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  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Development genes and evolution 183 (1977), S. 207-214 
    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
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Development genes and evolution 186 (1979), S. 139-149 
    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
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  • 3
    Electronic Resource
    Electronic Resource
    Springer
    Development genes and evolution 188 (1980), S. 133-139 
    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
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  • 4
    Electronic Resource
    Electronic Resource
    Springer
    Development genes and evolution 193 (1984), S. 117-118 
    ISSN: 1432-041X
    Keywords: Hydra ; Regeneration ; Head inhibitor ; Foot inhibitor
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary In a recent publication in this journal (Berking 1983) it was claimed (1) that the head inhibitor we isolated from hydra is a Dowex artefact, (2) that a separate foot inhibitor does not exist in hydra and (3) that the only inhibitor that has so far been isolated from hydra is one which inhibits head and foot regeneration equally well. These statements are incorrect and require a response. In the following, I would like to summarise our evidence that the inhibitors isolated from hydra, including Berking's inhibitor, have different specificities for head and foot regeneration. In addition, I would like to show that none of our substances are Dowex artefacts.
    Type of Medium: Electronic Resource
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