A class of nerve fibres in the skin that specifically transmit pleasure messages to the brain have been identified by U.S. and Swedish boffins, who say their finding could improve understanding of how touch sustains human relationships.

For many years, Scientists have been trying to understand the mechanisms behind how the body experiences pain, and the nerves involved in conveying those messages to the brain. Because, in conditions like Neuropathy, where the peripheral nervous system is damaged, people can suffer a great deal after the messaging system has gone wrong, and feel pain even when there is no cause.

Professor Francis McGlone, the author of the study said:

If you get a piece of grit in your eye, have a toothache, or bite your tongue, it hurts so much because there are more C fibres there. The research we have been doing is building evidence for another role of C fibres in the skin that are not pain receptors, but pleasure receptors.

In this research, published in the journal Nature Neuroscience, experts from the University of Gothenburg in Sweden and the University of North Carolina, including scientists from the company Unilever, identified “C-tactile” nerve fibres, which sent pleasure messages to the brain.

Then the scientists used a “robotic tactile stimulator” – basically, a computerized mechanical arm fitted with a soft brush – on twenty volunteers, to determine the speed at which C-fibres should be touched to activate the pleasure sensation.

It was observed that if the rate of being rubbed was faster or slower than an optimum speed of four to five centimetres per second, then the nerve fibres weren’t activated, and the touch wasn’t pleasurable. They also discovered that C-tactile fibres are only present on hairy skin and are absent in the palm of the hand.

Professor McGlone said these nerve fibres are part of the evolutionary mechanism that helps humans bond. People preferred being fondled in a manner similar to the one used by a mother to comfort a baby or by couples when demonstrating love.

He continued:

We believe this could be Mother Nature’s way of ensuring that mixed messages are not sent to the brain when it is in use as a functional tool. Our primary impulse as humans is procreation, but there are some mechanisms in place that are associated with behaviour and reward which are there to ensure relationships continue.

Posted by Jonathan as Biology, Sociobiology at 9:10 PM BST

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According to new research from the Royal Pharmaceutical Society of Great Britain, adults aged 45 and over, when starting new sexual relationships, are taking chances with their sexual health and are at risk of catching sexually transmitted infections (STIs).

When questioned, almost one in five 45-54 year olds (19%) admitted having had unprotected sex with someone other than a long-term partner in the past five years.

Surprisingly, nearly one-third of this age group (32%) described their risk of getting an STI when having unprotected sex with a new partner or someone other than their current partner as either unlikely or very unlikely. Even more worryingly, a further 20% believed that their chances of picking up an infection were ‘next to nothing’ in these circumstances.

When comparing the older and younger generations, just 13% of 18-24 year olds believed their chances of acquiring an STI from unprotected sex were ‘next to nothing’, compared to twice as many over 55s (25%).

A quarter of 45-54 year olds surveyed (23%) said they didn’t use contraception because they trusted the person they were sleeping with not to have an STI, with one in ten saying they didn’t like the feeling of condoms.

Heidi Wright, Head of Practice at the RPSGB, said:

The majority of safe sex messages are targeted at teenagers, but as more adults begin new relationships later in life, they quite clearly need advice too. Over the last decade STIs have risen significantly in the 45-64 age group.

You can’t always tell who has an STI and infections don’t discriminate on the basis of age. If you have unprotected sex with a new partner, you are at risk of STIs, which often show few symptoms but have can have serious consequences to health.

It can be difficult to know where to go for information about sexual health, but your local Pharmacy can be an excellent source of advice. Pharmacies are open long hours and weekends when GP surgeries are closed. Most now have a private consultation area where patients can discuss their problems confidentially and there is no need for an appointment.

Posted by Jonathan as Biology, Sociology at 11:59 PM BST

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A unique study of twins separated at birth suggests that genes may help determine the age at which a person first engages in sexual intercourse.

Psychologist Nancy Segal of California State University in Fullerton, USA, looked at 48 pairs of twins who were separated at birth as well as 23 individual twins to see how genes influenced their sexual maturity. Using this methodology, the researchers were able to avoid the influence of a common family environment, which might have led them to overestimate the effect of genes.

