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2015年5月13日星期三

How the brain balances hearing between our ears -- ScienceDaily

The landmark animal study also provides new insight into hearing loss and is likely to improve cochlear implants and hearing aids.

The findings of the NHMRC-funded research are published in the journal Nature Communications.

UNSW Professor Gary Housley, senior author of the research paper, said his team sought to understand the biological process behind the 'olivocochlear' hearing control reflex.

"The balance of hearing between the ears and how we discriminate between sounds versus noise is dependent upon this neural reflex that links the cochlea of each ear via the brain's auditory control centre," Professor Housley said.

"Until now we haven't fully understood what drives the olivocochlear reflex."

"Our hearing is so sensitive that we can hear a pin drop and that's because of the 'cochlear amplifier' in our inner ear. This stems from outer hair cells in the cochlea which amplify sound vibrations."

"When sound intensity increases, the olivocochlear reflex turns down the 'cochlear amplifier' to dynamically balance the input of each ear for optimal hearing, sound localisation and to protect hearing."

The study found that the cochlear's outer hair cells, which amplify sound vibrations, also provide the sensory signal to the brain for dynamic feedback control of this sound amplification, via a small group of auditory nerve fibres of previously unknown function.

In mice lacking the sensory fibre connection to the cochlear outer hair cells, loud sound presented to one ear had no effect on hearing sensitivity in the other ear. In normal control mice this produced an almost instant suppression of hearing.

Similarly, the olivocochlear reflex normally causes a rapid reduction in hearing in the ear receiving an increase in sound. This hearing adaptation was also absent in the mice lacking the sensory fibre connection.

The researchers speculate that some of the hearing loss that humans experience as they age may be related to the gradual breakdown of this sensory fibre connection to the outer hair cells.

"A major limitation of hearing aids and cochlear implants is their inability to work in tandem and support good hearing in noisy conditions," Professor Housley said

"The ultimate goal is for cochlear implants in both ears to communicate with each other so that the brain can receive the most accurate soundscape possible. This research will help us move closer to that goal."

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Scientists regenerate bone tissue using only proteins secreted by stem cells -- ScienceDaily

The new study, published in Scientific Reports, is is the first to extract the necessary bone-producing growth factors from stem cells and to show that these proteins are sufficient to create new bone. The stem cell-based approach was as effective as the current standard treatment in terms of the amount of bone created.

"This proof-of-principle work establishes a novel bone formation therapy that exploits the regenerative potential of stem cells," says senior author Todd McDevitt, PhD, a senior investigator at the Gladstone Institutes. "With this technique, we can produce new tissue that is completely stem cell-derived and that performs similarly with the gold standard in the field."

Instead of using stem cells themselves, the scientists extracted the proteins that the cells secrete--such as bone morphogenetic protein (BMP)--in order to harness their regenerative power. To do so, the researchers first treated stem cells with a chemical that helped coax them into early bone cells. Next, they mined the essential factors produced by the cells that send the signal to regenerate new tissue. Finally, the researchers delivered these proteins into mouse muscle tissue to facilitate new bone growth.

The current standard method involves grinding up old bones in order to extract the proteins and growth factors needed to stimulate new bone growth--a substance dubbed demineralized bone matrix (DBM). However, this approach has significant restrictions as it relies on bones taken from cadavers, which can be highly variable in terms of tissue quality and how much of the necessary signals they still produce. Moreover, as is the problem in organ donation, cadaver tissue is not always available.

"These limitations motivate the need for more consistent and reproducible source material for tissue regeneration," says Dr. McDevitt, who conducted the research while he was a professor at the Georgia Institute of Technology. "As a renewable resource that is both scalable and consistent in manufacturing, pluripotent stem cells are an ideal solution."

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Europa's mystery dark material could be sea salt, NASA research reveals -- ScienceDaily

The study is accepted for publication in the journal Geophysical Research Letters and is available online.

"We have many questions about Europa, the most important and most difficult to answer being is there life? Research like this is important because it focuses on questions we can definitively answer, like whether or not Europa is inhabitable," said Curt Niebur, Outer Planets Program scientist at NASA Headquarters in Washington. "Once we have those answers, we can tackle the bigger question about life in the ocean beneath Europa's ice shell."

