lowed by cervical dislocation, for experiments 2 weeks or 4 weeks after the operation. All the procedures performed on the animals were approved by the Institute of Laboratory Animal Resources (No. SNU-080415-1). Measurement of contractile activity After the animals were sacrificed, the bypass loop was removed, including the 2 cm segment of intestine prox- imal and distal to the anastomosis, and placed in Krebs-Ringer buffer (KRB). The luminal contents were flushed gently with KRB and the mesenteric tissues were cleared by sharp dissection, avoiding the injuries to the in- testinal wall. We designed a loop-holding frame with two S-shaped stainless rods and the intestine was held se- curely within this frame fixed into the bath chamber. The bath chamber was continuously perfused with warmed (37.0 ± 0.5°C) KRB, flowing at a rate of 10 mL/min and gassed (97% O2-3% CO2) throughout the experiment. For the control mice, ileum of the same portion (8 cm segment) were removed and fixed into the bath using straight stain- less rod (1.5 mm diameter). Four stainless steel clips (4 mm, micro-serrefines; Fine Science tools Inc., Foster City, CA, USA) were attached to the intestine for each recording channel; channel 1, 1 cm proximal to the anastomosis; channel 2 and 3, within the bypass loop (oral and anal), channel 4, 1 cm distal to the anastomosis (Fig. 1). Clips were attached 2 cm apart to each other. Silk sutures were used to connect each clip to a Migrating motor complex after ileal bypass force transducer (TST125C; Biopac Systems Inc., Santa Barbara, CA, USA). A single contraction is converted to a peak of wave by force transducer. Initial tension was set to below 5 mN to minimize local reflex stimulation of the bowel. Tension was monitored continuously using an MP150 interface and recorded on a PC running Acknow- ledge software ver. 3.2.6 (Biopac Systems Inc.). For the con- trol mice, clips were attached to each other 2 cm apart and the contractile activity was measured in the same way. Solutions The composition of the KRB was (in mM): NaCl 120.4; KCl 4.7; NaHCO3 15.5; Glucose 11.5; MgCl2 1.2; KH2PO4 1.2; CaCl2 2.5. The pH of the KRB was 7.3-7.4 when gassed with 97% O2-3% CO2 at 37.0 ± 0.5oC. Analysis of contractile activity Contractile activity was analyzed from computer traces, and 4 to 5 representative MMCs from each animal were sampled for analysis. Amplitude (mN), duration of each contraction (seconds) and the interval between each con- traction (seconds) were defined following the previously established parameters [8]. In brief, the amplitude and du- ration of each contraction was determined as the differ- ence between peak tension and resting tension of each con- traction, and the time between the half-maximal-ampli- tude points on the rising and falling phase, respectively (Fig. 2A). The interval between the contractions was de- Fig. 2. Definition of parameters for migrating motor complex. (A) Amplitude and duration of each wave and (B) interval between each wave. thesurgery.or.kr 253