Friday, March 23, 2007

A Climactic Hiccup Cure (and your chance to help test it)

"Sex is good for lots of things - now it seems we can add hiccup cure to the list."

If you follow the annual presentation of the tongue-in-cheek Ig Nobel Prize, then you already know that modern medicine has come up with at least one promising hiccup cure. As is often the case for the Nobel Prizes that the Ig Nobel parodies, the recognition of Francis Fesmire's work came much later than it should have.

Back in 1988 Fesmire published a revolutionary paper entitled Termination of intractable hiccups with digital rectal massage in the journal Annals of Emergency Medicine (annals . . . that's funny).

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Skip to the Tip in this week's post.

I've heard jokes about how he might have discovered the effect, but it's not really such a stretch. The key to Fesmire's discovery may be stimulation of the vagus nerve. Other researchers have noted the connection between the vagus nerve and hiccups. Unlike most of the nerves that make their way from your brain to other parts of your body through the spinal column, the vagus nerve is a major nerve bundle that starts at your brain stem and winds its way through your abdomen. In fact the FDA has approved an implantable vagus nerve stimulator for controlling hiccups with electrical bursts.

Personally, I think Fesmire's discovery is a much cleverer way to stimulate the nerve. It makes sense because, among other things, the vagus nerve connects to the sphincter muscles of the gastrointestinal system (including the anus) as well as many muscles and organs involved in hiccuping.

For those of you uncomfortable with the massage, there's an alternative. In 2000, Roni and Aya Peleg published a case report in The Canadian Family Physician journal reporting their observation of sexual intercourse as potential treatment for intractable hiccups.

Sex is good for lots of things - now it seems we can add hiccup cure to the list. That's cool, but it begs the question as to why (and if) sex has anything to do with hiccups.

Now, I consider myself to be a skeptic as a rule. But I also try to be open minded, so I've been withholding judgement on these particular cures until I could see further data. As it happens, I came down with a heavy duty case of hiccups a few days ago . . .

Naturally, I thought I would try one of the cures myself. The massage thing seemed a bit involved and messy, so I went with the alternative. Considering the fact that I was in a rush to try it before the hiccups ended on their own and I didn't want the confounding complication of involving anyone else in the experiment, I went solo.

It worked perfectly. At the climactic moment, my hiccups ceased.

As a result, I was inspired to see if any physicists had taken a look at hiccups and whether they had anything useful to say about the phenomenon.

It turns out that in 1995 W. A. Whitelaw of the University of Calgary, along with Parisians J.-Ph. Derenne of the Groupe hospitalier de la Pitié-Salpêtrière and J. Caban of the Hopital St. Antoine published a paper in the physics journal Chaos titled Hiccups as a Dynamical Disease."= They concluded that hiccups are produced by a central pattern generator (CPG). A CPG is a neuron circuit that generates a signal, which causes an action that in turn stimulates another signal, and the pattern repeats, sometimes indefinitely. Similar circuits apparently handle numerous other repetitive actions such as breathing and walking

The Hiccup Generator as a "Black Box"

Just what all the components are in the hiccup CPG isn't entirely clear. What's more, it doesn't really matter. Instead the researchers treated the hiccup CPG as a black box. To an engineer or scientist, a black box is a system that's studied in terms of what it does, rather than what it's made of. In other words, the physicists studied the behavior of the biological system that causes hiccups without worrying too much about the individual pieces that go into it. The work led to some interesting insights, including the fact that the rhythms of hiccups seem to be tied to breathing rates and heartbeats, but it didn't do much in the way of offering any new cures.

As I see it, the most important aspect of the research is the simplified perspective on hiccups. We have a hiccup black box in our bodies that normally is in the 'off' state. Any number of disturbances can turn it on: eating too quickly, coughing, drinking a hot liquid, drinking a cold liquid, a sudden shock, a sneeze, acid reflux, or even (though, thankfully, rarely) tumors, renal failure, or chemotherapy.

Many causes of hiccups (that aren't related to diseases, anyway) involve a chemical or physical shock that kicks the hiccup black box out of its resting state and into its annoying active state.

A simple way to generally illustrate this sort of thing is to imagine a bunch of kids playing soccer (football for those of you outside the US) at the bottom of a valley. When one of the kids kicks the ball hard enough, they might knock it over the ridge of the valley wall and into a neighboring valley. If the valley next door is not as deep, the kids over there will soon kick the ball back over the ridge to the soccer game. How long that takes depends in part on the height of the ridge between the valleys, and in part on the random chance that some kid kicks the ball hard enough to clear the hill.

