Displaying publications 41 - 60 of 146 in total

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  1. Sonophotocatalytic degradation of bisphenol A and its intermediates with graphitic carbon nitride
    Sunasee S, Leong KH, Wong KT, Lee G, Pichiah S, Nah I, et al.
    Environ Sci Pollut Res Int, 2019 Jan;26(2):1082-1093.
    PMID: 28290089 DOI: 10.1007/s11356-017-8729-7
    Since bisphenol A (BPA) exhibits endocrine disrupting action and high toxicity in aqueous system, there are high demands to remove it completely. In this study, the BPA removal by sonophotocatalysis coupled with nano-structured graphitic carbon nitride (g-C3N4, GCN) was conducted with various batch tests using energy-based advanced oxidation process (AOP) based on ultrasound (US) and visible light (Vis-L). Results of batch tests indicated that GCN-based sonophotocatalysis (Vis-L/US) had higher rate constants than other AOPs and especially two times higher degradation rate than TiO2-based Vis-L/US. This result infers that GCN is effective in the catalytic activity in Vis-L/US since its surface can be activated by Vis-L to transport electrons from valence band (VB) for utilizing holes (h+VB) in the removal of BPA. In addition, US irradiation exfoliated the GCN effectively. The formation of BPA intermediates was investigated in detail by using high-performance liquid chromatography-mass spectrometry (HPLC/MS). The possible degradation pathway of BPA was proposed.
  2. Titanium dioxide-based sonophotocatalytic mineralization of bisphenol A and its intermediates
    Sunasee S, Wong KT, Lee G, Pichiah S, Ibrahim S, Park C, et al.
    Environ Sci Pollut Res Int, 2017 Jun;24(18):15488-15499.
    PMID: 28512708 DOI: 10.1007/s11356-017-9124-0
    In this study, bisphenol A (BPA) removal by sonophotocatalysis coupled with commercially available titanium dioxide (TiO2, P25) was assessed in batch tests using energy-based advanced oxidation combining ultrasound (US) and ultraviolet (UV). The kinetics of BPA removal were systematically evaluated by changing operational parameters, such as US frequency and power, mechanical stirring speed, and temperature, but also comparison of single and coupled systems under the optimum US conditions (35 kHz, 50 W, 300 rpm stirring speed, and 20 °C). The combination of US/UV/P25 exhibited the highest BPA removal rate (28.0 × 10-3 min-1). In terms of the synergy index, the synergistic effect of sonophotocatalysis was found to be 2.2. This indicated that sonophotocatalysis has a considerably higher removal efficiency than sonocatalysis or photocatalysis. The removal of BPA was further investigated to identify BPA byproducts and intermediates using high-performance liquid chromatography-mass spectrometry. Five main intermediates were formed during sonophotocatalytic degradation, and complete removal of BPA and its intermediates was obtained after 3 h of operation. The degradation pathway of BPA by sonophotocatalysis was also elucidated.
  3. Relapsed and late-onset Nipah encephalitis
    Tan CT, Goh KJ, Wong KT, Sarji SA, Chua KB, Chew NK, et al.
    Ann Neurol, 2002 Jun;51(6):703-8.
    PMID: 12112075
    An outbreak of infection with the Nipah virus, a novel paramyxovirus, occurred among pig farmers between September 1998 and June 1999 in Malaysia, involving 265 patients with 105 fatalities. This is a follow-up study 24 months after the outbreak. Twelve survivors (7.5%) of acute encephalitis had recurrent neurological disease (relapsed encephalitis). Of those who initially had acute nonencephalitic or asymptomatic infection, 10 patients (3.4%) had late-onset encephalitis. The mean interval between the first neurological episode and the time of initial infection was 8.4 months. Three patients had a second neurological episode. The onset of the relapsed or late-onset encephalitis was usually acute. Common clinical features were fever, headache, seizures, and focal neurological signs. Four of the 22 relapsed and late-onset encephalitis patients (18%) died. Magnetic resonance imaging typically showed patchy areas of confluent cortical lesions. Serial single-photon emission computed tomography showed the evolution of focal hyperperfusion to hypoperfusion in the corresponding areas. Necropsy of 2 patients showed changes of focal encephalitis with positive immunolocalization for Nipah virus antigens but no evidence of perivenous demyelination. We concluded that a unique relapsing and remitting encephalitis or late-onset encephalitis may result as a complication of persistent Nipah virus infection in the central nervous system.
