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Biomedical subjects

T C Aw

Publications and source records attributed to T C Aw.

At least 19 recordsLinked to original sources
PubMed1999

Apolipoprotein B 5'-Ins/Del and 3'-VNTR polymorphisms in Chinese, malay and Indian singaporeans.

The allele frequencies for the apolipoprotein B (apo B) 5'-Ins/Del and 3'-VNTR polymorphisms varied significantly (p < 0.01) among Singaporeans of Chinese, Malay and Indian descent. We calculated the unbiased expected heterozygosities for the 5'-Ins/Del polymorphism as 0.3357, 0.1984 and 0.2418, and for the 3'-VNTR as 0.5980, 0.5260 and 0.6749, respectively, in the Chinese, Malays and Indians. Compared to heterozygosities reported for other populations, the Singaporeans differed from most Caucasians in having significantly lower values but were closely related to other non-Caucasians. Thirteen alleles, with a bimodal distribution, were observed at the 3'-VNTR polymorphic locus; the alleles occurring most frequently among the Chinese and Malays were of 35 or 53 repeats, and among the Indians, of 37 or 47 repeats. The Del allele was associated with elevated serum cholesterol (p = 0.023), LDL-cholesterol (LDL-C) (p = 0.001) in the Chinese, and apo B (p = 0.007) in the Indians. Likewise, the larger 3'-VNTR alleles (> 41 repeats) were associated with raised cholesterol (p = 0.018), LDL-C (p = 0.025), and triglyceride (p = 0.001) in the Chinese. The two polymorphisms were not in significant linkage disequilibrium (D = -0.0029, p = 0.494) in the three ethnic groups.

Adult↗
PubMed1999

Serum IGF-binding protein-6 and prostate specific antigen in breast cancer.

OBJECTIVE: Recent studies have demonstrated the presence of the IGF-binding proteins (IGFBPs) and prostate specific antigen (PSA), an IGFBP protease. in human breast tissue. We sought to investigate the differences in serum IGFs, IGFBP-1, -3 and -6, and PSA between patients with surgically proven breast cancer and patients with benign breast disease. DESIGN AND METHODS: Concentrations of IGFs, IGFBP-1, -3 and -6, and PSA were determined in the sera from 57 patients with breast cancer (CA), and 46 women with benign breast disease (BBD) using immunoassays for IGFs and IGFBPs and an ultrasensitive ELISA for PSA. RESULTS: The mean (+/- S.E.M.) serum IGFBP-6 level in the CA group, 127 (16) ng/ml, was statistically significantly lower than in the BBD group, 157 (10) ng/ml (P = 0.016). Patients with CA had an elevated geometric mean serum PSA level of 0.018 (range: 0.0015-0.107) ng/ml, compared with 0.007 (range: 0.0015-0.019) ng/ml in women with BBD (P = 0.025). Mean serum IGFBP-1 concentrations were significantly lower in the CA group, 16 (2) ng/ml, versus 37 (4) ng/ml in the BBD group (P = 0.001). Mean serum IGFBP-3 concentrations were also lower in the CA group versus the BBD group, at 1981 (65) ng/ml, versus 2603 (140) ng/ml (P = 0.002) respectively. In the CA group, statistically significant correlations between PSA and IGFBP-6 (r = 0.413; P = 0.001), and between PSA and IGFBP-1 (r = -0.329; P = 0.021) were seen. Differences in IGF-I and -II between the two groups were not statistically significant. CONCLUSION: Lower serum concentrations of IGFBP-6, -3 and -1, but higher PSA concentrations were seen in the breast cancer group, and collectively these would suggest that there is an increase in bioavailable IGF-I in breast cancer.

Breast Neoplasms↗
PubMed1998

Comparison of the qualified occupational physician systems in the United Kingdom and Japan.

The British educational system of occupational medicine was compared to the Japanese system. Furthermore, a comparison was carried out between the certified occupational physician (COP) recognized by the Japan Society for Occupational Health in Japan and the Associateship of the Faculty of Occupational Medicine (AFOM) by the Faculty of Occupational Medicine (FOM) which is a part of the Royal College of Physicians in the United Kingdom. Judging from the comparison of the minimum total training period, the clinical training period, the occupational health training period, the method of examination and the success rate between COP and AFOM, it is suggested that the British system of occupational physicians may be better as a training system for occupational medicine and may regard occupational clinical training as more important than the Japanese system does. A comparison of a Diploma in Occupational Medicine (Dip Occ Med) approved by the FOM and the certification of occupational physicians by the Japan Medical Association has shown that the former has an examination but there is no test system in the latter. It should be discussed whether an examination system for the certification of occupational physicians should be introduced into the Japanese system in the near future.

