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Search Results: 1 - 10 of 19513 matches for " Yee-Ling Lai "
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Evaluation of Chikungunya Diagnostic Assays: Differences in Sensitivity of Serology Assays in Two Independent Outbreaks
Grace Yap,Kwoon-Yong Pok,Yee-Ling Lai,Hapuarachchige-Chanditha Hapuarachchi,Angela Chow,Yee-Sin Leo,Li-Kiang Tan,Lee-Ching Ng
PLOS Neglected Tropical Diseases , 2010, DOI: 10.1371/journal.pntd.0000753
Abstract: Background The sensitivity and specificity of two in-house MAC-ELISA assays were tested and compared with the performance of commercially-available CTK lateral flow rapid test and EUROIMMUN IFA assays for the detection of anti-Chikungunya virus (CHIKV) IgM. Each MAC-ELISA assay used a whole virus-based antigen derived from genetically distinct CHIKV strains involved in two chikungunya disease outbreaks in Singapore (2008); a January outbreak strain with alanine at amino acid residue 226 of the E1 glycoprotein (CHIKV-A226) and a May-to-September outbreak strain that possessed valine at the same residue (CHIKV-226V). We report differences in IgM detection efficacy of different assays between the two outbreaks. The sensitivities of two PCR protocols were also tested. Methods and Findings For sera from January outbreak, the average detection threshold of CTK lateral flow test, MAC-ELISAs and EUROIMMUN IFA assays was 3.75, 4.38 and 4.88 days post fever onset respectively. In contrast, IgM detection using CTK lateral flow test was delayed to more than 7 days after fever onset in the second outbreak sera. However, MAC-ELISA using CHIKV-226V detected IgM in the second outbreak sera 3.96 days after fever onset, which was approximately one day earlier compared to the same assay using CHIKV-A226 (4.86 days). Specificity was 100% for both commercial assays, and 95.6% for the in-house MAC-ELISAs. For sensitivity determination of the PCR protocols, the probe-based real time RT-PCR method was found to be 10 times more sensitive than one based on SYBR Green. Conclusion Our findings suggested that the two strains of CHIKV using variants A226 and 226V resulted in variation in sensitivities of the assays evaluated. We postulated that the observed difference in antigen efficacy could be due to the amino acid substitution differences in viral E1 and E2 envelope proteins, especially the E1-A226V substitution. This evaluation demonstrates the importance of appraisal of different diagnostic assays before their application in clinical and operational settings.
Entomologic and molecular investigation into Plasmodium vivax transmission in Singapore, 2009
Lee-Ching Ng, Kim-Sung Lee, Cheong-Huat Tan, Peng-Lim Ooi, Sai-Gek Lam-Phua, Raymond Lin, Sook-Cheng Pang, Yee-Ling Lai, Suhana Solhan, Pei-Pei Chan, Kit-Yin Wong, Swee-Tuan Ho, Indra Vythilingam
Malaria Journal , 2010, DOI: 10.1186/1475-2875-9-305
Abstract: Epidemiological, entomological and molecular studies were carried out to investigate the three clusters, namely Mandai-Sungei Kadut, Jurong Island and Sembawang.A total of 29 malaria patients, with no recent travel history, were reported in the three clusters. Molecular analysis based on the msp3α and msp1 genes showed two independent local transmissions: one in Mandai-Sungei Kadut and another in Sembawang. Almost all cases within each cluster were epidemiologically linked. In Jurong Island cluster, epidemiological link remains uncertain, as almost all cases had a unique genetic profile. Only two cases shared a common profile and were found to be linked to the Mandai-Sungei Kadut cluster. Entomological investigation found Anopheles sinensis to be the predominant Anopheline in the two areas where local transmission of P. vivax was confirmed. Anopheles sinensis was found to be attracted to human bait and bites as early as 19:45 hrs. However, all Anopheles mosquitoes caught were negative for sporozoites and oocysts by dissection.Investigation of P. vivax cases from the three cluster areas confirmed the occurrence of local transmission in two areas. Although An. sinensis was the predominant Anopheline found in areas with confirmed transmission, the vector/s responsible for the outbreaks still remains cryptic.Singapore has been certified malaria free since November 1982 by the World Health Organization [1] and despite occasional local transmission, the country has maintained the standing due to its comprehensive system that prevents the re-establishment of malaria viz. vector surveillance and control, early case detection, and aggressive preventive and remedial actions upon detection of cases [2,3]. The incidence of reported malaria declined substantially from 8.0 per 100,000 population in 1977 to 2.0 per 100,000 population in 2007. In recent years, incidence has been maintained at between 2.0 and 2.6 per 100,000 population. Most infections were caused by Plasmodium viva
