title: Electron microscopic characterization of calcium-binding physodes in the green alga Mougeotia scalaris.
abstract: Effect of the covalently cross-linking agents glutardialdehyde and osmium tetroxide, and of adsorption of the vital dye, neutral red, to the matrix of the calcium-binding "vesicles" from the green alga Mougeotia scalaris has been analysed in situ, both in terms of structural preservation and of the calcium-binding capacity of the vesicles. Upon cell fixation in glutardialdehyde without OsO4, the vesicles appear to dissolve, but upon simultaneous fixation in glutardialdehyde with OsO4 (1% w/v), the vesicles retain a globular form, are evenly stained by osmium and appear to be surrounded by a membrane-like structure. This structure was also observed around the vesicles in cells preincubated for 10 min in 0.1 mM neutral red and then fixed in glutardialdehyde/OsO4 for 1 h. More detailed information of the matrix structure is obtained when simultaneous fixation of the Mougeotia cells was shortened to 15 min: a membrane-like structure was no longer observed around the vesicles. After cell treatment in the presence of neutral red, no calcium at all was found inside the vesicles. A small amount of calcium remained, when cells were fixed simultaneously and extensively in the absence of neutral red. However, calcium was found, to a considerable extent, inside the vesicles after short simultaneous fixation of the cells in the absence of neutral red. Based on the ultrastructural and elemental features presented here, the calcium-binding vesicles in Mougeotia appear to represent a member of the large family of (calcium-binding) physodes in lower plants (CaBP).
authors.affiliation: Nicolaus Copernicus University, Institute of Biology, Torun, Poland.
authors.forename: A
authors.initials: A
authors.lastname: Tretyn
authors.forename: F
authors.initials: F
authors.lastname: Grolig
authors.forename: G
authors.initials: G
authors.lastname: Magdowski
authors.forename: G
authors.initials: G
authors.lastname: Wagner
mesh_terms: D002118:Calcium / Q000378:metabolism*; D000460:Chlorophyta / Q000378:metabolism / Q000648:ultrastructure*; D004577:Electron Probe Microanalysis; D005404:Fixatives; D005976:Glutaral / Q000494:pharmacology; D008566:Membranes / Q000648:ultrastructure; D008854:Microscopy, Electron; D009499:Neutral Red; D009993:Osmium Tetroxide / Q000494:pharmacology
chemical_list: D005404:Fixatives; D009499:Neutral Red; D009993:Osmium Tetroxide; D002118:Calcium; D005976:Glutaral