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  1. Tiong KH, Yiap BC, Tan EL, Ismail R, Ong CE
    Drug Metab. Dispos., 2010 May;38(5):745-51.
    PMID: 20139165 DOI: 10.1124/dmd.109.031054
    Variation in CYP2A6 levels and activity can be attributed to genetic polymorphism and, thus, functional characterization of allelic variants is necessary to define the importance of CYP2A6 polymorphism in humans. The aim of the present study was to investigate the reported alleles CYP2A6*15, CYP2A6*16, CYP2A6*21, and CYP2A6*22, in terms of the functional consequences of their mutations on the enzyme catalytic activity. With use of the wild-type CYP2A6 cDNA as template, site-directed mutagenesis was performed to introduce nucleotide changes encoding K194E substitution in CYP2A6*15, R203S substitution in CYP2A6*16, K476R substitution in CYP2A6*21, and concurrent D158E and L160I substitutions in CYP2A6*22. Upon sequence verification, the CYP2A6 wild-type and mutant constructs were individually coexpressed with NADPH-cytochrome P450 reductase in Escherichia coli. A kinetic study using a coumarin 7-hydroxylase assay indicated that CYP2A6*15 exhibited higher V(max) than the wild type, whereas all mutant constructs, except for variant CYP2A6*16, exhibited higher K(m) values. Analysis of the V(max)/K(m) ratio revealed that all mutants demonstrated 0.85- to 1.05-fold differences from the wild type, with the exception of variant CYP2A6*22, which only portrayed 39% of the wild-type intrinsic clearance. These data suggested that individuals carrying the CYP2A6*22 allele are likely to have lower metabolism of CYP2A6 substrate than individuals expressing CYP2A6*15, CYP2A6*16, CYP2A6*21, and the wild type.
  2. Tan AK, Mallika P. S., Aziz S, Asokumaran T, Intan G, Faridah HA
    Malays Fam Physician, 2010;5(2):83-90.
    PMID: 25606193 MyJurnal
    OBJECTIVE: To determine the sensitivity and specificity of the conventional direct ophthalmoscope and the PanOptic ophthalmoscope in the detection of sight threatening retinopathy, as well as the "Ease of Use" of these equipments.
    METHODS: 200 diabetics, newly referred from primary health physicians were examined. Fundus examinations were performed with pupil dilatation in a dark room. The examinations were performed by a single investigator using the PanOptic ophthalmoscope, the conventional direct ophthalmoscope and slit lamp biomicroscopy.
    RESULTS: The overall sensitivity in detecting sight threatening retinopathy using the conventional direct ophthalmoscope was 73.2% (95% CI: 57.1-85.8%), specificity 93.7% (95% CI: 88.7-96.9%). For PanOptic ophthalmoscope, the overall sensitivity in detecting sight threatening retinopathy was 58.5% (95% CI: 42.1-73.7%), specificity 93.7% (95% CI: 88.7-96.9%). The conventional direct ophthalmoscope was 1.38 times (95% CI: 1.17-1.61 times) as easy to use compared to the PanOptic ophthalmoscope.
    CONCLUSION: The PanOptic ophthalmoscope is not superior to the conventional direct ophthalmoscope for the screening of Sight Threatening Retinopathy.
    KEYWORDS: PanOptic ophthalmoscope; conventional direct ophthalmoscope; sight threatening retinopathy
    Study site: Ophthalmology clinic, Sarawak General Hospital, Kuching, Sarawak, Malaysia
  3. Ho CW, Tan WS, Chong FC, Ling TC, Tey BT
    J Microbiol Biotechnol, 2009 Apr;19(4):416-23.
    PMID: 19421000
    Hepatitis B core antigen (HBcAg) is an important serological marker used in the diagnosis of hepatitis B virus (HBV) infections. In the current study, a fast and efficient preparative purification protocol for truncated HBcAg from Escherichia coli disruptate was developed. The recombinant HBcAg was first captured by anion exchange expanded bed adsorption chromatography integrated with a cell disruption process. This online capture process has shortened the process time and eliminated the "hold-up" period that may be detrimental to the quality of target protein. The eluted product from the expanded bed adsorption chromatography was subsequently purified using size-exclusion chromatography. The results showed that this novel purification protocol achieved a recovery yield of 45.1% with a product purity of 88.2%, which corresponds to a purification factor of 4.5. The recovered HBcAg is still biologically active as shown by ELISA test.
