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2013-12-12

Imagine bringing video game characters through your house: New system allows for high-accuracy, through-wall, 3-D motion tracking

Gaming could become this realistic, thanks to new technology developed by Dina Katabi's research group at the MIT Computer Science and Artificial Intelligence Lab (CSAIL) that allows for highly accurate, 3-D motion tracking. The new system, dubbed "WiTrack," uses radio signals to track a person through walls and obstructions, pinpointing her 3-D location to within 10 to 20 centimeters -- about the width of an adult hand.

The researchers will present their findings during the Usenix Symposium on Networked Systems Design and Implementation in April 2014.

"Today, if you are playing a game with the Xbox Kinect or Nintendo Wii, you have to stand right in front of your gaming console, which limits the types of games you can play," says Katabi, a professor of computer science and engineering and co-director of the MIT Center for Wireless Networks and Mobile Computing. "Imagine playing an interactive video game that transforms your entire home into a virtual world. The game console tracks you as you run down real hallways away from video game enemies, or as you hide from other players behind couches and walls. This is what WiTrack can bring to video gaming."

Earlier this year, Katabi and her graduate student Fadel Adib unveiled WiVi, a system that detects humans through walls and can track the direction of their movement using WiFi signals. Based on this earlier work, Katabi and Adib developed WiTrack in collaboration with Rob Miller, a professor of computer science and engineering, and graduate student Zach Kabelac. In comparison to WiVi, WiTrack has significantly higher accuracy and can track both two-dimensional and three-dimensional movement using specialized radio waves, as opposed to WiFi signals.

WiTrack operates by tracking specialized radio signals reflected off a person's body to pinpoint location and movement. The system uses multiple antennas: one for transmitting signals and three for receiving. The system then builds a geometric model of the user's location by transmitting signals between the antennas and using the reflections off a person's body to estimate the distance between the antennas and the user. WiTrack is able to locate motion with significantly increased accuracy, as opposed to tracking devices that rely on wireless signals, according to Adib.

"Because of the limited bandwidth, you cannot get very high location accuracy using WiFi signals," Adib says. "WiTrack transmits a very low-power radio signal, 100 times smaller than WiFi and 1,000 times smaller than what your cell phone can transmit. But the signal is structured in a particular way to measure the time from when the signal was transmitted until the reflections come back. WiTrack has a geometric model that maps reflection delays to the exact location of the person. The model can also eliminate reflections off walls and furniture to allow us to focus on tracking human motion."

In other motion-tracking systems, users must carry a wireless device or stand directly in front of the sensing device in order for the device to pick up movement. By using specialized radio signals, WiTrack frees users from wireless devices and allows them to roam spaces freely while still providing high-accuracy localization.

The system's ability to track motion through obstructions could make it particularly useful not only in gaming, but also in tracking elderly patients at high risk of falling. Current approaches to fall detection require individuals to continuously wear sensors or install cameras in the person's home. While WiTrack does not require individuals to wear sensors or install cameras, it can still detect falls with very high accuracy.

The ability of the WiTrack system to perform high-accuracy localization without expending enormous amounts of computational power is a promising new development in motion-tracking technology, according to Victor Bahl, a principal researcher and director of mobility and networking research at Microsoft Research.

"Motion tracking has generally been accomplished by analyzing images captured from strategically placed cameras inside the room. A limitation of such systems is that they only work when the moving object is directly in the camera's line of sight," Bahl says. "Another problem is [that] image analysis is a computationally heavyweight operation."

"The technology Professor Katabi and her students have developed does not have these limitations," he adds. "Their system detects movement without requiring a huge amount of computational power, and without having to be placed inside the room. The surprising thing is that it is very accurate. There is still more research to be done, but the approach is promising."

The team is currently working on advancing the WiTrack system so that it can track more than one person in motion at a time. The researchers believe the system should be easily adaptable to commercial settings. "The system is not expensive or time-consuming to produce and it could be miniaturized for easier production and use," Kabelac says.

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Differences in educational achievement owe more to genetics than environment

Dec. 11, 2013 — The degree to which students' exam scores differ owes more to their genes than to their teachers, schools or family environments, according to new research from King's College London published today in PLOS ONE.

