Researchers work to save endangered New England cottontail

Scientists with the NH Agricultural Experiment Station are working to restore New Hampshire and Maine’s only native rabbit after new research based on genetic monitoring has found that in the last decade, cottontail populations in northern New England have become more isolated and seen a 50 percent contraction of their range.The endangered New England cottontail is now is at risk of becoming extinct in the region, according to NH Agricultural Experiment Station researchers at the University of New Hampshire College of Life Sciences and Agriculture who believe that restoring habitats is the key to saving the species.”The New England cottontail is a species of great conservation concern in the Northeast. This is our only native rabbit and is an integral component of the native New England wildlife. Maintaining biodiversity gives resilience to our landscape and ecosystems,” said NHAES researcher Adrienne Kovach, research associate professor of natural resources at UNH.New England cottontails have been declining for decades. However, NHAES researchers have found that in the last decade, the New England cottontail population in New Hampshire and Maine has contracted by 50 percent; a decade ago, cottontails were found as far north as Cumberland, Maine.The majority of research on New England cottontails has come out of UNH, much of it under the leadership of John Litvaitis, professor of wildlife ecology, who has studied the New England cottontail for three decades. Kovach’s research expands on this knowledge by using DNA analysis to provide new information on the cottontail’s status, distribution, genetic diversity, and dispersal ecology.The greatest threat and cause of the decline of the New England cottontail is the reduction and fragmentation of their habitat, Kovach said. Fragmentation of habitats occurs when the cottontail’s habitat is reduced or eliminated due to the maturing of forests or land development. Habitats also can become fragmented by roads or natural landscape features, such as bodies of water.”Cottontails require thicketed habitats, which progress from old fields to young forests. Once you have a more mature forest, the cottontail habitat is reduced. A lot of other species rely on these thicket habitats, including bobcats, birds, and reptiles. Many thicket-dependent species are on decline, and the New England cottontail is a representative species for this kind of habitat and its conservation,” Kovach said.Kovach explained that for cottontail and most animal populations to be healthy and grow, it is important for adult animals to leave the place where they were born and relocate to a new habitat, which is known as dispersal. …

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Fish species unique to Hawaii dominate deep coral reefs in Northwestern Hawaiian Islands

Deep coral reefs in Papahanaumokuakea Marine National Monument (PMNM) may contain the highest percentage of fish species found nowhere else on Earth, according to a study by NOAA scientists published in the Bulletin of Marine Science. Part of the largest protected area in the United States, the islands, atolls and submerged habitats of the Northwestern Hawaiian Islands (NWHI) harbor unprecedented levels of biological diversity, underscoring the value in protecting this area, scientists said.Hawaii is known for its high abundance of endemic species — that is, species not found anywhere else on Earth. Previous studies, based on scuba surveys in water less than 100 feet, determined that on average 21 percent of coral reef fish species in Hawaii are unique to the Hawaiian Archipelago.However, in waters 100 to 300 feet deep, nearly 50 percent of the fish scientists observed over a two-year period in the monument were unique to Hawaii, a level higher than any other marine ecosystem in the world. The study also found that on some of PMNM’s deeper reefs, more than 90 percent of fish were unique to the region. These habitats can only be accessed by highly trained divers using advanced technical diving methods.”The richness of unique species in the NWHI validates the need to protect this area with the highest conservation measures available,” said Randy Kosaki, PMNM’s deputy superintendent and co-author of the study. “These findings also highlight the need for further survey work on the monument’s deeper reefs, ecosystems that remain largely unexplored.”Data for the study was collected during two research expeditions to the NWHI aboard NOAA Ship Hi’ialakai in the summers of 2010 and 2012. Some of the unique fish species that were observed include: Redtail Wrasse (Anampses chrysocephalus), Thompson’s Anthias (Pseudanthias thompsoni), Potter’s Angelfish (Centropyge potteri), Hawaiian Squirrelfish (Sargocentron xantherythrum), Chocolate Dip Chromis (Chromis hanui), Masked Angelfish (Genicanthus personatus), and Blueline Butterflyfish (Chaetodon fremblii).Story Source:The above story is based on materials provided by NOAA Headquarters. Note: Materials may be edited for content and length.

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Mechanism elucidated: How smell perception influences food intake

In animals, as in humans, hunger mechanisms are known to stimulate food intake. Hunger triggers a set of mechanisms that encourage feeding, for example by increasing sensory perceptions such as the sense of smell. The researchers have now succeeded in revealing what links hunger and increased smell perception in the brain, and the resulting urge to eat.The researchers have discovered how this mechanism is initiated in the endocannabinoid system in mice. This system interconnects receptors located in the brain and involved in different sensations such as euphoria, anxiety, or even pain, that are also sensitive to cannabinoid substances, such as cannabis.The researchers discovered that the CB1 cannabinoid receptors control a circuit that connects the olfactory bulb (the region in the nervous system that initially handles olfactory information, located above the nose) to the olfactory cortex (higher structures of the brain). When the sensation of hunger is felt, it triggers the activity of the cannabinoid receptors, which in turn activate the olfactory circuit, which then becomes more responsive.It is therefore this biological mechanism that brings about the increased sensitivity to smell during hunger, explaining one of the reasons for food intake and attraction to food.The researchers expect that the circuit involved in the olfactory system is altered in obese or anorexic patients, and that sensitivity to smell may be more or less strong compared to normal. Elucidation of the biological mechanism will allow better management of these types of pathologies.Story Source:The above story is based on materials provided by INSERM (Institut national de la sant et de la recherche mdicale). Note: Materials may be edited for content and length.

