Displaying publications 1 - 20 of 35 in total

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  1. Abdul Hamid Z, Lin Lin WH, Abdalla BJ, Bee Yuen O, Latif ES, Mohamed J, et al.
    ScientificWorldJournal, 2014;2014:258192.
    PMID: 25405216 DOI: 10.1155/2014/258192
    Hematopoietic stem cells- (HSCs-) based therapy requires ex vivo expansion of HSCs prior to therapeutic use. However, ex vivo culture was reported to promote excessive production of reactive oxygen species (ROS), exposing HSCs to oxidative damage. Efforts to overcome this limitation include the use of antioxidants. In this study, the role of Hibiscus sabdariffa L. (Roselle) in maintenance of cultured murine bone marrow-derived HSCs was investigated. Aqueous extract of Roselle was added at varying concentrations (0-1000 ng/mL) for 24 hours to the freshly isolated murine bone marrow cells (BMCs) cultures. Effects of Roselle on cell viability, reactive oxygen species (ROS) production, glutathione (GSH) level, superoxide dismutase (SOD) activity, and DNA damage were investigated. Roselle enhanced the survival (P < 0.05) of BMCs at 500 and 1000 ng/mL, increased survival of Sca-1(+) cells (HSCs) at 500 ng/mL, and maintained HSCs phenotype as shown from nonremarkable changes of surface marker antigen (Sca-1) expression in all experimental groups. Roselle increased (P < 0.05) the GSH level and SOD activity but the level of reactive oxygen species (ROS) was unaffected. Moreover, Roselle showed significant cellular genoprotective potency against H2O2-induced DNA damage. Conclusively, Roselle shows novel property as potential supplement and genoprotectant against oxidative damage to cultured HSCs.
  2. Abdul Hamid Z, Budin SB, Wen Jie N, Hamid A, Husain K, Mohamed J
    J Zhejiang Univ Sci B, 2012 Mar;13(3):176-85.
    PMID: 22374609 DOI: 10.1631/jzus.B1100133
    Paracetamol (PCM) overdose can cause nephrotoxicity with oxidative stress as one of the possible mechanisms mediating the event. In this study, the effects of ethyl acetate extract of Zingiber zerumbet rhizome [200 mg per kg of body weight (mg/kg) and 400 mg/kg] on PCM-induced nephrotoxicity were examined. Rats were divided into five groups containing 10 rats each. The control group received distilled water while other groups were treated with extract alone (400 mg/kg), PCM alone (750 mg/kg), 750 mg/kg PCM+200 mg/kg extract (PCM+200-extract), and 750 mg/kg PCM+400 mg/kg extract (PCM+400-extract), respectively, for seven consecutive days. The Z. zerumbet extract was given intraperitoneally concurrent with oral administration of PCM. Treatment with Z. zerumbet extract at doses of 200 and 400 mg/kg prevented the PCM-induced nephrotoxicity and oxidative impairments of the kidney, as evidenced by a significantly reduced (P<0.05) level of plasma creatinine, plasma and renal malondialdehyde (MDA), plasma protein carbonyl, and renal advanced oxidation protein product (AOPP). Furthermore, both doses were also able to induce a significant increment (P<0.05) of plasma and renal levels of glutathione (GSH) and plasma superoxide dismutase (SOD) activity. The nephroprotective effects of Z. zerumbet extract were confirmed by a reduced intensity of renal cellular damage, as evidenced by histological findings. Moreover, Z. zerumbet extract administered at 400 mg/kg was found to show greater protective effects than that at 200 mg/kg. In conclusion, ethyl acetate extract of Z. zerumbet rhizome has a protective role against PCM-induced nephrotoxicity and the process is probably mediated through its antioxidant properties.
  3. Abdul Hamid Z, Mohd Zulkifly MF, Hamid A, Lubis SH, Mohammad N, Ishak I, et al.
    Genes Environ, 2016;38:7.
    PMID: 27350827 DOI: 10.1186/s41021-016-0032-1
