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E F Stange

Publications and source records attributed to E F Stange.

At least 109 records · Page 6Linked to original sources
PubMed1994

HDL3-mediated cholesterol efflux from cultured enterocytes: the role of apoproteins A-I and A-II.

High density lipoproteins (HDL) were recently demonstrated in an enterocyte model (CaCo-2 cells) to mediate reverse cholesterol transport by retroendocytosis. The present study was carried out to define the role of the major HDL apoproteins (apo) A-I and apo A-II in this pathway. HDL3 was fractionated by heparin affinity chromatography into the two main fractions containing either apo A-I only (fraction A) or both apo A-I and apo A-II (fraction B). In addition, liposomes were reconstituted from purified apo A-I or apo A-II and dimyristoyl phosphatidylcholine. The cell binding properties and cholesterol efflux potential were studied in the lipoprotein fractions and the liposomes. Both fractions exhibited similar maximal binding capacities of 4427 (A) and 5041 (B) ng/mg cell protein, but their dissociation constants differed (40.5 and 167.7 micrograms/mL, respectively). Fraction A induced cholesterol efflux and stimulated cholesterol synthesis more than did fraction B. Fraction A mobilized both cellular free and esterified cholesterol, whereas fraction B preferentially mobilized cholesteryl esters. Liposomes, containing either apo A-I or apo A-II, showed specific binding, endocytosis and endosomal transport, and were released as intact particles. Apo A-I liposomes also mediated cholesterol efflux. In conclusion, there is evidence that the HDL3 subfractions A and B, as well as reconstituted liposomes containing either apo A-I or apo A-II, were specifically bound and entered a retroendocytosis pathway which was directly linked to cholesterol efflux. Quantitatively, the apo A-I subfraction appeared to play the dominant role in normal enterocytes. The apo A-II content of fraction B was related to the mobilization of cholesteryl esters.

Adenocarcinoma↗
PubMed1994

Biliary cholesterol secretion and bile acid formation in the hamster: the role of newly synthesized cholesterol.

In order to define the source of cholesterol for bile acid synthesis and biliary cholesterol, hamsters with an extracorporeal bile duct received an intraperitoneal bolus of [3H]water labeling newly synthesized cholesterol. Thereafter the enterohepatic circulation was interrupted and a nutrient solution was infused during the experimental period of 78 h. In a separate group, pravastatin was administered (54-78 h) to allow discrimination of 3H-labeled cholesterol recycling from plasma and newly synthesized hepatic cholesterol late during the experiment. In controls, newly synthesized biliary cholesterol and primary bile acids derived from cholesterol newly synthesized during the experiment amounted to 5% and 12% immediately after depletion of the bile acid pool (6-9 h), respectively. After longterm bile diversion these proportions increased to 56-63%, whereas 71% of plasma cholesterol was labeled. Pravastatin inhibited the secretion of biliary cholesterol, cholate, and chenodeoxycholate by 30, 50, and 44%, respectively. In contrast, the preinfusion tritium label was suppressed by a maximum of 16%, 14%, and 26%, respectively, reflecting the contribution of cholesterol newly synthesized in the hepatocyte as opposed to labeled cholesterol recycling from the plasma. It is concluded that in the hamster newly synthesized cholesterol is of minor importance as substrate for bile acid synthesis as well as biliary cholesterol, both under near physiologic conditions and after long-term bile diversion. Moreover, the hepatic cholesterol pools subserving the synthesis of the primary bile acids are identical but appear to be different from that of biliary cholesterol directly after the depletion of the enterohepatic bile acids.

Animals↗
PubMed1993

[Idiopathic ulcer of the small intestine].

The authors report on a female patient, 32 years old, suffering for eight years from recurrent and progressive abdominal pain, combined with chronic anemia, due to iron deficiency. Neither anamnesis and clinical course, nor technical examinations elucidated the etiology. Finally an explorative laparotomy with segmental resection of the small intestine led to diagnosis and healing of the rare "idiopathic small bowel ulcer". Possible differential diagnoses were lacking. This case report demonstrates the need of an invasive and aggressive diagnostic approach after excluding all common causes of disease, related to the symptoms, in order to prevent patients from suffering for years.

Adult↗
PubMed1993

Polyamine deficiency impairs proliferation and differentiation of cultured enterocytes (CaCo-2).

