BSE, Cervical Cancer and Toxoplasmosis

If you are going to predict the weather the first thing you need to know is what the weather is like now, the second thing you have to know is whether your prediction was right so you can improve your model.

One of the hardest things to measure is rainfall, rainfall radar covers large areas but isn't very accurate, and rain guages whilst being very accurate only give you a few points of data. Israeli Researchers from Tel-Aviv University have come up with a new source of data - mobile phone masts. When your phone shows a weak signal both your phone and the mast will crank up their power. Rain gets in the way of mobile signals, so by looking at the power mobile masts need to use, you can find out about the rain in the area. Hagit Messer-Yaron, an electrical engineer found that the data from the mobile masts was much closer to the rain guages than the weather radar, and using this resource wouldn't require any investment in equipment as it is already there.

This week Sheena Elliot and Derek Thorne demonstrate the science of Brownian motion...

Derek - Welcome to Downham Market High School, we have a very easy experiment for you to do at home. With us we have Sheena who has the experiment set up for us. What do we have today?

Sheena - We are just looking at how food colouring looks, and changes in hot and cold water.

Derek - So it sounds easy and indeed it is, and with us today we have a volunteer who is going to be doing the experiment. So could you introduce yourself?

Tom - I'm Tom and I'm in year 10

Derek - So do you like science?

Tom - Yeah it's ok.

Derek - That doesn't sound enthusiastic enough for the Naked Scientists, so we are going to try and turn you onto science. We have a very simple experiment for you to do and if you want to do it at home these are the things that you will need: two bowls which are able to hold, say, a litre each; a boiled kettle; and some food colouring. Now Sheena is going to tell us what we do with all these things

Sheena - First fill one bowl with cold water, and another with our boiled hot water. Then we just need to let them settle, so put a cover on the hot one to retain the heat and leave them to settle for 5-10 minutes.

Derek - A bowl of water may look like it is still but you are saying there is still some sort of movement in there?

Sheena - Yeah there will probably be some movement for quite some time, but if we leave it to settle for 5 - 10 minutes it should be fine

Derek - So we need to wait until the water is nice and still for 5-10 minutes.

Sheena - Then we add just a little food colouring in each bowl in a nice controlled way. So I would suggest dipping maybe a handle of a teaspoon into the food colouring and then just touch the surface of each bowl of water with it.

Derek - So you are not putting anywhere near a teaspoon full in there.

Sheena - Yeah just a tiny amount.

Derek - So Tom what do you think will happen?

Tom - No idea at all.

Derek - But we have one that is hot and one that is cold. When you put food colouring in the water what would you expect to see?

Tom - In one the food colouring is going to spread more than the other?

Derek - So if you at home are wondering what is going to happen you can do the experiment yourselves. It is very easy and you can tell us the result. So get those bowls filled with water and see what happens. We'll come back to you later with the results. Until then, back to the studio. LATER….

Derek - Hello there and welcome back to Downham Market High School. We've been waiting here to do this experiment with hot and cold bowls of water. Tom is here from Downham Market High School and Sheena set up the experiment too. So Sheena, would you care to instruct Tom over what to do right now.

Sheena - Ok so Tom, if you take the bottle of food colouring and then dip in the handle end of your spoon. Then put it into your bowl of cold water and just repeat for the hot water.

Derek - Tell us what you see.

Tom - It's moving a lot quicker in the hot water the cold water.

Derek - And in what way is it moving in the hot water when you look at that?

Tom - It's spreading far and then dropping down to the bottom, whereas in the cold water it's not spreading quite as far and then it's dropping down to the bottom.

Derek - Yeah and I suppose we've got a really definite shape in the cold water one. We've got this weird structure of food dye that's suspended in the water and it doesn't appear to be movign anywhere does it?

Tom - No, it's diffusing more in the hot water.

Derek - And we've been waiting here for a minute. Now, what does that hot water one look like?

Tom - It's all red, or a light pink.

Derek - So what do you think is going on here?

Tom - I thin it could be because of the heat in the hot water making the particles more energised, meaning the food colouring can diffuse more easily through it.

Derek - Sounds reasonable to me. What do you say Sheena?

Tom - That sounds like a perfectly good explanation. I think there are actually two things that might be happening here. First of all, in the hot water the molecules will be moving much faster and have much more kinetic energy. When we talk of heat, what we're actually talking about is kinetic energy and all these molecules are moving very fast. That's what we perceive as being hot.

Derek - If we were to look down an amazingly massive microscope at these particles, would they be moving around a lot?

