54 results on '"Foo SY"'
Search Results
2. Optimized Naive-Bayes and Decision Tree Approaches for fMRI Smoking Cessation Classification
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Tahmassebi, A, Gandomi, AH, Schulte, MHJ, Goudriaan, AE, Foo, SY, Meyer-Baese, A, Tahmassebi, A, Gandomi, AH, Schulte, MHJ, Goudriaan, AE, Foo, SY, and Meyer-Baese, A
- Abstract
This paper aims at developing new theory-driven biomarkers by implementing and evaluating novel techniques from resting-state scans that can be used in relapse prediction for nicotine-dependent patients and future treatment efficacy. Two classes of patients were studied. One class took the drug N-acetylcysteine and the other class took a placebo. Then, the patients underwent a double-blind smoking cessation treatment and the resting-state fMRI scans of their brains before and after treatment were recorded. The scientific research goal of this study was to interpret the fMRI connectivity maps based on machine learning algorithms to predict the patient who will relapse and the one who will not. In this regard, the feature matrix was extracted from the image slices of brain employing voxel selection schemes and data reduction algorithms. Then, the feature matrix was fed into the machine learning classifiers including optimized CART decision tree and Naive-Bayes classifier with standard and optimized implementation employing 10-fold cross-validation. Out of all the data reduction techniques and the machine learning algorithms employed, the best accuracy was obtained using the singular value decomposition along with the optimized Naive-Bayes classifier. This gave an accuracy of 93% with sensitivity-specificity of 99% which suggests that the relapse in nicotine-dependent patients can be predicted based on the resting-state fMRI images. The use of these approaches may result in clinical applications in the future.
- Published
- 2018
3. Multi-stage optimization of a deep model: A case study on ground motion modeling.
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Tahmassebi, A, Gandomi, AH, Fong, S, Meyer-Baese, A, Foo, SY, Tahmassebi, A, Gandomi, AH, Fong, S, Meyer-Baese, A, and Foo, SY
- Abstract
In this study, a multi-stage optimization procedure is proposed to develop deep neural network models which results in a powerful deep learning pipeline called intelligent deep learning (iDeepLe). The proposed pipeline is then evaluated by a challenging real-world problem, the modeling of the spectral acceleration experienced by a particle during earthquakes. This approach has three main stages to optimize the deep model topology, the hyper-parameters, and its performance, respectively. This pipeline optimizes the deep model via adaptive learning rate optimization algorithms for both accuracy and complexity in multiple stages, while simultaneously solving the unknown parameters of the regression model. Among the seven adaptive learning rate optimization algorithms, Nadam optimization algorithm has shown the best performance results in the current study. The proposed approach is shown to be a suitable tool to generate solid models for this complex real-world system. The results also show that the parallel pipeline of iDeepLe has the capacity to handle big data problems as well.
- Published
- 2018
4. Immune Mechanisms That Promote the Development of Inducible Bronchus-Associated Lymphoid Tissue (iBALT).
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Foo, SY, primary, Lam, CE, additional, Wark, PA, additional, Foster, PS, additional, and Phipps, S, additional
- Published
- 2009
- Full Text
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5. Repeated Stimulation of Toll-Like Receptor 4 Is Sufficient To Induce Emphysematous Lesions in Mice.
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Lam, CE, primary, Foo, SY, additional, Matthaei, KI, additional, Foster, PS, additional, and Phipps, S, additional
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- 2009
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6. Response gene to complement 32, a novel hypoxia-regulated angiogenic inhibitor.
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An X, Jin Y, Guo H, Foo SY, Cully BL, Wu J, Zeng H, Rosenzweig A, Li J, An, Xiaojin, Jin, Yi, Guo, Hongnian, Foo, Shi-Yin, Cully, Brittany L, Wu, Jiaping, Zeng, Huiyan, Rosenzweig, Anthony, and Li, Jian
- Published
- 2009
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7. Dosimetric comparison of hippocampal-sparing technologies in patients with low-grade glioma.
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Williamson A, Houston P, Paterson J, Chalmers AJ, McLoone P, Fullerton N, Foo SY, James A, and Nowicki S
- Abstract
Background: Radiotherapy (RT) plays an integral role in the management of low-grade gliomas (LGG). Late toxicity from RT can cause progressive neurocognitive dysfunction. Radiation-induced damage to the hippocampus (HCP) plays a considerable role in memory decline. Advancements in photon planning software have resulted in the development of multi-criteria optimization (MCO) and HyperArc technologies which may improve HCP sparing while maintaining planning target volume (PTV) target coverage., Methods: Three planning methods for hippocampal sparing (HS) were compared, volumetric modulated arc therapy (VMAT) without HS (VMAT_noHS), VMAT with HS (VMAT_HS), MCO with HS (MCO_HS), and HyperArc with HS (HyperArc_HS)., Results: Twenty-five patients were identified. The contralateral HCP was spared in 16 patients and bilateral HCP in 9 patients with superiorly located tumors. All 3 HS planning techniques showed significant reductions in dose to the spared HCP in contralateral cases but only VMAT_HS and MCO_HS achieved this in bilateral cases ( P < .008). Only MCO_HS was superior to VMAT_HS in lowering the dose to both contralateral HCP and bilateral HCP in all measured metrics ( P < .008). PTV and OAR (organ at risk) dose constraints were achieved for all plans., Conclusions: This retrospective dosimetric study demonstrated the feasibility of HS for low-grade glioma. All 3 HS planning techniques achieved significant dose reductions to the spared contralateral hippocampus, but only MCO_HS and VMAT_HS achieved this in bilateral cases. MCO was superior to other planning techniques for sparing both bilateral and contralateral hippocampi., Competing Interests: The authors have no relevant disclosures., (© The Author(s) 2024. Published by Oxford University Press, the Society for Neuro-Oncology and the European Association of Neuro-Oncology.)
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- 2024
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8. Cytotoxic activity and cell specificity of a novel LHRH peptide drug conjugate, D-Cys6-LHRH vedotin, against ovarian cancer cell lines.
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Vankadara S, Ke Z, Wang S, Foo SY, Gunaratne J, Lee MA, Koh X, and Chia CSB
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- Female, Humans, Gonadotropin-Releasing Hormone pharmacology, Cell Line, Ovarian Neoplasms drug therapy, Antineoplastic Agents pharmacology
- Abstract
Ovarian cancer is the most deadly female gynaecological malignancy in developed countries and new treatments are urgently needed. The luteinising hormone releasing hormone (LHRH) peptide drug conjugate Zoptarelin doxorubicin is one such potential new drug modality that entered clinical trials for treating LHRH receptor-positive gynaecological cancers. However, development stopped after disappointing Phase 3 results in 2017. We believe the lack of efficacy was due to linker instability and payload potency. In this work, we replaced its linker-toxin with vedotin (MC-VC-PABC-MMAE), yielding the novel peptide drug conjugate D-Cys6-LHRH vedotin. A GI
50 and cell specificity comparison against cancerous and non-cancerous ovarian cell lines showed significantly superior bioactivity and selectivity over Zoptarelin doxorubicin (GI50 4 vs. 453 nM) and other chemotherapeutic drugs used for treating ovarian cancers. Our results suggest D-Cys6-LHRH vedotin can potentially be used as a treatment for ovarian cancer., (© 2024 John Wiley & Sons Ltd.)- Published
- 2024
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9. Black blood MRI sequences in the acute management of ruptured and unruptured intracranial aneurysms.
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El Sheikh M, Koh SP, Omer M, Agyemang K, Bhattathiri P, Hassan S, Iqbal A, Izzath W, St George J, and Foo SY
- Abstract
We present an illustrative case series in which high spatial resolution black blood (BB) MRI sequences were used as an adjunct in the acute management of intracranial aneurysms with diagnostic uncertainty regarding rupture status. Several acute management dilemmas are discussed including the surveillance of previously treated ruptured intracranial aneurysms, identifying culprit lesion(s) amongst multiple ruptured intracranial aneurysms, and risk stratifying incidental unruptured intracranial aneurysms. We present our experience which supports the evaluation of this vessel wall imaging technique in larger multi-centre observational studies. MR imaging was performed on a 3.0 Tesla Siemens Somatom Vida system and sequences used included: Susceptibility Weighted Imaging, Diffusion Weighted Imaging & 3D T1 pre- and post-contrast-enhanced BB sequences.
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- 2023
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10. Outcomes of Fluorescence-Guided vs White Light Resection of Glioblastoma in a Single Institution.
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Wong LS, St George J, Agyemang K, Grivas A, Houston D, Foo SY, and Mullan T
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Background Glioblastoma (GBM) is the most common malignant primary brain tumour and confers a very poor prognosis. Maximal safe resection of tumour is the goal of neurosurgical intervention and may be more easily achieved through the use of surgical adjuncts such as fluorescence-guided surgery (FGS). 5-Aminolevulinic acid (5-ALA) accumulates in GBM tissue and fluoresce red, distinguishing tumour cells from the surrounding tissue and therefore making resection easier. 5-ALA-guided resection in GBM has been shown to increase resection rates and prolong progression-free survival without impacting post-operative morbidity. Radiotherapy and concomitant chemotherapy also improve survival in GBM. Other factors such as patient age and molecular status of the tumour also impact prognosis. Aims The aim of this study was to compare the outcomes of 5-ALA vs white light-guided resection for glioblastoma in the west of Scotland. Methods This was a retrospective analysis of baseline characteristics (age, sex, tumour molecular markers, radiotherapy, chemotherapy, anatomical location of tumour and treatment group) and outcomes (mortality, survival, degree of resection and performance status) of 239 patients who underwent primary resection of glioblastoma over a four-year period (2017-2020). A variety of statistical methods were used to analyse the relationship between each variable and surgical technique; multivariate Cox regression and the Kaplan-Meier method were used in survival analysis. Results 5-ALA-guided resection substantially improved resection rates (74.0% vs 40.2%). Mortality at 15 months was 5.1% lower in the 5-ALA group (52.0% vs 57.1%, p = 0.53), and patients lived an average of 68 days longer compared to the white light group (444 days vs 376 days, p = 0.21). There were negligible differences between treatment groups in terms of post-operative performance status (PS) and post-operative complications. In our multivariate Cox regression model, six factors were statistically significant at a level of p ≤ 0.05: age, radiotherapy, chemotherapy, O(6)-methylguanine-DNA methyltransferase (MGMT) methylation, anatomical location and >90% resection. Receiving chemotherapy and radiotherapy, MGMT methylation and undergoing >90% resection conferred a survival benefit at 15 months. Older age and multi-focal disease were related to a worsened mortality rate. Undergoing radiotherapy and maximal resection were the two greatest predictors of improved survival, reducing mortality risk by 58% and 51%, respectively. Conclusion 5-ALA-guided resection improved resection rates without impacting post-operative morbidity. 5-ALA-guided resection was associated with improved survival and lower mortality rate, but this was not statistically significant. Receiving chemoradiotherapy, MGMT methylation and undergoing maximal resection conferred a survival benefit, whilst older age and multi-focal disease were associated with a poorer prognosis., Competing Interests: The authors have declared that no competing interests exist., (Copyright © 2023, Wong et al.)
