Your Questions and the Science of Sword Swallowing

Tobacco causes around a quarter of all cancer deaths in the UK, as well as heart disease, lung disease and other heart problems.  And it's a fiercely addictive drug, meaning that people find it hard to give up. But some people do manage to quit the cigs relatively easily, while other fight a life-long battle.  And what makes some people become addicted after just a few puffs, while others can smoke a few cigarettes then just stop.

Now researchers from across the US have used the latest DNA analysis techniques to hunt for genes linked to smoking behaviour, with the hope of shedding light on this conundrum.

The team looked at DNA from over 2,300 men and more than 2,200 women - a mixture of smokers and non-smokers - and looked at their smoking behaviour. This included the number of cigarettes smoked per day, age they started smoking, how long they had smoked for, and pack years (for example, one pack year is the equivalent of smoking one pack  day for a year, or half a pack a day for two year). The scientists also looked at whether the people had ever smoked, or if they had managed to give up.

The researchers used so-called SNP ("snip") analysis to track down potential genes linked to specific smoking behaviours. In total, around 2,600 of the people in the study had ever smoked. Although they didn't find any new genes linked to smoking, the results provided more evidence to support the existence of an important gene on chromosome 15 linked to the number of cigarettes smoked per day.

The team also found evidence for variations in genes encoding nicotine receptors being involved in some smoking behaviours, as might be expected, including the number of cigs smoked per day, the number of pack years, and the age they started smoking. And they also found a link between variations in a gene region called MAOA on the X chromosome and whether people smoked more or less than 10 cigarettes per day.

This is an intriguing gene, as some studies have shown possible links with alcoholism and Parkinson's disease, so it needs more investigation.  And another interesting result was a link between variations at alcohol dehydrogenase genes and whether a person had ever smoked, or never smoked.  So perhaps these genes are linked to whether a person actually ever starts smoking.

But the main thing the team took from their study was that the links between any of these genes and specific smoking behaviours, although it has thrown up some interesting candidates that merit further research. But the true picture is likely to be very complex, involving social as well as genetic factors.

One of the most intriguing areas of neuroscience at the moment is the issue of the "sense of self" - basically, how we are aware of our own thoughts and personality. Previous research has shown that a few areas of the brain - the prefrontal cortex, the posterior cingulated cortex, and the parietal regions - are involved in self-reflection, and processing our sense of self.  

But can we draw a distinction between regions of the brain that are specifically involved in processing thoughts about our "self" from those that are involved in processing thoughts about people in general? New results from researchers in the Netherlands using functional MRI scanning have provided a clue - our sense of self may reside (at least partly) in a region called the anterior insula, deep in the forebrain, which is part of the brain linked to feelings and emotions.

The researchers used sixteen young male volunteers an put them in a functional MRI scanner, which looks at the activity levels of different regions of the brain. They were shown three different types of statements, and were asked to say whether they were true about them, like "I am a good friend", about someone they knew like a team-mate or classmate, like "So-and-so talks too much", or just a general knowledge fact like "a vertebra is a bone".

While asking the volunteers to carry out the task, the researchers monitored their brain activity. They found that when the volunteers were considering the statements about themselves, there was activity in the anterior insula, but this wasn't seen so much when they were thinking about the general knowledge statements. And, crucially, activity in the anterior insula wasn't seen when they were thinking about other people.

The team found activity in regions such as the medial prefrontal cortex and the posterior insula when the volunteers were thinking either about themselves or about another person. But the scientists only saw extra activity in the anterior insula when the volunteers thought about statements related to themselves.

These kind of studies are important, not only for scientific interest, but for psychiatrists. There are several illnesses in which a person's sense of self is disturbed, including schizophrenia. Understanding more about the parts of the brain that are involved could shed light on the roots of these complex diseases, if neuroscientists focus more on them.

Kat - That's my idea of fun. I don't know because if you have a bath...

Chris - If you drink the bath water...My children do!

Kat - If you drank it, it might. I don't know if we absorb stuff through our skin. I thin kthe skin's barricaded for the blood stream.

