Your Questions, Infectious Cancer and Louisiana Wetlands

05 February 2006

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This week we hand the show over to you, as Chris, Kat and Phil answer all your burning questions on science, technology and medicine. Anne-Maree Pearse joins us to describe the hellish plight of the Tasmanian Devil as it succumbs to an infectious facial cancer, Emma Marris discusses how scientists are bogged down in trying to prevent the Gulf of Mexico reclaiming large areas of Louisiana, and Derek and Dave put glow-sticks on ice in Kitchen Science.

In this episode

The Smog Blog

Scientists will soon be offering us a bird's eye view of pollution when they release a flock of 20 pigeons each equipped with a smog-monitoring backpack and a mobile phone! The birds will take to the skies over San Jose, California, in August this year and beam back text messages detailing the pollution they run into as they flutter about. The data they collect will be plotted in real time on an interactive map in an Internet "blog site", and cameras carried around their necks mean that the birds will also be sending back aerial photographs of their travels. The project is the brain child of researcher Beatriz da Costa from the University of California, Irvine, and her two students Cina Hazegh and Kevin Ponto. The team have so far built a prototype system comprising a cellphone circuit board and SIM card, a GPS receiver to pinpoint each of the bird's positions, and nitrogen dioxide and carbon monoxide sensors to monitor pollution. The next step is to shrink all of the components onto a single circuit-board to make a pigeon-pollution-pack for the birds to carry on their travels.

How Lying Down Affects your Sense of Smell

Valentine's day is approaching fast, and Dr Kat would welcome any card, flowers or chocolates that you might want to send her! But if you're giving your loved one flowers this year, you might want to make sure they don't take them lying down. Researchers in Montreal, Canada, have found that people smell more sensitively if they are upright than if they're lying down. To test this, they put volunteers in a brain scanner, and wafted them with the smell of roses. The scanner showed how intense the smelling activity in the volunteers' brains was. In fact, the researchers found that around two-thirds of the volunteers smelt worse when they were lying down - by which we mean they had less sense of smell! So far, the researchers can't figure out why this may be the case. Perhaps it's because our bodies prepare for sleep when we lie down, or maybe it's due to changes in blood flow to the brain when horizontal. So if you're planning on giving flowers or sprinkling rose petals before your beloved, make sure they stay upright!

The New Planet That's Bigger Than Pluto

Measurements of the size of a possible new planet by the astronomer Bertoldi from the University of Bonn in Germany along with co investigators have shown that it is bigger than Pluto. This is really making scientists think about what constitutes a planet. The planet's discovery was only announced last year and so far it doesn't have a name, just a designation - 2003 UB313. Unfortunately the object is so far away that we need to use a few tricks to work out its size and the new measurements have shown it is very cold, about -250 degrees Celsius, and has a size 50% larger than Pluto. Astronomers now have a dilemma because Pluto and UB313 are not alone. Pluto is the smallest planet in our solar system, smaller than our moon and we have recently discovered that it is part of a swarm of objects all about the same distance from the sun as Pluto in a band called the Kuiper Belt. So far we have found 1000 of these objects and UB313 is the only one to be discovered bigger than Pluto, but there could be others. Astronomers are now arguing whether they should call all new findings bigger than Pluto planets or demote Pluto to a non-planet. It's quite a bitter argument and could be raging for a long while but either way we will soon have to rewrite the textbooks because there are no longer nine planets in the solar system.

- Devil Facial Tumor Disease

The Naked Scientists spoke to Anne-Maree Pearse, Launceston Mount Pleasant Laboratories, Tasmania

Devil Facial Tumor Disease
with Anne-Maree Pearse, Launceston Mount Pleasant Laboratories, Tasmania

Chris - For the past few years, people have been noticing something horrible happening to an animal called a Tasmanian Devil. This is the world's only carnivorous marsupial, and they have some nasty habits, such as biting each other. They've been developing horrible facial tumours that eventually kill them by preventing the Devils from eating properly. Nobody knew where these tumours were coming from or what was causing them. But now they think they know, and what's really spine chilling about this is that it looks like this is an infectious cancer that one animal can pass to the next.

Anne - Maree- It became very clear about three years ago that the Tasmanian Devil's numbers were in great decline and they were in decline because they were dying of Devil Facial Tumour Disease. It generally starts around their mouths or around their lips and grows from there. Devils have the most disgusting behaviour. They fight over everything and they bite each other around the face. In other words they sort of jaw wrestle. These tumours are occurring where these wounds are more or less. They get very large and eventually the devils die, generally of starvation because they're unable to feed.

