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Biomedical subjects

M Y Chan

Publications and source records attributed to M Y Chan.

At least 19 recordsLinked to original sources
PubMed2006

Antecedent risk factors and their control in young patients with a first myocardial infarction.

INTRODUCTION: Identifying and controlling cardiovascular risk factors at an early age may prevent cases of young myocardial infarction (MI). We studied age-related differences in the cumulative incidence of risk factors and the adequacy of primary prevention by surveying 1,556 patients with a first MI admitted to a tertiary hospital in Singapore. METHODS: This is a single centre registry-based study on patients admitted with a first MI to a tertiary hospital in Singapore. We stratified the cohort into younger (45 years of age and younger) and older (older than 45 years of age) groups. The presence of five risk factors, namely: hypertension, diabetes mellitus (DM), smoking, a family history of premature MI, and hyperlipidaemia, was assessed at the point of care by interview and prior medical records when obtainable. We also determined by the same methods, if these patients were receiving active treatment for DM, hypertension or hyperlipidaemia prior to their first MI. Lipid levels were measured within 24 hours of admission. RESULTS: 96 percent of patients 45 years and younger and 92 percent of those older than 45 years had at least one antecedent risk factor. The 45 years and younger age group had a higher incidence of untreated hypertension (odds ratio 2.99, 95 percent confidence interval 2.00-4.46, p-value is less than 0.001) and hyperlipidaemia (odds ratio 1.71, 95 percent confidence interval 1.20 - 2.43, p-value is equal to 0.002). CONCLUSION: A majority of young patients with a first MI have at least one identifiable antecedent risk factor. There is significant undertreatment of hypertension and hyperlipidaemia in this age group.

Adult↗
PubMed2006

Ex-utero intrapartum treatment: a controlled approach to the management of anticipated airway problems in the newborn.

Airway problems in an unborn foetus that may cause obstruction can be safely managed using an ex-utero intrapartum technique. Advanced technology now allows many congenital airway problems to be diagnosed in the prenatal period. Careful prenatal planning of an ex-utero intrapartum treatment allows safe airway control while the foetus remains on uteroplacental support. It avoids the need for emergent intervention of an acutely obstructed airway in a neonate that often has disastrous consequences.

Adult↗
PubMed2005

Randomised controlled trial of qigong in the treatment of mild essential hypertension.

Exercise and relaxation decrease blood pressure. Qigong is a traditional Chinese exercise consisting of breathing and gentle movements. We conducted a randomised controlled trial to study the effect of Guolin qigong on blood pressure. In all, 88 patients with mild essential hypertension were recruited from the community and randomised to Goulin qigong or conventional exercise for 16 weeks. The main outcome measurements were blood pressure, health status (SF-36 scores), Beck Anxiety and Depression Inventory scores. In the qigong group, blood pressure decreased significantly from 146.3+/-7.8/93.0+/-4.1 mmHg at baseline to 135.5+/-10.0/87.1+/-7.7 mmHg at week 16. In the exercise group, blood pressure also decreased significantly from 140.9+/-10.9/93.1+/-3.5 mmHg to 129.7+/-11.1/86.0+/-7.0 mmHg. Heart rate, weight, BMI, waist circumference, total cholesterol, renin and 24 h urinary albumin excretion significantly decreased in both groups after 16 weeks. General health, bodily pain, social functioning and depression also improved in both groups. No significant differences between qigong and conventional exercise were found. In conclusion, Guolin qigong and conventional exercise have similar effects on blood pressure in patients with mild hypertension. While no additional benefits were identified, it is nevertheless an alternative to conventional exercise in the nondrug treatment of hypertension.

Aged↗
PubMed2005

Predictors of axillary lymph node metastases in women with early breast cancer in Singapore.

