CHROMATIN CONDENSATION AND HISTONE H1 KINASE-ACTIVITY DURING GROWTH AND MATURATION OF RABBIT OOCYTES

Fully grown rabbit oocytes, isolated from preovulatory follicles, exhi bit highly condensed bivalents within an intact germinal vesicle while a very low level of histone H1 kinase activity could be detected in t heir extracts. Chromatin condensation started in growing oocytes isola ted from antral follicles presenting a diameter of 0.5 mm. This event was accompanied by a transient rise in histone H1 kinase activity whic h culminated in large antral follicles measuring 0.75 to 1 mm in diame ter. However, the extent of histone H1 kinase activity observed in the se growing oocytes remained far less important than that recorded in e xtracts prepared from in vitro cultured metaphase I and metaphase II o ocytes. Moreover, this activity was insufficient to induce germinal ve sicle breakdown which will only occur with an increasing efficiency, f ollowing in vitro culture of medium, large, and fully grown antral fol licles. (C) 1994 Wiley-Liss, Inc.