Displaying publications 1 - 20 of 50 in total

  1. Wong YH, Cheong KY
    Nanoscale Res Lett, 2011;6:489.
    PMID: 21831264 DOI: 10.1186/1556-276X-6-489
    The band alignment of ZrO2/interfacial layer/Si structure fabricated by simultaneous oxidation and nitridation of sputtered Zr on Si in N2O at 700°C for different durations has been established by using X-ray photoelectron spectroscopy. Valence band offset of ZrO2/Si was found to be 4.75 eV, while the highest corresponding conduction offset of ZrO2/interfacial layer was found to be 3.40 eV; owing to the combination of relatively larger bandgaps, it enhanced electrical breakdown field to 13.6 MV/cm at 10-6 A/cm2.
  2. Wong YH, Abdul Kadir H
    PMID: 22203877 DOI: 10.1155/2012/684740
    Leea indica is a medicinal plant traditionally used to treat cancer. Through bioassay-guided approach, we isolated mollic acid arabinoside (MAA), for the first time from Leea indica. Here, we present the apoptosis-inducing effect of MAA on Ca Ski cervical cancer cells. Based on DAPI staining, MAA-treated cells manifested nuclear shrinkage, condensation, and fragmentation. We further confirmed the fragmentation of DNA using TUNEL assay. During early apoptosis, MAA caused the perturbation of plasma membrane through externalization of PS, followed by the formation of apoptotic blebs. Prior to these events, MAA triggered rapid dissipation of the mitochondrial membrane potential. In the upstream, MAA increased the expression of Bax, decreased the expression of Bcl-2, and augmented the Bax/Bcl-2 ratio. These findings suggested that MAA induced mitochondrial-mediated apoptosis in Ca Ski cells and thus provide the scientific explanation for the traditional application of this herbal medicine in cancer treatment.
  3. Wong YH, Kadir HA, Tayyab S
    Int J Biol Macromol, 2015 Feb;73:207-14.
    PMID: 25434804 DOI: 10.1016/j.ijbiomac.2014.11.015
    Effect of simulated honey sugar cocktail (SHSC) on chemical and thermal stability of ovalbumin (OVA) was investigated using multiple-spectroscopic techniques. Urea-induced denaturation of OVA produced a transition, characterized by the start-, the mid- and the end-points at 3.2 M, 5.9/5.6 M and 8.5/8.0 M urea, respectively, when studied by MRE222nm and tryptophan fluorescence measurements. Presence of 10% or 20% (w/v) SHSC in the incubation mixture shifted the transition curve towards higher urea concentration in a concentration dependent manner. A comparison of far- and near-UV CD, UV-difference, ANS fluorescence and 3-D fluorescence spectral results of native OVA and 5.9 M urea-denatured OVA (U-OVA), obtained in the absence and the presence of 20% (w/v) SHSC suggested SHSC-induced stabilization of U-OVA. Furthermore, a significant shift towards higher denaturant concentration was also noticed in the GdnHCl and thermal transition curves of OVA in the presence of 20% (w/v) SHSC. Taken together, all these results suggested stabilization of OVA against chemical and thermal denaturations by SHSC.
  4. Wong YH, Abdul Kadir H, Tayyab S
    ScientificWorldJournal, 2013;2013:981902.
    PMID: 24222758 DOI: 10.1155/2013/981902
    Protein stabilizing potential of honey was studied on a model protein, bovine serum albumin (BSA), using extrinsic fluorescence of fluorescein isothiocyanate (FITC) as the probe. BSA was labelled with FITC using chemical coupling, and urea and thermal denaturation studies were performed on FITC-labelled BSA (FITC-BSA) both in the absence and presence of 10% and 20% (w/v) honey using FITC fluorescence at 522 nm upon excitation at 495 nm. There was an increase in the FITC fluorescence intensity upon increasing urea concentration or temperature, suggesting protein denaturation. The results from urea and thermal denaturation studies showed increased stability of protein in the presence of honey as reflected from the shift in the transition curve along with the start point and the midpoint of the transition towards higher urea concentration/temperature. Furthermore, the increase in ΔG D (H2O) and ΔG D (25°C) in presence of honey also suggested protein stabilization.
