Displaying publications 1 - 20 of 49 in total

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  1. Mahendran R, Mahendran R, Chan YH
    Ann Acad Med Singap, 2004 May;33(3):320-3.
    PMID: 15175772
    INTRODUCTION: Most research in interleukin activity in schizophrenia has been in Caucasian populations. We examined interleukin-2 (IL-2) levels and their relation to the duration of the illness, psychopathology and treatment effects, in chronic schizophrenia patients of Asian origin.

    MATERIALS AND METHODS: Thirty chronic schizophrenia patients were recruited for the study and their demographic data and medication dosage were noted. Symptom severity was scored on the Positive And Negative Syndrome scale for Schizophrenia (PANSS) and blood sampling done. Ten healthy Chinese males were recruited as controls. Phytohaemagglutinin-stimulated production of serum levels of IL-2 were measured by enzyme-linked immunosorbent assay.

    RESULTS: IL-2 levels (1327 +/- 596.2) of all 30 patients were significantly lower than that of the Chinese controls (2420 +/- 342.5). This effect was noted throughout the entire duration of the illness. Ethnic and age differences in IL-2 levels were not found. There was, however, a negative correlation with the duration of the illness and a positive correlation with the dosage of medication.

    CONCLUSIONS: The results of this study of a population of mostly Chinese patients with schizophrenia replicate an important finding. Data such as this has not been reported previously on Asians of this racial group.

