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Biomedical subjects

J Reichen

Publications and source records attributed to J Reichen.

At least 19 recordsLinked to original sources
PubMed1999

Endothelium-dependent blunted membrane potential responses to ATP-sensitive K+ channel modulators in aortae from rats with cirrhosis.

BACKGROUND/AIMS: In vivo studies have shown that arterial vasodilation induced by synthetic openers of ATP-sensitive K+ (K(ATP)) channels is decreased in rats with cirrhosis. Since vasodilation induced by these substances is mediated by membrane potential hyperpolarization in arterial smooth muscle cells, membrane potential hyperpolarization in response to K(ATP) channel openers may be altered in cirrhotic smooth muscle cells. The aim of the present study was to investigate the effects of K(ATP) channel modulators (i.e. openers and blockers of these channels) on the membrane potential in smooth muscle cells in isolated aortae from cirrhotic and normal rats. The influence of endothelin-1 production by endothelial cells on smooth muscle cells membrane potential responses to K(ATP) channel modulators was also studied. METHODS: Cells were impaled in situ (in intact and endothelium-denuded aortae) with a microelectrode that was used to measure membrane potentials. K(ATP) channel openers were diazoxide or cromakalim; blockers were glibenclamide or tolbutamide. Bosentan (a mixed endothelin receptor antagonist) and exogenous endothelin-1 were also used. Preproendothelin-1 mRNA was assayed in aortae by RNase protection assay. Aortic wall endothelin-1 concentration was measured by double antibody radioimmunoassay technique. RESULTS: As expected, in smooth muscle cells in intact normal aortae, K(ATP) channel openers induced membrane potential hyperpolarization and K(ATP) channel blockers membrane potential depolarization. In smooth muscle cells in intact cirrhotic aortae, K(ATP) channel openers and blockers did not significantly change the membrane potential. Endothelium removal or exposure of intact aortae to bosentan restored normal membrane potential responses to K(ATP) channel modulators in cirrhotic smooth muscle cells and did not alter the effects of these substances in normal smooth muscle cells. In endothelium-denuded aortae, exposure to exogenous endothelin-1 suppressed membrane potential responses to K(ATP) channel modulators. In intact aortae, the abundance of preproendothelin-1 mRNA and endothelin-1 did not significantly differ between normal and cirrhotic rats. CONCLUSIONS: K(ATP) channel opener-induced membrane hyperpolarization and K(ATP) channel blocker-elicited membrane depolarization are blunted in smooth muscle cells in intact cirrhotic aortae. This blunting is due to the activation of the endothelin-1 pathway in the aortic wall, downstream to the endothelial production of endothelin-1.

Adenosine Triphosphate↗
PubMed1999

Differential immunodiagnosis between cystic hydatid disease and other cross-reactive pathologies.

We assessed an Echinococcus granulosus hydatid fluid antigen-ELISA (EgHF-ELISA) as a serologic prescreening test for E. granulosus infections, supplemented by more specific confirmatory tests, including arc-5 immunoprecipitation and antigen B subunit 8-kD immunoblotting. The diagnostic sensitivity of the EgHF-ELISA was 91%. With regard to the test specificity of the EgHF-ELISA (overall = 82%), we observed relatively frequent cross-reactions in tumor patients (6%) and in patients with other parasitic diseases. Cestode-related cross-reactivity can be resolved by the complementary use of E. multilocularis-specific antigens or Taenia solium cysticercosis-specific immunoblotting. Immunoblotting based upon the detection of antibody reactivity to the 8-kD antigen of EgHF, or if appropriately detectable, to the 29-kD and 34-kD bands exhibited a 91% diagnostic sensitivity and an overall specificity of 97% or 94%, respectively. Thus, immunoblotting provided a 99% discrimination between seropositive pre-operative cystic hydatid disease cases and cross-reactive non-cestode parasitic infections or malignancies.

Agglutination Tests↗
PubMed1998

Down-regulation of hepatic and renal 11 beta-hydroxysteroid dehydrogenase in rats with liver cirrhosis.

