Gastrointestinal stromal tumor in a patient with undiagnosed neurofibromatosis type I: an uncommon cause of extrahepatic cholestasis.

In this case report we present a 61-year-old patient with obstructive jaundice. Bile duct obstruction was caused by a tumor at the duodenal papilla and bile flow was restored by a plastic stent. Using endoscopic ultrasound and computed tomography imaging two additional tumors of the same morphology were found in the stomach wall and the pelvic region suggesting a multilocular gastrointestinal stroma tumor (GIST). Diagnosis of GIST was confirmed cytologically from the gastric lesion. Based on typical cutaneous manifestations (café-au-lait spots, several tiny dermal neurofibromata and Lisch nodules in the iris), a thus far unidentified neurofibromatosis type I was diagnosed which is known to promote multilocular GIST formation. Tumor resection failed because of cardiac decompensation due to a Takotsubo cardiomyopathy during induction of anesthesia. The patient has been started on imatinib instead and shows so far a stable disease over 6 months.

Mevinolin, a competitive inhibitor of hydroxymethylglutaryl coenzyme A reductase, suppresses enterocyte esterification of exogenous but not endogenous cholesterol.

Mevinolin (lovastatin), a competitive inhibitor of hydroxymethylglutaryl-coenzyme A reductase, directly inhibited acyl-CoA cholesteryl acyltransferase in rabbit intestinal microsomes at a dose of 20 micrograms/ml or more. Lineweaver-Burk analysis showed a competitive type of inhibition with respect to oleoyl-CoA. In cultured intestinal Caco-2 cells, mevinolin reduced [14C]oleate incorporation into cholesteryl-esters by 86% of controls at doses as low as 0.1 micrograms/ml. However, in cells whose activity of acyl-CoA cholesteryl acyltransferase was stimulated 7-fold by 10 mM mevalonolactone, a significant inhibitory effect on cholesteryl-ester formation could not be detected, even at 40 micrograms/ml of mevinolin. In contrast, cells supplied with liposomal cholesterol or cholesterol derived from low-density lipoproteins showed a marked reduction of cholesteryl-ester formation in the presence of 10 or 0.1 micrograms/ml of mevinolin, respectively. It is concluded that the observed suppressive effects of mevinolin on cholesterol esterification in cultured Caco-2 cells are indirect and possibly caused by changes in the acyl-CoA cholesteryl acyltransferase substrate pool or intracellular cholesterol transport.

Clathrin-mediated endocytosis of high density lipoprotein3 in human intestinal Caco-2 cells. A post-embedding immunocytochemical study.

The mechanism by which high density lipoprotein (HDL) removes excess cholesterol from intracellular sites has been the subject of much controversy. There is some evidence that HDL binds to specific cell surface receptors without internalization. Other evidence suggests that HDL is taken up by endocytosis, enters a pathway of endosomal trafficking and is resecreted from the cells (retroendocytsosis). In the present study, we investigated the distribution of apolipoprotein AI, the major protein constituent of HDL, in cultured intestinal Caco-2 cells employing post-embedding immunocytochemistry on LR White-embedded material. Cells grown under control conditions showed label for apolipoprotein AI in the endoplasmic reticulum. After incubation with native apolipoprotein E-free high density lipoprotein3 (HDL3) additional label for apolipoprotein AI was found in endosomes. These endosomes were observed near lipid droplets and in the basolateral cytoplasm. Further, it was demonstrated that label for apolipoprotein AI was colocalized with label for clathrin on the basolateral membrane. Our results support the concept that HDL3 is internalized and subsequently processed in an endosomal pathway in Caco-2 cells besides de novo synthesis of apolipoprotein AI.

Compartmentalization of cholesterol metabolism and cellular growth in cultured intestinal crypt cells.

Growth of rat intestinal crypt derived cells IEC-6 ceased when the key enzyme of cholesterol synthesis, hydroxymethylglutaryl-CoA reductase, was blocked by the competitive inhibitor mevinolin. This effect was reversed by the addition of mevalonolactone. LDL suppressed reductase activity as well as cholesterol synthesis from [14C]octanoate and stimulated acyl-CoA cholesterol acyltransferase, but failed to support cell growth despite rapid receptor mediated degradation even in the presence of low mevalonolactone concentrations. Inhibition of cholesterol esterification by Sandoz-Compound 58-035 enhanced cell growth in the presence of mevinolin, but did not promote proliferation in the additional presence of low-density lipoproteins. HDL3 but not HDL2 or tetranitromethane-modified HDL3 totally reversed the mevinolin induced inhibition of cell growth. This rescue by HDL3 was overcome by an increased dose of mevinolin. HDL3 derepressed reductase, stimulated cholesterol synthesis and reduced cholesterol esterification, but did not reverse the cholesterol synthesis inhibition by mevinolin. It is concluded that IEC-6 cells preferentially use endogenously synthesized cholesterol for membrane formation rather than low-density lipoprotein cholesterol. High-density lipoproteins appear to normalize cell growth in the presence of mevinolin by inhibition of cholesterol esterification and probably by inducing the formation of non sterol products of mevalonate.

