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Biomedical subjects

W C Tan

Publications and source records attributed to W C Tan.

At least 19 recordsLinked to original sources
PubMed1995

Effect of glucose on the respiratory burst of circulating neutrophils from asthmatics.

The respiratory burst is dependent on a source of glucose. We wished to investigate the effect of glucose on the superoxide production of circulating neutrophils. Superoxide production of neutrophils was significantly enhanced by glucose concentration of from 1 to 50 mmole/liter in the medium. The neutrophils from asthmatics in both the acute and remission phases showed greater production of superoxide than those of controls. When the neutrophils were made to undergo the respiratory burst, initially in the absence of glucose, and thereafter in the presence of 5 and 20 mmole/liter glucose, the rate of superoxide formation with higher glucose medium was decreased in the control cells but significantly increased in the cells of the acute asthmatics in remission. It is concluded that glucose as an energy source is potentially critical in determining the rate of the respiratory burst and that the neutrophils from asthmatic subjects in some way have an enhanced uptake or metabolism of this substrate. Glycemic status may then have some role in determining the amount of superoxide production, and therefore airway inflammation, in asthma.

Adolescent↗
PubMed1995

Tuberculosis and invasive pulmonary aspergillosis in a young woman with a myelodysplastic syndrome.

A 29-year-old Chinese woman developed pyrexia, multiple skin abscesses and bilateral fine nodular lung infiltrates about 3 months after the commencement of therapy for idiopathic thrombocytopenic purpura (ITP). Pseudomonas aeroginosa was isolated from the abscesses but multiple blood and sputum cultures, as well as a broncho-alveolar lavage did not yield any microorganisms. The persistence of fever and pulmonary infiltrates warranted an open lung biopsy which provided a definitive diagnosis of tuberculous-aspergillus granulomatous lung disease. Bone marrow re-examination revised the primary haematological disorder to that of a trisomy 8 associated myelodysplastic syndrome.

Adult↗
PubMed1995

Ventilatory function measured with the Micro Spirometer: performance evaluation and reference values.

The performance of the Micro Spirometer was compared with that of the Vitalograph by assessing the extent of agreement between the instruments and the repeatability of measurements with each instrument. The Micro Spirometer tended to give lower readings of forced expiratory volume in one second (FEV1), forced vital capacity (FVC) and peak expiratory flow rate (PEFR) than the Vitalograph, with wide limits of agreement. The values of these ventilatory functions measured with the Micro Spirometer were, therefore, not directly comparable with those obtained from the Vitalograph, and it is also not satisfactory to predict readings on the Micro Spirometer from those made on the Vitalograph. In the management of asthma patients, the PEFR would still be preferably measured with the mini Wright peak flow, given its low cost and established reliability compared with the standard Wright peak flow meter. The Micro Spiromoter has the practical advantages of portability, ease of operation and relative cheapness for the baseline and long-term assessment of FEV1 and FVC in ambulatory care, as well as in epidemiological studies. However, local users should not employ reference values provided by the manufacturer or those published in the literature, but those reported in this paper.

Adolescent↗
PubMed1994

Klebsiella bacteraemia: a report of 101 cases from National University Hospital, Singapore.

One hundred and one cases of Klebsiella bacteraemia from the National University Hospital, Singapore, were reviewed retrospectively. There were 54 (53.5%) males and 47 (46.5%) females. Mean (+/- SE) age was 54 (+/- 2.4) years. Overall mortality was 26%. Nosocomial infections accounted for 20%. Underlying diabetes mellitus and malignancy were present in 36 and 26% respectively. The source of the bacteraemia was not known in 33% of cases, 17% had liver abscess, 29% had urinary tract infections, 9% had pneumonia, 10% had an abscess separate from the liver, and 3% had biliary sepsis. Elevated alkaline phosphatase (> 100 U-1) was seen in all cases of liver abscess (sensitivity 100%, specificity 27%). Nonsurvivors had a significantly lower platelet count than survivors (104 +/- 25 x 10(9)/l vs. 176 +/- 15 x 10(9)/l, unpaired t-test P < 0.05), and a platelet count of less than 150 x 10(9)/l was associated with a significantly higher mortality (37% vs. 11%, chi 2 P < 0.01). Nosocomial infection was associated with 45% mortality, whereas community-acquired infection had a lower rate of 21%, this was not statistically significant. Seventy-eight per cent of these Klebsiella isolates were sensitive to gentamicin and cotrimoxazole, and 100% to imipenem.

