Displaying publications 21 - 40 of 73 in total

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  1. Ong HC, Quah SH, Low HC
    Med J Malaysia, 1998 Dec;53(4):385-91.
    PMID: 10971982
    The method of backcalculation estimates past HIV infection rates from available AIDS incidence data and an estimate of the incubation period. The method is used on the Malaysian data to model the AIDS epidemic because it makes use of the Malaysian AIDS incidence data which is fairly reliable and is more reflective of the trend of the epidemic as compared to the HIV infection rate recorded. An application is made on the monthly AIDS incidence data in Malaysia from January 1995 until August 1996 released by the Ministry of Health, Malaysia using the backcalculation program from Bacchetti et al and the incubation period distribution from Brookmeyer to generate the current HIV infection rate for Malaysia (until August 1996).
  2. Chee CF, Lee HB, Ong HC, Ho AS
    Chem Biodivers, 2005 Dec;2(12):1648-55.
    PMID: 17191961
    In our screening program for new photosensitizers from the Malaysian biodiversity, we found five pheophorbide-related compounds from the leaves and stems of Aglaonema simplex. Detailed spectroscopic analyses showed that compounds 1-3 and 5 are pheophorbide and hydroxy pheophorbide derivatives of chlorophyll a and b. Compound 4, identified as 15(1)-hydroxypurpurin-7-lactone ethyl methyl diester, was isolated for the first time from the Araceae family. An MTT-based short-term survival assay showed that all five compounds exhibit moderate-to-strong photocytotoxic activities towards human leukemia (HL60) and two oral squamous carcinoma cell lines (HSC-2 and HSC-3). Compounds 4 and 5 showed the strongest photocytotoxicities, with IC(50) values of 0.30-0.41 muM (Table 2). Compounds 1-3 with Et chains at C(17(3)) were less photocytotoxic than the parent pheophorbide a (5).
  3. Ong HC, Soo KL
    Med J Malaysia, 2006 Dec;61(5):616-20.
    PMID: 17623964 MyJurnal
    It has been almost two decades ago since the first AIDS case was reported in Malaysia. It has also been approximately eight years ago when the method of backcalculation was used to estimate the past HIV infection rate from the AIDS incidence data and an estimate of the incubation period distribution. This method is used because it makes use of the Malaysian AIDS incidence which is fairly reliable and reflects the trend of the epidemic as compared to the HIV infection rate recorded. The latest results generated show a slowdown in the increase of the number of estimated infected HIV+ cases in the late 1990s and this trend is supported by a slowdown in the increase of the number of AIDS cases recorded.
  4. Chai TT, Elamparuthi S, Yong AL, Quah Y, Ong HC, Wong FC
    Bot Stud, 2013 Dec;54(1):55.
    PMID: 28510890 DOI: 10.1186/1999-3110-54-55
    BACKGROUND: Ferns contain natural products with potential therapeutic applications. Current knowledge of the pharmacological properties of ferns, specifically those growing at high altitudes, is limited. This study aimed to evaluate the phytochemical contents as well as antibacterial, anti-glucosidase, and antioxidant activities of four highland ferns in Malaysia.

    RESULTS: Aqueous extracts of the leaves and rhizomes of Cyathea latebrosa, Dicranopteris curranii, Gleichenia truncata, and Phymatopteris triloba were analysed. P. triloba leaf extract had the highest contents of total flavonoids (118.6 mg/g dry matter), hydroxycinnamic acids (69.7 mg/g dry matter), and proanthocyanidins (29.4 mg/g dry matter). P. triloba leaf and rhizome extracts as well as G. truncata leaf extract inhibited the growth of both Gram-positive and Gram-negative bacteria. P. triloba leaf extract produced a minimum inhibitory concentration (MIC) value of 0.78 mg dry matter/mL when tested against Pseudomonas aeruginosa, which is 2.5-fold higher than that of ampicillin. Among all extracts, P. triloba leaf extract had the highest anti-glucosidase activity (EC50 = 56 μg dry matter/mL) and also the highest antioxidant potential based on DPPH radical scavenging and Ferric Reducing Antioxidant Power assays. Antioxidant activities of both the leaf and rhizome extracts correlated positively with total flavonoid and hydroxycinnamic acid contents (R(2) = 0.80-0.95). On the other hand, anti-glucosidase activity correlated with total proanthocyanidin contents in both the leaf and rhizome extracts (R(2) = 0.62-0.84).

