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Health Highlights: July 5, 2005

Study Casts Doubt on Male Bisexuality Why Are Identical Twins So Different? Genetic Flaw Signals Asthma Susceptibility Judge Denies Delay of First U.S. Vioxx Trial Children with High BMI Not Necessarily Fat: Report Birth Control Better than Abstinence-Only Approach, Experts Say

Here are some of the latest health and medical news developments, compiled by the editors of HealthDay:

Study Casts Doubt on Male Bisexuality

New research appears to question whether male bisexuality actually exists, The New York Times reported Tuesday.

Psychologists in Chicago and Toronto studied the genital arousal patterns of men who called themselves bisexual, finding that most were "exclusively aroused by either one sex or the other, usually by other men," the newspaper reported.

About 75 percent of 33 study participants who said they were bisexual had arousal patterns identical to those of gay men, while the rest were indistinguishable from heterosexuals, the Times said.

The study was small, however, and researchers who read it before its scheduled publication in the journal Psychological Science told the newspaper that it would have to be repeated with larger numbers of men who professed to be bisexual before clear conclusions could be reached.

"The last thing you want is for some therapists to see this study and start telling bisexual people that they're wrong, that they're really on their way to homosexuality," Dr. Randall Sell, an assistant professor of clinical socio-medical sciences at Columbia University, told the newspaper. "We don't know nearly enough about sexual orientation and identity" to reach these conclusions, he added.


Why Are Identical Twins So Different?

A little-understood biological mechanism that influences ways that genes perform after birth may account for the surprising differences between identical twins, researchers in Spain say.

While identical twins have exactly the same set of genes at birth, researchers have long thought that subtle environmental factors appeared to determine whether the twins began to look and act different as they got older. Now scientists at the Spanish National Cancer Center in Madrid offer a modified explanation: the epigenome. The term refers to natural chemical changes that affect a person's genome beginning shortly after birth, marking genes for increased or lessened activity.

The scientists studied the DNA of more than 40 pairs of twins between ages 3 and 70, according to the Washington Post. They were hoping to learn how environmental factors like exposure to pollutants, consumption of certain foods, and significant emotional experiences might cause changes in a person's DNA.

What they found was the young twins had almost identical epigenetic profiles, but their genetic characteristics became more and more different as they aged, the newspaper said.

An environmental event that triggers diminished activity in a gene that helps protect a person against cancer, for example, could explain why one identical twin goes on to develop the disease, while the other doesn't, the researchers said. Their study was published in the this week's issue of the Proceedings of the National Academy of Sciences.


Genetic Flaw Signals Asthma Susceptibility

Johns Hopkins University researchers believe they've identified a single gene that helps determine a person's susceptibility to asthma.

Absence of the gene known as Nrf2 appeared to exacerbate allergy-related asthma in mice, the scientists said. Not having the gene increased migration of inflammatory cells into the lungs' airways, leading to "an enhanced asthmatic response," the researchers said in a statement.

Cells that hasten inflammation cause the airway lining to swell and restrict. Controlling inflammation has been a traditional focus of asthma therapy, the researchers noted.

The study's findings were published in the July 4 issue of the Journal of Experimental Medicine.

The incidence of asthma has doubled over the past two decades, now affecting some 20 million Americans, the researchers' statement said.


Judge Denies Delay of First Vioxx Trial

A Texas judge on Tuesday denied Merck & Co's request to delay the first wrongful death trial in the United States related to the painkiller Vioxx, the Associated Press reported.

District Judge Ben Hardin declined to postpone jury selection, saying he would not assume potential jurors were biased by pretrial publicity.

But Hardin also told Merck lawyers that he would examine questionnaires answered by the pool of 100 potential jurors next week before making a final decision on Merck's request for a trial delay.

The trial is scheduled to begin July 11. The company had asked that the trial be delayed for at least 60 days due to recent negative publicity about Vioxx.

The case involves a woman suing Merck over her husband's death in 2001. The company had said a lawsuit launched last week by the Texas attorney general meant that the company could not receive a fair trial, the AP reported.

Vioxx was taken off the market last September after research showed that patients who took the drug for 18 months or longer had an increased risk of heart attack and stroke. More than 2,400 Vioxx lawsuits have been filed in the United States.


Children with High BMI Not Necessarily Fat: Report

Pediatricians shouldn't focus only on height and weight when they assess whether a child is too fat, says a report by the U.S. Preventive Services Task Force, a non-governmental panel of medical researchers.

The report says there's no evidence that all children with a high body mass index (BMI) need to lose weight. It also said there's no evidence that counseling by pediatricians results in weight loss and better health among their patients, the Associated Press reported.

While it can be fairly effective at identifying children with weight problems, BMI doesn't reveal whether body mass is mostly fat or lean tissue, noted task force member Dr. Virginia Moyer, a pediatrics professor at the University of Texas Health Science Center in Houston.

Pediatricians should pay close attention to children who experience rapid weight increases that aren't accompanied by increases in their height, Moyer told the AP.

The report appears in the July issue of the journal Pediatrics.


Birth Control Better than Abstinence-Only Approach, Experts Say

Birth control and emergency contraception are better for American teens than the abstinence-only approach to sex education promoted by religious groups and the White House, say new recommendations in the American Academy of Pediatrics' updated teen pregnancy policy.

The report, published Tuesday in the July issue of the journal Pediatrics, updates the teen pregnancy policy by omitting the statement that "abstinence counseling is an important role for all pediatricians," the Associated Press reported.

Instead, the new policy says that while doctors should encourage teens to postpone becoming sexual active, the doctors should also do their best to ensure that all teens have access to birth control, including emergency contraception.

"Even though there is great enthusiasm in some circles for abstinence-only interventions, the evidence does not support abstinence-only interventions as the best way to keep young people from unintended pregnancy," Dr. Jonathon Klein, chairman of the committee that wrote the new recommendations, told the AP.

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