#Leprosy bug turns adult cells into stem cells Leprosy bacteria can reprogram cells to revert to a stem-cell-like state,
able to mature into different cell types, researchers report today in Cell1. The scientists stumbled on the discovery
while researching the way leprosy spreads around the body. The mechanism of the hijacking is unclear,
but reproducing it could lead to new stem-cell-based therapeutic strategies. The initial target of the leprosy bacterium#Mycobacterium leprae#is Schwann cells,
which are part of the peripheral nervous system. Like rubber around an electric wire, the cells wrap around nerves to insulate the electric signals passing through.
The researchers isolated Schwann cells from mice and infected them with M. leprae. The bacteria reprogrammed the cells into a stem-like state,
turning off genes associated with mature Schwann cells and turning on embryonic or developmental ones. The bacteria appeared to trigger Schwann cells'plasticity,
the ability to revert to an immature state and turn into new types of cells. Healthy Schwann cells do so to help nerves recover
and regenerate after an injury.)""This is a very sophisticated mechanism#it seems that the bacterium knows the mechanistic interaction of the Schwann cell better than we do,
says Anura Rambukkana, a regeneration biologist at the University of Edinburgh, UK, who led the study.
The researchers do not know what triggers the reprogramming event but they suspect that the mechanism could exist in other infectious diseases."
"Cellular plasticity may represent an underlying mechanism of disease, as other cellular reprogramming events have been shown in cancers
and metabolic diseases, says Sheng Ding, a stem-cell biologist at the Gladstone Institute of Cardiovascular disease in San francisco, California.
A greater understanding of these precise mechanisms could improve treatment and earlier diagnosis of leprosy itself.
Before this experiment, scientists did not know how the bacteria spread through the body. The latest findings could provide clues about how to catch the disease before it does so.
In the future, bacteria could be used to change adult tissue cells into stem cells in the laboratory
potentially leading to new regenerative treatments for diseases such as diabetes and Alzheimer s z
#Nanomaterial rivals hardness of diamond An article by Scientific American. It s only a matter of time before a movie villain pulling off the crime of the century needs a cutting tool that is harder than anything else On earth.
Perhaps it s a burglary that involves cutting into a case made of diamond#which,
as we have learned all from countless heist films, is itself hard enough to cut glass. Or maybe it s a devious scheme predicated on boring a hole into the depths of the planet with the world s hardest drill bit.
Whatever the plot details scientifically minded scriptwriters would do well to turn their attention to cubic boron nitride,
a material that in many ways resembles diamond. Boron nitride can be compressed into a superhard, transparent form#but unlike diamond and many other materials known for their extreme hardness,
it is based not on carbon but on a latticework of boron and nitrogen atoms. Computer simulations have indicated that a rare crystalline form of boron nitride would resist indentation even better than diamond
if it could be synthesized into large samples, and laboratory experiments have shown that more attainable forms of the stuff already approach the hardness of diamond.
Now a new set of experiments on a nanostructured form of boron nitride have yielded even greater measures of hardness than before.
The new material exceeds that of some forms of diamond, according to the authors of a study reporting the findings in the January 17 issue of Nature.
Scientific American is part of Nature Publishing Group. But quantifying the properties of superhard materials is a tricky business,
and at least one leading researcher remains unconvinced that the study s authors have found anything new.
For years scientists have worked to shrink the individual grains within material structures, because the boundaries between grains can arrest internal motion
like a series of tiny walls within a larger structure. The essence of the researchers strategy for this latest effort, says lead study author Yongjun Tian of Yanshan University in China,
was to reduce the scale of the microstructures within the material by generating features called"ultrafine nanotwins.
As such, a polycrystal made of nanotwin domains is a bit like a slab of plywood where the wood grain reverses direction in each successive layer.
In the boron nitride polycrystals synthesized by Tian and his colleagues, the nanotwin segments are just 3. 8 nanometers wide on average.
A nanometer is one billionth of a meter. The researchers fabricated their samples from round nanoparticles of boron nitride in
which the atoms of nitrogen and boron form an onionlike structure of nested layers. Pressed into macroscopic pellets
and subjected to intense pressure and heat, the nanoparticles coalesced into tiny grains comprising numerous twin domains.
