235 results on '"Ho YK"'
Search Results
2. Do brokers' recommendation changes generate brokerage? Evidence from a central limit order market
- Author
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Smith, T, Chan, HWH, Faff, RW, Ho, YK, Brown, R, Smith, T, Chan, HWH, Faff, RW, Ho, YK, and Brown, R
- Abstract
We examine the short‐term response to recommendation changes on the Australian Securities Exchange, a central limit order market. In both central limit order markets and dealer‐driven markets, clients may reward the recommending broker with increased trade volumes. But a central limit order market does not have mandatory market makers and hence provides greater opportunity to free ride. We find evidence supporting the hypothesis that recommending brokers are rewarded with higher trade volumes and brokerage commission. Consistent with the tipping hypothesis, these rewards are concentrated in the period shortly before the release. There is no evidence of free riding.
- Published
- 2019
3. A selective inhibitor of the immunoproteasome subunit LMP2 induces apoptosis in PC-3 cells and suppresses tumour growth in nude mice
- Author
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Kyung Bo Kim, Jin Tae Hong, Marie Wehenkel, Jung-Ok Ban, Carmony Kc, and Ho Yk
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Male ,Cancer Research ,Transplantation, Heterologous ,Mice, Nude ,Apoptosis ,Pharmacology ,Biology ,immunoproteasome ,Mice ,In vivo ,Cell Line, Tumor ,medicine ,Animals ,Humans ,LMP2 ,Organosilicon Compounds ,RNA, Small Interfering ,Bortezomib ,Cancer ,Prostatic Neoplasms ,Dipeptides ,medicine.disease ,Transplantation ,inhibitor ,IκBα ,Cysteine Endopeptidases ,Oncology ,Proteasome ,target validation ,Cell culture ,Cancer cell ,Cancer research ,Translational Therapeutics ,antitumour activity ,Neoplasm Transplantation ,medicine.drug - Abstract
Background: Although the proteasome is a validated anticancer target, the clinical application of its inhibitors has been limited because of inherent systemic toxicity. To broaden clinical utility of proteasome inhibitors as anticancer agents, it is critical to develop strategies to selectively target proteasomes in cancer cells. The immunoproteasome is an alternative form of the constitutive proteasome that is expressed at high levels in cancer tissues, but not in most normal cells in the body. Methods: To validate the immunoproteasome as a chemotherapeutic target, an immunoproteasome catalytic subunit LMP2-targeting inhibitor and siRNA were used. The sensitivity of PC-3 prostate cancer cells to these reagents was investigated using viability assays. Further, a xenograft model of prostate cancer was studied to test the in vivo effects of LMP2 inhibition. Results: A small molecule inhibitor of the immunoproteasome subunit LMP2, UK-101, induced apoptosis of PC-3 cells and resulted in significant inhibition (∼50–60%) of tumour growth in vivo. Interestingly, UK-101 did not block degradation of IκBα in PC-3 cells treated with TNF-α, suggesting that its mode of action may be different from that of general proteasome inhibitors, such as bortezomib, which block IκBα degradation. Conclusion: These results strongly suggest that the immunoproteasome has important roles in cancer cell growth and thus provide a rationale for targeting the immunoproteasome in the treatment of prostate cancer.
- Published
- 2012
4. Electric-field effects on theN=31Po(1) resonance ofH−
- Author
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Callaway J and Ho Yk
- Subjects
Physics ,Nuclear magnetic resonance ,Autoionization ,Electric field ,Resonance ,Atomic and Molecular Physics, and Optics - Published
- 1994
5. Complex-coordinate calculations of doubly excited1,3Deresonant states ofPs−
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Bhatia Ak and Ho Yk
- Subjects
Physics ,Shape resonance ,Autoionization ,Excited state ,Resonance ,Physics::Atomic Physics ,Atomic physics ,Feshbach resonance ,Atomic and Molecular Physics, and Optics ,Exotic atom ,Ion ,Positronium - Abstract
Doubly excited 1,3 D e resonant states in positronium ions Ps - are calculated by using a method of complex-coordinate rotation. Resonance parameters (both resonance positions and widths) for doubly excited states associated with the n=2 and 3 thresholds of positronium atoms are evaluated using elaborate Hylleraas-type functions. In addition to Feshbach-type resonances lying below the Ps thresholds, we have also identified two 1 D e shape resonances lying above the n=3 Ps threshold
- Published
- 1993
6. Autoionizing1Postates of He between theN=2 and 3 thresholds ofHe+
- Author
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Ho Yk
- Subjects
Physics ,Crystallography ,Atomic physics ,Atomic and Molecular Physics, and Optics ,Slater-type orbital ,Calculation methods - Abstract
Doubly excited {sup 1}{ital P{ital o}} autoionizing states in He between the {ital N}=2 and 3 thresholds of He{sup +} ions are calculated by use of a method of complex-coordinate rotation. Hylleraas-type wave functions are used to calculate resonance parameters for the lowest ten resonances, and products of Slater orbitals are used for higher-lying resonances. In the {ital KTNn} notation, the states reported in the present work include six members in (113{ital n}) series with (3{le}{ital n}{le}8), four members in the ({minus}113{ital n}) series (3{le}{ital n}{le}6), four members in the (203{ital n}) series (4{le}{ital n}{le}7), four members in the (003{ital n}) series (4{le}{ital n}{le}7), and three members in the ({minus}203{ital n}) series with (4{le}{ital n}{le}6). Comparisons are made with other theoretical calculations and with experimental observations.
- Published
- 1991
7. Complex-coordinate calculation ofDe1resonances using Hylleraas functions
- Author
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Bhatia Ak and Ho Yk
- Subjects
Physics ,Quantum mechanics ,Atomic and Molecular Physics, and Optics - Published
- 1990
8. The effects of forecast specificity on the asymmetric short-window share market response to management earnings forecasts
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Chan, H, Faff, R, Ho, YK, Ramsay, A, Chan, H, Faff, R, Ho, YK, and Ramsay, A
- Abstract
Purpose This study aims to test the effects of forecast specificity on the asymmetric short‐window share market response to management earnings forecasts (MEF). Design/methodology/approach The paper examines a large sample of hand‐checked Australian data over the period 1994 to 2001. Using an analyst news benchmark, it estimates a series of regressions to investigate whether the short‐term impact from bad news announcements is greater in magnitude than from good news announcements and whether this differs between routine and non‐routine MEFs. Additionally, it examines whether (after controlling for news content of MEF) there is a differential market impact conditional on specificity: minimum versus maximum versus range versus point. Findings The results indicate that an asymmetric response is evident for the overall sample and a sub‐set of non‐routine forecasts. Contrary to predictions, the results show that forecast specificity, minimum, maximum, range and point MEFs make no additional contribution to the differences in the market reaction to bad or good news. Originality/value The study extends the research investigating the short‐run market impact of MEFs. The main element of innovation derives from the interaction between specificity and news content, as well as distinguishing between routine versus non‐routine cases. Notably, it found little support for the view that more specific forecasts elicit greater market responses. What the results do suggest is that managers appear to choose the form of the forecast to suit the news being delivered. In particular, bad news delivered in a minimum forecast seems to be ignored by the market.
- Published
- 2009
9. Analysts’ recommendation changes or disagreements with market consensus: from which signal does the market take its lead?
- Author
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Brown, RL, Chan, HWH, Ho, YK, Brown, RL, Chan, HWH, and Ho, YK
- Published
- 2007
10. The relation between R&D intensity and future market returns: Does expensing versus capitalization matter?
- Author
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Chan, HWH, Faff, RW, Gharghori, P, Ho, YK, Chan, HWH, Faff, RW, Gharghori, P, and Ho, YK
- Published
- 2007
11. Asymmetric market reactions of growth and value firms with management earnings forecasts
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CHAN, H, Faff, R, Ho, YK, Ramsay, A, CHAN, H, Faff, R, Ho, YK, and Ramsay, A
- Published
- 2007
12. TRENDS IN PLACE OF DEATH, AND THE EFFECT OF DEATH CERTIFICATE CLASSIFICATION AND CODING CHANGES, IN PARKINSONS DISEASE, MOTOR NEURONE DISEASE, AND MULTIPLE SCLEROSIS IN ENGLAND: 1993–2010
- Author
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Sleeman, K, primary, Ho, YK, additional, Verne, J, additional, Glickman, M, additional, Silber, E, additional, Gao, W, additional, and Higginson, IJ, additional
- Published
- 2012
- Full Text
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13. Low-density lipoprotein (LDL) receptor activity in human acute myelogenous leukemia cells
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Ho, YK, Smith, RG, Brown, MS, and Goldstein, JL
- Published
- 1978
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14. Regulation of cholesterol synthesis by low density lipoprotein in isolated human lymphocytes
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Ho, YK, JR, Faust, Bilheimer, DW, Brown, MS, and Goldstein, JL
- Abstract
The rate of cholesterol synthesis from [14C]acetate was low in circulating blood lymphocytes freshly isolated from 17 normal subjects and 4 subjects with homozygous FH. On the other hand, the rate of cholesterol synthesis was two to fourfold above normal in freshly isolated lymphocytes from two subjects with abetalipoproteinemia. When the lymphocytes from subjects with all three genotypes were incubated for 48-72 h in the absence of lipoproteins, the rate of cholesterol synthesis increased by 5-15-fold. The subsequent addition of plasma LDL, but not HDL, rapidly suppressed cholesterol synthesis in the lymphocytes from normal subjects. In contrast, lymphocytes from the FH homozygotes, which have been shown previously to be deficient in cell surface LDL receptors, were resistant to LDL-mediated suppression of cholesterol synthesis. In addition to its ability to suppress cholesterol synthesis after it had been elevated by incubation of the cells in the absence of lipoproteins, LDL was able to suppress the induction of the enhanced rate of sterol synthesis when added to normal lymphocytes immediately after their isolation from the bloodstream. In contrast to the former action of LDL, the latter action of LDL-i.e., the suppression of induction of sterol synthesis-also occurred to a limited extent in lymphocytes from FH homozygotes. However, the FH lymphocytes, but not the normal cells, could be made resistant to this action of LDL by inclusion in the incubation medium of lipoprotein-deficient serum (30 percent, vol/vol) plus HDL (1 mg protein/ml). Considered together with previous data demonstrating a deficiency of LDL receptors in freshly isolated lymphocytes from FH homozygotes, the current studies provide evidence in support of the hypothesis that the interaction of plasma LDL with its cell surface receptor serves to regulate cholesterol synthesis in human lymphocytes.
