Koyama H, Suzuki H, Yang X, Jiang S, Foote R H
Department of Animal Science, Cornell University, Ithaca, New York 14853-4801.
Biol Reprod. 1994 Jan;50(1):163-70. doi: 10.1095/biolreprod50.1.163.
Cellular polarization during preimplantation development of the embryo is believed to be a crucial event in the transition of a zygote to a blastocyst stage embryo with morphologically and functionally differentiated cell types. While extensive studies have been done on polarity development in mouse embryos, little information is available in other species, particularly in cattle. The objective of this study was to examine the initiation of polarity by microvilli distribution on blastomeres of cattle and rabbit embryos using scanning electron microscopy (SEM). Bovine embryos were obtained by in vitro fertilization of in vitro-matured follicular oocytes. Rabbit embryos of various stages were collected from superovulated rabbits. Intact embryos and isolated blastomeres were examined in both species. Blastomeres from 1- to 8-cell embryos in both cattle and rabbits showed no polarity. The onset of transitional polarization of microvillous distribution occurred in some blastomeres of cattle embryos at the 9- to 15-cell stage; but typical, distinct polarity was not manifested until after the 16-cell stage with approximately 40% polar cells per embryo. In the rabbit blastomere polarity occurred one cell cycle later, with 46% polar cells per embryo after the 32-cell stage. The difference in cell numbers at the time polarity is evident is probably related to the different cell stages for embryo compaction and blastocyst formation in the two species.
胚胎植入前发育过程中的细胞极化被认为是合子向具有形态和功能分化细胞类型的囊胚阶段胚胎转变的关键事件。虽然对小鼠胚胎的极性发育进行了广泛研究，但其他物种，特别是牛的相关信息却很少。本研究的目的是使用扫描电子显微镜（SEM），通过观察牛和兔胚胎卵裂球上微绒毛的分布来研究极性的起始。牛胚胎通过体外成熟卵泡卵母细胞的体外受精获得。从超排卵兔中收集不同阶段的兔胚胎。对两个物种的完整胚胎和分离的卵裂球进行了检查。牛和兔1至8细胞期胚胎的卵裂球均未显示极性。牛胚胎部分卵裂球在9至15细胞期出现微绒毛分布的过渡极化起始；但直到16细胞期后才表现出典型、明显的极性，每个胚胎约40%的极性细胞。兔卵裂球的极性在一个细胞周期后出现，32细胞期后每个胚胎有46%的极性细胞。极性明显时细胞数量的差异可能与两个物种胚胎致密化和囊胚形成的不同细胞阶段有关。
