Fig. 8. Effect of osteonectin and cytochrome C on `activation' of low levels of plasma fibronectin (P.FN), cellular fibronectin (C.FN), or human fibronectin alpha-chymotryptic fragments 40 (40 kDa FN) or 120 kDa (120 kDa FN) for cell adhesion. Fibronectin (0.1 µg ml^–1) or no protein (None) was mixed with either no protein (None, white bars) or with 4 µg ml^–1 of bovine bone osteonectin (light gray bars) or cytochrome C (dark gray bars). Cell adhesion was then assessed as described. Results (mean adhesion ± s.d.) are shown for MDA-231 breast carcinoma cells. ***P<0.001 significant difference between matrix protein alone and matrix protein + osteonectin or cytochrome C was determined by Bonferroni's multiple comparison post-test after finding a significant difference P<0.0001 among the groups by two-way analysis of variance (ANOVA).