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Shadowing in Sensor Images: NASA study points to ‘infrared-herring’ in apparent Amazon green-up

For the past eight years, scientists have been working to make sense of why some satellite data seemed to show the Amazon rain forest “greening-up” during the region’s dry season each year from June to October. The green-up indicated productive, thriving vegetation in spite of limited rainfall.Now, a new NASA study published today in the journal Nature shows that the appearance of canopy greening is not caused by a biophysical change in Amazon forests, but instead by a combination of shadowing within the canopy and the way that satellite sensors observe the Amazon during the dry season.Correcting for this artifact in the data, Doug Morton, of NASA’s Goddard Space Flight Center in Greenbelt, Md., and colleagues show that Amazon forests, at least on the large scale, maintain a fairly constant greenness and canopy structure throughout the dry season. The findings have implications for how scientists seek to understand seasonal and interannual changes in Amazon forests and other ecosystems.”Scientists who use satellite observations to study changes in Earth’s vegetation need to account for seasonal differences in the angles of solar illumination and satellite observation,” Morton said.Isolating the apparent green-up mechanismThe MODIS, or Moderate Resolution Imaging Spectroradiometer, sensors that fly aboard NASA’s Terra and Aqua satellites make daily observations over the huge expanse of Amazon forests. An area is likely covered in green vegetation if sensors detect a relatively small amount of red light — absorbed in abundance by plants for photosynthesis — but see a large amount of near-infrared light, which plants primarily reflect. Scientists use the ratio of red and near-infrared light as a measure of vegetation “greenness.”Numerous hypotheses have been put forward to explain why Amazon forests appear greener in MODIS data as the dry season progresses. Perhaps young leaves, known to reflect more near-infrared light, replace old leaves? Or, possibly trees add more leaves to capture sunlight in the dry season when the skies are less cloudy.Unsettled by the lack of definitive evidence explaining the magnitude of the green-up, Morton and colleagues set out to better characterize the phenomenon. They culled satellite observations from MODIS and NASA’s Ice Cloud and land Elevation Satellite (ICESat) Geosciences Laser Altimeter System (GLAS), which can provide an independent check on the seasonal differences in Amazon forest structure.The team next used a theoretical model to demonstrate how changes in forest structure or reflectance properties have distinct fingerprints in MODIS and GLAS data. Only one of the hypothesized mechanisms for the green-up, changes in sun-sensor geometry, was consistent with the satellite observations.”We think we have uncovered the mechanism for the appearance of seasonal greening of Amazon forests — shadowing within the canopy that changes the amount of near-infrared light observed by MODIS,” Morton said.Seeing the Amazon in a new lightIn June, when the sun is as low and far north as it will get, shadows are abundant. By September, around the time of the equinox, Amazon forests at the equator are illuminated from directly overhead. …

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Communities prepared to be resettled for sake of conserving tigers

Research from the University of Kent has revealed that people in the western Terai Arc Landscape, India, are prepared to relocate their homes and families to help conserve tigers.Undertaken by researchers from the University’s Durrell Institute for Conservation and Ecology (DICE), the research evaluates the ecological and habitat needs of wildlife in the region and the socio-economic needs and priorities of the local forest-dependent community, known as the Gujjars.The research aims to provide an objective framework for conservationists and policymakers to prioritize efforts in order to reach their goal of doubling tiger numbers by 2022.Described in two published papers, the research provides evidence that recovery of wild tiger populations can be achieved hand-in-hand with meeting the livelihood aspirations of the Gujjars.In the first part of the research, the team found that by reintroducing tigers into a section of the landscape that suffers from a lack of connectivity to high density tiger populations, as well as carrying out targeted actions to recover important tiger prey at specific sites across the landscape, there was the potential to increase tiger populations by around 68%.Results from the second part showed an overwhelming preference among Gujjars households interviewed for resettlement outside the forests. This signalled an unexpected opportunity to expand inviolate habitat for tigers in a specific human-dominated landscape by meeting larger livelihood issues for local people, such as better access to education and health services.Principal researcher, Abishek Harihar of DICE, said: ‘With targets to double tiger numbers by 2022, our research could mark a significant change in tiger conservation in India and across tiger range countries. Likewise, it can provide an objective framework for conservationists and policy makers to focus their conservation priorities on ways to delineate “inviolate core” and “areas of coexistence.”Story Source:The above story is based on materials provided by University of Kent. Note: Materials may be edited for content and length.