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The study, which took place in the UK, looked at students' scores for their GCSE's (General Certificate of Secondary Education), a UK-wide examination at the end of compulsory education at 16 years old.

The authors explain that the findings do not imply that educational achievement is genetically pre-determined, or that environmental interventions are not important, but rather that recognising the importance of children's natural predispositions may help improve learning.

Researchers compared the GCSE exam scores of over 11,000 identical and non-identical 16 year old twins from the Medical Research Council (MRC) funded Twins Early Development Study (TEDS). Identical twins share 100% of their genes, whereas fraternal (non-identical) twins share on average only half of the genes that vary between people. Therefore, if identical twins' exam scores are more alike than those of non-identical twins, the difference in exam scores between the two sets of twins is due to genetics, rather than environment.

The researchers found that for compulsory core subjects (English, Mathematics and Science), genetic differences between students explain on average 58% of the differences between GCSE scores. In contrast, 29% of the differences in core subject grades are due to shared environment -- such as schools, neighbourhoods or families which twins share. The remaining differences in GCSE scores were explained by non-shared environment, unique to each individual.

Overall, science grades (such as Biology, Chemistry, Physics) were found to be more heritable than Humanities grades (such as Media Studies, Art, Music) -- 58% vs 42%, respectively.

Nicholas Shakeshaft, PhD student at the Institute of Psychiatry at King's College London and lead author of the paper says: "Children differ in how easily they learn at school. Our research shows that differences in students' educational achievement owe more to nature than nurture. Since we are studying whole populations, this does not mean that genetics explains 60% of an individual's performance, but rather that genetics explains 60% of the differences between individuals, in the population as it exists at the moment. This means that heritability is not fixed -- if environmental influences change, then the influence of genetics on educational achievement may change too."

Professor Robert Plomin, senior author at the Institute of Psychiatry at King's College London and Director of the TEDS study, says: "Whilst these findings have no necessary or specific implications for educational policies, it's important to recognise the major role that genetics plays in children's educational achievement. It means that educational systems which are sensitive to children's individual abilities and needs, which are derived in part from their genetic predispositions, might improve educational achievement."

Professor Michael O'Donovan, from the Neurosciences and Mental Health board at the Medical Research Council (MRC), said "The findings from this substantial cohort add to a convincing body of evidence that genes influence characteristics that are ultimately reflected in educational performance. But it is equally important to stress that the researchers found that environments for students are also important and that the study does not imply that improvements in education will not have important benefits. For individuals living in the best and worst environments, this exposure is likely to make more of a difference to their educational prospects than their genes. Further research is needed to assess the implications of the findings for educational strategies. The MRC-funded TEDS cohort highlights the importance of long-term investment and how this can help improve our understanding of how genes and environment interact over the course of our lives."

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Dietary amino acids improve sleep problems in mice with traumatic brain injury

What scientists found helpful was giving the mice something all humans produce from foods in their normal diets -- something called branched chain amino acids.

"If further research confirms what this study suggests, we could develop a dietary supplement of these amino acids that could be a viable therapy to help people after a concussion," said Miranda Lim, M.D., Ph.D., a neurologist and sleep medicine specialist at the Portland VA Medical Center and an assistant professor of pulmonary and critical care medicine, neurology and behavioral neuroscience at Oregon Health & Science University. Lim is the first author of the study, published online today in Science Translational Medicine.

Lim performed this research during her sleep medicine fellowship at the University of Pennsylvania. Senior authors on the study are Akiva S. Cohen, Ph.D., a neuroscientist at The Children's Hospital of Philadelphia and Allan I. Pack, M.D., Ph.D., director of the Center for Sleep and Circadian Neurobiology in the Perelman School of Medicine at the University of Pennsylvania.

Nearly 2 million people a year in the United States suffer a traumatic brain injury, including concussion, which is considered a mild traumatic brain injury. Sleep disturbances are common in those with TBI; some studies show up to 72 percent of TBI patients -- including those who've suffered concussions -- have sleep problems.

Sleep problems impair attention and memory formation in TBI patients, who have a higher rate of functional disability and a higher cost of rehabilitation.

