Gallbladder emptying in vivo, bile composition, and nucleation of cholesterol crystals in patients with cholesterol gallstones

Impaired postprandial gallbladder emptying may provide time for progressive bile concentration with formation of instable cholesterol-rich vesicles and fast nucleation of cholesterol crystals. The aim of this study was to assess postprandial gallbladder emptying, bile composition, and nucleation of cholesterol crystals in the same patient. In 30 patients with cholesterol gallstones, postprandial gallbladder emptying was measured ultrasonographically. In each patient, gallbladder bile composition (obtained at cholecystectomy) and nucleation of cholesterol crystals was determined. Patients were divided in 22 strong contractors (>50% postprandial gallbladder emptying) and 8 weak contractors. In weak contractors, bile salt and phospholipid concentrations were much higher than in strong contractors ( and , respectively). Cholesterol concentrations were comparable in strong and weak contractors. Consequently, total lipid concentration was significantly higher (15.5 ± 1.4 and 9.2 ± 0.7 g/dL; P < 0.001) and cholesterol saturation index significantly lower (0.90 ± 0.08 and 1.61 ± 0.17; P < 0.001) in weak contractors. Nucleation time, percentage of cholesterol in vesicles, bile salt species, and molecular species of phosphatidylcholine were not significantly different. Differences in bile composition can be linked to different patterns of post-prandial gallbladder emptying and may point to two different pathways of gallstone formation.     

Decreased activity of intestinal and urinary intrinsic factor in Gräsbeck-Imerslund disease

The pathogenesis of inherited intestinal cobalamin malabsorption (Gräsbeck-Imerslund disease) remains unknown. The authors studied whether the disease corresponds to a defective expression and/or function of the intrinsic factor-cobalamin receptor in the ileum. Intrinsic factor-cobalamin receptor activity was measured using radioisotope assay and gel-filtration exclusion chromatography in ileal biopsy specimens and urine concentrates from 4 patients with Gräsbeck-Imerslund disease and 5 controls. Receptor activity was 164 ± 13 fmol/mg of protein in control biopsy specimens and <2.6 fmol/mg protein in specimens from patients. The association constant was estimated to be 3.8 ± 0.4 (nmol/L)⁻¹ in controls. A dramatic decrease in receptor activity was also observed in urine concentrate from patients with an association constant of 1.9 and 3.3 (nmol/L)⁻¹. Isoelectrofocusing of the cross-linked intrinsic factor-cobalamin receptor complex showed an isoelectric point at 4.8 in a patient as well as in control samples. It is concluded that Gräsbeck-Imerslund disease is related to decreased intrinsic factor-receptor activity in intestinal mucosa; the receptor assay in urine can be helpful for diagnosis.     

X region deletion mutants associated with surface antigen-positive hepatitis B virus infections

The finding of antibodies against the polymerase of hepatitis B virus in renal dialysis patients before the incubation phase of infection implies underlying virus replication. Hence, the aim of the study was to test for virus during infection. Viremia was assayed in virus-infected and control patients using the polymerase chain reaction and Southern blotting. Six months before the appearance of surface antigen, most patients had detectable core region, but few patients were X region positive. Three months after surface antigen appeared, most carriers had detectable core and X products. Three years after surface antigen appeared, 5 of 8 carriers with persistent hepatitis B e antigen and 1 of 8 carriers with corresponding antibody had these products. Cloning and sequencing showed deletions within the X/precore region of viral DNA. Infection with X region mutants precedes that of wild-type virus, and they reappear after wild-type virus is eliminated in carriers.     

Antioxidant activity of silybin in vivo during long-term iron overload in rats

Hepatic iron toxicity may be mediated by free radical species and lipid peroxidation of biological membranes. The antioxidant property of silybin, a main constituent of natural flavonoids, was investigated in vivo during experimental iron overload. Rats were fed a 2.5% carbonyl-iron diet and 100 mg · kg body wt⁻¹ · day⁻¹ silybin for 4 months and were assayed for accumulation of hepatic lipid peroxidation by-products by immunocytochemistry, mitochondrial energy-dependent functions, and mitochondrial malondialdehyde content. Iron overload caused a dramatic accumulation of malondialdehyde-protein adducts into iron-filled periportal hepatocytes that was decreased appreciably by silybin treatment. The same beneficial effect of silybin was found on the iron-induced accumulation of malondialdehyde in mitochondria. As to the liver functional efficiency, mitochondrial energy wasting and tissue adenosine triphosphate depletion induced by iron overload were successfully counteracted by silybin. Oral administration of silybin protects against iron-induced hepatic toxicity in vivo. This effect seems to be caused by the prominent antioxidant activity of this compound.     