Reduced cholesterol esterification in CaCo-2 cells by indirect action of pravastatin.

In microsomal preparations of CaCo-2 cells pravastatin decreased cholesterol esterifying activity at 25 micrograms/ml to 82.5% and at 800 micrograms/ml to 56.2% of controls. Pravastatin reduced cholesteryl ester formation dose-dependently also in viable CaCo-2 cells. However, the maximal inhibition was by 90.4% at pravastatin concentration of 25 micrograms/ml, half maximal inhibition occurred between concentrations of 5 and 10 micrograms/ml. Addition of mevalonolactone, which serves as endogenous source of cholesterol, antagonized this effect. At 10 mM mevalonolactone (MVL) even doses up to 200 micrograms/ml of pravastatin were ineffective. On the other hand, pravastatin suppressed cholesteryl ester formation when acyl-CoA cholesterol acyltransferase (ACAT) (E.C. 2.3.1.26) activity was stimulated by addition of exogenous liposomal or Low Density Lipoprotein (LDL)-derived cholesterol. This inhibition was refractory to increasing amounts of exogenous cholesterol up to 400 micrograms/ml. Therefore we conclude that only excessive doses of pravastatin suppress ACAT activity directly. In viable cells the observed inhibition of cholesteryl ester formation is due to the block in de novo synthesis of cholesterol, causing a lack of substrate for ACAT and of non-sterol products of mevalonic acid. Furthermore pravastatin interferes with the esterification and/or intracellular transport only of exogenous cholesterol, confirming former results of a compartmentalized cholesterol metabolism in the enterocyte.

[Sonographic course of alcoholic fatty liver by interobserver and digital evaluation of liver echogenicity]. / Sonografische Verlaufsbeurteilung der alkoholischen Fettleber durch untersucherbezogene und digitale Analyse der Echogenität des Binnenreflexmusters.

BACKGROUND: The reversibility of alcoholic fatty liver is well-known. The present study aims to investigate whether sonographic controls can document this reversibility under abstinence therapy with respect to inter-observer variability. METHODS: 59 male patients with alcohol dependency were examined by ultrasound at the beginning and the end of a long-term in-patient withdrawal therapy. Fatty liver was graded qualitatively (no, slight, moderate and severe fatty liver). The sonographic liver sections were registered digitally per examination and were subsequently evaluated by means of the PC by two independent experts. Additionally, a digital texture analysis of representative hepatic and renal regions was performed. The pixel intensity ratio of liver and kidney was used as a measure of liver echogenicity. RESULTS: In the ultrasound examination, the 59 patients had the following severity grade of fatty liver initially: 18 (31 %) severe, 19 (32 %) moderate, 22 (37 %) slight. 37 patients (63 %) showed sonographically an improvement of the initial severity grade within 79 +/- 26 days (p < 0.0001, 95 % confidence interval: 50 - 74 %). The evaluation by the independent experts revealed 47 and 54 % improvement, respectively. The overall degree of agreement between the 3 ratings concerning grading and course was high (intraclass coefficient = 0.896). However, there was a marked deviation between the several grading levels (agreement 15 - 86 %). The categorical differentiation between no/slight versus moderate/severe fatty liver revealed an agreement of between 81 and 91 %. The mean pixel intensity ratio showed an improvement of 17 % (p < 0.0001). CONCLUSIONS: After 3 months abstinence an improvement of alcoholic fatty liver can be consistently documented in about 50 % of the cases by sonography. The interobserver variability on differentiating no/slight versus moderate/severe fatty liver was low. The digital texture analysis confirmed the range of reversibility and could play a role in quantifying the sonographic degree of fatty infiltration.

[Diagnostics for diseases of the gallbladder and biliary tract from the viewpoint of the internist and surgeon. Demands made on radiological diagnostics]. / Diagnostik von Erkrankungen der Gallenblase und -wege aus Sicht des Internisten und Chirurgen. Anforderungen an die radiologische Diagnostik.

Jaundice and colic pain of the right upper quadrant are the main symptoms of biliary diseases. Gallstone-related diseases often lead to hospital admission. The evaluation of a patient with biliary symptoms requires a combination of history taking, physical examination, laboratory analysis, and imaging modalities. A high-quality magnetic resonance imaging (MRI) or computed tomography (CT) scan is usually sufficient to evaluate a patient with painless jaundice. Ultrasonography is helpful as an initial screening test to guide the diagnostic work-up. Invasive methods (e.g., ERCP) are mainly used for palliation of patients with incurable disease.