We see lots of situations like this in physics; an electron in its lowest orbit in a hydrogen atom can absorb a photon and get kicked into a higher orbit; an atom possessing a characteristic called spin can be flipped from one orientation along a magnetic field to the opposite orientation (this is critical for magnetic resonance imaging); and some types of glass that radically change state when heated in certain ways (a technology based on these glasses may eventually lead to novel data storage chips), to name just a few of the countless examples.

Often in physics we see systems that have been knocked from their ground states (the states they naturally prefer to be in) to higher states, which spontaneously drop back some random amount of time later. If you don't feel like waiting, hitting a system with another shock that's similar to the one that bumped it out of its ground state often knocks it back. In the case of an electron in a higher orbit around its atom, this is called stimulated emission. It takes a photon to get the electron up there in the first place, and another photon can induce the electron to fall back to the ground state immediately instead of randomly.

Hiccups work essentially the same way - a shock to your system bumps the hiccup CPG into its active state. Simply waiting will often be enough that the bout stops on its own as the CPG randomly returns to its resting state. But if you're impatient, any number of hiccup cures that rely on physical or chemical shocks to your system may do the trick immediately.

Trying to scare the hiccups out of someone is obviously a physical shock. The spoon full of sugar cure is a chemical shock to your mouth, throat, and stomach. Holding your breath, breathing into a paper bag, and related asphyxiating cures cause a chemical shock through a relatively rapid build up of carbon dioxide. I could keep going down the list, but as far as I know just about every folk cure involves the equivalent of stimulated emission to kick your CPG to its resting state.

The interesting thing about Fesmire's digital massage is that he is taking advantage of the fact that while we know very little about what's inside the hiccup black box, we know about one thing in there - the vagus nerve. (Remember, the vagus nerve stimulator implant is the only FDA approved hiccup cure.)

The other thing we know about the vagus nerve is that it's involved in orgasm. This was shown in recent studies with paraplegic women who had lost sensation in their lower bodies as the result of back injuries. The startling outcome of the experiments was that they could still experience orgasm from stimulation of their genitals. The researchers believe that the orgasms must involve the vagus nerve because it's the only intact nerve pathway back to their brain stems.

Some folks might prefer Fesmire's massage, but I'm guessing that most people would choose the orgasm stimulation to tickle their vagus nerves and kick the hiccup CPG back to its resting mode.

Do Your Part for Science

As most scientists will tell you, anecdotal evidence is pretty unreliable. And even though I experienced the cure myself, I'm willing to accept the possibility that the success was coincidental. The Pelegs’ case study adds to the evidence, but that's still only two tests.

We need more data. I'm willing to try again, but I don't get hiccups very often.

I'm hoping that you will help test the cure. The next time you get hiccups, and have enough time and privacy to do the experiment, have an orgasm (alone or with a friend) and write to me to let me know whether or not it cured the problem.

I'll compile the data and report back as soon as we have a clear answer one way or the other.

You can post your results in the comment section of this post or email me the results at "BuzzSkyline at gmail dot com."

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Thursday, March 22, 2007

Woman on Top: Closing the Feedback Loop

When I was on Tiffany Granath's show a few weeks ago, we took several questions from listeners who called in. A few of the topics lay at the very edge of the domain of physics as it applies to sex, but most were excellent questions that I was pretty comfortable dealing with.

One fellow in particular said that he and his wife have a good sex life, but she's only fully satisfied if she's on top when they make love. He was wondering why that is and what he could do to add some variety without neglecting her needs.

My guess (given the caveat that I was working with a minimum of data) was that he should take into account his wife's sexual feedback loop.

In physics, engineering, and other sciences, we often think of experimental systems as being open loops or closed loops.

An open loop system is one that has a control, which is also known as an input (think of a volume knob on your radio, or the handle on your water spigot), and an output (the radio volume or the amount of water flowing through your garden hose), but no feedback. That is, the person adjusting the radio volume is deaf and cannot hear when the sound level is correct, or the garden hose extends around a corner and you can't tell how much water is pouring out of it.

Alternatively, a closed system sends some information about the output back to the input. In other words, you turn the knob on the radio until the volume is correct, and then you either stop turning or turn it back a bit. By watching the spray coming from your sprinkler, you know whether you have turned the spigot handle as far as you need to in order to water your yard. In either case you're using information about the output to adjust the input.

