Displaying publications 1 - 20 of 67 in total

  1. Azlin, I., Leong, CF, Hamidah, N.H., Sharifah, N.A., Isa, M.R., Rohaizak, M.
    Medicine & Health, 2010;5(2):114-119.
    Primary thyroid lymphoma is a rare disorder accounting for about 2% of all malignant lymphomas and less than 5% of thyroid malignancies. It is an aggressive disease with poor outcome. The majority of thyroid lymphomas are non-Hodgkin lymphomas of Bcell origin. Majority of cases occur in women in the sixth decade. We report two cases of primary thyroid lymphoma and highlight the clinical issues and challenges posed by this rare disease. Both cases presented with respiratory obstructive symptoms that required surgical intervention. The optimal management for a primary thyroid lymphoma be it chemotherapy, radiotherapy, surgery or monoclonal antibodies is still debatable. The role for surgery has evolved through the years but its importance in emergency situations should not be overlooked. Both our patients had to undergo surgery but only one patient received additional chemotherapy and radiotherapy. These two case reports illustrated the difficulties in managing this rare disorder.
  2. Mok PL, Leong CF, Cheong SK
    Malays J Pathol, 2013 Jun;35(1):17-32.
    PMID: 23817392 MyJurnal
    Mesenchymal stem cells (MSC) are multipotent, self-renewing cells that can be found mainly in the bone marrow, and other post-natal organs and tissues. The ease of isolation and expansion, together with the immunomodulatory properties and their capability to migrate to sites of inflammation and tumours make them a suitable candidate for therapeutic use in the clinical settings. We review here the cellular mechanisms underlying the emerging applications of MSC in various fields.
  3. Rabeya Y, Abdul-Kahar AH, Leong CF
    Malays J Pathol, 2011 Jun;33(1):25-9.
    PMID: 21874748 MyJurnal
    Transfusion is an irreversible event which carries potential benefits as well as risk to the recipient. The objective of this study was to analyse all reported transfusion reactions of the year 2008 in the Blood Bank Unit of Universiti Kebangsaan Malaysia Medical Centre (UKMMC). This is a retrospective study that was carried out by retrieving data from the laboratory information system. A total of 27842 transfusions were documented and the total reported transfusion reactions were 149. The incidence of transfusion reaction was 1 in 187 of all transfusions (0.54%); in which 69 (0.25%) were allergic in nature and 61 (0.22%) were febrile non-haemolytic transfusion reactions (FNHTR). Hypotensive reactions were identified in 6 (0.02%) patients. There were 9 (0.03%) cases reported with haemoglobinuria where no serological evidence of haemolytic transfusion reaction (HTR) was found. One HTR (0.003%) was identified and this was due to an error in patient identification in the ward. Other specified reactions like transfusion-related acute lung injury (TRALI), bacterial infections, Graft verses host disease (GVHD) were not reported. The highest frequency of the reactions occurred in the red cell transfusions which accounted for 111 cases. In conclusion, the incidences of transfusion reactions are low when compared to those reported by other centres.
  4. Tan YF, Leong CF, Cheong SK
    Malays J Pathol, 2010 Dec;32(2):97-102.
    PMID: 21329180 MyJurnal
    Dendritic cells (DCs) are professional antigen presenting cells of the immune system. They can be generated in vitro from peripheral blood monocytes supplemented with GM-CSF, IL-4 and TNF alpha. During induction, DCs will increase in size and acquire multiple cytoplasmic projections when compared to their precursor cells such as monocytes or haematopoietic stem cells which are usually round or spherical. Morphology of DCs can be visualized by conventional light microscopy after staining or phase-contrast inverted microscopy or confocal laser scanning microscopy. In this report, we described the morphological appearances of DCs captured using the above-mentioned techniques. We found that confocal laser scanning microscopy yielded DCs images with greater details but the operating cost for such a technique is high. On the other hand, the images obtained through light microscopy after appropriate staining or phase contrast microscopy were acceptable for identification purpose. Besides, these equipments are readily available in most laboratories and the cost of operation is affordable. Nevertheless, morphological identification is just one of the methods to characterise DCs. Other methods such as phenotypic expression markers and mixed leukocyte reactions are additional tools used in the characterisation of DCs.
