Displaying publications 121 - 140 of 393 in total

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  1. Cross-mating between Malaysian strains of Aedes aegypti and Aedes albopictus in the laboratory
    Nazni WA, Lee HL, Dayang HA, Azahari AH
    Southeast Asian J Trop Med Public Health, 2009 Jan;40(1):40-6.
    PMID: 19323032
    Reciprocal and homologous mating experiments between Malaysian Aedes aegypti and Aedes albopictus mosquitoes were conducted in the laboratory. Two methods were employed, namely an artificial mating technique and a natural cage mating technique. The study demonstrated there exists a strong reproductive isolation between Ae. aegypti and Ae. albopictus. Insemination occurred in cross-mating experiments between Ae. aegypti females and Ae. albopictus males and also between Ae. albopictus females and Ae. aegypti males. Cross mating between Ae. aegypti females and Ae. albopictus males produced more eggs than that between Ae. albopictus females and Ae. aegypti males with both artificial mating and natural cage mating techniques. The matings did not result in the production of viable eggs by the females. No embryonation of these eggs was observed when the eggs were bleached. With homologous mating Aedes aegypti produced significantly greater numbers of eggs compared to Aedes albopictus mosquitoes, and all the eggs hatched successfully.
  2. Efficacy of commercial household insecticide aerosol sprays against Aedes aegypti (Linn.) under simulated field conditions
    Khadri MS, Kwok KL, Noor MI, Lee HL
    Southeast Asian J Trop Med Public Health, 2009 Nov;40(6):1226-34.
    PMID: 20578457
    A simulated field study on the efficacy of commercial household aerosol insecticides was conducted. The bioefficacy of three pyrethroid aerosols, designated as PA1, PA2 and PA3, was tested in cabins furnished to simulate bedroom conditions. Each aerosol product was tested against lab-bred Aedes aegypti mosquitoes based on the insecticide manufacturers' recommended dosages. Ten cages with mosquitoes were placed in the following locations: one cage in the middle of the room; two each on and underneath the bed; three each placed inside, behind and on top of the wardrobe; and four placed on and in the desk. With the desk, each cage was placed inside each of three drawers (totally closed, partially closed and opened). Prior to the experiments, the discharge rate of each aerosol can was determined. Ten to 20 lab-bred 2-5 day-old sugar-fed Ae. aegypti adult mosquitoes were placed inside the test cages. The aerosol was then discharged into the cabin at the recommended dosage. After 30 minutes, the mosquitoes were transferred into clean paper cups and their mortality recorded after 24 hours. All the aerosols induced complete or very high mortality in the caged Ae. aegypti females, except in the cages hidden completely inside the drawers and wardrobes. Insecticide droplet analysis indicated variable uniformity of the droplets was produced. The aerosol insecticides were effective against mosquitoes provided they were used in accordance with the manufacturers' recommendations.
  3. The effect of extrinsic incubation temperature on development of dengue serotype 2 and 4 viruses in Aedes aegypti (L.)
    Rohani A, Wong YC, Zamre I, Lee HL, Zurainee MN
    Southeast Asian J Trop Med Public Health, 2009 Sep;40(5):942-50.
    PMID: 19842378
    Dengue 2 and 4 viruses obtained from dengue-infected patients were maintained in a C6/36 Aedes albopictus Skuse cell line and used to infect adult female Aedes aegypti mosquitoes. Each serotype was mixed separately with fresh human erythrocytes and fed to adult female mosquitoes using an artificial membrane feeding technique. Fully engorged mosquitoes were selected and retained at 26 degrees C, 28 degrees C and 30 degrees C to observe dengue virus development in Aedes vectors. Virus detection was carried out by reverse-transcriptase polymerase chain reaction (RT-PCR). The virus was first detected on Day 9 at 26 degrees C and 28 degrees C and on Day 5 at 30 degrees C for both dengue 2 and 4. The study shows the incubation period of the viruses decreased when the extrinsic incubation temperature increases.