Chris - The skin is pretty good but you do absorb alcohol at the sites of mucus membranes. That's why French people love putting suppositories in their bottoms, for example. There are some tablets you can put under your tongue. Where you have a mucus membrane the blood vessels are very close to the surface and the skin Is very thin. You can get things that dissolve well in fats to go through. Kat - Would a lady, as well - through her lady parts - could get drunk by sitting in a bath of vodka?

Chris - Yes, men as well. I think you probably could absorb small amounts that way. Also your eyes, you cold get some of the vapour going in through your eyes, up your nose because it would volatilise. Presumably you'd make it warm sitting in a bath. You'd probably want it warm. Kat - Maybe a cocktail umbrella.

Chris - Maybe some fruit to go with it. Dave - I guess it'd also dry you out very quickly because osmosis would suck al the water out from inside you. Chris - You'd be quite dessicated. You wouldn't want to drink the vodka probably, afterwards.

Dave - Well when any bomb explodes the first thing you're going to get is a lot of high-pressure gas because you've taken a load of solid and turned it into gas. It wants to expand. Water isn't going to move away nearly as quickly as air does. The pressure's going to remain very high, pushing water away. The fastest the water can move away is roughly the speed of sound in water. That's 1400m/s. You're going to form a bubble. As that water is pushed away very fast you're going to get a second powerful sound wave or pressure wave moving away from it. If the water doesn't compress that's going to have a very high pressure and do a lot of damage which is why depth charges can destroy strong things like submarines, even 10-20m away. Apparently it's way that there's a theory of how you might be able to blow up safes. If you fill a safe with water an drop a small charge in then because the pressure change is so much greater it might blow the door off.

Chris - That's because all the pressure is being exerted on the safe. If you were to just stack a load or dynamite at the front of the safe, some of it would hit the safe but a lot of that pressure would go out.

Dave - The gas that's produced, all that extra volume that's produced is pushed on the side of the safe. Normally you can just compress the air inside the room. Kat - It would be more explosive if you fart in the bath as well.

Meera - 2009 is Darwin year and it's 200 years since the birth of Charles Darwin. This week I'm at St Jude's primary school in Herne Hill, London for the launch of the Wellcome Trust's Darwin initiatives.  These include resources such as the Tree of Life: a short film exploring evolution on Earth.  Today sees the launch of the great plant hunt where a treasure chest filled with activities has just been delivered by Sir David Attenborough to the kids here at St Jude's to help them explore nature and science the way Darwin did.  With me now is Angela MacFarlane, Director of Content and Learning at the Royal Botanic Gardens, Kew, who helped create this amazing treasure chests. Angela, tell me more about the great plant hunt.

Angela - The great plant hunt is a project to get every single primary school child in the country involved in some real outdoor hands-on science, following the steps of Darwin.

Meera - What kind of things are inside the chest?

Angela - There's a millennium seed bank, mini seed bank which is what our scientists use to preserve seed and to keep the seed viable over many years.  They've got a plant press, they've got magnifiers, they've got seeds, a story book and then on the website they've got a space where they can share photographs of the work they've done with every other school in the country.

Meera - How can things contained in this kit help them understand more about Darwin's principle?

Angela - All of the activities start off with a thinking walk.  The methods that Darwin used were actually pretty straight forward. He went out and made good observations.  He made records.  He made collections.  The key thing is he did a lot of very high quality thinking.  What we want to do is get the children thinking about what they're seeing.  If they live in an inner city area and they can't get out into the countryside they can actually do a thinking walk just in the playground, looking at the things that are growing on the walls, coming up through the concrete.  They start off by looking at what's growing around them, making collections, doing experiments and their thinking develops from that point onwards.

Meera - Why do you think it's important for children to know more and understand more about Darwin's theories and his science?

Angela - Well the thing about Darwin's science is it's actually very accessible.  It's a really good introduction to science generally, collecting evidence, doing experiments.  We need them to understand the importance of science and scientists to the everyday world around them.  For example, the fact that we don't know all there is to know about the natural world is a really important message.

Meera - Angela MacFarlane from the Royal Botanic Gardens at Kew.  It looks like we're about to set off on one of these thinking walks now with the kids to explore the kid's nature garden.  We've been wondering around the nature garden looking out for plant and, in particular, weeds to get them thinking about how they manage to grow in unusual places.  With me are some members of the year two class in St Jude's.  What have we all discovered about weeds today?

