Oxygen Consumption of the Parts of the Amphibian Gastrula. ∗

Abstract

Interest in the organizer has led to the determination of its oxygen consumption and the results of various investigators do not agree. Braehet, 1 Braehet and Shapiro, 2 and Fischer and Hartwig, 3 agree that the dorsal lip exhibits a higher rate, while Waddington, Needham and Brachet, 4 and Boell and Needham 5 report that the rates of O₂ consumption of the dorsal lip and ventral ectoderm are identical.

This seeming contradiction of results led to the present investigation. In one set of experiments the early gastrula was opened up and the roof of the blastocoel cut into 4 regions. Piece 1 contained the region just above the dorsal lip; 2 was composed chiefly of presumptive neural plate; 3 was chiefly presumptive epidermis, and 4 some epidermis and some cells which would give rise to the ventral lip. Numbers 1 and 4 were chosen carefully so as to contain about the same number of light-colored yolk cells and the regions were cut out so as to be in the same relative position to the equator of the gastrula. fn some cases the oxygen consumption of the mass of large yolk-laden endoderm cells was measured.

In the second series of experiments the roof of the blastocoel was cut into 3 parts. Measurements of O₂ consumption were made by a modified Winklers method and the pieces dried and weighed on a micro balance. The results are given in mm 3 of O₂ per hr per 100 mg dry weight.

The results, Tables I and II, show clearly that a gradient in respiration is obtained on the ventral side of the gastrula ranging from 21.2 to 10.3 to 4.1. (Table I, Rana pipiens pieces 3, 4, 5).