BACKGROUND & AIMS: 11 beta-Hydroxysteroid dehydrogenase (11 beta-OHSD) enzymes are responsible for the interconversion of active 11 beta-hydroxycorticosteroids into inactive 11-ketoglucocorticosteroids and by that mechanism regulate the intracellular access of the steroids to the cognate receptor. A down-regulation of the shuttle of active to inactive glucocorticoids enhances access of glucocorticosteroids to both the glucocorticoid and the mineralocorticoid receptors. In liver cirrhosis, enhanced mineralocorticoid and glucocorticoid effects are observed. We therefore investigated the impact of liver cirrhosis after bile duct ligation on the transcription and activity of 11 beta-OHSD1 and 11 beta-OHSD2 in the corresponding tissues. METHODS: Messenger RNA from 11 beta-OHSD1 and 11 beta-OHSD2 was assessed by reverse-transcription polymerase chain reaction; activity was assessed by measuring the interconversion of corticosterone to dehydrocorticosterone. The effect of bile and bile salts was determined using COS-1 cells transfected with 11 beta-OHSD1 or 11 beta-OHSD2. RESULTS: In liver tissue, the messenger RNA ratios of 11 beta-OHSD1 to glyceraldehyde-3-phosphate dehydrogenase (GAPDH) levels and, in kidney tissue, the ratios of 11 beta-OHSD2 to GAPDH levels decreased after induction of liver cirrhosis. The 11 beta-OHSD activities were correspondingly reduced. Bile and individual bile salts inhibited 11 beta-OHSD1 and 11 beta-OHSD2 oxidative activity in transfected COS-1 cells. CONCLUSIONS: These findings indicate that in liver cirrhosis the mineralocorticoid and glucocorticoid receptor-protecting effects by the 11 beta-OHSD isoenzymes are down-regulated and that by the same mechanism the glucocorticoid and mineralocorticoid effects are enhanced.

11-beta-Hydroxysteroid Dehydrogenases↗
PubMed1998

Detection of endothelin-1 and its receptors in rat liver endothelial cells by in situ reverse transcriptase-polymerase chain reaction.

BACKGROUND/AIMS: Endothelin (ET)-1 is a potent vasoconstrictor, also in the liver; it increases intrahepatic resistance by targeting hepatic stellate cells acting via the ET-A receptor. The role of the expression and regulation of ET-1 and its receptors in endothelial liver cells, an important site of ET production in normal liver, is not yet well documented. In the present study, we have developed an in situ reverse transcriptase (RT)-polymerase chain reaction method to elucidate the presence of prepro-ET-1, ET-A and ET-B receptors in isolated rat liver endothelial cells. METHODS: After in situ collagenase-pronase liver perfusion, endothelial cells were isolated using a Nycodenz gradient. RT-polymerase chain reaction and in situ RT-polymerase chain reaction were performed using specific primers for prepro-endothelin, ET-A and ET-B. RESULTS: Trypan blue exclusion test showed a viability of more than 90% in the freshly isolated non-parenchymal cells. RT-polymerase chain reaction showed expression of prepro-endothelin, ET-A and ET-B in RNA isolated from the endothelial cells. After in situ RT-polymerase chain reaction, we detected cytoplasmatic staining representing the presence of mRNA in the endothelial cells, with all sets of primers. About 60-80% of cells were positive. Negative controls, in which the RT step was omitted, did not show any cytoplasmatic staining. CONCLUSIONS: Endothelin 1 and both ET-A and ET-B receptors are expressed in rat endothelial liver cells. The expression of ET and its receptors in liver endothelial cells could be important in the development of liver diseases and the regulation of microvascular exchange.

Animals↗
PubMed1998

The effect of endothelin and its antagonist Bosentan on hemodynamics and microvascular exchange in cirrhotic rat liver.

