101,109 research outputs found
Experimental protocol for MRI mapping of the blood oxygenation-sensitive parameters T(2)* and T(2) in the kidney
No full textRenal hypoxia is generally accepted as a key pathophysiologic event in acute kidney injury of various origins, and has also been suggested to play a role in the development of chronic kidney disease. Here we describe a step-by-step experimental protocol for indirect monitoring of renal blood oxygenation in rodents via the deoxyhemoglobin sensitive MR parameters T(2)* and T(2)-a contrast mechanism known as the blood oxygenation level dependent (BOLD) effect. Since an absolute quantification of renal oxygenation from T(2)*/T(2) remains challenging, the effects of controlled and standardized variations in the fraction of inspired oxygen are used for bench marking. This MRI method may be useful for investigating renal blood oxygenation of small rodents in vivo under various experimental (patho)physiological conditions.This chapter is based upon work from the COST Action PARENCHIMA, a community-driven network funded by the European Cooperation in Science and Technology (COST) program of the European Union, which aims to improve the reproducibility and standardization of renal MRI biomarkers. This experimental protocol chapter is complemented by two separate chapters describing the basic concept and data analysis
Essential practical steps for MRI of the kidney in experimental research
No full textMagnetic resonance imaging (MRI) is an emerging method to obtain valuable functional and structural information about the kidney noninvasively. Before performing specialized MR measurements for probing tissue structure and function, some essential practical steps are needed, which are common for most applications. Here we describe in a step-by-step manner how to (1) achieve the double-oblique slice orientation coronal-to-the-kidney, (2) adapt the scan protocol for avoiding aortic flow artifacts and covering both kidneys, (3) perform localized shimming on the kidney, and (4) check perfusion in the large renal blood vessels using time-of-flight (TOF) angiography. The procedures are tailored to preclinical MRI but conceptionally are also applicable to human MRI.This chapter is based upon work from the COST Action PARENCHIMA, a community-driven network funded by the European Cooperation in Science and Technology (COST) program of the European Union, which aims to improve the reproducibility and standardization of renal MRI biomarkers. This experimental protocol chapter explains the initial and essential MRI steps that precede specific functional and structural MR imaging techniques (T(1)- and T(2)*-mapping, DWI , ASL , etc.), which are described in separate chapters
Analysis protocols for MRI mapping of the blood oxygenation-sensitive parameters T(2)* and T(2) in the kidney
No full textRenal hypoxia is generally accepted as a key pathophysiologic event in acute kidney injury of various origins and has also been suggested to play a role in the development of chronic kidney disease. Here we describe step-by-step data analysis protocols for MRI monitoring of renal oxygenation in rodents via the deoxyhemoglobin concentration sensitive MR parameters T(2)* and T(2)-a contrast mechanism known as the blood oxygenation level dependent (BOLD) effect.This chapter describes how to use the analysis tools provided by vendors of animal and clinical MR systems, as well as how to develop an analysis software. Aspects covered are: data quality checks, data exclusion, model fitting, fitting algorithm, starting values, effects of multiecho imaging, and result validation.This chapter is based upon work from the PARENCHIMA COST Action, a community-driven network funded by the European Cooperation in Science and Technology (COST) program of the European Union, which aims to improve the reproducibility and standardization of renal MRI biomarkers. This experimental protocol chapter is complemented by two separate chapters describing the basic concept and data analysis
Denoising for improved parametric MRI of the kidney: protocol for nonlocal means filtering
