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2/13/06 12:02 pm -  mochapixie - A new study suggests that male circumcision puts women at lower risk for contracting HIV. The study, which looked at more than 300 Ugandan couples in which the man infected the woman, found that 299 women contracted HIV from uncircumcised partners while only 44 were infected by circumcised men.Sounds clear then, right? Except that they don't indicate how many men in the sample were circumcised. Is this simply a matter of probability? If most of the men in the study are uncircumcised, it would logically follow that more women would contract the virus from uncircumcised than from circumcised men.Interestingly, while circumcision is popular in the rest of Africa, in Uganda it is practiced by only a small minority of people. That being the case, women could be less likely to contract HIV from a circumcised man because there are fewer of them around, rather than because of any inherent benefit in the circumcision itself. Not as exciting a conclusion, but equally valid.Some of what they conclude even sounds like a throw back to the popular western notion that men with a foreskin are unclean dangerous. According to researchers, the cells of the foreskin's inner lining bind to HIV more easily and can contain more of the virus than the outer layer of the foreskin. The doctors warn, however, that the removal of foreskin might simply reduce the degree of exposure to HIV for the sexual partner -- not remove the risk entirely. Might? I'd say that, if it truly has any effect, it is clearly only a matter of degree. It's not as if removing the foreskin instantly creates some sort of anti-HIV forcefield. Everything with HIV is a matter of degree. If you have sex with an infected person, you're at risk. How much risk can vary, but there's always risk.The thing that really gets me is this: they're arguing that circumcision prevents the spread of HIV because HIV viruses cannot stick to the circumcised head as easily as to the uncircumcised head. And fine, maybe that's true. But one of the reasons that women are at greater risk for contracting HIV than men is that during unprotected sex the man ejaculates in the woman's vagina leaving a deposit of semen which contains the HIV virus. That fluid remains inside the woman giving the viruses ample time and a happy environment in which to infect the woman. That is still going to happen with circumcised men. It's hard to imagine that the small deposit of virus under the foreskin could possibly be more dangerous than the very noticeable ejaculate.It's been suggested that circumcision decreases men's risk of contracting HIV. This logically follows because during sex the foreskin pulls back and the head of the penis is in contact with vaginal fluids. When the man pulls out, the foreskin moves back to cover the head, catching some of that virus containing fluid underneath the head and providing an opportunity for infection that would not have existed if he had no foreskin. This new study is trying to extend that research to make circumcision beneficial to women as well. If what they suggest is true, we will have discovered one more way to help prevent the spread of HIV. Unfortunately, the results that they are currently presenting do not explicitly lead to the conclusions that they've drawn. I'm interested, but I'm not hopping right on their train. Study: Male circumcision may protect women from AIDSMuseveni 'to ban' circumcisionStudy Links Male Circumcision To Woman's HIV Risk |
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2/13/06 10:33 am - mochapixie - Emergency contraception mechanism determined. There has been heated discussion about emergency contraception recently. New research into the mode of action of the drug may put an end to some of this debate.There are two basic ways that the drug could prevent pregnancy. It could prevent ovulation, therefore preventing an egg from being available to meet sperm. No fertilized egg means no pregnancy.The other possibility, that the drug might prevent a fertilized egg from becoming implanted in the uterine wall, is the one that has caused so much discussion. In this scenario, an egg is released and fertilized by a sperm that got through when the condom broke or was forgotten or whatever. When the woman takes the morning after pill, if this were the case, she would be preventing an already fertilized egg from continuing its life by preventing it from implanting in the womb where it would be warm and nourished.Those who object to the use of emergency contraception argue that the egg/sperm combo is a living creature and that we are killing it by using the morning after pill. The argument from here is pretty much the same as the argument against abortion, and many of the same people can be found in the two camps. To these folks, preventing the egg from implanting is as heinous as allowing a woman to terminate a pregnancy through abortion, as both involve the 'murder' of the egg/sperm combo.Until now we weren't really sure how the morning after pill exerted its effect. We could see that it worked, but couldn't say which of the two mechanisms was correct. New research published in the journal Contraception provides some answers.A randomized, double-blind, placebo-controlled study was carried out investigating the method of action of Plan B, the most common and effective form of emergency contraception. They discovered that in in 82% of the Plan B treated cycles, the women did not ovulate. This rate of non-ovulation is identical to the estimated efficacy rate of Plan B. Blood tests indicate that the drug affects ovulation by supressing the surge of lutenizing hormone that normally triggers ovulation. The researchers concluded that Plan B prevents pregnancy by preventing ovulation, rather than by preventing implantation.They suggest that the failure rate of the morning after pill is likely the result of failure to alter the surge of lutenizing hormone. This would occur if the woman took the drug too late in the fertile preovulatory period, when ovulation had already begun.This study was small, involving only about 60 women, but very thorough. Further research, to replicate these results with larger groups, is necessary, but this offers some insight into the way that emergency contraceptives work. Perhaps more research will quiet the anti-choice voices. |
