Lectin staining and intravital microscopy of dermal microvessels. (A) Light microscopy of H&E-stained sections and immunofluorescent microscopy of lectins (LCA indicates Lens culinaris agglutinin; and HP, Helix pomatia) and/or DAPI-stained sections from skeletal muscle (top) or skin (bottom). H&E staining of skeletal muscle shows several muscle fibers with intervening capillaries cut in cross section. Both LCA and HP label capillary endothelial cells between the myocytes. Light microscopy of H&E-stained skin reveals epidermis on top, dermis on bottom. The upper dermis contains several microvessels, which are cut in cross-section. Dermal microvessels bind LCA, but not HP (HP stains nonvascular tissue in upper epidermis). Scale bars represent 55 üm. (B) Hagfish blood smear after injection of fluorescein-conjugated dextran. A distinct population of leukocytes is labeled following intravenous injection of fluorescein-conjugated dextran (left panel). DAPI staining (middle and right panels) shows that the fluorescein-laden cell resembles a circulating neutrophil, as identified by the characteristic nuclear morphology. Scale bars represent 20 üm. (C) The hagfish dermal microvascular network was visualized by intravital microscopy (Video S1). Here, the quantitative analysis of neutrophil rolling (Ci) and firm adhesion (Cii) in response to intradermal injection of histamine or vehicle (PBS) is presented. Mean ± SEM (n = 3); *P<.05.