A manometric analysis of the metabolism in avian ontogenesis―II. The effects of fluoride, Iodoacetate, and other reagents on the respiration of blastoderm, embryo, and yolk-sac

Abstract

The study of cell-respiration by means of agents with a known action upon some one part of the cellular mechanisms has in recent years been much pursued, and it has to some extent been possible to make a differential attack upon the various co-operating processes which are so efficiently integrated in the intact cell. These methods suffer, it is true, from the disadvantage that the addition of an ion such as fluoride to the cell-interior may not merely inhibit a certain reaction which normally goes on there, but may also bring into being a number of distinctively pathological reactions which have no place in the normal cell. It is not surprising, therefore, that the results of experiments on cell-respiration are difficult to interpret. But difficulties of interpretation are no ground for failing to make use of any methods. which are available, and the possibility of complicated secondary effects is, after all, common to all biological methods in which the normal course of events within the organism is interfered with. Up to the present time, the study of the effect of agents such as fluoride, cyanide, iodoacetic acid, triphenylmethane dyes, sulphides, pyrophosphates, etc., has been confined to the cells of adult tissues ( cf . Dixon, 1929; wurmser, 1930) or to bacteria ( e. g ., Haldane, Cook and Mapson, 1931). But it would obviously be of much interest to observe their effects upon cells of early embryonic stages for we might hope in this way to discover something of the way in which the chemical machinery of the cell is laid down. To what extent, for instance, do the cells of a somite in a two-day old chick embryo resemble adult muscle cells in their reactions to the glycolysis-inhibiting action of iodoacetic acid ? Moreover, a good deal of evidence exists that embryos in the earlier stages of development combust carbohydrate molecules exclusively, and that later on the combustion of protein and fat sets in. What will happen then, to the metabolism of embryonic cells in the carbohydrate stage if their glycolysing power is artificially inhibited? Is the power of deaminating and combusting amino-acids already present and not used, or has it not yet developed ? In the former case the respiratory quotient should betray a change over to protein combustion; in the latter case the cells should cease to respire altogether. It was to answer questions such as these that the work described in the present paper was undertaken.