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A phage-displayed single chain variable fragment that interacts with hepatitis B core antigen: library construction, selection and diagnosis

Tan GH, Yusoff K, Seow HF, Tan WS

J Clin Virol, 2007 Jan;38(1):49-56.
PMID: 17074533

Phage display is an alternative method for constructing and selecting antibodies with desired specificity towards an antigen.
Inducing curricular change: Initial evaluation of outcomes

Azila NM, Tan NH, Tan CP

Med Educ, 2006 Nov;40(11):1125.
PMID: 17054624
Antigenicity and immunogenicity of the immunodominant region of hepatitis B surface antigen displayed on bacteriophage T7

Tan GH, Yusoff K, Seow HF, Tan WS

J Med Virol, 2005 Dec;77(4):475-80.
PMID: 16254965

The immunodominant region of hepatitis B virus (HBV) located in the viral small surface antigen (S-HBsAg) elicits virus-neutralizing and protective antibodies. In order to develop an easy and inexpensive method to produce this region without the need for extensive purification, amino acid residues 111-156 of S-HBsAg were fused to the C-terminal end of the 10B capsid protein of T7 phage. Western blotting and ELISA confirmed the expression of the recombinant protein on the surface of the phage particles. The recombinant phage exhibited the antigenic and immunogenic characteristics of HBsAg, illustrating its potential as an immunological reagent and vaccine.
A phage-displayed cyclic peptide that interacts tightly with the immunodominant region of hepatitis B surface antigen

Tan WS, Tan GH, Yusoff K, Seow HF

J Clin Virol, 2005 Sep;34(1):35-41.
PMID: 16087122

The surface antigen (HBsAg) of hepatitis B virus (HBV) is highly conformational and generally evokes protective humoral immune response in human. A disulfide constrained random heptapeptide library displayed on the coat protein III of filamentous bacteriophage M13 was employed to select specific ligands that interact with HBsAg subtype ad. Fusion phages carrying the amino acid sequence ETGAKPH and other related sequences were isolated. The binding site of peptide ETGAKPH was located on the immunodominant region of HBsAg. An equilibrium binding assay in solution showed that the phage binds tightly to HBsAg with a relative dissociation constant (KDrel) of 2.9+/-0.9 nM. The phage bearing this peptide has the potential to be used as a diagnostic reagent and two assays for detecting HBsAg in blood samples are described.
Fulltext Characterisation of beta-globin gene mutations in Malaysian children: a strategy for the control of beta-thalassaemia in a developing country

Thong MK, Tan JA, Tan KL, Yap SF

J Trop Pediatr, 2005 Dec;51(6):328-33.
PMID: 15967770 DOI: 10.1093/tropej/fmi052

beta-thalassaemia major, an autosomal recessive hemoglobinopathy, is one of the most common single gene disorders in multi-racial Malaysia. The control of beta-thalassaemia major requires a multi-disciplinary approach that includes population screening, genetic counselling, prenatal diagnosis and the option of termination of affected pregnancies. To achieve this objective, the molecular characterisation of the spectrum of beta-globin gene mutations in each of the affected ethnic groups is required. We studied 88 consecutive unrelated individuals and their respective families with beta-thalassaemia (74 beta-thalassaemia major, 12 HbE-beta-thalassaemia, 2 with HbE homozygotes) and four individuals with beta-thalassaemia trait that contributed a total 180 alleles for study. Using a 2-step molecular diagnostic strategy consisting of amplification refractory mutation system (ARMS) to identify the 8 most common mutations followed by other DNA-based diagnostic techniques, a total of 177 (98.3 per cent) of the 180 beta-thalassaemia alleles were characterised. One out of 91 (1 per cent) of the Chinese alleles, one out of 46 (2.2 per cent) Malay alleles and one out of two Indian alleles remained unknown. A 100 per cent success rate was achieved in studying the Kadazandusun community in this study. A strategy to identify beta-globin gene mutations in Malaysians with beta-thalassaemia is proposed based on this outcome.
Fulltext Genome analysis of quorum sensing Cedecea neteri SSMD04 leads to identification of its novel signaling synthase (cneI), cognate receptor (cneR) and an orphan receptor

