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  1. Fulltext Reassessment of functional dyspepsia: a topic review
    Chua AS
    World J Gastroenterol, 2006 May 07;12(17):2656-9.
    PMID: 16718748 DOI: 10.3748/wjg.v12.i17.2656
    Dyspepsia itself is not a diagnosis but stands for a constellation of symptoms referable to the upper gastrointestinal tract. It consists of a variable combination of symptoms including abdominal pain or discomfort, postprandial fullness, abdominal bloating, early satiety, nausea, vomiting, heartburn and acid regurgitation. Patients with heartburn and acid regurgitation invariably have gastroesophageal reflux disease and should be distinguished from those with dyspepsia. There is a substantial group of patients who do not have a definite structural or biochemical cause for their symptoms and are considered to be suffering from functional dyspepsia (FD). Gastrointestinal motor abnormalities, altered visceral sensation, dysfunctional central nervous system-enteral nervous system (CNS-ENS) integration and psychosocial factors have all being identified as important pathophysiological correlates. It can be considered as a biopsychosocial disorder with dysregulation of the brain-gut axis being central in origin of disease. FD can be categorized into different subgroups based on the predominant single symptom identified by the patient. This subgroup classification can assist us in deciding the appropriate symptomatic treatment for the patient.
  2. Fulltext Prevalence of irritable bowel syndrome in northern India
    Chua AS
    J Neurogastroenterol Motil, 2011 Jan;17(1):6-8.
    PMID: 21369486 DOI: 10.5056/jnm.2011.17.1.6
  3. Fulltext Role of Helicobacter pylori in Functional Dyspepsia: More Controversies Than Answers
    Lee YY, Chua AS
    J Neurogastroenterol Motil, 2013 Jul;19(3):417.
    PMID: 23875114 DOI: 10.5056/jnm.2013.19.3.417
  4. Fulltext Influence of gut microbes on the brain-gut axis (Gut 2011;60:307-317)
    Lee YY, Chua AS
    J Neurogastroenterol Motil, 2011 Oct;17(4):427-9.
    PMID: 22148116 DOI: 10.5056/jnm.2011.17.4.427
  5. Fulltext What indigestion means to the malays?
    Lee YY, Chua AS
    J Neurogastroenterol Motil, 2013 Jul;19(3):295-300.
    PMID: 23875095 DOI: 10.5056/jnm.2013.19.3.295
    Despite being a large ethnic group within the South-East Asia, there is a paucity of reported literatures on dyspepsia in the Malay population. Recent population-based studies indicate that uninvestigated dyspepsia, based on the Rome II criteria, is reported in 12.8% and 11.6% of Malays in the urban and rural communities respectively. Organic causes of dyspepsia including upper gastrointestinal tract cancers, its precancerous lesions, and erosive diseases are uncommon which is largely due to an exceptionally low prevalence of Helicobacter pylori infection in this population. On the other hand, functional dyspepsia and irritable bowel syndrome are relatively common in the Malays than expected. Within a primary care setting, functional dyspepsia, based on the Rome III criteria, is reported in 11.9% of Malays, of which epigastric pain syndrome is found to be more common. Married Malay females are more likely to have functional dyspepsia and psychosocial alarm symptoms. Also based on the Rome III criteria, irritable bowel syndrome, commonly overlapped with functional dyspepsia, is reported in 10.9% of Malays within a community-based setting. Rather than psychosocial symptoms, red flags are most likely to be reported among the Malays with irritable bowel syndrome despite having a low yield for organic diseases. Based upon the above observations, "proton pump inhibitor test" is probably preferable than the "test and treat H. pylori" strategy in the initial management of dyspepsia among the Malays.
  6. Fulltext Investigating functional dyspepsia in Asia
    Lee YY, Chua AS
    J Neurogastroenterol Motil, 2012 Jul;18(3):239-45.
    PMID: 22837871 DOI: 10.5056/jnm.2012.18.3.239
    The diagnosis of functional dyspepsia (FD) is challenging since it depends largely on symptoms which are often heterogeneous and overlapping. This is particularly so in Asia with many different cultures and languages. Symptom-based diagnosis of FD based on Rome III criteria has not been fully validated and it may not be suitable in some Asian populations. Clinicians often assume that investigations in FD are not rewarding and physiological tests are often not available unless in the research setting. Investigation of alarm features and role of Helicobacter pylori in FD remain controversial but experts agreed that both should be tested. Physiological tests including gastric accommodation and chemical hypersensitivity tests are underutilized in Asia and available studies were few. While experts do not recommend routine clinical use of gastric accommodation tests but they agree that these tests can be advocated if clinically indicated. Empiric therapeutic trial is not currently a diagnostic option. The pathogenesis of FD is still poorly understood and there is a substantial placebo response. As a conclusion, a diagnosis of FD is challenging especially so in the context of Asia and despite the limitations of available physiological tests experts agreed that these tests can be advocated if and when clinically indicated.
