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Biomedical subjects

U Rauen

Publications and source records attributed to U Rauen.

At least 37 records · Page 2Linked to original sources
PubMed1998

The critical role of Hepes in SIN-1 cytotoxicity, peroxynitrite versus hydrogen peroxide.

The cytotoxicity of the superoxide anion radical- and nitric oxide-releasing compound SIN-1 to L929 cells was studied in Krebs-Henseleit buffer. pH 7.4, in the presence and absence of Hepes. SIN-1 cytotoxicity was significantly higher in the presence of Hepes than in the absence of Hepes. The available amount of peroxynitrite formed from SIN-1, however, was significantly decreased by Hepes as indicated by decreased oxidation of dihydrorhodamine 123. On the other hand, Hepes largely increased the formation of H2O2 from SIN-1. Catalase protected the L929 cells from SIN-1 cytotoxicity in the buffer with Hepes. In the buffer without Hepes catalase did not have any protective effect. In contrast, tyrosine and tryptophan provided significant protection against SIN-1 cytotoxicity independent of the presence of Hepes. These results demonstrate that the immediate toxic agent formed from SIN-1 decisively depends on the presence of Hepes. In its absence cytotoxicity is most likely mediated by peroxynitrite while in the presence of Hepes, cytotoxicity is conveyed by co-operative action of hydrogen peroxide and reactive nitrogen species.

Animals↗
PubMed1998

Auxiliary liver transplantation with arterialization of the portal vein for acute hepatic failure.

Six adult patients suffering from acute hepatic failure and with a high urgent status underwent heterotopic auxiliary liver transplantation. In four of these patients, the portal vein of the liver graft was arterialized in order to leave the native liver and the liver hilum untouched and to be able to place the liver graft wherever space was available in the abdomen. The arterial blood flow via the portal vein was tapered by the width of the anastomosis. Two patients died, one of sepsis on postoperative day 17 (POD), the other after 3 months due to a severe CMV pneumonia. There were no technically related deaths. The native liver showed early regeneration in all cases. In one patient, the auxiliary graft was removed 6 weeks after transplantation. Four weeks later, he had to undergo orthotopic retransplantation due to a recurrent fulminant failure of the recovered native liver. This patient is alive more than 1 year after the operation. We conclude that heterotopic auxiliary liver transplantation with portal vein arterialization is a suitable approach to bridging the recovery of the acute failing native liver.

Acute Disease↗
PubMed1998

Cold-induced release of reactive oxygen species as a decisive mediator of hypothermia injury to cultured liver cells.

The mechanisms of hypothermia-induced cell injury are still unclear. The present study provides experimental evidence for the involvement of reactive oxygen species in hypothermia injury: cultured rat hepatocytes incubated in cold (4 degrees C) Krebs-Henseleit buffer or cell culture medium were injured under normoxic conditions and even more so under hyperoxic conditions, whereas the hepatocytes were protected under hypoxic conditions. During warm (37 degrees C) incubation in cell culture medium, on the other hand, cell injury was minimal under normoxic conditions, only slightly increased under hyperoxic conditions, but substantially increased under hypoxic conditions. The injury occurring during cold normoxic incubation was also largely decreased by the addition of the spin-trap 5,5-dimethyl-1-pyrroline N-oxide, the hydroxyl radical scavenger dimethyl sulfoxide, the flavonoid silibinin, or the transition metal chelator 2,2'-dipyridyl to the medium, or by preincubating the cells with the iron chelator deferoxamine or the lipophilic antioxidant alpha-tocopherol before the hypothermic incubation. In addition, marked lipid peroxidation was observed during cold incubations without inhibitors, but not during warm incubations. Similar results were obtained with cultured rat liver endothelial cells. These results suggest that in hepatocytes and in liver endothelial cells, cold-induced release of reactive oxygen species, most likely of hydroxyl radicals, is the main injurious factor under hypothermic conditions.