- Published
- 1977
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15. LED lighting development for intelligent clothing
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Kwok, Kf, Ho, Yk, Norbert Chow CHEUNG, Chan, Kwk, Kwok, Yl, Kwok, Kw, and Cheng, Kwe
16. Evaluating the potential of off-the-shelf engineered mesenchymal stem cells for targeted Hepatocellular Carcinoma treatment: A multisite proof-of-concept study.
- Author
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Ma XN, Ho YK, Goie JYG, Ma CX, Sun ZB, Yao LQ, Zhu XL, Woo JY, Too HP, and Li X
- Abstract
Although combining 5-fluorouracil (5-FU) and Interferon-beta (IFNb) improves response rates in Hepatocellular Carcinoma (HCC), the outcomes remain suboptimal. This study investigates the feasibility of using highly transfected Mesenchymal Stem Cells (MSCs) to deliver a chemotherapeutic (5-FU) and an immunomodulator (IFNb) for localized HCC treatment. Considering the crucial role of cold-chain transportation in off-the-shelf allogeneic therapy, the study also assesses the quality and efficacy of frozen-thawed engineered MSCs, simulating a multisite study process. The engineered MSCs maintained their phenotypes and tumour tropism. With just 10 % engineered MSCs, a killing efficiency of over 70 % was achieved in Huh-7 and HepG2 cell lines in vitro. Coculture studies, soft agar assays, and in vivo experiments confirmed that MSCs are neither tumorigenic nor tumour-promoting. Tumour mass growth was inhibited by >80 % in the treated mice group. TUNEL, Annexin-V, and Ki67 staining confirmed DNA damage, cell death, and proliferation inhibition post-treatment. Blood chemistry and the weight of the mice were comparable to the control group, indicating a good safety profile. This proof-of-concept study demonstrates the efficacy and safety of off-the-shelf CDUPRT-IFNβ_MSCs in targeting hepatocellular carcinoma (HCC) growth. Evaluating the complete value chain of MSC therapy in early-stage preclinical studies is essential for justifying further investigation and clinical translation of this cell product., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper, (Copyright © 2024. Published by Elsevier Masson SAS.)
- Published
- 2024
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17. Enhanced anti-tumor efficacy with multi-transgene armed mesenchymal stem cells for treating peritoneal carcinomatosis.
- Author
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Ho YK, Woo JY, Loke KM, Deng LW, and Too HP
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- Animals, Humans, Cell Line, Tumor, Interferon-beta metabolism, Interferon-beta genetics, Xenograft Model Antitumor Assays, Cytosine Deaminase genetics, Cytosine Deaminase metabolism, Mice, Female, Mesenchymal Stem Cells metabolism, Mesenchymal Stem Cells cytology, Peritoneal Neoplasms therapy, Peritoneal Neoplasms secondary, Peritoneal Neoplasms genetics, Peritoneal Neoplasms pathology, Mesenchymal Stem Cell Transplantation, Pentosyltransferases genetics, Pentosyltransferases metabolism, Transgenes
- Abstract
Background: Mesenchymal stem cells (MSCs) have garnered significant interest for their tumor-tropic property, making them potential therapeutic delivery vehicles for cancer treatment. We have previously shown the significant anti-tumour activity in mice preclinical models and companion animals with naturally occurring cancers using non-virally engineered MSCs with a therapeutic transgene encoding cytosine deaminase and uracil phosphoribosyl transferase (CDUPRT) and green fluorescent protein (GFP). Clinical studies have shown improved response rate with combinatorial treatment of 5-fluorouracil and Interferon-beta (IFNb) in peritoneal carcinomatosis (PC). However, high systemic toxicities have limited the clinical use of such a regime., Methods: In this study, we evaluated the feasibility of intraperitoneal administration of non-virally engineered MSCs to co-deliver CDUPRT/5-Flucytosine prodrug system and IFNb to potentially enhance the cGAS-STING signalling axis. Here, MSCs were engineered to express CDUPRT or CDUPRT-IFNb. Expression of CDUPRT and IFNb was confirmed by flow cytometry and ELISA, respectively. The anti-cancer efficacy of the engineered MSCs was evaluated in both in vitro and in vivo model. ES2, HT-29 and Colo-205 were cocultured with engineered MSCs at various ratio. The cell viability with or without 5-flucytosine was measured with MTS assay. To further compare the anti-cancer efficacy of the engineered MSCs, peritoneal carcinomatosis mouse model was established by intraperitoneal injection of luciferase expressing ES2 stable cells. The tumour burden was measured through bioluminescence tracking., Results: Firstly, there was no changes in phenotypes of MSCs despite high expression of the transgene encoding CDUPRT and IFNb (CDUPRT-IFNb). Transwell migration assays and in-vivo tracking suggested the co-expression of multiple transgenes did not impact migratory capability of the MSCs. The superiority of CDUPRT-IFNb over CDUPRT expressing MSCs was demonstrated in ES2, HT-29 and Colo-205 in-vitro. Similar observations were observed in an intraperitoneal ES2 ovarian cancer xenograft model. The growth of tumor mass was inhibited by ~ 90% and 46% in the mice treated with MSCs expressing CDUPRT-IFNb or CDUPRT, respectively., Conclusions: Taken together, these results established the effectiveness of MSCs co-expressing CDUPRT and IFNb in controlling and targeting PC growth. This study lay the foundation for the development of clinical trial using multigene-armed MSCs for PC., (© 2024. The Author(s).)
- Published
- 2024
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18. Impact of a novel pre-hospital stroke notification programme on acute stroke care key performance indicators in Hong Kong: a multicentre prospective cohort study with historical controls.
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Cheng KY, Yu ELM, Yamamoto T, Kwong JCL, Ho YK, Ngan HK, Lin WH, Lau JMT, Cheung CH, Lee GPC, Siu LH, Sheng B, Wong WWY, Man WY, Cheung CCC, and Tse CT
- Abstract
Introduction: Early identification and initiation of reperfusion therapy is essential for suspected acute ischaemic stroke. A pre-hospital stroke notification (PSN) protocol using FASE (facial drooping, arm weakness, speech difficulties, and eye palsy) was implemented to improve key performance indicators (KPIs) in acute stroke care delivery. We assessed KPIs and clinical outcomes before and after PSN implementation in Hong Kong., Methods: This prospective cohort study with historical controls was conducted in the Accident and Emergency Departments of four public hospitals in Hong Kong. Patients were screened using the PSN protocol between August 2021 and February 2022. Suspected stroke patients between August 2020 and February 2021 were included as historical controls. Door-to-needle (DTN) and door-to-computed tomography (DTC) times before and after PSN implementation were compared. Clinical outcomes including National Institutes of Health Stroke Scale score at 24 hours and modified Rankin Scale score at 3 months after intravenous recombinant tissue-type plasminogen activator (IV-rtPA) were also assessed., Results: Among the 715 patients (266 PSN and 449 non-PSN) included, 50.8% of PSN patients and 37.7% of non-PSN patients had a DTC time within 25 minutes (P<0.001). For the 58 PSN and 134 non-PSN patients given IV-rtPA, median DTN times were 67 and 75.5 minutes, respectively (P=0.007). The percentage of patients with a DTN time within 60 minutes was higher in the PSN group than in the non-PSN group (37.9% vs 21.6%; P=0.019). No statistically significant differences in clinical outcomes were observed., Conclusion: Although the PSN protocol shortened DTC and DTN times, clinical outcomes did not significantly differ., Competing Interests: All authors have disclosed no conflicts of interest.
- Published
- 2024
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19. Characteristics and Methodological Quality of the Top 50 Most Influential Articles on Stroke Rehabilitation: A Bibliometric Analysis.
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Ogihara H, Yamamoto N, Kurasawa Y, Kamo T, Hagiyama A, Hayashi S, and Momosaki R
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- Humans, Bibliometrics, Journal Impact Factor, Research Design, Stroke Rehabilitation, Medicine
- Abstract
Abstract: This study aimed to conduct a comprehensive review of the top 50 most influential articles on stroke rehabilitation to investigate characteristics, such as the number of citations, year of publication, study design, and research topic, as well as to assess the evidence level and methodological quality. Moreover, we performed a supplementary assessment of the top 10 articles published within the past 5 yrs in the same domain, aiming to discern potential shifts in trends and methodological quality. Web of Science was used to search for articles on stroke rehabilitation. The data extracted from the articles included title, journal impact factor, year of publication, total number of citations, article topic, study design, and others. The level of evidence and methodological quality were assessed by two reviewers. Noninvasive brain stimulation and robotic rehabilitation were frequently discussed in the top 50 articles. We found that there was no difference in methodology quality between the top 50 articles in all years and the top ten articles in the past 5 yrs. Furthermore, the number of citations and citation density were not associated with the methodological quality. The findings suggest that the number of citations alone may not be a reliable indicator of research quality., Competing Interests: Financial disclosure statements have been obtained, and no conflicts of interest have been reported by the authors or by any individuals in control of the content of this article., (Copyright © 2024 Wolters Kluwer Health, Inc. All rights reserved.)
