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Biomedical subjects

Y Calmus

Publications and source records attributed to Y Calmus.

At least 55 records · Page 3Linked to original sources
PubMed1998

Internal bioartificial liver with xenogeneic hepatocytes prevents death from acute liver failure: an experimental study.

OBJECTIVE: To demonstrate that a bioartificial liver, using allogeneic or xenogeneic hepatocytes protected from rejection by a semipermeable membrane, could prevent death from acute liver failure. SUMMARY BACKGROUND DATA: An implantable bioartificial liver using isolated hepatocytes could be an alternative to orthotopic liver transplantation to treat patients with acute liver failure. It could serve either as a bridge until liver transplantation or as the main treatment until recovery of the native liver. However, allogeneic or xenogeneic hepatocytes that could be used in clinical applications are spontaneously rejected. METHODS: Acute liver failure was induced in rats by 95% liver resection. Twenty-five million hepatocytes harvested in rats (allogeneic) or guinea pigs (xenogeneic) were encapsulated in a semipermeable membrane to protect them from rejection. The hollow fibers containing hepatocytes were transplanted into the peritoneum of recipient rats. Survival rates were compared between rats transplanted or not with hepatocytes. RESULTS: In groups not transplanted with viable hepatocytes, 73% to 93% of rats died after 95% liver resection. The mortality rate was reduced to 39% in rats transplanted with allogeneic hepatocytes and 36% in rats transplanted with xenogeneic hepatocytes. The bioartificial liver could be removed 1 month after transplantation, when regeneration of the native liver was complete. Allogeneic and xenogeneic hepatocytes remained viable. CONCLUSIONS: The implantable bioartificial liver was able to prevent death in this model of acute liver failure. This could be an important step toward clinical application of the method.

Animals↗
PubMed1998

Low level of interleukin 10 synthesis during liver allograft rejection.

Interleukin 10 (IL-10) is a macrophage and T-cell-derived cytokine with potent immunosuppressive properties. To assess its role in liver allograft rejection, we evaluated the plasma level and in situ production of IL-10 after liver transplantation and designed in vitro studies to asses the effects of IL-10 on the allogeneic response. Normal controls and liver transplant recipients with acute rejection, chronic rejection, other complications (recurrent hepatitis C, biliary complications), or no complications were evaluated. The plasma IL-10 level was measured by an immunoenzymatic technique. IL-10 expression in the liver was detected on frozen liver biopsies by in situ hybridization and immunohistochemistry. Plasma IL-10 levels were not elevated during acute or chronic rejection, when compared with liver recipients with uncomplicated transplants. IL-10 mRNA and protein expressions in the liver graft were restricted to rare scattered sinusoidal cells of transplant recipients with acute or chronic rejection, as well as in those with no complications. In mixed lymphocyte cultures performed with peripheral blood mononuclear cells (PBMC) from normal subjects, IL-10 decreased the cell proliferation in a dose-dependent manner, and this immunosuppression was synergistic with that of cyclosporine or FK506. These findings indicate that IL-10 production is low during allograft rejection. Thus, IL-10 therapy in association with cyclosporine or FK506 might be proposed after liver transplantation.

Acute Disease↗
PubMed1997

Common bile duct stenosis caused by chronic pancreatitis after liver transplantation for alcoholic cirrhosis.

BACKGROUND: The prevalence of chronic pancreatitis in patients with alcoholic cirrhosis ranges from 7% to 11% and is not considered a contraindication for liver transplantation. METHODS: Among 59 liver transplant recipients grafted for alcoholic cirrhosis, we report two observations of common bile duct stenosis due to chronic pancreatitis. RESULTS: In both cases, pretransplant work-up disclosed no clinical or radiological evidence of chronic pancreatitis. The diagnosis of common bile duct stricture was made 6 and 60 months after liver transplantation. One patient was reoperated upon, and his choledochocholedochostomy was converted into a Rouxen-Y choledochojejunostomy. The second patient experienced metastatic laryngeal carcinoma and died before reoperation. CONCLUSIONS: These observations suggest that common bile duct stricture caused by chronic pancreatitis may occur after liver transplantation for alcoholic cirrhosis, even after a long-standing history of abstinence.

