³H-thymidine injection on E15, 2 hr survival

Figure 30 shows a sagittal slice of an E15 embryo 2 hrs after its mother was injected with ³H‑thymidine.  All NEP areas have thick accumulations of precursor cells at their superficial borders except the tentatively identified olfactory bulb NEP.  The most well-defined subventricular zone is peppered with locally multiplying cells in the basal ganglionic eminence.  Heavily-labeled cells outside the NEP are most likely proliferating glial precursors.  The brain parenchyma is expanding and differentiating young neurons populate all areas, including the presumptive olfactory bulb; many are AOB output neurons.  The olfactory epithelium has a substantial amount of label uptake.  In some parts that are cut perpendicularly, labeled nuclei are in a superficial position—like the pseudostratified NEP that lines the brain ventricles.  Of course, the olfactory epithelium is also generating sensory neurons that are the source of the olfactory nerve.