Lead researcher, Nancy Segal said:

It’s not like there’s a gene for having a sex at a certain date. Instead, heritable behavioural traits such as impulsivity could help determine when people first have sex.

In comparing the twins sexual histories, Segal had each of the participants take a sexual life history interview, composed of a sexual meaning survey, a sexual life history timeline, and a sexual behaviour questionnaire.

Segal’s team found that genes explained a third of the differences in participants’ age at first intercourse (which was, on average, a little over 19 years old) – by comparison, roughly 80% of variations in height across a population can be explained by genes alone.

It might be argued that conservative social mores might delay a teen’s first sexual experience, causing scientists to underestimate the effect of genes, and indeed, the research team acknowledge a less pronounced genetic effect among twins born before 1948, compared with those who came of age in the 1960s or later. Other factors may also make the effects of genes harder to discern, for example, Segal’s team found that female participants who felt unhappy and unfulfilled in their home life were more likely to have sex at a younger age.

As for the specific genes involved, another team of researchers had found that a version of a gene encoding a receptor for the neurotransmitter Dopamine is associated with age at first intercourse. Others have linked the same version of the gene – called DRD4 – to impulsive, risk-taking behaviour.

The study “Age at first intercourse in twins reared apart: Genetic influence and life history events” is published in the journal Personality and Individual Differences.

Posted by Jonathan as Biology, Psychology at 6:41 AM BST

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Risky sexual behaviour, such as having unprotected sex with multiple partners puts people at risk of catching sexually transmitted infections, but not as much as the characteristics of their sexual partners, according to a new study.

The findings, which University of Florida and University of Pittsburgh researchers report in the April issue of Sexually Transmitted Diseases, could assist healthcare providers when screening patients for STD risks.

University of Florida College of Medicine, Assistant Professor of Epidemiology and Health policy research, Stephanie A. S. Staras, said:

If you are choosing high-risk partners, you are much more likely to have an STD, even when we account for your condom-use patterns. The theory is simple: You need to have sex with someone who has an STD to get an STD. Based on the prevalence of STDs in the United States, it seems like the public may not fully understand their risk.

The study examined the sexual activities, partner characteristics and STD diagnoses of 412 subjects between the ages of 15 and 24. Amongst the subjects whose partners were categorized as high-risk, half were diagnosed with an STD. By comparison, only 40 percent of the people whose own behaviours were labelled as high-risk were diagnosed with an STD.

University of Florida researchers measured five specific characteristics to gauge how risky certain partners were. The characteristics studied included whether their partner has a problem with marijuana or alcohol, was at least five years older or younger, had been in jail, had sex with other people in the past year or had been treated for an STD in the past year.

The researchers then created a composite, totalling up the number of negative partner characteristics for each subject and comparing them against the number of each person’s own individual risky behaviours, which ranged from how often they used condoms to how many people they had sex with.

Overall, researchers found considering all of the partner characteristics together was the strongest predictor for STDs. People whose partners had five or more risk characteristics were three times more likely to have an STD than those whose partners had no more than two characteristics.

Of these characteristics, the most prescient were if a partner had already had an STD and if a couple had an age difference of more than five years. Subjects whose partners were five years older or younger than themselves were more than twice as likely to be diagnosed with an STD than participants whose partners were about the same age, the researchers found.

Lead author of the study, Professor Staras said:

Healthcare providers usually ask patients about their own sexual behaviours, but inquiring only about a person’s own behaviours may cause some patients to slip through the cracks. For example, some subjects in the study reported very low-risk behaviours but were having sex with very high-risk partners.

Adding a few simple questions about partner characteristics during STD screenings could help providers catch more patients who need to be tested and educated about condom use and other protective measures.

Partner selection is an area of STD prevention that could complement what we are already doing with promoting condom use, and could possibly really help people. If somehow we could convince individuals to incorporate this information in a meaningful way into their decision-making, then we could reduce STDs.