    Pesticide exposure possesses risk of genotoxicity to humans, particularly farmers. Despite accumulating evidences linking genotoxicity to pesticide exposure, epidemiological studies to address pesticide toxicity in occupationally exposed farmers in Malaysia remain underreported. Thus, this study was aimed to determine the presence of nuclear abnormalities through the assessment of micronucleus (MN) and binucleus (BNu) frequencies in exfoliated buccal epithelial cells from farmers who were exposed to pesticides. A cross-sectional study of farmers among different agricultural activities farmers in Bachok and Pasir Puteh, Kelantan, North East of Peninsular Malaysia was done to evaluate the presence of nuclear abnormalities and its correlation with their health status and farming activities.
  4. Ahamad M, Louis SR, Hamid Z, Ho TM
    Trop Biomed, 2011 Aug;28(2):275-82.
    PMID: 22041746
    Scanning electron microscope (SEM) images of dust mites, Suidasia pontifica, is presented to provide an improved visualization of the taxonomic characters of these mites. Suidasia pontifica can easily be identified by its scale-like cuticle, presence of external vertical setae (ve), longer external scapular setae (sce) compared to internal scapular setae (sci) and 3 ventral spines on apex of tarsus I. The differences in morphology of male and female S. pontifica are also discussed.
  5. Alwi M, Hamid ZA, Zambahari R
    Br Heart J, 1992 Jul;68(1):6-8.
    PMID: 1515294
    Continuous wave Doppler recordings of the turbulent jet through the restrictive orifice of a left atrial partition in a patient with corrected transposition of the great arteries and cor triatriatum showed alternate bands of high intensity diastolic and low intensity systolic signals with preservation of the normal configuration of the diastolic E and A peaks. It is thought that Doppler studies in cor triatriatum will provide useful complementary haemodynamic information in the echocardiographic diagnosis of this anomaly.
  6. Ban A, Omar A, Chong LY, Lockman H, Ida Zaliza ZA, Ali I, et al.
    Malays Fam Physician, 2018;13(3):20-26.
    PMID: 30800229 MyJurnal
    Asthma is a chronic inflammatory disease of the airway which is often misdiagnosed and undertreated. Early diagnosis and vigilant asthma control are crucial to preventing permanent airway damage, improving quality of life and reducing healthcare burdens. The key approaches to asthma management should include patient empowerment through health education and self-management and, an effective patient-healthcare provider partnership.
  7. Bee SL, Bustami Y, Ul-Hamid A, Lim K, Abdul Hamid ZA
    J Mater Sci Mater Med, 2021 Aug 23;32(9):106.
    PMID: 34426879 DOI: 10.1007/s10856-021-06590-y
    Combination of bioactive material such as hydroxyapatite (HAp) with antibacterial agents would have great potential to be used as bone implant materials to avert possible bacterial infection that can lead to implant-associated diseases. The present study aimed to develop an antibacterial silver nanoparticle-decorated hydroxyapatite (HAp/AgNPs) nanocomposite using chemical reduction and thermal calcination approaches. In this work, natural HAp that was extracted from chicken bone wastes is used as support matrix for the deposition of silver nanoparticles (AgNPs) to produce HAp/AgNPs nanocomposite. XRD, FESEM-EDX, HRTEM, and XPS analyses confirmed that spherical AgNPs were successfully synthesized and deposited on the surface of HAp particles, and the amount of AgNPs adhered on the HAp surface increased with increasing AgNO3 concentration used. The synthesized HAp/AgNPs nanocomposites demonstrated strong antibacterial activity against Staphylococcus aureus bacteria, where the antibacterial efficiency is relied on the amount and size of deposited AgNPs. In addition, the in vitro bioactivity examination in Hank's balanced salt solution showed that more apatite were grown on the surface of HAp/AgNPs nanocomposite when AgNO3 concentration used >1 wt.%. Such nanocomposite with enhanced bioactivity and antibacterial properties emerged as a promising biomaterial to be applied for dentistry and orthopedic implantology.
