Displaying publications 1 - 20 of 44 in total

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  1. Yee CN, Ooi CHR, Tan LP, Misran M, Tang NT
    PLoS One, 2019;14(3):e0213697.
    PMID: 30913207 DOI: 10.1371/journal.pone.0213697
    That water may not be an inert medium was indicated by the presence at water's interfaces a negatively charged solute free zone of several hundred microns in thickness called the exclusion zone (EZ). Further evidence was demonstrated by Ovchinnikova's experiments (2009) showing that water can store and release substantial amount of charge. We demonstrate that the charge storage capacity of water arises from highly stable large-scale ionic structures with measurable charge imbalances and discrete levels of charge density. We also show evidence that the charge zones formation requires ionic solutes, and their formation correlate to large change in conductivity, by as much as 250%. Our experiments indicate that large-scale structuring plays a pivotal role in electrolysis and conductivity in ionic solution. We propose that water is an electrochemically active medium and present a new model of electrolysis and conductivity in ionic solution.
  2. Woo JO, Misran M, Lee PF, Tan LP
    ScientificWorldJournal, 2014;2014:205703.
    PMID: 24578624 DOI: 10.1155/2014/205703
    Lipid nanoparticles are colloidal carrier systems that have extensively been investigated for controlled drug delivery, cosmetic and pharmaceutical applications. In this work, a cost effective stearic acid-oleic acid nanoparticles (SONs) with high loading of salicylic acid, was prepared by melt emulsification method combined with ultrasonication technique. The physicochemical properties, thermal analysis and encapsulation efficiency of SONs were studied. TEM micrographs revealed that incorporation of oleic acid induces the formation of elongated spherical particles. This observation is in agreement with particle size analysis which also showed that the mean particle size of SONs varied with the amount of OA in the mixture but with no effect on their zeta potential values. Differential scanning calorimetry analysis showed that the SONs prepared in this method have lower crystallinity as compared to pure stearic acid. Different amount of oleic acid incorporated gave different degree of perturbation to the crystalline matrix of SONs and hence resulted in lower degrees of crystallinity, thereby improving their encapsulation efficiencies. The optimized SON was further incorporated in cream and its in vitro release study showed a gradual release for 24 hours, denoting the incorporation of salicylic acid in solid matrix of SON and prolonging the in vitro release.
  3. Teong YT, Teo ST, Tan LP, Wu BQ, Peh SC
    Med J Malaysia, 2006 Dec;61(5):526-33.
    PMID: 17623951 MyJurnal
    Gastrointestinal stromal tumour (GIST) is a rare but most common mesenchymal tumour in the gastrointestinal tract. Although GIST research has been carried out extensively worldwide, it has yet to be studied in Malaysia. To establish the immunohistochemical expression pattern of CD117 (c-KIT), CD34, S-100 and Desmin, the incidence of c-KIT and PDGFRA genes mutation in GISTs, and correlate it with clinicopathological parameters. Eleven clinically diagnosed GISTs were stained for CD117, CD34, Desmin and S-100 protein by immunohistochemical technique, and c-KITand PDGFRA gene mutations were studied by PCR-CSGE-DNA sequencing method. All GISTs (7 cases) stain positive for CD117, and co-expressed CD34. None of these cases express Desmin, and only one expressed S-100 protein focally. Fifty-seven percent (4/7 cases) of GIST harboured mutations at exon 11 of c-KIT gene, and they were all high risk and malignant cases. No mutation was detected at exons 9, 13 and 17 of KIT gene, and exons 12 and 18 of PDGFRA gene. Immunohistochemistry using a panel of antibodies shows consistent pattern of CD117 and CD34 expression in GIST, and mutational study may be a useful prognostic marker for kinase inhibitor treatment of GIST.
  4. Tan LP, Choong SS, Samsuddin AS, Lee SH
    Ticks Tick Borne Dis, 2019 10;10(6):101285.
