Sonic hedgehog, a gene that plays a crucial rule in the positioning and growth of limbs, fingers and toes, has been found in the ectoderm - the cell layer that gives rise to the skin - in the embryos of developing mice. The gene was previously thought to be exclusively present in the cell layer that builds bone and muscle, called the mesoderm.

The discovery, detailed in PNAS, suggests that Sonic hedgehog's role in the growth of appendages is far more complex than originally thought. Developmental biologists may have to rethink established theories about how limbs are patterned in vertebrates — an effort that could provide insight into human birth defects.

Writing in the latest issue of JAMA, Alec B. O'Connor, associate professor at the University of Rochester Medical Center, says the federal guidelines governing the approval of potential new drugs should be much more stringent. The FDA, according to the commentary, should require studies comparing the effectiveness and safety of a new drug to an established first-line drug when considering a drug for approval.

Currently the agency does not require such studies, known as "active comparator trials," though some large studies of new drugs do include them. In many cases, to gain approval, the main criterion besides safety is that a new drug must be shown to be more effective than placebo.

Researchers at Yale School of Medicine have discovered that exposure during pregnancy to Bisphenol A (BPA), a common component of plastics, causes permanent abnormalities in the uterus of offspring, including alteration in their DNA. The findings were reported the Journal of the Federation of American Societies for Experimental Biology (FASEB J.).

The authors say the study is the first to show that BPA exposure permanently affects sensitivity to estrogen.

Scientists from the U.S. department of Agriculture have discovered how The Aedes aegypti mosquito detects the chemical structure of a compound called octenol as one way to find a mammalian host for a blood meal.

Scientists have long known that mosquitoes can detect octenol, but this most recent finding, published in PLoS One, explains in greater detail how Ae. aegypti--and possibly other mosquito species--detect the compound.

Using data from two recent national surveys, University of Toronto sociologist Scott Schieman has found that most Americans believe God is concerned with their well-being and is directly involved in their personal affairs.

The research, he says, uncovered  the ways these beliefs about divine intervention differ across education and income levels. The results are published in Sociology of Religion.

Traditionally, scientists believed that nicotine inhaled in a puff of cigarette smoke took a mere seven seconds to be taken up by the brain, but new evidence indicates that nicotine takes much longer to reach peak levels in the brains of cigarette smokers, according to a new study in PNAS.

Using PET imaging, Duke investigators found for the first time that cigarette smokers actually experience a steady rise of brain nicotine levels during the course of smoking a whole cigarette.