JOURNAL ARTICLE

Positional Information and Positional Signalling in Hydra

Lewis WolpertAmata HornbruchMairi Clarke

Year: 1974 Journal:   American Zoologist Vol: 14 (2)Pages: 647-663   Publisher: Oxford University Press

Abstract

A model is proposed for regulation and regeneration of the head end of hydra in terms of positional information, which involves two gradients. One is a diffusible substance made at the head end, which may be regarded as a positional signal. The other is a more stable cellular parameter which is the positional value. The rule for head end formation is that the concentration of the diffusible substance falls a threshold amount below the positional value. This model, for which some computer simulation is provided, can account for head end formation in a wide variety of grafts. Evidence for a diffusable signal is provided by experiments in which the time/distance relationships for head inhibition by a grafted head are determined. Changes in positional value during regulation have been assayed and are much slower away from the boundary. Polarity is interpreted in terms of the interaction between the two gradients. The biochemical basis of the gradients is not known, but an approach to the problem has been made by treating hydra with a variety of chemical agents.

Keywords:
Lernaean Hydra Head (geology) Polarity (international relations) SIGNAL (programming language) Biological system Variety (cybernetics) Value (mathematics) Computer science Neuroscience Biology Artificial intelligence Cell biology Biochemistry Cell

Metrics

109
Cited By
13.24
FWCI (Field Weighted Citation Impact)
14
Refs
1.00
Citation Normalized Percentile
Is in top 1%
Is in top 10%

Citation History

Topics

Marine Invertebrate Physiology and Ecology
Physical Sciences →  Earth and Planetary Sciences →  Paleontology
Planarian Biology and Electrostimulation
Life Sciences →  Biochemistry, Genetics and Molecular Biology →  Molecular Biology
Developmental Biology and Gene Regulation
Life Sciences →  Biochemistry, Genetics and Molecular Biology →  Molecular Biology

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