Tag: Physiology (e.g. Exercise Physiology)

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Mystery of Australia’s five-legged animals cracked

Ever wished you had a spare leg to help you get around? Some Australian mammals had that thought and, well, went out and evolved one. And now we know what drove them to do such a thing.

Kangaroos were recently confirmed to use their tail as a fifth leg. While most ground-dwelling mammals simply use their tail for balance, kangaroos can firmly place theirs down on the ground and lift their body up and away, allowing them to swing their back legs forward while they support their weight on their front legs and tail.

When the kangaroos’ fifth leg was discovered, it was thought similar animals – like wallabies and pademelons – wouldn’t use their tail in the same way because they were too small to need a fifth leg. But now Rebekah Dawson from the University of Western Australia in Perth has documented the behaviour in both large and medium sized wallabies, and shown the behaviour is driven not just by size, but rather the animal’s habitat and overall body plan.

Dawson’s work also, for the first time, conclusively establishes that smaller macropods – those Australian animals that look like different sized kangaroos – don’t have a fifth leg. This includes rock wallabies, pademelons and the internet’s favourite animal, the quokka.

Dawson and her colleagues from Murdoch University in Australia looked at 16 species of macropod and examined the way each part of their body moved as they walked on four (or five) legs. They then looked at the relative size of different parts of each animal’s body, their overall sizes, and their habitats.

It turned out that animal size wasn’t the main predictor of whether the tail acted as a fifth leg or not. Instead, the best predictor was the relative size of the back legs compared to the rest of their body. When kangaroos and their cousins move quickly, they hop on two legs. But when they move more slowly, they lean over and use their arms too in a kind of jumpy-crawl.

Now, to hop efficiently at high speeds, especially if you’re a big kangaroo, you need very big back legs, says Dawson. But it seems those big back legs make for awkward crawling. So those macropods that grew big back legs evolved to use their tail to help them crawl on four legs – creating a fifth leg.

But that didn’t explain all the associations – some wallabies with relatively long hind legs didn’t make use of their fifth leg. It turned out habitat explained the rest. All of the species that use five legs live in open forests and grasslands. Those with the standard four legs are found in denser forests and areas of complex topography.

That’s a neat discovery and makes sense, says Terry Dawson from the University of New South Wales (no relation to Rebekah Dawson). “In open country fast hopping is required for predator avoidance,” he says – so macropods living there developed very long back legs to increase their hopping speeds. They then needed to begin using their tail as a fifth leg to help lift their awkwardly long back legs of the ground when moving at slower speeds.

But in densely vegetated or very rocky habitats, predator avoidance is more about manoeuvrability than moving at high speed. Although macropods in these environments still have relatively long back legs, they are short enough to allow the animals to get around on four legs without their tail. The work “nicely resolves a considerable puzzle”, says Terry Dawson.

Australian Journal of Zoology, DOI: 10.1071/ZO15007

https://www.newscientist.com/  New Scientist

https://www.newscientist.com/article/dn28043-mystery-of-australias-five-legged-animals-cracked/  Original web page at New Scientist

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Polar bear metabolism cannot cope with ice loss

Polar bears’ metabolism does not slow very much during the summer months when sea ice melts and food becomes scarce, according to a study published 16 July in Science. With the Arctic warming faster than the global average, the finding does not bode well  for the bears (Ursus maritimus), who use the ice as a hunting ground.

The Arctic ice is melting earlier each summer and freezing later each winter, limiting the animals’ chances to catch seals. With no way to save energy, polar bears are unlikely to survive the continued sea-ice loss caused by rising temperatures, says Merav Ben-David, a wildlife ecologist at the University of Wyoming in Laramie and a co-author of the study.

The research suggests that the bears do not use a strategy known as walking hibernation — a state of lowered activity and slowed metabolism — to survive summer fasts as some had suspected. Instead, they show a smaller decrease in their metabolic rate, similar to that seen in any mammal with a restricted diet.

Ben-David and her colleagues discovered this by affixing tracking collars and activity monitors to more than two dozen polar bears from a population in the Beaufort Sea, north of Alaska. They also implanted probes into 17 individuals to measure body temperature, which is tied to the animals’ metabolic rate.

They tracked the bears’ activity and temperature during 2008 and 2009, finding that the measurements were roughly the same for bears that moved off the ice to shore and those that followed the retreating ice farther north. A small reduction in body temperature — about 0.7 ºC in those on ice — was much too small to correspond to walking hibernation, but it did align with animals that are Fasting.

“It’s rare to get this kind of physiological measurement made on big, wild carnivores,” says Terrie Williams, a biologist at the University of California, Santa Cruz. “That’s the thing that’s remarkable.”

The remote location made collecting the data difficult. “You can imagine doing sterile surgery — extremely carefully doing sterile surgery — at -20 degrees Fahrenheit [-29 ºC] with the wind howling in your face,” says Ben-David. “When I say this was a logistically complicated project, I mean it.”

Tackling those logistical challenges took a coordinated effort between many agencies and organizations, including research and on-the-ground support from the US Geological Survey and the US Fish and Wildlife Service (FWS). The mission to tag the animals used two helicopters and an ice-breaking vessel; recapturing all of the bears to recover the temperature loggers took 36 days at sea.

Polar bears were designated a threatened species in 2008, but Ben-David says that move was mostly symbolic. “In reality, we cannot do much under the Endangered Species Act to save polar bears,” she says. “What we need to save polar bears is global action to reduce climate change.”

On 6 July, the FWS released a draft of a plan to boost the polar-bear population, which estimates put between 20,000 and 25,000 in 2008. The plan points to reductions in atmospheric greenhouse gases as the most important step to take for species conservation.

Nature doi:10.1038/nature.2015.17992

http://www.nature.com/news/index.html  Nature

http://www.nature.com/news/polar-bear-metabolism-cannot-cope-with-ice-loss-1.17992  Original web page at Nature

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Why offspring cope better with climate change: It’s all in the genes

In a collaborative project with scientists from the King Abdullah University of Science and Technology (KAUST) in Saudi Arabia, the researchers examined how the fish’s genes responded after several generations living at higher temperatures predicted under climate change.

“Some fish have a remarkable capacity to adjust to higher water temperatures over a few generations of exposure,” says Dr Heather Veilleux from the Coral CoE. “But until now, how they do this has been a mystery.” Using cutting-edge molecular methods the research team identified 53 key genes that are involved in long-term, multi-generational acclimation to higher temperatures.

“By understanding the function of these genes we can determine the biological processes that enable fish to cope with higher temperatures,” explains Dr Veilleux. “We found significantly higher levels of metabolic gene activity in fish exposed to higher temperatures for two generations, indicating that shifts in energy production are central to maintaining performance at higher temperatures.” “Immune and stress genes also responded at a higher level in the second generation, indicating that increased levels of these genes are required to allow these fish to better cope in warmer water,” Dr Veilleux says.

The project involved rearing coral reef fish at different temperatures for more than four years in purpose built facilities at James Cook University, and then testing their metabolic performance. “We used state-of-the-art genetic sequencing and bioinformatics to examine patterns of gene expression in the fish,” explains Professor Tim Ravasi from KAUST. “By correlating the patterns of gene expression with the metabolic performance of fish that had acclimated to the higher temperatures we were able to identify which genes had made this acclimation possible.”

“Surprisingly, we found that some proteins that respond to short-term thermal stress (called heat-shock proteins) did not respond over the long-term,” says Professor Philip Munday from the Coral CoE. “Heat shock proteins help maintain the structure of other essential proteins. Consequently, we thought they might also contribute to long-term acclimation to higher temperature,” Professor Munday says. “However, heat shock proteins were not involved in multigenerational acclimation to higher temperatures, suggesting that they are not good indicators of the capacity to cope with climate change.”

The study is the first to reveal the molecular processes that may help coral reef fishes and other marine species adjust to warmer conditions in the future. “Understanding which genes are involved in transgenerational acclimation, and how their expression is regulated, will improve our understanding of adaptive responses to rapid environmental change and help identify which species are most at risk from climate change and which species are more tolerant,” Dr Veilleux says.

http://www.sciencedaily.com/ Science Daily

http://www.sciencedaily.com/releases/2015/07/150720114739.htm Original web page at Science Daily

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Why offspring cope better with climate change: It’s all in the genes

In a world first study, researchers at the ARC Centre of Excellence for Coral Reef Studies (Coral CoE) at James Cook University have unlocked the genetic mystery of why some fish are able to adjust to warming oceans.

In a collaborative project with scientists from the King Abdullah University of Science and Technology (KAUST) in Saudi Arabia, the researchers examined how the fish’s genes responded after several generations living at higher temperatures predicted under climate change.

“Some fish have a remarkable capacity to adjust to higher water temperatures over a few generations of exposure,” says Dr Heather Veilleux from the Coral CoE. “But until now, how they do this has been a mystery.”

Using cutting-edge molecular methods the research team identified 53 key genes that are involved in long-term, multi-generational acclimation to higher temperatures. “By understanding the function of these genes we can determine the biological processes that enable fish to cope with higher temperatures,” explains Dr Veilleux.

“We found significantly higher levels of metabolic gene activity in fish exposed to higher temperatures for two generations, indicating that shifts in energy production are central to maintaining performance at higher temperatures.” “Immune and stress genes also responded at a higher level in the second generation, indicating that increased levels of these genes are required to allow these fish to better cope in warmer water,” Dr Veilleux says.

The project involved rearing coral reef fish at different temperatures for more than four years in purpose built facilities at James Cook University, and then testing their metabolic performance. “We used state-of-the-art genetic sequencing and bioinformatics to examine patterns of gene expression in the fish,” explains Professor Tim Ravasi from KAUST. “By correlating the patterns of gene expression with the metabolic performance of fish that had acclimated to the higher temperatures we were able to identify which genes had made this acclimation possible.”

“Surprisingly, we found that some proteins that respond to short-term thermal stress (called heat-shock proteins) did not respond over the long-term,” says Professor Philip Munday from the Coral CoE. “Heat shock proteins help maintain the structure of other essential proteins. Consequently, we thought they might also contribute to long-term acclimation to higher temperature,” Professor Munday says. “However, heat shock proteins were not involved in multigenerational acclimation to higher temperatures, suggesting that they are not good indicators of the capacity to cope with climate change.”

The study is the first to reveal the molecular processes that may help coral reef fishes and other marine species adjust to warmer conditions in the future. “Understanding which genes are involved in transgenerational acclimation, and how their expression is regulated, will improve our understanding of adaptive responses to rapid environmental change and help identify which species are most at risk from climate change and which species are more tolerant,” Dr Veilleux says.

http://www.sciencedaily.com/  Science Daily

http://www.sciencedaily.com/releases/2015/07/150720114739.htm  Original web page at Science Daily

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* The physics of swimming fish

Fish may seem to glide effortlessly through the water, but the tiny ripples they leave behind are evidence of a constant give-and-take of energy between the swimmer and its aqueous environment — a momentum exchange that propels the fish forward but is devilishly tricky to quantify. Now, new research shows that a fish’s propulsion can be understood by studying vortices in the surrounding water as individual units instead of examining the flow as a whole. Fish may seem to glide effortlessly through the water, but the tiny ripples they leave behind as they wriggle their way along are evidence of a constant give-and-take of energy between the swimmer and its aqueous environment — a momentum exchange that propels the fish forward but is devilishly tricky to quantify because of the continuous nature of a large, ever-flowing body of water.

