Traditional Chinese Medicines Wu Wei Zi (Schisandra chinensis Baill) and Gan Cao (Glycyrrhiza uralensis Fisch) Activate Pregnane X Receptor and Increase Warfarin Clearance in Rats Ying Mu, Jinnan Zhang, Shimin Zhang, Hong-Hao Zhou, David Toma, Songrong Ren, Leaf Huang, Maria Yaramus, Andrew Baum, Raman Venkataramanan, and Wen Xie