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Breaking Science

The Breaking Science team come to BBC Radio Five Live to break open this week's science stories.

The Breaking Science team discussed new research that might help our understanding of how we smell:

Kat Arney: They do say a rose by any other name would smell as sweet, but what does make us think that a rose smells nice but my feet smell bad? My feet don’t smell that bad. But until now scientists have known relatively little about how the smelly molecules, known as odorant molecules, are recognised by the receptors in our noses. But new research by Harumi Saito published in the journal Science Signalling this week could shed some light on this mystery.

Chris Smith: So come on then, tell us why does a rose to me smell like a rose and your feet smell, well let’s not go there.

Kat Arney: Well our sense of smell is an amazing thing and our noses have hundreds of olfactory receptors, each of which can pick up a different smelly molecule and this then sends a signal into the brain which gets interpreted as a smell. But we only know around about 50 of these smelly molecules and that somewhat limits our understanding of the whole system.

Chris Smith: So what are the researchers actually doing in this study to try and home in on what’s going on?

Kat Arney: Well they used a technique called high throughput screening which allowed them to carry out many, many experiments in a short time, and this allowed them to test 93 different odorants, these are the smelly molecules, against a panel of 464 different olfactory receptors, and they picked up 52 specific odorants that activate mouse receptors and the screen pulled out 10 new odorants that activate human receptors.

Smelling a flower.
[image © copyright Jupiterimages]

So this has, you know, made a big increase on what we know about the number of specific molecules that interact with the smell receptors. And the scientists used the knowledge from their screen to then develop a computer model that can help to predict what kind of odorant molecules might fit with different olfactory receptors.

Now it’s probably possible to look at a whole range of smelly chemicals and try and predict which olfactory receptors they might bind to. So this is basically going to speed up the process of research in this area so scientists will have better ideas of which routes to follow rather than just taking shots in the dark.

Chris Smith: It’s interesting because before Christmas I spoke with a perfumer who makes smells for a living, nice smells, and he had the chemical equivalent of synaesthesia, he could imagine a smell and see the molecule in his mind’s eye that would smell like that, so I guess he’d be very interested in a function or a model like that.

Kat Arney: Absolutely. Fascinating.

Listen to the whole programme, originally broadcast on BBC Radio Five Live, February 2009

The Breaking Science team revealed some new research suggesting 'a bad taste in your mouth' might be more than just metaphor. Here's a transcript:

Chris Smith: Hello, I’m Chris Smith and this is Breaking Science, which is produced in association with the Open University.

First, with news from across the scientific globe it’s time to join our science reporter, Dr Kat Arney. To kick us off, Kat, the headline in Science is quite funny but it only really works with an American accent which is ‘from oral to moral’, scientists are saying that the way we react to things that we find objectionable is all based originally on foods that we don’t like the taste of.

Kat Arney: Yes, we often use the phrase ‘it left a bad taste in my mouth’ to describe an activity or a situation that we find quite unpleasant. But now researchers writing in the journal Science have shown that there may actually be more to this metaphor than meets the eye.

Chris Smith: Pray tell why?

Kat Arney: Well the researchers, led by Hannah Chapman, wondered if there was any kind of link between the facial movements made when we eat disgusting food, you know, that sort of ‘urgh’, and when we see disgusting pictures or when we experience really unpleasant behaviour so they carried out some intriguing experiments using volunteers.

Chris Smith: I thought you were going to say for a moment you’ve been sampling my mother’s cooking. But go on, tell us, what did they do with their volunteers?

Close-up of dog taste buds.
[image © copyright Jupiterimages]

Kat Arney: Well to start with the researchers gave the volunteers different drinks, they were either neutral tasting, sweet or bitter, and then they took close up video images of their faces. And in particular they focused on the actions of a group of muscles called the levator labii, and these are the muscles that make us wrinkle up our noses and raise our upper lips when we taste something nasty. Now unsurprisingly they found that the bitter taste caused a big movement of these muscles compared to sweet or neutral tastes.

Chris Smith: Yes, but how does the disgust at things and the behaviour bit of it come into this?

Kat Arney: Well next the scientists showed people pictures of disgusting things, including poo, injuries, insects, things like that, and they compared these with pictures of sad things and then some neutral pictures for contrast, and the team found that only the disgusting pictures led again to the movement of these levator labii muscles, and the stronger the disgust that the person felt the more their muscles moved. So this is quite intriguing, and the team went on to look at situations where people experienced unpleasant or unfair situations. These were met with these same facial movements of disgust, say, seen with a nasty liquid or unpleasant pictures.

Chris Smith: So give us the bottom line, taking a financial analogy then, what does this mean in terms of how this behaviour maps onto what we actually do in real life?

Kat Arney: Well, the researchers think that this means that moral disgust and outrage actually has similar evolutionary roots to physical disgust, and they think that this physical response to something nasty has probably been co-opted during our social evolution to express our disgust at social and moral situations that we don’t like.