  4. Fulltext Hypercalcemia in a patient with tuberculous mediastinal lymphadenopathy
    Tan TT, Lee BC, Zainuddin BM, Wong KT, Samad A, Khalid BA
    Singapore Med J, 1991 Feb;32(1):87-9.
    PMID: 2017716
    We describe the case of a 48 year old Indian female with hypercalcemia due to tuberculosis. She presented with symptoms of hypercalcemia and chest radiographs showed bilateral hilar lymphadenopathy with normal lung fields. The diagnosis of tuberculosis was made histologically from biopsy of the enlarged hilar nodes. Her hypercalcemia resolved following one month of anti-tuberculous treatment. The prevalence of hypercalcemia in tuberculosis has been reported to be high in western series. There is, however, a paucity of local data on the subject. The presence of 1-alpha-hydroxylase-like activity in pulmonary alveolar macrophages with resulting increased formation of active vitamin D metabolites is the postulated mechanism of tuberculosis associated hypercalcemia.
  5. Idiopathic ileal volvulus with multiple concomitant infections in a starving man
    Tan LJ, Othman MS, Hiu J, Wong KT, Lai SK
    Malays J Pathol, 2021 Apr;43(1):81-85.
    PMID: 33903310
    BACKGROUND: Small bowel volvulus is defined as the torsion of the small intestine, potentially leading to bowel obstruction, gangrene and perforation. It is a rare condition, especially in adults.

    CASE PRESENTATION: A 30-year-old man was retrieved from the jungle with severe weight loss and abdominal symptoms. He succumbed to death despite 22 days of intensive medical treatment. An autopsy revealed a ruptured gangrenous ileal volvulus with peritonitis and subdiaphragmatic abscess. Further laboratory analysis detected systemic Candida tropicalis and intestinal gramnegative bacterial sepsis, systemic Zika virus viremia, leptospirosis complicating rhabdomyolysis and disseminated intravascular coagulopathy, Type I Herpes Simplex virus infection of the tongue and upper gastrointestinal tract. The cause of death was the ruptured ileal volvulus, complicated with upper gastrointestinal bleeding due to Herpes simplex virus esophagitis in a malnourished patient with resolving leptospirosis and underlying Zika virus co-infection.

    CONCLUSION: Rare clinical scenarios of adult-onset intestinal volvulus with concomitant multiple infections precludes clinical diagnosis and early treatment, leading to devastating consequences of clinical outcome. The positive clinical and postmortem correlation is a good learning lesson in many disciplines of medicine and science.

  6. Fulltext Clinical features of Nipah virus encephalitis among pig farmers in Malaysia
    Goh KJ, Tan CT, Chew NK, Tan PS, Kamarulzaman A, Sarji SA, et al.
    N Engl J Med, 2000 Apr 27;342(17):1229-35.
    PMID: 10781618 DOI: 10.1056/NEJM200004273421701
    BACKGROUND: Between September 1998 and June 1999, there was an outbreak of severe viral encephalitis due to Nipah virus, a newly discovered paramyxovirus, in Malaysia.
    METHODS: We studied the clinical features of the patients with Nipah virus encephalitis who were admitted to a medical center in Kuala Lumpur. The case definition was based on epidemiologic, clinical, cerebrospinal fluid, and neuroimaging findings.