  8. Chin SF, Hamid NA, Latiff AA, Zakaria Z, Mazlan M, Yusof YA, et al.
    Nutrition, 2008 Jan;24(1):1-10.
    PMID: 17884341
    The free radical theory of aging (FRTA) suggests that free radicals are the leading cause of deteriorating physiologic function during senescence. Free radicals attack cellular structures or molecules such as DNA resulting in various modifications to the DNA structures. Accumulation of unrepaired DNA contributes to a variety of disorders associated with the aging process.
  9. Chow PW, Abdul Hamid Z, Chan KM, Inayat-Hussain SH, Rajab NF
    Toxicol Appl Pharmacol, 2015 Apr 1;284(1):8-15.
    PMID: 25645895 DOI: 10.1016/j.taap.2015.01.016
    Hematopoietic stem cells (HSCs) and hematopoietic progenitor cells (HPCs) are sensitive targets for benzene-induced hematotoxicity and leukemogenesis. The impact of benzene exposure on the complex microenvironment of HSCs and HPCs remains elusive. This study aims to investigate the mechanism linking benzene exposure to targeting HSCs and HPCs using phenotypic and clonogenic analyses. Mouse bone marrow (BM) cells were exposed ex vivo to the benzene metabolite, 1,4-benzoquinone (1,4-BQ), for 24h. Expression of cellular surface antigens for HSC (Sca-1), myeloid (Gr-1, CD11b), and lymphoid (CD45, CD3e) populations were confirmed by flow cytometry. The clonogenicity of cells was studied using the colony-forming unit (CFU) assay for multilineage (CFU-GM and CFU-GEMM) and single-lineage (CFU-E, BFU-E, CFU-G, and CFU-M) progenitors. 1,4-BQ demonstrated concentration-dependent cytotoxicity in mouse BM cells. The percentage of apoptotic cells increased (p < 0.05) following 1,4-BQ exposure. Exposure to 1,4-BQ showed no significant effect on CD3e(+) cells but reduced the total counts of Sca-1(+), CD11b(+), Gr-1(+), and CD45(+) cells at 7 and 12 μM (p < 0.05). Furthermore, the CFU assay showed reduced (p < 0.05) clonogenicity in 1,4-BQ-treated cells. 1,4-BQ induced CFU-dependent cytotoxicity by significantly inhibiting colony growth for CFU-E, BFU-E, CFU-G, and CFU-M starting at a low concentration of exposure (5μM); whereas for the CFU-GM and CFU-GEMM, the inhibition of colony growth was remarkable only at 7 and 12μM of 1,4-BQ, respectively. Taken together, 1,4-BQ caused lineage-related cytotoxicity in mouse HPCs, demonstrating greater toxicity in single-lineage progenitors than in those of multi-lineage.
  10. Chow PW, Abd Hamid Z, Mathialagan RD, Rajab NF, Shuib S, Sulong S
    Toxics, 2021 May 12;9(5).
    PMID: 34065823 DOI: 10.3390/toxics9050107
    Previous reports on hematotoxicity and leukemogenicity related to benzene exposure highlighted its adverse effects on hematopoiesis. Despite the reported findings, studies concerning the mechanism of benzene affecting chromosomal integrity in lineage-committed hematopoietic stem/progenitor cells (HSPCs) remain unclear. Here, we studied the clastogenicity and aneugenicity of benzene in lineage-committed HSPCs via karyotyping. Isolated mouse bone marrow cells (MBMCs) were exposed to the benzene metabolite 1,4-benzoquinone (1,4-BQ) at 1.25, 2.5, 5, 7, and 12 μM for 24 h, followed by karyotyping. Then, the chromosomal aberration (CA) in 1,4-BQ-exposed hematopoietic progenitor cells (HPCs) comprising myeloid, Pre-B lymphoid, and erythroid lineages were evaluated following colony-forming cell (CFC) assay. Percentage of CA, predominantly via Robertsonian translocation (Rb), was increased significantly (p < 0.05) in MBMCs and all progenitors at all concentrations. As a comparison, Pre-B lymphoid progenitor demonstrated a significantly higher percentage of CA (p < 0.05) than erythroid progenitor at 1.25, 2.5, and 7 μM as well as a significantly higher percentage (p < 0.05) than myeloid progenitor at 7 μM of 1,4-BQ. In conclusion, 1,4-BQ induced CA, particularly via Rb in both MBMCs and HPCs, notably via a lineage-dependent response. The role of lineage specificity in governing the clastogenicity and aneugenicity of 1,4-BQ deserves further investigation.
