bluuebunny/crossref_metadata_2025 huggingface dataset:
Chronic exercise increases macrophage-mediated tumor cytolysis in young and old mice
Authors: Lu Q. , Ceddia M. A. , Price E. A. , Ye S.-M. , Woods J. A.
Published: December 2017

In this study, we determined the effects of age and chronic treadmill running (16 wk; 5 days/wk; 45 min/day; 18–22 m/min) on resident peritoneal macrophage responsiveness to interferon-γ (IFN-γ) and lipopolysaccharide (LPS) in young (6 mo) and aged (22 mo) male BALB/cByJ mice by measuring cytolytic ability and production of reactive nitrogen products. Macrophages (>90% Mac-3+) were incubated with various concentrations of IFN-γ and LPS for 24 h. After washing, P815 tumor cells were utilized as targets in a 16-h51Cr release assay. We found that aging resulted in a significant reduction in the ability of macrophages to respond to the highest doses of IFN-γ and LPS and kill P815 cells (46 ± 4 vs. 34 ± 2% in young and old mice, respectively). Exercise training significantly increased macrophage cytolysis in both age groups (66 + 7 vs. 44 + 2% in young and old mice, respectively); this effect was larger in the young mice. Macrophages from young exercised mice also produced significantly (50–60%) more[Formula: see text]; there was a tendency for higher[Formula: see text] in old exercisers. The inducible nitric oxide synthase (iNOS) inhibitor NG-monomethyl-l-arginine (l-NMMA) significantly reduced macrophage cytolysis and [Formula: see text]production and completely abrogated exercise-induced increases in these measures. RT-PCR analysis revealed significantly higher iNOS mRNA levels in macrophages obtained from the exercise-trained mice and significantly lower iNOS mRNA in old compared with young mice. We conclude that aging reduces and exercise training increases the capacity of resident peritoneal macrophages to respond to IFN-γ and LPS with increased tumor cytolysis. Enhanced iNOS gene expression and[Formula: see text] production are likely the contributing mechanisms of the exercise-induced enhancement of cytolysis in young mice. Whilel-NMMA did block the exercise-induced increase in cytolysis, exercise did not increase[Formula: see text] or iNOS gene expression in the old mice, indicating perhaps the contribution of other cytolytic mechanisms in old mice.
Actions of amylin on subfornical organ neurons and on drinking behavior in rats
Authors: Riediger Thomas , Rauch Matthias , Schmid Herbert A.
Published: December 2017

Amylin, a peptide hormone secreted by pancreatic β-cells after food intake, contributes to metabolic control by regulating nutrient influx into the blood, whereas insulin promotes nutrient efflux and storage. We now report that amylin activates neurons in the subfornical organ (SFO), a structure in which the lack of a functional blood-brain barrier and the presence of a high density of amylin receptors may render it accessible and sensitive to circulating amylin. In an in vitro slice preparation of the rat SFO, 73% of 78 neurons were excited by superfusion with rat amylin (10−8–10−7M); the remainder were insensitive. The threshold concentration for the excitatory response of amylin was <10−8 M and thus similar in potency to a previously reported excitatory effect of ANG II on the same neurons. The excitatory effect of amylin was completely blocked by coapplication of the selective amylin receptor antagonist AC-187 (10−6–10−5M) but was not affected by losartan (10−5 M). Subcutaneous injections of 40 nmol of amylin significantly increased water intake in euhydrated rats, as did an equimolar dose of ANG II, which is a well-described SFO-mediated effect of circulating ANG II. These results point to the SFO as a sensory central nervous target for amylin released systemically in response to metabolic changes. Furthermore, we suggest that amylin release during food intake may stimulate prandial drinking.
Stimulated mechanisms of Ca2+entry into vascular smooth muscle during NO synthesis inhibition in pregnant rats
Authors: Crews Janice K. , Novak Jacqueline , Granger Joey P. , Khalil Raouf A.
Published: December 2017

We have previously found that the vascular responsiveness to α1-adrenergic agonists is reduced in pregnant rats and enhanced in a rat model of pregnancy-induced hypertension produced by chronic treatment of pregnant rats with the nitric oxide (NO) synthase inhibitor N G-nitro-l-arginine methyl ester (l-NAME). The purpose of this study was to investigate whether the observed changes in vascular reactivity during normal pregnancy and during pregnancy-induced hypertension reflect changes in the mechanisms of Ca2+ entry into vascular smooth muscle.45Ca2+influx and active stress during α1-adrenergic stimulation by phenylephrine and membrane depolarization by 96 mM KCl were measured in deendothelialized aortic strips isolated from virgin and pregnant Sprague-Dawley rats untreated or treated with 1 mg/dayl-NAME for 4–6 days and incubated in Krebs solution containing increasing concentrations of extracellular Ca2+([Ca2+]e). In all groups of rats, both phenylephrine and 96 mM KCl caused [Ca2+]e-dependent increases in active stress and45Ca2+influx. The phenylephrine- and 96 mM KCl-induced active stress and Ca2+ influx were significantly reduced in pregnant rats but significantly enhanced in pregnant rats treated with l-NAME. The phenylephrine-induced Ca2+influx-stress relationship was significantly greater than that induced by 96 mM KCl in pregnant rats treated withl-NAME. The phenylephrine-induced Ca2+influx-stress relationship was reduced in pregnant rats but enhanced in pregnant rats treated withl-NAME. Chronic treatment withl-NAME had minimal effect on active stress, Ca2+ influx, and the Ca2+ influx-stress relationship in virgin rats. These results provide evidence that the mechanisms of Ca2+ entry into vascular smooth muscle are inhibited during pregnancy but enhanced during inhibition of NO synthesis in late pregnancy. The enhancement of the phenylephrine-induced Ca2+influx-stress relationship in pregnant rats treated withl-NAME suggests activation of other contractile mechanisms in addition to stimulation of Ca2+ entry. These mechanisms appear to be inhibited during normal pregnancy.
Effect of Ca2+agonists in the perfused liver: determination via laser scanning confocal microscopy
Authors: Motoyama Kentaro , Karl Irene E. , Flye M. Wayne , Osborne Dale F. , Hotchkiss Richard S.
Published: December 2017

