The Experts below are selected from a list of 114 Experts worldwide ranked by ideXlab platform
Thomas L Pannabecker - One of the best experts on this subject based on the ideXlab platform.
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Alternative channels for urea in the inner medulla of the Rat kidney
American Journal of Physiology-renal Physiology, 2015Co-Authors: C. Michele Nawata, William H Dantzler, Thomas L PannabeckerAbstract:The ascending thin limbs (ATLs) and lower descending thin limbs (DTLs) of Henle's loop in the inner medulla of the Rat are highly permeable to urea, and yet no urea transporters have been identified in these sections. We hypothesized that novel, yet-unidentified transporters in these tubule segments could explain the high urea permeability. cDNAs encoding for Na+-glucose transporter 1a (SGLT1a), Na+-glucose transporter 1 (NaGLT1), urea transporter (UT)-A2c, and UT-A2d were isolated and cloned from the Munich-Wistar Rat inner medulla. SGLT1a is a novel NH2-terminal truncated variant of SGLT1. NaGLT1 is a Na+-dependent glucose transporter primarily located in the proximal tubules and not previously described in the thin limbs. UT-A2c and UT-A2d are novel variants of UT-A2. UT-A2c is truncated at the COOH terminus, and UT-A2d has one exon skipped. When Rats underwent water restriction for 72 h, mRNA levels of SGLT1a increased in ATLs, NaGLT1 levels increased in both ATLs and DTLs, and UT-A2c increased in ATLs. [14C]urea uptake assays performed on Xenopus oocytes heterologously expressing these proteins revealed that despite having structural differences from their full-length versions, SGLT1a, UT-A2c, and UT-A2d enhanced urea uptake. NaGLT1 also facilitated urea uptake. Uptakes were Na+ independent and inhibitable by phloretin and/or phloridzin. Our data indicate that there are several alternative channels for urea in the Rat inner medulla that could potentially contribute to the high urea permeabilities in thin limb segments.
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isolation and perfusion of Rat inner medullary vasa recta
American Journal of Physiology-renal Physiology, 2015Co-Authors: Kristen K Evans, Michele C Nawata, Thomas L PannabeckerAbstract:Outer medullary isolated descending vasa recta have proven to be experimentally tractable, and consequently much has been learned about outer medullary vasa recta endothelial transport, pericyte contractile mechanisms, and tubulovascular interactions. In contrast, inner medullary vasa recta have never been isolated from any species, and therefore isolated vasa recta function has never been subjected to in vitro quantitative evaluation. As we teased out inner medullary thin limbs of Henle's loops from the Munich-Wistar Rat, we found that vasa recta could be isolated using similar protocols. We isolated ∼30 inner medullary vasa recta from 23 adult male Munich-Wistar Rats and prepared them for brightfield or electron microscopy, gene expression analysis by RT-PCR, or isolated tubule microperfusion. Morphological characteristics include branching and nonbranching segments exhibiting a thin endothelium, axial surface filaments radiating outward giving vessels a hairy appearance, and attached interstitial cells. Electron microscopy shows multiple cells, tight junctions, and either continuous or fenestRated endothelia. Isolated vasa recta express genes encoding the urea transporter UT-B and/or the fenestral protein PV-1, genes expressed in descending or ascending vasa recta, respectively. The transepithelial NaCl permeability (383.3 ± 60.0 × 10−5 cm/s, mean ± SE, n = 4) was determined in isolated perfused vasa recta. Future quantitative analyses of isolated inner medullary vasa recta should provide structural and functional details important for more fully understanding fluid and solute flows through the inner medulla and their associated regulatory pathways.
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transepithelial water and urea permeabilities of isolated perfused Munich Wistar Rat inner medullary thin limbs of henle s loop
American Journal of Physiology-renal Physiology, 2014Co-Authors: Michele C Nawata, Kristen K Evans, William H Dantzler, Thomas L PannabeckerAbstract:To better understand the role that water and urea fluxes play in the urine concentRating mechanism, we determined transepithelial osmotic water permeability (Pf) and urea permeability (Purea) in is...