The polyamine dependence of enterocyte growth and differentiation was studied in the human intestinal cell line CaCo-2 using a specific inhibitor of the key enzyme ornithine decarboxylase (ODC), difluoromethylornithine (DFMO). ODC was highest during the initial phase of rapid growth and was inhibited in a dose dependent fashion by DFMO at 0.06-2 mM. At low levels DFMO only delayed cell replication without affecting final cell count whereas at concentrations of 0.125 mM and above the final cell number was diminished by at least 53% compared to controls. In contrast, DFMO even at 0.03 mM reduced sucrase activity to 44% of controls when added at day 2 but was ineffective when supplemented at day 7 of culture or later. The inhibitor also diminished the number and length of microvilli in a dose dependent fashion, although this effect required higher DFMO levels than the reduction of sucrase activity. The DFMO mediated suppression of cell replication, enzymatic and morphologic differentiation was reversible in the presence of the ODC product putrescine. Putrescine alone did not affect any of the above parameters. In conclusion, the present data suggest that ODC and polyamines are involved both in enterocyte growth and differentiation.

Cell Differentiation↗
PubMed1993

Bile acid synthesis from newly synthesized vs. preformed cholesterol precursor pools in the rat.

The present study defines the origin of cholesterol subserving bile acid synthesis in male rats with an extracorporal bile duct by labeling newly formed cholesterol with tritiated water. Within 6 hr after interruption of the enterohepatic circulation, the bile acid pool was depleted. At this early time point the proportion from de novo cholesterol was 8% and 12% for biliary cholesterol and cholate, but 18% and 19% for muricholate and chenodeoxycholate, respectively. This proportion gradually rose to 40%, 34%, 51% and 51%, respectively, at 15 to 30 hr. At 78 hr after bile diversion, 64% of cholate was labeled, compared with 84% to 88% of the other biliary lipids and 71% of plasma cholesterol. Total and labeled bile acid secretion exhibited the same diurnal rhythm. To allow differentiation between direct hepatocytic de novo synthesis of bile acids from acetate and recycling of labeled plasma cholesterol, an inhibitor of 3-hydroxy-3-methylglutaryl coenzyme A reductase (pravastatin) was infused from 54 to 78 hr. It suppressed total synthesis of primary bile acids by 60% to 80% but decreased the tritium label of bile acids only from a range of 74% to 92% (54 hr) to a range of 54% to 63% (78 hr), which was in the range of plasma cholesterol (58%). We conclude that bile acids and biliary cholesterol are synthesized mostly from preformed (i.e., plasma) cholesterol, both immediately after depletion of the pool in enterohepatic circulation and after derepression. Moreover, the hepatic cholesterol pools subserving the synthesis of different bile acids and biliary cholesterol secretion are not identical.

Acetates↗
PubMed1992

[Extracorporeal shockwave therapy in endoscopic therapy-refractory gallstones].

Extracorporeal shock-wave lithotripsy (ESWL) was undertaken in 36 patients (12 men, 24 women; mean age 70.9 +/- 2.4 years) with extra- or intrahepatic bile duct stones which could not be removed endoscopically. Stone fragmentation was successful in 32 patients with stones in the choledochal duct and in one with stones in the left hepatic duct. Fragmentation failed in two patients with stones in the left hepatic duct and one with stones in the cystic duct. 26 of the 36 patients were free of stone after spontaneous passage (n = 3) or after endoscopic removal of the residual concrements (n = 23). Complications occurred in only five patients during or after ESWL (cardiac arrhythmias, respiratory failure, pancreatitis, cholangitis).--These data point to ESWL being clearly preferable to surgical intervention in bile duct stones refractory to endoscopic treatment, especially in the elderly with an increased perioperative risk.

Aged↗
PubMed1992

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.

Animals↗
PubMed1992

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.

Cholesterol↗
PubMed1992

Limited utilization of exogenous arachidonic acid by the prostaglandin cyclooxygenase in gastric mucosa: the role of protein binding, glutathione peroxidase, and hydrogen peroxides.

