Stem Cells, Brain Repair and Tricks of Light
Stretching our grey matter this week is developmental biologist Dr Adrian Pini, who describes how our brain grows, how our brain works, and how it can become damaged, and Dr Huseyin Mehmet, who discusses the potential application of stem cells in repairing central nervous system damage. Also in the studio is Tom Smith from Cambridge University, who has designed a new pump that could help thousands of people in the developing world, and Derek and Dave perform a vanishing act in Kitchen Science.
In this episode
The Never-emptying Beer Glass
Thirsty researchers at the University of Munich, led by Andreas Butz, have developed a beer mat that automatically prompts bar staff for a refill when a glass is empty. The mat uses a pressure sensor to detect when the glass is getting low, and then signals the bar by radio for a top up. The developers suggest that it could also be used as a bar-room voting device, for instance in the karaoke setting, whereby drinkers quite literally raise their glasses to a good act. Perhaps for UK beers an electric heating element could also be installed to ensure that they are adequately warm upon serving?
- Stem Cells And Brain Repair
Stem Cells And Brain Repair
with Dr Huseyin Mehmet from Imperial College, London
Chris - So tell us a bit about how stem cells fit into the whole picture. The whole nervous system arises from a class of cells that are essentially stem cells, as they arise and divide into all the cells in the body. Is it possible to extract these things and use them to put things right in the future?
Huseyin - Well that's what we're working on and we're hoping to convince the government that we can do that. One of the things that Adrian said that I think was really interesting is that as the brain develops, cells actually die naturally as well. I think the thing that attracted us to stem cell research is that babies that are born very early actually haven't formed all their brain cells properly. If you were to look at a baby that's been born three or four months early under a special machine called an MRI scanner, it would actually look like layers of an onion in two halves. If you then imagine the picture of a brain of a normal human being with all its convoluted twists and turns, this development has to happen in a premature baby outside of mum's tummy. That's why many premature baby's have problems with their brains developing. Brains do, of course, contain some stem cells. When I was a student, we were told that the brain only had very limited powers of repair, and of course, that's true. We always thought that once brain cells have finished developing, that was it. In other words, if a patient was to damage their brain through a disease or an accident, the brain had no power to regenerate itself. We now know that that's not true. There are two areas of the brain that have small areas of stem cells in them. I think the best example to discuss is how they were discovered in the brain of a songbird. Animals that have to relearn songs, for example, have a special part of their brains where they remember the songs that they hear. These specialised brain cells develop from a very small and specialised area of stem cells. I think the problem is that in most adults, we have enough stem cells to allow us to learn a new smell or two, but not enough cells to repair a large lesion or area of damage that might happen in a stroke patient. That's where stem cells come in.
Chris - Coming back to the songbird for a minute, when the adult learns a new song, it pumps some stem cells into that area of the brain whose job it is to encode new songs, and those cells take on that new role.
Huseyin - Those cells are already there, but when the actual song is heard, they're then programmed to begin to differentiate into the memory forming cells in a specialised region of the brain.
- A Water Pump For The Developing World
A Water Pump For The Developing World
with Tom Smith from Cambridge University
Chris - So what's your pump all about?
Tom - What I've invented is a pump without any moving parts. It uses heat rather than electricity as a power source. Most existing pump use electricity and have moving pistons to move the water along. My pump expands and contracts fluids by heating and cooling them, and this provides a movement of fluids which can be used to pump water. What distinguishes it form other pumps without moving parts is that it can use heat from sources at very low temperatures, for example, waste heat or heat from the sun. It could be useful for pumping water to irrigate fields, particularly in Third World countries, but it also has many here at home. These include pumping water round your domestic central heating system.
Chris - So talk us through a little more precisely exactly how this works and why it's better than what people have got at the moment.
Tom - That depends on the application we're looking at, but let's look at irrigation in developing countries. Farmers in developing countries earning less than a dollar a day typically tend to farm areas of about half a hectare in size. The only way they can get water is to lift it out of the ground by hand or to pump it out with pumps. In many cases, they spend up to four hours a day providing themselves with water. For some time we've had photovoltaic cells, which are solar electricity panels and can be used to produce electricity for water pumps. However, they are very expensive and tend to fail in the middle of nowhere where there's no-one to repair it. What we really need is a system that's very simple, and heat is much easier to work with than electricity.