Open loop systems work fine for lots of applications, and are particularly handy if you just want to turn something all the way up or entirely off. (In electronics, a common jargon for open loop amplifiers is to say that they "go to the rails," which means they can either put out the lowest voltage or the highest voltage that the power supply can handle, but they don't provide any intermediate voltages.)

If you need some reasonable amount of control over an output, you must have feedback. Sexual response can be considered one of nature's closed feedback loops. The input of of sensual contact leads to pleasurable signals passed through the nerves to the brain. In order to work well, information about the pleasurable signals have to make it back to adjust the sensual contact.

If you're masturbating, you don't need any help figuring it out - you just do what the feedback from your nerves tells you feels good. When you're making love with another person, feedback is a lot trickier. You can't share your partner's sensations directly, so you have to rely on secondary clues - by observing the way they're moving or the sounds they.remaking. The loop is more or less closed, but the feedback is relatively tenuous.

A woman who is on top during intercourse, however, can take advantage of her own strong sensory feedback to ensure that the right spot is being stimulated in the right way.

That is, it may not be the woman-on-top position itself that satisfied the caller's wife. It may instead be an issue of closing her feedback loop.

There are numerous ways for the caller and his wife to attempt to get the same result while making love in other positions. For one thing, he could work harder to interpret his wife's responses to his actions. Studying her movements or the sounds she makes during sex may strengthen the feedback enough to close the loop. Of course, it's important for the woman to broadcast her pleasure as much as possible as well. It can be very difficult to satisfy a woman who is too shy to communicate what she needs and enjoys.

Simply holding relatively still while she sets the pace may be enough to help the caller out. It's possible to accomplish this even in the traditional missionary position, if the man supports himself a bit as the woman thrusts her hips rhythmically. Placing a pillow under the woman's buttocks to raise her hips may make this easier to accomplish. It's worth experimenting with other sexual positions - any position that limits the man's motion while leaving his partner free to take charge will shift the focus and the feedback into the woman's control.

Another possibility is to encourage her help out by stimulating her clitoris or nipples to let her strengthen the sensory feedback loop herself, regardless of the sexual position they are using.

One advantage to focusing on your partner's feeback loop is that it often comes at the expense of your own feedback. That can help slow things down if you tend to finish sooner than your partner would like.

You'll get similar advice from traditional sex therapists and experts, but they usually talk about things like communication and sensitivity to your partner's needs. That's all good, but personally, I feel it's easier to think in terms of feedback loops. Of course, I'm just a physics nerd, and I tend to consider sex in terms of the little diagram you see here. If you click the picture, you can visit the Wikipedia entry that explains (in engineering jargon) the meaning of the components in the schematic.

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Monday, March 19, 2007

Physics, Sex, and Comics

I wasn't surprised to learn that other people have already noticed the intimate connection between sex and physics, but I was amazed to see how well Randall Munroe portrays the connection in comic strip form.

If you click the image here, you can see one of Munroe's takes on the intersection of passion, sex and physics.

Some of my other favorites include

Angular Momentum
The Romatic Drama Equation

In truth, only some of Munroe's comics are about physics and sex. Many of them touch on computer programming, math, or random topics that interest him, like this interesting supermarket prank.

It's funny stuff. Check out the rest of the 'toons to see what I mean.

Thanks to my good friend Davide the science writer for letting me know about

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Friday, March 16, 2007

Part 2 of The Physics Guide to Hooking Up: Why It's Better to Pursue than to be Pursued, or the Trouble with Rule 6

I'm sorry to burst the bubble of any Disney fans out there, but Prince Charming almost certainly lived more happily ever after than Snow White did.

I'm saying this horrible thing because a famous mathematical puzzle known as the Stable Marriage Problem shows that a person who pursues a mate is almost always more satisfied with their spouse than a person who is pursued.

This is a particularly important fact for women who adhere to The Rules, because physics and math suggest that rule number 6 of the top ten rules for women appears to be very, very wrong.

Skip to the Tip in this week's post.

The first analysis of the Stable Marriage Problem was described in a 1962 paper by mathematician David Gale and economist Lloyd Shapley. They were attempting to determine if a set of 100 men and 100 women could pair up in marriages in a way that no one could find a better mate in the bunch who would have them.

They way they set up the problem goes like this . . .

Each man ranks all 100 women from their first choice of potential partner to their last. The women all do the same for the men. Because the reasons one person finds another attractive is often mysterious, Gale and Shapley selected each person's ranking of potential mates at random. As a result, no two rankings were alike and one person's top choice would likely be farther down on any other person's list. Once everyone has their ranked list, the marriage game begins.

