Displaying publications 21 - 40 of 137 in total

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  1. Yap PS, Lim SH, Hu CP, Yiap BC
    Phytomedicine, 2013 Jun 15;20(8-9):710-3.
    PMID: 23537749 DOI: 10.1016/j.phymed.2013.02.013
    In this study we investigated the relationship between several selected commercially available essential oils and beta-lactam antibiotics on their antibacterial effect against multidrug resistant bacteria. The antibacterial activity of essential oils and antibiotics was assessed using broth microdilution. The combined effects between essential oils of cinnamon bark, lavender, marjoram, tea tree, peppermint and ampicillin, piperacillin, cefazolin, cefuroxime, carbenicillin, ceftazidime, meropenem, were evaluated by means of the checkerboard method against beta-lactamase-producing Escherichia coli. In the latter assays, fractional inhibitory concentration (FIC) values were calculated to characterize interaction between the combinations. Substantial susceptibility of the bacteria toward natural antibiotics and a considerable reduction in the minimum inhibitory concentrations (MIC) of the antibiotics were noted in some paired combinations of antibiotics and essential oils. Out of 35 antibiotic-essential oil pairs tested, four of them showed synergistic effect (FIC≤0.5) and 31 pairs showed no interaction (FIC>0.5-4.0). The preliminary results obtained highlighted the occurrence of a pronounced synergistic relationship between piperacillin/cinnamon bark oil, piperacillin/lavender oil, piperacillin/peppermint oil as well as meropenem/peppermint oil against two of the three bacteria under study with a FIC index in the range 0.26-0.5. The finding highlighted the potential of peppermint, cinnamon bark and lavender essential oils being as antibiotic resistance modifying agent. Reduced usage of antibiotics could be employed as a treatment strategy to decrease the adverse effects and possibly to reverse the beta-lactam antibiotic resistance.
  2. Lim SH, Guadamuz TE, Wei C, Chan R, Koe S
    AIDS Behav, 2012 Oct;16(7):1979-87.
    PMID: 22714116
    We examined socio-demographic and behavioral characteristics of men who have sex with men (MSM) residing in Asia and correlates of unprotected receptive intercourse with Internet ejaculation (URAIE). Asia Internet MSM Sex Survey, a behavioral survey of MSM in Asia was conducted from 1 January to 28 February 2010. Data analysis was limited to participants aged 18 or above, biological male, and had one regular or casual sex partner in the past 6 months (n = 10,413). Pearson's Chi-square test, t test and logistic regression were used to examine the correlates of URAIE in the past 6 months, the highest risk sexual behavior sampled. Of 7311 participants who had receptive anal intercourse, 47.5 % had URAIE, which was associated with the following attributes: less than high-school education and pre-college education compared to university (AOR = 1.53, 95 % CI: 1.28, 1.83; AOR = 1.22, CI: 1.08, 1.37), being in the heterosexual marriage (AOR = 1.35, CI: 1.18, 1.56), having regular partners or both regular and casual partners compared to having casual partners (AOR = 2.85, CI: 2.48, 3.27; AOR = 2.32, CI: 2.06, 2.62), HIV-positive compared to HIV-negative status (AOR = 1.39, 95 % CI: 1.08, 1.81), higher perception of HIV risk (AOR = 1.62, CI: 1.34, 1.95), use of recreational drug before sex (AOR = 1.30, CI: 1.14, 1.49), and use of the Internet as the main way to seek sex partners (AOR = 1.21, CI: 1.08, 1.36). MSM from certain Asian countries reported alarming rates of URAIE. The internet can be used as a platform for HIV surveillance and intervention.
  3. Lim SH, Tan SJ, Low YY, Kam TS
    J Nat Prod, 2011 Dec 27;74(12):2556-62.
    PMID: 22148233 DOI: 10.1021/np200730j
    Four new linearly fused bisindole alkaloids, lumutinines A-D (1-4), were isolated from the stem-bark extract of Alstonia macrophylla. Lumutinines A (1) and B (2) represent the first examples of linear, ring A/F-fused macroline-macroline-type bisindoles, while lumutinines C (3) and D (4) were constituted from the union of macroline and sarpagine moieties. A reinvestigation of the stereochemical assignment of alstoumerine (8) by NMR and X-ray diffraction analyses indicated that the configuration at C-16 and C-19 required revision.
