Tau association with MTs in the growth cone. Tau association with MTs in the growth cone. High-magnification views of growth cones were processed by combined fixation and extraction (according to procedure 3) and then double-stained for β-tubulin and tau using staining condition 1. Staining of two different growth cones is shown. A andD depict tubulin staining, B and Eshow tau staining, and C and F show pseudocolor representations of ratio images obtained by dividing, pixel by pixel, the image of tau staining by the image of tubulin staining. In the color key, red corresponds to relatively high ratios, whereas violet corresponds to relatively low ratios. The growth cone shown in A–C is representative of many growth cones examined, and shows that tau associates with MTs to or very near their tips, with no obvious decline in tau levels along the length of the MTs. The growth cone shown in D–F shows a distinct pattern that also occurred commonly in the cultures in which tau staining of growth cone MTs declines to near background levels over the distal few micrometers of the MTs. Scale bar, 13 μm. Mark M. Black et al. J. Neurosci. 1996;16:3601-3619 ©1996 by Society for Neuroscience