[1] MASSACHUSETTS GEN HOSP,DEPT PEDIAT,BOSTON,MA 02114
[2] MASSACHUSETTS GEN HOSP,DEPT NEUROSURG,BOSTON,MA 02114
[3] MASSACHUSETTS GEN HOSP,DEPT GYNECOL,BOSTON,MA 02114
[4] HARVARD UNIV,SCH MED,BOSTON,MA 02115
[5] UNIV MANITOBA,DEPT PHYSIOL,WINNIPEG R3T 2N2,MANITOBA,CANADA