  2. Kunnasegaran R, Chan YH
    Malays Orthop J, 2017 Mar;11(1):64-67.
    PMID: 28435578 DOI: 10.5704/MOJ.1703.007
    The treatment of fractures in osteopetrosis can be complicated and difficult. We describe the use of an industrial grade tungsten carbide drill bit in the treatment of one of these complex fractures. An industrial grade tungsten carbide drill bit was used to fashion a medullary canal in the surgical treatment of a left peri-implant fracture of the neck of femur in a patient with osteopetrosis. The patient was successfully treated with a hemiarthroplasty with good functional outcomes. A tungsten carbide drill bit serves as an effective and safe option in the treatment of osteopetrotic femoral neck fractures.
  3. Soh J, Sandham A, Chan YH
    Angle Orthod, 2005 Sep;75(5):814-20.
    PMID: 16279828
    The purpose of this study was to determine the occlusal status in young Asian male adults of three ethnic groups. Study models of a sample of male army recruits (N = 339, age 17-22 years) with no history of orthodontic treatment were assessed. The ethnic proportions of the sample were Chinese 76.1% (n = 258), Malay 17.7% (n = 60), and Indian 6.2% (n = 21). British Standard Institute (BSI) and Angle's classification were used to determine incisor and molar relationships, respectively. Chi-square test or Fisher's Exact test was performed to compare the occlusal traits between ethnic groups. The distribution of incisor relationships of the total sample consisted of Class I = 48.1%, Class II/1 = 26.3%, Class II/2 = 3.2%, and Class III = 22.4%. Right Angle's molar relationships were 49.9%, 24.5%, and 24.2% whereas left Angle's molar relationships were 53.1%, 25.1%, and 21.2% for Class I, II, and III, respectively. Comparison between ethnic groups found that Indian subjects were more likely to have Class II/1 malocclusions and clinically missing permanent teeth (P < .05). The study found that the overall prevalence of malocclusion (BSI) was Class I, Class II/1, Class III, and Class II/2 in descending order of proportions. Angle's Class I molar was most prevalent followed by Class II and Class III relations. A significant difference in occlusal status between the ethnic groups was found regarding incisor relationship and missing permanent teeth (P < .05).
  4. Khoo SP, Yap AU, Chan YH, Bulgiba AM
    J Orofac Pain, 2008;22(2):131-8.
    PMID: 18548842
    To develop a Malay-language version of the Axis II Research Diagnostic Criteria for Temporomandibular Disorders (RDC/TMD) through a formal translation/back-translation process and to summarize available data about the psychometric properties of the translated scales.
  5. Yeap GY, Hrishikesan E, Chan YH, Mahmood WA
    J Fluoresc, 2017 Jan;27(1):105-110.
    PMID: 27679994 DOI: 10.1007/s10895-016-1938-5
    A new chalcone-based probe containing coumarin and naphthol at both ends has been synthesized via aldol condensation. The uniqueness of the newly derived probe can be ascribed to the presence of naphthol and coumarin units acting as binding site and signaling element, respectively. The fluorogenic behaviors toward various anions were investigated. The probe was characterized by various spectroscopic techniques and the in-depth study led to show excellent selectivity and sensitivity for fluoride ions. The hydrogen bonding thus formed with fluoride anion provides remarkable fluorometric responses. The interactions of the probe with fluoride ions were determined by fluorescence, FT-IR and NMR spectroscopic techniques. The exploratory studies by fluorescent spectral changes augur well for the naked-eye sensing applications.
  6. Chan YH, Harith HH, Israf DA, Tham CL
    Front Cell Dev Biol, 2019;7:280.
    PMID: 31970155 DOI: 10.3389/fcell.2019.00280
    Endothelial cells lining the inner vascular wall form a monolayer that contributes to the selective permeability of endothelial barrier. This selective permeability is mainly regulated by an endothelium-specific adherens junctional protein, known as vascular endothelial-cadherin (VE-cadherin). In endothelial cells, the adherens junction comprises of VE-cadherin and its associated adhesion molecules such as p120, α-catenin, and β-catenin, in which α-catenin links cytoplasmic tails of VE-cadherin to actin cytoskeleton through β-catenin. Proinflammatory stimuli such as lipopolysaccharide (LPS) are capable of attenuating vascular integrity through the disruption of VE-cadherin adhesion in endothelial cells. To date, numerous studies demonstrated the disruption of adherens junction as a result of phosphorylation-mediated VE-cadherin disruption. However, the outcomes from these studies were inconsistent and non-conclusive as different cell fractions were used to examine the effect of LPS on the disruption of VE-cadherin. By using Western Blot, some studies utilized total protein lysate and reported decreased protein expression while some studies reported unchanged expression. Other studies which used membrane and cytosolic fractions of protein extract demonstrated decreased and increased VE-cadherin expression, respectively. Despite the irregularities, the results of immunofluorescence staining are consistent with the formation of intercellular gap. Besides that, the overall underlying disruptive mechanisms of VE-cadherin remain largely unknown. Therefore, this mini review will focus on different experiment approaches in terms of cell fractions used in different human endothelial cell studies, and relate these differences to the results obtained in Western blot and immunofluorescence staining in order to give some insights into the overall differential regulatory mechanisms of LPS-mediated VE-cadherin disruption and address the discrepancy in VE-cadherin expression.
  7. Fernandes ML, Seow A, Chan YH, Ho KY
    Am J Gastroenterol, 2006 Jul;101(7):1430-6.
    PMID: 16863543
    To describe the incidence trends in esophageal squamous cell carcinoma (SCC) and adenocarcinoma among the three major ethnic groups in Singapore from 1968 to 2002.
  8. Yeap GY, Chan YH, Mahmood WAK
    J Fluoresc, 2017 Nov;27(6):2017-2022.
    PMID: 28856483 DOI: 10.1007/s10895-017-2140-0
    A novel, 100% water-soluble chalcone based chemosensing receptor {1-[3-(2-Hydroxy-phenyl)-3-oxo-propenyl]-naphthalen-2-yloxy}-acetic acid, L was synthesized and characterized. The receptor L is designed based on the chelation enhanced fluorescence (CHEF) mechanism. The chemosensing properties of L were evaluated by UV-vis and fluorescence spectrometric methods. It exhibits highly selective recognition ability towards aluminum ions in water over other metal ions. The binding stoichiometry of L- Al3+complex is 2:1 by means of Job's plot and the detection limit is 5.66 × 10- 8M.