Education, Medical, Continuing↗
PubMed1998

Cardiovascular risk factors in non-insulin-dependent diabetics compared to non-diabetic controls: a population-based survey among Asians in Singapore.

Cardiovascular risk factors were compared between 126 people with non-insulin-dependent diabetes mellitus (NIDDM) and 530 non-diabetics (controls), in a random sample of people (Chinese, Malays, and Asian Indians) aged 40-69 years from the general population of Singapore. Data were adjusted for age and ethnicity. For both genders, people with NIDDM had higher mean body mass indices, waist-hip ratios and abdominal diameters. They also had a higher prevalence of hypertension, higher mean levels of fasting serum triglyceride, slightly lower mean levels of serum high-density-lipoprotein cholesterol, and higher mean levels of plasma plasminogen activator inhibitor-1 and tissue plasminogen activator (antigen). These factors are components of syndrome X (metabolic syndrome) and increase the risk of atherosclerosis and thrombosis. In contrast, there were no important differences for cigarette smoking, serum total and low-density-lipoprotein cholesterol, serum apolipoproteins A1 and B, plasma factor VIIc and plasma prothrombin fragment 1 + 2. Females with NIDDM, but not males, had a higher mean serum fibrinogen level than non-diabetics, which could explain why NIDDM has a greater cardiovascular effect in females than males. Serum lipoprotein(a) concentrations were lower in people with NIDDM. Mean levels of serum ferritin, a pro-oxidant, were higher in people with NIDDM than controls, but there were no important differences for plasma vitamins A, C and E, and serum selenium, which are anti-oxidants.

Arteriosclerosis↗
PubMed1998

Cardiovascular risk factors in relation to cigarette smoking: a population-based survey among Asians in Singapore.

To investigate how cigarette smoking increases the risk of cardiovascular disease, risk factors were compared between 166 cigarette smokers and 312 non-smokers, in a random sample of males (Chinese, Malays and Asian Indians) aged 30-69 years from the general population of Singapore. There was adjusted for age and ethnic group. The prevalence of hypertension was lower in cigarette smokers (15.2%) than non-smokers (21.9%), with the difference reduced by adjustment for body mass index (BMI). Smokers had: lower mean serum HDL-cholesterol (0.76 versus 0.81 mmol/l) and higher mean serum fasting triglyceride (1.92 versus 1.71 mmol/l), which will increase atherosclerosis; higher mean plasma fibrinogen (2.75 versus 2.67 g/l) and plasminogen activator inhibitor 1 [PAI-1] (24.9 versus 22.2 ng/ml), which will increase thrombosis; and lower mean plasma vitamin C (4.4 versus 6.4 mg/l) and serum selenium (118 versus 123 microg/l), which may increase atherosclerosis. Adjustment for BMI slightly increased the differences for HDL-cholesterol, fasting triglyceride, fibrinogen and PAI-1, indicating that less generalised obesity among smokers reduces their increased cardiovascular disease risk. Smoking was not found to be related to: diabetes mellitus; serum total cholesterol, LDL-cholesterol, apolipoproteins A1 and B and lipoprotein(a); plasma factor VIIc and prothrombin fragment 1 + 2; and plasma vitamins A and E and serum ferritin. There was no evidence of increased insulin resistance in smokers, as measured by mean fasting serum insulin.

Adult↗
PubMed1998

Effect of mixing technique on surface characteristics of impression materials.

