bluuebunny/crossref_metadata_2025 huggingface dataset:
Studies on the Nephron Segment with Reduced Sodium Reabsorption during Starvation Natriuresis
Authors: Satta Andrea , Faedda Rossana , Olmeo Antonina , Soggia Giovanni , Branca Franco , Bartoli Ettore
Published: November 2008

The segment of the nephron where carbohydrate deprivation depresses Na transport leading to natriuresis was sought by a new clearance technique designed to measure segmental reabsorption in each portion of the human renal tubule. Experiments were performed during maximal water diuresis before and 4 days after carbohydrate withdrawal. Proximal reabsorption had fallen from 70 ± 4 to 60 + 5 ml ■ min-1 p < 0.05, by the 4th day of sugar deprivation, accounting for the natriuresis and the associated weight loss of 1.8 kg. By the 4th day of fasting, when Na excretion had returned to control levels, GFR had fallen nonsignificantly from 99 ± 6 to 95 ± 5 ml · min-1, while Na reabsorption along distal segments had risen. In fact, Na transport, expressed by the equivalent volumes of solute free-water generated, rose from 17.4 ± 3.4 to 23.6 ± 2.1 along the ascending limb of Henle’s loop, and from 8.1 ± 0.8 to 9.2 ± 1.3 ml · min-1 · GFR-1 · 100 along the distal tubule. Thus, analysis of segmental Na transport by this method discloses that starvation natriuresis is a proximal tubular event, progressively counterbalanced by enhanced Na reclamation in more distal sites. Volume contraction and the attendant fall in GFR concur to curb delivery out of the proximal tubule which is matched by enhanced distal Na reabsorption till a new steady-state excretion is attained.
Effects of Phosphate and Calcium Infusion on Renal Phosphate Transport in the Dog
Authors: Wong Norman L.M. , Quamme Gary A. , Dirks John H. , Sutton Roger A.L.
Published: November 2008

The effect of phosphate infusion on renal tubular handling of calcium and phosphate was examined in dogs which had been thyroparathyroidectomized (TPTX) immediately prior to the studies. Phosphate infusions in TPTX animals caused a small decrease in total and ultrafilterable plasma calcium, and decreased phosphate reabsorptive capacity in the proximal tubule and loop segment. Infusion of CaCl2 during phosphate loading to offset the fall in plasma calcium prevented the reduction in proximal phosphate reabsorptive capacity. However, between the proximal and distal sampling site, the reduction in phosphate reabsorptive capacity could not be prevented by CaCl2 administration. These data are consistent with the presence of two phosphate transport systems; one in the early proximal tubule, modulated by changes in plasma calcium level, and a second in the loop segment, which is independent of calcium. While the data suggest that the depression of proximal phosphate reabsorption during phosphate infusion may be secondary to the fall in plasma calcium concentration, they do not exclude a direct effect of infused phosphate on proximal phosphate reabsorption that may be antagonized by an opposing direct effect of the calcium infusion.
Lysosomal Heterogeneity of Dipeptidyl Peptidase II Active on Collagen-Related Peptides
Authors: Andersen Knut-Jan , McDonald Ken
Published: November 2008

The subcellular distribution of dipeptidyl peptidase II (DPP II) in the rat kidney cortex, as determined by subfractionation of the mitochondrial/lysosomal fraction by rate sedimentation, indicated that this enzyme is mainly associated with the large, fast sedimenting lysosomes (protein droplets). The small lysosomes, on the other hand, displayed considerable size heterogeneity as indicated by the broad distribution of DPP II; cathepsin B, and a tripeptidyl peptidase active on Gly-Pro-Met-2-naphthylamide at pH 4 (TPP 4). Cathepsin D and N-acetyl-β-D-glucosaminidase were limited primarily to the slower-sedimenting, small lysosomes. Equilibrium banding in sucrose gradients of the two main DPP II-containing lysosomal populations showed that the large lysosomes banded at a density of 1.235-1.24 g/ml while small lysosomes banded at three densities: 1.11-1.15 g/ml (lysosomal fragments), 1.20 g/ml (light lysosomes), and 1.235 g/ml (dense lysosomes). Identical distribution pattern were obtained for DPP II using either Lys-Ala-7-(4-methyl)coumarylamide or Gly-Pro-2-naphthylamide as the substrate at pH 5.5 and 5.0, respectively. Notably, DPP II and TPP 4, and cathepsin B as well, gave banding densities and distributions that were consistent with a lysosomal localization. Since triplets of the Gly-Pro-X-type released by the TPP 4 are ideal substrates for DPP II, the integrated action of tripeptidyl and dipeptidyl peptidases could make a novel contribution to the renal depolymer-ization and reabsorption of polypeptides, in particular the proline-rich, collagen-derived sequences that possess repeating-triplet primary structures.
87Rb, 23Na and 31P Nuclear Magnetic Resonance Spectroscopy of the Perfused Rat Kidney
Authors: Allis Jonathan L. , Endre Zoltan H. , Radda George K.
Published: November 2008

87Rb, 23Na and 31P nuclear magnetic resonance (NMR) were used to monitor changes in renal cations and energetics during the induction of hypoxia in the isolated perfused rat kidney. The NMR-determined unidirectional Rb+ flux in normoxic kidneys was shown to be a good measure of net intracellular K+ influx in the perfused rat kidney model. The changes in 87Rb, 23Na and 31P spectra following the induction of hypoxia are consistent with hypoxic depletion of intracellular adenosine triphosphate (ATP) and a subsequent decrease in Na-K-ATPase transport activity. The exponential rate constant for 87Rb+ efflux measured during Rb+ uptake in normoxic kidneys (0.12 ± 0.01 min1) was not significantly different to the rate constant for 87Rb+ efflux during the induction of hypoxia (0.16+0.07 min-1). We conclude that there is no direct effect of hypoxia on renal cellular membrane integrity and that renal cell sensitivity to hypoxia is due to an inability to sustain cellular ion gradients following depletion of intracellular ATP.
Magnetic Resonance Study of Renal Transplantation
Authors: Chan Laurence , Shapiro Joseph I.
Published: November 2008