  9. Yeoh AE, Lu Y, Chan JY, Chan YH, Ariffin H, Kham SK, et al.
    Leuk. Res., 2010 Mar;34(3):276-83.
    PMID: 19651439 DOI: 10.1016/j.leukres.2009.07.003
    To study genetic epidemiology of childhood acute lymphoblastic leukemia (ALL) in the Chinese and Malays, we investigated 10 polymorphisms encoding carcinogen- or folate-metabolism and transport. Sex-adjusted analysis showed NQO1 609CT significantly protects against ALL, whilst MTHFR 677CT confers marginal protection. Interestingly, we observed that NQO1 609CT and MTHFR 1298 C-allele have greater genetic impact in boys than in girls. The combination of SLC19A1 80GA heterozygosity and 3'-TYMS -6bp/-6bp homozygous deletion is associated with reduced ALL risk in Malay boys. Our study has suggested the importance of gender and race in modulating ALL susceptibility via the folate metabolic pathway.
  10. Seow SC, Chai P, Lee YP, Chan YH, Kwok BW, Yeo TC, et al.
    J. Card. Fail., 2007 Aug;13(6):476-81.
    PMID: 17675062
    Prognostic indicators and mortality in multiethnic Southeast Asian patients with heart failure (HF) may be different.
  11. Yiin CL, Ho S, Yusup S, Quitain AT, Chan YH, Loy ACM, et al.
    Bioresour Technol, 2019 Oct;290:121797.
    PMID: 31327691 DOI: 10.1016/j.biortech.2019.121797
    The aim of this work was to recover the cellulose fibers from EFB using low-transition-temperature-mixtures (LTTMs) as a green delignification approach. The hydrogen bonding of LTTMs observed in 1H NMR tends to disrupt the three-dimensional structure of lignin and further remove the lignin from EFB. Delignification process of EFB strands and EFB powder were performed using standard l-malic acid and cactus malic acid-LTTMs. The recovered cactus malic acid-LTTMs showed higher glucose concentration of 8.07 mg/mL than the recovered l-malic acid LTTMs (4.15 mg/mL). This implies that cactus malic acid-LTTMs had higher delignification efficiency which led to higher amount of cellulose hydrolyzed into glucose. The cactus malic acid-LTTMs-delignified EFB was the most feasible fibers for making paper due to its lowest kappa number of 69.84. The LTTMs-delignified EFB has great potential to be used for making specialty papers in pulp and paper industry.
  12. Chan YH, Syed Abdul Rahman SNF, Lahuri HM, Khalid A
    Environ Pollut, 2021 Mar 01;278:116843.
    PMID: 33711630 DOI: 10.1016/j.envpol.2021.116843
    Carbon monoxide (CO) is a highly valuable component of syngas which could be used to synthesize various chemicals and fuels. Conventionally, syngas is derived from fossil-based natural gas and coal which are non-renewable. To curb the problem, CO2 gasification offers a win-win solution in which CO2 is converted with wastes to CO, achieving carbon emission mitigation and addressing waste disposal issue simultaneously. In this review, gasification of various wastes by CO2 with particular focus given to generation of CO-rich syngas is presented and critically discussed. This includes the effects of operating parameters (temperature, pressure and physicochemical properties of feedstocks) and advanced CO2 gasification techniques (catalytic CO2 gasification, CO2 co-gasification and microwave-driven CO2 gasification). Furthermore, associated technological challenges are highlighted and way forward in this field are proposed.
  13. Chan YH, Liew KY, Tan JW, Shaari K, Israf DA, Tham CL
    Front Pharmacol, 2021;12:736339.
    PMID: 34531753 DOI: 10.3389/fphar.2021.736339
    2,4,6-Trihydroxy-3-geranyl acetophenone (tHGA) is a bioactive phloroglucinol compound found in Melicope pteleifolia (Champ. ex Benth.) T.G.Hartley, a medicinal plant vernacularly known as "tenggek burung". A variety of phytochemicals have been isolated from different parts of the plant including leaves, stems, and roots by using several extraction methods. Specifically, tHGA, a drug-like compound containing phloroglucinol structural core with acyl and geranyl group, has been identified in the methanolic extract of the young leaves. Due to its high nutritional and medicinal values, tHGA has been extensively studied by using various experimental models. These studies have successfully discovered various interesting pharmacological activities of tHGA such as anti-inflammatory, endothelial and epithelial barrier protective, anti-asthmatic, anti-allergic, and anti-cancer. More in-depth investigations later found that these activities were attributable to the modulatory actions exerted by tHGA on specific molecular targets. Despite these findings, the association between the mechanisms and signaling pathways underlying each pharmacological activity remains largely unknown. Also, little is known about the medicinal potentials of tHGA as a drug lead in the current pharmaceutical industry. Therefore, this mini review aims to summarize and relate the pharmacological activities of tHGA in terms of their respective mechanisms of action and signaling pathways in order to present a perspective into the overall modulatory actions exerted by tHGA. Besides that, this mini review will also pinpoint the unexplored potentials of this compound and provide some valuable insights into the potential applications of tHGA which may serve as a guide for the development of modern medication in the future.
  14. Tan VM, Ooi DS, Kapur J, Wu T, Chan YH, Henry CJ, et al.
    Eur J Nutr, 2016 Jun;55(4):1573-81.
    PMID: 26160548 DOI: 10.1007/s00394-015-0976-0
    PURPOSE: There are wide inter-individual differences in glycemic response (GR). We aimed to examine key digestive parameters that influence inter-individual and ethnic differences in GR in healthy Asian individuals.
    METHODS: Seventy-five healthy male subjects (25 Chinese, 25 Malays, and 25 Asian-Indians) were served equivalent available carbohydrate amounts (50 g) of jasmine rice (JR) and basmati rice (BR) on separate occasions. Postprandial blood glucose concentrations were measured at fasting (-5 and 0 min) and at 15- to 30-min interval over 180 min. Mastication parameters (number of chews per mouth and chewing time per mouthful), saliva α-amylase activity, AMY1 gene copy numbers and gastric emptying rate were measured to investigate their relationships with GR.
    RESULTS: The GR for jasmine rice was significantly higher than for basmati rice (P 0.05).
    CONCLUSION: Mastication parameters contribute significantly to GR. Eating slowly and having larger food boluses before swallowing (less chewing), both potentially modifiable, may be beneficial in glycemic control.
  15. Pang KA, Pang KP, Pang EB, Tan YN, Chan YH, Siow JK
    Med J Malaysia, 2017 08;72(4):215-220.
    PMID: 28889132
    OBJECTIVE: To describe the prevalence of food allergy in Asian patients with allergic rhinitis.