INTRODUCTION: The presence of axillary lymph node metastases is an important prognostic factor in breast cancer. Sentinel lymph node biopsy (SLNB) is an emerging method for the staging of the axilla. It is hoped that with SLNB, the morbidity from axillary lymph node dissection (ALND) can be avoided without compromising the staging and management of early breast cancer. However, only patients found to be SLNB negative benefit from this procedure, as those with positive SLNB may still require ALND. Our objective is to study the various clinico-pathological factors to find predictive factors for axillary lymph node involvement in early breast cancer. It is hoped that with these factors, we will be better able to identify groups of patients most likely to benefit from SLNB. METHODS: A retrospective study of 380 early breast cancer cases (stage T1 and T2, N0, N1, M0) in women treated in the Department of General Surgery, Tan Tock Seng Hospital, between January 1999 and August 2002, was conducted. Incidence of nodal metastases was correlated with clinico-pathological factors, and analysed by univariate and multivariate analyses. RESULTS: Approximately 35 percent of the 380 cases of early breast cancer had nodal metastases. Multivariate analyses revealed four independent predictors of node positivity: tumour size (p-value equals 0.0001), presence of lymphovascular invasion (p-value is less than 0.0001), tumours with histology other than invasive ductal or lobular carcinoma (p-value equals 0.04), and presence of progesterone receptors (p-value equals 0.05). CONCLUSION: We have found independent preoperative predictive factors in our local population for the presence of nodal metastases. This information can aid patient selection for SLNB and improve patient counselling.

Adult↗
PubMed2003

Disease impact and patient insight--a study on a local population of asthmatics.

The cornerstone of asthma management is achieving adequate symptom control and patient education. We studied in our local population of asthmatic patients how well their symptoms were controlled with currently prescribed treatment and their insight into the disease and its management. Over a 6-month period, 93 asthmatics recruited from two local government health clinics and a state hospital were interviewed using a standard questionnaire. Patients were classified into 4 groups based on the treatment they were on according to Global Initiative for Asthma (GINA) treatment guidelines. The number of patients in Step 1 (rescue medication alone), Step 2 (1 controller medication), Step 3 (2 controller medications) and Step 4 (at least 3 controller medications) were 8, 39, 34 and 12, respectively. Except for day symptoms in Step 1 group, fewer than 50% achieved minimum day or night symptoms and no restriction of daily activities. Questions on patient insight were only available for 50 patients. Weather change (74%), air pollution (66%) and physical stress (46%) were the three highest ranked common asthma triggers. More than half correctly recognized the important symptoms of a serious asthma attack but fewer than 15% were familiar with the peak flow meter and its use or with the asthma self-management plan. Most patients perceived that their treatment had helped reduce disease severity and exacerbations. We conclude that symptom control and some aspect of patient education are still lacking in our local asthmatics.

Adolescent↗
PubMed2003

Efficient constrained multiple sequence alignment with performance guarantee.

The Constrained Multiple Sequence Alignment problem is to align a set of sequences subject to a given constrained sequence, which arises from some knowledge of the structure of the sequences. This paper presents new algorithms for this problem, which are more efficient in terms of time and space (memory) than the previous algorithms [14], and with a worst-case guarantee on the quality of the alignment. Saving the space requirement by a quadratic factor is particularly significant as the previous O(n(4))-space algorithm has limited application due to its huge memory requirement. Experiments on real data sets confirm that our new algorithms show improvements in both alignment quality and resource requirements.

Algorithms↗
PubMed2002

Paediatric extracranial germ cell tumours: a retrospective review.

INTRODUCTION: Germ cell tumours (GCTs) are rare, constituting 3% of all childhood malignancies. The aim of this study was to analyse the epidemiology and outcome of these patients. MATERIALS AND METHODS: A retrospective, cohort study was conducted on 38 paediatric patients presenting with extracranial GCTs, treated at the Singapore General Hospital, Tan Tock Seng Hospital and Kandang Kerbau Women's and Children's Hospital from 1 January 1989 to 30 June 1999. The median age at diagnosis was 1.7 years (0 to 13 years). RESULTS: There was no sex or racial preponderance. Eighteen patients (47.3%) had teratomas, 16 (42.1%) had yolk sac tumours, 1 (2.6%) had dysgerminoma and 3 (7.9%) had mixed GCTs. Thirty-four patients (89.5%) had Stage I disease, 1 (2.6%) had Stage II disease, 1 (2.6%) had Stage III disease and 2 (5.3%) had metastatic disease. Complete tumour resection was achieved in 36 of the 38 patients (95%). Cisplatin-based combination chemotherapy was given to 11 patients (28.9%). None of the patients received radiotherapy. Complications from chemotherapy included anaemia requiring packed red cell transfusion (n = 3), Port-a-cath sepsis requiring removal (n = 1), febrile neutropenia (n = 1) and nephropathy (n = 1). CONCLUSION: Using the Kaplan-Meier life tables, the overall and event-free survivals at 10 years for the patients with malignant GCTs were 96% and 88%, respectively, with a mean follow-up period of 5.1 years (0.7 to 10 years). The majority of the patients presented with early Stage I disease and this contributed to our high survival rate.