  5. Wong YH, Abdul Kadir H, Ling SK
    PMID: 22203865 DOI: 10.1155/2012/164689
    Leea indica is a medicinal plant used traditionally to cure cancer. In this study, the cytotoxic compounds of L. indica were isolated using bioassay-guided approach. Two cycloartane triterpenoid glycosides, mollic acid arabinoside (MAA) and mollic acid xyloside (MAX), were firstly isolated from L. indica. They inhibited the growth of Ca Ski cervical cancer cells with IC(50) of 19.21 μM (MAA) and 33.33 μM (MAX). MRC5 normal cell line was used to calculate selectivity index. MAA and MAX were about 8 and 4 times more cytotoxic to Ca Ski cells compared to MRC5. The cytotoxicity of MAA was characterized by both cytostatic and cytocidal effects. MAA decreased the expression of proliferative cell nuclear antigen, increased sub-G1 cells, and arrested cells in S and G2/M phases. This study provides the evidence for the ethnomedicinal use of L. indica and paves the way for future mechanism studies on the anticancer effects of MAA.
  6. Manoharan P, Wong YH, Tayyab S
    Protein Pept Lett, 2015;22(7):611-7.
    PMID: 25961707
    Stabilizing effect of diazepam and ketoprofen, Sudlow's site II markers on human serum albumin (HSA) against urea denaturation was studied using fluorescence spectroscopy. The two-step, three-state urea transition of HSA was transformed into a single-step, two-state transition with the abolishment of the intermediate state along with a shift of the transition curve towards higher urea concentrations in the presence of diazepam or ketoprofen. Interestingly, a greater shift in the transition curve of HSA was observed in the presence of ketoprofen compared to diazepam. A comparison of the intrinsic fluorescence and three-dimensional fluorescence spectra of HSA and partially-denatured HSAs, obtained in the absence and the presence of diazepam or ketoprofen suggested significant retention of native-like conformation in the partially-denatured states of HSA in the presence of Sudlow's site II markers. Taken together, all these results suggested stabilization of HSA in the presence of diazepam or ketoprofen, being greater in the presence of ketoprofen.
  7. Chin CS, Cheong YM, Wong YH
    Med J Malaysia, 1989 Sep;44(3):194-8.
    PMID: 2696871
    Thirty six clinical isolates of Cryptococcus neoformans were tested for their susceptibility to 5-fluorocytosine and amphotericin B by the determination of minimum inhibitory concentrations and minimum fungicidal concentrations. 22.2% of the isolates were resistant to 5-fluorocytosine and 36.1% indicated 5-fluorocytosine tolerance. All strains were sensitive to amphotericin B.
  8. Koh CL, Lim ME, Wong YH
    PMID: 6362015
    Six independent isolates of Klebsiella from hospital environmental sources in Malaysia were found to be resistant to at least ampicillin, carbenicillin, cefoperazone, chloramphenicol, gentamicin and tetracycline. On the basis of their antibiograms, they were divided into four antibiogroups. They transferred all or part of their multiple antibiotic resistance traits to E. coli by conjugation. The results suggest that these Klebsiella strains harbour self-transmissible R plasmids. The significance of these findings are discussed.
  9. Lim YS, Jegathesan M, Wong YH
    Med J Malaysia, 1984 Dec;39(4):285-8.
    PMID: 6544934
    The incidence of Campylobacter jejuni in patients with and without diarrhoea was studied in Kuala Lumpur, Malaysia. C. jejuni was recovered from 3.8% and 4.3% of diarrhoeal stools of children and adults, respectively. From the patients without diarrhoea, the relative isolation rates for children and adults were 2.6% and 0%, respectively. Dual infections occurred in two children, with Salmonella and enteropathogenic Escherichia coli being the other enteric pathogen in each case. Cary-Blair medium was found to be an effective transport medium in recovering C. jejuni. Campylobacter enteritis occurred in patients of various age groups, indicating that this organism should be sought routinely by diagnostic laboratories in faecal specimens from patients with diarrhoea.
