24 hr survival after a 3H-thymidine injection on E15 (coronal)
Figure 45. A coronal slice through the anterior forebrain that grazes the parenchyma of the evaginating olfactory bulb on the right side (unlabeled part) and the olfactory recess of the lateral ventricle on the left side in an E16 embryo killed 24 hrs after a single exposure to 3H-thymidine on E15. Unlabeled cells are the AOB output neurons and the MOB mitral and tufted cells generated before the morning of E15. Labeled cells outside the olfactory bulb NEP are cells migrating into the bulb—probably many are mitral cells because E15 is the peak day (45-48%) of generation. The olfactory and presumptive vomeronasal nerve fibers are surrounded by heavily labeled cells that proliferate outside the central nervous system. The heavy label uptake in the olfactory epithelium and Jacobson’s organ indicate active proliferation. The olfactory nerve blends with the ventral brain surface in the contact zone, obliterating the pial membrane.