PubMed Health⌕ Search

Biomedical subjects

W L Ng

Publications and source records attributed to W L Ng.

At least 19 recordsLinked to original sources
PubMed2006

Lymphopenia at presentation is associated with increased risk of infections in patients with systemic lupus erythematosus.

BACKGROUND: Patients with systemic lupus erythematosus (SLE) frequently suffer from infections, but the predisposing risk factors, as well as the exact frequency and nature of such infections, are not fully understood. AIM: To describe the frequency, types and risk factors for infections in a group of Chinese patients in the early stage of SLE in Hong Kong. DESIGN: Retrospective record study. METHODS: We reviewed the case records of 91 Chinese SLE patients, presenting <12 months after SLE diagnosis. Details of major infections (requiring intravenous antimicrobial therapy, or any confirmed mycobacterial infection) and minor infections were reviewed. Clinical and laboratory features, the systemic lupus erythematosus disease activity index (SLEDAI) at presentation and drug treatment were recorded and analysed. RESULTS: There were 48 major infections and 62 minor infections during 260 patient-years of follow-up. A lymphocyte count < or =1.0 x 10(9)/l at presentation was independently associated with an increased risk for major infection: hazard ratio 4.7 (95%CI 1.6-13.7), p = 0.005. SLEDAI, use of corticosteroids and immunosuppressive therapy were all not associated with increased risk of infection. DISCUSSION: Lymphopenia was an important risk factor for major infections in this group of Chinese patients in the early stages of SLE. SLE patients with lymphopenia at presentation should be closely monitored for the development of infective complications.

Adolescent↗
PubMed2004

The impact of diabetes mellitus on the prognostic value of a normal dobutamine stress echocardiogram in patients with intermediate to high cardiovascular risk.

INTRODUCTION: There is currently limited data on the prognostic value of a normal dobutamine stress echocardiogram (DSE) in patients with intermediate to high cardiovascular risk. The impact of diabetes mellitus, recently recognised as a cardiovascular risk-equivalent, has not been previously evaluated. This study aims to determine the prognostic value of a normal DSE in these patients. METHODS: The study population includes all patients with two cardiovascular risk factors or diabetes mellitus and a normal DSE (baseline and peak stress) with three months follow-up. A total of 122 patients (47 females, 75 males; mean age 59.6 years) were recruited. Impact of diabetes mellitus on subsequent cardiovascular events was determined. RESULTS: Diabetes mellitus was present in 32.8 percent, hypertension in 72.1 percent, smoking in 27.0 percent, family history of premature coronary artery disease in 15.6 percent, and hypercholesterolemia in 66.4 percent. On follow-up until 6.4 years (mean 4.1 years), there were four myocardial infarctions (0.8 percent per patient/year) and five revascularisation procedures (1.0 percent per patient/year). The majority of adverse events occurred among patients with diabetes mellitus (three out of four myocardial infarctions; four out of five revascularisations). Diabetes mellitus independently predicted subsequent cardiac events on both univariate and multivariate analyses (p value is equal to 0.015 and 0.011, respectively). Presence of diabetes mellitus also conferred a worse outcome on survival analysis (p value is equivalent to 0.0046). CONCLUSION: The presence of diabetes mellitus adversely affects clinical outcome despite a normal DSE. Patients without diabetes mellitus, but with intermediate to high cardiovascular risk, and a normal DSE have a better medium term outcome.

Adult↗
PubMed2003

Clinical progression and viral load in a community outbreak of coronavirus-associated SARS pneumonia: a prospective study.

BACKGROUND: We investigated the temporal progression of the clinical, radiological, and virological changes in a community outbreak of severe acute respiratory syndrome (SARS). METHODS: We followed up 75 patients for 3 weeks managed with a standard treatment protocol of ribavirin and corticosteroids, and assessed the pattern of clinical disease, viral load, risk factors for poor clinical outcome, and the usefulness of virological diagnostic methods. FINDINGS: Fever and pneumonia initially improved but 64 (85%) patients developed recurrent fever after a mean of 8.9 (SD 3.1) days, 55 (73%) had watery diarrhoea after 7.5 (2.3) days, 60 (80%) had radiological worsening after 7.4 (2.2) days, and respiratory symptoms worsened in 34 (45%) after 8.6 (3.0) days. In 34 (45%) patients, improvement of initial pulmonary lesions was associated with appearance of new radiological lesions at other sites. Nine (12%) patients developed spontaneous pneumomediastinum and 15 (20%) developed acute respiratory distress syndrome (ARDS) in week 3. Quantitative reverse-transcriptase (RT) PCR of nasopharyngeal aspirates in 14 patients (four with ARDS) showed peak viral load at day 10, and at day 15 a load lower than at admission. Age and chronic hepatitis B virus infection treated with lamivudine were independent significant risk factors for progression to ARDS (p=0.001). SARS-associated coronavirus in faeces was seen on RT-PCR in 65 (97%) of 67 patients at day 14. The mean time to seroconversion was 20 days. INTERPRETATION: The consistent clinical progression, shifting radiological infiltrates, and an inverted V viral-load profile suggest that worsening in week 2 is unrelated to uncontrolled viral replication but may be related to immunopathological damage.

