Displaying publications 41 - 60 of 162 in total

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  1. Magnetophoresis of Magnetic Pickering Emulsions Under Low Field Gradient: Macroscopic and Microscopic Motion
    Tham FK, Ng WM, Leong SS, Yeap SP, Low SC, Lee HL, et al.
    Langmuir, 2021 Jan 26.
    PMID: 33496594 DOI: 10.1021/acs.langmuir.0c03153
    Monodispersed iron oxide nanoparticles (IONPs) coated with polystyrenesulfonate (PSS) and cetrimonium bromide (CTAB) have been used to stabilize magnetic Pickering emulsions (MPEs). Magnetophoresis of MPEs under the influence of a low gradient magnetic field (∇B < 100 T/m) was investigated at the macroscopic and microscopic scale. At the macroscopic scale, for the case of pH 7, the MPE achieved a magnetophoretic velocity of 70.9 μm/s under the influence of ∇B at 93.8 T/m. The magnetic separation efficiency of the MPE at 90% was achieved within 30 min for pH 3, 7, and 10. At pH 10, the colloidal stability of the MPE was the lowest compared to that for pH 3 and 7. Thus, MPE at pH 10 required the shortest time for achieving the highest separation efficiency, as the MPE experienced cooperative magnetophoresis at alkaline pH. The creaming rate of the MPE at all conditions was still lower compared to magnetophoresis and was negligible in influencing its separation kinetics profiles. At the microscopic scale, the migration pathways of the MPEs (with diameters between 2.5 and 7.5 μm) undergoing magnetophoresis at ∇B ∼ 13.0 T/m were recorded by an optical microscope. From these experiments, and taking into consideration the MPE size distribution from the dynamic light scattering (DLS) measurement, we determined the averaged microscopic magnetophoretic velocity to be 7.8 ± 5.5 μm/s. By making noncooperative magnetophoresis assumptions (with negligible interactions between the MPEs along their migration pathways), the calculated velocity of individual MPEs was 9.8 μm/s. Such a value was within the percentage error of the experimental result of 7.8 ± 5.5 μm/s. This finding allows for an easy and quick estimation of the magnetophoretic velocity of MPEs at the microscale by using macroscopic separation kinetics data.
  2. In vitro antibacterial activity and physicochemical properties of a crude methanol extract of the larvae of the blow fly Lucilia cuprina
    Teh CH, Nazni WA, Lee HL, Fairuz A, Tan SB, Sofian-Azirun M
    Med Vet Entomol, 2013 Dec;27(4):414-20.
    PMID: 23650928 DOI: 10.1111/mve.12012
    The emergence of multidrug-resistant bacterial strains has prompted the reintroduction of maggot therapy in the treatment of chronic, infected wounds. Many previous studies have demonstrated the potent antibacterial activity of larval excretions/secretions of the blowfly Lucilia sericata (Meigen) (Diptera:Calliphoridae) against bacteria. However, the antibacterial activity of its sibling species, Lucilia cuprina (Wiedemann) (Diptera:Calliphoridae) against a wide range of pathogenic bacteria has never been determined. The aim of this study was to develop a new procedure to produce whole body extract of larvae of L. cuprina via methanol extraction as well as to demonstrate the in vitro antibacterial activity of this extract against seven selected wound pathogens (Staphylococcus aureus, methicillin-resistant S. aureus, S. epidermidis, Streptococcus pyogenes, Klebsiella pneumoniae, Pseudomonas aeruginosa and Escherichia coli). The turbidimetric assay demonstrated that L. cuprina larval extract was significantly potent against all bacteria tested (P 
  3. Mitochondrial DNA analyses reveal low genetic diversity in Culex quinquefasciatus from residential areas in Malaysia
    Low VL, Lim PE, Chen CD, Lim YA, Tan TK, Norma-Rashid Y, et al.
    Med Vet Entomol, 2014 Jun;28(2):157-68.
