PAI-1 in the CSS backcrosses. Panel A: Plasma PAI-1 antigen (ng/mL) and Panel B: Plasma PAI-1 activity (U/mL) were tested in heterosomic mice, (B6xCSS-5)F1 (5F1) and (B6xCSS-17)F1 (17F1) and doubly heterosomic mice for chromosomes 5 and 17 (5 × 17). Bars are the mean ± SEM of 5–18 mice. Statistical differences between B6 mice and CSS were determined with a t-test, and a Bonferroni correction was made to determine significance value (P < 0.01). Symbols indicate a significant difference between B6 values. *P < 0.01.