bluuebunny/crossref_metadata_2025 huggingface dataset:
Lack of TNF-α attenuates intimal hyperplasia after mouse carotid artery injury
Authors: Zimmerman Michael A. , Selzman Craig H. , Reznikov Leonid L. , Miller Stephanie A. , Raeburn Christopher D. , Emmick Julie , Meng Xianzhong , Harken Alden H.
Published: March 2015

This study sought to determine the influence of tumor necrosis factor-α (TNF-α) on intimal hyperplasia (IH) and characterize the mechanisms of transcriptional regulation after vascular injury. A murine model of wire carotid artery injury was employed to induce IH in wild-type (WT) and TNF-α-deficient [TNF(−/−)] animals. Three days after injury, TNF-α and nuclear factor-κB (NF-κB) protein expression was markedly increased in the injured WT carotid artery compared to control. Injury increased TNF-α and NF-κB mRNA expression 100- and 7.5-fold, respectively. Compared with WT specimens, injury in TNF(−/−) animals decreased both NF-κB mRNA and protein nearly 7.5- and 4-fold, respectively. Expression of the NF-κB-dependent cytokine monocyte chemotactic protein 1 was markedly diminished in injured TNF(−/−) animals. Finally, TNF(−/−) animals demonstrated a sevenfold reduction in IH compared with WT animals. Cumulatively, these data mechanistically link TNF-α and NF-κB in vivo and suggest an important influence of TNF-α on postinjury IH.
ICAM-1 and VCAM-1 mediate endotoxemic myocardial dysfunction independent of neutrophil accumulation
Authors: Raeburn Christopher D. , Calkins Casey M. , Zimmerman Michael A. , Song Yong , Ao Lihua , Banerjee Anirban , Harken Alden H. , Meng Xianzhong
Published: March 2015

Both intercellular adhesion molecule-1 (ICAM-1) and vascular cell adhesion molecule-1 (VCAM-1) have been implicated in neutrophil-mediated lung and liver injury during sepsis. However, the role of these adhesion molecules as well as the contribution of neutrophils in myocardial dysfunction during sepsis remains to be determined. The purpose of this study was to examine the role of ICAM-1, VCAM-1, and neutrophils in lipopolysaccharide (LPS)-induced myocardial dysfunction. Mice were subjected to LPS (0.5 mg/kg ip) or vehicle (normal saline), and left ventricular developed pressure (LVDP) was determined by the Langendorff technique. LVDP was depressed by nearly 40% at 6 h after LPS. Immunofluorescent staining revealed a temporal increase in myocardial ICAM-1/VCAM-1 expression and neutrophils after LPS. Antibody blockade of VCAM-1 reduced myocardial neutrophil accumulation and abrogated LPS-induced cardiac dysfunction. Antibody blockade or absence of ICAM-1 (gene knockout) also abrogated LPS-induced cardiac dysfunction but did not reduce neutrophil accumulation. Neutrophil depletion (vinblastine or antibody) did not protect from LPS-induced myocardial dysfunction. Our results suggest that although endotoxemic myocardial dysfunction requires both ICAM-1 and VCAM-1, it occurs independent of neutrophil accumulation.
Cholinergic neurotransmission participates in increased food intake induced by NMDA receptor blockade
Authors: Covasa Mihai , Ritter Robert C. , Burns Gilbert A.
Published: March 2015

MK-801, a noncompetitive N-methyl-d-aspartate (NMDA) receptor antagonist, enhances gastric emptying while increasing food intake. Although our previously reported results implicate the vagus in MK-801's effect on feeding, it is not clear whether vagal motor fibers participate in the feeding response. Control of gastric emptying is exerted, in part, by cholinergic vagal motor neurons. Therefore, we examined the ability of MK-801 to increase meal size in the presence or absence of the muscarinic receptor antagonist atropine methyl nitrate. Both central and systemic administration of MK-801 significantly increased intake of 15% sucrose. Intraperitoneal injection of atropine abolished MK-801-induced increase in sucrose intake, whereas administration into the fourth ventricle had no effect. To determine whether augmentation of cholinergic tone produces an enhancement of food intake in the absence of MK-801, we tested the ability of cisapride, a gastric prokinetic agent that promotes acetylcholine release through an action on presynaptic serotonin (5-HT4) receptors, to increase sucrose consumption. Cisapride (500 μg/kg ip) induced a small but significant increase in 15% sucrose intake (15.5 ± 0.5 ml) compared with NaCl (13.0 ± 0.6 ml). Furthermore, when MK-801 (100 μg/kg ip) was given in combination with cisapride, intake was significantly higher (19.8 ± 0.9 ml) than following either agent given alone. Pretreatment with atropine abolished the cisapride-induced increase in intake (12.1 ± 0.9 ml) as well as the increased intake induced by combining MK-801 and cisapride. These results suggest that blockade of NMDA-gated ion channels in the hindbrain increases food intake, in part, via a peripheral muscarinic cholinergic mechanism.
Fiber-type differences in muscle mitochondrial profiles
Authors: Leary S. C. , Lyons C. N. , Rosenberger A. G. , Ballantyne J. S. , Stillman J. , Moyes C. D.
Published: March 2015

