Neural crest ablation versus sham surgical effects in a chick embryo model of defective cardiovascular development

In chick embryos, ablation of premigratory neural crest destined for the third, fourth, and sixth pharyngeal arches results in persistent truncus arteriosus and interrupted aortic arch. Studies of cardiogenesis in these embryos have shown decreased ejection fraction and ventricular dilation with normal cardiac output. The experimental embryos that survive to d 11 of incubation have a higher cardiac output than nonsurvivors at the same earlier stage of development. We hypothesize that this survival is due to a surgically induced decrease in vascular resistance of the embryonic and vitelline vessels. Embryos from 15 opened eggs, eight sham-operated embryos, and 13 neural crest-ablated embryos were examined at stage 18. The sham-operated embryos were treated identically with the experimental embryos except that neural crest was not ablated. Ejection fraction and cardiac output were determined by cinephotography. Mean dorsal aortic and diastolic ventricular (approximates mean atrial) pressures were determined by a servo-null pressure technique and used to calculate vascular resistance. The experimental embryos had a significantly decreased ejection fraction in comparison with either sham-operated embryos or embryos from eggs that remained unopened until just before cinephotography. The experimental and sham-operated embryos had a higher cardiac output than embryos from unopened eggs. The calculated vascular resistance was also significantly lower in both the experimental and sham-operated embryos than in the embryos from unopened eggs. Neural crest ablation appears to cause a decreased ejection fraction. Sham surgery is associated with a higher cardiac output and lower vascular resistance.(ABSTRACT TRUNCATED AT 250 WORDS)