Fig. 3. Nuclear run-off assays examining transcriptional regulation of ferritin heavy chain. (A) Assays were performed using nuclei prepared from the hepatopancreas of normoxic and 48 h anoxic L. littorea. Transcripts labeled with [³²P]-UTP were hybridized to nylon membranes carrying immobilized inserts coding for the clones indicated. Ribosomal protein L26 was included as a positive control (Larade et al., 2001). (B) Histograms show the ratio of transcript levels in anoxic versus control samples, means ± S.E.M. for N=3 independent trials, each consisting of nuclei isolated from the hepatopancreas of five snails.