Fig. (4) Electron microscopic radioautogram of the adrenal medullary tissues of a newborn mouse at postnatal day 3, labeled with 3H-thymidine, showing DNA synthesis (several silver grains) in the nuclei as well as in a few mitochondria of 3 adenalin cells. x 3,000. (From Nagata [49]. Courtesy of J Cell Tiss Res 9: 1793-1802, 2009).