Scientists solve the riddle of zebras’ stripes: Those pesky bugs

Why zebras have black and white stripes is a question that has intrigued scientists and spectators for centuries. A research team led by the University of California, Davis, has now examined this riddle systematically. Their answer is published April 1 in the online journal Nature Communications.The scientists found that biting flies, including horseflies and tsetse flies, are the evolutionary driver for zebra’s stripes. Experimental work had previously shown that such flies tend to avoid black-and-white striped surfaces, but many other hypotheses for zebra stripes have been proposed since Alfred Russel Wallace and Charles Darwin debated the problem 120 years ago.These include:A form of camouflage Disrupting predatory attack by visually confusing carnivores A mechanism of heat management Having a social function Avoiding ectoparasite attack, such as from biting flies The team mapped the geographic distributions of the seven different species of zebras, horses and asses, and of their subspecies, noting the thickness, locations, and intensity of their stripes on several parts of their bodies. Their next step was to compare these animals’ geographic ranges with different variables, including woodland areas, ranges of large predators, temperature, and the geographic distribution of glossinid (tsetse flies) and tabanid (horseflies) biting flies. They then examined where the striped animals and these variables overlapped.After analyzing the five hypotheses, the scientists ruled out all but one: avoiding blood-sucking flies.”I was amazed by our results,” said lead author Tim Caro, a UC Davis professor of wildlife biology. “Again and again, there was greater striping on areas of the body in those parts of the world where there was more annoyance from biting flies.”While the distribution of tsetse flies in Africa is well known, the researchers did not have maps of tabanids (horseflies, deer flies). Instead, they mapped locations of the best breeding conditions for tabanids, creating an environmental proxy for their distributions. They found that striping is highly associated with several consecutive months of ideal conditions for tabanid reproduction.Why would zebras evolve to have stripes whereas other hooved mammals did not? The study found that, unlike other African hooved mammals living in the same areas as zebras, zebra hair is shorter than the mouthpart length of biting flies, so zebras may be particularly susceptible to annoyance by biting flies.”No one knew why zebras have such striking coloration,” Caro said. …

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Two forms of Parkinson’s disease identified

Oct. 11, 2013 — Why can the symptoms of Parkinson’s disease vary so greatly from one patient to another? A consortium of researchers, headed by a team from the Laboratoire CNRS d’Enzymologie et Biochimie Structurales, is well on the way to providing an explanation. Parkinson’s disease is caused by a protein known as alpha-synuclein, which forms aggregates within neurons, killing them eventually. The researchers have succeeded in characterizing and producing two different types of alpha-synuclein aggregates. Better still, they have shown that one of these two forms is much more toxic than the other and has a greater capacity to invade neurons. This discovery takes account, at the molecular scale, of the existence of alpha-synuclein accumulation profiles that differ from one patient to the next. These results, published on October 10 in Nature Communications, represent a notable advance in our understanding of Parkinson’s disease and pave the way for the development of specific therapies targeting each form of the disease.Parkinson’s disease, which is the second most frequent neurodegenerative disease after Alzheimer’s, affects some 150,000 people in France. According to those suffering from the disease, it can manifest itself in the form of uncontrollable shaking (in 60% of patients) or by less-localized symptoms such as depression, behavioral and motor disorders. These differences in symptoms point to different forms of Parkinson’s disease.This condition, for which no curative treatment currently exists, is caused by the aggregation in the form of fibrillar deposits of alpha-synuclein, a protein that is naturally abundant at neuron junctions. …

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Beetles in rubber boots: Scientists study ladybugs’ feet

Aug. 14, 2013 — During their evolution, insects have developed various unique features to survive in their environment. The knowledge of the working principles of insects’ microstructures holds great potential for the development of new materials, which could be of use to humans. With this idea in mind, Dr. Jan Michels, a scientist at the Institute of Zoology at Kiel University, investigates how insects manage to efficiently cling to diverse surfaces. Michels and his colleagues recently published their new findings on the adhesive structures of ladybirds in the scientific journal Nature Communications.Share This:A lot of insects are able to climb up walls or walk upside down on surfaces. The new study shows for the first time what astonishing materials allow for these abilities. Using special microscopy techniques, confocal laser scanning microscopy and atomic force microscopy, Michels and his colleagues investigated the legs of ladybirds. “Each leg is equipped with fine adhesive hair, which enable the insect to cling to surfaces in a most impressive way,” explains Michels. “Our results show that different parts of the single hair feature varying material compositions and properties. …

