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

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Ferm, 1965; l"larin-Padi r ¡a, r966; 1966). As these mesoctermal changes preceded
the development of open neuiar defects, they were regarded as the cause
of neural dys raph.i sn.
The relevance of these observat¡ons to the production of neurar
defects by maternal lnjection of trypan blue is complîcated by agent and
species dlfferences. Trypan.blue êppears to ""t
ln rats and rnlce by
Interfering with fetal n.utrition at the yolk sac (Beck et al., ,l967;
l{llllams et al., 1976), and signlflcant levels of the dye have not been
detected within the embryo (Waddlngton and Carrer, f953; tji lson et al.,
1963't. Vitamin A, however, appears to cross the placentê when given in
hlgh doses (cîroud and I'lartinet. , 1957), and the low molecular weight
of dimethyl sutfoxide suggests that placental transfer mí9ht occur (Ferm,
1966). A more direct action by trypan brue wîthout prâcentar intervention,
however, has also produced fluid accumulation, hematomas, and tlssue
damage in amphîbia (Waddíngton and perry, 1956) and chick embryos subjected
to ¡ntravascular injection at J days (Kaplan and Johnson, i970) , or
explantation on the f¡rst day (üurherkar, 1960) . rn each câse the brunr
of the damage was borne by mesodermal tissues, wíth less severe involvement
of neural tissue. The interpretation of trypan brue actívrty is further
conpllcated by the presence of various impurities în different commercial
samples, and the existence of three fractìons withd,n the dye (BecÉ and Lroyd,
r963) .
ln the present experíments' sectíoned embryos with myeroschîsis showed
no abnormal ities of notochord or somites, apart from the notàchordal
separation already discussed. l,lyeloschlsis could not.be regarded as
secondary to somî te defects.