Adult↗
PubMed1997

Evidence for survival and metabolic activity of encapsulated xenogeneic hepatocytes transplanted without immunosuppression in Gunn rats.

BACKGROUND: Hepatocyte transplantation could be an alternative to whole organ transplantation to correct enzymatic disorders. To this end, it would be of major importance to use xenogeneic cells without immunosuppression. The aim of this study was to investigate the survival and metabolic activity of encapsulated xenogeneic hepatocytes in the absence of immunosuppression. For this purpose, we used Gunn rats genetically incapable of bilirubin conjugation. METHODS: Xenogeneic (from guinea pigs) and allogeneic (from Lewis rats) hepatocytes (2x10(7)) were isolated, macroencapsulated in hydrogel hollow fibers made with an acrylonitrile-sodium methallyl-sulfonate copolymer, and transplanted into the peritoneum of Gunn rats without any immunosuppression. Plasma bilirubin levels were evaluated weekly. Bilirubin conjugates in bile and cell morphology were studied after 5 and 12 weeks, respectively. RESULTS: In Gunn rats transplanted with xenogeneic hepatocytes, a significant decrease in the serum bilirubin level was observed between 3 and 9 weeks after transplantation when compared with controls transplanted with empty hollow fibers: it fell to 62% of the initial level at weeks 5-7 (P < 0.01). A comparable result was observed in Gunn rats transplanted with encapsulated allogeneic cells. Bilirubin conjugates were observed in bile samples of rats transplanted with encapsulated hepatocytes. After explantation, hollow fibers appeared intact with minimal fibrosis. Cell viability and hepatocyte morphology were preserved. CONCLUSIONS: These results indicate that macroencapsulated xenogeneic hepatocytes can survive and remain functional for more than 2 months when transplanted in vivo in the absence of any immunosuppression.

Acrylic Resins↗
PubMed1997

Endothelin-1 induces liver vasoconstriction through both ETA and ETB receptors.

BACKGROUND/AIMS: We investigated which endothelin receptors mediate the vasoconstrictive effects of endothelin-1 on liver circulation. METHODS: An isolated perfused rat liver model in recirculation was used. RESULTS: The perfusion of 10(-10) M endothelin-1 had no significant influence on the liver flow, whereas 10(-9) M endothelin-1 induced significant vasoconstriction, with flow dropping from 3.20 +/- 0.34 to 1.48 +/- 0.28 ml. min-1.g-1 liver tissue (p < 0.01 vs controls). The liver flow was interrupted following the perfusion of 10(-8) M endothelin-1. Sarafatoxin C and BQ 3020, two agonists of ETB receptor, had vasoconstrictive effects in this model. Sarafatoxin C decreased the liver flow in a dose-dependent manner, from 3.32 +/- 0.21 to 2.18 +/- 0.20, 1.60 +/- 0.09, and 1.01 +/- 0.06 ml.min-1. g-1, respectively, with 10(-9) M, 10(-8) M, and 10(-7) M. While BQ 123, an antagonist of ETA receptor, or BQ 788, an antagonist of ETB receptor, partially reversed the effect of 10(-9) M endothelin-1, the simultaneous administration of BQ 123 and BQ 788 completely reversed these effects. CONCLUSIONS: These results indicate that the vasoconstrictive effects of endothelin-1 on the liver circulation are mediated through both ETA and ETB receptors.

Animals↗
PubMed1997

Protein-losing enteropathy secondary to hepatic venous outflow obstruction after liver transplantation.

