Displaying all 11 publications

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  1. Chan SW, Nathan S
    FEMS Immunol. Med. Microbiol., 2005 Jan 1;43(1):37-44.
    PMID: 15607634
    Filamentous phage random peptide libraries were used to identify the epitopes of Burkholderia pseudomallei protease by panning against IgG polyclonal sera that exhibited protease neutralizing properties. The isolated fusion peptides presented a consensus peptide sequence, TKSMALSG, which closely resembles part of the active site sequence, 435GTSMATPHVAG445, of B. pseudomallei serine metalloprotease. By comparing the consensus sequence, TKSMALSG, with the predicted three-dimensional molecular model of B. pseudomallei serine metalloprotease, it appears that the potential antibody binding epitope was buried within the molecule. This active site was conformational whereby one continuous sub-region (SMA) was located between two discontinuous sub-regions, supplied by the flanking residues in the same polypeptide. All phages selected from the biopanning with IgG polyclonal sera showed good binding towards the polyclonal antibodies when compared to the negative control. In addition, these peptide-bearing phages showed competitive inhibition of B. pseudomallei serine metalloprotease binding to the polyclonal IgG.
  2. Chan SW, Kallarakkal TG, Abraham MT
    Asian Pac J Cancer Prev, 2014;15(5):2145-52.
    PMID: 24716948
    BACKGROUND: The survival rate for oral squamous cell carcinoma (OSCC) has remained generally unchanged in the past three decades, underlining the need for more biomarkers to be developed to aid prognostication and effective management. The prognostic potential of E-cadherin expression in OSCCs has been variable in previous studies while galectin-9 expression has been correlated with improved prognosis in other cancers. The aim of the present study was to investigate the expression of galectin-9 and E-cadherin in OSCC and their potential as prognostic biomarkers.

    MATERIALS AND METHODS: E-cadherin and Galectin-9 expression was examined by immunohistochemistry in 32 cases of OSCC of the buccal mucosa (13 with and 19 without lymph node metastasis), as well as 6 samples of reactive lesions and 5 of normal buccal mucosa.

    RESULTS: The expression of E-cadherin in OSCC was significantly lower than the control tissues but galectin-9 expression was conversely higher. Median E-cadherin HSCOREs between OSCCs positive and negative for nodal metastasis were not significantly different. Mean HSCOREs for galectin-9 in OSCC without lymph node metastasis (127.7 ± 81.8) was higher than OSCC with lymph node metastasis (97.9 ± 62.9) but this difference was not statistically significant.

    CONCLUSIONS: E-cadherin expression is reduced whilst galectin-9 expression is increased in OSCC. However, the present results suggest that E-cadherin and galectin-9 expression may not be useful as prognostic markers for OSCC.

  3. Chan SW, Ong GI, Nathan S
    J. Biochem. Mol. Biol., 2004 Sep 30;37(5):556-64.
    PMID: 15479619
    A recombinant Fab monoclonal antibody (Fab) C37, previously obtained by phage display and biopanning of a random antibody fragment library against Burkholderia pseudomallei protease, was expressed in different strains of Escherichia coli. E. coli strain HB2151 was deemed a more suitable host for Fab expression than other E. coli strains when grown in media supplemented with 0.2 % glycerol. The expressed Fab fragment was purified by affinity chromatography on a Protein G-Sepharose column, and the specificity of the recombinant Fab C37 towards B. pseudomallei protease was proven by Western blotting, enzyme-linked immunosorbent assay (ELISA) and by proteolytic activity neutralization. In addition, polyclonal antibodies against B. pseudomallei protease were produced in rabbits immunized with the protease. These were isolated from high titer serum by affinity chromatography on recombinant-Protein A-Sepharose. Purified polyclonal antibody specificity towards B. pseudomallei protease was proven by Western blotting and ELISA.
  4. Chan SW, Ismail Z, Sumintono B
    PLoS One, 2016;11(11):e0163846.
    PMID: 27812091 DOI: 10.1371/journal.pone.0163846
    Based on a synthesis of literature, earlier studies, analyses and observations on high school students, this study developed an initial framework for assessing students' statistical reasoning about descriptive statistics. Framework descriptors were established across five levels of statistical reasoning and four key constructs. The former consisted of idiosyncratic reasoning, verbal reasoning, transitional reasoning, procedural reasoning, and integrated process reasoning. The latter include describing data, organizing and reducing data, representing data, and analyzing and interpreting data. In contrast to earlier studies, this initial framework formulated a complete and coherent statistical reasoning framework. A statistical reasoning assessment tool was then constructed from this initial framework. The tool was administered to 10 tenth-grade students in a task-based interview. The initial framework was refined, and the statistical reasoning assessment tool was revised. The ten students then participated in the second task-based interview, and the data obtained were used to validate the framework. The findings showed that the students' statistical reasoning levels were consistent across the four constructs, and this result confirmed the framework's cohesion. Developed to contribute to statistics education, this newly developed statistical reasoning framework provides a guide for planning learning goals and designing instruction and assessments.
  5. Goh YC, Chan SW, Siar CH
    Malays J Pathol, 2019 Dec;41(3):303-311.
    PMID: 31901915
    INTRODUCTION: Ameloblastoma is a benign but locally invasive odontogenic epithelial neoplasm with a high recurrence rate after treatment. The two main subsets encountered clinically are unicystic (UA) and solid/multicystic ameloblastoma (SMA). Currently neoplastic progression of many tumour types are believed to be related to parenchyma-stromal cell-cell interactions mediated by cytokines notably interleukins (IL). However their roles in ameloblastoma remain ill-understood.

