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Search Results: 1 - 7 of 7 matches for " Hapuarachchige-Chanditha Hapuarachchi "
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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.
Mosquito Cellular Factors and Functions in Mediating the Infectious entry of Chikungunya Virus
Regina Ching Hua Lee,Hapuarachchige Chanditha Hapuarachchi,Karen Caiyun Chen,Khairunnisa' Mohamed Hussain,Huixin Chen,Swee Ling Low,Lee Ching Ng,Raymond Lin,Mary Mah-Lee Ng,Justin Jang Hann Chu
PLOS Neglected Tropical Diseases , 2013, DOI: 10.1371/journal.pntd.0002050
Abstract: Chikungunya virus (CHIKV) is an arthropod-borne virus responsible for recent epidemics in the Asia Pacific regions. A customized gene expression microarray of 18,760 transcripts known to target Aedes mosquito genome was used to identify host genes that are differentially regulated during the infectious entry process of CHIKV infection on C6/36 mosquito cells. Several genes such as epsin I (EPN1), epidermal growth factor receptor pathway substrate 15 (EPS15) and Huntingtin interacting protein I (HIP1) were identified to be differentially expressed during CHIKV infection and known to be involved in clathrin-mediated endocytosis (CME). Transmission electron microscopy analyses further revealed the presence of CHIKV particles within invaginations of the plasma membrane, resembling clathrin-coated pits. Characterization of vesicles involved in the endocytic trafficking processes of CHIKV revealed the translocation of the virus particles to the early endosomes and subsequently to the late endosomes and lysosomes. Treatment with receptor-mediated endocytosis inhibitor, monodansylcadaverine and clathrin-associated drug inhibitors, chlorpromazine and dynasore inhibited CHIKV entry, whereas no inhibition was observed with caveolin-related drug inhibitors. Inhibition of CHIKV entry upon treatment with low-endosomal pH inhibitors indicated that low pH is essential for viral entry processes. CHIKV entry by clathrin-mediated endocytosis was validated via overexpression of a dominant-negative mutant of Eps15, in which infectious entry was reduced, while siRNA-based knockdown of genes associated with CME, low endosomal pH and RAB trafficking proteins exhibited significant levels of CHIKV inhibition. This study revealed, for the first time, that the infectious entry of CHIKV into mosquito cells is mediated by the clathrin-dependent endocytic pathway.
Ultrasensitive cDNA Detection of Dengue Virus RNA Using Electrochemical Nanoporous Membrane-Based Biosensor
Varun Rai, Hapuarachchige C. Hapuarachchi, Lee Ching Ng, Siew Hwa Soh, Yee Sin Leo, Chee-Seng Toh
PLOS ONE , 2012, DOI: 10.1371/journal.pone.0042346
Abstract: A nanoporous alumina membrane-based ultrasensitive DNA biosensor is constructed using 5′-aminated DNA probes immobilized onto the alumina channel walls. Alumina nanoporous membrane-like structure is carved over platinum wire electrode of 76 μm diameter dimension by electrochemical anodization. The hybridization of complementary target DNA with probe DNA molecules attached inside the pores influences the pore size and ionic conductivity. The biosensor demonstrates linear range over 6 order of magnitude with ultrasensitive detection limit of 9.55×10?12 M for the quantification of ss-31 mer DNA sequence. Its applicability is challenged against real time cDNA PCR sample of dengue virus serotype1 derived from asymmetric PCR. Excellent specificity down to one nucleotide mismatch in target DNA sample of DENV3 is also demonstrated.
