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Biomedical subjects

P Yap

Publications and source records attributed to P Yap.

At least 19 recordsLinked to original sources
PubMed2005

Liver transplantation using cavoportal transposition: an effective treatment in patients with complete splanchnic venous thrombosis.

Complete venous thrombosis of the splanchnic system remains a major challenge in liver transplantation surgery. Some of these patients have been treated successfully by multivisceral transplantation. Cavoportal transposition is another alternative to treat these patients. We reviewed our single-center experience with this technique. Five patients with operatively confirmed complete splanchnic thrombosis were transplanted with the cava portal transposition technique. All survived the procedure; 60% survived long term. This technique is a useful salvage procedure in moribund patients with diffuse portal thrombosis who would otherwise rapidly succumb.

Adult↗
PubMed1999

Local and systemic effects of intraoperative whole-colon washout with 5 per cent povidone-iodine.

BACKGROUND: Segmental intraluminal instillation of several tumoricidal agents including povidone-iodine has been advocated to prevent anastomotic recurrence after colonic resection for colorectal cancer. The local and systemic effects of on-table whole-colon washout using 5 per cent povidone-iodine were assessed in patients undergoing elective surgery for colorectal cancer. METHODS: The local effect of 5 per cent povidone-iodine on the colonic mucosa and the effect of colonic mucosal damage by povidone-iodine on tumour take was first investigated in Fischer 344 rats. In 12 euthyroid non-allergic patients, on-table whole-colon lavage via the appendix was performed. Systemic (thyroid function) and local (mucosal damage assessed by repeat biopsies) effects were studied, as well as the in vitro tumoricidal effect of the final anal effluent on tumour cell suspensions. RESULTS: After 30 min of contact with povidone-iodine the rat colonic mucosa was severely injured, with detachment of the epithelial cell layer. Povidone-iodine-induced 'colitis' did not result in tumour development after inoculation of 10(6) Mtln3 carcinoma cells in ten rats. Epithelial desquamation was also observed, in all but one patient, 1 and 4 h after colonic lavage. However, epithelial restitution started within 1 day and no abnormality was revealed after 3-7 days. Urinary iodine excretion increased markedly and was not within normal values after 1 week. Levels of thyroid hormones decreased significantly but became normal within 1 week. The anal effluent containing povidone-iodine was found to be tumoricidal in vitro on a human colonic carcinoma cell line and on a tumour cell suspension produced from the patient's tumour. CONCLUSION: On-table whole-colon washout using 5 per cent povidone-iodine seems clinically feasible. This technique deserves further study as a substitute for preoperative bowel preparation and may help to prevent recurrent cancer due to implantation of viable exfoliated tumour cells.

Adult↗
PubMed1999

Prevention of anastomotic tumour take by on-table colon washout with povidone-iodine. an experimental study in rats.

The presence of organic material in the intestinal lumen is reported to interfere with the efficacy of cancericidals when used in low concentrations to prevent anastomotic recurrence in colorectal cancer surgery. We aimed at investigating the efficacy of intra-operative whole-colon washout using povidone-iodine in an experimental model of anastomotic tumour growth. A large inoculum of highly 'tumorigenic' carcinoma cells was instilled in the colonic lumen of Fischer rats. The whole-colon water washout was intended to remove the luminal organic material. This was followed by irrigation of increasing concentrations of povidone-iodine up to 5% with or without additional incubation for 10-20 min. Five animals died after 30 min incubation with povidone-iodine 5%. Tumour take was observed in all control animals including after irrigation with physiological saline. Increasing the povidone-iodine concentration from 1 to 5% reduced the rate of tumour take, but not significantly. The anastomotic tumour growth was significantly reduced after tumour cell inoculation followed by whole-colon lavage and luminal incubation for 20 min with povidone-iodine 5%. Application of intra-operative whole-colon washout to remove the luminal 'organic material' followed by luminal application of povidone-iodine 5% for a sufficient incubation time could reduce the risk of anastomotic recurrence in colorectal cancer surgery.

Anastomosis, Surgical↗
PubMed1999

Transmission rates of hepatitis C virus by different batches of a contaminated anti-D immunoglobulin preparation.

