Iwamatsu Takashi, Oda Shoji, Kobayashi Hirokuni, Parenti Lynne R, Kobayashi Yasuhisa
Biol Bull. 2020 Apr;238(2):80-88. doi: 10.1086/708304. Epub 2020 Apr 27.
This study presents novel findings on the dynamics of growing oocytes in the ovary of the medaka fish, . In the ovary of mature females, all follicles are anchored tightly to the abdominal ovarian rete fibrous follicular stalks on the follicle surface. The follicular stalks lie at the end of the follicle opposite the site of its attachment to the ovarian wall. Various lengths of the follicular stalks reflect the spatial arrangement of follicles in the ovary. Herein, a line that connects the follicular stalk to the opposite side of the follicle toward or attaching to the ovarian wall is called the follicle axis. The animal-vegetal axis in late stage III oocytes is already recognizable as a line that connects the center of the oocyte nucleus and the vegetal pole area; this is ascertainable by the morphological landmark of a compact distribution of granulosa cells or rudimentary attachment filaments. In growing oocytes later than stage V, the beginning of vitellogenesis, the tufted attachment filaments are located on a discrete region of the vegetal pole area. Our observations reveal that during growth, oocytes are arranged randomly between the animal-vegetal axis and the follicle axis, whereas the vegetal pole area of full-grown oocytes in preovulatory follicles turns close to the inner surface of the ovarian wall, from which mature oocytes subsequently ovulate into the ovarian lumen. It is suggested that in the ovary, mature oocytes always transpose the vegetal pole area to the ovulatory site of the ovarian wall prior to ovulation. The expulsion of mature oocytes from the vegetal pole appears to be the regular mode of ovulation in .
本研究展示了关于青鳉卵巢中生长卵母细胞动态的新发现。在成熟雌性的卵巢中，所有卵泡都通过卵泡表面的纤维卵泡柄紧密锚定在腹部卵巢网。卵泡柄位于卵泡与卵巢壁附着部位相对的一端。卵泡柄的不同长度反映了卵泡在卵巢中的空间排列。在此，连接卵泡柄与卵泡朝向或附着于卵巢壁一侧相对端的线称为卵泡轴。III期末卵母细胞中的动物 - 植物轴已可识别为连接卵母细胞核中心与植物极区域的线；这可通过颗粒细胞紧密分布或原始附着丝的形态学标志来确定。在晚于V期（卵黄发生开始）的生长卵母细胞中，簇状附着丝位于植物极区域的一个离散区域。我们的观察结果表明，在生长过程中，卵母细胞在动物 - 植物轴和卵泡轴之间随机排列，而排卵前卵泡中成熟卵母细胞的植物极区域转向靠近卵巢壁的内表面，成熟卵母细胞随后从该部位排入卵巢腔。提示在青鳉卵巢中，成熟卵母细胞在排卵前总是将植物极区域转移到卵巢壁的排卵部位。成熟卵母细胞从植物极排出似乎是青鳉排卵的常规方式。