  11. Chow PW, Rajab NF, Chua KH, Chan KM, Abd Hamid Z
    Toxicol In Vitro, 2018 Feb;46:122-128.
    PMID: 28986286 DOI: 10.1016/j.tiv.2017.10.001
    Despite of reports on hematotoxic and leukemogenic evidences related to benzene exposure, the mechanism of benzene toxicity affecting the hematopoietic stem and progenitor cells (HSPCs) fate remains unclear. This study aims to elucidate the benzene's effect on the lineages-committed progenitors and genes-regulating self-renewal and differentiation of HSPCs. Isolated mouse bone marrow (BM) cells were exposed to the benzene metabolite, 1,4-benzoquinone (1,4-BQ) at 1.25, 2.5, and 5μM for 24h. The clonogenic potency of erythroid, myeloid, and Pre-B lymphoid progenitors was evaluated through colony-forming-cell assay. Quantitative real time-PCR was used to analyze the self-renewal (Bmi-1, HoxB4, and Wnt3) and differentiation (GATA1, GATA2, and GATA3)-related genes' expression levels. 1,4-BQ exposure significantly lowered the clonogenicity of the myeloid progenitor at 1.25 and 2.5μM (p<0.05), but affected neither the erythroid nor Pre-B lymphoid progenitors. Furthermore, significant upregulation of HoxB4 expression level was observed at all concentrations. GATA3 and Bmi-1 expressions were also significant upregulated at 2.5 and 5μM 1,4-BQ, respectively. In conclusion, 1,4-BQ could modulate the fate of HSPCs by altering the self-renewal and differentiation related genes. The definite role of lineages specificity and responsive genes in governing the hematotoxicity and leukemogenicity of 1,4-BQ should be further investigated.
  12. Dewi R, Hamid ZA, Rajab NF, Shuib S, Razak SA
    Hum Exp Toxicol, 2020 May;39(5):577-595.
    PMID: 31884827 DOI: 10.1177/0960327119895570
    Benzene is a known hematotoxic and leukemogenic agent with hematopoietic stem cells (HSCs) niche being the potential target. Occupational and environmental exposure to benzene has been linked to the incidences of hematological disorders and malignancies. Previous studies have shown that benzene may act via multiple modes of action targeting HSCs niche, which include induction of chromosomal and micro RNA aberrations, leading to genetic and epigenetic modification of stem cells and probable carcinogenesis. However, understanding the mechanism linking benzene to the HSCs niche dysregulation is challenging due to complexity of its microenvironment. The niche is known to comprise of cell populations accounted for HSCs and their committed progenitors of lymphoid, erythroid, and myeloid lineages. Thus, it is fundamental to address novel approaches via lineage-directed strategy to elucidate precise mechanism involved in benzene-induced toxicity targeting HSCs and progenitors of different lineages. Here, we review the key genetic and epigenetic factors that mediate hematotoxicological effects by benzene and its metabolites in targeting HSCs niche. Overall, the use of combined genetic, epigenetic, and lineage-directed strategies targeting the HSCs niche is fundamental to uncover the key mechanisms in benzene-induced hematological disorders and malignancies.
  13. Dewi R, Yusoff NA, Abdul Razak SR, Abd Hamid Z
    PeerJ, 2023;11:e15608.
    PMID: 37456886 DOI: 10.7717/peerj.15608
    BACKGROUND: HSPCs are targets for benzene-induced hematotoxicity and leukemogenesis. However, benzene toxicity targeting microRNAs (miRNAs) and transcription factors (TF) that are involve in regulating self-renewing and differentiation of HSPCs comprising of different hematopoietic lineages remains poorly understood. In this study, the effect of a benzene metabolite, 1,4-benzoquinone (1,4-BQ) exposure, in HSPCs focusing on the self-renewing (miRNAs: miR-196b and miR-29a; TF: HoxB4, Bmi-1) and differentiation (miRNAs: miR-181a, TF: GATA3) pathways were investigated.