    CONCLUSIONS: In conclusion, highland ferns are potential sources of antibacterial agents, glucosidase inhibitors, and antioxidants.

  5. Hamadneh N, Khan WA, Sathasivam S, Ong HC
    PLoS One, 2013;8(5):e66080.
    PMID: 23741525 DOI: 10.1371/journal.pone.0066080
    Particle swarm optimization (PSO) is employed to investigate the overall performance of a pin fin.The following study will examine the effect of governing parameters on overall thermal/fluid performance associated with different fin geometries, including, rectangular plate fins as well as square, circular, and elliptical pin fins. The idea of entropy generation minimization, EGM is employed to combine the effects of thermal resistance and pressure drop within the heat sink. A general dimensionless expression for the entropy generation rate is obtained by considering a control volume around the pin fin including base plate and applying the conservations equations for mass and energy with the entropy balance. Selected fin geometries are examined for the heat transfer, fluid friction, and the minimum entropy generation rate corresponding to different parameters including axis ratio, aspect ratio, and Reynolds number. The results clearly indicate that the preferred fin profile is very dependent on these parameters.
  6. Ooh KF, Ong HC, Wong FC, Sit NW, Chai TT
    Pharmacogn Mag, 2014 Aug;10(Suppl 3):S443-55.
    PMID: 25298659 DOI: 10.4103/0973-1296.139767
    The phytochemistry and bioactivity of wetland macrophytes are underexplored. Plants are known as the natural sources of phytochemical beneficial to health.
  7. Ganandran GS, Mahlia TM, Ong HC, Rismanchi B, Chong WT
    ScientificWorldJournal, 2014;2014:745894.
    PMID: 25133258 DOI: 10.1155/2014/745894
    This paper reports the result of an investigation on the potential energy saving of the lighting systems at selected buildings of the Universiti Tenaga Nasional. The scope of this project includes evaluation of the lighting system in the Library, Admin Building, College of Engineering, College of Information Technology, Apartments, and COE Food court of the university. The main objectives of this project are to design the proper retrofit scenario and to calculate the potential electricity saving, the payback period, and the potential environmental benefits. In this survey the policy for retrofitting the old lighting system with the new energy saving LEDs starts with 10% for the first year and continues constantly for 10 years until all the lighting systems have been replaced. The result of the life cycle analysis reveals that after four years, the selected buildings will bring profit for the investment.
  8. Wong FC, Yong AL, Ting EP, Khoo SC, Ong HC, Chai TT
    Iran J Pharm Res, 2014;13(4):1409-15.
    PMID: 25587331
    The purpose of this investigation was to determine the antioxidant potentials and anti-glucosidase activities of six tropical medicinal plants. The levels of phenolic constituents in these medicinal plants were also quantified and compared. Antioxidation potentials were determined colorimetrically for scavenging activities against DPPH and NO radicals. Metal chelating assay was based on the measurement of iron-ferrozine absorbance at 562 nm. Anti-diabetic potentials were measured by using α-glucosidase as target enzyme. Medicinal plants' total phenolic, total flavonoid and hydroxycinnamic acid contents were determined using spectrophotometric methods, by comparison to standard plots prepared using gallic acid, quercetin and caffeic acid standards, respectively. Radical scavenging and metal chelating activities were detected in all medicinal plants, in concentration-dependent manners. Among the six plants tested, C. nutans, C. formosana and H. diffusa were found to possess α-glucosidase inhibitory activities. Spectrophotometric analysis indicated that the total phenolic, total flavonoid and hydroxycinnamic acid contents ranged from 12.13-21.39 mg GAE per g of dry sample, 1.83-9.86 mg QE per g of dry sample, and 0.91-2.74 mg CAE per g of dry sample, respectively. Our results suggested that C. nutans and C. formosana could potentially be used for the isolation of potent antioxidants and anti-diabetic compounds. To the best of our knowledge, this study represents the first time that C. nutans (Acanthaceae family) was reported in literature with glucosidase inhibition activity.
