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Biomedical subjects

K H Tan

Publications and source records attributed to K H Tan.

At least 37 records · Page 2Linked to original sources
PubMed2003

The use and abuse of steroids in perinatal medicine.

Corticosteroids are one of the most powerful drugs increasingly used in the perinatal and neonatal period. This review discusses the merits and demerits of antenatal as well as postnatal use of steroids. A single course of antenatal corticosteroids in women at risk of premature delivery is highly effective in reducing respiratory distress syndrome (RDS), intraventricular haemorrhage and neonatal mortality and also neurodevelopmental sequelae including cerebral palsy. However, there is less evidence to support the practice of multiple courses of corticosteroids, with some animal and retrospective human studies suggesting an association with neurological impairment and reduction in birth weight as well as lung weight. Postnatal systemic corticosteroids have shown benefits in reducing chronic lung disease and improving survival for infants. However, besides short-term adverse effects, the follow-up studies have raised concern that they may increase the risk of neurodevelopmental disability, particularly cerebral palsy in survivors. Systemic corticosteroids may have a role in infants who had repeated and prolonged intubations and those with pressor-resistant hypotension. Alternative strategies for prevention of chronic lung disease, such as inhaled steroids, methylprednisolone and hydrocortisone, may need further studies with larger sample sizes. Data from animal research have revealed that fetal glucocorticoid exposure may have a role in programming the individual to adult degenerative diseases. Based on the current evidence, it is recommended that women at risk of preterm delivery receive a single course of glucocorticoids. Randomised controlled trials are needed to establish the true effects of multiple courses of antenatal corticosteroids. More research is also needed to study the long-term neurodevelopmental outcome of both multiple courses of antenatal corticosteroids, as well as postnatal corticosteroid therapy.

Animals↗
PubMed2003

Our experience with eclampsia in Singapore.

AIM: To assess the incidence, epidemiological factors, preceding symptoms and signs, management regimens and obstetric outcomes of eclampsia in a tertiary care hospital in Singapore. METHOD: A retrospective study of all obstetric patients who suffered one or more eclamptic seizures in our hospital between January 1994 and December 1999. RESULT: There were 62 cases of eclampsia among 92,305 deliveries (6.7 per 10,000 deliveries). The incidence was highest among Indians. Those aged between 25 and 34 had the lowest incidence, while women younger than 25 or older than 34 had a significantly higher incidence. Forty (64.5%) patients had symptom or sign of impending eclampsia of which headache was the most common. Most of the patients (81.6%) who received antenatal care with us suffered their first eclamptic seizure in hospital, compared to 50% of the unbooked patients. There was one maternal death (mortality rate 1.6%), and 15 (24.2%) women had significant morbidity. There were 61 singleton pregnancies and one twin pregnancy. There were six intrauterine deaths and 57 livebirths. The perinatal mortality rate was 95.2 per 1,000 births. CONCLUSION: Eclampsia is still a major cause of maternal and foetal mortality and morbidity in Singapore. Race and age appear to be risk factors for eclampsia with Indian women and those at the extremes of reproductive age at greater risk. Antenatal care is important in reducing perinatal mortality and possibly maternal complications.

Adolescent↗
PubMed2002

Birth prevalence of Down syndrome in Singapore from 1993 to 1998.

OBJECTIVE: To examine the livebirth prevalence rate of Down Syndrome in Singapore from 1993 to 1998. DESIGN: Index cases for the National Birth Defects Register were obtained from all neonatal nurseries in Singapore, all hospital discharge summaries, cytogenetic and pathology reports from all pathology laboratories in Singapore and from the compulsory reporting of all termination of pregnancy cases and stillbirths delivered. SETTING: Information for the Register was obtained from case notes retrieved from the medical record offices, antenatal clinics, cytogenetic laboratories, pathology departments and the Registry of Births and Deaths. SUBJECTS: All foetuses with Trisomy 21 diagnosed prenatally together with livebirths and stillbirths with Down Syndrome diagnosed at or after birth were identified from the Registry database. MAIN OUTCOME MEASURES: Prevalence of Down Syndrome RESULTS: From 1993 to 1998, there were 295 Down Syndrome livebirths, four stillbirths and 197 Down Syndrome foetuses aborted. There has been an increasing number of Down Syndrome foetuses diagnosed antenatally ending in termination and this is accompanied by a falling trend in the Down Syndrome livebirth rate in the same years from 1.17 to 0.89 per 1000 total live births. This is despite an expected increase in Down Syndrome livebirth rate obtained by modelling maternal Down Syndrome age-related risks on the maternal age distribution over the years. CONCLUSIONS: The livebirth prevalence of Down Syndrome in Singapore has fallen over the years from 1.17/1000 livebirths in 1993 to 0.89/1000 livebirths in 1998 due to antenatal diagnosis and selective termination.

