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Biomedical subjects

R Chong

Publications and source records attributed to R Chong.

17 recordsLinked to original sources
PubMed2004

Growth substrate selection and biodegradation of PCP by New Zealand white-rot fungi.

Nine New Zealand native white-rot fungi were studied for their ability to grow and survive on different substrates formulated from bark, wheat straw, sawdust, apple pomace and maize products in order to identify their pentachlorophenol (PCP) biodegradation potential and to select a fungal carrier for bioaugmentation of polluted soils. Isolates were also evaluated to mineralize (14)C-PCP in liquid culture and in soil. The American fungus Phanerochaete chrysosporium outgrew the native fungi on the substrates tested, but the high colonisation did not result in superior PCP dechlorination as measured by chloride release. Whilst Trametes versicolor inocula produced on wheat straw and SCS (sawdust-corn meal-starch-mix) gave the highest chloride release, colonization of these two substrates as measured by biological potential was lower compared to the pomace and pomace-sawdust-mix. Neither lignin peroxidase nor manganese peroxidase production were measured for New Zealand white-rot fungi during the experiments. Laccase was the only enzyme detected. In liquid culture, the mineralisation rate was higher for T. versicolor isolates compared to P. chyrysoporium. Very little to no pentachloroanisole (PCA) was captured in the volatile fraction of T. versicolor isolates, whereas 75% of the volatile fraction of P. chrysosporium consisted of PCA. The soil microcosms studies, using contaminated soil from a timber treatment site, clearly showed that the New Zealand T. versicolor isolates mineralized PCP. Degradation of PCP in non-sterile soil was higher in the presence of white-rot fungi than in soil without white-rot fungus. This demonstrates that viable white-rot fungus is necessary for significant PCP degradation and that T. versicolor isolates showed PCP remediation potential. Wheat straw and SCS could be suitable carriers for New Zealand native T. versicolor isolates for bioremediation of PCP polluted soil sites.

Biodegradation, Environmental↗
PubMed2001

Full-scale demonstration of biological nutrient removal in a single tank SBR process.

Complete biological nutrient removal (BNR) in a single tank, sequencing batch reactor (SBR) process, is demonstrated here at full-scale on a typical domestic wastewater. The unique feature of the UniFed process is the introduction of the influent into the settled sludge blanket during the settling and decant periods of the SBR operation. This achieves suitable conditions for denitrification and anaerobic phosphate release which is critical to successful biological phosphorus removal. It also achieves a "selector" effect, which helps in generating a compact, well settling biomass in the reactor. The results of this demonstration show that it is possible to achieve well over 90% removal of COD, nitrogen and phosphorus in such a process. Effluent quality achieved over a six-month operating period directly after commissioning was: 29 mg/l COD, 0.5 mg/l NH4-N 1.5 mg/l NOx-N and 1.5 mg/l PO4-P (50%-iles of daily samples). During an 8-day, intensive sampling period, the effluent BOD5 was < 2 mg/l in all samples and the total phosphorus averaged 0.17 mg/l in the effluent. Detailed sampling and analysis during one cycle and at various depths clearly showed the deliberate stratification achieved in the tank during the settling and decant period, allowing biochemical reactions to occur during this normally "non-productive" period. The simplicity and flexibility of the UniFed system allows it to be used in numerous applications, particularly for industrial situations where a high degree of uncertainty of the wastewater composition during the design stage or where changing requirements based on changes on the production side are present. The single tank operation without any recycle also reduces the capital costs for a full BNR system compared to the comparatively complex continuous flow processes.

Bioreactors↗
PubMed1999

Diabetic retinopathy and nephropathy in Fiji: comparison with data from an Australian diabetes centre.

