Adrenergic beta-Antagonists/pharmacology; Angiogenesis Inhibitors/pharmacology; Disease Models, Animal; Propranolol/pharmacology; Receptors, Adrenergic, beta/physiology; Retinal Neovascularization/prevention & control; Retinopathy of Prematurity/prevention & control; Animals; Animals, Newborn; Blood-Retinal Barrier/drug effects; Blotting, Western; Capillary Permeability/drug effects; Dose-Response Relationship, Drug; Enzyme-Linked Immunosorbent Assay; Female; Fluorescent Antibody Technique, Indirect; Humans; Infant, Newborn; Injections, Intraperitoneal; Injections, Subcutaneous; Insulin-Like Growth Factor I/genetics; Insulin-Like Growth Factor I/metabolism; Intravitreal Injections; Male; Mice; Mice, Inbred C57BL; Oxygen/toxicity; Podophyllotoxin/analogs & derivatives; Podophyllotoxin/pharmacology; RNA, Messenger/genetics; Receptor, IGF Type 1/antagonists & inhibitors; Receptor, IGF Type 1/genetics; Receptor, IGF Type 1/metabolism; Retinal Neovascularization/metabolism; Retinopathy of Prematurity/metabolism; Reverse Transcriptase Polymerase Chain Reaction; Vascular Endothelial Growth Factor A/administration & dosage; Vascular Endothelial Growth Factor A/metabolism