Displaying publications 21 - 33 of 33 in total

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  1. Fulltext Peptide Conjugate on Multilayer Graphene Oxide Film for the Osteogenic Differentiation of Human Wharton's Jelly-Derived Mesenchymal Stem Cells
    Puah PY, Moh PY, Sipaut CS, Lee PC, How SE
    Polymers (Basel), 2021 Sep 26;13(19).
    PMID: 34641106 DOI: 10.3390/polym13193290
    Graphene oxide (GO) is extensively studied as a template material for mesenchymal stem cell application due to its two-dimensional nature and unique functionalization chemistries. Herein, a new type of peptide-conjugated multilayer graphene oxide (peptide/m-GO film) was fabricated and used as biomaterial for culturing human Wharton's jelly-derived mesenchymal stem cells (WJ-MSCs). The characterization of the peptide/m-GO films was performed, and the biocompatibility of the WJ-MSCs on the peptide/m-GO films was investigated. The results demonstrated that the peptide conjugate on the m-GO film did not hamper the normal growth of WJ-MSCs but supported the growth of WJ-MSCs after the 6-day culture period. In addition, the osteogenic differentiation of WJ-MSCs on the peptide/m-GO films was enhanced as compared with the parent m-GO film. Therefore, such peptide-conjugated m-GO films could provide a highly biocompatible and multifunctional 2D material to tailor the potential application of WJ-MSCs in bone tissue regeneration.
  2. Fulltext High prevalence of alpha- and beta-thalassemia in the Kadazandusuns in East Malaysia: challenges in providing effective health care for an indigenous group
    Tan JA, Lee PC, Wee YC, Tan KL, Mahali NF, George E, et al.
    J Biomed Biotechnol, 2010;2010.
    PMID: 20871816 DOI: 10.1155/2010/706872
    Thalassemia can lead to severe transfusion-dependent anemia, and it is the most common genetic disorder in Malaysia. This paper aims to determine the prevalence of thalassemia in the Kadazandusuns, the largest indigenous group in Sabah, East Malaysia. α- and β-thalassemia were confirmed in 33.6% and 12.8%, of the individuals studied respectively. The high prevalence of α- and β-thalassemia in the Kadazandusuns indicates that thalassemia screening, genetic counseling, and prenatal diagnosis should be included as part of their healthcare system. This preliminary paper serves as a baseline for further investigations into the health and genetic defects of the major indigenous population in Sabah, East Malaysia.
  3. Fulltext Hexaplex PCR detection system for identification of five human Plasmodium species with an internal control
    Chew CH, Lim YA, Lee PC, Mahmud R, Chua KH
    J Clin Microbiol, 2012 Dec;50(12):4012-9.
    PMID: 23035191 DOI: 10.1128/JCM.06454-11
    Malaria remains one of the major killers of humankind and persists to threaten the lives of more than one-third of the world's population. Given that human malaria can now be caused by five species of Plasmodium, i.e., Plasmodium falciparum, Plasmodium vivax, Plasmodium malariae, Plasmodium ovale, and the recently included Plasmodium knowlesi, there is a critical need not only to augment global health efforts in malaria control but also, more importantly, to develop a rapid, accurate, species-sensitive/species-specific, and economically effective diagnostic method for malaria caused by these five species. Therefore, in the present study, a straightforward single-step hexaplex PCR system targeting five human Plasmodium 18S small-subunit rRNAs (ssu rRNAs) was designed, and the system successfully detected all five human malaria parasites. In addition, this system enables the differentiation of single infection as well as mixed infections up to the two-species level. This assay was validated with 50 randomly blinded test and 184 clinical samples suspected to indicate malaria. This hexaplex PCR system is not only an ideal alternative for routine malaria diagnosis in laboratories with conventional PCR machines but also adds value to diagnoses when there is a lack of an experienced microscopist or/and when the parasite morphology is confusing. Indeed, this system will definitely enhance the accuracy and accelerate the speed in the diagnosis of malaria, as well as improve the efficacy of malaria treatment and control, in addition to providing reliable data from epidemiological surveillance studies.
  4. Fulltext Pair-wise comparison analysis of differential expression of mRNAs in early and advanced stage primary colorectal adenocarcinomas
    Lau TP, Roslani AC, Lian LH, Chai HC, Lee PC, Hilmi I, et al.
    BMJ Open, 2014;4(8):e004930.
    PMID: 25107436 DOI: 10.1136/bmjopen-2014-004930
    To characterise the mRNA expression patterns of early and advanced stage colorectal adenocarcinomas of Malaysian patients.
  5. Variant Alleles in XRCC1 Arg194Trp and Arg399Gln Polymorphisms Increase Risk of Gastrointestinal Cancer in Sabah, North Borneo
    Halim NH, Chong ET, Goh LP, Chuah JA, See EU, Chua KH, et al.
    Asian Pac J Cancer Prev, 2016;17(4):1925-31.
    PMID: 27221877
    BACKGROUND: The XRCC1 protein facilitates various DNA repair pathways; single-nucleotide polymorphisms (SNPs) in this gene are associated with a risk of gastrointestinal cancer (GIC) with inconsistent results, but no data have been previously reported for the Sabah, North Borneo, population. We accordingly investigated the XRCC1 Arg194Trp and Arg399Gln SNPs in terms of GIC risk in Sabah.