The onionlike precursors, Tian explains, contain numerous defects where crystals can nucleate under high temperature and pressure but resist rapid crystal growth,
yielding numerous discrete pockets of crystalline order within a larger, somewhat disordered polycrystalline structure. At temperatures above 1, 800 degrees Celsius and pressures of up to 15 gigapascals (roughly 150
000 kilograms-force per square centimeter), the boron nitride pellets formed round lumps about two millimeters across that were"colorless and totally transparent,
so that they look like glass and diamond in appearance, Tian says. He and his colleagues determined that those samples had measured a hardness of up to 108 gigapascals#slightly harder than synthetic diamond
but less hard than polycrystalline diamonds made of nanoscale grains. But Natalia Dubrovinskaia, a crystallographer at the University of Bayreuth in Germany, notes that measuring the properties of superhard materials is problematic
because it requires the use of an even harder material for reference. The Vickers hardness test
for instance, which the new study s authors used to measure the hardness of nano-twinned boron nitride,
gauges how a material responds to pressure from the point of a pyramid-shaped piece of diamond called an indenter.
As increasing force (as measured in newtons) is applied to the diamond pyramid, the material s ability to resist indentation levels off at its so-called asymptotic value (as measured in gigapascals).
But the test is predicated on the idea that the diamond will do the indenting, and not the other way around."
"If the indenter is softer than the material under probe, it is absolutely meaningless, Dubrovinskaia says.
Boron nitride already finds use in cutters that can slice through extremely tough materials, and Dubrovinskaia cites drilling for resource extraction as another application."
In some respects, such as stability at high temperatures, boron nitride is superior to diamond. More from Scientific American. As such, she notes,
if researchers proved that polycrystalline boron nitride boasted hardness values over 100 gigapascals.""The paper doesn t provide any proof that the material is so hard,
The data in the new study only show how the nano-twinned boron nitride responded to indentation loads with up to seven newtons of force."
the true value for the boron nitride samples might be closer to 80 or 85 gigapascals.
and her colleagues reported in 2007 for another high-pressure, high-temperature synthesis of nanostructured boron nitride. In that work, published in Applied Physics Letters, Dubrovinskaia and her colleagues presented data from Vickers testing with loads of up to 10 newtons n
#Court lifts cloud over embryonic stem cells The US Supreme court s decision last week to throw out a lawsuit that would have blocked federal funding of all research on human embryonic stem cells
cleared the gloom that has hung over the field for more than three years. Yet the biggest boost from the decision might go not to work on embryonic stem (ES) cells,
Researchers flocked to the field soon after a recipe for deriving the cells from adult mouse cells was announced in 2006
say#for cell therapy. Although the number of published papers from ips-cell research has not yet caught up with that of ES-cell work (see Inducing a juggernaut),
US funding for each approach is matched now roughly at about US$120 million a year. C. T. Scott et al.
better behaved and backed by an extra decade s worth of data#promise to have an important supporting role.
researchers have been trying to understand just how similar they are to ES cells. ips cells begin with different patterns of gene expression,
and they can also acquire mutations during the reprogramming process, which means that every ips cell must be evaluated thoroughly before it can be used in any study."
who studies how stem cells retain embryo-like states at the University of Cambridge, UK.
The Supreme court s move has reassured investigators such as Candace Kerr, who studies early development of the brain at the University of Maryland School of medicine in Baltimore.
or fear adding to her work with experiments using ES cells, which she finds much easier to prompt into neurons than ips cells."
August 2001 US President George w bush restricts federal funding for work on human ES cells to a few extant lines.
March 2009 US President Barack Obama expands the number of human ES-cell lines eligible for funding.
April 2009 Paper reports successful derivation of human ips cells without the integration of genetic information into the cell genome.
September 2010 NIH-funded work is allowed to resume but eligibility for funding is uncertain as case works through the courts.
October 2010 Biotechnology company Geron doses first patient in world s first clinical trial to test an ES-cell product.
November 2011 Geron shuts down trial, saying it is a poor investment. January 2013 Supreme court lets stand ruling that the NIH can fund human ES-cell research.
January 2013 Geron agrees to sell stem-cell assets to a company run by two former Geron heads.
however, have a head start in the clinic. Former heads of the biotech company Geron, based in Menlo Park, California,
last week announced an agreement to acquire stem-cell assets including the company s flagship human ES-cell trial, in
which precursors of neural support cells grown from human ES cells were injected into people with spinal-cord injuries.
the spinal-cord trial would double the number of companies sponsoring human clinical trials for ES-cell therapies.
these are showing early evidence that a product made from human ES cells can help to rebuild the layer of cells that support photoreceptors in the eyes of people with certain types of blindness.
But ips cells are edging towards the clinic too. Advanced Cell Technology says that it will begin talking to the US Food
and Japan is setting up a stem-cell bank of some 75 ips-cell lines intended for future therapies.
