³H-thymidine injections from E19 to E20 and survival to postnatal day (P)5 (anterior coronal)

Figure 89.  This slice is through all layers of the main olfactory bulb (MOB).  By the morning of E19, 100% of the mitral cells have been generated; the small labeled cells in the mitral cell layer are endothelial cells (that can appear large depending how they lie in the slice), multiplying glia, and cells migrating to the external plexiform and glomerular layers.  Large labeled cells are probably tufted cells still migrating through the layer on P5.  Nearly all granule and periglomerular granule cells are labeled.  Most of the labeled cells in the internal plexiform layer are migrating toward superficial layers to settle.  The core of the MOB is full of small labeled cells that form the terminus of the rostral migratory stream—a conduit of new neurons steadily migrating (arrows) into the olfactory bulb from the proliferating subependymal layer surrounding the olfactory recess and anterior horn of the lateral ventricle.  The olfactory nerve layer is filled with labeled cells (glia).