BACKGROUND AND OBJECTIVES: The aim of this study was to determine the hepatitis C virus (HCV) infection rate of recipients of different batches of anti-D immunoglobulin associated with an outbreak of HCV infection which occurred in 1977 and its relationship to the polymerase chain reaction (PCR) status of the implicated batches. This study was undertaken to determine the predictive value of HCV genome detection and quantification for subsequent infection in recipients of an HCV-contaminated anti-D immunoglobulin product for intravenous use. MATERIALS AND METHODS: Sera from recipients of anti-D were tested by HCV enzyme immunoassay and if found positive were subsequently tested by recombinant immunoblot assay and HCV PCR in a national HCV anti-D screening programme set up in 1994. The HCV status of 1,342 known recipients of infectious or potentially infectious batches has been compared to the amount of HCV RNA in the anti-D batch they received so as to determine the value of PCR in the prediction of infectivity in immunoglobulin preparations. RESULTS: It has been demonstrated that HCV-infected plasma derived from batches of anti-D showing levels of viral genome in excess of 10(4) genomes per millilitre led to infection of up to 60% of recipients. In contrast, batches with undetectable levels of HCV genome very rarely transmitted infection. CONCLUSIONS: The presence of HCV RNA in intravenous immunoglobulin preparations which have not undergone a specific viral inactivation step is a predictor of HCV infection in recipients.

Disease Outbreaks↗
PubMed1998

Influence of blood components and faeces on the in vitro cancericidal activity of povidone-iodine.

BACKGROUND: Tumoricidal agents have been used to kill viable exfoliated tumour cells following colorectal cancer surgery. Recent in vivo experiments have thrown some doubt on the tumoricidal activity of povidone-iodine. METHODS: The cytotoxic effect of distilled water and of povidone-iodine at 0.04, 0.4, 0.8, 2 and 4 per cent final concentrations on human SW620 colonic cancer cells in the presence of red blood cells, purified haemoglobin and red blood cell (RBC) membranes, plasma, albumin, faeces and bacteria was investigated. Cell viability was assessed using the trypan blue assay and MTT test. RESULTS: The presence of albumin and plasma decreased the tumoricidal activity of povidone-iodine except for the highest concentration tested. Bacterial suspension did not influence the efficacy of povidone-iodine. Faecal material was found to have an intrinsic tumoricidal effect. Both intact and lysed RBCs very strongly inhibited the tumoricidal activity of all povidone-iodine concentrations tested. This inhibitory effect was due to haemoglobin, but not to RBC membranes. CONCLUSIONS: Low concentrations of povidone-iodine fail to kill all 'exfoliated' cancer cells in the presence of proteins, intact or lysed RBCs. Therefore, washing out of these organic materials before application of a relatively high povidone-iodine concentration (e.g. 5 per cent or greater) may be more useful in killing viable exfoliated tumour cells during surgery for colorectal cancer.

Antineoplastic Agents↗
PubMed1997

Tumoricidal activity of antiseptics with assessment of cell viability in mice with severe combined immunodeficiency.

Previously, we have assessed the efficacy of different cytotoxic agents on the viability of SW620 human colonic carcinoma cells in vitro. In this study, we have investigated the tumoricidal efficacy of some antiseptic agents on SW620 human colonic carcinoma cells which were subsequently inoculated into severe combined immunodeficient (SCID) mice. An inoculum of 5 x 10(6) cells suspended in 200 microliters buffer solution was found to be the minimum number of cells needed to result in tumour growth within 8 weeks after subcutaneous injection into SCID mice. The integrity of the cells was assessed in vitro with the trypan blue exclusion test after 30 min incubation in distilled water (DW), chloramine 0.5% in DW and polyvinyl pyrrolidone iodine (PVP-I) 0.01, 0.05, 0.1 and 5% in DW. DW and PVP-I 0.01% were not tumoricidal, neither in vitro nor in vivo. In contrast, PVP-I 5% and chloramine 0.5% 'killed' all or almost all tumour cells in vitro and prevented their growth in vivo. PVP-I 0.05 and 0.1% were less effective in vitro than 5%, but could prevent in vivo proliferation unless an adjustment of the residual number of viable tumour cells was performed. These data indicate the importance of the amount of the tumour inoculum and hence the need to use a maximally effective 'killing' agent.

