Displaying publications 81 - 100 of 375 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. Fulltext Intraventricular angiolipoma
    Lee HK, Ghani AR, Sayuthi S, Abdullah J, Mustaffa F, Othman N, et al.
    Med J Malaysia, 2007 Oct;62(4):339-40.
    PMID: 18551942 MyJurnal
    We report a case of 50-year-old man who was presented with recurrent episodes of left sided hemiparesis. CT scan and MRI brain revealed a large intraventricular fatty lesion. Histopathological examination showed a picture of angiolipoma.
  3. Modeling fish community dynamics in the Florida Everglades: role of temperature variation
    Al-Rabai'ah HA, Koh HL, DeAngelis D, Lee HL
    Water Sci Technol, 2002;46(9):71-8.
    PMID: 12448454
    Temperature variation is an important factor in Everglade wetlands ecology. A temperature fluctuation from 17 degrees C to 32 degrees C recorded in the Everglades may have significant impact on fish dynamics. The short life cycles of some of Everglade fishes has rendered this temperature variation to have even more impacts on the ecosystem. Fish population dynamic models, which do not explicitly consider seasonal oscillations in temperature, may fail to describe the details of such a population. Hence, a model for fish in freshwater marshes of the Florida Everglades that explicitly incorporates seasonal temperature variations is developed. The model's main objective is to assess the temporal pattern of fish population and densities through time subject to temperature variations. Fish population is divided into 2 functional groups (FGs) consisting of small fishes; each group is subdivided into 5-day age classes during their life cycles. Many governing sub-modules are set directly or indirectly to be temperature dependent. Growth, fecundity, prey availability, consumption rates and mortality are examples. Several mortality sub-modules are introduced in the model, of which starvation mortality is set to be proportional to the ratio of prey needed to prey available at that particular time step. As part of the calibration process, the model is run for 50 years to ensure that fish densities do not go to extinction, while the simulation period is about 8 years. The model shows that the temperature dependent starvation mortality is an important factor that influences fish population densities. It also shows high fish population densities at some temperature ranges when this consumption need is minimum. Several sensitivity analyses involving variations in temperature terms, food resources and water levels are conducted to ascertain the relative importance of temperature dependence terms.
  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. Fulltext Microdroplet application of mosquitocidal Bacillus thuringiensis using ultra-low-volume generator for the control of mosquitos
    Seleena P, Lee HL, Nazni WA, Rohani A, Kadri MS
    Southeast Asian J. Trop. Med. Public Health, 1996 Sep;27(3):628-32.
    PMID: 9185282
    In an effort to develop a more effective technique in dispersing a microbial control agent, Bacillus thuringiensis (Bt), a truck-mounted ultra low volume (ULV) generator (Scorpion) was used to disperse B. thuringiensis israelensis (Bti) and Bti with malathion. Complete larval and adult mortalities for all tested mosquito species within the first 70-80 feet from the ULV generator were achieved. Beyond that distance less than 50% mortality was achieved as insufficient sprayed particles reached the area. A minimum of 10(3) Bti colony forming units per ml is required to cause 100% larval mortality. The sprayed Bti larvicidal toxins were persistent in the test water 7 days post ULV. The effectiveness of B. thuringiensis jegathesan (Btj), a new mosquitocidal Bt serotype was also evaluated. Similar mortality results as Bti were achieved except that the Btj toxins underwent degradation in the test water, since less than 50% less in larval mortality was observed in 7 days post ULV samples. This ULV method has the potential to disperse Bt and malathion effectively for a simultaneous control of mosquito adults and larvae.
  6. Fulltext A case of human enteric myiasis due to larvae of Hermetia illucens (Family: Stratiomyiadae): first report in Malaysia
    Lee HL, Chandrawathani P, Wong WY, Tharam S, Lim WY
    Malays J Pathol, 1995 Dec;17(2):109-11.
