bluuebunny/crossref_metadata_2025 huggingface dataset:
Impaired autoregulation of renal blood flow in the fawn-hooded rat
Authors: Van Dokkum Richard P. E. , Alonso-Galicia Magdalena , Provoost Abraham P. , Jacob Howard J. , Roman Richard J.
Published: December 2017

The responses to changes in renal perfusion pressure (RPP) were compared in 12-wk-old fawn-hooded hypertensive (FHH), fawn-hooded low blood pressure (FHL), and August Copenhagen Irish (ACI) rats to determine whether autoregulation of renal blood flow (RBF) is altered in the FHH rat. Mean arterial pressure was significantly higher in conscious, chronically instrumented FHH rats than in FHL rats (121 ± 4 vs. 109 ± 6 mmHg). Baseline arterial pressures measured in ketamine-Inactin-anesthetized rats averaged 147 ± 2 mmHg ( n = 9) in FHH, 132 ± 2 mmHg ( n = 10) in FHL, and 123 ± 4 mmHg ( n = 9) in ACI rats. Baseline RBF was significantly higher in FHH than in FHL and ACI rats and averaged 9.6 ± 0.7, 7.4 ± 0.5, and 7.8 ± 0.9 ml ⋅ min−1⋅ g kidney wt−1, respectively. RBF was autoregulated in ACI and FHL but not in FHH rats. Autoregulatory indexes in the range of RPPs from 100 to 150 mmHg averaged 0.96 ± 0.12 in FHH vs. 0.42 ± 0.04 in FHL and 0.30 ± 0.02 in ACI rats. Glomerular filtration rate was 20–30% higher in FHH than in FHL and ACI rats. Elevations in RPP from 100 to 150 mmHg increased urinary protein excretion in FHH rats from 27 ± 2 to 87 ± 3 μg/min, whereas it was not significantly altered in FHL or ACI rats. The percentage of glomeruli exhibiting histological evidence of injury was not significantly different in the three strains of rats. These results indicate that autoregulation of RBF is impaired in FHH rats before the development of glomerulosclerosis and suggest that an abnormality in the control of renal vascular resistance may contribute to the development of proteinuria and renal failure in this strain of rats.
Role of nitric oxide in modulating renal function and arterial pressure during chronic aldosterone excess
Authors: Granger Joey P. , Kassab Salah , Novak Jacqueline , Reckelhoff Jane F. , Tucker Brett , Miller M. Todd
Published: December 2017

Chronic aldosterone (Aldo) excess is associated with transient sodium retention, extracellular fluid volume expansion, renal vasodilation, and hypertension. The purpose of this study was to determine the role of nitric oxide (NO) in mediating the renal vasodilation and the escape from the sodium-retaining actions of Aldo. To achieve this goal, we examined the long-term effects of Aldo (15 μg ⋅ kg−1 ⋅ min−1for 7 days) in conscious, chronically instrumented control dogs ( n = 9) and in dogs ( n = 12) pretreated with the NO synthesis inhibitor N G-nitro-l-arginine methyl ester (l-NAME; 10 μg ⋅ kg−1 ⋅ min−1). In control dogs, Aldo caused a transient sodium retention (126 ± 6 to 56 ± 2 meq/day) followed by a return of sodium excretion to normal levels. Aldo also increased renal plasma flow by 15% (205 ± 13 to 233 ± 16 ml/min), glomerular filtration rate by 20% (72 ± 3 to 87 ± 5 ml/min), and arterial pressure from 90 ± 3 to 102 ± 3 mmHg. Aldo increased urinary nitrate/nitrite excretion by 60% in the control dogs. Although the sodium-retaining (144 ± 7 to 56 ± 7 meq/day) and arterial pressure (122 ± 6 to 136 ± 5 mmHg) responses to Aldo were the same in dogs pretreated withl-NAME compared with control, the renal hemodynamic response was markedly attenuated. The results of this study suggest that NO plays an important role in mediating the renal vasodilation during chronic Aldo excess.
Cardiovascular and renal effects of adrenomedullin in rats with heart failure
Authors: Nagaya Noritoshi , Nishikimi Toshio , Horio Takeshi , Yoshihara Fumiki , Kanazawa Akio , Matsuo Hisayuki , Kangawa Kenji
Published: December 2017

Plasma adrenomedullin (AM), a novel hypotensive peptide, has been shown to increase in heart failure (HF). This study sought to examine the cardiovascular and renal effects of intravenous infusion of AM in HF rats and sham-operated rats (control) using two doses of AM that would not induce hypotension. Rat AM-(1—50) was intravenously administered at rates of 0.01 (low) and 0.05 (high) μg ⋅ kg body wt−1 ⋅ min−1. Low-dose AM increased urine flow (+21% in HF, +29% in control) and urinary sodium excretion (+109% in HF, +123% in control) without changes in any hemodynamic variables. In contrast, high-dose AM slightly decreased mean arterial pressure (−3% in HF, −5% in control) and significantly increased cardiac output (+20% in HF, +12% in control). Infusion of high-dose AM resulted in significant decreases in right ventricular systolic pressure (−11%) and right atrial pressure (−28%) only in HF rats. High-dose AM significantly increased glomerular filtration rate (+10% in HF, +16% in control) and effective renal plasma flow (+25% in HF, +46% in control) as well as urine flow and urinary sodium excretion. In summary, intravenous infusion of AM exerted diuresis and natriuresis without inducing hypotension and, in the higher dose, produced beneficial hemodynamic and renal vasodilator effects in rats with compensated HF.
Stimulation of intestinal glucoreceptors in rats increases pancreatic islet blood flow through vagal mechanisms
Authors: Carlsson Per-Ola , Iwase Masanori , Jansson Leif
Published: December 2017

