bluuebunny/crossref_metadata_2025 huggingface dataset:
Sex differences and role of nitric oxide in blood flow of canine urinary bladder
Authors: Pontari Michel A. , Ruggieri Michael R.
Published: December 2017

Continuous measurements were made of bladder blood flow by laser Doppler flowmetry in anesthetized dogs during bladder filling and emptying. In both mucosa and muscle, perfusion was inversely proportional to intravesical pressure. There was significantly greater perfusion in the bladder mucosa of males than females at baseline and up to 10 cm water filling pressure but not in the muscle. Intra-arterial infusion of the nitric oxide synthase inhibitor N G-nitro-l-arginine produced a significant decrease in resting bladder perfusion in the mucosa only, with no differences seen in the response to intravesical pressure. Intra-arterial infusion ofl-arginine produced a significant increase in the level of perfusion in the mucosa seen immediately after the bladder was drained. No changes were observed in muscle perfusion afterl-arginine. These results suggest that the perfusion of the bladder mucosa differs by gender and is regulated differently than the bladder muscle, possibly related to the different function of the two layers.
GABA receptors in the phrenic nucleus of the rat
Authors: Chitravanshi V. C. , Sapru H. N.
Published: December 2017

The phrenic nucleus was identified by microinjections of N-methyl-d-aspartic acid in urethan-anesthetized adult male Wistar rats. Microinjections of GABAAand GABABreceptor agonists (muscimol and baclofen, respectively) at the same site decreased the phrenic nerve burst amplitude. Microinjections of GABAAand GABABreceptor antagonists (bicuculline and 2-hydroxysaclofen, respectively) blocked as well as reversed the effects of their respective agonists. These results were confirmed by recording extracellular action potentials from single phrenic neurons. Micropressure applications of muscimol and baclofen decreased the activity of single neurons in the phrenic nucleus; this effect was blocked as well as reversed by micropressure applications of bicuculline and 2-hydroxysaclofen, respectively. These results demonstrated the presence of GABA receptors on the neurons in the phrenic nucleus and suggested that their activation results in the decrease of the phrenic nerve burst amplitude. The importance of these results in the identification of neural circuits mediating inhibition of phrenic neurons is discussed.
Sleep after arousal from hibernation is not homeostatically regulated
Authors: Larkin Jennie E. , Heller H. Craig
Published: December 2017

Electroencephalographic slow-wave activity (SWA) in non-rapid eye movement (NREM) sleep is directly related to prior sleep/wake history, with high levels of SWA following extended periods of wake. Therefore, SWA has been thought to reflect the level of accumulated sleep need. The discovery that euthermic intervals between hibernation bouts are spent primarily in sleep and that this sleep is characterized by high and monotonically declining SWA has led to speculation that sleep homeostasis may play a fundamental role in the regulation of the timing of bouts of hibernation and periodic arousals to euthermia. It was proposed that because the SWA profile seen after arousal from hibernation is strikingly similar to what is seen in nonhibernating mammals after extended periods of wakefulness, that hibernating mammals may arouse from hibernation with significant accumulated sleep need. This sleep need may accumulate during hibernation because the low brain temperatures during hibernation may not be compatible with sleep restorative processes. In the present study, golden-mantled ground squirrels were sleep deprived during the first 4 h of interbout euthermia by injection of caffeine (20 mg/kg ip). We predicted that if the SWA peaks after bouts of hibernation reflected a homeostatic response to an accumulated sleep need, sleep deprivation should simply have displaced and possibly augmented the SWA to subsequent recovery sleep. Instead we found that after caffeine-induced sleep deprivation of animals just aroused from hibernation, the anticipated high SWA typical of recovery sleep did not occur. Similar results were found in a study that induced sleep deprivation by gentle handling (19). These findings indicate that the SWA peak immediately after hibernation does not represent homeostatic regulation of NREM sleep, as it normally does after prolonged wakefulness during euthermia, but instead may reflect some other neurological process in the recovery of brain function from an extended period at low temperature.
Metabolic and contractile influence of carbonic anhydrase III in skeletal muscle is age dependent
Authors: Côté Claude H. , Ambrosio Fabrisia , Perreault Guylaine
Published: December 2017

Carbonic anhydrase (CA) III is very abundant in type I skeletal muscle, but its function is still debated. Our aims were to examine CA III expression during growth and determine whether the effects of CA inhibition previously observed in adult muscles could be seen in younger rats in which CA III levels are lower. CA III content and activity were measured in soleus muscles from 10- to 100-day-old rats, and the influence of CA inhibitor on fatigue and hexosemonophosphate content was quantified in vitro. CA III activity and content increased fivefold between 10 and 100 days of age. Data analysis revealed that the influence of CA inhibitor on fatigue was to some extent positively and linearly related to the level of CA III activity. Hexosemonophosphate accumulation with CA inhibition also became more significant with age. In conclusion, CA III level in soleus muscle does not stabilize before 3 mo after birth; data also confirm that the effects of CA inhibitors are due to inhibition of the CA III isoform.
ATP-dependent calcium uptake into basolateral vesicles from transporting epithelia of intermolt crayfish
Authors: Wheatly Michele G. , Pence Robert C. , Weil Jennifer R.
Published: December 2017