Probably because the paper was written way back in 1962, pairings among men and women occur when a man proposes and a woman accepts. To begin with, the first man proposes marriage to the woman at the top of his list. Because it's early in the game and this is the only marriage proposal the woman has gotten, she accepts (remember, it's just a simple model).

Once the first pairing is out of the way, the second man proposes to the top woman on his list. Assuming she's not engaged to the first man, she accepts. If, however, she happens to be the fiancé of the first man, the woman looks at the ranking of her two suitors and chooses to go with the one she ranked highest.

The game continues with each man in turn proposing to women in the order that he ranked them. As he goes down the list, a woman will accept his proposal if she is either unattached or engaged to a man who she ranks lower than him. Any man who has been thrown over for a higher ranking fellow eventually goes back down his list looking for a woman who is single or prefers him to her current fiancé.

Gale and Shapley found that there are always stable solutions to the problem (usually many solutions, in fact), regardless of the number of people involved. Stability in this case means that once everything is sorted out, a man who checks out all the other couples in the group would not find a woman he prefers over his own fiancé who also ranks him higher than her fiancé.

Mathematically speaking, that's a pretty interesting result. But it's not terribly useful or informative for real people like you and me. The truly fascinating revelation, in my opinion, is that something very surprising comes out of the study if you consider the relative satisfaction of men and women in the model. Specifically, if you look at the ranking of the women who the men ended up with, most men got engaged to a woman who was high on their list. Women, on the other hand, were stuck with men who ranked relatively low on their lists.

To put hard numbers on it, in an expanded a study of 1000 stable solutions to the problem when it included 512 couples, men on average hooked up with women who ranked 8th on their respective lists, while women were engaged to men who ranked an average of 80th. That's a huge discrepancy. Bear in mind that the only difference between men and women in the mathematical model is that men always proposed and women only accepted or rejected proposals.

You'd be right to take all this with a grain of salt. Mating in real life is a much more complicated affair. Even a slight modification of the problem, such as adding the potential for degrees of inherent beauty among the men and women, can radically change the numbers of stable solutions and the average degree of satisfaction. (Some realistic details can actually make the problem so complex that it's essentially unsolvable.) Nevertheless, in general when only men made proposals they were much better off than the women.

The world has changed a lot since '62. Back then, the Stable Marriage Problem didn't have a lot of relevance to the actual complexities of dating and mating. These days, there is one situation that pretty closely approximates the bare-bones problem that Gale and Shapley studied - online dating services.

When you join Yahoo Personals or some other matching service, you post your profile and often your picture. You then have a choice; you can sit and wait for invitations (for dates usually, rather than marriage) to come rolling in, or you can check out the profiles of other people and decide who you would like to contact.

If you passively wait for someone to write to you, you mimic the behavior of the women in the Stable Marriage Problem. That is, you sit on your hands waiting for an email or an instant message from a suitor, then you check out their profile and either accept or reject them.

If instead you take the initiative, you act like the men in the Stable Marriage Problem. You perform some sort of ranking and choose the person you want to contact most from all the people who have posted profiles. If the first person you write to rejects you, you are forced to move farther down in your list of possibilities.

According to the solutions of the Stable Marriage Problem, if you take the initiative in asking out the people you're most attracted to you will meet much more desirable people through online dating services than you would if you wait for someone to contact you.

This runs completely counter to rule number six of the top ten rules for women, which reads "When considering whether to use personal ads or other dating services, you should place the ad and let men respond to you."

Don't get me wrong, I think many of The Rules work just fine. Most of the rules will help a woman play a man like a starving trout hooked on a line. But if you ignore rule six and take the initiative in luring a mate, you dramatically increase your odds of landing a trophy catch rather than some loser you'll want to heave back into the pond.

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Tuesday, March 13, 2007

Book Review: Sex in Space

It turns out that my family has a tenuous connection to tabloid-headlining astronaut Lisa Nowak. Apparently, she's a few years younger than my uncle and they went to middle school together in the suburbs of Maryland's upscale Montgomery County.

According to my family's lore, one day my uncle was using crutches because of a leg injury, and Lisa kicked one crutch out from under him. He wasn't hurt as a result of the alleged assault, and knowing my uncle I'm pretty sure Lisa had a good reason to do it, assuming it's true (over years of retelling, we tend to embellish and distort stories like this in my clan).

My uncle and Lisa met up again years later when they were both flying in the US Navy. I don't think she attacked or threatened him the second time they crossed paths, but it's possible that they were both wearing diapers (my uncle has applied for astronaut slots on occasion, I'm guessing he might have had to wear the diapers as part of the flight testing process).

