Physiology

The Good Interred in Bones

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Science  08 Jun 2012:
Vol. 336, Issue 6086, pp. 1213
DOI: 10.1126/science.336.6086.1213-c

Our bones are constantly being replaced through a process of resorption and regrowth. This requires a healthy blood supply to the bones, which also transports necessary elements. Bones are the main reservoir of calcium in the body, and they favor the lighter calcium isotopes. In an experiment with patients undergoing bed rest, which drives gradual bone resorption, Morgan et al. show that assaying the isotopic distribution of calcium in urine (which is derived primarily from the residual calcium in soft tissues) can detect changes in the balance of bone mineralization more rapidly than other standard approaches. They quantify the loss in a physiological model that includes further isotope fractionation occurring in the kidneys. Separately, Jaouen et al. show that measuring both iron and copper isotopes in archaeological bone samples can be used to determine an individual's gender—an otherwise major challenge if certain distinguishing bones (e.g., pelvis) aren't preserved. Here, the isotope fractionation occurs elsewhere in the body, and differently in men and women, and the bones harbor these elements.

Proc. Natl. Acad. Sci. U.S.A. 109, 10.1073/pnas.1119587109 (2012); Am. J. Phys. Anthropol. 10.1002/ajpa.22053 (2012).

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