PGP and amyotrophic lateral sclerosis: Selected component proteins were stained in a subset of ALS cases with high hemoglobin leakage, at the level of cord with greatest leakage for that case (endothelial tight junction proteins claudin-5 and zonula occludens 1 (ZO-1), efflux transporter P-glycoprotein (P-gp), basement membrane protein collagen IV; lumbar or thoracic), or within all ALS cases (astrocyte filament markers aquaporin 4 (AQP4) and glial fibrillary acidic protein (GFAP); thoracic).