Researchers from the University of Bristol have discovered that a chemical compound in the brain can weaken the synaptic connections between neurons in a region of the brain important for the formation of long-term memories. The findings, published December 13 in the Journal of Neuroscience, may also provide a potential explanation for the loss of memory associated with Alzheimer's.
Acetylcholine, a neurotransmitter, is released in the brain and is known to play an important role in normal brain functions such as sleep, attention, and learning and memory. Until now the mechanisms by which this transmitter controls such processes were not well understood.
The findings, led by researchers from the University's MRC Centre for Synaptic Plasticity in the School of Physiology and Pharmacology, highlight the mechanisms by which acetylcholine controls communication between neurons located in the prefrontal cortex and may help in understanding how higher cognitive processing is controlled in this important brain area.
Professor of Cellular Neuroscience, Zafar Bashir and his team have demonstrated how electrical stimulation of the prefrontal cortex leads to the release of acetylcholine from synaptic terminals and the subsequent weakening of synaptic connections between neurons.
When acetylcholine is released it binds to specific receptors and starts a molecular cascade which triggers physiological alterations in how prefrontal cortical neurons are 'wired' together. The findings suggest that the persistent weakening of synaptic connections between neurons induced by the endogenous release of acetylcholine in the prefrontal cortex may underlie the formation of new associative memories.
The authors speculate that the memory impairments associated with Alzheimer's dementia may result, in part, from a loss of synaptic plasticity in the prefrontal cortex related to the depletion of brain acetylcholine that occurs in the disease.
Dr Douglas Caruana, who carried out the experiments, said: "Disruptions in cholinergic signaling in the prefrontal cortex are known to affect how the brain encodes lasting associations between objects and places, and a depletion of brain acetylcholine levels in the cortex is a classic hallmark of Alzheimer's dementia'."
Professor Bashir added: "Acetylcholinesterase inhibitors are the most widely used medication to treat individuals with Alzheimer's dementia and the enhancement of synaptic plasticity by acetylcholinesterase inhibition that we now demonstrate may be a way in which these drugs provide clinical efficacy."
Read more at Science Daily
Dec 17, 2011
Stink? Neanderthal Noses Didn't Notice
New three-dimensional medical imaging scans of fossil human skulls reveal that the so-called olfactory bulbs, the part of the brain that processes odors, are 12% larger in Homo sapiens than they were in Neanderthals.
Markus Bastir and Antonio Rosas of the Spanish Natural Science Museum and their colleagues carefully assessed the shape of the base of cranium to quantify the volume of gray matter that would have filled in above.
Their research, reported this week in Nature Communications, divulged another size difference: the temporal lobes, the part of the brain involved in language, memory and social functions, are also larger in Homo sapiens.
That latter finding may not come as a surprise, considering how modern humans have evolved linguistically and socially. But the researchers say that the fact that both the temporal lobes and olfactory bulbs are larger in modern humans suggests that our species evolved a combined use of brain functions related to cognition and olfaction that may not have been true for Neanderthals.
Evidence has been accumulating that Neanderthals and modern humans developed their large brains independently, and so the expectation, then, is that their brains might have worked differently.
For us modern humans, the tight relationship between sniffing ability and higher brain functions makes even more sense when you consider that olfaction is the only sense that establishes a direct connection between the brain and its environment. While information from our eyes and ears must pass through different filters in the brain, smell signals go straight into the highest centers of the brain—those directly responsible for processing emotion, motivation, fear, memory, pleasure, and attraction.
Read more at Discovery News
Dec 16, 2011
Remote Wilderness Polluted by Humans
The research is based on studies of sediment from 36 lakes in the USA, Canada, Greenland and Svalbard, Norway. The researchers have analysed how the chemical composition of the sediment has changed over the centuries. Twenty-five of the lakes all show the same sign -- that biologically active nitrogen from human sources can be traced back to the end of the 19th century.
The nitrogen analyses of the lake sediments show that the changes began around 1895. The results also show that the rate of change has accelerated over the past 60 years, which is in agreement with the commercialisation of artificial fertiliser production in the 1950s. Sofia Holmgren, a researcher in Quaternary Geology at Lund University, Sweden, is the only Swede to take part in the comprehensive study.
"I have studied lakes on Svalbard, where the effects of the increased nitrogen deposition are clearly visible in the algal flora," says Sofia Holmgren.
She explains that both the species composition and production of diatoms -- microscopic siliceous algae -- have changed dramatically in the lakes on Svalbard since the start of the 20th century, with the most significant changes over the past decades.
Combustion of fossil fuels and use of fertiliser are the main sources of the increasing amount of nitrogen in the atmosphere. The nitrogen is transported with air currents and reaches the ground in rain or snow. It can travel thousands of kilometres and the nitrogen thus reaches even the most remote lakes and ecosystems.