In the last few years, we have focused our research effort on the magnetic resonance spectroscopic (NMR) studies of organ transplantation in the rat. P-31 NMR was employed to study changes in high-energy phosphates, intracellular pH in vivo of transplanted kidneys either during normal function, while undergoing the rejection process or subjected to other insults (e.g. ischemia, cyclosporine nephrotoxicity, urinary obstruction) which may also cause graft dysfunction. Nuclear magnetic resonance (NMR) parameters, specifically relative peak areas and intracellular pH, accurately distinguished among the different causes of graft dysfunction. Ureteral obstruction was clearly identified by elevations in the phosphodiester/urine phosphate peak. Ischemia and rejection were both associated with increases in inorganic phosphates and phosphomonesters and decreases in the beta-phosphate peak of adenosine triphosphate but were distinguishable from each other by differences in intracellular pH which was normal in rejected allografts (7.33 ± 0.07, n = 3) and low in ischemic allografts (7.00 ± 0.05, n = 3, p < 0.05). Grafts insulted with cyclosporine toxicity were not distinguishable from normal allografts by any of the parameters studied. To determine the temporal relationship of NMR changes in allograft rejection, similar studies were performed serially in a group of rejecting (R) kidneys (n = 7) and compared with a control group of nonrejecting (NR) kidneys (n = 7). Major decrease in adenosine triphosphate (ATP) with increases in Pi and a marked increase in the Pi/ATP ratio were noted in the R allografts over time. The R allografts could be completely segregated from the NR allografts on the basis of the Pi/ATP ratio by day 7. These data suggest that 31P NMR spectroscopy may have potential clinical application in differentiating among the causes of graft failure of human renal allografts.
Acute Effects of Angiotensin II on Renal Haemodynamics and Excretion in Conscious Dogs
Authors: Keil J. , Lehnfeld R. , Reinhardt H.W. , Mohnhaupt R. , Kaczmarczyk Gabriele
Published: November 2008

The effects of a 60-min intravenous infusion of angiotensin II (A II; 4 or 20 ng A II/min/kg body weight) on renal blood flow (RBF; electromagnetic flow transducer, control value 19-25 ml/min/kg), glomerular filtration rate (GFR; control value 4.2–5.0 ml/min/kg), mean arterial blood pressure, sodium excretion, water excretion, and plasma AII and plasma aldoste-rone concentrations were examined in 6 chronically instrumented female conscious beagle dogs kept on three different dietary sodium intakes (SI): SI 0.5 or SI 2.5 mmol Na/kg/day or SI 4.5 mmol Na/kg/day plus an oral saline load prior to the experiment SI 4.5(+) dogs. Four nanograms A II decreased RBF and GFR in SI 4.5(+) dogs without changing the filtration fraction (FF%); in SI 0.5 dogs the RBF decreased, and the FF% increased. Twenty nanograms A II decreased RBF and increased FF% in all dietary protocols, less in SI 4.5(+) dogs. The mean arterial blood pressure increased in all dietary protocols by 10-15 mm Hg (4 ng A II) and 32-37 mm Hg (20 ng A II). Sodium and water excretions decreased by 32 and 46% respectively, in SI 4.5(+) dogs at both doses of A II. The plasma aldosterone concentration increased in all but one protocol: 4 ng A II, SI 4.5(+) dogs. It is concluded that when A II plasma concentrations are most likely borderline to pathophysiological conditions (up to an average of 370 pg/ml), the GFR is less decreased than the RBF. This phenomenon also can be observed at lower plasma AII concentrations (average 200 pg/ml), when the renin-angiotensin system had been previously moderately activated.
Production of Urea from Arginine in Pars recta and Collecting Duct of the Rat Kidney
Authors: Levillain Olivier , Hus-Citharel Annette , Morel François , Bankir Lise
Published: November 2008

Urea production from arginine was studied in vitro in the kidney of normal rats in tubule suspensions of the four different renal zones (cortex, outer and inner stripe of outer medulla, and inner medulla), and in individual microdissected nephron segments. Tissue was incubated with L-[guanido-14C]-arginine to measure cellular arginase activity. Addition of urease to the incubate freed 14CO2 from the 14C-urea formed by arginase and released from the cells. CO2 was trapped in KOH and counted. These experiments revealed that significant amounts of urea are produced in the outer stripe and in the inner medulla. This intrarenal urea generation takes place mainly in the proximal straight tubule and in the collecting duct, with increasing activity in these two structures from superficial to deep regions of the kidney. Urea is known to play a critical role in the urinary concentrating process. The fact that some urea can be produced in the mammalian kidney, and that the two structures showing this capacity are straight portions of the renal tubular system descending along the corticopapillary axis suggest that this urea production might play a role in the formation and/or maintenance of the medullary urea concentration gradient.
The Presence of HCO3- Does Not Inhibit Alpha-Adrenergic Increases in Proximal Tubular Intracellular pH
Authors: Gesek Frank A. , Schoolwerth Anton C.
Published: November 2008

