Displaying publications 1 - 20 of 39 in total

  1. Velayudhan M, Lee CW
    Med J Malaysia, 2014 Jun;69(3):140-1.
    PMID: 25326357 MyJurnal
    Prolonged fever in patients can be a diagnostic challenge. Clinicians generally consider infectious diseases, malignant diseases and collagen vascular diseases as possible causes of pyrexia of unknown origin (PUO). Even after extensive evaluation as many as 15 percent of patients with prolonged fever may remain undiagnosed. This case report describes subacute thyroiditis as a cause of prolonged fever and documents how that diagnosis was finally made after 40 days of fever.
  2. Liu KT, Lee CW
    Malays J Pathol, 2017 Aug;39(2):189-192.
    PMID: 28866703
    We report a case of symptomatic bradycardia caused by consumption of a Chinese herbal medicine which was initially undisclosed to the attending emergency physician. The scientific name of the herb is Panax japonicus. Electrocardiogram revealed sinus bradycardia. Laboratory tests were normal except for the detection of a high serum digoxin level. Further interrogation of the patient eventually disclosed ingestion of the herb which, however, did not contain any digoxin. Other active ingredients in the herb include various types of ginsenoside. These are digoxin-like substances that had caused the observed false-positive detection of digoxin by fluorescence polarization immunoassay due to cross-reactivity. Our case-report provides an important insight about a blind-spot in the field of laboratory medicine (clinical pathology), namely, the false positive detection of digoxin due to crossreactivity in the immunoassay when we come across digoxin-like substances in clinical scenarios, which has barely received attention in the medical literature. It also conveys a clear educational message that with full understanding of the laboratory methodology and its mechanistic rationale there are actually some tricks-of-the-trade that allow us to optimize the specificity of the biochemical tests and the treatment of digoxin-like substances overdose.
  3. Lim JH, Lee CW
    Environ Monit Assess, 2017 Aug 03;189(9):432.
    PMID: 28823015 DOI: 10.1007/s10661-017-6147-4
    Diatom abundance, biovolume and diversity were measured over a 2-year period along the Straits of Malacca at two stations with upper (Klang) and lower (Port Dickson) states of eutrophication. Diatom abundance, which ranged from 0.2 × 10(4) to 21.7 × 10(4) cells L(-1) at Klang and 0.9 × 10(3)- 41.3 × 10(3) cells L(-1) at Port Dickson, was influenced partly by nutrient concentrations. At Klang, the diatoms were generally smaller and less diverse (H' = 0.77 ± 0.48) and predominated by Skeletonema spp. (60 ± 32% of total diatom biomass). In contrast, diatoms were larger and more diverse (H' = 1.40 ± 0.67) at Port Dickson. Chaetoceros spp. were the most abundant diatoms at Port Dickson but attributed only 48 ± 30% of total diatom biomass. Comparison of both Klang and Port Dickson showed that their diatom community structure differed and that eutrophication reduced diatom diversity at Klang. We also observed how Si(OH)4 affected the abundance of Skeletonema spp. which in turn influenced the temporal variation of diatom community at Klang. Our results highlighted how eutrophication affects diatom diversity and community structure.
  4. Lee CW, Lim JH, Heng PL
    Environ Monit Assess, 2013 Dec;185(12):9697-704.
    PMID: 23748919 DOI: 10.1007/s10661-013-3283-3
    We sampled extensively (29 stations) at the Klang estuarine system over a 3-day scientific expedition. We measured physical and chemical variables (temperature, salinity, dissolved oxygen, total suspended solids, dissolved inorganic nutrients) and related them to the spatial distribution of phototrophic picoplankton (Ppico). Multivariate analysis of variance of the physicochemical variables showed the heterogeneity of the Klang estuarine system where the stations at each transect were significantly different (Rao's F₁₈, ₃₆ = 8.401, p < 0.001). Correlation analyses also showed that variables related to Ppico abundance and growth were mutually exclusive. Distribution of Ppico was best explained by the physical mixing between freshwater and seawater whereas Ppico growth was correlated with temperature.
  5. You KG, Bong CW, Lee CW
    Environ Monit Assess, 2016 Mar;188(3):171.
