MyMedR

Fulltext Effect of different cloning strategies in pET-28a on solubility and functionality of a staphylococcal phage endolysin

Tham HY, Song AA, Yusoff K, Tan GH

Biotechniques, 2020 09;69(3):161-170.

PMID: 32787565 DOI: 10.2144/btn-2020-0034

Endolysins have been studied intensively as an alternative to antibiotics. In this study, endolysin derived from a phage which infects methicillin-resistant Staphylococcus aureus (MRSA) was cloned and expressed in Escherichia coli pET28a. Initially, the endolysin was cloned using BamHI/XhoI, resulting in expression of a recombinant endolysin which was expressed in inclusion bodies. While solubilization was successful, the protein remained nonfunctional. Recloning the endolysin using NcoI/XhoI resulted in expression of soluble and functional proteins at 18°C. The endolysin was able to form halo zones on MRSA plates and showed a reduction in turbidity of MRSA growth. Therefore, cloning strategies should be chosen carefully even in an established expression system as they could greatly affect the functionality of the expressed protein.

Fulltext Electrochemical Preparation and Characterization of a Gold Nanoparticles Graphite Electrode: Application to Myricetin Antioxidant Analysis

Ng KL, Lee SM, Khor SM, Tan GH

Anal Sci, 2015;31(10):1075-81.

PMID: 26460374 DOI: 10.2116/analsci.31.1075

Graphite material is abundantly available from recyclable sources. It possesses a good electrical conductance property, which makes it an attractive material as a working electrode. However, due to a high activation overpotential it has limited applications as compared to other solid metal electrodes. In this present work, we obtained a graphite rod from a used battery, and carried out electrochemical improvements by electro-deposition with gold nanoparticles (AuNPs). The heterogeneous electron transfer rate and electron transfer resistance of the fabricated electrode were improved. The electrode overpotential has shown improvement by 50 mV, and the effective surface area has increased by 2 fold. To determine the practicability of the AuNPs/graphite electrode, we used the electrode in the analysis of myricetin. A square-wave voltammetry was used in the analysis, and the detection response increased by 2.5 fold, which suggested an improvement in the electrode sensitivity.

Efficiency of Hollow Fiber Liquid-Phase Microextraction Chromatography Methods in the Separation of Organic Compounds: A Review

Alsharif AM, Tan GH, Choo YM, Lawal A

J Chromatogr Sci, 2017 03 01;55(3):378-391.

PMID: 27903555 DOI: 10.1093/chromsci/bmw188

Hollow fiber liquid-phase microextraction (HF-LPME) techniques coupled to chromatographic systems have been widely used for extraction and determination of diverse compounds. HF-LPME was able to provide better results in precision, accuracy, selectivity and enrichment factor, in addition to reduction of matrix effect and carry over. It is applicable within a wide pH range and compatible with most analytical instruments which enable the utilization of HF-LPME in a wide variety of applications. This review focused on the modified HF-LPME techniques, efficiency, comparison to other LPME methods and applications.

Fulltext Paratesticular aggressive angiomyxoma: A rare case

Ismail MI, Wong YP, Tan GH, Fam XI

Urol Ann, 2017 5 10;9(2):197-199.

PMID: 28479778 DOI: 10.4103/UA.UA_168_16

Aggressive angiomyxoma (AAM) particularly testicular origin is a rare benign mesenchymal myxoid tumor which is locally aggressive, blatant for local recurrence, and may metastasize. It occurs mostly in females of childbearing age and extremely rare in males. AMM particular testicular origin is not reported in literature yet. This is a 65-year-old man who had a right scrotal swelling. Ultrasound scrotum showed a soft tissue tumor of the right testis. The patient underwent radical right orchidectomy of which histopathologically confirmed to be a paratesticular AAM with clear resection margins. There were no signs of local recurrence or metastasis 2 years postsurgical resection.

Gas chromatographic method validation for the analysis of major components in illicit heroin seized in Malaysia

Chan KW, Tan GH, Wong RC

Sci Justice, 2012 Mar;52(1):9-16.

