Sickled Blood Cell (IMAGE) University of California - Berkeley Caption Sickle hemoglobin polymerizes under low oxygen tensions in the tissues, causing the red blood cell to deform. This leads to obstruction in the capillaries and painful episodes for patients. Credit Frans Kuypers: RBClab.com, UCSF Benioff Children's Hospital Oakland 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.