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Soft shells and strange star clusters

Oct. 10, 2013 — PGC 6240 is an elliptical galaxy that resembles a pale rose in the sky, with hazy shells of stars encircling a very bright centre. Some of these shells are packed close to the centre of the galaxy, while others are flung further out into space. Several wisps of material have been thrown so far that they appear to be almost detached from the galaxy altogether.Astronomers have studied PGC 6240 in detail due to this structure, and also because of its surrounding globular clusters — dense, tightly packed groups of gravitationally bound stars that orbit galaxies. Over 150 of these clusters orbit our own galaxy, the Milky Way, all composed of old stars.All the globular clusters around a certain galaxy form at approximately the same time, giving them all the same age. This is echoed within the clusters — all the stars within a single cluster form at around the same time, too. Because of this, most galaxies have cluster populations of pretty similar ages, both in terms of overall cluster, and individual stars. However, PGC 6240 is unusual in that its clusters are varied — while some do contain old stars, as expected, others contain younger stars which formed more recently.The most likely explanation for both the galaxy’s stacked shell structure and the unexpectedly young star clusters is that PGC 6240 merged with another galaxy at some point in the recent past. Such a merger would send ripples through the galaxy and disrupt its structure, forming the concentric shells of material seen here. It would also ignite a strong burst of star formation in the galaxy, which would then trigger similar activity in nearby space — leading to the creation of new, younger globular clusters around PGC 6240.PGC 6240 is an elliptical galaxy in the southern constellation of Hydrus (The Water Snake). …

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New approach to celiac testing identifies more at risk

Aug. 27, 2013 — Australian researchers have developed a new approach to detecting coeliac disease, revealing this immune disorder is far more common than previously recognised.In a study of more than 2500 Victorians the researchers combined traditional antibody testing (measuring the immune response to gluten) with an assessment of specific genetic risk markers. They found more than half of Australians had genetic risk factors for developing coeliac disease. The research is published online today in the journal BMC Medicine.Dr Jason Tye-Din from the Immunology division at the Walter and Eliza Hall Institute and Dr Bob Anderson, chief scientific officer at US biotechnology company ImmusanT, worked with Barwon Health, Deakin University, Healthscope Pathology and the University of Queensland Diamantina Institute to develop and trial the new diagnostic approach.Dr Tye-Din said the new approach of combining the genetic test with a panel of antibody tests would increase the accuracy of testing, decrease overall medical costs by reducing invasive diagnostic tests, and avoid medically unnecessary use of a gluten-free diet.”Currently, bowel biopsies are recommended for anybody with positive antibody tests,” he said. “In this study the inclusion of a simple genetic test helped identify a substantial number of people whose antibody tests were falsely positive and who did not actually require a bowel biopsy to test for the possibility of coeliac disease.”Coeliac disease is caused by an inappropriate immune response to dietary gluten. Gluten can be found in wheat, rye, barley and oats. When gluten is consumed, it can cause a wide range of complaints from chronic tiredness, iron deficiency, osteoporosis, itchy rash, and headaches to various digestive symptoms. Coeliac disease damages the lining of the small intestine and can lead to significant medical complications such as autoimmune disease, infertility, liver failure and cancer. Coeliac disease usually develops in childhood and is life-long, but early diagnosis and treatment can reduce the risk of adverse health complications.Dr Tye-Din said the newly developed testing strategy showed coeliac disease potentially affected at least one in 60 Australian women and one in 80 men. Previous estimates had the number of Australians with coeliac disease as no more than one in 100. …

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Architecture of chromosomes: A key for success or failure

Aug. 23, 2013 — In a pioneer study published in the latest issue of the scientific journal Nature Communications, a research team at the Instituto Gulbenkian de Ciência (IGC; Portugal), led by Miguel Godinho Ferreira in collaboration with Isabel Gordo, show for the first time that chromosomes rearrangements (such as inversions or translocations) can provide advantages to the cells that harbor them depending on the environment they are exposed. This study contributes to better understand different biological problems such as: how cancer cells that have chromosomal rearrangements can outgrow normal cells or how organisms may evolve in the same physical location to form distinct species.Chromosomal rearrangements consist in parts of a chromosome being relocated to another region of the same chromosome or to a different one. These mutations are commonly found in cancer cells, but also exist in individuals that do not present any known disease. Until now it was unknown the impact that chromosomal rearrangements have in the fitness of an organism, i.e. in its ability to survive and reproduce. The team of Miguel Godinho Ferreira has proposed to answer this question.Using as a model organism the African beer yeast, Schizosaccharomyces pombe (S. pombe), the research team observed that chromosomal rearrangements occur in natural populations of yeast. To better investigate the effect these mutations have in the ability of yeast to grow, the researchers engineered yeast strains with segments of chromosomes allocated to different regions, without disrupting the expression of any gene, thus keeping an identical genetic code.Surprisingly, even though they all contained the same genetic information, mutant strains had different growth abilities, showing that some of the chromosomes rearrangements were beneficial whereas others were deleterious. More than that, when the environment where the strains were growing is changed, the apparently deleterious rearrangement could become beneficial, favoring the growth of that particular strain. …

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How sleep helps brain learn motor task

