Tubulovesicular transcytotic pathway in rat biliary epithelium: a study in perfused liver and in isolated intrahepatic bile duct.

Morphometric ultrastructural analysis of horseradish peroxidase-containing structures has been performed in vivo, in rat liver and, in vitro, in isolated bile ducts to determine whether a transcytotic vesicle pathway exists in biliary epithelial cells. In vivo, horseradish peroxidase (100 mg/kg body wt) was given by intraportal injection in normal rats (n = 15) or 1 hr after administration of 600 mg/kg valproic acid (n = 15). Ultrastructural morphometric analysis was conducted on livers between 1 and 40 min after horseradish peroxidase injection. In vitro, bile ducts were isolated on collagenase digestion, incubated in horseradish peroxidase for 3 min and prepared for electron microscopy immediately or after incubation for another 5, 10, 15 or 20 min in horseradish peroxidase-free medium at 37 degrees C. In four experiments, colchicine (10(-5) mol/L) or beta-lumicolchicine (10(-5) mol/L) was added to the culture medium 2 hr before horseradish peroxidase. In a separate series of experiments, 50 mumol/L taurocholic acid or 500 mumol/L ursodeoxycholic acid was added to the culture medium 12 min before horseradish peroxidase. The volume density (percent area) of horseradish peroxidase-containing structures was analyzed in the 1-microns-wide area of basolateral or apical cytoplasm. In vivo, horseradish peroxidase-containing structures maximally increased from the basolateral to the periluminal region over a 20-min interval (percent area increased from 0.09 +/- 0.12 to 2.02 +/- 0.33; p < 0.001) and over a 10-min interval in valproic acid-treated animals (from 0.17 +/- 0.11 to 2.05 +/- 0.36; p < 0.001). In vitro, horseradish peroxidase immediately labeled vesicles in the basolateral cytoplasm. Within 15 min, the vesicles were labeled in the periluminal region (percent area increased from 0.36 +/- 0.08 to 1.90 +/- 0.17; p < 0.001). Colchicine but not beta-lumicolchicine decreased the volume density of labeled structures in the apical cytoplasm (percent area at 15 min, 1.94 +/- 0.24 after beta-lumicolchicine and 1.04 +/- 0.29 after colchicine; p < 0.01). Taurocholic or ursodeoxycholic acid did not change the migration pattern of labeled vesicles, but peroxidase tended to appear earlier in the apical cytoplasm, especially after taurocholic acid. In addition, taurocholic acid increased the percentage of labeled tubules in the apical cytoplasm. These studies show that a polarized tubulovesicular transcytotic pathway exists in rat biliary epithelium and is microtubule dependent. These tubulovesicular structures are labeled with horseradish peroxidase, which is rapidly transported from the cell periphery to the luminal area.(ABSTRACT TRUNCATED AT 400 WORDS)

MR imaging of ulcerative colitis.

High-resolution magnetic resonance imaging (MRI) was used to study 16 resected rectosigmoid specimens of patients treated with total colectomy for severe ulcerative colitis (UC). Six normal colon specimens were also studied as a control group. Moreover, a parallel study of the pelvis of 24 patients with a proven diagnosis of UC was performed with the same MR system. Both in vitro and in vivo MRI findings [thickening and signal intensity (SI)] of the mural layers were qualitatively evaluated by two radiologists and compared with gross and microscopic aspects. In vitro results showed that MRI was able to identify all layers of the colonic wall. In particular in UC specimens, MRI identified thickening and the peculiar abnormal hyperintensity of the mucosal and submucosal layers on spin-echo (SE) T1-weighted images. In vivo results confirmed the high-signal intensity of the mucosal and submucosal layers. These findings were not observed in the control group in which the superficial layers appeared low in intensity on SE T1 images. Our preliminary experience suggests that MRI should be considered a new imaging modality for detecting UC colonic wall changes.