| Science/Tech news; nanotech, medical apps |
[Jan. 22nd, 2004|08:35 pm] |
Injectable scaffold aids rebuilding of nerves
A liquid that forms a gel-like mass of nanofibres on contact with water could provide the most promising vehicle yet for the regeneration of damaged spinal cords.
Many groups working in regenerative medicine are trying to develop artificial scaffolds that store or attract cells and then control their growth and final identity.
The most common approach has been to build fabrics, films or gels out of biopolymers such as collagen and then "seed" them with the cells to be regenerated. These have had varying degrees of success in encouraging cell growth. But when treating patients, one of the problems their designers face is how to get these scaffolds into the damaged tissue.
The least invasive option would be to develop a scaffold that can be injected as a liquid and assembles itself once in place, which is exactly what a team led by Gabriel Silva of the Institute for Bioengineering and Nanoscience in Advanced Medicine (IBNAM) at Northwestern University, Chicago believes it has done.
Growth promoter
Their scaffold consists of molecules containing a fragment of the natural protein laminin, called IKVAV. This is known to promote the growth of long neuronal fibres or axons.
Within seconds of these molecules coming into contact with water, electrostatic forces drive them to form a tangle of long, slender fibres that are thousands of nanometres long but only seven nanometres in diameter. In gross terms, this structural change means the solution turns into a gel.
Skinny endoscope squeezes into new niches
A new endoscope, made of a single optical fibre just half a millimetre wide, could one day help doctors avoid obstructions during cochlear implant surgery. The implants are designed to restore hearing to deaf patients but cannot always be fitted because of unexpected obstructions in the inner ear. The endoscope could also be used to peer inside other narrow structures such as blood vessels.
These are single fibres with microscopic holes running right through them, like the lettering in a stick of seaside rock. Light is channelled down each hole, only emerging when it reaches the end of the fibre.
Because the light entering each hole remains separate from light in all the other holes, the pattern of light leaving the fibre at the other end creates a discernible image. The plastic between the holes also guides the light in the same way as the holes themselves, effectively doubling the number of light channels.
Cochlear implants convert sound into electrical signals, which are used to stimulate the auditory nerve fibres in the cochlea of the inner ear. To fit the implant, an array of electrodes is fed down the cochlea around one and a half turns of its coiled, shell-like structure.
Surgeons do this work "by feel" and if they hit an obstacle the operation has to be abandoned. "In roughly 10 per cent of cases you have an obstruction," says Halit Sanli, a biomedical engineer at the Sydney Cochlear Implant Centre in Australia.
Panic attack patients lack key brain receptors
People who suffer from panic attacks lack a key neurochemical receptor in their brains, say US researchers. Their findings throw light on the molecular mechanisms that predispose a person to anxiety.
The study, led by Alexander Neumeister of the Mood and Anxiety Disorders Program at the National Institute of Mental Health in Bethesda, Maryland, is the first to identify a deficit in the 5HT1A receptor in living humans with panic disorder. Similar, but much smaller deficits have also been found in people with depression.
The work also means the 5HT1A receptor could provide a biological marker for the condition when considered with other factors. Panic disorder can run in families, so the marker may help to identify vulnerable relatives of a patient who has already been diagnosed.
The symptoms of panic disorder include feelings of intense fear, accelerated heartbeat and chest pain. It strikes about 2.4 million US citizens each year.
Neumeister and colleagues used positron emission tomography (PET) to image the brains of 16 panic disorder patients who had received no drug treatment and 15 healthy controls. Although seven of the patients also suffered from depression, panic disorder was their primary diagnosis.
PET tracks the behaviour of a radioactive tracer in the brain, but a novel aspect of the study was that the researchers used a new fluoride compound tracer called FCWAY that selectively binds to 5HT1A receptors.
Compared to the controls, the patients had a reduction of almost a third in the number of 5HT1A receptors in the anterior cingulate cortex, the posterior cingulate cortex and the raphe nucleus - three structures roughly in the middle of the brain. In other studies of depressed patients, researchers have found a reduction of around 10 per cent.
Animal experiments have shown that the 5HT1A receptor not only responds to serotonin but is also very sensitive to stress hormones such as cortisol. "So you could see the 5HT1A receptor as a marker for stress in general," Nash told New Scientist.
