Abstract
The aim of this study was to examine whether apoptosis of oocytes occurs and their frequency changes during the ovarian development of embryo and post-hatched chicks of Japanese quail. The ovaries of embryos and chicks were processed for paraffin sections and stained by terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling (TUNEL) method. The TUNEL positive cells were observed in both cortex and medulla of Day 14 embryo and day-old chicks, and there were some TUNEL positive oocyte-like cells in the cortex of day-old chicks. In the 7-day-old chicks many of the oocytes, which grew in size and contained germinal vesicle, were surrounded by follicular wall, and 5.8% oocytes were TUNEL-positive. In 14- to 35-day-old chicks, TUNEL-positive oocytes were negligible and only a few cells in the cortical tissue were stained positive for TUNEL reaction. These results suggest that apoptosis of oocytes occurs at pre- and post-hatching phase, and becomes negligible by Day 14 of post hatching, which probably play a role in eliminating the abnormal oocytes to ensure the quality of oocytes.
