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Sökning: WFRF:(Swärd Johan)

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1.
  • Turczynska, Karolina, et al. (författare)
  • Regulation of Smooth Muscle Dystrophin and Synaptopodin 2 Expression by Actin Polymerization and Vascular Injury.
  • 2015
  • Ingår i: Arteriosclerosis, Thrombosis and Vascular Biology. - 1524-4636. ; 35:6, s. 1489-1497
  • Tidskriftsartikel (refereegranskat)abstract
    • Actin dynamics in vascular smooth muscle is known to regulate contractile differentiation and may play a role in the pathogenesis of vascular disease. However, the list of genes regulated by actin polymerization in smooth muscle remains incomprehensive. Thus, the objective of this study was to identify actin-regulated genes in smooth muscle and to demonstrate the role of these genes in the regulation of vascular smooth muscle phenotype.
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2.
  • Brynolfsson, Johan, et al. (författare)
  • Least Squares and Maximum Likelihood Estimation of Mixed Spectra
  • 2018
  • Ingår i: 26th European Signal Processing Conference, EUSIPCO 2018.. - 9789082797015 ; , s. 2345-2349
  • Konferensbidrag (refereegranskat)abstract
    • In this paper, we propose a novel 1-D spectralestimator for signals with mixed spectra. The proposed methodis partly based on the recently introduced smooth spectralestimator LIMES, in which the smoothness is accounted for byassuming linearity within predefined segments of the spectrum.The proposed method utilizes this formulation but also allowssegments to change size to better estimate the spectrum, therebyallowing for the estimation of spectra that are neither completelysmooth or sparse in frequency, but rather contains a mixtureof such components. Using simulated data, we illustrate theperformance of the proposed estimator, comparing to other recentspectral estimation techniques.
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3.
  • Brynolfsson, Johan, et al. (författare)
  • Smooth Time-Frequency Estimation using Covariance Fitting
  • 2014
  • Ingår i: Acoustics, Speech and Signal Processing (ICASSP), 2014 IEEE International Conference on. - 1520-6149. ; , s. 779-783
  • Konferensbidrag (refereegranskat)abstract
    • In this paper, we introduce a time-frequency spectral estimator for smooth spectra, allowing for irregularly sampled measurements. A non-parametric representation of the time dependent (TD) covariance matrix is formed by assuming that the spectrum is piecewise linear. Using this representation, the time-frequency spectrum is then estimated by solving a convex covariance fitting problem, which also, as a byproduct, provides an enhanced estimation of the TD covariance matrix. Numerical examples using simulated non-stationary processes show the preferable performance of the proposed method as compared to the classical Wigner-Ville distribution and a smoothed spectrogram.
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4.
  • Hien Tran, Thi, et al. (författare)
  • Elevated glucose levels promote contractile and cytoskeletal gene expression in vascular smooth muscle via Rho/protein kinase C and actin polymerization.
  • 2016
  • Ingår i: Journal of Biological Chemistry. - 1083-351X. ; 291:7, s. 68-3552
  • Tidskriftsartikel (refereegranskat)abstract
    • Both type 1 and type 2 diabetes are associated with increased risk of cardiovascular disease. This is in part attributed to the effects of hyperglycemia on vascular endothelial and smooth muscle cells but the underlying mechanisms are not fully understood. In diabetic animal models, hyperglycemia results in hyper-contractility of vascular smooth muscle possibly due to increased activation of Rho-kinase. The aim of the present study was to investigate the regulation of contractile smooth muscle markers by glucose and to determine the signaling pathways that are activated by hyperglycemia in smooth muscle cells. Microarray, qPCR and western blot analyses revealed that both mRNA and protein expression of contractile smooth muscle markers was increased in isolated smooth muscle cells cultured under high compared to low glucose conditions. This effect was also observed in hyperglycemic Akita mice and in diabetic patients. Elevated glucose activated the protein kinase C and Rho/Rho-kinase signaling pathways and stimulated actin polymerization. Glucose-induced expression of contractile smooth muscle markers in cultured cells could be partially or completely repressed by inhibitors of advanced glycation end products, L-type calcium channels, protein kinase C, Rho-kinase, actin polymerization and myocardin related transcription factors. Furthermore, genetic ablation of the miR-143/145 cluster prevented the effects of glucose on smooth muscle marker expression. In conclusion, these data demonstrate a possible link between hyperglycemia and vascular disease states associated with smooth muscle contractility.
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5.
  • Swärd, Johan, et al. (författare)
  • Smooth 2-D frequency estimation using covariance fitting
  • 2014
  • Ingår i: European Signal Processing Conference. - 2219-5491.
  • Konferensbidrag (refereegranskat)abstract
    • In this paper, we introduce a non-parametric 2-D spectral estimator for smooth spectra, allowing for irregularly sampled measurements. The estimate is formed by assuming that the spectrum is smooth and will vary slowly over the frequency grids, such that the spectral density inside any given rectangle in the spectral grid may be approximated well as a plane. Using this framework, the 2-D spectrum is estimated by finding the solution to a convex covariance fitting problem, which has an analytic solution. %solved using the generalized alternating direction method of multipliers. Numerical simulations indicate the achievable performance gain as compared to the Blackman-Tukey estimator.
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6.
  • Swärd, Johan, et al. (författare)
  • Sparse Semi-Parametric Chirp Estimator
  • 2015
  • Ingår i: Signals, Systems and Computers, 2014 48th Asilomar Conference on. - 9781479982950 ; , s. 1236-1240
  • Konferensbidrag (refereegranskat)abstract
    • In this work, we present a method for estimating the parameters detailing an unknown number of linear chirp signals, using an iterative sparse reconstruction framework. The proposed method is initiated by a re-weighted Lasso approach, and then use an iterative relaxation-based refining step to allow for high resolution estimates. The resulting estimates are found to be statistically efficient, achieving the Cramér-Rao lower bound. Numerical simulations illustrate the achievable performance, offering a notable improvement as compared to other recent approaches.
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7.
  • Swärd, Johan, et al. (författare)
  • Sparse Semi-Parametric Estimation of Harmonic Chirp Signals
  • 2016
  • Ingår i: IEEE Transactions on Signal Processing. - 1053-587X. ; 64:7, s. 1798-1807
  • Tidskriftsartikel (refereegranskat)abstract
    • In this work, we present a method for estimating the parameters detailing an unknown number of linear, possibly harmonically related, chirp signals, using an iterative sparse reconstruction framework. The proposed method is initiated by a re-weighted group-sparsity approach, followed by an iterative relaxation-based refining step, to allow for high resolution estimates. Numerical simulations illustrate the achievable performance, offering a notable improvement as compared to other recent approaches. The resulting estimates are found to be statistically efficient, achieving the corresponding Cram´er-Rao lower bound.
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8.
  • Adalbjörnsson, Stefan, et al. (författare)
  • Conjugate priors for Gaussian emission plsa recommender systems
  • 2016
  • Ingår i: 2016 24th European Signal Processing Conference, EUSIPCO 2016. - 9780992862657 ; 2016-November, s. 2096-2100
  • Konferensbidrag (refereegranskat)abstract
    • Collaborative filtering for recommender systems seeks to learn and predict user preferences for a collection of items by identifying similarities between users on the basis of their past interest or interaction with the items in question. In this work, we present a conjugate prior regularized extension of Hofmann's Gaussian emission probabilistic latent semantic analysis model, able to overcome the over-fitting problem restricting the performance of the earlier formulation. Furthermore, in experiments using the EachMovie and MovieLens data sets, it is shown that the proposed regularized model achieves significantly improved prediction accuracy of user preferences as compared to the latent semantic analysis model without priors.