Prevention of carbon tetrachloride-induced rat liver injury by soluble tumor necrosis factor receptor

Considerable indirect evidence suggests that cytokine tumor necrosis factor α contributes to the hepatocellular damage caused by toxic liver injury. The effects of tumor necrosis factor α neutralization on liver cell injury were determined in an in vivo model of toxic liver injury. The in vivo effects of tumor necrosis factor α were examined in carbon tetrachloride liver injury through the administration of a soluble tumor necrosis factor receptor to neutralize the effects of this cytokine. Soluble tumor necrosis factor receptor treatment decreased the degree of liver injury as measured by reduced levels of serum liver enzymes and improved histology. Soluble tumor necrosis factor receptor administration also lowered the mortality from a lethal dose of carbon tetrachloride from 60% to 16%. Tumor necrosis factor α neutralization had no detrimental effect on liver regeneration as determined by the timing of histone gene expression and postinjury liver weight. These data provide direct evidence for a role of tumor necrosis factor α in toxin-induced liver cell injury. In addition, these investigations suggest that soluble tumor necrosis factor receptor therapy may be of benefit in the treatment of human liver disease.     

Cost-effectiveness model for colon cancer screening

The relative efficacy and effectiveness of different colon screening programs has not been assessed. The purpose of this analysis was to provide a model for comparing several colon screening programs and to determine the key variables that impact program effectiveness. Five screening programs were compared: annual fecal occult blood test (FOBT) alone, flexible sigmoidoscopy, flexible sigmoidoscopy and FOBT combined, one-time colonoscopy, and air-contrast barium enema. Key variables were adjusted for sensitivity analyses. Cost-effectiveness was defined as the cost per cancer death prevented. FOBT alone prevents fewer cancer deaths than the other programs. The addition of flexible sigmoidoscopy to the FOBT increases the rate of cancer prevention. One-time colonoscopy has the greatest impact on colorectal cancer mortality, largely because of assumptions that cancer would be prevented in most patients who undergo polypectomy. FOBT alone is the most cost-effective of the programs, but the cost is sensitive to several key variables. The model shows key variables that impact the cost-effectiveness of colon screening programs. Compliance is an important determinant of effectiveness of all of the screening programs. Future study should be focused on methods of patient education that improve patient compliance with screening.     

The effects of and interactions between fermentable dietary fiber and lipid in germfree and conventional mice

Dietary fiber can stimulate intestinal epithelial cell proliferation. The aim of this study was to resolve the different roles of fermentation and intraluminal viscosity on this trophic action and to investigate reported interactions between fiber and dietary fat. Conventional and germfree mice were fed guar gum in combination with low- or high-lipid diets for 2 weeks, and crypt cell production rates were determined. Guar gum significantly stimulated proliferation in the small intestine, especially when combined with fat. Lipid itself also stimulated proliferation in the small intestine and had a direct trophic effect in the cecum and colon of the germfree mice. Fiber markedly stimulated proliferation in the cecum and colon but only in the conventional group. Interactions between lipid and bacteria and between guar gum and bacteria were also observed in the small intestine. Guar gum has a trophic effect in the small bowel, probably related to viscosity, in addition to its fermentation-related actions in the colon. Positive interaction with lipid may be associated with delayed absorption. Lipid also has its own direct actions on small bowel mucosal proliferation, which are attenuated by the presence of bacteria.     

