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Biomedical subjects

G W McCaughan

Publications and source records attributed to G W McCaughan.

At least 73 records · Page 4Linked to original sources
PubMed1999

Fibroblast activation protein: a cell surface dipeptidyl peptidase and gelatinase expressed by stellate cells at the tissue remodelling interface in human cirrhosis.

Fibroblast activation protein (FAP) is a cell surface-bound protease of the prolyl oligopeptidase gene family expressed at sites of tissue remodelling. This study aimed to delineate the expression of FAP in cirrhotic human liver and examine its biochemical activities. Seventeen cirrhotic and 8 normal liver samples were examined by immunohistochemistry and reverse-transcriptase polymerase chain reaction (RT-PCR). Hepatic stellate cells (HSC) were isolated and immunostained. Recombinant FAP and immunopurified, natural FAP were analyzed for protease activities and similarities to dipeptidyl peptidase IV (DPPIV), a structurally related enzyme. FAP-specific messenger RNA and immunoreactivity were detected in cirrhotic, but not normal, livers. FAP immunoreactivity was most intense on perisinusoidal cells of the periseptal regions within regenerative nodules (15 of 15 cases); this pattern coincides with the tissue remodelling interface. In addition, human FAP was expressed by cells within the fibrous septa (10 of 15 cases). Cell morphology, location, and colocalization with glial fibrillary acidic protein (GFAP) indicated that FAP is present on HSC in vivo. Similarly, isolated HSC expressed FAP in vitro. Both natural FAP from cirrhotic liver and recombinant FAP were shown to have gelatinase and dipeptidyl peptidase activities. FAP is a cell-bound, dual-specificity dipeptidyl peptidase and gelatinase expressed by activated HSC at the tissue remodelling interface in human cirrhosis. FAP may contribute to the HSC-induced extracellular matrix (ECM) changes of cirrhosis.

Actins↗
PubMed1999

Nonspecificity of monoclonal antibody Tordji-22 for the detection of hepatitis C virus in liver transplant recipients with cholestatic hepatitis.

Detection of hepatitis C virus (HCV) antigens in liver tissue provides important diagnostic and pathological information. Limited studies have been performed on tissue taken after liver transplantation for HCV. In this study, serial post-liver transplantation biopsy tissue from patients with recurrent HCV was tested, with particular interest in patients showing severe cholestatic hepatitis. HCV-related antigens were detected using the commercial monoclonal antibody, Tordji-22. Initial results were promising, showing intense positive staining, especially in areas of hepatocyte ballooning. HCV-negative donor tissue was consistently negative by staining. However, as a final control for the level of tissue damage, HCV negative posttransplantation biopsy tissue showing hepatocyte ballooning was examined. These tissues also showed positive staining. All attempts to eliminate this nonspecific interaction failed. In conclusion, Tordji-22 was associated with nonspecificity in this posttransplantation population, and care is warranted when using this monoclonal antibody.

Antibodies, Monoclonal↗
PubMed1999

Evidence of continuing bone recovery at a mean of 7 years after liver transplantation.

Patients with end-stage liver disease have low bone-turnover osteoporosis, and there is often further bone loss of 20% to 30% after orthotopic liver transplantation (OLT). Bone recovery after OLT has been reported, but data are limited. We undertook studies to determine whether bone recovery continues in the long term. Twenty-eight adult patients alive at least 5 years after OLT were studied (14 men, 14 women). Bone mineral density (BMD), serum parathyroid hormone (PTH), osteocalcin, and vitamin D levels were measured pretransplantation, at 3 months, 12 months, a mean of 46 months, and a mean of 85 months (range, 63 to 117 months) after transplantation. When BMD is expressed as a z score, the results were as follows: x0.82 +/- 0.22 pre-OLT; -2.04 +/- 0.27 at 3 months; -1.68 +/- 0.24 at 12 months; -1.23 +/- 0.24 at a mean of 46 months; and -1.0 +/- 0.26 at a mean of 85 months after OLT. The results at 46 and 85 months were significantly greater than the measurement at 3 months after OLT (P <.05). Furthermore, mean BMD (expressed as a z score) returns to the pre-OLT level at a mean of 85 months. At final follow-up, 9 of 28 patients had elevated PTH levels, and 14 of 27 patients had elevated osteocalcin levels. Five patients had spontaneous fractures in the first 12 months after transplantation, and 5 more patients had fractures by final follow-up. Even at 7 years after OLT, there was a significant increase in BMD (expressed as a z score) compared with 3 months after transplantation. Elevation of serum PTH and osteocalcin levels in some patients suggests continuing bone remodeling.

