FIGURE 1.

(A) Measurements of the ratio of pulse aortic pressure (pAoP) to pulse aortic diameter (pAoD) are compared in young and old male monkeys both in the thoracic aorta and the abdominal aorta. The pAOP/pAOD ratio was significantly increased in old male monkeys, both in the thoracic and abdominal aorta. (B) Aortic stiffness was significantly increased in both the thoracic and abdominal aorta in old (26 ± 1 years) compared to young (9 ± 1 years) male monkeys. Correlation between aortic stiffness and collagen density (C), elastin density (D), and the collagen/elastin ratio (E) show linear relationships with aortic stiffness. Aortic stiffness was higher in the abdominal aorta than in the thoracic aorta in both young and old male monkeys and was higher in old vs. young male monkeys in both the thoracic and abdominal aorta. *p < 0.05 vs. corresponding young animals (reprint from Zhang et al., 2016).