  4. Chong FC, Tan WS, Biak DR, Ling TC, Tey BT
    J Chromatogr A, 2010 Feb 19;1217(8):1293-7.
    PMID: 20044094 DOI: 10.1016/j.chroma.2009.12.039
    A direct recovery of recombinant nucleocapsid protein of Nipah virus (NCp-NiV) from crude Escherichia coli (E. coli) homogenate was developed successfully using a hydrophobic interaction expanded bed adsorption chromatography (HI-EBAC). The nucleic acids co-released with the recombinant protein have increased the viscosity of the E. coli homogenate, thus affected the axial mixing in the EBAC column. Hence, DNase was added to reduce the viscosity of feedstock prior to its loading into the EBAC column packed with the hydrophobic interaction chromatography (HIC) adsorbent. The addition of glycerol to the washing buffer has reduced the volume of washing buffer applied, and thus reduced the loss of the NCp-NiV during the washing stage. The influences of flow velocity, degree of bed expansion and viscosity of mobile phase on the adsorption efficiency of HI-EBAC were studied. The dynamic binding capacity at 10% breakthrough of 3.2mg/g adsorbent was achieved at a linear flow velocity of 178 cm/h, bed expansion of two and feedstock viscosity of 3.4 mPas. The adsorbed NCp-NiV was eluted with the buffer containing a step gradient of salt concentration. The purification of hydrophobic NCp-NiV using the HI-EBAC column has recovered 80% of NCp-NiV from unclarified E. coli homogenate with a purification factor of 12.5.
  5. Tan SL, Sulaiman S, Pingguan-Murphy B, Selvaratnam L, Tai CC, Kamarul T
    Cell Tissue Bank, 2011 Feb;12(1):59-70.
    PMID: 19953328 DOI: 10.1007/s10561-009-9164-x
    This study investigates the feasibility of processed human amnion (HAM) as a substrate for chondrogenic differentiation of mesenchymal stem cells (MSCs). HAM preparations processed by air drying (AD) and freeze drying (FD) underwent histological examination and MSC seeding in chondrogenic medium for 15 days. Monolayer cultures were used as control for chondrogenic differentiation and HAMs without cell seeding were used as negative control. Qualitative observations were made using scanning electron microscopy analysis and quantitative analyses were based on the sulfated glycosaminoglycans (GAG) assays performed on day 1 and day 15. Histological examination of HAM substrates before seeding revealed a smooth surface in AD substrates, while the FD substrates exhibited a porous surface. Cell attachment to AD and FD substrates on day 15 was qualitatively comparable. GAG were significantly highly expressed in cells seeded on FD HAM substrates. This study indicates that processed HAM is a potentially valuable material as a cell-carrier for MSC differentiation.
  6. Tan SW, Ideris A, Omar AR, Yusoff K, Hair-Bejo M
    Arch Virol, 2010;155(1):63-70.
    PMID: 19898736 DOI: 10.1007/s00705-009-0540-4
    Sequence analysis of the fusion (F) gene of eight Malaysian NDV isolates showed that all the isolates were categorized as velogenic viruses, with the F cleavage site motif (112)R-R-Q-K-R(116) or (112)R-R-R-K-R(116) at the C-terminus of the F(2) protein and phenylalanine (F) at residue 117 at the N-terminus of the F(1) protein. Phylogenetic analysis revealed that all of the isolates were grouped in two distinct clusters under sub-genotype VIId. The isolates were about 4.8-11.7% genetically distant from sub-genotypes VIIa, VIIb, VIIc and VIIe. When the nucleotide sequences of the eight Malaysian isolates were compared phylogenetically to those of the old published local isolates, it was found that genotype VIII, VII, II and I viruses exist in Malaysia and caused sporadic infections. It is suggested that genotype VII viruses were responsible for most of the outbreaks in recent years.
  7. Tan KS, Armugam A, Sepramaniam S, Lim KY, Setyowati KD, Wang CW, et al.
    PLoS One, 2009;4(11):e7689.
    PMID: 19888324 DOI: 10.1371/journal.pone.0007689
    The methods currently available for diagnosis and prognosis of cerebral ischaemia still require further improvements. Micro-RNAs (small non-coding RNAs) have been recently reported as useful biomarkers in diseases such as cancer and diabetes. We therefore carried out microRNA (miRNA) profiling from peripheral blood to detect and identify characteristic patterns in ischaemic stroke.