    PMID: 26884358 DOI: 10.1007/s10661-016-5163-0
    Vibrio species isolated from four different sampling stations in the west coast of Peninsular Malaysia were screened for their antimicrobial resistance and plasmid profiles. A total of 138 isolates belonging to 15 different species were identified. Vibrio campbellii, V. parahaemolyticus, V. harveyi, and V. tubiashii were found to predominance species at all stations. High incidence of erythromycin, ampicillin, and mecillinam resistance was observed among the Vibrio isolates. In contrast, resistance against aztreonam, cefepime, streptomycin, sulfamethoxazole, and sulfonamides was low. All the Vibrio isolates in this study were found to be susceptible to imipenem, norfloxacin, ofloxacin, chloramphenicol, trimethoprim/sulfamethoxazole, and oxytetracycline. Ninety-five percent of the Vibrio isolates were resistant to one or more different classes of antibiotic, and 20 different resistance antibiograms were identified. Thirty-two distinct plasmid profiles with molecular weight ranging from 2.2 to 24.8 kb were detected among the resistance isolates. This study showed that multidrug-resistant Vibrio spp. were common in the aquatic environments of west coast of Peninsular Malaysia.
  6. Lim JH, Lee CW, Kudo I
    Environ Monit Assess, 2015 May;187(5):246.
    PMID: 25864082 DOI: 10.1007/s10661-015-4487-5
    Phytoplankton growth (μ) and grazing loss (g) rates were measured monthly by the Landry-Hassett dilution method over a 2-year period at both estuarine (Klang) and coastal water (Port Dickson) systems along the Straits of Malacca. Chlorophyll a (Chl a) concentration ranged from 0.20 to 4.47 μg L(-1) at Klang except on two occasions when Chl a spiked above 10 μg L(-1). In contrast, Chl a concentrations were relatively stable at Port Dickson (0.14 to 2.76 μg L(-1)). From the rate measurements, μ was higher (t = 2.01, df = 43, p  0.80). g ranged from 0.30 to 1.50 and 0.21 to 1.51 day(-1) at Klang and Port Dickson, respectively. In this study, grazing loss was coupled to phytoplankton growth, and the ratio of g/μ or grazing pressure which estimates the proportion of primary production grazed was 50% at Klang and lower than at Port Dickson (68%; t = 2.213, df = 36, p 
  7. Heng PL, Lim JH, Lee CW
    Environ Monit Assess, 2017 Mar;189(3):117.
    PMID: 28220442 DOI: 10.1007/s10661-017-5838-1
    Temporal variation of Synechococcus, its production (μ) and grazing loss (g) rates were studied for 2 years at nearshore stations, i.e. Port Dickson and Port Klang along the Straits of Malacca. Synechococcus abundance at Port Dickson (0.3-2.3 × 10(5) cell ml(-1)) was always higher than at Port Klang (0.3-7.1 × 10(4) cell ml(-1)) (p  0.25), but nutrient and light availability were important factors for their distribution. The relationship was modelled as log Synechococcus = 0.37Secchi - 0.01DIN + 4.52 where light availability (as Secchi disc depth) was a more important determinant. From a two-factorial experiment, nutrients were not significant for Synechococcus growth as in situ nutrient concentrations exceeded the threshold for saturated growth. However, light availability was important and elevated Synechococcus growth rates especially at Port Dickson (F = 5.94, p  0.30). In nearshore tropical waters, an estimated 69 % of Synechococcus production could be grazed.
  8. Lee CW, Choi HJ, Jeong H
    Nano Converg, 2020 Jan 20;7(1):3.
    PMID: 31956942 DOI: 10.1186/s40580-019-0213-2
    Demand on optical or photonic applications in the visible or short-wavelength infrared (SWIR) spectra, such as vision, virtual or augmented displays, imaging, spectroscopy, remote sensing (LIDAR), chemical reaction sensing, microscopy, and photonic integrated circuits, has envisaged new type of subwavelength-featured materials and devices for controlling electromagnetic waves. The study on metasurfaces, of which the thickness is either comparable to or smaller than the wavelength of the considered incoming electromagnetic wave, has been grown rapidly to embrace the needs of developing sub 100-micron active photonic pixelated devices and their arrayed form. Meta-atoms in metasurfaces are now actively controlled under external stimuli to lead to a large phase shift upon the incident light, which has provided a huge potential for arrayed two-dimensional active optics. This short review summarizes actively tunable or reconfigurable metasurfaces for the visible or SWIR spectra, to account for the physical operating principles and the current issues to overcome.
  9. Lee CW, Bong CW, Hii YS
    Appl Environ Microbiol, 2009 Dec;75(24):7594-601.