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2/13/06 10:32 am - mochapixie - Future non-hormonal contraceptive possible. At the moment those of us who wish to use a form of contraception that involves no planning ahead and is not intrusive are limited to hormonal methods such as the pill, the injection, and the ring. I've always felt a little bit weird about ingesting hormones every day, but I feel weirder about being a parent, so I rely on hormonal methods to prevent that.A new discovery might offer women an alternative to these hormonal contraceptives. Scientists have discovered a molecule called STAT3 that helps embryos implant. Apparently the molecule signals the cells of the uterus that they should allow an embryo to attach. If this signal is interrupted, a fertilized egg would be expelled from the body, rather than snuggly fed and cared for, thereby preventing pregnancy.Lest we be misled into believing that women's health has somehow received extra reserach funding, I'd like to point out that the relevance of this molecule to pregnancy was discovered quite by accident. The researchers have been investigating STAT3 because of it's implication in the formation of tumours and diabetes. It just so happens that they discovered it is also partially responsible for initiating pregnancy. They suggest that compounds already under development for the treatment of the other conditions might provide contraceptive benefits.It's still a few years off at best, but we may see a non-invasive, non-hormonal form of contraception. This would reduce some of the risks associated with hormonal forms, such as blood clots, and would do away with the androgenic side effects, such as weight gain, vaginal dryness, and mood swings, that some women experience with hormonal contraceptives. it would also, however, result in the loss of the many benefits related to the use of hormonal contraceptives, such as decreased risk of ovarian cancer and improvement of acne. |
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2/13/06 10:32 am - mochapixie - Female orgasm all in the genes? A recent study has concluded that the reason that some women have trouble reaching orgasm is genetic, rather than psycho-social. The researchers investigated more than 4000 women, aged 19-83, half of whom were identical twins, the other half were non-identical twins.This sort of study is often used to investigate genetic relationships in a wide variety of things. It is assumed that, since identical twins share DNA and non-genetic twins do not, any variation betwen the two groups is a result of genetic differences.In this particular study, the researchers concluded that "female orgasm is not all psycho-social as some suggest". What a revelation! That certainly wouldn't have been immediately obvious. I mean, really? I know that there are many out there who would like us to believe that orgasms are all in women's heads (that way, when women have trouble reaching orgasm it's all in their head as well), but it just seems so abundantly clear that it's not the case. The physical sexual parts of a woman's anatomy are no less real than a man's penis, they're just more poorly understood. To argue that orgasms are all in our heads when they are so clearly related to stimulation of specific parts of the body seems disingenuous.That said, however, their conclusion that "between 34 and 45% of the variation in ability to orgasm can be explained by underlying genetic variation" is premature. Twin studies are used to determine correlations between genetics and behaviour, rather than causes. The researchers jump from noticing differences between the two groups that could be genetically related to concluding that the ability to orgasm is heritable and somehow provides evolutionary benefit. As always, I am wary of anything that smells like evolutionary biology or psychology.The scientific world, it seems, will not rest until they find a reason for the female orgasm. They understand what the male orgasm is for. It is necessary for men to orgasm if they are to create offspring. The purpose of the female orgasm is less clear. Some research indicates that women are more likely to orgasm during periods of fertility, and some research indicates that sperm uptake is increased during female orgasm, but neither of these things has been consistently replicated. They're just theories presented in the hopes of explaining why it is that women should be allowed to enjoy themselves.Another twin study found that when women try to reach orgasm through masturbation, about half their chance of success was genetically related. This study also found that during penetrative sex genes accounted for only 31% of their success. The article then indicates that "researchers don't know why the frequency of orgasm during masturbation has a higher genetic component".I don't know about their genetic components, but I can certainly explain why there's more variation in success rates when partners are involved. Sex with other poeple is more complicated than sex with yourself, for a whole slew of reasons.Most glaringly, we know ourselves better than we can ever expect someone else to know us. I know exactly what to do to get myself off. Sometimes I vary it, sometimes it doesn't work, but I know. I have never had a partner who knows what I like as well as I do, nor do I expect that will ever be the case. I live in my head. They don't.Perhaps your partner knows you realy well, but is having an off day. Perhaps s/he's tired and isn't quite as into it as you. Perhaps you're irritated with them. Perhaps your partner knows you really well, and knows exactly how you like to be touched, and has been doing the same thing for three years and you now find it boring rather than erotic. Perhaps you're sleeping with someone you're really attracted to, but are still sort of nervous around and you can't relax enough to orgasm. There are so many reasons that variation exists in partnered sex that it's impossible to list them all.A final word on things comes from another researcher who points out that while research into the genetics of orgasm is interesting, it is of limited use. Sure, she says, there may be a genetic component, but that doesn't really help us to understand anything. Genes could "influence the reproductive tract, and also the development of the hormone system, the nervous system, and the brain, all of which can influence orgasm". Even with a genetic component, then, orgasm could be all in our heads.References1. BBC News - Female orgasm is 'down to genes' - 07/06/20052. News in science - female orgasm is in the genes - 21/02/2005 |