Although striated muscles differ in mitochondrial content, the extent of fiber-type specific mitochondrial specializations is not well known. To address this issue, we compared mitochondrial structural and functional properties in red muscle (RM), white muscle (WM), and cardiac muscle of rainbow trout. Overall preservation of the basic relationships between oxidative phosphorylation complexes among fiber types was confirmed by kinetic analyses, immunoblotting of native holoproteins, and spectroscopic measurements of cytochrome content. Fiber-type differences in mitochondrial properties were apparent when parameters were expressed per milligram mitochondrial protein. However, the differences diminished when expressed relative to cytochrome oxidase (COX), possibly a more meaningful denominator than mitochondrial protein. Expressed relative to COX, there were no differences in oxidative phosphorylation enzyme activities, pyruvate-based respiratory rates, H2O2production, or state 4 proton leak respiration. These data suggest most mitochondrial qualitative properties are conserved across fiber types. However, there remained modest differences (∼50%) in stoichiometries of selected enzymes of the Krebs cycle, β-oxidation, and antioxidant enzymes. There were clear differences in membrane fluidity (RM > cardiac, WM) and proton conductance (H+/min/mV/U COX: WM > RM > cardiac). The pronounced differences in mitochondrial content between fiber types could be attributed to a combination of differences in myonuclear domain and modest effects on the expression of nuclear- and mitochondrially encoded respiratory genes. Collectively, these studies suggest constitutive pathways that transcend fiber types are primarily responsible for determining most quantitative and qualitative properties of mitochondria.
Angiotensin II receptor (type 1 and 2) expression peaks when placental growth is maximal in sheep
Authors: Koukoulas Irene , Mustafa Tomris , Douglas-Denton Rebecca , Wintour E. Marelyn
Published: March 2015

In sheep, placental size is maximal by midgestation, but blood flow continues to increase until term. No nerves are present and ANG II is thought to be a major regulator of vascular tone. We hypothesized that angiotensin type 2 receptors (AT2) would predominate over type 1 (AT1) until late in gestation and be primarily expressed in the vasculature. Real-time PCR, hybridization histochemistry, and ligand-binding studies were performed on placentae and fetal membranes at 27, 45, 66 ± 1, 100 ± 4, 130, and 140 days of gestation (term ≈ 150 days) to determine quantitative changes and localization. The maximum level of AT1 expression occurred in the 45-day placenta and was located predominantly in the maternal stromal cells. AT1receptors were expressed in the endothelial cells of the chorion in the first half of pregnancy, where later in gestation, both AT1and AT2 receptors were predominant in blood vessels. These results suggest that ANG II, via the AT1 receptor, may have hitherto unsuspected important roles in the growth/function on the ovine placenta during the maximal growth phase.
Decreased antigen-induced eicosanoid release in conjugated linoleic acid-fed guinea pigs
Authors: Whigham Leah D. , Higbee Alan , Bjorling Dale E. , Park Yeonhwa , Pariza Michael W. , Cook Mark E.
Published: March 2015

This study investigated the capacity of conjugated linoleic acids (CLA) to reduce ex vivo antigen-induced release of eicosanoids in a type I hypersensitivity model. Guinea pigs were fed a diet containing 0.25% safflower oil (control) or 0.25% CLA [43% trans( t)10, cis ( c)12; 41% c9, t11/ t9, c11 18:2] for 2 wk before and during sensitization to ovalbumin (OVA). Lungs, tracheas, and bladders were incubated in physiological saline solution (PSS) for 1 h (basal mediator release) and challenged with OVA (0.01 g/l PSS) for 1 h (mediator release in response to antigen). Eicosanoids were quantified by HPLC/tandem mass spectrometry or enzyme immunoassay. CLA feeding resulted in no change in basal release but decreased eicosanoid release from sensitized tissues in response to antigen challenge in the following manner: thromboxane B2, 6-keto-prostaglandin (PG)F1α, PGF2α, PGD2, PGE2by 57–75% in lung, 45–65% in trachea, and 38–60% in bladder; and leukotriene C4/D4/E4by 87, 90, and 50% in lung, trachea, and bladder, respectively. These data indicate that feeding CLA reduces lipid-derived inflammatory mediators produced by this type I hypersensitivity model.
Dichloroacetate accelerates the fall in intracellular Po2at onset of contractions inXenopussingle muscle fibers
Authors: Howlett Richard A. , Hogan Michael C.
Published: March 2015

This study investigated the relationship between intracellular Po2(PiO2) and dichloroacetate (DCA) administration following a significant step-change increase in oxidative metabolism in intact isolated Xenopus single muscle fibers. Single fibers ( n = 22) were dissected from the lumbrical muscle, injected with the oxygen-sensitive compound palladium- meso-tetra (4-carboxyphenyl) porphine, and randomly assigned to one of two treatment groups. One group (DCA; n = 12) was incubated for 30 min with 1.2 mM DCA, whereas the second group [control (Con); n = 10] was incubated for 30 min in Ringer solution only. After incubation, fibers were electrically stimulated to elicit tetanic contractions (0.5 Hz) for 2 min during which PiO2was monitored. PiO2before contractions began was 32.0 ± 1.8 and 29.0 ± 1.8 Torr for DCA and Con, respectively, and fell to 6.0 ± 1.3 and 8.8 ± 2.4 Torr (no significant difference), respectively, after steady state was reached. The kinetics of the fall, determined by both the time delay (from the start of contractions to the initial decrease in PiO2) and the tau (63% of the change to a steady state in PiO2), were calculated. In DCA cells, the tau was significantly ( P < 0.05) faster than Con (22.1 ± 3.6 vs. 39.7 ± 5.8 s). In contrast, the time delay was not significantly ( P > 0.45) different between the two groups (11.4 ± 1.7 vs. 12.6 ± 2.3 s, respectively). The amount of fatigue, reflected by a decrease in force production from initial, was not significantly different between groups. These data suggest that by stimulating pyruvate dehydrogenase with DCA in isolated single skeletal muscle cells, the faster fall in PiO2is indicative of oxidative metabolism being more rapidly activated. This is the first evidence that oxygen uptake at the onset of contractions may be altered by DCA during moderate- to high-intensity contractile activity.
Mechanical strain regulation of the chicken glypican-4 gene expression in the avian eggshell gland
Authors: Lavelin Irena , Meiri Noam , Einat Miriam , Genina Olga , Pines Mark
Published: March 2015