The aim of the study was to evaluate whether intestinal glucoreceptors participate in the regulation of pancreatic islet blood flow. For this purpose, anesthetized rats were infused (0.1 ml/min for 3 min) with saline, glucose, or 3- O-methylglucose directly into the duodenum. The glucose (1 mg/kg body wt) infusion rate was chosen to prevent any effects on systemic or intraportal blood glucose concentrations. Intraduodenal infusion ofd-glucose increased both serum insulin concentration and islet blood flow, whereas the osmotic control substance 3- O-methylglucose had no such effects. A bilateral abdominal vagotomy performed before the infusions totally abolished both the insulin and blood flow response to glucose infusion. The absence of an increased islet blood flow in response to glucose infusion in the denervated, transplanted pancreas was a further indication of the crucial importance of the regulation of islet blood flow by the vagus nerves. It is concluded that intestinal glucoreceptors participate in the mediation of glucose-induced islet blood flow increase.
Preoptic recess noradrenergic receptors control modification of baroreflex sensitivity by hypertonicity
Authors: Bealer Steven L.
Published: December 2017

These studies examined the effects of α1- and α2-adrenoreceptor blockade in the anteroventral portion of the third cerebral ventricle (AV3V) on modification of baroreflex-induced changes in heart rate and renal sympathetic nerve activity (RSNA) induced by hyperosmolality. Local administration of hypertonic artificial cerebrospinal fluid (aCSF) in the AV3V significantly increased baroreflex-induced bradycardia during intravenous phenylephrine but did not alter changes in RSNA during the pressor response or alter tachycardia and neural responses evoked by decreased blood pressure. The enhanced cardiac response was not observed during simultaneous administration of phentolamine (α1- and α2-antagonist) or yohimbine (selective α2-antagonist) in the AV3V region. However, treatment with prazosin (α1-antagonist) did not alter the exaggerated cardiac response evoked by hypertonic aCSF to increased blood pressure. These data demonstrate that acute, local hypertonic stimulation in the AV3V region selectively enhances baroreflex-induced bradycardia by stimulation of α2-adrenergic receptors during acute pressor responses.
An antipyretic role for interleukin-10 in LPS fever in mice
Authors: Leon Lisa R. , Kozak Wieslaw , Rudolph Karin , Kluger Matthew J.
Published: December 2017

Interleukin (IL)-10 inhibits the synthesis of proinflammatory cytokines implicated in fever, including IL-1β, IL-6, and tumor necrosis factor (TNF)-α. We hypothesized that IL-10 functions as an antipyretic in the regulation of fevers to lipopolysaccharide (LPS) and turpentine. Body temperature was measured by biotelemetry. Swiss Webster (SW) mice treated with recombinant murine IL-10 were resistant to fever induced by a low dose of LPS (100 μg/kg ip) and to the hypothermic and febrile effects of a high (septiclike) dose of LPS (2.5 mg/kg ip). IL-10 knockout mice developed an exacerbated and prolonged fever in response to a low dose of LPS (50 μg/kg ip) compared with their wild-type counterparts. At 4 h after injection of the low dose of LPS, plasma levels of IL-6, but not TNF-α, were significantly elevated in the IL-10 knockout mice compared with their wild-type controls (ANOVA, P < 0.05). After injection of the same high dose of LPS injected into SW mice, wild-type mice developed a fever at 24 h whereas IL-10 knockout mice immediately developed a profound hypothermia that lasted through 41 h (ANOVA, P < 0.05). Body weight and food intake were more significantly depressed in response to the high dose of LPS in the knockout mice compared with their wild-type controls. Only 30% of the IL-10 knockout mice survived compared with 100% of the wild-type mice (Fisher’s exact test, P < 0.05). Fever in response to the injection of turpentine (100 μl/mouse sc) did not differ between wild-type and IL-10 knockout mice. These data support the hypotheses that 1) IL-10 functions as an endogenous antipyretic following exposure to LPS, 2) a putative mechanism of the early antipyretic action of IL-10 is through the inhibition of plasma levels of IL-6, 3) IL-10 has a protective role in the lethal effects of exposure to high levels of LPS, and 4) endogenous IL-10 does not have a role in fever induced by turpentine.
Antenatal steroids decrease blood-brain barrier permeability in the ovine fetus
Authors: Stonestreet Barbara S. , Petersson Katherine H. , Sadowska Grazyna B. , Pettigrew Karen D. , Patlak Clifford S.
Published: December 2017

Antenatal corticosteroid therapy reduces the incidence of intraventricular hemorrhage in premature infants. Enhanced microvascular integrity might provide protection against intraventricular hemorrhage. In the adult, there is evidence to suggest that the blood-brain barrier may be under hormonal control. We hypothesized that antenatal corticosteroids decrease blood-brain barrier permeability in the preterm ovine fetus. Chronically instrumented 120-day-gestation fetuses were studied 12 h after the last of four 6-mg dexamethasone ( n = 5) or placebo ( n = 6) injections had been given over 48 h to the ewes. Blood-brain barrier function was quantified with the blood-to-brain transfer constant ( K i) for α-aminoisobutyric acid (AIB). K i was significantly lower across brain regions in the fetuses of ewes that received antenatal dexamethasone compared with placebo (ANOVA; interaction, F = 2.54, P < 0.004). In fetuses of dexamethasone- and placebo-treated ewes, K i(μl ⋅ g brain wt−1 ⋅ min−1, mean ± SD) was, respectively, 2.43 ± 0.27 vs. 3.41 ± 0.74 in the cortex, 4.46 ± 0.49 vs. 5.29 ± 0.85 in the cerebellum, and 3.70 ± 0.49 vs. 5.11 ± 0.70 in the medulla. We conclude that antenatal treatment with corticosteroids reduces blood-brain permeability in the ovine fetus.
GABA-mediated inhibition of raphe pallidus neurons regulates sympathetic outflow to brown adipose tissue
Authors: Morrison Shaun F. , Sved Alan F. , Passerin Alicia M.
Published: December 2017

