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Biomedical subjects

K C Tan

Publications and source records attributed to K C Tan.

At least 109 records · Page 6Linked to original sources
PubMed1995

Hepatic venous outflow obstruction in patients with polycystic liver disease: pathogenesis and treatment.

Polycystic liver disease is commonly asymptomatic but may present with hepatomegaly, abdominal distension, and dull abdominal pain. Transudative ascites is a rare manifestation in these patients but may occur when portal hypertension is present resulting from associated hepatic fibrosis or after deroofing procedure of a cyst. Exudative ascites might suggest hepatic venous outflow obstruction. Four cases are described where hepatic venous outflow obstruction occurred in patients with polycystic liver disease. Three patients had orthotopic liver transplantation and one had a mesocaval shunt. Of the two patients that survived orthotopic liver transplantation both have shown considerable improvement in their symptoms. None of the patients had any confirmed procoagulant disorder. The mechanism of hepatic venous outflow obstruction in these patients seems to be mechanical compression of hepatic veins by the cysts and associated formation of thrombi in small hepatic vein tributaries. Patients with severe polycystic kidney/liver disease are at risk of hepatic venous outflow obstruction and the onset of this complication is heralded by tender hepatomegaly and presence of exudative ascites.

Adult↗
PubMed1995

Pretransplantation clinical status and outcome of emergency transplantation for acute liver failure.

Emergency transplantation for acute liver failure has a significantly inferior outcome than transplantations performed for elective indications. The severity of the pretransplantation clinical illness in this group will contribute to the reduced patient survival. We have reviewed the outcome of our first 100 consecutive adult patients who received transplants for acute liver failure and have evaluated and determined which recipient clinical parameters present on admission and at transplantation act as risk factors in early posttransplantation outcome. In patients who received transplants for nonacetaminophen-induced liver failure (n = 79), no static variable determinable on admission (including age, sex, year of transplantation, hospital admission to transplantation period, and fulminant or late-onset presentation) other than cause was predictive of 2-month patient survival. Fulminant Wilson's disease and idiosyncratic drug reactions with 2-month survival rates of 100% and 12.5%, respectively, had significantly different outcomes from other causes. By the time of transplantation, of four dynamic variables significant in a univariate analysis (serum creatinine, encephalopathy grade, Apache 111 and organ system failure scores, and P values < .05), only the creatinine level was an independent variable in a stepwise logistic regression for 2-month survival (r = .33). In patients who received transplants for acetaminophen hepatotoxicity (n = 21), overdose to hepatectomy period was the only significant static variable, with no parameter predictive of outcome present on admission.(ABSTRACT TRUNCATED AT 250 WORDS)

Acetaminophen↗
PubMed1995

Musculoskeletal disorders among operators of visual display terminals.

Using a visual display terminal (VDT) is today a common occupational task with both benefits and hazards. One of the hazards is the occurrence of musculoskeletal disorders. This paper examines the possible causes of such disorders and suggests some preventive strategies. The debate on the relationship between musculoskeletal disorders and VDT usage usually centers around occupational factors (eg, constrained posture, poor ergonomic design of the workplace, equipment design), work-related psychological factors (eg, perceived high job demands, mundane, boring and repetitive job activity, little control, poor support from colleagues and superiors), and psychosocial factors (eg, biodemographic characteristics such as age, previous musculoskeletal injuries, emotional stress, family burden, environmental factors). Improving the ergonomic design of VDT workstations, changing occupational legislation, and improving occupational health services have been suggested as means to decrease the incidence of musculoskeletal disorders among VDT workers. Much research with a multidisciplinary approach is still needed.

Computer Terminals↗
PubMed1995

Clinical course and survival after liver transplantation for hepatitis B virus infection complicated by hepatocellular carcinoma.

