A toxin that forces a condemned victim to smile really seems to exist. The Greek bard Homer coined the term "sardonic grin" after ceremonial killings that supposedly took place in Sardinia, where Phoenician colonists gave to elderly people who could no longer take care of themselves and to criminals an intoxicating potion that put a smile on their face. (They were then dropped from a high rock or beaten to death.) Scientists at the University of Eastern Piedmont in Italy and their colleagues think they now have identified the herb responsible: hemlock water dropwort (Oenanthe crocata), which is common on Sardinia, where it is popularly known as "water celery." Their analysis revealed the presence of highly toxic chemicals in the plant that could make facial muscles contract into a grimace, or rictus. The finding appears in the May 22 Journal of Natural Products. —Charles Q. Choi
Humanity is upsetting not just levels of carbon in the air but those of nitrogen as well. Although the burning of fossil fuels is known to release nitrogen oxides that can excessively fertilize ecosystems or react with other compounds to form smog and acid rain, researchers have had difficulty pinpointing the extent to which people have disrupted nitrogen levels in the atmosphere. To investigate, scientists at Brown University and the University of Washington analyzed an ice core from Greenland, which trapped nitrate deposits over the past three centuries. They found that levels of the rare nitrogen 15 isotope had plummeted over the past 150 years when compared with the more common nitrogen 14. This skewing likely results from an influx of nitrogen oxides from fuel combustion, which for uncertain reasons generates nitrogen oxides depleted in nitrogen 15. The shift, described in the June 5 Science, also coincides with the industrial age—indeed, the greatest rate of change happened between 1950 and 1980, after a rapid increase in fossil-fuel emissions. —Charles Q. Choi
Cancer Clue from Down Syndrome
People who have Down syndrome hardly ever get tumors, an observation that has long puzzled scientists. They suspected that patients might be getting a bonus dose of cancer-protective genes, because the disorder is caused by an extra copy of a chromosome—specifically, chromosome 21. Researchers at Children’s Hospital Boston and their colleagues found that an added copy of DSCR1, one of the 231 genes on chromosome 21, could inhibit the spread of mouse and human tumors. The gene suppresses the growth of new blood vessels that cancers need by blocking the activity of the protein calcineurin, suggesting a new target for future cancer drugs. The investigators, whose findings were posted online May 20 by Nature (Scientific American is part of the Nature Publishing Group), add that chromosome 21 might possess four or five antiangiogenesis genes.
The extra chromosome arises as a mistake in cell division during embryonic development. Researchers at Tufts Medical Center and their colleagues discovered that the amniotic fluid surrounding Down syndrome fetuses shows evidence of oxidative stress that could harm cells, particularly neural and cardiac tissue. The signs, unfortunately, appear in the second trimester, too late for antioxidants to treat the hallmarks of Down syndrome that arise in the first trimester, such as mental impairment. Still, the team suggests in the June 9 Proceedings of the National Academy of Sciences USA that second-trimester antioxidants might fend off aspects of the syndrome that are yet to be discovered. —Charles Q. Choi
Gallons per Mile
The Obama administration in May announced that the mileage of cars and light trucks sold in the U.S. must rise from the current 25 miles per gallon to 35.5 mpg by 2016. That’s a 40 percent improvement. But perhaps a more meaningful measure of fuel efficiency is fuel consumption per distance traveled. People who drive an average vehicle for 100 miles a week will see their weekly gas usage drop from four gallons to 2.8 gallons—a 30 percent reduction in both expenses and carbon dioxide emissions. And though significant, the efficiency gains will not be enough to bring the U.S. in line with what vehicles sold in Japan and Europe already consume now.