2,2'-Dipyridyl↗
PubMed1998

Tissue injury by reactive oxygen species and the protective effects of flavonoids.

Reactive oxygen species contribute decisively to a great variety of diseases. Flavonoids are benzo-gamma-pyrone derivatives of plant origin found in various fruits and vegetables but also in tea and in red wine. Some of the flavonoids, such as quercetin and silibinin, can effectively protect cells and tissues against the deleterious effects of reactive oxygen species. Their antioxidant activity results from scavenging of free radicals and other oxidizing intermediates, from the chelation of iron or copper ions and from inhibition of oxidases. For their free radical scavenging properties, scavenging of lipid- and protein-derived radicals is presumably of special importance. A non-radical reactive oxygen species effectively trapped by flavonoids is hypochlorous acid. In general, the antioxidative properties of flavonoids are favoured by a high degree of OH substitution. On the other hand, inhibition of enzymatic functions other than oxidases, e.g., inhibition of lipoxygenase and thus prevention of the formation of leukotrienes, may also participate in the cell and tissue protective properties of flavonoids.

Antioxidants↗
PubMed1997

[Auxiliary liver transplantation for acute liver failure after intake of 3,4-methylenedioxymethamphetamine ("Ecstasy")].

HISTORY AND CLINICAL FINDINGS: An 18-year-old patient had for 6 days been suffering from right upper abdominal pain, weight loss, vomiting and yellow discoloration of the skin. For the preceding 8 months he had been regularly taking 1-2 tablets of "ecstasy" (3,4-methylenedioxymethamphetamine--MDMA) per week, the last 8 days before the onset of the described signs. Physical examination was unremarkable, except for pain on pressure over the right upper abdomen and the jaundice. INVESTIGATIONS: The activities of SGOT (756 U/I), SGPT (1450 U/I). gamma GT (164 U/I) and lactate dehydrogenase (539 U/I) as well as total bilirubin level (7.5 mg/dl) were elevated. The synthesising functions of the liver were impaired (thromboplastin time 47%, fibrinogen 116 mg/dl). Abdominal sonography was unremarkable. All virological tests (hepatitis A, B, C and D; Epstein-Barr virus; cytomegalovirus; HIV 1 and 2) were negative. TREATMENT AND COURSE: The suspected diagnosis was acute liver failure after "ecstasy" intake. The cholestasis and the parameters of liver synthesis and hepatocellular functions deteriorated under symptomatic treatment. 15 days after onset of the first symptoms progressive hepatic encephalopathy occurred and required heterotopic auxiliary liver transplantation (piggy-back technique). 5 months later hepatobiliary sequential scintigraphy demonstrated regenerating of the patient's own liver an atrophy of the transplanted liver. Immunosuppression with cyclosporin A and prednisolone was gradually reduced, and the transplant was removed 6 months postoperatively because of an abscess in it. 11 months after the transplantation liver functions is normal and the patient well. CONCLUSION: In young patients with jaundice of unknown origin toxic hepatitis after "ecstasy" intake should be considered. Auxiliary liver transplantation can lead to regeneration during temporary relief of the patient's own liver. After its function has been restored immunosuppression is no longer needed.

Adolescent↗
PubMed1997

Rapid decrease in cellular sodium and chloride content during cold incubation of cultured liver endothelial cells and hepatocytes.

Hypothermia, as used for organ preservation in transplantation medicine, is generally supposed to lead to an intracellular accumulation of sodium, and subsequently of chloride, via inhibition of the Na+/K+-ATPase. However, on studying the cellular sodium concentration of cultured liver endothelial cells using fluorescence microscopy, we found a 55% decrease in the cellular sodium concentration after 30 min of cold incubation in University of Wisconsin (UW) solution. To confirm this surprising result, we set up a capillary electrophoresis method that allowed us to determine the cellular contents of inorganic cations and of inorganic anions. Using this method we measured a decrease in the cellular sodium content from 104+/-11 to 55+/-4 nmol/mg of protein, accompanied by a decrease in the chloride content from 71+/-9 to 25+/-5 nmol/mg of protein, after 30 min of cold incubation in UW solution. When the endothelial cells were incubated in cold Krebs-Henseleit buffer or in cold cell culture medium instead of UW solution, similar early decreases in cellular sodium and chloride contents were observed, thus excluding the possibility of the decreases being dependent on the preservation solution used. Furthermore, experiments with cultured rat hepatocytes yielded a similar decrease in sodium content during initiation of cold incubation in UW solution, so the decrease does not appear to be cell-specific either. These results suggest that, contrary to current opinion, sodium efflux predominates over sodium influx during the early phase of cold incubation of cells.