We investigated the utilization of exogenous 14C-labelled arachidonic acid by the cyclooxygenase system of the gastric mucosa and its alteration by cytosolic factors, protein binding, glutathione peroxidase (GSH-Px), and hydrogen peroxides. Total prostaglandin (PG) synthesis from gastric microsomes was reduced in a dose- dependent manner to 12% and 68% of controls by increasing amounts of the 105,000g supernatant or albumin (8mg protein/ml), respectively (p less than 0.01). The inhibitory cytosolic factor was heat labile, protease sensitive, and was retained by a 300,000 Dalton ultrafiltration membrane. Thus, it was likely a protein. Other possible inhibitory mechanisms like protease- or heme-induced destabilization of the cyclooxygenase, haptoglobin-mediated inhibition, or self-inactivation by endogenous substrate were excluded. N-ethylmaleimide (NEM), an agent that alkylates sulfhydryl-groups thereby inhibiting GSH-Px, abolished the inhibitory effect of cytosol in a dose-dependent fashion. In contrast to their inhibition of prostaglandin synthesis, the binding of arachidonic acid by albumin or cytosolic proteins accounted to 75% and 19% under comparable conditions, respectively, however, cytosolic fatty acid binding was unaffected by NEM. Thus, it was concluded that the inhibitory effect of cytosol, in contrast to albumin, was mediated by a sulfhydryl-depending process, probably a GSH-Px. This conclusion was supported by a qualitatively comparable inhibition by a purified GSH-Px from bovine erythrocytes. The inhibitory action of cytosolic proteins was reduced significantly by increasing concentrations or repeated application of arachidonic acid; therefore, cytosolic GSH-Px was likely to affect substrate utilization by the microsomal PGH synthase through reduction of activating substrate peroxides. Similarly, the in vitro formation of cyclooxygenase products by mucosal homogenate or gastric microsomes in the absence of cytosol was limited at substrate concentrations below 80 microM, despite sufficient nonesterified arachidonic acid remaining in the incubate. This limitation was mediated only partially by self-inactivation of the prostaglandin cyclooxygenase. Neither N-ethylmaleimide nor repeated application of hydrogen peroxides increased substrate utilization by isolated microsomes, excluding contamination by GSH-Px or simply a lack of hydrogen peroxides as possible mechanisms for the limited utilization. From these results, a special role of substrate-linked lipid peroxides in the activation of mucosal prostaglandin synthesis is proposed. The reduction of these peroxides by glutathione dependent or independent peroxidases, e.g. the PGH synthase-linked hydroperoxidase activity itself, could explain the reduced utilization of nonesterified arachidonic acid by the gastric mucosa.

Animals↗
PubMed1992

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.

Cholesterol↗
PubMed1992

Activation of PGE2-secretion from gastric mucosa by a type I phospholipase C is mediated by a direct release of arachidonic acid.

We investigated the effects of an exogenous Type I phospholipase C (PLC) from clostridium perfringens on arachidonic acid release and prostaglandin synthesis from gastric mucosa by determining PGE2 release from organ cultured rabbit mucosal biopsies as well as PGE2 synthesis and substrate-dependent inactivation of the prostaglandin cyclooxygenase from endogenously released arachidonic acid in mucosal homogenate. PLC dose dependently stimulated PGE2 secretion from organ cultured mucosa to 145% and 245% at 0.1 and 1.0 U/ml during a 60 minute culture period. This effect was not affected by the calmodulin antagonist N-(6-aminohexyl)-1-5-chloro-1-naphthalene-sulfonamide (W-7) or the intracellular calcium chelator 1,2-bis-(2-aminophenoxy)ethane-N,N,N',N',-tetraacetic acid-acetoxymethyl ester (BAPTA-AM). PLC could not be substituted by phorbol-12-myristate 13-acetate (PMA), an analogue of the diacylglycerol second messenger functions. During a 15 minute preincubation of mucosal homogenate at 37 degrees C, 1mM CaCl2 stimulated PGE2 synthesis from endogenous arachidonic acid about 5-fold compared to an EDTA-control. In contrast, the residual prostaglandin synthesizing capacity, determined by incubation with excess 14C-labelled arachidonic acid, was reduced by CaCl2 to 37% of the EDTA-value. Quinacrine, an inhibitor of arachidonic acid release from phosphatidylethanolamine, reduced both the stimulation of PGE2 synthesis and the inactivation of prostaglandin cyclooxygenase. Therefore we conclude, that this Ca(2+)-effect reflects activation of the Ca-dependent phospholipase A2 (PLA2) and, as a consequence, substrate-induced inactivation of the prostaglandin cyclooxygenase.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1992

Enterohepatic circulation in hamsters with an extracorporeal bile duct.