Aug. 20, 2013 — Sleep helps the brain consolidate what we’ve learned, but scientists have struggled to determine what goes on in the brain to make that happen for different kinds of learned tasks. In a new study, researchers pinpoint the brainwave frequencies and brain region associated with sleep-enhanced learning of a sequential finger tapping task akin to typing, or playing piano.You take your piano lesson, you go to sleep and when you wake up your fingers are better able to play that beautiful sequence of notes. How does sleep make that difference? A new study helps to explain what happens in your brain during those fateful, restful hours when motor learning takes hold.”The mechanisms of memory consolidations regarding motor memory learning were still uncertain until now,” said Masako Tamaki, a postdoctoral researcher at Brown University and lead author of the study that appears Aug. 21 in the Journal of Neuroscience. “We were trying to figure out which part of the brain is doing what during sleep, independent of what goes on during wakefulness. We were trying to figure out the specific role of sleep.”In part because it employed three different kinds of brain scans, the research is the first to precisely quantify changes among certain brainwaves and the exact location of that changed brain activity in subjects as they slept after learning a sequential finger-tapping task. The task was a sequence of key punches that is cognitively akin to typing or playing the piano.Cap of SensorsIn a sleep lab on Brown’s campus researchers use now using caps of EEG sensors in studies of how the brain works to consolidate learning visual tasks. Here graduate student Aaron Berard models the cap.Specifically, the results of complex experiments performed at Massachusetts General Hospital and then analyzed at Brown show that the improved speed and accuracy volunteers showed on the task after a few hours sleep was significantly associated with changes in fast-sigma and delta brainwave oscillations in their supplementary motor area (SMA), a region on the top-middle of the brain. …

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Maya pyramid decorated with rare polychrome-painted stucco frieze

Aug. 7, 2013 — A Maya pyramid beautifully decorated with a rare polychrome-painted stucco frieze was unearthed in July 2013 at the site of Holmul, a Classic Maya city in northeastern Peten region of Guatemala. The find came as archaeologist Francisco Estrada-Belli’s team excavated in a tunnel left open by looters. The stucco relief stands along the exterior of a multi-roomed rectangular building, measuring 8m in length and 2m in height. Much of the building still remains encased under the rubble of a later 20m-high structure. The carving is painted in red, with details in blue, green and yellow.”This is a unique find. It is a beautiful work of art and it tells us so much about the function and meaning of the building, which was what we were looking for,” says Estrada-Belli. The carving depicts human figures in a mythological setting, suggesting these may be deified rulers. The team had hoped to find clues to the function of this building, since the unearthing of an undisturbed tomb last year. The burial contained an individual accompanied by 28 ceramic vessels and a wooden funerary mask.An inscription below the figures tells us that this edifice was commissioned by the ruler of Naranjo, a powerful kingdom to the south of Holmul. …

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Scientists decipher structure of NatA, an enzyme complex that modifies most human proteins

Aug. 4, 2013 — A team of researchers from Philadelphia and Norway has determined the structure of an enzyme complex that modifies one end of most human proteins and is made at elevated levels in numerous forms of cancer. A study in Nature Structural & Molecular Biology, led by researchers at The Wistar Institute, depicts the structure and the means of action of a protein complex called NatA. Their findings, they believe, will allow them to create an inhibitor — a potential drug — that could knock out NatA in order to curb the growth of cancer cells.”NatA appears essential for the growth of cells and their ability to divide, and we can see elevated production of this enzyme in many forms of cancer” said Ronen Marmorstein, Ph.D., senior author, Hilary Koprowski, M.D. Professor, and leader of The Wistar Institute Cancer Center’s Gene Expression and Regulation program. “Obviously, this is a particularly appealing drug target and we are currently leveraging our recent understanding of how the protein works to develop small molecules that will bind to and inactivate NatA.”NatA is a member of a family of N-terminal acetyltransferase (NAT) enzymes (or enzyme complexes) that modify proteins in order to control their behavior — for example by turning proteins on, telling proteins where to move, and tagging proteins or the cell for destruction.According to Marmorstein, NatA works with an amazing specificity for a particular sequence of amino acids — the individual building blocks of proteins — and unraveling the roots of that specificity has proven an alluring puzzle for scientists.The Marmorstein laboratory has proven expertise in the study of acetylation enzymes, proteins that modify other molecules in the cell with an acetyl group “tag.” In the cellular world, structure dictates function, and acetylation is a universal process for controlling protein behavior and gene expression in living organisms.”Modifying protein structures is one way that our cells control how proteins function,” Marmorstein explained, “and enzymes in the NAT family modify nearly 85 percent of human proteins, and 50 percent of these are modified by NatA.”According to Marmorstein, NatA operates in a complex of two proteins, an enzymatic subunit and an auxiliary partner. When they developed the structure of NatA — by bombarding a crystallized sample of the enzyme with powerful X-rays — they found how the auxiliary partner protein is crucial for turning the enzymatic subunit on.Binding to an auxiliary protein causes a structural change in the enzymatic subunit that properly configures the active site of the protein — the region of the protein where the chemical reaction occurs — essentially acting as a switch that activates the enzyme.”When it binds to its auxiliary protein, the enzymatic subunit of NatA actually changes shape, reconfiguring the structure to allow it to properly grab its target protein N-terminal sequence for acetylation,” Marmorstein said.Importantly, others have found that NatA function is required for the proliferation of cancer cells. Marmorstein says, understanding the structure of NatA has allowed his team to better understand how to inactivate the protein in cancer cells. The structure has yielded targets for small molecules that will act as inhibitors, essentially stopping the protein by gumming up its structure.

