Biomaterial Database

Ultrastructural analysis of nematocyte removal in Hydra. 1982

M K Lyon, and G Kass-Simon, and L A Hufnagel

A consecutive series of ultrathin sections through the distal one-third of a Hydra tentacle has revealed at least four categories of nematocytes: (1) normal, mounted nematocytes, in specific arrangements within the battery cells; (2) degenerating nematocytes, within the battery cells; (3) mature nematocytes, enclosed within endodermal cells: (4) a mature nematocyte, in the enteric cavity. The degenerating nematocytes within the battery cells and the nematocytes in the endoderm and enteric cavity appeared to be aging nematocytes undergoing death and removal. The results provide the first ultrastructural evidence for nematocyte degeneration within battery cells and also suggest phagocytosis of mature nematocytes by endodermal cells.

UI	MeSH Term	Description	Entries
D007365	Intercellular Junctions	Direct contact of a cell with a neighboring cell. Most such junctions are too small to be resolved by light microscopy, but they can be visualized by conventional or freeze-fracture electron microscopy, both of which show that the interacting CELL MEMBRANE and often the underlying CYTOPLASM and the intervening EXTRACELLULAR SPACE are highly specialized in these regions. (From Alberts et al., Molecular Biology of the Cell, 2d ed, p792)	Cell Junctions,Cell Junction,Intercellular Junction,Junction, Cell,Junction, Intercellular,Junctions, Cell,Junctions, Intercellular
D008854	Microscopy, Electron	Microscopy using an electron beam, instead of light, to visualize the sample, thereby allowing much greater magnification. The interactions of ELECTRONS with specimens are used to provide information about the fine structure of that specimen. In TRANSMISSION ELECTRON MICROSCOPY the reactions of the electrons that are transmitted through the specimen are imaged. In SCANNING ELECTRON MICROSCOPY an electron beam falls at a non-normal angle on the specimen and the image is derived from the reactions occurring above the plane of the specimen.	Electron Microscopy
D010587	Phagocytosis	The engulfing and degradation of microorganisms; other cells that are dead, dying, or pathogenic; and foreign particles by phagocytic cells (PHAGOCYTES).	Phagocytoses
D002470	Cell Survival	The span of viability of a cell characterized by the capacity to perform certain functions such as metabolism, growth, reproduction, some form of responsiveness, and adaptability.	Cell Viability,Cell Viabilities,Survival, Cell,Viabilities, Cell,Viability, Cell
D004707	Endoderm	The inner of the three germ layers of an embryo.	Definitive Endoderm,Definitive Endoderms,Endoderm, Definitive,Endoderms
D006829	Hydra	A genus of freshwater polyps in the family Hydridae, order Hydroida, class HYDROZOA. They are of special interest because of their complex organization and because their adult organization corresponds roughly to the gastrula of higher animals.	Hydras
D000818	Animals	Unicellular or multicellular, heterotrophic organisms, that have sensation and the power of voluntary movement. Under the older five kingdom paradigm, Animalia was one of the kingdoms. Under the modern three domain model, Animalia represents one of the many groups in the domain EUKARYOTA.	Animal,Metazoa,Animalia