Delayed and disturbed morphogenesis of the umbilical blood vessels in insulin-like growth factor-II deficient conceptuses (Igf2m+/p-)

Insulin-like growth factor-II (IGF-II) deficiency occurs when a conceptus inherits an inactive gene from the father (Igf2m +/p-): fetal wet weight is reduced to 60% of wild-type, with the decline starting at E11. The umbilical cord vessels of mutant and wild-type were compared. At E8.0-E8.5, the timing of somite formation and chorioallantoic fusion was not altered. At E14.5-E16.5, the left umbilical artery degenerated approximately 1 day later in Igf2m +/p- conceptuses when compared with the wild-type. In the common umbilical artery at E15.5, muscle volume was reduced by one third in IGF-II deficiency. Treating the umbilical arteries as ideal tubes, the values of radius(4)/length suggest that blood flow through the placenta may be reduced by more than half in the Igf2m +/p- conceptuses. (c) 2005 Wiley-Liss, Inc.