"Sleep disturbances, such as excessive daytime sleepiness and nighttime insomnia, disrupt quality of life and can delay cognitive recovery in patients with TBI," Lim said. Although physicians can relieve the dangerous swelling that occurs after a severe TBI, there are no existing treatments to address the underlying brain damage associated with problems such as impaired memory, learning and sleep patterns.

In their study, the scientists compared mice with mild TBI to uninjured mice. They found that injured mice were much less able to stay awake for sustained periods of time. The scientists also found that the orexin neurons in the brains of injured mice were much less active than the same neurons in uninjured mice. Orexin neurons help to maintain wakefulness, in mice and in humans. Human studies have shown decreased orexin levels in the spinal fluid of people who have suffered a traumatic brain injury.

Based on prior research, the scientists gave the injured mice a dietary therapy of branched chain amino acids -- which humans get most often through foods high in protein, including red meat, poultry and eggs. Branched chain amino acids are the building blocks of neurotransmitters, the chemicals released by neurons in the brain. Like the oil in a car engine, branched chain amino acids keep neurons running smoothly and boost neuron excitability. The branched chain amino acids restored the orexin neurons in the injured mice to a normal activity level, and improved wakefulness.

"These results in an animal model provide a proof-of-principle for investigating this dietary intervention as a treatment for TBI patients," said Cohen. "If a dietary supplement can improve sleeping and waking patterns as well as cognitive problems, it could help brain-injured patients regain crucial functions."

The scientists note that human patients with a variety of disorders have been treated with branched chain amino acid therapy for up to two years without adverse effects, so with further study it may prove to be a viable therapy for sleep problems in TBI patients. Cohen cautioned, however, that current evidence does not support TBI patients medicating themselves with commercially available amino acid supplements.

The National Institutes of Health (grants HL007713, HL111725-01A1, NS069629 and HD059288) supported the study, as well as the University of Pennsylvania Department of Medicine/Measey Research Fellowship. Cohen and the Children's Hospital of Philadelphia hold a provisional U.S. patent for the use of branched chain amino acids as a therapy for traumatic brain injury.

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Liquid to gel to bone: Temperature-sensitive gelling scaffolds made to regenerate craniofacial bone

Dec. 11, 2013 — Rice University bioengineers have developed a hydrogel scaffold for craniofacial bone tissue regeneration that starts as a liquid, solidifies into a gel in the body and liquefies again for removal.

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The material developed in the Rice lab of bioengineer Antonios Mikos is a soluble liquid at room temperature that can be injected to the point of need. At body temperature, the material turns instantly into a gel to help direct the formation of new bone to replace that damaged by injury or disease.

The gel conforms to irregular three-dimensional spaces and provides a platform for functional and aesthetic tissue regeneration. It is intended as an alternative to prefabricated implantable scaffolds.

The invention is the subject of a new paper that appeared online this week in the American Chemical Society journal Biomacromolecules.

Lead author Tiffany Vo, a fourth-year doctoral graduate student in the Mikos lab, earned a Ruth L. Kirschstein National Research Service Award from the National Institute of Dental and Craniofacial Research for her work on the project.

"This new platform technology leverages injectable, thermally responsive, chemically crosslinkable and bioresorbable hydrogels for regenerative medicine applications," Mikos said. "It enables the formation of scaffolds locally and the delivery of growth factors and stem cells into defects of complex anatomical shapes with minimal surgical intervention."

Thermosensitive technologies are not new to the field of tissue engineering and regenerative medicine, Mikos said. What makes the poly(N-isopropylacrylamide), or PNiPAAm, scaffold promising is that its chemical cross-linking technology allows the researchers to eliminate gel shrinkage without reducing swelling; this improves its stability so that it serves as an effective delivery vehicle for growth factors and stem cell populations.

Once sufficient quality and quantity of bone tissue have regenerated to fill the defected site, the hydrogel scaffold can be transitioned back into a liquid state and released naturally.

As part of the project, the researchers will test the hydrogel's enhanced seeding capabilities and ability to promote cellular attachment, crosstalk and proliferation toward greater bone formation. The knowledge will improve the understanding of biomaterial-based therapies for minimally invasive tissue regeneration as viable clinical alternatives.