    RESULTS: Ninety-four patients with Nipah virus infection were seen from February to June 1999 (mean age, 37 years; ratio of male patients to female patients, 4.5 to 1). Ninety-three percent had had direct contact with pigs, usually in the two weeks before the onset of illness, suggesting that there was direct viral transmission from pigs to humans and a short incubation period. The main presenting features were fever, headache, dizziness, and vomiting. Fifty-two patients (55 percent) had a reduced level of consciousness and prominent brain-stem dysfunction. Distinctive clinical signs included segmental myoclonus, areflexia and hypotonia, hypertension, and tachycardia and thus suggest the involvement of the brain stem and the upper cervical spinal cord. The initial cerebrospinal fluid findings were abnormal in 75 percent of patients. Antibodies against Hendra virus were detected in serum or cerebrospinal fluid in 76 percent of 83 patients tested. Thirty patients (32 percent) died after rapid deterioration in their condition. An abnormal doll's-eye reflex and tachycardia were factors associated with a poor prognosis. Death was probably due to severe brain-stem involvement. Neurologic relapse occurred after initially mild disease in three patients. Fifty patients (53 percent) recovered fully, and 14 (15 percent) had persistent neurologic deficits.
    CONCLUSIONS: Nipah virus causes a severe, rapidly progressive encephalitis with a high mortality rate and features that suggest involvement of the brain stem. The infection is associated with recent contact with pigs.
  7. Fatal enterovirus 71 encephalomyelitis
    Lum LC, Wong KT, Lam SK, Chua KB, Goh AY, Lim WL, et al.
    J Pediatr, 1998 Dec;133(6):795-8.
    PMID: 9842048
    During an outbreak of hand-foot-mouth disease caused by enterovirus 71 (EV-71) in 1997, 4 children presented with sudden cardiopulmonary collapse and minimal neurologic features. All children received cardiopulmonary resuscitation but died within a few hours of admission. Postmortem studies showed infection by EV-71 with extensive damage to the medulla and pons. We postulate an etiologic link between EV-71 and brainstem encephalomyelitis as the cause of pulmonary edema and death.
  8. Fulltext Unusual manifestation of cutaneous toxoplasmosis in a HIV-positive patient
    Fong MY, Wong KT, Rohela M, Tan LH, Adeeba K, Lee YY, et al.
    Trop Biomed, 2010 Dec;27(3):447-50.
    PMID: 21399585 MyJurnal
    We report a case of unusual cutaneous toxoplasmosis manifestation in a HIV-positive patient. He presented with hard and painful nodular lesions on the arms, hands and chest. Serology tests for anti-Toxoplasma antibody were negative. However, histopathologic examination of the lesion revealed foci of macrophages containing crescent-shaped organisms resembling the zoites of the protozoan parasite Toxoplasma gondii. Ultrastructure examination under electron microscopy and PCR confirmed the organism as T. gondii.
  9. Fulltext Immunity and clinical efficacy of an inactivated enterovirus 71 vaccine in healthy Chinese children: a report of further observations
    Liu L, Mo Z, Liang Z, Zhang Y, Li R, Ong KC, et al.
    BMC Med, 2015;13:226.
    PMID: 26381232 DOI: 10.1186/s12916-015-0448-7
    To investigate the long-term effects on immunity of an inactivated enterovirus 71 (EV71) vaccine and its protective efficacy.
  10. Beyond Pattern Recognition: Radiology-Pathology-Clinical Correlation
    Wong KT, Tan CT, Lim T
    Neuroimaging Clin N Am, 2023 Feb;33(1):225-233.
    PMID: 36404045 DOI: 10.1016/j.nic.2022.07.018
    Radiology-pathology correlation is essential for multidisciplinary collaboration in diagnosis and understanding the mechanism of CNS damage in infectious processes. The microscopic acute inflammatory processes are well established and are supplemented by a variety of less-invasive microbial and immunohistochemical investigations. Understanding the pathogenesis of pathogen spread and neuroinvasion, vascular and immune-mediated brain, and spinal cord damage are essential for interpreting radiological images.
