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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.
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.
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.
Recovery of forensically important insect larvae from human cadavers in Malaysia (1993-1996)

Lee HL

Malays J Pathol, 1996 Dec;18(2):125-7.
PMID: 10879234

Forensically important entomological specimens recovered from 95 forensic cases of human cadavers from April 1993 to May 1996 in Malaysia were identified and analysed. The results indicated that 73.7% of these specimens were Chrysomya species, occurring either as single or mixed infestations. Of these, the most prominent species were Ch megacephala (F.) and Ch rufifacies (Macquart). Other fly maggots recovered included Sarcophaga spp., Lucilia spp. and Hermetia spp., mostly occurring together with other calliphorine flies. A member of Muscidae fly, Ophyra spp. was also recovered for the first time.
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.
Fulltext Insecticide resistance status and mechanisms in Malaysian Blattella germanica (Linnaeus)

Lee HL, Tien WD, Omar B

Southeast Asian J. Trop. Med. Public Health, 1997 Mar;28(1):212-7.
PMID: 9322308

The insecticide resistance status of 4 strains of adult male Blattella germanica, viz M (Malacca), E (England), F (restaurant) and K (cafeteria) against malathion and bendiocarb compared with a reference susceptible strain (S) was determined by using a modified WHO bioassay method. The results indicated that all the 4 strains were resistant to the insecticides albeit in different degrees. Resistance ratios for malathion ranged from 1.85-41.07-fold, whereas that of bendiocarb ranged from 1.68-4.83-fold. The biochemical microplate enzyme assays technique employed indicated that the resistance in M and E strains were attributed to acetylcholinesterase insensitivity. Multiple resistance was not detected in any of the 4 strains. Parameters of the identified resistance mechanism correlated well with the observed level of resistance. Agar gel electrophoresis showed that variations in esterase isoenzymes did not confer organophosphate and carbamate resistance to the 4 strains.
Fulltext Does transovarial transmission of dengue virus occur in Malaysian Aedes aegypti and Aedes albopictus?

Lee HL, Mustafakamal I, Rohani A

Southeast Asian J. Trop. Med. Public Health, 1997 Mar;28(1):230-2.
PMID: 9322311
Fulltext A randomised double-blind study of vaginal misoprostol vs dinoprostone for cervical ripening and labour induction in prolonged pregnancy

Lee HY

Singapore Med J, 1997 Jul;38(7):292-4.
PMID: 9339095

Dinoprostone, is presently used in our standard protocol for cervical ripening and labour induction. In search for a cheaper alternative, misoprostol has been found to be a good substitute. In view of the potential saving it might offer, we set out to test its efficacy against the standard dinoprostone.
Fulltext Effect of sublethal dosages of malathion on the oral susceptibility of Aedes aegypti to dengue-2 virus infection

Lee HL, Argubano RA, Ahmad R

Southeast Asian J. Trop. Med. Public Health, 1997 Sep;28(3):664-5.
PMID: 9561626
Mechanical transport of rotavirus by the legs and wings of Musca domestica (Diptera: Muscidae)

Tan SW, Yap KL, Lee HL

J Med Entomol, 1997 Sep;34(5):527-31.
PMID: 9379457

Factors affecting the mechanical transmission of rotavirus by the legs and wings of the housefly, Musca domestica L., were examined in a laboratory study. Rotavirus was picked up when houseflies walked on thin smears of clarified rotavirus suspensions. The addition of glycerol, which increased viscosity of the virus suspension, and particulate human feces slightly increased the proportion of flies contaminated with virus. However, the addition of glycerol greatly reduced the average number of virus particles picked up per fly, whereas feces greatly increased the number of particles. The proportion of flies with virus-contaminated legs, which transferred virus to > 1 contact surface, was increased by longer contact time with the surface and when the contact surface was agar instead of glass. Most virus particles were deposited on 1st contact with the surface. Most flies dislodged virus particles inoculated on the underside of their wings soon after the start of simulated flight. Our data indicated that the nature of the virus-suspending medium has a greater effect on the level of virus contamination than on the ability to become contaminated. The importance of walking as a mode of virus transport depends on the nature of the contact surface, the risk of the contaminated fly settling first on a surface likely to come into contact with humans, and fly numbers.
A novel insecticidal serotype of Clostridium bifermentans

