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Countercurrent multiplier

Kazuko Itoh, Yuichiro Izumi, Takeaki Inoue, Hideki Inoue, Yushi Nakayama, Takayuki Uematsu, Takashi Fukuyama, Taiga Yamazaki, Yukiko Yasuoka, Takeshi Makino, Yasushi Nagaba, Kimio Tomita, Noritada Kobayashi, Katsumasa Kawahara, Masashi Mukoyama, Hiroshi Nonoguchi
Sodium reabsorption via Na-K-2Cl cotransporter 2 (NKCC2) in the thick ascending limbs has a major role for medullary osmotic gradient and subsequent water reabsorption in the collecting ducts. We investigated intrarenal localization of three isoforms of NKCC2 mRNA expressions and the effects of dehydration on them in rats. To further examine the mechanisms of dehydration, the effects of hyperosmolality on NKCC2 mRNA expression in microdissected renal tubules was studied. RT-PCR and RT-competitive PCR were employed...
October 24, 2014: Biochemical and Biophysical Research Communications
Jörg C Gerlach, Marc Lübberstedt, Josefina Edsbagge, Alexander Ring, Mariah Hout, Matt Baun, Ingrid Rossberg, Fanny Knöspel, Grant Peters, Klaus Eckert, Annika Wulf-Goldenberg, Petter Björquist, Harald Stachelscheid, Thomas Urbaniak, Gerald Schatten, Toshio Miki, Eva Schmelzer, Katrin Zeilinger
We describe hollow fiber-based three-dimensional (3D) dynamic perfusion bioreactor technology for embryonic stem cells (ESC) which is scalable for laboratory and potentially clinical translation applications. We added 2 more compartments to the typical 2-compartment devices, namely an additional media capillary compartment for countercurrent 'arteriovenous' flow and an oxygenation capillary compartment. Each capillary membrane compartment can be perfused independently. Interweaving the 3 capillary systems to form repetitive units allows bioreactor scalability by multiplying the capillary units and provides decentralized media perfusion while enhancing mass exchange and reducing gradient distances from decimeters to more physiologic lengths of <1 mm...
2010: Cells, Tissues, Organs
Hiroko Nishimura
Although birds and mammals have evolved from primitive tetrapods and advanced divergently, both can conserve water by producing hyperosmotic urine. Unique aspects in the avian system include the presence of loopless and looped nephrons, lack of the thin ascending limb of Henle's loop, a corticomedullary osmotic gradient primarily consisting of NaCl without contribution of urea, and significant postrenal modification of final urine. The countercurrent multiplier mechanism operates between the descending and ascending limbs of Henle via recycling of a single solute (NaCl) with no water accompaniment, forming an osmotic gradient along the medullary cone...
July 2008: Pflügers Archiv: European Journal of Physiology
Xiao-Yue Zhai, Robert A Fenton, Arne Andreasen, Jesper Skovhus Thomsen, Erik I Christensen
In mammalian kidneys, aquaporin-1 is responsible for water reabsorption along the proximal tubule and is also thought to be involved in the concentration of urine that occurs in the medulla. It has been suggested, however, that aquaporin-1 is not expressed in the last part of the descending thin limbs of short loop nephrons in rats and mice, and its expression in this region in humans has not been studied. We examined the expression of aquaporin-1 and the urea transporter UT-A2 in serial sections of mouse nephrons in the inner stripe of the outer medulla using immunohistochemistry...
November 2007: Journal of the American Society of Nephrology: JASN
Hiroko Nishimura, Yimu Yang, Keith Lau, Rhonda J Kuykindoll, Zheng Fan, Ken'ichi Yamaguchi, Tadashi Yamamoto
Avian kidneys have loopless and looped nephrons; a countercurrent multiplier mechanism operates in the latter by NaCl recycling. We identified an aquaporin-2 (AQP2) homolog in apical/subapical regions of cortical and medullary collecting duct (CD) cells in kidneys of Japanese quail (q), Coturnix japonica. We investigated whether undernutrition during the embryonic/maturation period retards kidney and AQP2 development in quail and programs impaired volume regulation in adults. Protocols included 1) time course and 2) effects of 5-10% egg white withdrawal (EwW) or 48-h post-hatch food deprivation (FD) on nephron growth and qAQP2 mRNA expression, and 3) effects of EwW and FD on qAQP2 mRNA responses to 72-h water deprivation in adults...