Subcellular localization of hepatitis B core antigen in relation to hepatocyte regeneration in chronic hepatitis B

To test whether the dominant cytoplasmic expression of hepatitis B core antigen (HBcAg) in active chronic hepatitis B is secondary to liver damage and regeneration, the relationship between subcellular localization of HBcAg, liver inflammatory activity, and hepatocyte regeneration in chronic hepatitis B was studied. Correlation of the clinical and laboratory data with the topographical distribution of HBcAg was studied in 30 patients. The subcellular localization of HBcAg in relation to hepatocyte cell cycles was studied by double immunostaining of HBcAg and proliferating cell nuclear antigen. Patients with predominant cytoplasmic HBcAg had significantly higher levels of biochemical and histological activities and proliferating cell nuclear antigen expression than patients with predominant nuclear HBcAg. The levels of proliferating cell nuclear antigen expression correlated positively with biochemical and histological activities and degrees of cytoplasmic HBcAg expression but negatively with degrees of nuclear HBcAg expression. Proliferating cell nuclear antigen expression was shown in 49% of hepatocytes with cytoplasmic HBcAg but in only 2% of hepatocytes with nuclear HBcAg. These findings suggested that, following liver damage, the regeneration of surviving hepatocytes might cause the shift of intracellular HBcAg from nucleus to cytoplasm. As a result, the extent of nuclear HBcAg expression reduces with concomitant increase in cytoplasmic HBcAg expression.     

Attenuation of esophageal shortening during peristalsis with hiatus hernia

Minimal quantitative information exists on esophageal shortening during peristalsis in the human esophagus. The aim of this study was to ascertain the effect of hiatus hernia on longitudinal muscle-mediated peristaltic esophageal shortening. Seven volunteers and 11 patients with hiatal hernia had metal clips endoscopically affixed at the squamocolumnar junction and 3–5 cm proximal to it (n = 11). Location of the lower esophageal sphincter and axial clip movement were assessed using concurrent manometry and videofluoroscopy during barium swallows in a supine and upright posture with and without abdominal compression. Three subject groups were defined by the proximity of the squamocolumnar junction to the diaphragmatic hiatus: group 1, ≤0 cm; group 2, between 0 and 2 cm; and group 3, ≥2 cm. Peristaltic esophageal shortening was progressively diminished, re-elongation progressively prolonged, and the degree of contraction observed in the distal esophageal segment reduced with progressive degree of hiatus hernia. There was minimal mobility of the squamocolumnar junction relative to the hiatus with posture or abdominal compression. Longitudinal muscle contraction during peristalsis normally causes transient elevation of the squamocolumnar junction above the diaphragm. Esophageal shortening during primary peristalsis is reduced with increasing degree of hiatus hernia, suggesting that there is diminished opposition of longitudinal muscle contraction from the phrenoesophageal attachments.     

Histamine inhibits prostaglandin E2-stimulated rabbit duodenal bicarbonate secretion via H2 receptors and enteric nerves

The gastroduodenal epithelium is protected from acid peptic damage by an adherent mucus-bicarbonate layer. Bicarbonate is secreted by the surface epithelial cells into this mucus layer. Patients with duodenal ulcer disease have impaired proximal duodenal bicarbonate secretion. Mast cells, present in large numbers in the duodenal mucosa, release a number of inflammatory mediators, including histamine. Release of such mast cell mediators has been implicated in ulcer disease. In this study, the ability of histamine to regulate bicarbonate secretion was examined. Bicarbonate secretion by rabbit proximal duodenal mucosa was examined in vitro, and the effects of histamine, its agonists, and its antagonists were studied. Histamine essentially eliminated prostaglandin E₂-stimulated duodenal mucosal bicarbonate secretion, an effect reversed both by the neurotoxin, tetrodotoxin, and the histamine H₂-receptor antagonist, cimetidine, as well as reproduced by the H₂-receptor agonist, dimaprit. In addition to the stimulatory action of histamine on gastric acid secretion, histamine expresses an additional antidefensive action by inhibiting prostaglandin E₂-stimulated duodenal epithelial bicarbonate secretion. This effect of histamine is likely mediated via H₂ receptors located on enteric nerves.     