Hormonal stimulation of Na+/H+ exchange increased intracellular pH (pHi) in a dose-dependent manner in proximal tubules suspended in Krebs-Henseleit buffer (KHB) supplemented with 25 mM HCO3- and CO2 (KHB+HCO3). The maximum increase in pHi was approximately 45% of the response observed with segments suspended in bicarbonate-free buffer (KHB-HCO3) and the time required to achieve maximum pHi alterations was significantly increased (p < 0.05) in the presence of KHB + HCO3 when compared to responses obtained in KHB-HCO3. Dose-response curves for agonist-induced pH increases were shifted to the right by a factor of 10 for segments suspended in KHB + HCO3. Increases in pH, induced by agonists in KHB + HCO3 were effectively blocked by pretreatment with 10 µM ethylisopropyl amiloride but not with the Cl-/HCO3- inhibitor, DIDS (0.1 mM, 30 min). We conclude that stimulation of α-adrenergic receptors on proximal nephrons increased pH, due to activation of Na+/H+ exchange and can be detected in the presence of HCO3- although the time course and maximum level of change differ significantly from those observed in a HCO3--free buffer.
Modification of Membrane Protein Expression and Protein Secretion in LLC-PK1 Cultures Grown on Different Carbohydrates
Authors: Frick Harold , Gstraunthaler Gerhard , Pfaller Walter
Published: November 2008

Membrane glycoproteins and glycolipids play an important role in epithelial organization, transport and function. To study the effects of exogenous carbohydrates on the expression of glycoproteins, cells of the renal epithelial line LLC-PK1 were cultured on different nutritive carbohydrate sources and on uridine, which is, despite striking differences, known to substitute all essential nutritive functions of glucose. LLC-PK1 cultures were long-term adapted to growth in culture medium containing 0.5, 5, 10 and 25 mM glucose, and 5mM fructose, galactose and uridine, respectively, as the sole carbohydrate source. These growth conditions elicited adaptive changes in the expression of enzyme activities of alkaline phosphatase and γ-glutamyltranspeptidase, integral membrane glycoproteins exclusively localized in the apical membrane of LLC-PK1 cells. SDS-PAGE of membrane preparations of adapted LLC-PK1 cells revealed a strong induction of several protein bands between 13.5 and 47 kD in fructose-grown cells, while in plasma membranes of cells grown in galactose several protein bands between 62 and 70 kD decreased. Changes in the secretion pattern of proteins into the culture medium were most prominent in uridine-grown cells compared to controls grown on 25 mM glucose.
The Kinetics of Papillotoxic Doses of 3H-N-Phenylanthranilic Acid in Rats
Authors: Whittingham Alan , Delacruz Ligia , Gregg Neil J. , Albores Amulfo , Ijomah Patricia , Bach Peter H.
Published: November 2008

N-phenylanthranilic acid (N-PAA; 4mmol/kg/day p.o.) causes a diffuse renal papillary necrosis and a polyuria in 7 days. A single dose of 3H-N-PAA was widely distributed with second-order elimination kinetics, t½ ± 50 h for stomach, heart, kidney, and bladder and t½ ≧90 h for liver, spleen, muscle and lung. The estimated plasma t½ = 10.2 h, and over 75% was excreted via urine in 36h and 13% via faeces in 72 h. In chronically cannulated animals 29% of N-PAA-derived material was in bile and 24% in urine at 36 h, which suggests enterohepatic circulation. Bile and urine contained several metabolites but no parent compound. Multiple doses for 8 and 16 days increased urinary N-PAA excretion to 90% in 36 h, but faecal contents decreased to 6-8% in 72 h and plasma t1/2 to ≤ 7.5h.
Patch Clamp Studies of the Amphibian Nephron
Authors: Hunter Malcolm
Published: November 2008

Transepithelial transport, intracellular ion activities and membrane potentials are all affected by changes in the conductive properties of the membranes of polarised epithelial cells. Conventional electrophysiological techniques have already determined the major conductances of the apical and basolateral membranes of the various nephron segments. These conductances are presently being studied at the molecular level with the aid of the patch clamp technique. In the case of the amphibian nephron, single-channel studies have been carried out in the proximal and early distal (diluting) segments. Almost all of the channels described so far have been selective for potassium, and the properties of these channels are described in this review. In addition, the basic electrophysiological and transport properties of these two general nephron segments are briefly described. From the physiological stand-point, the results of single-channel studies are providing us with information concerning the regulation of the conductances by intracellular mediators, allowing us to make predictions about the effects of various perturbations on cell membrane conductances. On the other hand, biophysical analysis is giving information ranging from the voltage dependence and ion selectivity of the channels to clues concerning their submicroscopic structure.
Pelvic Pressure and Tubuloglomerular Feedback in Hydronephrosis
Authors: Morsing Peter , Persson Erik G.
Published: November 2008

From previous studies on hydronephrotic rats in our laboratory, an increased sensitivity of the tubuloglomerular feedback (TGF) mechanism was found during extracellular volume expansion (VE). In contrast, the mechanism resets to a lower sensitivity during VE in control animals. The resetting in hydronephrotic rats was reversed by blocking the thromboxane (Tx) system. The present study was performed to measure changes in pelvic pressure (Pp) in hydronephrotic kidneys during VE, and the effect of Tx inhibition on those changes. In addition, TGF was characterized during VE of hydronephrotic rats while Pp was kept at the pre-VE level. On VE, Pp increased moderately from a control value of 2.9 mm Hg to a plateau with a mean value of 6.0 mm Hg (control, 0.7 vs. 2.1 mm Hg). After Tx inhibition, Pp was increased by more than 100%, with a plateau value of 13.6 mm Hg. When Pp was normalized and fixed, the direction of resetting of TGF was normal. The results from this study indicate that the resetting of TGF is of importance to keep glomerular filtration rate low and reduce Pp in the hydronephrotic kidney. Tx and Pp are involved in the resetting of TGF.
Isovolumetric Regulation of Renal Proximal Tubules in Hypotonic Medium
Authors: Lohr James W.
Published: November 2008