Administration, Oral↗
PubMed2001

An efficient room-temperature silicon-based light-emitting diode.

There is an urgent requirement for an optical emitter that is compatible with standard, silicon-based ultra-large-scale integration (ULSI) technology. Bulk silicon has an indirect energy bandgap and is therefore highly inefficient as a light source, necessitating the use of other materials for the optical emitters. However, the introduction of these materials is usually incompatible with the strict processing requirements of existing ULSI technologies. Moreover, as the length scale of the devices decreases, electrons will spend increasingly more of their time in the connections between components; this interconnectivity problem could restrict further increases in computer chip processing power and speed in as little as five years. Many efforts have therefore been directed, with varying degrees of success, to engineering silicon-based materials that are efficient light emitters. Here, we describe the fabrication, using standard silicon processing techniques, of a silicon light-emitting diode (LED) that operates efficiently at room temperature. Boron is implanted into silicon both as a dopant to form a p-n junction, as well as a means of introducing dislocation loops. The dislocation loops introduce a local strain field, which modifies the band structure and provides spatial confinement of the charge carriers. It is this spatial confinement which allows room-temperature electroluminescence at the band-edge. This device strategy is highly compatible with ULSI technology, as boron ion implantation is already used as a standard method for the fabrication of silicon devices.

Journal Article↗
PubMed2001

Inflammatory pseudotumor of the heart causing aortic regurgitation.

Inflammatory pseudotumor is a tumor-like reactive lesion of unknown etiology that rarely affects the heart. We describe an unusual case of a cardiac inflammatory pseudotumor that involved the aortic valve and caused regurgitation in a 62-year-old man. The lesion was excised and the aortic valve was replaced, resulting in a favorable outcome for the patient.

Aortic Valve Insufficiency↗
PubMed2000

Cloning and characterization of two hydrophobin genes differentially expressed during fruit body development in Lentinula edodes.

Hydrophobins play important roles in morphogenesis and pathogenesis in fungi and fruit development in mushrooms. Two genes encoding hydrophobins (Le.hyd1 and Le.hyd2) were isolated during sequencing of random clones from a primordial cDNA library of Lentinula edodes. The nucleotide sequences of these two genes were determined. These two genes are 760 and 738 bp in length and the deduced amino acid sequences are homologous to various fungal hydrophobins with characteristic cysteine spacing. These hydrophobin genes are Class I hydrophobins judging by their conserved domains and hydropathy patterns. The transcript level of Le.hyd1 is high in primordium and that of Le.hyd2 is high in dikaryotic mycelial tissues. Poor expression of these two genes in monokaryotic parents indicates that these two genes are under mating-type regulation. We thus suggest that differential expression of these two L. edodes hydrophobins during fruit development may contribute to their distinct roles in fruiting of this mushroom.

Amino Acid Sequence↗
PubMed2000

Diagnosis of pacemaker lead infection using transoesophageal echocardiography: a case report.

INTRODUCTION: Vegetative lead infection is an uncommon complication of permanent pacemaker implantation. The diagnosis is difficult using conventional imaging methods. CLINICAL PICTURE: An elderly Indian woman with a history of diabetes mellitus developed Staphylococcus aureus infection after implementation of a permanent pacemaker. Following a non-diagnostic transthoracic echocardiogram, transoesophageal echocardiography was performed and showed a large vegetative mass attached to the pacemaker lead within the right atrium. TREATMENT: The pacemaker was removed and intravenous vancomycin administered for six weeks. OUTCOME: She was discharged well but demised two months later from a second episode of septicaemia. CONCLUSIONS: Pacemaker lead infection remains a challenging management problem. Transoesophageal echocardiography can facilitate its diagnosis.

