bluuebunny/crossref_metadata_2025 huggingface dataset:
Neuronal NO modulates spontaneous and ANG II-stimulated fetal swallowing behavior in the near-term ovine fetus
Authors: El-Haddad Mostafa A. , Chao Conrad R. , Ma Sheng-Xing , Ross Michael G.
Published: March 2015

Spontaneous fetal swallowing occurs at a markedly higher rate compared with spontaneous adult drinking activity. This high rate of fetal swallowing is critical for amniotic fluid volume regulation. Central NO is critical for maintaining the normal rate of fetal swallowing, as nonselective inhibition of NO (with central N G -nitro-l-arginine methyl ester) suppresses spontaneous and angiotensin II (ANG II)-stimulated swallowing. We sought to differentiate the contributions of central endothelial vs. neuronal NO in the regulation of spontaneous and stimulated fetal swallowing, using a selective neuronal NO synthase (nNOS) inhibitor. Six time-dated pregnant ewes and fetuses were chronically prepared with fetal vascular and intracerebroventricular (icv) catheters and electrocorticogram (ECoG) and esophageal electromyogram electrodes and studied at 130 ± 1 days of gestation. After an initial 2-h baseline period (0–2 h), the selective nNOS inhibitor N-propyl-l-arginine (NPLA) was injected icv (2–4 h). At 4 h, the dose of NPLA was repeated, together with ANG II, and fetal swallowing was monitored for a final 2 h. Four fetuses also received an identical control study (on an alternate day) in which NPLA was replaced with artificial cerebrospinal fluid (aCSF). Suppression of nNOS by icv NPLA significantly reduced mean (± SE) spontaneous fetal swallowing (1.35 ± 0.12 to 0.50 ± 0.07 swallows/min; P< 0.001). Injection of ANG II in the presence of NPLA had no dipsogenic effect on fetal swallowing (0.68 ± 0.09 swallows/min). In the aCSF study, icv aCSF did not change fetal swallowing (0.93 ± 0.10 vs. 0.95 ± 0.09 swallows/min), whereas icv ANG II resulted in a significant increase in the rate of fetal swallowing (2.0 ± 0.04 swallows/min; P = 0.001). We speculate that the suppressive dipsogenic effects of central NPLA indicate that spontaneous and ANG II- stimulated fetal swallowing is dependent on central nNOS activity.
Detection of myoglobin desaturation inMirounga angustirostrisduring apnea
Authors: Ponganis Paul J. , Kreutzer Ulrike , Sailasuta Napapon , Knower Torre , Hurd Ralph , Jue Thomas
Published: March 2015

1H NMR solution-state study of elephant seal ( Mirounga angustirostris) myoglobin (Mb) and hemoglobin (Hb) establishes the temperature-dependent chemical shifts of the proximal histidyl NδH signal, which reflects the respective intracellular and vascular Po2in vivo. Both proteins exist predominantly in one major isoform and do not exhibit any conformational heterogeneity. The Mb and Hb signals are detectable in M. angustirostris tissue in vivo. During eupnea M. angustirostris muscle maintains a well-saturated MbO2. However, during apnea, the deoxymyoglobin proximal histidyl NδH signal becomes visible, reflecting a declining tissue Po2. The study establishes a firm methodological basis for using NMR to investigate the metabolic responses during sleep apnea of the elephant seal and to secure insights into oxygen regulation in diving mammals.
Effects of central oxytocin receptor blockade on water and saline intake, mean arterial pressure, and c-Fos expression in rats
Authors: Fitts Douglas A. , Thornton Simon N. , Ruhf Alexandra A. , Zierath Dannielle K. , Johnson Alan Kim , Thunhorst Robert L.
Published: March 2015

Central injection of ANG II has been proposed to have dual effects on salt appetite including a direct stimulatory effect and an indirect inhibitory effect through an activation of central oxytocinergic neurons. The inhibition was demonstrated by pretreating rats with central ornithine vasotocin (OVT; oxytocin antagonist) 30 min before a central ANG II injection. The OVT pretreatment produced a large increase in ANG II-induced saline intake. The present paper reports a failure to replicate that influential experiment. However, we also report for the first time that OVT by itself: 1) provokes drinking of both water and saline solution with a latency almost as short as that produced by ANG II; 2) produces a mild pressor response; and 3) increases c-Fos expression in the organum vasculosum laminae terminalis (OVLT) and the median preoptic nucleus (MnPO). Oxytocin activity may provide an inhibitory control of drinking responses as has been suggested, but the inhibition is tonic and includes both water and saline drinking. Inhibition of this tonic activity may stimulate drinking by increasing neural activity in the OVLT and MnPO.
Elevated corticosterone and inhibition of ACTH responses to CRH and ether in the neonatal rat: effect of hypoxia from birth
Authors: Raff Hershel , Jacobson Lauren , Cullinan William E.
Published: March 2015

Hypoxia is a common cause of neonatal morbidity and mortality. We have previously demonstrated a dramatic ACTH-independent activation of adrenal steroidogenesis in hypoxic neonatal rats, leading to increases in circulating corticosterone levels. The purpose of the present study was to determine if this ACTH-independent increase in corticosterone inhibits the ACTH response to acute stimuli. Neonatal rats were exposed to normoxia (control) or hypoxia from birth to 5 or 7 days of age. At the end of the exposure, plasma ACTH and corticosterone were measured before and after either ether vapors were administered for 3 min or CRH (10 μg/kg) was given intraperitoneally. Thyroid function, pituitary pro-opiomelanocortin (POMC) mRNA and ACTH content, and hypothalamic corticotropin-releasing hormone (CRH), neuropeptide Y (NPY), and AVP mRNA were also assessed. Hypoxia led to a significant increase in corticosterone without a large increase in ACTH, confirming previous studies. The ACTH responses to ether or CRH administration were almost completely inhibited in hypoxic pups. Hypoxia did not affect the established regulators of the neonatal hypothalamic-pituitary-adrenal axis, including pituitary POMC or ACTH content, hypothalamic CRH, NPY, or AVP mRNA (parvo- or magnocellular), or thyroid function. We conclude that hypoxia from birth to 5 or 7 days of age leads to an attenuated ACTH response to acute stimuli, most likely due to glucocorticoid negative feedback. The neural and biochemical mechanism of this effect has yet to be elucidated.
Activity patterns of cardiac vagal motoneurons in rat nucleus ambiguus
Authors: Rentero N. , Cividjian A. , Trevaks D. , Pequignot J. M. , Quintin L. , McAllen R. M.
Published: March 2015