Adult↗
PubMed1999

Lamivudine therapy in patients undergoing liver transplantation for hepatitis B virus precore mutant-associated infection: high resistance rates in treatment of recurrence but universal prevention if used as prophylaxis with very low dose hepatitis B immune globulin.

Recurrent hepatitis B virus (HBV) infection remains a major cause of morbidity and mortality after liver transplantation. Recently, antiviral therapy, such as lamivudine, has become available for prophylaxis against HBV reactivation posttransplantation and for the treatment of HBV recurrent disease. We report our initial experience with lamivudine therapy in patients with precore mutant-associated HBV infection undergoing liver transplantation (n = 29). Outcomes were compared in three patient groups: group 1, precore mutant HBV infection not receiving lamivudine (n = 10); group 2, recurrent precore mutant HBV infection posttransplantation subsequently treated with lamivudine (n = 10); and group 3, HBV precore mutant patients undergoing liver transplantation and receiving lamivudine and low-dose hepatitis B immune globulin (HBIG) from the time of transplantation (n = 9). In group 1, HBV recurred in 9 of 10 patients, with subsequent graft loss in all 9 patients. In group 2, all patients developed HBV recurrence at a mean of 7.3 months posttransplantation and started lamivudine therapy at a median of 16 months posttransplantation. Follow-up on lamivudine therapy was for a median of 11 months. Six of these 10 patients developed mutations in the HBV polymerase gene associated with lamivudine resistance. There were two liver failure-related deaths in this group. In group 3 patients, there was one death from graft-versus-host disease. The remaining 8 patients have been followed up for a mean of 15.6 months posttransplantation, and all remain hepatitis B surface antigen negative and HBV DNA negative. In conclusion, lamivudine therapy in association with low-dose HBIG is effective in preventing HBV reactivation posttransplantation. Rescue therapy with lamivudine in patients with HBV recurrence is only moderately effective, with a 60% lamivudine resistance rate in patients treated for longer than 6 months.

Adult↗
PubMed1999

Activation of pancreatic stellate cells in human and experimental pancreatic fibrosis.

The mechanisms of pancreatic fibrosis are poorly understood. In the liver, stellate cells play an important role in fibrogenesis. Similar cells have recently been isolated from the pancreas and are termed pancreatic stellate cells. The aim of this study was to determine whether pancreatic stellate cell activation occurs during experimental and human pancreatic fibrosis. Pancreatic fibrosis was induced in rats (n = 24) by infusion of trinitrobenzene sulfonic acid (TNBS) into the pancreatic duct. Surgical specimens were obtained from patients with chronic pancreatitis (n = 6). Pancreatic fibrosis was assessed using the Sirius Red stain and immunohistochemistry for collagen type I. Pancreatic stellate cell activation was assessed by staining for alpha-smooth muscle actin (alphaSMA), desmin, and platelet-derived growth factor receptor type beta (PDGFRbeta). The relationship of fibrosis to stellate cell activation was studied by staining of serial sections for alphaSMA, desmin, PDGFRbeta, and collagen, and by dual-staining for alphaSMA plus either Sirius Red or in situ hybridization for procollagen alpha(1) (I) mRNA. The cellular source of TGFbeta was examined by immunohistochemistry. The histological appearances in the TNBS model resembled those found in human chronic pancreatitis. Areas of pancreatic fibrosis stained positively for Sirius Red and collagen type I. Sirius Red staining was associated with alphaSMA-positive cells. alphaSMA staining colocalized with procollagen alpha(1) (I) mRNA expression. In the rat model, desmin staining was associated with PDGFRbeta in areas of fibrosis. TGFbeta was maximal in acinar cells adjacent to areas of fibrosis and spindle cells within fibrotic bands. Pancreatic stellate cell activation is associated with fibrosis in both human pancreas and in an animal model. These cells appear to play an important role in pancreatic fibrogenesis.