  7. Fulltext Can a mathematical model be used to estimate the contribution of acute gastroenteritis to the overall prevalence of irritable bowel syndrome?
    Chong KM, Chua AS
    J Neurogastroenterol Motil, 2012 Apr;18(2):120-2.
    PMID: 22523720 DOI: 10.5056/jnm.2012.18.2.120
  8. Fulltext Cholecystokinin hyperresponsiveness in functional dyspepsia
    Chua AS, Keeling PW
    World J Gastroenterol, 2006 May 07;12(17):2688-93.
    PMID: 16718754 DOI: 10.3748/wjg.v12.i17.2688
    Functional dyspepsia (FD) is a common disorder of yet uncertain etiology. Dyspeptic symptoms are usually meal related and suggest an association to gastrointestinal (GI) sensorimotor dysfunction. Cholecystokinin (CCK) is an established brain-gut peptide that plays an important regulatory role in gastrointestinal function. It inhibits gastric motility and emptying via a capsaicin sensitive vagal pathway. The effects on emptying are via its action on the proximal stomach and pylorus. CCK is also involved in the regulation of food intake. It is released in the gut in response to a meal and acts via vagal afferents to induce satiety. Furthermore CCK has also been shown to be involved in the pathogenesis of panic disorder, anxiety and pain. Other neurotransmitters such as serotonin and noradrenaline may be implicated with CCK in the coordination of GI activity. In addition, intravenous administration of CCK has been observed to reproduce the symptoms in FD and this effect can be blocked both by atropine and loxiglumide (CCK-A antagonist). It is possible that an altered response to CCK may be responsible for the commonly observed gastric sensorimotor dysfunction, which may then be associated with the genesis of dyspeptic symptoms.
  9. Applying the least squares method for the titrimetric determination of the concentration of VFA
    Lee SK, Yeoh HK, Chua AS, Ngoh GC
    Water Sci Technol, 2012;66(3):620-6.
    PMID: 22744694 DOI: 10.2166/wst.2012.216
    The titrimetric method is used for on-site measurement of the concentration of volatile fatty acids (VFAs) in anaerobic treatment. In current practice, specific and interpolated pH-volume data points are used to obtain the concentration of VFA by solving simultaneous equations iteratively to convergence (denoted as SEq). Here, the least squares method (LSM) is introduced as an elegant alternative. Known concentrations of VFA (acetic acid and/or propionic acid) ranging from to 200 to 1,000 mg/L were determined using SEq and LSM. Using standard numbers of data points, SEq gave more accurate results compared with LSM. However, results favoured LSM when all data points in the range were included without any interpolation. For model refinement, unit monovalent activity coefficient (f(m) = 1) was found reasonable and arithmetic averages of dissociation constants and molecular weight of 80 mol% acetic acid were recommended in the model for VFA determination of mixtures. An accurate result was obtained with a mixture containing more VFA (butyric acid and valeric acid). In a typical VFA measurement of real anaerobic effluent, a satisfactory result with an error of 14% was achieved. LSM appears to be a promising mathematical model solver for determination of concentration of VFA in the titrimetric method. Validation of LSM in the presence of other electrolytes deserves further exploration.
  10. Comparative study of various pretreatment reagents on rice husk and structural changes assessment of the optimized pretreated rice husk
    Ang TN, Ngoh GC, Chua AS
    Bioresour Technol, 2013 May;135:116-9.
    PMID: 23138072 DOI: 10.1016/j.biortech.2012.09.045
    The performance of alkalis (NaOH and Ca(OH)2) and acids (H2SO4, HCl, H3PO4, CH3COOH, and HNO3) in the pretreatment of rice husk was screened, and a suitable reagent was assessed for subsequent optimization using response surface methodology. From the assessment, HCl that hydrolysed rice husk well was optimized with three parameters (HCl loading, pretreatment duration, and temperature) using Box-Behnken Design. The optimized condition (0.5% (w/v) HCl loading, 125 °C, 1.5 h) is relatively mild, and resulted in ~22.3mg TRS/ml hydrolysate. The reduced model developed has good predictability, where the predicted and experimental results differ by only 2%. The comprehensive structural characterization studies that involved FT-IR, XRD, SEM, and BET surface area determination showed that the pretreated rice husk consisted mainly of cellulose and lignin. Compared to untreated rice husk, pretreated rice husk possessed increased pore size and pore volume, which are expected to be beneficial for fungal growth during fermentation.