Comparison of RNA fingerprinting of the avian eggshell gland (ESG) without and with an egg revealed upregulation of a 382-bp cDNA fragment that showed high homology to the mammalian glypican 4 (GPC-4). The gene sequence revealed a conserved glypican signature, a glycosyl phosphatidyl inositol-anchorage site, and cystein residues, most of which were conserved. GPC-4 was expressed in the ESG in a circadian fashion only during the period of eggshell calcification, when maximal mechanical strain was imposed. Removal of the egg just before to its entry into the ESG, with consequent elimination of the mechanical strain, caused reduction in the gene expression. Artificial application of the mechanical strain induced expression of the GPC-4 gene that was related to the level of the strain. GPC-4 expression was strain dependent in other parts of the oviduct. In the ESG, GPC-4 was expressed exclusively by the glandular epithelium and not by the pseudostratified epithelium facing the lumen. In summary, we cloned the avian homologue of GPC-4, established its pattern of expression in the avian ESG, and demonstrated for the first time that this gene is regulated by mechanical strain.
The affinity of hemoglobin for oxygen affects ventilatory responses in mutant mice with Presbyterian hemoglobinopathy
Authors: Izumizaki Masahiko , Tamaki Masakatsu , Suzuki Yo-ichi , Iwase Michiko , Shirasawa Takuji , Kimura Hiroshi , Homma Ikuo
Published: March 2015

The purpose of this study was to test whether chronically enhanced O2 delivery to tissues, without arterial hyperoxia, can change acute ventilatory responses to hypercapnia and hypoxia. The effects of decreased hemoglobin (Hb)-O2 affinity on ventilatory responses during hypercapnia (0, 5, 7, and 9% CO2 in O2) and hypoxia (10 and 15% O2 in N2) were assessed in mutant mice expressing Hb Presbyterian (mutation in the β-globin gene, β108 Asn → Lys). O2 consumption during normoxia, measured via open-circuit methods, was significantly higher in the mutant mice than in wild-type mice. Respiratory measurements were conducted with a whole body, unrestrained, single-chamber plethysmograph under conscious conditions. During hypercapnia, there was no difference between the slopes of the hypercapnic ventilatory responses, whereas minute ventilation at the same levels of arterial PCO2 was lower in the Presbyterian mice than in the wild-type mice. During both hypoxic exposures, ventilatory responses were blunted in the mutant mice compared with responses in the wild-type mice. The effects of brief hyperoxia exposure (100% O2) after 10% hypoxia on ventilation were examined in anesthetized, spontaneously breathing mice with a double-chamber plethysmograph. No significant difference was found in ventilatory responses to brief hypoxia between both groups of mice, indicating possible involvement of central mechanisms in blunted ventilatory responses to hypoxia in Presbyterian mice. We conclude that chronically enhanced O2 delivery to peripheral tissues can reduce ventilation during acute hypercapnic and hypoxic exposures.
Tonic pulmonary stretch receptor feedback modulates both eupnea and gasping in an in situ rat preparation
Authors: Harris Michael B. , St.-John Walter M.
Published: March 2015

The perfused in situ juvenile rat preparation produces phrenic discharge patterns comparable to eupnea and gasping in vivo. These ventilatory patterns of eupnea and gasping differ in multiple aspects, including most prominently the rate of rise of inspiratory activity. Because gasping, but not eupnea, appeared similar after vagotomy in spontaneous breathing preparations, it has been assumed that gasping was unresponsive to afferent stimuli from pulmonary stretch receptors. In the present study, efferent activity of the phrenic nerve was recorded during eupnea and gasping in the in situ juvenile rat preparation. Gasping was induced in hypoxic-hypercapnia or ischemia. An increase in the pressure of tonic lung inflation from 1 to 10 cmH2O caused a prolongation of the duration between phrenic bursts in both eupnea or gasping. Bilateral vagotomy eliminated these changes. We conclude that the neural substrate mediating the Hering-Breuer reflex is retained in the in situ preparation and that the brain stem circuitry generating the respiratory patterns responds to tonic activation of pulmonary stretch receptors in a similar manner in eupnea and gasping. These findings support the homology of eupnea-like phrenic discharge patterns in the reduced in situ preparation and eupnea in vivo and disprove the common supposition that gasping is insensitive to vagal afferent feedback from pulmonary stretch receptor mechanisms.
Interaction between muscarinic receptor subtype signal transduction pathways mediating bladder contraction
Authors: Braverman Alan S. , Tallarida Ronald J. , Ruggieri Michael R.
Published: March 2015

M3 muscarinic receptors mediate cholinergic-induced contraction in most smooth muscles. However, in the denervated rat bladder, M2 receptors participate in contraction because M3-selective antagonists [ para-fluoro-hexahydro-sila-diphenidol ( p-F-HHSiD) and 4-DAMP] have low affinities. However, the affinity of the M2-selective antagonist methoctramine in the denervated bladder is consistent with M3 receptor mediating contraction. It is possible that two pathways interact to mediate contraction: one mediated by the M2 receptor and one by the M3 receptor. To determine whether an interaction exists, the inhibitory potencies of combinations of methoctramine and p-F-HHSiD for reversing cholinergic contractions were measured. In normal bladders, all combinations gave additive effects. In denervated bladders, synergistic effects were seen with the 10:1 and 1:1 (methoctramine: p-F-HHSiD wt/wt) combinations. After application of the sarcoplasmic reticulum ATPase inhibitor thapsigargin to normal tissue, the 10:1 and 1:1 ratios became synergistic, mimicking denervated tissue. Thus in normal bladders both M2 and M3 receptors can induce contraction. In the denervated bladder, the M2 and the M3 receptors interact in a facilitatory manner to mediate contraction.
Glucocorticoid-mediated attenuation of the hsp70 response in trout hepatocytes involves the proteasome
Authors: Boone Adrienne N. , Vijayan Mathilakath M.
Published: March 2015