PMID: 22325905 DOI: 10.1016/j.scijus.2011.07.005

Apart from routine analysis of total morphine content required by the criminal justice system, quantification of other major components in illicit heroin has not been considered by the Malaysian enforcement laboratory. In order to quantify various other cutting agents in addition to alkaloids, a gas chromatographic (GC) method was developed to facilitate simultaneous quantification of eight target analytes commonly found in illicit heroin seized in Malaysia within a 12 min run time. The validation results demonstrated high selectivity with the use of an HP Ultra 2 capillary column. Different solvents were studied and methanol:chloroform (1:9) proved best for sample dissolution. The method was repeatable and reproducible. The study ranges covering 50-150% of the preferred concentrations of the eight analytes obtained r(2)>0.9997. Limits of detection up to 6μg/mL were also obtained and the method achieved 99-102% recovery. The capability of the method in heroin profiling was verified using samples from ten case samples.

Investigation of trace inorganic elements in street doses of heroin

Chan KW, Tan GH, Wong RC

Sci Justice, 2013 Mar;53(1):73-80.

PMID: 23380066 DOI: 10.1016/j.scijus.2012.08.004

Sixteen trace elements found in 309 street heroin samples, piped water and contaminated water were determined using inductively coupled plasma-mass spectrometry. All the street heroin samples were found to contain high levels of sodium, a reflection of the use of sodium bicarbonate during heroin synthesis. Additionally, this element was also found to be one of the potential contaminants acquired from the piped water. Calcium could be derived from lime while iron, aluminum and zinc could have come from the metallic container used in the processing/cutting stage. The levels of these elements remained low in the heroin and it could be due to the dilution effects from the addition of adulterants. Statistical validation was performed with six links of related heroin samples using principal component analysis to find the best pretreatment for sample classification. It was obtained that normalization followed by fourth root showed promising results with 8% errors in the sample clustering. The technique was then applied to the case samples. Finally, the result suggested that the case samples could have originated from at least two major groups respectively showing unique elemental profiles at the street level.

A simplified clustering method for novice narcotic chemists

Chan KW, Tan GH, Wong RC

Sci Justice, 2012 Sep;52(3):136-41.

PMID: 22841136 DOI: 10.1016/j.scijus.2012.04.006

Statistical classification remains the most useful statistical tool for forensic chemists to assess the relationships between samples. Many clustering techniques such as principal component analysis and hierarchical cluster analysis have been employed to analyze chemical data for pattern recognition. Due to the feeble foundation of this statistics knowledge among novice drug chemists, a tetrahedron method was designed to simulate how advanced chemometrics operates. In this paper, the development of the graphical tetrahedron and computational matrices derived from the possible tetrahedrons are discussed. The tetrahedron method was applied to four selected parameters obtained from nine illicit heroin samples. Pattern analysis and mathematical computation of the differences in areas for assessing the dissimilarity between the nine tetrahedrons were found to be user-convenient and straightforward for novice cluster analysts.

The Will Rogers phenomenon in the staging of breast cancer - does it matter?

Tan GH, Bhoo-Pathy N, Taib NA, See MH, Jamaris S, Yip CH

Cancer Epidemiol, 2015 Feb;39(1):115-7.

PMID: 25475062 DOI: 10.1016/j.canep.2014.11.005

Changes in the American Joint Commission on Cancer staging for breast cancer occurred when the 5th Edition was updated to the 6th Edition.

Fulltext 50 MHz-10 GHz low-power resistive feedback current-reuse mixer with inductive peaking for cognitive radio receiver

Vitee N, Ramiah H, Chong WK, Tan GH, Kanesan J, Reza AW

ScientificWorldJournal, 2014;2014:683971.