    PMID: 31494069 DOI: 10.1016/j.ttbdis.2019.101285
    Two ticks were collected from a reticulated python (Malayopython reticulatus) caught in Tumpat District, Kelantan, Peninsular Malaysia. The ticks were first identified as Ambylomma sp. through morphological comparison with identification keys. Determination of the tick species was made through PCR and sequencing. However, BLAST analysis revealed 85-88% sequence nucleotide identity with Amblyomma nitidum and Amblyomma geoemydae. Additionally, the morphological features of the ticks collected in this study did not match either A. nitidum or A. geoemydae. Further examination of the ticks confirmed the species as Amblyomma cordiferum. This is the first record of A. cordiferum DNA sequence with morphological support of colour illustrations for adult A. cordiferum. This is also the most recent record of this host association in Peninsular Malaysia. Information from this report can serve as a reference for species identification using the described morphology or molecular sequences.
  5. Tan LP, Tan GW, Sivanesan VM, Goh SL, Ng XJ, Lim CS, et al.
    Int J Cancer, 2020 04 15;146(8):2336-2347.
    PMID: 31469434 DOI: 10.1002/ijc.32656
    Nasopharyngeal carcinoma (NPC) is originated from the epithelial cells of nasopharynx, Epstein-Barr virus (EBV)-associated and has the highest incidence and mortality rates in Southeast Asia. Late presentation is a common issue and early detection could be the key to reduce the disease burden. Sensitivity of plasma EBV DNA, an established NPC biomarker, for Stage I NPC is controversial. Most newly reported NPC biomarkers have neither been externally validated nor compared to the established ones. This causes difficulty in planning for cost-effective early detection strategies. Our study systematically evaluated six established and four new biomarkers in NPC cases, population controls and hospital controls. We showed that BamHI-W 76 bp remains the most sensitive plasma biomarker, with 96.7% (29/30), 96.7% (58/60) and 97.4% (226/232) sensitivity to detect Stage I, early stage and all NPC, respectively. Its specificity was 94.2% (113/120) against population controls and 90.4% (113/125) against hospital controls. Diagnostic accuracy of BamHI-W 121 bp and ebv-miR-BART7-3p were validated. Hsa-miR-29a-3p and hsa-miR-103a-3p were not, possibly due to lower number of advanced stage NPC cases included in this subset. Decision tree modeling suggested that combination of BamHI-W 76 bp and VCA IgA or EA IgG may increase the specificity or sensitivity to detect NPC. EBNA1 99 bp could identify NPC patients with poor prognosis in early and advanced stage NPC. Our findings provided evidence for improvement in NPC screening strategies, covering considerations of opportunistic screening, combining biomarkers to increase sensitivity or specificity and testing biomarkers from single sampled specimen to avoid logistic problems of resampling.
  6. Tan LP, Ng BK, Balraj P, Poh BH, Lim PK, Peh SC
    Hum Genet, 2005 Dec;118(3-4):539-40.
    PMID: 16521263
  7. Tan LP, Ng BK, Balraj P, Lim PK, Peh SC
    Pathology, 2007 Apr;39(2):228-34.
    PMID: 17454753
    BACKGROUND AND AIMS: Colorectal cancers of different subtypes involve different pathogenic pathways like the Wnt and the mutator pathways. In this study, we screened 73 colorectal cancer cases from a multi-racial group for genetic and expression profile defects with the aim of correlating these with patients' clinicopathological characteristics.
    METHODS: Mutation screening of the entire coding region of APC and exon 3 of CTNNB1, loss of heterozygosity (LOH) of APC, and microsatellite instability (MSI) status were assessed for 44 patients with available paired frozen normal and tumour tissues. In addition, 29 cases with available paraffin embedded tumour blocks were screened for mutation in exon 3 of CTNNB1, the APC mutation cluster region (codon 1286-1513), and hMLH1, hMSH2, hMSH6 protein expressions by immunohistochemistry method.
    RESULTS: In our study, 15/73 cases showed APC mutations (20.5%), 1/73 cases had CTNNB1 mutation (1.4%), 5/32 cases had APC LOH (15.6%), and 16/70 (22.9%) cases revealed at least some form of mismatch repair (MMR) defect. Tumour grade (poor differentiation) was found to correlate significantly with right-sided tumour and mucinous histology (p = 0.01879 and 0.00320, respectively). Patients of younger age (below 45 years) more often had tumours of mucinous histology (p = 0.00014), while patients of older age (above 75 years) more often had tumours on the right side of the colon (p = 0.02448). Tumours of the mucinous histology subtype often had MMR defects (p = 0.02686). There was no difference in the occurrence of APC and CTNNB1 mutations and MMR defects found within our multi-racial colorectal cancer patient cohort.