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Architecture of interstitial nodal spaces in the rodent renal inner medulla
American Journal of Physiology-renal Physiology, 2013Co-Authors: Rebecca L. Gilbert, Thomas L PannabeckerAbstract:Every collecting duct (CD) of the Rat inner medulla is uniformly surrounded by about four abutting ascending vasa recta (AVR) running parallel to it. One or two ascending thin limbs (ATLs) lie between and parallel to each abutting AVR pair, opposite the CD. These structures form boundaries of axially running interstitial compartments. Viewed in transverse sections, these compartments appear as four interstitial nodal spaces (INSs) positioned symmetrically around each CD. The axially running compartments are segmented by interstitial cells spaced at regular intervals. The pairing of ATLs and CDs bounded by an abundant supply of AVR carrying reabsorbed water, NaCl, and urea make a strong argument that the mixing of NaCl and urea within the INSs and countercurrent flows play a critical role in geneRating the inner medullary osmotic gradient. The results of this study fully support that hypothesis. We quantified interactions of all structures comprising INSs along the corticopapillary axis for two rodent species, the Munich-Wistar Rat and the kangaroo Rat. The results showed remarkable similarities in the configuRations of INSs, suggesting that the structural arrangement of INSs is a highly conserved architecture that plays a fundamental role in renal function. The number density of INSs along the corticopapillary axis directly correlated with a loop population that declines exponentially with distance below the outer medullary-inner medullary boundary. The axial configuRations were consistent with discrete association between near-bend loop segments and INSs and with upper loop segments lying distant from INSs.
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Architecture of kangaroo Rat inner medulla: segmentation of descending thin limb of Henle's loop.
American journal of physiology. Regulatory integrative and comparative physiology, 2012Co-Authors: Vinoo B Urity, Tadeh Issaian, Eldon J Braun, William H Dantzler, Thomas L PannabeckerAbstract:We hypothesize that the inner medulla of the kangaroo Rat Dipodomys merriami, a desert rodent that concentRates its urine to more than 6,000 mosmol/kgH(2)O water, provides unique examples of architectural features necessary for production of highly concentRated urine. To investigate this architecture, inner medullary nephron segments in the initial 3,000 μm below the outer medulla were assessed with digital reconstructions from physical tissue sections. Descending thin limbs of Henle (DTLs), ascending thin limbs of Henle (ATLs), and collecting ducts (CDs) were identified by immunofluorescence using antibodies that label segment-specific proteins associated with transepithelial water flux (aquaporin 1 and 2, AQP1 and AQP2) and chloride flux (the chloride channel ClC-K1); all tubules and vessels were labeled with wheat germ agglutinin. In the outer 3,000 μm of the inner medulla, AQP1-positive DTLs lie at the periphery of groups of CDs. ATLs lie inside and outside the groups of CDs. Immunohistochemistry and reconstructions of loops that form their bends in the outer 3,000 μm of the inner medulla show that, relative to loop length, the AQP1-positive segment of the kangaroo Rat is significantly longer than that of the Munich-Wistar Rat. The length of ClC-K1 expression in the prebend region at the terminal end of the descending side of the loop in kangaroo Rat is about 50% shorter than that of the Munich-Wistar Rat. Tubular fluid of the kangaroo Rat DTL may approach osmotic equilibrium with interstitial fluid by water reabsorption along a relatively longer tubule length, compared with Munich-Wistar Rat. A relatively shorter-length prebend segment may promote a steeper reabsorptive driving force at the loop bend. These structural features predict functionality that is potentially significant in the production of a high urine osmolality in the kangaroo Rat.
Yu Chen - One of the best experts on this subject based on the ideXlab platform.
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Automated quantification of microstructural dimensions of the human kidney using optical coherence tomography (OCT)
Optics Express, 2009Co-Authors: Qian Li, Andrew Paek, Maristela Onozato, James Jiang, Alex Cable, Peter M. Andrews, Chao-wei Chen, Renee Naphas, Shuai Yuan, Yu ChenAbstract:Optical coherence tomography (OCT) is a rapidly emerging imaging modality that can non-invasively provide cross-sectional, high-resolution images of tissue morphology in situ and in real-time. We previously demonstRated that OCT is capable of visualizing characteristic kidney anatomic structures, including blood vessels, uriniferous tubules, glomeruli, and renal capsules on a Munich–Wistar Rat model. Because the viability of a donor kidney is closely correlated with its tubular morphology, and a large amount of image datasets are expected when using OCT to scan the entire kidney to provide a global assessment of its viability, it is necessary to develop automatic image analysis methods to quantify the spatially-resolved morphometric parameters such as tubular diameter to provide potential diagnostic information. In this study, we imaged the human kidney in vitro and quantified the diameters of hollow structures such as blood vessels and uriniferous tubules automatically. The microstructures were first segmented from cross-sectional OCT images. Then the spatially-isolated region-of-interest (ROI) was automatically selected to quantify its dimension. This method enables the automatic selection and quantification of spatially-resolved morphometric parameters. The quantification accuracy was validated, and measured features are in agreement with known kidney morphology. This work can enable studies to determine the clinical utility of OCT for kidney imaging, as well as studies to evaluate kidney morphology as a biomarker for assessing kidney’s viability prior to transplantation.