  8. Tan GH, Taib NA, Choo WY, Teo SH, Yip CH
    Asian Pac J Cancer Prev, 2009 Jul-Sep;10(3):395-8.
    PMID: 19640180
    INTRODUCTION: Triple negative (TN) breast cancers are defined by a lack of expression of oestrogen, progesterone, and HER2 receptors. They tend to have a higher grade, with a poorer outcome compared to non-TN breast cancers.
    OBJECTIVE: The aim of this study is to determine the incidence of TN breast cancer in an Asian country consisting of Malays, Chinese and Indians, and to determine the factors associated with this type of breast cancer.
    RESULTS: The incidence of TN breast cancer in the University Malaya Medical Center is 17.6%. There is no significant difference amongst the Malays, Chinese and Indians. In bivariate analysis, TN breast cancer was significantly associated with younger age and Grade 3. However, in multivariate analysis using logistic regression, TN breast cancer was only associated with Grade 3.
    CONCLUSION: The incidence of TN breast cancer in our study is similar to other studies, and associated with a higher grade.
    Study site: University Malaya Medical Centre (UMMC)
  9. Tan GC, Sharifah NA, Shiran MS, Salwati S, Hatta AZ, Paul-Ng HO
    Asian Pac J Cancer Prev, 2008 Oct-Dec;9(4):781-4.
    PMID: 19256776
    The differentiation between cervical intraepithelial neoplasia 3 (CIN 3) and early squamous cell carcinoma (SCC) of the cervix may be difficult in certain situations. Identification of invasion beyond the basement membrane is the gold standard for the diagnosis of the latter. The objective of this study was to determine whether the use of Ki-67 and p53 could help in solving the above dilemma. This was a retrospective study on 61 cases of cervical neoplasms comprising of 25 cases of CIN 3 and 36 SCC. All cases were evaluated by immunohistochemistry using Ki-67 and p53 monoclonal antibodies. Results showed that the differences of Ki-67 and p53 expression between CIN 3 and SCC were statistically significant. In conclusion, Ki-67 and p53 may serve as helpful adjuncts to routinely-stained histological sections in differentiating between CIN 3 and SCC.
  10. Ramesh S, Tan CY, Aw KL, Yeo WH, Hamdi M, Sopyan I, et al.
    Med J Malaysia, 2008 Jul;63 Suppl A:89-90.
    PMID: 19024998
    The sintering behaviour of a commercial HA and synthesized HA was investigated over the temperature range of 700 degrees C to 1400 degrees C in terms of phase stability, bulk density, Young's modulus and Vickers hardness. In the present research, a wet chemical precipitation reaction was successfully employed to synthesize a submicron, highly crystalline, high purity and single phase stoichiometric HA powder that is highly sinteractive particularly at low temperature regimes below 1100 degrees C. It has been revealed that the sinterability of the synthesized HA was significantly greater than that of the commercial HA. The temperature for the onset of sintering and the temperature required to achieve densities above 98% of theoretical value were approximately 150 degrees C lower for the synthesized HA than the equivalent commercial HA. Nevertheless, decomposition of HA phase upon sintering was not observed in the present work for both powders.
  11. Luo N, Tan LC, Zhao Y, Lau PN, Au WL, Li SC
    Mov Disord, 2009 Jan 30;24(2):183-7.
    PMID: 18972545 DOI: 10.1002/mds.22240
    The aim of our study was to assess the longitudinal validity of the 8-item Parkinson's Disease Questionnaire (PDQ-8) in terms of responsiveness and test-retest reliability and to determine the minimally important difference (MID) for PDQ-8 using the anchor-based approach in Asians with Parkinson's disease (PD). A consecutive sample of PD patients attending a tertiary neuroscience clinic in Singapore completed the English or Chinese version of PDQ-8 twice during two different clinic visits. During the second visit, patients were also asked to rate their changes in health in general, PD severity, and overall impact of PD since at the time of their first visit 1 year ago using a 5-point response scale. A total of 96 patients participated in the study. For patients who reported changed conditions in the second visit, responsiveness measured by Cohen's effect size, standardized response mean, and Guyatt's responsiveness index ranged from 0.21 to 0.68. The intraclass correlation coefficient values calculated using patients reporting no change in health or PD status ranged from 0.64 to 0.76. The mean changed PDQ-8 summary index score in patients who reported that their health or PD status worsened only "a little bit" ranged from 5.8 to 7.4 points. Our current results show that PDQ-8 is a longitudinally reliable and responsive measure for assessing the health-related quality of life in patients with PD. The MID of the PDQ-8 estimated in the study will further support the use of this instrument in both clinical research and practice.