Extracellular recordings were made in the right nucleus ambiguus of urethane-anesthetized rats from 33 neurons that were activated at constant latency from the craniovagal cardiac branch. Their calculated conduction velocities were in the B-fiber range (1.6–13.8 m/s, median 4.2), and most (22/33) were silent. Active units were confirmed as cardiac vagal motoneurons (CVM) by the collision test for antidromic activation and by the presence of cardiac rhythmicity in their resting discharge (9/9). Brief arterial pressure rises of 20–50 mmHg increased the activity in five of five CVM by 0.1 ± 0.02 spikes · s−1 · mmHg−1 from a resting 3.8 ± 1.2 spikes/s; they also recruited activity in two of four previously silent cardiac branch-projecting neurons. CVM firing was modulated by the central respiratory cycle, showing peak activity during inspiration (8/8). Rat CVM thus show firing properties similar to those in other species, but their respiratory pattern is distinct. These findings are discussed in relation to mechanisms of respiratory sinus arrhythmia.
Effects of the opioid antagonist naltrexone on feeding induced by DAMGO in the ventral tegmental area and in the nucleus accumbens shell region in the rat
Authors: MacDonald Amy F. , Billington Charles J. , Levine Allen S.
Published: March 2015

The nucleus accumbens shell region (sNAcc) and the ventral tegmental area (VTA) are two major nodes in the mesolimbic dopamine pathway, which mediates reward for various survival behaviors, including feeding. Opioids increase and maintain food intake when injected peripherally and centrally. Opioids in the VTA cause increased release of dopamine in the sNAcc, and when injected into either site, cause an increase in food intake. Animals in this study were double cannulated in the VTA and in the sNAcc and injected with various combinations of naltrexone (NTX) (2.5, 5, and 25 μg/side) and Tyr-d-Ala-Gly-(Me)Phe-Gly-ol (DAMGO) (0.1, 0.3, 1, 3, and 5 nmol/side) in both sites. DAMGO was found to dose dependently increase intake to an equal extent when injected into either site. DAMGO-induced increases in food intake when injected into the VTA were blocked to control levels with the highest dose of NTX injected bilaterally into the sNAcc; however, increases in intake when injected into the sNAcc were blocked only partially by the highest dose of NTX injected bilaterally into the VTA. These results indicate opioid-opioid communication between the two sites; however, the communication may be quite indirect, requiring other sites and transmitters to elicit a change in behavior.
Differential suppression of hyperglycemic, feeding, and neuroendocrine responses in anorexia
Authors: Salter Dawna , Watts Alan G.
Published: March 2015

We have used the anorexia shown by rats given hypertonic saline to drink to investigate central mechanisms that can inhibit feeding. Rats dehydrated in this manner for 3 or 5 days showed a severe attenuation of the compensatory feeding observed after an overnight fast compared with control euhydrated rats or rats whose food was restricted to match the intake of anorexic rats. Food intake after injections of 2-deoxy-d-glucose (2-DG) was also significantly decreased in dehydrated animals compared with that after a 2-DG injection given before dehydration. However, all the dehydrated animals demonstrated a robust eating response after water was returned whether they had received injection of 2-DG or vehicle. Despite a profound reduction in 2-DG-induced feeding, other glucoregulatory responses to 2-DG remained intact in dehydrated animals. After 2-DG injection, corticosterone secretion and blood glucose were significantly elevated from preinjection values whether or not animals were dehydrated. Thus the mechanisms responsible for anorexia in dehydrated animals specifically target stimulatory feeding pathways but leave intact other counterregulatory glucometabolic motor events.
Orexin gene expression is increased during states of hypertriglyceridemia
Authors: Wortley Katherine E. , Chang Guo-Qing , Davydova Zoya , Leibowitz Sarah F.
Published: March 2015

Previous reports implicate the orexins in eating and body weight regulation. This study investigated possible functional relationships between hypothalamic orexins and circulating hormones or metabolites. In situ hybridization and quantitative PCR were used to examine orexin expression in the perifornical hypothalamus (PF) of rats and mice on diets varying in fat content and with differential propensity toward obesity. The results showed that orexin gene expression was stimulated by a high-fat diet in close association with elevated triglyceride levels, suggesting a functional relationship between these measures. Results obtained in obesity-prone rats and mice revealed a similar increase in orexin in close relation to triglycerides. A direct test of this orexin-triglyceride link was performed with Intralipid, which increased PF orexin expression along with circulating triglycerides. Whereas PF galanin is similarly stimulated by dietary fat, double-labeling immunofluorescence studies showed that orexin and galanin neurons are anatomically distinct. This evidence suggests that the orexins, like galanin, are “fat-responsive” peptides that respond to circulating lipids.
Cytochromecrelease from mitochondria in the aging heart: a possible mechanism for apoptosis with age
Authors: Phaneuf Sharon , Leeuwenburgh Christiaan
Published: March 2015

