by Robert F. Service According to George Bernard Shaw: "The most intolerable pain is produced by prolonging the keenest pleasure." Not to be picky George, but actually both sensations result from the activity of a diverse family of proteins on the surface of cells. This year's Nobel Prize in chemistry was awarded to two Americans—Robert Lefkowitz of Duke University in Durham, North Carolina, and Brian Kobilka of Stanford University School of Medicine in Palo Alto, California—who revealed the inner workings of these proteins, which also orchestrate a variety of things such as the way we see, smell, taste, feel, and fight infections. The notion that a single family of proteins was responsible for so many different physiological processes was far from evident early on. One hint came at the end of the 19th century, when scientists studying the effects of the hormone adrenaline discovered that it had different effects in various parts of the body. It made heart rate and blood pressure increase, but it decreased digestive activity and caused pupils to relax. One idea was that proteins called receptors on different cells somehow captured adrenaline molecules and either ferried the hormone into cells or transferred a message inside to trigger a response. In the 1940s, an American biologist named Raymond Ahlquist made enough progress to conclude that there must be two types of adrenaline receptors, one that caused smooth muscle cells to contract, and the other that stimulated the heart. © 2010 American Association for the Advancement of Science

Keyword: Pain & Touch; Vision
Link ID: 17354 - Posted: 10.11.2012

By Susan Milius A dollop of living yellow ooze has aced a test of navigation, showing that you don’t really need a mind to make spatial memories. The egg-yolk-colored slime mold Physarum polycephalum is a single cell without any nervous system. But this blob of a creature uses its slime trails as a form of external spatial memory, says complex systems biologist Chris R. Reid of the University of Sydney. Smears of goo left behind as a slime mold crawls act as records of past paths. Given a choice, slime molds won’t crawl over their old slime, Reid and his colleagues found. These simple external “memories” work quite well. When lured into a U-shaped dead-end in front of a sugar treat, slime molds were able to escape. Instead of just throbbing futilely against the closed end of the U or crawling around in circles, 39 out of 40 managed to ooze their way back out of the blind alley and creep to the treat by an outside route, Reid and his colleagues report October 8 in the Proceedings of the National Academy of Sciences. “It’s the first time any spatial memory system has been found in an organism without a brain,” Reid says. Ants, which Reid also studies, lay trails of scents as they scurry to food sources, and these scents can function as external memories of the whole colony. Ants do have brains though. © Society for Science & the Public 2000 - 2012

Keyword: Learning & Memory
Link ID: 17353 - Posted: 10.11.2012

By Jason G. Goldman My high school biology teacher once told me that nothing was binary in biology except for alive and dead, and pregnant and not pregnant. Any other variation, he said, existed along a continuum. Whether or not the claim is technically accurate, it serves to illustrate an important feature of biological life. That is, very little in the biological world falls neatly into categories. A new finding, published today in PLoS ONE by Gustavo Arriaga, Eric P. Zhou, and Erich D. Jarvis from Duke University adds to the list of phenomena that scientists once thought were categorical but may, in fact, not be. The consensus among researchers was that, in general, animals divide neatly into two categories: singers and non-singers. The singers include songbirds, parrots, hummingbirds, humans, dolphins, whales, bats, elephants, sea lions and seals. What these species all have in common – and what distinguishes them from the non-singers of the animal world – is that they are vocal learners. That is, these species can change the composition of their sounds that emanate from the larynx (for mammals) or syrinx (for birds), both in terms of the acoustic qualities such as pitch, and in terms of syntax (the particular ordering of the parts of the song). It is perhaps not surprising that songbirds and parrots have been extremely useful as models for understanding human speech and language acquisition. When other animals, such as monkeys or non-human apes, produce vocalizations, they are always innate, usually reflexive, and never learned. But is the vocal learner/non-learner dichotomy truly reflective of biological reality? Maybe not. It turns out that mice make things more complicated. © 2012 Scientific American

