Biomedical subjects

K L Tan

Publications and source records attributed to K L Tan.

At least 55 records · Page 3Linked to original sources

PubMed1996

Purification and characterization of a recombinant human Theta-class glutathione transferase (GSTT2-2).

A cDNA encoding the human Theta-class glutathione transferase GSTT2-2 was expressed in Escherichia coli as a ubiquitin fusion protein. The co-translational removal of the ubiquitin by a cloned ubiquitin-specific protease, Ubp1, generates enzymically active GSTT2-2 without any additional N-terminal residues. The recombinant isoenzyme was purified to apparent homogeneity by DEAE anion-exchange, gel filtration, dye ligand chromatography and high resolution anion-exchange chromatography on Mono Q FPLC. The recombinant enzyme had significant activity with a range of substrates, including cumene hydroperoxide and 1-menapthyl sulphate. The activity of GSTT2-2 with a range of secondary lipid peroxidation products such as the trans,trans-alka-2,4-dienals and trans-alk-2-enals, as well as its glutathione peroxidase activity with organic hydroperoxides, suggest that it may play a significant role in protection against the products of lipid peroxidation.

Base Sequence↗

PubMed1996

An immunohistochemical method for the diagnosis of melioidosis.

In order to assess the usefulness of immunohistochemistry in the diagnosis of melioidosis, an infection by Burkholderia pseudomallei, polyclonal antibodies were applied to tissues from known cases of melioidosis and to other infected tissues. Formalin-fixed, paraffin-embedded tissues were stained by a modified immunoperoxidase technique. In autopsy tissues with inflammatory lesions of melioidosis, the cytoplasm of phagocytes and intact bacilli, both intra- and extracellular, were stained very strongly positive. Relatively more focal positive staining was observed in some but not all surgical biopsies from proven cases of melioidosis. In granulomas staining was mainly found in the central necrotic areas, with little staining of peripheral phagocytes. All control materials stained negative. Immunohistochemistry appears to be a useful diagnostic tool in melioidosis.

Adolescent↗

PubMed1996

Effect of phototherapy on thyroid stimulatory hormone and free thyroxine levels.

OBJECTIVE: To study the effect of phototherapy for neonatal hyperbilirubinaemia on thyroid function as neonatal thyroid screening is sometimes performed during exposure to phototherapy. METHODOLOGY: Infants with non-haemolytic hyperbilirubinaemia were sequentially allocated to fibre-optic phototherapy, conventional daylight phototherapy, or a combination of both. Bilirubin concentration was monitored 12 hourly by capillary blood sampling; venous blood was sampled for thyroid stimulating hormone (TSH) and free thyroxine (fT4) determinations, at start of exposure, at 24 h, end of exposure and 1 day later. Comparable unexposed infants served as controls. RESULTS: All 123 study infants and 25 controls remained well during the study. Bilirubin levels declined during phototherapy, being most rapid in the combination group. The TSH and fT4 values at start of exposure were 3.86 +/- 0.41 mU/L (mean +/- SEM) and 33.20 +/- 1.16 pmol/L, respectively, in the fibre-optic group, 3.62 +/- 0.38 mU/L and 37.22 +/- 1.76 pmol/L in the daylight group, and 4.40 +/- 0.48 mU/L and 29.91 +/- 1.13 pmol/L in the combined group, compared with 5.77 +/- 0.40 mU/L and 34.46 +/- 1.68 pmol/L in the control group. The TSH and fT4 values declined with increasing age in the phototherapy and control groups with end of exposure values of 2.90 +/- 0.28 mU/L and 27.71 +/- 0.71 pmol/L, 2.77 +/- 0.31 mU/L and 33.52 +/- 1.22 pmol/L, and 3.44 +/- 0.30 mU/L and 27.54 +/- 0.88 pmol/L, respectively, compared with 4.21 +/- 0.61 mU/L and 27.19 +/- 2.33 pmol/L (at 72 h) in the control group. The pattern of TSH and fT4 decline in the exposed and control groups was similar, being related to increasing age. CONCLUSIONS: The validity of neonatal thyroid screening is not affected by fibre-optic or conventional phototherapy or by both combined.

Humans↗

PubMed1996

Phototherapy for neonatal jaundice.

Exchange transfusion for severe neonatal jaundice is a tedious and expensive procedure with high morbidity and mortality rates, and is followed by a prompt and marked bilirubin rebound. It has largely been replaced by phototherapy, which though more gradual in its effect results in a prolonged reduction of the bilirubin concentration. Its efficacy is influenced by the gestational age, birthweight and postnatal age of the infant, the aetiology of the jaundice, and the spectral emission and intensity (dose) of the light; its dose-response relationship enables it, at the optimal dose, to control very severe jaundice or a rapidly rising bilirubin concentration, including severe haemolysis. Its relative freedom from complications together with its non-invasive nature, ease of usage and convenience has resulted in widespread acceptance in virtually all neonatal units.

