Fig. 10. VCAM1 and FLK1 in isolated whole allantoises and allantoic subregions after 8 hours of culture. Whole allantoises and allantoic subregions were placed into the exocoelomic cavity or in isolation in test tubes and cultured for 8 hours, after which they were VCAM1 (A-G) or FLK1 immunostained (H-J) (brown color). Allantoises from wild-type unoperated cultured (D,G) and/or lacZ/+ ex vivo conceptuses (C) were used as controls. Sections were counterstained in nuclear fast red (A-D,H-J) or hematoxylin (E-G). In A-B, E-F and H-J, stages of synchronous donor allantoises and host conceptuses before and after culture are separated by a `/'. In D,G, stages of whole conceptuses before and after culture are separated by `/'. An ex vivo allantois is contained in C. (A) VCAM1 in distal region of whole X-gal-stained allantois in normal orientation. (B) VCAM1 is maintained in the distal region of a reversed polarity whole X-gal-stained allantois. The VCAM1-negative proximal region has made contact with the chorion. (C) Normal distal VCAM1 in X-gal-stained lacZ/+ ex vivo control conceptus from the same experiment as A,B. (D) Wild-type unoperated cultured conceptus from same experiment as A-C shows normal distal VCAM1 in the allantois. (E-G) Allantoises are from wild-type conceptuses. (E) Proximal allantoic third does not contain VCAM1. (F) Distal two-thirds of the same allantois in E contains VCAM1. (G) Unoperated cultured control conceptus from same experiment as E,F. (H-J) Whole X-gal-stained allantois (H), X-gal-stained distal two-thirds (I), and X-gal-stained proximal third (J) of the same allantois in I exhibit FLK1 throughout the allantoic core. Abbreviations as in Figs 1, 2, 8. Scale bar in J: 50 µm (E,F); 75 µm (A,H-J); 100 µm (B-D,G).