THE RELATION BETWEEN THE INTRACELLULAR RIBONUCLEIC ACID DISTRIBUTION AND AMINO ACID INCORPORATION IN THE LIVER OF THE DEVELOPING CHICK EMBRYO

The RNA-P and DNA-P content of the nucleus and the RNA-P content of the whole cell of the livers of 8- to 20-day chick embryos and of adult fowls have been determined. The DNA-P content of the liver nuclei was slightly higher in the 8- and 10-day embryo than in all the other stages examined. A significant decrease in the RNA content of the cell occurred during embryonic development. The RNA content of the adult cell was the same as that of the 14- to 16-day embryo. The proportion of the cellular RNA contributed by the nucleus also decreased during development. In respect to both nuclear RNA content and distribution of RNA between nucleus and cytoplasm, the adult resembled the 8- to 12-day embryo. Examination of the fine structure of the cell showed that, as development progressed, free ribosomes decreased in number and the rough membranes increased. Slices of 8-, 14-, and 20-day embryonic livers and of adult livers were incubated with ¹⁴C-leucine, and the amount of labeled amino acid incorporated into whole tissue protein and into the proteins of the subcellular fractions was measured. Embryonic liver incorporated ¹⁴C-leucine 15 to 30 times more rapidly than adult liver. The microsomal protein was always more highly labelled than the protein in any other subcellular fraction; however, in the 8-day embryonic and the adult liver the proportion of total counts found in the nuclear fraction was considerably higher than in the 14- or 20-day embryonic liver. The significance of an apparent correlation between the proportion of the cell's RNA contributed by the nucleus and the proportion of total counts in the nuclear fraction is discussed.     

Studies on the distribution of phosphorylase in eyes of the rabbit and the squirrel monkey

Summary Detailed studies on phosphorylase localization in various components of the eyeball of rabbit and squirrel monkey have been made. Corneal epithelium, endothelium, and stromal cells, extrinsic and intrinsic muscles of the eyeball, ciliary process, endothelial cells of the anterior chamber angle, vitreal cells, lens epithelium, inner segment of cones; plexiform layer, ganglion cell layer, internal and external limiting membrane and Muller cells show high phosphorylase activity. Surprisingly, we observed phosphorylase activity inside the nucleus in the posterior 2 to 3 layers of corneal epithelium. The significance of phosphorylase localization in relation to glycogen distribution in various components of the eyeball and their energy requirements is stressed.