de Wit A A, Wurth Y A, Kruip T A
Institute for Animal Science and Health (ID-DLO), Lelystad, The Netherlands.
J Anim Sci. 2000 May;78(5):1277-83. doi: 10.2527/2000.7851277x.
In order to study the effect of the follicular environment on the quality and developmental competence of cumulus-oocyte complexes (COC), COC were collected from nonatretic (NA), light atretic (LA), atretic (A), and heavily atretic (HA) follicles. Cumulus-oocyte complexes were also collected from early-luteal phase ovaries (EL), from late-luteal phase ovaries (LL), from follicular phase ovaries (F), and from ovaries from non-cyclic animals (NC). Each COC was assigned to one of three quality groups based on the appearance of the cumulus investment: 1) COC-A: compact and bright, 2) COC-B: less compact and dark, and 3) COC-C: strongly expanded cumulus with dark spots. There was a high correlation between follicle quality and the distribution of the COC over the three COC qualities. The COC-A were mainly but not exclusively derived from NA follicles, COC-B were mainly derived from all classes of atretic follicles, and COC-C nearly exclusively originated from HA follicles. The developmental capacity of COC-A and COC-B, which was measured by in vitro embryo production, was consistent over the follicle qualities, except for COC-B obtained from HA follicles. They showed lower development (10.6%, P < .05) compared with COC-B from the other follicle qualities (18.9, 18.7, and 19.8%, respectively, for COC-B from NA, A, and LA follicles). The COC-B from atretic follicles produced more blastocysts (19.8%) than COC-A (12.7%, P < .05). The overall percentage of produced embryos per follicle class seemed to increase with increasing signs of atresia, except if the COC were derived from HA follicles. This increased percentage of embryos was, however, not due to a better quality of COC, but to a higher percentage of COC-B coming from these follicles. The stage of the cycle had no effect on the distribution of the COC over the three COC qualities or on the developmental capacity of COC-A or COC-B, except for COC-A from EL ovaries, which produced more (P < .05) blastocysts than COC-A from the other luteal phases (12.5% vs approximately 8%). A follow-up study was performed trying to elucidate why COC-B possess a higher developmental potency than COC-A. The answer was sought in the oocyte maturation. At several time points during maturation, oocytes were evaluated for their nuclear stage. At all time points COC-B seemed to be a few hours ahead of COC-A, and after 24 h of maturation more COC-B had reached the metaphase-2 stage. This might mean that COC-A need a longer maturation period than COC-B.
为了研究卵泡环境对卵丘-卵母细胞复合体（COC）质量和发育能力的影响，从非闭锁（NA）、轻度闭锁（LA）、闭锁（A）和重度闭锁（HA）卵泡中收集COC。还从黄体早期卵巢（EL）、黄体晚期卵巢（LL）、卵泡期卵巢（F）以及非周期性动物的卵巢（NC）中收集卵丘-卵母细胞复合体。根据卵丘包裹的外观，将每个COC分为三个质量组之一：1）COC-A：致密且明亮；2）COC-B：不太致密且暗淡；3）COC-C：卵丘强烈扩张且有黑点。卵泡质量与COC在三种COC质量中的分布之间存在高度相关性。COC-A主要但并非仅来源于NA卵泡，COC-B主要来源于所有类型的闭锁卵泡，而COC-C几乎仅起源于HA卵泡。通过体外胚胎生产测量的COC-A和COC-B的发育能力在卵泡质量方面是一致的，但从HA卵泡获得的COC-B除外。与来自其他卵泡质量的COC-B（分别来自NA、A和LA卵泡的COC-B的发育率为18.9%、18.7%和19.8%）相比，它们的发育率较低（10.6%，P < 0.05）。来自闭锁卵泡的COC-B产生的囊胚（19.8%）比COC-A（12.7%，P < 0.05）更多。每个卵泡类别的胚胎总体产生率似乎随着闭锁迹象增多而增加，除非COC来源于HA卵泡。然而，胚胎产生率的增加并非由于COC质量更好，而是由于来自这些卵泡的COC-B比例更高。周期阶段对COC在三种COC质量中的分布或COC-A或COC-B的发育能力没有影响，但来自EL卵巢的COC-A除外，其产生的囊胚比来自其他黄体期的COC-A更多（P < 0.05）（分别为12.5%和约8%）。进行了一项后续研究，试图阐明为什么COC-B比COC-A具有更高的发育潜能。答案在于卵母细胞成熟过程。在成熟过程中的几个时间点，评估卵母细胞的核阶段。在所有时间点，COC-B似乎比COC-A提前几个小时，并且在成熟24小时后，更多的COC-B达到了中期-2阶段。这可能意味着COC-A比COC-B需要更长的成熟期。
