DISCOVERY ADDS CLUES TO COMPOSITION OF LIGNIN — The sugar glucose is part of the answer to a biochemical riddle — the exact composition of lignin. Lignin, which together with cellulose comprises wood, is a highly complex carbohydrate whose complete structure is unknown. It is considered a waste product.... Experiments … have shown that in Norway spruce trees the lignin is derived from glucose. The discovery was made by feeding the trees with radioactive glucose.… By studying where the radioactivity was located in the lignin the scientists were able to find how the glucose molecules were converted into these units…. They may some day be able to find as many uses for lignin as they have for cellulose.

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Snack addicts The experiment outlined in “Junk food turns rats into addicts” (SN: 11/21/09, p. 8) seems to have overlooked an ingredient list. The junk foods fed to the rats were junky, to be sure, but which foods were the most addictive? Many junk foods are filled with alarming amounts of things like mono­sodium glutamate. Were the rats more responsive to the MSG-laden foods? Did they crave salt over sugar? Fat over starch? This article left me hungry for specifics. Drew Massey, Los Angeles, Calif. In the study, researchers fed the rats a mishmash of junky foods (think bacon-wrapped cheesecake covered with frosting), so any ingredient’s individual effects were hidden. The researchers noticed that rats seemed to like foods laden with both fat and sugar most, making these ingredients the “likely culprits,” says Paul Kenny, a coauthor of the study. “It s...

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February 20–21 Free science discussion sessions and demos are open to the public at the AAAS annual meeting in San Diego. See www.aaas.org/meetings/2010  February 24–26 The International Stroke Conference 2010 is held in San Antonio. See strokeconference.org March 31 New nomination deadline for the 2010 National Medal of Science. Get forms at www.nsf.gov/od/nms/medal.jsp

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