THE DISTRIBUTION OF PHOSPHORUS (P³¹ AND P³²) IN DORSAL AND VENTRAL HALVES OF THE RANA PIPIENS GASTRULA

¹ Department of Zoology, Columbia University, New York 27, N. Y.

1. A preliminary investigation of the distribution of phosphorus in dorsal and ventral halves of the Rana pipiens gastrula was undertaken to demonstrate the possible existence of a metabolic gradient of phosphate compounds correlated with the apparent morphological gradient. Radioactive phosphorus was employed to permit an analysis of shifts of phosphorus.

2. A modified Schmidt-Thannhauser extraction procedure was applied to dorsal and ventral halves of stage 10 (Shumway) embryos obtained from a frog injected with approximately 0.1 mc. of P³² before inducing ovulation. Total acidsoluble phosphorus, RNA phosphorus, DNA phosphorus, phosphoprotein phosphorus, phospholipid phosphorus and a residue phosphorus were extracted and analyzed for specific activity.

3. The distribution of phosphorus (P³¹ and P³²), expressed either as micrograms P³¹ per half embryo or as per cent of total P³¹ or P³², exhibited no significant difference between dorsal and ventral halves. However, expressed as micrograms P³¹ per cell, a ventral-dorsal gradient was apparent. Data expressed as specific activity (counts per minute per microgram P³¹) exhibit no significant differences.