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Biomedical subjects

M Thick

Publications and source records attributed to M Thick.

At least 19 recordsLinked to original sources
PubMed1998

Comparison of the efficacy of University of Wisconsin solution and Newcastle organ perfusion fluid in the preservation of livers for transplantation.

University of Wisconsin solution (UW) is now used widely for the preservation of livers for transplantation. However, the use of commercial solutions has added considerably to the cost. We were able to produce a local version of organ perfusion fluid (NOPF) incorporating all the constituents of UW except for the hydroxyethyl starch and adenosine. We compared graft outcome using NOPF with imported grafts perfused with commercial UW solution. The two recipient groups (15 patients each) were similar with respect to age and sex distribution, urgency of transplantation, regraft status and patient and graft survival. Postoperative duration of ventilation, dialysis requirements, peak bilirubin, peak ALT and lowest unsupported prothrombin time were also similar in both groups. In conclusion, local perfusion fluids based on UW can be produced without detriment to graft outcome with considerable financial savings. At our institution, this represents a reduction of 33% in the cost of perfusion fluids.

Adenosine↗
PubMed1997

Oral glutamine challenge in cirrhotics pre- and post-liver transplantation: a psychometric and analyzed EEG study.

Latent or sub-clinical hepatic encephalopathy is a recognized complication of cirrhosis and is thought to represent one end of the spectrum of neuropsychiatric impairment, which occurrs as a result of portal-systemic shunting. We studied the psychometric, analyzed electroencephalography (EEG), and venous blood ammonia responses to an oral glutamine challenge in 17 patients with cirrhosis and in 4 normal controls. The cirrhotics were attending for liver transplant assessment and had no clinical evidence of hepatic encephalopathy. The oral glutamine challenge was repeated following liver transplantation. Five of sixteen patients (31%) showed impaired performance on at least one of the baseline psychometric tests. There was a correlation between fasting venous ammonia and choice reaction time (r = .7, P < .01). Following glutamine challenge there was a significant increase in blood ammonia from a mean fasting value ranging between 58 micromol/L to 120 micromol/L (P < .01), between significant prolongation of reaction times of 387 ms to 428 ms (P < .01), and an increase in mean EEG amplitude between 68.5 microV to 78.6 microV (P < .001). Four normal controls who were challenged with glutamine and 6 cirrhotic patients who were challenged with water showed no change in any of these parameters. Following orthotopic liver transplantation (OLT) the eight patients studied had normal baseline psychomotor performance with significant improvements in digit symbol, digit span, information processing, number connection tests (P < .05), and reaction time (P < .005). Posttransplantation, there were no significant changes in blood ammonia, analyzed EEG, or choice reaction time in response to oral glutamine challenge (six patients). We conclude that short lived changes in blood ammonia (in cirrhotics) can cause significant impairment of sensitive tests of brain function and that psychometric performance is improved following OLT.

Adult↗
PubMed1997

Immunogenicity of biliary epithelium: study of the adhesive interaction with lymphocytes.

BACKGROUND & AIMS: Intrahepatic bile ducts express a range of lymphocyte adhesion molecules during episodes of inflammation. This may contribute to the susceptibility of biliary epithelium to immunologic damage during liver allograft rejection, graft-versus-host disease, and primary biliary cirrhosis. However, no previous study has shown that these adhesion molecules are functional. The aim of this study was to define the molecular basis of lymphoepithelial interactions within the intrahepatic bile ducts. METHODS: Human intrahepatic biliary epithelial cells (HIBECs) were cultured, and their interaction with resting and activated lymphocytes was studied using a flow-cytometric assay that allowed characterization of the adherent cells and functional investigation of individual adhesive interactions. The capacity of adherent cytotoxic lymphoid cells to damage HIBEC was studied using a standard 51Cr release assay. RESULTS: Allogeneic lymphocytes were bound by HIBECs; this adherence was increased by activation of either participating cell type. Cells with cytotoxic capacity were bound preferentially. At least 50% of the overall adhesion was dependent on lymphocyte function-associated antigen 1. Cytotoxicity assays showed that HIBECs were susceptible to lysis by lymphokine-activated natural killer cells. CONCLUSIONS: This study shows that the adhesion molecules expressed by HIBECs are functional and necessary for the activity of cytotoxic effector lymphocytes.

