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Fulltext Environmental health and building related illnesses

Ambu, Stephen, Chu, Wan-Loy, Mak, Joon-Wah, Wong, Shew-Fung, Chan, Li-Li, Wong, Siew-Tung

International e-Journal of Science, Medicine & Education, 2008;2(3):-.
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Malaysia has good environmental laws to protect the outdoor environment and public health. However there are no laws governing indoor air quality (IAQ) and the knowledge among the public about its importance is also lacking. Environmental professionals think it is not a priority and this influences the policy decisions in the country. Therefore there is a need to create awareness by way of research, education and other promotional activities. What is much needed at this time is the establishment of standards for the conduct of risk assessment studies. To establish standards we need reliable data which can be used to develop appropriate guidelines for the purpose of mitigation and adaptation programmes. IAQ can have significant influence on health resulting in drop in productivity and economy of a country. It has been estimated that in the US, building related illnesses (BRI) symptoms have a relationship with decrease (3 to 5%) in work performance in an affected population resulting in an annual loss of US$60 billion in revenue. However, based on efficient management programmes they have also projected that the potential annual savings can be in the region of US$10 to 30 billion. This establishes that fact that good management programmes based on efficient guidelines is of economic value to a country and wellbeing of the population. The IMU has embarked on a research programme to collect the much-needed data for the framing of a good IAQ guideline for Malaysia.
Fulltext Toll-like receptor 9 and 4 gene polymorphisms in susceptibility and severity of malaria: a meta-analysis of genetic association studies

Naing C, Wong ST, Aung HH

Malar J, 2021 Jul 03;20(1):302.
PMID: 34217314 DOI: 10.1186/s12936-021-03836-6

BACKGROUND: Malaria is still a major public health problem in sub-Saharan Africa and South-east Asia. The clinical presentations of malaria infection vary from a mild febrile illness to life-threatening severe malaria. Toll like receptors (TLRs) are postulated to be involved in the innate immune responses to malaria. Individual studies showed inconclusive findings. This study aimed to assess the role of TLR4 (D299G, T399I) and TLR9 (T1237C, T1486C) in severity or susceptibility of malaria by meta-analysis of data from eligible studies.
METHODS: Relevant case-control studies that assessed the association between TLR 4/9 and malaria either in susceptibility or progression were searched in health-related electronic databases. Quality of included studies was evaluated with Newcastle-Ottawa scale. Pooled analyses for specific genetic polymorphisms were done under five genetic models. Stratified analysis was done by age and geographical region (Asian countries vs non-Asian countries).
RESULTS: Eleven studies (2716 cases and 2376 controls) from nine endemic countries were identified. Five studies (45.4%) obtained high score in quality assessment. Overall, a significant association between TLR9 (T1486C) and severity of malaria is observed in allele model (OR: 1.26, 95% CI: 1.08-1.48, I2 = 0%) or homozygous model (OR: 1.55, 95% CI: 1.08-2.28, I2 = 0%). For TLR9 (T1237C), a significant association with severity of malaria is observed in in heterozygous model (OR:1.89, 95% CI: 1.11-3.22, I2 = 75%). On stratifications, TLR9 (T1486C) is only significantly associated with a subgroup of children of non-Asian countries under allele model (OR: 1.25, 95% CI: 1.02-1.38), while 1237 is with a subgroup of adults from Asian countries under heterozygous model (OR: 2.0, 95% CI: 1.09-3.64, I2 = 39%). Regarding the susceptibility to malaria, TLR9 (T1237C) is significantly associated only with the children group under recessive model (OR: 2.21, 95% CI: 1.06-4.57, I2=85%) and homozygous model (OR: 1.49, 95% CI: 1.09-2.0, I2 = 0%). For TLR4 (D299G, T399I), none is significantly associated with either severity of malaria or susceptibility to malaria under any genetic models.
CONCLUSIONS: The findings suggest that TLR 9 (T1486C and T1237C) seems to influence the progression of malaria, under certain genetic models and in specific age group of people from specific geographical region. TLR 9 (T1237C) also plays a role in susceptibility to malaria under certain genetic models and only with children of non-Asian countries. To substantiate these, future well designed studies with larger samples across endemic countries are needed.
Fulltext Pteropine Orthoreovirus (PRV7S) does not Establish Persistent Infection in NP460 Cells but with Inflammatory Response Triggered

Loh MKA, Siew ZY, Leong PP, Koh RY, Chye SM, Wong ST, et al.

Biomed Environ Sci, 2023 Sep 20;36(9):886-891.
PMID: 37803902 DOI: 10.3967/bes2023.114
Fulltext Antioxidant and toxicity studies of 50% methanolic extract of Orthosiphon stamineus Benth

Yam MF, Lim CP, Fung Ang L, Por LY, Wong ST, Asmawi MZ, et al.

