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Biomedical subjects

Y C Chan

Publications and source records attributed to Y C Chan.

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

Integrating air pollution modelling with scenario testing in road transport planning: the TRAEMS approach.

Transport add-on environmental modelling system (TRAEMS) is a GIS-based environmental modelling system designed to evaluate the environmental consequences of road traffic in urban areas. Its development has been underpinned by the premises that the evaluation of road traffic impacts is best undertaken during the early planning stages of road networks, and that this can utilise much of the data generated by the transport planners themselves as they apply their travel demand models as to planning of road networks. The system integrates information about traffic-usually from travel-forecasting models-with information about land use, to provide the input data to a range of commonly used models that estimate pollution from a road traffic system, and the energy consumption of that system. TRAEMS facilitates this integration and allows land use, transport and environmental planners to have rapid feedback on the environmental effects of road transport network scenarios that are being developed and tested. Its purpose is to aid in the selection of environmentally-preferred road networks and to highlight where management of pollution levels on future road networks will be required. TRAEMS has a modular structure. This paper describes the main features of the air pollution and fuel consumption modules of the system and illustrates the system's utility through case studies at both metropolitan-wide- and local-area scales.

Air Pollution↗
PubMed2003

All that wheezes is not asthma.

Asthma is a common disease. Wheezing is not pathognomonic of asthma, however. One must be alert when appropriate asthmatic treatment does not provide adequate control. Other causes of airway obstruction must be considered, especially when stridor is heard. This report describes an elderly patient who had been managed as having asthma but had an endotracheal tumour.

Aged↗
PubMed2003

Sweet's syndrome associated with Mycobacterium chelonae and herpes simplex virus infections: a case report.

INTRODUCTION: We report a case of Sweet's syndrome associated with Mycobacterium chelonae and herpes simplex virus infection. CLINICAL PICTURE: A 56-year-old Chinese woman presented with a granulomatous subglottic mass and right lung nodules, which responded to a 9-month course of anti-tuberculous treatment. Subsequently, she developed genital herpes simplex virus infection, which was followed by a cutaneous eruption with vesicular plaques associated with fever, bilateral cervical lymph nodes and neutrophilia. Mycobacterium chelonae was isolated from lymph node cultures. The cutaneous presentation of Sweet's syndrome was confirmed on skin biopsy. There was no evidence of underlying immunosuppression, malignancy or connective tissue disease. TREATMENT: She was treated with rifampicin, clarithromycin and oral prednisolone. OUTCOME: There was complete resolution of her cutaneous lesions and cervical lymphadenopathy. CONCLUSION: The association between Sweet's syndrome and Mycobacterium chelonae as well as herpes simplex virus, though rare, should be considered in all patients presenting with Sweet's syndrome.

Female↗
PubMed2002

Cost-effectiveness of CT thorax and bronchoscopy in haemoptysis with normal CXR for exclusion of lung cancer.

As fibre-optic bronchoscopy and CT thorax become more widely used, patients with haemoptysis who had normal CXR and sputum results are more commonly offered both CT and bronchoscopy to exclude lung cancer. Doctors who are under possible litigation pressure arising from missed diagnoses of lung cancer are often exhaustive in their investigations, even when the haemoptysis has been transient. The present study aims to investigate the number of cancer patients who can be detected with the two investigations, and compare recent similar study results with archive results. We found that despite the use of more efficient investigation tools, the yield is paradoxically much lower and, hence, less cost-effective than that of previous studies. The likely reason is that doctors tend to over-investigate, even for short-term, minimal blood-streaked sputum, which is common among simple bronchitis. In order to be more cost-effective, these investigations should be used more selectively and for high risk patients such as those with prolonged haemoptysis and those who are heavy smokers.

Bronchoscopy↗
PubMed2002

Prevention of experimental myointimal hyperplasia by immunomodulation.