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9.
  • Adalbjörnsson, Stefan Ingi, et al. (författare)
  • A Sparse Approach for Estimation of Amplitude Modulated Sinusoids
  • 2014
  • Konferensbidrag (refereegranskat)abstract
    • We consider the problem of spectral analysis of signals composed of sums of multiple amplitude modulated, possibly harmonically related, sinusoids using a sparse approach. By separating the nonlinear frequency variables using a dictionary of possible frequency components as well as a spline basis for the amplitude modulation, results in a convex criterion which can be efficiently solved without worrisome local minima. The resulting method makes no model order assumption and automatically estimates both the signal parameters and their amplitude modulations
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10.
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11.
  • Adalbjörnsson, Stefan Ingi, et al. (författare)
  • Estimating Periodicities in Symbolic Sequences Using Sparse Modeling
  • 2015
  • Ingår i: IEEE Transactions on Signal Processing. - 1053-587X. ; 63:8, s. 2142-2150
  • Tidskriftsartikel (refereegranskat)abstract
    • In this paper, we propose a method for estimating statistical periodicities in symbolic sequences. Different from other common approaches used for the estimation of periodicities of sequences of arbitrary, finite, symbol sets, that often map the symbolic sequence to a numerical representation, we here exploit a likelihood-based formulation in a sparse modeling framework to represent the periodic behavior of the sequence. The resulting criterion includes a restriction on the cardinality of the solution; two approximate solutions are suggested—one greedy and one using an iterative convex relaxation strategy to ease the cardinality restriction. The performance of the proposed methods are illustrated using both simulated and real DNA data, showing a notable performance gain as compared to other common estimators.
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12.
  • Adalbjörnsson, Stefan Ingi, et al. (författare)
  • High resolution sparse estimation of exponentially decaying two-dimensional signals
  • 2014
  • Ingår i: European Signal Processing Conference. - 2219-5491.
  • Konferensbidrag (refereegranskat)abstract
    • In this work, we consider the problem of high-resolution estimation of the parameters detailing a two-dimensional (2-D) signal consisting of an unknown number of exponentially decaying sinusoidal components. Interpreting the estimation problem as a block (or group) sparse representation problem allows the decoupling of the 2-D data structure into a sum of outer-products of 1-D damped sinusoidal signals with unknown damping and frequency. The resulting non-zero blocks will represent each of the 1-D damped sinusoids, which may then be used as non-parametric estimates of the corresponding 1-D signals; this implies that the sought 2-D modes may be estimated using a sequence of 1-D optimization problems. The resulting sparse representation problem is solved using an iterative ADMM-based algorithm, after which the damping and frequency parameter can be estimated by a sequence of simple 1-D optimization problems.
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13.
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14.
  • Ahmad Tajudin, Asilah, et al. (författare)
  • Integrated acoustic immunoaffinity-capture (IAI) platform for detection of PSA from whole blood samples.
  • 2013
  • Ingår i: Lab on a Chip. - : Royal Society of Chemistry (RSC). - 1473-0189 .- 1473-0197. ; 13:9, s. 1790-1796
  • Tidskriftsartikel (refereegranskat)abstract
    • On-chip detection of low abundant protein biomarkers is of interest to enable point-of-care diagnostics. Using a simple form of integration, we have realized an integrated microfluidic platform for the detection of prostate specific antigen (PSA), directly in anti-coagulated whole blood. We combine acoustophoresis-based separation of plasma from undiluted whole blood with a miniaturized immunoassay system in a polymer manifold, demonstrating improved assay speed on our Integrated Acoustic Immunoaffinity-capture (IAI) platform. The IAI platform separates plasma from undiluted whole blood by means of acoustophoresis and provides cell free plasma of clinical quality at a rate of 10 uL/min for an online immunoaffinity-capture of PSA on a porous silicon antibody microarray. The whole blood input (hematocrit 38-40%) rate was 50 μl min(-1) giving a plasma volume fraction yield of ≈33%. PSA was immunoaffinity-captured directly from spiked female whole blood samples at clinically significant levels of 1.7-100 ng ml(-1) within 15 min and was subsequently detected via fluorescence readout, showing a linear response over the entire range with a coefficient of variation of 13%.
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15.
  • Alajbegovic, Azra, et al. (författare)
  • MRTFA overexpression promotes conversion of human coronary artery smooth muscle cells into lipid-laden foam cells
  • 2021
  • Ingår i: Vascular Pharmacology. - : Elsevier BV. - 1537-1891. ; 138
  • Tidskriftsartikel (refereegranskat)abstract
    • Objective: Smooth muscle cells contribute significantly to lipid-laden foam cells in atherosclerotic plaques. However, the underlying mechanisms transforming smooth muscle cells into foam cells are poorly understood. The purpose of this study was to gain insight into the molecular mechanisms regulating smooth muscle foam cell formation. Approach and results: Using human coronary artery smooth muscle cells we found that the transcriptional co-activator MRTFA promotes lipid accumulation via several mechanisms, including direct transcriptional control of LDL receptor, enhanced fluid-phase pinocytosis and reduced lipid efflux. Inhibition of MRTF activity with CCG1423 and CCG203971 significantly reduced lipid accumulation. Furthermore, we demonstrate enhanced MRTFA expression in vascular remodeling of human vessels. Conclusions: This study demonstrates a novel role for MRTFA as an important regulator of lipid homeostasis in vascular smooth muscle cells. Thus, MRTFA could potentially be a new therapeutic target for inhibition of vascular lipid accumulation.
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16.
  • Atterström, Andrea, et al. (författare)
  • Experiences about Reading and Writing Development Narrated by Students with Severe Speech and Physical Impairment
  • 2023
  • Ingår i: International journal of disability, development and education. - : Taylor & Francis Group. - 1034-912X .- 1465-346X. ; 70:6, s. 1101-1119
  • Tidskriftsartikel (refereegranskat)abstract
    • Earlier research shows an arrest in reading and writing development among 9-12-year-old students with severe speech and physical impairment, SSPI. This article explores what five students with SSPI who have reached beyond beginner's phase without arrest in their literacy development have experienced as significant for their reading and writing development. The research design was explorative and case based. It contained researcher-participant longitudinal dialogues focusing on the students' experiences of literacy learning. Computer assisted email interviews were used. A semi-structured interview manual guided each dialogue. With the use of augmentative and alternative communication (AAC) systems and assistive technology devices, the participants could read and write (with alphabetical print in Swedish) independently. The analysis revealed four themes of great importance for the students' development of alphabetical print literacy skills: assistive technology use in writing and reading, continuity in long-term pedagogical relationships, mutual persistence in communication, and visions of nearer goals and future work life. The results are discussed in relation to the theoretical frameworks of self-efficacy and the capability approach.
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17.
  • Butsenko, Maksim, et al. (författare)
  • The Zoomed Iterative Adaptive Approach
  • 2018
  • Ingår i: 2018 International Symposium on Intelligent Signal Processing and Communication Systems.
  • Konferensbidrag (refereegranskat)
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18.
