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Injected LPS macromolecules into tectal brain results in distribution of LPS within the facial lymphatic network and peripheral vasculature.(a) Schematic of the sagittal optical planes taken by in vivo multi-tiled z-stack confocal imaging. (b) Whole-mount side view of a representative LPS-injected four dpf larvae carrying the vasculature reporter kdrl:mCherry at 12 hpi showing LPS strongly retained in the hindbrain ventricle (hv) and surrounding brain interstitial space as well as the brain and facial lymphatics (blec and FL, arrows) and the peripheral vasculature (PCV and PHS, arrows), but not in the brain blood vessels (vas). (c) High magnification of dotted region in b) showing uptake of LPS as fluorescent puncta (arrows) by the PCV, but LPS is absent in the hepatic region. (d) Characterization of the same timepoint at 12 hpi as in b–c) using fish carrying the lymphatic reporter clearly show localization of LPS within the facial lymphatics (FL, arrows). By stark contrast, LPS is not localized to the brain vessels, thereby providing evidence for drainage of LPS from brain to peripheral circulation through the lymphatics via the interstitial fluid. (e) Higher magnification of dotted box region in d). FL, facial lymphatics; PHS, primary head sinus; PCV, posterior cardinal vein; blec, brain lymphatic endothelial cells; sc, spinal canal; hv, hindbrain ventricle; vas, brain vessels; mb, midbrain; *, interstitial space. Scale bars all show 50 µm.
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