Read more at Science Daily
The Physics Behind Great White Shark Attacks On Seals
University of Miami (UM) Rosenstiel School of Marine and Atmospheric Science assistant professor Dr. Neil Hammerschlag, and a colleague from the University of British Columbia, describe how sharks are camouflaged as they stalk their prey from below. Low-light conditions, from the optical scattering of light through water, along with a shark's dark grey back and the dimly light rocky reef habitat allow sharks to remain undetected by seals swimming at the water's surface.
"Animal hunting in the ocean is rarely observed by humans," said Hammerschalg, director of the RJ Dunlap Marine Conservation Program at UM. "The high frequency of attacks by white sharks on seals at our study site in South Africa provides a very unique opportunity to uncover new insights about predator-prey relationships."
Sharks typically search, stalk and strike their prey from below. The vast majority of predatory strikes by sharks and Cape fur seals occur against small groups of young-of-the-year seals. Predatory activity by sharks is most intense within two hours of sunrise and quickly decreases as light penetration in the water column increases.
"Stealth and ambush are key elements in the white shark's predatory strategy," said Hammerschlag.
Cape fur seals also have unique techniques to detect, avoid, outmaneuver and in some cases injure the white shark in order to avoid predation by sharks.
According to the authors, if a seal is not disabled during the shark's initial shark, the small seal can use its highly maneuverable body to leap away from the shark's jaws to evade a second strike.
Read more at Science Daily
Florida Reef Restoration Successful
The 35-foot long boat Lagniappe II plowed into a reef in the Florida Keys National Marine Sanctuary in August 2002. The boat's owner paid $56,671.27 in a negotiated settlement to partially cover the costs he had incurred for the American public. The money partly covered the restoration of the 376 square-feet of living coral he damaged.
NOAA went to work reattaching 473 corals, then monitored the reef's progress as it regained its health. NOAA researchers used photos and a specialized computer program to study the numbers and types of coral in the damaged area.
By 2009, the reattached coral looked just like a nearby area used as a reference. Another year later, and the damaged reef had more coral that the reference area.
“The monitoring allowed us to document changes to the restored coral and measure the success of this restoration,” said Hatsue Bailey, Florida Keys National Marine Sanctuary restoration biologist in a press release.
“With continued use of these methods, as well as additional monitoring, we learn more about habitat changes at this location and improve upon existing restoration strategies,” said Bailey.
Read more at Discovery News
Christopher Hitchens
Christopher Hitchens, who has died aged 62, described himself as an “essayist and a contrarian” and, as a journalist, critic, war correspondent and bon vivant, enjoyed a 40-year career as one of the world’s most ubiquitous, prolific and provocative public intellectuals.
He began as a leading iconoclast of the Left and, during the 1970s, was a voluble member of a talented and raffish gang, with Julian Barnes, Martin Amis, Ian McEwan and James Fenton, which gave the New Statesman magazine its glittery literary edge. But he got tired of British politics and, in 1981, moved to America where, despite occasional disagreements with his erstwhile comrades (as when he took Britain’s side against the Argentine junta in the Falklands conflict), his repeated assaults on such hate figures as Ronald Reagan and Henry Kissinger continued to guarantee him a welcome in radical circles.
All this changed after the 9/11 terrorist attacks on New York and Washington, an event he interpreted as a turning point in “a war to the finish between everything I love and everything I hate”. He became an outspoken opponent of “Islamofascism”, forging a breach with the Left which became a permanent rift after the invasion of Iraq in 2003. While his erstwhile colleagues were out on the streets proclaiming “Not in Our Name” (a slogan he found nauseating in its “unstinting self-regard”), Hitchens emerged as one of the fiercest cheerleaders for George W Bush’s strategy of “regime change”. To the inevitable accusations of betrayal (George Galloway described him as the “first ever metamorphosis of a butterfly back into a slug”), Hitchens responded with characteristic gusto: such attacks, he said, washed off him “like jizz off a porn star’s face”.
But, as Hitchens confessed in his memoir Hitch-22 (2010), there had always been a “Janus-faced” side to his personality. When he was a child, his mother told his father, during an argument over whether they could afford to send him to private school: “If there is going to be an upper class in this country, Christopher is going to be in it.”
At the time this was more her aspiration than his, yet Hitchens acknowledged that alongside the donkey-jacketed revolutionary “Chris”, veteran of the Aldermaston marches, there was the suave, good-looking and socially ambitious “Christopher” – “Hypocritchens”, as he was known at Balliol – who enjoyed the company of “confident young men who owned fast cars” and frequented the Union and the Gridiron Club.
The young man spraying pro-Vietcong slogans on car plant walls or marching the streets toting some insurgent flag, might, the same evening, be found at a Right-wing dining club happily gobbling up a pudding called “bombe Hanoi”. Friends later joked that the sentence least likely to emerge from Hitchens’s mouth was: “I don’t care how rich you are, I’m not coming to your party.”