  11. Long-term performance evaluation of EBPR process in tropical climate: start-up, process stability, and the effect of operational pH and influent C:P ratio
    Ong YH, Chua AS, Lee BP, Ngoh GC
    Water Sci Technol, 2013;67(2):340-6.
    PMID: 23168633 DOI: 10.2166/wst.2012.552
    To date, little information is known about the operation of the enhanced biological phosphorus removal (EBPR) process in tropical climates. Along with the global concerns on nutrient pollution and the increasing array of local regulatory requirements, the applicability and compliance accountability of the EBPR process for sewage treatment in tropical climates is being evaluated. A sequencing batch reactor (SBR) inoculated with seed sludge from a conventional activated sludge (CAS) process was successfully acclimatized to EBPR conditions at 28 °C after 13 days' operation. Enrichment of Candidatus Accumulibacter phosphatis in the SBR was confirmed through fluorescence in situ hybridization (FISH). The effects of operational pH and influent C:P ratio on EBPR were then investigated. At pH 7 or pH 8, phosphorus removal rates of the EBPR processes were relatively higher when operated at C:P ratio of 3 than C:P ratio of 10, with 0.019-0.020 and 0.011-0.012 g-P/g-MLVSS•day respectively. One-year operation of the 28 °C EBPR process at C:P ratio of 3 and pH 8 demonstrated stable phosphorus removal rate of 0.020 ± 0.003 g-P/g-MLVSS•day, corresponding to effluent with phosphorus concentration <0.5 mg/L. This study provides the first evidence on good EBPR activity at relatively high temperature, indicating its applicability in a tropical climate.
  12. Process optimization and performance evaluation on sequential ionic liquid dissolution-solid acid saccharification of sago waste
    Lee KM, Ngoh GC, Chua AS
    Bioresour Technol, 2013 Feb;130:1-7.
    PMID: 23280179 DOI: 10.1016/j.biortech.2012.11.124
    The production of reducing sugars from sago waste via sequential ionic liquid dissolution-solid acid saccharification was optimized in this study. Ionic liquid dissolution of sago waste with 1-butyl-3-methylimidazolium chloride ([BMIM]Cl) was conducted prior to the solid acid saccharification with Amberlyst 15 (A15). The effect of time, temperature and substrate loading during dissolution reaction; and the effect of time, temperature and catalyst loading during saccharification reaction were examined by applying central composite design (CCD) separately. Both dissolution and saccharification reactions were respectively modeled into quadratic polynomial equations with good predictive accuracies. A high reducing sugars yield of 98.3% was obtained under the optimized conditions, i.e. dissolution at 1.75h, 160°C, 1.5% substrate loading, and saccharification at 0.5h, 130°C, 4% catalyst loading. From comparison studies of different saccharification schemes, the sequential ionic liquid dissolution-solid acid saccharification has proven to be a potential method in reducing sugars production from the lignocellulosic biomass.
  13. Simultaneous production of cellulase and reducing sugar through modification of compositional and structural characteristic of sugarcane bagasse
    Yoon LW, Ngoh GC, Chua AS
    Enzyme Microb Technol, 2013 Sep 10;53(4):250-6.
    PMID: 23931690 DOI: 10.1016/j.enzmictec.2013.05.005
    This study examined the potential of untreated and alkali-pretreated sugarcane bagasse (SCB) in cellulase, reducing sugar (RS) and fungal biomass production via solid state fermentation (SSF) using Pycnoporus sanguineus. The impact of the composition, structure and cellulase adsorption ability of SCB on the production of cellulase, RS and fungal biomass was investigated. From the morphological and compositional analyses, untreated SCB has relatively more structural changes with a higher percentage of depolymerisation on the cellulose, hemicellulose and lignin content compared to alkali-pretreated SCB. Thus, untreated SCB favoured the production of cellulase and fungal biomass whereas alkali-pretreated SCB yielded a higher amount of RS. The composition and morphology of untreated SCB did not encourage RS production and this suggested that RS produced during SSF might be consumed in a faster rate by the more abundantly grown fungus. Besides that, alkali-pretreated SCB with higher cellulase adsorption ability could have adsorbed the cellulase produced and resulted in a lower cellulase titre. In short, the production of specific bioproducts via SSF is dependent on the structure and composition of the substrate applied.
