Displaying publications 81 - 100 of 162 in total

Abstract:
Sort:
  1. 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.
  2. Lee HL, Chen CD, Masri SM, Chiang YF, Chooi KH, Benjamin S
    PMID: 19058596
    The field bioefficacy of a wettable granule (WG) formulation of Bacillus thuringiensis israelensis (Bti), VectoBac WG (Bti strain AM65-52) against dengue vectors, Aedes aegypti and Ae albopictus; was evaluated in a suburban residential area (TST) and in a temporary settlement site (KB) in the state of Selangor, Malaysia. Pre-control ovitrap surveillance of the trial sites indicated a high population of both types of Aedes mosquitoes. The populations were monitored continuously by weekly ovitrapping. Bti was sprayed biweekly at a dosage of 500 g/ha by using a mist-blower. The spray application was targeted into outdoor larval habitats. If required, Bti formulation was also applied directly into indoor water-holding containers at 8 g/1,000 l. Based on ovitrap surveillance, a significant reduction in Aedes populations was evident 4 weeks after initiating the first Bti treatment. The ovitrap index (OI) and the larvae density decreased drastically in both trial sites. In TST, the indoor OI was significantly reduced from 57.50 +/- 7.50% to 19.13 +/- 5.49% (p<0.05), while the outdoor OI decreased from 38.89 +/- 11.11% to 15.36 +/- 5.93%. In KB, similarly, the OI was significantly reduced by more than half, from 66.66 +/- 6.67% to 30.26 +/- 2.99% (p< 0.05). In all cases, the reduction in OI was paralleled by reduction in larval density.
  3. Ee GC, Lim CK, Ong GP, Sukari MA, Lee HL
    J Asian Nat Prod Res, 2006 Sep;8(6):567-70.
    PMID: 16931434
    A new tetraoxygenated xanthone, daphnifolin (1,3,5-trihydroxy-4-methoxyxanthone), along with three other xanthones, were isolated from the stem bark extracts of Mesua daphnifolia. Their structures were characterized on the basis of 1D and 2D NMR spectral data.
  4. 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.
  5. Kavitha R, Nazni WA, Tan TC, Lee HL, Isa MN, Azirun MS
    Malays J Pathol, 2012 Dec;34(2):127-32.
    PMID: 23424775 MyJurnal
    Forensic entomology applies knowledge about insects associated with decedent in crime scene investigation. It is possible to calculate a minimum postmortem interval (PMI) by determining the age and species of the oldest blow fly larvae feeding on decedent. This study was conducted in Malaysia to identify maggot specimens collected during crime scene investigations. The usefulness of the molecular and morphological approach in species identifications was evaluated in 10 morphologically identified blow fly larvae sampled from 10 different crime scenes in Malaysia. The molecular identification method involved the sequencing of a total length of 2.2 kilo base pairs encompassing the 'barcode' fragments of the mitochondrial cytochrome oxidase I (COI), cytochrome oxidase II (COII) and t-RNA leucine genes. Phylogenetic analyses confirmed the presence of Chrysomya megacephala, Chrysomya rufifacies and Chrysomya nigripes. In addition, one unidentified blow fly species was found based on phylogenetic tree analysis.
  6. Low VL, Chen CD, Lee HL, Lim PE, Leong CS, Sofian-Azirun M
    J Med Entomol, 2013 Jan;50(1):103-11.
    PMID: 23427658
    A nationwide investigation was carried out to determine the current susceptibility status of Culex quinquefasciatus Say populations against four active ingredients representing four major insecticide classes: DDT, propoxur, malathion, and permethrin. Across 14 study sites, both larval and adult bioassays exhibited dissimilar trends in susceptibility. A correlation between propoxur and malathion resistance and between propoxur and permethrin resistance in larval bioassays was found. The results obtained from this study provide baseline information for vector control programs conducted by local authorities. The susceptibility status of this mosquito should be monitored from time to time to ensure the effectiveness of current vector control operations in Malaysia.
  7. 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.
