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  • 1
    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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  • 2
    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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  • 3
    Electronic Resource
    Electronic Resource
    Springer
    Development genes and evolution 184 (1978), S. 285-299 
    ISSN: 1432-041X
    Keywords: Embryonic induction ; Sepharose bound factors ; Biological activity
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Covalent binding to bromoacetyl-cellulose inactivates the vegetalizing factor. The bound factor is however still able to form a complex with an inhibitor for the factor. Covalent binding to CNBr-Sepharose likewise inactivates the vegetalizing factor. The neuralizing factor on the other hand is not inactivated when covalently bound to CNBr-Sepharose. When a crude fraction which contains the neuralizng factor as well as the vegetalizing factor is bound to CNBr-Sepharose the vegetalizing activity is greatly decreased whereas the neuralizing activity is not reduced. This suggests that the mechanisms of action of the two factors are quite different. Whereas the vegetalizing factor must be incorporated into the cells, the neuralizing factor interacts with the plasma membrane of competent ectoderm cells.
    Type of Medium: Electronic Resource
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  • 4
    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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  • 5
    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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  • 6
    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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  • 7
    ISSN: 1432-041X
    Keywords: Neural induction ; Protein factors ; Xenopus laevis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary High (Mr ≈ 90–110 kDa) and low (Mr ≈ 15–30 kDa) molecular weight forms of neural-inducing factors have been found in the supernatant of Xenopus gastrula homogenate. The factors, which are protein in nature, have been partially purified by size exclusion high-performance liquid chromatography (HPLC) and sodium dodecyl sulphate (SDS)-polyacrylamide gel electrophoresis. The factor of smaller size, which could be derived from a precursor, is associated with other proteins in a larger complex. The neural-inducing factors are not irreversibly inactivated after chemical deglycosylation with trifluoromethansulfonic acid. The neural-inducing protein which is found in ribonucleoprotein (RNP)-particles was partially purified by hydrophobic chromatography. Possible relationships of the factors in different subcellular fractions and their physiological significance are discussed.
    Type of Medium: Electronic Resource
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  • 8
    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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  • 9
    ISSN: 1432-041X
    Keywords: Neural induction ; Neural plate ; Activation of masked factor
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Neural plates which are induced in the dorsal ectoderm of Triturus by the underlying mesoderm acquire, in turn, neural-inducing activity. This process is correlated with the appearance of neural-inducing activity in the microsomal fraction of the neural plate homogenate. The high-speed supernatant also acquires inducing activity after neural induction, but to a lesser extent. The experiments suggest that a masked neuralizing factor, which is already present in the ectoderm, is in part activated and exported from the inducing neural plate cells.
    Type of Medium: Electronic Resource
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  • 10
    Electronic Resource
    Electronic Resource
    Springer
    Development genes and evolution 202 (1993), S. 316-320 
    ISSN: 1432-041X
    Keywords: Neuralizing inducing factor ; Vegetalizing inducing factor ; Activin A ; Proteoglycans ; Complex formation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Proteoglycans from chicken embryos bind neuralizing and vegetalizing inducing factors. The proteoglycan-factor complexes have no inducing activity. Enzymatic cleavage of the core proteins of the proteoglycans abolishes inhibition of the inducing activity by proteoglycans. The possible significance of the formation of complexes of inducing factors with proteoglycans is discussed.
    Type of Medium: Electronic Resource
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