  • Cang, Siyuan, et al. (författare)
  • Toeplitz-based blind deconvolution of underwater acoustic channels using wideband integrated dictionaries
  • 2021
  • Ingår i: Signal Processing. - : Elsevier BV. - 0165-1684. ; 179
  • Tidskriftsartikel (refereegranskat)abstract
    • In this paper, we propose a blind channel deconvolution method based on a sparse reconstruction framework exploiting a wideband dictionary under the (relatively weak) assumption that the transmitted signal may be assumed to be well modelled as a sum of sinusoids. Using a Toeplitz structured formulation of the received signal, we form an iterative blind deconvolution scheme, alternatively estimating the underwater impulse response and the transmitted waveform. The resulting optimization problems are convex, and we formulate a computationally efficient solver using the Alternating Direction Method of Multipliers (ADMM). We illustrate the performance of the resulting estimator using both simulated and measured underwater signals.
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19.
  • Carlström, Göran, et al. (författare)
  • Rapid NMR Relaxation Rate Measurements Using Optimal Non-Uniform Sampling of Multi-Dimensional Accordion Data Analyzed by a Sparse Reconstruction Method
  • 2019
  • Ingår i: The Journal of Physical Chemistry Part A: Molecules, Spectroscopy, Kinetics, Environment and General Theory. - : American Chemical Society (ACS). - 1089-5639. ; 123:27, s. 5718-5723
  • Tidskriftsartikel (refereegranskat)abstract
    • Nonuniform sampling (NUS) of multidimensional NMR data offers significant time savings while improving spectral resolution or increasing sensitivity per unit time. However, NUS has not been widely used for quantitative analysis because of the nonlinearity of most methods used to model NUS data, which leads to problems in estimating signal intensities, relaxation rate constants, and their error bounds. Here, we present an approach that avoids these limitations by combining accordion spectroscopy and NUS in the indirect dimensions of multidimensional spectra and then applying sparse exponential mode analysis, which is well suited for analyzing accordion-type relaxation data in a NUS context. By evaluating the Cramér-Rao lower bound of the variances of the estimated relaxation rate constants, we achieve a robust benchmark for the underlying reconstruction model. Furthermore, we design NUS schemes optimized with respect to the information theoretical lower bound of the error in the parameters of interest, given a specified number of sampling points. The accordion-NUS method compares favorably with conventional relaxation experiments in that it produces identical results, within error, while shortening the length of the experiment by an order of magnitude. Thus, our approach enables rapid acquisition of NMR relaxation data for optimized use of spectrometer time or accurate measurements on samples of limited lifetime.
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20.
  • Daoud, Fatima, et al. (författare)
  • Inducible Deletion of YAP and TAZ in Adult Mouse Smooth Muscle Causes Rapid and Lethal Colonic Pseudo-Obstruction
  • 2021
  • Ingår i: Cellular and Molecular Gastroenterology and Hepatology. - : Elsevier BV. - 2352-345X. ; 11:2, s. 623-637
  • Tidskriftsartikel (refereegranskat)abstract
    • Background & AimsYAP (Yap1) and TAZ (Wwtr1) are transcriptional co-activators and downstream effectors of the Hippo pathway, which play crucial roles in organ size control and cancer pathogenesis. Genetic deletion of YAP/TAZ has shown their critical importance for embryonic development of the heart, vasculature, and gastrointestinal mesenchyme. The aim of this study was to determine the functional role of YAP/TAZ in adult smooth muscle cells in vivo.MethodsBecause YAP and TAZ are mutually redundant, we used YAP/TAZ double-floxed mice crossed with mice that express tamoxifen-inducible CreERT2 recombinase driven by the smooth muscle–specific myosin heavy chain promoter.ResultsDouble-knockout of YAP/TAZ in adult smooth muscle causes lethality within 2 weeks, mainly owing to colonic pseudo-obstruction, characterized by severe distension and fecal impaction. RNA sequencing in colon and urinary bladder showed that smooth muscle markers and muscarinic receptors were down-regulated in the YAP/TAZ knockout. The same transcripts also correlated with YAP/TAZ in the human colon. Myograph experiments showed reduced contractility to depolarization by potassium chloride and a nearly abolished muscarinic contraction and spontaneous activity in colon rings of YAP/TAZ knockout.ConclusionsYAP and TAZ in smooth muscle are guardians of colonic contractility and control expression of contractile proteins and muscarinic receptors. The knockout model has features of human chronic intestinal pseudo-obstruction and may be useful for studying this disease.
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21.
  • Daoud, Fatima, et al. (författare)
  • Role of smooth muscle YAP and TAZ in protection against phenotypic modulation, inflammation, and aneurysm development
  • 2022
  • Ingår i: Biochemical Pharmacology. - : Elsevier BV. - 0006-2952. ; 206
  • Forskningsöversikt (refereegranskat)abstract
    • A ruptured arterial aneurysm, especially in the aorta, represents one of the most acute and mortal conditions encountered in clinical medicine. Population-based screening in elderly men, treatment of risk factors, such as hypertension, and endovascular or open repair of rupture-prone lesions, represent cornerstones in management. Surgical repair has a sizeable effect on life-expectancy, but medical therapy that retards aneurysm growth still represents a considerable and unmet clinical need. In the current review we survey recent findings implicating the mechano-responsive transcriptional co-activators YAP and TAZ in protection from aneurysm development. Arteries from mouse mutants that lack YAP and TAZ in vascular smooth muscle respond inadequately to mechanical stimulation, and they develop aneurysms characterized by elastin fragmentation, proteoglycan infiltration, and severe inflammation at breathtaking speed. This seems to be due, at least in part, to unscheduled activation of STING (stimulator of interferon genes), an arm of innate immunity that responds to double-stranded DNA in the cytoplasm. YAP and TAZ protect from STING activation by securing nuclear integrity. These novel insights suggest unanticipated medical therapies for sporadic and genetic aneurysms alike, involving inhibition of kinases in the Hippo pathway using small molecules, or inhibition of STING signaling itself. Translation of these novel findings into clinical therapies now represents an important priority.
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22.
  • Daoud, Fatima, et al. (författare)
  • YAP and TAZ in Vascular Smooth Muscle Confer Protection Against Hypertensive Vasculopathy
  • 2022
  • Ingår i: Arteriosclerosis, Thrombosis, and Vascular Biology. - 1079-5642. ; 42:4, s. 428-443
  • Tidskriftsartikel (refereegranskat)abstract
    • Background: Hypertension remains a major risk factor for cardiovascular diseases, but the underlying mechanisms are not well understood. We hypothesize that appropriate mechanotransduction and contractile function in vascular smooth muscle cells are crucial to maintain vascular wall integrity. The Hippo pathway effectors YAP (yes-associated protein 1) and TAZ (WW domain containing transcription regulator 1) have been identified as mechanosensitive transcriptional coactivators. However, their role in vascular smooth muscle cell mechanotransduction has not been investigated in vivo. Methods: We performed physiological and molecular analyses utilizing an inducible smooth muscle-specific YAP/TAZ knockout mouse model. Results: Arteries lacking YAP/TAZ have reduced agonist-mediated contraction, decreased myogenic response, and attenuated stretch-induced transcriptional regulation of smooth muscle markers. Moreover, in established hypertension, YAP/TAZ knockout results in severe vascular lesions in small mesenteric arteries characterized by neointimal hyperplasia, elastin degradation, and adventitial thickening. Conclusions: This study demonstrates a protective role of YAP/TAZ against hypertensive vasculopathy.