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Ripped apart by a black hole: Gas cloud makes closest approach to monster at center of Milky Way

July 17, 2013 — New observations from ESO’s Very Large Telescope show for the first time a gas cloud being ripped apart by the supermassive black hole at the centre of the galaxy. The cloud is now so stretched that its front part has passed the closest point and is travelling away from the black hole at more than 10 million km/h, whilst the tail is still falling towards it.In 2011 ESO’s Very Large Telescope (VLT) discovered a gas cloud with several times the mass of Earth accelerating towards the black hole at the centre of the Milky Way[1]. This cloud is now making its closest approach and new VLT observations show that it is being grossly stretched by the black hole’s extreme gravitational field.”The gas at the head of the cloud is now stretched over more than 160 billion kilometres around the closest point of the orbit to the black hole. And the closest approach is only a bit more than 25 billion kilometres from the black hole itself — barely escaping falling right in,” explains Stefan Gillessen (Max Planck Institute for Extraterrestrial Physics, Garching, Germany) who led the observing team [2]. “The cloud is so stretched that the close approach is not a single event but rather a process that extends over a period of at least one year.”As the gas cloud is stretched its light gets harder to see. But by staring at the region close to the black hole for more than 20 hours of total exposure time with the SINFONI instrument on the VLT — the deepest exposure of this region ever with an integral field spectrometer [3] — the team was able to measure the velocities of different parts of the cloud as it streaks past the central black hole [4].”The most exciting thing we now see in the new observations is the head of the cloud coming back towards us at more than 10 million km/h along the orbit — about 1% of the speed of light,” adds Reinhard Genzel, leader of the research group that has been studied this region for nearly twenty years. “This means that the front end of the cloud has already made its closest approach to the black hole.” The origin of the gas cloud remains mysterious, although there is no shortage of ideas [5]. The new observations narrow down the possibilities.”Like an unfortunate astronaut in a science fiction film, we see that the cloud is now being stretched so much that it resembles spaghetti. This means that it probably doesn’t have a star in it,” concludes Gillessen. “At the moment we think that the gas probably came from the stars we see orbiting the black hole.”The climax of this unique event at the centre of the galaxy is now unfolding and being closely watched by astronomers around the world. …

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A Malaysian beauty: Newly described endemic herb species under threat of extinction

July 10, 2013 — A new species of rare and beautiful plant has been described from the biodiversity rich Peninsular Malaysia. Ridleyandra chuana is endemic to the region and only known from two small montane forest populations. The conservation status of this recently described delicate flower is assessed as Endangered due to its restricted distribution.The new species was described and illustrated in the open access journal PhytoKeys.Ridleyandra chuana is a perennial herb with a woody usually unbranched stem crowned by an asymmetrical rosette of dark green leaves covered in fine hairs. The beautiful and delicate cone-like flowers are white with dark maroon purple stripes. They rarely appear in more than two in one go usually flowering in succession. Ridleyandra chuana grows on moss-covered granite rock embedded in soil or on low moss-covered granite boulders, in extremely damp, deeply shaded conditions on steep slopes in valleys.Although the species is only formally described now, it was in fact first encountered as early as 1932 at Fraser’s Hill, Pahang. However, it was only in 1999 when another population was discovered by L.S.L. Chua on Gunung Ulu Kali, Pahang, that sufficient material was available for its description. Since then, both these localities have been revisited and the Gunung Ulu Kali population is now the focus of conservation.The new species is named in honour of Dr Lillian Swee Lian Chua, botanist and conservationist, who first discovered this species on Gunung Ulu Kali while making an ecological inventory of the summit flora. Under the IUCN criteria, this species is assessed as Endangered because it is known from two localities, one of which is threatened, and only 130 known individuals.”The population at Fraser’s Hill falls within a Totally Protected Area and consists of about 30 plants that grow in an undisturbed site away from tourist trails and is too remote to be affected by development. …

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Altitude sickness may hinder ethnic integration in the world’s highest places

July 1, 2013 — Ethnic segregation in nations straddling the world’s steepest terrains may be reinforced by the biological tolerance different peoples have to altitude, according to one of the first studies to examine the effect of elevation on ethnic demographics.Research from Princeton University published in the journal Applied Geography suggests that people native to low-lying areas can be naturally barred from regions such as the Tibetan Plateau, the Andes or the Himalayas by altitude sickness, which is caused by low oxygen concentration in the air and can be life-threatening. As a result, the homogeny of the local population can increase with elevation. In nations shared by people of high- and lowland extractions, this separation can potentially increase ethnic tension.The researchers studied Tibet and found that elevation has heavily influenced the location of the surrounding region’s population of Han Chinese, who make up 92 percent of China’s population and originate from the country’s eastern plains. Tibet has an average elevation of roughly 14,370 feet (4,380 meters) above sea level. The number of settlements with a large Han Chinese population peaks at around 8,900 feet (2,700 meters), while Tibetan settlements only begin to peter out beyond 17,000 feet (5,200 meters), the researchers found. The researchers attribute the sudden drop in the Han Chinese population to altitude sickness, and cite existing research showing that Han Chinese are indeed susceptible to altitude sickness in areas in which Tibetans thrive.First author Christopher Paik, who undertook the study as a postdoctoral research scholar in the Empirical Studies of Conflict Project in Princeton’s Woodrow Wilson School of Public and International Affairs, said that the research adds a new dimension to the study of how terrain influences demographic patterns. The field already explores the role of factors such as soil quality and access to the sea. The biological effects of elevation make altitude a particularly objective and reliable measurement for helping determine and understand how populations around the world’s highest areas form, he said.”There is very little research about the effect of altitude on migration patterns,” said Paik, who is now an assistant professor of politics at New York University Abu Dhabi. “One of the nice things about using this geographical indicator as an independent variable is that there isn’t any human intervention in determining the altitude of the region because it’s established by nature.”Rather than saying there is merely a correlation between settlement patterns and altitude, our research takes it one step further and suggests that altitude can directly determine the settlement patterns we see today. There’s a causal story here,” Paik said.The separation that results from these settlement patterns could result in greater ethnic friction, Paik said. …

