L. Leatherbury et al., NEURAL CREST ABLATION VERSUS SHAM SURGICAL EFFECTS IN A CHICK-EMBRYO MODEL OF DEFECTIVE CARDIOVASCULAR DEVELOPMENT, Pediatric research, 33(6), 1993, pp. 628-631
In chick embryos, ablation of premigratory neural crest destined for t
he third, fourth, and sixth pharyngeal arches results in persistent tr
uncus arteriosus and interrupted aortic arch. Studies of cardiogenesis
in these embryos have shown decreased ejection fraction and ventricul
ar dilation with normal cardiac output. The experimental embryos that
survive to d 11 of incubation have a higher cardiac output than nonsur
vivors at the same earlier stage of development. We hypothesize that t
his survival is due to a surgically induced decrease in vascular resis
tance of the embryonic and vitelline vessels. Embryos from 15 opened e
ggs, eight sham-operated embryos, and 13 neural crest-ablated embryos
were examined at stage 18. The sham-operated embryos were treated iden
tically with the experimental embryos except that neural crest was not
ablated. Ejection fraction and cardiac output were determined by cine
photography. Mean dorsal aortic and diastolic ventricular (approximate
s mean atrial) pressures were determined by a servo-null pressure tech
nique and used to calculate vascular resistance. The experimental embr
yos had a significantly decreased ejection fraction in comparison with
either sham-operated embryos or embryos from eggs that remained unope
ned until just before cinephotography. The experimental and sham-opera
ted embryos had a higher cardiac output than embryos from unopened egg
s. The calculated vascular resistance was also significantly lower in
both the experimental and sham-operated embryos than in the embryos fr
om unopened eggs. Neural crest ablation appears to cause a decreased e
jection fraction. Sham surgery is associated with a higher cardiac out
put and lower vascular resistance. These hemodynamic changes may be re
lated to opening and resealing the egg-shell, which would interfere wi
th oxygen delivery and water vapor exchange.