For more than a decade, scientists have wondered about the nature of the dark material that coats long, linear fractures and other relatively young geological features on Europa's surface. Its association with young terrains suggests the material has erupted from within Europa, but with limited data available, the material's chemical composition has remained elusive.

"If it's just salt from the ocean below, that would be a simple and elegant solution for what the dark, mysterious material is," said research lead Kevin Hand, a planetary scientist at NASA's Jet Propulsion Laboratory in Pasadena, California.

One certainty is that Europa is bathed in radiation created by Jupiter's powerful magnetic field. Electrons and ions slam into the moon's surface with the intensity of a particle accelerator. Theories proposed to explain the nature of the dark material include this radiation as a likely part of the process that creates it.

Previous studies using data from NASA's Galileo spacecraft, and various telescopes, attributed the discolorations on Europa's surface to compounds containing sulfur and magnesium. While radiation-processed sulfur accounts for some of the colors on Europa, the new experiments reveal that irradiated salts could explain the color within the youngest regions of the moon's surface.

To identify the dark material, Hand and his co-author Robert Carlson, also at JPL, created a simulated patch of Europa's surface in a laboratory test apparatus for testing possible candidate substances. For each material, they collected spectra -- which are like chemical fingerprints -- encoded in the light reflected by the compounds.

"We call it our 'Europa in a can,'" Hand said. "The lab setup mimics conditions on Europa's surface in terms of temperature, pressure and radiation exposure. The spectra of these materials can then be compared to those collected by spacecraft and telescopes."

For this particular research, the scientists tested samples of common salt -- sodium chloride -- along with mixtures of salt and water, in their vacuum chamber at Europa's chilly surface temperature of minus 280 degrees Fahrenheit (minus 173 Celsius). They then bombarded the salty samples with an electron beam to simulate the intense radiation on the moon's surface.

After a few tens of hours of exposure to this harsh environment, which corresponds to as long as a century on Europa, the salt samples, which were initially white just like table salt, turned a yellowish-brown color similar to features on the icy moon. The researchers found the color of these samples, as measured in their spectra, showed a strong resemblance to the color within fractures on Europa that were imaged by NASA's Galileo mission.

"This work tells us the chemical signature of radiation-baked sodium chloride is a compelling match to spacecraft data for Europa's mystery material," Hand said.

Additionally, the longer the samples were exposed to radiation, the darker the resulting color. Hand thinks scientists could use this type of color variation to help determine the ages of geologic features and material ejected from any plumes that might exist on Europa.

Previous telescope observations have shown tantalizing hints of the spectral features seen by the researchers in their irradiated salts. But no telescope on or near Earth can observe Europa with sufficiently high resolving power to identify the features with certainty. The researchers suggest this could be accomplished by future observations with a spacecraft visiting Europa.

JPL built and managed NASA's Galileo mission for the agency's Science Mission Directorate in Washington, and is developing a concept for a future mission to Europa. The California Institute of Technology in Pasadena manages JPL for NASA.

For more information about Europa, visit: http://europa.jpl.nasa.gov

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Weather forecasts made for planets beyond our solar system -- ScienceDaily

Using sensitive observations from the Kepler space telescope, the researchers have uncovered evidence of daily weather cycles on six extra-solar planets seen to exhibit different phases. Such phase variations occur as different portions of these planets reflect light from their stars, similar to the way our own moon cycles though different phases.

Among the findings are indications of cloudy mornings on four of them and hot, clear afternoons on two others.

"We determined the weather on these alien worlds by measuring changes as the planets circle their host stars, and identifying the day-night cycle," said Lisa Esteves, a PhD candidate in the Department of Astronomy & Astrophysics at the University of Toronto, and lead author of the study published today in The Astrophysical Journal.

"We traced each of them going through a cycle of phases in which different portions of the planet are illuminated by its star, from fully lit to completely dark," said Esteves.

Because the planets are very near to their stars, they are expected to rotate counter-clockwise -- just as the majority of objects in our solar system do -- with the right side moving in the direction of each planet's orbit. This causes an eastward movement of the planet's surface and therefore an eastward circulation of atmospheric winds. As a result, clouds that form on the planet's night side, where temperatures are cooler while it faces away from its host star, would be blown to the planet's morning side.

