Is air fluid? Why did my oven explode? Do nerves regenerate? What came before the singularity? Can an HIV-negative person transmit HIV? Should I complete a course of antibiotics? How do wine flies find my wine? TalkRadio 702's Eusebius McKaiser and Dr Chris Smith go in search of the answers...
Eusebius - Good morning Chris.
Chris - Good morning.
Eusebius - Chris, this story fascinates me, our science story of the week. I thought that there was a little bit of a crisis out potentially around antibiotics in terms of I don't know what to be becoming more and more resistant to them. They're over prescribed by doctors and so forth. But what is this one about?
Chris - Well this is an interesting study because for a long time we've been counseling patients that antibiotics are for treating bacterial infections and that because the majority of colds and runny noses are caused by viruses then taking antibiotics will do no good whatsoever. So a very interesting paper has emerged in Nature Microbiology this week by researchers at Yale Medical School. This is a Akiko Iwasaki, who has a long track record of studying viruses, and they've made the unusual discovery that in fact some classes of antibiotic drug can put the body into an antiviral state. So they might actually have an antiviral or cold remedying effect after all. Now they're not saying we should rush out there and start giving antibiotics for colds. They are saying though that the observation is interesting because it might show us how we can find new ways to manage viral infections. Now in their studies which they did on mice admittedly, so you've got to be a little bit cautious about how you translate this to a human. But what they did was to use one class of antibiotics called amino glucosides. There are agents like neomycin that are members of this family of antibiotics. When mice receive these antibiotics rubbed onto say skin or rubbed onto the inside of the nose. They found that cells in the nose were much less easy to infect with viruses afterwards and the mechanism appears to be that these antibiotic molecules through a totally different mechanism through which they kill bacteria, trigger the immune cells in the area to stop pumping out signals, good interferons, which put the adjacent cells into this very profound virus resistant state. It's like sounding a burglar alarm as a result all the cells go into lockdown, and yet you don't grow new viruses in them. So what they're saying is if we can find out what it is about these molecules, these antibiotic molecules, that make the cells do this then what we could do is to focus on that aspect of their behavior and come up with a new class of drugs which will enable us to make anti virus drugs which will be potentially very useful in the treatment of a whole raft of different virus infections because they tried this against herpes virus that causes cold sores and genital disease. They tried again Zika virus tried it against flu and it had the same effect against all these viruses. So there may, you never know, be a way to cure the common cold. And the clue may come from antibiotics in the future if we can work out how these molecules are doing this.
Eusebius - Fol, in Centurion, good morning to you!
Fol - Good morning Eusebius. Good morning Dr. Chris. Great show!
Eusebius - Thank you sir. What's your question for us?
Fol - Two or three weeks ago, as I recall, you said that air was - or air is - a fluid. Did I hear that right, air is fluid? Could you please explain that scientifically.
Chris - Sure. And you have good listening. Congratulations! Air is a fluid. Yes, you're right. You did hear correctly. It's a gas, but it's also fluid and it behaves as a fluid. And all it is is more spread out fluid. When we have water we have a much more condensed or higher density fluid. When you have a gas it behaves in exactly the same way, the molecules are just a bit further apart. But but to all intents and purposes the fluid in the air the air behaves identically to a stream of water and you can do this yourself. If you take say a spoon and dribble water over the back of it you'll see it sticking to the surface of the spoon and then coming off at an angle. If you put that same spoon in a wind tunnel and blow smoke over the spoon, which is particles in gas, you'll see exactly the same trajectory. So the two things behave both physically and mathematically the same...
Fol - I still can't get my mind around that info. Your explaination is obviously a good one but I'm still trying to work it out.
Chris - Good luck!
Eusebius - Yes you can chew on that one.
Fol - All the best.
Eusebius - Cheers, thanks a lot. Let's go to Kenilworth. Caroline, good morning.
Caroline - Good morning Eusebius - Thanks as usual for super programme!
Eusebius - Thank you kindly. What's your question.
Caroline - I'd like to ask Chris: I was baking a cake a couple of weeks ago and the oven was set at 180 degrees. All of a sudden the oven door just exploded and I couldn't understand why. And then I realized that I had just turned my Keywood chef mixer on too to mix the icing. Could that have caused the oven door to explode?
Chris - What on earth did you put in the cake? They'll be my first question. What were you cooking in there, dynamite or something?
Caroline - I want ito tell you it's a cake that I've baked many many times. It's just an ordinary old cake.
Eusebius - The just don't make carrots like they used to.