    METHODS: Freshly isolated mouse BM cells were initially exposed to 1,4-BQ at 1.25 to 5 µM for 24 h, followed by miRNAs and TF studies in BM cells. Then, the miRNAs expression was further evaluated in HSPCs of different lineages comprised of myeloid, erythroid and pre-B lymphoid progenitors following 7-14 days of colony forming unit (CFU) assay.

    RESULTS: Exposure to 1,4-BQ in BM cells significantly (p 

  14. Ghani SMA, Goon JA, Azman NHEN, Zakaria SNA, Hamid Z, Ngah WZW
    Clinics (Sao Paulo), 2019 03 07;74:e688.
    PMID: 30864639 DOI: 10.6061/clinics/2019/e688
    OBJECTIVES: This study aims to compare the differential gene expression resulting from tocotrienol-rich fraction and α-tocopherol supplementation in healthy older adults.

    METHODS: A total of 71 eligible subjects aged 50 to 55 years from Gombak and Kuala Lumpur, Malaysia, were divided into three groups and supplemented with placebo (n=23), α-tocopherol (n=24) or tocotrienol-rich fraction (n=24). Blood samples were collected at baseline and at 3 and 6 months of supplementation for microarray analysis.

    RESULTS: The number of genes altered by α-tocopherol was higher after 6 months (1,410) than after 3 months (273) of supplementation. α-Tocopherol altered the expression of more genes in males (952) than in females (731). Similarly, tocotrienol-rich fraction modulated the expression of more genes after 6 months (1,084) than after 3 months (596) and affected more genes in males (899) than in females (781). α-Tocopherol supplementation modulated pathways involving the response to stress and stimuli, the immune response, the response to hypoxia and bacteria, the metabolism of toxins and xenobiotics, mitosis, and synaptic transmission as well as activated the mitogen-activated protein kinase and complement pathways after 6 months. However, tocotrienol-rich fraction supplementation affected pathways such as the signal transduction, apoptosis, nuclear factor kappa B kinase, cascade extracellular signal-regulated kinase-1 and extracellular signal-regulated kinase-2, immune response, response to drug, cell adhesion, multicellular organismal development and G protein signaling pathways.

    CONCLUSION: Supplementation with either α-tocopherol or tocotrienol-rich fraction affected the immune and drug response and the cell adhesion and signal transduction pathways but modulated other pathways differently after 6 months of supplementation, with sex-specific responses.