There is a loss of myocytes in the aging heart due to necrosis and apoptosis. Oxidative stress, an apoptosis-inducing signal, may also increase in the aging heart. Cytosol and mitochondria isolated from the left and right ventricle of the hearts of 6-, 16-, and 24-mo-old male Fischer 344 rats were used to measure key markers of apoptosis and to assess oxidative stress. Cytosolic cytochrome c content was significantly elevated in the 16- and 24-mo-old animals compared with the 6-mo-old animals. Furthermore, Bcl-2, an antiapoptotic protein, showed a strong tendency to decrease with age, whereas Bax, a proapoptotic protein, remained unchanged. Apoptotic protease-activating factor 1 levels and caspase-3 activities were not different among the three age groups. Indicative of the chronic oxidative stress with age, heart mitochondria from old animals showed increases in manganese superoxide dismutase and glutathione peroxidase activity and increases in lipid peroxidation. This is the first study to report cytochrome c release from the mitochondria and alterations in Bcl-2 with age in vivo, providing a potential mechanism for the increase in apoptosis seen in the aging heart.
Glucocorticoids modulate baroreflex control of heart rate in conscious normotensive rats
Authors: Scheuer Deborah A. , Bechtold Andrea G.
Published: March 2015

The effect of glucocorticoids on arterial baroreceptor reflex control of heart rate (HR) was determined in conscious rats. Corticosterone (Cort) treatment for 4–6 days doubled plasma Cort in Cort-treated relative to control rats. Cort had no significant effect on mean arterial pressure (MAP) or HR. Ramped changes in MAP were produced using infusions of phenylephrine and nitroprusside. Baroreflex control of HR was analyzed using a four-parameter logistic function. The midpoint of the baseline baroreflex function curve was significantly increased in Cort-treated ( n = 14) relative to control ( n = 14) rats (112 ± 2 vs. 98 ± 2 mmHg, n = 14), and the slope was significantly decreased (0.065 ± 0.002 vs. 0.091 ± 0.007). Three hours after the glucocorticoid type II receptor antagonist mifepristone (Mif) was administered to Cort-treated rats ( n = 8), the midpoint of the baroreflex function was significantly reduced from 113 ± 4 to 99 ± 2 mmHg, and the slope was significantly increased from 0.061 ± 0.004 to 0.083 ± 0.005. Mif decreased HR in Cort-treated rats from 355 ± 17 to 330 ± 14 beats/min ( P = 0.04) but did not alter MAP (111 ± 2 to 107 ± 3 mmHg, P = 0.14). Mif had no significant effects on baroreflex function in control rats. Therefore, a moderate elevation in Cort for several days causes pressure-independent modulation of baroreflex control of HR.
Localization and function of ATP-sensitive potassium channels in human skeletal muscle
Authors: Nielsen Jens Jung , Kristensen Michael , Hellsten Ylva , Bangsbo Jens , Juel Carsten
Published: March 2015

The present study investigated the localization of ATP-sensitive K+ (KATP) channels in human skeletal muscle and the functional importance of these channels for human muscle K+ distribution at rest and during muscle activity. Membrane fractionation based on the giant vesicle technique or the sucrose-gradient technique in combination with Western blotting demonstrated that the KATP channels are mainly located in the sarcolemma. This localization was confirmed by immunohistochemical measurements. With the microdialysis technique, it was demonstrated that local application of the KATP channel inhibitor glibenclamide reduced ( P < 0.05) interstitial K+ at rest from ∼4.5 to 4.0 mM, whereas the concentration in the control leg remained constant. Glibenclamide had no effect on the interstitial K+ accumulation during knee-extensor exercise at a power output of 60 W. In contrast to in vitro conditions, the present study demonstrated that under in vivo conditions the KATP channels are active at rest and contribute to the accumulation of interstitial K+.
L-type Ca2+channels in fetal and adult ovine cerebral arteries
Authors: Blood Arlin B. , Zhao Yu , Long Wen , Zhang Lubo , Longo Lawrence D.
Published: March 2015

Recently, we reported that, whereas in cerebral arteries of the adult a majority of norepinephrine (NE)-induced increase in intracellular Ca2+concentration ([Ca2+]i) comes from release of the sarcoplasmic reticulum (SR) Ca2+stores, in the fetus the SR Ca2+stores are relatively small, and NE-induced increase in [Ca2+]iresults mainly from activation of plasma membrane L-type Ca2+channels (20). In an effort to establish further the role of L-type Ca2+channels in the developing cerebral arteries, we tested the hypothesis that, in the fetus, increased reliance on plasmalemmal L-type Ca2+channels is mediated, in part, by increased L-type Ca2+channel density. We used3H-labeled (+)isopropyl-4-(2,1,3-benzoxadiazol-4-y1)-1,4-dihydro-(2,6-dimethyl-5-methoxycarbonyl)pyridine-3-carboxylate (PN200–110, isradipine) to measure L-type Ca2+channel density (Bmax) in the cerebral arteries, common carotid artery (CCA), and descending aortae of fetal (∼140 gestation days), newborn (7–10 days), and adult sheep. In the cerebral and common carotid arteries, Bmaxvalues (fmol/mg protein) of fetuses and newborns were significantly greater than those of adults. Western immunoblotting assay also revealed that the density of L-type Ca2+channel protein in the cerebral arteries and CCA was about twofold greater in the fetus than the adult. Finally, compared with the adult, fetal cerebral arteries demonstrated a significantly greater maximum tension and [Ca2+]iin response to stimulation with the L-type Ca2+channel agonist Bay K 8644. In addition, Bay K 8644-stimulated fetal vessels demonstrated a maximal tension and [Ca2+]isimilar to that observed in response to stimulation with 10−4NE. These results support the idea that fetal cerebrovascular smooth muscle relies more on extracellular Ca2+and L-type Ca2+channels for contraction than does the adult and that this increased reliance is mediated, in part, by greater L-type Ca2+channel density. This may have important implications in the regulation of cerebral blood flow in the developing organism.
Molecular and functional characterization of a urea transporter from the kidney of a short-finned pilot whale
Authors: Janech Michael G. , Chen Ruihua , Klein Janet , Nowak Mark W. , McFee Wayne , Paul Richard V. , Fitzgibbon Wayne R. , Ploth David W.
Published: March 2015