  5. Leong CF, Aini-Ardena M, Cheong SK, Norris N
    Malays J Pathol, 2009 Jun;31(1):45-52.
    PMID: 19694313 MyJurnal
    Normal platelet functions are critical for achieving primary haemostasis. Numerous medications have been shown to affect platelet functions. Pyridostigmine (Mestinon), an orally active cholinesterase inhibitor that is commonly used to treat myasthenia gravis has been documented to cause epistaxis and prolonged bleeding after a cut in anectodal reports. This study was initiated after a patient diagnosed to have myasthenia gravis, developed multiple bruises a week after being started on Mestinon. The objective of this study was to investigate the effect of Mestinon on platelet aggregation stimulated with various agonists in vitro.
  6. Mok PL, Cheong SK, Leong CF
    Malays J Pathol, 2008 Jun;30(1):11-9.
    PMID: 19108406 MyJurnal
    Mesenchymal stem cells are pluripotent progenitors that could be found in human bone marrow. Mesenchymal stem cells are capable of renewing themselves without differentiation in long-term culture. These cells also have low immunogenicity and can suppress alloreactive T cell responses. In the current study, mesenchymal stem cells isolated and propagated previously from the bone marrow of a megaloblastic anaemia patient were tested for their capabilities to differentiate into adipocytes, chondrocytes and osteoblasts in vitro. The differentiated cells were determined by Oil Red O, Alcian Blue-PAS and Alizarin Red S staining, and reverse transcriptase-polymerase chain reaction to determine the expression of mRNA specific for adipogenesis, chondrogenesis and osteogenesis. The results showed that the fibroblast-like cells were capable of differentiating into adipocytes, chondrocytes and osteoblasts upon chemical induction. The adipocytes, chondrocytes and osteoblasts were stained positively to Oil Red O, Alcian Blue-PAS and Alizarin Red S respectively. The differentiated cells were also found to express mRNA specific for adipogenesis ('peroxisome proliferation-activated receptor gamma2' and lipoprotein lipase), chondrogenesis (collagen type II) and osteogenesis (osteocalcin, osteopontin and alkaline phosphatase). In conclusion, this research has successfully isolated fibroblast-like cells from human bone marrow and these cells demonstrated morphological, cytochemical and immunochemical characteristics similar to mesenchymal stem cells. These cells maintain their proliferative properties and could be differentiated into the mesoderm lineage. The success of this study is vital because mesenchymal stem cells can be used in cellular therapy to regenerate or replace damaged tissues, or as a vehicle for therapeutic gene delivery in the future.
  7. Leong CF, Zainina S, Cheong SK
    Malays J Pathol, 2005 Jun;27(1):39-43.
    PMID: 16676692
    Anaemia is a frequent complication in patients with haematological malignancies and is caused by a variety of mechanisms including neoplastic cell infiltration into the bone marrow, haemolysis, nutritional deficiencies and defect in erythropoiesis or dysplastic anaemia as a result of the disease itself. However, acquired dysplastic anaemia which mimic congenital dyserythropoietic anaemia (CDA) type II morphology in the bone marrow is very rare. A 41-year-old Chinese man presented with refractory symptomatic anaemia in September 2001. He was clinically pale with no other significant physical finding. His initial peripheral blood picture showed normochromic normocytic anaemia with haemoglobin level of 26g/L, with no evidence of haemolysis and a poor reticulocyte response of 0.6%. Bone marrow aspiration was done and showed congenital dyserythropoietic anaemia (CDA) type II-like morphology. He was treated symptomatically with regular blood transfusions approximately every 3 weeks, until August 2002 when he developed multiple cervical lymphadenopathy with loss of appetite, loss of weight and low grade fever. Biopsy of the lymph node confirmed the diagnosis of small lymphocytic lymphoma. Staging with computed tomography and bone marrow aspirate revealed the infiltration of lymphoma cells into the marrow cavity consistent with the staging of IVB. This case report illustrates that CDA type II-like dysplastic anaemia can preceed the development of lymphoma.
