Percentage Incorporation of Leucine labelled with Carbon-14 into Isolated Mitotic Apparatus during Early Development of Sea Urchin Eggs

Abstract

THERE is evidence that during division in sea urchin eggs a certain amount of protein specifically necessary for division is synthesized. Hultin¹ has shown that the division of these eggs is blocked at ‘streak stage’ by puromycin. Gross and Cousineau² have found, in autoradiographs of Arbacia punctulata eggs, that most of the labelled amino-acid incorporated in earliest cleavage is found in the region of the mitotic apparatus; the localization of label is particularly pronounced when supernumerary asters (cytasters) are induced in developing eggs by treatment with heavy water. On this basis, these authors suggest that the protein synthesized in earliest cleavage plays a structural or catalytic part in the operation of the mitotic apparatus. The suggestion is substantiated by the finding of Stafford and Iverson³ that labelled amino-acid incorporated by fertilized eggs may be found in the isolated mitotic apparatus.