Ca2+is a critical intracellular second messenger, but few studies have examined Ca2+signaling in whole organs. The amplitude and frequency of Ca2+oscillations encode important cellular information. Using laser scanning confocal microscopy in the indo 1 acetoxymethyl ester dye-loaded rat liver, we investigated the effect of various Ca2+agonists that act at distinct mechanistic sites on Ca2+signaling. Perfusion with suprathreshold doses of arginine vasopressin (AVP) (2–20 nM) caused a single Ca2+wave that originated in the pericentral vein region and spread centrifugally to the periportal area. Lower doses of AVP (0.2–2 nM) caused multiple Ca2+waves and Ca2+oscillations. Perfusion with ATP (1.4–17.5 μM) caused rapid transient elevations in intracellular free Ca2+concentration ([Ca2+]i) occurring in isolated hepatocytes or groups of hepatocytes throughout the lobule and were of shorter duration than those due to AVP. Also in contrast to AVP, there was no specific anatomic location within the hepatic lobule that was more susceptible to ATP. Thapsigargin and cyclopiazonic acid did not cause a Ca2+wave but rather produced a uniform and fairly simultaneous increase in [Ca2+]iin all hepatocytes in the lobule. Perfusion with 14 μM ryanodine produced a single transient spike in [Ca2+]iin a small number (<2%) of hepatocytes. Dantrolene, an inhibitor of Ca2+release, reduced the increased [Ca2+]ioccurring after AVP. Insight into the mechanism of action of these Ca2+-active compounds on Ca2+signaling in the intact liver is provided.
AMPA receptor activation of area postrema neurons
Authors: Hay Meredith , Lindsley Kathy A.
Published: December 2017

This study reports on the effects of activation of ionotropic glutamate receptors on area postrema neuron cytosolic calcium concentration ([Ca2+]i). In 140 of 242 area postrema neurons isolated from postnatal rats, application of 100 μMl-glutamate (l-Glu) resulted in a significant increase in [Ca2+]i. The remaining neurons were unaffected. The effects ofl-Glu on area postrema [Ca2+]iwere dose dependent, with a threshold of response near 1.0 μM and maximal response near 100 μM. To determine if the response ofl-Glu in area postrema neurons was due to activation of ionotropic glutamate receptors, the effects of the broad-spectrum ionotropic glutamate receptor antagonist kynurinic acid (Kyn) was determined. Application of 1.0 mM Kyn resulted in a 62.6 ± 4% inhibition of thel-Glu-evoked response. Application of the selective N-methyl-d-aspartic acid (NMDA) antagonist 2-amino-5-phosphonopentanoic acid had no effect on the response of area postrema neurons to 100 μMl-Glu. In contrast, application of the selectivedl-α-amino-3-hydroxy-5-methylisoxazole-propionic acid (AMPA)/kainate receptor antagonist 6,7-dinitroquinoxaline (DNQX) effectively blocked the 100 μMl-Glu response. Application of (±)-AMPA mimicked the effects observed withl-Glu and was selectively blocked by DNQX. These results suggest thatl-Glu activation of area postrema neurons involves activation of AMPA receptors but not NMDA receptors.
Maintenance of adenosine A1receptor function during long-term anoxia in the turtle brain
Authors: Lutz Peter L. , Manuel Liscia
Published: December 2017

It has been established that adenosine has a critical role in the extraordinary ability of the turtle brain to survive anoxia. To further investigate this phenomenon we compared rat and turtle brain adenosine A1receptors using cyclopentyl-1,3-dipropylxanthine,8-[dipropyl-2,3-3H(N)] ([3H]DPCPX) saturation binding analyses and determined the effects of prolonged anoxia (6, 12, and 24 h) on the adenosine A1receptor of the turtle brain. The rat brain had a 10-fold greater density of A1receptors compared with the turtle [rat cortex receptor density (Bmax) = 1,400 ± 134.6 fmol/mg protein, turtle forebrain Bmax= 103.2 ± 4.60 fmol/mg protein] and a higher affinity [dissociation constant ( Kd) rat cortex = 0.328 ± 0.035 nM, Kdturtle forebrain = 1.16 ± 0.06 nM]. However, the turtle Kdis within the reported mammalian range, and the Bmaxis similar to that reported for other poikilotherms. Unlike the mammal, in which A1receptor function is rapidly compromised in anoxia, in the turtle forebrain no significant changes in the A1receptor population were seen during 24-h anoxia. However, in the hindbrain, whereas the Bmaxremained unchanged, the Kdsignificantly decreased from 2.1 to 0.5 nM after 6 h anoxia and this higher affinity was maintained at 12- and 24-h anoxia. These findings indicate that, unlike the GABAAreceptor, the protective effectiveness of adenosine in the anoxic turtle brain is not related to an enhanced receptor number. Protection from a hypoxia-induced compromise in A1receptor function and an increased A1sensitivity in the hindbrain may be important factors for maintaining the adenosine-mediated downregulation of energy demand during long-term anoxia.
Insulin resistance of muscle glucose transport in male and female rats fed a high-sucrose diet
Authors: Kim Jong-Yeon , Nolte Lorraine A. , Hansen Polly A. , Han Dong-Ho , Kawanaka Kentaro , Holloszy John O.
Published: December 2017