  9. Hasan SS, Teh KM, Ahmed SI, Chong DW, Ong HC, Naina B
    Public Health, 2015 Jul;129(7):954-62.
    PMID: 26138018 DOI: 10.1016/j.puhe.2015.05.014
    OBJECTIVES: To investigate association between quality of life (QoL) and International Normalized Ratio (INR) control, with the secondary aim of assessing QoL using generic and anticoagulation-specific, the Short Form Health Survey (SF-12) and the Duke Anticoagulation Satisfaction Scale (DASS).
    STUDY DESIGN: This study assessed anticoagulation related QoL at three time intervals in two groups of patients on long-term warfarin therapy.
    METHODS: Data of 326 randomly sampled patients (163 patients each in DASS and SF-12 groups) who had been on warfarin therapy for at least one year at anticoagulation clinics were analysed. QoL was assessed at three time intervals: at the start, six months and one year of warfarin therapy. Indications and target INR ranges and subjects INR values were recorded. Time in Therapeutic Range (TTR) was estimated for four subject subgroups, based on target ranges of INR for clustered indications.
    RESULTS: Of the total, 43% of the subjects were aged between 50 and 64 years, and 51% were female. DASS assessed subjects older than 35 years perceived significant decrease in overall mean scores of anticoagulation related QoL, whilst all SF-12 assessed subjects perceived an increase in QoL. The mean percentage days in range for all INR target range subgroups did not exceed more than 60% but there was only a weak correlation (Rs = 0.104, P > 0.05) between INR control and overall QoL.
    CONCLUSION: Malaysian urban outpatients on warfarin treatment longer than one year report a significant overall decrease in QoL, as measured using a validated condition-specific instrument. These patients appeared to adapt well to lifestyle limitations imposed by long-term anticoagulation.
    KEYWORDS: Anticoagulation therapy; International Normalized Ratio; Quality of life

    Study site: anticoagulation clinics at a
    suburban tertiary Ministry of Health hospital in Peninsular
    Malaysia
  10. Yong AL, Ooh KF, Ong HC, Chai TT, Wong FC
    Food Chem, 2015 Nov 1;186:32-6.
    PMID: 25976788 DOI: 10.1016/j.foodchem.2014.11.103
    In this paper, we investigated the antibacterial mechanism and potential therapeutic targets of three antibacterial medicinal plants. Upon treatment with the plant extracts, bacterial proteins were extracted and resolved using denaturing gel electrophoresis. Differentially-expressed bacterial proteins were excised from the gels and subjected to sequence analysis by MALDI TOF-TOF mass spectrometry. From our study, seven differentially expressed bacterial proteins (triacylglycerol lipase, N-acetylmuramoyl-L-alanine amidase, flagellin, outer membrane protein A, stringent starvation protein A, 30S ribosomal protein s1 and 60 kDa chaperonin) were identified. Additionally, scanning electron microscope study indicated morphological damages induced on bacterial cell surfaces. To the best of our knowledge, this represents the first time these bacterial proteins are being reported, following treatments with the antibacterial plant extracts. Further studies in this direction could lead to the detailed understanding of their inhibition mechanism and discovery of target-specific antibacterial agents.
  11. Chai TT, Kwek MT, Ong HC, Wong FC
    Food Chem, 2015 Nov 1;186:26-31.
