Summary
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1.
The inducing powers of the primary hypoblast of the chick embryo were studied by the insertion of a TH millipore filter between the hypoblast and the reacting epiblast.
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2.
Two successive inducing capacities were discovered in the hypoblast. The first to appear and disappear is the inductor of the primitive streak, while the second is a prosencephalic inductor.
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3.
The formation of a mature primitive streak which contains a Hensen's node is dependent on direct cellular contact between the epiblast and hypoblast, and most probably on the inclusion of hypoblastic cells in the forming node and notochord.
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4.
The formation of spinal cord-like structures and undifferentiated neural plates can be related to the presence of nodeless primitive streaks in the blastoderms. These neural structures are probably induced by the mesoderm produced by the defective primitive streaks, which were unable to form notochord or somites.
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5.
The primary hypoblast, by virtue of its prosencephalic inducing power, can be compared with the presumptive pharyngeal endoderm of the amphibian embryo.
Zusammenfassung
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1.
Die Induktionsfähigkeit des primären Hypoblasts des Hühnchenembryos wurde untersucht durch die Insertion eines TH-Millipore-Filters zwischen Hypoblast und reagierendem Epiblast.
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2.
Zwei aufeinanderfolgende Induktionsfähigkeiten wurden im Hypoblast entdeckt. Die zuerst erscheinende und auch zuerst wieder verschwindende Fähigkeit ist die Induktion des Primitivstreifens; die zweite ist der prosencephale Induktor.
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3.
Die Bildung eines reifen Primitivstreifens mit Hensenschem Knoten ist abhängig vom direkten cellulären Kontakt zwischen Epiblast und Hypoblast, und höchstwahrscheinlich abhängig von der Miteinschließung hypoblastischer Zellen in den sich bildenden Hensenschen Knoten und die Chorda.
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4.
Die Bildung von undifferenzierten Neuralplatten und Strukturen, die dem Rückenmark ähneln, sind korreliert mit der Gegenwart von Primitivstreifen ohne Hensensche Knoten. Diese Neuralstrukturen werden wahrscheinlich durch das Mesoderm induziert, das durch die defekten Primitivstreifen hervorgebracht wird; diese defekten Primitivstreifen sind nicht in der Lage, Chorda oder Somiten zu bilden.
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5.
Auf Grund seines prosencephalen Induktionsvermögens kann der primäre Hypoblast mit dem präsumtiven pharyngealen Endoderm des Amphibien-Embryos verglichen werden.
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This work was aided by a grant from the Fund for the Advancement of Research and Study of the Workers' Committee of the Histadrut.
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Eyal-Giladi, H., Wolk, M. The inducing capacities of the primary hypoblast as revealed by transfilter induction studies. W. Roux' Archiv f. Entwicklungsmechanik 165, 226–241 (1970). https://doi.org/10.1007/BF01380786
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DOI: https://doi.org/10.1007/BF01380786