It has been reported that, unlike high-fat diets, high-sucrose diets cause insulin resistance in the absence of an increase in visceral fat and that the insulin resistance develops only in male rats. This study was done to 1) determine if isolated muscles of rats fed a high-sucrose diet are resistant to stimulation of glucose transport when studied in vitro and 2) obtain information regarding how the effects of high-sucrose and high-fat diets on muscle insulin resistance differ. We found that, compared with rat chow, semipurified high-sucrose and high-starch diets both caused increased visceral fat accumulation and insulin resistance of skeletal muscle glucose transport. Insulin responsiveness of 2-deoxyglucose (2-DG) transport measured in epitrochlearis and soleus muscles in vitro was decreased ∼40% ( P < 0.01) in both male and female rats fed a high-sucrose compared with a chow diet. The high-sucrose diet also caused resistance of muscle glucose transport to stimulation by contractions. There was a highly significant negative correlation between stimulated muscle 2-DG transport and visceral fat mass. In view of these results, the differences in insulin action in vivo observed by others in rats fed isocaloric high-sucrose and high-starch diets must be due to additional, specific effects of sucrose that do not carry over in muscles studied in vitro. We conclude that, compared with rat chow, semipurified high-sucrose and high-cornstarch diets, like high-fat diets, cause increased visceral fat accumulation and severe resistance of skeletal muscle glucose transport to stimulation by insulin and contractions.
Cardiovascular, endocrine, and renal effects of urodilatin in normal humans
Authors: Bestle Morten Heiberg , Olsen Niels Vidiendal , Christensen Poul , Jensen Benny Vittrup , Bie Peter
Published: December 2017

Effects of urodilatin (5, 10, 20, and 40 ng ⋅ kg−1⋅ min−1) infused over 2 h on separate study days were studied in eight normal subjects with use of a randomized, double-blind protocol. All doses decreased renal plasma flow (hippurate clearance, 13–37%) and increased fractional Li+clearance (7–22%) and urinary Na+excretion (by 30, 76, 136, and 99% at 5, 10, 20, and 40 ng ⋅ kg−1⋅ min−1, respectively). Glomerular filtration rate did not increase significantly with any dose. The two lowest doses decreased cardiac output (7 and 16%) and stroke volume (10 and 20%) without changing mean arterial blood pressure and heart rate. The two highest doses elicited larger decreases in stroke volume (17 and 21%) but also decreased blood pressure (6 and 14%) and increased heart rate (15 and 38%), such that cardiac output remained unchanged. Hematocrit and plasma protein concentration increased with the three highest doses. The renin-angiotensin-aldosterone system was inhibited by the three lowest doses but activated by the hypotensive dose of 40 ng ⋅ kg−1⋅ min−1. Plasma vasopressin increased by factors of up to 5 during infusion of the three highest doses. Atrial natriuretic peptide immunoreactivity (including urodilatin) and plasma cGMP increased dose dependently. The urinary excretion rate of albumin was elevated up to 15-fold (37 ± 17 μg/min). Use of a newly developed assay revealed that baseline urinary urodilatin excretion rate was low (<10 pg/min) and that fractional excretion of urodilatin remained below 0.1%. The results indicate that even moderately natriuretic doses of urodilatin exert protracted effects on systemic hemodynamic, endocrine, and renal functions, including decreases in cardiac output and renal blood flow, without changes in arterial pressure or glomerular filtration rate, and that filtered urodilatin is almost completely removed by the renal tubules.
Electrophysiological properties of rat lateral parabrachial neurons in vitro
Authors: Hayward Linda F. , Felder Robert B.
Published: December 2017

Anatomical studies have demonstrated that the lateral parabrachial nucleus (LPBN) is composed of at least seven separate subnuclei distinguished by cell morphology, spatial clustering, and afferent and efferent connectivity. We hypothesized that neurons within the subnuclear clusters of the LPBN might have distinct electrophysiological properties that correlate with cellular morphology. An in vitro slice preparation was used to intracellularly record the intrinsic properties of 64 neurons located within the external lateral (EL) and central lateral (CL) subnuclei of the LPBN in adult rats. Analysis of intrinsic properties revealed that neurons in the EL subnucleus had significantly wider action potentials and on the average demonstrated more spike frequency adaptation during 2 s of depolarization compared with CL neurons. The majority of both EL and CL area neurons expressed delayed excitation (DE) after membrane hyperpolarization. DE was eliminated with the A-current blocker 4-aminopyridine (1.5–5 mM). Postinhibitory rebound was also observed in a subpopulation of EL and CL neurons. Morphological analysis of 11 LPBN neurons, which were electrophysiologically characterized and filled with 2% biocytin, failed to demonstrate an association between morphology and the electrophysiological profiles of LPBN neurons. The lack of distinct “type” of neuron within a single subnucleus of the LPBN is in agreement with recent findings reported from the neonatal rat.
Muscarinic blockade inhibits gastric emptying of mixed-nutrient meal: effects of weight and gender
Authors: Teff Karen L. , Alavi Abass , Chen Jergin , Pourdehnad Michael , Townsend Raymond R.
Published: December 2017

We compared the vagal contribution to gastric emptying in lean and obese subjects by monitoring gastric emptying of a meal during muscarinic blockade. Lean ( n = 6) and obese subjects ( n = 6) underwent two treatments: 1) saline infusion and 2) atropine infusion [0.4 mg/m2bolus, 0.4 mg ⋅ (m2)−1⋅ h−1] for 2 h, initiated 30 min before ingestion of a 600-kcal breakfast (64% carbohydrate, 23% fat, 13% protein) composed of orange juice (labeled with Indium-111), egg sandwich (labeled with Technetium-99m), cereal, milk, and banana. Anterior and posterior images were taken every 90 s for 90 min using a dual-headed camera. Atropine significantly delayed emptying of both solid ( P < 0.007) and liquid ( P < 0.002). Obese subjects exhibited a greater delay in liquid emptying during muscarinic blockade compared with lean subjects ( P < 0.02). Female subjects exhibited a slower rate of gastric emptying and were less sensitive to atropine. These data suggest that obese subjects exhibit altered gastric cholinergic activity compared with lean subjects and that gender differences in gastric emptying rate may be due to differences in autonomic tone.
Characterization of enteric functional changes evoked by in vivo anti-CD3 T cell activation
Authors: Radojevic Nikola , McKay Derek M. , Merger Michael , Vallance Bruce A. , Collins Stephen M. , Croitoru Kenneth
Published: December 2017