Though he claimed to keep “two sets of books” when it came to political purpose and social ambition, his “Mr Both Ways” approach was as much intellectual as social. He claimed to be faithful to the values of “Left opposition” heroes, such as Rosa Luxembourg, Leon Trotsky and George Orwell, but was always too sceptical and independent-minded to fall for the tedious dogmas of mainstream Marxism – or any other “ism”.
He took pride in “asking annoying questions at every opportunity” and, as a journalist, made a point of going out to see things for himself, whether it was a war zone or a convention of Civil War re-enactors. Even at the height of student radicalism in 1968, he spotted, on a trip to Cuba, the oppressive side of the Castro revolution, acknowledging, when he found himself bombarded by showers of pebbles and the taunt “Sovietico” from the street urchins of Havana, that he had been granted a glimpse of “unscripted public opinion”.
The author or co-author of 17 books, as well as pamphlets and essays, Hitchens was a prolific columnist and, particularly in America, a formidable participant in public debates. He found it difficult to see a sacred cow without lobbing a hand grenade, and his more eminent targets included Mother Teresa (whom he portrayed as a fundamentalist Catholic bigot who gladhanded totalitarian regimes and was “a friend of poverty” rather than of the poor); Bill Clinton (the subject in 1999 of No-One Left to Lie to: The Triangulations of William Jefferson Clinton); and God (the target in 2007 of God Is Not Great: How Religion Poisons Everything).
Hitchens’s natural pugnacity seems to have earned him grudging admiration in some unlikely quarters. In his memoir he recalled an encounter with Mrs Thatcher (whom he found “surprisingly sexy”) not long after her election to the Tory leadership; their inevitable argument ended with the future Iron Lady ordering him to bend over so that she could spank him on the bottom with a rolled-up parliamentary order paper, afterwards mouthing the words: “Naughty boy!”
It was only later, he confessed, that he appreciated the glimpse of the “smack of firm government” which he had been afforded.
The elder of two sons (his younger brother is the journalist and author Peter Hitchens), Christopher Eric Hitchens was born on April 13 1949 in Portsmouth, where his father, a naval officer, was stationed, and was brought up as “a Navy brat” in Malta and Scotland.
His father was a kindly, decent but emotionally inhibited man whose world view epitomised an old-fashioned English conservatism and whose way of showing affection to his son, while he was at prep school, was to send him complicated naval knots tied out of pipe-cleaners, which, of course, Christopher never mastered. (Later, Hitchens was much affected by the discovery that his father was secretly giving his friends Christmas gift subscriptions to his “pinko” magazine, the New Statesman).
His mother, Yvonne, a glamorous but tragic figure whose carefully concealed Jewish ancestry Christopher would discover only when he was in his 40s, eventually left her husband for an unfrocked vicar, with whom she became a devotee of the Maharishi Mahesh Yogi (“the sinister windbag who had brought enlightenment to the Beatles in the summer of love”), and with whom she died in a suicide pact in an Athens hotel when Christopher was 24.
Hitchens’s account of this “lacerating howling moment” in his life and his journey to a junta-governed Greece to identify Yvonne’s body is one of the most powerfully moving passages in his memoir, the tragedy compounded by the revelation that, in the hours before she died, she had tried to phone him repeatedly but had failed to get through. Characteristically, though, he still found the time to file a piece for the New Statesman on the political situation in Greece.
At the Leys School in Cambridge, Christopher discovered a passion for literature, dabbled in homosexuality and was introduced to the pleasures of Marxism by the headmaster who, in a vain attempt to inoculate him against such a heresy, presented him with a copy of the Communist Manifesto.
He developed all three interests at Balliol College, Oxford, where he went up ostensibly to read PPE, but devoted more energy to sit-in and picket line duties (as well as joining the Labour Party, he became a member of the Trotskyist International Socialists) and to cultivating friendships among a camp and reactionary circle of students and academics.
These included John Sparrow, Warden of All Souls and a hate-figure for the Left, who once mischievously ambushed Hitchens in full rant at some student demo to remind him they had a date for dinner. Hitchens’s claim, in his memoirs, that, while at Oxford, he had bedded two future government ministers under Margaret Thatcher would set off an – ultimately futile – orgy of press speculation which did little to damage sales of the book.
After graduating with an inevitable Third, Hitchens launched his career in journalism as “social science correspondent” at the Times, a “Gogol-like ghost job which I held for six months before its editor said something to me that made it impossible for me to go on working for him”. (In a footnote, Hitchens noted that the exact words were: “You’re fired.”)
In the 1970s, as well as working as a freelance, he took various “mainstream” jobs, from being a researcher for the Insight team at the Sunday Times to working as a foreign correspondent for the Daily Express, before joining the New Statesman as a staff writer and editor under Anthony Howard. At the same time he became a regular at the famous Bloomsbury “Friday lunches” at which such luminaries as Clive James, Peter Porter, the Amises (père et fils), Craig Raine and others would swap jokes and gossip.