A 42-year-old man with a history of repeated abdominal surgery and lymph node tuberculosis underwent orthotopic liver transplantation for primary sclerosing cholangitis. Two years after transplantation, this patient developed a severe protein-losing enteropathy with no evidence of cardiac disease or lymphoproliferative disorder. Imaging work-up revealed hemodynamically significant stenosis of the supra-hepatic caval anastomosis, which was treated by percutaneous balloon angioplasty. All clinical and biochemical disorders resolved within 1 month after percutaneous dilatation, but relapsed simultaneously with recurrent anastomotic stenosis 15 months later. Repeat caval angioplasty resulted in rapid recovery, which strongly suggests that hepatic venous outflow obstruction was responsible for the protein-losing enteropathy in this patient.

Adult↗
PubMed1997

Expression of the membrane attack complex of complement and its inhibitors during human liver allograft transplantation.

BACKGROUND/AIMS: In order to test the possible role of activated complement in human liver allograft rejection, we evaluated the expression of the membrane attack complex of complement, its soluble inhibitors clusterin and vitronectin and its membrane inhibitor protectin during the evolution of liver transplants. METHODS: An indirect immunoperoxidase technique was applied to biopsy specimens obtained from liver allografts in 16 patients without complications, nine with acute rejection, four with chronic rejection and five with biliary complications. RESULTS: Two types of membrane attack complex deposition were observed: (a) extracellular deposits in portal tracts and perisinusoidal matrix, associated with clusterin and vitronectin, similar to those found in the normal liver; and (b) intra-portal vascular deposits, devoid of clusterin and vitronectin. Vascular membrane attack complex deposition was detected in four clinically stable patients, three patients with chronic rejection and two patients with biliary complications. In clinically stable patients, vascular membrane attack complex deposition was restricted to large portal vessels and was detected in a minority of portal tracts. In patients with chronic rejection or biliary complications, vascular membrane attack complex deposition was detected along both large and small portal vessels and was present in the majority of portal tracts. Protectin induction on hepatocytes was detected in 33 cases. CONCLUSIONS: Our results suggest that membrane attack complex deposition is unlikely to play a major role in the pathogenesis of acute liver allograft rejection but may contribute to the vascular and biliary lesions observed in chronic rejection.

Adult↗
PubMed1997

NO-mediated vasodilation in the rat liver. Role of hepatocytes and liver endothelial cells.

BACKGROUND/AIMS: Nitric oxide (NO) is a potent vasodilator. We investigated the mechanisms responsible for this effect in the liver. METHODS: Isolated perfused rat liver and cultures of endothelial sinusoidal cells and hepatocytes were used. RESULTS: L-arginine (10(-3) M) and NO donor Sin-1 (10(-5) M) respectively increased the liver flow by 52% (p<0.01) and 93% (p<0.01) vs controls. The NO synthase inhibitor Nw-nitro-L-arginine (10(-3) M) and the guanylate cyclase inhibitor methylene blue (10(-5) M) respectively decreased the basal liver flow by 26% and 16% (p<0.05) and inhibited the vasodilating effects of L-arginine. L-arginine (10(-3) M) increased nitrite concentration in hepatocyte culture (77.25+/-7.40 micromol x l(-1) vs 14.70+/-3.55 micromol x l(-1) in controls; p<0.01) and in liver endothelial cell culture (0.36+/-0.09 micromol x l(-1) vs 0.12+/-0.05 micromol x l(-1) in controls; p<0.05). Nw-nitro-L-arginine inhibited the basal production and abolished the L-arginine-induced production of nitrites both in hepatocyte and in liver endothelial cell cultures. The concentration of nitrites in the hepatocyte supernatant rose from 14.70+/-3.55 micromol x l(-1) to 150.50+/-45.55 micromol x l(-1) in the presence of a combination of interleukin-1beta, TNF alpha and interferon gamma. CONCLUSIONS: Under basal conditions, NO regulates the vascular tone of liver circulation. Both liver endothelial cells and hepatocytes can be implicated. NO production by hepatocytes may increase during inflammation.

Animals↗
PubMed1996

Comparison between aortic and sinusoidal liver endothelial cells as targets of hyperacute xenogeneic rejection in the pig to human combination.

