bluuebunny/crossref_metadata_2025 huggingface dataset:
Molecular Sieve in Renal Glomerular and Tubular Basement Membranes as Revealed by Electron Microscopy
Authors: Ota Zensuke , Makino Hirofumi , Takaya Yasumasa , Ofuji Tadashi
Published: November 2008

Bovine glomerular basement membrane (GBM) was isolated and purified according to a modification of Spiro’s method. Rat and bovine tubular basement membranes (TBM) were isolated and purified by sonic disruption or by the method of Carlson et al. Electron microscopic studies on the ultrastructure of GBM and TBM were performed after negative staining with 1% phosphotungstic acid solution, pH 7.3. When negatively stained, GBM and TBM were seen as fragments varying in size. The surface of the membranes showed a characteristic felt-like or spongy appearance. At higher magnification, GBM and TBM showed a fine meshwork composed of strands and pores which three-dimensionally resembled a crystal lattice. Pores were fairly uniform in size and shape. They were round, oval or polygonal in shape. Some of the pores were elongated to form short straight or bent channels. Strands were also uniform in diameter and surrounded a pore or channel. For an average of 50 pores, the long dimension was 3.1 ± 0.6 nm and the short dimension 2.5 ± 0.3 nm in bovine GBM, 3.8 ± 1.2 and 2.5 + 0.7 nm in bovine TBM, and 4.9 ± 1.5 and 2.8 ± 0.6 nm in rat TBM, respectively. The strand was 1.8 ± 0.3 nm in diameter in bovine GBM, 2.5 ± 0.6 nm in bovine TBM and 3.7 ± 0.7 nm in rat TBM for an average of 50 strands. The diameters of the pores were less than or close to the short axis of an albumin molecule. It was concluded that renal GBM and TBM were molecular sieves composed of pores and strands.
Interactions of Starvation and Selective Phosphorus Depletion on Renal Phosphate Reabsorption
Authors: Steele Thomas H.
Published: November 2008

Renal phosphate (Pi) wastage following 7 days of starvation was investigated in normal rats (HI-P) and others previously stabilized on a low phosphorus (LO-P) diet. In LO-P animals, Pi excretion increased after starvation, but was significantly less than in starved HI-P rats. After thyroparathyroidectomy, the increase in Pi excretion after parathyroid hormone (PTH) was significantly greater in nonacidotic starved HI-P rats than in LO-P animals. However, PTH elicited a 31-fold increase in Pi excretion in both of these groups. Starved LO-P and HI-P rats responded equivalently to dibutyryl cyclic AMP. The renal response to phosphate depletion normally promotes Pi conservation, but is attenuated markedly by 7 days of subsequent starvation. This results from at least partial restoration of phosphaturic responsiveness to PTH during starvation.
Effects of Light Saline Loading on Renal Renin and Catecholamine Release in Hypertensive Humans
Authors: Cannella G. , Picotti G.B. , Cesura A.M. , Campanini M. , Bondiolotti G.P. , Maiorca R.
Published: November 2008

In 8 essential hypertensive patients infusion of 7.5 ml kg-1 b.w. of isotonic saline over 20 min decreased plasma renin activity but did not affect plasma adrenaline or noradrenaline concentrations in suprarenal aortic, renal venous and caval blood. Mean blood pressures and heart rates were unchanged throughout the saline infusion period, whereas the hematocrit was significantly decreased. These data suggest that inhibition of renin secretion after slight volume expansion with saline in hypertensive humans occurs without parallel inhibition of either renal neurosympathetic drive or humoral adrenergic tone to the kidney through circulating catecholamines.
Changes in the Molecular Sieve of Glomerular Basement Membrane in Rats with Masugi Nephritis
Authors: Makino Hirofumi
Published: November 2008

Sprague-Dawley rats developed severe proteinuria 24 h after an intravenous injection with rabbit anti-rat kidney serum. Accumulation of polymorphonuclear leukocytes in the capillary lumen and their attachment to the glomerular basement membrane (GBM) were observed. The isolated and purified GBM of normal and nephritis-induced rats were observed by electron microscopy after negative staining. Although the GBM of normal rats appeared as a molecular sieve with uniform pores, the GBM of rats with nephritis had enlarged and elongated pores. An increase in the radius of glomerular pores may be responsible for the proteinuria.
Handling of Human Pepsinogens by the Isolated Rat Kidney: Evidence for a High Glomerular Sieving Coefficient
Authors: ten Kate R.W. , Zwiers A. , Moons W.M. , Slegers J.F.G. , Donker A.J.M. , Meuwissen S.G.M.
Published: November 2008

Pepsinogen A (PGA) and pepsinogen C (PGC) are low-molecular-weight proteins synthesized by the gastric mucosa. Data in man suggest that both pepsinogens are almost freely filtered through the glomerular basement membrane despite a molecular weight of about 43,000 dalton and a strongly negative charge. This promoted us to investigate the glomerular sieving of PGA and PGC in the isolated rat kidney model by measuring their fractional excretions before and after inhibition of tubular function with sodium iodoacetate. During the control episode fractional excretion of PGA was 40 ± 0.04% and of PGC 42 ± 0.04% (mean ± SEM from 9 experiments). After complete inhibition of tubular function a large increase in fractional excretion was found for both pepsinogens: 87 ± 0.04% for PGA and 95 ± 0.09% for PGC. It is concluded that tubular secretion does not contribute to the high fractional excretion of pepsinogens and that both PGA and PGC are almost freely filtered through the glomerular basement membrane.
Renal Proton Magnetic Resonance in Experimental Acute Renal Failure in Rats
Authors: Iaina A. , Weininger J. , Abrashkin S. , Azoury R.
Published: November 2008