Specific in vivo T cell activation initiated by treatment with anti-CD3 antibodies leads to diarrhea and structural damage of the intestinal mucosa. In this study, the effect of T cell-induced mucosal damage on jejunal epithelial ion transport, muscle contractility, and neuronal ACh release was assessed in Ussing chambers, organ baths, and a specialized perfusion apparatus, respectively. Time-matched control mice received hamster serum containing irrelevant antibodies. Jejunal segments from anti-CD3-treated mice displayed a significantly elevated epithelial baseline short-circuit current (which indicates increased ion transport) and a concomitant reduction in responsiveness to prosecretory stimuli (nerve stimulation, carbachol, and forskolin). Longitudinal smooth muscle displayed altered spontaneous contractile activity, length-tension relationships, and carbachol-stimulated contraction in tissues excised from mice 20 and 40 h posttreatment. Anti-CD3 treatment did not affect stimulated ACh release from myenteric plexus neurons. We conclude that specific T cell activation via anti-CD3 antibody results in dramatic alterations in jejunal epithelial and smooth muscle function. Such T cell-induced changes in intestinal function may contribute to the symptomatology of T cell-mediated enteropathies, including graft-versus-host disease, celiac disease, and idiopathic inflammatory bowel disease.
Responses of sympathetic outflow to skin during caloric stimulation in humans
Authors: Cui Jian , Iwase Satoshi , Mano Tadaaki , Kitazawa Hiroki
Published: December 2017

We previously showed that caloric vestibular stimulation elicits increases in sympathetic outflow to muscle (MSNA) in humans. The present study was conducted to determine the effect of this stimulation on sympathetic outflow to skin (SSNA). The SSNA in the tibial and peroneal nerves and nystagmus was recorded in nine subjects when the external meatus was irrigated with 50 ml of cold (10°C) or warm (44°C) water. During nystagmus, the SSNA in tibial and peroneal nerves decreased to 50 ± 4% (with baseline value set as 100%) and 61 ± 4%, respectively. The degree of SSNA suppression in both nerves was proportional to the maximum slow-phase velocity of nystagmus. After nystagmus, the SSNA increased to 166 ± 7 and 168 ± 6%, respectively, and the degree of motion sickness symptoms was correlated with this SSNA increase. These results suggest that the SSNA response differs from the MSNA response during caloric vestibular stimulation and that the SSNA response elicited in the initial period of caloric vestibular stimulation is different from that observed during the period of motion sickness symptoms.
Ontogeny of intestinal safety factors: lactase capacities and lactose loads
Authors: O’Connor Timothy P. , Diamond Jared
Published: December 2017

We measured intestinal safety factors (ratio of a physiological capacity to the load on it) for lactose digestion in developing rat pups. Specifically, we assessed the quantitative relationships between lactose load and the series capacities of lactase and the Na+-glucose cotransporter (SGLT-1). Both capacities increased significantly with age in suckling pups as a result of increasing intestinal mass and maintenance of mass-specific activities. The youngest pups examined (5 days) had surprisingly high safety factors of 8–13 for both lactase and SGLT-1, possibly because milk contains lactase substrates other than lactose; it also, however, suggests that their intestinal capacities were being prepared to meet future demands rather than just current ones. By day 10 (and also at day 15), increased lactose loads resulted in lower safety factors of 4–6, values more typical of adult intestines. The safety factor of SGLT-1 in day 30 (weanling) and day 100 (adult) rats was only ∼1.0. This was initially unexpected, because most adult intestines maintain a modest reserve capacity beyond nutrient load values, but postweaning rats appear to use hindgut fermentation, assessed by gut morphology and hydrogen production assays, as a built-in reserve capacity. The series capacities of lactase and SGLT-1 varied in concert with each other over ontogeny and as lactose load was manipulated by experimental variation in litter size.
Endothelin-1 and CYP450 arachidonate metabolites interact to promote tissue injury in DOCA-salt hypertension
Authors: Oyekan A. O. , McAward K. , Conetta J. , Rosenfeld L. , McGiff John C.
Published: December 2017

Inhibition of cytochrome P-450 (CYP450) enzymes with cobalt chloride (CoCl2) prevented hypertension, organ hypertrophy, and renal injury induced by DOCA and salt (1% NaCl) in uninephrectomized (UNx) rats. Systolic blood pressure (SBP) rose to 193 ± 6 mmHg by day 21 from control levels of 150 ± 7 mmHg in response to DOCA-salt treatment, a rise that was prevented by CoCl2(24 mg ⋅ kg−1⋅ 24 h−1). The effects of DOCA-salt treatment, which increased protein excretion to 88.3 ± 6.9 mg/24 h on day 21 from 9.0 ± 1.1 mg/24 h on day 3, were prevented by CoCl2. CoCl2also attenuated the renal and left ventricular hypertrophy and the increase in media-to-lumen ratio in hypertensive rats. DOCA-salt treatment increased excretion of endothelin (ET)-1 from 81 ± 17 to 277 ± 104 pg ⋅ 100 g body wt−1⋅ 24 h−1associated with a fourfold increase in 20-hydroxyeicosatetraenoic acid (20-HETE) excretion from 3.0 ± 1.1 to 12.2 ± 1.9 ng ⋅ 100 g body wt−1⋅ 24 h−1( days 3 vs. 21). CoCl2blunted these increases by 58 and 72%, respectively. In aortic rings pulsed with [3H]thymidine, ET-1 increased its incorporation. Dibromododec-11-enoic acid, an inhibitor of 20-HETE synthesis, attenuated ET-1-induced increases in [3H]thymidine incorporation. We distinguished effects of CoCl2acting via CO generation vs. suppression of CYP450-arachidonic acid metabolism by treating UNx-salt-DOCA rats with 1-aminobenzotriazole (ABT), which suppresses CYP450 enzyme activity, and compared these results to those produced by CoCl2. ABT reduced hypertension, as did CoCl2. Unlike CoCl2, ABT did not prevent organ hypertrophy and proteinuria, suggesting that these effects were partially related to CO formation. Blockade of the ETAreceptor with BMS-182874 reduced SBP, organ hypertrophy, and proteinuria, indicating the importance of ET-initiated abnormalities to the progression of lesions in UNx-salt-DOCA.
Simultaneous identification of static and dynamic vagosympathetic interactions in regulating heart rate
Authors: Kawada Toru , Sugimachi Masaru , Shishido Toshiaki , Miyano Hiroshi , Sato Takayuki , Yoshimura Ryoichi , Miyashita Hiroshi , Nakahara Tsutomu , Alexander Joe , Sunagawa Kenji
Published: December 2017

