Vegetalization of the Sea-Urchin Egg by Dinitrophenol and Animalization

H E R B S T (1892) made the remarkable discovery that the differentiation of the sea-urchin egg was shifted in a vegetal direction when lithium ions were present in the sea-water. The vegetalization implies a failure of the apical tuft to appear, a displacement of the skeleton-forming cells in the animal direction, a reduction of the ectodermal region, and a corresponding enlargement of the endoderm, which often leads to exogastrulation. Strong lithium action may lead to complete endodermization of the egg. Many other substances have later been found to cause a change of differentiation, either in a vegetal or animal direction, e.g. a partial or complete animalization by treatment of unfertilized eggs with SCN- or 1-ions (also SO4, Br, and tartrate, Lindahl, 1936). The animal and vegetal principles are considered as two opposite, antagonistic gradients (Runnstrom, 1928 a, b) representing different types of metabolism (Lindahl, 1936). It is of particular interest to study the effect on determination of substances which are known to interfere with metabolism in a special way. This paper will deal with the action of dinitrophenol (DNP) which acts as an inhibitor of oxidative phosphorylation, and the proteolytic enzymes trypsin and ficin. MATERIALS AND METHODS The experiments were made on eggs of Paracentwtus lividus. The DNP used was a-DNP and /3-DNP from George T. Gurr, London, and y-DNP from E. Merck, Darmstadt. Cleavage is immediately brought to a standstill when eggs are put into a strong solution of DNP (Clowes & Krahl, 1936, and others). Concentrated solutions are toxic. The following concentrations were found suitable: a y^-saturated solution of a-DNP in sea-water, a ̂-saturated solution of /3-DNP, and a \- or ^-saturated solution of y-DNP. The treatment as a rule took place in the 16-cell stage, before the operation when animal and vegetal halves were separated, or also immediately after the operation. In some experiments the eggs were instead put in the DNP immediately after fertilization. The results were, as we shall see, very varied, but, as far as I can judge, it did not matte