bluuebunny/crossref_metadata_2025 huggingface dataset:
Developmental changes in spontaneous smooth muscle activity in the neonatal rat urinary bladder
Authors: Széll Enikoő A. , Somogyi George T. , de Groat William C. , Szigeti Gyula P.
Published: March 2015

Changes in spontaneous activity of the urinary bladder during postnatal development were examined in muscle strips from the base and dome of bladders from 1- to 5-wk-old rats. Activity was analyzed using fast Fourier transformation (FFT), nonlinear cross prediction, and the Shannon entropy test. Spontaneous activity was not detected in strips from 1- to 5-day-old rats but was observed in 50% of strips from 6- to 7-day-old rats and was prominent in strips from 2-wk-old animals. FFT analysis revealed one peak in activity, which was significantly faster in the bladder base (0.21 ± 0.03 Hz) than in the dome (0.08 ± 0.01 Hz). A second peak at ∼0.5 Hz was detected at 3-5 wk of age. Atropine but not tetrodotoxin decreased the amplitude of spontaneous contractions, whereas carbachol, a muscarinic agonist, unmasked or stimulated spontaneous activity. These data suggest that slow rhythmic activity observed previously in neonatal whole bladders is generated by pacemaker cells in the bladder base or dome. The emergence of faster activity in bladders from older animals may reflect the development of multiple pacemaker sites, which would reduce coordination within the bladder wall and improve storage function in the mature bladder.
Prolonged fasting and cortisol reduce myostatin mRNA levels in tilapia larvae; short-term fasting elevates
Authors: Rodgers Buel D. , Weber Gregory M. , Kelley Kevin M. , Levine Michael A.
Published: March 2015

Myostatin negatively regulates muscle growth and development and has recently been characterized in several fishes. We measured fasting myostatin mRNA levels in adult tilapia skeletal muscle and in whole larvae. Although fasting reduced some growth indexes in adults, skeletal muscle myostatin mRNA levels were unaffected. By contrast, larval myostatin mRNA levels were sometimes elevated after a short-term fast and were consistently reduced with prolonged fasting. These effects were specific for myostatin, as mRNA levels of glyceraldehyde-3-phosphate dehydrogenase and glucose-6-phosphatase were unchanged. Cortisol levels were elevated in fasted larvae with reduced myostatin mRNA, whereas in addition immersion of larvae in 1 ppm (2.8 μM) cortisol reduced myostatin mRNA in a time-dependent fashion. These results suggest that larval myostatin mRNA levels may initially rise but ultimately fall during a prolonged fast. The reduction is likely mediated by fasting-induced hypercortisolemia, indicating divergent evolutionary mechanisms of glucocorticoid regulation of myostatin mRNA, since these steroids upregulate myostatin gene expression in mammals.
Fetal anemia leads to augmented contractile response to hypoxic stress in adulthood
Authors: Broberg Craig S. , Giraud George D. , Schultz Jess M. , Thornburg Kent L. , Hohimer A. Roger , Davis Lowell E.
Published: March 2015

In response to chronic fetal anemia, coronary blood flow, maximal coronary conductance, and coronary reserve increase. We sought to determine whether chronic fetal anemia alters left ventricular (LV) function in adulthood. We studied adult sheep that had been made anemic for 20 days in utero by phlebotomy. They were transfused just before birth. At 7 mo of age, LV function was measured by pressure-volume loops at rest and during hypoxic stress. The in utero anemia group ( n = 8) did not differ from controls ( n = 5) with respect to hematocrit, heart and body weight, or baseline hemodynamic parameters. However, the effect of hypoxia (relative to baseline) on multiple indexes of systolic function was different between the two groups. End-systolic elastance increased in the in utero anemia group (baseline to hypoxia) by 4.15 ± 3.47 mmHg/ml (mean ± SD) but changed little in controls (0.24 ± 0.45), which shows that the response to hypoxia was significantly different ( P < 0.01) between groups. Similarly, the maximum derivative of LV pressure with respect to time increased in the in utero anemia group (486 ± 340 mmHg/s,) but on average fell in the controls (−503 ± 211 mmHg/s) with the response again being significantly different ( P < 0.03). We conclude that in sheep, perinatal anemia can alter cardiac responses to hypoxic stress in the adult long after restoration of normocythemia.
Elevated dietary salt suppresses renin secretion but not thirst evoked by arterial hypotension in rats
Authors: Stocker Sean D. , Smith Carrie A. , Kimbrough Celeste M. , Stricker Edward M. , Sved Alan F.
Published: March 2015

Increased dietary salt intake was used as a nonpharmacological tool to blunt hypotension-induced increases in plasma renin activity (PRA) in order to evaluate the contribution of the renin-angiotensin system (RAS) to hypotension-induced thirst. Rats were maintained on 8% NaCl (high) or 1% NaCl (standard) diet for at least 2 wk, and then arterial hypotension was produced by administration of the arteriolar vasodilator diazoxide. Despite marked reductions in PRA, rats maintained on the high-salt diet drank similar amounts of water, displayed similar latencies to drink, and had similar degrees of hypotension compared with rats maintained on the standard diet. Furthermore, blockade of ANG II production by an intravenous infusion of the angiotensin-converting enzyme inhibitor captopril attenuated the hypotension-induced water intake similarly in rats fed standard and high-salt diet. Additional experiments showed that increases in dietary salt did not alter thirst stimulated by the acetylcholine agonist carbachol administered into the lateral ventricle; however, increases in dietary salt did enhance thirst evoked by central ANG II. Collectively, the present findings suggest that hypotension-evoked thirst in rats fed a high-salt diet is dependent on the peripheral RAS despite marked reductions in PRA.
Frequency characteristics of long-term heart rate variability during constant-routine protocol
Authors: Aoyagi Naoko , Ohashi Kyoko , Yamamoto Yoshiharu
Published: March 2015