- Published
- 2023
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11. 3D printability and biochemical analysis of revalorized orange peel waste.
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Tan JD, Lee CP, Foo SY, Tan JCW, Tan SSY, Ong ES, Leo CH, and Hashimoto M
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Orange peels are often discarded as food waste despite being a nutritious source of vitamins and antioxidants. These orange peel wastes (OPW) are produced in millions of tons globally every year; discarding them results in detrimental environmental and economical impacts. This paper discusses the application of 3D printing technology to effectively upcycle the OPW into edible, healthy snacks for consumption. We aimed to develop a method to enable OPW to formulate 3D-printable inks for direct ink writing (DIW). Using DIW 3D printing, we successfully created edible constructs of rheologically modified inks containing OPW. The formulated ink possessed an initial viscosity of 22.5 kPa.s, a yield stress of 377 Pa, and a storage modulus of 44.24 kPa. To validate the method, we conducted a biochemical analysis of the OPW at each stage of the fabrication process. This study suggested that our ink formulation and 3D printing process did not affect the content of bioflavonoids and antioxidants of the OPW. The cell viability test using human dermal microvascular endothelium (HMEC-1) suggested that the OPW did not exhibit cytotoxicity throughout the entire process of the ink manipulation. Overall, this study has highlighted a potential scenario to revalorize food waste into the food value chain using 3D printing toward more sustainable and circular food manufacturing and consumption., Competing Interests: The authors declare no conflict of interests., (Copyright:© 2023, Tan JD, Lee CP, Foo SY, et al.)
- Published
- 2023
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12. Green Extraction of Orange Peel Waste Reduces TNFα-Induced Vascular Inflammation and Endothelial Dysfunction.
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Leo CH, Foo SY, Tan JCW, Tan UX, Chua CK, and Ong ES
- Abstract
Orange peel waste (OPW) is known to contain an abundant amount of polyphenols compounds such as flavonoids, well-reported for their antioxidant and anti-inflammatory properties. While OPW is generally regarded as a food waste, the opportunity to extract bioactive compounds from these "wastes" arises due to their abundance, allowing the investigation of their potential effects on endothelial cells. Hence, this study aims to use a green extraction method and pressurized hot water extraction (PHWE) to extract bioactive compounds from OPW. Liquid chromatography with UV detection (LC/UV) and liquid chromatography mass spectrometry (LC/MS) were subsequently used to identify the bioactive compounds present. Through the optimization of the extraction temperature for PHWE, our results demonstrated that extraction temperatures of 60 °C and 80 °C yield distinct bioactive compounds and resulted in better antioxidant capacity compared to other extraction temperatures or organic solvent extraction. Despite having similar antioxidant capacity, their effects on endothelial cells were distinct. Specifically, treatment of endothelial cells with 60 °C OPW extracts inhibited TNFα-induced vascular inflammation and endothelial dysfunction in vitro, suggesting that OPW possess vasoprotective effects likely mediated by anti-inflammatory effects., Competing Interests: The authors have no conflict of interest to declare that are relevant to the content of this article.
- Published
- 2022
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13. High frequency of anti-DSG 2 antibodies in post COVID-19 serum samples.
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Lee ECY, Tyler RE, Johnson D, Koh N, Ong BC, Foo SY, and Tan JWC
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- Autoantibodies immunology, Desmoglein 2 immunology, Humans, Post-Acute COVID-19 Syndrome, COVID-19 blood, COVID-19 complications, COVID-19 immunology
- Abstract
Background: There is growing recognition that COVID-19 does cause cardiac sequelae. The underlying mechanisms involved are still poorly understood to date. Viral infections, including COVID-19, have been hypothesized to contribute to autoimmunity, by exposing previously hidden cryptic epitopes on damaged cells to an activated immune system. Given the high incidence of cardiac involvement seen in COVID-19, our aim was to determine the frequency of anti-DSG2 antibodies in a population of post COVID-19 patients., Methods and Results: 300 convalescent serum samples were obtained from a group of post COVID-19 infected patients from October 2020 to February 2021. 154 samples were drawn 6 months post-COVID-19 infection and 146 samples were drawn 9 months post COVID infection. 17 samples were obtained from the same patient at the 6- and 9- month mark. An electrochemiluminescent-based immunoassay utilizing the extracellular domain of DSG2 for antibody capture was used. The mean signal intensity of anti-DSG2 antibodies in the post COVID-19 samples was significantly higher than that of a healthy control population (19 ± 83.2 in the post-COVID-19 sample vs. 2.1 ± 7.2 (p < 0. 0001) in the negative control healthy population). Of note, 29.3% of the post COVID-19 infection samples demonstrated a signal higher than the 90th percentile of the control population and 8.7% were higher than the median found in ARVC patients. The signal intensity between the 6-month and 9-month samples did not differ significantly., Conclusions: We report for the first time that recovered COVID-19 patients demonstrate significantly higher and sustained levels of anti-DSG2 autoantibodies as compared to a healthy control population, comparable to that of a diagnosed ARVC group., (Copyright © 2022 Elsevier Ltd. All rights reserved.)
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- 2022
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14. State of Charge Estimation of Lithium-Ion Batteries Using Stacked Encoder-Decoder Bi-Directional LSTM for EV and HEV Applications.
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Terala PK, Ogundana AS, Foo SY, Amarasinghe MY, and Zang H
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Energy storage technologies are being used excessively in industrial applications and in automobiles. Battery state of charge (SOC) is an important metric to be monitored in these applications to ensure proper and safe functionality. Since SOC cannot be measured directly, this paper puts forth a novel machine learning architecture to improve on the existing methods of SOC estimation. This method consists of using combined stacked bi-directional LSTM and encoder-decoder bi-directional long short-term memory architecture. This architecture henceforth represented as SED is implemented to overcome the nonparallel functionality observed in traditional RNN algorithms. Estimations were made utilizing different open-source datasets such as urban dynamometer driving schedule (UDDS), highway fuel efficiency test (HWFET), LA92 and US06. The least Mean Absolute Error observed was 0.62% at 25 °C for the HWFET condition, which confirms the good functionality of the proposed architecture.
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- 2022
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15. Valorization of avocado seeds with antioxidant capacity using pressurized hot water extraction.
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Ong ES, Low J, Tan JCW, Foo SY, and Leo CH
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- Antioxidants chemistry, Endothelial Cells, Phytochemicals analysis, Phytochemicals pharmacology, Plant Extracts chemistry, Seeds chemistry, Water analysis, Persea chemistry, Refuse Disposal
- Abstract
The pulp of avocado (Persea Americana) is widely consumed as the primary food source, while the seed is often discarded as food waste. Increased consumption of avocado would inevitably results in production of waste by-products such as avocado seeds, hence the ability to extract phytochemicals from such waste, and upcycling to potential nutraceutical products is of great interest. The overall aim of this study is to explore avocado seeds as potential functional food through the combined use of a green extraction method, chemical standardization and pattern recognition tools, and biological characterization assays. Specifically, this study utilized an organic solvent-free extraction method, pressurized hot water extraction (PHWE) to extract phytochemicals from avocado seeds and liquid chromatography mass spectrometry (LCMS) was used to identify the phytochemicals present in the avocado seeds. Our results demonstrated that avocado seed extracts have antioxidant activity and inhibited oxidative stress-induced metabolomics changes in endothelial cells, suggesting that avocado seed extracts have vasoprotective actions., (© 2022. The Author(s).)
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- 2022
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16. Prevalence and psychosocial impact of acne vulgaris among high school and university students in Sarawak, Malaysia.
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Lim TH, Badaruddin NSF, Foo SY, Bujang MA, and Muniandy P
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- Cross-Sectional Studies, Female, Humans, Malaysia epidemiology, Male, Prevalence, Schools, Students psychology, Universities, Acne Vulgaris epidemiology, Acne Vulgaris psychology, Quality of Life psychology
- Abstract
Background: Acne vulgaris is a common skin condition that affects adolescents and young adults. Its psychosocial impact can be significant. The primary objective of this study was to determine the prevalence of acne vulgaris and its psychosocial impact among high school and university students in Kuching, Sarawak. In addition, the clinical characteristics of acne and its potential predisposing factors were assessed., Methods: This cross-sectional study was conducted among high school and university students in Kuching, Sarawak. A team of dermatology-trained doctors examined a representative sample of high school and university students aged 16 to 25 years to identify acne vulgaris. The Dermatology Life Quality Index (DLQI) was used to assess the psychosocial impact of acne on affected individuals. The Global Acne Grading System (GAGS) was used to determine the severity of acne. Demographic data and clinical characteristics of acne were recorded., Results: A total of 582 students aged 16 to 25 years were recruited. The overall prevalence of acne vulgaris was 75.8% (n=441). The prevalence of acne was highest (85.5%) in the age group of 16-18 years. There was a significantly higher tendency for male students to have moderate to severe acne (p=0.010). A significantly higher proportion of female students had impaired quality of life (p<0.001) compared to male students. In comparison to male students, the mean DLQI scores were significantly higher in female students in the domains of 'Work and school' and 'Personal relationship' (p<0.05). There were 41 students who had a very large impact on the quality of life with a DLQI score of 11-20 and 34 (82.9%) of them had mild acne. There was a significantly higher proportion of students who had frequent insomnia in the group of students with acne compared to those without acne (11.6% vs. 4.3%, p=0.011). There was no significant association of acne vulgaris with dietary intakes, such as chocolates, sweets, potato chips, yoghurt, milk, fried chicken, ice cream, nuts and carbonated drinks (p>0.05). Of the 441 students with acne, 247 (56%) had not sought any medical attention., Conclusion: Acne vulgaris impacts the quality of life similarly to psoriasis, atopic eczema, and chronic urticaria. In mild acne cases, the quality of life may be significantly affected. Therefore, acne education is required in high schools and colleges to ensure that students understand their disease and are aware of available treatments.