  11. Fulltext Pulmonary involvement by Hodgkin's disease mimicking pneumonia
    Liam CK, Wong KT, Lim YC
    Med J Malaysia, 1997 Mar;52(1):84-6.
    PMID: 10968059
    A 24-year-old man who was initially thought to have nocardiosis of his mediastinal lymph node which progressed to involve his right lung, had to undergo a right pneumonectomy when he failed to respond to treatment with sulphadiazine. Histology of the right lung specimen and a subsequent axillary lymph node biopsy revealed that he actually had lymphocyte-depleted Hodgkin's disease.
  12. Fulltext Intraabdominal desmoplastic small round cell tumour in an 11-year-old boy
    Ariffin H, Ariffin WA, Wong KT, Ramanujam TM, Lin HP
    Singapore Med J, 1997 Apr;38(4):169-71.
    PMID: 9269398
    A case of desmoplastic small round cell tumour (DSRCT) is presented. This aggressive and rare neoplasm predominantly affects males and is almost exclusively intraabdominal in location. It is unique in that neural, mesenchymal and epithelial markers are co-expressed. Despite multi-modal therapy, the prognosis is extremely poor. The present report details the clinical features and typical pathological findings of DSRCT in an 11-year-old boy, who succumbed to the disease 16 months after diagnosis despite multiple chemotherapeutic regimes.
  13. Tonsillar crypt epithelium is an important extra-central nervous system site for viral replication in EV71 encephalomyelitis
    He Y, Ong KC, Gao Z, Zhao X, Anderson VM, McNutt MA, et al.
    Am J Pathol, 2014 Mar;184(3):714-20.
    PMID: 24378407 DOI: 10.1016/j.ajpath.2013.11.009
    Enterovirus 71 (EV71; family Picornaviridae, species human Enterovirus A) usually causes hand, foot, and mouth disease, which may rarely be complicated by fatal encephalomyelitis. We investigated extra-central nervous system (extra-CNS) tissues capable of supporting EV71 infection and replication, and have correlated tissue infection with expression of putative viral entry receptors, scavenger receptor B2 (SCARB2), and P-selectin glycoprotein ligand-1 (PSGL-1). Formalin-fixed, paraffin-embedded CNS and extra-CNS tissues from seven autopsy cases were examined by IHC and in situ hybridization to evaluate viral antigens and RNA. Viral receptors were identified with IHC. In all seven cases, the CNS showed stereotypical distribution of inflammation and neuronal localization of viral antigens and RNA, confirming the clinical diagnosis of EV71 encephalomyelitis. In six cases in which tonsillar tissues were available, viral antigens and/or RNA were localized to squamous epithelium lining the tonsillar crypts. Tissues from the gastrointestinal tract, pancreas, mesenteric nodes, spleen, and skin were all negative for viral antigens/RNA. Our novel findings strongly suggest that tonsillar crypt squamous epithelium supports active viral replication and represents an important source of viral shedding that facilitates person-to-person transmission by both the fecal-oral or oral-oral routes. It may also be a portal for viral entry. A correlation between viral infection and SCARB2 expression appears to be more significant than for PSGL-1 expression.
  14. Anisakiasis causing acute dysentery in Malaysia
    Amir A, Ngui R, Ismail WH, Wong KT, Ong JS, Lim YA, et al.
    Am J Trop Med Hyg, 2016 Aug 03;95(2):410-2.
    PMID: 27325803 DOI: 10.4269/ajtmh.16-0007
    Human anisakiasis is a zoonosis acquired by eating raw or undercooked infected seafood. Herein, we report a case of acute dysentery caused by anisakiasis in a 64-year-old man in Malaysia. A colonoscopy was performed and a nematode larva was found penetrating the mucosa of the ascending colon. Bleeding was observed at the site of penetration. Y-shaped lateral epidermal cords were seen from the cross section of the worm, which is a prominent feature of Anisakis larva. Molecular analysis using polymerase chain reaction of cytochrome oxidase 2 (cox2) gene confirmed the specimen to be larva of Anisakis simplex.
