Search PubMed⌕ Search

Biomedical subjects

C J Oon

Publications and source records attributed to C J Oon.

At least 55 records · Page 3Linked to original sources
PubMed1989

Treatment of primary liver cancer in Singapore. A review of 3200 cases seen between January 1, 1977, and July 31, 1987.

Between January 1977 and July 1987, 3200 patients with hepatocellular carcinoma (HCC) were studied in Singapore. HCC formed 90% of primary liver cancers seen in Singapore and is the second most common fatal malignancy seen in men in the country. Extensive clinical and basic research has defined certain treatment strategies. Of importance is the prompt detection of early nodular tumours, which can be resected. Resection, 'targetting' with anticancer drugs and, in selected cases, synchronised direct hepatic irradiation with adriamycin, used as a radiosensitiser, have been promising treatment methods. Biological modifiers, such as interferons and interleukins, offer potential for the future. Preliminary pilot studies suggest that interferons may prevent the development of HCC, but more studies are required. Similarly, selective localisation of anticancer agents with radio-isotopical agents opens opportunities for treatment.

Antineoplastic Agents↗
PubMed1989

The hepatitis B immunization programme in Singapore.

A voluntary immunization programme to prevent perinatal transmission of hepatitis B virus (HBV) infection in Singapore was implemented on 1 October 1985 as an integral component of the national childhood immunization programme. Up to April 1988, a total of 68,845 mothers who attended government maternal and child health clinics were screened for the disease. Of these, 2432 (3.5%) were positive for hepatitis B surface antigen (HBsAg) and 904 (1.3%) for hepatitis B e antigen (HBeAg). Virtually all the babies born to carrier mothers completed the full immunization schedule; and in addition, those of HBeAg-positive mothers were given a dose of hepatitis B immunoglobulin at birth. The hepatitis B immunization programme was extended on 1 September 1987 to cover all newborns. About 90% of the 15,943 babies delivered in government institutions from September 1987 to April 1988 were immunized at birth, with the subsequent doses being administered at maternal and child health clinics at 4-6 weeks and 5 months later. More than 85% of the children given the full course of plasma-derived and yeast-derived hepatitis B vaccine from birth continued to have protective antibody to HBV two years after immunization. The programme is being closely monitored to assess the duration of immunity and the need for booster doses, while seronegative adults are also being encouraged to be vaccinated.

Adolescent↗
PubMed1989

Evidence of viral replication in HBsAg positive patients with hepatocellular carcinoma: measurement of serum hepatitis B virus deoxyribonucleic acid (HBV-DNA).

Sera from 60 consecutive patients with hepatocellular carcinoma (HCC) diagnosed by either a positive histology or at least two of the following: CT scan, hepatic ultrasound, hepatic angiogram and raised alpha-foetoprotein levels, were studied to determine their Hepatitis B surface antigen (HBsAg) status and the frequency of continuing viral replication. Markers of Hepatitis B virus (HBV) infection were detected using enzyme and radioimmunoassays. Hepatitis B DNA (HBV-DNA) was measured by molecular hybridization using a labelled recombinant HBV-DNA probe. Sera from 30 HBsAg positive 'healthy' carriers were used as controls. Forty-seven (78%) patients were HBsAg positive. Evidence of previous HBV infection was present in 12 of 13 HBsAg negative patients. 30% of HBsAg positive patients were HBeAg positive, 62% were anti-HBe positive and 8% had no 'e' markers. Serum HBV-DNA was present in 21 (45%) HBsAg positive patients: 10 (71%) HBeAg positive patients, 10 (35%) anti-HBe positive patients and 1 (25%) patient without any 'e' markers. Serum HBV-DNA levels were less than 0.6 ng/ml in 16 (76%) patients. HBV-DNA was absent in all HCC patients who were HBsAg negative. The frequency of serum HBV-DNA positivity was higher in 30 patients with HCC when compared with 30 age and sex matched healthy HBsAg positive individuals (57% vs 13% p less than 0.01). A sizeable proportion of HBsAg positive HCC patients have on-going viral replication and this is present in patients who were thought to have stopped replicating (anti-HBe positive patients).(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1988

The prevalence of hepatitis B virus markers in dental personnel in Singapore.