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23.
  • Elvander, Filip, et al. (författare)
  • Grid-less estimation of saturated signals
  • 2017
  • Ingår i: 2017 51st Asilomar Conference on Signals, Systems, and Computers. - 9781538618233 ; , s. 372-376
  • Konferensbidrag (refereegranskat)abstract
    • This work proposes a frequency and amplitude estimator tailored for noise corrupted signals that have been clipped. Formulated as a sparse reconstruction problem, the proposed algorithm estimates the signal parameters by solving an atomic norm minimization problem. The estimator also exploits the waveform information provided by the clipped samples, incorporated in the form of linear constraints that have been augmented by slack variables as to provide robustness to noise. Numerical examples indicate that the algorithm offers preferable performance as compared to methods not exploiting the saturated samples.
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24.
  • Elvander, Filip, et al. (författare)
  • Multi-dimensional grid-less estimation of saturated signals
  • 2018
  • Ingår i: Signal Processing. - : Elsevier BV. - 0165-1684. ; 145, s. 37-47
  • Tidskriftsartikel (refereegranskat)abstract
    • This work proposes a multi-dimensional frequency and amplitude estimator tailored for noise corrupted signals that have been clipped. Formulated as a sparse reconstruction problem, the proposed algorithm estimates the signal parameters by solving an atomic norm minimization problem. The estimator also exploits the waveform information provided by the clipped samples, incorporated in the form of linear constraints that have been augmented by slack variables as to provide robustness to noise. Numerical examples indicate that the algorithm offers preferable performance as compared to methods not exploiting the saturated samples.
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25.
  • Elvander, Filip, et al. (författare)
  • Online Estimation of Multiple Harmonic Signals
  • 2017
  • Ingår i: IEEE/ACM Transactions on Audio, Speech, and Language Processing. - 2329-9290. ; 25:2, s. 273-284
  • Tidskriftsartikel (refereegranskat)abstract
    • In this paper, we propose a time-recursive multipitch estimation algorithm using a sparse reconstruction framework, assuming that only a few pitches from a large set of candidates are active at each time instant. The proposed algorithm does not require any training data, and instead utilizes a sparse recursive least-squares formulation augmented by an adaptive penalty term specifically designed to enforce a pitch structure on the solution. The amplitudes of the active pitches are also recursively updated, allowing for a smooth and more accurate representation. When evaluated on a set of ten music pieces, the proposed method is shown to outperform other general purpose multipitch estimators in either accuracy or computational speed, although not being able to yield performance as good as the state-of-the art methods, which are being optimally tuned and specifically trained on the present instruments. However, the method is able to outperform such a technique when used without optimal tuning, or when applied to instruments not included in the training data.
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26.
  • Elvander, Filip, et al. (författare)
  • Time Recursive Multi-Pitch Estimation Using Group Sparse Recursive Least Squares
  • 2017
  • Ingår i: 50th Asilomar Conference on Signals, Systems, and Computers, 2016. - 9781538639542 ; , s. 369-373
  • Konferensbidrag (refereegranskat)abstract
    • In this work, we propose a time-recursive multi-pitch estimation algorithm, using a sparse reconstruction framework, assuming only a few pitches from a large set of candidates to be active at each time instant. The proposed algorithm utilizes a sparse recursive least squares formulation augmented by an adaptive penalty term specifically designed to enforce a pitch structure on the solution. When evaluated on a set of ten music pieces, the proposed method is shown to outperform state-of-the-art multi-pitch estimators in either accuracy or computational spe
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27.
  • Gustafsson, Christian Jamtheim, et al. (författare)
  • Development and evaluation of a deep learning based artificial intelligence for automatic identification of gold fiducial markers in an MRI-only prostate radiotherapy workflow
  • 2020
  • Ingår i: Physics in Medicine and Biology. - : IOP Publishing. - 1361-6560 .- 0031-9155. ; 65:22
  • Tidskriftsartikel (refereegranskat)abstract
    • Identification of prostate gold fiducial markers in magnetic resonance imaging (MRI) images is challenging when CT images are not available, due to misclassifications from intra-prostatic calcifications. It is also a time consuming task and automated identification methods have been suggested as an improvement for both objectives. Multi-echo gradient echo (MEGRE) images have been utilized for manual fiducial identification with 100% detection accuracy. The aim is therefore to develop an automatic deep learning based method for fiducial identification in MRI images intended for MRI-only prostate radiotherapy. MEGRE images from 326 prostate cancer patients with fiducials were acquired on a 3T MRI, post-processed with N4 bias correction, and the fiducial center of mass (CoM) was identified. A 9 mm radius sphere was created around the CoM as ground truth. A deep learning HighRes3DNet model for semantic segmentation was trained using image augmentation. The model was applied to 39 MRI-only patients and 3D probability maps for fiducial location and segmentation were produced and spatially smoothed. In each of the three largest probability peaks, a 9 mm radius sphere was defined. Detection sensitivity and geometric accuracy was assessed. To raise awareness of potential false findings a 'BeAware' score was developed, calculated from the total number and quality of the probability peaks. All datasets, annotations and source code used were made publicly available. The detection sensitivity for all fiducials were 97.4%. Thirty-six out of thirty-nine patients had all fiducial markers correctly identified. All three failed patients generated a user notification using the BeAware score. The mean absolute difference between the detected fiducial and ground truth CoM was 0.7 ± 0.9 [0 3.1] mm. A deep learning method for automatic fiducial identification in MRI images was developed and evaluated with state-of-the-art results. The BeAware score has the potential to notify the user regarding patients where the proposed method is uncertain.
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28.
  • Halder, Amitava, et al. (författare)
  • Muscle electrical activity changes over time during stair ascending until exhaustion
  • 2018
  • Ingår i: 22nd Congress of the International Society of Electrophysiology and Kinesiology (ISEK).
  • Konferensbidrag (refereegranskat)abstract
    • BACKGROUND AND AIM Non-stop stair ascending at maximum speed is required to reach a safe refuge level from deep underground structures, such as subways and in high-rise buildings in an emergency evacuation situation. Endurance of stair climbing and identifying the time of the onset of leg’s local muscle fatigue (LMF) are interests in evacuation research. The objective of this laboratory study was to investigate leg muscles’ electrical activity changes in electromyography (EMG) over time during stair ascending until exhaustion on a stair machine. METHODS The developed muscle activity rate change (MARC) in muscle activity interpretation square (MAIS) was used to evaluate leg LMF at constant step rates equivalent to individual 100% VO2max level. This result is used to validate the MAIS. The MAIS is based on the four assumptions of EMG muscle activity (AMP and MDF) rate change (MARC) over the ascending durations. An increase in AMP and MDF is an indication of: 1) muscle force increase. An increase in AMP and a decrease in MDF is an indication of: 2) muscle fatigue. A decrease in AMP and MDF is an indication of: 3) muscle force decrease. A decrease in AMP and an increase in MDF is an indication of: 4) fatigue recovery. MARC was observed on the both AMP and MDF values of the ten equal length divisions (10%) in the total ascending period (100%). The averages of the MDF and normalized AMP for each equally divided 10% period were calculated for all subjects to yield 1 data point, and totally 10 data points. These 10 periodical average AMP and MDF data points (10-100%) and the changes between the unit times represent the MARC for each muscle during ascension. Later, both the AMP and MDF MARC values are combined to get one final point for each tenth percentile duration and presented into the MAIS, which is used to estimate muscle fatigue.MARC values are derived by the following equation:∆MARC = (x_n-x_(n-1))/(t ̅⁄10) where, ΔMARC is change in a selected parameter (AMP and MDF) over normalized time;x_n is the selected parameter (AMP and MDF) value at each normalized time point n;x_(n-1) is the selected parameter value at a normalized time point n-1;t ̅ is the average duration in seconds for the stair ascending;10 is the total number of normalized times.RESULTS The appearances of MARC points in the MAISs showed the state of muscle activity changes over time during this predetermined and constant ascending speed at 100% of VO2max on a stair machine. Most of the muscles’ MARC points at 90-100% periods were found in the muscle fatigue squares. Moreover, individual AMP and MDF analysis showed significantly increased and decreased, respectively, which supported the interpretations made by the MAIS.CONCLUSIONS These stair ascending EMG results supported the MARC and MAIS when interpreting muscle fatigue. They seem promising to interpret muscle activity changes per unit time during dynamic tasks over the whole working duration in different activities.