Professor Richard A. Crosby, Chairman of the Department of health behaviour at the University of Kentucky and a Co-director of the Rural Center for AIDS/STD Prevention, who was not involved with this study, said:

It’s important for people to remember that the risks mentioned in the study are just generalizations, not set-in-stone giveaways for STDs.

From a practical and prevention perspective, we still need to rely on people using valid methods of protection to avoid being infected or infecting.

Posted by Jonathan as Biology, Sociology at 2:11 AM BST

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Currently, the most practical ways to stop HIV transmission are protected sex, monogamy (with an uninfected partner) or abstaining from sex altogether. However, researchers have spent many years without success trying to develop another option – a gel that women (and possibly men) could use to kill the virus before it enters the body.

Whilst condoms can block the virus, many women who want to get pregnant won’t use them, and so they risk infection from their partners. However, now it seems that a new sexual gel might curb the spread of AIDS by stopping cells vulnerable to the virus from rushing to the site of infection.

Previously, researchers have had difficulties destroying the virus without harming the person in the process; and some gels have actually made virus transmission easier by causing tears in the lining of the vagina.

Now, according to a study appearing in the journal Nature, Scientists have reported that a common germ-killing compound has prevented transmission of SIV (an HIV-like virus found in monkeys) – which is an encouraging sign that it could also work in humans.

Dr. Ashley Haase and colleagues at the University of Minnesota in Minneapolis, USA, discovered that a few epithelial cells on the cervix of female macaques are the first point of entry for SIV. After which, nearby immune cells respond by releasing molecules that trigger inflammation and summon T-cells to the cervix.

Under normal circumstances, those T-cells would destroy invaders. However, T-cells are the very same cells that SIV (and also HIV) use to infect their new host.

Using information from studies of Toxic shock syndrome (a life-threatening bacterial infection that can affect women using tampons), chemicals have already been identified that can suppress vaginal inflammation. Therefore, Haase’s team examined a compound called Glycerol Monolaurate (GML), which is already recognized as safe for humans, since it’s a commonly found constituent of vegetable oils, various foods and deodorants – where it kills a variety of germs in addition to helping substances mix properly.

Haase and colleagues tested GML added to a sexual lubricant on five female rhesus macaques that were vaginally exposed to SIV. As a result, they found that four out of five monkeys treated with the gel avoided infection after repeated exposure to the virus, whilst five different monkeys in a control group that only received the lubricant without GML all became infected with SIV, after being exposed to it.

The research seems promising, but there are other important questions to be answered, including whether this treatment would protect men from infection when they have sex with other women (or men), and in any case more experiments in animals will be needed before GML can be tested on humans.

However, the next steps would be to move on to studies that would confirm the compound actually works, and to solve issues such as whether GML would block HIV in a woman’s cervix already inflamed by other infections, or whether blocking cervical immune responses could leave her less protected from other infections.

The surprising good news is that GML could eventually make its way into sexual lubricants that women could use, and would cost less than a cent per dose for each woman.

Thus, the researchers argue, even if the compound were only 60 percent effective, it would prevent nearly a million HIV infections a year, and might slow the spread of AIDS.

Posted by Jonathan as Biochemistry, Biology at 2:23 AM GMT

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A new study highlights a link between sexual quality of life and hormonal measures, independent from weight.

According to findings, due to be published in the Journal of Clinical Endocrinology & Metabolism, the more obese a man, the greater his hormonal changes and the worse his sex life. However, the study’s authors also found that gastric bypass surgery can help reverse those problems.

The researchers investigated the weight, body mass index (BMI) and reproductive hormone levels of 64 obese men at the start of the study and again two years later, after some of them had what’s known as Roux-en-Y gastric bypass surgery. The participants also asked to fill out questionnaires about the quality of their lives.

Lead Author, Dr. Ahmad Hammoud, of the University of Utah, said:

Previous studies have found that obesity is correlated to lower sperm count and can be associated with infertility, but we wanted to know if obesity was biologically associated with an unsatisfying sex life, and if so, could it be reversible. Our results show that the answer to both questions may be yes.

In our study population, we found that lower Testosterone levels and diminished ratings for sexual quality of life were correlated with increased BMI. Subjects who lost weight through bariatric surgery experienced a reduction in Estradiol levels, an increase in Testosterone levels and an increase in ratings of sexual quality of life.