ATP-dependent Ca2+uptake was determined into inside-out basolateral membrane vesicles (BLMV) from intermolt crayfish ( Procambarus clarkii) Ca2+-transporting epithelia: gill, hepatopancreas (liver), and antennal gland (kidney). Extravesicular (EV) ATP (5 mM) increased45Ca2+uptake (free Ca2+5 μM) by fivefold but was abolished by pretreatment with either vanadate or the ionophore A-23187. Addition of A-23187 to Ca2+-loaded vesicles produced 70% efflux. The saturable carrier exhibited a Kmfor Ca2+of 0.11–0.27 μM and maximal influx of 20–123 pmol ⋅ mg−1⋅ min−1. The Kmfor ATP was 0.01–0.04 mM. The temperature coefficient ranged from 1.43 to 2.06. EGTA treatment of hepatopancreas and antennal gland vesicles decreased45Ca2+uptake by 50–90%; uptake was restorable by calmodulin. However, in gill,45Ca2+uptake was unaffected by EGTA treatment and calmodulin decreased uptake in both EGTA-treated and untreated vesicles. Addition of EV Na+(5 mM) increased ATP-dependent Ca2+uptake into hepatopancreas and antennal gland BLMV by 60%; in hepatopancreas BLMV, this increase was inhibitable by ouabain. However, ATP-dependent Ca2+uptake in gill vesicles was Na+independent. The relative role of each epithelium in whole animal Ca2+homeostasis has been interpreted based on in vitro characteristics.
Acute-phase responses in transgenic mice with CNS overexpression of IL-1 receptor antagonist
Authors: Lundkvist Johan , Sundgren-Andersson Anna K. , Tingsborg Susanne , Östlund Pernilla , Engfors Catherine , Alheim Katarina , Bartfai Tamas , Iverfeldt Kerstin , Schultzberg Marianne
Published: December 2017

The interleukin-1 (IL-1) receptor antagonist (IL-1ra) is an endogenous antagonist that blocks the effects of the proinflammatory cytokines IL-1α and IL-1β by occupying the type I IL-1 receptor. Here we describe transgenic mice with astrocyte-directed overexpression of the human secreted IL-1ra (hsIL-1ra) under the control of the murine glial fibrillary acidic protein (GFAP) promoter. Two GFAP-hsIL-1ra strains have been generated and characterized further: GILRA2 and GILRA4. These strains show a brain-specific expression of the hsIL-1ra at the mRNA and protein levels. The hsIL-1ra protein was approximated to ∼50 ng/brain in cytosolic fractions of whole brain homogenates, with no differences between male and female mice or between the two strains. Furthermore, the protein is secreted, inasmuch as the concentration of hsIL-1ra in the cerebrospinal fluid was 13 (GILRA2) to 28 (GILRA4) times higher in the transgenic mice than in the control animals. To characterize the transgenic phenotype, GILRA mice and nontransgenic controls were injected with recombinant human IL-1β (central injection) or lipopolysaccharide (LPS, peripheral injection). The febrile response elicited by IL-1β (50 ng/mouse icv) was abolished in hsIL-1ra-overexpressing animals, suggesting that the central IL-1 receptors were occupied by antagonist. The peripheral LPS injection (25 μg/kg ip) triggered a fever in overexpressing and control animals. Moreover, no differences were found in LPS-induced (100 and 1,000 μg/kg ip; 1 and 6 h after injection) IL-1β and IL-6 serum levels between GILRA and wild-type mice. On the basis of these results, we suggest that binding of central IL-1 to central IL-1 receptors is not important in LPS-induced fever or LPS-induced IL-1β and IL-6 plasma levels.
Central administration of rat IL-6 induces HPA activation and fever but not sickness behavior in rats
Authors: Lenczowski M. J. P. , Bluthé R.-M. , Roth J. , Rees G. S. , Rushforth D. A. , van Dam A.-M. , Tilders F. J. H. , Dantzer R. , Rothwell N. J. , Luheshi G. N.
Published: December 2017

Interleukin (IL)-6 has been proposed to mediate several sickness responses, including brain-mediated neuroendocrine, temperature, and behavioral changes. However, the exact mechanisms and sites of action of IL-6 are still poorly understood. In the present study, we describe the effects of central administration of species-homologous recombinant rat IL-6 (rrIL-6) on the induction of hypothalamic-pituitary-adrenal (HPA) activity, fever, social investigatory behavior, and immobility. After intracerebroventricular administration of rrIL-6 (50 or 100 ng/rat), rats demonstrated HPA and febrile responses. In contrast, rrIL-6 alone did not induce changes in social investigatory and locomotor behavior at doses of up to 400 ng/rat. Coadministration of rrIL-6 (100 ng/rat) and rrIL-1β (40 ng/rat), which alone did not affect the behavioral responses, reduced social investigatory behavior and increased the duration of immobility. Compared with rhIL-6, intracerebroventricular administration of rrIL-6 (100 ng/rat) induced higher HPA responses and early-phase febrile responses. This is consistent with a higher potency of rrIL-6, compared with rhIL-6, in the murine B9 bioassay. We conclude that species-homologous rrIL-6 alone can act in the brain to induce HPA and febrile responses, whereas it only reduces social investigatory behavior and locomotor activity in the presence of IL-1β.
Norepinephrine stimulates lymphoid cell mobilization from the perfused rat spleen via β-adrenergic receptors
Authors: Rogausch Heinz , del Rey Adriana , Oertel Jörg , Besedovsky Hugo O.
Published: December 2017