  4. Lim SH, Wu L, Burgess K, Lee HB
    Anticancer Drugs, 2009 Jul;20(6):461-8.
    PMID: 19387338 DOI: 10.1097/CAD.0b013e32832b7bee
    Conventional cytotoxic anticancer drugs that target all rapidly dividing cells are nonselective in their mechanism of action, because they disrupt essential components that are crucial to both malignant and proliferating normal cells. Instead, targeting cellular functions that are distinctly different between normal and cancer cells may provide a basis for selective killing of tumor cells. One such strategy that is still largely unexplored is to utilize the relatively higher negative mitochondrial membrane potential in carcinoma cells compared with adjacent normal epithelial cells to enhance accumulation and retention of cytotoxic lipophilic cations in the former. In this study, the anticancer activities of a new class of rosamines with cyclic amine substituents and their structure-activity relationships were investigated. From an in-vitro cell growth inhibition assay, 14 of the rosamines inhibited the growth of human leukemia HL-60 cells by 50% at micromolar or lower concentrations. Derivatives containing hydrophilic substituents had less potent activity, whereas aryl substitution at the meso position conferred extra activity with thiofuran and para-iodo aryl substitutions being the most potent. In addition, both compounds were at least 10-fold more cytotoxic than rhodamine 123 against a panel of cell lines of different tissue origin and similar to rhodamine 123, exhibited more cytotoxicity against cancer cells compared with immortalized normal epithelial cells of the same organ type. In subsequent experiments, the para-iodo aryl substituted rosamine was found to localize exclusively within the mitochondria and induced apoptosis as the major mode of cell death. Our results suggest that these compounds offer potential for the design of mitochondria-targeting agents that either directly kill or deliver cytotoxic drugs to selectively kill cancer cells.
  5. Lim SH, Mahmood K, Komiyama K, Kam TS
    J Nat Prod, 2008 Jun;71(6):1104-6.
    PMID: 18462006 DOI: 10.1021/np800123g
    A new cycloartane, monocarpinine (1), incorporating a fused tetrahydrofuranyl ring, and a cytotoxic tetracyclic lactam, monomarginine (2), were isolated from a stem bark extract of the Malayan species Monocarpia marginalis. The structures of these compounds were determined using NMR and MS analysis. Monomarginine (2) showed appreciable cytotoxicity toward human KB (both drug-sensitive and drug-resistant) and Jurkat cells.
  6. Yang C, Guadamuz TE, Lim SH, Koe S, Wei C
    LGBT Health, 2016 Apr;3(2):168-74.
    PMID: 26789393 DOI: 10.1089/lgbt.2014.0041
    We explored factors associated with alcohol use before or during sex among a sample of 10,861 men who have sex with men (MSM) in Asia who were recruited online for the study. Multinomial logistic regression analysis indicated that having sex under the influence of alcohol was associated with having multiple male partners, seeking partners primarily through gay bar/gym/dance party/friends, selling sex and using multiple drugs during the past 6 months, and unprotected anal sex. More efforts are needed to better assess alcohol use and misuse among MSM in Asia and understand contextual influences on alcohol use and HIV-related behaviors in order to implement culturally-specific interventions.
  7. Teo KP, Jacob SCM, Lim SH
    Med J Malaysia, 1997 Dec;52(4):325-30.
    PMID: 10968108
    We reviewed all documented cases of septicaemia following caesarean deliveries in Kandang Kerbau Hospital between 1st January 1993 to 31st December 1995. There were 22 cases of septicaemia among 8201 caesarean births, and hence the incidence is 2.7:1000. There were 45,412 deliveries, and the overall caesarean section rate was 18.1%. Among the 22 documented cases of septicaemia which came under this study, the most common clinical conditions found were endomyometritis (7 cases), urinary tract infection (6 cases), and wound infection (3 cases). One of the three cases with wound infection also had pneumonia. There was one patient who had mild transient myocarditis. We could not determine with certainty any site of infection in five patients. The most common bloodstream bacterial isolates was Staphylococcus aureus (16), while the uncommon ones were Acinetobacter baumanii (2), Escherichia coli (1), Klebsiella sp. (1), Staphylococcus epidermidis (1), Streptococcus Group F (1), Peptostreptococcus species and Veillonella species (1). There was no mortality and prompt, vigorous treatment had led to uneventful recovery in all the cases.