STATEMENT OF PROBLEM: Previous studies have shown a relationship between the disinfection process, wettability, and mass change of impression materials. Hand-mixed high viscosity impression materials usually result in a material with numerous voids, which contribute to surface roughness and affect the surface characteristics of the material. PURPOSE: This study evaluated the effect of mixing technique on advancing contact angle, receding contact angle, imbibition, and mass loss of various high and low viscosity polyether and polyvinyl siloxane materials. The null hypothesis tested was no differences exist between the different mixing systems. MATERIAL AND METHODS: The Wilhelmy technique was used for deriving wetting properties of the materials used (Impregum F and Penta, Permadyne Syringe, Garant and Penta, Dimension Penta and Garant L, Aquasil). Conditions included no disinfection (0 hours) and 1, 5, and 18 hours of immersion disinfection in a full-strength solution of 2% acid glutaraldehyde disinfectant (Banicide). Weight changes before and after disinfection were measured to detect weight loss or mass increase over time. Weight loss in air was also measured to detect mass loss. Data were analyzed with a one-way analysis of variance at alpha = 0.05. RESULTS: All materials displayed some degree of imbibition of the disinfectant and experienced mass loss with polymerization, except the light viscosity polyvinyl that gained 0.18% at 5 hours. No significant differences were found in wettability among the polyether materials after 1 hour of disinfection. Less imbibition was observed for high viscosity mechanically mixed materials compared with the hand-mixed materials for both polyether and polyvinyl siloxane at 1-hour disinfection time. CONCLUSIONS: Polyether materials were more wettable than polyvinyl. Imbibition of high viscosity polyether and polyvinyl materials after 1 and 18 hours of disinfection were affected by the mixing system used.

Analysis of Variance↗
PubMed1997

Clinical and epidemiological data on lung cancer at a chromate plant.

The workforce of the only chromite ore processing plant in the United Kingdom at Eaglescliffe has been the subject of several epidemiological studies. There are also medical data available through a health surveillance program conducted by the plant's medical center. The clinical information has in part been collected to fulfill the requirements of health and safety legislation. Through this system, 18 cases of lung cancer among the workforce have been identified. The mean age at diagnosis was 57 years, with all but two cases occurring in smokers. There were no obvious histological or clinical features that could allow differentiation between the occupational and nonoccupational cancers. The epidemiological studies indicated an excess lung cancer risk among the workers beginning employment on the site before 1960. The risk appeared to have diminished after a major process change in 1960 which removed the addition of calcium carbonate to the process. Further studies including case-control analyses and construction of a job exposure matrix through use of recall by long-term workers and pensioners are in progress. The feasibility of an updated cohort mortality study at Eaglescliffe and possibly using the same protocol for other similar cohorts in U.S. and European plants should be considered.

Case-Control Studies↗
PubMed1997

Polymerization shrinkage of restorative resins using laser and visible light curing.

OBJECTIVE: This in vitro investigation compared the amount of linear shrinkage that occurs when a light-cured composite resin is cured with a visible light source, and also with an argon laser. SUMMARY BACKGROUND DATA: When composite resins are light-cured, they undergo a certain degree of polymerization shrinkage, which can be clinically significant and affect the efficacy of the restoration. A new protocol utilizes laser curing instead of conventional visible light. METHODS: Two hybrid composite resins were used, Z100 and TPH-Spectrum. Dimensional change was measured in a linear direction, using a calibrated light-microscope. A total of 40 samples of composite resin was tested using two curing lights, and two hybrid composite resins, resulting in four groups of 10 samples (n = 10) each. According to manufacturer instructions, curing time for the laser was 10 sec, and for visible light was 40 sec. RESULTS: With TPH-Spectrum, the mean shrinkage with visible light was 0.583% compared to that with laser light which was 0.591%. With Z100, the mean shrinkage with visible light was 0.565%, compared to that with laser light which was 0.551%. CONCLUSIONS: There was no significant difference in amount of shrinkage of hybrid composite resins between using visible light or laser light. There was also no significant difference in shrinkage between the two hybrid composites for either light source.

Analysis of Variance↗
PubMed1997

Ethical issues in occupational medicine practice: knowledge and attitudes of occupational physicians.

Views on ethical conduct in occupational medicine practice can vary from country to country and even between occupational health practitioners. However, there are many areas of common agreement, and this is apparent on comparing guidance documents on ethics produced by several different organizations. The usefulness of these documents will depend in part on how aware practitioners are of their existence. A standardized questionnaire administered to 70 occupational physicians in the Netherlands, UK, and Singapore showed that there was a lack of awareness of guidance documents on ethics, even for publications from their own countries. Only five of the 70 respondents consulted an ethics document in the past year. In addition to publications, other avenues were used for advice on ethical issues. There was a difference in opinion between the physicians from Singapore and those from the two European countries on whether specific occupational health activities were ethical. These findings reinforce the need for international guidance on ethics to take into account differences in attitudes and practice between countries. On many issues there was no unanimity of opinion, even between occupational physicians from the same country. This may be an indication of the complexity of ethical matters, and provides a rationale for publishing guidance on ethics in occupational medicine.