    PMID: 25976787 DOI: 10.1016/j.foodchem.2014.12.099
    This study aimed to isolate a potent antiglucosidase and antioxidant fraction from Stenochlaena palustris. Extraction was performed with hexane, chloroform, ethyl acetate, methanol, and water. Antiglucosidase, 2,2-diphenyl-1-picrylhydrazyl (DPPH) scavenging and ferric reducing antioxidant power (FRAP) assays found methanol extract (ME) to be the most active. Water fraction (WF) of ME was a stronger α-glucosidase inhibitor (EC50 2.9 μg/mL) than quercetin, with weak antiamylase activity. WF was a competitive α-glucosidase inhibitor. DPPH scavenging activity of WF (EC50 7.7 μg/mL) was weaker than quercetin. WF (EC50 364 μg/mL) was a stronger hydrogen peroxide scavenger than gallic acid (EC50 838 μg/mL) and was equally strong as quercetin in scavenging superoxide. WF possessed moderate copper chelating activity. WF was enriched in total phenolics (TP) and hydroxycinnamic acids (THC). TP correlated with antioxidant activity (R(2) > 0.76). Only THC correlated with antiglucosidase activity (R(2) = 0.86). Overall, WF demonstrated concurrent, potent antiglucosidase and antioxidant activities.
  12. Ong HC, Alih E
    PLoS One, 2015;10(4):e0125835.
    PMID: 25923739 DOI: 10.1371/journal.pone.0125835
    The tendency for experimental and industrial variables to include a certain proportion of outliers has become a rule rather than an exception. These clusters of outliers, if left undetected, have the capability to distort the mean and the covariance matrix of the Hotelling's T2 multivariate control charts constructed to monitor individual quality characteristics. The effect of this distortion is that the control chart constructed from it becomes unreliable as it exhibits masking and swamping, a phenomenon in which an out-of-control process is erroneously declared as an in-control process or an in-control process is erroneously declared as out-of-control process. To handle these problems, this article proposes a control chart that is based on cluster-regression adjustment for retrospective monitoring of individual quality characteristics in a multivariate setting. The performance of the proposed method is investigated through Monte Carlo simulation experiments and historical datasets. Results obtained indicate that the proposed method is an improvement over the state-of-art methods in terms of outlier detection as well as keeping masking and swamping rate under control.
  13. Pang YL, Lim S, Ong HC, Chong WT
    Ultrason Sonochem, 2016 Mar;29:317-27.
    PMID: 26585012 DOI: 10.1016/j.ultsonch.2015.10.003
    In this work, γ-Fe2O3 and TiO2 NTs/γ-Fe2O3 composites with good magnetism and sonocatalytic activity were prepared by a facile polyol method and utilize the principle of isoelectric point method, respectively. The structural and magnetic features of the prepared calcined γ-Fe2O3 and composite catalysts were investigated by transmission electron microscopy (TEM), powder X-ray diffraction (XRD), surface analysis, UV-Vis diffuse reflectance spectra (UV-Vis DRS), vibrating sample magnetometry (VSM) and zeta potential analysis. The effects of calcination temperature on γ-Fe2O3 phase variation, physical properties and sonocatalytic properties were investigated. The porosity, specific surface area, band gap energy and sonocatalytic activity of γ-Fe2O3 were gradually decreased with calcination temperature increased. TiO2 NTs/γ-Fe2O3 with appropriate composition and specific structural features possess synergetic effects such as efficient separation of charge carriers and hydroxyl radicals produced by heterogeneous fenton and fenton-like reactions. This enhanced the sonocatalytic activity for the degradation of Orange G under ultrasonic irradiation. The sonocatalytic reactions obeyed pseudo first-order kinetics. All these information provide insight into the design and development of high-efficiency catalyst for wastewater treatment.
  14. Ong HC, Ibrahim N, Wahab S
    PMID: 27574475 DOI: 10.2147/PRBM.S112129
    Nowadays, family members are gradually taking on the role of full-time caregivers for patients suffering from schizophrenia. The increasing burden and tasks of caretaking can cause them psychological distress such as depression or anxiety. The aim of this study was to measure the correlation between perceived stigma and coping, and psychological distress as well as determine the predictors of psychological distress among the caregivers. Results showed that 31.5% of the caregivers experienced psychological distress. "Community rejection" was found to be positively associated with psychological distress. In case of coping subscales, psychological distress had a positive correlation with substance use, use of emotional support, behavioral disengagement, venting, and self-blame, while it was negatively correlated with "positive reframing". Behavioral disengagement was the best predictor of psychological distress among caregivers of patients with schizophrenia, followed by positive reframing, use of emotional support, self-blame, and venting. Health practitioners can use adaptive coping strategies instead of maladaptive for caregivers to help ease their distress and prevent further deterioration of psychological disorders.