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- 2024
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20. Enhanced activity of Candida antarctica lipase B in cholinium aminoate ionic liquids: a combined experimental and computational analysis.
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Chan KK, Sundaram V, Tan J, Ho YK, Ramanan RN, and Ooi CW
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- Hydrophobic and Hydrophilic Interactions, Molecular Dynamics Simulation, Enzyme Stability, Models, Molecular, Choline chemistry, Lipase chemistry, Lipase metabolism, Ionic Liquids chemistry, Fungal Proteins chemistry, Fungal Proteins metabolism
- Abstract
As a class of ionic liquids with higher biocompatibility, cholinium aminoates ([Cho][AA]) hold potential as solvation media for enzymatic bioprocessing. Herein, solvation effect of [Cho][AA] on structural stability and enzymatic activity of Candida antarctica lipase B (CALB) was evaluated using experimental and computational approaches. Influence of [Cho][AA] on CALB stability was investigated using amino acid anions ([AA]
- ) with varying hydrophobicity levels. Choline phenylalaninate ([Cho][Phe]) resulted in 109.1% and 110.4% of relative CALB activity to buffer medium at 25 °C and 50 °C, respectively. Simulation results revealed the improvement of CALB's enzymatic activities by [AA]- with a strong hydrophobic character. Shielding of CALB from water molecules by [AA]- was observed. The level of CALB activity was governed by accumulation level of [AA]- at CALB's first hydration layer. The stronger interaction between His224 and Asp187 was postulated to be driven by [Cho][AA], resulting in the activity enhancement of CALB. The slight improvement of CALB activity in 0.05 M [Cho][Phe] at 50 °C could be due to the larger size of entrance to the catalytic site and the stronger interaction between the catalytic residues. The promising effect of [Cho][Phe] on CALB activation may stimulate research efforts in designing a 'fully green' bioreaction for various industrial applications.Communicated by Ramaswamy H. Sarma.- Published
- 2024
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21. Participatory design of an infographic to help support the care of people living with complex regional pain syndrome.
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Beales D, Ho YK, Lewin J, Loh BW, Yusof AB, Grieve S, Ranelli S, Holthouse D, Mitchell T, and Slater H
- Abstract
Background: Complex regional pain syndrome (CRPS) can be a debilitating pain condition with enduring physical, psychological and social impacts. CRPS is often poorly understood by healthcare professionals and management needs to be tailored to each individual's presentation. People with lived experience express difficulty in accessing reliable and meaningful information about the condition. This study aimed to co-create a trustworthy infographic to share information about the lived experience of CRPS., Methods: We adopted a seven-phase, iterative, participatory methodology to co-create the infographic. Potential infographic content was obtained from qualitative work investigating the lived experience of CRPS. Online consumer engagement (people with doctor diagnosed CRPS/their family, n =20) was used to prioritise content to be included in the infographic and then potential designs were sourced. The research team narrowed the selections down to two designs which were presented to consumers online for final selection ( n =25) and refinement ( n =34)., Results: An infographic for understanding the lived experience of CRPS was completed using participatory design, providing a resource aligned to the needs of people with this condition. Using the Patient Education Materials Assessment Tool, the final infographic rated highly for understandability (92%) and participants indicated significant willingness to share this infographic with others (93%)., Conclusion: A process of participatory design was an effective and efficient process for translation of evidence gathered from qualitative research into a trustworthy resource for people with CRPS and their support people., Competing Interests: The author(s) declared no potential conflicts of interest with respect to the research, authorship, and/or publication of this article., (© The Author(s) 2023.)
- Published
- 2023
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22. Variational perturbation theory for dynamic polarizabilities and dispersion coefficients.
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Xia WH, Zhou ZL, Jiao LG, Liu A, Montgomery HE, Ho YK, and Fritzsche S
- Abstract
An efficient method based on the variational perturbation theory (VPT) is proposed to conveniently calculate the atomic real- and imaginary-frequency dynamic polarizabilities and the interatomic dispersion coefficients. The developed method holds the great advantage that only the system ground state wave function and corresponding radial mean values are needed. Verification of the VPT method on one- and two-electron atoms indicates that the present approximation shows good agreement with calculations based on the sophisticated sum-over-states method. We apply the VPT method to examine the approximate Z-scaling laws of polarizabilities and dispersion coefficients in the He isoelectronic sequence, and to investigate the plasma screening effect on these quantities for embedded atoms. Our calculation demonstrates very well that the VPT method is capable of producing reasonably accurate static and dynamic polarizabilities as well as two- and three-atom dispersion coefficients for plasma-embedded atoms in a wide range of screening parameters.
- Published
- 2023
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23. Hyperpolarizabilities of hydrogenlike atoms in Debye and dense quantum plasmas.
- Author
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He YY, Zhou ZL, Jiao LG, Liu A, Montgomery HE, and Ho YK
- Abstract
The hyperpolarizabilities of the hydrogenlike atoms in Debye and dense quantum plasmas are calculated using the sum-over-states formalism based on the generalized pseudospectral method. The Debye-Hückel and exponential-cosine screened Coulomb potentials are employed to model the screening effects in, respectively, Debye and dense quantum plasmas. Our numerical calculation demonstrates that the present method shows exponential convergence in calculating the hyperpolarizabilities of one-electron systems and the obtained results significantly improve previous predictions in the strong screening environment. The asymptotic behavior of hyperpolarizability near the system bound-continuum limit is investigated and the results for some low-lying excited states are reported. By comparing the fourth-order corrected energies in terms of hyperpolarizability with the resonance energies using the complex-scaling method, we empirically conclude that the applicability of hyperpolarizability in perturbatively estimating the system energy in Debye plasmas lies in the range of [0,F_{max}/2], where F_{max} refers to the maximum electric field strength at which the fourth-order energy correction is equal to the second-order term.
- Published
- 2023
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24. Cryopreservation does not change the performance and characteristics of allogenic mesenchymal stem cells highly over-expressing a cytoplasmic therapeutic transgene for cancer treatment.
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Ho YK, Loke KM, Woo JY, Lee YL, and Too HP
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- Humans, Cell Proliferation, Cell Line, Tumor, Flucytosine pharmacology, Flucytosine metabolism, Cryopreservation, Transgenes, Mesenchymal Stem Cells metabolism, Neoplasms genetics, Neoplasms therapy, Neoplasms metabolism
- Abstract
Background: Mesenchymal stem cells (MSCs) driven gene directed enzyme prodrug therapy is a promising approach to deliver therapeutic agents to target heterogenous solid tumours. To democratize such a therapy, cryopreservation along with cold chain transportation is an essential part of the logistical process and supply chain. Previously, we have successfully engineered MSCs by a non-viral DNA transfection approach for prolonged and exceptionally high expression of the fused transgene cytosine deaminase, uracil phosphoribosyl transferase and green fluorescent protein (CD::UPRT::GFP). The aim of this study was to determine the effects of cryopreservation of MSCs engineered to highly overexpress this cytoplasmic therapeutic transgene., Methods: Modified MSCs were preserved in a commercially available, GMP-grade cryopreservative-CryoStor10 (CS10) for up to 11 months. Performance of frozen-modified MSCs was compared to freshly modified equivalents in vitro. Cancer killing potency was evaluated using four different cancer cell lines. Migratory potential was assessed using matrigel invasion assay and flow cytometric analysis for CXCR4 expression. Frozen-modified MSC was used to treat canine patients via intra-tumoral injections, or by intravenous infusion followed by a daily dose of 5-flucytosine (5FC)., Results: We found that cryopreservation did not affect the transgene expression, cell viability, adhesion, phenotypic profile, and migration of gene modified canine adipose tissue derived MSCs. In the presence of 5FC, the thawed and freshly modified MSCs showed comparable cytotoxicity towards one canine and three human cancer cell lines in vitro. These cryopreserved cells were stored for about a year and then used to treat no-option-left canine patients with two different types of cancers and notably, the patients showed progression-free interval of more than 20 months, evidence of the effectiveness in treating spontaneously occurring cancers., Conclusion: This study supports the use of cryopreserved, off-the-shelf transiently transfected MSCs for cancer treatment., (© 2022. The Author(s).)
- Published
- 2022
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25. Neutral particles pushed or pulled by laser pulses: erratum.
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Wang PX, Wei Q, Cai P, Wang JX, and Ho YK
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We present an erratum to our Letter [Opt. Lett.41, 230 (2016)10.1364/OL.41.000230]. This erratum corrects three typing errors. The corrections have no influence on the results and conclusions of the original Letter.
- Published
- 2022
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26. Effect of magnetic field on nano-magnetite composite exhibits in ion-adsorption.
