Survival of β3-null mice is compromised. Uteri from typical wild-type (a) and β3-null (b) females that had been bred to β3-null or wild-type males, respectively. Dark patches in (b) indicate bleeding in β3-null uterus. (c and d) Heterozygous E16 embryos in utero, in wild-type (c) or β3-null (d) mothers. Some pups die in β3-null mothers in utero, appearing pale, small and associated with a pale placenta (arrow). (e, f and h) H&E stained sections of placentae from β3-null females mated with wild-type males. H&E stained section of placenta from wild-type female mated with a β3-null male (g). Arrowhead indicates severe hemorrhage observed within the labyrinth (e) and under the Reichert's membrane (f). (g) Labyrinth of wild-type placenta; (h) Labyrinth of β3-null placenta where cell layers appear thick; this occurs in ∼25% of β3-null placentae. (i and j) E16 embryos, wild-type (i) and β3-null (j). Note hemorrhage in β3-null muzzle. Arrow indicates hemorrhage in the skin. (k, l, m, and n) After birth, some β3-null mice suffer hemorrhage in the skin. Petechiae around the mouth of a 1-day-old β3-null pup (k) and H&E-stained section of this region indicating bleeding under the epidermis (l). Purpura on the forelimb of a 1-day-old β3-null pup (m) and H&E-stained section of this region indicating bleeding within the dermis (n). (o and p) Gut from newborn pups. Wild-type (o) and β3-null pup with acute GI hemorrhage (p). Bar (e), 400 μm (f), 50 μm, and (g), 70 μm.