    Study site: Psychiatric Clinic, Hospital Canselor Tuanku Muhriz (Pusat Perubatan Universiti Kebangsaan Malaysia, PPUKM)
    Scales & Questionnaire: Kessler’s K10
    Psychological Distress Scale; Devaluation of Consumer Scale (DCS); Devaluation of Consumer Families Scale (DCFS); Brief COPE
  15. Ibrahim N, Ong HC, Wahab S
    Malays J Med Sci, 2017 May;24(3):83-91.
    PMID: 28814936 MyJurnal DOI: 10.21315/mjms2017.24.3.10
    INTRODUCTION: Caregivers often experience stressful situations while in the midst of the caregiving process. Thus, various methods of coping have been widely applied and studied in previous researches. The aim of this study was to develop a novel questionnaire to assess the coping strategies employed by those who provide care to patients, and to further validate it among caregivers of schizophrenia patients in Malaysia.

    METHODS: This study, which involved the caregivers of schizophrenia patients from a hospital in Kuala Lumpur, Malaysia, was comprised of three parts, namely in-depth interviews, a pilot study, and the validation of the developed questionnaire, known as Caregiver Cope (CgCopeTM).

    RESULTS: Part A originally consisted of eight themes, and it was later modified to seven themes with four items each after discussions with some experts. Part B initially had 28 items derived from the seven themes in Part A, which were then reduced to six components after a factor analysis. Part C of the questionnaire consisted of 19 items, with six components (Distraction, Caring for patient, Venting, Religion, Recreation, and Social support) having a moderate to high reliability ranging from a Cronbach's alpha coefficient of 0.54 to 0.82. A factor analysis showed that the six factors of coping accounted for 62.36% of the total variance.

    CONCLUSION: The CgCOPETM questionnaire is suitable for use among caregivers of schizophrenia patients. There is a need to further validate the instrument among caregivers of other patient populations.

  16. Silitonga AS, Hassan MH, Ong HC, Kusumo F
    Environ Sci Pollut Res Int, 2017 Nov;24(32):25383-25405.
    PMID: 28932948 DOI: 10.1007/s11356-017-0141-9
    The purpose of this study is to investigate the performance, emission and combustion characteristics of a four-cylinder common-rail turbocharged diesel engine fuelled with Jatropha curcas biodiesel-diesel blends. A kernel-based extreme learning machine (KELM) model is developed in this study using MATLAB software in order to predict the performance, combustion and emission characteristics of the engine. To acquire the data for training and testing the KELM model, the engine speed was selected as the input parameter, whereas the performance, exhaust emissions and combustion characteristics were chosen as the output parameters of the KELM model. The performance, emissions and combustion characteristics predicted by the KELM model were validated by comparing the predicted data with the experimental data. The results show that the coefficient of determination of the parameters is within a range of 0.9805-0.9991 for both the KELM model and the experimental data. The mean absolute percentage error is within a range of 0.1259-2.3838. This study shows that KELM modelling is a useful technique in biodiesel production since it facilitates scientists and researchers to predict the performance, exhaust emissions and combustion characteristics of internal combustion engines with high accuracy.
  17. Yu KL, Lau BF, Show PL, Ong HC, Ling TC, Chen WH, et al.
    Bioresour Technol, 2017 Dec;246:2-11.