Haemodynamic effects of dopexamine on postprandial splanchnic hyperaemia.

BACKGROUND: The synthetic beta(2)-adrenergic and dopaminergic agonist dopexamine is supposed to prevent splanchnic hypoperfusion in critically ill patients, thus potentially interacting with haemodynamic effects of early enteral nutrition. However, precise mechanism of action and interaction with postprandial splanchnic hyperaemia of the drug are largely unknown, even in healthy subjects. MATERIALS AND METHODS: Twelve healthy volunteers received dopexamine 1 microg x kg(-1) min(-1) and dopexamine and placebo (NaCl 0.9%) 3 microg x kg(-1) min(-1) in a randomized, double-blinded order (crossover-design). Splanchnic (Doppler ultrasound) and systemic (noninvasive cardiac monitoring) haemodynamic parameters were assessed at baseline and during infusion (fasted as well as 15, 30, 45 and 60 min after a standard liquid meal). RESULTS: In fasted humans, dopexamine enhanced time-averaged maximum velocity (TAMX) in the superior mesenteric artery (1 microg + 40%; 3 microg + 82%, P < 0.05), portal vein (+ 63%; + 121%, P < 0.05) and femoral artery (+ 66%; + 87%, P < 0.05), in proportion to the increase of cardiac index (+ 33%; + 77%, both P < 0.05). In the postprandial state, TAMX rose significantly in the superior mesenteric artery (+ 139%) and portal vein (+ 68%) in the placebo group, showing the same absolute extent as dopexamine. The physiological postprandial buffer response of hepatic artery was conserved under all conditions. CONCLUSIONS: Continuous infusion of dopexamine enhances mesenterial and portal perfusion in a dose-dependent manner without affecting the extent of physiological postprandial hyperaemia. Thus, dopexamine and enteral nutrition may interact with splanchnic haemodynamics by different pathways.

Synergistic sedation with low-dose midazolam and propofol for colonoscopies.

BACKGROUND AND STUDY AIMS: Patients undergoing colonoscopy are often sedated with benzodiazepines and long-acting opiates. Since low-dose midazolam also acts synergistically with short-acting propofol, we compared this synergistic sedation with a standard combination of midazolam and the opioid nalbuphine for colonoscopies. PATIENTS AND METHODS: A total of 79 patients presenting for colonoscopies were randomly assigned to the following protocols. Patients in group I (n = 32) received a median dose of 9 mg midazolam (interquartile range [IQR] 6 to 12); 20 patients (59%) needed additional nalbuphine (median 20 mg, IQR 10 to 20). Patients in group II (n = 47) received 2 mg midazolam and repeated injections of propofol (median 100 mg, IQR 53 to 145) with a maximal bolus of 50 mg. RESULTS: Patients treated with the synergistic sedation (group II) recovered remarkably sooner after the procedure compared with those in group I, with a median time to discharge of 17 minutes vs. 93 minutes (P<0.001). Of the patients treated with analgosedation (group I), 28 % were unable to take part in a reaction time measurement and attention awareness test 1 hour after the procedure. All patients treated with the synergistic sedation were able to participate (P=0.002), and performed better. Despite a lower proportion of complete amnesia, patients treated with synergistic sedation more often rated the procedure as comfortable (81% vs. 50 %). Quality of sedation from the point of view of the endoscopist, and cardiorespiratory parameters, were similar in both groups. CONCLUSIONS: Low-dose midazolam combined with propofol is an effective and economic alternative to benzodiazepine-based analgosedation. It is associated with a high degree of patient comfort and rapid recovery times, and has a potential cost benefit concerning nursing care and bed facilities.

[Regulation of intestinal cholesterol metabolism]. / Regulation des intestinalen Cholesterinstoffwechsels.

The small bowel epithelium is of major importance in the cholesterol homeostasis of the organism. The morphological and functional heterogeneity of the gut, complicates studies on intestinal cholesterol metabolism. Cholesterol from diet, de novo synthesis and lipoproteins is strictly compartmentalized intracellularly and supports different metabolic needs. Interactions of cholesterol and lipoproteins were studied in cultured intestinal cells (IEC-6, CaCo-2). Newly synthesized cholesterol is mainly utilized for local purposes like membrane synthesis and is essential for cell growth. In contrast to other cell systems it cannot be replaced by LDL cholesterol in case of blocked synthesis. LDL is specifically bound, internalized and degraded. HDL3 also displays specific binding, internalisation and retroendocytosis, but is not degraded. The observed induction of HMG-CoA reductase, suppression of ACAT, as well as cholesterol efflux after contact of HDL3 with lipid droplets argue for intracellular cholesterol transfer to intact HDL3 and finally resecretion into the medium. HDL3 therefore appears as a mediator of reverse cholesterol transport also in the small intestinal epithelial cell.