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Ecosystems change long before species are lost

Aug. 13, 2013 — Communities in nature are likely to be a lot more sensitive to change than previously thought, according to a new study at Rice University.The study, which appears this week in Nature Communications, shows that scientists concerned about human influence on the biosphere need to take a deeper look at how altering the dynamics of a population — for example, by removing large members of a species through overfishing — can have measurable consequences, said Rice ecologist Volker Rudolf.”Natural communities are increasingly altered through human impact, and ecologists have long strived to determine how these changes influence communities,” Rudolf said. He noted the disappearance of a species is the most extreme but not the only cause of biodiversity loss.”That’s the last thing that happens after you mess up the entire ecosystem for a long period of time,” he said. By then, changes forced upon the structure of a population — such as the ratio of young to old in a species — have already been felt up and down the food chain.Rudolf suspected species play various roles and their effects on the environment change as they progress through their lifecycles, to the degree that altering these life “stages” within a species could have a significant impact. He and Rice graduate student Nick Rasmussen made a considerable effort to prove it.For the painstaking experiments that started in 2009, Rudolf, Rasmussen and their colleagues chose dragonflies and water-diving beetles to represent species that have major impact on their respective communities — in this case, fishless ponds — and then created dozens of miniature environments to analyze that impact. Manipulating the presence of different developmental stages within a predator species in each pond helped the researchers determine that such changes did alter the dynamics of complex ecosystems in a measurable way.”Other than being the largest and most voracious predators in these communities, they’re totally different,” Rudolf said of the apex predators. “We figured if we saw any generalities across these two species, then there’s something to our theory.”They found that altering which classes of size were present in a population also altered the structure of the entire community and ultimately how the whole ecosystem functioned. Also important, Rudolf said, was that changing the structure of populations sometimes had bigger effects on the ecosystem than changing the predator species.The results, he said, “challenge classical assumptions and studies that say we can make predictions by assuming that all individuals of a species are the same. You don’t expect a toddler to do the same thing as a grownup, and the same is the case for animals.”The study could also explain why such human activities as size-selective harvesting can alter the structure of entire food webs in some ocean systems, even when no species had gone extinct and the total biomass of the targeted fish remained the same, he said.”While these changes would be hard to predict by the classical approach, our results suggests such changes are expected when human activities alter the population structure of keystone species in an ecosystem,” Rudolf said. “Thus, natural ecosystems are likely to be much more fragile then we previously thought.”

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Sleep deprivation linked to junk food cravings

Aug. 6, 2013 — A sleepless night makes us more likely to reach for doughnuts or pizza than for whole grains and leafy green vegetables, suggests a new study from UC Berkeley that examines the brain regions that control food choices. The findings shed new light on the link between poor sleep and obesity.Using functional magnetic resonance imaging (fMRI), UC Berkeley researchers scanned the brains of 23 healthy young adults, first after a normal night’s sleep and next, after a sleepless night. They found impaired activity in the sleep-deprived brain’s frontal lobe, which governs complex decision-making, but increased activity in deeper brain centers that respond to rewards. Moreover, the participants favored unhealthy snack and junk foods when they were sleep deprived.”What we have discovered is that high-level brain regions required for complex judgments and decisions become blunted by a lack of sleep, while more primal brain structures that control motivation and desire are amplified,” said Matthew Walker, a UC Berkeley professor of psychology and neuroscience and senior author of the study published Aug. 6 in the journal Nature Communications.Moreover, he added, “high-calorie foods also became significantly more desirable when participants were sleep-deprived. This combination of altered brain activity and decision-making may help explain why people who sleep less also tend to be overweight or obese.”Previous studies have linked poor sleep to greater appetites, particularly for sweet and salty foods, but the latest findings provide a specific brain mechanism explaining why food choices change for the worse following a sleepless night, Walker said.”These results shed light on how the brain becomes impaired by sleep deprivation, leading to the selection of more unhealthy foods and, ultimately, higher rates of obesity,” said Stephanie Greer, a doctoral student in Walker’s Sleep and Neuroimaging Laboratory and lead author of the paper. Another co-author of the study is Andrea Goldstein, also a doctoral student in Walker’s lab.In this newest study, researchers measured brain activity as participants viewed a series of 80 food images that ranged from high-to low-calorie and healthy and unhealthy, and rated their desire for each of the items. As an incentive, they were given the food they most craved after the MRI scan.Food choices presented in the experiment ranged from fruits and vegetables, such as strawberries, apples and carrots, to high-calorie burgers, pizza and doughnuts. The latter are examples of the more popular choices following a sleepless night.On a positive note, Walker said, the findings indicate that “getting enough sleep is one factor that can help promote weight control by priming the brain mechanisms governing appropriate food choices.”