  4. Fulltext Bionomics of important mosquito vectors in Malaysia
    Vythilingam I, Chiang GL, Lee HL, Singh KI
    Southeast Asian J Trop Med Public Health, 1992 Dec;23(4):587-603.
    PMID: 1363679
  5. Isolation and Identification of novel toxins from a new mosquitocidal isolate from Malaysia, Bacillus thuringiensis subsp. jegathesan
    Kawalek MD, Benjamin S, Lee HL, Gill SS
    Appl Environ Microbiol, 1995 Aug;61(8):2965-9.
    PMID: 7487029
    A new mosquitocidal Bacillus thuringiensis subsp., jegathesan, has recently been isolated from Malaysia. Parasporal crystal inclusions were purified from this strain and bioassayed against fourth-instar larvae of Culex quinquefasciatus, Aedes aegypti, Aedes togoi, Aedes albopictus, Anopheles maculatus, and Mansonia uniformis. The 50% lethal concentration of crystal inclusions for each species was 0.34, 8.08, 0.34, 17.59, 3.91, and 120 ng/ml, respectively. These values show that parasporal inclusions from this new subspecies have mosquitocidal toxicity comparable to that of inclusions isolated from B. thuringiensis subsp. israelensis. Solubilized and chymotrypsin-activated parasporal inclusions possessed low-level hemolytic activity. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis revealed that the crystals were composed of polypeptides of 77, 74, 72, 68, 55, 38, 35, 27, and 23 kDa. Analysis by Western blotting (immunoblotting) with polyclonal antisera raised against toxins purified from B. thuringiensis subsp. israelensis reveals that proteins in parasporal inclusions of subsp. jegathesan are distinct, because little cross-reactivity was shown. Analysis of the plasmid content of B. thuringiensis subsp. jegathesan indicates that the genes for toxin production may be located on 105- to 120-kb plasmids. Cry- clones that have been cured of these plasmids are nontoxic. Southern blot analysis of plasmid and chromosomal DNA from subsp. jegathesan showed little or low homology to the genes coding for CryIVA, CryIVB, and CryIVD from B. thuringiensis subsp. israelensis.
  6. Fulltext Unraveling In vivo Potential of Curcumin-loaded Graphene Quantum Dots on Drug Delivery and Release Kinetics Aspects of Cancer Treatment
    Fahmi MZ, Sugito SFA, Wibrianto A, Novania S, Widyastuti S, Ahmad MA, et al.
    Nanotheranostics, 2024;8(4):521-534.
    PMID: 39507106 DOI: 10.7150/ntno.96559
    This study introduces an innovative magnetic-based multifunctional anti-cancer drug carrier aiming to enhance the efficacy of curcumin in cancer therapy. The research investigates the potential of Graphene Quantum Dots (GQDs) as a curcumin drug delivery system for inhibiting in vivo cancer growth. GQDs with a particle diameter below 10 nm were synthesized via hydrothermal and Hummers methods, exhibiting homogeneity and crystalline structure according to AFM and XRD analyses. FTIR analysis confirmed functionalization success, revealing the formation of bonds between GQDs and curcumin. The optical properties of GQDs were assessed using a UV-Vis spectrophotometer and spectrofluorometer, resulting in vigorous fluorescence with a quantum yield of 1.32%. Subsequently, loading curcumin onto GQDs (CQDs/cur) resulted in an efficient system for delivering the anti-cancer drug, demonstrating significant in vivo efficacy. It was indicated by reduced tumor diameter and increased body weight in mice. Furthermore, the release kinetics of curcumin from GQDs were analyzed using the Peppas-Sahlin equation under varying pH conditions (4, 7, and 9), revealing the highest release rate in acidic conditions. In conclusion, this study highlights the potential of GQDs as highly efficient carriers for targeted curcumin delivery, showcasing promising prospects in cancer treatment.