Adult↗
PubMed1997

Occupational infection in an offal porter: a case of Q fever.

This case report describes the job activities of an offal porter who developed Q fever while processing livers from sheep. The diagnosis was confirmed by an increase in specific serial antibody titre. The main clinical features were anorexia, nausea, headache, pyrexia and elevated gamma-glutamyl transferase. Twenty-four cases of occupationally-acquired Q fever were noted by the Communicable Diseases Surveillance Centre (CDSC) between 1984 and 1994. This case report has an important feature in that a workplace visit was performed to evaluate the system of work and the circumstances of exposure to the infectious agent. Relevant preventive measures for this zoonotic infection are discussed.

Abattoirs↗
PubMed1997

Central obesity, insulin resistance, syndrome X, lipoprotein(a), and cardiovascular risk in Indians, Malays, and Chinese in Singapore.

STUDY OBJECTIVE: To examine the hypothesis that the higher rates of coronary heart disease (CHD) in Indians (South Asians) compared with Malays and Chinese is at least partly explained by central obesity, insulin resistance, and syndrome X (including possible components). DESIGN: Cross sectional study of the general population. SETTING: Singapore. PARTICIPANTS: Random sample of 961 men and women (Indians, Malays, and Chinese) aged 30 to 69 years. MAIN RESULTS: Fasting serum insulin concentration was correlated directly and strongly with body mass index (BMI), waist-hip ratio (WHR), and abdominal diameter. The fasting insulin concentration was correlated inversely with HDL cholesterol and directly with the fasting triglyceride concentration, blood pressures, plasminogen activator inhibitor 1 (PAI-1), and tissue plasminogen activator (tPA), but it was not correlated with LDL cholesterol, apolipoproteins B and A1, lipoprotein(a), (Lp(a)), fibrinogen, factor VIIc, or prothrombin fragment (F)1 + 2. This indicates that the former but not the latter are part of syndrome X. While Malays had the highest BMI, Indians had a higher WHR (men 0.93 and women 0.84) than Malays (men 0.91 and women 0.82) and Chinese (men 0.91 and women 0.82). In addition, Indians had higher fasting insulin values and more glucose intolerance than Malays and Chinese. Indians had lower HDL cholesterol, and higher PAI-1, tPA, and Lp(a), but not higher LDL cholesterol, fasting triglyceride, blood pressures, fibrinogen, factor VIIc, or prothrombin F1 + 2. CONCLUSIONS: Indians are more prone than Malays or Chinese to central obesity with insulin resistance and glucose intolerance and there are no apparent environmental reasons for this in Singapore. As a consequence, Indians develop some but not all of the features of syndrome X. They also have higher Lp(a) values. All this puts Indians at increased risk of atherosclerosis and thrombosis and must be at least part of the explanation for their higher rates of CHD.

Adult↗
PubMed1997

Hypercholesterolaemia and its treatment in Singapore with implications for screening.

The National University of Singapore Heart Study is a cross-sectional survey of the whole of Singapore from 1993 to 1995 with a random sample of 961 persons aged 30 to 69 years (response rate 71.2%). Serum lipids were measured enzymatically on an autoanalyser (Ektachem, kodak). Hypercholesterolaemia was diagnosed if the person was on lipid lowering drugs or had a serum cholesterol > or = 6.5 mmol/L (250 mg/dL). Results for the 40 to 64 age group are presented. The proportion and number in Singapore with hypercholesterolaemia were high, 23.7% and 186,544 persons respectively. However, they declined with the additional requirement of coronary heart disease (CHD) or risk factors (i.e. cigarette smoking, hypertension or diabetes mellitus), and were small if only hypercholesterolaemic persons with CHD were included, 1.6% and 13,126 persons respectively. For both genders, the proportions on drugs increased with the added options of CHD or risk factors, so that for persons with hypercholesterolaemia and CHD the proportion on drugs was very high i.e. 84.0%. However, 11.2% of persons with only hypercholesterolaemia (i.e. without CHD or other risk factors) had been prescribed drugs. The main conclusions were:1) The use of different criteria for the screening and treatment of hypercholesterolaemia would involve large differences in the number of Singaporeans on lipid lowering drugs and this should be considered when deciding policy and 2) Medical practitioners currently to some extent do consider the presence of CHD or other risk factors when prescribing lipid lowering drugs for hypercholesterolaemia.

Adult↗