23 results on '"Tham SY"'
Search Results
2. Biochemical Characterization of an Acid Phosphatase fromThermus thermophilus
- Author
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THAM, Sy-Jye, primary, CHANG, Ching-Dong, additional, HUANG, Hao-Jen, additional, LEE, Yueh-Feng, additional, HUANG, Tze-Sing, additional, and CHANG, Ching-Chun, additional
- Published
- 2010
- Full Text
- View/download PDF
3. Use of patient-reported experience and outcome measures within the colorectal cancer care continuum: a scoping review.
- Author
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Lau J, Ng JS, Lee D, Tan JK, Tan LL, Pang NQ, Tham SY, Ng CK, and Tan KK
- Abstract
Objective: Patient-reported outcome measures (PROM) are frequently adopted to evaluate colorectal cancer (CRC) care, but the use of patient-reported experience measures (PREM) appears to be underdeveloped and not widely validated. This scoping review aims to understand the contexts for deployment of PREMs in CRC care, reliability of measures, gaps in current use of PREMs, and how PREMs are associated with PROMs when deployed together., Methods: Four scientific databases (PubMed, CINAHL, PsycINFO, Scopus) were systematically searched from January 2011 to December 2023. Observational or interventional studies involving quantitative or mixed methodology with samples consisting CRC patients undergoing screening, treatment, or cancer surveillance and utilizing at least one PREM as an exposure or outcome were included., Results: The initial search resulted in 10,400 records. Only 13 relevant studies (consisting of 17,105 participants) met the eligibility criteria. Utilization of PREMs was heterogenous across our sample and the CRC care continuum, and about half of the studies (53.8%) evaluated the relationship between PREMs and PROMs. PREM usage across the CRC care continuum largely focused on treatment/survivorship. Better care experience was positively associated with improved patient-reported outcomes., Conclusions: Future work in CRC PREM development should focus on (1) establishing validated measures that aim to either capture disease/treatment-specific granularity or capitalize on applicability across care settings, (2) localizing novel or existing PREMs to consider different cultural contexts in healthcare, and (3) benchmarking associations between PREMs, PROMs, and other outcomes of interest., Implications for Cancer Survivors: Individuals progressing through the CRC care continuum often undergo a multitude of procedures from detection and diagnosis to treatment and surveillance. The establishment of validated PREMs specific to CRC would help to benchmark and further improve the quality of care received-which should translate to better patient-reported outcomes-and serve as process indicators for institutions and providers to maintain rigorous health service delivery standard for CRC survivors., (© 2024. The Author(s), under exclusive licence to Springer Science+Business Media, LLC, part of Springer Nature.)
- Published
- 2024
- Full Text
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4. Pilot Study on Therapeutic Horticulture for Chronic Low Back Pain: A Mixed Methods Study.
- Author
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Sharififar S, Sein M, Diehl E, Tham SY, Nixon RM, Sheppard C, Bolling J, Majid M, Apfelbaum C, and Vincent HK
- Subjects
- Humans, Female, Pilot Projects, Male, Middle Aged, Cross-Sectional Studies, Adult, Horticultural Therapy methods, Aged, Chronic Pain therapy, Pain Measurement methods, Surveys and Questionnaires, Low Back Pain therapy, Low Back Pain psychology
- Abstract
Background: Chronic low back pain (LBP) is common and associated with disability worldwide. Therapists trained in Therapeutic Horticulture (TH) use gardening activities and proximity to nature for therapy and rehabilitation. Patients seeking care for LBP would benefit physically and psychologically from participating in TH., Primary Study Objectives: The first aim of this study was to determine if and which patients who were receiving care for chronic LBP were interested in TH to help manage their pain. The second aim of the project was to quantify changes in LBP, functional tasks and anxiety upon completion of a TH session in patients with LBP., Methods/design: This was a 2-part study with a mixed methods design: the cross-sectional survey Group and the pilot experimental Group. The Cross-sectional Survey component comprised a total of 170 patients; age 55.9±17.3 years; 58% women. The Pilot Experimental component comprised a total of 9 patients; age 48±14.7 years; 78% women., Participants Cross-Sectional Component: Patients receiving medical care for LBP with or without additional joint pain sites (n=170; age 55.9 ± 17.3 years; 58% women., Participants Pilot Experimental Component: A total of 9 patients (7 women); mean age 48 ± 14.7 years and mean duration of back pain 12.6 ± 8.1 years., Setting: Patients were receiving medical care at the University of Florida Health Comprehensive Spine Center in the United States, in the tertiary care health system., Intervention: 1-hour TH session that involved trained therapists using propagating and harvesting herbs planted at various heights in an outdoor setting for therapy and rehabilitation., Primary Outcome Measures: A therapeutic horticulture interest survey, PROMIS Pain Interference and Physical Function scores, functional tests (timed-get-up-and-go [TUG], spine range of motion), Roland Morris Disability Questionnaire (RMDQ), 11-point Numerical Pain Rating Scale (NRSpain), 10-item PROMIS Global Health Questionnaire, Tampa Scale of Kinesiophobia-11 and patient enjoyment., Results: Cross-sectional survey component: A total of 2% of patients had not previously heard of TH and 68% were interested in learning more about it. Patients who expressed interest in TH reported a higher level of agreement that TH could improve mood, improve muscle strength, lower stress level, increase movement and enable patients to perform self-care activities with less pain (all P < .001). PROMIS Pain Interference and Physical Function scores did not differ by interest in TH (P > .05). Pilot Experimental component: In the pilot session, 44% reported using pain medication to manage their low back pain and 66% believed gardening could provide pain relief. Improvements were observed in anxiety (55.3%; P =.017), spine flexion (31.4%; P =.003) and spine rotation to the left (26.7%; P =.005). All participants believed that gardening improved overall health and spine motion while reducing low back pain. All patients reported having gardening experience at home and none had TH experience., Conclusion: Patients presenting to an outpatient spine clinic may be receptive to trying TH in conjunction with or in place of conventional medicine to promote health and well-being. The pilot experimental group data suggested that acute TH is enjoyable and may confer the benefits of reducing anxiety and improving spine motion. Future larger studies could use different dose response approaches, explore different TH activity types and involve participants from different geographic locations while controlling for LBP history and psychological status.
- Published
- 2024
5. Biocompatible graphene-zirconia nanocomposite as a cyto-safe immunosensor for the rapid detection of carcinoembryonic antigen.
- Author
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Lin LP, Tham SY, Loh HS, and Tan MTT
- Subjects
- Carcinoembryonic Antigen blood, Cell Line, Tumor, Cell Survival, Electrochemistry, Humans, Inhibitory Concentration 50, Limit of Detection, Tetrazolium Salts chemistry, Thiazoles chemistry, Biocompatible Materials chemistry, Biosensing Techniques methods, Graphite chemistry, Nanocomposites chemistry, Zirconium chemistry
- Abstract
Graphene-based materials have gained remarkable attention in numerous disciplines owing to their unique electrochemical properties. Out of various hybridized nanocomposites, graphene-zirconia nanocomposite (GZ) was distinctive due to its biocompatibility. Zirconia nanoparticles serve as spacers that reduce the stacking of graphene and improve the electrochemical performance of the material. Considering that lungs and skin suffer the greatest exposure to nanoparticles, this study aimed to evaluate the cytotoxicity of the as-synthesized GZ nanocomposites on MRC5 (lung cells) and HaCaT (skin cells) via morphological observation and cell viability assay using 3-(4,5 dimethylthiazol-2-yl)-(2,5-diphenyltetrazolium bromide) tetrazolium (MTT). GZ-treated cells showed a comparable proliferation rate and morphology with untreated cells under microscopic evaluation. Based on MTT results, the IC
50 values of GZ were > 500 µg/ml for MRC5 and HaCaT cells. The excellent biocompatibility was the supremacy of GZ over other nanocomposites applied as electrode materials in biosensors. GZ was functionalized with biolinker for the detection of carcinoembryonic antigen (CEA). The proposed immunosensor exhibited good responses towards CEA detection, with a 4.25 pg/ml LOD and correlation coefficient of R2 = 0.99 within a linear working range from 0.01 to 10 ng/ml. The performance of the immunosensor to detect CEA present in human serum was also evaluated. Good recovery of CEA was found, suggesting that the proposed immunosensor possess a high affinity to CEA even in a complex biological matrix, rendering it a promising sensing platform for real sample analysis and open a new way for the detection of cancer-associated proteins., (© 2021. The Author(s).)- Published
- 2021
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6. Parallel genome-wide RNAi screens identify lymphocyte-specific protein tyrosine kinase (LCK) as a targetable vulnerability of cell proliferation and chemoresistance in nasopharyngeal carcinoma.