Abortion, Induced↗
PubMed2001

A comparison of the induction of immortalized endothelial cell impermeability by astrocytes.

The suitability of various commercially available endothelial cell lines in studies of astrocytic/endothelial cell interactions was assessed. The endothelial-like cell line ECV304 was compared with T24/83, Eahy929, and b.End5 and rat cerebral endothelial cells in their ability, when co-cultured with rat (C6) glioma cells, to form a transendothelial electrical resistance (TEER), an indicator of tight junction formation which is an important property of the blood-brain barrier. As reported previously, the basal TEER of ECV304 cell monolayers was significantly enhanced upon co-culture, an effect reproduced by human 1321N1 astrocytes and primary rat astrocytes. T24/83 cells formed a patchy, gapped monolayer, which produced a poor basal TEER with little in the way of an increase upon co-culture. Similarly, all the other cell monolayers analysed demonstrated poor TEERs that were only moderately increased upon co-culture. These data confirm that while no endothelial cell line with ideal features is available, ECV304 cells remain an appropriate choice especially for studies of astrocyte/endothelial cell interactions.

Animals↗
PubMed2001

Fetal vibroacoustic stimulation for facilitation of tests of fetal wellbeing.

BACKGROUND: Acoustic stimulation of the fetus has been suggested to improve the efficiency of antepartum fetal heart rate testing. OBJECTIVES: The objective of this review was to assess the merits or adverse effects of the use of fetal vibroacoustic stimulation in conjunction with tests of fetal wellbeing. SEARCH STRATEGY: We searched the Cochrane Pregnancy and Childbirth Group trials register. Date of last search: October 2000. SELECTION CRITERIA: All published and unpublished randomized controlled trials assessing the merits of the use of fetal vibroacoustic stimulation in conjunction with tests of fetal wellbeing. DATA COLLECTION AND ANALYSIS: Both reviewers independently extracted data and assessed trial quality. Authors of published and unpublished trials were contacted for further information. MAIN RESULTS: A total of seven trials with a total of 4325 participants were included. Fetal vibroacoustic stimulation reduced the incidence of non-reactive antenatal cardiotocography test (odds ratio (OR) 0.61, 95% confidence interval (CI) 0.49-0.75) and reduced the overall mean cardiotocography testing time (weighted mean difference (WMD) -4.55 minutes, 95% CI -5.96 minutes to -3.14 minutes). Vibroacoustic stimulation evoked more than mock stimulation when used in conjunction with fetal heart rate testing (OR 0.08, 95% CI 0.06-0.12). REVIEWER'S CONCLUSIONS: Vibroacoustic stimulation offers benefits by decreasing the incidence of non-reactive cardiotocography and reducing the testing time. Further randomized trials should be encouraged to determine not only the optimum intensity, frequency, duration and position of the vibroacoustic stimulation, but also to evaluate the efficacy, predictive reliability, safety and perinatal outcome of these stimuli with cardiotocography and other tests of fetal wellbeing.

Acoustic Stimulation↗
PubMed2001

Fetal manipulation for facilitating tests of fetal wellbeing.