"The results demonstrate the ability to encapsulate stem cell populations with temperature-sensitive gelling scaffolds for injectable cell delivery with enormous implications for the development of novel therapeutics for craniofacial bone regeneration," Mikos said.

Co-authors include Adam Ekenseair, a former postdoctoral fellow in the Mikos Lab and currently an assistant professor of chemical engineering at Northeastern University, and Kurt Kasper, a faculty fellow in bioengineering at Rice. Mikos is Rice's Louis Calder Professor of Bioengineering and Chemical and Biomolecular Engineering.

The National Institutes of Health, the Baylor College of Medicine Scientific Training Program for Dental Academic Researchers and the Kirschstein fellowship supported the research.

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Nonconcussion head impacts in contact sports linked to brain changes and lower test scores

Using a form of magnetic resonance imaging, or MRI, researchers at the Indiana University School of Medicine and the Geisel School of Medicine at Dartmouth College found significant differences in brain white matter of varsity football and hockey players compared with a group of noncontact-sport athletes following one season of competition. White matter is composed primarily of axons, the long fibers that transmit signals between neurons.

"The contact sports and noncontact-sports groups differed, and the number of times the contact sports participants were hit, and the magnitude of the hits they sustained, were correlated with changes in the white matter measures," said Thomas W. McAllister, M.D., chair of the IU Department of Psychiatry.

"In addition, there was a group of contact sports athletes who didn't do as well as predicted on tests of learning and memory at the end of the season, and we found that the amount of change in the white matter measures was greater in this group," Dr. McAllister said.

The study was conducted while Dr. McAllister was Millennium Professor of Psychiatry at Dartmouth.

"This study raises the question of whether we should look not only at concussions but also the number of times athletes receive blows to the head and the magnitude of those blows, whether or not they are diagnosed with a concussion," Dr. McAllister said.

Two groups of Dartmouth athletes were studied: 80 football and ice hockey players in the contact sports group, and 79 athletes drawn from such noncontact sports as track, crew and Nordic skiing. The football and hockey players wore helmets equipped with accelerometers, which enabled the researchers to compile the number and severity of impacts to their heads. Players who sustained a concussion during the season were not included in the analysis.

The athletes were administered a form of MRI test known as diffusion tensor imaging, which is used to measure the integrity of the white matter. They were also given the California Verbal Learning Test II, a measure of verbal learning and memory.

The study did not find "large-scale, systematic differences" in the brain scan measures at the end of the season, which the authors found "somewhat reassuring" and consistent with the fact that thousands of individuals have played contact sports for many years without developing progressive neurodegenerative disorders.

However, the results do suggest that some athletes may be more susceptible to repeated head impacts that do not involve concussions, although much more research would be necessary to determine how to identify those athletes.

More work would also be necessary to determine whether the effects of the head impacts are long-lasting or permanent, and whether they are cumulative.

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Study finds biomaterials repair human heart

Their findings were published in The Annals of Thoracic Surgery.

The biomaterial extracellular matrix (ECM) is a naturally occurring substance that helps regulate cells and can be harvested and processed in such a way that removes all cells, leaving only the structural matrix, which is made of collagen. ECM can be molded into a "bioscaffold" for medical applications to enable a patient's cells to repopulate and repair damaged tissue.

The researchers were afforded the opportunity to clinically examine a bioscaffold that was implanted five years earlier to close the pericardium, a double-walled sac containing the human heart, following a coronary artery bypass surgery.

"Pathology results revealed that the bioscaffold had remodeled into viable, fully cellularized tissue similar to the native pericardium," said Meghan. "Essentially, the human body regrew its own tissue."

This research demonstrates the long-term effectiveness of this technology as an implant for pericardial closure and cardiac tissue repair.

"Anytime you can have the body regrow its own tissue instead of introducing a foreign object into it is a better outcome for the patient," she said.

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Even when test scores go up, some cognitive abilities don't

Dec. 11, 2013 — MIT neuroscientists find even high-performing schools don't influence their students' abstract reasoning.

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To evaluate school quality, states require students to take standardized tests; in many cases, passing those tests is necessary to receive a high-school diploma. These high-stakes tests have also been shown to predict students' future educational attainment and adult employment and income.

