bluuebunny/crossref_metadata_2025 huggingface dataset:
Étude expérimentale du chargement latéral cyclique répété des pieux isolés dans le sable en centrifugeuse
Authors: Bouafia Ali
Published: October 2008

This paper presents the results of repetitive cyclic lateral loading test carried out in a centrifuge on two reduced models of single piles instrumented with strain gauges. The pile models, their instrumentation, the experimental setup, and the construction of the soil model are described. Effects of the pile surface roughness and of sand density on the pile behaviour are studied. The latest part of this paper deals with the construction of P–Y lateral reaction curves and the variation of the horizontal subgrade modulus with the number of cycles. Key words : pile, centrifuge, sand, cyclic loading, density, roughness.
The Avalanche Lake rock avalanche, Mackenzie Mountains, Northwest Territories, Canada: description, dating, and dynamics
Authors: Evans S.G. , Hungr O. , Enegren E.G.
Published: October 2008

At Avalanche Lake, located in the Backbone Ranges of the Mackenzie Mountains, about 200 × 106 m3 of massive Devonian carbonate rock slid down remarkably planar bedding surfaces dipping at 30° and created a spectacular runup on the opposite valley side onto a topographic feature called the Shelf. The interpretation of events at Avalanche Lake has recently been subject to controversy. It has been argued by other workers that the rock avalanche could not have run onto the Shelf without glacier ice partially filling the valley, thus reducing the magnitude of the actual runup, and implying that the rock avalanche took place at the end of the Pleistocene. Evidence is presented indicating that the rock avalanche occurred in an ice-free environment. It consists of the nature of the detachment surface, the morphology and location of the rock avalanche debris, the presence of levees in the debris and isolated patches of debris on valley-side slopes, and the entrainment of alluvial deposits and conifer fragments from the valley floor in the Shelf Lobe debris. In addition, radiocarbon ages obtained from entrained wood in the debris, converted to calendric years, indicate that the landslide took place in this millennium, with a 95% probability of it having occurred no earlier than 1440 A.D. No glacier ice then existed in the valley. Based on this evidence the behaviour of the rock avalanche is reconstructed. It is characterized by dramatic mobility in which the rock avalanche split into two parts. The west part smashed into the opposite valley side and about 5 × 106 m3 rode up onto the Shelf. The remainder (155 × 106 m3) fell back into the valley, partially running back up the detachment surface to an elevation 360 m above the valley, and then, reversing direction again, ran back into the valley bottom where it was deposited. The east part, the South Lobe (40 × 106 m3), ran down a valley reentrant opposite the detachment surface. The maximum vertical drop in the path is 1220 m, and the maximum runup is 640 m. The fahrböschung is 8° for the Shelf Lobe and 10° for the South Lobe. An analysis of the movement of the centre of gravity using a version of Koerner's dynamic model simulates the runup onto the Shelf, indicating that the presence of glacier ice is not necessary to account for the runup magnitude. Estimated maximum velocities during the movement reached 80 m/s. The runup is the highest recorded and on an empirical runup plot is highly anomalous in relation to the height of the descent slope. The case history illustrates the limitation of a dynamic model applied to a rock avalanche when it is assumed that the centre of gravity of the mass is displaced from the highest point on the detachment surface to the farthest tip of the debris. It also demonstrates that massive detachments have taken place in the Mackenzie Mountains in the comparatively recent past. Key words : rock avalanche, runup, Avalanche Lake, dynamics, radiocarbon dating, Mackenzie Mountains.
Evolution of the plastic zone near a microfracture: a numerical Simulation and its implications on in situ stress measurement
Authors: Wang Yarlong , Shen Samuel S. , Cheng Haibing
Published: October 2008

The instantaneous shut-in pressure has been used to estimate the far-field in situ minimum principal stress during microfracture testing. A plastic zone can be induced near the fracture. Because of the early plastic (irreversible) deformation induced near the fracture, the irreversible deformation near the fracture surface reduces the fracture pressure and generates a discrepancy between the far-field minimum stress and the fracture closure pressure, which has been identified as the minimum in situ stress in the past. In this paper, a finite-element numerical model is used to investigate this discrepancy due to the plastic deformation near a fracture. It is concluded that a plastic zone can be generated near a hydraulic fracture in poorly consolidated media. The fracture closure pressure can be much smaller than the minimum in situ stress due to the irreversible deformation generated near the fracture during the active fracturing period. Thus, one cannot use the conventional hydraulic-fracturing technique to interpret the minifracture tests in a poorly consolidated medium such as oil sand. Key words : microfracturing, in situ stress measurements, oil sands, plasticity, numerical simulation.
Does the intracellular ionic concentration or the cell water content (cell volume) determine the activity of TonEBP in NIH3T3 cells?
Authors: Rødgaard Tina , Schou Kenneth , Friis Martin B. , Hoffmann Else K.
Published: October 2008

