Gardner R L, Davies T J, Carey M S
Imperial Cancer Research Fund, Department of Zoology, Oxford, UK.
Placenta. 1988 Jul-Aug;9(4):343-59. doi: 10.1016/0143-4004(88)90048-3.
Delayed implanting blastocysts recovered from both ovariectomized and lactating pregnant mice were examined for the presence of primitive endoderm. One or more of three different criteria were used to identify this tissue which was found to be present in nearly all such blastocysts, regardless of the length of time for which their implantation had been delayed. Furthermore, the tissue appeared to differentiate in blastocysts from ovariectomized females at approximately the same postcoital stage as in those from sham-operated controls. Formation of the parietal endoderm layer was not observed in a single instance during delay, but began approximately 10 h after it had been terminated by injecting ovariectomized females with oestradiol benzoate. Cells in mitosis were found both at longer intervals after the onset of implantation delay and at shorter intervals after its termination than reported previously. It is concluded that, contrary to what might have been anticipated from certain earlier studies, there seem to be no obvious advantages in using delayed implanting rather than nondelayed blastocysts for investigating initial steps in differentiation of the primitive endoderm. Delayed blastocysts may, nevertheless, be of value in elucidating factors controlling the differentiation or onset of migration of parietal endoderm cells.
从去卵巢和哺乳的怀孕小鼠中回收的延迟着床囊胚，被检查是否存在原始内胚层。使用了三种不同标准中的一种或多种来识别这种组织，结果发现几乎所有此类囊胚中都存在这种组织，无论其着床延迟的时间长短。此外，在去卵巢雌性小鼠的囊胚中，该组织似乎在与假手术对照组相同的交配后阶段开始分化。在延迟期间未观察到一例壁内胚层层的形成，但在给去卵巢雌性小鼠注射苯甲酸雌二醇终止延迟后约10小时开始形成。与之前报道相比，在着床延迟开始后较长时间间隔以及终止后较短时间间隔都发现了处于有丝分裂的细胞。得出的结论是，与某些早期研究可能预期的相反，在研究原始内胚层分化的初始步骤时，使用延迟着床而非未延迟的囊胚似乎没有明显优势。然而，延迟囊胚在阐明控制壁内胚层细胞分化或迁移开始的因素方面可能具有价值。