Sheena - Yeah, they'd be moving around like crazy in there. So that's what I originally thought would be causing the food dye to be bashed around. It's Brownian motion: they're all being hit by the hot molecules around them. In the cold water you still have these molecules moving but they won't be moving as fast. However I think there might be another explanation that's actually the one we're seeing so quickly here. I think that's convection currents. The hot water at the top of the surface where it's next to the cold air will evaporate and cool down and it will no longer be the hottest water in the bowl. Hot water from below will then rise and take its place because hot liquids rise. You then set up these currents where hot water from below keeps rising and the cold water gets pushed down. All these currents cause the mixture to mix up very quickly.

Derek - Ok, so do convection currents just happen continuously in something with warm water in it?

Sheena - Yes. As long as the vessel is a different temperature to the surrounding air, then it will continue to evaporate and you'll get this cooling effect at the surface.

Derek - So you've talked about two different effects. I suppose it's quite reasonable that they might both be happening.

Sheena - Yes I think they will both be happening to some extent but we can't really conclude which is the dominant one.

Derek - So Tom, your guess about diffusion was to do with one of those, but do you understand the whole thing a bit more now?

Tom - Yeah it's clear.

Derek - Well thanks. Did you enjoy it?

Tom - Yeah it was fun.

Derek - Thanks you for doing the experiment with us and we'll be back next week for some more science from somewhere in the East of England. Until then, it's goodbye!

Chris - Can you just tell us, what actually is BSE?

Tony - The disease is a disease that causes paralysis, coma and then death: it's a central nervous system disease. It's one of a group of diseases of this kind, but BSE is special because it appeared out of the blue in cows in the late 1980s. From almost nowhere it got to about 40 000 cases per year by around 1990. What was really horrible was that it proved to be transmissible to people but extremely inefficiently. So it turns out that there have been about 100 cases all told in the last ten years in people but there have been hundreds of thousands of cases in cattle.

Chris - If you zoom in with a very powerful microscope on the brains of cows and people that have been affected, what is the nature of the infectious agent?

Tony - It's really unusual and it's taken the last fifteen years to show that it's this totally new kind of disease not caused by a bacteria or a virus but by on eof our own proteins folding abnormally. It extremely rarely folds abnormally and then forms aggregates of that abnormally folded protein. It's strange because it seems that this abnormally folded protein that attracts other normal protein and recruits it. If you look at it with a really powerful microscope, what you see is rod - like aggregates of this material and they're the things that are called prions. You hear the term prion diseases, and prion diseases are this group of diseases caused by abnormal proteins.

Chris - It's not just BSE though: there are a whole clutch of these that occur naturally in people and animals and in different forms in people.

Tony - There are many different diseases of this kind. In sheep it's called scrapie; in man we've known for many years about a disease called ordinary-CJD which occurs spontaneously in every population in the world. About one person in a million every year gets CJD where the formation of the abnormal protein occurs spontaneously. Where it gets risky is when you start recycling into the same species. One of the famous example of that is Kuru. In the highlands of New Guinea in a particularly isolated area, they practise cannibalism as part of a funeral rite. When people died, they used to take the brain material and eat it as part of the funeral rites.

Chris - When they were doing that, how was the protein that was in that brain tissue getting into the person's brain?

Tony - When you eat a bit of the brain it goes into your stomach and it passes across the stomach wall into the lymph system. It's thought that in the lymphoid tissue and in the spleen it expands and begins to recruit more of the same protein. Then it appears to go along the nervous system into the brain, all the time recruiting more protein and converting more of the normal protein like a chain reaction. The dangerous thing jis obviously the cannibalism and recycling food back into the same species.

Chris - Is it just unlucky that it happened here in Britain?

Tony - I think that's probably right. I think we were just extremely unlucky because virtually every western country was certainly taking the remains of beef carcasses and then rendering that down into a high-protein supplement to feed back to more cows. So I think it could have happened anywhere.

Chris - So if anything, British beef is now safer than it's ever been, and perhaps we should be suspicious of beef from other countries.

Tony - Well I wouldn't like to say anything about other countries because we will end up getting sued, but I think you're right. We now take extra-ordinary precautions. First of all we don't recycle any bovine material back into the bovines and we don't make meat in bonemeal anymore. Secondly, we don't eat any animal that was born before 1996 when we stopped recycling food completely back into bovines. Thirdly, we remove all the dangerous tissue, such as the lymph and the brain tissue from the carcass before it's butchered and then finally animals are tested for the presence of prions when they go tot the abattoir. So it's an extra-ordinary range of tests that's done. Because we no longer recycle bovine meat into cows, the number of BSE cases in this country is now reducing. It's now a thousand-fold lower than it was ten years ago.

Chris - Margaret Stanley is someone from the Department of Pathology at Cambridge University and she's spent a lot of her life working on Human Papilloma Viruses, the viruses that cause warts and verrucas, but they also cause cervical cancer. Tell us about your research.

Margaret - My research has always been asking how does this virus change cells, and more importantly, how can we intervene early in the virus infection to prevent either infection or to prevent the consequences of it.

