WEDNESDAY, Nov. 28 (HealthDay News) - A gene long linked to suppressing the growth of cancer may also play a vital role in human reproduction, researchers report.

In experiments with mice, researchers found that females lacking the p53 gene had fewer embryos implanted in the uterus, less chance of becoming pregnant, and when they did conceive, they had fewer offspring. A lack of p53 did not affect the fertility of male mice, however.

"This is an amazing new function for a gene that everybody thought they knew what it did," said lead researcher Arnold J. Levine, a professor at the Institute for Advanced Study, in Princeton, N.J. "This is a gene that is not only watching over us so that we cannot get cancer, but it watches over our genome so that we can develop normally," he added.

The report appears in the Nov. 29 issue of Nature.

The p53 gene responds to a variety of stresses, such as radiation damage, in ways that allow it to protect cells against cancer, Levine explained. However, he added, "We found, quite by surprise, the normal function of p53 in the uterus of mice."

In order for embryos to implant in the uterus, a cytokine called LIF (leukemia inhibitory factor) is essential, and "p53 turns on the gene that makes LIF," Levine explained. "It's estrogen plus p53 making LIF that allows implantation."

In mice without the p53 gene, males are fine, but females only infrequently implant eggs and "the litter sizes go way down," Levine said. However, when these mice were given an injection of LIF, they reproduced normally.

Whether this finding has implications for humans isn't clear, Levine said. "We do know that humans require LIF in the uterus, but whether p53 has the same function in humans is something we are working on," he said.

Levine believes that p53 could play a part in human reproduction and infertility, but "there must be other factors as well," he said.

Defects in p53 are extremely rare in humans. "There are about 250 families in the United States that have defects in the p53 gene, a condition called Li-Fraumeni syndrome. This syndrome predisposes patients to cancer at an early age," Levine said.

One expert believes the finding could have clinical implications.

"Some humans show genetic variation in the amount of p53 they can produce and how well some of these variants of p53 function," said Colin Stewart, a principal investigator at the Institute of Medical Biology in Singapore and author of an accompanying editorial in the journal.

One study suggested that some women who have difficulty in getting pregnant tend to have the less efficient form of p53, Stewart noted.

"This may be why they have problems becoming pregnant, because the less efficient form of p53 does not make sufficient amounts of LIF that are necessary to get the embryo to attach to the wall of the uterus," Stewart said.

Drugs are currently being developed that would either improve the way p53 works or block the action of defective forms of p53, Stewart said.

"Some of these drugs may turn out to be useful in helping women conceive by improving the function of p53 in the uterus. Others may turn out to be possible contraceptives by blocking p53's function in the uterus," he added.

More information

For more information on p53, visit the National Center for Biotechnology Information.

SUNDAY, Nov. 4 (HealthDay News) -- Pregnant women who had a urinary tract infection (UTI) from one month before conception through the first trimester of pregnancy were 70 percent more likely than women without UTI to have a baby with a defect called hypoplastic left heart syndrome (underdeveloped left side of the heart), a U.S. study finds.

This association was independent of other factors, such as vitamin use, folic acid intake, alcohol consumption, race, ethnicity, mother's age, or exposure to sulfonamide ("sulfa") drugs, said the researchers.

The National Birth Defects Prevention Study included 3,690 women who had infants with "nonsyndromic" congenital birth defects and 4,760 mothers of babies without birth defects.

Detecting and treating asymptomatic bacteriuria and UTI in women at time of conception "may decrease the risk of having an infant with a left-sided obstructive cardiac defect," study author Sadia Malik, of the University of Arkansas Medical School in Little Rock, said in a prepared statement.

The study was expected to be presented Sunday at the American Heart Association annual meeting in Orlando, Fla.

More information

The American Heart Association has more about hypoplastic left heart syndrome  .

MONDAY, Oct. 29 (HealthDay News) High-dose precision radiation therapy doesn't harm the sexual function of prostate cancer patients, U.S. researchers say.

A team at Fox Chase Cancer Center in Philadelphia tracked 155 men with intermediate- to high-risk prostate cancer who underwent intensity-modulated radiation therapy (IMRT), a technique that more precisely targets the tumor.

"IMRT is revolutionizing how we treat men with prostate cancer, because it improves our ability to avoid normal tissue. As a result, more radiation dose can be delivered to the prostate by increasing the amount of radiation each day. Increasing the radiation used each day is particularly attractive, because it also shortens the treatment time by several days," study lead author Dr. Mark Buyyounouski, attending physician in the radiology department at Fox Chase, said in a prepared statement.

"We need to make sure there's a balance between risk and benefit, and sexual function is a major consideration. Fortunately, this study shows no decrease in sexual function from the higher doses of radiation," he said.

One group of men in the study received 2 Gy of radiation in 38 sessions over seven weeks, three days, while another group received 2.7 Gy in 26 sessions over five weeks, one day. At six months, one year, and two years after treatment, there were no significant differences in sexual function scores between the two groups.

The findings were expected to be presented Monday at the annual meeting of the American Society for Therapeutic Radiology and Oncology, in Los Angeles.

More information

The American Academy of Family Physicians outlines prostate cancer treatments  .

TUESDAY, May 22 (HealthDay News) -- Sleep apnea greatly increases the risk of diabetes and high blood pressure during pregnancy, according to a U.S. study that looked at nationwide data on millions of pregnancies in 2003.

Sleep apnea is a nighttime breathing disorder that disrupts sleep, causing multiple awakenings. Obesity is a major risk factor for sleep apnea.

Out of almost 4 million deliveries, 452 women had sleep apnea. Of the almost 168,000 women with gestational diabetes, 67 had sleep apnea. Of the almost 201,000 women with pregnancy-induced high blood pressure, 166 had sleep apnea.

The researchers concluded that sleep apnea was associated with a twofold increase in the risk of gestational diabetes and a fourfold increase in the risk of pregnancy-induced high blood pressure.

The findings were to be presented Tuesday at the American Thoracic Society's international conference in San Francisco.

"The repetitive decrease in oxygen that occurs during the night in someone with sleep apnea heightens the body's 'fight or flight' state, which can raise blood pressure," researcher Hatim Youssef of the Robert Wood Johnson Medical School at the University of Medicine & Dentistry of New Jersey, said in a prepared statement.

"The body also secretes more hormones such as cortisol and epinephrine, and the body responds by producing more glucose coupled with a decreased sensitivity to insulin, which can lead to diabetes," Youssef explained.

He noted that pregnancy can worsen sleep apnea, particularly during the third trimester when weight gain is the greatest.

"When a mother's oxygen level drops at night, it may also affect the oxygen level of the fetus, and we don't know what the long-term effects are," Youssef said. "That's why it's important for a pregnant woman with sleep apnea to be treated with CPAP (continuous positive airway pressure) during her pregnancy."

CPAP delivers air through a mask while a person sleeps.

More information

The U.S. National Heart, Lung, and Blood Institute has more about sleep apnea.