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High-resolution optical coherence tomography (OCT) imaging of human kidney ex vivo
2009 IEEE 35th Annual Northeast Bioengineering Conference, 2009Co-Authors: Anik Duttaroy, Andrew Paek, Maristela Onozato, Bobak Shirmahamoodi, James Jiang, Alex Cable, Peter M. Andrews, Yu ChenAbstract:Optical coherence tomography (OCT) is a rapidly emerging imaging modality that can provide non-invasive, cross-sectional, high-resolution images of tissue morphology in situ and in real-time. Previous studies have demonstRated that OCT can non-invasively visualize the pathological changes in the living kidney in real-time using the Munich-Wistar Rat model. In this work, we demonstRate, for the first time, the capability of OCT to non-invasively image the human kidney ex vivo. Characteristic kidney structures including the uriniferous tubules, blood vessels, and glomeruli can be readily discerned. And the diameter and volume of the uriniferous tubules can be automatically quantified. Those parameters might be important for the assessment of the donor kidney's viability prior to transplantation.
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Three-dimensional high-resolution optical coherence tomography (OCT) imaging of human kidney
2009 Annual International Conference of the IEEE Engineering in Medicine and Biology Society, 2009Co-Authors: Qian Li, Anik Duttaroy, Andrew Paek, Maristela Onozato, Bobak Shirmahamoodi, James Jiang, Alex Cable, Peter M. Andrews, Yu ChenAbstract:Optical coherence tomography (OCT) is a rapidly emerging imaging modality that can non-invasively provide cross-sectional, high-resolution images of tissue morphology in situ and in real-time. Previous studies have demonstRated that OCT is capable of accuRately visualizing the pathological changes in the living kidney in vivo using the Munich-Wistar Rat model. In this work, we establish, for the first time, the capability of OCT to image the intact human kidney ex vivo. Characteristic kidney anatomic structures including the blood vessels, uriniferous tubules, glomeruli, and kidney capsules can be readily discerned. The diameter and volume parameters of these structures can also be automatically quantified. These two parameters may be critical in clinical applications such as the assessment of the donor kidney's viability prior to transplantation, or image the kidney responses to ischemic insult.
Qian Li - One of the best experts on this subject based on the ideXlab platform.
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Automated quantification of microstructural dimensions of the human kidney using optical coherence tomography (OCT)
Optics Express, 2009Co-Authors: Qian Li, Andrew Paek, Maristela Onozato, James Jiang, Alex Cable, Peter M. Andrews, Chao-wei Chen, Renee Naphas, Shuai Yuan, Yu ChenAbstract:Optical coherence tomography (OCT) is a rapidly emerging imaging modality that can non-invasively provide cross-sectional, high-resolution images of tissue morphology in situ and in real-time. We previously demonstRated that OCT is capable of visualizing characteristic kidney anatomic structures, including blood vessels, uriniferous tubules, glomeruli, and renal capsules on a Munich–Wistar Rat model. Because the viability of a donor kidney is closely correlated with its tubular morphology, and a large amount of image datasets are expected when using OCT to scan the entire kidney to provide a global assessment of its viability, it is necessary to develop automatic image analysis methods to quantify the spatially-resolved morphometric parameters such as tubular diameter to provide potential diagnostic information. In this study, we imaged the human kidney in vitro and quantified the diameters of hollow structures such as blood vessels and uriniferous tubules automatically. The microstructures were first segmented from cross-sectional OCT images. Then the spatially-isolated region-of-interest (ROI) was automatically selected to quantify its dimension. This method enables the automatic selection and quantification of spatially-resolved morphometric parameters. The quantification accuracy was validated, and measured features are in agreement with known kidney morphology. This work can enable studies to determine the clinical utility of OCT for kidney imaging, as well as studies to evaluate kidney morphology as a biomarker for assessing kidney’s viability prior to transplantation.
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Three-dimensional high-resolution optical coherence tomography (OCT) imaging of human kidney
2009 Annual International Conference of the IEEE Engineering in Medicine and Biology Society, 2009Co-Authors: Qian Li, Anik Duttaroy, Andrew Paek, Maristela Onozato, Bobak Shirmahamoodi, James Jiang, Alex Cable, Peter M. Andrews, Yu ChenAbstract:Optical coherence tomography (OCT) is a rapidly emerging imaging modality that can non-invasively provide cross-sectional, high-resolution images of tissue morphology in situ and in real-time. Previous studies have demonstRated that OCT is capable of accuRately visualizing the pathological changes in the living kidney in vivo using the Munich-Wistar Rat model. In this work, we establish, for the first time, the capability of OCT to image the intact human kidney ex vivo. Characteristic kidney anatomic structures including the blood vessels, uriniferous tubules, glomeruli, and kidney capsules can be readily discerned. The diameter and volume parameters of these structures can also be automatically quantified. These two parameters may be critical in clinical applications such as the assessment of the donor kidney's viability prior to transplantation, or image the kidney responses to ischemic insult.