    PMID: 8935136
    A case of true enteric myiasis in a 7-year-old girl is reported. Two larvae were obtained from the vomitus of the patient. After processing and identification, the larvae were found to be those of Hermetia illucens (Soldier Fly). This is the first case of true enteric myiasis due to these larvae in Malaysia.
  7. Fulltext Non-Hodgkin's lymphoma in an Asian population: 1968-1992 time trends and ethnic differences in Singapore
    Seow A, Lee J, Sng I, Fong CM, Lee HP
    Cancer, 1996 May 1;77(9):1899-904.
    PMID: 8646691
    BACKGROUND: Non-Hodgkin's lymphoma has increased in incidence in many countries, particularly in the West. Advances in diagnostic methods and the understanding of the disease over time pose a challenge to the interpretation of these trends. The aim of this study was to determine if the disease has increased in Singapore, a newly industrialized Asian country, and to examine the possible factors that may account for any observed changes.
    METHODS: Data from the population-based Singapore Cancer Registry for the period 1968 to 1992 were reviewed to determine time trends based on sex and ethnic group. The Poisson regression model was fitted to the cross-tabulated data to obtain the adjusted incidence density ratios.
    RESULTS: A total of 1988 cases of non-Hodgkin's lymphoma were included in the analysis. There was an overall increase in incidence among both Chinese and Malaysians. However, the rate of increase was greater in females (age-standardized rate from 1.8 per 100,000 in 1968-1972 to 4.5 per 100,000 in 1988-1992) than in males (3.2 per 100,000 to 5.9 per 100,000 in the same time periods). Between ethnic groups, Malay females were at higher overall risk compared with their Chinese counterparts (incidence density ratio 1.32; 95% confidence interval, 1.08-1.61). Although a substantial proportion of patients diagnosed with Hodgkin's disease between 1968 and 1972 were reclassified on review, using present criteria, as having non-Hodgkin's lymphoma, it is unlikely that this, and other recent changes in histologic interpretation, could have accounted for an increase of this magnitude.
    CONCLUSIONS: Non-Hodgkin's lymphoma has increased in incidence among the Chinese and Malay populations in Singapore. The pattern of increase differs from that of the common cancer sites, and suggests the need to look for environmental and genetic factors that have not yet been elucidated.
  8. Breast cancer in Singapore: trends in incidence 1968-1992
    Seow A, Duffy SW, McGee MA, Lee J, Lee HP
    Int J Epidemiol, 1996 Feb;25(1):40-5.
    PMID: 8666502
    BACKGROUND: Breast cancer is the most commonly occurring cancer among women in Singapore, a country which has experienced significant changes in lifestyle over the past three decades. The increase in incidence of the disease is a matter of some concern.

    METHODS: Data from the population-based Singapore Cancer Registry for 1968-1992 were used to determine time trends, inter-ethnic differences and the contributions of age, period and cohort effects to the incidence of the disease.

    RESULTS: Our results revealed an average annual increase of 3.6% over the 25-year period for all women, form 20.2 per 100,000 women in the period 1968-1972 to 38.8 per 100,000 in 1988-1992. There was a statistically significant difference between the three major ethnic groups, the rate of increase being highest in Malays (4.4%) and lowest in Indians (1.4%). The overall increase was attributable to a strong cohort effect that remained significant when adjusted for time period for Chinese women and for all ethnic groups combined. The risk was observed to increase in successive birth cohorts from the 1890s to 1960s.

    CONCLUSIONS: Our results suggest that breast cancer incidence rates are likely to continue to increase more sharply in the future as women born after the mid-20th century reach the high-risk age groups. They also suggest the pattern by which important aetiological factors for the disease in our population have exerted their effects, and provide support for the role of demographic and lifestyle changes as possible risk factors.

  9. Fulltext An outbreak of dermatitis among stevodores
    Phoon WH, Lee HS, Ho SF, Ngui SJ
    Med J Malaysia, 1985 Sep;40(3):220-4.
