卵子受精早期现象的初步探讨

The judgement in early state of zygote

受精是一个复杂的过程，特征表现为多个连续步骤的串联反应。主要包括精子获能，精子和卵黄膜融合，卵母细胞恢复并完成减数分裂Ⅱ及排出第二极体，精子和卵母细胞的核开始去凝集，雄性和雌性原核形成，此后不久配子融合完成。在体外受精（in vitro fertilization，IVF）周期中，

Objective： To characterize the early phenomenon which appear after the fertilization of human oocyte, and evaluate their value for the judgement in early state of zygote. Methods： Four hundred and fifty-two human oocytes from thirty-eight patients undergoing IVF were divided into observed group and controlled group. IVF controlled group contained 220 oocytes, which were observed pronucleus only 18 h after fertilization. The inverted microscope equipped with Hoffman interference optics was used to observe the early phenomenon happen 2 h, 4 h, 6 h, 8 h, 18 h after the fertilization of 250 oocytes in IVF observed group and 139 oocytes from thirteen patients undergoing ICSI. The Spindle View was used to examine zona peliucida （ZP） of 125 MII oocytes before ICSI and embryos after ICSI. Results： Normal fertilization rate （77.66%） was significantly higher in IVF controlled group than in IVF observed group （59.82%, P〈0. 05）, while abnormal fertilization rate （7. 98%） was significantly lower in IVF controlled group than that in IVF observed group （17.86% ,P〈0.05）. About 78% in IVF observed group have extruded second polar body （2nd PB） by 4 h after fertilization. By 6 h, the extruded rate has climbed to 93%. About 49% zygotes have appeared obvious cytoplasm cortical reaction by 6 h. Approximately 71% zygotes could be seen pronucleus by 8h. Zygotes which appeared pronucleus 8 h after fertilization obtained significantly higher proportion of good quality embryos, compared with zygotes appeared this phenomenon 4 h,8 h or 18 h after fertilization （78.12% vs 33.33% ,48.24% and 38.00% ,P〈 0.05）. Among 125 MII oocytes undergonging ICSI, fertilization rate of ooeytes which have extruded 2 distinct and intact PB by 18 h after fertilization was 91.25% The rate for only one intact PB oocytes, disintegrated PB oocytes and three or more distinct PB oocytes was 37.50%, 89.65% and 87.50%, respectively. The ZP observation results showed that there were no differences in ZP birefringence before or 18 h after ICSI. Conclusions：Most zygotes have extruded 2nd PB by 6 h after fertilization and appeared pronucleus by 8 h. The extrusion of 2nd PB is not the only evaluation criterion of early fertilization. In order to judge whether the oocyte was fertilized in early state much more precisely, appearance of cytoplasm cortical reaction or pronucleus, enlargement of perivitelline space （PVS） and thickness of ZP should also be considered.