  12. Mohd Sidik S, Rampal L, Loh JW, Chan CL, Teh PC, Tan PO
    Med J Malaysia, 2008 Mar;63(1):26-30.
    PMID: 18935727
    Self-esteem is an important determinant of psychological well-being that is particularly problematic during adolescent life stage. There is a correlation between low self-esteem and other social problems among today's adolescents. This study was conducted to determine the mean self-esteem score, and to determine the association between self-esteem and age, sex, race, religion, number of siblings, ranking among siblings, family function, parental marital status and smoking among adolescents aged 12 to 20-years-old. A cross sectional study design using random cluster sampling method was done. Four out of a total of 35 secondary schools in Klang District, Selangor were selected. Respondents consisted of individual students in selected classes from the four selected schools. Data was collected using a self-administered, structured, pre-tested questionnaire and was analyzed using the SPSS version 12.0. Out of 1089 respondents, 793 completed the questionnaire (response rate 73.82%). The overall mean self-esteem score was 27.65. The mean self-esteem score for males (27.99) was slightly higher than females (27.31). The differences in the mean scores by race were statistically significant. There was a statistically significant relationship between mean self-esteem scores and sex, age, race, religion, number of siblings, smoking and family function. There was no statistically significant difference between mean self-esteem score with parental marital status and with ranking among siblings. The overall mean self-esteem score was 27.65. Self-esteem was associated with sex, age, race, religion, number of siblings, smoking and family function.
  13. Thye YL, Lim SK, Wong CM, Keng TC, Chong YB, Tan SY
    Transplant Proc, 2008 Sep;40(7):2435-6.
    PMID: 18790259 DOI: 10.1016/j.transproceed.2008.07.051
    Delayed graft function is a potentially challenging problem especially in cadaveric kidney transplant recipients. It adversely impacts long-term graft survival. It is rarely seen in living kidney transplants. Recovery of graft function usually occurs within a month. The chances of recovery of graft function diminish with further prolongation of delayed function. In fact, recovery of graft function after 3 months has rarely been described, we report herein recovery of graft function after 132 days of nonfunction in a living related kidney transplant.
  14. Suriya R, Hassan L, Omar AR, Aini I, Tan CG, Lim YS, et al.
    Zoonoses Public Health, 2008 Sep;55(7):342-51.
    PMID: 18667027 DOI: 10.1111/j.1863-2378.2008.01138.x
    Following a series of H5N1 cases in chickens and birds in a few states in Malaysia, there was much interest in the influenza A viruses subtypes that circulate among the local pig populations. Pigs may act as a mixing vessel for avian and mammal influenza viruses, resulting in new reassorted viruses. This study investigated the presence of antibodies against influenza H1N1 and H3N2 viruses in pigs from Peninsular Malaysia using Herdcheck Swine Influenza H1N1 and H3N2 Antibody Test Kits. At the same time, the presence of influenza virus was examined from the nasal swabs of seropositive pigs by virus isolation and real time RT-PCR. The list of pig farms was obtained from the headquarters of the Department of Veterinary Services, Malaysia, and pig herds were selected randomly from six of 11 states in Peninsular Malaysia. A total of 727 serum and nasal swab samples were collected from 4- to 6-month-old pigs between May and August 2005. By ELISA, the seroprevalences of swine influenza H1N1 and H3N2 among pigs were 12.2% and 12.1% respectively. Seropositivity for either of the virus subtypes was detected in less than half of the 41 sampled farms (41.4%). Combination of both subtypes was detected in 4% of all pigs and in 22% of sampled farms. However, no virus or viral nucleic acid was detected from nasal samples. This study identified that the seropositivity of pigs to H1N1 and H3N2 based on ELISA was significantly associated with factors such as size of farm, importation or purchase of pigs, proximity of farm to other pig farms and the presence of mammalian pets within the farm.
  15. Jahangir AW, Tan HJ, Norlinah MI, Nafisah WY, Ramesh S, Hamidon BB, et al.
    Med J Malaysia, 2007 Oct;62(4):319-22.