  8. Lim SH, Jahanshiri F, Rahim RA, Sekawi Z, Yusoff K
    Lett Appl Microbiol, 2010 Dec;51(6):658-64.
    PMID: 20973806 DOI: 10.1111/j.1472-765X.2010.02950.x
    A system for displaying heterologous respiratory syncytial virus (RSV) glycoproteins on the surface of Lactococcus lactis NZ9000 was developed.
  9. Ching SZ, Wong LP, Said MAB, Lim SH
    AIDS Educ Prev, 2020 10;32(5):416-431.
    PMID: 33112675 DOI: 10.1521/aeap.2020.32.5.416
    The aim of the study was to consolidate evidence on barriers and facilitators to PrEP adherence among men who have sex with men. PubMed, Science Direct, and EBSCO host were utilized to search for relevant articles. Six articles from PubMed, published between 2010 and 2018, were reviewed. Thematic analysis was employed to synthesize findings. At the individual level, HIV susceptibility, knowledge of PrEP, and individual lifestyle affected PrEP adherence. At the organizational level, cost of PrEP and quality of PrEP services influenced adherence to PrEP. At the societal level, social stigma, financial assistance or medical insurance, and family and peer support were determinants of PrEP adherence. Facilitators included perceived high risk of HIV infection and payment assistance, while barriers included social stigma and high cost of PrEP. Social stigma and structural level factors such as payment assistance and cost of PrEP need to be examined to ensure optimal adherence to PrEP.
  10. Lew SY, Lim SH, Lim LW, Wong KH
    BMC Complement Med Ther, 2020 Nov 11;20(1):340.
    PMID: 33176761 DOI: 10.1186/s12906-020-03132-x
    BACKGROUND: Hericium erinaceus is a culinary and medicinal mushroom in Traditional Chinese Medicines. It has numerous pharmacological effects including immunomodulatory, anti-tumour, anti-microbial, anti-aging and stimulation of nerve growth factor (NGF) synthesis, but little is known about its potential role in negating the detrimental effects of oxidative stress in depression. The present study investigated the neuroprotective effects of H. erinaceus standardised aqueous extract (HESAE) against high-dose corticosterone-induced oxidative stress in rat pheochromocytoma (PC-12) cells, a cellular model mimicking depression.

    METHODS: PC-12 cells was pre-treated with HESAE for 48 h followed by 400 μM corticosterone for 24 h to induce oxidative stress. Cells in complete medium without any treatment or pre-treated with 3.125 μg/mL desipramine served as the negative and positive controls, respectively. The cell viability, lactate dehydrogenase (LDH) release, endogenous antioxidant enzyme activities, aconitase activity, mitochondrial membrane potentials (MMPs), intracellular reactive oxygen species (ROS) levels and number of apoptotic nuclei were quantified. In addition, HESAE ethanol extract was separated into fractions by chromatographic methods prior to spectroscopic analysis.

    RESULTS: We observed that PC-12 cells treated with high-dose corticosterone at 400 μM had decreased cell viability, reduced endogenous antioxidant enzyme activities, disrupted mitochondrial function, and increased oxidative stress and apoptosis. However, pre-treatment with HESAE ranging from 0.25 to 1 mg/mL had increased cell viability, decreased LDH release, enhanced endogenous antioxidant enzyme activities, restored MMP, attenuated intracellular ROS and protected from ROS-mediated apoptosis. The neuroprotective effects could be attributed to significant amounts of adenosine and herierin III isolated from HESAE.

