Aroyo A, Yavin S, Arav A, Roth Z
Department of Animal Science, Faculty of Agricultural, Food and Environmental Quality Sciences, The Hebrew University of Jerusalem, POB 12, Rehovot 76100, Israel.
Theriogenology. 2007 Mar 15;67(5):1013-21. doi: 10.1016/j.theriogenology.2006.12.001. Epub 2007 Jan 8.
Mammalian oocytes are susceptible to thermal stress at various stages of follicular development. We examined whether the ovarian pool of oocytes is susceptible to maternal hyperthermia and if so, whether hyperthermia at the germinal vesicle (GV) stage further affects the developmental competence of preimplantation embryos and offspring quality. Synchronized female mice were exposed to thermal stress (40 degrees C, 65% RH) for 1.5-2h or maintained under normothermal conditions (25 degrees C, 45% RH). Thereafter, mice were paired with stud males. In the first experiment, mated mice were sacrificed 20h post hCG administration, and in vivo-derived zygotes were recovered and cultured in vitro. Maternal hyperthermia decreased the percentage of putative zygotes of apparent normal morphology in the heat-stressed group (81+/-1.3%) as compared to the control group (86+/-1.2%). Developmental competence was also compromised as expressed by the disruption in cleavage timing pattern, resulting in a reduced developmental rate to the blastocyst stage (57+/-2.6% versus 84+/-1.9%). In the second experiment, both groups were left with stud males until litter delivery. Litter size in the first delivery cycle was lower for the heat-stressed group (7.7+/-1.1 pups), followed by a slight increase throughout consecutive cycles as compared to the control group (11.3+/-1.0 pups). Behavioral examinations of 8-week-old pups revealed similar locomotor activity and learning potential between the groups. In summary, the findings indicate that a subpopulation of the ovarian pool of follicles is highly sensitive to thermal stress and that maternal hyperthermia disrupts developmental competence of GV-stage oocytes. Pups that developed from oocytes that survived thermal stress exhibited a developmental potential similar to that of the of control pups.
哺乳动物卵母细胞在卵泡发育的各个阶段都易受热应激影响。我们研究了卵巢中的卵母细胞库是否易受母体高温影响，如果是，那么生发泡（GV）期的高温是否会进一步影响植入前胚胎的发育能力和后代质量。将同步化的雌性小鼠暴露于热应激（40摄氏度，相对湿度65%）1.5 - 2小时，或维持在常温条件下（25摄氏度，相对湿度45%）。此后，将小鼠与种公鼠配对。在第一个实验中，在给予hCG后20小时处死交配后的小鼠，回收体内来源的受精卵并进行体外培养。与对照组（86±1.2%）相比，母体高温降低了热应激组中形态明显正常的假定受精卵的百分比（81±1.3%）。卵裂时间模式的破坏表明发育能力也受到了损害，导致发育至囊胚期的比率降低（57±2.6%对84±1.9%）。在第二个实验中，两组都与种公鼠留在一起直至产仔。热应激组第一个分娩周期的窝仔数较低（7.7±1.1只幼崽），与对照组（11.3±1.0只幼崽）相比，随后在连续周期中略有增加。对8周龄幼崽的行为检查显示两组之间的运动活动和学习潜力相似。总之，研究结果表明卵巢卵泡库中的一个亚群对热应激高度敏感，母体高温会破坏GV期卵母细胞的发育能力。由在热应激中存活的卵母细胞发育而来的幼崽表现出与对照幼崽相似的发育潜力。