    PMID: 19820145 DOI: 10.1128/AEM.01227-09
    We investigated the temporal variation of bacterial production, respiration, and growth efficiency in the tropical coastal waters of Peninsular Malaysia. We selected five stations including two estuaries and three coastal water stations. The temperature was relatively stable (averaging around 29.5 degrees C), whereas salinity was more variable in the estuaries. We also measured dissolved organic carbon and nitrogen (DOC and DON, respectively) concentrations. DOC generally ranged from 100 to 900 microM, whereas DON ranged from 0 to 32 microM. Bacterial respiration ranged from 0.5 to 3.2 microM O2 h(-1), whereas bacterial production ranged from 0.05 to 0.51 microM C h(-1). Bacterial growth efficiency was calculated as bacterial production/(bacterial production + respiration), and ranged from 0.02 to 0.40. Multiple correlation analyses revealed that bacterial production was dependent upon primary production (r2 = 0.169, df = 31, and P < 0.02) whereas bacterial respiration was dependent upon both substrate quality (i.e., DOC/DON ratio) (r2 = 0.137, df = 32, and P = 0.03) and temperature (r2 = 0.113, df = 36, and P = 0.04). Substrate quality was the most important factor (r2 = 0.119, df = 33, and P = 0.04) for the regulation of bacterial growth efficiency. Using bacterial growth efficiency values, the average bacterial carbon demand calculated was from 5.30 to 11.28 microM C h(-1). When the bacterial carbon demand was compared with primary productivity, we found that net heterotrophy was established at only two stations. The ratio of bacterial carbon demand to net primary production correlated significantly with bacterial growth efficiency (r2 = 0.341, df = 35, and P < 0.001). From nonlinear regression analysis, we found that net heterotrophy was established when bacterial growth efficiency was <0.08. Our study showed the extent of net heterotrophy in these waters and illustrated the importance of heterotrophic microbial processes in coastal aquatic food webs.
  10. Sim EU, Lee CW, Narayanan K
    Biomark Res, 2021 Jun 30;9(1):51.
    PMID: 34193301 DOI: 10.1186/s40364-021-00311-x
    Ribosomal protein genes encode products that are essential for cellular protein biosynthesis and are major components of ribosomes. Canonically, they are involved in the complex system of ribosome biogenesis pivotal to the catalysis of protein translation. Amid this tightly organised process, some ribosomal proteins have unique spatial and temporal physiological activity giving rise to their extra-ribosomal functions. Many of these extra-ribosomal roles pertain to cellular growth and differentiation, thus implicating the involvement of some ribosomal proteins in organogenesis. Consequently, dysregulated functions of these ribosomal proteins could be linked to oncogenesis or neoplastic transformation of human cells. Their suspected roles in carcinogenesis have been reported but not specifically explained for malignancy of the nasopharynx. This is despite the fact that literature since one and half decade ago have documented the association of ribosomal proteins to nasopharyngeal cancer. In this review, we explain the association and contribution of dysregulated expression among a subset of ribosomal proteins to nasopharyngeal oncogenesis. The relationship of these ribosomal proteins with the cancer are explained. We provide information to indicate that the dysfunctional extra-ribosomal activities of specific ribosomal proteins are tightly involved with the molecular pathogenesis of nasopharyngeal cancer albeit mechanisms yet to be precisely defined. The complete knowledge of this will impact future applications in the effective management of nasopharyngeal cancer.
  11. Chen Q, Lee CW, Sim EU, Narayanan K
    Hum Gene Ther Methods, 2014 Feb;25(1):40-7.
    PMID: 24134118 DOI: 10.1089/hgtb.2012.188
    Direct protein delivery into the cytosol of mammalian cells by invasive Escherichia coli (E. coli) bacterial vector will bypass the need to achieve nuclear entry and transcription of DNA, a major hurdle that is known to seriously limit gene transfer. The bacterial vector is induced to express the protein during its growth phase, before presentation for entry into mammalian cells and release of its content into the cellular environment. For this class of vector, crossing the plasma membrane becomes the primary step that determines the success of protein delivery. Yet, how the mechanics of protein expression within the vector affect its entry into the host is poorly understood. We found the vector's effectiveness to enter HeLa cells diminished together with its viability when phage N15 protelomerase (TelN) expression was induced continuously in the invasive E. coli despite producing an abundant amount of functional protein. By comparison, shorter induction, even as little as 3 hr, produced sufficient amounts of functional TelN and showed more effective invasion of HeLa cells, comparable to that of uninduced invasive E. coli. These results demonstrate that brief induction of protein expression during vector growth is essential for optimal entry into mammalian cells, an important step for achieving bacteria-mediated protein delivery.
