A morphological study of TUNEL positive dying cells in the developing inner ear of mouse embryos (the second report) – Ultrastructural classification – *
TdT-mediated dUTP nick end-labeling (TUNEL) positive dying cells in the inner ears of embryonic mice could be classified as involved in apoptotic cell death (ACD) and non-apoptotic cell death (NACD) by light microscopy. Approximately 90% of the inner ear dying cells were in ACD and remaining 10% were in NACD. Cis-diammine-dichloroplatinum (CDDP) decreased the ACD/NACD ratio as 70/30 without clear change in the number of total dying cells (Kawasaki Igakkai Shi 28( 4 ) : 287- 296, 2002). After observations under light microscope, using re-embedding maneuver, the same TUNEL positive dying cells were observed by transmission electron microscopy (TEM). According to the classification of dying cells by Clarke (1990) , the TUNEL positive dying cell's images were analyzed. The phagocytosis of dying cells and TUNEL negative dying cells in the inner ears were observed by ordinary TEM. The results clearly showed that ACD involved in type 1 (apoptotic) dying cells and NACD involved in type 2 (autophagic) dying cells in the inner ear of the mouse embryos, and that the type 1 dying cells were engulfed by neighboring cells. These images were not changed by the administration of CDDP. (Accepted on October 28, 2002)