Exchange Transfusion, Whole Blood↗

PubMed1996

Transcutaneous bilirubinometry in Chinese, Malay and Indian infants.

The objective of this study was to investigate the correlation of transcutaneous bilirubinometry (TcB) and plasma bilirubin concentrations in full-term Chinese, Malay and Indian infants. TcB was performed with the Minolta Airshields bilirubinometer on Chinese, Malay and Indian fullterm infants. The readings were taken on the chest (sternum) and forehead (glabella) when capillary blood was sampled for bilirubin determination. Five hundred and forty TcB indices in 253 Chinese infants, 282 in 169 Malay infants, and 182 in 120 Indian infants were obtained over the sternum and forehead. A good correlation between the TcB indices and the bilirubin concentrations was observed in Chinese, Malay and Indian infants: r = 0.78 (chest), r = 0.73 (forehead); r = 0.86 (chest), r = 0.84 (forehead); and r = 0.84 (chest), r = 0.82 (forehead). The correlation was just as good when the combined values were evaluated together: r = 0.80 (chest) r = 0.75 (forehead). In Chinese infants, correlation at values below 250 mumol l-1 was significantly better than that at values over 250 mumol l-1 r = 0.80 versus r = -0.20, p < 0.00001 (chest), and r = 0.74 versus r = 0.07, p < 0.00001 (forehead). However, a safer cut-off point clinically would be 200 mumol l-1, since only relatively few higher bilirubin values were encountered when TcB indices were below 200 mumol l-1. The same pattern was noticed with the other two groups, and the combined group. Thus, TcB provides a non-invasive, cost-effective screening method for significant neonatal jaundice, sparing infants and parents physical and emotional stress, and medical and nursing personnel extra work and inconvenience.

Bilirubin↗

PubMed1996

Paraganglioma with pulmonary metastases: a case report.

Distant metastases due to paraganglioma are a rare occurrence. We report a case of paraganglioma with pulmonary metastases and review the literature on paragangliomas. A 29-year-old female presented with cervical lymphadenopathy, excision biopsy of which confirmed the diagnosis of paraganglioma. She subsequently underwent tumour embolisation and received a course of radiotherapy. Seven years later, she was investigated for multiple pulmonary nodules noted on her chest roentgenogram. Histology of the wedge excision of the lung showed metastatic paraganglioma. Increased catecholamine production was documented; this was however not associated with symptoms of catecholamine excess. Reports concerning the treatment of paragangliomas with pulmonary metastases are few, given their rarity.

Adult↗

PubMed1996

Mortality of patients while on treatment for active tuberculosis.

In the era of effective antituberculous chemotherapy, some patients with tuberculosis still die while on treatment. The aim of this study was to review deaths occurring in patients while on treatment for active tuberculosis in Alexandra Hospital during the 4-year period from 1991 to 1994. Medical records of 30 such patients were reviewed retrospectively. Twenty-one patients were certified as dying from tuberculosis; in the remaining 9 patients, the principal cause of death was other than tuberculosis. Of the patients who died of tuberculosis, 7 (33.3%) died within a week and 19 (90.5%) died within a month of initiation of antituberculous treatment. Seventeen (81%) were males and 15 (71%) were smokers. All the 21 patients had pulmonary involvement and in 4 patients, there was disseminated disease. Chest roentgenographic findings of bilateral involvement were seen in 16 (76.2%) patients and of cavitary disease in 15 (71.4%) patients. Eighteen (86%) had a positive sputum smear result. Seven patients received corticosteroid cover. In 14 patients who had their weights recorded at initiation of antituberculous treatment, the mean weight was 36.3 kg (range 25.5k g-47k g). Notable biochemical derangements included hyponatraemia (86%) and hypoalbuminaemia (95%). Plasma cortisol and/or Synacthen stimulation test were performed in 4 patients; none was indicative of adrenal hypofunction. We conclude that death attributed to tuberculosis in patients while on treatment occurs early and is largely due to advanced disease.

Adult↗

PubMed1995

Molecular cloning of a cDNA and chromosomal localization of a human theta-class glutathione S-transferase gene (GSTT2) to chromosome 22.

