Second, our findings demonstrate that 12.5 mg/kg R(+) atenolol was similar to 12.5 mg/kg R(+) propranolol and 12.5 mg/kg propranolol in preventing vessel formation in the murine IH model, as observed macroscopically (Figure 6A, upper panel) and confirmed by assessment of red blood cell–filled lumens in the H&E-stained sections (Figure 6A, middle panel) as well as by anti–human CD31 staining (Figure 6B, lower panel). The gene discussed is PECAM1; the disease is isolated hemihyperplasia.