Quantitation of ¹²⁵I-labeled cross-linked fibrin in TM^−/− chimeric and wild-type mice.¹²⁵I-labeled fibrinogen was intravenously infused into mice and urea-insoluble extracts were prepared. ¹²⁵I-labeled urea-insoluble counts were quantitated and the cpm from five or six animals from each genotype was averaged. Cross-linked fibrin from lung and liver of 15- to 20-month-old mice (top) and 6- to 11-month-old mice (bottom) is shown. (░), TM^+/+; (▩), high-percentage chimeras; (), low-percentage chimeras.