Morphological changes in isolated lymphocytes during preparation for SEM: Freeze drying versus critical‐point drying

Abstract

A quantitative comparison of isolated lymphocytes prepared for SEM by the critical‐point drying (CPD) and freeze drying (FD) methods revealed that the mean cellular diameter dropped from 7.9 μm after fixation to a final diameter of 6.9 μm after FD, and to 5.7 μm after CPD. In addition to their larger sizes, FD lymphocytes were immediately distinguishable by their more complex surfaces, featuring wider microvilli which often emanated from ridges on the cell surface and branched extensively near their bases. The mean width of microvilli was 0.22 μm after FD and 0.12 μm after CPD. The number of microvilli per cell was essentially the same by the two methods. In view of these findings, a critical comparison of the CPD and FD methods using the particular cells or tissue to be investigated is an essential prelude to a rigorous SEM study.