Biomedical subjects

S T Chow

Publications and source records attributed to S T Chow.

13 recordsLinked to original sources

PubMed2005

Genetic data for the 13 CODIS STR loci in Singapore Chinese.

Allele frequencies for the 13 CODIS STR loci included in the AmpFISTR Profiler Plus and AmpFISTR Cofiler kits (Applied Biosystems, Foster City, USA) were determined in a sample of 209 unrelated Chinese in Singapore. The combined random match probability for the 13 loci is about 6.6 x10(-15) and the overall probability of excluding paternity is 0.9999899. The results demonstrate that the loci are useful for forensic human identification and parentage testing for the Chinese population in Singapore.

China↗

PubMed2005

STR data for the 13 CODIS loci in Singapore Malays.

Allele frequencies for the 13 CODIS (Combined DNA Index System, USA) STR loci included in the AmpFISTR Profiler Plus and AmpFISTR Cofiler kits (Applied Biosystems, Foster City, USA) were determined in a sample of 197 unrelated Malays in Singapore.

DNA Fingerprinting↗

PubMed2005

Genetic data for the 13 CODIS STR loci in Singapore Indians.

Allele frequencies for the 13 CODIS short tandem repeat (STR) loci included in the AmpFISTR Profiler Plus and AmpFISTR Cofiler kits (Applied Biosystems, Foster City, USA) were determined in a sample of 174 unrelated Indians in Singapore.

DNA Fingerprinting↗

PubMed1998

A 10-year review of drug seizures in Singapore.

The trend of illicit drug seizures and analysis in Singapore over a 10-year period from 1986 to 1995 was examined and reviewed. The main drugs were heroin, opium, cannabis, and illicit tablets containing benzodiazepines and amphetamines. The emergence of amphetamines in early 1996 was a major departure from the traditional drug abuse pattern in Singapore. Changes in the legal definitions of opium and cannabis were also reviewed.

Cross-Sectional Studies↗

PubMed1998

Population genetic characteristics of the STR Loci D21S11 and FGA in eight diverse human populations.

A highly polymorphic multiplex short tandem repeat (STR) system composed of D21S11, FGA, and the sex-typing system amelogenin (AMG) has been used to investigate allele frequency distributions in two Canadian Caucasian samples (British Columbia and Alberta), three Canadian aboriginal populations (Coastal Salishans from British Columbia, Ojibwa from northern Ontario, and Cree from Saskatchewan), and three ethnic groups from Singapore (Chinese, Malays, and Asian Indians). Using the automated fluorescence detection approach on an ABD 373A DNA Sequencer, we distinguished 20 D21S11 and 22 FGA alleles with a nearly equal representation of two- and four-base variants. An overlap in allele sizes for both STR loci across populations was observed, but frequency differences were noted. Statistical analysis revealed that (1) both D21S11 and FGA loci conform to Hardy-Weinberg equilibrium in all eight surveyed populations based on five different tests and (2) both STR loci are in linkage equilibrium. Results from the 2 x N contingency table exact tests for population differentiation demonstrated that the Canadian samples from two different provinces were not distinguishable from one another at either STR locus and therefore could be combined to form one Caucasian group. Likewise, Chinese and Malays from Singapore did not show significant differences at either STR locus. In contrast, all other examined populations exhibited differences deemed statistically significant. As a complement to our study, we compared D21S11 allele frequency distributions in 21 worldwide populations and FGA allele frequency distributions in 14 populations. Many alleles never previously reported in worldwide populations were identified in Canadian aboriginal and Asian samples from this study. Twenty-four D21S11 and 29 FGA alleles were distinguished in worldwide groups. Interesting similarities in allele frequency distribution patterns across populations suggest that the STR polymorphism at these loci predates the geographic dispersal of ancestral human populations. This study further demonstrates the utility of highly informative STR loci such as D21S11 and FGA in human population evolutionary history and in forensic medicine.

Canada↗

PubMed1997

Comparison of Hae-III-generated VNTR profiles of Chinese in Hong Kong and Singapore.

Some statistical analysis and experiments have been carried out on the single-locus VNTR reference databases collected separately from the Chinese in Hong Kong and Singapore to assess the issues of sample size and representativeness in the context of forensic science. We employed the bootstrap method and the Pearson chi-squared test for independence, and found that the different reference databases have very little effect in assessing the frequencies of occurrence of variable number of tandem repeats (VNTR) profiles. The results of random match probability assessment also indicate that the sample sizes studied appeared adequate to provide representative data. It has been found that a battery of four loci was enough to distinguish the 458 individuals under study.

Asian People↗

PubMed1996

Forensic applications of DNA profiling.

Deoxyribonucleic acid (DNA) profiling is a powerful forensic tool to identify and individualise biological evidence recovered at crime scenes. Its discriminating power and evidential value are exemplified by many actual forensic cases. Development of new DNA typing techniques, such as the amplification of fluorescently tagged short tandem repeats, would further enhance this capability in forensic investigation.

DNA↗

PubMed1994

Analysis of the D1S80 locus by amplified fragment length polymorphism technique in the Chinese, Malays and Indians in Singapore.

