Azambuja R M, Kraemer D C, Westhusin M E
Department of Animal Science, Texas A&M University, College Station, USA.
Mol Reprod Dev. 1997 Aug;47(4):435-9. doi: 10.1002/(SICI)1098-2795(199708)47:4<435::AID-MRD10>3.0.CO;2-V.
The objective of this research was to investigate the effects of cooling on the development of bovine zygotes. One-cell bovine embryos were maintained at 39 degrees C (control), 20 degrees C, 10 degrees C, or 0 degree C for 5, 10, or 20 minutes, then cultured in vitro for 7 days and the proportion of embryos developing to the compact morula or blastocyst stage compared between different treatments. Duration of exposure time had no effect on development. Development rates to the compact morula or blastocyst stage were 3.9%, 11.4%, 17.4%, and 24.4% for zygotes maintained at 0 degree C, 10 degrees C, 20 degrees C, and 39 degrees C, respectively, with differences in embryo yield between every treatment (P < 0.05). In a second experiment, bovine pronuclei (karyoplasts) and cytoplasts were cooled at 0 degree C or maintained at 39 degrees C for 5 minutes. Pronuclear transplantation was then utilized to create 4 types of reconstructed embryos, those with: 1) non-cooled pronuclei and non-cooled cytoplasm, 2) non-cooled pronuclei and cooled cytoplasm, 3) cooled pronuclei and non-cooled cytoplasm, and 4) cooled pronuclei and cooled cytoplasm. The proportion of embryos developing to the blastocyst stage was highest when non-cooled pronuclei were transferred into non-cooled cytoplasm (18.9%), and similar to that of non-cooled, non-manipulated control zygotes (13.2%, P > 0.05). No embryos developed to the blastocyst stage when pronuclei (cooled or non-cooled) were transferred into cooled cytoplasm. However, zygotes with cooled pronuclei transferred into non-cooled cytoplasm yielded 4.5% blastocysts (P < 0.05). More embryos developed to the compact morula or blastocyst stage when non-cooled vs. cooled cytoplasm was utilized, regardless of whether the pronuclei were cooled (P < 0.05). These data demonstrate that pronuclei are more tolerant to low temperature exposure than is ovum cytoplasm.
本研究的目的是调查冷却对牛受精卵发育的影响。将单细胞牛胚胎分别在39℃（对照）、20℃、10℃或0℃下保持5、10或20分钟，然后进行7天的体外培养，并比较不同处理之间发育至致密桑葚胚或囊胚阶段的胚胎比例。暴露时间的长短对发育没有影响。在0℃、10℃、20℃和39℃下保持的受精卵发育至致密桑葚胚或囊胚阶段的比率分别为3.9%、11.4%、17.4%和24.4%，各处理之间的胚胎产量存在差异（P<0.05）。在第二个实验中，将牛原核（核质体）和细胞质体在0℃下冷却或在39℃下保持5分钟。然后利用原核移植创建4种类型的重构胚胎，即：1）未冷却的原核和未冷却的细胞质，2）未冷却的原核和冷却的细胞质，3）冷却的原核和未冷却的细胞质，4）冷却的原核和冷却的细胞质。当将未冷却的原核移植到未冷却的细胞质中时，发育至囊胚阶段的胚胎比例最高（18.9%），与未冷却、未操作的对照受精卵相似（13.2%，P>0.05）。当原核（冷却或未冷却）移植到冷却的细胞质中时，没有胚胎发育至囊胚阶段。然而，将冷却的原核移植到未冷却的细胞质中时，受精卵产生了4.5%的囊胚（P<0.05）。无论原核是否冷却，使用未冷却的细胞质比冷却的细胞质时，有更多的胚胎发育至致密桑葚胚或囊胚阶段（P<0.05）。这些数据表明，原核对低温暴露的耐受性比卵细胞质更强。
