Universlty of Manitoba, ln Partîal Fulfiìlment - MSpace at the ...

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6.2 sPtIA! LFVELS 0F oPEN CORp DEF.ECTS rN 12 pAY EMBRYoS
The range of malformations produced by windowing at 26 hours încreases
wlth prolonged embryonic growth. Embryos recovered at 72 hóurs show neural
defects and trunk cysts. At 5 days non-neural defects are apparent, and these
êre more widespread by f2 days (Sect.ion j.2)..
The group of experimental embryos that survîved to 12 days were
examîned for external .malformations, and then :ubjected to cartìlage
staining with alcian blue .(Ojeda et aì., 1970) to display any skeletal .. .:
defects. This revealed the level and extent of the vertebral abnormal ities
associated with each open neural defect.
Because the distinction between myeloschisis and myelodysplasia was
not absolutely clear at 12 days, the two are combined în Table 33 and Figs.3?a38.
Control embryos (with no growth retârdation) were recovered at 11 days,
to provide a comparable range of Stages.
Figs. 39 and 40 demonstrate the difference in grosa appeârance between
the two types of open cord defects in their extreme forms. Myelosch,î.sis
consists of an exposed, regular neural plaque, while myelodysplasia
involves a more irregular defect, part¡ally covered by skin.
A coìlection of four embryos with open neural defects (Fig. 41)
demonstrates the fairly uniform level of the defects, with reduc.t¡on of the
rump and tail in two embryos.
Non-neural malformations (Fig. À2 ) consist of:
a) ectopia v i s cerum
b) uni lateral anophthalmia (wlth a crossed beak)
c) bilateral anophthalmia (wíth a short but central upper beak)
d) reduction of the rump and tail