The study authors note that further studies are needed to determine the cause-effect relationship.

Posted by Jonathan as Biology, Sociology at 12:53 AM GMT

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Australian researchers have made an interesting discovery: Consuming alcohol improves, rather than damages, men’s performance in the bedroom.

Dr Kew-Kim Chew, of Western Australia’s Keogh Institute for Medical Research, studied 1,580 Australian men and found that drinkers reported up to 30 percent fewer problems than teetotallers.

The finding, due to be published in The Journal of Sexual Medicine and presented to an international conference in April, should reassure men who worry that drinking might cause a type of erectile dysfunction known as “Brewer’s droop”.

More surprisingly, the research found that binge drinkers had lower rates of erectile dysfunction than those who never drank (although it’s important to note that this type of drinking can cause other health problems).

Lead author Dr Kew-Kim Chew said men who drank within safe guidelines appeared to have the best erectile function:

We found that, compared to those who have never touched alcohol, many people do benefit from some alcohol, including some people who drink outside the guidelines.

Even after other risk factors were excluded, Weekend drinkers, High-risk drinkers and those who exceeded alcohol-intake guidelines had lower rates of erectile dysfunction than those who drank one day a week or less. However, ex-drinkers had the highest risk.

Dr Chew said:

These findings suggest a favourable association between low-risk alcohol drinking and [positive] erectile function.

According to Australian National Health and Medical Research Council guidelines, low-risk drinking for men is defined as up to four drinks a day, for up to five days a week.

Dr Chew noted that he had patients with erectile dysfunction who had been previously been told to stop drinking completely, and commented that the latest finding should prevent them compounding their problem by feeling “guilty and stressed” about present or past drinking.

He concludes there is “no justification” to advise men with erectile dysfunction and who drink moderately, to stop or reduce their drinking. However, earlier parts of the study, did confirm that men who smoked or suffered heart disease were at higher risk of erectile dysfunction.

Posted by Jonathan as Biology, Sociology at 6:16 PM GMT

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Seduction can be a lot of fun, but why does it take so much time? Experienced Seductionists know that men can take a long time in declaring their interest in a woman; but once they have, the female then needs to determine their suitability, in order to screen out the men that she finds incompatible as mates.

Looking at this another way, sometimes things go wrong in a seduction – then, in human terms, we might say “The ‘Chemistry’ just wasn’t there!“. Alternatively, you might ask why not just have sex with everyone instead of waiting at all? And, if you wait, what does that say about the quality of the relationship?

To shed light on this matter Scientists have developed a mathematical model of the mating game to help explain why courtship is often so protracted. The study, carried out by researchers at University College London (UCL), University of Warwick and London School of Economics and Political Science (LSE), uses Game theory to show that extended courtship periods enable a male to signal his suitability to a female, and allows the female to weed out the male if he is found to be unsuitable as a potential mate.

From the perspective of Game theory, almost every decision we make is the result of a series of negotiations in which we try to reduce uncertainty by trading off what other people want in return for what we want ourselves. Therefore, just like Poker and Chess, real life can be thought of as a game of strategy, combined with contracts and deals to protect us from the Cheats and Liars.

But, unlike Poker and Chess, we can almost never expect to be a “winner” in these games. Choosing the option that we judge will bring us the best payoff tends to be the riskiest decision, since it will usually provoke the strongest defence from other players who stand to lose if we get what we want. Thus, we usually have to settle for compromise agreements, which may require us to make the best of a bad bargain. Some good examples would be drawing up an employment contract, buying a house, negotiating a loan with your Bank or even a classic logic puzzle such as the Sultan’s Dowry Problem, which may be of interest to mathematically minded Seductionists.

The findings of this latest research, published in the Journal of Theoretical Biology, analyse how males and females behave strategically towards each other in the mating game. Thus, the model is based on the idea that women have much to lose from any new relationship because they may end up with a baby fathered by an abusive or poor genetic quality father. Whilst a man may end up investing time and money in a “Gold digging” partner that has no intention of ever having sex with him.

