Intestinal transit and bacterial translocation in obstructive pancreatitis.

Pancreatic infection from gut-derived bacteria has emerged as the major cause of death in necrotizing pancreatitis. Bacterial overgrowth of indigenous enteric organisms as a consequence of guts stasis (ileus) represents a potential initial event in this process. The present study was designed to examine the interrelationships between intestinal transit, enteric bacteriology, and the translocation of bacteria from the gut lumen to mesenteric lymph nodes and splanchnic viscera during experimentally induced acute pancreatitis. Male rats underwent pancreaticobiliary duct ligation (PBDL) or sham surgery and were sacrificed after 24, 48, or 96 hr. Severity of pancreatitis was assessed with histology, tissue water content, and amylase and lipase levels. Intestinal transit was measured with fluorescent tracers. Blood, mesenteric lymph nodes (MLNs), splanchnic organs, and gut luminal contents were subjected to bacteriologic analysis. PBDL was followed by biochemical and histologic evidence of progressive pancreatic injury at each time interval. Enteric bacteria within the gut and in adjacent MLNs increased as intestinal transit decreased after PBDL-induced pancreatic inflammation. Surprisingly, all parameters returned to control levels by 96 hr in spite of progression of pancreatic inflammation.

Anatomy of the bilioduodenal junction of the opossum.

Prevention of reflux is a major function of the terminal biliary duct system at its junction with the duodenum. We examined this area via scanning electron microscopy and light microscopy to explore anatomic features that might play such a role in the Virginia opossum, a species with a highly developed sphincter of Oddi (SO). The terminal apparatus, most of which consists of a dilated extramural ampulla, has a lumen with abundant folds. Mucus is produced by the lining epithelium and by a plethora of glands. Three muscle layers constitute the SO: an inner longitudinal, an outer circular, and a less consistent outermost longitudinal. The terminal apparatus forms an acute angle and narrows as it enters the duodenum; at this point, the SO becomes continuous with the muscularis externa of the intestine. Four anatomical features with potential antireflux properties may be identified: mucus production, luminal folds, and the narrow opening and oblique course of the intramural duct.

Long-term cholesterol feeding stimulates increased bile phospholipids and gallbladder prostanoid synthesis.

The effect of long-term cholesterol feeding on male rabbit gallbladder prostanoid synthesis and bile phospholipid and bile acid levels was examined. In rabbits fed a 2% cholesterol diet for 2, 5, 7, 9, 12, 15, 18, and 21 weeks, serum cholesterol levels increased 12-fold or higher (68-fold at 21 weeks) when compared to the control levels. Total prostanoid synthesis was significantly increased at 7 weeks or more of cholesterol feeding with 6-keto PGF1 alpha (PGI2 metabolite) and PGE2 as the major products. By 21 weeks of cholesterol feeding, 6-keto PGF1 alpha and PGE2 levels were increased 15-fold and 11-fold higher, respectively, compared to the control. Total bile phospholipid levels were significantly increased at 12 weeks or more of cholesterol feeding, and total bile acids significantly increased only from 5 through 12 weeks of cholesterol feeding. These data show that long-term feeding male rabbits with a 2% cholesterol diet increased endogenous gallbladder prostanoid synthesis, which was associated with an increase in bile phospholipid levels. Increased rabbit gallbladder bile phospholipids may represent a compensation of the animal for toxic levels of tissue and bile cholesterol. Increased phospholipid levels in the bile or tissue could serve as a source of increased availability of arachidonic acid leading to a nonspecific increase in gallbladder prostanoid synthesis.

Actin and myosin isoforms in gallbladder smooth muscle following cholesterol feeding in prairie dogs.

Gallbladder smooth muscle contractility decreases after high-cholesterol feeding in prairie dogs. This decrease is not associated with alterations in the total amounts of the contractile proteins actin and myosin. The present study was designed to determine if cholesterol feeding results in alterations in the isoforms of actin and/or myosin heavy chain in gallbladder smooth muscle. Control prairie dogs were fed a trace-cholesterol diet and test animals were fed a high (1.2%)-cholesterol diet for 8 days. Although the proportion of beta-actin was unchanged, the proportion of alpha-actin in the gallbladder was less in the animals fed the high-cholesterol diet (32.6% +/- 1.5% in the control animals and 24.6% +/- 0.4% in the diet animals). On the other hand, the proportion of gamma-actin was significantly greater in the cholesterol-fed animals. There were no significant differences in the proportions of the myosin heavy-chain isoforms between the two groups. Also, there was no change in the volume fraction of smooth muscle in the gallbladders from the two groups. Thus, cholesterol feeding induces a shift in actin isoforms at the same time that there is a decrease in contractility. Whether the altered pattern of actin isoforms is related to the functional changes remains to be determined.

