a histological study of cell death in the developing olfactory epithelium of the mouse embryos *
The occurrcncc of cell death in developing olfactory epithelium was histologically studied in ICR-mouse embryos at 12, 14 and 16 days of gestation and neonates at 2 days after birth. The distribution of cell death was examined not only by the TUNEL (TdT-mediated dUTP nick end-labeling) method in paraffin sections, but also by observation of serial 1 μm plastic sections at 14 days of gestation. At 12 days of gestation, the nasal cavity was wholly covered by pseudostratified epithelium, and it was difficult to distinguish between olfactory epithelium and respiratory epithelium on histological sections. At 14 days of gestation, however, the epithelium of the upper nasal cavity became thick, consisting of three cell layers ; a superficial supporting cell layer, a middle olfactory cell layer and a basal cell layer. Under a scanning electron microscope, olfactory vesicles and olfactory cilia could also be observed. The olfactory epithelium contained dying cells with highly pyknotic nuclci in which a TUNEL-positive reaction appeared. Although both the respiratory epithelium and olfactory epithelium contained numerous mitotic figures, apoplotic cells could be observed in the olfactory part of the nasal cavity at 14 days of gestation. The dying cells, which were recognized in the supporting and olfactory cell layers, were observed more frequently in the olfactory epithelium on the lateral and roof walls than in the median olfactory epithelium on nasal septum. The relationship between programmed cell death and development of the olfactory epithelium was discussed. (Accepted on September 13, 1999) Kawasaki Igakkaishi 25(3) : 211-221, 1999