    PMID: 18551937 MyJurnal
    Botulinum toxin is effective in reducing spasticity post stroke. As there are limited data on post stroke spasticity in Asia, we undertake this study to determine the effectiveness and safety of intramuscular injection of botulinum toxin type-A (BTX-A), in the treatment of chronic focal post-stroke hand spasticity, and the impact of BTX-A on the activities of daily living and quality of life, in comparison to placebo, in Malaysian stroke patients. This was a randomized, double-blind, placebo-controlled study to assess the efficacy and safety of BTX-A in 27 subjects with wrist and finger spasticity after a stroke. The outcome measures were assessed with the Modified Ashworth Scale (MAS) to assess spasticity of the flexor muscles, Barthel Index (BI) for activities of daily living and EQ-5D and EQ VAS for quality of life. Assessments were performed at baseline and 1 and 3 months after injection. Compared to placebo, the BTX-A group had greater improvement in the flexor tone of the wrist and fingers (p = 0.001 and p < 0.001, respectively), at first month follow-up visit and sustained the improvement through to three months. Although there was an improvement in the measures of global function and quality of life in the BTX-A group, there was no significant improvement in between the two groups. No serious BTX-A related adverse effects were reported. The results of this study demonstrate that intramuscular injection of botulinum toxin A is safe and effective in the treatment of chronic focal post-stroke spasticity of the hand.
  16. Hilmi I, Singh R, Ganesananthan S, Yatim I, Radzi M, Chua AB, et al.
    J Dig Dis, 2009 Feb;10(1):15-20.
    PMID: 19236542 DOI: 10.1111/j.1751-2980.2008.00357.x
    To establish the clinical course of ulcerative colitis (UC) in the Malaysian population, comparing the three major ethnic groups: Malay, Chinese and Indian.
  17. Vani S, Lau SY, Lim BK, Omar SZ, Tan PC
    Int J Gynaecol Obstet, 2009 Jan;104(1):28-31.
    PMID: 18922525 DOI: 10.1016/j.ijgo.2008.08.014
    To evaluate the success of external cephalic version (ECV) using an adjusted bolus dose of intravenous salbutamol compared with no tocolysis.
  18. Ngiu CS, Ibrahim NM, Yahya WN, Tan HJ, Mustafa N, Basri H, et al.
    BMJ Case Rep, 2009;2009.
    PMID: 21709844 DOI: 10.1136/bcr.01.2009.1501
    Hashimoto encephalopathy (HE) is a poorly recognised steroid-responsive encephalopathy, with prominent neuropsychiatric features. Diagnosis is often difficult due to its heterogeneous clinical presentation, especially since the thyroid status or anti-thyroid antibody titres may not be related to the disease state. Here, the case of a 23-year-old Malay woman with Graves disease who presented with progressive encephalopathy diagnosed as HE is presented. She responded dramatically to high dose intravenous and then oral corticosteroid. A month after the initiation of treatment, she regained full independency.
  19. Tan GC, Yap YP, Shiran MS, Sabariah AR, Pathmanathan R
    BMJ Case Rep, 2009;2009.
    PMID: 21686408 DOI: 10.1136/bcr.11.2008.1221
    Mycobacterial spindle cell pseudotumour (MSCP) has been reported in various sites, including skin, lymph nodes, bone marrow, lung and spleen. Cutaneous lesions are extremely rare and the differential diagnoses include various spindle cell lesions. Literature review shows that this lesion has preponderance for upper limb involvement and occurs largely in immunosuppressed individuals. We report a case of MSCP of the skin due to atypical mycobacterium and discuss the risk of misdiagnosis as a sarcoma.
  20. Lim CK, Tan JT, Ravichandran A, Chan YC, Ton SH
    Malays J Pathol, 2007 Dec;29(2):79-90.
    PMID: 19108399 MyJurnal
    Hepatitis B virus (HBV) is classified into eight genotypes (A to H). In this study, three genotyping methods were compared for their sensitivity and accuracy, namely PCR-RFLP on the S region, PCR-RFLP on the pre-S region and nested PCR with type specific primers. Sixty HBV samples from infected sera were genotyped. The nested PCR with type specific primers was found to be the most sensitive and produced substantial numbers of co-infections by genotypes B and C. The sensitivities for both PCR-RFLP methods were lower and did not reveal co-infections. Generally, the three methods produced consistent genotyping results in samples infected by single genotypes but for co-infections by genotypes B and C, the two PCR-RFLP methods yielded only single genotypic results. For the cases of single genotypic infections, genotypes ascertained by sequencing were in concordance across all three methods. However, when co-infections occurred, PCR analysis on clones revealed only single genotypic infections.
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