Adenosine↗
PubMed1997

Decrease of ischemic injury to the isolated perfused rat liver by loop diuretics.

Recent studies suggest a major role played by sodium in the pathogenesis of ischemic liver injury: in these studies, sodium-free media have been shown to offer protection against hypoxic injury to isolated hepatocytes. As sodium-free perfusions of the isolated rat liver proved impossible because of extensive vasoconstriction, we assessed the effects of two inhibitors of the Na+-K+-2Cl- cotransporter, the loop diuretics furosemide and bumetanide, on ischemic liver injury. In untreated control livers lactate dehydrogenase (LDH) efflux immediately after reperfusion after 60 minutes of ischemia at 37 degrees C was 1666 +/- 473 U/L. When livers were pretreated with furosemide or bumetanide before the ischemic period, LDH efflux was only 773 +/- 292 U/L and 702 +/- 183 U/L respectively (P < .01). LDH activity in the effluent of the pretreated livers remained significantly below the values of ischemic control livers for the whole reperfusion period of 90 minutes. Bile flow in the postischemic phase was improved by pretreatment with furosemide or bumetanide. The increase in intracellular sodium, as measured by 23Na-NMR, was attenuated from 193% +/- 71% during 60 minutes of ischemia in controls to 148% +/- 80% after bumetanide application (P < .05). Also, after 120 minutes of warm ischemia, LDH and aspartate aminotransferase release were significantly decreased and bile flow increased by pretreatment with bumetanide. Thus, both furosemide and bumetanide showed a clear benificial effect on rat livers subjected to warm ischemia. These data suggest that one means by which sodium ions are accumulated during liver ischemia might be the Na+-K+-2Cl- cotransporter, which is blocked by furosemide and bumetanide.

Animals↗
PubMed1997

Oxygen-free radical-mediated injury to cultured rat hepatocytes during cold incubation in preservation solutions.

We have previously shown that the injury to cultured liver endothelial cells during cold incubation in University of Wisconsin (UW) solution is energy-dependent and is mediated by reactive oxygen species. Here we demonstrate that this reactive oxygen-mediated injury is specific neither to endothelial cells nor to UW solution: cultured hepatocytes incubated in cold (4 degrees C) UW solution or histidine-tryptophan-ketoglutarate (HTK) solution were injured under normoxic conditions (loss of viability, 63% +/- 10% after 48 hours of cold incubation in UW solution and 82% +/- 11% after 24 hours of cold incubation in HTK solution), whereas hypoxia was protective (loss of viability, 29% +/- 12% [UW] and 13% +/- 3% [HTK] after the same cold incubation times). The injury under normoxic conditions was also largely decreased by adding either the spin trap 5,5-dimethyl-1-pyrroline N-oxide (DMPO) or the flavonoid silibinin to the solutions, or by preincubating the cells with the iron chelator deferoxamine before the hypothermic incubation. Marked lipid peroxidation was observed during cold incubation in both preservation solutions. These results suggest that the injury to cultured hepatocytes during cold incubation in UW and HTK solutions is mediated by reactive oxygen species as is the injury to cultured liver endothelial cells.

Adenosine↗
PubMed1997

Preservation of pig liver allografts after warm ischemia: normothermic perfusion versus cold storage.