    MATERIALS AND METHODS: Thirty-nine formalin-fixed paraffin-embedded ameloblastoma cases comprising unicystic ameloblastoma (n=19) and solid/multicystic ameloblastoma (n=20) were subjected to IHC staining for IL-1α, IL-1β, IL-6 and IL-8. A semi-quantitative method was used to evaluate the expression levels of these cytokines according to cell types in the tumoural parenchyma and stroma.

    RESULTS: Major findings were upregulations of IL-1α and IL-6 in SMA compared to UA. Both cytokines were heterogeneously detected in the tumoural parenchyma and stroma. Within the neoplastic epithelial compartment, IL-1α expression was more frequently detected in PA-like cells in UA whereas it was more frequently encountered in SR-like cells in SMA. IL-6 demonstrated higher expression levels in the stromal compartment of SMA. IL-1β and IL-8 were markedly underexpressed in both tumour subsets.

    CONCLUSIONS: Overexpression of IL-1α in SMA suggests that this growth factor might play a role in promoting bone resorption and local invasiveness in this subtype. The expression levels of IL-1α and IL-6 in three cellular localizations indicate that parenchymal-stromal components of ameloblastoma interact reciprocally via IL-1α and IL-6 to create a microenvironment conducive for tumour progression.

  6. Chan SW, Liew LH, Wong GR, Kallarakkal TG, Abraham MT, Ramanathan A, et al.
    Int. J. Surg. Pathol., 2016 Aug;24(5):401-9.
    PMID: 27006298 DOI: 10.1177/1066896916639372
    BACKGROUND: Turnaround time (TAT) is the benchmark to assess the performance of a laboratory, pathologists, and pathology services, but there are few articles on TAT of surgical pathology, particularly in relation to oral or head and neck specimens. This study investigates the TAT for oral histopathology reporting in an academic institution's training laboratory and offers recommendations to achieve better overall quality of diagnostic services.

    METHODS: This study examined data obtained from biopsy request forms for specimens received from the Oro-Maxillofacial Surgery Department of Hospital Tengku Ampuan Rahimah Klang in the Oral Pathology Diagnostic Laboratory of the Faculty of Dentistry, University of Malaya, over a period of 3 years between January 2012 and October 2014.

    RESULTS: TAT for surgical and decalcified specimens were increased significantly compared to biopsies. Additional special handling did not influence TAT, but increased specimen volume resulted in greater TAT. Slide interpretation was the most time-consuming stage during histopathology reporting. Overall, mean TAT was acceptable for most specimens, but the TAT goals were less than satisfactory.

    CONCLUSION: A TAT goal appropriate for this laboratory may hence be established based on this study. Collective efforts to improve the TAT for various specimens are essential for better laboratory performance in the future.
  7. Lee YH, Baharuddin NA, Chan SW, Rahman MT, Bartold PM, Sockalingam S, et al.
    Clin Oral Investig, 2021 Mar;25(3):1441-1450.
    PMID: 32656595 DOI: 10.1007/s00784-020-03452-9
    OBJECTIVES: It has been proposed that citrullination and carbamylation occur in the inflamed periodontium and could be the plausible mechanisms for the generation of antigens involved in the development and progression of RA. The purpose of this study was to determine the presence and location of citrullinated and carbamylated proteins in the gingival tissues and compare their abundance in periodontitis (PD) patients with or without RA.

    MATERIALS AND METHODS: Gingival tissue samples of healthy (n = 5), PD with RA (n = 5) and PD without RA (n = 5) were collected. Specimens were formalin fixed, paraffin embedded and sectioned at 4 μm. The tissue sections were analysed for the presence of citrullinated and carbamylated proteins by immunohistochemistry. Semi-quantitative analysis was performed to quantify and compare the protein abundance between groups.

    RESULTS: The number of cells containing citrullinated and carbamylated proteins with higher intensity was markedly increased in gingival tissues from PD with or without RA in comparison with healthy controls.

