SVTR

http://www.futura-sciences.com/news-moelles-epinieres-souris-partie-reparees-nanotechnologie_10718.php Le Dr Samuel I. Stupp, directeur de l'Institute of BioNanotechnology in Medicine de la Northwestern University vient de faire une annonce stupéfiante lors d'une conférence du 23 avril dans le cadre du Project on Emerging Nanotechnologies. En injectant des nanomolécules, capables de s'auto-assembler pour former des nanofibres à l'intérieur des tissus vivants, lui et son équipe ont réussi à tellement stimuler les capacités autoréparatrices de souris dont la moelle épinière avait été endommagée...qu'elles ont retrouvé en partie l'usage de leurs membres !

Published online: 30 April 2007; | doi:10.1038/news070430-2

Seeing the blues

Having different words for light and dark blue may change how you see them.

Michael Hopkin

Which is different? Russians, who have different words for light and dark blue, can hit the answer more quickly. PNAS

The language you speak may influence how you perceive colours, according to new research. Russian speakers, who have separate words for light and dark blue, are better at discriminating between the two, suggesting that they do indeed perceive them as different colours.

Russian speakers divide what the English language regard as 'blue' into two separate colours, called 'goluboy' (light blue) and 'siniy' (dark blue). And a test now shows that this seems to help them view light and dark blue as distinct.

Researchers led by Jonathan Winawer of Massachusetts Institute of Technology in Cambridge presented Russian and English speakers with sets of three blue squares, two of which were identical shades with a third 'odd one out'. They asked the volunteers to pick out the identical squares.

Russian speakers performed the task more quickly when the two shades straddled their boundary between goluboy and siniy than when all shades fell into one camp. English speakers showed no such distinction.

What's more, when the researchers interfered with volunteers' verbal abilities by asking them to recite a string of numbers in their head while performing the task, the Russian effect vanished. This shows that linguistic effects genuinely do influence colour perception, they report in Proceedings of the National Academy of Sciences.

Do you see what I see? To English speakers, this is a range of a single colour. But that's not true in other languages. PNAS

"It could be that there is a pre-existing tendency to divide colours that exists in everyone, and that Russian has exploited but English has not," Winawer says.

I say blue, you say goluboy

The results support a theory called the Whorfian Hypothesis, proposed in the 1930s by American linguist Benjamin Whorf, that our words literally shape how we categorize things we observe in the world around us.

"The critical difference in this case is not that English speakers cannot distinguish between light and dark blues, but rather that Russian speakers cannot avoid distinguishing them: they must do so to speak Russian in a conventional manner," Winawer and his colleagues write.

"Russian is a very interesting test case," comments Angela Brown, who studies colour perception at Ohio State University in Columbus. Only around 5% of languages make a distinction between light and dark blue, she says.

But Brown argues that although Winawer's results are consistent with the theory that language shapes perception, they do not necessarily prove it. The order of cause and effect could be the other way around, she says. Most languages with a range of words for blue tend to be found at high northern latitudes, she points out. Perhaps there is a physiological effect that makes people in these climes more adept at seeing shades of blue.

There is no direct evidence for this. But it is known that many tropical peoples do not distinguish between blue and green - linguists call this combined colour 'grue'. It has been suggested that this is because their lenses are more yellowed, or their retinas damaged, by bright sunlight, Brown says. This implies that physical effects might shape language, rather than language shaping perception.

"The question the researchers will have to answer is whether Russians have a word for light blue because they see it as distinct, or whether it is the other way around," Brown says.

References : Winawer J., et al. Proc. Natl Acad. Sci. USA, doi:10.1073/pnas.0701644104 (2007).

Published online: 2 May 2007; | doi:10.1038/news070430-5 / http://www.nature.com/news/2007/070430/full/070430-5.html

Human ancestors went underground for dinner

Like mole rats, hominins may have had a diet rich in bulbs and tubers.

Michael Hopkin

Paranthropus robustus was perhaps smart enough to dig for food. MAURICIO ANTON/ SCIENCE PHOTO LIBRARY

Palaeontologists have turned to an unlikely source in a bid to uncover the dietary habits of some of humanity's oldest ancestors. They have studied the teeth of mole rats found in South Africa to bolster the theory that prehistoric hominins may have eaten underground bulbs and tubers, rather than meat or grass.

African mole rats, which live underground and eat starchy plant organs such as bulbs, have similar chemical signatures in their teeth to those of two ancient hominin species found at the same site, the new research shows. This suggests that they may have had similar diets.

The discovery helps to solve a paradox surrounding the diets of Australopithecus africanus and Paranthropus robustus, which lived in southern Africa around 2.5 million and 1.5 million years ago, respectively. When the chemical signatures of their teeth were recently analysed, the results suggested that these hominins ate grassy plants, or the remains of animals that had eaten such plants. But their flat, wide teeth, while good for crushing hard objects, would have been useless at tearing through these tough foods.

A group led by Justin Yeakel of the University of California, Santa Cruz, reasoned that one solution to this problem would be if hominins chewed on the starchy bulbs and tubers from those same grassy plants, rather than tearing up the upper green portions. That would explain both the chemical signature and the design of their teeth.

"Hominins had teeth like ours, which were designed to eat something really, really hard, like small seeds - not tough grasses or raw meat," says Yeakel's colleague Nathaniel Dominy.

Chew on this

The chemical signature in teeth comes about because different foods have a distinctive mixture of carbon isotopes, which shows up in the teeth of animals that eat those foods. Grassy plants, for example, give a particular isotopic signature.

The researchers looked for this signature in the teeth of present-day mole rats (Cryptomys) and in fossilized mole-rat remains from almost 2 million years ago. As they report in Proceedings of the Royal Society B¹, the range of isotopes seen in these species overlaps with that found in A. africanus and P. robustus.

"This study certainly adds to the body of evidence that the diet of early hominins included bulbs, corms and possibly tubers," says Dominy. These categories include modern-day foods such as the shallot, taro and yam, respectively.

Although one might expect creatures that live underground to feed primarily on underground plant material, how did early humans develop the habit? "Our early ancestors had the advantage of a relatively large brain to help recognize specific plants and to make simple tools for extracting them from the ground," Dominy says.

References : Yeakel J. D., Bennett N. C., Koch P. L. & Dominy N. J. Proc. R. Soc. B, doi:10.1098/rspb.2007.0330 (2007).