  7. Impact of phytic acid on nutrient bioaccessibility and antioxidant properties of dehusked rice
    Lee HH, Loh SP, Bong CF, Sarbini SR, Yiu PH
    J Food Sci Technol, 2015 Dec;52(12):7806-16.
    PMID: 26604353 DOI: 10.1007/s13197-015-1918-9
    Whole grains consumption promotes health benefits, but demonstrates controversial impacts from phytic acid in meeting requirements of good health. Therefore, this study was aimed to determine the nutrient bioaccessibility and antioxidant properties of rice cultivars named "Adan" or "Bario" and deduce the nutritional impact of phytic acid. Majority of the dehusked rice in the collection showed an acceptable level of in-vitro starch digestibility and in-vitro protein digestibility, but were poor in antioxidant properties and bioaccessibility of minerals (Ca, Fe and Zn). The drawbacks identified in the rice cultivars were due to relatively high phytic acid content (2420.6 ± 94.6 mg/100 g) and low phenolic content (152.39 ± 18.84 μg GAE/g). The relationship between phytic acid content and mineral bioaccessibility was strongest in calcium (r = 0.60), followed by iron (r = 0.40) and zinc (r = 0.27). Phytic acid content did not significantly correlate with in-vitro starch digestibility and in-vitro protein digestibility but showed a weak relationship with antioxidant properties. These suggest that phytic acid could significantly impair the mineral bioaccessibility of dehusked rice, and also act as an important antioxidant in non-pigmented rice. Bario rice cultivars offered dehusked rice with wide range of in-vitro digestibility of starch and protein, and also pigmented rice as a good source of antioxidants. However, there is a need to reduce phytic acid content in dehusked rice for improved mineral bioaccessibility among Bario rice cultivars.
  8. Eco-virological survey of Aedes mosquito larvae in selected dengue outbreak areas in Malaysia
    Rohani A, Aidil Azahary AR, Malinda M, Zurainee MN, Rozilawati H, Wan Najdah WM, et al.
    J Vector Borne Dis, 2014 Dec;51(4):327-32.
    PMID: 25540966
    BACKGROUND & OBJECTIVESI: Transovarial transmission of dengue virus in the Aedes vectors is now a well-documented phenomenon reported from many parts of the endemic areas in the world, which played an important role in initiating and maintaining the outbreak in human populations. This study investigated the factors affecting breeding habitats and the relationship with transovarial dengue virus in larvae of Aedes aegypti and Ae. albopictus.
  9. Fulltext Isolation and characterization of CCoAOMT in interspecific hybrid of Acacia auriculiformis x Acacia mangium--a key gene in lignin biosynthesis
    Pang SL, Ong SS, Lee HH, Zamri Z, Kandasamy KI, Choong CY, et al.
    Genet. Mol. Res., 2014;13(3):7217-38.
    PMID: 25222227 DOI: 10.4238/2014.September.5.7
    This study was directed at the understanding of the function of CCoAOMT isolated from Acacia auriculiformis x Acacia mangium. Full length cDNA of the Acacia hybrid CCoAOMT (AhCCoAOMT) was 1024-bp long, containing 750-bp coding regions, with one major open reading frame of 249 amino acids. On the other hand, full length genomic sequence of the CCoAOMT (AhgflCCoAOMT) was 2548 bp long, containing three introns and four exons with a 5' untranslated region (5'UTR) of 391 bp in length. The 5'UTR of the characterized CCoAOMT gene contains various regulatory elements. Southern analysis revealed that the Acacia hybrid has more than three copies of the CCoAOMT gene. Real-time PCR showed that this gene was expressed in root, inner bark, leaf, flower and seed pod of the Acacia hybrid. Downregulation of the homologous CCoAOMT gene in tobacco by antisense (AS) and intron-containing hairpin (IHP) constructs containing partial AhCCoAOMT led to reduction in lignin content. Expression of the CCoAOMT in AS line (pART-HAS78-03) and IHP line (pART-HIHP78-06) was reduced respectively by 37 and 75% compared to the control, resulting in a decrease in the estimated lignin content by 24 and 56%, respectively. AhCCoAOMT was found to have altered not only S and G units but also total lignin content, which is of economic value to the pulp industry. Subsequent polymorphism analysis of this gene across eight different genetic backgrounds each of A. mangium and A. auriculiformis revealed 47 single nucleotide polymorphisms (SNPs) in A. auriculiformis CCoAOMT and 30 SNPs in A. mangium CCoAOMT.