The possibility that norepinephrine (NE) influences lymphoid cell outflow independently of its vasoconstrictor action was investigated in the perfused rat spleen. Using agents that affect the vasoconstrictor tonus of the spleen, we observed an inverse correlation between flow resistance and splenic cell output. The curve obtained served as a reference for evaluating effects of different treatments on the number of cells that are mobilized at defined levels of flow resistance. Perfusion of the β-adrenergic blocker propranolol either alone or in combination with NE lowered splenic leukocyte outflow clearly beyond the number of cells expected at the corresponding flow resistance. No comparable effects were observed when the α-adrenergic blocker phentolamine was perfused. When the vasoconstrictor effect of NE was counteracted by papaverine, splenic cell outflow was significantly higher than expected for the level of flow resistance attained. Furthermore, when NE was perfused together with endotoxin, which does not inhibit the vasoconstriction induced by catecholamines, splenic cell mobilization was severalfold higher than expected at increased flow resistance. Propranolol abrogated this effect to a large extent. Furthermore, perfusion of the β-agonist isoproterenol stimulated lymphoid cell outflow from the spleen despite increased flow resistance. These studies show a dual effect of NE on cell mobilization from the spleen: cell retention by decreasing blood flow and stimulation of cell output by a β-adrenergically mediated, smooth muscle-independent mechanism.
Neurogenic origin of articular hyperemia in early degenerative joint disease
Authors: McDougall Jason J. , Ferrell William R. , Bray Robert C.
Published: December 2017

It has been speculated that joint instability resulting from anterior cruciate ligament (ACL) rupture could be exacerbated by changes in vasomotor activity in the remaining supporting structures. In this study, the effect of ACL transection on medial collateral ligament (MCL) basal perfusion and its responsiveness to calcitonin gene-related peptide (CGRP) and sympathetic adrenergic influences was examined. Using urethan-anesthetized rabbits, we tested the effects of CGRP and its antagonist CGRP-(8—37) by topical application of these agents to the exposed knee while sympathetic influences were tested by electrically stimulating the saphenous nerve. It was found that MCL basal perfusion was elevated in ACL-sectioned joints; however, this effect was abrogated by prior resection of the articular nerve supply. At the doses tested, the normal vasodilator response to CGRP was abolished in ACL-sectioned joints, whereas the response to CGRP-(8—37) was attenuated. Even under the influence of increased constrictor tone, MCL and capsule blood vessels still showed substantially reduced responses to exogenous CGRP administration. By contrast, nerve-mediated constrictor responses were mostly unaffected by joint instability. This study suggests that posttraumatic knee joint hyperemia is neurogenically mediated, possibly by increased secretion of CGRP.
Hypoglycemia and torpor in Siberian hamsters
Authors: Dark John , Lewis Daniel A. , Zucker Irving
Published: December 2017

We tested whether reduced blood glucose concentrations are necessary and sufficient for initiation of torpor in Siberian hamsters. During spontaneous torpor bouts, body temperature (Tb) decreases from the euthermic value of 37 to <31°C. Among hamsters that displayed torpor during maintenance in a short-day length (10 h light/day) at an air temperature of 15°C, blood glucose concentrations decreased significantly by 28% as Tbfell from 37 to <31°C and increased during rewarming so that by the time Tbfirst was >36°C, glucose concentrations had returned to the value preceding torpor. Hamsters did not display torpor when maintained in a long-day length (16 h light/day) and injected with a range of insulin doses (1–50 U/kg body mass), some of which resulted in sustained, pronounced hypoglycemia. We conclude that changes in blood glucose concentrations may be a consequence rather than a cause of the torpid state and question whether induction of torpor by 2-deoxy-d-glucose is due to its general glucoprivic actions.
Impact of development and chronic hypoxia on NE release from adrenergic nerves in sheep arteries
Authors: Buchholz John , Edwards-Teunissen Kim , Duckles Sue P.
Published: December 2017

To examine effects of development and chronic high-altitude hypoxia on sympathetic nerve function in sheep, norepinephrine release was measured in vitro from middle cerebral and facial arteries. Capsaicin was used to test the role of capsaicin-sensitive sensory nerves; norepinephrine release was not altered by capsaicin treatment. N ω-nitro-l-arginine methyl ester (l-NAME), an inhibitor of NO synthase, decreased stimulation-evoked norepinephrine release in middle cerebral arteries from normoxic sheep with no effect in hypoxic arteries or facial arteries. Thus NO-releasing nerves augmented norepinephrine release. Furthermore, the function of NO-releasing nerves declined after chronic hypoxia. Despite loss of the augmenting effects of NO, stimulation-evoked fractional norepinephrine release was unchanged after chronic hypoxia, suggesting that middle cerebral arteries adapt to hypoxia by increasing stimulation-evoked norepinephrine release. In fetal facial arteries, chronic hypoxia resulted in a decline in stimulation-evoked norepinephrine release, but there was an increase in the adult facial artery. In the adult, adaptation to chronic hypoxia is similar in both cerebral and facial arteries. However, differential adaptation in fetal adrenergic nerves may reflect differences in fetal redistribution of blood flow in the face of chronic hypoxia but could also possibly contribute to increased incidence of fetal morbidity.
Time-dependent and tissue-specific effects of circulating glucose on fetal ovine glucose transporters
Authors: Das Utpala G. , Schroeder Robert E. , Hay William W. , Devaskar Sherin U.
Published: December 2017

To determine the cellular adaptations to fetal hyperglycemia and hypoglycemia, we examined the time-dependent effects on basal (GLUT-1 and GLUT-3) and insulin-responsive (GLUT-4) glucose transporter proteins by quantitative Western blot analysis in fetal ovine insulin-insensitive (brain and liver) and insulin-sensitive (myocardium, skeletal muscle, and adipose) tissues. Maternal glucose infusions causing fetal hyperglycemia resulted in a transient 30% increase in brain GLUT-1 but not GLUT-3 levels and a decline in liver and adipose GLUT-1 and myocardial and skeletal muscle GLUT-1 and GLUT-4 levels compared with gestational age-matched controls. Maternal insulin infusions leading to fetal hypoglycemia caused a decline in brain GLUT-3, an increase in brain GLUT-1, and a subsequent decline in liver GLUT-1, with no significant change in insulin-sensitive myocardium, skeletal muscle, and adipose tissue GLUT-1 or GLUT-4 concentrations, compared with gestational age-matched sham controls. We conclude that fetal glucose transporters are subject to a time-dependent and tissue- and isoform-specific differential regulation in response to altered circulating glucose and/or insulin concentrations. These cellular adaptations in GLUT-1 (and GLUT-3) are geared toward protecting the conceptus from perturbations in substrate availability, and the adaptations in GLUT-4 are geared toward development of fetal insulin resistance.
Contribution of extracranial lymphatics and arachnoid villi to the clearance of a CSF tracer in the rat
Authors: Boulton M. , Flessner M. , Armstrong D. , Mohamed R. , Hay J. , Johnston M.
Published: December 2017