    PMID: 23848279 DOI: 10.1111/mve.12022
    The present study explored the intraspecific genetic diversity, dispersal patterns and phylogeographic relationships of Culex quinquefasciatus Say (Diptera: Culicidae) in Malaysia using reference data available in GenBank in order to reveal this species' phylogenetic relationships. A statistical parsimony network of 70 taxa aligned as 624 characters of the cytochrome c oxidase subunit I (COI) gene and 685 characters of the cytochrome c oxidase subunit II (COII) gene revealed three haplotypes (A1-A3) and four haplotypes (B1-B4), respectively. The concatenated sequences of both COI and COII genes with a total of 1309 characters revealed seven haplotypes (AB1-AB7). Analysis using tcs indicated that haplotype AB1 was the common ancestor and the most widespread haplotype in Malaysia. The genetic distance based on concatenated sequences of both COI and COII genes ranged from 0.00076 to 0.00229. Sequence alignment of Cx. quinquefasciatus from Malaysia and other countries revealed four haplotypes (AA1-AA4) by the COI gene and nine haplotypes (BB1-BB9) by the COII gene. Phylogenetic analyses demonstrated that Malaysian Cx. quinquefasciatus share the same genetic lineage as East African and Asian Cx. quinquefasciatus. This study has inferred the genetic lineages, dispersal patterns and hypothetical ancestral genotypes of Cx. quinquefasciatus.
  4. Fulltext Development and Validation of a High-Density SNP Genotyping Array for African Oil Palm
    Kwong QB, Teh CK, Ong AL, Heng HY, Lee HL, Mohamed M, et al.
    Mol Plant, 2016 Aug 01;9(8):1132-1141.
    PMID: 27112659 DOI: 10.1016/j.molp.2016.04.010
    High-density single nucleotide polymorphism (SNP) genotyping arrays are powerful tools that can measure the level of genetic polymorphism within a population. To develop a whole-genome SNP array for oil palms, SNP discovery was performed using deep resequencing of eight libraries derived from 132 Elaeis guineensis and Elaeis oleifera palms belonging to 59 origins, resulting in the discovery of >3 million putative SNPs. After SNP filtering, the Illumina OP200K custom array was built with 170 860 successful probes. Phenetic clustering analysis revealed that the array could distinguish between palms of different origins in a way consistent with pedigree records. Genome-wide linkage disequilibrium declined more slowly for the commercial populations (ranging from 120 kb at r(2) = 0.43 to 146 kb at r(2) = 0.50) when compared with the semi-wild populations (19.5 kb at r(2) = 0.22). Genetic fixation mapping comparing the semi-wild and commercial population identified 321 selective sweeps. A genome-wide association study (GWAS) detected a significant peak on chromosome 2 associated with the polygenic component of the shell thickness trait (based on the trait shell-to-fruit; S/F %) in tenera palms. Testing of a genomic selection model on the same trait resulted in good prediction accuracy (r = 0.65) with 42% of the S/F % variation explained. The first high-density SNP genotyping array for oil palm has been developed and shown to be robust for use in genetic studies and with potential for developing early trait prediction to shorten the oil palm breeding cycle.
  5. Study of structural properties and defects of Ni-doped SnO2 nanorods as ethanol gas sensors
    Inderan V, Arafat MM, Kumar S, Haseeb ASMA, Jiang ZT, Altarawneh M, et al.
    Nanotechnology, 2017 Jun 30;28(26):265702.
    PMID: 28593932 DOI: 10.1088/1361-6528/aa731c
    An ethanol gas sensor with enhanced sensor response was fabricated using Ni-doped SnO2 nanorods, synthesized via a simple hydrothermal method. It was found that the response (R = R 0/R g) of a 5.0 mol% Ni-doped SnO2 (5.0Ni:SnO2) nanorod sensor was 1.4 × 104 for 1000 ppm C2H5OH gas, which is about 13 times higher than that of pure SnO2 nanorods, (1.1 × 103) at the operating temperature of 450 °C. Moreover, for 50 ppm C2H5OH gas, the 5.0Ni:SnO2 nanorod sensor still recorded a significant response reading, namely 2.0 × 103 with a response time of 30 s and recovery time of 10 min. To investigate the effect of Ni dopant (0.5-5.0 mol%) on SnO2 nanorods, structural characterizations were demonstrated using field emission scanning electron microscopy, high-resolution transmission electron microscopy, Fourier transform infrared spectroscopy, x-ray diffraction (XRD) analysis, x-ray photoelectron spectroscopy and an ultraviolet-visible spectrometer. XRD results confirmed that all the samples consisted of tetragonal-shaped rutile SnO2 nanorods. It was found that the average diameter and length of the nanorods formed in 5.0Ni:SnO2 were four times smaller (∼6 and ∼35 nm, respectively) than those of the nanorods formed in pure SnO2 (∼25 and 150 nm). Interestingly, both samples had the same aspect ratio, ∼6. It is proposed that the high response of the 5.0Ni:SnO2 nanorod sensor can be attributed to the particle size, which causes an increase in the thickness of the charge depletion layer, and the presence of oxygen vacancies within the matrix of SnO2 nanorods.
