Posts Tagged ‘biology’

Not having enough vitamin B12 can shrivel your brain. No, really. [Neuroscience]

29 Sep
Anyone ever told you that if you don't get your vitamins, your brain will shrink? No? Well they should. It turns out that having a vitamin B12 deficiency later in life is pretty bad for your grey matter. A group of researchers looked at over-65s from the South Side of Chicago, and measured the amount of vitamin B12 and B12-related metabolites in their blood, their cognitive skills, and took MRIs of them. More »

Bird Flight Might Have Started With Legs, Not Wings

18 Aug

To take flight, first strengthen your legs: It sounds like a self-help proverb, but it could explain how birds first took wing.

Until now, most explanations of the evolution of flight have assumed that going airborne was an end in itself, driven by the need of some early dinosaur to glide down from trees or up off the ground.

But flight could have instead been an incidental benefit of beefier muscles needed to compensate for losing a heat-generating protein.

“Flight is seen as the hallmark of bird evolution,” said developmental biologist Stuart Newman of the New York Medical College. “But you can make the argument that the particular form bird skeletons took that opened the way for flight was a side effect.”

Newman’s research shows that all birds and reptiles lack a single gene that codes for a protein called UCP1 or, with a nod to its function, thermogenin. It’s an essential part of the metabolic reaction that burns brown fat, helping bodies self-regulate internal temperature and generate heat without shivering.

Thermogenin’s absence from birds and reptiles hints at its loss in some early common ancestor, with the thermogenin-retaining relative later giving rise to mammals. But whereas reptiles became cold-blooded, basking in sunshine when needed, birds stayed warm-blooded.

Image: Markiza/Flickr

As Newman describes in a September Bioessays paper, the key to their warmth is muscles. Muscles are powerful generators of heat, which is a byproduct of the chemical reaction that makes them contract. Bird muscles also have further heat-generating adaptations. And birds are, in a word, jacked.

In ounce-for-ounce comparison, mammals and reptiles are scrawny weaklings next to birds. And it’s not just avian breast muscles that are pumped, as would be expected in flyers, but their legs too.

“My hypothesis is that birds basically salvaged their existence by developing very large skeletal muscles,” said Newman.

Once heavily muscled, he believes proto-birds would naturally have gravitated towards bipedalism, which isn’t a particularly challenging transition. Indeed, walking on two legs was widespread in dinosaurs.

Bipedality releases upper limbs, both literally and in evolutionary terms, allowing them to accumulate large mutations with relatively little risk. Combine that with powerful breast muscles, and wings would soon follow.

Testing Newman’s hypothesis may not be possible, as it would require comparing early bird and dinosaur skeletons and genes, and DNA is lost in the fossil record. But that flight could plausibly have been a fortunate side effect of some unrelated adaptation, rather than the original driver of bird development, is a useful evolutionary lesson.

Newman also suggests people at least reconsider the phenomenon of flightlessness in birds, which is generally portrayed in terms of loss.

“It’s almost universally accepted that all flightless birds come from flighted ancestors,” said Newman. “That might be true — but maybe it’s flying birds that have flightless ancestors. Maybe flightless birds were the leading edge.”

Top image: Lip Kee Yap/Flickr

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Citation:”Thermogenesis, muscle hyperplasia, and the origin of birds.” By Stuart Newman. Bioessays, Vol. 33 No. 9, September 2011.


Gibbons defy their own evolution to jump as high as they can [Monkey News]

10 Aug
Most jumping animals - such as frogs and grasshoppers - have some powerful adaptations that basically make their legs into giant springs. But our ape cousins manage to leap insane distances through sheer force of will, without any helpful adaptations. More »

Potato chips — the other natural way to get stoned [Food Science]

05 Jul
Scientists have found out why people can put the brakes on eating sugar, but will go through an entire bag of potato chips, followed by a plate of fries. It turns out that fats get us stoned. More »

Learning how the brain does its coding

06 May

Most organisms with brains can store and process a staggering range of information. The fundamental unit of the brain, a single neuron, however, can only communicate in the simplest of manners, by sending a simple electrical pulse. The challenge of understanding how information is contained in the pattern of these pulses has been bothering neurobiologists for decades, and has been given its own name: neural coding.

In principle, there are two ways coding could be handled. In dense coding, a single neuron would convey lots of information through a complex series of voltage spikes. To a degree, however, this creates as many problems as it solves, since the neuron on the receiving end will have to be able to interpret this complex series properly, and separate it from operating noise.

The alternative, sparse coding, tends to be used for memory recall and sensory representations. Here, a single neuron only conveys a limited amount of information (i.e., there's something moving horizontally in the field of vision) through a simple pulse of activity. Detailed information is then constructed by aggregating the inputs of lots of these neurons.

A study released in yesterday's Science provides some perspective on just how flexible this sort of system can be. Researchers worked with the olfactory system of insects, where structures in the brain called mushroom bodies integrate the inputs from sensory neurons. (they're called mushroom bodies for the highly technical reason that they're shaped kind of like a mushroom.) The mushroom bodies use sparse coding to interpret and recall odors, with most neurons only firing a few times in response to a scent.