  10. 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.
  11. Fulltext Formation of biofilm by Listeria monocytogenes ATCC 19112 at different incubation temperatures and concentrations of sodium chloride
    Lee HY, Chai LC, Pui CF, Mustafa S, Cheah YK, Nishibuchi M, et al.
    Braz J Microbiol, 2013;44(1):51-5.
    PMID: 24159283 DOI: 10.1590/S1517-83822013005000004
    Biofilm formation can lead to various consequences in the food processing line such as contamination and equipment breakdowns. Since formation of biofilm can occur in various conditions; this study was carried out using L. monocytogenes ATCC 19112 and its biofilm formation ability tested under various concentrations of sodium chloride and temperatures. Cultures of L. monocytogenes ATCC 19112 were placed in 96-well microtitre plate containing concentration of sodium chloride from 1-10% (w/v) and incubated at different temperature of 4 °C, 30 °C and 45 °C for up to 60 h. Absorbance reading of crystal violet staining showed the density of biofilm formed in the 96-well microtitre plates was significantly higher when incubated in 4 °C. The formation of biofilm also occurs at a faster rate at 4 °C and higher optical density (OD 570 nm) was observed at 45 °C. This shows that storage under formation of biofilm that may lead to a higher contamination along the processing line in the food industry. Formation of biofilm was found to be more dependent on temperature compared to sodium chloride stress.
  12. Fulltext An unusual entry site of an intraorbital foreign body in a child
    Mallika PS, Chong YJ, Tan AK, Tang IP, Aziz S, Lee HK
    Med J Malaysia, 2011 Oct;66(4):361-2.
    PMID: 22299559 MyJurnal
    Intraorbital foreign bodies (IOrbFB) are associated with both sight and life threatening injuries. We report a case of an IOrbFB associated with retrobulbar hemorrhage and injury of the frontal sinus in an 11 year-old boy, after history of fall from the tree. Imaging studies revealed a metallic foreign body (FB) in the orbit and fracture of the walls of the frontal sinus. The usual entry route of an IOrbFB is either through the eye or orbital walls and extremely rare through the paranasal sinuses. This is the first reported case of a FB entering the orbit through the frontal sinus.
  13. 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.
  14. Daphnifolin, a new xanthone from Mesua daphnifolia (Guttiferae)
    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.
  15. 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.
  16. Current susceptibility status of Malaysian Culex quinquefasciatus (Diptera: Culicidae) against DDT, propoxur, malathion, and permethrin
    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.
  17. Fulltext Brain and spinal tumour
    Goh CH, Lu YY, Lau BL, Oy J, Lee HK, Liew D, et al.
    Med J Malaysia, 2014 Dec;69(6):261-7.
    PMID: 25934956 MyJurnal
    This study reviewed the epidemiology of brain and spinal tumours in Sarawak from January 2009 till December 2012. The crude incidence of brain tumour in Sarawak was 4.6 per 100,000 population/year with cumulative rate 0.5%. Meningioma was the most common brain tumour (32.3%) and followed by astrocytoma (19.4%). Only brain metastases showed a rising trend and cases were doubled in 4 years. This accounted for 15.4% and lung carcinoma was the commonest primary. Others tumour load were consistent. Primitive neuroectodermal tumour (PNET) and astrocytoma were common in paediatrics (60%). We encountered more primary spinal tumour rather than spinal metastases. Intradural schwannoma was the commonest and frequently located at thoracic level. The current healthcare system in Sarawak enables a more consolidate data collection to reflect accurate brain tumours incidence. This advantage allows subsequent future survival outcome research and benchmarking for healthcare resource planning.