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Lo FF, Kow KW, Kung F, Ahamed F, Kiew PL, Yeap SP, Chua HS, Chan CH, Yusoff R, and Ho YK
- Abstract
Nano-magnetites are widely researched for its potential as an excellent adsorbent in many applications. However, the efficiency of the nano-magnetites are hindered by their tendency to agglomerate. In this work, we dispersed and embedded the nano-magnetites in a porous silica gel matrix to form a nanocomposite to reduce the extent of agglomeration and to enhance the adsorption performance. Our experimental results showed that the removal efficiency of Cu
2+ ion has improved by 46% (22.4 ± 2.2%) on the nano-magnetite-silica-gel (NMSG) nanocomposite as compared to pure nano-magnetites (15.3 ± 0.6%). The adsorption capacity is further enhanced by 39% (from 11.2 ± 1.1 to 15.6 ± 1.6 mg/g) by subjecting the NMSG to a magnetic field prior to adsorption. We infer that the magnetic field aligned the magnetic domains within the nano-magnetites, resulting in an increased Lorentz force during adsorption. Similar alignment of magnetic domains is near to impossible in pure nano-magnetites due to severe agglomeration. We further found that the adsorption capacity of the NMSG can be manipulated with an external magnetic field by varying the strength and the configurations of the field. Equipped with proper process design, our finding has great potentials in processes that involve ion-adsorptions, for example, NMSG can: (i) replace/reduce chemical dosing in controlling adsorption kinetics, (ii) replace/reduce complex chemicals required in ion-chromatography columns, and (iii) reduce wastage of nano-adsorbents by immobilizing it in a porous matrix., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2021 Elsevier B.V. All rights reserved.)- Published
- 2021
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27. Peri-procedural Trans-esophageal Echocardiographic Sizing of the Native Left Ventricular Outflow Tract During Edwards INTUITY Valve Implantation.
- Author
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Lim K, Ho YK, Chow SCY, Fujikawa T, Lee AP, and Wong RHL
- Abstract
Background: The Edwards INTUITY rapid deployment valve was anchored on the left ventricular outflow tract (LVOT) by radial force akin to transcatheter balloon-expandable valves. This design feature facilitates minimally invasive and complex procedures but comes at the price of compressing the atrioventricular conduction bundle and potential requirement for pacemaker implantation. Methods: A retrospective observational study was conducted on 30 consecutive patients who received the INTUITY valve at our institution from August 2018 to January 2021. Demographical, clinical, and echocardiographic parameters were collected for 90 days post-operatively. The diameter of the native LVOT at the landing site of the sub-annular stent was retrospectively measured using archived trans-esophageal echocardiographic images. A line was drawn from the inner edge of the septal endocardium to the inner edge of the anterior mitral leaflet in mid-systole, parallel to the aortic annulus, 6-8 mm apical to the aortic annulus depending on the valve size and the corresponding stent length. Risk factors associated with new onset conduction disturbances, defined as the occurrence of bundle branch block or complete heart block, were analyzed. Results: Operative mortality was 3.3%. Pre-operatively, permanent pacemakers were required for two patients who were excluded from the subsequent analysis. New onset conduction disturbances occurred in four of the remaining 28 patients (14.3%). This included two incidences of persistent left bundle branch block and two incidences of permanent pacemaker implantation due to complete heart block. Univariate analysis identified over-sizing of the native LVOT by 5 mm or more as a significant risk factor associated with conduction disturbance. Conclusion: During INTUITY vale implantation, in addition to the aortic annulus, the landing site of the sub-annular stent within the native LVOT should also be sized pre-bypass. Over-sizing the native LVOT by 5 mm or more was associated with an increased risk of new onset conduction disturbances and should be avoided., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2021 Lim, Ho, Chow, Fujikawa, Lee and Wong.)
- Published
- 2021
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28. Modeling coordinated enzymatic control of saccharification and fermentation by Clostridium thermocellum during consolidated bioprocessing of cellulose.
- Author
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Ahamed F, Song HS, and Ho YK
- Subjects
- Fermentation, Metabolic Engineering, Metabolic Networks and Pathways physiology, Cellulose metabolism, Clostridium thermocellum enzymology, Clostridium thermocellum metabolism, Models, Biological
- Abstract
Consolidated bioprocessing (CBP) of cellulose is a cost-effective route to produce valuable biochemicals by integrating saccharification, fermentation and cellulase synthesis in a single step. However, the lack of understanding of governing factors of interdependent saccharification and fermentation in CBP eludes reliable process optimization. Here, we propose a new framework that synergistically couples population balances (to simulate cellulose depolymerization) and cybernetic models (to model enzymatic regulation of fermentation) to enable improved understanding of CBP. The resulting framework, named the unified cybernetic-population balance model (UC-PBM), enables simulation of CBP driven by coordinated control of enzyme synthesis through closed-loop interactions. UC-PBM considers two key aspects in controlling CBP: (1) heterogeneity in cellulose properties and (2) cellular regulation of competing cell growth and cellulase secretion. In a case study on Clostridium thermocellum, UC-PBM not only provides a decent fit with various exometabolomic data, but also reveals that: (i) growth-decoupled cellulase-secreting pathways are only activated during famine conditions to promote the production of growth substrates, and (ii) starting cellulose concentration has a strong influence on the overall flux distribution. Equipped with mechanisms of cellulose degradation and fermentative regulations, UC-PBM is practical to explore phenotypic functions for primary evaluation of microorganisms' potential for metabolic engineering and optimal design of bioprocess., (© 2021 Wiley Periodicals LLC.)
- Published
- 2021
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29. A facile and scalable in production non-viral gene engineered mesenchymal stem cells for effective suppression of temozolomide-resistant (TMZR) glioblastoma growth.
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Tu GXE, Ho YK, Ng ZX, Teo KJ, Yeo TT, and Too HP
- Subjects
- Animals, Cell Line, Tumor, Humans, Mice, Mice, Nude, Reproducibility of Results, Temozolomide pharmacology, Xenograft Model Antitumor Assays, Brain Neoplasms genetics, Brain Neoplasms therapy, Glioblastoma genetics, Glioblastoma therapy, Mesenchymal Stem Cells
- Abstract
Background: Mesenchymal stem cells (MSCs) serve as an attractive vehicle for cell-directed enzyme prodrug therapy (CDEPT) due to their unique tumour-nesting ability. Such approach holds high therapeutic potential for treating solid tumours including glioblastoma multiforme (GBM), a devastating disease with limited effective treatment options. Currently, it is a common practice in research and clinical manufacturing to use viruses to deliver therapeutic genes into MSCs. However, this is limited by the inherent issues of safety, high cost and demanding manufacturing processes. The aim of this study is to identify a facile, scalable in production and highly efficient non-viral method to transiently engineer MSCs for prolonged and exceptionally high expression of a fused transgene: yeast cytosine deaminase::uracil phosphoribosyl-transferase::green fluorescent protein (CD::UPRT::GFP)., Methods: MSCs were transfected with linear polyethylenimine using a cpg-free plasmid encoding the transgene in the presence of a combination of fusogenic lipids and β tubulin deacetylase inhibitor (Enhancer). Process scalability was evaluated in various planar vessels and microcarrier-based bioreactor. The transfection efficiency was determined with flow cytometry, and the therapeutic efficacy of CD::UPRT::GFP expressing MSCs was evaluated in cocultures with temozolomide (TMZ)-sensitive or TMZ-resistant human glioblastoma cell lines. In the presence of 5-fluorocytosine (5FC), the 5-fluorouracil-mediated cytotoxicity was determined by performing colometric MTS assay. In vivo antitumor effects were examined by local injection into subcutaneous TMZ-resistant tumors implanted in the athymic nude mice., Results: At > 90% transfection efficiency, the phenotype, differentiation potential and tumour tropism of MSCs were unaltered. High reproducibility was observed in all scales of transfection. The therapeutically modified MSCs displayed strong cytotoxicity towards both TMZ-sensitive and TMZ-resistant U251-MG and U87-MG cell lines only in the presence of 5FC. The effectiveness of this approach was further validated with other well-characterized and clinically annotated patient-derived GBM cells. Additionally, a long-term suppression (> 30 days) of the growth of a subcutaneous TMZ-resistant U-251MG tumour was demonstrated., Conclusions: Collectively, this highly efficient non-viral workflow could potentially enable the scalable translation of therapeutically engineered MSC for the treatment of TMZ-resistant GBM and other applications beyond the scope of this study.
- Published
- 2020
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30. A highly efficient non-viral process for programming mesenchymal stem cells for gene directed enzyme prodrug cancer therapy.
- Author
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Ho YK, Woo JY, Tu GXE, Deng LW, and Too HP
- Subjects
- Adolescent, Animals, Cell Line, Tumor, Female, Glioblastoma therapy, Humans, Mesenchymal Stem Cell Transplantation, Mesenchymal Stem Cells metabolism, Mice, Mice, Nude, Polyethyleneimine, Transfection methods, Young Adult, Genetic Engineering methods, Genetic Therapy methods, Genetic Vectors, Mesenchymal Stem Cells enzymology, Neoplasms therapy, Prodrugs metabolism
- Abstract
Mesenchymal stem cells (MSCs) driven gene-directed enzyme prodrug therapy has emerged as a potential strategy for cancer treatment. The tumour-nesting properties of MSCs enable these vehicles to target tumours and metastases with effective therapies. A crucial step in engineering MSCs is the delivery of genetic material with low toxicity and high efficiency. Due to the low efficiency of current transfection methods, viral vectors are used widely to modify MSCs in preclinical and clinical studies. We show, for the first time, the high transfection efficiency (> 80%) of human adipose tissue derived-MSCs (AT-MSCs) using a cost-effective and off-the-shelf Polyethylenimine, in the presence of histone deacetylase 6 inhibitor and fusogenic lipids. Notably, the phenotypes of MSCs remained unchanged post-modification. AT-MSCs engineered with a fused transgene, yeast cytosine deaminase::uracil phosphoribosyltransferase (CDy::UPRT) displayed potent cytotoxic effects against breast, glioma, gastric cancer cells in vitro. The efficiency of eliminating gastric cell lines were effective even when using 7-day post-transfected AT-MSCs, indicative of the sustained expression and function of the therapeutic gene. In addition, significant inhibition of temozolomide resistant glioma tumour growth in vivo was observed with a single dose of therapeutic MSC. This study demonstrated an efficient non-viral modification process for MSC-based prodrug therapy.
