Biomedical Engineering Reference
In-Depth Information
FIGURE 5.1 Incidence of prevalent malformations in fetuses following
single exposures of pregnant CD-1 mice to 10,000 ppm methanol for 7 hours
on the indicated day. Fetuses were examined on gestation day 17. Source:
From Rogers and Mole (1997).
vertebra six (C6) and various foramina and other features evident in
disarticulated vertebrae. The number of free (e.g., ventrally unattached)
ribs and ribs attached to the sternum were counted, and ribs found on C7
were categorized as partial or full (i.e., attached to the sternum).Methanol
caused homeotic shifts of segment identity. Specifically, a posterioriza-
tion of vertebral elements, especially in the cervical region, was observed
(Figure 5.2). That is, certain of these vertebrae had structural features
normally found on the next vertebra posteriad. Methanol-treated fetuses
often had cartilaginous tubercula anterior on C5 rather than their normal
position on C6, and full ribs attached to the sternumwere observed onC7.
Further, morphological abnormalities of the atlas and axis (fusions, splits,
and duplications) gave the appearance of disrupted segmentation. The
biological basis for these striking skeletal alterations is unknown, but
similar phenotypes have been observed in mice in which homeobox gene
function has been ablated.
A prominent mouse model of the fetal alcohol syndrome has been
developed in the C57BL/6J mouse (Sulik et al., 1981; Sulik and
Johnston 1983; Webster et al., 1983). To examine potential similarities
