Fig. 1. Section of the olfactory epithelium showing BrdU-ir in single and clustered cells. Positive staining appears as a black precipitate. (A) Typical round morphology of a BrdU-ir cell in the basal cell layer. (B) Elongated morphology typical of a BrdU-ir cell in the mid-apical cell layer. (C) An example of a BrdU-labeled cluster of four cells situated in the basal region of the epithelium. Labeled cells are black and appear to be in close juxtaposition to each other. Length bars (10 µm) distinguish the extent of the basal region in A, B and C. Scale bar in B, 10 µm.