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29.
  • Jamtheim Gustafsson, Christian, et al. (författare)
  • Deep learning-based classification and structure name standardization for organ at risk and target delineations in prostate cancer radiotherapy
  • 2021
  • Ingår i: Journal of Applied Clinical Medical Physics. - : John Wiley & Sons. - 1526-9914. ; 22:12, s. 51-63
  • Tidskriftsartikel (refereegranskat)abstract
    • Radiotherapy (RT) datasets can suffer from variations in annotation of organ at risk (OAR) and target structures. Annotation standards exist, but their description for prostate targets is limited. This restricts the use of such data for supervised machine learning purposes as it requires properly annotated data. The aim of this work was to develop a modality independent deep learning (DL) model for automatic classification and annotation of prostate RT DICOM structures.Delineated prostate organs at risk (OAR), support- and target structures (gross tumor volume [GTV]/clinical target volume [CTV]/planning target volume [PTV]), along with or without separate vesicles and/or lymph nodes, were extracted as binary masks from 1854 patients. An image modality independent 2D InceptionResNetV2 classification network was trained with varying amounts of training data using four image input channels. Channel 1–3 consisted of orthogonal 2D projections from each individual binary structure. The fourth channel contained a summation of the other available binary structure masks. Structure classification performance was assessed in independent CT (n = 200 pat) and magnetic resonance imaging (MRI) (n = 40 pat) test datasets and an external CT (n = 99 pat) dataset from another clinic.A weighted classification accuracy of 99.4% was achieved during training. The unweighted classification accuracy and the weighted average F1 score among different structures in the CT test dataset were 98.8% and 98.4% and 98.6% and 98.5% for the MRI test dataset, respectively. The external CT dataset yielded the corresponding results 98.4% and 98.7% when analyzed for trained structures only, and results from the full dataset yielded 79.6% and 75.2%. Most misclassifications in the external CT dataset occurred due to multiple CTVs and PTVs being fused together, which was not included in the training data.Our proposed DL-based method for automated renaming and standardization of prostate radiotherapy annotations shows great potential. Clinic specific contouring standards however need to be represented in the training data for successful use. Source code is available at https://github.com/jamtheim/DicomRTStructRenamerPublic
  •  
30.
  • Juhlin, Maria, et al. (författare)
  • Estimating faults modes in ball bearing machinery using a sparse reconstruction framework
  • 2018
  • Ingår i: 2018 26th European Signal Processing Conference, EUSIPCO 2018. - 9789082797015 ; 2018-September, s. 2330-2334
  • Konferensbidrag (refereegranskat)abstract
    • In this work, we present a computationally efficient algorithm for estimating fault modes in ball bearing systems. The presented method generalizes and improves upon earlier developed sparse reconstruction techniques, allowing for detecting multiple fault modes. The measured signal is corrupted with additive and multiplicative noise, yielding a signal that is highly erratic. Fortunately, the damaged ball bearings give rise to strong periodical structures which may be exploited when forming the proposed detector. Numerical simulations illustrate the preferred performance of the proposed method.
  •  
31.
  • Juhlin, Maria, et al. (författare)
  • Fast Gridless Estimation of Damped Modes
  • 2018
  • Ingår i: 2018 International Symposium on Intelligent Signal Processing and Communication Systems.
  • Konferensbidrag (refereegranskat)
  •  
32.
  • Juhlin, Maria, et al. (författare)
  • Sparse Chroma Estimation for Harmonic Non-Stationary Audio
  • 2015
  • Ingår i: Signal Processing Conference (EUSIPCO), 2015 23rd European. ; , s. 26-30
  • Konferensbidrag (refereegranskat)abstract
    • In this work, we extend on our recently proposed block sparse chroma estimator, such that the method also allows for signals with time-varying envelopes. Using a spline-based amplitude modulation of the chroma dictionary, the refined estimator is able to model longer frames than our earlier approach, as well as to model highly time-localized signals, and signals containing sudden bursts, such as trumpet or trombone signals, thus retaining more signal information than other methods for chroma estimation. The performance of the proposed estimator is evaluated on a recorded trumpet signal, clearly illustrating the improved performance, as compared to other used techniques.
  •  
33.
  • Jälmby, Martin, et al. (författare)
  • Computationally Efficient Estimation of Multi-dimensional Damped Modes using Sparse Wideband Dictionaries
  • 2018
  • Ingår i: 26th European Signal Processing Conference, EUSIPCO 2018. - 9789082797015 ; , s. 1759-1763
  • Konferensbidrag (refereegranskat)abstract
    • Estimating the parameters of non-uniformly sampled multi-dimensional damped modes is computationally cumbersome, especially if the model order of the signal is not assumed to be known a priori. In this work, we examine the possibility of using the recently introduced wideband dictionary framework to formulate a computationally efficient estimator that iteratively refines the estimates of the candidate frequency and damping coefficients for each component. The proposed wideband dictionary allows for the use of a coarse initial grid without increasing the risk of not identifying closely spaced components, resulting in a substantial reduction in computational complexity. The performance of the proposed method is illustrated using both simulated and real spectroscopy data, clearly showing the improved performance as compared to previous techniques.
  •  
34.
  • Kijowski, R, et al. (författare)
  • Imaging following acute knee trauma.
  • 2014
  • Ingår i: Osteoarthritis and Cartilage. - : Elsevier BV. - 1063-4584. ; 22:10, s. 1429-1443
  • Forskningsöversikt (refereegranskat)abstract
    • Joint injury has been recognized as a potent risk factor for the onset of osteoarthritis. The vast majority of studies using imaging technology for longitudinal assessment of patients following joint injury have focused on the injured knee joint, specifically in patients with anterior cruciate ligament injury and meniscus tears where a high risk for rapid onset of post-traumatic osteoarthritis is well known. Although there are many imaging modalities under constant development, magnetic resonance (MR) imaging is the most important instrument for longitudinal monitoring after joint injury. MR imaging is sensitive for detecting early cartilage degeneration and can evaluate other joint structures including the menisci, bone marrow, tendons, and ligaments which can be sources of pain following acute injury. In this review, focusing on imaging following acute knee trauma, several studies were identified with promising short-term results of osseous and soft tissue changes after joint injury. However, studies connecting these promising short-term results to the development of osteoarthritis were limited which is likely due to the long follow-up periods needed to document the radiographic and clinical onset of the disease. Thus, it is recommended that additional high quality longitudinal studies with extended follow-up periods be performed to further investigate the long-term consequences of the early osseous and soft tissue changes identified on MR imaging after acute knee trauma.