Kristen K Evans - One of the best experts on this subject based on the ideXlab platform.
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isolation and perfusion of Rat inner medullary vasa recta
American Journal of Physiology-renal Physiology, 2015Co-Authors: Kristen K Evans, Michele C Nawata, Thomas L PannabeckerAbstract:Outer medullary isolated descending vasa recta have proven to be experimentally tractable, and consequently much has been learned about outer medullary vasa recta endothelial transport, pericyte contractile mechanisms, and tubulovascular interactions. In contrast, inner medullary vasa recta have never been isolated from any species, and therefore isolated vasa recta function has never been subjected to in vitro quantitative evaluation. As we teased out inner medullary thin limbs of Henle's loops from the Munich-Wistar Rat, we found that vasa recta could be isolated using similar protocols. We isolated ∼30 inner medullary vasa recta from 23 adult male Munich-Wistar Rats and prepared them for brightfield or electron microscopy, gene expression analysis by RT-PCR, or isolated tubule microperfusion. Morphological characteristics include branching and nonbranching segments exhibiting a thin endothelium, axial surface filaments radiating outward giving vessels a hairy appearance, and attached interstitial cells. Electron microscopy shows multiple cells, tight junctions, and either continuous or fenestRated endothelia. Isolated vasa recta express genes encoding the urea transporter UT-B and/or the fenestral protein PV-1, genes expressed in descending or ascending vasa recta, respectively. The transepithelial NaCl permeability (383.3 ± 60.0 × 10−5 cm/s, mean ± SE, n = 4) was determined in isolated perfused vasa recta. Future quantitative analyses of isolated inner medullary vasa recta should provide structural and functional details important for more fully understanding fluid and solute flows through the inner medulla and their associated regulatory pathways.
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transepithelial water and urea permeabilities of isolated perfused Munich Wistar Rat inner medullary thin limbs of henle s loop
American Journal of Physiology-renal Physiology, 2014Co-Authors: Michele C Nawata, Kristen K Evans, William H Dantzler, Thomas L PannabeckerAbstract:To better understand the role that water and urea fluxes play in the urine concentRating mechanism, we determined transepithelial osmotic water permeability (Pf) and urea permeability (Purea) in is...
Michele C Nawata - One of the best experts on this subject based on the ideXlab platform.
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isolation and perfusion of Rat inner medullary vasa recta
American Journal of Physiology-renal Physiology, 2015Co-Authors: Kristen K Evans, Michele C Nawata, Thomas L PannabeckerAbstract:Outer medullary isolated descending vasa recta have proven to be experimentally tractable, and consequently much has been learned about outer medullary vasa recta endothelial transport, pericyte contractile mechanisms, and tubulovascular interactions. In contrast, inner medullary vasa recta have never been isolated from any species, and therefore isolated vasa recta function has never been subjected to in vitro quantitative evaluation. As we teased out inner medullary thin limbs of Henle's loops from the Munich-Wistar Rat, we found that vasa recta could be isolated using similar protocols. We isolated ∼30 inner medullary vasa recta from 23 adult male Munich-Wistar Rats and prepared them for brightfield or electron microscopy, gene expression analysis by RT-PCR, or isolated tubule microperfusion. Morphological characteristics include branching and nonbranching segments exhibiting a thin endothelium, axial surface filaments radiating outward giving vessels a hairy appearance, and attached interstitial cells. Electron microscopy shows multiple cells, tight junctions, and either continuous or fenestRated endothelia. Isolated vasa recta express genes encoding the urea transporter UT-B and/or the fenestral protein PV-1, genes expressed in descending or ascending vasa recta, respectively. The transepithelial NaCl permeability (383.3 ± 60.0 × 10−5 cm/s, mean ± SE, n = 4) was determined in isolated perfused vasa recta. Future quantitative analyses of isolated inner medullary vasa recta should provide structural and functional details important for more fully understanding fluid and solute flows through the inner medulla and their associated regulatory pathways.
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transepithelial water and urea permeabilities of isolated perfused Munich Wistar Rat inner medullary thin limbs of henle s loop
American Journal of Physiology-renal Physiology, 2014Co-Authors: Michele C Nawata, Kristen K Evans, William H Dantzler, Thomas L PannabeckerAbstract:To better understand the role that water and urea fluxes play in the urine concentRating mechanism, we determined transepithelial osmotic water permeability (Pf) and urea permeability (Purea) in is...