As the decade wore on and Old Labour tottered towards the political graveyard (“Weimar without the sex”, as Hitchens described the Callaghan government), Hitchens became increasingly disillusioned with the British Left and confessed to harbouring an “odi et amo” complex about Mrs Thatcher, whom he felt was “right on essential matters”. By the 1979 election (in which, for the first time, he did not vote Labour) he was starting to feel “the strong gravitational pull of the great American planet”.
Hitchens’s decision to settle in the United States was a turning point in his life, both personally and politically. As a columnist for The Nation, he continued to fulminate against familiar targets – American imperialism, military fascism, religious fundamentalism – but his rightward political odyssey rolled inexorably on, driven by a disgust with the empty pieties of the Left and an appreciation of the dynamism of the American political tradition.
Gradually he expanded his columns to the pages of mainstream publications such as The Washington Post, The Boston Globe, Harper’s Magazine, Newsday and, appropriately, Dissent. He also lectured and accepted visiting professorships at the Universities of Pittsburgh and California and the New York School for Social Research.
Hitchens’s ideological shift was driven also by a concern at the growing threat of Islamic extremism to Western freedoms. He was appalled by the “tepid reaction” of the European Left following Ayatollah Khomeini’s issue of a fatwa against his friend Salman Rushdie, and also by the events of September 11 2001 which, in his view, opened up a “whole new terrain of struggle”. In 2007 he took the oath of American citizenship at a ceremony at the Jefferson Memorial presided over by George W Bush’s Secretary of Homeland Security, Michael Chertoff.
Hitchens opened his memoir Hitch-22 with a story about a false rumour of his own mortality. A catalogue for an exhibition of photographs at the National Portrait Gallery had mistakenly described him as “the late” Christopher Hitchens, a mistake he used as a peg to muse on the subject of mortality (it was not so much the mourners at the funeral that came to mind, he wrote, but the “steady thunk of emails into my in-box on the day of my demise”). But as he toured to promote the book, he was diagnosed with oesophagal cancer and forced to cancel the remainder of his engagements.
Read more at The Telegraph
All this changed after the 9/11 terrorist attacks on New York and Washington, an event he interpreted as a turning point in “a war to the finish between everything I love and everything I hate”. He became an outspoken opponent of “Islamofascism”, forging a breach with the Left which became a permanent rift after the invasion of Iraq in 2003. While his erstwhile colleagues were out on the streets proclaiming “Not in Our Name” (a slogan he found nauseating in its “unstinting self-regard”), Hitchens emerged as one of the fiercest cheerleaders for George W Bush’s strategy of “regime change”. To the inevitable accusations of betrayal (George Galloway described him as the “first ever metamorphosis of a butterfly back into a slug”), Hitchens responded with characteristic gusto: such attacks, he said, washed off him “like jizz off a porn star’s face”.
But, as Hitchens confessed in his memoir Hitch-22 (2010), there had always been a “Janus-faced” side to his personality. When he was a child, his mother told his father, during an argument over whether they could afford to send him to private school: “If there is going to be an upper class in this country, Christopher is going to be in it.”
At the time this was more her aspiration than his, yet Hitchens acknowledged that alongside the donkey-jacketed revolutionary “Chris”, veteran of the Aldermaston marches, there was the suave, good-looking and socially ambitious “Christopher” – “Hypocritchens”, as he was known at Balliol – who enjoyed the company of “confident young men who owned fast cars” and frequented the Union and the Gridiron Club.
The young man spraying pro-Vietcong slogans on car plant walls or marching the streets toting some insurgent flag, might, the same evening, be found at a Right-wing dining club happily gobbling up a pudding called “bombe Hanoi”. Friends later joked that the sentence least likely to emerge from Hitchens’s mouth was: “I don’t care how rich you are, I’m not coming to your party.”
Though he claimed to keep “two sets of books” when it came to political purpose and social ambition, his “Mr Both Ways” approach was as much intellectual as social. He claimed to be faithful to the values of “Left opposition” heroes, such as Rosa Luxembourg, Leon Trotsky and George Orwell, but was always too sceptical and independent-minded to fall for the tedious dogmas of mainstream Marxism – or any other “ism”.
He took pride in “asking annoying questions at every opportunity” and, as a journalist, made a point of going out to see things for himself, whether it was a war zone or a convention of Civil War re-enactors. Even at the height of student radicalism in 1968, he spotted, on a trip to Cuba, the oppressive side of the Castro revolution, acknowledging, when he found himself bombarded by showers of pebbles and the taunt “Sovietico” from the street urchins of Havana, that he had been granted a glimpse of “unscripted public opinion”.
