24 hr survival after a ³H-thymidine injection on E16 (sagittal)

Figure 60.  This sagittal slice through the most prominent part of the evaginating olfactory bulb on E17 shows heavy label uptake after a ³H-thymidine exposure on the morning of E16.  Unlabeled cells were generated before the morning of E16.  The unlabeled cells in the parenchyma outside the olfactory NEP are AOB output neurons and mitral cells generated before E16 (nearly 90%).  Heavily labeled cells infiltrating the parenchyma outside the basal telencephalic NEP and SVZ may be rapidly migrating mitral cells generated on E16.  There is only faint lamination in the olfactory bulb itself, and one cannot distinguish an MOB from an AOB; the AOB output neurons may be accumulating in a pod-like area on the dorsal-anterior side of the olfactory bulb.  The olfactory nerve is full of large cells, some unlabeled and many labeled that coalesce with the brain surface where the bulb continues to evaginate—much farther than E16 embryos.  The presumptive olfactory epithelium—as in all cells lining the nasal cavity—are actively proliferating and have heavy label uptake.  (Areas outlined with dashed red lines are artifacts and tears in the slice.)