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Biology textbooks may be due for a rewrite. For the first time, scientists have detected a DNA structure inside living human cells that looks more like a four-stranded knot than the elegant double helix we learned about in school. The tangled shape, known as an i-motif, had been seen before in the lab, but few researchers expected it to occur in human cells. The new work shows not only that i-motifs do indeed exist in human cells, but that they may be quite common. (Netburn, 4/23)

Joshua Coleman remembers watering down a glass of wine before giving it to his father, then in his 90s. “What the hell is this?” he recalls his father asking. “I feel a little guilty about that now,” says Dr. Coleman, whose father died in 2001. “The poor old guy had few remaining pleasures left. But I would have felt bad had he gone back to assisted living and slipped.” (Ansberry, 4/23)

Eight sick prisoners in Nome, Alaska, have provided a clue to authorities about the origin of a nationwide outbreak of dangerous E. coli infections from romaine lettuce, but U.S. officials said Monday they still haven't pinpointed the source of the contamination. Instead, the Food and Drug Administration and the Centers for Disease Control and Prevention are sticking with a broad warning to consumers, telling them to throw away romaine, in any form, that comes from the Yuma, Ariz., growing region, and to avoid eating romaine of unknown origin. Most of the romaine sold in the United States during the winter is grown in the Yuma region. (Sun and Achenbach, 4/23)

In an ominous sign for patient safety, 71 percent of reusable medical scopes deemed ready for use on patients tested positive for bacteria at three major U.S. hospitals, according to a new study. The paper, published last month in the American Journal of Infection Control, underscores the infection risk posed by a wide range of endoscopes commonly used to peer deep into the body. It signals a lack of progress by manufacturers, hospitals and regulators in reducing contamination despite numerous reports of superbug outbreaks and patient deaths, experts say. (Terhune, 4/23)

We all remember going through puberty, though some of us might like to forget. Now imagine starting that formative transition — developing breasts or pubic hair — at 6 years old, just as you’re starting first grade. Now new research has found a likely cause: The heavier the mom-to-be, the more likely her daughter will bloom early, according to a study by the Kaiser Permanente Department of Research. (Lanese, 4/23)