Isolated nonperfused proximal tubules maintained their cell volume at a constant level (isovolumetric regulation, IVR), when osmolality of the bathing medium was gradually decreased from 290 to 190mosm at 1.5 and 5.0mosm/min. Hypotonic IVR was blocked by inhibiting the Na+-K+ pump with ouabain (10-4M) when osmolality was decreased at 1.5 or 5 mosm/min. Concentration-dependent inhibition of cell volume maintenance was observed in the presence of the K+ channel blocker barium (10-3-10-2 M) when osmolality decreased at 5 mosm/min. Quinine (10-3M), another K+ channnel blocker, also inhibited IVR at osmolality decreases of 1.5 and 5 mosm/min. These results suggest that the maintenance of constant cell volume during gradual hypoosmotic exposure involves mechanisms that depend on intact Na-K-ATPase and the controlled loss of intracellular K+.
Renal Ammoniagenesis during the Recovery Phase of Postischemic Acute Renal Failure in the Dog1
Authors: Montañés Inmaculada , Badia Alfredo , Réngel Manuel A. , López-Novoa José M.
Published: November 2008

Renal ammoniagenesis has been studied in 6 dogs before and 48 h after a 60-min period of renal ischemia induced by clamping the renal artery and in 6 sham-operated animals. Two days after temporary renal ischemia, the dogs showed a 25% decrease in glomerular filtration rate and renal plasma flow and a similar decrease in sodium reabsorption. Renal production of ammonium was not significantly different under basal conditions or 2 days after ischemia, but more ammonia was released by the urine in the postischemic dogs. Renal uptake of glutamine was similar in control and in postischemic kidneys. It is concluded that during the recovery phase of the ischemia, renal ammoniagenesis is conserved.
Calcium-Dependent Effect of Gentamicin on Glucose Formation in Isolated Rabbit Kidney-Cortex Tubules
Authors: Michalik Mariusz , Biedermann Ireneusz , Bryla Jadwiga
Published: November 2008

In contrast to the inhibition by gentamicin of glucose production from propionate, pyruvate and lactate in renal tubules incubated at 2.5 mM Ca2+, this antibiotic does not affect gluconeogenesis from propionate and lactate, and significantly stimulates this process from other substrates at 0.5 mM Ca2+. This may be due to the gentamicin-induced increase of the cytosolic manganese content (from 1.7 to 2.7 nmol/mg protein), resulting in a stimulation of cytosolic phosphoenolpyruvate carboxykinase activity. At 2.5 mM Ca2+ the cytosolic Mn content (2.7 nmol/mg protein) seems to be high enough to accomplish activation of the enzyme.
Electrophysiological Study of L-Lysine Transport across Triturus Proximal Tubule: Evidence for Na+-Independent Entry and Na+-Dependent Exit
Authors: Nunokawa Tomoh , Hoshi Takeshi
Published: November 2008

Cell membrane depolarization induced by intraluminal injection of lysine was entirely independent of the presence of Na+ in Triturus proximal tubule, confirming our previous observation. The amplitude of the depolarization conformed to Michaelis-Menten kinetics regardless of the presence or absence of Na+ in the perfusion solutions. pH of the intraluminal solution had no effect on the electrical response in its range from 5.5 to 8.5. In a Na+-free medium, particularly in a Tris-substituted medium, the depolarization induced by a constant concentration of lysine gradually decreased in its size when injection followed by washout of lysine was repetitively tested. The addition of Na+ to the peritubular side after extinction of the responsiveness resulted in a significant restoration of the voltage response to intraluminal lysine. In addition, influx of Na+ from the peritubular fluid into the cells was significantly greater in lysine-loaded tubules than in nonloaded tubules as indicated by a greater rate of increase in intracellular Na+ activity in the presence of ouabain. The data strongly suggest that lysine enters the cells via an electrogenic uniport mechanism and leaves the cells via Na+:amino acid exchange transport mechanism.
Tetraethylammonium and ρ-Aminohippurate as Clearance Markers for Renal Plasma Flow in the Rat during Saline and Glucose Infusion
Authors: Rasmussen Sven Nybo , Shalmi Michael , Hansen Michael , Christensen Sten
Published: November 2008

Renal plasma clearances (C) of 14C-tetraethylammonium (TEA) and ρ-aminohippurate (PAH) as estimates of arterial renal plasma flow (ARPF) were evaluated in anesthetized rats during control conditions and during intravenous glucose infusion. Venous renal blood flow was measured directly by means of a servo-controlled pump, keeping the renal venous pressure constant. Arteriovenous extraction fractions (E = 1 – Prenalvenous/Prenalarterial) for PAH averaged 88.3 ± (SE) 0.8% in control rats and 82.0 ± 0.9% in glucose-infused rats (p < 0.001); ETEA averaged 92.0 ± 0.6 and 90.1 ± 0.6%, respectively (p < 0.05). Under both experimental conditions, (C/E)PAH did not differ significantly from ARPF, while (C/E)TEA underestimated ARPF; the rate of extraction of TEA exceeded the rate of excretion by 15–20%, probably due to accumulation of TEA in renal tissue. It is concluded that, when corrected for E, CPAh is in general a more accurate estimate for ARPF than CTEA. However, under conditions involving changes in plasma glucose levels CTea may provide a better estimate of the effective renal plasma flow than CPAH.
Circadian Variation in Renal Function of the Obese Rat
Authors: Luke David R. , Wasan Kishor M. , Vadiei Kiumars
Published: November 2008