BACKGROUND: Manual fetal manipulation has been suggested to improve the efficiency of antepartum fetal heart rate testing. OBJECTIVES: The objective of this review was to assess the merits or adverse effects of the use of manual fetal manipulation in conjunction with tests of fetal wellbeing. SEARCH STRATEGY: We searched the Cochrane Pregnancy and Childbirth Group trials register in June 2001. SELECTION CRITERIA: All published and unpublished randomized controlled trials assessing the merits of the use of fetal manipulation in conjunction with tests of fetal wellbeing. DATA COLLECTION AND ANALYSIS: Both reviewers independently extracted data and assessed trial quality. Authors of published and unpublished trials were contacted for further information. MAIN RESULTS: Only two trials with a total of 1090 women with 2110 episodes of participation were included. Manual fetal manipulation did not decrease the incidence of non-reactive antenatal cardiotocography test (odds ratio 1.28 confidence interval 0.94-1.74). REVIEWER'S CONCLUSIONS: Manual fetal manipulation has not been shown to reduce the incidence of non-reactive cardiotocography. Trials of manual fetal manipulation should take into consideration that there have not been any benefits demonstrated as yet.

Abdomen↗
PubMed2001

Maternal glucose administration for facilitating tests of fetal wellbeing.

BACKGROUND: Antenatal maternal glucose administration has been suggested to improve the efficiency of antepartum fetal heart rate testing. OBJECTIVES: The objective of this review was to assess the merits or adverse effects of antenatal maternal glucose administration in conjunction with tests of fetal wellbeing. SEARCH STRATEGY: We searched the Cochrane Pregnancy and Childbirth Group trials register in June 2001. SELECTION CRITERIA: All published and unpublished randomized controlled trials assessing the merits of antenatal maternal (oral or intravenous) glucose administration in conjunction with tests of fetal wellbeing. DATA COLLECTION AND ANALYSIS: Both reviewers independently extracted data and assessed trial quality. Authors of published and unpublished trials were contacted for further information. MAIN RESULTS: A total of two trials with a total of 708 participants were included. Antenatal maternal glucose administration did not decrease the incidence of non-reactive antenatal cardiotocography tests. REVIEWER'S CONCLUSIONS: Antenatal maternal glucose administration has not been shown to reduce non-reactive cardiotocography. More trials are needed to further substantiate this and to determine not only the optimum dose, but also to evaluate the efficacy, predictive reliability, safety and perinatal outcome of glucose administration in conjunction with cardiotocography and also other tests of fetal wellbeing.

Administration, Oral↗
PubMed2001

Allomonal and hepatotoxic effects following methyl eugenol consumption in Bactrocera papayae male against Gekko monarchus.

Methyl eugenol (ME), is converted into two major phenylpropanoids, 2-allyl-4,5-dimethoxyphenol and trans-coniferyl alcohol, following consumption by the male fruit fly Bactrocera papayae. Chemical analysis of wild male B. papayae rectal glands, where the compounds are sequestered, revealed the presence of ME metabolites in varying quantities. These phenylpropanoids are shown to be involved in the fruit fly defense both in no-choice and choice feeding tests against the Malayan spiny gecko, Gekko monarchus. After being acclimatized to feeding on fruit flies, geckos consumed significantly fewer ME-fed male flies than controls that consumed all the ME-deprived male flies offered throughout a two-week period. Diagnosis of dissected livers from geckos that consumed ME-fed male flies revealed various abnormalities. These included discoloration and hardening of liver tissue, whitening of the gallbladder, or presence of tumor-like growths in all geckos that consumed ME-fed male flies. Control geckos fed on ME-deprived male flies had healthy livers. When given an alternative prey, geckos preferred to eat untreated house flies, Musca domestica to avoid preying on ME-fed fruit flies.

Animals↗
PubMed2001

Existence of homologous sequences corresponding to cDNA of the ver gene in diverse higher plant species.

The presence of DNA homologues corresponding to verc203 (vernalization-related cDNA clone) was investigated by molecular hybridization techniques. The genes were detected in 16 plant species that cover 12 subclasses of the Takhtajan system of angiosperms classification including diverse model species. The results of Southern blot analysis showed a low copy number of this gene existed in rice, wheat, barley and Arabidopsis. The hybridization result of PCR products demonstrated the conservation of the gene corresponding to ver203 in diverse plants. The phylogenetic tree of the ver203 gene in tested plants was supported by evolution relationship of species. The ver203 gene expressed in a vernalized plumule winter wheat, instead of the root. And the endosperm before the treatment was essential for the ver203 expression during vernalization in wheat. In Arabidopsis thaliana, the pattern of expression showed that the gene corresponding to ver203 was expressed at low temperature for 14 days. Gibberellin (GA3) may accelerate the expression of ver203 gene in Arabidopsis exposed to low temperature. However, it could not replace vernalization treatment to initiate the gene expression.