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Switching between habitual and goal-directed actions: A ‘two in one’ system in our brain

Aug. 6, 2013 — “Pressing the button of the lift at your work place, or apartment building is an automatic action — a habit. You don’t even really look at the different buttons; your hand is almost reaching out and pressing on its own. But what happens when you use the lift in a new place? In this case, your hand doesn’t know the way, you have to locate the buttons, find the right one, and only then your hand can press a button. Here, pushing the button is a goal-directed action.” It is with this example that Rui Costa, principal investigator at the Champalimaud Neuroscience Programme (CNP), explains how critical it is to be able to shift between habits and goal-direct actions, in a fast and accurate way, in everyday life.Share This:To unravel the circuit that underlies this capacity, the capacity to “break habits,” was the goal of this study, carried out by Christina Gremel and Rui Costa, at NIAAA, National Institutes of Health, USA and the Champalimaud Foundation, in Portugal, that is published today in Nature Communications.”We developed a task where mice would shift between making the same action in a goal-directed or habitual manner. We could then, for the first time, directly examine brain areas controlling the capacity to break habits,” explains the study’s lead author Christina Gremel from NIAAA. Evidence from previous studies has shown that two neighbouring regions of the brain are necessary for these different functions — the dorsal medial striatum is necessary for goal-directed actions and the dorsal lateral striatum is necessary for habitual actions. What was not known, and this new study reveals, is that a third region, the orbital frontal cortex (OFC), is critical for shifting between these two types of actions. As explained by Rui Costa, “when neurons in the OFC were inhibited, the generation of goal-directed actions was disrupted, while activation of these neurons, by means of a technique called optogenetics, selectively increased goal-directed actions.”For Costa, the results of this study suggest “something quite extraordinary — the same neural circuits function in a dynamic way, enabling the learning of automatic and goal-directed actions in parallel.”These results have important implications for understanding neuropsychiatric disorders where the balance between habits and goal-directed actions is disrupted, such as obsessive-compulsive disorder.The neural bases of behaviour, and their connection to neuropsychiatric disorders, are at the core of ongoing work by neuroscientists and clinicians at the Champalimaud Foundation.Share this story on Facebook, Twitter, and Google:Other social bookmarking and sharing tools:|Story Source: The above story is based on materials provided by Champalimaud Foundation, via EurekAlert!, a service of AAAS. …

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A faster vessel for charting the brain