BACKGROUND/AIMS: To characterize the effects of endothelin-1 and of Bosentan, a mixed endothelin antagonist, on hepatic hemodynamics in cirrhotic animals in vivo and on hepatic microvascular exchange in the perfused rat liver. METHODS: Biliary cirrhosis was induced by bile duct ligation, and micronodular cirrhosis by chronic exposure to phenobarbital/CCl4 in male rats. Hepatic hemodynamics were studied under basal conditions and after administration of Bosentan (3-30 mg/kg) by the microsphere technique. Microvascular exchange was assessed in the in situ perfused rat liver by the multiple indicator dilution technique. RESULTS: Bosentan lowered portal pressure in a dose-dependent fashion; at the highest dose tested, this decrease averaged -29+/-11 and -26+/-8% in biliary and micronodular cirrhosis, respectively (p<0.01). This was achieved mainly via a marked decrease in hepatic arterial flow. In the perfused liver, endothelin-1 induced a dose-dependent vasoconstriction; up to 10(-9) mol/l; this was not associated with any effect on viability. At this dose, endothelin-1 markedly decreased extravascular albumin space in both controls and micronodular cirrhosis; this could be antagonized by Bosentan 10(-5) mol/l. CONCLUSIONS: Endothelin-1 affects hepatic microvascular exchange, presumably by a direct effect on hepatic sinusoidal endothelial cells. A mixed endothelin antagonist lowers portal pressure in vivo, presumably by acting on hepatic stellate cells, and counteracts the microvascular effects of endothelin-1 in vitro. These properties could prove useful in treatment of portal hypertension.

Animals↗
PubMed1998

False positive staining in the TUNEL assay to detect apoptosis in liver and intestine is caused by endogenous nucleases and inhibited by diethyl pyrocarbonate.

BACKGROUND: The terminal transferase uridyl nick end labelling (TUNEL) assay allows the easy demonstration of cell death as a result of apoptosis. However, when this assay is applied to liver tissue, the number of TUNEL positive cells is dependent on the time of incubation with proteinase K. AIM: To test whether false positive results are the result of the release of endogenous endonucleases by proteinase K and can be abolished by pretreatment with diethyl pyrocarbonate (DEPC). METHODS: Involution of hyperplastic ductules in bile duct ligated rats after biliary decompression by Roux-en-Y anastomosis and acute CCl4 intoxication were studied as models of apoptosis and necrosis, respectively. A standard TUNEL assay was applied to formalin fixed tissue sections mounted with cement. To inhibit putative endogenous endonucleases, tissue slides were pre-incubated with DEPC. RESULTS: In the standard TUNEL assay, the number of positive nuclei was highly dependent upon the length of time that sections were incubated with proteinase K. After pretreatment with DEPC, only cells that also exhibited morphological features of apoptosis stained positive. DEPC pretreatment abolished false positive staining in CCl4 induced hepatocyte necrosis and blocked interference by endogenous alkaline phosphatase in intestine. The method of gluing the tissue section to the glass slide was found to be of utmost importance because the effect of DEPC was abolished on silanised slides. CONCLUSIONS: False positive staining in the TUNEL assay in the liver is caused by the release of endogenous endonucleases as a result of proteinase treatment. This can be abolished by pretreatment of tissue slides with DEPC.

Animals↗
PubMed1998

Targeting of naproxen covalently linked to HSA to sinusoidal cell types of the liver.

The kinetic behaviour of a naproxen human serum albumin conjugate (Nap23-HSA) was investigated in rats and in isolated perfused rat livers (IPRL), as compared to its active metabolite naproxen-lysine (Nap-lysine) and free naproxen. Through covalently linking the anti-inflammatory drug naproxen to HSA, this drug can be selectively delivered to non parenchymal cells of the liver. Liver endothelial and Kupffer cells play an important role in the pathogenesis of inflammatory liver diseases. Targeting naproxen to these cells might increase its efficacy and reduce the side effects. The altered kinetic properties of Nap23-HSA, after i.v. injection of 22 mg x kg(-1), as compared to an equimolar amount of the uncoupled drug, were demonstrated in vivo by a decrease in the steady state volume of distribution (41 +/- 5 vs. 134 +/- 19 ml x kg(-1)), a decrease in its clearance (0.48 +/- 0.05 vs. 0.63 +/- 0.1 ml x min(-1) x kg(-1)), a shorter plasma half life (60 +/- 11 vs. 152 +/- 44 min) and a sustained biliary excretion. Liver targeting of Nap23-HSA was clearly demonstrated: drug content of the liver 180 min after injection was about 30 times higher for Nap23-HSA as compared to naproxen itself. The IPRL experiments showed that the Vmax of hepatic removal of the conjugate was 40 microg x min(-1) x g liver(-1). With doses below receptor saturation a rapid removal of the conjugate (t1/2 = 6 min) from the perfusion medium was found. In conclusion, this study demonstrates the saturable uptake of Nap23-HSA and its lysosomal degradation in both in vivo and IPRL experiments. Covalently linked naproxen is released as Nap-lysine. This active metabolite accumulates in Kupffer and endothelial cells in which it reaches therapeutic concentrations. Release from these cells leads to rapid uptake by hepatocytes and carrier mediated excretion into bile. Levels of Nap-lysine in bile and plasma reflect the slowest step in its generation: the proteolytic release in endothelial and Kupffer cells.

