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Search Results: 1 - 10 of 100417 matches for " I-Mei Siu "
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Ferromagnetic Dissection in a Rat Glioma Model  [PDF]
Sina Tok, Marian C. Neidert, Momen Sharab, I-Mei Siu, Jeanine P. Reyes, Vanessa Charubhumi, Robert T. Wicks, Charles Eberhart, George I. Jallo, Betty M. Tyler
Journal of Cancer Therapy (JCT) , 2015, DOI: 10.4236/jct.2015.67067
Abstract: Background: We compared cutting and coagulation of a novel ferromagnetic tool (FMwand) with modalities currently used in the clinical setting. Methods: 24 F344 rats with 9L gliosarcoma flank tumours were randomized into 2 groups (n = 12): 1) Five parallel incisions were made into the tumor of each rat using monopolar electrosurgery (MES) cut mode, MES coagulation (coag) mode, FMwand, carbon dioxide (CO2) laser and cold scalpel. 2) Two parallel incisions were made comparing the MES and the FMwand, both with resecting loop tips. The study was then repeated by a second surgeon. The surgeons applied a grading scale (1 = worst, 5 = best) based on their observations. Results: Average scores for FMwand were superior in ease of tissue dissection (3.58), distortion upon tissues (3.67), and smoke production (2.87). CO2 laser led in effectiveness of hemostasis (4.32). MES cut mode had the highest scores for ease of cleaning of tip (3.17) and speed of dissection (3.92). The FMwand loop device led in all attributes except for ease of cleaning. Conclusions: The FMwand outperformed CO2 laser significantly in ease and speed. It was superior compared to MES cut mode for hemostasis and superior compared to coag mode in ease and speed, distortion upon tissues and smoke production. The FMwand loop was significantly better compared to MES loop for hemostasis, distortion, ease and speed. The FMwand was shown to be safe and effective for hemostatic soft tissue cutting and coagulation.
Evaluation of Tyrosine Kinase Inhibitor Combinations for Glioblastoma Therapy
Avadhut D. Joshi, Watcharin Loilome, I-Mei Siu, Betty Tyler, Gary L. Gallia, Gregory J. Riggins
PLOS ONE , 2012, DOI: 10.1371/journal.pone.0044372
Abstract: Glioblastoma multiforme (GBM) is the most common intracranial cancer but despite recent advances in therapy the overall survival remains about 20 months. Whole genome exon sequencing studies implicate mutations in the receptor tyrosine kinase pathways (RTK) for driving tumor growth in over 80% of GBMs. In spite of various RTKs being mutated or altered in the majority of GBMs, clinical studies have not been able to demonstrate efficacy of molecular targeted therapies using tyrosine kinase inhibitors in GBMs. Activation of multiple downstream signaling pathways has been implicated as a possible means by which inhibition of a single RTK has been ineffective in GBM. In this study, we sought a combination of approved drugs that would inhibit in vitro and in vivo growth of GBM oncospheres. A combination consisting of gefitinib and sunitinib acted synergistically in inhibiting growth of GBM oncospheres in vitro. Sunitinib was the only RTK inhibitor that could induce apoptosis in GBM cells. However, the in vivo efficacy testing of the gefitinib and sunitinib combination in an EGFR amplified/ PTEN wild type GBM xenograft model revealed that gefitinib alone could significantly improve survival in animals whereas sunitinib did not show any survival benefit. Subsequent testing of the same drug combination in a different syngeneic glioma model that lacked EGFR amplification but was more susceptible to sunitinib in vitro demonstrated no survival benefit when treated with gefitinib or sunitinib or the gefitinib and sunitinib combination. Although a modest survival benefit was obtained in one of two animal models with EGFR amplification due to gefitinib alone, the addition of sunitinib, to test our best in vitro combination therapy, did not translate to any additional in vivo benefit. Improved targeted therapies, with drug properties favorable to intracranial tumors, are likely required to form effective drug combinations for GBM.
Erlotinib Inhibits Growth of a Patient-Derived Chordoma Xenograft
I-Mei Siu, Jacob Ruzevick, Qi Zhao, Nick Connis, Yuchen Jiao, Chetan Bettegowda, Xuewei Xia, Peter C. Burger, Christine L. Hann, Gary L. Gallia
PLOS ONE , 2013, DOI: 10.1371/journal.pone.0078895
Abstract: Chordomas are rare primary bone tumors that occur along the neuraxis. Primary treatment is surgery, often followed by radiotherapy. Treatment options for patients with recurrence are limited and, notably, there are no FDA approved therapeutic agents. Development of therapeutic options has been limited by the paucity of preclinical model systems. We have established and previously reported the initial characterization of the first patient-derived chordoma xenograft model. In this study, we further characterize this model and demonstrate that it continues to resemble the original patient tumor histologically and immunohistochemically, maintains nuclear expression of brachyury, and is highly concordant with the original patient tumor by whole genome genotyping. Pathway analysis of this xenograft demonstrates activation of epidermal growth factor receptor (EGFR). In vitro studies demonstrate that two small molecule inhibitors of EGFR, erlotinib and gefitinib, inhibit proliferation of the chordoma cell line U-CH 1. We further demonstrate that erlotinib significantly inhibits chordoma growth in vivo. Evaluation of tumors post-treatment reveals that erlotinib reduces phosphorylation of EGFR. This is the first demonstration of antitumor activity in a patient-derived chordoma xenograft model and these findings support further evaluation of EGFR inhibitors in this disease.