Animals↗
PubMed1996

Levels of hepatitis C virus in blood donors infected with different viral genotypes. International HCV Collaborative Study Group.

The level of hepatitis C virus (HCV) in the serum of 337 blood donors infected with different viral genotypes was investigated by branched DNA assay. Viral genotype was deduced by restriction analysis of the virus 5'-noncoding region. Samples included genotypes 1a, 1b, 2a, 2b, 3,4,5, and 6. Multivariate analysis revealed that the ranges of HCV levels were similar for all viral genotypes and subtypes (P=.18), with the possible exception of genotype 4. Virus levels were significantly lower in female than in male subjects (P<.001) but did not correlate with donor age (P=.06) or genotype or with donor age, sex, or country. These results indicate a similar replicative capacity in vivo for different HCV genotypes and clarify the influence of host and virus factors on disease severity and responsiveness to interferon treatment.

Blood Donors↗
PubMed1996

Comparative study of classical, colorimetric and immunologic staining methods for the assessment of tumor cell viability.

The trypan blue exclusion test, the MTT test and an immunostaining test for apoptosis were performed before and after incubation of SW620 human colonic carcinoma cells with different cytotoxic agents (CTAs) in order to assess tumor cell viability and CTA efficacy in vitro. A modified MTT test using light microscopy was also performed. A good correlation was found between the trypan blue assay and the MTT test, as determined by spectrophotometry. There was no 'overestimation' of cell viability as measured by the trypan blue test. The monitoring of formazan formation by light microscopy was feasible, but not very reliable since it did not show a good correlation with findings determined by spectrophotometry. The apoptosis test failed to show good correlation with other tests. Distilled water had no relevant cytotoxic effect, while chlorhexidine cetrimide (HAC 3.5%), chloramine 0.5% and polyvinylpyrrolidone iodine (PVP-I) > or = 0.05% damaged a large majority of cells. PVP-I at a concentration of > or = 5% was found to be the most effective CTA.

Antineoplastic Agents↗
PubMed1995

Parathyroid hormone-related peptide is expressed and rapidly inducible in human liver cell cultures that have a bile duct phenotype.

Parathyroid hormone-related peptide is the major factor responsible for hypercalcemia of malignancy. There is increasing evidence that parathyroid hormone-related peptide also plays an important role in the growth and differentiation of both neoplastic and non-neoplastic cells. Recently we found that reactive human bile ductules and cholangiocarcinomas, but not normal bile ducts, human hepatocytes nor hepatocellular carcinomas, express parathyroid hormone-related peptide and we speculated that parathyroid hormone-related peptide may function as a growth and differentiation factor for bile ductular epithelial cells. Using a specific polyclonal antibody for immunostaining and a digoxigenin-random prime-labeled probe for in situ hybridization assay, we found that only cell lines with a bile duct phenotype expressed parathyroid hormone-related peptide and its mRNA. HepG2 cells with hepatocellular phenotype (CK19-, CK7-, CK8+, CK18+, albumin+) do not express parathyroid hormone-related peptide. However, A16 (HepG2 derived cell line) expressing bile duct marker CK19, also expressed parathyroid hormone-related peptide, while hepatocyte markers CK8, CK18, CALLA and albumin were negative. In addition, the H1 cell line (adult human hepatocytes immortalized in our laboratory by SV40 DNA transfection, passaged at least 40 times and cultured for 13 months) expressed bile duct marker CK7 and parathyroid hormone-related peptide, while hepatocyte markers CK8, CK18, CALLA and albumin were negative. Previous studies demonstrated that parathyroid hormone-related peptide gene expression in keratinocytes can be modulated by serum, growth factors and cycloheximide although there is a species and cellular specificity.(ABSTRACT TRUNCATED AT 250 WORDS)

Bile Ducts↗
PubMed1995

Genotypic variation, clinical and histological characteristics of chronic hepatitis C detected at blood donor screening.