PMID: 25133252 DOI: 10.1155/2014/683971

A low-power wideband mixer is designed and implemented in 0.13 µm standard CMOS technology based on resistive feedback current-reuse (RFCR) configuration for the application of cognitive radio receiver. The proposed RFCR architecture incorporates an inductive peaking technique to compensate for gain roll-off at high frequency while enhancing the bandwidth. A complementary current-reuse technique is used between transconductance and IF stages to boost the conversion gain without additional power consumption by reusing the DC bias current of the LO stage. This downconversion double-balanced mixer exhibits a high and flat conversion gain (CG) of 14.9 ± 1.4 dB and a noise figure (NF) better than 12.8 dB. The maximum input 1-dB compression point (P1dB) and maximum input third-order intercept point (IIP3) are -13.6 dBm and -4.5 dBm, respectively, over the desired frequency ranging from 50 MHz to 10 GHz. The proposed circuit operates down to a supply headroom of 1 V with a low-power consumption of 3.5 mW.

Fulltext Ultra-low-voltage CMOS-based current bleeding mixer with high LO-RF isolation

Tan GH, Sidek RM, Ramiah H, Chong WK, Lioe de X

ScientificWorldJournal, 2014;2014:163414.

PMID: 25197694 DOI: 10.1155/2014/163414

This journal presents an ultra-low-voltage current bleeding mixer with high LO-RF port-to-port isolation, implemented on 0.13 μm standard CMOS technology for ZigBee application. The architecture compliments a modified current bleeding topology, consisting of NMOS-based current bleeding transistor, PMOS-based switching stage, and integrated inductors achieving low-voltage operation and high LO-RF isolation. The mixer exhibits a conversion gain of 7.5 dB at the radio frequency (RF) of 2.4 GHz, an input third-order intercept point (IIP3) of 1 dBm, and a LO-RF isolation measured to 60 dB. The DC power consumption is 572 µW at supply voltage of 0.45 V, while consuming a chip area of 0.97 × 0.88 mm(2).

Fulltext Iatrogenic ureter injuries: eleven years experience in a tertiary hospital

Mahendran HA, Singam P, Ho C, Goh EH, Tan GH, Zuklifli MZ

Med J Malaysia, 2012 Apr;67(2):169-72.

PMID: 22822637 MyJurnal

Iatrogenic ureteric injuries are rare complications of abdomino-pelvic surgery but associated with high morbidity from infection and possible loss of renal function. A successful repair is related to the timing of diagnosis, site of injury and method of repair. This study was a retrospective review of outcomes of iatrogenic ureteric injury and factors contributing to successful operative repair. Twenty consecutive cases referred to the Urology Unit of the UKM Medical Center during an 11-year period from 1998 to 2009 were reviewed. Thirteen patients were diagnosed intraoperatively and underwent immediate repair. Seven patients had delayed diagnosis but also underwent immediate repair. In our series, there was no significant difference in outcome between injuries diagnosed intraoperatively versus injuries with delayed diagnosis. There was significant difference in the outcomes between methods of ureteric repair where ureter reimplantation via psoas hitch or Boari flap yielded better results than primary end-to-end anastomosis Three patients suffered loss of renal function from unsuccessful ureter repair. We conclude that all iatrogenic ureteric injury should be repaired immediately in the absence of overt sepsis. Ureter reimplantation using a Boari flap or psoas hitch is preferred to the end-to-end anastomosis especially when there is delayed diagnosis

Clinicopathological features and survival of testicular tumours in a Southeast Asian university hospital: a ten-year review

Tan GH, Azrif M, Shamsul AS, Ho CC, Praveen S, Goh EH, et al.

Asian Pac J Cancer Prev, 2011;12(10):2727-30.

PMID: 22320982

INTRODUCTION: Testicular cancer mainly affects young men worldwide. There is lack of published data on patients with this malignant condition from the Southeast Asian region. The aim of this study was therefore to determine the clinicopathologic features of testicular cancer patients treated in a Southeast Asian university hospital and their overall survival rate.

MATERIALS AND METHODS: This was a retrospective study of testicular cancer patients treated between January 2001 and February 2011. Their epidemiological data, clinical presentation, pathologic diagnosis, stage of disease and treatment were gathered and the overall survival rate of this cohort was analyzed.

