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  • 1
    Electronic Resource
    Electronic Resource
    Hemmung der Reaggregation dissoziierter Amphibienzellen durch Inhibitoren der RNS- und Proteinsynthese (1969)
    Springer
    Development genes and evolution 163 (1969), S. 184-196 
    Details
    ISSN: 1432-041X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Description / Table of Contents: Zusammenfassung l. Actidion (Cycloheximid), Hemmer der RNS-abhängigen Proteinsynthese, verhindert reversibel in einer Konzentration von 0,5–2 Μg/ml die Reaggregation EDTA-oder Trypsin-dissoziierter Zellen. Bei dieser Konzentration ist die Proteinsynthese zu über 90% gehemmt. Nach überführen der Zellen in Kulturmedium ohne Inhibitor setzt selbst nach 48stündiger Actidionbehandlung die Aggregatbildung wieder ein. Werden die Zellen erst 3 Std nach der Dissoziation mit Actidion behandelt, so ist keine Hemmung der Reaggregation zu beobachten. 2. Puromycin unterbindet in einer Konzentration von 20 Μg/ml reversibel die Reaggregation der Zellen. Die Proteinsynthese ist bei dieser Konzentration zu 66 % gehemmt. 3. Auch bei Anwesenheit von Proteinsynthesehemmern ist nach EDTA-Dissoziation eine initiale Bildung von kleinen Reaggregaten mit jeweils 5–10 Zellen (Primäraggregation) zu beobachten. Diese Primäraggregation kann jedoch verhindert werden, wenn bereits während der Dissoziation eine Behandlung der Zellen mit Actidion erfolgt. 4. Nach Zugabe von Actinomycin-D (l–2 Μg/ml) findet wie in den Kontrollen eine Reaggregation statt. Erst nach 30 Std kommt es zu einem zunehmenden Zerfall der Reaggregate. 5. Das unterschiedliche Verhalten der Zellen nach EDTA- und Trypsin-Behandlung wird diskutiert.
    Notes: Summary 1. Aggregation of embryonic Amphibian cells dissociated by Trypsin or EDTA is supressed reversibly by actidion (cycloheximid 0.5–2 Μg/ml), an inhibitor of protein synthesis. Protein synthesis is inhibited more than 90% at these concentrations. The inhibition by actidion was still reversible after 48 hours, when the cells were transferred to normal medium. Actidion added to cells, cultured in Flickinger solution for 3 h, was no longer able to stop further aggregation. 2. Puromycin reversibly suppresses aggregation at a concentration of 20 (Μg/ml, when protein synthesis is inhibited to 66 %. 3. After EDTA-dissociation the formation of initial small clusters of 5–10 cells (primary aggregation) occurred even in the presence of inhibitors of protein synthesis. The primary aggregation is however suppressed if actidion or puromycin are already added during the dissociation procedure. 4. In the presence of actinomycin-D (1–2 Μg/ml) the cells continue to aggregate like the controls. After 30 h further aggregation is stopped and the aggregates loose single cells. 5. Differences in the aggregation of cells after EDTA and Trypsin treatment are discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00579320
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  • 2
    Electronic Resource
    Electronic Resource
    Experimentelle Untersuchungen über die Kompetenzverhältnisse früher Entwicklungsstadien des Amphibien-Ektoderms (1968)
    Springer
    Development genes and evolution 160 (1968), S. 344-374 
    Details
    ISSN: 1432-041X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Description / Table of Contents: Zusammenfassung In den vorliegenden Untersuchungen wurde präsumptives Ektoderm Keimen von Ambystoma mexicanum und Triturus vulgaris im 16–32-Zellstadmrn bis zur frühen mittleren Gastrula entnommen und mit Lithiumchloridlösung behandelt. Dabei wurden folgende Ergebnisse erzielt: 1. Bezüglich der mesodermalen Differenzierungsleistungen konnte sowohl für Ambystoma- als auch für Triturusektoderm grundsätzlich eine ähnliche zeitliche Reaktionsbereitschaft verzeichnet werden. Mesodermale Differenzierungen wurden vom Morulastadium (bei Triturus in zwei Fällen auch im 16–32-Zellstadium) bis zur frühen Gastrula gebildet. In der mittleren und späten Blastula realisierte Trituras- und Ambystomaektoderm die meisten und umfangreichsten mesodermalen Induktionsgebilde. 2. Entodermale Differenzierungen wurden bei beiden Urodelenarten in allen untersuchten Entwicklungsstadien verwirklicht. Zur frühen mittleren Gastrula wird eine Abnahme der entodermalen Induktionsgebilde beobachtet. In der Morula, frühen Blastula und in der frühen mittleren Gastrula werden in wenigen Explantaten bei beiden Spezies entodermale Differenzierungen unabhängig von mesodermalen Induktionsgebilden hervorgerufen. 3. Die entodermalen Strukturen weisen hinsichtlich des Differenzierungsgrades beträchtliche Unterschiede in Abhängigkeit von dem Entwicklungsstadium auf, in dem Lithiumchlorid einwirken konnte. Gut differenzierte Darmstrukturen und peripheres Entoderm werden in den älteren Stadien häufiger als in den frühen realisiert. 4. Beim Vergleich der Ergebnisse von Ambystoma und Trituras können beträchtliche Unterschiede bezüglich der induzierten Organkomplexe verzeichnet werden. Während Ambystomaektoderm entodermale und spinocaudale Strukturen bildete, verwirklichte Triturusektoderm entodermale, mesodermale und deuterencephale Differenzierungen. Die analysierten Strukturen können in ihrer Zusammensetzung und in ihrer Anordnung mit bestimmten Regionen in der jungen Larve verglichen werden. So entsprachen die induzierten Organkomplexe bei Ambystoma der hinteren Rumpf- und Schwanzregion, bei Triturus der vorderen und mittleren Rumpfregion des jungen Larvenstadiums.