When dealing with discrete objects it is relatively easy to compute the force that each exerts on the other. Imagine a cross-country skier propelling herself across a field using ski poles. The skier and her poles are discrete objects, and we can relatively easily compute the forces they exert on each other. But since the water around a swimming fish is continuous, it can be hard to pick out which regions of the fluid are most relevant for propulsion.

Now, a group of Swiss scientists has found that a fish’s propulsion through water can be understood by studying vortices in the surrounding water as individual units instead of examining the flow as a whole. Their technique, published June 23 in the journal Chaos, from AIP Publishing, could also be useful in other fluid dynamic analyses — for example, when studying unsteady vortices detaching from the wing of an airplane.

In a series of modeling experiments, the researchers focused on the swirls in the water nearest to the fish. “These vortices are believed to play a crucial role for the propulsion mechanism of fish. The fact that they rotate is already a clear indication that the fluid has strongly interacted with the fish,” said Florian Huhn, the lead researcher on the project.

The researchers identified discrete vortex regions in the water by detecting and tracking shapes called Lagrangian coherent structures — regions of a flow field that undergo similar experiences. Specifically, they looked at regions where the fluid formed discrete vortices — that is, places where the water moved in a self-contained pattern such that, if one were to draw an invisible loop around it, no material would cross that line.

“The closed line engulfs the fluid inside the vortex,” said Huhn. “Once we find this closed boundary, we trace back the whole fluid patch inside and can observe how it contributes to the propulsion mechanism of the fish.” Identifying these structures within the fluid makes them into a discrete space whose forces can be more easily calculated.

The team simulated these flow fields for two different types of swimming. The first was a steady movement, characterized by regular undulations. The second was an escape response known as the C-start, in which the fish quickly curves into a “C” shape before flipping outwards and propelling itself rapidly forward. The researchers found that for a steadily swimming fish, the fish’s movement can be largely attributed to momentum exchange between the fish and the discrete vortices.

For the C-start response, the vortices also explained a large part of the motion, but “an additional non-rotating jet fluid region enclosed by the vortex region is found to be crucial for the propulsion,” said Huhn. Huhn believes that his methodology may be useful in future fluid analyses as well. “Whenever a body propagates through fluid at a certain speed, be it birds and fish in nature or planes and ships in engineering, vortices are created, and the presented method can be used to track and understand the formation and evolution of the vortices,” he said. “Our findings further support the usefulness of Lagrangian coherent structures to decompose unsteady fluid flows into dynamically different regions.”

http://www.sciencedaily.com/  Nature

http://www.sciencedaily.com/releases/2015/06/150623113140.htm  Original web page at Science Daily

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Missing link found between brain, immune system; major disease implications

In a stunning discovery that overturns decades of textbook teaching, researchers at the University of Virginia School of Medicine have determined that the brain is directly connected to the immune system by vessels previously thought not to exist. That such vessels could have escaped detection when the lymphatic system has been so thoroughly mapped throughout the body is surprising on its own, but the true significance of the discovery lies in the effects it could have on the study and treatment of neurological diseases ranging from autism to Alzheimer’s disease to multiple sclerosis.

“Instead of asking, ‘How do we study the immune response of the brain?’ ‘Why do multiple sclerosis patients have the immune attacks?’ now we can approach this mechanistically. Because the brain is like every other tissue connected to the peripheral immune system through meningeal lymphatic vessels,” said Jonathan Kipnis, PhD, professor in the UVA Department of Neuroscience and director of UVA’s Center for Brain Immunology and Glia (BIG). “It changes entirely the way we perceive the neuro-immune interaction. We always perceived it before as something esoteric that can’t be studied. But now we can ask mechanistic questions.” “We believe that for every neurological disease that has an immune component to it, these vessels may play a major role,” Kipnis said. “Hard to imagine that these vessels would not be involved in a [neurological] disease with an immune component.”

Kevin Lee, PhD, chairman of the UVA Department of Neuroscience, described his reaction to the discovery by Kipnis’ lab: “The first time these guys showed me the basic result, I just said one sentence: ‘They’ll have to change the textbooks.’ There has never been a lymphatic system for the central nervous system, and it was very clear from that first singular observation — and they’ve done many studies since then to bolster the finding — that it will fundamentally change the way people look at the central nervous system’s relationship with the immune system.”  Even Kipnis was skeptical initially. “I really did not believe there are structures in the body that we are not aware of. I thought the body was mapped,” he said. “I thought that these discoveries ended somewhere around the middle of the last century. But apparently they have not.”

The discovery was made possible by the work of Antoine Louveau, PhD, a postdoctoral fellow in Kipnis’ lab. The vessels were detected after Louveau developed a method to mount a mouse’s meninges — the membranes covering the brain — on a single slide so that they could be examined as a whole. “It was fairly easy, actually,” he said. “There was one trick: We fixed the meninges within the skullcap, so that the tissue is secured in its physiological condition, and then we dissected it. If we had done it the other way around, it wouldn’t have worked.”

After noticing vessel-like patterns in the distribution of immune cells on his slides, he tested for lymphatic vessels and there they were. The impossible existed. The soft-spoken Louveau recalled the moment: “I called Jony [Kipnis] to the microscope and I said, ‘I think we have something.'” As to how the brain’s lymphatic vessels managed to escape notice all this time, Kipnis described them as “very well hidden” and noted that they follow a major blood vessel down into the sinuses, an area difficult to image. “It’s so close to the blood vessel, you just miss it,” he said. “If you don’t know what you’re after, you just miss it.” “Live imaging of these vessels was crucial to demonstrate their function, and it would not be possible without collaboration with Tajie Harris,” Kipnis noted. Harris, a PhD, is an assistant professor of neuroscience and a member of the BIG center. Kipnis also saluted the “phenomenal” surgical skills of Igor Smirnov, a research associate in the Kipnis lab whose work was critical to the imaging success of the study.

The unexpected presence of the lymphatic vessels raises a tremendous number of questions that now need answers, both about the workings of the brain and the diseases that plague it. For example, take Alzheimer’s disease. “In Alzheimer’s, there are accumulations of big protein chunks in the brain,” Kipnis said. “We think they may be accumulating in the brain because they’re not being efficiently removed by these vessels.” He noted that the vessels look different with age, so the role they play in aging is another avenue to explore. And there’s an enormous array of other neurological diseases, from autism to multiple sclerosis, that must be reconsidered in light of the presence of something science insisted did not exist.

http://www.sciencedaily.com/  Science Daily

http://www.sciencedaily.com/releases/2015/06/150601122445.htm  Original web page at Science Daily

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Researchers analyze the structure of bird feathers to create hues without dye

Work from a research team is seeking to produce synthetic particles that mimic the tiny packets of melanin found in feathers. These tiny packets of synthetic melanin produce structural color, like in a bird’s feather, when they are packed into layers. Structural color occurs through the interaction of light with materials that have patterns on a tiny scale, which reflect light to make some wavelengths brighter and others darker.

Imagine a favorite T-shirt that does not dull with time, or a car that never needs a new coat of paint. A study done at The University of Akron may be able to make this a reality in the near future. Research performed at UA sought to recreate structural color patterns found in bird feathers to generate color without the timely and outdated use of pigments and dyes. Structural color should never diminish in hue and could even potentially be altered at someone’s preference.

UA associate professor of biology, Dr. Matthew Shawkey, his colleague Dr. Ali Dhinojwala, Morton Professor of Polymer Science, and Ming Xiao, graduate student, recently published a paper in a joint project with the University of California, San Diego. Shawkey and his team sought to produce synthetic particles that mimic the tiny packets of melanin found in feathers.

These tiny packets of synthetic melanin produce structural color, like in a bird’s feather, when they are packed into layers. Structural color occurs through the interaction of light with materials that have patterns on a tiny scale, which reflect light to make some wavelengths brighter and others darker.

The discoveries published in the journal ACS Nano reflect a milestone in biomimicry research. These findings are just the beginning in a growing field that seeks to improve human life by imitating the success of natural designs and methods. Structural color in particular has many potential functions. According to Dhinojwala, ‘One could think about applications as sensors, photo-protectors, and even perhaps an approach to create a wide range of colors without using any pigments,’ he says. Shawkey praises the benefits of structural color, saying, ‘Pigments are both financially and environmentally costly, and can only change color by fading. Structural colors can, in theory, be produced from more common, environmentally friendly materials and could potentially be changed depending on the environment or your whims.’

http://www.sciencedaily.com/  Science Daily

http://www.sciencedaily.com/releases/2015/06/150608152030.htm  Original web page at Science Daily

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How the brain balances hearing between our ears

UNSW researchers have answered the longstanding question of how the brain balances hearing between our ears, which is essential for localizing sound, hearing in noisy conditions and for protection from noise damage. 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.”

http://www.sciencedaily.com/  Science Daily

http://www.sciencedaily.com/releases/2015/05/150512124134.htm  Original web page at Science Daily

 

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Secrets of the seahorse tail revealed

A team of engineers and biologists reports new progress in using computer modeling and 3D shape analysis to understand how the unique grasping tails of seahorses evolved. These prehensile tails combine the seemingly contradictory characteristics of flexibility and rigidity, and knowing how seahorses accomplish this feat could help engineers create devices that are both flexible and strong. “The project brought together engineers who know computer modeling and biologists who can provide the evolutionary questions,” said leader of the research team, evolutionary biologist Dominique Adriaens, Ph.D., professor at Ghent University. “From a biological point of view, we want to understand how natural selection modified a relatively rigid ancestral tail covered with bony, armored plates into the complex seahorse tail, which is still completely covered in armored plates but is very flexible.” Adriaens, a member of the American Association of Anatomists (AAA), will present this research at the AAA Annual Meeting during Experimental Biology 2015.

The team used information from the muscles and bones of a real seahorse tail to develop a computer model they can use to decipher how the tail gets its remarkable traits. For example, the model allows researchers to test how specific muscles and skeletal structures contribute to the tail’s grasping movement and affect the angles of bending. The computer model allows researchers to manipulate anatomy in a way that isn’t possible with living seahorses. The output can be visualized as a 3D animation of the tail and be used to estimate the energy needed to bend the tail. The research team used thousands of 3D points from the computer model to quantify and map the seahorse’s unique armor and the muscular and skeletal system within. They then compared the anatomy of the tail to that of other fish species within the seahorse’s family, some of which do not have tails that bend or grasp. “We hypothesized that the variation in the grasping species would be much less than non-grasping fish because it would require certain building blocks to construct a tail that is flexible and rigid at the same time,” said Adriaens. “To our surprise, we found differences in the ways a grasping tail was made, based on the same skeletal and muscular elements. Although a grasping tail is highly exceptional for a fish, it evolved multiple times independently within the family that seahorses belong to.”

“Understanding the mechanisms involved in the evolution of the seahorse tail lets us eliminate engineering optimization and instead use biology as our optimization model,” Porter said. “This knowledge allows us to tweak properties to achieve desired flexibility and strength characteristics. Because the seahorse armor allows for a lot of flexibility, it would be interesting to see if we can develop armored devices that have flexibility, and while not necessarily prehensile, would have a large range of motion with multiple degrees of freedom.”

