Displaying publications 1 - 20 of 39 in total

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  1. Farah Diyana, A., Abdullah, A., Shahrul Hisham, Z.A., Chan, K. M.
    MyJurnal
    Antioxidants in seaweeds have attracted increasing interest for its role in protecting human health. Therefore, the aim of this study was to assess the Total phenolic content (TPC) values and antioxidant activities in red seaweeds Kappaphycus alvarezii and Kappaphycus striatum of different solvent extracts. Total phenolic content (TPC) and antioxidant activities (DPPH scavenging assay and Trolox equivalent antioxidant capacity assay, TEAC) for both K. alvarezii and K. striatum extracts were determined using different solvents at different concentrations (ethanol: 50%, 70%, 100%; acetone: 50%, 70%, 100%; methanol: 50%, 70%, 100%). The TPC value was measured using the Folin-Ciocalteu’s method. The antioxidant activities were measured by 2, 2-diphenyl-1-picrylhydrazyl (DPPH) free radical scavenging assay and Trolox Equivalent Antioxidant Capacity (TEAC) assay. The highest TPC value of K. alvarezii antioxidant extract was obtained by 50% ethanol extracts while for K. striatum obtained by 50% methanol extract. The highest percentage of DPPH free radical inhibition for K. alvarezii was shown by 50% acetone extract while K. striatum was shown using 50% methanol extract. The highest TEAC value for K. alvarezii was shown by 50% acetone while K. striatum extract was shown by 50% ethanol extract. The TPC values and antioxidant activities of all solvent extracts of K. striatum were significantly higher (p< 0.05) than K. alvarezii antioxidant extracts. The TPC values showed strong correlation (r = 0.797) with TEAC values for K. alvarezii antioxidant extract (p< 0.01). The TEAC values also showed strong correlation (r = 0.735) with percentage of DPPH free radical inhibition for K. alvarezii (p< 0.01). The TPC value, DPPH free radical scavenging assay and TEAC assay for K. striatum extracts showed strong correlation (r> 0.8) with each other (p< 0.01). In summary, K. striatum showed better antioxidant activity and higher TPC value than K. alvarezii.
  2. Ang CS, Chan KM
    Med J Malaysia, 2016 06;71(Suppl 1):42-57.
    PMID: 27801387 MyJurnal
    Coronary artery disease is the major cause of mortality and morbidity in Malaysia and worldwide. This paper reviews all research and publications on coronary artery disease in Malaysia published between 2000-2015. 508 papers were identified of which 146 papers were selected and reviewed on the basis of their relevance. The epidemiology, etiology, risk factors, prevention, assessment, treatment, and outcomes of coronary artery disease in the country are reviewed and summarized. The clinical relevance of the studies done in the country are discussed along with recommendations for future research.
  3. Kan CS, Chan KM
    Med J Malaysia, 2016 06;71(Suppl 1):70-78.
    PMID: 27801389 MyJurnal
    Lung cancer is a major cause of mortality and morbidity in Malaysia and worldwide. This paper reviews all research and publications on lung cancer in Malaysia published between 2000-2015. 89 papers were identified, of which 64 papers were selected and reviewed on the basis of their relevance to the review. The epidemiology, risk factors, cell types, clinical presentation, diagnosis, treatment, outcomes, prevention, and the social impact of lung cancer in the country are reviewed and summarized. The clinical relevance of the studies done in the country are discussed along with recommendations for future research.
  4. Anwar A, Chan KMJ, Awang Y, Ping DC
    Med J Malaysia, 2019 Oct;74(5):436-438.
    PMID: 31649223
    Anomalous Aortic Origin of a Coronary Artery (AAOCA) is a rare anomaly of the coronary artery with a considerable risk of sudden cardiac death due to ischaemia of the heart. Symptoms may include chest pain on exertion, breathlessness or dizziness. We encountered a case of a 46- year-old female who complained of exertional chest pain with a positive-stress test and subsequently diagnosed with AAOCA through CT angiography (CTA). She successfully underwent a coronary artery bypass graft (CABG) surgery using a saphenous vein graft with uneventful recovery. Right internal mammary artery (RIMA) was not used as it was flimsy and the flow was very poor.
  5. Dulguerov F, Marcacci C, Alexandrescu C, Chan KM, Dreyfus GD
    Eur J Cardiothorac Surg, 2016 Jul;50(1):61-5.
    PMID: 26792931 DOI: 10.1093/ejcts/ezv473
    OBJECTIVES: As we strongly believe that treating the mitral valve abnormalities is a key feature of hypertrophic obstructive cardiomyopathy (HOCM), we have systematically corrected both the anterior and posterior leaflet (PL) size and geometry. We have analysed our immediate results and at mid-term follow-up.