The effects of such behavioral factors as physical activity, food intake, and circadian rhythm on long-term heart rate variability (HRV) in humans remain poorly understood. We therefore studied their effects on HRV using a constant-routine protocol that included simultaneous core body temperature (CBT) correction. Seven healthy subjects completed the constant-routine and daily-routine protocols, during which HRV and CBT were continuously monitored. During the constant routine, subjects were kept awake for 27 h in a semirecumbent posture with minimal physical activity; small isocaloric meals were provided every 2 h. During the daily routine, subjects carried on their lives normally. Data were analyzed using generic spectral analysis based on a fast Fourier transform; coarse-graining spectral analysis was also used to eliminate periodicity due to the regular meals for raw HRV and for the CBT-corrected HRV without circadian and/or low-frequency ultradian components. The results showed that 1) the power spectra of HRV in the constant routine and daily routine had similar power-law scalings at frequencies above ∼10-3.5 Hz, while 2) below that crossover frequency, HRV was smaller in the constant routine than in the daily routine, with the difference becoming significant ( P < 0.05) at <10-4 Hz, 3) coarse-graining spectral analysis eliminated diet-induced peaks in generic spectral analysis-based HRV spectra during the constant routine and emphasized the crossover at ∼10-3.5 Hz, and 4) CBT correction did not alter the results. Below a frequency of ∼10-3.5 Hz (a period >1 h), HRV is strongly influenced by behavioral factors; above that crossover frequency, HRV is behavior independent, possibly reflecting an intrinsic regulatory system.
Dynamics of sympathetic baroreflex control of arterial pressure in rats
Authors: Sato Takayuki , Kawada Toru , Inagaki Masashi , Shishido Toshiaki , Sugimachi Masaru , Sunagawa Kenji
Published: March 2015

By a white noise approach, we characterized the dynamics of the sympathetic baroreflex system in 11 halothane-anesthetized rats. We measured sympathetic nerve activity (SNA) and systemic arterial pressure (SAP), while carotid sinus baroreceptor pressure (BRP) was altered randomly. We estimated the transfer functions from BRP to SNA (mechanoneural arc), from SNA to SAP (neuromechanical arc), and from BRP to SAP (total arc). The gain of the mechanoneural arc gradually increased about threefold as the frequency of BRP change increased from 0.01 to 0.8 Hz. In contrast, the gain of the neuromechanical arc rapidly decreased to 0.4% of the steady-state gain as the frequency increased from 0.01 to 1 Hz. Although the total arc also had low-pass characteristics, the rate of attenuation in its gain was significantly slower than that of the neuromechanical arc, reflecting the compensatory effect of the mechanoneural arc for the sluggish response of the neuromechanical arc. We conclude that the quantitative estimation of the baroreflex dynamics is vital for an integrative understanding of baroreflex function in rats.
Melatonin and activity rhythm responses to light pulses in mice with theClockmutation
Authors: Kennaway David J. , Voultsios Athena , Varcoe Tamara J. , Moyer Robert W.
Published: March 2015

Melatonin and wheel-running rhythmicity and the effects of acute and chronic light pulses on these rhythms were studied in ClockΔ19mutant mice selectively bred to synthesize melatonin. Homozygous melatonin-proficient ClockΔ19mutant mice ( ClockΔ19/Δ19-MEL) produced melatonin rhythmically, with peak production 2 h later than the wild-type controls (i.e., just before lights on). By contrast, the time of onset of wheel-running activity occurred within a 20-min period around lights off, irrespective of the genotype. Melatonin production in the mutants spontaneously decreased within 1 h of the expected time of lights on. On placement of the mice in continuous darkness, the melatonin rhythm persisted, and the peak occurred 2 h later in each cycle over the first two cycles, consistent with the endogenous period of the mutant. This contrasted with the onset of wheel-running activity, which did not shift for several days in constant darkness. A light pulse around the time of expected lights on followed by constant darkness reduced the expected 2-h delay of the melatonin peak of the mutants to ∼1 h and advanced the time of the melatonin peak in the wild-type mice. When the ClockΔ19/Δ19-MEL mice were maintained in a skeleton photoperiod of daily 15-min light pulses, a higher proportion entrained to the schedule (57%) than melatonin-deficient mutants (9%). These results provide compelling evidence that mice with the ClockΔ19mutation express essentially normal rhythmicity, albeit with an underlying endogenous period of 26–27 h, and they can be entrained by brief exposure to light. They also raise important questions about the role of Clock in rhythmicity and the usefulness of monitoring behavioral rhythms compared with hormonal rhythms.
NOS inhibition restores renal responses to atrial distension during pregnancy
Authors: Tam Siu Lin , Kaufman Susan
Published: March 2015

