MECHANISM OF STARFISH SPAWNING. IV. TENSION GENERATION IN THE OVARIAN WALL BY 1-METHYLADENINE AT THE TIME OF SPAWNING

¹ Department of Developmental Biology, National Institute for Basic Biology, Okazaki 444, Japan
² Department of Cell Biology, National Institute for Basic Biology, Okazaki 444, Japan

Tension generation in the starfish ovaries at the time of spawning was investigated using an isometric tensiometer. Ovarian fragments containing oocytes gradually generated tension after 1-methyladenine application; before 1-methyladenine application the ovarian walls were not under strong tension. Isolated ovarian walls did not generate tension after l-methyladenine treatment, but did after the application of jelly substance. As the hormone 1-methyladenine is known to act on oocytes surrounded by follicle envelopes to induce germinal vesicle breakdown, which inevitably results in the breakdown of follicle envelopes, it is concluded that (1) jelly substance acts directly to induce contraction of ovarian walls, (2) 1-methyladenine acts indirectly, contraction being caused as a result of the hormone's action on breakdown of germinal vesicles and follicle envelopes, after which jelly substance contacts the ovarian wall.