FIGURE 2.

Active NORs in donor cells and in 4-cell embryos. Metaphase spreads of ESCS, CCs, and MEFs were stained with AgNO₃, then the active NORs numbers were counted (A). ICSI, ESNT, CCNT, and MEFNT embryos at the 4-cell stage were blocked to metaphase by nocodazole treatment, then the UBF signal spots were labeled and counted (B). Columns with different letters indicate significant difference (p < 0.05). ESCs had significantly more active NORs than CCs and MEFs (7.66 versus 6.45 versus 4.70, p < 0.05), and MEFs had the least. ICSI and ESNT embryos had no significant difference in active NORs numbers at the 4-cell stage, but their active NORs numbers were significantly more than CCNT and MEFNT embryos (7.44 versus 7.19 versus 6.68 versus 5.77).