Archive for May, 2008

Stem cells only grow up properly in the right environment

By Ed Yong | May 31, 2008 2:00 pm


Blogging on Peer-Reviewed Research
Children can be fed with good food but they will only become productive members of society if they’re raised in a rich, nurturing environment. Now scientists have shown that the same is true for stem cells.

mouse_embryonic_stem_cells.jpgOur bodies are made up of hundreds of different types of cells, but stem cells can become all of them. For example, one group – the mesenchymal stem cells (MSCs) – can give rise to nerve cells, muscle-building cells, and bone-building cells.

Because of this ability, many scientists have lauded stem cell treatments as the next big thing in medicine. Injuries and diseases could be treated by using a patient’s own stem cells to grow genetically matching tissues and organ.

Some therapies, such as bone marrow transplants for leukaemia patients, are now in limited use and others are at the experimental stage. But overall, progress has been slow and stem cell research has been beset by a range of technical (not to mention moral) difficulties.

One of the main challenges has been finding out how to consistently get stem cells to produce the right type of daughter cell. Stem cells take a wide range of variables into account before they commit to becoming a specific cell type. These include the chemicals and proteins that they are exposed to, how closely packed they are, and even their shape. Adam Engler and colleagues from the University of Pennsylvania can now add another thing to this list – their surroundings.

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CATEGORIZED UNDER: Medicine & health

Computer predicts brain activity associated with different objects

By Ed Yong | May 29, 2008 2:00 pm

Blogging on Peer-Reviewed ResearchThink of celery, an airplane or a dog. Each of these words, along with the thousands of others in the English language, create a different and unique pattern of activity in your brain. Now, a team of scientists has developed the first computer programme that can predict these patterns for concrete nouns – tangible things that you can experience with your senses.

With an accuracy of around 70%, the technique is far from perfect but it’s still a significant technological step. Earlier work may have catalogued patterns of brain activity associated with categories of words, but this is the first to predict activity using a computer model. More fundamentally and perhaps more importantly, it sheds new light on how our brains organise and represent knowledge.

Tom Mitchell and colleagues from Carnegie Mellon University built their model by using a technique called functional magnetic resonance imaging (fMRI) to visualise the brain activity of nine volunteers, as they concentrated on 60 different nouns. This ‘training set’ consisted of five words from each of 12 categories, such as animals, body parts, tools and vehicles.

Mitchell analysed how these words are used with the help of a “text corpus“, a massive set of texts containing over a trillion words. A text corpus reflects how words are typically used in the English language. Linguists have used these tools to show that a word’s meaning is captured to some extent by other words and phrases that it frequently appears next to.

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Monkey see, monkey control prosthetic arm with thoughts

By Ed Yong | May 28, 2008 1:00 pm

Blogging on Peer-Reviewed ResearchThe realm of science-fiction has just taken a big stride towards the world of science fact, with the creation of a prosthetic arm that can be moved solely by thought. Two monkeys, using only electrodes implanted in their brains, were able to feed themselves with the robotic arm complete with working joints.

Monkeyreach.jpgBionic limbs have been fitted to people before but they have always worked by connecting to the nerve endings in the chest. This is the first time that a prosthetic has been placed under direct control of the relevant part of the brain.

The study, carried out by Meel Velliste from the University of Pittsburgh, is a massive leap forward in technology that lets the brain interface directly with machines. Previously, the best that people could do was to use a cap of electrodes to control the movement of an animated computer cursor in three-dimensional space. Velliste’s work shows that signals from the brain can be used to operate a realistically jointed arm that properly interacts with objects in real-time.

The applications of the technology are both significant and obvious. Amputees and paralysed people could be kitted out with realistic prosthetics that afford them the same level of control as their lost limbs.

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'Wolverine' frogs pop retractable claws from their toes

By Ed Yong | May 27, 2008 7:00 pm

Blogging on Peer-Reviewed ResearchIn the X-Men comics, the superhero Wolverine is armed with three sharp claws on each arm. They extend through the skin of his hand, and the resulting wounds are closed by up his superhuman ability to heal. Now, in a bizarre case of life imitating art, scientists from Harvard University have discovered that a group of African frogs use similar weapons.