  8. Lau KW, Chen CD, Lee HL, Norma-Rashid Y, Sofian-Azirun M
    J Med Entomol, 2015 Mar;52(2):199-206.
    PMID: 26336304 DOI: 10.1093/jme/tju019
    Susceptibility status of Aedes aegypti (L.) and Aedes albopictus Skuse larvae obtained from 12 states in Malaysia were evaluated against five insect growth regulators (IGRs), namely, pyriproxyfen, methoprene, diflubenzuron, cyromazine, and novaluron under laboratory conditions. Field populations of Ae. aegypti exhibited moderate resistance toward methoprene and low resistance toward pyriproxyfen, with resistance ratios of 12.7 and 1.4, respectively, but susceptibility to diflubenzuron, cyromazine, and novaluron. On the other hand, field populations of Ae. albopictus exhibited low resistance against diflubenzuron and novaluron, with resistance ratio of 2.1 and 1.0, respectively, but susceptibility to other tested IGRs. Our study concluded that the tested IGRs provide promising results and can be used to control field population of Ae. aegypti and Ae. albopictus, especially cyromazine. The use of IGR should be considered as an alternative when larvae develop resistance to conventional insecticides.
  9. Afizah AN, Mahirah MN, Azahari AH, Asuad MK, Nazni WA, Lee HL
    PMID: 26863856
    Ovitrap surveillance was conducted in 2012 and 2006 in Malay and Aboriginal Villages on Carey Island. In each village, standard ovitraps were placed indoors and outdoors at randomly selected houses/locations. All L3 larvae recovered were identified up to species level. Results demonstrated that only larvae of Aedes albopictus were found in all the positive ovitraps placed indoors and outdoors. In 2012, a high ovitrap index (OI) of 66.7% indoor and 84.0% outdoor in the Malay Village; and 62.5% indoor and 88.0% outdoor in Aboriginal Village with an apparent absence of Aedes aegypti. In 2006, a 100% OI was recorded in all ovitraps set indoors and outdoors in both villages.
  10. Choong YK, Lan J, Lee HL, Chen XD, Wang XG, Yang YP
    PMID: 26186395 DOI: 10.1016/j.saa.2015.07.054
    Many macrofungus sclerotia are well-known medicinal herbs, health food and nutritional supplements. However, the prevalent adulterant commercial products are major hindrances to their incorporation into mainstream medical use in many countries. The mushroom sclerotia of Lignosus rhinocerotis, Poria cocos, Polyporus umbellatus, Pleurotus tuber-regium and Omphalia lapidescens are commonly used in traditional Chinese medicine. In this study, IR macro-fingerprint method was used in the identification of these sclerotia. The results showed that the spectrum of L. rhinocerotis (LR) was comparable with P. cocos with 94.4% correlation, except that the peak at 1543cm(-1) of LR appeared in lower intensity. The spectrum of P. umbellatus and P. tuber-regium was also correlated (91.5%), as both spectra could be clearly discriminated in that P. umbellatus spectrum has small base peaks located at the range of 1680-1500cm(-1). O. lapidescens was not comparable with all the other sclerotia as its spectrum was totally different. Its base peak was broad and derivated equally along the range. The first IR has revealed the dissimilarity among five mushrooms sclerotia. The second derivative and 2DIR further enhanced the identification in detail.
  11. Ahmad R, Chu WL, Ismail Z, Lee HL, Phang SM
    PMID: 15272748
    The effect of ten microalgal chlorophytes isolated from mosquito breeding containers on the survival, larval development and adult body size of the mosquito Aedes aegypti was investigated. All larvae fed with six of the microalgal isolates died after 7 days. These isolates were found to be resistant to digestion by mosquito larvae. Delayed pupation and body size reduction of the mosquitos fed with Chlorococcum UMACC 218 and Scenedesmus UMACC 220 were observed. In contrast, larvae fed with Ankistrodesmus convolutus UMACC 101 and Chlorococcum UMACC 213 were bigger in size than those fed with normal insectory feed. The present study showed that microalgal chlorophytes have the potential to be used as larvicidal agents for mosquitos.
