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 A woman is sexually attracted to men who smell like a good genetic match, but birth control pills make her desire the “wrong” men, a U.K. study shows.

Who is the right man? Studies suggest women are attracted to men whose genetic makeup differs from their own. Having a genetically different mate increases the chances for a healthy pregnancy and a healthy baby .

“If this really happens in the real world, women on the pill would end up choosing a more genetically similar mate than she would otherwise choose and the implications go on from there ,” study researcher S. Craig Roberts, PhD, tells WebMD.

Roberts notes that in an earlier U.S. study, women who were genetically similar to their partners reported being less satisfied in their sexual relationship with their partner — and were seeking more new sex partners — than were women with genetically dissimilar partners.

Animal studies show that female mammals can smell out males whose MHC genes are different from their own. MHC genes affect important immune responses. By mating with males who have different MHC genes, females give their offspring a better disease-fighting repertoire.

It’s true of humans, too. In laboratory studies, women who sniff men’s sweaty T-shirts find them more attractive when they come from men whose MHC genes don’t match theirs. It’s not that certain MHC genes smell better to women — it’s the difference that counts.

Rachel Herz, PhD, author of The Scent of Desire and a faculty member at Brown University, says there is a real connection between body odor, MHC, and the mates a woman chooses.

“My own research says the way a man smells to a woman is the main determinant of sexual attraction,” Herz tells WebMD.

In earlier T-shirt-sniffing studies, women taking birth control pills seemed to be attracted to the “wrong” men. Intrigued, Roberts and colleagues took a closer look.

They paid 37 women to smell men’s T-shirts before and after going on the pill. Then they compared the women’s before- and after-pill ratings of the odors to those of 60 women who did not use oral contraceptives .

The result: After taking the pill, women shifted toward preferring genetically similar men. Women who did not take the pill slightly increased their preference for genetically different men.

Why? Roberts notes that when they become pregnant, female animals switch to preferring the scent of genetically similar males. This may allow them to seek out males that will help them protect and raise the baby. Claus Wedekind, PhD, who performed the original T-shirt-sniffing studies, has suggested that birth control pills somehow mimic this process.

The question, of course, is what happens when a woman taking birth control pills marries a man to whom she’s attracted — and then stops taking the pill.

Herz says marriage counselors who have never heard about these studies tell her that the No. 1 complaint among women no longer sexually interested in their husbands is that they can no longer stand how he smells.

“If you can’t stand how someone smells, you cannot become intimate,” Herz says.

Does this mean the birth control pill is a divorce pill? Herz says it’s not that simple.

“A woman’s response to a man’s natural body odor will be colored by her feelings for him,” she says. “So if you fell in love with a man online, it would be hard to be repelled by his smell.”

ScienceDaily (July 10, 2008) — While Maria Lyzen was being treated for breast cancer, she found she couldn’t concentrate or decipher information, and just functioning day-to-day at home was difficult.

“I didn’t know if it was a reaction to the trauma of being told that I had breast cancer. I was in my late 50’s – was it the beginning of an aging symptom? Or was it the drugs that I was getting in terms of my chemotherapy? My doctor ordered a brain scan, and there was nothing unusual there, and I said, ‘But there is something wrong with me,’” Lyzen says.

Researchers are only beginning to understand what Lyzen and others experience during cancer treatment. Patients often call this phenomenon – which includes loss of concentration, difficulty remembering and difficulty thinking clearly – “chemo brain.” Now, researchers are beginning to study this phenomenon and all the possible factors that contribute to it.

“Women have complained for a long time now about cognitive changes that have occurred during the time that they’ve been treated for breast cancer. We now have some research that shows cognitive changes can and do occur during chemotherapy and also may persist for several years following the completion of chemotherapy,” says Bernadine Cimprich, Ph.D., R.N., associate professor of nursing at the U-M School of Nursing and a researcher at the U-M Comprehensive Cancer Center.

Cimprich has begun a new study to look at problems of attention and working memory, including what causes these cognitive impairments, what effect chemotherapy has on these brain functions and how much other influences may play a role.

The researchers will use functional magnetic resonance imaging, or fMRI, which can test brain function while a person performs a mental task. Breast cancer patients receiving chemotherapy will be compared with patients not receiving chemotherapy and with healthy women who do not have breast cancer.

“The first step is to see whether there are changes in brain function related to adjuvant chemotherapy for breast cancer. Chemotherapy is one of the possible sources of these kinds of cognitive changes. But actually, there are other possible reasons that a woman might experience cognitive problems,” Cimprich says.

The traumatic impact of a cancer diagnosis and making important life-or-death decisions could affect cognitive function even before cancer treatment begins. The researchers also suspect that since not all women report experiencing chemo brain, some women may have a genetic susceptibility that makes them more sensitive to the effects of chemotherapy, including cognitive issues.

“Our ultimate goal and hope for this research is that it will give us information that will be a kind of basis or foundation for designing care or interventions so we can help women from the very beginning of their treatment to maintain their cognitive function and to conserve cognitive effort so that they can function at the highest possible level over the course of their breast cancer treatment and beyond,” Cimprich says.

Lyzen says she regained much of her concentration since having completed breast cancer treatment two years ago. But, while concentration is much more difficult for her now, she’s happy to know that researchers are taking the chemo brain phenomenon seriously.

