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Re: Calcium Regulation of Tight Junction Permeability
IMAGING
173
issue impacting the clinical usefulness of this technology, and thus may need to be tailored. Dean Assimos, M.D.
Re: Calcium Regulation of Tight Junction Permeability M. Bleich, Q. Shan and N. Himmerkus Institute of Physiology, Christian Albrechts University of Kiel, Kiel, Germany Ann N Y Acad Sci 2012; 1258: 93–99.
Calcium transport in the kidney is a key element in Ca(2⫹) homeostasis. Ca(2⫹) concentration, or more precisely the activity of freely dissociated Ca(2⫹) ions, is a prerequisite for the appropriate function of virtually every cell. Along the renal tubule, about 85% of the filtered Ca(2⫹) is transported across tight junctions at the paracellular route of reabsorption. Therefore, claudins, which form the conductive and selective part of the tight junctions, have moved into the focus of interest with respect to regulatory events in the control of Ca(2⫹) transport. This control is of particular interest for the kidney since it has to defend itself against nephrocalcinosis and kidney stones. Tight junction proteins provide pathways, driving forces, and regulatory targets for Ca(2⫹) transport. Direct regulation of tight junctions by changing Ca(2⫹) concentrations allows fast and efficient feedback loops to adapt Ca(2⫹) transport to the requirements of kidney function and plasma Ca(2⫹) concentration. Editorial Comment: The majority of calcium is reabsorbed in the proximal tubule (60%) and in the thick ascending loop of Henle (25%). This process occurs via paracellular transport in these respective areas of the nephron via tight junctions. A group of proteins called claudins comprise the conductive portion of this paracellular pathway, and they determine if operating as a barrier or facilitating calcium transport. Three potential mechanisms to control calcium transport in these portions of the nephron include changes in the protein composition of tight junctions, controlling the driving forces for calcium absorption through the tight junctions and interference with either claudins or transcellular proteins at a molecular level. This review article nicely summarizes these mechanisms. Dean Assimos, M.D.
Imaging Re: What the Radiologist Needs to Know About Urolithiasis: Part 1—Pathogenesis, Types, Assessment, and Variant Anatomy P. M. Cheng, P. Moin, M. D. Dunn, W. D. Boswell and V. A. Duddalwar Department of Radiology, Keck School of Medicine, University of Southern California, Los Angeles, California AJR Am J Roentgenol 2012; 198: W540 –W547.
Objective: This article reviews types of urinary calculi and their imaging appearances, presents direct and secondary imaging findings of urolithiasis, and provides an overview of treatment methods. Pertinent imaging findings that impact clinical management are highlighted. The implications of complex or variant genitourinary anatomy are reviewed. We outline a standard format for the reporting of urolithiasis to facilitate informed clinical management decisions. Conclusion: Unenhanced CT is the preferred examination for evaluation of urolithiasis because of its availability, ease of performance, and high sensitivity. An awareness of the important imaging findings to report allows appropriate and efficient therapy.
173
issue impacting the clinical usefulness of this technology, and thus may need to be tailored. Dean Assimos, M.D.
Re: Calcium Regulation of Tight Junction Permeability M. Bleich, Q. Shan and N. Himmerkus Institute of Physiology, Christian Albrechts University of Kiel, Kiel, Germany Ann N Y Acad Sci 2012; 1258: 93–99.
Calcium transport in the kidney is a key element in Ca(2⫹) homeostasis. Ca(2⫹) concentration, or more precisely the activity of freely dissociated Ca(2⫹) ions, is a prerequisite for the appropriate function of virtually every cell. Along the renal tubule, about 85% of the filtered Ca(2⫹) is transported across tight junctions at the paracellular route of reabsorption. Therefore, claudins, which form the conductive and selective part of the tight junctions, have moved into the focus of interest with respect to regulatory events in the control of Ca(2⫹) transport. This control is of particular interest for the kidney since it has to defend itself against nephrocalcinosis and kidney stones. Tight junction proteins provide pathways, driving forces, and regulatory targets for Ca(2⫹) transport. Direct regulation of tight junctions by changing Ca(2⫹) concentrations allows fast and efficient feedback loops to adapt Ca(2⫹) transport to the requirements of kidney function and plasma Ca(2⫹) concentration. Editorial Comment: The majority of calcium is reabsorbed in the proximal tubule (60%) and in the thick ascending loop of Henle (25%). This process occurs via paracellular transport in these respective areas of the nephron via tight junctions. A group of proteins called claudins comprise the conductive portion of this paracellular pathway, and they determine if operating as a barrier or facilitating calcium transport. Three potential mechanisms to control calcium transport in these portions of the nephron include changes in the protein composition of tight junctions, controlling the driving forces for calcium absorption through the tight junctions and interference with either claudins or transcellular proteins at a molecular level. This review article nicely summarizes these mechanisms. Dean Assimos, M.D.
Imaging Re: What the Radiologist Needs to Know About Urolithiasis: Part 1—Pathogenesis, Types, Assessment, and Variant Anatomy P. M. Cheng, P. Moin, M. D. Dunn, W. D. Boswell and V. A. Duddalwar Department of Radiology, Keck School of Medicine, University of Southern California, Los Angeles, California AJR Am J Roentgenol 2012; 198: W540 –W547.
Objective: This article reviews types of urinary calculi and their imaging appearances, presents direct and secondary imaging findings of urolithiasis, and provides an overview of treatment methods. Pertinent imaging findings that impact clinical management are highlighted. The implications of complex or variant genitourinary anatomy are reviewed. We outline a standard format for the reporting of urolithiasis to facilitate informed clinical management decisions. Conclusion: Unenhanced CT is the preferred examination for evaluation of urolithiasis because of its availability, ease of performance, and high sensitivity. An awareness of the important imaging findings to report allows appropriate and efficient therapy.