  6. Electrospun (Nickel and palladium) tin(IV) oxide/polyaniline/polyhydroxy-3-butyrate biodegradable nanocomposite fibers for low temperature ethanol gas sensing
    Inderan V, Arafat MM, Haseeb ASMA, Sudesh K, Lee HL
    Nanotechnology, 2020 Jun 29;31(42):425503.
    PMID: 32599573 DOI: 10.1088/1361-6528/aba0f1
    Tin (IV) oxide (SnO2) nanostructures are regarded as one of the most popular materials for conventional gas sensors, due to their high surface area and fast response in regard to most reducing and oxidizing gases. However, their high operating temperature (>200 °C) leads to high power consumption and limits their applications. Here, a new nanocomposite fiber materials, consisting of undoped and doped (nickel and palladium) SnO2 nanorods, polyaniline (PANI), and polyhydroxy-3-butyrate (P3HB) are synthesized via the hydrothermal method,followed by an in situ polymerization and electrospinning technique. The as-synthesized nanocomposites are tested using ethanol gas at different operating temperatures: 25 °C (room temperature), 60 °C, and 80 °C. The results reveal that all samples began to show a response at 80 °C. Pd:SnO2/PANI/P3HB nanocomposite fiber sensors demonstrate a relatively higher response than that of SnO2/PANI/P3HB and Ni:SnO2/PANI/P3HB nanocomposite sensors. At 80 °C , the Pd:SnO2/PANI/P3HB nanocomposite sensor records a response (R0/Rg ) of 1610, with a response time (Tres) of 90 s and a recovery time (Trec ) of 9 min in relation to 1000 ppm ethanol gas in N2. The sensor also displays a good level of response (R0/Rg = 200) at a low concentration level (50 ppm) of ethanol gas. Structural and chemical characterizations indicate that the ethanol gas sensing performance of Pd:SnO2/PANI/P3HB nanocomposite fibers can mainly be attributed to the p-n heterojunction, fiber geometry, and one-dimensional structure of SnO2 and to the presence of the Pd catalyst. This bio-nanocomposite fiber has the potential to be a breakthrough material in biodegradable low temperature ethanol sensing applications.
  7. A new anthraquinone from Morinda citrifolia roots
    Ee GC, Wen YP, Sukari MA, Go R, Lee HL
    Nat Prod Res, 2009;23(14):1322-9.
    PMID: 19735047 DOI: 10.1080/14786410902753138
    An investigation of Morinda citrifolia roots afforded a new anthraquinone, 2-ethoxy-1-hydroxyanthraquinone (1), along with five other known anthraquinones: 1-hydroxy-2-methylanthraquinone (2), damnacanthal (3), nordamnacanthal (4), 2-formyl-1-hydroxyanthraquinone (5) and morindone-6-methyl-ether (6). This is the first report on the isolation of morindone-6-methyl-ether (6) from this plant. The structures of these compounds were elucidated based on spectroscopic analyses such as NMR, MS and IR. Biological evaluation of five pure compounds and all the extracts against the larvae of Aedes aegypti indicated 1-hydroxy-2-methylanthraquinone (2) and damnacanthal (3) were the extracts to exhibit promising larvicidal activities.
  8. Inophyllin A, a new pyranoxanthone from Calophyllum inophyllum (Guttiferae)
    Ee GC, Kua AS, Lim CK, Jong V, Lee HL
    Nat Prod Res, 2006 May 10;20(5):485-91.
    PMID: 16644547
    In the authors' continuing search for new natural products, their recent studies on the roots of Calophyllum inophyllum (Guttiferae) have yielded a new prenylated pyranoxanthone, Inophyllin A together with the common triterpenes friedelin and stigmasterol. Structural elucidations of these compounds were achieved through (1)H, (13)C, DEPT, COSY, HSQC and HMBC experiments. The molecular mass was determined using MS techniques. The authors report here the isolation of and structural elucidation for Inophyllin A as well as its toxicity test result. The discovery of this new natural product from the unexploited Malaysian forest will certainly contribute to the search for potential natural larvicides.