  12. Liang Y, Ahmad Mohiddin MN, Bahauddin R, Hidayatul FO, Nazni WA, Lee HL, et al.
    Comput Math Methods Med, 2019;2019:1923479.
    PMID: 31481976 DOI: 10.1155/2019/1923479
    In this paper, we will start off by introducing the classical Ross-Macdonald model for vector-borne diseases which we use to describe the transmission of dengue between humans and Aedes mosquitoes in Shah Alam, which is a city and the state capital of Selangor, Malaysia. We will focus on analysing the effect of using the Mosquito Home System (MHS), which is an example of an autodissemination trap, in reducing the number of dengue cases by changing the Ross-Macdonald model. By using the national dengue data from Malaysia, we are able to estimate λ, which represents the initial growth rate of the dengue epidemic, and this allows us to estimate the number of mosquitoes in Malaysia. A mathematical expression is also constructed which allows us to estimate the potential number of breeding sites of Aedes mosquitoes. By using the data available from the MHS trial carried out in Section 15 of Shah Alam, we included the potential effect of the MHS into the dengue model and thus modelled the impact MHS has on the spread of dengue within the trial area. We then extended our results to analyse the effect of the MHSs on reducing the number of dengue cases in the whole of Malaysia. A new model was constructed with a basic reproduction number, R0,MalaMHS, which allows us to identify the required MHSs coverage needed to achieve extinction in Malaysia. Numerical simulations and tables of results were also produced to illustrate our results.
  13. Low VL, Chen CD, Lee HL, Lim PE, Leong CS, Sofian-Azirun M
    J Am Mosq Control Assoc, 2012 Sep;28(3):160-9.
    PMID: 23833895
    A standardized larval dipping method was used to determine the infestation rates of Culex and other species of mosquitoes in stagnant water at 20 residential areas. This study also examined the associations between Culex distribution and various habitat characteristics across all states in Malaysia. Identification of 7,848 specimens yielded 6 species dominated by Culex quinquefasciatus (82.74%), followed by Cx. vishui (14.39%), Cx. gelidus (2.70%), Lutzia fuscanus (0.11%), Armigeres subalbatus (0.05%), and Anopheles separatus (0.01%). The Culex larvae occurred in stagnant water with pH ranging from 6.4 to 8.2; conductivity, 139.7 to 6635.2 micros/cm; salinity, 0.07 to 3.64 ppt; total dissolved solids, 0.09 to 4.27g/liter; and dissolved oxygen, 5.11 to 8.11 mg/liter. The mean number of Culex larvae was positively correlated with pH, conductivity, salinity, and total dissolved solids. In contrast, the elevation and dissolved oxygen were found negatively correlated with mean number of Culex larvae. This study documented baseline information on the habitat characteristics of Culex species for the 1st time at different residential areas in Malaysia. The findings of this study will be a timely reminder to local authorities that effective control measures should be monitored regularly in order to reduce the nuisance of these mosquitoes and the risks of disease transmission.
  14. Teh CK, Lee HL, Abidin H, Ong AL, Mayes S, Chew FT, et al.
    BMC Plant Biol, 2019 Nov 05;19(1):470.
    PMID: 31690276 DOI: 10.1186/s12870-019-2062-x
    BACKGROUND: Legitimacy in breeding and commercial crop production depends on optimised protocols to ensure purity of crosses and correct field planting of material. In oil palm, the presence of three fruit forms permits these assumptions to be tested, although only after field planting. The presence of incorrect fruit forms in a cross is a clear sign of illegitimacy. Given that tenera forms produce 30% more oil for the same weight of fruit as dura, the presence of low levels of dura contamination can have major effect during the economic lifespan of an oil palm, which is around 25 years. We evaluated two methods for legitimacy test 1) The use of SHELL markers to the gene that determines the shell-thickness trait 2) The use of SNP markers, to determine the legitimacy of the cross.