November 2007: American Journal of Physiology. Regulatory, Integrative and Comparative Physiology
Robert A Fenton, Mark A Knepper
Since the turn of the 21st century, gene knockout mice have been created for all major urea transporters that are expressed in the kidney: the collecting duct urea transporters UT-A1 and UT-A3, the descending thin limb isoform UT-A2, and the descending vasa recta isoform UT-B. This article discusses the new insights that the results from studies in these mice have produced in the understanding of the role of urea in the urinary concentrating mechanism and kidney function. Following is a summary of the major findings: (1) Urea accumulation in the inner medullary interstitium depends on rapid transport of urea from the inner medullary collecting duct (IMCD) lumen via UT-A1 and/or UT-A3; (2) as proposed by Robert Berliner and colleagues in the 1950s, the role of IMCD urea transporters in water conservation is to prevent a urea-induced osmotic diuresis; (3) the absence of IMCD urea transport does not prevent the concentration of NaCl in the inner medulla, contrary to what would be predicted from the passive countercurrent multiplier mechanism in the form proposed by Kokko and Rector and Stephenson; (4) deletion of UT-B (vasa recta isoform) has a much greater effect on urinary concentration than deletion of UT-A2 (descending limb isoform), suggesting that the recycling of urea between the vasa recta and the renal tubules quantitatively is less important than classic countercurrent exchange; and (5) urea reabsorption from the IMCD and the process of urea recycling are not important elements of the mechanism of protein-induced increases in GFR...
March 2007: Journal of the American Society of Nephrology: JASN
Ryan G Morris, Shinichi Uchida, Heddwen Brooks, Mark A Knepper, Chung-Lin Chou
Aquaporin-1 is the major protein responsible for transport of water across the epithelia of the proximal tubule and thin descending limbs. Rapid water efflux across the thin descending limb is required for the normal function of the countercurrent multiplier mechanism. Therefore, urinary concentrating capacity is severely impaired in aquaporin-1 knockout (AQP1 -/-) mice. Here, we have investigated the long-term consequences of deletion of the AQP1 gene product by profiling abundance changes in transporters expressed in the inner medullas of AQP1 (-/-) mice vs...
July 2005: American Journal of Physiology. Renal Physiology
Matthew R McReynolds, Katherine M Taylor-Garcia, Kevin A Greer, James B Hoying, Heddwen L Brooks
Mice that lack the aquaporin-1 gene (AQP1) lack a functional countercurrent multiplier mechanism, fail to concentrate the inner medullary (IM) interstitium, and present with a urinary concentrating defect. In this study, we use DNA microarrays to identify the gene expression profile of the IM of AQP1 null mice and corresponding changes in gene expression resulting from a loss of a hypertonic medullary interstitium. An ANOVA analysis model, CARMA, was used to isolate the knockout effect while taking into account experimental variability associated with microarray studies...
February 2005: American Journal of Physiology. Renal Physiology
Y Yang, Y Cui, W Wang, L Zhang, L Bufford, S Sasaki, Z Fan, H Nishimura
Both mammals and birds can concentrate urine hyperosmotic to plasma via a countercurrent multiplier mechanism, although evolutionary lines leading to mammals and birds diverged at an early stage of tetrapod evolution. We reported earlier (Nishimura H, Koseki C, and Patel TB. Am J Physiol Regul Integr Comp Physiol 271: R1535-R1543, 1996) that arginine vasotocin (AVT; avian antidiuretic hormone) increases diffusional water permeability in the isolated, perfused medullary collecting duct (CD) of the quail kidney...
October 2004: American Journal of Physiology. Regulatory, Integrative and Comparative Physiology
No abstract text is available yet for this article.
February 1960: Medical Bulletin
The capacity to conserve urinary water by producing a concentrated urine is directly related to the number of Henle's loops in the kidneys of three terrestrial birds. This suggests that a Henle's loop countercurrent multiplier is responsible for urine concentration in these birds. Several features of the organization of the kidneys of these birds may account for the importance of multiplier number, as contrasted to multiplier length in mammals, in determining maximum urine concentration.
