Fly Flu Clue to Combating Virus

Scientists have modified an influenza virus so that it can infect fruit flies, enabling them to identify over 100 new ways to fight flu in future.

Writing in this weeks Nature, Howard Hughes Medical Institute researcher Paul Ahlquist and his colleagues describe how, by replacing the outer coat of the flu virus with proteins from a different virus that can infect fly cells, they were able to produce a form of fly flu.  The team infected fly cells with this viral variant and then used a technique called RNA interference to selectively switch off each of the fly cells' 13,000 genes, one at a time, to identify those which are essential for the virus to grow.  The analysis flushed out over 100 cellular genes, which have direct equivalents in mammalian cells like our own, that the virus depends upon for growth.  

To confirm that the results would be relevant to normal strains of flu the team then tested the ability of natural strains to infect mammalian cells lacking three of the genes uncovered by the fly cell tests.  They found that suppressing the function of any of the three genes, known as ATP6V0D1, COX6A1 and NXF1, prevented flu viruses, including the pandemic contender H5N1, from replicating, suggesting that the 100 genes they've identified are likely to highlight many novel therapeutic strategies for swatting the flu in future.

13th Jul 2008

Fossilised Feathers Show Their True Colours

Over the years there have been hundreds of films and thousands of pictures made of dinosaurs, where scientists have carefully pieced together their shape and lifestyle. One critical piece of information for painting an accurate picture has been missing however – the colour.

Colours in mammals and most animals are produced by pigment molecules which don't survive the fossilisation process. However Jakob Vintner and colleagues from Yale University may have found a way of filling in the gaps for at least some dinosaurs.

They have been studying fossilised feathers from birds that lived over 70 million years ago in what is now Brazil. They noticed that there were bands of small lumps of carbon running across the feathers. Up until now these were thought to be the remnants of feather eating bacteria, but Vintner thinks they are actually fossilised melanosomes – small lumps within the feather which contain the dark pigment eumelanin which is related to the pigment in your skin cells which give you a sun tan.

This pigment is known to inhibit the growth of bacteria and the parts of the feather with lots of the lumps seem to be better preserved than the areas with fewer.

In modern feathers the shape and distribution of these melanosomes give the colour of the feather, so if enough of them are preserved one should be able to tell what colour the feather was before it was fossilised. Birds are dinosaurs’ closest living relatives, and several dinosaur feathers have been preserved, so there is every chance we could be able to tell their colour from any melanosomes preserved in them.

13th Jul 2008

Stem cells rescue muscular dystrophy in mice

Scientists have shown that satellite cells, a form of muscle stem cell, can be used to repair muscles affected by muscular dystrophy.

Working with mice and writing in the journal Cell, Harvard researcher Amy Wagers and here colleagues used chemical markers to identify a sub-population of adult muscle cells called satellite cells, some of which behave like muscle stem cells.  To explore whether they could be used to repair diseased muscles, the satellite cells were labelled with a glowing green protein and injected into the muscles of mice carrying a mutation in their dystrophin genes, giving them the rodent equivalent of muscular dystropy.

In humans this disease is characterised by the progressive destruction of muscle leaving sufferers weakened and eventually almost immobile.  Amongst the mice, when their muscles were examined four weeks after the injections, the team found that the stem cells had turned into new muscle and replaced up to 94% of the original muscle fibres.  This repair of the muscle was also matched by an almost six-fold increase in muscle strength to near-normal levels.

The trick works because skeletal muscles form what is known as a syncitium; this is where many muscle cells join together to form what is effectively one giant cell containing many muscle fibres.  As a result, when the stem cells merge with the syncitium, they bring with them a healthy copy of the dystrophin gene, which enables the rest of the muscle to function much better.

Although the team are not suggesting that this is the cure for muscular dystrophy at this stage, what they have shown is that there are cells that can be used to effectively repair adult muscle, which might be useful for a host of different diseases.

"Taken together, these data indicate that skeletal muscle precursors [the satellite cells] act as renewable, transplantable stem cells for adult skeletal muscle," says Wagers.

13th Jul 2008

A Window on Solar Power

Solar cells are expensive and difficult to produce, as they have to be made in a computer chip plant, so you want to maximise the amount of energy you can get out of each one.  One way is to concentrate the light onto a cell using relatively cheap mirrors, or lenses.  This means that several times more sunlight will fall on the solar cell so you can get more power out for your money.  However, the more you concentrate the light using lenses or mirrors, the more accurately you have to point them at the sun, meaning that these systems need expensive and high maintenance mechanical systems.  They also need costly cooling systems as they tend to waste a lot of energy as heat.