Adolescent↗
PubMed2001

Seventy percent of the Mycobacterium tuberculosis isolates in Hong Kong represent the Beijing genotype.

We used spoligotyping to study 500 randomly selected pretreatment Mycobacterium tuberculosis (MTB) strains isolated in Hong Kong during the 2 year period 1998-9. It was found that amongst all MTB strains studied, the 'Beijing' genotype strains were highly prevalent in our geographic area, representing about 70% of the isolates. Unlike previous observations in Vietnam, no significant associations were found either between 'Beijing' genotype strains and all other anti-tuberculosis drug resistance phenotypes, or with particular patients' age groups, except for a weak association with isoniazid susceptibility. Eighteen of these strains exhibited spoligotype patterns that were similar but not identical to the 'Beijing' specific pattern. This is the first geographical area where genetic diversity among 'Beijing' genotype of MTB strains has been observed on this scale.

China↗
PubMed2001

Association of human beta-herpesviruses with the development of cervical cancer: bystanders or cofactors.

BACKGROUND/AIM: Human papillomaviruses (HPVs) are important, but not sufficient, for the development of cervical cancer. All three human beta-herpesviruses--cytomegalovirus (CMV) and human herpesviruses (HHV) types 6 and 7--have been detected in the cervix. In addition, CMV and HHV-6 can interact with HPVs in vivo. This study examined the possible role of beta-herpesviruses in cervical cancer development. METHODS: HPV, CMV, HHV-6, and HHV-7 were detected by the polymerase chain reaction using cervical scrapes taken at colposcopy from 388 women. HPV types were identified using restriction fragment length polymorphisms. Colposcopy guided biopsies were taken from abnormal areas, and the histological findings were regarded as the final diagnoses. The associations between herpesvirus infection and the degree of cervical lesion were analysed with respect to HPV status. RESULTS: Of the 388 women, 51.8% had a normal cervix, 14.4% had cervical intraepithelial neoplasia grade 1 (CIN1), 8.2% had CIN2, 19.3% had CIN3, and 6.2% had invasive carcinoma. Overall, the positive rates for high, intermediate, and low risk HPVs were 18.8%, 21.4%, and 5.2%, respectively. Fifteen patients harboured HPVs for which the genotype could not be identified. Positive rates for CMV, HHV-6, and HHV-7 were 9.5%, 3.6%, and 3.4%, respectively. HPV positive patients carried a higher risk for high grade lesions (CIN2/3 or carcinoma) (odds ratio (OR), 5.24; 95% confidence interval (CI), 3.19 to 8.62; chi 2 = 51.79; p < 0.001), whereas those positive for CMV, HHV-6, or HHV-7 did not. Thirteen of 131 patients with high grade lesions had HPV/herpesvirus coinfections, but no association with the cervical lesion was noted. Furthermore, positive rates for herpesviruses among HPV negative, high/intermediate risk HPV negative, and high risk HPV negative subgroups were similarly low and without a significant association. CONCLUSIONS: The ubiquitous nature of herpesviruses may pose difficulty in elucidating their pathogenic role. These results indicate that CMV, HHV-6, and HHV-7 are bystanders rather than cofactors in the oncogenesis of cervical cancer.

Adolescent↗
PubMed2001

Mucinous cystadenoma of the appendix--an unusual cause of intestinal obstruction.

INTRODUCTION: Report of a rare presentation of mucinous cystadenoma of the vermiform appendix. CLINICAL PICTURE: A lady who presented with intestinal obstruction and peritonitis was found to have gangrenous small bowel caused by strangulation by a tumour of the appendix. TREATMENT: Right hemicolectomy. OUTCOME: The histology of the appendicular tumour was mucinous cystadenoma. The patient recovered well. CONCLUSION: Mucinous cystadenoma of the appendix can present in many ways and it is important to recognise the pathology at operation.

Aged↗
PubMed2001

The Alvarado score and acute appendicitis.

