Morphological comparison of apoptotic with non-apoptotic dying cells in the developing inner ear of mouse embryos.
Dying cells studied by the TdT-mediated dUTP nick end-labeling (TUNEL) method have been classified as "apoptotic" and "non-apoptotic" cells. In this study, in which 12-day-old mouse embryos were used because of a high frequency of "natural cell death" due to changing inner ear morphology [Kaufman, M.H., 1992. The Atlas of Mouse Development, first ed., Academic Press, London, p. 147], the percentages of "apoptotic" and "non-apoptotic" dying cells (ADC and NADC) among total dying cells in the inner ear were calculated. Observation of consecutive paraffin sections showed about 90% of the dying inner ear cells to be ADC and about 10% to be NADC. ADC and NADC TUNEL positive dying cells in resin sections observed by light microscopy were examined again by transmission electron microscopy using a re-embedding procedure. ADC and NADC were then analyzed based on the classification of dying cells (types 1, 2, 3A, and 3B) as described by Clarke [Anat. Embryol. 181 (1990) 195]. It was clear that ADC were the equivalent of type 1 (apoptotic) dying cells and NADC were the equivalent of type 2 (autophagic) dying cells. We consider these findings to be important baselines for determining the process underlying abnormal development of the inner ear and its functional disorders such as hearing loss.
Hirai
Shigeo
S
Department of Otorhinolaryngology, Kawasaki Medical School, 577 Matsushima, Kurashiki, Okayama 701-0192, Japan. shigezo@mx1.tiki.ne.jp
Harada
Tamotsu
T
D000818:Animals; D017209:Apoptosis; D007758:Ear, Inner / Q000166:cytology / Q000196:embryology* / Q000648:ultrastructure; D047108:Embryonic Development / Q000502:physiology; D020287:In Situ Nick-End Labeling; D051379:Mice; D008813:Mice, Inbred ICR; D018345:Mice, Knockout; D046529:Microscopy, Electron, Transmission