Presence of accelerator and retarding cleavage factors in an extract of ovary in sea urchins

• 1.1. An aqueous extract has been prepared by homogenizing the ovarian tissue of the sea urchin, Arbacia punctulata. This whole extract induces no significant effect on cleavage development of the fertilized sea urchin ova, or it may elicit either slight accelerating or retarding effects on the developing ova.
• 2.2. Centrifugalization of the extract yields on the part of the supernatant an accelerating effect on cleavage development; while the residual or sedimented portion induces a retarding cleavage effect on developing eggs.
• 3.3. Dialysis for several days of the supernatant fraction in the cold against distilled water favors the passage of an accelerating cleavage factor in the diffusate. This accelerator cleavage factor is also found to be thermostable, and ultraviolet spectral absorption studies indicate that one is dealing with a nucleic acid derivative. Diffusibility, thermostability, and absorption at 265 to around 270 millimicra suggest that the accelerator cleavage factor is a nucleotide.
• 4.4. The indiffusible fraction following dialysis yields inconstant results. There may be merely a slight inhibitory or retarding effect on the incidence of cleavage. There is the possibility from absorption and by simple tests for proteins that one may be dealing with a nucleoprotein in the indiffusible fraction.
• 5.5. The presence of an accelerator cleavage factor and of a retarding or antimitotic factor in the extract of the ovary in Arbacia punctulata suggests that the rate and therefore the regulation of cell division may perhaps be in part referable to a balance between these two basic and opposed factors.