Seahorses use their strong and flexible tails to anchor themselves to plants and other materials on coral reefs or the sea floor, allowing them to hide from predators.

http://www.sciencedaily.com/  Science Daily

http://www.sciencedaily.com/releases/2015/03/150331100901.htm  Original web page at Science Daily

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Clues to aging from long-lived lemurs

When Jonas the lemur died in January, just five months short of his thirtieth birthday, he was the oldest of his kind. A primate called a fat-tailed dwarf lemur, Jonas belonged to a long-lived clan. Dwarf lemurs live two to three times longer than similar-sized animals. In a new study, Duke University researchers combed through more than 50 years of medical records on hundreds of dwarf lemurs and three other lemur species at the Duke Lemur Center for clues to their exceptional longevity. The conventional wisdom in longevity research is that smaller species live shorter lives than larger ones. For example, humans and whales can live to be over 100; yet the average lab mouse doesn’t live beyond its third birthday. The researchers found an exception to this pattern in a group of hamster-sized lemurs with a physiological quirk — they are able to put their bodies in standby mode.

How long the animals live and how fast they age correlates with the amount of time they spend in a state of suspended animation known as torpor, the data show. Hibernating lemurs live up to ten years longer than their non-hibernating cousins. Dwarf lemurs like Jonas were the most extreme examples in their study, spending up to half the year in deep hibernation in the wild. Dwarf lemurs go into a semi-hibernation state for three months or less in captivity, “but even that seems to confer added longevity,” said study co-author Sarah Zehr, a researcher at the Duke Lemur Center. Hibernating dwarf lemurs can reduce their heart rate from 200 to eight beats per minute. Breathing slows, and the animals’ internal thermostat shuts down. Instead of maintaining a steady body temperature, they warm up and cool down with the outside air. “Everything gets slower,” Zehr said

For most primates such vital statistics would be life-threatening, but for lemurs, they’re a way to conserve energy during times of year when food and water are in short supply. Hibernating lemurs not only live longer, they also stay healthier. While non-hibernators are able to reproduce for roughly six years after they reach maturity, hibernators continue to have kids for up to 14 years after maturity, the researchers found. Although all species they examined suffered from cataracts and other age-related eye diseases as they got older, the hibernators managed to stave off symptoms until much later in life. Some researchers have suggested that hibernators live longer and stay healthier simply because they avoid predators who may be looking for a snack. A lemur is much less likely to be eaten when it is curled up underground or snoozing in a tree. “But the fact that we see the same pattern in captivity, where they’re protected from predators, suggests that other factors are at work,” Zehr said. It may also be that torpor increases longevity by protecting cells against the buildup of oxidative damage that is a normal by-product of breathing and metabolism, said study co-author Marina Blanco. “If your body is not ‘working full time’ metabolically-speaking, you will age more slowly and live longer,” Blanco said. Because lemurs are more closely related to humans than mice are, the research may eventually help scientists identify “anti-aging” genes in humans.

http://www.sciencedaily.com/ Science Daily

http://www.sciencedaily.com/releases/2015/03/150330163334.htm Original web page at Science Daily

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* Researchers reveal how hearing evolved

Lungfish and salamanders can hear, despite not having an outer ear or tympanic middle ear. These early terrestrial vertebrates were probably also able to hear 300 million years ago, as shown in a new study by Danish researchers. Lungfish and salamander ears are good models for different stages of ear development in these early terrestrial vertebrates. Two new studies published in the journals Proceedings of the Royal Society B and The Journal of Experimental Biology show that lungfish and salamanders can hear, despite not having an outer ear or tympanic middle ear. The study therefore indicates that the early terrestrial vertebrates were also able to hear prior to developing the tympanic middle ear. The research findings thus provide more knowledge about the development of hearing 250-350 million years ago. The physical properties of air and tissue are very different, which means in theory that up to 99.9% of sound energy is reflected when sound waves reach animals through the air. In humans and many other terrestrial vertebrates, the ear can be divided into three sections: the outer ear, the middle ear and the inner ear. The outer ear catches sound waves and directs them into the auditory canal. In the middle ear, pressure oscillations in the air are transferred via the tympanic membrane (eardrum) and one or three small bones (ossicles) to fluid movements in the inner ear, where the conversion of sound waves to nerve signals takes place. The tympanic middle ear improves the transfer of sound energy from the surroundings to the sensory cells in the inner ear by up to 1,000 times, and is therefore very important for hearing in terrestrial vertebrates. This is reflected in the fact that different configurations are found in the vast majority of present-day terrestrial mammals, birds, reptiles and amphibians. However, available palaeontological data indicate that the tympanic middle ear most likely evolved in the Triassic period, approximately 100 million years after the transition of the vertebrates from an aquatic to a terrestrial habitat during the Early Carboniferous. The vertebrates could therefore have been deaf for the first 100 million years on land. It is obviously not possible to study the hearing of the early terrestrial vertebrates, which became extinct long ago. However, by studying the hearing of present-day vertebrates with a comparable ear structure, it is possible to learn about the hearing of the early terrestrial vertebrates and the development of aerial hearing. A team of Danish researchers from Aarhus University, Aarhus University Hospital and the University of Southern Denmark therefore studied the hearing of lungfish and salamanders, which have an ear structure that is comparable to that of different kinds of early terrestrial vertebrates. They studied the hearing of lungfish and salamanders by measuring auditory nerve signals and neural signals in the brainstem as a function of sound stimulation at different frequencies and at different levels. Surprisingly, the measurements showed that not only the terrestrial adult salamanders, but also the fully aquatic juvenile salamanders — and even the lungfish, which are completely maladapted to aerial hearing — were able to detect airborne sound despite not having a tympanic middle ear. By studying the animals’ sense of vibration, the researchers were able to demonstrate that both lungfish and salamanders detect sound by sensing the vibrations induced by sound waves. The results show that even vertebrates without outer and middle ears are capable of detecting airborne sound. This means that adaptation to aerial hearing following the transition from aquatic to terrestrial lifestyles during the Early Carboniferous was presumably a gradual process, and that the early terrestrial vertebrates without tympanic middle ears were not deaf to airborne sound during the first 100 million years on land. In addition to making us wiser about hearing in general, the results can provide inspiration in the future to developing clinical treatments for hearing loss.

http://www.sciencedaily.com/  Science Daily

http://www.sciencedaily.com/releases/2015/02/150206125257.htm  Original web page at Science Daily

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* Why do zebras have stripes? Temperature counts

A team of life scientists led by UCLA’s Brenda Larison has found at least part of the answer: The amount and intensity of striping can be best predicted by the temperature of the environment in which zebras live. In the January cover story of the Royal Society’s online journal, Open Science, the researchers make the case that the association between striping and temperature likely points to multiple benefits — including controlling zebras’ body temperature and protecting them from diseases carried by biting flies. “While past studies have typically focused their search for single mechanisms, we illustrate in this study how the cause of this extraordinary phenomenon is actually likely much more complex than previously appreciated, with temperature playing an important role,” said Thomas B. Smith, professor of ecology and evolutionary biology in the UCLA College and senior author of the research. Larison, a researcher in UCLA’s department of ecology and evolutionary biology and the study’s lead author, and her colleagues examined the plains zebra, which is the most common of three zebra species and has a wide variety of stripe patterns. On zebras in warmer climes, the stripes are bold and cover the entire body. On others — particularly those in regions with colder winters such as South Africa and Namibia — the stripes are fewer in number and are lighter and narrower. In some cases, the legs or other body parts have virtually no striping. Zebras evolved from horses more than 2 million years ago, biologists have found. Scientists have previously hypothesized that zebras’ stripes evolved for one, or a combination of, four main reasons: confusing predators, protecting against disease-carrying insects, controlling body temperature and social cohesion. And while numerous previous studies of the phenomenon focused on a single hypothesis, the Larison-led study was the first to fully test a large set of hypotheses against one another. Analyzing zebras at 16 locations in Africa and considering more two dozen environmental factors, the researchers found that temperature was the strongest predictor of zebras’ striping. The finding provides the first evidence that controlling body temperature, or thermoregulation, is the main reason for the stripes and the patterns they form. Separate research by Daniel Rubenstein, a Princeton University professor of ecology and evolutionary biology and a co-author of the Open Science paper, and Princeton undergraduate Damaris Iriondo strongly suggests that boldly striped zebras have external body temperatures about five degrees Fahrenheit cooler than other animals of the same size — like antelopes — that do not have stripes but live in the same areas. The Rubenstein study is not yet published, but it is cited in the Open Science paper. Larison has studied many zebras during her field work throughout Africa — including in Kenya, South Africa, Tanzania, Uganda and Zimbabwe. Using the fact that their stripes are unique like fingerprints, she is able to distinguish one zebra from another. In addition to Rubenstein, arguably the world’s leading expert on zebras, the study’s co-authors were Alec Chan-Golston and Elizabeth Li, former UCLA undergraduates in mathematics; Ryan Harrigan, an assistant adjunct professor in UCLA’s Center for Tropical Research; and Henri Thomassen, a former UCLA postdoctoral scholar and current research associate at the Institute for Evolution and Ecology at Germany’s University of Tübingen. Larison and her research team have also collected zebra tissue samples and have used cutting-edge technology to sequence zebra DNA to try to identify which genes code for striping. The team is continuing to study the benefits stripes provide.

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http://www.sciencedaily.com/releases/2015/01/150130092923.htm  Original web page at Science Daily

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Heart arrhythmias detected in deep-diving marine mammals

A new study of dolphins and seals shows that despite their remarkable adaptations to aquatic life, exercising while holding their breath remains a physiological challenge for marine mammals. The study, published January 15 in Nature Communications, found a surprisingly high frequency of heart arrhythmias in bottlenose dolphins and Weddell seals during the deepest dives. The normal dive response in marine mammals has long been understood to involve a marked reduction in heart rate (called bradycardia) and other physiological changes to conserve limited oxygen reserves while the air-breathing animals are underwater. How marine mammals cope with the exertion needed to pursue prey at depth has been unclear, however, since the normal physiological response to exercise is an increase in heart rate (called tachycardia). The new study shows that these conflicting signals to the heart can lead to cardiac arrhythmias, said lead author Terrie Williams, a professor of ecology and evolutionary biology at UC Santa Cruz.

“This study changes our understanding of bradycardia in marine mammals,” Williams said. “The heart is receiving conflicting signals when the animals exercise intensely at depth, which often happens when they are starting their ascent. We’re not seeing lethal arrhythmias, but it is putting the heart in an unsteady state that could make it vulnerable to problems.” Instead of a single level of reduced heart rate during dives, the researchers found that heart rates of diving animals varied with both depth and exercise intensity, sometimes alternating rapidly between periods of bradycardia and tachycardia. Cardiac arrhythmias occurred in more than 70 percent of deep dives. “We tend to think of marine mammals as completely adapted to life in the water. However, in terms of the dive response and heart rate, it’s not a perfect system,” Williams said. “Even 50 million years of evolution hasn’t been able to make that basic mammalian response impervious to problems.” The conflict between dive-induced bradycardia and exercise-induced tachycardia involves two different neural circuits that regulate heart rate, she said. The sympathetic nervous system stimulates the heart during exercise, whereas the parasympathetic nervous system controls the slowing of the heart rate during the dive response.