    CONCLUSIONS: HESAE demonstrated neuroprotective effects against high-dose corticosterone-induced oxidative stress in an in vitro model mimicking depression. HESAE could be a potential dietary supplement to treat depression.

  11. Ong LY, Pang T, Lim SH, Tan EL, Puthucheary SD
    J Med Microbiol, 1989 Jul;29(3):195-8.
    PMID: 2473209
    A simple adherence test to detect IgM antibodies in patients with typhoid is described. The test utilises the IgM-"capture" approach, in which the test serum is applied to microtitration plate wells previously coated with anti-human IgM, followed by application of a stained Salmonella typhi antigen suspension which shows adherence in positive cases. By this test, 58 (95%) of 61 sera from confirmed cases of typhoid possessed IgM antibodies to the H or O or both antigens of S. typhi. In patients for whom a diagnosis of typhoid was based only on a significant Widal-test titre, 31 (41%) of 76 sera had IgM antibodies to the H or O or both antigens of S. typhi. Some cross-reactivity of the IgM antibodies was detected, especially with the O antigens of S. paratyphi A and B. A total of 82 sera from non-typhoidal fevers (leptospirosis, typhus, dengue fever) showed no reactivity in this test. In normal sera there was no detectable IgM to the O antigen of S. typhi and only a small number (3.9%) had low levels of IgM to the H antigen. The significance and potential importance of this simple, sensitive, specific and economical test is discussed.
  12. Chong SCS, Hollingshead BM, Lim SH, Bourne A
    Glob Public Health, 2021 07;16(7):1014-1027.
    PMID: 32985388 DOI: 10.1080/17441692.2020.1822901
    The Malaysian government has committed to 'Fast Tracking the HIV Response' to achieve UNAIDS 2030 targets to end AIDS. The epidemic is concentrated among key populations and has shifted from people who inject drugs to HIV infection through sexual transmission among men who have sex with men, sex workers and transgender people. The aim of this scoping review was to examine social and behavioural research published since 2005 that can inform understanding of each stage of the 90:90:90 treatment cascade (as proposed by UNAIDS), including HIV risk behaviours and testing practices that precede entry. We found a concentration of studies related to predictors or correlates of HIV infections (mostly among men who have sex with men) and a shortfall in literature pertaining to sex workers or transgender people. While several studies examined factors associated with HIV testing, only one examined uptake of antiretroviral therapy and two explored issues of treatment adherence. No study examined broader care and support of people living with HIV. To scale-up effective programmes and apprise investment to achieve the ambitious targets set-out in the Malaysian National HIV/AIDS Strategic Plan, a combination of comprehensive strategic information and evidence generated through primary research is critical.
  13. Lim SH, Tunku Ahmad TS, Devarajooh C, Gunasagaran J
    J Orthop Surg (Hong Kong), 2022 2 2;30(1):23094990221075376.
    PMID: 35103531 DOI: 10.1177/23094990221075376
    BACKGROUND: Upper limb infections are common among patients with diabetes mellitus and their sequelae can be debilitating. They tend to present with severe infections but minimal symptoms probably due to neuropathy and vasculopathy among diabetics. The study aims to compare the demographic characteristics, clinical presentations and outcomes of upper limb infections between diabetic and non-diabetic patients.

    METHODS: All patients with upper limb infections who were admitted in a tertiary hospital from June 2017 to December 2020 were included in this study. Demographic data, clinical presentations, investigations and outcomes were obtained retrospectively from electronic medical record. There were 117 patients with diabetes mellitus and 127 with no diabetes mellitus. Comparisons were made between these two groups, and statistical analysis was done with SPSS.

    RESULTS: There were 244 patients included; 117 were diabetic and 127 were non-diabetic. Diabetic patients were more likely to present with emergent scenarios, especially necrotizing fasciitis and infective tenosynovitis (p < .05) with higher erythrocyte sedimentation rate (ESR) and C-reactive protein (CRP) readings (p < .05). Their microbiological cultures were less likely to be negative (p < .05). Diabetic patients also had poorer clinical outcomes with higher risk of amputation, re-operation and longer duration of hospital stay (p < .05).