The transcription factor, tonicity-responsive enhancer binding protein (TonEBP), is involved in the adaptive response against hypertonicity. TonEBP regulates the expression of genes that catalyze the accumulation of osmolytes, and its transcriptional activity is increased by hypertonicity. The goal of the present investigation was to investigate whether cell shrinkage or high intracellular ionic concentration induced the activation of TonEBP. We designed a model system for isotonically shrinking cells over a prolonged period of time. Cells swelled in hypotonic medium and performed a regulatory volume decrease. Upon return to the original isotonic medium, cells shrank initially, followed by a regulatory volume increase. To maintain cell shrinkage, the RVI process was inhibited as follows: ethyl-isopropyl-amiloride inhibited the Na+/H+ antiport, bumetanide inhibited the Na+-K+-2Cl− cotransporter, and gadolinium inhibited shrinkage-activated Na+ channels. Cells remained shrunken for at least 4 h (isotonically shrunken cells). The activity of TonEBP was investigated with a Luciferase assay after isotonic shrinkage and after shrinkage in a high-NaCl hypertonic medium. We found that TonEBP was strongly activated after 4 and 16 h in cells in high-NaCl hypertonic medium, but not after 4 or 16 h in isotonically shrunken cells. Cells treated with high-NaCl hypertonic medium for 4 h had significantly higher intracellular concentrations of both K+ and Na+ than isotonically shrunken cells. This strongly suggested that an increase in intracellular ionic concentration and not cell shrinkage is involved in TonEBP activation.
Signaling cascade of insulin-induced stimulation of l-dopa uptake in renal proximal tubule cells
Authors: Carranza Andrea , Musolino Patricia L. , Villar Marcelo , Nowicki Susana
Published: October 2008

The inward l-dihydroxyphenylalanine (l-dopa) transport supplies renal proximal tubule cells (PTCs) with the precursor for dopamine synthesis. We have previously described insulin-induced stimulation of l-dopa uptake into PTCs. In the present paper we examined insulin-related signaling pathways involved in the increase of l-dopa transport into isolated rat PTCs. Insulin (50–500 μU/ml) increased l-dopa uptake by PTCs, reaching the maximal increment (60% over the control) at 200 μU/ml. At this concentration, insulin also increased insulin receptor tyrosine phosphorylation. Both effects were abrogated by the tyrosine kinase inhibitor genistein (5 μM). In line, inhibition of the protein tyrosine phosphatase by pervanadate (0.2–100 μM) caused a concentration-dependent increase in both the uptake of l-dopa (up to 400%) and protein tyrosine phosphorylation. A synergistic effect between pervanadate and insulin on l-dopa uptake was observed only when threshold (0.2 μM), but not maximal (5 μM), concentrations of pervanadate were assayed. Insulin-induced stimulation of l-dopa uptake was also abolished by inhibition of phosphatidylinositol 3-kinase (PI3K; 100 nM wortmannin, and 25 μM LY-294002) and protein kinase C (PKC; 1 μM RO-318220). Insulin-induced activation of PKC-ζ was confirmed in vitro by its translocation from the cytosol to the membrane fraction, and in vivo by immunohistochemistry studies. Insulin caused a wortmannin-sensitive increase in Akt/protein kinase B (Akt/PKB) phosphorylation and a dose-dependent translocation of Akt/PKB to the membrane fraction. Our findings suggest that insulin activates PKC-ζ, and Akt/PKB downstream of PI3K, and that these pathways contribute to the insulin-induced increase of l-dopa uptake into PTCs.
Masticatory myosin unveiled: first determination of contractile parameters of muscle fibers from carnivore jaw muscles
Authors: Toniolo Luana , Cancellara Pasqua , Maccatrozzo Lisa , Patruno Marco , Mascarello Francesco , Reggiani Carlo
Published: October 2008

Masticatory myosin heavy chain (M MyHC) is a myosin subunit isoform with expression restricted to muscles derived from the first branchial arch, such as jaw-closer muscles, with pronounced interspecies variability. Only sparse information is available on the contractile properties of muscle fibers expressing M MyHC (M fibers). In this study, we characterized M fibers isolated from the jaw-closer muscles ( temporalis and masseter) of two species of domestic carnivores, the cat and the dog, compared with fibers expressing slow or fast (2A, 2X, and 2B) isoforms. In each fiber, during maximally calcium-activated contractions at 12°C, we determined isometric-specific tension (Po), unloaded shortening velocity ( vo) with the slack test protocol, and the rate constant of tension redevelopment ( KTR) after a fast shortening-relengthening cycle. At the end of the mechanical experiment, we identified MyHC isoform composition of each fiber with gel electrophoresis. Electrophoretic migration rate of M MyHC was similar in both species. We found that in both species the kinetic parameters vo and KTR of M fibers were similar to those of 2A fibers, whereas Po values were significantly greater than in any other fiber types. The similarity between 2A and M fibers and the greater tension development of M fibers were confirmed also in mechanical experiments performed at 24°C. Myosin concentration was determined in single fibers and found not different in M fibers compared with slow and fast fibers, suggesting that the higher tension developed by M fibers does not find an explanation in a greater number of force generators. The specific mechanical characteristics of M fibers might be attributed to a diversity in cross-bridge kinetics.
Methylglyoxal mediates vascular inflammation via JNK and p38 in human endothelial cells
Authors: Yamawaki Hideyuki , Saito Kazuaki , Okada Muneyoshi , Hara Yukio
Published: October 2008

Methylglyoxal (MGO) is a reactive metabolite of glucose. Since the plasma concentration of MGO is increased in diabetic patients, MGO is implicated in diabetes-associated vascular endothelial cells (ECs) injury, which might be responsible for atherosclerosis. In the present study, we examined effects of treatment of human umbilical vein ECs with MGO on EC morphology and inflammatory responses. MGO (24 h) induced cytotoxic morphological changes in a concentration-dependent manner (0–420 μM). MGO induced mRNA and protein expression of cyclooxygenase (COX)-2 in a concentration (0–420 μM)- and time (6–24 h)-dependent manner. COX-2 induction was associated with increased PGE2release. Acute treatment with MGO (20 min) induced concentration-dependent (0–420 μM) activation of JNK and p38 MAP kinase but not ERK or NF-κB. Both the JNK inhibitor SP600125 and the p38 inhibitor SB203580 prevented the MGO induction of COX-2. However, inhibiting JNK and p38 or COX-2 was ineffective to the morphological damage by MGO (420 μM, 24 h). EUK134, a synthetic combined superoxide dismutase/catalase mimetic, had no effect on MGO-induced COX-2. Present results indicated that MGO mediates JNK- and p38-dependent EC inflammatory responses, which might be independent of oxidative stress. On the other hand, MGO-induced morphological cell damage seems unlikely to be associated with COX-2-PGE2.
Linoleic acid stimulates gluconeogenesis via Ca2+/PLC, cPLA2, and PPAR pathways through GPR40 in primary cultured chicken hepatocytes
Authors: Suh Han Na , Huong Huang Thi , Song Chang Hun , Lee Jang Hern , Han Ho Jae
Published: October 2008