A seroepidemiological survey of the prevalence of hepatitis B virus (HBV) markers was conducted in a group of 693 dental personnel in Singapore where HBV infection is endemic. The overall prevalence of HBsAg (4.5%) and anti-HBc (29%) was no higher than that in the general population. However, dentists had a significantly higher HBsAg prevalence (11.4%) compared with that in the general population (4.2%) (P less than 0.01) and of other categories of dental personnel (3.1%) (P less than 0.001). Similarly, the anti-HBc prevalence of the dentists (45.6%) was significantly higher than that of the general population (29.7%) (P less than 0.01) and of other categories of dental personnel (25.7%) (P less than 0.0001). It appears that dentists in the endemic area have a definite occupational risk of acquiring HBV infection.

Dental Staff↗
PubMed1988

Clinical evaluation of a yeast recombinant hepatitis B vaccine in healthy hospital staff in Singapore.

A yeast recombinant hepatitis B vaccine (subtype adw), derived from purification of HBsAg particles, expressed in the yeast Saccharomyces cerevisiae which contained the gene for HBsAg, was evaluated in 31 healthy adult hospital staff members in Singapore. Each subject received a 10 mcg dose of vaccine intramuscularly at 0, 1 and 6 months. One month after the first two injections of vaccine the seroconversion rate (defined as greater than or equal to 2.7 mIU/ml) was 90%. Two months after the third injection 100% of participants had anti-HBs levels higher than 2.7 mIU/ml and 97% had titers of anti-HBs greater than 10 mIU/ml. The geometric mean titer (GMT) of anti-HBs levels at 2, 3, 6, 8 and 12 months were 21.9, 38.6, 57.6, 1253.4 and 354.1 mIU/ml, respectively. All clinical complaints were mild and transient. They consisted of mild soreness at the injection site, transient fever and headache. There was no correlation between the presence of antibodies to S. cerevisiae with any allergic manifestations. The vaccine was safe and immunogenic for staff exposed to an infection risk and should now be widely used in the extension of hepatitis B immunization programs.

Ethnicity↗
PubMed1987

Prevalence of hepatitis B markers in psychiatric in-patients in Singapore: a pilot study.

The prevalence of hepatitis B infection among 71 patients in an adult psychiatric hospital was determined by testing for hepatitis B surface antigen (HBsAg), its antibody (anti-HBs) and antibody against hepatitis B core antigen (anti-HBc). The results showed 12.7 per cent positive for HBsAg, 63.4 per cent positive for anti-HBs and 69 per cent positive for anti-HBc. This assessment of the prevalence of hepatitis B in a group of adult long-term institutional patients may be used as a guide when hepatitis B vaccination is being considered for use in a psychiatric hospital. The need for a similar study on health care personnel working in the same institution is emphasized.

Adolescent↗
PubMed1986

Evaluation of a low dose of hepatitis B vaccine given within a childhood immunisation programme in Singapore.