    METHODS: From March 2010 until June 2015, 16 patients with HOCM underwent surgical correction of obstruction. The mean age was 51 years old (range, 32-72 years). All were symptomatic being New York Heart Association (NYHA) class 3 (n = 4) or 4 (n = 12). All had systolic anterior motion at echocardiogram with severe mitral regurgitation (MR). Intraventricular gradient preoperatively was 73.5 mmHg (range, 50-120 mmHg). All patients underwent a double-stage procedure: first septal resection through (i) the aortic valve and (ii) the detached anterior leaflet (AL) of the mitral valve and at second, mitral valve repair by (i) reducing PL height (leaflet resection or artificial neochordae) (ii) increasing AL height with pericardial patch.

    RESULTS: There was no in-hospital or late death. All patients were Class 1 NYHA at latest follow-up. Control echocardiography showed no MR, mean rest intraventricular gradient was 15 mmHg (range, 9-18 mmHg).

    CONCLUSIONS: Our good mid-term results support the concept that HOCM is not only a septal disease and that the mitral valve pathology is a key component that should be addressed. For most patients, the ideal surgical treatment should consist in a two-step procedure. It is even necessary to be studied whether treating the mitral valve alone could not suffice.

  6. Dreyfus GD, Martin RP, Chan KM, Dulguerov F, Alexandrescu C
    J Am Coll Cardiol, 2015 Jun 2;65(21):2331-6.
    PMID: 26022823 DOI: 10.1016/j.jacc.2015.04.011
    The assessment of the etiology and severity of functional tricuspid regurgitation (FTR) has many limitations, especially when tricuspid regurgitation (TR) is more than severe. Instead of relying solely on TR severity, a new approach not only takes into account the severity of TR, but also pays strict attention to tricuspid annular dilation (size), the mode of tricuspid leaflet coaptation, and tricuspid leaflet tethering-factors often influenced by right ventricular enlargement and dysfunction. To simplify things, we propose a new staging system for functional tricuspid valve pathology using 3 parameters that may more accurately reflect the severity of the disease: TR severity, annular dilation, and mode of leaflet coaptation (extent of tethering). We believe that by utilizing these parameters, cardiologists and cardiac surgeons will be offered a better system for appraisal and decision-making in FTR.
  7. Khoo PLZ, Poon JS, Tan GJS, Yahya A, Chan KMJ
    Med J Malaysia, 2020 11;75(6):722-730.
    PMID: 33219184
    INTRODUCTION: Heart valve disease comprises a cluster of conditions affecting the aortic, mitral, pulmonary and tricuspid valves. This paper reviews all the research on heart valve disease in Malaysia published between the years 2000- 2016.

    METHODS: The methodology was based on the search process described in the paper, "Bibliography of clinical research in Malaysia: methods and brief results". The search databases included PubMed, Scopus and several Malaysian journals such as MyJurnal and UKM Journal Repository, by using the following keywords: (heart valve disease OR infective endocarditis OR rheumatic heart disease) and (Malaysia).