Fatty acids serve vital functions as sources of energy, building materials for cellular structures, and modulators of physiological responses. Therefore, this study examined the effect of linoleic acid on glucose production and its related signal pathways in primary cultured chicken hepatocytes. Linoleic acid (double-unsaturated, long chain) increased glucose production in a dose (≥10−4 M)- and time (≥8 h)-dependent manner. Both oleic acid (monounsaturated, long chain) and palmitic acid (saturated, long chain) also increased glucose production, whereas caproic acid (saturated, short chain) failed to increase glucose production. Linoleic acid increased G protein-coupled receptor 40 (GPR40; also known as free fatty acid receptor-1) protein expression and glucose production that was blocked by GPR40-specific small interfering RNA. Linoleic acid increased intracellular calcium concentration, which was blocked by EGTA (extracellular calcium chelator)/BAPTA-AM (intracellular calcium chelator), U-73122 (phospholipase C inhibitor), nifedipine, or methoxyverapamil (L-type calcium channel blockers). Linoleic acid increased cytosolic phospholipase A2 (cPLA2) phosphorylation and the release of [3H]-labeled arachidonic acid. Moreover, linoleic acid increased the level of cyclooxygenase-2 (COX-2) protein expression, which stimulated the synthesis of prostaglandin E2 (PGE2). The increase in PGE2 production subsequently stimulated peroxisome proliferator-activated receptor (PPAR) expression, and MK-886 (PPAR-α antagonist) and GW-9662 (PPAR-δ antagonist) inhibited glucose-6-phosphatase and phosphoenolpyruvate carboxykinase. In addition, linoleic acid-induced glucose production was blocked by inhibition of extracellular and intracellular calcium, cPLA2, COX-2, or PPAR pathways. In conclusion, linoleic acid promoted glucose production via Ca2+/PLC, cPLA2/COX-2, and PPAR pathways through GPR40 in primary cultured chicken hepatocytes.
Resveratrol alleviates alcoholic fatty liver in mice
Authors: Ajmo Joanne M. , Liang Xiaomei , Rogers Christopher Q. , Pennock Brandi , You Min
Published: October 2008

Alcoholic fatty liver is associated with inhibition of sirtuin 1 (SIRT1) and AMP-activated kinase (AMPK), two critical signaling molecules regulating the pathways of hepatic lipid metabolism in animals. Resveratrol, a dietary polyphenol, has been identified as a potent activator for both SIRT1 and AMPK. In the present study, we have carried out in vivo animal experiments that test the ability of resveratrol to reverse the inhibitory effects of chronic ethanol feeding on hepatic SIRT1-AMPK signaling system and to prevent the development of alcoholic liver steatosis. Resveratrol treatment increased SIRT1 expression levels and stimulated AMPK activity in livers of ethanol-fed mice. The resveratrol-mediated increase in activities of SIRT1 and AMPK was associated with suppression of sterol regulatory element binding protein 1 (SREBP-1) and activation of peroxisome proliferator-activated receptor γ coactivator α (PGC-1α). In parallel, in ethanol-fed mice, resveratrol administration markedly increased circulating adiponectin levels and enhanced mRNA expression of hepatic adiponectin receptors (AdipoR1/R2). In conclusion, resveratrol treatment led to reduced lipid synthesis and increased rates of fatty acid oxidation and prevented alcoholic liver steatosis. The protective action of resveratrol is in whole or in part mediated through the upregulation of a SIRT1-AMPK signaling system in the livers of ethanol-fed mice. Our study suggests that resveratrol may serve as a promising agent for preventing or treating human alcoholic fatty liver disease.
Interrelationships between circulating gastrin and iron status in mice and humans
Authors: Kovac Suzana , Smith Kelly , Anderson Gregory J. , Burgess John R. , Shulkes Arthur , Baldwin Graham S.
Published: October 2008

The observations that the peptide hormone gastrin interacts with transferrin in vitro and that circulating gastrin concentrations are increased in the iron-loading disorder hemochromatosis suggest a possible link between gastrin and iron homeostasis. This study tested the hypothesis that gastrin and iron status are interrelated by measurement of iron homeostasis in mice and humans with abnormal circulating gastrin concentrations. Intestinal iron absorption was determined by59Fe uptake following oral gavage, and concentrations of duodenal divalent metal transporter-1 (DMT-1) and hepatic hepcidin mRNAs were determined by quantitative real-time PCR in agastrinemic (GasKO), hypergastrinemic cholecystokinin 2 receptor-deficient (CCK2RKO), or wild-type mice. Iron status was measured by standard methods in the same mice and in hypergastrinemic humans with multiple endocrine neoplasia type 1 (MEN-1). Iron absorption was increased sixfold and DMT-1 mRNA concentration fourfold, and transferrin saturation was reduced 0.8-fold and hepcidin mRNA expression 0.5-fold in juvenile GasKO mice compared with age-matched wild-type mice. In mature mice, few differences were observed between the strains. Juvenile CCK2RKO mice were hypergastrinemic and had a 5.4-fold higher DMT-1 mRNA concentration than wild-type mice without any increase in iron absorption. In contrast to juvenile GasKO mice, juvenile CCK2RKO mice had a 1.5-fold greater transferrin saturation, which was reflected in a twofold increase in liver iron deposition at maturity compared with wild-type mice. The correlation between transferrin saturation and circulating gastrin concentration observed in mutant mice was also observed in human patients with MEN, in whom hypergastrinemia correlated positively ( P = 0.004) with an increased transferrin saturation. Our data indicate that, in juvenile animals when iron demand is high, circulating gastrin concentrations may alter iron status by a CCK2R-independent mechanism.
Interleukin-10-independent anti-inflammatory actions of glucagon-like peptide 2
Authors: Ivory Catherine P. A. , Wallace Laurie E. , McCafferty Donna-Marie , Sigalet David L.
Published: October 2008