The new findings have implications for efforts to understand stranding events involving deep-diving marine mammals such as beaked whales. The authors note that the behaviors associated with cardiac anomalies in this study (increased physical exertion, deep diving, and rapid ascent from depth) are the same as those involved in the flight response of beaked whales and blue whales exposed to shipping noise and mid-frequency sonars. “This study is not saying that these deep-diving animals will die if they exercise hard at depth,” Williams said. “Rather, it raises questions about what happens physiologically when extreme divers are disturbed during a dive, and it needs further investigation.”

The study’s findings may also be relevant in humans, she said. The mammalian dive response or dive reflex, though most pronounced in marine mammals, also occurs in humans and other terrestrial animals and is triggered when the face contacts cold water. A 2010 study of triathlons found that the swimming segment of cold water triathlons accounts for over 90 percent of race day deaths. “It may be that the same conflicting signals we saw in dolphins and seals are causing arrhythmias in some triathletes,” Williams said. She is currently working with triathlon groups to help mitigate such problems during races. To conduct the study, the researchers developed a monitoring device to record heart rate, swimming stroke frequency, depth, and time throughout the dives of trained bottlenose dolphins diving in pools or open water, as well as free-ranging Weddell seals swimming beneath the ice in McMurdo Sound, Antarctica. Williams said the animals typically used low-intensity swimming modes as much as possible during dives. When hunting fish beneath the ice, Weddell seals alternated between easy glides and short chases in pursuit of prey. This behavior appeared to enable the marine mammals to avoid cardiac conflicts and associated arrhythmias during hunting.
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http://www.sciencedaily.com/releases/2015/01/150116085554.htm Original web page at Science Daily

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How do small birds survive cold winters?

Norway’s small birds face many challenges during the winter, including short days and long energy-intensive nights, tough weather conditions and food shortages, along with the risk of becoming a meal for hungry predators. Many of the smallest birds live on the edge of survival with this enormous physical pressure. Northern winters are the limiting factor for many creatures. This is especially true for the smallest birds, which have to use every daylight minute to find food. They are constantly adjusting to shifts in weather and trying to fend off starvation. Cold temperatures, strong winds and snow-covered branches increase the stress factors for birds that primarily reside in trees. The birds optimize their energy balance by changing location continuously depending on the weather. In cold, sunny weather, small birds conserve their energy by keeping to the trees’ sunny side. The goldcrest, Norway’s smallest bird at only 5-6 grams, and the slightly larger coniferous tits (coal tit, crested tit, and willow tit) all take advantage of this sun exposure. Even small changes in wind speed affect birds’ energy balance. Coniferous tits move to the lee side of trees when winds approach moderate breeze level (5-6 m/second), which offers a significant advantage. Small birds need to find enough food to get through the day and also build up adequate fat reserves for the coming night — all in the course of the limited daylight hours. Long-tailed tits at 8-9 grams and willow tits at 10-12 grams, for example, need to increase their body weight by 10 per cent to survive an 18-19 hour night. Unlike the willow tit, the somewhat larger great tit does not normally have the ability to lower its body temperature and thereby reduce heat and energy loss, and has to lay on even more body fat. Dead great tits have been found in birdhouses when nighttime temperatures have dropped to -30°C. Survival requires more than just finding food. It’s also a matter of not becoming the next meal for hungry owls or sparrowhawks. Birds are always gauging whether to hunt for food or to keep an eye out for potential predators. They often congregate in flocks in difficult periods, presumably to take advantage of more pairs of eyes to spot predators. Birds search for food where they are less likely to be preyed upon. The safest places are in the upper parts of trees. Bird flocks have a shared interest in protecting themselves from their enemies as well as efficient foraging. And at the same time they are also competitors. Willow tits live in small multi-age flocks except during the breeding season. On average about 75 per cent of the older birds, versus only about 40 per cent of the young ones, survive the winter. What accounts for this difference? Mature birds are socially dominant over younger ones and generally have better access to resources such as food and good nighttime roosts. The older birds also occupy the safest places, with the result that the young birds lead a much more uncertain and stressed existence than older birds do.

Young birds maintain a little distance from the dominant older birds in mild weather when the temperature reaches 0°C or warmer, but both groups stay mainly in the upper half of the trees where they are safer from hungry predators. Birds distribute themselves in pine trees in different conditions. When conditions are favorable with no wind and mild weather, both the old and young tits keep mostly to the upper reaches. The birds need to spend more time foraging for food as soon as the temperature drops and their energy requirements increase. They then flock together to reduce their risk of predation and can spend more time feeding. In these colder conditions the distribution of the birds changes, as the mature birds search for food above where it is safer, and force the young birds to stay in the lower part of the tree.

When tree branches are snow-laden, both older and younger birds prefer to be in the lower branches where it is easiest to find food. To avoid heat loss in strong winds, most tits congregate on the lower branches of the trees’ lee side, where the wind penetrates least. In both of these weather situations, young birds have less time to forage since they need to keep an eye out for the older birds and other predators. Young birds, especially in cold weather, are forced to be vigilant for both predators and the dominant older birds, resulting in young willow tits spending only about 60 per cent of their time foraging versus 85 per cent for the mature birds. The birds have to use their days optimally so they can put on a critical amount of fat needed to survive the night. Recurring disturbances due to changing weather conditions and dangerous predators give birds less time to build up the fat reserves they need to survive their long nighttime fasts. The higher mortality rate among young willow tits is due in great part to having less time to find food. As might be expected, more young than old willow tit remains have been found in the regurgitated pellets of Eurasian pygmy owls and northern hawk owls. Despite young birds losing valuable foraging time when together with their mature species-mates, their company has some positive sides. The young learn the territory from the older birds, and greater bird numbers also warn against predators more effectively. Every bird must carefully adjust its tactics — all depending on ever-shifting meteorological conditions and its social situation — to increase its chances of surviving one more day or week or month, until the milder days of spring finally arrive.

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http://www.sciencedaily.com/releases/2015/01/150127100159.htm  Original web page at Science Daily

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The brain thinks, the spinal cord implements: Research team identifies important control mechanisms for walking

Even after complete spinal paralysis, the human spinal cord is able to trigger activity in the leg muscles using electrical pulses from an implanted stimulator. This has already been demonstrated in earlier studies conducted in Vienna. Now, as part of a joint international project, a team of young researchers at the Center for Medical Physics and Biomedical Engineering at MedUni Vienna has succeeded in identifying the mechanisms the spinal cord uses to control this muscle activity. These mechanisms still work even if the neural pathways from the brain are physically interrupted as the result of a spinal cord injury. This is the first time throughout the world that the spinal-cord activation patterns for walking have been decoded. Paraplegics still have neural connections (so-called locomotion centers) below the site of the injury and these can trigger rhythmic movements in the legs. “Using statistical methods, we were able to identify a small number of basic patterns that underlie muscle activities in the legs and control periodic activation or deactivation of muscles to produce cyclical movements, such as those associated with walking. Just like a set of building blocks, the neural network in the spinal cord is able to combine these basic patterns flexibly to suit the motor requirement,” explains study author Simon Danner, from the Center for Medical Physics and Biomedical Engineering of MedUni Vienna. The results have now been published in the leading journal Brain. Although the brain or brain stem acts as the command center, it is the neural networks in the spinal cord that actually generate the complex motor patterns. These locomotion centers are to be found in most vertebrates. A well-known example of this is when the spinal cord continues to transmit signals even when the brain is no longer involved, as in the headless chicken running around the farmyard. Even after control by the brain has been lost, the spinal cord continues to send out motor signals, which are translated into movements of the legs and/or wings. New possibilities for rehabilitation following spinal paralysis These new findings relating to the basic patterns for triggering and coordinating muscle movements in the legs should also help in developing new approaches to rehabilitation aimed at utilizing those neural networks that are still functional following an accident and the resulting paralysis by stimulating them electrically. This opens the way to new therapeutic options for helping paraplegics to at least partially regain lost rhythmic movements. Exactly how the neural networks need to be stimulated depends upon the patient’s individual injury profile and is the subject of further studies. To help with this, the scientists at MedUni Vienna have developed a unique, non-invasive method for stimulating the spinal cord, which involves attaching electrodes to the surface of the skin. “This method allows easy access to the neural connections in the spinal cord below a spinal injury and can therefore be offered to those suffering from paraplegia without exposing them to any particular medical risks or stresses,” says Karen Minassian, senior author of the current publication. The publication is the result of a collaboration between the Medical University of Vienna (Center for Medical Physics and Biomedical Engineering, working group led by Winfried Mayr), the Otto-Wagner Hospital (Neurology Center, Heinrich Binder), Vienna University of Technology (Institute for Analysis und Scientific Computing, Frank Rattay) and Baylor College of Medicine, Houston, TX (Milan R. Dimitrijevic).

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http://www.sciencedaily.com/releases/2015/01/150112082942.htm  Original web page at Science Daily

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* How birds get by without external ears

Unlike mammals, birds have no external ears. The outer ears of mammals play an important function in that they help the animal identify sounds coming from different elevations. But birds are also able to perceive whether the source of a sound is above them, below them, or at the same level. Now a research team from Technische Universität München (TUM) has discovered how birds are able to localize these sounds, namely by utilizing their entire head. Their findings were published recently in the PLOS ONE journal. It is springtime, and two blackbirds are having a sing-off. They are both competing for the attentions of a female. But to pick a successful suitor, the female must first be able to find him. “Because birds have no external ears, it has long been believed that they are unable to differentiate between sounds coming from different elevations,” explains Hans A. Schnyder from the TUM Chair of Zoology. “But a female blackbird should be able to locate her chosen mate even if the source of the serenade is above her.” Mammals identify sound sources in the vertical plane using their external ears, which absorb, reflect or diffract the sound waves because of their special structure. Their sense of hearing uses this information to determine the elevation of the sound source. But how do birds perceive these differences? By studying three avian species — crow, duck and chicken — Schnyder discovered that birds are also able to identify sounds from different elevation angles. It seems that their slightly oval-shaped head transforms sound waves in a similar way to external ears. “We measured the volume of sounds coming from different angles of elevation at the birds’ eardrums,” relates Schnyder. All sounds originating from the same side as the ear were similarly loud, regardless of their elevation. The ear on the opposite side of the head registered different elevations much more accurately — in the form of different volume levels. It all comes down to the shape of the avian head. Depending on where the sound waves hit the head, they are reflected, absorbed or diffracted. What the scientists discovered was that the head completely screens the sound coming from certain directions. Other sound waves pass through the head and trigger a response in the opposite ear. The avian brain determines whether a sound is coming from above or below from the different sound volumes in both ears. “This is how birds identify where exactly a lateral sound is coming from — for example at eye height,” continues Schnyder. “The system is highly accurate: at the highest level, birds can identify lateral sounds at an angle of elevation from -30° to +30°.” Why have birds developed sound localization on the vertical plane? Most birds have eyes on the sides of their heads, giving them an almost 360° field of vision. Since they have also developed the special ability to process lateral sounds coming from different elevations, they combine information from their senses of hearing and vision to useful effect when it comes to evading predators. A few birds of prey like the barn owl have developed a totally different strategy. This species hunts at night, and like humans its eyes are front-facing. The feather ruff on their face modifies sounds in a similar way to external ears. The owl hears sounds coming from in front of it better than the other bird species studied by Schnyder. So there is a perfect interaction between the information they hear and the information they see — as earlier studies were able to demonstrate. “Our latest findings are pointing in the same direction: it seems that the combination of sight and hearing is an important principle in the evolution of animals,” concludes Schnyder

