Displaying all 17 publications

  1. Sim JH, Kamaruddin AH
    Bioresour Technol, 2008 May;99(8):2724-35.
    PMID: 17697778
    Efforts in optimizing reducing agents, cysteine-HCl.H2O and sodium sulfide in order to attain satisfactory responses during acetic acid fermentation have been carried out in this study. Cysteine-HCl.H2O each with five concentrations (0.00-0.50 g/L) was optimized one at a time and followed by sodium sulfide component (0.00-0.50 g/L). Response surface methodology (RSM) was used to determine the optimum concentrations of cysteine-HCl.H2O and sodium sulfide. The statistical analysis showed that the amount of cells produced and efficiency in CO conversion were not affected by sodium sulfide concentration. However, sodium sulfide is required as it does influence the acetic acid production. The optimum reducing agents for acetic acid fermentation was at 0.30 g/L cysteine-HCl.H2O and sodium sulfide respectively and when operated for 60 h cultivation time resulted in 1.28 g/L acetic acid production and 100% CO conversion.
  2. Sim JH, Kamaruddin AH, Bhatia S
    Bioresour Technol, 2010 Dec;101(23):8948-54.
    PMID: 20675129 DOI: 10.1016/j.biortech.2010.07.039
    The objective of this research is to investigate the potential of transesterification of crude palm oil (CPO) to biodiesel at 30 degrees C. The mass transfer limitations problem crucial at 30 degrees C due to the viscosity of CPO has been addressed. The process parameters that are closely related to mass transfer effects like enzyme loading, agitation speed and reaction time were optimized. An optimum methanol to oil substrate molar ratio at 6.5:1 was observed and maintained throughout the experiments. The optimum operating condition for the transesterification process was found at 6.67 wt% of enzyme loading and at 150 rpm of agitation speed. The corresponding initial reaction and FAME yield obtained at 6 h were 89.29% FAME yield/hr and 85.01%, respectively. The 85% FAME yield obtained at 30 degrees C operation of CPO transesterification shows that the process is potentially feasible for the biodiesel synthesis.
  3. Khoo CH, Sim JH, Salleh NA, Cheah YK
    Antonie Van Leeuwenhoek, 2015 Jan;107(1):23-37.
    PMID: 25312847 DOI: 10.1007/s10482-014-0300-7
    Salmonella is an important food-borne pathogen causing disease in humans and animals worldwide. Salmonellosis may be caused by any one of over 2,500 serovars of Salmonella. Nonetheless, Salmonella enterica serovar Typhimurium and Salmonella enterica serovar Agona are the second most prevalent serovars isolated from humans and livestock products respectively. Limited knowledge is available about the virulence mechanisms responsible for diarrheal disease caused by them. To investigate the contribution of sopB, sopD and pipD as virulence factors in intracellular infections and the uniqueness of these bacteria becoming far more prevalent than other serovars, the infection model of Caenorhabditis elegans and phenotypic microarray were used to characterize their mutants. The strains containing the mutation in sopB, sopD and pipD genes were constructed by using latest site-specific group II intron mutagenesis approach to reveal the pathogenicity of the virulence factors. Overall, we observed that the mutations in sopB, sopD and pipD genes of both serovars did not exhibit significant decrease in virulence towards the nematode. This may indicate that these virulence effectors may not be universal virulence factors involved in conserved innate immunity. There are significant phenotypic differences amongst strains carrying sopB, sopD and pipD gene mutations via the analysis of biochemical profiles of the bacteria. Interestingly, mutant strains displayed different susceptibility to chemical stressors from several distinct pharmacological and structural classes when compared to its isogenic parental strains. These metabolic and chemosensitivity assays also revealed multiple roles of Salmonella virulence factors in nutrient metabolism and antibiotic resistance.
  4. Hong WH, Vadivelu J, Daniel EG, Sim JH
    Med Educ Online, 2015;20:27561.