  •  
35.
  • Klasson, Marcus, et al. (författare)
  • Conjugate-prior-regularized multinomial pLSA for collaborative filtering
  • 2017
  • Ingår i: 25th European Signal Processing Conference, EUSIPCO 2017. - 9780992862671 ; 2017-January, s. 2501-2505
  • Konferensbidrag (refereegranskat)abstract
    • We consider the over-fitting problem for multinomial probabilistic Latent Semantic Analysis (pLSA) in collaborative filtering, using a regularization approach. For big data applications, the computational complexity is at a premium and we, therefore, consider a maximum a posteriori approach based on conjugate priors that ensure that complexity of each step remains the same as compared to the un-regularized method. In the numerical section, we show that the proposed regularization method and training scheme yields an improvement on commonly used data sets, as compared to previously proposed heuristics.
  •  
36.
  • Kronvall, Ted, et al. (författare)
  • Non-Parametric Data-Dependent Estimation of Specroscopic Echo-Train Signals
  • 2013
  • Ingår i: Acoustics, Speech and Signal Processing (ICASSP), 2013 IEEE International Conference on. - 1520-6149. ; , s. 6259-6263
  • Konferensbidrag (refereegranskat)abstract
    • This paper proposes a novel non-parametric estimator for spectroscopic echo-train signals, termed ETCAPA, to be used as a robust and reliable first-approach-technique for new, unknown, or partly disturbed substances. Exploiting the complete echo structure for the signal of interest, the method reliably estimates all parameters of interest, enabling initial estimates for the identification procedure to follow. Extending the recent dCapon and dAPES algorithms, ETCAPA exploits a data-dependent filter-bank formulation together with a non-linear minimization to give a hitherto unobtained non-parametric estimate of the echo train decay. The proposed estimator is evaluated on both simulated and measured NQR signals, clearly showing the excellent performance of the method, even in the case of strong interferences.
  •  
37.
  • Kronvall, Ted, et al. (författare)
  • Sparse Modeling of Chroma Features
  • 2017
  • Ingår i: Signal Processing. - : Elsevier BV. - 0165-1684. ; 130, s. 105-117
  • Tidskriftsartikel (refereegranskat)abstract
    • This work treats the estimation of chroma features for harmonic audio signals using a sparse reconstruction framework. Chroma has been used for decades as a key tool in audio analysis, and is typically formed using a periodogram-based approach that maps the fundamental frequency of a musical tone to its corresponding chroma. Such an approach often leads to problems with tone ambiguity. We address this ambiguity via sparse modeling, allowing us to appropriately penalize ambiguous estimates while taking the harmonic structure of tonal audio into account. Furthermore, we also allow for signals to have time-varying envelopes. Using a spline-based amplitude modulation of the chroma dictionary, the presented estimator is able to model longer frames than what is conventional for audio, as well as to model highly time-localized signals, and signals containing sudden bursts, such as trumpet or trombone signals. Thus, we may retain more signal information as compared to alternative methods. The performances of the proposed methods are evaluated by analyzing the average estimation errors for synthetic signals, as compared to the Cramér–Rao lower bound, and by visual inspection for estimates of real instrument signals. The results show strong visual clarity, as compared to other commonly used methods.
  •  
38.
  • Lei, Shiwen, et al. (författare)
  • Computationality efficient multi-pitch estimation using sparsity
  • 2016
  • Ingår i: 11th IMA International Conference on Mathematics in Signal Processing.
  • Konferensbidrag (refereegranskat)abstract
    • In this work, we introduce a computationally efficient multi-pitch estimation algorithm making use of an approximative frequency domain reformulation of a recent block-sparse multi-pitch estimator. Different to most other pitch estimators, the proposed method does not require a prior knowledge of the number of sources present, nor the number of overtones of each such source. Evaluated on measured audio signals, the estimator is shown to offer excellent performance at a low computational cost.
  •  
39.
  • Lenshof, Andreas, et al. (författare)
  • Acoustic Whole Blood Plasmapheresis Chip for Prostate Specific Antigen Microarray Diagnostics.
  • 2009
  • Ingår i: Analytical Chemistry. - : American Chemical Society (ACS). - 1520-6882 .- 0003-2700. ; 81:Jul 13, s. 6030-6037
  • Tidskriftsartikel (refereegranskat)abstract
    • The generation of high quality plasma from whole blood is of major interest for many biomedical analyses and clinical diagnostic methods. However, it has proven to be a major challenge to make use of microfluidic separation devices to process fluids with high cell content, such as whole blood. Here, we report on an acoustophoresis based separation chip that prepares diagnostic plasma from whole blood linked to a clinical application. This acoustic separator has the capacity to sequentially remove enriched blood cells in multiple steps to yield high quality plasma of low cellular content. The generated plasma fulfills the standard requirements (<6.0 x 10(9) erythrocytes/L) recommended by the Council of Europe. Further, we successfully linked the plasmapheresis microchip to our previously developed porous silicon sandwich antibody microarray chip for prostate specific antigen (PSA) detection. PSA was detected by good linearity (R(2) > 0.99) in the generated plasma via fluorescence readout without any signal amplification at clinically relevant levels (0.19-21.8 ng/mL).
  •  
40.
  • Lenshof, Andreas, et al. (författare)
  • Acoustic whole blood plasmapheresis chip for PSA microarray diagnostics
  • 2009
  • Ingår i: Proceedings of Conference, MicroTAS 2009 : The 13th International Conference on Miniaturized Systems for Chemistry and Life Sciences - The 13th International Conference on Miniaturized Systems for Chemistry and Life Sciences. - 9780979806421 ; , s. 1330-1332
  • Konferensbidrag (refereegranskat)abstract
    • An acoustic device for generating high quality blood plasma for PSA microarray diagnostics is presented.
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41.
  •  
42.
