Fig. 7. Ultrastructural analysis of nullpB1 and nullPKP1 cells grown for 3 days and subjected to a Ca²⁺ switch of 1 hour identifies differences in DM length and number. In all cases columns are: 1, nullpB1 no switch; 2, nullpB1 low Ca²⁺ switch; 3, nullPKP1 no switch; 4, nullPKP1 low Ca²⁺ switch. (A) Relative DM density (mean±s.e.m.) in cells after 3 days of confluent culture before and after a 1-hour Ca²⁺ switch. Graph displays the DM number from 14-17 micrographs, taken at 5,000x magnification, from sections of cells in culture expressed as density relative to cytoplasm. Data show a reduced DM number in nullpB1 cells compared to nullPKP1 cells. (B) DM length in cells after 3 days of confluent culture before and after a 1-hour Ca²⁺ switch. Bar chart shows mean±s.e.m. of DM length from 13-17 micrographs taken at 13,000x magnification from sections of cells in culture for 3 days. Data show a reduction of nullpB1 DM length when compared to nullPKP1. Lower images are representative DMs from nullpB1 and nullPKP1. Scale bar: 1 µm.