RESULTS: Thirty-one patients were included in this study. The majority of them were of Malay ethnicity. The average age at presentation was 33.7 years. The commonest testicular cancer was non-seminomatous germ cell tumour, followed by seminoma, lymphoma and rhabdomyosarcoma. More than half of all testicular germ cell tumour (GCT) patients had some form of metastasis at diagnosis. All the patients were treated with radical orchidectomy. Adjuvant chemotherapy was given to those with metastatic disease. Four seminoma patients received radiotherapy to the para-aortic lymph nodes. The 5-year survival rate for all testicular cancers in this cohort was 83.9%. The survival rate was 88.9% in 5 years when GCT were analyzed separately.

CONCLUSION: GCT affects patients in their third and fourth decades of life while lymphoma patients are generally older. Most of the patients treated for GCT are of Malay ethnicity. The majority have late presentation for treatment. The survival rate of GCT patients treated here is comparable to other published series in other parts of the world.

Evaluation of power Doppler ultrasonography for prostate biopsy in men with elevated serum prostate specific antigen levels

Ho CC, Khor TW, Singam P, Goh EH, Tan GH, Bahadzor B, et al.

Clin Ter, 2012;163(3):211-4.

PMID: 22964693

OBJECTIVE: To evaluate power doppler ultrasonography (PDU)-directed prostate biopsy in patients with elevated serum prostate specific antigen (PSA) levels.
MATERIALS AND METHODS: Men with serum total PSA levels of more than 4 ng/ml undergoing biopsy for the first time were included. Grey-scale transrectal ultrasound (TRUS) and PDU were performed. PDU signal on vascularity accumulation and perfusion characteristics were recorded and graded as normal or abnormal in the peripheral zone of the prostate. Abnormalities were defined on transverse image as radial or arc hypervascularities. A biopsy regime based on Vienna-normogram was performed in all patients.
RESULTS: Overall, prostate adenocarcinoma detection rate was 21.4% and abnormal accumulation on PDU signal was identified in 96.7% of those patients (p = 0.01). PDU directed prostate biopsies were positive in 66.7% of the patients with prostate cancer. The sensitivity, specificity, positive predictive value and negative predictive value of PDU signal alone for prostate cancer detection was 96.7%, 24.5% and 96.4% respectively, and PDU guided biopsies were 66.7%, 24.5%, 19.4% and 73% respectively.
CONCLUSIONS: The high sensitivity and negative predictive value of PDU makes it useful as an aid for TRUS biopsy in selected patient with previous negative biopsies at risk of harbouring prostate cancer.

Fulltext Clinical characteristics of triple-negative breast cancer: experience in an Asian developing country

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)

Fulltext Progressive supra-axial cervical instability in Down syndrome: a case report emphasising the role of extended short-segment fusion

Tan GH, Tan KK, Afian MS, Liew WF, Mohamad AR

Med J Malaysia, 2005 Jul;60 Suppl C:111-3.

PMID: 16381295

We report a case of upper cervical instability associated with Down syndrome to highlight its potential progression to inflict cord compression and the rationale for surgical decompression and extended short segment occipito-axial fusion.

Strategy for generating tissue-engineered human bone construct

Tan KK, Aminuddin BS, Tan GH, Sabarul Afian M, Ng MH, Fauziah O, et al.

Med J Malaysia, 2004 May;59 Suppl B:43-4.

PMID: 15468810

The strategy used to generate tissue-engineered bone construct, in view of future clinical application is presented here. Osteoprogenitor cells from periosteum of consenting scoliosis patients were isolated. Growth factors viz TGF-B2, bFGF and IGF-1 were used in concert to increase cell proliferation during in vitro cell expansion. Porous tricalcium phosphate (TCP)-hydroxyapatite (HA) scaffold was used as the scaffold to form 3D bone construct. We found that the addition of growth factors, greatly increased cell growth by 2 to 7 fold. TCP/HA proved to be the ideal scaffold for cell attachment and proliferation. Hence, this model will be further carried out on animal trial.

The use of bone marrow stem cells for bone tissue engineering

Ng MH, Aminuddin BS, Tan KK, Tan GH, Sabarul Afian M, Ruszymah BH

Med J Malaysia, 2004 May;59 Suppl B:41-2.