    CONCLUSION: Inflamed gingival tissue is a potential source of citrullinated and carbamylated proteins other than synovial tissues. The extent to which the local accumulation of these proteins contributes to the pathogenesis of RA needs further elucidation.

    CLINICAL RELEVANCE: If PD is a potential source of post-translationally modified proteins, untreated PD should not be taken lightly in the context of RA. Hence, addressing gingival inflammation should be viewed as an important preventive measure in the general population not only for the progression of periodontal disease but also reducing the risk of developing extra-oral comorbidities.

  8. Chan SW, Mirhosseini H, Taip FS, Ling TC, Nehdi IA, Tan CP
    Food Sci Biotechnol, 2016;25(Suppl 1):53-62.
    PMID: 30263486 DOI: 10.1007/s10068-016-0098-3
    The present study is aimed to prepare κ-carrageenan microparticles for the encapsulation of model drug, coenzyme Q10 (CoQ10). A face-centered central composite design was employed to study the effects of three different formulation variables (κ-carrageenan, emulsifier, and oil). The powder yield was found inversely affected by the κ-carrageenan and oil concentration. The encapsulation efficiency was maximized in the region of the middle level κ-carrageenan concentration, the high level emulsifier concentration, and the low level oil concentration. The emulsifier concentration was the most influential variable on the particle size of powder. The optimal formulation was reported as 0.91% (w/v) κ-carrageenan concentration, 0.64% (w/v) emulsifier, and 1.0% (w/w) oil. Both differential scanning colorimeter and X-ray diffraction analyses proved that incorporation of CoQ10 into κ- carrageenan microcapsules resulted in amorphous powder with significantly (p<0.05) higher water solubility compared to pure CoQ10 and physical mixture in the crystalline form.
  9. Chan SW, Looi CK, Ho WK, Huang W, Seow P, Wu L
    Heliyon, 2021 Sep;7(9):e07922.
    PMID: 34527824 DOI: 10.1016/j.heliyon.2021.e07922
    Despite the increasing presence of computational thinking (CT) in the mathematics context, the connection between CT and mathematics in a practical classroom context is an important area for further research. This study intends to investigate the impact of CT activities in the topic of number patterns on the learning performance of secondary students in Singapore. The Rasch model analysis was employed to assess differences of ability between students from the experimental group and control group. 106 Secondary One students (age 13 years old) from a secondary school in Singapore took part in this study. A quasi-experimental non-equivalent groups design was utilized where 70 students were assigned into the experimental group, and 36 students were assigned into the control group. The experimental group was given intervention with CT-infused activities both on- and off-computer, while the control group received no such intervention. Both groups were administered the pretest before the intervention and the posttest after the intervention. The data gathered were analyzed using the partial credit version of the Rasch model. Analysis of pretest and posttest results revealed that the performance of the experimental group was similar to the control group. The findings did not support the hypothesis that integrating CT in lessons can result in improved mathematics learning. However, the drastic improvement was observed in individual students from the experimental group, while there is no obvious or extreme improvement for the students from the control group. This study provides some new empirical evidence and practical contributions to the infusion of CT practices in the mathematics classroom.
  10. Haron N, Rajendran S, Kallarakkal TG, Zain RB, Ramanathan A, Abraham MT, et al.
    Oral Dis, 2023 Mar;29(2):380-389.
    PMID: 33914993 DOI: 10.1111/odi.13892
    OBJECTIVE: To evaluate the accuracy of MeMoSA®, a mobile phone application to review images of oral lesions in identifying oral cancers and oral potentially malignant disorders requiring referral.

    SUBJECTS AND METHODS: A prospective study of 355 participants, including 280 with oral lesions/variants was conducted. Adults aged ≥18 treated at tertiary referral centres were included. Images of the oral cavity were taken using MeMoSA®. The identification of the presence of lesion/variant and referral decision made using MeMoSA® were compared to clinical oral examination, using kappa statistics for intra-rater agreement. Sensitivity, specificity, concordance and F1 score were computed. Images were reviewed by an off-site specialist and inter-rater agreement was evaluated. Images from sequential clinical visits were compared to evaluate observable changes in the lesions.

    RESULTS: Kappa values comparing MeMoSA® with clinical oral examination in detecting a lesion and referral decision was 0.604 and 0.892, respectively. Sensitivity and specificity for referral decision were 94.0% and 95.5%. Concordance and F1 score were 94.9% and 93.3%, respectively. Inter-rater agreement for a referral decision was 0.825. Progression or regression of lesions were systematically documented using MeMoSA®.

    CONCLUSION: Referral decisions made through MeMoSA® is highly comparable to clinical examination demonstrating it is a reliable telemedicine tool to facilitate the identification of high-risk lesions for early management.

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