Chris - So the fact that you've got an injury on one devil which then turns into a tumour, and it's inflicted by another devil kind of suggests that this must be some kind of infectious phenomenon.

Anne - Maree - Yes. Normally in tumours you will find a common cytogenetical or chromosomal break point which actually defines the disease. I expected to find this in the devil with various random rearrangements around it. When I looked at them they were just totally rearranged. It was a massive amount of rearrangement. I looked at the next animal and it was exactly the same, and there were no sex chromosomes in animals of either sex. When you get something as complicated as the mix up in these chromosomes in this cancer, and when you can't find any sex chromosomes in the cancers in animals of either sex, you start to think that you've got an infectious cell line.

Chris - But this raises the obvious question, if you can transmit tissue from one devil to the other, that's almost analogous to an organ transplant. So why isn't it rejected? Why doesn't the devil's immune system just kick in and get rid of the hostile tissue?

Anne - Maree - Well this is another part of the puzzle. The devils' immune system isn't doing it. We know that either the cell line itself or the infectious cell line is capable of sliding under the devil's immunological radar, or that there's something wrong with the devils' immunity.

Chris - Is this the first time that anyone's spotted a disease like this, or are there other examples?

Anne - Maree - There is an infectious dog tumour, a canine venereal sarcoma, which is believed to be spread that way. There is a difference between it and the devil disease, which is that the dog's immune system can overcome it, and it regresses.

Chris - So to what sort of extent is this affecting devil populations in Tasmania? Is this restricted to a small part of the population or is it having a major impact?

Anne - Maree - We're talking about a major impact. The devils are affected in slightly over 50% of the Tasmanian mass, and it seems to be spreading.

Chris - And is there any chance of curing it?

Anne - Maree - We've had no attempts at curing it because you can't catch every devil in Tasmania and give it chemotherapy. But wouldn't it be lovely if we could find a vaccine?

- Bogged Down in The Louisiana Wetlands

The Naked Scientists spoke to Emma Marris, Nature magazine

Bogged Down in The Louisiana Wetlands
with Emma Marris, Nature magazine

Chris - now it's time to take a trip down to New Orleans and the Louisiana wetlands. This area is a very important economic resource for the local population because it supplies enormous amounts of sea food, oil and gas. But they're also disappearing into the sea at the rate of something like the area of a football pitch every thirty minutes. Unfortunately, experts down there seem to be getting bogged down in trying to decide what to do about the problem. Emma Marris has been down there to look at the scale of it, especially in the wake of Hurricane Katrina's visit late last year.

Emma - The major problem has been going on since humans began there. The whole place is sinking and normally what would happen is that the Mississippi river would tumble down sediment from the rest of the country and that would make up the difference. But in order to live in Southern Louisiana they had to cordon off the Mississippi river so that it wouldn't flood them out every year. As a result, all the sediment goes shooting out into the Gulf of Mexico and none of it ends up on the plain. This makes the plain turn into the Gulf of Mexico, and we're losing about 62 square kilometres a year.

Chris - 62 square kilometres a year? That's a significant amount: a football field a day or so.

Emma - In fact it's a football field every thirty minutes.

Chris - A staggering amount of loss. Is there any way to offset that?

Emma - There are various approaches but scientists tend to disagree about which is the best. One is that you can let a little bit of the river out of its levees so that it can bring some natural sediment onto the marsh. Another option is that you can actually build land, islands or terraces and set them up to stop the waves eroding the shore. You can even pipe sediment from one place to another with pipes like the ones used in the oil industry.

Chris - Have any of these strategies been shown to be effective?

Emma - It depends on what time scale you're looking for. The Caernarvon Diversion, which is one of the largest fresh water diversions in the world, is only saving something like 61 square kilometres over 50 years, which is less than the average yearly loss. But it is pushing out some of the salt water, which is another great problem. When the salt water penetrates up these marshes, it changes the whole ecosystem.

Chris - What was the effect of the hurricane? Did it speed up the inevitable?

Emma - Yes, the USGS has suggested that perhaps we lost a 161 square kilometres just due to the hurricane. It ripped up the marsh and threw marsh balls around everywhere, tumbled the trees back and killed animals. I saw alligators lying upside down, and complete sections were just completely destroyed.

Chris - Here in the UK, there's a strategy called Managed Retreat. The idea is to give in to nature and let the sea come back to a certain extent. Is this something that people have considered doing, and just sacrificing a bit of economic output for this area in order to let nature take its course?

