On the Cover: Nodular wild-type rat hepatocytes transplanted into the liver of dipeptidylpeptidase type IV-deficient (DPPIV^–) syngenic hosts pretreated with retrorsine. Tissue samples were stained for DPPIV enzyme activity (rust-orange color); note the sharp demarcation between nodular and surrounding hepatocytes. Such liver cell growth results in subsequent progression to hepatocellular carcinoma. (See Review on page 857).