The influence of food and water intake on renal function was assessed by comparisons between the hyperphagic Zucker obese rat and its lean littermate, which demonstrates nocturnal dominance in activity. Serum creatinine and cortisol levels, creatine kinase activities, creatinine and urine clearances, and sodium and potassium excretion rates were measured over a 24-hour period in both lean and obese rats (n = 24 each). Six rats in each group were studied every 8 h to permit characterization over a 12-hour light/dark cycle at 2-hour intervals. Urine and creatinine clearances were increased in lean rats during the dark phase coincident with onset of eating. Similarly, renal sodium and potassium excretion rates were markedly increased during the dark cycle, despite relatively constant serum potassium and sodium levels over the 24-hour period. In contrast, no circadian patterns in urine and creatinine clearances were found in the obese rat, which exhibits continuous feeding habits throughout the 24-hour period. Moreover, renal electrolyte excretion in the obese rat was modestly increased during the dark cycle, unlike the significant differences over time observed in lean rats. Serum creatinine levels were increased during the dark cycle in both rat groups. Creatine kinase activity, a measure of ambulatory activity, was constant in lean rats during the study period. Although creatine kinase activity was increased in obese rats during the dark cycle, no correlations with renal functional parameters were found. These results indicate that differences in food and water intake are significant determinants in diurnal cyclic changes in renal function.
Differences in Rat Kidney Morphology between Males, Females and Testosterone-Treated Females
Authors: Oudar Olivier , Elger Marlies , Bankir Lise , Ganten Detler , Ganten Ursula , Kriz Wilhelm
Published: November 2008

Kidneys of normal female and male Wistar-Kyoto rats were studied by standard morphological techniques and morphometry in order to evaluate possible differences in the overall kidney morphology between both sexes. Furthermore, we investigated the role of testosterone (DHT) on kidney morphology by treating females with daily DHT injections. Kidney weight and volume in relation to body weight were not significantly different between males and females and were not affected by DHT. Differences were found in the volume distribution among the kidney zones. The cortex was larger in males than in females, whereas the medulla was conspicuously larger in females than in males. The greater volume of the cortex in males was mainly due to a more extensive development of proximal tubules. DHT treatment in females increased the volume of their proximal tubules. Glomerular volume was similar among the three groups. Within the medulla, the difference was most prominent in the inner stripe (14.9% of the total kidney volume in females vs. 8.9% in males) and was also important in the inner medulla (7.0 vs. 4.8%). The absolute epithelial volume of thick ascending limbs in this zone was larger in females than in males. This difference was more pronounced in short loops (≈20%) than in long loops (≈10%). The values of the DHT-treated females ranged in between. In spite of the greater development of medulla and thick ascending limbs in females, urine concentration was higher in males than in females and maximum urinary concentrating ability after 48 h dehydration was not different between both sexes.
Mechanisms of the Early and Late Response of the Kidney to Contralateral Nephrectomy
Authors: Shohat J. , Erman A. , Boner G. , Rosenfeld J.
Published: November 2008

The immediate (1 day, D1) and late (90 days, D90) effects of unilateral nephrectomy on contralateral renal hemodynamics, and the renal handling of electrolytes and water were investigated in the whole animal. The immediate and late ability of the remnant kidney to autoregulate perfusate flow and glomerular filtration rate (GFR) was studied in the isolated perfused kidney of the rat. In the whole animal, in D1 rats as compared to controls, GFR calculated for a single kidney increased from 0.85 ± 0.3 to 1.1 ± 0.2ml/min (p < 0.05). In D90 rats GFR increased further and was similar to prenephrectomy GFR (1.4 ± 0.5 vs. 1.7 ± 0.5 ml/min, p NS). Urinary prostanoid excretion in 24 h, calculated for one kidney, increased by 50–500% in D1 rats, but returned to prenephrectomy values in D90 rats. In the isolated perfused kidney, decreasing perfusion pressure (PP) from 100 to 70mm Hg did not change the renal vascular resistance (RVR) in control and D90 kidneys, but in D1 kidneys RVR decreased from 8.6 ± 1.3 to 7 ± 1.3 mmHg/ml/min (p < 0.05). In D90 kidneys RVR was significantly lower as compared to control and D1 kidneys at all perfusion pressures. Decreasing PP from 100 to 70 mm Hg resulted in a significant decrease in perfusion flow in control, D1 and D90 kidneys, while with the increase in PP from 100 to 130 mm Hg the perfusion flow increased significantly in all three kidney groups. GFR was not influenced by the decrease in PP from 100 to 70 mm Hg in control and Dl kidneys, but in D90 kidneys GFR decreased from 532.7 ± 171.0 to 227.8 ± 70.0 µl/min (p < 0.01). In Dl kidneys, GFR was similar to that of controls at all perfusion pressures, while in D90 kidneys GFR was significantly higher than control or D1 kidneys at all perfusion pressures. These results indicate that: (a) the recovery in GFR observed at 90 days after uninephrectomy is not related to renal prostanoids; (b) the early increase in GFR is due to systemic factors (an increased GFR in Dl in the whole animal, and unchanged GFR in the isolated perfused kidney); (c) the late increase in GFR is due to both systemic and intrarenal factors (an increased GFR in D90 in both, whole animal and isolated perfused kidney); (d) control, D1 and D90 isolated perfused kidneys failed to autoregulate renal perfusate flow, however, control and D1 isolated kidneys autoregulated GFR when PP was lowered from 100 to 70 mm Hg, while D90 kidneys did not, and (e) the remarkable vasodilation found in D90 kidneys may potentially predispose these kidneys to pressure-related damage.
Macula densa Control of Renin Secretion
Authors: Briggs Josie P. , Lorenz John N. , Weihprecht Horst , Schnermann Jürgen
Published: November 2008

The technique of perfusing isolated tubular segments from rabbit kidneys was used to study macula densa (MD) control of renin secretion. Renin secretion was found to be markedly and reversibly increased when perfusate NaCl concentration was reduced. This response of renin secretion occurred within the physiological concentration range, i.e. between 80 and 20 mM. The stimulatory effect of reduced NaCl was seen even when total solute concentration was kept constant. In this preparation a reduction of NaCl concentration was a stronger stimulus than a fall in NaCl load. Loop diuretics were found to stimulate renin secretion. Suppression of renin secretion was seen when most of the Na was replaced by Rb or choline, but not when Cl was replaced with isethionate or acetate. Activation of adenosine-1-receptors inhibited MD-stimulated renin secretion, an effect that was blocked by an A1-antagonist. This agent partially blocked NaCl-induced inhibition of renin release, suggesting a possible role of adenosine in MD control of renin secretion.
Angiotensin II Actions in the Rabbit Proximal Tubule
Authors: Romero Michael F. , Hopfer Ulrich , Madhun Zuhayr T. , Zhou Wei , Douglas Janice G.
Published: November 2008