Such tests are designed to measure the knowledge and skills that students have acquired in school -- what psychologists call "crystallized intelligence." However, schools whose students have the highest gains on test scores do not produce similar gains in "fluid intelligence" -- the ability to analyze abstract problems and think logically -- according to a new study from MIT neuroscientists working with education researchers at Harvard University and Brown University.

In a study of nearly 1,400 eighth-graders in the Boston public school system, the researchers found that some schools have successfully raised their students' scores on the Massachusetts Comprehensive Assessment System (MCAS). However, those schools had almost no effect on students' performance on tests of fluid intelligence skills, such as working memory capacity, speed of information processing, and ability to solve abstract problems.

"Our original question was this: If you have a school that's effectively helping kids from lower socioeconomic environments by moving up their scores and improving their chances to go to college, then are those changes accompanied by gains in additional cognitive skills?" says John Gabrieli, the Grover M. Hermann Professor of Health Sciences and Technology, professor of brain and cognitive sciences, and senior author of a forthcoming Psychological Science paper describing the findings.

Instead, the researchers found that educational practices designed to raise knowledge and boost test scores do not improve fluid intelligence. "It doesn't seem like you get these skills for free in the way that you might hope, just by doing a lot of studying and being a good student," says Gabrieli, who is also a member of MIT's McGovern Institute for Brain Research.

Measuring cognition

This study grew out of a larger effort to find measures beyond standardized tests that can predict long-term success for students. "As we started that study, it struck us that there's been surprisingly little evaluation of different kinds of cognitive abilities and how they relate to educational outcomes," Gabrieli says.

The data for the Psychological Science study came from students attending traditional, charter, and exam schools in Boston. Some of those schools have had great success improving their students' MCAS scores -- a boost that studies have found also translates to better performance on the SAT and Advanced Placement tests.

The researchers calculated how much of the variation in MCAS scores was due to the school that students attended. For MCAS scores in English, schools accounted for 24 percent of the variation, and they accounted for 34 percent of the math MCAS variation. However, the schools accounted for very little of the variation in fluid cognitive skills -- less than 3 percent for all three skills combined.

In one example of a test of fluid reasoning, students were asked to choose which of six pictures completed the missing pieces of a puzzle -- a task requiring integration of information such as shape, pattern, and orientation.

"It's not always clear what dimensions you have to pay attention to get the problem correct. That's why we call it fluid, because it's the application of reasoning skills in novel contexts," says Amy Finn, an MIT postdoc and lead author of the paper.

Even stronger evidence came from a comparison of about 200 students who had entered a lottery for admittance to a handful of Boston's oversubscribed charter schools, many of which achieve strong improvement in MCAS scores. The researchers found that students who were randomly selected to attend high-performing charter schools did significantly better on the math MCAS than those who were not chosen, but there was no corresponding increase in fluid intelligence scores.

However, the researchers say their study is not about comparing charter schools and district schools. Rather, the study showed that while schools of both types varied in their impact on test scores, they did not vary in their impact on fluid cognitive skills.

"What's nice about this study is it seems to narrow down the possibilities of what educational interventions are achieving," says Daniel Willingham, a professor of psychology at the University of Virginia who was not part of the research team. "We're usually primarily concerned with outcomes in schools, but the underlying mechanisms are also important."

The researchers plan to continue tracking these students, who are now in 10th grade, to see how their academic performance and other life outcomes evolve. They have also begun to participate in a new study of high school seniors to track how their standardized test scores and cognitive abilities influence their rates of college attendance and graduation.

Implications for education

Gabrieli notes that the study should not be interpreted as critical of schools that are improving their students' MCAS scores. "It's valuable to push up the crystallized abilities, because if you can do more math, if you can read a paragraph and answer comprehension questions, all those things are positive," he says.

He hopes that the findings will encourage educational policymakers to consider adding practices that enhance cognitive skills. Although many studies have shown that students' fluid cognitive skills predict their academic performance, such skills are seldom explicitly taught.

"Schools can improve crystallized abilities, and now it might be a priority to see if there are some methods for enhancing the fluid ones as well," Gabrieli says.