    CONCLUSION: Upper limb infections among diabetic patients should be treated aggressively. Early diagnosis and surgical intervention might decrease the morbidity and mortality in this group. Prevention of infections should be emphasized.

  14. Lim SH, Lee HB, Ho AS
    Photochem Photobiol, 2011 Sep-Oct;87(5):1152-8.
    PMID: 21534974 DOI: 10.1111/j.1751-1097.2011.00939.x
    In our screening for photosensitizers from natural resources, 15(1)-hydroxypurpurin-7-lactone ethyl methyl diester (compound 1) was isolated for the first time from an Araceae plant. To evaluate the efficacy of compound 1 as a photosensitizer for head and neck cancers, compound 1 was studied in reference to a known photosensitizer pheophorbide-a (Pha), in terms of photophysical properties, singlet oxygen generation and in in vitro experiments (intracellular uptake and phototoxicity assays) in two oral (HSC2 and HSC3) and two nasopharyngeal (HK1 and C666-1) cancer cell lines. In this study, compound 1 exhibited higher intracellular uptake over 24 h compared with Pha in both HSC3 and HK1 cells. When activated by ≥4.8 J cm(-2) of light, compound 1 was slightly more potent as a photosensitizer than Pha by consistently having marginally lower IC(50) values across different cell lines. In flow cytometry experiments to study the mechanism of photoactivated cell death in HSC3, compound 1 was observed to induce more pronounced apoptosis compared with Pha, which may have been driven by the transient G(2)/M cell cycle block which was also observed. These promising results on compound 1 warrant its further investigation as a clinically useful photodynamic therapy agent for head and neck cancer.
  15. Yap WS, Gan CY, Sim KS, Lim SH, Low YY, Kam TS
    J Nat Prod, 2016 Jan 22;79(1):230-9.
    PMID: 26717050 DOI: 10.1021/acs.jnatprod.5b00992
    Eleven new indole alkaloids (1-11) comprising seven aspidofractinine and four eburnane alkaloids, were isolated from the stem-bark extract of Kopsia pauciflora occurring in Malaysian Borneo. The aspidofractinine alkaloids include a ring-contracted, an additional ring-fused, a paucidactine regioisomer, two paucidactine, and one kopsine alkaloid. The structures of several of these alkaloids were also confirmed by X-ray diffraction analyses. The bisindole alkaloids isolated, norpleiomutine and kopsoffinol, showed in vitro growth inhibitory activity against human PC-3, HCT-116, MCF-7, and A549 cells and moderate effects in reversing multidrug-resistance in vincristine-resistant human KB cells.
  16. Gan CY, Yoganathan K, Sim KS, Low YY, Lim SH, Kam TS
    Phytochemistry, 2014 Dec;108:234-42.
    PMID: 25442910 DOI: 10.1016/j.phytochem.2014.09.014
    Eleven indole alkaloids, comprising four corynanthean, two eburnane, one aspidofractinine, one secoleuconoxine, one andranginine, and two pauciflorine type alkaloids were isolated from the stem-bark and leaf extracts of Kopsia pauciflora. Their structures were determined using NMR and MS analyses. The catharinensine type alkaloid kopsirensine B and the secoleuconoxine alkaloid arboloscine A showed moderate to weak activity in reversing MDR in vincristine-resistant KB cells. The alkaloid content was markedly different compared to that of a sample from Malaysian Borneo.
  17. Yap IK, Kho MT, Lim SH, Ismail NH, Yam WK, Chong CW
    Mol Biosyst, 2015 Jan;11(1):297-306.
    PMID: 25382376 DOI: 10.1039/c4mb00463a
    Understanding the basal gut bacterial community structure and the host metabolic composition is pivotal for the interpretation of laboratory treatments designed to answer questions pertinent to host-microbe interactions. In this study, we report for the first time the underlying gut microbiota and systemic metabolic composition in BALB/c mice during the acclimatisation period. Our results showed that stress levels were reduced in the first three days of the study when the animals were subjected to repetitive handling daily but the stress levels were increased when handling was carried out at lower frequencies (weekly). We also observed a strong influence of stress on the host metabolism and commensal compositional variability. In addition, temporal biological compartmental variations in the responses were observed. Based on these results, we suggest that consistency in the frequency and duration of laboratory handling is crucial in murine models to minimise the impact of stress levels on the commensal and host metabolism dynamics. Furthermore, caution is advised in consideration of the temporal delay effect when integrating metagenomics and metabonomics data across different biological matrices (i.e. faeces and urine).