  8. Cheong SK, Eow GI, Leong CF
    Malays J Pathol, 2002 Jun;24(1):1-8.
    PMID: 16329549
    Allogeneic bone marrow or peripheral blood stem cell transplantation traditionally uses myeloablative regimen for conditioning to enable grafting of donor's stem cells. Animal experiments have shown that a milder non-myeloablative conditioning regimen does allow engraftment to occur. Nonmyeloablative conditioning regimens are low-intensity immunosuppressive treatment given to the recipient before infusion of donor's stem cells. It was reported to have decreased immediate procedural mortality, in particular those secondary to acute graft versus host reaction. However, it did give rise to higher risks of graft rejection, tumour tolerance and disease progression. Fortunately, appropriately administered donor lymphocyte infusion has been shown to establish full donor chimerism (complete donor stem cell grafting in the recipient's bone marrow) and potentiate antitumour effect (graft versus tumour reaction). The reduction of immediate transplant mortality allows the procedure to be carried out in older age groups, patients with concomitant diseases that otherwise would have made the patients unfit for the procedure, patients with non-malignant disorders such as congenital immune deficiencies, autoimmune disorders or thalassaemia majors. The regimen also allows transplantation of genetically manipulated haemopoietic stem cells (gene thrapy) to be carried out more readily in the immediate future. Lastly, the regimen may serve as a platform for immunotherapy using specific T cell clones for anti-tumour therapy with or without the knowledge of known tumour antigen.
  9. Yousuf R, Mobin MH, Leong CF
    Malays J Pathol, 2015 Aug;37(2):91-4.
    PMID: 26277664 MyJurnal
    Gamma-irradiation of blood components is regarded a safe procedure used for prevention of transfusion associated graft-versus-host disease. However, reports showed that irradiation can cause erythrocyte haemolysis and damage to the RBC membrane. In University Kebangsaan Malaysia Medical Centre (UKMMC), a number of suspected transfusion reactions (TR) featured unusual isolated episodes of red-coloured-urine or haemoglobinuria among paediatric patients without clinical features of acute haemolytic TR. Haemolysis of irradiated red cells was suspected as a cause. This study was conducted to evaluate haemolytic changes of RBC components following irradiation. A prospective, pre- and post- irradiation comparative study was conducted on 36 paired RBC-components in the blood-bank, UKMMC in the year 2013. Samples were tested for plasma-Hb, percent-haemolysis, plasma-potassium (K⁺) and lactate dehydrogenase (LDH) level. Post-irradiation mean plasma-Hb and percent-haemolysis were significantly higher than pre-irradiation values at 0.09 ±0.06g/dl VS 0.10 ± 0.06g/dl and 0.19 ± 0.13% VS 0.22 ± .13% respectively, while plasma-K⁺ and LDH values did not show significant difference. However, the mean percent-haemolysis level was still within recommended acceptable levels for clinical use, supporting that irradiated RBC units were safe and of acceptable quality for transfusion. There was no conclusive reason for isolated haemoglobinuria following transfusion of irradiated red-cell products. Further research is suggested to investigate the other possible causes.
  10. Leong CF, Cheong SK, Fadilah SA
    Med J Malaysia, 1999 Dec;54(4):517-9.