- Published
- 2022
17. Dilated MMA sign in cDAVF and other arterial feeders on 3D TOF MRA.
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Foo SY, Swaminathan SK, and Krings T
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- Angiography, Digital Subtraction, Humans, Meningeal Arteries, Skull, Central Nervous System Vascular Malformations diagnostic imaging, Magnetic Resonance Angiography
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Background: Among the varied causes of pulsatile tinnitus, the condition that can cause severe mortality and morbidity is a cranial dural arteriovenous fistula (cDAVF). This study aimed to assess the diagnostic accuracy of the dilated middle meningeal artery on three-dimensional time-of-flight magnetic resonance angiography in cranial dural arteriovenous fistula and to identify other feeders that can aid in the detection of these lesions., Method: Magnetic resonance angiography and digital subtraction angiography data of all patients with cranial dural arteriovenous fistula treated in a single tertiary referral center between 2007-2020 were included. The middle meningeal artery and other feeders recorded from digital subtraction angiography were assessed on magnetic resonance angiography., Results: The overall agreement between readers in identifying the dilated middle meningeal artery was substantial (κ = 0.878, 95% confidence interval: 0.775-0.982). The dilated middle meningeal artery indicated the presence of a cranial dural arteriovenous fistula with a sensitivity of 79.49% (95% confidence interval: 66.81-92.16), specificity of 100% (95% confidence interval: 100.00-100.00), and negative predictive value of 94.56% (95% confidence interval: 90.89-98.02). An area under the curve of 0.8341 was observed for the ipsilateral middle meningeal artery, with a sensitivity of 92.2% and a specificity of 75.0% at a cut-off of 0.30 mm for identifying a cranial dural arteriovenous fistula. Of 73 other feeders, the occipital, meningohypophyseal trunk, ascending pharyngeal, and posterior meningeal arteries contributed to a large proportion visualized on magnetic resonance angiography (83.6% (41/49))., Conclusion: The dilated middle meningeal artery sign is useful for identifying a cranial dural arteriovenous fistula. Dilatation of the occipital and ascending pharyngeal arteries and meningohypophyseal trunk should be assessed to facilitate the detection of a cranial dural arteriovenous fistula, particularly in the transverse-sigmoid and petrous regions.
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- 2022
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18. The Magnetic Resonance Imaging "Spot" Sign: A Sign of Imminent Intracranial Hemorrhage?
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Foo SY, Nicholson P, and Krings T
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- Cerebral Angiography methods, Cerebral Hemorrhage, Humans, Intracranial Hemorrhages diagnostic imaging, Magnetic Resonance Imaging
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- 2022
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19. Pressurized Hot Water Extraction of Okra Seeds Reveals Antioxidant, Antidiabetic and Vasoprotective Activities.
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Ong ES, Oh CLY, Tan JCW, Foo SY, and Leo CH
- Abstract
Abelmoschus esculentus L. Moench (okra) is a commonly consumed vegetable that consists of the seeds and peel component which are rich in polyphenolic compounds. The aim of this study is to utilize pressurized hot water extraction (PHWE) for the extraction of bioactive phytochemicals from different parts of okra. A single step PHWE was performed at various temperatures (60 °C, 80 °C, 100 °C and 120 °C) to determine which extraction temperature exhibits the optimum phytochemical profile, antioxidant and antidiabetic activities. The optimum temperature for PHWE extraction was determined at 80 °C and the biological activities of the different parts of okra (Inner Skin, Outer Skin and Seeds) were characterized using antioxidant (DPPH and ABTS), α-glucosidase and vasoprotective assays. Using PHWE, the different parts of okra displayed distinct phytochemical profiles, which consist of primarily polyphenolic compounds. The okra Seeds were shown to have the most antioxidant capacity and antidiabetic effects compared to other okra parts, likely to be attributed to their higher levels of polyphenolic compounds. Similarly, okra Seeds also reduced vascular inflammation by downregulating TNFα-stimulated VCAM-1 and SELE expression. Furthermore, metabolite profiling by LC/MS also provided evidence of the cytoprotective effect of okra Seeds in endothelial cells. Therefore, the use of PHWE may be an alternative approach for the environmentally friendly extraction and evaluation of plant extracts for functional food applications.
- Published
- 2021
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20. Structural basis for broad sarbecovirus neutralization by a human monoclonal antibody.
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Tortorici MA, Czudnochowski N, Starr TN, Marzi R, Walls AC, Zatta F, Bowen JE, Jaconi S, di Iulio J, Wang Z, De Marco A, Zepeda SK, Pinto D, Liu Z, Beltramello M, Bartha I, Housley MP, Lempp FA, Rosen LE, Dellota E Jr, Kaiser H, Montiel-Ruiz M, Zhou J, Addetia A, Guarino B, Culap K, Sprugasci N, Saliba C, Vetti E, Giacchetto-Sasselli I, Silacci Fregni C, Abdelnabi R, Caroline Foo SY, Havenar-Daughton C, Schmid MA, Benigni F, Cameroni E, Neyts J, Telenti A, Snell G, Virgin HW, Whelan SPJ, Bloom JD, Corti D, Veesler D, and Pizzuto MS
- Abstract
The recent emergence of SARS-CoV-2 variants of concern (VOC) and the recurrent spillovers of coronaviruses in the human population highlight the need for broadly neutralizing antibodies that are not affected by the ongoing antigenic drift and that can prevent or treat future zoonotic infections. Here, we describe a human monoclonal antibody (mAb), designated S2X259, recognizing a highly conserved cryptic receptor-binding domain (RBD) epitope and cross-reacting with spikes from all sarbecovirus clades. S2X259 broadly neutralizes spike-mediated entry of SARS-CoV-2 including the B.1.1.7, B.1.351, P.1 and B.1.427/B.1.429 VOC, as well as a wide spectrum of human and zoonotic sarbecoviruses through inhibition of ACE2 binding to the RBD. Furthermore, deep-mutational scanning and in vitro escape selection experiments demonstrate that S2X259 possesses a remarkably high barrier to the emergence of resistance mutants. We show that prophylactic administration of S2X259 protects Syrian hamsters against challenges with the prototypic SARS-CoV-2 and the B.1.351 variant, suggesting this mAb is a promising candidate for the prevention and treatment of emergent VOC and zoonotic infections. Our data unveil a key antigenic site targeted by broadly-neutralizing antibodies and will guide the design of pan-sarbecovirus vaccines.
- Published
- 2021
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21. Cyclic di-AMP Oversight of Counter-Ion Osmolyte Pools Impacts Intrinsic Cefuroxime Resistance in Lactococcus lactis.
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Pham HT, Shi W, Xiang Y, Foo SY, Plan MR, Courtin P, Chapot-Chartier MP, Smid EJ, Liang ZX, Marcellin E, and Turner MS
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- Amino Acids metabolism, Bacterial Proteins metabolism, Biological Transport, Lactococcus lactis metabolism, Potassium metabolism, Second Messenger Systems, Anti-Bacterial Agents pharmacology, Cefuroxime pharmacology, Cyclic AMP metabolism, Gene Expression Regulation, Bacterial, Lactococcus lactis drug effects, Lactococcus lactis genetics
- Abstract
The broadly conserved cyclic di-AMP (c-di-AMP) is a conditionally essential bacterial second messenger. The pool of c-di-AMP is fine-tuned through diadenylate cyclase and phosphodiesterase activities, and direct binding of c-di-AMP to proteins and riboswitches allows the regulation of a broad spectrum of cellular processes. c-di-AMP has a significant impact on intrinsic β-lactam antibiotic resistance in Gram-positive bacteria; however, the reason for this is currently unclear. In this work, genetic studies revealed that suppressor mutations that decrease the activity of the potassium (K
+ ) importer KupB or the glutamine importer GlnPQ restore cefuroxime (CEF) resistance in diadenylate cyclase ( cdaA ) mutants of Lactococcus lactis Metabolite analyses showed that glutamine is imported by GlnPQ and then rapidly converted to glutamate, and GlnPQ mutations or c-di-AMP negatively affects the pools of the most abundant free amino acids (glutamate and aspartate) during growth. In a high-c-di-AMP mutant, GlnPQ activity could be increased by raising the internal K+ level through the overexpression of a c-di-AMP-insensitive KupB variant. These results demonstrate that c-di-AMP reduces GlnPQ activity and, therefore, the level of the major free anions in L. lactis through its inhibition of K+ import. Excessive ion accumulation in cdaA mutants results in greater spontaneous cell lysis under hypotonic conditions, while CEF-resistant suppressors exhibit reduced cell lysis and lower osmoresistance. This work demonstrates that the overaccumulation of major counter-ion osmolyte pools in c-di-AMP-defective mutants of L. lactis causes cefuroxime sensitivity. IMPORTANCE The bacterial second messenger cyclic di-AMP (c-di-AMP) is a global regulator of potassium homeostasis and compatible solute uptake in many Gram-positive bacteria, making it essential for osmoregulation. The role that c-di-AMP plays in β-lactam resistance, however, is unclear despite being first identified a decade ago. Here, we demonstrate that the overaccumulation of potassium or free amino acids leads to cefuroxime sensitivity in Lactococcus lactis mutants partially defective in c-di-AMP synthesis. It was shown that c-di-AMP negatively affects the levels of the most abundant free amino acids (glutamate and aspartate) in L. lactis Regulation of these major free anions was found to occur via the glutamine transporter GlnPQ, whose activity increased in response to intracellular potassium levels, which are under c-di-AMP control. Evidence is also presented showing that they are major osmolytes that enhance osmoresistance and cell lysis. The regulatory reach of c-di-AMP can be extended to include the main free anions in bacteria., (Copyright © 2021 Pham et al.)- Published
- 2021
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22. N-terminal domain antigenic mapping reveals a site of vulnerability for SARS-CoV-2.
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McCallum M, Marco A, Lempp F, Tortorici MA, Pinto D, Walls AC, Beltramello M, Chen A, Liu Z, Zatta F, Zepeda S, di Iulio J, Bowen JE, Montiel-Ruiz M, Zhou J, Rosen LE, Bianchi S, Guarino B, Fregni CS, Abdelnabi R, Caroline Foo SY, Rothlauf PW, Bloyet LM, Benigni F, Cameroni E, Neyts J, Riva A, Snell G, Telenti A, Whelan SPJ, Virgin HW, Corti D, Pizzuto MS, and Veesler D
- Abstract
SARS-CoV-2 entry into host cells is orchestrated by the spike (S) glycoprotein that contains an immunodominant receptor-binding domain (RBD) targeted by the largest fraction of neutralizing antibodies (Abs) in COVID-19 patient plasma. Little is known about neutralizing Abs binding to epitopes outside the RBD and their contribution to protection. Here, we describe 41 human monoclonal Abs (mAbs) derived from memory B cells, which recognize the SARS-CoV-2 S N-terminal domain (NTD) and show that a subset of them neutralize SARS-CoV-2 ultrapotently. We define an antigenic map of the SARS-CoV-2 NTD and identify a supersite recognized by all known NTD-specific neutralizing mAbs. These mAbs inhibit cell-to-cell fusion, activate effector functions, and protect Syrian hamsters from SARS-CoV-2 challenge. SARS-CoV-2 variants, including the 501Y.V2 and B.1.1.7 lineages, harbor frequent mutations localized in the NTD supersite suggesting ongoing selective pressure and the importance of NTD-specific neutralizing mAbs to protective immunity.
- Published
- 2021
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23. Perioperative anaphylaxis: A five-year review in a tertiary paediatric hospital.