Actins↗
PubMed1999

An active liver transplant programme for hepatocellular carcinoma in cirrhotic patients: is it justified?

Even at an early stage, hepatocellular carcinoma (HCC) in patients with cirrhosis is often deemed unresectable because of limited liver reserve. In these circumstances, liver transplantation (LTx) offers some hope for palliation or cure. The results of LTx for selected cirrhotic patients with HCC were analysed. The outcomes were compared with those of patients who underwent LTx for other forms of hepatic malignancy and those who underwent LTx for non-malignant conditions. Four hundred and eighty LTx were performed in 441 patients between January 1986 and December 1998. Twenty-eight LTx recipients (25 males, 3 females) of mean age 51 (14 63) yr had cirrhosis and HCC. Twenty-seven patients had underlying predisposing conditions (11 had hepatitis B, 10 had hepatitis C, 2 had hepatitis B and C, 1 had haemochromatosis, 1 had autoimmune hepatitis, 1 had alcoholic cirrhosis and 1 had alpha-1 antitrypsin deficiency). In 22 patients, HCC was diagnosed pre-LTx, and in 6 patients, the cancers were discovered incidentally. The average tumour size and number were 2.8 (0.4-11.5) cm and 1.3 (1-4), respectively. Two patients with known HCC died during and shortly after the LTx operation. Of the other patients, 3 died; 1 died of HCC recurrence 18 months post-LTx, 1 died of graft failure from recurrent hepatitis C and 1 died of fungal sepsis. Twenty-three (82%) patients survived to 22.5 (0.5-96) months post-LTx without HCC recurrence and with 1- and 3-yr actuarial patient survival rates of 87 and 76%, respectively. Equivalent survival rates of patients who underwent LTx for other malignancies (n = 11) were 82 and 46% (p = NS), and for those who underwent LTx for benign causes (n = 402), they were 77 and 73% (p = NS). All 15 patients with known HCC, who met the selection criteria now in use, survived. LTx can result in prolonged. cancer-free survival in a good proportion of patients with cirrhosis and HCC, particularly when the cancers are incidental, or when diagnosed pre-LTx, conforming to established selection criteria. An active LTx programme for this group of patients is justified.

Adult↗
PubMed1999

Binding to human dipeptidyl peptidase IV by adenosine deaminase and antibodies that inhibit ligand binding involves overlapping, discontinuous sites on a predicted beta propeller domain.

Dipeptidyl peptidase IV (DPPIV) is an atypical serine protease that modifies the biological activities of certain chemokines and neuropeptides. In addition, human DPPIV, also known as the T-cell activation antigen CD26, binds adenosine deaminase (ADA) to the T-cell surface, thus protecting the T-cell from adenosine-mediated inhibition of proliferation. Mutations were engineered into DPPIV (five point, 16 single point and six deletion mutations) to examine the binding of ADA and 19 monoclonal antibodies. Deletions of C-terminal residues from the 738-residue extracellular portion of DPPIV showed that the 214 residues C-terminal to Ser552 were not required for ADA binding and that peptidase activity could be ablated by deletion of 20 residues from the C-terminus. Point mutations at either of two locations, Leu294 and Val341, ablated ADA binding. Binding by six anti-DPPIV antibodies that inhibited ADA binding was found to require Leu340 to Arg343 and Thr440/Lys441 but not the 214 residues C-terminal to Ser552. The 13 other antibodies studied bound to a truncated DPPIV consisting of amino acids 1-356. Therefore, the binding sites on DPPIV of ADA and antibodies that inhibit ADA binding are discontinuous and overlapping. Moreover, the 47 and 97 residue spacing of amino acids in these binding sites concords with their location on a beta propeller fold consisting of repeated beta sheets of about 50 amino acids.

