was expressed at such high levels in that region, and what would happen if it were eliminated. They created a strain of mice in which BRCA1 was knocked out only in neural stem cells. As the mice developed, Verma’s team found that the rodents’ brains were only a third of their normal size, with particularly striking reductions in brain areas involved in learning and memory. The grown mice also had a wobbly, drunken gait—a telltale symptom of ataxia, a neurological disorder that affects muscle control and balance, the researchers report online today in the Proceedings of the National Academy of Sciences. © 2014 American Association for the Advancement of Science.
Keyword: Development of the Brain
Link ID: 19378 - Posted: 03.18.2014
|By Shannon Firth A dog will do anything for a biscuit—over and over again. Most people will, too, because when sugar touches the taste buds it excites reward regions in the brain. A new study shows that people with eating disorders do not react to sweet flavors the way healthy people do, however, lending evidence to the hypothesis that brain differences predispose people toward bulimia and anorexia. A team of psychiatrists at U.C. San Diego studied 14 recovered anorexic women, 14 recovered bulimic women (who used to binge and purge) and 14 women who had never had an eating disorder, matched by age and weight. None of the women had had any pathological eating-related behaviors in the 12 months preceding the study. After fasting overnight, subjects received a modest breakfast to ensure similar levels of satiety. They were then fed small tastes of sugar every 20 seconds through a syringe pump while their brains were scanned. The women who had recovered from anorexia—those who formerly starved themselves—showed less activity than the healthy women in a reward center in the brain known as the primary gustatory cortex. The participants who were no longer bulimic showed more activity than the healthy women did. The results were published in October 2013 in the American Journal of Psychiatry. The researchers believe these abnormal responses to sugar predispose people to eating disorders, adding to a growing body of work suggesting that genetic and biological risk factors underlie most cases, according to study co-author Walter Kaye, director of U.C.S.D.'s Eating Disorders Research and Treatment Program. © 2014 Scientific American
Keyword: Anorexia & Bulimia
Link ID: 19377 - Posted: 03.18.2014
by Tania Lombrozo St. Patrick's Day is my excuse to present you with the following illusion in green, courtesy of , a psychology professor at Ritsumeikan University in Japan. In this perceptual illusion, the two spirals appear to be different shades of green. In fact, they are the same. In this perceptual illusion, the two spirals appear to be different shades of green. In fact, they are the same. This image includes two spirals in different shades of green, one a yellowish light green and the other a darker turquoise green. Right? Wrong. At least, that's not what the pixel color values on your monitor will tell you, or what you'd find if you used a photometer to measure the distribution of lightwaves bouncing back from the green-looking regions of either spiral. In fact, the two spirals are the very same shade of green. If you don't believe me, here's a trick to make the illusion go away: replace the yellow and blue surrounding the green segments with a uniform background. Here I've replaced the blue with black: And here the yellow is gone, too: Tada! The very same green. The fact that the illusion disappears when the surrounding colors are replaced with a uniform background illustrates an important feature of color perception. Our experience of color for a given region of space isn't just a consequence of the wavelengths of light reaching our retinas from that region. Instead, the context matters a lot! ©2014 NPR
Link ID: 19375 - Posted: 03.18.2014
By FLORENCE WILLIAMS So there’s this baby who has swallowed a .22-caliber bullet. The mother rushes into a drugstore, crying, “What shall I do?” “Give him a bottle of castor oil,” replies the druggist, “but don’t point him at anybody.” Whether you find this joke amusing depends on many more variables than you probably ever realized. It depends on a common cultural understanding of the technical properties of castor oil. It depends, as many funny jokes do and as any fourth grader can attest, on our own squeamishness about bodily functions. Getting less obvious, your sense of humor can also depend on your age, your gender, your I.Q., your political inclinations, how extroverted you are and the health of your dopamine reward circuit. If you think all this analysis sounds a bit, well, unfunny, E. B. White would back you up. He once wrote that picking apart jokes is like dissecting frogs: Few people are interested, and the subject always dies in the end. Fortunately, the cognitive neuroscientist Scott Weems isn’t afraid of being unfunny. Humor is worthy of serious academic study, he argues in his book, “Ha! The Science of When We Laugh and Why,” (Read an excerpt.) because it yields insights into how our brains process a complex world and how that, in turn, makes us who we are. Though animals laugh, humans spend more time laughing than exhibiting any other emotion. But what gives some people a better sense of humor than others? Not surprisingly, extroverts tend to laugh more and produce more jokes; yet in tests measuring the ability to write cartoon captions, people who were more neurotic, assertive, manipulative and dogmatic were actually funnier. As the old saw holds, many of the best comics really are miserable. © 2014 The New York Times Company
Link ID: 19373 - Posted: 03.18.2014
by Colin Barras Amyloid plaques, a hallmark of diseases like Alzheimer's, are bad news for humans – but they could have been drivers of the earliest life on Earth. A new study shows that these amyloid clusters can behave as catalysts, backing a theory that they helped trigger the reactions that sustain life, long before modern enzymes appeared. Without enzymes, life's metabolic reactions simply wouldn't occur. But making enzymes from scratch isn't easy. They are normally large, complicated proteins folded into a specific three-dimensional shape. It's difficult to see how these large proteins could have popped out of the primordial soup fully formed. Even if they did, nature faced another problem. There are 20 naturally occurring amino acids, which are the building blocks for all proteins, and each enzyme is made up of a unique sequence of at least 100 amino acids. This means there is a mind-bogglingly vast number – 20100 – of possible enzymes, each with a different amino acid sequence and a slightly different 3D structure. But very few of these 3D structures will work effectively as enzymes because they have to be an exact fit for the substrate they react with – in the same way that a lock can only be opened by one particular key. Even with millions of years to work at the problem, says Ivan Korendovych at Syracuse University in New York, nature would have struggled to build and test all possible enzyme molecules to identify the relatively few that catalyse today's metabolic reactions. © Copyright Reed Business Information Ltd.
Link ID: 19372 - Posted: 03.17.2014