Development of the skeleton in normal rats and in rats with trypan blue induced spina bifida.

: In this study skeletal abnormalities in trypan blue induced axial dysraphic disorders were investigated and compared with the normal ontogenesis of the rat skeleton. The first appearance and developmental sequence of the cartilaginous and osseous structures in embryos and fetuses of normal dams were described and discussed in relation to the literature. Two main types of spina bifida were found in the offspring of trypan blue treated dams: open and occult spina bifida. Vertebral abnormalities in open spina bifida fetuses were most frequently present in the lower thoracic region and were always accompanied by rib malformations. In occult spina bifida on the contrary the abnormalities in the vertebral arches were mainly restricted to the sacral region. Both types of spina bifida were accompanied by hypoplastic tails. Apart from a delay in the onset and progress of ossification no other skeletal abnormalities were seen following trypan blue treatment. A human fetus with spina bifida was X-rayed and the vertebral abnormalities detected were very similar to those in rat fetuses.