    PMID: 28844690 DOI: 10.1016/j.biortech.2017.08.009
    Algal biomass is known as a promising sustainable feedstock for the production of biofuels and other valuable products. However, since last decade, massive amount of interests have turned to converting algal biomass into biochar. Due to their high nutrient content and ion-exchange capacity, algal biochars can be used as soil amendment for agriculture purposes or adsorbents in wastewater treatment for the removal of organic or inorganic pollutants. This review describes the conventional (e.g., slow and microwave-assisted pyrolysis) and newly developed (e.g., hydrothermal carbonization and torrefaction) methods used for the synthesis of algae-based biochars. The characterization of algal biochar and a comparison between algal biochar with biochar produced from other feedstocks are also presented. This review aims to provide updated information on the development of algal biochar in terms of the production methods and the characterization of its physical and chemical properties to justify and to expand their potential applications.
  18. Chen WH, Hsu HJ, Kumar G, Budzianowski WM, Ong HC
    Bioresour Technol, 2017 Dec;246:12-19.
    PMID: 28803060 DOI: 10.1016/j.biortech.2017.07.184
    This study focuses on the biochar formation and torrefaction performance of sugarcane bagasse, and they are predicted using the bilinear interpolation (BLI), inverse distance weighting (IDW) interpolation, and regression analysis. It is found that the biomass torrefied at 275°C for 60min or at 300°C for 30min or longer is appropriate to produce biochar as alternative fuel to coal with low carbon footprint, but the energy yield from the torrefaction at 300°C is too low. From the biochar yield, enhancement factor of HHV, and energy yield, the results suggest that the three methods are all feasible for predicting the performance, especially for the enhancement factor. The power parameter of unity in the IDW method provides the best predictions and the error is below 5%. The second order in regression analysis gives a more reasonable approach than the first order, and is recommended for the predictions.
  19. Ibrahim N, Amit N, Che Din N, Ong HC
    Psychol Res Behav Manag, 2017;10:129-135.
    PMID: 28496374 DOI: 10.2147/PRBM.S125176
    Suicide is a global phenomenon that has been showing an upward trend in recent years. It is the second leading cause of death among youth. Studies on suicidal ideation warrant greater attention, as it leads to suicide attempts and other health risk behaviors. Thus, the objective of this study was to compare gender differences in suicidal ideation and determine the predictors of suicidal ideation among youth. This cross-sectional study was carried out among 232 youths aged between 15 and 25 years from selected urban areas in Malaysia. The results showed that suicidal ideation was higher among male participants compared with female participants. Age was the predictor of suicidal ideation for males, while depression and loss of motivation, as components of hopelessness, were the predictors of suicidal ideation among females. Hence, it is important that professionals conduct early identification tests for suicidality among young people. This will facilitate the early detection of depression and hopelessness, which is important, in order to prevent suicidal behaviors or other problems before these occur.
  20. Chan YS, Cheah YH, Chong PZ, Khor HL, Teh WS, Khoo KS, et al.
    Pak J Pharm Sci, 2018 Jan;31(1):119-127.
    PMID: 29348093
    This study was conducted to investigate the antifungal potential and cytotoxicity of selected medicinal plants from Malaysia. The extracts from the stem of Cissus quadrangularis and the leaves of Asplenium nidus, Pereskia bleo, Persicaria odorata and Sauropus androgynus were assayed against six fungi using p-iodonitrotetrazolium-based on colorimetric broth microdilution method. All the plant extracts were found to be fungicidal against at least one type of fungus. The strongest fungicidal activity (minimum fungicidal concentration=0.16 mg/mL) were exhibited by the hexane extract of C. quadrangularis, the hexane, chloroform, ethanol and methanol extracts of P. bleo, the hexane and ethyl acetate extracts of P. odorata, and the water extract of A. nidus. In terms of cytotoxicity on the African monkey kidney epithelial (Vero) cells, the chloroform extract of P. odorata produced the lowest 50% cytotoxic concentration (100.3 ± 4.2 μ g/mL). In contrast, none of the water extracts from the studied plants caused significant toxicity on the cells. The water extract of A. nidus warrants further investigation since it showed the strongest fungicidal activity and the highest total activity (179.22 L/g) against Issatchenkia orientalis, and did not cause any toxicity to the Vero cells.
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