INTRODUCTION: This is a retrospective study to assess the accuracy of the Alvarado score in predicting appendicitis for patients with right iliac fossa pain. MATERIALS AND METHODS: This is a retrospective study of consecutive patients with suspected appendicitis. The Alvarado score was computed from the admission notes and correlated with the final outcome of the patient. Patients discharged without surgery were reviewed in the outpatient's clinic to ascertain that they did not need surgery. RESULTS: There were 148 patients in the study and 63 had appendectomies with intention to treat appendicitis. The normal appendicectomy rate was 21%. The number of patients with score 1-4, 5-6, 7-8 and 9-10 were 46, 40, 44 and 18, respectively, while the number of appendicitis in each group were 0, 2 (5%), 30 (68%) and 18 (100%), respectively. The positive and negative predictive values of Alvarado's scores of 7 or more were 77% and 97.6%, respectively. CONCLUSION: Alvarado score is a useful tool in the diagnosis of appendicitis, especially at both ends of the scale.

Acute Disease↗
PubMed2001

Incidence of oral tissue trauma after the administration of general anesthesia.

BACKGROUND: Administration of general anesthesia necessitates certain amounts of manipulation or instrumentation within the mouth that may cause some oral tissue injuries. The purpose of this study was to determine the incidence of oral tissue trauma after receiving general anesthesia. Some possible risk factors were explored. METHODS: Four hundred and four adult patients receiving surgical procedures under general anesthesia facilitated by endotracheal intubation were included in this prospective survey. In each patient detailed oral and dental conditions were evaluated and recorded by an oral surgeon before and after operation. The extent of oral tissue trauma were computed and the type and character of the injury were recorded. RESULTS: Twenty-eight patients (6.9%) were found to sustain various degrees of oral trauma that included soft tissue laceration, tooth fracture, prosthesis damage, tooth avulsion, ecchymosis and numbness of tongue. Preexistence of missing tooth, crown, and residual root were some possible risk factors that might predispose to complication. CONCLUSIONS: Oral tissue trauma as it seems to be a common anesthetic complication that should be considered as a recognized hazard of general anesthesia. Understanding and recognizing oral anatomical condition and pathological change before anesthesia may help the anesthesiologists in preventing oral and dental complications and thus to avoid legal suits.

Adolescent↗
PubMed1999

F1Aalpha, a death receptor-binding protein homologous to the Caenorhabditis elegans sex-determining protein, FEM-1, is a caspase substrate that mediates apoptosis.

Apoptosis is an evolutionarily conserved process that is critical for tissue homeostasis and development including sex determination in essentially all multicellular organisms. Here, we report the cloning of an ankyrin repeat-containing protein, termed F1Aalpha, in a yeast two-hybrid screen using the cytoplasmic domain of Fas (CD95/APO-1) as bait. Amino acid sequence analysis indicates that F1Aalpha has extensive homology to the sex-determining protein FEM-1 of the Caenorhabditis elegans, which is required for the development of all aspects of the male phenotype. F1Aalpha associates with the cytoplasmic domains of Fas and tumor necrosis factor receptor 1, two prototype members of the "death receptor" family. The F1Aalpha protein also oligomerizes. Overexpression of F1Aalpha induces apoptosis in mammalian cells, and co-expression of Bcl-XL or the dominant negative mutants of either FADD or caspase-9 blocks this effect. Deletion analysis revealed the center region of F1Aalpha, including a cluster of five ankyrin repeats to be necessary and sufficient for maximum apoptotic activity, and the N-terminal region appears to regulate negatively this activity. Furthermore, F1Aalpha is cleaved by a caspase-3-like protease at Asp(342), and the cleavage-resistant mutant is unable to induce apoptosis upon overexpression. F1Aalpha is therefore a member of a growing family of death receptor-associated proteins that mediates apoptosis.

Amino Acid Sequence↗
PubMed1999

Efficacy of media enriched with nonlactate-generating substrate for organ preservation: in vitro and clinical studies using the cornea model.