Adenosine Deaminase↗
PubMed1999

Liver transplantation for hepatocellular carcinoma in cirrhotic patients.

BACKGROUND: Hepatocellular carcinoma (HCC) in patients with cirrhosis, due to a limited liver reserve, is often deemed unresectable, even at an early stage. METHODS: In order to evaluate the ongoing transplant programme for cirrhotic patients with HCC at Royal Prince Alfred Hospital, the results of liver transplantation (LTx) for HCC were analysed and the patient actuarial survival was compared with that of those LTx patients without malignancy. RESULTS: A total of 441 LTx were performed in 404 patients between January 1986 and April 1998. Twenty-four LTx recipients (22 men; two women) of mean age 49 (15-62) years had HCC. Twenty-one had underlying aetiology for their cirrhosis (hepatitis B: n = 9; hepatitis C: n = 8; hepatitis B and C: n = 1; haemochromatosis: n = 1; autoimmune hepatitis: n = 1; alcoholism: n = 1), while three patients had cryptogenic cirrhosis. Six patients had incidental tumours and another two cases were of the fibrolamellar type. The average tumour size and tumour number were 2.9 (0.4-11.5) cm and 1.3 (1-4), respectively. Operative mortality was 4.2% (1/24). The HCC recurrence appeared in one (4.2%) patient (with a 11.5-cm HCC) who died 18 months after LTx. A further two patients died (one graft failure from recurrent hepatitis C and one from fungal sepsis) during follow-up. The overall 1- and 3-year actuarial patient survival rates were 87% and 76%, respectively, and that of patients with benign causes (n = 369) were 77% and 72% (P = NS). CONCLUSION: With careful patient selection, long-term tumour-free patient survival can be achieved. The results support an active transplant programme for selected HCC.

Adolescent↗
PubMed1999

Pancreatic stellate cells are activated by proinflammatory cytokines: implications for pancreatic fibrogenesis.

BACKGROUND: The pathogenesis of pancreatic fibrosis is unknown. In the liver, stellate cells play a major role in fibrogenesis by synthesising increased amounts of collagen and other extracellular matrix (ECM) proteins when activated by profibrogenic mediators such as cytokines and oxidant stress. AIMS: To determine whether cultured rat pancreatic stellate cells produce collagen and other ECM proteins, and exhibit signs of activation when exposed to the cytokines platelet derived growth factor (PDGF) or transforming growth factor beta (TGF-beta). METHODS: Cultured pancreatic stellate cells were immunostained for the ECM proteins procollagen III, collagen I, laminin, and fibronectin using specific polyclonal antibodies. For cytokine studies, triplicate wells of cells were incubated with increasing concentrations of PDGF or TGF-beta. RESULTS: Cultured pancreatic stellate cells stained strongly positive for all ECM proteins tested. Incubation of cells with 1, 5, and 10 ng/ml PDGF led to a significant dose related increase in cell counts as well as in the incorporation of 3H-thymidine into DNA. Stellate cells exposed to 0.25, 0.5, and 1 ng/ml TGF-beta showed a dose dependent increase in alpha smooth muscle actin expression and increased collagen synthesis. In addition, TGF-beta increased the expression of PDGF receptors on stellate cells. CONCLUSIONS: Pancreatic stellate cells produce collagen and other extracellular matrix proteins, and respond to the cytokines PDGF and TGF-beta by increased proliferation and increased collagen synthesis. These results suggest an important role for stellate cells in pancreatic fibrogenesis.

Actins↗
PubMed1998

Kinetics of intragraft cytokine expression, cellular infiltration, and cell death in rejection of renal allografts compared with acceptance of liver allografts in a rat model: early activation and apoptosis is associated with liver graft acceptance.

