Figure 3

Electrical stimulation subsystem. (a) Subsystem composition: PC, Electrical stimulation block, Culture environment for cellular tissue, Biosensing block, Imaging block. Photographs of implemented electrical stimulation subsystem was also presented. A cell culture dish on a stage of microscope was equipped with stimulation electrodes. (b) Single waveform together with waveform for 5 s. Pictures of real signals captured from display of an oscilloscope and corresponding drawing were shown. Rectangular waves were 40 signals of 4 ms for electrical stimulation were applied in 1 s with the aim of inducing maximum contraction due to complete tetanus. Generated outputs according to PC instruction and measured signals were captured as shown in the lower part of (b). The time and the voltage were taken on the lateral and vertical axes, respectively and voltage. Scales of each axis were 10 V and 500 ms. 40 rectangular waves were generated in 1 s as the stimulation signal. The stimulation signal was repeatedly measured every 4 s relaxation. (c) Evaluation of SM cellular tissue contraction induced by electrical stimulation. A 10 cm dish was prepared for culture of SM cellular tissue and electrodes were set at distance of 5 cm. Imaging subsystem was used to observe SM cellular tissue. Two regions of SM cellular tissue cultured in a dish were extracted and magnified. Images without and with the stimulation were compared for both of two regions in upper part of (c). The contraction of SM was confirmed at both regions. (d) Measurement of l-lactic acid as a metabolite from the SM cellular tissue (n = 3 in each condition). The time course change in l-lactic acid concentration showed interaction between condition and time (p < 0.001). Electrical stimulation caused higher concentration of l-lactic acid after 1, 9, and 24 h than control (*p < 0.05, **p < 0.01).