    RESULTS: Our results indicate that the SHELL markers can theoretically reduce the major losses due to dura contamination of tenera planting material. However, these markers cannot distinguish illegitimate tenera, which reduces the value of having bred elite tenera for commercial planting and in the breeding programme, where fruit form is of limited utility, and incorrect identity could lead to significant problems. We propose an optimised approach using SNPs for routine quality control.

    CONCLUSIONS: Both dura and tenera contamination can be identified and removed at or before the nursery stage. An optimised legitimacy assay using SNP markers coupled with a suitable sampling scheme is now ready to be deployed as a standard control for seed production and breeding in oil palm. The same approach will also be an effective solution for other perennial crops, such as coconut and date palm.

  15. 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.
  16. Teh CH, Nazni WA, Nurulhusna AH, Norazah A, Lee HL
    BMC Microbiol, 2017 Feb 16;17(1):36.
    PMID: 28209130 DOI: 10.1186/s12866-017-0936-3
    BACKGROUND: Antimicrobial resistance is currently a major global issue. As the rate of emergence of antimicrobial resistance has superseded the rate of discovery and introduction of new effective drugs, the medical arsenal now is experiencing shortage of effective drugs to combat diseases, particularly against diseases caused by the dreadful multidrug-resistant strains, such as the methicillin-resistant Staphylococcus aureus (MRSA). The ability of fly larvae to thrive in septic habitats has prompted us to determine the antibacterial activity and minimum inhibitory concentrations (MICs) of larval extract of flies, namely Lucilia cuprina, Sarcophaga peregrina and Musca domestica against 4 pathogenic bacteria [Staphylococcus aureus, methicillin-resistant S. aureus (MRSA), Pseudomonas aeruginosa and Escherichia coli] via a simple and sensitive antibacterial assay, resazurin-based turbidometric (TB) assay as well as to demonstrate the preliminary chemical profile of larval extracts using gas chromatography-mass spectrophotometry (GC-MS).

    RESULTS: The resazurin-based TB assay demonstrated that the L. cuprina larval extract was inhibitory against all tested bacteria, whilst the larval extract of S. peregrina and M. domestica were only inhibitory against the MRSA, with a MIC of 100 mg ml(-1). Subsequent sub-culture of aliquots revealed that the larval extract of L. cuprina was bactericidal against MRSA whilst the larval extracts of S. peregrina and M. domestica were bacteriostatic against MRSA. The GC-MS analysis had quantitatively identified 20 organic compounds (fatty acids or their derivatives, aromatic acid esters, glycosides and phenol) from the larval extract of L. cuprina; and 5 fatty acid derivatives with known antimicrobial activities from S. peregrina and M. domestica.

    CONCLUSION: The resazurin-based turbidometric assay is a simple, reliable and feasible screening assay which evidently demonstrated the antibacterial activity of all fly larval extracts, primarily against the MRSA. The larval extract of L. cuprina exerted a broad spectrum antibacterial activity against all tested bacteria. The present study revealed probable development and use of novel and effective natural disinfectant(s) and antibacterial agent(s) from flies and efforts to screen more fly species for antibacterial activity using resazurin-based TB assay should be undertaken for initial screening for subsequent discovery and isolation of potential novel antimicrobial substances, particularly against the multi-drug resistant strains.

  17. Lee HL, Tang MM, Bakhtiar MF, Mohamad Yadzir ZH, Johar A
    Int Arch Allergy Immunol, 2021;182(2):153-157.
    PMID: 32927463 DOI: 10.1159/000510314
    BACKGROUND: Seafood is an important source of nutrition in Asia. However, it was believed to cause or aggravate atopic dermatitis (AD).

    OBJECTIVES: We aim to determine relevant seafood sensitization among adults with AD and investigate cross-sensitization to aeroallergens.

    METHODS: One hundred thirty-two adults with AD who were subjected to skin prick test (SPT) with 7 common local seafood allergens (anchovy, tuna, mackerel, squid, giant freshwater prawn, shrimp, and crab), house dust mites (HDMs), and cockroach were analyzed retrospectively.

    RESULTS: The median age of the study subjects was 32 years (range 17-77 years) with a male to female ratio of 1:3. The mean duration of AD was 16 years. Eighty-two patients (62.2%) had other atopic conditions. Using SCORAD, 44.7% had mild, 42.4% moderate, and 12.9% severe disease. Eighty-six patients (65.2%) self-reported to have seafood allergy, with the main symptoms of transient pruritus and erythema within 2 h of ingestion. SPT revealed 51.5% of the patients were sensitized to at least 1 of the 7 seafood allergens. The relevant sensitization rate was 45.1%. Interestingly, 46% of those without a history of seafood allergy developed at least 1 positive reaction in the SPT. Prawn, shrimp, and crab were the 3 most frequently sensitized allergens. Nearly all patients (98.3%) who were sensitized to crustaceans were also sensitized to HDMs and/or cockroach. There was no significant correlation between a positive SPT to seafood with age, age of onset of AD, duration, and severity of AD, and the presence of other atopic diatheses.