    CONCLUSION: Our findings support the notion that racial factor may not be related to the occurrence of MMR defects and APC and CTNNB1 mutations in our multi-racial patient cohort.
  8. Tan LP, Megat Abd Rani PA, Sharma RSK, Syed Hussain SS, Watanabe M
    Trop Biomed, 2020 Sep 01;37(3):756-762.
    PMID: 33612788 DOI: 10.47665/tb.37.3.756
    Tritrichomonas foetus is known to cause chronic diarrhea in the feline species in many different regions of the world. However, there is a paucity of information on T. foetus among cats in Malaysia. This study was conducted to determine the prevalence of Tritrichomonas foetus in the pet and stray cat population in Klang Valley, Malaysia. A total of 201 pet and stray cats' fecal samples were collected in Klang Valley. 24 samples were cultured in the InPouch® TF Feline to observe for motile trophozoites. A nested PCR protocol was used to screen for T. foetus in the collected samples. The prevalence of T. foetus in the cat population in Klang Valley was 33%. There was no association between Tritrichomonas infection and age, sex, breed or management of the cats. However, statistical analysis revealed that stray cats were more likely to be infected with T. foetus compared to pet cats. This study confirmed for the first time the presence of T. foetus among the cat population in Klang Valley, Malaysia.
  9. Tan LP, Megat Abd Rani PA, Sharma RSK, Syed Hussain SS, Watanabe M
    Trop Biomed, 2020 Sep 01;37(3):542-550.
    PMID: 33612769 DOI: 10.47665/tb.37.3.542
    Toxoplasma gondii, a zoonotic protozoan that has a worldwide distribution, is known to infect many warm-blooded vertebrates. The feline species including domestic cats are the definitive hosts for Toxoplama gondii and shed the infective oocyst. There is lack of information on the prevalence of Toxoplasma gondii in cats in Malaysia. The objective of this study was to determine both the seroprevalence of T. gondii and the prevalence of T. gondii DNA in cats' feces in Klang Valley, Malaysia. 198 blood and 201 fecal samples were collected from pet and stray cats from the local council, Dewan Bandaraya Kuala Lumpur (DBKL) and University Veterinary Hospital, Universiti Putra Malaysia respectively. The overall seroprevalence of Toxoplasma gondii in cats in the Klang Valley was found to be 5.5%. There was a high prevalence (10.5%) of T. gondii DNA detected in the cat fecal samples in both pet and stray cats suggestive of T. gondii oocyst shedding. Stray cats showed a higher seroprevalence and molecular prevalence of T. gondii than the pet cats. However, comparative analysis using Chi-square test showed no significant difference between both groups (P>0.05). Higher prevalence (10.5%) of cats shedding T. gondii DNA as compared to the seroprevalence (5.5%) was found in the cat population in the Klang Valley. The high prevalence of cats shedding T. gondii DNA is alarming as this may directly reflect the number of oocysts excreted into the environment posing a significant public health hazard.
  10. Tan LP, Foong KK, Yvonne Ai LL
    Med J Malaysia, 2018 10;73(5):334-335.
    PMID: 30350818 MyJurnal
    Amebiasis is one of the major causes of diarrhea in the developing countries and it can present with a wide range of gastrointestinal symptoms depending on the phase of infection. We described a case of 50 year-old male patient who presented with abdominal pain, diarrhea and vomiting. After right hemicolectomy for appendicular abscess with tumour over the ileum, histopathological examinations revealed numerous trophozoites of Entamoeba histolytica in a background of inflammations (Figure 1). Following resection of the ameboma, he received intravenous metronidazole treatment for total of two weeks duration.
  11. Tan LP, Mohd Rajdi NZI, Mohamad MA, Mohamed M, Hamdan RH, Goriman Khan MAK, et al.
    J Equine Vet Sci, 2022 01;108:103807.
