Callebaut M, van Nueten E, Bortier H, Harrisson F, van Nassauw L
Laboratory of Human Anatomy and Embryology, RUCA, UA, Antwerpen, Belgium.
Eur J Morphol. 1996 Dec;34(5):347-61. doi: 10.1076/ejom.34.5.347.13056.
By excision at different sites of rectangular fragments from unincubated chicken blastoderms and replacement by isotopic fragments from unincubated quail blastoderms, we could make the first complete map of the Anlage fields in the freshly laid avian blastoderm. All the Anlage fields (Fig. 11) are found in the upper layer (UL) of the caudal half of the area centralis (bordered by the Rauber-Koller's sickle). In the UL of the area marginalis, peripheral to Rauber-Koller's sickle, neither gastrulation nor neurulation phenomena could be observed. Similar heterotopic replacement experiments indicate that before incubation, the different parts of the UL of the area centralis are still uncommitted or reversibly committed. The Anlage fields of chordamesoblast and definitive endoderm (gut endoderm) in unincubated avian blastoderms appeared to be disposed caudally in the caudal half of the area centralis. As far as we know we are the first to demonstrate that the Anlage field of the definitive gut endoderm (which is derived from the upper layer: Hunt, 1937; Vakaet, 1962b) is localized in the most caudal upper layer part of the area centralis just centrally to the Rauber-Koller's sickle. The Anlage field of the neural plate is localized in the upper layer over the more cranial endophyll. The Anlage of the brain is shield-shaped, whilst the other Anlage fields are sickle-shaped, parallel with the Rauber-Koller's sickle. Their general hemicircular disposition and form still seem to reflect (together with the Rauber-Koller's sickle) the original ooplasmic radial symmetry (Callebaut, 1972) combined with the eccentricity of the deep layer components, which was observed during early symmetrization by gravitational orientation of the egg yolk (Callebaut, 1993a,b). The Rauber-Koller's sickle might be homologous with the vegetal dorsalizing cells or centre of Nieuwkoop (1973) in amphibian blastulas.
通过从未孵化的鸡胚盘的不同部位切除矩形片段，并用未孵化的鹌鹑胚盘的同位素片段进行替换，我们能够绘制出刚产下的鸟类胚盘中原基区域的首张完整图谱。所有原基区域（图11）都位于中央区后半部的上层（UL）（由劳伯-科勒氏镰界定）。在边缘区的UL中，劳伯-科勒氏镰外围区域，未观察到原肠胚形成和神经胚形成现象。类似的异位替换实验表明，在孵化前，中央区UL的不同部分仍未确定或可逆地确定。未孵化的鸟类胚盘中脊中胚层和确定内胚层（肠内胚层）的原基区域似乎位于中央区后半部的尾部。据我们所知，我们是第一个证明确定肠内胚层的原基区域（其源自上层：亨特，1937年；瓦卡特，1962b）位于中央区最尾端上层部分，恰好在劳伯-科勒氏镰的中央。神经板的原基区域位于更靠前的内胚层上方的上层。脑的原基呈盾形，而其他原基区域呈镰形，与劳伯-科勒氏镰平行。它们大致的半圆形排列和形态似乎仍反映出（与劳伯-科勒氏镰一起）最初的卵质径向对称（卡勒博特，1972年），再加上深层成分的偏心性，这是在卵黄通过重力定向进行早期对称化过程中观察到的（卡勒博特，1993a，b）。劳伯-科勒氏镰可能与两栖类囊胚中的植物背化细胞或尼乌科普中心（1973年）同源。