    MATERIALS AND METHODS: We performed genotyping for both SNPs for 250 GIC patients and 572 healthy volunteers using a polymerase chain reaction- restriction fragment length polymorphism approach. We validated heterozygosity and homozygosity for both SNPs using direct sequencing.

    RESULTS: The presence of a variant 194Trp allele in the Arg194Trp SNP was significantly associated with a higher risk of GIC, especially with gastric and colorectal cancers. We additionally found that the variant 399Gln allele in Arg399Gln SNP was associated with a greater risk of developing gastric cancer. Our combined analysis revealed that inheritance of variant alleles in both SNPs increased the GIC risk in Sabah population. Based on our etiological analysis, we found that subjects ≥50 years and males who carrying the variant 194Trp allele, and Bajau subjects carrying the 399Gln allele had a significantly increased risk of GIC.

    CONCLUSIONS: Our findings suggest that inheritance of variant alleles in XRCC1 Arg194Trp and Arg399Gln SNPs may act as biomarkers for the early detection of GIC, especially for gastric and colorectal cancers in the Sabah population.

  6. Lack of correlation between X-ray repair cross-complementing group 1 gene polymorphisms and the susceptibility to colorectal cancer in a Malaysian cohort
    Lau TP, Lian LH, Cheah PL, Looi LM, Roslani AC, Goh KL, et al.
    Eur J Cancer Prev, 2017 11;26(6):506-510.
    PMID: 28059856 DOI: 10.1097/CEJ.0000000000000336
    X-ray repair cross-complementing group 1 (XRCC1) is one of the key components in the base excision repair pathway that repairs erroneous DNA lesions and removes nonbulky base adducts for the maintenance of genome integrity. Studies have revealed that differences in individual DNA repair capacity can impact the interindividual variation in cancer susceptibility, tumour aggressiveness and treatment response. The relationship between XRCC1 and sporadic colorectal cancer (CRC) susceptibility, which is hitherto inconclusive, has been explored in many association studies of different populations. In view of the conflicting findings generated, we aimed to investigate the association between XRCC1 and genetic predisposition to CRC among Malaysians. The present case-control association study was conducted on 130 CRC patients and 212 age-matched healthy controls. The genotyping of XRCC1 Arg194Trp, Arg280His and Arg399Gln single nucleotide polymorphisms was performed with allele-specific real-time PCR approach. This was followed by basic statistical analysis on the single nucleotide polymorphisms and haplotype data obtained. No significant difference in the allele and genotype frequencies was observed between CRC patients and healthy controls (P>0.05). There was also no association observed between XRCC1 haplotypes and CRC (P>0.05). In conclusion, a positive association between XRCC1 gene polymorphisms and CRC risk was not established in our Malaysian population.
  7. Fulltext Genetic diversity of circumsporozoite protein in Plasmodium knowlesi isolates from Malaysian Borneo and Peninsular Malaysia
    Chong ETJ, Neoh JWF, Lau TY, Lim YA, Chai HC, Chua KH, et al.
    Malar J, 2020 Oct 22;19(1):377.
    PMID: 33092594 DOI: 10.1186/s12936-020-03451-x
    BACKGROUND: Understanding the genetic diversity of candidate genes for malaria vaccines such as circumsporozoite protein (csp) may enhance the development of vaccines for treating Plasmodium knowlesi. Hence, the aim of this study is to investigate the genetic diversity of non-repeat regions of csp in P. knowlesi from Malaysian Borneo and Peninsular Malaysia.

