Acid phosphatase activity in yolk droplets of chick notochordal cells.

The fine localization of acid phosphatase activity in yolk droplets in the notochordal cells of the developing chick (stage 12-13) has been investigated by electron microscopy. The enzyme reaction products are mainly found on the peripheries of yolk droplets of various different sizes, which are often clustered together to form larger masses. The rough endoplasmic reticulum and Golgi complexes with the substantial or small amounts of reaction product are closely, and occasionally directly, associated with the yolk droplets and their masses. These findings strongly suggested that both the rough and endoplasmic reticulum and Golgi complexes supply the acid phosphatase for the utilization of yolk in the differentiating notochordal cells.