Treatment of infected pancreatic pseudocysts by endoscopic ultrasonography-guided cystogastrostomy.

It has been appreciated for a long time that surgery is the treatment of choice for symptomatic, and especially infected, pancreatic pseudocysts. This paradigm is now being challenged by endoscopic cystoenterostomy and cystogastrostomy, which have both been employed with success in selected patients. We present three cases in which infected pancreatic pseudocysts resolved following endoscopic cystogastrostomy guided by endoscopic ultrasonography (EUS).

[Gastrointestinal problems in elderly patients]. / Gastroenterologische Probleme des alten Patienten.

The following article contains a short review on gastrointestinal problems of the elderly. The diseases of the esophagus occurring in the elderly are not much different from those in younger patients. Clinically relevant in the stomach are above all bleeding ulcerations and the gastric carcinoma occurring more frequently in advanced age. The pyogenic liver abscess is diagnosed primarily in the elderly and is at a rule the consequence of an infection of the gall bladder and other abdominal sites. The hepatocellular carcinoma does not grow rapidly in the elderly, but its accompanying unfavourable survival rate at five years is also approximately 5 per cent. In the case of symptomatic cholelithiasis, older high risk patients do especially profit from minimally invasive laparoscopic surgical procedures. Today, bile duct calculi are preferably treated by endoscopic papillotomy and following extraction of the calculi. The pancreas is subjected to atrophy, lipomatosis and fibrosis at the advanced age. However, these changes are rarely of clinical relevance. A frequent problem in clinical practice is that of constipation, from which 35% of patients suffer above the age of 65 years. Another typical symptom of the elderly is the incontinence, the different causes are being discussed. In advanced age, gastrointestinal hemorrhages are mostly occurring above the Treitz's ligament. Hemorrhages of the lower gastrointestinal tract occur mostly in the form of diverticle bleedings and those of angiodysplasias in the elderly. The diverticulosis is also a disease observed in over 50 per cent of patients above 70 years, but it is symptomatic in only part of the patients. When suspecting an inflammatory bowel disease in the elderly, the possibility of a mesenterial ischemia must always be considered as differential diagnosis. The classical chronic inflammatory bowel diseases can, however, also occur at advanced age. The colon carcinoma is one of the most frequent lethal causes in the Western countries 90 per cent of the cases of colon carcinoma are found in patients older than 50 years of age. Intensive attention is therefore required in this age group.

Regulation of cholesterol metabolism and low-density lipoprotein binding in human intestinal Caco-2 cells.

In the present paper, the regulation of 3-hydroxy-3-methylglutarylcoenzyme A (HMG-CoA) reductase, acylcoenzyme A cholesterol acyltransferase (ACAT) and low-density lipoprotein (LDL) binding was studied in the human colon cancer carcinoma cell line Caco-2. LDL down-regulated HMG-CoA reductase activity in a dose-dependent fashion to a minimum of 28% of control at 200 micrograms/ml and LDL binding to 52% of control. The activity of ACAT was stimulated by LDL. High-density lipoprotein 3 (HDL3) increased HMG-CoA reductase activity, whereas cholesteryl ester formation was slightly decreased. Inhibition of the endogenous cholesterol biosynthesis by mevinolin increased both LDL binding and activity of HMG-CoA reductase. This effect was reversed by the addition of mevalonolactone but not by LDL. It is concluded that regulation of HMG-CoA reductase and LDL binding is subject to the availability of non-sterol products of mevalonic acid and of exogenous cholesterol. ACAT is regulated mainly by the level of its substrate cholesterol.

High-density lipoprotein 3 retroendocytosis: a new lipoprotein pathway in the enterocyte (Caco-2).

The present study in Caco-2 cells, derived from a human colon carcinoma and capable of enterocyte differentiation in culture, describes a retroendocytotic pathway for high-density lipoprotein 3 (HDL3). These cells exhibit specific binding of apolipoprotein E-free HDL3 which was competed for by HDL3 but not by low-density lipoproteins. At 37 degrees C, degradation was negligible and intact particles were internalized and resecreted into the medium within 2 hours. Electron microscopy showed binding and internalization of gold-labeled HDL3 in coated pit regions and transport in endosomes distinct from lysosomes to lipid droplets. The fusion of these endosomes with lipid droplets was followed by their dissolution and the subsequent extrusion of HDL particles from the cells. Fluorescence labeling studies of HDL3 supported cytosolic transport in vesicles. Specific binding showed negative feedback regulation by HDL3, was modulated by alterations in cellular cholesterol content, and increased with the cellular state of differentiation. HDL3 mediated efflux of endogenously labeled cholesterol. It is concluded that intact HDL3 is bound specifically by Caco-2 cells, leading to a subsequent intracellular passage and resecretion through a process of retroendocytosis effecting the efflux of cellular cholesterol.