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

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0n examlning. the survivi.ng embryos (table I ), the commonest malformations
were found to lnvolve the central nervous system and the eyes.
The braln was often reduced în slze Ìn the experlmental embryos, as well
as ¡n some controls. Two embryos windowed at 26 hours, and one control
enbryo showed an open anterlor neuropore. As. the bráin normally closes by
Stage 12 (Haml I ton, 1965),. these embryos were regarded as showìng open
braln defects after Stage 12. Closure of the rhomboid sinus, which is
normal ly complete by Stage 15 (Haml t ton, t965), was êssessed in the four
groups. ln many embryos wlndowed at 26 hours the neural folds proximal
Éo the rhomboîd slnus were st¡ll open. At Stãges 13 and 14 these open
areas were adjacent to the rhombold slnus, but after Stage 1! they
extended up lnto the somlte reglon. As these defects were ín continuity
wlth the rhombold sinus they appeared to aríse through non-closure of the
neural folds. ln embryos older than stage l6 they are therefore recorded
as open defects of the neural tube.
Many embryos, especially those dead by /2 hours, showed hemorrhages
and cysts of the trunk, sometimes causîng great distorsion, and obscuring
the structures in this region. There were few non-neural defects apparent
by 72 hours.