Cortical, medullary and papillary T1 and T2 water proton relaxation times were measured at 37°C, 20 MHz. The measurements were made using kidneys from rats affected by many forms of experimental acute renal failure (ARF), namely acute hemorrhagic hypovolemia, angiotensin II administration, antidiuretic hormone (ADH) administration, glycerol, and other nephrotoxins (gentamicin, cisplatinum, cyclosporine), renal artery occlusion for different periods of time, and ureteral ligation. From the T1· and PW (percent tissue water content) the bound water (FB) and HF (percent water bound/g solid) were calculated according to a fast proton diffusion model. In most experimental models studied, the experiments were repeated following paramagnetic enhancement with GdDTPA administration (70 mmol/kg BW). By profiling the deviations from normal, it was possible to differentiate the ischemic (shortened T1; prolonged T2), obstructive (very high T1· and T2 in both cortex and medulla) and nephrotoxic (prolonged T2) forms of ARF Significant changes in free/bound water compartments occurred, though their biological significance is unknown. T1· and T2 ratios before and after paramagnetic enhancement correlated well with estimates of glomerular filtration rate. In the first minutes following acute hemorrhagic hypovolemia, the intrarenal water distribution remained unchanged. After GdDTPA significant water proton T1 and T2 changes characterized the immediate posthemor-rhagic state similar to the effect of ADH.
Anemia Induces 5’-Nucleotidase in Fibroblasts of Cortical Labyrinth of Rat Kidney
Authors: Le Hir M. , Eckardt K.-U. , Kaissling B.
Published: November 2008

We recently observed a strong increase of 5’-nucleotidase in renal fibroblasts of rats that were anemic due to an immunity against erythropoietin. In order to test if the change of 5’-nucleotidase was related with anemia, we studied the distribution of the enzyme in irradiated rats treated with phenylhydrazine. The hematocrit of these rats decrased to 15% within 4 days and erythropoietin levels were more than 200 times over controls. After 7 days a histochemical study showed that the enzymatic activity and the immunoreactivity for 5’-nucleotidase was markedly enhanced in the fibroblasts of the cortical labyrinth. There was no modification of 5’-nucleotidase in other cell types of the kidney. The 5’-nucleotidase activity of renal fibroblasts in cell culture increased by 72% upon addition of 160 µM 5’-AMP to the culture medium for 8 days. We propose that anemia provokes an energy deficit in some structure in the cortical labyrinth. This might increase the concentration of 5’-AMP which would induce 5’-nucleotidase. An interesting consequence of these events would be an increased production of adenosine in the direct vicinity of some of its putative targets, the glomerular arterioles and the erythropoietin-producing cells.
Carbonic Anhydrase Activity in Madin Darby Canine Kidney Cells
Authors: Pfaller Walter , Gstraunthaler Gerhard , Kersting Ulrich , Oberleithner Hans
Published: November 2008

Madin Darby canine kidney (MDCK) renal epithelial cell cultures have been investigated with respect to their potency to express carbonic anhydrase activity using histochemical methods. Acetazolamide inhibitable carbonic anhydrase activity could be detected in the cytoplasmic compartment as well as in the apical membrane of cells when grown on solid culture supports. Cells forming domes in MDCK monolayers exhibit the highest histochemically detectable enzyme activity. The attempt to subculture clonal cell lines from MDCK monolayer cultures resulted in the establishment of 5 clones, slightly different with respect to size and shape of cells and their potency to form domes. Scanning electron microscopy ensured the identification of one clone (1A4), which distinctly differed from the others with respect to the apical membrane architecture. Co-localization of peanut agglutinin and carbonic anhydrase activity at the plasma membrane always revealed a combined occurrence of enzyme reactivity and lectin binding in the apical membrane domain. Both, lectin binding and carbonic anhydrase activity were distinctly more intense in plasma membrane regions equipped with microvilli. From the results it is concluded that MDCK cells in tissue culture retained properties of intercalated cells of the nephron collecting duct segment.
Endocytosis and Phosphate Transport in OK Epithelial Cells
Authors: Kempson Stephen A. , Helmle Corinna , Murer Heini
Published: November 2008

Endocytosis was studied in OK epithelial cells, an established cell line from opossum kidney. The presence of fluid-phase endocytosis in these cells was demonstrated by measuring cell uptake of lucifer yellow and horseradish peroxidase. The intracellular distribution of lucifer yellow fluorescence was consistent with uptake by endocytosis. Endocytosis was inhibited in medium made hyperosmolar by addition of sucrose. In hyperosmolar medium the action of parathyroid hormone on Na+/phosphate cotransport was significantly diminished. We suggest that an intact endocytic mechanism is required for the full inhibitory effect of parathyroid hormone on Na+/phosphate cotransport.
Fluorescence Measurement of Intracellular pH on Proximal Tubule Suspensions
Authors: Noël J. , Tejedor A. , Vinay P. , Laprade R.
Published: November 2008