- Published
- 2020
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31. Cost of Cerebellar Ataxia in Hong Kong: A Retrospective Cost-of-Illness Analysis.
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Stanley WJ, Kelly CKL, Tung CC, Lok TW, Ringo TMK, Ho YK, and Cheung R
- Abstract
Background: Cerebellar ataxia affects the coordination and balance of patients. The impact of this disease increases burden in patients, caregivers and society. Costs and the burden of this disease have not been investigated in Hong Kong. Objectives: (1) To estimate the socioeconomic cost of cerebellar ataxia in Hong Kong for the base year 2019, (2) to assess the health-related quality of life (HRQoL) and severity of ataxia, and (3) to establish the correlation between the severity and cost of cerebellar ataxia and to examine the correlation between the severity of cerebellar ataxia and HRQoL. Methods: A retrospective cross-sectional study was conducted amongst 31 patients with cerebellar ataxia. Cost-related data were obtained through self-reported questionnaires. The severity of ataxia was assessed using the Scale for Assessment and Rating of Ataxia, and HRQoL was assessed using the Short Form (36) Health Survey (SF-36). Pearson correlation was used for normally distributed data, whereas Spearman correlation was used otherwise. Results: The mean severity of ataxia was 21 out of 40. The average direct and indirect costs of a patient with ataxia in 6 months were HKD 51,371 and HKD 93,855, respectively. The mean difference between the independent to minimally dependent in activities of daily living (ADL) group and the moderate to maximally dependent in ADL group for direct and indirect costs was HKD 33,829 and HKD 51,444, respectively. Significant expenditure was related to production lost (42%), caregiver salary (17%), and in-patient care (16%). The physical functioning ( r = -0.58) and general health ( r = -0.41) of SF-36 were negatively correlated with disease severity ( p < 0.05). A significant, positive correlation was found between disease severity and direct cost (Spearman's rho = 0.39) and the cost of hiring a caregiver (Spearman's rho = 0.43). Conclusion: The mean cost for 6 months for patients with cerebellar ataxia in Hong Kong is HKD 146,832. Additional support, including employment, access to specialist consultants, informal home care and community participation, are some areas that should be addressed. Future study on a larger population with a prospective design is necessary to confirm the aforementioned claims., (Copyright © 2020 Stanley, Kelly, Tung, Lok, Ringo, Ho and Cheung.)
- Published
- 2020
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32. RNF8 Dysregulation and Down-regulation During HTLV-1 Infection Promote Genomic Instability in Adult T-Cell Leukemia.
- Author
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Zhi H, Guo X, Ho YK, Pasupala N, Engstrom HAA, Semmes OJ, and Giam CZ
- Subjects
- DNA Breaks, Double-Stranded, DNA Repair genetics, DNA Repair immunology, DNA-Binding Proteins genetics, Gene Products, tax genetics, Gene Products, tax immunology, HTLV-I Infections genetics, HTLV-I Infections pathology, HeLa Cells, Human T-lymphotropic virus 1 genetics, Humans, Leukemia-Lymphoma, Adult T-Cell genetics, Leukemia-Lymphoma, Adult T-Cell pathology, Neoplasm Proteins genetics, Ubiquitin-Protein Ligases genetics, DNA-Binding Proteins immunology, Down-Regulation immunology, Genomic Instability immunology, HTLV-I Infections immunology, Human T-lymphotropic virus 1 immunology, Leukemia-Lymphoma, Adult T-Cell immunology, Neoplasm Proteins immunology, Ubiquitin-Protein Ligases immunology
- Abstract
The genomic instability associated with adult T cell leukemia/lymphoma (ATL) is causally linked to Tax, the HTLV-1 viral oncoprotein, but the underlying mechanism is not fully understood. We have previously shown that Tax hijacks and aberrantly activates ring finger protein 8 (RNF8) - a lysine 63 (K63)-specific ubiquitin E3 ligase critical for DNA double-strand break (DSB) repair signaling - to assemble K63-linked polyubiquitin chains (K63-pUbs) in the cytosol. Tax and the cytosolic K63-pUbs, in turn, initiate additional recruitment of linear ubiquitin assembly complex (LUBAC) to produce hybrid K63-M1 pUbs, which trigger a kinase cascade that leads to canonical IKK:NF-κB activation. Here we demonstrate that HTLV-1-infected cells are impaired in DNA damage response (DDR). This impairment correlates with the induction of microscopically visible nuclear speckles by Tax known as the Tax-speckle structures (TSS), which act as pseudo DNA damage signaling scaffolds that sequester DDR factors such as BRCA1, DNA-PK, and MDC1. We show that TSS co-localize with Tax, RNF8 and K63-pUbs, and their formation depends on RNF8. Tax mutants defective or attenuated in inducing K63-pUb assembly are deficient or tempered in TSS induction and DDR impairment. Finally, our results indicate that loss of RNF8 expression reduces HTLV-1 viral gene expression and frequently occurs in ATL cells. Thus, during HTLV-1 infection, Tax activates RNF8 to assemble nuclear K63-pUbs that sequester DDR factors in Tax speckles, disrupting DDR signaling and DSB repair. Down-regulation of RNF8 expression is positively selected during infection and progression to disease, and further exacerbates the genomic instability of ATL., Competing Interests: The authors have declared that no competing interests exist.
- Published
- 2020
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33. Recent advances of characterization techniques for the formation, physical properties and stability of Pickering emulsion.
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Low LE, Siva SP, Ho YK, Chan ES, and Tey BT
- Abstract
Recently, there have been increasing demand for the application of Pickering emulsions in various industries due to its combined advantage in terms of cost, quality and sustainability. This review aims to provide a complete overview of the available methodology for the physical characterization of emulsions that are stabilized by solid particles (known as Pickering emulsion). Current approaches and techniques for the analysis of the formation and properties of the Pickering emulsion were outlined along with the expected results of these methods on the emulsions. Besides, the application of modelling techniques has also been elaborated for the effective characterization of Pickering emulsions. Additionally, approaches to assess the stability of Pickering emulsions against physical deformation such as coalescence and gravitational separation were reviewed. Potential future developments of these characterization techniques were also briefly discussed. This review can act as a guide to researchers to better understand the standard procedures of Pickering emulsion assessment and the advanced methods available to date to study these emulsions, down to the minute details., (Copyright © 2020 Elsevier B.V. All rights reserved.)
- Published
- 2020
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34. Peripheral CD56 + CD16 + NK Cell Populations in the Early Follicular Phase Are Associated With Successful Clinical Outcomes of Intravenous Immunoglobulin Treatment in Women With Repeated Implantation Failure.
- Author
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Ho YK, Chen HH, Huang CC, Lee CI, Lin PY, Lee MS, and Lee TH
- Abstract
The percentage of peripheral CD56
+ CD16+ NK cells in the early follicular phase on days 2-3 of the menstrual cycle in repeated implantation failure (RIF) patients was used to evaluate the impact of intravenous immunoglobulin (IVIG) on ART cycles. A total 283 patients with RIF consisting of at least 3 ART failures and at least 2 high quality embryo transfers were recruited. A logistic regression analysis for the peripheral immunological profile was completed to predict implantation success and compare the implantation and pregnancy rates between groups with ≤10.6 and >10.6% of CD56+ CD16+ NK cells in the early follicular phase. The logistic regression and receiving operating curve analyses showed that patients with ≤ 10.6% of peripheral CD56+ CD16+ NK cells in the early follicular phase showed a lower pregnancy rate within the RIF group without IVIG. Patients with peripheral CD56+ CD16+ NK cells ≤ 10.6% and without IVIG treatment showed significantly lower implantation and pregnancy rates (12.3 and 30.3%, respectively) when compared with the CD56+ CD16+ NK cells >10.6% group (24.9 and 48.0%, respectively, p < 0.05). Furthermore, the patients with CD56+ CD16+ NK cells ≤ 10.6% given IVIG starting before ET had significantly higher implantation, pregnancy, and live birth rates (27.5, 57.4, and 45.6%, respectively) when compared with the non-IVIG group (12.3, 30.3, and 22.7%, respectively, p < 0.05). Our results showed that a low percentage of peripheral CD56+ CD16+ NK cells (≤10.6%) in the early follicular phase is a potential indicator of reduced pregnancy and implantation success rates in RIF patients, and IVIG treatment will likely benefit this patient subgroup., (Copyright © 2020 Ho, Chen, Huang, Lee, Lin, Lee and Lee.)- Published
- 2020
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35. Development of a laboratory scalable process for enhancing lentivirus production by transient transfection of HEK293 adherent cultures.