The physiological implication of elevated cortisol levels on cellular heat-shock protein 70 (hsp70) response was examined using primary cultures of rainbow trout ( Oncorhynchus mykiss) hepatocytes. Trout hepatocytes treated with cortisol, the predominant glucocorticoid in teleosts, responded to the heat shock (+15°C for 1 h) with a significant drop in hsp70 accumulation over a 24-h recovery period. [35S]methionine incorporation and pulse-chase studies confirmed that this cortisol impact was due to decreased hsp70 synthesis and not enhanced protein breakdown. Cortisol also significantly decreased glucocorticoid receptor (GR) expression in trout hepatocytes. This receptor downregulation was inhibited by the proteasomal inhibitors, lactacystin and MG-132, implying a role for the proteasome in GR downregulation by cortisol. Inhibiting the proteasome did not significantly modify heat-induced hsp70 accumulation in the absence of cortisol but significantly elevated hsp70 expression in the presence of cortisol in heat-shocked trout hepatocytes. Taken together, our results suggest proteasome-mediated GR degradation as a mechanism for the attenuation of hsp70 response by cortisol in heat-shocked hepatocytes.
Heart rate control and mechanical cardiopulmonary coupling to assess central volume: a systems analysis
Authors: Barbieri Riccardo , Triedman John K. , Saul J. Philip
Published: March 2015

Small negative changes of central volume reduce cardiac output without significant alterations of arterial blood pressure (ABP), suggesting an adequate regulatory response. Furthermore, evidence has arisen supporting a Bainbridge reflex (tachycardia with hypervolemia) in humans. To investigate these phenomena, multivariate autoregressive techniques were used to evaluate the beat-to-beat interactions between respiration, R-R interval, and ABP at six levels of decreased and increased central volume. With reductions of central volume below control, baroreflex and respiratory sinus arrhythmia gains were reduced, while with increases of volume above control, gains increased for the first two levels but decreased again at the highest volume level, suggesting the presence of a Bainbridge reflex in healthy human subjects. The mechanical influence of respiration on central venous pressure (CVP) had an unexpected shift in phase at the point of mild central hypervolemia, with the expected negative relation at lower volumes (inspiration lowers CVP) but a positive relation at higher volumes (inspiration raises CVP). We conclude that multivariate techniques can quantify the relations between a variety of respiratory and hemodynamic parameters, allowing for the in vivo assessment of complex cardiorespiratory interactions during manipulations of central volume. The results identify the presence of a Bainbridge reflex in humans and suggest that short-term cardiovascular control is optimized at mild hypervolemia.
Intrinsic cardiac nervous system in tachycardia induced heart failure
Authors: Arora Rakesh C. , Cardinal René , Smith Frank M. , Ardell Jeffrey L. , Dell'Italia Louis J. , Armour J. Andrew
Published: March 2015

The purpose of this study was to test the hypothesis that early-stage heart failure differentially affects the intrinsic cardiac nervous system's capacity to regulate cardiac function. After 2 wk of rapid ventricular pacing in nine anesthetized canines, cardiac and right atrial neuronal function were evaluated in situ in response to enhanced cardiac sensory inputs, stimulation of extracardiac autonomic efferent neuronal inputs, and close coronary arterial administration of neurochemicals that included nicotine. Right atrial neuronal intracellular electrophysiological properties were then evaluated in vitro in response to synaptic activation and nicotine. Intrinsic cardiac nicotine-sensitive, neuronally induced cardiac responses were also evaluated in eight sham-operated, unpaced animals. Two weeks of rapid ventricular pacing reduced the cardiac index by 54%. Intrinsic cardiac neurons of paced hearts maintained their cardiac mechano- and chemosensory transduction properties in vivo. They also responded normally to sympathetic and parasympathetic preganglionic efferent neuronal inputs, as well as to locally administered α-or β-adrenergic agonists or angiotensin II. The dose of nicotine needed to modify intrinsic cardiac neurons was 50 times greater in failure compared with normal preparations. That dose failed to alter monitored cardiovascular indexes in failing preparations. Phasic and accommodating neurons identified in vitro displayed altered intracellular membrane properties compared with control, including decreased membrane resistance, indicative of reduced excitability. Early-stage heart failure differentially affects the intrinsic cardiac nervous system's capacity to regulate cardiodynamics. While maintaining its capacity to transduce cardiac mechano- and chemosensory inputs, as well as inputs from extracardiac autonomic efferent neurons, intrinsic cardiac nicotine-sensitive, local-circuit neurons differentially remodel such that their capacity to influence cardiodynamics becomes obtunded.
Activity of the unique β-adrenergic Na+/H+exchanger in trout erythrocytes is controlled by a novel β3-AR subtype
Authors: Nickerson James G. , Dugan Stephen G. , Drouin Guy , Perry Steve F. , Moon Thomas W.
Published: March 2015