    Notes: Summary The inductive effect of lithium chloride was examined on isolated presumptive ectoderm from different developmental stages (16–32-cell stage up to the early middle gastrula stage) of Triturus vulgaris and Ambystoma mexicanum. The following results were obtained: 1. Nearly the same temporal sequence of differentiation tendencies were found for treated ectoderm of comparable stages of Ambystoma- and Triturus ectoderm. The lithium treatment brought about mesodermal differentiations in the morula stage up to the early gastrula stage (at Triturus also two cases in the 16–32-cell stage). The most frequent and largest mesodermal inductions were obtained in the middle and late blastula. 2. In both species entodermal differentiations were formed in all examined stages. Entodermal inductions decreased in the late blastula to the early middle gastrula. In the morula, early blastula and in the early middle gastrula ectoderm of Ambystoma and Triturus entodermal differentiations appeared independent of mesodermal tissues. 3. There are clear differences in the degree of the differentiation of entodermal structures in relation to the developmental stage. Intestine and peripheral entoderm were more frequent in the older stages than in the earlier ones. 4. Comparing the results of Ambystoma and Triturus there are significant differences with respect to the regionality of the induced tissue complexes. Ambystoma ectoderm forms entodermal and spinocaudal structures, while Triturus ectoderm brings about entodermal, mesodermal and deuterencephalic inductions. The parts and the composition of the analyzed tissue formations correspond with certain regions of the young larva. Thus the treated ectoderm of Ambystoma forms tissues corresponding to the region of the tail, while Triturus ectoderm produces differentiations of the posterior and middle part of the trunk of the young larva.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00586152
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  • 3
    Electronic Resource
    Electronic Resource
    Influence of cyclic nucleotides on amphibian ectoderm (1977)
    Springer
    Development genes and evolution 181 (1977), S. 261-265 
    Details
    ISSN: 1432-041X
    Keywords: Amphibian ectoderm ; Cyclic nucleotides ; Primary embryonic induction
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Isolated amphibian (Triturus alpestris) gastrula ectoderm was treated with cyclic nucleotides for 24 h and cultured up to 12 days. Explants treated with$cyclic N6-Monobutyryl-adenosine-3′∶5′-monophosphate, cyclic Dibutyryladenosine-3′∶5′-monophosphate and cyclic Dibutyrylguanosine-3′∶5′-monophosphate in a concentration of 10−3 and 10−5 M did not differentiate into mesoderm- or endoderm-derived tissues. The number of explants with small neural and neuroid structures did not exceed the percentage found in the control series. Inductions could also not be obtained when ectoderm was dissociated prior to the treatment with cyclic nucleotides, or when theophylline (which inhibits phosphodiesterase) was added to the culture medium. The results are discussed with regard to the possible mode of action of the vegetalizing factor.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00848425
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  • 4
    Electronic Resource
    Electronic Resource
    Change in the differentiation pattern ofXenopus laevis ectoderm by variation of the incubation time and concentration of vegetalizing factor (1983)
    Springer
    Development genes and evolution 192 (1983), S. 130-137 
    Details
    ISSN: 1432-041X
    Keywords: Vegetalizing factor ; Inducer concentration ; Incubation time with inducer ; Pattern formation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Early amphibian gastrula ectoderm (Xenopus laevis) has been treated with vegetalizing factor using the sandwich technique, varying the period of incubation and the inducer concentration. The pattern of induced tissues depends on three factors: the inducer concentration, the size of inducer pellet and the time of exposure of ectodermal target cells to inducer. Short treatment with inducer will result in the formation of blood cells and heart structures. An increase in incubation time or inducer concentration, or both, will cause the formation of increasing amounts of such dorsal mesodermal structures as pronephros, somites and notochord. Neural structures can only be observed in explants with considerable amounts of somites and notochord. Ectoderm treated with high concentrations of vegetalizing factor for the whole period of competence will differentiate into endoderm. Furthermore, the results show thatX. laevis ectoderm does not show any autoneuralizing tendency under our experimental conditions. It therefore seems to be a suitable tool for the study of primary embryonic induction.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00848681