OBJECTIVES AND METHODS: The outcome after liver transplantation for HBsAg-positive liver disease complicated by hepatocellular carcinoma is not clearly defined, and in the present study we analyzed the clinical course in 39 patients transplanted for hepatitis B virus (HBV)-related liver disease (group 1) compared with 16 patients with chronic HBV and hepatocellular carcinoma (group 2) and 52 patients with primary hepatocellular carcinoma seronegative for HBsAg (group 3). RESULTS: Despite similar pretransplant viral serology, HBV recurred more often in patients with tumor (group 2) than in nontumor cases (group 1), with 1-yr actuarial cumulative reinfection rates of 85.4% versus 65.0%, respectively (p < 0.05). In group 2 cases, we observed a more aggressive pattern of HBV-related graft injury with a higher frequency of graft loss (56.3% vs. 12.8%, p < 0.001). Long-term outcome was worse in the group 2 cases, with 5-yr actuarial survival rates of 16.7% compared with 73.2% and 28.2% for groups 1 and 3, respectively. In group 2, recurrence of HBV in the graft, rather than tumor recurrence, was the principal cause of the high mortality observed (56.2% vs. 12.5%), which, in some cases, may have been potentiated by adjuvant chemotherapy. CONCLUSION: The poor outcome of patients transplanted for HBsAg-positive cirrhosis and hepatocellular carcinoma is due to HBV reinfection of the graft, rather than tumor recurrence. Antiviral agents in association with hepatitis B immunoglobulin would be the most promising approach to improving survival in this patient population.

Actuarial Analysis↗
PubMed1994

Fibrinolytic activity during orthotopic liver transplantation with and without aprotinin.

Hyperfibrinolysis during orthotopic liver transplantation (OLT) has been attributed to high plasma levels of tissue plasminogen activator (t-PA). This study investigated the contribution of urokinase plasminogen activator (u-PA) to hyperfibrinolysis and the effects of high-dose perioperative aprotinin (Trasylol) on fibrinolytic activation. Plasma samples were collected before, during, and after OLT in fifty five patients receiving either high dose aprotinin or placebo in a randomized double-blind trial. t-PA antigen and u-PA antigen and activity levels were increased preoperatively compared with normal controls (P < 0.05). Hyperfibrinolysis was seen during the anhepatic phase as shown by shortened euglobulin clot lysis times (ECLT) and an increase in D-dimer titers. t-PA levels peaked on reperfusion and fell at the end of the operation, and u-PA levels did not increase during OLT, but showed a decrease at the end of the operation. With aprotinin treatment, t-PA levels were lower on graft reperfusion than the placebo group (P < 0.05), but there was no difference in u-PA antigen or activity levels between groups. Fibrinolytic inhibition during OLT by aprotinin was demonstrated by prolonged ECLT (P < 0.05), reduced D-dimer levels (P < 0.05), and an increase in antiplasmin activity (P < 0.05). This study showed that the main antifibrinolytic action of aprotinin is as an antiplasmin agent with some effect on t-PA-but not u-PA-mediated fibrinolysis.

Adult↗
PubMed1994

Orthotopic liver transplantation in patients over 60 years old.

A retrospective examination was performed, including a case control study, of 40 patients aged 60 years and over who underwent liver transplantation at King's College Hospital, London, UK, between 1988 and September 1993. There was no significant difference between elderly patients and younger patients in preoperative condition, intraoperative interventions, or outcome assessed by survival, complication rate, and duration of stay on the intensive care unit. The only significant difference between age groups was the median length of hospital stay, which was 24 days for the elderly versus 20 days for younger patients. We conclude that age up to 70 years should not be a barrier to liver transplantation.

Adolescent↗
PubMed1994

Comparison of enteral feeding and total parenteral nutrition after liver transplantation.

Total parenteral nutrition is used for nutritional support in patients undergoing orthotopic liver transplantation but is associated with complications. We compared the efficacy and tolerability of early enteral feeding with total parenteral nutrition after liver transplantation. 24 patients were studied: 14 received enteral feeding and 10 total parenteral nutrition. A double-lumen enteral tube was used to deliver the feed directly into the jejunum with the second lumen of the tube being used for gastric aspiration. Enteral feeding was started post-operatively within 18 h, was well-tolerated, and of comparable efficacy to total parenteral nutrition. The median number of days for patients to start eating (4) and to achieve 70% of estimated requirements orally (5) did not differ significantly between the two groups. Mid-arm circumference, triceps skinfold thickness, and biceps skinfold thickness were, by comparison with pre-operative values, maintained on the tenth postoperative day in both groups. Early postoperative absorptive capacity, as assessed by a combined carbohydrate test, was reduced significantly in both groups but insufficiently to be of nutritional concern. Intestinal mucosal integrity, as assessed by an intestinal permeability test, was maintained throughout. We conclude that the practical aspects of enteral feeding after liver transplantation are surmountable and that enteral feeding is as effective at maintaining nutritional status as total parenteral nutrition, and has potential benefits in terms of reduced complications and costs.