BACKGROUND: As part of a project to improve diabetes care in Fiji, we assessed the magnitude of problems posed by diabetic retinopathy in that country and compared the findings with those from an Australian diabetes centre. The relationship between diabetic retinopathy and nephropathy was also examined in a subset of patients. METHODS: A medical team from Australia screened a total of 446 type 2 diabetic patients (ethnicity: Fijian/Indian 16/84%) for diabetic retinopathy in five towns from the Division of Viti Levu, Fiji. The findings were compared with data obtained from 1659 type 2 diabetic patients who had attended an Australian diabetes centre (ethnicity Indian/ Anglo-Celtic 12/88%). In both cohorts, retinopathy was assessed by direct fundoscopy and a spot urine sample was collected for determination of albuminuria (defined as a concentration > 50 mg/L). RESULTS: The prevalence of diabetic retinopathy increased linearly with duration of diabetes. It was higher in Fiji, even when cases from the same ethnicity (i.e. Indians) and duration were compared (P < 0.05). Extrapolation of the data points suggests a delay in the diagnosis of diabetes in Fiji. Of those patients with retinopathy in Fiji, more than half had moderate to severe non-proliferative diabetic retinopathy or proliferative diabetic retinopathy, significantly higher than patients in the Australian cohort (chi2 = 29.2; P < 0.0001). Retinopathy was not a predictor of albuminuria in Fijian Indians (chi2 = 0.4; P = 0.5). In contrast, Australian Indians with retinopathy had significantly more albuminuria (chi2 = 10.2; P = 0.001). CONCLUSIONS: Severe diabetic retinopathy is common in both ethnic groups in Fiji. A delay in the diagnosis of diabetes as well as poor glycaemic control are possible factors. The availability of laser therapy is important to prevent loss of vision, but it is also essential that appropriate training of health professionals is integrated with a programme of diabetic complication screening to support this form of therapy.

Adult↗
PubMed1998

Crohn's disease in the Singapore Chinese population.

Crohn's disease (CD) is rare in the Chinese population, but lately there seems to be an increasing trend of CD in the Singapore Chinese population. We carried out a retrospective study of all Chinese patients with CD seen from 1987 to 1993 at the Singapore General Hospital. All patients were regularly followed up and treated. Disease activity was defined by the Organisation Mondiale de Gastroenterologie index. We also compared our series with our first series reported in 1987 and a Western series. There were 32 patients (20 men, 12 women) giving a hospital prevalence of 26.7 per 100,000 patients compared with 3.5 per 100,000 patients in 1986. The mean age was 37.1 years (range, 19-80 years). Twelve patients had small intestinal disease, 9 had colonic disease, and 11 had both. The common presenting symptoms were bloody diarrhea (67%), abdominal pain (53%), loss of weight (47%), and fever (34%). Extraintestinal manifestations were rare. Six patients had no relapse during the follow-up period, whereas the remaining 26 patients had an average of two relapses (range, 1-5). These relapses were complicated by fistulas in 8 patients and strictures in 11 patients. Response to steroids and sulfasalazine was good in most patients. Four patients required repeated surgery despite medical treatment. The prevalence of CD appears to be increasing among the Singapore Chinese population. The clinical features are similar to those of the Western population. Most of our patients responded to standard medical therapy, but further follow-up is needed to assess their long-term clinical outcome.

Adult↗
PubMed1997

Acute viral hepatitis E: clinical and serologic studies in Singapore.

Seroprevalence of hepatitis E is now documented in many countries around the world, but studies of its clinical manifestations and serologic course have been confined to endemic areas. We have prospectively evaluated the occurrence, evolution, and outcome of acute hepatitis E in our patients. Fifteen patients (11 men, 4 women; median age: 41 years) were diagnosed to have acute, sporadic hepatitis E between July 1993 and January 1995; 10 of the 15 were followed up. Sera anti-hepatitis E virus (HEV) immunoglobulin (Ig)G and IgM antibodies and HEV ribonucleic acid in the blood and stool were tested at weeks 1 and 2; serial tests for hepatitis E antibodies and liver function were carried out at months 1, 3, 6, 9, 12, and 18. Coinfection with hepatitis A and superinfection on chronic hepatitis B were found in 3 and 2 patients, respectively. One patient had transient passage of virus in the stool, but none was viremic. Eighty-seven percent of patients lost their IgM antibodies within 3 months, but anti-HEV IgG, once present, persisted throughout follow-up. All patients but one had complete recovery. A higher than reported level of alanine transaminase (mean: 28.5 times normal) and the lack of viremia during acute infection in our patients may be due to increased immune-mediated viral clearance.

Acute Disease↗
PubMed1996

Exacerbation of hepatitis in hepatitis B carriers following chemotherapy for haematological malignancies.

