Circadian single cell bioluminescence of primary mouse fibroblasts follows external temperature cycles.

<p>A: Representative examples of PER2::LUC bioluminescence (gray values) emitted from single mouse ear fibroblasts in confluent cell cultures exposed to six repeats of 10h of 33°C (cold): 10h 37°C (warm) (T20, left) or 12h cold: 12h warm (T24, right), respectively. The periods of the oscillations were determined by cosine fit <i>Before</i> (blue), <i>During</i> (red), and <i>After</i> (green) the temperature cycles. Dotted horizontal line: mean magnitude of bioluminescence. B: Double-plotted peaks (dots) of the cells shown in A) reveal that oscillations assume a semi-stable phase relationship with the cold phase. Light blue: cold phase.