Tan KH, Tan JY, Yin WF, Chan KG

PeerJ, 2015;3:e1216.
PMID: 26355540 DOI: 10.7717/peerj.1216

Cedecea neteri is a very rare human pathogen. We have isolated a strain of C. neteri SSMD04 from pickled mackerel sashimi identified using molecular and phenotypics approaches. Using the biosensor Chromobacterium violaceum CV026, we have demonstrated the presence of short chain N-acyl-homoserine lactone (AHL) type quorum sensing (QS) activity in C. neteri SSMD04. Triple quadrupole LC/MS analysis revealed that C. neteri SSMD04 produced short chain N-butyryl-homoserine lactone (C4-HSL). With the available genome information of C. neteri SSMD04, we went on to analyse and identified a pair of luxI/R homologues in this genome that share the highest similarity with croI/R homologues from Citrobacter rodentium. The AHL synthase, which we named cneI(636 bp), was found in the genome sequences of C. neteri SSMD04. At a distance of 8bp from cneI is a sequence encoding a hypothetical protein, potentially the cognate receptor, a luxR homologue which we named it as cneR. Analysis of this protein amino acid sequence reveals two signature domains, the autoinducer-binding domain and the C-terminal effector which is typical characteristic of luxR. In addition, we found that this genome harboured an orphan luxR that is most closely related to easR in Enterobacter asburiae. To our knowledge, this is the first report on the AHL production activity in C. neteri, and the discovery of its luxI/R homologues, the orphan receptor and its whole genome sequence.
Fulltext Novel calcium infusion regimen after parathyroidectomy for renal hyperparathyroidism

Tan JH, Tan HC, Loke SC, Arulanantham SA

Nephrology (Carlton), 2017 Apr;22(4):308-315.
PMID: 26952689 DOI: 10.1111/nep.12761

AIM: Calcium infusion is used after parathyroid surgery for renal hyperparathyroidism to treat postoperative hypocalcaemia. We compared a new infusion regimen to one commonly used in Malaysia based on 2003 K/DOQI guidelines.
METHODS: Retrospective data on serum calcium and infusion rates was collected from 2011-2015. The relationship between peak calcium efflux (PER) and time was determined using a scatterplot and linear regression. A comparison between regimens was made based on treatment efficacy (hypocalcaemia duration, total infusion amount and time) and calcium excursions (outside target range, peak and trough calcium) using bar charts and an unpaired t-test.
RESULTS: Fifty-one and 34 patients on the original and new regimens respectively were included. Mean PER was lower (2.16 vs 2.56 mmol/h; P = 0.03) and occurred earlier (17.6 vs 23.2 h; P = 0.13) for the new regimen. Both scatterplot and regression showed a large correlation between PER and time (R-square 0.64, SE 1.53, P
Fulltext Cytotoxic data of 14-deoxy-11, 12-didehydroandrographolide (14-DDA), double transfection and DDIT3 silencing data in T-47D breast carcinoma cells

Tan HK, Tengku Muhammad TS, Tan ML

Data Brief, 2016 Jun;7:1506-10.
PMID: 27182548 DOI: 10.1016/j.dib.2016.04.046

The data presented in this article are related to the research article entitled "14-deoxy-11,12-didehydroandrographolide induces DDIT3-dependent endoplasmic reticulum stress-mediated autophagy in T-47D breast carcinoma cells", which the mechanistic toxicology properties of 14-deoxy-11,12-didehydroandrographolide (14-DDA) were investigated (Tan et al., 2016 [1]). This article describes the derivation of cytotoxic parameters of 14-DDA, cell viability data after double transfection and DDIT3 silencing in T-47D cells.
Prevalence of diabetes and ethnic differences in cardiovascular risk factors. The 1992 Singapore National Health Survey

Tan CE, Emmanuel SC, Tan BY, Jacob E

Diabetes Care, 1999 Feb;22(2):241-7.
PMID: 10333940 DOI: 10.2337/diacare.22.2.241

OBJECTIVE: The purpose of the 1992 Singapore National Health Survey was to determine the current distribution of major noncommunicable diseases and their risk factors, including the prevalence of diabetes and dyslipidemia, in Singapore.