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Brain’s ‘dark side’ as key to cocaine addiction

June 12, 2013 — Scientists at The Scripps Research Institute (TSRI) have found evidence that an emotion-related brain region called the central amygdala — whose activity promotes feelings of malaise and unhappiness — plays a major role in sustaining cocaine addiction.In experiments with rats, the TSRI researchers found signs that cocaine-induced changes in this brain system contribute to anxiety-like behavior and other unpleasant symptoms of drug withdrawal — symptoms that typically drive an addict to keep using. When the researchers blocked specific brain receptors called kappa opioid receptors in this key anxiety-mediating brain region, the rats’ signs of addiction abated.”These receptors appear to be a good target for therapy,” said Marisa Roberto, associate professor in TSRI’s addiction research group, the Committee on the Neurobiology of Addictive Disorders. Roberto was the principal investigator for the study, which appears in the journal Biological Psychiatry.Carrot or Stick?In addition to its clinical implications, the finding represents an alternative to the pleasure-seeking, “positive” motivational circuitry that is traditionally emphasized in addiction.While changes in these pleasure-seeking brain networks may dominate the early period of drug use, scientists have been finding evidence of changes in the “negative” motivational circuitry as well — changes that move a person to take a drug not for its euphoric effects but for its (temporary) alleviation of the anxiety-ridden dysphoria of drug withdrawal. George F. Koob, chair of TSRI’s Committee on the Neurobiology of Addictive Disorders, has argued that these “dark side” brain changes mark the transition to a more persistent drug dependency.In a series of recent studies, TSRI researchers including Roberto and Koob have highlighted the role of one of these dark-side actors: the receptor for the stress hormone CRF. Found abundantly in the central amygdala, CRF receptors become persistently overactive there as drug use increases, and that overactivity helps account for the negative symptoms of drug withdrawal.The central amygdala also contains a high concentration of a class of neurotransmitters called dynorphins, which bind to kappa opioid receptors. Much like the CRF system, the dynorphin/kappa opioid system mediates negative, dysphoric feelings — and there have been hints from previous studies that CRF doesn’t work alone in producing such feelings during addiction.”Our hypothesis was that the dynorphin/kappa opioid receptor system in the central amygdala also becomes overactive with excessive cocaine use,” said Marsida Kallupi, first author of the paper, who was a postdoctoral research associate in Roberto’s laboratory at the time of the study.Such overactivity would be expected to arise as the brain struggles to maintain “reward homeostasis” — a middle-of-the-road balance between pleasure and displeasure — despite frequent drug-induced swerves toward euphoria. “Dynorphin possibly acts to balance the euphoric effects produced by other opioid systems during recreational drug use,” said Scott Edwards, who is a research associate in the Koob laboratory and a co-author of the study.Reducing Signs of AddictionWhen the TSRI researchers gave rats extended access to cocaine, the rats escalated their daily intake as many human users would. Sensitive electrophysiological measurements revealed signs of a persistent functional overactivity of the GABAergic system in the rats’ central amygdalae — which corresponds to an anxiety-like state in the animals. Probing with compounds that activate or block kappa opioid receptors, the scientists found signs that these receptors, like CRF receptors, do indeed help drive the central amygdala into overactivity during excessive cocaine use.When the researchers blocked the kappa opioid receptors, central amygdala overactivity was greatly reduced. …

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Pollution in Northern Hemisphere helped cause 1980s African drought

June 6, 2013 — Decades of drought in central Africa reached their worst point in the 1980s, causing Lake Chad, a shallow lake used to water crops in neighboring countries, to almost dry out completely.The shrinking lake and prolonged drought was initially blamed on overgrazing and bad agricultural practices. More recently, Lake Chad became an example of global warming. New University of Washington research, to be published in Geophysical Research Letters, shows that the drought were caused at least in part by Northern Hemisphere air pollution.Aerosols emanating from coal-burning factories in the United States and Europe during the 1960s, ’70s and ’80s cooled the entire Northern Hemisphere, shifting tropical rain bands south. Rains no longer reached the Sahel region, a band that spans the African continent just below the Sahara desert.When clean-air legislation passed in the U.S. and Europe, the rain band shifted back, and the drought lessened. Related research by the UW researchers and their collaborators shows that global warming is now causing the land-covered Northern Hemisphere to warm faster than the Southern Hemisphere, further reversing the pre-1980s trend.Previous research has suggested a connection between coal-burning and the Sahel drought, but this was the first study that used decades of historical observations to find that this drought was part of a global shift in tropical rainfall, and then used multiple climate models to determine why.”One of our research strategies is to zoom out,” said lead author Yen-Ting Hwang, a UW doctoral student in atmospheric sciences. “Instead of studying rainfall at a particular place, we try to look for the larger-scale patterns.”To determine that the Sahel drought was part of a broader shift, the authors looked at precipitation from all rain gauges that had continuous readings between 1930 and 1990. Other places on the northern edge of the tropical rain band, including northern India and South America, also experienced dryer climates in the 1970s and ’80s. Meanwhile, places on the southern edge of the rain band, such as northeast Brazil and the African Great Lakes, were wetter than normal.To understand the reason, authors looked at all 26 climate models used by the Intergovernmental Panel on Climate Change. Researchers discovered that almost all the models also showed some southward shift, and that cooling from sulfate aerosols in the Northern Hemisphere was the primary cause.”We think people should know that these particles not only pollute air locally, but they also have these remote climate effects,” Hwang said.Light-colored sulfate aerosols are emitted mainly by dirty burning of coal. …