We earlier reported that stimulation of either one of the sympathetic and vagal nerves augments the dynamic heart rate (HR) response to concurrent stimulation of its counterpart. We explained this phenomenon by assuming a sigmoidal static relationship between nerve activity and HR. To confirm this assumption, we stimulated the sympathetic and/or vagal nerve in anesthetized rabbits using large-amplitude Gaussian white noise and determined the static and dynamic characteristics of HR regulation by a neural network analysis. The static characteristics approximated a sigmoidal relationship between the linearly predicted and the measured HRs (response range: 212.4 ± 46.3 beats/min, minimum HR: 96.0 ± 28.4 beats/min, midpoint of operation: 196.7 ± 31.3 beats/min, maximum slope: 1.65 ± 0.51). The maximum step responses determined from the dynamic characteristics were 7.9 ± 2.9 and −14.0 ± 4.9 beats ⋅ min−1 ⋅ Hz−1for the sympathetic and the vagal system, respectively. Because of these characteristics, changes in sympathetic or vagal tone alone can alter the dynamic HR response to stimulation of the other nerve.
Hemodynamic and renal effects of U-46619, a TXA2/PGH2analog, in late-pregnant rats
Authors: Kriston Tünde , Venuto Rocco C. , Baylis Christine , Losonczy György
Published: December 2017

The vasoconstrictor effects of pressor agents are attenuated during pregnancy. Thromboxane A2(TXA2) is produced in great quantities during hypertension in pregnancy, and therefore it is important to know whether pregnancy modifies the pressor effects of TXA2. The TXA2 analog U-46619 was infused in anesthetized, acutely prepared and conscious, chronically prepared late-pregnant and nonpregnant female rats to examine its systemic hemodynamic and renal effects. Mean arterial pressure (MAP) and total peripheral resistance (TPR) were lower in anesthetized pregnant than nonpregnant rats ( P < 0.01). The infusion of U-46619 into the aortic arch resulted in elevation of MAP only in pregnant rats, due to a greater elevation of TPR (60 ± 17%) compared with nonpregnant rats (36 ± 6%, P < 0.05). The pressor effect of intravenously infused U-46619 was also enhanced in conscious pregnant versus nonpregnant rats, and the increase in renal vascular resistance was undiminished. U-46619 increased hematocrit and plasma protein concentration more during pregnancy, which suggested greater reduction of plasma volume. The urinary excretion of sodium (−1.49 ± 0.25 vs. −0.54 ± 0.24 μmol/min) and water was reduced more in pregnant than nonpregnant rats during U-46619 ( P < 0.01). Thus the MAP and renal effects of the TXA2 analog are exaggerated during pregnancy in the rat.
A unique Na+/H+exchanger, analogous to NHE1, in the chicken embryonic fibroblast
Authors: Bhartur Sheela G. , Ballarin Leszek J. , Musch Mark W. , Bookstein Crescence , Chang Eugene B. , Rao M. C.
Published: December 2017

We report the characterization of an Na+/H+exchanger (NHE) in embryonic fibroblasts (SL-29 cells) of the chicken, a terrestrial vertebrate, where Na+conservation is important. This exchanger is electroneutral, has a single Na+binding site, and is highly sensitive to amiloride (IC502 μM), dimethyl amiloride (350 nM), and ethyl-isopropyl amiloride (25 nM). It is stimulated by serum, transforming growth factor-α, hypertonicity, and okadaic acid. Although these features make it resemble mammalian NHE1, other characteristics suggest distinct differences. First, in contrast to mammalian NHE1 it is inhibited by cAMP and shows a biphasic response to phorbol esters and a highly variable response to increased intracellular Ca2+concentration. Second, whereas full-length human and rat NHE1 cDNA probes recognize a 4.8-kb transcript in rat tissues, they recognize only a 3.9-kb transcript in chicken tissues. An antibody against amino acids 631–746 of human NHE1 sequence fails to recognize a protein in SL-29 cells. Rat NHE2 and NHE3 probes do not recognize any transcript in chicken fibroblasts. The SL-29 exchanger differs markedly from the previously characterized chicken intestinal apical exchanger in its amiloride sensitivity and regulation by phorbol esters. These results suggest that a modified version of mammalian NHE1 is present in chicken tissues and imply that another functionally distinct Na+/H+exchanger is expressed in aves.
Vasopressin V2 receptor enhances gain of baroreflex in conscious spontaneously hypertensive rats
Authors: Sampey Donella B. , Burrell Louise M. , Widdop Robert E.
Published: December 2017