- Author
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Toh TS, Foo SY, Loh W, Chong KW, En Goh A, Hee HI, and Goh SH
- Subjects
- Adolescent, Australia, Child, Child, Preschool, Hospitals, Pediatric, Humans, Male, New Zealand, Retrospective Studies, Skin Tests, Anaphylaxis diagnosis, Anaphylaxis epidemiology, Anaphylaxis etiology, Drug Hypersensitivity diagnosis, Drug Hypersensitivity epidemiology
- Abstract
Making a diagnosis of perioperative anaphylaxis and identifying culprit drugs are diagnostic challenges. The aim of this study is to describe the perioperative presentation of anaphylaxis and results of patients who underwent allergy evaluation. This is a retrospective review of perioperative anaphylaxis of severity Grade 2 and above based on the Australian and New Zealand Anaesthetic Allergy Group criteria from 2015 to 2019 in a tertiary paediatric hospital. Data collected were demographics, clinical features, investigations and management. Of the 35,361 cases of paediatric anaesthesia, there were 15 cases of perioperative anaphylaxis, giving an incidence of four in 10,000. The median age was seven years (interquartile range four-15 years) with a male predominance of 86.7% (13/15). The severity of anaphylaxis was Grade 2 in 33.3% (5/15) and Grade 3 in 66.7% (10/15). The commonest presenting feature was hypotension (13/15, 86.7%) while the earliest symptom was respiratory change (9/15, 60.0%). Dynamic tryptase was raised in 75% (6/8) of the patients with adequate tryptase samples. Eight patients (53.3%) completed allergy testing, of whom five patients (62.5%) had IgE-mediated anaphylaxis with skin test positive to cefazolin ( n = 3), atracurium ( n = 1) and rocuronium ( n = 1). Three patients (25.0%) had non-IgE-mediated reactions with negative skin tests. Although only half the patients completed allergy evaluation, a culprit drug could be identified in 62.5%, with antibiotics being the commonest. This emphasises the need for appropriate evaluation in cases of suspected perioperative anaphylaxis.
- Published
- 2021
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24. Efficient, Stable, and Low-Cost PbS Quantum Dot Solar Cells with Cr-Ag Electrodes.
- Author
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Khanam JJ, Foo SY, Yu Z, Liu T, and Mao P
- Abstract
PbS quantum dots (QDs) are a promising nanostructured material for solar cells. However, limited works have been done to explore the active layer thickness, layer deposition techniques, stability improvement, and cost reduction for PbS QD solar cells. We address those issues of device fabrication herein and suggest their possible solutions. In our work, to get the maximum current density from a PbS QD solar cell, we estimated the optimized active layer thickness using Matlab simulation. After that, we fabricated a high-performance and low-cost QD photovoltaic (PV) device with the simulated optimized active layer thickness. We implemented this low-cost device using a 10 mg/mL PbS concentration. Here, spin coating and drop-cast layer deposition methods were used and compared. We found that the device prepared by the spin coating method was more efficient than that by the drop cast method. The spin-coated PbS QD solar cell provided 6.5% power conversion efficiency (PCE) for the AM1.5 light spectrum. Besides this, we observed that Cr (chromium) interfaced with the Ag (Cr-Ag) electrode can provide a highly air-stable electrode.
- Published
- 2019
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25. A Phase 1 Randomized Study of Single Intravenous Infusions of the Novel Nitroxyl Donor BMS-986231 in Healthy Volunteers.
- Author
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Cowart D, Venuti RP, Lynch K, Guptill JT, Noveck RJ, and Foo SY
- Subjects
- Adult, Blood Pressure drug effects, Cohort Studies, Dose-Response Relationship, Drug, Double-Blind Method, Female, Healthy Volunteers, Heart Failure drug therapy, Heart Rate drug effects, Hemodynamics, Humans, Infusions, Intravenous, Male, Nitric Oxide Donors adverse effects, Nitric Oxide Donors blood, Nitric Oxide Donors pharmacology, Nitrogen Oxides adverse effects, Nitrogen Oxides blood, Nitrogen Oxides pharmacology, Young Adult, Nitric Oxide Donors pharmacokinetics, Nitrogen Oxides pharmacokinetics
- Abstract
Nitroxyl (HNO) is a reactive nitrogen molecule that has potential therapeutic benefits for patients with acute heart failure. The results of the first-in-human study for BMS-986231, a novel HNO donor, are reported. The aim of this sequential cohort study was to evaluate the safety, tolerability, and pharmacokinetic profile of BMS-986231 after 24- and 48-hour intravenous infusions in healthy volunteers. Eighty subjects were randomized and dosed. Seven cohorts (stratum A) received BMS-986231 0.1, 0.33, 1, 3, 5, 10, and 15 μg/kg/min or placebo, infused over 24 hours. An additional cohort (stratum B) received 10 μg/kg/min or placebo, infused over 48 hours. Adverse events (AEs) were reported for 30 days after completion of infusion. Blood/urine samples were collected at regular intervals; other parameters (blood pressure, heart rate/rhythm, cardiac index) were also assessed. Headaches were the most commonly reported drug-related AE (48%) in those who received BMS-986231, although their severity was reduced by hydration. No other significant drug-related AEs were noted. BMS-986231 was associated with dose-dependent and well-tolerated reductions in systolic and diastolic blood pressure versus baseline; cardiac index, as measured noninvasively, was increased. BMS-986231 had no clinically significant effect on heart rate/rhythm or laboratory parameters. Its mean elimination half-life was 0.7-2.5 hours. BMS-986231 was safe and well-tolerated for up to 24 hours (15 μg/kg/min) or 48 hours (10 μg/kg/min), with a favorable hemodynamic profile observed. Ongoing studies continue to evaluate the potential benefit of BMS-986231 in patients with acute heart failure., (© 2019, The Authors. The Journal of Clinical Pharmacology published by Wiley Periodicals, Inc. on behalf of American College of Clinical Pharmacology.)
- Published
- 2019
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26. Modeling of High-Efficiency Multi-Junction Polymer and Hybrid Solar Cells to Absorb Infrared Light.
- Author
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Khanam JJ and Foo SY
- Abstract
In this paper, we present our work on high-efficiency multi-junction polymer and hybrid solar cells. The transfer matrix method is used for optical modeling of an organic solar cell, which was inspired by the McGehee Group in Stanford University. The software simulation calculates the optimal thicknesses of the active layers to provide the best short circuit current (J
SC ) value. First, we show three designs of multi-junction polymer solar cells, which can absorb sunlight beyond the 1000 nm wavelengths. Then we present a novel high-efficiency hybrid (organic and inorganic) solar cell, which can absorb the sunlight with a wavelength beyond 2500 nm. Approximately 12% efficiency was obtained for the multi-junction polymer solar cell and 20% efficiency was obtained from every two-, three- and four-junction hybrid solar cell under 1 sun AM1.5 illumination.- Published
- 2019
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27. Mosquitoes (Diptera: Culicidae) of Singapore: Updated Checklist and New Records.
- Author
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Lam-Phua SG, Yeo H, Lee RM, Chong CS, Png AB, Foo SY, Liew C, Ng LC, Tang CS, Rueda LM, Pecor JE, and Harrison BA
- Subjects
- Animals, Checklist, Female, Male, Mosquito Vectors, Singapore, Biodiversity, Culicidae
- Abstract
Prior to 1965, Singapore was part of the Malaya (now Malaysia) and was usually not mentioned when mosquito records were reported for Malaya. Consequently, many species that occurred in Singapore were not listed in the world mosquito catalog, and the available checklist for Singapore since 1986 is incomplete, with some imprecise species information. In updating this checklist, we examined and verified mosquito specimens collected from Singapore in various depositories, including a thorough review of past taxonomic literature. Here, we report a checklist of 182 mosquito species, 33 new distribution records, and a consolidated status list of vectors for Singapore. As Singapore is a travel hub and hosts one of the busiest container ports in the world, there is a risk of introducing mosquito species and their associated pathogens of human disease to the country. Hence, the distribution records are important to increase our knowledge on mosquito ecology as well as to understand the risk of newly introduced vectors and their associated pathogens.
- Published
- 2019
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28. Correction: Serine 207 phosphorylated lysyl-tRNA synthetase predicts disease-free survival of non-small-cell lung carcinoma.
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Boulos S, Park MC, Zeibak M, Foo SY, Jeon YK, Kim YT, Motzik A, Tshori S, Hamburger T, Kim S, Nechushtan H, and Razin E
- Abstract
[This corrects the article DOI: 10.18632/oncotarget.18053.].
- Published
- 2018
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29. Multi-stage optimization of a deep model: A case study on ground motion modeling.
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Tahmassebi A, Gandomi AH, Fong S, Meyer-Baese A, and Foo SY
- Subjects
- Algorithms, Computer Simulation, Data Analysis, Deep Learning, Machine Learning, Motion, Neural Networks, Computer
- Abstract
In this study, a multi-stage optimization procedure is proposed to develop deep neural network models which results in a powerful deep learning pipeline called intelligent deep learning (iDeepLe). The proposed pipeline is then evaluated by a challenging real-world problem, the modeling of the spectral acceleration experienced by a particle during earthquakes. This approach has three main stages to optimize the deep model topology, the hyper-parameters, and its performance, respectively. This pipeline optimizes the deep model via adaptive learning rate optimization algorithms for both accuracy and complexity in multiple stages, while simultaneously solving the unknown parameters of the regression model. Among the seven adaptive learning rate optimization algorithms, Nadam optimization algorithm has shown the best performance results in the current study. The proposed approach is shown to be a suitable tool to generate solid models for this complex real-world system. The results also show that the parallel pipeline of iDeepLe has the capacity to handle big data problems as well., Competing Interests: The authors have declared that no competing interests exist.
- Published
- 2018
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30. Cystic degeneration of hepatic adenoma: a rare complication of hepatic adenoma.
- Author
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Foo SY, Paul L, and Viswanathan S
- Abstract
This case report describes a rare complication of hepatic adenomata in a 33-year-old female. The patient initially presented with abdominal pain, and baseline imaging demonstrated several hepatic adenomas, the largest of which (approximately 8 cm) was adjacent to the inferior vena cava. Owing to the location of this adenoma, surgical/vascular intervention was deemed inappropriate. The patient was actively observed for approximately 4 years, and managed supportively during any recurrent episodes. With follow-up CT/MRI scans, the "natural history" of this particular lesion, including haemorrhage, thrombosis and infarction, was observed. However, as intervention was unsuitable, further MRI was performed in view of these complications, allowing observation of the end-stage features of the adenoma. Appearances were consistent with a rare complication of hepatic adenoma, i.e . cystic degeneration, a process well documented in uterine leiomyoma.
- Published
- 2017
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31. A Phase 2a dose-escalation study of the safety, tolerability, pharmacokinetics and haemodynamic effects of BMS-986231 in hospitalized patients with heart failure with reduced ejection fraction.