    PMID: 34875427 DOI: 10.1016/j.jevs.2021.103807
    Trypanosoma (Megatrypanum) theileri is a non-pathogenic or weakly pathogenic parasite of domestic cattle that is cyclically transmitted by blood-sucking insects, mainly tabanid flies. It has been reported in several countries like Brazil, Venezuela, Japan, Taiwan, Thailand, Vietnam, and the Philippines. Although the ruminant industry is actively expanded in Malaysia, T. theileri and T. theileri-like trypanosomes have never been reported from Malaysia. The low pathogenicity of this species might be the main reason for overlooking T. theileri in this country. This paper describes an unforeseen finding of T. theileri from the outbreak of T. evansi in the state of Kelantan, Malaysia. This is the first time T. theileri reported in Malaysia, and also the first time T. theileri is reported in equid. Clinical signs compatible with infection by blood protozoa were observed; however, it was uncertain whether they were due to T. theileri infection. The detection of T. theileri from the blood sample and Tabanus sp. were confirmed through molecular analysis with PCR and DNA sequencing. In the present study, T. theileri from one horse and one Tabanus sp. were clustered with sequences of the previously described phylogenetic lineages from Japan, Chad and Brazil cattle. Even though this species is claimed to be host-specific with ruminant host restriction, the finding from this study suggested that T. theileri can infect equine whilst other isolates are known to infect ruminant species only. It is suspected there were two genotypes of T. theileri circulating in at least two districts of Kelantan. Thus, further study on multiple DNA regions should be conducted to determine the strains of detected T. theileri in Malaysia. Its impact on the horse and cattle industry should also be revised.
  12. Tan LP, Sadiq M, Aldeehani TM, Ehsanullah S, Mutira P, Vu HM
    Environ Sci Pollut Res Int, 2022 Apr;29(18):26322-26335.
    PMID: 34853996 DOI: 10.1007/s11356-021-17774-y
    This paper investigates the effect of different categories of essential COVID-19 data from 2020 to 2021 towards stock price dynamics and options markets. It applied the hypothetical method in which investors develop depression based on the understanding suggested by various green finance divisions. Furthermore, additional elements like panic, sentiment, and social networking sites may impact the attitude, size, and direction of green finance, subsequently impacting the security prices. We created new emotion proxies based on five groups of information, namely COVID-19, marketplace, lockdown, banking sector, and government relief using Google search data. The results show that (1) if the proportional number of traders' conduct exceeds the stock market, the effect of sentimentality indexes on jump volatility is expected to change; (2) the volatility index component jump radically increases with the COVID-19 index, city and market lockdown index, and banking index; and (3) expanding the COVID-19 index gives rise to the stock market index. Moreover, all indexes decreased in jump volatility but only after 5 days. These findings comply with the hypotheses proposed by our model.
  13. Tan LP, Hamdan RH, Hassan BNH, Reduan MFH, Okene IA, Loong SK, et al.
    Pathogens, 2021 Jun 30;10(7).
    PMID: 34208961 DOI: 10.3390/pathogens10070821
    Rhipicephalus species are distributed globally with a notifiable presence in Southeast Asia (SEA) within animal and human populations. The Rhipicephalus species are highly adaptive and have established successful coexistence within human dwellings and are known to be active all year round, predominantly in tropical and subtropical climates existing in SEA. In this review, the morphological characteristics, epidemiology, and epizootiology of Rhipicephalus tick species found in SEA are reviewed. There are six commonly reported Rhipicephalus ticks in the SEA region. Their interactions with their host species that range from cattle, sheep, and goats, through cats and dogs, to rodents and man are discussed in this article. Rhipicephalus-borne pathogens, including Anaplasma species, Ehrlichia species, Babesia species, and Theileria species, have been highlighted as are relevant to the region in review. Pathogens transmitted from Rhipicepahalus ticks to host animals are usually presented clinically with signs of anemia, jaundice, and other signs of hemolytic changes. Rhipicephalus ticks infestation also account for ectoparasitic nuisance in man and animals. These issues are discussed with specific interest to the SEA countries highlighting peculiarities of the region in the epidemiology of Rhipicephalus species and attendant pathogens therein. This paper also discusses the current general control strategies for ticks in SEA proffering measures required for increased documentation. The potential risks associated with rampant and improper acaricide use are highlighted. Furthermore, such practices lead to acaricide resistance among Rhipicephalus species are highlighted.
  14. Tan KE, Ng WL, Marinov GK, Yu KH, Tan LP, Liau ES, et al.
    Sci Rep, 2021 Jul 13;11(1):14392.