    RESULTS: In all 94 papers were identified of which 39 papers were selected and reviewed on the basis of their relevance. The local studies contributed to the knowledge and understanding of the epidemiology, aetiology, pathophysiology, clinical presentations, investigations, treatment, and outcomes of heart valve disease in the country.

    DISCUSSION: The clinical relevance of the studies performed in the country is discussed along with recommendations for future research.

  8. Tan GJS, Khoo PLZ, Sailesh MK, Chan KMJ
    Med J Malaysia, 2019 02;74(1):67-78.
    PMID: 30846666
    INTRODUCTION: Aortic disease includes conditions such as chronic aortic aneurysms, acute aortic syndromes and congenital aortic abnormalities, amongst others. This paper reviews all research on aortic disease performed in Malaysia and published between 2000-2016.

    METHODS: A literature search was conducted in PubMed, Scopus, MyJurnal and the UKM Journal Repository. The search process was based on a previously published methodology. The medical subject headings (MeSH) search terms used were "aortic", "aorta" and "Malaysia".

    RESULTS: Two-hundred-thirteen papers were identified, of which 60 papers were selected and reviewed on the basis of their relevance. The epidemiology, pathophysiology, clinical presentations, case reports, investigations, treatment and outcomes of aortic disease in Malaysia were reviewed and summarised. The clinical relevance of the studies performed are discussed.

    CONCLUSION: The review provided an insight into the pathophysiology, prevalence and epidemiology of aortic diseases in Malaysia, how the condition is managed, and the outcomes of treatment. Limitations of the research performed in Malaysia to date were identified and recommendations for further research and improvement in clinical practice were recommended.