Endothelial cells of aortic origin are usually used in vitro as targets of hyperacute xenogeneic rejection, although endothelial cells from organs may have different properties. The sensitivities of aortic and liver endothelial cells to hyperacute xenogeneic rejection were compared in the pig to human combination. Sinusoidal liver endothelial cells were isolated and purified by collagenase perfusion of pig livers, sedimentation on a percoll gradient and selective adherence. Purity and viability of isolated liver endothelial cells after adherence were 85+/-6% and >95%, respectively. Endothelial cells from pig aortae (purity and viability >95%) were isolated by scraping. Immunoblotting analysis of xenoantigens on liver and aortic endothelial cell membranes preparations showed identical patterns. The strongest bands revealed by human IgM were located between 110 and 135 kD, while human IgG detected two major bands at 115 and 75kD. The membrane expression of xenoantigens recognized by human sera, analyzed by flow cytometry, was significantly lower on liver than on aortic endothelial cells (IgM: P=0.0006; IgG: P=0.0009). However, the complement-dependent cytotoxic activity of human sera was the same whether liver (54.5+/-1.4%) or aortic endothelial cells (50.0+/-4.2%) were used as targets. Taken together, those results allow the use of aortic instead of sinusoidal liver endothelial cells in the characterization of pig antigens recognized by human natural antibodies.

Acute Disease↗
PubMed1996

Immunosuppressive effects of endotoxins and bile acids in vivo in the rat.

Cell-mediated immunity is impaired during cholestasis. The aim of this study was to evaluate in vivo the effects on this immune defect of high serum levels of endotoxin and bile acids. Heterotopic cardiac allotransplantations were performed in the DA/Lewis rat combination. Cholestasis, induced by ligation/section of the common bile duct, was responsible for a significant delay in the rejection time (16 +/- 0.5 vs. 7.1 +/- 0.4 days in controls, P < 0.01). Elimination of Gram-negative intestinal bacteria from cholestatic rats by a vancocin/colimycin/tobramycin (VCT) mixture induced a significant reduction in endotoxin levels and a reduction in rejection times (9.5 +/- 1.0 days, P < 0.01) that remained, however, significantly longer than those of controls (P < 0.05). Oral administration of chenodeoxycholic acid in non-cholestatic rats significantly enhanced the serum concentration of total bile acids (60.6 +/- 15.3 mumol L(-1) vs. 17.4 +/- 1.9 mol L(-1) in controls, P < 0.01) and postponed allograft rejection (10.7 +/- 0.6 days, P < 0.01 vs. controls). These data suggest that increased endotoxin level and serum bile acid concentration may play a role in the immunosuppressive effect of cholestasis.

Animals↗
PubMed1996

[A good model of acute hepatic failure: 95% hepatectomy. Treatment by transplantation of hepatocytes].

The aim of this study was to develop in rats, a model of acute hepatic failure that mimics human fulminant hepatitis and to study the effect on survival of transplantation of isolated hepatocytes. This study showed that the mortality after 90% hepatectomy was reduced by the sole correction of hypoglycemia. On the other hand, 95% hepatectomy appeared as a reliable and reproductable model, associated with a period of hepatic coma, a deep disorder of coagulation, and a high mortality rate (> 80%) despite correction of hypoglycemia. In this model of acute hepatic failure, intraperitoneal transplantation of encapsulated isolated hepatocytes significantly reduced the mortality rate from 80% in the control groups to 31% in the transplanted group. A complete regeneration of the native liver was observed in all rats surviving. All animals survived after explantation of the hollow fibers. Well preserved hepatocytes were observed in hollow fibers two months after transplantation.

Animals↗
PubMed1995

Enhanced risk of steroid-resistant acute rejection following pretransplant steroid therapy in liver graft recipients.