We describe nine asymptomatic chronic carriers of hepatitis B virus, four males and five females, with a mean age of forty-six years and all were Chinese, who developed exacerbation of hepatitis following chemotherapy for haematological malignancies. Seven patients had non-Hodgkin's lymphoma of whom three were treated with MACOP-B, two with BCEPP, one with PROMACE-CYTABOM and one with CHOP. Two patients had acute myeloid leukaemia and were treated with daunorubicin and cytosine arabinoside. Exacerbation of hepatitis occurred between one to four weeks following the last course of chemotherapy in eight patients. Two patients developed exacerbation of hepatitis when the dosage of prednisolone was reduced after they had ten weeks of high dose prednisolone. The outcome was fatal in six patients; all of whom developed hepatic encephalopathy. In four of these patients, alanine transaminase levels exceeded 1000 iu/l. Cytotoxic and immunosuppressive therapy permit enhanced viral replication. Withdrawal of the drugs results in partial restoration of immunocompetence and leads to rapid destruction of hepatocytes with consequent hepatic necrosis. Hence, patients who are hepatitis B virus carriers undergoing chemotherapy should be closely monitored. The fatal outcome of reactivation of chronic hepatitis B virus warrants prospective trials addressing preventive measures.

Adult↗
PubMed1996

Endoscopic stenting in the management of biliary stones.

INTRODUCTION: Endoscopic sphincterotomy and stenting are established modes of treatment in the management of bile duct stones and cholangitis. It is the first choice of treatment when the patients are elderly and have other medical conditions rendering them unfit for surgery. AIMS: We studied the immediate and long-term outcome of endoscopic stenting in patients who underwent Endoscopic Retrograde Cholangiopancreatography (ERCP) for ductal stones. PATIENTS AND METHODS: From January 1990 to December 1992, 366 patients had ERCP done for biliary stone disease. Fifty-five of these patients received a 10 French biliary stent for the treatment of bile duct stones. Most of these patients (60%) had an advanced age of more than 70 years and 45% had co-existing medical conditions rendering them high risk for surgery. Ninety-one percent had stones greater than 1.2 cm in diameter and 82% had multiple stones. RESULTS: Eighty-nine percent of the patients had relief of jaundice and cholangitis resolved in 96% of the patients after stenting. None required immediate surgery after ERCP. Temporary bile drainage was achieved in 19 patients who went for surgery at a later date when they became more stable. Twenty-nine patients were on long-term follow-up for a mean period of 13 months. Nineteen patients still have their stents in place and remained well. The stents were repeatedly changed in 15 patients after an average duration of 5.5 months. Late complications were cholangitis in 2 patients and stent migration in one patient. There was no related mortality. In 5 patients, the stones have either disappeared spontaneously or become smaller and have been removed at subsequent ERCP. CONCLUSION: Endoscopic stenting is a valuable alternative to surgical bile duct exploration. It can be the definitive mode of treatment for large or multiple bile duct stones in the elderly and patients with multiple medical problems who are unfit for surgery.

Adult↗
PubMed1995

Seroprevalence of antibodies against hepatitis A (anti-HAV) in Singapore: the NFDD experience.

At the 4th National Foundation for Digestive Disease (NFDD) Day in 1991 where public lectures on prevention of hepatitis and early detection of hepatocellular carcinoma were given, screening of sera obtained from 364 registrants for antibodies to Hepatitis A (IgG) was undertaken. The overall sero-prevalence rate was 50%, with 55% for males and 46% for females with antibodies for HAV. None of the subjects below 20 years old had antibodies to HAV. This rose to 16% for those 21-30 years old and 92% for those above 61 years. This study shows that in Singapore, prevalence of anti-HAV antibodies rise with age and is approaching the low endemicity pattern that is seen in developed countries.

Adolescent↗
PubMed1994

A study of needle-stick injuries among house officers in a major hospital.

House officers (HO) undergoing housemanship in the departments of Surgery, Medicine and Orthopaedics in a major hospital were studied with regard to the incidence and causes of needle-stick injuries via a self-administered recall questionnaire. A response rate of 79% (44 out of 56 HOs) was obtained, of which 35 HOs had completed 2 months of housemanship and 9 had completed 8 months. A total of 171 needle-stick injuries (1.2 per HO-month) were reported with 6 HOs never sustaining an injury. The more experienced HOs had less injuries than the less experienced HOs with an incidence rate of 4.65 (95% confidence interval of 4.08-8.87). Resheathing was the commonest reported cause of injury (45% of 113 described cases). Forty-three HOs (90%) reported that they frequently resheathed used needles before disposal. Most HOs (61%) felt that they were at nil to moderate risk of contracting an infectious disease from a needle-stick injury. A system of reporting and policies on management of infected personnel may be needed to monitor this health hazard.