  9. Inayat-Hussain SH, Ibrahim HA, Siew EL, Rajab NF, Chan KM, G T Williams, et al.
    Chem Biol Interact, 2010 Mar 19;184(1-2):310-2.
    PMID: 20025857 DOI: 10.1016/j.cbi.2009.12.009
  10. Chan KM, Rajab NF, Ishak MH, Ali AM, Yusoff K, Din LB, et al.
    Chem Biol Interact, 2006 Feb 1;159(2):129-40.
    PMID: 16297902
    Restenosis represents a major impediment to the success of coronary angioplasty. Abnormal proliferation of vascular smooth muscle cells (VSMCs) has been shown to be an important process in the pathogenesis of restenosis. A number of agents, particularly rapamycin and paclitaxel, have been shown to impact on this process. This study was carried out to determine the mechanisms of cytotoxicity of goniothalamin (GN) on VSMCs. Results from MTT cytotoxicity assay showed that the IC(50) for GN was 4.4 microg/ml (22 microM), which was lower compared to the clinically used rapamycin (IC(50) of 25 microg/ml [27.346 microM]). This was achieved primarily via apoptosis where up to 25.83 +/- 0.44% of apoptotic cells were detected after 72 h treatment with GN. In addition, GN demonstrated similar effects as rapamycin in inhibiting VSMCs proliferation using bromodeoxyuridine (BrdU) cell proliferation assay after 72 h treatment at IC(50) concentration (p > 0.05). In order to understand the mechanisms of GN, DNA damage detection using comet assay was determined at 2h post-treatment with GN. Our results showed that there was a concentration-dependent increase in DNA damage in VSMCs prior to cytotoxicity. Moreover, GN effects were comparable to rapamycin. In conclusion, our data show that GN initially induces DNA damage which subsequently leads to cytotoxicity primarily via apoptosis in VSMCs.
  11. Mustafa NM, Jumaah FN, Ludin NA, Akhtaruzzaman M, Hassan NH, Ahmad A, et al.
    Heliyon, 2024 Apr 15;10(7):e27381.
    PMID: 38560257 DOI: 10.1016/j.heliyon.2024.e27381
    Tetraalkylammonium salt (TAS) is an organic salt widely employed as a precursor, additive or electrolyte in solar cell applications, such as perovskite or dye-sensitized solar cells. Notably, Perovskite solar cells (PSCs) have garnered acclaim for their exceptional efficiency. However, PSCs have been associated with environmental and health concerns due to the presence of lead (Pb) content, the use of hazardous solvents, and the incorporation of TAS in their fabrication processes, which significantly contributes to environmental and human health toxicity. As a response, there is a growing trend towards transitioning to safer and biobased materials in PSC fabrication to address these concerns. However, the potential health hazards associated with TAS necessitate a thorough evaluation, considering the widespread use of this substance. Nevertheless, the overexploitation of TAS could potentially increase the disposal of TAS in the ecosystem, thus, posing a major health risk and severe pollution. Therefore, this review article presents a comprehensive discussion on the in vitro and in vivo toxicity assays of TAS as a potential material in solar energy applications, including cytotoxicity, genotoxicity, in vivo dermal, and systemic toxicity. In addition, this review emphasizes the toxicity of TAS compounds, particularly the linear tetraalkyl chain structures, and summarizes essential findings from past studies as a point of reference for the development of non-toxic and environmentally friendly TAS derivatives in future studies. The effects of the TAS alkyl chain length, polar head and hydrophobicity, cation and anion, and other properties are also included in this review.
  12. Siew EL, Chan KM, Williams GT, Ross D, Inayat-Hussain SH
    Free Radic Biol Med, 2012 Oct 15;53(8):1616-24.
    PMID: 22687461 DOI: 10.1016/j.freeradbiomed.2012.05.046
    The Fau gene (Finkel-Biskis-Reilly murine sarcoma virus (FBR-MuSV)-associated ubiquitously expressed gene) was identified as a potential tumor suppressor gene using a forward genetics approach. Downregulation of Fau by overexpression of its reverse sequence has been shown to inhibit apoptosis induced by DNA-damaging agents. To address a potential role of Fau in benzene toxicity, we investigated the apoptotic effects of hydroquinone (HQ), a major benzene metabolite, in W7.2 mouse thymoma cells transfected with either a plasmid construct expressing the antisense sequence of Fau (rfau) or the empty vector (pcDNA3.1) as a control. HQ induced apoptosis via increased production of reactive oxygen species and DNA damage, measured using dihydroethidine (HE) staining and alkaline Comet assay, respectively, in W7.2 pcDNA3.1 cells. In contrast, when Fau was downregulated by the antisense sequence in W7.2 rfau cells, HQ treatment did not cause DNA damage and oxidative stress and these cells were markedly more resistant to HQ-induced apoptosis. Further investigation revealed that there was an upregulation of NAD(P)H: quinone oxidoreductase 1 (NQO1), a detoxification enzyme for benzene-derived quinones, in W7.2 rfau cells. Compromising cellular NQO1 by use of a specific mechanism-based inhibitor (MAC 220) and NQO1 siRNA resensitized W7.2 rfau cells to HQ-induced apoptosis. Silencing of Fau in W7.2 wild-type cells resulted in increased levels of NQO1, confirming that downregulation of Fau results in NQO1 upregulation which protects against HQ-induced apoptosis.
