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  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Development genes and evolution 160 (1968), S. 375-400 
    ISSN: 1432-041X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Description / Table of Contents: Zusammenfassung Ribonucleinsäuren wurden nach dem Phenolverfahren aus Hühner- undTriturus-Embryonen gewonnen und in der Gewebekultur am undeterminierten Ektoderm der Amphibiengastrula ausgetestet: Im Vergleich zu den aus Hühnerembryonen gewonnenen Induktionsfaktoren mit Proteinnatur zeigten Ribonucleinsäuren aus Hühnerembryonen nur ein geringes Induktionsvermögen (wenige unspezifische Neuralstrukturen, Mesenchymzellen, Melanophoren). Der Anteil an differenziertem Gewebe ist aber höher als bei Aufzucht in Flickingerlösung (einer physiologischen Salzlösung, die als Grundmedium verwandt wurde). Er wird verringert, wenn der noch vorhandene Proteingehalt durch weitere Reinigung der RNS-Fraktion (Trägerelektrophorese oder Schütteln mit Chloroform-Octylalkohol) herabgesetzt wird. Zusatz von inaktiven Proteinen erhöht die Induktionswirkung nicht. Ribonucleinsäuren aus Triturusembryonen, einschließlich m-RNS, zeigten ebenfalls nur eine sehr geringe Induktionswirkung. Ein höheres Induktionsvermögen (aber immer noch gering gegenüber dem aktiver Proteine) zeigten RNS-Fraktionen aus Hühnerembryo-Zellkernen, die neben RNS viel DNS und auch noch Proteine enthielten. Neben Neuralstrukturen wurden Zellkomplexe aus hohen zylindrischen Zellen mit basal liegenden Kernen gebildet.
    Notes: Summary Ribonucleic acids were extracted from chick- andTriturus embryos by the phenol method and tested for their inducing ability: Ribonucleic acids from chick embryos had only a weak inducing capacity compared with that exerted by inducing chick embryo protein fractions. In tissue cultures of undetermined amphibian ectoderm they induced unspecific neural structures, mesenchymal cells and melanophores only to a small extent. But the differentiated part of the tissue was still higher than in control series where the ectoderm was cultivated in Flickinger solution alone. If the protein content of the RNA fractions is reduced by zone-electrophoresis or shaking with chloroformoctanol, the inducing ability of the RNA further decreases. Inactive proteins added to the RNA-containing solutions did not promote their inducing ability. Ribonucleic acids fromTriturus embryos including m-RNA had only a weak inducing capacity too. RNA fractions from chick embryo nuclei, containing much DNA and some proteins in addition to their RNA, had a higher inducing capacity (but still much less than had active proteins). Neural structures and complexes of cylindrical cells with basally located nuclei were induced.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Development genes and evolution 184 (1978), S. 171-180 
    ISSN: 1432-041X
    Keywords: Xenopus ; Blastula ; Neurula ; Tail-bud stage ; Nuclear proteins ; Electrophoresis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The changes in saline-soluble, 0.35 M NaCl-soluble and the residual fraction of nuclear proteins during early development ofXenopus were studied by analytical electrophoresis on sodium dodecyl sulfate polyacrylamide gel. The fractions were obtained by consecutive extraction of nuclei from the blastula, neurula and tail-bud stage of development. No qualitative and only limited quantitative differences were found when the proteins of any of the three fractions isolated from the neurula stage were compared with the proteins of the corresponding fraction isolated from the tail-bud stage. But the electrophoretic pattern of each of the three fractions of the nuclear proteins from the blastula stage differs significantly from the electrophoretic pattern of the same fraction isolated from the neurula or tail-bud stage. Compared with the blastula stage, in the two later stages the relative amounts of chromosomal proteins with apparent molecular weights below 30,000 are decreased. Proteins which migrate in electrophoresis in the positions of the very lysine-rich histones and of the proteins of the nuclear ribonucleo-protein particles are indicated among the chromosomal proteins of the blastula stage, and are visible as strong bands in the electrophorogram of 0.35 M NaCl-soluble proteins extracted from neurula or tail-bud stage nuclei.
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 1432-041X
    Keywords: Immobilized inducing factors ; Biological activity
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The inducing activity of the vegetalizing factor decreases after covalent coupling to CNBr-Sepharose with reduced binding capacity. The residual inducing activity is probably due to the release of a small amount of the factor from Sepharose beads. Covalent coupling to activated CH-Sepharose completely inactivated the vegetalizing factor, whereas the neuralizing factor retained its full activity. The biological activity was also very much reduced when the vegetalizing factor was bound to Sephadex beads, a derivative of dextran. Fully active factor was recovered after enzymatic degradation of the dextran matrix with dextranase. The experiments suggest that the neuralizing factor acts on the cell surface of ectoderm cells, whereas the vegetalizing factor must probably be internalized to become biologically active.