Bile Ducts, Intrahepatic↗
PubMed1996

Immunogenicity of biliary epithelium: investigation of antigen presentation to CD4+ T cells.

The intrahepatic biliary epithelium is susceptible to extensive T-cell-mediated damage during primary biliary cirrhosis, primary sclerosing cholangitis, and hepatic allograft rejection. During these processes, human intrahepatic biliary epithelial cells (HIBEC) become activated and express high levels of the lymphocyte adhesion molecules, intercellular adhesion molecule-1 (ICAM-1) and lymphocyte-associated antigen (LFA)-3, and of class II MHC antigens. It follows that activated HIBEC may also play a direct role in the activation of antigen-specific CD4+ T lymphocytes. The capacity of class II MHC antigen-expressing HIBEC to present antigen and induce specific proliferation of CD4+ T cells was examined in this study. Lines of purified HIBEC were activated by culture with the proinflammatory cytokines interferon gamma (IFN-gamma) and tumor necrosis factor a and were mixed in coculture with allogeneic CD4+ T cells. The result of interaction between these cells was assessed by measurement of lymphoproliferation and IL-2 production. Class II MHC antigen-expressing HIBEC failed to induce either lymphoproliferation or IL-2 production. However, both of these parameters of T-cell activation were positive in cocultures when a costimulation signal was delivered to T cells by adding bivalent anti-CD28 antibodies. The antigen-specific activation of these T cells was further enhanced by the addition of a cross-linking secondary antibody that caused CD28 receptor aggregation. The failure of cytokine-stimulated HIBEC to induce T-cell activation is consistent with the observation that HIBEC do not express the costimulatory CD28 ligands B7-1 or B7-2 at either mRNA or protein levels. It may be concluded that HIBEC are unlikely to play a direct role in activation of antigen-specific CD4+ T lymphocytes within the inflamed liver.

Antibodies, Monoclonal↗
PubMed1996

Hepatic allograft rejection: regulation of the immunogenicity of human intrahepatic biliary epithelial cells.

Intrahepatic biliary epithelial cells were immunomagnetically purified from specimens of disaggregated human liver and were propagated in vitro. After three passes in culture, the cells were shown to be over 85% pure with contaminating leukocytes and endothelial cells constituting less than 2% of the population. Sensitive flow microfluorimetric analysis was performed after immunofluorescence labeling to quantify expression of both class 1 and class II major histocompatibility (MHC) antigens and the adhesion molecules intercellular adhesion molecule-1 (ICAM-1), vascular cell adhesion molecule-1 (VCAM-1), and lymphocyte function-associated antigen-3 (LFA-3). It was shown that resting human intrahepatic biliary epithelial cells (HIBEC) expressed class 1 MHC antigens, ICAM-1, and relatively low levels of LFA-3. Stimulation with tumour necrosis factor-alpha (TNF-alpha) upregulated expression of ICAM-1, whereas Interferon-gamma (IFN-gamma) and a combination of IFN-gamma and TNF-alpha upregulated class I MHC antigens and ICAM-1 and induced class II MHC molecules. The level of expression of MHC antigens and of ICAM-1 and LFA-3 after stimulation of HIBEC with combined IFN-gamma and TNF-alpha was comparable with the expression of these antigens by an Epstein-Barr virus-transformed B-cell line. The phenotypic similarity between cytokine-stimulated HIBEC and a known antigen presenting cell is consistent with a potential role for biliary epithelial cells in antigen presentation.

Bile Ducts↗
PubMed1995

The flow cytometric crossmatch in liver transplantation.