The author or co-author of 17 books, as well as pamphlets and essays, Hitchens was a prolific columnist and, particularly in America, a formidable participant in public debates. He found it difficult to see a sacred cow without lobbing a hand grenade, and his more eminent targets included Mother Teresa (whom he portrayed as a fundamentalist Catholic bigot who gladhanded totalitarian regimes and was “a friend of poverty” rather than of the poor); Bill Clinton (the subject in 1999 of No-One Left to Lie to: The Triangulations of William Jefferson Clinton); and God (the target in 2007 of God Is Not Great: How Religion Poisons Everything).
Hitchens’s natural pugnacity seems to have earned him grudging admiration in some unlikely quarters. In his memoir he recalled an encounter with Mrs Thatcher (whom he found “surprisingly sexy”) not long after her election to the Tory leadership; their inevitable argument ended with the future Iron Lady ordering him to bend over so that she could spank him on the bottom with a rolled-up parliamentary order paper, afterwards mouthing the words: “Naughty boy!”
It was only later, he confessed, that he appreciated the glimpse of the “smack of firm government” which he had been afforded.
The elder of two sons (his younger brother is the journalist and author Peter Hitchens), Christopher Eric Hitchens was born on April 13 1949 in Portsmouth, where his father, a naval officer, was stationed, and was brought up as “a Navy brat” in Malta and Scotland.
His father was a kindly, decent but emotionally inhibited man whose world view epitomised an old-fashioned English conservatism and whose way of showing affection to his son, while he was at prep school, was to send him complicated naval knots tied out of pipe-cleaners, which, of course, Christopher never mastered. (Later, Hitchens was much affected by the discovery that his father was secretly giving his friends Christmas gift subscriptions to his “pinko” magazine, the New Statesman).
His mother, Yvonne, a glamorous but tragic figure whose carefully concealed Jewish ancestry Christopher would discover only when he was in his 40s, eventually left her husband for an unfrocked vicar, with whom she became a devotee of the Maharishi Mahesh Yogi (“the sinister windbag who had brought enlightenment to the Beatles in the summer of love”), and with whom she died in a suicide pact in an Athens hotel when Christopher was 24.
Hitchens’s account of this “lacerating howling moment” in his life and his journey to a junta-governed Greece to identify Yvonne’s body is one of the most powerfully moving passages in his memoir, the tragedy compounded by the revelation that, in the hours before she died, she had tried to phone him repeatedly but had failed to get through. Characteristically, though, he still found the time to file a piece for the New Statesman on the political situation in Greece.
At the Leys School in Cambridge, Christopher discovered a passion for literature, dabbled in homosexuality and was introduced to the pleasures of Marxism by the headmaster who, in a vain attempt to inoculate him against such a heresy, presented him with a copy of the Communist Manifesto.
He developed all three interests at Balliol College, Oxford, where he went up ostensibly to read PPE, but devoted more energy to sit-in and picket line duties (as well as joining the Labour Party, he became a member of the Trotskyist International Socialists) and to cultivating friendships among a camp and reactionary circle of students and academics.
These included John Sparrow, Warden of All Souls and a hate-figure for the Left, who once mischievously ambushed Hitchens in full rant at some student demo to remind him they had a date for dinner. Hitchens’s claim, in his memoirs, that, while at Oxford, he had bedded two future government ministers under Margaret Thatcher would set off an – ultimately futile – orgy of press speculation which did little to damage sales of the book.
After graduating with an inevitable Third, Hitchens launched his career in journalism as “social science correspondent” at the Times, a “Gogol-like ghost job which I held for six months before its editor said something to me that made it impossible for me to go on working for him”. (In a footnote, Hitchens noted that the exact words were: “You’re fired.”)
In the 1970s, as well as working as a freelance, he took various “mainstream” jobs, from being a researcher for the Insight team at the Sunday Times to working as a foreign correspondent for the Daily Express, before joining the New Statesman as a staff writer and editor under Anthony Howard. At the same time he became a regular at the famous Bloomsbury “Friday lunches” at which such luminaries as Clive James, Peter Porter, the Amises (père et fils), Craig Raine and others would swap jokes and gossip.
As the decade wore on and Old Labour tottered towards the political graveyard (“Weimar without the sex”, as Hitchens described the Callaghan government), Hitchens became increasingly disillusioned with the British Left and confessed to harbouring an “odi et amo” complex about Mrs Thatcher, whom he felt was “right on essential matters”. By the 1979 election (in which, for the first time, he did not vote Labour) he was starting to feel “the strong gravitational pull of the great American planet”.
Hitchens’s decision to settle in the United States was a turning point in his life, both personally and politically. As a columnist for The Nation, he continued to fulminate against familiar targets – American imperialism, military fascism, religious fundamentalism – but his rightward political odyssey rolled inexorably on, driven by a disgust with the empty pieties of the Left and an appreciation of the dynamism of the American political tradition.
Gradually he expanded his columns to the pages of mainstream publications such as The Washington Post, The Boston Globe, Harper’s Magazine, Newsday and, appropriately, Dissent. He also lectured and accepted visiting professorships at the Universities of Pittsburgh and California and the New York School for Social Research.