Arabidopsis↗
PubMed2001

Obstetric admissions to the intensive therapy unit of a tertiary care institution.

INTRODUCTION: Between 0.1% and 0.9% of women develop pregnancy complications which require admission to an intensive therapy unit. The aim of this study was to review all obstetric admissions to the intensive therapy unit at the KK Women's and Children's Hospital from 1998 to 1999 with respect to indications for admission, interventions employed and clinical outcome. METHOD: The medical records of all obstetric patients admitted to the intensive therapy unit during the 2-year period were analysed retrospectively. Subjects were included if they were admitted during pregnancy up to 42 days postpartum. RESULTS: There were 31,725 deliveries in our hospital during the study period of which there were 239 admissions to the intensive therapy unit. Of these, 42% were Malays, 41% Chinese, 12% Indians and 5% other races. 65% stayed 1 day, 24% 2 days, 7% 3 days and 4% more than 3 days. The patients' ages ranged from 18 to 44 years. The indications for admission were hypertension (50%), haemorrhage (24%), respiratory insufficiency (10%), neurological problems (11%) and sepsis (3%). Intervention-wise, 43% of patients required vasoactive infusions, 35% had arterial line placement, 22% central venous pressure monitoring, 21% ventilatory support and 2% pulmonary artery catheter placement. The maternal mortality and stillbirth rates were 1.3% and 3.7% of intensive therapy unit admissions, respectively. CONCLUSION: The admission rate to the intensive therapy unit in our institution was 0.73% of all deliveries during the 2-year study period. Hypertensive disease and haemorrhage were the predominant admitting diagnoses.

Adolescent↗
PubMed2000

First results from the Canadian SGM beamline at SRC.

The first experimental results obtained from the Canadian SGM beamline at SRC (Synchrotron Radiation Centre, University of Wisconsin-Madison, USA) are reported. The beamline is based on the Dragon-type design, with a constant deviation angle, using photons from a second-generation bending-magnet light source. The medium-energy grating on this beamline covers a photon energy range from 240 to 700 eV, with a ruling density of 600 lines mm(-1). A maximum resolving power of approximately 10000 is achieved at a photon energy of approximately 400 eV. Gas-phase absorption spectra collected at the N, O and C K-edges are presented to demonstrate the excellent performance of this beamline. High-resolution absorption spectra of some C- and Ti-containing solid-state samples are also reported.

Journal Article↗
PubMed2000

Variable-energy photoelectron spectroscopy of substituted rhenium and manganese pentacarbonyls: molecular orbital assignments and the interatomic resonant effect.

High-resolution variable-energy photoelectron spectra of M(CO)5X [M = Re, X = Re(CO)5, Cl, Br, and I; and M = Mn, X = Mn(CO)5 and Br] are reported. Tunable synchrotron radiation is used to distinguish the Re 5d and Br 4p orbital based peaks for the controversial Re(CO)5Br. Our results provide firm molecular orbital assignments for all of these molecules. The valence orbital in the ordering of ionization energies for M(CO)5Cl (M = Mn and Re) and Mn(CO)5Br is a 1(M-X) > e(X) > b2(M) > e(M); but for M(CO)5I (M = Mn and Re) and Re(CO)5Br the ordering is a1(M-X) > e(M) > b2(M) > e(X). The crossover of the HOMO in the Re molecules due to the change in the halogen electronegativities occurs at Re(CO)5Br. The metal np-->nd resonance is observed for all of these molecules. For molecules like M2(CO)10 (M = Re and Mn) and Mn(CO)5Br, the observation of this np-->nd resonance is useful in assigning the metal nd based orbitals in their valence level spectra. However, for molecules like Re(CO)5X (X = Br and Cl), a np-->nd type resonance is observed on bands arising from both Re 5d and halogen mp based orbitals. This new resonant effect on the ligand-based orbitals is shown to be mainly due to the interatomic resonant effect. The core and valence level chemical shifts of these compounds are treated using Jolly's approach to confirm the assignments for the valence level spectra of some of these molecules. The high-resolution inner valence and core level spectra of these compounds are reported. Broadening of Re 4f, Br 3d, and I 4d core level spectra is discussed. The Auger peaks are observed in the high-resolution, high-intensity Br 3d of Re(CO)5Br and I 4d of Re(CO)5I spectra.

