Fibrinogen internalization by ADP-stimulated blood platelets. Ultrastructural studies with fibrinogen-colloidal gold probes.

Interaction of gel filtered, ADP-stimulated human platelets with low (0.05 mg/ml) and high (1 mg/ml) fibrinogen (Fg) was examined by transmission electron microscopy. To visualize exogenous Fg in a course of its interaction with stimulated platelets, Fg coupled to 18-nm colloidal gold (Fg-Au) was employed.

Fibrinogen-containing membrane-associated structures arising at the surfaces of ADP-stimulated blood platelets.

Ultrastructural studies of ADP-stimulated gel-filtered human platelets incubated with different concentrations of fibrinogen reveal unusual extracellular structures composed at least partly of the aggregated fibrinogen. Development of these structures depends on the exogenous fibrinogen concentration and duration of the incubation. Fibrinogen-containing extracellular material exists in two different structural forms.

Interaction of positively charged liposomes with erythrocyte membrane. An ultrastructural study.

Structural perturbations of positively charged sonicated liposomes (L) induced by incubation with human erythrocytes have been studied by thin-section electron microscopy. It has been found that just after mixing with cells L bind to cell surfaces and fuse with each other, first forming larger L and then flattened multilamellar structures. Successive fusion events occurring in the latter result in a reduced number of bilayers which gradually comes to a single one.