  9. Fulltext A neurotoxin that specifically targets Anopheles mosquitoes
    Contreras E, Masuyer G, Qureshi N, Chawla S, Dhillon HS, Lee HL, et al.
    Nat Commun, 2019 06 28;10(1):2869.
    PMID: 31253776 DOI: 10.1038/s41467-019-10732-w
    Clostridial neurotoxins, including tetanus and botulinum neurotoxins, generally target vertebrates. We show here that this family of toxins has a much broader host spectrum, by identifying PMP1, a clostridial-like neurotoxin that selectively targets anopheline mosquitoes. Isolation of PMP1 from Paraclostridium bifermentans strains collected in anopheline endemic areas on two continents indicates it is widely distributed. The toxin likely evolved from an ancestral form that targets the nervous system of similar organisms, using a common mechanism that disrupts SNARE-mediated exocytosis. It cleaves the mosquito syntaxin and employs a unique receptor recognition strategy. Our research has an important impact on the study of the evolution of clostridial neurotoxins and provides the basis for the use of P. bifermentans strains and PMP1 as innovative, environmentally friendly approaches to reduce malaria through anopheline control.
  10. Fulltext Insecticide resistance in dengue vectors from hotspots in Selangor, Malaysia
    Rasli R, Cheong YL, Che Ibrahim MK, Farahininajua Fikri SF, Norzali RN, Nazarudin NA, et al.
    PLoS Negl Trop Dis, 2021 Mar;15(3):e0009205.
    PMID: 33755661 DOI: 10.1371/journal.pntd.0009205
    BACKGROUND: In Malaysia, dengue remains a top priority disease and usage of insecticides is the main method for dengue vector control. Limited baseline insecticide resistance data in dengue hotspots has prompted us to conduct this study. The present study reports the use of a map on the insecticide susceptibility status of Aedes aegypti and Aedes albopictus to provide a quick visualization and overview of the distribution of insecticide resistance.

    METHOD AND RESULTS: The insecticide resistance status of Aedes populations collected from 24 dengue hotspot areas from the period of December 2018 until June 2019 was proactively monitored using the World Health Organization standard protocol for adult and larval susceptibility testing was conducted, together with elucidation of the mechanisms involved in observed resistance. For resistance monitoring, susceptibility to three adulticides (permethrin, deltamethrin, and malathion) was tested, as well as susceptibility to the larvicide, temephos. Data showed significant resistance to both deltamethrin and permethrin (pyrethroid insecticides), and to malathion (organophosphate insecticide) in all sampled Aedes aegypti populations, while variable resistance patterns were found in the sampled Aedes albopictus populations. Temephos resistance was observed when larvae were tested using the diagnostic dosage of 0.012mg/L but not at the operational dosage of 1mg/L for both species.

    CONCLUSION: The present study highlights evidence of a potential threat to the effectiveness of insecticides currently used in dengue vector control, and the urgent requirement for insecticide resistance management to be integrated into the National Dengue Control Program.

  11. First description of the male of Phlebotomus betisi Lewis and Wharton, 1963 (Diptera: Psychodidae)
    Khadri MS, Depaquit J, Bargues MD, Ferté H, Mas-coma S, Lee HL, et al.
    Parasitol Int, 2008 Sep;57(3):295-9.
    PMID: 18378490 DOI: 10.1016/j.parint.2008.01.003
    The male of Phlebotomus (Larroussius) betisi is described from Malayan caves. Several males have been caught in association with P. betisi females. Males and females have been associated by ecology, biogeography, morphology and molecular biology (homology of the ND4 mtDNA sequences).
  12. First molecular genotyping of insensitive acetylcholinesterase associated with malathion resistance in Culex quinquefasciatus Say populations in Malaysia
    Low VL, Chen CD, Lim PE, Lee HL, Lim YA, Tan TK, et al.
    Pest Manag Sci, 2013 Dec;69(12):1362-8.
    PMID: 23404830 DOI: 10.1002/ps.3512
    Given that there is limited available information on the insensitive acetylcholinesterase in insect species in Malaysia, the present study aims to detect the presence of G119S mutation in the acetylcholinesterase gene of Culex quinquefasciatus from 14 residential areas across 13 states and a federal territory in Malaysia.