Until recently the Theta-class glutathione S-transferases (GSTs) were largely overlooked due to their low activity with the model substrate 1-chloro-2,4-dinitrobenzene (CDNB) and their failure to bind to immobilized glutathione affinity matrices. Little is known about the number of genes in this class. Recently, Pemble et al. (Biochem J. 300: 271-276, 1994) reported the cDNA cloning of a human Theta-class GST, termed GSTT1. In this study, we describe the molecular cloning of a cDNA encoding a second human Theta-class GST (GSTT2) from a lambda gt11 human liver 5'-stretch cDNA library. The encoded protein contains 244 amino acids and has 78.3% sequence identity with the rat subunit 12 and only 55.0% identity with human GSTT1. GSTT2 has been mapped to chromosome 22 by somatic cell hybrid analysis. The precise position of the gene was localized to subband 22q11.2 by in situ hybridization. The absence of other regions of hybridization suggests that there are no closely related sequences (e.g., reverse transcribed pseudogenes) scattered throughout the genome and that if there are closely related genes, they must be clustered near GSTT2. Southern blot analysis of human DNA digested with BamHI shows that the size of the GSTT2 gene is relatively small, as the coding sequence falls within a 3.6-kb BamHI fragment.

Amino Acid Sequence↗

PubMed1995

Molecular epidemiology of hepatitis B virus vaccine variants in Singapore.

Perinatal infection with variants of hepatitis B virus occurs despite combined immunoprophylaxis with hepatitis B immunoglobulin and currently licensed plasma-derived and recombinant yeast hepatitis B vaccines. Several variants have been detected during a large study of infants born to carrier mothers in Singapore. The most frequent variant was a virus in which a single amino acid substitution Gly to Arg occurred at amino acid position 145 of the outer protein coat of the virus. Similar mutations have been described in Italy, Japan, the USA and a number of other countries. The emergence of antibody escape mutants is a cause for concern for the detection of virus and possibly for future immunization programmes.

Amino Acids↗

PubMed1995

Efficacy of phototherapy for hyperbilirubinaemia in infants with the respiratory distress syndrome.

OBJECTIVE: To evaluate the efficacy of phototherapy for hyperbilirubinaemia in preterm infants with and without the respiratory distress syndrome (RDS). METHODOLOGY: Prospective cohort study of preterm infants cared for at Kandang Kerbau Hospital, Singapore: 170 with RDS and 477 without RDS, sepsis or other complications (control group) presenting with non-haemolytic hyperbilirubinaemia at about the same time were exposed to daylight phototherapy when bilirubin concentrations exceeded 255 mumol/L or 222 mumol/L if < 48 h of age. Bilirubin values were monitored 6-hourly during exposure, and daily for at least 2 days post-phototherapy. RESULTS: The infants were comparable in birthweight, gestational age, postnatal age, haemoglobin, haematocrit and bilirubin values, at start. The response to phototherapy of the infants with RDS was comparable to that of the well preterm infants; the duration of exposure was 50.1 +/- 1.6 (mean +/- s.e.m.) versus 50.1 +/- 1.4 h, 24-hour decline rate 25.71 +/- 1.29% versus 26.32 +/- 0.65, and overall decline rate 0.96 +/- 0.03%/h versus 0.95 +/- 0.02%/h. CONCLUSION: The presence of RDS did not affect the efficacy of phototherapy for neonatal hyperbilirubinaemia in preterm infants.

Bilirubin↗

PubMed1995

Trends in the practice of arterial surgery in Western Australia.

An overview of arterial surgery in Western Australia and the Department of Vascular Surgery at Royal Perth Hospital was undertaken for the ten year period from 1983 to 1992. The annual number of arterial procedures increased 116% from 937 to 2027 and lower limb amputations increased 44% from 335 to 483. Five arterial procedures were examined in detail. There was a marked increase in carotid endarterectomy and angioplasty, a moderate increase in aortic aneurysm repair and a small increase in aortofemoral and femoropopliteal bypass surgery. The major amputation rate was not influenced by bypass surgery. It rose from 113 per million population in 1983 to a peak of 148 in 1986, and then fell to 113 per million population in 1992. From June 1982 to June 1992 the population of Western Australia rose 24%, from 1.34 to 1.66 million (and for persons 60 years and over, rose 38% from 0.16 to 0.23 million). At Royal Perth Hospital similar trends were observed. Mean duration of operation for all vascular procedures and for the individual procedures of carotid endarterectomy, angioplasty, aortic aneurysm repair and aortofemoral and femoropopliteal bypass remained unchanged. Average length of stay decreased for carotid endarterectomy (29%) and angioplasty (74%), but remained unchanged for aortic aneurysm repair and aortofemoral and femoropopliteal bypass.

Angioplasty↗

PubMed1995

Phototherapy for neonatal jaundice in infants with cephalhematomas.