- Author
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Liew K, Yu GQS, Wei Pua LJ, Wong LZ, Tham SY, Hii LW, Lim WM, OuYong BM, Looi CK, Mai CW, Fei-Lei Chung F, Tan LP, Ahmad M, Soo-Beng Khoo A, and Leong CO
- Subjects
- Antineoplastic Agents pharmacology, Cell Line, Tumor, Humans, Nasopharyngeal Carcinoma enzymology, Nasopharyngeal Carcinoma pathology, Nasopharyngeal Neoplasms enzymology, Nasopharyngeal Neoplasms pathology, Antineoplastic Agents therapeutic use, Cell Proliferation drug effects, Drug Resistance, Neoplasm genetics, Lymphocytes enzymology, Nasopharyngeal Carcinoma drug therapy, Nasopharyngeal Neoplasms drug therapy, Protein-Tyrosine Kinases genetics, RNA Interference
- Abstract
Despite recent in advances in the management of nasopharyngeal carcinoma (NPC), development of targeted therapy remains challenging particularly in patients with recurrent or metastatic disease. To search for clinically relevant targets for the treatment of NPC, we carried out parallel genome-wide functional screens to identified essential genes that are required for NPC cells proliferation and cisplatin resistance. We identified lymphocyte-specific protein tyrosine kinase (LCK) as a key vulnerability of both proliferation and cisplatin resistance. Depletion of endogenous LCK or treatment of cells with LCK inhibitor induced tumor-specific cell death and synergized cisplatin sensitivity in EBV-positive C666-1 and EBV-negative SUNE1 cells. Further analyses demonstrated that LCK is regulating the proliferation and cisplatin resistance through activation of signal transducer and activator of transcription 5 (STAT5). Taken together, our study provides a molecular basis for targeting LCK and STAT5 signaling as potential druggable targets for the management of NPC., (Copyright © 2021. Published by Elsevier B.V.)
- Published
- 2021
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7. Translation, Validation and Reliability Testing of Community Integration Questionnaire-Revised (CIQ-R) Malay Version: A Preliminary Study.
- Author
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Razaob NA, Tham SY, Mohd Rasdi HF, Wan Yunus F, and Kadar M
- Subjects
- Adult, Cross-Sectional Studies, Female, Humans, Malaysia, Male, Middle Aged, Psychometrics, Reproducibility of Results, Self Report, Community Integration, Persons with Disabilities rehabilitation, Occupational Therapy, Surveys and Questionnaires, Translations
- Abstract
The Community Integration Questionnaire-Revised (CIQ-R) is a self-report standardized instrument designed to assess an individual's degree of community integration. The aim of this study was to translate, validate and conduct a reliability test of the CIQ-R Malay version. The development involved the three phases of translation, content validation and cognitive interviewing, test-retest reliability and internal consistency of the CIQ-R Malay version. The Content Validity Index (CVI) showed perfect agreement between the panel experts. The Intra-class Correlation Coefficient (ICC) demonstrated a moderate to excellent level of test-retest agreement (ICC 0.72 to 0.93). The Total CIQ-R Malay version and Home Integration subscale showed good internal consistency, with values of Cronbach's alpha ranging from 0.81 to 0.90. The findings from the present study provided preliminary support for the psychometric properties of the CIQ-R Malay version as a valid and reliable instrument to be used in Malaysia.
- Published
- 2020
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8. Tocotrienols Modulate a Life or Death Decision in Cancers.