"As the winds continue to transport the clouds to the day side, they heat up and dissipate, leaving the afternoon sky cloud-free," said Esteves. "These winds also push the hot air eastward from the meridian, where it is the middle of the day, resulting in higher temperatures in the afternoon."

For four of the planets, the researchers saw excess brightness in the Kepler data that corresponds to when the morning side is visible. For the other two, they saw an excess when the evening side is visible.

"By comparing the planets' previously determined temperatures to the phase cycle measurements provided by Kepler, we found that the excess brightness on the morning side is most likely generated by reflected starlight," said Esteves. "These four planets are not hot enough to generate this excess light through thermal emission.

"The excess light seen on the two very hot planets can be explained by thermal emission," said Esteves. "A likely explanation is that on these two planets, the winds are moving heat towards the evening side, resulting in the excess brightness."

The Kepler telescope was the ideal instrument for the study of exoplanet phase variations. The very precise measurements it provided and the vast amount of data it collected allowed astronomers to measure the tiny signals from these distant worlds. Most of the planets examined in this study are very hot and large, with temperatures greater than 1600 degrees Celsius and sizes comparable to Jupiter -- conditions far from hospitable to life but excellent for phase measurements.

Kepler data has been used in the past to measure the temperature of these planets, but this is the first instance in which phase variations were used to measure the morning- and evening-side specific brightnesses of a collection of planets.

"The detection of light from these planets hundreds to thousands of light years away is on its own remarkable," said study co-author Dr. Ernst de Mooij, the Michael West Fellow at the Astrophysics Research Centre from the School of Mathematics and Physics at Queen's University Belfast. "But when we consider that phase cycle variations can be up to 100,000 times fainter than the host star, these detections become truly astonishing."

"Upcoming space missions should reveal many more small planets around bright stars that will make great targets for detailed studies," said co-author Ray Jayawardhana of York University. "Someday soon we hope to be talking about weather reports for alien worlds not much bigger than Earth, and to be making comparisons with our home planet."

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Superhydrophobic glass coating offers clear benefits -- ScienceDaily

The discovery by researchers at the Department of Energy's Oak Ridge National Laboratory, detailed in a paper published in the Journal of Materials Chemistry C, is based on a mechanically robust nanostructured layer of porous glass film. The coating can be customized to be superhydrophobic, fog-resistant and antireflective.

"While lotus leaves repel water and self-clean when it rains, a moth's eyes are antireflective because of naturally covered tapered nanostructures where the refractive index gradually increases as light travels to the moth's cornea," said Tolga Aytug, lead author of the paper and a member of ORNL's Materials Chemistry Group. "Combined, these features provide truly game-changing ability to design coatings for specific properties and performance."

To be superhydrophobic, a surface must achieve a water droplet contact angle exceeding 150 degrees. ORNL's coating has a contact angle of between 155 and 165 degrees, so water literally bounces off, carrying away dust and dirt. This property combined with the suppression of light reflection from a glass surface is critical for improved performance in numerous optical applications, Aytug said.

The base material -- a special type of glass coating -- is also highly durable, which sets it apart from competing technologies, according to Aytug, who described the process.

"We developed a method that starts with depositing a thin layer of glass material on a glass surface followed by thermal processing and selective material removal by etching," he said. "This produces a surface consisting of a porous three-dimensional network of high-silica content glass that resembles microscopic coral."

The fact the coating can be fabricated through industry standard techniques makes it easy and inexpensive to scale up and apply to a wide variety of glass platforms.

"The unique three-dimensionality interconnected nanoporous nature of our coatings significantly suppresses Fresnel light reflections from glass surfaces, providing enhanced transmission over a wide range of wavelengths and angles," Aytug said. The Fresnel effect describes the amount of light that is reflected versus the amount transmitted.

Where solar panels are concerned, the suppression of reflected light translates into a 3-6 percent relative increase in light-to-electricity conversion efficiency and power output of the cells. Coupled with the superhydrophobic self-cleaning ability, this could also substantially reduce maintenance and operating costs of solar panels. In addition, the coating is highly effective at blocking ultraviolet light.