Most episodes of acute rejection will resolve after steroid therapy without detrimental consequences on the liver allograft. However, steroid-resistant acute rejection may induce irreversible lesions of the graft and is associated with an increased risk of chronic rejection. The aim of this study was to determine whether there were predictive factors for steroid-resistant acute rejection after liver transplantation. A total of 108 adult liver recipients with a follow-up of at least 2 years have been analyzed; sixty-two (57%) patients had at least one episode of acute rejection. The rates of steroid resistance were 35%, 52% and 83% after a first (n = 62), second (n = 25), or third (n = 7) episode of acute rejection, respectively. Steroid resistance of acute rejection was significantly associated with a past history of pretransplant steroid therapy (P = 0.004). High levels of ALT (P = 0.03) and serum bilirubin (P = 0.002) were also predictive of steroid-resistant acute rejection. Eight (7%) patients eventually developed chronic rejection. Predictive factors for chronic rejection included steroid-resistant acute rejection (P = 0.01), recurrent acute rejection (P = 0.03), and CMV infection (P = 0.01). In conclusion, this study suggests that pretransplant steroid administration or high levels of ALT and bilirubin in rejecting patients are risk factors for steroid resistance and should lead to aggressive antirejection therapy without delay.

Adolescent↗
PubMed1995

Effect of cholestasis and bile acids on interferon-induced 2',5'-adenylate synthetase and NK cell activities.

BACKGROUND/AIMS: The mechanisms involved in resistance to interferon alfa in patients with chronic hepatitis C are unclear. Both cirrhosis and cholestasis have been shown to be predictive of resistance. The aim of this study was to evaluate the influence of cholestasis and bile acids on 2',5'-oligoadenylate synthetase and natural killer activities, which are both involved in the antiviral activity of interferon. METHODS: 2',5'-Oligoadenylate synthetase activity was evaluated in spleen, liver, and isolated hepatocytes from bile duct-ligated rats, and the effect of bile acids in vitro on interferon-induced 2',5'-oligoadenylate synthetase and natural killer activities was examined in fresh mononuclear cells from healthy subjects. RESULTS: Cholestasis had a time-dependent inhibitory effect on 2',5'-oligoadenylate synthetase activity in liver, spleen, and isolated hepatocytes from cholestatic rats (-70%, 86%, and 70% relative to baseline, respectively). In vitro, endogenous bile acids had a concentration-dependent inhibitory effect on interferon-induced 2',5'-oligoadenylate synthetase and natural killer activities, which was related to their structure. This inhibitory effect correlated with the surface activity index. CONCLUSIONS: Cholestasis and bile acids diminish the biological activity of interferon and natural killer activity. The results suggest a decrease in the antiviral defenses in cholestatic conditions.

2',5'-Oligoadenylate Synthetase↗
PubMed1995

Evidence for the detrimental role of proteolysis during liver preservation in humans.

BACKGROUND/AIMS: Proteolysis may persist in the liver allograft during cold storage. The aim of this study was to determine the significance of proteolysis within liver allografts stored at 4 degrees C in University of Wisconsin preservation fluid. METHODS: Thirty recipients of 32 liver allografts were studied prospectively. Amino acid content of the preservation fluid was analyzed at the end of cold storage and was correlated to graft and patient outcome after transplantation. RESULTS: Analysis of the preservation fluid showed the presence of free amino acids, the profile of which was different from that of stored liver parenchyma. Concentrations of amino acids (alanine, cysteine, leucine, isoleucine, methionine, lysine, ornithine, and threonine) and transaminases (alanine aminotransferase and aspartate aminotransferase) in the preservation fluid correlated with the duration of cold ischemia. Indexes of graft dysfunction (serum alanine aminotransferase and aspartate aminotransferase peaks and prothrombin rate) correlated with concentrations of cysteine, alanine, isoleucine, leucine, methionine, lysine, ornithine, and threonine, whereas enzyme concentrations in the fluid were not predictive of graft dysfunction. CONCLUSIONS: These data suggest that liver proteolysis occurs during cold storage and may have a detrimental effect on the outcome after transplantation. The measurement of the amino acids in the preservation fluid at the end of the cold storage period could help to identify the most severely damaged organs.

Adenosine↗