Chris - How does a virus trigger cancer, because for many people that will be a pretty unusual thing to have said?

Margaret - It's rare. Viruses exist to make more viruses but as part of their life cycle they turn cells on to divide and make DNA. If there is an accident during the virus's replication, when the virus is making its own DNA, and the virus proteins are expressed at the wrong time or in the wrong amount, then they can change the behaviour of the cell. That's basically how this virus causes cancer. It's a rare accident.

Chris - How was it first picked up that this was linked to cervical cancer?

Margaret - That all starts in the 1970s. Everyone's heard of the Pap smear. Well there was a smart cytologist in Canada who realised that some of the cells you saw in the Pap smears were the same types of cells you saw in warts. We'd always assumed from the epidemiology of cervical cancer that it was a disease that had an infectious basis, and so as soon as this was found there was a big effort to find out whether these viruses were involved. The next big step was a German scientist that isolated virus DNA from a cervix cancer, identified what it was and it turned out to be a papilloma virus.

Chris - Was there some anecdotal evidence that nuns were very rare among the bunch of people that got cervical cancer and Jews and Muslims were also very rarely implicated?

Margaret - In essence, you're right. It's an apocryphal story. About 15 000 Belgian nuns were surveyed and only one of these ladies had cervical cancer. Her behaviour before taking the veil was rather extreme.

Chris - So that was a weak link for the nuns. But how did you go about making a vaccine to stop this virus?

Margaret - Again, that was tricky. What you need to do is present the body with the protein that the body first sees with the natural virus infection. In other words, the protein against which you make antibodies. This is actually very difficult for papilloma viruses for all sorts of reasons. Microbiology, recombinant DNA technology, came to the rescue. You isolate the gene that makes the protein of the virus coat. A virus is like and egg: it's got a coat and it's got an interior. So you isolate the gene that makes the protein of the coat and then you express this gene in something like a yeast that grows extraordinarily quickly. As the yeast grows, it expresses the gene and makes the protein, so you make huge amounts of the virus protein. When you make the virus that way, the protein forms its natural shape. In other words, it forms what we call 'the native shape'. It looks like a ball of wool with a set of railway lines. It's the ball of wool that you need for an immune response to be made.

Chris - And at what age is this effective? At what age would you need to challenge someone with this vaccine to guarantee that they're going to be protected?

Margaret - When you immunise someone with a prophylactic or a preventative vaccine, you must give it before they're infected. This is a virus that you acquire as a consequence of sexual activity. I have to say that everybody gets this. This is not a rare virus infection. The only other thing you get as much of with sex is pregnancy so this is very common. So obviously you've got to immunise people before they start having sex. The best age at which to immunise is at childhood. The reason for that is that children make much better antibody responses than adults. I have bad news: as soon as you hit puberty, then immune system goes downhill, so that's why you immunise children. So the optimal age is probably nine or ten.

Chris - Where is it in clinical trials now? It's in humans isn't it?

Margaret - Yes, it's in the large trials called phase three trails and at the moment we've got five year data on about 8000women. I can tell you that it's 100% effective in the women who've been vaccinated.

Chris - So internationally what are the implications?

Margaret - This is the biggest killer from cancer in the Third World. This is a vaccine that prevents infection.

Chris - And I guess, sensitive subject as it is, that this couldn't have been developed with out the use of an animal research model?

Margaret - Absolutely. This has depended on rabbits and dogs because rabbits and dogs were the animals with natural warts and we showed the virus worked there before we went to people.

Chris - So you can actually cure animals and dogs from their own infections if they actually had it?

Margaret - You can indeed.

When your light switch is just on the border of making a circuit, you are creating a switch which is almost closed. At some point the switch will create a spark. When you create a spark you will create a little surge of current in the wire. The spark will then finish and break the circuit again. You will keep getting sparks, each creating it's own surge of current. Your light bulb is flickering because you have a changing current, and a changing current will produce a changing magnetic field. A changing magnetic field produces a changing electric current. So when we create a radio wave, what you've got is a transmitter which is applying a changing electric field to a piece of metal (the aerial). The changing current going up and down that piece of metal then induces a changing magnetic field around the metal and the changing magnetic field then creates a change in electrical current in the fabric of space around it. That electrical current in space time produce a wiggle of magnetic field, and so you get this wave that propagates as an alternating magnetic field and electrical field. This propagates through space at roughly the speed of light. That's a radio wave. So why did your interfere with your radio? Well when you're just on the verge of completing a circuit with your light, it's creating enormous amounts of changing current in the wire. This creates lots of funny frequencies of radio waves at a fairly low power. These then come out around the wire, spread out into the room and are picked up by the aerial of your radio. They interfere destructively. In other words they cancel out the radio waves of the station you were listening to. That's why you get the interference.