Aged↗
PubMed2000

Initial experience of radiofrequency catheter ablation of supraventricular tachycardia in paediatric patients.

INTRODUCTION: The management of supraventricular tachycardia (SVT) in paediatric patients until recently has frequently been pharmacologic therapy, but this approach suffers from the drawbacks of treatment failure, development of drug intolerance and/or side-effects. AIM: In keeping with recent advances in paediatric cardiology, we share our experience with radiofrequency catheter ablation as an alternative and definitive modality of therapy. MATERIALS AND METHOD: 4 young patients with recurrent SVT underwent electrophysiologic study followed by radiofrequency ablation of the accessory pathways. RESULTS: Resolution of symptoms was achieved in all patients and no major complication was encountered. CONCLUSIONS: The ability to ablate permanently the reentrant circuit responsible for SVT has now permitted cure by non-surgical means, and is an important alternative to drug therapy in the management of SVT in children.

Adolescent↗
PubMed1999

Negative selection: a method for obtaining low-abundance cDNAs using high-density cDNA clone arrays.

The identification of the entire complement of genes expressed in a cell, tissue, or organism provides a framework for understanding biological properties and establishes a tool set for subsequent functional studies. The large-scale sequencing of randomly selected clones from cDNA libraries has been successfully employed as a method for identifying a large fraction of these expressed genes. However, this approach is limited by the inherent redundancy of cellular transcripts reflecting widely variant levels of gene transcription. As a result, a high percentage of transcript duplications are encountered as the number of sequenced clones accrues. To address this problem, we have developed a negative hybridization selection method that employs the hybridization of complex cDNA probes to high-density arrays of cDNA clones and the subsequent selection of clones with a null or low hybridization signal. This approach was applied to a cDNA library constructed from normal human prostate tissue and resulted in the reduction of highly expressed prostate cDNAs from 6.8 to 0.57% with an overall decline in clone redundancy from 33 to 11%. The selected clones also reflected a more diverse cDNA population, with 89% of the clones representing distinctly different cDNAs compared with 67% of the randomly selected clones. This method compares favorably with cDNA library re-association normalization approaches and offers several distinct advantages, including the flexibility to use previously prepared libraries, and the ability to employ an iterative screening approach for continued accrual of cDNAs representing rare transcripts.

DNA, Complementary↗
PubMed1999

Prostate cancer expression profiling by cDNA sequencing analysis.

Prostate cancer is a frequently diagnosed solid tumor that is originated mostly from prostate epithelium. One of the key issues in prostate cancer research is to develop molecular markers that can effectively detect and distinguish the progression and malignancy of prostate tumors. Automated, single-pass cDNA sequencing was utilized to rapidly identify expressed genes in a number of cDNA libraries constructed from various normal and tumor prostatic tissues. These included cell lines as well as short-term epithelial culture. A total of 6604 expressed sequence tags (ESTs) were generated and searched against on-line nucleotide and protein databases. A relational database centric software system was constructed to process, store, and analyze EST data rapidly. cDNA contigs were also obtained by assembly of multiple EST sequences. Protein structural signatures were annotated using motif analysis tools including BLOCKS and an in-house-designed neural network. Cross-library comparisons revealed their unique gene expression profiles. Several differentially expressed cDNA clones were identified, and their expression patterns were confirmed by RNA dot blot and RT-PCR analyses.

Cell Line↗
PubMed1999

Co-existing left atrial thrombus and myxoma in mitral stenosis--a diagnostic challenge.

We report an unusual case of an adult who underwent a mitral valve replacement with concomitant excision of the left atrial myxoma and thrombus. Echocardiography showed the presence of a large "thrombus" within the left atrial appendage, body and atrial septum. There was difficulty in trying to distinguish between the atrial thrombus and myxoma due to their morphological similarities. At time of surgery, frozen section confirmed the atrial septal component of the thrombus to be an atrial myxoma and the atrial septum was excised to obtain a clear margin.

Diagnosis, Differential↗
PubMed1998

An expressed-sequence-tag database of the human prostate: sequence analysis of 1168 cDNA clones.