Keyword: Hearing; Sexual Behavior
Link ID: 17352 - Posted: 10.11.2012

By Janet Raloff For pregnant women, diets rich in fish can offer their babies protection against developing behaviors associated with attention-deficit/hyperactivity disorder, or ADHD, a new study finds. Yet for most Americans, fish consumption is the leading source of exposure to mercury — a potent neurotoxic pollutant that has been linked to a host of health problems, including delays in neural development. Data from the new study, published online October 8 in Archives of Pediatrics and Adolescent Medicine, demonstrate that low-mercury diets and regular fish consumption are not mutually exclusive, says epidemiologist and study leader Susan Korrick of Brigham and Women’s Hospital in Boston. “It really depends on the type of fish that you’re eating,” she says. In fact, some study participants had been eating more than two servings of fish weekly yet accumulated relatively little mercury. As part of a long-running study of children born during the 1990s in New Bedford, Mass., 515 women who had just given birth completed a dietary survey. About 420 also provided samples of their hair for mercury testing. About eight years later, Korrick’s team administered a battery of IQ and other tests to assess behaviors associated with ADHD in the children. The children spanned a continuum running from almost no ADHD-related behaviors to those with outright clinical disease. A mom’s hair-mercury level tended to be associated with where her child fell along this spectrum. © Society for Science & the Public 2000 - 2012

Keyword: ADHD; Neurotoxins
Link ID: 17351 - Posted: 10.09.2012

Mo Costandi The growth pattern of long-range connections in the brain predicts how a child’s reading skills will develop, according to research published today in Proceedings of the National Academy of Sciences1. Literacy requires the integration of activity in brain areas involved in vision, hearing and language. These areas are distributed throughout the brain, so efficient communication between them is essential for proficient reading. Jason Yeatman, a neuroscientist at Stanford University in California, and his colleagues studied how the development of reading ability relates to growth in the brain’s white-matter tracts, the bundles of nerve fibres that connect distant regions of the brain. They tested how the reading skills of 55 children aged between 7 and 12 years old developed over a three-year period. There were big differences in reading ability between the children, and these differences persisted — the children who were weak readers relative to their peers at the beginning of the study were still weak three years later. The researchers also scanned the brains of 39 of the children at least three times during the same period, to visualize the growth of two major white-matter tracts: the arcuate fasciculus, which conects the brain's language centres, and the inferior longitudinal fasciculus, which links the language centres with the parts of the brain that process visual information. © 2012 Nature Publishing Group,

Keyword: Language; Dyslexia
Link ID: 17350 - Posted: 10.09.2012

By Courtney Humphries A. Fainting, also called syncope, is a sudden and brief loss of consciousness followed by a spontaneous return to wakefulness — people who “black out” and then “come to” on their own without outside intervention. During the faint, they’re in danger of falls and injuries if they lose muscle control. There are several possible causes of fainting, but they all stem from a temporary decrease in blood flow to the brain. The typical Victorian-era swoon is one of the most common forms, called vasovagal syncope. Lewis Lipsitz, a geriatrician at Beth Israel Deaconess Medical Center and Hebrew SeniorLife, explains that it’s caused by a reflexive response to a stimulus, such as stress, a sudden shock, or the sight of blood. Fainting without an obvious trigger can be a sign of an underlying health problem, such as an irregular heart rhythm, heart disease, or severe dehydration. “The elderly have syncope more commonly than any other group,” Lipsitz says, which can put them at risk of falls and fractures. Often the spells are caused by actions as simple as changing position or eating a meal. When we stand up, Lipsitz says, “about half a liter of blood immediately goes to the legs and the lower abdomen,” and eating also pulls blood from the brain to the gut. Our bodies compensate by raising the heart rate to get blood to the brain. But elderly people can’t always restore their blood flow, and dehydration or certain medications can exacerbate the problem. © Copyright 2012 Globe Newspaper Company.