The objective of this study was to determine the relative roles of arachnoid villi and cervical lymphatics in the clearance of a cerebrospinal fluid (CSF) tracer in rats.125I-labeled human serum albumin (125I-HSA; 100 μg) was injected into one lateral ventricle, and an Evans blue dye-rat protein complex was injected intravenously. Arterial blood was sampled for 3 h. Immediately after this, multiple cervical vessels were ligated in the same animals, and plasma recoveries were monitored for a further 3 h after the intracerebroventricular injection of 100 μg131I-HSA. Tracer recovery in plasma at 3 h averaged (%injected dose) 0.697 ± 0.042 before lymphatic ligation and dropped significantly to 0.357 ± 0.060 after ligation. Estimates of the rate constant associated with the transport of the CSF tracer to plasma were also significantly lower after obstruction of cervical lymphatics (from 0.584 ± 0.072/h to 0.217 ± 0.056/h). No significant changes were observed in sham-operated animals. Assuming that the movement of the CSF tracer to plasma in lymph-ligated animals was a result of arachnoid villi clearance, we conclude that arachnoid villi and extracranial lymphatic pathways contributed equally to the clearance of the CSF tracer from the cranial vault.
Alterations in endogenous circadian rhythm of core temperature in senescent Fischer 344 rats
Authors: McDonald Roger B. , Hoban-Higgins Tana M. , Ruhe Rodney C. , Fuller Charles A. , Horwitz Barbara A.
Published: December 2017

We assessed whether alterations in endogenous circadian rhythm of core temperature (CRT) in aging rats are associated with chronological time or with a biological marker of senescence, i.e., spontaneous rapid body weight loss. CRT was measured in male Fischer 344 (F344) rats beginning at age 689 days and then continuously until death. Young rats were also monitored. The rats were housed under constant dim red light at 24–26°C, and core temperature was recorded every 10 min via biotelemetry. The CRT amplitude of the body weight-stable (presenescent) old rats was significantly less than that of young rats at all analysis periods. At the onset of spontaneous rapid weight loss (senescence), all measures of endogenous CRT differed significantly from those in the presenescent period. The suprachiasmatic nucleus (a circadian pacemaker) of the senescent rats maintained its light responsiveness as determined by an increase in c- fos expression after a brief light exposure. These data demonstrate that some characteristics of the CRT are altered slowly with chronological aging, whereas others occur rapidly with the onset of senescence.
Brown adipose tissue triacylglycerol synthesis in rats adapted to a high-protein, carbohydrate-free diet
Authors: Brito M. N. , Brito N. A. , Brito S. R. C. , Moura M. A. F. , Kawashita N. H. , Kettelhut I. C. , Migliorini R. H.
Published: December 2017

Adaptation of rats to a high-protein, carbohydrate-free (HP) diet induced a marked reduction of brown adipose tissue (BAT) fatty acid (FA) synthesis from both3H2O and [14C]glucose in vivo, with pronounced decreases in the activities of four enzymes associated with lipogenesis: glucose-6-phosphate dehydrogenase, malic enzyme, citrate lyase, and acetyl-CoA carboxylase. In both HP-adapted and control rats, in vivo incorporation of3H2O and [14C]glucose into BAT glyceride-glycerol was much higher than into FA. It could be estimated that most of the glycerol synthetized was used to esterify preformed FA. Glycerol synthesis from nonglucose sources (glyceroneogenesis) was increased in BAT from HP rats, as evidenced by an increased capacity of tissue fragments to incorporate [1-14C]pyruvate into glycerol and by a fourfold increase in the activity of phospho enolpyruvate carboxykinase activity, a key glyceroneogenic enzyme. The data suggest that high rates of glyceroneogenesis and of esterification of preformed FA in BAT from HP-adapted rats are essential for preservation of tissue lipid stores, necessary for heat generation when BAT is recruited in nonshivering thermogenesis.
Central and peripheral administration of endothelin-1 induces an increase in blood pressure in conscious trout
Authors: le Mével Jean-Claude , Delarue Catherine , Mabin Dominique , Vaudry Hubert
Published: December 2017

The central and peripheral cardiovascular effects of endothelin (ET)-1 and ET-3 were investigated in conscious rainbow trout. Both intracerebroventricular and intra-arterial injections of ET-1 (6.25–25 pmol) but not ET-3 (25 pmol) caused a dose-dependent increase in mean dorsal aortic blood pressure and a concomitant decrease in heart rate. The hypertensive effects induced by intra-arterial and intracerebroventricular injection of ET-1 were associated with a significant ( P < 0.05) increase in systemic vascular resistance. Intracerebroventricular injection of ET-1 induced a twofold higher pressor response than that caused by intra-arterial injection of ET-1 and provoked a barostatic gain that was reduced by 2.5- to 3-fold compared with that calculated after intra-arterial administration of the peptide. The ET receptor antagonist bosentan significantly ( P< 0.05) attenuated these responses regardless of the route of administration. Finally, intra-arterial injection of ET-1 did not significantly modify plasma cortisol level. The present data demonstrate that intracerebroventricular and intra-arterial administration of very low doses of ET-1 produces hypertension in conscious trout. The lack of effect of ET-3 indicates that the hemodynamic actions of ET-1 are mediated both centrally and peripherally through ETAreceptors.
Long-term CCK-leptin synergy suggests a role for CCK in the regulation of body weight
Authors: Matson Claire A. , Ritter Robert C.
Published: December 2017