Emma - Yes. A lot of the researchers that I spoke to were very much in favour of this. If you only have a certain amount of money you have to prioritise and there are a lot of people who suggest we just depopulate certain parts of Louisiana and focus our energies on protecting places like New Orleans that have the most economic value. This is, of course, politically dicey and difficult.

Chris - So in your view, who's going to win in the long term?

Emma - I think in the long term unless very large amounts of money are thrown at this problem, the winner in the end will be the Gulf of Mexico.

- Why have I lost my accent but my parents have not?

My family moved to Chicago from London three years ago and since then, I've lost my accent, yet Mum and Dad still have theirs. Why is thi...

Why have I lost my accent but my parents have not?

I definitely think that some people are accent sponges and other people aren't. You pick up dialects and accents from the people around you when you're learning to speak. This gives you a similar accent to your mum or dad. Accents are, afterall, just imitation. The reason things like this occur, is that if you get a group of people together in one place, the strongest people tend to attract imitation amongst the other people. So if someone has a particular way of speaking, people try and blend in and talk in the same way. So someone with an English accent in America is likely to pick up some of the American accent.

- How can active transport in plants possibly work?

How can active transport in plants possibly work?

How can active transport in plants possibly work?

In a plant, you have a leaf which is receiving sunlight and taking in carbon dioxide from the atmosphere to make sugars and some proteins from photosynthesis. The sugars then get redistributed round the plant. How does that actually happen? There are two transport systems in a plant. One of them just works in one direction. Essentially there's a series of long tubes between the roots and the leaves called xylem. These are dead cells which have been waterproofed with a special material called lignin and they have cellulose around them. They are about 0.01 millimetres across, and at that kind of thickness, the column of water that flows into them has a tensile strength stronger than that of steel. As the water evaporates from the leaf at the top end of the plant, it pulls the water up from the root. That's fairly intuitive. But how do the sugars go from the leaf down to the root? Well scientists have wondered about this for quite a long time, and thought that it might be just 'source and sink'. In other words, if you make a lot of something in one place, it tends to move away from where there's a lot of it to where there's not much of it. That's one possibility of how things are moved around. However, there's a second transport system called phloem and these are individual living cells that have individual plates between the cells that act like sieves. They can actually control the direction in which things move in those cells. Although it's pretty sketchy exactly how they know how to control whether something goes up or down, there's very good evidence that it does work like that because plants do distribute things in the right direction according to which way they need it to go. If you kill those cells, the process stops. This shows that it uses energy. That's really the extent of our knowledge at the moment. If you look at the cells in your body, there's an electrical gradient between the inside and outside of the cell. In other words, the inside of a cell is slightly more negative than the outside. The way cells manage to do that is that they have the cellular equivalent of a revolving door. It picks up three versions of a sodium on the inside of the cell and boots it out, and picks up two potassiums on the outside of the cell and brings it in. Overall, the cell is exchanging three plusses for two plusses, which creates an electrical difference. You can use that electrical difference to do some work for you, such as grabbing something that you want. This all requires energy, and is active transport. Cells are doing it all around your body to transport glucose into your cells. That's how cells like the liver, even though they're stuffed with glucose most of the time, an get even more packed in. I think plants are probably up to the same trick.

- Why does my dog's urine kill the grass?

We occasionally look after a dog when our friends go on holiday. We noticed that when it wees on the grass, the grass dies. However, abou...

Why does my dog's urine kill the grass?

Your urine contains lots of waste products including a chemical called urea, which is a by-product of protein. Urine is quite concentrated unless you've been drinking a lot of water. When you put concentrated urine on the ground, it essentially dries out the grass roots like a prune and kills it. Urea is also a rich source of nitrogen, which is a good fertiliser and a boost for the grass when new shoots start to grow. So it kills off the grass, and then causes better grass to grow.

- If my parents are blood group A, why am I group O?

My blood group is O-negative, my parents are Group A, and my brother is Group A. I was wondering how I came to be this blood group? I've ...

If my parents are blood group A, why am I group O?