Biomed Res Int, 2013;2013:351602.
PMID: 24490155 DOI: 10.1155/2013/351602

The present study evaluated the antioxidant activity and potential toxicity of 50% methanolic extract of Orthosiphon stamineus (Lamiaceae) leaves (MEOS) after acute and subchronic administration in rats. Superoxide radical scavenging, hydroxyl radical scavenging, and ferrous ion chelating methods were used to evaluate the antioxidant properties of the extract. In acute toxicity study, single dose of MEOS, 5000 mg/kg, was administered to rats by oral gavage, and the treated rats were monitored for 14 days. While in the subchronic toxicity study, MEOS was administered orally, at doses of 1250, 2500, and 5000 mg/kg/day for 28 days. From the results, MEOS showed good superoxide radical scavenging, hydroxyl radical scavenging, ferrous ion chelating, and antilipid peroxidation activities. There was no mortality detected or any signs of toxicity in acute and subchronic toxicity studies. Furthermore, there was no significant difference in bodyweight, relative organ weight, and haematological and biochemical parameters between both male and female treated rats in any doses tested. No abnormality of internal organs was observed between treatment and control groups. The oral lethal dose determined was more than 5000 mg/kg and the no-observed-adverse-effect level (NOAEL) of MEOS for both male and female rats is considered to be 5000 mg/kg per day.
Fulltext Dengue fever and insecticide resistance in Aedes mosquitoes in Southeast Asia: a review

Gan SJ, Leong YQ, Bin Barhanuddin MFH, Wong ST, Wong SF, Mak JW, et al.

Parasit Vectors, 2021 Jun 10;14(1):315.
PMID: 34112220 DOI: 10.1186/s13071-021-04785-4

Dengue fever is the most important mosquito-borne viral disease in Southeast Asia. Insecticides remain the most effective vector control approach for Aedes mosquitoes. Four main classes of insecticides are widely used for mosquito control: organochlorines, organophosphates, pyrethroids and carbamates. Here, we review the distribution of dengue fever from 2000 to 2020 and its associated mortality in Southeast Asian countries, and we gather evidence on the trend of insecticide resistance and its distribution in these countries since 2000, summarising the mechanisms involved. The prevalence of resistance to these insecticides is increasing in Southeast Asia, and the mechanisms of resistance are reported to be associated with target site mutations, metabolic detoxification, reduced penetration of insecticides via the mosquito cuticle and behavioural changes of mosquitoes. Continuous monitoring of the status of resistance and searching for alternative control measures will be critical for minimising any unpredicted outbreaks and improving public health. This review also provides improved insights into the specific use of insecticides for effective control of mosquitoes in these dengue endemic countries.
Fulltext A novel strategy for community screening of SARS-CoV-2 (COVID-19): Sample pooling method

Lim KL, Johari NA, Wong ST, Khaw LT, Tan BK, Chan KK, et al.

PLoS One, 2020;15(8):e0238417.
PMID: 32857823 DOI: 10.1371/journal.pone.0238417

The rapid global spread of the coronavirus disease (COVID-19) has inflicted significant health and socioeconomic burden on affected countries. As positive cases continued to rise in Malaysia, public health laboratories experienced an overwhelming demand for COVID-19 screening. The confirmation of positive cases of COVID-19 has solely been based on the detection of the Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) using real-time reverse transcription polymerase chain reaction (qRT-PCR). In efforts to increase the cost-effectiveness and efficiency of COVID-19 screening, we evaluated the feasibility of pooling clinical Nasopharyngeal/Oropharyngeal (NP/OP) swab specimens during nucleic acid extraction without a reduction in sensitivity of qRT-PCR. Pools of 10 specimens were extracted and subsequently tested by qRT-PCR according to the WHO-Charité protocol. We demonstrated that the sample pooling method showed no loss of sensitivity. The effectiveness of the pooled testing strategy was evaluated on both retrospective and prospective samples, and the results showed a similar detection sensitivity compared to testing individual sample alone. This study demonstrates the feasibility of using a pooled testing strategy to increase testing capacity and conserve resources, especially when there is a high demand for disease testing.
Fulltext COVID-19 Sample Pooling: From RNA Extraction to Quantitative Real-time RT-PCR

Voon K, Johari NA, Lim KL, Wong ST, Khaw LT, Wong SF, et al.

Bio Protoc, 2021 May 05;11(9):e4005.
PMID: 34124305 DOI: 10.21769/BioProtoc.4005

The COVID-19 pandemic requires mass screening to identify those infected for isolation and quarantine. Individually screening large populations for the novel pathogen, Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2), is costly and requires a lot of resources. Sample pooling methods improve the efficiency of mass screening and consume less reagents by increasing the capacity of testing and reducing the number of experiments performed, and are therefore especially suitable for under-developed countries with limited resources. Here, we propose a simple, reliable pooling strategy for COVID-19 testing using clinical nasopharyngeal (NP) and/or oropharyngeal (OP) swabs. The strategy includes the pooling of 10 NP/OP swabs for extraction and subsequent testing via quantitative real-time reverse transcription polymerase chain reaction (RT-qPCR), and may also be applied to the screening of other pathogens.
Human cytokeratin 1 plays a role in the interaction of Pteropine orthoreovirus with Hek293 cells but not HeLa cells

Siew ZY, Tan YF, Iswara RP, Wong SF, Wong ST, Tan BK, et al.

Microbes Infect, 2024;26(1-2):105243.
PMID: 38380604 DOI: 10.1016/j.micinf.2023.105243

Pteropine orthoreovirus (PRV) causes respiratory tract infections in humans. Despite its emergence as a zoonotic and respiratory virus, little is known about its cell tropism, which hampers progress in fully understanding its pathogenesis in humans. Hek293 cells are most susceptible to PRV infection, while HeLa cells are the least. Human cytokeratin 1 (CK1) was identified as the protein that interacts with PRV. The immunofluorescence assay and qPCR results revealed prior treatment with anti-CK1 may provide Hek293 cells protection against PRV. The KRT1-knockout Hek293 cells were less susceptible to PRV infection. Further study into the pathogenesis of PRV in humans is needed.