3-O-Methylglucose↗
PubMed1994

Nitric oxide generation. A predictive parameter of acute allograft rejection.

The L-arginine:nitric oxide (NO) biosynthetic pathway has been proposed as an important mediator in host defense mechanisms and may therefore play a role in the acute allograft response. We have studied NO generation in liver allograft rejection and determined its value in immunological monitoring. Stable end products of this pathway have been determined serially in 50 primary liver recipients and compared with 2 known mediators and markers of acute allograft rejection (IL-2R positive lymphocytes and circulating TNF alpha). Plasma concentrations of acid-labile nitrosocompounds (NOx), which increased during acute allograft rejection (P < 0.0001), correlated with rejection severity and were reduced after administration of supplemental high dose glucocorticoids. Concentrations were significantly lower in nonrejection graft complications but were elevated during episodes of sepsis. Correlations between plasma NOx levels and circulating TNF-alpha (r = 0.451, P < 0.001) and IL-2R-positive lymphocytes in peripheral blood (r = 0.781, P < 0.001) were demonstrated. In a logistic analysis of these variables, plasma NOx was the most predictive parameter of an episode of acute cellular rejection. Nitric oxide generation in FK506-treated patients was lower compared with patients receiving a CsA-based immunosuppression regimen and was associated with a reduced frequency of acute rejection in the FK506 group. These data are consistent with a role for NO in the cellular alloantigen immune response and indicate that monitoring of plasma levels of NOx may be useful in the detection of acute allograft rejection.

Biomarkers↗
PubMed1994

Epidermal cell presentation of tumor-associated antigens for induction of tolerance.

Intravenous administration of hapten-coupled epidermal cells (EC) induces tolerance in mice. To assess the relevance of this observation to cutaneous tumors, the ability of EC to induce tolerance to the S1509a spindle cell tumor (H-2a) was examined. ECs were prepared from CAF1 (H-2a/d) mice and the supernatant from a freeze-thaw lysate of S1509a cells was used as a source of soluble tumor-associated Ag (TAA). ECs were incubated in TAA or medium alone followed by washing. Two hundred thousand TAA-pulsed ECs, non-TAA-pulsed ECs, or TAA-pulsed ECs killed by freeze-thawing were injected i.v. into groups of CAF1 mice. To determine whether this regimen induced tolerance, a tumor-specific delayed-type hypersensitivity (DTH) response was measured in mice subsequently immunized to the S1509a tumor. To assess the degree of immunity induced in these animals, ECs were prepared and deleted of Thy-1-bearing cells by Ab and complement-mediated lysis. These cells were then pulsed with TAA and 5 x 10(5) were injected into the right hind footpad of each mouse. Footpad swelling was assessed at 24 to 48 h as a measure of the DTH. Mice primed i.v. with viable TAA-pulsed EC but not killed TAA-pulsed EC demonstrated a greatly suppressed DTH response. Other experiments demonstrated that exposure of EC to a dose of ultraviolet radiation (200 J/m2), which inhibits the ability of these cells to induce immunity by subcutaneous injection either before or after TAA pulsing, did not prevent induction of tolerance.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1994

Accuracy of radiology in detection of hepatocellular carcinoma before liver transplantation.

BACKGROUND/AIMS: Recurrence of hepatocellular carcinoma (HCC) after orthotopic liver transplantation (OLT) depends on tumor size and number; the accuracy of radiology in detecting HCC is uncertain. This study compared tumor size at radiological and pathological examination in 30 patients with HCC who underwent OLT. METHODS: Pre-OLT radiology included ultrasonography (US), computerized tomography (CT), and hepatic angiography (HA). Sensitivity of radiology was calculated by comparison with pathology. RESULTS: Radiology missed HCC in two patients but showed five with small (< 4 cm) and eight with large (> 4 cm) lesions. Multicentricity was shown in 15 cases at radiological examination and 24 at pathological examination, including one incidental and 4 of 5 radiologically small HCC. Mean tumor bulk was 3.4, 74, 338, and 1375 cm3, respectively, in patients with incidental, small, large, and multicentric HCC at radiology. Sensitivities of US, CT, and HA in detection of HCC (and multicentricity) were 80% (16.6%), 86.6% (58.3%), and 90% (58.3%). No recurrence was found in patients with incidental or small HCC; even when multicentric. CONCLUSIONS: US, CT, and HA identified patients with small or large tumor bulk, but sensitivity in detecting satellites was poor; their finding in patients with radiologically small or incidental tumors does not affect outcome. The failure of US, CT, and HA to detect satellites must be considered in patients undergoing partial hepatectomy for HCC.