    PMID: 26314338 DOI: 10.3402/meo.v20.27561
    Studies have shown the importance of metacognition in medical education. Metacognitive skills consist of two dimensions: knowledge of metacognition and regulation of metacognition.
  5. Khor GK, Sim JH, Kamaruddin AH, Uzir MH
    Bioresour Technol, 2010 Aug;101(16):6558-61.
    PMID: 20363621 DOI: 10.1016/j.biortech.2010.03.047
    In order to characterize enzyme activity and stability corresponding to temperature effects, thermodynamic studies on commercial immobilized lipase have been carried out via enzymatic transesterification. An optimum temperature of 40 degrees C was obtained in the reaction. The decreasing reaction rates beyond the optimum temperature indicated the occurrence of reversible enzyme deactivation. Thermodynamic studies on lipase denaturation exhibited a first-order kinetics pattern, with considerable stability through time shown by the lipase as well. The activation and deactivation energies were 22.15 kJ mol(-1) and 45.18 kJ mol(-1), respectively, implying more energy was required for the irreversible denaturation of the enzyme to occur. At water content of 0.42%, the initial reaction rate and FAME yield displayed optimum values of 3.317 g/L min and 98%, respectively.
  6. Sim JH, Khoo CH, Lee LH, Cheah YK
    J. Microbiol. Biotechnol., 2010 Apr;20(4):651-8.
    PMID: 20467234
    Garcinia is commonly found in Malaysia, but limited information is available regarding endophytic fungi associated with this plant. In this study, 24 endophytic fungi were successfully recovered from different parts of two Garcinia species. Characterization of endophytic fungi was performed based on the conserved internal transcribed spacer (ITS) region sequence analysis and the antimicrobial properties. Results revealed that fruits of the plant appeared to be the highest inhabitation site (38 %) as compared with others. Glomerella sp., Guignardia sp., and Phomopsis sp. appeared to be the predominant endophytic fungi group in Garcinia mangostana and Garcinia parvifolia. Phylogenetic relationships of the isolated endophytic fungi were estimated from the sequences of the ITS region. On the other hand, antibacterial screening showed 11 of the isolates possessed positive response towards pathogenic and nonpathogenic bacteria. However, there was no direct association between certain antibacterial properties with the specific genus observed.
  7. Sim JH, Ngan OMY, Ng HK
    J Med Educ Curric Dev, 2019 12 02;6:2382120519883887.
    PMID: 31832540 DOI: 10.1177/2382120519883887
    Introduction: A global trend in medical education is the inclusion of bioethics teaching in medical programme. The objective of this article is to describe the current state of bioethics education in the medical programme among Malaysian medical schools.

    Method: A national survey was conducted among Malaysian medical schools between January and March 2019. One representative from each medical school was invited to respond to the survey. Respondents were faculty members involved in teaching and assessment of bioethics in their medical schools, or/and in developing and coordinating bioethics curriculum. Descriptive statistics were reported.

    Findings: Out of 30 medical schools, 11 completed and returned the survey (overall response rate = 36.7%). Of these 11 schools, 6/10 (60%) were from public institutions while 5/20 (25%) were from private institutions. All except 1 school implemented a formal bioethics curriculum. A wide range of bioethics topics are currently taught in the medical programme. The majority involved in teaching bioethics were health care professionals (mainly clinicians), followed by lawyers. Lecture and attendance, respectively, are the most common teaching and assessment method. Major barriers to the implementation of bioethics education included limited qualified teaching staff (6/11 = 54.5%), no established curriculum to follow (5/11 = 45.5%), limited financial resources to hire qualified staff (4/11 = 36.4%), and no consensus among faculty members (4/11 = 36.4%).

    Conclusion: Bioethics education in Malaysia is relatively new and mostly limited by a shortage of scholars in bioethics. National support and institutional collaboration in providing bioethics training is the key to enhance the quality of bioethics education.