Wolverinefrog.jpgThe frogs defend themselves with sharp bone claws on their hind feet but to do so, the animals have to drive the claws through their own skin. It’s an extreme defence that is completely unique in the animal world.

The clawed frogs belong to a family called Arthroleptidae that were discovered in Central Africa more than a century ago. At first, people wondered if the claws just stuck through the skin as a side effect of the preservation process. Alternatively, the frogs may have used them to grip or climb. Their true function as defensive weapons only became clear when naturalists first described actually picking up and handling live animals.

Doing so is a mistake, and anyone who makes it is punished with a series of deep, bleeding wounds inflicted by the struggling animal as it kicks out violently with its claws. The ability is well known to the people of Cameroon, who only ever hunt the frogs with machetes or spears.

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Hatena – when two cells are better than one

By Ed Yong | May 24, 2008 12:00 pm

Revisited.jpgThe prisoner was plucked from a free-living existence and plunged, without trial, into a cell from which it will never leave. It will be provided with food but will have to cater to the needs of its jailer, bereft of its own independence. And yet, this apparent injustice will go unchallenged. No liberal hackles will be raised and no bags of angry letters from Amnesty International will flood the oppressor’s mailbox.

Blogging on Peer-Reviewed ResearchFor this event did not occur in the world of autocrats and tyrants, but in that of a microscope slide. The captor measures less than a thirtieth of a millimetre across and its captive is smaller still. Even so, their relationship is a snapshot of one of the most important events in the planet’s history.

Mitochondrion.jpgThis story begins with scientists Noriko Okamoto and Isao Inouye from the University of Tsukuba, Japan. During a routine sampling of sand from a local beach, they discovered a unique microscopic creature, so puzzling that they named it Hatena, the Japanese word for ‘enigmatic’. Hatena is a made up of just a single cell, like the famous Amoeba.

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CATEGORIZED UNDER: Cooperation, Evolution, Plants

Gut bacteria reflect diet and evolutionary past

By Ed Yong | May 22, 2008 2:00 pm

Blogging on Peer-Reviewed ResearchOur bodies are rife with genes and the majority of them aren’t even ours. We all have a strong sense of our own individuality, but the truth is that our bodies are hotels for a diverse array of microbes including bacteria and fungi. The numbers are simultaneously creepy and humbling. Tot up all the cells in our bodies and the microbial ones would outnumber our own by a factor of ten. The five feet of our large intestine houses the majority of these microorganisms and contain up to 100 trillion of them.

EscherichiaColi_NIAID.jpgThese single-celled tenants are known as the microbiota and they carry their own sets of genes. Some of these are incredibly important to us because they allow us to break down food and nutrients (including dairy products) that we couldn’t digest by relying on our own genomes. They might even affect our bodyweight. Despite the importance of the microbiota, it’s still unclear how unique our particular array of species is, how it has evolved over time and how it relates to our broad diets (that’s broad in mammalian terms; I know some people only seem to ever eat fast food…)

Ruth Ley from the Washington University School of Medicine has started to answer that question by carrying out the first extensive comparison of the bacterial communities that live in the guts of different mammals. Her analysis found that these communities have co-evolved with their hosts and their members are strongly influenced by both diet and evolutionary history.

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Snake proteins have gone through massive evolutionary redesign

By Ed Yong | May 21, 2008 8:00 am

Blogging on Peer-Reviewed Research
The era of genetic sequencing has revealed as much about the ties that bind us to other animals as the differences that set us apart. Often, comparing the genomes of different species shows that large changes in body size, shape and form are not mirrored by similar changes at a genetic level. New adaptations typically come about through small changes that redeploy existing genes to different ends, rather than raw innovation.

Python3.jpg Snakes are an exception. A new study by Todd Castoe and Zhi Jiang at the University of Colorado has shown that the lifestyle of serpents is so unique that some of their core proteins, which vary very little in other animal species, have gone through massive changes. These bursts of evolution have been so dramatic that Castoe and Jiang refer to them as “evolutionary redesigns”.