    METHODS: A total of 46 csp genes were subjected to polymerase chain reaction amplification. The genes were obtained from P. knowlesi isolates collected from different divisions of Sabah, Malaysian Borneo, and Peninsular Malaysia. The targeted gene fragments were cloned into a commercial vector and sequenced, and a phylogenetic tree was constructed while incorporating 168 csp sequences retrieved from the GenBank database. The genetic diversity and natural evolution of the csp sequences were analysed using MEGA6 and DnaSP ver. 5.10.01. A genealogical network of the csp haplotypes was generated using NETWORK ver. 4.6.1.3.

    RESULTS: The phylogenetic analysis revealed indistinguishable clusters of P. knowlesi isolates across different geographic regions, including Malaysian Borneo and Peninsular Malaysia. Nucleotide analysis showed that the csp non-repeat regions of zoonotic P. knowlesi isolates obtained in this study underwent purifying selection with population expansion, which was supported by extensive haplotype sharing observed between humans and macaques. Novel variations were observed in the C-terminal non-repeat region of csp.

    CONCLUSIONS: The csp non-repeat regions are relatively conserved and there is no distinct cluster of P. knowlesi isolates from Malaysian Borneo and Peninsular Malaysia. Distinctive variation data obtained in the C-terminal non-repeat region of csp could be beneficial for the design and development of vaccines to treat P. knowlesi.

  8. Case-Control Study and Meta-Analysis of the Association Between LIPG rs9958947 SNP and Stroke Risk
    Phneh KY, Chong ETJ, Shah SS, Chia YK, Daud DMBA, Jalil E, et al.
    J Mol Neurosci, 2021 Oct;71(10):2085-2094.
    PMID: 33479916 DOI: 10.1007/s12031-021-01795-w
    The rs9958947 single nucleotide polymorphism (SNP) resides in the promoter region of the lipase G (LIPG) gene. This newly discovered SNP increases the risk of stroke in some Asian populations, including Chinese and Korean populations. Stroke is one of the top 5 leading causes of death in Malaysia, so it is of interest to investigate whether this SNP is associated with stroke risk in the Malaysian population. Therefore, this study investigates this association through a case-control study on a Malaysian population along with a comprehensive meta-analysis. Genotyping of LIPG rs9958947 SNP was performed for 241 Malaysians using real-time polymerase chain reaction, and the odds ratios (OR) with 95% confidence intervals were calculated. The meta-analysis was conducted using the software Comprehensive Meta-Analysis ver. 2.2.064. A p value less than 0.05 was considered statistically significant. We observed that the mean age of Malaysian stroke patients was less than that of stroke patients from Korea and China. The meta-analysis showed that the LIPG rs9958947 SNP was significantly associated with an increased risk of ischemic stroke in Asian populations (dominant (CC vs. CT + TT): OR = 1.45, p  0.05) and blood lipid levels.
  9. Esterification of residual palm oil using solid acid catalyst derived from rice husk
    Balan WS, Janaun J, Chung CH, Semilin V, Zhu Z, Haywood SK, et al.
    J Hazard Mater, 2021 02 15;404(Pt B):124092.
    PMID: 33091694 DOI: 10.1016/j.jhazmat.2020.124092
    In this study, carbon-silica based acid catalysts derived from rice husks (RH) were successfully synthesised using microwave (MW) technology. The results showed that MW sulphonation produced Sulphur (S) content of 17.2-18.5 times higher than in raw RH. Fourier-transform Infrared Spectroscopy (FTIR) showed peak at 1035 cm-1 which corresponded to O˭S˭O stretching of sulphonic (-SO3H) group. XRD showed sulfonated RH catalysts (SRHCs) have amorphous structure, and through SEM, broadening of the RH voids and also formation of pores is observed. RH600 had the highest surface area of 14.52 m2/g. SRHCs showed high catalytic activity for esterification of oleic acid with methanol with RH600 had the highest initial formation rate (6.33 mmolL-1min-1) and yield (97%). The reusability of the catalyst showed gradually dropped yield of product for every recycle, which might be due to leaching of -SO3H. Finally, esterification of oil recovered from palm oil mill effluent (POME) with methanol achieved a conversion of 87.3% free fatty acids (FFA) into fatty acid methyl esters (FAME).
  10. Fulltext Increased detection of Plasmodium knowlesi in Sandakan division, Sabah as revealed by PlasmoNex™
    Goh XT, Lim YA, Vythilingam I, Chew CH, Lee PC, Ngui R, et al.
    Malar J, 2013 Jul 31;12:264.
    PMID: 23902626 DOI: 10.1186/1475-2875-12-264
    BACKGROUND: Plasmodium knowlesi is a simian malaria parasite that is widespread in humans in Malaysian Borneo. However, little is known about the incidence and distribution of this parasite in the Sandakan division, Malaysian Borneo. Therefore, the aim of the present epidemiological study was to investigate the incidence and distribution of P. knowlesi as well as other Plasmodium species in this division based on a most recent developed hexaplex PCR system (PlasmoNex™).