BCECF is used for intracellular pH (pHi) measurement in microperfused tubules. In this case, the perfusate washes out all BCECF leaking from the cells away from the optical light path. We have explored the use of BCECF for pHi determination on suspensions of dog renal proximal tubules (Percoll). This raises specific problems due to the accumulation of BCECF in the extracellular compartment generated by desesterification of BCECF-AM during loading and to leaking of BCECF into the extracellular medium occurring during the waiting time and during the measurement procedure. Repeated washing of the suspension reduced in part this contamination but did not eliminate the continuous leakage of BCECF: the specific intracellular signal is progressively reduced. We have examined the use of anion exchange resin (Dowex 1X-8, 200-400 mesh, Cl- form) to bind the extracellular BCECF (negatively charged). Dowex beads glued to one wall of the cuvette out of the optical path constitute an optically neutral sink removing BCECF as it leaks out of the cells. Using this technique, we had estimated the pHi of dog proximal tubule to 7.374 ± 0.032 at extracellular pH of 7.325 ± 0.021. The cellular pH is acutely, but transiently, alkalinized by NH4Cl and acidified by Na acetate. The BCECF signal was calibrated using nigericin. This technique improves significantly the measurement of pHi by BCECF fluorescence in tissue suspensions.
Effect of Intrarenal Adenosine on Urinary Excretion of Prostaglandins and Leukotrienes in the Anesthesized Dog
Authors: Refoyo Antonia , Cosmes Pedro G. , Hidalgo Froilan , Diez Javier , Holgado Marina , García Jacinto , Macias Juan
Published: November 2008

Adenosine is a renal vasoconstrictor that plays an important role in mediating renal adaptive responses to decreases in renal perfusion pressure. It is known that adenosine acts on the metabolism of arachidonic acid, but the direct repercussions of adenosine in the production of renal prostaglandins and leukotrienes have not been studied. This study was undertaken to evaluate the effect of the intrarenal infusion of adenosine upon the urinary elimination of arachidonic acid derivatives. Samples of urine were collected with lysine acetylsalicylate and determination of prostaglandins (PGs) and leukotrienes (LTs) was performed by radioimmunoassay of samples previously separated by HPLC. The infusion of adenosine decreases the urinary excretion of 6-keto-PGF1α and TxB2 significantly. There was no significant change in urinary excretion of PGE2 while LTB4 and LTC4 showed a tendency to increase. These results suggest that a fall in the synthesis of PGI2 along with an increase in LTC4, which is a constrictor of mesangial cells, could be responsible for the renal vasoconstriction phase of adenosine. Therefore, it was concluded that adenosine vasoconstriction is mediated through the inhibition of the cyclo-oxygenase pathway, diminishing the synthesis of PG vasodilators.
Ion Channels in Urinary Bladder
Authors: Frings S.M. , Purves Robert D. , Macknight Anthony D.C.
Published: November 2008

Urinary epithelia separate urine from interstitial fluid. In the mammal, this tight epithelium has a limited transport capacity but is capable of moving sodium from urine to blood through an aldosterone-sensitive cellular pathway. In lower vertebrates, absorption of ions and water from the urine can contribute significantly to fluid and electrolyte homeostasis. Transepithelial ion transport and maintenance of cellular composition are interdependent, requiring a balance between movements across the apical and basolateral plasma membranes through a variety of pathways including electrodiffusion through ion channels. A variety of such channels has been identified in urinary epithelia. Apical membranes contain amiloride-sensitive, highly selective sodium channels of low conductance (≈5-10 pS). There is evidence that in mammalian bladders trypsin-like enzymes in the urine continually degrade these channels, decrease in cation selectivity being followed by loss of the channels from the membrane. New channels stored in the cytoplasm appear to provide a source for replenishment of the membrane. Other channels of higher conductance and lower selectivity have also been described in both mammalian and amphibian bladders, but their physiological significance remains to be established. Basolateral membranes contain potassium channels. In the mammalian bladder, in which chloride appears to be distributed at electrochemical equilibrium, chloride conductance exceeds potassium conductance and patch clamp studies have revealed a chloride channel of conductance ≈60 pS detectable immediately on patch excision and active at normal membrane potentials. In the amphibian bladdder, a variety of findings indicates the presence of a basolateral membrane chloride conductance, but patch clamp data are not yet available.
Kaliuretic Response to Potassium Loading in Amiloride-Treated Dogs
Authors: Yeyati Nesmo L. , Etcheverry Julio C. , Adrogué Horacio J.
Published: November 2008

To assess whether an intact mechanism of sodium transport in the distal nephron is a prerequisite for the development of a kaliuresis in response to an acute potassium load (0.4 M KCl, l ml/min), the effects of a simultaneous infusion of KCl and amiloride (1 mg/kg/h) were evaluated in anesthetized dogs. A major reduction in potassium excretion mainly due to a sharp decrease in urine + concentration to one tenth of control levels was found after amiloride. The simultaneous infusion of KCl and amiloride resulted in a rapid and major increase in kaliuresis that was accounted for mostly by the rise in urine K+ concentration. The increased kaliuresis after the acute potassium infusion was of similar magnitude when expressed as percent value of control to that previously reported in dogs not receiving amiloride; the absolute rates of K+ excretion, however, were only 2.7 and 7.3% (before and after KCl infusion, respectively) of the values in dogs not receiving amiloride. Our observations suggest that potassium infusion in the intact dog increases kaliuresis primarily as a result of a more favorable chemical gradient of this cation between blood and/or distal tubular cells and urine. Yet, when a chemical gradient is the only driving force of potassium secretion, as was the case in our amiloride-treated dogs, the absolute rate of kaliuresis is very modest. The presence of an unimpaired electrical profile and sodium transport mechanisms in the distal nephron, although not critical for the development of kaliuresis in response to a K+ load, accounts for a severalfold rise in renal potassium excretion above basal levels.
Evidence for Separate Carriers for Purine Nucleosides and for Pyrimidine Nucleosides in the Renal Brush Border Membrane
Authors: Le Hir Michel
Published: November 2008