    PMID: 11072473
    A 56-year-old Chinese lady with valvular heart disease and atrial fibrillation was referred to us from a private hospital for further management of autoimmune haemolytic anaemia. Physical examination and laboratory investigations did not support the diagnosis of haemolytic anaemia. However, direct antiglobulin test (DAT) was strongly positive with anti-IgG and negative with anti-C3d. There was also mild anaemia and reticulocytosis, which was attributable to persistent haematuria. The DAT became positive after commencing Unasyn and cessation was associated with decreasing reactivity of the positive DAT. We believe that the positive DAT in this patient was most likely due to the Unasyn therapy.
  11. Kuan JW, Su AT, Leong CF
    J Clin Apher, 2017 Dec;32(6):517-542.
    PMID: 28485020 DOI: 10.1002/jca.21550
    Granulocyte-colony stimulating factor (G-CSF) mobilizes and increases the amount of hematopoietic stem cells in peripheral blood, enabling its harvest by few apheresis procedures. The pegylated G-CSF has longer half-life and is given once only, which is more comfortable for patients, whereas the non-pegylated requires multiple daily injection because of its short half-life. We summarized results of randomized trials comparing the efficacy and safety of pegylated and non-pegylated G-CSF for peripheral blood stem cell mobilization. We searched the Cochrane CENTRAL, MEDLINE, EMBASE, and two conference proceedings. Two authors made the selection, extracted data and evaluated methodological quality using GRADE independently. We used random-effects model for meta-analysis. We found 3956 records and retrieved 47 full texts. We included eight randomized trials with a total number of 554 randomized and 532 analyzed subjects. The meta-analysis included five trials because not all trials reported the same outcomes. Pooling data from two studies shows no evidence for a difference in the successful mobilization rate (CD34+ cell ≥ 2 × 106 /kg collected) between pegfilgrastim 6 mg (early administration) and filgrastim 5 µg/kg/day (147 participants; risk ratio (RR) 0.87, 95% confidence interval (95%CI) 0.67-1.11; P = .26). Pooling data from three studies shows no difference in the incidence of adverse events between pegylated and non-pegylated G-CSF (170 participants; RR 0.86, 95%CI 0.34-2.17; P = .75). No difference found on the quantity of CD34+ cells collected, number of apheresis procedure in successful mobilization, level of peak PB CD34+ cells achieved, and day of neutrophil and platelet engraftment.
  12. Ahadon M, Abdul Aziz S, Wong CL, Leong CF
    Malays J Pathol, 2018 Apr;40(1):41-48.
    PMID: 29704383 MyJurnal
    INTRODUCTION: Microparticles are membrane bound vesicles, measuring less than 1.0 um, which are released during cellular activation or during apoptosis. Studies have shown that these circulating microparticles play a role in coagulation, cell signaling and cellular interactions. Increased levels of circulating microparticles have been observed in a number of conditions where there is vascular dysfunction, thrombosis and inflammation. The objective of this study was to determine the various plasma-derived microparticles in patients with polycythaemia vera (PV) in Universiti Kebangsaan Malaysia Medical Centre and to compare them with normal control.

    METHODS: A total of 15 patients with PV and 15 healthy volunteers were included in this cross-sectional descriptive study. Plasma samples from both patients and healthy volunteers were prepared and further processed for isolation of microparticles. Flow cytometry analyses were then carried out in all samples to determine the cellular origin of the microparticles. Full blood count parameters for both groups were also collected. Data collected were analyzed using SPSS version 12.0.

    RESULTS: Patients with PV had a significantly higher percentage of platelet derived microparticles compared to healthy controls (P <0.05). The control group had a higher level of endothelial derived microparticles but the differences were not statistically significant (P > 0.05).

    CONCLUSION: The median percentage of positive events for platelet derived microparticles was higher in patients with PV compared to normal healthy controls.

  13. Suria AA, Nurasyikin Y, Adibah AG, Cheah FC, Leong CF
    Clin Ter, 2014;165(3):151-4.