  14. Fulltext Elucidation of the effect of ionic liquid pretreatment on rice husk via structural analyses
    Ang TN, Ngoh GC, Chua AS, Lee MG
    Biotechnol Biofuels, 2012 Sep 07;5(1):67.
    PMID: 22958710 DOI: 10.1186/1754-6834-5-67
    BACKGROUND: In the present study, three ionic liquids, namely 1-butyl-3-methylimidazolium chloride ([BMIM]Cl), 1-ethyl-3-methylimidazolium acetate ([EMIM]OAc), and 1-ethyl-3-methylimidazolium diethyl phosphate ([EMIM]DEP), were used to partially dissolve rice husk, after which the cellulose were regenerated by the addition of water. The aim of the investigation is to examine the implications of the ionic liquid pretreatments on rice husk composition and structure.

    RESULTS: From the attenuated total reflectance Fourier transform-infrared (ATR FT-IR) spectroscopy, X-ray diffraction (XRD) and scanning electron microscopy (SEM) results, the regenerated cellulose were more amorphous, less crystalline, and possessed higher structural disruption compared with untreated rice husk. The major component of regenerated cellulose from [BMIM]Cl and [EMIM]DEP pretreatments was cellulose-rich material, while cellulose regenerated from [EMIM]OAc was a matrix of cellulose and lignin. Cellulose regenerated from ionic pretreatments could be saccharified via enzymatic hydrolysis, and resulted in relatively high reducing sugars yields, whereas enzymatic hydrolysis of untreated rice husk did not yield reducing sugars. Rice husk residues generated from the ionic liquid pretreatments had similar chemical composition and amorphousity to that of untreated rice husk, but with varying extent of surface disruption and swelling.

    CONCLUSIONS: The structural architecture of the regenerated cellulose and rice husk residues showed that they could be used for subsequent fermentation or derivation of cellulosic compounds. Therefore, ionic liquid pretreatment is an alternative in the pretreatment of lignocellulosic biomass in addition to the conventional chemical pretreatments.

  15. Kinetic and stoichiometric characterization for efficient enhanced biological phosphorus removal (EBPR) process at high temperatures
    Liau KF, Shoji T, Ong YH, Chua AS, Yeoh HK, Ho PY
    Bioprocess Biosyst Eng, 2015 Apr;38(4):729-37.
    PMID: 25381606 DOI: 10.1007/s00449-014-1313-3
    A recently reported stable and efficient EBPR system at high temperatures around 30 °C has led to characterization of kinetic and stoichiometric parameters of the Activated Sludge Model no. 2d (ASM2d). Firstly, suitable model parameters were selected by identifiability analysis. Next, the model was calibrated and validated. ASM2d was found to represent the processes well at 28 and 32 °C except in polyhyroxyalkanoate (PHA) accumulation of the latter. The values of the kinetic parameters for PHA storage (q PHA), polyphosphate storage (q PP) and growth (μ PAO) of polyphosphate-accumulating organisms (PAOs) at 28 and 32 °C were found to be much higher than those reported by previous studies. Besides, the value of the stoichiometric parameter for the requirement of polyphosphate for PHA storage (Y PO4) was found to decrease as temperature rose from 28 to 32 °C. Values of two other stoichiometric parameters, i.e. the growth yield of heterotrophic organisms (Y H) and PAOs (Y PAO), were high at both temperatures. These calibrated parameters imply that the extremely active PAOs of the study were able to store PHA, store polyphosphate and even utilize PHA for cell growth. Besides, the parameters do not follow the Arrhenius correlation due to the previously reported unique microbial clade at 28 and 32 °C, which actively performs EBPR at high temperatures.
  16. Fulltext A Rome III survey of functional dyspepsia among the ethnic Malays in a primary care setting
    Lee YY, Wahab N, Mustaffa N, Daud N, Mohd Noor N, Shaaban J, et al.
    BMC Gastroenterol, 2013;13:84.
