Leo K Y So

The University of Hong Kong, Hong Kong, Hong Kong

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Publications (6)24.7 Total impact

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    ABSTRACT: Tissues infected with highly pathogenic avian influenza viruses such as H5N1 and H7N7 are normally required to be fixed in formalin or paraformaldehyde before examination in order to inactivate the virus. In this study commercially available monoclonal antibodies to the influenza nucleoprotein (NP) were evaluated in order to determine which antibodies would identify positive cells in tissues fixed in formalin or paraformaldehyde. An assessment of which antigen retrieval process would unmask antigens blocked by formalin fixation was also made. Of six commercially available monoclonal antibodies tested, only one (HB65, European Veterinary Laboratories) was able to identify all formalin fixed avian, swine and human influenza virus infected tissues, and this was after pronase induced epitope retrieval. This monoclonal antibody is recommended for routine diagnostic use for the detection of influenza A infected tissues that have been fixed in formalin or paraformaldehyde.
    Journal of virological methods 11/2011; 179(2):409-13. DOI:10.1016/j.jviromet.2011.11.006 · 1.78 Impact Factor
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    ABSTRACT: The sensitivities of using hepatic and intestinal ethoxyresorufin-O-deethylase (EROD) activities and hepatic accumulation of secondary/tertiary (2 degrees/3 degrees) lysosomes to detect xenobiotic exposures were assessed in the rabbitfish Siganus oramin in a metropolitan harbour, subtropical Hong Kong, over a complete seasonal cycle of one year. Additional information on the body-burden pollutants and physiological indices in S. oramin, and seasonal variables in seawater quality, were extracted from published data and re-analyzed. Under the influences of pollutant cocktail and seasonal factors, neither the hepatic nor intestinal EROD activity was indicative of total polycyclic aromatic hydrocarbons (Sigma PAH), total polychlorinated biphenyls, condition factor and hepatosomatic index (HSI) in S. oramin. However, the relative ratio of hepatic to intestinal EROD activities provided an indication to differentiate the xenobiotic intake route in the fish through diffusion via gills/skin or consumption of contaminated food. In addition, the elevated hepatic accumulation of 2 degrees/3 degrees lysosomes was closely associated with the dominant temporal trends of zinc and Sigma PAH, as well as reduced HSI, in S. oramin. Being minimally influenced by any investigated seasonal factors, the hepatic 2 degrees/3 degrees lysosomes in S. oramin was recommended as an effective biomarker of xenobiotic exposures and toxic effects for use in coastal pollution monitoring programmes.
    Science of The Total Environment 09/2010; 408(20):4833-40. DOI:10.1016/j.scitotenv.2010.06.003 · 4.10 Impact Factor

  • Chemistry - A European Journal 03/2010; 16(13):3868. DOI:10.1002/chem.201090058 · 5.73 Impact Factor
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    Xian Wang · Kenneth K K Lau · Leo K Y So · Yun Wah Lam ·
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    ABSTRACT: Nonhistone chromosomal proteins in concert with histones play important roles in the replication and repair of DNA and in the regulation of gene expression. The deregulation of these proteins can contribute to the development of a variety of diseases such as cancer. As a nonhistone chromosomal protein, chromodomain helicase DNA binding protein 5 (CHD5) has recently been identified as the product of a novel tumor suppressor gene (TSG), promoting the transcription of p19ink4a and p16arf. The inactivation of CHD5 was achieved partly through genetic deletion since it is located in 1p36, a region frequently deleted in human tumors. In this study, we aim to study the involvement of CHD5 in gastric cancer, the second most common cancer worldwide. CHD5 expression in a panel of gastric cancer cells were determined by quantitative RT-PCR. The methylation of CHD5 was evaluated by methylation specific PCR and bisulfite genome sequencing. The effect of CHD5 on growth of gastric cancer cells was tested by colony formation assay. CHD5 expression was down-regulated in all of gastric cancer cell lines used (100%, 7/7) and significantly restored after pharmacological demethylation. Methylation of CHD5 promoter was detected in all of seven gastric cancer cell lines and in the majority of primary gastric carcinoma tissues examined (73%, 11/15). Finally, ectopic expression of CHD5 in gastric cancer cells led to a significant growth inhibition. CHD5 was a TSG epigenetically down-regulated in gastric cancer.
    Journal of Biomedical Science 10/2009; 16(1):95. DOI:10.1186/1423-0127-16-95 · 2.76 Impact Factor
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    ABSTRACT: Transcription factories have been characterized in cultured mammalian cells, but little is known about the regulation of these nuclear structures in different primary cell types. Using marine medaka, we observed transcription sites labeled by the metabolic incorporation of 5-fluorouridine (5-FU) into nascent RNA. Medaka was permeable to 5-FU in ambient water and became fully labeled within 4 hr of incubation. The incorporation of 5-FU was inhibited by the transcription inhibitor actinomycin D. The 5-FU incorporation sites were detected in the cell nucleus, and could be abolished by RNase digestion. The tissue distribution of 5-FU incorporation was visualized by immunocytochemistry on whole-mount specimens and histological sections. The 5-FU labeling appeared highly cell type specific, suggesting a regulation of the overall transcription activities at tissue level. Mapping of transcription factories by 5-FU incorporation in fish provides a useful and physiologically relevant model for studying the control of gene expression in the context of the functional organization of the cell nucleus. This manuscript contains online supplemental material at http://www.jhc.org. Please visit this article online to view these materials. (J Histochem Cytochem 58:173-181, 2010).
    Journal of Histochemistry and Cytochemistry 10/2009; 58(2):173-81. DOI:10.1369/jhc.2009.954511 · 1.96 Impact Factor
  • Jiyang Fan · Hongxia Li · Jiang Jiang · Leo K Y So · Yun Wah Lam · Paul K Chu ·
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    ABSTRACT: A study was conducted to demonstrate the use of 3C-SiC nanocrystals as biological labels in cell imaging, and fluorescence dynamics and surface chemistry of the nanoparticles. The study also demonstrated that 3C-SiC quantum dots, prepared by electrochemical etching with ultrasonic stirring, can be introduced into cells for robust nontoxic biological probes with low photobleaching and long-term stability. The study used nontoxic and highly resistant against photobleaching nanocrystals. The study found that the 3C-SiC nanocrystals can be used for fluorescent biological probes. The study found that the nanoparticles show a nonotonically increasing UV/Vis spectrum with an onset at 2.8eV. The study confirmed that the nanoparticles can be used in multicolor imaging in various biological systems by improving their size monodispersity.
    Small 08/2008; 4(8):1058-62. DOI:10.1002/smll.200800080 · 8.37 Impact Factor