  13. First molecular genotyping of voltage gated sodium channel alleles in Culex quinquefasciatus populations in Malaysia
    Low VL, Chen CD, Lim PE, Lee HL, Tan TK, Lim YA, et al.
    Pestic Biochem Physiol, 2013 Sep;107(1):127-31.
    PMID: 25149246 DOI: 10.1016/j.pestbp.2013.06.004
    A nationwide investigation was performed to detect the presence of 1014 mutation(s) in voltage gated sodium channel (kdr) gene of Culex quinquefasciatus from 14 residential areas across 13 states and a federal territory in Malaysia. Molecular genotyping of kdr mutation was performed via a modified three tubes allele-specific-polymerase chain reaction (AS-PCR) and direct sequencing of kdr gene. Based on the results of AS-PCR, homozygous susceptible (SS) genotype was found in nine out of 14 populations with 38 individuals from a total sample size of 140. Heterozygous (RS) genotype was most predominant (99 individuals) and distributed across all study sites. Homozygous resistance (RR) genotype was detected in Perak (one individual) and Selangor (two individuals). The resistance kdr allele frequencies ranged from 0.1 to 0.55, with the highest being detected in Cx. quinquefasciatus population from Selangor. This study has documented the first field-evolved instance of 1014F mutation in Malaysian mosquitoes and the findings of this study could be utilized in the implementation of strategic measures in vector control programs in Malaysia.
  14. Fulltext Enzymatic characterization of insecticide resistance mechanisms in field populations of Malaysian Culex quinquefasciatus say (Diptera: Culicidae)
    Low VL, Chen CD, Lee HL, Tan TK, Chen CF, Leong CS, et al.
    PLoS One, 2013;8(11):e79928.
    PMID: 24278220 DOI: 10.1371/journal.pone.0079928
    There has been no comprehensive study on biochemical characterization of insecticide resistance mechanisms in field populations of Malaysian Culex quinquefasciatus. To fill this void in the literature, a nationwide investigation was performed to quantify the enzyme activities, thereby attempting to characterize the potential resistance mechanisms in Cx. quinquefasciatus in residential areas in Malaysia.
  15. Fulltext Oral ingestion of transgenic RIDL Ae. aegypti larvae has no negative effect on two predator Toxorhynchites species
    Nordin O, Donald W, Ming WH, Ney TG, Mohamed KA, Halim NA, et al.
    PLoS One, 2013;8(3):e58805.
    PMID: 23527029 DOI: 10.1371/journal.pone.0058805
    Dengue is the most important mosquito-borne viral disease. No specific treatment or vaccine is currently available; traditional vector control methods can rarely achieve adequate control. Recently, the RIDL (Release of Insect carrying Dominant Lethality) approach has been developed, based on the sterile insect technique, in which genetically engineered 'sterile' homozygous RIDL male insects are released to mate wild females; the offspring inherit a copy of the RIDL construct and die. A RIDL strain of the dengue mosquito, Aedes aegypti, OX513A, expresses a fluorescent marker gene for identification (DsRed2) and a protein (tTAV) that causes the offspring to die. We examined whether these proteins could adversely affect predators that may feed on the insect. Aedes aegypti is a peri-domestic mosquito that typically breeds in small, rain-water-filled containers and has no specific predators. Toxorhynchites larvae feed on small aquatic organisms and are easily reared in the laboratory where they can be fed exclusively on mosquito larvae. To evaluate the effect of a predator feeding on a diet of RIDL insects, OX513A Ae. aegypti larvae were fed to two different species of Toxorhynchites (Tx. splendens and Tx. amboinensis) and effects on life table parameters of all life stages were compared to being fed on wild type larvae. No significant negative effect was observed on any life table parameter studied; this outcome and the benign nature of the expressed proteins (tTAV and DsRed2) indicate that Ae. aegypti OX513A RIDL strain is unlikely to have any adverse effects on predators in the environment.
  16. Fulltext Diurnal biomarkers reveal key photosynthetic genes associated with increased oil palm yield
    Neoh BK, Wong YC, Teh HF, Ng TLM, Tiong SH, Ooi TEK, et al.
    PLoS One, 2019;14(3):e0213591.
