1978 Volume 18 Issue 1 Pages 33-40
Gross and light microscopic craniofacial features of a severely malformed, day 21 rat fetus are described. The holoprosencephalic-type of anomaly illustrated resulted from a single maternal injection of the niacin anti-metabolite, 6-aminonicotinamide (6-AN), on day 9 of gestation. Twenty-four hours later a countertherapy injection of nicotinamide (NAM) was similarly given. The markedly defective fetus had primarily right-sided anomalies of the face, eye and brain combined with pituitary agenesis. Proposed fetal hemorrhage and neural crest cell damage are discussed.