INTRODUCTION: we have tested the hypothesis that treatment with a mycobacterial preparation that modulates the antibody response, would diminish restenosis in a rat angioplasty model. MATERIALS/METHODS: male Sprague-Dawley rats were used. All immunisations were given subcutaneously. Group A (control) received normal saline on days 0, 21, and 42. Group B received SRL172 on days 0, 21, and 42. Group C received SRL172 on days 0, 21, and 42, and hsp65/Incomplete Freund's on days 21 and 42. Group D received hsp65/Freund's on days 21 and 42. Right common carotid arteries were balloon-injured on day 63 using a standard technique known to produce MIH and animals were sacrificed on day 77. For each carotid 6 microm cross sections were cut from paraffin blocks. Cross-sectional areas were measured by computerised planimetry. RESULTS: balloon injury resulted in MIH in all animals. Data represents mean+/-SEM for the percentage of area enclosed within the internal elastic lamina occupied by MIH (% MIH); which for groups A, B, C, and D was 85+/-11, 24+/-3, 27+/-7, and 17+/-3 respectively. All the treatment groups had significantly less MIH when compared to the control group but no statistically significant difference was found between any of the treatment groups. CONCLUSIONS: this is the first report that immunomodulation with mycobacterial material suitable for use in man, can reduce MIH. Since such modulation has low risk, this raises the prospect of an important new therapeutic modality to combat restenosis.

Adjuvants, Immunologic↗
PubMed2002

Allopurinol hypersensitivity syndrome and acute myocardial infarction--two case reports.

INTRODUCTION: Allopurinol hypersensitivity syndrome is an idiosyncratic drug reaction characterised by an acute and severe multiorgan disease. It usually begins 2 to 6 weeks after starting allopurinol. The most important and critical characteristics are the presence of visceral involvement and haematological abnormalities; hepatitis, interstitial nephritis and eosinophilia are most frequently seen. However, cardiac involvement has not been previously reported. CLINICAL PICTURE: Two previously well young Chinese men presented with fever, rash and hepatitis 3 weeks after taking allopurinol. The clinicopathological presentation was typical of allopurinol hypersensitivity syndrome. TREATMENT AND OUTCOME: Both men received systemic corticosteroid therapy and had full recovery. A few months later, they each had an acute myocardial infarction with a fatal outcome, despite minimal cardiac risk factors and no family history of coronary artery disease. CONCLUSION: The immunologic process in allopurinol hypersensitivity syndrome may have caused coronary vasculitis and subsequent myocardial infarct. Alternatively, the idiosyncratic reaction may have damaged myocardium, with the resultant myocarditis masquerading as coronary artery disease. Patients with allopurinol hypersensitivity syndrome should be followed up for cardiac involvement.

Adult↗
PubMed2002

The epidemiology and treatment of anogenital warts in Singapore: a retrospective evaluation.

INTRODUCTION: A retrospective study in the referral centre for sexually transmitted infections (STIs) in Singapore to describe the epidemiology and treatment outcome of patients with anogenital warts. SUBJECTS AND METHODS: We reviewed the case records of 301 patients with anogenital warts who were seen over a 1-year period (1999). We also attempted to interview every patient by telephone to find out if they had any clinical recurrences for which treatment was sought elsewhere. RESULTS: There were 255 males and 46 females with a mean age of 34 years. Two hundred and nineteen (72.8%) presented with symptoms lasting 12 weeks or less. In males, warts occurred most frequently in the preputial cavity (52.5%) and on the penile shaft (40.8%). In females, they occurred most frequently on the external genitalia (91.3%). Two hundred and thirty-five males were treated with cryotherapy and 69% (95% CI, 62.6% to 74.8%) achieved clinical resolution after a mean of 6 treatment cycles. Seven males were treated with podophyllin 0.25% in ethanol and 71% (95% CI, 29.0% to 96.3%) were clinically cured after a mean of 4 treatment cycles. Thirty-nine females were treated with cryotherapy and 67% (95% CI, 49.8% to 80.9%) achieved clinical cure after a mean of 4 treatment cycles. Of the 290 patients treated at the centre, 212 (73%; 95% CI, 67.3% to 77.8%) patients (184 males, 28 females) achieved clinical cure after a mean of 7 weeks (range, 1 to 34 weeks); 90% (95% CI, 86.0% to 93.2%) of them by 15 weeks. Seven-two patients defaulted follow-up and 6 responded partially to treatment. Of the 212 patients who achieved clinical cure, 195 were interviewed by telephone, on an average, 17.7 months after clinical resolution. Thirty-seven (19%; 95% CI, 13.7% to 25.2%), all males, relapsed clinically after a mean of 100 days (range, 5 to 329 days); 90% (95% CI, 84.6% to 93.6%) relapsed by 228 days. CONCLUSIONS: Podophyllin 0.25% in ethanol was the most cost-effective treatment for males. One in 5 patients had a recurrence of their warts and most had their recurrence within 8 months of initial resolution.