Journal Article↗
PubMed2000

Foreign metallothionein-I expression by transient transfection in MT-I and MT-II null astrocytes confers increased protection against acute methylmercury cytotoxicity.

The mechanisms associated with metallothionein (MT) gene regulation are complex and poorly understood. Only a modest increase in brain MT expression levels is attained by exposure to metals, MT gene transfection, and MT gene knock-in techniques. Accordingly, in the present study, MT null astrocytes isolated from transgenic mice deficient in MT-I and MT-II genes were introduced as a zero background model of MT expression. MT protein levels were determined by western blot analysis. MT proteins in MT-I and MT-II null astrocytes were undetectable. Transient MT-I gene transfection increased the levels of foreign MT expression in MT-I and MT-II null astrocytes by 2.3-fold above basal levels in wild-type astrocytes. Intracellular Na(2)51CrO(4) efflux and D-[2,3-3H]aspartate uptake were studied as indices of acute methylmercury (MeHg) (5 microM) cytotoxicity. In MT-I and MT-II knockout astrocytes MeHg led to significant (p<0.01) increase in Na(2)51CrO(4) efflux and a significant (p<0.05) decrease in the initial rate (1 min) of D-[2, 3-3H]aspartate uptake compared to MT-I and MT-II knockout controls. Transfection of the MT-I gene in MT-I and MT-II null mice significantly (p<0.01) decreased the effect of MeHg on Na(2)51CrO(4) efflux in MT null, as well as wild-type astrocytes. MT-I gene transfection in MT-I and MT-II null astrocytes reversed the inhibitory effect of MeHg on D-[2,3-3H]aspartate uptake, such that initial rates of uptake in MT-I transfected cells in the presence and absence of MeHg (5 microM) were indistinguishable. These results demonstrate that: (1) astrocytes lacking MTs are more sensitive to MeHg than those with basal MT protein levels, (2) the MT-I gene can be overexpressed in MT-I and MT-II null astrocytes by transient MT-I gene transfection, and (3) that foreign MT expression endows astrocytes with increased resistance to MeHg.

Animals↗
PubMed2000

Exercise training and peripheral vascular disease.

BACKGROUND: Conservative management is advocated as a treatment of choice for patients with intermittent claudication. This is a review of the mechanisms behind the improvement following an exercise rehabilitation programme. METHODS: All Medline articles from the National Library of Medicine, USA containing the text words 'claudication' or 'peripheral vascular disease' and 'exercise' were reviewed. Cross-referencing from relevant articles was carried out. RESULTS AND CONCLUSION: The poor physical status of a patient with intermittent claudication is not solely due to a reduction in blood flow to the lower limbs; associated factors, such as metabolic inefficiency, poor cardiorespiratory reserve and exercise-induced inflammation contribute. An exercise programme frequently improves both the physical aspect and quality of life, and the success of such exercise is multifactorial. An increase in the blood flow to the lower extremity is uncommon. Other factors, such as a redistribution of blood flow, changes in oxidative capacity of the skeletal muscles and greater utilization of oxygen, occur and the associated metabolic dysfunction of the skeletal muscles is rectified. Following exercise training, blood rheology improves and exercise-induced inflammation is ameliorated; cardiorespiratory status also benefits and the oxygen cost of exercise decreases.

Biomechanical Phenomena↗
PubMed2000

Exercise training for claudicants: changes in blood flow, cardiorespiratory status, metabolic functions, blood rheology and lipid profile.