PMID: 15468809

Bone marrow stem cells (BMSC), known for its multipotency to differentiate into various mesenchymal cells such as chodrocyte, osteoblasts, adipocytes, etc, have been actively applied in tissue engineering. BMSC have been successfully isolated from bone marrow aspirate and bone marrow scraping from patients of various ages (13-56 years) with as little as 2ml to 5ml aspirate. BMSC isolated from our laboratory showed the presence of a heterogenous population that showed varying prevalence of surface antigens and the presence of telomerase activity albeit weak. Upon osteogenic induction, alkaline phosphatase activity and mineralization activity were observed.

An unusual cause of a penetrating injury to the anterior urethra: a thorny situation

Tan GH, Ho CC, Bahadzor B, Praveen S, Goh EH, Afdzillah AR, et al.

Clin Ter, 2013;164(1):35-7.

PMID: 23455741 DOI: 10.7417/T.2013.1509

Concurrent penetrating injury to the male external genitalia and the anterior urethra is uncommon. This case illustrates an unusual cause of such an injury, and its subsequent management and outcome. A 69-year-old man had his scrotum and anterior urethra pierced by a long thorn when he fell in his farm. He presented with urine leakage from the scrotal wound each time he micturated. Cystoscopic examination confirmed the cause and extent of the injury, and also facilitated the extraction of the thorn. The injury was allowed time to heal by urinary diversion with a urinary catheter. There were no stricture or fistula formations and the patient remained symptom-free at 3 months follow-up. Careful cystoscopic examination was both diagnostic and therapeutic in this case. A conservative approach is a feasible option in the management of selected cases of penetrating anterior urethral injury.

Predictors of axillary lymph node metastases in breast cancer: is there a role for minimal axillary surgery?

Yip CH, Taib NA, Tan GH, Ng KL, Yoong BK, Choo WY

World J Surg, 2009 Jan;33(1):54-7.

PMID: 18958521 DOI: 10.1007/s00268-008-9782-7

Axillary nodal status is one of the most important prognostic factors in breast cancer. In the present study we used it to determine the predictors of axillary lymph node metastases in breast cancer and to determine if there is a group of patients in whom minimal axillary surgery is indicated.

Fulltext Urethral strictures after bipolar transurethral resection of prostate may be linked to slow resection rate

Tan GH, Shah SA, Ali NM, Goh EH, Singam P, Ho CCK, et al.

Investig Clin Urol, 2017 05;58(3):186-191.

PMID: 28480344 DOI: 10.4111/icu.2017.58.3.186

PURPOSE: This study aimed to determine the urethral stricture (US) rate and identify clinical and surgical risk factors associated with US occurrence after transurethral resection of the prostate using the bipolar Gyrus PlasmaKinetic Tissue Management System (PK-TURP).

MATERIALS AND METHODS: This was an age-matched case-control study of US occurrence after PK-TURP. Retrospective data were collected from the hospital records of patients who had a minimum of 36 months of follow-up information. Among the data collected for analysis were prostate-specific antigen level, estimated prostate weight, the amount of prostate resected, operative time, history of urinary tract infection, previous transurethral resection of the prostate, and whether the PK-TURP was combined with other endourological procedures. The resection rate was calculated from the collected data. Univariate and multivariate analyses were performed to identify clinical and surgical risk factors related to US formation.

RESULTS: A total of 373 patients underwent PK-TURP between 2003 and 2009. There were 13 cases of US (3.5%), and most of them (10 of 13, 76.9%) presented within 24 months of surgery. Most of the US cases (11 of 13, 84.6%) occurred at the bulbar urethra. Multivariable logistic regression analyses identified slow resection rate as the only risk factor significantly associated with US occurrence.

CONCLUSIONS: The US rate of 3.5% after PK-TURP in this study is comparable to contemporary series. A slow resection rate seems to be related to US occurrence. This should be confirmed by further studies; meanwhile, we must be mindful of this possibility when operating with the PK-TURP system.

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