Chris - So some heat comes out of an exhaust pipe from a boiler, but what does it do to your pump. How does it work?
Tom - Imagine two columns of liquid side by side, and imagine that they're joined at the top and the bottom. This looks a bit like a rectangle if we look at it. If we heat the left hand column at the top end and cool it at the bottom end, then what happens is that as we heat it, the water starts to boil. As it boils, the pressure rises, steam is produced and pushes liquid out of the right hand column at the right hand side of the rectangle. We'll come onto what happens at the right hand corner in a minute. As liquid leaves the system, we get a level difference between the two columns. Gravity then causes the level difference to even out, and we get hot vapours moving down into the cold end. When hot vapours see cold surfaces they condense and the pressure lowers. This sucks the liquid back up in the right hand column.
Chris - So you get an oscillation. It goes up and down.
Tom - That's right. The liquid in the two columns is moving up and down, heat is being added, and heat is being rejected. Down in the right hand corner of this rectangle, there are two non-return valves. These are one - way valves that allow water to move in one direction. As liquid is moving up and down, it's sucking water from below, such as in a hole, and delivering it to a field above.
Chris - So this is going to save these guys hours and hours of back-breaking work and use energy that would otherwise be seen as a waste product.
Tom - Yes, and I've heard the figure that 10% of the energy we use in our homes in winter is for pumping water around heating systems, because these systems are running for several hours a day. If we could use some of the heat that's there anyway to do this job, then the whole system becomes significantly more efficient.
Chris - So it not only ha applications in the Third World, but it could also help the rest of the world to live a cleaner, greener life.
Tom - Absolutely, and so the idea behind my company is that I'll try to commercialise this pump for several of these green-type applications here at home and use the finds from that to help with some of the charitable application sin developing countries.
- How does one fertilised egg turn into trillions of cells?
How does one fertilised egg turn into trillions of cells?
with Adrian Pini, Kings College London
Chris Smith spoke to Adrian Pini to hear how embryos develop...
Adrian - As the question suggests, it's incredibly complicated and not that well understood at all. Essentially what happens is that the first cell that gets fertilised by a sperm divides in two, and the daughter cells themselves divide. So the first thing that happens is that you generate a whole load of cells. As the division goes on, you then begin to get sub-specialisation of different cells into different regions. For example, you get cells that are going to become the skin, cells that are going to become you bones, and your blood and guts and so on. All these differentiation events, as they're called, are beginning to occur as the embryo is beginning to get bigger. In the nervous system especially, you get a layer of flat cells, and within that thing you get changes which first of all are at a genetic level so you can't really see much of what's going on. Then different genetic processes seem to kick in in different orders throughout the nervous system that give rise to further specialisations that will eventually become the brain and other parts of the nervous system.
Chris - It's amazing to think that the brain, which has a million million nerve cells in it, can work out exactly where to connect all the different nerve cells together. How does a nerve cell in my brain that's supposed to control my finger know where to connect to and get it right? Adrian - It is a very complicated process. Nerve cells can communicate with one another and read signals. There are two sorts of signals that nerve cells can read. One is a signal that diffuses in from elsewhere, like a dog sniffing a scent. The other way that two nerve cells can talk is by simply touching it. Here there is an exchange of chemical signals, which usually involves proteins but can be other molecules as well. These are the signalling things that do the talking. For example, if a nerve cell is sitting up in the brain somewhere, it has to navigate quite along distance. One of the signals it can read are signals from the area to which it is going to be directed. The target zone will secrete an attractant, so that the nerve cell can extend a very thin process called an axon. This can go from where the cell is in the brain, down the spinal cord and to wherever it's going, which may be a metre away. The thing to remember is that embryos are very small, and so the distances the nerve fibres have to grow over are also very manageable.
Kat - I think I remember hearing once that the brain is still making these connections once you're born. What's the key time in life for that, and can you improve a baby's intelligence by stimulating it in the right ways?
Adrian - Certainly, a lot of the construction of the brain is activity dependent. This means that, for example, as your visual system is developing, it's useful if you can actually see. The old doctrine is that cells that fire together, wire together. That means that you get functional connections between cells that are going to be useful later on. One of the important things about the way the nervous system develops is that you actually make a lot more nerve cells than you're actually ever going to need. What happens is that there's a control process in which you over-produce cells and they undergo an almost Darwinian selection amongst themselves, so that the right connections get established. What happens then is that the cells that are not properly connected die.