Chris Smith: Indeed.

Listen to the whole programme, as broadcast on BBC Radio Five Live February 2009

Blogging about

Breaking Science

The Breaking Science team come to BBC Radio Five Live to break open this week's science stories.

The Breaking Science team met two researchers who’ve been following the hum of insect wings

Chris Smith: In some countries it’s traditional to woo or serenade a woman by singing beneath her balcony. Well now it turns out that things aren’t so different in the insect world. Here’s Lauren Cator.

Lauren Cator: I’m interested in how mosquitoes choose their mate, and my hypothesis is that they may use flight tone as a way to get information about the quality of potential mates.

Chris Smith: So in other words how fast the wings are flapping?

Lauren Cator: It’s not a direct relationship but that sound that’s created by the wings flapping, yes.

Chris Smith: So what was the big unknown then that you were trying to investigate here?

Lauren Cator: There was a paper published in 2006 by Gibson and Russell, and they found that in Toxorhynchites, a large non-blood feeding mosquitoes, that a similar behaviour was occurring, and, as a medical entomologist, I was interested in seeing if medically important mosquitoes, mosquitoes that feed on human blood and transmit pathogens that infect people, were doing similar things.

Chris Smith: Well this seems like a very good time to bring in Ben Arthur who’s another researcher on this paper. Ben, how did you actually investigate what was going on with these mosquitoes to see how they were tuning into each other’s wing beat frequencies?

Ben Arthur: Well it was a two-part study. We had behavioural methods and some physiological data as well. In the behavioural data, what we did was we tethered individual mosquitoes to a fine insect pin with some glue and positioned them next to a special microphone which could sense the wing flight tone very finely and just listened to what they were doing.

[Sound of mosquito]

So what you’re listening to right now is a male mosquito singing along at around 600Hz, and he’s next to a microphone. And we’re going to bring in a female here.

[Sound of mosquito]

And she’s singing at 400Hz. And the higher harmonics at 1200Hz, the shared harmonic, if you listen real close, you can hear the beats produced because those two frequencies are so close together. And that’s what’s happening when they’re courting.

Chris Smith: So which sex is changing its wing beats in response to the other?

Ben Arthur: They both do. So if the male’s relatively stationary and the female comes in she’ll modulate her tone up or down to match his, or if the female is stationary and then the male can move his and they’ll just synchronise to actively both match each other.

Chris Smith: You’re saying it’s not actually the frequency the wings are beating at, but the harmonics, the multiples of the frequency the wings are beating at, which seems to be important?

Ben Arthur: That’s right. So the natural occurring frequency of the female wing beat is at 400Hz and that of the male’s at 600 and those are different enough that they don’t try to match the fundamental but rather the shared harmonics are the integer multiple at 1200Hz.

Chris Smith: How does the mosquito that’s the recipient of these frequencies, how does it actually detect them, and how do you know that it’s actually responding to the frequencies, and then how does it then know, right now I need to mate?

Ben Arthur: Right, well it has these very plumose antennae, and these antennae sense the movements of the particles in the air, and there’s a sensory organ at the base of the antennae called the Johnston’s organ which transduces that movement of the antennae into an electrical voltage that the nervous system can then use to detect where the sound is, and what it is and whether it’s a mate or not.

And the second part of our study then recorded from the Johnston’s organ and saw these electrical voltages and we found that we could measure electrical voltages all the way up to 2kHz which includes that shared harmonic at 1200Hz.

Chris Smith: Wasn’t there some claim previously by other people though that mosquitoes a) were deaf anyway and b) that they couldn’t hear sounds that high in frequency, so you’ve really scuppered both those myths haven’t you?

Ben Arthur: That’s right, exactly, and we’ve shown it with both behavioural data and physiological data in the same paper.

Chris Smith: Lauren, what do you think that the major impacts - apart from obviously this being academically very interesting - what do you think the main other impacts are from a medical point of view?

Easy to repel - but how would you attract a mosquito?
[image © copyright Jupiterimages]

Lauren Cator: Well just generally we know very little about mosquito mating behaviour, and we have no idea who’s choosing who or how they’re choosing them, and one of the control strategies that’s been proposed is to create transgenic mosquitoes - so mosquitoes that through genetic manipulation are either unable to transmit pathogens or are sterilised. The idea would be that if you release these into the wild that males carrying your desired genotype would be able to compete with wild males for female mates, and drive the genotype through the population. Unfortunately we have no idea what constitutes a sexy male mosquito.

Chris Smith: Hopefully they’ll find out soon. That was Lauren Cator and before her Ben Arthur. They’re both based at Cornell University, and they’ve published that work in this week’s edition of the journal Science. And if you’d like to read a bit more about how animals use sounds to track down a mate or find their way around there are links to a number of articles about those subjects on the Breaking Science website.

You can hear the mosquitos - and the whole programme - on the Breaking Science website. This interview was originally broadcast in January 2009 on BBC Radio Five Live

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