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

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6.1 .4 DeveloÞñent of oÞen Neúr¿il Deþslq
l,lhen embryos are analysed in experlmental and control groups
(Section 6.1.3) the exact tlmîng of neural closure cannot be assessed
because each group incorporates a range of Stages. Analysîs of the
comblned experímental groups and the coribined control groups ¡n terms
of indlvÌdual Stages. (including group 0C ín both categories), provides
more Information about neural closure after Stage 6.
ln Table 2l and Fis. 3t , closure of the ânterîor neuropore is ._ "i
complete in the control embryos by Stage .l3, so that an open neuropore
after thís Stêge cên be regarded as an open brain defect.
Closure of the rhomboid sinus (taUle Z8 e Fig,32 ) occurs at
Stages l!:.l6 ¡n both experimental ênd control groups. A triangular
rhomboid sînus is seen only in experimental embryos between Stages 11
and 16. Open cord defects first appear at Stage i3 (Table 29 and FiS. 33 ),
and occur at all Stages in the experímental group, as well as in three
control embryos. The first appearance of open cord defects at Stage 13
ls consístent w¡th the suggest¡on that they are preceded by a triangular
rhomboid s i nus.