The relationship of a fluid membrane structure to cell agglutination and surface topography.

The external barrier af the platelet or any type af cell is .the plasma membrane and associated structures; this is the important site for cell-cell interactian leading to' adhesian and other cell surface phenomena. Some knawledge af the structure and arganizatian af bialagical membranes and particularly the structure and arganization af platelet membranes is required to' understand cell-cell interactians such as platelet adhesian. In recent years it has became apparent that classical formulatians of membrane structure such as the Danielli-Davson Model (13) or Unit Membrane Model (52) do not take intO' accaunt the variety of experimental data an thermodynamic (58), spectroscapic (31, 68, 19, 66), enzymatic (57, 71, 60), paramagnetic resanance (24, 30, 29), X-ray (17, 4, 70), freeze-etch and other electron microscopic evidence (48, 63, 64, 45) and protein structural characterization (53, 33, 56) of biological membranes. Furthermore, recent data suggests that mast biolagical membranes are in a fluid state under physiological conditions where mast components are mabile in the plane of the membrane (18, 62, 14, 16, 65). I will discuss some general aspects of cell membrane structure and organization, and present some experimental examples of cellular control of surface tapography and specific versus non-specific cell-cell interaction. Finally, in keeping with the goals af this canference, an attempt will be made