Yong F. Li

Endotoxemia after relief of biliary obstruction by internal and external drainage in rats

Systemic and portal endotoxemia were studied in rats with biliary obstruction and after relief of the obstruction by internal and external drainage. Endotoxemia was increased after bile duct ligation (p less than 0.001) compared with control values. The incidence of systemic and portal endotoxemia was significantly reduced after internal drainage (p less than 0.001). A significantly higher incidence of portal (86 percent) and systemic (57 percent) endotoxemia, however, was found after external drainage. The persistence of endotoxemia after external drainage, when serum bilirubin levels returned to normal units, indicates that bile flow is important in controlling endotoxemia during preoperative biliary drainage. These results suggest that the systemic endotoxemia observed after relief of obstruction by external drainage may contribute to the increased mortality, as found in previous rat studies. This observation may contribute to an understanding of why patients with preoperative external drainage of biliary obstruction have a higher incidence of septic complications.

Calcium-Induced Contraction and Contractile Protein Content of Gallbladder Smooth Muscle After High-Cholesterol Feeding of Prairie Dogs

Feeding a high-cholesterol diet to prairie dogs causes a reduction in contractile responses of gallbladder smooth muscle from these animals. In this study, the influence of cholesterol feeding on the contractile response to calcium and on the concentration of the contractile proteins actin and myosin was determined. Strips of gallbladder smooth muscle, at their optimal length for tension development, were stimulated maximally with carbachol. Then the muscle cell membranes were made permeable and strips were exposed to a maximally effective concentration of calcium. Strips from cholesterol fed animals developed less stress than those from control animals under all conditions. The concentration of actin and myosin was determined by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. There were no differences in the concentrations of either protein between the cholesterol-fed and control animals. Our results indicate that the decreased contractile response seen in muscle from cholesterol-fed animals is not due to alterations in membrane excitation, excitation-contraction coupling, or in total contractile proteins.

Experimental evaluation of gastric banding for treatment of morbid obesity in pigs

The effectiveness and complications of gastric banding were evaluated in 15 miniature pigs. A Gore-tex or Dacron graft was employed to encircle the stomach. The animals were divided into five groups, three pigs in each group. Group 1 had a 13 mm pouch stoma with a Gore-tex band, Group 2 had a 16 mm pouch stoma with a Gore-tex band, Group 3 had a 13 mm pouch stoma with a Dacron band, Group 4 had a 16 mm pouch stoma with a Dacron band, and Group 5 had a sham operation. The weight variation in the control group was significantly higher than that in the other groups at the ninth postoperative week (p less than 0.05). There was no significant difference among Groups 1, 2, 3, and 4. The gastric band had migrated distally in seven pigs. It was located in the body of the stomach in four animals and in the pylorus in three. These three pigs died from stenosis of the pylorus. The band had eroded and penetrated all stomach layers in three other animals. There was no difference in the incidence of postoperative complications between the Gore-tex and Dacron band groups. The use of this simple operation in the treatment of the morbidly obese patient should be applied with caution.

Gastrointestinal motility following small bowel obstruction in the opossum

The motility of the gastrointestinal tract of six opossums with total and four with partial small bowel obstruction was evaluated. Following the establishment of small bowel obstruction, the migrating myoelectric complex was substituted by a new pattern which was characterized by periods of intense spike activity interspersed with quiescent periods. In the experiments with total intestinal obstruction, the frequency and duration of the periods of intense spike activity were related to the recording site and the time after establishment of intestinal obstruction. The frequency of spike bursts in the ileum proximal and distal to the obstruction was the greatest in the first 2 days after the establishment of the obstruction, while in the antrum and proximal small bowel, the frequency of bursts of spike potentials increased gradually from the first to the fourth postobstruction day (P less than 0.01). However, there was no change in the frequency, duration, and localization of periods of intense spike activity during the 5 days following the establishment of partial intestinal obstruction. We concluded that following intestinal obstruction, the migrating myoelectric complex is substituted by a myoelectric pattern that is characterized by periods of intense spike activity interspersed with quiescent periods. In the animals with total intestinal obstruction, the periods of increased motility are initially more frequent in the bowel proximal and distal to the obstruction and afterwards in the stomach and upper small bowel.

Gallbladder contractility in aspirin- and cholesterol-fed prairie dogs

BACKGROUND/AIMS Whether aspirin prevents cholesterol gallstone formation is controversial. This study aimed to investigate this issue and determine the depression of gallbladder smooth muscle contractility associated with cholesterol feeding in the prairie dog. METHODS Prairie dogs were divided into four subgroups. Animals were fed control or 1.2% cholesterol diet and treated with placebo or aspirin for 2 weeks. The presence of crystals and stones was determined, and contractile force in response to cholecystokinin octapeptide (CCK-8) of gallbladder muscle strips was measured. RESULTS Maximal stress of 2.66 +/- 0.23 x 10(4) N/m2 was measured in muscle strips from animals on control diet. Maximal stress was significantly lower in strips from animals on high-cholesterol diet, being 1.49 +/- 0.16 x 10(4) N/m2 with placebo and 1.62 +/- 0.23 x 10(4) N/m2 with aspirin. The difference in maximal stress between aspirin-treated and placebo-treated animals was not significant. Although none of the animals on control diet had crystals or stones, all animals on the high-cholesterol diet, whether receiving placebo or aspirin, had crystals in the bile, and more than 65% had cholesterol stones. CONCLUSIONS Aspirin has no effect on stone formation, nor does it prevent the decrease in contractility despite a profound decrease in endogenous 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.

Biliary and gut function following shock

The aim of this study was to characterize the alterations in gallbladder and intestinal function after hemorrhagic shock and blood reperfusion in opossums. Animals were subjected to a shock of 30 mm Hg of arterial blood pressure for 60 minutes and resuscitated with blood reinfusion. Gallbladder epithelial ion transport, gallbladder motility in vitro and in vivo, gastrointestinal motility, and flora of the stomach and small bowel were studied 2 and 24 hours after shock. Changes at 2 hours included decreased gallbladder contractility in vitro and decreased emptying in vivo, loss of coordination with intestinal motor activity, decrease in frequency of intestinal electrical slow waves, and reduced duration of the intestinal migrating motor complex cycle. By 24 hours, gallbladder epithelial permeability was increased and in vitro contractility remained reduced but the in vivo functions showed partial recovery. Gastrointestinal flora was not affected by these changes. These data demonstrate that hemorrhagic shock and reperfusion affect digestive motility. The early timing of the alterations observed and the partial recovery 24 hours post shock suggest an ischemia-hypoxia mechanism of injury.