Restoration of neurogastrulation by subgerminal ooplasm in endophyll free caudal quail blastoderm quadrants
1995
Callebaut, M. | Nueten, E. van | Nassauw, L. van | Harrisson, F. (Rijksuniversitair Centrum Antwerpen (Belgium). Lab. of Human Anatomy and Embryology)
Caudal quadrants of unincubated quail or chicken prestreak blastoderms, from which the endophyll was removed (but with RAUBER'S sickle (1876) stil in situ) were cultured in vitro : no primitive streak (PS) developed. If however endophyll was replaced, the gastrulation and neurulation potencies were restored. A normal PS developed in the caudal quadrant only when both endophyll and RAUBER'S sickle were present. Our study also indicates that in this condition endophyll cannot regenerate, neither from the upper layer, nor from RAUBER'S sickle. By contrast in not quartered unincubated blastoderms from which the endophyll was removed as a sheet, a PS coming from the presumed lateral parts usually appears after further incubation. The endophyll also seems to have an influence on the formation of the future neuroectoblastic region by induction. If instead of endophyll, central subgerminal quail ooplasm (containing the nucleus of PANDER (1817)) was placed on an endophyll free caudal quail quadrant, a primary gastrula (without mesoderm) or a neurula (without differentiating mesodermal structures) or a normal miniature embryo (with differentiating mesodermal structures) will form. Most obvious on the sections through these germs is the reappearance of endophyll and the presence of many quail nuclei with typical central chromatin granule in the ooplasm of the nucleus of PANDER. The colonization of the latter could be demonstrated by placing a chicken nucleus of PANDER on an endophyll free quail caudal quadrant. This is the first report on quail nucleus-chicken ooplasm cell formation. This suggests de novo formation of endophyll (containing delta ooplasm) probably by colonization of the subgerminal ooplasm of the nucleus of PANDER (also containing delta ooplasm) by RAUBER'S sickle or by upper layer cells.
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