Sympathetic nerve activity to brown adipose tissue (BAT) regulates adipocyte metabolism of its stored lipid fuel and thus the thermogenesis in BAT. To determine if the discharge of neurons in the rostral raphe pallidus (RPa) can influence BAT thermogenesis, changes in sympathetic nerve activity to BAT were recorded after microinjection (60 nl) of the GABAA receptor antagonist bicuculline (500 μM) into the RPa in chloralose-urethan-anesthetized, ventilated rats. Bicuculline caused a large, rapid rise in the sympathetic nerve activity to BAT (which had also increased during acute hypothermia) from very low, normothermic control levels to maximum values (mean: 1,949 ± 604% control; n = 13) after 4–6 min. The sympathetic nerve discharge to BAT had a mean burst frequency (3.5 ± 0.3 Hz) that was significantly less than the heart rate (7.3 ± 0.2 beats/min), and it was not inhibited during baroreceptor reflex activation. Bicuculline-stimulated increases in the sympathetic nerve activity to BAT and cold-evoked increases in neuronal fos expression were localized to the RPa at the level of the caudal half of the facial nucleus. This dramatic increase in sympathetic nerve activity to BAT after disinhibition of neurons in rostral RPa is consistent with a major role for RPa neurons, perhaps as sympathetic premotoneurons for BAT, in medullary control of BAT thermogenesis.
Effects of urea and trimethylamineN-oxide on fluidity of liposomes and membranes of an elasmobranch
Authors: Barton Kimby N. , Buhr Mary M. , Ballantyne James S.
Published: December 2017

The effects on membrane fluidity of two solutes of biological importance in elasmobranch fishes, urea and trimethylamine oxide (TMAO), were determined using elasmobranch red blood cell plasma membranes and artificial liposomes. Fluorescence polarizations of three probes with differing sites of insertion (1,6-diphenylhexatriene, cis-parinaric acid, and trans-parinaric acid) were used to study the effects of physiological levels of urea (400 mM) and TMAO (200 mM) separately and together in a 2:1 urea:TMAO ratio (400 mM:200 mM). In the elasmobranch erythrocyte membrane, there was a trend toward an increase in the order of the gel-phase domains when treated with urea, although this was not statistically significant. This effect was counteracted by the presence of TMAO. To determine if the organic solutes were acting directly on the membrane lipids or on the integral proteins, phase-transition profiles of protein-free dipalmitoyl phosphatidylcholine liposomes were determined. These profiles showed that urea again increased the order of the gel-phase domains of the bilayer; however, this effect was not counteracted by the presence of TMAO. We suggest that the increased order in the gel-phase domains may be an indirect effect of a decrease in the order of the fluid-phase domains. This increase in fluidity may be due either to a disruptive effect of urea on the hydrophobic core of the membrane or to indirect effects mediated by changes in the integral membrane proteins. This study is the first to demonstrate that urea and TMAO may act as counteracting solutes in the elasmobranch erythrocyte membrane and that the counteraction appears to be at the level of the integral proteins rather than the membrane lipids.
Effect of endurance exercise on myosin heavy chain gene regulation in human skeletal muscle
Authors: O’Neill D. Sean , Zheng Donghai , Anderson Wade K. , Dohm G. Lynis , Houmard Joseph A.
Published: December 2017

The purpose of this study was to determine the effect of endurance-oriented exercise on myosin heavy chain (MHC) isoform regulation in human skeletal muscle. Exercise consisted of 1 h of cycle ergometer work per day at 75% maximal oxygen consumption for seven consecutive days. Muscle was obtained before the first bout of exercise, 3 h after the first bout of exercise, and before and 3 h after the final exercise bout on day 7( n = 9 subjects). No changes in MHC mRNA (I, IIa, IIx) were evident after the first exercise period. There was, however, a significant ( P < 0.05) decline (−30%) in MHC IIx mRNA 3 h after the final training bout. An interesting finding was that a higher pretraining level of MHC IIx mRNA was associated with a greater decline in the transcript before ( r = 0.68, P < 0.05) and 3 h after ( r = 0.82, P < 0.05) the final exercise bout. These findings suggest that MHC IIx mRNA is downregulated during the early phase of endurance-oriented exercise training in human skeletal muscle but only after repeated contractile activity. Pretraining MHC IIx mRNA content may influence the magnitude of this response.
Leptin disinhibits nonshivering thermogenesis in infants after maternal separation
Authors: Blumberg Mark S. , Deaver Kara , Kirby Robert F.
Published: December 2017

Prolonged maternal separation inhibits endogenous heat production in infant mammals exposed to cold. This inhibition of thermogenesis occurs many hours before energy stores have been fully depleted. The need to protect energy resources during separation-induced starvation may be signaled by declining levels of leptin, a hormone that acts as a “fat signal” and a regulator of energy utilization; in fact, starvation reduces leptin levels in adult mice and infant rats. It is not known, however, whether leptin has a functional role during starvation in infants. Such a role may be found in the regulation of nonshivering thermogenesis by brown adipose tissue (BAT), a specialized organ that provides heat to infant mammals, including humans, during cold exposure. Heat produced by BAT allows the cold-exposed infant to prevent the detrimental effects of hypothermia on physiology and behavior and, ultimately, growth. Here we show that leptin disinhibits BAT thermogenesis during cold exposure in infant rats after 18 h of maternal separation. This finding demonstrates that leptin is more than simply an adipostat for the regulation of body weight; specifically, leptin modulates thermogenesis and energy utilization in the early postnatal period.
Chronic eccentric exercise: improvements in muscle strength can occur with little demand for oxygen
Authors: Lastayo P. C. , Reich T. E. , Urquhart M. , Hoppeler H. , Lindstedt S. L.
Published: December 2017