Nitric oxide (NO) biosynthesis increases during pregnancy and has been shown to suppress baroreceptor activity. The renal response to a simulated increase in circulating blood volume (atrial distension) is also attenuated at this time. We hypothesized that blocking NO biosynthesis during pregnancy would restore the renal response. Female rats were implanted with indwelling intracardiac balloons and central venous cannulas. After recovery, they were mated, and on day 14 of pregnancy, osmotic minipumps containing the NO synthase inhibitor N G-nitro-l-arginine methyl ester (l-NAME) or its inactive enantiomer N G-nitro-d-arginine methyl ester (d-NAME) (120 mg/2 ml at 10 μg/min) were implanted. In response to atrial distension (1 h), urine output increased in the d- and l-NAME-treated virgin rats. During pregnancy ( day 20), this response was attenuated in the d-NAME-treated, but not thel-NAME-treated, animals, i.e., after a simulated increase in circulating blood volume, inhibition of NO biosynthesis restored the renal response of pregnant rats to that seen in virgin animals. We conclude that, during normal pregnancy, increased NO biosynthesis blunts the reflex renal response to atrial distension.
Vampire bat, shrew, and bear: comparative physiology and chronic renal failure
Authors: Singer Michael A.
Published: March 2015

In the typical mammal, energy flux, protein metabolism, and renal excretory processes constitute a set of closely linked and quantitatively matched functions. However, this matching has limits, and these limits become apparent when animals adapt to unusual circumstances. The vampire bat and shrew have an extremely high protein intake, and the glomerular filtration rate (GFR) is not commensurate with the large urea load to be excreted. The vampire bat is chronically azotemic (blood urea concentration 27–57 mmol/l); yet there is no information as to how this animal has adjusted to such an azotemic internal environment. A high protein intake should also lead to chronic glomerular hyperfiltration; yet neither animal appears to develop progressive renal failure. The American black bear, on the other hand, has adapted to a prolonged period without intake or urine output. Despite continued amino acid catabolism with urea production, this mammal is able to completely salvage and reutilize urea nitrogen for protein synthesis, although the signals that initiate this metabolic adaptation are not known. The vampire bat, shrew, and bear are natural models adapted to circumstances analogous to chronic renal failure. Unraveling these adaptations could lead to new interventions for the prevention/treatment of chronic renal failure.
Control of glyceroneogenic activity in rat brown adipose tissue
Authors: Festuccia W. T. L. , Kawashita N. H. , Garofalo M. A. R. , Moura M. A. F. , Brito S. R. C. , Kettelhut I. C. , Migliorini R. H.
Published: March 2015

Brown adipose tissue (BAT) glyceroneogenesis was evaluated in rats either fasted for 48 h or with streptozotocin-diabetes induced 3 days previously or adapted for 20 days to a high-protein, carbohydrate-free (HP) diet, conditions in which BAT glucose utilization is reduced. The three treatments induced an increase in BAT glyceroneogenic activity, evidenced by increased rates of incorporation of [1-14C]pyruvate into triacylglycerol (TAG)-glycerol in vitro and a marked, threefold increase in the activity of BAT phospho enolpyruvate carboxykinase (PEPCK). BAT glycerokinase activity was not significantly affected by fasting or diabetes. After unilateral BAT denervation of rats fed either the HP or a balanced diet, glyceroneogenesis activity increased in denervated pads, evidenced by increased rates of nonglucose carbon incorporation into TAG-glycerol in vivo (difference between3H2O and [14C]glucose incorporations) and of [1-14C]pyruvate in vitro. PEPCK activity was not significantly affected by denervation. The data suggest that BAT glyceroneogenesis is not under sympathetic control but is sensitive to hormonal/metabolic factors. In situations of reduced glucose use there is an increase in BAT glyceroneogenesis that may compensate the decreased generation of glycerol-3-phosphate from the hexose.
Characterization and cardiovascular actions of endothelin-1 and endothelin-3 from the American alligator
Authors: Platzack Björn , Wang Yuqi , Crossley Dane , Lance Valentine , Hicks James W. , Conlon J. Michael
Published: March 2015

The structures and biological activities of the isoforms of endothelin (ET) in a reptile are unknown. ET-3, whose primary structure is identical to human ET-3 except for the substitution Phe4→ Tyr, and a peptide identical to human ET-1 were isolated from an extract of the lung of the alligator, Alligator mississipiensis. Bolus intravenous injections of alligator ET-3 (10, 30, and 100 pmol/kg) into anesthetized alligators produced dose-dependent decreases in systemic blood pressure (Psys) and systemic vascular resistance (Rsys) without change in heart rate (HR), systemic blood flow (Qsys), pulmonary pressure (Ppul), pulmonary vascular resistance (Rpul), or pulmonary blood flow (Qpul). At a dose of 300 pmol/kg, the initial vasodilatation was followed by an increase in Rsysand decreases in Qsysand Ppul. The response to intravenous human/alligator ET-1 (10, 30, 100, and 300 pmol/kg) was biphasic at all doses with initial decreases in Psysand Rsysbeing followed by sustained increases in these parameters. In the pulmonary circulation, ET-1 produced a dose-dependent decrease in Qpuland an increase in Rpulduring the first phase of the response but no significant change during the second phase. There was no change in HR in response to ET-1. The vasodilatator action of arginine, but not ET-1, was attenuated by Nω-nitro-l-arginine methyl ester, indicating that the effect of the peptide is probably not mediated through increased synthesis of nitric oxide. The data demonstrate that the structure of the ET isoforms has been strongly conserved during the evolution of vertebrates but that cardiovascular actions differ significantly between the alligator and mammals, especially in the magnitude and duration of the hypotensive response.
Loss of albumin and megalin binding to renal cubilin in rats results in albuminuria after total body irradiation
Authors: Yammani Raghunatha R. , Sharma Mukut , Seetharam Shakuntla , Moulder John E. , Dahms Nancy M. , Seetharam Bellur
Published: March 2015