- Author
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Tita C, Gilbert EM, Van Bakel AB, Grzybowski J, Haas GJ, Jarrah M, Dunlap SH, Gottlieb SS, Klapholz M, Patel PC, Pfister R, Seidler T, Shah KB, Zieliński T, Venuti RP, Cowart D, Foo SY, Vishnevsky A, and Mitrovic V
- Subjects
- Cardiovascular Agents pharmacokinetics, Dose-Response Relationship, Drug, Double-Blind Method, Hemodynamics, Hospitalization, Humans, Nitric Oxide Donors pharmacokinetics, Nitric Oxide Donors therapeutic use, Treatment Outcome, Cardiovascular Agents therapeutic use, Heart Failure drug therapy, Heart Failure physiopathology, Stroke Volume
- Abstract
Aims: This study was designed to evaluate the safety, tolerability and haemodynamic effects of BMS-986231, a novel second-generation nitroxyl donor with potential inotropic, lusitropic and vasodilatory effects in patients hospitalized with decompensated heart failure and reduced ejection fraction (HFrEF)., Methods and Results: Forty-six patients hospitalized with decompensated HFrEF were enrolled into four sequential dose-escalation cohorts in this double-blind, randomized, placebo-controlled Phase 2a study. Patients with baseline pulmonary capillary wedge pressure (PCWP) of ≥20 mmHg and a cardiac index of ≤2.5 L/min/m
2 received one 6-h i.v. infusion of BMS-986231 (at 3, 5, 7 or 12 µg/kg/min) or placebo. BMS-986231 produced rapid and sustained reductions in PCWP, as well as consistent reductions in time-averaged pulmonary arterial systolic pressure, pulmonary arterial diastolic pressure and right atrial pressure. BMS-986231 increased non-invasively measured time-averaged stroke volume index, cardiac index and cardiac power index values, and decreased total peripheral vascular resistance. There was no evidence of increased heart rate, drug-related arrhythmia or symptomatic hypotension with BMS-986231. Analyses of adverse events throughout the 30-day follow-up did not identify any toxicities specific to BMS-986231, with the potential exception of infrequent mild-to-moderate headaches during infusion. There were no treatment-related serious adverse events., Conclusions: BMS-986231 demonstrated a favourable safety and haemodynamic profile in patients hospitalized with advanced heart failure. Based on preclinical data and these study's findings, it is possible that the haemodynamic benefits may be mediated by inotropic and/or lusitropic as well as vasodilatory effects. The therapeutic potential of BMS-986231 should be further assessed in patients with heart failure., (© 2017 The Authors. European Journal of Heart Failure published by John Wiley & Sons Ltd on behalf of European Society of Cardiology.)- Published
- 2017
- Full Text
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32. Serine 207 phosphorylated lysyl-tRNA synthetase predicts disease-free survival of non-small-cell lung carcinoma.
- Author
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Boulos S, Park MC, Zeibak M, Foo SY, Jeon YK, Kim YT, Motzik A, Tshori S, Hamburger T, Kim S, Nechushtan H, and Razin E
- Abstract
It has been shown that various tRNA synthetases exhibit non-canonical activities unrelated to their original role in translation. We have previously described a signal transduction pathway in which serine 207 phosphorylated lysyl-tRNA synthetase (P-s207 LysRS) is released from the cytoplasmic multi-tRNA synthetase complex (MSC) into the nucleus, where it activates the transcription factor MITF in stimulated cultured mast cells and cardiomyocytes. Here we describe a similar transformation of LysRS due to EGFR signaling activation in human lung cancer. Our data shows that activation of the EGFR results in phosphorylation of LysRS at position serine 207, its release from the MSC and translocation to the nucleus. We then generated a P-s207 LysRS rabbit polyclonalantibody and tested 242 tissue micro-array samples derived from non-small-cell lung cancer patients. Highly positive nuclear staining for P-s207 LysRS was noted in patients with EGFR mutations as compared to WT EGFR patients and was associated with improved mean disease-free survival (DFS). In addition, patients with mutated EGFR and negative lymph node metastases had better DFS when P-s207 LysRS was present in the nucleus. The data presented strongly suggests functional and prognostic significance of P-s207 LysRS in non-small-cell lung cancer., Competing Interests: CONFLICTS OF INTEREST The authors have declared that no conflicts of interest exist.
- Published
- 2017
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- View/download PDF
33. Atherosclerotic Carotid Plaque Composition: A 3T and 7T MRI-Histology Correlation Study.
- Author
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Lopez Gonzalez MR, Foo SY, Holmes WM, Stewart W, Muir KW, Condon B, Welch G, and Forbes KP
- Subjects
- Aged, Aged, 80 and over, Endarterectomy, Carotid, Female, Humans, Image Interpretation, Computer-Assisted, Male, Middle Aged, Necrosis, Statistics as Topic, Carotid Artery Diseases diagnostic imaging, Carotid Artery Diseases pathology, Carotid Stenosis diagnostic imaging, Carotid Stenosis pathology, Magnetic Resonance Imaging methods
- Abstract
Background and Purpose: Carotid artery atherosclerotic plaque composition may influence plaque stability and risk of thromboembolic events, and noninvasive plaque imaging may therefore permit risk stratification for clinical management. Plaque composition was compared using noninvasive in vivo (3T) and ex vivo (7T) MRI and histopathological examination., Methods: Thirty-three endarterectomy cross-sections, from 13 patients, were studied. The data sets consisted of in vivo 3T MRI, ex vivo 7T MRI, and histopathology. Semiautomated segmentation methods were used to measure areas of different plaque components. Bland-Altman plots and mean difference with 95% confidence interval were carried out., Results: There was general quantitative agreement between areas derived from semiautomated segmentation of MRI data and histology measurements. The mean differences and 95% confidence bounds in the relative to total plaque area between 3T versus Histology were: fibrous tissue 4.99%(-4.56 to 14.56), lipid-rich/necrotic core (LR/NC) with hemorrhage -1.81%(-14.11 to 10.48), LR/NC without hemorrhage -2.43%(-13.04 to 8.17), and calcification -3.18%(-11.55 to 5.18). The mean differences and 95% confidence bounds in the relative to total plaque area between 7T and histology were: fibrous tissue 3.17%(-3.17 to 9.52), LR/NC with hemorrhage -0.55%(-9.06 to 7.95), LR/NC without hemorrhage -12.62%(-19.8 to -5.45), and calcification -2.43%(-9.97 to 4.73)., Conclusions: This study provides evidence that semiautomated segmentation of 3T/7T MRI techniques can help to determine atherosclerotic plaque composition. In particular, the high resolution of ex vivo 7T data was able to highlight greater detail in the atherosclerotic plaque composition. High-field MRI may therefore have advantages for in vivo carotid plaque MRI., (Copyright © 2016 by the American Society of Neuroimaging.)
- Published
- 2016
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34. Regulatory T cells prevent inducible BALT formation by dampening neutrophilic inflammation.
- Author
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Foo SY, Zhang V, Lalwani A, Lynch JP, Zhuang A, Lam CE, Foster PS, King C, Steptoe RJ, Mazzone SB, Sly PD, and Phipps S
- Subjects
- Animals, Animals, Newborn, Cellular Microenvironment immunology, Cytokines biosynthesis, Inflammation metabolism, Inflammation pathology, Lipopolysaccharides administration & dosage, Lipopolysaccharides immunology, Lymphocyte Depletion, Lymphoid Tissue metabolism, Male, Mice, Neutrophils metabolism, T-Lymphocytes, Regulatory metabolism, Tumor Necrosis Factor Ligand Superfamily Member 13 metabolism, Inflammation immunology, Lymphoid Tissue immunology, Neutrophils immunology, T-Lymphocytes, Regulatory immunology
- Abstract
Inducible BALT (iBALT) can amplify pulmonary or systemic inflammatory responses to the benefit or detriment of the host. We took advantage of the age-dependent formation of iBALT to interrogate the underlying mechanisms that give rise to this ectopic, tertiary lymphoid organ. In this study, we show that the reduced propensity for weanling as compared with neonatal mice to form iBALT in response to acute LPS exposure is associated with greater regulatory T cell expansion in the mediastinal lymph nodes. Ab- or transgene-mediated depletion of regulatory T cells in weanling mice upregulated the expression of IL-17A and CXCL9 in the lungs, induced a tissue neutrophilia, and increased the frequency of iBALT to that observed in neonatal mice. Remarkably, neutrophil depletion in neonatal mice decreased the expression of the B cell active cytokines, a proliferation-inducing ligand and IL-21, and attenuated LPS-induced iBALT formation. Taken together, our data implicate a role for neutrophils in lymphoid neogenesis. Neutrophilic inflammation is a common feature of many autoimmune diseases in which iBALT are present and pathogenic, and hence the targeting of neutrophils or their byproducts may serve to ameliorate detrimental lymphoid neogenesis in a variety of disease contexts., (Copyright © 2015 by The American Association of Immunologists, Inc.)
- Published
- 2015
- Full Text
- View/download PDF
35. Non-canonical roles of lysyl-tRNA synthetase in health and disease.
- Author
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Motzik A, Nechushtan H, Foo SY, and Razin E
- Subjects
- Amyotrophic Lateral Sclerosis genetics, Animals, HIV Infections genetics, Health, Humans, Lysine-tRNA Ligase genetics, Peripheral Nervous System Diseases genetics, Amyotrophic Lateral Sclerosis enzymology, HIV Infections enzymology, Lysine-tRNA Ligase metabolism, Peripheral Nervous System Diseases enzymology
- Abstract
Lysyl-tRNA synthetase (LysRS) is a highly conserved enzyme that is part of the translational machinery in all living cells. Besides its canonical role in translation, LysRS gained additional domains and functions throughout evolution. These include its essential role in HIV replication and its roles in transcriptional regulation, cytokine-like signaling, and transport of proteins to the cell membrane. These diverse processes are tightly regulated through post-transcriptional modifications, interactions with other proteins, and targeting to the various cell compartments. The emerging variety of tasks performed by LysRS may therefore be utilized by various processes and pathological conditions that are described in this review, and their ongoing investigation is of extreme importance for our understanding of basic cellular regulatory mechanisms., (Copyright © 2013 Elsevier Ltd. All rights reserved.)
- Published
- 2013
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36. RTEF-1, an upstream gene of hypoxia-inducible factor-1α, accelerates recovery from ischemia.
