Beaker bytes
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Hyponatremia:
Too much of a good thing
Children's Hospital Boston cardiac fellow Chris Almond, MD, found himself in the spotlight with his April 14 New England Journal of Medicine paper, timed to appear just before the Boston Marathon. Despite nearly universal advice to load up on fluids, Almond's study found that over-hydration is a bigger and potentially deadly problem for runners than previously thought, especially among non-elite runners. The study surveyed 488 runners in 2002's Boston Marathon about their fluid intake, recorded their weights before and after the race and analyzed blood samples. Thirteen percent of runners finished with hyponatremia, a dangerously low salt concentration in the blood that in rare instances can be fatal. The major cause was excessive fluid intake, diluting the blood's salt content. Surprisingly, runners who drank electrolyte-containing sports drinks, as opposed to plain water, were equally at risk. Runners who gained weight during the race because of fluid loading were at especially high risk, as were slower and slimmer runners. The study garnered front page coverage in The New York Times and was reported by the Boston Globe, The Associated Press, National Public Radio, NBC Nightly News and more than 100 other media outlets. David Greenes, MD, was senior author.
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Placenta could be a source of blood stem cells
Researchers, led by Stuart Orkin, MD, Howard Hughes Medical Institute investigator at Children's Hospital Boston and chair of Pediatric Oncology for the Dana-Farber Cancer Institute, report a surprising finding: the placenta that nurtures the developing fetus harbors a large supply of hematopoietic (blood-forming) stem cells, which can give rise to a complete blood system when transplanted into an adult.
The finding in mice is surprising because blood stem cells were thought to be made only in the fetus itself; the placenta was seen as simply a place for nutrient exchange between mother and baby. "This research reveals a new organ for blood development," says Orkin. "If we figure out what's special about the placenta, we may learn how to grow blood stem cells in large numbers for clinical application."
That would be a boon for patients with leukemia and other blood diseases and for patients receiving transplants. Blood stem cells multiply poorly in the lab, so they must be harvested from bone marrow by a painful needle aspiration or coaxed into the blood and collected. Both methods yield only limited numbers of cells. The study appeared in the March Developmental Cell. Hanna Mikkola, MD, PhD, was senior author.