Other potential applications include goggles, periscopes, optical instruments, photodetectors and sensors. In addition, the superhydrophobic property can be effective at preventing ice and snow buildup on optical elements and can impede biofouling in marine applications.

Aytug emphasized that the impact abrasion resistance of the coating completes the package, making it suitable for untold applications.

"This quality differentiates it from traditional polymeric and powder-based counterparts, which are generally mechanically fragile," Aytug said. "We have shown that our nanostructure glass coatings exhibit superior mechanical resistance to impact abrasion -- like sand storms -- and are thermally stable to temperatures approaching 500 degrees Celsius."

Other ORNL authors of the paper, titled "Monolithic Graded-Refractive-Index Glass-based Antireflective Coatings: Broadband/Omnidirectional Light Harvesting and Self-Cleaning Characteristics," were Andrew Lupini, Gerald Jellison, Pooran Joshi, Ilia Ivanov, Tao Liu, Peng Wang, Rajesh Menon, Rosa Trejo, Edgar Lara-Curzio, Scott Hunter, John Simpson, Parans Paranthaman and David Christen.

The work was supported by the Laboratory Directed Technology Innovation Program. STEM research was supported by the DOE Office of Science Basic Energy Sciences. A portion of the research was conducted at the Center for Nanophase Materials Sciences, a DOE Office of Science User Facility. Photovoltaic device measurements were done at the University of Utah.

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Tweaking the beak: Retracing the bird's beak to its dinosaur origins, in the laboratory -- ScienceDaily

Just don't call them dino-chickens.

"Our goal here was to understand the molecular underpinnings of an important evolutionary transition, not to create a 'dino-chicken' simply for the sake of it," said Bhullar, lead author of the study, published online May 12 in the journal Evolution.

Finding the mechanism to recreate elements of dinosaur physiology has been a topic of popular interest for some time. It has been featured in everything from molecular biologist Jack Horner's 2009 book, "How to Build a Dinosaur," to the upcoming Hollywood movie "Jurassic World."

In this case, the fascination derives from the importance of the beak to avian anatomy. "The beak is a crucial part of the avian feeding apparatus, and is the component of the avian skeleton that has perhaps diversified most extensively and most radically -- consider flamingos, parrots, hawks, pelicans, and hummingbirds, among others," Bhullar explained. "Yet little work has been done on what exactly a beak is, anatomically, and how it got that way either evolutionarily or developmentally."

In the new study, Bhullar and his colleagues detail a novel approach to finding the molecular mechanism involved in creating the skeleton of the beak. First, they did a quantitative analysis of the anatomy of related fossils and extant animals to generate a hypothesis about the transition; next, they searched for possible shifts in gene expression that correlated with the transition.

The team looked at gene expression in the embryos of emus, alligators, lizards, and turtles. The researchers discovered that both major living lineages of birds (the common neognaths and the rarer paleognaths) differ from the major lineages of non-bird reptiles (crocodiles, turtles, and lizards) and from mammals in having a unique, median gene expression zone of two different facial development genes early in embryonic development. This median gene expression had previously only been observed in chickens.

Using small-molecule inhibitors to eliminate the activity of the proteins produced by the bird-specific, median signaling zone in chicken embryos, the researchers were able to induce the ancestral molecular activity and the ancestral anatomy. Not only did the beak structure revert, but the process also caused the palatine bone on the roof of the mouth to go back to its ancestral state. "This was unexpected and demonstrates the way in which a single, simple developmental mechanism can have wide-ranging and unexpected effects," Bhullar said.

The work took Bhullar from the alligator nests at Rockefeller Wildlife Refuge in southern Louisiana to an emu farm in Massachusetts. He extracted DNA from various species in order to clone fragments of genetic material to look for specific gene expression.

Bhullar said the research has several implications. For example, he said, if a single molecular mechanism was responsible for this transformation, there should be a corresponding, linked transformation in the fossil record. "This is borne out by the fact that Hesperonis -- discovered by Othniel Charles Marsh of the Yale Peabody Museum of Natural History -- which is a near relative of modern birds that still retains teeth and the most primitive stem avian with a modernized beak in the form of fused, elongate premaxillae, also possesses a modern bird palatine bone," he said.