Chris - No. They come laced with dynamite or something! I suspect that you're right. When we heat things up then as a result of the change in temperature often the metal in the oven is going to be the first thing to start changing shape the most radically. The metal is going to expand. This is going to change the loading on the fabric of the cooker; how the forces are transferred across it. Glass, the oven door. I presume it's a glass door oven is relatively inflexible...
Caroline - It's a glass door oven and it's supposed to be shatterproof glass.
Chris - Yeah. But the thing is that the glass is going to be under stress, because the thermal changes in the shape of the oven and the metal expanding could apply uneven forces across the door of the oven. A number of things can make a difference to how the glass also responds to heating, because if you get a lot of deposits. I don't know how clean your oven is you might have a very very pristine open door. Many of us, myself included, do not. If you've got deposits on the glass, they can absorb heat asymmetrically which transfer heat or prevent the transfer of heat into the glass so the glass doesn't heat symmetrically. So a range of factors including the expansion of the metal of the oven, the glass not heating symmetrically, the glass becoming a bit older, and then you perhaps having some vibrations which could make a difference. This is going to lead to possibly resonances in the glass or a focus of force in one place which could encourage the glass to suddenly give. But my money would be on it being the fact that as the oven gets hot then you're going to get expansion, shape changes, and uneven loading by forces of the glass and that's going to focus force in one place and cause it to crack, especially if the glass over time has developed a weakness. Because every time you turn the oven on it heats up and then cools down, and this is going to cause things to expand and contract, expand and contract and you might get tiny fractures in the glass just because it's getting older. And with repeated use and cleaning and so on you do get these micro fractures in the surface and they're going to focus forces at one particular point which is going to make the glass more likely to go eventually in that place.
Eusebius -Thank you Caroline. Let's take one from Twitter. Yes one Chris, Brian has got an interesting one I think. Brian says why can I hear my phone's alarm but not my wife's alarm, and yet she wakes up earlier than I do?
Chris - Well, it might be something to do with the frequency that's used because, perhaps - Brian doesn't say what he does for a living but perhaps - he has a degree of hearing loss with older age. Perhaps the frequency that the alarm is running at, the sound frequency, he has a relative or a slightly lower sensitivity to than his own phone. If his own phone is closer to to him, obviously it's going to be louder because the further away you are from a sound source the quieter the sound is, so that might be part of it. We also answered the question a few weeks ago here on the programme which was: "why do I always wake up before my alarm clock?" And we discussed the fact that we're conditioned - because we have a body clock - we get conditioned and into a pattern where we predict what time of day it is and we use that to optimize our activity. So it might well be he's just very tuned into waking up at that time and so he's closer to the threshold of waking so his alarm has an easier job waking him up or his or whatever because of the time of day that he's got habituated to being woken at..
Eusebius - It makes sense. Lebo good morning.
Lebo - Morning. My question to do with nerves. Do nerves regenerate? In particular, I lost my sight and apparently there's nothing wrong with my own eyes. What happened was my nerves were swollen; and then they gave me a steroid called salmeterol, and it brought the swelling down from my nose. But after the swelling came down, the nerves did not return to their original shape, hence I've lost my sight.
Chris - Good morning. I'm very sorry to hear about your sight loss. The answer is, it depends on which sort of nerves were talking about because the body can be considered in two zones. There's the central nervous system which is your brain and spinal cord, and then the peripheral nervous system which is nerves around the rest of the body. Now, as a general rule if you injure nerves in the periphery, so say I injured a finger or heaven forbid amputated an arm with a chainsaw or something, if this tissue is promptly reattached and the nerve endings are brought together, nerve cells in the periphery can regrow down the nerve and reconnect to their original target. And you can get back motor function the ability to move and you can get back the ability to feel sensation. It takes a while because the nerve takes a while to grow back down the conduit or the path of the old nerve. It uses that as a pathway to find its target but it definitely happens. Now in the central nervous system things are quite different and the central nervous system is it does include the optic nerve. So the problem with yourself by the sound of it is that there's been damage to the optic nerve and as a result the nerve cells. Although the optic nerves is outside the brain, its got a connect into the brain substance to make the connections so you can see. And if you've damaged those nerve cells theres a high likelihood that they won't regrow because the cells that provide the nerve tissue in the first place have been damaged. In other words the ganglion cells that make the optic nerve may have been damaged irrevocably by the injury and that may be why it hasn't come back. So the bottom line is that the central nervous system regenerates very poorly and that's why people who have strokes, for example, do find that they have a limited ability, not a zero ability, but a limited ability to recover and the stroke is obviously damage to central nervous system tissue. In your case it sounds like swelling could have caused damage and that's probably why the nerve cells have not regenerated.
