Comparative prenatal development of the spinal cord in normal and dysraphic dogs: embryonic stage
Engel, H.N.; Draper, D.D.
American Journal of Veterinary Research 43(10): 1729-1734
1982
ISSN/ISBN: 0002-9645 PMID: 6756221 Document Number: 183856
Embryos and fetuses resulting from normal matings or from mating severely dysraphic Weimeraner dogs were removed between 24 and 28 days (embryos) and between 41 and 44 days (fetuses) of gestation for comparative histology of spinal cord development. In 7 of 10 dysraphic embryos, mantle cells were dispersed between the ependymal and marginal layers ventrad to the central canal. The aberrant position of mantle cells was generally confined to the spinal cord segments at the level of the caudal limb buds, and absence of distinct basal plates was notable. In dysraphic specimens, mantle cells were spaced closer together and stained more basophilic than normal. In 3 of 10 dysraphic embryos the neural tube showed a transversely oriented doubling of the terminal part of the central canal. Dysraphic embryos had significantly smaller transverse diameters of the grey matter and of the spinal cord than normal. Major histological differences between normal and dysraphic fetuses were confined to the lumbosacral region of the cord. In 7 of 10 dysraphic fetuses the central canal underwent dorsoventral enlargement and narrowing at several levels. Two dysraphic fetuses showed misplaced grey matter causing extreme reduction in size of the central canal. In 8 of 10 dysraphic specimens failure of differentiation of the ectomeninx dorsolaterally into the dura mater was observed, with lack of separation between the ectomeninx and periosteum of the vertebral arch. In 70% of dysraphic fetuses the ventral median fissure was either less developed or completely absent. There was loss of distinct separation between ventral horns and some flattening of the cord ventrally. The ratio of grey matter diameter to spinal cord diameter was significantly greater in dysraphic fetuses.