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Publications (6)30.4 Total impact

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    ABSTRACT: Visualizing early changes in valvular cell functions in vivo may predict the future risk and identify therapeutic targets for prevention of aortic valve stenosis. To test the hypotheses that (1) aortic stenosis shares a similar pathogenesis to atherosclerosis and (2) molecular imaging can detect early changes in aortic valve disease, we used in vivo a panel of near-infrared fluorescence imaging agents to map endothelial cells, macrophages, proteolysis, and osteogenesis in aortic valves of hypercholesterolemic apolipoprotein E-deficient mice (30 weeks old, n=30). Apolipoprotein E-deficient mice with no probe injection (n=10) and wild-type mice (n=10) served as controls. Valves of apolipoprotein E-deficient mice contained macrophages, were thicker than wild-type mice (P<0.001), and showed early dysfunction detected by MRI in vivo. Fluorescence imaging detected uptake of macrophage-targeted magnetofluorescent nanoparticles (24 hours after injection) in apolipoprotein E-deficient valves, which was negligible in controls (P<0.01). Valvular macrophages showed proteolytic activity visualized by protease-activatable near-infrared fluorescence probes. Ex vivo magnetic resonance imaging enhanced with vascular cell adhesion molecule-1-targeted nanoparticles detected endothelial activation in valve commissures, the regions of highest mechanical stress. Osteogenic near-infrared fluorescence signals colocalized with alkaline phosphatase activity and expression of osteopontin, osteocalcin, Runx2/Cbfa1, Osterix, and Notch1 despite no evidence of calcium deposits, which suggests ongoing active processes of osteogenesis in inflamed valves. Notably, the aortic wall contained advanced calcification. Quantitative image analysis correlated near-infrared fluorescence signals with immunoreactive vascular cell adhesion molecule-1, macrophages, and cathepsin-B (P<0.001). Molecular imaging can detect in vivo the key cellular events in early aortic valve disease, including endothelial cell and macrophage activation, proteolytic activity, and osteogenesis.
    Circulation 02/2007; 115(3):377-86. · 15.20 Impact Factor
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    ABSTRACT: Studies to define the overall contribution of lymphocytes to lesion formation in atherosclerosis-susceptible mice have demonstrated relatively subtle effects; the use of lymphocyte-deficient mice, however, compromises both the effector and regulatory arms of the immune system. Here, we tested the hypothesis that deletion of CXCL10 (IP-10), a chemokine specific for effector T cells that has been localized within atherosclerotic lesions, would significantly inhibit atherogenesis. Compound deficient Apoe(-/-)/Cxcl10(-/-) mice fed a Western-style diet for either 6 or 12 weeks demonstrated significant reductions in atherogenesis as compared with Apoe(-/-) controls, as assessed by both aortic en face and cross-sectional analyses. Immunohistochemical studies revealed a decrease in the accumulation of CD4+ T cells, whereas quantitative polymerase chain reaction analysis of lesion-rich aortic arches demonstrated a marked reduction in mRNA for CXCR3, the CXCL10 chemokine receptor. Although overall T-cell accumulation was diminished significantly, we found evidence to suggest that regulatory T-cell (Treg) numbers and activity were enhanced, as assessed by increased message for the Treg-specific marker Foxp3, as well as increases in immunostaining for the Treg-associated cytokines interleukin-10 and transforming growth factor-beta1. We also documented naturally occurring Treg cells in human atherosclerotic lesions. We provide novel evidence for a functional role for the effector T-cell chemoattractant CXCL10 in atherosclerotic lesion formation by modulating the local balance of the effector and regulatory arms of the immune system.
    Circulation 06/2006; 113(19):2301-12. · 15.20 Impact Factor
  • Proceeding of an international workshop on VLSI for neural networks and artificial intelligence; 01/1995
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    W. Luk, V. Lok, I. Page
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    ABSTRACT: The authors describe a method for speeding up divide-and-conquer algorithms with a hardware coprocessor, using sorting as an example. The method employs a conventional processor for the `divide' and `merge' phases, while the `conquer' phase is handled by a purpose-built coprocessor. It is shown how transformation techniques from the Ruby language can be adopted in developing a family of systolic sorters, and how one of the resulting designs is prototyped in eight FPGAs on a PC coprocessor board known as CHS2×4 from Algotronix. The execution of the hardware unit is embedded in a sorting program, with the PC host merging the sorted sequences from the hardware sorter. The performance of this implementation is compared against various sorting algorithms on a number of PC systems
    FPGAs for Custom Computing Machines, 1993. Proceedings. IEEE Workshop on; 05/1993
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    Vincent Lok, Catherine Dower