Figure 5.

The branchial arch arteries persist in embryos subjected to ablation of the presumptive cardiac neural crest at stage 7. (A) All 3 pairs of branchial arch arteries are equally patent at Day 4 in control embryos. (B) By Day 6 in control embryos, the left 4^th artery is undergoing regression. By Day 6, the left 4^th artery is undergoing regression. (C) In embryos ablated at stage 7, the arch arteries also remain patent by Day 4 (C) but remodel by Day 6 in ablated embryos (D, E). The left 3^rd and 4^th arteries undergo variable regression in some cases (exemplified in D). In other cases, the left 4^th alone regresses or the 6^th arteries may regress. (F) In an embryo subjected to cardiac neural crest ablation at stage 10, the arch arteries regress unpredictably, as seen here. The right 3^rd, as well as the left 3^rd and 4^th (arrow), are regressed while the right 4^th and 6^th are enlarged.

Abbreviations: eso- esophagus; L3, L4, L6- left third, fourth and sixth arch arteries; R3, R4, R6- right third, fourth and sixth arch arteries.

Scale bar: 300mm.