The efficacy of phototherapy in a group of infants with nonhemolytic hyperbilirubinemia and no cephalhematomas was compared with a second group of infants with large cephalhematomas (> 7 cm across), but similar in all other aspects. The cephalhematoma group demonstrated significantly lower hemoglobin (Hb) and hematocrit (hct) values (P < .0001, P < .002 respectively) than the standard group, even after the latter group had been adjusted by stratification (P < .0001, P < .005) such that the starting bilirubin concentration, birth weight, and gestational age were highly comparable to the cephalhematoma group. The bilirubin concentrations of the cephalhematoma, original, and adjusted groups were 277.8 +/- 5.8 mumol/L (16.24 +/- 0.03 mg/dL), [mean +/- sem], 265.2 +/- 0.5 mumol/L (15.50 +/- 0.03 mg/dL), and 275.2 +/- 0.9 mumol/L (16.09 +/- 0.05 mg/dL), respectively. The postnatal age at the start of phototherapy in the cephalhematoma group was comparable with that of the standard group before and after adjustment. Phototherapy was equally effective in the cephalhematoma and standard (original and adjusted) groups of infants, in terms of duration, 24-hr decline, and overall decline/hr for the duration of exposure. The proportionate 24-hr decline was 24.02 +/- 1.90% vs 20.99 +/- 0.23% and 22.61 +/- 0.48% and overall decline/hr was 0.83 +/- 0.06% vs 0.74 +/- 0.01% and 0.78 +/- 0.01%. We conclude that the sequestrated blood in the cephalhematomas did not significantly interfere with the efficacy of phototherapy.

Bilirubin↗

PubMed1995

Risk factors for birth defects in Singapore: a case control study.

To explore possible risk factors for birth defects, a matched case-control study was carried out at Kandang Kerbau Hospital in Singapore from January 1986 to December 1988. Cases and controls were selected from livebirths born in that hospital during that period. Cases were babies who were clinically detected as having defects at birth and the diagnosis reconfirmed at 6 weeks post partum. Each case was matched to a control by maternal age, ethnic background of mother, the same class of maternity ward and time of delivery. Five hundred and seventy-two matched pairs were accrued for the study. The parents of both cases and controls were interviewed at 6 weeks post partum. Information on the medical and birth history of both mother and baby was obtained from medical records. Using conditional logistic regression analysis to adjust for potential confounders, the strongest risk factors for birth defects were family history of birth defects (OR 3.3; 95% CI 1.8-6.4) and parents having a previous abnormal baby (OR 2.4; 95% CI 1.1-5.3). Other notable risk factors included drug history during pregnancy (OR 1.2; 95% CI 0.8-2.0), the ingestion of traditional medicine during pregnancy (OR 1.4; 95% CI 1.0-2.0), injuries or accidents during pregnancy (OR 2.2; 95% CI 1.5-3.2) and maternal diabetes mellitus (OR 1.3, 95% CI 0.3-7.1). Mothers in professional occupations (OR 1.4, 95% CI 0.7-2.6) and those in production occupation (OR 1.2, 95% CI 0.9-1.7) had an increased risk for birth defects compared to housewives.(ABSTRACT TRUNCATED AT 250 WORDS)

Case-Control Studies↗

PubMed1995

Delta bilirubin changes following phototherapy for neonatal jaundice.

The effect of phototherapy for neonatal jaundice on the serum concentrations of total, unconjugated, conjugated and delta bilirubins were studied in 91 infants. Only unconjugated bilirubin concentration declined during phototherapy, from 254.7 +/- 7.0 mumol/l (mean +/- SD) at start to 161.4 +/- 37.4 mumol/l at cessation after 50.2 +/- 22.1 hours of exposure. Conjugated and delta bilirubin concentrations, initially already very low, were not significantly affected. Phototherapy was only efficacious for unconjugated bilirubin and did not have any effect on delta or conjugated bilirubin.

Bilirubin↗

PubMed1994

Immunogenicity of recombinant yeast-derived hepatitis B vaccine in nonresponders to perinatal immunization.