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PET finds increased cognitive reserve levels in highly educated pre-Alzheimer’s patients

June 3, 2013 — Highly educated individuals with mild cognitive impairment that later progressed to Alzheimer’s disease cope better with the disease than individuals with a lower level of education in the same situation, according to research published in the June issue of The Journal of Nuclear Medicine. In the study “Metabolic Networks Underlying Cognitive Reserve in Prodromal Alzheimer Disease: A European Alzheimer Disease Consortium Project,”neural reserve and neural compensation were both shown to play a role in determining cognitive reserve, as evidenced by positron emission tomography (PET).Cognitive reserve refers to the hypothesized capacity of an adult brain to cope with brain damage in order to maintain a relatively preserved functional level. Understanding the brain adaptation mechanisms underlying this process remains a critical question, and researchers of this study sought to investigate the metabolic basis of cognitive reserve in individuals with higher (more than 12 years) and lower (less than 12 years) levels of education who had mild cognitive impairment that progressed to Alzheimer’s disease, also known as prodromal Alzheimer’s disease.”This study provides new insight into the functional mechanisms that mediate the cognitive reserve phenomenon in the early stages of Alzheimer’s disease,” said Silvia Morbelli, MD, lead author of the study. “A crucial role of the dorso-lateral prefrontal cortex was highlighted by demonstrating that this region is involved in a wide fronto-temporal and limbic functional network in patients with Alzheimer’s disease and high education, but not in poorly educated Alzheimer’s disease patients.”In the study, 64 patients with prodromal Alzheimer’s disease and 90 control subjects — coming from the brain PET project (chaired by Flavio Nobili, MD, in Genoa, Italy) of the European Alzheimer Disease Consortium — underwentbrain 18F-FDG PET scans. Individuals were divided into a subgroup with a low level of education (42 controls and 36 prodromal Alzheimer’s disease patients) and a highly educated subgroup (40 controls and 28 prodromal Alzheimer’s disease patients). Brain metabolism was compared between education-matched groups of patients and controls, and then between highly and poorly educated prodromal Alzheimer’s disease patients.Higher metabolic activity was shown in the dorso-lateral prefrontal cortex for prodromal Alzheimer’s disease patients. More extended and significant correlations of metabolism within the right dorso-lateral prefrontal cortex and other brain regions were found with highly educated than less educated prodromal Alzheimer’s disease patients or even highly educated controls.This result suggests that neural reserve and neural compensation are activated in highly educated prodromal Alzheimer’s disease patients. Researchers concluded that evaluation of the implication of metabolic connectivity in cognitive reserve further confirms that adding a comprehensive evaluation of resting 18F-FDG PET brain distribution to standard inspection may allow a more complete comprehension of Alzheimer’s disease pathophysiology and possibly may increase 18F-FDG PET diagnostic sensitivity.”This work supports the notion that employing the brain in complex tasks and developing our own education may help in forming stronger ‘defenses’ against cognitive deterioration once Alzheimer knocks at our door,” noted Morbelli.”It’s possible that, in the future, a combined approach evaluating resting metabolic connectivity and cognitive performance can be used on an individual basis to better predict cognitive decline or response to disease-modifying therapy.”

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Human activity echoes through Brazilian rainforest

May 30, 2013 — The disappearance of large, fruit-eating birds from tropical forests in Brazil has caused the region’s forest palms to produce smaller, less successful seeds over the past century, researchers say. The findings provide evidence that human activity can trigger fast-paced evolutionary changes in natural populations.

Mauro Galetti from the Universidade Estadual Paulista in São Paulo, Brazil, along with an international team of colleagues, used patches of rainforest that had been fragmented by coffee and sugar cane development during the 1800’s to set up their natural experiment. They collected more than 9,000 seeds from 22 different Euterpe edulis palm populations and used a combination of statistics, genetics and evolutionary models to determine that the absence of large, seed-dispersing birds in the area was the main reason for the observed decrease in the palm’s seed size.

The study appears in the 31 May issue of the journal Science.

“Unfortunately, the effect we document in our work is probably not an isolated case,” said Galetti. “The pervasive, fast-paced extirpation of large vertebrates in their natural habitats is very likely causing unprecedented changes in the evolutionary trajectories of many tropical species.”

In general, researchers estimate that human activity, such as deforestation, drives species to extinction about 100 times faster than natural evolutionary processes. However, very few studies have successfully documented such rapid evolutionary changes in ecosystems that have been modified by human activity.