β-Adrenoceptors (β-ARs) are seven-transmembrane domain, G protein-coupled receptors that transduce the cellular effects of epinephrine and norepinephrine and play a pivotal role in the vertebrate stress response. This study reports the cloning and characterization of two previously unreported β-ARs from the rainbow trout ( Oncorhynchus mykiss). Phylogenetic analysis of amino acid sequences indicates that both β-ARs are homologs of the mammalian β3-AR. Analysis of tissue expression patterns indicates that one of these trout β3-adrenoceptors (β3a-AR) is highly expressed in gill and heart, whereas the second (β3b-AR) is highly expressed by red blood cells (RBC). Expression of the β3b-AR in the RBC coupled with the finding of a single category of β-AR binding sites on RBC membranes provides strong evidence for the control of the trout RBC β-AR Na+/H+exchanger (β-NHE) activity by signaling through this β3b-subtype and not through a β1-subtype as previously proposed. The RBC-specific trout β3b-AR exhibits binding characteristics that distinguish this receptor from each of the three pharmacologically defined categories of mammalian β-ARs (β1-, β2-, and β3-AR). This study is the first to report the presence of a β3-AR subtype in a fish species, and the proposal that the β3b-AR controls RBC β-NHE activity represents a novel role for the β3-AR subtype in vertebrates.
Noradrenergic neurons in the rat solitary nucleus participate in the esophageal-gastric relaxation reflex
Authors: Rogers R. C. , Travagli R. A. , Hermann G. E.
Published: March 2015

Activation of esophageal mechanosensors excites neurons in and near the central nucleus of the solitary tract (NSTc). In turn, NSTc neurons coordinate the relaxation of the stomach [i.e., the receptive relaxation reflex (RRR)] by modulating the output of vagal efferent neurons of the dorsal motor nucleus of the vagus (DMN). The NSTc area contains neurons with diverse neurochemical phenotypes, including a large population of catecholaminergic and nitrergic neurons. The aim of the present study was to determine whether either one of these prominent neuronal phenotypes was involved in the RRR. Immunohistochemical techniques revealed that repetitive esophageal distension caused 53% of tyrosine hydroxylase-immunoreactive (TH-ir) neurons to colocalize c-Fos in the NSTc. No nitric oxide synthase (NOS)-ir neurons in the NSTc colocalized c-Fos in either distension or control conditions. Local brain stem application (2 ng) of α-adrenoreceptor antagonists (i.e., α1-prazosin or α2-yohimbine) significantly reduced the magnitude of the esophageal distension-induced gastric relaxation to ∼55% of control conditions. The combination of yohimbine and prazosin reduced the magnitude of the reflex to ∼27% of control. In contrast, pretreatment with either the NOS-inhibitor NG-nitro-l-arginine methyl ester or the β-adrenoceptor antagonist propranolol did not interfere with esophageal distension-induced gastric relaxation. Unilateral microinjections of the agonist norepinephrine (0.3 ng) directed at the DMN were sufficient to mimic the transient esophageal-gastric reflex. Our data suggest that noradrenergic, but not nitrergic, neurons of the NSTc play a prominent role in the modulation of the RRR through action on α1- and α2-adrenoreceptors. The finding that esophageal afferent stimulation alone is not sufficient to activate NOS-positive neurons in the NSTc suggests that these neurons may be strongly gated by other central nervous system inputs, perhaps related to the coordination of swallowing or emesis with respiration.
Cardiovascular responses to static and dynamic contraction during comparable workloads in humans
Authors: Stebbins Charles L. , Walser Buddy , Jafarzadeh Mehrdad
Published: March 2015

Previous studies suggest that the blood pressure response to static contraction is greater than that caused by dynamic exercise. In anesthetized cats, however, pressor responses to electrically induced static and dynamic contraction of the same muscle group are similar during equivalent workloads and peak tension development [i.e., similar tension-time index (TTI)]. To determine if the same relationship exists in humans, where contraction is voluntary and central command is present, dynamic (180 s; 1/s) and static (90 s) contractions at 30% of maximal voluntary contraction (MVC) were performed. Dynamic contraction also was repeated at the same TTI for 90 s at 60% MVC. Mean arterial pressure (MAP), heart rate (HR), cardiac output (CO), MAP during postexercise arterial occlusion (an index of the metaboreceptor-induced activation of the exercise pressor reflex), and relative perceived exertion (RPE) (an index of central command) were assessed. No differences in these variables were found between static and dynamic contraction at a tension of 30% MVC. During dynamic contraction at 60% MVC, changes in MAP (16 ± 3 vs. 19 ± 4 mmHg) and absolute HR (92 ± 6 vs. 69 ± 5 beats/min), CO (7.9 ± 0.4 vs. 6.3 ± 0.3 l/min), RPE (16 ± 1 vs. 13 ± 1), and MAP during postexercise arterial occlusion (115 ± 3 vs. 100 ± 4 mmHg) were greater than during static contraction ( P < 0.05). Thus increases in MAP and HR, activation of central command, and muscle metabolite-induced stimulation of the exercise pressor reflex during static and dynamic contraction in humans seem to be similar when peak tension and TTI are equal. Augmented responses to dynamic contraction at 60% MVC are likely related to greater activation of these two mechanisms.
IGF alters jejunal glucose transporter expression and serum glucose levels in immature rats
Authors: Lane Robert H. , Dvorak Bohuslav , MacLennan Nicole K. , Dvorakova Katerina , Halpern Melissa D. , Pham Tho D. , Philipps Anthony F.
Published: March 2015

