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. Author manuscript; available in PMC: 2017 Jul 27.
Published in final edited form as: Nat Neurosci. 2016 Sep 19;19(12):1592–1598. doi: 10.1038/nn.4394

Figure 2. In vivo brain mechanics.

Figure 2

(a) Schematic of the experimental setup. (b) Xenopus brain. The dashed red line indicates the stiffness map area. (c, d) Images of Xenopus embryos with overlaid AFM-based stiffness maps of exposed in vivo brain tissue. Colour encodes the apparent elastic modulus K assessed at an indentation force of 7 nN. Blue shape in (d) shows the OT location (based on fluorescence images, Supplementary Fig. 3). Scale bar: 200 µm. At both stage 33/34 (c) and stages 39-40 (d), brain tissue was mechanically heterogeneous and displayed clearly visible stiffness gradients. Green dashed lines indicate tectum boundaries. The grey dashed square in (d) indicates a region as shown in (e). (e) Immunohistochemistry demonstrated a significantly higher density of cell nuclei (blue) rostral to the OT (yellow) than caudal to it. Scale bar: 20 µm. (f) The tectum was softer than the tel-/diencephalon at stage 33/34 (Mann-Whitney-Test; P = 2.26 × 10-9, Z = 5.978) and (g) than the OT at stages 39-40 (P = 0.0033, Z = 2.933). (h) At stages 39-40, tissue rostral of the OT was significantly stiffer than caudal of it (P = 2.97 × 10-5, Z = 4.163). (i) Quantification of cell density on both sides of the OT; cell density was significantly higher rostral to the OT (paired two-tailed t-test; P = 3.96 × 10-6, t = 9.879). n = number of measurements, N = animal numbers. All representative images and stiffness maps shown are from three biological replicates. Boxes show the 25th, 50th (the median), and 75th percentiles, whiskers the spread of the data.