A method is described for the adsorption of selected macromolecules to colloidal gold which is then used as an electron dense marker for the indirect detection of specific cell surface molecules. Membrane bound concanavalin A, which binds specific sugars on horse. radish peroxidase, and wheat germ agglutinin, which binds specific sugars on ovomucoid are detected indirectly with gold labeled horseradish peroxidase and ovomucoid, respectively. Goat anti.human 1gM on blood lymphocytes is detected with gold labeled rabbit anti-goat IgG. In the preparation of colloidal gold labeled proteins, the problems of flocculation of colloidal gold by proteins and nonadsorption of proteins to colloidal gold, are solved through a combination of concentration of protein and pH variable adsorption isotherms, which allows one to determine the conditions for adsorption of proteins to colloidal gold. Adsorption is pH dependent, the pH conditions correlating with the isoelectric point(s) of the major protein fraction(s); adsorption is influenced by interfacial tension, solubility and by the electrical charge on the molecules. Colloidal gold is inexpensive and preparation of a useful label is rapid, reproducible and the results easily quantitated from electron micrographs.

By seven days of gestation, the yolk sac of the mouse has a sheet of mesoderm adjacent to the basement membrane separating it from the endodermal epithelium. Localized proliferations of this mesoderm produces thickened cellular regions which transform into the angioblastic cords; all of these developmental cells are attached by tight junctions and desmosomes. By eight and onehalf days, lumina appear within the angioblastic cords; the peripheral cells become attenuated and form endothelial cells which will line the primitive vessels while the more central cells become the primitive erythroblasts of the blood island.The process of vasculogenesis and lumenization occurs between eight and onehalf and nine days of gestation and has been correlated with the reduction of cellular junctions between angioblasts and fixed primitive erythroblasts, a loss of the visceral basement membrane and the formation of wide intercellular channels between endodermal epithelial cells. The primitive erythroblasts comprising the blood islands have abundant polysomes, sparse rough endoplasmic reticulum and possess coated vesicles and ferritin aggregates in their cytoplasm and coated invaginations of their plasma membrane. By nine days of gestation, the primitive erythroblasts lose their attachments and become free in the vitelline vessels. Mitochondria of the primitive and free erythroblasts are slightly enlarged and have lighter matrices than angioblasts and mesodermal cells. By 10 to 11 days of gestation, as differentiation proceeds, coated vesicles and invaginations become more numerous and the developing erythroblasts gradually decrease in both cell and nuclear size. Concomitant with these changes is the decrease in the number and size of the mitochondria, a decrease in polysomal numbers and an increase in hemoglobin and cytoplasmic density.The inter-and intracellular events that occur during the formation of the primitive blood vessels and erythrocytic precursors of the yolk sac have not been thoroughly documented from an ultrastructural standpoint. The developmental stages in the process of hemopoiesis occur rapidly with the undifferentiated cells undergoing irreversible specialization along distinct pathways. Submicroscopic analysis has the dual potential of determining the earliest morphological features which signal the initial steps of differentiation and illuminating the changes in structural and functional relationships that occur during subsequent maturation and specialization. Previous studies have dealt with such features as the cellular versus syncytial nature of the primitive angioblastic cords, how ANAT. REC., 170: 199-224. vascular lumen form and the developmental pathway and structural features of erythrocyte differentiation and maturation (Bloom, '38; Danchakoff, '16a,b; Haar, '70; Jones, '64; Kovach et al., '67; Maximow, '09, '24; Sorenson, '61). It is the purpose of this correlated phase and electron microscopic study to expand and clarify the early developmental processes involved in erythropoiesis and vas...

Since high-dose corticosteroid therapy appears to impair cellular defense mechanisms, this study examined its effect on human monocyte function. Fifteen normal volunteers were studied before and after a three-day course of prednisone therapy (50 mg every 12 hours for six doses). A transient period of monocytopenia occurred during the first few hours of therapy. Monocyte killing of Staphylococcus aureus was reduced in nine subjects from 5.6 plus or minus 0.2 (plus or minus S.E.) X 10-6 organisms before to 1.3 plus or minus 0.4 x 10-6 organisms at completion of therapy (p less than 0.01). Similary, killing of Candida tropicalis four subjects fell from 9.3 plus or minus 0.6 to 0.6 plus or minus 0.3 x 10-6 organisma (p less than 0.01). Bactericidal activity returned to normal levels 48 hours after the last dose of prednisone. These same monocyte preparations had normal or increased chemotactic response, phagocytic rate of cryptococci, hexosemonophosphate-shunt response to phagocytosis and ultrastructural characteristics. This impairment of bactericidal and fungicidal activity during prednisone therapy may contribute to the infectious complications seen in patients receiving comparable doses of corticosteroids.

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