    METHODS: A total of 189 whole blood samples were collected from Telupid Health Clinic, Sabah, Malaysia, from 2008 to 2011. All patients who participated in the study were microscopically malaria positive before recruitment. Complete demographic details and haematological profiles were obtained from 85 patients (13 females and 72 males). Identification of Plasmodium species was conducted using PlasmoNex™ targeting the 18S ssu rRNA gene.

    RESULTS: A total of 178 samples were positive for Plasmodium species by using PlasmoNex™. Plasmodium falciparum was identified in 68 samples (38.2%) followed by 64 cases (36.0%) of Plasmodium vivax, 42 (23.6%) cases of P. knowlesi, two (1.1%) cases of Plasmodium malariae and two (1.1%) mixed-species infections (i e, P. vivax/P. falciparum). Thirty-five PlasmoNex™ positive P. knowlesi samples were misdiagnosed as P. malariae by microscopy. Plasmodium knowlesi was detected in all four districts of Sandakan division with the highest incidence in the Kinabatangan district. Thrombocytopaenia and anaemia showed to be the most frequent malaria-associated haematological complications in this study.

    CONCLUSIONS: The discovery of P. knowlesi in Sandakan division showed that prospective studies on the epidemiological risk factors and transmission dynamics of P. knowlesi in these areas are crucial in order to develop strategies for effective malaria control. The availability of advanced diagnostic tool PlasmoNex™ enhanced the accuracy and accelerated the speed in the diagnosis of malaria.