Eccentric contractions, the lengthening of muscle while producing force, are a common part of our everyday movements. This study presents a challenge to the accepted notion that eccentric work causes obligatory muscle injury while demonstrating that an increase in muscle strength, via eccentric work, can occur with little demand for oxygen. Nine healthy subjects, ages 18–34, were randomly placed in either an eccentric or a concentric training group. Both groups trained for 6 wk while progressively increasing training frequency and duration. Significant gains in isometric leg strength were seen in the eccentrically trained subjects only. While training, the oxygen consumption required to do the eccentric work was equal to or less than that required to do the concentric work. The results demonstrate that by progressively increasing the eccentric work rate, significant isometric strength gains can be made without muscle injury and with minimal increase in metabolic demand for oxygen. The potential clinical implications of an eccentric training program that uncouples skeletal muscle strength improvements from the demand for oxygen are alluring.
Fatty acid binding protein in heart and skeletal muscles of the migratory barnacle goose throughout development
Authors: Pelsers Maurice M. A. L. , Butler Patrick J. , Bishop Charles M. , Glatz Jan F. C.
Published: December 2017

The long-distance migratory flights of birds are predominantly fueled by the oxidation of fatty acids, which are sourced primarily from extracellular adipose stores. These fatty acids have to be transported, via the circulatory system, to the mitochondria of the active muscles. An important facilitator of fatty acid transport within the cytoplasm of muscle cells is fatty acid binding protein (FABP), which serves as an intracellular carrier of long-chain fatty acids. In mammals, the muscular FABP content is related to the fatty acid oxidation capacity of the tissue. The aim of this study was to measure FABP in samples taken from the cardiac, pectoralis, and semimembranosus muscles of a long-distance avian migrant, the barnacle goose ( Branta leucopsis), at various stages of development. Western blot analysis identified a single goose muscle protein of 15 kDa that was able to bind fatty acids and showed a 66% cross-reactivity with antibodies against human heart-type FABP. Captive goslings showed no significant changes in FABP content of either the heart (62.6 ± 10.6 μg/g wet wt) or the semimembranosus muscle (8.4 ± 1.9 μg/g wet wt) during development. However, in both peripheral and deep sites within the pectoralis muscle, FABP content of samples taken from captive goslings were ∼10-fold higher throughout development and reached values of 30–40 μg/g wet wt in fledging goslings at 7 wk of age. A further twofold higher value was seen in wild but not in captive goslings immediately before migration (12 wk of age). Similarly, FABP content was significantly higher in pectoralis samples taken from wild adults (94.3 ± 3.6 μg/g wet wt) compared with those from captive adults (60.5 ± 3.6 μg/g wet wt). These results suggest that the experience of flight activity may be of critical importance in achieving maximal expression of FABP in the pectoralis muscles of postfledging and mature geese immediately before migration.
Developmental regulation of genes mediating murine brain glucose uptake
Authors: Khan Janine Y. , Rajakumar Rosario A. , McKnight Robert A. , Devaskar Uday P. , Devaskar Sherin U.
Published: December 2017

We examined the molecular mechanisms that mediate the developmental increase in murine whole brain 2-deoxyglucose uptake. Northern and Western blot analyses revealed an age-dependent increase in brain GLUT-1 (endothelial cell and glial) and GLUT-3 (neuronal) membrane-spanning facilitative glucose transporter mRNA and protein concentrations. Nuclear run-on experiments revealed that these developmental changes in GLUT-1 and -3 were regulated posttranscriptionally. In contrast, the mRNA and protein levels of the mitochondrially bound glucose phosphorylating hexokinase I enzyme were unaltered. However, hexokinase I enzyme activity increased in an age-dependent manner suggestive of a posttranslational modification that is necessary for enzymatic activation. Together, the postnatal increase in GLUT-1 and -3 concentrations and hexokinase I enzymatic activity led to a parallel increase in murine brain 2-deoxyglucose uptake. Whereas the molecular mechanisms regulating the increase in the three different gene products may vary, the age-dependent increase of all three constituents appears essential for meeting the increasing demand of the maturing brain to fuel the processes of cellular growth, differentiation, and neurotransmission.
System identification of closed-loop cardiovascular control mechanisms: diabetic autonomic neuropathy
Authors: Mukkamala Ramakrishna , Mathias Joanne M. , Mullen Thomas J. , Cohen Richard J. , Freeman Roy
Published: December 2017

We applied cardiovascular system identification (CSI) to characterize closed-loop cardiovascular regulation in patients with diabetic autonomic neuropathy (DAN). The CSI method quantitatively analyzes beat-to-beat fluctuations in noninvasively measured heart rate, arterial blood pressure (ABP), and instantaneous lung volume (ILV) to characterize four physiological coupling mechanisms, two of which are autonomically mediated (the heart rate baroreflex and the coupling of respiration, measured in terms of ILV, to heart rate) and two of which are mechanically mediated (the coupling of ventricular contraction to the generation of the ABP wavelet and the coupling of respiration to ABP). We studied 37 control and 60 diabetic subjects who were classified as having minimal, moderate, or severe DAN on the basis of standard autonomic tests. The autonomically mediated couplings progressively decreased with increasing severity of DAN, whereas the mechanically mediated couplings were essentially unchanged. CSI identified differences between the minimal DAN and control groups, which were indistinguishable based on the standard autonomic tests. CSI may provide a powerful tool for assessing DAN.
Cyclooxygenase-2 plays a significant role in regulating the tone of the fetal lamb ductus arteriosus
Authors: Clyman Ronald I. , Hardy Pierre , Waleh Nahid , Chen Yao Qi , Mauray Françoise , Fouron Jean-Claude , Chemtob Sylvain
Published: December 2017