Angiotensin II (Angll) is a potent regulator of electrolyte transport with biphasic effects on salt and HCO3-resorption in proximal tubule epithelia (PCT). In cultured PCT cells, pM to nM Angll activates a GTP-binding protein to inhibit cAMP formation and thus releases inhibition of apical Na/H exchange. Phospholipase A2 is activated by nM to µM Angll releasing arachidonate which is metabolized by a novel P450 epoxygenase to form 5,6-epoxy-eicosatrienoic acid (5,6-EET). 5,6-EET and nM apical Angll cause dihydropyridine-sensitive Ca2+ influx from the extracellular space, inhibition of apical-to-basolateral Na flux, and decrease in epithelial monolayer short circuit current. 5,6-EET also inhibits Na/K-ATPase by 50%. This P450 epoxygenase is physiologically important in the AngII -signaling system because the P450 inhibitor ketoconazole blocks Angll effects while potentiating exogenous 5,6-EET effects. Finally, these AngII-mediated signaling systems are polarized in the PCT with pM basolateral Angll inhibiting adenylate cyclase and nM apical Angll activating PLA2 and subsequent generation of 5,6-EET.
Atrial Natriuretic Factor Infusion following Acute Renal Ischemia in Anesthetized Dogs
Authors: Klein Hanns-Georg , Dimitrov Dragomir , Atanasova Irina , Hohenfellner Rudolf Markus , Schmausser Uta , Natcheff Natcho , Thurau Klaus
Published: November 2008

Atrial natriuretic factor (ANF) has been shown to be effective in reversing renal functional impairments following renal ischemia. We studied the effects of a nonhypotensive intravenous ANF infusion (100ng/min × kg BW, 60 min) after 90 min unilateral renal arterial occlusion in anesthetized dogs with an intact contralateral kidney. ANF plasma levels remained unchanged in controls (group 1) and increased in ANF-infused animals (group 2) from 22 ± 3 to 552 ± 124 pg/ml. Blood pressure increased in both groups during renal ischemia, but returned to control values in group 2 when ANF infusion was started. Plasma vasopressin did not change in groupl, but increased in group 2 (0.77 ± 0.29 vs. 1.10 ± 0.49 pg/ml) after terminating ANF infusion. The postischemic fall in creatinine clearance (CCr) filtration fraction (FF) and renal blood flow (RBF) was prevented by infusion of ANF (Ccr: group 1, 0.16 ± 0.05 vs. group 2, 1.01 ± 0.25 ml/min × kg BW; FF: groupl, 4.0 ± 1.6 vs group2, 14.114.1%; RBF: groupl, 6.0 ± 1.2 vs. group 2,9.2 ± 1.6 ml/min × kg BW); however, the effects were limited to the time of infusion and the postischemic increase in urinary excretion of the proximal tubular enzyme N-acetyl-beta-D-glucosaminidase (NAG; group 1, 317.7 ± 163.6 vs. group 2, 672.4 ± 245.7 µU/min × kg BW) was not improved by ANF Our data suggest that infusion of ANF transiently reverses postischemic renal impairment. However, the failure to demonstrate a sustained postischemic improvement of renal functional parameters and to ameliorate massive NAG excretion casts doubt on the benefit of ANF infusion in preventing cellular damage.
Effect of Bradykinin on the Cytosolic Free Calcium Activity and Phosphoinositol Turnover in Human Glomerular Epithelial Cells
Authors: Pavenstädt Hermann , Späth Michael , Fiedler Christof , Fischer Rüdiger , Schlunck Günther , Wanner Christoph , Schollmeyer Peter
Published: November 2008

The effect of bradykinin (BK) on the intracellular free calcium activity [Ca2+]i and phosphoinositide (PI) turnover was investigated in human glomerular epithelial cells (GEC) in culture. Human GEC exhibited a baseline [Ca2+]i of 114 ± 3nmol (n = 81). BK (ED50 10-9 mol/l) caused a rapid and transient increase in [Ca2+]i, which could also be observed in the absence of extracellular calcium. The effect of BK (10-8 mol/l) on the [Ca2+]i was inhibited by the BK2 antagonist Hoe 140 (IC50 10-8 mol/l). BK also induced PI turnover in a time- and dosedependent manner. A transient increase in (l,4,5)-inositoltriphosphate (InsP3) formation from 1,445 ± 119 to 4,629 ± 323 cpm occurred after 5 s. Stimulation of protein kinase C (PKC) by short-term preincubation (15 min) of human GEC with phorbol-12-myristate-13-acetate (PMA) induced a dose-dependent inhibition of the BK-stimulated (10-7 mol/l) inositol-phosphate formation. Downregulation of PKC by preincubation of human GEC with PMA (24 h, 10-6 mol/l) or inhibition of PKC by pretreatment with staurosporin (1 h, 10-6 mol/l) resulted in a slight but significant augmention of the BK-induced InsP3 stimulation. The data indicate that BK induces stimulation of [Ca2+]i and PI turnover via a BK2 receptor in human GEC. PKC might exert a negative feedback function for the BK-induced PI turnover.
Inhibition of Sodium-Dependent Transport Systems in LLC-PK1 Cells by Metabolites of Ifosfamide
Authors: Mohrmann M. , Pauli A. , Ritzer M. , Schönfeld B. , Seifert B. , Brandis M.
Published: November 2008