The proteins in question are all involved in aerobic metabolism, the breakdown of molecules like sugars and fats in the presence of oxygen to release energy. Large-scale changes in these proteins may have contributed to the incredible metabolic abilities of snakes, which are unique in the animal world.

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CATEGORIZED UNDER: Animals, Evolution, Genetics, Reptiles, Snakes

Carbon nanotubes could behave like asbestos

By Ed Yong | May 20, 2008 1:00 pm

Blogging on Peer-Reviewed Research
In the late 19th century, asbestos became a building material of choice. Resistant to heat, electricity and corrosion, it found many uses including  home insulation, brake pads and ship-building. By the time that the first health problems were reported, the material was commonplace. In the UK, the material was only restricted in 1983 after thousands of people were exposed during the post-war era. The result is a latent epidemic of related diseases including a rare type of cancer called mesothelioma, which is becoming more common and is only expected to peak in incidence over the next decade or so.

Carbon-nanotubes.jpgThe glacial pace with which governments started to regulate asbestos use has put thousands of lives in jeopardy and it’s a disaster that we could do with not repeating. But while asbestos is yesterday’s construction material, a new substance being heralded as the building material of tomorrow has the potential to cause similar health risks – carbon nanotubes.

A new study suggests that carbon nanotubes can cause asbestos-like damage if they are injected into the bodies of mice. The results are cause for concern but not panic. The study didn’t show that the nanotubes can build up in body cavities of their own accord, nor if this damage would eventually result in the mesotheliomas that asbestos can cause. It does however show that we are running before we can walk if the widespread commercial use of carbon nanotubes goes unregulated without rigorous research on their safety.

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Feeling powerless impairs higher mental abilities

By Ed Yong | May 19, 2008 12:00 pm

Blogging on Peer-Reviewed ResearchFeeling powerless is no fun. A lack of control can make the difference between contented and unhappy employees. But new research shows that a lack of power doesn’t just make people feel disgruntled. It has a more fundamental effect on their mental skills.

Cartman.jpgIn a series of experiments, Pamela Smith from Radboud University Nijmegen has shown that the powerless actually take a measurable hit to important mental abilities. Even if people are subconsciously primed with the concept of being powerless, they perform more poorly at tasks designed to assess their ability to plan, focus on goals and ignore distractions.

According to previous research, a lack of power forces people to constantly re-evaluate their own goals and monitor more senior individuals. Without authority, a person’s actions rely on instructions and may constantly change at the whim of their superiors, whose own motives and goals must be guessed at. Monkeys show similar behaviour. Studies have found that subordinate rhesus males follow the gaze of those with higher status, while dominant individuals only look in the same direction as others with greater standing.

Smith reasoned that this constant re-evaluation draws the brain’s resources away from other needs, including a set of mental abilities known as “executive functions“. The term is loosely defined but accurately named and refers to a set of master processes that govern and control more basic abilities, like attention and motor skills. They allow us to plan for the future, adapt to new situations and carry out our goals. They allow us to carry out actions that further our goals while restraining us from those that hamper them.

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CATEGORIZED UNDER: Neuroscience and psychology

Aphids get superpowers through sex

By Ed Yong | May 17, 2008 12:00 pm

Revisited.jpgAs far as humans are concerned, sexually-transmitted infections are things to avoid. But imagine if these infections didn’t cause death and disease, but gave you superpowers instead. It may sound like a bizarre fantasy, but it’s just part of life for aphids.

Blogging on Peer-Reviewed ResearchAphids mostly reproduce without sex, giving rise to many all-female generations that are exact copies (clones) of their parents. They only have sex once in autumn, the only time when mothers give birth to males. Asexual reproduction makes sense for aphid mothers since they pass on all of their genes to their daughters. If they reproduced sexually, their offspring would only inherit half of their genes, diminishing their legacy. Why then would a female aphid choose to have sex at all?

Nancy Moran and Helen Dunbar at the University of Tuscon a surprising answer. They may be trying to receive sexually-transmitted infections from other aphids. Aphids carry various strains of bacteria inside their bodies. These ‘symbionts’, far from causing disease, actually provide the aphids with useful abilities. Some strains allow them to feed off a greater variety of plants, while others give them the ability to withstand higher temperatures. Some can even save their lives.

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