title: Use of colloidal gold and ruthenium red in stereo high-voltage electron microscopic study of Con A-binding sites in mouse macrophages.
abstract: Concanavalin A (Con A)-binding sites were labeled with colloidal gold (CG), stained with ruthenium red, and observed under a high-voltage electron microscope. Mouse peritoneal macrophages were labeled by the indirect Con A/CG labeling method at 0 degree C. After washing, some of the cells were incubated in phosphate-buffered saline (PBS) at 37 degrees C. The specimens were then stained with ruthenium red, to enhance the contrast of the cell surface, and embedded in Epon. Sections (0.3 approximately 3 micron thick) were cut and examined by high-voltage electron microscopy at accelerating voltages of 200 approximately 1,000 kV. Staining with ruthenium red provided a strong contrast of the cell surface and the invaginating tubules beneath it against the cytoplasm; in thick sections, both of them were clearly seen by stereomicroscopy. CG particles which represented Con A-binding sites were also sufficiently electron dense to be recognized by high-voltage electron microscopy of thick sections. The two- and three-dimensional distribution of CG particles on the ruthenium-red-positive cell surface was clearly visualized. At 0 degree C, Con A-binding sites were randomly distributed on the cell surface. The redistribution and endocytosis of Con A-binding sites were seen at 37 degrees C. The three-dimensional organization of membrane invagination, which represented the process of endocytosis, was clearly seen by stereomicroscopy. The combination of CG labeling and ruthenium red staining is a useful method for high-voltage electron microscopic analysis of the two- and three-dimensional distribution of CG-labeled ligands on the cell surface in thick sections.
mesh_terms: D000818:Animals; D002462:Cell Membrane / Q000276:immunology / Q000648:ultrastructure; D003208:Concanavalin A; D006046:Gold; D006651:Histocytochemistry; D008024:Ligands; D008264:Macrophages / Q000276:immunology* / Q000648:ultrastructure; D008297:Male; D051379:Mice; D051381:Rats; D011919:Rats, Inbred Strains; D011952:Receptors, Concanavalin A / Q000378:metabolism*; D012430:Ruthenium Red
chemical_list: D008024:Ligands; D011952:Receptors, Concanavalin A; D003208:Concanavalin A; D012430:Ruthenium Red; D006046:Gold