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http://www.sciencedaily.com/releases/2014/12/141211115700.htm  Original web page at Science Daily

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* Origin of the unique ventilatory apparatus of turtles: How the tortoise’s ribs got embedded in its shell

Through the careful study of modern and early fossil tortoise, researchers now have a better understanding of how tortoises breathe and the evolutionary processes that helped shape their unique breathing apparatus and tortoise shell. The findings published in a paper, titled: Origin of the unique ventilatory apparatus of turtles, in the scientific journal, Nature Communications, on Friday, 7 November 2014, help determine when and how the unique breathing apparatus of tortoises evolved. Lead author Dr Tyler Lyson of Wits University’s Evolutionary Studies Institute, the Smithsonian Institution and the Denver Museum of Nature and Science said: “Tortoises have a bizarre body plan and one of the more puzzling aspects to this body plan is the fact that tortoises have locked their ribs up into the iconic tortoise shell. No other animal does this and the likely reason is that ribs play such an important role in breathing in most animals including mammals, birds, crocodilians, and lizards.” Instead tortoises have developed a unique abdominal muscular sling that wraps around their lungs and organs to help them breathe. When and how this mechanism evolved has been unknown. “It seemed pretty clear that the tortoise shell and breathing mechanism evolved in tandem, but which happened first? It’s a bit of the chicken or the egg causality dilemma,” Lyson said. By studying the anatomy and thin sections (also known as histology), Lyson and his colleagues have shown that the modern tortoise breathing apparatus was already in place in the earliest fossil tortoise, an animal known as Eunotosaurus africanus. This animal lived in South Africa 260 million years ago and shares many unique features with modern day tortoises, but lacked a shell. A recognisable tortoise shell does not appear for another 50 million years. Lyson said Eunotosaurus bridges the morphological gap between the early reptile body plan and the highly modified body plan of living tortoises, making it the Archaeopteryx of turtles. “Named in 1892, Eunotosaurus is one of the earliest tortoise ancestors and is known from early rocks near Beaufort West,” said Professor Bruce Rubidge, Director of the Evolutionary Studies Institute at Wits University and co-author of the paper. “There are some 50 specimen of Eunotosaurus. The rocks of the Karoo are remarkable in the diversity of fossils of early tortoises they have produced. The fact that we find Eunotosaurus at the base of the Karoo succession strongly suggest that there are more ancestral forms of tortoises still to be discovered in the Karoo,” Rubidge added. The study suggests that early in the evolution of the tortoise body plan a gradual increase in body wall rigidity produced a division of function between the ribs and abdominal respiratory muscles. As the ribs broadened and stiffened the torso, they became less effective for breathing which caused the abdominal muscles to become specialised for breathing, which in turn freed up the ribs to eventually — approximately 50 million years later — to become fully integrated into the characteristic tortoise shell. Lyson and his colleagues now plan to investigate reasons why the ribs of early tortoises starting to broaden in the first place. “Broadened ribs are the first step in the general increase in body wall rigidity of early basal tortoises, which ultimately leads to both the evolution of the tortoise shell and this unique way of breathing. We plan to study this key aspect to get a better understanding why the ribs started to broaden.”

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http://www.sciencedaily.com/releases/2014/11/141107111042.htm  Original web page at Science Daily

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* Heart’s own immune cells can help it heal

Most of the time when the heart is injured, these beneficial immune cells are supplanted by immune cells from the bone marrow, which are spurred to converge in the heart and cause inflammation that leads to further damage. In both cases, these immune cells are called macrophages, whether they reside in the heart or arrive from the bone marrow. Although they share a name, where they originate appears to determine whether they are helpful are harmful to an injured heart. In a mouse model of heart failure, the researchers showed that blocking the bone marrow’s macrophages from entering the heart protects the organ’s beneficial pool of macrophages, allowing them to remain in the heart, where they promote regeneration and recovery. The findings may have implications for treating heart failure in humans. The study is now available in The Proceedings of the National Academy of Sciences Early Edition. “Researchers have known for a long time that the neonatal mouse heart can recover well from injury, and in some cases can even regenerate,” said first author Kory J. Lavine, MD, PhD, instructor in medicine. “If you cut off the lower tip of the neonatal mouse heart, it can grow back. But if you do the same thing to an adult mouse heart, it forms scar tissue.” This disparity in healing capacity was long a mystery because the same immune cells appeared responsible for both repair and damage. Until recently, it was impossible to distinguish the helpful macrophages that reside in the heart from the harmful ones that arrive from the bone marrow. The new research and past work by the same group — led by Douglas L. Mann, MD, the Tobias and Hortense Lewin Professor of Medicine and cardiologist-in-chief at Barnes-JewishHospital — appear to implicate these immune cells of different origins as responsible for the difference in healing capacity seen in neonatal and adult hearts, at least in mice. “The same macrophages that promote healing after injury in the neonatal heart also are present in the adult heart, but they seem to go away with injury,” Lavine said. “This may explain why the young heart can recover while the adult heart can’t.” Because they are interested in human heart failure, Lavine and his colleagues developed a method to progressively damage mouse cardiac tissue in a way that mimicked heart failure. They compared the immune response to cardiac damage in neonatal and adult mouse hearts.

The investigators found that the helpful macrophages originate in the embryonic heart and harmful macrophages originate in the bone marrow and could be distinguished by whether they express a protein on their surface called CCR2. Macrophages without CCR2 originate in the heart; those with CCR2 come from the bone marrow, the research showed. Lavine and his colleagues asked whether a compound that inhibits the CCR2 protein would block the bone marrow’s macrophages from entering the heart. “When we did that, we found that the macrophages from the bone marrow did not come in,” Lavine said. “And the macrophages native to the heart remained. We saw reduced inflammation in these injured adult hearts, less oxidative damage and improved repair. We also saw new blood vessel growth. By blocking the CCR2 signaling, we were able to keep the resident macrophages around and promote repair.” Some CCR2 inhibitors are being tested in phase 1 and 2 clinical trials for treating rheumatoid arthritis. But before these drugs can be evaluated in people with heart failure, more work must be done to find out whether the same mechanisms are at work in human hearts, according to the researchers. “We have identified similar immune cell subtypes that are present in the human heart,” Lavine said. “We need to find out more about their roles in heart failure in patients and understand more about how macrophages that reside in the heart promote repair.”

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http://www.sciencedaily.com/releases/2014/10/141030150634.htm Original web page at Science Daily

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Running robots of future may learn from world’s best two-legged runners: Birds

Although birds are designed primarily for flight, scientists have learned that species that predominately live on land and scurry around on the ground are also some of the most sophisticated runners of any two-legged land animals. These characteristics may have been evolving since the time of the dinosaurs and, some would say, now transcend the ability of other bipedal runners, including humans. In a study published today in the Journal of Experimental Biology, researchers from Oregon State University, the Royal Veterinary College and other institutions outline how running birds have achieved an impressive ability to run while minimizing energy cost, avoiding falls or injury, and maintaining speed and direction. “Birds appear to be the best of bipedal terrestrial runners, with a speed and agility that may trace back 230 million years to their dinosaur ancestors,” said Jonathan Hurst, an associate professor and robotics expert in the OSU College of Engineering. Running birds come in an enormous range of sizes, from tiny quails to an ostrich that has 500 times as much body mass. Most, but not all, can fly, but spend most of their lives on the ground, and they don’t always look the most graceful when they run. But researchers found that they maximize the results while keeping their priorities straight — save energy and don’t break a leg. In the wild, an injury could lead to predation and death; and in like fashion, when food resources are limited, economy of motion is essential. “These animals don’t care that they appear a little unstable or have a waver in their gait,” Hurst said. “Their real goal is to limit peak forces, avoid falling, be safe and be as efficient as possible. If their upper body seems to lurch around a little as a result, that’s okay. What they are accomplishing is really quite elegant.” Even more surprisingly, a wide variety of ground-running bird species with very different body sizes use essentially the same strategy to accomplish these sometimes conflicting tasks. In order to hop over obstacles on uneven ground, they use a motion that’s about 70 percent a “vaulting” movement as they approach the obstacle, and 30 percent a more-crouched posture while on top of the obstacle. “Evolution has shaped running birds into all different sizes and skeletal structures,” said Christian Hubicki, a doctoral student at OregonState who co-authored the study. “But we found their behavior in how they run is essentially the same.” In collaboration with Monica Daley at the RoyalVeterinaryCollege in London, the researchers studied five species of birds and developed a computer model in OSU’s Dynamic Robotics Laboratory that closely matches that behavior. “We should ultimately be able to encode this understanding into legged robots so the robots can run with more speed and agility in rugged terrain,” Hubicki said. “These insights may also help us understand the walking and running behaviors of all the common ancestors involved, including theropod dinosaurs such as the velociraptor.” The researchers began the study with a hypothesis that body stability would be a priority, since it might help avoid falls and leg injuries. That’s not what they found, however. Instead, running birds have a different definition of stability — they do avoid falls, but also allow their upper bodies to bounce around some, just so long as they don’t fall. Like a scrambling football runner, their leg motion may sometimes speed up or slow down, in the interest of staying upright, dealing with obstacles and generally staying on course to where they are going. The process isn’t always pretty, but it’s functional.

Large animals are limited by the strength of their legs because peak loads increase with body mass, and they run with somewhat straighter legs to compensate. But the basic approach large birds use to run is similar to much smaller birds, and remains highly efficient. Modern robots, by contrast, are usually built with an emphasis on total stability, which often includes maintaining a steady gait. This can be energy-intensive and sometimes limits their mobility. What robots could learn from running birds, the scientists said, is that it’s okay to deviate from normal steady motions, because it doesn’t necessarily mean you’re going to fall or break something. Robotic control approaches “must embrace a more relaxed notion of stability, optimizing dynamics based on key task-level priorities without encoding an explicit preference for a steady gait,” the researchers said in their conclusion. Collaborators on the research were from the RoyalVeterinaryCollege in the United Kingdom. The work was supported by the Biotechnology and Biological Sciences Research Council in the United Kingdom and the Human Frontier Science Program. “The running robots of the future are going to look a lot less robotic,” Hurst said. “They will be more fluid, like the biological systems in nature. We’re not necessarily trying to copy animals, but we do want to match their capabilitie

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http://www.sciencedaily.com/releases/2014/10/141029204139.htm  Original web page at Science Daily

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* Improving bladder function among people with spinal cord injuries

People who have suffered spinal cord injuries are often susceptible to bladder infections, and those infections can cause kidney damage and even death. New UCLA research may go a long way toward solving the problem. A team of scientists studied 10 paralyzed rats that were trained daily for six weeks with epidural stimulation of the spinal cord and five rats that were untrained and did not receive the stimulation. They found that training and epidural stimulation enabled the rats to empty their bladders more fully and in a timelier manner. The study was published in the online journal PLOS ONE. “The big deal here is the immediate effect,” said V. Reggie Edgerton, a distinguished professor of integrative biology and physiology, neurobiology, and neurosurgery at UCLA and senior author of the research. “There may be a way that when people have bladder problems, you can turn the stimulator on and they can release urine at will. This strategy could have a major impact in improving the quality of life and longevity of human patients.”