The aim of the present study was to test if the transport of all nucleosides in rat renal brush border membranes occurs via a common carrier or if specific carriers exist for various groups of nucleosides. We measured the inward transport of radiolabeled nucleosides into brush border vesicles. The effect of unlabeled nucleosides present inside of the vesicles (trans-stimulation) or outside of the vesicles (cis-inhibition) was studied. Uphill influx of a nucleoside into the vesicles could be driven by the efflux of another nucleoside (trans-stimulation) if they were both purines or both pyrimidines but not if one nucleoside was a purine and the other one a pyrimidine. Thus, there exist a carrier that transports various purine nucleosides, and a carrier that transports various pyrimidine nucleosides, but the tested purine nucleosides and the tested pyrimidine nucleosides do not appear to be transported by the same carrier. Uridine and thymidine were similarly potent for the inhibition of cytidine transport whereas uridine was much more potent than thymidine for the inhibition of adenosine transport. This suggests that cytidine and adenosine can use different carriers. Preincubation of the vesicles with N-ethylmaleimide resulted in a marked decrease of the rate of transport of purine nucleosides but it had little effect on the transport of pyrimidine nucleosides. These data are best explained by the presence in the renal brush border membrane of two carriers, one for purine nucleosides, the other one for pyrimidine nucleosides. However the discrimination between purine nucleosides and pyrimidine nucleosides by the two putative carriers may not be absolute, as indicated by the finding that adenosine inhibited the transport of pyrimidine nucleosides and reciprocally.
Effect of Phosphate Deprivation on Enzymes of the Cyclic Adenosine Monophosphate Metabolism in Rat Proximal Convoluted and Proximal Straight Tubules
Authors: Berndt Theresa J. , Homma Sumiko , Yusufi Ahad N.K. , Dousa Thomas P. , Knox Franklyn G.
Published: November 2008

Phosphate deprivation causes a resistance to the phosphaturic effect of parathyroid hormone (PTH). The present study determined whether acute phosphate deprivation alters basal or stimulated activities of key enzymes of the cyclic adenosine menophosphate (cAMP) metabolism in microdissected proximal convoluted and proximal straight tubules, since blunted cAMP levels in these proximal subsegments might account for refractoriness to the effect of PTH on phosphate reabsorption in the proximal convoluted and proximal straight tubule segments. In the proximal convoluted tubules of rats fed a normal-phosphate diet (NPD), PTH increased the adenylate cyclase activity by tenfold. In the proximal convoluted tubule of rats fed a low-phosphate diet (LPD), PTH also increased the adenylate cyclase activity by tenfold. In addition, forskolin increased the adenylate cyclase activity to levels similar to PTH in the proximal convoluted tubule of rats fed NPD or LPD. In the proximal straight tubule of rats fed NPD PTH resulted in an approximately fivefold increase in adenylate cyclase activity. In the proximal straight tubule of rats fed LPD PTH resulted in a fourfold increase in adenylate cyclase activity. The forskolin-stimulated adenylate cyclase activity was markedly decreased (46%) in the proximal straight tubule of phosphate-deprived rats. The cAMP-phosphodiesterase activity in the proximal convoluted tubule was significantly increased by 26% in phosphate-deprived rats. The cAMP-phosphodiesterase activities in the proximal straight tubules from rats fed NPD or LPD were similar. We conclude that distinct differences in key enzymes of cAMP metabolism exist in the proximal convoluted and proximal straight tubule subsegments. Further, phosphate deprivation affects the cAMP-phosphodiesterase and adenylate cyclase activities differently in these nephron subsegments. These changes in cAMP-phosphodiesterase activity in the proximal convoluted tubule and the blunted adenylate cyclase activity in the proximal straight tubule due to phosphate deprivation would favor lower cAMP levels in those segments.
Electrophysiological Identification of Cell Types in Cortical Collecting Duct Monolayers
Authors: Bello-Reuss Elsa
Published: November 2008

Double-barrel microelectrodes were used to determine membrane voltages and the intracellular pH (pHi) in primary cultures of cortical collecting duct cells (CCD) grown in the absence of aldosterone. Electrophysiologically, two main cell types were identified. In cell type 1, the apical membrane voltage (Va) was -60 ± 5 mV. The fractional resistance of the apical membrane (fRa) was 0.40 ± 0.03, and pHi was 7.21 ± 0.04. Exposure to 50 mM K+ on the apical side depolarized Va by 21 ± 4 mV. When Cl- was replaced by cyclamate two types of responses were observed: (a) depolarization of Va by 26 ± 3 mV while pHi remained unchanged, and (b) no change in Va. In cell type 2, Va was -36 ± 5 mV, fRa was 0.91 ± 0.03 and increasing apical [K+] from 5 to 50 mM did not change Va. Two subpopulations were distinguished by the response of pHi to lowering apical [Cl-]. In one of them pHi increased from 6.99 ± 0.05 to 7.11 ± 0.07. In the other, pHi was significantly decreased from 7.16 ± 0.08 to 7.03 ± 0.07. These results are compatible with the conclusion that about 50% of the impaled cells type 2 have a Cl-/HCO-3 exchanger at the apical membrane. In summary, two different cell types can be identified electrophysiologically in CCD monolayers. Cell type 1 has the electrical characteristics of principal cells. Cell type 2 resembles the intercalated cells. The cell alkalinization observed in approximately 50% of the cells type 2 in response to Cl- removal suggests the presence of an apical Cl-/HCO-3 exchanger. Thus, these cells should be the bicarbonate-secreting cells. The remaining cells should correspond to the acid-secreting cells.
Na:K Pump Abundance and Function in MDCK Cells: Effect of Low Ambient Potassium
Authors: Kumar Satish , Berg Jeffrey A. , Katz Adrian I.
Published: November 2008