'O' is referred to as a recessive allele. In other words, if you have group O, your cells don't make any markers on their surface. These markers are like little flags that the body uses to recognise them. People who are Group A can be Group A because they have one gene for making 'A' markers, and another gene that doesn't make any markers. So someone can be Group A if they have one gene for A and one gene for O, because you have two copies of these genes. One is from your mother and one is from your father. The other way someone can be group A is if they have two copies of the A gene. If both your parents are Group A, they must have genes A and O each. When a sperm with an O gene in it meets and egg with an O gene in it, you end up with two O genes and blood group O. It's also right that you are the universal donor. You can only receive blood from a person like you: O rhesus negative. Only 15% of the population has this blood. The rhesus factor is an additional gene or flag on the surface of the cell. This is known as the D allele. If you have that, then your cells just make an additional marker. This becomes important is if a pregnant lady is O rhesus negative and has a husband who is rhesus positive. The baby can be rhesus positive and the result is that some of the baby's blood can mix with some of the mum's blood when the baby's born. This can make the mum make antibodies against rhesus blood. That's fine for the first pregnancy, but if you get pregnant again, those antibodies can end up in the baby and cause all sorts of problems. It is normal for antibodies to be passed from mum to baby, wither through the blood or through breast milk. However, if you've produced antibodes to something in the baby's blood, then the antibodies latch onto the blood cells and damage them. That's why you end up with a baby that looks bruised. This is just where the blood cells are breaking down. Luckily, this can be dealt with by giving the mother a dose of antibodies at birth. Overall, your blood is so useful because it has no markers on it, so when it's put into someone's body, they have nothing to latch onto.

- How do turtles stretch out their necks?

How do turtles stretch out their neck? What is their bone structure?

How do turtles stretch out their necks?

Their shells are actually an extension of their body, so they can't crawl out of their shell. The shell is anchored by the ribs on the inside of the shell. It's made of keratin, which is the same stuff that hair, nails and horns are made of. Inside that shell, a turtle's body is very muscular and is suspended from the ribcage. A turtle's neck can form a s-shape either sideways or vertically. When a turtle wants to pop his head in and out, they either fold their neck sideways or fold it long ways and upwards.

- Why does water make surfaces slippery but help your fingers to grip?

If you spill some water on the kitchen floor, it's obviously very slippery. Yet when you want to turn the pages over in a magazine, you p...

Why does water make surfaces slippery but help your fingers to grip?

It's a very good point. If you look at your fingers, you'll see that there are lots of little ridges. If you lick your finger, you create a little area of dampness on the tip of the finger. When you press it hard onto a surface, you squeeze water out in exactly the same way as if you were squeezing a sucker onto a window. You get this attraction of the water locking onto the molecules on the surface of the page and locking onto the ridges on your finger and it gives you a bit more grip. However, when you've got your kitchen floor with a big puddle on it, what you end up with is a very thick layer of water. You have a layer of water coating your foot, a layer of water coating the floor and a layer of water between the two. You end up with a layer of water sandwiched between two other layers of water and that it very slippery. This is exactly the reason why tyres on cars have tread. The tread means that your tyre squashes the water out through the tread pattern and stops you getting this slippery sandwich and gives you a better grip on the road.

- How do doctors take photographs of the inside of the eye?

I understand x-rays and how they work, but a couple of years ago, my son had a very serious eye injury. Over a period, it improved, but h...

How do doctors take photographs of the inside of the eye?

It's actually not as difficult as it sounds. You have this amazing system on the front of your eye ball called the cornea. Just beneath that is the lens, which helps to tweak the process. However, the cornea alone has this amazing focusing ability and is there to focus light precisely onto your retina. All you have to do is look with your camera in the front of the eye and shine a light so you can see what's happening inside the eye. The front of the eye, the cornea and the lens, does the rest of the job for you. It focuses the light straight onto the back of the eye. If it's not quite in focus, you can adjust the camera to make the picture clearer. If you look on the back of the eye, you'll see this white patch. This is where the optic nerve comes into the back of the eyeball and all the nerves from the retina bundle together. The reason they are in one bundle is so that they don't take up that much space in the back of the eye, which would of course create a blind spot. The other way to take a picture of the back of the eye is to inject a glowing yellow dye called fluorescein. When this flows into the blood vessels in the back of the eye, it makes them glow when you shine a certain wavelength of light on them. This shows you where the blood vessels are.

- Why does ouzo turn milky white when water is added?

Why does ouzo turn milky white when water is added? It must be mainly water to start with and as the concentration of alcohol decreases, ...

Why does ouzo turn milky white when water is added?

It's an emulsion. The oil which makes the delicate flavours of ouzo dissolves very nicely in alcohol, but it doesn't dissolve very well in water. When you add water, it binds to the alcohol, which dissolves well in water. The oil eventually stops binding to the alcohol and starts hanging around with other oil molecules. These little aggregations of oil in the water make the drink turn milky white. If you were to zoom in with a very powerful camera, you would see these tiny globules of oil being completely surrounded by water molecules. This is exactly how emulsion paint works, where you have globules of oily paint molecules surrounded by water.

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