Nearly 1.3 million Americans have spinal cord injuries, and those with complete spinal cord injuries typically have two to six bladder infections per year. Edgerton said the advance could eventually treat or even cure one of their highest priority health concerns. “We’re not saying it will restore this part of their lives to normal, but we think it will lead to a significant improvement in quality of life,” he said. The researchers also found that after they filled a rat’s bladder with saline, and turned on an epidural electrical stimulator, the rat released urine within 90 seconds, said lead author Parag Gad, an assistant researcher in Edgerton’s laboratory.

The research was funded by the National Institutes of Health’s National Institute of Biomedical Imaging and Bioengineering (grants R01EB007615 and R01NS062009) and the Christopher and Dana Reeve Foundation. Other co-authors were Dr. Daniel Lu, assistant professor of neurosurgery at the David Geffen School of Medicine at UCLA; researcher Roland Roy and project scientist Hui Zhong, both of Edgerton’s laboratory; and Yury Gerasimenko, professor and director of the laboratory of movement physiology at Russia’s Pavlov Institute in St. Petersburg and a researcher in Edgerton’s lab.

Edgerton believes there is a connection between the neural networks that control walking and bladder function, and is planning to investigate the connection. To research bladder control with human subjects, his team plans to place electrodes on the skin over a critical part of the spinal cord and evaluating their improvement. Edgerton and colleagues from the University of Louisville reported in the medical journal Brain in April a fundamentally new intervention strategy that enabled four young men who had been paralyzed for years to move their legs, hips, ankles and toes as a result of epidural electrical stimulation of the spinal cord, and were able to execute voluntary movements immediately following the implantation and activation of the stimulator. In that study, researchers used a stimulator to deliver a continuous electrical current to the participants’ lower spinal cords, mimicking signals the brain normally transmits to initiate movement. The electrical current was applied at varying frequencies and intensities to specific locations on the lumbosacral spinal cord, corresponding to the dense neural bundles that largely control the movement of the hips, knees, ankles and toes. Once the signal was triggered, the men’s spinal cords reengaged their neural networks to control and direct muscle movements.

“The circuitry in the spinal cord is remarkably resilient,” said Edgerton, who has been conducting fundamental research in this area for 38 years and is a member of the Reeve Foundation International Research Consortium on Spinal Cord Injury. “Once you get them up and active, many physiological systems that are intricately connected and that were dormant come back into play.”

http://www.sciencedaily.com/  Science Daily

http://www.sciencedaily.com/releases/2014/10/141017093124.htm  Original web page at Science Daily

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Dolphins are attracted to magnets: Add dolphins to the list of magnetosensitive animals, French researchers say

Add dolphins to the list of magnetosensitive animals, French researchers say. Dolphins are indeed sensitive to magnetic stimuli, as they behave differently when swimming near magnetized objects. So says Dorothee Kremers and her colleagues at Ethos unit of the Université de Rennes in France, in a study in Springer’s journal Naturwissenschaften — The Science of Nature. Their research, conducted in the delphinarium of Planète Sauvage in France, provides experimental behavioral proof that these marine animals are magnetoreceptive. Magnetoreception implies the ability to perceive a magnetic field. It is supposed to play an important role in how some land and aquatic species orientate and navigate themselves. Some observations of the migration routes of free-ranging cetaceans, such as whales, dolphins and porpoises, and their stranding sites suggested that they may also be sensitive to geomagnetic fields. Because experimental evidence in this regard has been lacking, Kremers and her colleagues set out to study the behavior of six bottlenose dolphins in the dolphinarium of Planète Sauvage in Port-Saint-Père. This outdoor facility consists of four pools, covering 2,000 m² of water surface. They watched the animals’ spontaneous reaction to a barrel containing a strongly magnetized block or a demagnetized one. Except from this characteristic, the blocks were identical in form and density. The barrels were therefore indistinguishable as far as echolocation was concerned, the method by which dolphins locate objects by bouncing sound waves off them. During the experimental sessions, the animals were free to swim in and out of the pool where the barrel was installed. All six dolphins were studied simultaneously, while all group members were free to interact at any time with the barrel during a given session. The person who was assigned the job to place the barrels in the pools did not know whether it was magnetized or not. This was also true for the person who analyzed the videos showing how the various dolphins reacted to the barrels.

The analyses of Ethos team revealed that the dolphins approached the barrel much faster when it contained a strongly magnetized block than when it contained a similar not magnetized one. However, the dolphins did not interact with both types of barrels differently. They may therefore have been more intrigued than physically drawn to the barrel with the magnetized block. “Dolphins are able to discriminate between objects based on their magnetic properties, which is a prerequisite for magnetoreception-based navigation,” says Kremers. “Our results provide new, experimentally obtained evidence that cetaceans have a magenetic sense, and should therefore be added to the list of magnetosensitive species.”

http://www.sciencedaily.com/  Science Daily

http://www.sciencedaily.com/releases/2014/09/140929105237.htm Original web page at Science Daily

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Female baboons with male companions live longer

Numerous studies have linked social interaction to improved health and survival in humans, and new research confirms that the same is true for baboons. A long-term study of more than 200 wild female baboons from the plains of southern Kenya finds that the most sociable females — measured by how often they engaged in social grooming relative to their peers — live two to three years longer than their socially isolated counterparts. Socializing with males gave females an even bigger longevity boost than socializing with other females, the researchers found. A handful of previous studies in baboons, rats and dolphins suggested that same-sex friendships can improve animal health and survival, but this is one of the first studies to show that opposite-sex friendships in animals can have similar effects, said co-author Elizabeth Archie of the University of Notre Dame. In a study published in Proceedings of the Royal Society B, Archie and four other researchers, including co-authors Susan Alberts and Jenny Tung from Duke University, analyzed 27 years’ worth of near-daily records for yellow baboons living near Mount Kilimanjaro in Kenya. Baboons take turns grooming each other to make friends and cement social bonds — an activity that involves picking dirt and parasites and dead skin out of each other’s fur. “Grooming is the baboon equivalent of gossip, or having a good conversation over a cup of coffee,” Alberts said. he researchers estimated social connectedness for 204 females by measuring how often each engaged in social grooming sessions relative to the rest of the group. They found that the friendliest females lived two to three years longer than their more socially isolated peers — an effect that held up even after the researchers accounted for factors such as a female’s rank, group size and number of female relatives.

There are many possible ways that social interactions could improve a baboon’s odds of survival and lengthen her life, Archie and Alberts say, ranging from reducing chronic stress and boosting immune function to improving her access to food and water. The females that socialized with both sexes lived the longest. But when the researchers looked at female-female and male-female interactions separately, they found that the survival benefits of male companionship were even bigger than the benefits of friendships with other females: The females that socialized with other females the most were 34 percent less likely to die in a given period than those who rarely interacted with other females, whereas socializing a lot with males lessened the chances of dying by 45 percent. While the primary perks of male-female friendships are thought to be better care and protection for infants and more mating opportunities for males, the results show that females benefit directly too, Archie said. “Males’ larger size may make them better than females at defending their friends against potential bullies,” Alberts added. If social connection is so good for survival, why are some baboons less sociable than others? “Forces that aren’t exactly ‘friendly’ might be at play,” said biologist Lauren Brent, a specialist in animal friendships who wasn’t involved with the research. “If social relationships are a valuable commodity, competition for them should be intense, which could result in social exclusion for some animals,” said Brent, who is currently a research associate at DukeUniversity and the University of Exeter. “There may also be benefits to being on the periphery, where the risk of disease and the costs of socializing — which can include serious injuries from competing for relationships — are likely to be mitigated.” Archie and Alberts and their colleagues found that females’ interactions with other females grew less frequent with age, whereas their interactions with males stayed the same. The result sheds light on the social isolation so often experienced by older adults. “If social isolation is simply an inevitable consequence of age-related declines in health and energy, then we would expect to see similar declines in both same-sex and opposite-sex relationships,” Archie said. But their results suggest otherwise. “When females get older, many of their female peers start to pass away, and their daughters become tied up with their own infants, leaving less time for social interaction,” Alberts said. “It suggests that social isolation isn’t an inevitable part of aging, but instead may simply be a consequence of declines in potential friends’ availability.” Whether the most sociable females live longer lives because they have a few close friends or a lot of acquaintances remains an open question, the researchers say. Their next step is to find out if male-female friendships lengthen lifespan in males, too.

http://www.sciencedaily.com/  Science Daily

http://www.sciencedaily.com/releases/2014/09/140910093225.htm  Original web page at Science Daily

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How hummingbirds evolved to detect sweetness

Hummingbirds’ ability to detect sweetness evolved from an ancestral savory taste receptor that is mostly tuned to flavors in amino acids. Feasting on nectar and the occasional insect, the tiny birds expanded throughout North and South America, numbering more than 300 species over the 40 to 72 million years since they branched off from their closest relative, the swift.

Everything about hummingbirds is rapid. An iridescent blur to the human eye, their movements can be captured with clarity only by high-speed video. Slowed down on replay, their wings thrum like helicopter blades as they hover near food. Their hearts beat 20 times a second and their tongues dart 17 times a second to slurp from a feeding station. It takes only three licks of their forked, tube-like tongues to reject water when they expect nectar. They pull their beaks back, shake their heads and spit out the tasteless liquid. They also are not fooled by the sugar substitute that sweetens most diet cola. These hummingbirds look mad. The birds’ preference for sweetness is plain, but only now can scientists explain the complex biology behind their taste for sugar. Their discovery required an international team of scientists, fieldwork in the California mountains and at Harvard University’s Concord Field Station, plus collaborations from Harvard labs on both sides of the Charles River. Now, in a paper published in Science, the scientists show how hummingbirds’ ability to detect sweetness evolved from an ancestral savory taste receptor that is mostly tuned to flavors in amino acids. Feasting on nectar and the occasional insect, the tiny birds expanded throughout North and South America, numbering more than 300 species over the 40 to 72 million years since they branched off from their closest relative, the swift. “It’s a really nice example of how a species evolved at a molecular level to adopt a very complex phenotype,” said Stephen Liberles, HMS associate professor of cell biology. “A change in a single receptor can actually drive a change in behavior and, we propose, can contribute to species diversification.” This sweet discovery all started with the chicken genome. Before scientists sequenced its genes, people assumed that chickens and all birds taste things the same way that mammals do: with sensory receptors for salty, sour, bitter, sweet and the more recently recognized umami taste, which comes from the Japanese word for savory.

