Alterations in vesicle transport and cell polarity in rat hepatocytes subjected to mechanical or chemical cholestasis.

BACKGROUND & AIMS: The molecular mechanisms that contribute to the cholestatic condition in hepatocytes are poorly defined. It has been postulated that a disruption of normal vesicle-based protein trafficking may lead to alterations in hepatocyte polarity. METHODS: To determine if vesicle motility is reduced by cholestasis, hepatocytes cultured from livers of bile duct ligation (BDL)- or ethinyl estradiol (EE)-injected rats, were viewed and recorded by high-resolution video microscopy. Cholestatic hepatocytes were analyzed by phalloidin staining and electron microscopy. Functional analysis was done by the sodium fluorescein sequestration assay. RESULTS: In cholestatic hepatocytes, there was a significant decrease in the number of motile cytoplasmic vesicles observed compared with control cells. Further examination of cells from BDL- or EE-treated livers revealed the presence of numerous large intracellular lumina. More than 24% of cells in BDL-treated livers and 19% of cells in EE-treated livers displayed these structures, compared with 1.1% found in control hepatocytes. Phalloidin staining of hepatocytes showed a prominent sheath of actin surrounding the lumina, reminiscent of those seen about bile canaliculi. Electron microscopy revealed that these structures were lined by actin-filled microvilli. Further, these pseudocanaliculi perform many of the functions exhibited by bona fide canaliculi, such as sequestering sodium fluorescein. CONCLUSIONS: Both mechanically and chemically induced cholestasis have substantial effects on vesicle-based transport, leading to marked disruption of hepatocellular polarity.

Impact of an encounter-based prompting system on resident vaccine administration performance and immunization knowledge.

OBJECTIVES: To evaluate an encounter-based immunization prompting system on resident performance in administering vaccines and knowledge of immunization guidelines. DESIGN/METHODS: Prospective randomized, controlled trial. Subjects were first- and second-year pediatric residents in a hospital-based continuity clinic. The intervention group received manual prompts of immunizations due. Postclinic chart review compared immunizations due with those administered. Acceptable and unacceptable reasons for not administering vaccines were assigned. Resident knowledge was measured by a 70-item examination. RESULTS: The intervention group had significantly less missed opportunities/vaccine administration errors (11.4% vs 21.6%). The most common reason for unacceptable errors in the intervention group: vaccine was given too early; in the control group: vaccine was postponed to next visit. Pre- and postintervention knowledge scores were similar: intervention group (75.5% vs 80.7%, control group; 76.5% vs 81.3%). CONCLUSION: An immunization prompting system in a hospital-based pediatric resident continuity clinic reduced missed opportunities/vaccine administration errors without significantly impacting resident knowledge of immunization guidelines.immunization schedule, vaccination, immunization, prompting systems, resident education.