The mathematics considers a male and a female in a simplified courtship encounter of unspecified duration, in a society without contraception, with the game ending when either partner quits, or the female accepts the male as a mate. The first courtship model presented assumes that from the female perspective, a male is either “Good” (i.e. Healthy and willing to stick around and help raise any children he fathers) or “Bad” (i.e. Unhealthy or unwilling to help raise any children) – Whilst from the male perspective a man (of either type) makes a subjective assessment of whether the female is attractive or unattractive and then proceeds with the courtship encounter or not, as the case may be.

Thus, a male gets a positive payoff from mating with any female he chooses to pursue, even though his payoff is higher if he is “good” than if he is “bad”. Whereas, in contrast, the female only gets a positive payoff from mating with a “good” male but a negative payoff from mating with one that is “bad”. Therefore, it is in her interest to gain more information about the male’s type with the aim of avoiding mating with a “bad” male, since she would like to mate with a “good” male, but cannot tell a male’s type from his appearance alone.

So, the study looks for behaviours that are evolutionarily stable and in equilibrium. That is to say, females are doing as well as they can against male behaviour and males are doing as well as they can against female behaviour in a so called “Battle of the sexes” with both sides compromising on the point in the developing relationship where they agree to have sex.

The model shows that extended courtships can take place, with a “good” male being willing to court for longer than a “bad” male and the female delaying mating. In this way the duration of a male’s courtship effort carries information about his type, and by delaying mating, the female is able to make some use of this information to achieve a degree of screening. Therefore, since “bad” males have a greater tendency to quit the courtship game early, as time goes on and the male has not quit it becomes increasingly probable that he is a “good” male.

Lead Author, Professor Robert Seymour, of UCL Mathematics, said:

Courtship in a number of animal species occurs over an extended period of time. Human courtship, for example, can involve a sequence of dinners, theatre trips and other outings lasting months or even years. One partner – often the male – may pay the greater part of the financial cost, but to both sexes there is a significant cost of time which could be spent on other productive activities. Why don’t people and other animals speed things up to reduce these costs? The answer seems to be that longer courtship is a way for the female to acquire information about the male.

By delaying mating, the female is able to reduce the chance that she will mate with a “bad” male. A male’s willingness to court for a long time is a signal that he is likely to be a “good” male. Long courtship is a price paid for increasing the chance that mating, if it occurs, will be a harmonious match which benefits both sexes. This may help to explain the commonly held belief that a woman is best advised not to sleep with a man on a first date.

Dr Peter Sozou, of Warwick Medical School and LSE Centre for Philosophy of Natural and Social Science said:

The strategic problem the female faces is how to screen out “bad” males, and this is where long courtship comes into play. A male is assumed to always want to mate with a female, but a “good” male is more willing to pay the cost of a long courtship in order to claim the prize of mating. This leads to an outcome in which the female is not willing to mate immediately, but instead requires the male to wait for an indeterminate time before she agrees to mate with him. During this time, the male may give up on courting the female.

“Bad” males give up at some random time if the female has not by then mated with them, but “good” males are more persistent and do not give up. The female’s strategy is a compromise – a trade-off between on the one hand the greater risk of mating with a “bad” male if she mates too quickly, and on the other hand the time cost of delay. Under this compromise there remains some risk that she will mate with the wrong type of male.

She cannot eliminate this risk completely unless she decides never to mate.

Of course, this model will not work so well in a society where contraception removes much of the risk of becoming pregnant, and it should also be noted that the model ignores factors such as social and peer group pressures.

However, Professor Seymour believes that it helps explain how the extended courtship of humans may have evolved in Prehistoric societies.

The original paper can be seen here.

Posted by Jonathan as Biology, Philosophy at 3:10 AM GMT

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Love is a many splendoured thing; it influences most of our music and art, and Poets would even have us believe that it is beyond comprehension. Although Evolutionary scientists would no doubt be keen to point out that Love has evolved to help keep pairs bonded together.