Anti-Bacterial Agents↗
PubMed1994

Epidemiology of allergic rhinitis and its associated risk factors in Singapore.

BACKGROUND: Few studies have evaluated the relationship between allergic rhinitis and risk factors in the environment which promote aeroallergenic exposures, but knowledge of these are of practical importance from the point of view of community prevention. METHOD: A cross-sectional population-based study of 2868 adults aged 20-74 years was carried out. Allergic rhinitis was defined as the self-reported presence, in the previous year, of usual nasal blockage and discharge apart from colds or the flu, provoked by allergens, with or without conjunctivitis. RESULTS: Allergic rhinitis was reported by 4.5% of the subjects. Higher crude prevalences were observed in males, younger adults, Indians compared to Chinese and Malays, those with higher socioeconomic status, and in three of five residential areas studied. Significant environmental factors included cockroach infestation, occupational exposure, past smoking habit, outdoor air pollution, and frequent heavy exposure to cooking fumes. Keeping pets, having rugs or carpets in the home, and passive exposure to tobacco smoke showed weak and statistically insignificant associations. There was no apparent association with use of mosquito coils or incense. The significant determinants after multivariate adjustment of all risk factors were age, race, flat size, area of residence, cockroach infestation, past smoking, and occupational and cooking fumes exposure. CONCLUSION: The study underscores the importance of environmental control of inhalational exposure to common allergens and irritants in the prevention of allergic rhinitis.

Adult↗
PubMed1994

Prevalence of asthma and risk factors among Chinese, Malay, and Indian adults in Singapore.

BACKGROUND: The prevalence and morbidity of asthma vary greatly among different ethnic communities and geographical locations, but the roles of environmental and genetic factors are not fully understood. The differences in prevalence of adult asthma among Chinese, Malay, and Indian ethnic groups in Singapore were examined, and the extent to which these could be explained by personal and environmental factors were investigated. METHODS: A stratified disproportionate random sample (n = 2868) of Chinese (n = 1018), Malays (n = 967), and Indians (n = 883) of both sexes was drawn from households in five public housing estates, and an interviewer administered questionnaire was used to determine cumulative and current prevalence of "physician diagnosed asthma" (symptoms with a physician diagnosis of asthma). RESULTS: Lifetime cumulative prevalence (standardised to the general population) of "physician diagnosed asthma" was 4.7% in men and 4.3% in women; 12 month period prevalences were 2.4% and 2.0%, respectively. Cumulative prevalence of asthma was significantly higher in Indians (6.6%) and Malays (6.0%) than in Chinese (3.0%); period prevalences of asthma were 4.5% in Indians, 3.3% in Malays, and 0.9% in Chinese. Ownership of cats or dogs was more frequent in Malays (15.4%) and Indians (11.2%) than in Chinese (8.8%). Rugs and carpets were also more frequently used by Malays (52.2%) and Indians (40.7%) than by Chinese (8.9%). Current smoking prevalences were higher in Malays (27.3%) than in Indians (19.4%) and Chinese (23.0%). Malays and Indians did not have higher rates of atopy (11.1% and 15.2%, respectively) than Chinese (15.4%). Adjustment for these factors in multivariate analyses reduced the greater odds of asthma in Malays and Indians, but not to a significant extent. CONCLUSIONS: There are ethnic differences in the prevalence of asthma in Singapore which are not entirely explained by differences in smoking, atopy, or other risk factors. Other unmeasured environmental factors or genetic influences are likely to account for residual differences in the prevalence of asthma.

Adult↗
PubMed1994

Fatal haemoptysis in Salmonella typhimurium septicaemia--a cautionary tale.