  18. Tan SJ, Lim JL, Low YY, Sim KS, Lim SH, Kam TS
    J Nat Prod, 2014 Sep 26;77(9):2068-80.
    PMID: 25211145 DOI: 10.1021/np500439u
    A total of 20 new indole alkaloids comprising mainly oxidized derivatives of macroline- (including alstofonidine, a macroline indole incorporating a butyrolactone ring-F), pleiocarpamine-, and sarpagine-type alkaloids were isolated from the bark and leaf extracts of Alstonia angustifolia. The structures and relative configurations of these alkaloids were determined using NMR and MS analyses and in some instances confirmed by X-ray diffraction analyses. Alkaloids 3, 7, 35, and 41 showed moderate to weak activity, while 21 showed strong activity in reversing multidrug resistance in vincristine-resistant KB cells.
  19. Lim SH, Wu L, Kiew LV, Chung LY, Burgess K, Lee HB
    PLoS One, 2014;9(3):e82934.
    PMID: 24622277 DOI: 10.1371/journal.pone.0082934
    Reprogramming of energy metabolism is pivotal to cancer, so mitochondria are potential targets for anticancer therapy. A prior study has demonstrated the anti-proliferative activity of a new class of mitochondria-targeting rosamines. This present study describes in vitro cytotoxicity of second-generation rosamine analogs, their mode of action, and their in vivo efficacies in a tumor allografted mouse model. Here, we showed that these compounds exhibited potent cytotoxicity (average IC50<0.5 µM), inhibited Complex II and ATP synthase activities of the mitochondrial oxidative phosphorylation pathway and induced loss of mitochondrial transmembrane potential. A NCI-60 cell lines screen further indicated that rosamine analogs 4 and 5 exhibited potent antiproliferative effects with Log10GI50 = -7 (GI50 = 0.1 µM) and were more effective against a colorectal cancer sub-panel than other cell lines. Preliminary in vivo studies on 4T1 murine breast cancer-bearing female BALB/c mice indicated that treatment with analog 5 in a single dosing of 5 mg/kg or a schedule dosing of 3 mg/kg once every 2 days for 6 times (q2d×6) exhibited only minimal induction of tumor growth delay. Our results suggest that rosamine analogs may be further developed as mitochondrial targeting agents. Without a doubt proper strategies need to be devised to enhance tumor uptake of rosamines, i.e. by integration to carrier molecules for better therapeutic outcome.
  20. Dangerfield DT, Gravitt P, Rompalo AM, Yap I, Tai R, Lim SH
    Int J STD AIDS, 2015 Jan;26(1):20-6.
    PMID: 24676132 DOI: 10.1177/0956462414528685
    In Malaysia, homosexuality is illegal; little is known about access to HIV prevention services among Malaysian men who have sex with men (MSM). We analysed PT Foundation outreach data to describe the profiles among MSM who accessed PT Foundation services and to examine factors associated with being aware of PT Foundation and having visited the organization. A survey was administered during weekly outreach throughout Kuala Lumpur from March-December 2012. Pearson's Chi square tests were used to compare demographic and behavioural characteristics of participants who were and were not aware of the PT Foundation. Binary logistic regression was used to identify correlates of MSM visiting the PT Foundation among those who had heard of the organization. Of 614 MSM, this study found significantly higher awareness of the PT Foundation among MSM who perceived they had "good" HIV knowledge (p = .026) and participants who reported always using condoms (p = .009). MSM who reported being paid for sex were 2.81 times as likely to visit the PT Foundation compared to men who did not. A subgroup of MSM known to be at high risk for HIV infection is accessing prevention services. Future studies should uncover motivations and barriers of accessing these services among MSM in Malaysia.
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