The present study describes a novel technique for investigations of the enterohepatic circulation in the hamster with an extracorporeal bile duct that allows long-term bile collection in the free-moving animal. The animals recovered for 7 days after the operation before the external loop was cut and bile was collected over a period of 78 h. Under these optimal conditions, initial bile flow (651 +/- 89 microliters per 100 g.h-1) and the secretion rates of biliary lipids were several-fold higher than reported in an earlier study using the acute fistula hamster. Biliary cholesterol secretion amounted to 369 +/- 32 nmol per 100 g.h-1, phospholipid secretion was 2.6 +/- 0.3 mumol per 100 g.h-1, and total bile acid secretion was 31.9 +/- 2.2 mumol per 100 g.h-1. A clearcut diurnal rhythm was demonstrated for bile flow and all biliary constituents. After 9 h the depletion of the bile acid pool was complete and cholic acid synthesis derepressed 1.4-fold from a basal rate of 818 nmol per 100 g.h-1, whereas the derepression of chenodeoxycholic acid synthesis was even less pronounced. Biliary cholesterol output increased 2.2-fold, but the phospholipid secretion was constant during the full experiment. It may be concluded that the technique of an extracorporeal bile duct in the free-moving animal allows studies of bile secretion under optimal conditions. Most likely the bile secretion rates given above approach the physiological rates in the hamster.

Animals↗
PubMed1992

[Extracorporeal shock wave lithotripsy in patients with bile duct calculi].

21 patients with choledocholithiasis, in whom methods such as endoscopy or mechanical lithotripsy were unsuccessful, extracorporeal shock wave lithotripsy was performed. Fragmentation could be achieved in 90%, complete stone clearance after endoscopic stone extraction occurred in 76%. Extracorporeal shock wave lithotripsy has proven highly effective with a low complication rate and zero lethality. Therefore, its role in the management of gall stone disease in the elderly patient at high perioperative risk cannot be overemphasized.

Aged↗
PubMed1992

[Endogenous prostaglandin synthesis and gastritis: lack of correlation with endoscopic findings, Helicobacter colonization and leukocytic infiltration of the mucosa].

We determined the capacity and the profile of prostaglandin synthesis in the antral mucosa of patients with erosive (n = 43) or non-erosive (n = 24) Type B gastritis in comparison with normal controls (n = 24). Prostaglandin synthesis was measured by the incorporation of 14C-labelled arachidonic acid into cyclooxygenase products in mucosal homogenate. There was no significant difference between controls and patients with antral gastritis. Furthermore, there was no correlation of the prostaglandin synthesis with helicobacter colonisation or with the degree of inflammation. In another group of 15 patients there was a 17% increased synthesizing capacity nearby the erosions, compared to a non-erosive area (p = 0.05). In these patients with chronic Type B gastritis the treatment with an antacid (Maalox 70, 4 x 10 ml) for 4 weeks did not affect the synthesizing capacity or the profile of mucosal prostaglandin synthesis.

Adult↗
PubMed1991

HDL3-retroendocytosis in cultured small intestinal crypt cells: a novel mechanism of cholesterol efflux.

The present study in IEC-6 crypt-derived rat epithelial cells describes a retroendocytotic pathway for HDL3. These intestinal cells exhibited specific binding of apoE free HDL3 with a maximal binding capacity of 2980 ng/mg cell protein and a Kd of 36.4 micrograms/ml. Specific binding was competed for by HDL3 but not by LDL. Apparent internalisation of HDL3 was low, degradation was negligible and intact particles were resecreted into the medium within 2 h. Electron microscopic studies showed binding and internalisation of gold-labeled HDL3 in coated pit regions and transport in endosomes distinct from lysosomes to lipid droplets. De novo cholesterol synthesis from [14C]octanoate was enhanced nearly 2-fold by HDL3 and the surplus of newly formed cholesterol was recovered in the medium. It was concluded that intact HDL3 was bound specifically to intestinal cells and was resecreted through a process of retroendocytosis probably mediating efflux of cellular cholesterol.

Animals↗
PubMed1991

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.

Animals↗