Absence of correlation between transient cranial hemorrhages and congenital malformations following neural crest ablation in chicks.

Ablation of premigratory cardiac neural crest has been used to produce and study extensively a model of abnormal cardiovascular dysmorphology. Previous and continuing research in this laboratory concerns different aspects of the involvement of cranial neural crest in the development of cranial, cervical and cardiac tissues in chick embryos. Recently, we detected the occurrence of transient cranial hemorrhages 24-48 hr after the ablation of selected segments of premigratory cranial neural crest. Since one possible mechanism of action for certain teratogens involves nonreparable damage to a primordial embryonic tissue by an antecedent hemorrhage, the objective of this study was to determine which of three different neural crest ablations is associated with hemorrhages and whether subsequent congenital abnormalities were correlated with the ablation procedure and/or hemorrhage. Premigratory neural crest was ablated from 3 different sites, designated cardiac, mesencephalic and trunk crest, respectively, of stage 8-10 chick embryos. Sham-operated embryos were controls. At 24, 30, and 48 hr after ablation, each embryo was observed for the presence of hemorrhages. On incubation day 11 all the living embryos were killed, fixed, weighed, and analyzed for selected length measurements, developmental stage, and the types and rates of congenital abnormalities. Cardiac and mesencephalic ablation group embryos exhibited significant incidences of cranial hemorrhages and changes in many of the parameters analyzed. It was concluded that the cardiac and mesencephalic, but not the trunk neural crest ablations, produced significant changes in incubation day 11 embryos. However, there was no correlation between the abnormalities and the prior occurrence of the transient cranial hemorrhages.