  13. Inayat-Hussain SH, Chan KM, Rajab NF, Din LB, Chow SC, Kizilors A, et al.
    Toxicol Lett, 2010 Mar 1;193(1):108-14.
    PMID: 20026395 DOI: 10.1016/j.toxlet.2009.12.010
    Goniothalamin (GTN) isolated from Goniothalamus sp. has been demonstrated to induce apoptosis in a variety of cancer cell lines including Jurkat T leukemia cells. However, the mechanism of GTN-induced apoptosis upstream of mitochondria is still poorly defined. In this study, GTN caused a decrease in GSH with an elevation of reactive oxygen species as early as 30 min and DNA damage as assessed by Comet assay. Analysis using topoisomerase II processing of supercoiled pBR 322 DNA showed that GTN caused DNA damage via a topoisomerase II-independent pathway suggesting that cellular oxidative stress may contribute to genotoxicity. A 12-fold increase of caspase-2 activity was observed in GTN-treated Jurkat cells after 4h treatment and this was confirmed using Western blotting. Although the caspase-2 inhibitor Z-VDVAD-FMK inhibited the proteolytic activity of caspase-2, apoptosis ensued confirming that caspase-2 activity was not crucial for GTN-induced apoptosis. However, GTN-induced apoptosis was completely abrogated by N-acetylcysteine further confirming the role of oxidative stress. Since cytochrome c release was observed as early as 1h without any appreciable change in Bcl-2 protein expression, we further investigated whether overexpression of Bcl-2 confers resistance in GTN-induced cytotoxicity. Using a panel of Jurkat Bcl-2 transfectants, GTN cytotoxicity was not abrogated in these cells. In conclusion, GTN induces DNA damage and oxidative stress resulting in apoptosis which is independent of both caspase-2 and Bcl-2.
  14. Inayat-Hussain SH, Wong LT, Chan KM, Rajab NF, Din LB, Harun R, et al.
    Toxicol Lett, 2009 Dec 15;191(2-3):118-22.
    PMID: 19698770 DOI: 10.1016/j.toxlet.2009.08.012
    Goniothalamin, a styryllactone, has been shown to induce cytotoxicity via apoptosis in several tumor cell lines. In this study, we have examined the potential role of several genes, which were stably transfected into T-cell lines and which regulate apoptosis in different ways, on goniothalamin-induced cell death. Overexpression of full-length receptor for activated protein C-kinase 1 (RACK-1) and pc3n3, which up-regulates endogenous RACK-1, in both Jurkat and W7.2 T cells resulted in inhibition of goniothalamin-induced cell death as assessed by MTT and clonogenic assays. However, overexpression of rFau (antisense sequence to Finkel-Biskis-Reilly murine sarcoma virus-associated ubiquitously expressed gene) in W7.2 cells did not confer resistance to goniothalamin-induced cell death. Etoposide, a clinically used cytotoxic agent, was equipotent in causing cytotoxicity in all the stable transfectants. Assessment of DNA damage by Comet assay revealed goniothalamin-induced DNA strand breaks as early as 1 h in vector control but this effect was inhibited in RACK-1 and pc3n3 stably transfected W7.2 cells. This data demonstrate that RACK-1 plays a crucial role in regulating cell death signalling pathways induced by goniothalamin.
  15. Khachatryan V, Sirunyan AM, Tumasyan A, Adam W, Bergauer T, Dragicevic M, et al.
    Phys Rev Lett, 2015 Feb 13;114(6):061801.
    PMID: 25723204
    A search for new long-lived particles decaying to leptons is presented using proton-proton collisions produced by the LHC at √[s]=8  TeV. Data used for the analysis were collected by the CMS detector and correspond to an integrated luminosity of 19.7  fb(-1). Events are selected with an electron and muon with opposite charges that both have transverse impact parameter values between 0.02 and 2 cm. The search has been designed to be sensitive to a wide range of models with nonprompt e-μ final states. Limits are set on the "displaced supersymmetry" model, with pair production of top squarks decaying into an e-μ final state via R-parity-violating interactions. The results are the most restrictive to date on this model, with the most stringent limit being obtained for a top squark lifetime corresponding to cτ=2  cm, excluding masses below 790 GeV at 95% confidence level.
  16. Khachatryan V, Sirunyan AM, Tumasyan A, Adam W, Bergauer T, Dragicevic M, et al.
    Phys Rev Lett, 2015 Feb 6;114(5):051801.
    PMID: 25699433