- Author
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Tham SY, Loh HS, Mai CW, and Fu JY
- Subjects
- Animals, Autophagy drug effects, Cell Survival drug effects, Endoplasmic Reticulum Stress drug effects, Humans, Apoptosis drug effects, Neoplasms pathology, Tocotrienols pharmacology
- Abstract
Malignancy often arises from sophisticated defects in the intricate molecular mechanisms of cells, rendering a complicated molecular ground to effectively target cancers. Resistance toward cell death and enhancement of cell survival are the common adaptations in cancer due to its infinite proliferative capacity. Existing cancer treatment strategies that target a single molecular pathway or cancer hallmark fail to fully resolve the problem. Hence, multitargeted anticancer agents that can concurrently target cell death and survival pathways are seen as a promising alternative to treat cancer. Tocotrienols, a minor constituent of the vitamin E family that have previously been reported to induce various cell death mechanisms and target several key survival pathways, could be an effective anticancer agent. This review puts forward the potential application of tocotrienols as an anticancer treatment from a perspective of influencing the life or death decision of cancer cells. The cell death mechanisms elicited by tocotrienols, particularly apoptosis and autophagy, are highlighted. The influences of several cell survival signaling pathways in shaping cancer cell death, particularly NF-κB, PI3K/Akt, MAPK, and Wnt, are also reviewed. This review may stimulate further mechanistic researches and foster clinical applications of tocotrienols via rational drug designs., Competing Interests: The authors declare no conflict of interest.
- Published
- 2019
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9. One-step green hydrothermal synthesis of biocompatible graphene/TiO 2 nanocomposites for non-enzymatic H 2 O 2 detection and their cytotoxicity effects on human keratinocyte and lung fibroblast cells.
- Author
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Siew QY, Tham SY, Loh HS, Khiew PS, Chiu WS, and Tan MTT
- Abstract
Highly sensitive and selective immunosensors that can detect disease biomarkers at ultra-low levels in early stages are urgently needed to reduce mortality risks. A facile and efficient approach using sonochemical-assisted solvent graphene exfoliation and a hydrothermal synthesis method has been used to prepare graphene/titanium dioxide (G/TiO
2 ) nanocomposites. Nanocomposites containing different ratios of graphene and TiO2 precursors were prepared to determine the optimum composition of G/TiO2 that has the highest conductivity and electrocatalytic properties. Characterisation methods such as X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDX), transmission electron microscopy (TEM), and high resolution TEM (HRTEM) were used to study the crystallinity, surface characteristics, elemental composition, and morphology of the synthesised nanocomposites. The synthesised materials were also confirmed via Raman spectroscopy. Using ferricyanide as the redox active probe, cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) analyses indicated that 1 : 8 ratio of G/TiO2 exhibited the best current response and the lowest charge transfer resistance (Rct ) of 1525 Ω. The potential of G/TiO2 for electrochemical sensing application was investigated using hydrogen peroxide (H2 O2 ), a by-product of most enzymatic processes, as the analyte of interest. The sensitivity of the sensor towards H2 O2 was 0.557 μA mM-1 , with a limit of detection (LOD) at 56.89 μM. An in vitro cell proliferation assay was carried out to investigate the biocompatibility of the nanocomposites. The half-maximal inhibitory concentration (IC50 ) values obtained were >500 μg ml-1 for human lung fibroblasts (MRC5) and 5-25 μg ml-1 for human skin cells (HaCat).- Published
- 2018
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10. Does oral lansoprazole really reduce gastric acidity in VLBW premature neonates?
- Author
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Tham SY, Rogers IM, Samuel KF, Singh A, and Ong KK
- Subjects
- 2-Pyridinylmethylsulfinylbenzimidazoles pharmacology, Anti-Ulcer Agents pharmacology, Female, Gastric Acid chemistry, Gastroesophageal Reflux physiopathology, Humans, Hydrogen-Ion Concentration drug effects, Infant, Newborn, Infant, Premature, Diseases physiopathology, Infant, Very Low Birth Weight, Lansoprazole, Male, 2-Pyridinylmethylsulfinylbenzimidazoles therapeutic use, Anti-Ulcer Agents therapeutic use, Gastric Acid metabolism, Gastroesophageal Reflux drug therapy, Infant, Premature, Diseases drug therapy
- Abstract
Premature neonates of very low birth weight (VLBW) whose treatment required the use of naso-gastric tube feeding were investigated. 10 infants suspected of having GERD (gastroesophageal reflux) received oral lansoprazole therapy by tube administration. 9 other infants formed a control group. In the treated group a fasting pH was determined before treatment and again after 7 days treatment. The control group was similarly assessed at an interval of 7 days. Despite acid reduction, the post-treatment pH mean of 1.31 would continue to pose a threat to the esophageal mucosa. The physiology of neonatal acid secretion is discussed to explain these findings.