Hitchens’s ideological shift was driven also by a concern at the growing threat of Islamic extremism to Western freedoms. He was appalled by the “tepid reaction” of the European Left following Ayatollah Khomeini’s issue of a fatwa against his friend Salman Rushdie, and also by the events of September 11 2001 which, in his view, opened up a “whole new terrain of struggle”. In 2007 he took the oath of American citizenship at a ceremony at the Jefferson Memorial presided over by George W Bush’s Secretary of Homeland Security, Michael Chertoff.
Hitchens opened his memoir Hitch-22 with a story about a false rumour of his own mortality. A catalogue for an exhibition of photographs at the National Portrait Gallery had mistakenly described him as “the late” Christopher Hitchens, a mistake he used as a peg to muse on the subject of mortality (it was not so much the mourners at the funeral that came to mind, he wrote, but the “steady thunk of emails into my in-box on the day of my demise”). But as he toured to promote the book, he was diagnosed with oesophagal cancer and forced to cancel the remainder of his engagements.
Read more at The Telegraph
Dec 15, 2011
Dinosaurs With Killer Claws Yield New Theory About Evolution of Flight
In a paper published Dec. 14 in PLoS ONE, MSU researchers Denver W. Fowler, Elizabeth A. Freedman, John B. Scannella and Robert E. Kambic (now at Brown University in Rhode Island), describe how comparing modern birds of prey helped develop a new behavior model for sickle-clawed carnivorous dinosaurs like Velociraptor.
"This study is a real game-changer," said lead author Fowler. "It completely overhauls our perception of these little predatory dinosaurs, changing the way we think about their ecology and evolution."
The study focuses on dromaeosaurids; a group of small predatory dinosaurs that include the famous Velociraptor and its larger relative, Deinonychus. Dromaeosaurids are closely related to birds, and are most famous for possessing an enlarged sickle-claw on digit two (inside toe) of the foot. Previous researchers suggested that this claw was used to slash at prey, or help climb up their hides, but the new study proposes a different behavior.
"Modern hawks and eagles possess a similar enlarged claw on their digit 2's, something that hadn't been noted before we published on it back in 2009," Fowler said. "We showed that the enlarged D-2 claws are used as anchors, latching into the prey, preventing their escape. We interpret the sickle claw of dromaeosaurids as having evolved to do the same thing: latching in, and holding on."
As in modern birds of prey, precise use of the claw is related to relative prey size.
"This strategy is only really needed for prey that are about the same size as the predator; large enough that they might struggle and escape from the feet," Fowler said. "Smaller prey are just squeezed to death, but with large prey all the predator can do is hold on and stop it from escaping, then basically just eat it alive. Dromaeosaurs lack any obvious adaptations for dispatching their victims, so just like hawks and eagles, they probably ate their prey alive too."
Other features of bird of prey feet gave clues as to the functional anatomy of their ancient relatives; toe proportions of dromaeosaurids seemed more suited for grasping than running, and the metatarsus (bones between the ankles and the toes) is more adapted for strength than speed.
"Unlike humans, most dinosaurs and birds only walk on their toes, so the metatarsus forms part of the leg itself," Fowler said. "A long metatarsus lets you take bigger strides to run faster; but in dromaeosaurids, the metatarsus is very short, which is odd."
Fowler thinks that this indicates that Velociraptor and its kin were adapted for a strategy other than simply running after prey.
"When we look at modern birds of prey, a relatively short metatarsus is one feature that gives the bird additional strength in its feet," Fowler continued. "Velociraptor and Deinonychus also have a very short, stout metatarsus, suggesting that they had great strength but wouldn't have been very fast runners."
The ecological implications become especially interesting when dromaeosaurids are contrasted with their closest relatives: a very similar group of small carnivorous dinosaurs called troodontids, Fowler said.
"Troodontids and dromaeosaurids started out looking very similar, but over about 60 million years they evolved in opposite directions, adapting to different niches," Fowler said. "Dromaeosaurids evolved towards stronger, slower feet; suggesting a stealthy ambush predatory strategy, adapted for relatively large prey. By contrast, troodontids evolved a longer metatarsus for speed and a more precise, but weaker grip, suggesting they were swift but probably took relatively smaller prey."
The study also has implications for the next closest relatives of troodontids and dromaeosaurids: birds. An important step in the origin of modern birds was the evolution of the perching foot.
"A grasping foot is present in the closest relatives of birds, but also in the earliest birds like Archaeopteryx," Fowler said. "We suggest that this originally evolved for predation, but would also have been available for use in perching. This is what we call 'exaptation:' a structure evolved originally for one purpose that can later be appropriated for a different use."
The new study proposes that a similar mechanism may be responsible for the evolution of flight.
