Bidirectional flow of cerebrospinal fluid in the central canal of the spinal cord. a Single frames from time lapses of 24?h post fertilization (hpf) Tg(?-actin:Arl13B-GFP) embryos expressing GFP in cilia. Images taken from progressively dorsal focal planes. Scale: 25?µm. b Quantification of ciliary motion from time lapses; ventral planes exhibit more ciliary motion than dorsal planes (one-way ANOVA F?=?12.2, p?=?5.92?×?10?7, see Methods for motion index quantification) SC spinal cord, CC central canal. c Lateral view of the central canal in transmitted light (top) and filled with fluorescent beads (bottom). Scale: 20?µm. d Schematic of horizontal slices taken for kymograph analysis for velocities of beads or endogenous particles. e Representative kymographs of beads in the central canal. Analyzed trajectories are in red (dorsal) or blue (ventral). f Imaging setup for full-field optical coherence tomography (FF-OCT). g Lateral view of the central canal showing endogenous particles obtained from FF-OCT. Scale: 20?µm. h Representative kymographs of endogenous particles in the central canal. Analyzed trajectories are in red (dorsal) or blue (ventral). i Velocities of exogenous particles (beads) and endogenous particles. Beads: 307 trajectories from n?=?7 embryos; endogenous particles: 452 trajectories from n?=?7 embryos. Error bars represent s.e.m. D dorsal, V ventral, R rostral, C caudal
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