RESPIRATORY METABOLISM OF AMPHIBIAN GASTRULA EXPLANTS

¹ Department of Zoology, Columbia University, New York 27, New York

1. In full-strength Holtfreter's solution, dorsal explants from Rana pipiens gastrulae respire some 20% faster than ventral explants from the same gastrulae (with respect to dry weight). Lateral halves of dorsal explants respire at the same rate; and lateral halves of ventral explants respire at the same rate.

2. Azide, cyanide, malonate, p-chloromercuribenzoate, fluoride and 2,4 dinitrophenol in low concentrations all either completely block or greatly retard the gastrulation movements of Rana pipiens embryos.

3. Azide, cyanide, malonate, p-chloromercuribenzoate and fluoride all sharply reduce the respiratory rate of both dorsal and ventral explants from 29% (0.0001 M KCN) to 72% (0.001 M NaN₃).

4. 2,4 dinitrophenol (9.5 x 10^-6 M) more than doubles the respiratory rate of both dorsal and ventral explants.

5. If these inhibitors block the movements of gastrulation by differential effects upon dorsal and ventral tissues, then these effects are not of such a nature as to be revealed by respiratory measurements—for the relative respiratory rates of dorsal and ventral tissues exposed to inhibitors are the same as those of controls in Holtfreter's solution.

6. Respiratory activity is not linked in any simple way with the movements of gastrulation, for compounds that reduce the former may have no effect upon the latter (0.0005 M KCN), and compounds that may completely block the latter have no effect upon the former (0.0001 M p-chloromercuribenzoate).

7. Dorsal and ventral explants of ^{Rana pipiens} gastrulae produce carbon dioxide anaerobically, but at rates that are not significantly different.