Induction of Cytokinesis and Mechanism of Cleavage Furrow Formation.

以海胆卵卵裂和海星卵母细胞极体形成为例，分析了皮质和有丝分裂器在胞质分裂中的作用。1.通过测量从中期到末期在海胆卵细胞表面上看到的微绒毛之间的距离，发现在细胞赤道区域的细胞表面的收缩开始与分裂沟形成之前的细胞伸长的开始同时开始。2.细胞的形状几乎没有改变，通过移动有丝分裂装置与插入到细胞中的显微针或通过施加离心力的细胞，虽然有丝分裂装置与皮质接触显着变形。这一事实表明，皮质与有丝分裂器相比是足够刚性的，因此，卵裂过程几乎不受卵裂过程中有丝分裂器主动或被动变形的影响。3.将海胆卵中有丝分裂器的原生质移植到相同或不同细胞的皮层下区域，以证明有丝分裂器中负责分裂刺激的因子。皮质既无收缩也无扩张。通过在人工培养基中操作细胞，从分裂的海胆卵中分离出具有沟形成活性的鬼细胞或皮层碎片。试验部分成功，但不能确定在鬼细胞和分离的皮层中总是形成分裂沟的人工培养基的化学成分。5.通过测量微注射到细胞中的水母发光蛋白的发光，测量海胆卵在卵裂前和卵裂过程中以及海星卵母细胞在成熟过程中的细胞内钙离子浓度。细胞内钙离子浓度随细胞有丝分裂活动无明显变化。

Roles of cortex and mitotic apparatus in cytokinesis were analyzed in cleavage of sea urchin eggs and in polar-body formation of starfish oocytes. 1. By measuring distances among microvilli seen on the cell surface in sea urchin eggs from metaphase through telophase, it was found that contraction of the cell surface at the equatorial region of the cell starts simultaneously with the start of elongation of the cell in advance of the formation of cleavage furrow. 2. The cell shape was scarcely changed by moving mitotic apparatus with a microneedle inserted into the cell or by applying a centrifugal force to the cell, although the mitotic apparatus was significantly deformed by contact with cortex. This fact indicates the cortex is sufficiently rigid as compared with the mitotic apparatus, and therefore, that the cleavage process is scarcely affected by active or passive deformation of the mitotic apparatus during cleavage. 3. Protoplasm of the mitotic apparatus in sea urchin eggs was transplanted to the subcortical regions of the same or different cells to demonstrate factor(s) responsible for cleavage stimulus in mitotic apparatus. Neither contraction nor expansion of the cortex was found. 4. A trial was made to isolate ghost cells or a fragment of the cortex with furrow-forming activity from dividing sea urchin eggs, by manipulating the cells in an artificial medium. The trial was partially succeeded, though chemical composition of the artificial medium in which the cleavage furrow was always formed in the ghost cells and isolated cortex could not be determined. 5. Intracellular concentration of calcium ions was measured in sea urchin eggs before and during cleavage and in starfish oocytes during maturation by measuring luminescence of aequorin microinjected into the cell. No distinct change in the intracellular calcium ion concentration accompanying mitotic activity of the cell was found.