The gut peptide CCK is a nutrient-related signal important to the control of food intake. In the present studies, we observed that a single intraperitoneal injection of CCK (1–2 μg/kg) given 2–3 h after intracerebroventricular leptin (2–5 μg) reduced body weight and chow intake over the ensuing 48 h more than did leptin alone. CCK alone had no effect on either 48-h chow intake or body weight but significantly reduced feeding during a 30-min sucrose test. However, reduction of 30-min sucrose intake by CCK was not enhanced by prior intracerebroventricular leptin. The present data suggest that CCK can contribute to the regulation of body weight when central leptin levels are elevated.
Effects of adrenomedullin and PAMP on adrenal catecholamine release in dogs
Authors: Masada Kimiya , Nagayama Takahiro , Hosokawa Akio , Yoshida Makoto , Suzuki-Kusaba Mizue , Hisa Hiroaki , Kimura Tomohiko , Satoh Susumu
Published: December 2017

We examined the effects of proadrenomedullin-derived peptides on the release of adrenal catecholamines in response to cholinergic stimuli in pentobarbital sodium-anesthetized dogs. Drugs were administered into the adrenal gland through the phrenicoabdominal artery. Splanchnic nerve stimulation (1, 2, and 3 Hz) and ACh injection (0.75, 1.5, and 3 μg) produced frequency- or dose-dependent increases in adrenal catecholamine output. These responses were unaffected by infusion of adrenomedullin (1, 3, and 10 ng ⋅ kg−1 ⋅ min−1) or its selective antagonist adrenomedullin-(22—52) (5, 15, and 50 ng ⋅ kg−1 ⋅ min−1). Proadrenomedullin NH2-terminal 20 peptide (PAMP; 5, 15, and 50 ng ⋅ kg−1 ⋅ min−1) suppressed both the splanchnic nerve stimulation- and ACh-induced increases in catecholamine output in a dose-dependent manner. PAMP also suppressed the catecholamine release responses to the nicotinic agonist 1,1-dimethyl-4-phenylpiperazinium (0.5, 1, and 2 μg) and to muscarine (0.5, 1, and 2 μg), although the muscarine-induced response was relatively resistant to PAMP. These results suggest that PAMP, but not adrenomedullin, can act as an inhibitory regulator of adrenal catecholamine release in vivo.
Cholinergic systems in the nucleus of the solitary tract of rats
Authors: Shihara Miwako , Hori Nobuaki , Hirooka Yoshitaka , Eshima Kenichi , Akaike Norio , Takeshita Akira
Published: December 2017

The pharmacological and physiological properties of excitatory amino acid and ACh systems in the nucleus of the solitary tract (NTS) were studied in slices of rat brain stem by extracellular and intracellular recordings from neurons activated by solitary tract (ST) stimulation. These neurons were characterized as having several long dendrites with multiple varicosities. Synaptic activation of the medial NTS (mNTS) neurons by ST stimulation was mediated by non- N-methyl-d-aspartate (NMDA) glutamate (Glu) receptors, because the excitation was blocked by 6-cyano-7-nitro-quinoxaline-2,3-dione but not by NMDA, nicotinic, or muscarinic antagonists. Identified mNTS neurons were excited by iontophoresis of both Glu and ACh. The most sensitive region of the cell was on the dendrites ∼100 μm from the cell body for both putative neurotransmitters. Nicotinic and/or muscarinic excitatory ACh responses were detected on the mNTS neurons. Our observations suggest that both types of ACh receptors may contribute to the attenuation of the baroreceptor reflex, but the functional correlation of this receptor profile remains to be determined.
Mechanism of biphasic response of renal nerve activity during acute cardiac tamponade in conscious rabbits
Authors: Hagiike Masanobu , Maeta Hajime , Murakami Hiroshi , Okada Kenji , Morita Hironobu
Published: December 2017

Renal sympathetic nerve activity (RSNA) responses to acute cardiac tamponade were studied in conscious rabbits with all reflexes intact (Int) or after either surgical sinoaortic denervation (SAD) or administration of intrapericardial procaine (ip-Pro) or intravenous procaine (iv-Pro). In Int rabbits, the mean arterial pressure (MAP) remained relatively constant until the pericardial volume reached 7.7 ml, whereas the RSNA increased to 226% [compensated cardiac tamponade (CCT)], then, at a pericardial volume of 9.3 ml, the MAP fell sharply and RSNA decreased to 34% [decompensated cardiac tamponade (DCT)]; 1 min after cessation of pericardial infusion, an intravenous injection of naloxone resulted in increases in both MAP and RSNA. In SAD rabbits, RSNA did not alter throughout CCT and DCT, but increased on injection of naloxone. In ip-Pro rabbits, RSNA increased during CCT but did not decrease during DCT, whereas, in iv-Pro rabbits, the RSNA response was similar to that in Int rabbits. These results indicate that RSNA responses to cardiac tamponade are biphasic, with an increase during CCT and a decrease during DCT. Sinoaortic baroreceptors are involved in mediating the increase in RSNA, whereas cardiac receptors may be involved in mediating the decrease in RSNA. An endogenous opioid may be responsible for the decrease in RSNA seen during DCT.
PGE2 increases substance P release from renal pelvic sensory nerves via activation of N-type calcium channels
Authors: Kopp Ulla C. , Cicha Michael Z.
Published: December 2017

