Hypoxia (1% oxygen) impairs the formation of neurospheres: (A) 1% oxygen tension impairs the formation of neurospheres. U251 cells were cultured as neurospheres with seeding density of 20,000 cells/well in a 24-well plate. At day 0 of setup, indicated groups were either maintained in normoxia or transferred to hypoxia. The condition of each group is indicated beside the pictures. The pictures are representative of experiment conducted at least 3 times. Scale bar = 100 µm. n = Normoxia, H = Hypoxia, D = Day. (B,C) Diameter of neurospheres formed in U251 (B) and U87 (C) following exposure to hypoxia: a Nikon confocal microscope was used to measure the width of neurospheres at the indicated days. The error bar indicates the average from two independent experiments. NS = Not significant, NO = Not obtained. * p < 0.05.