Monoclonal Antibodies againstAntigens of Hydra vulgaris and Hydra oligactis

The goal of the study was to obtain a panel of monoclonal antibodies (MAb) against antigens of freshwater polyps of the genus Hydra. Hybrid mice F₁(Balb/c × SJL/J) were immunized with cell membrane fraction of H. vulgaris and three months later their splenocytes were fused with cultured mouse myeloma cells 653A. Testing of culture fluids in ELISA with immobilized H. vulgaris cells, 82 hybridomas producing MAb were revealed. Study of MAb specificity in ELISA with H. vulgaris and H. oligactis cells indicated that 22% of them recognized only H. vulgaris antigens. About 50% of MAb recognized equally antigens of the both species. The rest of MAb reacted with H. vulgaris and H. oligactis antigens to different degree. Eight hybridomas producing MAb of all three above groups were adapted for growth as ascitic tumors. The distribution of antigens binding these MAb was studied in indirect immunofluorescence on fixed polyps, living or fixed cells, and on paraffin- embedded sections. Among the best studied MAb, of the greatest interest were the following reagents. One of them (1A10) revealed an antigen on surface membranes of ectodermal epithelial cells of H. vulgaris. The second one (1G10) was specific of the antigen located in mesoglea and basal cytoplasmic areas of ectodermal and entodermal epithelial cells of the both hydra species. The MAb 4G3 interacted with cytoplasmic antigen of ectodermal epithelia-muscular cells of the both hydra species. MAb 4H1 revealed nematocytes in H. vulgaris and H. oligactis. The data obtained indicate that in two species of hydra the epitopes binding the same MAb might be located in cells of different types.     

Proportioning a Hydra

SYNOPSIS. Pieces of hydra tissue of various sizes and shapeswere cut from the body columns of adult hydra and allowed toregenerate. The proportions of the resulting animals were determinedfirst by counting cells in the head and body, and secondly bymeasuring the structures directly using an ocular micrometer. Head-body proportions were found to be constant over a tenfoldsize range. Very small regenerates had a larger head fractionand large budding regenerates had a smaller head fraction. Extrastructures developed in certain shape pieces, but total head-bodytissue remained proportional. More detailed measurement of thehead showed that the hypostome regulated only slightly withtotal size change, while the tentacle tissue varied considerablyto maintain the head-body ratio. This suggested that the patterningof the hypostome and the tentacles might involve separate processes,with the latter being responsible for proportion regulation.While the body mass appeared to be determined by the proportioningmechanism, its circumference was related to the circumferenceof the hypostome, suggesting a causal relationship between thetwo organizers and the column shaping. The basal disc remainedproportional to the body except in the smallest pieces. A Gierer-Meinhardtpattern formation scheme could account for the results found.     

The Hydra Model System

The freshwater Hydra polyp emerged as a model system in 1741 when Abraham Trembley not only discovered its amazing regenerative potential, but also demonstrated that experimental manipulations pave the way to research in biology. Since then, Hydra flourished as a potent and fruitful model system to help answer questions linked to cell and developmental biology, as such as the setting up of an organizer to regenerate a complex missing structure, the establishment and maintainance of polarity in a multicellular organism, the development of mathematical models to explain the robust developmental rules observed in this animal, the maintainance of stemness and multipotency in a highly dynamic environment, the plasticity of differentiated cells, to name but a few. However the Hydra model system is not restricted to cell and developmental biology; during the past 270 years it has also been heavily used to investigate the relationships between Hydra and its environment, opening new horizons concerning neurophysiology, innate immunity, ecosystems, ecotoxicology, symbiosis...     

Peptide signaling in Hydra

Peptides play a number of crucial roles as signaling molecules in metazoans. In order to elaborate a more complete picture of the roles played by peptides in a single organism, we launched the "Hydra Peptide Project". For this project, we used Hydra magnipapillata, a species belonging to Cnidaria, one of the most basal metazoan phyla, and using a peptidomic approach, we systematically identified a number of peptide signaling molecules, their encoding genes and their functions. In this article, we report the peptides isolated from Hydra and other cnidarians, as well as their synthesis, processing and release from the cells to the target. Possible peptide signaling pathways are overviewed and finally we discuss the evolution of the peptide signaling system.     

Positional Signalling along Hydra

Experiments on head grafting and regeneration in Hydra have been used to show quantitatively that diffusion of a morphogen is a plausible basis for the control of differentiation.     

Zytologische Studien an Hydra

Ohne Zusammenfassung     

Proteome of Hydra nematocyst

Stinging cells or nematocytes of jellyfish and other cnidarians represent one of the most poisonous and sophisticated cellular inventions in animal evolution. This ancient cell type is unique in containing a giant secretory vesicle derived from the Golgi apparatus. The organelle structure within the vesicle comprises an elastically stretched capsule (nematocyst) to which a long tubule is attached. During exocytosis, the barbed part of the tubule is accelerated with >5 million g in <700 ns, enabling a harpoon-like discharge (Nüchter, T., Benoit, M., Engel, U., Ozbek, S., and Holstein, T. W. (2006) Curr. Biol. 16, R316-R318). Hitherto, the molecular components responsible for the organelle's biomechanical properties were largely unknown. Here, we describe the proteome of nematocysts from the freshwater polyp Hydra magnipapillata. Our analysis revealed an unexpectedly complex secretome of 410 proteins with venomous and lytic but also adhesive or fibrous properties. In particular, the insoluble fraction of the nematocyst represents a functional extracellular matrix structure of collagenous and elastic nature. This finding suggests an evolutionary scenario in which exocytic vesicles harboring a venomous secretome assembled a sophisticated predatory structure from extracellular matrix motif proteins.     