"When a modern hawk has latched its enlarged claws into its prey, it can no longer use the feet for stabilization and positioning," Fowler said. "Instead the predator flaps its wings so that the prey stays underneath its feet, where it can be pinned down by the predator's bodyweight."
The researchers suggest that this 'stability flapping' uses less energy than flight, making it an intermediate flapping behavior that may be key to understanding how flight evolved.
"The predator's flapping just maintains its position, and does not need to be as powerful or vigorous as full flight would require. Get on top, stay on top; it's not trying to fly away," Fowler said. "We see fully formed wings in exquisitely preserved dromaeosaurid fossils, and from biomechanical studies we can show that they were also able to perform a rudimentary flapping stroke. Most researchers think that they weren't powerful enough to fly; we propose that the less demanding stability flapping would be a viable use for such a wing, and this behavior would be consistent with the unusual adaptations of the feet."
Another group of researchers has proposed that understanding flapping behaviors is key to understanding the evolution of flight, a view with which Fowler agrees.
"If we look at modern birds, we see flapping being used for all sorts of behaviors outside of flight. In our paper, we are formally proposing the 'flapping first' model: where flapping evolved for other behaviors first, and was only later exapted for flight by birds."
Read more at Science Daily
Scientists Discover Second-Oldest Gene Mutation
A new study has identified a gene mutation that researchers estimate dates back to 11,600 B.C., making it the second oldest human disease mutation yet discovered.
Researchers with the Ohio State University Comprehensive Cancer Center -- Arthur G. James Cancer Hospital and Richard J. Solove Research Institute led the study and estimate that the mutation arose in the Middle East some 13,600 years ago. Only a mutation seen in cystic fibrosis that arose between 11,000 and 52,000 years ago is believed to be older.
The investigators described the mutation in people of Arabic, Turkish and Jewish ancestry. It causes a rare, inherited vitamin B12 deficiency called Imerslund-Gräsbeck Syndrome (IGS).
The researchers say that although the mutation is found in vastly different ethnic populations, it originated in a single, prehistoric individual and was passed down to that individual's descendents. This is unusual because such "founder mutations" usually are restricted to specific ethnic groups or relatively isolated populations.
The findings were published recently in the Orphanet Journal of Rare Diseases.
"Diagnosing IGS is oftentime-consuming and inconclusive mainly because vitamin B12 deficiencies have many causes, so identifying this condition usually involves excluding other possibilities," says principal investigator Stephan M. Tanner, research assistant professor of molecular virology, immunology and medical genetics.
"Our findings permit reliable genetic diagnostics in suspected cases of IGS in that this mutation should be considered first when genetically screening patients from these populations."
Even in rare disorders, founder mutations can cause a significant fraction of all cases, he says.This mutation accounts for more than half of the cases in these populations and for about 15 percent of cases worldwide. "It is also often seen in expatriates living abroad," Tanner says.
IGS was identified just over 50 years ago. It occurs in children born with two mutated copies of either the amnionless (AMN) or the cubilin (CUBN) gene. When a genetic mistake is present in both copies of either of these two genes, a person cannot absorb vitamin B12 in the small intestine, resulting in the deficiency.
Children with IGS experience a high risk of infections, fatigue, attention deficit, paralysis and, ultimately, a form of anemia that can be fatal if left untreated. An estimated 400 to 500 cases of IGS have been described worldwide thus far. The incidence rate remains unknown. The syndrome is treatable with life-long injections of vitamin B12.
For this study, the researchers examined a total of 20 patients, 24 parents, 8 unaffected siblings, and 4 grandparents from 16 IGS families. Because the researchers found the mutation in such diverse populations, they were unsure whether it was a true founder mutation that first arose in one individual and was passed down through many generations, or whether it was simply a mutation that recurred frequently over time in different populations.
Read more at Science Daily
Researchers with the Ohio State University Comprehensive Cancer Center -- Arthur G. James Cancer Hospital and Richard J. Solove Research Institute led the study and estimate that the mutation arose in the Middle East some 13,600 years ago. Only a mutation seen in cystic fibrosis that arose between 11,000 and 52,000 years ago is believed to be older.
The investigators described the mutation in people of Arabic, Turkish and Jewish ancestry. It causes a rare, inherited vitamin B12 deficiency called Imerslund-Gräsbeck Syndrome (IGS).
The researchers say that although the mutation is found in vastly different ethnic populations, it originated in a single, prehistoric individual and was passed down to that individual's descendents. This is unusual because such "founder mutations" usually are restricted to specific ethnic groups or relatively isolated populations.
The findings were published recently in the Orphanet Journal of Rare Diseases.
"Diagnosing IGS is oftentime-consuming and inconclusive mainly because vitamin B12 deficiencies have many causes, so identifying this condition usually involves excluding other possibilities," says principal investigator Stephan M. Tanner, research assistant professor of molecular virology, immunology and medical genetics.