RESEARCH DESIGN AND METHODS: A combination of disproportionate stratified sampling and systematic sampling were used to select the sample for the survey. The final number of respondents was 3,568, giving a response rate of 72.6%. All subjects fasted for 10 h and were given a 75-g glucose load, except those known to have diabetes. Blood was taken before and 2 h after the glucose load. Diagnosis of diabetes was based on 2-h glucose alone.

RESULTS: The age-standardized prevalence of diabetes in Singapore residents aged 18-69 years was 8.4%, with more than half (58.5%) previously undiagnosed. Prevalence of diabetes was high across all three ethnic groups. The prevalence of impaired glucose tolerance was 16.1%, that of hypertension was 6.5%, and 19.0% were regular smokers. The total cholesterol (mean +/- SD) of nondiabetic Singaporeans was 5.18 +/- 1.02 mmol/l; 47.9% had cholesterol > 5.2 mmol/l, while 15.4% had levels > 6.3 mmol/l. Mean LDL cholesterol was 3.31 +/- 0.89 mmol/l; HDL cholesterol was 1.30 +/- 0.32 mmol/l, and triglyceride was 1.23 +/- 0.82 mmol/l.

CONCLUSIONS: Prevalence of diabetes was high across all three ethnic groups. Ethnic differences in prevalence of diabetes, insulin resistance, central obesity, hypertension, smoking, and lipid profile could explain the differential coronary heart disease rates in the three major ethnic groups in Singapore.
Prevalence of peripheral artery disease in urban high-risk Malaysian patients

Amudha K, Chee KH, Tan KS, Tan CT, Lang CC

Int J Clin Pract, 2003 Jun;57(5):369-72.
PMID: 12846339

Atherosclerosis is a progressive, disseminated condition that affects all the vascular beds. Peripheral arterial disease (PAD), a manifestation of atherosclerosis, measured non-invasively in the legs by ankle-brachial index (ABI) is associated with increased cardiovascular morbidity and mortality. Though several studies in the western industrialised countries have shown that PAD is widely prevalent in the general older population at risk, not much data are available in the South East Asian developing countries. We have conducted an epidemiological survey on the prevalence of PAD in high-risk patients at an urban hospital in Malaysia. A total of 301 consecutive patients aged 32-90 years were recruited during their follow-up clinic visits for established cardiovascular disease, ischaemic stroke or diabetes mellitus > or = 5 years. All participants underwent ABI measurement and were subjected to the Edinburgh claudication questionnaire to assess leg symptoms. The prevalence of PAD in our high-risk population was 23%, of which only 27% were symptomatic with the classical intermittent claudication. All the patients with PAD were diagnosed at the time of the study. PAD was found in 33% of patients with pre-existent cardiovascular disease, 28% in patients with ischaemic stroke and 24% in diabetic patients. PAD was also highly prevalent among the younger patients. Our study has shown that PAD is highly prevalent among high-risk Malaysian patients and is not necessarily a disease of older age. Only 27% of these patients were symptomatic. All the subjects with PAD were diagnosed at the time of the study, which would suggest it is an unrecognised and underdiagnosed condition, even in patients with atherosclerotic risk factors.
Six isoforms of cardiotoxin in malayan spitting cobra (Naja naja sputatrix) venom: cloning and characterization of cDNAs