Nonselective cyclooxygenase (COX) inhibitors are potent tocolytic agents but have adverse effects on the fetal ductus arteriosus. We hypothesized that COX-2 inhibitors may not affect the ductus if the predominant COX isoform is COX-1. To examine this hypothesis, we used ductus arteriosus obtained from late-gestation fetal lambs. In contrast to our hypothesis, fetal lamb ductus arteriosus expressed both COX-1- and COX-2-immunoreactive protein (by Western analysis). Although COX-1 was found in both endothelial and smooth muscle cells, COX-2 was found only in the endothelial cells lining the ductus lumen (by immunohistochemistry). The relative contribution of COX-1 and COX-2 to PGE2synthesis was consistent with the immunohistochemical results: in the intact ductus, PGE2formation was catalyzed by both COX-1 and COX-2 in equivalent proportions; in the endothelium-denuded ductus, COX-2 no longer played a significant role in PGE2synthesis. NS-398, a selective inhibitor of COX-2, was 66% as effective as the selective COX-1 inhibitor valeryl salicylate and the nonselective COX inhibitor indomethacin in causing contraction of the ductus in vitro. At this time, caution should be used when recommending COX-2 inhibitors for use in pregnant women.
Agonist-specific impairment of coronary vascular function in genetically altered, hyperlipidemic mice
Authors: Lamping Kathryn G. , Nuno Daniel W. , Chappell David A. , Faraci Frank M.
Published: December 2017

The objectives of the present study were to 1) examine mechanisms involved in endothelium-dependent responses of coronary arteries from normal mice and 2) determine whether vascular responses of coronary arteries are altered in two genetic models of hypercholesterolemia [apolipoprotein E (apoE)-deficient mice (apoE −/−) and combined apoE and low-density lipoprotein receptor (LDLR)-deficient mice (apoE + LDLR −/−)]. Plasma cholesterol levels were higher in both apoE −/− and apoE + LDLR −/− compared with normal mice on normal and high-cholesterol diets (normal chow: normal 110 ± 5 mg/dl, apoE −/− 680 ± 40 mg/dl, apoE + LDLR −/− 810 ± 40 mg/dl; high-cholesterol chow: normal 280 ± 60 mg/dl, apoE −/− 2,490 ± 310 mg/dl, apoE + LDLR −/− 3,660 ± 290 mg/dl). Coronary arteries from normal (C57BL/6J), apoE −/−, and apoE + LDLR −/− mice were isolated and cannulated, and diameters were measured using videomicroscopy. In normal mice, vasodilation in response to ACh and serotonin was markedly reduced by 10 μM Nω-nitro-l-arginine (an inhibitor of nitric oxide synthase) or 20 μM 1 H-[1,2,4]oxadiazolo[4,3- a]quinoxalin-1-one (ODQ; an inhibitor of soluble guanylate cyclase). Vasodilation to nitroprusside, but not papaverine, was also inhibited by ODQ. Dilation of arteries from apoE −/− and apoE + LDLR −/− mice on normal diet in response to ACh was similar to that observed in normal mice. In contrast, dilation of arteries in response to serotonin from apoE −/− and apoE + LDLR −/− mice was impaired compared with normal. In arteries from both apoE −/− and apoE + LDLR −/− mice on high-cholesterol diet, dilation to ACh was decreased. In apoE + LDLR −/− mice on high-cholesterol diet, dilation of coronary arteries to nitroprusside was increased. These findings suggest that dilation of coronary arteries from normal mice in response to ACh and serotonin is dependent on production of nitric oxide and activation of soluble guanylate cyclase. Hypercholesterolemia selectively impairs dilator responses of mouse coronary arteries to serotonin. In the absence of both apoE and the LDL receptor, high levels of cholesterol result in a greater impairment in coronary endothelial function.
Midline medullary depressor responses are mediated by inhibition of RVLM sympathoexcitatory neurons in rats
Authors: Verberne Anthony J. M. , Sartor Daniela M. , Berke Ayse
Published: December 2017

Mechanisms underlying the depressor and sympathoinhibitory responses evoked from the caudal medullary raphe (MR) region were investigated in pentobarbital sodium-anesthetized, paralyzed rats. Intermittent electrical stimulation (0.5 Hz, 0.5-ms pulses, 200 μA) of the MR elicited a mixed sympathetic response that consisted of a long-latency sympathoexcitatory (SE) peak (onset = 146 ± 7 ms) superimposed on an inhibitory phase (onset = 59 ± 10 ms). Chemical stimulation of the MR (glutamate; Glu) most frequently elicited depressor responses accompanied by inhibition of sympathetic nerve discharge. Occasionally, these responses were preceded by transient pressor and SE responses. We examined the influence of intermittent electrical stimulation (0.5 Hz, 0.5-ms pulses, 25–200 μA) and Glu stimulation of the MR on the discharge of rostral ventrolateral medulla (RVLM) premotor SE neurons. Peristimulus-time histograms of RVLM unit discharge featured a prominent inhibitory phase in response to MR stimulation (onset = 20 ± 2 ms; duration = 42 ± 4 ms; n = 12 units). Glu stimulation of the MR reduced blood pressure (−37 ± 2 mmHg, n = 19) and inhibited the discharge of RVLM SE neurons (15 of 19 neurons). Depressor and sympathoinhibitory responses elicited by chemical and electrical stimulation of the MR region are mediated by inhibition of RVLM premotor SE neurons and withdrawal of sympathetic vasomotor discharge.
Interstrain differences in activity pattern, pineal function, and SCN melatonin receptor density of rats
Authors: Klante Gabriela , Secci Karin , Masson-Pévet Mireille , Pévet Paul , Vivien-Roels Berthe , Steinlechner Stephan , Wollnik Franziska
Published: December 2017

