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  • 1
    Electronic Resource
    Electronic Resource
    Morphogenetic substances in nerve-depletedhydra (1979)
    Springer
    Development genes and evolution 187 (1979), S. 323-328 
    Details
    ISSN: 1432-041X
    Keywords: Nerve-depletedhydra ; Morphogenetic substances
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary By a double colchicine treatment the nerve-cell population ofhydra was reduced to less than 1% of the normal complement. Such severely nerve-depletedhydra contained normal or higher than normal concentrations of head activator, head inhibitor, foot activator and foot inhibitor which in normal animals are produced by nerve cells. According to typical chromatographic properties all four morphogenetic substances were chemically identical to those found in normal animals. It is suggested that in nervedepletedhydra the epithelial cells, as the only remaining cell type, have taken over the morphogen-producing function of nerve cells.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00848467
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  • 2
    Electronic Resource
    Electronic Resource
    Head regeneration inHydra is initiated release of head activator and inhibitor (1976)
    Springer
    Development genes and evolution 180 (1976), S. 287-295 
    Details
    ISSN: 1432-041X
    Keywords: Hydra ; Head regeneration ; Morphogenetic substances
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Hydra regenerating heads release at least two substances into the surrounding medium: one stimulates and one inhibits head formation. The inhibitor is released mainly during the first hour after cutting, the activator is released more slowly with a maximum in the second hour and with substantial release still during the following six hours. The release of both substances seems to be specific for head regeneration: it is not found in animals regenerating feet. The sequential release of these substances leads to the early changes observed at the cellular level during head regeneration inhydra: the inhibitor produces a decrease, the activator an increase in the mitotic activity of interstitial and epithelial cells, if assayed on intact animals. Head regeneration is blocked, if the release of the head activator is prevented. It is therefore suggested that these substances are necessary to initiate head regeneration inhydra.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00848775
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    Paper (German National Licenses)
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  • 3
    Electronic Resource
    Electronic Resource
    Analysis of morphogenetic mutants of hydra (1977)
    Springer
    Development genes and evolution 183 (1977), S. 193-206 
    Details
    ISSN: 1432-041X
    Keywords: Hydra mutant ; Morphogenetic substances ; Head formation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary A mutant ofHydra attenuata is analysed, theaberrant, which is distinct from the wild type in having a smaller head with fewer tentacles and only half the number of head-specific cells. The rate of head and foot regeneration and the doubling time are slower inaberrants than in normal hydra. The lower head-forming potential is paralleled by a reduced concentration of head-specific morphogens: compared to the wild type, in theaberrant the concentration of head activator is reduced to 70% in the head and to 50% in the body, the concentration of head inhibitor is reduced to 50% in the head and to 80% in the body. Theaberrant is more sensitive (3 times) to added head activator and less sensitive (〉5 times) to added head inhibitor than the wild type. The slower rate of foot regeneration is paralleled by a lower content of foot-specific morphogens: compared to the wild type, in theaberrant the foot activator is reduced to 40% and the foot inhibitor to 70%.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00867320
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  • 4
    Electronic Resource
    Electronic Resource
    Analysis of morphogenetic mutants of hydra (1977)
    Springer
    Development genes and evolution 183 (1977), S. 215-222 
    Details
    ISSN: 1432-041X
    Keywords: Hydra mutants ; Morphogenetic substances ; Size regulation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Minis have a doubling time of 2.4 days,maxis of 8 days.Minis regenerate head and foot 5 h faster thanmaxis.Minis have fewer tentacles (4.6) per head thanmaxis (6.1). Inmini the concentration of the head activator is equal to that inHydraattenuata, but the concentration of the head inhibitor is reduced (2-fold in the head, 1.2-fold in the body). The concentrations of the foot factors are normal.Minis respond likeHydra attenuata to head activator, foot activator and foot inhibitor, but they are less sensitive to head inhibitor Inmaxi the concentration of the head activator is higher than inmini (5-fold in the head, 10-fold in the body) and that of the head inhibitor is also higher (4-fold in the head, 5-fold in the body). The concentration of the foot inhibitor is normal, that of the foot activator is doubled.Maxis are insensitive to added head activator and less sensitive to added head inhibitor and foot inhibitor. Their response to foot activator is normal.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00867322
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  • 5
    Electronic Resource
    Electronic Resource
    Analysis of morphogenetic mutants of hydra (1977)
    Springer
    Development genes and evolution 183 (1977), S. 207-214 
    Details
    ISSN: 1432-041X
    Keywords: Hydra mutant ; Morphogenetic substances ; Bud formation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Non-budding mutants ofChlorohydra viridissima regenerate heads 6 h faster thanHydra attenuata and the number of tentacles per head is higher. The polarity in pieces from the gastric region is the more labile, the smaller the pieces are. In regenerates heads and tentacles form much more frequently than feet, giving rise to bipolar or multiheaded structures. Buds very seldom form under normal conditions, but they occasionally occur in regenerating animals with two cut surfaces. The higher head-forming potential in the mutant is paralleled by a higher head-activator concentration (20-fold in head, 4-fold in body), than inHydra attenuata, which is not accompanied by an equivalent increase in head-inhibitor concentration (1.4-fold in head, 2-fold in body). The foot-activator concentration is slightly reduced (1.3-fold), the foot-inhibitor concentration is higher (1.6-fold) than inH. attenuata. The mutant is extremely insensitive to head activator, relatively insensitive to head inhibitor and foot inhibitor, but sensitive to foot activator.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00867321
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  • 6
    Electronic Resource
    Electronic Resource
    Separation and specificity of action of four morphogens from hydra (1979)
    Springer
    Development genes and evolution 186 (1979), S. 139-149 
    Details
    ISSN: 1432-041X
    Keywords: Hydra ; Morphogenetic substances ; Regeneration ; Budding
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary A procedure is presented by which four previously described morphogenetic substances can be purified from hydra: an activator and an inhibitor of head formation and an activator and an inhibitor of foot formation. We show that all four substances act specifically. At low concentrations, the head factors only influence head and not foot formation, and the foot factors only influence foot and not head formation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00848175
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  • 7
    Electronic Resource
    Electronic Resource
    Properties of the foot inhibitor from hydra (1980)
    Springer
    Development genes and evolution 188 (1980), S. 133-139 
    Details
    ISSN: 1432-041X
    Keywords: Hydra ; Morphogenetic substances ; Regeneration ; Pattern formation ; Sea anemones
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary A substance was isolated from crude extracts of hydra that inhibits foot regeneration. This substance, the foot inhibitor, has a molecular weight of ≦500 daltons. It is a hydrophilic molecule, slightly basic in character and it has no peptide bonds. The pruified substance acts specifically and at concentrations lower than 10−7 M. At this low concentration only foot and not head regeneration is inhibited. Hydra are sensitive to purified foot inhibitor between the second and eight hour after initiation of foot regeneration by cutting. In normal animals the foot inhibitor is most likely produced by nerve cells. A substance with similar biological and physico-chemical properties is found in other coelenterates.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00848805
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    Paper (German National Licenses)
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