As to the question of what is Love? Neuroscientist Larry Young believes that he may have the answer. Writing in a paper published in the scientific journal Nature, Professor Young argues that Love is a series of neurochemical events in specific brain areas, and has a “biological basis that we can understand”.

Professor Young, of Emory University in Atlanta, Georgia, USA, analyzed the responses of North American Prairie Voles (which, unlike most other animals, form lifelong pairs and raise their young together) to various chemicals, and found that a dose of the right hormone could drastically alter their relationships.

Oxytocin is one of the main hormones involved in generating feelings of love, especially in females. But, Prairie voles artificially injected with large quantities of Oxytocin were found to be very likely to become strongly attached to the first male they encountered – whereas, in the case of males, larger amounts of Vasopressin triggered bonding and nesting effects.

Extrapolating the results obtained with Voles to Humans, Professor Young believes that using this knowledge, a theoretical love potion could be manufactured, which would make the consumer fall in love with the first person that he or she encountered. All that the “cocktail” would do, says Young, would be to trigger a “biochemical chain of events” that would ensure that whoever drank it was convinced that the other person was the right one for him or her. Conversely, an anti-love vaccine could also be invented as an antidote to unrequited love, by reversing the principles that lead to the creation of the love drug in the first place.

Professor Young noted:

If we give an Oxytocin blocker to female voles, they become like 95 percent of other mammal species. They will not bond no matter how many times they mate with a male or how hard he tries to bond. They mate, it feels really good and they move on if another male comes along. If love is similarly Biochemically based, you should in theory be able to suppress it in a similar way.

These experiments have not been conducted on humans, and Professor Young does not advocate that they should be, although he does note:

It would be completely unethical to give the drug to someone else, but if you’re in a marriage and want to maintain that relationship, you might take a little booster shot yourself every now and then. Even now it’s not such a far-out possibility that you could use drugs in conjunction with marital therapy.

However, Professor Young claims that his ultimate goal is not to create a love drug, but to shed light on serious conditions like Autism – by studying brain chemicals involved in emotional attachment. Thus, a milder form of the theoretical love substance might be used to endow Schizophrenics and Autistics with more social skills, in order to help them better integrate into society, and help stop them becoming a burden for others.

Finally, regarding love, Professor Young is convinced that love does not simply boil down to one single hormone. There have been studies where it has been shown that differences in a cluster of genes known as the Major Histocompatibility Complex may be involved in initial sexual attraction, Young pointed out. Adding that variations in this gene cluster have predicted the quality of the relationship between the male vole and its partner.

Posted by Jonathan as Biochemistry, Biology at 10:47 PM GMT

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They say that love is blind, and now, new research shows that it also seems to make things smell differently too.

According to Johan Lundström and Marilyn Jones-Gotman of McGill University in Montreal, Canada, women who are madly in love have difficulty recognising the body odours of male friends, but their ability to distinguish their partner’s smell is unaffected.

The researchers asked twenty young women with boyfriends to fill in a Passionate Love Scale questionnaire, in order to rate how deeply in love they were. They also persuaded the women’s partners and friends of both sexes to sleep for seven nights in a cotton T-shirt with pads sewn into the underarms, to soak up their sweat.

Each woman was then asked to select lover’s or a friend’s T-shirt from three garments, two of which had been worn by strangers. The more deeply in love a woman was, the less well she did at distinguishing a male friend’s odour from those of strangers.

The results showed that the women’s scores on the Passionate Love Scale made no difference to their ability to recognise a lover’s shirt, or even one worn by a female friend. However, those who were more deeply in love were worse at distinguishing a male friend’s odour from those of strangers.

This suggests a lover doesn’t necessarily pay more attention to her partner, and supports a theory of romantic attraction known as “Deflection“, which argues that being in love with someone involves a reduction in the amount of attention given to other potential suitors.

Lundström, now at the Monell Chemical Senses Center in Philadelphia, Pennsylvania, admits that he isn’t a love guru, noting:

The main focus of the project is to look at how the brain processes odours.

He next plans to investigate what happens in lovers’ brains as they perceive the odours of their partners, friends and strangers.

Posted by Jonathan as Biochemistry, Biology at 7:43 PM GMT

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