OBJECTIVE: Nonresponse to hepatitis B vaccine in the perinatal period occasionally occurs. This report documents the results of reimmunization of nonresponders to perinatal immunization. DESIGN: From a cohort of 1154 infants immunized with plasma-based vaccine in the perinatal period and followed up for more than 8 years, 45 nonresponders were identified. These children were reimmunized at 4 years of age. Each child received a yeast-derived recombinant hepatitis B vaccine on a 0-, 1-, and 5-month schedule, 33 children with 10-micrograms and 12 with 5-micrograms doses. Blood was sampled 1 month after the third vaccination and thereafter at 1, 2, and 4 years. SETTING: The follow-up clinic where the cohort of children was regularly seen. PATIENTS: Forty-five 4-year-old children who had no antibody to hepatitis B despite perinatal immunization. MAIN OUTCOME MEASURE: Antibody levels to hepatitis B surface antigen. RESULTS: Seroconversion with titers higher than 10 mIU/mL occurred in all children. More than 70% still had titers higher than 10 mIU/mL 4 years after vaccination. CONCLUSION: Nonresponders to perinatal hepatitis B vaccination respond well to subsequent vaccination.

Child↗

PubMed1994

Comparison of the efficacy of fiberoptic and conventional phototherapy for neonatal hyperbilirubinemia.

A comparative evaluation of the efficacy of fiberoptic phototherapy using the Ohmeda Billiblanket fiberoptic device, conventional phototherapy using daylight fluorescent lamps, and a combination of the two forms of phototherapy was made in 165 term healthy infants and 105 preterm infants with hyperbilirubinemia. In the term infants, the 24-hour decline rate for fiberoptic phototherapy was 9.2% +/- 1.6% (mean +/- SEM) versus 21.5% +/- 1.8% for daylight phototherapy (p < 0.01), and the overall decline rate was 0.49% +/- 0.03%/hr versus 0.70% +/- 0.04%/hr (p < 0.001). Combination phototherapy, with a 24-hour decline rate of 29.9% +/- 1.0% and an overall decline rate of 0.97% %/- 0.04%/hr, was significantly better than daylight phototherapy in both respects (p < 0.01 and < 0.01, respectively). The duration of exposure for fiberoptic phototherapy was significantly longer than that for daylight phototherapy, which in turn was significantly longer than that for combination phototherapy. Response to exposure in the preterm infants was significantly better than that in the term infants with the respective types of phototherapy. The nursing personnel unanimously felt more comfortable with fiberoptic phototherapy, which did not disturb the swaddled infants as much as conventional phototherapy. The parents also felt more reassured. Fiberoptic phototherapy proved adequate in controlling hyperbilirubinemia in preterm infants; in term infants, failures often occurred. Combination phototherapy can be recommended for severe or rapidly increasing jaundice in preterm infants, but its efficacy in term infants is uncertain.

Bilirubin↗

PubMed1993

Efficacy of phototherapy in neonatal hyperbilirubinaemia associated with glucose-6-phosphate dehydrogenase deficient status.

The efficacy of phototherapy in a group of 427 infants with hyperbilirubinaemia associated with glucose-6-phosphate dehydrogenase (G6PD) deficiency and a comparable group of 3924 G6PD normal infants with non-haemolytic hyperbilirubinaemia was evaluated. Phototherapy was highly effective in reducing bilirubin levels in both groups of infants, being significantly more effective in the group with normal G6PD status. Failure rate was very low (2.03/1000) in the group with normal G6PD status and nil in the G6PD deficient group. Bilirubin rebound after phototherapy was unremarkable with very few infants requiring a second exposure--4.68/1000 in the G6PD deficient group and 6.37/1000 in the G6PD normal group. All the babies tolerated phototherapy well. Phototherapy would therefore seem to be a simple and effective method for the management of severe jaundice associated with G6PD deficiency.

Glucosephosphate Dehydrogenase Deficiency↗

PubMed1993

Free thyroxine as a supplement to thyrotropin in cord screening for hypothyroidism.

The low specificity of cord serum T4 levels for detecting hypothyroidism, the need to reduce recall rates and the availability of a reliable and quick assay system led to this study designed to determine the advantages of using cord serum free thyroxine levels over total thyroxine levels as a supplement to cord thyroid stimulating hormone (TSH) determination. Sixty-eight out of 75 newborns with a cord TSH > 23 mU/l had both free thyroxine (fT4) and T4 levels measured in the cord serum. All were recalled within the first month of life for reevaluation of their thyroid status. In the majority of cases (46), the fT4 and T4 values corresponded. Hypothyroidism was diagnosed in eight cases; both fT4 and T4 were below the mean in five cases and above the mean in one case; only T4 was below the mean in one and in the remaining one, only fT4 was below the mean. Recall rates were 0.9% with TSH alone and 0.7% when either a fT4 or T4 level that was less than 1 sd above the mean was used as a supplement to TSH. In this cohort, using the fT4 levels instead of the T4 levels brought no change to the specificity or the sensitivity of the screening. The diagnostic sensitivity would have dropped from 100% to 75% if either T4 or fT4 values below the mean were used as a cut-off point for recall.

Congenital Hypothyroidism↗