Shc is a substrate of the rat intestinal epidermal growth factor receptor tyrosine kinase

Epidermal growth factor (EGF) has been shown to induce intestinal proliferation and maturation; however, little information is available regarding substrates of the intestinal EGF receptor tyrosine kinase. The purpose of this study was to determine if src homologous collagen-like protein (Shc) was an in vivo substrate of the intestinal EGF receptor. Ten-day-old rats were treated with EGF or were breast-fed. In some experiments, IEC-6 cells were treated with EGF. Intestinal tissue and cell fractions were studied by immunodetection to compare the tyrosine phosphorylation state and the subcellular localization of intestinal proteins. The total tyrosine phosphorylation state of intestinal proteins was increased threefold by EGF. Tyrosine phosphorylation of the EGF receptor and Shc were rapidly increased by EGF. The association of Grb2 with Shc increased fourfold and fivefold. Plasma membrane translocation of Shc and associated phosphotyrosyl proteins was increased within 30 seconds of EGF treatment. Shc is a substrate of the intestinal EGF receptor in vivo. EGF-induced association of Shc with the adapter protein Grb2 may have implications for activation of the p21^ras signaling pathway in the intestine. The EGF-induced membrane association of Shc with two other phosphotyrosyl proteins suggests involvement of Shc in additional aspects of EGF-receptor signaling in the intestine.     

Nitric oxide modulates pancreatic basal secretion and response to cerulein in the rat: Effects in acute pancreatitis

Nitric oxide synthase activity is detected in the pancreas, but the role of NO on pancreatic function has not been fully characterized. The aim of this study was to evaluate the role of NO in normal and diseased pancreatic function. Amylase and NO secretion were measured in vivo in rats and in vitro in dispersed acini, with and without NO synthesis blockade, by N^G-nitro-l-arginine methyl ester (l-NAME). Rats were subjected to cerulein-induced pancreatitis, and the effects of l-NAME or NO donors were assessed. l-NAME reduced amylase output to 60% of basal. This effect was reversed by l-arginine. The secretory response to optimal doses of cerulein induced a poor amylase secretion and a marked release of NO. High doses of cerulein in combination with l-NAME inhibited NO formation and amylase secretion. In dispersed acini, supramaximal cerulein concentrations induced NO release, but the amylase dose-response curve was not modified by NO inhibition. In acute pancreatitis, l-NAME increased amylasemia and tissue myeloperoxidase activities, whereas NO donors reduced amylasemia, lipasemia, and the histological damage score. The l-arginine/NO pathway facilitates basal and stimulated pancreatic secretion in vivo. NO donor drugs may improve the course of acute pancreatitis.     

A 7-year experience of severe acetaminophen-induced hepatotoxicity (1987–1993)

Five hundred sixty patients admitted between January 1, 1987, and December 31, 1993, with severe acetaminophen-induced hepatotoxicity were studied. The aim of this study was to identify why severe acetaminophen-induced hepatotoxicity still occurs and to determine how known risk factors and advances in management have affected the pattern of illness and outcome. This was a retrospective study of the etiologic factors and the clinical course of all acetaminophen-related admissions. The number of admissions increased from 58 in 1987 to 123 in 1993. During the corresponding period, overall survival improved from just <50% to 78%. The percentage of admissions treated with N-acetylcysteine increased from 40% in 1987 to 83% in 1993. The frequency with which grade III or IV encephalopathy developed decreased from 62% in 1987 to 40% in 1993, and the percentage of these patients who developed cerebral edema decreased from 61% to 45% during the same period. There was an increase in both the number of patients transplanted and the survival of those managed medically. Severe acetaminophen-induced hepatotoxicity remains a serious condition, but the increasing use of N-acetylcysteine, advances in medical management, and the increasing availability of transplantation have resulted in a significant improvement in survival rates.     

Human cholangiocarcinomas express somatostatin receptors and respond to somatostatin with growth inhibition

Cholangiocarcinoma, a malignancy of biliary epithelia, is usually fatal because of absence of tests for early detection and lack of effective therapy. Somatostatin (SS) receptors are expressed in several malignancies and in rodent biliary epithelia. We tested the hypothesis that SS receptors are present in cholangiocarcinomas. We examined tissue from seven surgically resected human cholangiocarcinomas and a human bile duct cancer cell line for the messenger RNA for one subtype of SS receptors (SSTR2) and studied binding and growth-active properties of SS and its analogues. SSTR2 messenger RNA was expressed in all seven human cholangiocarcinoma specimens. Experiments with the human cholangiocarcinoma cell line showed specific, saturable binding of an SS analogue (MK-678) with high affinity for SSTR2 on cholangiocarcinoma membranes; inhibition in vitro of tumor cell proliferation by SS-14 and its analogue, octreotide; and inhibition in vivo of tumor growth in athymic mice implanted with human cholangiocarcinoma cells and treated with lanreotide, another SS analogue. Experiments to elucidate a possible mechanism of growth inhibition by SS showed it was not through changes in cellular cyclic adenosine monophosphate or calcium levels. Using gamma camera imaging with an ¹¹¹In-SS analogue, we localized a histologically proven cholangiocarcinoma in a patient. These results suggest that SS analogues may be useful for diagnostic localization and treatment of biliary tract malignancies.     