The canonical view stated there was a sweet receptor present in animals, much smaller than the large families of receptors involved in smell and bitter taste perception — vital for sensing safe food or dangerous predators. Some animals have lost certain taste abilities. The panda, for example, feeds exclusively on bamboo and lacks savory taste receptors. Carnivores, notably cats, are indifferent to sweet tastes. The gene for tasting sweetness is present in their genomes, but it’s nonfunctional. Scientists suspect that an interplay between taste receptors and diet may effectively relegate the sweet taste receptor into a pseudogene that does not get turned on and eventually disappears. The chicken genome is another story: It has no trace of a sweet-taste receptor gene. Faced with this all-or-nothing scenario, Maude Baldwin, co-first author of the paper, had one reaction. “The immediate question to ornithologists or to anybody who has a birdfeeder in the backyard was: What about hummingbirds?” she recalled. “If they are missing the single sweet receptor, how are they detecting sugar?” More bird genomes were sequenced, and still no sweet receptor. So began Baldwin’s quest to understand how hummingbirds detected sugar and became highly specialized nectar feeders. A doctoral student in organismic and evolutionary biology and Museum of Comparative Zoology, she is a member of the lab of Scott Edwards, Professor of Organismic and Evolutionary Biology and Curator of Ornithology in the Museum of Comparative Zoology. She sought out Liberles at a meeting of the International Symposium on Smell and Taste in San Francisco. They agreed to work together on experiments that would eventually reveal how hummingbirds evolved and diversified, based on a change in their taste receptor. After cloning the genes for taste receptors from chickens, swifts and hummingbirds — a three-year process — Baldwin needed to test what the proteins expressed by these genes were responding to. She joined forces with another scientist at another International Taste and Smell meeting. Yasuka Toda, a graduate student of the University of Tokyo and co-first author of the paper, had devised a method for testing taste receptors in cell culture. Together they showed that in chickens and swifts the receptor responds strongly to amino acids — the umami flavors — but in hummingbirds only weakly. But the receptor in hummingbirds responds strongly to carbohydrates — the sweet flavors. “This is the first time that this umami receptor has ever been shown to respond to carbohydrates,” Baldwin said. Toda mixed and matched different subunits of the chicken and hummingbird taste receptors into hybrid chimeras to understand which parts of the gene were involved in this change in function. All told, she found 19 mutations, but there are likely more contributing to this sweet switch, Baldwin and Liberles suspect. “If you look at the structure of the receptor, it involved really dramatic changes over its entire surface to accomplish this complex feat,” Liberles said. “Amino acids and sugars look very different structurally so in order to recognize them and sense them in the environment, you need a completely different lock and key. The key looks very different, so you have to change the lock almost entirely.” Once the mutations were discovered, the next question was, do they matter? Does this different taste receptor subunit drive behavior in the hummingbirds? Back at the feeding stations, the birds answered yes. They spat out the water, but they siphoned up both the sweet nectar and one artificial sweetener that evoked a response in the cell-culture assay, unlike aspartame and its ilk. It’s not nectar, with its nutritional value, but it’s still sweet. “That gave us the link between the receptor and behavior,” Liberles said. “This dramatic change in the evolution of a new behavior is a really powerful example of how you can explain evolution on a molecular level.” “Sensory systems give us a window into the brain to define what we understand about the world around us,” he said. “The taste system is arguably a really direct line to pleasure and aversion, reward and punishment, sweet and bitter. Understanding how neural circuits can encode these differentially gives us a window into other aspects of perception.”

http://www.sciencedaily.com/  Science Daily

http://www.sciencedaily.com/releases/2014/08/140821141449.htm  Original web page at Science Daily

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Running for life: How speed restricts evolutionary change of the vertebral column

One of the riddles of mammal evolution explained: the strong conservation of the number of trunk vertebrae. Researchers of the NaturalisBiodiversityCenter and the University of Utah show that this conservation is probably due to the essential role of speed and agility in survival of fast running mammals. They measured variation in vertebrae of 774 individual mammal skeletons of both fast and slow running species. The researchers found that a combination of developmental and biomechanical problems prevents evolutionary change in the number of trunk vertebrae in fast running and agile mammals. In contrast, these problems barely affect slow and sturdy mammals. The study appeared on 14 July 2014 in PNAS. The mammal vertebral column is highly variable among species, reflecting adaptations to a wide range of lifestyles, from burrowing in moles to flying in bats. Yet, as a rule, the number of trunk vertebrae varies little between most mammal species. The vertebral column and its high evolutionary potential is considered to be of central importance for the evolution of vertebrates, which is why the constancy is both puzzling and important. The authors propose, on biomechanical and developmental grounds that evolutionary change is virtually impossible in fast running and agile mammals, but only marginally affects slow and sturdy mammals. The rationale is that several mutations are necessary to change the number of trunk vertebrae, with single mutations leading to irregularly shaped transitional lumbosacral vertebrae that are incompletely and asymmetrically fused to the sacrum. These irregular lumbosacral joints reduce flexibility, thus severely hampering running and jumping. Their observations indeed show that selection against these initial changes is strong in fast and agile mammals and weak in slower and sturdier ones. In total, 774 skeletons of 90 different species were analysed. The skeletons belonged to collections of 9 European natural history museums including NaturalisBiodiversityCenter, Leiden.

“The stiffness of the back of a mammal is key to whether evolutionary change is possible or not,” said Frietson Galis, one of the authors of the study. “`the locomotion of slow mammals with a stiff back is only marginally affected by irregular lumbosacral joints, but for fast running mammals such joints are fatal ” continued Clara ten Broek another author of the study. “A combination of developmental, biomechanical and evolutionary insights and a large dataset were necessary to solve this puzzle of mammal evolution,” said Frietson Galis. “The stiffness of the back of a mammal is key to whether evolutionary change is possible or not,” said Frietson Galis, researcher at NaturalisBiodiversityCenter and one of the authors of the study. “the locomotion of slow mammals with a stiff back is only marginally affected by irregular lumbosacral joints, but for fast running mammals such joints are fatal” continued Clara ten Broek another author of the study. “A combination of developmental, biomechanical and evolutionary insights and a large dataset were necessary to solve this puzzle of mammal evolution,” said Frietson Galis.

http://www.sciencedaily.com/

http://www.sciencedaily.com/releases/2014/07/140714152427.htm Original web page at Science Daily

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Possible new plan of attack for opening, closing blood-brain barrier

Like a bouncer at an exclusive nightclub, the blood-brain barrier allows only select molecules to pass from the bloodstream into the fluid that bathes the brain. Vital nutrients get in; toxins and pathogens are blocked. The barrier also ensures that waste products are filtered out of the brain and whisked away. The blood-brain barrier helps maintain the delicate environment that allows the human brain to thrive. There’s just one problem: The barrier is so discerning, it won’t let medicines pass through. Researchers haven’t been able to coax it to open up because they don’t know enough about how the barrier forms or functions. Now, a team from Harvard Medical School has identified a gene in mice, Mfsd2a, that may beresponsible for limiting the barrier’s permeability — and the molecule it produces, Mfsd2a, works in a way few researchers expected. “Right now, 98 percent of small-molecule drugs and 100 percent of large-molecule drugs and antibodies can’t get through the blood-brain barrier,” said Chenghua Gu, associate professor of neurobiology at HMS and senior author of the study. “Less than 1 percent of pharmaceuticals even try to target the barrier, because we don’t know what the targets are. Mfsd2a could be one.” Most attempts to understand and manipulate blood-brain barrier function have focused on tight junctions, seals that prevent all but a few substances from squeezing between barrier cells. Gu and her team discovered that Mfsd2a appears to instead affect a second barrier-crossing mechanism that has received much less attention, transcytosis, a process in which substances are transported through the barrier cells in bubbles called vesicles.

Transcytosis occurs frequently at other sites in the body but is normally suppressed at the blood-brain barrier. Mfsd2a may be one of the suppressors. “It’s exciting because this is the first molecule identified that inhibits transcytosis,” said Gu. “It opens up a new way of thinking about how to design strategies to deliver drugs to the central nervous system.” Because Mfsd2a has a human equivalent, blocking its activity in people could allow doctors to open the blood-brain barrier briefly and selectively to let in drugs to treat life-threatening conditions such as brain tumors and infections. Conversely, because researchers have begun to link blood-brain barrier degradation to several brain diseases, boosting Mfsd2a or Mfsd2a could allow doctors to strengthen the barrier and perhaps alleviate diseases such as Alzheimer’s, amyotrophic lateral sclerosis (ALS) and multiple sclerosis. The findings may also have implications for other areas of the body that rely on transcytosis, such as the retina and kidney. The study was published May 14 in Nature.

http://www.sciencedaily.com/  Science Daily

June 10, 2014

http://www.sciencedaily.com/releases/2014/05/140514133434.htm  Original web page at Science Daily

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Nanoparticles make turkey eggs tough to crack

The eggs of the Australian brush turkey (Alectura lathami) repel moisture that can harbor harmful microbes. Australian brush turkeys incubate their eggs where few might — in moist piles of rotting vegetation. The eggs are kept warm by the heat generated as microbes in the soil and compost decompose organic matter, but those same microbes can also get through eggshells and kill the embryos. Despite the risk, infections occur in only about 9% of eggs laid by Australian brush turkeys (Alectura lathami). Now researchers think they know why: the shells are covered in a layer of nanometre-sized spheres of calcium phosphate, which makes them more water-repellent than chicken eggs and helps them to fend off bacterial attachment and penetration. The results, published this month in the Journal of Experimental Biology, could one day lead to new antimicrobial coatings for plastics and other surfaces. Most eggshells create a tough barrier for pathogens to crack, and microbes that succeed encounter an antimicrobial enzyme called lysozyme, found in the whites of bird eggs. But brush-turkey eggs have roughly the same amount of lysozyme as chicken eggs, and their shells are 1.5 times thinner than those of chickens, which should make them more susceptible to invading microbes, not less. The key difference between the turkey and chicken eggs, the researchers found, is the turkey eggs’ extreme ability to repel water. Droplets of water that were absorbed by chicken shells beaded up on the turkey eggs’ surface, which is made hydrophobic by the layer of naturally occurring calcium phosphate nanospheres. Because microbes are usually transmitted into eggs by moisture, resistance to water absorption is likely to have a key role in protecting brush-turkey chicks. “The lotus leaf is considered the most hydrophobic material in nature,” says first author Liliana D’Alba, a behavioural ecologist at the University of Akron, Ohio. “These eggshells are pretty close to that, to being super-hydrophobic.”

Tests revealed that more than three times as many bacteria adhered to chicken eggs as to the brush-turkey shells. Two bacterial species, Pseudomonas aeruginosa and Escherichia coli, infiltrated chicken shells within 2 to 6 days of contacting their surfaces, but required significantly more time to enter brush-turkey eggshells. The turkey eggs’ ability to ward off moisture is “not just protection against the school of hard knocks, it’s also protection against the microbial world,” says Maxwell Hincke, a biomaterials researcher at the University of Ottawa in Canada, who was not involved with the study. The calcium phosphate nanospheres found in this species’ eggs seem uncommon — preliminary observations have not revealed similar structures in the eggs of other species. However, a 1982 study described similar nanospheres in the eggs of malleefowl (Leipoa ocellata), another Australian bird that nests in soil mounds. In the future, D’Alba plans to study how diverse nesting environments may have shaped the shell composition of other birds or reptiles. Understanding how the nanospheres work could help to create better antimicrobial coatings for use on a wide range of materials, according to study co-author Matthew Shawkey, an evolutionary biologist at the University of Akron. Hincke suggests that future work in this area may lead to innovative biomedical applications. “Hydrophobic nanoparticles on the surface of medical devices could change the way bacteria adhere or form biofilms,” he says. Nature doi:10.1038/nature.2014.15039

http://www.nature.com/news/index.html  Nature

May 13, 2014

http://www.nature.com/news/nanoparticles-make-turkey-eggs-tough-to-crack-1.15039  Original web page at Nature

 

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Gut capacity limits bird’s ability to adapt to rapid climate change

An ornithologist at the University of Rhode Island who studies the physiological changes that birds undergo to migrate has found that the capacity of a bird’s gut to change with environmental conditions is a primary limiting factor in their ability to adapt to the rapidly changing climate. And he believes that most other animals are also limited in a similar way.  Scott McWilliams, URI professor of natural resources science, says that spare capacity — the extent to which animals can modify their physiology to deal with ecological changes — varies from species to species, with some having great capacity to change while others do not. “It’s all about the time scale over which evolution occurs in relation to the timing of the changes now occurring in the environment, because there are likely to be mismatches,” he said. “Our rapid climate change is happening too quickly for most animals to evolve a response.” His research, funded by the National Science Foundation, was published last week in The Proceedings of the Royal Society. McWilliams and a colleague at the University of Wisconsin measured the spare capacity of white-throated sparrows, a common migratory songbird in eastern North America. He found that birds acclimated to a very cold environment (-29C) were able to eat 2 to 4 times as much food as sparrows acclimated to summer temperatures, although the sparrows could not eat enough to live at temperatures colder than -29C. “They dramatically increase the size of their gut to accommodate the greater amount of food they must eat to meet their energy needs in the cold, yet they are able to just as efficiently digest their food when they eat much more,” said McWilliams. “That tells us something about their ability to flexibly respond to climate change. Plenty of birds migrate south because they have too limited a capacity to respond in this way. But white-throated sparrows have the spare capacity to modify their physiology to deal with substantial environmental change.”