Now Michael Currie and colleagues from the Massachusetts Institute of Technology (MIT) have developed a system that will concentrate light whatever direction it is coming from.  They have taken a sheet of glass and covered it with a dye which absorbs light at one wavelength and then re-emits it at a slightly longer wavelength.  This re-emitted light is going in random directions and most of it gets trapped within the glass sheet by a process known as total internal reflection.  You could do something similar to this by adding some dirt to the surface of the glass.  This would scatter the light and some would get trapped in the glass but the dirt would also scatter the light in all other directions.  The MIT team’s dye is specially designed not to absorb the light which it has emitted, meaning that a huge amount of light is trapped in the sheet of glass, and you just put your solar cells around the outside.  Each cell produces about 10 times the amount of electricity they would do normally.

Another advantage is that you can pick the wavelength of light that your dye is producing to be the optimum wavelength for the solar cell to absorb.  This means that much less energy is wasted as heat in the solar cell so it doesn't overheat so easily, reducing the need for expensive coolants.

This system converts about 6.8% of the sun's energy which isn't great, but it should be much cheaper to make and you could use it wherever you have tinted windows in a building, so skyscrapers could generate electricity rather than just using vast amounts of it.

13th Jul 2008

Anaconda Advances Wave Power

Chris - Scientists have been exploring how they can use a giant rubber tube which has been called the Anaconda to generate electricity from the sea. Professor Grant Hearn is from the University  of Southampton. Hello, Grant.

Grant - Hey.

Chris - Welcome to the Naked Scientists. What actually is your device?

Grant - The device was really invented by Francis Farley and Rod Rainey. Essentially it’s a long rubber tube and it’s closed off at one end and moored. At the other end you have a power take-off system. Essentially you keep the rubber tube close to the free surface. It’s actually facing the on-coming wave. It’s like it’s at right-angles to the wave-front. As the waves come past the tube then they set off what is called a bulge wave inside the tube. As this bulge wave travels along the tube it gradually gathers more and more energy. One power take-off system we’ve tried is that as the wave travels along the tube essentially you can convert that energy into potential energy by allowing the water, which is being pumped to go through a valve system, and you generate a high pressure level. Then,  you have a low level and you pass the water from one to the other through a turbine. Hopefully you can take the energy out of the bulge wave.

Chris - How much energy do you think you could make this way?

Grant - What they’re thinking about is devices which will generate of the order on average one megawatt which may have a peak of three megawatts and an average over a year of one megawatt. If you assume that you have essentially half a kilowatt per person then that’s one device that will provide energy for around 2000 homes.

Chris - Would you just have one tube in isolation or would you have rafts of these out at sea somewhere?

Grant - You would probably have a farm and at the moment what we’re trying to do is understand how best to operate the tube in terms of things such as the pressure in it. The question would be, would you have tubes which are all identical or would you have tubes with different properties? If you put a tube with a different pressure in then you can take energy from a different wave frequency. So what you might then do is use a range of devices such that they’re all taking power from a mixed sea state.

Dave - There’s been lots of other ideas of getting energy out of waves. What’s the advantage of the Anaconda over them?

Grant - If we look back in the mid 70s-early 80s most of them were mechanical devices. Salter’s Duck was essentially a set of segmented sections which rotated around the cylinder and you essentially used the relative pitch of the ducks as they’re called and the back spine to actually take the energy out. Cockerell Rafts were simply using the relative motion of the rigid structure. You have to have squash plates. Then you have things like oscillating water columns. In this case the only movable part is the rubber so you’re actually using the stored elastic energy in the walls of the tube to actually convert the energy external into the energy which flows internally.

Chris - So it should be a lot more robust. Finally, what stage of development is this at and when can we see it in the North Sea?

Grant - I can’t answer when it will be. Rod Rainey and Francis think that once we’ve finished the work it’ll be possibly five years. At the moment myself, with John Chaplain, are entering a two year research programme sponsored by the Engineering and Physical Sciences Research Council in the UK. There we’re doing both experiments at different scales and we’re also developing mathematical models because the difficulty with this structure is that we know the physical boundary conditions but we can’t actually put numbers on them. We have an interesting mathematical problem which is: how do you solve the problem and determine the boundary conditions at the same time?

July 2008

Monster Bounces

Make a tennis ball bounce much higher than the height you dropped it from using a neat piece of physics.

What you need

What to Do

What may Happen

You should find that the tennis ball bounces far higher than the height it was dropped from.