    PMID: 30856213 DOI: 10.1371/journal.pone.0213591
    To investigate limiters of photosynthate assimilation in the carbon-source limited crop, oil palm (Elaeis guineensis Jacq.), we measured differential metabolite, gene expression and the gas exchange in leaves in an open field for palms with distinct mesocarp oil content. We observed higher concentrations of glucose 1-phosphate, glucose 6-phosphate, sucrose 6-phosphate, and sucrose in high-oil content palms with the greatest difference being at 11:00 (p-value ≤0.05) immediately after the period of low morning light intensity. Three important photosynthetic genes were identified using differentially expressed gene analysis (DEGs) and were found to be significantly enriched through Gene Ontology (GO) and pathway enrichment: chlorophyll a-b binding protein (CAB-13), photosystem I (PSI), and Ferredoxin-NADP reductase (FNR), particularly for sampling points at non-peak light (11:00 and 19:00), ranging from 3.3-fold (PSI) and 5.6-fold (FNR) to 10.3-fold (CAB-13). Subsequent gas exchange measurements further supported increased carbon assimilation through higher level of internal CO2 concentration (Ci), stomatal conductance (gs) and transpiration rate (E) in high-oil content palms. The selection for higher expression of key photosynthesis genes together with CO2 assimilation under low light is likely to be important for crop improvement, in particular at full maturity and under high density planting regimes where light competition exists between palms.
  17. Fulltext Indoor and outdoor residual spraying of a novel formulation of deltamethrin K-Othrine® (Polyzone) for the control of simian malaria in Sabah, Malaysia
    Rohani A, Fakhriy HA, Suzilah I, Zurainee MN, Najdah WMAW, Ariffin MM, et al.
    PLoS One, 2020;15(5):e0230860.
    PMID: 32413033 DOI: 10.1371/journal.pone.0230860
    Since 2000, human malaria cases in Malaysia were rapidly reduced with the use of insecticides in Indoor Residual Spray (IRS) and Long-Lasting Insecticide Net (LLIN). Unfortunately, monkey malaria in humans has shown an increase especially in Sabah and Sarawak. The insecticide currently used in IRS is deltamethrin K-Othrine® WG 250 wettable granule, targeting mosquitoes that rest and feed indoor. In Sabah, the primary vector for knowlesi malaria is An. balabacensis a species known to bite outdoor. This study evaluates an alternative method, the Outdoor Residual Spray (ORS) using a novel formulation of deltamethrin K-Othrine® (PolyZone) to examine it suitability to control knowlesi malaria vector in Sabah, compared to the current method. The study was performed at seven villages in Sabah having similar type of houses (wood, bamboo and concrete). Houses were sprayed with deltamethrin K-Othrine® (PolyZone) at two different dosages, 25 mg/m2 and 30 mg/m2 and deltamethrin K-Othrine® WG 250 wettable granule at 25 mg/m2, sprayed indoor and outdoor. Residual activity on different walls was assessed using standard cone bioassay techniques. For larval surveillances, potential breeding sites were surveyed. Larvae were collected and identified, pre and post spraying. Adult survey was done using Human Landing Catch (HLC) performed outdoor and indoor. Detection of malaria parasite in adults was conducted via microscopy and molecular methods. Deltamethrin K-Othrine® (PolyZone) showed higher efficacy when sprayed outdoor. The efficacy was found varied when sprayed on different types of wall surfaces. Deltamethrin K-Othrine® (PolyZone) at 25 mg/m2 was the most effective with regards to ability to high mortality and effective knock down (KD). The vector population was reduced significantly post-spraying and reduction in breeding sites as well. The number of simian malaria infected vector, human and simian malaria transmission were also greatly reduced.
  18. Fulltext Factors determining dengue outbreak in Malaysia
    Ahmad R, Suzilah I, Wan Najdah WMA, Topek O, Mustafakamal I, Lee HL
    PLoS One, 2018;13(2):e0193326.