The site-specific delivery of ursodeoxycholic acid to the rat colon by sulfate conjugation

Because ursodeoxycholate has been shown to act as a tumor-suppressive agent in the colon, the absorption and metabolism of its sulfate conjugates were examined in rats to show that sulfation would facilitate the site-specific delivery of ursodeoxycholate to the colon. Bile acids were measured in intestinal contents, feces, urine, plasma, and liver tissue after oral administration of ursodeoxycholate and its C-3, C-7, and C-3,7 sulfate derivatives. Ursodeoxycholate was found in the jejunum after administration of all bile acids, but the mass was greatest for ursodeoxycholic acid administration. In the colon, lithocholic acid, normally found in negligible amounts, became the major bile acid after ursodeoxycholate administration. In contrast, reductions in mass and proportions of lithocholate and deoxycholate occurred after administering the C-7 sulfates. The fecal lithocholate/deoxycholate ratio, a risk marker for colon cancer, increased markedly after administration of ursodeoxycholate and its C-3 sulfate, but did not change after administering the C-7 sulfates. Unlike ursodeoxycholate or its C-3 sulfate, which increased liver concentrations of lithocholate and ursodeoxycholate, the C-7 sulfates had the opposite effect, which was consistent with poor absorption. Sulfation of ursodeoxycholate, specifically at the C-7 position, protects the molecule from bacterial degradation and inhibits its intestinal absorption, thereby facilitating delivery to the colon.     

Role of hepatocytes in direct clearance of lipopolysaccharide in rats

The liver is the clearance organ for lipopolysaccharide (LPS). The aim of this study was to investigate the biliary excretion of LPS using fluorescein isothiocyanate (FITC)-labeled LPS. After FITC-LPS was injected intravenously into rats, the cellular localization of fluorescence in the liver was examined and the biliary excretion of fluorescence was measured. The effects of gadolinium chloride, a blocker of Kupffer cells, and colchicine, an inhibitor of microtubules, on the biliary excretion of fluorescence was investigated, and bile was analyzed using high-performance liquid chromatography. Laser scanning confocal microscopy showed that fluorescence was taken up by hepatocytes 5 minutes after injection of FITC-LPS into the portal vein. When FITC-LPS was injected into the portal vein, fluorescence was rapidly secreted into bile, peaking at 20 minutes, and 25.1% of the injected dose appeared in bile within 60 minutes. When the same dose of FITC-LPS was injected into the tail vein, 15.8% appeared in bile within 60 minutes. Chromatography showed that FITC-LPS was excreted into bile in an unchanged form over a period of 20 minutes after injection. Colchicine significantly reduced the biliary excretion of fluorescence, but gadolinium chloride had no effect. LPS was directly and effectively processed by hepatocytes and secreted into the bile canalicular system via a microtubule-dependent vesicular pathway.     

Psychosensory modulation of colonic sensation in the human transverse and sigmoid colon

Psychosensory stimulation increases the perception of stimuli in different regions of the human colon. The aim of this study was to determine the perception of pain and gas during distention of two colonic regions in healthy volunteers during stress and relaxation. In 22 healthy subjects, phasic distentions of transverse and sigmoid colon were performed using infinitely compliant balloons, and symptoms were measured before and during one of three randomized treatments: sham or active relaxation or mental stress. Anxiety ratings and somatic cold-pain sensitivity were included in a multivariate regression model. Mental stress increased levels of anxiety (P < 0.05) and the sensation of gas (P < 0.01), but not pain (P = NS), during transverse colon distentions and the sensations of gas and pain during sigmoid distentions (P < 0.05). Active relaxation reduced only sensation of gas in the sigmoid colon. Somatic pain sensitivity and pretreatment colonic sensory scores were significantly associated with the sensory scores during treatments. Psychosensory stimulation increases colonic sensation during short-term distention in two regions of the human colon; relaxation alone exerts a smaller influence on sensations arising in the sigmoid colon.