    PMID: 2948100
    Cement is a common cause of dermatitis. Workers affected are usually those in cement factories and at building construction sites. Cement dermatitis among port-workers is not so commonly reported. This paper describes an outbreak of dermatitis among stevodores at a port handling cement. The cement was imported in bags, and because of breakage, there was much spillage. It was also hot and dusty inside the hatch of the ship, and some of the stevodores worked bare-bodied. Cases of dermatitis began to appear in January 1983 and reached a peak in April 1983, gradually subsiding over the next few months to August 1983. This coincided with the increased tonnage of cement handled at the port. A total of 33 stevodores were reported as having dermatitis over this period. Of the 15 cases examined, 13 had eczema, and in 19 the hands and wrists were affected. However, most of the cases had multiple site involvement, including the arms, legs and abdomen.
    Samples of cement showed the presence of water-soluble chromium, varying from 9.9 to 17.8pg/g. As the stevodores were reluctant to go for skin patch-testing, only four were tested, but two did not return for the reading of the results. The other two were found to have a positive reaction to dichromates. The outbreak of dermatitis was probably due to several factors which are discussed.
  10. [Clostridium bifermentans serovar malaysia, a new anaerobic bacterium pathogen to mosquito and blackfly larvae]
    de Barjac H, Sebald M, Charles JF, Cheong WH, Lee HL
    C. R. Acad. Sci. III, Sci. Vie, 1990;310(9):383-7.
    PMID: 1972899
    A strain of Clostridium bifermentans individualized as serovar malaysia (C.b.m.) according to its specific H antigen is toxic to mosquito and blackfly larvae when given orally. The toxicity occurs in sporulated cells which contain, in addition to spores, proteinic parasporal inclusion bodies and feather-like appendages; the amino acid content of the inclusion bodies is similar to that of Bacillus thuringiensis serovar israelensis (B.t.i.) and B. sphaericus crystals. The toxicity to Anopheles stephensi is as high as that of B.t.i. and the best strains of B. sphaericus. Culex pipiens is somewhat less susceptible, and Aedes aegypti much less. Pure parasporal inclusion bodies, isolated by ultracentrifugation on sucrose gradients, are highly toxic to mosquito larvae. The larvicidal power is destroyed by heating at 80 degrees C or by treatment with 50 mM NaOH. It is preserved by freeze-drying. The innocuity to mice of the sporulated cells is shown by different routes of administration: force-feeding, percutaneous, subcutaneous, intraperitoneal or intravenous injections. The potential for the biological control of mosquito and blackfly larvae is suggested.
  11. Idiopathic scoliosis. Prevalence and ethnic distribution in Singapore schoolchildren
    Daruwalla JS, Balasubramaniam P, Chay SO, Rajan U, Lee HP
    J Bone Joint Surg Br, 1985 Mar;67(2):182-4.
    PMID: 3980521
    Routine examination for spinal deformity as part of a school health screening programme was introduced in Singapore in 1981. The three different ethnic groups included in the study provided figures for the prevalence of idiopathic scoliosis in an Asian population. A three-tier system of examination was used and a total of 110744 children in three age groups were studied. In those aged 6 to 7 years the prevalence was 0.12%. The prevalence in those aged 11 to 12 years was 1.7% for girls and 0.4% for boys, a ratio of 3.2 to 1. In girls aged 16 to 17 years the prevalence was 3.1%. In the latter two age groups there was a significantly higher prevalence in Chinese girls as compared with Malay and Indian girls. The optimal age for school screening seemed to be 11 to 12 years, but repeated examinations may be worthwhile.
  12. Ultralow volume application of Bacillus thuringiensis ssp. israelensis for the control of mosquitoes
    Lee HL, Gregorio ER, Khadri MS, Seleena P
    J Am Mosq Control Assoc, 1996 Dec;12(4):651-5.