Adolescent↗
PubMed2002

"On the other hand": a case of hereditary, congenital mirror movement.

We describe a 20-year-old male Singaporean army recruit with hereditary, congenital mirror movements who presented with difficulties in military training because releasing the grip of one hand resulted in a similar release by the other hand. His father has mirror movements with a significant decrease in symptoms with time, a phenomenon that has not been previously described. Both father and son have no associated neurological abnormalities. Bilateral cortical representation for hand muscles and the presence of active ipsilateral corticospinal projections have been postulated as the mechanisms responsible for this condition.

Adult↗
PubMed2002

Adult community acquired bacterial meningitis in a Singaporean teaching hospital. A seven-year overview (1993-2000).

BACKGROUND: The objective of this study is to describe the bacteriological, clinical and laboratory features of community acquired bacterial meningitis in adults admitted to a Singapore tertiary-care hospital. METHODS: Two hundred sixty-nine cases of meningitis or meningoencephalitis admitted between 1993 and 2000 were identified by their discharge diagnosis codes. All case records except for 57 which could not be retrieved were retrospectively reviewed. Patients less than 14 years or with skull fractures, post-neurosurgery or with indwelling intracranial devices were excluded. Inclusion criteria was a clinical picture compatible with a diagnosis of bacterial meningitis with either (1) positive cerebral-spinal fluid (CSF) cultures or latex coagglutination or CSF neutrophilic pleocytosis accompanied by positive blood cultures or (2) in the absence of positive blood cultures, CSF cultures and latex agglutination, presence of CSF pleocytosis of at least 100 neutrophils per microL. RESULTS: Fifteen "culture-positive" and 11 "culture negative" cases were identified. Six (55%) of the "culture-negative" cases received antibiotics prior to admission. Cultures grew Streptococcus pneumoniae in four cases, three cases each of Group B streptococci and Neisseria meningitides. Listeria monocytogenes and Klebsiella pneumoniae were each seen twice and Streptococcus suis once. All cases of Group B streptococci occurred in the year 1998. Mortality was 19% (n = 5), six developed infections in other sites, three epileptic seizures, three developed hydrocephalus, and two hearing loss. CONCLUSIONS: Pathogens are similar to those reported in other studies but for an outbreak of Group B Streptococcus in 1998. There were a high number of "culture-negative" cases which may be due to preceding antibiotic intervention.

Adolescent↗
PubMed2001

Systemic administration of a water-soluble hexasulfonated C(60) (FC(4)S) reduces cerebral ischemia-induced infarct volume in gerbils.

Buckminsterfullerence and its derivatives have recently been shown to exhibit considerable in vivo biological activities. A water-soluble hexasulfonated C(60) (FC(4)S) has been shown to protect against oxidative stress. Neuroprotective effects of FC(4)S were investigated in the present study. Focal cerebral ischemia was produced by a permanent occlusion of the right middle cerebral artery in gerbils. Infarct volumes were determined by 2,3,5-triphenyltetrazolium chloride transcardiac perfusion 24 h after cerebral ischemia. Chronic pretreatment of FC(4)S (0.5 and 5.0 mg/kg/day, intraperitoneally for 2 weeks) significantly reduced the infarct volume (by 42% and 68%, respectively) when compared to that of the control group. Results revealed that chronic pretreatment of FC(4)S may protect the brain against focal cerebral ischemia.

Animals↗
PubMed2001

Intermediate inhibition in the heterogeneous UV-catalysis using a TiO2 suspension system.