Keyword: Consciousness
Link ID: 17349 - Posted: 10.09.2012

There was nothing sweet about Kaitlyn Terrana's 16th birthday. And she has virtually no recollection of her last birthday, her 17th, either. She slept through both of them. At a time when the teenager should be living each day to the fullest, she is trapped in a roughly six-week cycle in which she has no choice but to take to her bed, slumbering for about 10 days at a time. Kaitlyn has developed an extremely rare condition called Kleine-Levin syndrome, or KLS, and it is stealing her life away. "Kind of like the day before, I start feeling really tired and it's really hard for me to focus in class," she says from her home in Winona, Ont., near Hamilton. "And then after that, I'm just gone for 10 days. I have to sleep, I can't stay awake." Her mom, Kathy Terrana, has to closely monitor Kaitlyn when she experiences one of these sleeping periods, saying her daughter can't be left alone. "In the beginning of her episodes, she starts off being very, very tired," she says. "By late evening I can usually tell that, yes, she is starting an episode, because she doesn't talk, she doesn't converse with anybody. "It's not very nice to say, but it's almost like she's a walking zombie, because when they're in their episodes they can be walking around but they don't know what's going on around them. So there's no empathy, there's no feeling whatsoever. She's in a complete fog." © CBC 2012

Keyword: Sleep
Link ID: 17348 - Posted: 10.09.2012

By Scicurious Ok, I know it’s not Friday Weird Science time, but this paper is both interesting science AND somewhat odd. And who can’t use extra weird in their day, right? I know that Ed has already been here before me, but I can’t let this one go. I like studies on sleep, and I like studies on sex, and this has both! This paper is not actually about gettin’ laid. Though it IS about getting laid…but what it’s really about is the purpose of sleep. What is the purpose of sleep? After all, 8 hours a night (ish, for humans) is an awfully long time to spend unconscious and relatively defenseless. But almost all animals (all mammals and birds, definitely) that have more than a rudimentary brain do it. This leads us to think that it must really be an important thing to do. But why? There are several hypotheses as to why we need to sleep. The one I see most often is that our brains need that relatively inactive time (though there is still a lot of activity) to perform restorative processes and promote the best brain performance. But we don’t know, exactly, what the restorative processes are. We just know that animals and humans perform very badly on tasks when sleep deprived. But there is another hypothesis. This is the hypothesis that sleep is not really all that necessary for optimal performance. Instead, sleep is a way to preserve energy when it’s a better idea to be inactive. So, for example, humans might sleep at night because we’re at a disadvantage in the dark and would waste energy attempting activities. Support for this hypothesis comes from the fact that sleep needs vary massively across the animal kingdom. Some animals need 14 hours (see cats), while others need just 2-3. © 2012 Scientific American,

Keyword: Sexual Behavior; Sleep
Link ID: 17347 - Posted: 10.09.2012

By Tina Hesman Saey The 2012 Nobel Prize in physiology or medicine was awarded for the discovery that adult cells can be reprogrammed, as scientists did to these neurons, created from skin cells reprogrammed into a type of primordial stem cell and then coaxed into brain cells that control movement.G. Croft and M. Weygandt/The Cell: An Image Library Two scientists who showed that a cell's fate is reversible have won the 2012 Nobel Prize in physiology or medicine. The Nobel committee announced October 8 that John Gurdon and Shinya Yamanaka are being honored for showing that cells once thought to be locked into a specific identity could remember and revert to the supremely flexible state they have in an early embryo. Gurdon’s 1962 work forever changed the view that adult cells are stuck in their fate. In a series of experiments, he transplanted the nucleus — the cellular compartment that contains DNA — from an intestinal cell of an adult frog into a frog egg cell from which the nucleus had been removed. The cell developed into a normal tadpole, demonstrating that DNA contains all the information necessary to make an embryo. More than four decades later, Yamanaka, of Kyoto University in Japan, changed the debate over stem cells when he created induced pluripotent stem cells, which are capable of becoming nearly any cell in the body. He was trying to understand the factors that make stem cells isolated from embryos so malleable; many genes seemed to be involved. Yamanaka used viruses to insert combinations of candidate genes into skin cells, and found that only four genes are required to turn a mouse skin cell into a stem cell. The technique has since been used to convert adult human cells into embryonic-like cells and even to convert skin cells directly into heart or brain cells. © Society for Science & the Public 2000 - 2012

