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Biomedical subjects

S G Tan

Publications and source records attributed to S G Tan.

At least 19 recordsLinked to original sources
PubMed1992

Population genetic evidence for species A, B, C and D of the Anopheles dirus complex in Thailand and enzyme electromorphs for their identification.

Mixtures of chromosomal forms A, B, C and D in natural populations of Anopheles dirus Peyton & Harrison sensu lato in Thailand show significant positive values of Wright's fixation index for six enzyme-electromorph loci. The mean value of FIS over all loci was found to be +0.28 (SD 0.02), with a range of +0.57 (Odh) to +0.10 (Idh-2). Partitioning electromorph data for the chromosomal forms reduces the mean FIS to 0.03 (SD 0.01), which suggests that positive assortative mating is a characteristic of each form. This supports the hypothesis that the chromosomal/electrophoretic forms A, B, C and D represent four distinct biological species within the An. dirus complex. An example is given of the use of enzyme electromorphs as a means of vector identification during a malaria entomological field study involving a mixture of An. dirus species A and D. Electromorph identifications of 323 sp. A and 161 sp. D were more than 98% correct when cross-referenced to specific DNA probes.

Alleles↗
PubMed1991

Primary resection and anastomosis in obstructed descending colon due to cancer.

Intraoperative colonic irrigation followed by one-stage resection is gaining popularity as the optimal surgical treatment for left-sided colonic obstruction. However, its efficacy and potential hazards have not been adequately tested in obstruction due to colonic cancer. We analyzed the early results of 23 consecutive patients with obstructive left-sided colonic carcinoma treated by primary resection and anastomosis following intraoperative antegrade colonic lavage. Two patients (8.6%) died, one from complication of anastomotic leakage. The significant postoperative complications were chest infection in three (13%) and wound infection in seven (30.4%). The average hospital stay was 16.5 days. The results of this study suggest that intraoperative bowel irrigation permits one-stage resection and anastomosis to be conducted with reasonable safety provided care is taken in operative techniques.

Adenocarcinoma↗
PubMed1991

Population genetic analysis of host seeking and resting behaviors in the malaria vector, Anopheles balabacensis (Diptera: Culicidae).

During the intermonsoon period from mid-September to mid-October 1986, wild-caught Anopheles balabacensis Baisas females were marked and released in a host-choice experiment. Association between capture and recapture of marked mosquitoes from human and bovid hosts and blood meal host identification of recaptured females were determined on a daily basis. Although the mark-recapture and blood meal data indicated behavioral heterogeneity between buffalo and human biters, restriction endonuclease fragment length polymorphism analysis revealed no differences in repeat sequence profiles. Doubly-marked recaptures strongly indicated a "learning" component involved in a separate host preference experiment. In a "habitat loyalty" experiment conducted in January 1987, females of An. balabacensis preferentially returned to the resting sites (indoor surfaces and exit traps) where they were first caught. Of nine isozyme loci found to be polymorphic, the genotypic frequencies of Esterase-3 and Isocitrate dehydrogenase-3 were different in "faithfully" endophilic and exophilic subpopulations. Genetic heterozygosity, as determined by polyacrylamide gel electrophoresis, was greater in exophilic than endophilic population components. These results confirm that genetic and learning components can significantly influence house resting and host seeking behavior and may contribute to local epidemiological patterns of malaria transmission observed in Sabah, Malaysia.

Animals↗
PubMed1986

Genetics of esterases and 6-phosphogluconate dehydrogenase in the Anopheles maculatus complex.

Electromorphic variation for some esterases and 6-phosphogluconate dehydrogenase enzymes in the Anopheles maculatus complex is controlled by four loci which are unlinked to sex. Esterase loci are linked to each other: Est-1-36%-Est-4-16.5%-Est-3; but unlinked to Pgd-2. Linkage data were obtained by selfing the F1 generation from selected parents and analysing genotypes in the F2; the classical dihybrid-cross. The analysis consists of testing observed data for goodness of fit to a) ratios expected from Mendelian ratios without linkage and b) if they do not fit then computing a likely degree of linkage and computing expected ratios with such linkage for further tests. Confidence limits are given for the most likely levels of linkage. This method can provide useful information for population-genetic studies on anopheline mosquitoes, whose laboratory rearing is generally difficult. Through indirect evidence, the enzyme loci are correlated to polytene chromosomes. The esterases probably lie on chromosome three (polytene arms 3 and 4) and Pgd-2 on the second chromosome (arms 2 and 5).

Animals↗
PubMed1986

Immunization of neonates with trivalent oral poliomyelitis vaccine (Sabin).

