Fig. 9. Ultrastructural analysis of the elongating Wolffian duct and lung. Ultrastructural analysis demonstrates a well-developed basement membrane separating the air-blood space of the alveoli (arrows) in control tissue (A) at 18.5 dpc. In the mutant lungs, normal (B), amorphously deposited (C) and missing (B) basement membranes are present (arrows). Note the cell protrusion when basement membranes are missing (B). At 10.5 dpc, basement membranes of the elongating Wolffian duct show discontinuities (asterisk) next to normal electron dense structures (arrows) in the mutant (E) when compared with controls (D). ery, erythrocyte. Scale bars: 100 nm in A-C; 50 nm in D,E.