Island-wide diversity in single nucleotide polymorphisms of the Plasmodium vivax dihydrofolate reductase and dihydropteroate synthetase genes in Sri Lanka
Mette L Schousboe, Rupika S Rajakaruna, Ali Salanti, Hapuarachchige C Hapuarachchi, Gawrie NL Galappaththy, Ib C Bygbjerg, Priyanie H Amerasinghe, Flemming Konradsen, Michael Alifrangis
Malaria Journal , 2007, DOI: 10.1186/1475-2875-6-28
Abstract: P. vivax-positive samples were collected from subjects presenting at government health facilities across nine of the major malaria endemic districts on the island. The samples were analysed for SNPs/haplotypes at codon 57, 58, 61 and 117 of the Pvdhfr gene and 383, 553 and 585 of the Pvdhps gene by applying PCR followed by a hybridization step using sequence specific oligonucleotide probes (SSOPs) in an ELISA format.In the study period, the government of Sri Lanka recorded 2,149 P. vivax cases from the nine districts out of which, 454 (21.1%) blood samples were obtained. Pvdhfr haplotypes could be constructed for 373 of these. The FSTS wild-haplotype was represented in 257 samples (68.9%), the double mutant LRTS haplotype was the most frequently observed mutant (24.4%) while the triple mutation (LRTN) was only identified once. Except for two samples of the single mutated Pvdhps GAV haplotype, the remaining samples were wildtype. Geographical differences were apparent, notably a significantly higher frequency of mutant Pvdhfr haplotypes was observed in the Northern districts.Since SP is rarely used in Sri Lanka, the high frequency and diversity of Pvdhfr mutations was unexpected indicating the emergence of drug resistant parasites despite a low level of SP drug pressure.Plasmodium vivax is the most geographically widespread of the four Plasmodium species infective to humans found throughout South and Central America, Asia, the Middle East, and parts of Africa and infects an estimated 70–80 million people annually [1]. Chloroquine (CQ)-resistant Plasmodium falciparum, and to a lesser extent CQ resistant P. vivax, is almost as endemic as malaria itself and alternatives such as the drug combination sulphadoxine/pyrimethamine (SP) have replaced CQ. Resistance to SP has recently emerged for P. falciparum, while for P. vivax it has been observed sporadically [2]. The molecular mechanisms involved in the development of SP resistance of the two species are most likely simila
Multiple origins of resistance-conferring mutations in Plasmodium vivax dihydrofolate reductase
Vivian N Hawkins, Alyson Auliff, Surendra Prajapati, Kanchana Rungsihirunrat, Hapuarachchige C Hapuarachchi, Amanda Maestre, Michael T O'Neil, Qin Cheng, Hema Joshi, Kesara Na-Bangchang, Carol Sibley
Malaria Journal , 2008, DOI: 10.1186/1475-2875-7-72
Abstract: The P. vivax dhfr coding region, 792 bp upstream and 683 bp downstream were amplified and sequenced from 137 contemporary patient isolates from Colombia, India, Indonesia, Papua New Guinea, Sri Lanka, Thailand, and Vanuatu. A repeat motif located 2.6 kb upstream of dhfr was also sequenced from 75 of 137 patient isolates, and mutational relationships among the haplotypes were visualized using the programme Network.Synonymous and non-synonymous single nucleotide polymorphisms (SNPs) within the dhfr coding region were identified, as was the well-documented in-frame insertion/deletion (indel). SNPs were also identified upstream and downstream of dhfr, with an indel and a highly polymorphic repeat region identified upstream of dhfr. The regions flanking dhfr were highly variable. The double mutant (58R/117N) dhfr allele has evolved from several origins, because the 58R is encoded by at least 3 different codons. The triple (58R/61M/117T) and quadruple (57L/61M/117T/173F, 57I/58R/61M/117T and 57L/58R/61M/117T) mutant alleles had at least three independent