A study was carried out between November 1981 and April 1982 on the immunological effect of administering trivalent live, oral polio vaccine to 200 mature healthy neonates from Henan Province, China. The initial dose of vaccine was given at 3 days of age, and 2 months thereafter antibodies to poliovirus types 1, 2, and 3, respectively, were detected in 46.7%, 60.7% and 48.6% of the neonates; after the second dose, the levels were 86.9%, 95.3%, and 97.2%, with geometric mean titres of 1:106.2, 1:349.8, and 1:232.5. Almost 100% of neonates exhibited antibodies after the fourth dose of vaccine. Eighty-two percent of the neonates excreted poliovirus for at least a week after the initial dose of vaccine, and this increased to 99% after the second dose. Seroconversion at 4 months of age was similar to that of a group of controls who received their initial dose of vaccine at 2 months of age; however, immunization of neonates induced immunity to poliovirus at the earliest possible age.

China↗
PubMed1979

Biochemical genetic markers in the Kadazans of Sabah, Malaysia.

Kadazans, the largest indigenous group in Sabah, northern Borneo, were surveyed for glyoxalase I, phosphoglucomutase I, red cell acid phosphatase, esterase D, adenosine deaminase, soluble glutamate pyruvate transaminase, soluble glutamate oxaloacetate transaminase, 6-phosphogluconate dehydrogenase, uridine monophosphate kinase, adenylate kinase, peptidase B and D, superoxide dismutase, C5, group specific component, haptoglobin and transferrin. Kadazans were found to be polymorphic for GLO I, PGM I, RCAP, esterase D, ADA, s-Gpt, 6PGD, UMPK, Gc, C5, haptoglobin and peptidase B. Rare variants were found for transferrin and peptidase D. No variant was found for s-Got, SOD and AK.

Acid Phosphatase↗
PubMed1979

Acid alpha-glucosidase in Malaysians. Population studies and the occurrence of a new variant.

Acid alpha-glucosidase from the placenta was electrophoretically surveyed in a total of 633 Malaysians, 236 of Malay, 261 of Chinese and 136 of Indian ancestries. A new variant, alpha-glucosidase 3-1 was observed in 1 Malay and 3 Indians. A polymorphism for this enzyme was observed among Indians, but in Chinese and Malays variants are rare. Phenotype 2-1 was observed once in a Chinese and once in a Malay.

China↗
PubMed1979

Saliva acid phosphatases in Malaysians: report of a new variant.

A total of 640 Malaysians, 355 of Malay, 155 of Chinese, and 130 of Indian ancestries have been examined for saliva acid phosphatases. The three ethnic groups were polymorphic for saliva acid phosphatase A (Sap-A) and saliva acid phosphatase (B (Sap-B). The gene frequencies were: Sap-A, Malays: A = 0.469, A' = 0.001, A degrees = 0.530; Chinese: A = 0.436, A' = 0.010, A degrees = 0.555; Indians: A = 0.533, A' = 0.012, A degrees = 0.456. For Sap-B, Malays: B = 0.925, B degrees = 0.075; Chinese: B = 0.797, B1 = 0.016, B degrees = 0.187; Indians: B 0.752, B degrees = 0.248. Phenotype ABB1 is described.

Acid Phosphatase↗
PubMed1979

Human saliva as a source of biochemical genetic markers. I. Techniques.

The number of genetic markers identified in human saliva is still small compared to known genetic markers of blood. Enzyme activities that can be detected in human saliva by spectrophotometric techniques are listed. The methodologies currently available for the detection of biochemical genetic markers by polyacrylamide-gel electrophoresis are summarized.

Electrophoresis, Polyacrylamide Gel↗
PubMed1978

Genetic markers in Malaysians: variants of soluble and mitochondrial glutamic oxaloacetic transaminase and salivary and pancreatic amylase, phosphoglucomutase III and saliva esterase polymorphisms.

Malaysians of Malay, Chinese, and Indian ancestries were electrophoretically phenotyped for Amy1 and saliva esterase region 1 (Set-1) from saliva, Amy2 from plasma, soluble and mitochondrial GOT and PGM3 from leukocyte and placenta. Kadazans and Bajaus, the indigenous people of Sabah, East Malaysia were surveyed for Amy2. Three types of variants were observed for Amy1, one type for Amy2. Only Indians were found to be polymorphic for Amy1. Two GOTs 2-1 and three GOTm 2-1 variants were found among 281 Chinese while three GOTm 2-1 variants were found among 311 Malays. Malaysian Malays, Chinese, and Indians were found to be polymorphic for Set-1 and PGM3. The gene frequencies in Malays are Set-1F=0.601 +/- 0.021, Set-1S = 0.399 +/- 0.021; PGM13 = 0.788 +/- 0.020, PGM23 = 0.212 +/- 0.020; in Chinese Set-1F = 0.497 +/- 0.028, Set-1S = 0.503 +/- 0.028; PGM13 = 0.745 +/- 0.24, PGM23 = 0.255 +/- 0.024; in Indians, Set-1F = 0.449 +/- 0.031, Set-1S = 0.551 +/- 0.031; PGM13 = 0.755 +/- 0.029, PGM23 = 0.245 +/- 0.029.

Amylases↗