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. 2021 Mar 23;12:612233. doi: 10.3389/fphys.2021.612233

FIGURE 2.

FIGURE 2

Quantifying oscillatory intracellular Ca2+ activity in pancreatic beta cells. Dynamics of two different oscillatory phenotypes of pancreatic beta cells stimulated with 8 mM glucose (A,B) and 12 mM glucose (C,D). Blue and red lines in panels (A–D) show average calcium signals of all beta cells in a given islet (before filtering). Panels (E–H) feature the corresponding relative phase-dependent activity of fast oscillations, i.e., relative density of fast oscillations at different phases of the slow oscillatory component. Islets presented in panels (A,C) exhibit well-pronounced slow oscillations, and the frequency of fast oscillations depends profoundly on the phase of the slow component. In contrast, the islet in presented panels (B,D) exhibits rather weakly pronounced slow oscillations and a very subtle slow-phase-dependency of fast oscillations. Panels (I,K) show the relative phase-dependent activity of fast oscillations obtained from pooled data of all beta cells and all islets for 8 and 12 mM glucose concentrations, respectively (927 traces from 9 islets for 8 mM glc and 743 traces and 8 islets for 12 mM glc), irrespective of their response phenotype. In panel (J), the lowest value of slow-phase-dependent relative density of fast oscillations, Ffmin, is shown separately for each islet and both glucose concentrations. Cohen’s d value is 1.05. Islets 2 and 8 for 8 mM and 1 and 4 for 12 mM correspond to data from panels (E–H). Panels (L–R) feature the calcium signaling parameters: frequency of slow oscillations Fs (L), frequency of fast oscillations Fs (M), time required for the cells to respond to stimulation TS (N), time required for the cells to reach the phase of sustained activity, i.e., the plateau phase, TP (O), duration of individual oscillations (P), and the average active time (R). Cohen’s d values are 0.14 (L), 1.80 (M), 1.38 (N), 1.36 (O), 0.76 (P), and 2.89 (Q). Black dots denote average values in individual islets, error bars reflect the standard deviation, and the column height displays the average value over all islets.