origins in Thailand, Indonesia, and Papua New Guinea/Vanuatu.It was found that the P. vivax dhfr coding region and its flanking intergenic regions are highly polymorphic and that mutations in P. vivax dhfr that confer antifolate resistance have arisen several times in the Asian region. This contrasts sharply with the selective sweep of rare antifolate resistant alleles observed in the P. falciparum populations in Asia and Africa. The finding of multiple origins of resistance-conferring mutations has important implications for drug policy.In order to maximize the useful therapeutic life of antimalarial drugs, it is crucial to understand the mechanisms by which parasites resistant to antimalarial drugs are selected and subsequently spread in natural populations. This is a major issue in Plasmodium falciparum, where resistance to two safe, inexpensive drugs, chloroquine and sulphadoxine-pyrimethamine, has spread widely in en
SWAT模型在斯里兰卡河流径流预测中的运用
H.,A.,Prasantha,HAPUARACHCHI,李致家,Fliigel,Albert,WOLFGANG
湖泊科学 , 2003, DOI: 10.18307/2003.sup18
Abstract: 本文运用SWAT模型和新安江模型对斯里兰卡卡鲁河流域上游地区日径流进行了预测.卡鲁河是斯里兰卡的第二大河,由于流域的降雨量很大,上游地区河流沿峡谷流下,中下游平原地区河床平坦.卡鲁河流域的洪水变的很正常.应用SWAT模型来对卡鲁河的日径流量进行预测,并同应用新安江模型所得到的结果做对比.研究表明,新安江模型要比SWAT(分布式水文模型)模型在卡鲁河日径流量预测上稍微好一些.实际上,或许数据质量不高或不恰当是部分原因,因为SWAT的输出成果严格取决于其输入的数据质量.此外,在斯里兰卡,许多人的日常用水是靠井水.当把流域看作一个整体,通常都是一个很大的范围,那样的话就不可能详尽的记录所有各个小规模的水利用,例如:小灌溉、小规模的家畜管理和工业水利用.这些水利用累积起来或许就很可观.这些数据的缺失对分布式水文模型在水平衡的应用有着独特的影响.但是概念水文模型(如新安江模型)可以根据实际情况在校正中调节它的参数,因为这些参数并没有实质的物理含义.因此,在流域特征和模型输入数据有限或不完整的情况下,概念水文模型比分布式水文模型更具优势.
Torsion of parietal-peritoneal fat mimicking acute appendicitis: a case report
Kamal Sanjiva Hapuarachchi, Edward Douglas Courtney, Szabolcs Gergely, Tjun Yip Tang
Journal of Medical Case Reports , 2009, DOI: 10.1186/1752-1947-3-6980
Abstract: A 41-year-old Caucasian woman presented with clinical signs of acute appendicitis. On diagnostic laparoscopy, a non-inflamed appendix was found. Further exploration revealed a necrotic torted appendage of fat overlying the parietal peritoneum of the right iliac fossa of the anterior abdominal wall.Torted fatty appendages can be a diagnostic dilemma often mimicking more common causes of an acute abdomen. Laparoscopy is an excellent tool making the correct diagnosis in such cases.Appendices epiploicae are small pouches of fat-filled peritoneum, which protrude from the serosal surface of the colon, and are usually arranged in two separate longitudinal rows extending from the caecum to the recto-sigmoid junction. They are typically between 1 and 2 cm wide and 2 to 5 cm long, and approximately 50 to 100 are present on average. They are usually supplied via their stalk by one or two arterioles from the vasa recta of the colon and drained by a single tortuous venule [1]. Appendices epiploicae can undergo ischaemia and localized inflammation due to either spontaneous torsion leading to compromise of their blood supply or venous thrombosis of the draining appendageal vein.Infarctions of appendices epiploicae and the greater omentum are uncommon, but well documented causes of acute abdominal pain. Torsion of intraperitoneal fat on the parietal peritoneum is an even rarer phenomenon, with only two previously reported cases, both of which were found at laparotomy [2,3]. One case occurred in a 20-year-old Russian woman with a 12-hour history of right-sided abdominal pain and peritonism, and exploratory laparotomy revealed a 3 cm × 2 cm necrotic piece of fat on the parietal peritoneum 10 cm to the right of the umbilicus [2]. The other case occurred in a 25-year-old African-American man with a three-day history of symptoms and signs suggestive of appendicitis, but the patient was subsequently found to have a normal appendix at open appendicectomy. Further exploration revealed an i
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