Electron microscopic radioautographic study on DNA synthesis in perinatal mouse retina

For the purpose of comparing the quantitative changes in both labelled and unlabelled retinal cells with 3H-thymidine radioautography, normal ddY mice from early embryonic stage (E 9.5) to postnatal 2 weeks were utilized as materials. About 200 electron microscopic radioautograms were taken from the middle portions of retina in the early embryonic stages and from the inner half of outer neuroblastic layers of retina of 9 groups of litter mice at the late embryonic and postnatal ages, and the enlarged photographs were quantitatively analyzed by image analysis. The results showed that the area of nuclei, cytoplasm, mitochondria and the number of mitochondria, per retinal cell, decreased from early embryonic stages to postnatal ages in both labelled and unlabelled cells (p < 0.05). However, no significant changes occurred in the area of ER per retinal cell in both labelled and unlabeled cells. Significant differences of the ultrastructural changes between labelled and unlabelled cells were not statistically detected except the area of nuclei at P 1 and the number of mitochondria at P 3.