Some studies have found that educational programs that focus on improving memory, attention, executive function, and inductive reasoning can boost fluid intelligence, but there is still much disagreement over what programs are consistently effective.

The research was a collaboration with the Center for Education Policy Research at Harvard University, Transforming Education, and Brown University, and was funded by the Bill and Melinda Gates Foundation and the National Institutes of Health.

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The mystery of lizard breath: One-way air flow may be 270 million years old

The findings -- published online Dec. 11 in the journal Nature -- raise the possibility this breathing pattern originated 270 million years ago, about 20 million years earlier than previously believed and 100 million years before the first birds. Why remains a mystery.

"It appears to be much more common and ancient than anyone thought," says C.G. Farmer, the study's senior author and an associate professor of biology at the University of Utah. "It has been thought to be important for enabling birds to support strenuous activity, such as flight. We now know it's not unique to birds. It shows our previous notions about the function of these one-way patterns of airflow are inadequate. They are found in animals besides those with fast metabolisms."

But Farmer cautions that because lizard lungs have a different structure than bird and alligator lungs, it is also possible that one-way airflow evolved independently about 30 million years ago in the ancestors of monitor lizards and about 250 million years ago in the archosaurs, the group that gave rise to alligators, dinosaurs and birds. More lizard species, such as geckos and iguanas, must be studied to learn the answer, she says.

Farmer conducted the study with two University of Utah biologists -- first author and postdoctoral fellow Emma Schachner and doctoral student Robert Cieri -- and with James Butler, a Harvard University physiologist.

The research was funded by the American Association of Anatomists, the American Philosophical Society, the National Science Foundation and private donor Sharon Meyer.

Tidal Versus One-Way Airflow in the Lungs

Humans and most other animals have a "tidal" breathing pattern: Air flows into the lungs' branching, progressively smaller airways or bronchi until dead-ending at small chambers called alveoli, where oxygen enters the blood and carbon dioxide leaves the blood and enters the lungs. Then the air flows back out the same way.

Birds, on the other hand, have some tidal airflow into and out of air sacs, but their breathing is dominated by one-way airflow in the lung itself. The air flows through the lung in one direction, making a loop before exiting the lung.

In 2010, Farmer published a study showing that a mostly one-way or "unidirectional" airflow controlled by aerodynamic valves exists in alligators. That means the breathing pattern likely evolved before 250 million years ago, when crocodilians -- the ancestors of alligators and crocodiles -- split from the archosaur family tree that led to the evolution of flying pterosaurs, dinosaurs and eventually birds.

The new study found a mostly one-way, looping air flow in African savannah monitor lizards, Varanus exanthematicus -- one of roughly 73 species of monitor lizards -- although there was some tidal airflow in regions of the lungs. That means one-way airflow may have arisen not among the early archosaurs about 250 million years ago, but as early as 270 million years ago among cold-blooded diapsids, which were the common, cold-blooded ancestors of the archosaurs and Lepidosauromorpha, a group of reptiles that today includes lizards, snakes and lizard-like creatures known as tuataras.

One-way airflow may help birds to fly without passing out at high altitudes, where oxygen levels are low. Before the new study, Farmer and others had speculated that the one-way airflow may have helped dinosaurs' ancestors dominate the Earth when atmospheric oxygen levels were low after the Permian-Triassic mass extinction -- the worst in Earth's history -- 251 million years ago.

"But if it evolved in a common ancestor 20 million years earlier, this unidirectional flow would have evolved under very high oxygen levels," she says. "And so were are left with a deeper mystery on the evolutionary origin of one-way airflow."

How the Study was Performed

As in her earlier research on alligators, Farmer and colleagues demonstrated predominantly one-way airflow in the lungs of monitor lizards in several ways. They performed CT scans and made 3-D images of lizard lungs to visualize the anatomy of the lungs. They surgically implanted flow meters in the bronchi of five monitor lizards to measure airflow direction.

Using lungs removed from 10 deceased lizards, the researchers measured air flow as they pumped air into and out of the lungs. They also pumped water laden with sunflower pollen particles or plastic microspheres through lizard lungs, and the movement of the pollen and spheres also showed the unidirectional airflow.