- Published
- 2012
11. Studies on diuretic and hypouricemic effects of Orthosiphon stamineus methanol extracts in rats.
- Author
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Arafat OM, Tham SY, Sadikun A, Zhari I, Haughton PJ, and Asmawi MZ
- Subjects
- Allopurinol pharmacology, Animals, Chromatography, Thin Layer, Hydrogen-Ion Concentration, Male, Plant Extracts analysis, Rats, Rats, Sprague-Dawley, Sodium urine, Diuretics pharmacology, Orthosiphon chemistry, Plant Extracts pharmacology, Uric Acid blood
- Abstract
Aim of the Study: Orthosiphon stamineus (Labiatae) is a traditional folk medicine widely used in Southeast Asia for the treatment of several kidney disorders, gout and as a diuretic. This study was conducted to examine the diuretic and hypouricemic effects of Orthosiphon stamineus leaf extracts., Materials and Methods: The diuretic effect of different methanol extracts was examined by treating different groups of Sprague-Dawley rats with single (2g/kg) oral doses of methanol and methanol:water (1:1) extracts. Hydrochlorothiazide (10mg/kg) was used as positive control in acute study. Methanol and methanol water (1:1) extracts at 0.5 g/kg were administered for a period of 7 consecutive days. Cumulative urine volume and electrolytes (Na+ and K+) concentrations at different time intervals were measured. On the other hand, hypouricemic activity of methanol:water extract (1:1) was experimented using different oral single doses (0.25, 0.5, 1 and 2g/kg). Allopurinol was used as positive control. Uric acid concentration in serum was analyzed by using RP-HPLC at 280 nm., Results: Sodium and potassium excretion increased significantly (p<0.05 and <0.01) in the first 8h of treatment with a single dose (2g/kg) of the extracts in a pattern comparable to that of the known diuretic hydrochlorothiazide. Meanwhile, repeated administration of 0.5 g/kg methanol:water (1:1) extract showed a significant increase in urine volume (from day 3 to day 7) (p<0.01) and electrolytes excretion (Na+ and K+) from day 2 to day 7 (p<0.05 and <0.01). On the other hand, 0.5, 1 and 2g/kg of methanol:water (1:1) extract and the standard allopurinol reduced the serum urate level in hyperuricemic rats at hour 6., Conclusion: These results provided an evidence of the high tendency of methanol:water (1:1) extract of Orthosiphon stamineus towards diuretic and hypouricemic effects in rats.
- Published
- 2008
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12. Biologically active components of Physostigma venenosum.
- Author
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Zhao B, Moochhala SM, and Tham SY
- Subjects
- Chromatography, Thin Layer methods, Electrophoresis methods, Physostigma chemistry
- Abstract
Physostigmine is a major alkaloid found in the seeds of the fabaceous plant Physostigma venenosum. It is a powerful and reversible acetylcholine esterase inhibitor which effectively increases the concentration of acetylcholine at the sites of cholinergic transmission. It exerts its cholinesterase inhibitor effect in both the periphery and central nervous system. Many studies on physostigmine have involved the reliance on techniques that extract and quantify physostigmine in biological samples. This paper presents an overview of the currently applied methodologies for the determination of physostigmine and its metabolites in various biological samples. Papers published from January 1980 to December 2003 were taken into consideration for the discussion of the metabolism and analytical method of physostigmine. HPLC methods have been discussed and used in most of the references cited in this review. A few CE and RIA methods that have been recently reported are also mentioned in this paper. Basic information about the sample assayed, sample preparation, chromatographic column, mobile phase, detection mode and validation data are summarized in a table.
- Published
- 2004
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13. Simultaneous determination of vitamins C, E and beta-carotene in human plasma by high-performance liquid chromatography with photodiode-array detection.
