Effects of in vitro hypoxia on the expression of mouse HIF-1α in HIF-1α+/- and HIF-1α+/+ astrocytes. Confluent astrocyte monolayers of both cell types were exposed to a 6 h in vitro hypoxia. HIF-1α mRNA expression was determined by RT-PCR as described in Materials and Methods. Each bar represents the mean ± SD of relative density/volumes of the bands on film negatives from at least three experiments. Asterisks and number sign indicate significant difference (p < 0.01; one-way ANOVA, followed by multiple comparisons among means).