Eusebius - Indeed. We're taking your questions from you from science. Bongani, good morning.
Woganda - Good morning Eusebius, and to the Naked Scientists good morning!
Eusebius - Good morning Bongani. What's your question?
Bongani -Yes. OK. So my question is this. I'm very interested on the Big Bang Theory. So I've been doing some research on the past few months. I just wanted to ask the scientist there because I've been buoggling with this question and can't get to the bottom of it. I just want to ask you see what came before the Big Bang Theory? What is the evidence that is to how do we know that the small dot that was spinning is smaller than a dot on a paper? And everything like how do we know it even existed in all of that stuff? I can't get my mind. I'm still reading but I just think that the Naked Scientists can explain. Where did that dot come from and where was it spinning in? What caused it to spin and is there evidence or is this just a sort of beleif or whatever? I just need to know with regard to that piece.
Chris - What's being referred to here is what happened about thirteen point eight billion years ago. Because that's the time when we believe, based on our current measurements and modelling, that the universe first began to exist. And we think the universe came from a singularity, that's the dot that's being referred to by Bongiorni here, and we think this singularity is extremely small but extremely energetic and for some reason, that we dont understand, this energy unleashes, the universe pops into existence and very rapidly begins to inflate like a balloon blowing up, and it inflates very very fast and its very very hot. And then as the universe inflates and expands it cools down. As it cools down then some of these very hot soup of material begins to condense and you get the first matter and you get hydrogen helium and a tiny bit of lithium. Over time, because all this material is randomly moving around under gravity, it begins to bunch together and because everything's moving around it can't not move around so all the momentum or movement or spinning of these objects materials coalesces into balls and thats why the objects, the galaxies, the stars that condense in their planets that form around those stars. Thats why theyre all spinning and turning to because everything's got momentum and you have this thing called conservation of angular momentum. The universe then slows down its growth for a bit, and as it ages though it's speeding up again. And we know that because if we look far away in the universe we can see that things are moving away from us, and the further away we look the faster they're moving away evidence that the universe is growing and as it ages it's growing faster. Now what came before the universe we don't know. No one was there to see it. No one was there to see the beginning of the universe but we can infer what happened because there are still what people dub the echoes of the Big Bang knocking around in the universe today. There's something called the cosmic microwave background radiation and this is effectively radiation left over from when those initial phases of the big bang happened. And because the universe is stretched out and grown the light, those radio signals, have stretched out and become very long wavelength radiation but they're still there. And there are signals hidden or written into those radio signals, those microwaves, that we can read today and they give us clues as to what was happening in the early phases of the big bang. So we can work out what was happening and we can work out roughly when it was happening by looking indirectly at these other measurements and other things that are around today. And physicists are running very complicated simulations saying well we know where the galaxies are, give or take today, or many of them. If we put this into a computer we can model how it must be growing and evolving, and if you can model how it's growing and evolving getting bigger you can then win the clock back to ask what would it look like in the early days? And that's what they're doing to try to get a model of where we came from and where we might ultimately end up.
Eusebius - Okay. Let's say this is a such highly theoretical question in terms of circumstance but let's go there from Mike on the SMS line. Is it possible for me to be HIV negative, to have sexual intercourse with someone is HIV positive and then test negatively after but, nevertheless, remain infectious?
Chris - Okay. I mean first thing one must be very very cautious because HIV is transmissible and one must be very careful about this and don't have unsafe sex because HIV, currently, we have no way of curing people who acquire this virus. So it's not something to take risks with.
Deusebius - That's why I was hesitant from a public health point of view. But nevertheless let's deal with it for the moment.
Chris - Now the way we test for HIV is a person who has had an exposure in the past, or just wants to know their status will supply a blood sample. Now we tend to look at least three months after a person's last potential exposure because it takes time for what we're looking for in our blood tests to register and to be there at a level that means it's safely detectable. And what we look for are antibodies to HIV. We also look for antigen which is proteins made by the virus as it grows in the body and so we were effectively looking in two different ways at two different targets and with several different tests to make sure there are no false positives or false negatives. And if we register a positive we then go back to the person and we test them again on an independent blood sample to make sure we've got the diagnosis right because it's possible a test sometimes gives a false positive or false negative. A test also might be tested or carried out on the wrong blood sample. These things happen so we always retest. Now if you do this, the likelihood of getting the wrong result is extremely low because we're using multiple different tests which look for different things. You're coming at the problem from different angles so it's very unlikely that you're going to miss something. It's not impossible though because you can never say never in medicine. And it's also not impossible that somebody could acquire HIV and then shed the virus and and then cease to be infected because they have an effective immune response to the virus. And these people do exist and we occasionally find them. In fact, we think we found somebody in this situation in our hospital recently who had clear evidence of having been HIV positive in the past and appears to have mounted a successful immune response and cleared the infection and has an undetectable viral load in their body. Now this does happen but these people are rare. And at the moment we're trying to study them to try and work out how they do this. Because if the immune system is capable of doing this, which it clearly is, it might be possible to try and find a way to persuade everyone elses immune system to do the same thing and clear the virus in their body as well. But at the moment we dont know how this happens and its pretty unlikely that for an average person you would test positive or acquire the virus and then suddenly test negative. And if you're testing negative, then actually you can't be shedding the virus because you have to have virus growing in your body and be detectable in the bloodstream to be infectious for HIV I would say.