- Author
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Ho YK and Too HP
- Subjects
- Genetic Vectors genetics, HEK293 Cells, Humans, Plasmids genetics, Transfection, Laboratories, Lentivirus genetics
- Abstract
Transfection of surface adherent cells remain as a standard methodology for lentiviral production for early phase clinical studies and research purposes. Production today is based on transient co-transfection of three or four plasmids, where the viral elements are encoded separately for safety reasons. Assembly of functional lentiviral particles requires all plasmids to be efficiently transfected into each cell, a notable challenge with many currently available methods for transient transfection. We have previously demonstrated the significant improvement of cationic polymer-based transfection in various cell types using a combination of fusogenic lipids and histone deacetylase 6 inhibitor (Enhancers). In this report, we focused on the transfection step and the feasibility of improving lentiviral production using the Enhancers. After optimization of DNA amount and N/P ratio, transfection using seven commercial gene carriers showed comparable maximal efficiency of production with high cell viability. In the presence of Enhancers, the production of functional lentivirus using LPEI was increased by as much as tenfold and outperformed lentiviral production using Lipofectamine 3000. We demonstrate a scalable and optimized workflow where the use of the Enhancers significantly improved the lentiviral particle production in various HEK293 cell lines.
- Published
- 2019
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36. Prediction of droplet sizes for oil-in-water emulsion systems assisted by ultrasound cavitation: Transient scaling law based on dynamic breakup potential.
- Author
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Siva SP, Kow KW, Chan CH, Tang SY, and Ho YK
- Abstract
The dynamics of droplet breakup during emulsification is a complicated process due to the interplay between multiple physico-chemical and hydrodynamic factors, especially in an energy-intensive ultrasound-assisted emulsification process. In this work, by mapping the physical processing parameters of ultrasound emulsification into a reduced domain that is governed by the power density and the initial average droplet diameter, a dimensionless parameter that resembles the dynamic breakup potential (η) was established via dimensional analysis. In addition to shedding important insights into the emulsification process, η further facilitates the establishment of a transient scaling relationship that is a function of the characteristic value (a) of the emulsion system. Experimental case study on a cellulose nanocrystals (CNC)-based olein-in-water emulsion system prepared via ultrasound cavitation confirmed the validity of the scaling relationship and sub-universal self-similarity was observed. Using the proposed model, good predictions of the transient of droplet size evolution were attained where the value of η, i.e. the proportionality constant, can be conveniently computed using data from a single time point. Application on other emulsion systems further suggested that the value of a possibly indicates the relative minimum size limit of a particular fluids-emulsifier system. Our approach is general, which encourages widespread adoption for emulsification related studies., (Copyright © 2018 Elsevier B.V. All rights reserved.)
- Published
- 2019
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37. Two New Plasmid Post-segregational Killing Mechanisms for the Implementation of Synthetic Gene Networks in Escherichia coli.
- Author
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Fedorec AJH, Ozdemir T, Doshi A, Ho YK, Rosa L, Rutter J, Velazquez O, Pinheiro VB, Danino T, and Barnes CP
- Abstract
Plasmids are the workhorse of both industrial biotechnology and synthetic biology, but ensuring they remain in bacterial cells is a challenge. Antibiotic selection cannot be used to stabilize plasmids in most real-world applications, and inserting dynamical gene networks into the genome remains challenging. Plasmids have evolved several mechanisms for stability, one of which, post-segregational killing (PSK), ensures that plasmid-free cells do not survive. Here we demonstrate the plasmid-stabilizing capabilities of the axe/txe toxin-antitoxin system and the microcin-V bacteriocin system in the probiotic bacteria Escherichia coli Nissle 1917 and show that they can outperform the commonly used hok/sok. Using plasmid stability assays, automated flow cytometry analysis, mathematical models, and Bayesian statistics we quantified plasmid stability in vitro. Furthermore, we used an in vivo mouse cancer model to demonstrate plasmid stability in a real-world therapeutic setting. These new PSK systems, plus the developed Bayesian methodology, will have wide applicability in clinical and industrial biotechnology., (Copyright © 2019 The Authors. Published by Elsevier Inc. All rights reserved.)
- Published
- 2019
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38. Enhanced transfection of a macromolecular lignin-based DNA complex with low cellular toxicity.
- Author
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Ho YK, Kai D, Tu GXE, Deen GR, Too HP, and Loh XJ
- Subjects
- Cations chemistry, DNA pharmacology, Histone Deacetylase Inhibitors chemistry, Histone Deacetylase Inhibitors pharmacology, Humans, Lignin chemistry, Lignin pharmacology, Lipids chemistry, Macromolecular Substances chemistry, Methacrylates chemistry, Methacrylates pharmacology, Nitrogen chemistry, Phosphates chemistry, Polyethylene Glycols chemistry, Polyethylene Glycols pharmacology, Polymethacrylic Acids chemistry, Polymethacrylic Acids pharmacology, DNA chemistry, Gene Transfer Techniques, Macromolecular Substances pharmacology, Transfection methods
- Abstract
Cationic polymers remain attractive tools for non-viral gene transfer. The effectiveness of these vectors rely on the ability to deliver plasmid DNA (pDNA) into the nucleus of cells. While we have previously demonstrated the potential of Lignin-PGEA-PEGMA as a non-viral gene delivery vector, alterations of cellular phenotype and cytotoxicity were observed post transfection. The present study aims to explore transfection conditions for high efficiency and low toxicity of the Lignin-PGEA-PEGMA based gene delivery system. Cellular toxicity was significantly reduced by using the centrifugation protocol, which enables rapid deposition of DNA complexes. Replacement of media post centrifugation resulted in minimal exposure of cells to excess polymers, which were toxic to cells. At an optimized DNA amount (500-750 ng) and molar ratios of nitrogen (N) in polymer to phosphate (P) in pDNA (N/P = 30-40), with the use of a novel transfection enhancer that facilitates endosomal escape and nuclear trafficking, the efficiency of gene delivery was increased significantly 24 h post transfection. The present study demonstrated an appropriately optimized protocol that enabled the utility of a novel cationic polymer blend with a mixture of fusogenic lipids and a histone deacetylate inhibitor in non-viral transfection, thereby providing an attractive alternative to costly commercial gene carriers., (© 2018 The Author(s).)
- Published
- 2018
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39. Cross-sectional survey of biosimilar insulin utilization in Asia: The Joint Asia Diabetes Evaluation Program.
- Author
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Gani L, Lau E, Luk A, Sobrepena L, Tran QK, Kesavadev J, Jia W, Yu W, Tsang CC, Mukhopadhyay M, Jha S, Sheu W, Ho YK, Nguyen TK, Ozaki R, So WY, Kwan C, Fu AWC, Mirasol R, Phatak SR, Kumar KMP, Aravind S, Janakiraman H, and Chan JCN
- Subjects
- Asia epidemiology, Biosimilar Pharmaceuticals, Cross-Sectional Studies, Diabetes Mellitus, Type 1 epidemiology, Diabetes Mellitus, Type 2 epidemiology, Female, Humans, Insulin analogs & derivatives, Male, Middle Aged, Treatment Outcome, Diabetes Mellitus, Type 1 drug therapy, Diabetes Mellitus, Type 2 drug therapy, Hypoglycemic Agents therapeutic use, Insulin therapeutic use
- Abstract
Aims/introduction: Biosimilar insulin can reduce treatment costs, although the extent of its use is largely unknown. We examined biosimilar insulin use and its associations with the quality of glycemic control using the Joint Asia Diabetes Evaluation register., Materials and Methods: We carried out a cross-sectional analysis in 81,531 patients with type 1 and type 2 diabetes enrolled into the Joint Asia Diabetes Evaluation Program from 2007 to 2014. All insulin related terms are extracted from the Joint Asia Diabetes Evaluation portal, and compared clinical profiles between biosimilar and originator insulin users. Multivariate analysis was performed to assess the association of biosimilar insulin compared with originator insulin with dosage, glycated hemoglobin and hypoglycemia events., Results: Amongst 81,531 patients, 20.5% (n = 16,738) were insulin-treated. In four countries with high use of biosimilar insulin, 4.7% (n = 719) of insulin users (n = 10,197) were treated with biosimilar insulin (India n = 507, 70.3%; the Philippines n = 90, 12.5%; China n = 62, 8.6%; Vietnam n = 60, 8.3%). Biosimilar insulin users were younger and had higher body mass index, glycated hemoglobin, insulin dosage and more frequent hypoglycemia than originator insulin users. These associations were non-significant after adjustment for confounders. Only age, college education, diabetes education, lipid control, physical activity and history of cardiovascular complications were independently associated with these quality measures., Conclusions: Biosimilar insulin use is not uncommon in Asia. Data exclusion due to incomplete capturing of brand names suggests possibly higher use. The multiple determinants of the quality of glycemic control call for establishment of prospective cohorts and diabetes registers to monitor the safety and efficacy of different brands of biosimilar insulin and their impacts on clinical outcomes., (© 2018 The Authors. Journal of Diabetes Investigation published by Asian Association for the Study of Diabetes (AASD) and John Wiley & Sons Australia, Ltd.)
- Published
- 2018
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40. Effects of growth hormone plus gonadotropins on controlled ovarian stimulation in infertile women of advanced age, poor responders, and previous in vitro fertilization failure patients.