BACKGROUND: Using a rabbit cornea model, our recent study demonstrated that Chen Medium (CM), an isotonic media enriched with nonlactate-generating high-energy substrates, is very effective for organ preservation. In the present study, the efficacy of CM is further evaluated with human corneas METHODS: The effectiveness of CM and Optisol for preserving the endothelial integrity of human corneas in vitro was evaluated by scanning electron microscopy. Clinical efficacy was evaluated in a total of 83 patients: 10 patients with keratoconus grafted randomly with either CM- or Optisol-stored cornea of the same donor, and 73 patients with various conditions grafted with CM-stored corneas. After surgery, visual acuity and quality of the graft were monitored for up to 4.6 years. RESULTS: The scanning electron microscopic study revealed that after 11-day storage at 4 degrees C, the CM-stored cornea had only marginal disruptive changes, 9.4+/-1.1%, in endothelial cells, as opposed to 42.4+/-4.6% of the Optisol-stored cornea. All 78 CM-stored corneas, including 67 with 12.2- to 17.7-hr death-to-storage time, 3-7.6 days of storage time, and initial marginal quality before storage, were successfully transplanted. These grafts were thin and clear, with an excellent epithelial integrity and without significant changes in endothelial cell density. Five Optisol-stored corneas were also successfully grafted; one of them, however, was edematous for about 4 weeks, and all the grafts were slightly thicker with substantial endothelial cell loss. CONCLUSION: Using a cornea model, present and recent studies show that CM is very effective for preserving tissue viability and endothelial integrity. Previous study revealed that CM-stored tissues maintained high levels of ATP and metabolic function, with suppression of lactate formation and accumulation. Thus, these findings support the concept that preservation of tissue viability is closely associated with the ability of the tissues to retain metabolic activity, to generate ATP efficiently, and to prevent acidosis effectively during storage.

Adenosine↗
PubMed1999

Regulation and immunohistochemical localization of betagamma-stimulated adenylyl cyclases in mouse hippocampus.

Specific forms of synaptic plasticity such as long-term potentiation (LTP) are modulated by or require increases in cAMP. The various adenylyl cyclase isoforms possess unique regulatory properties, and thus cAMP increases in a given cell type or tissue in response to converging signals are subject to the properties of the adenylyl cyclase isoforms expressed. In most tissues, adenylyl cyclase activity is stimulated by neurotransmitters or hormones via stimulatory G-protein (Gs)-coupled receptors and is inhibited via inhibitory G-protein (Gi)-linked receptors. However, in the hippocampus, stimulation of Gi-coupled receptors potentiates Gs-stimulated cAMP levels. This effect may be associated with the regulatory properties of adenylyl cyclase types 2 and 4 (AC2 and AC4), isoforms that are potentiated by the betagamma subunit of Gi in vitro. Although AC2 has been shown to be stimulated by betagamma in whole cells, reports describing the sensitivity of AC4 to betagamma in vivo have yet to emerge. Our results demonstrate that Gs-mediated stimulation of AC4 is potentiated by betagamma released from activated Gi-coupled receptors in intact human embryonic kidney (HEK) 293 cells. Furthermore, we show that the AC2 and AC4 proteins are expressed in the mouse hippocampal formation and that they colocalize with MAP2, a dendritic and/or postsynaptic marker. The presence of AC2 and AC4 in the hippocampus and the ability of each of these enzymes to detect coincident activation of Gs- and Gi-coupled receptors suggest that they may play a crucial role in certain forms of synaptic plasticity by coordinating such overlapping synaptic inputs.

Adenylate Cyclase Toxin↗
PubMed1999

IS6110 dot blot hybridization for the identification of Mycobacterium tuberculosis complex.

To explore a simple, rapid, and inexpensive way to identify Mycobacterium tuberculosis complex culture, dot blot hybridization using IS6110 as the marker was performed against 2788 known clinical isolates of mycobacteria including M. tuberculosis (n = 721), M. kansasii (177), M. marinum (10), M. avium complex (700), M. terrae complex (203), M. fortuitum (476), M. chelonae (439), and other nonpigmented Runyon's Group IV mycobacteria (62). We found that the sensitivity and specificity of the test were 94.3% and 100%, respectively. When this method was evaluated in a laboratory blind study of 1253 initially unknown clinical isolates, its sensitivity and specificity were 91.2% and 100%, respectively. Because this identification test is technically simple, rapid, and can be done in batches, together with its high sensitivity and specificity, it is a cost-effective method for routine identification of M. tuberculosis complex in laboratories of areas with a high incidence of tuberculosis.

DNA Transposable Elements↗