Eusebius - Amanda good morning.
Amanda - Good morning. I wanted to ask you about an article in the UK Guardian a couple of months ago that said that new research has shown that if you're feeling better in the middle of a course of antibiotics, you should stop taking the antibiotics instead of finishing the course. And I wanted to know if you could explain why?
Chris - Yeah. The reason that people have this sort of mantra about always complete your course of antibiotics. It's based on some sound science in the sense that if we take TB as an example, one of the reasons why tuberculosis is such a massive problem, and in fact there's probably about 2 billion people around the world who are infected with TB. One of the reasons it's such a challenge and why we now have antibiotic resistance forms of this all over the place is that the drugs are expensive, they're inconvenient, they have side effects so if people take a little bit of a drug they feel better very quickly and then they think I'm cured, so then they stop because they dont want the expense and the inconvenience. They haven't completely removed the infection so it then comes back with a flourish. And then they take more drugs, but those drugs now the bug has become resistant so they have to take some different drugs. And as a result we then get resistance to the next batch of drugs and the next batch of drugs. And so the idea of getting people to complete a course and eradicate an infection from their body, that's the whole point of why people are urged make sure you complete the course. Now the evidence from the Guardian on the other hand, the article you're referring to, is slightly different. What that's saying is at the moment what we do when a person has a bacterial infection is we say right you have say a urine infection we'll give you X number of days of this drug, take this and then you'll be better. Actually, that's based on the fact that when people take a drug, we know that if we give it for that long we're going to cure everybody. But in fact there are some people in the population who dont need it for anything like that long and we just haven't looked. And so now people are beginning to go back and they're beginning to ask whats the time that is actually better to give the drug for that will achieve cure in those people and minimise the side effects and minimise the cost. Those are the sorts of questions that are being asked now in order to do better stewardship with our antibiotics and also to minimise the cost and inconvenience and side effects for patients. We're not in a position where we have gold standard advice or everything yet though. So the best thing to do is to follow the advice of your doctor who should already be giving you the minimum duration of antibiotic exposure that you need and tailoring your therapy accordingly. But certainly these questions are being asked and people are looking to minimise the exposure that people have to antibiotics because there are always side effects.
Eusebius - Okay. Thankyou so much for that question Amanda. Very much appreciated. Let's see, we've got enouh time let's squeeze in one more. Andre, can you open your question for us?
Andre - Yeah. I just want to ask, once you open up a good bottle of wine, all of a sudden you just have wine flies coming from where?
Chris - I know what you mean because I do this; you open a nice bottle of Shiraz and, within seconds, it's full of fruitflies isn't it? The answer is they're all over the place and they have an exquisitely sensitive sense of smell. The antennae on the flies are decorated with nerve endings which have these chemical receptors on them for the very same volatile agents which are given off by wine. Because these flies would normally track down fruit, rotting fruit, and fermenting fruit that's dropped on the floor. They go and drink the sugar that's being released by that fruit, they lay eggs on the fruit and then more fruit flies are born. Ao their nervous system is programmed to detect those chemicals at very very low levels and to fly around detecting when they are flying upstream, so they can compare between the two antennae the concentrations of those volatile chemicals in the air. And as they fly backwards and forwards they can work out when they are flying towards the source. And they can smell these things from very great distances away, and they will hang around in the environment and as soon as they pick up that smell they think aha, that's lunch. that's my chance to go and get a sugary meal, meet some other fruit flies, make sweet fruit fly love and lay eggs and they're looking to do that in your wine because they think the wine is some fruit because, at the end of the day, it came from fruit and it was grapes.
Eusebius - Absolutely. So if you have it. Thank you Andre. Thank you so much Chris love your work. We'll do it again next week.
Chris - All right. Thanks everybody and see you soon. Bye bye!