Animals↗
PubMed1998

Effect of chronic bile duct obstruction and LPS upon targeting of naproxen to the liver using naproxen-albumin conjugate.

Naproxen covalently linked to human serum albumin (NAP-HSA) is efficiently targeted to endothelial and Kupffer cells of the liver and may offer a new therapeutic approach in the treatment of liver disease associated with inflammatory processes. In the present investigation we explored the pharmacokinetic behaviour of targeted and non-targeted naproxen as well as the pharmacokinetic properties of the active metabolite, Naproxen lysine (Nap lysine), in rats rendered fibrotic by bile duct ligation (BDL) for 4 weeks. Furthermore, we studied the effect of endotoxemia, experimentally induced by intravenous injection of 800 microg/kg lipopolysaccaride (LPS) upon the pharmacokinetics of these agents in order to investigate the feasibility of targeting naproxen to non-parenchymal cells in the inflamed and fibrotic liver. Our studies demonstrate that liver disease altered the pharmacokinetic behaviour of the different naproxen compounds. Thus, initial plasma concentrations of NAP HSA and naproxen were markedly lower in BDL rats accompanied by an increase of the volume of distribution during the terminal elimination phase (Vd(beta) BDL vs control 114 +/- 63 vs 50 +/- 7 and 202 +/- 24 vs 115 +/- 11 ml/kg for naproxen and NAP-HSA, respectively). After injection of LPS, no significant change in the pharmacokinetics of NAP-HSA was found whereas the naproxen treated control animals showed an increase in the terminal volume of distribution (176 +/- 34 vs 115 +/- 11 ml/kg) as well as an elevation of the plasma half-life (171 +/- 27 vs 116 +/- 14 min). The feasibility of targeting naproxen to the chronically diseased liver could be clearly demonstrated: 15 min after administration of the conjugate 46% and 55% of the administered dose was found in the liver of CTR and BDL rats, whereas after injection of free naproxen only 5% and 12% of the dose was detected in liver tissue, respectively. We conclude that targeting albumin-linked naproxen to non-parenchymal cells in the liver is still feasible under the pathological conditions induced in the present study. Liver fibrosis induced significant alterations in the pharmacokinetic behaviour of the studied compounds.

Animals↗
PubMed1997

[Liver injury under tuberculostatic treatment].

We report the case of a patient with nausea, loss of appetite and increase of the aminotransferase levels to eight times the upper normal limit occurring two weeks after she was started on isoniazide, rifampicine and pyrazinamide for treatment of tuberculosis. Isoniazide is the most likely cause of liver injury occurring during combined antituberculosis therapy, whereas pyrazinamide or rifampicine are only rarely responsible. The case presented is used to review and compare the different recommendations concerning the monitoring of patients receiving antituberculous therapy and the clinical management of patients developing liver injury.

Aged↗
PubMed1997

[Are diuretics in the treatment of portal hypertension rational?].