Keyword: Stem Cells; Regeneration
Link ID: 17346 - Posted: 10.09.2012

By RICHARD A. FRIEDMAN, M.D. Speed, instant gratification, accessibility — these are a few of the appealing hallmarks of digital technology. It’s no coincidence that we love our smart wireless devices: Humans are a notoriously impatient species, born with a preference for immediate rewards. But the virtues of the digital age are not always aligned with those of psychotherapy. It takes time to change behavior and alleviate emotional pain, and for many patients constant access is more harmful than helpful. These days, as never before, therapists are struggling to recalibrate their approach to patients living in a wired world. For some, the new technology is clearly a boon. Let’s say you have the common anxiety disorder social phobia. You avoid speaking up in class or at work, fearful you’ll embarrass yourself, and the prospect of going to a party inspires dread. You will do anything to avoid social interactions. You see a therapist who sensibly recommends cognitive-behavioral therapy, which will challenge your dysfunctional thoughts about how people see you and as a result lower your social anxiety. You find that this treatment involves a fair amount of homework: You typically have to keep a written log of your thoughts and feelings to examine them. And since you see your therapist weekly, most of the work is done solo. As it turns out, there is a smartphone app that will prompt you at various times during the day to record these social interactions and your emotional response to them. You can take the record to your therapist, and you are off and running. © 2012 The New York Times Company

Keyword: Depression
Link ID: 17345 - Posted: 10.09.2012

It may be possible to use a drug to prevent some of the lasting and crippling damage caused by a stroke, according to doctors in the US and Canada. A safety trial, published in the Lancet Neurology medical journal, suggested the chemical NA-1 was safe to use. The study on 185 people also hinted that patients given the drug developed fewer regions of damaged brain tissue. The Stroke Association said that it was promising, but needed more research. Tests in primates had suggested NA-1 prevented brain cells dying when a stroke starved them of oxygen. A small trial was set up at 14 hospitals in the US and Canada. Patients who took part were having an operation to repair a brain aneurysm, a weakened blood vessel which could rupture, are at increased risk of a stroke. Ninety-two people had the drug injected into a vein, while another 93 were injected with salty water. The doctors concluded that NA-1 was safe, with only two patients having mild side effects. However, brain scans also showed that fewer brain lesions, damaged areas of tissue, formed in patients given the drug. BBC © 2012

Keyword: Stroke
Link ID: 17344 - Posted: 10.08.2012

By NORIMITSU ONISHI LOS ANGELES — One year after federal law enforcement officials began cracking down on California’s medical marijuana industry with a series of high-profile arrests around the state, they finally moved into Los Angeles last month, giving 71 dispensaries until Tuesday to shut down. At the same time, because of a well-organized push by a new coalition of medical marijuana supporters, the City Council last week repealed a ban on the dispensaries that it had passed only a couple of months earlier. Despite years of trying fruitlessly to regulate medical marijuana, California again finds itself in a marijuana-laced chaos over a booming and divisive industry. Nobody even knows how many medical marijuana dispensaries are in Los Angeles. Estimates range from 500 to more than 1,000. The only certainty, supporters and opponents agree, is that they far outnumber Starbucks. “That’s the ongoing, ‘Alice in Wonderland’ circus of L.A.,” said Michael Larsen, president of the Neighborhood Council in Eagle Rock, a middle-class community that has 15 dispensaries within a one-and-a-half-mile radius of the main commercial area, many of them near houses. “People here are desperate, and there’s nothing they can do.” Though the neighborhood’s dispensaries were among those ordered to close by Tuesday, many are still operating. As he looked at a young man who bounded out of the Together for Change dispensary on Thursday morning, Mr. Larsen said, “I’m going to go out on a limb, but that’s not a cancer patient.” In the biggest push against medical marijuana since California legalized it in 1996, the federal authorities have shut at least 600 dispensaries statewide since last October. California’s four United States attorneys said the dispensaries violated not only federal law, which considers all possession and distribution of marijuana to be illegal, but state law, which requires operators to be nonprofit primary caregivers to their patients and to distribute marijuana strictly for medical purposes. © 2012 The New York Times Company

