Fig. 1: Islets Show Intrinsic Ca²⁺ Oscillation Modes under High Glucose Stimulation.

a Experimental flow chart. Islets are isolated from mice. After overnight culture, the islets are loaded onto the microfluidic chip for imaging with spinning-disk confocal microscopy. The chip comprises five reagent channels, an inlet channel and an outlet channel. The islet chamber traps the islet with a gradient height from 270 μm to 50 μm. b Representative recordings of whole islet Ca²⁺ signal in Cal-520 AM loaded islets isolated from C57BL/6 J mouse. The islet is stimulated with a repeated protocol: 10 min 3 mM glucose (3 G), 40 min 10 mM glucose (10 G), 30 min 3 G and 40 min 10 G. The first panel, the islet displays fast oscillations with a period of ~20 s (31 of 46 islets); the second panel, slow oscillations at ~3.5 min (9 of 46 islets); the third panel, mixed oscillations at ~20 s and 2.45 min (6 of 46 islets); Enlarged images of the shaded region are shown on the right. c The mean Ca²⁺ oscillation period during the first versus the second round of 10 G stimulation (n = 14 islets). Bars represent mean ± s.d. (standard deviation). d Cell activation sequence in the first and second round of 10 G stimulation. We subtract the previous frame from the following frame of the original Ca²⁺ images (frame interval 3 s). Shown is the cell activation sequence averaged across oscillation cycles in a 5 min interval (aligned with the maximum activation frame). The left panels summarize the time sequence shown in the 7 right panels, with the pseudo-color representing the activation time. e The same islet shows a high similarity index between the first and the second round of 10 G stimulation (5 islets from 3 mice in 3 independent isolations).