- Author
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Jin Y, Wu J, Song X, Song Q, Cully BL, Messmer-Blust A, Xu M, Foo SY, Rosenzweig A, and Li J
- Subjects
- Animals, Base Sequence, Blood Circulation genetics, Cell Hypoxia genetics, Cell Line, Cell Proliferation, Endothelial Cells cytology, Endothelial Cells metabolism, Endothelial Cells pathology, Gene Expression Regulation, Humans, Ischemia genetics, Ischemia pathology, Mice, Neovascularization, Pathologic genetics, Neovascularization, Pathologic metabolism, Regulatory Sequences, Nucleic Acid genetics, TEA Domain Transcription Factors, Transcription, Genetic genetics, DNA-Binding Proteins genetics, DNA-Binding Proteins metabolism, Hypoxia-Inducible Factor 1, alpha Subunit genetics, Ischemia metabolism, Ischemia physiopathology, Muscle Proteins genetics, Muscle Proteins metabolism, Transcription Factors genetics, Transcription Factors metabolism
- Abstract
The amount of available hypoxia-inducible factor (HIF)-1α has been considered to be largely a consequence of post-translational modification by multiple ubiquitin-proteasome pathways. However, the role of transcriptional regulation of HIF-1α is less certain, and the mechanisms of transcriptional regulation of HIF-1α require further investigation. Here we report that related transcriptional enhancer factor-1 (RTEF-1), a member of the TEF transcriptional factor family, transcriptionally regulates the HIF-1α gene under normoxic and hypoxic conditions. The expression of HIF-1α mRNA was decreased in endothelial cells in which RTEF-1 was knocked down with siRNA. Sequential deletional analysis of the HIF-1α promoter revealed that the MCAT-like element in the HIF-1α promoter was essential for HIF-1α transcription. Binding of RTEF-1 to the MCAT-like element was confirmed by ChIP. Treatment of endothelial cells with a HIF-1 inhibitor resulted in retardation of RTEF-1-induced proliferation and tube formation. Moreover, increased HIF-1α expression was observed in transgenic mice expressing RTEF-1 under the VE-cadherin promoter (VE-Cad/RTEF-1). VE-Cad/RTEF-1 mice subjected to hindlimb ischemia demonstrated increased levels of HIF-1α, accelerated recovery of blood flow, and increased capillary density compared with littermate controls. These results identify RTEF-1 as a regulator of HIF-1α transcription, which results in up-regulation of HIF-1α and acceleration of recovery from ischemia.
- Published
- 2011
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- View/download PDF
37. Plasmacytoid dendritic cells promote host defense against acute pneumovirus infection via the TLR7-MyD88-dependent signaling pathway.
- Author
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Davidson S, Kaiko G, Loh Z, Lalwani A, Zhang V, Spann K, Foo SY, Hansbro N, Uematsu S, Akira S, Matthaei KI, Rosenberg HF, Foster PS, and Phipps S
- Subjects
- Adaptive Immunity, Adoptive Transfer, Animals, Interferons genetics, Interferons immunology, Membrane Glycoproteins genetics, Mice, Mice, Inbred BALB C, Mice, Knockout, Myeloid Differentiation Factor 88 genetics, Signal Transduction, Toll-Like Receptor 7 genetics, Dendritic Cells immunology, Membrane Glycoproteins immunology, Membrane Glycoproteins metabolism, Murine pneumonia virus immunology, Myeloid Differentiation Factor 88 metabolism, Pneumovirus Infections immunology, Toll-Like Receptor 7 immunology, Toll-Like Receptor 7 metabolism
- Abstract
Human respiratory syncytial virus (RSV) is the leading cause of lower respiratory tract infection in infants. In human infants, plasmacytoid dendritic cells (pDC) are recruited to the nasal compartment during infection and initiate host defense through the secretion of type I IFN, IL-12, and IL-6. However, RSV-infected pDC are refractory to TLR7-mediated activation. In this study, we used the rodent-specific pathogen, pneumonia virus of mice (PVM), to determine the contribution of pDC and TLR7 signaling to the development of the innate inflammatory and early adaptive immune response. In wild-type, but not TLR7- or MyD88-deficient mice, PVM inoculation led to a marked infiltration of pDC and increased expression of type I, II, and III IFNs. The delayed induction of IFNs in the absence of TLR7 or MyD88 was associated with a diminished innate inflammatory response and augmented virus recovery from lung tissue. In the absence of TLR7, PVM-specific CD8(+) T cell cytokine production was abrogated. The adoptive transfer of TLR7-sufficient, but not TLR7-deficient pDC to TLR7 gene-deleted mice recapitulated the antiviral responses observed in wild-type mice and promoted virus clearance. In summary, TLR7-mediated signaling by pDC is required for appropriate innate responses to acute pneumovirus infection. It is conceivable that as-yet-unidentified defects in the TLR7 signaling pathway may be associated with elevated levels of RSV-associated morbidity and mortality among otherwise healthy human infants.
- Published
- 2011
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38. IKKβ regulates essential functions of the vascular endothelium through kinase-dependent and -independent pathways.
- Author
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Ashida N, Senbanerjee S, Kodama S, Foo SY, Coggins M, Spencer JA, Zamiri P, Shen D, Li L, Sciuto T, Dvorak A, Gerszten RE, Lin CP, Karin M, and Rosenzweig A
- Subjects
- Animals, Cell Movement, Endothelium, Vascular cytology, Female, I-kappa B Kinase genetics, Male, Mice, Mice, Knockout, Proto-Oncogene Proteins c-akt genetics, Endothelium, Vascular enzymology, I-kappa B Kinase metabolism, Proto-Oncogene Proteins c-akt metabolism, Signal Transduction
- Abstract
Vascular endothelium provides a selective barrier between the blood and tissues, participates in wound healing and angiogenesis, and regulates tissue recruitment of inflammatory cells. Nuclear factor (NF)-κB transcription factors are pivotal regulators of survival and inflammation, and have been suggested as potential therapeutic targets in cancer and inflammatory diseases. Here we show that mice lacking IKKβ, the primary kinase mediating NF-κB activation, are smaller than littermates and born at less than the expected Mendelian frequency in association with hypotrophic and hypovascular placentae. IKKβ-deleted endothelium manifests increased vascular permeability and reduced migration. Surprisingly, we find that these defects result from loss of kinase-independent effects of IKKβ on activation of the serine-threonine kinase, Akt. Together, these data demonstrate essential roles for IKKβ in regulating endothelial permeability and migration, as well as an unanticipated connection between IKKβ and Akt signalling.
- Published
- 2011
- Full Text
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39. Regulation of inducible BALT formation and contribution to immunity and pathology.
- Author
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Foo SY and Phipps S
- Subjects
- Animals, Chemokines immunology, Homeostasis immunology, Humans, Immunity, Lymphoid Tissue pathology, Organogenesis genetics, Organogenesis immunology, Respiratory Tract Infections pathology, T-Lymphocytes, Regulatory immunology, Transcriptional Activation, Bronchi, Choristoma, Dendritic Cells immunology, Lymphoid Tissue immunology, Respiratory Tract Infections immunology
- Abstract
Inducible bronchus-associated lymphoid tissue (iBALT) is an organized tertiary lymphoid structure that is not pre-programmed but develops in response to infection or under chronic inflammatory conditions. Emerging research has shown that iBALT provides a niche for T-cell priming and B-cell education to assist in the clearance of infectious agents, highlighting the prospect that iBALT may be engineered and harnessed to enhance protective immunity against respiratory pathogens. Although iBALT formation is associated with several canonical factors of secondary lymphoid organogenesis such as lymphotoxin-α and the homeostatic chemokines, CXCL13, CCL19, and CCL21, these cytokines are not mandatory for its formation, even though they influence its organization and function. Similarly, lymphoid tissue-inducer cells are not a requisite of iBALT formation. In contrast, dendritic cells are emerging as pivotal players required to form and sustain the presence of iBALT. Regulatory T cells appear to be able to attenuate the development of iBALT, although the underlying mechanisms remain ill-defined. In this review, we discuss facets unique to iBALT induction, the cellular subsets, and molecular cues that govern this process, and the contribution of this ectopic structure toward the generation of immune responses in the pulmonary compartment.
- Published
- 2010
- Full Text
- View/download PDF
40. Allergic sensitization is enhanced in early life through toll-like receptor 7 activation.
- Author
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Phipps S, Hansbro N, Lam CE, Foo SY, Matthaei KI, and Foster PS
- Subjects
- Adjuvants, Immunologic pharmacology, Animals, Animals, Newborn, Eosinophilia pathology, Flagellin pharmacology, Gene Expression genetics, Gene Expression immunology, Hyperplasia pathology, Hypersensitivity metabolism, Hypersensitivity pathology, Immunoglobulin G blood, Immunoglobulin G immunology, Interferon-gamma metabolism, Interleukin-13 genetics, Interleukin-13 metabolism, Interleukin-4 metabolism, Interleukin-5 metabolism, Lipopolysaccharides pharmacology, Lung metabolism, Lung pathology, Lymph Nodes immunology, Lymph Nodes metabolism, Mice, Mice, Inbred BALB C, Mucous Membrane pathology, Ovalbumin administration & dosage, Ovalbumin immunology, RNA, Viral pharmacology, Teichoic Acids pharmacology, Th2 Cells immunology, Th2 Cells metabolism, Toll-Like Receptor 2 physiology, Vaccination, Hypersensitivity etiology, Hypersensitivity immunology, Membrane Glycoproteins physiology, Toll-Like Receptor 7 physiology
- Abstract
Background: Prospective cohort studies suggest that children hospitalized in early life with severe infections are significantly more likely to develop recurrent wheezing and asthma., Objective: Using an inhalational mouse model of allergic airways inflammation, we sought to determine the effect of viral and bacterial-associated molecular patterns on the magnitude of the allergic inflammatory response and whether this effect was age dependent., Methods: BALB/c mice were sensitized by intranasal administration of endotoxin(low) ovalbumin (OVA) in the absence or presence of viral single-stranded (ss)RNA, lipoteichoic acid or flagellin as neonates (within the first 24 h of life) or as weanlings (4 weeks of age). Mice were challenged four times with OVA at 6 weeks of age and end-points (bronchoalveolar lavage cytology, histology, antigen-specific T and B cell responses) determined at 7 weeks of age., Results: Inhalational sensitization (<24 h or 4 weeks of age) and challenge with OVA induced a mild allergic inflammatory response in the airways as indicated by increased numbers of eosinophils and mucus cells, elevated serum OVA-specific IgG1, and production of T helper 2 (Th2) cytokines. Mice sensitized to endotoxin(low) OVA at birth in the presence of ssRNA or lipoteichoic acid, but not flagellin, showed an increase in the numbers of airway and tissue eosinophils, mucus producing cells and antigen-specific production of IL-13 as compared with mice exposed only to endotoxin(low) OVA. By contrast, all three TLR ligands failed to increase the magnitude of OVA-induced allergic inflammation in mice sensitized as weanlings., Conclusions: Recognition of distinct microbial-associated patterns in early life may preferentially promote the de novo differentiation of bystander, antigen-specific CD4(+) T cells toward a Th2 phenotype, and promote an asthma-like phenotype upon cognate antigen exposure in later life.