Common bile ligation in the rabbit: an appropriate model for investigating the relationship of endogenous gallbladder prostanoid synthesis with evolving acute inflammation.

Gallbladder prostanoid (PG) synthesis and histologic inflammatory changes were compared after 6, 24, and 72 hours of bile duct ligation (BDL) or cystic duct ligation (CDL) in the male rabbit. At each time interval the gallbladder was scored for degree of acute inflammation, examined by radiochromatography for endogenous PG synthesis and analyzed by ANOVA. BDL induced progressive increases in acute inflammation whereas prostanoid synthesis significantly increased only after the 6 and 72 hour groups. Indomethacin treatment inhibited PG synthesis in all BDL groups but only decreased the inflammation score in the 6 and 24 hour BDL groups. CDL did not induce progressive gallbladder inflammatory changes or prostanoid synthesis. These data show that prostanoids are intimately involved with the development of early acute gallbladder inflammation following BDL. Inhibition of PG synthesis could attenuate or retard the progression of early acute gallbladder inflammation if started prior to development of established disease.

Morphology of the prairie dog gallbladder: normal characteristics and changes during early lithogenesis.

Studies were undertaken to describe the normal structure of the prairie dog gallbladder and adjacent cystic duct, and then to determine sequential changes that occurred as abnormalities in bile composition developed during high cholesterol feeding. Control animals were fed a diet with trace cholesterol, while experimental animals were fed a diet enriched with 1.2% cholesterol for 1, 2, 3, or 4 weeks. Light microscopy and scanning and transmission electron microscopy were used to characterize morphologic changes at each time interval. Biliary lipid composition was altered in all experimental groups, evidenced by significant decreases in bile-acid-to-cholesterol ratios. Cholesterol crystals appeared in experimental bile at 1 and 2 weeks, while stones formed at 3 and 4 weeks. The cystic duct and neck of the gallbladder occasionally displayed goblet cells. Little mucus was demonstrable in principal cells of the gallbladder, but much more in those lining the cystic duct. After 2 weeks of lithogenic diet, there was an increase in mucus content and secretion from all areas, as well as an influx of polymorphonuclear and mononuclear leukocytes. Accumulation of plasma cells in the lamina propria was an especially prominent feature of experimental tissues. These results suggest that 1) there is regional heterogeneity in the mucus content of the gallbladder and cystic duct of the prairie dog, and 2) both regions respond to lithogenesis with mucus hypersecretion and acute and chronic inflammatory changes prior to the appearance of cholesterol gallstones.

The effects of lithogenic bile on gallbladder epithelium.

Prairie dogs were fed a 1.2% cholesterol diet for up to 24 weeks to evaluate the effects of lithogenic bile on the mucosa of the gallbladder. There was a progressive increase in the lithogenic index of the gallbladder bile (1.44 +/- 0.15 at 4 weeks, p less than 0.05). Fifty-five of 70 animals developed gallstones between the second and fourth week. Increasing stone burden was associated with a 27% (p less than 0.05) decrease in the electrical resistance of the epithelium and a 60% (p less than 0.05) decrease in net sodium transport when measured isotopically in an Ussing chamber (3 weeks). After 4 months, seven of ten animals developed inflammatory mucosal polyps characterized by a heavy infiltration of plasma cells into an expanded matrix. Cellular infiltration began as early as 2 weeks. These changes occurred without alterations in the ultrastructural appearance of the epithelium.

Common bile duct ligation in rabbit: a new model of acute cholecystitis description of histology and bile analysis.

The early stages of acute cholecystitis have been difficult to investigate due to the animal models developed and utilized over the past 60 years. A new model of animal acute cholecystitis induced by common bile duct ligation in the rabbit for 1 to 4 days produces histologic changes which are nearly identical to acute human cholecystitis. These changes include subserosal edema, hemorrhage, white cell infiltration, and dilatation of lymphatics. An inflammation scoring system is described with a range from 0 (not present) to 11 (the most severe). The inflammation score was 2 +/- 0.7 in control rising to 6.3 +/- 1.2 at 1 day of ligation and increasing further with time of duct ligation (P less than 0.01 all groups compared to control). Analysis of bile lithogenic index and concentrations of cholesterol, bile acids, and phospholipids showed no differences among control and experimental groups. Our findings show that the model of rabbit common bile duct ligation produces a histologic picture identical to human cholecystitis without chemical or physical manipulation of the gallbladder or significant changes in the bile lithogenic index.