“Whether people are having troubles because they’re just having a traumatic response or whether it’s chemo brain or whether it is because they are aging, it doesn’t really matter. What matters is that they are getting the support and the acknowledgement that they are being heard. And that is very important not to be dismissed,” Lyzen says.

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ScienceDaily (July 13, 2008) — A gene that is overexpressed in 20 percent of breast cancers increases the number of cancer stem cells, the cells that fuel a tumor’s growth and spread, according to a new study from the University of Michigan Comprehensive Cancer Center.

The gene, HER2, causes cancer stem cells to multiply and spread, explaining why HER2 has been linked to a more aggressive type of breast cancer and to metastatic disease, in which the cancer has spread beyond the breast, the researchers say.

Further, the drug Herceptin, which is used to treat HER2-positive breast cancer, was found to target and destroy the cancer stem cells. “This work suggests that the reason drugs that target HER2, such as Herceptin and Lapatanib, are so effective in breast cancer is that they target the cancer stem cell population. This finding provides further evidence for the cancer stem cell hypothesis,” says study author Max S. Wicha, M.D., Distinguished Professor of Oncology and director of the U-M Comprehensive Cancer Center.

The cancer stem cell hypothesis says that tumors originate in a small number of cells, called cancer stem cells, and that these cells are responsible for fueling a tumor’s growth. These cells represent fewer than 5 percent of the cells in a tumor. Wicha’s lab was part of the team that first identified stem cells in human breast cancer in 2003.

In the current study, researchers found that breast cancer cells overexpressing the HER2 gene had four to five times more cancer stem cells, compared to HER2-negative cancers. In addition, the HER2-positive cells caused the cancer stem cells to invade surrounding tissue, suggesting that HER2 is driving the invasiveness and spread of cancer.

The researchers then looked at the drug Herceptin, which is used to treat HER2-positive breast cancer. They found Herceptin reduced the number of cancer stem cells in the HER2-positive breast cancer cell lines by 80 percent, dropping it to the same levels seen in HER2-negative cell lines.

When HER2 was not overexpressed in the cell cultures, the researchers found, the cancer stem cell population did not increase. Nor did Herceptin have any effect on the HER2-negative cells, which is consistent with how Herceptin is used in the clinic.

“We are now studying what pathways are activated by HER2 overexpression. Our hope is that we could develop inhibitors of these pathways that might be effective in targeting cancer stem cells in women whose tumors do not overexpress HER2 or those who are resistant to Herceptin,” says study author Hasan Korkaya, Ph.D., a U-M research fellow in internal medicine.

Breast cancer statistics: 184,450 Americans will be diagnosed with breast cancer this year and 40,930 will die from the disease, according to the American Cancer Society. About 20 percent of breast cancers are considered HER2-positive.

Additional authors: Amanda K. Paulson, a U-M undergraduate student, and Flora Iovino, a U-M research fellow in internal medicine.

Funding: National Institutes of Health, National Cancer Institute, A. Alfred Taubman Medical Research Institute at the U-M Medical School.

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ScienceDaily (July 15, 2008) — Enlisting an army of plant viruses to their cause, materials researchers at the National Institute of Standards and Technology (NIST) have identified a small biomolecule that binds specifically to one of the key crystal structures of the body–the calcium compound that is the basic building block of teeth and bone. With refinements, the researchers say, the new molecule can be a highly discriminating probe for a wide range of diagnostic and therapeutic applications related to bones and teeth.

Although they have somewhat different mechanical properties, the major structural component of both teeth and bones is a crystalline compound of calcium phosphate called hydroxyapatite. Subtle variations in the way the crystal forms account for the differences. Identifying and monitoring the formation of this particular crystal is of paramount importance to biomedical researchers working on a variety of problems including the remineralization of teeth to repair decay damage, the integration of prosthetic joints and tissue-engineered bone materials for joint and bone replacement, and cell-based therapies to regrow bone tissue.

To date, however, there is no specific, practical method to spot the formation of hydroxyapatite in living systems or tissue samples. Materials scientists can identify the crystal structure with high reliability by the pattern it makes scattering X rays, but it’s a complex procedure, requires fairly pure samples and certainly can’t be used on living systems. There are some widely used chemical assays–the von Kossa assay, for example–but these also are destructive tests, and more importantly they really test simply for the presence of the elements calcium or phosphorus. They can’t distinguish, for example, between deposits of amorphous calcium phosphate–a precursor–and the hydroxyapatite crystal.

To find a more specific, less destructive probe, the NIST team used a relatively new technique called “phage display” that can rapidly create and screen huge numbers of biomolecules for specific interactions. Phages are a primitive and ubiquitous class of viruses that infect bacteria. Some simple phages can be genetically modified to randomly assemble short sequences of amino acids–small proteins called peptides–on their outer shells as binding sites. An engineered population of phages will synthesize billions of random peptides. If these phages are exposed to the target surface–hydroxyapatite crystal in this case–and then washed off, those left behind are the ones that tend to stick. Cloning the survivors and repeating in several cycles with increasingly stringent conditions eventually isolates a handful of candidate peptides that can be further tested to measure their affinity for the target.

As reported in a recent paper,* the NIST team used the technique to identify a new peptide that relies both on the chemical composition and the crystal structure of hydroxyapatite to bind to the mineral’s surface. The peptide’s ability to “recognize” the specific structure of hydroxapatite, say the researchers, could be exploited as a nondestructive tag to monitor the progress of bone and tooth mineralization for diagnostic and therapeutic applications.

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