INTRODUCTION: Notochord is a midline structure extending from primitive streak to prechordal plate and serves as an axial skeleton for the developing embryo (1).
During third week of development, pre-notochordal cells invaginating inside the primitive pit move forward and cephalad upto prechordal plate. These pre-notochordal cells intercalate with underlying hypoblast so that, for a short time a double layered plate called notochordal plate is found in the midline of the embryo.
The exposure effects appear to intersect with an early, critical signaling pathway, the canonical Wnt/[beta]-catenin pathway, important in the prechordal plate
, in cardiac induction, valve development [24, 44-47], and in placentation [48, 49] and neurogenesis [50-52].