    PMID: 29474401 DOI: 10.1371/journal.pone.0193326
    A large scale study was conducted to elucidate the true relationship among entomological, epidemiological and environmental factors that contributed to dengue outbreak in Malaysia. Two large areas (Selayang and Bandar Baru Bangi) were selected in this study based on five consecutive years of high dengue cases. Entomological data were collected using ovitraps where the number of larvae was used to reflect Aedes mosquito population size; followed by RT-PCR screening to detect and serotype dengue virus in mosquitoes. Notified cases, date of disease onset, and number and type of the interventions were used as epidemiological endpoint, while rainfall, temperature, relative humidity and air pollution index (API) were indicators for environmental data. The field study was conducted during 81 weeks of data collection. Correlation and Autoregressive Distributed Lag Model were used to determine the relationship. The study showed that, notified cases were indirectly related with the environmental data, but shifted one week, i.e. last 3 weeks positive PCR; last 4 weeks rainfall; last 3 weeks maximum relative humidity; last 3 weeks minimum and maximum temperature; and last 4 weeks air pollution index (API), respectively. Notified cases were also related with next week intervention, while conventional intervention only happened 4 weeks after larvae were found, indicating ample time for dengue transmission. Based on a significant relationship among the three factors (epidemiological, entomological and environmental), estimated Autoregressive Distributed Lag (ADL) model for both locations produced high accuracy 84.9% for Selayang and 84.1% for Bandar Baru Bangi in predicting the actual notified cases. Hence, such model can be used in forestalling dengue outbreak and acts as an early warning system. The existence of relationships among the entomological, epidemiological and environmental factors can be used to build an early warning system for the prediction of dengue outbreak so that preventive interventions can be taken early to avert the outbreaks.
  19. Fulltext Development of permethrin resistance in Culex quinquefasciatus Say in Kuala Lumpur, Malaysia
    Wan-Norafikah O, Nazni WA, Lee HL, Zainol-Ariffin P, Sofian-Azirun M
    Saudi J Biol Sci, 2013 Jul;20(3):241-50.
    PMID: 23961241 DOI: 10.1016/j.sjbs.2013.02.001
    The resistance status towards permethrin among the laboratory strain, the permethrin-selected strain and four field strains of Culex quinquefasciatus collected in Kuala Lumpur, Malaysia was determined using three standard laboratory methods: WHO larval bioassay, WHO adult bioassay and biochemical microplate assay. Cx. quinquefasciatus permethrin-selected strain larvae were the least susceptible to permethrin with a resistance ratio of 47.28-folds, whereas all field strain larvae of the same species were tolerant to permethrin with resistance ratios of more than 3-folds. In contrast, in adult stage, the permethrin exposed permethrin-selected strain (resistance ratio = 1.27) was found to be more susceptible to permethrin than all permethrin-exposed field strains (resistance ratios = 2.23-2.48). Complete mortalities for all strains of Cx. quinquefasciatus adults proved the effectiveness of the synergist; piperonyl butoxide (PBO). For the biochemical microplate assay, the reduction of the mean optical density of elevated oxidase activity of three field strains upon exposure to PBO confirmed the association between oxidase activity and permethrin tolerance. On the other hand, irregular patterns of the mean optical density of elevated oxidase activity in the laboratory strain, permethrin-selected strain and Jalan Fletcher strain illustrated the gene variation within these mosquito colonies as well as the involvement of other enzyme activities in the permethrin resistance occurred.
  20. Fulltext Technologies for Assessment of Motor Disorders in Parkinson's Disease: A Review
    Oung QW, Muthusamy H, Lee HL, Basah SN, Yaacob S, Sarillee M, et al.
    Sensors (Basel), 2015 Aug 31;15(9):21710-45.
    PMID: 26404288 DOI: 10.3390/s150921710
    Parkinson's Disease (PD) is characterized as the commonest neurodegenerative illness that gradually degenerates the central nervous system. The goal of this review is to come out with a summary of the recent progress of numerous forms of sensors and systems that are related to diagnosis of PD in the past decades. The paper reviews the substantial researches on the application of technological tools (objective techniques) in the PD field applying different types of sensors proposed by previous researchers. In addition, this also includes the use of clinical tools (subjective techniques) for PD assessments, for instance, patient self-reports, patient diaries and the international gold standard reference scale, Unified Parkinson Disease Rating Scale (UPDRS). Comparative studies and critical descriptions of these approaches have been highlighted in this paper, giving an insight on the current state of the art. It is followed by explaining the merits of the multiple sensor fusion platform compared to single sensor platform for better monitoring progression of PD, and ends with thoughts about the future direction towards the need of multimodal sensor integration platform for the assessment of PD.
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