The role of the cytotoxic crossmatch in liver transplantation is generally considered controversial. The development of the flow cytometric crossmatch has allowed the detection of lower levels of donor-directed IgG than is possible with the conventional crossmatch. This assay has been shown to be useful in renal transplantation. However, with the controversial role of the standard cytotoxic crossmatch, the flow cytometric crossmatch has not been used in liver transplantation. Twenty-seven human orthotopic liver allograft recipients were tested for donor-directed IgG using the flow cytometric crossmatch. Thirteen recipients were identified with either T or B lymphocyte-directed IgG. This group had a significantly increased incidence of clinical rejection (75%) as compared with the negative group (29%, P = 0.02, Fisher's exact test). The differences were greatest with B lymphocyte-directed IgG and the rejections were generally steroid sensitive. In this series, the flow cytometric crossmatch proved to be a better prognostic indicator of rejection than the conventional cytotoxic crossmatch. In addition, the association of a positive flow cytometric crossmatch with rejection indicates that the liver follows the same pattern seen in renal and cardiac grafts.

Adult↗
PubMed1994

Reversal of post-reperfusion coagulopathy by protamine sulphate in orthotopic liver transplantation.

We report details of two liver transplant procedures in which post-reperfusion coagulopathy was reversed by administration of protamine sulphate. Both procedures were uncomplicated until about 30 min after reperfusion of the graft, when the cut surfaces began to ooze blood. Failure of coagulation was confirmed by thrombelastography and in both cases routine coagulation tests revealed a prolonged kaolin cephalin clotting time (KCT). A heparin-like effect was suspected. Protamine sulphate 50 mg was given i.v., resulting in cessation of bleeding and normalization of the thrombelastogram and KCT.

Adult↗
PubMed1989

Removal of anti-HLA antibodies by extracorporeal immunoadsorption to enable renal transplantation.

10 highly and persistently sensitised patients awaiting renal transplantation underwent extracorporeal immunoadsorption to remove anti-HLA antibodies. 7 patients have since received transplants. Only 1 allograft has been lost because of rejection, and there have been no serious side-effects attributable to treatment. Extracorporeal immunoadsorption may therefore be of considerable value in the management of highly sensitised patients.

Adult↗
PubMed1988

Outcome of orthotopic liver transplantation in the aetiological and clinical variants of acute liver failure.

Thirty-three patients with acute liver failure underwent orthotopic liver transplantation, including 16 with fulminant hepatic failure, 15 with late-onset hepatic failure and two with severe acute liver failure (coagulopathy without encephalopathy). Twenty-three (70 per cent) survived to leave hospital and 21 of these are currently alive and well. Outcome correlated with the serum bilirubin level before transplantation (p less than 0.05) but no correlation was found with the variant of acute liver failure, grade of encephalopathy, cerebral oedema, serum creatinine, white cell count, prothrombin time or platelet count at the time of transplantation. Severe coagulation factor deficiencies did not constitute a clinical problem. One patient developed a neurological deficit secondary to cerebral oedema, but otherwise the morbidity reflected that observed in the general population after transplantation. Careful monitoring of intracranial pressure and surveillance (with early aggressive therapy) for bacterial and fungal infections is very important in achieving a successful outcome after transplantation.

Acute Disease↗
PubMed1987

Evidence for an immune response to HLA class I antigens in the vanishing-bileduct syndrome after liver transplantation.

The relation between donor and recipient status for HLA class I and II antigens in 62 patients undergoing liver transplantation was examined with particular reference to a well-defined variant of chronic rejection, the vanishing-bileduct (VBD) syndrome. A complete mismatch for class I antigens was more common in those with the VBD syndrome than in those with normal graft function or chronic graft malfunction unrelated to the syndrome (p less than 0.025). In contrast, a complete mismatch for class II antigens was considerably less common in those with the VBD syndrome than in those without (p less than 0.02). The association of a complete mismatch for class I and a partial or complete match for class II antigens with the VBD syndrome was highly significant (p less than 0.0005). These findings support the hypothesis that in the VBD syndrome both class I antigen expression on bileduct epithelium and immunological interaction at the level of class II antigens are required for the rejection process to occur. In addition, high-titre donor-specific antibodies to class I antigen, which were present in 6 of 14 of those with the VBD syndrome but in none of those without (p less than 0.0005), may be involved in the pathogenesis of bileduct damage.

Adolescent↗