Jaffe L A, Terasaki M
Department of Physiology, University of Connecticut Health Center, Farmington 06032.
Dev Biol. 1994 Aug;164(2):579-87. doi: 10.1006/dbio.1994.1225.
The endoplasmic reticulum (ER) of live starfish oocytes was observed during meiotic maturation and fertilization. The ER was visualized by injection into the cytoplasm of an oil drop saturated with the fluorescent lipophilic dye DiI; DiI spread throughout the oocyte endoplasmic reticulum and the pattern was imaged by confocal microscopy. The ER in the immature (germinal vesicle stage) oocyte was composed of interconnected membrane sheets. In response to 1-methyladenine, the sheets of ER appeared to become associated with the yolk platelets, forming spherical shells. A few of these spherical shells could sometimes be seen in immature oocytes, but their number was much greater in the egg at the first meiotic spindle stage. At about the time that the first polar body formed, the spherical shells disappeared, and the ER returned to a form like that of the immature oocyte. The spherical shells did not reappear during the second meiotic cycle. During maturation, the ER also began to move; the movement was apparent by the time of germinal vesicle breakdown and continued throughout both meiotic cycles and in eggs with second polar bodies. When eggs at the first meiotic spindle stage were fertilized, the form of the ER changed. Within 1 min after sperm addition to the observation chamber, the circular cross sections of the spherical shells of the unfertilized egg ER were no longer distinct. At this point, the form of the ER could not be discerned with the resolution of the light microscope; however, the rate of spreading of DiI from an injected oil drop decreased, providing strong evidence that the ER had become fragmented. The ER remained in this form for several minutes and then gradually, the appearance of the ER and the rate of DiI spreading returned to be like those of the unfertilized egg. Injection of inositol trisphosphate caused a similar change in the ER structure. These results indicate that the ER is a dynamic structure, the form of which changes during oocyte maturation and fertilization.
在减数分裂成熟和受精过程中观察了活海星卵母细胞的内质网。通过将饱和荧光亲脂性染料DiI的油滴注射到细胞质中来观察内质网；DiI扩散到整个卵母细胞内质网中，并通过共聚焦显微镜对其模式进行成像。未成熟（生发泡期）卵母细胞中的内质网由相互连接的膜片组成。响应1-甲基腺嘌呤，内质网膜片似乎与卵黄小板结合，形成球形壳。在未成熟卵母细胞中有时可以看到一些这样的球形壳，但在第一次减数分裂纺锤体期的卵中其数量要多得多。在第一极体形成时，球形壳消失，内质网恢复到未成熟卵母细胞的形态。在第二次减数分裂周期中球形壳不再出现。在成熟过程中，内质网也开始移动；在生发泡破裂时这种移动很明显，并在整个减数分裂周期以及含有第二极体的卵中持续存在。当处于第一次减数分裂纺锤体期的卵受精时，内质网的形态发生变化。在将精子添加到观察室后1分钟内，未受精卵内质网球形壳的圆形横截面不再清晰。此时，用光镜分辨率无法辨别内质网的形态；然而，从注射油滴中扩散的DiI速率降低，这提供了内质网已破碎的有力证据。内质网保持这种形态几分钟，然后逐渐地，内质网的外观和DiI扩散速率恢复到未受精卵的状态。注射肌醇三磷酸会导致内质网结构发生类似变化。这些结果表明内质网是一种动态结构，其形态在卵母细胞成熟和受精过程中会发生变化。