The role of the renal apical brush-border membrane (BBM) endocytic receptors cubilin and megalin in the onset of albuminuria in rats exposed to a single dose of total body irradiation (TBI) has been investigated. Albuminuria was evident as immunoblot (IB) analysis of the urine samples from TBI rats revealed excretion of large amounts of albumin. IB analysis of the BBM proteins did not reveal any significant changes in cubilin or megalin levels, but125I-albumin binding to BBM from TBI rats declined by 80% with a fivefold decrease (from 0.5 to 2.5 μM) in the affinity for albumin. IB analysis of cubilin from the BBM demonstrated a 75% loss when purified using albumin, but not intrinsic factor (IF)-cobalamin (Cbl) ligand affinity chromatography. Immunoprecipitation (IP) of Triton X-100 extract of the BBM with antiserum to cubilin followed by IB of the immune complex with an antiserum to megalin revealed a 75% loss of association between megalin and cubilin. IP studies with antiserum to cubilin or megalin and IB with antiserum to the cation-independent mannose 6-phosphate/insulin-like growth factor II-receptor (CIMPR) revealed that CIMPR interacted with both cubilin and megalin. In addition, TBI did not disrupt the association of CIMPR with either cubilin or megalin in BBM. These results suggest that albuminuria noted in TBI rats is due to selective loss of albumin and megalin, but not CIMPR or IF-Cbl binding by cubilin. Furthermore, these results also suggest that albumin and IF-Cbl binding to cubilin occur at distinct sites and that in the rat renal BBM, CIMPR interacts with both cubilin and megalin.
Vascular NAD(P)H oxidases: specific features, expression, and regulation
Authors: Lassègue Bernard , Clempus Roza E.
Published: March 2015

The importance of reactive oxygen species (ROS) in vascular physiology and pathology is becoming increasingly evident. All cell types in the vascular wall produce ROS derived from superoxide-generating protein complexes similar to the leukocyte NADPH oxidase. Specific features of the vascular enzymes include constitutive and inducible activities, substrate specificity, and intracellular superoxide production. Most phagocyte enzyme subunits are found in vascular cells, including the catalytic gp91phox (aka, nox2), which was the earliest member of the newly discovered nox family. However, smooth muscle frequently expresses nox1 rather than gp91phox, and nox4 is additionally present in all cell types. In cell culture, agonists increase ROS production by activating multiple signals, including protein kinase C and Rac, and by upregulating oxidase subunits. The oxidases are also upregulated in vascular disease and are involved in the development of atherosclerosis and a significant part of angiotensin II-induced hypertension, possibly via nox1 and nox4. Likewise, enhanced vascular oxidase activity is associated with diabetes. Therefore, members of this enzyme family appear to be important in vascular biology and disease and constitute promising targets for future therapeutic interventions.
Estrogen modulation of baroreflex function in conscious mice
Authors: Pamidimukkala Jaya , Taylor Julia A. , Welshons Wade V. , Lubahn Dennis B. , Hay Meredith
Published: March 2015

It has been suggested that estrogen modulates baroreflex regulation of autonomic function. The present study evaluated the effects of estrogen on baroreflex regulation of heart rate in response to changes in blood pressure with phenylephrine (PE), ANG II, and sodium nitroprusside (SNP) in a conscious mouse model. Males and ovariectomized females with (OvxE+) and without (OvxE−) estradiol replacement chronically implanted with arterial and venous catheters were used in these studies. The slope of the baroreflex bradycardic responses to PE was significantly facilitated in OvxE+ females (−7.65 ± 1.37) compared with OvxE− females (−4.5 ± 0.4). Likewise, the slope of the baroreflex bradycardic responses to ANG II was significantly facilitated in OvxE+ females (−7.97 ± 1.06) compared with OvxE− females (−4.8 ± 1.6). Reflex tachycardic responses to SNP were comparable in all the groups. Finally, in male mice, the slope of ANG II-induced baroreflex bradycardia (−5.17 ± 0.95) was significantly less than that induced by PE (−8.50 ± 0.92), but this ANG II-mediated attenuation of reflex bradycardia was not observed in the female mice. These data support the hypothesis that estrogen facilitates baroreflex function in female mice and suggest that ANG II-mediated acute blunting of baroreflex regulation of heart rate may be sex dependent.
Maternal DDAVP-induced hyponatremia preserves fetal urine flow during acute fetal hemorrhage
Authors: Desai Mina , Xu Zhice , Guerra Catalina , Kallichanda Nathash , Ross Michael G.
Published: March 2015

Maternal administration of DDAVP induces maternal and fetal plasma hyponatremia, accentuates fetal urine flow, and increases amniotic fluid volume. Fetal hemorrhage represents an acute stress that results in fetal AVP secretion and reduced urine flow rate. In view of the potential therapeutic use of DDAVP for pregnancies with reduced amniotic fluid volume, we sought to examine the impact of maternal hypotonicity during acute fetal hemorrhage. Chronically catheterized pregnant ewes (130 ± 2 days) were allocated to control or to DDAVP-induced hyponatremia groups. In the latter group, tap water (2,000 ml) was administered intragastrically to the ewe followed by DDAVP (20 μg bolus, 4 μg/h) and a maintenance intravenous infusion of 5% dextrose water for 4 h to achieve maternal hyponatremia of 10–12 meq/l. Thereafter, ovine fetuses from both groups were continuously hemorrhaged to 30% of estimated blood volume over a 60-min period. DDAVP caused similar degree of reductions in plasma sodium and osmolality in pregnant ewes and their fetuses. In response to hemorrhage, DDAVP fetuses showed greater reduction in hematocrit than control fetuses (14 vs. 10%). Both groups of fetuses demonstrated similar increases in plasma AVP concentration. However, the AVP-hemorrhage threshold was greater in DDAVP fetuses (22.5%) than in control (17.5%). Hemorrhage had no significant impact on plasma osmolality, electrolyte levels, or cardiovascular responses in either group of fetuses. Despite similar increases in plasma AVP, DDAVP fetuses preserved fetal urine flow rates, with values threefold those of control fetuses. These results suggest that under conditions of acute fetal stress of hemorrhage, maternal DDAVP may preserve fetal urine flow and amniotic fluid volume.
Sodium appetite and Fos activation in serotonergic neurons
Authors: Franchini Lucia F. , Johnson Alan Kim , de Olmos José , Vivas Laura
Published: March 2015