The aim of the present study was to determine the receptor subtype involved in arginine vasopressin (AVP)-induced modulation of baroreflex function in spontaneously hypertensive rats (SHR) and Wistar-Kyoto (WKY) rats using novel nonpeptide AVP V1- and V2-receptor antagonists. Baroreceptor heart rate (HR) reflex was investigated in both SHR and WKY rats which were intravenously administered the selective V1- and V2-receptor antagonists OPC-21268 and OPC-31260, respectively. Baroreflex function was assessed by obtaining alternate pressor and depressor responses to phenylephrine and sodium nitroprusside, respectively, to construct baroreflex curves. In both SHR and WKY rats baroreflex activity was tested before and after intravenous administration of vehicle (20% DMSO), OPC-21268 (10 mg/kg), and OPC-31260 (1 and 10 mg/kg). Vehicle did not significantly alter basal mean arterial pressure (MAP) and HR values or baroreflex function in SHR or WKY rats. The V1-receptor antagonist had no significant effect on resting MAP or HR values or on baroreflex parameters in both groups of rats, although this dose was shown to significantly inhibit the pressor response to AVP (5 ng iv; ANOVA, P < 0.05). In SHR but not WKY rats the V2-receptor antagonist significantly attenuated the gain (or slope) of the baroreflex curve (to 73 ± 3 and 79 ± 7% of control for 1 and 10 mg/kg, respectively), although AVP-induced pressor responses were also attenuated with the higher dose of the V2-receptor antagonist. These findings suggest that AVP tonically enhances baroreflex function through a V2 receptor in the SHR.
Lateral hypothalamic NMDA receptor subunits NR2A and/or NR2B mediate eating: immunochemical/behavioral evidence
Authors: Khan Arshad M. , Currás Margarita C. , Dao Jennifer , Jamal Faizi A. , Turkowski Chuck A. , Goel Rishi K. , Gillard Elizabeth R. , Wolfsohn Stefany D. , Stanley B. Glenn
Published: December 2017

Cells within the lateral hypothalamic area (LHA) are important in eating control. Glutamate or its analogs, kainic acid (KA) and N-methyl-d-aspartate (NMDA), elicit intense eating when microinjected there, and, conversely, LHA-administered NMDA receptor antagonists suppress deprivation- and NMDA-elicited eating. The subunit composition of LHA NMDA receptors (NMDA-Rs) mediating feeding, however, has not yet been determined. Identifying this is important, because distinct second messengers/modulators may be activated by NMDA-Rs with differing compositions. To begin to address this, we detected LHA NR2A and NR2B subunits by immunoblotting and NR2B subunits by immunohistochemistry using subunit-specific antibodies. To help determine whether NMDA-Rs mediating feeding might contain these subunits, we conducted behavioral studies using LHA-administered ifenprodil, an antagonist selective for NR2A- and/or NR2B-containing NMDA-Rs at the doses we used (0.001–100 nmol). Ifenprodil maximally suppressed NMDA- and deprivation-elicited feeding by 63 and 39%, respectively, but failed to suppress KA-elicited eating, suggesting its actions were behaviorally specific. Collectively, these results suggest that LHA NMDA-Rs, some of which contribute to feeding control, are composed of NR2A and/or NR2B subunits, and implicate NR2A- and/or NR2B-linked signal transduction in feeding behavior.
Genetic control of renal thiazide receptor response to dietary NaCl and hypertension
Authors: Fanestil Darrell D. , Vaughn Duke A. , Hyde Ronald H. , Blakely Patricia
Published: December 2017

Excess NaCl increases blood pressure in some strains of animals but not others. An 8% NaCl diet did not change renal thiazide receptor (TZR) density in two salt-resistant normotensive rat strains (Wistar-Kyoto and Sprague-Dawley) [Fanestil, D. D., D. A. Vaughn, and P. Blakely. Am. J. Physiol. 273 ( Regulatory Integrative Comp. Physiol.42): R1241–R1245, 1997]. However, the renal response to salt differs in normal and hypertensive kidneys [Rettig, R., N. Bandelow, O. Patschan, B. Kuttler, B. Frey, and A. Uber. J. Hum. Hypertens. 10: 641–644, 1996]. Therefore, we examined two strains with salt-aggravated hypertension. Renal TZR did not change when Dahl-S (salt sensitive) animals became hypertensive with 8% dietary NaCl. In contrast, renal TZR decreased 34%, whereas blood pressure increased further, in SHR with 8% dietary NaCl. Blood pressure increased after NG-nitro-l-arginine in SHR, but renal TZR did not change, indicating the salt-induced decrease in TZR in SHR cannot be attributed nonspecifically to elevated arterial pressure. We conclude that the renal response to NaCl-induced increases in blood pressure can be genetically modulated independently of the genes that mediate either the primary hypertension or the salt sensitivity of the hypertension. This finding may be of use in future studies directed at identifying genotypes associated with salt-dependent hypertension.
Reduced glucose availability attenuates circadian responses to light in mice
Authors: Challet Etienne , Losee-Olson Susan , Turek Fred W.
Published: December 2017

To test whether circadian responses to light are modulated by decreased glucose availability, we analyzed photic phase resetting of the circadian rhythm of locomotor activity in mice exposed to four metabolic challenges: 1) blockade of glucose utilization induced by 2-deoxy-d-glucose (2-DG), 2) fasting (food was removed for 30 h), 3) insulin administration, and 4) insulin treatment after fasting. In mice housed in constant darkness, light pulses applied during early subjective night induced phase delays of the rhythm of locomotor activity, whereas light pulses applied during late subjective night caused phase advances. There was an overall reduction of light-induced phase shifts, with a more pronounced effect for delays, in mice pretreated with 500 mg/kg ip 2-DG compared with mice injected with saline. Administration of glucose with 2-DG prevented the reduction of light-induced phase delays. Furthermore, phase delays were reduced in fed mice pretreated with 5 IU/kg sc insulin and in fasted mice injected with saline or insulin compared with control fed mice. These results show that circadian responses to light are reduced when brain glucose availability is decreased, suggesting a metabolic modulation of light-induced phase shifts.
Elevation of blood pressure by genetic and pharmacological disruption of the ETBreceptor in mice
Authors: Ohuchi Takashi , Kuwaki Tomoyuki , Ling Guang-Yi , Dewit Damiane , Ju Ki-Hwan , Onodera Makoto , Cao Wei-Hua , Yanagisawa Masashi , Kumada Mamoru
Published: December 2017

