The Thyroid and the Rate of Cell Division

Abstract

Among the many investigations on the thyroid gland, few have dealt directly with the relation of the thyroid secretion to the rate of cell division. These few experiments, with a single exception, have been carried out on cultures of protozoa and since they have been subject to certain difficulties of control, due to the material used, the results have given rise to a rather great divergence of opinion. Nowikoff, 1 Shumway, 2 and others have found that the addition of total thyroid to Paramecium cultures accelerated the rate of cell division and more recently Cori 3 has reported that pure thyroxin exerts the same effect, although the acceleration is less marked. Woodruff and Swingle 4 and Torrey, Riddle and Brodie, 5 on the other hand, have found that the addition of thyroxin depresses the division rate of Paramecia and Torrey 6 reports that thyroxin has the same effect on the eggs of Echinometra and Phallusia.

In the present work, of which this paper is a preliminary report, the writer has undertaken to follow critically the effect of thyroxin solutions on the cleavage rate of Arbacia eggs. Previous work has shown that the developing eggs of Arbacia punctulata, properly handled, are very satisfactory for quantitative work. In each experiment, eggs from a single mature female were fertilized with sperm from a single mature male and then placed in experimental and control dishes kept side by side in a large vessel of water, so that errors due to temperature differences were eliminated. Samples of eggs removed at intervals of 1 or 2 minutes from experimental and control dishes were transferred to watch glasses containing formalin which immediately arrested development. Counts of 200 to 300 eggs were made from each sample taken.