A LIGHT AND ELECTRON-MICROSCOPIC AUTORADIOGRAPHIC STUDY ON RNA-SYNTHESIS IN THE RETINA OF CHICK-EMBRYO

The incorporation of H-3-uridine into RNA of chick embryo retina was s tudied by light and electron microscopic radioautography. The numbers of silver grains were counted over the nucleus, nucleolus and cytoplas m of the cells in three different regions of the same retina of 2, 3, 4, and 7 day chick embryos. The results showed an increase of H-3-urid ine incorporation from embryonic day 2 to 7. In every stage of develop ment of the chick embryo retina, the number of silver grains was highe r in the anterior than in the other two regions of the retina. In the three cell compartments of every embryo group, the number of silver gr ains was higher in the nucleus than in the nucleolus and cytoplasm. Th e results show further that the grains were less in the cytoplasm of t he retinal cells of the day 2 embryo group and higher in the other gro ups especially in the day 7 embryos. Ultrastructural changes were also observed during the studied period of retina development.