Savannah monitor lizards were used in the research because they are relatively large and thus easier to study, weighing about a pound and measuring roughly 15 inches from head to tail tip. Monitor lizards also have some of the highest rates of oxygen consumption, partly because they breathe using not only their trunk muscles and ribs, but also using "gular pumping," which is when the lizards flare out their throat and pump air into their lungs.

Monitor lizards' lungs have more than a dozen chambers or bronchi in each lung. The primary airway runs the length of the lung, with lateral bronchi branching off of it.

The study showed that air enters the lizard's trachea or windpipe, then flows into the two primary airways, which enter the lung. But then, instead of flowing tidally back out the same way, the air instead loops back in a tail-to-head direction moving from one lateral airway to the next through small perforations between them.

The walls containing perforations that allow air to flow from one chamber to the next "are like lace curtains," Farmer says.

There appear to be no mechanical valves or sphincters, so the one-way airflow appears "to arise simply from jetting," or aerodynamic valves created when air flows around bends within the lung airways. That is supported by the fact that one-way airflow was observed even in lungs removed from dead lizards.

A 60-megabyte movie of CT scans of a lizard's airways may be downloaded here: http://www.hightail.com/download/OGhkQndONEg5eFZFQmNUQw

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New strain of bird flu packs a punch even after becoming drug-resistant

Dec. 11, 2013 — Researchers at the Icahn School of Medicine at Mount Sinai reported that a virulent new strain of influenza -- the virus that causes the flu -- appears to retain its ability to cause serious disease in humans even after it develops resistance to antiviral medications. The finding was included in a study that was published today in the journal Nature Communications.

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It is not uncommon for influenza viruses to develop genetic mutations that make them less susceptible to anti-flu drugs. However, these mutations usually come at a cost to the virus, weakening its ability to replicate and to spread from one person to another.

Initial reports suggested that H7N9, an avian strain of influenza A that emerged in China last spring, could rapidly develop a mutation that made it resistant to treatment with the antiviral medication Tamiflu (oseltamivir). However, patients in whom drug resistance developed often had prolonged, severe infections and poor clinical outcomes. No vaccine is currently available to prevent H7N9, which infected at least 135 people and caused 44 deaths during the outbreak. In the absence of a vaccine, antiviral drugs are the only means of defense for patients who are infected with new strains of the flu.

"In this outbreak, we saw some differences in the behavior of H7N9 and other avian influenza strains that can infect humans, beginning with the rapid development of antiviral resistance in some people who were treated with oseltamivir and the persistence of high viral loads in those patients," said lead investigator Nicole Bouvier, MD, Assistant Professor of Medicine, Infectious Diseases at the Icahn School of Medicine at Mount Sinai.

Specifically, the investigators found that a drug-resistant H7N9 virus retained its ability to replicate in human respiratory cells and was comparable to a non-resistant form of the virus in producing severe illness in animal models. And although H7N9 appears to have a limited ability to spread readily from human to human, transmissibility in animal models was comparable between drug-susceptible and drug-resistant strains. "Transmission was inefficient for both of the H7N9 viruses that we tested in our experiments," said Dr. Bouvier. "But surprisingly, transmission of the drug-resistant virus was no less efficient than that of the drug-sensitive version."

"Many of the people infected with H7N9 during the outbreak in China were elderly or had other conditions that predisposed them to severe influenza illness," observed Dr. Bouvier. "Nevertheless, our study suggests that flu viruses can indeed develop drug-resistant mutations without suffering a penalty in terms of their own fitness."

Older antiviral drugs such as amantadine are no longer effective in treating most strains of the flu that infect humans. Newer antiviral drugs called neuraminidase inhibitors block an enzyme that helps the virus replicate. These drugs include Tamiflu, a pill, and Relenza (zanamivir), a powder that is inhaled. Both medications have drawbacks: flu viruses can develop resistance to the medications in people who take them, and, in many parts of the world, neither drug is available in an intravenous form to treat those with severe infections.

"Our study underscores the need to develop a bigger arsenal of antiviral drugs and vaccines, which will allow us to outsmart the influenza virus," said Dr. Bouvier. "Researchers at Mount Sinai are actively engaged in identifying new targets for drug therapy and are working to develop a universal vaccine that will prevent multiple strains of influenza."

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