Carcinoma, Hepatocellular↗
PubMed1994

Impact of immunoprophylaxis and patient selection on outcome of transplantation for HBsAg-positive liver recipients.

We have studied the roles of immunoprophylaxis, patient selection policy and coexistent hepatitis D virus infection in the outcome of 56 HBsAg-positive elective liver transplant recipients. Twenty-nine unselected patients not treated with immunoprophylaxis formed group 1 and were compared to a recent consecutive series of 27 patients (group 2) in whom pre-transplant serological status was determined and who received immunoprophylaxis. One-year actuarial HBsAg serological recurrence rates were 48% in group 2 and 90% in group 1 with particular improvement in recipients who were either HBV DNA-negative or who had co-existent hepatitis delta virus infection. One-year patient survival has improved from 62% in group 1 to 86% in group 2 with improvements in hepatitis delta virus-negative and replicating recipients. Patients who have either co-existent hepatitis delta virus infection or are in group 2 have 1-year survival rates comparable to elective HBsAg-negative recipients (19/21 (90%), 22/27 (86%) vs 87%, respectively). In the event of recurrence, severe graft injury is diminished in recent patients and in those with coexistent delta infection who also have lower levels of circulating HBV DNA. Retransplantation for associated graft injury has a poor prognosis irrespective of administration of immunoprophylaxis. In elective liver recipients, immunoprophylaxis and/or hepatitis delta virus infection modulate hepatitis B virus recurrence and associated graft injury with consequent improvement in patient survival.

Adult↗
PubMed1994

Recurrence of hepatitis C following orthotopic liver transplantation: a polymerase chain reaction and histological study.

Hepatitis C virus was sought by nested polymerase chain reaction in the preoperative biopsy or the explanted liver of 100 consecutive adult patients undergoing orthotopic liver transplantation. In those found to be positive preoperatively, polymerase chain reaction was performed on subsequent biopsies. Of the 12 patients in whom HCV-RNA was identified in the liver by polymerase chain reaction preoperatively, viral recurrence was documented in ten of the 11 with posttransplant liver tissues available for study. In the one exception, hepatitis C virus was undetectable in the liver graft despite repeated co-amplification of albumin mRNA as an internal control, which may indicate viral clearance. In eight of the ten positive cases, HCV-RNA was also detectable in serum postoperatively, while HCV-RNA was undetectable in serum in both the cases in whom HCV-RNA was undetectable in tissue and in the patient who declined post-transplant biopsy. Two of the 12 patients infected with hepatitis C virus preoperatively have died during the follow-up period from causes unrelated to hepatitis C virus infection. While biochemical liver function in seven of those remaining has been excellent, histological evidence of at least mild chronic active hepatitis has been present in all ten cases for whom long-term biopsies are available. Three cases have progressed to severe, symptomatic chronic active hepatitis within 2 years of transplantation. Recurrent hepatitis C is associated with progressive liver disease and appreciable morbidity in a significant proportion of patients.

Adult↗
PubMed1994

The use of percutaneous transluminal angioplasty in hepatic artery stenosis after transplantation.

Graft ischemia following liver transplantation is associated with a high incidence of morbidity and mortality. The present report concerns a group of seven patients in whom an anastomotic stenosis of the hepatic artery was identified. Three patients had unexplained allograft dysfunction at a median time of 28 days (range 13-64 days), and 3 had a biliary leak at a median time of 42 days after liver transplantation (range 35-270 days). In one patient the stenosis was diagnosed by routine Doppler ultrasound one week after transplant. Management was by percutaneous transluminal angioplasty at a median time of 35 days (range 13-270 days) after transplantation. After angioplasty there was a marked improvement in clinical appearance, liver function, and liver histology in 5 of the 7 patients. Those patients who had a biliary leak subsequently developed strictures that eventually required biliary tract reconstruction (hepaticojejunostomy) in two and retransplantation in one. Percutaneous transluminal angioplasty is an effective way of improving arterial blood flow in cases of anastomotic stenosis, reducing the likelihood of complete occlusion by thrombosis. If recognized early and treated promptly ischemic changes in the graft can resolve and the development of biliary strictures may be avoided.

