Development of the embryonic trisomy 1 XXXX .

@entity1 @entity851 @entity75 @entity4118 @entity19 @entity245 @entity12081 @entity10146 @entity601
Trisomic and normal control embryos 9.5 through 12 gestational days were examined externally and on serial section with standard light microscopy techniques. Trisomic embryos showed significant retardation in length, weight, optic angle, and somite numbers at most times (p less than .05), and were 1/2 day behind normal animals in overall development. The eye showed the most defects, and these appeared at every period. They included @entity4118 , large intraretinal space, and dysmorphia of optic cup layers. @entity75 were found at all times. The most common were narrow brain vesicles and folding of the vesicle walls. Some animals showed @entity601 . The major defect in neural crest derivatives was deficient frontonasal processes in the most defective embryos. The study supports the conclusion of previous investigators that @entity12081 is a syndrome of growth and @entity851 with a wide range of defects. Definitive evidence, previously lacking, indicates that @entity245 and defective morphogenesis are apparent before 11 days of gestation. In addition, according to our measurements, optic angles are larger in trisomic @entity19 than in normal littermates. This is in contrast to the only previous investigation that included such measurements. Our data do not give definitive support to the suggestion that trisomy 1 belongs to the holoprosencephaly- @entity10146 spectrum. However, the hypothesis that @entity19 trisomy 1 shows a parallel in development to @entity1 trisomy 13 is not supported by our data. Possible causal mechanisms for the defects and @entity245 are discussed.