Podocalyxin-Like Protein Is Expressed in Glioblastoma Multiforme Stem-Like Cells and Is Associated with Poor Outcome
Zev A. Binder, I-Mei Siu, Charles G. Eberhart, Colette ap Rhys, Ren-Yuan Bai, Verena Staedtke, Hao Zhang, Nicolas R. Smoll, Steven Piantadosi, Sara G. Piccirillo, Francesco DiMeco, Jon D. Weingart, Angelo Vescovi, Alessandro Olivi, Gregory J. Riggins, Gary L. Gallia
PLOS ONE , 2013, DOI: 10.1371/journal.pone.0075945
Abstract: Glioblastoma multiforme (GBM) is the most common primary malignant adult brain tumor and is associated with poor survival. Recently, stem-like cell populations have been identified in numerous malignancies including GBM. To identify genes whose expression is changed with differentiation, we compared transcript profiles from a GBM oncosphere line before and after differentiation. Bioinformatic analysis of the gene expression profiles identified podocalyxin-like protein (PODXL), a protein highly expressed in human embryonic stem cells, as a potential marker of undifferentiated GBM stem-like cells. The loss of PODXL expression upon differentiation of GBM stem-like cell lines was confirmed by quantitative real-time PCR and flow cytometry. Analytical flow cytometry of numerous GBM oncosphere lines demonstrated PODXL expression in all lines examined. Knockdown studies and flow cytometric cell sorting experiments demonstrated that PODXL is involved in GBM stem-like cell proliferation and oncosphere formation. Compared to PODXL-negative cells, PODXL-positive cells had increased expression of the progenitor/stem cell markers Musashi1, SOX2, and BMI1. Finally, PODXL expression directly correlated with increasing glioma grade and was a marker for poor outcome in patients with GBM. In summary, we have demonstrated that PODXL is expressed in GBM stem-like cells and is involved in cell proliferation and oncosphere formation. Moreover, high PODXL expression correlates with increasing glioma grade and decreased overall survival in patients with GBM.
Myocardial dysfunction in patients with type 2 diabetes mellitus: role of endothelial progenitor cells and oxidative stress
Chun Zhao, Mei Wang, Chung Siu, Ying Hou, Tian Wang, Hung Tse, Kai Yiu
Cardiovascular Diabetology , 2012, DOI: 10.1186/1475-2840-11-147
Abstract: Eighty-seven patients with T2DM and no history of coronary artery disease were recruited. Transthoracic echocardiography and detailed evaluation of left ventricular (LV) systolic function by 2-dimensional (2D) speckle tracking derived strain analysis in 3 orthogonal directions was performed. Four subpopulations of EPCs, including CD34+, CD133+, CD34+/kinase insert domain-containing receptor (KDR)?+?and CD133+/KDR?+?EPCs, were measured by flow cytometry. Oxidative stress was assessed by superoxide dismutase (SOD).The mean age of the patients was 62?±?9?years and 39.6% were male. Those with an impaired longitudinal strain had a lower number of CD34+ EPCs (2.82?±?1.87% vs. 3.74?±?2.12%, P?<?0.05) than those with preserved longitudinal strain. When compared with those with preserved circumferential strain, patients with an impaired circumferential strain had a lower number of CD34+ EPCs (2.63?±?1.80% vs. 3.87?±?2.10%, P?<?0.01) and SOD level (0.13?±?0.06U/ml vs. 0.20?±?0.08U/ml, P?<?0.01). Patients with an impaired radial strain nonetheless had a lower number of CD34+ EPCs (2.62?±?2.08% vs. 3.69?±?1.99%, P?<?0.05). Multivariate analysis demonstrated that only impaired global circumferential strain remained significantly associated with CD34?+?EPCs and SOD.LV global circumferential strain was independently associated with number of CD34+ EPCs and SOD. These findings suggest that myocardial dysfunction in patients with T2DM is related to depletion of EPCs and increased oxidative stress.Type 2 diabetes mellitus (T2DM) is associated with myocardial dysfunction, independent of underlying coronary artery disease. Patients with T2DM have a 2–5 fold higher risk of developing heart failure than those without [1,2]. Although the pathology of myocardial dysfunction in these patients is unclear, it is likely multifactorial and includes increased oxidative stress, [3] microangiopathy, [4] and altered myocardial metabolism and structure with fibrosis [5].Increasing evidence is emergi
A Chinese Mind-Body Exercise Improves Self-Control of Children with Autism: A Randomized Controlled Trial
Agnes S. Chan, Sophia L. Sze, Nicolson Y. Siu, Eliza M. Lau, Mei-chun Cheung
PLOS ONE , 2013, DOI: 10.1371/journal.pone.0068184
Abstract: Self-control problems commonly manifest as temper outbursts and repetitive/rigid/impulsive behaviors, in children with autism spectrum disorders (ASD), which often contributes to learning difficulties and caregiver burden. The present study aims to compare the effect of a traditional Chinese Chan-based mind-body exercise, Nei Yang Gong, with that of the conventional Progressive Muscle Relaxation (PMR) technique in enhancing the self-control of children with ASD. Forty-six age- and IQ-matched ASD children were randomly assigned to receive group training in Nei Yang Gong (experimental group) or PMR (control group) twice per week for four weeks. The participants’ self-control was measured by three neuropsychological tests and parental rating on standardized questionnaires, and the underlying neural mechanism was assessed by the participants’ brain EEG activity during an inhibitory-control task before and after intervention. The results show that the experimental group demonstrated significantly greater improvement in self-control than the control group, which concurs with the parental reports of reduced autistic symptoms and increased control of temper and behaviors. In addition, the experimental group showed enhanced EEG activity in the anterior cingulate cortex, a region that mediates self-control, whereas the PMR group did not. The present findings support the potential application of Chinese Chan-based mind-body exercises as a form of neuropsychological rehabilitation for patients with self-control problems. Chinese Clinical Trial Registry; Registration No.: ChiCTR-TRC-12002561; URL: www.chictr.org.
