Fig. 2. Extent of nucleosome formation in primmorphs, determined by photometric immunoassay. Primmorphs were grown for the initial period of 5 days in the non-attached manner, followed by an additional 3 days (total 8 days), 10 days (total 15 days) or 15 days (total 20 days) on galectin-coated culture dishes. The cultures remained either non-treated or were treated with 1 µmol l^–1 or 50 µmol l^–1 of retinoic acid (RA) for the last 2 days of incubation. Then the cells (100–200 mg protein) were lysed and the released nucleosomes were quantitated immunochemically as described in Materials and methods. The amount of colored product was measured spectrophotometrically. The absorbance values were correlated to 50 ng of DNA (present in the samples before lysis). Values are means ± S.D., from five parallel determinations for each sample, and show the amount of nucleosomes released in primmorphs grown on the galectin matrix for 3 days (white bars); 10 days (gray bars) and 15 days (black bars).