Kat - I've heard that that's the Darwinian theory of drinking. You kill off some brain cells and hope that the strongest ones hang on in there!
Adrian - But the problem is that it kills off all sorts of other cells as well!
- When petrol is spilt on the ground and mixed with water, how come it's so colourful?
When petrol is spilt on the ground and mixed with water, how come it's so colourful?
That's a really good observation. When oil is put on water, it floats. However, when it floats, it doesn't form globules like soap; it spreads out as thinly as possible. This creates a layer of oil so thin in some places that it's as thin as the wavelength of light that's enabling you to see the oil. However in other places, it's slightly thicker When light goes towards the oil and tries to get through, some of the light gets reflected back by the layers of oil before it hits the water. The oil is acting a bit like a mirror on top of the water. Because the oil is thicker in some places than others, the light that is reflected back into your eye has had to travel further in some places than others. The light is split into different wavelengths and gives you pretty patterns.
- Why do my surgical scars itch more with exercise?
Why do my surgical scars itch more with exercise?
When you have surgery, the surgeon has to cut through the skin. In the process of cutting through the skin, they will almost certainly cut through some nerves.
Scientists have now come round to thinking that itching is caused by a special class of nerve fibre that seems to convey the sensation of itchiness.
The reason that scars and scabs itch so much is perhaps that when these tiny nerves try to re-grow, it's possible that they sometimes fire off inappropriately and fool the brain into thinking that there's an itch there when in reality there isn't.
Another possibility is that when the tissue is putting itself back together when you have a scar, then you get lots of tension and funny pulling within the skin. It's possible that this may be triggering off the itch sensitive nerves as well.
How do we get brain damage?
There are lots of ways in which the brain can be damaged. Sometimes the brain is born incorrectly, so it might have some of the special genes that make up the brain missing. This would make the brain damaged from the outset. Unfortunately, some babies are born with brain damage if their mum has difficulties during labour and the brain doesn't get enough oxygen. As I said earlier, if a baby is born very prematurely before their brain is properly formed, that can also lead to brain damage. There are lots of adult diseases such as Alzheimer's and Parkinson's disease which will damage and kill off the brain cells. Largely speaking, many of these brain cells cannot be repaired. Perhaps one of the most common forms of brain damage, and let's not forget that your brain also includes your spinal cord, are accidents. Unfortunately, many people who have bad accidents or falls will damage part of their back, spine or brain. Sadly, it's something that we can't cure at the moment.
- What's the largest organ in the human body?
What's the largest organ in the human body?
I'm pleased to tell you that you're right and your friend is wrong. The skin is actually classed as an organ as it performs a function in its own right and has specialised tissues to do it. I hope for your friend's sake that there wasn't too much riding on the bet!
- How fast can brain cells repair the brain?
How fast can brain cells repair the brain?
That's an extremely good question. The brain is a funny organ because it's made up of lots of different cell types. Some of these are brain cells and some of them aren't. What do I mean by this? Well, you have blood vessels in your brain, specialised cells that mop us damage and infection, and if you damage your brain, the non-brain cells in your brain actually repair themselves very quickly. The problem is that most of the really important brain cells that carry signals and tell your limbs how to move, your brain how to think and your body how to behave, unfortunately repair very slowly, if at all. That's why we've been working on a very special population of cells called stem cells. We hope that these cells have two very special properties. One is that you can grow them for a very long time in a dish in a laboratory. This will let us take a few cells out and grow them up into as many as we need. The second thing is that we want to be able to coax them into becoming brain cells. Hopefully you can inject them into people with brain damage and repair the damage. Of course, at the moment this is very early days and it's very experimental. However, some of the results we have at the moment from these early experiments are very exciting, and we hope that in many years' time, it will lead to a treatment for people with brain damage.
Why is the sun so hot?
The sun is so hot because the sun is a giant nuclear reactor in the sky. It's mixing on hydrogen with another hydrogen to make another light gas called helium. You can find helium in the funky balloons that float. When you mix the two hydrogens together, you get a lot of heat energy, and so the sun on its surface is at least six thousand degrees centigrade. That's what keeps us warm.