- Published
- 2009
- Full Text
- View/download PDF
41. Vascular effects of a low-carbohydrate high-protein diet.
- Author
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Foo SY, Heller ER, Wykrzykowska J, Sullivan CJ, Manning-Tobin JJ, Moore KJ, Gerszten RE, and Rosenzweig A
- Subjects
- Analysis of Variance, Animals, Apolipoproteins E genetics, Cholesterol blood, Chromatography, Liquid, Dietary Proteins administration & dosage, Flow Cytometry, Mice, Mice, Knockout, Proto-Oncogene Proteins c-akt metabolism, Stem Cells cytology, Stem Cells drug effects, Atherosclerosis etiology, Diet, Carbohydrate-Restricted adverse effects, Dietary Proteins adverse effects, Neovascularization, Physiologic drug effects
- Abstract
The cardiovascular complications of obesity have prompted interest in dietary interventions to reduce weight, including low-carbohydrate diets that are generally high in protein and fat. However, little is known about the long-term effects of these diets on vascular health. We examined the cardiovascular effects of a low-carbohydrate, high-protein diet (LCHP) in the ApoE(-/-) mouse model of atherosclerosis and in a model of ischemia-induced neovascularization. Mice on a LCHP were compared with mice maintained on either the standard chow diet (SC) or the Western diet (WD) which contains comparable fat and cholesterol to the LCHP. LCHP-fed mice developed more aortic atherosclerosis and had an impaired ability to generate new vessels in response to tissue ischemia. These changes were not explained by alterations in serum cholesterol, inflammatory mediators or infiltrates, or oxidative stress. The LCHP diet substantially reduced the number of bone marrow and peripheral blood endothelial progenitor cells (EPCs), a marker of vascular regenerative capacity. EPCs from mice on a LCHP diet also manifest lower levels of activated (phosphorylated) Akt, a serine-threonine kinase important in EPC mobilization, proliferation, and survival. Taken together, these data demonstrate that in animal models LCHP diets have adverse vascular effects not reflected in serum markers and that nonlipid macronutrients can modulate vascular progenitor cells and pathophysiology.
- Published
- 2009
- Full Text
- View/download PDF
42. Toll/IL-1 signaling is critical for house dust mite-specific helper T cell type 2 and type 17 [corrected] responses.
- Author
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Phipps S, Lam CE, Kaiko GE, Foo SY, Collison A, Mattes J, Barry J, Davidson S, Oreo K, Smith L, Mansell A, Matthaei KI, and Foster PS
- Subjects
- Administration, Intranasal, Animals, Asthma etiology, Cell Movement immunology, Dendritic Cells immunology, Disease Models, Animal, Eosinophilia immunology, Epitopes, Goblet Cells immunology, Humans, Immunity, Innate immunology, Immunoglobulin G biosynthesis, Immunoglobulin G immunology, Inflammation immunology, Interleukin-17 biosynthesis, Interleukin-5 biosynthesis, Mice, Mice, Inbred BALB C, Mice, Transgenic, Myeloid Differentiation Factor 88 deficiency, Neutrophils immunology, Receptors, Cytokine biosynthesis, Receptors, Interleukin, Toll-Like Receptors biosynthesis, Toll-Like Receptors deficiency, Asthma immunology, Myeloid Differentiation Factor 88 immunology, Pyroglyphidae immunology, Receptors, Cytokine immunology, Th1 Cells immunology, Th2 Cells immunology, Toll-Like Receptors immunology
- Abstract
Rationale: One of the immunopathological features of allergic inflammation is the infiltration of helper T type 2 (Th2) cells to the site of disease. Activation of innate pattern recognition receptors such as Toll-like receptors (TLRs) plays a critical role in helper T type 1 cell differentiation, yet their contribution to the generation of Th2 responses to clinically relevant aeroallergens remains poorly defined., Objectives: To determine the requirement for TLR2, TLR4, and the Toll/IL-1 receptor domain adaptor protein MyD88 in a murine model of allergic asthma., Methods: Wild-type and factor-deficient ((-/-)) mice were sensitized intranasally to the common allergen house dust mite (HDM) and challenged 2 weeks later on four consecutive days. Measurements of allergic airway inflammation, T-cell cytokine production, and airway hyperreactivity were performed 24 hours later., Measurements and Main Results: Mice deficient in MyD88 were protected from the cardinal features of allergic asthma, including granulocytic inflammation, Th2 cytokine production and airway hyperreactivity. Although HDM activated NF-kappaB in TLR2- or TLR4-expressing HEK cells, only in TLR4(-/-) mice was the magnitude of allergic airway inflammation and hyperreactivity attenuated. The diminished Th2 response present in MyD88(-/-) and TLR4(-/-) mice was associated with fewer OX40 ligand-expressing myeloid dendritic cells in the draining lymph nodes during allergic sensitization. Finally, HDM-specific IL-17 production and airway neutrophilia were attenuated in MyD88(-/-) but not TLR4(-/-) mice., Conclusions: Together, these data suggest that Th2- and Th17-mediated inflammation generated on inhalational HDM exposure is differentially regulated by the presence of microbial products and the activation of distinct MyD88-dependent pattern recognition receptors.
- Published
- 2009
- Full Text
- View/download PDF
43. HIF-independent regulation of VEGF and angiogenesis by the transcriptional coactivator PGC-1alpha.
- Author
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Arany Z, Foo SY, Ma Y, Ruas JL, Bommi-Reddy A, Girnun G, Cooper M, Laznik D, Chinsomboon J, Rangwala SM, Baek KH, Rosenzweig A, and Spiegelman BM
- Subjects
- Animals, Cell Hypoxia, Cells, Cultured, Gene Expression Regulation, Hypoxia-Inducible Factor 1 metabolism, Mice, Mice, Transgenic, Muscle, Skeletal metabolism, Oxygen metabolism, Peroxisome Proliferator-Activated Receptor Gamma Coactivator 1-alpha, Receptors, Estrogen metabolism, Trans-Activators deficiency, Trans-Activators genetics, Transcription Factors, Transgenes genetics, ERRalpha Estrogen-Related Receptor, Ischemia metabolism, Neovascularization, Physiologic, Trans-Activators metabolism, Vascular Endothelial Growth Factor A metabolism
- Abstract
Ischaemia of the heart, brain and limbs is a leading cause of morbidity and mortality worldwide. Hypoxia stimulates the secretion of vascular endothelial growth factor (VEGF) and other angiogenic factors, leading to neovascularization and protection against ischaemic injury. Here we show that the transcriptional coactivator PGC-1alpha (peroxisome-proliferator-activated receptor-gamma coactivator-1alpha), a potent metabolic sensor and regulator, is induced by a lack of nutrients and oxygen, and PGC-1alpha powerfully regulates VEGF expression and angiogenesis in cultured muscle cells and skeletal muscle in vivo. PGC-1alpha-/- mice show a striking failure to reconstitute blood flow in a normal manner to the limb after an ischaemic insult, whereas transgenic expression of PGC-1alpha in skeletal muscle is protective. Surprisingly, the induction of VEGF by PGC-1alpha does not involve the canonical hypoxia response pathway and hypoxia inducible factor (HIF). Instead, PGC-1alpha coactivates the orphan nuclear receptor ERR-alpha (oestrogen-related receptor-alpha) on conserved binding sites found in the promoter and in a cluster within the first intron of the VEGF gene. Thus, PGC-1alpha and ERR-alpha, major regulators of mitochondrial function in response to exercise and other stimuli, also control a novel angiogenic pathway that delivers needed oxygen and substrates. PGC-1alpha may provide a novel therapeutic target for treating ischaemic diseases.
- Published
- 2008
- Full Text
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44. A structural hypothesis for the transition between bent and extended conformations of the leukocyte beta2 integrins.
- Author
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Shi M, Foo SY, Tan SM, Mitchell EP, Law SK, and Lescar J
- Subjects
- Amino Acid Sequence, Cell Adhesion, Cloning, Molecular, Crystallography, X-Ray methods, Cysteine chemistry, Egtazic Acid chemistry, Humans, Magnesium chemistry, Molecular Conformation, Molecular Sequence Data, Protein Binding, Protein Conformation, Protein Structure, Tertiary, CD18 Antigens chemistry, Leukocytes metabolism, Lymphocyte Function-Associated Antigen-1 chemistry
- Abstract
Integrins mediate cell adhesion in response to activation signals that trigger conformational changes within their ectodomain. It is thought that a compact bent conformation of the molecule represents its physiological low affinity state and extended conformations its active state. We have determined the structure of two integrin fragments of the beta2 subunit. The first structure, consisting of the plexin-semaphorin-integrin domain, hybrid, integrin-epidermal growth factor 1 (I-EGF1), and I-EGF2 domains (PHE2), showed an L-shaped conformation with the bend located between the I-EGF1 and I-EGF2 domains. The second structure, which includes, in addition, the I-EGF3 domain, showed an extended conformation. The major reorientation of I-EGF2 with respect to the other domains in the two structures is accompanied by a change of torsion angle of the disulfide bond between Cys(461)-Cys(492) by 180 degrees and the conversion of a short alpha-helix (residues Ser(468)-Cys(475)) into a flexible coil. Based on the PHE2 structure, we introduced a disulfide bond between the plexin-semaphorin-integrin domain and I-EGF2 domains in the beta2 subunit. The resultant alphaLbeta2 integrin (leukocyte function-associated antigen-1) variant was locked in a bent state and could not be detected with the monoclonal antibody KIM127 in Mg(2+)/EGTA. However, it retained the binding activity to ICAM-1. These results provide a structural hypothesis for our understanding of the transition between the resting and active states of leukocyte function-associated antigen-1.
- Published
- 2007
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45. Mutation of a conserved asparagine in the I-like domain promotes constitutively active integrins alphaLbeta2 and alphaIIbbeta3.
- Author
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Cheng M, Foo SY, Shi ML, Tang RH, Kong LS, Law SKA, and Tan SM
- Subjects
- Amino Acid Sequence, Antigens, CD metabolism, Cell Adhesion, Cell Adhesion Molecules metabolism, Cell Membrane metabolism, Humans, Intercellular Adhesion Molecule-1 metabolism, Molecular Conformation, Molecular Sequence Data, Protein Structure, Tertiary, Sequence Homology, Amino Acid, Signal Transduction, Asparagine chemistry, Lymphocyte Function-Associated Antigen-1 genetics, Mutation, Platelet Glycoprotein GPIIb-IIIa Complex genetics
- Abstract
The leukocyte beta2 integrins are heterodimeric adhesion receptors required for a functional immune system. Many leukocyte adhesion deficiency-1 (LAD-1) mutations disrupt the expression and function of beta2 integrins. Herein, we further characterized the LAD-1 mutation N329S in the beta2 inserted (I)-like domain. This mutation converted alphaLbeta2 from a resting into a high affinity conformer because alphaLbeta2N329S transfectants adhered avidly to ligand intercellular adhesion molecule (ICAM)-3 in the absence of additional activating agent. An extended open conformation is adopted by alphaLbeta2N329S because of its reactivity with the beta2 activation reporter monoclonal antibodies MEM148 and KIM127. A corresponding mutation in beta3 generated constitutively active alphaIIbbeta3 that adhered to fibrinogen. This Asn is conserved in all human beta subunits, and it resides before the last helix of the I-like domain, which is known to be important in activation signal propagation. By mutagenesis studies and review of existing integrin structures, we conjectured that this conserved Asn may have a primary role in shaping the I-like domain by stabilizing the conformation of the alpha7 helix and the beta6-alpha7 loop in the I-like domain.