    PMID: 9046471
    Evaluation of the effectiveness of Bacillus thuringiensis ssp. israelensis (B.t.i.) against mosquito larvae dispersed by ultralow volume (ULV) spraying was conducted in simulated field trials. Effectiveness was measured using 3 different indicators: larval mortality, colony-forming unit enumeration, and droplet analysis. B.t.i. was dispersed with a ULV generator using 2 different flow rates: 0.3 and 0.5 liter/min on 2 different days. Based on the results of this study, it can be concluded that an output of 0.3 liter/min is effective for controlling Aedes aegypti. although a dosage of 0.5 liter/min can be used when high residual activity is desired. For Culex quinquefasciatus control, both dosages were effective but with low residual activity. For Anopheles maculatus control, only a discharge rate of 0.5 liter/min was effective with low residual activity. B.t.i. application at both dosages penetrated tires well, indicating that B.t.i. ULV application is an effective method for controlling container-inhabiting mosquitoes. Good coverage of target area and penetration were attributed to satisfactory droplet profiles.
  13. TEMPO-oxidized nanocellulose films derived from coconut residues: Physicochemical, mechanical and electrical properties
    Hassan SH, Velayutham TS, Chen YW, Lee HV
    Int J Biol Macromol, 2021 Jun 01;180:392-402.
    PMID: 33737185 DOI: 10.1016/j.ijbiomac.2021.03.066
    The present work focuses on the development of cellulose nanofibrils (CNF) film that derived from sustainable biomass resources, which potentially to work as bio-based conductive membranes that assembled into supercapacitors. The chemically purified cellulose was isolated from different parts of coconut (coconut shell and its husk) and further subjected to 2,2,6,6-tetramethylpiperidine-1-oxyl radical (TEMPO)-mediated oxidation for CNF preparation. Physicochemical properties of prepared CNFs were studied in terms of chemical characteristics & crystallinity, surface functionalities, surface morphology, and thermal properties. Both coconut shell-derived CNF and coconut husk-derived CNF fulfilled with nanocellulose's characteristics with fibres width ranged of 70-120 nm and 150-330 nm, respectively. CNF films were further prepared by solvent casting method to measure the modulus elasticity, piezoelectric and dielectric properties of the films. Mechanical study indicated that coconut shell-derived CNF film showed a higher value of elastic modulus than the coconut husk-derived CNF film, which was 8.39 GPa and 5.36 GPa, respectively. The effectiveness of electrical aspects for CNF films are well correlated with the crystallinity and thermal properties, associated with it's composition of different coconut's part.
  14. A case of xanthogranulomatous appendicitis in the female pelvis
    Yung WH, Siew CHC, Lee HY, Low HM
    Med J Malaysia, 2021 Jan;76(1):114-117.
    PMID: 33510122
    Xanthogranulomatous inflammation is an uncommon form of chronic inflammatory process. Only a few isolated case reports of xanthogranulomatous appendicitis (XA) have been published. XA has nonspecific imaging findings and cannot be reliably differentiated on imaging from locally advanced malignancy. XA however follows a benign course and can potentially be treated with surgical resection.
  15. A case of co-infection: First reported case of severe plasmodium knowlesi malaria and dengue co-infection in Sabah, Malaysia
    Wong CK, Md Fuzi NH, Baherin MF, Lee HG
    Med J Malaysia, 2020 03;75(2):171-172.
    PMID: 32281602
    We report a rare case of severe Plasmodium knowlesi malaria and dengue co-infection in a 36-year-old lady with hyperparasitaemia, metabolic acidosis, haemolysis and acute kidney injury. She was in shock requiring inotropic support and elective intubation. She had pericardial tamponade which necessitate pericardiocentesis to allow for haemodynamic stability during haemodialysis. She underwent haemodialysis, was ventilated for six days and stayed in hospital for 29 days. She was discharged home well with almost complete renal recovery. Physicians must have a high degree of suspicion for dengue co-infection in malaria patients with plasma leakage such as pericardial effusion to allow for prompt management.
