Migrating motor complex after ileal bypass Fig. 5. Representative traces of the migrating motor complexes (MMCs) recorded from the total bypass for 2 weeks (A) and for 4 weeks (B, C). (A) MMCs proximal to the anastomosis have no temporal relationship with those within the bypass loop. (B) MMCs lost temporal relationship and (C) regular MMCs were lost within the bypass loop. that intact, undisturbed continuity of the intestinal tract is necessary for orderly aboral propagation of the MMCs. The decreased AUC following the bypass operation im- plies the significant loss of contractile activity in the by- passed loop, which might explain the progressive dilata- tion of the bypass loop observed in blind loop syndrome. In the total bypass model, where the proximal portion of the bypassed loop was occluded, the MMCs in channel 1 (proximal to the anastomosis) did not propagate to chan- nel 2 (oral side of the bypassed loop). Our previous study indicated that partial obstruction in the mouse ileum blocked the propagation of the MMCs at the obstruction site and MMCs distal to the obstruction paced at a rhythm different from that proximal to the obstruction. This in- dicates that a site distal to the obstruction serves as a new pacemaker for MMCs [12]. We speculate that a similar mechanism might explain the different rhythm between channel 1 (proximal to the anastomosis) and channel 2 thesurgery.or.kr (oral side of the bypassed loop) in total bypass model. The site distal to the obstruction (i.e., proximal loop) became the new pacemaker and served to provide one-way (aboral) propagation within the loop. This contrasts with the partial bypass model, where passage is maintained and MMCs are sequentially related between the segment proximal to the anastomosis (channel 1) and bypass loop (channel 2, 3), irrespective of the direction of propagation. As the duration of total bypass became longer, MMCs within the loop lost its temporal relationship and paced independently. Moreover, in some cases, meaningful MMCs disappeared and irregular contractions remained. This might reflect the loss of physiological role of MMCs (periodically cleansing the bowel) secondary to the com- plete disuse of the bypass loop in a total bypass model. Interestingly in our bypass model, the MMCs were con- sistently irregular or could not be detected in the segment distal to the anastomosis (channel 4). However, using pel- 257