Jeyaseelan K, Armugam A, Lachumanan R, Tan CH, Tan NH

Biochim. Biophys. Acta, 1998 Apr 10;1380(2):209-22.
PMID: 9565688

Cardiotoxins are the most abundant toxin components of cobra venom. Although many cardiotoxins have been purified and characterized by amino acid sequencing and other pharmacological and biochemical studies, to date only five cardiotoxin cDNAs from Taiwan cobra (Naja naja atra), three cDNAs from Chinese cobra (Naja atra) and two more of uncertain origin (either Chinese or Taiwan cobra) have been reported. In this paper we show the existence of four isoforms of cardiotoxin by protein analysis and nine cDNA sequences encoding six isoforms of cardiotoxins (CTX 1-3, 4a, 4b and 5) from N. n. sputatrix by cDNA cloning. This forms the first report on the cloning and characterization of several cardiotoxin genes from a single species of a spitting cobra. The cDNAs encoding these isoforms, obtained by reverse transcription-polymerase chain reaction (RT-PCR), were subsequently expressed in Escherichia coli. The native and recombinant cardiotoxins were first characterized by Western blotting and N-terminal protein sequencing. These proteins were also found to have different levels of cytolytic activity on cultured baby hamster kidney cells. Four of the isoforms (CTX 1, 2, 4 and 5) are unique to N. n. sputatrix, with CTX 2 being the most abundant species constituting about 50% of the total cardiotoxins. The isoform CTX 3 (20% constitution) is highly homologous to the cardiotoxins of N. n. atra and N. n. naja, indicating that it may be universally present in all Naja naja subspecies. Our studies suggest that the most hydrophilic isoform (CTX 5) could have evolved first followed by the hydrophobic isoforms (CTX 1, 2, 3 and 4). We also speculate that Asiatic cobras could be the modern descendants of the African and Egyptian counterparts.
Solubilities of trace copper and lead species and the complexing capacity of river water in the Linggi River Basin

Tan WT, Tan GS, Nather Khan IS

Environ Pollut, 1988;52(3):221-35.
PMID: 15092608

Chemical forms of copper and lead in river water of the Linggi River Basin have been fractionated into ASV labile, moderately labile, slowly labile, and inert metal species, based on a previously proposed scheme. Free (hydrated) metal ions were identified by a potentiometric method using an ion selective electrode. Speciation results showed that the soluble copper and lead species occurred mainly in the moderately labile and slowly labile fractions. The speciation results are primarily interpreted in terms of organic interaction due to agricultural based and light industries, and urban discharges. The measured metal complexing capacity (MCC) of the samples reveals consistency of the results with the nature of the discharge. MCC correlates reasonably well with the value from the permanganate test on the river water. In general, the speciation pattern was found to be consistent with the findings of other workers.
Detection of Newcastle disease virus using a SYBR Green I real time polymerase chain reaction

Tan SW, Omar AR, Aini I, Yusoff K, Tan WS

Acta Virol., 2004;48(1):23-8.
PMID: 15230471

A two-step SYBR Green I real time polymerase chain reaction (PCR, real time PCR) for the detection of Newcastle disease virus (NDV) was developed. A melting curve analysis was performed to distinguish specific from non-specific products and primer dimers. Regardless of different virus pathotypes the melting temperature (Tm) ranged from 86 degrees C to 87 degrees C. The sensitivity of the real time PCR was compared with the reverse transcription (RT)-nested PCR enzyme-linked immunosorbent assay (ELISA, RT-nested PCR ELISA). Whereas the detection limit of the real time PCR was 10 pg DNA, the RT-nested PCR ELISA and conventional PCR could only detect up to 1 ng and 10 ng DNA, respectively. Thus the real time PCR offers a sensitive, rapid and convenient method for screening large number of NDV specimens.
Fulltext Post-colonoscopy diverticulitis: A systematic review

Ng ZQ, Tan JH, Tan HCL, Theophilus M

World J Gastrointest Endosc, 2021 Mar 16;13(3):82-89.
PMID: 33763188 DOI: 10.4253/wjge.v13.i3.82

BACKGROUND: Post-colonoscopy diverticulitis is increasingly recognized as a potential complication. However, the evidence is sparse in the literature.
AIM: To systematically review all available evidence to describe the incidence, clinical course with management and propose a definition.
METHODS: The databases PubMed, EMBASE and Cochrane databases were searched using with the keywords up to June 2020. Additional manual search was performed and cross-checked for additional references. Data collected included demographics, reason for colonoscopy, time to diagnosis, method of diagnosis (clinical vs imaging) and management outcomes.
RESULTS: A total of nine studies were included in the final systematic review with a total of 339 cases. The time to diagnosis post-colonoscopy ranged from 2 h to 30 d. Clinical presentation for these patients were non-specific including abdominal pain, nausea/vomiting, per rectal bleeding and chills/fever. Majority of the cases were diagnosed based on computed tomography scan. The management for these patients were similar to the usual patients presenting with diverticulitis where most resolve with non-operative intervention (i.e., antibiotics and bowel rest).
CONCLUSION: The entity of post-colonoscopy diverticulitis remains contentious where there is a wide duration post-procedure included. Regardless of whether this is a true complication post-colonoscopy or a de novo event, early diagnosis is vital to guide appropriate treatment. Further prospective studies especially registries should include this as a complication to try to capture the true incidence.
Diagnosis and management of fatty liver