July 25, 2013 — Princeton University researchers have created “souped up” versions of the calcium-sensitive proteins that for the past decade or so have given scientists an unparalleled view and understanding of brain-cell communication.Reported July 18 in the journal Nature Communications, the enhanced proteins developed at Princeton respond more quickly to changes in neuron activity, and can be customized to react to different, faster rates of neuron activity. Together, these characteristics would give scientists a more precise and comprehensive view of neuron activity.The researchers sought to improve the function of proteins known as green fluorescent protein/calmodulin protein (GCaMP) sensors, an amalgam of various natural proteins that are a popular form of sensor proteins known as genetically encoded calcium indicators, or GECIs. Once introduced into the brain via the bloodstream, GCaMPs react to the various calcium ions involved in cell activity by glowing fluorescent green. Scientists use this fluorescence to trace the path of neural signals throughout the brain as they happen.GCaMPs and other GECIs have been invaluable to neuroscience, said corresponding author Samuel Wang, a Princeton associate professor of molecular biology and the Princeton Neuroscience Institute. Scientists have used the sensors to observe brain signals in real time, and to delve into previously obscure neural networks such as those in the cerebellum. GECIs are necessary for the BRAIN Initiative President Barack Obama announced in April, Wang said. The estimated $3 billion project to map the activity of every neuron in the human brain cannot be done with traditional methods, such as probes that attach to the surface of the brain. “There is no possible way to complete that project with electrodes, so you have to do it with other tools — GECIs are those tools,” he said.Despite their value, however, the proteins are still limited when it comes to keeping up with the fast-paced, high-voltage ways of brain cells, and various research groups have attempted to address these limitations over the years, Wang said.”GCaMPs have made significant contributions to neuroscience so far, but there have been some limits and researchers are running up against those limits,” Wang said.One shortcoming is that GCaMPs are about one-tenth of a second slower than neurons, which can fire hundreds of times per second, Wang said. The proteins activate after neural signals begin, and mark the end of a signal when brain cells have (by neuronal terms) long since moved on to something else, Wang said. A second current limitation is that GCaMPs can only bind to four calcium ions at a time. …

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Mapping a room in a snap: Four microphones and a computer algorithm are enough to produce a 3-D model of a simple, convex room

June 17, 2013 — Blind people sometimes develop the amazing ability to perceive the contours of the room they’re in based only on auditory information. Bats and dolphins use the same echolocation technique for navigating in their environment.At EPFL, a team from the Audiovisual Communications Laboratory (LCAV), under the direction of Professor Martin Vetterli, has developed a computer algorithm that can accomplish this from a sound that’s picked up by four microphones. Their experiment is being published this week in the Proceedings of the National Academy of Sciences (PNAS). “Our software can build a 3D map of a simple, convex room with a precision of a few millimeters,” explains PhD student Ivan Dokmanić.Randomly placed microphonesAs incredible as it may seem, the microphones don’t need to be carefully placed. “Each microphone picks up the direct sound from the source, as well as the echoes arriving from various walls,” Dokmanić continues. “The algorithm then compares the signal from each microphone. The infinitesimal lags that appear in the signals are used to calculate not only the distance between the microphones, but also the distance from each microphone to the walls and the sound source.”This ability to “sort out” the various echoes picked up by the microphones is in itself a first. By analyzing each echo’s signal using “Euclidean distance matrices,” the system can tell whether the echo is rebounding for the first or second time, and determine the unique “signature” of each of the walls.The researchers tested the algorithm at EPFL using a “clean” sound source in an empty room in which they changed the position of a movable wall. Their results confirmed the validity of the approach. A second experiment carried out in a much more complex environment — an alcove in the Lausanne Cathedral — gave good partial results. …

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Whispering light hears liquids talk

