title: Role of intestinal mucus in crystal biogenesis: an electron-microscopical, diffraction and X-ray microanalytical study.
abstract: In the posterior intestine of the sea-water eel, mucus plays an important role in biocrystallization of calcium ions. By means of transmission and scanning electron microscopy associated with X-ray microanalysis and X-ray diffraction it has been possible to determine the role of mucous fibers as nucleation sites. Biocrystallization occurs in 2 steps: (1) Calcification of mucus. As soon as mucus is excreted in the intestinal lumen, it is loaded with calcium, as shown by lanthanum affinity and X-ray microanalysis on freeze-dried tissues. (2) Genesis of crystals. Needle-shaped crystallites build up in coalescent spherites in the intestinal lumen near the microvilli. Genesis occurs as follows: (a) crystallite mineralization by nucleation in an organic matrix composed of glycoproteinaceous mucous fibers, followed by the appearance of spherites; (b) coalescence in spherites and association of spherites in rhombohedra; (c) extrusion of organic material during the final step of crystallization.
authors.affiliation: Université Louis Pasteur, Laboratoire de Zoologie, CNRS URA 226, Strasbourg, France.
authors.forename: W
authors.initials: W
authors.lastname: Humbert
authors.forename: J C
authors.initials: JC
authors.lastname: Voegel
authors.forename: R
authors.initials: R
authors.lastname: Kirsch
authors.forename: V
authors.initials: V
authors.lastname: Simonneaux
mesh_terms: D000818:Animals; D002118:Calcium / Q000378:metabolism*; D002119:Calcium Carbonate / Q000096:biosynthesis*; D003460:Crystallization; D004524:Eels / Q000378:metabolism*; D004577:Electron Probe Microanalysis; D007413:Intestinal Mucosa / Q000378:metabolism*; D007422:Intestines / Q000648:ultrastructure; D009093:Mucus / Q000378:metabolism*
chemical_list: D002119:Calcium Carbonate; D002118:Calcium