The head and the foot inhibitor from hydra are not dowex artefacts

Abstract

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.

Methionine in pattern control of Hydra

“…Following application of gel permeation one active fraction was detected which antagonizes both head and foot regeneration [12,13,14]. A separation into a fraction which specifically antagonizes head regeneration and a fraction which specifically antagonizes foot regeneration [2,15] was in the following argued to be an artifact [14]. We have used a separation procedure based on a head regeneration assay.…”

“…Head regeneration was studied in budless animals one day after the last feeding [2,[12][13][14][15]. The animals were sectioned at about one half of the body length and the aboral (foot-bearing) fragments were studied.…”

“…In head-regenerating animals new tentacles became visible the following day. The ability of foot-regenerating animals to attach to a surface was used to test for the presence of a new foot [2,[12][13][14][15]. Animals regenerating a foot were transferred to new dishes with fresh culture medium (after one washing) 22 hours after sectioning and sampling from the dishes.…”

Actions of head activator and head inhibitor during regeneration in hydra

“…The fact that in head regenerating tissue the concentration of head inhibitor dropped to almost zero indicates that no component derived from the resin was present. A detailed discussion will be published elsewhere [21].…”

“…Addition of head inhibitor to the medium of regenerating animals reversibly blocks their development [3]. At low concentrations (-=lo-' M) it retards specifically head and not foot regeneration [21,25]. The head inhibitor also interferes with budding Within the animal, the head-specific substances are stored in a structure-bound form, probably in nerve cells [2, 231.…”