Weinberger Clement, Brick Irving
Department of Biology, Seton Hall University, 07079, South Orange, New Jersey, USA.
Department of Biology, New York University, 10003, New York, New York.
Wilehm Roux Arch Dev Biol. 1982 Mar;191(2):119-126. doi: 10.1007/BF00848449.
Scanning electron microscopy (SEM) indicates that the primary hypoblast forms beneath the area pellucida during the first 8 h of incubation mainly by establishment of contact among cells which move downward out of the epiblast. This movement, polyingression, begins posteriorly and continues antero-laterally during the period of primary hypoblast formation. Polyingression produces many pits and possibly a crescentic fold in the embryo upper surface with corresponding cell clusters and a ridge on the lower surface. Fixationin situ helps prevent formation of artifactual folds and wrinkles facilitating interpretation of the SEM images.Formation of intercellular adhesions which lead to development of an epithelial primary hypoblast proceeds in a posterior to anterior direction along with polyingression. This epithelialization begins with elaboration of numerous filamentous processes by cells as they arrive from the epiblast, and continues with ongoing input of cells, merging of cells and cell clusters, and cell flattening. We have also shown (Weinberger and Brick 1982) that proliferation of ingressing cells provides additional cells for hypoblast development.
扫描电子显微镜（SEM）显示，在孵化的最初8小时内，原始下胚层在明区下方形成，主要是通过从外胚层向下移动的细胞之间建立接触。这种多内陷运动从后部开始，在原始下胚层形成期间继续向前外侧进行。多内陷在胚胎上表面产生许多凹坑，并可能形成新月形褶皱，在下表面有相应的细胞簇和一条脊。原位固定有助于防止人为褶皱的形成，便于对SEM图像进行解读。导致上皮性原始下胚层发育的细胞间粘附的形成与多内陷一起从后向前进行。这种上皮化始于细胞从外胚层到达时形成大量丝状突起，并随着细胞的持续输入、细胞和细胞簇的融合以及细胞扁平化而继续。我们还表明（Weinberger和Brick，1982年），内陷细胞的增殖为下胚层发育提供了额外的细胞。