BACKGROUND: Liver transplants in the rat strain combination PVG-to-Dark Agouti are spontaneously tolerated, whereas kidney transplants in the same strain combination are rejected in 7-9 days. METHODS: To identify organ-specific differences that might yield further information about the mechanism of tolerance induction in this strain combination, liver or kidney grafts, spleen, and draining lymph nodes were harvested at days 1, 3, 5, and 7, and examined by immunohistochemistry, terminal deoxynucleotide transferase-mediated dUTP nick end labeling assay, and reverse transcriptase-polymerase chain reaction for interferon-gamma, interleukin (IL)-2, IL-4, and IL-10. RESULTS: Renal allograft rejection was associated with the progressive development of an intense mononuclear cell infiltrate. Markers of lymphocyte activation and cytokine up-regulation appeared from day 3, and many apoptotic parenchymal cells were noted on days 5-7, at the peak of rejection. Conversely, liver allograft tolerance was associated with more rapid infiltration by activated T cells and earlier increases in cytokine expression, but with a more limited degree of cellular infiltration. Concurrent with the early activation, high levels of apoptosis were found in areas of leukocyte infiltrate, paralleling the disappearance of activated T cells from the graft between days 3 and 5. CONCLUSIONS: Apoptosis of infiltrating leukocytes in liver allografts may represent an important process in the induction of spontaneous liver transplant tolerance and may underlie the abortive nature of the effector response observed within tolerated livers. In contrast, activated cells in renal allografts in the same strain combination survive and proliferate, express high levels of cytokines, and are efficient in bringing about graft destruction.

Animals↗
PubMed1998

Cholestatic hepatitis after liver transplantation is associated with persistently high serum hepatitis C virus RNA levels.

Viral recurrence is universal after transplantation for hepatitis C infection. This may lead to difficulties in differentiating allograft dysfunction caused by chronic rejection from hepatitis C virus (HCV) recurrence. Cases of severe cholestatic hepatitis have also been reported in conjunction with reinfection of the graft with HCV. Patients receiving transplants for HCV-related liver disease were studied before and after transplantation by HCV RNA quantitation of serial serum samples. Four major clinical patterns of HCV recurrence could be distinguished posttransplantation: group 1, asymptomatic hepatitis with no significant symptoms; group 2, cholestatic hepatitis with centrilobular ballooning; group 3, hepatitis leading to chronic allograft rejection; and group 4, persistently normal serum aminotransferase levels. Pretransplantation viral load was shown to be an important indicator of disease severity because the group 2 patients had significantly higher pretransplantation viral loads than patients in group 1 (P = 0.01) and group 4 (P = 0.005). The group 2 patients also had persistently significantly higher posttransplantation viral loads than the patients in group 1 (P = 0.01) and group 4 (P = 0.02), whereas patients who developed chronic allograft rejection showed marked decreases in serum HCV RNA before retransplantation. Patients from group 4 had the lowest viral loads after transplantation. These results show that persisting graft cholestasis due to HCV is associated with persistently high HCV RNA levels compared with other etiologies of graft dysfunction. Prospective studies are needed to determine whether such quantitation may be diagnostically helpful in distinguishing the different patterns of HCV-related graft dysfunction observed after liver transplantation.

Adult↗
PubMed1998

Paradoxical early immune activation during acceptance of liver allografts compared with rejection of skin grafts in a rat model of transplantation.

Liver allografts in many animal models are often spontaneously accepted across a complete histocompatibility barrier without requirement for immunosuppression. In contrast, skin allografts are usually rejected, even across minor histocompatibility barriers. To identify the mechanism of liver allograft acceptance we have compared skin rejection with liver acceptance in DA rat strain recipients of PVG donors, a major histocompatibility complex (MHC) class I plus II mismatch. In spite of the established role of draining lymph nodes (LN) in induction of rejection of skin allografts, there was much greater involvement of LN after liver than after skin transplantation. Few donor cells migrated to these organs from transplanted skin but many cells migrated from transplanted liver. There was also a paradoxical increase in interleukin-2 (IL-2) and interferon-gamma (IFN-gamma) mRNA in LN and spleen of liver allograft recipients that greatly exceeded their expression in skin allograft recipients. For example, there were 2. 7+/-1.6x104 molecules of IFN-gamma per 106 molecules of beta-actin mRNA in the LN draining liver allografts 1 day after transplantation compared with 2.0+/-0.3x103 molecules/106 beta-actin in LN draining skin allografts and 8.1+/-1.8x102 molecules/106 beta-actin in LN draining skin isografts. Examination of the graft showed that infiltration and cytokine mRNA up-regulation occurred more slowly in the transplanted skin than in liver but progressed inexorably in skin grafts until rejection. These results show that liver acceptance is associated with a paradoxical marked early activation then subsequent decline of the immune response.

