Fig. 2. Histological analysis, cell proliferation and apoptosis in radius and ulna condensations of Hoxa11/Hoxd11 double mutant embryos. (A) Paraffin section of forelimb bud of a control E12.5 embryo stained with Hematoxylin and Eosin. (B) Section from E12.5 Hoxa11^-/-Hoxd11^-/- forelimb bud. Although the size of the radius condensation appears similar to control, the ulna condensation is significantly smaller. (C) Forelimb bud of control E13.5 embryo stained with Alcian Blue. (D) Double mutant E13.5 forelimb stained with Alcian Blue. (E,F) Sections of an E13.5 control (E) and (F) double mutant forelimb bud staind with Hematoxylin and Eosin. (G,H) Adjacent sections to those shown in E,F, respectively, stained with an anti-BrdU antibody. Brackets mark distal end of the ulna where more labeled cells are seen in control than in double mutant embryo section. (I-L) TUNEL analysis performed on E12.5 control (I,K) and double mutant (J,L) embryo sections. A greater number of apoptotic cells (arrowheads) are detected in double mutant embryo.