The feasibility of introducing low dose (5 micrograms) hepatitis B (HB) virus vaccination at birth and again 1 and 2 months later as part of an existing primary immunisation programme of childhood, was assessed in 662 healthy newborn Singapore children. The vaccine (B-Hepavac, Menck, Sharp and Dohme) was given to three neonatal groups: those born to HB surface antigen (sAg)-negative mothers, HBsAg-positive/HBeAg-positive mothers and HBsAg-positive/HBeAg-negative mothers. A dose of 5 micrograms was compared in a randomised study with the more usual 10 micrograms dose given at the same intervals. Neonates born to HBsAg-positive/HBeAg-positive mothers were also given hepatitis B immunoglobulin (HBIg) at birth. The 5 microgram dose of vaccine was as immunogenic as the 10 microgram dose in all three groups of children studied. At 1 year, anti-HBsAg seroconversion among infants of antigen-negative mothers was 95.8% for the 5 microgram dose and 91.9% for the 10 microgram dose. Suppression of anti-HBsAg formation was not seen even when maternal anti-HBsAg was present or HBIg given. Among infants born to HBsAg-positive/HBeAg-positive mothers, passive plus active immunisation was 100% protective at doses of 5 micrograms and 10 micrograms vaccine in the newborns who were HBsAg-negative at 24 h. Seroconversion after both the 5 and 10 microgram doses of vaccine was reduced, however, to 88% in each group of infants who were already HBsAg-positive at 24 h of age. Overall, passive plus active immunisation as well as HB vaccine alone (5 micrograms dose), given within the existing but expanded primary immunisation programme of childhood, was effective in preventing infection and the chronic carrier state in newborns exposed to risk of HB virus infection during infancy.

Carrier State↗
PubMed1986

Problems and strategies in the prevention of viral hepatitis in the Asian Pacific Region.

Viral hepatitis is endemic in the Asian Pacific Region, and seasonal outbreaks of these acute infections diseases occur regularly and annually. In this region, which extends from zones of temperate climate to tropical rain belt, vast distances, insufficient medical and laboratory services, and differences in the distribution of vaccines are further accentuated by local socio-economic factors. Prevention and control of these viral infections is one of the most important health issues because of their linkages with high mortality and morbidity due to their infections and to liver cancer, which is a foremost cancer in the region. Viral hepatitis A, B, delta region and Non A Non B are now present in the region. Strategies to prevent and control the spread of these diseases require the support of national authorities and the guidance of the World Health Organisation. Such strategies include public health education programmes on modes of transmission and their prevention, the use of suitable vaccines in susceptible populations, and the building up of local scientific know-how for regional collaboration and information on the dissemination of serious outbreaks.

Asia↗
PubMed1986

Treatment of irresectible hepatocellular carcinoma with intrahepatic arterial lipoidal mixed with adriamycin and mitomycin C.

Four patients with advanced hepatocellular carcinoma, but with stage I functional disease, were treated with intrahepatic arterial lipoidal mixed with small doses of Adriamycin (20 mg) and Mitomycin C (10 mg). Regression was seen in 3 out of the 4 patients. In 2 patients, there was substantial regression of tumour clinically, radiologically and biochemically. The treatment was tolerable without marrow depression or deterioration of liver function. Mild fever (37 degrees C) was seen in 2 and epigastric pain in 1. This form of treatment opens up scope for further improvement in the management of irresectable hepatocellular carcinoma.

Adult↗
PubMed1986

A preliminary survey on aflatoxin exposure in Singapore.

Aflatoxins (naturally occurring chemicals of fungal origin) are powerful liver carcinogens, and increased incidence of hepatocellular carcinoma has been observed in areas where exposure to this mycotoxin is high (e.g., Africa, China). These areas also have a high incidence of HBV infection. It has been suggested that this environmental carcinogen interact with HBV in the aetiogenesis of hepatocellular carcinoma in these areas. The aim of this study was to determine the level of aflatoxin exposure in the local population. Fifty healthy adults were studied. Details of dinner taken the previous evening were obtained. Early morning urine was collected and aflatoxin quantitated by ELISA following purification on an antibody affinity column. Rabbit polyclonal antibody to aflatoxin B1 was used, and the mean of at least two assays were determined. Six individuals (12%) showed ELISA inhibition values of more than 25%, equivalent to aflatoxin levels of more than 100 pg/ml in urine. Levels ranged from 185 pg/ml to 2300 pg/ml aflatoxin B1 equivalents. All 6 individuals consumed fried food. The highest level was found in a medical student who had 'satay' (crushed peanut) sauce with dinner. This is in contrast to 52% individuals from Gambia with urine aflatoxin levels between 100 and 1000 pg/ml.

Adult↗
PubMed1986

Estradiol binding capacity of breast cancer cell line in correlation with cell cycle.