    PMID: 34257379 DOI: 10.1038/s41598-021-93781-w
    Epstein-Barr virus (EBV) has been recently found to generate novel circular RNAs (circRNAs) through backsplicing. However, comprehensive catalogs of EBV circRNAs in other cell lines and their functional characterization are still lacking. In this study, we have identified a list of putative EBV circRNAs in GM12878, an EBV-transformed lymphoblastoid cell line, with a significant majority encoded from the EBV latent genes. A novel EBV circRNA derived from the exon 5 of LMP-2 gene which exhibited highest prevalence, was further validated using RNase R assay and Sanger sequencing. This circRNA, which we term circLMP-2_e5, can be universally detected in a panel of EBV-positive cell lines modelling different latency programs. It ranges from lower expression in nasopharyngeal carcinoma (NPC) cells to higher expression in B cells, and is localized to both the cytoplasm and the nucleus. We provide evidence that circLMP-2_e5 is expressed concomitantly with its cognate linear LMP-2 RNA upon EBV lytic reactivation, and may be produced as a result of exon skipping, with its circularization possibly occurring without the involvement of cis elements in the short flanking introns. Furthermore, we show that circLMP-2_e5 is not involved in regulating cell proliferation, host innate immune response, its linear parental transcripts, or EBV lytic reactivation. Taken together, our study expands the current repertoire of putative EBV circRNAs, broadens our understanding of the biology of EBV circRNAs, and lays the foundation for further investigation of their function in the EBV life cycle and disease development.
  15. Tan GW, Khoo AS, Tan LP
    Sci Rep, 2015;5:9430.
    PMID: 25800946 DOI: 10.1038/srep09430
    MicroRNAs regulate gene expression at the post-transcriptional level. Differential expression of miRNAs can potentially be used as biomarkers for early diagnosis and prediction for outcomes. Failure in validation of miRNA profiles is often caused by variations in experimental parameters. In this study, the performance of five extraction kits and three RT-qPCR systems were evaluated using BioMark high-throughput platform and the effects of different experimental parameters on circulating miRNA levels were determined. Differences in the performance of extraction kits as well as varying accuracy, sensitivity and reproducibility in qPCR systems were observed. Normalisation of RT-qPCR data to spike-in controls can reduce extraction bias. However, the extent of correlation for different qPCR systems varies in different assays. At different time points, there was no significant fold change in eight of the plasma miRNAs that we evaluated. Higher level of miRNAs was detected in plasma as compared to serum of the same cohort. In summary, we demonstrated that high-throughput RT-qPCR with pre-amplification step had increased sensitivity and can be achieved with accuracy and high reproducibility through stringent experimental controls. The information provided here is useful for planning biomarker validation studies involving circulating miRNAs.
  16. Tan GW, Tan LP
    Methods Mol Biol, 2017;1580:7-19.
    PMID: 28439823 DOI: 10.1007/978-1-4939-6866-4_2
    Reverse transcription followed by real-time or quantitative polymerase chain reaction (RT-qPCR) is the gold standard for validation of results from transcriptomic profiling studies such as microarray and RNA sequencing. The current need for most studies, especially biomarker studies, is to evaluate the expression levels or fold changes of many transcripts in a large number of samples. With conventional low to medium throughput qPCR platforms, many qPCR plates would have to be run and a significant amount of RNA input per sample will be required to complete the experiments. This is particularly challenging when the size of study material (small biopsy, laser capture microdissected cells, biofluid, etc.), time, and resources are limited. A sensitive and high-throughput qPCR platform is therefore optimal for the evaluation of many transcripts in a large number of samples because the time needed to complete the entire experiment is shortened and the usage of lab consumables as well as RNA input per sample are low. Here, the methods of high-throughput RT-qPCR for the analysis of circulating microRNAs are described. Two distinctive qPCR chemistries (probe-based and intercalating dye-based) can be applied using the methods described here.
  17. Tan GW, Visser L, Tan LP, van den Berg A, Diepstra A
    Pathogens, 2018 04 13;7(2).