  • Liu, Li, et al. (författare)
  • Itga8-Cre-mediated deletion of YAP and TAZ impairs bladder contractility with minimal inflammation and chondrogenic differentiation
  • 2023
  • Ingår i: American Journal of Physiology - Cell Physiology. - 0363-6143 .- 1522-1563. ; 325:6
  • Tidskriftsartikel (refereegranskat)abstract
    • A role of Yes1-associated transcriptional regulator (YAP) and WW domain-containing transcription regulator 1 (TAZ) in vascular and gastrointestinal contractility due to control of myocardin (Myocd) expression, which in turn activates contractile genes, has been demonstrated. Whether this transcriptional hierarchy applies to the urinary bladder is unclear. We found that YAP/TAZ are expressed in human detrusor myocytes and therefore exploited the Itga8-CreERT2 model for the deletion of YAP/TAZ. Recombination occurred in detrusor, and YAP/TAZ transcripts were reduced by >75%. Bladder weights were increased (by ͌22%), but histology demonstrated minimal changes in the detrusor, while arteries in the mucosa were inflamed. Real-time quantitative reverse transcription PCR (RT-qPCR) using the detrusor demonstrated reductions of Myocd (-79±18%) and serum response factor (Srf) along with contractile genes. In addition, the cholinergic receptor muscarinic 2 (Chrm2) and Chrm3 were suppressed (-80±23% and -80±10%), whereas minute increases of Il1b and Il6 were seen. Unlike YAP/TAZ-deficient arteries, SRY (sex-determining region Y)-box 9 (Sox9) did not increase, and no chondrogenic differentiation was apparent. Reductions of smooth muscle myosin heavy chain 11 (Myh11), myosin light-chain kinase gene (Mylk), and Chrm3 were seen at the protein level. Beyond restraining the smooth muscle cell (SMC) program of gene expression, YAP/TAZ depletion silenced SMC-specific splicing, including exon 2a of Myocd. Reduced contractile differentiation was associated with weaker contraction in response to myosin phosphatase inhibition (-36%) and muscarinic activation (reduced by 53% at 0.3 lM carbachol). Finally, short-term overexpression of constitutively active YAP in human embryonic kidney 293 (HEK293) cells increased myocardin (greater than eightfold) along with archetypal target genes, but contractile genes were unaffected or reduced. YAP and TAZ thus regulate myocardin expression in the detrusor, and this is important for SMC differentiation and splicing as well as for contractility.
  •  
43.
  • Malmqvist, Johan, 1960-, et al. (författare)
  • But was it Trustworthy? : Methodological Experiences From a Study of a Hard-to-Reach Group of Students in Need of a Flexible Research Approach
  • 2024
  • Ingår i: International Journal of Qualitative Methods. - : Sage Publications. - 1609-4069. ; 23
  • Tidskriftsartikel (refereegranskat)abstract
    • Pedagogical research on experiences of learning among students with severe speech and physical impairment (SSPI) is sparse. This may be due to a lack of research-on-research methodology literature about students with SSPI, as they are difficult to find and there are barriers to their participation in mainstream research. Hence, method development is especially important regarding these students, who cannot participate when traditional inquiry methods are used. This article's objective is therefore to advance method development by means of a retrospective investigation. The empirical findings consist of documented experiences from a previous study of students with SSPI (henceforth, "literacy study"). A computer-assisted email dialogue technique was developed in the literacy study's pilot study and eventually used in the main study, to investigate the students' experiences of their literacy development. The aim of this study is to retrospectively and critically examine the scientific trustworthiness of a methodological research approach based on an email dialogue technique used exploratively in the literacy study, to investigate the literacy development among the students grounded in their own experiences, and to contribute methodological experiences gained from that study regarding the relationship between the use of verification strategies and checking techniques. The computer-assisted email dialogue approach was necessary because the few participants were spread over great geographical distances. The approach was developed as an explorative and flexible inclusive research design and was used within the tradition of participatory research. The students in both the pilot and main studies (8-16 years of age) were treated as collaborators rather than research subjects. Both the verification strategies and techniques regarding trustworthiness criteria were found to be important for trustworthiness. The main conclusion, based on our experiences in this retrospective investigation, is that it is necessary to continuously and thoroughly focus on trustworthiness issues throughout the research process to obtain trustworthy findings.
  •  
44.
  • Martínez, Marycarmen Arévalo, et al. (författare)
  • Vascular smooth muscle–specific YAP/TAZ deletion triggers aneurysm development in mouse aorta
  • 2023
  • Ingår i: JCI Insight. - 2379-3708. ; 8:17
  • Tidskriftsartikel (refereegranskat)abstract
    • Inadequate adaption to mechanical forces, including blood pressure, contributes to development of arterial aneurysms. Recent studies have pointed to a mechanoprotective role of YAP and TAZ in vascular smooth muscle cells (SMCs). Here, we identified reduced expression of YAP1 in human aortic aneurysms. Vascular SMC–specific knockouts (KOs) of YAP/TAZ were thus generated using the integrin α8–Cre (Itga8-Cre) mouse model (i8-YT-KO). i8-YT-KO mice spontaneously developed aneurysms in the abdominal aorta within 2 weeks of KO induction and in smaller arteries at later times. The vascular specificity of Itga8-Cre circumvented gastrointestinal effects. Aortic aneurysms were characterized by elastin disarray, SMC apoptosis, and accumulation of proteoglycans and immune cell populations. RNA sequencing, proteomics, and myography demonstrated decreased contractile differentiation of SMCs and impaired vascular contractility. This associated with partial loss of myocardin expression, reduced blood pressure, and edema. Mediators in the inflammatory cGAS/STING pathway were increased. A sizeable increase in SOX9, along with several direct target genes, including aggrecan (Acan), contributed to proteoglycan accumulation. This was the earliest detectable change, occurring 3 days after KO induction and before the proinflammatory transition. In conclusion, Itga8-Cre deletion of YAP and TAZ represents a rapid and spontaneous aneurysm model that recapitulates features of human abdominal aortic aneurysms.
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45.
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46.
  • Redfors, Bengt, et al. (författare)
  • Acute renal failure is NOT an "acute renal success"--a clinical study on the renal oxygen supply/demand relationship in acute kidney injury.
  • 2010
  • Ingår i: Critical Care Medicine. - 1530-0293. ; 38:8, s. 1695-701
  • Tidskriftsartikel (refereegranskat)abstract
    • OBJECTIVES: Acute kidney injury occurs frequently after cardiac or major vascular surgery and is believed to be predominantly a consequence of impaired renal oxygenation. However, in patients with acute kidney injury, data on renal oxygen consumption (RVO2), renal blood flow, glomerular filtration, and renal oxygenation, i.e., the renal oxygen supply/demand relationship, are lacking and current views on renal oxygenation in the clinical situation of acute kidney injury are presumptive and largely based on experimental studies. DESIGN: Prospective, two-group comparative study. SETTING: Cardiothoracic intensive care unit of a tertiary center. PATIENTS: Postcardiac surgery patients with (n = 12) and without (n = 37) acute kidney injury were compared with respect to renal blood flow, glomerular filtration, RVO2, and renal oxygenation. INTERVENTIONS: None MEASUREMENTS AND MAIN RESULTS: Data on systemic hemodynamics (pulmonary artery catheter) and renal variables were obtained during two 30-min periods. Renal blood flow was measured using two independent techniques: the renal vein thermodilution technique and the infusion clearance of paraaminohippuric acid, corrected for renal extraction of paraaminohippuric acid. The filtration fraction was measured by the renal extraction of Cr-EDTA and the renal sodium resorption was measured as the difference between filtered and excreted sodium. Renal oxygenation was estimated from the renal oxygen extraction. Cardiac index and mean arterial pressure did not differ between the two groups. In the acute kidney injury group, glomerular filtration (-57%), renal blood flow (-40%), filtration fraction (-26%), and sodium resorption (-59%) were lower, renal vascular resistance (52%) and renal oxygen extraction (68%) were higher, whereas there was no difference in renal oxygen consumption between groups. Renal oxygen consumption for one unit of reabsorbed sodium was 2.4 times higher in acute kidney injury. CONCLUSIONS: Renal oxygenation is severely impaired in acute kidney injury after cardiac surgery, despite the decrease in glomerular filtration and tubular workload. This was caused by a combination of renal vasoconstriction and tubular sodium resorption at a high oxygen demand.