The specific estrogen binding capacity of the MCF-7 cells has been studied throughout the cell cycle. Two days after plating 1-4 X 10(5) cells per well, we observed that cell number, protein concentration and DNA level began to rise but the estrogen binding capacity was lowered. At logarithmic phase the binding increased gradually then sharply to just before confluency. When the cells reached the quiescent phase the estrogen binding capacity fell rapidly. Since estrogen binding capacity of the intact MCF-7 cells varies with different phases in the cell cycle as well as the incubation temperature and time and the plating density, all these factors should be taken into consideration when this cell line is used for hormone studies.

Breast↗
PubMed1986

Quality control of estrogen and progesterone receptor assays.

The intra-laboratory QC materials for estrogen and progesterone receptor assays were prepared using different methods. The most convenient and economical method was found to be the use of lyophilized rat uterine cytosol. The level of receptors remained stable for 12 months when stored at -70 degrees C with the inclusion of 10 mM phenylmethyl sulfonyl-fluoride in the cytosol extraction buffer. For inter-laboratory comparison, we received QC materials from Dr E D Ryan (McMaster University, Canada) monthly and our results fell within +/- 1SD of the mean value of 15 centres from North America and Europe participating in this program.

Animals↗
PubMed1985

Maternal-child hepatitis B virus transmission in Singapore.

A study of maternal-infant transmission of hepatitis B virus (HBV) was conducted in Singapore between June 1980 and June 1982. HBsAg carrier rate was highest among Chinese (6.2%) followed by Malay (2.3%) and Indian (0.6%) mothers. The presence of HBeAg in maternal sera correlated well with high titre HBsAg (p = 7.34 X 10(-5)). Overall HBV transmission occurred in 27/56 (48.2%) infants from carrier mothers. The majority of the transmission was perinatal. There was a very strong correlation between transmission and HBeAg status of the mother (p = 1.85 X 10(-9); odds ratio = 68.44) and to a lesser extent with high titre HBsAg (p = 0.002; odds ratio = 6.38). A strong negative correlation was seen between transmission and anti-HBeAg (p = 8.19 X 10(-7); odds ratio = 0.04). At one year 19 (70.4%) infants were still HBsAg positive while seven (25.9%) lost the antigenemia and acquired anti-HBsAg and one developed HBsAg after one year. It could be calculated that perinatal HBV transmission contributed about 18% to the total pool of HBsAg positive infants of one year of age.

Carrier State↗
PubMed1985

Hepatitis B infection in households of acute cases.

Seroepidemiological studies conducted in 369 household contacts of 80 acute cases of hepatitis B in Singapore showed that asymptomatic chronic carriers of hepatitis B surface antigen (HBs Ag) are the main source of acute hepatitis B infection. The HBs Ag prevalence rate in asymptomatic household members was 20% compared with a 6% prevalence for the general population. The majority of the household carriers (60%) were highly infectious with positive hepatitis e antigen (HBe Ag). The overall prevalence of HBV infection (with at least one HBV marker) of the household contacts was 40.7%. Spouses and parents of acute cases had a significantly higher prevalence of HBV infection than other members of the families. HBV prevalence rate showed no association with the household size. Factors associated with the risk of transmission of HBV infection included sharing of various personal and household articles, such as toothbrush, towel, handkerchief, clothing, razor, comb, bed and bedding. Sleeping in the same bedroom, eating together at meals, and sharing of eating and drinking utensils were not associated with an increased risk of transmission of infection. Follow-up studies six months later showed that 30% of the acute cases became chronic HBs Ag carriers (with 46% HBe Ag positive), thus providing an additional source of infection in the families, while 8% of the susceptible household members acquired asymptomatic HBV infection. Health education on the prevention of HBV transmission in the homes of acute cases should be based on sound epidemiological information. Household contacts of acute cases of hepatitis B should be routinely screened and the susceptible vaccinated against the disease as soon as possible.

Acute Disease↗