Activation of renal pelvic sensory nerves by increased pelvic pressure results in a renal pelvic release of substance P that is dependent on intact prostaglandin synthesis. An isolated renal pelvic wall preparation was used to examine whether PGE2increases the release of substance P from renal pelvic sensory nerves and by what mechanisms. The validity of the model was tested by examining whether 50 mM KCl increased substance P release from the pelvic wall. Fifty millimolar KCl produced an increase in substance P release, from 9.6 ± 1.6 to 26.8 ± 4.0 pg/min, P < 0.01, that was blocked by the L-type calcium blocker verapamil (10 μM). PGE2 (0.14 μM) increased the release of substance P from the pelvic wall from 8.9 ± 0.9 to 20.6 ± 3.3 pg/min, P < 0.01. PGE2 failed to increase substance P release in a calcium-free medium. The PGE2-induced substance P release was blocked by the N-type calcium blocker ω-conotoxin (0.1 μM) but was unaffected by verapamil. In conclusion, PGE2 increases the release of substance P from renal pelvic sensory nerves by a calcium-dependent mechanism that requires influx of calcium via N-type calcium channels.
Cx32 mRNA in rat liver: effects of inflammation on poly(A) tail distribution and mRNA degradation
Authors: Theodorakis Nicholas G. , de Maio Antonio
Published: December 2017

Previous studies showed that the expression of connexin 32 (Cx32), the polypeptide subunit component of the major hepatic gap junction, is reduced in liver by changes in mRNA stability during bacterial lipopolysaccharide (LPS)-induced inflammation. In this study, we examined the distribution of Cx32 mRNA poly(A) tail lengths during LPS-induced inflammation, because this is considered the first step in the degradation of many mRNAs. During LPS treatment the first detectable change in Cx32 mRNA was a gradual shortening of its poly(A) tail, which reached a final size of ∼20 nucleotides. However, the poly(A) tail did not disappear entirely before the bulk of Cx32 mRNA was degraded. Treatment with actinomycin D, which blocks the degradation of Cx32 mRNA after LPS administration, resulted in the appearance of a completely deadenylated mRNA, which otherwise could not be detected. On the contrary, treatment with cycloheximide resulted in a decrease in the stability of Cx32 mRNA without an apparent change of the poly(A) tail size. The effect of cycloheximide on Cx32 mRNA stability seems to be due indirectly to the induction of an inflammatory response by this drug. These results suggest that, similar for many mRNAs, shortening of the poly(A) tail is one of the first steps in the degradation of Cx32 mRNA during inflammation.
α-MSH and its receptors in regulation of tumor necrosis factor-α production by human monocyte/macrophages
Authors: Taherzadeh S. , Sharma S. , Chhajlani V. , Gantz I. , Rajora N. , Demitri M. T. , Kelly L. , Zhao H. , Ichiyama T. , Catania A. , Lipton J. M.
Published: December 2017

The hypothesis that macrophages contain an autocrine circuit based on melanocortin [ACTH and α-melanocyte-stimulating hormone (α-MSH)] peptides has major implications for neuroimmunomodulation research and inflammation therapy. To test this hypothesis, cells of the THP-1 human monocyte/macrophage line were stimulated with lipopolysaccharide (LPS) in the presence and absence of α-MSH. The inflammatory cytokine tumor necrosis factor (TNF)-α was inhibited in relation to α-MSH concentration. Similar inhibitory effects on TNF-α were observed with ACTH peptides that contain the α-MSH amino acid sequence and act on melanocortin receptors. Nuclease protection assays indicated that expression of the human melanocortin-1 receptor subtype (hMC-1R) occurs in THP-1 cells; Southern blots of RT-PCR product revealed that additional subtypes, hMC-3R and hMC-5R, also occur. Incubation of resting macrophages with antibody to hMC-1R increased TNF-α concentration; the antibody also markedly reduced the inhibitory influence of α-MSH on TNF-α in macrophages treated with LPS. These results in cells known to produce α-MSH at rest and to increase secretion of the peptide when challenged are consistent with an endogenous regulatory circuit based on melanocortin peptides and their receptors. Targeting of this neuroimmunomodulatory circuit in inflammatory diseases in which myelomonocytic cells are prominent should be beneficial.
Cytokine-induced glucose uptake in skeletal muscle: redox regulation and the role of α-lipoic acid
Authors: Khanna Savita , Roy Sashwati , Packer Lester , Sen Chandan K.
Published: December 2017

In L6 myotubes, glucose uptake stimulated by interferon (IFN)-γ or lipopolysaccharides (LPS) and a combination of LPS, IFN-γ, and tumor necrosis factor (TNF)-α was inhibited by the antioxidant pyrrolidinedithiocarbamate and potentiated in reduced glutathione (GSH)-deficient cells. Also, the stimulatory effect of LPS and IFN-γ individually, and of a combination of LPS, IFN-γ, and TNF-α, on glucose uptake was associated with an increased level of intracellular oxidants (dichlorofluorescein assay) and loss of intracellular GSH. Study of the individual effects of LPS, IFN-γ, and TNF-α as well as of a combination of the three activators provided evidence against a role of nitric oxide in mediating the stimulatory effect of the above-mentioned agents on glucose uptake. We also observed that the insulin-mimetic nutrient α-lipoic acid (LA; R-enantiomer) is able to stimulate glucose uptake in cytokine-treated cells that are insulin resistant. This study shows that cytokine-induced glucose uptake in skeletal muscle cells is redox sensitive and that, under conditions of acute infection that is accompanied with insulin resistance, LA may have therapeutic implications in restoring glucose availability in tissues such as the skeletal muscle.
Upright posture reduces forearm blood flow early in exercise
Authors: Shoemaker J. Kevin , McQuillan Patrick M. , Sinoway Lawrence I.
Published: December 2017