  •  
47.
  • Redfors, Bengt, et al. (författare)
  • Dopamine increases renal oxygenation: a clinical study in post-cardiac surgery patients.
  • 2010
  • Ingår i: Acta Anaesthesiol Scand. - : Wiley. - 1399-6576. ; 54:2, s. 183-90
  • Tidskriftsartikel (refereegranskat)abstract
    • BACKGROUND: Imbalance of the renal medullary oxygen supply/demand relationship can cause ischaemic acute renal failure (ARF). The use of dopamine for prevention/treatment of ischaemic ARF has been questioned. It has been suggested that dopamine may increase renal oxygen consumption (RVO(2)) due to increased solute delivery to tubular cells, which may jeopardize renal oxygenation. Information on the effects of dopamine on renal perfusion, filtration and oxygenation in man is, however, lacking. We evaluated the effects of dopamine on renal blood flow (RBF), glomerular filtration rate (GFR), RVO(2) and renal O(2) demand/supply relationship, i.e. renal oxygen extraction (RO(2)Ex). METHODS: Twelve uncomplicated, mechanically ventilated and sedated post-cardiac surgery patients with pre-operatively normal renal function were studied. Dopamine was sequentially infused at 2 and 4 ug/kg/min. Systemic haemodynamics were evaluated by a pulmonary artery catheter. Absolute RBF was measured using two independent techniques: by the renal vein thermodilution technique and by infusion clearance of paraaminohippuric acid (PAH), with a correction for renal extraction of PAH. The filtration fraction (FF) was measured by the renal extraction of (51)Cr-EDTA. RESULTS: Neither GFR, tubular sodium reabsorption nor RVO(2) was affected by dopamine, which increased RBF (45-55%) with both methods, decreased renal vascular resistance (30-35%), FF (21-26%) and RO(2)Ex (28-34%). The RBF/CI ratio increased with dopamine. Dopamine decreased renal PAH extraction, suggestive of a flow distribution to the medulla. CONCLUSIONS: In post-cardiac surgery patients, dopamine increases the renal oxygenation by a pronounced renal pre-and post-glomerular vasodilation with no increases in GFR, tubular sodium reabsorption or renal oxygen consumption.
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48.
  • Redfors, Bengt, et al. (författare)
  • Effects of mannitol alone and mannitol plus furosemide on renal oxygen consumption, blood flow and glomerular filtration after cardiac surgery.
  • 2009
  • Ingår i: Intensive care medicine. - : Springer Science and Business Media LLC. - 1432-1238 .- 0342-4642. ; 35:1, s. 115-22
  • Tidskriftsartikel (refereegranskat)abstract
    • OBJECTIVE: Imbalance of the renal medullary oxygen supply/demand relationship can cause hypoxic medullary damage and ischaemic acute renal failure (ARF). The use of mannitol for prophylaxis/treatment of clinical ischaemic ARF is controversial and the effect of mannitol on renal oxygenation in man has not yet been investigated. We evaluated the effects of mannitol on renal oxygen consumption (RVO(2))(,) renal blood flow (RBF) and glomerular filtration rate (GFR) in postoperative patients. DESIGN: Prospective interventional study. SETTING: University hospital cardiothoracic ICU. PATIENTS: Ten uncomplicated mechanically ventilated and sedated postcardiac surgery patients with preoperatively normal renal function. INTERVENTIONS: Mannitol infusion (225 mg/kg + 75 mg/kg/h) and combined mannitol and furosemide infusion (0.25 mg/kg + 0.25 mg/kg/h). MEASUREMENTS AND RESULTS: Systemic haemodynamics were evaluated by a pulmonary artery catheter. RBF and GFR were measured by the renal vein thermodilution technique and by renal extraction of (51)Cr-EDTA, respectively. Mannitol increased urine flow (60%), GFR (20%) and filtration fraction (FF) (20%) with no change in RBF. This was accompanied by an increase in renal sodium reabsorption (18%), RVO(2) (19%) and renal oxygen extraction (21%). When combined with mannitol, furosemide normalised sodium reabsorption, RVO(2), renal oxygen extraction with no change in RBF, while GFR and FF were still elevated compared to control. CONCLUSIONS: In patients with normal renal function, mannitol increases GFR, which increases tubular sodium load, sodium reabsorption and RVO(2) after cardiac surgery. The lack of effect on RBF, indicates that mannitol impairs the renal oxygen supply/demand relationship. Furosemide normalised renal oxygenation when combined with mannitol.
  •  
49.
  • Redfors, Bengt, et al. (författare)
  • Effects of norepinephrine on renal perfusion, filtration and oxygenation in vasodilatory shock and acute kidney injury.
  • 2011
  • Ingår i: Intensive Care Medicine. - : Springer Science and Business Media LLC. - 1432-1238 .- 0342-4642. ; 37:1, s. 60-7
  • Tidskriftsartikel (refereegranskat)abstract
    • The use of norepinephrine (NE) in patients with volume-resuscitated vasodilatory shock and acute kidney injury (AKI) remains the subject of much debate and controversy. The effects of NE-induced variations in mean arterial blood pressure (MAP) on renal blood flow (RBF), oxygen delivery (RDO(2)), glomerular filtration rate (GFR) and the renal oxygen supply/demand relationship (renal oxygenation) in vasodilatory shock with AKI have not been previously studied.
  •  
50.
  • Rippe, Catarina, et al. (författare)
  • NG2/CSPG4, CD146/MCAM and VAP1/AOC3 are regulated by myocardin-related transcription factors in smooth muscle cells
  • 2021
  • Ingår i: Scientific Reports. - : Springer Science and Business Media LLC. - 2045-2322. ; 11:1
  • Tidskriftsartikel (refereegranskat)abstract
    • The present work addressed the hypothesis that NG2/CSPG4, CD146/MCAM, and VAP1/AOC3 are target genes of myocardin-related transcription factors (MRTFs: myocardin/MYOCD, MRTF-A/MKL1, MRTF-B/MKL2) and serum response factor (SRF). Using a bioinformatics approach, we found that CSPG4, MCAM, and AOC3 correlate with MYOCD, MRTF-A/MKL1, and SRF across human tissues. No other transcription factor correlated as strongly with these transcripts as SRF. Overexpression of MRTFs increased both mRNA and protein levels of CSPG4, MCAM, and AOC3 in cultured human smooth muscle cells (SMCs). Imaging confirmed increased staining for CSPG4, MCAM, and AOC3 in MRTF-A/MKL1-transduced cells. MRTFs exert their effects through SRF, and the MCAM and AOC3 gene loci contained binding sites for SRF. SRF silencing reduced the transcript levels of these genes, and time-courses of induction paralleled the direct target ACTA2. MRTF-A/MKL1 increased the activity of promoter reporters for MCAM and AOC3, and transcriptional activation further depended on the chromatin remodeling enzyme KDM3A. CSPG4, MCAM, and AOC3 responded to the MRTF-SRF inhibitor CCG-1423, to actin dynamics, and to ternary complex factors. Coincidental detection of these proteins should reflect MRTF-SRF activity, and beyond SMCs, we observed co-expression of CD146/MCAM, NG2/CSPG4, and VAP1/AOC3 in pericytes and endothelial cells in the human brain. This work identifies highly responsive vascular target genes of MRTF-SRF signaling that are regulated via a mechanism involving KDM3A.
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