Laurence Rockwell Fitzgerald

Changes in riboflavin during embryonic development as functions of the embryo.

tion of the substance, especially in the pharyngeal and anal regions. In the case of a worm with fission, the two adjacent sides of the fission zone appear to develop new gradients. These disappear following starvation of the worm. A piece that is cut from any body level of the worm reveals the same reaction as that region would show in an intact worm. If it is allowed to regenerate for 2 or 3 days, the regenerating tissue will develop a new gradient pattern, decreasing from the cut end or ends, the intensity of the color reaction depending on the amount of tissues regenerated. A possible relationship between the sulphydryl gradient and the regeneration potency gradient is discussed.

Riboflavin and other fluorescent compounds in a developing egg (Orthoptera).

inorganic phosphate at all stages investigated. The relative amount of ATP breakdown at different stages in response to nitrogen was found to parallel the amount of inhibition of development. Cleavage proceeds normally in nitrogen with relatively little ATP breakdown, while gastrulation is arrested in response to a nitrogen atmosphere, with correspondingly greater ATP breakdown. The release of inorganic phosphate from ATP appears to occur rapidly after exclusion of air and to be readily reversible. Sodium azide inhibition of gastrulation was found to be accompanied by increased inorganic phosphate at the expense of the ATP content of gastrulae. Evidence that phosphate-bond energy is coupled to gastrulation came also from the study of arrested hybrid gastrulae, whose lower rate of respiration and glycolysis was found to be accompanied by a decreased capacity to keep ATP (as well as an unidentified organic phosphate ester) in the phosphorylated condition.

The Effects of Methylene Blue and Urethane (Ethyl Carbamate) upon the Oxygen Uptake of Embryonic Cells

THAT redox dyes, such as methylene blue, stimulate the oxygen uptake of most living cells seems well established (Barron, 1929; Barron and Hamburger, 1932). Cyanides, although depressants of respiration, are more or less completely antagonized by methylene blue in the case of most living cells (Barron, 1929; Barron and Hamburger, 1932; Brooks, 1932a, b, c, I933; Green, I940). Considerable variation in the quantitative relations between effective antagonistic concentrations of cyanide and methylene blue for different types of cells seems to exist (Bodine and Boell, I936, i937). Cyanides have been thought to inhibit respiratory processes by forming complex compounds with the ironor copper-containing respiratory enzymes (Keilin and Hartree, 1938; Schultze, 1939), while the oxidative action of methylene blue is thought of as an oxidative dehydrogenation (Barron, 1929). Narcotics, such as urethane (ethyl carbamate), in low doses stimulate, while in

The Effects of Homologous Carbamates on the Respiration of Blocked and Active Embryos

experiments employing the homologous series of carbamates or urethanes. The effectiveness of these compounds as carcinogenic agents has also recently been emphasized, and rather marked differences in this activity as compared to their narcotic action have been pointed out (Larsen, 1947). The effects of carbamates on basic cellular activities, such as mitosis, have also shown them to be useful experimental tools in the analysis of many different cellular phenomena (Macht, 1948). The present discussion has to do with results of extensive experiments on the effects of a homologous series of carbamates on the respiration of mitotically active and blocked embryonic cells of the grasshopper, Melanoplus differentialis.