Fig. 9. Immunofluorescence of the cytoskeleton in untransfected PtK2 cells. Untransfected PtK2 epithelial cells were fixed and stained for actin, tubulin and intermediate filaments as described in Materials and Methods. Representative images are shown of the keratin filament network (K8/K18) (A,B), actin (C) and microtubules (D). Image (A) is acquired with 2x2 binning, whereas (B) is a high-resolution image (1x1 binning) showing keratin filaments in more detail. At higher power, the keratin filaments (only) have a granular appearance, which was not detected with other fixations regimes.