Milk-borne insulin-like growth factors (IGFs) enhance nutrient absorption in the immature intestine, which is characterized by low levels of glucose oxidation. We therefore hypothesized that feeding a rat milk substitute (RMS) devoid of growth factors to rat pups would lower serum glucose levels relative to dam-fed control rats and that supplementation of RMS with physiological doses of either IGF-I or IGF-II would normalize serum glucose levels via increased jejunal glucose transporter 2 (GLUT2) and high-affinity Na+-glucose cotransporter (SGLT1) expression. We found lower serum glucose concentrations in RMS-fed pups; in contrast, serum glucose levels in the IGF-supplemented pups were similar to those of dam-fed controls. RT-PCR and laser scanning confocal microscopy similarly demonstrated that IGF supplementation increased expression of jejunal glucose transporters. Further experiments demonstrated that IGF supplementation altered mRNA levels of key mitochondrial enzymes without altering jejunal lactase activity. We conclude that IGF-I and IGF-II supplementation increases serum glucose levels in the immature rat pup fed artificial formula and alters gene expression of the jejunal glucose transporters.
Mendelian hypertension with brachydactyly as a molecular genetic lesson in regulatory physiology
Authors: Luft Friedrich C. , Toka Okan , Toka Hakan R. , Jordan Jens , Bähring Sylvia
Published: March 2015

Mendelian forms of hypertension have delivered a treasure trove of novel genes. To date, the molecular mechanisms of five such syndromes have been largely clarified, including glucocorticoid-remediable aldosteronism, Liddle's syndrome, apparent mineralocorticoid excess, an activating mutation of the mineralocorticoid receptor, and pseudohypoaldosteronism type 2. Each of these conditions features salt sensitivity with increased sodium and volume reabsorption by the kidney and low plasma renin activity. None of the gene loci for these syndromes has been convincingly linked to hypertension in the general population. We are investigating kindreds who have autosomal-dominant hypertension and brachydactyly. Affected persons invariably have both anomalies. The hypertension is severe and results in death at about age 50 years from stroke. The condition resembles essential hypertension, because renin, aldosterone, and norepinephrine responses are normal and no salt sensitivity is present. The response to antihypertensive drugs is general. Another feature is diminished baroreflex sensitivity with markedly impaired blood pressure buffering. Furthermore, the ventrolateral medulla may be compromised in these patients, because neurovascular anomalies are a regular finding. We mapped the gene(s) for this disease to chromosome 12p and narrowed the chromosomal region by studying more affected families. Interestingly, the same locus was recently mapped in Chinese families with essential hypertension. Our 3-centimorgan region contains genes encoding a phosphodiesterase, an ATP-dependent potassium channel, and its regulator the sulfonylurea receptor 2. Screening of the coding regions revealed that none of these candidate genes harbor obvious mutations; however, other genetic mechanisms may nevertheless compromise their function. Our study underscores the importance of regulatory physiology to the understanding of a complex genetic syndrome.
Cocaine- and amphetamine-regulated transcript peptide attenuates phenylephrine-induced bradycardia in anesthetized rats
Authors: Scruggs Phouangmala , Dun Siok L. , Dun Nae J.
Published: March 2015

The present study was undertaken to investigate the origin of cocaine- and amphetamine-regulated transcript (CART) peptide immunoreactive (irCART) fibers observed in the nucleus of the solitary tract (NTS) and assess the role of CART peptide on phenylephrine (PE)-induced baroreflex. Immunohistochemical and retrograde tract-tracing studies showed that some of the irCART fibers observed in the NTS may have their cell bodies in the nodose ganglia. In urethane-anesthetized rats, intracisternal or bilateral intra-NTS microinjection of the CART peptide fragment 55-102 (0.1-3 nmol), referred to herein as CARTp, consistently and dose dependently attenuated PE-induced bradycardia. CARTp, in the doses used here, caused no significant changes of resting blood pressure or heart rate. Bilateral intra-NTS injections of CART antibody (1:500) potentiated PE-induced bradycardia. Injections of saline, normal rabbit serum, or concomitant injection of CARTp and CART antiserum into the NTS caused no significant changes of PE-induced baroreflex. The result suggests that endogenously released CARTp from primary afferents or exogenously administered CARTp modulates PE-induced baroreflex.
Increased cellular activity in rat insular cortex after water and salt ingestion induced by fluid depletion
Authors: Pastuskovas Cinthia V. , Cassell Martin D. , Johnson Alan Kim , Thunhorst Robert L.
Published: March 2015

Insular cortex (IC) receives inputs from multiple sensory systems, including taste, and from receptors that monitor body electrolyte and fluid balance and blood pressure. This work analyzed metabolic activity of IC cells after water and sodium ingestion induced by sodium depletion. Rats were injected with the diuretic furosemide (10 mg/kg body wt), followed 5 min later by injections of the angiotensin-converting enzyme inhibitor captopril (5 mg/kg body wt). After 90 min, some rats received water and 0.3 M NaCl to drink for 2 h while others did not. A third group had access to water and saline but was not depleted of fluids. All rats were killed for processing of brain tissue for Fos-immunoreactivity (Fos-ir). Nondepleted animals had weak-to-moderate levels of Fos-ir within subregions of IC. Fluid-depleted rats without fluid access had significantly increased Fos-ir in all areas of IC. Levels of Fos-ir were highest in fluid-depleted rats that drank water and sodium. Fos-ir levels were highest in anterior regions of IC and lowest in posterior regions of IC. These results implicate visceral, taste, and/or postingestional factors in the increased metabolic activity of cells in IC.
Cerebral leucine uptake and protein synthesis in the near-term ovine fetus: relation to fetal behavioral state
Authors: Czikk Marie J. , Sweeley John C. , Homan Jacobus H. , Milley J. Ross , Richardson Bryan S.
Published: March 2015