Side-specific expression and activity of Na:K pump was studied in Madin-Darby canine kidney (MDCK) cells, a tissue culture model of distal renal tubular epithelium, exposed to low ambient potassium. Confluent monolayers grown on teflon filters in dual chambers were treated with a low K+ medium from 45 min to 72 h. After both acute (45 min) and longer-term (24-72 h) exposure to low K+ (0.7 mM), cation cycling rate of existing pump units increased substantially, while there was no significant change in total cell Na-K-ATPase activity or in basolateral surface pump density. Although a small quantity of Na:K pumps ( < 10%) was consistently present apically, it also did not increase after exposure to low K+ or when the monolayers were provided K+ only from the apical side. In MDCK monolayers low K+ enhances the rate of K+ uptake by the existing pump units but does not increase the total number of pumps or their deployment on either cell surface.
Metabolic Heterogeneity of Isolated Cortical and Juxtamedullary Glomeruli in Adriamycin Nephrotoxicity
Authors: Kastner Sabine , Wilks Martin F. , Gwinner Wilfried , Soose Mechthild , Bach Peter H. , Stolte Hilmar
Published: November 2008

The anticancer drug adriamycin (ADR) is selectively toxic to glomerular cells when administered intravenously (5 mg/kg b.w.) to female MWF/Ztm rats. Recent data have shown that the proteinuria associated with the lesion does not occur in cortical glomeruli, suggesting the selective injury of juxtamedullary glomeruli. In the present study, the effect of ADR on glomerular metabolism was studied with special reference to possible differences between cortical and juxtamedullary glomeruli. On day 7 after ADR treatment, cortical and juxtamedullary glomeruli were separately isolated by the sieving method and 14C glucose oxidation to 14C02 and the incorporation of 3H proline into macromolecules were measured in vitro and used to study target selective injury in ADR-treated rats compared to control rats. The investigations revealed differences in the response of cortical and juxtamedullary glomeruli to ADR. ADR treatment increased proline incorporation over a 4-hour incubation period in both glomerular populations compared to controls, but the effect was significantly (p < 0.05) more pronounced in juxtamedullary glomeruli (juxtamedullary: 187 ± 8% of control; cortical: 167 ± 4% of control). Glucose oxidation was enhanced after 4 h only in juxtamedullary glomeruli (juxtamedullary: 132 ± 3% of control; cortical: 82 ± 10% of control). These data show that glomerular damage caused by ADR is associated with a stimulating effect on glomerular metabolism which is more marked in juxtamedullary than in cortical glomeruli, thus indicating a heterogenous response of different glomerular populations and supporting the concept that the selective damage of juxtamedullary glomeruli accounts for the proteinuria.
Evolving Concepts of the Intrarenal Renin-Angiotensin System in Health and Disease: Contributions of Molecular Biology
Authors: Schunkert Heribert , Ingelfinger Julie R. , Dzau Victor J.
Published: November 2008

Previous physiological and biochemical studies suggest the existence of an endogenous renin-angiotensin system (RAS) in the kidney. However, these data cannot exclude the contribution of the circulating RAS. Proof of the local synthesis of RAS components in the kidney has been obtained recently through the use of molecular biological techniques. Using Northern blot analysis, we have demonstrated the intrarenal expression of renin, angiotensinogen, and angiotensin-converting enzyme messenger RNAs. Employing in situ hybridization histochemistry, we have localized the intrarenal tissue sites of renin and angiotensinogen messenger RNA synthesis. Renin gene expression was found in cells of the juxtaglomerular apparatus. Angiotensinogen mRNA was primarily produced in the proximal convoluted tubule with lesser amounts in glomerular tufts and vasculature. These findings led us to hypothesize that the proximal tubule is a major site of renal Ang II synthesis and that locally synthesized Ang II might directly modulate tubular function. Both genes are subject to feedback regulation. Our studies showed that Ang II exerted a stimulatory effect on angiotensinogen but a negative feedback effect on renin gene expression. Dietary NaCl restriction stimulated the expression of both genes, although the onset of renin gene activation required more prolonged sodium chloride restriction. Furthermore, our data indicated that the sodium cation, irrespective of the anion, was primarily important in regulating renal angiotensinogen mRNA levels. Our studies also showed altered intrarenal renin or angiotensinogen expressions in pathophysiological states, e.g. in experimental heart failure and the spontaneously hypertensive rat. Taken together, these data support the existence of a intrarenal RAS and suggest its potential roles in the regulation of renal function in health and disease.
The Munich Wistar Frömter Rat: Proteinuria and Blood Pressure in Correlation to the Number of Superficial Glomeruli
Authors: Hackbarth Hansjoachim , Gwinner Wilfried , Alt Jeannette M. , Hagemann Inge , Thiemann Anke , Finke Barbara
Published: November 2008