Premaxillae are the small bones at the tip of the upper jaw of most animals, but are enlarged and fused to form the beak of birds.

Bhullar noted that this same approach could be used to investigate the underlying developmental mechanisms of a host of great evolutionary transformations.

The other corresponding authors are Zachary Morris, Elizabeth Sefton, Bumjin Namkoong, and Jasmin Camacho, all of Harvard; Atalay Tok, of Uppsala University; Masayoshi Tokita, of Toho University; and David Burnham, of the University of Kansas.

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Controlling swarms of cooperative robots with light and a single finger -- ScienceDaily

The new Georgia Tech algorithm that fuels this system demonstrates the potential of easily controlling large teams of robots, which is relevant in manufacturing, agriculture and disaster areas.

"It's not possible for a person to control a thousand or a million robots by individually programming each one where to go," said Magnus Egerstedt, Schlumberger Professor in Georgia Tech's School of Electrical and Computer Engineering. "Instead, the operator controls an area that needs to be explored. Then the robots work together to determine the best ways to accomplish the job."

Egerstedt envisions a scenario in which an operator sends a large fleet of machines into a specific area of a tsunami-ravaged region. The robots could search for survivors, dividing themselves into equal sections. If some machines were suddenly needed in a new area, a single person could quickly redeploy them.

The Georgia Tech model is different from many other robotic coverage algorithms because it's not static. It's flexible enough to allow robots to "change their minds" effectively, rather than just performing the single job they're programmed to do.

"The field of swarm robotics gets difficult when you expect teams of robots to be as dynamic and adaptive as humans," Egerstedt explained. "People can quickly adapt to changing circumstances, make new decisions and act. Robots typically can't. It's hard for them to talk and form plans when everything is changing around them."

In the Georgia Tech demonstration, each robot is constantly measuring how much light is in its local "neighborhood." It's also chatting with its neighbor. When there's too much light in its area, the robot moves away so that another can steal some of its light.

"The robots are working together to make sure that each one has the same amount of light in its own area," said Egerstedt.

The tablet-based control system has one final benefit: it was designed with everyone in mind. Anyone can control the robots, even if they don't have a background in robotics.

"In the future, farmers could send machines into their fields to inspect the crops," said Georgia Tech Ph.D. candidate Yancy Diaz-Mercado. "Workers on manufacturing floors could direct robots to one side of the warehouse to collect items, then quickly direct them to another area if the need changes."

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Fish and other animals produce their own sunscreen: Copied for potential use in humans -- ScienceDaily

In the study published in the journal eLife, scientists found that zebrafish are able to produce a chemical called gadusol that protects against UV radiation. They successfully reproduced the method that zebrafish use by expressing the relevant genes in yeast. The findings open the door to large-scale production of gadusol for sunscreen and as an antioxidant in pharmaceuticals.

"The fact that the compound is produced by fish, as well as by other animals including birds, makes it a safe prospect to ingest in pill form," says Professor Taifo Mahmud, lead author of the study.

However, further studies will be needed to test if and how gadusol is absorbed, distributed, and metabolised in the body to check its efficacy and safety.

Gadusol was originally identified in cod roe and has since been discovered in the eyes of the mantis shrimp, sea urchin eggs, sponges, and in the dormant eggs and newly hatched larvae of brine shrimps. It was previously thought that fish can only acquire the chemical through their diet or through a symbiotic relationship with bacteria.

Marine organisms in the upper ocean and on reefs are subject to intense and often unrelenting sunlight. Gadusol and related compounds are of great scientific interest for their ability to protect against DNA damage from UV rays. There is evidence that amphibians, reptiles, and birds can also produce gadusol, while the genetic machinery is lacking in humans and other mammals.

The team were investigating compounds similar to gadusol that are used to treat diabetes and fungal infections. It was believed that the biosynthetic enzyme common to all of them, EEVS, was only present in bacteria. The scientists were surprised to discover that fish and other vertebrates contain similar genes to those that code for EEVS.