  10. Boo NY, Wong YH, Lim VK
    Med J Malaysia, 1989 Sep;44(3):189-93.
    PMID: 2626133
    Over a 12 months period, out of 25,411 livebirths, 155 neonates (6.1 per 1000 livebirths) had proven septicemia by blood culture. The mortality rate was 26.5%. Septicemia was more common among the very low birthweight and preterm neonates of gestation of 30 weeks or less. 45.8% of the septicemia occurred during the first 48 hours of life. Staphylococcus epidermidis was the most common causative organism. However, mortality was highest among neonates who acquired multiresistant nosocomial infection during the later part of neonatal life.
  11. Koh CL, Lim ME, Wong YH
    Med J Malaysia, 1983 Dec;38(4):320-4.
    PMID: 6599991
    A clinical isolate of Salmonella typhi (Vi phage type 25), resistant to chloramphenicol, streptomycin and tetracycline, was examined for the presence of R plasmids. Results from conjugation, agarose gel electrophoresis and transformation experiments indicated that it harboured a single large self-transmissible R plasmid which coded for both the chloramphenicol and tetracycline resistance traits.
  12. Wong YH, Kadir HA, Tayyab S
    Protein Pept Lett, 2016;23(10):898-904.
    PMID: 27586182
    Urea and thermal denaturations of bovine serum albumin (BSA) were studied in the absence and the presence of honey or simulated honey sugar cocktail (SHSC) using far-UV CD and ANS fluorescence spectroscopy. Presence of 20% (w/v) honey or SHSC in the incubation mixture shifted the urea transition curve towards higher urea concentrations, being higher in the presence of honey and transformed the two-step, three-state transition into a single-step, two-state transition. A comparison of the far-UV CD and the ANS fluorescence spectra of 4.6 M urea-denatured BSA (U-BSA) in the absence and the presence of 20% (w/v) honey or SHSC suggested greater stabilizing potential of honey than SHSC, as U-BSA maintained native like conformation in the presence of 20% (w/v) honey. Furthermore, thermal transition curves of BSA were also shifted towards higher temperature range in the presence of 20% (w/v) SHSC and honey, showing greater shift in the presence of honey. The far-UV CD spectra of the heat-denatured BSA also showed greater stabilization in the presence of honey. Taken together all these results suggested greater protein stabilizing potential of honey than SHSC against chemical and thermal denaturations of BSA.
  13. Yap KL, Wong YH, Khor CM, Ooi YE
    Can J Microbiol, 1992 Sep;38(9):996-9.
    PMID: 1334446
    A 12-month study was carried out on the molecular epidemiology of rotavirus in urban and suburban Malaysian children. Analysis of faecal samples from 973 hospitalized diarrhoeic children by polyacrylamide gel electrophoresis detected 268 rotaviruses (28%). All isolates were group A rotaviruses, which produced 22 electropherotypes: 16 (91.5%) with long RNA migration patterns and 6 (8.5%) with short patterns. One of the long-pattern electropherotypes was the predominant strain (71.1% of the total electropherotypes) isolated during this study. Although 3 other strains were detected sporadically over the study period, 16 others were present only during the first 7 months and 2 others were confined to the last 5 months. Long- and short-pattern electropherotypes were found to co-circulate extensively. There was a significant association of short-pattern electropherotypes with infection in older children. In addition, the prevalence of vomiting and mean duration of diarrhoea were significantly associated with different electropherotypes.
  14. Rasool NB, Hamzah M, Jegathesan M, Wong YH, Qian Y, Green KY
    J Med Virol, 1994 Jul;43(3):209-11.
    PMID: 7931180
    Stool specimens from 334 infants and young children hospitalized with diarrhea in the General Hospital, Kuala Lumpur, Malaysia between August and November, 1987 were analyzed for the presence of rotavirus double-stranded (ds) RNA by polyacrylamide gel electrophoresis. Of the 334 specimens analyzed, 32 (9.6%) were positive for rotavirus RNA. One specimen (designated G147) exhibited a ds RNA electropherotype profile characteristic of Group C rotavirus and was selected for further characterization. In Northern blot hybridization studies, the gene 5 segment of strain G147 hybridized with a cDNA probe generated from the cloned gene 5 (which encodes the VP6 inner capsid protein that is group specific) of porcine Group C rotavirus strain Cowden, confirming the classification of strain G147 in Group C. The association of Group C rotavirus with diarrheal illness in Malaysia is consistent with earlier studies that suggest a global distribution of this virus and supports the need for additional epidemiologic studies.