Septicaemia and mycotic aneurysm may occur in a patient who is an enteric-carrier of Salmonella typhimurium. We report such a case of an elderly man who presented with chest pain and fatal massive haemoptysis from a likely mycotic thoracic aneurysm. This report underscores the importance of increased awareness of the disease which may allow more frequent and earlier diagnosis.

Aged↗
PubMed1994

Epidemiology of chronic (perennial) rhinitis in Singapore: prevalence estimates, demographic variation and clinical allergic presentation.

We conducted a population-based study involving a stratified cluster disproportionate random sample of 2868 adults aged 20 to 74 years selected from five housing estates (Yishun, Toa Payoh, Jurong East, Geylang/Eunos and Bukit Merah). Chronic rhinitis was defined as the usual presence of symptoms of blocked or running nose, apart from colds or the flu, lasting for more than a year. Allergic rhinitis was considered to be present if these symptoms were associated with conjunctivitis or recognisable provocation by commonly known allergens, namely house dust, dogs, cats, birds, pollen, or medicines. The estimated general population prevalence of chronic rhinitis was 10.8% (95% confidence interval (CI) 8.8-12.7). Higher prevalences were noted in males, in younger adults, in Indians and Chinese, in those with higher socio-economic status, and in Toa Payoh, Jurong East and Geylang/Eunos. The prevalence of allergic rhinitis was 5.5% (95% CI 4.5-6.5). The most common 'allergenic' factor in allergic rhinitis was house dust (73%); provocation by birds, cats or dogs (5%), grass or tree pollens (5%), and medicine (5%) was less common but likely to have been under-recognised. Provocation by change in temperature (54%) and early in the morning (64%) was equally frequent in both 'allergic' and 'non-allergic' rhinitis; cigarette smoke, petrol and diesel fumes, food and work environment were less common (4-12%). Allergic rhinitis was highly significantly associated with asthma (13.9% in allergic rhinitis, 4.4% in non-allergic rhinitis, and 2.2% in non-rhinitic subjects).

Adult↗
PubMed1993

Nonfatal and fatal infections caused by Chromobacterium violaceum.

Human infection caused by Chromobacterium violaceum is rare, but when it occurs it is associated with a high mortality rate. We report the cases of two patients with infection due to Chromobacterium violaceum. One patient presented early in the course of disease and survived after receiving appropriate antibiotic therapy. The other patient presented late in the course of disease and died of fulminant sepsis with abscesses in multiple organs. We discuss the similarity between C. violaceum infection and the septicemic form of melioidosis.

Adult↗
PubMed1993

Respiratory symptoms and lung function effects of domestic exposure to tobacco smoke and cooking by gas in non-smoking women in Singapore.

STUDY OBJECTIVES: To investigate the effects of passive exposure to tobacco smoke and gas cooking at home on respiratory symptoms and lung function of non-smoking women. SETTING: Evidence on the effects of passive smoking and exposure to nitrogen dioxide from gas cooking on the respiratory health of adults is limited and variable. Over 97% of women in Singapore do not smoke, and a principal source of indoor air pollution for housewives is passive smoking and gas cooking. DESIGN: This was a cross sectional (prevalence) study of a population based sample of 2868 adults aged 20 to 74 years in Singapore. A structured questionnaire administered by trained interviewers was used to collect data on passive smoking, gas cooking, respiratory symptoms, and other relevant variables. Passive smoking was defined as exposure to cigarette smoke from one or more members of the household who had ever smoked. Gas cooking was defined in terms of the weekly frequency of gas cooking, as well as the frequency with which the respondent's kitchen was filled with heavy cooking fumes (rarely, occasionally, often). Forced expiratory volume in one second (FEV1) was measured by using a portable Micro-spirometer. Multivariate analyses were used to estimate relative odds of association for respiratory symptoms and FEV1 effect, with adjustment for potential confounding variables. PARTICIPANTS: Of a total of 1438 women in the sample, 1282 women who had never smoked provided questionnaire data and 1008 women provided acceptable readings of FEV1 for analysis. MAIN RESULTS: Passive smoking was significantly associated with greater relative odds of usual or chronic cough and phlegm, wheezing, and breathlessness on exertion, as well as lower FEV1. Greater relative odds of respiratory symptoms were also associated with the weekly frequency of gas cooking, although these results were statistically insignificant. Chronic cough and phlegm and breathlessness on exertion, however, were significantly associated with the frequency with which the kitchen was filled with heavy cooking fumes. A lower FEV1 was found in women who cooked frequently (more than thrice a week). CONCLUSION: Domestic exposure to cigarette smoke and gas cooking is associated with increased risks of respiratory symptoms and impairment of lung function in non-smoking women in Singapore.