We investigated the possibility that strain-dependent differences in the diurnal pattern of wheel running activity rhythms are also reflected in the melatonin profiles. The inbred rat strains ACI/Ztm, BH/Ztm, and LEW/Ztm. LEW were examined for diurnal [12:12-h light-dark (LD)] wheel running activity, urinary 6-sulphatoxymelatonin (aMT6s) excretion, melatonin concentrations of plasma and pineal glands, and melatonin receptor density in the suprachiasmatic nuclei (SCN). ACI rats displayed unimodal activity patterns with a high level of activity, whereas BH and LEW rats showed multimodal activity patterns with ultradian components and reduced activity levels. In contrast, the individual daily profiles of aMT6s excretion and mean melatonin synthesis followed a unimodal time pattern in all three strains, suggesting that different output pathways of the SCN are responsible for the temporal organization of locomotor activity and pineal melatonin synthesis. In addition, melatonin synthesis at night and SCN melatonin receptor density at day were significantly higher in BH and LEW rats than in ACI rats. These results support the hypothesis of a long-term stimulating effect of melatonin on its own receptor density in the SCN.
A rapid feedback signal is not always necessary for termination of a drinking bout
Authors: Houpt T. Richard , Yang-Preyer Hosook , Geyer Jessica , Norris Moria L.
Published: December 2017

When a pig is deprived of drinking water, a deficit of body water develops that is corrected when the pig drinks to satiation. If food is available during the deprivation, the stimulus to drinking is plasma hyperosmolality. Because of the delay in correction of plasma hyperosmolality as ingested water is slowly absorbed, it has been thought that a rapid inhibitory signal from the digestive tract is necessary to prevent overdrinking. This concept was tested by measuring changes in plasma osmolality before and during drinking after such deprivation and also after infusion of hypertonic saline. As drinking began, there was a rapid fall of plasma osmolality to levels insufficient to drive drinking by the time drinking ended. This fall of plasma hyperosmolality to subthreshold levels while the pig is drinking seems to make a rapid inhibitory control signal from the digestive tract unnecessary to terminate the drinking bout under these conditions.
How dolphins use their blubber to avoid heat stress during encounters with warm water
Authors: Heath M. E. , Ridgway S. H.
Published: December 2017

Dolphins have been observed swimming in inshore tropical waters as warm as 36–38°C. A simple protocol that mimicked the thermal conditions encountered by a dolphin moving from cool pelagic to warm inshore water was used to determine how dolphins avoid hyperthermia in water temperatures (Tw) at and above their normal core temperature (Tc). Tw(2 sites), rectal temperature (Tre; 3 depths), and skin temperature (Tsk; 7 sites) and rate of heat flow (4–5 sites) between the skin and the environment were measured while the dolphin rested in a chamber during a 30-min baseline and 40–60 min while water was warmed at ∼0.43°C/min until temperatures of 34–36°C were attained. Instead of the expected increase, Treconsistently showed declines during the warming ramp, sometimes by amounts that were remarkable both in their magnitude (1.35°C) and rapidity (8–15 min). The reduction in Treoccurred even while heat loss to the environment was prevented by continued controlled warming of the water that kept Twslightly above Tskand while metabolic heat production alone should have added 1.6–2°C/h to the Tc. This reduction in Tccould only be due to a massive redistribution of heat from the core to the blubber layer.
Cold acclimation of guinea pig depressed contraction of cardiac papillary muscle
Authors: Takagi Shuichi , Kihara Yasuki , Toyoda Futoshi , Morita Tetsuo , Sasayama Shigetake , Mitsuiye Tamotsu
Published: December 2017

Guinea pigs were exposed to 5°C for 3 wk, and the contractions of myocardial papillary muscle were compared with preparations dissected from control animals kept at ∼25°C. Developed tension of the papillary muscle per cross-sectional area was significantly ( t-test, P < 0.05) decreased after cold exposure (19,200 ± 8,160 vs. 3,020 ± 2,890 dyne/cm2; 1 Hz). Time to peak tension was significantly faster in cold-exposed guinea pigs (126.4 ± 11.1 ms; 1 Hz) than in controls (162.7 ± 8.7 ms). The magnitude of the developed tension after application of ryanodine (2 mM) to muscles from cold-exposed animals was decreased to 37.5 ± 8.3% of control at 1 Hz, whereas in muscles from control animals, tension was decreased to 82.4 ± 7.7%. The ryanodine-sensitive component of contraction was not significantly changed in control guinea pigs at frequencies >0.5 Hz, whereas in muscles from cold-acclimated guinea pigs, there was a “positive staircase.” These results suggested that reversal of the Na+/Ca2+exchanger is predominantly involved in the positive staircase in control guinea pigs, whereas rate-dependent increases in the Ca2+ store in the sarcoplasmic reticulum may be involved in the staircase after cold acclimation.
Insulin-like growth factor I improves renal function in patients with end-stage chronic renal failure
Authors: Vijayan Anitha , Franklin Samuel C. , Behrend Terry , Hammerman Marc R. , Miller Steven B.
Published: December 2017