    CONCLUSION: The relevant sensitization rate of local seafood among adults with AD was 45.1%.

  18. Paul AG, Ahmad NW, Lee HL, Ariff AM, Saranum M, Naicker AS, et al.
    Int Wound J, 2009 Feb;6(1):39-46.
    PMID: 19291114 DOI: 10.1111/j.1742-481X.2008.00564.x
    This is prospective case-control study of more than 18 months performed to assess the effectiveness of maggot debridement therapy (MDT) with the sterile larvae of Lucilia cuprina (a tropical blowfly maggot) for the treatment of diabetic foot ulcers. Literature thus far has only reported results with the temperate maggot, Lucilia sericata. This study documents outcome in diabetic foot wounds treated with maggot debridement versus those treated by conventional debridement alone. In this series of 29 patients treated with MDT, 14 wounds were healed, 11 were unhealed and 4 were classified under others. The control group treated by conventional debridement had 30 patients of which 18 wounds were healed, 11 unhealed and 1 classified under others. There was no significant difference in outcome between the two groups. The conclusion that can be made from this study is that MDT with L. cuprina is as effective as conventional debridement in the treatment of diabetic foot ulcers. It would be a feasible alternative to those at high risk for surgery or for those who refuse surgery.
  19. Rozilawati H, Tanaselvi K, Nazni WA, Mohd Masri S, Zairi J, Adanan CR, et al.
    Trop Biomed, 2015 Mar;32(1):49-64.
    PMID: 25801254 MyJurnal
    Entomological surveillance was conducted in order to determine the abundance and to evaluate any changes of biological vectors or ecology, especially in the dengue outbreak areas. The abundance and breeding preference of Aedes albopictus and Aedes aegypti were conducted in selected dengue outbreak localities in three states of peninsular Malaysia namely Selangor, Federal Territory of Kuala Lumpur, and Penang Island using ovitraps and larval survey method. It was determined that Ae. albopictus was predominant in most of the localities and found to breed more outdoor than indoor. A wide range of breeding foci were recorded in this study. It was also determined that ovitrap method was more effective to detect the presence of Aedes mosquitoes when the larval survey was at low rate of infestation. The abundance of Ae. albopictus in dengue outbreak localities emphasis that the vector control programme should also target this species together with the primary dengue vector, Ae. aegypti.
  20. Chen CD, Nazni WA, Lee HL, Norma-Rashid Y, Lardizabal ML, Sofian-Azirun M
    Trop Biomed, 2013 Jun;30(2):220-30.
    PMID: 23959487 MyJurnal
    Larvae of Aedes albopictus obtained from dengue endemic areas in Selangor, Malaysia were evaluated for their susceptibility to operational dosage of temephos (1 mg/L). Larval bioassays were carried out in accordance to modified WHO standard methods. Biochemical microassay of enzymes in Ae. albopictus was conducted to detect the emergence of insecticide resistance and to define the mechanisms involved in temephos resistance. The 50% mortality lethal time (LT50) for Ae. albopictus tested against temephos ranged between 58.65 to 112.50 minutes, with resistance ratio ranging from 0.75 - 1.45. This study addressed the fluctuation of time-related susceptibility status of Ae. albopictus towards insecticide. Significant difference on the weekly enzyme levels of non-specific esterases, mixed function oxidases and glutathione S-transferases was detected (p ≤ 0.05). No significant correlation was found between temephos resistance and enzyme activity (p > 0.05). Only glutathione S-transferases displayed high level of activity, indicating that Ae. albopictus may be resistant to other groups of insecticide. The insensitive acetylcholinesterase was detected in some field collected Ae. albopictus populations, indicating the possibility of emergence of carbamate or other organophosphate resistance in the field populations. Continuous resistance monitoring should be conducted regularly to confirm the efficacy of insecticides for dengue control.
Filters
Contact Us

Please provide feedback to Administrator (afdal@afpm.org.my)

External Links