The distributions of the D1S80 alleles and genotypes in the Chinese, Malays and Indians in Singapore were determined by amplified fragment length polymorphism (AMP-FLP) analysis. The distributions of the observed genotypes for the three races conformed to Hardy-Weinberg expectations. The system was applied to 19 families whose paternity had been established by restriction fragment length polymorphism (RFLP) analysis. In all cases, Mendelian inheritance of the alleles at the D1S80 locus could be demonstrated. D1S80 typing on DNA recovered by differential extraction of forensic specimens which included vaginal swabs, urethral swabs and seminal stains yielded consistent results.

Alleles↗

PubMed1993

The application of restriction fragment length polymorphism to disputed paternity.

The Hae III restriction fragment length polymorphism (RFLP) system with four variable number tandem repeats (VNTR) loci has been used to resolve disputed paternity. The system exhibits an average power of exclusion of 99.96% and a mean probability of paternity of 99.96%. In all the casework examined, three VNTR loci provided a minimum 98.11% of probability of paternity. With four VNTR loci, the minimum probability of paternity was 99.69%. The alleged fathers in these cases were of different races: Chinese, Malay, Indian, Caucasian and Black, suggesting that the RFLP system is not biased for any race. This RFLP system has also been used to resolve disputed paternity cases involving related alleged fathers and cases of "motherless children". To date, we have not observed any mutation or recombination on either the maternal or paternal alleles. These results suggest that the RFLP system with four VNTR loci can decisively resolve the biological relationship in disputed paternity cases.

Female↗

PubMed1993

The development of DNA profiling database in an HAE III based RFLP system for Chinese, Malays, and Indians in Singapore.

Deoxyribonucleic acid (DNA) restriction fragment length polymorphism (RFLP) profiles were obtained for blood specimens from the three population groups--Chinese, Malays and Indians--in Singapore. The population databases were collected from Hae III digested high molecular weight DNA hybridized with four variable number of tandem repeats (VNTR) loci--D2S44, D10S28, D4S139 and D1S7. The data were analyzed statistically using the fixed bin system. Comparison of ratio of bin frequencies of these population data with published data on whites, blacks, and hispanics shows that the alleleic distribution at these loci is not seriously different among the six groups. This has important implications to the statistical significance of forensic DNA applications.

Alleles↗

PubMed1990

The computerisation of scientific services.

A full computerised laboratory information management system has been developed in the Department of Scientific Services. The system manages the acquisition and flow of laboratory data. A novel automated reporting procedure has been developed to generate customised laboratory reports. Based on the workload values of laboratory tests, the system integrates the laboratory data with management information to provide rapid and reliable productivity measurement and cost and pricing computations.

Clinical Laboratory Information Systems↗

PubMed1978

Heroin abuse and a gas chromatographic method for determining illicit heroin samples in Singapore.

The abuse of heroin (diacetylmorphine) in Singapore escalated sharply in 1975 and 1976, as indicated by the 35-fold increase in the number of heroin seizures and the 20-fold increase in the urine samples containing morphine since 1974. A rapid and simple GC method has been described to estimate diacetylmorphine (and caffeine). Monoacetylmorphine and acetylcodeine may be ascertained by an additional step involving acetylation. All gas chromatograms of a large number of samples analyzed consistently had the same pattern, indicating that they possibly had a common origin. This GC "fingerprint," together with the quantitative data, appears to be characteristic of the illicit Asian or Chinese type of heroin found in Singapore. The proportions of the four major ingredients in some twelve typical samples have been tabulated. Statistical data confirming the accuracy and reproducibility of the analytical method have also been presented.

Calibration↗

PubMed1974

Differential interaction of cholesterol with phosphatidylcholine on the inner and outer surfaces of lipid bilayer vesicles.

The separate identification of the -N(+)-(CH(3))(3) groups located on the outside and inside of phospholipid bilayers observed in proton magnetic resonance spectroscopy upon addition of low concentrations of praseodymium ion was exploited to investigate the effects of incorporated cholesterol. Only about 7% of the phosphate groups on the outside of the bilayer belong to a class of strong binding or shifting sites. Upon addition of up to about 30% cholesterol to egg lecithin bilayers, no changes in chemical shift or ratio of areas of peaks due to outer and inner -N(+)(CH(3))(3) groups appear. At about 30% incorporated cholesterol, an abrupt decrease occurs in the chemical-shift difference between -N(+)(CH(3))(3) groups located on the outer and inner bilayer surfaces, and an abrupt increase occurs in the ratio of the areas of the two peaks. For L-alpha-dipalmitoyl lecithin bilayers, an abrupt change in chemical-shift difference occurring between 10 and 20% cholesterol is not accompanied by a change in the relative number of -N(+)(CH(3))(3) groups located on the outer and inner surfaces. These results are interpreted as due to the homogeneous distribution of up to 30% cholesterol in egg lecithin bilayers. Above 30%, cholesterol is asymmetrically distributed in favor of the inner layer. In egg lecithin with a variety of polyunsaturated side chains, the side chains with the greater number of double bonds are preferentially displaced by high concentrations of cholesterol, which accounts for the increase in the ratio of outer to inner -N(+)(CH(3))(3) groups. Such preferential displacement by cholesterol cannot occur with the saturated L-alpha-dipalmitoyl lecithin. It is suggested that modified phospholipid vesicles of low radii of curvature may provide high concentrations of "active sites" present in membranes.

Binding Sites↗