Glucagon-like peptide 2 (GLP-2) is an important intestinal growth factor with anti-inflammatory activity. We hypothesized that GLP-2 decreases mucosal inflammation and the associated increased epithelial proliferation by downregulation of Th1 cytokines attributable to reprogramming of lamina propria immune regulatory cells via an interleukin-10 (IL-10)-independent pathway. The effects of GLP-2 treatment were studied using the IL-10-deficient (IL-10−/−) mouse model of colitis. Wild-type and IL-10−/− mice received saline or GLP-2 (50 μg/kg sc) treatment for 5 days. GLP-2 treatment resulted in significant amelioration of animal weight loss and reduced intestinal inflammation as assessed by histopathology and myeloperoxidase levels compared with saline-treated animals. In colitis animals, GLP-2 treatment also reduced crypt cell proliferation and crypt cell apoptosis. Proinflammatory (IL-1β, TNF-α, IFN-γ,) cytokine protein levels were significantly reduced after GLP-2 treatment, whereas IL-4 was significantly increased and IL-6 production was unchanged. Fluorescence-activated cell sorting analysis of lamina propria cells demonstrated a decrease in the CD4+ T cell population following GLP-2 treatment in colitic mice and an increase in CD11b+/F4/80+ macrophages but no change in CD25+FoxP3 T cells or CD11c+ dendritic cells. In colitis animals, intracellular cytokine analysis demonstrated that GLP-2 decreased lamina propria macrophage TNF-α production but increased IGF-1 production, whereas transforming growth factor-β was unchanged. GLP-2-mediated reduction of crypt cell proliferation was associated with an increase in intestinal epithelial cell suppressor of cytokine signaling (SOCS)-3 expression and reduced STAT-3 signaling. This study shows that the anti-inflammatory effects of GLP-2 are IL-10 independent and that GLP-2 alters the mucosal response of inflamed intestinal epithelial cells and macrophages. In addition, the suggested mechanism of the reduction in inflammation-induced proliferation is attributable to GLP-2 activation of the SOCS-3 pathway, which antagonizes the IL-6-mediated increase in STAT-3 signaling.
Sleep-wake regulation is altered in leptin-resistant (db/db) genetically obese and diabetic mice
Authors: Laposky A. D. , Bradley M. A. , Williams D. L. , Bass J. , Turek F. W.
Published: October 2008

Recent epidemiological and clinical studies indicate that the control of sleep-wake states may be an important factor in the regulation of energy metabolism. Leptin is a peripherally synthesized hormone that has critical signaling properties in the brain for the control of long-term energy homeostasis. In this study, we examined the hypothesis that leptin signaling exerts a role in sleep-wake regulation and that leptin may represent an important mechanistic link in the coordination of sleep-wake states and metabolism. Sleep-wake patterns were recorded in a genetic mouse model of obesity and diabetes, the db/db mouse, which harbors a mutation in a particular isoform of the leptin receptor (long form, LRb). We found that db/db mice exhibit a variety of alterations in sleep regulation, including an increase in overall sleep time, a dramatic increase in sleep fragmentation, attenuated diurnal rhythmicity in rapid eye movement sleep and non-rapid eye movement EEG delta power (a measure of sleep homeostatic drive), and a decrease in the compensatory response to acute (i.e., 6 h) sleep deprivation. The db/db mice also generated low amounts of locomotor activity and a reduction in the diurnal rhythm of activity. These results indicate that impaired leptin signaling has deleterious effects on the regulation of sleep amount, sleep architecture, and temporal consolidation of these arousal states. In summary, leptin may represent an important molecular component in the integration of sleep, circadian rhythms, and energy metabolism.
Behavioral and electrophysiological taste responses change after brief or prolonged dietary sodium deprivation
Authors: Garcia Joanne M. , Curtis Kathleen S. , Contreras Robert J.
Published: October 2008

Dietary Na+ deprivation elicits a hormonal response to promote sodium conservation and a behavioral response to increase sodium ingestion. It has generally been accepted that the former occurs within 24 h after sodium deprivation, while the latter is delayed and may not appear until as much as 10 days later. Na+ deprivation of similar duration also decreases the sensitivity of the chorda tympani nerve (CT) to NaCl, suggesting that changes in CT responses are necessary for increased NaCl intake. However, previous work from our laboratory showed that licking responses to NaCl solutions increase after only 2 days of Na+ deprivation, suggesting rapidly occurring changes in response to NaCl taste. The present experiments examined the effects of 2 days of dietary Na+ deprivation on CT responses to NaCl and patterns of NaCl consumption and found that Na+-deficient rats licked significantly more during the first NaCl intake bout compared with control rats. CT responses to NaCl were reduced at all concentrations after brief Na+ deprivation compared with Na+-replete control rats and did not decrease further with prolonged (10 days) dietary Na+ deficiency. Moreover, amiloride, which suppressed CT responses to NaCl by ∼30% in control rats, had virtually no effect on CT responses in Na+-deprived rats. Thus, 2 days of Na+ deprivation is sufficient to alter patterns of ingestion of concentrated NaCl and to reduce gustatory responses to NaCl. Furthermore, changes in gustatory responses to NaCl during dietary Na+ deprivation may involve the amiloride-sensitive component of the CT.
Effect of food availability and leptin on the physiology and hypothalamic gene expression of the golden spiny mouse: a desert rodent that does not hoard food
Authors: Gutman Roee , Hacmon-Keren Ronit , Choshniak Itzhak , Kronfeld-Schor Noga
Published: October 2008