  12. Narayanan K, Lee CW, Radu A, Sim EU
    Anal Biochem, 2013 Aug 15;439(2):142-4.
    PMID: 23608053 DOI: 10.1016/j.ab.2013.04.010
    Successful gene delivery into mammalian cells using bactofection requires entry of the bacterial vector via cell surface integrin receptors followed by release of plasmid DNA into the cellular environment. We show, for the first time, that addition of the DNA transfection reagent Lipofectamine improves entry of invasive Escherichia coli into HeLa cells and enhances up to 2.8-fold green fluorescent protein (GFP) expression from a reporter plasmid. The addition of Lipofectamine may be applicable to other bacterial vectors to increase their DNA delivery efficiency into mammalian cells.
  13. Lee CW, Foo QC, Wong LV, Leung YY
    Craniomaxillofac Trauma Reconstr, 2017 Mar;10(1):16-21.
    PMID: 28210403 DOI: 10.1055/s-0036-1584893
    The aims of this study were to provide an overview of maxillofacial trauma and its relationship to patient's demographic data and alcohol consumption within the state of Sabah. It was a retrospective study of maxillofacial trauma cases treated by Oral and Maxillofacial Surgery Department, Queen Elizabeth Hospital, Kota Kinabalu, Sabah, from January 1, 2009, until December 31, 2013. A total of 630 maxillofacial trauma cases were included. Details of the trauma were collected from patients' record, including patients' cause of injuries, injuries suffered, treatment indications, and treatment received. Patients' demographic data (age, gender), alcohol consumption in relation to causes, and type of maxillofacial injury were analyzed. There were 538 male (85.4%) and 92 female (14.6%) patients (ratio: 5.8:1), with mean age of 31.0 years. Most common causes of maxillofacial injury were motor vehicle accident (MVA; 66.3%), followed by fall (12.4%) and assault (11.6%). Motorcyclists made up more than half of the total cases (53.1%). Cases referred were primarily due to soft-tissue injury (458 cases). Other cases were dentoalveolar and maxillofacial bone fractures. Treatment provided for the fractures included open reduction and internal fixation (22.9%), closed reduction (28.7%), and conservative management (48.4%). Toilet and suturing were done for all patients with soft-tissue injury. Maxillofacial trauma is a major problem in Sabah. It affects mostly males in the age group of 21 to 30 years. Most of the MVA patients were motorcyclists. Mandibular fracture with parasymphysis involvement recorded the highest number. Most of the patients preferred conservative management, probably due to financial and logistic issue.
  14. Sim EU, Ng KL, Lee CW, Narayanan K
    Biomed Res Int, 2017;2017:4876954.
    PMID: 28791303 DOI: 10.1155/2017/4876954
    The association of ribosomal proteins with carcinogenesis of nasopharyngeal carcinoma (NPC) has been established in a limited subset of ribosomal protein genes. To date, three ribosomal protein genes, eL27 (L27), eL41 (L41), and eL43 (L37a), have been found to be differentially expressed in cell lines derived from NPC tumors. This raises the possibility of more ribosomal protein genes that could be associated with NPC. In this study, we investigated the expression profiles of eight ribosomal protein genes, uS8 (S8), uS4 (S9), eS31 (S27a), eL6 (L6), eL18 (L18), uL14 (L23), eL24 (L24), and eL30 (L30), in six NPC-derived cell lines (HONE-1, SUNE1, HK1, TW01, TW04, and C666-1). Their expression levels were compared with that of a nonmalignant nasopharyngeal epithelial cell line (NP69) using quantitative real-time PCR (RT-qPCR) assay. Of the eight genes studied, the expressions of four ribosomal protein genes uS8 (S8), uS4 (S9), eS31 (S27a), and uL14 (L23) were found to be significantly downregulated in NPC cell lines relative to NP69. Our findings provide novel empirical evidence of these four ribosomal protein genes as NPC-associated genetic factors and reinforce the relevance of ribosomal proteins in the carcinogenesis of nasopharyngeal cancer.
  15. Lim JH, Lee CW, Bong CW, Kudo I
    Mar Pollut Bull, 2021 May 25;169:112524.