Cetaceans (whales and dolphins) always excrete urine with an osmolality markedly higher than that of plasma. Although the mechanisms by which cetaceans concentrate urine have not been elucidated, data support a role for medullary urea accumulation in this process, as is the case for terrestrial mammals. Therefore, we hypothesized that facilitated urea transporters are present in the kidney of cetaceans. Using 5′/3′-rapid amplification of cDNA ends, we cloned a 2.7-kb cDNA from the kidney of the short-finned pilot whale Globicephala macrorhynchus. The putative open-reading frame encoded a 397-amino acid protein [pilot whale urea transporter A2 (whUT-A2)] that has 94% amino acid sequence identity to the A2 isoform of the human urea transporter (hUT-A2). Heterologous expression of whUT-A2 cRNA in Xenopus oocytes induced phloretin-inhibitable urea transport. Although Northern analysis and RT-PCR indicated that whUT-A2 was exclusively expressed in kidney, Western blotting using a polyclonal antibody to rat UT-A1/UT-A2 detected various immunoreactive proteins in kidney and other tissues. Furthermore, RT-PCR analysis suggested the presence of alternatively spliced UT-A transcripts in the kidney as well as extrarenal tissues. We conclude that renal urea transporters are highly conserved among mammals inhabiting terrestrial and pelagic environments. A urea-based concentrating mechanism, presumably evolved to meet the demands of an arid terrestrial environment, may have contributed a fortuitous preadaptation that enabled the ancestors of cetaceans to reinvade the sea.
Molecular mechanisms involved in the regulation of the endothelial nitric oxide synthase
Authors: Fleming Ingrid , Busse Rudi
Published: March 2015

The endothelial nitric oxide synthase (eNOS), the expression of which is regulated by a range of transcriptional and posttranscriptional mechanisms, generates nitric oxide (NO) in response to a number of stimuli. The physiologically most important determinants for the continuous generation of NO and thus the regulation of local blood flow are fluid shear stress and pulsatile stretch. Although eNOS activity is coupled to changes in endothelial cell Ca2+levels, an increase in Ca2+alone is not sufficient to affect enzyme activity because the binding of calmodulin (CaM) and the flow of electrons from the reductase to the oxygenase domain of the enzyme is dependent on protein phosphorylation and dephosphorylation. Two amino acids seem to be particularly important in regulating eNOS activity and these are a serine residue in the reductase domain (Ser1177) and a threonine residue (Thr495) located within the CaM-binding domain. Simultaneous alterations in the phosphorylation of Ser1177and Thr495in response to a variety of stimuli are regulated by a number of kinases and phosphatases that continuously associate with and dissociate from the eNOS signaling complex. eNOS associated proteins, such as caveolin, heat shock protein 90, eNOS interacting protein, and possibly also motor proteins provide the scaffold for the formation of the protein complex as well as its intracellular localization.
β2-Agonist fenoterol has greater effects on contractile function of rat skeletal muscles than clenbuterol
Authors: Ryall James G. , Gregorevic Paul , Plant David R. , Sillence Martin N. , Lynch Gordon S.
Published: March 2015

Potential treatments for skeletal muscle wasting and weakness ideally possess both anabolic and ergogenic properties. Although the β2-adrenoceptor agonist clenbuterol has well-characterized effects on skeletal muscle, less is known about the therapeutic potential of the related β2-adrenoceptor agonist fenoterol. We administered an equimolar dose of either clenbuterol or fenoterol to rats for 4 wk to compare their effects on skeletal muscle and tested the hypothesis that fenoterol would produce more powerful anabolic and ergogenic effects. Clenbuterol treatment increased fiber cross-sectional area (CSA) by 6% and maximal isometric force (Po) by 20% in extensor digitorum longus (EDL) muscles, whereas fiber CSA in soleus muscles decreased by 3% and Po was unchanged, compared with untreated controls. In the EDL muscles, fenoterol treatment increased fiber CSA by 20% and increased Po by 12% above values achieved after clenbuterol treatment. Soleus muscles of fenoterol-treated rats exhibited a 13% increase in fiber CSA and a 17% increase in Po above that of clenbuterol-treated rats. These data indicate that fenoterol has greater effects on the functional properties of rat skeletal muscles than clenbuterol.
Adaptation to lengthening contractions is independent of voluntary muscle recruitment but relies on inflammation
Authors: Lapointe Benoît M. , Frémont Pierre , Côté Claude H.
Published: March 2015

Lengthening contractions trigger an adaptive response decreasing the susceptibility to exercise-induced muscle damage (EIMD). We hypothesized that 1) this adaptation can be observed when voluntary muscle recruitment is bypassed and 2) inflammation repression lessens the adaptive response. Rat ankle dorsiflexors were submitted to two bouts of elicited lengthening contractions 14 days apart; in vitro force production and macrophage concentrations were obtained before and 2 days after each bout in rats treated or not for 2 or 7 days with diclofenac. The first bout caused a 45% force deficit in the placebo group vs. 25% in the diclofenac group, whereas the ED1+macrophage concentration increased by 10- and 5-fold, respectively. After the second bout, only diclofenac-treated rats (2 or 7 days) presented significant force deficits and increases in ED1+and ED2+ macrophage concentrations, but this was more pronounced in the 7-day group. We conclude that adaptation to lengthening contractions does not depend on neural components but is likely mediated by strengthening of muscle structural/cellular elements and that inflammation is important for this process.
Sympathetic activity and the underlying action potentials in sympathetic nerves: a simulation
Authors: Tang Xiaorui , Chander Ankit R. , Schramm Lawrence P.
Published: March 2015