Tan PO, Mustaffa N, Tan SS, Lee YY

J R Coll Physicians Edinb, 2020 Sep;50(3):256-261.
PMID: 32936098 DOI: 10.4997/JRCPE.2020.308

Globally, the prevalence of non-alcoholic fatty liver disease (NAFLD) is increasing rapidly and constitutes a significant healthcare burden due to associated complications including hepatic (cirrhosis and hepatocellular cancer) and non-hepatic (cardiovascular deaths) disorders. It is closely linked to insulin resistance and metabolic syndrome but moderate alcohol consumption frequently coexists. Recently, genetic polymorphisms were implicated in the development of non-obese NAFLD. Apart from liver biopsy, in order to assess for steatosis, fibrosis and non-alcoholic steatohepatitis (NASH), advances in non-invasive serum tests and elastography have provided similarly accurate, more accessible and safer alternatives for risk stratification. As for treatment in 2020, weight loss and lifestyle modification remain the central strategy. Unfortunately, no pharmacological agents have been approved thus far, but there are a number of potential therapies in the pipeline for fibrosis and NASH. Treatment of underlying metabolic disorders is important. While the term NAFLD was coined in the 1980s, more recent understanding may support a change in nomenclature highlighting its strong metabolic roots.
Silent microaspirations: The forerunner to the diagnosis of bulbar onset myasthenia gravis in a young woman

Tan TL, Tan HJ, Cheah CF, Kumaresh R, Azzahra NA

Med J Malaysia, 2020 05;75(3):295-297.
PMID: 32467548

Recurrent pneumonia warrants a diligent work-up to identify the underlying cause that perpetuates the disease process. Insidious bulbar dysfunction is arguably the most devastating as it would be diagnosed late after significant pulmonary complications due to chronic micro-aspiration. Bulbar disorder should be considered as the potential aetiology of recurrent pulmonary infections in the young population after excluding immunodeficiency disorder and respiratory anatomical anomaly. This report illustrates a rare case of bulbar onset myasthenia gravis which manifested as focal bronchiolectasis due to recurrent undiagnosed aspiration pneumonia three years earlier. Absence of hallmark features of Myasthenia Gravis (MG) such as ptosis, opthalmoplegia and proximal muscle weakness contributed to the diagnostic delay and challenges in this case. The diagnosis was established with the collaboration of multidisciplinary teams. Subsequent correct therapeutic interventions resulted in remarkable recovery in functional status and prevented her from further aspiration in the long run.
Fulltext Streptococcus pneumoniae Meningitis and Intracranial Vasculopathy: Clinical Correlation with Improving Transcranial Doppler Hemodynamics

Idris MI, Tai SML, Tan CT, Tan KS

Case Rep Neurol, 2020 12 14;12(Suppl 1):106-109.
PMID: 33505281 DOI: 10.1159/000500950

Streptococcus pneumoniae are Gram-positive bacteria that are responsible for many types of illnesses including pneumonia, sinus infections, and community-acquired meningitis. One important complication of bacterial meningitis is intracranial vasculopathy. Possible etiologies include vasculitis, vasospasm, endocarditis, or intra-arterial thrombosis. We present a case report of S. pneumoniae meningitis treated with antibiotics in which clinical improvement correlated with serial transcranial Doppler ultrasonography (TCD) improvement, suggesting vasospasm or vasculitis as a possible mechanism for intracranial vasculopathy.
Fulltext First Feasibility Study and Short-term Outcomes of Laparoscopic-Assisted Anterior Resection in Colorectal Cancer in Malaysia

Tan HCL, Tan JH, Nur Dzainuddin NA, Chan KK

Ann Coloproctol, 2020 Apr;36(2):94-101.
PMID: 32178501 DOI: 10.3393/ac.2019.05.10

