Sickle erythrocytes become adherent (arrows) to bone marrow venules in eNOS-deficient mice infused with labeled sickle cell blood compared with control mice. The number of adherent sickle erythrocytes increases in both control (A,C) and eNOS-deficient (B,D) mice under experimental hypoxia (C-D). This figure has been adapted with color enhancement from Figure 3B in the article by Gutsaeva et al that begins on page 1917. Professional illustration by Debra T. Dartez.