Safe hosting

Remember two-hour rule: When planning your holiday party, be sure the foods you serve aren't inviting unwanted guests - bacteria.

"To deter bacteria growth, holiday party hosts should remember the two-hour rule," explains Vickie Vaclavik, assistant professor of clinical nutrition at the University of Texas Southwestern Medical Center in Dallas. "Foods should not sit unprotected at room temperature for more than about two hours."

Cream-based products, eggs, meats and milk can naturally promote bacteria growth that causes food-borne illness. To avoid problems, frequently replace platters with fresh platters, keep hot foods at 140 degrees or warmer consistently and cold foods at 40 degrees or colder.

Knee crisis

Keep yours healthy: Between the weekend sports warriors and the growing number of Americans who are overweight, knees everywhere are wearing out. The intricate design of bone, ligament, muscle and tendon give this joint an amazing range of motion. But the complexity also increases the chance of injury. Learn how to prevent and treat injuries with The Knee Crisis Handbook (Rodale; $13.95). The book, by Dr. Brian Halpern with Laura Tucker, addresses all ages and conditions, from kids to pregnant women to the disabled.

Shelf help

Spiritual bliss: It's hard to get past the perky title Happy Yoga (ReganBooks; $15.95). But any yoga book that quotes Public Enemy ("Don't believe the hype") deserves a second look. Happy Yoga, by Steve Ross with Olivia Rosewood, is less an exercise guide than a treatise on how yoga's principles inform daily living. Ross, a Los Angeles yoga instructor and host of Inhale on the Oxygen network, also provides playlist suggestions, with music ranging from Frank Sinatra to U2.

Biochemistry news

Rebuild muscles: Muscles may shrink with age because the reservoir for new muscle cells shuts down, a new study suggests.

Preventing that shutdown could reverse muscle atrophy due to old age, lack of use or even space flight.

In the latest issue of the journal Science, researchers from Stanford University School of Medicine in California pinpoint a biochemical pathway that, with age, slows down in special cells that normally replenish injured or atrophied muscle cells.

The researchers were able to reactivate the pathway in mice and restore new muscle cell formation, offering hope for people with muscle problems.

Fewer babies

Birth news: America's birth rate fell to a record low last year as both teenagers and women in their prime childbearing years had fewer babies, government officials reported recently. But the percentages of premature and low-birth weight babies climbed, continuing the rise of recent years.

The latest figure is the lowest in government records that go back to the turn of the 20th century, according to Brady Hamilton, a demographer at the National Center for Health Statistics.

A major factor in the decline has been the reduction in births to teenagers in recent years. Other factors also play a part, including the aging of the population.

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