    A study of vector boson scattering in pp collisions at a center-of-mass energy of 8 TeV is presented. The data sample corresponds to an integrated luminosity of 19.4  fb(-1) collected with the CMS detector. Candidate events are selected with exactly two leptons of the same charge, two jets with large rapidity separation and high dijet mass, and moderate missing transverse energy. The signal region is expected to be dominated by electroweak same-sign W-boson pair production. The observation agrees with the standard model prediction. The observed significance is 2.0 standard deviations, where a significance of 3.1 standard deviations is expected based on the standard model. Cross section measurements for W(±)W(±) and WZ processes in the fiducial region are reported. Bounds on the structure of quartic vector-boson interactions are given in the framework of dimension-eight effective field theory operators, as well as limits on the production of doubly charged Higgs bosons.
  17. Chatrchyan S, Khachatryan V, Sirunyan AM, Tumasyan A, Adam W, Bergauer T, et al.
    Phys Rev Lett, 2014 Apr 25;112(16):161802.
    PMID: 24815637
    Results are presented of a search for a "natural" supersymmetry scenario with gauge mediated symmetry breaking. It is assumed that only the supersymmetric partners of the top quark (the top squark) and the Higgs boson (Higgsino) are accessible. Events are examined in which there are two photons forming a Higgs boson candidate, and at least two b-quark jets. In 19.7  fb-1 of proton-proton collision data at s=8  TeV, recorded in the CMS experiment, no evidence of a signal is found and lower limits at the 95% confidence level are set, excluding the top squark mass below 360 to 410 GeV, depending on the Higgsino mass.
  18. CMS Collaboration, Khachatryan V, Sirunyan AM, Tumasyan A, Adam W, Bergauer T, et al.
    Eur Phys J C Part Fields, 2014 09 26;74(9):3036.
    PMID: 25814912
    Searches for the direct electroweak production of supersymmetric charginos, neutralinos, and sleptons in a variety of signatures with leptons and [Formula: see text], [Formula: see text], and Higgs bosons are presented. Results are based on a sample of proton-proton collision data collected at center-of-mass energy [Formula: see text] with the CMS detector in 2012, corresponding to an integrated luminosity of 19.5 [Formula: see text]. The observed event rates are in agreement with expectations from the standard model. These results probe charginos and neutralinos with masses up to 720 [Formula: see text], and sleptons up to 260 [Formula: see text], depending on the model details.
  19. Khachatryan V, Sirunyan AM, Tumasyan A, Adam W, Bergauer T, Dragicevic M, et al.
    Phys Rev Lett, 2015 Mar 13;114(10):101801.
    PMID: 25815923
    Results are presented from a search for new decaying massive particles whose presence is inferred from an imbalance in transverse momentum and which are produced in association with a single top quark that decays into a bottom quark and two light quarks. The measurement is performed using 19.7  fb^{-1} of data from proton-proton collisions at a center-of-mass energy of 8 TeV, collected with the CMS detector at the CERN LHC. No deviations from the standard model predictions are observed and lower limits are set on the masses of new invisible bosons. In particular, scalar and vector particles, with masses below 330 and 650 GeV, respectively, are excluded at 95% confidence level, thereby substantially extending a previous limit published by the CDF Collaboration.
  20. Khachatryan V, Sirunyan AM, Tumasyan A, Adam W, Bergauer T, Dragicevic M, et al.
    Eur Phys J C Part Fields, 2015 06 09;75(6):251.
    PMID: 26097407
    A search for a standard model Higgs boson produced in association with a top-quark pair and decaying to bottom quarks is presented. Events with hadronic jets and one or two oppositely charged leptons are selected from a data sample corresponding to an integrated luminosity of 19.5[Formula: see text] collected by the CMS experiment at the LHC in [Formula: see text] collisions at a centre-of-mass energy of 8[Formula: see text]. In order to separate the signal from the larger [Formula: see text]  + jets background, this analysis uses a matrix element method that assigns a probability density value to each reconstructed event under signal or background hypotheses. The ratio between the two values is used in a maximum likelihood fit to extract the signal yield. The results are presented in terms of the measured signal strength modifier, [Formula: see text], relative to the standard model prediction for a Higgs boson mass of 125[Formula: see text]. The observed (expected) exclusion limit at a 95 % confidence level is [Formula: see text] (3.3), corresponding to a best fit value [Formula: see text].
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