Understanding the relationship between activity recorded in sympathetic nerves and the action potentials of the axons that contribute to that activity is important for understanding the processing of sympathetic activity by the central nervous system. Because this relationship cannot be determined experimentally and is difficult to predict analytically, we simulated the summed action potentials of 300 axons. This simulation closely resembled actual sympathetic activity and permitted us to know how many action potentials contributed to each burst of simulated sympathetic activity and the durations and amplitudes of each burst. We used these simulated data to examine a statistical method (cluster analysis) that has been used to identify and quantify bursts of sympathetic activity. Simulation indicated that the integrals of bursts, whether determined directly from the simulation or by integrating bursts detected by cluster analysis, were linearly correlated to the number of action potentials contributing to bursts. The variances of samples of the simulated signal were also linearly correlated to the number of action potentials. The amplitudes of bursts of sympathetic activity were less well correlated to the number of underlying action potentials. A linear relationship existed between the average number of action potentials contributing to simulated bursts and the integral of the amplitude spectra obtained by Fourier transform of the simulated activity. Finally, simulated experiments indicated that relatively brief recordings might be sufficient to detect statistically significant changes in sympathetic activity.
Increased GABAA inhibition of the RVLM after hindlimb unloading in rats
Authors: Moffitt Julia A. , Heesch Cheryl M. , Hasser Eileen M.
Published: March 2015

Attenuated baroreflex-mediated increases in renal sympathetic nerve activity (RSNA) in hindlimb unloaded (HU) rats apparently are due to changes within the central nervous system. We hypothesized that GABAA receptor-mediated inhibition of the rostral ventrolateral medulla (RVLM) is increased after hindlimb unloading. Responses to bilateral microinjection of the GABAA antagonist (−)-bicuculline methiodide (BIC) into the RVLM were examined before and during caudal ventrolateral medulla (CVLM) inhibition in Inactin-anesthetized control and HU rats. Increases in mean arterial pressure (MAP), heart rate (HR), and RSNA in response to BIC in the RVLM were significantly enhanced in HU rats. Responses to bilateral CVLM blockade were not different. When remaining GABAA inhibition in the RVLM was blocked by BIC during CVLM inhibition, the additional increases in MAP and RSNA were significantly greater in HU rats. These data indicate that GABAAreceptor-mediated inhibition of RVLM neurons is augmented after hindlimb unloading. Effects of input from the CVLM were unaltered. Thus, after cardiovascular deconditioning in rodents, the attenuated increase in sympathetic nerve activity in response to hypotension is associated with greater GABAA receptor-mediated inhibition of RVLM neurons originating at least in part from sources other than the CVLM.
Superoxide dismutase and oxidative stress in Dahl salt-sensitive and -resistant rats
Authors: Meng Shumei , Roberts L. Jackson , Cason Garrick W. , Curry Travis S. , Manning R. Davis
Published: March 2015

The roles of oxidative stress and renal superoxide dismutase (SOD) levels and their association with renal damage were studied in Dahl salt-sensitive (S) and salt-resistant (R)/Rapp strain rats during changes in Na intake. After 3 wk of a high (8%)-Na diet in S rats, renal medullary Cu/Zn SOD was 56% lower and Mn SOD was 81% lower than in R high Na-fed rats. After 1, 2, and 3 wk of high Na, urinary excretion of F2-isoprostanes, an index of oxidative stress, was significantly greater in S rats compared with R rats. Plasma F2-isoprostane concentration increased in the 2-wk S high Na-fed group. After 3 wk, renal cortical and medullary superoxide production was significantly increased in Dahl S rats on high Na intake, and urinary protein excretion, an index of renal damage, was 273 ± 32 mg/d in S high Na-fed rats and 35 ± 4 mg/d in R high Na-fed rats ( P < 0.05). In conclusion, salt-sensitive hypertension in the S rat is accompanied by marked decreases in renal medullary SOD and greater renal oxidative stress and renal damage than in R rats.
Prostaglandin E2-synthesizing enzymes in fever: differential transcriptional regulation
Authors: Ivanov Andrei I. , Pero Ralph S. , Scheck Adrienne C. , Romanovsky Andrej A.
Published: March 2015

The febrile response to lipopolysaccharide (LPS) consists of three phases ( phases I–III), all requiring de novo synthesis of prostaglandin (PG) E2. The major mechanism for activation of PGE2-synthesizing enzymes is transcriptional upregulation. The triphasic febrile response of Wistar-Kyoto rats to intravenous LPS (50 μg/kg) was studied. Using real-time RT-PCR, the expression of seven PGE2-synthesizing enzymes in the LPS-processing organs (liver and lungs) and the brain “febrigenic center” (hypothalamus) was quantified. Phase I involved transcriptional upregulation of the functionally coupled cyclooxygenase (COX)-2 and microsomal (m) PGE synthase (PGES) in the liver and lungs. Phase II entailed robust upregulation of all enzymes of the major inflammatory pathway, i.e., secretory (s) phospholipase (PL) A2-IIA → COX-2 → mPGES, in both the periphery and brain. Phase III was accompanied by the induction of cytosolic (c) PLA2-α in the hypothalamus, further upregulation of sPLA2-IIA and mPGES in the hypothalamus and liver, and a decrease in the expression of COX-1 and COX-2 in all tissues studied. Neither sPLA2-V nor cPGES was induced by LPS. The high magnitude of upregulation of mPGES and sPLA2-IIA (1,257-fold and 133-fold, respectively) makes these enzymes attractive targets for anti-inflammatory therapy.
Ontogenesis of epithelial phosphate transport systems in goats
Authors: Huber Korinna , Roesler Uta , Muscher Alexandra , Hansen Kathrin , Widiyono Irkham , Pfeffer Ernst , Breves Gerhard
Published: March 2015