Device 'quarantines' infected network computers
A new device that quarantines different portions of a computer network could stop worms and viruses infecting an entire company once they have breached its perimeter defences.
The InterSpect system, unveiled by California-based network security company Check Point on Tuesday, monitors network traffic for signs of suspicious activity. It can then automatically isolate a single computer or a group of machines to prevent wider infection.
Most companies have numerous defences at the perimeter of a network, including anti-virus software, firewalls and intrusion detection systems. But once one computer has been infected, there is normally little to prevent it from spreading viral code to every other machine on the network. A common way for a worm to wriggle through perimeter defences is aboard a laptop brought into the office.
'Sleeping on it' really can solve problems
A tricky problem really can be solved by "sleeping on it", new experiments have shown. The researchers suggest our brains re-juggle data while we slumber to present us with a solution when we wake.
Anecdotal evidence has long suggested that a night's rest can bring clarity to a complex dilemma. For example, the Russian chemist Dmitri Mendeleyev devised the periodic table following a moment of nocturnal "insight". "He said he had a dream where all the elements fell down in the right positions," says Ullrich Wagner at the University of Lübeck in Germany.
In the experiments conducted by Wagner and his colleagues, volunteers tackled arithmetic problems and then took an eight-hour break. Those who slept during the break were twice as likely to realise that there was a hidden rule that substantially simplified the calculations.
"We think the strongest explanation is that sleep acts on the patterns created during the training, restructuring them to give insight to the hidden rule," says Wagner.
He thinks the data is sifted in the hippocampus and the prefrontal cortex, areas of the brain which store and analyse memories. The team hopes next to scan the brains of people doing similar problems to spot which brain areas distinguish states of "insight" and "non-insight"
Sleepers and wakers
The arithmetic problem set for the volunteers required transforming a sequence of numbers into a second sequence by applying two simple rules. But they were only to provide the final number in the second sequence.
The hidden rule was that the final number in the second sequence was in fact always the same as the second number. Realising this would mean the volunteers could save a lot of needless calculation.
Only one of the three groups of 22 volunteers was allowed to sleep during the interlude between training and re-testing. The other two groups remained awake, one during the day and one at night, to rule out "circadian" rhythm effects.
The "sleepers" were more than twice as likely as the "wakers" to spot and exploit the short cut. "We recorded all the responses, and we could see very clearly the 'Eureka moment'," says Wagner.
In an accompanying experiment, the team also showed that the poor performance of the "wakers" was not simply because they were tired.
all my best ideas come between 4 and 4:30am :)
Chip promises faster multiple virus tests
A new silicon chip could enable patients to be tested for a multitude of different viral infections in just a few minutes, says a US company. The chip, developed by BioForce Nanosciences in Ames, Iowa, uses a microscopic array of antibodies to catch the microbes.
The antibodies are printed onto the silicon chip using a "nano-arrayer". This places a few thousand antibody molecules on a region measuring one micron in diameter. The process is then repeated for each different antibody. The molecules stick to the silicon thanks to a pre-treatment which coats it with chemicals.
To test for viruses, the chip is simply dipped into a small blood sample. Any viruses present are then captured by the relevant antibodies. This creates telltale ridges on the chip that are detected using an atomic force microscope (AFM).
"The chip uses a very simple concept," says Eric Henderson, founder and chief scientist at BioForce Nanosciences. He says the chip is faster than existing virus detection techniques, because the dipping only takes a moment and the AFM analysis can be done in minutes.
Online games to generate real - and academic - riches
Multiplayer online computer games are expected to generate more than $1 billion in revenue for the first time in 2004, according to a new prediction.
But as well as providing financial riches, some researchers believe the virtual communities built within these complex artificial worlds may also provide academic riches by providing a unique new way to study social, economic and legal phenomena.
The parallels between such virtual worlds and real life was highlighted last week when a report alleging organised crime and prostitution within a precinct of The Sims Online caused controversy.
Peter Ludlow, a philosophy professor at the University of Michigan, published an online newspaper for the virtual Sims community of Alphaville called The Alphaville Herald. Ludlow reported that some players routinely befriended new characters in order to trick them into handing over possessions.
He also described a virtual brothel in which characters offered sex chat for "simoleans", the game's currency. Ludlow's character has since been ejected from the game, allegedly because he linked to web sites carrying code that can be used to cheat inside the game. |
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