Blood-Borne Pathogens↗
PubMed1990

Human and mouse LSP1 genes code for highly conserved phosphoproteins.

With use of the mouse LSP1 cDNA we isolated a human homologue of the mouse LSP1 gene from a human CTL cDNA library. The predicted protein sequence of human LSP1 is compared with the predicted mouse LSP1 protein sequence and regions of homology are identified in order to predict structural features of the LSP1 protein that might be important for its function. Both the human and mouse LSP1 proteins consist of two domains, an N-terminal acidic domain and a C-terminal basic domain. The C-terminal domains of the mouse and human LSP1 proteins are highly conserved and include several conserved, putative serine/threonine phosphorylation sites. Immunoprecipitation of LSP1 protein from 32P-orthophosphate-loaded cells show that both the mouse and human LSP1 proteins are phosphoproteins. The sequences of the putative Ca2(+)-binding sites present in the N-terminal domain of the mouse LSP1 protein are not conserved in the human LSP1 protein; however, a different Ca2(+)-binding site may exist in the human protein, indicating a functional conservation rather than a strict sequence conservation of the two proteins. The expression of the human LSP1 gene follows the same pattern as the expression of the mouse LSP1 gene. Southern analysis of human genomic DNA shows multiple LSP1-related fragments of varying intensity in contrast to the simple pattern found after similar analysis of mouse genomic DNA. By using different parts of the human LSP1 cDNA as a probe, we show that most of these multiple bands contain sequences homologous to the conserved C-terminal region of the LSP1 cDNA. This suggests that there are several LSP1-related genes present in the human genome.

Amino Acid Sequence↗
PubMed1989

Lymphocyte-specific Ca2+-binding protein LSP1 is associated with the cytoplasmic face of the plasma membrane.

The gene for LSP1 is a lymphocyte-specific gene previously isolated by us using a subtractive hybridization technique. LSP1 mRNA is found in normal and transformed B lymphocytes and in normal T lymphocytes but not in transformed T lymphocytes. To study the expression of the mouse LSP1 protein, we prepared a polyclonal antiserum specific for the LSP1 protein. Here we report that the gene for LSP1 was expressed in transformed B-lymphoma cell lines and in normal mouse thymocytes as a protein doublet with apparent molecular masses of 52 and 50.5 kilodaltons when analyzed on a sodium dodecyl sulfate-10% polyacrylamide gel. BW5147 cells transfected with an LSP1 cDNA clone expressed only the 52-kilodalton protein. No LSP1 protein was expressed in nine T-lymphoma cell lines tested. Immunofluorescence studies of intact and permeabilized cells and subcellular fractionation experiments showed that the LSP1 protein was associated with the cytoplasmic side of the plasma membrane in transformed B-lymphoma cell lines and in normal thymocytes. Using a simple filter-binding assay, we showed that recombinant LSP1 protein was Ca2+ binding, as predicted on the basis of its deduced amino acid sequence. On the basis of the particular expression pattern, the subcellular localization, and the Ca2+-binding property of the LSP1 protein, we hypothesize that the LSP1 protein is a lymphocyte-specific component of a signal transduction pathway involved in the regulation of lymphocyte growth.

Animals↗
PubMed1982

Hydrolysis of some natural and synthetic bile acid conjugates by Cercospora melonis.

Analogs of natural bile acid conjugates were incubated with both whole-cell cultures and cell-free extracts of the fungus Cercospora melonis CBS 162.60. Those conjugates containing both an alpha-amino group and a carboxylic acid group in the amino acid moiety were the most susceptible to hydrolysis. Substitution with a beta-amino group and (or) a sulfonic acid group greatly reduced the extent of hydrolysis. With all conjugates tested, significant losses of total bile acid were observed on incubation with whole-cell cultures. Two factors have been implicated as contributing to these losses. First, bile acids may be degraded to nonsteroidal products by an inducible enzyme system. Second, bile acids may be bound to mycelia in a manner not reversed by the extraction technique.

Amino Acids↗