We evaluated serotonergic hindbrain groups of cells for their involvement in the generation and inhibition of sodium appetite. For that purpose, we analyzed the number of Fos-immunoreactive (Fos-ir) cells and double-labeled Fos-serotonin (5-HT)-ir neurons within different nuclei of the hindbrain raphe system and the area postrema (AP). Sodium depletion and sodium appetite were induced by peritoneal dialysis. Twenty-four hours after peritoneal dialysis, a 2% NaCl solution intake test was given to peritoneal dialyzed animals [PD-with access (PD-A) group] and to control dialyzed animals [CD-with access (CD-A) group]. Two additional groups of animals received either peritoneal dialysis or control dialysis but were not given access to the 2% NaCl [CD-no access (CD-NA) group or PD-no access (PD-NA) group]. The number of Fos-ir neurons within different nuclei of the raphe system was increased in spontaneous and induced sodium ingestion of CD-A and PD-A groups compared with the CD-NA and PD-NA groups. The PD-NA group had significantly fewer double-labeled cells along the raphe system compared with the animals in near-normal sodium balance (CD-NA and CD-A) or in the process of restoring sodium balance by consuming NaCl (PD-A). The AP of the PD-A group showed a significant increase in the number of Fos-ir and Fos-5-HT-ir cells compared with the PD-NA and CD groups. Our results suggest that serotonergic pathways with cell bodies in the AP and the raphe system are involved in the control of sodium appetite.
Appetite-inducing accumbens manipulation activates hypothalamic orexin neurons and inhibits POMC neurons
Authors: Zheng Huiyuan , Corkern Michele , Stoyanova Irina , Patterson Laurel M. , Tian Rui , Berthoud Hans-Rudolf
Published: March 2015

Corticolimbic circuits involving the prefrontal cortex, amygdala, and ventral striatum determine the reward value of food and might play a role in environmentally induced obesity. Chemical manipulation of the nucleus accumbens shell (AcbSh) has been shown to elicit robust feeding and Fos expression in the hypothalamus and other brain areas of satiated rats. To determine the neurochemical phenotype of hypothalamic neurons receiving input from the AcbSh, we carried out c-Fos/peptide double-labeling immunohistochemistry in various hypothalamic areas known to contain feeding peptides, from rats that exhibited a significant feeding response after AcbSh microinjection of the GABAA agonist muscimol. In the perifornical area, a significantly higher percentage of orexin neurons expressed Fos after muscimol compared with saline injection. In contrast, Fos expression was not induced in melanin-concentrating hormone and cocaine-amphetamine-related transcript (CART) neurons. In the arcuate nucleus, Fos activation was significantly lower in neurons coexpressing CART and proopiomelanocortin, and there was a tendency for higher Fos expression in neuropeptide Y neurons. In the paraventricular nucleus, no significant activation of oxytocin and CART neurons was found. Thus AcbSh manipulation may elicit food intake through coordinated stimulation of hypothalamic neurons expressing orexigenic peptides and suppression of neurons expressing anorexigenic peptides. However, activation of many neurons not expressing these peptides suggests that additional peptides/transmitters in the lateral hypothalamus and accumbens projections to other brain areas might also be involved.
Mechanisms used to dispose of progressively increasing alkali load in rats
Authors: Cheema-Dhadli Surinder , Lin Shih-Hua , Halperin Mitchell L.
Published: March 2015

Our objective was to describe the process of alkali disposal in rats. Balance studies were performed while incremental loads of alkali were given to rats fed a low-alkali diet or their usual alkaline ash diet. Control groups received equimolar NaCl or KCl. Virtually all of the alkali was eliminated within 24 h when the dose exceeded 750 μmol. The most sensitive response to alkali input was a decline in the excretion of NH[Formula: see text]. The next level of response was to increase the excretion of unmeasured anions; this rise was quantitatively the most important process in eliminating alkali. The maximum excretion of citrate was ∼70% of its filtered load. An even higher alkali load augmented the excretion of 2-oxoglutarate to >400% of its filtered load. Only with the largest alkali load did bicarbonaturia become quantitatively important. We conclude that renal mechanisms eliminate alkali while minimizing bicarbonaturia. This provides a way of limiting changes in urine pH without sacrificing acid-base balance, a process that might lessen the risk of kidney stone formation.
Male gender increases sensitivity to renal injury in response to cholesterol loading
Authors: Attia Diana M. , Goldschmeding Roel , Attia Mahmoud A. , Boer Peter , Koomans Hein A. , Joles Jaap A.
Published: March 2015