  18. Doses to patients in routine X-ray examinations in Malaysia
    Ng KH, Rassiah P, Wang HB, Hambali AS, Muthuvellu P, Lee HP
    Br J Radiol, 1998 Jun;71(846):654-60.
    PMID: 9849390
    A collaborative national survey initiated by the University of Malaya and the Ministry of Health was conducted from 1993 to 1995 to establish baseline patient dose data for seven common types (12 projections) of X-ray examinations in Malaysia. A total of 12 randomly selected public hospitals and 867 patients were included in this survey. The entrance surface doses (ESD) received by the patients were measured using thermoluminescent dosemeters (TLDs) attached to the patient's skin. Histograms are presented showing wide, positively skewed distributions of measured entrance surface doses for each examination. Mean, median, first and third quartile values of ESD and median effective dose are reported. Survey results are generally comparable with those reported in the UK, USA and by the International Atomic Energy Agency (IAEA). The results also provide information on dose level for a lower weight population (mean weight 60 kg) compared with the international reference dose values based on a 70 kg standard. The findings support the importance of the on-going national quality assurance programme to ensure doses are kept to a level consistent with optimum image quality. The data will also be useful for the formulation of national guidance levels as recommended by the IAEA. Furthermore, this study provides patient dosimetry information on healthcare level II countries.
  19. Urine as a diagnostic specimen for the detection of Chlamydia trachomatis in Malaysia by ligase chain reaction
    Gaydos CA, Ngeow YF, Lee HH, Canavaggio M, Welsh LE, Johanson J, et al.
    Sex Transm Dis, 1996 9 1;23(5):402-6.
    PMID: 8885072
    BACKGROUND AND OBJECTIVES: Noninvasive urine screening for Chlamydia trachomatis infections offers a valuable public health tool, which could be of vast importance in chlamydial control programs. The authors evaluated a new DNA amplification method, ligase chain reaction (LCR).

    GOALS: The goal was to ascertain whether urine testing could be used as screening method to detect C. trachomatis infections in commercial sex workers, patients at sexually transmitted diseases clinic, and asymptomatic patients in Kuala Lumpur, Malaysia.

    METHODS: First-void urine specimens from 300 men and 300 women were tested by LCR, as well as by a commercially available enzyme immunoassay. The LCR assay amplifies specific sequences within the chlamydial plasmid with ligand-labeled probes, and the resultant amplicons are detected by an automated immunoassay. Specimens with discrepant results were confirmed by another LCR of the specimen that targeted the gene for the major outer membrane protein (OMP1).

    RESULTS: There were 31 LCR-positive male urine and 37 LCR-positive female urine specimens. The resolved sensitivity and specificity for the LCR of the male urine specimens were 100% and 99.6%, respectively, whereas for female urine specimens, the sensitivity and specificity were 100% and 98.5%, respectively. After resolution of discrepant test results by OMP1 LCR, the prevalence was 10% for men and 11% for women. The urine enzyme immunoassay was not useful in diagnosing C. trachomatis infections in either men or women, as the resolved sensitivities were 10% and 15.2%, respectively. The specificities were 99.6% for men and 98.9% for women.

    CONCLUSIONS: Testing first-void urine specimens by LCR is a highly sensitive and specific method to diagnose C. trachomatis infections in men and women, providing health care workers and public health officials with a new molecular amplification assay that uses noninvasive urine specimens for population-based screening purposes.

  20. Fulltext Modelling the Effect of a Novel Autodissemination Trap on the Spread of Dengue in Shah Alam and Malaysia
    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.
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