H. Chica Schaller

A new biochemical marker for foot-specific cell differentiation in hydra

SummaryMucous cells in the basal disk of hydra contain a peroxidase-like enzyme allowing specific staining of these cells with substrates for peroxidases. The peroxidase activity provides an excellent marker for foot mucous cell, differentiation and was used to follow the reappearance of footspecific cells during foot regeneration after amputation. By choosing the appropriate either soluble or precipitable substrate the peroxidase reaction was used both for a qualitative and for a quantitative evaluation of foot-specific differentiation in hydra. For histological studies diaminobenzidien was found to be a suitable substrate which forms a dark brown precipitate within the cells containing the peroxidase activity. For a quantitative evaluation of foot regeneration the soluble substrate 2,2-azino-di(3-ethyl-benzthiazoline-sulfonic acid-6) ammonium salt was used which after reaction with the enzyme gives rise to a diffusible green reaction product the concentration of which can be measured by its specific absorption at 415 nm. Based on the diffusible enzyme product a new quantitative assay for foot regenration was developed and applied to confirm the effect and specificity of morphogenetic substances which either inhibit or activate foot or head regeneration in hydra.

The Hydra head activator in human blood circulation: Degradation of the synthetic peptide by plasma angiotensin-converting enzyme

Hydra head activator Radioimmunoassay Human plasma HPLC Neuropeptide Angiotensin‐converting enzyme

Head activator controls head formation in reaggregated cells of hydra

Abstract The head forming potential of reaggregated cells from gastric regions of hydra can be increased either by adding cells with a high head-activator content or by incubating animals or cells with purified head activator. This is further evidence that the head activator is one of the morphogens responsible for head formation in hydra.

Analysis of morphogenetic mutants of hydra

The mutantreg-16 is deficient in head regeneration and abnormal in size regulation. The gastric region becomes twice as long as that of normal animals before the first bud is produced. Both mutant characteristics are due to changes in head-specific morphogen concentrations.Reg-16 contains twice as much head inhibitor and only half as much head activator in its head as normal animals. This leads to a higher level of free head inhibitor in the whole animal resulting on one hand in a greater distance of buds from the head, and on the other hand in a total blockage of release of head activator and head inhibitor which would be necessary to initiate head regeneration.

Morphogene substanzen ausHydra

We use hydra as a model system to understand how growth and differentiation and, as a consequence of this, pattern formation are controlled at the molecular level. We have found that four substances control head and foot formation in hydra: an activator and an inhibitor of head formation and an activator and an inhibitor of foot formation. The two activators are peptides with molecular weights around 1000 daltons, the inhibitors are smaller in molecular weight (<500), have an overall positive charge and do not contain peptide bonds. In normal animals all four substances are present and most likely produced by nerve cells. We hope to understand how these substances act and interact to create the spatial and temporal pattern of growth and differentiation typical for hydra.

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

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 Berkings inhibitor, have different specificities for head and foot regeneration. In addition, I would like to show that none of our substances are Dowex artefacts.SummaryIn 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 Berkings inhibitor, have different specificities for head and foot regeneration. In addition, I would like to show that none of our substances are Dowex artefacts.

Structure and Function of the Head Activator in Hydra and in Mammals

Publisher Summary This chapter focuses on the structure and function of the head activator (HA) in hydra and in mammals. In normal hydra, the HA is produced by nerve cells. Within the nerve cells, HA is stored in neurosecretory granules. The chapter discusses the effects of the HA on cellular growth and differentiation in hydra. The HA is also present in other animals, such as artemia, drosophila, frogs, and mammals. In the mammalian system, the HA occurs in three main locations—the hypothalamus, the retina, and the gastrointestinal tract. It is also present in smaller amounts in the other parts of the neuronal, neuroendocrine, or paracrine system. The HA occurs also in body fluids, such as the blood and cerebrospinal fluid, and in tumors or tumor cell lines predominantly of neuronal or endocrine origin. The physiological role of this peptide in mammals is that (1) it is involved as a modulator of brain function possibly as an information intermediary between hypothalamus and hypophysis, (2) it is involved in digestion control processes as indicated by elevated levels in the blood after a meal and by its stimulatory effect on pancreas secretion, and (3) as a possible growth-promoting agent in autocrine control processes.