Warm ischemia is known to induce substantial damage to the liver parenchyma. With respect to clinical liver transplantation, the tolerance of the liver to warm ischemia and the preservation of these organs have not been studied in detail. In isolated reperfused pig livers we proceeded according to the following concept: Livers were subjected to 1 or 3 h of warm ischemia. Subsequently, these organs were preserved by either normothermic perfusion or cold storage (histidine-tryptophan-alpha-ketoglutarate, HTK) for 3 h each. After storage, liver function was assessed in a reperfusion circuit for another 3 h. Parameters under evaluation were bile flow, perfusion flow, oxygen consumption, enzyme release into the perfusate (creatine kinase, glutamic oxaloacetic transaminase (GOT), lactic dehydrogenase, and glutamic pyruvic transaminase), and histomorphology. Damage to the liver was lowest after warm ischemia of 1 h. The results after cold storage were superior to those after normothermic perfusion (GOT: 3.2 +/- 0.3 and 2.6 +/- 0.2 U/g liver; cumulative bile production: 14.7 +/- 2.1 and 9.4 +/- 1 ml, respectively; P < 0.05). In contrast, we found substantial damage at the end of reperfusion in livers undergoing 3 h of warm ischemia under both preservation techniques with severe hepatocellular pyknoses and essentially altered nonparenchymal cells. The results suggest that pig livers undergoing 1 h of warm ischemia and cold storage for 3 h with HTK solution may lead to functioning after transplantation.

Alanine Transaminase↗
PubMed1997

Involvement of reactive oxygen species in the preservation injury to cultured liver endothelial cells.

We have previously demonstrated an energy-dependent injury to cultured liver endothelial cells during cold incubation in University of Wisconsin (UW) solution. In the present study, we report experimental evidence for the involvement of reactive oxygen species in this injury: LDH release during 48 h of cold incubation in UW solution was decreased from 40-55% under aerobic conditions to less than 20% under hypoxic conditions or by the presence of KCN (1 mM). Similar protection was achieved by the addition of the spin trap 5,5-dimethyl-1-pyrroline N-oxide, the hydroxyl radical scavenger dimethyl sulfoxide, or the flavonoid silibinin to UW solution under aerobic conditions. Preincubating the cells with the iron chelator deferoxamine even decreased the injury to less than 5%. The residual injury (as observed after longer incubation times) under hypoxic conditions or in cells preincubated with deferoxamine was no longer energy dependent. The amount of thiobarbituric acid-reactive substances markedly increased during cold incubation of the cells in UW solution. This increase was not observed in UW solution to which KCN had been added, i.e., under the conditions of energy depletion. These results suggest that an iron-dependent generation of reactive oxygen species with subsequent lipid peroxidation is involved in the pathogenesis of the injury to cultured liver endothelial cells in cold UW solution.

Animals↗
PubMed1997

Injury to cultured liver endothelial cells after cold preservation: mediation by reactive oxygen species that are released independently of the known trigger hypoxia/reoxygenation.

When cultured liver endothelial cells were incubated in cold University of Wisconsin (UW) solution under hypoxic conditions, 3 +/- 2% of cells had lost viability after 25 h. Simulating reperfusion by returning the cells to normal cell culture conditions increased the injury to 30 +/- 11% after 3 h of recultivation. An injury of similar time course was observed after cold normoxic incubation in UW solution when the loss of viability increased from 20 +/- 5% after the cold incubation to 60 +/- 8% during a 3 h recultivation period. The loss of viability during recultivation was decreased by hypoxia, by the addition of 5,5-dimethyl-1-pyrroline N-oxide or of dimethyl sulfoxide to the cell culture medium, or by preincubating the cells with deferoxamine. The injury was accompanied by lipid peroxidation and was dependent on the period of cold incubation in UW solution. These results suggest the occurrence of a cold-preservation-induced "recultivation injury" mediated by reactive oxygen species. This cold-preservation-induced injury--occurring independently of hypoxia/reoxygenation--is likely to constitute an additional component of reperfusion injury after cold preservation of the liver.