Food availability and quality in desert habitats are spatially and temporally unpredictable, and animals face periods of food shortage. The golden spiny mouse ( Acomys russatus) is an omnivorous desert rodent that does not hoard food, requiring it to withstand such periods by physiological means alone. In response to food restriction, plasma leptin concentrations, core body temperature, and energy expenditure of the spiny mouse decrease significantly after 24 h, and most spiny mice are able to maintain their body mass to ∼85% of ad libitum for a prolonged period of time. Both 1-day food deprivation and long-term food restriction had a significant effect on body mass and plasma leptin concentrations, which decreased significantly with a high correlation, as well as on the orexigenic agouti-related protein, which increased significantly as a result of the 24-h food deprivation; and on neuropeptide Y (NPY), in which the increase was more pronounced under long-term food restriction. Food restriction and food deprivation had no effect, however, on the anorexigenic pro-opiomelanocortin and cocaine and amphetamine-related transcript. Leptin administration to food-restricted spiny mice did not affect food intake or the rate of decrease in body mass, indicating that it cannot overcome the drive to eat when food is scarce. However, it did result in a significant decrease in NPY levels, and the spiny mice spent less time at low body temperatures compared with PBS-treated golden spiny mice. These results show that in food-restricted golden spiny mice, leptin affects thermogenesis, but not food consumption, and suggest that the thermoregulatory effects of leptin are mediated by NPY.
Adverse effects of chronic circadian desynchronization in animals in a “challenging” environment
Authors: Preuss Fabian , Tang Yueming , Laposky Aaron D. , Arble Deanna , Keshavarzian Ali , Turek Fred W.
Published: October 2008

Continuous disruption of circadian rhythms, as seen in human shift workers, has been associated with the development of a number of adverse mental and physiological conditions. However, scientific evidence linking circadian disruption to overall health, particularly in animal models, is not well documented. In this study, we have demonstrated that exposing C57BL/6J mice to 12-h phase shifts every 5 days for 3 mo had no effect on body weight or intestinal physiology. However, when animals were further challenged with dextran sodium sulfate to induce colitis, chronic shifting of the light-dark cycle led to a dramatic increase in the progression of the colitis as indicated by reduced body weight, abnormal intestinal histopathology, and an exacerbated inflammatory response. These data indicate that circadian disruption is an important predisposing factor that may provoke the onset or worsening of various disease states such as inflammatory disorders. This study provides further evidence for continued investigations using animal models of circadian disruption to examine the consequences of circadian disruption on health when organisms are faced with a “challenging” environment.
Tetradecylthioacetic acid downregulates cyclooxygenase 2 in the renal cortex of two-kidney, one-clip hypertensive rats
Authors: Bivol Liliana Monica , Hultström Michael , Gudbrandsen Oddrun A. , Berge Rolf K. , Iversen Bjarne M.
Published: October 2008

The effect of tetradecylthioacetic acid (TTA) on the cyclooxygenase (COX) system was investigated in two-kidney, one-clip (2K1C) hypertensive rats. The systolic blood pressure (BP) was increased 6 wk after clipping to 183 ± 4 vs.127 ± 3 mmHg in TTA-treated 2K1C rats. The COX1 protein expression was not affected either by the 2K1C procedure or by TTA treatment. COX2 expression was upregulated in both kidneys, but to a greater extent in the clipped kidney. COX2 activity was 16 ± 3% in control and 38 ± 2% ( P < 0.001) in the clipped kidney, and COX2 protein expression was 1.3 ± 0.04 in control and 1.6 ± 0.12 in the clipped kidney ( P = 0.006). TTA reduced COX2 activity to control levels. Subcutaneously infusion of a COX2 inhibitor did not reduce BP. Peroxisome proliferator-activated receptors (PPARs) were detected in both kidneys, and PPARδ was upregulated in the nonclipped kidney after TTA treatment. PGE2in renal cortex was increased in 2K1C (31 ± 0.3 in the clipped and 28 ± 0.2 pg/ml nonclipped kidney, P < 0.001 compared with control). TTA lowered the PGE2to control levels. Renal blood flow (RBF) response to exogenous ANG II injected in the control and nonclipped kidney was exaggerated after indomethacin treatment but unchanged in the nonclipped kidney of the K1C TTA group. Overall, these results indicate that, after 6 wk of treatment, TTA downregulated the COX2 activity, which have potentially important effects on the regulation of renal hemodynamics but does not explain TTAs ability to lower BP.
Differential [Ca2+]isignaling of vasoconstriction in mesenteric microvessels of normal and reduced uterine perfusion pregnant rats
Authors: Chen Wensheng , Khalil Raouf A.
Published: October 2008