Keyword: Drug Abuse
Link ID: 17343 - Posted: 10.08.2012

Two pioneers of stem cell research have shared the Nobel prize for medicine or physiology. John Gurdon from the UK and Shinya Yamanaka from Japan were awarded to prize for transforming specialised cells into stem cells.

Keyword: Stem Cells; Regeneration
Link ID: 17342 - Posted: 10.08.2012

By RONI CARYN RABIN When Patrick Murphy was 6, he became obsessed with vacuum cleaners. The boy, who has autism, used to slip out of his house near Buffalo without telling his parents, running to a nearby appliance store or into strangers’ homes to marvel at vacuum cleaners. Patrick is now 14, and his parents have double bolts on the doors in their home and brackets on their windows. Still, Patrick — who is now focused on dogs — manages to sneak out. Two weeks ago, he crept from the house after his mother went to bed. When his father came home, he alerted the police. They found Patrick running barefoot in his pajamas at 2 a.m., three miles from his home. “That was very scary,” said Patrick’s father, Brian Murphy, who has now added an alarm system to the house to keep his son safe. “He has broken through brackets, windows, picked locks, you name it. It’s absolutely the most stressful part of parenting a child with autism.” The behavior, called wandering or elopement, has led to numerous deaths in autistic children by drowning and in traffic accidents. Now a new study of more than 1,200 families with autistic children suggests wandering is alarmingly common. Nearly half of parents with an autistic child age 4 or older said their children had tried to leave a safe place at least once, the study reported. One in four said their children had disappeared long enough to cause concern. Many parents said their wandering children had narrowly escaped traffic accidents or had been in danger of drowning. © 2012 The New York Times Company

Keyword: Autism
Link ID: 17341 - Posted: 10.08.2012

By DAVID P. BARASH ZOMBIE bees? That’s right: zombie bees. First reported in California in 2008, these stranger-than-fiction creatures have spread to North Dakota and, just recently, to my home in Washington State. Of course, they’re not really zombies, although they act disquietingly like them, showing abnormal behavior like flying at night (almost unheard-of in healthy bees), moving erratically and then dying. These “zombees” are victims of a parasitic fly, Apocephalus borealis. The fly lays eggs within honeybees, inducing their hosts to make a nocturnal “flight of the living dead,” after which the larval flies emerge, having consumed the bee from the inside out. These events, although bizarre, aren’t all that unusual in the animal world. Many fly and wasp species lay their eggs inside hosts. What is especially interesting, and a bit more unusual, is the way an internal parasite not only feeds on its host, but also frequently alters its behavior, in a way that favors the continued survival and reproduction of the parasite. Not all internal parasites kill their hosts, of course: pretty much every multicellular animal is home to numerous fellow travelers, each of which has its own agenda, which in some cases involves influencing, or taking control of, part or all of the body in which they temporarily reside. And this, in turn, leads to the question: who’s in charge of your own mind? Think of the morgue scene in the movie “Men in Black,” when a human corpse is revealed to be a robot, its skull inhabited by a little green man from outer space. Science fiction, but less bizarre than you might expect, or want to believe. © 2012 The New York Times Company