Exogenously administered endothelin (ET) elicits both pressor and depressor responses through the ETAand/or the ETBreceptor on vascular smooth muscle cells and ETBon endothelial cells. To test whether ETBhas pressor or depressor effects under basal physiological conditions, we determined arterial blood pressure (BP) in ETB-deficient mice obtained by crossing inbred mice heterozygous for targeted disruption of the ETBgene with mice homozygous for the piebald ( s) mutation of the ETBgene ( ETBs/s). F1ETB−/sand ETB+/sprogeny share an identical genetic background but have ETBlevels that are ∼[Formula: see text]and [Formula: see text], respectively, of wild-type mice ( ETB+/+). BP in ETB−/smice was significantly higher, by ∼20 mmHg, than that in ETB+/sor ETB+/+mice. Immunoreactive ET-1 concentration in plasma as well as respiratory parameters was not different between ETB−/sand ETB+/smice. A selective ETBantagonist, BQ-788, increased BP in ETB+/sand ETB+/+but not in ETB−/smice. Pretreatment with indomethacin, but not with NG-monomethyl-l-arginine, can attenuate the observed pressor response to BQ-788. The selective ETAantagonist BQ-123 did not ameliorate the increased BP in ETB−/smice. Moreover, BP in mice heterozygous for targeted disruption of the ETAgene was not different from that in wild-type controls. These results suggest that endogenous ET elicits a depressor effect through ETBunder basal conditions, in part through tonic production of prostaglandins, and not through secondary mechanisms involving respiratory control or clearance of circulating ET.
Contribution of endogenous carbon monoxide to regulation of diameter in resistance vessels
Authors: Kozma Fruzsina , Johnson Robert A. , Zhang Fan , Yu Changhua , Tong Xianglan , Nasjletti Alberto
Published: December 2017

Endogenous carbon monoxide was proposed to subserve vasodepressor functions. If so, inhibition of heme oxygenase may be expected to promote vascular contraction. This hypothesis was examined in large and small arteries and in isolated first-order gracilis muscle arterioles of rat. The heme oxygenase inhibitors chromium mesoporphyrin (CrMP) and cobalt protoporphyrin (0.175–102 μmol/l) decreased the diameter of pressurized (80 mmHg) gracilis muscle arterioles, whereas magnesium protoporphyrin, a weak heme oxygenase inhibitor, did not. CrMP also elicited development of isometric tension in the muscular branch of the femoral artery but not in the aorta or femoral artery. Arteriolar constrictor responses to CrMP varied in relation to the intravascular pressure, were blunted in preparations exposed to exogenous carbon monoxide (100 μmol/l), and were unaffected by an endothelin receptor antagonist. Importantly, CrMP amplified the constrictor response to increases of pressure in gracilis arterioles. Accordingly, the constrictor effect of heme oxygenase inhibitors is attributable to magnification of myogenic tone due to withdrawal of a vasodilatory mechanism mediated by endogenous carbon monoxide. The study suggests that the vascular carbon monoxide system plays a role in the regulation of basal tone in resistance vessels.
Core temperature and sweating onset in humans acclimated to heat given at a fixed daily time
Authors: Shido Osamu , Sugimoto Naotoshi , Tanabe Minoru , Sakurada Sotaro
Published: December 2017

The thermoregulatory functions of rats acclimated to heat given daily at a fixed time are altered, especially during the period in which they were previously exposed to heat. In this study, we investigated the existence of similar phenomena in humans. Volunteers were exposed to an ambient temperature (Ta) of 46°C and a relative humidity of 20% for 4 h (1400–1800) for 9–10 consecutive days. In the first experiment, the rectal temperatures (Tre) of six subjects were measured over 24 h at a Ta of 27°C with and without heat acclimation. Heat acclimation significantly lowered Tre only between 1400 and 1800. In the second experiment, six subjects rested in a chair at a Ta of 28°C and a relative humidity of 40% with both legs immersed in warm water (42°C) for 30 min. The Tre and sweating rates at the forearm and chest were measured. Measurements were made in the morning (0900–1100) and afternoon (1500–1700) on the same day before and after heat acclimation. Heat acclimation shortened the sweating latency and decreased the threshold Tre for sweating. However, these changes were significant only in the afternoon. The results suggest that repeated heat exposure in humans, limited to a fixed time daily, alters the core temperature level and thermoregulatory function, especially during the period in which the subjects had previously been exposed to heat.
Influence of right atrial pressure on the cardiac pacemaker response to vagal stimulation
Authors: Bolter Chris P. , Wilson Suzanne J.
Published: December 2017

We have recently shown that the intrinsic rate response to an increase in right atrial pressure is augmented when cardiac muscarinic receptors are activated. This present study examines the cardiac pacemaker response to vagal stimulation at different values of right atrial pressure in isolated rat right atrium and in the rabbit heart in situ. In the rat atrium, when pressure was raised in steps from 2 to 10 mmHg, there was a progressive reduction in the response to vagal stimulation [40.5 ± 7.2% reduction (mean ± SE) at 8 mmHg, P < 0.01], which was independent of the level of vagal bradycardia, that persisted in the presence of the β-adrenergic agonist isoproterenol. In barbiturate-anesthetized rabbits with cervical vagi cut and β-adrenergic blockade, raising right atrial pressure ∼2.5 mmHg by blood volume expansion reduced the bradycardia elicited by electrical stimulation of the peripheral end of the right vagus nerve (9.1 ± 1.1% reduction, P < 0.0001). These results demonstrate that vagal bradycardia is modulated by the level of right atrial pressure and suggest that normally right atrial pressure may interact with cardiac vagal activity in the control of heart rate.
Distribution of Fos immunoreactivity in rat brain after sodium consumption induced by peritoneal dialysis
Authors: Franchini Lucia F. , Vivas Laura
Published: December 2017

