Host/symbiont specificity has been investigated in non-symbiotic and aposymbiotic brown and green hydra infected with various free-living and symbiotic species and strains of Chlorella and Chlorococcum. Morphology and ultrastructure of the symbioses obtained have been compared. Aposymbiotic Swiss Hydra viridis and Japanese H. magnipapillata served as controls. In two strains of H. attenuata sta...

This slim monograph contains the author's research observations on the Hydra and a review of the work of other investigators. It presents a brief historical account of early work on the Hydra, particularly that of Trembley, followed by a brief description of the anatomy and physiology based on light microscopy, and a short account of the growth and regenerative capacities of the Hydra. The seco...

This paper presents a multipurpose system for wordnet (WN) development, named Hydra. Hydra is an application for data editing and validation, as well as for data retrieval and synchronization between wordnets for different languages. The use of modal language for wordnet, the representation of wordnet as a relational database and the concurrent access are among its main advantages (Rizov, 2006).

This paper presents an overview of the software for wordnet processing Hydra. The system has fully-fledged GUI and API, both working with powerful modal query language. Hydra has been used for the development of the Bulgarian WordNet for the last 7 years and recently was improved, became open source and is distributed as part of the Meta-Share platform.

Adult stem cells face the challenge of maintaining tissue homeostasis by self-renewal while maintaining their proliferation potential over the lifetime of an organism. Continuous proliferation can cause genotoxic/metabolic stress that can compromise the genomic integrity of stem cells. To prevent stem cell exhaustion, highly proliferative adult tissues maintain a pool of quiescent stem cells th...

Regardless of the source or mission, the analysis of astrophysical data invariably relies on the interplay between predictive physical models, a detailed understanding of the observing instruments, and the discriminating comparison of predictions and actual observations. With HYDRA, we are developing a new platform which will provide scientists a more flexible and extensible way of constructing...

As a member of the phylum Cnidaria, the sister group to all bilaterians, Hydra can shed light on fundamental biological processes shared among multicellular animals. Hydra is used as a model for the study of regeneration, pattern formation, and stem cells. However, research efforts have been hampered by lack of a reliable method for gene perturbations to study molecular function. The developmen...

Hydra and its fellow cnidarians - sea anemones, corals and jellyfish - are simple, mostly sessile animals that depend on bioactive chemicals for survival. In this review, we briefly describe what is known about the chemical armament of Hydra, and detail future research directions where Hydra can help illuminate major questions in chemical ecology, pharmacology, developmental biology and evoluti...

Hydra is a unique model for studying the mechanisms underlying stem cell biology. The activity of the three stem cell lineages structuring its body constantly replenishes mature cells lost due to normal tissue turnover. By a poorly understood mechanism, stem cells are maintained through self-renewal while concomitantly producing differentiated progeny. In vertebrates, one of many genes that par...

Hydra tissue consists of the ectodermal and the endodermal layers. When the two layers were separated by procaine treatment and then recombined, the ectodermal epithelial cells spread as a single cell layer over the endoderm as in epiboly in vertebrate embryogenesis, and the resultant spherical structure subsequently regenerated into a complete hydra. In this study, light and electron microscop...