There is no pharmacological treatment to increase the glomerular filtration rate in end-stage renal disease (ESRD). The administration of 100 μg/kg of insulin-like growth factor (IGF) I twice a day to patients with ESRD increases inulin clearance. However, its effect is short-lived and IGF-I has major side effects when given this way. To assess whether the use of a lower intermittent dose of IGF-I would effect sustained improved function with tolerable side effects we performed 1) a prospective open-labeled 24-day trial in which we enrolled five patients and 2) a 31-day randomized, double-blinded, placebo-controlled trial in which we enrolled 10 patients. Patients with ESRD [creatinine clearance of <15 ml ⋅ min−1 ⋅ (1.73 m2)−1] and scheduled to initiate renal replacement therapy received subcutaneous IGF-I, 50 μg ⋅ kg−1 ⋅ day−1, or vehicle. Treatment with IGF I resulted in significantly increased glomerular filtration rates (inulin clearances) during the 3rd and 4th wk of therapy in both prospective and double-blinded studies. Vehicle had no effect. No patient required discontinuation of drug secondary to side effects. We conclude that IGF-I effects sustained improvement of renal function (clearances comparable to those generally achieved by dialysis) in patients with ESRD and is well tolerated.
RVLM and raphe differentially regulate sympathetic outflows to splanchnic and brown adipose tissue
Authors: Morrison Shaun F.
Published: December 2017

To determine whether neurons in the rostral raphe pallidus (RPa) specifically control the sympathetic nerve activity to brown adipose tissue (BAT SNA), thereby regulating adipocyte metabolism and BAT thermogenesis, the responses in BAT SNA to disinhibition of RPa neurons and to disinhibition of neurons in the vasomotor region of the rostral ventrolateral medulla (RVLM) were compared with those in splanchnic (Spl) SNA, which primarily regulates visceral vasoconstriction. In urethan-chloralose-anesthetized ventilated rats, both acute hypothermia and microinjection of bicuculline into RPa produced significantly larger increases in BAT SNA (542 and 1,949% of control) than in Spl SNA (19 and 24% of control). The enhanced burst discharge in BAT SNA was not coherent with that in Spl SNA or with the arterial pressure (AP) at any frequency except the central respiratory frequency. Microinjections of bicuculline into RVLM evoked increases in Spl SNA (86% of control) and AP (32 mmHg), but reduced BAT SNA to low, normothermic levels. Microinjections of muscimol into RVLM reduced Spl SNA (−82% of control) and AP (−59 mmHg), but did not prevent the increase in BAT SNA after disinhibition of RPa neurons. These results indicate that the neural networks generating BAT SNA in response to disinhibition of RPa neurons are independent of those generating basal Spl SNA and support a model in which sympathetic outflow to tissues involved in thermoregulation and metabolism is regulated by central pathways, including neurons in RPa, that are distinct from those involved in the sympathetic control of the cardiovascular system.
Interactions between gastric volume and duodenal nutrients in the control of liquid gastric emptying
Authors: Moran Timothy H. , Wirth James B. , Schwartz Gary J. , McHugh Paul R.
Published: December 2017

We examined the relationships between gastric volume and duodenal glucose load in the regulation of gastric emptying in adult male rhesus monkeys. Intragastric glucose loads (0.125 g/ml) of volumes ranging from 150 to 375 ml empty from the stomach at the same rate from 20 to 120 min. However, to achieve these equivalent emptying rates, progressively larger volumes were emptied in the initial 20 min with increasing gastric volume. Duodenal glucose infusions dose dependently inhibited the 10-min emptying of various volumes of intragastric saline. Although increasing gastric volume resulted in increased emptying, duodenal glucose right-shifted the relationship between initial gastric volume and volume emptied. These data demonstrate that liquid nutrient gastric emptying represents an interaction between gastric volume and nutrient-induced duodenal feedback. For controlled duodenal caloric delivery rates to be established, sufficient nutrient emptying must occur to increase the magnitude of duodenal feedback to withhold a given gastric volume.
Meal-synchronized CEA in rats: effects of meal size, intragastric feeding, and subdiaphragmatic vagotomy
Authors: White Wesley , Schwartz Gary J. , Moran Timothy H.
Published: December 2017

Within a feeding schedule of intermittent food access, large meals have the ability to induce activity at the same time the next day [circadian ensuing activity (CEA)]. In these experiments, we evaluated the minimum meal size necessary to induce CEA and whether oral-pharyngeal factors and afferent vagal activity played necessary roles in the induction of the underlying process. In experiment 1, every 33 h rats were given two meals separated by a 2-h interval. The size of the first meal was varied, while total intake every feeding cycle was held constant. When the initial meal was <10 g (34 kcal) CEA occurred later, indicating that such a meal size was subthreshold for inducing CEA. In experiment 2, rats were given intragastric (IG) meals every 33 h, before and after complete subdiaphragmatic vagotomy. IG nutrient meals induced CEA, indicating that extensive oral-pharyngeal experience was not necessary for CEA induction. CEA occurred in vagotomized rats but, compared with intact rats, appeared to occur later relative to nutrient infusion, indicating that afferent vagal activity may be sufficient but not necessary to induce CEA.
Thermal dehydration-induced thirst in spontaneously hypertensive rats
Authors: Barney Christopher C. , Smith Gina L. , Folkerts Michael M.
Published: December 2017

