Strategy and tactics in electron microscopy of cell surfaces

Over the past decade new methods have been developed to visualize both the external and the protoplasmic surfaces of cultured cells in the electron microscope. In this review the emphasis is on cell monolayers, though some of the techniques are also applicable to cells in suspension.

There is no universal method which would satisfy all our requirements i.e. the preservation of native structure and antigenicity and the visualization of the whole cell surface at high resolution. While surface replicas of freeze-dried or critical point-dried cells are eminently suited for high resolution studies including gold immunolabelling, scanning electron microscopy provides a view of the whole cell and a large sample for ‘statistical’ evaluation. Whole mount preparations of cleaved cells prove useful in studies of plasma membrane associated structures such as the cytoskeleton.

A series of new procedures have been developed for studies of cytoskeleton/membrane interactions, identification of intramembrane particles and their contacts with the glycocalyx, to mention some of the biological problems. Although the lysis-squirting technique appears most suitable for the visualization and immunolabelling of protoplasmic surfaces of ventral membranes, dry- or wet-cleaving represent a useful alternative for studies of the protoplasmic surfaces of dorsal membranes and of the ventral membrane associated cytoplasmic domains.

An assessment of the methods is given though this should only serve as guidance and it is up to the experimentor to choose the most useful technique for the project under study. Briefly the aim of the project determines the choice of the method. A multi-methodical approach is recommended when one method does not provide satisfactory results.