- Author
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Zhao B, Tham SY, Lu J, Lai MH, Lee LK, and Moochhala SM
- Subjects
- Adult, Chromatography, High Pressure Liquid instrumentation, Chromatography, High Pressure Liquid methods, Humans, Male, Photochemistry instrumentation, Regression Analysis, Reproducibility of Results, Spectrophotometry, Ultraviolet, Antioxidants analysis, Ascorbic Acid blood, Vitamin E blood, beta Carotene blood
- Abstract
Purpose: To develop a high-performance liquid chromatography (HPLC) method with photodiode-array ultraviolet detection for the simultaneous determination of vitamin C, vitamin E and beta-carotene., Methods: Following liquid-phase extraction from the human plasma samples, these three vitamins were successfully separated on the LiChrospher 100 RP-18 column (125 x 4 mm I.D.; particle size, 5 microm) at a flow-rate of 1.2 ml/min, with a mobile phase of methanol-acetonitrile-tetrahydrofuran (75: 20: 5, v/v/v)., Results: The limits of quantitation were 100, 0.25 and 0.25 microg/ml for vitamin C, vitamin E and beta-carotene respectively. The method is linear over the studied range of 0.25 to 5 g/ml for vitamin E and beta-carotene and 100 to 5000 microg/ml for vitamin C. The extraction recoveries were greater than 83% for these three vitamins. The within day and between-day precision of the analysis did not exceed 15.3 and 16.2%, respectively., Conclusion: A suitable method to determine the concentration of vitamin C, vitamin E and beta-carotene following oral administration of antioxidant supplement capsules to a healthy Chinese volunteer.
- Published
- 2004
14. Relationship between angiotensin-converting enzyme ID polymorphism and VO(2max) of Chinese males.
- Author
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Zhao B, Moochhala SM, Tham Sy, Lu J, Chia M, Byrne C, Hu Q, and Lee LK
- Subjects
- Adult, China ethnology, Genotype, Humans, Isoenzymes genetics, Male, Oxygen Consumption physiology, Reverse Transcriptase Polymerase Chain Reaction, Singapore, Anaerobic Threshold genetics, Peptidyl-Dipeptidase A genetics, Polymorphism, Genetic genetics
- Abstract
Several studies have shown that the angiotensin-converting enzyme (ACE) I allele is associated with enhanced physical performance. We investigated whether this phenomenon is observed in a cohort of 67 Chinese men in Singapore. Angiotensin-converting enzyme ID polymorphism was typed with PCR method and maximal oxygen uptake (VO(2max)) of the DD, ID, and II genotypes was compared. Analysis of covariance revealed that VO(2max) was significantly higher (p<0.05) for the DD genotype (57.86 +/- 3.5 ml.kg.(-1)min(-1)) versus the ID (50.58 +/- 1.80 ml.kg.(-1)min(-1)) or II (50.48 +/- 1.58 ml.kg.(-1) min(-1)) genotype. Our findings suggest that the ACE DD genotype in young adult Chinese males is associated with higher levels of VO(2max).
- Published
- 2003
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15. Immunoaffinity extraction and tandem mass spectrometric analysis of human chorionic gonadotropin in doping analysis.
- Author
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Gam LH, Tham SY, and Latiff A
- Subjects
- Amino Acid Sequence, Chorionic Gonadotropin chemistry, Humans, Molecular Sequence Data, Peptide Mapping, Chorionic Gonadotropin urine, Chromatography, Affinity methods, Chromatography, High Pressure Liquid methods, Spectrometry, Mass, Electrospray Ionization methods
- Abstract
A confirmatory and quantitative HPLC-tandem mass spectrometry (MS-MS) method for human chorionic gonadotropin hormone (hCG) at concentrations as low as 5 IU/l following immunoaffinity extraction of the glycoprotein from urine was developed. The extraction method involved retention of urinary hCG in the immunoaffinity column via specific antigen-antibody interaction. A variety of eluents were then used to quantitatively elute hCG from the immunoaffinity column. Qualitative and quantitative analysis of hCG were undertaken using MS-MS by identifying the amino acid sequence of the marker peptide betaT5 obtained from hCG by tryptic digestion and the peak areas of three product ions b(6)(+), b(9)(+) and y(11)(+), respectively.
- Published
- 2003
- Full Text
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16. Molecular descriptors that influence the amount of drugs transfer into human breast milk.