Spontaneously hypertensive (SH) rats and normotensive Wistar-Kyoto (WKY) rats were exposed to either 25 or 37.5°C for 3.5 h, and their thermal and water balance responses were compared. After exposure, either a blood sample was obtained or the rats were allowed to rehydrate for 4 h. SH rats had both higher core temperatures and evaporative water losses during heat exposure. Measurements of hematocrit, hemoglobin concentration, plasma protein and sodium concentrations, and plasma osmolality indirectly showed that the SH rats were dehydrated relative to the WKY rats after exposure to either 25 or 37.5°C. SH rats drank significantly more water but also had significantly higher urine volumes than the WKY rats and thus rehydrated only slightly better than the WKY rats. SH and WKY rats had similar levels of water intake and urine output after 24 h of water deprivation. The elevated thermal response of SH rats to heat exposure does not appear to lead to uncompensatable changes in body water status.
STZ-induced diabetes decreases and insulin normalizes POMC mRNA in arcuate nucleus and pituitary in rats
Authors: Kim Eun-Mee , Grace Martha K. , Welch Catherine C. , Billington Charles J. , Levine Allen S.
Published: December 2017

Effects of streptozotocin (STZ)-induced diabetes and insulin on opioid peptide gene expression were examined in rats. In experiment 1, three groups were administered STZ (75 mg/kg ip single injection). Two groups were killed at either 2 or 4 wk. In the third group, insulin treatment (7.0 IU/kg × 1 day for 3 wk) was initiated 1 wk after STZ injection. STZ induced hyperphagia and reduced weight gain. Insulin decreased food intake and increased body weight relative to diabetes. Proopiomelanocortin (POMC) mRNA in arcuate nucleus (Arc) and pituitary decreased in diabetes and normalized after insulin treatment. Prodynorphin (proDyn) mRNA increased in diabetes and normalized in the pituitary after insulin but not in the Arc. Diabetes did not alter proenkephalin (proEnk) expression in the Arc or pituitary, nor dynorphin A1–17 or β-endorphin in paraventricular nucleus (PVN). α-Melanocyte-stimulating hormone (α-MSH) peptide levels were decreased in the PVN and normalized following insulin treatment. Diabetes increased Arc neuropeptide Y mRNA, and insulin suppressed this increase. In experiment 2, insulin (2.5 IU/kg sc) daily for 1 wk in normal rats increased Arc POMC mRNA, but not proDyn and proEnk mRNA. These results suggest that Arc POMC expression and PVN α-MSH peptide levels decrease in diabetes. Also, insulin may influence Arc and pituitary POMC activity in neurons that regulate energy metabolism.
Brain-derived neurotrophic factor enhances spontaneous sleep in rats and rabbits
Authors: Kushikata Tetsuya , Fang Jidong , Krueger James M.
Published: December 2017

Various growth factors are involved in sleep regulation. Brain-derived neurotrophic factor (BDNF) belongs to the neurotrophin family; it and its receptors are found in normal brain. Furthermore, cerebral cortical levels of BDNF mRNA have a diurnal variation and increase after sleep deprivation. Therefore, we investigated whether BDNF would promote sleep. Twenty-four male Sprague-Dawley rats (320–380 g) and 25 male New Zealand White rabbits (4.5–5.5 kg) were surgically implanted with electroencephalographic (EEG) electrodes, a brain thermistor, and a lateral intracerebroventricular cannula. The animals were injected intracerebroventricularly with pyrogen-free saline and, on a separate day, one of the following doses of BDNF: 25 or 250 ng in rabbits; 10, 50, or 250 ng in rats. The EEG, brain temperature, and motor activity were recorded for 23 h after the intracerebroventricular injections. BDNF increased time spent in non-rapid eye movement sleep (NREMS) in rats and rabbits and REMS in rabbits. Current results provide further evidence that various growth factors are involved in sleep regulation.
Sodium depletion and aldosterone decrease dopamine transporter activity in nucleus accumbens but not striatum
Authors: Roitman Mitchell F. , Patterson Terrell A. , Sakai Randall R. , Bernstein Ilene L. , Figlewicz Dianne P.
Published: December 2017

Motivated behaviors, including sodium (Na) appetite, are correlated with increased dopamine (DA) transmission in the nucleus accumbens (NAc). DA transporter (DAT) modulation affects DA transmission and may play a role in motivated behaviors. In vivo Na depletion, which reliably induces Na appetite, was correlated with robust decreases in DA uptake via the DAT in the rat NAc with rotating disk electrode voltammetry [1,277 ± 162 vs. 575 ± 89 pmol ⋅ s−1 ⋅ g−1; Vmax of transport for control vs. Na-depleted tissue]. Plasma aldosterone (Aldo) levels increase after in vivo Na depletion and contribute to Na appetite. Decreased DAT activity in the NAc was observed after in vitro Aldo treatment (428 ± 28 vs. 300 ± 25 pmol ⋅ s−1 ⋅ g−1). Neither treatment affected DAT activity in the striatum. These results suggest that a direct action of Aldo is one possible mechanism by which Na depletion induces a reduction in DAT activity in the NAc. Reduced DAT activity may play a role in generating increased NAc DA transmission during Na appetite, which may underlie the motivating properties of Na for the Na-depleted rat.
17β-Estradiol rapidly facilitates chemoinvestigation and mounting in castrated male rats
Authors: Cross Ericha , Roselli Charles E.
Published: December 2017

Testosterone and estradiol act synergistically to stimulate male sexual behavior. Previous studies demonstrated that testosterone’s actions are mediated genomically. Attempts to show that estradiol acts in a similar fashion have been inconclusive. However, estrogens have been shown to exert short-latency effects by acting directly on neuronal membranes. The present experiment examined whether testosterone or estradiol rapidly facilitates copulatory behaviors in castrated sexually experienced rats. Within 35 min of administration, estradiol stimulated chemoinvestigation and frequency of mounting and reduced mount latency in a dose-dependent manner. In contrast, acute administration of testosterone did not alter sexual activity. These data demonstrate for the first time that estradiol exerts short-latency effects on copulatory behavior, providing indirect evidence that this action is mediated through a nontranscriptional mechanism.