The Lisa Nowak love triangle naturally led me to wonder about the status of sex in space. Lisa never flew on a shuttle mission with the astronaut who was the object of her affections, so it seems unlikely that she had a chance to do a zero-g tango. The question is: have any other space travelers attempted sexual relations in orbit or beyond?

There's more to it than simple titillation. President Bush has declared travel to Mars and the establishment of a lunar base to be official goals of our space program. In either case, humans will spend extended periods in low gravity environments. Sex is an important part of human interactions. Whether or not astronauts have attempted to make love during past missions, it's hard to imagine that at least some of them won't try it during excursions lasting months to years.

This raises several concerns. We don't know whether prophylactics will work properly in space. We can't be certain that we can conceive children in low-g. And if we can, we have no idea what effect it would have on the fetus. Is gravity necessary for fetal development, or will space children suffer birth defects? Assuming the lack of Earth-like gravity itself is not a problem, will we find ways to protect sperm, ova and fetuses, not to mention astronaut parents, from the increased levels of radiation in extraterrestrial environments?

Fortunately, Laura Woodmansee has taken time to investigate the latest wisdom on all these issues and more, and compiled them in a very tasteful book entitled Sex in Space. Woodmansee is a science journalist who specializes in covering the space program. Two of her other books, Women Astronauts and Women in Space: Cool Careers on the Final Frontier specifically focus on the female astronaut contingent.

Although Sex in Space is a brief 136 pages long, Woodmansee covers topics such as whether or not anyone has had sex in space (the official answer is 'no, but the extensive hours that people have spent in space in the past 50 years and the numerous opportunities available to them suggests that there's a strong possibilty that the true answer is 'a few times'), how they might make love if given the chance, the effect of low-g on astronaut libidos, and the future potential for honeymoon trips to space.

OK, I confess, I turned first to Chapter 2 - How to make love in space. Woodmanse includes several instructional diagrams of possible positions, and brings up issues I never thought of - like just how sloppy space sex is likely to be. But once I finished that portion and went back to read the rest of the book, I found there was plenty to learn about space sex that never would have crossed my mind without Woodmansee's guidance.

One thing that didn't surprise me in reading Woodmansee's book is that NASA has not conducted any official studies of sex between humans in space. Large, formal institutions don't deal with sex well, as Nowak's troubles seem to confirm. In my opinion, however, turning a blind eye to a natural and important part of human behavior is nothing short of irresponsible, particularly if they seriously mean to put people into space for long periods.

Even a simple mission to Mars and back is going to take years. During that time, it's highly likely that some astronauts will experiment with sex. Besides, sexual intimacy is probably a good way to maintain a happy and cohesive crew, provided the whole thing is carefully thought out. After all, they will likely spend most of their time cooped up in a craft about the size of a school bus (at best). The intrepid explorers are going to need all the stress relief they can get.

Ideally, I think NASA administrators and scientists should read Woodmansee's book, and then get to work designing a comprehensive study of sex in space. At the very least, it would be a powerful rebuttal to the concerns of critics who feel that the International Space Station is a waste of time and money that could be better spent on unmanned and robotic missions. Robots can do just about everything humans can do in space except help us to anticipate the various aspects of low-g sex and conception.

Whether we like it or not, sex is going to be among the most important issues we will face if we are ever to truly to break free of Earth's gravitational bonds and move out into the vast galaxy that surrounds us. So NASA might as well face the facts and start investigating the science of sex is space.

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Friday, March 09, 2007

Those ain't just your daddy's genes (and maybe not your momma's)

You probably get half of your genes from your mother and half from your father, but it's possible that you got some of your genes from someone - or something - else.

A new model proposed by Jeong-Man Park of Rice University in Houston and his colleague Michael Deem (the same guy working on the HIV vaccination scheme I mentioned a few posts back) suggests that much a significant portion of our DNA was donated by viruses and bacteria that infected our ancestors over the ages. Although the chances are slim, it's possible that some of your DNA comes from microbes that infected your mother or father.

Park and Deem were led to the conclusion as they sought a theoretical answer to the question of why evolution proceeded fairly slowy for 2.5 billion years, as simple multi-cellular organisms developed, and then raced ahead for the next billion years to produce you and me and Brad and Angelina.

