Since the Women's Health Initiative study found that long-term therapy with estrogen or estrogen plus progestin may increase the risk of heart attack and stroke, many women have found it difficult to decide whether to take hormone therapy at menopause.

Subsequently, several researchers have speculated that the timing of estrogen treatment may be important for estrogen's effects.

A group of authors therefore designed an animal study to determine if estrogen would be beneficial for females who are going through menopause (perimenopausal) but not for women who are postmenopausal for many years. Since it is not possible to measure "risk" in animal studies, the authors measured severity of stroke injury.

Bioengineers at the University of California, Berkeley in a new study published in Nature say they have identified two key regulatory pathways that control how well adult stem cells repair and replace damaged tissue. They then tweaked how those stem cells reacted to those biochemical signals to revive the ability of muscle tissue in old mice to repair itself nearly as well as the muscle in the mice's much younger counterparts.

Because the findings relate to adult stem cells that reside in existing tissue, this approach to rejuvenating degenerating muscle eliminates the ethical and medical complications associated with transplanting tissues grown from embryonic stem cells.

The researchers focused on the interplay of two competing molecular pathways that control the stem cells, which sit next to the mature, differentiated cells that make up our working body parts. When the mature cells are damaged or wear out, the stem cells are called into action to begin the process of rebuilding.

Whether your summer vacation plans involve staying close to home or crossing the globe, you'll want to put as much thought into protecting your health while traveling as you do choosing your destination. A new report, Healthy Travel: A 10-Minute Consult from Harvard Medical School, includes this list of important health-related items to take along:

Lockheed Martin's Aegis Ballistic Missile Defense (BMD) Weapon System successfully detected, tracked and intercepted a short- range unitary ballistic missile target in the terminal phase of its trajectory during a test at the Pacific Missile Range off the coast of Hawaii.

In the test mission, the SPY-1B radar on the Aegis BMD cruiser USS Lake Erie (CG 70) detected and tracked the ballistic missile target, and computed a targeting solution to guide two SM-2 Block IV missiles to a successful endo-atmospheric (within the atmosphere) intercept. Once the SM-2s were launched from the ship’s Lockheed Martin-developed MK-41 Vertical Launching System (VLS), Aegis guided the missiles through the terminal phase of the intercept. The SM-2 Block IV missiles were recently modified to perform the terminal phase endo-atmospheric intercept of a ballistic missile.

If you are curious about Earth's periodic mass extinction events such as the sudden demise of the dinosaurs 65 million years ago, you might consider crashing asteroids and sky-darkening super volcanoes as culprits.

But a new study suggests that it is the ocean, and in particular the epic ebbs and flows of sea level and sediment over the course of geologic time, that is the primary cause of the world's periodic mass extinctions during the past 500 million years.[1]

"The expansions and contractions of those environments have pretty profound effects on life on Earth," says Shanan Peters, a University of Wisconsin-Madison assistant professor of geology and geophysics and the author of the new Nature report.

Overweight men are not more likely to be infertile, as past research has shown to be true in obese women, according to a new study. The results will be presented at The Endocrine Society’s 90th Annual Meeting in San Francisco.

Findings of the study, performed in New York in nearly 300 very overweight men, were unexpected, said coauthor Nanette Santoro, MD, an Albert Einstein College of Medicine obstetrician-gynecologist who is trained in reproductive endocrinology.

Santoro and her colleagues studied 292 men who gave semen samples at fertility clinics. The men were ages 18 to 50 and, on average, had a body mass index (BMI) of 28, which is considered nearly obese. The authors found that greater body weight was not associated with worse sperm production or sperm motility. Impaired sperm production is the cause of infertility in 90 percent of infertile men, according to Santoro. About 6 percent of reproductive-age men are infertile, she said.