ABSTRACT
BACKGROUND & AIMS: To investigate the role of the cholinergic system in regulation of cholangiocyte functions, we evaluated the effects of vagotomy on cholangiocyte proliferation and secretion in rats that underwent bile duct ligation (BDL rats). METHODS: After bile duct ligation (BDL), the vagus nerve was resected; 7 days later, expression of M3 acetylcholine receptor was evaluated. Cholangiocyte proliferation was assessed by morphometry and measurement of DNA synthesis. Apoptosis was evaluated by light microscopy and annexin-V staining. Ductal secretion was evaluated by measurement of secretin-induced choleresis, secretin receptor (SR) gene expression, and cyclic adenosine 3',5'-monophosphate (cAMP) levels. RESULTS: Vagotomy decreased the expression of M3 acetylcholine receptors in cholangiocytes. DNA synthesis and ductal mass were markedly decreased, whereas cholangiocyte apoptosis was increased by vagotomy. Vagotomy decreased ductal secretion. Forskolin treatment prevented the decrease in cAMP levels induced by vagotomy, maintained cholangiocyte proliferation, and decreased cholangiocyte apoptosis caused by vagotomy in BDL rats. Cholangiocyte secretion was also maintained by forskolin. CONCLUSIONS: Vagotomy impairs cholangiocyte proliferation and enhances apoptosis, leading to decreased ductal mass in response to BDL. Secretin-induced choleresis of BDL rats was virtually eliminated by vagotomy in association with decreased cholangiocyte cAMP levels. Maintenance of cAMP levels by forskolin administration prevents the effects of vagotomy on cholangiocyte proliferation, apoptosis, and secretion.
Subject(s)
Bile Ducts/cytology , Bile Ducts/physiology , Cholinergic Fibers/physiology , Animals , Apoptosis/physiology , Bile Ducts/drug effects , Bile Ducts/metabolism , Body Weight/physiology , Cell Division/physiology , Colforsin/pharmacology , Cyclic AMP/antagonists & inhibitors , Cyclic AMP/metabolism , Hormones/blood , Ligation , Liver/anatomy & histology , Male , Organ Size/physiology , Rats , Rats, Inbred F344 , Receptors, Cholinergic/metabolism , VagotomyABSTRACT
The objective of this study was to compare recovery of microorganisms for various beef samples and beef contact surfaces using conventional pour plating techniques and Petrifilm methods. Comparisons for aerobic plate count (APC), coliform count (CC), and Escherichia coli count (ECC) were done for 104 fresh or frozen retail cuts and 56 food surface or food contact surfaces. Samples were taken at a midwestern retail ground beef processing plant during a 12-month project. APC comparisons were made for pour plating using Trypticase soy agar versus Aerobic Plate Count Petrifilm. CC and ECC were compared for pour plating using violet red bile + MUG agar versus E. coli Petrifilm. Overall, paired t tests revealed a significantly higher recovery for APC from fresh and frozen beef samples using the pour plating technique (P ≤ 0.05). No significant differences (P > 0.05) were observed for CC from fresh and frozen meat samples. Recovery of E. coli from many beef samples was better using Petrifilm. Significantly higher ECCs were observed from fresh and frozen meat samples using Petrifilm compared to the pour plating technique (P ≤ 0.05). For food surfaces and food contact surfaces, a comparison between pour plating and Petrifilm was done for aerobic plate count. No significant differences (P > 0.05) in recovery could be found between methods. A comparison between neutralizing buffer and letheen broth for recovery of surface microorganisms was done for both the APC pour plating method and APC Petrifilm. In both cases, recovery when using letheen broth was significantly (P ≤ 0.05) higher than neutralizing buffer. Because it is convenient and gave comparative results, Petrifilm offers a good alternative for environmental microbial testing and red meat product testing.