Rats with a high number of superficial nephrons (MWF/Ztm) also show an elevated urinary protein excretion and a high systolic blood pressure. To investigate a possible correlation between the number of superficial glomeruli and these physiological changes, MWF/Ztm rats were crossed and backcrossed to Wistar cryptorchic (WC/Ztm) animals with no superficial nephrons in order to produce genotypes with differing numbers of superficial glomeruli. In the parental strains, the F1 hybrids and the 8 possible backcrosses, the number of superficial glomeruli, the distance of the 10 most superficial glomeruli to the renal surface, and the diameter of Bowman’s capsules were determined by morphometric analysis. The excretion of total protein, in detail low molecular weight proteins, albumin, and high molecular weight proteins were measured quantitatively in 5 males of each genotype. Systolic blood pressure was determined by a tail-cuff method in conscious rats. Means of each variate of the 12 available genotypes were linearly correlated and demonstrate a close correlation between the amount of superficial nephrons and the observed physiological changes, i.e. the more superficial the glomeruli the higher the urinary protein excretion, especially albumin, and the higher the systolic blood pressure.
Elevation of Renal Glutathione Enhances Ischemic Injury
Authors: Scaduto, Jr. Russell C. , Gattone, II Vincent H. , Martin Louis F. , Yang Harold C.
Published: November 2008

In a previous study, we tested the hypothesis that an elevated level of renal glutathione (GSH) would protect the kidney from ischemic injury. However, prior elevation of GSH with GSH monoethylester enhanced the injury induced by 35 min of ischemia and blood reflow [Scaduto RC Jr, Gattone VH, Grotyohann LW, et al; Effect of an altered glutathione content on renal ischemic injury. Am J Physiol 1988;255:F911-F921]. Additionally, GSH monoethylester produced morphologic alterations in the absence of ischemia. Thus the greater ischemic injury observed after GSH ester pretreatment could have been due to a synergistic effect between the events caused by ischemia and the pretreatment. The present study was conducted to evaluate the utility of elevating renal GSH levels by administration of GSH. Administration of GSH (1 mmol/kg body weight) caused a 3-fold elevation of renal GSH levels and a 6-fold elevation of renal cysteine levels after 60 min without causing changes in renal morphology or GFR. After 35 min of renal artery occlusion and 90 min of blood reflow, animals pretreated with GSH had a much greater decline in GFR than untreated control animals. This enhancement of renal ischemic injury in GSH-treated animals was similar to that observed following administration of GSH monoethylester. We conclude that administration of GSH is the method of choice for elevation of renal GSH and that elevation of renal GSH leads to an enhanced ischemia-induced injury which is independent of the method employed to elevate renal GSH.
Permeability of the Macula densa Basement Membrane Area to High Molecular Weight Molecules
Authors: Bell Darwin , St. John Patricia L. , Speyer Matthew , Abrahamson Dale R.
Published: November 2008

To investigate the permeability properties of the basement membrane beneath macula densa cells and between extraglomerular mesangial cells, thick ascending limbs with attached glomeruli were dissected from rabbit kidney and incubated in a Ringers solution containing either horseradish peroxidase (HRP) (1 mg/ml; molecular weight -40,000) or native or cationic ferritin (both at 5 mg/ml molecular weight -450,000) for 5 and 20 min at room temperature. Tubules were processed for electron microscopy. At both time points, HRP reaction product fully permeated the matrix material between extraglomerular mesangial cells, the basement membrane underneath the macula densa, and also was occasionally located in intercellular spaces and intracellular vesicles within macula densa cells. Similar results were obtained with native and cationic ferritin. In separate experiments, thick ascending limbs with attached glomeruli were perfused for 20 min at room temperature with a Ringer solution containing HRP (1 mg/ml). HRP was found in tubulovesicular bodies within the apical cytoplasm of macula densa cells again indicating that these cells exhibit endocytotic activity. However, HRP did not gain access to intercellular spaces indicating that the apical junctional complex was impermeable to HRP. These results demonstrate that the macula densa basement membrane and matrix material between extraglomerular mesangial cells is permeable to high molecular weight molecules and suggest unhindered diffusion of water and solutes within this area.
Mechanism of Acetazolamide-Induced Rise in Renal Vascular Resistance Assessed in the Dog Whole Kidney
Authors: Yeyati Nesmo L. , Altenberg Guillermo A. , Adrogué Horacio J.
Published: November 2008

The reduction in renal blood flow (RBF) and glomerular filtration rate (GFR) observed after the administration of the carbonic anhydrase inhibitors acetazolamide and benzolamide had been explained as due to activation of the tubuloglomerular feedback mechanism. If correct, pharmacologic blockade of this pathway should prevent the development of renal vasoconstriction with the carbonic anhydrase inhibitors. Thus, the current study evaluates in the dog whole kidney the effect of acetazolamide (20 mg/ kg body weight) in the presence or absence of furosemide (5 mg/kg body weight), a drug which blocks the tubuloglomerular feedback. Acetazolamide resulted in a large increase in urinary bicarbonate excretion accompanied by a significant reduction in GFR (16%) and RBF (18%). By contrast with the effects of acetazolamide, furosemide did not alter GFR and increased RBF. In addition, the loop diuretic induced a large chloruresis without changes in urinary bicarbonate excretion. The infusion of acetazolamide in furosemide-treated dogs resulted in a significant increment in renal bicarbonate excretion and in a significant reduction in the levels of both GFR (28%) and RBF (13%). Therefore, furosemide pretreatment did not block the effects of acetazolamide on renal hemodynamic parameters. Consequently, the acetazolamide-induced reduction in both GFR and RBF cannot ba accounted for by changes in chloride levels in the juxtaglomerular region due to enhanced salt transport in the macula densa/distal nephron. The increased renal vascular resistance observed with acetazolamide might occur by either a direct effect of this agent on the renal circulation or as a result of changes in intrarenal pressure secondary to the inhibition of proximal fluid reabsorption.
Tubular CO2 Production from Glutamine in the Rat: Segmental Profile and Modulation
Authors: Mujais Salim K. , Zahid Mohammed
Published: November 2008