    PMID: 24999569 DOI: 10.7417/CT.2014.1714
    ABO incompatibility and glucose-6-phosphate dehydrogenase deficiency G6PD are common haematological problems affecting the newborn. The resulting haemolytic disease of foetus and newborn (HDFN) caused by either of these pathologies generally follows a benign course. It is typically characterized by mild jaundice without significant anaemia. ABO incompatibility alone as a cause of foetal hydrops is extremely rare. We report a case of a newborn baby girl with an anti-B isoimmunisation and G6PD deficiency manifesting with hydrops foetalis, anaemia and hyperbilirubinaemia, born to a mother with blood group O.
  14. Mok PL, Cheong SK, Leong CF, Chua KH, Ainoon O
    Tissue Cell, 2012 Aug;44(4):249-56.
    PMID: 22560724 DOI: 10.1016/j.tice.2012.04.002
    Mesenchymal stromal cells (MSC) are an attractive cell-targeting vehicle for gene delivery. MIDGE (an acronym for Minimalistic, Immunologically Defined Gene Expression) construct is relatively safer than the viral or plasmid expression system as the detrimental eukaryotic and prokaryotic gene and sequences have been eliminated. The objective of this study was to test the ability of the human MSC (hMSC) to deliver the erythropoietin (EPO) gene in a nude mice model following nucleofection using a MIDGE construct. hMSC nucleofected with MIDGE encoding the EPO gene was injected subcutaneously in Matrigel at the dorsal flank of nude mice. Subcutaneous implantation of nucleofected hMSC resulted in increased hemoglobin level with presence of human EPO in the peripheral blood of the injected nude mice in the first two weeks post-implantation compared with the control groups. The basal layer of the hair shaft in the dermal layer was found to be significantly positive for immunohistochemical staining of a human EPO antibody. However, only a few basal layers of the hair shaft were found to be positively stained for CD105. In conclusion, hMSC harboring MIDGE-EPO could deliver and transiently express the EPO gene in the nude mice model. These cells could be localized to the hair follicle and secreted EPO protein might have possible role in hair regeneration.
  15. Yousuf R, Abdul Aziz S, Yusof N, Leong CF
    J Med Case Rep, 2012;6:71.
    PMID: 22348809 DOI: 10.1186/1752-1947-6-71
    Hemolytic disease of the fetus and newborn is most commonly caused by anti-D alloantibody. It is usually seen in Rhesus D (RhD)-negative mothers that have been previously sensitized. We report here a case of hemolytic disease of the fetus and newborn in a newborn baby caused by anti-D and anti-S alloantibodies, born to a mother who was RhD negative, but with no previous serological evidence of RhD alloimmunization.
  16. Mok PL, Cheong SK, Leong CF, Chua KH, Ainoon O
    Cytotechnology, 2012 Mar;64(2):203-16.
    PMID: 22160354 DOI: 10.1007/s10616-011-9413-2
    Human mesenchymal stromal cell (hMSC) is a potential target for cell and gene therapy-based approaches against a variety of different diseases. Whilst cationic lipofection has been widely experimented, the Nucleofector technology is a relatively new non-viral transfection method designed for primary cells and hard-to-transfect cell lines. Herein, we compared the efficiency and viability of nucleofection with cationic lipofection, and used the more efficient transfection method, nucleofection, to deliver a construct of minimalistic, immunologically defined gene expression encoding the erythropoietin (MIDGE-EPO) into hMSC. MIDGE construct is relatively safer than the viral and plasmid expression systems as the detrimental eukaryotic and prokaryotic gene and sequences have been eliminated. Using a plasmid encoding the luciferase gene, we demonstrated a high transfection efficiency using the U-23 (21.79 ± 1.09%) and C-17 (5.62 ± 1.09%) pulsing program in nucleofection. The cell viabilities were (44.93 ± 10.10)% and (21.93 ± 5.72)%, respectively 24 h post-nucleofection. On the other hand, lipofection treatment only yielded less than 0.6% efficiencies despite showing higher viabilities. Nucleofection did not affect hMSC renewability, immunophenotype and differentiation potentials. Subsequently, we nucleofected MIDGE-EPO using the U-23 pulsing program into hMSC. The results showed that, despite a low nucleofection efficiency with this construct, the EPO protein was stably expressed in the nucleofected cells up to 55 days when determined by ELISA or immunocytochemical staining. In conclusion, nucleofection is an efficient non-viral transfection approach for hMSC, which when used in conjunction with a MIDGE construct, could result in extended and stable transgene expression in hMSC.