Fos immunoreactivity was used to map the neuronal population groups activated after sodium ingestion induced by peritoneal dialysis (PD) in rats. Oxytocin immunoreactivity in combination with Fos immunoreactivity was also analyzed to evaluate whether the oxytocinergic neurons of the paraventricular nucleus of the hypothalamus (PVN) are activated during the satiety process of sodium appetite. Sodium ingestion stimulated by PD produced Fos immunoreactivity within defined cells groups of the lamina terminalis and hindbrain areas such us the nucleus of the solitary tract, area postrema, and lateral parabrachial nucleus. On the other hand, particular parvocellular and magnocellular oxytocinergic subdivisions of the PVN and supraoptic nucleus were double labeled after PD-induced sodium consumption. Approximately 27 and 2.1%, respectively, of the activated dorsomedial cap and parvocellular posterior subnuclei of the PVN, which project to the hindbrain, were oxytocinergic. Our data indicate that specific neuronal groups are activated during the satiety process of sodium appetite, suggesting they may form a circuit subserving sodium balance regulation. They also support a functional role for the oxytocinergic neurons in this circuit.
Tonic drive to sympathetic premotor neurons of rostral ventrolateral medulla from caudal pressor area neurons
Authors: Campos R. R. , McAllen R. M.
Published: December 2017

The responses of sympathetic premotor neurons in the rostral ventrolateral medulla (RVLM) to activation or inactivation of neurons in the caudal pressor area (CPA) were studied in urethan-anesthetized rats. Extracellular recordings were made from 32 barosensitive single units in the RVLM, of which 26 were antidromically activated from the cervical cord. Unilateral microinjections ofl-glutamate (0.5–5 nmol) into the CPA increased firing in 13 of 14 premotor neurons by 90 ± 30% while raising blood pressure. Both ipsilateral and contralateral injections were effective. Unilateral or bilateral inhibition of CPA neuron activity by microinjecting glycine (5–200 nmol/side) lowered blood pressure, while it reduced firing in 9 of 10 and 16 of 17 premotor neurons, respectively, by 45 ± 9 and 39 ± 6%. A significant proportion of tonic activity in RVLM sympathetic premotor neurons is thus driven, directly or indirectly, by neurons in the CPA.
Altered airway and cardiac responses in mice lacking G protein-coupled receptor kinase 3
Authors: Walker Julia K. L. , Peppel Karsten , Lefkowitz Robert J. , Caron Marc G. , Fisher John T.
Published: December 2017

Contraction and relaxation of airway smooth muscles is mediated, in part, by G protein-coupled receptors (GPCRs) and dysfunction of these receptors has been implicated in asthma. Phosphorylation of GPCRs, by G protein-coupled receptor kinase (GRK), is an important mechanism involved in the dampening of GPCR signaling. To determine whether this mechanism might play a role in airway smooth muscle physiology, we examined the airway pressure time index and heart rate (HR) responses to intravenous administration of the cholinergic agonist methacholine (MCh) in genetically altered mice lacking one copy of GRK2 (GRK2 +/−), homozygous GRK3 knockout (GRK3 −/−), and wild-type littermates. (GRK2 −/− mice die in utero.) GRK3 −/− mice demonstrated a significant enhancement in the airway response to 100 and 250 μg/kg doses of MCh compared with wild-type and GRK2 +/− mice. GRK3 −/− mice also displayed an enhanced sensitivity of the airway smooth muscle response to MCh. In addition, GRK3 −/− mice displayed an altered HR recovery from MCh-induced bradycardia. Although direct stimulation of cardiac muscarinic receptors measured as vagal stimulation-induced bradycardia was similar in GRK3 −/− and wild-type mice, the baroreflex increase in HR associated with sodium nitroprusside-induced hypotension was significantly greater in GRK3 −/− than wild-type mice. Therefore, these data demonstrate that in the mouse, GRK3 may be involved in modulating the cholinergic response of airway smooth muscle and in regulating the chronotropic component of the baroreceptor reflex.
Glutamatergic and dopaminergic contributions to rat bladder hyperactivity after cerebral artery occlusion
Authors: Yokoyama Osamu , Yoshiyama Mitsuharu , Namiki Mikio , de Groat William C.
Published: December 2017

The contribution of glutamatergic and dopaminergic mechanisms to bladder hyperactivity after left middle cerebral artery occlusion was evaluated by determining the effects of intravenous cumulative doses of an N-methyl-d-aspartate (NMDA) glutamatergic antagonist (MK-801) and D1-selective (Sch-23390), D2-selective (sulpiride), or nonselective (haloperidol) dopaminergic antagonists on bladder activity in sham-operated (SO) and cerebral-infarcted (CI) rats. MK-801 (1 and 10 mg/kg) or sulpiride (3–30 mg/kg) significantly increased bladder capacity (BC) in CI but decreased or had no effect, respectively, on BC in SO. Sch-23390 (0.1–3 mg/kg) decreased BC in both SO and CI. In both CI and SO, low doses of haloperidol (0.1–1 mg/kg) increased BC, but a higher dose (3 mg/kg) reversed this effect. Administration of haloperidol (0.3 mg/kg) or sulpiride (10 mg/kg) in combination with MK-801 (0.01–10 mg/kg) markedly increased BC in CI but produced small decreases or increases in BC depending on the dose of MK-801 in SO. These results indicate that the bladder hyperactivity induced by cerebral infarction is mediated in part by NMDA glutamatergic and D2dopaminergic excitatory mechanisms.