The hypothesis that upright posture could modulate forearm blood flow (FBF) early in exercise was tested in six subjects. Both single (2-s duration) and repeated (1-s work/2-s rest cadence for 12 contractions) handgrip contractions (12 kg) were performed in the supine and 70° head-up tilt (HUT) positions. The arm was maintained at heart level to diminish myogenic effects. Baseline brachial artery diameters were assessed at rest in each position. Brachial artery mean blood velocity (MBV; Doppler) and mean arterial pressure (MAP) (Finapres) were measured continuously to calculate FBF and vascular conductance. MAP was not changed with posture. Antecubital venous pressure (Pv) was reduced in HUT (4.55 ± 1.3 mmHg) compared with supine (11.3 ± 1.9 mmHg) ( P < 0.01). For the repeated contractions, total excess FBF (TEF) was reduced in the HUT position compared with supine ( P < 0.02). With the single contractions, peak FBF, peak vascular conductance, and TEF during 30 s after release of the contraction were reduced in the HUT position compared with supine ( P < 0.01). Sympathetic blockade augmented the FBF response to a single contraction in HUT ( P < 0.05) and tended to increase this response while supine ( P = 0.08). However, sympathetic blockade did not attenuate the effect of HUT on peak FBF and TEF after the single contractions. Raising the arm above heart level while supine, to diminish Pv, resulted in FBF dynamics that were similar to those observed during HUT. Alternatively, lowering the arm while in HUT to restore Pv to supine levels restored the peak FBF and vascular conductance responses, but not TEF response, after a single contraction. It was concluded that upright posture diminishes the hyperemic response early in exercise. The data demonstrate that sympathetic constriction restrains the hyperemic response to a single contraction but does not modulate the postural reduction in postcontraction hyperemia. Therefore, the attenuated blood flow response in the HUT posture was largely related to factors associated with diminished venous pressures and not sympathetic vasoconstriction.
Adrenergic induction of bimodal myocardial protection: signal transduction and cardiac gene reprogramming
Authors: Meng Xianzhong , Shames Brian D. , Pulido Edward J. , Meldrum Daniel R. , Ao Lihua , Joo Kyung S. , Harken Alden H. , Banerjee Anirban
Published: December 2017

This study tested the hypothesis that in vivo norepinephrine (NE) treatment induces bimodal cardiac functional protection against ischemia and examined the roles of α1-adrenoceptors, protein kinase C (PKC), and cardiac gene expression in cardiac protection. Rats were treated with NE (25 μg/kg iv). Cardiac functional resistance to ischemia-reperfusion (25/40 min) injury was examined 30 min and 1, 4, and 24 h after NE treatment with the Langendorff technique, and effects of α1-adrenoceptor antagonism and PKC inhibition on the protection were determined. Northern analysis was performed to examine cardiac expression of mRNAs encoding α-actin and myosin heavy chain (MHC) isoforms. Immunofluorescent staining was performed to localize PKC-βI in the ventricular myocardium. NE treatment improved postischemic functional recovery at 30 min, 4 h, and 24 h but not at 1 h. Pretreatment with prazosin or chelerythrine abolished both the early adaptive response at 30 min and the delayed adaptive response at 24 h. NE treatment induced intranuclear translocation of PKC-βI in cardiac myocytes at 10 min and increased skeletal α-actin and β-MHC mRNAs in the myocardium at 4–24 h. These results demonstrate that in vivo NE treatment induces bimodal myocardial functional adaptation to ischemia in a rat model. α1-Adrenoceptors and PKC appear to be involved in signal transduction for inducing both the early and delayed adaptive responses. The delayed adaptive response is associated with the expression of cardiac genes encoding fetal contractile proteins, and PKC-βI may transduce the signal for reprogramming of cardiac gene expression.
Renal endothelial and macula densa NOS: integrated response to changes in extracellular fluid volume
Authors: Braam Branko
Published: December 2017

If, only 20 years ago, anyone had postulated that the absence of nitric oxide gas (NO) would lead to severe hypertension and destruction of the vascular bed of the kidney within weeks, it is not unlikely that smiles of pity would have appeared on the faces of fellow researchers. By now, this has become common knowledge, and hundreds of reports have appeared on the regulation of vascular and renal function by nitric oxide. The amount of information complicates the design of a concept on how NO participates in control of extracellular fluid volume (ECFV) by the kidney. This review analyzes the function of endothelial and macula densa NO synthase (NOS) in the regulation of renal function. From this analysis, endothelial NOS (eNOS)-derived NO is considered a modulator of vascular responses and of renal autoregulation in particular. Increases in renal perfusion pressure and sodium loading will increase eNOS activity, resulting in vasodilatation and depression of tubuloglomerular feedback system responsiveness. Endothelium-derived NO seems important to buffer minute-to-minute variations in perfusion pressure and rapid changes in ANG II activity. In contrast, macula densa NOS is proposed to drive adaptations to long-term changes in distal delivery and is considered a mediator of renin formation. Increases in perfusion pressure and distal delivery will depress the activity and expression of the enzyme that coincides with, and possibly mediates, diminished renin activity. Together, the opposite responses of eNOS and macula densa NOS-derived NO to changes in ECFV lead to an appropriate response to restore sodium balance. The concept that the two enzymes with different localizations in the kidney and in the cell are producing the same product, displaying contrasting responses to the same stimulus but nevertheless exhibiting an integrated response to perturbation of the most important regulated variable by the kidney, i.e., the ECFV, may be applicable to other tissues.
Functional evidence for subfornical organ-intrinsic conversion of angiotensin I to angiotensin II
Authors: Rauch Matthias , Schmid Herbert A.
Published: December 2017