The rapid development of precocial goats in the first weeks after birth requires an adequate adaptation of phosphate transport systems to maintain the P homeostasis at each developmental stage. Here we examined the age-related development of Na+-Pitransport systems in small intestines, kidneys, and parotid glands of goats. Kinetic parameters were determined by brush-border membrane vesicle uptake studies, and relative expression of NaPi type II mRNA and protein was recorded by molecular biological methods. High intestinal Pitransport capacity was already present on the first day of life. Within the first 3 wk of life there seemed to be a change in the type of Na+-dependent Pitransporter, and NaPi IIb was expressed increasingly up to the fifth month of life. Renal Na+-Pitransport capacity was also high at birth, and this was associated with high expression levels of NaPi IIa mRNA, indicating the important role of this transporter for renal Pireabsorption. At weaning an increase in both intestinal and renal Na+-Pitransport balanced the increasing requirements for Pito establish the endogenous Picycle. Salivary Piconcentration and parotid NaPi II mRNA rose markedly to guarantee an adequate Pisupply for rumen microbes. We concluded that the high demand for Piin young goats was assured by high basal Na+-Pitransport capacity of small intestines and kidney expressed continuously during ontogenesis.
Constant darkness restores entrainment to phase-delayed Siberian hamsters
Authors: Ruby Norman F. , Joshi Nirav , Heller H. Craig
Published: March 2015

Over 90% of Siberian hamsters ( Phodopus sungorus) fail to reentrain to a 5-h phase delay of a 16:8-h photocycle. Because constant darkness (DD) restores rhythms disrupted by constant light, we tested whether DD could also restore entrainment. DD began 0, 5, or 14 days after a 5-h phase delay, and the light-dark cycle was reinstated 14 days later. All hamsters exposed to DD on day 0 reentrained, whereas 42% reentrained irrespective of whether DD began 5 or 14 days later. For these latter two groups, tau (τ) and alpha (α) in DD predicted reentrainment; animals that reentrained had a mean τ and α of 24.1 and 8.9 h, respectively, whereas those that failed to reentrain maintained a mean τ and α of 25.0 and of 7.1 h, respectively. Restoration of entrainment by DD is somewhat paradoxical because it suggests that reentrainment to the photocycle was prevented by continued exposure to that same photocycle. The dichotomy of circadian responses to DD suggests “entrainment” phenotypes that are similar to those of photoperiodic responders and nonresponders.
Fever responses of Zucker rats with and withoutfatty mutation of the leptin receptor
Authors: Ivanov Andrei I. , Romanovsky Andrej A.
Published: March 2015

Leptin is thought to be involved in febrigenic signaling from the periphery to the brain. Zucker obese rats have a so-called fatty mutation in the leptin receptor gene and express a dysfunctional protein. Studies comparing the fever responses of fatty ( fa/fa) rats and of their lean ( Fa/Fa and Fa/fa) counterparts yield contradictory results. To resolve these contradictions, we evaluated the effect of fatty mutation on infectious and stress-associated fevers at thermoneutrality (29°C) and in a cool environment (20°C). Zucker fa/fa and Fa/? rats were infused with Escherichia coli lipopolysaccharide (LPS; 10 μg/kg) through a jugular catheter (infectious fever) or with saline through the catheter (control) or received a painful intramuscular injection of saline (stress fever). At thermoneutrality, the colonic temperature (Tc) responses of fattyrats to all stimuli tested were no different from the responses of lean rats. In a cool environment, Tc responses of fatty rats to all stimuli were ∼0.5°C lower than those of lean rats. The observed attenuation of LPS-induced and stress-associated fevers in Zucker fatty rats in the cold agrees with the literature data showing that brown adipose tissue (the major heat production effector) is morphologically and functionally defective in these rats. The normal febrile responses of fatty Zucker rats to pyrogenic stimuli at thermoneutrality indicate that fatty mutation does not interrupt febrigenic signaling from the periphery to the brain.
The spleen modulates the febrile response of guinea pigs to LPS
Authors: Feleder Carlos , Li Zhonghua , Perlik Vit , Evans Allison , Blatteis Clark M.
Published: March 2015

The febrile responses of splenectomized (Splex) or sham-operated (Sham) guinea pigs challenged intravenously or intraperitoneally with lipopolysaccharide (LPS) 7 and 30 days after surgery were evaluated. FITC-LPS uptake by Kupffer cells (KC) was additionally assessed 15, 30, and 60 min after injection. LPS at 0.05 μg/kg iv did not evoke fever in Sham animals but caused a 1.2°C core temperature (Tc) rise in the Splex animals. LPS at 2 μg/kg iv induced a 1.8°C greater Tcrise of the Splex animals than of their controls. LPS at 2 and 8 μg/kg ip 7 days postsurgery induced 1.4 and 1.8°C higher fevers, respectively, in the Splex than Sham animals. LPS at 2 and 8 μg/kg ip 30 days postsurgery also increased the febrile responses of the asplenic animals by 1.6 and 1.8°C, respectively. FITC-LPS at 7 days was detected in the controls within KC 15 min after its administration; the label density was reduced at 30 min and almost 0 at 60 min. In the Splex group, in contrast, the labeling was significantly denser and remained unchanged through all three time points; this effect was still present 30 days after surgery. Similar results were obtained at 60 min after FITC-LPS intraperitoneal injection. Gadolinium chloride pretreatment (−3 days) of the Splex group significantly reduced both their febrile responses to LPS (8 μg/kg ip) and their KC uptake of FITC-LPS 7 days postsurgery. Thus splenectomy increases the magnitude of the febrile response of guinea pigs and the uptake of systemically administered LPS.
Cholecystokinin and D-fenfluramine inhibit food intake in oxytocin-deficient mice
Authors: Mantella Rose C. , Rinaman Linda , Vollmer Regis R. , Amico Janet A.
Published: March 2015