Langmuir-Hinshelwood (L-H) kinetic expression was used to develop a basic mathematical model, which could describe the inhibition of intermediates in the photocatalysis of 2-chlorophenol (2-CP) in a suspended TiO2 system. Results showed that the photocatalytic oxidation of 2-chlorophenol followed the L-H type behavior and the reaction by-products displayed an inhibiting effect on the degradation rate. The inhibition was estimated by comparing to observed and estimated half-lives. The higher the initial concentration of 2-chlorophenol, the higher the inhibition of photocatalytic reaction. The L-H kinetic has been modified slightly in this study to rationalize the contrast of inhibited behavior and to improve in favor of a surface reaction. The concentrations of 2-chlorophenol were investigated ranging from 7.78 x 10(-5) to 7.78 x 10(-4) mol l(-1). The degradation of 2-chlorophenol in this reaction condition approximates a first-order kinetics to near-complete degradation. Calculated kinetic profiles are in an excellent agreement with the experimental observation. The results of the theoretical analysis can be used to estimate reaction rates in different initial concentrations of target compound.

Chlorophenols↗
PubMed2001

Positive patch-test reactions to para-phenylenediamine, their clinical relevance and the concept of clinical tolerance.

406 patients were patch tested over an 18-month period (January 1998 to June 1999) at a dermatology referral centre. 33 patients (8.1%) had a positive reaction to para-phenylenediamine (PPD). 20 patients were experiencing PPD hair dye dermatitis (present relevance, 61%), 2 were using PPD hair dyes without developing dermatitis (clinical tolerance, 6%), 4 had previously used PPD hair dyes with dermatitis in the past (past relevance, 12%), 3 had previously used PPD hair dyes without dermatitis (past exposure, 9%) and 4 had no known exposure to PPD (unknown relevance, 12%). Of the 20 patients whose test results were of present relevance, 17 avoided PPD hair dyes, resulting in total clearance of the dermatitis in all except 3, who had concurrent endogenous eczema. 3 continued using PPD hair dyes: 2 had recurrent contact dermatitis and 1 avoided dermatitis with meticulous technique. The 2 patients with clinical tolerance continued using PPD hair dyes with no dermatitis.

Adult↗
PubMed2001

Soy protein hydrolyzate with bound phospholipids reduces serum cholesterol levels in hypercholesterolemic adult male volunteers.

This study was done to evaluate the effects of soy protein hydrolyzate with bound phospholipids (c-SPHP), on the serum cholesterol levels in hypercholesterolemic subjects over a three-month period. Subjects were Taiwanese adult male volunteers whose serum total cholesterol levels were above 220 mg/dl. Twenty-one subjects were divided into three groups randomly, and each group was given c-SPHP zero, 3, or 6 g per day. Test diets were orally administered in a powdered drink form that contained c-SPHP or casein hydrolyzate (placebo). The subjects were given the test diet four times daily. The study consisted of a two-week pre-feeding period, a three-month feeding period, followed by a two-week post-feeding period. After 3 months of c-SPHP administration, 3 g per day, serum total cholesterol decreased significantly from the initial level (15.0%, p<0.01) and compared with the placebo group (p<0.05). Furthermore, LDL-cholesterol decreased significantly (27.7%, p<0.01) and the LDL/HDL ratio also decreased significantly (47.4%, p<0.01) from the initial levels. These effects of c-SPHP were dose-dependent. This study suggests that c-SPHP has remarkable improving effects on the serum cholesterol levels in hypercholesterolemic subjects.

Adult↗
PubMed2001

A retrospective study of incontinentia pigmenti seen at the National Skin Centre, Singapore over a 10-year period.