  8. Sim JH, Tong WT, Hong WH, Vadivelu J, Hassan H
    Med Educ Online, 2015;20:28612.
    PMID: 26511792 DOI: 10.3402/meo.v20.28612
    INTRODUCTION: Assessment environment, synonymous with climate or atmosphere, is multifaceted. Although there are valid and reliable instruments for measuring the educational environment, there is no validated instrument for measuring the assessment environment in medical programs. This study aimed to develop an instrument for measuring students' perceptions of the assessment environment in an undergraduate medical program and to examine the psychometric properties of the new instrument.
    METHOD: The Assessment Environment Questionnaire (AEQ), a 40-item, four-point (1=Strongly Disagree to 4=Strongly Agree) Likert scale instrument designed by the authors, was administered to medical undergraduates from the authors' institution. The response rate was 626/794 (78.84%). To establish construct validity, exploratory factor analysis (EFA) with principal component analysis and varimax rotation was conducted. To examine the internal consistency reliability of the instrument, Cronbach's α was computed. Mean scores for the entire AEQ and for each factor/subscale were calculated. Mean AEQ scores of students from different academic years and sex were examined.
    RESULTS: Six hundred and eleven completed questionnaires were analysed. EFA extracted four factors: feedback mechanism (seven items), learning and performance (five items), information on assessment (five items), and assessment system/procedure (three items), which together explained 56.72% of the variance. Based on the four extracted factors/subscales, the AEQ was reduced to 20 items. Cronbach's α for the 20-item AEQ was 0.89, whereas Cronbach's α for the four factors/subscales ranged from 0.71 to 0.87. Mean score for the AEQ was 2.68/4.00. The factor/subscale of 'feedback mechanism' recorded the lowest mean (2.39/4.00), whereas the factor/subscale of 'assessment system/procedure' scored the highest mean (2.92/4.00). Significant differences were found among the AEQ scores of students from different academic years.
    CONCLUSIONS: The AEQ is a valid and reliable instrument. Initial validation supports its use to measure students' perceptions of the assessment environment in an undergraduate medical program.
    KEYWORDS: assessment environment; development; instrument; psychometric properties; validation
  9. Sim JH, Abdul Aziz YF, Mansor A, Vijayananthan A, Foong CC, Vadivelu J
    Med Educ Online, 2015;20:26185.
    PMID: 25697602 DOI: 10.3402/meo.v20.26185
    INTRODUCTION: The purpose of this study was to compare students' performance in the different clinical skills (CSs) assessed in the objective structured clinical examination.
    METHODS: Data for this study were obtained from final year medical students' exit examination (n=185). Retrospective analysis of data was conducted using SPSS. Means for the six CSs assessed across the 16 stations were computed and compared.
    RESULTS: Means for history taking, physical examination, communication skills, clinical reasoning skills (CRSs), procedural skills (PSs), and professionalism were 6.25±1.29, 6.39±1.36, 6.34±0.98, 5.86±0.99, 6.59±1.08, and 6.28±1.02, respectively. Repeated measures ANOVA showed there was a significant difference in the means of the six CSs assessed [F(2.980, 548.332)=20.253, p<0.001]. Pairwise multiple comparisons revealed significant differences between the means of the eight pairs of CSs assessed, at p<0.05.
    CONCLUSIONS: CRSs appeared to be the weakest while PSs were the strongest, among the six CSs assessed. Students' unsatisfactory performance in CRS needs to be addressed as CRS is one of the core competencies in medical education and a critical skill to be acquired by medical students before entering the workplace. Despite its challenges, students must learn the skills of clinical reasoning, while clinical teachers should facilitate the clinical reasoning process and guide students' clinical reasoning development.
    KEYWORDS: OSCE; clinical skills; student performance
  10. Khoo CH, Cheah YK, Lee LH, Sim JH, Salleh NA, Sidik SM, et al.
    Antonie Van Leeuwenhoek, 2009 Nov;96(4):441-57.