PURPOSE: The purpose of this study was to demonstrate the feasibility and safety of laparoscopic-assisted anterior resection (LAAR) for colorectal cancer in a local Asian population.
METHODS: This is a retrospective review of all patients with colorectal cancer operated from November 2017 to October 2018. Main variables of interest were demography, type and surgery, length of stay (LOS), and the involvement of proximal and distal doughnut. Postoperative complications were analysed using chi-square or Fisher exact and Mann-Whitney tests.
RESULTS: There were 23 patients with a mean age of 62.5 ± 12.2 years. The mean time from diagnosis to surgery was 97.1 ± 154.84 days. There were 12 patients in the LAAR group and 11 in the open anterior resection (OAR) group. Duration of surgery was shorter in OAR (129.58 ± 51.38 minutes) compared to LAAR (147.91 ± 39.37 minutes). Mean LOS was shorter in the LAAR group with 5±1.5 days compared to the OAR group of 7.42 ± 4.25 days. However, there was no significant P-value for both duration of surgery (P = 0.322) or LOS (P = 0.87). A total of 3 complications were recorded after OAR and 2 after LAAR. Both groups had clear proximal and distal margins with 16 (12-18.5) harvested lymph nodes in LAAR and 18 (16-22) in OAR, which were equal (P = 0.155).
CONCLUSION: This study reports a shorter LOS in the minimally invasive group of 2 days with similar oncologic resection outcomes. This shows that LAAR is feasible in Malaysia and has potential outcome benefits.
Protein decomplexation and proteomics: A complementary assessment method of the physicochemical purity of antivenom

Tan CH, Liew JL, Chong HP, Tan NH

Biologicals, 2021 Jan;69:22-29.
PMID: 33431232 DOI: 10.1016/j.biologicals.2020.12.004

The quality of antivenom is governed by its safety and efficacy profiles. These quality characteristics are much influenced by the purity of antivenom content. Rigorous assessment and meticulous monitoring of antivenom purity at the preclinical setting is hence crucial. This study aimed to explore an integrative proteomic method to assess the physicochemical purity of four commercially available antivenoms in the region. The antivenoms were subjected to Superdex 200 HR 10/30 size-exclusion fast-protein liquid chromatography (SE-FPLC). The proteins in each fraction were trypsin-digested and analyzed by nano-ESI-liquid chromatography-tandem mass spectrometry (LC-MS/MS). SE-FPLC resolved the antivenom proteins into three major protein components of very high (>200 kDa), high (100-120 kDa) and medium (<60 kDa) molecular weights. The major components (80-95% of total proteins) in the antivenoms were proteins of 100-120 kDa consisting of mainly the light and partially digested heavy immunoglobulin chains, consistent with F(ab')2 as the active principle of the antivenoms. However, LC-MS/MS also detected substantial quantity of large proteins (e.g. alpha-2-macroglobulins), immunoglobulin aggregates and impurities e.g. albumins in some products. The method is practical and able to unveil the quantitative and qualitative aspects of antivenom protein compositions. It is therefore a potentially useful preclinical assessment tool of antivenom purity.
Fulltext Being Creative Makes You Happier: The Positive Effect of Creativity on Subjective Well-Being

Tan CY, Chuah CQ, Lee ST, Tan CS

Int J Environ Res Public Health, 2021 07 06;18(14).
PMID: 34299693 DOI: 10.3390/ijerph18147244

The impact of happiness on creativity is well-established. However, little is known about the effect of creativity on well-being. Two studies were thus conducted to examine the impact of creativity on subjective well-being. In the first study, 256 undergraduate students (Study 1a) and 291 working adults (Study 1b) self-reported their creativity, stress, and subjective well-being. Hierarchical multiple regression analysis showed a positive relationship between creativity and subjective well-being after controlling the effect of self-perceived stress and demographics in both samples. Study 2 then employed an experimental design to examine the causal relationship between creativity and subjective well-being. Half of the 68 undergraduates underwent a creativity priming task followed by a divergent thinking test as well as self-reported stress and subjective well-being. The priming task was found to boost creative performance in the pilot study (Study 2a) and the actual study (Study 2b). Moreover, after controlling the effect of self-perceived stress, ANCOVA analysis showed that participants receiving the priming reported higher subjective well-being scores than their counterparts in the control group. The overall findings not only shed light on the facilitative effect of creativity on subjective well-being but also highlight the necessity of considering the reciprocal relationship of the two constructs in future research.

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