The present study was designed to test whether tubular carbon dioxide production from the carbon skeleton of uniformly 14C-labelled glutamine exhibits quantitative and qualitative segmental heterogeneity. Our results show that CO2 production from glutamine in the proximal convoluted tubule (PCT) was dependent on substrate concentrations and is saturable at 10-4M of glutamine. Glutamine oxidation was demonstrable in all nephron segments examined. The PCT is the quantitatively predominant site of glutamine oxidation. Intermediate nephron segments, however, such as the thick ascending limb (MAL) and the distal convoluted tubule possess a significant capacity for glutamine oxidation, particularly when examined in terms of tubular protein content. Modulation of glutamine oxidation by extracellular pH was segment specific. Stimulation by acidosis and inhibition by alkalosis were observed in the PCT while carbon dioxide production from glutamine in the MAL was pH-insensitive. Glutamine oxidation was closely linked to sodium transport and greatly decreased by inhibition of Na-K-ATPase. In both the PCT and MAL, glutamine oxidation was inhibited by high extracellular potassium concentrations and in the PCT enhanced by extracellular hypokalemia. N-Ethyl maleiamide, an inhibitor of proton ATPase, led to almost complete cessation of CO2 production from the substrate in both PCT and MAL. Acetazolamide, an inhibitor of carbonic anhydrase, led to a partial reduction in carbon dioxide formation in the PCT, but did not affect glutamine oxidation in the MAL. We conclude that segmental qualitative heterogeneity characterizes oxidation of the carbon skeleton of glutamine with proximal segments showing the predictable effects of pH changes and carbonic anhydrase inhibition. The MAL appears to be nonmodulating.
Isoproterenol Infusion Increases the Maximal Tubular Capacity of Phosphate Reabsorption
Authors: LeClaire Michele , Berndt Theresa J. , Knox Franklyn G.
Published: November 2008

Isoproterenol, a β-adrenoreceptor agonist, decreases urinary phosphate (Pi) excretion; however, plasma phosphate concentration also decreases. The purpose of the present study was to determine the effect of isoproterenol infusion on phosphate reabsorption with concomitant phosphate infusions and in the presence and absence of parathyroid hormone (PTH). Clearance experiments were performed on male Sprague-Dawley rats which were acutely thyroparathyroidectomized (TPTX) and successive infusions of phosphate (1, 2, and 3 µmol/min) were used to determine the maximal tubular capacity of phosphate reabsorption (TmPi) factored for the glomerular filtration rate (GFR) in four groups of rats. In the saline-infused control group the Tmpi/GFR was 2.87 ± 0.19 µmol/ml (n=8). When isoproterenol was infused intravenously at a rate of 0.005 mg/kg/min, urinary cAMP excretion was significantly increased and the TmPi/GFR was 3.53 ± 0.17 µmol/ml (n=10, p < 0.05). In the PTH-infused group (33 U/kg bolus followed by a sustaining infusion of 1 U/kg/min) Tmpi/GFR was 1.69 ± 0.15 µmol/ml (n=9). Coadministration of isoproterenol and PTH significantly increased the TmPi/GFR to 3.25 ± 0.64 µmol/ml (n=9). Basal cAMP excretion was similar in both groups. These results demonstrate that the stimulation of renal β-adrenoreceptors by isoproterenol infusion markedly increases phosphate reabsorption and reverses the decrease in the maximal tubular capacity of phosphate reabsorption induced by PTH infusion.
Renal Transport of Endogenous Amino Acids
Authors: Fleck Ch.
Published: November 2008

Repeated adminisatration of triiodothyronine (T3, 20 µg/l00 g b.w., once daily for 3 days) or dexamethasone (60 µg/l00 g b.w., once daily for 3 days) caused significant changes of amino acid plasma concentrations in young (10 days old) and adult rats (2 months old). After treatment with T3, in young animals concentrations of β-alanine, aspartic acid, glutamic acid, ornithine, asparagine, leucine, taurine, serine, alanine, and glutamine were enhanced, whereas those of tyrosine, arginine, and threonine were significantly diminished. In adult rats only slight changes occurred after both T3 and dexamethasone. In the kidney, the reabsorbed fraction of amino acids was enhanced after both T3 and dexamethasone treatment in young rats, whereas in adult rats the two hormones were without influence on tubular reabsorption of amino acids. Taken together, both different plasma concentrations of amino acids and changes in amounts of amino acids reabsorbed in the tubuli, in adult rats the fractional excretion of amino acids was nearly unchanged following hormone treatment (exception: significant increase in taurine clearance). But in young animals the fractional excretion was reduced in 15 of 22 amino acids after dexamethasone and in 12 of 23 amino acids after T3 treatment, indicating stimulatory effects of both hormones on tubular amino acid carrier systems in immature animals.
C-Reactive Protein and Reclassification of Cardiovascular Risk in the Framingham Heart Study
Authors: Wilson Peter W.F. , Pencina Michael , Jacques Paul , Selhub Jacob , D'Agostino Ralph , O'Donnell Christopher J.
Published: November 2008

Background—

The relationship of circulating levels of high-sensitivity C-reactive protein (CRP) with cardiovascular disease (CVD) risk, particularly with consideration of effects at intermediate levels of risk, has not been fully assessed.