  16. Fulltext Evaluation of Sumithion L-40 against Aedes aegypti (L.) and Aedes albopictus Skuse
    Loke SR, Sing KW, Teoh GN, Lee HL
    Trop Biomed, 2015 Mar;32(1):76-83.
    PMID: 25801256 MyJurnal
    Space spraying of chemical insecticides is still an important mean of controlling Aedes mosquitoes and dengue transmission. For this purpose, the bioefficacy of space-sprayed chemical insecticide should be evaluated from time to time. A simulation field trial was conducted outdoor in an open field and indoor in unoccupied flat units in Kuala Lumpur, to evaluate the adulticidal and larvicidal effects of Sumithion L-40, a ULV formulation of fenitrothion. A thermal fogger with a discharge rate of 240 ml/min was used to disperse Sumithion L-40 at 3 different dosages (350 ml/ha, 500 ml/ha, 750 ml/ha) against lab-bred larvae and adult female Aedes aegypti and Aedes albopictus. An average of more than 80% adult mortality was achieved for outdoor space spray, and 100% adult mortality for indoor space spray, in all tested dosages. Outdoor larvicidal effect was noted up to 14 days and 7 days at a dosage of 500 and 750 ml/ha for Ae. aegypti and Ae. albopictus, respectively. Indoor larvicidal effect was up to 21 days (500 ml/ha) and 14 days (750 ml/ha), respectively, after spraying with larval mortality > 50% against Ae. aegypti. This study concluded that the effective dosage of Sumithion L-40 thermally applied against adult Ae. aegypti and Ae. albopictus indoor and outdoor is 500 and 750 ml/ha. Based on these dosages, effective indoor spray volume is 0.4 - 0.6 ml/m³. Additional indoor and outdoor larvicidal effect will be observed at these application dosages, in addition to adult mortality.
  17. Fulltext Effects of preservatives and killing methods on morphological features of a forensic fly, Chrysomya megacephala (Fabricius, 1794) larva
    Rosilawati R, Baharudin O, Syamsa RA, Lee HL, Nazni WA
    Trop Biomed, 2014 Dec;31(4):785-91.
    PMID: 25776605 MyJurnal
    Preservation of larvae retrieved from cadavers is important in ensuring the quality and integrity of entomological specimens used for the estimation of post-mortem interval (PMI). The process of killing and preserving larvae could distort the larvae leading to inaccurate estimation of PMI. In this study, the effects of killing Chrysomya megacephala larvae with hot water at different temperatures and subsequent maintenance in various preservatives were determined. Larvae not killed by hot water but preserved directly were used as control. The types of preservative used were 10% formalin, 70% ethanol and Kahle's solution. The morphological features examined were length, turgidity, curvature and coloration of larvae. Larvae killed in 80ºC hot water have shorter mean length (12.47 ± 2.86 mm) compared to those in 60ºC hot water (12.95 ± 2.69 mm). Increasing the duration of preservation in all types of preservative caused elongations of larvae treated or untreated with hot water. There were no significant changes in larval turgidity preserved in Kahle's solution compared to other two preservatives and were unaffected by the duration of storage. Larvae preserved in Kahle's solution experienced the least changes in coloration and shape compared to other preserved larvae in 70% ethanol or 10% formalin. Larvae directly immersed alive in 70% ethanol experienced the most changes in curvature, coloration and turgidity. This study suggested that killing larvae with hot water at 80ºC and preservation in Kahle's solution is the optimum method resulting in least changes in morphological features of Ch. megacephala larvae.
  18. Fulltext Current insecticide susceptibility status of Malaysian Anopheles maculatus Theobald to malathion, permethrin, DDT and deltamethrin
    Rohani A, Aziz I, Zurainee MN, Rohana SH, Zamree I, Lee HL
    Trop Biomed, 2014 Mar;31(1):159-65.