  15. Cheong I, Tan SC, Wong YH, Zainudin BM, Rahman MZ
    Med J Malaysia, 1994 Mar;49(1):24-8.
    PMID: 8057986
    Between August 1990 to November 1991, 905 of 2583 (35.4%) isolates of Staphylococcus aureus were found to be methicillin-resistant in a general hospital in Malaysia. A detailed study of 539 of these isolates showed a high prevalence of methicillin resistant Staphylococcus aureus (MRSA) in the surgical/orthopaedic wards, paediatric wards and the special care unit. The yield of MRSA was highest from wounds/ulcers/skin swabs accounting for 64.2 per cent followed by 6.9 per cent in blood cultures. Vancomycin remains the drug of choice with no resistance detected. The resistance to ciprofloxacin was 6.7 per cent, rifampicin 4.5 per cent and fusidic acid 2.0 per cent. Most isolates were resistant to aminoglycosides. In view of the high prevalence of MRSA in this hospital, the authorities must introduce more effective measures to control its spread as a nosocomial pathogen. Otherwise it may seriously disrupt the efficient delivery of health care services in the country.
  16. Tan SC, Wong YH, Jegathesan M, Chang SM
    Malays J Pathol, 1989 Aug;11:25-7.
    PMID: 2632996
    Tatumella ptyseos, the type species for the genus Tatumella, is a newly established member of the Family Enterobacteriaceae. It is a Gram-negative, oxidase negative, fermentative rod that grows on Mac Conkey agar. This first isolate was obtained from the blood culture of a neonate having neonatal jaundice with presumed sepsis. The organism was in vitro sensitive to Gentamicin, Chloramphenicol, Cotrimoxazole and Ampicillin. The patient was treated with Ampicillin and Gentamicin and recovered uneventfully.
  17. Kong NC, Shaariah W, Morad Z, Suleiman AB, Wong YH
    Aust N Z J Med, 1990 Oct;20(5):645-9.
    PMID: 2285381
    Cryptococcosis is a known opportunistic infection in immunosuppressed hosts. We report our experience of all cases presenting to our Department between December 1975 and September 1988. Eight post-renal transplant patients and three systemic lupus erythematosus (SLE) patients were affected. All were receiving treatment with steroids, in association with either azathioprine or cyclosporin. The diagnosis of cryptococcal meningitis was initially based on a positive cerebrospinal fluid (CSF) cryptococcal antigen, by latex agglutination test, and subsequently confirmed by cultures. Common clinical presentations, in descending order of frequency, included headaches, fever, mental confusion, epilepsy and papilloedema. Meningism was not a prominent feature. CT brain scans were obtained in eight patients and one showed a focal lesion and one showed cerebral atrophy. Four patients also had an abnormal chest X-ray (CXR) and one had disseminated cryptococcosis. Amphotericin and 5-fluorocytosine were the mainstay of therapy, although ketoconazole alone was subsequently used in three selected patients with cure. Four early deaths occurred in patients with delayed diagnosis and treatment, usually in association with other severe concurrent infections. We conclude that awareness of cryptococcosis is essential in immunocompromised hosts presenting with headache with, or without, mental confusion or fever.
  18. Arumugasamy N, Chin CS, Wong YH, Chew PH
    Aust N Z J Surg, 1985 Oct;55(5):517-8.
    PMID: 3868419
    A patient with a solitary intracranial cryptococcoma of the occipital lobe of the brain and a concomitant granuloma of similar aetiology in the breast is reported. Despite resistance of the causative fungus to 5-fluorocytosine in vitro, the patient responded well to radical excisional surgery and therapy with 5-fluorocytosine.
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