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Updated: Aug 13, 2026

Generation of Transgenic Hydra by Embryo Microinjection
Published on: September 11, 2014
The head activator is released from regenerating Hydra bound to a carrier molecule
H C Schaller1, M Roberge, B Zachmann
1ZMBH, Zentrum für Molekulare Biologie, Im Neuenheimer Feld 282, 6900 Heidelberg, FRG.
Abstract:
Hydra forced to regenerate a head releases head activator and head inhibitor during the first hours after cutting to induce head-specific growth and differentiation processes. Analysis of the size distribution demonstrated that the head-activator peptide is co-released with (a) large molecular weight carrier molecule(s) to which it is non-covalently bound. The carrier-bound head activator is fully active on Hydra indicating that a carrier does not hinder the interaction with receptors. In contrast to this the head inhibitor is released in its naked, low molecular mass form. The association or non-association with a carrier molecule results in marked differences in biological properties. The head activator has a short range of action, but a long half-life, the head inhibitor has a global range of action, but a short half-life. These results provide a plausible explanation why two antagonistically acting substances, although they are released from the same site and simultaneously nevertheless can give rise to a well-defined temporal and spatial pattern of differentiation as occurs, for example, during head regeneration in Hydra.
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