Animals↗
PubMed1996

Determination of hepatocellular enzymes in effluent of human liver grafts for preoperative evaluation of transplant quality.

In 50 human livers harvested for transplantation, injury was assessed by determination of liver enzymes (lactate dehydrogenase, aspartate aminotransferase, alanine aminotransferase, glutamate dehydrogenase, and creatine kinase) and of thrombomodulin in the effluent perfusate after cold ischemia. The results were compared with the morphology and the clinical course after transplantation. Whereas the release of the markers of endothelial cell injury correlated neither with the history of the graft nor with the postoperative course, the release of hepatocellular enzymes into the perfusate did indicate the severity of liver injury, even when biopsy showed normal liver tissue. Seven of 12 livers with high activities of hepatocellular enzymes in the effluent (activity of more than twice the median) showed delayed onset of function or primary nonfunction. In the other 38 livers with enzyme activities below this borderline, no delayed functioning or primary nonfunction was observed. Thus, determination of liver enzyme activities in the effluent makes it possible to identify those livers in which initial nonfunction is very unlikely, a potential that is especially valuable in livers shown by anamnesis or morphology to be of borderline quality.

Biomarkers↗
PubMed1996

Injury to hepatocytes and non-parenchymal cells during the preservation of human livers with UW or HTK solution: a determination of hepatocellular enzymes in the effluent perfusate for preoperative evaluation of the transplant quality.

In 50 livers harvested for transplantation, injury was assessed by determination of the enzymes in the effluent perfusate after cold ischemia. The results were compared to the histology and the clinical course after transplantation. Whereas the release of the markers of endothelial cell injury did neither correlate with the history of the graft nor with the postoperative course, the release of hepatocellular enzymes in the perfusate did indicate preexisting damage of the liver even when the biopsy showed normal liver tissue. Of 12 livers with high activity of hepatocellular enzymes in the effluent (activity of more than twice the median), 7 showed delayed onset of function or a primary non-function. In the other 38 livers with an enzyme activity below this borderline no delayed function or primary non-function was observed. Because of additional influences a prognosis of the function after transplantation was not possible, but the determination of the enzymes in the effluent of marginal livers probably allows the preoperative recognition of organs which will do well.

Adenosine↗
PubMed1996

[Auxiliary liver transplantation in urgent and emergency indications].

This report will focus on seven patients treated with auxiliary liver transplantation. In two cases the indication was severe metabolic disorder and in five cases a fulminant hepatic failure. The clinical course was highly complicated in both cases with metabolic disorder (the transplant was lost, one patient died), but satisfactory in the patients suffering from fulminant hepatic disease: three of five are off immunosuppression, one is under therapy and one patient died of sepsis in the early phase.

Adolescent↗
PubMed1995

Evidence for increased nitric oxide production after liver transplantation in humans.

To evaluate the role of in vivo-produced nitric oxide (NO) after orthotopic liver transplantation, nitrate, a stable end product of spontaneous NO conversion in blood, was assayed in plasma samples of 32 patients. In 31 patients, nitrate increased from 36 +/- 2 microM to 137 +/- 8 microM within the first 6 postoperative days. In 11 out of 12 patients with an uneventful early postoperative course, nitrate increased from 33 +/- 2 microM to 70 +/- 8 microM, and returned to baseline levels within 2-3 days. In the remaining 20 patients with episodes of rejection and/or infection, the nitrate peak was augmented and prolonged. Ten patients suffering from these events in the later postoperative course showed a second nitrate elevation. In 31 patients, effective plasma levels of cyclosporine were reached 4-5 days after OLT. The patient without significant elevation in plasma nitrate had effective levels already at day 1. After liver resection or coronary bypass grafting, the median nitrate level remained at 21 microM (range 15-36 microM; healthy persons: median 24 microM, range 18-32 microM). After kidney transplantation nitrate was elevated in the early postoperative course. Thus, NO formation appears to be increased after solid organ transplantation, but not after other surgeries. After OLT, the increase appears to occur (a) in response to rejection and/or infection, and (b) 4-6 days after surgery in the absence of overt complications. In the latter case, NO might be involved in subclinical rejection and its production is possibly dependent upon the effectiveness of the immunosuppressive therapy.

