Experimental Approaches to Evaluate Mechanisms of Developmental Toxicity

I. Introduction ..........................................................................................................................16 A. Definitions....................................................................................................................16 B. General Mechanistic Considerations...........................................................................16 C. Guidelines for Evaluating Critical Events ..................................................................18 D. Levels of Mechanistic Inquiry.....................................................................................20 E. Genomic Conservation ................................................................................................21 F. Processes of Organogenesis and Implication of Three-Dimensional

Context of Evaluation..................................................................................................23 1. Cell-Signaling Pathways........................................................................................23 2. Cell-Cell Communication......................................................................................27