title: Inducing activity of subcellular fractions from amphibian embryos.
abstract: The homogenate from unfertilized eggs, gastrulae, neurulae and hatched embryos ofXenopus laevis was fractionated by differential centrifugation and subsequent repeated centrifugation on discontinuous sucrose gradients. A high archencephalic-neural inducing activity was found in RNP particles, which were released from the high-speed ("microsomal") sediment by treatment with EDTA, and in a fraction of heterogeneous small vesicles. The highest archencephalic inducing activity was observed in RNP particles from unfertilized eggs and from gastrulae. RNP particles isolated from hatched embryos had a lower inducing activity. The neuralizing factor can be extracted from the small vesicles with pyrophosphate buffer at pH 8.6, but it is not solubilized with a non-ionic detergent (Triton X 100). The high-speed supernatant from the gastrula homogenate contains soluble neuralizing factor, whereas the supernatant from egg homogenate has a low inducing activity. The plasma membrane fraction (isolated from gastrulae) also has only a low inducing activity. The possible significance of the subcellular distribution of neuralizing factors for the transmission of neuralizing inducer from the mesoderm to competent gastrula ectoderm and the processing of signals which are generated on the plasma membrane of induced cells is discussed.
authors.affiliation: Institut für Molekularbiologie und Biochemie, Freie Universität Berlin, Arnimallee 22, D-1000, Berlin 33.
authors.forename: Jutta
authors.initials: J
authors.lastname: Janeczek
authors.affiliation: Institut für Molekularbiologie und Biochemie, Freie Universität Berlin, Arnimallee 22, D-1000, Berlin 33.
authors.forename: Manorama
authors.initials: M
authors.lastname: John
authors.affiliation: Institut für Molekularbiologie und Biochemie, Freie Universität Berlin, Arnimallee 22, D-1000, Berlin 33.
authors.forename: Jochen
authors.initials: J
authors.lastname: Born
authors.affiliation: Institut für Molekularbiologie und Biochemie, Freie Universität Berlin, Arnimallee 22, D-1000, Berlin 33.
authors.forename: Heinz
authors.initials: H
authors.lastname: Tiedemann
authors.affiliation: Institut für Molekularbiologie und Biochemie, Freie Universität Berlin, Arnimallee 22, D-1000, Berlin 33.
authors.forename: Hildegard
authors.initials: H
authors.lastname: Tiedemann
keywords: Neural-inducing activity; RNP particles; Subcellular fractions; Vesicular fractions; Xenopus laevis eggs and embryos