Males are at greater risk for renal injury than females. This may relate to nitric oxide (NO) availability, because female rats have higher renal endothelial NO synthase (NOS) levels. Previously, our laboratory found susceptibility to proteinuria induced by NOS inhibition in male compared with female rats. Dyslipidemia and hypercholesterolemia dose dependently decreased renal NOS activity and caused renal injury in female rats. We hypothesized that exposure of male rats to hypercholesterolemia would lead to more renal injury in male than in female rats due to an a priori lower renal NO system. Female and male rats were fed no, low-dose, or high-dose cholesterol for 24 wk. Cholesterol feeding dose dependently increased proteinuria in both female and male rats, but male rats developed more proteinuria at similar plasma cholesterol ( P < 0.001). Control males had lower renal NOS activity than control females (4.44 ± 0.18 vs. 7.46 ± 0.37 pmol · min−1· mg protein−1; P < 0.05), and cholesterol feeding decreased renal NOS activity in males and in females ( P < 0.05). Cholesterol-fed males developed significantly more vascular, glomerular, and tubulointerstitial monocyte/macrophage influx and injury than females. Thus under baseline conditions, male rats have lower renal NOS activity than female rats. This may explain why male rats are more sensitive to renal injury by factors that decrease NO availability, such as hypercholesterolemia.
Phosphatase inhibitors increase the open probability of ENaC in A6 cells
Authors: Becchetti A. , Malik B. , Yue G. , Duchatelle P. , Al-Khalili O. , Kleyman T. R. , Eaton D. C.
Published: March 2015

We studied the cellular phosphatase inhibitors okadaic acid (OKA), calyculin A, and microcystin on the epithelial sodium channel (ENaC) in A6 renal cells. OKA increased the amiloride-sensitive current after ∼30 min with maximal stimulation at 1–2 h. Fluctuation analysis of cell-attached patches containing a large number of ENaC yielded power spectra with corner frequencies in untreated cells almost two times as large as in cells pretreated for 30 min with OKA, implying an increase in single channel open probability ( Po) that doubled after OKA. Single channel analysis showed that, in cells pretreated with OKA, Poand mean open time approximately doubled. Two other phosphatase inhibitors, calyculin A and microcystin, had similar effects on Poand mean open time. An analog of OKA, okadaone, that does not inhibit phosphatases had no effect. Pretreatment with 10 nM OKA, which blocks protein phosphatase 2A (PP2A) but not PP1 in mammalian cells, had no effect even though both phosphatases are present in A6 cells. Several proteins were differentially phosphorylated after OKA, but ENaC subunit phosphorylation did not increase. We conclude that, in A6 cells, there is an OKA-sensitive phosphatase that suppresses ENaC activity by altering the phosphorylation of a regulatory molecule associated with the channel.
Identification and expression analysis of the human μ-protocadherin gene in fetal and adult kidneys
Authors: Goldberg Michael , Wei Michelle , Tycko Benjamin , Falikovich Inna , Warburton Dorothy
Published: March 2015

We recently cloned μ-protocadherin, a developmentally regulated cell adhesion molecule that contains an extracellular region with four cadherin-like ectodomains and a triply repeating mucin domain in its longer isoform. Expression of μ-protocadherin in L929 cells resulted in cellular aggregation, confirming its role in intercellular adhesion. We now identify the human μ-protocadherin ortholog and study its distribution in vivo and its targeting in polarized epithelia. Basic Local Alignment Search Tool searches and fluorescent in situ hybridization analysis on the basis of human-mouse synteny reveal that μ-protocadherin maps to 11p15.5, matching a previously identified gene called MUCDHL. At least three different splicing isoforms exist for MUCDHL that vary in expression in the fetal kidney. μ-Protocadherin is apically expressed along the brush border of the proximal convoluted tubule of the adult kidney. Transfection of truncated forms of μ-protocadherin into polarized Madin-Darby canine kidney cells reveals that the NH2terminus is essential for targeting to the apical surface. These results suggest that although human μ-protocadherin may mediate a homotypic adhesive interaction, it may have additional functions in terminally differentiated epithelia.
Effect of renal nerve stimulation on responsiveness of the rat renal vasculature
Authors: DiBona Gerald F. , Sawin Linda L.
Published: March 2015

When the renal nerves are stimulated with sinusoidal stimuli over the frequency range 0.04–0.8 Hz, low (≤0.4 Hz)- but not high (≥0.4 Hz)-frequency oscillations appear in renal blood flow (RBF) and are proposed to increase responsiveness of the renal vasculature to stimuli. This hypothesis was tested in anesthetized rats in which RBF responses to intrarenal injection of norepinephrine and angiotensin and to reductions in renal arterial pressure (RAP) were determined during conventional rectangular pulse and sinusoidal renal nerve stimulation. Conventional rectangular pulse renal nerve stimulation decreased RBF at 2 Hz but not at 0.2 or 1.0 Hz. Sinusoidal renal nerve stimulation elicited low-frequency oscillations (≤0.4 Hz) in RBF only when the basal carrier signal frequency produced renal vasoconstriction, i.e., at 5 Hz but not at 1 Hz. Regardless of whether renal vasoconstriction occurred, neither conventional rectangular pulse nor sinusoidal renal nerve stimulation altered renal vasoconstrictor responses to norepinephrine and angiotensin. The RBF response to reduction in RAP was altered by both conventional rectangular pulse and sinusoidal renal nerve stimulation only when renal vasoconstriction occurred: the decrease in RBF during reduced RAP was greater. Sinusoidal renal nerve stimulation with a renal vasoconstrictor carrier frequency results in a decrease in RBF with superimposed low-frequency oscillations. However, these low-frequency RBF oscillations do not alter renal vascular responsiveness to vasoconstrictor stimuli.
Expression of the Na+-HCO 3 − cotransporter NBC4 in rat kidney and characterization of a novel NBC4 variant
Authors: Xu Jie , Wang Zhaohui , Barone Sharone , Petrovic Milan , Amlal Hassane , Conforti Laura , Petrovic Snezana , Soleimani Manoocher
Published: March 2015