    PMID: 19565351 DOI: 10.1007/s10482-009-9358-z
    The increased occurrence of Salmonella occurrence in local indigenous vegetables and poultry meat can be a potential health hazards. This study is aimed to detect the prevalence of twenty different virulence factors among Salmonella enterica strains isolated from poultry and local indigenous vegetables in Malaysia via an optimized, rapid and specific multiplex PCR assay. The assay encompasses a total of 19 Salmonella pathogenicity islands genes and a quorum sensing gene (sdiA) in three multiplex reaction sets. A total of 114 Salmonella enterica isolates belonging to 38 different serovars were tested. Each isolate in under this study was found to possess up to 70% of the virulence genes tested and exhibited variable pathogenicity gene patterns. Reproducibility of the multiplex PCR assay was found to be 100% and the detection limit of the optimized multiplex PCR was tested with lowest detectable concentration of DNA 0.8 pg microl(-1). This study demonstrated various Salmonella pathogenicity island virulence gene patterns even within the same serovar. This sets of multiplex PCR system provide a fast and reliable typing approach based on Salmonella pathogenicity islands, thus enabling an effective monitoring of emerging pathogenic Salmonella strains as an additional tool in Salmonella surveillance studies.
  11. Jamaludin NS, Goh ZJ, Cheah YK, Ang KP, Sim JH, Khoo CH, et al.
    Eur J Med Chem, 2013 Sep;67:127-41.
    PMID: 23856069 DOI: 10.1016/j.ejmech.2013.06.038
    The synthesis and characterisation of R3PAu[S2CN((i)Pr)CH2CH2OH], for R = Ph (1), Cy (2) and Et (3)4, is reported. Compounds 1-3 are cytotoxic against the doxorubicin-resistant breast cancer cell line, MCF-7R, with 1 exhibiting greater potency and cytotoxicity than either of doxorubicin and cisplatin. Based on human apoptosis PCR-array analysis, caspase activities, DNA fragmentation, cell apoptotic assays, intracellular reactive oxygen species (ROS) measurements and human topoisomerase I inhibition, induction of apoptosis by 1, and necrosis by 2 and 3, are demonstrated, by both extrinsic and intrinsic pathways. Compound 1 activates the p53 gene, 2 activates only the p73 gene, whereas 3 activates both the p53 and p73 genes. Compounds 1 and 3 activate NF-κB, and each inhibits topoisomerase I.
  12. Chen BJ, Jamaludin NS, Khoo CH, See TH, Sim JH, Cheah YK, et al.
    J. Inorg. Biochem., 2016 10;163:68-80.
    PMID: 27529597 DOI: 10.1016/j.jinorgbio.2016.08.002
    Four compounds, R3PAu[S2CN(CH2CH2OH)2], R=Ph (1) and cyclohexyl (2), and Et3PAuS2CNRꞌ2, Rꞌ=Rꞌ=Et (3) and Rꞌ2=(CH2)4(4), have been evaluated for antibacterial activity against a panel of 24 Gram positive (8) and Gram negative (16) bacteria. Based on minimum inhibitory concentration (MIC) scores, compounds 1 and 2 were shown to be specifically potent against Gram positive bacteria whereas compounds 3 and, to a lesser extent, 4 exhibited broad range activity. All four compounds were active against methicillin resistant Staphylococcus aureus (MRSA). Time kill assays revealed the compounds to exhibit both time- and concentration-dependent pharmacokinetics against susceptible bacteria. Each compound was bactericidal against one or more bacteria with 3 being especially potent after 8h exposure; compounds 1 and 3 were bactericidal against MRSA. Compound 3 was the most effective bactericide across the series especially toward B. subtilis, S. saprophyticus, A. hydrophila, P. vulgaris, and V. parahaemolyticus. This study demonstrates the potential of this class of compounds as antibacterial agents, either broad range or against specific bacteria.
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