Using extracellular electrophysiological recording in an in vitro slice preparation, we investigated whether ANG I can be locally converted to the functionally active ANG II within the rat subfornical organ (SFO). ANG I and ANG II (10−8–10−7M) excited ∼75% of all neurons tested with both peptides ( n = 25); the remainder were insensitive. The increase in firing rate and the duration and the latency of the responses of identical neurons, superfused with equimolar concentrations of ANG I and ANG II, were not different. The threshold concentrations of the ANG I- and ANG II-induced excitations were both 10−9M. Inhibition of the angiotensin-converting enzyme by captopril (10−4M; n = 8) completely blocked the ANG I-induced excitation, a 10-fold lower dose was only effective in two of four neurons. The AT1-receptor antagonist losartan (10−5M; n = 6) abolished the excitation caused by ANG I and ANG II. Subcutaneous injections of equimolar doses of ANG I and ANG II (200 μl; 2 × 10−4M) in water-sated rats similarly increased water intake by 2.4 ± 0.5 ( n = 16) and 2.7 ± 0.4 ml ( n = 20) after 1 h, respectively. Control rats receiving saline drank 0.07 ± 0.06 ml under these conditions. Pretreatment with a low dose of captopril (2.3 × 10−3M) 10 min before the injection of ANG I caused a water intake of 2.8 ± 0.5 ml ( n = 10), whereas a high dose of captopril (4.6 × 10−1M) suppressed the dipsogenic response of ANG I entirely ( n = 11). These data provide direct functional evidence for an SFO-intrinsic renin-angiotensin system (RAS) and underline the importance of the SFO as a central nervous interface connecting the peripheral with the central RAS.
Pressor reflex evoked by static muscle contraction: role of nitric oxide in the dorsal horn
Authors: Wilson L. Britt , Engbretson John , Crews Angela D.
Published: December 2017

In this study, we tested the hypothesis that nitric oxide (NO) production in the dorsal horn is involved in producing the pressor reflex elicited by static contraction of skeletal muscle. Cats were anesthetized with α-chloralose (80 mg/kg) and urethane (100 mg/kg), and a laminectomy was performed. With the exception of the L7 dorsal root, the dorsal and ventral roots from L5 to S2 were sectioned on one side and static contraction of the ipsilateral triceps surae muscle was evoked by electrically stimulating the peripheral ends of the L7 and S1 ventral roots. Dialysis of the NO synthase inhibitor N G-nitro-l-arginine methyl ester (l-NAME; 50 mmol/l syringe concentration, based upon dose-response data) into the dorsal horn at L6 and S1 failed to attenuate the peak change in mean arterial pressure (MAP) evoked by static contraction (ΔMAP in mmHg: 57 ± 5 before and 50 ± 6 after 2 h of l-NAME). However, this dialysis of l-NAME reduced the magnitude of the initial pressor response as the MAP at 10 s of the contraction fell from 27 ± 4 to 17 ± 4 mmHg. On the other hand, 2 h of l-arginine dialysis (50 mmol/l) shifted the curve representing the time course of the pressor response upward and increased the peak pressor response to static contraction from 51 ± 9 to 68 ± 9 mmHg. A 2-h dialysis of d-NAME (50 mmol/l), the inactive enantiomer of l-NAME, had no effect on the time course or the peak pressor response (ΔMAP in mmHg: 78 ± 12 before and 72 ± 15 after). These data suggest that NO production in the dorsal horn has a modulatory influence on the pressor reflex evoked by static contraction of skeletal muscle and that increasing the level of NO in the dorsal horn enhances the excitability of dorsal horn cells to muscle afferent input.
Acetazolamide-induced cerebral and ocular vasodilation in humans is independent of nitric oxide
Authors: Kiss Barbara , Dallinger Susanne , Findl Oliver , Rainer Georg , Eichler Hans-Georg , Schmetterer Leopold
Published: December 2017

Acetazolamide, a carbonic anhydrase inhibitor, is used orally in the treatment of primary and secondary open-angle glaucoma and induces ocular and cerebral vasodilation. Several in vitro studies have shown that carbonic anhydrase pharmacology and thel-arginine-nitric oxide (NO) pathway are closely related. We investigated the role of NO in acetazolamide-induced vasodilation on cerebral and ocular vessels in 12 healthy subjects in the presence or absence of N G-monomethyl-l-arginine (l-NMMA), a NO synthase inhibitor, and in the presence or absence ofl-arginine, the precursor of NO. Acetazolamide was administered after pretreatment with eitherl-NMMA or placebo and eitherl-arginine or placebo. Pulsatile choroidal blood flow was assessed with laser interferometric measurement of fundus pulsation. In addition, mean blood flow velocity (MFV) in the middle cerebral artery (MCA) and ophthalmic artery (OA) was measured with Doppler sonography. Acetazolamide increased ocular fundus pulsation amplitude (FPA; +27%, P < 0.001) and MFV in the MCA (+38%, P < 0.001) and in the OA (+19%, P = 0.003). Administration of l-NMMA alone reduced FPA (−21%, P < 0.001) and MFV in the MCA (−11%, P = 0.030) but did not change MFV in the OA. All hemodynamic effects ofl-NMMA were reversed byl-arginine. However, neitherl-NMMA norl-arginine altered acetazolamide-induced changes in cerebral or ocular hemodynamic parameters. The present data indicate that acetazolamide-induced hemodynamic changes are not mediated by NO. Which mediators other than NO are involved in the hemodynamic effects as induced by carbonic anhydrase inhibitors remains to be elucidated.