Since blood donor screening for the hepatitis C virus (HCV) began in 1991 a large number of seropositive subjects have been detected and several reports have suggested a high prevelance of liver disease. The aim of this study was to evaluate the severity of liver disease in HCV-positive blood donors in terms of the clinical, biochemical and histological abnormalities and to investigate the relationships between these features and the mode of transmission, duration of infection and viral genotype. We evaluated 54 consecutive blood donors who were positive for HCV both on serological testing and polymerase chain reaction. Twenty-three (43%) had a history of intravenous drug abuse and 17 (31%) had received blood transfusions. In only two (4%) was no risk factor identified. The mean duration of infection in those with a clear history of HCV exposure was 12 years. Eighty-three percent were HCV genotypes 1 or 3. All had abnormal liver biopsies with chronic hepatitis and several patients had periportal or portal-portal fibrous septa, but there was none with architectural distortion or cirrhosis. There was no correlation between severity of liver disease and duration of HCV infection, mode of transmission or viral genotype. In the majority of HCV carriers detected at donor screening there is a chronic hepatitis with bridging necrosis in one third, but the degree of fibrosis is minimal and cirrhosis was not present in our patients. The long period of infection of many patients suggests that irreversible liver injury does not necessarily develop at an early stage despite persistent infection.

Blood Donors↗
PubMed1995

Heparan sulfate proteoglycan expression in normal human liver.

Because increasing evidence implicates heparan sulfate proteoglycans (HSPGs) as essential cofactors in receptor-growth factor interactions, in cell-cell recognition systems, and in cell-matrix adhesion processes and yet little is known about their cellular distribution pattern and cellular sources in liver tissue, we used monoclonal antibodies specific for the core proteins of syndecan1, 2, 3, 4, glypican, and perlecan to investigate their immunohistochemical expression in normal adult human liver biopsy specimens. Syndecan1 was expressed in sinusoidal endothelial cells, whereas the endothelium of the portal tract vessels was negative. Hepatocytes showed a membranous staining pattern of the sinusoidal and intercellular domain. Bile duct epithelial cells showed basolateral membrane positivity. Immunoreactivity for syndecan2 was seen in mesenchymal cells, accentuated around bile ducts. Syndecan3 showed intense staining of hepatic arterial and portal venous endothelial cells, of mesenchymal cells, and of Ito cells. Immunohistochemistry for syndecan4 showed a granular staining pattern of hepatocytes at their bile canalicular pole. Glypican showed weak positivity in portal tract mesenchymal cells and clear positivity in nerve bundles. Perlecan was present in Disse's space, in endothelial cells, in basement membranes surrounding bile ducts and vessels, in vessel walls, and in mesenchymal cells. The highly differential expression of these HSPGs in the different cell compartments of the liver, as well as in basement membranes and in Disse's space, suggests that each of these proteoglycans has a specific function in the interplay of cells, matrix molecules, growth factors, and proteinases.

Cells, Cultured↗
PubMed1992

Acute colonic pseudo-obstruction.

We present two cases of acute colonic pseudo-obstruction, one complicated with perforation. Orthopedic surgery was the pathogenetic factor in both cases. Recovery was successful in both patients after appropriate treatment. The importance of conventional X-ray techniques, and more specially the plain X-ray of the abdomen, is stressed regarding early diagnosis and follow-up.

Aged↗
PubMed1990

Etiology of hypercalcemia in hemodialysis patients on calcium carbonate therapy.

Fourteen of 39 dialysis patients (36%) became hypercalcemic after switching to calcium carbonate as their principal phosphate binder. In order to identify risk factors associated with the development of hypercalcemia, indirect parameters of intestinal calcium reabsorption and bone turnover rate in these 14 patients were compared with results in 14 eucalcemic patients matched for age, sex, length of time on dialysis, and etiology of renal disease. In addition to experiencing hypercalcemic episodes with peak calcium values of 2.7 to 3.8 mmol/L (10.7 to 15.0 mg/dL), patients in the hypercalcemic group exhibited a significant increase in the mean calcium concentration obtained during 6 months before the switch, compared with the mean value obtained during the 7 months of observation after the switch (2.4 +/- 0.03 to 2.5 +/- 0.03 mmol/L [9.7 +/- 0.2 to 10.2 +/- 0.1 mg/dL], P = 0.006). In contrast, eucalcemic patients exhibited no change in mean calcium values over the same time period (2.3 +/- 0.05 to 2.3 +/- 0.05 mmol/L [9.2 +/- 0.2 to 9.2 +/- 0.2 mg/dL]). CaCO3 dosage, calculated dietary calcium intake, and circulating levels of vitamin D metabolites were similar in both groups. Physical activity index and predialysis serum bicarbonate levels also were similar in both groups. However, there was a significant difference in parameters reflecting bone turnover rates between groups.(ABSTRACT TRUNCATED AT 250 WORDS)