Vascular resistance and blood pressure (BP) are reduced during late normal pregnancy (Norm-Preg). In contrast, studies in human preeclampsia and in animal models of hypertension in pregnancy (HTN-Preg) have suggested that localized reduction in uterine perfusion pressure (RUPP) in late pregnancy is associated with increased systemic vascular resistance and BP; however, the vascular mechanisms involved are unclear. Because Ca2+is a major determinant of vascular contraction, we hypothesized that the intracellular free calcium concentration ([Ca2+]i) signaling of vasoconstriction is differentially regulated in systemic microvessels during normal and RUPP in late pregnancy. Pressurized mesenteric microvessels from Norm-Preg and RUPP rats were loaded with fura 2 in preparation for simultaneous measurement of diameter and [Ca2+]i(presented as fura 2 340/380 ratio). Basal [Ca2+]iwas lower in RUPP (0.73 ± 0.03) compared with Norm-Preg rats (0.82 ± 0.03). Membrane depolarization by 96 mM KCl, phenylephrine (Phe, 10−5M), angiotensin II (ANG II, 10−7M), or endothelin-1 (ET-1, 10−7M) caused an initial peak followed by maintained vasoconstriction and [Ca2+]i. KCl caused similar peak vasoconstriction and [Ca2+]iin Norm-Preg (45.5 ± 3.3 and 0.89 ± 0.02%) and RUPP rats (46.3 ± 2.1 and 0.87 ± 0.01%). Maximum vasoconstriction to Phe, ANG II, and ET-1 was not significantly different between Norm-Preg (28.6 ± 4.8, 32.5 ± 6.3, and 40 ± 4.6%, respectively) and RUPP rats (27.8 ± 5.9, 34.4 ± 4.3, and 38.8 ± 4.1%, respectively). In contrast, the initial Phe-, ANG II-, and ET-1-induced 340/380 ratio ([Ca2+]i) was reduced in RUPP (0.83 ± 0.02, 0.82 ± 0.02, and 0.83 ± 0.03, respectively) compared with Norm-Preg rats (0.95 ± 0.04, 0.93 ± 0.01, and 0.92 ± 0.02, respectively). Also, the [Ca2+]i-vasoconstriction relationship was similar in KCl-treated but shifted to the left in Phe-, ANG II-, and ET-1-treated microvessels of RUPP compared with Norm-Preg rats. The lower agonist-induced [Ca2+]isignal of vasoconstriction and the leftward shift in the [Ca2+]i-vasoconstriction relationship in microvessels of RUPP compared with Norm-Preg rats suggest activation of [Ca2+]isensitization pathway(s). The similarity in vasoconstriction in RUPP and Norm-Preg rats suggests that such a [Ca2+]isensitization pathway(s) may also provide a feedback effect on Ca2+mobilization/homeostatic mechanisms to protect against excessive vasoconstriction in systemic microvessels during RUPP in late pregnancy.
Mammalian hibernation as a model of disuse osteoporosis: the effects of physical inactivity on bone metabolism, structure, and strength
Authors: McGee-Lawrence Meghan E. , Carey Hannah V. , Donahue Seth W.
Published: October 2008

Reduced skeletal loading typically leads to bone loss because bone formation and bone resorption become unbalanced. Hibernation is a natural model of musculoskeletal disuse because hibernating animals greatly reduce weight-bearing activity, and therefore, they would be expected to lose bone. Some evidence suggests that small mammals like ground squirrels, bats, and hamsters do lose bone during hibernation, but the mechanism of bone loss is unclear. In contrast, hibernating bears maintain balanced bone remodeling and preserve bone structure and strength. Differences in the skeletal responses of bears and smaller mammals to hibernation may be due to differences in their hibernation patterns; smaller mammals may excrete calcium liberated from bone during periodic arousals throughout hibernation, leading to progressive bone loss over time, whereas bears may have evolved more sophisticated physiological processes to recycle calcium, prevent hypercalcemia, and maintain bone integrity. Investigating the roles of neural and hormonal control of bear bone metabolism could give valuable insight into translating the mechanisms that prevent disuse-induced bone loss in bears into novel therapies for treating osteoporosis.
Inhibition of cystathionine-β-synthase activity during renal ischemia-reperfusion: role of pH and nitric oxide
Authors: Prathapasinghe Gamika A. , Siow Yaw L. , Xu Zhibin , O Karmin
Published: October 2008

Our recent study (Prathapasinghe GA, Siow YL, O K. Am J Physiol Renal Physiol 292: F1354–F1363, 2007) indicates that homocysteine (Hcy) plays a detrimental role in ischemia-reperfusion-induced renal injury. Elevation of renal Hcy concentration during ischemia-reperfusion is attributed to reduced activity of cystathionine-β-synthase (CBS) that catalyzes the rate-limiting step in the transsulfuration pathway for the metabolism of the majority of Hcy in the kidney. However, the mechanisms of impaired CBS activity in the kidney are unknown. The aim of this study was to investigate the effects of pH and nitric oxide (NO) on the CBS activity in the kidney during ischemia-reperfusion. The left kidney of a Sprague-Dawley rat was subjected to ischemia-reperfusion. The CBS activity was significantly reduced in kidneys subjected to ischemia alone (15–60 min) or subjected to ischemia followed by reperfusion for 1–24 h. The pH was markedly reduced in kidneys upon ischemia. Injection of alkaline solution into the kidney partially restored the CBS activity during ischemia. Further analysis revealed that reduction of CBS activity during reperfusion was accompanied by an elevation of NO metabolites (nitrate and nitrite) in the kidney tissue. Injection of a NO scavenger, 2-phenyl-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide (PTIO), restored the CBS activity in the kidneys subjected to ischemia-reperfusion. Treatment with PTIO could abolish ischemia-reperfusion-induced lipid peroxidation and prevent cell death in the kidney. These results suggested that metabolic acidosis during ischemia and accumulation of NO metabolites during reperfusion contributed, in part, to reduced CBS activity leading to an elevation of renal Hcy levels, which in turn, played a detrimental role in the kidney.
Heme oxygenase attenuates angiotensin II-mediated superoxide production in cultured mouse thick ascending loop of Henle cells
Authors: Kelsen Silvia , Patel Bijal J. , Parker Lawson B. , Vera Trinity , Rimoldi John M. , Gadepalli Rama S. V. , Drummond Heather A. , Stec David E.
Published: October 2008

