Fig. 2. C. difficile toxin B completely inhibits EC morphogenesis in both collagen and fibrin matrices. (A) Photographs of three-dimensional cultures fixed and stained with toluidine blue. ECs were allowed to undergo morphogenesis in collagen and fibrin matrices for 8, 24 or 48 hours as indicated. Arrowheads indicate vacuoles; arrows indicate developing lumins. Cells pretreated with toxin B are shown in lower panel. Note the complete lack of vacuoles and lumenal structures in toxin B group. Quantification of cells forming vacuoles and lumens in three-dimensional collagen (B) and fibrin matrices (C). Cultures were fixed and stained at various time points following pretreatment with toxin B and C3 ribosyltransferase (collagen only). Data are expressed as a percentage of cells forming vacuoles±s.d. (n=3). Bar=30 µm.