- Published
- 2007
- Full Text
- View/download PDF
46. Prevalence of heparin/platelet factor 4 antibodies before and after cardiac surgery.
- Author
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Everett BM, Yeh R, Foo SY, Criss D, Van Cott EM, Laposata M, Avery EG, Hoffman WD, Walker J, Torchiana D, and Jang IK
- Subjects
- Aged, Anticoagulants adverse effects, Anticoagulants therapeutic use, Female, Heparin adverse effects, Humans, Incidence, Male, Middle Aged, Postoperative Period, Predictive Value of Tests, Preoperative Care, Prospective Studies, Thrombocytopenia chemically induced, Thromboembolism epidemiology, Thromboembolism prevention & control, Antibodies blood, Anticoagulants immunology, Cardiac Surgical Procedures adverse effects, Heparin immunology, Platelet Factor 4 immunology, Thromboembolism etiology
- Abstract
Background: The clinical significance of heparin/platelet factor 4 (PF4) antibodies in subjects undergoing cardiac surgery has not been systematically studied. We prospectively investigated whether the presence of heparin/PF4 antibodies would predict clinical thrombosis in this population., Methods: In 299 patients scheduled for cardiac surgery between October 2003 and March 2005, the heparin/PF4 antibodies and platelet count were measured immediately prior to, and 5 days after, surgery. The patients were followed up at 30 days for thrombotic complications., Results: The prevalence of the heparin/PF4 antibodies was 4.3% (13 of 299) prior to surgery and increased more than fivefold to 22.4% (62 of 277) postoperatively (p < 0.0001). Thromboembolic events occurred in 8.8% of patients with negative antibody and in 6.3% of patients with positive antibody (p = 0.77). Of the 62 patients with positive heparin/PF4 antibodies postoperatively, 22 (35.5%) were treated with a nonheparin anticoagulant. There was a trend toward higher rates of thromboembolic events in subjects who were thrombocytopenic compared with those who were not (17.1% and 6.7%, respectively, p = 0.06), regardless of antibody status. Two out of 8 patients (25%) with both thrombocytopenia and a positive antibody (clinical heparin-induced thrombocytopenia [HIT]) suffered a thromboembolic event, compared with 17 of 222 (7.7%) without clinical HIT (p = 0.13)., Conclusions: The high prevalence of antibodies to the heparin/PF4 complex after cardiac surgery and the low rate of thromboembolic complications in this population suggest that the antibody alone does not confer an increased risk of thrombotic complications. Monitoring for thrombocytopenia is recommended.
- Published
- 2007
- Full Text
- View/download PDF
47. Prevalence of heparin-induced thrombocytopenia in patients undergoing cardiac catheterization.
- Author
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Foo SY, Everett BM, Yeh RW, Criss D, Laposata M, Van Cott EM, and Jang IK
- Subjects
- Aged, Antibodies analysis, Anticoagulants adverse effects, Coronary Disease diagnosis, Female, Heparin adverse effects, Humans, Male, Middle Aged, Platelet Count, Platelet Factor 4 immunology, Prospective Studies, Thrombocytopenia chemically induced, Cardiac Catheterization, Coronary Disease immunology, Thrombocytopenia epidemiology
- Abstract
Background: Heparin is ubiquitously used in cardiac catheterization but predisposes to the development of heparin-induced thrombocytopenia. The objective was to examine prospectively the prevalence of anti-platelet factor 4 (PF4)/heparin antibodies and heparin-induced thrombocytopenia in the population undergoing cardiac catheterization., Methods: This is a prospective study of 500 consecutive patients presenting for cardiac catheterization at our institution who were enrolled over the course of 1 year. Anti-PF4/heparin antibodies and concurrent platelet counts were measured at catheterization and 5 days thereafter. Thrombotic complications were assessed 30 days after the procedure via telephone interview. All patients presenting for cardiac catheterization at our institution were screened. Inclusion criteria were (a) males and nonpregnant females with age >18 years and (b) patients scheduled to undergo cardiac catheterization. Patients with a known history of heparin-induced thrombocytopenia, with documented bleeding or hypercoagulability, and those at high risk for bleeding were excluded., Results: Of 500 patients, 15 (3%) had anti-PF4/heparin antibodies before catheterization. After catheterization, the prevalence of anti-PF4/heparin antibodies increased to 10.1% (36 of 357) of the patients. Overall rates of thrombotic complications were low (4 of 445, 0.9%) and did not correlate with anti-PF4/heparin antibody status. Patients with an initial positive test for anti-PF4/heparin antibodies were more likely to have prior coronary disease (73.3% vs 45.2%; P < .05). Patients who developed anti-PF4/heparin antibodies after catheterization were more likely to have increased length of stay (3.7 vs 2.4 days; P = .02). The platelet count at the time of catheterization was lower in the cohort of patients who developed the second positive anti-PF4/heparin antibody test versus patients without a second positive antibody test (mean values of 191,800/microL vs 222,300/microL; P = .008)., Conclusions: The prevalence of antibodies to PF4/heparin is low in the population presenting for cardiac catheterization. However, a significant proportion of patients develop antibodies to PF4/heparin after a small exposure to heparin during catheterization. Clinically significant thrombotic complications were rare and did not correlate with antibody status.
- Published
- 2006
- Full Text
- View/download PDF
48. Predictors for the development of elevated anti-heparin/platelet factor 4 antibody titers in patients undergoing cardiac catheterization.
- Author
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Yeh RW, Everett BM, Foo SY, Dorer DJ, Laposata M, Van Cott EM, and Jang IK
- Subjects
- Anticoagulants administration & dosage, Anticoagulants adverse effects, Anticoagulants immunology, Cardiac Catheterization adverse effects, Enzyme-Linked Immunosorbent Assay, Female, Follow-Up Studies, Heparin administration & dosage, Heparin adverse effects, Humans, Male, Middle Aged, Prognosis, Prospective Studies, Risk Factors, Thrombocytopenia chemically induced, Antibodies immunology, Cardiac Catheterization methods, Heparin immunology, Platelet Factor 4 immunology, Thrombocytopenia immunology
- Abstract
A substantial proportion of patients who undergo cardiac catheterization develop antibodies directed against the heparin/platelet factor 4 (PF4) complex after the procedure, which have been implicated in the pathogenesis of heparin-induced thrombocytopenia. This study attempted to identify factors that predicted the development of these antibodies in a prospective cohort study. Antiheparin/PF4 antibody titers were measured at baseline and again 5 +/- 2 days after cardiac catheterization by enzyme-linked immunosorbent assay. A total of 311 patients who underwent cardiac catheterization were included in the analysis. Of these, 25 (8.0%) developed positive antibody levels after catheterization. Patients who had positive antibody test results after catheterization had significantly greater baseline antiheparin/PF4 antibody titers compared with those whose titers remained low (optical density 0.227 vs 0.158, p < 0.001). In a logistic regression model, greater baseline antibody titers, a history of heparin exposure, and a lower platelet count at enrollment were the strongest predictors of conversion to positive antiheparin/PF4 antibody titers after cardiac catheterization. It is possible to identify patients at high risk for developing elevated titers of antiheparin/PF4 antibodies on the basis of their baseline clinical characteristics.
- Published
- 2006
- Full Text
- View/download PDF
49. A lentiviral RNAi library for human and mouse genes applied to an arrayed viral high-content screen.
- Author
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Moffat J, Grueneberg DA, Yang X, Kim SY, Kloepfer AM, Hinkle G, Piqani B, Eisenhaure TM, Luo B, Grenier JK, Carpenter AE, Foo SY, Stewart SA, Stockwell BR, Hacohen N, Hahn WC, Lander ES, Sabatini DM, and Root DE
- Subjects
- Animals, Cell Cycle Proteins genetics, Cell Cycle Proteins physiology, Cells, Cultured, Humans, Libraries, Mice, Microarray Analysis, Gene Library, Genetic Engineering methods, Genetic Vectors, Lentivirus genetics, RNA, Small Interfering genetics
- Abstract
To enable arrayed or pooled loss-of-function screens in a wide range of mammalian cell types, including primary and nondividing cells, we are developing lentiviral short hairpin RNA (shRNA) libraries targeting the human and murine genomes. The libraries currently contain 104,000 vectors, targeting each of 22,000 human and mouse genes with multiple sequence-verified constructs. To test the utility of the library for arrayed screens, we developed a screen based on high-content imaging to identify genes required for mitotic progression in human cancer cells and applied it to an arrayed set of 5,000 unique shRNA-expressing lentiviruses that target 1,028 human genes. The screen identified several known and approximately 100 candidate regulators of mitotic progression and proliferation; the availability of multiple shRNAs targeting the same gene facilitated functional validation of putative hits. This work provides a widely applicable resource for loss-of-function screens, as well as a roadmap for its application to biological discovery.
- Published
- 2006
- Full Text
- View/download PDF
50. Recombinant protein-based enzyme-linked immunosorbent assay and immunochromatographic tests for detection of immunoglobulin G antibodies to severe acute respiratory syndrome (SARS) coronavirus in SARS patients.
- Author
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Guan M, Chen HY, Foo SY, Tan YJ, Goh PY, and Wee SH
- Subjects
- Antibodies, Viral analysis, Antibodies, Viral immunology, Humans, Immunoglobulin G analysis, Immunoglobulin G immunology, Predictive Value of Tests, Recombinant Proteins immunology, Sensitivity and Specificity, Enzyme-Linked Immunosorbent Assay methods, Severe acute respiratory syndrome-related coronavirus immunology, Severe acute respiratory syndrome-related coronavirus isolation & purification, Severe Acute Respiratory Syndrome diagnosis, Severe Acute Respiratory Syndrome immunology
- Abstract
An enzyme-linked immunosorbent assay (ELISA) and a rapid immunochromatographic test for detection of immunoglobulin G (IgG) antibodies in severe acute respiratory syndrome (SARS) patients were developed by utilizing the well-characterized recombinant proteins Gst-N and Gst-U274. The ELISA detected IgG antibodies to SARS-CoV in all 74 convalescent-phase samples from SARS patients while weakly cross-reacting to only 1 of the 210 control sera from healthy donors. This finding thus led to a kit sensitivity, specificity, and accuracy of 100, 99.5, and 99.6%, respectively. The test thus provided a positive predictive value (PPV) of 98.7% and a negative predictive value (NPV) of 100%. In addition, the ELISA gave a positive delta of 5.4 and a negative delta of 3.6, indicating an excellent differentiation between positives and negatives. The same recombinant proteins were also applied to a newly developed platform for the development of a 15-min rapid test. The resulting rapid test has an excellent agreement of 99.6%, with a kappa value of 1.00, with the ELISA. Again, this rapid test was able to detect 100% of the samples tested (n = 42) while maintaining a specificity of 99.0% (n = 210). The PPV and NPV for the rapid test thus reached 95.3 and 100%, respectively.
- Published
- 2004
- Full Text
- View/download PDF
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