  15. Ghazali AR, Abdul Razak NE, Othman MS, Othman H, Ishak I, Lubis SH, et al.
    J Environ Public Health, 2012;2012:758349.
    PMID: 22536276 DOI: 10.1155/2012/758349
    Heavy metals, particularly cadmium, lead, and arsenic, constitute a significant potential threat to human health. This study was conducted to determine the levels of cadmium, lead, and arsenic in nail samples from farmers at Muda Agricultural Development Authority (MADA), Kedah, Malaysia, and evaluate factors that can contribute to their accumulations. A total of 116 farmers participated in this study. Inductively coupled plasma mass spectrometry (ICP-MS) was used to analyze concentration of heavy metals in the nail samples and questionnaires were given to participants to get demographic, health status, and their agricultural activities data. In this paper, the level of heavy metals was within the normal range and varies according to demographic factors. We found that there were significant correlations between working period with level of lead and arsenic (r=0.315 and r=0.242, resp., P<0.01) and age with lead level (r=0.175, P<0.05). Our findings suggested that agricultural activities could contribute to the accumulation of heavy metals in farmers. Hence, the control of environmental levels of and human exposure to these metals to prevent adverse health effects is still an important public health issue.
  16. Goon JA, Nor Azman NHE, Abdul Ghani SM, Hamid Z, Wan Ngah WZ
    Clin Nutr ESPEN, 2017 10;21:1-12.
    PMID: 30014863 DOI: 10.1016/j.clnesp.2017.07.004
    Vitamin E is a fat-soluble compound and powerful antioxidant that have been shown to protect the cell membranes against damage caused by free radicals. Human vitamin E supplementation studies are usually limited to α-tocopherol but currently tocotrienols are also available. This study aims to compare the effects of tocotrienol rich fraction (TRF) with α-tocopherol (α-TF) supplementation on oxidative stress in healthy male and female older adults aged 50-55 years old. A total of 71 subjects both male and female aged between 50 and 55 years were divided into groups receiving placebo (n = 23), α-TF (n = 24) and TRF (n = 24) for six months. Blood was taken at baseline (month 0), 3 months and 6 months osf supplementation for determination of plasma malondialdehyde (MDA), protein carbonyl, total DNA damage, vitamin D concentration and vitamin E isomers. α-TF supplementation reduced plasma MDA and protein carbonyl in female subjects after 3 and 6 months. TRF supplementation reduced MDA levels in both males and females as early as 3 months while DNA damage was reduced in females only at 6 months. Supplementation with α-TF and TRF increased plasma vitamin D concentration in both males and females after 6 months, but vitamin D concentration in male subjects were significantly higher compared to female subjects in TRF group. Vitamin E isomer determination showed α-TF, α-tocotrienol and γ-tocotrienol were increased in both male and female subjects. In conclusion, TRF supplementation effects were different from α-TF in reducing oxidative stress markers and vitamin D levels with a more pronounced effect in female subjects.
  17. Hashim H, Muda AS, Abdul Aziz A, Abdul Hamid Z
    Malays J Med Sci, 2016 Jul;23(4):59-64.
    PMID: 27660546 MyJurnal DOI: 10.21315/mjms2016.23.4.8
    Embolisation has long been used as an adjunct to surgical resection in the treatment of brain arteriovenous malformation (bAVM). The most commonly used embolic material, n-butylcyanoacrylate glue, requires experience and skill to handle its quick and unpredictable flow and polymerisation. A new liquid embolic agent, ethylene vinyl alcohol copolymer (Onyx), is less adhesive and polymerises slowly, which provides better control for radiologists performing embolisation.
  18. Heng EC, Karsani SA, Abdul Rahman M, Abdul Hamid NA, Hamid Z, Wan Ngah WZ
    Eur J Nutr, 2013 Oct;52(7):1811-20.
    PMID: 23287846 DOI: 10.1007/s00394-012-0485-3
    PURPOSE: Tocotrienol possess beneficial effects not exhibited by tocopherol. In vitro studies using animal models have suggested that these effects are caused via modulation of gene and protein expression. However, human supplementation studies using tocotrienol-rich isomers are limited. This study aims to identify plasma proteins that changed in expression following tocotrienol-rich fraction (TRF) supplementation within two different age groups.

    METHODS: Subjects were divided into two age groups-32 ± 2 (young) and 52 ± 2 (old) years old. Four subjects from each group were assigned with TRF (78% tocotrienol and 22% tocopherol, 150 mg/day) or placebo capsules for 6 months. Fasting plasma were obtained at 0, 3, and 6 months. Plasma tocopherol and tocotrienol levels were determined. Plasma proteome was resolved by 2DE, and differentially expressed proteins identified by MS. The expressions of three proteins were validated by Western blotting.

    RESULTS: Six months of TRF supplementation significantly increased plasma levels of tocopherols and tocotrienols. Proteins identified as being differentially expressed were related to cholesterol homeostasis, acute-phase response, protease inhibitor, and immune response. The expressions of Apolipoprotein A-I precursor, Apolipoprotein E precursor, and C-reactive protein precursor were validated. The old groups showed more proteins changing in expression.

    CONCLUSIONS: TRF appears to not only affect plasma levels of tocopherols and tocotrienols, but also the levels of plasma proteins. The identity of these proteins may provide insights into how TRF exerts its beneficial effects. They may also be potentially developed into biomarkers for the study of the effects and effectiveness of TRF supplementation.