    PMID: 29652813 DOI: 10.3390/pathogens7020040
    The Epstein–Barr virus (EBV) can cause a wide variety of cancers upon infection of different cell types and induces a highly variable composition of the tumor microenvironment (TME). This TME consists of both innate and adaptive immune cells and is not merely an aspecific reaction to the tumor cells. In fact, latent EBV-infected tumor cells utilize several specific mechanisms to form and shape the TME to their own benefit. These mechanisms have been studied largely in the context of EBV+ Hodgkin lymphoma, undifferentiated nasopharyngeal carcinoma, and EBV+ gastric cancer. This review describes the composition, immune escape mechanisms, and tumor cell promoting properties of the TME in these three malignancies. Mechanisms of susceptibility which regularly involve genes related to immune system function are also discussed, as only a small proportion of EBV-infected individuals develops an EBV-associated malignancy.
  18. Tan GW, Sivanesan VM, Abdul Rahman FI, Hassan F, Hasbullah HH, Ng CC, et al.
    Int J Cancer, 2019 Oct 15;145(8):2260-2266.
    PMID: 30698824 DOI: 10.1002/ijc.32173
    Nasopharyngeal carcinoma (NPC) is an epithelial cancer of the nasopharynx which is highly associated with Epstein-Barr virus (EBV). Worldwide, most of the top 20 countries with the highest incidence and mortality rates of NPC are low- and middle-income countries. Many studies had demonstrated that EBV could be detected in the tissue, serum and plasma of NPC patients. In this study, we explored the potential of assays based on non-invasive nasal washings (NW) as a diagnostic and prognostic tool for NPC. A total of 128 patients were evaluated for NW EBV DNA loads and a subset of these samples were also tested for 27 EBV and human miRNAs shortlisted from literature. EBV DNA and seven miRNAs showed area under the receiver operating characteristic curve (AUC) values of more than 0.7, suggestive of their potential utility to detect NPC. Logistic regression analyses suggested that combination of two NW assays that test for EBNA-1 and hsa-miR-21 had the best performance in detecting NPC. The trend of NW EBV DNA load matched with clinical outcome of 71.4% (10 out of 14) NPC patients being followed-up. In summary, the non-invasive NW testing panel may be particularly useful for NPC screening in remote areas where healthcare facilities and otolaryngologists are lacking, and may encourage frequent testing of individuals in the high risk groups who are reluctant to have their blood tested. However, further validation in an independent cohort is required to strengthen the utility of this testing panel as a non-invasive detection tool for NPC.
  19. Syamsul VS, Okene IA, Yahya SNC, Hamdan RH, Lee SH, Tan LP
    Trop Life Sci Res, 2020 Apr;31(1):45-56.
    PMID: 32963710 DOI: 10.21315/tlsr2020.31.1.3
    Kelantan is a chiefly agrarian state with abundant small-holder ruminant farms in the East Coast economic Region of Malaysia. Ectoparasitism affects small ruminant production in Malaysia. It often causes reduction in meat quality and milk production which affect the farmers' income. To date, no report for the prevalence of ectoparasitism on small ruminant in Kelantan compared to other state in Malaysia. This study aims to determine the prevalence and associated risk factor of ruminant ectoparasitism in Kelantan. Ectoparasites were collected by manual picking and skin scrapping from 462 sheep and goats in Kelantan between April and September 2017 (during dry season). 60% of the sampled animals were infested with at least one species of the ectoparasites. In this study, lice and ticks were the most prevalent ectoparasites on small ruminant, which were 43.64% and 22.98%, respectively. The high biotic potential of lice population on host might be one of the factors they become the most prevalent species found on the animals. There was no significant relationship between ectoparasitism prevalence and species of small ruminants (χ2 = 1.12, p = 0.293). However, there was significant variations in prevalence between the regions where the animals were sampled from (χ2 = 30.25, p = 0.002) and farm management system for both species. This present study provides baseline epidemiological data on the prevalence of ectoparasitism in small ruminant. This information is useful for the formulation of prevention and control measures in order to enhance ruminant productivity in Kelantan.
  20. Shah B, Kirpalani A, Sunder S, Gupta A, Khanna U, Chafekar D, et al.
    BMC Nephrol, 2015;16:215.
    PMID: 26696239 DOI: 10.1186/s12882-015-0191-5
    The objective of this article is to describe the organisation of an international, clinical registry, the Chronic Kidney Disease Observational Database (CKDOD), the processes of enrolling patients and entering data and preliminary results to date.
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