Executive Functions of Six-Year-Old Boys with Normal Birth Weight and Gestational Age
Desiree Yee-Ling Phua, Anne Rifkin-Graboi, Seang-Mei Saw, Michael J. Meaney, Anqi Qiu
PLOS ONE , 2012, DOI: 10.1371/journal.pone.0036502
Abstract: Impaired fetal development, reflected by low birth weight or prematurity, predicts an increased risk for psychopathology, especially attention deficit hyperactivity disorder (ADHD). Such effects cut across the normal range of birth weight and gestation. Despite the strength of existing epidemiological data, cognitive pathways that link fetal development to mental health are largely unknown. In this study we examined the relation of birth weight (>2500 g) and gestational age (37–41 weeks) within the normal range with specific executive functions in 195 Singaporean six-year-old boys of Chinese ethnicity. Birth weight adjusted for gestational age was used as indicator of fetal growth while gestational age was indicative of fetal maturity. Linear regression revealed that increased fetal growth within the normal range is associated with an improved ability to learn rules during the intra/extra-dimensional shift task and to retain visual information for short period of time during the delayed matching to sample task. Moreover, faster and consistent reaction times during the stop-signal task were observed among boys born at term, but with higher gestational age. Hence, even among boys born at term with normal birth weight, variations in fetal growth and maturity showed distinct effects on specific executive functions.
Upregulated mRNA expression of desaturase and elongase, two enzymes involved in highly unsaturated fatty acids biosynthesis pathways during follicle maturation in zebrafish
Sairatul D Ishak, Sze-Huey Tan, Hou-Keat Khong, Annette Jaya-Ram, Yee-Ling Enyu, Meng-Kiat Kuah, Alexander Shu-Chien
Reproductive Biology and Endocrinology , 2008, DOI: 10.1186/1477-7827-6-56
Abstract: mRNA levels of fadsd6 and elovl5 in different ovarian follicle stages were determined by semi-quantitative reverse transcription-polymerase chain reaction (RT-PCR) assays. For analysis of the ovarian follicular fatty acid composition, gas chromatography was used.Our results have shown that desaturase displayed significant upregulation in expression during the oocyte maturation stage. Expression of elongase was significantly highest in pre-vitellogenic follicles, followed by maturation stage. Fatty acid composition analysis of different ovarian follicle stages also showed that ARA level was significantly highest in pre-vitellogenic and matured follicles. DHA level was highest in both late vitellogenic and maturation stage.Collectively, our findings seem to suggest the existence of a HUFA synthesis system, which could be responsible for the synthesis of HUFA to promote oocyte maturation and possibly ovulation processes. The many advantages of zebrafish as model system to understand folliculogenesis will be useful platform to further elucidate the regulatory and mechanism aspects of ovarian HUFA synthesis.Polyunsaturated fatty acids (PUFA) have long been implicated in various aspects of vertebrate reproduction. Both the n-6 and n-3 PUFA influence reproductive processes through a variety of mechanisms, which includes provision of precursors for prostaglandin synthesis, inducement of steroidogenesis and regulation of transcription factors involved in reproductive process [1]. Among the PUFA, eicosapentaenoic acid (EPA, C20:5n-3), docosahexaenoic acid (DHA, C22:6n-3) and arachidonic acid (ARA, C20:4n-6), also collectively known as highly unsaturated fatty acids (HUFA) have been shown to play pivotal role in regulation of oocyte maturation and ovulation [2,3]. In aquaculture, supplement of HUFA in broodstock diet is essential to increase probability of spawning success [4,5]. In vitro studies using teleost follicles have reported the stimulation of maturation and ovulation
Giemsa-Stained Wet Mount Based Method for Reticulocyte Quantification: A Viable Alternative in Resource Limited or Malaria Endemic Settings
Wenn-Chyau Lee, Bruce Russell, Yee-Ling Lau, Mun-Yik Fong, Cindy Chu, Kanlaya Sriprawat, Rossarin Suwanarusk, Francois Nosten, Laurent Renia
PLOS ONE , 2013, DOI: 10.1371/journal.pone.0060303
Abstract: The quantity of circulating reticulocytes is an important indicator of erythropoietic activity in response to a wide range of haematological pathologies. While most modern laboratories use flow cytometry to quantify reticulocytes, most field laboratories still rely on ‘subvital’ staining. The specialist ‘subvital’ stains, New Methylene Blue (NMB) and Brilliant Crésyl Blue are often difficult to procure, toxic, and show inconsistencies between batches. Here we demonstrate the utility of Giemsa's stain (commonly used microbiology and parasitology) in a ‘subvital’ manner to provide an accurate method to visualize and count reticulocytes in blood samples from normal and malaria-infected individuals.