The purpose of the present studies was to examine the renal distribution and functional properties of Na+-HCO[Formula: see text] cotransporter type 4 (NBC4), the latest NBC isoform to be identified. Zonal distribution studies in rat kidney by Northern blot hybridization and RT-PCR demonstrated that NBC4 is highly abundant in the outer medulla and cortex but is low in the inner medulla. Nephron segment distribution studies indicated that NBC4 is predominantly expressed in the medullary and cortical thick ascending limb of the loop of Henle. Using specific primers on the basis of the published sequence (GenBank accession no. AF-207661), a full-length NBC4 variant was cloned from human liver and examined. The sequence of this variant (called NBC4e) is shorter by 86 amino acids vs. the published sequence. Xenopus laevisoocytes injected with the full-length NBC4e cRNA were compared with NBC1-expressing oocytes. Although exposure of NBC1-expressing oocytes to CO2/HCO[Formula: see text] resulted in immediate hyperpolarization, the NBC4-expressing oocytes did not show any alteration in membrane potential. NBC activity in oocytes, assayed as the Na+-dependent, HCO[Formula: see text]-mediated intracellular pH recovery from acidosis, indicated that NBC4 is a DIDS-inhibitable NBC. We propose that NBC4 is expressed in the thick ascending limb of the loop of Henle and mediates cellular HCO[Formula: see text] uptake in this segment.
Regulation of renal CYP4A expression and 20-HETE synthesis by nitric oxide in pregnant rats
Authors: Wang Mong-Heng , Wang Jishi , Chang Hsin-Hsin , Zand Barbara A. , Jiang Miao , Nasjletti Alberto , Laniado-Schwartzman Michal
Published: March 2015

20-Hydroxyeicosatetraenoic acid (20-HETE), which promotes renal vasoconstriction, is formed in the rat kidney primarily by cytochrome P-450 (CYP) 4A isoforms (4A1, 4A2, 4A3, 4A8). Nitric oxide (NO) has been shown to bind to the heme moiety of the CYP4A2 protein and to inhibit 20-HETE synthesis in renal arterioles of male rats. However, it is not known whether NO interacts with and affects the activity of CYP4A1 and CYP4A3, the major renal CYP4A isoforms in female rats. Incubation of recombinant CYP4A1 and 4A3 proteins with sodium nitroprusside (SNP) shifted the absorbance at 440 nm, indicating the formation of a ferric-nitrosyl-CYP4A complex. The absorbance for CYP4A3 was about twofold higher than that of CYP4A1. Incubation of SNP or peroxynitrite (PN; 0.01–1 mM) with CYP4A recombinant membranes caused a concentration-dependent inhibition of 20-HETE synthesis, with both chemicals having a greater inhibitory effect on CYP4A3-catalyzed activity. Moreover, incubation of CYP4A1 and 4A3 proteins with PN (1 mM) resulted in nitration of tyrosine residues in both proteins. In addition, PN and SNP inhibited 20-HETE synthesis in renal microvessels from female rats by 65 and 59%, respectively. We previously showed that microvessel CYP4A1/CYP4A3 expression and 20-HETE synthesis are decreased in late pregnancy. Therefore, we investigated whether such a decrease is dependent on NO, the synthesis of which has been shown to increase in late pregnancy. Administration of NG-nitro-l-arginine methyl ester (l-NAME) to pregnant rats for 6 days ( days 15- 20 of pregnancy) caused a significant increase in systolic blood pressure, which was prevented by concurrent treatment with the CYP4A inhibitor 1-aminobenzotriazole (ABT). Urinary NO2/NO3excretion decreased by 40 and 52% in l-NAME- and l-NAME + ABT-treated groups, respectively. Interestingly, renal microvessel 20-HETE synthesis showed a marked increase following l-NAME treatment, and this increase was diminished with coadministration of ABT. These results demonstrate that NO interacts with CYP4A proteins in a distinct manner and it interferes with renal microvessel 20-HETE synthesis, which may play an important role in the regulation of blood pressure and renal function during pregnancy.
Concentration of solutes in the renal inner medulla: interstitial hyaluronan as a mechano-osmotic transducer
Authors: Knepper Mark A. , Saidel Gerald M. , Hascall Vincent C. , Dwyer Terry
Published: March 2015

Although the concentrating process in the renal outer medulla is well understood, the concentrating mechanism in the renal inner medulla remains an enigma. The purposes of this review are fourfold. 1) We summarize a theoretical basis for classifying all possible steady-state inner medullary countercurrent concentrating mechanisms based on mass balance principles. 2) We review the major hypotheses that have been proposed to explain the axial osmolality gradient in the interstitium of the renal inner medulla. 3) We summarize and expand on the Schmidt-Nielsen hypothesis that the contractions of the renal pelvocalyceal wall may provide an important energy source for concentration in the inner medulla. 4) We discuss the special properties of hyaluronan, a glycosaminoglycan that is the chief component of a gel-like renal inner medullary interstitial matrix, which may allow it to function as a mechano-osmotic transducer, converting energy from the contractions of the pelvic wall to an axial osmolality gradient in the medulla. These considerations set the stage for renewed experimental investigation of the urinary concentrating process and a new generation of mathematical models of the renal concentrating mechanism, which treat the inner medullary interstitium as a viscoelastic system rather than a purely hydraulic system.
Abnormal regulation of ENaC: syndromes of salt retention and salt wasting by the collecting duct
Authors: Schafer James A.
Published: March 2015