Even James Thomson at the University of Wisconsin-Madison who isolated the first human ES cells in 1998,
#Quantum dots go on display Live from your living room, in super#saturated colour: it s the quantum dot TV!
Researchers working with nanoscale fluorescent particles called quantum dots have predicted long groundbreaking achievements, such as ultra-efficient light-emitting diodes (LEDS) and solar cells,
but the technology has found mainly niche applications. That could change with the announcement last week that QD Vision,
based in Lexington, Massachusetts, would supply Sony Corporation of Tokyo with quantum dots for flat-screen televisions that will transmit more richly coloured images than other TVS on the market.
Demand for quantum dot displays, say industry watchers, could benefit quantum dot companies, bring down the price of these nanomaterials
and boost other applications that have stalled.""Displays are a potential market that could help quantum dot companies find traction,
says Jonathan Melnick, an analyst at Lux Research in Boston, Massachusetts. Quantum dots are crystals about 10 nano#metres in diameter,
made from a semiconductor material, commonly cadmium selenide. They are so tiny that their shape
and size affect the quantum properties of their electrons, in particular their energy gap#the energy needed to kick electrons into a higher energy band#which determines the colour of light that the mater#ial can emit.
Whereas a bulk semiconductor is limited to emitting a single colour of light researchers can tune the precise colour a quantum dot will absorb
and re-emit by tailoring its size. Discovered in 1981, quantum dots did not find applications until 2002.
That was when the Quantum dot Corporation of Hayward, California, began selling them to cell biologists, who prize them as fluorescent imaging labels for proteins and other biological molecules.
As recently as 2010, the biomedical sector was responsible for US$48#million of $67#million in total quantum dot revenues, according to BCC Research of Wellesley, Massachusetts.
Quantum dots have shown promise for electronics, too#for example in solar cells in which a mix of quantum dots tuned to absorb different wavelengths of light could capture more of the energy in the solar spectrum.
But one hurdle to their exploitation was their temperature sensitivity. Near the backlight of a liquid-crystal display (LCD), for example, temperatures can be around 100#C. At this temperature,
the dots lose efficiency and up to half of their brightness, says QD Vision cofounder and chief technology officer Seth Coe-Sullivan.
He says that the company spent a long time tuning the chemistry of its quantum dots to make them stable at higher temperatures.
Moungi Bawendi a chemist at the Massachusetts institute of technology in Cambridge and a cofounder of QD Vision, admits that the company also made some business miscalculations.
For its first product, in 2009, it provided Nexxus Lighting of Charlotte, North carolina, with quantum dot coatings to convert the harsh glare of LEDS into a warmer glow,
to make them more appealing as long-life, low energy light bulbs. But Bawendi says that LED designs
and technology for the light-bulb market evolved too fast for the quantum dot coatings to keep up."
"You design something, and six months later it doesn t work, Bawendi says.""Television technology is more stable.
His optimism will be tested this spring with the company s quantum dot debut in Sony LCD televisions,
to be sold under the Tri#luminos brand name. The contrast with today s flat screens begins with the light source.
Conventional LCDS use a high-intensity blue LED backlight whose glow is converted by a phosphor coating to create a broadband,
white light used to make the moving TV images. The new Triluminos tele#visions instead pair an uncoated blue LED with a thin glass tube filled with quantum dots.
Two kinds of quantum dots in the tube absorb some of the blue light from the backlight
and re-emit it as pure red andgreen light. The resulting white light is more intense at the wavelengths of these three specific colours than the white light made by a phosphor-coated LED,
so that more colour comes through in the images. Another quantum dot company, Nanosys of Palo alto, California, is providing 3m of St paul, Minnesota,
with material for a similar product. 3m will make a polymer film seeded with quantum dots that does the same jobas QD Vision s glass tube.
The film is layered between the LCD s stack of light filters, diffusers and polarizers, and similarly converts raw blue light into white light made up of pure colours.
Nanosys and 3m announced their partnership in June 2012 but have not yet named any customers.
BCC predicts that, by 2015, optoelectronics, including display components, will make up $310#million of a total $666 million in quantum dot revenues.
Melnick says that these numbers might be overly optimistic, because quantum dots remain expensive.""Even on the low end, they still cost in the hundreds of dollars per gram,
and range up to $10, 000 per gram, he says. But demand from 3m and Sony could help to bring prices down.