Results from previous studies indicate that oxytocin (OT)-containing neural pathways are activated in laboratory rats after systemic administration of CCK or d-fenfluramine and that centrally released OT may participate in the anorexigenic effects of these treatments. To explore the relationship between feeding behavior and OT function, the effects of CCK and d-fenfluramine on feeding and central c-Fos expression were compared in wild-type (OT+/+) and OT-deficient mice (OT-/-) of C57BL/6 background. Male OT+/+ and OT-/- mice were administered saline or CCK (1, 3, or 10 μg/kg ip) after overnight food deprivation. Saline-treated OT+/+ and OT-/- mice consumed equivalent amounts of food after an overnight fast. CCK inhibited deprivation-induced food intake in a dose-dependent manner to a similar extent in both genotypes. CCK treatment also induced similar hindbrain and forebrain patterns of increased c-Fos expression in mice of both genotypes. After treatment with d-fenfluramine (10 mg/kg ip), both OT+/+ and OT-/- mice consumed significantly less food than untreated controls, with no difference between genotypes. We conclude that OT signaling pathways are unnecessary for the anorexigenic effects of systemically administered CCK and d-fenfluramine in C57BL/6 mice.
Actions of a novel synthetic natriuretic peptide on hemodynamics and ventricular function in the dog
Authors: Lainchbury John G. , Lisy Ondrej , Burnett John C. , Meyer Donna M. , Redfield Margaret M.
Published: March 2015

Dendroaspis natriuretic peptide (DNP) is a recently discovered peptide with structural similarity to known natriuretic peptides. DNP has been shown to possess potent renal actions. Our objectives were to define the acute hemodynamic actions of DNP in normal anesthetized dogs and the acute effects of DNP on left ventricular (LV) function in conscious chronically instrumented dogs. In anesthetized dogs, DNP, but not placebo, decreased mean arterial pressure (141 ± 6 to 109 ± 7 mmHg, P < 0.05) and pulmonary capillary wedge pressure (5.8 ± 0.3 to 3.4 ± 0.2 mmHg, P < 0.05). Cardiac output decreased and systemic vascular resistance increased with DNP and placebo. DNP-like immunoreactivity and guanosine 3′,5′-cyclic monophosphate concentration increased without changes in other natriuretic peptides. In conscious dogs, DNP decreased LV end-systolic pressure (120 ± 7 to 102 ± 6 mmHg, P < 0.05) and volume (32 ± 6 to 28 ± 6 ml, P < 0.05) and LV end-diastolic volume (38 ± 5 to 31 ± 4 ml, P < 0.05) but not arterial elastance. LV end-systolic elastance increased (6.1 ± 0.7 to 7.4 ± 0.6 mmHg/ml, P < 0.05), and Tau decreased (31 ± 2 to 27 ± 1 ms, P < 0.05). The effects on hemodynamics, LV function, and second messenger generation suggest synthetic DNP may have a role as a cardiac unloading and lusitropic peptide.
Molecular characterization of a multidrug resistance-associated protein, Mrp2, from the little skate
Authors: Cai Shi-Ying , Soroka Carol J. , Ballatori Nazzareno , Boyer James L.
Published: March 2015

Multidrug resistance protein Mrp2 (symbol Abcc2) in liver plays a significant role in the biliary excretion of organic anionic conjugates. Mutations in human MRP2 result in defects in excretion of conjugated bilirubin and other cholephiles known as the Dubin-Johnson syndrome. Previous studies indicate that transporters with Mrp2-like functions are present in ancient vertebrates. We have now characterized an Mrp2 ortholog at the molecular level from the liver of the small skate, Raja erinacea, a marine vertebrate that evolved ∼200 million years ago. The full-length skate Mrp2 cDNA is 6 kb and encodes for a 1,564-amino acid peptide with 56% identity to human Mrp2. Northern blot analysis demonstrated that skate Mrp2 is abundantly expressed in skate liver, intestine, and kidney. Immunoblots reveal a 180-kDa protein in skate liver. Immunofluorescence studies locate skate Mrp2 to the apical membrane of hepatocytes, renal tubules, and intestine. A PDZ-interacting motif is also found at its COOH terminus. Further sequence analysis indicates that transmembrane domains 1, 9, 11, 16, and 17 are the most highly conserved transmembrane domains between skate Mrp2 and mammalian MRP2/Mrp2s. This analysis indicates that Mrp2 orthologs evolved early in vertebrate evolution and that conserved domains may be important determinants of Mrp2 substrate specificity.
Attenuated fever in pregnant rats is associated with blunted syntheses of brain cyclooxygenase-2 and PGE2
Authors: Imai-Matsumura Kyoko , Matsumura Kiyoshi , Terao Akira , Watanabe Yasuyoshi
Published: March 2015