When ascites develops in a patient with cirrhosis his probability to survive the following 2 years amounts to 50%. It is determined essentially by the residual functional capacity of the liver. In 80 to 90% of patients ascites due to portal hypertension can be managed by salt restriction and diuretics. Aldosterone-antagonists are more efficient and have fewer side effects than loop diuretics. They may lower portal tension by an additional direct effect on the vasculature. A daily reduction of body weight of 0.5 to 0.75 kg should not be exceeded because (prerenal) renal failure may become a threat. If diuretics are insufficient or when a rapid therapeutic success is needed paracentesis of 4-6.1 is a safe option if intravascular volume is substituted simultaneously. Albumin has proven superior to other plasma expanders (protection of renal function, survival). Only in the few patients whose ascites is intractable by the forementioned measures should alternatives such as peritoneo-, venous or porto-systemic shunts (nowadays mostly by interventional techniques via a transjugular catheter) be evaluated. The only treatment which not only attacks ascites symptomatically but also corrects the underlying disease is liver transplantation.

Ascites↗
PubMed1997

Ectopic expression of the calcium-binding protein parvalbumin in mouse liver endothelial cells.

To elucidate the physiological role of the Ca2+ binding protein parvalbumin, we have generated transgenic mice carrying the full-length complementary DNA (cDNA) of rat parvalbumin under the control of the heavy-metal inducible metallothionein IIA promoter. Immunohistochemical and biochemical methods have been used to detect the presence of ectopic parvalbumin expression in different tissues. Here we show the expression of parvalbumin in endothelial cells lining the liver sinusoids in situ and after isolation in vitro. The hemodynamic effects of endothelin 1, a peptide hormone mediating potent vasoconstriction via calcium signalling, were investigated in the mouse liver perfused in situ. Vasoconstriction, thought to be mediated by the Ito cell, was not affected in the transgenic animals, whereas microvascular exchange, probed with the multiple indicator dilution technique, was markedly decreased in normal mice but virtually not affected in the transgenic animals. This suggests that ectopically expressed parvalbumin is involved in the regulation of Ca2+ signals in the sinusoidal endothelial cells. This animal model could be of interest to those working on the physiology of liver circulation.

Animals↗
PubMed1997

Hepatic mitochondrial proliferation in rats with secondary biliary cirrhosis: time course and mechanisms.

It is well known that the hepatic mitochondrial protein content is increased in rats 4 weeks after bile duct ligation. In the present study, we measured the time course of this increase and assessed the levels of selected mitochondrial messenger RNA (mRNA) species and the rate of mitochondrial protein synthesis by isolated mitochondria. Three days after surgery, the mitochondrial protein content was not significantly different between bile duct-ligated (BDL) and control rats, averaging 1,140 +/- 220 mg/liver in BDL and 1,260 +/- 50 mg/liver in sham-operated control rats. However, in comparison with control rats, it was increased in BDL rats by 35% at 7 days, by 81% at 14 days, and by 27% at 28 days after surgery. In vitro mitochondrial protein synthesis, which was assessed as the fractional incorporation of [35S]-methionine into mitochondrial protein, was not different between BDL and control rats at 3 days after surgery, but was decreased in BDL rats by 63% at 7 days, by 55% at 14 days, and by 36% at 28 days after surgery. Northern blot analysis revealed an increase in the mRNA levels of adenosine triphosphate (ATP)ase subunit 6 and apocytochrome b in BDL rats at day 7, but no significant differences between BDL and control rats in mitochondrial mRNA and ribosomal RNA species 14 and 28 days after surgery. These results show that the hepatic mitochondrial protein content rises early after surgery in BDL rats, but this rise cannot be ascribed to elevated rates of mitochondrial protein synthesis. Thus, increased synthesis of nuclearly encoded mitochondrial proteins and/or decreased degradation of mitochondrial proteins appear likely mechanisms that lead to the observed increase in the hepatic mitochondrial protein content in BDL rats.

Animals↗
PubMed1997

Targeting naproxen coupled to human serum albumin to nonparenchymal cells reduces endotoxin-induced mortality in rats with biliary cirrhosis.

