Night and Day (IMAGE) University of Pennsylvania School of Medicine Caption The 24-hour rhythm of permeability of a fly’s blood (hemolymph) brain barrier. Credit The lab of Amita Sehgal, PhD, Perelman School of Medicine, University of Pennsylvania Usage Restrictions None License Licensed content Disclaimer: AAAS and EurekAlert! are not responsible for the accuracy of news releases posted to EurekAlert! by contributing institutions or for the use of any information through the EurekAlert system.