FIG. 4.

Cholecystokinin-induced gallbladder contraction and fecal shedding. Normal, uninfected BALB/c mice were starved for 4 to 6 h and anesthetized, and the gallbladder was imaged using ultrasound. Cholecystokinin octapeptide fragment 26-33 (CCK8) was then injected intraperitoneally, and 300 images at 3 images per min were acquired to track the gallbladder size. Representative data from one animal are shown. (A) Image before administration; (B) image 400 s postadministration; (C) serial BLI of a representative CD1 mouse infected with virulent L. monocytogenes strain 2C and injected with CCK8; (D) imaging of petri plates of CFU from fecal pellets sequentially collected from the mouse shown in C for 2 h after the fast-and-feed procedure.