    PMID: 23672671 DOI: 10.1186/1471-230X-13-84
    Backgrounds: The study aimed to survey for FD in a primary care setting in a population known to have an extremely low prevalence of Helicobacter pylori (H. pylori) infection, with the hypothesis that in such a population, dyspepsia should have been relatively less common.
    Methods: The Rome III FD Diagnostic Questionnaire was translated into the Malay language and later tested for reliability. A prospective cross-sectional survey was then performed involving 160 Malay patients attending primary care clinic after informed consent. Patients positive for symptoms of FD were subjected to upper endoscopy and exclusion of H. pylori infection. Univariable and multivariable analyses were used to test for associated risk factors.
    Results: The back-translated questionnaire was similar to the original English version and was reliable (Cronbach Alpha-coefficient 0.85). Of the 160 surveyed subjects, 19 of them (11.9%) had symptoms of FD. With exclusion of erosive diseases (3/160 or 1.9%) from endoscopy, 16 subjects or 10% had FD. None of the 19 subjects were positive for H. pylori infection. Epigastric pain syndrome was present in 11/16 (68.8%) and the rest, overlap with postprandial distress syndrome. With multivariable analysis, a married status (OR = 8.1; 95% CI 1.0-36.5) and positive psychosocial alarm symptoms (OR = 3.8; 95% CI 1.0-14.0) were associated with FD. Of those married subjects, females were more likely to have FD and psychosocial symptoms than men (6.3% vs. 1.9%), P = 0.04.
    Conclusions: FD was more common than one had expected among Malays attending primary care clinic in an area with low prevalence of H. pylori.
    Keywords: Functional dyspepsia, Malays, Rome III, Females, Marriage, Psychosocial alarm
    Questionnaire: Rome III Functional Dyspepsia Diagnostic questionnaire; Red Flag Questionnaire; Psychosocial Alarm Questionnaire; Hospital Anxiety Depression Scale; HADS

    Study site: primary care clinic within the university hospital of Universiti Sains Malaysia (USM)
  17. An observation on sludge granulation in an enhanced biological phosphorus removal process
    Ong YH, Chua AS, Lee BP, Ngoh GC, Hashim MA
    Water Environ Res, 2012 Jan;84(1):3-8.
    PMID: 22368821
    A sequencing batch reactor (SBR) seeded with flocculated sludge and fed with synthetic wastewater was operated for an enhanced biological phosphorus removal (EBPR) process. Eight weeks after reactor startup, sludge granules were observed. The granules had a diameter of 0.5 to 3.0 mm and were brownish in color and spherical or ellipsoidal in shape. No significant change was observed in sludge granule size when operational pH was changed from 7 to 8. The 208-day continuous operation of the SBR showed that sludge granules were stably maintained with a sludge volume index (SVI) between 30 to 55 mL/g while securing a removal efficiency of 83% for carbon and 97% for phosphorus. Fluorescent in situ hybridization (FISH) confirmed the enrichment of polyphosphate accumulating organisms (PAOs) in the SBR. The observations of sludge granulation in this study encourage further studies in the development of granules-based EBPR process.
  18. Fulltext Rome III survey of irritable bowel syndrome among ethnic Malays
    Lee YY, Waid A, Tan HJ, Chua AS, Whitehead WE
    World J Gastroenterol, 2012 Nov 28;18(44):6475-80; discussion p. 6479.
    PMID: 23197894 DOI: 10.3748/wjg.v18.i44.6475
    To survey irritable bowel syndrome (IBS) using Rome III criteria among Malays from the north-eastern region of Peninsular Malaysia.
  19. Fulltext Development, Translation and Validation of Enhanced Asian Rome III Questionnaires for Diagnosis of Functional Bowel Diseases in Major Asian Languages: A Rome Foundation-Asian Neurogastroenterology and Motility Association Working Team Report
    Ghoshal UC, Gwee KA, Chen M, Gong XR, Pratap N, Hou X, et al.
    J Neurogastroenterol Motil, 2015 Jan 1;21(1):83-92.
    PMID: 25537673 DOI: 10.5056/jnm14045
    The development-processes by regional socio-cultural adaptation of an Enhanced Asian Rome III questionnaire (EAR3Q), a cultural adaptation of the Rome III diagnostic questionnaire (R3DQ), and its translation-validation in Asian languages are presented. As English is not the first language for most Asians, translation-validation of EAR3Q is essential. Hence, we aimed to culturally adapt the R3DQ to develop EAR3Q and linguistically validate it to show that the EAR3Q is able to allocate diagnosis according to Rome III criteria.
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