Surface localization of an endogenous lectin in rabbit bone marrow

Topographical mapping of GnRH receptors on dispersed mouse pituitary cells by backscattered electron imaging

Mouse anterior pituitary cells cultured for 2 days were stimulated with one of three biotinylated-GnRH probes ([biotinyl-Lys6]-[D-Lys6]GnRH, [biotinyl-Ser4]-[D-Lys6]GnRH, [biotinyl-Ser4]-[D-Trp6, des-Gly10]GnRH) in the cold (4 degrees C) for 1 hr. These cells were subsequently fixed and an avidin-gold complex was conjugated to the bound GnRH. After a second fixation, the gold label was silver-enhanced for viewing with a scanning electron microscope. Gonadotropes were identified as a result of the labeling procedure, measured for size, and the number of GnRH receptor sites counted. Gonadotropes ranged from 3 to 13 microns in diameter and contained from 23.2 +/- 3.3 to 338.4 +/- 25.2 sites per cell depending upon the size of the cell and the ligand employed. The methods described should be applicable for studying the topographical distribution of a variety of cellular receptors.

Ultrastructural localization of peanut lectin binding to extravascular white blood cells in the bone marrow of embryonic chicks

Labelling by the galactose-specific lectin peanut agglutinin was studied in bone marrow of the embryonic chick at the electron-microscopic level by use of both a gold-conjugated lectin and an indirect, ferritin-conjugated, biotinylated lectin. Cell surface labelling is exclusively restricted to developing and mature heterophilic granulocytes, monocyte/macrophages, mast cells/basophils, all of which appear to develop and reside in the extravascular spaces of the bone marrow. Resident small lymphocytes, which comprise a minor portion of the cell population, are also labelled. Erythroid cells and thrombocytic cells, which develop inside venous sinusoidal vessels, display no labelling. The latter cells, like extravascular leukocytes, contain surface galactosyl residues located in subterminal positions on cell surfaces, since they are labelled by the galactose-specific Ricinus communis agglutinin-I. It is postulated that terminal galactosyl residues might be involved in interactions between the surfaces of extravascular leukocytes and extracellular matrix and/or stromal cell surfaces.

Silver-enhanced colloidal gold probes as markers for scanning electron microscopy

Silver enlargement of small colloidal gold particles has been extensively used for the light microscopical visualization of gold probes. Very recently, a few investigators have employed physical developers in electron microscopy (both pre-embedding and on-grid staining methods). We now demonstrate that physical development of small colloidal gold particles advantageously can be exploited for labelling biological surfaces in scanning electron microscopy. This novel application of silver enhancement of colloidal gold particles is characterized by a high detection efficiency. Thus, specimens are labelled with small gold probes affording high immunocytochemical efficiency but being impossible to detect with the present scanning microscopes. These particles are subsequently scanning electronmicroscopically visualized by silver enhancement.