  15. Fulltext HIV-Associated CD8 Encephalitis: A UK Case Series and Review of Histopathologically Confirmed Cases
    Lucas SB, Wong KT, Nightingale S, Miller RF
    Front Neurol, 2021;12:628296.
    PMID: 33868143 DOI: 10.3389/fneur.2021.628296
    HIV-associated CD8-encephalitis (HIV-CD8E) is a severe inflammatory disorder dominated by infiltration of the brain by CD8+ T-lymphocytes. It occurs in people with HIV, typically when the virus is apparently well-controlled by antiretroviral treatment (ART). HIV-CD8E presents with symptoms and signs related to marked cerebral inflammation and swelling, and can lead to coma and death unless treated promptly with corticosteroids. Risk events such as intercurrent infection, antiretroviral therapy interruption, immune reconstitution inflammatory syndrome (IRIS) after starting ART, and concomitant associations such as cerebrospinal fluid (CSF) HIV viral escape have been identified, but the pathogenesis of the disorder is not known. We present the largest case series of HIV-CD8E to date (n = 23), representing histopathologically confirmed cases in the UK. We also summarize the global literature representing all previously published cases with histopathological confirmation (n = 30). A new variant of HIV-CD8E is described, occurring on a background of HIV encephalitis (HIVE).Together these series, totalling 53 patients, provide new insights. CSF HIV viral escape was a frequent finding in HIV-CD8E occurring in 68% of those with CSF available and tested; ART interruption and IRIS were important, both occurring in 27%. Black ethnicity appeared to be a key risk factor; all but two UK cases were African, as were the majority of the previously published cases in which ethnicity was stated. We discuss potential pathogenic mechanisms, but there is no unifying explanation over all the HIV-CD8E scenarios.
  16. Fulltext Intramolecular Dimerization Quenching of Delayed Emission in Asymmetric D-D'-A TADF Emitters
    Woon KL, Yi CL, Pan KC, Etherington MK, Wu CC, Wong KT, et al.
    J Phys Chem C Nanomater Interfaces, 2019 May 16;123(19):12400-12410.
    PMID: 32952765 DOI: 10.1021/acs.jpcc.9b01900
    Understanding the excited-state dynamics and conformational relaxation in thermally activated delayed fluorescence (TADF) molecules, including conformations that potentially support intramolecular through-space charge transfer, can open new avenues for TADF molecular design as well as elucidate complex photophysical pathways in structurally complex molecules. Emissive molecules comprising a donor (triphenylamine, TPA) and an acceptor (triphenyltriazine, TRZ) bridged by a second donor (9,9-dimethyl-9-10-dihydroacridin, DMAC, or phenoxazine, PXZ) are synthesized and characterized. In solution, the flexibility of the sp3-hybridized carbon atom in DMAC of DMAC-TPA-TRZ, compared to the rigid PXZ, allows significant conformational reorganization, giving rise to multiple charge-transfer excited states. As a result of such a reorganization, the TRZ and TPA moieties become cofacially aligned, driven by a strong dipole-dipole attraction between the TPA and TRZ units, forming a weakly charge-transfer dimer state, in stark contrast to the case of PXZ-TPA-TRZ where the rigid PXZ bridge only supports a single PXZ-TRZ charge transfer (CT) state. The low-energy TPA-TRZ dimer is found to have a high-energy dimer local triplet state, which quenches delayed emission because the resultant singlet CT local triplet energy gap is too large to mediate efficient reverse intersystem crossing. However, organic light-emitting diodes using PXZ-TPA-TRZ as an emitting dopant resulted in external quantum efficiency as high as 22%, more than two times higher than that of DMAC-TPA-TRZ-based device, showing the impact that such intramolecular reorganization and donor-acceptor dimerization have on TADF performance.