  19. Kho SS, Aziz AA, Sia TLL, Ramarmuty HY, Sirol Aflah SS, Mohamed Gani Y, et al.
    Med J Malaysia, 2023 May;78(3):279-286.
    PMID: 37271836
    INTRODUCTION: Cluster-associated transmission has contributed to the majority of COVID-19 cases in Malaysia. Although widely used, the performance of the World Health Organization (WHO) case definition for suspected COVID19 in environments with high numbers of such cases has not been reported.

    MATERIALS AND METHODS: All suspected cases of COVID-19 that self-presented to hospitals or were cluster screened from 1st April to 31st May 2020 were included. Positive SARS-CoV-2 rRT-PCR was used as the diagnostic reference for COVID-19.

    RESULTS: 540 individuals with suspected COVID-19 were recruited. Two-third of patients were identified through contact screening, while the rest presented sporadically. Overall COVID-19 positivity rate was 59.4% (321/540) which was higher in the cluster screened group (85.6% vs. 11.6%, p<0.001). Overall, cluster-screened COVID-19 cases were significantly younger, had fewer comorbidities and were less likely to be symptomatic than those present sporadically. Mortality was significantly lower in the cluster-screened COVID-19 cases (0.3% vs. 4.5%, p<0.05). A third of all chest radiographs in confirmed COVID-19 cases were abnormal, with consolidation, ground-glass opacities or both predominating in the peripheral lower zones. The WHO suspected case definition for COVID-19 accurately classified 35.4% of all COVID-19 patients, a rate not improved by the addition of baseline radiographic data. Misclassification rate was higher among the cluster-associated cases (80.6%) compared to sporadic cases (35.3%).

    CONCLUSION: COVID-19 cases in Malaysia identified by active tracing of community cluster outbreaks had lower mortality rate. The WHO suspected COVID-19 performed poorly in this setting even when chest radiographic information was available, a finding that has implications for future spikes of the disease in countries with similar transmission characteristics.

  20. Mathialagan RD, Abd Hamid Z, Ng QM, Rajab NF, Shuib S, Binti Abdul Razak SR
    PMID: 32823552 DOI: 10.3390/ijerph17165865
    Hematopoietic stem/progenitor cells (HSPCs) are susceptible to benzene-induced genotoxicity. However, little is known about the mechanism of DNA damage response affecting lineage-committed progenitors for myeloid, erythroid, and lymphoid. Here, we investigated the genotoxicity of a benzene metabolite, 1,4-benzoquinone (1,4-BQ), in HSPCs using oxidative stress and lineage-directed approaches. Mouse bone marrow cells (BMCs) were exposed to 1,4-BQ (1.25-12 μM) for 24 h, followed by oxidative stress and genotoxicity assessments. Then, the genotoxicity of 1,4-BQ in lineage-committed progenitors was evaluated using colony forming cell assay following 7-14 days of culture. 1,4-BQ exposure causes significant decreases (p < 0.05) in glutathione level and superoxide dismutase activity, along with significant increases (p < 0.05) in levels of malondialdehyde and protein carbonyls. 1,4-BQ exposure induces DNA damage in BMCs by significantly (p < 0.05) increased percentages of DNA in tail at 7 and 12 μM and tail moment at 12 μM. We found crucial differences in genotoxic susceptibility based on percentages of DNA in tail between lineage-committed progenitors. Myeloid and pre-B lymphoid progenitors appeared to acquire significant DNA damage as compared with the control starting from a low concentration of 1,4-BQ exposure (2.5 µM). In contrast, the erythroid progenitor showed significant damage as compared with the control starting at 5 µM 1,4-BQ. Meanwhile, a significant (p < 0.05) increase in tail moment was only notable at 7 µM and 12 µM 1,4-BQ exposure for all progenitors. Benzene could mediate hematological disorders by promoting bone marrow oxidative stress and lineage-specific genotoxicity targeting HSPCs.
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