  17. Maha A, Cheong SK, Leong CF, Seow HF
    Malays J Pathol, 2009 Dec;31(2):81-91.
    PMID: 20514850 MyJurnal
    Signal transduction pathways are constitutively expressed in leukaemic cells resulting in aberrant survival of the cells. It is postulated that in cells of chemo-sensitive patients, chemotherapy induces apoptotic signals leading to cell death while survival signals are maintained in cells of chemo-resistant patients. There is very little information currently, on the expression of these mediators in patients immediately after chemotherapy initiation. We examined the expression pattern of proinflammatory cytokines, signaling molecules of the PI3K and MAPK pathways molecules and death receptor, DR5 on paired samples at diagnosis and during chemotherapy in acute myeloid leukaemia patients treated with cytosine arabinoside and daunorubicin. The results were correlated with remission status one month after chemotherapy. We found that in chemo-sensitive patients, chemotherapy significantly increased the percentage of cases expressing TNF-alpha (p = 0.025, n = 9) and IL-6 (p = 0.002, n = 11) compared to chemo-resistant cases. We also observed an increased percentage of chemo-sensitive cases expressing DR5 and phosphorylated p38, and Jnk. Thus, expression of TNF-alpha, IL-6, DR5, phospho-p38 and phospho-Jnk may regulate cell death in chemo-sensitive cases. In contrast, a significantly higher percentage of chemo-resistant cases expressed phospho-Bad (p = 0.027, n = 9). IL-beta and IL-18 were also found to be higher in chemo-resistant cases at diagnosis and during chemotherapy. Thus, expression of various cellular molecules in leukaemic blasts during chemotherapy may be useful in predicting treatment outcome. These cellular molecules may also be potential targets for alternative therapy.
  18. Yap FL, Cheong SK, Ammu R, Leong CF
    Malays J Pathol, 2009 Dec;31(2):113-20.
    PMID: 20514854 MyJurnal
    In this study, we evaluated the biological properties of human mesenchymal stem cells transfected (hMSC) with a plasmid vector expressing human cytokine interleukin-12 (IL-12). Surface markers were analysed by immunophenotyping using flow cytometry. Differentiation capability was evaluated towards adipogenesis and osteogenesis. We demonstrated that successfully transfected hMSC retained their surface immunophenotypes and differentiation potential into adipocytes and osteocytes. These results indicate that hMSC may be a suitable vehicle for gene transduction.
  19. Noor-Fadzilah Z, Leong CF, Sabariah MN, Cheong SK
    Malays J Pathol, 2009 Dec;31(2):129-32.
    PMID: 20514856 MyJurnal
    Idiopathic myelofibrosis occurs predominantly in older adults. It is very rarely seen in children. We describe a 3-year-old girl with Down's syndrome who presented with recurrent chest infections associated with anaemia and easy bruising. There was mild hepatosplenomegaly. Full blood picture revealed pancytopaenia with leucoerythroblastosis with absence of circulating blast cells. Repeated attempts at bone marrow aspiration and trephine biopsy were unsuccessful. A trephine biopsy from the tibia showed depressed myelopoiesis and erythropoiesis, megakaryocytes with atypical morphology and increased bone marrow reticulin fibres, findings compatible with idiopathic myelofibrosis. She was treated symptomatically as she was clinically stable. Review of the English literature online yielded 46 reported cases of childhood idiopathic myelofibrosis with variable outcome from spontaneous remission to an indolent course with shortened survival. 6 cases evolved to another malignancy. 5 cases were associated with Down's syndrome.
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