First Pupil - They grow in different places like in the walls and the trees and soil and even stones.

Second Pupil - I'm wondering, how do they come through if there's loads of stones all over the place?

Third Pupil - The seeds of one of the flowers must have made a weed grow through one of the stones.

Meera - What about Charles Darwin? Do you know much about him yet?

First Pupil - He went on the HMS Beagle and discovered al sorts of things.

Second Pupil - Well I know that he was born February 12^th. He died when he was 200.

Third Pupil  - He was idle at school, he wrote lots of pages about worms and he played with dogs. He was born 200 years ago.

Meera - He was indeed, born 200 years ago, rather than living for 200 years!  Thanks to the Year 2s at St Jude's primary school.  The great plant hunt was kicked off here today by Sir David Attenborough who's been walking around with the kids, exploring the garden himself.  I caught up with him earlier to talk about why Darwin's theories have been so important to science today.

David - Well, it is the unifying theory of the life sciences and it continually throws up new problems and produces and suggests new answer.  A precise detailed mechanism whereby variation can arise and why different varieties and different variations become selected.  There's a lot of work to be done on that.  It also threw up a number of problems.  If it was true there are a number of difficulties which scientists at the time very properly said:  'We don't understand that. How could that be if Darwin was right?'  In the hundred and fifty years since publication of the Origin of the Species every one of those major problems by scientists sometimes working in a quite different field.  Suddenly you'll discover that they have found something which has validated Darwin's theory.

Meera - So one project you've been working on has been the tree of life project.  What is this and how does it represent Darwin's thoughts?

David - Well, when Darwin in one of his early notebooks was speculating about how life might have developed he drew a tree.  It looks like a trunk and then it branches into different branches and the branches then branch into small branches and so on.  That was the way he thought life could develop.  Everything that we've known since then has proved that is indeed the way that the tree of life has developed.  In recent years we've discovered DNA.  Darwin didn't know anything about DNA but DNA enables you to establish the relationships of and organism.  Just as in our law courts DNA is used, DNA fingerprinting, to establish the paternity of a child.  Now that kind of DNA fingerprinting can also establish the relationship between, say, a lion or a tiger or a chimpanzee and a gorilla and a man.  An enormous amount of work has been done by DNA scientists now so that we can draw the diagram which is the tree of life with complete confidence.

We put this to Peter Djiewulski, Plastic and Reconstructive Surgeon, Director of Burns Centre at St Andrew's Centre for Burns.

What happens when somebody gets burned and their tissue is burned is that heat causes direct damage to cells. It denatures proteins within and without cells. It's that injury and the breakup of cells and the contents with in the cells, particularly some of the enzymes within the cells that will initially cause pain but secondarily bits of cells that break down cause local irritation. The cell wall breaks down and that leads to a number of breakdown products which are involved in inflammation and the inflammatory response. Most people have burnt themselves and therefore would be well-aware of the local effects that the burn and the body's reaction to the burn will cause. That is usually swelling, redness and tenderness. At a molecular level these events are mediated by the inflammatory mediators which have effects on, particularly, the tiny ittle blood vessels that go up to and into the skin to make them leaky. This allows fluid which is usually in the blood vessels to leak out and this gives rise to swelling.

Chris Smith answered this question...

Chris - The reason for that is because you have various reflexes that are designed to protect your airway: there's a nerve supply, the internal laryngeal nerve, which is sensitive to everything touching your epiglottis inwards and down into your airway.

You need to defend your airway very carefully because if anything goes in there it could threaten your ability to breathe. There's a very profound choking reflex and that triggers a cough. It also triggers various secretions to happen, the idea being that it will lubricate your mouth and anything that's stuck will get free.

At the same time, the same secretory-motor system also makes your eyes water a bit. It makes tears come to your eyes and also what you're doing when you're coughing and choking, you're blowing air up your tear duct. Normally the tears that you've got in your eyes drain down little punctum which is a little plug hole in your lower eyelid towards the middle. They go down towards the naso-lacrymal duct and drip into your nose. If you raise the pressure in your nose by coughing, sneezing, blowing your nose the pressure is reversed. It pushes the tears back up your tear duct and into your eye.

So there's two things going on: one - you increase the secretions, and two, you probably jettison some tears back into your eyes!