    STUDY DESIGN: A non-randomized prospectively collected patients over a three year period, with complaints of nose congestion, rhinorrhea and/or nasal discharge.

    RESULTS: There were 435 patients enrolled, 213 children and 222 adults. The children group had a high prevalence of allergen specific IgE to Dermatophagoides pteryonysinus (70%), Dermatophagoides farina (69%), and Blomia tropicalis (55%); followed by dogs (32%), cats (19%) and cockroaches (19%). In the children food allergy category, the top three allergens were egg white (54%), milk (31%) and soya bean (13%). The adult group had results of Dermatophagoides pteryonysinus (71%), Dermatophagoides farina (72%), and Blomia tropicalis (59%); the adult food allergy category, the top 3 allergens were egg white (13%), milk (6%) and soya bean (5%). There was a statistically significant difference in the child and adult group for Dust, D. pteryonysinus, D. farina, B.tropicalis, egg white, wheat, gluten and soya bean. In the age specific child groups, there was an increased in egg food allergy levels, with a peak at the age of five-nine years old and decreasing thereafter (p=0.04). In the children group, the mean Total Nasal Symptom Score (TNSS) was 10.3 (range of 7 to 13); the adult group was similar, with a mean TNSS of 9.8 (range 5 to 12).

    CONCLUSION: The prevalence of food allergy in paediatric patients with allergic rhinitis is fairly high and should be considered when treating these children.