Adult↗
PubMed1993

Factors influencing pulse oximetry as compared to functional arterial saturation in multi-ethnic Singapore.

Noninvasive oximetry provides continuous monitoring of arterial oxygen saturation and hence, early detection of hypoxia. This has proved to be a useful adjunct to patients' safety, and is considered indispensable in certain settings. However, errors may be present in the pulse oximeter estimation (SpO2) of arterial oxygen saturation (SaO2), which may be due to various parameters. We have studied a multi-ethnic population where the skin pigmentation is different, and also under different conditions comparing SpO2 with SaO2. Our results showed that SpO2 estimation of SaO2 amongst the three racial groups (Chinese, Malays, and Indians) varied significantly (ANOVA, p < 0.05). The over-estimation was more pronounced by hypoxic conditions and jaundice. Haemoglobin and systolic blood pressure did not affect the difference between SpO2 and SaO2.

Adult↗
PubMed1992

The effect of platelet activating factor antagonist on ozone-induced airway inflammation and bronchial hyperresponsiveness in guinea pigs.

We investigated the role of platelet-activating factor (PAF) in ozone-induced airway responses by examining the effects of L659,989, a potent PAF antagonist, on bronchial hyperresponsiveness and airway inflammation. Twenty-four male guinea pigs were studied in four equal groups. Total lung resistance (RL) in intubated and spontaneously breathing animals was measured in a constant-volume body plethysmograph. Dose-response curves to methacholine were determined in all animals at the start of the experiment. These were repeated on a separate day after the following types of treatments: air exposure in Group 1, intraperitoneally administered alcohol and air exposure in Group 2; intraperitoneally administered alcohol and ozone exposure in Group 3, and intraperitoneally administered L659,989 (a specific PAF antagonist), 5 mg/kg dissolved in alcohol, and ozone exposure in Group 4. Bronchoalveolar lavage (BAL) was performed after the second methacholine challenge, and the bronchial mucosa was also examined for inflammatory cells. Exposure to 3 ppm ozone for 2 h resulted in a three-doubling concentration increase in bronchial responsiveness, which was not significantly inhibited by prior treatment with L659,989. Ozone induced a 1.8-fold increase in BAL total cell count, increased eosinophilic influx into the airways, and increased eosinophilic infiltration in the bronchial mucosa, which were all not inhibited by L659,989 pretreatment. The results suggest that PAF may not have an essential role in ozone-induced airway hyperresponsiveness and nonallergic airway inflammation.

Animals↗
PubMed1992

Single-dose and steady-state effects of controlled-release salbutamol on drug level and airflow obstruction in patients with asthma.

Oral medication remains the mainstay of treatment for many asthmatics. We compared the single dose and steady-state effects of twice daily 4 mg and 8 mg controlled-release salbutamol (CRS) on plasma salbutamol and FEV1 in 10 asthmatic patients in a double-blind, double-dummy, cross-over study. On 5 separate days, one week apart, we measured FEV1 and plasma salbutamol hourly for 12 hours after a single dose and, after twice daily doses (4 mg, 8 mg or placebo CRS) for one week. Controlled-release salbutamol showed controlled release properties and dose effect for the two doses. At steady-state, it provided relatively constant plasma levels for 12 hours. Significant and similar bronchodilatation occurred after both 4 mg and 8 mg CRS taken either as a single dose or a steady-state regime.

Adolescent↗