Wakahara M, Neff A W, Malacinski G M
Department of Biology, Indiana University, Bloomington 47405, USA.
Differentiation. 1984 May;26(3):203-10. doi: 10.1111/j.1432-0436.1984.tb01396.x.
Inverted Xenopus eggs have reduced numbers of primordial germ cells (PGCs). The extent of the reduction varies from spawning to spawning. Histologic examination revealed that PGC counts were lowest in inverted eggs which displayed the greatest amount of shift in the vegetal mass of large yolk platelets, although the germ plasm itself always remained localized in the egg's original vegetal hemisphere. Even at blastulation the germ plasm continued to be localized in the egg's original vegetal hemisphere. In many cases, however, it was confined to the periphery of the embryo, which probably accounts for the reduced PGC number in some tadpoles. In other cases it may have been dispersed and therefore not detectable in histologic analyses. Although the altered site of involution in inverted embryos did not influence PGC development, subsequent cell movement patterns apparently did. Those embryos which displayed the largest degree of pattern reversal at the tail-bud stage also exhibited the most extreme reduction in PGC numbers. A brief cold shock (4 degrees C, 10 min) prior to first cleavage leads to a further reduction in PGC numbers in inverted embryos, probably as a result of the displacement of the germ plasm away from its original vegetal pole location.
倒置的非洲爪蟾卵中原始生殖细胞（PGC）数量减少。减少的程度在不同批次的产卵中有所不同。组织学检查显示，在倒置卵中PGC数量最少，这些卵在大卵黄小板的植物性物质中表现出最大程度的移位，尽管生殖质本身始终位于卵原来的植物性半球。即使在囊胚形成时，生殖质仍继续位于卵原来的植物性半球。然而，在许多情况下，它局限于胚胎的周边，这可能是一些蝌蚪中PGC数量减少的原因。在其他情况下，它可能已经分散，因此在组织学分析中无法检测到。尽管倒置胚胎中内陷部位的改变不影响PGC的发育，但随后的细胞运动模式显然有影响。那些在尾芽期表现出最大程度模式反转的胚胎，其PGC数量也减少得最为极端。第一次卵裂前的短暂冷休克（4摄氏度，10分钟）会导致倒置胚胎中PGC数量进一步减少，这可能是生殖质从其原来的植物极位置移位的结果。