  11. Fulltext A protocol and training guidelines for mosquito sampling in remote areas with limited power supply
    Ong SQ, Dawood MM, Rahman H, Alias MF, Moideen MA, Lee PC, et al.
    MethodsX, 2024 Jun;12:102563.
    PMID: 38328504 DOI: 10.1016/j.mex.2024.102563
    Mosquito-borne diseases pose a significant threat in many Southeast Asian countries, particularly through the sylvatic cycle, which has a wildlife reservoir in forests and rural areas. Studying the composition and diversity of vectors and pathogen transmission is especially challenging in forests and rural areas due to their remoteness, limited accessibility, lack of power, and underdeveloped infrastructure. This study is based on the WHO mosquito sampling protocol, modifies technical details to support mosquito collection in difficult-to-access and resource-limited areas. Specifically, we describe the procedure for using rechargeable lithium batteries and solar panels to power the mosquito traps, demonstrate a workflow for processing and storing the mosquitoes in a -20 °C freezer, data management tools including microclimate data, and quality assurance processes to ensure the validity and reliability of the results. A pre- and post-test was utilized to measure participant knowledge levels. Additional research is needed to validate this protocol for monitoring vector-borne diseases in hard-to-reach areas within other countries and settings.
  12. Fulltext R54C Mutation of NOTCH3 Gene in the First Rungus Family with CADASIL
    Lim KS, Tan AH, Lim CS, Chua KH, Lee PC, Ramli N, et al.
    PLoS One, 2015;10(8):e0135470.
    PMID: 26270344 DOI: 10.1371/journal.pone.0135470
    Cerebral autosomal dominant arteriopathy with subcortical infarcts and leukoencephalopathy (CADASIL) is a rare hereditary stroke caused by mutations in NOTCH3 gene. We report the first case of CADASIL in an indigenous Rungus (Kadazan-Dusun) family in Kudat, Sabah, Malaysia confirmed by a R54C (c.160C>T, p.Arg54Cys) mutation in the NOTCH3. This mutation was previously reported in a Caucasian and two Korean cases of CADASIL. We recruited two generations of the affected Rungus family (n = 9) and found a missense mutation (c.160C>T) in exon 2 of NOTCH3 in three siblings. Two of the three siblings had severe white matter abnormalities in their brain MRI (Scheltens score 33 and 50 respectively), one of whom had a young stroke at the age of 38. The remaining sibling, however, did not show any clinical features of CADASIL and had only minimal changes in her brain MRI (Scheltens score 17). This further emphasized the phenotype variability among family members with the same mutation in CADASIL. This is the first reported family with CADASIL in Rungus subtribe of Kadazan-Dusun ethnicity with a known mutation at exon 2 of NOTCH3. The penetrance of this mutation was not complete during the course of this study.
  13. Fulltext Prevalence of Coronavirus Disease 2019 (COVID-19) in Different Clinical Stages before the National COVID-19 Vaccination Programme in Malaysia: A Systematic Review and Meta-Analysis
    Ng JW, Chong ETJ, Tan YA, Lee HG, Chan LL, Lee QZ, et al.
    Int J Environ Res Public Health, 2022 Feb 16;19(4).
    PMID: 35206404 DOI: 10.3390/ijerph19042216
    More than 1.75 million COVID-19 infections and 16 thousand associated deaths have been reported in Malaysia. A meta-analysis on the prevalence of COVID-19 in different clinical stages before the National COVID-19 Vaccination Program in Malaysia is still lacking. To address this, the disease severity of a total of 215 admitted COVID-19 patients was initially recorded in the early phase of this study, and the data were later pooled into a meta-analysis with the aim of providing insight into the prevalence of COVID-19 in 5 different clinical stages during the outset of the COVID-19 pandemic in Malaysia. We have conducted a systematic literature search using PubMed, Web of Science, Scopus, ScienceDirect, and two preprint databases (bioRxiv and medRxiv) for relevant studies with specified inclusion and exclusion criteria. The quality assessment for the included studies was performed using the Newcastle-Ottawa Scale. The heterogeneity was examined with an I2 index and a Q-test. Funnel plots and Egger's tests were performed to determine publication bias in this meta-analysis. Overall, 5 studies with 6375 patients were included, and the pooled prevalence rates in this meta-analysis were calculated using a random-effect model. The highest prevalence of COVID-19 in Malaysia was observed in Stage 2 cases (32.0%), followed by Stage 1 (27.8%), Stage 3 (17.1%), Stage 4 (7.6%), and Stage 5 (3.4%). About two-thirds of the number of cases have at least one morbidity, with the highest percentage of hypertension (66.7%), obesity (55.5%), or diabetes mellitus (33.3%) in Stage 5 patients. In conclusion, this meta-analysis suggested a high prevalence of COVID-19 occurred in Stage 2. The prevalence rate in Stage 5 appeared to be the lowest among COVID-19 patients before implementing the vaccination program in Malaysia. These meta-analysis data are critically useful for designing screening and vaccination programs and improving disease management in the country.
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