OBJECTIVE: Exercise training improves the walking distance of claudicants. The aim of this study was to investigate factors associated with the improvement in the maximum walking distance (MWD) in respect to cardiovascular, respiratory and metabolic adaptations. METHODS: Forty claudicants were studied. Common femoral artery blood flow (BF), heart rate (HR), oxygen consumption (VO(2)), respiratory exchange ratio (RER), lactate levels, blood rheology and lipid profiles were measured. Tests were repeated after 3 months of exercise training. RESULTS: Fifteen patients did not complete the exercise program. For patients who did complete the program, MWD improved by 82%. A significant reduction in HR and VO(2)during exercise was demonstrated. No significant changes occurred in BF or RER. Although MWD increased significantly, there was no increase in recovery VO(2)(oxygen debt). A significant reduction in post-exercise lactate levels occurred. Blood rheology was unchanged, but an improvement in HDL levels was noted. CONCLUSIONS: Many claudicants could not complete an exercise program, mainly due to osteoarthritis. Exercise training improved exercise tolerance significantly without any increase in BF. The HR and oxygen cost of similar exercise was reduced. An improved MWD did not correlate with a higher oxygen debt or lactate load. Favourable changes in lipid profiles occurred.

Aged↗
PubMed2000

A randomised comparison of simvastatin versus simvastatin and low cholesterol diet in the treatment of hypercholesterolaemia.

There is little evidence to show that strict dietary modification alone confers any significant impact on cardiac events in primary and secondary prevention of coronary heart disease. Given the efficacy of the statins, the need for strict dietary modification in patients on statin therapy has been questioned. This study was performed to assess 1) the added benefit on serum lipid levels of a strict low-fat dietary regimen in patients with hypercholesterolaemia already treated with simvastatin; 2) the efficacy of simvastatin on the lipid profile of our sample Asian population; and 3) the tolerability and side-effect profile of simvastatin. This study was a prospective evaluation of 60 patients with hypercholesterolaemia treated with simvastatin who were subjected to either a normal diet or a dietitian guided low-fat diet. Assessment of the effects on serum lipid levels, side-effects, biochemical and haematological markers were performed. After 24 weeks of treatment, a strict dietitian guided low-fat diet conferred no additional benefit over and above what was achieved by simvastatin alone. Furthermore, a higher dose of simvastatin was needed in the dietitian guided diet group to achieve the target LDL-cholesterol level. Simvastatin resulted in a significant positive alteration of lipid profiles in all patients. The drug was well tolerated, with no significant change in either haematological or biochemical indices. Simvastatin is a highly effective cholesterol-lowering drug with a beneficial effect on the entire lipid spectrum in a cross-section of Asian patients, and is well tolerated. A dietitian guided dietary approach confers no additional advantage once statin therapy has been initiated.

Adult↗
PubMed2000

Seroprevalence of cytomegalovirus, toxoplasma and parvovirus in pregnancy.

AIM OF STUDY: The aim of our study was to determine the seroprevalence of cytomegalovirus (CMV), toxoplasma and parvovirus infection in our local antenatal population, and to see the effects, if any, of age, race, parity and nationality on its seroprevalence. METHODOLOGY: The sera of 120 consecutive antenatal women seen in KK Women's and Children's Hospital between the period of October 1997 and March 1998 were screened for cytomegalovirus (CMV) IgG, toxoplasma IgG and parvovirus B19 IgG and IgM. An antibody titer greater than 1:32 was regarded as positive. RESULTS: A total of 87.0% of patients were tested seropositive for CMV IgG, 17.2% seropositive for toxoplasma IgG and 30.0% seropositive for parvovirus IgG. There seemed to be a trend of increasing seropositivity with age in all three groups, however only parovirus B19 reached statistical significance. The incidence of all three infections were higher among the Malays, Indians and other races compared to the Chinese. CONCLUSION: CMV is endemic in our population and hence the most common infection. Toxoplasmosis and parvovirus is relatively low in our population but this implies that a large proportion of our antenatal women are still susceptible to these infections. Prevention of congenital CMV, toxoplasmosis and parvovirus infection is mainly by educating the antenatal population.

Adult↗