  16. Lim WY, Kwek K, Chong YS, Lee YS, Yap F, Chan YH, et al.
    J Hypertens, 2014 Apr;32(4):857-64.
    PMID: 24390251 DOI: 10.1097/HJH.0000000000000096
    OBJECTIVE: Greater maternal adiposity is a potentially modifiable risk factor for elevated blood pressure during pregnancy; however, the association has been little studied in Asian populations, and no study has evaluated potential differences in the adiposity-blood pressure relation between ethnic groups or interaction with gestational diabetes.

    METHODS: We performed a cross-sectional evaluation of a Singapore mother-offspring cohort comprising 799 pregnant Chinese, Malay and Indian women. Data on body weight, height, skinfold thickness and glycaemia (oral glucose tolerance test) were collected during the 2nd trimester; peripheral SBP and DBP were measured using an oscillometric device and central pressures by noninvasive radial applanation tonometry. The associations between adiposity measures BMI and sum of skinfold thickness and blood pressure outcomes were examined by linear regression with adjustment for potential confounders.

    RESULTS: Higher maternal BMI was associated with elevated peripheral and central pressures: the increases in pressure (mmHg) for each kg/m(2) increase in BMI were 1.19 (95% confidence interval, 1.03-1.36) for peripheral SBP, 0.76 (0.63-0.89) for peripheral DBP, 1.02 (0.87-1.17) for central systolic pressure and 0.26 (0.16-0.37) for central pulse pressure. The associations were generally stronger in Chinese women (P-interaction = 0.03 for central pulse pressure) and individuals with gestational diabetes (P-interaction = 0.03 for DBP and P-interaction = 0.046 for central systolic pressure). Similar patterns of results were found when using skinfold thickness as the measure of adiposity.

    CONCLUSION: Maternal adiposity is associated with higher peripheral and central blood pressures during pregnancy. Stronger associations in Chinese women and individuals with gestational diabetes warrant further investigation.
  17. Foong SY, Chan YH, Cheah WY, Kamaludin NH, Tengku Ibrahim TNB, Sonne C, et al.
    Bioresour Technol, 2021 Jan;320(Pt A):124299.
    PMID: 33129091 DOI: 10.1016/j.biortech.2020.124299
    Hydrogen and gaseous fuel derived from wastes have opened up promising alternative pathways for the production of renewable and sustainable fuels to substitute classical fossil energy resources that cause global warming and pollution. Existing review articles focus mostly on gasification, reforming and pyrolysis processes, with limited information on particularly gaseous fuel production via pyrolysis of various waste products. This review provides an overview on the recent advanced pyrolysis technology used in hydrogen and gaseous fuel production. The key parameters to maximize the production of specific compounds were discussed. More studies are needed to optimize the process parameters and improve the understanding of reaction mechanisms and co-relationship between these advanced techniques. These advanced techniques provide novel environmentally sustainable and commercially procedures for waste-based production of hydrogen and gaseous fuels.
  18. Pang KP, Baptista PM, Olszewska E, Braverman I, Carrasco-Llatas M, Kishore S, et al.
    Med J Malaysia, 2020 03;75(2):117-123.
    PMID: 32281591
    OBJECTIVE: To demonstrate SLEEP-GOAL as a more holistic and comprehensive success criterion for Obstructive Sleep Apnoea (OSA) treatment.

    METHODS: A prospective 7-country clinical trial of 302 OSA patients, who met the selection criteria, and underwent nose, palate and/or tongue surgery. Pre- and post-operative data were recorded and analysed based on both the Sher criteria (apnoea hypopnea index, AHI reduction 50% and <20) and the SLEEP-GOAL.