Cyclosporine↗
PubMed1994

Endothelial cell toxicity of preservation solutions: comparison of endothelial cells of different origin and dependence on growth state.

Previously, we have shown that cultured liver endothelial cells are affected by an energy-dependent injury when incubated in cold University of Wisconsin (UW) or histidine-tryptophan-ketoglutarate solution. Here, we studied the susceptibility of other endothelial cells to this type of injury. Aortic endothelial cells in early-confluent, i.e., still proliferating, monolayer cultures were damaged more quickly during cold incubation in UW solution than during cold incubation in Krebs-Henseleit buffer. At this stage the addition of KCN did not alter the loss of viability in UW solution, but when the culture period was prolonged, cells were protected by the addition of cyanide. A paradoxical, protective effect of KCN could also be observed in late-confluent, i.e., nonproliferating, cultures of coronary endothelial cells incubated in UW solution. Similarly, liver endothelial cells in subconfluent, growing cultures were damaged by the addition of cyanide (loss of viability after 48 h, 3 +/- 1% in UW, 65 +/- 19% in UW + KCN), whereas in late-confluent cultures the addition of cyanide to UW solution was protective (loss of viability after 48 h, 100 +/- 0% in UW, 31 +/- 15% in UW + KCN). Variations of culture period and seeding density and the use of inhibitors of cell proliferation demonstrated that liver endothelial cells acquire their susceptibility to energy-dependent injury along with confluence. Subcultured cells retained this susceptibility for some hours. These results suggest that the energy-dependent injury described previously is not confined to liver endothelial cells and that the occurrence of energy-dependent injury requires a capacity of the cells that develops only after cultures have grown to confluence.

Adenosine↗
PubMed1994

Nonparenchymal cell and hepatocellular injury to human liver grafts assessed by enzyme-release into the perfusate.

Experimental studies have demonstrated preferential injury to the sinusoidal endothelium during liver preservation with University of Wisconsin (UW) or Euro-Collins solution. This endothelial cell injury has an unclear pathogenesis, and it has not yet been studied in the human liver. Therefore, we analyzed the effluent of 21 human liver allografts after cold storage. Markers of hepatocellular and nonparenchymal cell injury were assessed. After preservation with UW solution, early effluent samples contained 1823 +/- 1494 U/l lactate dehydrogenase (LDH), 493 +/- 516 U/l alanine aminotransferase (ALT) and 132 +/- 97 U/l creatine kinase (CK; 92 +/- 92 U/l CK-BB). The effluent of livers preserved in histidine-tryptophan-ketoglutarate (HTK) solution contained 3681 +/- 2009 U/l LDH, 1139 +/- 599 U/l ALT and 282 +/- 120 U/l CK (165 +/- 91 U/l CK-BB). Comparison of effluent enzyme activities with liver tissue enzyme activities indicates that the release of the endothelial cell/nonparenchymal cell marker creatine kinase was higher, by a factor of 7-8, than the release of hepatocellular enzymes. Effluent thrombomodulin concentrations were 123 +/- 248 ng/ml (UW) and 604 +/- 299 ng/ml (HTK), and effluent glucose concentrations, 40.3 +/- 27.0 mM (726 +/- 486 mg/dl; UW) and 10.4 +/- 4.5 mM (187 +/- 81 mg/dl; HTK). We conclude that prominent endothelial cell injury also occurs in human liver grafts after preservation with UW solution or HTK solution. This endothelial cell injury is unlikely to be caused by hypoxia-induced energy deficiency, as it affects a cell type with a high glycolytic capacity in the presence of high glucose levels.(ABSTRACT TRUNCATED AT 250 WORDS)

Adenosine↗