INTRODUCTION: Incontinentia pigmenti is a rare X-linked dominant disease which affects the ectodermal tissues, usually lethal in males. MATERIALS AND METHODS: A retrospective analysis of clinical data obtained from the photographic documentation and casenotes of patients diagnosed to have incontinentia pigmenti at the National Skin Centre. The study covered the period from January 1990 to December 1999. RESULTS: Twenty-six patients were diagnosed to have incontinentia pigmenti of the Bloch-Sulzberger type; 23 (88.5%) were females and 3 (11.5%) were males. There were 20 Chinese, 3 Malay and 3 Indian patients. Most patients had cutaneous manifestations at birth or within the first week of life. Cutaneous features included vesicles, papules, verrucous plaques and splash-like hyperpigmentation along the lines of Blaschko. The cutaneous lesions were widespread in 21 (81%) and localised in 5 (19%) patients. In some cases, hypopigmented atrophic streaks (2 patients) or whorled scarring alopecia (4 patients) were seen. Extracutaneous manifestations, seen in 5 (19%) patients, included neurological, dental and ocular defects. One Malay girl had severe neurological involvement associated with ocular abnormalities. A positive family history was present in 6 (23%) patients. The 3 male patients were Chinese without any family history. CONCLUSIONS: Each stage of the disease comes with its own set of differential diagnosis, including infections e.g. herpes virus infection and other types of genodermatoses e.g. linear and whorled nevoid hypermelanosis. The phenomenon of whorled scarring alopecia, hitherto unreported in the literature, corresponded to the lines of Blaschko. In the 3 Chinese male patients, the disorder probably originated from a new mutation. X chromosome inactivation in females during early embryogenesis results in a mosaic population of cells and this explains the linear and patchy manifestations of incontinentia pigmenti.

Adolescent↗
PubMed2001

A young male patient with persistent fever due to tuberculous peritonitis.

Tuberculous peritonitis is an uncommon disease in Hong Kong. We report a case of tuberculous peritonitis in a young male. The patient presented with persistent fever and intermittent cough for 1 month, but had no gastrointestinal symptoms. It was only through detection of slight abdominal ascites that subsequent abdominal paracentesis and laparoscopic biopsy confirmed the diagnosis. Appropriate antituberculous treatment was prescribed. Progress was complicated by persistent fever and liver function derangement, successfully managed by careful titration of antituberculous medications.

Adult↗
PubMed2001

Clinical efficacy of proton pump inhibitor therapy in neurologically impaired children with gastroesophageal reflux: prospective study.

OBJECTIVE: To study the effects of proton pump inhibitors in reducing vomiting, gastrointestinal bleeding, and chest infections in institutionalised neurologically impaired children with gastroesophageal reflux. DESIGN: Prospective study. SETTING: A regional hospital, Hong Kong. PATIENTS: Neurologically impaired children with refractory gastroesophageal reflux. MAIN OUTCOME MEASURES: Episodes of vomiting, gastrointestinal bleeding, and pneumonia in the baseline and proton pump inhibitor treatment periods. RESULTS: Nine children received proton pump inhibitor therapy for a median duration of 81 days. Mean reflux index was 9.3% (standard deviation, 5%). Dosage of omeprazole used was 1.0-2.3 mg/kg/d. Vomiting was reduced significantly with proton pump inhibitor treatment (median vomiting index [baseline]=0.4, median vomiting index [proton pump inhibitors]=0.2; P<0.05). No significant decrease in gastrointestinal bleeding or chest infection was observed. CONCLUSION: Proton pump inhibitors significantly reduced vomiting episodes in neurologically impaired children with gastroesophageal reflux.

Child↗
PubMed2001

Listeria meningoencephalitis: two cases and a review of the literature.

INTRODUCTION: Although presently uncommon locally, Listeria is increasing an important cause of central nervous system (CNS) infection worldwide. It differs from the common meningitis pathogens in its clinical features and treatment. CLINICAL PICTURE: We present 2 recently encountered cases of Listeria meningoencephalitis. In case 1, a previously healthy 42-year-old man presented with clinical features of meningoencephalitis. In case 2, a 64-year-old woman had clinical features of pneumonia and meningoencephalitis. Both had a predominantly lymphocytic picture in their cerebrospinal fluid (CSF) samples. Listeria grew in blood cultures of both patients and the CSF culture of the first. TREATMENT: In both cases, Listeria was resistant to the empirical antibiotics used. Intravenous ampicillin was eventually used in both patients, with gentamicin, added for synergistic action in the first. OUTCOME: The first patient developed complications of hydrocephalus, subdural collection and extensive cerebritis and ventriculitis. The second patient had focal seizures and a pontine infarct. Both did not survive. CONCLUSION: These 2 recent cases with different presentations of intracranial listerosis highlight the increasing importance of listerial infections in Singapore. Clinicians need to be familiar with the features of this lethal disease in order to recognize and manage it successfully.

Adult↗