Keyword: Attention; Consciousness
Link ID: 17340 - Posted: 10.08.2012

By Ashutosh Jogalekar In a previous post I described the benefits and enduring value of Small Science. I emphasized the fact that in the current economy and funding environment, Small Science is likely to be consistent while Big Science happens in fits and starts. And I talked about how crowdsourcing and crowdfunding could bring great value to both Big and Small Science. Now I want to describe a crowd funded Small Science project that could prove very valuable in understanding the root causes of one of the most pernicious scourges of our time – methamphetamine addiction. Ethan Perlstein at Princeton and David Sulzer at Columbia are interested in dissecting the different ways in which meth acts in and on the brain and they have taken the bold step of pitching this as a crowdfunding project. Their project and others like it could not only help us develop new treatments for meth addition but they could address a more general and key question; how do psychotropic drugs work? It turns out that in spite of the legions of psychiatrists prescribing a record number of antidepressants and other medications every year, we still don’t have a good idea how these compounds work. The same lack of understanding permeates our efforts in tackling the addiction epidemic. From a chemical standpoint the simplicity of psychotropic drugs like meth and PCP is breathtaking. The fact that a few carbon, hydrogen, oxygen and nitrogen atoms arranged in and around a simple ring can cause such profound behavioral changes in human beings continues to beguile and fascinate us. Sadly, our knowledge of the mechanism of action of these molecules as well as legal psychotropic drugs has reached a kind of roadblock. © 2012 Scientific American

Keyword: Drug Abuse
Link ID: 17339 - Posted: 10.06.2012

By LISA SANDERS, M.D. On Thursday, we challenged Well readers to try their hand at solving the case of a comatose young woman dropped off at the emergency room by her friends after attending a concert the previous night. More than 350 people wrote in, and more than 90 of you were able to figure it out. The Correct Diagnosis Is … … Ecstasy-induced hyponatremia. Over the past 20 years there have been many reports of young people, mostly young women, who have had seizures or become unconscious after taking the illegal drug Ecstasy, also known as MDMA. The cause is a dangerously low level of sodium in the bloodstream. The brain is exquisitely sensitive to the exact right balance of sodium and water, and when they are out of whack, nausea, confusion and seizures can follow. It’s a rare but dangerous side effect of the drug. Nearly one in five patients reported to have this complication died. Others had permanent brain damage. When this complication was first observed, it was thought to be because of an overconsumption of water. The drug was used widely at concerts or “raves,” and attendees were told to drink lots of water to replace what was sweated out in the crowded, hot concert and dance floors. Further research revealed that the drug actually alters the way the brain and the kidney work so that the body holds on to water and dumps sodium. This change is exaggerated by the presence of estrogen, so women are far more likely to be affected than men. Why the drug can have this effect on any given individual is not well understood, but it is clear that it is not because of an overdose or a contaminant. It appears to be a response to the drug itself. Copyright 2012 The New York Times Company

Keyword: Drug Abuse
Link ID: 17338 - Posted: 10.06.2012

By Jason G. Goldman When my brother and I were young, we were very careful to share the last bit of dessert equally. It’s not that we were particularly magnanimous. In their wisdom, my parents instituted a rule in our house: one of us would divide the snack in half, and the other would select his half. “You cut, I choose” was a common phrase in the Goldman household throughout the 1990s. The rule ensured that we’d each be as equitable as possible when in the role of divider. The kitchen ruler was retrieved on more than one occasion. If I thought I could have gotten away with scarfing down the last cookie without him noticing, I’m sure I would have done it. And I would not have been sorry. Imagine, however, what would have happened if my brother had decided to keep the entire last cookie for himself and run into the living room with it. Here’s one way he might have kept me from snatching my fair share of the snack: find a decent hiding spot, and if I got too close, he could run back into the kitchen. Once back in the kitchen, if I got too close to him, he could have gotten up and run back to the living room. This is called a “stimulus-response rule.” Eventually, being the bright child that I was, I would have caught onto the pattern and found a way to block his path from one room to the other, increasing the chance of getting some of the dessert. Here’s a better method that my brother could use to protect his treat: keep his eyes on me the entire time, always moving away from me so that the distance between us was, on average, fixed. If I go right, he goes left. If I move towards him, he backs up. Short of backing him into a corner, my efforts would be futile. That’s because instead of using a small set of predictable actions, my brother could call upon a wider range of behaviors. Its much harder for a thief to learn how you protect your food if your behaviors are variable than if they are predictable. This is called a “cybernetic rule.” © 2012 Scientific American