Seleena P, Lee HL, Lecadet MM

J Am Mosq Control Assoc, 1997 Dec;13(4):395-7.
PMID: 9474569

A novel Clostridium bifermentans strain toxic to mosquito larvae on ingestion was isolated from a soil sample collected from secondary forest floor. This strain was designated as serovar paraiba (C. b. paraiba) according to its specific H antigen. Clostridium bifermentans paraiba is most toxic to Anopheles maculatus Theobald larvae (LC50 = 0.038 mg/liter), whereas toxicity to Aedes aegypti (Linn.) (LC50 = 0.74 mg/liter) and Culex quinquefasciatus Say (LC50 = 0.11 mg/liter) larvae was 20 and 3 times lower, respectively. The toxicity to An. maculatus larvae is as high as that of Bacillus thuringiensis serovar israelensis. C. b. paraiba was also found to exhibit significant per os insecticidal activity toward adult Musca domestica (Linn.).
Preliminary field evaluation of the combined adulticidal, larvicidal, and wall residual activity of ULV-applied bifenthrin against mosquitoes

Lee HL, Khadri MS, Chiang YF

J Vector Ecol, 1997 Dec;22(2):146-9.
PMID: 9491365

The combined adulticidal, larvicidal, and wall residual activity of ULV-applied bifenthrin, a synthetic pyrethroid, was evaluated in houses in Kuala Lumpur, Malaysia, against larvae and adults of lab-bred Aedes aegypti and Culex quinquefasciatus. A portable ULV sprayer was used to disperse a ULV formulation of bifenthrin at a discharge rate of 45 ml/min. The results indicated that bifenthrin sprayed at this rate exhibited all the three activities against the test mosquitoes. Complete adult mortalities were achieved, while very high larvicidal activity was also effected, which persisted for seven days. Wall bioassay with adults of Ae aegypti also resulted in very high mortality, which also persisted for one week. The combined mosquitocidal activities of bifenthrin is considered more effective especially in the control of dengue vectors.
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.
Fulltext Rate of resistance development in wild Culex quinquefasciatus (Say) selected by malathion and permethrin

Nazni WA, Lee HL, Sa'diyah I

Southeast Asian J. Trop. Med. Public Health, 1998 Dec;29(4):849-55.
PMID: 10772575

Wild caught female Culex quinquefasciatus (Say) from Kuala Lumpur were blood fed and reared in the insectarium. The late third stage of the F1 larvae which survived the high selection pressure of malathion and permethrin were reared and colonies were established from adults that emerged. Larvae from these colonies were then subjected in the subsequent 9 generations to higher selection pressure. The rate of resistance development were measured by LC50 value of larval bioassay, LT50 value of adult bioassay and the frequency of the elevated esterase levels. In another set of experiments using the same batch of Culex mosquitos, the larvae were not exposed to any insecticides and the decrease in resistance rate was monitored in each subsequent 9 generations by using similar methods. The heterozygous standard laboratory strain was selected for susceptibility using the single raft sib-selection method. The result showed that the field collected F1 generation was 96.0 and 6.3 fold more resistant to malathion and permethrin, respectively. After selection for about 9 generations the resistance ratio to malathion and permethrin was 6.2 and 767.3 fold more compared to the LC50 values of F1 generations, respectively. Esterase in F1 larvae was 6.0 fold more than the standard laboratory strain.
Fulltext Education of the public on cardio-pulmonary resuscitation: issues and challenges

Lee HT, Low BT

Med J Malaysia, 1999 Jun;54(2):167-8.
PMID: 10972024
Susceptibility of Musca domestica L. (Diptera: Muscidae) from various breeding sites to commonly used insecticides

Nazni WA, Ursula MP, Lee HL, Sa'diyah I

J Vector Ecol, 1999 Jun;24(1):54-60.
PMID: 10436878

Field strains of house flies, Musca domestica L., from three different breeding sites-garbage dump (IMR), poultry farm (Kundang, Selangor), and agricultural farm (Kampung Batu, Kuala Lumpur), were evaluated against five insecticides. Resistance status of adult female flies was determined using the modified WHO bioassay methods. The WHO susceptibility strain was used as a reference strain for comparison. Flies from the garbage dump and poultry farm were more resistant to the insecticides than the strain from the agricultural farm. Results obtained from bioassay tests were confirmed by in-vitro microenzyme assays of non-specific esterases and glutathione-S-transferases. Significant differences between the esterase levels of WHO and field strains were observed. Levels of glutathion-S-transferases were approximately the same, which may indicate that other enzymes are involved in house fly resistance.
Compatibility of Bacillus thuringiensis serovar israelensis and chemical insecticides for the control of Aedes mosquitoes