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  • 5
    Electronic Resource
    Electronic Resource
    Biological activity of the vegetalizing factor: Decrease after coupling to polysaccharide matrix and enzymatic recovery of active factor (1980)
    Springer
    Development genes and evolution 189 (1980), S. 47-56 
    Details
    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
    URL: http://dx.doi.org/10.1007/BF00848566
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  • 6
    Electronic Resource
    Electronic Resource
    Crystallins during Xenopus laevis free lens formation (1988)
    Springer
    Development genes and evolution 197 (1988), S. 190-192 
    Details
    ISSN: 1432-041X
    Keywords: Xenopus laevis ; Free lens ; Crystallin ; Indirect immunofluorescence ; Antigen ; Antiserum
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The ontogeny and localization of crystallins during free lens development (i.e. lens development without the optic vesicle) were investigated in Xenopus laevis using the indirect immunofluorescence staining method with an antiserum raised against homologous total lens soluble proteins. Since the developing free lenses pass through stages similar to those of the lenses regenerated from the inner cell layer of the outer cornea following lentectomy in the same species Freeman's classification was used to identify the stages of free lens development. The first appearance of a positive reaction occurred at early stage IV in a number of cells in an area where future lens fibre cells would develop. With further differentiation of the free lens more and more cells in the fibre area started to show a positive reaction and the first positive reaction in the epithelium was observed late in stage V. Histological examination revealed that a fully differentiated free lens and a normally developed lens are similar but that the free lens is smaller.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00427923
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  • 7
    Electronic Resource
    Electronic Resource
    Basic fibroblast growth factor can induce exclusively neural tissue in Triturus ectoderm explants (1994)
    Springer
    Development genes and evolution 203 (1994), S. 304-309 
    Details
    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
    URL: http://dx.doi.org/10.1007/BF00457801
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  • 8
    Electronic Resource
    Electronic Resource
    Einflu\ von Inhibitoren der RNS- und Protein-Synthese und Induktoren auf die ZellaffinitÄt von Amphibiengewebe (1972)
    Springer
    Development genes and evolution 169 (1972), S. 41-55 
    Details
    ISSN: 1432-041X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Description / Table of Contents: Zusammenfassung Isoliertes Gastrula-Ektoderm wurde nach unterschiedlicher Behandlung mit Induktoren und Hemmern der RNS- bzw. Protein-Synthese mit isoliertem Entoderm kombiniert. 1. Unbehandeltes Ektoderm separiert sich von Entoderm mehrere Tage nach der Kombination. 2. Mit vegetalisierenden Faktor induziertes Ektoderm separiert sich nicht von Entoderm,. sondern wird völlig von Entoderm überwachsen. 3. Bei gleichzeitiger Einwirkung von Induktor und Actidion, einem Hemmer der Proteinsynthese, wird durch hohe Konzentration (2 Μg/ml) bei relativ kurzer Einwirkungszeit (5 Std) oder durch geringe Konzentration (1 Μg/ml) bei langer Einwirkungszeit (20 Std) die überwachsung verhindert. 4. Durch AcD, einem Hemmer der RNS-Synthese, wird dagegen die überwachsung von induziertem Ektoderm nicht unterbunden. 5. Behandlung von Ektoderm mit AcD ohne Induktor hat bereits einen Einflu\ auf die AffinitÄtseigenschaften des Ektoderms. Bei geringer AcD-Konzentration (1 Μg/ml) überwÄchst das Ektoderm das Entoderm in Form eines dünnen Epithels. Mit hoher AcD-Konzentration (2 Μg/ml) behandeltes Ektoderm wird dagegen in einigen FÄllen von Entoderm überwachsen.
