Figure 4.

Fibroblasts in 0 mM K⁺ lose rhythmicity at the single cell level. Fibroblasts were cultured in control medium (A) and in 0 mM K⁺ (B) for 7 d. X-axis shows time after start of recording and Y-axis show photons/min/cell. (C) Average brightness of single cells. Brightness was not significantly different in 0 mM K⁺ compared to control (Student’s t-test, ns; p > 0.05). (D) Percentage of single cells in each condition judged rhythmic by spectral analysis. (E) Amplitudes of rhythmic cells, relative to control (Student’s t-test, **; p < 0.01). (F) Periods of rhythmic cells. There was no significant difference from control (Student’s t-test, p > 0.05). Columns show average values ± SE. Numbers of cells in each condition are indicated by white numerals within columns. Bioluminescence rhythms of all 53 fibroblasts from 5 experiments (G) and 44 fibroblasts from 3 experiments (H) are represented in raster plots. Each horizontal raster line represents a single cell, with elapsed time plotted left to right. Bioluminescence intensity data from all cells were normalized for average brightness and then color-coded: higher than average values are white, and lower than average values are black. The cells are sorted in order of start phase, so that emergence of desynchrony can be more easily appreciated.