Heme oxygenase (HO)-1 induction can attenuate the development of angiotensin II (ANG II)-dependent hypertension. However, the mechanism by which HO-1 lowers blood pressure is not clear. The goal of this study was to test the hypothesis that induction of HO-1 can reduce the ANG II-mediated increase in superoxide production in cultured thick ascending loop of Henle (TALH) cells. Studies were performed on an immortalized cell line of mouse TALH (mTALH) cells. HO-1 was induced in cultured mTALH cells by treatment with cobalt protoporphyrin (CoPP, 10 μM) or hemin (50 μM) or by transfection with a plasmid containing the human HO-1 isoform. Treatment of mTALH cells with 10−9 M ANG II increased dihydroethidium (DHE) fluorescence (an index of superoxide levels) from 35.5 ± 5 to 136 ± 18 relative fluorescence units (RFU)/μm2. Induction of HO-1 via CoPP, hemin, or overexpression of the human HO-1 isoform significantly reduced ANG II-induced DHE fluorescence to 64 ± 5, 64 ± 8, and 41 ± 4 RFU/μm2, respectively. To determine which metabolite of HO-1 is responsible for reducing ANG II-mediated increases in superoxide production in mTALH cells, cells were preincubated with bilirubin or carbon monoxide (CO)-releasing molecule (CORM)-A1 (each at 100 μM) before exposure to ANG II. DHE fluorescence averaged 80 ± 7 RFU/μm2 after incubation with ANG II and was significantly decreased to 55 ± 7 and 53 ± 4 RFU/μm2 after pretreatment with bilirubin and CORM-A1. These results demonstrate that induction of HO-1 in mTALH cells reduces the levels of ANG II-mediated superoxide production through the production of both bilirubin and CO.
Role of oxidative stress in the renal abnormalities induced by experimental hyperuricemia
Authors: Sánchez-Lozada Laura G. , Soto Virgilia , Tapia Edilia , Avila-Casado Carmen , Sautin Yuri Y. , Nakagawa Takahiko , Franco Martha , Rodríguez-Iturbe Bernardo , Johnson Richard J.
Published: October 2008

Endothelial dysfunction is a characteristic feature during the renal damage induced by mild hyperuricemia. The mechanism by which uric acid reduces the bioavailability of intrarenal nitric oxide is not known. We tested the hypothesis that oxidative stress might contribute to the endothelial dysfunction and glomerular hemodynamic changes that occur with hyperuricemia. Hyperuricemia was induced in Sprague-Dawley rats by administration of the uricase inhibitor, oxonic acid (750 mg/kg per day). The superoxide scavenger, tempol (15 mg/kg per day), or placebo was administered simultaneously with the oxonic acid. All groups were evaluated throughout a 5-wk period. Kidneys were fixed by perfusion and afferent arteriole morphology, and tubulointerstitial 3-nitrotyrosine, 4-hydroxynonenal, NOX-4 subunit of renal NADPH-oxidase, and angiotensin II were quantified. Hyperuricemia induced intrarenal oxidative stress, increased expression of NOX-4 and angiotensin II, and decreased nitric oxide bioavailability, systemic hypertension, renal vasoconstriction, and afferent arteriolopathy. Tempol treatment reversed the systemic and renal alterations induced by hyperuricemia despite equivalent hyperuricemia. Moreover, because tempol prevented the development of preglomerular damage and decreased blood pressure, glomerular pressure was maintained at normal values as well. Mild hyperuricemia induced by uricase inhibition causes intrarenal oxidative stress, which contributes to the development of the systemic hypertension and the renal abnormalities induced by increased uric acid. Scavenging of the superoxide anion in this setting attenuates the adverse effects induced by hyperuricemia.
Regulation of V2R transcription by hypertonicity and V1aR-V2R signal interaction
Authors: Izumi Yuichiro , Nakayama Yushi , Memetimin Hasiyet , Inoue Takeaki , Kohda Yukimasa , Nonoguchi Hiroshi , Tomita Kimio
Published: October 2008

Arginine vasopressin (AVP) and hypertonicity in the renal medulla play a major role in the urine concentration mechanism. Previously, we showed that rat vasopressin V2 receptor (rV2R) promoter activity was increased by vasopressin V2R stimulation and decreased by vasopressin V1a receptor (V1aR) stimulation in a LLC-PK1 cell line stably expressing rat V1aR (LLC-PK1/rV1aR). In the present study, we investigated the effects of hypertonicity on the rV2R promoter activity and on the suppression of rV2R promoter activity by V1aR stimulation in LLC-PK1/rV1aR cells. rV2R promoter activity was increased in NaCl- or mannitol-induced hypertonicity. The hypertonicity-responsive site in the rV2R promoter region was limited to 10 bp, including the Sp1 motif. The increase of V2R promoter activity by hypertonicity was significantly inhibited by a JNK inhibitor (SP600125) and PKA inhibitor (H89). In contrast, rV2R promoter activity was remarkably suppressed by V1aR stimulation in the hypertonic condition rather than in the isotonic condition. The AVP-stimulated intracellular Ca2+ concentration was increased in the hypertonic condition, suggesting the functional activation of V1aR by hypertonicity. In conclusion, 1) V2R promoter activity is increased by hypertonicity via the JNK and PKA pathways, 2) suppression of V2R expression by the V1aR-Ca2+ pathway is enhanced by hypertonicity, and 3) hypertonicity enhances the V1aR-Ca2+ pathway. The counteractivity of V2R and V1aR could be required to maintain minimum urine volume in the dehydrated state.
Proteomic analysis of renal calculi indicates an important role for inflammatory processes in calcium stone formation
Authors: Merchant Michael L. , Cummins Timothy D. , Wilkey Daniel W. , Salyer Sarah A. , Powell David W. , Klein Jon B. , Lederer Eleanor D.
Published: October 2008