The answer may be horizontal gene transfer (HGT). When it was first proposed as a mechanism for bacteria to trade chunks of DNA and effectively adapt without reproducing, the idea of HGT was very controversial. By looking at common sections of DNA in species that should not be related, many scientists have come to the conclusion that we must be exhanging DNA through HGT. In fact, it seems to be at least as important for evolution as the passing on of mutations through sexual reproduction. Among other things, it appears that our immune systems arose from a gene transfer that must have occurred about 400 million years ago.

Park and Deem presented their model of HGT enhanced evolution in a paper published in the journal Physical Review Letters in January. In addition, Deem and Jun Sun (also of Rice University) presented a paper at this week's APS March meeting that shows how genes consist of modular chunks that lead to various traits, rather than having the genetic information spread throughout your genes. This modularity could be handy when it comes to swapping useful blocks of DNA.

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Thursday, March 08, 2007

A More Modest Security Scanner

At the Physics of Sex blog, we're huge supporters of freedom and tolerance. But part of ensuring those prescious commodities includes protecting personal privacy. Recently, some airports have installed backscatter x-ray scanners that see through clothing, revealing weapons in the very rare case that someone tries sneaking something on board, while giving security staff a gander at the most intimate details of the bodies of terrorists and innocents alike. You can see some examples in this Google image search. In addition, although the risk is low, you have to get at least a small x-ray dose to suffer the indignity.

Tomorrow morning at the APS March Meeting in Denver, Panu Helisto of the Finnish research company VTT will describe a new imaging system that measures some of the heat-radiation your body emits all the time. It is inherently unable to reveal personal details because it simply lacks resolution to produce a picture of anything smaller than several inches across. And yet it measures terahertz radiation (a type of radiation that's somewhere between infrared light and radio waves) that passes through all but the heaviest clothing, to provide enough detail to pick out the shapes of most knives, guns, and other dangerous stuff. Check out the pictures here that Helisto and colleagues at VTT and NIST made with a microbolometer. The shot on the right is a microbolometer image of the guy in the photo on the left. Looks like he's packin' some heat.

The system will be built of detectors called microbolometers that heat up and change electrical properties when light radiation is focused on them. They were initially developed as parts of antennas for imaging faint radiation from space. A bolometer-based radio antenna measured echoes of the Big Bang that started the universe running, and earned a Nobel Prize for Arno Penzias and Robert Wilson in 1978.

Coincidentally, their antenna lacked resolution to produce pictures of small objects like Uranus, and Helisto's system lacks resolution to reveal details of your a. . .

I'm not going to say it, but I bet you can figure out what I was going to type. I'm not being modest, it's just too lousy a joke. (Feel free to use it though, if you need a bad joke for the pub.)

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Wednesday, March 07, 2007

An innovative HIV vaccination scheme

I'm currently in Denver looking for Physics of Sex topics at the year's largest gathering of physicists, the American Physical Society's annual March meeting.

Yesterday I saw a presentation by physicist Michael Deem of Rice University. He applies the math of physics (including things like field theory) to look at all kinds of things in biology and medicine.

One of the papers he presented at the conference analyzed the ways that HIV manages to evade the immune response. His research suggests an intriguing vaccination technique that could cope with the ability of HIV to rapidly evolve in the human body.

One of the problems with viruses like HIV is that it mutates after infection and produces of several different virus strains. Your body's immune system develops T-cells to fight each of the strains, but tends to focus on just one variety. That means you are pretty good at fending off only one strain, while the rest of the strains run amock.

Deem's analysis of HIV suggests that once vaccines against the disease are developed, similar problems would arise if we tried to vaccinate against more than one strain at a time with a single shot containing a blend of vaccines - that is, only one of the vaccine varieties would take effect.

In order to counteract the problem, Deem proposes that future HIV vaccines should be given with several shots simultaneously injected at different locations around the body. The reason is that T-cells are produced in the lymph nodes located primarily near your joints (behind your jaw, under your armpits, etc.). Introducing different vaccines near different joints induces lymph nodes at one location to concentrate on fighting one particular viral strain, while leaving other strains to other lymph nodes.

When HIV vaccines are finally developed, a person at risk might get a shot in each shoulder, one near each hip, and maybe even at the knees or elbows.

In the meantime, Deem thinks the scheme could help in the prevention of dengue fever. Apparently there are vaccines for several strains of dengue fever, but getting the shot for one strain prevents the others from taking effect, and can increase the risk of developing life-threatening dengue hemorrhagic fever. Deem is hoping to get some medical studies started to see of his multi-shot vaccination scheme works against dengue fever, and eventually against HIV.

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Friday, March 02, 2007