Adult↗
PubMed1994

Development of techniques for obtaining monodispersed human islet cells.

The aim of this study was to develop techniques to obtain monodispersed, human islet cells in large quantities, since these constitute a potentially transplantable beta cell mass with which to treat established type 1 diabetes, as well as provide the most appropriate substrate for studying the immune pathogenesis of the disease. Human islets were isolated from the pancreas of beating-heart organ donors by collagenase digestion. Enzymatic (collagenase types II, IV, V, and XI, trypsin, DNAse, and hyaluronidase) and chemical (EDTA and EGTA) conditions were then used to find the optimum requirements for digestion of intact human islets into their constituent cells. The combination of trypsin with EDTA provided the highest yield of monodispersed islet cells (963 cells/islet) and highest viability (88%). DNAse with EGTA gave high yields (710 cells/islet) but viability was low (55%). Lower yields and viability were obtained using collagenase types II, IV, V, and XI (47-243 cells/islet; viability 45-62%), hyaluronidase (410 cells/islet; 75% viability), and EDTA alone (253 cells/islet; viability 43%). Human islet cells monodispersed using trypsin 0.125 mg/ml in 0.1 mM EDTA retained an insulin secretory response to glucose, and had intact surface class I MHC molecules when analyzed immediately after digestion by flow cytofluorimetry. Our results indicate that functionally intact, single, human islet cells may be obtained in abundance, and provide a potential substrate for islet cell transplantation in the treatment of patients with type 1 diabetes.

Cell Separation↗
PubMed1994

Papuloerythroderma of Ofuji: a report of three cases and review of the literature.

Papuloerythroderma of Ofuji is a rare, distinctive entity featuring widespread erythematous, flat-topped papules, with a striking sparing of body folds (the so-called 'deck-chair' sign), and peripheral eosinophilia. We report three elderly men who showed the typical features of this disease, and who responded to corticosteroid therapy. Immunohistochemical studies with anti-S-100 and UCHL-1 (CD45 RO) antibodies indicated the presence of abundant dendritic cells and mature T cells in the dermis. In addition, one patient had concomitant tinea corporis. Treatment with griseofulvin alone resulted in clearing of the fungal infection and improvement of his papuloerythroderma, and, worsening of his papuloerythroderma occurred when the tinea relapsed.

Aged↗
PubMed1994

Platelet transmembrane signalling responses to collagen in familial hypercholesterolaemia.

Washed platelets from patients with familial hypercholesterolaemia (FH) were found to be more reactive towards collagen than those from control subjects. The dose required to achieve half maximum aggregation was found to be 0.6 ml-1 for FH patients whilst that for control subjects was 1.25 micrograms ml-1. In both types of platelet, intracellular Ca2+ levels, as monitored by the Ca(2+)-dependent photoprotein, aequorin, rose on stimulation with collagen and then fell to basal levels, probably due to resequestration by the reticular system. This effect was not due to exhaustion of the supply of aequorin since sustained Ca2+ influx induced by the ionophore, A23187, gave a stable signal that did not return to baseline. Similarly, inositol 1,4,5, trisphosphate levels increased in the cytosol after stimulation and then fell to unstimulated values. When stimulated with collagen, platelets from FH patients showed a greater extent of cytoplasmic calcium mobilization (P < 0.05) when compared to controls, coupled with a greater extent of inositol phospholipid hydrolysis (P < 0.05). At doses of collagen sufficient to give either 100% or 50% aggregation, platelets from patients or control subjects showed the same amplitude of ATP release at either dose suggesting that the trigger for vesicle release is more sensitive in FH.

Adult↗
PubMed1994

Platelet function in patients with hypercholesterolaemia.

Platelets and plasma lipoproteins, particularly low density lipoprotein, have important roles in atherogenesis. Evidence from several sources suggests that important interactions occur between these individual components of the atherogeneic process. Here we review work from our own laboratory on platelet function in normal individuals and patients heterozygous for familial hypercholesterolaemia (FH). Data is presented on the role of platelet noradrenaline and also on altered cellular signalling in platelets from FH individuals who have plasma low density lipoprotein concentrations which are approximately double those seen in normal subjects.

Blood Platelets↗