Endotoxin is thought to play a major role in cirrhotic liver disease. Cyclo-oxygenase inhibitors were shown to be partially protective against endotoxin but cannot be used in cirrhotic patients because of renal side-effects. We argued that administration of naproxen (NAP) linked to human serum albumin (HSA), which results in specific delivery of NAP to endothelial cells (EC) and Kupffer cells (KC) and exhibited hepatoprotective effects against lipopolysaccharide (LPS) in vitro, could protect cirrhotic rats from LPS toxicity while preserving renal function. The studies were performed in rats rendered cirrhotic by bile duct ligation (BDL); animals received LPS (Escherichia coli, 800 microg/kg) intravenously. Five groups were studied: LPS alone, rats pretreated with a conventional dose of NAP (50 mg/kg), NAP-HSA (22 mg/kg), NAP equimolar to NAP-HSA (1.5 mg/kg), or the HSA carrier. LPS induced significant mortality (55%); this was not affected by equimolar NAP (57%) but accentuated by conventional NAP (88%). In contrast, NAP-HSA provided significant protection (9%; P < .05). After conventional NAP treatment, significant renal toxicity was observed as evidenced by a marked reduction in sodium excretion (LPS vs. NAP-HSA vs. NAP [50 mg/kg] 33 +/- 22 vs. 50 +/- 39 vs. 4 +/- 3 micromol/h; P < .05). Renal prostaglandin E2 (PGE2) excretion was reduced by NAP in all groups, but most markedly at the conventional dosage (LPS vs. NAP-HSA vs. NAP [50 mg/kg] 132 +/- 115 vs. 39 +/- 19 vs. 9 +/- 8 ng/mL; P < .05). Successful targeting was evidenced by a significant hepatic enrichment of NAP in the NAP-HSA group compared with the equimolar untargeted group (30.16 +/- 9.33 vs. 1.13 +/- 1.95 nmol/g liver). Thus, targeting NAP to EC/KC results in improved survival, higher efficacy, and sparing of renal function in cirrhotic rats.

Animals↗
PubMed1997

[Liver transplantation in a small center: feasibility, efficacy and prospects].

Today, orthotopic liver transplantation is the treatment of choice for the end-stage of various liver diseases, and a 1-year survival rate of 80% and a 5-year survival rate of 70% in elective patients without tumor are reported in international surveys. The liver transplant programme of the Inselspital in Bern is small compared with international centres, which may raise questions about the results and the justification for such a programme. Over a period of 66 months, 62 liver transplantations were performed in 60 patients at the Inselspital. The hospital mortality was 3.3%, and the 2.5-year overall survival rate was 92% for elective cases without tumor. After a median follow-up of 30 months, 68% of all patients were re-integrated in housework or full- or part-time in their profession, and 83% were independent from the help of others. We conclude that a small liver transplant programme based only on routine resources can achieve results comparable to the international standards.

Academic Medical Centers↗
PubMed1997

Detection and characterization of mitochondrial DNA rearrangements in Pearson and Kearns-Sayre syndromes by long PCR.

We used a strategy based on long PCR (polymerase chain reaction) for detection and characterization of mitochondrial DNA (mtDNA) rearrangements in two patients with clinical signs suggesting Pearson syndrome and Kearns-Sayre syndrome (KSS), respectively, and one patient with myopathic symptoms of unidentified origin. Mitochondrial DNA rearrangements were detected by amplification of the complete mitochondrial genome (16.6 kb) using long PCR with primers located in essential regions of the mitochondrial genome and quantified by three-primer PCR. Long PCR with deletion-specific primers was used for identification and quantitative estimation of the different forms of rearranged molecules, such as deletions and duplications. We detected significant amounts of a common 7.4-kb deletion flanked by a 12-bp direct repeat in all tissues tested from the patient with Pearson syndrome. In skeletal muscle from the patient with clinical signs of KSS we found significant amounts of a novel 3.7-kb rearrangement flanked by a 4-bp inverted repeat that was present in the form of deletions as well as duplications. In the patient suffering from myopathic symptoms of unidentified origin we did not detect rearranged mtDNA in blood but found low levels of two rearranged mtDNA populations in skeletal muscle, a previously described 7-kb deletion flanked by a 7-bp direct repeat and a novel 6.6-kb deletion with no repeat. These two populations, however, were unlikely to be the cause of the myopathic symptoms as they were present at low levels (10-40 ppm). Using a strategy based on screening with long PCR we were able to detect and characterize high as well as low levels of mtDNA rearrangements in three patients.

Adolescent↗