Ds. Gonzales et al., TROPHECTODERM PROJECTIONS - A POTENTIAL MEANS FOR LOCOMOTION, ATTACHMENT AND IMPLANTATION OF BOVINE, EQUINE AND HUMAN BLASTOCYSTS, Human reproduction, 11(12), 1996, pp. 2739-2745
The behaviour of bovine, equine and human blastocysts was studied in v
itro by time-lapse videomicrography and computer imaging, This study r
evealed that cytoplasmic extensions of the trophectoderm ['trophectode
rm projections' (TEP)] were expressed by embryos of all three species,
prior to or during zona escape, Bovine and human blastocysts escaped
their zonae with a combination of blastocoele expansion, collapse and
re-expansion coupled with the penetration of the zona pellucida by TEP
, In equine embryos, after several cycles of blastocoele expansion and
collapse, trophectoderm ruptured the zona with the concomitant appear
ance of TEP, This study provides documentation that TEP are expressed
by a diverse range of mammalian species, bringing the total number of
species in which this phenomenon is found to six, since TEP are also k
nown to be expressed by guinea-pig, hamster and rhesus monkey blastocy
sts, representing rodents, ungulates and primates, In all species stud
ied, the dynamic nature (extension, retraction, and angular movement)
of the TEP was similar, moving in an undulating manner with rapid cycl
es of extension and retraction, Because TEP appear to be a general fea
ture of mammalian blastocysts, they are implicated in one or more key
events in early development, namely zona escape, attachment and/or imp
lantation.