Keyword: Aggression
Link ID: 17337 - Posted: 10.06.2012

By Bruce Bower A new study suggests that present-day Europeans share more genes with now-extinct Neandertals than do living Africans, at least partly because of interbreeding that took place between 37,000 and 86,000 years ago. Cross-species mating occurred when Stone Age humans left Africa and encountered Neandertals, or possibly a close Neandertal relative, upon reaching the Middle East and Europe in the latter part of the Stone Age, says a team led by geneticist Sriram Sankararaman of Harvard Medical School. The new study, published online October 4 in PLOS Genetics, indicates that at least some interbreeding must have occurred between Homo sapiens and Neandertals, Sankararaman says. But it’s not yet possible to estimate how much of the Neandertal DNA found in modern humans comes from that interbreeding and how much derives from ancient African hominid populations ancestral to both groups. A separate analysis of gene variants in Neandertals and in people from different parts of the world also found signs of Stone Age interbreeding outside Africa. That study, published online April 18 in Molecular Biology and Evolution, was led by evolutionary geneticist Melinda Yang of the University of California, Berkeley. Results from Sankararaman and Yang’s groups “convincingly show that the finding of a higher proportion of Neandertal DNA in non-Africans compared to Africans can be best explained by gene flow from Neandertals into modern humans,” says evolutionary geneticist Johannes Krause of the University of Tübingen in Germany. © Society for Science & the Public 2000 - 2012

Keyword: Evolution; Sexual Behavior
Link ID: 17336 - Posted: 10.06.2012

by Michael Marshall THE human brain might be the most complex object in the known universe, but a much simpler set of neurons is also proving to be a tough nut to crack. A tiny wasp has brain cells so small, physics predicts they shouldn't work at all. These miniature neurons might harbour subtle modifications, or they might work completely differently from all other known neurons - mechanically. The greenhouse whitefly parasite (Encarsia formosa) is just half a millimetre in length. It parasitises the larvae of whiteflies and so it has long been used as a natural pest-controller. To find out how its neurons have adapted to miniaturisation, Reinhold Hustert of the University of Göttingen in Germany examined the insect's brain with an electron microscope. The axons - fibres that shuttle messages between neurons - were incredibly thin. Of 528 axons measured, a third were less than 0.1 micrometre in diameter, an order of magnitude narrower than human axons. The smallest were just 0.045 μm (Arthropod Structure & Development, doi.org/jfn). That's a surprise, because according to calculations by Simon Laughlin of the University of Cambridge and colleagues, axons thinner than 0.1 μm simply shouldn't work. Axons carry messages in waves of electrical activity called action potentials, which are generated when a chemical signal causes a large number of channels in a cell's outer membrane to open and allow positively charged ions into the axon. At any given moment some of those channels may open spontaneously, but the number involved isn't enough to accidentally trigger an action potential, says Laughlin - unless the axon is very thin. An axon thinner than 0.1 μm will generate an action potential if just one channel opens spontaneously (Current Biology, doi.org/frfwpz). © Copyright Reed Business Information Ltd

Keyword: Miscellaneous; Evolution
Link ID: 17335 - Posted: 10.06.2012