  17. Fulltext The distribution of inflammation and virus in human enterovirus 71 encephalomyelitis suggests possible viral spread by neural pathways
    Wong KT, Munisamy B, Ong KC, Kojima H, Noriyo N, Chua KB, et al.
    J. Neuropathol. Exp. Neurol., 2008 Feb;67(2):162-9.
    PMID: 18219253 DOI: 10.1097/nen.0b013e318163a990
    Previous neuropathologic studies of Enterovirus 71 encephalomyelitis have not investigated the anatomic distribution of inflammation and viral localization in the central nervous system (CNS) in detail. We analyzed CNS and non-CNS tissues from 7 autopsy cases from Malaysia and found CNS inflammation patterns to be distinct and stereotyped. Inflammation was most marked in spinal cord gray matter, brainstem, hypothalamus, and subthalamic and dentate nuclei; it was focal in the cerebrum, mainly in the motor cortex, and was rare in dorsal root ganglia. Inflammation was absent in the cerebellar cortex, thalamus, basal ganglia, peripheral nerves, and autonomic ganglia. The parenchymal inflammatory response consisted of perivascular cuffs, variable edema, neuronophagia, and microglial nodules. Inflammatory cells were predominantly CD68-positive macrophage/microglia, but there were a few CD8-positive lymphocytes. There were no viral inclusions; viral antigens and RNA were localized only in the somata and processes of small numbers of neurons and in phagocytic cells. There was no evidence of virus in other CNS cells, peripheral nerves, dorsal root autonomic ganglia, or non-CNS organs. The results indicate that Enterovirus 71 is neuronotropic, and that, although hematogenous spread cannot be excluded, viral spread into the CNS could be via neural pathways, likely the motor but not peripheral sensory or autonomic pathways. Viral spread within the CNS seems to involve motor and possibly other pathways.
  18. Fulltext R54C Mutation of NOTCH3 Gene in the First Rungus Family with CADASIL
    Lim KS, Tan AH, Lim CS, Chua KH, Lee PC, Ramli N, et al.
    PLoS One, 2015;10(8):e0135470.
    PMID: 26270344 DOI: 10.1371/journal.pone.0135470
    Cerebral autosomal dominant arteriopathy with subcortical infarcts and leukoencephalopathy (CADASIL) is a rare hereditary stroke caused by mutations in NOTCH3 gene. We report the first case of CADASIL in an indigenous Rungus (Kadazan-Dusun) family in Kudat, Sabah, Malaysia confirmed by a R54C (c.160C>T, p.Arg54Cys) mutation in the NOTCH3. This mutation was previously reported in a Caucasian and two Korean cases of CADASIL. We recruited two generations of the affected Rungus family (n = 9) and found a missense mutation (c.160C>T) in exon 2 of NOTCH3 in three siblings. Two of the three siblings had severe white matter abnormalities in their brain MRI (Scheltens score 33 and 50 respectively), one of whom had a young stroke at the age of 38. The remaining sibling, however, did not show any clinical features of CADASIL and had only minimal changes in her brain MRI (Scheltens score 17). This further emphasized the phenotype variability among family members with the same mutation in CADASIL. This is the first reported family with CADASIL in Rungus subtribe of Kadazan-Dusun ethnicity with a known mutation at exon 2 of NOTCH3. The penetrance of this mutation was not complete during the course of this study.
  19. Fulltext Alleged paraquat poisoning in Perak
    Wong KT, Ng TS
    Med J Malaysia, 1984 Mar;39(1):52-5.
    PMID: 6334801
    This communication describes a survey on 94 cases of alleged paraquat poisoning for a period of one-and a-half years in Perak state. The highest prevalence of such cases was noted in the district of Batang Padang. The incidences between males and females as well as between married and single persons were found to be equal, 81.9% were Indians and 73.4% were suicidal cases. More than 80% of the cases were in the 10-to-40-years age group.
  20. Fulltext Paraquat poisoning
    Wong KT, Ng TS
    Family Practitioner, 1982;5(3):35-36.
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