Specific, sensitive and rapid detection of human plasmodium knowlesi infection by loop-mediated isothermal amplification (LAMP) in blood samples
Yee-Ling Lau, Mun-Yik Fong, Rohela Mahmud, Phooi-Yee Chang, Vanitha Palaeya, Fei-Wen Cheong, Lit-Chein Chin, Claudia N Anthony, Abdulsalam M Al-Mekhlafi, Yeng Chen
Malaria Journal , 2011, DOI: 10.1186/1475-2875-10-197
Abstract: LAMP assay was developed based on P. knowlesi genetic material targeting the apical membrane antigen-1 (AMA-1) gene. The method uses six primers that recognize eight regions of the target DNA and it amplifies DNA within an hour under isothermal conditions (65°C) in a water-bath.LAMP is highly sensitive with the detection limit as low as ten copies for AMA-1. LAMP detected malaria parasites in all confirm cases (n = 13) of P. knowlesi infection (sensitivity, 100%) and none of the negative samples (specificity, 100%) within an hour. LAMP demonstrated higher sensitivity compared to nested PCR by successfully detecting a sample with very low parasitaemia (< 0.01%).With continuous efforts in the optimization of this assay, LAMP may provide a simple and reliable test for detecting P. knowlesi malaria parasites in areas where malaria is prevalent.Malaria still poses a major threat in most parts of the world. It is widespread in tropical and subtropical regions, including parts of America, Asia and Africa. Plasmodium knowlesi is one of the simian malaria that causes human infection. In 2004, a large focus of human P. knowlesi infection was reported in the Kapit Division of Sarawak. It was reported that 101 out of 141 (71.6%) of human malaria cases at Kapit Hospital, which had been identified by microscopy as single Plasmodium malariae infections, were actually P. knowlesi and other non-P. malariae species by nested polymerase chain reaction (PCR) assays [1]. More recently, out of 111 human blood samples received (July 2006 - March 2008) by the Institute for Medical Research (IMR), 62 (55.9%) were positive for P. knowlesi by nested PCR. Positive P. knowlesi cases were observed in most states in Peninsular Malaysia [2].Microscopic examination has been the mainstay of malaria diagnosis. Microscopy is relatively inexpensive, rapid, and relatively sensitive procedure when used appropriately. However, interpretations of smears require considerable expertise particularly at low-le
Is There a Risk of Suburban Transmission of Malaria in Selangor, Malaysia?
Kamil A. Braima, Jia-Siang Sum, Amir-Ridhwan M. Ghazali, Mustakiza Muslimin, John Jeffery, Wenn-Chyau Lee, Mohammed R. Shaker, Alaa-Eldeen M. Elamin, Ibrahim Jamaiah, Yee-Ling Lau, Mahmud Rohela, Adeeba Kamarulzaman, Frankie Sitam, Rosnida Mohd-Noh, Noraishah M. Abdul-Aziz
PLOS ONE , 2013, DOI: 10.1371/journal.pone.0077924
Abstract: Background The suburban transmission of malaria in Selangor, Malaysia’s most developed and populous state still remains a concern for public health in this region. Despite much successful control efforts directed at its reduction, sporadic cases, mostly brought in by foreigners have continued to occur. In addition, cases of simian malaria caused by Plasmodium knowlesi, some with fatal outcome have caused grave concern to health workers. The aim of this study was to investigate the possibility of local malaria transmission in suburban regions of Selangor, which are adjacent to secondary rainforests. Findings A malaria survey spanning 7 years (2006 - 2012) was conducted in Selangor. A total of 1623 laboratory confirmed malaria cases were reported from Selangor’s nine districts. While 72.6% of these cases (1178/1623) were attributed to imported malaria (cases originating from other countries), 25.5% (414/1623) were local cases and 1.9% (31/1623) were considered as relapse and unclassified cases combined. In this study, the most prevalent infection was P. vivax (1239 cases, prevalence 76.3%) followed by P. falciparum (211, 13.0%), P. knowlesi (75, 4.6%), P. malariae (71, 4.4%) and P. ovale (1, 0.06%). Mixed infections comprising of P. vivax and P. falciparum were confirmed (26, 1.6%). Entomological surveys targeting the residences of malaria patients’ showed that the most commonly trapped Anopheles species was An. maculatus. No oocysts or sporozoites were found in the An. maculatus collected. Nevertheless, the possibility of An. maculatus being the malaria vector in the investigated locations was high due to its persistent occurrence in these areas. Conclusions Malaria cases reported in this study were mostly imported cases. However the co-existence of local cases and potential Plasmodium spp. vectors should be cause for concern. The results of this survey reflect the need of maintaining closely monitored malaria control programs and continuous extensive malaria surveillance in Peninsula Malaysia.
