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

uler. Accurate Staging (Hamburger and Hamllton, t95l) at the tlme of
wlndowlng was not attempted,as thls necessltêtes vltal stalnlng, whlch
has several disadvantages:
a) the tlme cluring whîch the egg rs out of the incubator rs increased
b) dlrect manipulation of the embryo ls unavoídable
c) teratogeníc effects bave been demonstrèted for several of the vltal
stains commonly used such as Nl le blue sulfate and neutrat red (Menkes,
et al., 1964).
For...lhese reâsons embryonic age êt the time of treatment was assessed in ":
terns of sîze rather than Stage.
\.2.\ Closure of Eggs
After measurement of the blastoderm, each e99 was sealed with a 3 cm.
clrcle of sterile parafilm applied to the shell with a 2 cm. ring of
plastícine, leaving ên artîfícial air space above the embryo (FÌS.7 ).
The eggs were reíncubated in a horizontar positíon without being turned.
' Thls technîc of wíndowing eggs with medium-sized embryos at 26 to 30
hours of incubation was found to produce open neurar defects ín about 502
of the treated ernb ryos .
4.2.5 Effec! of gmbryolíc Age
The relationshíp between embryonìc êge at the time of wrndowlng and
the development of neural defects rvas investigated by perforring'thu ,"r"
procedure on eggs at f4 and J8 hours of incubation.
l{here appl icabie, the significance of differences between experímentar
and control values in windowing experîments was determined Uy the Cni
Square test.