Fig. 4

Immunostaining for BrdU (red Cy3 fluorescence) in cryosections of an intrapulmonary airway (a) and small intestine (b) of the same mouse that received no treatment, except for the BrdU injections (i.p.), 48 h and 24 h prior to sacrifice. a The airway epithelium rarely harbors divided BrdU-positive cells. The majority of BrdU-labeled nuclei (arrowheads) are located in subepithelial layers. b In the crypts (asterisks) and the basal parts of the villus epithelium of the small intestine, a large number of BrdU-labeled nuclei (arrowheads) ̶̶ i.e., originating from cells that have divided during the 48 h experimental window ̶̶ can be observed. L: airway lumen, E: airway epithelium