    Notes: Summary Isolated Amphibian gastrula ectoderm, pretreated in different ways, was combined with endoderm. 1. Untreated ectoderm separates from endoderm after several days. 2. Ectoderm, treated with the vegetalizing inducing factor, is surrounded by endoderm, which spreads over the treated ectoderm as an uni- or multicellular layer. 3. Treatment of ectoderm with actidion (2 Μg/ml for 5 h or 1 Μg/ml for 20 h), an inhibitor of protein synthesis, prior to induction prevents the spreading of endoderm over ectoderm. 4. Treatment of ectoderm with AcD, an inhibitor of RNA synthesis, prior to induction does not prevent the spreading of endoderm over ectoderm. 5. Treatment of ectoderm with AcD without inductor changes the affinity of ectoderm to endoderm. Ectoderm, treated with 1 Μg/ml AcD, spreads over the endoderm as a thin layer. After treatment with 2 Μg/ml AcD, in some cases endoderm spreads over the ectoderm.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00575792
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  • 9
    Electronic Resource
    Electronic Resource
    The ultrastructure of amphibian ectoderm treated with an inductor or actinomycin D (1973)
    Springer
    Development genes and evolution 173 (1973), S. 283-293 
    Details
    ISSN: 1432-041X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Description / Table of Contents: Zusammenfassung Amphibien-(Triturus alpestris)-Ektoderm wurde isoliert und nach 2–16 Tagen elektronenmikroskopisch untersucht. Es konnte gezeigt werden, daß sich Ektoderm, früher oft als „undifferenziertes Ektoderm“ bezeichnet, zu Epithelzellen differenziert, die zum Teil Cilien tragen. Diese Epithelzellen unterscheiden sich in ihrer Ultrastruktur nicht von Epidermiszellen, die sich in situ (also im Ganzkeim) entwickelt haben, lassen jedoch die typische flächige Anordnung der Epidermis vermissen. Die Cilien besitzen die gleiche Feinstruktur, wie sie bei Cilien der Protozoa oder Spermien von Insekten oder Wirbeltieren zu finden sind. Nach 4 Tagen Aufzucht bildet sich im Bereich der Peripherie der Epidermiszellen eine Zone aus, die frei ist von Dotterschollen, Mitochondrien und Embryonalpigment. Diese Zone ist reich an vacuolenähnlichen Strukturen und Basalkörpern der Cilien. Ektoderm, das mit vegetalisierendem (mesodermal/entodermal) induzierendem Faktor behandelt wurde, differenziert sich zu mesodermalen und entodermalen Geweben. Sowohl Cilien als auch die charakteristische periphere Zone werden in induziertem Gewebe nicht gebildet. In Ektoderm, das über 6 Std mit Aktinomycin D (1 μg/ml) behandelt wurde, ist die Bildung der peripheren Zone und der Cilien verzögert.
    Notes: Summary Amphibian (Triturus alpestris) ectoderm was isolated and after 2–16 days in culture examined by electron microscopy. It has been shown that the ectoderm, formerly called “undifferentiated ectoderm”, forms in part ciliated epithelial cells, which cannot be distiguished from the cells of the epidermis, which has developed in situ (except for the alignment of the cells which depends on the mesenchyme underlying the epidermis). The ultrastructure of the cilia is similar to that of cilia of protozoa or sperms of insects or vertebrates. A zone at the periphery of the epidermal cells, free of yolk platelets, mitochondria and pigment granules (embryonic pigment) is observed after 4 days. This area is rich in vacuolous structures and basal bodies of the cilia. Ectoderm, which was treated with the vegetalizing factor differentiates into mesodermal and endodermal tissues. Cilia, as well as the characteristic peripheral zone, are not formed in the induced ectoderm. In ectoderm treated with actinomycin D (1 μg/ml for 6 h) the differentiation of the peripheral zone and the cilia is delayed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00575835
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  • 10
    Electronic Resource
    Electronic Resource
    The differentiation of isolated amphibian ectoderm with or without treatment with an inductor (1975)
    Springer
    Development genes and evolution 178 (1975), S. 277-284 
    Details
    ISSN: 1432-041X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Amphibian gastrula ectoderm was isolated and examined by scanning electron microscopy after 24 h, 48 h, 6 and 10 days in culture. Contrary to the view which was formerly held, ectoderm is already detemined to form epidermis at the early gastrula stage. The ultrastructural differentiation of the epidermal cellsin vitro is very similar to their developmentin vivo (Billettet al., 1973). The surface of the individual epidermal cell is curved convexly like a hemisphere and is covered by numerous microvilli. About 1 in 10 of the epidermal cells is ciliated. Ectoderm treated with vegetalizing (mesodermal/endodermal inducing) factor for 24 h differentiates predominantly into endodermal tissues. Already 24 h after the implantation of the inducer (employing the sandwich-technique) there is an obvious difference between the test series and the controls. The surface of the cells is flattened and covered by projections resembling processes of antlers. After 10 days (culture the cells with flat surfaces are arranged like an irregular honeycomb. Ciliated cells cannot be detected. The morphological differences in the surface of the untreated and induced ectoderm are discussed with regard to changes in cell affinity demonstrated in former experiments.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00848063
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