Axial Patterning in Hydra

Morphogen gradients play an important role in pattern formation during early stages of embryonic development in many bilaterians. In an adult hydra, axial patterning processes are constantly active because of the tissue dynamics in the adult. These processes include an organizer region in the head, which continuously produces and transmits two signals that are distributed in gradients down the body column. One signal sets up and maintains the head activation gradient, which is a morphogenetic gradient. This gradient confers the capacity of head formation on tissue of the body column, which takes place during bud formation, hydra''s mode of asexual reproduction, as well as during head regeneration following bisection of the animal anywhere along the body column. The other signal sets up the head inhibition gradient, which prevents head formation, thereby restricting bud formation to the lower part of the body column in an adult hydra. Little is known about the molecular basis of the two gradients. In contrast, the canonical Wnt pathway plays a central role in setting up and maintaining the head organizer.Morphogen gradients play a critical role in the early stages of embryogenesis in a number of metazoans in that they initiate and are involved in axial patterning processes. Such a gradient also plays a role in axial patterning in hydra, a primitive metazoan. However, unlike in most metazoans, this gradient is continuously active in an adult hydra as part of the tissue dynamics of the adult animal.The structure of a hydra is fairly simple (Fig. ​(Fig.1).1). It consists of a single axis with radial symmetry, which contains a head, body column, and foot along the axis. The head consist of two parts: the hypostome in the apex, and the tentacle zone from which the tentacles emerge in the basal part of the head. The body column has three parts: the gastric region and peduncle in the apical, and basal parts with a budding zone between the gastric region and peduncle. Buds, hydra''s mode of asexual reproduction, emerge from the budding zone between the gastric region and peduncle.Open in a separate windowFigure 1.Longitudinal cross section of an adult hydra. The multiple regions are labeled. The two protrusions from the body column are early and late stages of bud development. The arrows indicate the direction of tissue displacement. (Reprinted from Bode 2001.)Three cell lineages are involved. The axis consists of a cylindrical shell that is made up of two concentric epithelial layers, the ectoderm and endoderm, which are separated by a basement membrane. Interspersed among the epithelial cells of both layers are the cells of the third lineage, the interstitial cell lineage. It consists of interstitial cells, which are multipotent stem cells (David and Murphy 1977), located primarily in the ectoderm throughout the body column. They give rise to neurons, secretory cells, and nematocytes, which are the stinging cells that are typical of cnidarians, as well as gametes when a hydra undergoes sexual reproduction (David and Murphy 1977).In an adult hydra, the epithelial cells of both layers are constantly in the mitotic cycle (David and Campbell 1972; Campbell and David 1974). The expanding tissue in the upper part of the body column is continuously displaced apically into the head (Fig. 1). Once there, it is displaced onto and along the tentacles or into the hypostome, and eventually sloughed when reaching the extremities (Campbell 1967; Otto and Campbell 1977). Tissue in the remainder of the body column is displaced basally either onto developing buds, or further down onto the foot, where it is sloughed at the bottom of the foot. Thus, the tissues of an adult hydra are continuously in a steady state of production and loss. As a hydra has no defined lifetime (Martinez 1998), this activity goes on indefinitely.     

水螅的有性生殖

介绍了水螅的有性生殖,包括精卵发生,受精和胚胎发育,并讨论了杂交受精在水螅分类问题上的意义。     

The head organizer in Hydra

Organizers and organizing centers play critical roles in axis formation and patterning during the early stages of embryogenesis in many bilaterians. The presence and activity of an organizer was first described in adult Hydra about 100 years ago, and in the following decades organizer regions were identified in a number of bilaterian embryos. In an adult Hydra, the cells of the body column are constantly in the mitotic cycle resulting in continuous displacement of the tissue to the extremities where it is sloughed. In this context, the head organizer located in the hypostome is continuously active sending out signals to maintain the structure and morphology of the head, body column and foot of the animal. The molecular basis of the head organizer involves the canonical Wnt pathway, which acts in a self-renewing manner to maintain itself in the context of the tissue dynamics of Hydra. During bud formation, Hydra's mode of asexual reproduction, a head organizer based on the canonical Wnt pathway is set up to initiate and control the development of a new Hydra. As this pathway plays a central role in vertebrate embryonic organizers, its presence and activity in Hydra indicate that the molecular basis of the organizer arose early in metazoan evolution.     

gamma-Glutamyl transpeptidase in Hydra.

γ-Glutamyl transpeptidase (EC 2.3.2.2) activity is described in the coelenterate, $\text{Hydra}$$\text{attenuata}$, using the substrate γ-glutamyl-p-nitroanilide. The properties of the γ-glutamyl donor required for binding to the transpeptidase were investigated by measuring the ability of GSH analogs to inhibit the release of p-nitroaniline. Whereas no binding was observed when the γ-glutamyl moiety was altered, analogs with substitution in the Cys residue were capable of binding to the enzyme. A specificity for the Gly residue was indicated because analogs containing Leu or Tyr in place of Gly exhibited decreased binding capacities for the hydra transpeptidase. A comparison of these data with those obtained using the same analogs in the GSH induced feeding response bioassay shows that γ-glutamyl transpeptidase activity and the GSH receptor for the hydra feeding response have different specificities.     

Über Sauerstoffempfindlichkeit bei Hydra

Ohne Zusammenfassung