The authors of the paper traced the connections among the neurons in the mushroom body, and found that most were contacted by a single, giant interneuron that sent them inhibitory signals. By toning all the other neurons down, this giant cell enforces sparse coding by limiting the amount of activity that is elicited by a new odor. It also allows the fine tuning of activity for the entire mushroom body. Increasing its activity is sufficient to shut the entire system down, essentially making the insect blind to smells, while decreasing its activity will make the insect hypersensitive to scents.

Although us mammals don't have neurons of this sort—they appear to be an innovation exclusive to the insects—the authors predict that a system that functions similarly may be found in vertebrates, simply because it's so simple and functional.

Science, 2011. DOI: 10.1126/science.1201835  (About DOIs).

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The first sign that humans are on the verge of evolving into another species [Evolution]

28 Apr
A scientist who studies the small, silver elephantfish may have stumbled on the key to speciation, the process that allows one species to evolve into two or more. And it's all about developing new sensory perceptions. More »

We can reverse the aging process in bees’ brains. Could humans be next? [Neuroscience]

21 Mar
Bees can become mentally young again with just a few simple alterations to their otherwise fixed routines. Because the brains of bees are surprisingly like our own, this trick could help fight dementia and keep human minds young and flexible. More »

Nerve-Electronic Hybrid Could Meld Mind and Machine

21 Mar

Nerve-cell tendrils readily thread their way through tiny semiconductor tubes, researchers find, forming a crisscrossed network like vines twining toward the sun. The discovery that offshoots from nascent mouse nerve cells explore the specially designed tubes could lead to tricks for studying nervous system diseases or testing the effects of potential drugs. Such a system may even bring researchers closer to brain-computer interfaces that seamlessly integrate artificial limbs or other prosthetic devices.

sciencenews“This is quite innovative and interesting,” says nanomaterials expert Nicholas Kotov of the University of Michigan in Ann Arbor. “There is a great need for interfaces between electronic and neuronal tissues.”

To lay the groundwork for a nerve-electronic hybrid, graduate student Minrui Yu of the University of Wisconsin–Madison and his colleagues created tubes of layered silicon and germanium, materials that could insulate electric signals sent by a nerve cell. The tubes were various sizes and shapes and big enough for a nerve cell’s extensions to crawl through but too small for the cell’s main body to get inside.

When the team seeded areas outside the tubes with mouse nerve cells, the cells went exploring, sending their threadlike projections into the tubes and even following the curves of helical tunnels, the researchers report in an upcoming ACS Nano.

“They seem to like the tubes,” says biomedical engineer Justin Williams, who led the research. The approach offers a way to create elaborate networks with precise geometries, says Williams. “Neurons left to their own devices will kind of glom on to one another or connect randomly to other cells, neither of which is a good model for how neurons work.”

At this stage, the researchers have established that nerve cells are game for exploring the tiny tubes, which seem to be biologically friendly, and that the cell extensions will follow the network to link up physically. But it isn’t clear if the nerves are talking to each other, sending signals the way they do in the body. Future work aims to get voltage sensors and other devices into the tubes so researchers can eavesdrop on the cells. The confining space of the little tunnels should be a good environment for listening in, perhaps allowing researchers to study how nerve cells respond to potential drugs or to compare the behavior of healthy neurons with malfunctioning ones such as those found in people with multiple sclerosis or Parkinson’s.

Eventually, the arrangement may make it easier to couple living cells with technology on a larger scale, but getting there is no small task, says neuroengineer Ravi Bellamkonda of the Georgia Institute of Technology in Atlanta.

“There’s a lot of nontrivial engineering that has to happen, that’s the real challenge,” says Bellamkonda. “It’s really cool engineering, but what it means for neuroscience remains to be seen.”

Images: Minrui Yu

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"The most delicious fruit known to men" has been bioengineered to be even better [Food Science]

18 Mar
One of the reasons bananas enjoy their rampant popularity is that the kinds you buy in stores are hideously mutated versions of the original, bred to not have the inedible seeds their wild brethren so proudly display. Thanks to new research we may soon be seeing other fruit making the transition to seedlessness, and filling our grocery shelves. Bioengineers have successfully tweaked the custard apple, charimoya (called by Mark Twain "the most delicious fruit known to men") and the sugar apple — all of which are delicious but require nimble teeth if you want to avoid their seeds. These plants could provide new farming opportunities and delights in the produce section - plus, there's a possibility the research could be adapted to even more fruit. Get ready for the delicious, seedless future! More »

Semiconductors threaded with nerve cells could be the first step toward biological computers [Cyborgs]

18 Mar
We assumed that in the future humans, or other biological entities, would receive mechanical or electronic 'upgrades'. It looks like it could be the other way around. Machines might be getting biological upgrades. More »