- Author
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Agatonovic-Kustrin S, Ling LH, Tham SY, and Alany RG
- Subjects
- Animals, Humans, Intestinal Absorption, Pharmaceutical Preparations metabolism, Structure-Activity Relationship, Milk, Human chemistry, Neural Networks, Computer, Pharmaceutical Preparations blood, Pharmacokinetics
- Abstract
Most drugs are excreted into breast milk to some extent and are bioavailable to the infant. The ability to predict the approximate amount of drug that might be present in milk from the drug structure would be very useful in the clinical setting. The aim of this research was to simplify and upgrade the previously developed model for prediction of the milk to plasma (M/P) concentration ratio, given only the molecular structure of the drug. The set of 123 drug compounds, with experimentally derived M/P values taken from the literature, was used to develop, test and validate a predictive model. Each compound was encoded with 71 calculated molecular structure descriptors, including constitutional descriptors, topological descriptors, molecular connectivity, geometrical descriptors, quantum chemical descriptors, physicochemical descriptors and liquid properties. Genetic algorithm was used to select a subset of the descriptors that best describe the drug transfer into breast milk and artificial neural network (ANN) to correlate selected descriptors with the M/P ratio and develop a QSAR. The averaged literature M/P values were used as the ANN's output and calculated molecular descriptors as the inputs. A nine-descriptor nonlinear computational neural network model has been developed for the estimation of M/P ratio values for a data set of 123 drugs. The model included the percent of oxygen, parachor, density, highest occupied molecular orbital energy (HOMO), topological indices (chiV2, chi2 and chi1) and shape indices (kappa3, kappa2), as the inputs had four hidden neurons and one output neuron. The QSPR that was developed indicates that molecular size (parachor, density) shape (topological shape indices, molecular connectivity indices) and electronic properties (HOMO) are the most important for drug transfer into breast milk. Unlike previously reported models, the QSPR model described here does not require experimentally derived parameters and could potentially provide a useful prediction of M/P ratio of new drugs only from a sketch of their structure and this approach might also be useful for drug information service. Regardless of the model or method used to estimate drug transfer into breast milk, these predictions should only be used to assist in the evaluation of risk, in conjunction with assessment of the infant's response.
- Published
- 2002
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17. Application of the artificial neural network in quantitative structure-gradient elution retention relationship of phenylthiocarbamyl amino acids derivatives.
- Author
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Tham SY and Agatonovic-Kustrin S
- Subjects
- Artificial Intelligence, Chromatography, High Pressure Liquid, Indicators and Reagents, Neural Networks, Computer, Nonlinear Dynamics, Reference Standards, Solubility, Structure-Activity Relationship, Amino Acids analysis, Thiocarbamates analysis
- Abstract
Quantitative structure-retention relationship(QSRR) method was used to model reversed-phase high-performance liquid chromatography (RP-HPLC) separation of 18 selected amino acids. Retention data for phenylthiocarbamyl (PTC) amino acids derivatives were obtained using gradient elution on ODS column with mobile phase of varying acetonitrile, acetate buffer and containing 0.5 ml/l of triethylamine (TEA). Molecular structure of each amino acid was encoded with 36 calculated molecular descriptors. The correlation between the molecular descriptors and the retention time of the compounds in the calibration set was established using the genetic neural network method. A genetic algorithm (GA) was used to select important molecular descriptors and supervised artificial neural network (ANN) was used to correlate mobile phase composition and selected descriptors with the experimentally derived retention times. Retention time values were used as the network's output and calculated molecular descriptors and mobile phase composition as the inputs. The best model with five input descriptors was chosen, and the significance of the selected descriptors for amino acid separation was examined. Results confirmed the dominant role of the organic modifier in such chromatographic systems in addition to lipophilicity (log P) and molecular size and shape (topological indices) of investigated solutes.
- Published
- 2002
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18. Short-term fluoride release from various aesthetic restorative materials.