Ifosfamide (IF) is an alkylating cytostatic derived from nitrogen mustard. In addition to its well-known urotoxic effects (hemorrhagic cystitis), several cases of Fanconi syndrome following IF therapy have been reported. No information is available concerning the pathomechanisms of this tubulotoxicity. We used the permanent renal epithelial cell line LLC-PK1 in order to investigate whether major metabolites of IF (i.e. 4-OH-IF, acrolein and chloracetyldehyde) induce the transport defects most frequently detected after IF therapy in vivo. LLC-PK1 cells of passages 162-177, grown in plastic culture dishes, were used in a confluent state. Sodium-dependent and independent fluxes of l-[3H]alanine and of D-[3H] glucose were determined by standard techniques. Activities of marker enzymes of apical and basolateral membranes, of mitochondria and of endoplasmic reticulum were determined in cell homogenates. IF itself has no detectable effect on fluxes of /-alanine and D-glucose in LLC-PK, cells. The IF metabolite 4-OOH-IF induces a clear inhibition of sodium-dependent fluxes of both substrates after a 24-hour exposure of cells to 100 µmol/l of 4-OOH-IF. Chloracetaldehyde induces a biphasic response of sodium-dependent fluxes of l-alanine with increased uptake rates at low concentrations ( < 200 µmol/l) and with a short incubation time, while higher concentrations and long exposure of the cells leads to a reduction in sodium coupled transport. Glucose transport is affected in a comparable way, however, in contrast to alanine transport, chloracetaldehyde also stimulates sodium-independent fluxes of glucose. Acrolein is the most toxic substance tested. It severely damages cell monolayers at concentrations beyond 75 µmol/l. Sodium-coupled glucose and alanine transport is inhibited by acrolein at concentrations higher than 50 µmol/l. Sodium-coupled glucose transport is more sensitive to all metabolites tested than alanine transport. While acrolein strongly affects both transport systems, marker enzymes of the apical plasma membrane, i.e. alkaline phosphatase and leucine aminopeptidase, are not significantly inhibited, suggesting a specificity of the toxic effect for the transport proteins. We conclude that LLC-PK1 cells represent a good model for further investigation of the pathogenesis of Fanconi syndrome after IF therapy. Sodium-dependent transport systems are more sensitive to acrolein than other cell surface proteins.
Transmembrane Signalling of Cholinergic-Stimulated Contraction in Isolated Rat Glomeruli
Authors: Hurst Roger D. , Whiteside Catharine I. , Thompson Jill C.
Published: November 2008

Exposure of isolated rat glomeruli to carbachol (Carb) 1 mM induces glomerular (mesangial cell) contraction which is inhibited by pirenzepine. To identify the cellular signalling mechanism, we analyzed Carb-activated phosphoinositide hydrolysis in myo-[2-3H] inositol preloaded cells of isolated rat glomeruli. Carb evoked a rapid (5 s, 30.4 ± 8.3% of basal) and sustained (60s, 157.2 ± 1.2% of basal) inositol trisphosphate (IP3) response. Acetylcholine 100 µM (Ach) in the presence of eserine also evoked IP3 formation. Mobilization of Ca2+ was monitored by preloading glomerular cells with 45Ca2+ (200 µCi/ ml) and analyzing the cellular efflux using a constant perifusion system. Both Carb and Ach induced transient 45Ca2+ efflux, with peak values above baseline of 69.0 ± 19.9 and 71.5 ± 7.9%, respectively. Incubation with pirenzepine or prior release of Ca2+ from an IP3-sensitive intracellular pool by Thapsigargin (2 µM) prevented Carb-evoked Ca2+ release (100 and 60%, respectively). Therefore, glomerular cells possess functional cholinergic receptors which stimulate contraction via IP3-mediated intracellular Ca2+ release.
Role of Prostacyclin in the Renal Response to Acetylcholine
Authors: Oriji Gibson , Gill, Jr. John R. , Yun John C.H. , Keiser Harry
Published: November 2008

Renal arterial infusion of acetylcholine (ACh; 40 µg/min) in control dogs produced a sustained rise in urinary sodium excretion (UNaV) and in renal plasma flow (RPF). When prostaglandin (PG) synthesis was inhibited with indomethacin (5 mg/kg) ACh produced only a transient rise in UNaV and RPF followed by a progressive decline in UNaV and RPF. Renal arterial infusion of PGI2 (0.2 µg/min) restored the response to ACh to normal in indomethacin-treated dogs. The RPF was 84 ± 9 ml/min during control and increased to 132 ± 19 ml/min with the infusion of PGI2 (p < 0.01). RPF increased further to 188 ± 18 ml/min at 20-min infusion of ACh and was maintained at 189+14 ml/min at 100-min infusion of ACh (p < 0.01). Our data suggest that the initial rise in RPF by ACh is independent of the PG system, whereas maintenance of the rise in RPF by ACh requires an intact synthesis of PGs, presumably PGI2 synthesized in the vascular tissues.
Transarterial Embolization for Inferior Epigastric Artery Injury
Authors: Yalamanchili Srigouri , Harvey Sara M. , Friedman Adie , Shams Joseph N. , Silberzweig James E.
Published: November 2008

The inferior epigastric artery represents a potentially overlooked source of pelvic arterial hemorrhage. The authors describe 3 patients with massive inferior epigastric artery bleeding following cesarean section, paracentesis, and blunt trauma that were successfully treated with transarterial embolization. The inferior epigastric artery should be considered as a possible source of arterial hemorrhage if arteriography of internal iliac artery branches does not yield a bleeding source.
Microemulsion route to the synthesis of nanoparticles
Authors: Ganguli Ashok K. , Ahmad Tokeer , Vaidya Sonalika , Ahmed Jahangeer
Published: November 2008

