Thadani V M
J Exp Zool. 1980 Jun;212(3):435-53. doi: 10.1002/jez.1402120316.
Hetero-specific fertilization of zone-free eggs is used in these experiments as a tool to analyze the barriers to hybridization and to gain insight into the mechanisms of normal fertilization. When the zonae of rat eggs, which are a barrier to hetero-specific fertilization, are removed with pronase, the eggs can be fertilized by mouse sperm and the zygotes start to develop normally. A rat egg fertilized with mouse sperm completes meiosis and forms both male and female pronuclei. Chromosomes from both parents are found on he spindle at the metaphase stage of the first cleavage division. Under present culture conditions, embryos develop only to the two-cell stage, but this initial development of the hybrid is apparently normal. The question of whether sperm and egg membrane fusion is requisite for normal development is addressed by injecting sperm directly into the cytoplasm of unfertilized eggs. The injection of mouse sperm into rat eggs frequently leads to activation and formation of male and female pronuclei. The first cleavage division is indistinguishable from that following hetero-specific fertilization. Capacitated and uncapacitated sperm react alike when injected into eggs. Egg activation, however, is necessary for male pronucleus formation. Sperm from the deer mouse Peromyscus maniculatus bairdii, which are incapable of fertilizing even zonea-free eggs, respond like mouse sperm when injected into rat eggs. These data indicate that sperm interactions with the egg cytoplasm are less species-specific than interactions at the egg surface. Furthermore, the normal surface interactions of sperm and eggs are not essential for the start of development.
在这些实验中，使用无透明带卵子的异种受精作为一种工具，来分析杂交障碍并深入了解正常受精的机制。当用链霉蛋白酶去除大鼠卵子的透明带（透明带是异种受精的障碍）后，这些卵子就能被小鼠精子受精，并且受精卵开始正常发育。用小鼠精子受精的大鼠卵子完成减数分裂并形成雄原核和雌原核。在第一次卵裂分裂的中期阶段，双亲的染色体都出现在纺锤体上。在目前的培养条件下，胚胎仅发育到二细胞阶段，但这种杂种的初始发育显然是正常的。通过将精子直接注入未受精卵的细胞质中，来探讨精卵膜融合对于正常发育是否必要这一问题。将小鼠精子注入大鼠卵子中常常会导致卵子激活以及雄原核和雌原核的形成。第一次卵裂分裂与异种受精后的情况无法区分。当注入卵子时，获能精子和未获能精子的反应相似。然而，卵子激活对于雄原核的形成是必要的。白足鼠（Peromyscus maniculatus bairdii）的精子即使对无透明带的卵子也无法受精，但当注入大鼠卵子时，其反应与小鼠精子相似。这些数据表明，精子与卵细胞质的相互作用比在卵表面的相互作用物种特异性更低。此外，精子与卵子的正常表面相互作用对于发育的起始并非必不可少。
