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翻訳と辞書　辞書検索 [ 開発暫定版 ] スポンサード リンク Cortical granule ： ウィキペディア英語版 Cortical granule Cortical granules are regulatory secretory organelles (ranging from 0.2 um to 0.6 um in diameter) found within oocytes and are most associated with polyspermy prevention after the event of fertilization. Cortical granules are found among all mammals, many vertebrates, and some invertebrates. Within the oocyte, cortical granules are located along the cortex, the region furthest from the cell's center. Following fertilization, a signaling pathway induces the cortical granules to fuse with the oocyte's cell membrane and release their contents into the oocyte's extracellular matrix. This exocytosis of cortical granules is known as the cortical reaction. In mammals, the oocyte's extracellular matrix includes a surrounding layer of perivitelline space, zona pellucida, and finally cumulus cells. Experimental evidence has demonstrated that the released contents of the cortical granules modify the oocyte's extracellular matrix, particularly the zone pellucida. This alteration of the zona pellucida components is known as the zona reaction. The cortical reaction does not occur in all mammals, suggesting the likelihood of other functional purposes for cortical granules.〔 In addition to modifying the oocyte's extracellular matrix and establishing a block to polyspermy, the exocytosis of cortical granules may also contribute towards protection and support of the developing embryo during preimplantation. Once the cortical granules complete their functions, the oocyte does not replenish them.〔 ==Formation== Cortical granule formation occurs during the early stages of oocyte growth. More specifically, in the human, monkey, hamster, and rabbit, cortical granules are established once the ovarian follicle is multilayered. In the rat and mouse, cortical granules have been observed earlier in follicle development when the ovarian follicle is only single layered. During the early stages of oocyte growth, the Golgi complex increases in size, proliferates, and produces small vesicles that migrate to the cell's subcortical region. These small vesicles will fuse with one another to form mature cortical granules, which are thus established as separate entities from the Golgi.〔 In some organisms, such as in hamsters, the secreted vesicle from the Golgi may fuse with a secreted vesicle from the rough endoplasmic reticulum to ultimately form a cortical granule. In mammals, the oocyte continuously produces and translocates cortical granules to the cortex until ovulation occurs. It has been shown in both mammalian and non-mammalian animal models that cortical granule migration depends on cytoskeleton processes, particularly microfilament activity. For mammals, cortical granule migration is considered an indication of oocyte maturity and organelle organization.〔 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Cortical granule」の詳細全文を読む スポンサード リンク 翻訳と辞書 : 翻訳のためのインターネットリソース Copyright(C) kotoba.ne.jp 1997-2016. All Rights Reserved.