Attenuation of fever occurs in pregnant animals. This study examined a hypothesis that brain production of PGE2, the final mediator of fever, is suppressed in pregnant animals. Near-term pregnant rats and age-matched nonpregnant female rats were injected with lipopolysaccharide (100 μg/kg) intraperitoneally. Four hours later, colonic temperature was measured, their cerebrospinal fluid (CSF) was sampled for PGE2assay, and their brains were processed for immunohistochemistry of cyclooxygenase-2, an enzyme involved in PGE2biosynthesis. In the pregnant rats, lipopolysaccharide injection resulted in significantly smaller elevations in both colonic temperature and CSF-PGE2level than in nonpregnant rats. In the pregnant rats, lipopolysaccharide-induced cyclooxygenase-2 expression was blunted in terms of the number of positive cells. There was a significant correlation between PGE2level in CSF and the number of cyclooxygenase-2-positive endothelial cells. These results suggest that suppressed PGE2production in the brain is one cause for the attenuated fever response at near-term pregnancy and that this suppressed PGE2production is due to the suppressed induction of cyclooxygenase-2 in brain endothelial cells.
Primary causes of decreased mitochondrial oxygen consumption during metabolic depression in snail cells
Authors: Bishop Tammie , St-Pierre Julie , Brand Martin D.
Published: March 2015

Cells isolated from the hepatopancreas of estivating snails ( Helix aspersa) have strongly depressed mitochondrial respiration compared with controls. Mitochondrial respiration was divided into substrate oxidation (which produces the mitochondrial membrane potential) and ATP turnover and proton leak (which consume it). The activity of substrate oxidation (and probably ATP turnover) decreased, whereas the activity of proton leak remained constant in estivation. These primary changes resulted in a lower mitochondrial membrane potential in hepatopancreas cells from estivating compared with active snails, leading to secondary decreases in respiration to drive ATP turnover and proton leak. The respiration to drive ATP turnover and proton leak decreased in proportion to the overall decrease in mitochondrial respiration, so that the amount of ATP turned over per O2consumed remained relatively constant and aerobic efficiency was maintained in this hypometabolic state. At least 75% of the total response of mitochondrial respiration to estivation was caused by primary changes in the kinetics of substrate oxidation, with only 25% or less of the response occurring through primary effects on ATP turnover.
Maternal obesity alters adiposity and monoamine function in genetically predisposed offspring
Authors: Levin Barry E. , Dunn-Meynell Ambrose A.
Published: March 2015

The impact of maternal obesity on brain monoamine function in adult offspring of dams selectively bred to express diet-induced obesity (DIO) or diet resistance (DR) was assessed by making dams obese or lean during gestation and lactation. After 12 wk on chow and 4 wk on a 31% fat diet, offspring hypothalamic nucleus size and [3H]nisoxetine binding to norepinephrine transporters (NET) and [3H]paroxetine binding to serotonin transporters (SET) were measured. Offspring of obese DIO dams became more obese than all other groups, but maternal obesity did not alter weight gain in DR offspring (25). Maternal obesity was associated with 10–17% enlargement of ventromedial nuclei (VMN) and dorsomedial nuclei in both DIO and DR offspring. Offspring of obese DIO dams had 25–88% lower NET binding in the paraventricular nuclei (PVN), arcuate nuclei, VMN, and the central amygdalar nuclei, while offspring of obese DR dams had 43–67% higher PVN and 90% lower VMN NET binding and a generalized increase in SET binding across all hypothalamic areas compared with other groups. Thus maternal obesity was associated with alterations in offspring brain monoamine metabolism, which varied as a function of genotype and the development of offspring obesity.
Peripheral O2chemoreceptors mediate humoral catecholamine secretion from fish chromaffin cells
Authors: Reid Stephen G. , Perry Steve F.
Published: March 2015

This study addressed the hypothesis that the secretion of catecholamines from trout ( Oncorhynchus mykiss) chromaffin cells, during hypoxia, is triggered by stimulation of O2chemoreceptors located within the gills. Sodium cyanide was administered into the inspired water (external cyanide) or injected into the gill circulation (internal cyanide) to pharmacologically stimulate external (water sensing) or internal (blood sensing) O2chemoreceptors, respectively. Both of these treatments caused an elevation of circulating catecholamine levels. The response to external, but not internal, cyanide was abolished by removal of the first gill arch. Hypoxia produced an increase in circulating catecholamine levels that was unaffected by removal of the first gill arch or by denervation of the pseudobranch. Cyanide and hypoxia both caused the well-documented cardiorespiratory reflexes normally observed in this species. This study demonstrates, for the first time, that gill O2chemoreceptors can initiate the reflex that leads to catecholamine release from the chromaffin cells and that stimulation of internally oriented O2receptors on all gill arches appears to be the physiologically important mechanism for initiating release.
Subcellular distribution of ryanodine receptors in the cardiac muscle of carp (Cyprinus carpio)
Authors: Chugun Akihito , Taniguchi Kazumi , Murayama Takashi , Uchide Tsuyoshi , Hara Yukio , Temma Kyosuke , Ogawa Yasuo , Akera Tai
Published: March 2015

We examined the subcellular localization of ryanodine receptors (RyR) in the cardiac muscle of carp using biochemical, immunohistochemical, and electron microscopic methods and compared it with those of rats and guinea pigs. To achieve this goal, an anti-RyR antibody was newly raised against a synthetic peptide corresponding to an amino acid sequence that was conserved among all sequenced RyRs. Western blot analysis using this antibody detected a single RyR band following the SDS-PAGE of sarcoplasmic reticulum (SR) membranes from carp atrium and ventricle as well as from mammalian hearts and skeletal muscles. The carp heart band had slightly greater mobility than those of mammalian hearts. Although immunohistochemical staining showed evident striations corresponding to the Z lines in longitudinal sections of mammalian hearts, clusters of punctate staining, in contrast, were distributed ubiquitously throughout carp atrium and ventricle. Electron microscopic images of the carp myocardium showed that the SR was observed largely as the subsarcolemmal cisternae and the reticular SR, suggesting that the RyR is localized in the junctional and corbular SR.