Behavioral/sleep state activity may impact on synthetic processes within the brain, thus accounting for the developmental change in such activity and suggesting a role in the brain's growth and development. We have therefore determined the cerebral uptake of leucine and [14C]leucine during continuous tracer infusion as measures of leucine metabolism in relation to behavioral state activity, as well as the regional flux of leucine into brain tissue in the ovine fetus near term. The cerebral fractional protein synthetic rate and the absolute protein synthetic rate averaged ∼20%/day and ∼1 g/day, respectively, as measured for the whole brain, which is considerably higher than anticipated protein accretion and indicates a high rate of protein turnover with protein synthesis closely linked to protein degradation. Measures of protein synthesis were significantly higher in the pituitary gland, which may be attributed to the active synthesis and export of peptide hormones from this region. Cerebral leucine and [14C]leucine uptakes averaged ∼630 and ∼1,000 nmol · 100 g−1 · min−1, with the latter higher than leucine unidirectional flux and thus supporting a degree of leucine oxidation by the brain. Cerebral leucine metabolism as studied was affected by behavioral state activity, with uptake measurements for both leucine and [14C]leucine significantly increased during the high-voltage electrocortical/non-rapid eye movement state by 1.7-fold and 2.8-fold, respectively, indicating that protein synthesis and degradation must also be increased at this time, and supporting a role for behavioral state activity in the brain's growth and development.
Influence of oxygen partial pressures on protein synthesis in feeding crabs
Authors: Mente Eleni , Legeay Alexia , Houlihan Dominic F. , Massabuau Jean-Charles
Published: March 2015

Many water-breathing animals have a strategy that consists of maintaining low blood Po2values in a large range of water oxygenation level (4–40 kPa). This study examines the postprandial changes in O2consumption, arterial blood Po2, and tissue protein synthesis in the shore crab Carcinus maenas in normoxic, O2-depleted, and O2-enriched waters to study the effects of this strategy on the O2consumption and peptide bond formation after feeding. In normoxic water (21 kPa), the arterial Po2was 1.1 kPa before feeding and 1.2 kPa 24 h later. In water with a Po2of 3 kPa (arterial Po20.6 kPa), postprandial stimulation of protein synthesis and O2consumption were blocked. The blockade was partial at a water Po2of 4 kPa (arterial Po20.8 kPa). An increase in environmental Po2(60 kPa, arterial Po210 kPa) resulted in an increase in protein synthesis compared with normoxic rates. It is concluded that the arterial Po2spontaneously set in normoxic Carcinus limits the rates of protein synthesis. The rationale for such a strategy is discussed.
Central leptin gene therapy fails to overcome leptin resistance associated with diet-induced obesity
Authors: Wilsey Jared , Zolotukhin Sergei , Prima Victor , Scarpace Philip J.
Published: March 2015

The objective of this study was to determine if central overexpression of leptin could overcome the leptin resistance caused by 100 days of high-fat feeding. Three-month old-F344XBN male rats were fed either control low fat chow (Chow), which provides 15% of energy as fat, or a high-fat/high-sucrose diet (HF), which provides 59% of energy as fat. Over several weeks, the HF-fed animals spontaneously split into two groups of animals: those that became obese on the HF diet (DIO) and those that did not gain extra weight on the HF diet [diet resistant (DR)]. After 100 days of HF feeding, animals were given a single intracerebroventricular injection containing 5.75E10 particles of rAAV encoding leptin (rAAV-leptin) or control virus (rAAV-con). Chow animals responded robustly to rAAV-leptin, including significant anorexia, weight loss, and lipopenia. In contrast, DIO were completely unresponsive to rAAV-leptin. DR rats responded to rAAV-leptin, but in a more variable fashion than Chow. Unlike what was observed in Chow, the anorectic response to rAAV-leptin rapidly attenuated and was no longer significant by day 14 postvector delivery. Both DIO and DR animals were found to have reduced long-form leptin receptor expression and enhanced basal P-STAT-3 in the hypothalamus with respect to Chow. rAAV-leptin caused an increase in STAT3 phosphorylation and proopiomelanocortin expression in the hypothalamus and an increase in uncoupling protein-1 in brown adipose tissue in both Chow and DR animals, but failed to do so in DIO. This suggests that central overexpression of leptin is not a viable strategy to reverse diet-induced obesity.
Regulation mode of evaporative cooling underlying a strategy of the heat-tolerant FOK rat for enduring ambient heat
Authors: Furuyama Fujiya , Murakami Masataka , Tanaka Etsuro , Hida Hideki , Miyazawa Daisuke , Oiwa Takanori , Isobe Yoshiaki , Nishino Hitoo
Published: March 2015

Compared with other rat strains, the inbred FOK rat is extremely heat tolerant. This increased heat tolerance is due largely to the animal's enhanced saliva spreading abilities. The aims of the present study were to 1) quantify the heat tolerance capacity of FOK rats and 2) determine the regulatory mode of the enhanced salivary cooling in these animals. Various strains of rats were acutely exposed to heat. In the heat-intolerant strains, saliva spreading was insufficient and the core temperature (Tc) rose rapidly. In contrast, FOK rats maintained an elevated Tcplateau (39.5 ± 0.7°C) for 5-6 h over a wide range of ambient temperatures (Ta) (37.5-42.5°C). In hot environments the FOK rats secreted copious amounts of saliva and spread it over more than the entire ventral body surface. FOK rats had a low Tcthreshold for salivation, and the salivation rate increased linearly in proportion to the Tcdeviation from the threshold. No strain difference or temperature effect was observed in the saliva secretion rate from in vitro submandibular glands perfused by sufficient doses of ACh. These results suggest that 1) the ability of FOK rats to maintain a moderate steady-state hyperthermia (39.5 ± 0.7°C) over a wide Tarange is enabled by a lowered threshold Tcfor salivation and functional negative-feedback control of saliva secretion and 2) strain differences in ability to endure heat stress are mainly attributable to changes in the thermoregulatory control system rather than altered secretory abilities of the salivary glands.
A role for cyclooxygenase-2 in lipopolysaccharide-induced anorexia in rats
Authors: Lugarini F. , Hrupka B. J. , Schwartz G. J. , Plata-Salaman C. R. , Langhans W.
Published: March 2015