Thermal conductivity of III-V semiconductor superlattices
S. Mei,I. Knezevic
Physics , 2015, DOI: 10.1063/1.4935142
Abstract: This paper presents a semiclassical model for the anisotropic thermal transport in III-V semiconductor superlattices (SLs). An effective interface rms roughness is the only adjustable parameter. Thermal transport inside a layer is described by the Boltzmann transport equation in the relaxation time approximation and is affected by the relevant scattering mechanisms (three-phonon, mass-difference, and dopant and electron scattering of phonons), as well as by diffuse scattering from the interfaces captured via an effective interface scattering rate. The in-plane thermal conductivity is obtained from the layer conductivities connected in parallel. The cross-plane thermal conductivity is calculated from the layer thermal conductivities in series with one another and with thermal boundary resistances (TBRs) associated with each interface; the TBRs dominate cross-plane transport. The TBR of each interface is calculated from the transmission coefficient obtained by interpolating between the acoustic mismatch model (AMM) and the diffuse mismatch model (DMM), where the weight of the AMM transmission coefficient is the same wavelength-dependent specularity parameter related to the effective interface rms roughness that is commonly used to describe diffuse interface scattering. The model is applied to multiple III-arsenide superlattices, and the results are in very good agreement with experimental findings. The method is both simple and accurate, easy to implement, and applicable to complicated SL systems, such as the active regions of quantum cascade lasers. It is also valid for other SL material systems with high-quality interfaces and predominantly incoherent phonon transport.
The Non-Catalytic Carboxyl-Terminal Domain of ARFGAP1 Regulates Actin Cytoskeleton Reorganization by Antagonizing the Activation of Rac1
Ka Yu Siu,Mei Kuen Yu,Xinggang Wu,Min Zong,Michael G. Roth,Hsiao Chang Chan,Sidney Yu
PLOS ONE , 2012, DOI: 10.1371/journal.pone.0018458
Abstract: The regulation of the actin cytoskeleton and membrane trafficking is coordinated in mammalian cells. One of the regulators of membrane traffic, the small GTP-binding protein ARF1, also activates phosphatidylinositol kinases that in turn affect actin polymerization. ARFGAP1 is a GTPase activating protein (GAP) for ARF1 that is found on Golgi membranes. We present evidence that ARFGAP1 not only serves as a GAP for ARF1, but also can affect the actin cytoskeleton.
A New Species of Asarum from Hong Kong

Hwang Shu-Mei,Wong Siu Tak-Ping,

中国科学院研究生院学报 , 1990,
Abstract: One new species of the genus Asarum (Aristolochiaceae) is described fr-om Hongkong, i.e. Asarum hongkongense S. M. Hwang et T. P. Wong Siu.
Is Distributed Medical Education the Solution?
Eric Siu
University of Toronto Medical Journal , 2010, DOI: 10.5015/utmj.v87i3.1249
Abstract: Despite the focus on increasing medical school enrollment to combat the physician shortage, the number of physicians isn’t the only problem that Canada is faced with, but also the distribution of physicians throughout Canada. Physician maldsitribution is a major concern calling into question whether the principle of “accessibility” is truly being met under the Canada Health Act. A new approach to training physicians – Distributed Medical Education (DME) – has gained tremendous support with 7 of Canada’s 17 medical school opening satellite campuses in rural, underserviced communities to date. It is the goal of these satellite campuses to increase enrollment as well as promote future physician practice in smaller communities. Although innovative and promising, medical schools should continue to re-define and evaluate their curricula to ensure the needs of Canada’s population are being met.
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