Although neither QD Vision nor Nanosys would comment on the volume of material they expect to make this year,
or their selling price, both say that they are scaling up their manufacturing volume. Bawendi is not surprised that it took quantum dots so long to find their footing."
"You could argue that 30 years is about the right amount of time from fundamental discovery to applications,
he says
#Genomes link Aboriginal australians to Indians Some Aboriginal australians can trace as much as 11%of their genomes to migrants who reached the island around 4, 000 years ago from India,
a study suggests. Along with their genes, the migrants brought different toolmaking techniques and the ancestors of the dingo, researchers say1.
This scenario is the result of a large genetic analysis outlined today in the Proceedings of the National Academy of Sciences1.
It contradicts a commonly held view that Australia had no contact with the rest of the world between the arrival of the first humans around 45
000 years ago and the coming of Europeans in the eighteenth century.""Australia is thought to represent one of the earliest migrations for humans after they left Africa,
but it seemed pretty isolated after that, says Mark Stoneking, a geneticist at the Max Planck Institute for Evolutionary Anthropology in Leipzig, Germany,
who led the study. Irina Pugach, a postdoctoral researcher in Stoneking s laboratory, discovered signs of the Indian migration by comparing genetic variation across the entire genomes of 344 individuals, including Aboriginal australians from the Northern territory, highlanders
from Papua new guinea, several populations from Southeast Asian and India and a handful of people from the United states and China.
Pugach confirmed an ancient association between the genomes of Australians New Guineans and the Mamanwa#a Negrito group from the Philippines.
These populations diverged around 36,000 years ago, suggesting that they all descended from an early southward migration out of Africa.
But Pugach also found evidence of more recent genetic mixing, or gene flow, between the Indian and northern Australian populations#taking place around 141 generations ago.
because it is absent from New Guinean and Mamanwa genomes, and it is too uniformly spread across the northern Aboriginal genomes to have come from European colonists.
The genetic mingling coincided with the arrival in Australia of microliths#small stone tools that formed the tips of weapons
#and the first appearance in the fossil record of the dingo, which most closely resembles Indian dogs.
and not anything like the dense, genome-wide study we carried out. A few smaller studies of MITOCHONDRIAL DNA and the Y chromosome have hinted at recent gene flow between India and Australia2, 3,
but a genome-wide study in 2010 missed it by not including any Indian populations4,
and a project that sequenced a full Aboriginal genome dismissed signs of gene flow from India as a spurious result5.
Sheila van Holst Pellekaan, a geneticist at the University of New south wales, Australia, and a co-author of the earlier genome-wide study,
welcomes the latest research, but warns that the finding is"definitely not representative of Australia,
Van Holst Pellekaan wants to know whether people from other parts of Australia also show signs of the gene flow that Stoneking and his team found.
But a legacy of distrust of biological research among aboriginal groups means that genetic studies are viewed suspiciously
#Vaccine switch urged for polio endgame By sunrise on a warm December morning, Janila Shulu s team are out in the dirt roads and alleyways of Ungwan Rimi, a poor neighbourhood in a predominantly Muslim section of Kaduna city in northern Nigeria.
Three female health workers, accompanied by a community leader, dart from house to house, squeezing a few drops of polio vaccine into the mouths of all the young children they can find,
even those who pass by on the street. By 1#p m.,after giving hundreds of doses, they stop for the day###the first of a national five-day effort.
but this month the World health organization (WHO) in Geneva, Switzerland, proposed a shift in vaccination strategy from oral vaccines to injected ones that may have to be administered in clinics.
but experts say that it poses challenges in places such as Kaduna city, which have poor access to health care.
The new policy is an important step towards eradication, says Nicholas Grassly, an epidemiologist at Imperial College London,
but implementing it will be difficult.""There are some big ifs as to whether it can happen, he says.
Jonas Salk is credited with developing the first polio vaccine in 1955, an injected vaccine containing killed virus,
but the oral live vaccine devised a little later by his competitor Albert Sabin is the workhorse of the Global Polio Eradication Initiative.
This public-private effort, started in 1988 and coordinated by THE WHO, has cost about US$8#billion so far.
But the live viruses in the Sabin vaccine can revert to disease-causing forms especially in populations where immunity is not widespread.
Northern Nigeria has been battling such vaccine-derived outbreaks since 2005, and one emerged last year in Pakistan (see Nature 485,563;
2012). ) In a 4 january announcement, THE WHO called for oral polio vaccine containing the polio strain type 2, one of the Sabin vaccine strains,
to be phased out###perhaps in as little as two years. The wild form of type 2 has been stamped out globally,
but vaccine-derived forms of the strain still circulate in Nigeria and neighbouring countries. Oral polio vaccination will continue,
but it will use a vaccine that protects against just the two other types of polio virus that are still circulating in their wild form in Nigeria, Pakistan and Afghanistan.