April 16, 1965: Science
The secretion of carbon dioxide accompanying the secretion of oxygen into the swim-bladder of the bluefish is examined in order to distinguish among several theories which have been proposed to describe the operation of the rete mirabile, a vascular countercurrent exchange organ. Carbon dioxide may comprise 27 per cent of the gas secreted, corresponding to a partial pressure of 275 mm Hg. This is greater than the partial pressure that would be generated by acidifying arterial blood (about 55 mm Hg). The rate of secretion is very much greater than the probable rate of metabolic formation of carbon dioxide in the gas-secreting complex...
November 1964: Journal of General Physiology
No abstract text is available yet for this article.
November 1960: American Journal of Physiology
No abstract text is available yet for this article.
September 12, 1958: Science
S Kurbel, K Dodig, R Radić
This article is an attempt to simplify lecturing about the osmotic gradient in the kidney medulla. In the model presented, the kidneys are described as a limited space with a positive interstitial hydrostatic pressure. Traffic of water, sodium, and urea is described in levels (or horizons) of different osmolarity, governed by osmotic forces and positive interstitial pressure. In this way, actions of the countercurrent multiplier in nephron tubules and of the countercurrent exchanger in vasa recta are integrated in each horizon...
December 2002: Advances in Physiology Education
P B Bijlsma, B M Fihn, A Sjöqvist, J A Groot, J A J M Taminiau, M Jodal
BACKGROUND: Recently, we hypothesized that mannitol absorption in human intestinal permeability tests is a reflection of small intestinal water absorption and is dependent mainly on the efficiency of the countercurrent multiplier in the villi. This may affect the outcome of clinical double-sugar permeability tests. We tested the hypothesis in cats, another species with an efficient countercurrent multiplier. METHODS: The lumen-to-tissue transport of [14C]mannitol and [51Cr]EDTA was studied in in situ perfused jejunum of eight anaesthetized cats using four isotonic perfusion solutions with varying sodium and glucose content...
July 2002: Scandinavian Journal of Gastroenterology
S R Thomas
The mechanism by which the mammalian kidney creates the osmotic gradient necessary for urine concentration remains an open question. We present a brief survey of the give-and-take between theory and experiment on this question over the last half century. We start with the introduction of the countercurrent multiplier paradigm in 1951. We finish with a description of a recent suggestion that the explanation for the enigmatic inner medullary osmotic gradient may reside in the very metabolism of the inner medullary cells, which are required by the region's hypoxia to obtain their ATP largely from anaerobic glycolysis and which thus, by the same token, furnish net osmoles to the medullary interstitium by converting glucose to lactate...
2001: Acta Biotheoretica
F V Osorio, I Teitelbaum
The kidney's concentrating capacity is impaired in chronic renal failure (CRF) resulting in a relatively large rate of urine formation and nocturia. Normal renal concentrating ability depends on the maintenance of a hypertonic medullary interstitium, a structurally intact countercurrent multiplier system, and normal water permeability of the collecting tubules in response to arginine vasopressin (AVP). Each of these three components may be compromised in the setting of CRF. This review presents current knowledge regarding mechanisms of impaired renal concentrating ability in CRF, from the whole kidney level to the cellular and molecular level...
September 1997: Journal of Nephrology
S Weinbaum, L X Xu, L Zhu, A Ekpene
A new model for muscle tissue heat transfer has been developed using Myrhage and Eriksson's [23] description of a muscle tissue cylinder surrounding secondary (s) vessels as the basic heat transfer unit. This model provides a rational theory for the venous return temperature for the perfusion source term in a modified Pennes bioheat equation, and greatly simplifies the anatomical description of the microvascular architecture required in the Weinbaum-Jiji bioheat equation. An easy-to-use closed-from analytic expression has been derived for the difference between the inlet artery and venous return temperatures using a model for the countercurrent heat exchange in the individual muscle tissue cylinders...
August 1997: Journal of Biomechanical Engineering
G Mancino, R Placido, S Bach, F Mariani, C Montesano, L Ercoli, M Zembala, V Colizzi
Mycobacterium tuberculosis and human immunodeficiency virus type 1 (HIV-1) are virulent intracellular pathogens that invade and multiply within macrophages. The effect of M. tuberculosis on HIV-1 infection and replication was analyzed in vitro using human monocyte-derived macrophages (MDM) isolated from peripheral blood mononuclear cells by countercurrent centrifugal elutriation. Preinfection of MDM with M. tuberculosis followed by HIV-1 infection resulted in an increase in p24 release, reverse transcriptase activity, and infective virus production...
June 1997: Journal of Infectious Diseases
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