Even though renal stones/calculi occur in ∼10% of individuals, they are an enormous economic burden to the entire US health system. While the relative metabolic composition of renal calculi is generally known, there is no clear understanding of the genetics of renal stone formation, nor are there clear prognostic indicators of renal stone formation. The application of proteomics to the analysis of renal calculi axiomatically holds that insight into renal stone pathobiology can be gained by a more comprehensive understanding of renal calculus protein composition. We analyzed isolated renal stone matrix proteins with mass spectrometric and immunohistochemical methods identifying 158 proteins with high confidence, including 28 common proteins. The abundant proteins included those identified previously in stones and proteins identified here for the first time, such as myeloid lineage-specific, integral membrane and lipid regulatory proteins. Pathway analyses of all proteins identified suggested that a significant fraction of the most abundant matrix proteins participate in inflammatory processes. These proteomic results support the hypothesis that stone formation induces a cellular inflammatory response and the protein components of this response contribute to the abundant stone matrix proteome.
Magnesium stimulates renal phosphate reabsorption
Authors: Thumfart Julia , Jung Susanne , Amasheh Salah , Krämer Stephanie , Peters Harm , Sommer Kerstin , Biber Jürg , Murer Heini , Meij Iwan , Querfeld Uwe , Wagner Carsten A. , Müller Dominik
Published: October 2008

In the kidney, ∼80% of the filtered phosphate (Pi) is reabsorbed along the proximal tubule. Changes in renal Pireabsorption are associated with modulation of the sodium-dependent Picotransporter type IIa (NaPi-IIa) and type IIc (NaPi-IIc) protein abundance in the brush-border membrane (BBM) of proximal tubule cells. NaPi-IIa is mainly regulated by dietary Piintake and parathyroid hormone (PTH). The purpose of the present study was to elucidate the effect of alteration in dietary magnesium (Mg2+) intake on renal Pihandling. Urinary Piexcretion and renal expression of NaPi-IIa and NaPi-IIc were analyzed in rats fed a normal (0.2%) or high-Mg2+(2.5%) diet. A high-Mg2+diet resulted in decreased renal Piexcretion and increased protein expression of NaPi-IIa and NaPi-IIc. Serum FGF-23 (fibroblast growth factor 23) levels were unchanged under a high-Mg2+diet. Serum PTH levels were slightly decreased under a high-Mg2+diet. To examine whether the observed changes in renal Pireabsorption are PTH dependent, expression of NaPi-IIa and NaPi-IIc was also analyzed in parathyroidectomized (PTX) rats fed a normal or high-Mg2+diet. In PTX rats, Mg2+had no significant effect on renal Piexcretion or NaPi-IIa protein expression. Mg2+increased NaPi-IIc protein expression in PTX rats. This experiment shows for the first time on the molecular level how Mg2+stimulates renal Pireabsorption. Under a high-Mg2+diet, NaPi-IIa expression is dependent on PTH levels, whereas NaPi-IIc expression seems to be independent of PTH levels.
β-Adrenergic relaxation of mouse urinary bladder smooth muscle in the absence of large-conductance Ca2+-activated K+ channel
Authors: Brown Sean M. , Bentcheva-Petkova Lilia M. , Liu Lei , Hristov Kiril L. , Chen Muyan , Kellett Whitney F. , Meredith Andrea L. , Aldrich Richard W. , Nelson Mark T. , Petkov Georgi V.
Published: October 2008

In urinary bladder smooth muscle (UBSM), stimulation of β-adrenergic receptors (β-ARs) leads to activation of the large-conductance Ca2+-activated K+ (BK) channel currents (Petkov GV and Nelson MT. Am J Physiol Cell Physiol 288: C1255–C1263, 2005). In this study we tested the hypothesis that the BK channel mediates UBSM relaxation in response to β-AR stimulation using the highly specific BK channel inhibitor iberiotoxin (IBTX) and a BK channel knockout (BK-KO) mouse model in which the gene for the pore-forming subunit was deleted. UBSM strips isolated from wild-type (WT) and BK-KO mice were stimulated with 20 mM K+ or 1 μM carbachol to induce phasic and tonic contractions. BK-KO and WT UBSM strips pretreated with IBTX had increased overall contractility, and UBSM BK-KO cells were depolarized with ∼12 mV. Isoproterenol, a nonspecific β-AR agonist, and forskolin, an adenylate cyclase activator, decreased phasic and tonic contractions of WT UBSM strips in a concentration-dependent manner. In the presence of IBTX, the concentration-response curves to isoproterenol and forskolin were shifted to the right in WT UBSM strips. Isoproterenol- and forskolin-mediated relaxations were enhanced in BK-KO UBSM strips, and a leftward shift in the concentration-response curves was observed. The leftward shift was eliminated upon PKA inhibition with H-89, suggesting upregulation of the β-AR-cAMP pathway in BK-KO mice. These results indicate that the BK channel is a key modulator in β-AR-mediated relaxation of UBSM and further suggest that alterations in BK channel expression or function could contribute to some pathophysiological conditions such as overactive bladder and urinary incontinence.