- Author
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Ho YK, Lee TH, Lee CI, Cheng EH, Huang CC, Huang LS, and Lee MS
- Subjects
- Adult, Age Factors, Drug Therapy, Combination, Embryo Implantation drug effects, Female, Fertilization in Vitro methods, Humans, Oocytes drug effects, Pregnancy, Pregnancy Rate, Retrospective Studies, Gonadotropins therapeutic use, Growth Hormone therapeutic use, Infertility, Female drug therapy, Ovulation Induction methods
- Abstract
Objective: To investigate the effects of growth hormone (GH) cotreatment in ovarian stimulation in infertile women of advanced age, poor responders, and patients with one or more previous IVF treatment failures., Materials and Methods: We conducted a retrospective observational study of 436 patients undergoing GH cotreatment in ovarian stimulation. The first arm included 134 infertile women of advanced age. The second arm included 236 patients with one or more IVF previous treatment failures, and the third arm included 66 younger poor responders. Main outcome measures were the number of oocytes and embryos, quality of embryos, and implantation and pregnancy rates., Results: In infertile women of advanced age, GH plus ovarian stimulation yielded no statistical differences in the numbers of oocytes and embryos, quality of embryo, and rates of implantation and pregnancy. In the second arm, the mature oocyte number (8.2 vs. 6.8), implantation rate (16.1% vs. 0%), and pregnancy rate (33.9% vs. 0%) in the GH cotreatment group differed significantly from those in the control group; the rate of good-quality embryos in the GH cotreatment group improved from 35.5% ± 31.1%-41.4% ± 30.6% in this arm. Similar results were observed in the third arm; in this arm, the clinical pregnancy rate was 30.3% in the GH cotreatment group and 6.1% in the control group., Conclusion: No significant differences were observed in infertile women of advanced age, which may be due to the low GH dose. The GH adjuvant therapy for patients with one or more previous IVF treatment failures and for poor responders significantly improved the oocyte and embryo numbers as well as implantation and pregnancy rates., (Copyright © 2017. Published by Elsevier B.V.)
- Published
- 2017
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41. Enlarged Cavum Septi Pellucidi and Vergae in the Fetus: A Cause for Concern.
- Author
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Ho YK, Turley M, Marc-Aurele KL, Jones MC, Housman E, Engelkemier D, Romine LE, Khanna PC, and Pretorius DH
- Subjects
- Adolescent, Adult, Brain embryology, Congenital Abnormalities pathology, Female, Follow-Up Studies, Humans, Organ Size, Pregnancy, Retrospective Studies, Septum Pellucidum diagnostic imaging, Septum Pellucidum embryology, Septum Pellucidum pathology, Young Adult, Brain diagnostic imaging, Brain pathology, Congenital Abnormalities diagnostic imaging, Ultrasonography, Prenatal methods
- Abstract
Objectives: To investigate fetal cases identified at our institution to determine whether an enlarged cavum septi pellucidi or cavum vergae is associated with other fetal abnormalities and whether its presence warrants more detailed investigation of the fetus., Methods: In a retrospective study, 15 high- and low-risk patients undergoing prenatal sonography who had an enlarged cavum septi pellucidi or cavum vergae identified were reviewed. Data were collected for the sonographic study indication, gestation age at diagnosis of a prominent cavum, and associated anomalies. Follow-up outcome data regarding further imaging, karyotype, diagnosis of brain anomaly, and associated congenital abnormalities were obtained., Results: Fifteen patients met the inclusion criteria. Nine patients were identified as having a prominent cavum septi pellucidi, and 6 were identified as having a prominent cavum vergae. The mean gestational age ± SD was 22.7 ± 5.9 weeks. Eleven patients made it to delivery. Of the 15 patients, 4 were thought to have trisomy 21, and 13 had congenital anomalies. Outcomes included 10 major adverse outcomes, 4 cases with normal development or minor abnormalities, and 1 lost to follow-up. An isolated dilated cavum on prenatal sonography was seen in 5 cases: 1 with lissencephaly on a neonatal examination, 3 premature deliveries (1 demise, 1 hospice, and 1 normal), and 1 unknown., Conclusions: Our cohort had many associated clinical anomalies: 3 confirmed trisomy 21 and 1 probable trisomy 21, 2 genetic disorders, and 10 major adverse outcomes, 5 of which were grave. Although we studied a small cohort, we conclude that an enlarged cavum septi pellucidi or cavum vergae warrants consideration of genetic counseling, which may include noninvasive prenatal testing (cell-free DNA), amniocentesis with microarray testing, or both., (© 2017 by the American Institute of Ultrasound in Medicine.)
- Published
- 2017
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42. Enhanced non-viral gene delivery by coordinated endosomal release and inhibition of β-tubulin deactylase.
- Author
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Ho YK, Zhou LH, Tam KC, and Too HP
- Subjects
- Acetylation, Animals, Biological Transport, Cell Differentiation, Cell Line, Cells, Cultured, DNA analysis, Hydrogen-Ion Concentration, Hydroxamic Acids pharmacology, Indoles pharmacology, Mice, Neural Stem Cells cytology, Polymers chemistry, Endosomes metabolism, Histone Deacetylase Inhibitors pharmacology, Transfection methods, Tubulin metabolism
- Abstract
Efficient non-viral gene delivery is highly desirable but often unattainable with some cell-types. We report here that non-viral DNA polyplexes can efficiently transfect differentiated neuronal and stem cells. Polyplex transfection centrifugation protocols was enhanced by including a simultaneous treatment with a DOPE/CHEMS lipid suspension and a microtubule inhibitor, Tubastatin A. Lipoplex transfection protocols were not improved by this treatment. This mechanism of action was unravelled by systematically identifying and rationally mitigating barriers limiting high transfection efficiency, allowing unexpected improvements in the transfection of mesenchymal stem cells (MSC), primary neuron and several hard-to-transfect cell types beyond what are currently achievable using cationic polymers. The optimized formulation and method achieved high transfection efficiency with no adverse effects on cell viability, cell proliferation or differentiation. High efficiency modification of MSC for cytokine overexpression, efficient generation of dopaminergic neuron using neural stem cells and enhanced genome editing with CRISPR-Cas9 were demonstrated. In summary, this study described a cost-effective method for efficient, rapid and scalable workflow for ex vivo gene delivery using a myriad of nucleic acids including plasmid DNA, mRNA, siRNA and shRNA., (© The Author(s) 2016. Published by Oxford University Press on behalf of Nucleic Acids Research.)
- Published
- 2017
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43. Neutral particles pushed or pulled by laser pulses.
- Author
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Wang PX, Wei Q, Cai P, Wang JX, and Ho YK
- Abstract
Acceleration of neutral particles is of great importance in many areas, such as controlled chemical reactions, atomic nanofabrication, and atom optics. Recent experimental studies have shown that pulsed lasers can be used to push neutral Rydberg atoms forward [Nature 461, 1261 (2009)10.1038/nature08481; Nat. Photonics 6, 386 (2012)10.1038/nphoton.2012.87]. Our simulation shows that pulsed lasers can also be used to pull Rydberg atoms back toward a light source. In particular, we proposed a method of using two laser pulses on a neutral atom, then selective operations on the neutral atom (pushing or pulling) can be performed by adjusting the delay time between the two laser pulses.
- Published
- 2016
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44. Interlinked population balance and cybernetic models for the simultaneous saccharification and fermentation of natural polymers.
- Author
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Ho YK, Doshi P, Yeoh HK, and Ngoh GC
- Subjects
- Computer Simulation, Fermentation, Hydrolysis, Biopolymers metabolism, Saccharomyces cerevisiae growth & development, Saccharomyces cerevisiae metabolism
- Abstract
Simultaneous Saccharification and Fermentation (SSF) is a process where microbes have to first excrete extracellular enzymes to break polymeric substrates such as starch or cellulose into edible nutrients, followed by in situ conversion of those nutrients into more valuable metabolites via fermentation. As such, SSF is very attractive as a one-pot synthesis method of biological products. However, due to the co-existence of multiple biochemical steps, modeling SSF faces two major challenges. The first is to capture the successive chain-end and/or random scission of the polymeric substrates over time, which determines the rate of generation of various fermentable substrates. The second is to incorporate the response of microbes, including their preferential substrate utilization, to such a complex broth. Each of the above-mentioned challenges has manifested itself in many related areas, and has been competently but separately attacked with two diametrically different tools, i.e., the Population Balance Modeling (PBM) and the Cybernetic Modeling (CM), respectively. To date, they have yet to be applied in unison on SSF resulting in a general inadequacy or haphazard approaches to examine the dynamics and interactions of depolymerization and fermentation. To overcome this unsatisfactory state of affairs, here, the general linkage between PBM and CM is established to model SSF. A notable feature is the flexible linkage, which allows the individual PBM and CM models to be independently modified to the desired levels of detail. A more general treatment of the secretion of extracellular enzyme is also proposed in the CM model. Through a case study on the growth of a recombinant Saccharomyces cerevisiae capable of excreting a chain-end scission enzyme (glucoamylase) on starch, the interlinked model calibrated using data from the literature (Nakamura et al., Biotechnol. Bioeng. 53:21-25, 1997), captured features not attainable by existing approaches. In particular, the effect of various enzymatic actions on the temporal evolution of the polymer distribution and how the microbes respond to the diverse polymeric environment can be studied through this framework., (© 2015 Wiley Periodicals, Inc.)
- Published
- 2015
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45. Delayed recurrent bleeding from central venous catheter track after catheter removal in a haemophilia patient.
- Author
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Idros R, Ho YK, and Ng HJ
- Subjects
- Adult, Hematoma etiology, Humans, Male, Recurrence, Central Venous Catheters adverse effects, Device Removal adverse effects, Hemophilia A etiology, Hemorrhage etiology
- Published
- 2015
- Full Text
- View/download PDF
46. HTLV-1 Tax Stimulates Ubiquitin E3 Ligase, Ring Finger Protein 8, to Assemble Lysine 63-Linked Polyubiquitin Chains for TAK1 and IKK Activation.