    PMID: 24862056 MyJurnal
    Chemical insecticides are still considered as important control agents for malaria vector control. However, prolonged use of these chemicals may select mosquito vectors for resistance. In this study, susceptibility status of adult Anopheles maculatus collected from 9 localities in peninsular Malaysia, viz., Jeli, Temerloh, Pos Banun, Senderut, Jeram Kedah, Segamat, Kota Tinggi, Kluang and Pos Lenjang were determined using the standard WHO bioassay method in which the adult mosquitoes were exposed to standard insecticide impregnated papers malathion, permethrin, DDT and deltamethrin--at pre-determined diagnostic dosage. Deltamethrin was most effective insecticide among the four insecticides tested, with the LT50 of 29.53 min, compared to malathion (31.67 min), DDT (47.76 min) and permethrin (48.01 min). The effect of all insecticides on the laboratory strain was greater (with all insecticides demonstrated LT50 < 1 hour) than the field strains (deltamethrin 32.7, malathion 53.0, permethrin 62.0, DDT 67.4 min). An. maculatus exhibited low degree of resistance to all test insecticides, indicating that these chemical insecticides are still effective in the control of malaria vector.
  19. Fulltext Molecular identification of Malaysian Chrysomya megacephala (Fabricius) and Chrysomya rufifacies (Macquart) using life stage specific mitochondrial DNA
    Kavitha R, Tan TC, Lee HL, Nazni WA, Sofian AM
    Trop Biomed, 2013 Jun;30(2):211-9.
    PMID: 23959486 MyJurnal
    DNA identification of blow fly species can be a very useful tool in forensic entomology. One of the potential benefits that mitochondrial DNA (mtDNA) has offered in the field of forensic entomology is species determination. Conventional identification methods have limitations for sibling and closely related species of blow fly and stage and quality of the specimen used. This could be overcome by DNA-based identification methods using mitochondrial DNA which does not demand intact or undamaged specimens. Mitochondrial DNA is usually isolated from whole blow fly and legs. Alternate sources for mitochondrial DNA isolation namely, egg, larva, puparium and empty puparium were explored in this study. The sequence of DNA obtained for each sample for every life cycle stage was 100% identical for a particular species, indicating that the egg, 1st instar, 2nd instar, 3rd instar, pupa, empty puparium and adult from the same species and obtained from same generation will exhibit similar DNA sequences. The present study also highlighted the usefulness of collecting all life cycle stages of blow fly during crime scene investigation with proper preservation and subsequent molecular analysis. Molecular identification provides a strong basis for species identification and will prove an invaluable contribution to forensic entomology as an investigative tool in Malaysia.
  20. Fulltext DNA typing of Calliphorids collected from human corpses in Malaysia
    Kavitha R, Tan TC, Lee HL, Nazni WA, Sofian-Azirun M
    Trop Biomed, 2013 Mar;30(1):119-24.
    PMID: 23665717 MyJurnal
    Estimation of post-mortem interval (PMI) is crucial for time of death determination. The advent of DNA-based identification techniques forensic entomology saw the beginning of a proliferation of molecular studies into forensically important Calliphoridae (Diptera). The use of DNA to characterise morphologically indistinguishable immature calliphorids was recognised as a valuable molecular tool with enormous practical utility. The local entomofauna in most cases is important for the examination of entomological evidences. The survey of the local entomofauna has become a fundamental first step in forensic entomological studies, because different geographical distributions, seasonal and environmental factors may influence the decomposition process and the occurrence of different insect species on corpses. In this study, calliphorids were collected from 13 human corpses recovered from indoors, outdoors and aquatic conditions during the post-mortem examination by pathologists from the government hospitals in Malaysia. Only two species, Chrysomya megacephala and Chrysomya rufifacies were recovered from human corpses. DNA sequencing was performed to study the mitochondrial encoded COI gene and to evaluate the suitability of the 1300 base pairs of COI fragments for identification of blow fly species collected from real crime scene. The COI gene from blow fly specimens were sequenced and deposited in GenBank to expand local databases. The sequenced COI gene was useful in identifying calliphorids retrieved from human corpses.
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