The seemingly inefficient way our bodies replace worn-out cells is a defense against cancer, according to new research.

Having the neighboring cell just split into two identical daughter cells would seem to be the simplest way to keep bodies from falling apart.

However that would be a recipe for uncontrolled growth, said John W. Pepper of The University of Arizona in Tucson. We wrote of the paper by Pepper and his colleagues,, "Animal Cell Differentiation Patterns Suppress Somatic Evolution", last week.

"If there were only one cell type in the group, it would act like an evolving population of cells.

UC Davis researchers have dated the earliest step in the formation of the solar system -- when microscopic interstellar dust coalesced into mountain-sized chunks of rock -- to 4,568 million years ago, within a range of about 2,080,000 years.

UC Davis postdoctoral researcher Frederic Moynier, Qing-zhu Yin, assistant professor of geology, and graduate student Benjamin Jacobsen established the dates by analyzing a particular type of meteorite, called a carbonaceous chondrite, which represents the oldest material left over from the formation of the solar system.

The physics and timing of this first stage of planet formation are not well understood, Yin said. So, putting time constraints on the process should help guide the physical models that could be used to explain it.

Heart attacks among cigarette smokers may have less to do with tobacco than genetics. A common defect in a gene controlling cholesterol metabolism boosts smokers’ risk of an early heart attack, according to a new study in Annals of Noninvasive Electrocardiology. The findings also show that smokers without the defect normally have heart attacks no sooner than their non-smoking peers.

Although the link between smoking and heart disease was established decades ago, the reasons for that link were unclear. More recent studies suggest smoking interferes with cholesterol metabolism, lowering smokers’ levels of high-density lipoprotein, the good cholesterol that protects against heart-attack risk.

A research team led by Dr. Pierre Moffatt of the Shriners Hospital for Children in Montreal and McGill University’s Department of Human Genetics has uncovered the molecular mechanism by which the protein osteocrin controls bone growth – a discovery that may have important implications for people suffering from bone diseases affecting skeletal growth. The study can be read in the December 14 edition of the Journal of Biological Chemistry.

Osteocrin is a small protein produced by the body’s bone-forming cells, or osteoblasts. In this study, mice that were genetically engineered to over-express osteocrin developed hunchbacks and elongated bones. This led Dr.

A new brain imaging study by researchers in the Abramson Cancer Center of the University of Pennsylvania shows that cigarette cravings in smokers who are deprived of nicotine are linked with increased activation in specific regions of the brain.

Using a novel method of measuring brain blood flow developed by John Detre, MD, associate professor of Neurology at Penn, this study is the first to show how abstinence from nicotine produces brain activation patterns that relate to urges to smoke. The findings were published in the December 19, 2007 issue of The Journal of Neuroscience and make an important contribution to understanding smoking urges, a key risk factor for relapse, at the brain level.

Twelve healthy subjects in their 60s and 70s showed a different pattern of brain activations during thirst and satiation than did 10 healthy subjects in their 20s who drank the same amounts and underwent imaging with positron-emission tomography (PET). Dysfunction in activated neural regions could help explain why older adults show the dangerous tendency toward reduced drinking in response to dehydration.

San Antonio and Australian researchers reported the PET study of thirst in this week’s Proceedings of the National Academy of Sciences Online Early Edition.

The team has conducted a series of studies to catalog brain activations to basic physiologic necessities such as thirst, body temperature regulation, air hunger and pain relief.