- Author
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Yap AU, Tham SY, Zhu LY, and Lee HK
- Subjects
- Analysis of Variance, Dental Restoration, Permanent, Diffusion, Electrophoresis, Capillary, Esthetics, Dental, Factor Analysis, Statistical, Humans, Immersion, Materials Testing, Methacrylates chemistry, Resins, Synthetic chemistry, Silicates chemistry, Statistics as Topic, Temperature, Time Factors, Water chemistry, Cariostatic Agents chemistry, Compomers chemistry, Fluorides chemistry, Glass Ionomer Cements chemistry, Resin Cements chemistry
- Abstract
The short-term fluoride release of a giomer (Reactmer), a compomer (Dyract AP), a conventional glass ionomer cement (Fuji II Cap) and a resin-modified glass ionomer cement (Fuji II LC) was evaluated and compared. Specimen discs (6 +/-0.2 mm diameter and 1 +/- 0.2 mm thick) were prepared for each material using custom molds. Each disc was placed in 1 ml of deionized for 24 hours at 37 degrees C. After one day, the water was extracted and analyzed. The specimen discs were then re-immersed into another 1 ml of fresh deionized water. The procedure of removing and refilling the water was repeated for 28 days. Sample solutions taken during the first seven days and at days 14, 21 and 28 were introduced into a capillary electrophoresis system using field amplified sample injection (FASI) to determine fluoride release. Data was analyzed using factorial ANOVA/Scheffe's post-hoc test at significance level 0.05. An initial fluoride "burst" effect was observed with glass ionomers. Both compomer and giomer did not show an initial fluoride "burst" effect. With the exception of the compomer, fluoride release at day one was generally significantly greater than at the other time intervals. The glass ionomers released significantly more fluoride than the compomer and giomer at day one. Although fluoride release of the giomer was significantly greater than the other materials at day seven, it became significantly lower at day 28.
- Published
- 2002
19. Rapid thin-layer chromatographic semiquantification of morphine in urine via dabsylation: comparison with EMIT and thin-layer chromatographic-iodoplatinate methods.
- Author
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Wang SY, Tham SY, and Poon MK
- Subjects
- Chromatography, Thin Layer methods, Humans, Immunoenzyme Techniques, Morphine urine
- Published
- 1989
20. Co-operativity in chlorpromazine-human serum albumin interactions [proceedings].
- Author
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Tham SY and Rosen A
- Subjects
- Binding Sites, Humans, Kinetics, Phenylbutazone, Protein Binding, Chlorpromazine, Serum Albumin
- Published
- 1978
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21. Recommendations for a maximum surgical blood ordering schedule in obstetrics and gynaecology.
- Author
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Arulkumaran S, Ong YW, Ratnam SS, Tham SY, and Lun KC
- Subjects
- Female, Humans, Pregnancy, Prospective Studies, Singapore, Blood Grouping and Crossmatching methods, Blood Transfusion, Genital Diseases, Female surgery, Obstetric Labor Complications surgery, Pregnancy Complications surgery
- Published
- 1984
22. The binding of chlorpromazine to some fractions of homogenized rat brain.
- Author
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Rosen A and Tham SY
- Subjects
- Animals, Dialysis, In Vitro Techniques, Lipid Metabolism, Lipoproteins metabolism, Male, Nerve Tissue Proteins metabolism, Protein Binding, Rats, Brain metabolism, Chlorpromazine metabolism
- Published
- 1980
- Full Text
- View/download PDF
23. Thin-layer chromatographic and column liquid chromatographic analyses of morphine in urine via dabsylation.
- Author
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Wang SY, Tham SY, and Poon MK
- Subjects
- Chromatography, Liquid, Chromatography, Thin Layer, Heroin Dependence urine, Humans, Hydrolysis, p-Dimethylaminoazobenzene analogs & derivatives, Morphine urine
- Abstract
A semiquantitative screening method for morphine in urine and a quantitative assay method for the drug were developed. In the semiquantitative method, morphine in urine was directly reacted with 4-dimethylaminoazobenzene-4'-sulphonyl chloride (dabsyl chloride) in a slightly alkaline medium. The orange-coloured dabsyl morphine was separated by silica gel thin-layer chromatography and the spot intensity was visually compared with that of the standards. The limit of detection is 0.075 microgram/ml. In the quantitative method, morphine was extracted from urine before dabsylation. The dabsylation reaction is very fast and is complete within 5-10 min at room temperature. Dabsylation yield is maximum at a dabsyl chloride concentration of 6.2 mM. Total recovery of morphine using the extraction and dabsylation procedures described is 66%. Dabsyl morphine, thus formed, was analysed using high-performance liquid chromatography by monitoring its absorbance at 436 nm on a normal-phase mu Porasil column. The limit of quantitation using high-performance liquid chromatography is 0.26 microM (0.075 microgram/ml), which corresponds to 10.5 pmol of injected dabsyl morphine. Quantitative assay was also carried out by thin-layer chromatography on silica gel followed by densitometry. The limit of quantitation is 1.3 microM (0.375 microgram/ml).
- Published
- 1986
- Full Text
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