Galetti and the other researchers found that palms produced significantly smaller seeds in patches of forest that had been fragmented by coffee and sugar cane plantations and were no longer capable of supporting large-gaped birds, or those whose beaks are more than 12 millimeters wide, such as toucans and large cotingas. In undisturbed patches of forest, on the other hand, large-gaped birds still make their homes and palms continue to produce large seeds, successfully dispersed by the birds, they say.

“Small seeds are more vulnerable to desiccation and cannot withstand projected climate change,” explained Galetti. But, small-gaped birds, such as thrushes, that populate the fragmented patches of forest are unable to swallow and disperse large seeds. As a result of this impaired dispersal, palm regeneration became less successful in the area, with less-vigorous seedlings germinating from smaller seeds.

The researchers considered the influence of a wide range of environmental factors, such as climate, soil fertility and forest cover, but none could account for the change in palm seed size over the years in the fragmented forests. They performed genetic analyses to determine that the shrinkage of seeds among forest palms in the region could have taken place within 100 years of an initial disturbance.

This timescale suggests that the conversion of tropical forests for agriculture, which began back in the 1800’s and displaced many large bird populations in the region, triggered a rapid evolution of forest palms that resulted in smaller, less successful seeds.

Long periods of drought and increasingly warmer climate (as predicted by climate model projections for South America) could be particularly harmful to tropical tree populations that depend on animals to disperse their seeds. About 80 percent of the entire Atlantic rainforest biome remains in small fragments, according to the researchers, and the successful restoration of these habitats critically depends on the preservation of mutualistic interactions between animals and plants.

“Habitat loss and species extinction is causing drastic changes in the composition and structure of ecosystems, because critical ecological interactions are being lost,” said Galetti. “This involves the loss of key ecosystem functions that can determine evolutionary changes much faster than we anticipated. Our work highlights the importance of identifying these key functions to quickly diagnose the functional collapse of ecosystems.”

The report by Galetti et al. was supported by the Fundação de Amparo do Estado de São Paulo, Conselho Nacional de Desenvolvimento Científico and Programa Iberoamericano de Ciencia y Tecnología para el Desarollo.

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Evolution shapes new rules for ant behavior, research finds

May 15, 2013 — In ancient Greece, the city-states that waited until their own harvest was in before attacking and destroying a rival community’s crops often experienced better long-term success.

It turns out that ant colonies that show similar selectivity when gathering food yield a similar result. The latest findings from Stanford biology Professor Deborah M. Gordon’s long-term study of harvester ants reveal that the colonies that restrain their foraging except in prime conditions also experience improved rates of reproductive success.

Importantly, the study provides the first evidence of natural selection shaping collective behavior, said Gordon, who is also a senior fellow at the Stanford Woods Institute for the Environment.

A long-held belief in biology has posited that the amount of food an animal acquires can serve as a proxy for its reproductive success. The hummingbirds that drink the most nectar, for example, stand the best chance of surviving to reproduce.

But the math isn’t always so straightforward. The harvester ants that Gordon studies in the desert in southeast Arizona, for instance, have to spend water to obtain water: an ant loses water while foraging, and obtains water from the fats in the seeds it eats.

The ants use simple positive feedback interactions to regulate foraging activity. Foragers wait near the opening of the nest, and bump antennae with ants returning with food. The faster outgoing foragers meet ants returning with seeds, the more ants go out to forage. (Last year, Gordon, Katie Dektar, an undergraduate, and Balaji Prabhakar, a professor of computer science and of electrical engineering at Stanford, showed that the ants’ “Anternet” algorithm follows the same rules as the protocols that regulate data traffic congestion in the Internet).

Colonies differ, however, in how they use these interactions to regulate foraging. Some colonies are likely to forage less when conditions are dry. These same, more successful colonies are also more likely to forage more steadily when conditions are good.

Gordon found that it’s more important for the ants to not waste water than to forage for every last piece of food. There’s no survival cost to this strategy, even though the colonies sometimes forgo foraging for an entire day. Instead, not only do the colonies that hunker down on the bad days live just as long as those that go all out, they also have more offspring colonies.

“Natural selection is not favoring the behavior that sends out the most ants to get the most food, but instead regulating foraging to hold back when conditions are bad,” Gordon said. “This is natural selection shaping a collective behavior exhibited by the entire colony.”

Gordon’s group is still investigating how the ants gauge humidity, but they have determined that the collective response of the colony to conditions is heritable from parent colony to offspring colony. Even though a daughter queen will establish her new colony so far from the parent colony that the two colonies will never interact, the offspring colonies resemble parent colonies in their sensitivity to conditions.

Although the foraging activity of the offspring colonies and the parent colony didn’t entirely match up on all days, they were similar on extreme days: parent and offspring colonies made similar judgments about when to lie low or take advantage of ideal conditions.

While the region has experienced 10 to 15 years of protracted drought, and the more restrained colonies will most likely fare better reproductively as that trend continues, Gordon can’t yet say whether the emphasis on sustainability evolved in response to climate change pressures.

“What’s evolving here are simple rules for how ants participate in a network that regulates the collective behavior of the colony,” she said.

The work is published in the May 16 issue of the journal Nature.

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