Computer software was used to determine the percent of the inner region of the aorta that consisted of elastin , as detailed in the methods section, and as shown for representative examples in Fig. 2. For normal dogs, 5 animals were evaluated at 3 months and are shown as the black circle that shows the average percentage elastin +/− SEM , while 6 adult dogs are shown as individual black circles, with the linear regression line shown for those values. The indicated number of MPS VII dogs were evaluated at the indicated age; values for two 3 month-old MPS VII dogs compared with those from five 3 month-old normal dogs, and values from the nine 6 month-old, four 12 month-old, and four 24 month-old MPS VII dogs were compared with the values in six adult normal dogs using the Student’s t test. Four RV-treated MPS VII dogs were evaluated at 6 months (M1312, M2420, M2427, and M2428 with 281, 317, 1227, and 752 U/ml of serum GUSB activity, respectively) and values were compared with 6 month-old MPS VII dogs and with adult normal dogs. Three additional RV-treated MPS VII dogs were evaluated at older ages (M1653 at 4 years with 88 U/ml, M1328 at 7.7 years with 503 U/ml, and M1337 at 8.3 years with 281 U/ml) and are shown as individual data points.