Plasma concentration of D-dimer fibrin degradation product in mutant mice. Steady-state D-dimer concentration in the plasma of hyperfibrinogenemic mice (Hifib and Hifib/TMPro), wild-type (wt), and thrombomodulin-deficient mice (TMPro) was determined by ELISA. Values are given as apparent D-dimer concentration determined from a standard constructed with purified human D-dimer. Augmented D-dimer levels in hyperfibrinogenemic mice enhanced formation and subsequent degradation of fibrin. Bars indicate the average; asterisks denote statistical significance below the 0.05 confidence level (Student t test).