    PMID: 34049069 DOI: 10.1016/j.marpolbul.2021.112524
    The dissolved organic nutrient conditions and bacterial process rates at two tropical coastal sites in Peninsular Malaysia (Port Klang and Port Dickson) were initially studied in 2004-2005 period and later revisited in 2010-2011. We observed that dissolved organic nitrogen (DON) increased about two- and ten-fold at Port Klang and Port Dickson, respectively and resulted in a significant change in DOC:DON ratio (t ≥ 2.077, p 
  16. Akinsola RO, Lee CW, Sim EUH, Narayanan K
    Anal Biochem, 2021 03 01;616:114088.
    PMID: 33358938 DOI: 10.1016/j.ab.2020.114088
    Endosomal escape is considered a crucial barrier that needs to be overcome by integrin-mediated E. coli for gene delivery into mammalian cells. Bafilomycin, a potent inhibitor of the H+ proton pump commonly employed to lower endosomal pH, was evaluated as part of the E. coli protocol during delivery. We found an increase in green fluorescent protein expression up 6.9, 3.2, 5.0, 2.8, and 4.5 fold in HeLa, HEK-293, A549, HT1080, and MCF-7 respectively, compared to untreated cells. Our result showed for the first time that Inhibition of lysosomal V-ATPase enhances E. coli efficiency.
  17. Osahor AN, Tan CY, Sim EU, Lee CW, Narayanan K
    Anal Biochem, 2014 Oct 1;462:26-8.
    PMID: 24929088 DOI: 10.1016/j.ab.2014.05.030
    When recombineering bacterial artificial chromosomes (BACs), it is common practice to design the ends of the donor molecule with 50 bp of homology specifying its insertion site. We demonstrate that desired recombinants can be produced using intermolecular homologies as short as 15 bp. Although the use of shorter donor end regions decreases total recombinants by several fold, the frequency of recombinants with correctly inserted donor molecules was high enough for easy detection by simple polymerase chain reaction (PCR) screening. This observation may have important implications for the design of oligonucleotides for recombineering, including significant cost savings, especially for high-throughput projects that use large quantities of primers.
  18. Sim EU, Ang CH, Ng CC, Lee CW, Narayanan K
    J Hum Genet, 2010 Feb;55(2):118-20.
    PMID: 19927161 DOI: 10.1038/jhg.2009.124
    Extraribosomal functions of human ribosomal proteins (RPs) include the regulation of cellular growth and differentiation, and are inferred from studies that linked congenital disorders and cancer to the deregulated expression of RP genes. We have previously shown the upregulation and downregulation of RP genes in tumors of colorectal and nasopharyngeal carcinomas (NPCs), respectively. Herein, we show that a subset of RP genes for the large ribosomal subunit is differentially expressed among cell lines derived from the human nasopharyngeal epithelium. Three such genes (RPL27, RPL37a and RPL41) were found to be significantly downregulated in all cell lines derived from NPC tissues compared with a nonmalignant nasopharyngeal epithelial cell line. The expression of RPL37a and RPL41 genes in human nasopharyngeal tissues has not been reported previously. Our findings support earlier suspicions on the existence of NPC-associated RP genes, and indicate their importance in human nasopharyngeal organogenesis.
  19. Lim JH, Lee CW, Bong CW, Affendi YA, Hii YS, Kudo I
    Mar Pollut Bull, 2018 Mar;128:415-427.
    PMID: 29571392 DOI: 10.1016/j.marpolbul.2018.01.037
    Particulate phosphorus was the dominant phosphorus species and accounted for 72 ± 5% of total phosphorus in coastal habitats, 63 ± 4% in estuaries, 58 ± 6% in lakes and 80 ± 7% in aquaculture farms whereas dissolved inorganic phosphorus (DIP) and dissolved organic phosphorus (DOP) were minor components. Correlation analyses (DIP vs Chl a; R2 = 0.407, df = 31, p 
  20. Osahor A, Deekonda K, Lee CW, Sim EU, Radu A, Narayanan K
    Anal Biochem, 2017 10 01;534:46-48.
    PMID: 28693990 DOI: 10.1016/j.ab.2017.07.008
    Sample preparation for scanning electron microscope analysis involves reagents and equipment that are expensive and often hazardous. Here we demonstrate a circumvention of Osmium tetroxide and critical point drying, greatly reducing the duration, complexity and cost of the process. We captured early stage interactions of invasive-bacteria and HeLa cells during the process of bacteria-mediated gene delivery and illustrate sufficient clarity can be obtained using this procedure to preserve and clearly visualize relevant cellular structures. This protocol is significantly cheaper and easier to adapt compared to conventional methods, and will allow routine preparation/viewing of eukaryotic or bacterial samples for basic morphological studies.
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