This study has been approved by Shanghai
Institute of Nutrition (Ethical Certification 2013-002). Prior to
the experiment, all rats were examined for vaginal cytology
twice per day for two continuous estrous cycles to monitor
menstrual cycles in all experimental rats.12 At the end of experiments,
all rats were anesthetized and the ovaries were
removed for electron microscopy study. Blood was collected
from inferior vena cava for detecting serum levels of 17bestradiol
and progesterone, respectively. In order to compare
the levels of ovarian hormone and microstructure of ovary at
same stage of menstrual cycle, all rats were sacrificed during
anestrous phase determined by vaginal smears.