However, when the birds were given no time to acclimate to the cold temperatures, they were only able to increase their food intake by about 50 percent. The researchers found that the birds needed at least two days to acclimate to the new conditions before they were able to eat more. One implication of this finding is that birds that fly long distances in migration — an activity that causes their gut size to decrease because they do not eat while flying — need a day or two to reconstitute their gut before they can resume the maximum food intake required to continue their migration. McWilliams says that his study has defined the ultimate limits of the gut capacity of white-throated sparrows. If similar limits could be established for other species, that data could be incorporated into climate models to better understand which species will likely be able to survive the coming environmental changes. “All organisms have some level of spare capacity,” McWilliams said. “The animals that live in constant environments haven’t had to evolve much capacity, so those animals are probably going to have the greatest challenge adapting to changing conditions.” According to the researchers, the limits of spare capacity have been studied in very few other species, with most work focused on several varieties of snakes. But they say that the limitations all animals face are in their ability to convert food into usable energy. “The gut limits the overall design of the animal,” McWilliams said.

http://www.sciencedaily.com/  Science Daily

May 13, 2014

http://www.sciencedaily.com/releases/2014/04/140415133819.htm  Original web page at Science Daily

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* Running geese give insight into low oxygen tolerance

A new study into how the world’s highest flying bird, the bar-headed goose, is able to survive at extreme altitudes may have future implications for low oxygen medical conditions in humans. An international team of scientists recently tracked the bar-headed goose while it migrated across the Himalayas. Now they have shown how these birds are able to tolerate running at top speed while breathing only 7% oxygen. Exercising at high altitude is a massive challenge since at the top of the highest mountains the air is only made up of 7% oxygen, compared with 21% at sea level. This is why human climbers often use supplemental oxygen when scaling the world’s tallest peaks. Dr Lucy Hawkes of the University of Exeter led the study, along with colleagues Dr Charles Bishop (BangorUniversity) and Prof. Pat Butler (University of Birmingham). They tested how good the geese were at coping with exercise in reduced oxygen environments by simulating the conditions of Mount Everest in a clear box and then getting the birds to run as fast as possible on a treadmill inside the box. They discovered that the geese had a remarkable tolerance of low oxygen conditions — at rest and while they were exercising for 15 minutes at top speed — at oxygen levels that would render most humans completely immobile. The researchers also conducted the experiments with the barnacle goose, which migrates at sea-level, and found that they did not have the same ability in low oxygen conditions.

Dr Lucy Hawkes, of the Centre for Ecology and Conservation at the University of Exeter’s Penryn Campus, said: “It all seems to come down to how much oxygen bar-headed geese can supply to their heart muscles. The more they can supply, the faster they can beat their hearts and keep the supply of oxygen to the rest of the body going. This suggests that other species, including humans, are limited more by what our hearts can do than by how fit the rest of our muscle are at altitude.” Dr Hawkes, formerly of BangorUniversity, added: “The wider implications of these findings are for low oxygen medical conditions in humans, such as heart attack and stroke — suggesting what adaptations might help prevent problems in the first place and learning how animals have managed to cope with really extreme environments.” Bar-headed geese and barnacle geese undertake similar long distance migratory flights between breeding and wintering grounds, usually covering thousands of miles, during the autumn and spring. Bar-headed geese travel from Indian wintering grounds and high Asian breeding grounds in China and Mongolia, which means that they have to cross the HimalayanMountains en route while flying as high as 7,290m (23,917ft). The animals have been shown to possess a number of specific physiological adaptations that may increase their performance relative to other species of geese when exposed to severe environmental hypoxia (inadequate oxygen supply). In particular, their heart and locomotor muscles contain more blood vessels.

http://www.sciencedaily.com/  Science Daily

April 29, 2014

http://www.sciencedaily.com/releases/2014/04/140407192800.htm  Original web page at Science Daily

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Ancient shrimp-like animals had ‘modern’ hearts and blood vessels

In 520 million-year-old fossil deposits resembling an ‘invertebrate version of Pompeii,’ researchers have found an ancestor of modern crustaceans revealing the first-known cardiovascular system in exquisitely preserved detail. An international team of researchers from the University of Arizona, China and the United Kingdom has discovered the earliest known cardiovascular system, and the first to clearly show a sophisticated system complete with heart and blood vessels, in fossilized remains of an extinct marine creature that lived over half a billion years ago. The finding sheds new light on the evolution of body organization in the animal kingdom and shows that even the earliest creatures had internal organizational systems that strongly resemble those found in their modern descendants. “This is the first preserved vascular system that we know of,” said Nicholas Strausfeld, a Regents’ Professor of Neuroscience at the University of Arizona’s Department of Neuroscience, who helped analyze the find. Being one of the world’s foremost experts in arthropod morphology and neuroanatomy, Strausfeld is no stranger to finding meaningful and unexpected answers to long-standing mysteries in the remains of creatures that went extinct so long ago scientists still argue over where to place them in the evolutionary tree. The 3-inch-long fossil was entombed in fine dustlike particles — now preserved as fine-grain mudstone — during the Cambrian Period 520 million years ago in what today is the Yunnan province in China. Found by co-author Peiyun Cong near Kunming, it belongs to the species Fuxianhuia protensa, an extinct lineage of arthropods combining advanced internal anatomy with a primitive body plan.

“Fuxianhuia is relatively abundant, but only extremely few specimens provide evidence of even a small part of an organ system, not even to speak of an entire organ system,” said Strausfeld, who directs the UA Center for Insect Science. “The animal looks simple, but its internal organization is quite elaborate. For example, the brain received many arteries, a pattern that appears very much like a modern crustacean.” In fact, Strausfeld pointed out, Fuxianhuia‘s vascular system is more complex than what is found in many modern crustaceans. “It appears to be the ground pattern from which others have evolved,” he said. “Different groups of crustaceans have vascular systems that have evolved into a variety of arrangements but they all refer back to what we see in Fuxianhuia.” “Over the course of evolution, certain segments of the animals’ body became specialized for certain things, while others became less important and, correspondingly, certain parts of the vascular system became less elaborate,” Strausfeld said. Strausfeld helped identify the oldest known fossilized brain in a different specimen of the same fossil species, as well as the first evidence of a completely preserved nervous system similar to that of a modern chelicerates, such as a horseshoe crab or a scorpion. “This is another remarkable example of the preservation of an organ system that nobody would have thought could become fossilized,” he said. In addition to the exquisitely preserved heart and blood vessels, outlined as traces of carbon embedded in the surrounding mineralized remains of the fossil, it also features the eyes, antennae and external morphology of the animal. Using a clever imaging technique that selectively reveals different structures in the fossil based on their chemical composition, collaborator Xiaoya Ma at London’s Natural History Museum was able to identify the heart, which extended along the main part of the body, and its many lateral arteries corresponding to each segment. Its arteries were composed of carbon-rich deposits and gave rise to long channels, which presumably took blood to limbs and other organs.

With that, we can now start speculating about behavior,” Strausfeld explained. “Because of well-supplied blood vessels to its brain, we can assume this was a very active animal capable of making many different behavioral choices.” Researchers can only speculate as to why the chemical reactions that occurred during the process of fossilization allowed for this unusual and rare kind of preservation, and as to why only select tissues were preserved between a few rare and different specimen. “Presumably the conditions had to be just right,” Strausfeld said. “We believe that these animals were preserved because they were entombed quickly under very fine-grained deposits during some kind of catastrophic event, and were then permeated by certain chemicals in the water while they were squashed flat. It is an invertebrate version of Pompeii.” Possibly, only one in thousands of fossils might have such a well-preserved organ system, Strausfeld said. At the time Fuxianhuia crawled on the seafloor or swam through water, life had not yet conquered land. “Terrible sand storms must have occurred because there were probably no plants that could hold the soils,” Strausfeld said. “The habitats of these creatures must have been inundated with massive fallouts from huge storms.” “As the water withdraws, animals on the seafloor dry,” Strausfeld said. “When the water rushed back in, they might become inundated with mud. Under normal circumstances, when animals die and are left to rot on the seafloor, they become unrecognizable. What happened to provide the kinds of fossils we are seeing must have been very different.”

http://www.sciencedaily.com/  Science Daily

April 29, 2014

http://www.sciencedaily.com/releases/2014/04/140407090727.htm  Original web page at Science Daily

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Researchers examined how muscle physiology effects leanness

We all know the type: The friend or colleague who stays slim and trim without much effort and despite eating the same high-calorie fare that causes everyone else to gain weight. As it turns out, the way the muscles of the inherently thin work may give them the edge. Daily physical activity is an inherited trait with a strong association to how fat or thin a person is. Chaitanya K. Gavini et al. previously found that aerobic capacity is a major predictor of daily physical activity level among humans and laboratory animals. In their new study, they compared female rats with high aerobic capacity (genetic tendency toward leanness) or low aerobic capacity (genetic tendency toward obesity) to investigate how muscle physiology affects leanness. Though the rats in each group were similar in weight and lean body mass, the rats with a high aerobic capacity were consistently more active than the low capacity rats. While all the rats had similar energy expenditures when at rest, big differences in energy expenditure (calorie burn) occurred during mild exercise. The researchers found the muscles of rats with lean genes demonstrated “poor fuel economy,” meaning that they burned more calories when performing the same exercise as those with fat genes. This may be due to more lean rats having higher levels of proteins that support energy expenditure and lower levels of proteins that encourage energy conservation and/or an increased sympathetic nervous system role in powering the muscles of lean rats. According to the researchers: “This has implications for how we consider metabolism when attempting to prevent or treat obesity. Targeting of pathways maximizing skeletal muscle energy use during physical activity may take advantage of already existing mechanisms that are endogenously employed to a greater extent in naturally lean people.” The article “Leanness and heightened nonresting energy expenditure: role of skeletal muscle activity thermogenesis” is published in the March 2014 issue of the American Journal of Physiology — Endocrinology and Metabolism.

http://www.sciencedaily.com/ Science Daily

April 15, 2014

http://www.sciencedaily.com/releases/2014/03/140320173416.htm  Original web page at Science Daily