- Author
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Ho YK, Zhi H, Bowlin T, Dorjbal B, Philip S, Zahoor MA, Shih HM, Semmes OJ, Schaefer B, Glover JN, and Giam CZ
- Subjects
- Cell Line, DNA-Binding Proteins metabolism, Fluorescent Antibody Technique, Gene Knockdown Techniques, Humans, I-kappa B Kinase metabolism, Immunoblotting, MAP Kinase Kinase Kinases metabolism, Polymerase Chain Reaction, Transfection, Ubiquitin-Protein Ligases metabolism, Cell Transformation, Neoplastic metabolism, Gene Products, tax metabolism, Signal Transduction physiology
- Abstract
Human T lymphotropic virus type 1 (HTLV-1) trans-activator/oncoprotein, Tax, impacts a multitude of cellular processes, including I-κB kinase (IKK)/NF-κB signaling, DNA damage repair, and mitosis. These activities of Tax have been implicated in the development of adult T-cell leukemia (ATL) in HTLV-1-infected individuals, but the underlying mechanisms remain obscure. IKK and its upstream kinase, TGFβ-activated kinase 1 (TAK1), contain ubiquitin-binding subunits, NEMO and TAB2/3 respectively, which interact with K63-linked polyubiquitin (K63-pUb) chains. Recruitment to K63-pUb allows cross auto-phosphorylation and activation of TAK1 to occur, followed by TAK1-catalyzed IKK phosphorylation and activation. Using cytosolic extracts of HeLa and Jurkat T cells supplemented with purified proteins we have identified ubiquitin E3 ligase, ring finger protein 8 (RNF8), and E2 conjugating enzymes, Ubc13:Uev1A and Ubc13:Uev2, to be the cellular factors utilized by Tax for TAK1 and IKK activation. In vitro, the combination of Tax and RNF8 greatly stimulated TAK1, IKK, IκBα and JNK phosphorylation. In vivo, RNF8 over-expression augmented while RNF8 ablation drastically reduced canonical NF-κB activation by Tax. Activation of the non-canonical NF-κB pathway by Tax, however, is unaffected by the loss of RNF8. Using purified components, we further demonstrated biochemically that Tax greatly stimulated RNF8 and Ubc13:Uev1A/Uev2 to assemble long K63-pUb chains. Finally, co-transfection of Tax with increasing amounts of RNF8 greatly induced K63-pUb assembly in a dose-dependent manner. Thus, Tax targets RNF8 and Ubc13:Uev1A/Uev2 to promote the assembly of K63-pUb chains, which signal the activation of TAK1 and multiple downstream kinases including IKK and JNK. Because of the roles RNF8 and K63-pUb chains play in DNA damage repair and cytokinesis, this mechanism may also explain the genomic instability of HTLV-1-transformed T cells and ATL cells.
- Published
- 2015
- Full Text
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47. Behind the color switching in gasochromic VO2.
- Author
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Chen JL, Chang CC, Ho YK, Chen CL, Hsu CC, Jang WL, Wei DH, Dong CL, Pao CW, Lee JF, Chen JM, Guo J, and Wu MK
- Abstract
Gasochromic VO2 thin films were fabricated by the sol-gel spin-coating technique. The results of X-ray absorption spectroscopy and resonant inelastic X-ray scattering spectroscopy reveal that the origin of gasochromic coloration in VO2 is strongly related to the modulation of its structure and the electron-electron correlation. Upon gasochromic coloration, not only does the valence state change with the incorporation of hydrogen, but also the film undergoes the modification of the local atomic structure. The structural distortion varies the strength of hybridization of the O 2p-V 3d states and the bond distance of V-O and V-O varies. In the hydric process, the local atomic structure of VO2 changes from that of an un-symmetric to that of a symmetric V-O framework. The incorporated hydrogen adds electrons into the V 3d t2g orbital, enhancing the electron-electron correlation by reducing the V-V distance. This work presents a new physical insight in which the modulation of the electron-electron correlation is exploited to control the bleached and colored states, giving rise to the gasochromic phenomenon. The strong correlation among atomic spatial rearrangement, electronic structures, and transmittance supports a cooperative mechanism of the VO2 gasochromic transition. These results reveal a clear correlation between the dynamics of the lattice structure and the electronic properties and suggest a possible pathway to gasochromism and elucidation of its mechanism.
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- 2015
- Full Text
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48. Pulmonary embolism after cesarean section and successful treatment with early application of extracorporeal membrane oxygenation system and anticoagulant agents.
- Author
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Ho YK, Wang CP, Wu YL, Lee TH, Ying TH, and Lee MS
- Subjects
- Adult, Female, Humans, Pulmonary Embolism etiology, Time Factors, Anticoagulants therapeutic use, Cesarean Section adverse effects, Extracorporeal Membrane Oxygenation, Pulmonary Embolism therapy
- Published
- 2014
- Full Text
- View/download PDF
49. Does ethnicity affect where people with cancer die? A population-based 10 year study.
- Author
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Koffman J, Ho YK, Davies J, Gao W, and Higginson IJ
- Subjects
- Demography, Female, Hospice Care statistics & numerical data, Humans, London, Male, Parturition, Regression Analysis, Ethnicity statistics & numerical data, Neoplasms ethnology, Neoplasms mortality, Terminal Care statistics & numerical data
- Abstract
Background: Ageing is a growing issue for people from UK black, Asian and minority ethnic (BAME) groups. The health experiences of these groups are recognised as a 'tracer' to measure success in end of life patient-preferred outcomes that includes place of death (PoD)., Aim: To examine patterns in PoD among BAME groups who died of cancer., Material and Methods: Mortality data for 93,375 cancer deaths of those aged ≥65 years in London from 2001-2010 were obtained from the UK Office for National Statistics (ONS). Decedent's country of birth was used as a proxy for ethnicity. Linear regression examined trends in place of death across the eight ethnic groups and Poisson regression examined the association between country of birth and place of death., Results: 76% decedents were born in the UK, followed by Ireland (5.9%), Europe(5.4%) and Caribbean(4.3%). Most deaths(52.5%) occurred in hospital, followed by home(18.7%). During the study period, deaths in hospital declined with an increase in home deaths; trend for time analysis for those born in UK(0.50%/yr[0.36-0.64%]p<0.001), Europe (1.00%/yr[0.64-1.30%]p<0.001), Asia(1.09%/yr[0.94-1.20%]p<0.001) and Caribbean(1.03%/yr[0.72-1.30%]p<0.001). However, time consistent gaps across the geographical groups remained. Following adjustment hospital deaths were more likely for those born in Asia(Proportion ratio(PR)1.12[95%CI1.08-1.15]p<0.001) and Africa(PR 1.11[95%CI1.07-1.16]p<0.001). Hospice deaths were less likely for those born in Asia(PR 0.73 [0.68-0.80] p<0.001), Africa (PR 0.83[95%CI0.74-0.93]p<0.001), and 'other' geographical regions (PR0.90[95% 0.82-0.98]p<0.001). Home deaths were less likely for those born in the Caribbean(PR0.91[95%CI 0.85-0.98]p<0.001)., Conclusions: Location of death varies by country of birth. BAME groups are more likely to die in a hospital and less likely to die at home or in a hospice. Further investigation is needed to determine whether these differences result from patient-centred preferences, or other environment or service-related factors. This knowledge will enable strategies to be developed to improve access to relevant palliative care and related services, where necessary.
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- 2014
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50. Regulation of human T-lymphotropic virus type I latency and reactivation by HBZ and Rex.
- Author
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Philip S, Zahoor MA, Zhi H, Ho YK, and Giam CZ
- Subjects
- Basic-Leucine Zipper Transcription Factors genetics, Cell Nucleus genetics, Cell Nucleus metabolism, Cell Nucleus virology, Gene Products, rex genetics, Gene Products, tax, HTLV-I Infections genetics, HeLa Cells, Humans, RNA, Viral biosynthesis, RNA, Viral genetics, Retroviridae Proteins, Viral Proteins genetics, Basic-Leucine Zipper Transcription Factors metabolism, Gene Expression Regulation, Viral physiology, Gene Products, rex metabolism, HTLV-I Infections metabolism, Human T-lymphotropic virus 1 physiology, Transcriptional Activation physiology, Viral Proteins metabolism, Virus Latency physiology
- Abstract
Human T lymphotropic virus type I (HTLV-I) infection is largely latent in infected persons. How HTLV-1 establishes latency and reactivates is unclear. Here we show that most HTLV-1-infected HeLa cells become senescent. By contrast, when NF-κB activity is blocked, senescence is averted, and infected cells continue to divide and chronically produce viral proteins. A small population of infected NF-κB-normal HeLa cells expresses low but detectable levels of Tax and Rex, albeit not Gag or Env. In these "latently" infected cells, HTLV-1 LTR trans-activation by Tax persists, but NF-κB trans-activation is attenuated due to inhibition by HBZ, the HTLV-1 antisense protein. Furthermore, Gag-Pol mRNA localizes primarily in the nuclei of these cells. Importantly, HBZ was found to inhibit Rex-mediated export of intron-containing mRNAs. Over-expression of Rex or shRNA-mediated silencing of HBZ led to viral reactivation. Importantly, strong NF-κB inhibition also reactivates HTLV-1. Hence, during HTLV-1 infection, when Tax/Rex expression is robust and dominant over HBZ, productive infection ensues with expression of structural proteins and NF-κB hyper-activation, which induces senescence. When Tax/Rex expression is muted and HBZ is dominant, latent infection is established with expression of regulatory (Tax/Rex/HBZ) but not structural proteins. HBZ maintains viral latency by down-regulating Tax-induced NF-κB activation and senescence, and by inhibiting Rex-mediated expression of viral structural proteins.
- Published
- 2014
- Full Text
- View/download PDF
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