Rivera Rocio M, Kelley Karen L, Erdos Gregory W, Hansen Peter J
Department of Animal Sciences, University of Florida, Gainesville, Florida 32611, USA.
Biol Reprod. 2003 Dec;69(6):2068-77. doi: 10.1095/biolreprod.103.020347. Epub 2003 Aug 20.
Exposure of cultured preimplantation embryos to temperatures similar to those experienced by heat-stressed cows inhibits subsequent development. In this study, the effects of heat shock on the ultrastructure of two-cell bovine embryos were examined to determine mechanisms for inhibition of development. Two-cell embryos produced in vitro were harvested at approximately 28 h postinsemination and cultured for 6 h at one of three temperatures: 38.5 degrees C (cow body temperature), 41.0 degrees C (characteristic temperature for heat-stressed cows), or 43.0 degrees C (severe heat shock). Ultrastructural examinations revealed that both heat shocks resulted in the movement of organelles towards the center of the blastomere. In addition, heat shock increased the percentage of mitochondria exhibiting a swollen morphology. Distance between the membranes comprising the nuclear envelope was increased but only when embryos were treated at 43.0 degrees C. To determine whether ultrastructural responses to heat shock in culture were similar for embryos produced in vitro and in vivo, two-cell embryos were collected from superovulated Angus cows 48 h postinsemination and treated ex vivo for 6 h at 38.5 degrees C or 41.0 degrees C. Again, heat shock caused an increase in number of swollen mitochondria and movement of organelles away from the periphery of the blastomere. Exposure of two-cell bovine embryos to physiologically relevant elevated temperatures causes disruption in ultrastructural morphology that is inimical to development. The observation that overall morphology and response to heat was similar for embryos produced in vitro and in vivo implies that the former can be a good model for understanding embryonic responses to heat shock.
将培养的植入前胚胎暴露于与热应激奶牛经历的温度相似的环境中会抑制其后续发育。在本研究中，检测了热休克对二细胞期牛胚胎超微结构的影响，以确定发育受抑制的机制。在授精后约28小时收集体外产生的二细胞胚胎，并在以下三种温度之一培养6小时：38.5℃（奶牛体温）、41.0℃（热应激奶牛的特征温度）或43.0℃（严重热休克）。超微结构检查显示，两种热休克均导致细胞器向卵裂球中心移动。此外，热休克增加了呈现肿胀形态的线粒体的百分比。仅当胚胎在43.0℃处理时，构成核膜的膜之间的距离才会增加。为了确定体外和体内产生的胚胎对培养中热休克的超微结构反应是否相似，在授精后48小时从超排的安格斯奶牛收集二细胞胚胎，并在38.5℃或41.0℃离体处理6小时。同样，热休克导致肿胀线粒体数量增加，细胞器从卵裂球周边移开。将二细胞期牛胚胎暴露于生理相关的高温会导致超微结构形态破坏，这对发育不利。体外和体内产生的胚胎总体形态和对热的反应相似这一观察结果表明，前者可以作为理解胚胎对热休克反应的良好模型。
