Figure 4.

Active microrheology. (a) Fluorescence intensity of a gut gavaged with 150 kDa fluorescein-conjugated dextran shows that fluid is cleared from the gut within 2 h. (b) Typical response curves ${\theta }_0\left(\omega \right)$ from driven magnetic microparticles in the intestinal mucus of germ-free (upper panel) and conventional (lower panel) zebrafish larvae. In each case, the smooth curve shows the fit of the experimental data to Eq. 1, with the fit parameter ${\omega }^{\text{∗}}$ indicated by the vertical dashed line. (c) Measured viscosities of intestinal mucus in conventional and germ-free zebrafish larvae. Circles indicate the weighted mean values, and bars show SE of the weighted mean (with calibration error included). To see this figure in color, go online.