Seleena P, Lee HL, Chiang YF

J Vector Ecol, 1999 Dec;24(2):216-23.
PMID: 10672551

The compatibility of the commercial aqueous Bacillus thuringiensis serovar israelensis (B.t.i.) formulation, Vectobac 12AS, with the chemical insecticides Actellic 50EC, Aqua Resigen, Resigen, and Fendona SC, for the simultaneous control of Aedes larvae and adults was studied by dispersing nine different formulations using a portable mist blower, in single story half-brick houses. The effectiveness of the treatment was evaluated by measuring the larval mortality, adult mortality, and droplet analysis at varying distances from the sprayer. Persistence of the larvicidal activity of the chemical insecticides and B.t.i was also determined by measuring the larval mortality in the test samples 7 days posttreatment. The sprayed particles in all the trials were 50-60 microns in size, indicating that the particles were those of mist spray. Test samples placed within 3 m from the sprayer gave the maximum larval and adult mortality. Chemical insecticides exhibited maximum larval mortality in the 1 h posttreatment test samples and it was comparable to the larvicidal activity of B.t.i. The larvicidal toxins of B.t.i were more stable and were able to affect sufficient larval mortality for 7 days posttreatment. The larvicidal activity of the mixtures, i.e., chemical insecticides with B.t.i, in the 1 h posttreatment test samples was not significantly different from the larvicidal activity of the chemical insecticides and it was comparable to the larvicidal activity of B.t.i alone. However, the larvicidal activity of the mixtures was significantly more than the chemical insecticides alone in the 7 days posttreatment test samples except for the Actellic 50EC and Vectobac 12AS mixture. In all the trials, with or without B.t.i, there was no significant difference in adult mortality, indicating that this B.t.i formulation, Vectobac 12AS, was not antagonistic to the adulticidal activity of the chemical insecticides. From this study, it can be concluded that chemical insecticides can be used effectively for both adult and larval control, but the chemical insecticides do not exhibit residual larvicidal activity. Hence, for an effective control of both Aedes larvae and adults, it is advisable to add B.t.i. to the chemical insecticides, as B.t.i is specifically larvicidal and is also able to effect extended residual larvicidal activity.
Spatial patterns in the distribution of tropical tree species

Condit R, Ashton PS, Baker P, Bunyavejchewin S, Gunatilleke S, Gunatilleke N, et al.

Science, 2000 May 26;288(5470):1414-8.
PMID: 10827950

Fully mapped tree census plots of large area, 25 to 52 hectares, have now been completed at six different sites in tropical forests, including dry deciduous to wet evergreen forest on two continents. One of the main goals of these plots has been to evaluate spatial patterns in tropical tree populations. Here the degree of aggregation in the distribution of 1768 tree species is examined based on the average density of conspecific trees in circular neighborhoods around each tree. When all individuals larger than 1 centimeter in stem diameter were included, nearly every species was more aggregated than a random distribution. Considering only larger trees (>/= 10 centimeters in diameter), the pattern persisted, with most species being more aggregated than random. Rare species were more aggregated than common species. All six forests were very similar in all the particulars of these results.
Thermal application of Bacillus thuringiensis serovar israelensis for dengue vector control

Seleena P, Lee HL, Chiang YF

J Vector Ecol, 2001 Jun;26(1):110-3.
PMID: 11469179
Fulltext Serological evidence of hantavirus infections in Malaysia

Lam SK, Chua KB, Myshrall T, Devi S, Zainal D, Afifi SA, et al.

Southeast Asian J. Trop. Med. Public Health, 2001 Dec;32(4):809-13.
PMID: 12041558

Hantaviruses are primarily rodent-borne and transmission is by inhalation of virus-contaminated aerosols of rodent excreta, especially urine and saliva. The genus Hantavirus, family Bunyaviridae, comprises at least 14 serotypes and the symptoms of clinical illness range from mild fever to severe hemorrhagic manifestations with renal complications. Many countries in Southeast Asia are unaware of the importance of hantavirus infections and give them low priority. Malaysia, like other countries in the region, has conducted very few studies on the epidemiology of hantaviruses - and even these were conducted in the 1980s. Using a more extensive range of hantavirus antigens, we conducted a seroprevalence study of rodents and humans and found further evidence of hantavirus infections. Moreover, the data from the antibody profiles strongly suggest the presence of different hantaviruses at the study sites.

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