Meanwhile the policy also calls for the introduction, as quickly as possible, of the oral vaccine s old competitor:
the inactivated Salk vaccine. That costs more than ten times as much as the oral vaccine and requires trained health workers to administer it,
says Roland Sutter, a vaccinologist at THE WHO. But it carries no risk of causing polio.
By giving children an inactivated vaccine that protects against all three subtypes of polio, health workers hope to gradually stamp out vaccine-derived outbreaks."
"You have to have a transition period in which both oral and inactivated vaccines are used,
"because if you stop cold turkey you re going to have outbreaks, says Vincent Racaniello, a virologist at Columbia University in New york city.
Once the remaining wild polio types are wiped out, THE WHO will phase out all oral polio vaccines.
The high cost of the inactivated polio vaccine remains a significant hurdle for the plan,
which depends on a reduction in cost to less than 50 cents per dose from the current cost of more than $2,
and delivering the vaccine under the skin instead of into muscle, could help to lower the dose required and cut costs,
as could new kinds of vaccine, he says. Health infrastructure poses another big hurdle, says Grassly.
Delivering the vaccine in clinics instead of door to door will pose a challenge for Nigeria,
which has one of the lowest rates of routine immunization in the world. Less than 50%of children receive a complete schedule of childhood vaccinations,
and in parts of northern Nigeria that figure is around 10%."%"We as a global community have to do a much better job of integrating polio
and routine immunization, says Zulfiqar Bhutta, an immunization expert at Aga khan University in Karachi, Pakistan,
and a member of THE WHO committee that issued the new vaccination policy. He sees the eventual switch to inactivated vaccines as an opportunity to align polio eradication with routine immunization."
"We should have done this a lot earlier, he says
#The time? About a quarter past a kilogram Physicists have created an atomic clock that relies on a fundamental link between time and mass.
The researchers, at the University of California, Berkeley, say that the pulse of the clock is determined solely by the mass of its beating heart, a caesium atom.
US energy secretary Steven Chu, a physics Nobel laureate and a former adviser to the team's leader
declares the experiment"very significant work that shakes up the mainstream beliefs in a whole class of atomic experiments.
Current atomic clocks are based on the microwave signals emitted by electrons inside an atom as they move from one energy level to another.
M#ller and his colleagues say that their work goes back to the basics of quantum mechanics#to Arthur Compton's demonstration in 1923 that X-ray photons can deliver a detectable momentum impulse to an electron,
"This paper opens up the possibility that the standard of mass can be redefined in term of an atomic quantity instead of a lump of metal,
The work is already running into criticism, however. Claude Cohen-Tannoudji, who won the 1997 Nobel prize alongside Steven Chu,
John Close, a quantum physicist at the Australian National University, has taken a close interest in the to and fro of the debate,
"His experiments have forced a lot of people to think very clearly about profound aspects in this arena of atomic physics and relativity i
says synthetic chemist Dave Leigh at the University of Manchester, UK, who led the team behind the development."
Miriam Wilsonwith molecules for moving parts, this nanorobot links together amino acids (colored balls) by attaching them to a moving ring (blue.
"It s one of Dave s best papers, says physical organic chemist Alan Rowan at Radboud University Nijmegen in The netherlands, who also works with rotaxanes."
Although Leigh s rotaxane mimics the ribosome in its sequential building of peptides, the sulphur-assisted amino acid transfer is found elsewhere in biology:
some bacteria rely on it to synthesize proteins. It has also become a standard technique in laboratory protein synthesis.#Running about 1018 of Leigh s molecular machines at once can produce tens of milligrams of peptide.
In its present incarnation, the nanomachine requires the axle to be preloaded with amino acids in the correct sequence.
Its axle would have selective binding sites. Once the amino acids have been stripped off the axle, the axle would'reload,
'with new amino acids binding to those sites in the right order. Leigh s machine will probably never compete with automated methods of making peptides.
"It s laborious and not as effective as biology, says Leigh. Leigh and other chemists have used already rotaxanes to move droplets of fluid around2;
Molecular machines inspired by biology could eventually enable chemists to build materials with a specific sequence of molecules#a strand of polystyrene in which each component bears one of a range of extra chemical groups, for example.
"That s how biology does it, so why can t we? asks Leigh s
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