[1] UNIV VIENNA, HISTOL EMBRYOL INST, SCHWARZPANIER STR 17, A-1090 VIENNA, AUSTRIA
[2] COLUMBIA UNIV, COLL PHYS & SURG, DEPT MICROBIOL, NEW YORK, NY 10603 USA
[3] COLUMBIA UNIV, COLL PHYS & SURG, DEPT HUMAN GENET & DEV, NEW YORK, NY 10603 USA
[4] COLUMBIA UNIV, COLL PHYS & SURG, DEPT OBSTET & GYNECOL, NEW YORK, NY 10603 USA