INITIAL PLACENTATION IN FARM-ANIMALS MORPHOLOGICAL EVENTS WHERE GROWTH-FACTORS MUST BE IMPLICATED

The major morphological events during implantation is described for fa rm animals with emphasis on the pig. Here the developmental changes in vascularisation and not least the cellular interactions during capill ary dislodgement to epithelial indentations is described on both mater nal and embryonic sides. The architectural changes of the interhemal i nterface. to create a sufficient surface area for the exchange between maternal and embryonic sides, seem to originate at the capillary - co nnective tissue - basal membrane -level with implication of the base o f maternal and embryonic epithelium respectively These developmental c hanges are related to changes in enzyme activity and localization of p latelet derived growth factor (PDGF-a), insulin-like growth factor 1 ( IGF-1) and epidermal growth factor (EGF)