    RESULTS: There were 229 males and 73 females, mean age of 42.4±17.3 years, mean BMI 27.9±4.2. The mean VAS score improved from 7.7±1.4 to 2.5±1.7 (p<0.05), mean Epworth score (ESS) improved from 12.2±4.6 to 4.9±2.8 (p<0.05), mean body mass index (BMI) decreased from 27.9±4.2 to 26.1±3.7 (p>0.05), gross weight decreased from 81.9±14.3kg to 76.6±13.3kg. The mean AHI decreased 33.4±18.9 to 14.6±11.0 (p<0.05), mean lowest oxygen saturation (LSAT) improved 79.4±9.2% to 86.9±5.9% (p<0.05), and mean duration of oxygen <90% decreased from 32.6±8.9 minutes to 7.3±2.1 minutes (p<0.05). The overall success rate (302 patients) based on the Sher criteria was 66.2%. Crosstabulation of respective major/minor criteria fulfilment, based on fulfilment of two major and two minor or better, the success rate (based on SLEEP-GOAL) was 69.8%. Based solely on the Sher criteria, 63 patients who had significant blood pressure reduction, 29 patients who had BMI reduction and 66 patients who had clinically significant decrease in duration of oxygen <90% would have been misclassified as "failures".

    CONCLUSION: AHI as a single parameter is unreliable. Assessing true success outcomes of OSA treatment, requires comprehensive and holistic parameters, reflecting true end-organ injury/function; the SLEEP-GOAL meets these requirements.

  19. Yiin CL, Yap KL, Ku AZE, Chin BLF, Lock SSM, Cheah KW, et al.
    Bioresour Technol, 2021 Aug;333:125195.
    PMID: 33932810 DOI: 10.1016/j.biortech.2021.125195
    Biomass wastes exhibit a great potential to be used as a source of non-depleting renewable energy and synthesis of value-added products. The key to the valorization of excess lignocellulosic biomass wastes in the world lies on the pretreatment process to recalcitrant barrier of the lignocellulosic material for the access to useful substrates. A wide range of pretreatment techniques are available and advances in this field is continuously happening, in search for cheap, effective, and environmentally friendly methods. This review starts with an introduction to conventional approaches and green solvents for pretreatment of lignocellulosic biomass. Subsequently, the mechanism of actions along with the advantages and disadvantages of pretreatment techniques were reviewed. The roles of choline chloride (ChCl) in green solvents and their potential applications were also comprehensively reviewed. The collection of ideas in this review serve as an insight for future works or interest on biomass-to-energy conversion using green solvents.
  20. Chan YH, Musa NF, Chong YJ, Saat SA, Hafiz F, Shaari K, et al.
    Pharm Biol, 2021 Dec;59(1):732-740.
    PMID: 34155953 DOI: 10.1080/13880209.2021.1933083
    CONTEXT: Lipopolysaccharide (LPS) exacerbates systemic inflammatory responses and causes excessive fluid leakage. 2,4,6-Trihydroxy-3-geranyl acetophenone (tHGA) has been revealed to protect against LPS-induced vascular inflammation and endothelial hyperpermeability in vitro.

    OBJECTIVE: This study assesses the in vivo protective effects of tHGA against LPS-induced systemic inflammation and vascular permeability in endotoxemic mice.

    MATERIALS AND METHODS: BALB/c mice were intraperitoneally pre-treated with tHGA for 1 h, followed by 6 h of LPS induction. Evans blue permeability assay and leukocyte transmigration assay were performed in mice (n = 6) pre-treated with 2, 20 and 100 mg/kg tHGA. The effects of tHGA (20, 40 and 80 mg/kg) on LPS-induced serum TNF-α secretion, lung dysfunction and lethality were assessed using ELISA (n = 6), histopathological analysis (n = 6) and survivability assay (n = 10), respectively. Saline and dexamethasone were used as the negative control and drug control, respectively.

    RESULTS: tHGA significantly inhibited vascular permeability at 2, 20 and 100 mg/kg with percentage of inhibition of 48%, 85% and 86%, respectively, in comparison to the LPS control group (IC50=3.964 mg/kg). Leukocyte infiltration was suppressed at 20 and 100 mg/kg doses with percentage of inhibition of 73% and 81%, respectively (IC50=17.56 mg/kg). However, all tHGA doses (20, 40 and 80 mg/kg) failed to prevent endotoxemic mice from lethality because tHGA could not suppress TNF-α overproduction and organ dysfunction.

    DISCUSSION AND CONCLUSIONS: tHGA may be developed as a potential therapeutic agent for diseases related to uncontrolled vascular leakage by combining with other anti-inflammatory agents.

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