    Type of Medium: Electronic Resource
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  • 4
    ISSN: 1432-041X
    Keywords: Neural induction ; Basic fibroblast growth factor ; Triturus alpestris
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Ectoderm was isolated from early gastrulae of Triturus alpestris and induced with recombinant basic fibroblast growth factor (b-FGF). Neural tissue differentiated in about 38% of the explants which were induced by 2,5 μg/ml FGF. These explants do not contain other tissues, or contain only small amounts of mesenchyme and melanophores which are probably derived from induced neural crest. It is therefore unlikely that these neural tissues are secondarily induced. The other explants contain predominantly blastema tissue, endothelium/ mesothelium, small amounts of skeletal muscle and, rarely, notochord besides neural tissues. The mitotic rate was enhanced in about 20% of the induced explants. Possible mechanisms for the unexpected neural-inducing activity of b-FGF in Triturus ectoderm are discussed.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    Springer
    Development genes and evolution 163 (1969), S. 316-324 
    ISSN: 1432-041X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Description / Table of Contents: Zusammenfassung Rohfraktionen aus 9 Tage alten Hühnerembryonen, die neuralisierenden und mesodermalisierenden Induktionsfaktor enthielten, sowie angereicherter mesodermalisierender Faktor wurden mit Thioglykolsäure sowie mit 2-Mercaptoäthanol behandelt. Die Fraktionen wurden an Gastrulen vonTriturus alpestris oderAmbystoma nach der Implantationsmethode getestet. Der mesodermalisierende Faktor wird inaktiviert. Die Aktivität des neuralisierenden Faktors bleibt dagegen erhalten.
    Notes: Summary Crude extracts from 9 days old chicken embryos containing neuralizing and mesodermalizing inducing factors as well as purified mesodermalizing factor were incubated with thioglycolic acid and with 2-Mercaptoethanol. The fractions were tested by implanting into early gastrulae ofTriturus orAmbystoma. The mesodermalizing factor is inactivated whereas the neuralizing factor does not lose its activity.
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    Springer
    Development genes and evolution 187 (1979), S. 211-217 
    ISSN: 1432-041X
    Keywords: Amphibian ectoderm ; Induction ; Amino acid transport ; Protein synthesis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Isolated gastrula ectoderm ofTriturus alpestris orAmbystoma mexicanum was induced by the vegetalizing factor. Protein synthesis in the induced and uninduced control explants was measured by double labelling with3H-and14C-amino acids after different periods of cultivation. Slight differences were observed in the pattern of nuclear proteins after 12 h of cultivation and in the pattern of cytoplasmic proteins after 48 h of cultivation. The uptake of leucine started to increase in induced explants after 48 h of cultivation and after 96 h was about 50 times greater than in uninduced control explants. The uptake is reduced under partially anaerobic conditions. Ouabain inhibits the uptake by about 50%.
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    Springer
    Development genes and evolution 187 (1979), S. 231-244 
    ISSN: 1432-041X
    Keywords: Amphibia ; Mesoderm formation ; Secondary factors
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary A highly purified vegetalizing factor induces endoderm preferentially in amphibian gastrula ectoderm. After combination of this factor with less pure fractions, a high percentage of trunks and tails with notochord and somites are induced. The induction of these mesodermal tissues depends on secondary factors which may act on plasma membrane receptors of the target cells. The secondary factors are probably proteins as they are inactivated by trypsin or cellulose-bound proteinase K. They are not inactivated by thioglycolic acid. The implication of these findings for tissue determination and differentiation in normal development in relation to the anlageplan for endoderm and mesodermal tissues is discussed.
    Type of Medium: Electronic Resource
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  • 8
    Electronic Resource
    Electronic Resource
    Springer
    Development genes and evolution 193 (1984), S. 13-18 
    ISSN: 1432-041X
    Keywords: Amphibia ; Neural induction ; Ectoderm ; Activation of masked factor
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Isolated gastrula ectoderm has no neural-inducing activity and does not differentiate into neural tissues. It has, however, a high neural-inducing capacity, but the inducing factors are present in a masked, inactive form. The inducing factors are partially activated by homogenization and by freezing of the homogenate and are fully activated by treatment with ethanol. The relative distribution of inducing factors in different subcellular fractions changes after treatment with demecolcine and cytochalasin B or after autolytic incubation of the homogenate. The inducing activity of the high-speed supernatant is enhanced under these conditions. The experiments suggest that the activation of neuralizing factor(s) depends on the release from complex structures. Cytoskeletal elements seem to be involved. When early neural plate homogenate was fractionated, the high-speed supernatant showed neural-inducing activity. This is in contrast to the high-speed supernatant from the ectoderm homogenate, which shows no such activity.
    Type of Medium: Electronic Resource
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  • 9
    Electronic Resource
    Electronic Resource
    Springer
    Development genes and evolution 195 (1986), S. 117-122 
    ISSN: 1432-041X
    Keywords: Plasma membranes ; Amphibian embryogenesis ; Neural induction ; Xenopus laevis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Plasma membranes were isolated in high yield from Xenopus gastrulae by repeated sedimentation in discontinuous sucrose gradients. Most of the yolk was separated by lowspeed sedimentation before centrifugation on the discontinuous sucrose gradients. The isolation of plasma membranes was followed by covalent labelling of the surface of dissociated gastrula cells with diazoniobenzene sulphonate, by electron microscopy and the distribution of enzymatic markers. The isolated plasma membranes have a low neural inducing activity as compared to other cell constituents.
    Type of Medium: Electronic Resource
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  • 10
    Electronic Resource
    Electronic Resource
    Springer
    Development genes and evolution 192 (1983), S. 45-47 
    ISSN: 1432-041X
    Keywords: Neuralizing factor ; Transmission ; Mesoderm ; Extracellular material ; Triturus embryo
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The neural plates of very early neurula stages of Triturus alpestris were removed, the material which is released from the extracellular space between mesoderm and neural plate to the medium in which the embryos were dissected was isolated and extracted with phenol. The protein isolated from the phenol layer showed neural inducting activity. Proteoglycans isolated from the aqueous layer did not show such inducing activity. These results together with previously published experiments (Wilhelm Roux's Arch 184: 285–299) suggest that a neuralizing factor which is released from the mesoderm acts on the inner surface of the overlying dorsal ectoderm.
    Type of Medium: Electronic Resource
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