Methods and Results—

Among 3006 offspring participants in the Framingham Heart Study free of CVD (mean age, 46 years at baseline), there were 129 hard coronary heart disease (CHD) events and 286 total CVD events during 12 years of follow-up. Cox regression, discrimination with area under the receiver operating characteristic curve, and net reclassification improvement were used to assess the role of CRP on vascular risk. In an age-adjusted model that included both sexes, the hazard ratios for new hard CHD and total CVD were significantly associated with higher CRP levels. Similar analyses according to increasing homocysteine level showed significant protective associations for hard CHD but not for total CVD. In multivariable analyses that included age, sex, systolic blood pressure, total cholesterol, high-density lipoprotein cholesterol, diabetes mellitus, current smoking, hypertension treatment, and homocysteine, the log CRP level remained significantly related to development of hard CHD and total CVD and provided moderate improvement in the discrimination of events. The net reclassification improvement when CRP was added to traditional factors was 5.6% for total CVD (
P
=0.014) and 11.8% for hard CHD (
P
=0.009).

Conclusions—

Circulating levels of CRP help to estimate risk for initial cardiovascular events and may be used most effectively in persons at intermediate risk for vascular events, offering moderate improvement in reclassification of risk.
Topical Review: Long-Term Developmental Outcome of Asphyxiated Term Neonates
Authors: Dilenge Marie-Emmanuelle , Majnemer Annette , Shevell Michael I.
Published: November 2008

Asphyxia remains one of the main causes of later disability in term infants. Despite many publications identifying possible predictors of outcome in this population of interest, little is known of the long-term developmental outcome of asphyxiated term neonates. Observational studies have largely focused on short-term outcomes, with an emphasis on significant neurologic sequelae and intellectual impairments. This article reviews the literature that has described the developmental outcome of asphyxiated term newborns. As part of this review, we have also highlighted the evolution of the definition of asphyxia and delineated appropriate markers that should be used in future research on this population. ( J Child Neurol 2001;16:781—792).
Muromonab-CD3—Induced Neurotoxicity
Authors: Thaisetthawatkul Pariwat , Weinstock Arie , Kerr Susan L. , Cohen Michael E.
Published: November 2008

Muromonab-CD3 is widely used for immunosuppression in patients undergoing solid organ transplant. We report two siblings with oligomeganephronia and end-stage renal disease who developed encephalopathy and seizures from muromonab-CD3 following renal transplant. The first case is a 13-year-old girl who developed encephalopathy, seizure, and triparesis following renal transplant while muromonab-CD3 was used for immunosuppression. The second case was the 6-year-old sister of the first case, who also developed recurrent focal seizures while she was on muromonab-CD3 for renal transplant immunosuppression. In both cases, a sequential brain magnetic resonance image (MRI) showed progression of abnormalities from the cerebral cortex to the white matter. In the first case, the MRI normalized after muromonab-CD3 was discontinued. In the second case, the patient developed a leukoencephalopathy following cyclosporin administration. The pathophysiology of muromonab-CD3 encephalopathy is believed to be a disturbance to the blood—brain barrier mediated by cytokine release from lymphocyte stimulation by muromonab-CD3. Because the major histocompatibility complex genes are known to regulate cytokine responses, it is possible that the excessive production of cytokines that causes encephalopathy may occur in patients who share close major histocompatibility complex genes. Muromonab-CD3 in a patient whose sibling has developed cerebral complications from its use should be administered with caution. The second case suggests that muromonab-CD3 encephalopathy predisposes patients to develop cyclosporin neurotoxicity. Because the pathogenesis of muromonab-CD3 encephalopathy and cyclosporin-related cerebral complications are both potentially mediated through a disturbance of the blood—brain barrier, it is possible that one agent may predispose a patient to the complication of the other. ( J Child Neurol 2001;16:825—831).
Congenital Hydranencephalic-Hydrocephalic Syndrome With Proliferative Vasculopathy: A Possible Relation With Mitochondrial Dysfunction
Authors: Castro-Gago Manuel , Iglesias-Diz Manuel , Ucieda-Somoza Rafael , Silva-Villar Inés , Codesido-Lopez José , Viso-Lorenzo Augusto , Arenas Joaquin , Eiris-Punal Jesus
Published: November 2008

We report the case of a fetus aborted at gestation week 20 because of hydranencephalic-hydrocephalic syndrome. The fetus was the third pregnancy of a nonconsanguineous couple whose first child exhibited congenital hydranencephalic-hydrocephalic syndrome associated with muscle histology findings consistent with mitochondrial cytopathy and deficiency of complexes III and IV of the respiratory chain and whose second pregnancy had terminated in an elective abortion on detection of progressive hydrocephalus at gestation week 19. The third pregnancy had a normal course according to obstetric and ultrasonography examinations performed at gestation weeks 5, 10, and 15, and negative results were obtained in standard serologic and polymerase chain reaction (PCR) tests for prenatal infections of the mother. However, the ultrasonography examination at gestation week 18 revealed hydrocephalus, in response to which the parents requested an abortion, which was performed at gestation week 20; the fetus was male and with no evident external malformations. Histopathologic studies of the brain and medulla oblongata revealed proliferative vasculopathy (glomeruloid vessels, intracytoplasmic inclusions, and microcalcifications) and intracytoplasmic inclusions in the voluntary muscle. Microbiologic and PCR tests of hepatic and spleen tissue were negative for prenatal infections. In view of the precedent of a sister with mitochondrial dysfunction, these findings raise the possibility that at least some cases of familial syndrome of congenital hydranencephalic-hydrocephalic syndrome with proliferative vasculopathy can be attributed to alterations in the mitochondrial respiratory chain. ( J Child Neurol 2001;16:858—862).