The human prostate is a complex glandular organ with functional development under hormonal regulation. Diseases of the prostate result in significant morbidity and mortality in the form of benign prostatic hypertrophy and prostate adenocarcinoma. The characterization of the molecular framework of the human prostate at the level of expressed genes will facilitate the understanding of normal and pathological prostate biology. The purposes of this study were to acquire an initial assessment of the qualitative and quantitative diversity of gene expression in the normal human prostate and to determine the extent that genes with prostate-restricted expression can be assessed using an expressed sequence tag approach. We have constructed a directional cDNA library from normal adult human prostate tissue and partially sequenced the 5' end of 1168 randomly selected cDNA clones, resulting in more than 400 kb of DNA sequence. Homology searches of the sequenced cDNAs against the GenBank and dbEST databases revealed that 43% of the sequences are identical to human genes whose functions are known, 5% are similar but not identical to known genes in humans or lower organisms, 5% match the mitochondrial genome, 9% are composed of interspersed DNA repeats, 30% are homologous to sequences in the dbEST database without a described function, and 6% are novel sequences. A total of 780 distinct species were identified. In addition to the 74 novel transcripts, 4 genes, prostate-specific antigen (PSA), prostate secretory protein (PSP), prostate acid phosphatase (PAP), and human glandular kallekrein 2 (HK2), have no homologous sequences in the databases that originate from sources other than prostate and thus may represent genes with prostate-restricted expression. Sequences matching PSA, PSP, and PAP each accounted for > 1% of the total ESTs and represent highly abundant transcripts, correlating with the abundance of these proteins in the prostate gland. No novel transcripts were represented by more than one EST and thus are expressed at levels much lower than the known prostate-specific genes.

Adult↗
PubMed1998

Gastroesophageal reflux disease is a common cause of noncardiac chest pain in a country with a low prevalence of reflux esophagitis.

Gastroesophageal reflux disease is believed to be uncommon in the East. This study aimed to determine if such a condition was a significant cause of noncardiac chest pain in Singapore. Eighty consecutive patients with recurrent chest pain, who had cardiac and other obvious causes excluded, underwent esophagogastroduodenoscopy, standard manometry, acid perfusion test, and prolonged ambulatory pH and pressure monitoring. Endoscopic esophagitis, positive acid perfusion tests, pathologic reflux, and positive chest pain-reflux correlation were detected in 7/80 (8.8%), 11/70 (15.7%), 14/61 (23.0%), and 12/25 (48.0%) patients, respectively. Among those with pathologic reflux, endoscopic esophagitis was present in only two (14.3%). Overall, 32 (40%) patients had gastroesophageal reflux disease. Esophageal motility disorder, alone or in association with gastroesophageal reflux disease, was demonstrated in only five (6.3%) patients. Our results confirmed western reports that gastroesophageal reflux disease was a common cause of noncardiac chest pain, whereas motility disorder was an infrequent cause of such pain.

Adult↗
PubMed1998

Non-cardiac, non-oesophageal chest pain: the relevance of psychological factors.

BACKGROUND: No cause has been determined for chest pain that is neither cardiac nor oesophageal in origin. AIMS: To compare the prevalence of life-time psychiatric disorders and current psychological distress in three consecutive series of patients with chronic chest or abdominal pain. PATIENTS: Thirty nine patients with non-cardiac chest pain and no abnormality on oesophagogastroduodenoscopy, oesophageal manometry, and 24 hour pH monitoring; 22 patients with non-cardiac chest pain having endoscopic abnormality, oesophageal dysmotility, and/or pathological reflux; and 36 patients with biliary colic. METHODS: The Diagnostic Interview Schedule and the 28 item General Health Questionnaire were administered to all patients. RESULTS: Patients with non-cardiac chest pain and no upper gastrointestinal disease had a higher proportion of panic disorder (15%), obsessive-compulsive disorder (21%), and major depressive episodes (28%) than patients with gallstone disease (0%, p < 0.02; 3%, p < 0.02; and 8%, p < 0.05, respectively). In contrast, there were no differences between patients with non-cardiac chest pain and upper gastrointestinal disease and patients with gallstone disease in any of the DSM-111 defined lifetime psychiatric diagnoses. Using the General Health Questionnaire, 49% of patients with non-cardiac chest pain without upper gastrointestinal disease scored above the cut off point (that is, more than 4), which was considered indicative of non-psychotic psychiatric disturbance, whereas only 14% of patients with gallstones did so (p < 0.005). The proportions of such cases were however similar between patients with non-cardiac chest pain and upper gastrointestinal disease (27%) and patients with gallstones. CONCLUSIONS: Psychological factors may play a role in the pathogenesis of chest pain that is neither cardiac nor oesophagogastric in origin.

Adult↗