Fig. 3

Microtubule number and organization influence SH signal intensity. a A low number of microtubules will generate SH signals with lower intensities as compared to a high number of microtubules and thus SH emitters. b SH signals correlated with α-tubulin staining intensities as a measure for the amount of microtubules present in the fiber (n = 81 cells from three independent experiments; p < 0.01 Spearman r = 0.2979). c SHG from three parallel regions in a fibroblast protrusion (arrows in fibroblast overview image (left)) indicate the region enlarged in the image at the top) correlated with a transmission electron micrograph of a cross section to visualize individual microtubules (red dots). Dotted line boxes in the micrograph represent the regions generating SH in the protrusion. d In a disorganized microtubule network, the resulting induced dipoles will be less aligned leading to a lower SH signal compared to a network that has more parallel-organized microtubules. e A cell with two processes, one that generates low (arrow) and one high (arrowhead) intensity SH signals (left) and its matched correlated transmission electron micrographs (TEM, right) to visualize microtubule organization at the ultrastructural level. The low- and high-intensity SH fibers correspond to a disorganized (arrow) and parallel-organized (arrowhead) microtubule network respectively. Neuronal cultures were imaged at 7 DIV. All source data are provided as a Source Data file