Nanoparticles of several titanates and zirconates in the range of 20-60 nm have been obtained using the reverse micellar route. Important oxides like CeO2 (mixture of nanorods; 7 nm diameter and 30 nm length and nanoparticles; 10 nm), ZrO2 (3-4 nm) and SnO2 (8 nm) have also been synthesized. Nanorods and nanoparticles of CaCO3 in all three forms (aragonite, vaterite, and calcite) have been obtained using reverse micelles as nanoreactors. The specific reactions vary depending on the nature of the target nanomaterial. For synthesis of ternary oxides like BaTiO3, a modified and convenient route using microemulsions (avoiding Ba-alkoxide) has evolved. Monophasic tin dioxide (SnO2) was obtained when liquid NH3 was used as precipitating agent. Transmission electron microscopy (TEM) studies show that the SnO2 nanoparticles are highly uniform and particle size was found to be 6-8 nm at 500 °C. The gas sensing characteristics of SnO2 have also been investigated using n-butane, which shows high sensitivity and fast recovery time. Reverse micelles have been used, for the first time, to mimic the conditions suitable for the room-temperature synthesis of the high-temperature and -pressure orthorhombic phase of calcium carbonate (aragonite). Other forms of calcium carbonate (vaterite and calcite) could be obtained by varying the atmospheric conditions. At a lower temperature (5 °C), homogeneous and monodisperse spheres of vaterite are obtained. The spherical particles aggregate after longer aging (168 h) to form nanorods, and the self-assembly is clearly seen at various stages by electron microscopy images. The samples were well characterized using powder X-ray diffraction (PXRD), line-broadening studies, TEM, variation in the dielectric properties with frequency and temperature, were measured on disks sintered at high temperature.
Determination of Volumetric Properties for Permeable Friction Course Mixtures
Authors: Alvarez Allex E. , Martin Amy Epps , Estakhri Cindy , Izzo Richard
Published: November 2008

Current hot mix asphalt (HMA) mix design procedures used to determine the optimum asphalt content (OAC) for permeable or porous friction course (PFC) mixtures are based on volumetric properties, primarily total air void (AV) content. This calculated volumetric parameter depends on the bulk specific gravity (Gmb) and the theoretical maximum specific gravity (Gmm) of the mixture, which are generally difficult to measure in a laboratory due to the high asphalt contents, high total AV contents, and the use of modified asphalts for PFC mixtures. This study evaluated two methodologies for determining Gmb (vacuum and dimensional analysis) and two methodologies for determining Gmm (measured and calculated) for use in calculations of total AV content. For the mixtures assessed in this study, originally designed with a total AV content of 20 %, the alternative methodologies studied led to total AV content values outside the design range (18 to 22 %), which implies the necessity of gradation modifications or changes in the fiber content to meet AV requirements and define an OAC. Dimensional analysis and a calculation procedure, based on values of Gmm measured in the laboratory at low asphalt contents, are recommended for determining Gmb and Gmm values, respectively. In addition, dimensional analysis is preliminarily recommended to compute the water-accessible AV content of PFC mixtures based on the assessment of two methods (vacuum and a methodology proposed for dimensional analysis) to compute this parameter. Water-accessible AV content is considered as an alternative parameter for mix design and evaluation.
Biology of Dendroctonus murrayanae (Coleoptera: Curculionidae: Scolytinae) in Idaho and Montana and Comparative Taxonomic Notes
Authors: Furniss Malcolm M , Kegley Sandra J
Published: November 2008

We studied the biology of Dendroctonus murrayanae Hopkins (Coleoptera: Curculionidae: Scolytinae) in lodgepole pine, Pinus contorta Douglas, in Idaho and Montana. The beetle was not a primary agent of tree mortality. Susceptible host trees were physically damaged, had thin foliage, or were otherwise predisposed to infestation. Beetles attacked individual trees, not in groups, near ground level and at low density. Life stages and their behavior are described. Egg galleries were constructed upward and usually had short spurs. Mating occurred in the egg gallery. Eggs were laid in an elongated group, not in niches, in a shallow excavation along only one side of the egg gallery. Larvae aggregated in a communal chamber, feeding side by side, but separated before pupation. D. murrayanae has four instars. One annual generation is indicated, overwintering as larvae. D. murrayanae occurred in some trees with Pseudips (=Ips) mexicanus (Hopkins), Ips pini (Say), and Hylurgops porosus (LeConte) but seldom with the mountain pine beetle, Dendroctonus ponderosae Hopkins. No natural enemy or commensal insect was observed in brood chambers. A new character on the frons is described and the relationship of D. murrayanae and the spruce beetle, Dendroctonus rufipennis (Kirby), is discussed.
Diet Effects on Intrinsic Rate of Increase and Rearing of Proprioseiopsis asetus (Acari: Phytoseiidae)
Authors: Emmert C J , Mizell R F , Andersen P C , Frank J H , Stimac J L
Published: November 2008

The intrinsic rate of increase (rm) was estimated for Proprioseiopsis asetus Muma (Acari: Phytoseiidae) on pollen and two prey species at 35°C. Cattail, Typha latifolia L., pollen and Frankliniella occidentalis (Pergande) were equally favorable as food and superior to Tetranychus urticae Koch. More females were produced in a shorter time when P. asetus was fed F. occidentalis or pollen; however, survivorship was longer when the predator was fed T. urticae. On an F. occidentalis diet, calculated rm values ranged from 0.2789 to 0.2925. The net reproductive rate was lower on a diet of T. urticae (6.48) than on pollen (9.76) or on F. occidentalis (21.39). The finite rate of increase was lower on T. urticae (1.1868) than on pollen (1.3274) or F. occidentalis (1.3398). The mean generation time was similar on the three diets. That the data reported here were collected at 35°C makes it remarkable. P. asetus may have great potential as a biological control agent of arthropods, especially thrips under climatic conditions of high temperatures such as in protected culture.