"Our findings permit reliable genetic diagnostics in suspected cases of IGS in that this mutation should be considered first when genetically screening patients from these populations."
Even in rare disorders, founder mutations can cause a significant fraction of all cases, he says.This mutation accounts for more than half of the cases in these populations and for about 15 percent of cases worldwide. "It is also often seen in expatriates living abroad," Tanner says.
IGS was identified just over 50 years ago. It occurs in children born with two mutated copies of either the amnionless (AMN) or the cubilin (CUBN) gene. When a genetic mistake is present in both copies of either of these two genes, a person cannot absorb vitamin B12 in the small intestine, resulting in the deficiency.
Children with IGS experience a high risk of infections, fatigue, attention deficit, paralysis and, ultimately, a form of anemia that can be fatal if left untreated. An estimated 400 to 500 cases of IGS have been described worldwide thus far. The incidence rate remains unknown. The syndrome is treatable with life-long injections of vitamin B12.
For this study, the researchers examined a total of 20 patients, 24 parents, 8 unaffected siblings, and 4 grandparents from 16 IGS families. Because the researchers found the mutation in such diverse populations, they were unsure whether it was a true founder mutation that first arose in one individual and was passed down through many generations, or whether it was simply a mutation that recurred frequently over time in different populations.
Read more at Science Daily
Spiders’ Hundreds of Fine Hairs Are Hundreds of Ears
How their tiny specialized hairs do it has puzzled researchers for decades, but one team of scientists may have found a break. Their physics-focused work suggests each hair acts like a single, independent ear — not a network of ear parts that, together, turn a spider’s exoskeleton into one giant ear, as was previously assumed.
“Nobody had looked at these hairs in just the right way. When you look at what they are mechanically optimized to do, you could design better ones,” said physicist Brice Bathellier of the Institute Of Molecular Pathology in Vienna, who co-authored a study of trichobothria hairs Dec. 14 in the Journal of the Royal Society Interface.
“But nature optimizes. Animals evolve under stringent conditions,” Bathellier said. “So it became a question of what [the hairs] actually do, what type of signals tell animals ‘I should leave’ or ‘that’s just wind blowing on me.’”
Trichobothria are fine hairs found on spiders, insects and other animals with exoskeletons. The hairs are so sensitive that some can pick up air movement down to one ten-billionth of a meter, roughly the width of an atom, allowing animals to feel the presence of nearby predators and prey. (Crickets and flies, for example, have tufts of them on their rumps to sense prowling enemies.)
Researchers in the past thought each hair acted like those found in the cochlea of the human inner ear. In that organ, a forest of different lengths and thicknesses of hair breaks up incoming sound waves into discrete chunks, rather than picking up a wide range.
Previous experiments agreed with the assumption: Spider and insect trichobothria resonated at very specific frequencies, showing “peaks” at one particular sound frequency.
But Bathellier said almost all of the research focused on the distance the sound waves wiggled the hairs back and forth — not on how fast they wiggled them.
To measure the hairs’ wiggling velocities, Bathellier and his colleagues placed hunting spiders and crickets in a sealed glass box with a speaker mounted to it. Then they painted a laser sheet down the box and across a specimen’s trichobothria, then puffed microscopic drops of oil that lit up in the plane of the laser.
As they tweaked the speaker’s sounds, a video camera recorded the oil particles moving around the hairs. Later, a computer program deduced the speed of the moving oil droplets around the hairs.
Instead of one peak response to a single frequency, “these hairs operate at the physical limits of sensitivity across a much broader range of frequencies,” Bathellier said.
The hairs responded best to sounds between about 40 Hz, a low rumble of bass, and 600 Hz, a car horn (humans ears can detect between 20 Hz and 20,000 Hz). That they picked up such a wide range of frequencies at all could overturn previous assumptions about how trichobothria work.
“They operate like band-pass filters or microphones, not like the hairs in a human ear,” Bathellier said.
Read more at Wired Science
Found Coins May Unveil a Lost Viking
Found some 16 inches beneath the surface of a field in Silverdale, a village in north Lancashire, UK, the hoard materialized as Darren Webster, a 39-year-old stonemason, lifted a lead box signalled by his detector.
A shower of 201 pieces of silver revealed an abundance of arm-rings, brooch fragments, ingots and coins.
Indeed, the treasure, possibly buried by a Viking warrior before he went into battle, includes coins which evoke Viking kings such as Alfred the Great, who reigned from 871 to 899. At that time, the Vikings were fighting the Anglo-Saxons to keep control of the North of England.
On one side, the coin bears an inscription in the shape of a cross which reads DNS (Dominus) REX (many Vikings had converted to Christianity within a generation of settling in Britain).
More intriguingly, the inscription on the other side reads AIRDECONUT -- "an attempt to represent the Scandinavian name Harthacnut," said Richardson.
Read more at Discovery News
Subscribe to:
Posts (Atom)