An Improved Differential Evolution and Its Industrial Application  [PDF]
Johnny Chung Yee Lai, Frank Hung Fat Leung, Sai Ho Ling, Edwin Chao Shi
Journal of Intelligent Learning Systems and Applications (JILSA) , 2012, DOI: 10.4236/jilsa.2012.42008
Abstract: In this paper, an improved Differential Evolution (DE) that incorporates double wavelet-based operations is proposed to solve the Economic Load Dispatch (ELD) problem. The double wavelet mutations are applied in order to enhance DE in exploring the solution space more effectively for better solution quality and stability. The first stage of wavelet operation is embedded in the DE mutation operation, in which the scaling factor is governed by a wavelet function. In the second stage, a wavelet-based mutation operation is embedded in the DE crossover operation. The trial population vectors are modified by the wavelet function. A suite of benchmark test functions is employed to evaluate the performance of the proposed DE in different problems. The result shows empirically that the proposed method out-performs signifycantly the conventional methods in terms of convergence speed, solution quality and solution stability. Then the proposed method is applied to the Economic Load Dispatch with Valve-Point Loading (ELD-VPL) problem, which is a process to share the power demand among the online generators in a power system for minimum fuel cost. Two different conditions of the ELD problem have been tested in this paper. It is observed that the proposed method gives satisfactory optimal costs when compared with the other techniques in the literature.
Social Psychology Meets School Mathematics in PISA 2012: An Application of the Theory of Planned Behaviour in Australia  [PDF]
Grace Skrzypiec, Mun Yee Lai
Psychology (PSYCH) , 2017, DOI: 10.4236/psych.2017.813137
Abstract: Educators and government administrators are keen to find interventions to change the rapidly declining enrollments in senior high school mathematics. In 2012, PISA introduced measures to examine the Theory of Planned Behaviour (TPB), a prominent theory from social psychology for encouraging changes in behavior (and perhaps mathematics enrollments). This paper sought to examine the applicability of the TPB for predicting the relationship between students’ intentions, their mathematics attitudes, subject norms, perceived controllability and self-efficacy as well as their mathematics behaviour, using items created by PISA 2012 question designers to assess these TPB constructs. Australian PISA 2012 data from 14,481 students found that the hypothesized TPB antecedents for studying mathematics were very poor predictors of mathematical intentions and indirectly, weak predictors of mathematical behaviour. The Attitudes factor i.e. an interest in mathematics, was found to be the strongest predictor of mathematical intentions. The poor predictive capacity of the TPB was proposed to have been due to ill-defined indicator items in the PISA 2012 measuring instruments, which did not comply with the TPB’s principles of compatibility and aggregation. Future studies testing the TPB in the context of studying mathematics would benefit from undertaking Elicitation studies to identify appropriate TPB antecedents and indicators of the mathematics behaviour being targeted.
Bioassay-Directed Isolation of Active Compounds with Antiyeast Activity from a Cassia fistula Seed Extract
Subramanion L. Jothy,Zuraini Zakaria,Yeng Chen,Yee Ling Lau,Lachimanan Yoga Latha,Lai Ngit Shin,Sreenivasan Sasidharan
Molecules , 2011, DOI: 10.3390/molecules16097583
Abstract: Background and objective: Cassia fistula L belongs to the family Leguminosae, and it is one of the most popular herbal products in tropical countries. C. fistula seeds have been used as a herbal medicine and have pharmacological activity which includes anti-bacterial, anti-fungal, and antioxidant properties. The goal of this study was to identify compounds from C. fistula seeds which are responsible for anti-Candida albicans activity using bioassay-directed isolation. Results: The preliminary phytochemical screening of the plant seed revealed the presence of anthraquinones, flavonoids, saponins, tannins and terpenoids. The isolation of active compounds was carried out in four steps: multiple extractions, fractionation using column chromatography and purification using preparative thin-layer chromatography (TLC) and liquid chromatography/mass spectrometry (LC/MS). The structure of separated compounds was determined on the basis of mass spectrometry data. One compound was identified is roseanone. Conclusions: The MS analysis on the active fraction from seed extract of C. fistula confirmed the presence of roseanone with antiyeast activity.
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