No full textIn order to tackle the challenges caused by the variability in estimated MRI parameters (e.g., T(2)* and T(2)) due to low SNR a number of strategies can be followed. One approach is postprocessing of the acquired data with a filter. The basic idea is that MR images possess a local spatial structure that is characterized by equal, or at least similar, noise-free signal values in vicinities of a location. Then, local averaging of the signal reduces the noise component of the signal. In contrast, nonlocal means filtering defines the weights for averaging not only within the local vicinity, bur it compares the image intensities between all voxels to define "nonlocal" weights. Furthermore, it generally compares not only single-voxel intensities but small spatial patches of the data to better account for extended similar patterns. Here we describe how to use an open source NLM filter tool to denoise 2D MR image series of the kidney used for parametric mapping of the relaxation times T(2)* and T(2).This chapter is based upon work from the COST Action PARENCHIMA, a community-driven network funded by the European Cooperation in Science and Technology (COST) program of the European Union, which aims to improve the reproducibility and standardization of renal MRI biomarkers
Palladium-catalyzed additions of silyl-element bonds to bicyclopropylidene - A new access to bicyclopropyl and functionally substituted cyclopropylidenepropane derivatives
No full textPalladium-catalyzed additions of disilanes, silylboranes, silylstannanes, and silyl cyanides across the double bond of bicyclopropylidene proceed with remarkable ease by two modes yielding either bicyclopropyl or cyclopropylidenepropane derivatives
Lula, Moro and the Top Managers – „Operation Car Wash“ and the Fight Against Corruption in Brazil
No full textBy Elizangela Valarini und Markus Pohlmann Despite the fanfare of the Rio Olympics had subsided, Brazil is no longer politically calm. Sérgio Moro, a fededal judge, detonated a political tinderbox when he lashed out against Luiz Inácio Lula da Silva, a former president, and political corruption in the Workers' Party (PT) Lula had helped found. Source: Pixabay Not only have the accusations against two-term ex-President Lula, the impeachment against his successor Dilma Roussef, the arrest of t..
Gattaca in China: Die Geburt der ersten gentechnisch veränderten Menschen
No full textvon Markus Pohlmann Gattaca ist ein bereits 1997 erschienener Hollywood-Film, in dem es um die Unterschiede zwischen gentechnisch verbesserten Menschen und natürlich Geborenen, sog. Invaliden oder Gotteskindern, geht. Der Titel „Gattaca“ ist aus den Abkürzungen der vier Nukleinbasen der DNA zusammengesetzt: A für Adenin, C für Cytosin, G für Guanin und T für Thymin. Die Abfolge dieser Basen als GATTACA kann erstaunlich oft in der menschlichen DNA gefunden werden. In China scheint nun zum erst..
Renal MRI diffusion: experimental protocol
No full textRenal diffusion-weighted imaging (DWI) can be used to obtain information on the microstructure of kidney tissue, and has the potential to provide MR-biomarkers for functional renal imaging. Here we describe in a step-by-step experimental protocol the MRI method for measuring renal diffusion coefficients in rodents using ADC or IVIM models. Both methods provide quantification of renal diffusion coefficients; however, IVIM, a more complex model, allows for the calculation of the pseudodiffusion and fraction introduced by tissue vascular and tubular components. DWI provides information of renal microstructure contributing to the understanding of the physiology and the underlying processes that precede the beginning of pathologies.This chapter is based upon work from the COST Action PARENCHIMA, a community-driven network funded by the European Cooperation in Science and Technology (COST) program of the European Union, which aims to improve the reproducibility and standardization of renal MRI biomarkers. This experimental protocol chapter is complemented by two separate chapters describing the basic concept and data analysis
Monitoring renal hemodynamics and oxygenation by invasive probes: experimental protocol
No full textRenal tissue hypoperfusion and hypoxia are early key elements in the pathophysiology of acute kidney injury of various origins, and may also promote progression from acute injury to chronic kidney disease. Here we describe methods to study control of renal hemodynamics and tissue oxygenation by means of invasive probes in anesthetized rats. Step-by-step protocols are provided for two setups, one for experiments in laboratories for integrative physiology and the other for experiments within small-animal magnetic resonance scanners.This publication is based upon work from the COST Action PARENCHIMA, a community-driven network funded by the European Cooperation in Science and Technology (COST) program of the European Union, which aims to improve the reproducibility and standardization of renal MRI biomarkers. This experimental protocol chapter is complemented by a separate chapter describing the basic concepts of quantitatively assessing renal perfusion and oxygenation with invasive probes
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