title: Ca2+-dependent deposits at the plasmalemma of Chara internodal cells.
abstract: Electron dense deposits (EDD) were observed on the extracellular side of the plasmalemma of Chara internodal cells by a calcium-glutaraldehyde fixation technique. The number and size of EDD were greatly increased when cells had been preincubated in Ca2+-enriched medium before fixation. The addition of Na+, Mg2+, or La3+ instead of Ca2+ in incubation and fixation media produced no deposits at all, Sr2+ caused deposits with similar distribution to those formed by Ca2+, and Ba2+ addition resulted in deposits localized at different sites within the cell. Microprobe analysis of single EDD from Ca2+ incubated cells ascertained the presence of calcium in these deposits. Possible functions of the Ca2+-binding sites at the plasma membrane of Chara cells are discussed.
mesh_terms: D002118:Calcium / Q000378:metabolism*; D002462:Cell Membrane / Q000378:metabolism; D056890:Eukaryota / Q000378:metabolism*; D006651:Histocytochemistry
chemical_list: D002118:Calcium