Curious about their function in animals, they expressed the zebrafish gene in E. coli and analysis suggested that fish combine EEVS with another protein, whose production may be induced by light, to produce gadusol. To check that this combination is really sufficient, the scientists transferred the genes to yeast and set them to work to see what they would create. This confirmed the production of gadusol. Its successful production in yeast provides a viable route to commercialisation.

As well as providing UV protection, gadusol may also play a role in stress responses, in embryonic development, and as an antioxidant.

"In the future it may be possible to use yeast to produce large quantities of this natural compound for sunscreen pills and lotions, as well as for other cosmetics sold at your local supermarket or pharmacy," says Professor Mahmud.

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Rats will try to save other rats from drowning -- ScienceDaily

Recent research has shown that a rat will help members of its own species to escape from a tubelike cage. The helping rat will show such prosocial behavior even if it does not gain any advantage from it. To see whether these rodents will also help when one of their own is about to drown, Sato's team conducted three sets of experiments involving a pool of water. One rat was made to swim for its life in the pool, with another being in a cage adjacent to it. The soaked rat could only gain access to a dry and safe area in the cage if its cagemate opened a door for it.

Sato's team found that rats quickly learned that to help their distressed and soaked fellow rat, they had to open the door. The rats were, however, only quick to open the door when there was actually a truly distressed cagemate nearby who needed to be saved. The experiments also showed that rats dislike being soaked. Those who had a previous experience of being immersed in water were also much quicker at learning how to save a cagemate than those who had not been immersed.

The researchers also watched what happened when rats had to choose between opening the door to help their distressed cagemate or accessing a different door to obtain a chocolate treat for themselves. In most cases, rats chose to help their cagemate before going for the food. According to Sato, this suggests that, for a rat, the relative value of helping others is greater than the benefit of a food reward.

The results indicate that rats show empathy. These rodents can share in the emotional state of members of their own species, in this case that of distressed animals.

"Our findings suggest that rats can behave prosocially and that helper rats may be motivated by empathy-like feelings towards their distressed cagemate," says Sato, who believes that studies of sociality, such as empathy in rodents, are important for understanding the underlying neural basis of prosocial behavior as well as evolutionary aspects.

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2015年5月12日星期二

Ease of weight loss influenced by individual biology -- ScienceDaily

Researchers at the Phoenix Epidemiology and Clinical Research Branch (PECRB), part of the NIH's National Institute of Diabetes and Digestive and Kidney Diseases, studied 12 men and women with obesity in the facility's metabolic unit. Using a whole-room indirect calorimeter -- which allows energy expenditure to be calculated based on air samples -- researchers took baseline measurements of the participants' energy expenditure in response to a day of fasting, followed by a six-week inpatient phase of 50 percent calorie reduction. After accounting for age, sex, race and baseline weight, the researchers found that the people who lost the least weight during the calorie-reduced period were those whose metabolism decreased the most during fasting. Those people have what the researchers call a "thrifty" metabolism, compared to a "spendthrift" metabolism in those who lost the most weight and whose metabolism decreased the least.

"When people who are obese decrease the amount of food they eat, metabolic responses vary greatly, with a 'thrifty' metabolism possibly contributing to less weight lost," said Susanne Votruba, Ph.D., study author and PECRB clinical investigator. "While behavioral factors such as adherence to diet affect weight loss to an extent, our study suggests we should consider a larger picture that includes individual physiology -- and that weight loss is one situation where being thrifty doesn't pay."

Researchers do not know whether the biological differences are innate or develop over time. Further research is needed to determine whether individual responses to calorie reduction can be used to prevent weight gain.

"The results corroborate the idea that some people who are obese may have to work harder to lose weight due to metabolic differences," said Martin Reinhardt, M.D., lead author and PECRB postdoctoral fellow. "But biology is not destiny. Balanced diet and regular physical activity over a long period can be very effective for weight loss."

More than one-third of American adults are obese. Complications from obesity can include heart disease, type 2 diabetes and certain types of cancer, some of the leading causes of preventable death.

"What we've learned from this study may one day enable a more personalized approach to help people who are obese achieve a healthy weight," said NIDDK Director Griffin P. Rodgers, M.D. "This study represents the latest advance in NIDDK's ongoing efforts to increase understanding of obesity."

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