Because nonselective cycloooxygenase (COX) inhibition attenuated anorexia after lipopolysaccharide (LPS) administration, we tested the ability of resveratrol (2.5, 10, and 40 mg/kg) and NS-398 (2.5, 10, and 40 mg/kg), selective inhibitors of the two COX isoforms COX-1 and -2, respectively, to attenuate LPS (100 μg/kg ip)-induced anorexia. NS-398 (10 and 40 mg/kg) administered with LPS at lights out attenuated LPS-induced anorexia, whereas resveratrol at all doses tested did not. Because prostaglandin (PG) E2 is considered the major metabolite synthesized by COX, we measured plasma and cerebrospinal fluid (CSF) PGE2levels after LPS administration. LPS induced a time-dependent increase of PGE2 in CSF but not in plasma. NS-398 (5, 10, and 40 mg/kg) blocked the LPS-induced increase in CSF PGE2, whereas resveratrol (10 mg/kg) did not. These results support a role of COX-2 in mediating the anorectic response to peripheral LPS and point at PGE2 as a potential neuromodulator involved in this response.
Distribution of aquaporins in the colon of Octodon degus, a South American desert rodent
Authors: Gallardo Pedro , Olea Nancy , Sepúlveda Francisco V.
Published: March 2015

Octodon degus is a desert rodent of northern Chile, adapted to survive with a limited supply of water. This rodent has a high degree of fecal dehydration, related to colon water absorption. With the hypothesis that aquaporins (AQPs) might be present in the colon epithelium of O. degus and involved in fluid absorption, we studied colon water absorption in vivo and the distribution of AQPs and Na+ transporters by immunocytochemistry. AQP-1 was found in apical and basolateral membranes of surface-absorptive and crypt epithelial cells. AQP-8 was found in the cytoplasm of enterocytes of surface colon. AQP-3 immunolabeling, on the other hand, was absent from the epithelium but present in a subepithelial fibroblast layer, pericryptal cells, and muscularis mucosae. The hydration state did not modify the amount of immunostaining for any of the AQPs. Colon water absorption was markedly decreased by the mercurial agent p-chloromercuribenzenesulfonic acid and was not affected by water deprivation. The NHE3 isoform of Na+/H+exchanger and α-1 subunit of the Na+-K+-ATPase were found in apical and basolateral membranes of surface-absorptive cells, respectively. These results suggest that colon water absorption is mostly transcellular and mediated by water channels like AQP-1. Apical Na+/H+ exchanger and basolateral Na+-K+-ATPase in surface cells could be part of the Na+ absorption pathway. It is hypothesized that this transport is necessary to provide an osmotic gradient for water absorption. The roles of AQP-8 and AQP-3 in water absorption remain to be established.
Melatonin in rat milk and the likelihood of its role in postnatal maternal entrainment of rhythms
Authors: Rowe Shawn A. , Kennaway David J.
Published: March 2015

The rhythm of melatonin in rat milk and the capacity of pups to synthesize and metabolize melatonin were studied. Melatonin was undetectable in milk in the light (<21 pM), but increased rapidly 2–4 h after dark to peak at 357 ± 66 pM at mid-dark. Oral or subcutaneous administration of melatonin to 5- and 10-day-old pups resulted in peak plasma melatonin levels 30 min after administration and rapid metabolism. Increases in pineal and plasma melatonin levels at night were detected at 5 and 6 days of age, respectively. Isoproterenol administration (2 μg/g body wt) at mid-light to day 10 pups increased plasma melatonin from 312 ± 40 pM to 1,298 ± 160 pM, whereas propranolol (2 μg/g body wt) suppressed nocturnal melatonin secretion from 1,270 ± 128 pM to 395 ± 66 pM. The rise of pineal and plasma melatonin in day 10 pups occurred 1 and 2 h after dark onset, respectively, preceding the onset in dams by 3 and 4 h, respectively. Propranolol administration to 2- and 5-day lactating dams inhibited plasma and milk melatonin at night but had no effect on their suckling pups. Transfer of melatonin via the milk is unlikely to provide an entraining signal for rat pups.
Repeated administration of the anorectic factor prolactin-releasing peptide leads to tolerance to its effects on energy homeostasis
Authors: Ellacott Kate L. J. , Lawrence Catherine B. , Pritchard Lynn E. , Luckman Simon M.
Published: March 2015

Central administration of a single dose of prolactin-releasing peptide (PrRP) causes a reduction in both fast-induced and nocturnal food intake and body weight gain. The aim of this study was to examine the effect of repeated administration of PrRP on energy homeostasis, including a measure of the expression of the mitochondrial uncoupling protein-1 (UCP-1) in brown adipose tissue. Conscious, free-feeding animals received central injections of PrRP (4 nmol icv) or vehicle. A single injection at 1000 caused a sustained hyperthermia over the 4-h test period and an increase in the expression of UCP-1 mRNA. Repeated, twice daily injection caused a reduction in body weight gain greater than that seen in pair-fed animals for the first 48-72 h. After 72 h, the animals became refractory to the actions of PrRP. The pair-fed group showed a reduction in UCP-1 mRNA expression at 48 h, which was reversed by PrRP treatment. This study indicates that PrRP exerts its effects on energy homeostasis in the short-medium term by reducing food intake and increasing energy expenditure.