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e) encroachment of somitîc mesoderm towards the mîdline dorsal to
areas of myelodysplasiã was assocîated wíth reduced neural volume
f) below the level of myelodysplasia rhere was slight reduction ln
the volume of protosomite and unsegmented mesoderm, wìth some local
cystic changes but no loss of contact with neural tissue.
Groúp lV (Staqe l7-20 Embrvos)
a) myeloschisis showed clear demarcation between neurar prate materíal
and tâ î I -bud material
b) ln most cases the notochord was wldely separated from the upper
thlrd of an area of myelosihisls (derived from neural plate material)
c) somite mesoderm showed loss of contact *lth nuur"l tissue at areas
of myeloschisis when compa red to the contro.l s
d) myelodysplasia occurred at a slightly more caudal .level than
myeloschîsis, and consisted of hemimyel ia, diplomyel ia, or amyel ía
e) in myelodysplasla there hras no separêtÍon between neural plête ênd
ta i I -bud mater¡âls
f) the myelodysplasias showed reduction in neural volume, and were
pêrtly covered by ectoderm
S) three embryos with myelodysplasia showed prolonged retention of
accessory canalsh)
somitic mesoderm often encroached on the midrine dorsar to ãreas
of myelodysplasîa and the caudêl cord
¡) somitic mesoderm adjacent to myerodysprasia was in contact with
neural tube, but often cyst¡c and reduced in volume.
These histological findings were tabulated by regions for all control
and experimental embyos (See Section 6.4).