Although the aldosterone-responsive segments of the nephron together reabsorb <10% of the filtered Na+, certain single-gene defects that affect the epithelial Na+channel (ENaC) in the luminal membrane of the collecting duct (CD) or its regulation by aldosterone cause severe hypertension, whereas others cause salt wasting and hypotension. These rare defects illustrate the key role of the distal nephron in maintaining normal extracellular volume and blood pressure. Genetic defects that increase the Cl−conductance of the junctional complexes may also lead to salt retention and hypertension. Less dramatic alterations in regulatory actions of other hormones such as vasopressin (VP), either alone or with other genetic variations, diet, or environmental factors, may also produce Na+retention or loss. Although VP acts primarily to regulate water balance, it is also an antinatriuretic hormone. Elevated basal plasma VP levels, and/or augmented VP release with increased Na+intake, have been linked to essential hypertension in humans and in animal models of congestive heart failure and cirrhosis. Norepinephrine, dopamine, and prostaglandin E2can inhibit the antinatriuretic effects of VP, and changes in the actions of these autocrine and paracrine regulators may also be involved in abnormal regulation of Na+reabsorption.
Noncoordinate regulation of ENaC: paradigm lost?
Authors: Weisz Ora A. , Johnson John P.
Published: March 2015

The epithelial sodium channel (ENaC) is composed of the three homologous subunits α, β, and γ. The basic oligomerization process inferred from all studies in heterologous systems is preferential assembly of the three subunits into a single oligomeric form. However, there is also considerable evidence that channels composed of only α-, αβ-, or αγ-subunits can form under some circumstances and that individual subunits expressed in heterologous systems can traffic to the cell membrane. In cells that express endogenous ENaC, the three subunits are often synthesized in a differential fashion, with one or two subunits expressed constitutively while the other(s) are induced by different physiological stimuli in parallel with increased ENaC activity. This phenomenon, which we term noncoordinate regulation, has been observed for both whole cell and apical membrane ENaC subunit expression. Several other heteromeric membrane proteins have also been observed to have differential rates of either turnover or trafficking of individual subunits after biosynthesis and membrane localization. Here, we examine the possibility that noncoordinate regulation of ENaC subunits may represent another mechanism in the arsenal of physiological responses to diverse stimuli.
A role for Wnt-4 in renal fibrosis
Authors: Surendran Kameswaran , McCaul Sean P. , Simon Theodore C.
Published: March 2015

Wnt-4 is a secreted glycoprotein that is critical for genitourinary development but found only in the most distal collecting duct epithelium in the normal murine adult kidney. Wnt4 expression is induced throughout the collecting ducts in four murine models of renal injury that produce tubulointerstitial fibrosis: folic acid-induced nephropathy, unilateral ureteral obstruction, renal needle puncture, and genetic polycystic kidney disease. Wnt4 activation induced by injury is limited to collecting ducts, with initial activation in the collecting duct epithelium followed by activation in fibrotic lesions surrounding the collecting ducts. The highest cellular Wnt4 expression is in interstitial fibroblasts in the fibrotic lesions that also express high levels of collagen-α1(I) mRNA and α-smooth muscle actin. In support of a functional role for Wnt-4 in these activated myofibroblasts, Wnt-4 induces stabilization of cytosolic β-catenin in a cultured myofibroblast cell line. Furthermore, Wnt-4-producing fibroblasts placed under the renal capsule of adult mice induce lesions with tubular epithelial destruction. These observations suggest a role for Wnt-4 in the pathogenesis of renal fibrosis.
Acute application of TNF stimulates apical 70-pS K+channels in the thick ascending limb of rat kidney
Authors: Wei Yuan , Babilonia Elisa , Pedraza Paulina L. , Ferreri Nicholas R. , Wang Wen-Hui
Published: March 2015

TNF has been shown to be synthesized by the medullary thick ascending limb (mTAL) ( 21 ). In the present study, we used the patch-clamp technique to study the acute effect of TNF on the apical 70-pS K+channel in the mTAL. Addition of TNF (10 nM) significantly stimulated activity of the 70-pS K+channel and increased NPo[a product of channel open probability ( Po) and channel number ( N)] from 0.20 to 0.97. The stimulatory effect of TNF was observed only in cell-attached patches but not in excised patches. Moreover, addition of TNF had no effect on the ROMK-like small-conductance K+channels in the TAL. The dose-response curve of the TNF effect yielded a Kmvalue of 1 nM, a concentration that increased channel activity to 50% maximal stimulatory effect of TNF. The concentrations required for reaching the plateau of the TNF effect were between 5 and 10 nM. The stimulatory effect of TNF on the 70-pS K+channel was observed in the presence of Nω-nitro-l-arginine methyl ester. This indicated that the effect of TNF was not mediated by a nitric oxide-dependent pathway. Also, inhibition of PKA did not affect the stimulatory effect of TNF. In contrast, inhibition of protein tyrosine kinase not only increased activity of the 70-pS K+channel but also abolished the effect of TNF. Moreover, inhibition of protein tyrosine phosphatase (PTP) blocked the stimulatory effect of TNF on the 70-pS K+channel. The notion that the TNF effect results from stimulation of PTP activity is supported by PTP activity assay in which treatment of mTAL cells with TNF significantly increased the activity of PTP. We conclude that TNF stimulates the 70-pS K+channel via stimulation of PTP in the mTAL.