Nuclear protein expression of HIF-1α in human U373, U251 and GaMG glioblastoma cells after in vitro application of different hypoxic conditions. For experimental settings refer to Fig. 2. (A) Western-blots. β-tubulin served as loading control. (B) HIF-1α protein expression strength shown as bar graphs after densitometric evaluation and normalization to the corresponding β-tubulin expression. HIF-1α was strongly expressed after 1 h at 0.1% O2, and still increased for up to 24 h hypoxia. It showed stable reduced expression after up to 48 h reoxygenation. Similar data were obtained in three independent experiments.