Bone and Bones↗
PubMed1990

Ureteric catheterization in the diagnosis of pyelonephritis--an experimental evaluation.

Experimental models of renal infections have been used to determine the accuracy with which the cellular and microbiologic components of ureteric and voided urine reflected the pathologic status of the kidney in pyelonephritis. In acute pyelonephritis, the composition of the ureteric urine reflected the pathologic status of the kidney, although in a few cases ureteric samples were either sterile or cell free. Animals with chronic pyelonephritis in which the lesions were either infected or sterile commonly had sterile ureteric urine. Pyuria, however, was demonstrable in both these situations. In subclinical pyelonephritis, ureteric samples from infected kidneys were variably culture positive, although pyuria was a common observation. Discriminate function analysis based on actual renal status and ureteric data gave an overall correct classification rate of 67% and demonstrated at least 80% agreement in four of the five classification groups.

Animals↗
PubMed1983

[Roentgenology of cancer of the gastric stump].

The carcinoma of the stomach stump is a late complication after partial resection of the stomach and gastroenterostomy. The risk for carcinoma increases with the interval, but in older people the interval is shorter. 12 patients with carcinoma of the stomach stump are discussed. The average interval from the primary operation of the stomach until the carcinoma was 23.8 years. With x-ray examination the diagnosis was correct in 11 patients, in 1 patient the examination was interpreted falsely.

Female↗
PubMed1982

Surgical management of gastric carcinoma. Follow-up results in 465 consecutive cases.

A retrospective study was made of a consecutive series of 465 patients with histologically proven gastric carcinoma operated on from December 1950 to December 1974. There were 352 men and 113 women, for a male-female ratio of 3.1 to 1. The peak age of incidence was 51 to 55 years. Noncurative surgical procedures were performed in 49.5 percent with no 5 year survivors; 50.5 percent had curative gastric resection. The ulcerating type was the most common lesion, and the pylorus and antrum were the most common primary sites of tumor. Applying the TNM pathologic stage grouping, the study revealed that 3.4 percent of the patients with curative resections were in stage I, 25.5 percent were in stage II and 71 percent in stage III. The 5 year survival rate was 100 percent for stage I, 70 percent for stage II and 20 percent for stage III. Eighty-four patients or 35.7 percent of those with curative gastric resection survived 5 years or longer. The operative mortality was 3.5 percent for the group with noncurative surgical procedures and 2.1 percent for the group with curative gastric resections, giving an overall operative mortality of 2.8 percent for the entire series.

Adult↗
PubMed1977

Sequential clearance and dialysance measurements in chronic peritoneal dialysis patients.

The long-term efficiency of chronic peritoneal dialysis was investigated during a 10-months follow-up period in eight patients with indwelling Tenckhoff catheters by determining sequential urea, creatine and glucose clearances. Dialysis was performed in the hospital with nurses changing commercially prepared 2-liter dialysate bottles. Mean +/- SE urea clearance declined from an initial valua of 23.6 +/- 1.5 ml/min to 17.7 +/- 1.2 at the termination of the study. The mean glucose and creatinine clearance also decreased from 14.1 +/- 0.9 to 10.2 +/- 0.7 and from 17.5 +/- 1.9 to 12.9 +/- 1.0, respectively. All of these decreases were statistically significant (p less than 0.05) by paired t testing analysis. It is concluded that the efficiency of chronic peritoneal dialysis may decline during maintenance therapy and that sequential clearance measurements should be obtained in all chronic peritoneal dialysis patients.

Adult↗