June 7, 2013 — Ever been to a whispering gallery — a quiet, circular space underneath an old cathedral dome that captures and amplifies sounds as quiet as a whisper? Researchers at the University of Illinois at Urbana-Champaign are applying similar principles in the development optomechanical sensors that will help unlock vibrational secrets of chemical and biological samples at the nanoscale.”Optomechanics is an area of research in which extremely minute forces exerted by light (for example: radiation pressure, gradient force, electrostriction) are used to generate and control high-frequency mechanical vibrations of microscale and nanoscale devices,” explained Gaurav Bahl, an assistant professor of mechanical science and engineering at Illinois.In glass microcavities that function as optical whispering galleries, according to Bahl, these miniscule optical forces can be enhanced by many orders-of-magnitude, which enables ‘conversations’ between light (photons) and vibration (phonons). These devices are of interest to condensed matter physics as the strong phonon-photon coupling enables experiments targeting quantum information storage (i.e. qubits), quantum-mechanical ground state (i.e. optomechanical cooling), and ultra-sensitive force measurements past the standard quantum limit.Researchers developed a hollow optomechanical device made of fused silica glass, through which fluids and gases could flow. Employing a unique optomechanical interaction called Brillouin Optomechanics (described previously in Bahl et al, Nature Communications 2:403, 2011; Bahl et al, Nature Physics, vol.8, no.3, 2012), the researchers achieved the optical excitation of mechanical whispering-gallery modes at a phenomenal range of frequencies spanning from 2 MHz to 11,000 MHz.”These mechanical vibrations can, in turn, ‘talk’ to liquids within the hollow device and provide optical readout of the mechanical properties,” said Bahl, who is first author of the paper, “Brillouin cavity optomechanics with microfluidic devices,” published this week in Nature Communications.By confining various liquids inside a hollow microfluidic optomechanical (μFOM) resonator, researchers built the first-ever bridge between optomechanics and microfluidics.”We found that the optomechanical interaction in the μFOM device is dependent on the fluid contained within,” Bahl said. “These results are a step towards novel experiments probing optomechanics on non-solid phases of matter. In particular, the high frequency, high quality-factor mechanical vibrations demonstrated in this work may enable strongly localized, high-sensitivity, optomechanical interaction with chemical and biological samples.”Potential uses for this technology include optomechanical biosensors that can measure various optical and mechanical properties of a single cell, ultra-high-frequency analysis of fluids, and the optical control of fluid flow.

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High-efficiency zinc-air battery developed

May 29, 2013 — Stanford University scientists have developed an advanced zinc-air battery with higher catalytic activity and durability than similar batteries made with costly platinum and iridium catalysts. The results, published in the May 7 online edition of the journal Nature Communications, could lead to the development of a low-cost alternative to conventional lithium-ion batteries widely used today.

“There have been increasing demands for high-performance, inexpensive and safe batteries for portable electronics, electric vehicles and other energy storage applications,” said Hongjie Dai, a professor chemistry at Stanford and lead author of the study. “Metal-air batteries offer a possible low-cost solution.”

According to Dai, most attention has focused on lithium-ion batteries, despite their limited energy density (energy stored per unit volume), high cost and safety problems. “With ample supply of oxygen from the atmosphere, metal-air batteries have drastically higher theoretical energy density than either traditional aqueous batteries or lithium-ion batteries,” he said. “Among them, zinc-air is technically and economically the most viable option.”

Zinc-air batteries combine atmospheric oxygen and zinc metal in a liquid alkaline electrolyte to generate electricity with a byproduct of zinc oxide. When the process is reversed during recharging, oxygen and zinc metal are regenerated.

“Zinc-air batteries are attractive because of the abundance and low cost of zinc metal, as well as the non-flammable nature of aqueous electrolytes, which make the batteries inherently safe to operate,” Dai said. “Primary (non-rechargeable) zinc-air batteries have been commercialized for medical and telecommunication applications with limited power density. However, it remains a grand challenge to develop electrically rechargeable batteries, with the stumbling blocks being the lack of efficient and robust air catalysts, as well as the limited cycle life of the zinc electrodes.”

Active and durable electrocatalysts on the air electrode are required to catalyze the oxygen-reduction reaction during discharge and the oxygen-evolution reaction during recharge. In zinc-air batteries, both catalytic reactions are sluggish, Dai said.

Recently, his group has developed a number of high-performance electrocatalysts made with non-precious metal oxide or nanocrystals hybridized with carbon nanotubes. These catalysts produced higher catalytic activity and durability in alkaline electrolytes than catalysts made with platinum and other precious metals.

“We found that similar catalysts greatly boosted the performance of zinc-air batteries,” Dai said. both primary and rechargeable. “A combination of a cobalt-oxide hybrid air catalyst for oxygen reduction and a nickel-iron hydroxide hybrid air catalyst for oxygen evolution resulted in a record high-energy efficiency for a zinc-air battery, with a high specific energy density more than twice that of lithium-ion technology.”

The novel battery also demonstrated good reversibility and stability over long charge and discharge cycles over several weeks. “This work could be an important step toward developing practical rechargeable zinc-air batteries, even though other challenges relating to the zinc electrode and electrolyte remain to be solved,” Dai added.

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