Animals↗
PubMed1998

Cytochrome P4502E1 is present in rat pancreas and is induced by chronic ethanol administration.

BACKGROUND: The mechanisms responsible for the initiation of alcoholic pancreatitis remain elusive. However, there is an increasing body of evidence that reactive oxygen species play a role in both acute and chronic pancreatitis. In the liver, cytochrome P4502E1 (CYP2E1, the inducible ethanol metabolising enzyme) is one of the proposed pathways by which ethanol induces oxidative stress. AIMS: To determine whether CYP2E1 is present in the pancreas and, if so, whether it is inducible by chronic ethanol feeding. METHODS: Eighteen male Sprague-Dawley rats were pair fed liquid diets with or without ethanol as 36% of energy for four weeks. CYP2E1 levels were determined by western blotting of microsomal protein from both pancreas and liver. Messenger RNA (mRNA) levels for CYP2E1 were quantified using dot blots of total pancreatic RNA. RESULTS: CYP2E1 was found in the pancreas. Furthermore, the amount of CYP2E1 was greater in the pancreas of rats fed ethanol compared with controls (mean increase over controls 5.1-fold, 95% confidence intervals 2.4 to 7.7, p < 0.02). In the liver, induction by ethanol of CYP2E1 was similar (mean increase over controls 7.9-fold, 95% confidence intervals 5.2 to 10.6, p < 0.005). Pancreatic mRNA levels for CYP2E1 were similar in ethanol fed and control rats. CONCLUSIONS: CYP2E1 is present in the rat pancreas and is inducible by chronic ethanol administration. Induction of pancreatic CYP2E1 is not regulated at the mRNA level. The metabolism of ethanol via CYP2E1 may contribute to oxidative stress in the pancreas during chronic ethanol consumption.

Animals↗
PubMed1998

Periacinar stellate shaped cells in rat pancreas: identification, isolation, and culture.

BACKGROUND: The pathogenesis of pancreatic fibrosis is unknown. In the liver, stellate cells (vitamin A storing cells) play a significant role in the development of fibrosis. AIMS: To determine whether cells resembling hepatic stellate cells are present in rat pancreas, and if so, to compare their number with the number of stellate cells in the liver, and isolate and culture these cells from rat pancreas. METHODS: Liver and pancreatic sections from chow fed rats were immunostained for desmin, glial fibrillary acidic protein (GFAP), and alpha smooth muscle actin (alpha-SMA). Pancreatic stellate shaped cells were isolated using a Nycodenz gradient, cultured on plastic, and examined by phase contrast and fluorescence microscopy, and by immunostaining for desmin, GFAP, and alpha-SMA. RESULTS: In both liver and pancreatic sections, stellate shaped cells were observed; these were positive for desmin and GFAP and negative for alpha-SMA. Pancreatic stellate shaped cells had a periacinar distribution. They comprised 3.99% of all pancreatic cells; hepatic stellate cells comprised 7.94% of all hepatic cells. The stellate shaped cells from rat pancreas grew readily in culture. Cells cultured for 24 hours had an angular appearance, contained lipid droplets manifesting positive vitamin A autofluorescence, and stained positively for desmin but negatively for alpha-SMA. At 48 hours, cells were positive for alpha-SMA. CONCLUSIONS: Cells resembling hepatic stellate cells are present in rat pancreas in a number comparable with that of stellate cells in the liver. These stellate shaped pancreatic cells can be isolated and cultured in vitro.

Animals↗